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129 | .\" ======================================================================== |
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131 | .IX Title ""<STANDARD INPUT>" 1" |
126 | .IX Title "LIBEV 3" |
132 | .TH "<STANDARD INPUT>" 1 "2007-11-27" "perl v5.8.8" "User Contributed Perl Documentation" |
127 | .TH LIBEV 3 "2012-02-04" "libev-4.11" "libev - high performance full featured event loop" |
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128 | .\" For nroff, turn off justification. Always turn off hyphenation; it makes |
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129 | .\" way too many mistakes in technical documents. |
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130 | .if n .ad l |
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131 | .nh |
133 | .SH "NAME" |
132 | .SH "NAME" |
134 | libev \- a high performance full\-featured event loop written in C |
133 | libev \- a high performance full\-featured event loop written in C |
135 | .SH "SYNOPSIS" |
134 | .SH "SYNOPSIS" |
136 | .IX Header "SYNOPSIS" |
135 | .IX Header "SYNOPSIS" |
137 | .Vb 1 |
136 | .Vb 1 |
138 | \& #include <ev.h> |
137 | \& #include <ev.h> |
139 | .Ve |
138 | .Ve |
140 | .SH "DESCRIPTION" |
139 | .SS "\s-1EXAMPLE\s0 \s-1PROGRAM\s0" |
141 | .IX Header "DESCRIPTION" |
140 | .IX Subsection "EXAMPLE PROGRAM" |
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141 | .Vb 2 |
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142 | \& // a single header file is required |
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143 | \& #include <ev.h> |
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144 | \& |
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145 | \& #include <stdio.h> // for puts |
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146 | \& |
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147 | \& // every watcher type has its own typedef\*(Aqd struct |
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148 | \& // with the name ev_TYPE |
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149 | \& ev_io stdin_watcher; |
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150 | \& ev_timer timeout_watcher; |
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151 | \& |
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152 | \& // all watcher callbacks have a similar signature |
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153 | \& // this callback is called when data is readable on stdin |
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154 | \& static void |
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155 | \& stdin_cb (EV_P_ ev_io *w, int revents) |
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156 | \& { |
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157 | \& puts ("stdin ready"); |
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158 | \& // for one\-shot events, one must manually stop the watcher |
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159 | \& // with its corresponding stop function. |
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160 | \& ev_io_stop (EV_A_ w); |
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161 | \& |
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162 | \& // this causes all nested ev_run\*(Aqs to stop iterating |
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163 | \& ev_break (EV_A_ EVBREAK_ALL); |
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164 | \& } |
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165 | \& |
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166 | \& // another callback, this time for a time\-out |
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167 | \& static void |
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168 | \& timeout_cb (EV_P_ ev_timer *w, int revents) |
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169 | \& { |
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170 | \& puts ("timeout"); |
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171 | \& // this causes the innermost ev_run to stop iterating |
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172 | \& ev_break (EV_A_ EVBREAK_ONE); |
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173 | \& } |
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174 | \& |
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175 | \& int |
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176 | \& main (void) |
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177 | \& { |
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178 | \& // use the default event loop unless you have special needs |
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179 | \& struct ev_loop *loop = EV_DEFAULT; |
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180 | \& |
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181 | \& // initialise an io watcher, then start it |
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182 | \& // this one will watch for stdin to become readable |
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183 | \& ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
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184 | \& ev_io_start (loop, &stdin_watcher); |
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185 | \& |
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186 | \& // initialise a timer watcher, then start it |
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187 | \& // simple non\-repeating 5.5 second timeout |
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188 | \& ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
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189 | \& ev_timer_start (loop, &timeout_watcher); |
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190 | \& |
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191 | \& // now wait for events to arrive |
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192 | \& ev_run (loop, 0); |
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193 | \& |
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194 | \& // break was called, so exit |
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195 | \& return 0; |
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196 | \& } |
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197 | .Ve |
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198 | .SH "ABOUT THIS DOCUMENT" |
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199 | .IX Header "ABOUT THIS DOCUMENT" |
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200 | This document documents the libev software package. |
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201 | .PP |
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202 | The newest version of this document is also available as an html-formatted |
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203 | web page you might find easier to navigate when reading it for the first |
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204 | time: <http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
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205 | .PP |
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206 | While this document tries to be as complete as possible in documenting |
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207 | libev, its usage and the rationale behind its design, it is not a tutorial |
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208 | on event-based programming, nor will it introduce event-based programming |
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209 | with libev. |
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210 | .PP |
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211 | Familiarity with event based programming techniques in general is assumed |
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212 | throughout this document. |
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213 | .SH "WHAT TO READ WHEN IN A HURRY" |
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214 | .IX Header "WHAT TO READ WHEN IN A HURRY" |
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215 | This manual tries to be very detailed, but unfortunately, this also makes |
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216 | it very long. If you just want to know the basics of libev, I suggest |
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217 | reading \*(L"\s-1ANATOMY\s0 \s-1OF\s0 A \s-1WATCHER\s0\*(R", then the \*(L"\s-1EXAMPLE\s0 \s-1PROGRAM\s0\*(R" above and |
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218 | look up the missing functions in \*(L"\s-1GLOBAL\s0 \s-1FUNCTIONS\s0\*(R" and the \f(CW\*(C`ev_io\*(C'\fR and |
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219 | \&\f(CW\*(C`ev_timer\*(C'\fR sections in \*(L"\s-1WATCHER\s0 \s-1TYPES\s0\*(R". |
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220 | .SH "ABOUT LIBEV" |
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221 | .IX Header "ABOUT LIBEV" |
142 | Libev is an event loop: you register interest in certain events (such as a |
222 | Libev is an event loop: you register interest in certain events (such as a |
143 | file descriptor being readable or a timeout occuring), and it will manage |
223 | file descriptor being readable or a timeout occurring), and it will manage |
144 | these event sources and provide your program with events. |
224 | these event sources and provide your program with events. |
145 | .PP |
225 | .PP |
146 | To do this, it must take more or less complete control over your process |
226 | To do this, it must take more or less complete control over your process |
147 | (or thread) by executing the \fIevent loop\fR handler, and will then |
227 | (or thread) by executing the \fIevent loop\fR handler, and will then |
148 | communicate events via a callback mechanism. |
228 | communicate events via a callback mechanism. |
149 | .PP |
229 | .PP |
150 | You register interest in certain events by registering so-called \fIevent |
230 | You register interest in certain events by registering so-called \fIevent |
151 | watchers\fR, which are relatively small C structures you initialise with the |
231 | watchers\fR, which are relatively small C structures you initialise with the |
152 | details of the event, and then hand it over to libev by \fIstarting\fR the |
232 | details of the event, and then hand it over to libev by \fIstarting\fR the |
153 | watcher. |
233 | watcher. |
154 | .SH "FEATURES" |
234 | .SS "\s-1FEATURES\s0" |
155 | .IX Header "FEATURES" |
235 | .IX Subsection "FEATURES" |
156 | Libev supports select, poll, the linux-specific epoll and the bsd-specific |
236 | Libev supports \f(CW\*(C`select\*(C'\fR, \f(CW\*(C`poll\*(C'\fR, the Linux-specific \f(CW\*(C`epoll\*(C'\fR, the |
157 | kqueue mechanisms for file descriptor events, relative timers, absolute |
237 | BSD-specific \f(CW\*(C`kqueue\*(C'\fR and the Solaris-specific event port mechanisms |
158 | timers with customised rescheduling, signal events, process status change |
238 | for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), the Linux \f(CW\*(C`inotify\*(C'\fR interface |
159 | events (related to \s-1SIGCHLD\s0), and event watchers dealing with the event |
239 | (for \f(CW\*(C`ev_stat\*(C'\fR), Linux eventfd/signalfd (for faster and cleaner |
160 | loop mechanism itself (idle, prepare and check watchers). It also is quite |
240 | inter-thread wakeup (\f(CW\*(C`ev_async\*(C'\fR)/signal handling (\f(CW\*(C`ev_signal\*(C'\fR)) relative |
161 | fast (see this benchmark comparing |
241 | timers (\f(CW\*(C`ev_timer\*(C'\fR), absolute timers with customised rescheduling |
162 | it to libevent for example). |
242 | (\f(CW\*(C`ev_periodic\*(C'\fR), synchronous signals (\f(CW\*(C`ev_signal\*(C'\fR), process status |
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243 | change events (\f(CW\*(C`ev_child\*(C'\fR), and event watchers dealing with the event |
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244 | loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR, \f(CW\*(C`ev_embed\*(C'\fR, \f(CW\*(C`ev_prepare\*(C'\fR and |
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245 | \&\f(CW\*(C`ev_check\*(C'\fR watchers) as well as file watchers (\f(CW\*(C`ev_stat\*(C'\fR) and even |
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246 | limited support for fork events (\f(CW\*(C`ev_fork\*(C'\fR). |
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247 | .PP |
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248 | It also is quite fast (see this |
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249 | benchmark <http://libev.schmorp.de/bench.html> comparing it to libevent |
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250 | for example). |
163 | .SH "CONVENTIONS" |
251 | .SS "\s-1CONVENTIONS\s0" |
164 | .IX Header "CONVENTIONS" |
252 | .IX Subsection "CONVENTIONS" |
165 | Libev is very configurable. In this manual the default configuration |
253 | Libev is very configurable. In this manual the default (and most common) |
166 | will be described, which supports multiple event loops. For more info |
254 | configuration will be described, which supports multiple event loops. For |
167 | about various configuration options please have a look at the file |
255 | more info about various configuration options please have a look at |
168 | \&\fI\s-1README\s0.embed\fR in the libev distribution. If libev was configured without |
256 | \&\fB\s-1EMBED\s0\fR section in this manual. If libev was configured without support |
169 | support for multiple event loops, then all functions taking an initial |
257 | for multiple event loops, then all functions taking an initial argument of |
170 | argument of name \f(CW\*(C`loop\*(C'\fR (which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR) |
258 | name \f(CW\*(C`loop\*(C'\fR (which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR) will not have |
171 | will not have this argument. |
259 | this argument. |
172 | .SH "TIME REPRESENTATION" |
260 | .SS "\s-1TIME\s0 \s-1REPRESENTATION\s0" |
173 | .IX Header "TIME REPRESENTATION" |
261 | .IX Subsection "TIME REPRESENTATION" |
174 | Libev represents time as a single floating point number, representing the |
262 | Libev represents time as a single floating point number, representing |
175 | (fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near |
263 | the (fractional) number of seconds since the (\s-1POSIX\s0) epoch (in practice |
176 | the beginning of 1970, details are complicated, don't ask). This type is |
264 | somewhere near the beginning of 1970, details are complicated, don't |
177 | called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use too. It usually aliases |
265 | ask). This type is called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use |
178 | to the \f(CW\*(C`double\*(C'\fR type in C, and when you need to do any calculations on |
266 | too. It usually aliases to the \f(CW\*(C`double\*(C'\fR type in C. When you need to do |
179 | it, you should treat it as such. |
267 | any calculations on it, you should treat it as some floating point value. |
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268 | .PP |
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269 | Unlike the name component \f(CW\*(C`stamp\*(C'\fR might indicate, it is also used for |
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270 | time differences (e.g. delays) throughout libev. |
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271 | .SH "ERROR HANDLING" |
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272 | .IX Header "ERROR HANDLING" |
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273 | Libev knows three classes of errors: operating system errors, usage errors |
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274 | and internal errors (bugs). |
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275 | .PP |
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276 | When libev catches an operating system error it cannot handle (for example |
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277 | a system call indicating a condition libev cannot fix), it calls the callback |
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278 | set via \f(CW\*(C`ev_set_syserr_cb\*(C'\fR, which is supposed to fix the problem or |
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279 | abort. The default is to print a diagnostic message and to call \f(CW\*(C`abort |
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280 | ()\*(C'\fR. |
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281 | .PP |
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282 | When libev detects a usage error such as a negative timer interval, then |
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283 | it will print a diagnostic message and abort (via the \f(CW\*(C`assert\*(C'\fR mechanism, |
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284 | so \f(CW\*(C`NDEBUG\*(C'\fR will disable this checking): these are programming errors in |
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285 | the libev caller and need to be fixed there. |
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286 | .PP |
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287 | Libev also has a few internal error-checking \f(CW\*(C`assert\*(C'\fRions, and also has |
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288 | extensive consistency checking code. These do not trigger under normal |
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289 | circumstances, as they indicate either a bug in libev or worse. |
180 | .SH "GLOBAL FUNCTIONS" |
290 | .SH "GLOBAL FUNCTIONS" |
181 | .IX Header "GLOBAL FUNCTIONS" |
291 | .IX Header "GLOBAL FUNCTIONS" |
182 | These functions can be called anytime, even before initialising the |
292 | These functions can be called anytime, even before initialising the |
183 | library in any way. |
293 | library in any way. |
184 | .IP "ev_tstamp ev_time ()" 4 |
294 | .IP "ev_tstamp ev_time ()" 4 |
185 | .IX Item "ev_tstamp ev_time ()" |
295 | .IX Item "ev_tstamp ev_time ()" |
186 | Returns the current time as libev would use it. Please note that the |
296 | Returns the current time as libev would use it. Please note that the |
187 | \&\f(CW\*(C`ev_now\*(C'\fR function is usually faster and also often returns the timestamp |
297 | \&\f(CW\*(C`ev_now\*(C'\fR function is usually faster and also often returns the timestamp |
188 | you actually want to know. |
298 | you actually want to know. Also interesting is the combination of |
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299 | \&\f(CW\*(C`ev_now_update\*(C'\fR and \f(CW\*(C`ev_now\*(C'\fR. |
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300 | .IP "ev_sleep (ev_tstamp interval)" 4 |
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301 | .IX Item "ev_sleep (ev_tstamp interval)" |
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302 | Sleep for the given interval: The current thread will be blocked |
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303 | until either it is interrupted or the given time interval has |
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304 | passed (approximately \- it might return a bit earlier even if not |
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305 | interrupted). Returns immediately if \f(CW\*(C`interval <= 0\*(C'\fR. |
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306 | .Sp |
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307 | Basically this is a sub-second-resolution \f(CW\*(C`sleep ()\*(C'\fR. |
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308 | .Sp |
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309 | The range of the \f(CW\*(C`interval\*(C'\fR is limited \- libev only guarantees to work |
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310 | with sleep times of up to one day (\f(CW\*(C`interval <= 86400\*(C'\fR). |
189 | .IP "int ev_version_major ()" 4 |
311 | .IP "int ev_version_major ()" 4 |
190 | .IX Item "int ev_version_major ()" |
312 | .IX Item "int ev_version_major ()" |
191 | .PD 0 |
313 | .PD 0 |
192 | .IP "int ev_version_minor ()" 4 |
314 | .IP "int ev_version_minor ()" 4 |
193 | .IX Item "int ev_version_minor ()" |
315 | .IX Item "int ev_version_minor ()" |
194 | .PD |
316 | .PD |
195 | You can find out the major and minor version numbers of the library |
317 | You can find out the major and minor \s-1ABI\s0 version numbers of the library |
196 | you linked against by calling the functions \f(CW\*(C`ev_version_major\*(C'\fR and |
318 | you linked against by calling the functions \f(CW\*(C`ev_version_major\*(C'\fR and |
197 | \&\f(CW\*(C`ev_version_minor\*(C'\fR. If you want, you can compare against the global |
319 | \&\f(CW\*(C`ev_version_minor\*(C'\fR. If you want, you can compare against the global |
198 | symbols \f(CW\*(C`EV_VERSION_MAJOR\*(C'\fR and \f(CW\*(C`EV_VERSION_MINOR\*(C'\fR, which specify the |
320 | symbols \f(CW\*(C`EV_VERSION_MAJOR\*(C'\fR and \f(CW\*(C`EV_VERSION_MINOR\*(C'\fR, which specify the |
199 | version of the library your program was compiled against. |
321 | version of the library your program was compiled against. |
200 | .Sp |
322 | .Sp |
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323 | These version numbers refer to the \s-1ABI\s0 version of the library, not the |
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324 | release version. |
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325 | .Sp |
201 | Usually, it's a good idea to terminate if the major versions mismatch, |
326 | Usually, it's a good idea to terminate if the major versions mismatch, |
202 | as this indicates an incompatible change. Minor versions are usually |
327 | as this indicates an incompatible change. Minor versions are usually |
203 | compatible to older versions, so a larger minor version alone is usually |
328 | compatible to older versions, so a larger minor version alone is usually |
204 | not a problem. |
329 | not a problem. |
205 | .Sp |
330 | .Sp |
206 | Example: make sure we haven't accidentally been linked against the wrong |
331 | Example: Make sure we haven't accidentally been linked against the wrong |
207 | version: |
332 | version (note, however, that this will not detect other \s-1ABI\s0 mismatches, |
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333 | such as \s-1LFS\s0 or reentrancy). |
208 | .Sp |
334 | .Sp |
209 | .Vb 3 |
335 | .Vb 3 |
210 | \& assert (("libev version mismatch", |
336 | \& assert (("libev version mismatch", |
211 | \& ev_version_major () == EV_VERSION_MAJOR |
337 | \& ev_version_major () == EV_VERSION_MAJOR |
212 | \& && ev_version_minor () >= EV_VERSION_MINOR)); |
338 | \& && ev_version_minor () >= EV_VERSION_MINOR)); |
213 | .Ve |
339 | .Ve |
214 | .IP "unsigned int ev_supported_backends ()" 4 |
340 | .IP "unsigned int ev_supported_backends ()" 4 |
215 | .IX Item "unsigned int ev_supported_backends ()" |
341 | .IX Item "unsigned int ev_supported_backends ()" |
216 | Return the set of all backends (i.e. their corresponding \f(CW\*(C`EV_BACKEND_*\*(C'\fR |
342 | Return the set of all backends (i.e. their corresponding \f(CW\*(C`EV_BACKEND_*\*(C'\fR |
217 | value) compiled into this binary of libev (independent of their |
343 | value) compiled into this binary of libev (independent of their |
… | |
… | |
220 | .Sp |
346 | .Sp |
221 | Example: make sure we have the epoll method, because yeah this is cool and |
347 | Example: make sure we have the epoll method, because yeah this is cool and |
222 | a must have and can we have a torrent of it please!!!11 |
348 | a must have and can we have a torrent of it please!!!11 |
223 | .Sp |
349 | .Sp |
224 | .Vb 2 |
350 | .Vb 2 |
225 | \& assert (("sorry, no epoll, no sex", |
351 | \& assert (("sorry, no epoll, no sex", |
226 | \& ev_supported_backends () & EVBACKEND_EPOLL)); |
352 | \& ev_supported_backends () & EVBACKEND_EPOLL)); |
227 | .Ve |
353 | .Ve |
228 | .IP "unsigned int ev_recommended_backends ()" 4 |
354 | .IP "unsigned int ev_recommended_backends ()" 4 |
229 | .IX Item "unsigned int ev_recommended_backends ()" |
355 | .IX Item "unsigned int ev_recommended_backends ()" |
230 | Return the set of all backends compiled into this binary of libev and also |
356 | Return the set of all backends compiled into this binary of libev and |
231 | recommended for this platform. This set is often smaller than the one |
357 | also recommended for this platform, meaning it will work for most file |
|
|
358 | descriptor types. This set is often smaller than the one returned by |
232 | returned by \f(CW\*(C`ev_supported_backends\*(C'\fR, as for example kqueue is broken on |
359 | \&\f(CW\*(C`ev_supported_backends\*(C'\fR, as for example kqueue is broken on most BSDs |
233 | most BSDs and will not be autodetected unless you explicitly request it |
360 | and will not be auto-detected unless you explicitly request it (assuming |
234 | (assuming you know what you are doing). This is the set of backends that |
361 | you know what you are doing). This is the set of backends that libev will |
235 | libev will probe for if you specify no backends explicitly. |
362 | probe for if you specify no backends explicitly. |
236 | .IP "unsigned int ev_embeddable_backends ()" 4 |
363 | .IP "unsigned int ev_embeddable_backends ()" 4 |
237 | .IX Item "unsigned int ev_embeddable_backends ()" |
364 | .IX Item "unsigned int ev_embeddable_backends ()" |
238 | Returns the set of backends that are embeddable in other event loops. This |
365 | Returns the set of backends that are embeddable in other event loops. This |
239 | is the theoretical, all\-platform, value. To find which backends |
366 | value is platform-specific but can include backends not available on the |
240 | might be supported on the current system, you would need to look at |
367 | current system. To find which embeddable backends might be supported on |
241 | \&\f(CW\*(C`ev_embeddable_backends () & ev_supported_backends ()\*(C'\fR, likewise for |
368 | the current system, you would need to look at \f(CW\*(C`ev_embeddable_backends () |
242 | recommended ones. |
369 | & ev_supported_backends ()\*(C'\fR, likewise for recommended ones. |
243 | .Sp |
370 | .Sp |
244 | See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info. |
371 | See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info. |
245 | .IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4 |
372 | .IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4 |
246 | .IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))" |
373 | .IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))" |
247 | Sets the allocation function to use (the prototype is similar to the |
374 | Sets the allocation function to use (the prototype is similar \- the |
248 | realloc C function, the semantics are identical). It is used to allocate |
375 | semantics are identical to the \f(CW\*(C`realloc\*(C'\fR C89/SuS/POSIX function). It is |
249 | and free memory (no surprises here). If it returns zero when memory |
376 | used to allocate and free memory (no surprises here). If it returns zero |
250 | needs to be allocated, the library might abort or take some potentially |
377 | when memory needs to be allocated (\f(CW\*(C`size != 0\*(C'\fR), the library might abort |
251 | destructive action. The default is your system realloc function. |
378 | or take some potentially destructive action. |
|
|
379 | .Sp |
|
|
380 | Since some systems (at least OpenBSD and Darwin) fail to implement |
|
|
381 | correct \f(CW\*(C`realloc\*(C'\fR semantics, libev will use a wrapper around the system |
|
|
382 | \&\f(CW\*(C`realloc\*(C'\fR and \f(CW\*(C`free\*(C'\fR functions by default. |
252 | .Sp |
383 | .Sp |
253 | You could override this function in high-availability programs to, say, |
384 | You could override this function in high-availability programs to, say, |
254 | free some memory if it cannot allocate memory, to use a special allocator, |
385 | free some memory if it cannot allocate memory, to use a special allocator, |
255 | or even to sleep a while and retry until some memory is available. |
386 | or even to sleep a while and retry until some memory is available. |
256 | .Sp |
387 | .Sp |
257 | Example: replace the libev allocator with one that waits a bit and then |
388 | Example: Replace the libev allocator with one that waits a bit and then |
258 | retries: better than mine). |
389 | retries (example requires a standards-compliant \f(CW\*(C`realloc\*(C'\fR). |
259 | .Sp |
390 | .Sp |
260 | .Vb 6 |
391 | .Vb 6 |
261 | \& static void * |
392 | \& static void * |
262 | \& persistent_realloc (void *ptr, long size) |
393 | \& persistent_realloc (void *ptr, size_t size) |
263 | \& { |
394 | \& { |
264 | \& for (;;) |
395 | \& for (;;) |
265 | \& { |
396 | \& { |
266 | \& void *newptr = realloc (ptr, size); |
397 | \& void *newptr = realloc (ptr, size); |
267 | .Ve |
398 | \& |
268 | .Sp |
|
|
269 | .Vb 2 |
|
|
270 | \& if (newptr) |
399 | \& if (newptr) |
271 | \& return newptr; |
400 | \& return newptr; |
272 | .Ve |
401 | \& |
273 | .Sp |
|
|
274 | .Vb 3 |
|
|
275 | \& sleep (60); |
402 | \& sleep (60); |
276 | \& } |
403 | \& } |
277 | \& } |
404 | \& } |
278 | .Ve |
405 | \& |
279 | .Sp |
|
|
280 | .Vb 2 |
|
|
281 | \& ... |
406 | \& ... |
282 | \& ev_set_allocator (persistent_realloc); |
407 | \& ev_set_allocator (persistent_realloc); |
283 | .Ve |
408 | .Ve |
284 | .IP "ev_set_syserr_cb (void (*cb)(const char *msg));" 4 |
409 | .IP "ev_set_syserr_cb (void (*cb)(const char *msg))" 4 |
285 | .IX Item "ev_set_syserr_cb (void (*cb)(const char *msg));" |
410 | .IX Item "ev_set_syserr_cb (void (*cb)(const char *msg))" |
286 | Set the callback function to call on a retryable syscall error (such |
411 | Set the callback function to call on a retryable system call error (such |
287 | as failed select, poll, epoll_wait). The message is a printable string |
412 | as failed select, poll, epoll_wait). The message is a printable string |
288 | indicating the system call or subsystem causing the problem. If this |
413 | indicating the system call or subsystem causing the problem. If this |
289 | callback is set, then libev will expect it to remedy the sitution, no |
414 | callback is set, then libev will expect it to remedy the situation, no |
290 | matter what, when it returns. That is, libev will generally retry the |
415 | matter what, when it returns. That is, libev will generally retry the |
291 | requested operation, or, if the condition doesn't go away, do bad stuff |
416 | requested operation, or, if the condition doesn't go away, do bad stuff |
292 | (such as abort). |
417 | (such as abort). |
293 | .Sp |
418 | .Sp |
294 | Example: do the same thing as libev does internally: |
419 | Example: This is basically the same thing that libev does internally, too. |
295 | .Sp |
420 | .Sp |
296 | .Vb 6 |
421 | .Vb 6 |
297 | \& static void |
422 | \& static void |
298 | \& fatal_error (const char *msg) |
423 | \& fatal_error (const char *msg) |
299 | \& { |
424 | \& { |
300 | \& perror (msg); |
425 | \& perror (msg); |
301 | \& abort (); |
426 | \& abort (); |
302 | \& } |
427 | \& } |
303 | .Ve |
428 | \& |
304 | .Sp |
|
|
305 | .Vb 2 |
|
|
306 | \& ... |
429 | \& ... |
307 | \& ev_set_syserr_cb (fatal_error); |
430 | \& ev_set_syserr_cb (fatal_error); |
308 | .Ve |
431 | .Ve |
|
|
432 | .IP "ev_feed_signal (int signum)" 4 |
|
|
433 | .IX Item "ev_feed_signal (int signum)" |
|
|
434 | This function can be used to \*(L"simulate\*(R" a signal receive. It is completely |
|
|
435 | safe to call this function at any time, from any context, including signal |
|
|
436 | handlers or random threads. |
|
|
437 | .Sp |
|
|
438 | Its main use is to customise signal handling in your process, especially |
|
|
439 | in the presence of threads. For example, you could block signals |
|
|
440 | by default in all threads (and specifying \f(CW\*(C`EVFLAG_NOSIGMASK\*(C'\fR when |
|
|
441 | creating any loops), and in one thread, use \f(CW\*(C`sigwait\*(C'\fR or any other |
|
|
442 | mechanism to wait for signals, then \*(L"deliver\*(R" them to libev by calling |
|
|
443 | \&\f(CW\*(C`ev_feed_signal\*(C'\fR. |
309 | .SH "FUNCTIONS CONTROLLING THE EVENT LOOP" |
444 | .SH "FUNCTIONS CONTROLLING EVENT LOOPS" |
310 | .IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP" |
445 | .IX Header "FUNCTIONS CONTROLLING EVENT LOOPS" |
311 | An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR. The library knows two |
446 | An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR (the \f(CW\*(C`struct\*(C'\fR is |
312 | types of such loops, the \fIdefault\fR loop, which supports signals and child |
447 | \&\fInot\fR optional in this case unless libev 3 compatibility is disabled, as |
313 | events, and dynamically created loops which do not. |
448 | libev 3 had an \f(CW\*(C`ev_loop\*(C'\fR function colliding with the struct name). |
314 | .PP |
449 | .PP |
315 | If you use threads, a common model is to run the default event loop |
450 | The library knows two types of such loops, the \fIdefault\fR loop, which |
316 | in your main thread (or in a separate thread) and for each thread you |
451 | supports child process events, and dynamically created event loops which |
317 | create, you also create another event loop. Libev itself does no locking |
452 | do not. |
318 | whatsoever, so if you mix calls to the same event loop in different |
|
|
319 | threads, make sure you lock (this is usually a bad idea, though, even if |
|
|
320 | done correctly, because it's hideous and inefficient). |
|
|
321 | .IP "struct ev_loop *ev_default_loop (unsigned int flags)" 4 |
453 | .IP "struct ev_loop *ev_default_loop (unsigned int flags)" 4 |
322 | .IX Item "struct ev_loop *ev_default_loop (unsigned int flags)" |
454 | .IX Item "struct ev_loop *ev_default_loop (unsigned int flags)" |
323 | This will initialise the default event loop if it hasn't been initialised |
455 | This returns the \*(L"default\*(R" event loop object, which is what you should |
324 | yet and return it. If the default loop could not be initialised, returns |
456 | normally use when you just need \*(L"the event loop\*(R". Event loop objects and |
325 | false. If it already was initialised it simply returns it (and ignores the |
457 | the \f(CW\*(C`flags\*(C'\fR parameter are described in more detail in the entry for |
326 | flags. If that is troubling you, check \f(CW\*(C`ev_backend ()\*(C'\fR afterwards). |
458 | \&\f(CW\*(C`ev_loop_new\*(C'\fR. |
|
|
459 | .Sp |
|
|
460 | If the default loop is already initialised then this function simply |
|
|
461 | returns it (and ignores the flags. If that is troubling you, check |
|
|
462 | \&\f(CW\*(C`ev_backend ()\*(C'\fR afterwards). Otherwise it will create it with the given |
|
|
463 | flags, which should almost always be \f(CW0\fR, unless the caller is also the |
|
|
464 | one calling \f(CW\*(C`ev_run\*(C'\fR or otherwise qualifies as \*(L"the main program\*(R". |
327 | .Sp |
465 | .Sp |
328 | If you don't know what event loop to use, use the one returned from this |
466 | If you don't know what event loop to use, use the one returned from this |
329 | function. |
467 | function (or via the \f(CW\*(C`EV_DEFAULT\*(C'\fR macro). |
|
|
468 | .Sp |
|
|
469 | Note that this function is \fInot\fR thread-safe, so if you want to use it |
|
|
470 | from multiple threads, you have to employ some kind of mutex (note also |
|
|
471 | that this case is unlikely, as loops cannot be shared easily between |
|
|
472 | threads anyway). |
|
|
473 | .Sp |
|
|
474 | The default loop is the only loop that can handle \f(CW\*(C`ev_child\*(C'\fR watchers, |
|
|
475 | and to do this, it always registers a handler for \f(CW\*(C`SIGCHLD\*(C'\fR. If this is |
|
|
476 | a problem for your application you can either create a dynamic loop with |
|
|
477 | \&\f(CW\*(C`ev_loop_new\*(C'\fR which doesn't do that, or you can simply overwrite the |
|
|
478 | \&\f(CW\*(C`SIGCHLD\*(C'\fR signal handler \fIafter\fR calling \f(CW\*(C`ev_default_init\*(C'\fR. |
|
|
479 | .Sp |
|
|
480 | Example: This is the most typical usage. |
|
|
481 | .Sp |
|
|
482 | .Vb 2 |
|
|
483 | \& if (!ev_default_loop (0)) |
|
|
484 | \& fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
|
|
485 | .Ve |
|
|
486 | .Sp |
|
|
487 | Example: Restrict libev to the select and poll backends, and do not allow |
|
|
488 | environment settings to be taken into account: |
|
|
489 | .Sp |
|
|
490 | .Vb 1 |
|
|
491 | \& ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
|
|
492 | .Ve |
|
|
493 | .IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4 |
|
|
494 | .IX Item "struct ev_loop *ev_loop_new (unsigned int flags)" |
|
|
495 | This will create and initialise a new event loop object. If the loop |
|
|
496 | could not be initialised, returns false. |
|
|
497 | .Sp |
|
|
498 | This function is thread-safe, and one common way to use libev with |
|
|
499 | threads is indeed to create one loop per thread, and using the default |
|
|
500 | loop in the \*(L"main\*(R" or \*(L"initial\*(R" thread. |
330 | .Sp |
501 | .Sp |
331 | The flags argument can be used to specify special behaviour or specific |
502 | The flags argument can be used to specify special behaviour or specific |
332 | backends to use, and is usually specified as \f(CW0\fR (or \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). |
503 | backends to use, and is usually specified as \f(CW0\fR (or \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). |
333 | .Sp |
504 | .Sp |
334 | The following flags are supported: |
505 | The following flags are supported: |
… | |
… | |
339 | The default flags value. Use this if you have no clue (it's the right |
510 | The default flags value. Use this if you have no clue (it's the right |
340 | thing, believe me). |
511 | thing, believe me). |
341 | .ie n .IP """EVFLAG_NOENV""" 4 |
512 | .ie n .IP """EVFLAG_NOENV""" 4 |
342 | .el .IP "\f(CWEVFLAG_NOENV\fR" 4 |
513 | .el .IP "\f(CWEVFLAG_NOENV\fR" 4 |
343 | .IX Item "EVFLAG_NOENV" |
514 | .IX Item "EVFLAG_NOENV" |
344 | If this flag bit is ored into the flag value (or the program runs setuid |
515 | If this flag bit is or'ed into the flag value (or the program runs setuid |
345 | or setgid) then libev will \fInot\fR look at the environment variable |
516 | or setgid) then libev will \fInot\fR look at the environment variable |
346 | \&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will |
517 | \&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will |
347 | override the flags completely if it is found in the environment. This is |
518 | override the flags completely if it is found in the environment. This is |
348 | useful to try out specific backends to test their performance, or to work |
519 | useful to try out specific backends to test their performance, or to work |
349 | around bugs. |
520 | around bugs. |
|
|
521 | .ie n .IP """EVFLAG_FORKCHECK""" 4 |
|
|
522 | .el .IP "\f(CWEVFLAG_FORKCHECK\fR" 4 |
|
|
523 | .IX Item "EVFLAG_FORKCHECK" |
|
|
524 | Instead of calling \f(CW\*(C`ev_loop_fork\*(C'\fR manually after a fork, you can also |
|
|
525 | make libev check for a fork in each iteration by enabling this flag. |
|
|
526 | .Sp |
|
|
527 | This works by calling \f(CW\*(C`getpid ()\*(C'\fR on every iteration of the loop, |
|
|
528 | and thus this might slow down your event loop if you do a lot of loop |
|
|
529 | iterations and little real work, but is usually not noticeable (on my |
|
|
530 | GNU/Linux system for example, \f(CW\*(C`getpid\*(C'\fR is actually a simple 5\-insn sequence |
|
|
531 | without a system call and thus \fIvery\fR fast, but my GNU/Linux system also has |
|
|
532 | \&\f(CW\*(C`pthread_atfork\*(C'\fR which is even faster). |
|
|
533 | .Sp |
|
|
534 | The big advantage of this flag is that you can forget about fork (and |
|
|
535 | forget about forgetting to tell libev about forking) when you use this |
|
|
536 | flag. |
|
|
537 | .Sp |
|
|
538 | This flag setting cannot be overridden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR |
|
|
539 | environment variable. |
|
|
540 | .ie n .IP """EVFLAG_NOINOTIFY""" 4 |
|
|
541 | .el .IP "\f(CWEVFLAG_NOINOTIFY\fR" 4 |
|
|
542 | .IX Item "EVFLAG_NOINOTIFY" |
|
|
543 | When this flag is specified, then libev will not attempt to use the |
|
|
544 | \&\fIinotify\fR \s-1API\s0 for its \f(CW\*(C`ev_stat\*(C'\fR watchers. Apart from debugging and |
|
|
545 | testing, this flag can be useful to conserve inotify file descriptors, as |
|
|
546 | otherwise each loop using \f(CW\*(C`ev_stat\*(C'\fR watchers consumes one inotify handle. |
|
|
547 | .ie n .IP """EVFLAG_SIGNALFD""" 4 |
|
|
548 | .el .IP "\f(CWEVFLAG_SIGNALFD\fR" 4 |
|
|
549 | .IX Item "EVFLAG_SIGNALFD" |
|
|
550 | When this flag is specified, then libev will attempt to use the |
|
|
551 | \&\fIsignalfd\fR \s-1API\s0 for its \f(CW\*(C`ev_signal\*(C'\fR (and \f(CW\*(C`ev_child\*(C'\fR) watchers. This \s-1API\s0 |
|
|
552 | delivers signals synchronously, which makes it both faster and might make |
|
|
553 | it possible to get the queued signal data. It can also simplify signal |
|
|
554 | handling with threads, as long as you properly block signals in your |
|
|
555 | threads that are not interested in handling them. |
|
|
556 | .Sp |
|
|
557 | Signalfd will not be used by default as this changes your signal mask, and |
|
|
558 | there are a lot of shoddy libraries and programs (glib's threadpool for |
|
|
559 | example) that can't properly initialise their signal masks. |
|
|
560 | .ie n .IP """EVFLAG_NOSIGMASK""" 4 |
|
|
561 | .el .IP "\f(CWEVFLAG_NOSIGMASK\fR" 4 |
|
|
562 | .IX Item "EVFLAG_NOSIGMASK" |
|
|
563 | When this flag is specified, then libev will avoid to modify the signal |
|
|
564 | mask. Specifically, this means you have to make sure signals are unblocked |
|
|
565 | when you want to receive them. |
|
|
566 | .Sp |
|
|
567 | This behaviour is useful when you want to do your own signal handling, or |
|
|
568 | want to handle signals only in specific threads and want to avoid libev |
|
|
569 | unblocking the signals. |
|
|
570 | .Sp |
|
|
571 | It's also required by \s-1POSIX\s0 in a threaded program, as libev calls |
|
|
572 | \&\f(CW\*(C`sigprocmask\*(C'\fR, whose behaviour is officially unspecified. |
|
|
573 | .Sp |
|
|
574 | This flag's behaviour will become the default in future versions of libev. |
350 | .ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4 |
575 | .ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4 |
351 | .el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4 |
576 | .el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4 |
352 | .IX Item "EVBACKEND_SELECT (value 1, portable select backend)" |
577 | .IX Item "EVBACKEND_SELECT (value 1, portable select backend)" |
353 | This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as |
578 | This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as |
354 | libev tries to roll its own fd_set with no limits on the number of fds, |
579 | libev tries to roll its own fd_set with no limits on the number of fds, |
355 | but if that fails, expect a fairly low limit on the number of fds when |
580 | but if that fails, expect a fairly low limit on the number of fds when |
356 | using this backend. It doesn't scale too well (O(highest_fd)), but its usually |
581 | using this backend. It doesn't scale too well (O(highest_fd)), but its |
357 | the fastest backend for a low number of fds. |
582 | usually the fastest backend for a low number of (low-numbered :) fds. |
|
|
583 | .Sp |
|
|
584 | To get good performance out of this backend you need a high amount of |
|
|
585 | parallelism (most of the file descriptors should be busy). If you are |
|
|
586 | writing a server, you should \f(CW\*(C`accept ()\*(C'\fR in a loop to accept as many |
|
|
587 | connections as possible during one iteration. You might also want to have |
|
|
588 | a look at \f(CW\*(C`ev_set_io_collect_interval ()\*(C'\fR to increase the amount of |
|
|
589 | readiness notifications you get per iteration. |
|
|
590 | .Sp |
|
|
591 | This backend maps \f(CW\*(C`EV_READ\*(C'\fR to the \f(CW\*(C`readfds\*(C'\fR set and \f(CW\*(C`EV_WRITE\*(C'\fR to the |
|
|
592 | \&\f(CW\*(C`writefds\*(C'\fR set (and to work around Microsoft Windows bugs, also onto the |
|
|
593 | \&\f(CW\*(C`exceptfds\*(C'\fR set on that platform). |
358 | .ie n .IP """EVBACKEND_POLL"" (value 2, poll backend, available everywhere except on windows)" 4 |
594 | .ie n .IP """EVBACKEND_POLL"" (value 2, poll backend, available everywhere except on windows)" 4 |
359 | .el .IP "\f(CWEVBACKEND_POLL\fR (value 2, poll backend, available everywhere except on windows)" 4 |
595 | .el .IP "\f(CWEVBACKEND_POLL\fR (value 2, poll backend, available everywhere except on windows)" 4 |
360 | .IX Item "EVBACKEND_POLL (value 2, poll backend, available everywhere except on windows)" |
596 | .IX Item "EVBACKEND_POLL (value 2, poll backend, available everywhere except on windows)" |
361 | And this is your standard \fIpoll\fR\|(2) backend. It's more complicated than |
597 | And this is your standard \fIpoll\fR\|(2) backend. It's more complicated |
362 | select, but handles sparse fds better and has no artificial limit on the |
598 | than select, but handles sparse fds better and has no artificial |
363 | number of fds you can use (except it will slow down considerably with a |
599 | limit on the number of fds you can use (except it will slow down |
364 | lot of inactive fds). It scales similarly to select, i.e. O(total_fds). |
600 | considerably with a lot of inactive fds). It scales similarly to select, |
|
|
601 | i.e. O(total_fds). See the entry for \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR, above, for |
|
|
602 | performance tips. |
|
|
603 | .Sp |
|
|
604 | This backend maps \f(CW\*(C`EV_READ\*(C'\fR to \f(CW\*(C`POLLIN | POLLERR | POLLHUP\*(C'\fR, and |
|
|
605 | \&\f(CW\*(C`EV_WRITE\*(C'\fR to \f(CW\*(C`POLLOUT | POLLERR | POLLHUP\*(C'\fR. |
365 | .ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4 |
606 | .ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4 |
366 | .el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4 |
607 | .el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4 |
367 | .IX Item "EVBACKEND_EPOLL (value 4, Linux)" |
608 | .IX Item "EVBACKEND_EPOLL (value 4, Linux)" |
|
|
609 | Use the linux-specific \fIepoll\fR\|(7) interface (for both pre\- and post\-2.6.9 |
|
|
610 | kernels). |
|
|
611 | .Sp |
368 | For few fds, this backend is a bit little slower than poll and select, |
612 | For few fds, this backend is a bit little slower than poll and select, but |
369 | but it scales phenomenally better. While poll and select usually scale like |
613 | it scales phenomenally better. While poll and select usually scale like |
370 | O(total_fds) where n is the total number of fds (or the highest fd), epoll scales |
614 | O(total_fds) where total_fds is the total number of fds (or the highest |
371 | either O(1) or O(active_fds). |
615 | fd), epoll scales either O(1) or O(active_fds). |
372 | .Sp |
616 | .Sp |
|
|
617 | The epoll mechanism deserves honorable mention as the most misdesigned |
|
|
618 | of the more advanced event mechanisms: mere annoyances include silently |
|
|
619 | dropping file descriptors, requiring a system call per change per file |
|
|
620 | descriptor (and unnecessary guessing of parameters), problems with dup, |
|
|
621 | returning before the timeout value, resulting in additional iterations |
|
|
622 | (and only giving 5ms accuracy while select on the same platform gives |
|
|
623 | 0.1ms) and so on. The biggest issue is fork races, however \- if a program |
|
|
624 | forks then \fIboth\fR parent and child process have to recreate the epoll |
|
|
625 | set, which can take considerable time (one syscall per file descriptor) |
|
|
626 | and is of course hard to detect. |
|
|
627 | .Sp |
|
|
628 | Epoll is also notoriously buggy \- embedding epoll fds \fIshould\fR work, |
|
|
629 | but of course \fIdoesn't\fR, and epoll just loves to report events for |
|
|
630 | totally \fIdifferent\fR file descriptors (even already closed ones, so |
|
|
631 | one cannot even remove them from the set) than registered in the set |
|
|
632 | (especially on \s-1SMP\s0 systems). Libev tries to counter these spurious |
|
|
633 | notifications by employing an additional generation counter and comparing |
|
|
634 | that against the events to filter out spurious ones, recreating the set |
|
|
635 | when required. Epoll also erroneously rounds down timeouts, but gives you |
|
|
636 | no way to know when and by how much, so sometimes you have to busy-wait |
|
|
637 | because epoll returns immediately despite a nonzero timeout. And last |
|
|
638 | not least, it also refuses to work with some file descriptors which work |
|
|
639 | perfectly fine with \f(CW\*(C`select\*(C'\fR (files, many character devices...). |
|
|
640 | .Sp |
|
|
641 | Epoll is truly the train wreck among event poll mechanisms, a frankenpoll, |
|
|
642 | cobbled together in a hurry, no thought to design or interaction with |
|
|
643 | others. Oh, the pain, will it ever stop... |
|
|
644 | .Sp |
373 | While stopping and starting an I/O watcher in the same iteration will |
645 | While stopping, setting and starting an I/O watcher in the same iteration |
374 | result in some caching, there is still a syscall per such incident |
646 | will result in some caching, there is still a system call per such |
375 | (because the fd could point to a different file description now), so its |
647 | incident (because the same \fIfile descriptor\fR could point to a different |
376 | best to avoid that. Also, \fIdup()\fRed file descriptors might not work very |
648 | \&\fIfile description\fR now), so its best to avoid that. Also, \f(CW\*(C`dup ()\*(C'\fR'ed |
377 | well if you register events for both fds. |
649 | file descriptors might not work very well if you register events for both |
|
|
650 | file descriptors. |
378 | .Sp |
651 | .Sp |
379 | Please note that epoll sometimes generates spurious notifications, so you |
652 | Best performance from this backend is achieved by not unregistering all |
380 | need to use non-blocking I/O or other means to avoid blocking when no data |
653 | watchers for a file descriptor until it has been closed, if possible, |
381 | (or space) is available. |
654 | i.e. keep at least one watcher active per fd at all times. Stopping and |
|
|
655 | starting a watcher (without re-setting it) also usually doesn't cause |
|
|
656 | extra overhead. A fork can both result in spurious notifications as well |
|
|
657 | as in libev having to destroy and recreate the epoll object, which can |
|
|
658 | take considerable time and thus should be avoided. |
|
|
659 | .Sp |
|
|
660 | All this means that, in practice, \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR can be as fast or |
|
|
661 | faster than epoll for maybe up to a hundred file descriptors, depending on |
|
|
662 | the usage. So sad. |
|
|
663 | .Sp |
|
|
664 | While nominally embeddable in other event loops, this feature is broken in |
|
|
665 | all kernel versions tested so far. |
|
|
666 | .Sp |
|
|
667 | This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as |
|
|
668 | \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
382 | .ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4 |
669 | .ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4 |
383 | .el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4 |
670 | .el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4 |
384 | .IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)" |
671 | .IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)" |
385 | Kqueue deserves special mention, as at the time of this writing, it |
