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131 | .IX Title ""<STANDARD INPUT>" 1" |
134 | .IX Title "LIBEV 3" |
132 | .TH "<STANDARD INPUT>" 1 "2007-11-18" "perl v5.8.8" "User Contributed Perl Documentation" |
135 | .TH LIBEV 3 "2008-12-14" "libev-3.52" "libev - high performance full featured event loop" |
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137 | .\" way too many mistakes in technical documents. |
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138 | .if n .ad l |
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139 | .nh |
133 | .SH "NAME" |
140 | .SH "NAME" |
134 | libev \- a high performance full\-featured event loop written in C |
141 | libev \- a high performance full\-featured event loop written in C |
135 | .SH "SYNOPSIS" |
142 | .SH "SYNOPSIS" |
136 | .IX Header "SYNOPSIS" |
143 | .IX Header "SYNOPSIS" |
137 | .Vb 1 |
144 | .Vb 1 |
138 | \& #include <ev.h> |
145 | \& #include <ev.h> |
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146 | .Ve |
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147 | .Sh "\s-1EXAMPLE\s0 \s-1PROGRAM\s0" |
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148 | .IX Subsection "EXAMPLE PROGRAM" |
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149 | .Vb 2 |
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150 | \& // a single header file is required |
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151 | \& #include <ev.h> |
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152 | \& |
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153 | \& #include <stdio.h> // for puts |
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154 | \& |
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155 | \& // every watcher type has its own typedef\*(Aqd struct |
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156 | \& // with the name ev_TYPE |
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157 | \& ev_io stdin_watcher; |
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158 | \& ev_timer timeout_watcher; |
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159 | \& |
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160 | \& // all watcher callbacks have a similar signature |
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161 | \& // this callback is called when data is readable on stdin |
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162 | \& static void |
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163 | \& stdin_cb (EV_P_ ev_io *w, int revents) |
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164 | \& { |
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165 | \& puts ("stdin ready"); |
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166 | \& // for one\-shot events, one must manually stop the watcher |
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167 | \& // with its corresponding stop function. |
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168 | \& ev_io_stop (EV_A_ w); |
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169 | \& |
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170 | \& // this causes all nested ev_loop\*(Aqs to stop iterating |
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171 | \& ev_unloop (EV_A_ EVUNLOOP_ALL); |
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172 | \& } |
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173 | \& |
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174 | \& // another callback, this time for a time\-out |
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175 | \& static void |
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176 | \& timeout_cb (EV_P_ ev_timer *w, int revents) |
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177 | \& { |
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178 | \& puts ("timeout"); |
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179 | \& // this causes the innermost ev_loop to stop iterating |
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180 | \& ev_unloop (EV_A_ EVUNLOOP_ONE); |
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181 | \& } |
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182 | \& |
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183 | \& int |
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184 | \& main (void) |
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185 | \& { |
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186 | \& // use the default event loop unless you have special needs |
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187 | \& struct ev_loop *loop = ev_default_loop (0); |
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188 | \& |
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189 | \& // initialise an io watcher, then start it |
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190 | \& // this one will watch for stdin to become readable |
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191 | \& ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
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192 | \& ev_io_start (loop, &stdin_watcher); |
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193 | \& |
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194 | \& // initialise a timer watcher, then start it |
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195 | \& // simple non\-repeating 5.5 second timeout |
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196 | \& ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
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197 | \& ev_timer_start (loop, &timeout_watcher); |
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198 | \& |
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199 | \& // now wait for events to arrive |
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200 | \& ev_loop (loop, 0); |
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201 | \& |
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202 | \& // unloop was called, so exit |
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203 | \& return 0; |
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204 | \& } |
139 | .Ve |
205 | .Ve |
140 | .SH "DESCRIPTION" |
206 | .SH "DESCRIPTION" |
141 | .IX Header "DESCRIPTION" |
207 | .IX Header "DESCRIPTION" |
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208 | The newest version of this document is also available as an html-formatted |
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209 | web page you might find easier to navigate when reading it for the first |
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210 | time: <http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
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211 | .PP |
142 | Libev is an event loop: you register interest in certain events (such as a |
212 | 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 |
213 | file descriptor being readable or a timeout occurring), and it will manage |
144 | these event sources and provide your program with events. |
214 | these event sources and provide your program with events. |
145 | .PP |
215 | .PP |
146 | To do this, it must take more or less complete control over your process |
216 | 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 |
217 | (or thread) by executing the \fIevent loop\fR handler, and will then |
148 | communicate events via a callback mechanism. |
218 | communicate events via a callback mechanism. |
149 | .PP |
219 | .PP |
150 | You register interest in certain events by registering so-called \fIevent |
220 | You register interest in certain events by registering so-called \fIevent |
151 | watchers\fR, which are relatively small C structures you initialise with the |
221 | 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 |
222 | details of the event, and then hand it over to libev by \fIstarting\fR the |
153 | watcher. |
223 | watcher. |
154 | .SH "FEATURES" |
224 | .Sh "\s-1FEATURES\s0" |
155 | .IX Header "FEATURES" |
225 | .IX Subsection "FEATURES" |
156 | Libev supports select, poll, the linux-specific epoll and the bsd-specific |
226 | 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 |
227 | 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 |
228 | 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 |
229 | (for \f(CW\*(C`ev_stat\*(C'\fR), relative timers (\f(CW\*(C`ev_timer\*(C'\fR), absolute timers |
160 | loop mechanism itself (idle, prepare and check watchers). It also is quite |
230 | with customised rescheduling (\f(CW\*(C`ev_periodic\*(C'\fR), synchronous signals |
161 | fast (see this benchmark comparing |
231 | (\f(CW\*(C`ev_signal\*(C'\fR), process status change events (\f(CW\*(C`ev_child\*(C'\fR), and event |
162 | it to libevent for example). |
232 | watchers dealing with the event loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR, |
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233 | \&\f(CW\*(C`ev_embed\*(C'\fR, \f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR watchers) as well as |
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234 | file watchers (\f(CW\*(C`ev_stat\*(C'\fR) and even limited support for fork events |
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235 | (\f(CW\*(C`ev_fork\*(C'\fR). |
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236 | .PP |
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237 | It also is quite fast (see this |
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238 | benchmark comparing it to libevent |
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239 | for example). |
163 | .SH "CONVENTIONS" |
240 | .Sh "\s-1CONVENTIONS\s0" |
164 | .IX Header "CONVENTIONS" |
241 | .IX Subsection "CONVENTIONS" |
165 | Libev is very configurable. In this manual the default configuration |
242 | Libev is very configurable. In this manual the default (and most common) |
166 | will be described, which supports multiple event loops. For more info |
243 | configuration will be described, which supports multiple event loops. For |
167 | about various configuration options please have a look at the file |
244 | 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 |
245 | \&\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 |
246 | 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) |
247 | name \f(CW\*(C`loop\*(C'\fR (which is always of type \f(CW\*(C`ev_loop *\*(C'\fR) will not have |
171 | will not have this argument. |
248 | this argument. |
172 | .SH "TIME REPRESENTATION" |
249 | .Sh "\s-1TIME\s0 \s-1REPRESENTATION\s0" |
173 | .IX Header "TIME REPRESENTATION" |
250 | .IX Subsection "TIME REPRESENTATION" |
174 | Libev represents time as a single floating point number, representing the |
251 | Libev represents time as a single floating point number, representing the |
175 | (fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near |
252 | (fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near |
176 | the beginning of 1970, details are complicated, don't ask). This type is |
253 | the beginning of 1970, details are complicated, don't ask). This type is |
177 | called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use too. It usually aliases |
254 | called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use too. It usually aliases |
178 | to the double type in C. |
255 | to the \f(CW\*(C`double\*(C'\fR type in C, and when you need to do any calculations on |
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256 | it, you should treat it as some floating point value. Unlike the name |
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257 | component \f(CW\*(C`stamp\*(C'\fR might indicate, it is also used for time differences |
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258 | throughout libev. |
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259 | .SH "ERROR HANDLING" |
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260 | .IX Header "ERROR HANDLING" |
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261 | Libev knows three classes of errors: operating system errors, usage errors |
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262 | and internal errors (bugs). |
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263 | .PP |
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264 | When libev catches an operating system error it cannot handle (for example |
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265 | a system call indicating a condition libev cannot fix), it calls the callback |
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266 | set via \f(CW\*(C`ev_set_syserr_cb\*(C'\fR, which is supposed to fix the problem or |
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267 | abort. The default is to print a diagnostic message and to call \f(CW\*(C`abort |
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268 | ()\*(C'\fR. |
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269 | .PP |
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270 | When libev detects a usage error such as a negative timer interval, then |
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271 | it will print a diagnostic message and abort (via the \f(CW\*(C`assert\*(C'\fR mechanism, |
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272 | so \f(CW\*(C`NDEBUG\*(C'\fR will disable this checking): these are programming errors in |
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273 | the libev caller and need to be fixed there. |
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274 | .PP |
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275 | Libev also has a few internal error-checking \f(CW\*(C`assert\*(C'\fRions, and also has |
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276 | extensive consistency checking code. These do not trigger under normal |
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277 | circumstances, as they indicate either a bug in libev or worse. |
179 | .SH "GLOBAL FUNCTIONS" |
278 | .SH "GLOBAL FUNCTIONS" |
180 | .IX Header "GLOBAL FUNCTIONS" |
279 | .IX Header "GLOBAL FUNCTIONS" |
181 | These functions can be called anytime, even before initialising the |
280 | These functions can be called anytime, even before initialising the |
182 | library in any way. |
281 | library in any way. |
183 | .IP "ev_tstamp ev_time ()" 4 |
282 | .IP "ev_tstamp ev_time ()" 4 |
184 | .IX Item "ev_tstamp ev_time ()" |
283 | .IX Item "ev_tstamp ev_time ()" |
185 | Returns the current time as libev would use it. Please note that the |
284 | Returns the current time as libev would use it. Please note that the |
186 | \&\f(CW\*(C`ev_now\*(C'\fR function is usually faster and also often returns the timestamp |
285 | \&\f(CW\*(C`ev_now\*(C'\fR function is usually faster and also often returns the timestamp |
187 | you actually want to know. |
286 | you actually want to know. |
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287 | .IP "ev_sleep (ev_tstamp interval)" 4 |
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288 | .IX Item "ev_sleep (ev_tstamp interval)" |
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289 | Sleep for the given interval: The current thread will be blocked until |
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290 | either it is interrupted or the given time interval has passed. Basically |
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291 | this is a sub-second-resolution \f(CW\*(C`sleep ()\*(C'\fR. |
188 | .IP "int ev_version_major ()" 4 |
292 | .IP "int ev_version_major ()" 4 |
189 | .IX Item "int ev_version_major ()" |
293 | .IX Item "int ev_version_major ()" |
190 | .PD 0 |
294 | .PD 0 |
191 | .IP "int ev_version_minor ()" 4 |
295 | .IP "int ev_version_minor ()" 4 |
192 | .IX Item "int ev_version_minor ()" |
296 | .IX Item "int ev_version_minor ()" |
193 | .PD |
297 | .PD |
194 | You can find out the major and minor version numbers of the library |
298 | You can find out the major and minor \s-1ABI\s0 version numbers of the library |
195 | you linked against by calling the functions \f(CW\*(C`ev_version_major\*(C'\fR and |
299 | you linked against by calling the functions \f(CW\*(C`ev_version_major\*(C'\fR and |
196 | \&\f(CW\*(C`ev_version_minor\*(C'\fR. If you want, you can compare against the global |
300 | \&\f(CW\*(C`ev_version_minor\*(C'\fR. If you want, you can compare against the global |
197 | symbols \f(CW\*(C`EV_VERSION_MAJOR\*(C'\fR and \f(CW\*(C`EV_VERSION_MINOR\*(C'\fR, which specify the |
301 | symbols \f(CW\*(C`EV_VERSION_MAJOR\*(C'\fR and \f(CW\*(C`EV_VERSION_MINOR\*(C'\fR, which specify the |
198 | version of the library your program was compiled against. |
302 | version of the library your program was compiled against. |
199 | .Sp |
303 | .Sp |
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304 | These version numbers refer to the \s-1ABI\s0 version of the library, not the |
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305 | release version. |
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306 | .Sp |
200 | Usually, it's a good idea to terminate if the major versions mismatch, |
307 | Usually, it's a good idea to terminate if the major versions mismatch, |
201 | as this indicates an incompatible change. Minor versions are usually |
308 | as this indicates an incompatible change. Minor versions are usually |
202 | compatible to older versions, so a larger minor version alone is usually |
309 | compatible to older versions, so a larger minor version alone is usually |
203 | not a problem. |
310 | not a problem. |
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311 | .Sp |
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312 | Example: Make sure we haven't accidentally been linked against the wrong |
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313 | version. |
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314 | .Sp |
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315 | .Vb 3 |
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316 | \& assert (("libev version mismatch", |
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317 | \& ev_version_major () == EV_VERSION_MAJOR |
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318 | \& && ev_version_minor () >= EV_VERSION_MINOR)); |
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319 | .Ve |
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320 | .IP "unsigned int ev_supported_backends ()" 4 |
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321 | .IX Item "unsigned int ev_supported_backends ()" |
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322 | Return the set of all backends (i.e. their corresponding \f(CW\*(C`EV_BACKEND_*\*(C'\fR |
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323 | value) compiled into this binary of libev (independent of their |
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324 | availability on the system you are running on). See \f(CW\*(C`ev_default_loop\*(C'\fR for |
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325 | a description of the set values. |
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326 | .Sp |
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327 | Example: make sure we have the epoll method, because yeah this is cool and |
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328 | a must have and can we have a torrent of it please!!!11 |
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329 | .Sp |
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330 | .Vb 2 |
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331 | \& assert (("sorry, no epoll, no sex", |
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332 | \& ev_supported_backends () & EVBACKEND_EPOLL)); |
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333 | .Ve |
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334 | .IP "unsigned int ev_recommended_backends ()" 4 |
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335 | .IX Item "unsigned int ev_recommended_backends ()" |
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336 | Return the set of all backends compiled into this binary of libev and also |
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337 | recommended for this platform. This set is often smaller than the one |
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338 | returned by \f(CW\*(C`ev_supported_backends\*(C'\fR, as for example kqueue is broken on |
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339 | most BSDs and will not be auto-detected unless you explicitly request it |
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340 | (assuming you know what you are doing). This is the set of backends that |
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341 | libev will probe for if you specify no backends explicitly. |
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342 | .IP "unsigned int ev_embeddable_backends ()" 4 |
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343 | .IX Item "unsigned int ev_embeddable_backends ()" |
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344 | Returns the set of backends that are embeddable in other event loops. This |
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345 | is the theoretical, all-platform, value. To find which backends |
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346 | might be supported on the current system, you would need to look at |
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347 | \&\f(CW\*(C`ev_embeddable_backends () & ev_supported_backends ()\*(C'\fR, likewise for |
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348 | recommended ones. |
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349 | .Sp |
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350 | See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info. |
204 | .IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4 |
351 | .IP "ev_set_allocator (void *(*cb)(void *ptr, long size)) [\s-1NOT\s0 \s-1REENTRANT\s0]" 4 |
205 | .IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))" |
352 | .IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]" |
206 | Sets the allocation function to use (the prototype is similar to the |
353 | Sets the allocation function to use (the prototype is similar \- the |
207 | realloc C function, the semantics are identical). It is used to allocate |
354 | semantics are identical to the \f(CW\*(C`realloc\*(C'\fR C89/SuS/POSIX function). It is |
208 | and free memory (no surprises here). If it returns zero when memory |
355 | used to allocate and free memory (no surprises here). If it returns zero |
209 | needs to be allocated, the library might abort or take some potentially |
356 | when memory needs to be allocated (\f(CW\*(C`size != 0\*(C'\fR), the library might abort |
210 | destructive action. The default is your system realloc function. |
357 | or take some potentially destructive action. |
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358 | .Sp |
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359 | Since some systems (at least OpenBSD and Darwin) fail to implement |
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360 | correct \f(CW\*(C`realloc\*(C'\fR semantics, libev will use a wrapper around the system |
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361 | \&\f(CW\*(C`realloc\*(C'\fR and \f(CW\*(C`free\*(C'\fR functions by default. |
211 | .Sp |
362 | .Sp |
212 | You could override this function in high-availability programs to, say, |
363 | You could override this function in high-availability programs to, say, |
213 | free some memory if it cannot allocate memory, to use a special allocator, |
364 | free some memory if it cannot allocate memory, to use a special allocator, |
214 | or even to sleep a while and retry until some memory is available. |
365 | or even to sleep a while and retry until some memory is available. |
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366 | .Sp |
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367 | Example: Replace the libev allocator with one that waits a bit and then |
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368 | retries (example requires a standards-compliant \f(CW\*(C`realloc\*(C'\fR). |
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369 | .Sp |
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370 | .Vb 6 |
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371 | \& static void * |
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372 | \& persistent_realloc (void *ptr, size_t size) |
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373 | \& { |
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374 | \& for (;;) |
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375 | \& { |
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376 | \& void *newptr = realloc (ptr, size); |
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377 | \& |
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378 | \& if (newptr) |
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379 | \& return newptr; |
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380 | \& |
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381 | \& sleep (60); |
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382 | \& } |
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383 | \& } |
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384 | \& |
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385 | \& ... |
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386 | \& ev_set_allocator (persistent_realloc); |
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387 | .Ve |
215 | .IP "ev_set_syserr_cb (void (*cb)(const char *msg));" 4 |
388 | .IP "ev_set_syserr_cb (void (*cb)(const char *msg)); [\s-1NOT\s0 \s-1REENTRANT\s0]" 4 |
216 | .IX Item "ev_set_syserr_cb (void (*cb)(const char *msg));" |
389 | .IX Item "ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]" |
217 | Set the callback function to call on a retryable syscall error (such |
390 | Set the callback function to call on a retryable system call error (such |
218 | as failed select, poll, epoll_wait). The message is a printable string |
391 | as failed select, poll, epoll_wait). The message is a printable string |
219 | indicating the system call or subsystem causing the problem. If this |
392 | indicating the system call or subsystem causing the problem. If this |
220 | callback is set, then libev will expect it to remedy the sitution, no |
393 | callback is set, then libev will expect it to remedy the situation, no |
221 | matter what, when it returns. That is, libev will generally retry the |
394 | matter what, when it returns. That is, libev will generally retry the |
222 | requested operation, or, if the condition doesn't go away, do bad stuff |
395 | requested operation, or, if the condition doesn't go away, do bad stuff |
223 | (such as abort). |
396 | (such as abort). |
|
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397 | .Sp |
|
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398 | Example: This is basically the same thing that libev does internally, too. |
|
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399 | .Sp |
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400 | .Vb 6 |
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401 | \& static void |
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402 | \& fatal_error (const char *msg) |
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403 | \& { |
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404 | \& perror (msg); |
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405 | \& abort (); |
|
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406 | \& } |
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407 | \& |
|
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408 | \& ... |
|
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409 | \& ev_set_syserr_cb (fatal_error); |
|
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410 | .Ve |
224 | .SH "FUNCTIONS CONTROLLING THE EVENT LOOP" |
411 | .SH "FUNCTIONS CONTROLLING THE EVENT LOOP" |
225 | .IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP" |
412 | .IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP" |
226 | An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR. The library knows two |
413 | An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR (the \f(CW\*(C`struct\*(C'\fR |
227 | types of such loops, the \fIdefault\fR loop, which supports signals and child |
414 | is \fInot\fR optional in this case, as there is also an \f(CW\*(C`ev_loop\*(C'\fR |
228 | events, and dynamically created loops which do not. |
415 | \&\fIfunction\fR). |
229 | .PP |
416 | .PP |
230 | If you use threads, a common model is to run the default event loop |
417 | The library knows two types of such loops, the \fIdefault\fR loop, which |
231 | in your main thread (or in a separate thread) and for each thread you |
418 | supports signals and child events, and dynamically created loops which do |
232 | create, you also create another event loop. Libev itself does no locking |
419 | not. |
233 | whatsoever, so if you mix calls to the same event loop in different |
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234 | threads, make sure you lock (this is usually a bad idea, though, even if |
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235 | done correctly, because it's hideous and inefficient). |
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236 | .IP "struct ev_loop *ev_default_loop (unsigned int flags)" 4 |
420 | .IP "struct ev_loop *ev_default_loop (unsigned int flags)" 4 |
237 | .IX Item "struct ev_loop *ev_default_loop (unsigned int flags)" |
421 | .IX Item "struct ev_loop *ev_default_loop (unsigned int flags)" |
238 | This will initialise the default event loop if it hasn't been initialised |
422 | This will initialise the default event loop if it hasn't been initialised |
239 | yet and return it. If the default loop could not be initialised, returns |
423 | yet and return it. If the default loop could not be initialised, returns |
240 | false. If it already was initialised it simply returns it (and ignores the |
424 | false. If it already was initialised it simply returns it (and ignores the |
241 | flags). |
425 | flags. If that is troubling you, check \f(CW\*(C`ev_backend ()\*(C'\fR afterwards). |
242 | .Sp |
426 | .Sp |
243 | If you don't know what event loop to use, use the one returned from this |
427 | If you don't know what event loop to use, use the one returned from this |
244 | function. |
428 | function. |
245 | .Sp |
429 | .Sp |
|
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430 | Note that this function is \fInot\fR thread-safe, so if you want to use it |
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431 | from multiple threads, you have to lock (note also that this is unlikely, |
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432 | as loops cannot be shared easily between threads anyway). |
|
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433 | .Sp |
|
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434 | The default loop is the only loop that can handle \f(CW\*(C`ev_signal\*(C'\fR and |
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435 | \&\f(CW\*(C`ev_child\*(C'\fR watchers, and to do this, it always registers a handler |
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436 | for \f(CW\*(C`SIGCHLD\*(C'\fR. If this is a problem for your application you can either |
|
|
437 | create a dynamic loop with \f(CW\*(C`ev_loop_new\*(C'\fR that doesn't do that, or you |
|
|
438 | can simply overwrite the \f(CW\*(C`SIGCHLD\*(C'\fR signal handler \fIafter\fR calling |
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439 | \&\f(CW\*(C`ev_default_init\*(C'\fR. |
|
|
440 | .Sp |
246 | The flags argument can be used to specify special behaviour or specific |
441 | The flags argument can be used to specify special behaviour or specific |
247 | backends to use, and is usually specified as 0 (or \s-1EVFLAG_AUTO\s0). |
442 | backends to use, and is usually specified as \f(CW0\fR (or \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). |
248 | .Sp |
443 | .Sp |
249 | It supports the following flags: |
444 | The following flags are supported: |
250 | .RS 4 |
445 | .RS 4 |
251 | .ie n .IP """EVFLAG_AUTO""" 4 |
446 | .ie n .IP """EVFLAG_AUTO""" 4 |
252 | .el .IP "\f(CWEVFLAG_AUTO\fR" 4 |
447 | .el .IP "\f(CWEVFLAG_AUTO\fR" 4 |
253 | .IX Item "EVFLAG_AUTO" |
448 | .IX Item "EVFLAG_AUTO" |
254 | The default flags value. Use this if you have no clue (it's the right |
449 | The default flags value. Use this if you have no clue (it's the right |
255 | thing, believe me). |
450 | thing, believe me). |
256 | .ie n .IP """EVFLAG_NOENV""" 4 |
451 | .ie n .IP """EVFLAG_NOENV""" 4 |
257 | .el .IP "\f(CWEVFLAG_NOENV\fR" 4 |
452 | .el .IP "\f(CWEVFLAG_NOENV\fR" 4 |
258 | .IX Item "EVFLAG_NOENV" |
453 | .IX Item "EVFLAG_NOENV" |
259 | If this flag bit is ored into the flag value (or the program runs setuid |
454 | If this flag bit is or'ed into the flag value (or the program runs setuid |
260 | or setgid) then libev will \fInot\fR look at the environment variable |
455 | or setgid) then libev will \fInot\fR look at the environment variable |
261 | \&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will |
456 | \&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will |
262 | override the flags completely if it is found in the environment. This is |
457 | override the flags completely if it is found in the environment. This is |
263 | useful to try out specific backends to test their performance, or to work |
458 | useful to try out specific backends to test their performance, or to work |
264 | around bugs. |
459 | around bugs. |
|
|
460 | .ie n .IP """EVFLAG_FORKCHECK""" 4 |
|
|
461 | .el .IP "\f(CWEVFLAG_FORKCHECK\fR" 4 |
|
|
462 | .IX Item "EVFLAG_FORKCHECK" |
|
|
463 | Instead of calling \f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR manually after |
|
|
464 | a fork, you can also make libev check for a fork in each iteration by |
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|
465 | enabling this flag. |
|
|
466 | .Sp |
|
|
467 | This works by calling \f(CW\*(C`getpid ()\*(C'\fR on every iteration of the loop, |
|
|
468 | and thus this might slow down your event loop if you do a lot of loop |
|
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469 | iterations and little real work, but is usually not noticeable (on my |
|
|
470 | GNU/Linux system for example, \f(CW\*(C`getpid\*(C'\fR is actually a simple 5\-insn sequence |
|
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471 | without a system call and thus \fIvery\fR fast, but my GNU/Linux system also has |
|
|
472 | \&\f(CW\*(C`pthread_atfork\*(C'\fR which is even faster). |
|
|
473 | .Sp |
|
|
474 | The big advantage of this flag is that you can forget about fork (and |
|
|
475 | forget about forgetting to tell libev about forking) when you use this |
|
|
476 | flag. |
|
|
477 | .Sp |
|
|
478 | This flag setting cannot be overridden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR |
|
|
479 | environment variable. |
265 | .ie n .IP """EVMETHOD_SELECT"" (portable select backend)" 4 |
480 | .ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4 |
266 | .el .IP "\f(CWEVMETHOD_SELECT\fR (portable select backend)" 4 |
481 | .el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4 |
267 | .IX Item "EVMETHOD_SELECT (portable select backend)" |
482 | .IX Item "EVBACKEND_SELECT (value 1, portable select backend)" |
268 | .PD 0 |
483 | This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as |
|
|
484 | libev tries to roll its own fd_set with no limits on the number of fds, |
|
|
485 | but if that fails, expect a fairly low limit on the number of fds when |
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|
486 | using this backend. It doesn't scale too well (O(highest_fd)), but its |
|
|
487 | usually the fastest backend for a low number of (low-numbered :) fds. |
|
|
488 | .Sp |
|
|
489 | To get good performance out of this backend you need a high amount of |
|
|
490 | parallelism (most of the file descriptors should be busy). If you are |
|
|
491 | writing a server, you should \f(CW\*(C`accept ()\*(C'\fR in a loop to accept as many |
|
|
492 | connections as possible during one iteration. You might also want to have |
|
|
493 | a look at \f(CW\*(C`ev_set_io_collect_interval ()\*(C'\fR to increase the amount of |
|
|
494 | readiness notifications you get per iteration. |
|
|
495 | .Sp |
|
|
496 | 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 |
|
|
497 | \&\f(CW\*(C`writefds\*(C'\fR set (and to work around Microsoft Windows bugs, also onto the |
|
|
498 | \&\f(CW\*(C`exceptfds\*(C'\fR set on that platform). |
269 | .ie n .IP """EVMETHOD_POLL"" (poll backend, available everywhere except on windows)" 4 |
499 | .ie n .IP """EVBACKEND_POLL"" (value 2, poll backend, available everywhere except on windows)" 4 |
270 | .el .IP "\f(CWEVMETHOD_POLL\fR (poll backend, available everywhere except on windows)" 4 |
500 | .el .IP "\f(CWEVBACKEND_POLL\fR (value 2, poll backend, available everywhere except on windows)" 4 |
271 | .IX Item "EVMETHOD_POLL (poll backend, available everywhere except on windows)" |
501 | .IX Item "EVBACKEND_POLL (value 2, poll backend, available everywhere except on windows)" |
|
|
502 | And this is your standard \fIpoll\fR\|(2) backend. It's more complicated |
|
|
503 | than select, but handles sparse fds better and has no artificial |
|
|
504 | limit on the number of fds you can use (except it will slow down |
|
|
505 | considerably with a lot of inactive fds). It scales similarly to select, |
|
|
506 | i.e. O(total_fds). See the entry for \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR, above, for |
|
|
507 | performance tips. |
|
|
508 | .Sp |
|
|
509 | This backend maps \f(CW\*(C`EV_READ\*(C'\fR to \f(CW\*(C`POLLIN | POLLERR | POLLHUP\*(C'\fR, and |
|
|
510 | \&\f(CW\*(C`EV_WRITE\*(C'\fR to \f(CW\*(C`POLLOUT | POLLERR | POLLHUP\*(C'\fR. |
272 | .ie n .IP """EVMETHOD_EPOLL"" (linux only)" 4 |
511 | .ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4 |
273 | .el .IP "\f(CWEVMETHOD_EPOLL\fR (linux only)" 4 |
512 | .el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4 |
274 | .IX Item "EVMETHOD_EPOLL (linux only)" |
513 | .IX Item "EVBACKEND_EPOLL (value 4, Linux)" |