672 | Kqueue deserves special mention, as at the time of this writing, it |
386 | was broken on all BSDs except NetBSD (usually it doesn't work with |
673 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
387 | anything but sockets and pipes, except on Darwin, where of course its |
674 | with anything but sockets and pipes, except on Darwin, where of course |
388 | completely useless). For this reason its not being \*(L"autodetected\*(R" |
675 | it's completely useless). Unlike epoll, however, whose brokenness |
|
|
676 | is by design, these kqueue bugs can (and eventually will) be fixed |
|
|
677 | without \s-1API\s0 changes to existing programs. For this reason it's not being |
389 | unless you explicitly specify it explicitly in the flags (i.e. using |
678 | \&\*(L"auto-detected\*(R" unless you explicitly specify it in the flags (i.e. using |
390 | \&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR). |
679 | \&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR) or libev was compiled on a known-to-be-good (\-enough) |
|
|
680 | system like NetBSD. |
|
|
681 | .Sp |
|
|
682 | You still can embed kqueue into a normal poll or select backend and use it |
|
|
683 | only for sockets (after having made sure that sockets work with kqueue on |
|
|
684 | the target platform). See \f(CW\*(C`ev_embed\*(C'\fR watchers for more info. |
391 | .Sp |
685 | .Sp |
392 | It scales in the same way as the epoll backend, but the interface to the |
686 | It scales in the same way as the epoll backend, but the interface to the |
393 | kernel is more efficient (which says nothing about its actual speed, of |
687 | kernel is more efficient (which says nothing about its actual speed, of |
394 | course). While starting and stopping an I/O watcher does not cause an |
688 | course). While stopping, setting and starting an I/O watcher does never |
395 | extra syscall as with epoll, it still adds up to four event changes per |
689 | cause an extra system call as with \f(CW\*(C`EVBACKEND_EPOLL\*(C'\fR, it still adds up to |
396 | incident, so its best to avoid that. |
690 | two event changes per incident. Support for \f(CW\*(C`fork ()\*(C'\fR is very bad (but |
|
|
691 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
|
|
692 | cases |
|
|
693 | .Sp |
|
|
694 | This backend usually performs well under most conditions. |
|
|
695 | .Sp |
|
|
696 | While nominally embeddable in other event loops, this doesn't work |
|
|
697 | everywhere, so you might need to test for this. And since it is broken |
|
|
698 | almost everywhere, you should only use it when you have a lot of sockets |
|
|
699 | (for which it usually works), by embedding it into another event loop |
|
|
700 | (e.g. \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR (but \f(CW\*(C`poll\*(C'\fR is of course |
|
|
701 | also broken on \s-1OS\s0 X)) and, did I mention it, using it only for sockets. |
|
|
702 | .Sp |
|
|
703 | This backend maps \f(CW\*(C`EV_READ\*(C'\fR into an \f(CW\*(C`EVFILT_READ\*(C'\fR kevent with |
|
|
704 | \&\f(CW\*(C`NOTE_EOF\*(C'\fR, and \f(CW\*(C`EV_WRITE\*(C'\fR into an \f(CW\*(C`EVFILT_WRITE\*(C'\fR kevent with |
|
|
705 | \&\f(CW\*(C`NOTE_EOF\*(C'\fR. |
397 | .ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4 |
706 | .ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4 |
398 | .el .IP "\f(CWEVBACKEND_DEVPOLL\fR (value 16, Solaris 8)" 4 |
707 | .el .IP "\f(CWEVBACKEND_DEVPOLL\fR (value 16, Solaris 8)" 4 |
399 | .IX Item "EVBACKEND_DEVPOLL (value 16, Solaris 8)" |
708 | .IX Item "EVBACKEND_DEVPOLL (value 16, Solaris 8)" |
400 | This is not implemented yet (and might never be). |
709 | This is not implemented yet (and might never be, unless you send me an |
|
|
710 | implementation). According to reports, \f(CW\*(C`/dev/poll\*(C'\fR only supports sockets |
|
|
711 | and is not embeddable, which would limit the usefulness of this backend |
|
|
712 | immensely. |
401 | .ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4 |
713 | .ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4 |
402 | .el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4 |
714 | .el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4 |
403 | .IX Item "EVBACKEND_PORT (value 32, Solaris 10)" |
715 | .IX Item "EVBACKEND_PORT (value 32, Solaris 10)" |
404 | This uses the Solaris 10 port mechanism. As with everything on Solaris, |
716 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
405 | it's really slow, but it still scales very well (O(active_fds)). |
717 | it's really slow, but it still scales very well (O(active_fds)). |
406 | .Sp |
718 | .Sp |
407 | Please note that solaris ports can result in a lot of spurious |
719 | While this backend scales well, it requires one system call per active |
408 | notifications, so you need to use non-blocking I/O or other means to avoid |
720 | file descriptor per loop iteration. For small and medium numbers of file |
409 | blocking when no data (or space) is available. |
721 | descriptors a \*(L"slow\*(R" \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR backend |
|
|
722 | might perform better. |
|
|
723 | .Sp |
|
|
724 | On the positive side, this backend actually performed fully to |
|
|
725 | specification in all tests and is fully embeddable, which is a rare feat |
|
|
726 | among the OS-specific backends (I vastly prefer correctness over speed |
|
|
727 | hacks). |
|
|
728 | .Sp |
|
|
729 | On the negative side, the interface is \fIbizarre\fR \- so bizarre that |
|
|
730 | even sun itself gets it wrong in their code examples: The event polling |
|
|
731 | function sometimes returns events to the caller even though an error |
|
|
732 | occurred, but with no indication whether it has done so or not (yes, it's |
|
|
733 | even documented that way) \- deadly for edge-triggered interfaces where you |
|
|
734 | absolutely have to know whether an event occurred or not because you have |
|
|
735 | to re-arm the watcher. |
|
|
736 | .Sp |
|
|
737 | Fortunately libev seems to be able to work around these idiocies. |
|
|
738 | .Sp |
|
|
739 | This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as |
|
|
740 | \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
410 | .ie n .IP """EVBACKEND_ALL""" 4 |
741 | .ie n .IP """EVBACKEND_ALL""" 4 |
411 | .el .IP "\f(CWEVBACKEND_ALL\fR" 4 |
742 | .el .IP "\f(CWEVBACKEND_ALL\fR" 4 |
412 | .IX Item "EVBACKEND_ALL" |
743 | .IX Item "EVBACKEND_ALL" |
413 | Try all backends (even potentially broken ones that wouldn't be tried |
744 | Try all backends (even potentially broken ones that wouldn't be tried |
414 | with \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). Since this is a mask, you can do stuff such as |
745 | with \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). Since this is a mask, you can do stuff such as |
415 | \&\f(CW\*(C`EVBACKEND_ALL & ~EVBACKEND_KQUEUE\*(C'\fR. |
746 | \&\f(CW\*(C`EVBACKEND_ALL & ~EVBACKEND_KQUEUE\*(C'\fR. |
|
|
747 | .Sp |
|
|
748 | It is definitely not recommended to use this flag, use whatever |
|
|
749 | \&\f(CW\*(C`ev_recommended_backends ()\*(C'\fR returns, or simply do not specify a backend |
|
|
750 | at all. |
|
|
751 | .ie n .IP """EVBACKEND_MASK""" 4 |
|
|
752 | .el .IP "\f(CWEVBACKEND_MASK\fR" 4 |
|
|
753 | .IX Item "EVBACKEND_MASK" |
|
|
754 | Not a backend at all, but a mask to select all backend bits from a |
|
|
755 | \&\f(CW\*(C`flags\*(C'\fR value, in case you want to mask out any backends from a flags |
|
|
756 | value (e.g. when modifying the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR environment variable). |
416 | .RE |
757 | .RE |
417 | .RS 4 |
758 | .RS 4 |
418 | .Sp |
759 | .Sp |
419 | If one or more of these are ored into the flags value, then only these |
760 | If one or more of the backend flags are or'ed into the flags value, |
420 | backends will be tried (in the reverse order as given here). If none are |
761 | then only these backends will be tried (in the reverse order as listed |
421 | specified, most compiled-in backend will be tried, usually in reverse |
762 | here). If none are specified, all backends in \f(CW\*(C`ev_recommended_backends |
422 | order of their flag values :) |
763 | ()\*(C'\fR will be tried. |
423 | .Sp |
764 | .Sp |
424 | The most typical usage is like this: |
765 | Example: Try to create a event loop that uses epoll and nothing else. |
425 | .Sp |
766 | .Sp |
426 | .Vb 2 |
767 | .Vb 3 |
427 | \& if (!ev_default_loop (0)) |
768 | \& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
428 | \& fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
769 | \& if (!epoller) |
|
|
770 | \& fatal ("no epoll found here, maybe it hides under your chair"); |
429 | .Ve |
771 | .Ve |
430 | .Sp |
772 | .Sp |
431 | Restrict libev to the select and poll backends, and do not allow |
773 | Example: Use whatever libev has to offer, but make sure that kqueue is |
432 | environment settings to be taken into account: |
774 | used if available. |
433 | .Sp |
775 | .Sp |
434 | .Vb 1 |
776 | .Vb 1 |
435 | \& ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
|
|
436 | .Ve |
|
|
437 | .Sp |
|
|
438 | Use whatever libev has to offer, but make sure that kqueue is used if |
|
|
439 | available (warning, breaks stuff, best use only with your own private |
|
|
440 | event loop and only if you know the \s-1OS\s0 supports your types of fds): |
|
|
441 | .Sp |
|
|
442 | .Vb 1 |
|
|
443 | \& ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
777 | \& struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE); |
444 | .Ve |
778 | .Ve |
445 | .RE |
779 | .RE |
446 | .IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4 |
|
|
447 | .IX Item "struct ev_loop *ev_loop_new (unsigned int flags)" |
|
|
448 | Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is |
|
|
449 | always distinct from the default loop. Unlike the default loop, it cannot |
|
|
450 | handle signal and child watchers, and attempts to do so will be greeted by |
|
|
451 | undefined behaviour (or a failed assertion if assertions are enabled). |
|
|
452 | .Sp |
|
|
453 | Example: try to create a event loop that uses epoll and nothing else. |
|
|
454 | .Sp |
|
|
455 | .Vb 3 |
|
|
456 | \& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
|
|
457 | \& if (!epoller) |
|
|
458 | \& fatal ("no epoll found here, maybe it hides under your chair"); |
|
|
459 | .Ve |
|
|
460 | .IP "ev_default_destroy ()" 4 |
780 | .IP "ev_loop_destroy (loop)" 4 |
461 | .IX Item "ev_default_destroy ()" |
781 | .IX Item "ev_loop_destroy (loop)" |
462 | Destroys the default loop again (frees all memory and kernel state |
782 | Destroys an event loop object (frees all memory and kernel state |
463 | etc.). None of the active event watchers will be stopped in the normal |
783 | etc.). None of the active event watchers will be stopped in the normal |
464 | sense, so e.g. \f(CW\*(C`ev_is_active\*(C'\fR might still return true. It is your |
784 | sense, so e.g. \f(CW\*(C`ev_is_active\*(C'\fR might still return true. It is your |
465 | responsibility to either stop all watchers cleanly yoursef \fIbefore\fR |
785 | responsibility to either stop all watchers cleanly yourself \fIbefore\fR |
466 | calling this function, or cope with the fact afterwards (which is usually |
786 | calling this function, or cope with the fact afterwards (which is usually |
467 | the easiest thing, youc na just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them |
787 | the easiest thing, you can just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them |
468 | for example). |
788 | for example). |
469 | .IP "ev_loop_destroy (loop)" 4 |
|
|
470 | .IX Item "ev_loop_destroy (loop)" |
|
|
471 | Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an |
|
|
472 | earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR. |
|
|
473 | .IP "ev_default_fork ()" 4 |
|
|
474 | .IX Item "ev_default_fork ()" |
|
|
475 | This function reinitialises the kernel state for backends that have |
|
|
476 | one. Despite the name, you can call it anytime, but it makes most sense |
|
|
477 | after forking, in either the parent or child process (or both, but that |
|
|
478 | again makes little sense). |
|
|
479 | .Sp |
789 | .Sp |
480 | You \fImust\fR call this function in the child process after forking if and |
790 | Note that certain global state, such as signal state (and installed signal |
481 | only if you want to use the event library in both processes. If you just |
791 | handlers), will not be freed by this function, and related watchers (such |
482 | fork+exec, you don't have to call it. |
792 | as signal and child watchers) would need to be stopped manually. |
483 | .Sp |
793 | .Sp |
484 | The function itself is quite fast and it's usually not a problem to call |
794 | This function is normally used on loop objects allocated by |
485 | it just in case after a fork. To make this easy, the function will fit in |
795 | \&\f(CW\*(C`ev_loop_new\*(C'\fR, but it can also be used on the default loop returned by |
486 | quite nicely into a call to \f(CW\*(C`pthread_atfork\*(C'\fR: |
796 | \&\f(CW\*(C`ev_default_loop\*(C'\fR, in which case it is not thread-safe. |
487 | .Sp |
797 | .Sp |
488 | .Vb 1 |
798 | Note that it is not advisable to call this function on the default loop |
489 | \& pthread_atfork (0, 0, ev_default_fork); |
799 | except in the rare occasion where you really need to free its resources. |
490 | .Ve |
800 | If you need dynamically allocated loops it is better to use \f(CW\*(C`ev_loop_new\*(C'\fR |
491 | .Sp |
801 | and \f(CW\*(C`ev_loop_destroy\*(C'\fR. |
492 | At the moment, \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and \f(CW\*(C`EVBACKEND_POLL\*(C'\fR are safe to use |
|
|
493 | without calling this function, so if you force one of those backends you |
|
|
494 | do not need to care. |
|
|
495 | .IP "ev_loop_fork (loop)" 4 |
802 | .IP "ev_loop_fork (loop)" 4 |
496 | .IX Item "ev_loop_fork (loop)" |
803 | .IX Item "ev_loop_fork (loop)" |
497 | Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by |
804 | This function sets a flag that causes subsequent \f(CW\*(C`ev_run\*(C'\fR iterations to |
498 | \&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop |
805 | reinitialise the kernel state for backends that have one. Despite the |
499 | after fork, and how you do this is entirely your own problem. |
806 | name, you can call it anytime, but it makes most sense after forking, in |
|
|
807 | the child process. You \fImust\fR call it (or use \f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR) in the |
|
|
808 | child before resuming or calling \f(CW\*(C`ev_run\*(C'\fR. |
|
|
809 | .Sp |
|
|
810 | Again, you \fIhave\fR to call it on \fIany\fR loop that you want to re-use after |
|
|
811 | a fork, \fIeven if you do not plan to use the loop in the parent\fR. This is |
|
|
812 | because some kernel interfaces *cough* \fIkqueue\fR *cough* do funny things |
|
|
813 | during fork. |
|
|
814 | .Sp |
|
|
815 | On the other hand, you only need to call this function in the child |
|
|
816 | process if and only if you want to use the event loop in the child. If |
|
|
817 | you just fork+exec or create a new loop in the child, you don't have to |
|
|
818 | call it at all (in fact, \f(CW\*(C`epoll\*(C'\fR is so badly broken that it makes a |
|
|
819 | difference, but libev will usually detect this case on its own and do a |
|
|
820 | costly reset of the backend). |
|
|
821 | .Sp |
|
|
822 | The function itself is quite fast and it's usually not a problem to call |
|
|
823 | it just in case after a fork. |
|
|
824 | .Sp |
|
|
825 | Example: Automate calling \f(CW\*(C`ev_loop_fork\*(C'\fR on the default loop when |
|
|
826 | using pthreads. |
|
|
827 | .Sp |
|
|
828 | .Vb 5 |
|
|
829 | \& static void |
|
|
830 | \& post_fork_child (void) |
|
|
831 | \& { |
|
|
832 | \& ev_loop_fork (EV_DEFAULT); |
|
|
833 | \& } |
|
|
834 | \& |
|
|
835 | \& ... |
|
|
836 | \& pthread_atfork (0, 0, post_fork_child); |
|
|
837 | .Ve |
|
|
838 | .IP "int ev_is_default_loop (loop)" 4 |
|
|
839 | .IX Item "int ev_is_default_loop (loop)" |
|
|
840 | Returns true when the given loop is, in fact, the default loop, and false |
|
|
841 | otherwise. |
|
|
842 | .IP "unsigned int ev_iteration (loop)" 4 |
|
|
843 | .IX Item "unsigned int ev_iteration (loop)" |
|
|
844 | Returns the current iteration count for the event loop, which is identical |
|
|
845 | to the number of times libev did poll for new events. It starts at \f(CW0\fR |
|
|
846 | and happily wraps around with enough iterations. |
|
|
847 | .Sp |
|
|
848 | This value can sometimes be useful as a generation counter of sorts (it |
|
|
849 | \&\*(L"ticks\*(R" the number of loop iterations), as it roughly corresponds with |
|
|
850 | \&\f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR calls \- and is incremented between the |
|
|
851 | prepare and check phases. |
|
|
852 | .IP "unsigned int ev_depth (loop)" 4 |
|
|
853 | .IX Item "unsigned int ev_depth (loop)" |
|
|
854 | Returns the number of times \f(CW\*(C`ev_run\*(C'\fR was entered minus the number of |
|
|
855 | times \f(CW\*(C`ev_run\*(C'\fR was exited normally, in other words, the recursion depth. |
|
|
856 | .Sp |
|
|
857 | Outside \f(CW\*(C`ev_run\*(C'\fR, this number is zero. In a callback, this number is |
|
|
858 | \&\f(CW1\fR, unless \f(CW\*(C`ev_run\*(C'\fR was invoked recursively (or from another thread), |
|
|
859 | in which case it is higher. |
|
|
860 | .Sp |
|
|
861 | Leaving \f(CW\*(C`ev_run\*(C'\fR abnormally (setjmp/longjmp, cancelling the thread, |
|
|
862 | throwing an exception etc.), doesn't count as \*(L"exit\*(R" \- consider this |
|
|
863 | as a hint to avoid such ungentleman-like behaviour unless it's really |
|
|
864 | convenient, in which case it is fully supported. |
500 | .IP "unsigned int ev_backend (loop)" 4 |
865 | .IP "unsigned int ev_backend (loop)" 4 |
501 | .IX Item "unsigned int ev_backend (loop)" |
866 | .IX Item "unsigned int ev_backend (loop)" |
502 | Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in |
867 | Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in |
503 | use. |
868 | use. |
504 | .IP "ev_tstamp ev_now (loop)" 4 |
869 | .IP "ev_tstamp ev_now (loop)" 4 |
505 | .IX Item "ev_tstamp ev_now (loop)" |
870 | .IX Item "ev_tstamp ev_now (loop)" |
506 | Returns the current \*(L"event loop time\*(R", which is the time the event loop |
871 | Returns the current \*(L"event loop time\*(R", which is the time the event loop |
507 | received events and started processing them. This timestamp does not |
872 | received events and started processing them. This timestamp does not |
508 | change as long as callbacks are being processed, and this is also the base |
873 | change as long as callbacks are being processed, and this is also the base |
509 | time used for relative timers. You can treat it as the timestamp of the |
874 | time used for relative timers. You can treat it as the timestamp of the |
510 | event occuring (or more correctly, libev finding out about it). |
875 | event occurring (or more correctly, libev finding out about it). |
|
|
876 | .IP "ev_now_update (loop)" 4 |
|
|
877 | .IX Item "ev_now_update (loop)" |
|
|
878 | Establishes the current time by querying the kernel, updating the time |
|
|
879 | returned by \f(CW\*(C`ev_now ()\*(C'\fR in the progress. This is a costly operation and |
|
|
880 | is usually done automatically within \f(CW\*(C`ev_run ()\*(C'\fR. |
|
|
881 | .Sp |
|
|
882 | This function is rarely useful, but when some event callback runs for a |
|
|
883 | very long time without entering the event loop, updating libev's idea of |
|
|
884 | the current time is a good idea. |
|
|
885 | .Sp |
|
|
886 | See also \*(L"The special problem of time updates\*(R" in the \f(CW\*(C`ev_timer\*(C'\fR section. |
|
|
887 | .IP "ev_suspend (loop)" 4 |
|
|
888 | .IX Item "ev_suspend (loop)" |
|
|
889 | .PD 0 |
|
|
890 | .IP "ev_resume (loop)" 4 |
|
|
891 | .IX Item "ev_resume (loop)" |
|
|
892 | .PD |
|
|
893 | These two functions suspend and resume an event loop, for use when the |
|
|
894 | loop is not used for a while and timeouts should not be processed. |
|
|
895 | .Sp |
|
|
896 | A typical use case would be an interactive program such as a game: When |
|
|
897 | the user presses \f(CW\*(C`^Z\*(C'\fR to suspend the game and resumes it an hour later it |
|
|
898 | would be best to handle timeouts as if no time had actually passed while |
|
|
899 | the program was suspended. This can be achieved by calling \f(CW\*(C`ev_suspend\*(C'\fR |
|
|
900 | in your \f(CW\*(C`SIGTSTP\*(C'\fR handler, sending yourself a \f(CW\*(C`SIGSTOP\*(C'\fR and calling |
|
|
901 | \&\f(CW\*(C`ev_resume\*(C'\fR directly afterwards to resume timer processing. |
|
|
902 | .Sp |
|
|
903 | Effectively, all \f(CW\*(C`ev_timer\*(C'\fR watchers will be delayed by the time spend |
|
|
904 | between \f(CW\*(C`ev_suspend\*(C'\fR and \f(CW\*(C`ev_resume\*(C'\fR, and all \f(CW\*(C`ev_periodic\*(C'\fR watchers |
|
|
905 | will be rescheduled (that is, they will lose any events that would have |
|
|
906 | occurred while suspended). |
|
|
907 | .Sp |
|
|
908 | After calling \f(CW\*(C`ev_suspend\*(C'\fR you \fBmust not\fR call \fIany\fR function on the |
|
|
909 | given loop other than \f(CW\*(C`ev_resume\*(C'\fR, and you \fBmust not\fR call \f(CW\*(C`ev_resume\*(C'\fR |
|
|
910 | without a previous call to \f(CW\*(C`ev_suspend\*(C'\fR. |
|
|
911 | .Sp |
|
|
912 | Calling \f(CW\*(C`ev_suspend\*(C'\fR/\f(CW\*(C`ev_resume\*(C'\fR has the side effect of updating the |
|
|
913 | event loop time (see \f(CW\*(C`ev_now_update\*(C'\fR). |
511 | .IP "ev_loop (loop, int flags)" 4 |
914 | .IP "ev_run (loop, int flags)" 4 |
512 | .IX Item "ev_loop (loop, int flags)" |
915 | .IX Item "ev_run (loop, int flags)" |
513 | Finally, this is it, the event handler. This function usually is called |
916 | Finally, this is it, the event handler. This function usually is called |
514 | after you initialised all your watchers and you want to start handling |
917 | after you have initialised all your watchers and you want to start |
515 | events. |
918 | handling events. It will ask the operating system for any new events, call |
|
|
919 | the watcher callbacks, an then repeat the whole process indefinitely: This |
|
|
920 | is why event loops are called \fIloops\fR. |
516 | .Sp |
921 | .Sp |
517 | If the flags argument is specified as \f(CW0\fR, it will not return until |
922 | If the flags argument is specified as \f(CW0\fR, it will keep handling events |
518 | either no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called. |
923 | until either no event watchers are active anymore or \f(CW\*(C`ev_break\*(C'\fR was |
|
|
924 | called. |
519 | .Sp |
925 | .Sp |
520 | Please note that an explicit \f(CW\*(C`ev_unloop\*(C'\fR is usually better than |
926 | Please note that an explicit \f(CW\*(C`ev_break\*(C'\fR is usually better than |
521 | relying on all watchers to be stopped when deciding when a program has |
927 | relying on all watchers to be stopped when deciding when a program has |
522 | finished (especially in interactive programs), but having a program that |
928 | finished (especially in interactive programs), but having a program |
523 | automatically loops as long as it has to and no longer by virtue of |
929 | that automatically loops as long as it has to and no longer by virtue |
524 | relying on its watchers stopping correctly is a thing of beauty. |
930 | of relying on its watchers stopping correctly, that is truly a thing of |
|
|
931 | beauty. |
525 | .Sp |
932 | .Sp |
|
|
933 | This function is also \fImostly\fR exception-safe \- you can break out of |
|
|
934 | a \f(CW\*(C`ev_run\*(C'\fR call by calling \f(CW\*(C`longjmp\*(C'\fR in a callback, throwing a \*(C+ |
|
|
935 | exception and so on. This does not decrement the \f(CW\*(C`ev_depth\*(C'\fR value, nor |
|
|
936 | will it clear any outstanding \f(CW\*(C`EVBREAK_ONE\*(C'\fR breaks. |
|
|
937 | .Sp |
526 | A flags value of \f(CW\*(C`EVLOOP_NONBLOCK\*(C'\fR will look for new events, will handle |
938 | A flags value of \f(CW\*(C`EVRUN_NOWAIT\*(C'\fR will look for new events, will handle |
527 | those events and any outstanding ones, but will not block your process in |
939 | those events and any already outstanding ones, but will not wait and |
528 | case there are no events and will return after one iteration of the loop. |
940 | block your process in case there are no events and will return after one |
|
|
941 | iteration of the loop. This is sometimes useful to poll and handle new |
|
|
942 | events while doing lengthy calculations, to keep the program responsive. |
529 | .Sp |
943 | .Sp |
530 | A flags value of \f(CW\*(C`EVLOOP_ONESHOT\*(C'\fR will look for new events (waiting if |
944 | A flags value of \f(CW\*(C`EVRUN_ONCE\*(C'\fR will look for new events (waiting if |
531 | neccessary) and will handle those and any outstanding ones. It will block |
945 | necessary) and will handle those and any already outstanding ones. It |
532 | your process until at least one new event arrives, and will return after |
946 | will block your process until at least one new event arrives (which could |
533 | one iteration of the loop. This is useful if you are waiting for some |
947 | be an event internal to libev itself, so there is no guarantee that a |
534 | external event in conjunction with something not expressible using other |
948 | user-registered callback will be called), and will return after one |
|
|
949 | iteration of the loop. |
|
|
950 | .Sp |
|
|
951 | This is useful if you are waiting for some external event in conjunction |
|
|
952 | with something not expressible using other libev watchers (i.e. "roll your |
535 | libev watchers. However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is |
953 | own \f(CW\*(C`ev_run\*(C'\fR"). However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is |
536 | usually a better approach for this kind of thing. |
954 | usually a better approach for this kind of thing. |
537 | .Sp |
955 | .Sp |
538 | Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does: |
956 | Here are the gory details of what \f(CW\*(C`ev_run\*(C'\fR does (this is for your |
|
|
957 | understanding, not a guarantee that things will work exactly like this in |
|
|
958 | future versions): |
539 | .Sp |
959 | .Sp |
540 | .Vb 18 |
960 | .Vb 10 |
541 | \& * If there are no active watchers (reference count is zero), return. |
961 | \& \- Increment loop depth. |
542 | \& - Queue prepare watchers and then call all outstanding watchers. |
962 | \& \- Reset the ev_break status. |
|
|
963 | \& \- Before the first iteration, call any pending watchers. |
|
|
964 | \& LOOP: |
|
|
965 | \& \- If EVFLAG_FORKCHECK was used, check for a fork. |
|
|
966 | \& \- If a fork was detected (by any means), queue and call all fork watchers. |
|
|
967 | \& \- Queue and call all prepare watchers. |
|
|
968 | \& \- If ev_break was called, goto FINISH. |
543 | \& - If we have been forked, recreate the kernel state. |
969 | \& \- If we have been forked, detach and recreate the kernel state |
|
|
970 | \& as to not disturb the other process. |
544 | \& - Update the kernel state with all outstanding changes. |
971 | \& \- Update the kernel state with all outstanding changes. |
545 | \& - Update the "event loop time". |
972 | \& \- Update the "event loop time" (ev_now ()). |
546 | \& - Calculate for how long to block. |
973 | \& \- Calculate for how long to sleep or block, if at all |
|
|
974 | \& (active idle watchers, EVRUN_NOWAIT or not having |
|
|
975 | \& any active watchers at all will result in not sleeping). |
|
|
976 | \& \- Sleep if the I/O and timer collect interval say so. |
|
|
977 | \& \- Increment loop iteration counter. |
547 | \& - Block the process, waiting for any events. |
978 | \& \- Block the process, waiting for any events. |
548 | \& - Queue all outstanding I/O (fd) events. |
979 | \& \- Queue all outstanding I/O (fd) events. |
549 | \& - Update the "event loop time" and do time jump handling. |
980 | \& \- Update the "event loop time" (ev_now ()), and do time jump adjustments. |
550 | \& - Queue all outstanding timers. |
981 | \& \- Queue all expired timers. |
551 | \& - Queue all outstanding periodics. |
982 | \& \- Queue all expired periodics. |
552 | \& - If no events are pending now, queue all idle watchers. |
983 | \& \- Queue all idle watchers with priority higher than that of pending events. |
553 | \& - Queue all check watchers. |
984 | \& \- Queue all check watchers. |
554 | \& - Call all queued watchers in reverse order (i.e. check watchers first). |
985 | \& \- Call all queued watchers in reverse order (i.e. check watchers first). |
555 | \& Signals and child watchers are implemented as I/O watchers, and will |
986 | \& Signals and child watchers are implemented as I/O watchers, and will |
556 | \& be handled here by queueing them when their watcher gets executed. |
987 | \& be handled here by queueing them when their watcher gets executed. |
557 | \& - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
988 | \& \- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT |
558 | \& were used, return, otherwise continue with step *. |
989 | \& were used, or there are no active watchers, goto FINISH, otherwise |
|
|
990 | \& continue with step LOOP. |
|
|
991 | \& FINISH: |
|
|
992 | \& \- Reset the ev_break status iff it was EVBREAK_ONE. |
|
|
993 | \& \- Decrement the loop depth. |
|
|
994 | \& \- Return. |
559 | .Ve |
995 | .Ve |
560 | .Sp |
996 | .Sp |
561 | Example: queue some jobs and then loop until no events are outsanding |
997 | Example: Queue some jobs and then loop until no events are outstanding |
562 | anymore. |
998 | anymore. |
563 | .Sp |
999 | .Sp |
564 | .Vb 4 |
1000 | .Vb 4 |
565 | \& ... queue jobs here, make sure they register event watchers as long |
1001 | \& ... queue jobs here, make sure they register event watchers as long |
566 | \& ... as they still have work to do (even an idle watcher will do..) |
1002 | \& ... as they still have work to do (even an idle watcher will do..) |
567 | \& ev_loop (my_loop, 0); |
1003 | \& ev_run (my_loop, 0); |
568 | \& ... jobs done. yeah! |
1004 | \& ... jobs done or somebody called break. yeah! |
569 | .Ve |
1005 | .Ve |
570 | .IP "ev_unloop (loop, how)" 4 |
1006 | .IP "ev_break (loop, how)" 4 |
571 | .IX Item "ev_unloop (loop, how)" |
1007 | .IX Item "ev_break (loop, how)" |
572 | Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it |
1008 | Can be used to make a call to \f(CW\*(C`ev_run\*(C'\fR return early (but only after it |
573 | has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either |
1009 | has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either |
574 | \&\f(CW\*(C`EVUNLOOP_ONE\*(C'\fR, which will make the innermost \f(CW\*(C`ev_loop\*(C'\fR call return, or |
1010 | \&\f(CW\*(C`EVBREAK_ONE\*(C'\fR, which will make the innermost \f(CW\*(C`ev_run\*(C'\fR call return, or |
575 | \&\f(CW\*(C`EVUNLOOP_ALL\*(C'\fR, which will make all nested \f(CW\*(C`ev_loop\*(C'\fR calls return. |
1011 | \&\f(CW\*(C`EVBREAK_ALL\*(C'\fR, which will make all nested \f(CW\*(C`ev_run\*(C'\fR calls return. |
|
|
1012 | .Sp |
|
|
1013 | This \*(L"break state\*(R" will be cleared on the next call to \f(CW\*(C`ev_run\*(C'\fR. |
|
|
1014 | .Sp |
|
|
1015 | It is safe to call \f(CW\*(C`ev_break\*(C'\fR from outside any \f(CW\*(C`ev_run\*(C'\fR calls, too, in |
|
|
1016 | which case it will have no effect. |
576 | .IP "ev_ref (loop)" 4 |
1017 | .IP "ev_ref (loop)" 4 |
577 | .IX Item "ev_ref (loop)" |
1018 | .IX Item "ev_ref (loop)" |
578 | .PD 0 |
1019 | .PD 0 |
579 | .IP "ev_unref (loop)" 4 |
1020 | .IP "ev_unref (loop)" 4 |
580 | .IX Item "ev_unref (loop)" |
1021 | .IX Item "ev_unref (loop)" |
581 | .PD |
1022 | .PD |
582 | Ref/unref can be used to add or remove a reference count on the event |
1023 | Ref/unref can be used to add or remove a reference count on the event |
583 | loop: Every watcher keeps one reference, and as long as the reference |
1024 | loop: Every watcher keeps one reference, and as long as the reference |
584 | count is nonzero, \f(CW\*(C`ev_loop\*(C'\fR will not return on its own. If you have |
1025 | count is nonzero, \f(CW\*(C`ev_run\*(C'\fR will not return on its own. |
585 | a watcher you never unregister that should not keep \f(CW\*(C`ev_loop\*(C'\fR from |
1026 | .Sp |
586 | returning, \fIev_unref()\fR after starting, and \fIev_ref()\fR before stopping it. For |
1027 | This is useful when you have a watcher that you never intend to |
|
|
1028 | unregister, but that nevertheless should not keep \f(CW\*(C`ev_run\*(C'\fR from |
|
|
1029 | returning. In such a case, call \f(CW\*(C`ev_unref\*(C'\fR after starting, and \f(CW\*(C`ev_ref\*(C'\fR |
|
|
1030 | before stopping it. |
|
|
1031 | .Sp |
587 | example, libev itself uses this for its internal signal pipe: It is not |
1032 | As an example, libev itself uses this for its internal signal pipe: It |
588 | visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if |
1033 | is not visible to the libev user and should not keep \f(CW\*(C`ev_run\*(C'\fR from |
589 | no event watchers registered by it are active. It is also an excellent |
1034 | exiting if no event watchers registered by it are active. It is also an |
590 | way to do this for generic recurring timers or from within third-party |
1035 | excellent way to do this for generic recurring timers or from within |
591 | libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR. |
1036 | third-party libraries. Just remember to \fIunref after start\fR and \fIref |
|
|
1037 | before stop\fR (but only if the watcher wasn't active before, or was active |
|
|
1038 | before, respectively. Note also that libev might stop watchers itself |
|
|
1039 | (e.g. non-repeating timers) in which case you have to \f(CW\*(C`ev_ref\*(C'\fR |
|
|
1040 | in the callback). |
592 | .Sp |
1041 | .Sp |
593 | Example: create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR |
1042 | Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_run\*(C'\fR |
594 | running when nothing else is active. |
1043 | running when nothing else is active. |
595 | .Sp |
1044 | .Sp |
596 | .Vb 4 |
1045 | .Vb 4 |
597 | \& struct dv_signal exitsig; |
1046 | \& ev_signal exitsig; |
598 | \& ev_signal_init (&exitsig, sig_cb, SIGINT); |
1047 | \& ev_signal_init (&exitsig, sig_cb, SIGINT); |
599 | \& ev_signal_start (myloop, &exitsig); |
1048 | \& ev_signal_start (loop, &exitsig); |
600 | \& evf_unref (myloop); |
1049 | \& ev_unref (loop); |
601 | .Ve |
1050 | .Ve |
602 | .Sp |
1051 | .Sp |
603 | Example: for some weird reason, unregister the above signal handler again. |
1052 | Example: For some weird reason, unregister the above signal handler again. |
604 | .Sp |
1053 | .Sp |
605 | .Vb 2 |
1054 | .Vb 2 |
606 | \& ev_ref (myloop); |
1055 | \& ev_ref (loop); |
607 | \& ev_signal_stop (myloop, &exitsig); |
1056 | \& ev_signal_stop (loop, &exitsig); |
608 | .Ve |
1057 | .Ve |
|
|
1058 | .IP "ev_set_io_collect_interval (loop, ev_tstamp interval)" 4 |
|
|
1059 | .IX Item "ev_set_io_collect_interval (loop, ev_tstamp interval)" |
|
|
1060 | .PD 0 |
|
|
1061 | .IP "ev_set_timeout_collect_interval (loop, ev_tstamp interval)" 4 |
|
|
1062 | .IX Item "ev_set_timeout_collect_interval (loop, ev_tstamp interval)" |
|
|
1063 | .PD |
|
|
1064 | These advanced functions influence the time that libev will spend waiting |
|
|
1065 | for events. Both time intervals are by default \f(CW0\fR, meaning that libev |
|
|
1066 | will try to invoke timer/periodic callbacks and I/O callbacks with minimum |
|
|
1067 | latency. |
|
|
1068 | .Sp |
|
|
1069 | Setting these to a higher value (the \f(CW\*(C`interval\*(C'\fR \fImust\fR be >= \f(CW0\fR) |
|
|
1070 | allows libev to delay invocation of I/O and timer/periodic callbacks |
|
|
1071 | to increase efficiency of loop iterations (or to increase power-saving |
|
|
1072 | opportunities). |
|
|
1073 | .Sp |
|
|
1074 | The idea is that sometimes your program runs just fast enough to handle |
|
|
1075 | one (or very few) event(s) per loop iteration. While this makes the |
|
|
1076 | program responsive, it also wastes a lot of \s-1CPU\s0 time to poll for new |
|
|
1077 | events, especially with backends like \f(CW\*(C`select ()\*(C'\fR which have a high |
|
|
1078 | overhead for the actual polling but can deliver many events at once. |
|
|
1079 | .Sp |
|
|
1080 | By setting a higher \fIio collect interval\fR you allow libev to spend more |
|
|
1081 | time collecting I/O events, so you can handle more events per iteration, |
|
|
1082 | at the cost of increasing latency. Timeouts (both \f(CW\*(C`ev_periodic\*(C'\fR and |
|
|
1083 | \&\f(CW\*(C`ev_timer\*(C'\fR) will not be affected. Setting this to a non-null value will |
|
|
1084 | introduce an additional \f(CW\*(C`ev_sleep ()\*(C'\fR call into most loop iterations. The |
|
|
1085 | sleep time ensures that libev will not poll for I/O events more often then |
|
|
1086 | once per this interval, on average (as long as the host time resolution is |
|
|
1087 | good enough). |
|
|
1088 | .Sp |
|
|
1089 | Likewise, by setting a higher \fItimeout collect interval\fR you allow libev |
|
|
1090 | to spend more time collecting timeouts, at the expense of increased |
|
|
1091 | latency/jitter/inexactness (the watcher callback will be called |
|
|
1092 | later). \f(CW\*(C`ev_io\*(C'\fR watchers will not be affected. Setting this to a non-null |
|
|
1093 | value will not introduce any overhead in libev. |
|
|
1094 | .Sp |
|
|
1095 | Many (busy) programs can usually benefit by setting the I/O collect |
|
|
1096 | interval to a value near \f(CW0.1\fR or so, which is often enough for |
|
|
1097 | interactive servers (of course not for games), likewise for timeouts. It |
|
|
1098 | usually doesn't make much sense to set it to a lower value than \f(CW0.01\fR, |
|
|
1099 | as this approaches the timing granularity of most systems. Note that if |
|
|
1100 | you do transactions with the outside world and you can't increase the |
|
|
1101 | parallelity, then this setting will limit your transaction rate (if you |
|
|
1102 | need to poll once per transaction and the I/O collect interval is 0.01, |
|
|
1103 | then you can't do more than 100 transactions per second). |
|
|
1104 | .Sp |
|
|
1105 | Setting the \fItimeout collect interval\fR can improve the opportunity for |
|
|
1106 | saving power, as the program will \*(L"bundle\*(R" timer callback invocations that |
|
|
1107 | are \*(L"near\*(R" in time together, by delaying some, thus reducing the number of |
|
|
1108 | times the process sleeps and wakes up again. Another useful technique to |
|
|
1109 | reduce iterations/wake\-ups is to use \f(CW\*(C`ev_periodic\*(C'\fR watchers and make sure |
|
|
1110 | they fire on, say, one-second boundaries only. |
|
|
1111 | .Sp |
|
|
1112 | Example: we only need 0.1s timeout granularity, and we wish not to poll |
|
|
1113 | more often than 100 times per second: |
|
|
1114 | .Sp |
|
|
1115 | .Vb 2 |
|
|
1116 | \& ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1); |
|
|
1117 | \& ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
|
|
1118 | .Ve |
|
|
1119 | .IP "ev_invoke_pending (loop)" 4 |
|
|
1120 | .IX Item "ev_invoke_pending (loop)" |
|
|
1121 | This call will simply invoke all pending watchers while resetting their |
|
|
1122 | pending state. Normally, \f(CW\*(C`ev_run\*(C'\fR does this automatically when required, |
|
|
1123 | but when overriding the invoke callback this call comes handy. This |
|
|
1124 | function can be invoked from a watcher \- this can be useful for example |
|
|
1125 | when you want to do some lengthy calculation and want to pass further |
|
|
1126 | event handling to another thread (you still have to make sure only one |
|
|
1127 | thread executes within \f(CW\*(C`ev_invoke_pending\*(C'\fR or \f(CW\*(C`ev_run\*(C'\fR of course). |
|
|
1128 | .IP "int ev_pending_count (loop)" 4 |
|
|
1129 | .IX Item "int ev_pending_count (loop)" |
|
|
1130 | Returns the number of pending watchers \- zero indicates that no watchers |
|
|
1131 | are pending. |
|
|
1132 | .IP "ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(\s-1EV_P\s0))" 4 |
|
|
1133 | .IX Item "ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))" |
|
|
1134 | This overrides the invoke pending functionality of the loop: Instead of |
|
|
1135 | invoking all pending watchers when there are any, \f(CW\*(C`ev_run\*(C'\fR will call |
|
|
1136 | this callback instead. This is useful, for example, when you want to |
|
|
1137 | invoke the actual watchers inside another context (another thread etc.). |
|
|
1138 | .Sp |
|
|
1139 | If you want to reset the callback, use \f(CW\*(C`ev_invoke_pending\*(C'\fR as new |
|
|
1140 | callback. |
|
|
1141 | .IP "ev_set_loop_release_cb (loop, void (*release)(\s-1EV_P\s0), void (*acquire)(\s-1EV_P\s0))" 4 |
|
|
1142 | .IX Item "ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))" |
|
|
1143 | Sometimes you want to share the same loop between multiple threads. This |
|
|
1144 | can be done relatively simply by putting mutex_lock/unlock calls around |
|
|
1145 | each call to a libev function. |
|
|
1146 | .Sp |
|
|
1147 | However, \f(CW\*(C`ev_run\*(C'\fR can run an indefinite time, so it is not feasible |
|
|
1148 | to wait for it to return. One way around this is to wake up the event |
|
|
1149 | loop via \f(CW\*(C`ev_break\*(C'\fR and \f(CW\*(C`ev_async_send\*(C'\fR, another way is to set these |
|
|
1150 | \&\fIrelease\fR and \fIacquire\fR callbacks on the loop. |
|
|
1151 | .Sp |
|
|
1152 | When set, then \f(CW\*(C`release\*(C'\fR will be called just before the thread is |
|
|
1153 | suspended waiting for new events, and \f(CW\*(C`acquire\*(C'\fR is called just |
|
|
1154 | afterwards. |
|
|
1155 | .Sp |
|
|
1156 | Ideally, \f(CW\*(C`release\*(C'\fR will just call your mutex_unlock function, and |
|
|
1157 | \&\f(CW\*(C`acquire\*(C'\fR will just call the mutex_lock function again. |
|
|
1158 | .Sp |
|
|
1159 | While event loop modifications are allowed between invocations of |
|
|
1160 | \&\f(CW\*(C`release\*(C'\fR and \f(CW\*(C`acquire\*(C'\fR (that's their only purpose after all), no |
|
|
1161 | modifications done will affect the event loop, i.e. adding watchers will |
|
|
1162 | have no effect on the set of file descriptors being watched, or the time |
|
|
1163 | waited. Use an \f(CW\*(C`ev_async\*(C'\fR watcher to wake up \f(CW\*(C`ev_run\*(C'\fR when you want it |
|
|
1164 | to take note of any changes you made. |
|
|
1165 | .Sp |
|
|
1166 | In theory, threads executing \f(CW\*(C`ev_run\*(C'\fR will be async-cancel safe between |
|
|
1167 | invocations of \f(CW\*(C`release\*(C'\fR and \f(CW\*(C`acquire\*(C'\fR. |
|
|
1168 | .Sp |
|
|
1169 | See also the locking example in the \f(CW\*(C`THREADS\*(C'\fR section later in this |
|
|
1170 | document. |
|
|
1171 | .IP "ev_set_userdata (loop, void *data)" 4 |
|
|
1172 | .IX Item "ev_set_userdata (loop, void *data)" |
|
|
1173 | .PD 0 |
|
|
1174 | .IP "void *ev_userdata (loop)" 4 |
|
|
1175 | .IX Item "void *ev_userdata (loop)" |
|
|
1176 | .PD |
|
|
1177 | Set and retrieve a single \f(CW\*(C`void *\*(C'\fR associated with a loop. When |
|
|
1178 | \&\f(CW\*(C`ev_set_userdata\*(C'\fR has never been called, then \f(CW\*(C`ev_userdata\*(C'\fR returns |
|
|
1179 | \&\f(CW0\fR. |
|
|
1180 | .Sp |
|
|
1181 | These two functions can be used to associate arbitrary data with a loop, |
|
|
1182 | and are intended solely for the \f(CW\*(C`invoke_pending_cb\*(C'\fR, \f(CW\*(C`release\*(C'\fR and |
|
|
1183 | \&\f(CW\*(C`acquire\*(C'\fR callbacks described above, but of course can be (ab\-)used for |
|
|
1184 | any other purpose as well. |
|
|
1185 | .IP "ev_verify (loop)" 4 |
|
|
1186 | .IX Item "ev_verify (loop)" |
|
|
1187 | This function only does something when \f(CW\*(C`EV_VERIFY\*(C'\fR support has been |
|
|
1188 | compiled in, which is the default for non-minimal builds. It tries to go |
|
|
1189 | through all internal structures and checks them for validity. If anything |
|
|
1190 | is found to be inconsistent, it will print an error message to standard |
|
|
1191 | error and call \f(CW\*(C`abort ()\*(C'\fR. |
|
|
1192 | .Sp |
|
|
1193 | This can be used to catch bugs inside libev itself: under normal |
|
|
1194 | circumstances, this function will never abort as of course libev keeps its |
|
|
1195 | data structures consistent. |
609 | .SH "ANATOMY OF A WATCHER" |
1196 | .SH "ANATOMY OF A WATCHER" |
610 | .IX Header "ANATOMY OF A WATCHER" |
1197 | .IX Header "ANATOMY OF A WATCHER" |
|
|
1198 | In the following description, uppercase \f(CW\*(C`TYPE\*(C'\fR in names stands for the |
|
|
1199 | watcher type, e.g. \f(CW\*(C`ev_TYPE_start\*(C'\fR can mean \f(CW\*(C`ev_timer_start\*(C'\fR for timer |
|
|
1200 | watchers and \f(CW\*(C`ev_io_start\*(C'\fR for I/O watchers. |
|
|
1201 | .PP |
611 | A watcher is a structure that you create and register to record your |
1202 | A watcher is an opaque structure that you allocate and register to record |
612 | interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to |
1203 | your interest in some event. To make a concrete example, imagine you want |
613 | become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that: |
1204 | to wait for \s-1STDIN\s0 to become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher |
|
|
1205 | for that: |
614 | .PP |
1206 | .PP |
615 | .Vb 5 |
1207 | .Vb 5 |
616 | \& static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1208 | \& static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
617 | \& { |
1209 | \& { |
618 | \& ev_io_stop (w); |
1210 | \& ev_io_stop (w); |
619 | \& ev_unloop (loop, EVUNLOOP_ALL); |
1211 | \& ev_break (loop, EVBREAK_ALL); |
620 | \& } |
1212 | \& } |
621 | .Ve |
1213 | \& |
622 | .PP |
|
|
623 | .Vb 6 |
|
|
624 | \& struct ev_loop *loop = ev_default_loop (0); |
1214 | \& struct ev_loop *loop = ev_default_loop (0); |
|
|
1215 | \& |
625 | \& struct ev_io stdin_watcher; |
1216 | \& ev_io stdin_watcher; |
|
|
1217 | \& |
626 | \& ev_init (&stdin_watcher, my_cb); |
1218 | \& ev_init (&stdin_watcher, my_cb); |
627 | \& ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
1219 | \& ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
628 | \& ev_io_start (loop, &stdin_watcher); |
1220 | \& ev_io_start (loop, &stdin_watcher); |
|
|
1221 | \& |
629 | \& ev_loop (loop, 0); |
1222 | \& ev_run (loop, 0); |
630 | .Ve |
1223 | .Ve |
631 | .PP |
1224 | .PP |
632 | As you can see, you are responsible for allocating the memory for your |
1225 | As you can see, you are responsible for allocating the memory for your |
633 | watcher structures (and it is usually a bad idea to do this on the stack, |
1226 | watcher structures (and it is \fIusually\fR a bad idea to do this on the |
634 | although this can sometimes be quite valid). |
1227 | stack). |
635 | .PP |
1228 | .PP |
|
|
1229 | Each watcher has an associated watcher structure (called \f(CW\*(C`struct ev_TYPE\*(C'\fR |
|
|
1230 | or simply \f(CW\*(C`ev_TYPE\*(C'\fR, as typedefs are provided for all watcher structs). |
|
|
1231 | .PP |
636 | Each watcher structure must be initialised by a call to \f(CW\*(C`ev_init |
1232 | Each watcher structure must be initialised by a call to \f(CW\*(C`ev_init (watcher |
637 | (watcher *, callback)\*(C'\fR, which expects a callback to be provided. This |
1233 | *, callback)\*(C'\fR, which expects a callback to be provided. This callback is |
638 | callback gets invoked each time the event occurs (or, in the case of io |
1234 | invoked each time the event occurs (or, in the case of I/O watchers, each |
639 | watchers, each time the event loop detects that the file descriptor given |
1235 | time the event loop detects that the file descriptor given is readable |
640 | is readable and/or writable). |
1236 | and/or writable). |
641 | .PP |
1237 | .PP |
642 | Each watcher type has its own \f(CW\*(C`ev_<type>_set (watcher *, ...)\*(C'\fR macro |
1238 | Each watcher type further has its own \f(CW\*(C`ev_TYPE_set (watcher *, ...)\*(C'\fR |
643 | with arguments specific to this watcher type. There is also a macro |
1239 | macro to configure it, with arguments specific to the watcher type. There |
644 | to combine initialisation and setting in one call: \f(CW\*(C`ev_<type>_init |
1240 | is also a macro to combine initialisation and setting in one call: \f(CW\*(C`ev_TYPE_init (watcher *, callback, ...)\*(C'\fR. |
645 | (watcher *, callback, ...)\*(C'\fR. |
|
|
646 | .PP |
1241 | .PP |
647 | To make the watcher actually watch out for events, you have to start it |
1242 | To make the watcher actually watch out for events, you have to start it |
648 | with a watcher-specific start function (\f(CW\*(C`ev_<type>_start (loop, watcher |
1243 | with a watcher-specific start function (\f(CW\*(C`ev_TYPE_start (loop, watcher |
649 | *)\*(C'\fR), and you can stop watching for events at any time by calling the |
1244 | *)\*(C'\fR), and you can stop watching for events at any time by calling the |
650 | corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR. |
1245 | corresponding stop function (\f(CW\*(C`ev_TYPE_stop (loop, watcher *)\*(C'\fR. |
651 | .PP |
1246 | .PP |
652 | As long as your watcher is active (has been started but not stopped) you |
1247 | As long as your watcher is active (has been started but not stopped) you |
653 | must not touch the values stored in it. Most specifically you must never |
1248 | must not touch the values stored in it. Most specifically you must never |
654 | reinitialise it or call its \f(CW\*(C`set\*(C'\fR macro. |
1249 | reinitialise it or call its \f(CW\*(C`ev_TYPE_set\*(C'\fR macro. |
655 | .PP |
1250 | .PP |
656 | Each and every callback receives the event loop pointer as first, the |
1251 | Each and every callback receives the event loop pointer as first, the |
657 | registered watcher structure as second, and a bitset of received events as |
1252 | registered watcher structure as second, and a bitset of received events as |
658 | third argument. |
1253 | third argument. |
659 | .PP |
1254 | .PP |
… | |
… | |
668 | .el .IP "\f(CWEV_WRITE\fR" 4 |
1263 | .el .IP "\f(CWEV_WRITE\fR" 4 |
669 | .IX Item "EV_WRITE" |
1264 | .IX Item "EV_WRITE" |
670 | .PD |
1265 | .PD |
671 | The file descriptor in the \f(CW\*(C`ev_io\*(C'\fR watcher has become readable and/or |
1266 | The file descriptor in the \f(CW\*(C`ev_io\*(C'\fR watcher has become readable and/or |
672 | writable. |
1267 | writable. |
673 | .ie n .IP """EV_TIMEOUT""" 4 |
1268 | .ie n .IP """EV_TIMER""" 4 |
674 | .el .IP "\f(CWEV_TIMEOUT\fR" 4 |
1269 | .el .IP "\f(CWEV_TIMER\fR" 4 |
675 | .IX Item "EV_TIMEOUT" |
1270 | .IX Item "EV_TIMER" |
676 | The \f(CW\*(C`ev_timer\*(C'\fR watcher has timed out. |
1271 | The \f(CW\*(C`ev_timer\*(C'\fR watcher has timed out. |
677 | .ie n .IP """EV_PERIODIC""" 4 |
1272 | .ie n .IP """EV_PERIODIC""" 4 |
678 | .el .IP "\f(CWEV_PERIODIC\fR" 4 |
1273 | .el .IP "\f(CWEV_PERIODIC\fR" 4 |
679 | .IX Item "EV_PERIODIC" |
1274 | .IX Item "EV_PERIODIC" |
680 | The \f(CW\*(C`ev_periodic\*(C'\fR watcher has timed out. |
1275 | The \f(CW\*(C`ev_periodic\*(C'\fR watcher has timed out. |
… | |
… | |
700 | .PD 0 |
1295 | .PD 0 |
701 | .ie n .IP """EV_CHECK""" 4 |
1296 | .ie n .IP """EV_CHECK""" 4 |
702 | .el .IP "\f(CWEV_CHECK\fR" 4 |
1297 | .el .IP "\f(CWEV_CHECK\fR" 4 |
703 | .IX Item "EV_CHECK" |
1298 | .IX Item "EV_CHECK" |
704 | .PD |
1299 | .PD |
705 | All \f(CW\*(C`ev_prepare\*(C'\fR watchers are invoked just \fIbefore\fR \f(CW\*(C`ev_loop\*(C'\fR starts |
1300 | All \f(CW\*(C`ev_prepare\*(C'\fR watchers are invoked just \fIbefore\fR \f(CW\*(C`ev_run\*(C'\fR starts |
706 | to gather new events, and all \f(CW\*(C`ev_check\*(C'\fR watchers are invoked just after |
1301 | to gather new events, and all \f(CW\*(C`ev_check\*(C'\fR watchers are invoked just after |
707 | \&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any |
1302 | \&\f(CW\*(C`ev_run\*(C'\fR has gathered them, but before it invokes any callbacks for any |