275 | .ie n .IP """EVMETHOD_KQUEUE"" (some bsds only)" 4 |
514 | For few fds, this backend is a bit little slower than poll and select, |
276 | .el .IP "\f(CWEVMETHOD_KQUEUE\fR (some bsds only)" 4 |
515 | but it scales phenomenally better. While poll and select usually scale |
277 | .IX Item "EVMETHOD_KQUEUE (some bsds only)" |
516 | like O(total_fds) where n is the total number of fds (or the highest fd), |
|
|
517 | epoll scales either O(1) or O(active_fds). |
|
|
518 | .Sp |
|
|
519 | The epoll mechanism deserves honorable mention as the most misdesigned |
|
|
520 | of the more advanced event mechanisms: mere annoyances include silently |
|
|
521 | dropping file descriptors, requiring a system call per change per file |
|
|
522 | descriptor (and unnecessary guessing of parameters), problems with dup and |
|
|
523 | so on. The biggest issue is fork races, however \- if a program forks then |
|
|
524 | \&\fIboth\fR parent and child process have to recreate the epoll set, which can |
|
|
525 | take considerable time (one syscall per file descriptor) and is of course |
|
|
526 | hard to detect. |
|
|
527 | .Sp |
|
|
528 | Epoll is also notoriously buggy \- embedding epoll fds \fIshould\fR work, but |
|
|
529 | of course \fIdoesn't\fR, and epoll just loves to report events for totally |
|
|
530 | \&\fIdifferent\fR file descriptors (even already closed ones, so one cannot |
|
|
531 | even remove them from the set) than registered in the set (especially |
|
|
532 | on \s-1SMP\s0 systems). Libev tries to counter these spurious notifications by |
|
|
533 | employing an additional generation counter and comparing that against the |
|
|
534 | events to filter out spurious ones, recreating the set when required. |
|
|
535 | .Sp |
|
|
536 | While stopping, setting and starting an I/O watcher in the same iteration |
|
|
537 | will result in some caching, there is still a system call per such |
|
|
538 | incident (because the same \fIfile descriptor\fR could point to a different |
|
|
539 | \&\fIfile description\fR now), so its best to avoid that. Also, \f(CW\*(C`dup ()\*(C'\fR'ed |
|
|
540 | file descriptors might not work very well if you register events for both |
|
|
541 | file descriptors. |
|
|
542 | .Sp |
|
|
543 | Best performance from this backend is achieved by not unregistering all |
|
|
544 | watchers for a file descriptor until it has been closed, if possible, |
|
|
545 | i.e. keep at least one watcher active per fd at all times. Stopping and |
|
|
546 | starting a watcher (without re-setting it) also usually doesn't cause |
|
|
547 | extra overhead. A fork can both result in spurious notifications as well |
|
|
548 | as in libev having to destroy and recreate the epoll object, which can |
|
|
549 | take considerable time and thus should be avoided. |
|
|
550 | .Sp |
|
|
551 | All this means that, in practice, \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR can be as fast or |
|
|
552 | faster than epoll for maybe up to a hundred file descriptors, depending on |
|
|
553 | the usage. So sad. |
|
|
554 | .Sp |
|
|
555 | While nominally embeddable in other event loops, this feature is broken in |
|
|
556 | all kernel versions tested so far. |
|
|
557 | .Sp |
|
|
558 | This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as |
|
|
559 | \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
|
|
560 | .ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4 |
|
|
561 | .el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4 |
|
|
562 | .IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)" |
|
|
563 | Kqueue deserves special mention, as at the time of this writing, it |
|
|
564 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
|
|
565 | with anything but sockets and pipes, except on Darwin, where of course |
|
|
566 | it's completely useless). Unlike epoll, however, whose brokenness |
|
|
567 | is by design, these kqueue bugs can (and eventually will) be fixed |
|
|
568 | without \s-1API\s0 changes to existing programs. For this reason it's not being |
|
|
569 | \&\*(L"auto-detected\*(R" unless you explicitly specify it in the flags (i.e. using |
|
|
570 | \&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR) or libev was compiled on a known-to-be-good (\-enough) |
|
|
571 | system like NetBSD. |
|
|
572 | .Sp |
|
|
573 | You still can embed kqueue into a normal poll or select backend and use it |
|
|
574 | only for sockets (after having made sure that sockets work with kqueue on |
|
|
575 | the target platform). See \f(CW\*(C`ev_embed\*(C'\fR watchers for more info. |
|
|
576 | .Sp |
|
|
577 | It scales in the same way as the epoll backend, but the interface to the |
|
|
578 | kernel is more efficient (which says nothing about its actual speed, of |
|
|
579 | course). While stopping, setting and starting an I/O watcher does never |
|
|
580 | cause an extra system call as with \f(CW\*(C`EVBACKEND_EPOLL\*(C'\fR, it still adds up to |
|
|
581 | two event changes per incident. Support for \f(CW\*(C`fork ()\*(C'\fR is very bad (but |
|
|
582 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
|
|
583 | cases |
|
|
584 | .Sp |
|
|
585 | This backend usually performs well under most conditions. |
|
|
586 | .Sp |
|
|
587 | While nominally embeddable in other event loops, this doesn't work |
|
|
588 | everywhere, so you might need to test for this. And since it is broken |
|
|
589 | almost everywhere, you should only use it when you have a lot of sockets |
|
|
590 | (for which it usually works), by embedding it into another event loop |
|
|
591 | (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 |
|
|
592 | also broken on \s-1OS\s0 X)) and, did I mention it, using it only for sockets. |
|
|
593 | .Sp |
|
|
594 | This backend maps \f(CW\*(C`EV_READ\*(C'\fR into an \f(CW\*(C`EVFILT_READ\*(C'\fR kevent with |
|
|
595 | \&\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 |
|
|
596 | \&\f(CW\*(C`NOTE_EOF\*(C'\fR. |
278 | .ie n .IP """EVMETHOD_DEVPOLL"" (solaris 8 only)" 4 |
597 | .ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4 |
279 | .el .IP "\f(CWEVMETHOD_DEVPOLL\fR (solaris 8 only)" 4 |
598 | .el .IP "\f(CWEVBACKEND_DEVPOLL\fR (value 16, Solaris 8)" 4 |
280 | .IX Item "EVMETHOD_DEVPOLL (solaris 8 only)" |
599 | .IX Item "EVBACKEND_DEVPOLL (value 16, Solaris 8)" |
|
|
600 | This is not implemented yet (and might never be, unless you send me an |
|
|
601 | implementation). According to reports, \f(CW\*(C`/dev/poll\*(C'\fR only supports sockets |
|
|
602 | and is not embeddable, which would limit the usefulness of this backend |
|
|
603 | immensely. |
281 | .ie n .IP """EVMETHOD_PORT"" (solaris 10 only)" 4 |
604 | .ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4 |
282 | .el .IP "\f(CWEVMETHOD_PORT\fR (solaris 10 only)" 4 |
605 | .el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4 |
283 | .IX Item "EVMETHOD_PORT (solaris 10 only)" |
606 | .IX Item "EVBACKEND_PORT (value 32, Solaris 10)" |
284 | .PD |
607 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
285 | If one or more of these are ored into the flags value, then only these |
608 | it's really slow, but it still scales very well (O(active_fds)). |
286 | backends will be tried (in the reverse order as given here). If one are |
609 | .Sp |
287 | specified, any backend will do. |
610 | Please note that Solaris event ports can deliver a lot of spurious |
|
|
611 | notifications, so you need to use non-blocking I/O or other means to avoid |
|
|
612 | blocking when no data (or space) is available. |
|
|
613 | .Sp |
|
|
614 | While this backend scales well, it requires one system call per active |
|
|
615 | file descriptor per loop iteration. For small and medium numbers of file |
|
|
616 | descriptors a \*(L"slow\*(R" \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR backend |
|
|
617 | might perform better. |
|
|
618 | .Sp |
|
|
619 | On the positive side, with the exception of the spurious readiness |
|
|
620 | notifications, this backend actually performed fully to specification |
|
|
621 | in all tests and is fully embeddable, which is a rare feat among the |
|
|
622 | OS-specific backends (I vastly prefer correctness over speed hacks). |
|
|
623 | .Sp |
|
|
624 | This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as |
|
|
625 | \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
|
|
626 | .ie n .IP """EVBACKEND_ALL""" 4 |
|
|
627 | .el .IP "\f(CWEVBACKEND_ALL\fR" 4 |
|
|
628 | .IX Item "EVBACKEND_ALL" |
|
|
629 | Try all backends (even potentially broken ones that wouldn't be tried |
|
|
630 | with \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). Since this is a mask, you can do stuff such as |
|
|
631 | \&\f(CW\*(C`EVBACKEND_ALL & ~EVBACKEND_KQUEUE\*(C'\fR. |
|
|
632 | .Sp |
|
|
633 | It is definitely not recommended to use this flag. |
288 | .RE |
634 | .RE |
289 | .RS 4 |
635 | .RS 4 |
|
|
636 | .Sp |
|
|
637 | If one or more of these are or'ed into the flags value, then only these |
|
|
638 | backends will be tried (in the reverse order as listed here). If none are |
|
|
639 | specified, all backends in \f(CW\*(C`ev_recommended_backends ()\*(C'\fR will be tried. |
|
|
640 | .Sp |
|
|
641 | Example: This is the most typical usage. |
|
|
642 | .Sp |
|
|
643 | .Vb 2 |
|
|
644 | \& if (!ev_default_loop (0)) |
|
|
645 | \& fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
|
|
646 | .Ve |
|
|
647 | .Sp |
|
|
648 | Example: Restrict libev to the select and poll backends, and do not allow |
|
|
649 | environment settings to be taken into account: |
|
|
650 | .Sp |
|
|
651 | .Vb 1 |
|
|
652 | \& ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
|
|
653 | .Ve |
|
|
654 | .Sp |
|
|
655 | Example: Use whatever libev has to offer, but make sure that kqueue is |
|
|
656 | used if available (warning, breaks stuff, best use only with your own |
|
|
657 | private event loop and only if you know the \s-1OS\s0 supports your types of |
|
|
658 | fds): |
|
|
659 | .Sp |
|
|
660 | .Vb 1 |
|
|
661 | \& ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
662 | .Ve |
290 | .RE |
663 | .RE |
291 | .IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4 |
664 | .IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4 |
292 | .IX Item "struct ev_loop *ev_loop_new (unsigned int flags)" |
665 | .IX Item "struct ev_loop *ev_loop_new (unsigned int flags)" |
293 | Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is |
666 | Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is |
294 | always distinct from the default loop. Unlike the default loop, it cannot |
667 | always distinct from the default loop. Unlike the default loop, it cannot |
295 | handle signal and child watchers, and attempts to do so will be greeted by |
668 | handle signal and child watchers, and attempts to do so will be greeted by |
296 | undefined behaviour (or a failed assertion if assertions are enabled). |
669 | undefined behaviour (or a failed assertion if assertions are enabled). |
|
|
670 | .Sp |
|
|
671 | Note that this function \fIis\fR thread-safe, and the recommended way to use |
|
|
672 | libev with threads is indeed to create one loop per thread, and using the |
|
|
673 | default loop in the \*(L"main\*(R" or \*(L"initial\*(R" thread. |
|
|
674 | .Sp |
|
|
675 | Example: Try to create a event loop that uses epoll and nothing else. |
|
|
676 | .Sp |
|
|
677 | .Vb 3 |
|
|
678 | \& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
|
|
679 | \& if (!epoller) |
|
|
680 | \& fatal ("no epoll found here, maybe it hides under your chair"); |
|
|
681 | .Ve |
297 | .IP "ev_default_destroy ()" 4 |
682 | .IP "ev_default_destroy ()" 4 |
298 | .IX Item "ev_default_destroy ()" |
683 | .IX Item "ev_default_destroy ()" |
299 | Destroys the default loop again (frees all memory and kernel state |
684 | Destroys the default loop again (frees all memory and kernel state |
300 | etc.). This stops all registered event watchers (by not touching them in |
685 | etc.). None of the active event watchers will be stopped in the normal |
301 | any way whatsoever, although you cannot rely on this :). |
686 | sense, so e.g. \f(CW\*(C`ev_is_active\*(C'\fR might still return true. It is your |
|
|
687 | responsibility to either stop all watchers cleanly yourself \fIbefore\fR |
|
|
688 | calling this function, or cope with the fact afterwards (which is usually |
|
|
689 | the easiest thing, you can just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them |
|
|
690 | for example). |
|
|
691 | .Sp |
|
|
692 | Note that certain global state, such as signal state (and installed signal |
|
|
693 | handlers), will not be freed by this function, and related watchers (such |
|
|
694 | as signal and child watchers) would need to be stopped manually. |
|
|
695 | .Sp |
|
|
696 | In general it is not advisable to call this function except in the |
|
|
697 | rare occasion where you really need to free e.g. the signal handling |
|
|
698 | pipe fds. If you need dynamically allocated loops it is better to use |
|
|
699 | \&\f(CW\*(C`ev_loop_new\*(C'\fR and \f(CW\*(C`ev_loop_destroy\*(C'\fR). |
302 | .IP "ev_loop_destroy (loop)" 4 |
700 | .IP "ev_loop_destroy (loop)" 4 |
303 | .IX Item "ev_loop_destroy (loop)" |
701 | .IX Item "ev_loop_destroy (loop)" |
304 | Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an |
702 | Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an |
305 | earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR. |
703 | earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR. |
306 | .IP "ev_default_fork ()" 4 |
704 | .IP "ev_default_fork ()" 4 |
307 | .IX Item "ev_default_fork ()" |
705 | .IX Item "ev_default_fork ()" |
|
|
706 | This function sets a flag that causes subsequent \f(CW\*(C`ev_loop\*(C'\fR iterations |
308 | This function reinitialises the kernel state for backends that have |
707 | to reinitialise the kernel state for backends that have one. Despite the |
309 | one. Despite the name, you can call it anytime, but it makes most sense |
708 | name, you can call it anytime, but it makes most sense after forking, in |
310 | after forking, in either the parent or child process (or both, but that |
709 | the child process (or both child and parent, but that again makes little |
311 | again makes little sense). |
710 | sense). You \fImust\fR call it in the child before using any of the libev |
|
|
711 | functions, and it will only take effect at the next \f(CW\*(C`ev_loop\*(C'\fR iteration. |
312 | .Sp |
712 | .Sp |
313 | You \fImust\fR call this function after forking if and only if you want to |
713 | On the other hand, you only need to call this function in the child |
314 | use the event library in both processes. If you just fork+exec, you don't |
714 | process if and only if you want to use the event library in the child. If |
315 | have to call it. |
715 | you just fork+exec, you don't have to call it at all. |
316 | .Sp |
716 | .Sp |
317 | The function itself is quite fast and it's usually not a problem to call |
717 | The function itself is quite fast and it's usually not a problem to call |
318 | it just in case after a fork. To make this easy, the function will fit in |
718 | it just in case after a fork. To make this easy, the function will fit in |
319 | quite nicely into a call to \f(CW\*(C`pthread_atfork\*(C'\fR: |
719 | quite nicely into a call to \f(CW\*(C`pthread_atfork\*(C'\fR: |
320 | .Sp |
720 | .Sp |
… | |
… | |
323 | .Ve |
723 | .Ve |
324 | .IP "ev_loop_fork (loop)" 4 |
724 | .IP "ev_loop_fork (loop)" 4 |
325 | .IX Item "ev_loop_fork (loop)" |
725 | .IX Item "ev_loop_fork (loop)" |
326 | Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by |
726 | Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by |
327 | \&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop |
727 | \&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop |
328 | after fork, and how you do this is entirely your own problem. |
728 | after fork that you want to re-use in the child, and how you do this is |
|
|
729 | entirely your own problem. |
|
|
730 | .IP "int ev_is_default_loop (loop)" 4 |
|
|
731 | .IX Item "int ev_is_default_loop (loop)" |
|
|
732 | Returns true when the given loop is, in fact, the default loop, and false |
|
|
733 | otherwise. |
|
|
734 | .IP "unsigned int ev_loop_count (loop)" 4 |
|
|
735 | .IX Item "unsigned int ev_loop_count (loop)" |
|
|
736 | Returns the count of loop iterations for the loop, which is identical to |
|
|
737 | the number of times libev did poll for new events. It starts at \f(CW0\fR and |
|
|
738 | happily wraps around with enough iterations. |
|
|
739 | .Sp |
|
|
740 | This value can sometimes be useful as a generation counter of sorts (it |
|
|
741 | \&\*(L"ticks\*(R" the number of loop iterations), as it roughly corresponds with |
|
|
742 | \&\f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR calls. |
329 | .IP "unsigned int ev_method (loop)" 4 |
743 | .IP "unsigned int ev_backend (loop)" 4 |
330 | .IX Item "unsigned int ev_method (loop)" |
744 | .IX Item "unsigned int ev_backend (loop)" |
331 | Returns one of the \f(CW\*(C`EVMETHOD_*\*(C'\fR flags indicating the event backend in |
745 | Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in |
332 | use. |
746 | use. |
333 | .IP "ev_tstamp ev_now (loop)" 4 |
747 | .IP "ev_tstamp ev_now (loop)" 4 |
334 | .IX Item "ev_tstamp ev_now (loop)" |
748 | .IX Item "ev_tstamp ev_now (loop)" |
335 | Returns the current \*(L"event loop time\*(R", which is the time the event loop |
749 | Returns the current \*(L"event loop time\*(R", which is the time the event loop |
336 | got events and started processing them. This timestamp does not change |
750 | received events and started processing them. This timestamp does not |
337 | as long as callbacks are being processed, and this is also the base time |
751 | change as long as callbacks are being processed, and this is also the base |
338 | used for relative timers. You can treat it as the timestamp of the event |
752 | time used for relative timers. You can treat it as the timestamp of the |
339 | occuring (or more correctly, the mainloop finding out about it). |
753 | event occurring (or more correctly, libev finding out about it). |
|
|
754 | .IP "ev_now_update (loop)" 4 |
|
|
755 | .IX Item "ev_now_update (loop)" |
|
|
756 | Establishes the current time by querying the kernel, updating the time |
|
|
757 | returned by \f(CW\*(C`ev_now ()\*(C'\fR in the progress. This is a costly operation and |
|
|
758 | is usually done automatically within \f(CW\*(C`ev_loop ()\*(C'\fR. |
|
|
759 | .Sp |
|
|
760 | This function is rarely useful, but when some event callback runs for a |
|
|
761 | very long time without entering the event loop, updating libev's idea of |
|
|
762 | the current time is a good idea. |
|
|
763 | .Sp |
|
|
764 | See also \*(L"The special problem of time updates\*(R" in the \f(CW\*(C`ev_timer\*(C'\fR section. |
340 | .IP "ev_loop (loop, int flags)" 4 |
765 | .IP "ev_loop (loop, int flags)" 4 |
341 | .IX Item "ev_loop (loop, int flags)" |
766 | .IX Item "ev_loop (loop, int flags)" |
342 | Finally, this is it, the event handler. This function usually is called |
767 | Finally, this is it, the event handler. This function usually is called |
343 | after you initialised all your watchers and you want to start handling |
768 | after you initialised all your watchers and you want to start handling |
344 | events. |
769 | events. |
345 | .Sp |
770 | .Sp |
346 | If the flags argument is specified as 0, it will not return until either |
771 | If the flags argument is specified as \f(CW0\fR, it will not return until |
347 | no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called. |
772 | either no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called. |
|
|
773 | .Sp |
|
|
774 | Please note that an explicit \f(CW\*(C`ev_unloop\*(C'\fR is usually better than |
|
|
775 | relying on all watchers to be stopped when deciding when a program has |
|
|
776 | finished (especially in interactive programs), but having a program |
|
|
777 | that automatically loops as long as it has to and no longer by virtue |
|
|
778 | of relying on its watchers stopping correctly, that is truly a thing of |
|
|
779 | beauty. |
348 | .Sp |
780 | .Sp |
349 | A flags value of \f(CW\*(C`EVLOOP_NONBLOCK\*(C'\fR will look for new events, will handle |
781 | A flags value of \f(CW\*(C`EVLOOP_NONBLOCK\*(C'\fR will look for new events, will handle |
350 | those events and any outstanding ones, but will not block your process in |
782 | those events and any already outstanding ones, but will not block your |
351 | case there are no events and will return after one iteration of the loop. |
783 | process in case there are no events and will return after one iteration of |
|
|
784 | the loop. |
352 | .Sp |
785 | .Sp |
353 | A flags value of \f(CW\*(C`EVLOOP_ONESHOT\*(C'\fR will look for new events (waiting if |
786 | A flags value of \f(CW\*(C`EVLOOP_ONESHOT\*(C'\fR will look for new events (waiting if |
354 | neccessary) and will handle those and any outstanding ones. It will block |
787 | necessary) and will handle those and any already outstanding ones. It |
355 | your process until at least one new event arrives, and will return after |
788 | will block your process until at least one new event arrives (which could |
|
|
789 | be an event internal to libev itself, so there is no guarantee that a |
|
|
790 | user-registered callback will be called), and will return after one |
356 | one iteration of the loop. |
791 | iteration of the loop. |
357 | .Sp |
792 | .Sp |
358 | This flags value could be used to implement alternative looping |
793 | This is useful if you are waiting for some external event in conjunction |
359 | constructs, but the \f(CW\*(C`prepare\*(C'\fR and \f(CW\*(C`check\*(C'\fR watchers provide a better and |
794 | with something not expressible using other libev watchers (i.e. "roll your |
360 | more generic mechanism. |
795 | own \f(CW\*(C`ev_loop\*(C'\fR"). However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is |
|
|
796 | usually a better approach for this kind of thing. |
361 | .Sp |
797 | .Sp |
362 | Here are the gory details of what ev_loop does: |
798 | Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does: |
363 | .Sp |
799 | .Sp |
364 | .Vb 15 |
800 | .Vb 10 |
365 | \& 1. If there are no active watchers (reference count is zero), return. |
801 | \& \- Before the first iteration, call any pending watchers. |
|
|
802 | \& * If EVFLAG_FORKCHECK was used, check for a fork. |
|
|
803 | \& \- If a fork was detected (by any means), queue and call all fork watchers. |
366 | \& 2. Queue and immediately call all prepare watchers. |
804 | \& \- Queue and call all prepare watchers. |
367 | \& 3. If we have been forked, recreate the kernel state. |
805 | \& \- If we have been forked, detach and recreate the kernel state |
|
|
806 | \& as to not disturb the other process. |
368 | \& 4. Update the kernel state with all outstanding changes. |
807 | \& \- Update the kernel state with all outstanding changes. |
369 | \& 5. Update the "event loop time". |
808 | \& \- Update the "event loop time" (ev_now ()). |
370 | \& 6. Calculate for how long to block. |
809 | \& \- Calculate for how long to sleep or block, if at all |
|
|
810 | \& (active idle watchers, EVLOOP_NONBLOCK or not having |
|
|
811 | \& any active watchers at all will result in not sleeping). |
|
|
812 | \& \- Sleep if the I/O and timer collect interval say so. |
371 | \& 7. Block the process, waiting for events. |
813 | \& \- Block the process, waiting for any events. |
|
|
814 | \& \- Queue all outstanding I/O (fd) events. |
372 | \& 8. Update the "event loop time" and do time jump handling. |
815 | \& \- Update the "event loop time" (ev_now ()), and do time jump adjustments. |
373 | \& 9. Queue all outstanding timers. |
816 | \& \- Queue all expired timers. |
374 | \& 10. Queue all outstanding periodics. |
817 | \& \- Queue all expired periodics. |
375 | \& 11. If no events are pending now, queue all idle watchers. |
818 | \& \- Unless any events are pending now, queue all idle watchers. |
376 | \& 12. Queue all check watchers. |
819 | \& \- Queue all check watchers. |
377 | \& 13. Call all queued watchers in reverse order (i.e. check watchers first). |
820 | \& \- Call all queued watchers in reverse order (i.e. check watchers first). |
|
|
821 | \& Signals and child watchers are implemented as I/O watchers, and will |
|
|
822 | \& be handled here by queueing them when their watcher gets executed. |
378 | \& 14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
823 | \& \- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
379 | \& was used, return, otherwise continue with step #1. |
824 | \& were used, or there are no active watchers, return, otherwise |
|
|
825 | \& continue with step *. |
|
|
826 | .Ve |
|
|
827 | .Sp |
|
|
828 | Example: Queue some jobs and then loop until no events are outstanding |
|
|
829 | anymore. |
|
|
830 | .Sp |
|
|
831 | .Vb 4 |
|
|
832 | \& ... queue jobs here, make sure they register event watchers as long |
|
|
833 | \& ... as they still have work to do (even an idle watcher will do..) |
|
|
834 | \& ev_loop (my_loop, 0); |
|
|
835 | \& ... jobs done or somebody called unloop. yeah! |
380 | .Ve |
836 | .Ve |
381 | .IP "ev_unloop (loop, how)" 4 |
837 | .IP "ev_unloop (loop, how)" 4 |
382 | .IX Item "ev_unloop (loop, how)" |
838 | .IX Item "ev_unloop (loop, how)" |
383 | Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it |
839 | Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it |
384 | has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either |
840 | has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either |
385 | \&\f(CW\*(C`EVUNLOOP_ONE\*(C'\fR, which will make the innermost \f(CW\*(C`ev_loop\*(C'\fR call return, or |
841 | \&\f(CW\*(C`EVUNLOOP_ONE\*(C'\fR, which will make the innermost \f(CW\*(C`ev_loop\*(C'\fR call return, or |
386 | \&\f(CW\*(C`EVUNLOOP_ALL\*(C'\fR, which will make all nested \f(CW\*(C`ev_loop\*(C'\fR calls return. |
842 | \&\f(CW\*(C`EVUNLOOP_ALL\*(C'\fR, which will make all nested \f(CW\*(C`ev_loop\*(C'\fR calls return. |
|
|
843 | .Sp |
|
|
844 | This \*(L"unloop state\*(R" will be cleared when entering \f(CW\*(C`ev_loop\*(C'\fR again. |
|
|
845 | .Sp |
|
|
846 | It is safe to call \f(CW\*(C`ev_unloop\*(C'\fR from otuside any \f(CW\*(C`ev_loop\*(C'\fR calls. |
387 | .IP "ev_ref (loop)" 4 |
847 | .IP "ev_ref (loop)" 4 |
388 | .IX Item "ev_ref (loop)" |
848 | .IX Item "ev_ref (loop)" |
389 | .PD 0 |
849 | .PD 0 |
390 | .IP "ev_unref (loop)" 4 |
850 | .IP "ev_unref (loop)" 4 |
391 | .IX Item "ev_unref (loop)" |
851 | .IX Item "ev_unref (loop)" |
392 | .PD |
852 | .PD |
393 | Ref/unref can be used to add or remove a reference count on the event |
853 | Ref/unref can be used to add or remove a reference count on the event |
394 | loop: Every watcher keeps one reference, and as long as the reference |
854 | loop: Every watcher keeps one reference, and as long as the reference |
395 | count is nonzero, \f(CW\*(C`ev_loop\*(C'\fR will not return on its own. If you have |
855 | count is nonzero, \f(CW\*(C`ev_loop\*(C'\fR will not return on its own. |
|
|
856 | .Sp |
396 | a watcher you never unregister that should not keep \f(CW\*(C`ev_loop\*(C'\fR from |
857 | If you have a watcher you never unregister that should not keep \f(CW\*(C`ev_loop\*(C'\fR |
397 | returning, \fIev_unref()\fR after starting, and \fIev_ref()\fR before stopping it. For |
858 | from returning, call \fIev_unref()\fR after starting, and \fIev_ref()\fR before |
|
|
859 | stopping it. |
|
|
860 | .Sp |
398 | example, libev itself uses this for its internal signal pipe: It is not |
861 | As an example, libev itself uses this for its internal signal pipe: It is |
399 | visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if |
862 | not visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting |
400 | no event watchers registered by it are active. It is also an excellent |
863 | if no event watchers registered by it are active. It is also an excellent |
401 | way to do this for generic recurring timers or from within third-party |
864 | way to do this for generic recurring timers or from within third-party |
402 | libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR. |
865 | libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR |
|
|
866 | (but only if the watcher wasn't active before, or was active before, |
|
|
867 | respectively). |
|
|
868 | .Sp |
|
|
869 | Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR |
|
|
870 | running when nothing else is active. |
|
|
871 | .Sp |
|
|
872 | .Vb 4 |
|
|
873 | \& ev_signal exitsig; |
|
|
874 | \& ev_signal_init (&exitsig, sig_cb, SIGINT); |
|
|
875 | \& ev_signal_start (loop, &exitsig); |
|
|
876 | \& evf_unref (loop); |
|
|
877 | .Ve |
|
|
878 | .Sp |
|
|
879 | Example: For some weird reason, unregister the above signal handler again. |
|
|
880 | .Sp |
|
|
881 | .Vb 2 |
|
|
882 | \& ev_ref (loop); |
|
|
883 | \& ev_signal_stop (loop, &exitsig); |
|
|
884 | .Ve |
|
|
885 | .IP "ev_set_io_collect_interval (loop, ev_tstamp interval)" 4 |
|
|
886 | .IX Item "ev_set_io_collect_interval (loop, ev_tstamp interval)" |
|
|
887 | .PD 0 |
|
|
888 | .IP "ev_set_timeout_collect_interval (loop, ev_tstamp interval)" 4 |
|
|
889 | .IX Item "ev_set_timeout_collect_interval (loop, ev_tstamp interval)" |
|
|
890 | .PD |
|
|
891 | These advanced functions influence the time that libev will spend waiting |
|
|
892 | for events. Both time intervals are by default \f(CW0\fR, meaning that libev |
|
|
893 | will try to invoke timer/periodic callbacks and I/O callbacks with minimum |
|
|
894 | latency. |
|
|
895 | .Sp |
|
|
896 | Setting these to a higher value (the \f(CW\*(C`interval\*(C'\fR \fImust\fR be >= \f(CW0\fR) |
|
|
897 | allows libev to delay invocation of I/O and timer/periodic callbacks |
|
|
898 | to increase efficiency of loop iterations (or to increase power-saving |
|
|
899 | opportunities). |
|
|
900 | .Sp |
|
|
901 | The idea is that sometimes your program runs just fast enough to handle |
|
|
902 | one (or very few) event(s) per loop iteration. While this makes the |
|
|
903 | program responsive, it also wastes a lot of \s-1CPU\s0 time to poll for new |
|
|
904 | events, especially with backends like \f(CW\*(C`select ()\*(C'\fR which have a high |
|
|
905 | overhead for the actual polling but can deliver many events at once. |
|
|
906 | .Sp |
|
|
907 | By setting a higher \fIio collect interval\fR you allow libev to spend more |
|
|
908 | time collecting I/O events, so you can handle more events per iteration, |
|
|
909 | at the cost of increasing latency. Timeouts (both \f(CW\*(C`ev_periodic\*(C'\fR and |
|
|
910 | \&\f(CW\*(C`ev_timer\*(C'\fR) will be not affected. Setting this to a non-null value will |
|
|
911 | introduce an additional \f(CW\*(C`ev_sleep ()\*(C'\fR call into most loop iterations. |
|
|
912 | .Sp |
|
|
913 | Likewise, by setting a higher \fItimeout collect interval\fR you allow libev |
|
|
914 | to spend more time collecting timeouts, at the expense of increased |
|
|
915 | latency/jitter/inexactness (the watcher callback will be called |
|
|
916 | later). \f(CW\*(C`ev_io\*(C'\fR watchers will not be affected. Setting this to a non-null |
|
|
917 | value will not introduce any overhead in libev. |
|
|
918 | .Sp |
|
|
919 | Many (busy) programs can usually benefit by setting the I/O collect |
|
|
920 | interval to a value near \f(CW0.1\fR or so, which is often enough for |
|
|
921 | interactive servers (of course not for games), likewise for timeouts. It |
|
|
922 | usually doesn't make much sense to set it to a lower value than \f(CW0.01\fR, |
|
|
923 | as this approaches the timing granularity of most systems. |
|
|
924 | .Sp |
|
|
925 | Setting the \fItimeout collect interval\fR can improve the opportunity for |
|
|
926 | saving power, as the program will \*(L"bundle\*(R" timer callback invocations that |
|
|
927 | are \*(L"near\*(R" in time together, by delaying some, thus reducing the number of |
|
|
928 | times the process sleeps and wakes up again. Another useful technique to |
|
|
929 | reduce iterations/wake\-ups is to use \f(CW\*(C`ev_periodic\*(C'\fR watchers and make sure |
|
|
930 | they fire on, say, one-second boundaries only. |
|
|
931 | .IP "ev_loop_verify (loop)" 4 |
|
|
932 | .IX Item "ev_loop_verify (loop)" |
|
|
933 | This function only does something when \f(CW\*(C`EV_VERIFY\*(C'\fR support has been |
|
|
934 | compiled in, which is the default for non-minimal builds. It tries to go |
|
|
935 | through all internal structures and checks them for validity. If anything |
|
|
936 | is found to be inconsistent, it will print an error message to standard |
|
|
937 | error and call \f(CW\*(C`abort ()\*(C'\fR. |
|
|
938 | .Sp |
|
|
939 | This can be used to catch bugs inside libev itself: under normal |
|
|
940 | circumstances, this function will never abort as of course libev keeps its |
|
|
941 | data structures consistent. |
403 | .SH "ANATOMY OF A WATCHER" |
942 | .SH "ANATOMY OF A WATCHER" |
404 | .IX Header "ANATOMY OF A WATCHER" |
943 | .IX Header "ANATOMY OF A WATCHER" |
|
|
944 | In the following description, uppercase \f(CW\*(C`TYPE\*(C'\fR in names stands for the |
|
|
945 | watcher type, e.g. \f(CW\*(C`ev_TYPE_start\*(C'\fR can mean \f(CW\*(C`ev_timer_start\*(C'\fR for timer |
|
|
946 | watchers and \f(CW\*(C`ev_io_start\*(C'\fR for I/O watchers. |
|
|
947 | .PP |
405 | A watcher is a structure that you create and register to record your |
948 | A watcher is a structure that you create and register to record your |
406 | interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to |
949 | interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to |
407 | become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that: |
950 | become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that: |
408 | .PP |
951 | .PP |
409 | .Vb 5 |
952 | .Vb 5 |
410 | \& static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
953 | \& static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
411 | \& { |
954 | \& { |
412 | \& ev_io_stop (w); |
955 | \& ev_io_stop (w); |
413 | \& ev_unloop (loop, EVUNLOOP_ALL); |
956 | \& ev_unloop (loop, EVUNLOOP_ALL); |
414 | \& } |
957 | \& } |
415 | .Ve |
958 | \& |
416 | .PP |
|
|
417 | .Vb 6 |
|
|
418 | \& struct ev_loop *loop = ev_default_loop (0); |
959 | \& struct ev_loop *loop = ev_default_loop (0); |
|
|
960 | \& |
419 | \& struct ev_io stdin_watcher; |
961 | \& ev_io stdin_watcher; |
|
|
962 | \& |
420 | \& ev_init (&stdin_watcher, my_cb); |
963 | \& ev_init (&stdin_watcher, my_cb); |
421 | \& ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
964 | \& ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
422 | \& ev_io_start (loop, &stdin_watcher); |
965 | \& ev_io_start (loop, &stdin_watcher); |
|
|
966 | \& |
423 | \& ev_loop (loop, 0); |
967 | \& ev_loop (loop, 0); |
424 | .Ve |
968 | .Ve |
425 | .PP |
969 | .PP |
426 | As you can see, you are responsible for allocating the memory for your |
970 | As you can see, you are responsible for allocating the memory for your |
427 | watcher structures (and it is usually a bad idea to do this on the stack, |
971 | watcher structures (and it is \fIusually\fR a bad idea to do this on the |
428 | although this can sometimes be quite valid). |
972 | stack). |
|
|
973 | .PP |
|
|
974 | Each watcher has an associated watcher structure (called \f(CW\*(C`struct ev_TYPE\*(C'\fR |
|
|
975 | or simply \f(CW\*(C`ev_TYPE\*(C'\fR, as typedefs are provided for all watcher structs). |
429 | .PP |
976 | .PP |
430 | Each watcher structure must be initialised by a call to \f(CW\*(C`ev_init |
977 | Each watcher structure must be initialised by a call to \f(CW\*(C`ev_init |
431 | (watcher *, callback)\*(C'\fR, which expects a callback to be provided. This |
978 | (watcher *, callback)\*(C'\fR, which expects a callback to be provided. This |
432 | callback gets invoked each time the event occurs (or, in the case of io |
979 | callback gets invoked each time the event occurs (or, in the case of I/O |
433 | watchers, each time the event loop detects that the file descriptor given |
980 | watchers, each time the event loop detects that the file descriptor given |
434 | is readable and/or writable). |
981 | is readable and/or writable). |
435 | .PP |
982 | .PP |
436 | Each watcher type has its own \f(CW\*(C`ev_<type>_set (watcher *, ...)\*(C'\fR macro |
983 | Each watcher type further has its own \f(CW\*(C`ev_TYPE_set (watcher *, ...)\*(C'\fR |
437 | with arguments specific to this watcher type. There is also a macro |
984 | macro to configure it, with arguments specific to the watcher type. There |
438 | to combine initialisation and setting in one call: \f(CW\*(C`ev_<type>_init |
985 | is also a macro to combine initialisation and setting in one call: \f(CW\*(C`ev_TYPE_init (watcher *, callback, ...)\*(C'\fR. |
439 | (watcher *, callback, ...)\*(C'\fR. |
|
|
440 | .PP |
986 | .PP |
441 | To make the watcher actually watch out for events, you have to start it |
987 | To make the watcher actually watch out for events, you have to start it |
442 | with a watcher-specific start function (\f(CW\*(C`ev_<type>_start (loop, watcher |
988 | with a watcher-specific start function (\f(CW\*(C`ev_TYPE_start (loop, watcher |
443 | *)\*(C'\fR), and you can stop watching for events at any time by calling the |
989 | *)\*(C'\fR), and you can stop watching for events at any time by calling the |
444 | corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR. |
990 | corresponding stop function (\f(CW\*(C`ev_TYPE_stop (loop, watcher *)\*(C'\fR. |
445 | .PP |
991 | .PP |
446 | As long as your watcher is active (has been started but not stopped) you |
992 | As long as your watcher is active (has been started but not stopped) you |
447 | must not touch the values stored in it. Most specifically you must never |
993 | must not touch the values stored in it. Most specifically you must never |
448 | reinitialise it or call its set method. |
994 | reinitialise it or call its \f(CW\*(C`ev_TYPE_set\*(C'\fR macro. |
449 | .PP |
|
|
450 | You can check whether an event is active by calling the \f(CW\*(C`ev_is_active |
|
|
451 | (watcher *)\*(C'\fR macro. To see whether an event is outstanding (but the |
|
|
452 | callback for it has not been called yet) you can use the \f(CW\*(C`ev_is_pending |
|
|
453 | (watcher *)\*(C'\fR macro. |
|
|
454 | .PP |
995 | .PP |