708 | received events. Callbacks of both watcher types can start and stop as |
1303 | received events. Callbacks of both watcher types can start and stop as |
709 | many watchers as they want, and all of them will be taken into account |
1304 | many watchers as they want, and all of them will be taken into account |
710 | (for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep |
1305 | (for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep |
711 | \&\f(CW\*(C`ev_loop\*(C'\fR from blocking). |
1306 | \&\f(CW\*(C`ev_run\*(C'\fR from blocking). |
|
|
1307 | .ie n .IP """EV_EMBED""" 4 |
|
|
1308 | .el .IP "\f(CWEV_EMBED\fR" 4 |
|
|
1309 | .IX Item "EV_EMBED" |
|
|
1310 | The embedded event loop specified in the \f(CW\*(C`ev_embed\*(C'\fR watcher needs attention. |
|
|
1311 | .ie n .IP """EV_FORK""" 4 |
|
|
1312 | .el .IP "\f(CWEV_FORK\fR" 4 |
|
|
1313 | .IX Item "EV_FORK" |
|
|
1314 | The event loop has been resumed in the child process after fork (see |
|
|
1315 | \&\f(CW\*(C`ev_fork\*(C'\fR). |
|
|
1316 | .ie n .IP """EV_CLEANUP""" 4 |
|
|
1317 | .el .IP "\f(CWEV_CLEANUP\fR" 4 |
|
|
1318 | .IX Item "EV_CLEANUP" |
|
|
1319 | The event loop is about to be destroyed (see \f(CW\*(C`ev_cleanup\*(C'\fR). |
|
|
1320 | .ie n .IP """EV_ASYNC""" 4 |
|
|
1321 | .el .IP "\f(CWEV_ASYNC\fR" 4 |
|
|
1322 | .IX Item "EV_ASYNC" |
|
|
1323 | The given async watcher has been asynchronously notified (see \f(CW\*(C`ev_async\*(C'\fR). |
|
|
1324 | .ie n .IP """EV_CUSTOM""" 4 |
|
|
1325 | .el .IP "\f(CWEV_CUSTOM\fR" 4 |
|
|
1326 | .IX Item "EV_CUSTOM" |
|
|
1327 | Not ever sent (or otherwise used) by libev itself, but can be freely used |
|
|
1328 | by libev users to signal watchers (e.g. via \f(CW\*(C`ev_feed_event\*(C'\fR). |
712 | .ie n .IP """EV_ERROR""" 4 |
1329 | .ie n .IP """EV_ERROR""" 4 |
713 | .el .IP "\f(CWEV_ERROR\fR" 4 |
1330 | .el .IP "\f(CWEV_ERROR\fR" 4 |
714 | .IX Item "EV_ERROR" |
1331 | .IX Item "EV_ERROR" |
715 | An unspecified error has occured, the watcher has been stopped. This might |
1332 | An unspecified error has occurred, the watcher has been stopped. This might |
716 | happen because the watcher could not be properly started because libev |
1333 | happen because the watcher could not be properly started because libev |
717 | ran out of memory, a file descriptor was found to be closed or any other |
1334 | ran out of memory, a file descriptor was found to be closed or any other |
|
|
1335 | problem. Libev considers these application bugs. |
|
|
1336 | .Sp |
718 | problem. You best act on it by reporting the problem and somehow coping |
1337 | You best act on it by reporting the problem and somehow coping with the |
719 | with the watcher being stopped. |
1338 | watcher being stopped. Note that well-written programs should not receive |
|
|
1339 | an error ever, so when your watcher receives it, this usually indicates a |
|
|
1340 | bug in your program. |
720 | .Sp |
1341 | .Sp |
721 | Libev will usually signal a few \*(L"dummy\*(R" events together with an error, |
1342 | Libev will usually signal a few \*(L"dummy\*(R" events together with an error, for |
722 | for example it might indicate that a fd is readable or writable, and if |
1343 | example it might indicate that a fd is readable or writable, and if your |
723 | your callbacks is well-written it can just attempt the operation and cope |
1344 | callbacks is well-written it can just attempt the operation and cope with |
724 | with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded |
1345 | the error from \fIread()\fR or \fIwrite()\fR. This will not work in multi-threaded |
725 | programs, though, so beware. |
1346 | programs, though, as the fd could already be closed and reused for another |
|
|
1347 | thing, so beware. |
726 | .Sh "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0" |
1348 | .SS "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0" |
727 | .IX Subsection "GENERIC WATCHER FUNCTIONS" |
1349 | .IX Subsection "GENERIC WATCHER FUNCTIONS" |
728 | In the following description, \f(CW\*(C`TYPE\*(C'\fR stands for the watcher type, |
|
|
729 | e.g. \f(CW\*(C`timer\*(C'\fR for \f(CW\*(C`ev_timer\*(C'\fR watchers and \f(CW\*(C`io\*(C'\fR for \f(CW\*(C`ev_io\*(C'\fR watchers. |
|
|
730 | .ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4 |
1350 | .ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4 |
731 | .el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4 |
1351 | .el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4 |
732 | .IX Item "ev_init (ev_TYPE *watcher, callback)" |
1352 | .IX Item "ev_init (ev_TYPE *watcher, callback)" |
733 | This macro initialises the generic portion of a watcher. The contents |
1353 | This macro initialises the generic portion of a watcher. The contents |
734 | of the watcher object can be arbitrary (so \f(CW\*(C`malloc\*(C'\fR will do). Only |
1354 | of the watcher object can be arbitrary (so \f(CW\*(C`malloc\*(C'\fR will do). Only |
… | |
… | |
738 | which rolls both calls into one. |
1358 | which rolls both calls into one. |
739 | .Sp |
1359 | .Sp |
740 | You can reinitialise a watcher at any time as long as it has been stopped |
1360 | You can reinitialise a watcher at any time as long as it has been stopped |
741 | (or never started) and there are no pending events outstanding. |
1361 | (or never started) and there are no pending events outstanding. |
742 | .Sp |
1362 | .Sp |
743 | The callback is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher, |
1363 | The callback is always of type \f(CW\*(C`void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
744 | int revents)\*(C'\fR. |
1364 | int revents)\*(C'\fR. |
|
|
1365 | .Sp |
|
|
1366 | Example: Initialise an \f(CW\*(C`ev_io\*(C'\fR watcher in two steps. |
|
|
1367 | .Sp |
|
|
1368 | .Vb 3 |
|
|
1369 | \& ev_io w; |
|
|
1370 | \& ev_init (&w, my_cb); |
|
|
1371 | \& ev_io_set (&w, STDIN_FILENO, EV_READ); |
|
|
1372 | .Ve |
745 | .ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4 |
1373 | .ie n .IP """ev_TYPE_set"" (ev_TYPE *watcher, [args])" 4 |
746 | .el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4 |
1374 | .el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *watcher, [args])" 4 |
747 | .IX Item "ev_TYPE_set (ev_TYPE *, [args])" |
1375 | .IX Item "ev_TYPE_set (ev_TYPE *watcher, [args])" |
748 | This macro initialises the type-specific parts of a watcher. You need to |
1376 | This macro initialises the type-specific parts of a watcher. You need to |
749 | call \f(CW\*(C`ev_init\*(C'\fR at least once before you call this macro, but you can |
1377 | call \f(CW\*(C`ev_init\*(C'\fR at least once before you call this macro, but you can |
750 | call \f(CW\*(C`ev_TYPE_set\*(C'\fR any number of times. You must not, however, call this |
1378 | call \f(CW\*(C`ev_TYPE_set\*(C'\fR any number of times. You must not, however, call this |
751 | macro on a watcher that is active (it can be pending, however, which is a |
1379 | macro on a watcher that is active (it can be pending, however, which is a |
752 | difference to the \f(CW\*(C`ev_init\*(C'\fR macro). |
1380 | difference to the \f(CW\*(C`ev_init\*(C'\fR macro). |
753 | .Sp |
1381 | .Sp |
754 | Although some watcher types do not have type-specific arguments |
1382 | Although some watcher types do not have type-specific arguments |
755 | (e.g. \f(CW\*(C`ev_prepare\*(C'\fR) you still need to call its \f(CW\*(C`set\*(C'\fR macro. |
1383 | (e.g. \f(CW\*(C`ev_prepare\*(C'\fR) you still need to call its \f(CW\*(C`set\*(C'\fR macro. |
|
|
1384 | .Sp |
|
|
1385 | See \f(CW\*(C`ev_init\*(C'\fR, above, for an example. |
756 | .ie n .IP """ev_TYPE_init"" (ev_TYPE *watcher, callback, [args])" 4 |
1386 | .ie n .IP """ev_TYPE_init"" (ev_TYPE *watcher, callback, [args])" 4 |
757 | .el .IP "\f(CWev_TYPE_init\fR (ev_TYPE *watcher, callback, [args])" 4 |
1387 | .el .IP "\f(CWev_TYPE_init\fR (ev_TYPE *watcher, callback, [args])" 4 |
758 | .IX Item "ev_TYPE_init (ev_TYPE *watcher, callback, [args])" |
1388 | .IX Item "ev_TYPE_init (ev_TYPE *watcher, callback, [args])" |
759 | This convinience macro rolls both \f(CW\*(C`ev_init\*(C'\fR and \f(CW\*(C`ev_TYPE_set\*(C'\fR macro |
1389 | This convenience macro rolls both \f(CW\*(C`ev_init\*(C'\fR and \f(CW\*(C`ev_TYPE_set\*(C'\fR macro |
760 | calls into a single call. This is the most convinient method to initialise |
1390 | calls into a single call. This is the most convenient method to initialise |
761 | a watcher. The same limitations apply, of course. |
1391 | a watcher. The same limitations apply, of course. |
|
|
1392 | .Sp |
|
|
1393 | Example: Initialise and set an \f(CW\*(C`ev_io\*(C'\fR watcher in one step. |
|
|
1394 | .Sp |
|
|
1395 | .Vb 1 |
|
|
1396 | \& ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
|
|
1397 | .Ve |
762 | .ie n .IP """ev_TYPE_start"" (loop *, ev_TYPE *watcher)" 4 |
1398 | .ie n .IP """ev_TYPE_start"" (loop, ev_TYPE *watcher)" 4 |
763 | .el .IP "\f(CWev_TYPE_start\fR (loop *, ev_TYPE *watcher)" 4 |
1399 | .el .IP "\f(CWev_TYPE_start\fR (loop, ev_TYPE *watcher)" 4 |
764 | .IX Item "ev_TYPE_start (loop *, ev_TYPE *watcher)" |
1400 | .IX Item "ev_TYPE_start (loop, ev_TYPE *watcher)" |
765 | Starts (activates) the given watcher. Only active watchers will receive |
1401 | Starts (activates) the given watcher. Only active watchers will receive |
766 | events. If the watcher is already active nothing will happen. |
1402 | events. If the watcher is already active nothing will happen. |
|
|
1403 | .Sp |
|
|
1404 | Example: Start the \f(CW\*(C`ev_io\*(C'\fR watcher that is being abused as example in this |
|
|
1405 | whole section. |
|
|
1406 | .Sp |
|
|
1407 | .Vb 1 |
|
|
1408 | \& ev_io_start (EV_DEFAULT_UC, &w); |
|
|
1409 | .Ve |
767 | .ie n .IP """ev_TYPE_stop"" (loop *, ev_TYPE *watcher)" 4 |
1410 | .ie n .IP """ev_TYPE_stop"" (loop, ev_TYPE *watcher)" 4 |
768 | .el .IP "\f(CWev_TYPE_stop\fR (loop *, ev_TYPE *watcher)" 4 |
1411 | .el .IP "\f(CWev_TYPE_stop\fR (loop, ev_TYPE *watcher)" 4 |
769 | .IX Item "ev_TYPE_stop (loop *, ev_TYPE *watcher)" |
1412 | .IX Item "ev_TYPE_stop (loop, ev_TYPE *watcher)" |
770 | Stops the given watcher again (if active) and clears the pending |
1413 | Stops the given watcher if active, and clears the pending status (whether |
|
|
1414 | the watcher was active or not). |
|
|
1415 | .Sp |
771 | status. It is possible that stopped watchers are pending (for example, |
1416 | It is possible that stopped watchers are pending \- for example, |
772 | non-repeating timers are being stopped when they become pending), but |
1417 | non-repeating timers are being stopped when they become pending \- but |
773 | \&\f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor pending. If |
1418 | calling \f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor |
774 | you want to free or reuse the memory used by the watcher it is therefore a |
1419 | pending. If you want to free or reuse the memory used by the watcher it is |
775 | good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function. |
1420 | therefore a good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function. |
776 | .IP "bool ev_is_active (ev_TYPE *watcher)" 4 |
1421 | .IP "bool ev_is_active (ev_TYPE *watcher)" 4 |
777 | .IX Item "bool ev_is_active (ev_TYPE *watcher)" |
1422 | .IX Item "bool ev_is_active (ev_TYPE *watcher)" |
778 | Returns a true value iff the watcher is active (i.e. it has been started |
1423 | Returns a true value iff the watcher is active (i.e. it has been started |
779 | and not yet been stopped). As long as a watcher is active you must not modify |
1424 | and not yet been stopped). As long as a watcher is active you must not modify |
780 | it. |
1425 | it. |
781 | .IP "bool ev_is_pending (ev_TYPE *watcher)" 4 |
1426 | .IP "bool ev_is_pending (ev_TYPE *watcher)" 4 |
782 | .IX Item "bool ev_is_pending (ev_TYPE *watcher)" |
1427 | .IX Item "bool ev_is_pending (ev_TYPE *watcher)" |
783 | Returns a true value iff the watcher is pending, (i.e. it has outstanding |
1428 | Returns a true value iff the watcher is pending, (i.e. it has outstanding |
784 | events but its callback has not yet been invoked). As long as a watcher |
1429 | events but its callback has not yet been invoked). As long as a watcher |
785 | is pending (but not active) you must not call an init function on it (but |
1430 | is pending (but not active) you must not call an init function on it (but |
786 | \&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe) and you must make sure the watcher is available to |
1431 | \&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe), you must not change its priority, and you must |
787 | libev (e.g. you cnanot \f(CW\*(C`free ()\*(C'\fR it). |
1432 | make sure the watcher is available to libev (e.g. you cannot \f(CW\*(C`free ()\*(C'\fR |
|
|
1433 | it). |
788 | .IP "callback = ev_cb (ev_TYPE *watcher)" 4 |
1434 | .IP "callback ev_cb (ev_TYPE *watcher)" 4 |
789 | .IX Item "callback = ev_cb (ev_TYPE *watcher)" |
1435 | .IX Item "callback ev_cb (ev_TYPE *watcher)" |
790 | Returns the callback currently set on the watcher. |
1436 | Returns the callback currently set on the watcher. |
791 | .IP "ev_cb_set (ev_TYPE *watcher, callback)" 4 |
1437 | .IP "ev_cb_set (ev_TYPE *watcher, callback)" 4 |
792 | .IX Item "ev_cb_set (ev_TYPE *watcher, callback)" |
1438 | .IX Item "ev_cb_set (ev_TYPE *watcher, callback)" |
793 | Change the callback. You can change the callback at virtually any time |
1439 | Change the callback. You can change the callback at virtually any time |
794 | (modulo threads). |
1440 | (modulo threads). |
795 | .Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0" |
1441 | .IP "ev_set_priority (ev_TYPE *watcher, int priority)" 4 |
796 | .IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER" |
1442 | .IX Item "ev_set_priority (ev_TYPE *watcher, int priority)" |
797 | Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change |
1443 | .PD 0 |
798 | and read at any time, libev will completely ignore it. This can be used |
1444 | .IP "int ev_priority (ev_TYPE *watcher)" 4 |
799 | to associate arbitrary data with your watcher. If you need more data and |
1445 | .IX Item "int ev_priority (ev_TYPE *watcher)" |
800 | don't want to allocate memory and store a pointer to it in that data |
1446 | .PD |
801 | member, you can also \*(L"subclass\*(R" the watcher type and provide your own |
1447 | Set and query the priority of the watcher. The priority is a small |
802 | data: |
1448 | integer between \f(CW\*(C`EV_MAXPRI\*(C'\fR (default: \f(CW2\fR) and \f(CW\*(C`EV_MINPRI\*(C'\fR |
|
|
1449 | (default: \f(CW\*(C`\-2\*(C'\fR). Pending watchers with higher priority will be invoked |
|
|
1450 | before watchers with lower priority, but priority will not keep watchers |
|
|
1451 | from being executed (except for \f(CW\*(C`ev_idle\*(C'\fR watchers). |
|
|
1452 | .Sp |
|
|
1453 | If you need to suppress invocation when higher priority events are pending |
|
|
1454 | you need to look at \f(CW\*(C`ev_idle\*(C'\fR watchers, which provide this functionality. |
|
|
1455 | .Sp |
|
|
1456 | You \fImust not\fR change the priority of a watcher as long as it is active or |
|
|
1457 | pending. |
|
|
1458 | .Sp |
|
|
1459 | Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR is |
|
|
1460 | fine, as long as you do not mind that the priority value you query might |
|
|
1461 | or might not have been clamped to the valid range. |
|
|
1462 | .Sp |
|
|
1463 | The default priority used by watchers when no priority has been set is |
|
|
1464 | always \f(CW0\fR, which is supposed to not be too high and not be too low :). |
|
|
1465 | .Sp |
|
|
1466 | See \*(L"\s-1WATCHER\s0 \s-1PRIORITY\s0 \s-1MODELS\s0\*(R", below, for a more thorough treatment of |
|
|
1467 | priorities. |
|
|
1468 | .IP "ev_invoke (loop, ev_TYPE *watcher, int revents)" 4 |
|
|
1469 | .IX Item "ev_invoke (loop, ev_TYPE *watcher, int revents)" |
|
|
1470 | Invoke the \f(CW\*(C`watcher\*(C'\fR with the given \f(CW\*(C`loop\*(C'\fR and \f(CW\*(C`revents\*(C'\fR. Neither |
|
|
1471 | \&\f(CW\*(C`loop\*(C'\fR nor \f(CW\*(C`revents\*(C'\fR need to be valid as long as the watcher callback |
|
|
1472 | can deal with that fact, as both are simply passed through to the |
|
|
1473 | callback. |
|
|
1474 | .IP "int ev_clear_pending (loop, ev_TYPE *watcher)" 4 |
|
|
1475 | .IX Item "int ev_clear_pending (loop, ev_TYPE *watcher)" |
|
|
1476 | If the watcher is pending, this function clears its pending status and |
|
|
1477 | returns its \f(CW\*(C`revents\*(C'\fR bitset (as if its callback was invoked). If the |
|
|
1478 | watcher isn't pending it does nothing and returns \f(CW0\fR. |
|
|
1479 | .Sp |
|
|
1480 | Sometimes it can be useful to \*(L"poll\*(R" a watcher instead of waiting for its |
|
|
1481 | callback to be invoked, which can be accomplished with this function. |
|
|
1482 | .IP "ev_feed_event (loop, ev_TYPE *watcher, int revents)" 4 |
|
|
1483 | .IX Item "ev_feed_event (loop, ev_TYPE *watcher, int revents)" |
|
|
1484 | Feeds the given event set into the event loop, as if the specified event |
|
|
1485 | had happened for the specified watcher (which must be a pointer to an |
|
|
1486 | initialised but not necessarily started event watcher). Obviously you must |
|
|
1487 | not free the watcher as long as it has pending events. |
|
|
1488 | .Sp |
|
|
1489 | Stopping the watcher, letting libev invoke it, or calling |
|
|
1490 | \&\f(CW\*(C`ev_clear_pending\*(C'\fR will clear the pending event, even if the watcher was |
|
|
1491 | not started in the first place. |
|
|
1492 | .Sp |
|
|
1493 | See also \f(CW\*(C`ev_feed_fd_event\*(C'\fR and \f(CW\*(C`ev_feed_signal_event\*(C'\fR for related |
|
|
1494 | functions that do not need a watcher. |
803 | .PP |
1495 | .PP |
|
|
1496 | See also the \*(L"\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0\*(R" and \*(L"\s-1BUILDING\s0 \s-1YOUR\s0 |
|
|
1497 | \&\s-1OWN\s0 \s-1COMPOSITE\s0 \s-1WATCHERS\s0\*(R" idioms. |
|
|
1498 | .SS "\s-1WATCHER\s0 \s-1STATES\s0" |
|
|
1499 | .IX Subsection "WATCHER STATES" |
|
|
1500 | There are various watcher states mentioned throughout this manual \- |
|
|
1501 | active, pending and so on. In this section these states and the rules to |
|
|
1502 | transition between them will be described in more detail \- and while these |
|
|
1503 | rules might look complicated, they usually do \*(L"the right thing\*(R". |
|
|
1504 | .IP "initialiased" 4 |
|
|
1505 | .IX Item "initialiased" |
|
|
1506 | Before a watcher can be registered with the event loop it has to be |
|
|
1507 | initialised. This can be done with a call to \f(CW\*(C`ev_TYPE_init\*(C'\fR, or calls to |
|
|
1508 | \&\f(CW\*(C`ev_init\*(C'\fR followed by the watcher-specific \f(CW\*(C`ev_TYPE_set\*(C'\fR function. |
|
|
1509 | .Sp |
|
|
1510 | In this state it is simply some block of memory that is suitable for |
|
|
1511 | use in an event loop. It can be moved around, freed, reused etc. at |
|
|
1512 | will \- as long as you either keep the memory contents intact, or call |
|
|
1513 | \&\f(CW\*(C`ev_TYPE_init\*(C'\fR again. |
|
|
1514 | .IP "started/running/active" 4 |
|
|
1515 | .IX Item "started/running/active" |
|
|
1516 | Once a watcher has been started with a call to \f(CW\*(C`ev_TYPE_start\*(C'\fR it becomes |
|
|
1517 | property of the event loop, and is actively waiting for events. While in |
|
|
1518 | this state it cannot be accessed (except in a few documented ways), moved, |
|
|
1519 | freed or anything else \- the only legal thing is to keep a pointer to it, |
|
|
1520 | and call libev functions on it that are documented to work on active watchers. |
|
|
1521 | .IP "pending" 4 |
|
|
1522 | .IX Item "pending" |
|
|
1523 | If a watcher is active and libev determines that an event it is interested |
|
|
1524 | in has occurred (such as a timer expiring), it will become pending. It will |
|
|
1525 | stay in this pending state until either it is stopped or its callback is |
|
|
1526 | about to be invoked, so it is not normally pending inside the watcher |
|
|
1527 | callback. |
|
|
1528 | .Sp |
|
|
1529 | The watcher might or might not be active while it is pending (for example, |
|
|
1530 | an expired non-repeating timer can be pending but no longer active). If it |
|
|
1531 | is stopped, it can be freely accessed (e.g. by calling \f(CW\*(C`ev_TYPE_set\*(C'\fR), |
|
|
1532 | but it is still property of the event loop at this time, so cannot be |
|
|
1533 | moved, freed or reused. And if it is active the rules described in the |
|
|
1534 | previous item still apply. |
|
|
1535 | .Sp |
|
|
1536 | It is also possible to feed an event on a watcher that is not active (e.g. |
|
|
1537 | via \f(CW\*(C`ev_feed_event\*(C'\fR), in which case it becomes pending without being |
|
|
1538 | active. |
|
|
1539 | .IP "stopped" 4 |
|
|
1540 | .IX Item "stopped" |
|
|
1541 | A watcher can be stopped implicitly by libev (in which case it might still |
|
|
1542 | be pending), or explicitly by calling its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function. The |
|
|
1543 | latter will clear any pending state the watcher might be in, regardless |
|
|
1544 | of whether it was active or not, so stopping a watcher explicitly before |
|
|
1545 | freeing it is often a good idea. |
|
|
1546 | .Sp |
|
|
1547 | While stopped (and not pending) the watcher is essentially in the |
|
|
1548 | initialised state, that is, it can be reused, moved, modified in any way |
|
|
1549 | you wish (but when you trash the memory block, you need to \f(CW\*(C`ev_TYPE_init\*(C'\fR |
|
|
1550 | it again). |
|
|
1551 | .SS "\s-1WATCHER\s0 \s-1PRIORITY\s0 \s-1MODELS\s0" |
|
|
1552 | .IX Subsection "WATCHER PRIORITY MODELS" |
|
|
1553 | Many event loops support \fIwatcher priorities\fR, which are usually small |
|
|
1554 | integers that influence the ordering of event callback invocation |
|
|
1555 | between watchers in some way, all else being equal. |
|
|
1556 | .PP |
|
|
1557 | In libev, Watcher priorities can be set using \f(CW\*(C`ev_set_priority\*(C'\fR. See its |
|
|
1558 | description for the more technical details such as the actual priority |
|
|
1559 | range. |
|
|
1560 | .PP |
|
|
1561 | There are two common ways how these these priorities are being interpreted |
|
|
1562 | by event loops: |
|
|
1563 | .PP |
|
|
1564 | In the more common lock-out model, higher priorities \*(L"lock out\*(R" invocation |
|
|
1565 | of lower priority watchers, which means as long as higher priority |
|
|
1566 | watchers receive events, lower priority watchers are not being invoked. |
|
|
1567 | .PP |
|
|
1568 | The less common only-for-ordering model uses priorities solely to order |
|
|
1569 | callback invocation within a single event loop iteration: Higher priority |
|
|
1570 | watchers are invoked before lower priority ones, but they all get invoked |
|
|
1571 | before polling for new events. |
|
|
1572 | .PP |
|
|
1573 | Libev uses the second (only-for-ordering) model for all its watchers |
|
|
1574 | except for idle watchers (which use the lock-out model). |
|
|
1575 | .PP |
|
|
1576 | The rationale behind this is that implementing the lock-out model for |
|
|
1577 | watchers is not well supported by most kernel interfaces, and most event |
|
|
1578 | libraries will just poll for the same events again and again as long as |
|
|
1579 | their callbacks have not been executed, which is very inefficient in the |
|
|
1580 | common case of one high-priority watcher locking out a mass of lower |
|
|
1581 | priority ones. |
|
|
1582 | .PP |
|
|
1583 | Static (ordering) priorities are most useful when you have two or more |
|
|
1584 | watchers handling the same resource: a typical usage example is having an |
|
|
1585 | \&\f(CW\*(C`ev_io\*(C'\fR watcher to receive data, and an associated \f(CW\*(C`ev_timer\*(C'\fR to handle |
|
|
1586 | timeouts. Under load, data might be received while the program handles |
|
|
1587 | other jobs, but since timers normally get invoked first, the timeout |
|
|
1588 | handler will be executed before checking for data. In that case, giving |
|
|
1589 | the timer a lower priority than the I/O watcher ensures that I/O will be |
|
|
1590 | handled first even under adverse conditions (which is usually, but not |
|
|
1591 | always, what you want). |
|
|
1592 | .PP |
|
|
1593 | Since idle watchers use the \*(L"lock-out\*(R" model, meaning that idle watchers |
|
|
1594 | will only be executed when no same or higher priority watchers have |
|
|
1595 | received events, they can be used to implement the \*(L"lock-out\*(R" model when |
|
|
1596 | required. |
|
|
1597 | .PP |
|
|
1598 | For example, to emulate how many other event libraries handle priorities, |
|
|
1599 | you can associate an \f(CW\*(C`ev_idle\*(C'\fR watcher to each such watcher, and in |
|
|
1600 | the normal watcher callback, you just start the idle watcher. The real |
|
|
1601 | processing is done in the idle watcher callback. This causes libev to |
|
|
1602 | continuously poll and process kernel event data for the watcher, but when |
|
|
1603 | the lock-out case is known to be rare (which in turn is rare :), this is |
|
|
1604 | workable. |
|
|
1605 | .PP |
|
|
1606 | Usually, however, the lock-out model implemented that way will perform |
|
|
1607 | miserably under the type of load it was designed to handle. In that case, |
|
|
1608 | it might be preferable to stop the real watcher before starting the |
|
|
1609 | idle watcher, so the kernel will not have to process the event in case |
|
|
1610 | the actual processing will be delayed for considerable time. |
|
|
1611 | .PP |
|
|
1612 | Here is an example of an I/O watcher that should run at a strictly lower |
|
|
1613 | priority than the default, and which should only process data when no |
|
|
1614 | other events are pending: |
|
|
1615 | .PP |
804 | .Vb 7 |
1616 | .Vb 2 |
805 | \& struct my_io |
1617 | \& ev_idle idle; // actual processing watcher |
|
|
1618 | \& ev_io io; // actual event watcher |
|
|
1619 | \& |
|
|
1620 | \& static void |
|
|
1621 | \& io_cb (EV_P_ ev_io *w, int revents) |
806 | \& { |
1622 | \& { |
807 | \& struct ev_io io; |
1623 | \& // stop the I/O watcher, we received the event, but |
808 | \& int otherfd; |
1624 | \& // are not yet ready to handle it. |
809 | \& void *somedata; |
1625 | \& ev_io_stop (EV_A_ w); |
810 | \& struct whatever *mostinteresting; |
1626 | \& |
|
|
1627 | \& // start the idle watcher to handle the actual event. |
|
|
1628 | \& // it will not be executed as long as other watchers |
|
|
1629 | \& // with the default priority are receiving events. |
|
|
1630 | \& ev_idle_start (EV_A_ &idle); |
811 | \& } |
1631 | \& } |
812 | .Ve |
1632 | \& |
813 | .PP |
1633 | \& static void |
814 | And since your callback will be called with a pointer to the watcher, you |
1634 | \& idle_cb (EV_P_ ev_idle *w, int revents) |
815 | can cast it back to your own type: |
|
|
816 | .PP |
|
|
817 | .Vb 5 |
|
|
818 | \& static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) |
|
|
819 | \& { |
1635 | \& { |
820 | \& struct my_io *w = (struct my_io *)w_; |
1636 | \& // actual processing |
821 | \& ... |
1637 | \& read (STDIN_FILENO, ...); |
|
|
1638 | \& |
|
|
1639 | \& // have to start the I/O watcher again, as |
|
|
1640 | \& // we have handled the event |
|
|
1641 | \& ev_io_start (EV_P_ &io); |
822 | \& } |
1642 | \& } |
|
|
1643 | \& |
|
|
1644 | \& // initialisation |
|
|
1645 | \& ev_idle_init (&idle, idle_cb); |
|
|
1646 | \& ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ); |
|
|
1647 | \& ev_io_start (EV_DEFAULT_ &io); |
823 | .Ve |
1648 | .Ve |
824 | .PP |
1649 | .PP |
825 | More interesting and less C\-conformant ways of catsing your callback type |
1650 | In the \*(L"real\*(R" world, it might also be beneficial to start a timer, so that |
826 | have been omitted.... |
1651 | low-priority connections can not be locked out forever under load. This |
|
|
1652 | enables your program to keep a lower latency for important connections |
|
|
1653 | during short periods of high load, while not completely locking out less |
|
|
1654 | important ones. |
827 | .SH "WATCHER TYPES" |
1655 | .SH "WATCHER TYPES" |
828 | .IX Header "WATCHER TYPES" |
1656 | .IX Header "WATCHER TYPES" |
829 | This section describes each watcher in detail, but will not repeat |
1657 | This section describes each watcher in detail, but will not repeat |
830 | information given in the last section. Any initialisation/set macros, |
1658 | information given in the last section. Any initialisation/set macros, |
831 | functions and members specific to the watcher type are explained. |
1659 | functions and members specific to the watcher type are explained. |
… | |
… | |
836 | watcher is stopped to your hearts content), or \fI[read\-write]\fR, which |
1664 | watcher is stopped to your hearts content), or \fI[read\-write]\fR, which |
837 | means you can expect it to have some sensible content while the watcher |
1665 | means you can expect it to have some sensible content while the watcher |
838 | is active, but you can also modify it. Modifying it may not do something |
1666 | is active, but you can also modify it. Modifying it may not do something |
839 | sensible or take immediate effect (or do anything at all), but libev will |
1667 | sensible or take immediate effect (or do anything at all), but libev will |
840 | not crash or malfunction in any way. |
1668 | not crash or malfunction in any way. |
841 | .ie n .Sh """ev_io"" \- is this file descriptor readable or writable?" |
1669 | .ie n .SS """ev_io"" \- is this file descriptor readable or writable?" |
842 | .el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable?" |
1670 | .el .SS "\f(CWev_io\fP \- is this file descriptor readable or writable?" |
843 | .IX Subsection "ev_io - is this file descriptor readable or writable?" |
1671 | .IX Subsection "ev_io - is this file descriptor readable or writable?" |
844 | I/O watchers check whether a file descriptor is readable or writable |
1672 | I/O watchers check whether a file descriptor is readable or writable |
845 | in each iteration of the event loop, or, more precisely, when reading |
1673 | in each iteration of the event loop, or, more precisely, when reading |
846 | would not block the process and writing would at least be able to write |
1674 | would not block the process and writing would at least be able to write |
847 | some data. This behaviour is called level-triggering because you keep |
1675 | some data. This behaviour is called level-triggering because you keep |
… | |
… | |
852 | In general you can register as many read and/or write event watchers per |
1680 | In general you can register as many read and/or write event watchers per |
853 | fd as you want (as long as you don't confuse yourself). Setting all file |
1681 | fd as you want (as long as you don't confuse yourself). Setting all file |
854 | descriptors to non-blocking mode is also usually a good idea (but not |
1682 | descriptors to non-blocking mode is also usually a good idea (but not |
855 | required if you know what you are doing). |
1683 | required if you know what you are doing). |
856 | .PP |
1684 | .PP |
857 | You have to be careful with dup'ed file descriptors, though. Some backends |
|
|
858 | (the linux epoll backend is a notable example) cannot handle dup'ed file |
|
|
859 | descriptors correctly if you register interest in two or more fds pointing |
|
|
860 | to the same underlying file/socket/etc. description (that is, they share |
|
|
861 | the same underlying \*(L"file open\*(R"). |
|
|
862 | .PP |
|
|
863 | If you must do this, then force the use of a known-to-be-good backend |
|
|
864 | (at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and |
|
|
865 | \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR). |
|
|
866 | .PP |
|
|
867 | Another thing you have to watch out for is that it is quite easy to |
1685 | Another thing you have to watch out for is that it is quite easy to |
868 | receive \*(L"spurious\*(R" readyness notifications, that is your callback might |
1686 | receive \*(L"spurious\*(R" readiness notifications, that is, your callback might |
869 | be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block |
1687 | be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block |
870 | because there is no data. Not only are some backends known to create a |
1688 | because there is no data. It is very easy to get into this situation even |
871 | lot of those (for example solaris ports), it is very easy to get into |
1689 | with a relatively standard program structure. Thus it is best to always |
872 | this situation even with a relatively standard program structure. Thus |
1690 | use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning \f(CW\*(C`EAGAIN\*(C'\fR is far |
873 | it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning |
|
|
874 | \&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives. |
1691 | preferable to a program hanging until some data arrives. |
875 | .PP |
1692 | .PP |
876 | If you cannot run the fd in non-blocking mode (for example you should not |
1693 | If you cannot run the fd in non-blocking mode (for example you should |
877 | play around with an Xlib connection), then you have to seperately re-test |
1694 | not play around with an Xlib connection), then you have to separately |
878 | wether a file descriptor is really ready with a known-to-be good interface |
1695 | re-test whether a file descriptor is really ready with a known-to-be good |
879 | such as poll (fortunately in our Xlib example, Xlib already does this on |
1696 | interface such as poll (fortunately in the case of Xlib, it already does |
880 | its own, so its quite safe to use). |
1697 | this on its own, so its quite safe to use). Some people additionally |
|
|
1698 | use \f(CW\*(C`SIGALRM\*(C'\fR and an interval timer, just to be sure you won't block |
|
|
1699 | indefinitely. |
|
|
1700 | .PP |
|
|
1701 | But really, best use non-blocking mode. |
|
|
1702 | .PP |
|
|
1703 | \fIThe special problem of disappearing file descriptors\fR |
|
|
1704 | .IX Subsection "The special problem of disappearing file descriptors" |
|
|
1705 | .PP |
|
|
1706 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
|
|
1707 | descriptor (either due to calling \f(CW\*(C`close\*(C'\fR explicitly or any other means, |
|
|
1708 | such as \f(CW\*(C`dup2\*(C'\fR). The reason is that you register interest in some file |
|
|
1709 | descriptor, but when it goes away, the operating system will silently drop |
|
|
1710 | this interest. If another file descriptor with the same number then is |
|
|
1711 | registered with libev, there is no efficient way to see that this is, in |
|
|
1712 | fact, a different file descriptor. |
|
|
1713 | .PP |
|
|
1714 | To avoid having to explicitly tell libev about such cases, libev follows |
|
|
1715 | the following policy: Each time \f(CW\*(C`ev_io_set\*(C'\fR is being called, libev |
|
|
1716 | will assume that this is potentially a new file descriptor, otherwise |
|
|
1717 | it is assumed that the file descriptor stays the same. That means that |
|
|
1718 | you \fIhave\fR to call \f(CW\*(C`ev_io_set\*(C'\fR (or \f(CW\*(C`ev_io_init\*(C'\fR) when you change the |
|
|
1719 | descriptor even if the file descriptor number itself did not change. |
|
|
1720 | .PP |
|
|
1721 | This is how one would do it normally anyway, the important point is that |
|
|
1722 | the libev application should not optimise around libev but should leave |
|
|
1723 | optimisations to libev. |
|
|
1724 | .PP |
|
|
1725 | \fIThe special problem of dup'ed file descriptors\fR |
|
|
1726 | .IX Subsection "The special problem of dup'ed file descriptors" |
|
|
1727 | .PP |
|
|
1728 | Some backends (e.g. epoll), cannot register events for file descriptors, |
|
|
1729 | but only events for the underlying file descriptions. That means when you |
|
|
1730 | have \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors or weirder constellations, and register |
|
|
1731 | events for them, only one file descriptor might actually receive events. |
|
|
1732 | .PP |
|
|
1733 | There is no workaround possible except not registering events |
|
|
1734 | for potentially \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors, or to resort to |
|
|
1735 | \&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
|
|
1736 | .PP |
|
|
1737 | \fIThe special problem of files\fR |
|
|
1738 | .IX Subsection "The special problem of files" |
|
|
1739 | .PP |
|
|
1740 | Many people try to use \f(CW\*(C`select\*(C'\fR (or libev) on file descriptors |
|
|
1741 | representing files, and expect it to become ready when their program |
|
|
1742 | doesn't block on disk accesses (which can take a long time on their own). |
|
|
1743 | .PP |
|
|
1744 | However, this cannot ever work in the \*(L"expected\*(R" way \- you get a readiness |
|
|
1745 | notification as soon as the kernel knows whether and how much data is |
|
|
1746 | there, and in the case of open files, that's always the case, so you |
|
|
1747 | always get a readiness notification instantly, and your read (or possibly |
|
|
1748 | write) will still block on the disk I/O. |
|
|
1749 | .PP |
|
|
1750 | Another way to view it is that in the case of sockets, pipes, character |
|
|
1751 | devices and so on, there is another party (the sender) that delivers data |
|
|
1752 | on its own, but in the case of files, there is no such thing: the disk |
|
|
1753 | will not send data on its own, simply because it doesn't know what you |
|
|
1754 | wish to read \- you would first have to request some data. |
|
|
1755 | .PP |
|
|
1756 | Since files are typically not-so-well supported by advanced notification |
|
|
1757 | mechanism, libev tries hard to emulate \s-1POSIX\s0 behaviour with respect |
|
|
1758 | to files, even though you should not use it. The reason for this is |
|
|
1759 | convenience: sometimes you want to watch \s-1STDIN\s0 or \s-1STDOUT\s0, which is |
|
|
1760 | usually a tty, often a pipe, but also sometimes files or special devices |
|
|
1761 | (for example, \f(CW\*(C`epoll\*(C'\fR on Linux works with \fI/dev/random\fR but not with |
|
|
1762 | \&\fI/dev/urandom\fR), and even though the file might better be served with |
|
|
1763 | asynchronous I/O instead of with non-blocking I/O, it is still useful when |
|
|
1764 | it \*(L"just works\*(R" instead of freezing. |
|
|
1765 | .PP |
|
|
1766 | So avoid file descriptors pointing to files when you know it (e.g. use |
|
|
1767 | libeio), but use them when it is convenient, e.g. for \s-1STDIN/STDOUT\s0, or |
|
|
1768 | when you rarely read from a file instead of from a socket, and want to |
|
|
1769 | reuse the same code path. |
|
|
1770 | .PP |
|
|
1771 | \fIThe special problem of fork\fR |
|
|
1772 | .IX Subsection "The special problem of fork" |
|
|
1773 | .PP |
|
|
1774 | Some backends (epoll, kqueue) do not support \f(CW\*(C`fork ()\*(C'\fR at all or exhibit |
|
|
1775 | useless behaviour. Libev fully supports fork, but needs to be told about |
|
|
1776 | it in the child if you want to continue to use it in the child. |
|
|
1777 | .PP |
|
|
1778 | To support fork in your child processes, you have to call \f(CW\*(C`ev_loop_fork |
|
|
1779 | ()\*(C'\fR after a fork in the child, enable \f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR, or resort to |
|
|
1780 | \&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
|
|
1781 | .PP |
|
|
1782 | \fIThe special problem of \s-1SIGPIPE\s0\fR |
|
|
1783 | .IX Subsection "The special problem of SIGPIPE" |
|
|
1784 | .PP |
|
|
1785 | While not really specific to libev, it is easy to forget about \f(CW\*(C`SIGPIPE\*(C'\fR: |
|
|
1786 | when writing to a pipe whose other end has been closed, your program gets |
|
|
1787 | sent a \s-1SIGPIPE\s0, which, by default, aborts your program. For most programs |
|
|
1788 | this is sensible behaviour, for daemons, this is usually undesirable. |
|
|
1789 | .PP |
|
|
1790 | So when you encounter spurious, unexplained daemon exits, make sure you |
|
|
1791 | ignore \s-1SIGPIPE\s0 (and maybe make sure you log the exit status of your daemon |
|
|
1792 | somewhere, as that would have given you a big clue). |
|
|
1793 | .PP |
|
|
1794 | \fIThe special problem of \fIaccept()\fIing when you can't\fR |
|
|
1795 | .IX Subsection "The special problem of accept()ing when you can't" |
|
|
1796 | .PP |
|
|
1797 | Many implementations of the \s-1POSIX\s0 \f(CW\*(C`accept\*(C'\fR function (for example, |
|
|
1798 | found in post\-2004 Linux) have the peculiar behaviour of not removing a |
|
|
1799 | connection from the pending queue in all error cases. |
|
|
1800 | .PP |
|
|
1801 | For example, larger servers often run out of file descriptors (because |
|
|
1802 | of resource limits), causing \f(CW\*(C`accept\*(C'\fR to fail with \f(CW\*(C`ENFILE\*(C'\fR but not |
|
|
1803 | rejecting the connection, leading to libev signalling readiness on |
|
|
1804 | the next iteration again (the connection still exists after all), and |
|
|
1805 | typically causing the program to loop at 100% \s-1CPU\s0 usage. |
|
|
1806 | .PP |
|
|
1807 | Unfortunately, the set of errors that cause this issue differs between |
|
|
1808 | operating systems, there is usually little the app can do to remedy the |
|
|
1809 | situation, and no known thread-safe method of removing the connection to |
|
|
1810 | cope with overload is known (to me). |
|
|
1811 | .PP |
|
|
1812 | One of the easiest ways to handle this situation is to just ignore it |
|
|
1813 | \&\- when the program encounters an overload, it will just loop until the |
|
|
1814 | situation is over. While this is a form of busy waiting, no \s-1OS\s0 offers an |
|
|
1815 | event-based way to handle this situation, so it's the best one can do. |
|
|
1816 | .PP |
|
|
1817 | A better way to handle the situation is to log any errors other than |
|
|
1818 | \&\f(CW\*(C`EAGAIN\*(C'\fR and \f(CW\*(C`EWOULDBLOCK\*(C'\fR, making sure not to flood the log with such |
|
|
1819 | messages, and continue as usual, which at least gives the user an idea of |
|
|
1820 | what could be wrong (\*(L"raise the ulimit!\*(R"). For extra points one could stop |
|
|
1821 | the \f(CW\*(C`ev_io\*(C'\fR watcher on the listening fd \*(L"for a while\*(R", which reduces \s-1CPU\s0 |
|
|
1822 | usage. |
|
|
1823 | .PP |
|
|
1824 | If your program is single-threaded, then you could also keep a dummy file |
|
|
1825 | descriptor for overload situations (e.g. by opening \fI/dev/null\fR), and |
|
|
1826 | when you run into \f(CW\*(C`ENFILE\*(C'\fR or \f(CW\*(C`EMFILE\*(C'\fR, close it, run \f(CW\*(C`accept\*(C'\fR, |
|
|
1827 | close that fd, and create a new dummy fd. This will gracefully refuse |
|
|
1828 | clients under typical overload conditions. |
|
|
1829 | .PP |
|
|
1830 | The last way to handle it is to simply log the error and \f(CW\*(C`exit\*(C'\fR, as |
|
|
1831 | is often done with \f(CW\*(C`malloc\*(C'\fR failures, but this results in an easy |
|
|
1832 | opportunity for a DoS attack. |
|
|
1833 | .PP |
|
|
1834 | \fIWatcher-Specific Functions\fR |
|
|
1835 | .IX Subsection "Watcher-Specific Functions" |
881 | .IP "ev_io_init (ev_io *, callback, int fd, int events)" 4 |
1836 | .IP "ev_io_init (ev_io *, callback, int fd, int events)" 4 |
882 | .IX Item "ev_io_init (ev_io *, callback, int fd, int events)" |
1837 | .IX Item "ev_io_init (ev_io *, callback, int fd, int events)" |
883 | .PD 0 |
1838 | .PD 0 |
884 | .IP "ev_io_set (ev_io *, int fd, int events)" 4 |
1839 | .IP "ev_io_set (ev_io *, int fd, int events)" 4 |
885 | .IX Item "ev_io_set (ev_io *, int fd, int events)" |
1840 | .IX Item "ev_io_set (ev_io *, int fd, int events)" |
886 | .PD |
1841 | .PD |
887 | Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to |
1842 | Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to |
888 | rceeive events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or |
1843 | receive events for and \f(CW\*(C`events\*(C'\fR is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or |
889 | \&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR to receive the given events. |
1844 | \&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR, to express the desire to receive the given events. |
890 | .IP "int fd [read\-only]" 4 |
1845 | .IP "int fd [read\-only]" 4 |
891 | .IX Item "int fd [read-only]" |
1846 | .IX Item "int fd [read-only]" |
892 | The file descriptor being watched. |
1847 | The file descriptor being watched. |
893 | .IP "int events [read\-only]" 4 |
1848 | .IP "int events [read\-only]" 4 |
894 | .IX Item "int events [read-only]" |
1849 | .IX Item "int events [read-only]" |
895 | The events being watched. |
1850 | The events being watched. |
896 | .PP |
1851 | .PP |
|
|
1852 | \fIExamples\fR |
|
|
1853 | .IX Subsection "Examples" |
|
|
1854 | .PP |
897 | Example: call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well |
1855 | Example: Call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well |
898 | readable, but only once. Since it is likely line\-buffered, you could |
1856 | readable, but only once. Since it is likely line-buffered, you could |
899 | attempt to read a whole line in the callback: |
1857 | attempt to read a whole line in the callback. |
900 | .PP |
1858 | .PP |
901 | .Vb 6 |
1859 | .Vb 6 |
902 | \& static void |
1860 | \& static void |
903 | \& stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1861 | \& stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents) |
904 | \& { |
1862 | \& { |
905 | \& ev_io_stop (loop, w); |
1863 | \& ev_io_stop (loop, w); |
906 | \& .. read from stdin here (or from w->fd) and haqndle any I/O errors |
1864 | \& .. read from stdin here (or from w\->fd) and handle any I/O errors |
907 | \& } |
1865 | \& } |
908 | .Ve |
1866 | \& |
909 | .PP |
|
|
910 | .Vb 6 |
|
|
911 | \& ... |
1867 | \& ... |
912 | \& struct ev_loop *loop = ev_default_init (0); |
1868 | \& struct ev_loop *loop = ev_default_init (0); |
913 | \& struct ev_io stdin_readable; |
1869 | \& ev_io stdin_readable; |
914 | \& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1870 | \& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
915 | \& ev_io_start (loop, &stdin_readable); |
1871 | \& ev_io_start (loop, &stdin_readable); |
916 | \& ev_loop (loop, 0); |
1872 | \& ev_run (loop, 0); |
917 | .Ve |
1873 | .Ve |
918 | .ie n .Sh """ev_timer"" \- relative and optionally repeating timeouts" |
1874 | .ie n .SS """ev_timer"" \- relative and optionally repeating timeouts" |
919 | .el .Sh "\f(CWev_timer\fP \- relative and optionally repeating timeouts" |
1875 | .el .SS "\f(CWev_timer\fP \- relative and optionally repeating timeouts" |
920 | .IX Subsection "ev_timer - relative and optionally repeating timeouts" |
1876 | .IX Subsection "ev_timer - relative and optionally repeating timeouts" |
921 | Timer watchers are simple relative timers that generate an event after a |
1877 | Timer watchers are simple relative timers that generate an event after a |
922 | given time, and optionally repeating in regular intervals after that. |
1878 | given time, and optionally repeating in regular intervals after that. |
923 | .PP |
1879 | .PP |
924 | The timers are based on real time, that is, if you register an event that |
1880 | The timers are based on real time, that is, if you register an event that |
925 | times out after an hour and you reset your system clock to last years |
1881 | times out after an hour and you reset your system clock to January last |
926 | time, it will still time out after (roughly) and hour. \*(L"Roughly\*(R" because |
1882 | year, it will still time out after (roughly) one hour. \*(L"Roughly\*(R" because |
927 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1883 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
928 | monotonic clock option helps a lot here). |
1884 | monotonic clock option helps a lot here). |
|
|
1885 | .PP |
|
|
1886 | The callback is guaranteed to be invoked only \fIafter\fR its timeout has |
|
|
1887 | passed (not \fIat\fR, so on systems with very low-resolution clocks this |
|
|
1888 | might introduce a small delay, see \*(L"the special problem of being too |
|
|
1889 | early\*(R", below). If multiple timers become ready during the same loop |
|
|
1890 | iteration then the ones with earlier time-out values are invoked before |
|
|
1891 | ones of the same priority with later time-out values (but this is no |
|
|
1892 | longer true when a callback calls \f(CW\*(C`ev_run\*(C'\fR recursively). |
|
|
1893 | .PP |
|
|
1894 | \fIBe smart about timeouts\fR |
|
|
1895 | .IX Subsection "Be smart about timeouts" |
|
|
1896 | .PP |
|
|
1897 | Many real-world problems involve some kind of timeout, usually for error |
|
|
1898 | recovery. A typical example is an \s-1HTTP\s0 request \- if the other side hangs, |
|
|
1899 | you want to raise some error after a while. |
|
|
1900 | .PP |
|
|
1901 | What follows are some ways to handle this problem, from obvious and |
|
|
1902 | inefficient to smart and efficient. |
|
|
1903 | .PP |
|
|
1904 | In the following, a 60 second activity timeout is assumed \- a timeout that |
|
|
1905 | gets reset to 60 seconds each time there is activity (e.g. each time some |
|
|
1906 | data or other life sign was received). |
|
|
1907 | .IP "1. Use a timer and stop, reinitialise and start it on activity." 4 |
|
|
1908 | .IX Item "1. Use a timer and stop, reinitialise and start it on activity." |
|
|
1909 | This is the most obvious, but not the most simple way: In the beginning, |
|
|
1910 | start the watcher: |
|
|
1911 | .Sp |
|
|
1912 | .Vb 2 |
|
|
1913 | \& ev_timer_init (timer, callback, 60., 0.); |
|
|
1914 | \& ev_timer_start (loop, timer); |
|
|
1915 | .Ve |
|
|
1916 | .Sp |
|
|
1917 | Then, each time there is some activity, \f(CW\*(C`ev_timer_stop\*(C'\fR it, initialise it |
|
|
1918 | and start it again: |
|
|
1919 | .Sp |
|
|
1920 | .Vb 3 |
|
|
1921 | \& ev_timer_stop (loop, timer); |
|
|
1922 | \& ev_timer_set (timer, 60., 0.); |
|
|
1923 | \& ev_timer_start (loop, timer); |
|
|
1924 | .Ve |
|
|
1925 | .Sp |
|
|
1926 | This is relatively simple to implement, but means that each time there is |
|
|
1927 | some activity, libev will first have to remove the timer from its internal |
|
|
1928 | data structure and then add it again. Libev tries to be fast, but it's |
|
|
1929 | still not a constant-time operation. |
|
|
1930 | .ie n .IP "2. Use a timer and re-start it with ""ev_timer_again"" inactivity." 4 |
|
|
1931 | .el .IP "2. Use a timer and re-start it with \f(CWev_timer_again\fR inactivity." 4 |
|
|
1932 | .IX Item "2. Use a timer and re-start it with ev_timer_again inactivity." |
|
|
1933 | This is the easiest way, and involves using \f(CW\*(C`ev_timer_again\*(C'\fR instead of |
|
|
1934 | \&\f(CW\*(C`ev_timer_start\*(C'\fR. |
|
|
1935 | .Sp |
|
|
1936 | To implement this, configure an \f(CW\*(C`ev_timer\*(C'\fR with a \f(CW\*(C`repeat\*(C'\fR value |
|
|
1937 | of \f(CW60\fR and then call \f(CW\*(C`ev_timer_again\*(C'\fR at start and each time you |
|
|
1938 | successfully read or write some data. If you go into an idle state where |
|
|
1939 | you do not expect data to travel on the socket, you can \f(CW\*(C`ev_timer_stop\*(C'\fR |
|
|
1940 | the timer, and \f(CW\*(C`ev_timer_again\*(C'\fR will automatically restart it if need be. |
|
|
1941 | .Sp |
|
|
1942 | That means you can ignore both the \f(CW\*(C`ev_timer_start\*(C'\fR function and the |
|
|
1943 | \&\f(CW\*(C`after\*(C'\fR argument to \f(CW\*(C`ev_timer_set\*(C'\fR, and only ever use the \f(CW\*(C`repeat\*(C'\fR |
|
|
1944 | member and \f(CW\*(C`ev_timer_again\*(C'\fR. |
|
|
1945 | .Sp |
|
|
1946 | At start: |
|
|
1947 | .Sp |
|
|
1948 | .Vb 3 |
|
|
1949 | \& ev_init (timer, callback); |
|
|
1950 | \& timer\->repeat = 60.; |
|
|
1951 | \& ev_timer_again (loop, timer); |
|
|
1952 | .Ve |
|
|
1953 | .Sp |
|
|
1954 | Each time there is some activity: |
|
|
1955 | .Sp |
|
|
1956 | .Vb 1 |
|
|