455 | Each and every callback receives the event loop pointer as first, the |
996 | Each and every callback receives the event loop pointer as first, the |
456 | registered watcher structure as second, and a bitset of received events as |
997 | registered watcher structure as second, and a bitset of received events as |
457 | third argument. |
998 | third argument. |
458 | .PP |
999 | .PP |
… | |
… | |
483 | The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread. |
1024 | The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread. |
484 | .ie n .IP """EV_CHILD""" 4 |
1025 | .ie n .IP """EV_CHILD""" 4 |
485 | .el .IP "\f(CWEV_CHILD\fR" 4 |
1026 | .el .IP "\f(CWEV_CHILD\fR" 4 |
486 | .IX Item "EV_CHILD" |
1027 | .IX Item "EV_CHILD" |
487 | The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change. |
1028 | The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change. |
|
|
1029 | .ie n .IP """EV_STAT""" 4 |
|
|
1030 | .el .IP "\f(CWEV_STAT\fR" 4 |
|
|
1031 | .IX Item "EV_STAT" |
|
|
1032 | The path specified in the \f(CW\*(C`ev_stat\*(C'\fR watcher changed its attributes somehow. |
488 | .ie n .IP """EV_IDLE""" 4 |
1033 | .ie n .IP """EV_IDLE""" 4 |
489 | .el .IP "\f(CWEV_IDLE\fR" 4 |
1034 | .el .IP "\f(CWEV_IDLE\fR" 4 |
490 | .IX Item "EV_IDLE" |
1035 | .IX Item "EV_IDLE" |
491 | The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do. |
1036 | The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do. |
492 | .ie n .IP """EV_PREPARE""" 4 |
1037 | .ie n .IP """EV_PREPARE""" 4 |
… | |
… | |
502 | \&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any |
1047 | \&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any |
503 | received events. Callbacks of both watcher types can start and stop as |
1048 | received events. Callbacks of both watcher types can start and stop as |
504 | many watchers as they want, and all of them will be taken into account |
1049 | many watchers as they want, and all of them will be taken into account |
505 | (for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep |
1050 | (for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep |
506 | \&\f(CW\*(C`ev_loop\*(C'\fR from blocking). |
1051 | \&\f(CW\*(C`ev_loop\*(C'\fR from blocking). |
|
|
1052 | .ie n .IP """EV_EMBED""" 4 |
|
|
1053 | .el .IP "\f(CWEV_EMBED\fR" 4 |
|
|
1054 | .IX Item "EV_EMBED" |
|
|
1055 | The embedded event loop specified in the \f(CW\*(C`ev_embed\*(C'\fR watcher needs attention. |
|
|
1056 | .ie n .IP """EV_FORK""" 4 |
|
|
1057 | .el .IP "\f(CWEV_FORK\fR" 4 |
|
|
1058 | .IX Item "EV_FORK" |
|
|
1059 | The event loop has been resumed in the child process after fork (see |
|
|
1060 | \&\f(CW\*(C`ev_fork\*(C'\fR). |
|
|
1061 | .ie n .IP """EV_ASYNC""" 4 |
|
|
1062 | .el .IP "\f(CWEV_ASYNC\fR" 4 |
|
|
1063 | .IX Item "EV_ASYNC" |
|
|
1064 | The given async watcher has been asynchronously notified (see \f(CW\*(C`ev_async\*(C'\fR). |
507 | .ie n .IP """EV_ERROR""" 4 |
1065 | .ie n .IP """EV_ERROR""" 4 |
508 | .el .IP "\f(CWEV_ERROR\fR" 4 |
1066 | .el .IP "\f(CWEV_ERROR\fR" 4 |
509 | .IX Item "EV_ERROR" |
1067 | .IX Item "EV_ERROR" |
510 | An unspecified error has occured, the watcher has been stopped. This might |
1068 | An unspecified error has occurred, the watcher has been stopped. This might |
511 | happen because the watcher could not be properly started because libev |
1069 | happen because the watcher could not be properly started because libev |
512 | ran out of memory, a file descriptor was found to be closed or any other |
1070 | ran out of memory, a file descriptor was found to be closed or any other |
|
|
1071 | problem. Libev considers these application bugs. |
|
|
1072 | .Sp |
513 | problem. You best act on it by reporting the problem and somehow coping |
1073 | You best act on it by reporting the problem and somehow coping with the |
514 | with the watcher being stopped. |
1074 | watcher being stopped. Note that well-written programs should not receive |
|
|
1075 | an error ever, so when your watcher receives it, this usually indicates a |
|
|
1076 | bug in your program. |
515 | .Sp |
1077 | .Sp |
516 | Libev will usually signal a few \*(L"dummy\*(R" events together with an error, |
1078 | Libev will usually signal a few \*(L"dummy\*(R" events together with an error, for |
517 | for example it might indicate that a fd is readable or writable, and if |
1079 | example it might indicate that a fd is readable or writable, and if your |
518 | your callbacks is well-written it can just attempt the operation and cope |
1080 | callbacks is well-written it can just attempt the operation and cope with |
519 | with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded |
1081 | the error from \fIread()\fR or \fIwrite()\fR. This will not work in multi-threaded |
520 | programs, though, so beware. |
1082 | programs, though, as the fd could already be closed and reused for another |
|
|
1083 | thing, so beware. |
|
|
1084 | .Sh "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0" |
|
|
1085 | .IX Subsection "GENERIC WATCHER FUNCTIONS" |
|
|
1086 | .ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4 |
|
|
1087 | .el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4 |
|
|
1088 | .IX Item "ev_init (ev_TYPE *watcher, callback)" |
|
|
1089 | This macro initialises the generic portion of a watcher. The contents |
|
|
1090 | of the watcher object can be arbitrary (so \f(CW\*(C`malloc\*(C'\fR will do). Only |
|
|
1091 | the generic parts of the watcher are initialised, you \fIneed\fR to call |
|
|
1092 | the type-specific \f(CW\*(C`ev_TYPE_set\*(C'\fR macro afterwards to initialise the |
|
|
1093 | type-specific parts. For each type there is also a \f(CW\*(C`ev_TYPE_init\*(C'\fR macro |
|
|
1094 | which rolls both calls into one. |
|
|
1095 | .Sp |
|
|
1096 | You can reinitialise a watcher at any time as long as it has been stopped |
|
|
1097 | (or never started) and there are no pending events outstanding. |
|
|
1098 | .Sp |
|
|
1099 | The callback is always of type \f(CW\*(C`void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
|
|
1100 | int revents)\*(C'\fR. |
|
|
1101 | .Sp |
|
|
1102 | Example: Initialise an \f(CW\*(C`ev_io\*(C'\fR watcher in two steps. |
|
|
1103 | .Sp |
|
|
1104 | .Vb 3 |
|
|
1105 | \& ev_io w; |
|
|
1106 | \& ev_init (&w, my_cb); |
|
|
1107 | \& ev_io_set (&w, STDIN_FILENO, EV_READ); |
|
|
1108 | .Ve |
|
|
1109 | .ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4 |
|
|
1110 | .el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4 |
|
|
1111 | .IX Item "ev_TYPE_set (ev_TYPE *, [args])" |
|
|
1112 | This macro initialises the type-specific parts of a watcher. You need to |
|
|
1113 | call \f(CW\*(C`ev_init\*(C'\fR at least once before you call this macro, but you can |
|
|
1114 | call \f(CW\*(C`ev_TYPE_set\*(C'\fR any number of times. You must not, however, call this |
|
|
1115 | macro on a watcher that is active (it can be pending, however, which is a |
|
|
1116 | difference to the \f(CW\*(C`ev_init\*(C'\fR macro). |
|
|
1117 | .Sp |
|
|
1118 | Although some watcher types do not have type-specific arguments |
|
|
1119 | (e.g. \f(CW\*(C`ev_prepare\*(C'\fR) you still need to call its \f(CW\*(C`set\*(C'\fR macro. |
|
|
1120 | .Sp |
|
|
1121 | See \f(CW\*(C`ev_init\*(C'\fR, above, for an example. |
|
|
1122 | .ie n .IP """ev_TYPE_init"" (ev_TYPE *watcher, callback, [args])" 4 |
|
|
1123 | .el .IP "\f(CWev_TYPE_init\fR (ev_TYPE *watcher, callback, [args])" 4 |
|
|
1124 | .IX Item "ev_TYPE_init (ev_TYPE *watcher, callback, [args])" |
|
|
1125 | This convenience macro rolls both \f(CW\*(C`ev_init\*(C'\fR and \f(CW\*(C`ev_TYPE_set\*(C'\fR macro |
|
|
1126 | calls into a single call. This is the most convenient method to initialise |
|
|
1127 | a watcher. The same limitations apply, of course. |
|
|
1128 | .Sp |
|
|
1129 | Example: Initialise and set an \f(CW\*(C`ev_io\*(C'\fR watcher in one step. |
|
|
1130 | .Sp |
|
|
1131 | .Vb 1 |
|
|
1132 | \& ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
|
|
1133 | .Ve |
|
|
1134 | .ie n .IP """ev_TYPE_start"" (loop *, ev_TYPE *watcher)" 4 |
|
|
1135 | .el .IP "\f(CWev_TYPE_start\fR (loop *, ev_TYPE *watcher)" 4 |
|
|
1136 | .IX Item "ev_TYPE_start (loop *, ev_TYPE *watcher)" |
|
|
1137 | Starts (activates) the given watcher. Only active watchers will receive |
|
|
1138 | events. If the watcher is already active nothing will happen. |
|
|
1139 | .Sp |
|
|
1140 | Example: Start the \f(CW\*(C`ev_io\*(C'\fR watcher that is being abused as example in this |
|
|
1141 | whole section. |
|
|
1142 | .Sp |
|
|
1143 | .Vb 1 |
|
|
1144 | \& ev_io_start (EV_DEFAULT_UC, &w); |
|
|
1145 | .Ve |
|
|
1146 | .ie n .IP """ev_TYPE_stop"" (loop *, ev_TYPE *watcher)" 4 |
|
|
1147 | .el .IP "\f(CWev_TYPE_stop\fR (loop *, ev_TYPE *watcher)" 4 |
|
|
1148 | .IX Item "ev_TYPE_stop (loop *, ev_TYPE *watcher)" |
|
|
1149 | Stops the given watcher if active, and clears the pending status (whether |
|
|
1150 | the watcher was active or not). |
|
|
1151 | .Sp |
|
|
1152 | It is possible that stopped watchers are pending \- for example, |
|
|
1153 | non-repeating timers are being stopped when they become pending \- but |
|
|
1154 | calling \f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor |
|
|
1155 | pending. If you want to free or reuse the memory used by the watcher it is |
|
|
1156 | therefore a good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function. |
|
|
1157 | .IP "bool ev_is_active (ev_TYPE *watcher)" 4 |
|
|
1158 | .IX Item "bool ev_is_active (ev_TYPE *watcher)" |
|
|
1159 | Returns a true value iff the watcher is active (i.e. it has been started |
|
|
1160 | and not yet been stopped). As long as a watcher is active you must not modify |
|
|
1161 | it. |
|
|
1162 | .IP "bool ev_is_pending (ev_TYPE *watcher)" 4 |
|
|
1163 | .IX Item "bool ev_is_pending (ev_TYPE *watcher)" |
|
|
1164 | Returns a true value iff the watcher is pending, (i.e. it has outstanding |
|
|
1165 | events but its callback has not yet been invoked). As long as a watcher |
|
|
1166 | is pending (but not active) you must not call an init function on it (but |
|
|
1167 | \&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe), you must not change its priority, and you must |
|
|
1168 | make sure the watcher is available to libev (e.g. you cannot \f(CW\*(C`free ()\*(C'\fR |
|
|
1169 | it). |
|
|
1170 | .IP "callback ev_cb (ev_TYPE *watcher)" 4 |
|
|
1171 | .IX Item "callback ev_cb (ev_TYPE *watcher)" |
|
|
1172 | Returns the callback currently set on the watcher. |
|
|
1173 | .IP "ev_cb_set (ev_TYPE *watcher, callback)" 4 |
|
|
1174 | .IX Item "ev_cb_set (ev_TYPE *watcher, callback)" |
|
|
1175 | Change the callback. You can change the callback at virtually any time |
|
|
1176 | (modulo threads). |
|
|
1177 | .IP "ev_set_priority (ev_TYPE *watcher, priority)" 4 |
|
|
1178 | .IX Item "ev_set_priority (ev_TYPE *watcher, priority)" |
|
|
1179 | .PD 0 |
|
|
1180 | .IP "int ev_priority (ev_TYPE *watcher)" 4 |
|
|
1181 | .IX Item "int ev_priority (ev_TYPE *watcher)" |
|
|
1182 | .PD |
|
|
1183 | Set and query the priority of the watcher. The priority is a small |
|
|
1184 | integer between \f(CW\*(C`EV_MAXPRI\*(C'\fR (default: \f(CW2\fR) and \f(CW\*(C`EV_MINPRI\*(C'\fR |
|
|
1185 | (default: \f(CW\*(C`\-2\*(C'\fR). Pending watchers with higher priority will be invoked |
|
|
1186 | before watchers with lower priority, but priority will not keep watchers |
|
|
1187 | from being executed (except for \f(CW\*(C`ev_idle\*(C'\fR watchers). |
|
|
1188 | .Sp |
|
|
1189 | This means that priorities are \fIonly\fR used for ordering callback |
|
|
1190 | invocation after new events have been received. This is useful, for |
|
|
1191 | example, to reduce latency after idling, or more often, to bind two |
|
|
1192 | watchers on the same event and make sure one is called first. |
|
|
1193 | .Sp |
|
|
1194 | If you need to suppress invocation when higher priority events are pending |
|
|
1195 | you need to look at \f(CW\*(C`ev_idle\*(C'\fR watchers, which provide this functionality. |
|
|
1196 | .Sp |
|
|
1197 | You \fImust not\fR change the priority of a watcher as long as it is active or |
|
|
1198 | pending. |
|
|
1199 | .Sp |
|
|
1200 | The default priority used by watchers when no priority has been set is |
|
|
1201 | always \f(CW0\fR, which is supposed to not be too high and not be too low :). |
|
|
1202 | .Sp |
|
|
1203 | Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR is |
|
|
1204 | fine, as long as you do not mind that the priority value you query might |
|
|
1205 | or might not have been clamped to the valid range. |
|
|
1206 | .IP "ev_invoke (loop, ev_TYPE *watcher, int revents)" 4 |
|
|
1207 | .IX Item "ev_invoke (loop, ev_TYPE *watcher, int revents)" |
|
|
1208 | 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 |
|
|
1209 | \&\f(CW\*(C`loop\*(C'\fR nor \f(CW\*(C`revents\*(C'\fR need to be valid as long as the watcher callback |
|
|
1210 | can deal with that fact, as both are simply passed through to the |
|
|
1211 | callback. |
|
|
1212 | .IP "int ev_clear_pending (loop, ev_TYPE *watcher)" 4 |
|
|
1213 | .IX Item "int ev_clear_pending (loop, ev_TYPE *watcher)" |
|
|
1214 | If the watcher is pending, this function clears its pending status and |
|
|
1215 | returns its \f(CW\*(C`revents\*(C'\fR bitset (as if its callback was invoked). If the |
|
|
1216 | watcher isn't pending it does nothing and returns \f(CW0\fR. |
|
|
1217 | .Sp |
|
|
1218 | Sometimes it can be useful to \*(L"poll\*(R" a watcher instead of waiting for its |
|
|
1219 | callback to be invoked, which can be accomplished with this function. |
521 | .Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0" |
1220 | .Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0" |
522 | .IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER" |
1221 | .IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER" |
523 | Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change |
1222 | Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change |
524 | and read at any time, libev will completely ignore it. This can be used |
1223 | and read at any time: libev will completely ignore it. This can be used |
525 | to associate arbitrary data with your watcher. If you need more data and |
1224 | to associate arbitrary data with your watcher. If you need more data and |
526 | don't want to allocate memory and store a pointer to it in that data |
1225 | don't want to allocate memory and store a pointer to it in that data |
527 | member, you can also \*(L"subclass\*(R" the watcher type and provide your own |
1226 | member, you can also \*(L"subclass\*(R" the watcher type and provide your own |
528 | data: |
1227 | data: |
529 | .PP |
1228 | .PP |
530 | .Vb 7 |
1229 | .Vb 7 |
531 | \& struct my_io |
1230 | \& struct my_io |
532 | \& { |
1231 | \& { |
533 | \& struct ev_io io; |
1232 | \& ev_io io; |
534 | \& int otherfd; |
1233 | \& int otherfd; |
535 | \& void *somedata; |
1234 | \& void *somedata; |
536 | \& struct whatever *mostinteresting; |
1235 | \& struct whatever *mostinteresting; |
537 | \& } |
1236 | \& }; |
|
|
1237 | \& |
|
|
1238 | \& ... |
|
|
1239 | \& struct my_io w; |
|
|
1240 | \& ev_io_init (&w.io, my_cb, fd, EV_READ); |
538 | .Ve |
1241 | .Ve |
539 | .PP |
1242 | .PP |
540 | And since your callback will be called with a pointer to the watcher, you |
1243 | And since your callback will be called with a pointer to the watcher, you |
541 | can cast it back to your own type: |
1244 | can cast it back to your own type: |
542 | .PP |
1245 | .PP |
543 | .Vb 5 |
1246 | .Vb 5 |
544 | \& static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) |
1247 | \& static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
545 | \& { |
1248 | \& { |
546 | \& struct my_io *w = (struct my_io *)w_; |
1249 | \& struct my_io *w = (struct my_io *)w_; |
547 | \& ... |
1250 | \& ... |
548 | \& } |
1251 | \& } |
549 | .Ve |
1252 | .Ve |
550 | .PP |
1253 | .PP |
551 | More interesting and less C\-conformant ways of catsing your callback type |
1254 | More interesting and less C\-conformant ways of casting your callback type |
552 | have been omitted.... |
1255 | instead have been omitted. |
|
|
1256 | .PP |
|
|
1257 | Another common scenario is to use some data structure with multiple |
|
|
1258 | embedded watchers: |
|
|
1259 | .PP |
|
|
1260 | .Vb 6 |
|
|
1261 | \& struct my_biggy |
|
|
1262 | \& { |
|
|
1263 | \& int some_data; |
|
|
1264 | \& ev_timer t1; |
|
|
1265 | \& ev_timer t2; |
|
|
1266 | \& } |
|
|
1267 | .Ve |
|
|
1268 | .PP |
|
|
1269 | In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more |
|
|
1270 | complicated: Either you store the address of your \f(CW\*(C`my_biggy\*(C'\fR struct |
|
|
1271 | in the \f(CW\*(C`data\*(C'\fR member of the watcher (for woozies), or you need to use |
|
|
1272 | some pointer arithmetic using \f(CW\*(C`offsetof\*(C'\fR inside your watchers (for real |
|
|
1273 | programmers): |
|
|
1274 | .PP |
|
|
1275 | .Vb 1 |
|
|
1276 | \& #include <stddef.h> |
|
|
1277 | \& |
|
|
1278 | \& static void |
|
|
1279 | \& t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
1280 | \& { |
|
|
1281 | \& struct my_biggy big = (struct my_biggy * |
|
|
1282 | \& (((char *)w) \- offsetof (struct my_biggy, t1)); |
|
|
1283 | \& } |
|
|
1284 | \& |
|
|
1285 | \& static void |
|
|
1286 | \& t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
1287 | \& { |
|
|
1288 | \& struct my_biggy big = (struct my_biggy * |
|
|
1289 | \& (((char *)w) \- offsetof (struct my_biggy, t2)); |
|
|
1290 | \& } |
|
|
1291 | .Ve |
553 | .SH "WATCHER TYPES" |
1292 | .SH "WATCHER TYPES" |
554 | .IX Header "WATCHER TYPES" |
1293 | .IX Header "WATCHER TYPES" |
555 | This section describes each watcher in detail, but will not repeat |
1294 | This section describes each watcher in detail, but will not repeat |
556 | information given in the last section. |
1295 | information given in the last section. Any initialisation/set macros, |
|
|
1296 | functions and members specific to the watcher type are explained. |
|
|
1297 | .PP |
|
|
1298 | Members are additionally marked with either \fI[read\-only]\fR, meaning that, |
|
|
1299 | while the watcher is active, you can look at the member and expect some |
|
|
1300 | sensible content, but you must not modify it (you can modify it while the |
|
|
1301 | watcher is stopped to your hearts content), or \fI[read\-write]\fR, which |
|
|
1302 | means you can expect it to have some sensible content while the watcher |
|
|
1303 | is active, but you can also modify it. Modifying it may not do something |
|
|
1304 | sensible or take immediate effect (or do anything at all), but libev will |
|
|
1305 | not crash or malfunction in any way. |
557 | .ie n .Sh """ev_io"" \- is this file descriptor readable or writable" |
1306 | .ie n .Sh """ev_io"" \- is this file descriptor readable or writable?" |
558 | .el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable" |
1307 | .el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable?" |
559 | .IX Subsection "ev_io - is this file descriptor readable or writable" |
1308 | .IX Subsection "ev_io - is this file descriptor readable or writable?" |
560 | I/O watchers check whether a file descriptor is readable or writable |