1957 | \& ev_timer_again (loop, timer); |
|
|
1958 | .Ve |
|
|
1959 | .Sp |
|
|
1960 | It is even possible to change the time-out on the fly, regardless of |
|
|
1961 | whether the watcher is active or not: |
|
|
1962 | .Sp |
|
|
1963 | .Vb 2 |
|
|
1964 | \& timer\->repeat = 30.; |
|
|
1965 | \& ev_timer_again (loop, timer); |
|
|
1966 | .Ve |
|
|
1967 | .Sp |
|
|
1968 | This is slightly more efficient then stopping/starting the timer each time |
|
|
1969 | you want to modify its timeout value, as libev does not have to completely |
|
|
1970 | remove and re-insert the timer from/into its internal data structure. |
|
|
1971 | .Sp |
|
|
1972 | It is, however, even simpler than the \*(L"obvious\*(R" way to do it. |
|
|
1973 | .IP "3. Let the timer time out, but then re-arm it as required." 4 |
|
|
1974 | .IX Item "3. Let the timer time out, but then re-arm it as required." |
|
|
1975 | This method is more tricky, but usually most efficient: Most timeouts are |
|
|
1976 | relatively long compared to the intervals between other activity \- in |
|
|
1977 | our example, within 60 seconds, there are usually many I/O events with |
|
|
1978 | associated activity resets. |
|
|
1979 | .Sp |
|
|
1980 | In this case, it would be more efficient to leave the \f(CW\*(C`ev_timer\*(C'\fR alone, |
|
|
1981 | but remember the time of last activity, and check for a real timeout only |
|
|
1982 | within the callback: |
|
|
1983 | .Sp |
|
|
1984 | .Vb 3 |
|
|
1985 | \& ev_tstamp timeout = 60.; |
|
|
1986 | \& ev_tstamp last_activity; // time of last activity |
|
|
1987 | \& ev_timer timer; |
|
|
1988 | \& |
|
|
1989 | \& static void |
|
|
1990 | \& callback (EV_P_ ev_timer *w, int revents) |
|
|
1991 | \& { |
|
|
1992 | \& // calculate when the timeout would happen |
|
|
1993 | \& ev_tstamp after = last_activity \- ev_now (EV_A) + timeout; |
|
|
1994 | \& |
|
|
1995 | \& // if negative, it means we the timeout already occured |
|
|
1996 | \& if (after < 0.) |
|
|
1997 | \& { |
|
|
1998 | \& // timeout occurred, take action |
|
|
1999 | \& } |
|
|
2000 | \& else |
|
|
2001 | \& { |
|
|
2002 | \& // callback was invoked, but there was some recent |
|
|
2003 | \& // activity. simply restart the timer to time out |
|
|
2004 | \& // after "after" seconds, which is the earliest time |
|
|
2005 | \& // the timeout can occur. |
|
|
2006 | \& ev_timer_set (w, after, 0.); |
|
|
2007 | \& ev_timer_start (EV_A_ w); |
|
|
2008 | \& } |
|
|
2009 | \& } |
|
|
2010 | .Ve |
|
|
2011 | .Sp |
|
|
2012 | To summarise the callback: first calculate in how many seconds the |
|
|
2013 | timeout will occur (by calculating the absolute time when it would occur, |
|
|
2014 | \&\f(CW\*(C`last_activity + timeout\*(C'\fR, and subtracting the current time, \f(CW\*(C`ev_now |
|
|
2015 | (EV_A)\*(C'\fR from that). |
|
|
2016 | .Sp |
|
|
2017 | If this value is negative, then we are already past the timeout, i.e. we |
|
|
2018 | timed out, and need to do whatever is needed in this case. |
|
|
2019 | .Sp |
|
|
2020 | Otherwise, we now the earliest time at which the timeout would trigger, |
|
|
2021 | and simply start the timer with this timeout value. |
|
|
2022 | .Sp |
|
|
2023 | In other words, each time the callback is invoked it will check whether |
|
|
2024 | the timeout cocured. If not, it will simply reschedule itself to check |
|
|
2025 | again at the earliest time it could time out. Rinse. Repeat. |
|
|
2026 | .Sp |
|
|
2027 | This scheme causes more callback invocations (about one every 60 seconds |
|
|
2028 | minus half the average time between activity), but virtually no calls to |
|
|
2029 | libev to change the timeout. |
|
|
2030 | .Sp |
|
|
2031 | To start the machinery, simply initialise the watcher and set |
|
|
2032 | \&\f(CW\*(C`last_activity\*(C'\fR to the current time (meaning there was some activity just |
|
|
2033 | now), then call the callback, which will \*(L"do the right thing\*(R" and start |
|
|
2034 | the timer: |
|
|
2035 | .Sp |
|
|
2036 | .Vb 3 |
|
|
2037 | \& last_activity = ev_now (EV_A); |
|
|
2038 | \& ev_init (&timer, callback); |
|
|
2039 | \& callback (EV_A_ &timer, 0); |
|
|
2040 | .Ve |
|
|
2041 | .Sp |
|
|
2042 | When there is some activity, simply store the current time in |
|
|
2043 | \&\f(CW\*(C`last_activity\*(C'\fR, no libev calls at all: |
|
|
2044 | .Sp |
|
|
2045 | .Vb 2 |
|
|
2046 | \& if (activity detected) |
|
|
2047 | \& last_activity = ev_now (EV_A); |
|
|
2048 | .Ve |
|
|
2049 | .Sp |
|
|
2050 | When your timeout value changes, then the timeout can be changed by simply |
|
|
2051 | providing a new value, stopping the timer and calling the callback, which |
|
|
2052 | will agaion do the right thing (for example, time out immediately :). |
|
|
2053 | .Sp |
|
|
2054 | .Vb 3 |
|
|
2055 | \& timeout = new_value; |
|
|
2056 | \& ev_timer_stop (EV_A_ &timer); |
|
|
2057 | \& callback (EV_A_ &timer, 0); |
|
|
2058 | .Ve |
|
|
2059 | .Sp |
|
|
2060 | This technique is slightly more complex, but in most cases where the |
|
|
2061 | time-out is unlikely to be triggered, much more efficient. |
|
|
2062 | .IP "4. Wee, just use a double-linked list for your timeouts." 4 |
|
|
2063 | .IX Item "4. Wee, just use a double-linked list for your timeouts." |
|
|
2064 | If there is not one request, but many thousands (millions...), all |
|
|
2065 | employing some kind of timeout with the same timeout value, then one can |
|
|
2066 | do even better: |
|
|
2067 | .Sp |
|
|
2068 | When starting the timeout, calculate the timeout value and put the timeout |
|
|
2069 | at the \fIend\fR of the list. |
|
|
2070 | .Sp |
|
|
2071 | Then use an \f(CW\*(C`ev_timer\*(C'\fR to fire when the timeout at the \fIbeginning\fR of |
|
|
2072 | the list is expected to fire (for example, using the technique #3). |
|
|
2073 | .Sp |
|
|
2074 | When there is some activity, remove the timer from the list, recalculate |
|
|
2075 | the timeout, append it to the end of the list again, and make sure to |
|
|
2076 | update the \f(CW\*(C`ev_timer\*(C'\fR if it was taken from the beginning of the list. |
|
|
2077 | .Sp |
|
|
2078 | This way, one can manage an unlimited number of timeouts in O(1) time for |
|
|
2079 | starting, stopping and updating the timers, at the expense of a major |
|
|
2080 | complication, and having to use a constant timeout. The constant timeout |
|
|
2081 | ensures that the list stays sorted. |
|
|
2082 | .PP |
|
|
2083 | So which method the best? |
|
|
2084 | .PP |
|
|
2085 | Method #2 is a simple no-brain-required solution that is adequate in most |
|
|
2086 | situations. Method #3 requires a bit more thinking, but handles many cases |
|
|
2087 | better, and isn't very complicated either. In most case, choosing either |
|
|
2088 | one is fine, with #3 being better in typical situations. |
|
|
2089 | .PP |
|
|
2090 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
|
|
2091 | rather complicated, but extremely efficient, something that really pays |
|
|
2092 | off after the first million or so of active timers, i.e. it's usually |
|
|
2093 | overkill :) |
|
|
2094 | .PP |
|
|
2095 | \fIThe special problem of being too early\fR |
|
|
2096 | .IX Subsection "The special problem of being too early" |
|
|
2097 | .PP |
|
|
2098 | If you ask a timer to call your callback after three seconds, then |
|
|
2099 | you expect it to be invoked after three seconds \- but of course, this |
|
|
2100 | cannot be guaranteed to infinite precision. Less obviously, it cannot be |
|
|
2101 | guaranteed to any precision by libev \- imagine somebody suspending the |
|
|
2102 | process with a \s-1STOP\s0 signal for a few hours for example. |
|
|
2103 | .PP |
|
|
2104 | So, libev tries to invoke your callback as soon as possible \fIafter\fR the |
|
|
2105 | delay has occurred, but cannot guarantee this. |
|
|
2106 | .PP |
|
|
2107 | A less obvious failure mode is calling your callback too early: many event |
|
|
2108 | loops compare timestamps with a \*(L"elapsed delay >= requested delay\*(R", but |
|
|
2109 | this can cause your callback to be invoked much earlier than you would |
|
|
2110 | expect. |
|
|
2111 | .PP |
|
|
2112 | To see why, imagine a system with a clock that only offers full second |
|
|
2113 | resolution (think windows if you can't come up with a broken enough \s-1OS\s0 |
|
|
2114 | yourself). If you schedule a one-second timer at the time 500.9, then the |
|
|
2115 | event loop will schedule your timeout to elapse at a system time of 500 |
|
|
2116 | (500.9 truncated to the resolution) + 1, or 501. |
|
|
2117 | .PP |
|
|
2118 | If an event library looks at the timeout 0.1s later, it will see \*(L"501 >= |
|
|
2119 | 501\*(R" and invoke the callback 0.1s after it was started, even though a |
|
|
2120 | one-second delay was requested \- this is being \*(L"too early\*(R", despite best |
|
|
2121 | intentions. |
|
|
2122 | .PP |
|
|
2123 | This is the reason why libev will never invoke the callback if the elapsed |
|
|
2124 | delay equals the requested delay, but only when the elapsed delay is |
|
|
2125 | larger than the requested delay. In the example above, libev would only invoke |
|
|
2126 | the callback at system time 502, or 1.1s after the timer was started. |
|
|
2127 | .PP |
|
|
2128 | So, while libev cannot guarantee that your callback will be invoked |
|
|
2129 | exactly when requested, it \fIcan\fR and \fIdoes\fR guarantee that the requested |
|
|
2130 | delay has actually elapsed, or in other words, it always errs on the \*(L"too |
|
|
2131 | late\*(R" side of things. |
|
|
2132 | .PP |
|
|
2133 | \fIThe special problem of time updates\fR |
|
|
2134 | .IX Subsection "The special problem of time updates" |
|
|
2135 | .PP |
|
|
2136 | Establishing the current time is a costly operation (it usually takes |
|
|
2137 | at least one system call): \s-1EV\s0 therefore updates its idea of the current |
|
|
2138 | time only before and after \f(CW\*(C`ev_run\*(C'\fR collects new events, which causes a |
|
|
2139 | growing difference between \f(CW\*(C`ev_now ()\*(C'\fR and \f(CW\*(C`ev_time ()\*(C'\fR when handling |
|
|
2140 | lots of events in one iteration. |
929 | .PP |
2141 | .PP |
930 | The relative timeouts are calculated relative to the \f(CW\*(C`ev_now ()\*(C'\fR |
2142 | The relative timeouts are calculated relative to the \f(CW\*(C`ev_now ()\*(C'\fR |
931 | time. This is usually the right thing as this timestamp refers to the time |
2143 | time. This is usually the right thing as this timestamp refers to the time |
932 | of the event triggering whatever timeout you are modifying/starting. If |
2144 | of the event triggering whatever timeout you are modifying/starting. If |
933 | you suspect event processing to be delayed and you \fIneed\fR to base the timeout |
2145 | you suspect event processing to be delayed and you \fIneed\fR to base the |
934 | on the current time, use something like this to adjust for this: |
2146 | timeout on the current time, use something like this to adjust for this: |
935 | .PP |
2147 | .PP |
936 | .Vb 1 |
2148 | .Vb 1 |
937 | \& ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
2149 | \& ev_timer_set (&timer, after + ev_now () \- ev_time (), 0.); |
938 | .Ve |
2150 | .Ve |
939 | .PP |
2151 | .PP |
940 | The callback is guarenteed to be invoked only when its timeout has passed, |
2152 | If the event loop is suspended for a long time, you can also force an |
941 | but if multiple timers become ready during the same loop iteration then |
2153 | update of the time returned by \f(CW\*(C`ev_now ()\*(C'\fR by calling \f(CW\*(C`ev_now_update |
942 | order of execution is undefined. |
2154 | ()\*(C'\fR. |
|
|
2155 | .PP |
|
|
2156 | \fIThe special problem of unsynchronised clocks\fR |
|
|
2157 | .IX Subsection "The special problem of unsynchronised clocks" |
|
|
2158 | .PP |
|
|
2159 | Modern systems have a variety of clocks \- libev itself uses the normal |
|
|
2160 | \&\*(L"wall clock\*(R" clock and, if available, the monotonic clock (to avoid time |
|
|
2161 | jumps). |
|
|
2162 | .PP |
|
|
2163 | Neither of these clocks is synchronised with each other or any other clock |
|
|
2164 | on the system, so \f(CW\*(C`ev_time ()\*(C'\fR might return a considerably different time |
|
|
2165 | than \f(CW\*(C`gettimeofday ()\*(C'\fR or \f(CW\*(C`time ()\*(C'\fR. On a GNU/Linux system, for example, |
|
|
2166 | a call to \f(CW\*(C`gettimeofday\*(C'\fR might return a second count that is one higher |
|
|
2167 | than a directly following call to \f(CW\*(C`time\*(C'\fR. |
|
|
2168 | .PP |
|
|
2169 | The moral of this is to only compare libev-related timestamps with |
|
|
2170 | \&\f(CW\*(C`ev_time ()\*(C'\fR and \f(CW\*(C`ev_now ()\*(C'\fR, at least if you want better precision than |
|
|
2171 | a second or so. |
|
|
2172 | .PP |
|
|
2173 | One more problem arises due to this lack of synchronisation: if libev uses |
|
|
2174 | the system monotonic clock and you compare timestamps from \f(CW\*(C`ev_time\*(C'\fR |
|
|
2175 | or \f(CW\*(C`ev_now\*(C'\fR from when you started your timer and when your callback is |
|
|
2176 | invoked, you will find that sometimes the callback is a bit \*(L"early\*(R". |
|
|
2177 | .PP |
|
|
2178 | This is because \f(CW\*(C`ev_timer\*(C'\fRs work in real time, not wall clock time, so |
|
|
2179 | libev makes sure your callback is not invoked before the delay happened, |
|
|
2180 | \&\fImeasured according to the real time\fR, not the system clock. |
|
|
2181 | .PP |
|
|
2182 | If your timeouts are based on a physical timescale (e.g. \*(L"time out this |
|
|
2183 | connection after 100 seconds\*(R") then this shouldn't bother you as it is |
|
|
2184 | exactly the right behaviour. |
|
|
2185 | .PP |
|
|
2186 | If you want to compare wall clock/system timestamps to your timers, then |
|
|
2187 | you need to use \f(CW\*(C`ev_periodic\*(C'\fRs, as these are based on the wall clock |
|
|
2188 | time, where your comparisons will always generate correct results. |
|
|
2189 | .PP |
|
|
2190 | \fIThe special problems of suspended animation\fR |
|
|
2191 | .IX Subsection "The special problems of suspended animation" |
|
|
2192 | .PP |
|
|
2193 | When you leave the server world it is quite customary to hit machines that |
|
|
2194 | can suspend/hibernate \- what happens to the clocks during such a suspend? |
|
|
2195 | .PP |
|
|
2196 | Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes |
|
|
2197 | all processes, while the clocks (\f(CW\*(C`times\*(C'\fR, \f(CW\*(C`CLOCK_MONOTONIC\*(C'\fR) continue |
|
|
2198 | to run until the system is suspended, but they will not advance while the |
|
|
2199 | system is suspended. That means, on resume, it will be as if the program |
|
|
2200 | was frozen for a few seconds, but the suspend time will not be counted |
|
|
2201 | towards \f(CW\*(C`ev_timer\*(C'\fR when a monotonic clock source is used. The real time |
|
|
2202 | clock advanced as expected, but if it is used as sole clocksource, then a |
|
|
2203 | long suspend would be detected as a time jump by libev, and timers would |
|
|
2204 | be adjusted accordingly. |
|
|
2205 | .PP |
|
|
2206 | I would not be surprised to see different behaviour in different between |
|
|
2207 | operating systems, \s-1OS\s0 versions or even different hardware. |
|
|
2208 | .PP |
|
|
2209 | The other form of suspend (job control, or sending a \s-1SIGSTOP\s0) will see a |
|
|
2210 | time jump in the monotonic clocks and the realtime clock. If the program |
|
|
2211 | is suspended for a very long time, and monotonic clock sources are in use, |
|
|
2212 | then you can expect \f(CW\*(C`ev_timer\*(C'\fRs to expire as the full suspension time |
|
|
2213 | will be counted towards the timers. When no monotonic clock source is in |
|
|
2214 | use, then libev will again assume a timejump and adjust accordingly. |
|
|
2215 | .PP |
|
|
2216 | It might be beneficial for this latter case to call \f(CW\*(C`ev_suspend\*(C'\fR |
|
|
2217 | and \f(CW\*(C`ev_resume\*(C'\fR in code that handles \f(CW\*(C`SIGTSTP\*(C'\fR, to at least get |
|
|
2218 | deterministic behaviour in this case (you can do nothing against |
|
|
2219 | \&\f(CW\*(C`SIGSTOP\*(C'\fR). |
|
|
2220 | .PP |
|
|
2221 | \fIWatcher-Specific Functions and Data Members\fR |
|
|
2222 | .IX Subsection "Watcher-Specific Functions and Data Members" |
943 | .IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4 |
2223 | .IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4 |
944 | .IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" |
2224 | .IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" |
945 | .PD 0 |
2225 | .PD 0 |
946 | .IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4 |
2226 | .IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4 |
947 | .IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" |
2227 | .IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" |
948 | .PD |
2228 | .PD |
949 | Configure the timer to trigger after \f(CW\*(C`after\*(C'\fR seconds. If \f(CW\*(C`repeat\*(C'\fR is |
2229 | Configure the timer to trigger after \f(CW\*(C`after\*(C'\fR seconds. If \f(CW\*(C`repeat\*(C'\fR |
950 | \&\f(CW0.\fR, then it will automatically be stopped. If it is positive, then the |
2230 | is \f(CW0.\fR, then it will automatically be stopped once the timeout is |
951 | timer will automatically be configured to trigger again \f(CW\*(C`repeat\*(C'\fR seconds |
2231 | reached. If it is positive, then the timer will automatically be |
952 | later, again, and again, until stopped manually. |
2232 | configured to trigger again \f(CW\*(C`repeat\*(C'\fR seconds later, again, and again, |
|
|
2233 | until stopped manually. |
953 | .Sp |
2234 | .Sp |
954 | The timer itself will do a best-effort at avoiding drift, that is, if you |
2235 | The timer itself will do a best-effort at avoiding drift, that is, if |
955 | configure a timer to trigger every 10 seconds, then it will trigger at |
2236 | you configure a timer to trigger every 10 seconds, then it will normally |
956 | exactly 10 second intervals. If, however, your program cannot keep up with |
2237 | trigger at exactly 10 second intervals. If, however, your program cannot |
957 | the timer (because it takes longer than those 10 seconds to do stuff) the |
2238 | keep up with the timer (because it takes longer than those 10 seconds to |
958 | timer will not fire more than once per event loop iteration. |
2239 | do stuff) the timer will not fire more than once per event loop iteration. |
959 | .IP "ev_timer_again (loop)" 4 |
2240 | .IP "ev_timer_again (loop, ev_timer *)" 4 |
960 | .IX Item "ev_timer_again (loop)" |
2241 | .IX Item "ev_timer_again (loop, ev_timer *)" |
961 | This will act as if the timer timed out and restart it again if it is |
2242 | This will act as if the timer timed out, and restarts it again if it is |
962 | repeating. The exact semantics are: |
2243 | repeating. It basically works like calling \f(CW\*(C`ev_timer_stop\*(C'\fR, updating the |
|
|
2244 | timeout to the \f(CW\*(C`repeat\*(C'\fR value and calling \f(CW\*(C`ev_timer_start\*(C'\fR. |
963 | .Sp |
2245 | .Sp |
964 | If the timer is started but nonrepeating, stop it. |
2246 | The exact semantics are as in the following rules, all of which will be |
|
|
2247 | applied to the watcher: |
|
|
2248 | .RS 4 |
|
|
2249 | .IP "If the timer is pending, the pending status is always cleared." 4 |
|
|
2250 | .IX Item "If the timer is pending, the pending status is always cleared." |
|
|
2251 | .PD 0 |
|
|
2252 | .IP "If the timer is started but non-repeating, stop it (as if it timed out, without invoking it)." 4 |
|
|
2253 | .IX Item "If the timer is started but non-repeating, stop it (as if it timed out, without invoking it)." |
|
|
2254 | .ie n .IP "If the timer is repeating, make the ""repeat"" value the new timeout and start the timer, if necessary." 4 |
|
|
2255 | .el .IP "If the timer is repeating, make the \f(CWrepeat\fR value the new timeout and start the timer, if necessary." 4 |
|
|
2256 | .IX Item "If the timer is repeating, make the repeat value the new timeout and start the timer, if necessary." |
|
|
2257 | .RE |
|
|
2258 | .RS 4 |
|
|
2259 | .PD |
965 | .Sp |
2260 | .Sp |
966 | If the timer is repeating, either start it if necessary (with the repeat |
2261 | This sounds a bit complicated, see \*(L"Be smart about timeouts\*(R", above, for a |
967 | value), or reset the running timer to the repeat value. |
2262 | usage example. |
|
|
2263 | .RE |
|
|
2264 | .IP "ev_tstamp ev_timer_remaining (loop, ev_timer *)" 4 |
|
|
2265 | .IX Item "ev_tstamp ev_timer_remaining (loop, ev_timer *)" |
|
|
2266 | Returns the remaining time until a timer fires. If the timer is active, |
|
|
2267 | then this time is relative to the current event loop time, otherwise it's |
|
|
2268 | the timeout value currently configured. |
968 | .Sp |
2269 | .Sp |
969 | This sounds a bit complicated, but here is a useful and typical |
2270 | That is, after an \f(CW\*(C`ev_timer_set (w, 5, 7)\*(C'\fR, \f(CW\*(C`ev_timer_remaining\*(C'\fR returns |
970 | example: Imagine you have a tcp connection and you want a so-called |
2271 | \&\f(CW5\fR. When the timer is started and one second passes, \f(CW\*(C`ev_timer_remaining\*(C'\fR |
971 | idle timeout, that is, you want to be called when there have been, |
2272 | will return \f(CW4\fR. When the timer expires and is restarted, it will return |
972 | say, 60 seconds of inactivity on the socket. The easiest way to do |
2273 | roughly \f(CW7\fR (likely slightly less as callback invocation takes some time, |
973 | this is to configure an \f(CW\*(C`ev_timer\*(C'\fR with \f(CW\*(C`after\*(C'\fR=\f(CW\*(C`repeat\*(C'\fR=\f(CW60\fR and calling |
2274 | too), and so on. |
974 | \&\f(CW\*(C`ev_timer_again\*(C'\fR each time you successfully read or write some data. If |
|
|
975 | you go into an idle state where you do not expect data to travel on the |
|
|
976 | socket, you can stop the timer, and again will automatically restart it if |
|
|
977 | need be. |
|
|
978 | .Sp |
|
|
979 | You can also ignore the \f(CW\*(C`after\*(C'\fR value and \f(CW\*(C`ev_timer_start\*(C'\fR altogether |
|
|
980 | and only ever use the \f(CW\*(C`repeat\*(C'\fR value: |
|
|
981 | .Sp |
|
|
982 | .Vb 8 |
|
|
983 | \& ev_timer_init (timer, callback, 0., 5.); |
|
|
984 | \& ev_timer_again (loop, timer); |
|
|
985 | \& ... |
|
|
986 | \& timer->again = 17.; |
|
|
987 | \& ev_timer_again (loop, timer); |
|
|
988 | \& ... |
|
|
989 | \& timer->again = 10.; |
|
|
990 | \& ev_timer_again (loop, timer); |
|
|
991 | .Ve |
|
|
992 | .Sp |
|
|
993 | This is more efficient then stopping/starting the timer eahc time you want |
|
|
994 | to modify its timeout value. |
|
|
995 | .IP "ev_tstamp repeat [read\-write]" 4 |
2275 | .IP "ev_tstamp repeat [read\-write]" 4 |
996 | .IX Item "ev_tstamp repeat [read-write]" |
2276 | .IX Item "ev_tstamp repeat [read-write]" |
997 | The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out |
2277 | The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out |
998 | or \f(CW\*(C`ev_timer_again\*(C'\fR is called and determines the next timeout (if any), |
2278 | or \f(CW\*(C`ev_timer_again\*(C'\fR is called, and determines the next timeout (if any), |
999 | which is also when any modifications are taken into account. |
2279 | which is also when any modifications are taken into account. |
1000 | .PP |
2280 | .PP |
|
|
2281 | \fIExamples\fR |
|
|
2282 | .IX Subsection "Examples" |
|
|
2283 | .PP |
1001 | Example: create a timer that fires after 60 seconds. |
2284 | Example: Create a timer that fires after 60 seconds. |
1002 | .PP |
2285 | .PP |
1003 | .Vb 5 |
2286 | .Vb 5 |
1004 | \& static void |
2287 | \& static void |
1005 | \& one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
2288 | \& one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1006 | \& { |
2289 | \& { |
1007 | \& .. one minute over, w is actually stopped right here |
2290 | \& .. one minute over, w is actually stopped right here |
1008 | \& } |
2291 | \& } |
1009 | .Ve |
2292 | \& |
1010 | .PP |
|
|
1011 | .Vb 3 |
|
|
1012 | \& struct ev_timer mytimer; |
2293 | \& ev_timer mytimer; |
1013 | \& ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
2294 | \& ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1014 | \& ev_timer_start (loop, &mytimer); |
2295 | \& ev_timer_start (loop, &mytimer); |
1015 | .Ve |
2296 | .Ve |
1016 | .PP |
2297 | .PP |
1017 | Example: create a timeout timer that times out after 10 seconds of |
2298 | Example: Create a timeout timer that times out after 10 seconds of |
1018 | inactivity. |
2299 | inactivity. |
1019 | .PP |
2300 | .PP |
1020 | .Vb 5 |
2301 | .Vb 5 |
1021 | \& static void |
2302 | \& static void |
1022 | \& timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
2303 | \& timeout_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1023 | \& { |
2304 | \& { |
1024 | \& .. ten seconds without any activity |
2305 | \& .. ten seconds without any activity |
1025 | \& } |
2306 | \& } |
1026 | .Ve |
2307 | \& |
1027 | .PP |
|
|
1028 | .Vb 4 |
|
|
1029 | \& struct ev_timer mytimer; |
2308 | \& ev_timer mytimer; |
1030 | \& ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
2309 | \& ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1031 | \& ev_timer_again (&mytimer); /* start timer */ |
2310 | \& ev_timer_again (&mytimer); /* start timer */ |
1032 | \& ev_loop (loop, 0); |
2311 | \& ev_run (loop, 0); |
1033 | .Ve |
2312 | \& |
1034 | .PP |
|
|
1035 | .Vb 3 |
|
|
1036 | \& // and in some piece of code that gets executed on any "activity": |
2313 | \& // and in some piece of code that gets executed on any "activity": |
1037 | \& // reset the timeout to start ticking again at 10 seconds |
2314 | \& // reset the timeout to start ticking again at 10 seconds |
1038 | \& ev_timer_again (&mytimer); |
2315 | \& ev_timer_again (&mytimer); |
1039 | .Ve |
2316 | .Ve |
1040 | .ie n .Sh """ev_periodic"" \- to cron or not to cron?" |
2317 | .ie n .SS """ev_periodic"" \- to cron or not to cron?" |
1041 | .el .Sh "\f(CWev_periodic\fP \- to cron or not to cron?" |
2318 | .el .SS "\f(CWev_periodic\fP \- to cron or not to cron?" |
1042 | .IX Subsection "ev_periodic - to cron or not to cron?" |
2319 | .IX Subsection "ev_periodic - to cron or not to cron?" |
1043 | Periodic watchers are also timers of a kind, but they are very versatile |
2320 | Periodic watchers are also timers of a kind, but they are very versatile |
1044 | (and unfortunately a bit complex). |
2321 | (and unfortunately a bit complex). |
1045 | .PP |
2322 | .PP |
1046 | Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time) |
2323 | Unlike \f(CW\*(C`ev_timer\*(C'\fR, periodic watchers are not based on real time (or |
1047 | but on wallclock time (absolute time). You can tell a periodic watcher |
2324 | relative time, the physical time that passes) but on wall clock time |
1048 | to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a |
2325 | (absolute time, the thing you can read on your calender or clock). The |
1049 | periodic watcher to trigger in 10 seconds (by specifiying e.g. \f(CW\*(C`ev_now () |
2326 | difference is that wall clock time can run faster or slower than real |
1050 | + 10.\*(C'\fR) and then reset your system clock to the last year, then it will |
2327 | time, and time jumps are not uncommon (e.g. when you adjust your |
1051 | take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger |
2328 | wrist-watch). |
1052 | roughly 10 seconds later and of course not if you reset your system time |
|
|
1053 | again). |
|
|
1054 | .PP |
2329 | .PP |
1055 | They can also be used to implement vastly more complex timers, such as |
2330 | You can tell a periodic watcher to trigger after some specific point |
1056 | triggering an event on eahc midnight, local time. |
2331 | in time: for example, if you tell a periodic watcher to trigger \*(L"in 10 |
|
|
2332 | seconds\*(R" (by specifying e.g. \f(CW\*(C`ev_now () + 10.\*(C'\fR, that is, an absolute time |
|
|
2333 | not a delay) and then reset your system clock to January of the previous |
|
|
2334 | year, then it will take a year or more to trigger the event (unlike an |
|
|
2335 | \&\f(CW\*(C`ev_timer\*(C'\fR, which would still trigger roughly 10 seconds after starting |
|
|
2336 | it, as it uses a relative timeout). |
1057 | .PP |
2337 | .PP |
|
|
2338 | \&\f(CW\*(C`ev_periodic\*(C'\fR watchers can also be used to implement vastly more complex |
|
|
2339 | timers, such as triggering an event on each \*(L"midnight, local time\*(R", or |
|
|
2340 | other complicated rules. This cannot be done with \f(CW\*(C`ev_timer\*(C'\fR watchers, as |
|
|
2341 | those cannot react to time jumps. |
|
|
2342 | .PP |
1058 | As with timers, the callback is guarenteed to be invoked only when the |
2343 | As with timers, the callback is guaranteed to be invoked only when the |
1059 | time (\f(CW\*(C`at\*(C'\fR) has been passed, but if multiple periodic timers become ready |
2344 | point in time where it is supposed to trigger has passed. If multiple |
1060 | during the same loop iteration then order of execution is undefined. |
2345 | timers become ready during the same loop iteration then the ones with |
|
|
2346 | earlier time-out values are invoked before ones with later time-out values |
|
|
2347 | (but this is no longer true when a callback calls \f(CW\*(C`ev_run\*(C'\fR recursively). |
|
|
2348 | .PP |
|
|
2349 | \fIWatcher-Specific Functions and Data Members\fR |
|
|
2350 | .IX Subsection "Watcher-Specific Functions and Data Members" |
1061 | .IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4 |
2351 | .IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)" 4 |
1062 | .IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" |
2352 | .IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)" |
1063 | .PD 0 |
2353 | .PD 0 |
1064 | .IP "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 4 |
2354 | .IP "ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)" 4 |
1065 | .IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" |
2355 | .IX Item "ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)" |
1066 | .PD |
2356 | .PD |
1067 | Lots of arguments, lets sort it out... There are basically three modes of |
2357 | Lots of arguments, let's sort it out... There are basically three modes of |
1068 | operation, and we will explain them from simplest to complex: |
2358 | operation, and we will explain them from simplest to most complex: |
1069 | .RS 4 |
2359 | .RS 4 |
1070 | .IP "* absolute timer (interval = reschedule_cb = 0)" 4 |
2360 | .IP "\(bu" 4 |
1071 | .IX Item "absolute timer (interval = reschedule_cb = 0)" |
2361 | absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0) |
|
|
2362 | .Sp |
1072 | In this configuration the watcher triggers an event at the wallclock time |
2363 | In this configuration the watcher triggers an event after the wall clock |
1073 | \&\f(CW\*(C`at\*(C'\fR and doesn't repeat. It will not adjust when a time jump occurs, |
2364 | time \f(CW\*(C`offset\*(C'\fR has passed. It will not repeat and will not adjust when a |
1074 | that is, if it is to be run at January 1st 2011 then it will run when the |
2365 | time jump occurs, that is, if it is to be run at January 1st 2011 then it |
1075 | system time reaches or surpasses this time. |
2366 | will be stopped and invoked when the system clock reaches or surpasses |
1076 | .IP "* non-repeating interval timer (interval > 0, reschedule_cb = 0)" 4 |
2367 | this point in time. |
1077 | .IX Item "non-repeating interval timer (interval > 0, reschedule_cb = 0)" |
2368 | .IP "\(bu" 4 |
|
|
2369 | repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0) |
|
|
2370 | .Sp |
1078 | In this mode the watcher will always be scheduled to time out at the next |
2371 | In this mode the watcher will always be scheduled to time out at the next |
1079 | \&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N) and then repeat, regardless |
2372 | \&\f(CW\*(C`offset + N * interval\*(C'\fR time (for some integer N, which can also be |
1080 | of any time jumps. |
2373 | negative) and then repeat, regardless of any time jumps. The \f(CW\*(C`offset\*(C'\fR |
|
|
2374 | argument is merely an offset into the \f(CW\*(C`interval\*(C'\fR periods. |
1081 | .Sp |
2375 | .Sp |
1082 | This can be used to create timers that do not drift with respect to system |
2376 | This can be used to create timers that do not drift with respect to the |
1083 | time: |
2377 | system clock, for example, here is an \f(CW\*(C`ev_periodic\*(C'\fR that triggers each |
|
|
2378 | hour, on the hour (with respect to \s-1UTC\s0): |
1084 | .Sp |
2379 | .Sp |
1085 | .Vb 1 |
2380 | .Vb 1 |
1086 | \& ev_periodic_set (&periodic, 0., 3600., 0); |
2381 | \& ev_periodic_set (&periodic, 0., 3600., 0); |
1087 | .Ve |
2382 | .Ve |
1088 | .Sp |
2383 | .Sp |
1089 | This doesn't mean there will always be 3600 seconds in between triggers, |
2384 | This doesn't mean there will always be 3600 seconds in between triggers, |
1090 | but only that the the callback will be called when the system time shows a |
2385 | but only that the callback will be called when the system time shows a |
1091 | full hour (\s-1UTC\s0), or more correctly, when the system time is evenly divisible |
2386 | full hour (\s-1UTC\s0), or more correctly, when the system time is evenly divisible |
1092 | by 3600. |
2387 | by 3600. |
1093 | .Sp |
2388 | .Sp |
1094 | Another way to think about it (for the mathematically inclined) is that |
2389 | Another way to think about it (for the mathematically inclined) is that |
1095 | \&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible |
2390 | \&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible |
1096 | time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps. |
2391 | time where \f(CW\*(C`time = offset (mod interval)\*(C'\fR, regardless of any time jumps. |
1097 | .IP "* manual reschedule mode (reschedule_cb = callback)" 4 |
2392 | .Sp |
1098 | .IX Item "manual reschedule mode (reschedule_cb = callback)" |
2393 | The \f(CW\*(C`interval\*(C'\fR \fI\s-1MUST\s0\fR be positive, and for numerical stability, the |
|
|
2394 | interval value should be higher than \f(CW\*(C`1/8192\*(C'\fR (which is around 100 |
|
|
2395 | microseconds) and \f(CW\*(C`offset\*(C'\fR should be higher than \f(CW0\fR and should have |
|
|
2396 | at most a similar magnitude as the current time (say, within a factor of |
|
|
2397 | ten). Typical values for offset are, in fact, \f(CW0\fR or something between |
|
|
2398 | \&\f(CW0\fR and \f(CW\*(C`interval\*(C'\fR, which is also the recommended range. |
|
|
2399 | .Sp |
|
|
2400 | Note also that there is an upper limit to how often a timer can fire (\s-1CPU\s0 |
|
|
2401 | speed for example), so if \f(CW\*(C`interval\*(C'\fR is very small then timing stability |
|
|
2402 | will of course deteriorate. Libev itself tries to be exact to be about one |
|
|
2403 | millisecond (if the \s-1OS\s0 supports it and the machine is fast enough). |
|
|
2404 | .IP "\(bu" 4 |
|
|
2405 | manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback) |
|
|
2406 | .Sp |
1099 | In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR are both being |
2407 | In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`offset\*(C'\fR are both being |
1100 | ignored. Instead, each time the periodic watcher gets scheduled, the |
2408 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1101 | reschedule callback will be called with the watcher as first, and the |
2409 | reschedule callback will be called with the watcher as first, and the |
1102 | current time as second argument. |
2410 | current time as second argument. |
1103 | .Sp |
2411 | .Sp |
1104 | \&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher, |
2412 | \&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher, ever, |
1105 | ever, or make any event loop modifications\fR. If you need to stop it, |
2413 | or make \s-1ANY\s0 other event loop modifications whatsoever, unless explicitly |
1106 | return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop it afterwards (e.g. by |
2414 | allowed by documentation here\fR. |
1107 | starting a prepare watcher). |
|
|
1108 | .Sp |
2415 | .Sp |
|
|
2416 | If you need to stop it, return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop |
|
|
2417 | it afterwards (e.g. by starting an \f(CW\*(C`ev_prepare\*(C'\fR watcher, which is the |
|
|
2418 | only event loop modification you are allowed to do). |
|
|
2419 | .Sp |
1109 | Its prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic *w, |
2420 | The callback prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(ev_periodic |
1110 | ev_tstamp now)\*(C'\fR, e.g.: |
2421 | *w, ev_tstamp now)\*(C'\fR, e.g.: |
1111 | .Sp |
2422 | .Sp |
1112 | .Vb 4 |
2423 | .Vb 5 |
|
|
2424 | \& static ev_tstamp |
1113 | \& static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
2425 | \& my_rescheduler (ev_periodic *w, ev_tstamp now) |
1114 | \& { |
2426 | \& { |
1115 | \& return now + 60.; |
2427 | \& return now + 60.; |
1116 | \& } |
2428 | \& } |
1117 | .Ve |
2429 | .Ve |
1118 | .Sp |
2430 | .Sp |
1119 | It must return the next time to trigger, based on the passed time value |
2431 | It must return the next time to trigger, based on the passed time value |
1120 | (that is, the lowest time value larger than to the second argument). It |
2432 | (that is, the lowest time value larger than to the second argument). It |
1121 | will usually be called just before the callback will be triggered, but |
2433 | will usually be called just before the callback will be triggered, but |
1122 | might be called at other times, too. |
2434 | might be called at other times, too. |
1123 | .Sp |
2435 | .Sp |
1124 | \&\s-1NOTE:\s0 \fIThis callback must always return a time that is later than the |
2436 | \&\s-1NOTE:\s0 \fIThis callback must always return a time that is higher than or |
1125 | passed \f(CI\*(C`now\*(C'\fI value\fR. Not even \f(CW\*(C`now\*(C'\fR itself will do, it \fImust\fR be larger. |
2437 | equal to the passed \f(CI\*(C`now\*(C'\fI value\fR. |
1126 | .Sp |
2438 | .Sp |
1127 | This can be used to create very complex timers, such as a timer that |
2439 | This can be used to create very complex timers, such as a timer that |
1128 | triggers on each midnight, local time. To do this, you would calculate the |
2440 | triggers on \*(L"next midnight, local time\*(R". To do this, you would calculate the |
1129 | next midnight after \f(CW\*(C`now\*(C'\fR and return the timestamp value for this. How |
2441 | next midnight after \f(CW\*(C`now\*(C'\fR and return the timestamp value for this. How |
1130 | you do this is, again, up to you (but it is not trivial, which is the main |
2442 | you do this is, again, up to you (but it is not trivial, which is the main |
1131 | reason I omitted it as an example). |
2443 | reason I omitted it as an example). |
1132 | .RE |
2444 | .RE |
1133 | .RS 4 |
2445 | .RS 4 |
… | |
… | |
1136 | .IX Item "ev_periodic_again (loop, ev_periodic *)" |
2448 | .IX Item "ev_periodic_again (loop, ev_periodic *)" |
1137 | Simply stops and restarts the periodic watcher again. This is only useful |
2449 | Simply stops and restarts the periodic watcher again. This is only useful |
1138 | when you changed some parameters or the reschedule callback would return |
2450 | when you changed some parameters or the reschedule callback would return |
1139 | a different time than the last time it was called (e.g. in a crond like |
2451 | a different time than the last time it was called (e.g. in a crond like |
1140 | program when the crontabs have changed). |
2452 | program when the crontabs have changed). |
|
|
2453 | .IP "ev_tstamp ev_periodic_at (ev_periodic *)" 4 |
|
|
2454 | .IX Item "ev_tstamp ev_periodic_at (ev_periodic *)" |
|
|
2455 | When active, returns the absolute time that the watcher is supposed |
|
|
2456 | to trigger next. This is not the same as the \f(CW\*(C`offset\*(C'\fR argument to |
|
|
2457 | \&\f(CW\*(C`ev_periodic_set\*(C'\fR, but indeed works even in interval and manual |
|
|
2458 | rescheduling modes. |
|
|
2459 | .IP "ev_tstamp offset [read\-write]" 4 |
|
|
2460 | .IX Item "ev_tstamp offset [read-write]" |
|
|
2461 | When repeating, this contains the offset value, otherwise this is the |
|
|
2462 | absolute point in time (the \f(CW\*(C`offset\*(C'\fR value passed to \f(CW\*(C`ev_periodic_set\*(C'\fR, |
|
|
2463 | although libev might modify this value for better numerical stability). |
|
|
2464 | .Sp |
|
|
2465 | Can be modified any time, but changes only take effect when the periodic |
|
|
2466 | timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called. |
1141 | .IP "ev_tstamp interval [read\-write]" 4 |
2467 | .IP "ev_tstamp interval [read\-write]" 4 |
1142 | .IX Item "ev_tstamp interval [read-write]" |
2468 | .IX Item "ev_tstamp interval [read-write]" |
1143 | The current interval value. Can be modified any time, but changes only |
2469 | The current interval value. Can be modified any time, but changes only |
1144 | take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being |
2470 | take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being |
1145 | called. |
2471 | called. |
1146 | .IP "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read\-write]" 4 |
2472 | .IP "ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read\-write]" 4 |
1147 | .IX Item "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]" |
2473 | .IX Item "ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]" |
1148 | The current reschedule callback, or \f(CW0\fR, if this functionality is |
2474 | The current reschedule callback, or \f(CW0\fR, if this functionality is |
1149 | switched off. Can be changed any time, but changes only take effect when |
2475 | switched off. Can be changed any time, but changes only take effect when |
1150 | the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called. |
2476 | the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called. |
1151 | .PP |
2477 | .PP |
|
|
2478 | \fIExamples\fR |
|
|
2479 | .IX Subsection "Examples" |
|
|
2480 | .PP |
1152 | Example: call a callback every hour, or, more precisely, whenever the |
2481 | Example: Call a callback every hour, or, more precisely, whenever the |
1153 | system clock is divisible by 3600. The callback invocation times have |
2482 | system time is divisible by 3600. The callback invocation times have |
1154 | potentially a lot of jittering, but good long-term stability. |
2483 | potentially a lot of jitter, but good long-term stability. |
1155 | .PP |
2484 | .PP |
1156 | .Vb 5 |
2485 | .Vb 5 |
1157 | \& static void |
2486 | \& static void |
1158 | \& clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
2487 | \& clock_cb (struct ev_loop *loop, ev_periodic *w, int revents) |
1159 | \& { |
2488 | \& { |
1160 | \& ... its now a full hour (UTC, or TAI or whatever your clock follows) |
2489 | \& ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1161 | \& } |
2490 | \& } |
1162 | .Ve |
2491 | \& |
1163 | .PP |
|
|
1164 | .Vb 3 |
|
|
1165 | \& struct ev_periodic hourly_tick; |
2492 | \& ev_periodic hourly_tick; |
1166 | \& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
2493 | \& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1167 | \& ev_periodic_start (loop, &hourly_tick); |
2494 | \& ev_periodic_start (loop, &hourly_tick); |
1168 | .Ve |
2495 | .Ve |
1169 | .PP |
2496 | .PP |
1170 | Example: the same as above, but use a reschedule callback to do it: |
2497 | Example: The same as above, but use a reschedule callback to do it: |
1171 | .PP |
2498 | .PP |
1172 | .Vb 1 |
2499 | .Vb 1 |
1173 | \& #include <math.h> |
2500 | \& #include <math.h> |
1174 | .Ve |
2501 | \& |
1175 | .PP |
|
|
1176 | .Vb 5 |
|
|
1177 | \& static ev_tstamp |
2502 | \& static ev_tstamp |
1178 | \& my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
2503 | \& my_scheduler_cb (ev_periodic *w, ev_tstamp now) |
1179 | \& { |
2504 | \& { |
1180 | \& return fmod (now, 3600.) + 3600.; |
2505 | \& return now + (3600. \- fmod (now, 3600.)); |
1181 | \& } |
2506 | \& } |
1182 | .Ve |
2507 | \& |
1183 | .PP |
|
|
1184 | .Vb 1 |
|
|
1185 | \& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
2508 | \& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1186 | .Ve |
2509 | .Ve |
1187 | .PP |
2510 | .PP |
1188 | Example: call a callback every hour, starting now: |
2511 | Example: Call a callback every hour, starting now: |
1189 | .PP |
2512 | .PP |
1190 | .Vb 4 |
2513 | .Vb 4 |
1191 | \& struct ev_periodic hourly_tick; |
2514 | \& ev_periodic hourly_tick; |
1192 | \& ev_periodic_init (&hourly_tick, clock_cb, |
2515 | \& ev_periodic_init (&hourly_tick, clock_cb, |
1193 | \& fmod (ev_now (loop), 3600.), 3600., 0); |
2516 | \& fmod (ev_now (loop), 3600.), 3600., 0); |
1194 | \& ev_periodic_start (loop, &hourly_tick); |
2517 | \& ev_periodic_start (loop, &hourly_tick); |
1195 | .Ve |
2518 | .Ve |
1196 | .ie n .Sh """ev_signal"" \- signal me when a signal gets signalled!" |
2519 | .ie n .SS """ev_signal"" \- signal me when a signal gets signalled!" |
1197 | .el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled!" |
2520 | .el .SS "\f(CWev_signal\fP \- signal me when a signal gets signalled!" |
1198 | .IX Subsection "ev_signal - signal me when a signal gets signalled!" |
2521 | .IX Subsection "ev_signal - signal me when a signal gets signalled!" |
1199 | Signal watchers will trigger an event when the process receives a specific |
2522 | Signal watchers will trigger an event when the process receives a specific |
1200 | signal one or more times. Even though signals are very asynchronous, libev |
2523 | signal one or more times. Even though signals are very asynchronous, libev |
1201 | will try it's best to deliver signals synchronously, i.e. as part of the |
2524 | will try its best to deliver signals synchronously, i.e. as part of the |
1202 | normal event processing, like any other event. |
2525 | normal event processing, like any other event. |
1203 | .PP |
2526 | .PP |
|
|
2527 | If you want signals to be delivered truly asynchronously, just use |
|
|
2528 | \&\f(CW\*(C`sigaction\*(C'\fR as you would do without libev and forget about sharing |
|
|
2529 | the signal. You can even use \f(CW\*(C`ev_async\*(C'\fR from a signal handler to |
|
|
2530 | synchronously wake up an event loop. |
|
|
2531 | .PP |
1204 | You can configure as many watchers as you like per signal. Only when the |
2532 | You can configure as many watchers as you like for the same signal, but |
|
|
2533 | only within the same loop, i.e. you can watch for \f(CW\*(C`SIGINT\*(C'\fR in your |
|
|
2534 | default loop and for \f(CW\*(C`SIGIO\*(C'\fR in another loop, but you cannot watch for |
|
|
2535 | \&\f(CW\*(C`SIGINT\*(C'\fR in both the default loop and another loop at the same time. At |
|
|
2536 | the moment, \f(CW\*(C`SIGCHLD\*(C'\fR is permanently tied to the default loop. |
|
|
2537 | .PP |
1205 | first watcher gets started will libev actually register a signal watcher |
2538 | When the first watcher gets started will libev actually register something |
1206 | with the kernel (thus it coexists with your own signal handlers as long |
2539 | with the kernel (thus it coexists with your own signal handlers as long as |
1207 | as you don't register any with libev). Similarly, when the last signal |
2540 | you don't register any with libev for the same signal). |
1208 | watcher for a signal is stopped libev will reset the signal handler to |
2541 | .PP |
1209 | \&\s-1SIG_DFL\s0 (regardless of what it was set to before). |
2542 | If possible and supported, libev will install its handlers with |
|
|
2543 | \&\f(CW\*(C`SA_RESTART\*(C'\fR (or equivalent) behaviour enabled, so system calls should |
|
|
2544 | not be unduly interrupted. If you have a problem with system calls getting |
|
|
2545 | interrupted by signals you can block all signals in an \f(CW\*(C`ev_check\*(C'\fR watcher |
|
|
2546 | and unblock them in an \f(CW\*(C`ev_prepare\*(C'\fR watcher. |
|
|
2547 | .PP |
|
|
2548 | \fIThe special problem of inheritance over fork/execve/pthread_create\fR |
|
|
2549 | .IX Subsection "The special problem of inheritance over fork/execve/pthread_create" |
|
|
2550 | .PP |
|
|
2551 | Both the signal mask (\f(CW\*(C`sigprocmask\*(C'\fR) and the signal disposition |
|
|
2552 | (\f(CW\*(C`sigaction\*(C'\fR) are unspecified after starting a signal watcher (and after |
|
|
2553 | stopping it again), that is, libev might or might not block the signal, |
|
|
2554 | and might or might not set or restore the installed signal handler (but |
|
|
2555 | see \f(CW\*(C`EVFLAG_NOSIGMASK\*(C'\fR). |
|
|
2556 | .PP |
|
|
2557 | While this does not matter for the signal disposition (libev never |
|
|
2558 | sets signals to \f(CW\*(C`SIG_IGN\*(C'\fR, so handlers will be reset to \f(CW\*(C`SIG_DFL\*(C'\fR on |
|
|
2559 | \&\f(CW\*(C`execve\*(C'\fR), this matters for the signal mask: many programs do not expect |
|
|
2560 | certain signals to be blocked. |
|
|
2561 | .PP |
|
|
2562 | This means that before calling \f(CW\*(C`exec\*(C'\fR (from the child) you should reset |
|
|
2563 | the signal mask to whatever \*(L"default\*(R" you expect (all clear is a good |
|
|
2564 | choice usually). |
|
|
2565 | .PP |
|
|
2566 | The simplest way to ensure that the signal mask is reset in the child is |
|
|
2567 | to install a fork handler with \f(CW\*(C`pthread_atfork\*(C'\fR that resets it. That will |
|
|
2568 | catch fork calls done by libraries (such as the libc) as well. |
|
|
2569 | .PP |
|
|
2570 | In current versions of libev, the signal will not be blocked indefinitely |
|
|
2571 | unless you use the \f(CW\*(C`signalfd\*(C'\fR \s-1API\s0 (\f(CW\*(C`EV_SIGNALFD\*(C'\fR). While this reduces |
|
|
2572 | the window of opportunity for problems, it will not go away, as libev |
|
|
2573 | \&\fIhas\fR to modify the signal mask, at least temporarily. |
|
|
2574 | .PP |
|
|
2575 | So I can't stress this enough: \fIIf you do not reset your signal mask when |
|
|
2576 | you expect it to be empty, you have a race condition in your code\fR. This |
|
|
2577 | is not a libev-specific thing, this is true for most event libraries. |
|
|
2578 | .PP |
|
|
2579 | \fIThe special problem of threads signal handling\fR |
|
|
2580 | .IX Subsection "The special problem of threads signal handling" |
|
|
2581 | .PP |
|
|
2582 | \&\s-1POSIX\s0 threads has problematic signal handling semantics, specifically, |
|
|
2583 | a lot of functionality (sigfd, sigwait etc.) only really works if all |
|
|
2584 | threads in a process block signals, which is hard to achieve. |
|
|
2585 | .PP |
|
|
2586 | When you want to use sigwait (or mix libev signal handling with your own |
|
|
2587 | for the same signals), you can tackle this problem by globally blocking |
|
|
2588 | all signals before creating any threads (or creating them with a fully set |
|
|
2589 | sigprocmask) and also specifying the \f(CW\*(C`EVFLAG_NOSIGMASK\*(C'\fR when creating |
|
|
2590 | loops. Then designate one thread as \*(L"signal receiver thread\*(R" which handles |
|
|
2591 | these signals. You can pass on any signals that libev might be interested |
|
|
2592 | in by calling \f(CW\*(C`ev_feed_signal\*(C'\fR. |
|
|
2593 | .PP |
|
|
2594 | \fIWatcher-Specific Functions and Data Members\fR |
|
|
2595 | .IX Subsection "Watcher-Specific Functions and Data Members" |
1210 | .IP "ev_signal_init (ev_signal *, callback, int signum)" 4 |
2596 | .IP "ev_signal_init (ev_signal *, callback, int signum)" 4 |
1211 | .IX Item "ev_signal_init (ev_signal *, callback, int signum)" |
2597 | .IX Item "ev_signal_init (ev_signal *, callback, int signum)" |
1212 | .PD 0 |
2598 | .PD 0 |
1213 | .IP "ev_signal_set (ev_signal *, int signum)" 4 |
2599 | .IP "ev_signal_set (ev_signal *, int signum)" 4 |
1214 | .IX Item "ev_signal_set (ev_signal *, int signum)" |
2600 | .IX Item "ev_signal_set (ev_signal *, int signum)" |
… | |
… | |
1216 | Configures the watcher to trigger on the given signal number (usually one |
2602 | Configures the watcher to trigger on the given signal number (usually one |
1217 | of the \f(CW\*(C`SIGxxx\*(C'\fR constants). |
2603 | of the \f(CW\*(C`SIGxxx\*(C'\fR constants). |
1218 | .IP "int signum [read\-only]" 4 |
2604 | .IP "int signum [read\-only]" 4 |
1219 | .IX Item "int signum [read-only]" |
2605 | .IX Item "int signum [read-only]" |
1220 | The signal the watcher watches out for. |
2606 | The signal the watcher watches out for. |
|
|
2607 | .PP |
|
|
2608 | \fIExamples\fR |
|
|
2609 | .IX Subsection "Examples" |
|
|
2610 | .PP |
|
|
2611 | Example: Try to exit cleanly on \s-1SIGINT\s0. |
|
|
2612 | .PP |
|
|
2613 | .Vb 5 |
|
|
2614 | \& static void |
|
|
2615 | \& sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
|
|
2616 | \& { |
|
|
2617 | \& ev_break (loop, EVBREAK_ALL); |
|
|
2618 | \& } |
|
|
2619 | \& |
|
|
2620 | \& ev_signal signal_watcher; |
|
|
2621 | \& ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
|
|
2622 | \& ev_signal_start (loop, &signal_watcher); |
|
|
2623 | .Ve |
1221 | .ie n .Sh """ev_child"" \- watch out for process status changes" |
2624 | .ie n .SS """ev_child"" \- watch out for process status changes" |
1222 | .el .Sh "\f(CWev_child\fP \- watch out for process status changes" |
2625 | .el .SS "\f(CWev_child\fP \- watch out for process status changes" |
1223 | .IX Subsection "ev_child - watch out for process status changes" |
2626 | .IX Subsection "ev_child - watch out for process status changes" |
1224 | Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to |
2627 | Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to |
1225 | some child status changes (most typically when a child of yours dies). |
2628 | some child status changes (most typically when a child of yours dies or |
|
|
2629 | exits). It is permissible to install a child watcher \fIafter\fR the child |
|
|
2630 | has been forked (which implies it might have already exited), as long |
|
|
2631 | as the event loop isn't entered (or is continued from a watcher), i.e., |
|
|
2632 | forking and then immediately registering a watcher for the child is fine, |
|
|
2633 | but forking and registering a watcher a few event loop iterations later or |
|
|
2634 | in the next callback invocation is not. |
|
|
2635 | .PP |
|
|
2636 | Only the default event loop is capable of handling signals, and therefore |
|
|
2637 | you can only register child watchers in the default event loop. |
|
|
2638 | .PP |
|
|
2639 | Due to some design glitches inside libev, child watchers will always be |
|
|
2640 | handled at maximum priority (their priority is set to \f(CW\*(C`EV_MAXPRI\*(C'\fR by |
|
|
2641 | libev) |
|
|
2642 | .PP |
|
|
2643 | \fIProcess Interaction\fR |
|
|
2644 | .IX Subsection "Process Interaction" |
|
|
2645 | .PP |
|
|
2646 | Libev grabs \f(CW\*(C`SIGCHLD\*(C'\fR as soon as the default event loop is |
|
|
2647 | initialised. This is necessary to guarantee proper behaviour even if the |
|
|
2648 | first child watcher is started after the child exits. The occurrence |
|
|
2649 | of \f(CW\*(C`SIGCHLD\*(C'\fR is recorded asynchronously, but child reaping is done |
|
|
2650 | synchronously as part of the event loop processing. Libev always reaps all |
|
|
2651 | children, even ones not watched. |
|
|
2652 | .PP |
|
|
2653 | \fIOverriding the Built-In Processing\fR |
|
|
2654 | .IX Subsection "Overriding the Built-In Processing" |
|
|
2655 | .PP |
|
|
2656 | Libev offers no special support for overriding the built-in child |
|
|
2657 | processing, but if your application collides with libev's default child |
|
|
2658 | handler, you can override it easily by installing your own handler for |
|
|
2659 | \&\f(CW\*(C`SIGCHLD\*(C'\fR after initialising the default loop, and making sure the |
|
|
2660 | default loop never gets destroyed. You are encouraged, however, to use an |
|
|
2661 | event-based approach to child reaping and thus use libev's support for |
|
|
2662 | that, so other libev users can use \f(CW\*(C`ev_child\*(C'\fR watchers freely. |
|
|
2663 | .PP |
|
|
2664 | \fIStopping the Child Watcher\fR |
|
|
2665 | .IX Subsection "Stopping the Child Watcher" |
|
|
2666 | .PP |
|
|
2667 | Currently, the child watcher never gets stopped, even when the |
|
|
2668 | child terminates, so normally one needs to stop the watcher in the |
|
|
2669 | callback. Future versions of libev might stop the watcher automatically |
|
|
2670 | when a child exit is detected (calling \f(CW\*(C`ev_child_stop\*(C'\fR twice is not a |
|
|
2671 | problem). |
|
|
2672 | .PP |
|
|
2673 | \fIWatcher-Specific Functions and Data Members\fR |
|
|
2674 | .IX Subsection "Watcher-Specific Functions and Data Members" |
1226 | .IP "ev_child_init (ev_child *, callback, int pid)" 4 |
2675 | .IP "ev_child_init (ev_child *, callback, int pid, int trace)" 4 |
1227 | .IX Item "ev_child_init (ev_child *, callback, int pid)" |
2676 | .IX Item "ev_child_init (ev_child *, callback, int pid, int trace)" |
1228 | .PD 0 |
2677 | .PD 0 |
1229 | .IP "ev_child_set (ev_child *, int pid)" 4 |
2678 | .IP "ev_child_set (ev_child *, int pid, int trace)" 4 |
1230 | .IX Item "ev_child_set (ev_child *, int pid)" |
2679 | .IX Item "ev_child_set (ev_child *, int pid, int trace)" |
1231 | .PD |
2680 | .PD |
1232 | Configures the watcher to wait for status changes of process \f(CW\*(C`pid\*(C'\fR (or |
2681 | Configures the watcher to wait for status changes of process \f(CW\*(C`pid\*(C'\fR (or |
1233 | \&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look |
2682 | \&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look |
1234 | at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see |
2683 | at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see |
1235 | the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems |
2684 | the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems |
1236 | \&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the |
2685 | \&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the |
1237 | process causing the status change. |
2686 | process causing the status change. \f(CW\*(C`trace\*(C'\fR must be either \f(CW0\fR (only |
|
|
2687 | activate the watcher when the process terminates) or \f(CW1\fR (additionally |
|
|
2688 | activate the watcher when the process is stopped or continued). |
1238 | .IP "int pid [read\-only]" 4 |
2689 | .IP "int pid [read\-only]" 4 |
1239 | .IX Item "int pid [read-only]" |
2690 | .IX Item "int pid [read-only]" |
1240 | The process id this watcher watches out for, or \f(CW0\fR, meaning any process id. |
2691 | The process id this watcher watches out for, or \f(CW0\fR, meaning any process id. |
1241 | .IP "int rpid [read\-write]" 4 |
2692 | .IP "int rpid [read\-write]" 4 |
1242 | .IX Item "int rpid [read-write]" |
2693 | .IX Item "int rpid [read-write]" |
… | |
… | |
1244 | .IP "int rstatus [read\-write]" 4 |
2695 | .IP "int rstatus [read\-write]" 4 |
1245 | .IX Item "int rstatus [read-write]" |
2696 | .IX Item "int rstatus [read-write]" |
1246 | The process exit/trace status caused by \f(CW\*(C`rpid\*(C'\fR (see your systems |
2697 | The process exit/trace status caused by \f(CW\*(C`rpid\*(C'\fR (see your systems |
1247 | \&\f(CW\*(C`waitpid\*(C'\fR and \f(CW\*(C`sys/wait.h\*(C'\fR documentation for details). |
2698 | \&\f(CW\*(C`waitpid\*(C'\fR and \f(CW\*(C`sys/wait.h\*(C'\fR documentation for details). |
1248 | .PP |
2699 | .PP |
1249 | Example: try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0. |
2700 | \fIExamples\fR |
|
|
2701 | .IX Subsection "Examples" |
1250 | .PP |
2702 | .PP |
|
|
2703 | Example: \f(CW\*(C`fork()\*(C'\fR a new process and install a child handler to wait for |
|
|
2704 | its completion. |
|
|
2705 | .PP |
1251 | .Vb 5 |
2706 | .Vb 1 |
|
|
2707 | \& ev_child cw; |
|
|
2708 | \& |
1252 | \& static void |
2709 | \& static void |
1253 | \& sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
2710 | \& child_cb (EV_P_ ev_child *w, int revents) |
1254 | \& { |
2711 | \& { |
1255 | \& ev_unloop (loop, EVUNLOOP_ALL); |
2712 | \& ev_child_stop (EV_A_ w); |
|
|
2713 | \& printf ("process %d exited with status %x\en", w\->rpid, w\->rstatus); |
1256 | \& } |
2714 | \& } |
|
|
2715 | \& |
|
|
2716 | \& pid_t pid = fork (); |
|
|
2717 | \& |
|
|
2718 | \& if (pid < 0) |
|
|
2719 | \& // error |
|
|
2720 | \& else if (pid == 0) |
|
|
2721 | \& { |
|
|
2722 | \& // the forked child executes here |
|
|
2723 | \& exit (1); |
|
|
2724 | \& } |
|
|
2725 | \& else |
|
|
2726 | \& { |
|
|
2727 | \& ev_child_init (&cw, child_cb, pid, 0); |
|
|
2728 | \& ev_child_start (EV_DEFAULT_ &cw); |
|
|
2729 | \& } |
1257 | .Ve |
2730 | .Ve |
1258 | .PP |
|
|
1259 | .Vb 3 |
|
|
1260 | \& struct ev_signal signal_watcher; |
|
|
1261 | \& ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
|
|
1262 | \& ev_signal_start (loop, &sigint_cb); |
|
|
1263 | .Ve |
|
|
1264 | .ie n .Sh """ev_stat"" \- did the file attributes just change?" |
2731 | .ie n .SS """ev_stat"" \- did the file attributes just change?" |
1265 | .el .Sh "\f(CWev_stat\fP \- did the file attributes just change?" |
2732 | .el .SS "\f(CWev_stat\fP \- did the file attributes just change?" |
1266 | .IX Subsection "ev_stat - did the file attributes just change?" |
2733 | .IX Subsection "ev_stat - did the file attributes just change?" |
1267 | This watches a filesystem path for attribute changes. That is, it calls |
2734 | This watches a file system path for attribute changes. That is, it calls |
1268 | \&\f(CW\*(C`stat\*(C'\fR regularly (or when the \s-1OS\s0 says it changed) and sees if it changed |
2735 | \&\f(CW\*(C`stat\*(C'\fR on that path in regular intervals (or when the \s-1OS\s0 says it changed) |
1269 | compared to the last time, invoking the callback if it did. |
2736 | and sees if it changed compared to the last time, invoking the callback if |
|
|
2737 | it did. |
1270 | .PP |
2738 | .PP |
1271 | The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does |
2739 | The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does |
1272 | not exist\*(R" is a status change like any other. The condition \*(L"path does |
2740 | not exist\*(R" is a status change like any other. The condition \*(L"path does not |
1273 | not exist\*(R" is signified by the \f(CW\*(C`st_nlink\*(C'\fR field being zero (which is |
2741 | exist\*(R" (or more correctly \*(L"path cannot be stat'ed\*(R") is signified by the |
1274 | otherwise always forced to be at least one) and all the other fields of |
2742 | \&\f(CW\*(C`st_nlink\*(C'\fR field being zero (which is otherwise always forced to be at |
1275 | the stat buffer having unspecified contents. |
2743 | least one) and all the other fields of the stat buffer having unspecified |
|
|
2744 | contents. |
1276 | .PP |
2745 | .PP |
1277 | Since there is no standard to do this, the portable implementation simply |
2746 | The path \fImust not\fR end in a slash or contain special components such as |
1278 | calls \f(CW\*(C`stat (2)\*(C'\fR regulalry on the path to see if it changed somehow. You |
2747 | \&\f(CW\*(C`.\*(C'\fR or \f(CW\*(C`..\*(C'\fR. The path \fIshould\fR be absolute: If it is relative and |
1279 | can specify a recommended polling interval for this case. If you specify |
2748 | your working directory changes, then the behaviour is undefined. |
1280 | a polling interval of \f(CW0\fR (highly recommended!) then a \fIsuitable, |
2749 | .PP |
1281 | unspecified default\fR value will be used (which you can expect to be around |
2750 | Since there is no portable change notification interface available, the |
1282 | five seconds, although this might change dynamically). Libev will also |
2751 | portable implementation simply calls \f(CWstat(2)\fR regularly on the path |
1283 | impose a minimum interval which is currently around \f(CW0.1\fR, but thats |
2752 | to see if it changed somehow. You can specify a recommended polling |
1284 | usually overkill. |
2753 | interval for this case. If you specify a polling interval of \f(CW0\fR (highly |
|
|
2754 | recommended!) then a \fIsuitable, unspecified default\fR value will be used |
|
|
2755 | (which you can expect to be around five seconds, although this might |
|
|
2756 | change dynamically). Libev will also impose a minimum interval which is |
|
|
2757 | currently around \f(CW0.1\fR, but that's usually overkill. |
1285 | .PP |
2758 | .PP |
1286 | This watcher type is not meant for massive numbers of stat watchers, |
2759 | This watcher type is not meant for massive numbers of stat watchers, |
1287 | as even with OS-supported change notifications, this can be |
2760 | as even with OS-supported change notifications, this can be |
1288 | resource\-intensive. |
2761 | resource-intensive. |
1289 | .PP |
2762 | .PP |
1290 | At the time of this writing, no specific \s-1OS\s0 backends are implemented, but |
2763 | At the time of this writing, the only OS-specific interface implemented |
1291 | if demand increases, at least a kqueue and inotify backend will be added. |
2764 | is the Linux inotify interface (implementing kqueue support is left as an |
|
|
2765 | exercise for the reader. Note, however, that the author sees no way of |
|
|
2766 | implementing \f(CW\*(C`ev_stat\*(C'\fR semantics with kqueue, except as a hint). |
|
|
2767 | .PP |
|
|
2768 | \fI\s-1ABI\s0 Issues (Largefile Support)\fR |
|
|
2769 | .IX Subsection "ABI Issues (Largefile Support)" |
|
|
2770 | .PP |
|
|
2771 | Libev by default (unless the user overrides this) uses the default |
|
|
2772 | compilation environment, which means that on systems with large file |
|
|
2773 | support disabled by default, you get the 32 bit version of the stat |
|
|
2774 | structure. When using the library from programs that change the \s-1ABI\s0 to |
|
|
2775 | use 64 bit file offsets the programs will fail. In that case you have to |
|
|
2776 | compile libev with the same flags to get binary compatibility. This is |
|
|
2777 | obviously the case with any flags that change the \s-1ABI\s0, but the problem is |
|
|
2778 | most noticeably displayed with ev_stat and large file support. |
|
|
2779 | .PP |
|
|
2780 | The solution for this is to lobby your distribution maker to make large |
|
|
2781 | file interfaces available by default (as e.g. FreeBSD does) and not |
|
|
2782 | optional. Libev cannot simply switch on large file support because it has |
|
|
2783 | to exchange stat structures with application programs compiled using the |
|
|
2784 | default compilation environment. |
|
|
2785 | .PP |
|
|
2786 | \fIInotify and Kqueue\fR |
|
|
2787 | .IX Subsection "Inotify and Kqueue" |
|
|
2788 | .PP |
|
|
2789 | When \f(CW\*(C`inotify (7)\*(C'\fR support has been compiled into libev and present at |
|
|
2790 | runtime, it will be used to speed up change detection where possible. The |
|
|
2791 | inotify descriptor will be created lazily when the first \f(CW\*(C`ev_stat\*(C'\fR |
|
|
2792 | watcher is being started. |
|
|
2793 | .PP |
|
|
2794 | Inotify presence does not change the semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers |
|
|
2795 | except that changes might be detected earlier, and in some cases, to avoid |
|
|
2796 | making regular \f(CW\*(C`stat\*(C'\fR calls. Even in the presence of inotify support |
|
|
2797 | there are many cases where libev has to resort to regular \f(CW\*(C`stat\*(C'\fR polling, |
|
|
2798 | but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too |
|
|
2799 | many bugs), the path exists (i.e. stat succeeds), and the path resides on |
|
|
2800 | a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and |
|
|
2801 | xfs are fully working) libev usually gets away without polling. |
|
|
2802 | .PP |
|
|
2803 | There is no support for kqueue, as apparently it cannot be used to |
|
|
2804 | implement this functionality, due to the requirement of having a file |
|
|
2805 | descriptor open on the object at all times, and detecting renames, unlinks |
|
|
2806 | etc. is difficult. |
|
|
2807 | .PP |
|
|
2808 | \fI\f(CI\*(C`stat ()\*(C'\fI is a synchronous operation\fR |
|
|
2809 | .IX Subsection "stat () is a synchronous operation" |
|
|
2810 | .PP |
|
|
2811 | Libev doesn't normally do any kind of I/O itself, and so is not blocking |
|
|
2812 | the process. The exception are \f(CW\*(C`ev_stat\*(C'\fR watchers \- those call \f(CW\*(C`stat |
|
|
2813 | ()\*(C'\fR, which is a synchronous operation. |
|
|
2814 | .PP |
|
|
2815 | For local paths, this usually doesn't matter: unless the system is very |
|
|
2816 | busy or the intervals between stat's are large, a stat call will be fast, |
|
|
2817 | as the path data is usually in memory already (except when starting the |
|
|
2818 | watcher). |
|
|
2819 | .PP |
|
|
2820 | For networked file systems, calling \f(CW\*(C`stat ()\*(C'\fR can block an indefinite |
|
|
2821 | time due to network issues, and even under good conditions, a stat call |
|
|
2822 | often takes multiple milliseconds. |
|
|
2823 | .PP |
|
|
2824 | Therefore, it is best to avoid using \f(CW\*(C`ev_stat\*(C'\fR watchers on networked |
|
|
2825 | paths, although this is fully supported by libev. |
|
|
2826 | .PP |
|
|
2827 | \fIThe special problem of stat time resolution\fR |
|
|
2828 | .IX Subsection "The special problem of stat time resolution" |
|
|
2829 | .PP |
|
|
2830 | The \f(CW\*(C`stat ()\*(C'\fR system call only supports full-second resolution portably, |
|
|
2831 | and even on systems where the resolution is higher, most file systems |
|
|
2832 | still only support whole seconds. |
|
|
2833 | .PP |
|
|
2834 | That means that, if the time is the only thing that changes, you can |
|
|
2835 | easily miss updates: on the first update, \f(CW\*(C`ev_stat\*(C'\fR detects a change and |
|
|
2836 | calls your callback, which does something. When there is another update |
|
|
2837 | within the same second, \f(CW\*(C`ev_stat\*(C'\fR will be unable to detect unless the |
|
|
2838 | stat data does change in other ways (e.g. file size). |
|
|
2839 | .PP |
|
|
2840 | The solution to this is to delay acting on a change for slightly more |
|
|
2841 | than a second (or till slightly after the next full second boundary), using |
|
|
2842 | a roughly one-second-delay \f(CW\*(C`ev_timer\*(C'\fR (e.g. \f(CW\*(C`ev_timer_set (w, 0., 1.02); |
|
|
2843 | ev_timer_again (loop, w)\*(C'\fR). |
|
|
2844 | .PP |
|
|
2845 | The \f(CW.02\fR offset is added to work around small timing inconsistencies |
|
|
2846 | of some operating systems (where the second counter of the current time |
|
|
2847 | might be be delayed. One such system is the Linux kernel, where a call to |
|
|
2848 | \&\f(CW\*(C`gettimeofday\*(C'\fR might return a timestamp with a full second later than |
|
|
2849 | a subsequent \f(CW\*(C`time\*(C'\fR call \- if the equivalent of \f(CW\*(C`time ()\*(C'\fR is used to |
|
|
2850 | update file times then there will be a small window where the kernel uses |
|
|
2851 | the previous second to update file times but libev might already execute |
|
|
2852 | the timer callback). |
|
|
2853 | .PP |
|
|
2854 | \fIWatcher-Specific Functions and Data Members\fR |
|
|
2855 | .IX Subsection "Watcher-Specific Functions and Data Members" |
1292 | .IP "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 4 |
2856 | .IP "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 4 |
1293 | .IX Item "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" |
2857 | .IX Item "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" |
1294 | .PD 0 |
2858 | .PD 0 |
1295 | .IP "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" 4 |
2859 | .IP "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" 4 |
1296 | .IX Item "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" |
2860 | .IX Item "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" |
… | |
… | |
1299 | \&\f(CW\*(C`path\*(C'\fR. The \f(CW\*(C`interval\*(C'\fR is a hint on how quickly a change is expected to |
2863 | \&\f(CW\*(C`path\*(C'\fR. The \f(CW\*(C`interval\*(C'\fR is a hint on how quickly a change is expected to |
1300 | be detected and should normally be specified as \f(CW0\fR to let libev choose |
2864 | be detected and should normally be specified as \f(CW0\fR to let libev choose |
1301 | a suitable value. The memory pointed to by \f(CW\*(C`path\*(C'\fR must point to the same |
2865 | a suitable value. The memory pointed to by \f(CW\*(C`path\*(C'\fR must point to the same |
1302 | path for as long as the watcher is active. |
2866 | path for as long as the watcher is active. |
1303 | .Sp |
2867 | .Sp |
1304 | The callback will be receive \f(CW\*(C`EV_STAT\*(C'\fR when a change was detected, |
2868 | The callback will receive an \f(CW\*(C`EV_STAT\*(C'\fR event when a change was detected, |
1305 | relative to the attributes at the time the watcher was started (or the |
2869 | relative to the attributes at the time the watcher was started (or the |
1306 | last change was detected). |
2870 | last change was detected). |
1307 | .IP "ev_stat_stat (ev_stat *)" 4 |
2871 | .IP "ev_stat_stat (loop, ev_stat *)" 4 |
1308 | .IX Item "ev_stat_stat (ev_stat *)" |
2872 | .IX Item "ev_stat_stat (loop, ev_stat *)" |
1309 | Updates the stat buffer immediately with new values. If you change the |
2873 | Updates the stat buffer immediately with new values. If you change the |
1310 | watched path in your callback, you could call this fucntion to avoid |
2874 | watched path in your callback, you could call this function to avoid |
1311 | detecting this change (while introducing a race condition). Can also be |
2875 | detecting this change (while introducing a race condition if you are not |
1312 | useful simply to find out the new values. |
2876 | the only one changing the path). Can also be useful simply to find out the |
|
|
2877 | new values. |
1313 | .IP "ev_statdata attr [read\-only]" 4 |
2878 | .IP "ev_statdata attr [read\-only]" 4 |
1314 | .IX Item "ev_statdata attr [read-only]" |
2879 | .IX Item "ev_statdata attr [read-only]" |
1315 | The most-recently detected attributes of the file. Although the type is of |
2880 | The most-recently detected attributes of the file. Although the type is |
1316 | \&\f(CW\*(C`ev_statdata\*(C'\fR, this is usually the (or one of the) \f(CW\*(C`struct stat\*(C'\fR types |
2881 | \&\f(CW\*(C`ev_statdata\*(C'\fR, this is usually the (or one of the) \f(CW\*(C`struct stat\*(C'\fR types |
|
|
2882 | suitable for your system, but you can only rely on the POSIX-standardised |
1317 | suitable for your system. If the \f(CW\*(C`st_nlink\*(C'\fR member is \f(CW0\fR, then there |
2883 | members to be present. If the \f(CW\*(C`st_nlink\*(C'\fR member is \f(CW0\fR, then there was |
1318 | was some error while \f(CW\*(C`stat\*(C'\fRing the file. |
2884 | some error while \f(CW\*(C`stat\*(C'\fRing the file. |
1319 | .IP "ev_statdata prev [read\-only]" 4 |
2885 | .IP "ev_statdata prev [read\-only]" 4 |
1320 | .IX Item "ev_statdata prev [read-only]" |
2886 | .IX Item "ev_statdata prev [read-only]" |
1321 | The previous attributes of the file. The callback gets invoked whenever |
2887 | The previous attributes of the file. The callback gets invoked whenever |
1322 | \&\f(CW\*(C`prev\*(C'\fR != \f(CW\*(C`attr\*(C'\fR. |
2888 | \&\f(CW\*(C`prev\*(C'\fR != \f(CW\*(C`attr\*(C'\fR, or, more precisely, one or more of these members |
|
|
2889 | differ: \f(CW\*(C`st_dev\*(C'\fR, \f(CW\*(C`st_ino\*(C'\fR, \f(CW\*(C`st_mode\*(C'\fR, \f(CW\*(C`st_nlink\*(C'\fR, \f(CW\*(C`st_uid\*(C'\fR, |
|
|
2890 | \&\f(CW\*(C`st_gid\*(C'\fR, \f(CW\*(C`st_rdev\*(C'\fR, \f(CW\*(C`st_size\*(C'\fR, \f(CW\*(C`st_atime\*(C'\fR, \f(CW\*(C`st_mtime\*(C'\fR, \f(CW\*(C`st_ctime\*(C'\fR. |
1323 | .IP "ev_tstamp interval [read\-only]" 4 |
2891 | .IP "ev_tstamp interval [read\-only]" 4 |
1324 | .IX Item "ev_tstamp interval [read-only]" |
2892 | .IX Item "ev_tstamp interval [read-only]" |
1325 | The specified interval. |
2893 | The specified interval. |
1326 | .IP "const char *path [read\-only]" 4 |
2894 | .IP "const char *path [read\-only]" 4 |
1327 | .IX Item "const char *path [read-only]" |
2895 | .IX Item "const char *path [read-only]" |
1328 | The filesystem path that is being watched. |
2896 | The file system path that is being watched. |
|
|
2897 | .PP |
|
|
2898 | \fIExamples\fR |
|
|
2899 | .IX Subsection "Examples" |
1329 | .PP |
2900 | .PP |
1330 | Example: Watch \f(CW\*(C`/etc/passwd\*(C'\fR for attribute changes. |
2901 | Example: Watch \f(CW\*(C`/etc/passwd\*(C'\fR for attribute changes. |
1331 | .PP |
2902 | .PP |
1332 | .Vb 15 |
2903 | .Vb 10 |
1333 | \& static void |
2904 | \& static void |
1334 | \& passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) |
2905 | \& passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) |
1335 | \& { |
2906 | \& { |
1336 | \& /* /etc/passwd changed in some way */ |
2907 | \& /* /etc/passwd changed in some way */ |
1337 | \& if (w->attr.st_nlink) |
2908 | \& if (w\->attr.st_nlink) |
1338 | \& { |
2909 | \& { |
1339 | \& printf ("passwd current size %ld\en", (long)w->attr.st_size); |
2910 | \& printf ("passwd current size %ld\en", (long)w\->attr.st_size); |
1340 | \& printf ("passwd current atime %ld\en", (long)w->attr.st_mtime); |
2911 | \& printf ("passwd current atime %ld\en", (long)w\->attr.st_mtime); |
1341 | \& printf ("passwd current mtime %ld\en", (long)w->attr.st_mtime); |
2912 | \& printf ("passwd current mtime %ld\en", (long)w\->attr.st_mtime); |
1342 | \& } |
2913 | \& } |
1343 | \& else |
2914 | \& else |
1344 | \& /* you shalt not abuse printf for puts */ |
2915 | \& /* you shalt not abuse printf for puts */ |
1345 | \& puts ("wow, /etc/passwd is not there, expect problems. " |
2916 | \& puts ("wow, /etc/passwd is not there, expect problems. " |
1346 | \& "if this is windows, they already arrived\en"); |
2917 | \& "if this is windows, they already arrived\en"); |
1347 | \& } |
2918 | \& } |
|
|
2919 | \& |
|
|
2920 | \& ... |
|
|
2921 | \& ev_stat passwd; |
|
|
2922 | \& |
|
|
2923 | \& ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.); |
|
|
2924 | \& ev_stat_start (loop, &passwd); |
1348 | .Ve |
2925 | .Ve |
|
|
2926 | .PP |
|
|
2927 | Example: Like above, but additionally use a one-second delay so we do not |
|
|
2928 | miss updates (however, frequent updates will delay processing, too, so |
|
|
2929 | one might do the work both on \f(CW\*(C`ev_stat\*(C'\fR callback invocation \fIand\fR on |
|
|
2930 | \&\f(CW\*(C`ev_timer\*(C'\fR callback invocation). |
1349 | .PP |
2931 | .PP |
1350 | .Vb 2 |
2932 | .Vb 2 |
|
|
2933 | \& static ev_stat passwd; |
|
|
2934 | \& static ev_timer timer; |
|
|
2935 | \& |
|
|
2936 | \& static void |
|
|
2937 | \& timer_cb (EV_P_ ev_timer *w, int revents) |
|
|
2938 | \& { |
|
|
2939 | \& ev_timer_stop (EV_A_ w); |
|
|
2940 | \& |
|
|
2941 | \& /* now it\*(Aqs one second after the most recent passwd change */ |
|
|
2942 | \& } |
|
|
2943 | \& |
|
|
2944 | \& static void |
|
|
2945 | \& stat_cb (EV_P_ ev_stat *w, int revents) |
|
|
2946 | \& { |
|
|
2947 | \& /* reset the one\-second timer */ |
|
|
2948 | \& ev_timer_again (EV_A_ &timer); |
|
|
2949 | \& } |
|
|
2950 | \& |
1351 | \& ... |
2951 | \& ... |
1352 | \& ev_stat passwd; |
|
|
1353 | .Ve |
|
|
1354 | .PP |
|
|
1355 | .Vb 2 |
|
|
1356 | \& ev_stat_init (&passwd, passwd_cb, "/etc/passwd"); |
2952 | \& ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
1357 | \& ev_stat_start (loop, &passwd); |
2953 | \& ev_stat_start (loop, &passwd); |
|
|
2954 | \& ev_timer_init (&timer, timer_cb, 0., 1.02); |
1358 | .Ve |
2955 | .Ve |
1359 | .ie n .Sh """ev_idle"" \- when you've got nothing better to do..." |
2956 | .ie n .SS """ev_idle"" \- when you've got nothing better to do..." |
1360 | .el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do..." |
2957 | .el .SS "\f(CWev_idle\fP \- when you've got nothing better to do..." |
1361 | .IX Subsection "ev_idle - when you've got nothing better to do..." |
2958 | .IX Subsection "ev_idle - when you've got nothing better to do..." |
1362 | Idle watchers trigger events when there are no other events are pending |
2959 | Idle watchers trigger events when no other events of the same or higher |
1363 | (prepare, check and other idle watchers do not count). That is, as long |
2960 | priority are pending (prepare, check and other idle watchers do not count |
1364 | as your process is busy handling sockets or timeouts (or even signals, |
2961 | as receiving \*(L"events\*(R"). |
1365 | imagine) it will not be triggered. But when your process is idle all idle |
2962 | .PP |
1366 | watchers are being called again and again, once per event loop iteration \- |
2963 | That is, as long as your process is busy handling sockets or timeouts |
|
|
2964 | (or even signals, imagine) of the same or higher priority it will not be |
|
|
2965 | triggered. But when your process is idle (or only lower-priority watchers |
|
|
2966 | are pending), the idle watchers are being called once per event loop |
1367 | until stopped, that is, or your process receives more events and becomes |
2967 | iteration \- until stopped, that is, or your process receives more events |
1368 | busy. |
2968 | and becomes busy again with higher priority stuff. |
1369 | .PP |
2969 | .PP |
1370 | The most noteworthy effect is that as long as any idle watchers are |
2970 | The most noteworthy effect is that as long as any idle watchers are |
1371 | active, the process will not block when waiting for new events. |
2971 | active, the process will not block when waiting for new events. |
1372 | .PP |
2972 | .PP |
1373 | Apart from keeping your process non-blocking (which is a useful |
2973 | Apart from keeping your process non-blocking (which is a useful |
1374 | effect on its own sometimes), idle watchers are a good place to do |
2974 | effect on its own sometimes), idle watchers are a good place to do |
1375 | \&\*(L"pseudo\-background processing\*(R", or delay processing stuff to after the |
2975 | \&\*(L"pseudo-background processing\*(R", or delay processing stuff to after the |
1376 | event loop has handled all outstanding events. |
2976 | event loop has handled all outstanding events. |
|
|
2977 | .PP |
|
|
2978 | \fIWatcher-Specific Functions and Data Members\fR |
|
|
2979 | .IX Subsection "Watcher-Specific Functions and Data Members" |
1377 | .IP "ev_idle_init (ev_signal *, callback)" 4 |
2980 | .IP "ev_idle_init (ev_idle *, callback)" 4 |
1378 | .IX Item "ev_idle_init (ev_signal *, callback)" |
2981 | .IX Item "ev_idle_init (ev_idle *, callback)" |
1379 | Initialises and configures the idle watcher \- it has no parameters of any |
2982 | Initialises and configures the idle watcher \- it has no parameters of any |
1380 | kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless, |
2983 | kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless, |
1381 | believe me. |
2984 | believe me. |
1382 | .PP |
2985 | .PP |
|
|
2986 | \fIExamples\fR |
|
|
2987 | .IX Subsection "Examples" |
|
|
2988 | .PP |
1383 | Example: dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR, start it, and in the |
2989 | Example: Dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR watcher, start it, and in the |
1384 | callback, free it. Alos, use no error checking, as usual. |
2990 | callback, free it. Also, use no error checking, as usual. |
1385 | .PP |
2991 | .PP |
1386 | .Vb 7 |
2992 | .Vb 7 |
1387 | \& static void |
2993 | \& static void |
1388 | \& idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
2994 | \& idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
1389 | \& { |
2995 | \& { |
1390 | \& free (w); |
2996 | \& free (w); |
1391 | \& // now do something you wanted to do when the program has |
2997 | \& // now do something you wanted to do when the program has |
1392 | \& // no longer asnything immediate to do. |
2998 | \& // no longer anything immediate to do. |
1393 | \& } |
2999 | \& } |
1394 | .Ve |
3000 | \& |
1395 | .PP |
|
|
1396 | .Vb 3 |
|
|
1397 | \& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
3001 | \& ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
1398 | \& ev_idle_init (idle_watcher, idle_cb); |
3002 | \& ev_idle_init (idle_watcher, idle_cb); |
1399 | \& ev_idle_start (loop, idle_cb); |
3003 | \& ev_idle_start (loop, idle_watcher); |
1400 | .Ve |
3004 | .Ve |
1401 | .ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop!" |
3005 | .ie n .SS """ev_prepare"" and ""ev_check"" \- customise your event loop!" |
1402 | .el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!" |
3006 | .el .SS "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!" |
1403 | .IX Subsection "ev_prepare and ev_check - customise your event loop!" |
3007 | .IX Subsection "ev_prepare and ev_check - customise your event loop!" |
1404 | Prepare and check watchers are usually (but not always) used in tandem: |
3008 | Prepare and check watchers are usually (but not always) used in pairs: |
1405 | prepare watchers get invoked before the process blocks and check watchers |
3009 | prepare watchers get invoked before the process blocks and check watchers |
1406 | afterwards. |
3010 | afterwards. |
1407 | .PP |
3011 | .PP |
1408 | You \fImust not\fR call \f(CW\*(C`ev_loop\*(C'\fR or similar functions that enter |
3012 | You \fImust not\fR call \f(CW\*(C`ev_run\*(C'\fR or similar functions that enter |
1409 | the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR |
3013 | the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR |
1410 | watchers. Other loops than the current one are fine, however. The |
3014 | watchers. Other loops than the current one are fine, however. The |
1411 | rationale behind this is that you do not need to check for recursion in |
3015 | rationale behind this is that you do not need to check for recursion in |
1412 | those watchers, i.e. the sequence will always be \f(CW\*(C`ev_prepare\*(C'\fR, blocking, |
3016 | those watchers, i.e. the sequence will always be \f(CW\*(C`ev_prepare\*(C'\fR, blocking, |
1413 | \&\f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each kind they will always be |
3017 | \&\f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each kind they will always be |
1414 | called in pairs bracketing the blocking call. |
3018 | called in pairs bracketing the blocking call. |
1415 | .PP |
3019 | .PP |
1416 | Their main purpose is to integrate other event mechanisms into libev and |
3020 | Their main purpose is to integrate other event mechanisms into libev and |
1417 | their use is somewhat advanced. This could be used, for example, to track |
3021 | their use is somewhat advanced. They could be used, for example, to track |
1418 | variable changes, implement your own watchers, integrate net-snmp or a |
3022 | variable changes, implement your own watchers, integrate net-snmp or a |
1419 | coroutine library and lots more. They are also occasionally useful if |
3023 | coroutine library and lots more. They are also occasionally useful if |
1420 | you cache some data and want to flush it before blocking (for example, |
3024 | you cache some data and want to flush it before blocking (for example, |
1421 | in X programs you might want to do an \f(CW\*(C`XFlush ()\*(C'\fR in an \f(CW\*(C`ev_prepare\*(C'\fR |
3025 | in X programs you might want to do an \f(CW\*(C`XFlush ()\*(C'\fR in an \f(CW\*(C`ev_prepare\*(C'\fR |
1422 | watcher). |
3026 | watcher). |
1423 | .PP |
3027 | .PP |
1424 | This is done by examining in each prepare call which file descriptors need |
3028 | This is done by examining in each prepare call which file descriptors |
1425 | to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for |
3029 | need to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers |
1426 | them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries |
3030 | for them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many |
1427 | provide just this functionality). Then, in the check watcher you check for |
3031 | libraries provide exactly this functionality). Then, in the check watcher, |
1428 | any events that occured (by checking the pending status of all watchers |
3032 | you check for any events that occurred (by checking the pending status |
1429 | and stopping them) and call back into the library. The I/O and timer |
3033 | of all watchers and stopping them) and call back into the library. The |
1430 | callbacks will never actually be called (but must be valid nevertheless, |
3034 | I/O and timer callbacks will never actually be called (but must be valid |
1431 | because you never know, you know?). |
3035 | nevertheless, because you never know, you know?). |
1432 | .PP |
3036 | .PP |
1433 | As another example, the Perl Coro module uses these hooks to integrate |
3037 | As another example, the Perl Coro module uses these hooks to integrate |
1434 | coroutines into libev programs, by yielding to other active coroutines |
3038 | coroutines into libev programs, by yielding to other active coroutines |
1435 | during each prepare and only letting the process block if no coroutines |
3039 | during each prepare and only letting the process block if no coroutines |
1436 | are ready to run (it's actually more complicated: it only runs coroutines |
3040 | are ready to run (it's actually more complicated: it only runs coroutines |
1437 | with priority higher than or equal to the event loop and one coroutine |
3041 | with priority higher than or equal to the event loop and one coroutine |
1438 | of lower priority, but only once, using idle watchers to keep the event |
3042 | of lower priority, but only once, using idle watchers to keep the event |
1439 | loop from blocking if lower-priority coroutines are active, thus mapping |
3043 | loop from blocking if lower-priority coroutines are active, thus mapping |
1440 | low-priority coroutines to idle/background tasks). |
3044 | low-priority coroutines to idle/background tasks). |
|
|
3045 | .PP |
|
|
3046 | It is recommended to give \f(CW\*(C`ev_check\*(C'\fR watchers highest (\f(CW\*(C`EV_MAXPRI\*(C'\fR) |
|
|
3047 | priority, to ensure that they are being run before any other watchers |
|
|
3048 | after the poll (this doesn't matter for \f(CW\*(C`ev_prepare\*(C'\fR watchers). |
|
|
3049 | .PP |
|
|
3050 | Also, \f(CW\*(C`ev_check\*(C'\fR watchers (and \f(CW\*(C`ev_prepare\*(C'\fR watchers, too) should not |
|
|
3051 | activate (\*(L"feed\*(R") events into libev. While libev fully supports this, they |
|
|
3052 | might get executed before other \f(CW\*(C`ev_check\*(C'\fR watchers did their job. As |
|
|
3053 | \&\f(CW\*(C`ev_check\*(C'\fR watchers are often used to embed other (non-libev) event |
|
|
3054 | loops those other event loops might be in an unusable state until their |
|
|
3055 | \&\f(CW\*(C`ev_check\*(C'\fR watcher ran (always remind yourself to coexist peacefully with |
|
|
3056 | others). |
|
|
3057 | .PP |
|
|
3058 | \fIWatcher-Specific Functions and Data Members\fR |
|
|
3059 | .IX Subsection "Watcher-Specific Functions and Data Members" |
1441 | .IP "ev_prepare_init (ev_prepare *, callback)" 4 |
3060 | .IP "ev_prepare_init (ev_prepare *, callback)" 4 |
1442 | .IX Item "ev_prepare_init (ev_prepare *, callback)" |
3061 | .IX Item "ev_prepare_init (ev_prepare *, callback)" |
1443 | .PD 0 |
3062 | .PD 0 |
1444 | .IP "ev_check_init (ev_check *, callback)" 4 |
3063 | .IP "ev_check_init (ev_check *, callback)" 4 |
1445 | .IX Item "ev_check_init (ev_check *, callback)" |
3064 | .IX Item "ev_check_init (ev_check *, callback)" |
1446 | .PD |
3065 | .PD |
1447 | Initialises and configures the prepare or check watcher \- they have no |
3066 | Initialises and configures the prepare or check watcher \- they have no |
1448 | parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR |
3067 | parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR |
1449 | macros, but using them is utterly, utterly and completely pointless. |
3068 | macros, but using them is utterly, utterly, utterly and completely |
|
|
3069 | pointless. |
1450 | .PP |
3070 | .PP |
1451 | Example: To include a library such as adns, you would add \s-1IO\s0 watchers |
3071 | \fIExamples\fR |
1452 | and a timeout watcher in a prepare handler, as required by libadns, and |
3072 | .IX Subsection "Examples" |
|
|
3073 | .PP |
|
|
3074 | There are a number of principal ways to embed other event loops or modules |
|
|
3075 | into libev. Here are some ideas on how to include libadns into libev |
|
|
3076 | (there is a Perl module named \f(CW\*(C`EV::ADNS\*(C'\fR that does this, which you could |
|
|
3077 | use as a working example. Another Perl module named \f(CW\*(C`EV::Glib\*(C'\fR embeds a |
|
|
3078 | Glib main context into libev, and finally, \f(CW\*(C`Glib::EV\*(C'\fR embeds \s-1EV\s0 into the |
|
|
3079 | Glib event loop). |
|
|
3080 | .PP |
|
|
3081 | Method 1: Add \s-1IO\s0 watchers and a timeout watcher in a prepare handler, |
1453 | in a check watcher, destroy them and call into libadns. What follows is |
3082 | and in a check watcher, destroy them and call into libadns. What follows |
1454 | pseudo-code only of course: |
3083 | is pseudo-code only of course. This requires you to either use a low |
|
|
3084 | priority for the check watcher or use \f(CW\*(C`ev_clear_pending\*(C'\fR explicitly, as |
|
|
3085 | the callbacks for the IO/timeout watchers might not have been called yet. |
1455 | .PP |
3086 | .PP |
1456 | .Vb 2 |
3087 | .Vb 2 |
1457 | \& static ev_io iow [nfd]; |
3088 | \& static ev_io iow [nfd]; |
1458 | \& static ev_timer tw; |
3089 | \& static ev_timer tw; |
1459 | .Ve |
3090 | \& |
1460 | .PP |
|
|
1461 | .Vb 9 |
|
|
1462 | \& static void |
3091 | \& static void |
1463 | \& io_cb (ev_loop *loop, ev_io *w, int revents) |
3092 | \& io_cb (struct ev_loop *loop, ev_io *w, int revents) |
1464 | \& { |
3093 | \& { |
1465 | \& // set the relevant poll flags |
|
|
1466 | \& // could also call adns_processreadable etc. here |
|
|
1467 | \& struct pollfd *fd = (struct pollfd *)w->data; |
|
|
1468 | \& if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; |
|
|
1469 | \& if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; |
|
|
1470 | \& } |
3094 | \& } |
1471 | .Ve |
3095 | \& |
1472 | .PP |
|
|
1473 | .Vb 7 |
|
|
1474 | \& // create io watchers for each fd and a timer before blocking |
3096 | \& // create io watchers for each fd and a timer before blocking |
1475 | \& static void |
3097 | \& static void |
1476 | \& adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
3098 | \& adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents) |
1477 | \& { |
3099 | \& { |
1478 | \& int timeout = 3600000;truct pollfd fds [nfd]; |
3100 | \& int timeout = 3600000; |
|
|
3101 | \& struct pollfd fds [nfd]; |
1479 | \& // actual code will need to loop here and realloc etc. |
3102 | \& // actual code will need to loop here and realloc etc. |
1480 | \& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
3103 | \& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
1481 | .Ve |
3104 | \& |
1482 | .PP |
|
|
1483 | .Vb 3 |
|
|
1484 | \& /* the callback is illegal, but won't be called as we stop during check */ |
3105 | \& /* the callback is illegal, but won\*(Aqt be called as we stop during check */ |
1485 | \& ev_timer_init (&tw, 0, timeout * 1e-3); |
3106 | \& ev_timer_init (&tw, 0, timeout * 1e\-3, 0.); |
1486 | \& ev_timer_start (loop, &tw); |
3107 | \& ev_timer_start (loop, &tw); |
1487 | .Ve |
3108 | \& |
1488 | .PP |
|
|
1489 | .Vb 6 |
|
|
1490 | \& // create on ev_io per pollfd |
3109 | \& // create one ev_io per pollfd |
1491 | \& for (int i = 0; i < nfd; ++i) |
3110 | \& for (int i = 0; i < nfd; ++i) |
1492 | \& { |
3111 | \& { |
1493 | \& ev_io_init (iow + i, io_cb, fds [i].fd, |
3112 | \& ev_io_init (iow + i, io_cb, fds [i].fd, |
1494 | \& ((fds [i].events & POLLIN ? EV_READ : 0) |
3113 | \& ((fds [i].events & POLLIN ? EV_READ : 0) |
1495 | \& | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
3114 | \& | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
|
|
3115 | \& |
|
|
3116 | \& fds [i].revents = 0; |
|
|
3117 | \& ev_io_start (loop, iow + i); |
|
|
3118 | \& } |
|
|
3119 | \& } |
|
|
3120 | \& |
|
|
3121 | \& // stop all watchers after blocking |
|
|
3122 | \& static void |
|
|
3123 | \& adns_check_cb (struct ev_loop *loop, ev_check *w, int revents) |
|
|
3124 | \& { |
|
|
3125 | \& ev_timer_stop (loop, &tw); |
|
|
3126 | \& |
|
|
3127 | \& for (int i = 0; i < nfd; ++i) |
|
|
3128 | \& { |
|
|
3129 | \& // set the relevant poll flags |
|
|
3130 | \& // could also call adns_processreadable etc. here |
|
|
3131 | \& struct pollfd *fd = fds + i; |
|
|
3132 | \& int revents = ev_clear_pending (iow + i); |
|
|
3133 | \& if (revents & EV_READ ) fd\->revents |= fd\->events & POLLIN; |
|
|
3134 | \& if (revents & EV_WRITE) fd\->revents |= fd\->events & POLLOUT; |
|
|
3135 | \& |
|
|
3136 | \& // now stop the watcher |
|
|
3137 | \& ev_io_stop (loop, iow + i); |
|
|
3138 | \& } |
|
|
3139 | \& |
|
|
3140 | \& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
|
|
3141 | \& } |
1496 | .Ve |
3142 | .Ve |
|
|
3143 | .PP |
|
|
3144 | Method 2: This would be just like method 1, but you run \f(CW\*(C`adns_afterpoll\*(C'\fR |
|
|
3145 | in the prepare watcher and would dispose of the check watcher. |
|
|
3146 | .PP |
|
|
3147 | Method 3: If the module to be embedded supports explicit event |
|
|
3148 | notification (libadns does), you can also make use of the actual watcher |
|
|
3149 | callbacks, and only destroy/create the watchers in the prepare watcher. |
1497 | .PP |
3150 | .PP |
1498 | .Vb 5 |
3151 | .Vb 5 |
1499 | \& fds [i].revents = 0; |
|
|
1500 | \& iow [i].data = fds + i; |
|
|
1501 | \& ev_io_start (loop, iow + i); |
|
|
1502 | \& } |
|
|
1503 | \& } |
|
|
1504 | .Ve |
|
|
1505 | .PP |
|
|
1506 | .Vb 5 |
|
|
1507 | \& // stop all watchers after blocking |
|
|
1508 | \& static void |
3152 | \& static void |
1509 | \& adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
3153 | \& timer_cb (EV_P_ ev_timer *w, int revents) |
1510 | \& { |
3154 | \& { |
1511 | \& ev_timer_stop (loop, &tw); |
3155 | \& adns_state ads = (adns_state)w\->data; |
1512 | .Ve |
3156 | \& update_now (EV_A); |
1513 | .PP |
3157 | \& |
1514 | .Vb 2 |
3158 | \& adns_processtimeouts (ads, &tv_now); |
1515 | \& for (int i = 0; i < nfd; ++i) |
|
|
1516 | \& ev_io_stop (loop, iow + i); |
|
|
1517 | .Ve |
|
|
1518 | .PP |
|
|
1519 | .Vb 2 |
|
|
1520 | \& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
|
|
1521 | \& } |
3159 | \& } |
|
|
3160 | \& |
|
|
3161 | \& static void |
|
|
3162 | \& io_cb (EV_P_ ev_io *w, int revents) |
|
|
3163 | \& { |
|
|
3164 | \& adns_state ads = (adns_state)w\->data; |
|
|
3165 | \& update_now (EV_A); |
|
|
3166 | \& |
|
|
3167 | \& if (revents & EV_READ ) adns_processreadable (ads, w\->fd, &tv_now); |
|
|
3168 | \& if (revents & EV_WRITE) adns_processwriteable (ads, w\->fd, &tv_now); |
|
|
3169 | \& } |
|
|
3170 | \& |
|
|
3171 | \& // do not ever call adns_afterpoll |
1522 | .Ve |
3172 | .Ve |
|
|
3173 | .PP |
|
|
3174 | Method 4: Do not use a prepare or check watcher because the module you |
|
|
3175 | want to embed is not flexible enough to support it. Instead, you can |
|
|
3176 | override their poll function. The drawback with this solution is that the |
|
|
3177 | main loop is now no longer controllable by \s-1EV\s0. The \f(CW\*(C`Glib::EV\*(C'\fR module uses |
|
|
3178 | this approach, effectively embedding \s-1EV\s0 as a client into the horrible |
|
|
3179 | libglib event loop. |
|
|
3180 | .PP |
|
|
3181 | .Vb 4 |
|
|
3182 | \& static gint |
|
|
3183 | \& event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
|
|
3184 | \& { |
|
|
3185 | \& int got_events = 0; |
|
|
3186 | \& |
|
|
3187 | \& for (n = 0; n < nfds; ++n) |
|
|
3188 | \& // create/start io watcher that sets the relevant bits in fds[n] and increment got_events |
|
|
3189 | \& |
|
|
3190 | \& if (timeout >= 0) |
|
|
3191 | \& // create/start timer |
|
|
3192 | \& |
|
|
3193 | \& // poll |
|
|
3194 | \& ev_run (EV_A_ 0); |
|
|
3195 | \& |
|
|
3196 | \& // stop timer again |
|
|
3197 | \& if (timeout >= 0) |
|
|
3198 | \& ev_timer_stop (EV_A_ &to); |
|
|
3199 | \& |
|
|
3200 | \& // stop io watchers again \- their callbacks should have set |
|
|
3201 | \& for (n = 0; n < nfds; ++n) |
|
|
3202 | \& ev_io_stop (EV_A_ iow [n]); |
|
|
3203 | \& |
|
|
3204 | \& return got_events; |
|
|
3205 | \& } |
|
|
3206 | .Ve |
1523 | .ie n .Sh """ev_embed"" \- when one backend isn't enough..." |
3207 | .ie n .SS """ev_embed"" \- when one backend isn't enough..." |
1524 | .el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..." |
3208 | .el .SS "\f(CWev_embed\fP \- when one backend isn't enough..." |
1525 | .IX Subsection "ev_embed - when one backend isn't enough..." |
3209 | .IX Subsection "ev_embed - when one backend isn't enough..." |
1526 | This is a rather advanced watcher type that lets you embed one event loop |
3210 | This is a rather advanced watcher type that lets you embed one event loop |
1527 | into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded |
3211 | into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded |
1528 | loop, other types of watchers might be handled in a delayed or incorrect |
3212 | loop, other types of watchers might be handled in a delayed or incorrect |
1529 | fashion and must not be used). |
3213 | fashion and must not be used). |
… | |
… | |
1532 | prioritise I/O. |
3216 | prioritise I/O. |
1533 | .PP |
3217 | .PP |
1534 | As an example for a bug workaround, the kqueue backend might only support |
3218 | As an example for a bug workaround, the kqueue backend might only support |
1535 | sockets on some platform, so it is unusable as generic backend, but you |
3219 | sockets on some platform, so it is unusable as generic backend, but you |
1536 | still want to make use of it because you have many sockets and it scales |
3220 | still want to make use of it because you have many sockets and it scales |
1537 | so nicely. In this case, you would create a kqueue-based loop and embed it |
3221 | so nicely. In this case, you would create a kqueue-based loop and embed |
1538 | into your default loop (which might use e.g. poll). Overall operation will |
3222 | it into your default loop (which might use e.g. poll). Overall operation |
1539 | be a bit slower because first libev has to poll and then call kevent, but |
3223 | will be a bit slower because first libev has to call \f(CW\*(C`poll\*(C'\fR and then |
1540 | at least you can use both at what they are best. |
3224 | \&\f(CW\*(C`kevent\*(C'\fR, but at least you can use both mechanisms for what they are |
|
|
3225 | best: \f(CW\*(C`kqueue\*(C'\fR for scalable sockets and \f(CW\*(C`poll\*(C'\fR if you want it to work :) |
1541 | .PP |
3226 | .PP |
1542 | As for prioritising I/O: rarely you have the case where some fds have |
3227 | As for prioritising I/O: under rare circumstances you have the case where |
1543 | to be watched and handled very quickly (with low latency), and even |
3228 | some fds have to be watched and handled very quickly (with low latency), |
1544 | priorities and idle watchers might have too much overhead. In this case |
3229 | and even priorities and idle watchers might have too much overhead. In |
1545 | you would put all the high priority stuff in one loop and all the rest in |
3230 | this case you would put all the high priority stuff in one loop and all |
1546 | a second one, and embed the second one in the first. |
3231 | the rest in a second one, and embed the second one in the first. |
1547 | .PP |
3232 | .PP |
1548 | As long as the watcher is active, the callback will be invoked every time |
3233 | As long as the watcher is active, the callback will be invoked every |
1549 | there might be events pending in the embedded loop. The callback must then |
3234 | time there might be events pending in the embedded loop. The callback |
1550 | call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single sweep and invoke |
3235 | must then call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single |
1551 | their callbacks (you could also start an idle watcher to give the embedded |
3236 | sweep and invoke their callbacks (the callback doesn't need to invoke the |