1309 | I/O watchers check whether a file descriptor is readable or writable |
561 | in each iteration of the event loop (This behaviour is called |
1310 | in each iteration of the event loop, or, more precisely, when reading |
562 | level-triggering because you keep receiving events as long as the |
1311 | would not block the process and writing would at least be able to write |
563 | condition persists. Remember you can stop the watcher if you don't want to |
1312 | some data. This behaviour is called level-triggering because you keep |
564 | act on the event and neither want to receive future events). |
1313 | receiving events as long as the condition persists. Remember you can stop |
|
|
1314 | the watcher if you don't want to act on the event and neither want to |
|
|
1315 | receive future events. |
565 | .PP |
1316 | .PP |
566 | In general you can register as many read and/or write event watchers per |
1317 | In general you can register as many read and/or write event watchers per |
567 | fd as you want (as long as you don't confuse yourself). Setting all file |
1318 | fd as you want (as long as you don't confuse yourself). Setting all file |
568 | descriptors to non-blocking mode is also usually a good idea (but not |
1319 | descriptors to non-blocking mode is also usually a good idea (but not |
569 | required if you know what you are doing). |
1320 | required if you know what you are doing). |
570 | .PP |
1321 | .PP |
571 | You have to be careful with dup'ed file descriptors, though. Some backends |
1322 | If you cannot use non-blocking mode, then force the use of a |
572 | (the linux epoll backend is a notable example) cannot handle dup'ed file |
1323 | known-to-be-good backend (at the time of this writing, this includes only |
573 | descriptors correctly if you register interest in two or more fds pointing |
1324 | \&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and \f(CW\*(C`EVBACKEND_POLL\*(C'\fR). |
574 | to the same underlying file/socket etc. description (that is, they share |
|
|
575 | the same underlying \*(L"file open\*(R"). |
|
|
576 | .PP |
1325 | .PP |
577 | If you must do this, then force the use of a known-to-be-good backend |
1326 | Another thing you have to watch out for is that it is quite easy to |
578 | (at the time of this writing, this includes only \s-1EVMETHOD_SELECT\s0 and |
1327 | receive \*(L"spurious\*(R" readiness notifications, that is your callback might |
579 | \&\s-1EVMETHOD_POLL\s0). |
1328 | be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block |
|
|
1329 | because there is no data. Not only are some backends known to create a |
|
|
1330 | lot of those (for example Solaris ports), it is very easy to get into |
|
|
1331 | this situation even with a relatively standard program structure. Thus |
|
|
1332 | it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning |
|
|
1333 | \&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives. |
|
|
1334 | .PP |
|
|
1335 | If you cannot run the fd in non-blocking mode (for example you should |
|
|
1336 | not play around with an Xlib connection), then you have to separately |
|
|
1337 | re-test whether a file descriptor is really ready with a known-to-be good |
|
|
1338 | interface such as poll (fortunately in our Xlib example, Xlib already |
|
|
1339 | does this on its own, so its quite safe to use). Some people additionally |
|
|
1340 | use \f(CW\*(C`SIGALRM\*(C'\fR and an interval timer, just to be sure you won't block |
|
|
1341 | indefinitely. |
|
|
1342 | .PP |
|
|
1343 | But really, best use non-blocking mode. |
|
|
1344 | .PP |
|
|
1345 | \fIThe special problem of disappearing file descriptors\fR |
|
|
1346 | .IX Subsection "The special problem of disappearing file descriptors" |
|
|
1347 | .PP |
|
|
1348 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
|
|
1349 | descriptor (either due to calling \f(CW\*(C`close\*(C'\fR explicitly or any other means, |
|
|
1350 | such as \f(CW\*(C`dup2\*(C'\fR). The reason is that you register interest in some file |
|
|
1351 | descriptor, but when it goes away, the operating system will silently drop |
|
|
1352 | this interest. If another file descriptor with the same number then is |
|
|
1353 | registered with libev, there is no efficient way to see that this is, in |
|
|
1354 | fact, a different file descriptor. |
|
|
1355 | .PP |
|
|
1356 | To avoid having to explicitly tell libev about such cases, libev follows |
|
|
1357 | the following policy: Each time \f(CW\*(C`ev_io_set\*(C'\fR is being called, libev |
|
|
1358 | will assume that this is potentially a new file descriptor, otherwise |
|
|
1359 | it is assumed that the file descriptor stays the same. That means that |
|
|
1360 | 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 |
|
|
1361 | descriptor even if the file descriptor number itself did not change. |
|
|
1362 | .PP |
|
|
1363 | This is how one would do it normally anyway, the important point is that |
|
|
1364 | the libev application should not optimise around libev but should leave |
|
|
1365 | optimisations to libev. |
|
|
1366 | .PP |
|
|
1367 | \fIThe special problem of dup'ed file descriptors\fR |
|
|
1368 | .IX Subsection "The special problem of dup'ed file descriptors" |
|
|
1369 | .PP |
|
|
1370 | Some backends (e.g. epoll), cannot register events for file descriptors, |
|
|
1371 | but only events for the underlying file descriptions. That means when you |
|
|
1372 | have \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors or weirder constellations, and register |
|
|
1373 | events for them, only one file descriptor might actually receive events. |
|
|
1374 | .PP |
|
|
1375 | There is no workaround possible except not registering events |
|
|
1376 | for potentially \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors, or to resort to |
|
|
1377 | \&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
|
|
1378 | .PP |
|
|
1379 | \fIThe special problem of fork\fR |
|
|
1380 | .IX Subsection "The special problem of fork" |
|
|
1381 | .PP |
|
|
1382 | Some backends (epoll, kqueue) do not support \f(CW\*(C`fork ()\*(C'\fR at all or exhibit |
|
|
1383 | useless behaviour. Libev fully supports fork, but needs to be told about |
|
|
1384 | it in the child. |
|
|
1385 | .PP |
|
|
1386 | To support fork in your programs, you either have to call |
|
|
1387 | \&\f(CW\*(C`ev_default_fork ()\*(C'\fR or \f(CW\*(C`ev_loop_fork ()\*(C'\fR after a fork in the child, |
|
|
1388 | enable \f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR, or resort to \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or |
|
|
1389 | \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
|
|
1390 | .PP |
|
|
1391 | \fIThe special problem of \s-1SIGPIPE\s0\fR |
|
|
1392 | .IX Subsection "The special problem of SIGPIPE" |
|
|
1393 | .PP |
|
|
1394 | While not really specific to libev, it is easy to forget about \f(CW\*(C`SIGPIPE\*(C'\fR: |
|
|
1395 | when writing to a pipe whose other end has been closed, your program gets |
|
|
1396 | sent a \s-1SIGPIPE\s0, which, by default, aborts your program. For most programs |
|
|
1397 | this is sensible behaviour, for daemons, this is usually undesirable. |
|
|
1398 | .PP |
|
|
1399 | So when you encounter spurious, unexplained daemon exits, make sure you |
|
|
1400 | ignore \s-1SIGPIPE\s0 (and maybe make sure you log the exit status of your daemon |
|
|
1401 | somewhere, as that would have given you a big clue). |
|
|
1402 | .PP |
|
|
1403 | \fIWatcher-Specific Functions\fR |
|
|
1404 | .IX Subsection "Watcher-Specific Functions" |
580 | .IP "ev_io_init (ev_io *, callback, int fd, int events)" 4 |
1405 | .IP "ev_io_init (ev_io *, callback, int fd, int events)" 4 |
581 | .IX Item "ev_io_init (ev_io *, callback, int fd, int events)" |
1406 | .IX Item "ev_io_init (ev_io *, callback, int fd, int events)" |
582 | .PD 0 |
1407 | .PD 0 |
583 | .IP "ev_io_set (ev_io *, int fd, int events)" 4 |
1408 | .IP "ev_io_set (ev_io *, int fd, int events)" 4 |
584 | .IX Item "ev_io_set (ev_io *, int fd, int events)" |
1409 | .IX Item "ev_io_set (ev_io *, int fd, int events)" |
585 | .PD |
1410 | .PD |
586 | Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The fd is the file descriptor to rceeive |
1411 | Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to |
587 | events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or \f(CW\*(C`EV_READ | |
1412 | 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 |
588 | EV_WRITE\*(C'\fR to receive the given events. |
1413 | \&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR, to express the desire to receive the given events. |
|
|
1414 | .IP "int fd [read\-only]" 4 |
|
|
1415 | .IX Item "int fd [read-only]" |
|
|
1416 | The file descriptor being watched. |
|
|
1417 | .IP "int events [read\-only]" 4 |
|
|
1418 | .IX Item "int events [read-only]" |
|
|
1419 | The events being watched. |
|
|
1420 | .PP |
|
|
1421 | \fIExamples\fR |
|
|
1422 | .IX Subsection "Examples" |
|
|
1423 | .PP |
|
|
1424 | Example: Call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well |
|
|
1425 | readable, but only once. Since it is likely line-buffered, you could |
|
|
1426 | attempt to read a whole line in the callback. |
|
|
1427 | .PP |
|
|
1428 | .Vb 6 |
|
|
1429 | \& static void |
|
|
1430 | \& stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents) |
|
|
1431 | \& { |
|
|
1432 | \& ev_io_stop (loop, w); |
|
|
1433 | \& .. read from stdin here (or from w\->fd) and handle any I/O errors |
|
|
1434 | \& } |
|
|
1435 | \& |
|
|
1436 | \& ... |
|
|
1437 | \& struct ev_loop *loop = ev_default_init (0); |
|
|
1438 | \& ev_io stdin_readable; |
|
|
1439 | \& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
|
|
1440 | \& ev_io_start (loop, &stdin_readable); |
|
|
1441 | \& ev_loop (loop, 0); |
|
|
1442 | .Ve |
589 | .ie n .Sh """ev_timer"" \- relative and optionally recurring timeouts" |
1443 | .ie n .Sh """ev_timer"" \- relative and optionally repeating timeouts" |
590 | .el .Sh "\f(CWev_timer\fP \- relative and optionally recurring timeouts" |
1444 | .el .Sh "\f(CWev_timer\fP \- relative and optionally repeating timeouts" |
591 | .IX Subsection "ev_timer - relative and optionally recurring timeouts" |
1445 | .IX Subsection "ev_timer - relative and optionally repeating timeouts" |
592 | Timer watchers are simple relative timers that generate an event after a |
1446 | Timer watchers are simple relative timers that generate an event after a |
593 | given time, and optionally repeating in regular intervals after that. |
1447 | given time, and optionally repeating in regular intervals after that. |
594 | .PP |
1448 | .PP |
595 | The timers are based on real time, that is, if you register an event that |
1449 | The timers are based on real time, that is, if you register an event that |
596 | times out after an hour and you reset your system clock to last years |
1450 | times out after an hour and you reset your system clock to January last |
597 | time, it will still time out after (roughly) and hour. \*(L"Roughly\*(R" because |
1451 | year, it will still time out after (roughly) one hour. \*(L"Roughly\*(R" because |
598 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1452 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
599 | monotonic clock option helps a lot here). |
1453 | monotonic clock option helps a lot here). |
|
|
1454 | .PP |
|
|
1455 | The callback is guaranteed to be invoked only \fIafter\fR its timeout has |
|
|
1456 | passed, but if multiple timers become ready during the same loop iteration |
|
|
1457 | then order of execution is undefined. |
|
|
1458 | .PP |
|
|
1459 | \fIBe smart about timeouts\fR |
|
|
1460 | .IX Subsection "Be smart about timeouts" |
|
|
1461 | .PP |
|
|
1462 | Many real-world problems involve some kind of timeout, usually for error |
|
|
1463 | recovery. A typical example is an \s-1HTTP\s0 request \- if the other side hangs, |
|
|
1464 | you want to raise some error after a while. |
|
|
1465 | .PP |
|
|
1466 | What follows are some ways to handle this problem, from obvious and |
|
|
1467 | inefficient to smart and efficient. |
|
|
1468 | .PP |
|
|
1469 | In the following, a 60 second activity timeout is assumed \- a timeout that |
|
|
1470 | gets reset to 60 seconds each time there is activity (e.g. each time some |
|
|
1471 | data or other life sign was received). |
|
|
1472 | .IP "1. Use a timer and stop, reinitialise and start it on activity." 4 |
|
|
1473 | .IX Item "1. Use a timer and stop, reinitialise and start it on activity." |
|
|
1474 | This is the most obvious, but not the most simple way: In the beginning, |
|
|
1475 | start the watcher: |
|
|
1476 | .Sp |
|
|
1477 | .Vb 2 |
|
|
1478 | \& ev_timer_init (timer, callback, 60., 0.); |
|
|
1479 | \& ev_timer_start (loop, timer); |
|
|
1480 | .Ve |
|
|
1481 | .Sp |
|
|
1482 | Then, each time there is some activity, \f(CW\*(C`ev_timer_stop\*(C'\fR it, initialise it |
|
|
1483 | and start it again: |
|
|
1484 | .Sp |
|
|
1485 | .Vb 3 |
|
|
1486 | \& ev_timer_stop (loop, timer); |
|
|
1487 | \& ev_timer_set (timer, 60., 0.); |
|
|
1488 | \& ev_timer_start (loop, timer); |
|
|
1489 | .Ve |
|
|
1490 | .Sp |
|
|
1491 | This is relatively simple to implement, but means that each time there is |
|
|
1492 | some activity, libev will first have to remove the timer from its internal |
|
|
1493 | data structure and then add it again. Libev tries to be fast, but it's |
|
|
1494 | still not a constant-time operation. |
|
|
1495 | .ie n .IP "2. Use a timer and re-start it with ""ev_timer_again"" inactivity." 4 |
|
|
1496 | .el .IP "2. Use a timer and re-start it with \f(CWev_timer_again\fR inactivity." 4 |
|
|
1497 | .IX Item "2. Use a timer and re-start it with ev_timer_again inactivity." |
|
|
1498 | This is the easiest way, and involves using \f(CW\*(C`ev_timer_again\*(C'\fR instead of |
|
|
1499 | \&\f(CW\*(C`ev_timer_start\*(C'\fR. |
|
|
1500 | .Sp |
|
|
1501 | To implement this, configure an \f(CW\*(C`ev_timer\*(C'\fR with a \f(CW\*(C`repeat\*(C'\fR value |
|
|
1502 | of \f(CW60\fR and then call \f(CW\*(C`ev_timer_again\*(C'\fR at start and each time you |
|
|
1503 | successfully read or write some data. If you go into an idle state where |
|
|
1504 | you do not expect data to travel on the socket, you can \f(CW\*(C`ev_timer_stop\*(C'\fR |
|
|
1505 | the timer, and \f(CW\*(C`ev_timer_again\*(C'\fR will automatically restart it if need be. |
|
|
1506 | .Sp |
|
|
1507 | That means you can ignore both the \f(CW\*(C`ev_timer_start\*(C'\fR function and the |
|
|
1508 | \&\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 |
|
|
1509 | member and \f(CW\*(C`ev_timer_again\*(C'\fR. |
|
|
1510 | .Sp |
|
|
1511 | At start: |
|
|
1512 | .Sp |
|
|
1513 | .Vb 3 |
|
|
1514 | \& ev_timer_init (timer, callback); |
|
|
1515 | \& timer\->repeat = 60.; |
|
|
1516 | \& ev_timer_again (loop, timer); |
|
|
1517 | .Ve |
|
|
1518 | .Sp |
|
|
1519 | Each time there is some activity: |
|
|
1520 | .Sp |
|
|
1521 | .Vb 1 |
|
|
1522 | \& ev_timer_again (loop, timer); |
|
|
1523 | .Ve |
|
|
1524 | .Sp |
|
|
1525 | It is even possible to change the time-out on the fly, regardless of |
|
|
1526 | whether the watcher is active or not: |
|
|
1527 | .Sp |
|
|
1528 | .Vb 2 |
|
|
1529 | \& timer\->repeat = 30.; |
|
|
1530 | \& ev_timer_again (loop, timer); |
|
|
1531 | .Ve |
|
|
1532 | .Sp |
|
|
1533 | This is slightly more efficient then stopping/starting the timer each time |
|
|
1534 | you want to modify its timeout value, as libev does not have to completely |
|
|
1535 | remove and re-insert the timer from/into its internal data structure. |
|
|
1536 | .Sp |
|
|
1537 | It is, however, even simpler than the \*(L"obvious\*(R" way to do it. |
|
|
1538 | .IP "3. Let the timer time out, but then re-arm it as required." 4 |
|
|
1539 | .IX Item "3. Let the timer time out, but then re-arm it as required." |
|
|
1540 | This method is more tricky, but usually most efficient: Most timeouts are |
|
|
1541 | relatively long compared to the intervals between other activity \- in |
|
|
1542 | our example, within 60 seconds, there are usually many I/O events with |
|
|
1543 | associated activity resets. |
|
|
1544 | .Sp |
|
|
1545 | In this case, it would be more efficient to leave the \f(CW\*(C`ev_timer\*(C'\fR alone, |
|
|
1546 | but remember the time of last activity, and check for a real timeout only |
|
|
1547 | within the callback: |
|
|
1548 | .Sp |
|
|
1549 | .Vb 1 |
|
|
1550 | \& ev_tstamp last_activity; // time of last activity |
|
|
1551 | \& |
|
|
1552 | \& static void |
|
|
1553 | \& callback (EV_P_ ev_timer *w, int revents) |
|
|
1554 | \& { |
|
|
1555 | \& ev_tstamp now = ev_now (EV_A); |
|
|
1556 | \& ev_tstamp timeout = last_activity + 60.; |
|
|
1557 | \& |
|
|
1558 | \& // if last_activity + 60. is older than now, we did time out |
|
|
1559 | \& if (timeout < now) |
|
|
1560 | \& { |
|
|
1561 | \& // timeout occured, take action |
|
|
1562 | \& } |
|
|
1563 | \& else |
|
|
1564 | \& { |
|
|
1565 | \& // callback was invoked, but there was some activity, re\-arm |
|
|
1566 | \& // the watcher to fire in last_activity + 60, which is |
|
|
1567 | \& // guaranteed to be in the future, so "again" is positive: |
|
|
1568 | \& w\->repeat = timeout \- now; |
|
|
1569 | \& ev_timer_again (EV_A_ w); |
|
|
1570 | \& } |
|
|
1571 | \& } |
|
|
1572 | .Ve |
|
|
1573 | .Sp |
|
|
1574 | To summarise the callback: first calculate the real timeout (defined |
|
|
1575 | as \*(L"60 seconds after the last activity\*(R"), then check if that time has |
|
|
1576 | been reached, which means something \fIdid\fR, in fact, time out. Otherwise |
|
|
1577 | the callback was invoked too early (\f(CW\*(C`timeout\*(C'\fR is in the future), so |
|
|
1578 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1579 | a timeout then. |
|
|
1580 | .Sp |
|
|
1581 | Note how \f(CW\*(C`ev_timer_again\*(C'\fR is used, taking advantage of the |
|
|
1582 | \&\f(CW\*(C`ev_timer_again\*(C'\fR optimisation when the timer is already running. |
|
|
1583 | .Sp |
|
|
1584 | This scheme causes more callback invocations (about one every 60 seconds |
|
|
1585 | minus half the average time between activity), but virtually no calls to |
|
|
1586 | libev to change the timeout. |
|
|
1587 | .Sp |
|
|
1588 | To start the timer, simply initialise the watcher and set \f(CW\*(C`last_activity\*(C'\fR |
|
|
1589 | to the current time (meaning we just have some activity :), then call the |
|
|
1590 | callback, which will \*(L"do the right thing\*(R" and start the timer: |
|
|
1591 | .Sp |
|
|
1592 | .Vb 3 |
|
|
1593 | \& ev_timer_init (timer, callback); |
|
|
1594 | \& last_activity = ev_now (loop); |
|
|
1595 | \& callback (loop, timer, EV_TIMEOUT); |
|
|
1596 | .Ve |
|
|
1597 | .Sp |
|
|
1598 | And when there is some activity, simply store the current time in |
|
|
1599 | \&\f(CW\*(C`last_activity\*(C'\fR, no libev calls at all: |
|
|
1600 | .Sp |
|
|
1601 | .Vb 1 |
|
|
1602 | \& last_actiivty = ev_now (loop); |
|
|
1603 | .Ve |
|
|
1604 | .Sp |
|
|
1605 | This technique is slightly more complex, but in most cases where the |
|
|
1606 | time-out is unlikely to be triggered, much more efficient. |
|
|
1607 | .Sp |
|
|
1608 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1609 | callback :) \- just change the timeout and invoke the callback, which will |