1552 | loop strictly lower priority for example). You can also set the callback |
3237 | \&\f(CW\*(C`ev_embed_sweep\*(C'\fR function directly, it could also start an idle watcher |
1553 | to \f(CW0\fR, in which case the embed watcher will automatically execute the |
3238 | to give the embedded loop strictly lower priority for example). |
1554 | embedded loop sweep. |
|
|
1555 | .PP |
3239 | .PP |
1556 | As long as the watcher is started it will automatically handle events. The |
3240 | You can also set the callback to \f(CW0\fR, in which case the embed watcher |
1557 | callback will be invoked whenever some events have been handled. You can |
3241 | will automatically execute the embedded loop sweep whenever necessary. |
1558 | set the callback to \f(CW0\fR to avoid having to specify one if you are not |
|
|
1559 | interested in that. |
|
|
1560 | .PP |
3242 | .PP |
1561 | Also, there have not currently been made special provisions for forking: |
3243 | Fork detection will be handled transparently while the \f(CW\*(C`ev_embed\*(C'\fR watcher |
1562 | when you fork, you not only have to call \f(CW\*(C`ev_loop_fork\*(C'\fR on both loops, |
3244 | is active, i.e., the embedded loop will automatically be forked when the |
1563 | but you will also have to stop and restart any \f(CW\*(C`ev_embed\*(C'\fR watchers |
3245 | embedding loop forks. In other cases, the user is responsible for calling |
1564 | yourself. |
3246 | \&\f(CW\*(C`ev_loop_fork\*(C'\fR on the embedded loop. |
1565 | .PP |
3247 | .PP |
1566 | Unfortunately, not all backends are embeddable, only the ones returned by |
3248 | Unfortunately, not all backends are embeddable: only the ones returned by |
1567 | \&\f(CW\*(C`ev_embeddable_backends\*(C'\fR are, which, unfortunately, does not include any |
3249 | \&\f(CW\*(C`ev_embeddable_backends\*(C'\fR are, which, unfortunately, does not include any |
1568 | portable one. |
3250 | portable one. |
1569 | .PP |
3251 | .PP |
1570 | So when you want to use this feature you will always have to be prepared |
3252 | So when you want to use this feature you will always have to be prepared |
1571 | that you cannot get an embeddable loop. The recommended way to get around |
3253 | that you cannot get an embeddable loop. The recommended way to get around |
1572 | this is to have a separate variables for your embeddable loop, try to |
3254 | this is to have a separate variables for your embeddable loop, try to |
1573 | create it, and if that fails, use the normal loop for everything: |
3255 | create it, and if that fails, use the normal loop for everything. |
1574 | .PP |
3256 | .PP |
1575 | .Vb 3 |
3257 | \fI\f(CI\*(C`ev_embed\*(C'\fI and fork\fR |
1576 | \& struct ev_loop *loop_hi = ev_default_init (0); |
3258 | .IX Subsection "ev_embed and fork" |
1577 | \& struct ev_loop *loop_lo = 0; |
|
|
1578 | \& struct ev_embed embed; |
|
|
1579 | .Ve |
|
|
1580 | .PP |
3259 | .PP |
1581 | .Vb 5 |
3260 | While the \f(CW\*(C`ev_embed\*(C'\fR watcher is running, forks in the embedding loop will |
1582 | \& // see if there is a chance of getting one that works |
3261 | automatically be applied to the embedded loop as well, so no special |
1583 | \& // (remember that a flags value of 0 means autodetection) |
3262 | fork handling is required in that case. When the watcher is not running, |
1584 | \& loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
3263 | however, it is still the task of the libev user to call \f(CW\*(C`ev_loop_fork ()\*(C'\fR |
1585 | \& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
3264 | as applicable. |
1586 | \& : 0; |
|
|
1587 | .Ve |
|
|
1588 | .PP |
3265 | .PP |
1589 | .Vb 8 |
3266 | \fIWatcher-Specific Functions and Data Members\fR |
1590 | \& // if we got one, then embed it, otherwise default to loop_hi |
3267 | .IX Subsection "Watcher-Specific Functions and Data Members" |
1591 | \& if (loop_lo) |
|
|
1592 | \& { |
|
|
1593 | \& ev_embed_init (&embed, 0, loop_lo); |
|
|
1594 | \& ev_embed_start (loop_hi, &embed); |
|
|
1595 | \& } |
|
|
1596 | \& else |
|
|
1597 | \& loop_lo = loop_hi; |
|
|
1598 | .Ve |
|
|
1599 | .IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4 |
3268 | .IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4 |
1600 | .IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" |
3269 | .IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" |
1601 | .PD 0 |
3270 | .PD 0 |
1602 | .IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4 |
3271 | .IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4 |
1603 | .IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" |
3272 | .IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" |
1604 | .PD |
3273 | .PD |
1605 | Configures the watcher to embed the given loop, which must be |
3274 | Configures the watcher to embed the given loop, which must be |
1606 | embeddable. If the callback is \f(CW0\fR, then \f(CW\*(C`ev_embed_sweep\*(C'\fR will be |
3275 | embeddable. If the callback is \f(CW0\fR, then \f(CW\*(C`ev_embed_sweep\*(C'\fR will be |
1607 | invoked automatically, otherwise it is the responsibility of the callback |
3276 | invoked automatically, otherwise it is the responsibility of the callback |
1608 | to invoke it (it will continue to be called until the sweep has been done, |
3277 | to invoke it (it will continue to be called until the sweep has been done, |
1609 | if you do not want thta, you need to temporarily stop the embed watcher). |
3278 | if you do not want that, you need to temporarily stop the embed watcher). |
1610 | .IP "ev_embed_sweep (loop, ev_embed *)" 4 |
3279 | .IP "ev_embed_sweep (loop, ev_embed *)" 4 |
1611 | .IX Item "ev_embed_sweep (loop, ev_embed *)" |
3280 | .IX Item "ev_embed_sweep (loop, ev_embed *)" |
1612 | Make a single, non-blocking sweep over the embedded loop. This works |
3281 | Make a single, non-blocking sweep over the embedded loop. This works |
1613 | similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most |
3282 | similarly to \f(CW\*(C`ev_run (embedded_loop, EVRUN_NOWAIT)\*(C'\fR, but in the most |
1614 | apropriate way for embedded loops. |
3283 | appropriate way for embedded loops. |
1615 | .IP "struct ev_loop *loop [read\-only]" 4 |
3284 | .IP "struct ev_loop *other [read\-only]" 4 |
1616 | .IX Item "struct ev_loop *loop [read-only]" |
3285 | .IX Item "struct ev_loop *other [read-only]" |
1617 | The embedded event loop. |
3286 | The embedded event loop. |
|
|
3287 | .PP |
|
|
3288 | \fIExamples\fR |
|
|
3289 | .IX Subsection "Examples" |
|
|
3290 | .PP |
|
|
3291 | Example: Try to get an embeddable event loop and embed it into the default |
|
|
3292 | event loop. If that is not possible, use the default loop. The default |
|
|
3293 | loop is stored in \f(CW\*(C`loop_hi\*(C'\fR, while the embeddable loop is stored in |
|
|
3294 | \&\f(CW\*(C`loop_lo\*(C'\fR (which is \f(CW\*(C`loop_hi\*(C'\fR in the case no embeddable loop can be |
|
|
3295 | used). |
|
|
3296 | .PP |
|
|
3297 | .Vb 3 |
|
|
3298 | \& struct ev_loop *loop_hi = ev_default_init (0); |
|
|
3299 | \& struct ev_loop *loop_lo = 0; |
|
|
3300 | \& ev_embed embed; |
|
|
3301 | \& |
|
|
3302 | \& // see if there is a chance of getting one that works |
|
|
3303 | \& // (remember that a flags value of 0 means autodetection) |
|
|
3304 | \& loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
|
|
3305 | \& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
|
|
3306 | \& : 0; |
|
|
3307 | \& |
|
|
3308 | \& // if we got one, then embed it, otherwise default to loop_hi |
|
|
3309 | \& if (loop_lo) |
|
|
3310 | \& { |
|
|
3311 | \& ev_embed_init (&embed, 0, loop_lo); |
|
|
3312 | \& ev_embed_start (loop_hi, &embed); |
|
|
3313 | \& } |
|
|
3314 | \& else |
|
|
3315 | \& loop_lo = loop_hi; |
|
|
3316 | .Ve |
|
|
3317 | .PP |
|
|
3318 | Example: Check if kqueue is available but not recommended and create |
|
|
3319 | a kqueue backend for use with sockets (which usually work with any |
|
|
3320 | kqueue implementation). Store the kqueue/socket\-only event loop in |
|
|
3321 | \&\f(CW\*(C`loop_socket\*(C'\fR. (One might optionally use \f(CW\*(C`EVFLAG_NOENV\*(C'\fR, too). |
|
|
3322 | .PP |
|
|
3323 | .Vb 3 |
|
|
3324 | \& struct ev_loop *loop = ev_default_init (0); |
|
|
3325 | \& struct ev_loop *loop_socket = 0; |
|
|
3326 | \& ev_embed embed; |
|
|
3327 | \& |
|
|
3328 | \& if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
|
|
3329 | \& if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
|
|
3330 | \& { |
|
|
3331 | \& ev_embed_init (&embed, 0, loop_socket); |
|
|
3332 | \& ev_embed_start (loop, &embed); |
|
|
3333 | \& } |
|
|
3334 | \& |
|
|
3335 | \& if (!loop_socket) |
|
|
3336 | \& loop_socket = loop; |
|
|
3337 | \& |
|
|
3338 | \& // now use loop_socket for all sockets, and loop for everything else |
|
|
3339 | .Ve |
|
|
3340 | .ie n .SS """ev_fork"" \- the audacity to resume the event loop after a fork" |
|
|
3341 | .el .SS "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork" |
|
|
3342 | .IX Subsection "ev_fork - the audacity to resume the event loop after a fork" |
|
|
3343 | Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because |
|
|
3344 | whoever is a good citizen cared to tell libev about it by calling |
|
|
3345 | \&\f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the |
|
|
3346 | event loop blocks next and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called, |
|
|
3347 | and only in the child after the fork. If whoever good citizen calling |
|
|
3348 | \&\f(CW\*(C`ev_default_fork\*(C'\fR cheats and calls it in the wrong process, the fork |
|
|
3349 | handlers will be invoked, too, of course. |
|
|
3350 | .PP |
|
|
3351 | \fIThe special problem of life after fork \- how is it possible?\fR |
|
|
3352 | .IX Subsection "The special problem of life after fork - how is it possible?" |
|
|
3353 | .PP |
|
|
3354 | Most uses of \f(CW\*(C`fork()\*(C'\fR consist of forking, then some simple calls to set |
|
|
3355 | up/change the process environment, followed by a call to \f(CW\*(C`exec()\*(C'\fR. This |
|
|
3356 | sequence should be handled by libev without any problems. |
|
|
3357 | .PP |
|
|
3358 | This changes when the application actually wants to do event handling |
|
|
3359 | in the child, or both parent in child, in effect \*(L"continuing\*(R" after the |
|
|
3360 | fork. |
|
|
3361 | .PP |
|
|
3362 | The default mode of operation (for libev, with application help to detect |
|
|
3363 | forks) is to duplicate all the state in the child, as would be expected |
|
|
3364 | when \fIeither\fR the parent \fIor\fR the child process continues. |
|
|
3365 | .PP |
|
|
3366 | When both processes want to continue using libev, then this is usually the |
|
|
3367 | wrong result. In that case, usually one process (typically the parent) is |
|
|
3368 | supposed to continue with all watchers in place as before, while the other |
|
|
3369 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
3370 | .PP |
|
|
3371 | The cleanest and most efficient way to achieve that with libev is to |
|
|
3372 | simply create a new event loop, which of course will be \*(L"empty\*(R", and |
|
|
3373 | use that for new watchers. This has the advantage of not touching more |
|
|
3374 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
3375 | disadvantage of having to use multiple event loops (which do not support |
|
|
3376 | signal watchers). |
|
|
3377 | .PP |
|
|
3378 | When this is not possible, or you want to use the default loop for |
|
|
3379 | other reasons, then in the process that wants to start \*(L"fresh\*(R", call |
|
|
3380 | \&\f(CW\*(C`ev_loop_destroy (EV_DEFAULT)\*(C'\fR followed by \f(CW\*(C`ev_default_loop (...)\*(C'\fR. |
|
|
3381 | Destroying the default loop will \*(L"orphan\*(R" (not stop) all registered |
|
|
3382 | watchers, so you have to be careful not to execute code that modifies |
|
|
3383 | those watchers. Note also that in that case, you have to re-register any |
|
|
3384 | signal watchers. |
|
|
3385 | .PP |
|
|
3386 | \fIWatcher-Specific Functions and Data Members\fR |
|
|
3387 | .IX Subsection "Watcher-Specific Functions and Data Members" |
|
|
3388 | .IP "ev_fork_init (ev_fork *, callback)" 4 |
|
|
3389 | .IX Item "ev_fork_init (ev_fork *, callback)" |
|
|
3390 | Initialises and configures the fork watcher \- it has no parameters of any |
|
|
3391 | kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless, |
|
|
3392 | really. |
|
|
3393 | .ie n .SS """ev_cleanup"" \- even the best things end" |
|
|
3394 | .el .SS "\f(CWev_cleanup\fP \- even the best things end" |
|
|
3395 | .IX Subsection "ev_cleanup - even the best things end" |
|
|
3396 | Cleanup watchers are called just before the event loop is being destroyed |
|
|
3397 | by a call to \f(CW\*(C`ev_loop_destroy\*(C'\fR. |
|
|
3398 | .PP |
|
|
3399 | While there is no guarantee that the event loop gets destroyed, cleanup |
|
|
3400 | watchers provide a convenient method to install cleanup hooks for your |
|
|
3401 | program, worker threads and so on \- you just to make sure to destroy the |
|
|
3402 | loop when you want them to be invoked. |
|
|
3403 | .PP |
|
|
3404 | Cleanup watchers are invoked in the same way as any other watcher. Unlike |
|
|
3405 | all other watchers, they do not keep a reference to the event loop (which |
|
|
3406 | makes a lot of sense if you think about it). Like all other watchers, you |
|
|
3407 | can call libev functions in the callback, except \f(CW\*(C`ev_cleanup_start\*(C'\fR. |
|
|
3408 | .PP |
|
|
3409 | \fIWatcher-Specific Functions and Data Members\fR |
|
|
3410 | .IX Subsection "Watcher-Specific Functions and Data Members" |
|
|
3411 | .IP "ev_cleanup_init (ev_cleanup *, callback)" 4 |
|
|
3412 | .IX Item "ev_cleanup_init (ev_cleanup *, callback)" |
|
|
3413 | Initialises and configures the cleanup watcher \- it has no parameters of |
|
|
3414 | any kind. There is a \f(CW\*(C`ev_cleanup_set\*(C'\fR macro, but using it is utterly |
|
|
3415 | pointless, I assure you. |
|
|
3416 | .PP |
|
|
3417 | Example: Register an atexit handler to destroy the default loop, so any |
|
|
3418 | cleanup functions are called. |
|
|
3419 | .PP |
|
|
3420 | .Vb 5 |
|
|
3421 | \& static void |
|
|
3422 | \& program_exits (void) |
|
|
3423 | \& { |
|
|
3424 | \& ev_loop_destroy (EV_DEFAULT_UC); |
|
|
3425 | \& } |
|
|
3426 | \& |
|
|
3427 | \& ... |
|
|
3428 | \& atexit (program_exits); |
|
|
3429 | .Ve |
|
|
3430 | .ie n .SS """ev_async"" \- how to wake up an event loop" |
|
|
3431 | .el .SS "\f(CWev_async\fP \- how to wake up an event loop" |
|
|
3432 | .IX Subsection "ev_async - how to wake up an event loop" |
|
|
3433 | In general, you cannot use an \f(CW\*(C`ev_loop\*(C'\fR from multiple threads or other |
|
|
3434 | asynchronous sources such as signal handlers (as opposed to multiple event |
|
|
3435 | loops \- those are of course safe to use in different threads). |
|
|
3436 | .PP |
|
|
3437 | Sometimes, however, you need to wake up an event loop you do not control, |
|
|
3438 | for example because it belongs to another thread. This is what \f(CW\*(C`ev_async\*(C'\fR |
|
|
3439 | watchers do: as long as the \f(CW\*(C`ev_async\*(C'\fR watcher is active, you can signal |
|
|
3440 | it by calling \f(CW\*(C`ev_async_send\*(C'\fR, which is thread\- and signal safe. |
|
|
3441 | .PP |
|
|
3442 | This functionality is very similar to \f(CW\*(C`ev_signal\*(C'\fR watchers, as signals, |
|
|
3443 | too, are asynchronous in nature, and signals, too, will be compressed |
|
|
3444 | (i.e. the number of callback invocations may be less than the number of |
|
|
3445 | \&\f(CW\*(C`ev_async_sent\*(C'\fR calls). In fact, you could use signal watchers as a kind |
|
|
3446 | of \*(L"global async watchers\*(R" by using a watcher on an otherwise unused |
|
|
3447 | signal, and \f(CW\*(C`ev_feed_signal\*(C'\fR to signal this watcher from another thread, |
|
|
3448 | even without knowing which loop owns the signal. |
|
|
3449 | .PP |
|
|
3450 | \fIQueueing\fR |
|
|
3451 | .IX Subsection "Queueing" |
|
|
3452 | .PP |
|
|
3453 | \&\f(CW\*(C`ev_async\*(C'\fR does not support queueing of data in any way. The reason |
|
|
3454 | is that the author does not know of a simple (or any) algorithm for a |
|
|
3455 | multiple-writer-single-reader queue that works in all cases and doesn't |
|
|
3456 | need elaborate support such as pthreads or unportable memory access |
|
|
3457 | semantics. |
|
|
3458 | .PP |
|
|
3459 | That means that if you want to queue data, you have to provide your own |
|
|
3460 | queue. But at least I can tell you how to implement locking around your |
|
|
3461 | queue: |
|
|
3462 | .IP "queueing from a signal handler context" 4 |
|
|
3463 | .IX Item "queueing from a signal handler context" |
|
|
3464 | To implement race-free queueing, you simply add to the queue in the signal |
|
|
3465 | handler but you block the signal handler in the watcher callback. Here is |
|
|
3466 | an example that does that for some fictitious \s-1SIGUSR1\s0 handler: |
|
|
3467 | .Sp |
|
|
3468 | .Vb 1 |
|
|
3469 | \& static ev_async mysig; |
|
|
3470 | \& |
|
|
3471 | \& static void |
|
|
3472 | \& sigusr1_handler (void) |
|
|
3473 | \& { |
|
|
3474 | \& sometype data; |
|
|
3475 | \& |
|
|
3476 | \& // no locking etc. |
|
|
3477 | \& queue_put (data); |
|
|
3478 | \& ev_async_send (EV_DEFAULT_ &mysig); |
|
|
3479 | \& } |
|
|
3480 | \& |
|
|
3481 | \& static void |
|
|
3482 | \& mysig_cb (EV_P_ ev_async *w, int revents) |
|
|
3483 | \& { |
|
|
3484 | \& sometype data; |
|
|
3485 | \& sigset_t block, prev; |
|
|
3486 | \& |
|
|
3487 | \& sigemptyset (&block); |
|
|
3488 | \& sigaddset (&block, SIGUSR1); |
|
|
3489 | \& sigprocmask (SIG_BLOCK, &block, &prev); |
|
|
3490 | \& |
|
|
3491 | \& while (queue_get (&data)) |
|
|
3492 | \& process (data); |
|
|
3493 | \& |
|
|
3494 | \& if (sigismember (&prev, SIGUSR1) |
|
|
3495 | \& sigprocmask (SIG_UNBLOCK, &block, 0); |
|
|
3496 | \& } |
|
|
3497 | .Ve |
|
|
3498 | .Sp |
|
|
3499 | (Note: pthreads in theory requires you to use \f(CW\*(C`pthread_setmask\*(C'\fR |
|
|
3500 | instead of \f(CW\*(C`sigprocmask\*(C'\fR when you use threads, but libev doesn't do it |
|
|
3501 | either...). |
|
|
3502 | .IP "queueing from a thread context" 4 |
|
|
3503 | .IX Item "queueing from a thread context" |
|
|
3504 | The strategy for threads is different, as you cannot (easily) block |
|
|
3505 | threads but you can easily preempt them, so to queue safely you need to |
|
|
3506 | employ a traditional mutex lock, such as in this pthread example: |
|
|
3507 | .Sp |
|
|
3508 | .Vb 2 |
|
|
3509 | \& static ev_async mysig; |
|
|
3510 | \& static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER; |
|
|
3511 | \& |
|
|
3512 | \& static void |
|
|
3513 | \& otherthread (void) |
|
|
3514 | \& { |
|
|
3515 | \& // only need to lock the actual queueing operation |
|
|
3516 | \& pthread_mutex_lock (&mymutex); |
|
|
3517 | \& queue_put (data); |
|
|
3518 | \& pthread_mutex_unlock (&mymutex); |
|
|
3519 | \& |
|
|
3520 | \& ev_async_send (EV_DEFAULT_ &mysig); |
|
|
3521 | \& } |
|
|
3522 | \& |
|
|
3523 | \& static void |
|
|
3524 | \& mysig_cb (EV_P_ ev_async *w, int revents) |
|
|
3525 | \& { |
|
|
3526 | \& pthread_mutex_lock (&mymutex); |
|
|
3527 | \& |
|
|
3528 | \& while (queue_get (&data)) |
|
|
3529 | \& process (data); |
|
|
3530 | \& |
|
|
3531 | \& pthread_mutex_unlock (&mymutex); |
|
|
3532 | \& } |
|
|
3533 | .Ve |
|
|
3534 | .PP |
|
|
3535 | \fIWatcher-Specific Functions and Data Members\fR |
|
|
3536 | .IX Subsection "Watcher-Specific Functions and Data Members" |
|
|
3537 | .IP "ev_async_init (ev_async *, callback)" 4 |
|
|
3538 | .IX Item "ev_async_init (ev_async *, callback)" |
|
|
3539 | Initialises and configures the async watcher \- it has no parameters of any |
|
|
3540 | kind. There is a \f(CW\*(C`ev_async_set\*(C'\fR macro, but using it is utterly pointless, |
|
|
3541 | trust me. |
|
|
3542 | .IP "ev_async_send (loop, ev_async *)" 4 |
|
|
3543 | .IX Item "ev_async_send (loop, ev_async *)" |
|
|
3544 | Sends/signals/activates the given \f(CW\*(C`ev_async\*(C'\fR watcher, that is, feeds |
|
|
3545 | an \f(CW\*(C`EV_ASYNC\*(C'\fR event on the watcher into the event loop, and instantly |
|
|
3546 | returns. |
|
|
3547 | .Sp |
|
|
3548 | Unlike \f(CW\*(C`ev_feed_event\*(C'\fR, this call is safe to do from other threads, |
|
|
3549 | signal or similar contexts (see the discussion of \f(CW\*(C`EV_ATOMIC_T\*(C'\fR in the |
|
|
3550 | embedding section below on what exactly this means). |
|
|
3551 | .Sp |
|
|
3552 | Note that, as with other watchers in libev, multiple events might get |
|
|
3553 | compressed into a single callback invocation (another way to look at |
|
|
3554 | this is that \f(CW\*(C`ev_async\*(C'\fR watchers are level-triggered: they are set on |
|
|
3555 | \&\f(CW\*(C`ev_async_send\*(C'\fR, reset when the event loop detects that). |
|
|
3556 | .Sp |
|
|
3557 | This call incurs the overhead of at most one extra system call per event |
|
|
3558 | loop iteration, if the event loop is blocked, and no syscall at all if |
|
|
3559 | the event loop (or your program) is processing events. That means that |
|
|
3560 | repeated calls are basically free (there is no need to avoid calls for |
|
|
3561 | performance reasons) and that the overhead becomes smaller (typically |
|
|
3562 | zero) under load. |
|
|
3563 | .IP "bool = ev_async_pending (ev_async *)" 4 |
|
|
3564 | .IX Item "bool = ev_async_pending (ev_async *)" |
|
|
3565 | Returns a non-zero value when \f(CW\*(C`ev_async_send\*(C'\fR has been called on the |
|
|
3566 | watcher but the event has not yet been processed (or even noted) by the |
|
|
3567 | event loop. |
|
|
3568 | .Sp |
|
|
3569 | \&\f(CW\*(C`ev_async_send\*(C'\fR sets a flag in the watcher and wakes up the loop. When |
|
|
3570 | the loop iterates next and checks for the watcher to have become active, |
|
|
3571 | it will reset the flag again. \f(CW\*(C`ev_async_pending\*(C'\fR can be used to very |
|
|
3572 | quickly check whether invoking the loop might be a good idea. |
|
|
3573 | .Sp |
|
|
3574 | Not that this does \fInot\fR check whether the watcher itself is pending, |
|
|
3575 | only whether it has been requested to make this watcher pending: there |
|
|
3576 | is a time window between the event loop checking and resetting the async |
|
|
3577 | notification, and the callback being invoked. |
1618 | .SH "OTHER FUNCTIONS" |
3578 | .SH "OTHER FUNCTIONS" |
1619 | .IX Header "OTHER FUNCTIONS" |
3579 | .IX Header "OTHER FUNCTIONS" |
1620 | There are some other functions of possible interest. Described. Here. Now. |
3580 | There are some other functions of possible interest. Described. Here. Now. |
1621 | .IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4 |
3581 | .IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4 |
1622 | .IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" |
3582 | .IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" |
1623 | This function combines a simple timer and an I/O watcher, calls your |
3583 | This function combines a simple timer and an I/O watcher, calls your |
1624 | callback on whichever event happens first and automatically stop both |
3584 | callback on whichever event happens first and automatically stops both |
1625 | watchers. This is useful if you want to wait for a single event on an fd |
3585 | watchers. This is useful if you want to wait for a single event on an fd |
1626 | or timeout without having to allocate/configure/start/stop/free one or |
3586 | or timeout without having to allocate/configure/start/stop/free one or |
1627 | more watchers yourself. |
3587 | more watchers yourself. |
1628 | .Sp |
3588 | .Sp |
1629 | If \f(CW\*(C`fd\*(C'\fR is less than 0, then no I/O watcher will be started and events |
3589 | If \f(CW\*(C`fd\*(C'\fR is less than 0, then no I/O watcher will be started and the |
1630 | is being ignored. Otherwise, an \f(CW\*(C`ev_io\*(C'\fR watcher for the given \f(CW\*(C`fd\*(C'\fR and |
3590 | \&\f(CW\*(C`events\*(C'\fR argument is being ignored. Otherwise, an \f(CW\*(C`ev_io\*(C'\fR watcher for |
1631 | \&\f(CW\*(C`events\*(C'\fR set will be craeted and started. |
3591 | the given \f(CW\*(C`fd\*(C'\fR and \f(CW\*(C`events\*(C'\fR set will be created and started. |
1632 | .Sp |
3592 | .Sp |
1633 | If \f(CW\*(C`timeout\*(C'\fR is less than 0, then no timeout watcher will be |
3593 | If \f(CW\*(C`timeout\*(C'\fR is less than 0, then no timeout watcher will be |
1634 | started. Otherwise an \f(CW\*(C`ev_timer\*(C'\fR watcher with after = \f(CW\*(C`timeout\*(C'\fR (and |
3594 | started. Otherwise an \f(CW\*(C`ev_timer\*(C'\fR watcher with after = \f(CW\*(C`timeout\*(C'\fR (and |
1635 | repeat = 0) will be started. While \f(CW0\fR is a valid timeout, it is of |
3595 | repeat = 0) will be started. \f(CW0\fR is a valid timeout. |
1636 | dubious value. |
|
|
1637 | .Sp |
3596 | .Sp |
1638 | The callback has the type \f(CW\*(C`void (*cb)(int revents, void *arg)\*(C'\fR and gets |
3597 | The callback has the type \f(CW\*(C`void (*cb)(int revents, void *arg)\*(C'\fR and is |
1639 | passed an \f(CW\*(C`revents\*(C'\fR set like normal event callbacks (a combination of |
3598 | passed an \f(CW\*(C`revents\*(C'\fR set like normal event callbacks (a combination of |
1640 | \&\f(CW\*(C`EV_ERROR\*(C'\fR, \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or \f(CW\*(C`EV_TIMEOUT\*(C'\fR) and the \f(CW\*(C`arg\*(C'\fR |
3599 | \&\f(CW\*(C`EV_ERROR\*(C'\fR, \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or \f(CW\*(C`EV_TIMER\*(C'\fR) and the \f(CW\*(C`arg\*(C'\fR |
1641 | value passed to \f(CW\*(C`ev_once\*(C'\fR: |
3600 | value passed to \f(CW\*(C`ev_once\*(C'\fR. Note that it is possible to receive \fIboth\fR |
|
|
3601 | a timeout and an io event at the same time \- you probably should give io |
|
|
3602 | events precedence. |
|
|
3603 | .Sp |
|
|
3604 | Example: wait up to ten seconds for data to appear on \s-1STDIN_FILENO\s0. |
1642 | .Sp |
3605 | .Sp |
1643 | .Vb 7 |
3606 | .Vb 7 |
1644 | \& static void stdin_ready (int revents, void *arg) |
3607 | \& static void stdin_ready (int revents, void *arg) |
|
|
3608 | \& { |
|
|
3609 | \& if (revents & EV_READ) |
|
|
3610 | \& /* stdin might have data for us, joy! */; |
|
|
3611 | \& else if (revents & EV_TIMER) |
|
|
3612 | \& /* doh, nothing entered */; |
|
|
3613 | \& } |
|
|
3614 | \& |
|
|
3615 | \& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
|
|
3616 | .Ve |
|
|
3617 | .IP "ev_feed_fd_event (loop, int fd, int revents)" 4 |
|
|
3618 | .IX Item "ev_feed_fd_event (loop, int fd, int revents)" |
|
|
3619 | Feed an event on the given fd, as if a file descriptor backend detected |
|
|
3620 | the given events. |
|
|
3621 | .IP "ev_feed_signal_event (loop, int signum)" 4 |
|
|
3622 | .IX Item "ev_feed_signal_event (loop, int signum)" |
|
|
3623 | Feed an event as if the given signal occurred. See also \f(CW\*(C`ev_feed_signal\*(C'\fR, |
|
|
3624 | which is async-safe. |
|
|
3625 | .SH "COMMON OR USEFUL IDIOMS (OR BOTH)" |
|
|
3626 | .IX Header "COMMON OR USEFUL IDIOMS (OR BOTH)" |
|
|
3627 | This section explains some common idioms that are not immediately |
|
|
3628 | obvious. Note that examples are sprinkled over the whole manual, and this |
|
|
3629 | section only contains stuff that wouldn't fit anywhere else. |
|
|
3630 | .SS "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0" |
|
|
3631 | .IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER" |
|
|
3632 | Each watcher has, by default, a \f(CW\*(C`void *data\*(C'\fR member that you can read |
|
|
3633 | or modify at any time: libev will completely ignore it. This can be used |
|
|
3634 | to associate arbitrary data with your watcher. If you need more data and |
|
|
3635 | don't want to allocate memory separately and store a pointer to it in that |
|
|
3636 | data member, you can also \*(L"subclass\*(R" the watcher type and provide your own |
|
|
3637 | data: |
|
|
3638 | .PP |
|
|
3639 | .Vb 7 |
|
|
3640 | \& struct my_io |
|
|
3641 | \& { |
|
|
3642 | \& ev_io io; |
|
|
3643 | \& int otherfd; |
|
|
3644 | \& void *somedata; |
|
|
3645 | \& struct whatever *mostinteresting; |
|
|
3646 | \& }; |
|
|
3647 | \& |
|
|
3648 | \& ... |
|
|
3649 | \& struct my_io w; |
|
|
3650 | \& ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
3651 | .Ve |
|
|
3652 | .PP |
|
|
3653 | And since your callback will be called with a pointer to the watcher, you |
|
|
3654 | can cast it back to your own type: |
|
|
3655 | .PP |
|
|
3656 | .Vb 5 |
|
|
3657 | \& static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
3658 | \& { |
|
|
3659 | \& struct my_io *w = (struct my_io *)w_; |
|
|
3660 | \& ... |
|
|
3661 | \& } |
|
|
3662 | .Ve |
|
|
3663 | .PP |
|
|
3664 | More interesting and less C\-conformant ways of casting your callback |
|
|
3665 | function type instead have been omitted. |
|
|
3666 | .SS "\s-1BUILDING\s0 \s-1YOUR\s0 \s-1OWN\s0 \s-1COMPOSITE\s0 \s-1WATCHERS\s0" |
|
|
3667 | .IX Subsection "BUILDING YOUR OWN COMPOSITE WATCHERS" |
|
|
3668 | Another common scenario is to use some data structure with multiple |
|
|
3669 | embedded watchers, in effect creating your own watcher that combines |
|
|
3670 | multiple libev event sources into one \*(L"super-watcher\*(R": |
|
|
3671 | .PP |
|
|
3672 | .Vb 6 |
|
|
3673 | \& struct my_biggy |
|
|
3674 | \& { |
|
|
3675 | \& int some_data; |
|
|
3676 | \& ev_timer t1; |
|
|
3677 | \& ev_timer t2; |
|
|
3678 | \& } |
|
|
3679 | .Ve |
|
|
3680 | .PP |
|
|
3681 | In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more |
|
|
3682 | complicated: Either you store the address of your \f(CW\*(C`my_biggy\*(C'\fR struct in |
|
|
3683 | the \f(CW\*(C`data\*(C'\fR member of the watcher (for woozies or \*(C+ coders), or you need |
|
|
3684 | to use some pointer arithmetic using \f(CW\*(C`offsetof\*(C'\fR inside your watchers (for |
|
|
3685 | real programmers): |
|
|
3686 | .PP |
|
|
3687 | .Vb 1 |
|
|
3688 | \& #include <stddef.h> |
|
|
3689 | \& |
|
|
3690 | \& static void |
|
|
3691 | \& t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
3692 | \& { |
|
|
3693 | \& struct my_biggy big = (struct my_biggy *) |
|
|
3694 | \& (((char *)w) \- offsetof (struct my_biggy, t1)); |
|
|
3695 | \& } |
|
|
3696 | \& |
|
|
3697 | \& static void |
|
|
3698 | \& t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
3699 | \& { |
|
|
3700 | \& struct my_biggy big = (struct my_biggy *) |
|
|
3701 | \& (((char *)w) \- offsetof (struct my_biggy, t2)); |
|
|
3702 | \& } |
|
|
3703 | .Ve |
|
|
3704 | .SS "\s-1AVOIDING\s0 \s-1FINISHING\s0 \s-1BEFORE\s0 \s-1RETURNING\s0" |
|
|
3705 | .IX Subsection "AVOIDING FINISHING BEFORE RETURNING" |
|
|
3706 | Often you have structures like this in event-based programs: |
|
|
3707 | .PP |
|
|
3708 | .Vb 4 |
|
|
3709 | \& callback () |
1645 | \& { |
3710 | \& { |
1646 | \& if (revents & EV_TIMEOUT) |
3711 | \& free (request); |
1647 | \& /* doh, nothing entered */; |
|
|
1648 | \& else if (revents & EV_READ) |
|
|
1649 | \& /* stdin might have data for us, joy! */; |
|
|
1650 | \& } |
3712 | \& } |
|
|
3713 | \& |
|
|
3714 | \& request = start_new_request (..., callback); |
1651 | .Ve |
3715 | .Ve |
1652 | .Sp |
3716 | .PP |
|
|
3717 | The intent is to start some \*(L"lengthy\*(R" operation. The \f(CW\*(C`request\*(C'\fR could be |
|
|
3718 | used to cancel the operation, or do other things with it. |
|
|
3719 | .PP |
|
|
3720 | It's not uncommon to have code paths in \f(CW\*(C`start_new_request\*(C'\fR that |
|
|
3721 | immediately invoke the callback, for example, to report errors. Or you add |
|
|
3722 | some caching layer that finds that it can skip the lengthy aspects of the |
|
|
3723 | operation and simply invoke the callback with the result. |
|
|
3724 | .PP |
|
|
3725 | The problem here is that this will happen \fIbefore\fR \f(CW\*(C`start_new_request\*(C'\fR |
|
|
3726 | has returned, so \f(CW\*(C`request\*(C'\fR is not set. |
|
|
3727 | .PP |
|
|
3728 | Even if you pass the request by some safer means to the callback, you |
|
|
3729 | might want to do something to the request after starting it, such as |
|
|
3730 | canceling it, which probably isn't working so well when the callback has |
|
|
3731 | already been invoked. |
|
|
3732 | .PP |
|
|
3733 | A common way around all these issues is to make sure that |
|
|
3734 | \&\f(CW\*(C`start_new_request\*(C'\fR \fIalways\fR returns before the callback is invoked. If |
|
|
3735 | \&\f(CW\*(C`start_new_request\*(C'\fR immediately knows the result, it can artificially |
|
|
3736 | delay invoking the callback by e.g. using a \f(CW\*(C`prepare\*(C'\fR or \f(CW\*(C`idle\*(C'\fR watcher |
|
|
3737 | for example, or more sneakily, by reusing an existing (stopped) watcher |
|
|
3738 | and pushing it into the pending queue: |
|
|
3739 | .PP |
1653 | .Vb 1 |
3740 | .Vb 2 |
1654 | \& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3741 | \& ev_set_cb (watcher, callback); |
|
|
3742 | \& ev_feed_event (EV_A_ watcher, 0); |
1655 | .Ve |
3743 | .Ve |
1656 | .IP "ev_feed_event (ev_loop *, watcher *, int revents)" 4 |
3744 | .PP |
1657 | .IX Item "ev_feed_event (ev_loop *, watcher *, int revents)" |
3745 | This way, \f(CW\*(C`start_new_request\*(C'\fR can safely return before the callback is |
1658 | Feeds the given event set into the event loop, as if the specified event |
3746 | invoked, while not delaying callback invocation too much. |
1659 | had happened for the specified watcher (which must be a pointer to an |
3747 | .SS "\s-1MODEL/NESTED\s0 \s-1EVENT\s0 \s-1LOOP\s0 \s-1INVOCATIONS\s0 \s-1AND\s0 \s-1EXIT\s0 \s-1CONDITIONS\s0" |
1660 | initialised but not necessarily started event watcher). |
3748 | .IX Subsection "MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS" |
1661 | .IP "ev_feed_fd_event (ev_loop *, int fd, int revents)" 4 |
3749 | Often (especially in \s-1GUI\s0 toolkits) there are places where you have |
1662 | .IX Item "ev_feed_fd_event (ev_loop *, int fd, int revents)" |
3750 | \&\fImodal\fR interaction, which is most easily implemented by recursively |
1663 | Feed an event on the given fd, as if a file descriptor backend detected |
3751 | invoking \f(CW\*(C`ev_run\*(C'\fR. |
1664 | the given events it. |
3752 | .PP |
1665 | .IP "ev_feed_signal_event (ev_loop *loop, int signum)" 4 |
3753 | This brings the problem of exiting \- a callback might want to finish the |
1666 | .IX Item "ev_feed_signal_event (ev_loop *loop, int signum)" |
3754 | main \f(CW\*(C`ev_run\*(C'\fR call, but not the nested one (e.g. user clicked \*(L"Quit\*(R", but |
1667 | Feed an event as if the given signal occured (\f(CW\*(C`loop\*(C'\fR must be the default |
3755 | a modal \*(L"Are you sure?\*(R" dialog is still waiting), or just the nested one |
1668 | loop!). |
3756 | and not the main one (e.g. user clocked \*(L"Ok\*(R" in a modal dialog), or some |
|
|
3757 | other combination: In these cases, \f(CW\*(C`ev_break\*(C'\fR will not work alone. |
|
|
3758 | .PP |
|
|
3759 | The solution is to maintain \*(L"break this loop\*(R" variable for each \f(CW\*(C`ev_run\*(C'\fR |
|
|
3760 | invocation, and use a loop around \f(CW\*(C`ev_run\*(C'\fR until the condition is |
|
|
3761 | triggered, using \f(CW\*(C`EVRUN_ONCE\*(C'\fR: |
|
|
3762 | .PP |
|
|
3763 | .Vb 2 |
|
|
3764 | \& // main loop |
|
|
3765 | \& int exit_main_loop = 0; |
|
|
3766 | \& |
|
|
3767 | \& while (!exit_main_loop) |
|
|
3768 | \& ev_run (EV_DEFAULT_ EVRUN_ONCE); |
|
|
3769 | \& |
|
|
3770 | \& // in a modal watcher |
|
|
3771 | \& int exit_nested_loop = 0; |
|
|
3772 | \& |
|
|
3773 | \& while (!exit_nested_loop) |
|
|
3774 | \& ev_run (EV_A_ EVRUN_ONCE); |
|
|
3775 | .Ve |
|
|
3776 | .PP |
|
|
3777 | To exit from any of these loops, just set the corresponding exit variable: |
|
|
3778 | .PP |
|
|
3779 | .Vb 2 |
|
|
3780 | \& // exit modal loop |
|
|
3781 | \& exit_nested_loop = 1; |
|
|
3782 | \& |
|
|
3783 | \& // exit main program, after modal loop is finished |
|
|
3784 | \& exit_main_loop = 1; |
|
|
3785 | \& |
|
|
3786 | \& // exit both |
|
|
3787 | \& exit_main_loop = exit_nested_loop = 1; |
|
|
3788 | .Ve |
|
|
3789 | .SS "\s-1THREAD\s0 \s-1LOCKING\s0 \s-1EXAMPLE\s0" |
|
|
3790 | .IX Subsection "THREAD LOCKING EXAMPLE" |
|
|
3791 | Here is a fictitious example of how to run an event loop in a different |
|
|
3792 | thread from where callbacks are being invoked and watchers are |
|
|
3793 | created/added/removed. |
|
|
3794 | .PP |
|
|
3795 | For a real-world example, see the \f(CW\*(C`EV::Loop::Async\*(C'\fR perl module, |
|
|
3796 | which uses exactly this technique (which is suited for many high-level |
|
|
3797 | languages). |
|
|
3798 | .PP |
|
|
3799 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
3800 | variable to wait for callback invocations, an async watcher to notify the |
|
|
3801 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
3802 | .PP |
|
|
3803 | First, you need to associate some data with the event loop: |
|
|
3804 | .PP |
|
|
3805 | .Vb 6 |
|
|
3806 | \& typedef struct { |
|
|
3807 | \& mutex_t lock; /* global loop lock */ |
|
|
3808 | \& ev_async async_w; |
|
|
3809 | \& thread_t tid; |
|
|
3810 | \& cond_t invoke_cv; |
|
|
3811 | \& } userdata; |
|
|
3812 | \& |
|
|
3813 | \& void prepare_loop (EV_P) |
|
|
3814 | \& { |
|
|
3815 | \& // for simplicity, we use a static userdata struct. |
|
|
3816 | \& static userdata u; |
|
|
3817 | \& |
|
|
3818 | \& ev_async_init (&u\->async_w, async_cb); |
|
|
3819 | \& ev_async_start (EV_A_ &u\->async_w); |
|
|
3820 | \& |
|
|
3821 | \& pthread_mutex_init (&u\->lock, 0); |
|
|
3822 | \& pthread_cond_init (&u\->invoke_cv, 0); |
|
|
3823 | \& |
|
|
3824 | \& // now associate this with the loop |
|
|
3825 | \& ev_set_userdata (EV_A_ u); |
|
|
3826 | \& ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
3827 | \& ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
3828 | \& |
|
|
3829 | \& // then create the thread running ev_run |
|
|
3830 | \& pthread_create (&u\->tid, 0, l_run, EV_A); |
|
|
3831 | \& } |
|
|
3832 | .Ve |
|
|
3833 | .PP |
|
|
3834 | The callback for the \f(CW\*(C`ev_async\*(C'\fR watcher does nothing: the watcher is used |
|
|
3835 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
3836 | that might have been added: |
|
|
3837 | .PP |
|
|
3838 | .Vb 5 |
|
|
3839 | \& static void |
|
|
3840 | \& async_cb (EV_P_ ev_async *w, int revents) |
|
|
3841 | \& { |
|
|
3842 | \& // just used for the side effects |
|
|
3843 | \& } |
|
|
3844 | .Ve |
|
|
3845 | .PP |
|
|
3846 | The \f(CW\*(C`l_release\*(C'\fR and \f(CW\*(C`l_acquire\*(C'\fR callbacks simply unlock/lock the mutex |
|
|
3847 | protecting the loop data, respectively. |
|
|
3848 | .PP |
|
|
3849 | .Vb 6 |
|
|
3850 | \& static void |
|
|
3851 | \& l_release (EV_P) |
|
|
3852 | \& { |
|
|
3853 | \& userdata *u = ev_userdata (EV_A); |
|
|
3854 | \& pthread_mutex_unlock (&u\->lock); |
|
|
3855 | \& } |
|
|
3856 | \& |
|
|
3857 | \& static void |
|
|
3858 | \& l_acquire (EV_P) |
|
|
3859 | \& { |
|
|
3860 | \& userdata *u = ev_userdata (EV_A); |
|
|
3861 | \& pthread_mutex_lock (&u\->lock); |
|
|
3862 | \& } |
|
|
3863 | .Ve |
|
|
3864 | .PP |
|
|
3865 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
3866 | into \f(CW\*(C`ev_run\*(C'\fR: |
|
|
3867 | .PP |
|
|
3868 | .Vb 4 |
|
|
3869 | \& void * |
|
|
3870 | \& l_run (void *thr_arg) |
|
|
3871 | \& { |
|
|
3872 | \& struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
3873 | \& |
|
|
3874 | \& l_acquire (EV_A); |
|
|
3875 | \& pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
3876 | \& ev_run (EV_A_ 0); |
|
|
3877 | \& l_release (EV_A); |
|
|
3878 | \& |
|
|
3879 | \& return 0; |
|
|
3880 | \& } |
|
|
3881 | .Ve |
|
|
3882 | .PP |
|
|
3883 | Instead of invoking all pending watchers, the \f(CW\*(C`l_invoke\*(C'\fR callback will |
|
|
3884 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
3885 | writes? \f(CW\*(C`Async::Interrupt\*(C'\fR?) and then waits until all pending watchers |
|
|
3886 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
3887 | and b) skipping inter-thread-communication when there are no pending |
|
|
3888 | watchers is very beneficial): |
|
|
3889 | .PP |
|
|
3890 | .Vb 4 |
|
|
3891 | \& static void |
|
|
3892 | \& l_invoke (EV_P) |
|
|
3893 | \& { |
|
|
3894 | \& userdata *u = ev_userdata (EV_A); |
|
|
3895 | \& |
|
|
3896 | \& while (ev_pending_count (EV_A)) |
|
|
3897 | \& { |
|
|
3898 | \& wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
3899 | \& pthread_cond_wait (&u\->invoke_cv, &u\->lock); |
|
|
3900 | \& } |
|
|
3901 | \& } |
|
|
3902 | .Ve |
|
|
3903 | .PP |
|
|
3904 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
3905 | will grab the lock, call \f(CW\*(C`ev_invoke_pending\*(C'\fR and then signal the loop |
|
|
3906 | thread to continue: |
|
|
3907 | .PP |
|
|
3908 | .Vb 4 |
|
|
3909 | \& static void |
|
|
3910 | \& real_invoke_pending (EV_P) |
|
|
3911 | \& { |
|
|
3912 | \& userdata *u = ev_userdata (EV_A); |
|
|
3913 | \& |
|
|
3914 | \& pthread_mutex_lock (&u\->lock); |
|
|
3915 | \& ev_invoke_pending (EV_A); |
|
|
3916 | \& pthread_cond_signal (&u\->invoke_cv); |
|
|
3917 | \& pthread_mutex_unlock (&u\->lock); |
|
|
3918 | \& } |
|
|
3919 | .Ve |
|
|
3920 | .PP |
|
|
3921 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
3922 | event loop, you will now have to lock: |
|
|
3923 | .PP |
|
|
3924 | .Vb 2 |
|
|
3925 | \& ev_timer timeout_watcher; |
|
|
3926 | \& userdata *u = ev_userdata (EV_A); |
|
|
3927 | \& |
|
|
3928 | \& ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
3929 | \& |
|
|
3930 | \& pthread_mutex_lock (&u\->lock); |
|
|
3931 | \& ev_timer_start (EV_A_ &timeout_watcher); |
|
|
3932 | \& ev_async_send (EV_A_ &u\->async_w); |
|
|
3933 | \& pthread_mutex_unlock (&u\->lock); |
|
|
3934 | .Ve |
|
|
3935 | .PP |
|
|
3936 | Note that sending the \f(CW\*(C`ev_async\*(C'\fR watcher is required because otherwise |
|
|
3937 | an event loop currently blocking in the kernel will have no knowledge |
|
|
3938 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
3939 | watchers in the next event loop iteration. |
|
|
3940 | .SS "\s-1THREADS\s0, \s-1COROUTINES\s0, \s-1CONTINUATIONS\s0, \s-1QUEUES\s0... \s-1INSTEAD\s0 \s-1OF\s0 \s-1CALLBACKS\s0" |
|
|
3941 | .IX Subsection "THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS" |
|
|
3942 | While the overhead of a callback that e.g. schedules a thread is small, it |
|
|
3943 | is still an overhead. If you embed libev, and your main usage is with some |
|
|
3944 | kind of threads or coroutines, you might want to customise libev so that |
|
|
3945 | doesn't need callbacks anymore. |
|
|
3946 | .PP |
|
|
3947 | Imagine you have coroutines that you can switch to using a function |
|
|
3948 | \&\f(CW\*(C`switch_to (coro)\*(C'\fR, that libev runs in a coroutine called \f(CW\*(C`libev_coro\*(C'\fR |
|
|
3949 | and that due to some magic, the currently active coroutine is stored in a |
|
|
3950 | global called \f(CW\*(C`current_coro\*(C'\fR. Then you can build your own \*(L"wait for libev |
|
|
3951 | event\*(R" primitive by changing \f(CW\*(C`EV_CB_DECLARE\*(C'\fR and \f(CW\*(C`EV_CB_INVOKE\*(C'\fR (note |
|
|
3952 | the differing \f(CW\*(C`;\*(C'\fR conventions): |
|
|
3953 | .PP |
|
|
3954 | .Vb 2 |
|
|
3955 | \& #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3956 | \& #define EV_CB_INVOKE(watcher) switch_to ((watcher)\->cb) |
|
|
3957 | .Ve |
|
|
3958 | .PP |
|
|
3959 | That means instead of having a C callback function, you store the |
|
|
3960 | coroutine to switch to in each watcher, and instead of having libev call |
|
|
3961 | your callback, you instead have it switch to that coroutine. |
|
|
3962 | .PP |
|
|
3963 | A coroutine might now wait for an event with a function called |
|
|
3964 | \&\f(CW\*(C`wait_for_event\*(C'\fR. (the watcher needs to be started, as always, but it doesn't |
|
|
3965 | matter when, or whether the watcher is active or not when this function is |
|
|
3966 | called): |
|
|
3967 | .PP |
|
|
3968 | .Vb 6 |
|
|
3969 | \& void |
|
|
3970 | \& wait_for_event (ev_watcher *w) |
|
|
3971 | \& { |
|
|
3972 | \& ev_cb_set (w) = current_coro; |
|
|
3973 | \& switch_to (libev_coro); |
|
|
3974 | \& } |
|
|
3975 | .Ve |
|
|
3976 | .PP |
|
|
3977 | That basically suspends the coroutine inside \f(CW\*(C`wait_for_event\*(C'\fR and |
|
|
3978 | continues the libev coroutine, which, when appropriate, switches back to |
|
|
3979 | this or any other coroutine. |
|
|
3980 | .PP |
|
|
3981 | You can do similar tricks if you have, say, threads with an event queue \- |
|
|
3982 | instead of storing a coroutine, you store the queue object and instead of |
|
|
3983 | switching to a coroutine, you push the watcher onto the queue and notify |
|
|
3984 | any waiters. |
|
|
3985 | .PP |
|
|
3986 | To embed libev, see \s-1EMBEDDING\s0, but in short, it's easiest to create two |
|
|
3987 | files, \fImy_ev.h\fR and \fImy_ev.c\fR that include the respective libev files: |
|
|
3988 | .PP |
|
|
3989 | .Vb 4 |
|
|
3990 | \& // my_ev.h |
|
|
3991 | \& #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3992 | \& #define EV_CB_INVOKE(watcher) switch_to ((watcher)\->cb); |
|
|
3993 | \& #include "../libev/ev.h" |
|
|
3994 | \& |
|
|
3995 | \& // my_ev.c |
|
|
3996 | \& #define EV_H "my_ev.h" |
|
|
3997 | \& #include "../libev/ev.c" |
|
|
3998 | .Ve |
|
|
3999 | .PP |
|
|
4000 | And then use \fImy_ev.h\fR when you would normally use \fIev.h\fR, and compile |
|
|
4001 | \&\fImy_ev.c\fR into your project. When properly specifying include paths, you |
|
|
4002 | can even use \fIev.h\fR as header file name directly. |
1669 | .SH "LIBEVENT EMULATION" |
4003 | .SH "LIBEVENT EMULATION" |
1670 | .IX Header "LIBEVENT EMULATION" |
4004 | .IX Header "LIBEVENT EMULATION" |
1671 | Libev offers a compatibility emulation layer for libevent. It cannot |
4005 | Libev offers a compatibility emulation layer for libevent. It cannot |
1672 | emulate the internals of libevent, so here are some usage hints: |
4006 | emulate the internals of libevent, so here are some usage hints: |
|
|
4007 | .IP "\(bu" 4 |
|
|
4008 | Only the libevent\-1.4.1\-beta \s-1API\s0 is being emulated. |
|
|
4009 | .Sp |
|
|
4010 | This was the newest libevent version available when libev was implemented, |
|
|
4011 | and is still mostly unchanged in 2010. |
|
|
4012 | .IP "\(bu" 4 |
1673 | .IP "* Use it by including <event.h>, as usual." 4 |
4013 | Use it by including <event.h>, as usual. |
1674 | .IX Item "Use it by including <event.h>, as usual." |
4014 | .IP "\(bu" 4 |
1675 | .PD 0 |
4015 | The following members are fully supported: ev_base, ev_callback, |
1676 | .IP "* The following members are fully supported: ev_base, ev_callback, ev_arg, ev_fd, ev_res, ev_events." 4 |
4016 | ev_arg, ev_fd, ev_res, ev_events. |
1677 | .IX Item "The following members are fully supported: ev_base, ev_callback, ev_arg, ev_fd, ev_res, ev_events." |
4017 | .IP "\(bu" 4 |
1678 | .IP "* Avoid using ev_flags and the EVLIST_*\-macros, while it is maintained by libev, it does not work exactly the same way as in libevent (consider it a private \s-1API\s0)." 4 |
4018 | Avoid using ev_flags and the EVLIST_*\-macros, while it is |
1679 | .IX Item "Avoid using ev_flags and the EVLIST_*-macros, while it is maintained by libev, it does not work exactly the same way as in libevent (consider it a private API)." |
4019 | maintained by libev, it does not work exactly the same way as in libevent (consider |
1680 | .IP "* Priorities are not currently supported. Initialising priorities will fail and all watchers will have the same priority, even though there is an ev_pri field." 4 |
4020 | it a private \s-1API\s0). |
1681 | .IX Item "Priorities are not currently supported. Initialising priorities will fail and all watchers will have the same priority, even though there is an ev_pri field." |
4021 | .IP "\(bu" 4 |
|
|
4022 | Priorities are not currently supported. Initialising priorities |
|
|
4023 | will fail and all watchers will have the same priority, even though there |
|
|
4024 | is an ev_pri field. |
|
|
4025 | .IP "\(bu" 4 |
|
|
4026 | In libevent, the last base created gets the signals, in libev, the |
|
|
4027 | base that registered the signal gets the signals. |
|
|
4028 | .IP "\(bu" 4 |
1682 | .IP "* Other members are not supported." 4 |
4029 | Other members are not supported. |
1683 | .IX Item "Other members are not supported." |
4030 | .IP "\(bu" 4 |
1684 | .IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4 |
4031 | The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need |
1685 | .IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library." |
4032 | to use the libev header file and library. |
1686 | .PD |
|
|
1687 | .SH "\*(C+ SUPPORT" |
4033 | .SH "\*(C+ SUPPORT" |
1688 | .IX Header " SUPPORT" |
4034 | .IX Header " SUPPORT" |
1689 | Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow |
4035 | Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow |
1690 | you to use some convinience methods to start/stop watchers and also change |
4036 | you to use some convenience methods to start/stop watchers and also change |
1691 | the callback model to a model using method callbacks on objects. |
4037 | the callback model to a model using method callbacks on objects. |
1692 | .PP |
4038 | .PP |
1693 | To use it, |
4039 | To use it, |
1694 | .PP |
4040 | .PP |
1695 | .Vb 1 |
4041 | .Vb 1 |
1696 | \& #include <ev++.h> |
4042 | \& #include <ev++.h> |
1697 | .Ve |
4043 | .Ve |
1698 | .PP |
4044 | .PP |
1699 | (it is not installed by default). This automatically includes \fIev.h\fR |
4045 | This automatically includes \fIev.h\fR and puts all of its definitions (many |
1700 | and puts all of its definitions (many of them macros) into the global |
4046 | of them macros) into the global namespace. All \*(C+ specific things are |
1701 | namespace. All \*(C+ specific things are put into the \f(CW\*(C`ev\*(C'\fR namespace. |
4047 | put into the \f(CW\*(C`ev\*(C'\fR namespace. It should support all the same embedding |
|
|
4048 | options as \fIev.h\fR, most notably \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. |
1702 | .PP |
4049 | .PP |
1703 | It should support all the same embedding options as \fIev.h\fR, most notably |
4050 | Care has been taken to keep the overhead low. The only data member the \*(C+ |
1704 | \&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. |
4051 | classes add (compared to plain C\-style watchers) is the event loop pointer |
|
|
4052 | that the watcher is associated with (or no additional members at all if |
|
|
4053 | you disable \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR when embedding libev). |
|
|
4054 | .PP |
|
|
4055 | Currently, functions, static and non-static member functions and classes |
|
|
4056 | with \f(CW\*(C`operator ()\*(C'\fR can be used as callbacks. Other types should be easy |
|
|
4057 | to add as long as they only need one additional pointer for context. If |
|
|
4058 | you need support for other types of functors please contact the author |
|
|
4059 | (preferably after implementing it). |
1705 | .PP |
4060 | .PP |
1706 | Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace: |
4061 | Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace: |
1707 | .ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4 |
4062 | .ie n .IP """ev::READ"", ""ev::WRITE"" etc." 4 |
1708 | .el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4 |
4063 | .el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4 |
1709 | .IX Item "ev::READ, ev::WRITE etc." |
4064 | .IX Item "ev::READ, ev::WRITE etc." |
1710 | These are just enum values with the same values as the \f(CW\*(C`EV_READ\*(C'\fR etc. |
4065 | These are just enum values with the same values as the \f(CW\*(C`EV_READ\*(C'\fR etc. |
1711 | macros from \fIev.h\fR. |
4066 | macros from \fIev.h\fR. |
1712 | .ie n .IP """ev::tstamp""\fR, \f(CW""ev::now""" 4 |
4067 | .ie n .IP """ev::tstamp"", ""ev::now""" 4 |
1713 | .el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4 |
4068 | .el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4 |
1714 | .IX Item "ev::tstamp, ev::now" |
4069 | .IX Item "ev::tstamp, ev::now" |
1715 | Aliases to the same types/functions as with the \f(CW\*(C`ev_\*(C'\fR prefix. |
4070 | Aliases to the same types/functions as with the \f(CW\*(C`ev_\*(C'\fR prefix. |
1716 | .ie n .IP """ev::io""\fR, \f(CW""ev::timer""\fR, \f(CW""ev::periodic""\fR, \f(CW""ev::idle""\fR, \f(CW""ev::sig"" etc." 4 |
4071 | .ie n .IP """ev::io"", ""ev::timer"", ""ev::periodic"", ""ev::idle"", ""ev::sig"" etc." 4 |
1717 | .el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4 |
4072 | .el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4 |
1718 | .IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc." |
4073 | .IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc." |
1719 | For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of |
4074 | For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of |
1720 | the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR |
4075 | the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR |
1721 | which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro |
4076 | which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro |
1722 | defines by many implementations. |
4077 | defined by many implementations. |
1723 | .Sp |
4078 | .Sp |
1724 | All of those classes have these methods: |
4079 | All of those classes have these methods: |
1725 | .RS 4 |
4080 | .RS 4 |
1726 | .IP "ev::TYPE::TYPE (object *, object::method *)" 4 |
4081 | .IP "ev::TYPE::TYPE ()" 4 |
1727 | .IX Item "ev::TYPE::TYPE (object *, object::method *)" |
4082 | .IX Item "ev::TYPE::TYPE ()" |
1728 | .PD 0 |
4083 | .PD 0 |
1729 | .IP "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)" 4 |
4084 | .IP "ev::TYPE::TYPE (loop)" 4 |
1730 | .IX Item "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)" |
4085 | .IX Item "ev::TYPE::TYPE (loop)" |
1731 | .IP "ev::TYPE::~TYPE" 4 |
4086 | .IP "ev::TYPE::~TYPE" 4 |
1732 | .IX Item "ev::TYPE::~TYPE" |
4087 | .IX Item "ev::TYPE::~TYPE" |
1733 | .PD |
4088 | .PD |
1734 | The constructor takes a pointer to an object and a method pointer to |
4089 | The constructor (optionally) takes an event loop to associate the watcher |
1735 | the event handler callback to call in this class. The constructor calls |
4090 | with. If it is omitted, it will use \f(CW\*(C`EV_DEFAULT\*(C'\fR. |
1736 | \&\f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the \f(CW\*(C`set\*(C'\fR method |
4091 | .Sp |
1737 | before starting it. If you do not specify a loop then the constructor |
4092 | The constructor calls \f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the |
1738 | automatically associates the default loop with this watcher. |
4093 | \&\f(CW\*(C`set\*(C'\fR method before starting it. |
|
|
4094 | .Sp |
|
|
4095 | It will not set a callback, however: You have to call the templated \f(CW\*(C`set\*(C'\fR |
|
|
4096 | method to set a callback before you can start the watcher. |
|
|
4097 | .Sp |
|
|
4098 | (The reason why you have to use a method is a limitation in \*(C+ which does |
|
|
4099 | not allow explicit template arguments for constructors). |
1739 | .Sp |
4100 | .Sp |
1740 | The destructor automatically stops the watcher if it is active. |
4101 | The destructor automatically stops the watcher if it is active. |
|
|
4102 | .IP "w\->set<class, &class::method> (object *)" 4 |
|
|
4103 | .IX Item "w->set<class, &class::method> (object *)" |
|
|
4104 | This method sets the callback method to call. The method has to have a |
|
|
4105 | signature of \f(CW\*(C`void (*)(ev_TYPE &, int)\*(C'\fR, it receives the watcher as |
|
|
4106 | first argument and the \f(CW\*(C`revents\*(C'\fR as second. The object must be given as |
|
|
4107 | parameter and is stored in the \f(CW\*(C`data\*(C'\fR member of the watcher. |
|
|
4108 | .Sp |
|
|
4109 | This method synthesizes efficient thunking code to call your method from |
|
|
4110 | the C callback that libev requires. If your compiler can inline your |
|
|
4111 | callback (i.e. it is visible to it at the place of the \f(CW\*(C`set\*(C'\fR call and |
|
|
4112 | your compiler is good :), then the method will be fully inlined into the |
|
|
4113 | thunking function, making it as fast as a direct C callback. |
|
|
4114 | .Sp |
|
|
4115 | Example: simple class declaration and watcher initialisation |
|
|
4116 | .Sp |
|
|
4117 | .Vb 4 |
|
|
4118 | \& struct myclass |
|
|
4119 | \& { |
|
|
4120 | \& void io_cb (ev::io &w, int revents) { } |
|
|
4121 | \& } |
|
|
4122 | \& |
|
|
4123 | \& myclass obj; |
|
|
4124 | \& ev::io iow; |
|
|
4125 | \& iow.set <myclass, &myclass::io_cb> (&obj); |
|
|
4126 | .Ve |
|
|
4127 | .IP "w\->set (object *)" 4 |
|
|
4128 | .IX Item "w->set (object *)" |
|
|
4129 | This is a variation of a method callback \- leaving out the method to call |
|
|
4130 | will default the method to \f(CW\*(C`operator ()\*(C'\fR, which makes it possible to use |
|
|
4131 | functor objects without having to manually specify the \f(CW\*(C`operator ()\*(C'\fR all |
|
|
4132 | the time. Incidentally, you can then also leave out the template argument |
|
|
4133 | list. |
|
|
4134 | .Sp |
|
|
4135 | The \f(CW\*(C`operator ()\*(C'\fR method prototype must be \f(CW\*(C`void operator ()(watcher &w, |
|
|
4136 | int revents)\*(C'\fR. |
|
|
4137 | .Sp |
|
|
4138 | See the method\-\f(CW\*(C`set\*(C'\fR above for more details. |
|
|
4139 | .Sp |
|
|
4140 | Example: use a functor object as callback. |
|
|
4141 | .Sp |
|
|
4142 | .Vb 7 |
|
|
4143 | \& struct myfunctor |
|
|
4144 | \& { |
|
|
4145 | \& void operator() (ev::io &w, int revents) |
|
|
4146 | \& { |
|
|
4147 | \& ... |
|
|
4148 | \& } |
|
|
4149 | \& } |
|
|
4150 | \& |
|
|
4151 | \& myfunctor f; |
|
|
4152 | \& |
|
|
4153 | \& ev::io w; |
|
|
4154 | \& w.set (&f); |
|
|
4155 | .Ve |
|
|
4156 | .IP "w\->set<function> (void *data = 0)" 4 |
|
|
4157 | .IX Item "w->set<function> (void *data = 0)" |
|
|
4158 | Also sets a callback, but uses a static method or plain function as |
|
|
4159 | callback. The optional \f(CW\*(C`data\*(C'\fR argument will be stored in the watcher's |
|
|
4160 | \&\f(CW\*(C`data\*(C'\fR member and is free for you to use. |
|
|
4161 | .Sp |
|
|
4162 | The prototype of the \f(CW\*(C`function\*(C'\fR must be \f(CW\*(C`void (*)(ev::TYPE &w, int)\*(C'\fR. |
|
|
4163 | .Sp |
|
|
4164 | See the method\-\f(CW\*(C`set\*(C'\fR above for more details. |
|
|
4165 | .Sp |
|
|
4166 | Example: Use a plain function as callback. |
|
|
4167 | .Sp |
|
|
4168 | .Vb 2 |
|
|
4169 | \& static void io_cb (ev::io &w, int revents) { } |
|
|
4170 | \& iow.set <io_cb> (); |
|
|
4171 | .Ve |
1741 | .IP "w\->set (struct ev_loop *)" 4 |
4172 | .IP "w\->set (loop)" 4 |
1742 | .IX Item "w->set (struct ev_loop *)" |
4173 | .IX Item "w->set (loop)" |
1743 | Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only |
4174 | Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only |
1744 | do this when the watcher is inactive (and not pending either). |
4175 | do this when the watcher is inactive (and not pending either). |
1745 | .IP "w\->set ([args])" 4 |
4176 | .IP "w\->set ([arguments])" 4 |
1746 | .IX Item "w->set ([args])" |
4177 | .IX Item "w->set ([arguments])" |
1747 | Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same args. Must be |
4178 | Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same arguments. Either this |
1748 | called at least once. Unlike the C counterpart, an active watcher gets |
4179 | method or a suitable start method must be called at least once. Unlike the |
1749 | automatically stopped and restarted. |
4180 | C counterpart, an active watcher gets automatically stopped and restarted |
|
|
4181 | when reconfiguring it with this method. |
1750 | .IP "w\->start ()" 4 |
4182 | .IP "w\->start ()" 4 |
1751 | .IX Item "w->start ()" |
4183 | .IX Item "w->start ()" |
1752 | Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument as the |
4184 | Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the |
1753 | constructor already takes the loop. |
4185 | constructor already stores the event loop. |
|
|
4186 | .IP "w\->start ([arguments])" 4 |
|
|
4187 | .IX Item "w->start ([arguments])" |
|
|
4188 | Instead of calling \f(CW\*(C`set\*(C'\fR and \f(CW\*(C`start\*(C'\fR methods separately, it is often |
|
|
4189 | convenient to wrap them in one call. Uses the same type of arguments as |
|
|
4190 | the configure \f(CW\*(C`set\*(C'\fR method of the watcher. |
1754 | .IP "w\->stop ()" 4 |
4191 | .IP "w\->stop ()" 4 |
1755 | .IX Item "w->stop ()" |
4192 | .IX Item "w->stop ()" |
1756 | Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument. |
4193 | Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument. |
1757 | .ie n .IP "w\->again () ""ev::timer""\fR, \f(CW""ev::periodic"" only" 4 |
4194 | .ie n .IP "w\->again () (""ev::timer"", ""ev::periodic"" only)" 4 |
1758 | .el .IP "w\->again () \f(CWev::timer\fR, \f(CWev::periodic\fR only" 4 |
4195 | .el .IP "w\->again () (\f(CWev::timer\fR, \f(CWev::periodic\fR only)" 4 |
1759 | .IX Item "w->again () ev::timer, ev::periodic only" |
4196 | .IX Item "w->again () (ev::timer, ev::periodic only)" |
1760 | For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding |
4197 | For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding |
1761 | \&\f(CW\*(C`ev_TYPE_again\*(C'\fR function. |
4198 | \&\f(CW\*(C`ev_TYPE_again\*(C'\fR function. |
1762 | .ie n .IP "w\->sweep () ""ev::embed"" only" 4 |
4199 | .ie n .IP "w\->sweep () (""ev::embed"" only)" 4 |
1763 | .el .IP "w\->sweep () \f(CWev::embed\fR only" 4 |
4200 | .el .IP "w\->sweep () (\f(CWev::embed\fR only)" 4 |
1764 | .IX Item "w->sweep () ev::embed only" |
4201 | .IX Item "w->sweep () (ev::embed only)" |
1765 | Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR. |
4202 | Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR. |
1766 | .ie n .IP "w\->update () ""ev::stat"" only" 4 |
4203 | .ie n .IP "w\->update () (""ev::stat"" only)" 4 |
1767 | .el .IP "w\->update () \f(CWev::stat\fR only" 4 |
4204 | .el .IP "w\->update () (\f(CWev::stat\fR only)" 4 |
1768 | .IX Item "w->update () ev::stat only" |
4205 | .IX Item "w->update () (ev::stat only)" |
1769 | Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR. |
4206 | Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR. |
1770 | .RE |
4207 | .RE |
1771 | .RS 4 |
4208 | .RS 4 |
1772 | .RE |
4209 | .RE |
1773 | .PP |
4210 | .PP |
1774 | Example: Define a class with an \s-1IO\s0 and idle watcher, start one of them in |
4211 | Example: Define a class with two I/O and idle watchers, start the I/O |
1775 | the constructor. |
4212 | watchers in the constructor. |
1776 | .PP |
4213 | .PP |
1777 | .Vb 4 |
4214 | .Vb 5 |
1778 | \& class myclass |
4215 | \& class myclass |
1779 | \& { |
4216 | \& { |
1780 | \& ev_io io; void io_cb (ev::io &w, int revents); |
4217 | \& ev::io io ; void io_cb (ev::io &w, int revents); |
|
|
4218 | \& ev::io io2 ; void io2_cb (ev::io &w, int revents); |
1781 | \& ev_idle idle void idle_cb (ev::idle &w, int revents); |
4219 | \& ev::idle idle; void idle_cb (ev::idle &w, int revents); |
|
|
4220 | \& |
|
|
4221 | \& myclass (int fd) |
|
|
4222 | \& { |
|
|
4223 | \& io .set <myclass, &myclass::io_cb > (this); |
|
|
4224 | \& io2 .set <myclass, &myclass::io2_cb > (this); |
|
|
4225 | \& idle.set <myclass, &myclass::idle_cb> (this); |
|
|
4226 | \& |
|
|
4227 | \& io.set (fd, ev::WRITE); // configure the watcher |
|
|
4228 | \& io.start (); // start it whenever convenient |
|
|
4229 | \& |
|
|
4230 | \& io2.start (fd, ev::READ); // set + start in one call |
|
|
4231 | \& } |
|
|
4232 | \& }; |
1782 | .Ve |
4233 | .Ve |
|
|
4234 | .SH "OTHER LANGUAGE BINDINGS" |
|
|
4235 | .IX Header "OTHER LANGUAGE BINDINGS" |
|
|
4236 | Libev does not offer other language bindings itself, but bindings for a |
|
|
4237 | number of languages exist in the form of third-party packages. If you know |
|
|
4238 | any interesting language binding in addition to the ones listed here, drop |
|
|
4239 | me a note. |
|
|
4240 | .IP "Perl" 4 |
|
|
4241 | .IX Item "Perl" |
|
|
4242 | The \s-1EV\s0 module implements the full libev \s-1API\s0 and is actually used to test |
|
|
4243 | libev. \s-1EV\s0 is developed together with libev. Apart from the \s-1EV\s0 core module, |
|
|
4244 | there are additional modules that implement libev-compatible interfaces |
|
|
4245 | to \f(CW\*(C`libadns\*(C'\fR (\f(CW\*(C`EV::ADNS\*(C'\fR, but \f(CW\*(C`AnyEvent::DNS\*(C'\fR is preferred nowadays), |
|
|
4246 | \&\f(CW\*(C`Net::SNMP\*(C'\fR (\f(CW\*(C`Net::SNMP::EV\*(C'\fR) and the \f(CW\*(C`libglib\*(C'\fR event core (\f(CW\*(C`Glib::EV\*(C'\fR |
|
|
4247 | and \f(CW\*(C`EV::Glib\*(C'\fR). |
|
|
4248 | .Sp |
|
|
4249 | It can be found and installed via \s-1CPAN\s0, its homepage is at |
|
|
4250 | <http://software.schmorp.de/pkg/EV>. |
|
|
4251 | .IP "Python" 4 |
|
|
4252 | .IX Item "Python" |
|
|
4253 | Python bindings can be found at <http://code.google.com/p/pyev/>. It |
|
|
4254 | seems to be quite complete and well-documented. |
|
|
4255 | .IP "Ruby" 4 |
|
|
4256 | .IX Item "Ruby" |
|
|
4257 | Tony Arcieri has written a ruby extension that offers access to a subset |
|
|
4258 | of the libev \s-1API\s0 and adds file handle abstractions, asynchronous \s-1DNS\s0 and |
|
|
4259 | more on top of it. It can be found via gem servers. Its homepage is at |
|
|
4260 | <http://rev.rubyforge.org/>. |
|
|
4261 | .Sp |
|
|
4262 | Roger Pack reports that using the link order \f(CW\*(C`\-lws2_32 \-lmsvcrt\-ruby\-190\*(C'\fR |
|
|
4263 | makes rev work even on mingw. |
|
|
4264 | .IP "Haskell" 4 |
|
|
4265 | .IX Item "Haskell" |
|
|
4266 | A haskell binding to libev is available at |
|
|
4267 | http://hackage.haskell.org/cgi\-bin/hackage\-scripts/package/hlibev <http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
|
|
4268 | .IP "D" 4 |
|
|
4269 | .IX Item "D" |
|
|
4270 | Leandro Lucarella has written a D language binding (\fIev.d\fR) for libev, to |
|
|
4271 | be found at <http://www.llucax.com.ar/proj/ev.d/index.html>. |
|
|
4272 | .IP "Ocaml" 4 |
|
|
4273 | .IX Item "Ocaml" |
|
|
4274 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
|
|
4275 | http://modeemi.cs.tut.fi/~flux/software/ocaml\-ev/ <http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
|
|
4276 | .IP "Lua" 4 |
|
|
4277 | .IX Item "Lua" |
|
|
4278 | Brian Maher has written a partial interface to libev for lua (at the |
|
|
4279 | time of this writing, only \f(CW\*(C`ev_io\*(C'\fR and \f(CW\*(C`ev_timer\*(C'\fR), to be found at |
|
|
4280 | http://github.com/brimworks/lua\-ev <http://github.com/brimworks/lua-ev>. |
|
|
4281 | .SH "MACRO MAGIC" |
|
|
4282 | .IX Header "MACRO MAGIC" |
|
|
4283 | Libev can be compiled with a variety of options, the most fundamental |
|
|
4284 | of which is \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most) |
|
|
4285 | functions and callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument. |
1783 | .PP |
4286 | .PP |
|
|
4287 | To make it easier to write programs that cope with either variant, the |
|
|
4288 | following macros are defined: |
|
|
4289 | .ie n .IP """EV_A"", ""EV_A_""" 4 |
|
|
4290 | .el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4 |
|
|
4291 | .IX Item "EV_A, EV_A_" |
|
|
4292 | This provides the loop \fIargument\fR for functions, if one is required (\*(L"ev |
|
|
4293 | loop argument\*(R"). The \f(CW\*(C`EV_A\*(C'\fR form is used when this is the sole argument, |
|
|
4294 | \&\f(CW\*(C`EV_A_\*(C'\fR is used when other arguments are following. Example: |
|
|
4295 | .Sp |
|
|
4296 | .Vb 3 |
|
|
4297 | \& ev_unref (EV_A); |
|
|
4298 | \& ev_timer_add (EV_A_ watcher); |
|
|
4299 | \& ev_run (EV_A_ 0); |
|
|
4300 | .Ve |
|
|
4301 | .Sp |
|
|
4302 | It assumes the variable \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR is in scope, |
|
|
4303 | which is often provided by the following macro. |
|
|
4304 | .ie n .IP """EV_P"", ""EV_P_""" 4 |
|
|
4305 | .el .IP "\f(CWEV_P\fR, \f(CWEV_P_\fR" 4 |
|
|
4306 | .IX Item "EV_P, EV_P_" |
|
|
4307 | This provides the loop \fIparameter\fR for functions, if one is required (\*(L"ev |
|
|
4308 | loop parameter\*(R"). The \f(CW\*(C`EV_P\*(C'\fR form is used when this is the sole parameter, |
|
|
4309 | \&\f(CW\*(C`EV_P_\*(C'\fR is used when other parameters are following. Example: |
|
|
4310 | .Sp |
1784 | .Vb 2 |
4311 | .Vb 2 |
1785 | \& myclass (); |
4312 | \& // this is how ev_unref is being declared |
1786 | \& } |
4313 | \& static void ev_unref (EV_P); |
|
|
4314 | \& |
|
|
4315 | \& // this is how you can declare your typical callback |
|
|
4316 | \& static void cb (EV_P_ ev_timer *w, int revents) |
1787 | .Ve |
4317 | .Ve |
|
|
4318 | .Sp |
|
|
4319 | It declares a parameter \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR, quite |
|
|
4320 | suitable for use with \f(CW\*(C`EV_A\*(C'\fR. |
|
|
4321 | .ie n .IP """EV_DEFAULT"", ""EV_DEFAULT_""" 4 |
|
|
4322 | .el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4 |
|
|
4323 | .IX Item "EV_DEFAULT, EV_DEFAULT_" |
|
|
4324 | Similar to the other two macros, this gives you the value of the default |
|
|
4325 | loop, if multiple loops are supported (\*(L"ev loop default\*(R"). The default loop |
|
|
4326 | will be initialised if it isn't already initialised. |
|
|
4327 | .Sp |
|
|
4328 | For non-multiplicity builds, these macros do nothing, so you always have |
|
|
4329 | to initialise the loop somewhere. |
|
|
4330 | .ie n .IP """EV_DEFAULT_UC"", ""EV_DEFAULT_UC_""" 4 |
|
|
4331 | .el .IP "\f(CWEV_DEFAULT_UC\fR, \f(CWEV_DEFAULT_UC_\fR" 4 |
|
|
4332 | .IX Item "EV_DEFAULT_UC, EV_DEFAULT_UC_" |
|
|
4333 | Usage identical to \f(CW\*(C`EV_DEFAULT\*(C'\fR and \f(CW\*(C`EV_DEFAULT_\*(C'\fR, but requires that the |
|
|
4334 | default loop has been initialised (\f(CW\*(C`UC\*(C'\fR == unchecked). Their behaviour |
|
|
4335 | is undefined when the default loop has not been initialised by a previous |
|
|
4336 | execution of \f(CW\*(C`EV_DEFAULT\*(C'\fR, \f(CW\*(C`EV_DEFAULT_\*(C'\fR or \f(CW\*(C`ev_default_init (...)\*(C'\fR. |
|
|
4337 | .Sp |
|
|
4338 | It is often prudent to use \f(CW\*(C`EV_DEFAULT\*(C'\fR when initialising the first |
|
|
4339 | watcher in a function but use \f(CW\*(C`EV_DEFAULT_UC\*(C'\fR afterwards. |
1788 | .PP |
4340 | .PP |
|
|
4341 | Example: Declare and initialise a check watcher, utilising the above |
|
|
4342 | macros so it will work regardless of whether multiple loops are supported |
|
|
4343 | or not. |
|
|
4344 | .PP |
1789 | .Vb 6 |
4345 | .Vb 5 |
1790 | \& myclass::myclass (int fd) |
4346 | \& static void |
1791 | \& : io (this, &myclass::io_cb), |
4347 | \& check_cb (EV_P_ ev_timer *w, int revents) |
1792 | \& idle (this, &myclass::idle_cb) |
|
|
1793 | \& { |
4348 | \& { |
1794 | \& io.start (fd, ev::READ); |
4349 | \& ev_check_stop (EV_A_ w); |
1795 | \& } |
4350 | \& } |
|
|
4351 | \& |
|
|
4352 | \& ev_check check; |
|
|
4353 | \& ev_check_init (&check, check_cb); |
|
|
4354 | \& ev_check_start (EV_DEFAULT_ &check); |
|
|
4355 | \& ev_run (EV_DEFAULT_ 0); |
1796 | .Ve |
4356 | .Ve |
1797 | .SH "EMBEDDING" |
4357 | .SH "EMBEDDING" |
1798 | .IX Header "EMBEDDING" |
4358 | .IX Header "EMBEDDING" |
1799 | Libev can (and often is) directly embedded into host |
4359 | Libev can (and often is) directly embedded into host |
1800 | applications. Examples of applications that embed it include the Deliantra |
4360 | applications. Examples of applications that embed it include the Deliantra |
1801 | Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe) |
4361 | Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe) |
1802 | and rxvt\-unicode. |
4362 | and rxvt-unicode. |
1803 | .PP |
4363 | .PP |
1804 | The goal is to enable you to just copy the neecssary files into your |
4364 | The goal is to enable you to just copy the necessary files into your |
1805 | source directory without having to change even a single line in them, so |
4365 | source directory without having to change even a single line in them, so |
1806 | you can easily upgrade by simply copying (or having a checked-out copy of |
4366 | you can easily upgrade by simply copying (or having a checked-out copy of |
1807 | libev somewhere in your source tree). |
4367 | libev somewhere in your source tree). |
1808 | .Sh "\s-1FILESETS\s0" |
4368 | .SS "\s-1FILESETS\s0" |
1809 | .IX Subsection "FILESETS" |
4369 | .IX Subsection "FILESETS" |
1810 | Depending on what features you need you need to include one or more sets of files |
4370 | Depending on what features you need you need to include one or more sets of files |
1811 | in your app. |
4371 | in your application. |
1812 | .PP |
4372 | .PP |
1813 | \fI\s-1CORE\s0 \s-1EVENT\s0 \s-1LOOP\s0\fR |
4373 | \fI\s-1CORE\s0 \s-1EVENT\s0 \s-1LOOP\s0\fR |
1814 | .IX Subsection "CORE EVENT LOOP" |
4374 | .IX Subsection "CORE EVENT LOOP" |
1815 | .PP |
4375 | .PP |
1816 | To include only the libev core (all the \f(CW\*(C`ev_*\*(C'\fR functions), with manual |
4376 | To include only the libev core (all the \f(CW\*(C`ev_*\*(C'\fR functions), with manual |
1817 | configuration (no autoconf): |
4377 | configuration (no autoconf): |
1818 | .PP |
4378 | .PP |
1819 | .Vb 2 |
4379 | .Vb 2 |
1820 | \& #define EV_STANDALONE 1 |
4380 | \& #define EV_STANDALONE 1 |
1821 | \& #include "ev.c" |
4381 | \& #include "ev.c" |
1822 | .Ve |
4382 | .Ve |
1823 | .PP |
4383 | .PP |
1824 | This will automatically include \fIev.h\fR, too, and should be done in a |
4384 | This will automatically include \fIev.h\fR, too, and should be done in a |
1825 | single C source file only to provide the function implementations. To use |
4385 | single C source file only to provide the function implementations. To use |
1826 | it, do the same for \fIev.h\fR in all files wishing to use this \s-1API\s0 (best |
4386 | it, do the same for \fIev.h\fR in all files wishing to use this \s-1API\s0 (best |
1827 | done by writing a wrapper around \fIev.h\fR that you can include instead and |
4387 | done by writing a wrapper around \fIev.h\fR that you can include instead and |
1828 | where you can put other configuration options): |
4388 | where you can put other configuration options): |
1829 | .PP |
4389 | .PP |
1830 | .Vb 2 |
4390 | .Vb 2 |
1831 | \& #define EV_STANDALONE 1 |
4391 | \& #define EV_STANDALONE 1 |
1832 | \& #include "ev.h" |
4392 | \& #include "ev.h" |
1833 | .Ve |
4393 | .Ve |
1834 | .PP |
4394 | .PP |
1835 | Both header files and implementation files can be compiled with a \*(C+ |
4395 | Both header files and implementation files can be compiled with a \*(C+ |
1836 | compiler (at least, thats a stated goal, and breakage will be treated |
4396 | compiler (at least, that's a stated goal, and breakage will be treated |
1837 | as a bug). |
4397 | as a bug). |
1838 | .PP |
4398 | .PP |
1839 | You need the following files in your source tree, or in a directory |
4399 | You need the following files in your source tree, or in a directory |
1840 | in your include path (e.g. in libev/ when using \-Ilibev): |
4400 | in your include path (e.g. in libev/ when using \-Ilibev): |
1841 | .PP |
4401 | .PP |
1842 | .Vb 4 |
4402 | .Vb 4 |
1843 | \& ev.h |
4403 | \& ev.h |
1844 | \& ev.c |
4404 | \& ev.c |
1845 | \& ev_vars.h |
4405 | \& ev_vars.h |
1846 | \& ev_wrap.h |
4406 | \& ev_wrap.h |
1847 | .Ve |
4407 | \& |
1848 | .PP |
|
|
1849 | .Vb 1 |
|
|
1850 | \& ev_win32.c required on win32 platforms only |
4408 | \& ev_win32.c required on win32 platforms only |
1851 | .Ve |
4409 | \& |
1852 | .PP |
|
|
1853 | .Vb 5 |
|
|
1854 | \& ev_select.c only when select backend is enabled (which is by default) |
4410 | \& ev_select.c only when select backend is enabled (which is enabled by default) |
1855 | \& ev_poll.c only when poll backend is enabled (disabled by default) |
4411 | \& ev_poll.c only when poll backend is enabled (disabled by default) |
1856 | \& ev_epoll.c only when the epoll backend is enabled (disabled by default) |
4412 | \& ev_epoll.c only when the epoll backend is enabled (disabled by default) |
1857 | \& ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
4413 | \& ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
1858 | \& ev_port.c only when the solaris port backend is enabled (disabled by default) |
4414 | \& ev_port.c only when the solaris port backend is enabled (disabled by default) |
1859 | .Ve |
4415 | .Ve |
1860 | .PP |
4416 | .PP |
1861 | \&\fIev.c\fR includes the backend files directly when enabled, so you only need |
4417 | \&\fIev.c\fR includes the backend files directly when enabled, so you only need |
1862 | to compile this single file. |
4418 | to compile this single file. |
1863 | .PP |
4419 | .PP |
… | |
… | |
1865 | .IX Subsection "LIBEVENT COMPATIBILITY API" |
4421 | .IX Subsection "LIBEVENT COMPATIBILITY API" |
1866 | .PP |
4422 | .PP |
1867 | To include the libevent compatibility \s-1API\s0, also include: |
4423 | To include the libevent compatibility \s-1API\s0, also include: |
1868 | .PP |
4424 | .PP |
1869 | .Vb 1 |
4425 | .Vb 1 |
1870 | \& #include "event.c" |
4426 | \& #include "event.c" |
1871 | .Ve |
4427 | .Ve |
1872 | .PP |
4428 | .PP |
1873 | in the file including \fIev.c\fR, and: |
4429 | in the file including \fIev.c\fR, and: |
1874 | .PP |
4430 | .PP |
1875 | .Vb 1 |
4431 | .Vb 1 |
1876 | \& #include "event.h" |
4432 | \& #include "event.h" |
1877 | .Ve |
4433 | .Ve |
1878 | .PP |
4434 | .PP |
1879 | in the files that want to use the libevent \s-1API\s0. This also includes \fIev.h\fR. |
4435 | in the files that want to use the libevent \s-1API\s0. This also includes \fIev.h\fR. |
1880 | .PP |
4436 | .PP |
1881 | You need the following additional files for this: |
4437 | You need the following additional files for this: |
1882 | .PP |
4438 | .PP |
1883 | .Vb 2 |
4439 | .Vb 2 |
1884 | \& event.h |
4440 | \& event.h |
1885 | \& event.c |
4441 | \& event.c |
1886 | .Ve |
4442 | .Ve |
1887 | .PP |
4443 | .PP |
1888 | \fI\s-1AUTOCONF\s0 \s-1SUPPORT\s0\fR |
4444 | \fI\s-1AUTOCONF\s0 \s-1SUPPORT\s0\fR |
1889 | .IX Subsection "AUTOCONF SUPPORT" |
4445 | .IX Subsection "AUTOCONF SUPPORT" |
1890 | .PP |
4446 | .PP |
1891 | Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your config in |
4447 | Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your configuration in |
1892 | whatever way you want, you can also \f(CW\*(C`m4_include([libev.m4])\*(C'\fR in your |
4448 | whatever way you want, you can also \f(CW\*(C`m4_include([libev.m4])\*(C'\fR in your |
1893 | \&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR undefined. \fIev.c\fR will then |
4449 | \&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR undefined. \fIev.c\fR will then |
1894 | include \fIconfig.h\fR and configure itself accordingly. |
4450 | include \fIconfig.h\fR and configure itself accordingly. |
1895 | .PP |
4451 | .PP |
1896 | For this of course you need the m4 file: |
4452 | For this of course you need the m4 file: |
1897 | .PP |
4453 | .PP |
1898 | .Vb 1 |
4454 | .Vb 1 |
1899 | \& libev.m4 |
4455 | \& libev.m4 |
1900 | .Ve |
4456 | .Ve |
1901 | .Sh "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0" |
4457 | .SS "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0" |
1902 | .IX Subsection "PREPROCESSOR SYMBOLS/MACROS" |
4458 | .IX Subsection "PREPROCESSOR SYMBOLS/MACROS" |
1903 | Libev can be configured via a variety of preprocessor symbols you have to define |
4459 | Libev can be configured via a variety of preprocessor symbols you have to |
1904 | before including any of its files. The default is not to build for multiplicity |
4460 | define before including (or compiling) any of its files. The default in |
1905 | and only include the select backend. |
4461 | the absence of autoconf is documented for every option. |
|
|
4462 | .PP |
|
|
4463 | Symbols marked with \*(L"(h)\*(R" do not change the \s-1ABI\s0, and can have different |
|
|
4464 | values when compiling libev vs. including \fIev.h\fR, so it is permissible |
|
|
4465 | to redefine them before including \fIev.h\fR without breaking compatibility |
|
|
4466 | to a compiled library. All other symbols change the \s-1ABI\s0, which means all |
|
|
4467 | users of libev and the libev code itself must be compiled with compatible |
|
|
4468 | settings. |
|
|
4469 | .IP "\s-1EV_COMPAT3\s0 (h)" 4 |
|
|
4470 | .IX Item "EV_COMPAT3 (h)" |
|
|
4471 | Backwards compatibility is a major concern for libev. This is why this |
|
|
4472 | release of libev comes with wrappers for the functions and symbols that |
|
|
4473 | have been renamed between libev version 3 and 4. |
|
|
4474 | .Sp |
|
|
4475 | You can disable these wrappers (to test compatibility with future |
|
|
4476 | versions) by defining \f(CW\*(C`EV_COMPAT3\*(C'\fR to \f(CW0\fR when compiling your |
|
|
4477 | sources. This has the additional advantage that you can drop the \f(CW\*(C`struct\*(C'\fR |
|
|
4478 | from \f(CW\*(C`struct ev_loop\*(C'\fR declarations, as libev will provide an \f(CW\*(C`ev_loop\*(C'\fR |
|
|
4479 | typedef in that case. |
|
|
4480 | .Sp |
|
|
4481 | In some future version, the default for \f(CW\*(C`EV_COMPAT3\*(C'\fR will become \f(CW0\fR, |
|
|
4482 | and in some even more future version the compatibility code will be |
|
|
4483 | removed completely. |
1906 | .IP "\s-1EV_STANDALONE\s0" 4 |
4484 | .IP "\s-1EV_STANDALONE\s0 (h)" 4 |
1907 | .IX Item "EV_STANDALONE" |
4485 | .IX Item "EV_STANDALONE (h)" |
1908 | Must always be \f(CW1\fR if you do not use autoconf configuration, which |
4486 | Must always be \f(CW1\fR if you do not use autoconf configuration, which |
1909 | keeps libev from including \fIconfig.h\fR, and it also defines dummy |
4487 | keeps libev from including \fIconfig.h\fR, and it also defines dummy |
1910 | implementations for some libevent functions (such as logging, which is not |
4488 | implementations for some libevent functions (such as logging, which is not |
1911 | supported). It will also not define any of the structs usually found in |
4489 | supported). It will also not define any of the structs usually found in |
1912 | \&\fIevent.h\fR that are not directly supported by the libev core alone. |
4490 | \&\fIevent.h\fR that are not directly supported by the libev core alone. |
|
|
4491 | .Sp |
|
|
4492 | In standalone mode, libev will still try to automatically deduce the |
|
|
4493 | configuration, but has to be more conservative. |
|
|
4494 | .IP "\s-1EV_USE_FLOOR\s0" 4 |
|
|
4495 | .IX Item "EV_USE_FLOOR" |
|
|
4496 | If defined to be \f(CW1\fR, libev will use the \f(CW\*(C`floor ()\*(C'\fR function for its |
|
|
4497 | periodic reschedule calculations, otherwise libev will fall back on a |
|
|
4498 | portable (slower) implementation. If you enable this, you usually have to |
|
|
4499 | link against libm or something equivalent. Enabling this when the \f(CW\*(C`floor\*(C'\fR |
|
|
4500 | function is not available will fail, so the safe default is to not enable |
|
|
4501 | this. |
1913 | .IP "\s-1EV_USE_MONOTONIC\s0" 4 |
4502 | .IP "\s-1EV_USE_MONOTONIC\s0" 4 |
1914 | .IX Item "EV_USE_MONOTONIC" |
4503 | .IX Item "EV_USE_MONOTONIC" |
1915 | If defined to be \f(CW1\fR, libev will try to detect the availability of the |
4504 | If defined to be \f(CW1\fR, libev will try to detect the availability of the |
1916 | monotonic clock option at both compiletime and runtime. Otherwise no use |
4505 | monotonic clock option at both compile time and runtime. Otherwise no |
1917 | of the monotonic clock option will be attempted. If you enable this, you |
4506 | use of the monotonic clock option will be attempted. If you enable this, |
1918 | usually have to link against librt or something similar. Enabling it when |
4507 | you usually have to link against librt or something similar. Enabling it |
1919 | the functionality isn't available is safe, though, althoguh you have |
4508 | when the functionality isn't available is safe, though, although you have |
1920 | to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR |
4509 | to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR |
1921 | function is hiding in (often \fI\-lrt\fR). |
4510 | function is hiding in (often \fI\-lrt\fR). See also \f(CW\*(C`EV_USE_CLOCK_SYSCALL\*(C'\fR. |
1922 | .IP "\s-1EV_USE_REALTIME\s0" 4 |
4511 | .IP "\s-1EV_USE_REALTIME\s0" 4 |
1923 | .IX Item "EV_USE_REALTIME" |
4512 | .IX Item "EV_USE_REALTIME" |
1924 | If defined to be \f(CW1\fR, libev will try to detect the availability of the |
4513 | If defined to be \f(CW1\fR, libev will try to detect the availability of the |
1925 | realtime clock option at compiletime (and assume its availability at |
4514 | real-time clock option at compile time (and assume its availability |
1926 | runtime if successful). Otherwise no use of the realtime clock option will |
4515 | at runtime if successful). Otherwise no use of the real-time clock |
1927 | be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get |
4516 | option will be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR |
1928 | (CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See tzhe note about libraries |
4517 | by \f(CW\*(C`clock_get (CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect |
1929 | in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though. |
4518 | correctness. See the note about libraries in the description of |
|
|
4519 | \&\f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though. Defaults to the opposite value of |
|
|
4520 | \&\f(CW\*(C`EV_USE_CLOCK_SYSCALL\*(C'\fR. |
|
|
4521 | .IP "\s-1EV_USE_CLOCK_SYSCALL\s0" 4 |
|
|
4522 | .IX Item "EV_USE_CLOCK_SYSCALL" |
|
|
4523 | If defined to be \f(CW1\fR, libev will try to use a direct syscall instead |
|
|
4524 | of calling the system-provided \f(CW\*(C`clock_gettime\*(C'\fR function. This option |
|
|
4525 | exists because on GNU/Linux, \f(CW\*(C`clock_gettime\*(C'\fR is in \f(CW\*(C`librt\*(C'\fR, but \f(CW\*(C`librt\*(C'\fR |
|
|
4526 | unconditionally pulls in \f(CW\*(C`libpthread\*(C'\fR, slowing down single-threaded |
|
|
4527 | programs needlessly. Using a direct syscall is slightly slower (in |
|
|
4528 | theory), because no optimised vdso implementation can be used, but avoids |
|
|
4529 | the pthread dependency. Defaults to \f(CW1\fR on GNU/Linux with glibc 2.x or |
|
|
4530 | higher, as it simplifies linking (no need for \f(CW\*(C`\-lrt\*(C'\fR). |
|
|
4531 | .IP "\s-1EV_USE_NANOSLEEP\s0" 4 |
|
|
4532 | .IX Item "EV_USE_NANOSLEEP" |
|
|
4533 | If defined to be \f(CW1\fR, libev will assume that \f(CW\*(C`nanosleep ()\*(C'\fR is available |
|
|
4534 | and will use it for delays. Otherwise it will use \f(CW\*(C`select ()\*(C'\fR. |
|
|
4535 | .IP "\s-1EV_USE_EVENTFD\s0" 4 |
|
|
4536 | .IX Item "EV_USE_EVENTFD" |
|
|
4537 | If defined to be \f(CW1\fR, then libev will assume that \f(CW\*(C`eventfd ()\*(C'\fR is |
|
|
4538 | available and will probe for kernel support at runtime. This will improve |
|
|
4539 | \&\f(CW\*(C`ev_signal\*(C'\fR and \f(CW\*(C`ev_async\*(C'\fR performance and reduce resource consumption. |
|
|
4540 | If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
|
|
4541 | 2.7 or newer, otherwise disabled. |
1930 | .IP "\s-1EV_USE_SELECT\s0" 4 |
4542 | .IP "\s-1EV_USE_SELECT\s0" 4 |
1931 | .IX Item "EV_USE_SELECT" |
4543 | .IX Item "EV_USE_SELECT" |
1932 | If undefined or defined to be \f(CW1\fR, libev will compile in support for the |
4544 | If undefined or defined to be \f(CW1\fR, libev will compile in support for the |
1933 | \&\f(CW\*(C`select\*(C'\fR(2) backend. No attempt at autodetection will be done: if no |
4545 | \&\f(CW\*(C`select\*(C'\fR(2) backend. No attempt at auto-detection will be done: if no |
1934 | other method takes over, select will be it. Otherwise the select backend |
4546 | other method takes over, select will be it. Otherwise the select backend |
1935 | will not be compiled in. |
4547 | will not be compiled in. |
1936 | .IP "\s-1EV_SELECT_USE_FD_SET\s0" 4 |
4548 | .IP "\s-1EV_SELECT_USE_FD_SET\s0" 4 |
1937 | .IX Item "EV_SELECT_USE_FD_SET" |
4549 | .IX Item "EV_SELECT_USE_FD_SET" |
1938 | If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR |
4550 | If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR |
1939 | structure. This is useful if libev doesn't compile due to a missing |
4551 | structure. This is useful if libev doesn't compile due to a missing |
1940 | \&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it misguesses the bitset layout on |
4552 | \&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it mis-guesses the bitset layout |
1941 | exotic systems. This usually limits the range of file descriptors to some |
4553 | on exotic systems. This usually limits the range of file descriptors to |
1942 | low limit such as 1024 or might have other limitations (winsocket only |
4554 | some low limit such as 1024 or might have other limitations (winsocket |
1943 | allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation, might |
4555 | only allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation, |
1944 | influence the size of the \f(CW\*(C`fd_set\*(C'\fR used. |
4556 | configures the maximum size of the \f(CW\*(C`fd_set\*(C'\fR. |
1945 | .IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4 |
4557 | .IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4 |
1946 | .IX Item "EV_SELECT_IS_WINSOCKET" |
4558 | .IX Item "EV_SELECT_IS_WINSOCKET" |
1947 | When defined to \f(CW1\fR, the select backend will assume that |
4559 | When defined to \f(CW1\fR, the select backend will assume that |
1948 | select/socket/connect etc. don't understand file descriptors but |
4560 | select/socket/connect etc. don't understand file descriptors but |
1949 | wants osf handles on win32 (this is the case when the select to |
4561 | wants osf handles on win32 (this is the case when the select to |
1950 | be used is the winsock select). This means that it will call |
4562 | be used is the winsock select). This means that it will call |
1951 | \&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise, |
4563 | \&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise, |
1952 | it is assumed that all these functions actually work on fds, even |
4564 | it is assumed that all these functions actually work on fds, even |
1953 | on win32. Should not be defined on non\-win32 platforms. |
4565 | on win32. Should not be defined on non\-win32 platforms. |
|
|
4566 | .IP "\s-1EV_FD_TO_WIN32_HANDLE\s0(fd)" 4 |
|
|
4567 | .IX Item "EV_FD_TO_WIN32_HANDLE(fd)" |
|
|
4568 | If \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR is enabled, then libev needs a way to map |
|
|
4569 | file descriptors to socket handles. When not defining this symbol (the |
|
|
4570 | default), then libev will call \f(CW\*(C`_get_osfhandle\*(C'\fR, which is usually |
|
|
4571 | correct. In some cases, programs use their own file descriptor management, |
|
|
4572 | in which case they can provide this function to map fds to socket handles. |
|
|
4573 | .IP "\s-1EV_WIN32_HANDLE_TO_FD\s0(handle)" 4 |
|
|
4574 | .IX Item "EV_WIN32_HANDLE_TO_FD(handle)" |
|
|
4575 | If \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR then libev maps handles to file descriptors |
|
|
4576 | using the standard \f(CW\*(C`_open_osfhandle\*(C'\fR function. For programs implementing |
|
|
4577 | their own fd to handle mapping, overwriting this function makes it easier |
|
|
4578 | to do so. This can be done by defining this macro to an appropriate value. |
|
|
4579 | .IP "\s-1EV_WIN32_CLOSE_FD\s0(fd)" 4 |
|
|
4580 | .IX Item "EV_WIN32_CLOSE_FD(fd)" |
|
|
4581 | If programs implement their own fd to handle mapping on win32, then this |
|
|
4582 | macro can be used to override the \f(CW\*(C`close\*(C'\fR function, useful to unregister |
|
|
4583 | file descriptors again. Note that the replacement function has to close |
|
|
4584 | the underlying \s-1OS\s0 handle. |
1954 | .IP "\s-1EV_USE_POLL\s0" 4 |
4585 | .IP "\s-1EV_USE_POLL\s0" 4 |
1955 | .IX Item "EV_USE_POLL" |
4586 | .IX Item "EV_USE_POLL" |
1956 | If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2) |
4587 | If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2) |
1957 | backend. Otherwise it will be enabled on non\-win32 platforms. It |
4588 | backend. Otherwise it will be enabled on non\-win32 platforms. It |
1958 | takes precedence over select. |
4589 | takes precedence over select. |
1959 | .IP "\s-1EV_USE_EPOLL\s0" 4 |
4590 | .IP "\s-1EV_USE_EPOLL\s0" 4 |
1960 | .IX Item "EV_USE_EPOLL" |
4591 | .IX Item "EV_USE_EPOLL" |
1961 | If defined to be \f(CW1\fR, libev will compile in support for the Linux |
4592 | If defined to be \f(CW1\fR, libev will compile in support for the Linux |
1962 | \&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime, |
4593 | \&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime, |
1963 | otherwise another method will be used as fallback. This is the |
4594 | otherwise another method will be used as fallback. This is the preferred |
1964 | preferred backend for GNU/Linux systems. |
4595 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
|
|
4596 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
1965 | .IP "\s-1EV_USE_KQUEUE\s0" 4 |
4597 | .IP "\s-1EV_USE_KQUEUE\s0" 4 |
1966 | .IX Item "EV_USE_KQUEUE" |
4598 | .IX Item "EV_USE_KQUEUE" |
1967 | If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style |
4599 | If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style |
1968 | \&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime, |
4600 | \&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime, |
1969 | otherwise another method will be used as fallback. This is the preferred |
4601 | otherwise another method will be used as fallback. This is the preferred |
… | |
… | |
1979 | 10 port style backend. Its availability will be detected at runtime, |
4611 | 10 port style backend. Its availability will be detected at runtime, |
1980 | otherwise another method will be used as fallback. This is the preferred |
4612 | otherwise another method will be used as fallback. This is the preferred |
1981 | backend for Solaris 10 systems. |
4613 | backend for Solaris 10 systems. |
1982 | .IP "\s-1EV_USE_DEVPOLL\s0" 4 |
4614 | .IP "\s-1EV_USE_DEVPOLL\s0" 4 |
1983 | .IX Item "EV_USE_DEVPOLL" |
4615 | .IX Item "EV_USE_DEVPOLL" |
1984 | reserved for future expansion, works like the \s-1USE\s0 symbols above. |
4616 | Reserved for future expansion, works like the \s-1USE\s0 symbols above. |
|
|
4617 | .IP "\s-1EV_USE_INOTIFY\s0" 4 |
|
|
4618 | .IX Item "EV_USE_INOTIFY" |
|
|
4619 | If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify |
|
|
4620 | interface to speed up \f(CW\*(C`ev_stat\*(C'\fR watchers. Its actual availability will |
|
|
4621 | be detected at runtime. If undefined, it will be enabled if the headers |
|
|
4622 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
|
|
4623 | .IP "\s-1EV_NO_SMP\s0" 4 |
|
|
4624 | .IX Item "EV_NO_SMP" |
|
|
4625 | If defined to be \f(CW1\fR, libev will assume that memory is always coherent |
|
|
4626 | between threads, that is, threads can be used, but threads never run on |
|
|
4627 | different cpus (or different cpu cores). This reduces dependencies |
|
|
4628 | and makes libev faster. |
|
|
4629 | .IP "\s-1EV_NO_THREADS\s0" 4 |
|
|
4630 | .IX Item "EV_NO_THREADS" |
|
|
4631 | If defined to be \f(CW1\fR, libev will assume that it will never be called |
|
|
4632 | from different threads, which is a stronger assumption than \f(CW\*(C`EV_NO_SMP\*(C'\fR, |
|
|
4633 | above. This reduces dependencies and makes libev faster. |
|
|
4634 | .IP "\s-1EV_ATOMIC_T\s0" 4 |
|
|
4635 | .IX Item "EV_ATOMIC_T" |
|
|
4636 | Libev requires an integer type (suitable for storing \f(CW0\fR or \f(CW1\fR) whose |
|
|
4637 | access is atomic and serialised with respect to other threads or signal |
|
|
4638 | contexts. No such type is easily found in the C language, so you can |
|
|
4639 | provide your own type that you know is safe for your purposes. It is used |
|
|
4640 | both for signal handler \*(L"locking\*(R" as well as for signal and thread safety |
|
|
4641 | in \f(CW\*(C`ev_async\*(C'\fR watchers. |
|
|
4642 | .Sp |
|
|
4643 | In the absence of this define, libev will use \f(CW\*(C`sig_atomic_t volatile\*(C'\fR |
|
|
4644 | (from \fIsignal.h\fR), which is usually good enough on most platforms, |
|
|
4645 | although strictly speaking using a type that also implies a memory fence |
|
|
4646 | is required. |
1985 | .IP "\s-1EV_H\s0" 4 |
4647 | .IP "\s-1EV_H\s0 (h)" 4 |
1986 | .IX Item "EV_H" |
4648 | .IX Item "EV_H (h)" |
1987 | The name of the \fIev.h\fR header file used to include it. The default if |
4649 | The name of the \fIev.h\fR header file used to include it. The default if |
1988 | undefined is \f(CW\*(C`<ev.h>\*(C'\fR in \fIevent.h\fR and \f(CW"ev.h"\fR in \fIev.c\fR. This |
4650 | undefined is \f(CW"ev.h"\fR in \fIevent.h\fR, \fIev.c\fR and \fIev++.h\fR. This can be |
1989 | can be used to virtually rename the \fIev.h\fR header file in case of conflicts. |
4651 | used to virtually rename the \fIev.h\fR header file in case of conflicts. |
1990 | .IP "\s-1EV_CONFIG_H\s0" 4 |
4652 | .IP "\s-1EV_CONFIG_H\s0 (h)" 4 |
1991 | .IX Item "EV_CONFIG_H" |
4653 | .IX Item "EV_CONFIG_H (h)" |
1992 | If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override |
4654 | If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override |
1993 | \&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to |
4655 | \&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to |
1994 | \&\f(CW\*(C`EV_H\*(C'\fR, above. |
4656 | \&\f(CW\*(C`EV_H\*(C'\fR, above. |
1995 | .IP "\s-1EV_EVENT_H\s0" 4 |
4657 | .IP "\s-1EV_EVENT_H\s0 (h)" 4 |
1996 | .IX Item "EV_EVENT_H" |
4658 | .IX Item "EV_EVENT_H (h)" |
1997 | Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea |
4659 | Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea |
1998 | of how the \fIevent.h\fR header can be found. |
4660 | of how the \fIevent.h\fR header can be found, the default is \f(CW"event.h"\fR. |
1999 | .IP "\s-1EV_PROTOTYPES\s0" 4 |
4661 | .IP "\s-1EV_PROTOTYPES\s0 (h)" 4 |
2000 | .IX Item "EV_PROTOTYPES" |
4662 | .IX Item "EV_PROTOTYPES (h)" |
2001 | If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function |
4663 | If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function |
2002 | prototypes, but still define all the structs and other symbols. This is |
4664 | prototypes, but still define all the structs and other symbols. This is |
2003 | occasionally useful if you want to provide your own wrapper functions |
4665 | occasionally useful if you want to provide your own wrapper functions |
2004 | around libev functions. |
4666 | around libev functions. |
2005 | .IP "\s-1EV_MULTIPLICITY\s0" 4 |
4667 | .IP "\s-1EV_MULTIPLICITY\s0" 4 |
… | |
… | |
2007 | If undefined or defined to \f(CW1\fR, then all event-loop-specific functions |
4669 | If undefined or defined to \f(CW1\fR, then all event-loop-specific functions |
2008 | will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create |
4670 | will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create |
2009 | additional independent event loops. Otherwise there will be no support |
4671 | additional independent event loops. Otherwise there will be no support |
2010 | for multiple event loops and there is no first event loop pointer |
4672 | for multiple event loops and there is no first event loop pointer |
2011 | argument. Instead, all functions act on the single default loop. |
4673 | argument. Instead, all functions act on the single default loop. |
2012 | .IP "\s-1EV_PERIODIC_ENABLE\s0" 4 |
4674 | .Sp |
2013 | .IX Item "EV_PERIODIC_ENABLE" |
4675 | Note that \f(CW\*(C`EV_DEFAULT\*(C'\fR and \f(CW\*(C`EV_DEFAULT_\*(C'\fR will no longer provide a |
2014 | If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If |
4676 | default loop when multiplicity is switched off \- you always have to |
2015 | defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of |
4677 | initialise the loop manually in this case. |
2016 | code. |
|
|
2017 | .IP "\s-1EV_EMBED_ENABLE\s0" 4 |
|
|
2018 | .IX Item "EV_EMBED_ENABLE" |
|
|
2019 | If undefined or defined to be \f(CW1\fR, then embed watchers are supported. If |
|
|
2020 | defined to be \f(CW0\fR, then they are not. |
|
|
2021 | .IP "\s-1EV_STAT_ENABLE\s0" 4 |
|
|
2022 | .IX Item "EV_STAT_ENABLE" |
|
|
2023 | If undefined or defined to be \f(CW1\fR, then stat watchers are supported. If |
|
|
2024 | defined to be \f(CW0\fR, then they are not. |
|
|
2025 | .IP "\s-1EV_MINIMAL\s0" 4 |
4678 | .IP "\s-1EV_MINPRI\s0" 4 |
2026 | .IX Item "EV_MINIMAL" |
4679 | .IX Item "EV_MINPRI" |
|
|
4680 | .PD 0 |
|
|
4681 | .IP "\s-1EV_MAXPRI\s0" 4 |
|
|
4682 | .IX Item "EV_MAXPRI" |
|
|
4683 | .PD |
|
|
4684 | The range of allowed priorities. \f(CW\*(C`EV_MINPRI\*(C'\fR must be smaller or equal to |
|
|
4685 | \&\f(CW\*(C`EV_MAXPRI\*(C'\fR, but otherwise there are no non-obvious limitations. You can |
|
|
4686 | provide for more priorities by overriding those symbols (usually defined |
|
|
4687 | to be \f(CW\*(C`\-2\*(C'\fR and \f(CW2\fR, respectively). |
|
|
4688 | .Sp |
|
|
4689 | When doing priority-based operations, libev usually has to linearly search |
|
|
4690 | all the priorities, so having many of them (hundreds) uses a lot of space |
|
|
4691 | and time, so using the defaults of five priorities (\-2 .. +2) is usually |
|
|
4692 | fine. |
|
|
4693 | .Sp |
|
|
4694 | If your embedding application does not need any priorities, defining these |
|
|
4695 | both to \f(CW0\fR will save some memory and \s-1CPU\s0. |
|
|
4696 | .IP "\s-1EV_PERIODIC_ENABLE\s0, \s-1EV_IDLE_ENABLE\s0, \s-1EV_EMBED_ENABLE\s0, \s-1EV_STAT_ENABLE\s0, \s-1EV_PREPARE_ENABLE\s0, \s-1EV_CHECK_ENABLE\s0, \s-1EV_FORK_ENABLE\s0, \s-1EV_SIGNAL_ENABLE\s0, \s-1EV_ASYNC_ENABLE\s0, \s-1EV_CHILD_ENABLE\s0." 4 |
|
|
4697 | .IX Item "EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE, EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE, EV_ASYNC_ENABLE, EV_CHILD_ENABLE." |
|
|
4698 | If undefined or defined to be \f(CW1\fR (and the platform supports it), then |
|
|
4699 | the respective watcher type is supported. If defined to be \f(CW0\fR, then it |
|
|
4700 | is not. Disabling watcher types mainly saves code size. |
|
|
4701 | .IP "\s-1EV_FEATURES\s0" 4 |
|
|
4702 | .IX Item "EV_FEATURES" |
2027 | If you need to shave off some kilobytes of code at the expense of some |
4703 | If you need to shave off some kilobytes of code at the expense of some |
2028 | speed, define this symbol to \f(CW1\fR. Currently only used for gcc to override |
4704 | speed (but with the full \s-1API\s0), you can define this symbol to request |
2029 | some inlining decisions, saves roughly 30% codesize of amd64. |
4705 | certain subsets of functionality. The default is to enable all features |
|
|
4706 | that can be enabled on the platform. |
|
|
4707 | .Sp |
|
|
4708 | A typical way to use this symbol is to define it to \f(CW0\fR (or to a bitset |
|
|
4709 | with some broad features you want) and then selectively re-enable |
|
|
4710 | additional parts you want, for example if you want everything minimal, |
|
|
4711 | but multiple event loop support, async and child watchers and the poll |
|
|
4712 | backend, use this: |
|
|
4713 | .Sp |
|
|
4714 | .Vb 5 |
|
|
4715 | \& #define EV_FEATURES 0 |
|
|
4716 | \& #define EV_MULTIPLICITY 1 |
|
|
4717 | \& #define EV_USE_POLL 1 |
|
|
4718 | \& #define EV_CHILD_ENABLE 1 |
|
|
4719 | \& #define EV_ASYNC_ENABLE 1 |
|
|
4720 | .Ve |
|
|
4721 | .Sp |
|
|
4722 | The actual value is a bitset, it can be a combination of the following |
|
|
4723 | values: |
|
|
4724 | .RS 4 |
|
|
4725 | .ie n .IP "1 \- faster/larger code" 4 |
|
|
4726 | .el .IP "\f(CW1\fR \- faster/larger code" 4 |
|
|
4727 | .IX Item "1 - faster/larger code" |
|
|
4728 | Use larger code to speed up some operations. |
|
|
4729 | .Sp |
|
|
4730 | Currently this is used to override some inlining decisions (enlarging the |
|
|