|
|
1610 | fix things for you. |
|
|
1611 | .IP "4. Wee, just use a double-linked list for your timeouts." 4 |
|
|
1612 | .IX Item "4. Wee, just use a double-linked list for your timeouts." |
|
|
1613 | If there is not one request, but many thousands (millions...), all |
|
|
1614 | employing some kind of timeout with the same timeout value, then one can |
|
|
1615 | do even better: |
|
|
1616 | .Sp |
|
|
1617 | When starting the timeout, calculate the timeout value and put the timeout |
|
|
1618 | at the \fIend\fR of the list. |
|
|
1619 | .Sp |
|
|
1620 | Then use an \f(CW\*(C`ev_timer\*(C'\fR to fire when the timeout at the \fIbeginning\fR of |
|
|
1621 | the list is expected to fire (for example, using the technique #3). |
|
|
1622 | .Sp |
|
|
1623 | When there is some activity, remove the timer from the list, recalculate |
|
|
1624 | the timeout, append it to the end of the list again, and make sure to |
|
|
1625 | update the \f(CW\*(C`ev_timer\*(C'\fR if it was taken from the beginning of the list. |
|
|
1626 | .Sp |
|
|
1627 | This way, one can manage an unlimited number of timeouts in O(1) time for |
|
|
1628 | starting, stopping and updating the timers, at the expense of a major |
|
|
1629 | complication, and having to use a constant timeout. The constant timeout |
|
|
1630 | ensures that the list stays sorted. |
|
|
1631 | .PP |
|
|
1632 | So which method the best? |
|
|
1633 | .PP |
|
|
1634 | Method #2 is a simple no-brain-required solution that is adequate in most |
|
|
1635 | situations. Method #3 requires a bit more thinking, but handles many cases |
|
|
1636 | better, and isn't very complicated either. In most case, choosing either |
|
|
1637 | one is fine, with #3 being better in typical situations. |
|
|
1638 | .PP |
|
|
1639 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
|
|
1640 | rather complicated, but extremely efficient, something that really pays |
|
|
1641 | off after the first million or so of active timers, i.e. it's usually |
|
|
1642 | overkill :) |
|
|
1643 | .PP |
|
|
1644 | \fIThe special problem of time updates\fR |
|
|
1645 | .IX Subsection "The special problem of time updates" |
|
|
1646 | .PP |
|
|
1647 | Establishing the current time is a costly operation (it usually takes at |
|
|
1648 | least two system calls): \s-1EV\s0 therefore updates its idea of the current |
|
|
1649 | time only before and after \f(CW\*(C`ev_loop\*(C'\fR collects new events, which causes a |
|
|
1650 | growing difference between \f(CW\*(C`ev_now ()\*(C'\fR and \f(CW\*(C`ev_time ()\*(C'\fR when handling |
|
|
1651 | lots of events in one iteration. |
600 | .PP |
1652 | .PP |
601 | The relative timeouts are calculated relative to the \f(CW\*(C`ev_now ()\*(C'\fR |
1653 | The relative timeouts are calculated relative to the \f(CW\*(C`ev_now ()\*(C'\fR |
602 | time. This is usually the right thing as this timestamp refers to the time |
1654 | time. This is usually the right thing as this timestamp refers to the time |
603 | of the event triggering whatever timeout you are modifying/starting. If |
1655 | of the event triggering whatever timeout you are modifying/starting. If |
604 | you suspect event processing to be delayed and you \fIneed\fR to base the timeout |
1656 | you suspect event processing to be delayed and you \fIneed\fR to base the |
605 | on the current time, use something like this to adjust for this: |
1657 | timeout on the current time, use something like this to adjust for this: |
606 | .PP |
1658 | .PP |
607 | .Vb 1 |
1659 | .Vb 1 |
608 | \& ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1660 | \& ev_timer_set (&timer, after + ev_now () \- ev_time (), 0.); |
609 | .Ve |
1661 | .Ve |
610 | .PP |
1662 | .PP |
611 | The callback is guarenteed to be invoked only when its timeout has passed, |
1663 | If the event loop is suspended for a long time, you can also force an |
612 | but if multiple timers become ready during the same loop iteration then |
1664 | update of the time returned by \f(CW\*(C`ev_now ()\*(C'\fR by calling \f(CW\*(C`ev_now_update |
613 | order of execution is undefined. |
1665 | ()\*(C'\fR. |
|
|
1666 | .PP |
|
|
1667 | \fIWatcher-Specific Functions and Data Members\fR |
|
|
1668 | .IX Subsection "Watcher-Specific Functions and Data Members" |
614 | .IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4 |
1669 | .IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4 |
615 | .IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" |
1670 | .IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" |
616 | .PD 0 |
1671 | .PD 0 |
617 | .IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4 |
1672 | .IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4 |
618 | .IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" |
1673 | .IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" |
619 | .PD |
1674 | .PD |
620 | Configure the timer to trigger after \f(CW\*(C`after\*(C'\fR seconds. If \f(CW\*(C`repeat\*(C'\fR is |
1675 | Configure the timer to trigger after \f(CW\*(C`after\*(C'\fR seconds. If \f(CW\*(C`repeat\*(C'\fR |
621 | \&\f(CW0.\fR, then it will automatically be stopped. If it is positive, then the |
1676 | is \f(CW0.\fR, then it will automatically be stopped once the timeout is |
622 | timer will automatically be configured to trigger again \f(CW\*(C`repeat\*(C'\fR seconds |
1677 | reached. If it is positive, then the timer will automatically be |
623 | later, again, and again, until stopped manually. |
1678 | configured to trigger again \f(CW\*(C`repeat\*(C'\fR seconds later, again, and again, |
|
|
1679 | until stopped manually. |
624 | .Sp |
1680 | .Sp |
625 | The timer itself will do a best-effort at avoiding drift, that is, if you |
1681 | The timer itself will do a best-effort at avoiding drift, that is, if |
626 | configure a timer to trigger every 10 seconds, then it will trigger at |
1682 | you configure a timer to trigger every 10 seconds, then it will normally |
627 | exactly 10 second intervals. If, however, your program cannot keep up with |
1683 | trigger at exactly 10 second intervals. If, however, your program cannot |
628 | the timer (because it takes longer than those 10 seconds to do stuff) the |
1684 | keep up with the timer (because it takes longer than those 10 seconds to |
629 | timer will not fire more than once per event loop iteration. |
1685 | do stuff) the timer will not fire more than once per event loop iteration. |
630 | .IP "ev_timer_again (loop)" 4 |
1686 | .IP "ev_timer_again (loop, ev_timer *)" 4 |
631 | .IX Item "ev_timer_again (loop)" |
1687 | .IX Item "ev_timer_again (loop, ev_timer *)" |
632 | This will act as if the timer timed out and restart it again if it is |
1688 | This will act as if the timer timed out and restart it again if it is |
633 | repeating. The exact semantics are: |
1689 | repeating. The exact semantics are: |
634 | .Sp |
1690 | .Sp |
|
|
1691 | If the timer is pending, its pending status is cleared. |
|
|
1692 | .Sp |
635 | If the timer is started but nonrepeating, stop it. |
1693 | If the timer is started but non-repeating, stop it (as if it timed out). |
636 | .Sp |
1694 | .Sp |
637 | If the timer is repeating, either start it if necessary (with the repeat |
1695 | If the timer is repeating, either start it if necessary (with the |
638 | value), or reset the running timer to the repeat value. |
1696 | \&\f(CW\*(C`repeat\*(C'\fR value), or reset the running timer to the \f(CW\*(C`repeat\*(C'\fR value. |
639 | .Sp |
1697 | .Sp |
640 | This sounds a bit complicated, but here is a useful and typical |
1698 | This sounds a bit complicated, see \*(L"Be smart about timeouts\*(R", above, for a |
641 | example: Imagine you have a tcp connection and you want a so-called idle |
1699 | usage example. |
642 | timeout, that is, you want to be called when there have been, say, 60 |
1700 | .IP "ev_tstamp repeat [read\-write]" 4 |
643 | seconds of inactivity on the socket. The easiest way to do this is to |
1701 | .IX Item "ev_tstamp repeat [read-write]" |
644 | configure an \f(CW\*(C`ev_timer\*(C'\fR with after=repeat=60 and calling ev_timer_again each |
1702 | The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out |
645 | time you successfully read or write some data. If you go into an idle |
1703 | or \f(CW\*(C`ev_timer_again\*(C'\fR is called, and determines the next timeout (if any), |
646 | state where you do not expect data to travel on the socket, you can stop |
1704 | which is also when any modifications are taken into account. |
647 | the timer, and again will automatically restart it if need be. |
1705 | .PP |
|
|
1706 | \fIExamples\fR |
|
|
1707 | .IX Subsection "Examples" |
|
|
1708 | .PP |
|
|
1709 | Example: Create a timer that fires after 60 seconds. |
|
|
1710 | .PP |
|
|
1711 | .Vb 5 |
|
|
1712 | \& static void |
|
|
1713 | \& one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents) |
|
|
1714 | \& { |
|
|
1715 | \& .. one minute over, w is actually stopped right here |
|
|
1716 | \& } |
|
|
1717 | \& |
|
|
1718 | \& ev_timer mytimer; |
|
|
1719 | \& ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
|
|
1720 | \& ev_timer_start (loop, &mytimer); |
|
|
1721 | .Ve |
|
|
1722 | .PP |
|
|
1723 | Example: Create a timeout timer that times out after 10 seconds of |
|
|
1724 | inactivity. |
|
|
1725 | .PP |
|
|
1726 | .Vb 5 |
|
|
1727 | \& static void |
|
|
1728 | \& timeout_cb (struct ev_loop *loop, ev_timer *w, int revents) |
|
|
1729 | \& { |
|
|
1730 | \& .. ten seconds without any activity |
|
|
1731 | \& } |
|
|
1732 | \& |
|
|
1733 | \& ev_timer mytimer; |
|
|
1734 | \& ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
|
|
1735 | \& ev_timer_again (&mytimer); /* start timer */ |
|
|
1736 | \& ev_loop (loop, 0); |
|
|
1737 | \& |
|
|
1738 | \& // and in some piece of code that gets executed on any "activity": |
|
|
1739 | \& // reset the timeout to start ticking again at 10 seconds |
|
|
1740 | \& ev_timer_again (&mytimer); |
|
|
1741 | .Ve |
648 | .ie n .Sh """ev_periodic"" \- to cron or not to cron" |
1742 | .ie n .Sh """ev_periodic"" \- to cron or not to cron?" |
649 | .el .Sh "\f(CWev_periodic\fP \- to cron or not to cron" |
1743 | .el .Sh "\f(CWev_periodic\fP \- to cron or not to cron?" |
650 | .IX Subsection "ev_periodic - to cron or not to cron" |
1744 | .IX Subsection "ev_periodic - to cron or not to cron?" |
651 | Periodic watchers are also timers of a kind, but they are very versatile |
1745 | Periodic watchers are also timers of a kind, but they are very versatile |
652 | (and unfortunately a bit complex). |
1746 | (and unfortunately a bit complex). |
653 | .PP |
1747 | .PP |
654 | Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time) |
1748 | Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time) |
655 | but on wallclock time (absolute time). You can tell a periodic watcher |
1749 | but on wall clock time (absolute time). You can tell a periodic watcher |
656 | to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a |
1750 | to trigger after some specific point in time. For example, if you tell a |
657 | periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now () |
1751 | periodic watcher to trigger in 10 seconds (by specifying e.g. \f(CW\*(C`ev_now () |
658 | + 10.>) and then reset your system clock to the last year, then it will |
1752 | + 10.\*(C'\fR, that is, an absolute time not a delay) and then reset your system |
|
|
1753 | clock to January of the previous year, then it will take more than year |
659 | take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger |
1754 | to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would still trigger |
660 | roughly 10 seconds later and of course not if you reset your system time |
1755 | roughly 10 seconds later as it uses a relative timeout). |
661 | again). |
|
|
662 | .PP |
1756 | .PP |
663 | They can also be used to implement vastly more complex timers, such as |
1757 | \&\f(CW\*(C`ev_periodic\*(C'\fRs can also be used to implement vastly more complex timers, |
664 | triggering an event on eahc midnight, local time. |
1758 | such as triggering an event on each \*(L"midnight, local time\*(R", or other |
|
|
1759 | complicated rules. |
665 | .PP |
1760 | .PP |
666 | As with timers, the callback is guarenteed to be invoked only when the |
1761 | As with timers, the callback is guaranteed to be invoked only when the |
667 | time (\f(CW\*(C`at\*(C'\fR) has been passed, but if multiple periodic timers become ready |
1762 | time (\f(CW\*(C`at\*(C'\fR) has passed, but if multiple periodic timers become ready |
668 | during the same loop iteration then order of execution is undefined. |
1763 | during the same loop iteration, then order of execution is undefined. |
|
|
1764 | .PP |
|
|
1765 | \fIWatcher-Specific Functions and Data Members\fR |
|
|
1766 | .IX Subsection "Watcher-Specific Functions and Data Members" |
669 | .IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4 |
1767 | .IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4 |
670 | .IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" |
1768 | .IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" |
671 | .PD 0 |
1769 | .PD 0 |
672 | .IP "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 4 |
1770 | .IP "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 4 |
673 | .IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" |
1771 | .IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" |
674 | .PD |
1772 | .PD |
675 | Lots of arguments, lets sort it out... There are basically three modes of |
1773 | Lots of arguments, lets sort it out... There are basically three modes of |
676 | operation, and we will explain them from simplest to complex: |
1774 | operation, and we will explain them from simplest to most complex: |
677 | .RS 4 |
1775 | .RS 4 |
|
|
1776 | .IP "\(bu" 4 |
678 | .IP "* absolute timer (interval = reschedule_cb = 0)" 4 |
1777 | absolute timer (at = time, interval = reschedule_cb = 0) |
679 | .IX Item "absolute timer (interval = reschedule_cb = 0)" |
1778 | .Sp |
680 | In this configuration the watcher triggers an event at the wallclock time |
1779 | In this configuration the watcher triggers an event after the wall clock |
681 | \&\f(CW\*(C`at\*(C'\fR and doesn't repeat. It will not adjust when a time jump occurs, |
1780 | time \f(CW\*(C`at\*(C'\fR has passed. It will not repeat and will not adjust when a time |
682 | that is, if it is to be run at January 1st 2011 then it will run when the |
1781 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
683 | system time reaches or surpasses this time. |
1782 | only run when the system clock reaches or surpasses this time. |
|
|
1783 | .IP "\(bu" 4 |
684 | .IP "* non-repeating interval timer (interval > 0, reschedule_cb = 0)" 4 |
1784 | repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
685 | .IX Item "non-repeating interval timer (interval > 0, reschedule_cb = 0)" |
1785 | .Sp |
686 | In this mode the watcher will always be scheduled to time out at the next |
1786 | In this mode the watcher will always be scheduled to time out at the next |
687 | \&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N) and then repeat, regardless |
1787 | \&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N, which can also be negative) |
688 | of any time jumps. |
1788 | and then repeat, regardless of any time jumps. |
689 | .Sp |
1789 | .Sp |
690 | This can be used to create timers that do not drift with respect to system |
1790 | This can be used to create timers that do not drift with respect to the |
691 | time: |
1791 | system clock, for example, here is a \f(CW\*(C`ev_periodic\*(C'\fR that triggers each |
|
|
1792 | hour, on the hour: |
692 | .Sp |
1793 | .Sp |
693 | .Vb 1 |
1794 | .Vb 1 |
694 | \& ev_periodic_set (&periodic, 0., 3600., 0); |
1795 | \& ev_periodic_set (&periodic, 0., 3600., 0); |
695 | .Ve |
1796 | .Ve |
696 | .Sp |
1797 | .Sp |
697 | This doesn't mean there will always be 3600 seconds in between triggers, |
1798 | This doesn't mean there will always be 3600 seconds in between triggers, |
698 | but only that the the callback will be called when the system time shows a |
1799 | but only that the callback will be called when the system time shows a |
699 | full hour (\s-1UTC\s0), or more correctly, when the system time is evenly divisible |
1800 | full hour (\s-1UTC\s0), or more correctly, when the system time is evenly divisible |
700 | by 3600. |
1801 | by 3600. |
701 | .Sp |
1802 | .Sp |
702 | Another way to think about it (for the mathematically inclined) is that |
1803 | Another way to think about it (for the mathematically inclined) is that |
703 | \&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible |
1804 | \&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible |
704 | time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps. |
1805 | time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps. |
705 | .IP "* manual reschedule mode (reschedule_cb = callback)" 4 |
1806 | .Sp |
706 | .IX Item "manual reschedule mode (reschedule_cb = callback)" |
1807 | For numerical stability it is preferable that the \f(CW\*(C`at\*(C'\fR value is near |
|
|
1808 | \&\f(CW\*(C`ev_now ()\*(C'\fR (the current time), but there is no range requirement for |
|
|
1809 | this value, and in fact is often specified as zero. |
|
|
1810 | .Sp |
|
|
1811 | Note also that there is an upper limit to how often a timer can fire (\s-1CPU\s0 |
|
|
1812 | speed for example), so if \f(CW\*(C`interval\*(C'\fR is very small then timing stability |
|
|
1813 | will of course deteriorate. Libev itself tries to be exact to be about one |
|
|
1814 | millisecond (if the \s-1OS\s0 supports it and the machine is fast enough). |
|
|
1815 | .IP "\(bu" 4 |
|
|
1816 | manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
|
|
1817 | .Sp |
707 | In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR are both being |
1818 | In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR are both being |
708 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1819 | ignored. Instead, each time the periodic watcher gets scheduled, the |
709 | reschedule callback will be called with the watcher as first, and the |
1820 | reschedule callback will be called with the watcher as first, and the |
710 | current time as second argument. |
1821 | current time as second argument. |
711 | .Sp |
1822 | .Sp |
712 | \&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher, |
1823 | \&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher, |
713 | ever, or make any event loop modifications\fR. If you need to stop it, |
1824 | ever, or make \s-1ANY\s0 event loop modifications whatsoever\fR. |
714 | return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop it afterwards (e.g. by |
|
|
715 | starting a prepare watcher). |
|
|
716 | .Sp |
1825 | .Sp |
|
|
1826 | If you need to stop it, return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop |
|
|
1827 | it afterwards (e.g. by starting an \f(CW\*(C`ev_prepare\*(C'\fR watcher, which is the |
|
|
1828 | only event loop modification you are allowed to do). |
|
|
1829 | .Sp |
717 | Its prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic *w, |
1830 | The callback prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(ev_periodic |