4731 | code size by roughly 30% on amd64). |
|
|
4732 | .Sp |
|
|
4733 | When optimising for size, use of compiler flags such as \f(CW\*(C`\-Os\*(C'\fR with |
|
|
4734 | gcc is recommended, as well as \f(CW\*(C`\-DNDEBUG\*(C'\fR, as libev contains a number of |
|
|
4735 | assertions. |
|
|
4736 | .ie n .IP "2 \- faster/larger data structures" 4 |
|
|
4737 | .el .IP "\f(CW2\fR \- faster/larger data structures" 4 |
|
|
4738 | .IX Item "2 - faster/larger data structures" |
|
|
4739 | Replaces the small 2\-heap for timer management by a faster 4\-heap, larger |
|
|
4740 | hash table sizes and so on. This will usually further increase code size |
|
|
4741 | and can additionally have an effect on the size of data structures at |
|
|
4742 | runtime. |
|
|
4743 | .ie n .IP "4 \- full \s-1API\s0 configuration" 4 |
|
|
4744 | .el .IP "\f(CW4\fR \- full \s-1API\s0 configuration" 4 |
|
|
4745 | .IX Item "4 - full API configuration" |
|
|
4746 | This enables priorities (sets \f(CW\*(C`EV_MAXPRI\*(C'\fR=2 and \f(CW\*(C`EV_MINPRI\*(C'\fR=\-2), and |
|
|
4747 | enables multiplicity (\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR=1). |
|
|
4748 | .ie n .IP "8 \- full \s-1API\s0" 4 |
|
|
4749 | .el .IP "\f(CW8\fR \- full \s-1API\s0" 4 |
|
|
4750 | .IX Item "8 - full API" |
|
|
4751 | This enables a lot of the \*(L"lesser used\*(R" \s-1API\s0 functions. See \f(CW\*(C`ev.h\*(C'\fR for |
|
|
4752 | details on which parts of the \s-1API\s0 are still available without this |
|
|
4753 | feature, and do not complain if this subset changes over time. |
|
|
4754 | .ie n .IP "16 \- enable all optional watcher types" 4 |
|
|
4755 | .el .IP "\f(CW16\fR \- enable all optional watcher types" 4 |
|
|
4756 | .IX Item "16 - enable all optional watcher types" |
|
|
4757 | Enables all optional watcher types. If you want to selectively enable |
|
|
4758 | only some watcher types other than I/O and timers (e.g. prepare, |
|
|
4759 | embed, async, child...) you can enable them manually by defining |
|
|
4760 | \&\f(CW\*(C`EV_watchertype_ENABLE\*(C'\fR to \f(CW1\fR instead. |
|
|
4761 | .ie n .IP "32 \- enable all backends" 4 |
|
|
4762 | .el .IP "\f(CW32\fR \- enable all backends" 4 |
|
|
4763 | .IX Item "32 - enable all backends" |
|
|
4764 | This enables all backends \- without this feature, you need to enable at |
|
|
4765 | least one backend manually (\f(CW\*(C`EV_USE_SELECT\*(C'\fR is a good choice). |
|
|
4766 | .ie n .IP "64 \- enable OS-specific ""helper"" APIs" 4 |
|
|
4767 | .el .IP "\f(CW64\fR \- enable OS-specific ``helper'' APIs" 4 |
|
|
4768 | .IX Item "64 - enable OS-specific helper APIs" |
|
|
4769 | Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by |
|
|
4770 | default. |
|
|
4771 | .RE |
|
|
4772 | .RS 4 |
|
|
4773 | .Sp |
|
|
4774 | Compiling with \f(CW\*(C`gcc \-Os \-DEV_STANDALONE \-DEV_USE_EPOLL=1 \-DEV_FEATURES=0\*(C'\fR |
|
|
4775 | reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb |
|
|
4776 | code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O |
|
|
4777 | watchers, timers and monotonic clock support. |
|
|
4778 | .Sp |
|
|
4779 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
|
|
4780 | when you use \f(CW\*(C`\-Wl,\-\-gc\-sections \-ffunction\-sections\*(C'\fR) functions unused by |
|
|
4781 | your program might be left out as well \- a binary starting a timer and an |
|
|
4782 | I/O watcher then might come out at only 5Kb. |
|
|
4783 | .RE |
|
|
4784 | .IP "\s-1EV_API_STATIC\s0" 4 |
|
|
4785 | .IX Item "EV_API_STATIC" |
|
|
4786 | If this symbol is defined (by default it is not), then all identifiers |
|
|
4787 | will have static linkage. This means that libev will not export any |
|
|
4788 | identifiers, and you cannot link against libev anymore. This can be useful |
|
|
4789 | when you embed libev, only want to use libev functions in a single file, |
|
|
4790 | and do not want its identifiers to be visible. |
|
|
4791 | .Sp |
|
|
4792 | To use this, define \f(CW\*(C`EV_API_STATIC\*(C'\fR and include \fIev.c\fR in the file that |
|
|
4793 | wants to use libev. |
|
|
4794 | .Sp |
|
|
4795 | This option only works when libev is compiled with a C compiler, as \*(C+ |
|
|
4796 | doesn't support the required declaration syntax. |
|
|
4797 | .IP "\s-1EV_AVOID_STDIO\s0" 4 |
|
|
4798 | .IX Item "EV_AVOID_STDIO" |
|
|
4799 | If this is set to \f(CW1\fR at compiletime, then libev will avoid using stdio |
|
|
4800 | functions (printf, scanf, perror etc.). This will increase the code size |
|
|
4801 | somewhat, but if your program doesn't otherwise depend on stdio and your |
|
|
4802 | libc allows it, this avoids linking in the stdio library which is quite |
|
|
4803 | big. |
|
|
4804 | .Sp |
|
|
4805 | Note that error messages might become less precise when this option is |
|
|
4806 | enabled. |
|
|
4807 | .IP "\s-1EV_NSIG\s0" 4 |
|
|
4808 | .IX Item "EV_NSIG" |
|
|
4809 | The highest supported signal number, +1 (or, the number of |
|
|
4810 | signals): Normally, libev tries to deduce the maximum number of signals |
|
|
4811 | automatically, but sometimes this fails, in which case it can be |
|
|
4812 | specified. Also, using a lower number than detected (\f(CW32\fR should be |
|
|
4813 | good for about any system in existence) can save some memory, as libev |
|
|
4814 | statically allocates some 12\-24 bytes per signal number. |
|
|
4815 | .IP "\s-1EV_PID_HASHSIZE\s0" 4 |
|
|
4816 | .IX Item "EV_PID_HASHSIZE" |
|
|
4817 | \&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by |
|
|
4818 | pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_FEATURES\*(C'\fR disabled), |
|
|
4819 | usually more than enough. If you need to manage thousands of children you |
|
|
4820 | might want to increase this value (\fImust\fR be a power of two). |
|
|
4821 | .IP "\s-1EV_INOTIFY_HASHSIZE\s0" 4 |
|
|
4822 | .IX Item "EV_INOTIFY_HASHSIZE" |
|
|
4823 | \&\f(CW\*(C`ev_stat\*(C'\fR watchers use a small hash table to distribute workload by |
|
|
4824 | inotify watch id. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_FEATURES\*(C'\fR |
|
|
4825 | disabled), usually more than enough. If you need to manage thousands of |
|
|
4826 | \&\f(CW\*(C`ev_stat\*(C'\fR watchers you might want to increase this value (\fImust\fR be a |
|
|
4827 | power of two). |
|
|
4828 | .IP "\s-1EV_USE_4HEAP\s0" 4 |
|
|
4829 | .IX Item "EV_USE_4HEAP" |
|
|
4830 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
|
|
4831 | timer and periodics heaps, libev uses a 4\-heap when this symbol is defined |
|
|
4832 | to \f(CW1\fR. The 4\-heap uses more complicated (longer) code but has noticeably |
|
|
4833 | faster performance with many (thousands) of watchers. |
|
|
4834 | .Sp |
|
|
4835 | The default is \f(CW1\fR, unless \f(CW\*(C`EV_FEATURES\*(C'\fR overrides it, in which case it |
|
|
4836 | will be \f(CW0\fR. |
|
|
4837 | .IP "\s-1EV_HEAP_CACHE_AT\s0" 4 |
|
|
4838 | .IX Item "EV_HEAP_CACHE_AT" |
|
|
4839 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
|
|
4840 | timer and periodics heaps, libev can cache the timestamp (\fIat\fR) within |
|
|
4841 | the heap structure (selected by defining \f(CW\*(C`EV_HEAP_CACHE_AT\*(C'\fR to \f(CW1\fR), |
|
|
4842 | which uses 8\-12 bytes more per watcher and a few hundred bytes more code, |
|
|
4843 | but avoids random read accesses on heap changes. This improves performance |
|
|
4844 | noticeably with many (hundreds) of watchers. |
|
|
4845 | .Sp |
|
|
4846 | The default is \f(CW1\fR, unless \f(CW\*(C`EV_FEATURES\*(C'\fR overrides it, in which case it |
|
|
4847 | will be \f(CW0\fR. |
|
|
4848 | .IP "\s-1EV_VERIFY\s0" 4 |
|
|
4849 | .IX Item "EV_VERIFY" |
|
|
4850 | Controls how much internal verification (see \f(CW\*(C`ev_verify ()\*(C'\fR) will |
|
|
4851 | be done: If set to \f(CW0\fR, no internal verification code will be compiled |
|
|
4852 | in. If set to \f(CW1\fR, then verification code will be compiled in, but not |
|
|
4853 | called. If set to \f(CW2\fR, then the internal verification code will be |
|
|
4854 | called once per loop, which can slow down libev. If set to \f(CW3\fR, then the |
|
|
4855 | verification code will be called very frequently, which will slow down |
|
|
4856 | libev considerably. |
|
|
4857 | .Sp |
|
|
4858 | The default is \f(CW1\fR, unless \f(CW\*(C`EV_FEATURES\*(C'\fR overrides it, in which case it |
|
|
4859 | will be \f(CW0\fR. |
2030 | .IP "\s-1EV_COMMON\s0" 4 |
4860 | .IP "\s-1EV_COMMON\s0" 4 |
2031 | .IX Item "EV_COMMON" |
4861 | .IX Item "EV_COMMON" |
2032 | By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining |
4862 | By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining |
2033 | this macro to a something else you can include more and other types of |
4863 | this macro to something else you can include more and other types of |
2034 | members. You have to define it each time you include one of the files, |
4864 | members. You have to define it each time you include one of the files, |
2035 | though, and it must be identical each time. |
4865 | though, and it must be identical each time. |
2036 | .Sp |
4866 | .Sp |
2037 | For example, the perl \s-1EV\s0 module uses something like this: |
4867 | For example, the perl \s-1EV\s0 module uses something like this: |
2038 | .Sp |
4868 | .Sp |
2039 | .Vb 3 |
4869 | .Vb 3 |
2040 | \& #define EV_COMMON \e |
4870 | \& #define EV_COMMON \e |
2041 | \& SV *self; /* contains this struct */ \e |
4871 | \& SV *self; /* contains this struct */ \e |
2042 | \& SV *cb_sv, *fh /* note no trailing ";" */ |
4872 | \& SV *cb_sv, *fh /* note no trailing ";" */ |
2043 | .Ve |
4873 | .Ve |
2044 | .IP "\s-1EV_CB_DECLARE\s0 (type)" 4 |
4874 | .IP "\s-1EV_CB_DECLARE\s0 (type)" 4 |
2045 | .IX Item "EV_CB_DECLARE (type)" |
4875 | .IX Item "EV_CB_DECLARE (type)" |
2046 | .PD 0 |
4876 | .PD 0 |
2047 | .IP "\s-1EV_CB_INVOKE\s0 (watcher, revents)" 4 |
4877 | .IP "\s-1EV_CB_INVOKE\s0 (watcher, revents)" 4 |
… | |
… | |
2049 | .IP "ev_set_cb (ev, cb)" 4 |
4879 | .IP "ev_set_cb (ev, cb)" 4 |
2050 | .IX Item "ev_set_cb (ev, cb)" |
4880 | .IX Item "ev_set_cb (ev, cb)" |
2051 | .PD |
4881 | .PD |
2052 | Can be used to change the callback member declaration in each watcher, |
4882 | Can be used to change the callback member declaration in each watcher, |
2053 | and the way callbacks are invoked and set. Must expand to a struct member |
4883 | and the way callbacks are invoked and set. Must expand to a struct member |
2054 | definition and a statement, respectively. See the \fIev.v\fR header file for |
4884 | definition and a statement, respectively. See the \fIev.h\fR header file for |
2055 | their default definitions. One possible use for overriding these is to |
4885 | their default definitions. One possible use for overriding these is to |
2056 | avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use |
4886 | avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use |
2057 | method calls instead of plain function calls in \*(C+. |
4887 | method calls instead of plain function calls in \*(C+. |
|
|
4888 | .SS "\s-1EXPORTED\s0 \s-1API\s0 \s-1SYMBOLS\s0" |
|
|
4889 | .IX Subsection "EXPORTED API SYMBOLS" |
|
|
4890 | If you need to re-export the \s-1API\s0 (e.g. via a \s-1DLL\s0) and you need a list of |
|
|
4891 | exported symbols, you can use the provided \fISymbol.*\fR files which list |
|
|
4892 | all public symbols, one per line: |
|
|
4893 | .PP |
|
|
4894 | .Vb 2 |
|
|
4895 | \& Symbols.ev for libev proper |
|
|
4896 | \& Symbols.event for the libevent emulation |
|
|
4897 | .Ve |
|
|
4898 | .PP |
|
|
4899 | This can also be used to rename all public symbols to avoid clashes with |
|
|
4900 | multiple versions of libev linked together (which is obviously bad in |
|
|
4901 | itself, but sometimes it is inconvenient to avoid this). |
|
|
4902 | .PP |
|
|
4903 | A sed command like this will create wrapper \f(CW\*(C`#define\*(C'\fR's that you need to |
|
|
4904 | include before including \fIev.h\fR: |
|
|
4905 | .PP |
|
|
4906 | .Vb 1 |
|
|
4907 | \& <Symbols.ev sed \-e "s/.*/#define & myprefix_&/" >wrap.h |
|
|
4908 | .Ve |
|
|
4909 | .PP |
|
|
4910 | This would create a file \fIwrap.h\fR which essentially looks like this: |
|
|
4911 | .PP |
|
|
4912 | .Vb 4 |
|
|
4913 | \& #define ev_backend myprefix_ev_backend |
|
|
4914 | \& #define ev_check_start myprefix_ev_check_start |
|
|
4915 | \& #define ev_check_stop myprefix_ev_check_stop |
|
|
4916 | \& ... |
|
|
4917 | .Ve |
2058 | .Sh "\s-1EXAMPLES\s0" |
4918 | .SS "\s-1EXAMPLES\s0" |
2059 | .IX Subsection "EXAMPLES" |
4919 | .IX Subsection "EXAMPLES" |
2060 | For a real-world example of a program the includes libev |
4920 | For a real-world example of a program the includes libev |
2061 | verbatim, you can have a look at the \s-1EV\s0 perl module |
4921 | verbatim, you can have a look at the \s-1EV\s0 perl module |
2062 | (<http://software.schmorp.de/pkg/EV.html>). It has the libev files in |
4922 | (<http://software.schmorp.de/pkg/EV.html>). It has the libev files in |
2063 | the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public |
4923 | the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public |
2064 | interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file |
4924 | interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file |
2065 | will be compiled. It is pretty complex because it provides its own header |
4925 | will be compiled. It is pretty complex because it provides its own header |
2066 | file. |
4926 | file. |
2067 | .Sp |
4927 | .PP |
2068 | The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file |
4928 | The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file |
2069 | that everybody includes and which overrides some autoconf choices: |
4929 | that everybody includes and which overrides some configure choices: |
2070 | .Sp |
4930 | .PP |
2071 | .Vb 4 |
4931 | .Vb 8 |
|
|
4932 | \& #define EV_FEATURES 8 |
|
|
4933 | \& #define EV_USE_SELECT 1 |
|
|
4934 | \& #define EV_PREPARE_ENABLE 1 |
|
|
4935 | \& #define EV_IDLE_ENABLE 1 |
|
|
4936 | \& #define EV_SIGNAL_ENABLE 1 |
|
|
4937 | \& #define EV_CHILD_ENABLE 1 |
2072 | \& #define EV_USE_POLL 0 |
4938 | \& #define EV_USE_STDEXCEPT 0 |
2073 | \& #define EV_MULTIPLICITY 0 |
|
|
2074 | \& #define EV_PERIODICS 0 |
|
|
2075 | \& #define EV_CONFIG_H <config.h> |
4939 | \& #define EV_CONFIG_H <config.h> |
2076 | .Ve |
4940 | \& |
2077 | .Sp |
|
|
2078 | .Vb 1 |
|
|
2079 | \& #include "ev++.h" |
4941 | \& #include "ev++.h" |
2080 | .Ve |
4942 | .Ve |
2081 | .Sp |
4943 | .PP |
2082 | And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled: |
4944 | And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled: |
2083 | .Sp |
4945 | .PP |
2084 | .Vb 2 |
4946 | .Vb 2 |
2085 | \& #include "ev_cpp.h" |
4947 | \& #include "ev_cpp.h" |
2086 | \& #include "ev.c" |
4948 | \& #include "ev.c" |
2087 | .Ve |
4949 | .Ve |
|
|
4950 | .SH "INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT" |
|
|
4951 | .IX Header "INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT" |
|
|
4952 | .SS "\s-1THREADS\s0 \s-1AND\s0 \s-1COROUTINES\s0" |
|
|
4953 | .IX Subsection "THREADS AND COROUTINES" |
|
|
4954 | \fI\s-1THREADS\s0\fR |
|
|
4955 | .IX Subsection "THREADS" |
|
|
4956 | .PP |
|
|
4957 | All libev functions are reentrant and thread-safe unless explicitly |
|
|
4958 | documented otherwise, but libev implements no locking itself. This means |
|
|
4959 | that you can use as many loops as you want in parallel, as long as there |
|
|
4960 | are no concurrent calls into any libev function with the same loop |
|
|
4961 | parameter (\f(CW\*(C`ev_default_*\*(C'\fR calls have an implicit default loop parameter, |
|
|
4962 | of course): libev guarantees that different event loops share no data |
|
|
4963 | structures that need any locking. |
|
|
4964 | .PP |
|
|
4965 | Or to put it differently: calls with different loop parameters can be done |
|
|
4966 | concurrently from multiple threads, calls with the same loop parameter |
|
|
4967 | must be done serially (but can be done from different threads, as long as |
|
|
4968 | only one thread ever is inside a call at any point in time, e.g. by using |
|
|
4969 | a mutex per loop). |
|
|
4970 | .PP |
|
|
4971 | Specifically to support threads (and signal handlers), libev implements |
|
|
4972 | so-called \f(CW\*(C`ev_async\*(C'\fR watchers, which allow some limited form of |
|
|
4973 | concurrency on the same event loop, namely waking it up \*(L"from the |
|
|
4974 | outside\*(R". |
|
|
4975 | .PP |
|
|
4976 | If you want to know which design (one loop, locking, or multiple loops |
|
|
4977 | without or something else still) is best for your problem, then I cannot |
|
|
4978 | help you, but here is some generic advice: |
|
|
4979 | .IP "\(bu" 4 |
|
|
4980 | most applications have a main thread: use the default libev loop |
|
|
4981 | in that thread, or create a separate thread running only the default loop. |
|
|
4982 | .Sp |
|
|
4983 | This helps integrating other libraries or software modules that use libev |
|
|
4984 | themselves and don't care/know about threading. |
|
|
4985 | .IP "\(bu" 4 |
|
|
4986 | one loop per thread is usually a good model. |
|
|
4987 | .Sp |
|
|
4988 | Doing this is almost never wrong, sometimes a better-performance model |
|
|
4989 | exists, but it is always a good start. |
|
|
4990 | .IP "\(bu" 4 |
|
|
4991 | other models exist, such as the leader/follower pattern, where one |
|
|
4992 | loop is handed through multiple threads in a kind of round-robin fashion. |
|
|
4993 | .Sp |
|
|
4994 | Choosing a model is hard \- look around, learn, know that usually you can do |
|
|
4995 | better than you currently do :\-) |
|
|
4996 | .IP "\(bu" 4 |
|
|
4997 | often you need to talk to some other thread which blocks in the |
|
|
4998 | event loop. |
|
|
4999 | .Sp |
|
|
5000 | \&\f(CW\*(C`ev_async\*(C'\fR watchers can be used to wake them up from other threads safely |
|
|
5001 | (or from signal contexts...). |
|
|
5002 | .Sp |
|
|
5003 | An example use would be to communicate signals or other events that only |
|
|
5004 | work in the default loop by registering the signal watcher with the |
|
|
5005 | default loop and triggering an \f(CW\*(C`ev_async\*(C'\fR watcher from the default loop |
|
|
5006 | watcher callback into the event loop interested in the signal. |
|
|
5007 | .PP |
|
|
5008 | See also \*(L"\s-1THREAD\s0 \s-1LOCKING\s0 \s-1EXAMPLE\s0\*(R". |
|
|
5009 | .PP |
|
|
5010 | \fI\s-1COROUTINES\s0\fR |
|
|
5011 | .IX Subsection "COROUTINES" |
|
|
5012 | .PP |
|
|
5013 | Libev is very accommodating to coroutines (\*(L"cooperative threads\*(R"): |
|
|
5014 | libev fully supports nesting calls to its functions from different |
|
|
5015 | coroutines (e.g. you can call \f(CW\*(C`ev_run\*(C'\fR on the same loop from two |
|
|
5016 | different coroutines, and switch freely between both coroutines running |
|
|
5017 | the loop, as long as you don't confuse yourself). The only exception is |
|
|
5018 | that you must not do this from \f(CW\*(C`ev_periodic\*(C'\fR reschedule callbacks. |
|
|
5019 | .PP |
|
|
5020 | Care has been taken to ensure that libev does not keep local state inside |
|
|
5021 | \&\f(CW\*(C`ev_run\*(C'\fR, and other calls do not usually allow for coroutine switches as |
|
|
5022 | they do not call any callbacks. |
|
|
5023 | .SS "\s-1COMPILER\s0 \s-1WARNINGS\s0" |
|
|
5024 | .IX Subsection "COMPILER WARNINGS" |
|
|
5025 | Depending on your compiler and compiler settings, you might get no or a |
|
|
5026 | lot of warnings when compiling libev code. Some people are apparently |
|
|
5027 | scared by this. |
|
|
5028 | .PP |
|
|
5029 | However, these are unavoidable for many reasons. For one, each compiler |
|
|
5030 | has different warnings, and each user has different tastes regarding |
|
|
5031 | warning options. \*(L"Warn-free\*(R" code therefore cannot be a goal except when |
|
|
5032 | targeting a specific compiler and compiler-version. |
|
|
5033 | .PP |
|
|
5034 | Another reason is that some compiler warnings require elaborate |
|
|
5035 | workarounds, or other changes to the code that make it less clear and less |
|
|
5036 | maintainable. |
|
|
5037 | .PP |
|
|
5038 | And of course, some compiler warnings are just plain stupid, or simply |
|
|
5039 | wrong (because they don't actually warn about the condition their message |
|
|
5040 | seems to warn about). For example, certain older gcc versions had some |
|
|
5041 | warnings that resulted in an extreme number of false positives. These have |
|
|
5042 | been fixed, but some people still insist on making code warn-free with |
|
|
5043 | such buggy versions. |
|
|
5044 | .PP |
|
|
5045 | While libev is written to generate as few warnings as possible, |
|
|
5046 | \&\*(L"warn-free\*(R" code is not a goal, and it is recommended not to build libev |
|
|
5047 | with any compiler warnings enabled unless you are prepared to cope with |
|
|
5048 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
5049 | warnings, not errors, or proof of bugs. |
|
|
5050 | .SS "\s-1VALGRIND\s0" |
|
|
5051 | .IX Subsection "VALGRIND" |
|
|
5052 | Valgrind has a special section here because it is a popular tool that is |
|
|
5053 | highly useful. Unfortunately, valgrind reports are very hard to interpret. |
|
|
5054 | .PP |
|
|
5055 | If you think you found a bug (memory leak, uninitialised data access etc.) |
|
|
5056 | in libev, then check twice: If valgrind reports something like: |
|
|
5057 | .PP |
|
|
5058 | .Vb 3 |
|
|
5059 | \& ==2274== definitely lost: 0 bytes in 0 blocks. |
|
|
5060 | \& ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
5061 | \& ==2274== still reachable: 256 bytes in 1 blocks. |
|
|
5062 | .Ve |
|
|
5063 | .PP |
|
|
5064 | Then there is no memory leak, just as memory accounted to global variables |
|
|
5065 | is not a memleak \- the memory is still being referenced, and didn't leak. |
|
|
5066 | .PP |
|
|
5067 | Similarly, under some circumstances, valgrind might report kernel bugs |
|
|
5068 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
|
|
5069 | although an acceptable workaround has been found here), or it might be |
|
|
5070 | confused. |
|
|
5071 | .PP |
|
|
5072 | Keep in mind that valgrind is a very good tool, but only a tool. Don't |
|
|
5073 | make it into some kind of religion. |
|
|
5074 | .PP |
|
|
5075 | If you are unsure about something, feel free to contact the mailing list |
|
|
5076 | with the full valgrind report and an explanation on why you think this |
|
|
5077 | is a bug in libev (best check the archives, too :). However, don't be |
|
|
5078 | annoyed when you get a brisk \*(L"this is no bug\*(R" answer and take the chance |
|
|
5079 | of learning how to interpret valgrind properly. |
|
|
5080 | .PP |
|
|
5081 | If you need, for some reason, empty reports from valgrind for your project |
|
|
5082 | I suggest using suppression lists. |
|
|
5083 | .SH "PORTABILITY NOTES" |
|
|
5084 | .IX Header "PORTABILITY NOTES" |
|
|
5085 | .SS "\s-1GNU/LINUX\s0 32 \s-1BIT\s0 \s-1LIMITATIONS\s0" |
|
|
5086 | .IX Subsection "GNU/LINUX 32 BIT LIMITATIONS" |
|
|
5087 | GNU/Linux is the only common platform that supports 64 bit file/large file |
|
|
5088 | interfaces but \fIdisables\fR them by default. |
|
|
5089 | .PP |
|
|
5090 | That means that libev compiled in the default environment doesn't support |
|
|
5091 | files larger than 2GiB or so, which mainly affects \f(CW\*(C`ev_stat\*(C'\fR watchers. |
|
|
5092 | .PP |
|
|
5093 | Unfortunately, many programs try to work around this GNU/Linux issue |
|
|
5094 | by enabling the large file \s-1API\s0, which makes them incompatible with the |
|
|
5095 | standard libev compiled for their system. |
|
|
5096 | .PP |
|
|
5097 | Likewise, libev cannot enable the large file \s-1API\s0 itself as this would |
|
|
5098 | suddenly make it incompatible to the default compile time environment, |
|
|
5099 | i.e. all programs not using special compile switches. |
|
|
5100 | .SS "\s-1OS/X\s0 \s-1AND\s0 \s-1DARWIN\s0 \s-1BUGS\s0" |
|
|
5101 | .IX Subsection "OS/X AND DARWIN BUGS" |
|
|
5102 | The whole thing is a bug if you ask me \- basically any system interface |
|
|
5103 | you touch is broken, whether it is locales, poll, kqueue or even the |
|
|
5104 | OpenGL drivers. |
|
|
5105 | .PP |
|
|
5106 | \fI\f(CI\*(C`kqueue\*(C'\fI is buggy\fR |
|
|
5107 | .IX Subsection "kqueue is buggy" |
|
|
5108 | .PP |
|
|
5109 | The kqueue syscall is broken in all known versions \- most versions support |
|
|
5110 | only sockets, many support pipes. |
|
|
5111 | .PP |
|
|
5112 | Libev tries to work around this by not using \f(CW\*(C`kqueue\*(C'\fR by default on this |
|
|
5113 | rotten platform, but of course you can still ask for it when creating a |
|
|
5114 | loop \- embedding a socket-only kqueue loop into a select-based one is |
|
|
5115 | probably going to work well. |
|
|
5116 | .PP |
|
|
5117 | \fI\f(CI\*(C`poll\*(C'\fI is buggy\fR |
|
|
5118 | .IX Subsection "poll is buggy" |
|
|
5119 | .PP |
|
|
5120 | Instead of fixing \f(CW\*(C`kqueue\*(C'\fR, Apple replaced their (working) \f(CW\*(C`poll\*(C'\fR |
|
|
5121 | implementation by something calling \f(CW\*(C`kqueue\*(C'\fR internally around the 10.5.6 |
|
|
5122 | release, so now \f(CW\*(C`kqueue\*(C'\fR \fIand\fR \f(CW\*(C`poll\*(C'\fR are broken. |
|
|
5123 | .PP |
|
|
5124 | Libev tries to work around this by not using \f(CW\*(C`poll\*(C'\fR by default on |
|
|
5125 | this rotten platform, but of course you can still ask for it when creating |
|
|
5126 | a loop. |
|
|
5127 | .PP |
|
|
5128 | \fI\f(CI\*(C`select\*(C'\fI is buggy\fR |
|
|
5129 | .IX Subsection "select is buggy" |
|
|
5130 | .PP |
|
|
5131 | All that's left is \f(CW\*(C`select\*(C'\fR, and of course Apple found a way to fuck this |
|
|
5132 | one up as well: On \s-1OS/X\s0, \f(CW\*(C`select\*(C'\fR actively limits the number of file |
|
|
5133 | descriptors you can pass in to 1024 \- your program suddenly crashes when |
|
|
5134 | you use more. |
|
|
5135 | .PP |
|
|
5136 | There is an undocumented \*(L"workaround\*(R" for this \- defining |
|
|
5137 | \&\f(CW\*(C`_DARWIN_UNLIMITED_SELECT\*(C'\fR, which libev tries to use, so select \fIshould\fR |
|
|
5138 | work on \s-1OS/X\s0. |
|
|
5139 | .SS "\s-1SOLARIS\s0 \s-1PROBLEMS\s0 \s-1AND\s0 \s-1WORKAROUNDS\s0" |
|
|
5140 | .IX Subsection "SOLARIS PROBLEMS AND WORKAROUNDS" |
|
|
5141 | \fI\f(CI\*(C`errno\*(C'\fI reentrancy\fR |
|
|
5142 | .IX Subsection "errno reentrancy" |
|
|
5143 | .PP |
|
|
5144 | The default compile environment on Solaris is unfortunately so |
|
|
5145 | thread-unsafe that you can't even use components/libraries compiled |
|
|
5146 | without \f(CW\*(C`\-D_REENTRANT\*(C'\fR in a threaded program, which, of course, isn't |
|
|
5147 | defined by default. A valid, if stupid, implementation choice. |
|
|
5148 | .PP |
|
|
5149 | If you want to use libev in threaded environments you have to make sure |
|
|
5150 | it's compiled with \f(CW\*(C`_REENTRANT\*(C'\fR defined. |
|
|
5151 | .PP |
|
|
5152 | \fIEvent port backend\fR |
|
|
5153 | .IX Subsection "Event port backend" |
|
|
5154 | .PP |
|
|
5155 | The scalable event interface for Solaris is called \*(L"event |
|
|
5156 | ports\*(R". Unfortunately, this mechanism is very buggy in all major |
|
|
5157 | releases. If you run into high \s-1CPU\s0 usage, your program freezes or you get |
|
|
5158 | a large number of spurious wakeups, make sure you have all the relevant |
|
|
5159 | and latest kernel patches applied. No, I don't know which ones, but there |
|
|
5160 | are multiple ones to apply, and afterwards, event ports actually work |
|
|
5161 | great. |
|
|
5162 | .PP |
|
|
5163 | If you can't get it to work, you can try running the program by setting |
|
|
5164 | the environment variable \f(CW\*(C`LIBEV_FLAGS=3\*(C'\fR to only allow \f(CW\*(C`poll\*(C'\fR and |
|
|
5165 | \&\f(CW\*(C`select\*(C'\fR backends. |
|
|
5166 | .SS "\s-1AIX\s0 \s-1POLL\s0 \s-1BUG\s0" |
|
|
5167 | .IX Subsection "AIX POLL BUG" |
|
|
5168 | \&\s-1AIX\s0 unfortunately has a broken \f(CW\*(C`poll.h\*(C'\fR header. Libev works around |
|
|
5169 | this by trying to avoid the poll backend altogether (i.e. it's not even |
|
|
5170 | compiled in), which normally isn't a big problem as \f(CW\*(C`select\*(C'\fR works fine |
|
|
5171 | with large bitsets on \s-1AIX\s0, and \s-1AIX\s0 is dead anyway. |
|
|
5172 | .SS "\s-1WIN32\s0 \s-1PLATFORM\s0 \s-1LIMITATIONS\s0 \s-1AND\s0 \s-1WORKAROUNDS\s0" |
|
|
5173 | .IX Subsection "WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS" |
|
|
5174 | \fIGeneral issues\fR |
|
|
5175 | .IX Subsection "General issues" |
|
|
5176 | .PP |
|
|
5177 | Win32 doesn't support any of the standards (e.g. \s-1POSIX\s0) that libev |
|
|
5178 | requires, and its I/O model is fundamentally incompatible with the \s-1POSIX\s0 |
|
|
5179 | model. Libev still offers limited functionality on this platform in |
|
|
5180 | the form of the \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR backend, and only supports socket |
|
|
5181 | descriptors. This only applies when using Win32 natively, not when using |
|
|
5182 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
|
|
5183 | as every compiler comes with a slightly differently broken/incompatible |
|
|
5184 | environment. |
|
|
5185 | .PP |
|
|
5186 | Lifting these limitations would basically require the full |
|
|
5187 | re-implementation of the I/O system. If you are into this kind of thing, |
|
|
5188 | then note that glib does exactly that for you in a very portable way (note |
|
|
5189 | also that glib is the slowest event library known to man). |
|
|
5190 | .PP |
|
|
5191 | There is no supported compilation method available on windows except |
|
|
5192 | embedding it into other applications. |
|
|
5193 | .PP |
|
|
5194 | Sensible signal handling is officially unsupported by Microsoft \- libev |
|
|
5195 | tries its best, but under most conditions, signals will simply not work. |
|
|
5196 | .PP |
|
|
5197 | Not a libev limitation but worth mentioning: windows apparently doesn't |
|
|
5198 | accept large writes: instead of resulting in a partial write, windows will |
|
|
5199 | either accept everything or return \f(CW\*(C`ENOBUFS\*(C'\fR if the buffer is too large, |
|
|
5200 | so make sure you only write small amounts into your sockets (less than a |
|
|
5201 | megabyte seems safe, but this apparently depends on the amount of memory |
|
|
5202 | available). |
|
|
5203 | .PP |
|
|
5204 | Due to the many, low, and arbitrary limits on the win32 platform and |
|
|
5205 | the abysmal performance of winsockets, using a large number of sockets |
|
|
5206 | is not recommended (and not reasonable). If your program needs to use |
|
|
5207 | more than a hundred or so sockets, then likely it needs to use a totally |
|
|
5208 | different implementation for windows, as libev offers the \s-1POSIX\s0 readiness |
|
|
5209 | notification model, which cannot be implemented efficiently on windows |
|
|
5210 | (due to Microsoft monopoly games). |
|
|
5211 | .PP |
|
|
5212 | A typical way to use libev under windows is to embed it (see the embedding |
|
|
5213 | section for details) and use the following \fIevwrap.h\fR header file instead |
|
|
5214 | of \fIev.h\fR: |
|
|
5215 | .PP |
|
|
5216 | .Vb 2 |
|
|
5217 | \& #define EV_STANDALONE /* keeps ev from requiring config.h */ |
|
|
5218 | \& #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
|
|
5219 | \& |
|
|
5220 | \& #include "ev.h" |
|
|
5221 | .Ve |
|
|
5222 | .PP |
|
|
5223 | And compile the following \fIevwrap.c\fR file into your project (make sure |
|
|
5224 | you do \fInot\fR compile the \fIev.c\fR or any other embedded source files!): |
|
|
5225 | .PP |
|
|
5226 | .Vb 2 |
|
|
5227 | \& #include "evwrap.h" |
|
|
5228 | \& #include "ev.c" |
|
|
5229 | .Ve |
|
|
5230 | .PP |
|
|
5231 | \fIThe winsocket \f(CI\*(C`select\*(C'\fI function\fR |
|
|
5232 | .IX Subsection "The winsocket select function" |
|
|
5233 | .PP |
|
|
5234 | The winsocket \f(CW\*(C`select\*(C'\fR function doesn't follow \s-1POSIX\s0 in that it |
|
|
5235 | requires socket \fIhandles\fR and not socket \fIfile descriptors\fR (it is |
|
|
5236 | also extremely buggy). This makes select very inefficient, and also |
|
|
5237 | requires a mapping from file descriptors to socket handles (the Microsoft |
|
|
5238 | C runtime provides the function \f(CW\*(C`_open_osfhandle\*(C'\fR for this). See the |
|
|
5239 | discussion of the \f(CW\*(C`EV_SELECT_USE_FD_SET\*(C'\fR, \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR and |
|
|
5240 | \&\f(CW\*(C`EV_FD_TO_WIN32_HANDLE\*(C'\fR preprocessor symbols for more info. |
|
|
5241 | .PP |
|
|
5242 | The configuration for a \*(L"naked\*(R" win32 using the Microsoft runtime |
|
|
5243 | libraries and raw winsocket select is: |
|
|
5244 | .PP |
|
|
5245 | .Vb 2 |
|
|
5246 | \& #define EV_USE_SELECT 1 |
|
|
5247 | \& #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
|
|
5248 | .Ve |
|
|
5249 | .PP |
|
|
5250 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
|
|
5251 | complexity in the O(nA\*^X) range when using win32. |
|
|
5252 | .PP |
|
|
5253 | \fILimited number of file descriptors\fR |
|
|
5254 | .IX Subsection "Limited number of file descriptors" |
|
|
5255 | .PP |
|
|
5256 | Windows has numerous arbitrary (and low) limits on things. |
|
|
5257 | .PP |
|
|
5258 | Early versions of winsocket's select only supported waiting for a maximum |
|
|
5259 | of \f(CW64\fR handles (probably owning to the fact that all windows kernels |
|
|
5260 | can only wait for \f(CW64\fR things at the same time internally; Microsoft |
|
|
5261 | recommends spawning a chain of threads and wait for 63 handles and the |
|
|
5262 | previous thread in each. Sounds great!). |
|
|
5263 | .PP |
|
|
5264 | Newer versions support more handles, but you need to define \f(CW\*(C`FD_SETSIZE\*(C'\fR |
|
|
5265 | to some high number (e.g. \f(CW2048\fR) before compiling the winsocket select |
|
|
5266 | call (which might be in libev or elsewhere, for example, perl and many |
|
|
5267 | other interpreters do their own select emulation on windows). |
|
|
5268 | .PP |
|
|
5269 | Another limit is the number of file descriptors in the Microsoft runtime |
|
|
5270 | libraries, which by default is \f(CW64\fR (there must be a hidden \fI64\fR |
|
|
5271 | fetish or something like this inside Microsoft). You can increase this |
|
|
5272 | by calling \f(CW\*(C`_setmaxstdio\*(C'\fR, which can increase this limit to \f(CW2048\fR |
|
|
5273 | (another arbitrary limit), but is broken in many versions of the Microsoft |
|
|
5274 | runtime libraries. This might get you to about \f(CW512\fR or \f(CW2048\fR sockets |
|
|
5275 | (depending on windows version and/or the phase of the moon). To get more, |
|
|
5276 | you need to wrap all I/O functions and provide your own fd management, but |
|
|
5277 | the cost of calling select (O(nA\*^X)) will likely make this unworkable. |
|
|
5278 | .SS "\s-1PORTABILITY\s0 \s-1REQUIREMENTS\s0" |
|
|
5279 | .IX Subsection "PORTABILITY REQUIREMENTS" |
|
|
5280 | In addition to a working ISO-C implementation and of course the |
|
|
5281 | backend-specific APIs, libev relies on a few additional extensions: |
|
|
5282 | .ie n .IP """void (*)(ev_watcher_type *, int revents)"" must have compatible calling conventions regardless of ""ev_watcher_type *""." 4 |
|
|
5283 | .el .IP "\f(CWvoid (*)(ev_watcher_type *, int revents)\fR must have compatible calling conventions regardless of \f(CWev_watcher_type *\fR." 4 |
|
|
5284 | .IX Item "void (*)(ev_watcher_type *, int revents) must have compatible calling conventions regardless of ev_watcher_type *." |
|
|
5285 | Libev assumes not only that all watcher pointers have the same internal |
|
|
5286 | structure (guaranteed by \s-1POSIX\s0 but not by \s-1ISO\s0 C for example), but it also |
|
|
5287 | assumes that the same (machine) code can be used to call any watcher |
|
|
5288 | callback: The watcher callbacks have different type signatures, but libev |
|
|
5289 | calls them using an \f(CW\*(C`ev_watcher *\*(C'\fR internally. |
|
|
5290 | .IP "pointer accesses must be thread-atomic" 4 |
|
|
5291 | .IX Item "pointer accesses must be thread-atomic" |
|
|
5292 | Accessing a pointer value must be atomic, it must both be readable and |
|
|
5293 | writable in one piece \- this is the case on all current architectures. |
|
|
5294 | .ie n .IP """sig_atomic_t volatile"" must be thread-atomic as well" 4 |
|
|
5295 | .el .IP "\f(CWsig_atomic_t volatile\fR must be thread-atomic as well" 4 |
|
|
5296 | .IX Item "sig_atomic_t volatile must be thread-atomic as well" |
|
|
5297 | The type \f(CW\*(C`sig_atomic_t volatile\*(C'\fR (or whatever is defined as |
|
|
5298 | \&\f(CW\*(C`EV_ATOMIC_T\*(C'\fR) must be atomic with respect to accesses from different |
|
|
5299 | threads. This is not part of the specification for \f(CW\*(C`sig_atomic_t\*(C'\fR, but is |
|
|
5300 | believed to be sufficiently portable. |
|
|
5301 | .ie n .IP """sigprocmask"" must work in a threaded environment" 4 |
|
|
5302 | .el .IP "\f(CWsigprocmask\fR must work in a threaded environment" 4 |
|
|
5303 | .IX Item "sigprocmask must work in a threaded environment" |
|
|
5304 | Libev uses \f(CW\*(C`sigprocmask\*(C'\fR to temporarily block signals. This is not |
|
|
5305 | allowed in a threaded program (\f(CW\*(C`pthread_sigmask\*(C'\fR has to be used). Typical |
|
|
5306 | pthread implementations will either allow \f(CW\*(C`sigprocmask\*(C'\fR in the \*(L"main |
|
|
5307 | thread\*(R" or will block signals process-wide, both behaviours would |
|
|
5308 | be compatible with libev. Interaction between \f(CW\*(C`sigprocmask\*(C'\fR and |
|
|
5309 | \&\f(CW\*(C`pthread_sigmask\*(C'\fR could complicate things, however. |
|
|
5310 | .Sp |
|
|
5311 | The most portable way to handle signals is to block signals in all threads |
|
|
5312 | except the initial one, and run the default loop in the initial thread as |
|
|
5313 | well. |
|
|
5314 | .ie n .IP """long"" must be large enough for common memory allocation sizes" 4 |
|
|
5315 | .el .IP "\f(CWlong\fR must be large enough for common memory allocation sizes" 4 |
|
|
5316 | .IX Item "long must be large enough for common memory allocation sizes" |
|
|
5317 | To improve portability and simplify its \s-1API\s0, libev uses \f(CW\*(C`long\*(C'\fR internally |
|
|
5318 | instead of \f(CW\*(C`size_t\*(C'\fR when allocating its data structures. On non-POSIX |
|
|
5319 | systems (Microsoft...) this might be unexpectedly low, but is still at |
|
|
5320 | least 31 bits everywhere, which is enough for hundreds of millions of |
|
|
5321 | watchers. |
|
|
5322 | .ie n .IP """double"" must hold a time value in seconds with enough accuracy" 4 |
|
|
5323 | .el .IP "\f(CWdouble\fR must hold a time value in seconds with enough accuracy" 4 |
|
|
5324 | .IX Item "double must hold a time value in seconds with enough accuracy" |
|
|
5325 | The type \f(CW\*(C`double\*(C'\fR is used to represent timestamps. It is required to |
|
|
5326 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
|
|
5327 | good enough for at least into the year 4000 with millisecond accuracy |
|
|
5328 | (the design goal for libev). This requirement is overfulfilled by |
|
|
5329 | implementations using \s-1IEEE\s0 754, which is basically all existing ones. |
|
|
5330 | .Sp |
|
|
5331 | With \s-1IEEE\s0 754 doubles, you get microsecond accuracy until at least the |
|
|
5332 | year 2255 (and millisecond accuracy till the year 287396 \- by then, libev |
|
|
5333 | is either obsolete or somebody patched it to use \f(CW\*(C`long double\*(C'\fR or |
|
|
5334 | something like that, just kidding). |
|
|
5335 | .PP |
|
|
5336 | If you know of other additional requirements drop me a note. |
2088 | .SH "COMPLEXITIES" |
5337 | .SH "ALGORITHMIC COMPLEXITIES" |
2089 | .IX Header "COMPLEXITIES" |
5338 | .IX Header "ALGORITHMIC COMPLEXITIES" |
2090 | In this section the complexities of (many of) the algorithms used inside |
5339 | In this section the complexities of (many of) the algorithms used inside |
2091 | libev will be explained. For complexity discussions about backends see the |
5340 | libev will be documented. For complexity discussions about backends see |
2092 | documentation for \f(CW\*(C`ev_default_init\*(C'\fR. |
5341 | the documentation for \f(CW\*(C`ev_default_init\*(C'\fR. |
2093 | .RS 4 |
5342 | .PP |
|
|
5343 | All of the following are about amortised time: If an array needs to be |
|
|
5344 | extended, libev needs to realloc and move the whole array, but this |
|
|
5345 | happens asymptotically rarer with higher number of elements, so O(1) might |
|
|
5346 | mean that libev does a lengthy realloc operation in rare cases, but on |
|
|
5347 | average it is much faster and asymptotically approaches constant time. |
2094 | .IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4 |
5348 | .IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4 |
2095 | .IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" |
5349 | .IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" |
|
|
5350 | This means that, when you have a watcher that triggers in one hour and |
|
|
5351 | there are 100 watchers that would trigger before that, then inserting will |
|
|
5352 | have to skip roughly seven (\f(CW\*(C`ld 100\*(C'\fR) of these watchers. |
|
|
5353 | .IP "Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)" 4 |
|
|
5354 | .IX Item "Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)" |
|
|
5355 | That means that changing a timer costs less than removing/adding them, |
|
|
5356 | as only the relative motion in the event queue has to be paid for. |
|
|
5357 | .IP "Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)" 4 |
|
|
5358 | .IX Item "Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)" |
|
|
5359 | These just add the watcher into an array or at the head of a list. |
|
|
5360 | .IP "Stopping check/prepare/idle/fork/async watchers: O(1)" 4 |
|
|
5361 | .IX Item "Stopping check/prepare/idle/fork/async watchers: O(1)" |
2096 | .PD 0 |
5362 | .PD 0 |
2097 | .IP "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)" 4 |
|
|
2098 | .IX Item "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)" |
|
|
2099 | .IP "Starting io/check/prepare/idle/signal/child watchers: O(1)" 4 |
|
|
2100 | .IX Item "Starting io/check/prepare/idle/signal/child watchers: O(1)" |
|
|
2101 | .IP "Stopping check/prepare/idle watchers: O(1)" 4 |
|
|
2102 | .IX Item "Stopping check/prepare/idle watchers: O(1)" |
|
|
2103 | .IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))" 4 |
5363 | .IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4 |
2104 | .IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))" |
5364 | .IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))" |
|
|
5365 | .PD |
|
|
5366 | These watchers are stored in lists, so they need to be walked to find the |
|
|
5367 | correct watcher to remove. The lists are usually short (you don't usually |
|
|
5368 | have many watchers waiting for the same fd or signal: one is typical, two |
|
|
5369 | is rare). |
2105 | .IP "Finding the next timer per loop iteration: O(1)" 4 |
5370 | .IP "Finding the next timer in each loop iteration: O(1)" 4 |
2106 | .IX Item "Finding the next timer per loop iteration: O(1)" |
5371 | .IX Item "Finding the next timer in each loop iteration: O(1)" |
|
|
5372 | By virtue of using a binary or 4\-heap, the next timer is always found at a |
|
|
5373 | fixed position in the storage array. |
2107 | .IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4 |
5374 | .IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4 |
2108 | .IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" |
5375 | .IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" |
2109 | .IP "Activating one watcher: O(1)" 4 |
5376 | A change means an I/O watcher gets started or stopped, which requires |
2110 | .IX Item "Activating one watcher: O(1)" |
5377 | libev to recalculate its status (and possibly tell the kernel, depending |
2111 | .RE |
5378 | on backend and whether \f(CW\*(C`ev_io_set\*(C'\fR was used). |
2112 | .RS 4 |
5379 | .IP "Activating one watcher (putting it into the pending state): O(1)" 4 |
|
|
5380 | .IX Item "Activating one watcher (putting it into the pending state): O(1)" |
|
|
5381 | .PD 0 |
|
|
5382 | .IP "Priority handling: O(number_of_priorities)" 4 |
|
|
5383 | .IX Item "Priority handling: O(number_of_priorities)" |
2113 | .PD |
5384 | .PD |
|
|
5385 | Priorities are implemented by allocating some space for each |
|
|
5386 | priority. When doing priority-based operations, libev usually has to |
|
|
5387 | linearly search all the priorities, but starting/stopping and activating |
|
|
5388 | watchers becomes O(1) with respect to priority handling. |
|
|
5389 | .IP "Sending an ev_async: O(1)" 4 |
|
|
5390 | .IX Item "Sending an ev_async: O(1)" |
|
|
5391 | .PD 0 |
|
|
5392 | .IP "Processing ev_async_send: O(number_of_async_watchers)" 4 |
|
|
5393 | .IX Item "Processing ev_async_send: O(number_of_async_watchers)" |
|
|
5394 | .IP "Processing signals: O(max_signal_number)" 4 |
|
|
5395 | .IX Item "Processing signals: O(max_signal_number)" |
|
|
5396 | .PD |
|
|
5397 | Sending involves a system call \fIiff\fR there were no other \f(CW\*(C`ev_async_send\*(C'\fR |
|
|
5398 | calls in the current loop iteration and the loop is currently |
|
|
5399 | blocked. Checking for async and signal events involves iterating over all |
|
|
5400 | running async watchers or all signal numbers. |
|
|
5401 | .SH "PORTING FROM LIBEV 3.X TO 4.X" |
|
|
5402 | .IX Header "PORTING FROM LIBEV 3.X TO 4.X" |
|
|
5403 | The major version 4 introduced some incompatible changes to the \s-1API\s0. |
|
|
5404 | .PP |
|
|
5405 | At the moment, the \f(CW\*(C`ev.h\*(C'\fR header file provides compatibility definitions |
|
|
5406 | for all changes, so most programs should still compile. The compatibility |
|
|
5407 | layer might be removed in later versions of libev, so better update to the |
|
|
5408 | new \s-1API\s0 early than late. |
|
|
5409 | .ie n .IP """EV_COMPAT3"" backwards compatibility mechanism" 4 |
|
|
5410 | .el .IP "\f(CWEV_COMPAT3\fR backwards compatibility mechanism" 4 |
|
|
5411 | .IX Item "EV_COMPAT3 backwards compatibility mechanism" |
|
|
5412 | The backward compatibility mechanism can be controlled by |
|
|
5413 | \&\f(CW\*(C`EV_COMPAT3\*(C'\fR. See \*(L"\s-1MACROS\s0\*(R" in \s-1PREPROCESSOR\s0 \s-1SYMBOLS\s0 in the \s-1EMBEDDING\s0 |
|
|
5414 | section. |
|
|
5415 | .ie n .IP """ev_default_destroy"" and ""ev_default_fork"" have been removed" 4 |
|
|
5416 | .el .IP "\f(CWev_default_destroy\fR and \f(CWev_default_fork\fR have been removed" 4 |
|
|
5417 | .IX Item "ev_default_destroy and ev_default_fork have been removed" |
|
|
5418 | These calls can be replaced easily by their \f(CW\*(C`ev_loop_xxx\*(C'\fR counterparts: |
|
|
5419 | .Sp |
|
|
5420 | .Vb 2 |
|
|
5421 | \& ev_loop_destroy (EV_DEFAULT_UC); |
|
|
5422 | \& ev_loop_fork (EV_DEFAULT); |
|
|
5423 | .Ve |
|
|
5424 | .IP "function/symbol renames" 4 |
|
|
5425 | .IX Item "function/symbol renames" |
|
|
5426 | A number of functions and symbols have been renamed: |
|
|
5427 | .Sp |
|
|
5428 | .Vb 3 |
|
|
5429 | \& ev_loop => ev_run |
|
|
5430 | \& EVLOOP_NONBLOCK => EVRUN_NOWAIT |
|
|
5431 | \& EVLOOP_ONESHOT => EVRUN_ONCE |
|
|
5432 | \& |
|
|
5433 | \& ev_unloop => ev_break |
|
|
5434 | \& EVUNLOOP_CANCEL => EVBREAK_CANCEL |
|
|
5435 | \& EVUNLOOP_ONE => EVBREAK_ONE |
|
|
5436 | \& EVUNLOOP_ALL => EVBREAK_ALL |
|
|
5437 | \& |
|
|
5438 | \& EV_TIMEOUT => EV_TIMER |
|
|
5439 | \& |
|
|
5440 | \& ev_loop_count => ev_iteration |
|
|
5441 | \& ev_loop_depth => ev_depth |
|
|
5442 | \& ev_loop_verify => ev_verify |
|
|
5443 | .Ve |
|
|
5444 | .Sp |
|
|
5445 | Most functions working on \f(CW\*(C`struct ev_loop\*(C'\fR objects don't have an |
|
|
5446 | \&\f(CW\*(C`ev_loop_\*(C'\fR prefix, so it was removed; \f(CW\*(C`ev_loop\*(C'\fR, \f(CW\*(C`ev_unloop\*(C'\fR and |
|
|
5447 | associated constants have been renamed to not collide with the \f(CW\*(C`struct |
|
|
5448 | ev_loop\*(C'\fR anymore and \f(CW\*(C`EV_TIMER\*(C'\fR now follows the same naming scheme |
|
|
5449 | as all other watcher types. Note that \f(CW\*(C`ev_loop_fork\*(C'\fR is still called |
|
|
5450 | \&\f(CW\*(C`ev_loop_fork\*(C'\fR because it would otherwise clash with the \f(CW\*(C`ev_fork\*(C'\fR |
|
|
5451 | typedef. |
|
|
5452 | .ie n .IP """EV_MINIMAL"" mechanism replaced by ""EV_FEATURES""" 4 |
|
|
5453 | .el .IP "\f(CWEV_MINIMAL\fR mechanism replaced by \f(CWEV_FEATURES\fR" 4 |
|
|
5454 | .IX Item "EV_MINIMAL mechanism replaced by EV_FEATURES" |
|
|
5455 | The preprocessor symbol \f(CW\*(C`EV_MINIMAL\*(C'\fR has been replaced by a different |
|
|
5456 | mechanism, \f(CW\*(C`EV_FEATURES\*(C'\fR. Programs using \f(CW\*(C`EV_MINIMAL\*(C'\fR usually compile |
|
|
5457 | and work, but the library code will of course be larger. |
|
|
5458 | .SH "GLOSSARY" |
|
|
5459 | .IX Header "GLOSSARY" |
|
|
5460 | .IP "active" 4 |
|
|
5461 | .IX Item "active" |
|
|
5462 | A watcher is active as long as it has been started and not yet stopped. |
|
|
5463 | See \*(L"\s-1WATCHER\s0 \s-1STATES\s0\*(R" for details. |
|
|
5464 | .IP "application" 4 |
|
|
5465 | .IX Item "application" |
|
|
5466 | In this document, an application is whatever is using libev. |
|
|
5467 | .IP "backend" 4 |
|
|
5468 | .IX Item "backend" |
|
|
5469 | The part of the code dealing with the operating system interfaces. |
|
|
5470 | .IP "callback" 4 |
|
|
5471 | .IX Item "callback" |
|
|
5472 | The address of a function that is called when some event has been |
|
|
5473 | detected. Callbacks are being passed the event loop, the watcher that |
|
|
5474 | received the event, and the actual event bitset. |
|
|
5475 | .IP "callback/watcher invocation" 4 |
|
|
5476 | .IX Item "callback/watcher invocation" |
|
|
5477 | The act of calling the callback associated with a watcher. |
|
|
5478 | .IP "event" 4 |
|
|
5479 | .IX Item "event" |
|
|
5480 | A change of state of some external event, such as data now being available |
|
|
5481 | for reading on a file descriptor, time having passed or simply not having |
|
|
5482 | any other events happening anymore. |
|
|
5483 | .Sp |
|
|
5484 | In libev, events are represented as single bits (such as \f(CW\*(C`EV_READ\*(C'\fR or |
|
|
5485 | \&\f(CW\*(C`EV_TIMER\*(C'\fR). |
|
|
5486 | .IP "event library" 4 |
|
|
5487 | .IX Item "event library" |
|
|
5488 | A software package implementing an event model and loop. |
|
|
5489 | .IP "event loop" 4 |
|
|
5490 | .IX Item "event loop" |
|
|
5491 | An entity that handles and processes external events and converts them |
|
|
5492 | into callback invocations. |
|
|
5493 | .IP "event model" 4 |
|
|
5494 | .IX Item "event model" |
|
|
5495 | The model used to describe how an event loop handles and processes |
|
|
5496 | watchers and events. |
|
|
5497 | .IP "pending" 4 |
|
|
5498 | .IX Item "pending" |
|
|
5499 | A watcher is pending as soon as the corresponding event has been |
|
|
5500 | detected. See \*(L"\s-1WATCHER\s0 \s-1STATES\s0\*(R" for details. |
|
|
5501 | .IP "real time" 4 |
|
|
5502 | .IX Item "real time" |
|
|
5503 | The physical time that is observed. It is apparently strictly monotonic :) |
|
|
5504 | .IP "wall-clock time" 4 |
|
|
5505 | .IX Item "wall-clock time" |
|
|
5506 | The time and date as shown on clocks. Unlike real time, it can actually |
|
|
5507 | be wrong and jump forwards and backwards, e.g. when you adjust your |
|
|
5508 | clock. |
|
|
5509 | .IP "watcher" 4 |
|
|
5510 | .IX Item "watcher" |
|
|
5511 | A data structure that describes interest in certain events. Watchers need |
|
|
5512 | to be started (attached to an event loop) before they can receive events. |
2114 | .SH "AUTHOR" |
5513 | .SH "AUTHOR" |
2115 | .IX Header "AUTHOR" |
5514 | .IX Header "AUTHOR" |
2116 | Marc Lehmann <libev@schmorp.de>. |
5515 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
|
|
5516 | Magnusson and Emanuele Giaquinta, and minor corrections by many others. |