718 | ev_tstamp now)\*(C'\fR, e.g.: |
1831 | *w, ev_tstamp now)\*(C'\fR, e.g.: |
719 | .Sp |
1832 | .Sp |
720 | .Vb 4 |
1833 | .Vb 5 |
|
|
1834 | \& static ev_tstamp |
721 | \& static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1835 | \& my_rescheduler (ev_periodic *w, ev_tstamp now) |
722 | \& { |
1836 | \& { |
723 | \& return now + 60.; |
1837 | \& return now + 60.; |
724 | \& } |
1838 | \& } |
725 | .Ve |
1839 | .Ve |
726 | .Sp |
1840 | .Sp |
727 | It must return the next time to trigger, based on the passed time value |
1841 | It must return the next time to trigger, based on the passed time value |
728 | (that is, the lowest time value larger than to the second argument). It |
1842 | (that is, the lowest time value larger than to the second argument). It |
729 | will usually be called just before the callback will be triggered, but |
1843 | will usually be called just before the callback will be triggered, but |
730 | might be called at other times, too. |
1844 | might be called at other times, too. |
731 | .Sp |
1845 | .Sp |
732 | \&\s-1NOTE:\s0 \fIThis callback must always return a time that is later than the |
1846 | \&\s-1NOTE:\s0 \fIThis callback must always return a time that is higher than or |
733 | 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. |
1847 | equal to the passed \f(CI\*(C`now\*(C'\fI value\fR. |
734 | .Sp |
1848 | .Sp |
735 | This can be used to create very complex timers, such as a timer that |
1849 | This can be used to create very complex timers, such as a timer that |
736 | triggers on each midnight, local time. To do this, you would calculate the |
1850 | triggers on \*(L"next midnight, local time\*(R". To do this, you would calculate the |
737 | next midnight after \f(CW\*(C`now\*(C'\fR and return the timestamp value for this. How |
1851 | next midnight after \f(CW\*(C`now\*(C'\fR and return the timestamp value for this. How |
738 | you do this is, again, up to you (but it is not trivial, which is the main |
1852 | you do this is, again, up to you (but it is not trivial, which is the main |
739 | reason I omitted it as an example). |
1853 | reason I omitted it as an example). |
740 | .RE |
1854 | .RE |
741 | .RS 4 |
1855 | .RS 4 |
… | |
… | |
744 | .IX Item "ev_periodic_again (loop, ev_periodic *)" |
1858 | .IX Item "ev_periodic_again (loop, ev_periodic *)" |
745 | Simply stops and restarts the periodic watcher again. This is only useful |
1859 | Simply stops and restarts the periodic watcher again. This is only useful |
746 | when you changed some parameters or the reschedule callback would return |
1860 | when you changed some parameters or the reschedule callback would return |
747 | a different time than the last time it was called (e.g. in a crond like |
1861 | a different time than the last time it was called (e.g. in a crond like |
748 | program when the crontabs have changed). |
1862 | program when the crontabs have changed). |
|
|
1863 | .IP "ev_tstamp ev_periodic_at (ev_periodic *)" 4 |
|
|
1864 | .IX Item "ev_tstamp ev_periodic_at (ev_periodic *)" |
|
|
1865 | When active, returns the absolute time that the watcher is supposed to |
|
|
1866 | trigger next. |
|
|
1867 | .IP "ev_tstamp offset [read\-write]" 4 |
|
|
1868 | .IX Item "ev_tstamp offset [read-write]" |
|
|
1869 | When repeating, this contains the offset value, otherwise this is the |
|
|
1870 | absolute point in time (the \f(CW\*(C`at\*(C'\fR value passed to \f(CW\*(C`ev_periodic_set\*(C'\fR). |
|
|
1871 | .Sp |
|
|
1872 | Can be modified any time, but changes only take effect when the periodic |
|
|
1873 | timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called. |
|
|
1874 | .IP "ev_tstamp interval [read\-write]" 4 |
|
|
1875 | .IX Item "ev_tstamp interval [read-write]" |
|
|
1876 | The current interval value. Can be modified any time, but changes only |
|
|
1877 | take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being |
|
|
1878 | called. |
|
|
1879 | .IP "ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read\-write]" 4 |
|
|
1880 | .IX Item "ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]" |
|
|
1881 | The current reschedule callback, or \f(CW0\fR, if this functionality is |
|
|
1882 | switched off. Can be changed any time, but changes only take effect when |
|
|
1883 | the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called. |
|
|
1884 | .PP |
|
|
1885 | \fIExamples\fR |
|
|
1886 | .IX Subsection "Examples" |
|
|
1887 | .PP |
|
|
1888 | Example: Call a callback every hour, or, more precisely, whenever the |
|
|
1889 | system time is divisible by 3600. The callback invocation times have |
|
|
1890 | potentially a lot of jitter, but good long-term stability. |
|
|
1891 | .PP |
|
|
1892 | .Vb 5 |
|
|
1893 | \& static void |
|
|
1894 | \& clock_cb (struct ev_loop *loop, ev_io *w, int revents) |
|
|
1895 | \& { |
|
|
1896 | \& ... its now a full hour (UTC, or TAI or whatever your clock follows) |
|
|
1897 | \& } |
|
|
1898 | \& |
|
|
1899 | \& ev_periodic hourly_tick; |
|
|
1900 | \& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
|
|
1901 | \& ev_periodic_start (loop, &hourly_tick); |
|
|
1902 | .Ve |
|
|
1903 | .PP |
|
|
1904 | Example: The same as above, but use a reschedule callback to do it: |
|
|
1905 | .PP |
|
|
1906 | .Vb 1 |
|
|
1907 | \& #include <math.h> |
|
|
1908 | \& |
|
|
1909 | \& static ev_tstamp |
|
|
1910 | \& my_scheduler_cb (ev_periodic *w, ev_tstamp now) |
|
|
1911 | \& { |
|
|
1912 | \& return now + (3600. \- fmod (now, 3600.)); |
|
|
1913 | \& } |
|
|
1914 | \& |
|
|
1915 | \& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
|
|
1916 | .Ve |
|
|
1917 | .PP |
|
|
1918 | Example: Call a callback every hour, starting now: |
|
|
1919 | .PP |
|
|
1920 | .Vb 4 |
|
|
1921 | \& ev_periodic hourly_tick; |
|
|
1922 | \& ev_periodic_init (&hourly_tick, clock_cb, |
|
|
1923 | \& fmod (ev_now (loop), 3600.), 3600., 0); |
|
|
1924 | \& ev_periodic_start (loop, &hourly_tick); |
|
|
1925 | .Ve |
749 | .ie n .Sh """ev_signal"" \- signal me when a signal gets signalled" |
1926 | .ie n .Sh """ev_signal"" \- signal me when a signal gets signalled!" |
750 | .el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled" |
1927 | .el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled!" |
751 | .IX Subsection "ev_signal - signal me when a signal gets signalled" |
1928 | .IX Subsection "ev_signal - signal me when a signal gets signalled!" |
752 | Signal watchers will trigger an event when the process receives a specific |
1929 | Signal watchers will trigger an event when the process receives a specific |
753 | signal one or more times. Even though signals are very asynchronous, libev |
1930 | signal one or more times. Even though signals are very asynchronous, libev |
754 | will try it's best to deliver signals synchronously, i.e. as part of the |
1931 | will try it's best to deliver signals synchronously, i.e. as part of the |
755 | normal event processing, like any other event. |
1932 | normal event processing, like any other event. |
756 | .PP |
1933 | .PP |
|
|
1934 | If you want signals asynchronously, just use \f(CW\*(C`sigaction\*(C'\fR as you would |
|
|
1935 | do without libev and forget about sharing the signal. You can even use |
|
|
1936 | \&\f(CW\*(C`ev_async\*(C'\fR from a signal handler to synchronously wake up an event loop. |
|
|
1937 | .PP |
757 | You can configure as many watchers as you like per signal. Only when the |
1938 | You can configure as many watchers as you like per signal. Only when the |
758 | first watcher gets started will libev actually register a signal watcher |
1939 | first watcher gets started will libev actually register a signal handler |
759 | with the kernel (thus it coexists with your own signal handlers as long |
1940 | with the kernel (thus it coexists with your own signal handlers as long as |
760 | as you don't register any with libev). Similarly, when the last signal |
1941 | you don't register any with libev for the same signal). Similarly, when |
761 | watcher for a signal is stopped libev will reset the signal handler to |
1942 | the last signal watcher for a signal is stopped, libev will reset the |
762 | \&\s-1SIG_DFL\s0 (regardless of what it was set to before). |
1943 | signal handler to \s-1SIG_DFL\s0 (regardless of what it was set to before). |
|
|
1944 | .PP |
|
|
1945 | If possible and supported, libev will install its handlers with |
|
|
1946 | \&\f(CW\*(C`SA_RESTART\*(C'\fR behaviour enabled, so system calls should not be unduly |
|
|
1947 | interrupted. If you have a problem with system calls getting interrupted by |
|
|
1948 | signals you can block all signals in an \f(CW\*(C`ev_check\*(C'\fR watcher and unblock |
|
|
1949 | them in an \f(CW\*(C`ev_prepare\*(C'\fR watcher. |
|
|
1950 | .PP |
|
|
1951 | \fIWatcher-Specific Functions and Data Members\fR |
|
|
1952 | .IX Subsection "Watcher-Specific Functions and Data Members" |
763 | .IP "ev_signal_init (ev_signal *, callback, int signum)" 4 |
1953 | .IP "ev_signal_init (ev_signal *, callback, int signum)" 4 |
764 | .IX Item "ev_signal_init (ev_signal *, callback, int signum)" |
1954 | .IX Item "ev_signal_init (ev_signal *, callback, int signum)" |
765 | .PD 0 |
1955 | .PD 0 |
766 | .IP "ev_signal_set (ev_signal *, int signum)" 4 |
1956 | .IP "ev_signal_set (ev_signal *, int signum)" 4 |
767 | .IX Item "ev_signal_set (ev_signal *, int signum)" |
1957 | .IX Item "ev_signal_set (ev_signal *, int signum)" |
768 | .PD |
1958 | .PD |
769 | Configures the watcher to trigger on the given signal number (usually one |
1959 | Configures the watcher to trigger on the given signal number (usually one |
770 | of the \f(CW\*(C`SIGxxx\*(C'\fR constants). |
1960 | of the \f(CW\*(C`SIGxxx\*(C'\fR constants). |
|
|
1961 | .IP "int signum [read\-only]" 4 |
|
|
1962 | .IX Item "int signum [read-only]" |
|
|
1963 | The signal the watcher watches out for. |
|
|
1964 | .PP |
|
|
1965 | \fIExamples\fR |
|
|
1966 | .IX Subsection "Examples" |
|
|
1967 | .PP |
|
|
1968 | Example: Try to exit cleanly on \s-1SIGINT\s0. |
|
|
1969 | .PP |
|
|
1970 | .Vb 5 |
|
|
1971 | \& static void |
|
|
1972 | \& sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
|
|
1973 | \& { |
|
|
1974 | \& ev_unloop (loop, EVUNLOOP_ALL); |
|
|
1975 | \& } |
|
|
1976 | \& |
|
|
1977 | \& ev_signal signal_watcher; |
|
|
1978 | \& ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
|
|
1979 | \& ev_signal_start (loop, &signal_watcher); |
|
|
1980 | .Ve |
771 | .ie n .Sh """ev_child"" \- wait for pid status changes" |
1981 | .ie n .Sh """ev_child"" \- watch out for process status changes" |
772 | .el .Sh "\f(CWev_child\fP \- wait for pid status changes" |
1982 | .el .Sh "\f(CWev_child\fP \- watch out for process status changes" |
773 | .IX Subsection "ev_child - wait for pid status changes" |
1983 | .IX Subsection "ev_child - watch out for process status changes" |
774 | Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to |
1984 | Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to |
775 | some child status changes (most typically when a child of yours dies). |
1985 | some child status changes (most typically when a child of yours dies or |
|
|
1986 | exits). It is permissible to install a child watcher \fIafter\fR the child |
|
|
1987 | has been forked (which implies it might have already exited), as long |
|
|
1988 | as the event loop isn't entered (or is continued from a watcher), i.e., |
|
|
1989 | forking and then immediately registering a watcher for the child is fine, |
|
|
1990 | but forking and registering a watcher a few event loop iterations later is |
|
|
1991 | not. |
|
|
1992 | .PP |
|
|
1993 | Only the default event loop is capable of handling signals, and therefore |
|
|
1994 | you can only register child watchers in the default event loop. |
|
|
1995 | .PP |
|
|
1996 | \fIProcess Interaction\fR |
|
|
1997 | .IX Subsection "Process Interaction" |
|
|
1998 | .PP |
|
|
1999 | Libev grabs \f(CW\*(C`SIGCHLD\*(C'\fR as soon as the default event loop is |
|
|
2000 | initialised. This is necessary to guarantee proper behaviour even if |
|
|
2001 | the first child watcher is started after the child exits. The occurrence |
|
|
2002 | of \f(CW\*(C`SIGCHLD\*(C'\fR is recorded asynchronously, but child reaping is done |
|
|
2003 | synchronously as part of the event loop processing. Libev always reaps all |
|
|
2004 | children, even ones not watched. |
|
|
2005 | .PP |
|
|
2006 | \fIOverriding the Built-In Processing\fR |
|
|
2007 | .IX Subsection "Overriding the Built-In Processing" |
|
|
2008 | .PP |
|
|
2009 | Libev offers no special support for overriding the built-in child |
|
|
2010 | processing, but if your application collides with libev's default child |
|
|
2011 | handler, you can override it easily by installing your own handler for |
|
|
2012 | \&\f(CW\*(C`SIGCHLD\*(C'\fR after initialising the default loop, and making sure the |
|
|
2013 | default loop never gets destroyed. You are encouraged, however, to use an |
|
|
2014 | event-based approach to child reaping and thus use libev's support for |
|
|
2015 | that, so other libev users can use \f(CW\*(C`ev_child\*(C'\fR watchers freely. |
|
|
2016 | .PP |
|
|
2017 | \fIStopping the Child Watcher\fR |
|
|
2018 | .IX Subsection "Stopping the Child Watcher" |
|
|
2019 | .PP |
|
|
2020 | Currently, the child watcher never gets stopped, even when the |
|
|
2021 | child terminates, so normally one needs to stop the watcher in the |
|
|
2022 | callback. Future versions of libev might stop the watcher automatically |
|
|
2023 | when a child exit is detected. |
|
|
2024 | .PP |
|
|
2025 | \fIWatcher-Specific Functions and Data Members\fR |
|
|
2026 | .IX Subsection "Watcher-Specific Functions and Data Members" |
776 | .IP "ev_child_init (ev_child *, callback, int pid)" 4 |
2027 | .IP "ev_child_init (ev_child *, callback, int pid, int trace)" 4 |
777 | .IX Item "ev_child_init (ev_child *, callback, int pid)" |
2028 | .IX Item "ev_child_init (ev_child *, callback, int pid, int trace)" |
778 | .PD 0 |
2029 | .PD 0 |
779 | .IP "ev_child_set (ev_child *, int pid)" 4 |
2030 | .IP "ev_child_set (ev_child *, int pid, int trace)" 4 |
780 | .IX Item "ev_child_set (ev_child *, int pid)" |
2031 | .IX Item "ev_child_set (ev_child *, int pid, int trace)" |
781 | .PD |
2032 | .PD |
782 | Configures the watcher to wait for status changes of process \f(CW\*(C`pid\*(C'\fR (or |
2033 | Configures the watcher to wait for status changes of process \f(CW\*(C`pid\*(C'\fR (or |
783 | \&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look |
2034 | \&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look |
784 | at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see |
2035 | at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see |
785 | the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems |
2036 | the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems |
786 | \&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the |
2037 | \&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the |
787 | process causing the status change. |
2038 | process causing the status change. \f(CW\*(C`trace\*(C'\fR must be either \f(CW0\fR (only |
|
|
2039 | activate the watcher when the process terminates) or \f(CW1\fR (additionally |
|
|
2040 | activate the watcher when the process is stopped or continued). |
|
|
2041 | .IP "int pid [read\-only]" 4 |
|
|
2042 | .IX Item "int pid [read-only]" |
|
|
2043 | The process id this watcher watches out for, or \f(CW0\fR, meaning any process id. |
|
|
2044 | .IP "int rpid [read\-write]" 4 |
|
|
2045 | .IX Item "int rpid [read-write]" |
|
|
2046 | The process id that detected a status change. |
|
|
2047 | .IP "int rstatus [read\-write]" 4 |
|
|
2048 | .IX Item "int rstatus [read-write]" |
|
|
2049 | The process exit/trace status caused by \f(CW\*(C`rpid\*(C'\fR (see your systems |
|
|
2050 | \&\f(CW\*(C`waitpid\*(C'\fR and \f(CW\*(C`sys/wait.h\*(C'\fR documentation for details). |
|
|
2051 | .PP |
|
|
2052 | \fIExamples\fR |
|
|
2053 | .IX Subsection "Examples" |
|
|
2054 | .PP |
|
|
2055 | Example: \f(CW\*(C`fork()\*(C'\fR a new process and install a child handler to wait for |
|
|
2056 | its completion. |
|
|
2057 | .PP |
|
|
2058 | .Vb 1 |
|
|
2059 | \& ev_child cw; |
|
|
2060 | \& |
|
|
2061 | \& static void |
|
|
2062 | \& child_cb (EV_P_ ev_child *w, int revents) |
|
|
2063 | \& { |
|
|
2064 | \& ev_child_stop (EV_A_ w); |
|
|
2065 | \& printf ("process %d exited with status %x\en", w\->rpid, w\->rstatus); |
|
|
2066 | \& } |
|
|
2067 | \& |
|
|
2068 | \& pid_t pid = fork (); |
|
|
2069 | \& |
|
|
2070 | \& if (pid < 0) |
|
|
2071 | \& // error |
|
|
2072 | \& else if (pid == 0) |
|
|
2073 | \& { |
|
|
2074 | \& // the forked child executes here |
|
|
2075 | \& exit (1); |
|
|
2076 | \& } |
|
|
2077 | \& else |
|
|
2078 | \& { |
|
|
2079 | \& ev_child_init (&cw, child_cb, pid, 0); |
|
|
2080 | \& ev_child_start (EV_DEFAULT_ &cw); |
|
|
2081 | \& } |
|
|
2082 | .Ve |
|
|
2083 | .ie n .Sh """ev_stat"" \- did the file attributes just change?" |
|
|
2084 | .el .Sh "\f(CWev_stat\fP \- did the file attributes just change?" |
|
|
2085 | .IX Subsection "ev_stat - did the file attributes just change?" |
|
|
2086 | This watches a file system path for attribute changes. That is, it calls |
|
|
2087 | \&\f(CW\*(C`stat\*(C'\fR on that path in regular intervals (or when the \s-1OS\s0 says it changed) |
|
|
2088 | and sees if it changed compared to the last time, invoking the callback if |
|
|
2089 | it did. |
|
|
2090 | .PP |
|
|
2091 | The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does |
|
|
2092 | not exist\*(R" is a status change like any other. The condition \*(L"path does not |
|
|
2093 | exist\*(R" (or more correctly \*(L"path cannot be stat'ed\*(R") is signified by the |
|
|
2094 | \&\f(CW\*(C`st_nlink\*(C'\fR field being zero (which is otherwise always forced to be at |
|
|
2095 | least one) and all the other fields of the stat buffer having unspecified |
|
|
2096 | contents. |
|
|
2097 | .PP |
|
|
2098 | The path \fImust not\fR end in a slash or contain special components such as |
|
|
2099 | \&\f(CW\*(C`.\*(C'\fR or \f(CW\*(C`..\*(C'\fR. The path \fIshould\fR be absolute: If it is relative and |
|
|
2100 | your working directory changes, then the behaviour is undefined. |
|
|
2101 | .PP |
|
|
2102 | Since there is no portable change notification interface available, the |
|
|
2103 | portable implementation simply calls \f(CWstat(2)\fR regularly on the path |
|
|
2104 | to see if it changed somehow. You can specify a recommended polling |
|
|
2105 | interval for this case. If you specify a polling interval of \f(CW0\fR (highly |
|
|
2106 | recommended!) then a \fIsuitable, unspecified default\fR value will be used |
|
|
2107 | (which you can expect to be around five seconds, although this might |
|
|
2108 | change dynamically). Libev will also impose a minimum interval which is |
|
|
2109 | currently around \f(CW0.1\fR, but that's usually overkill. |
|
|
2110 | .PP |
|
|
2111 | This watcher type is not meant for massive numbers of stat watchers, |
|
|
2112 | as even with OS-supported change notifications, this can be |
|
|
2113 | resource-intensive. |
|
|
2114 | .PP |
|
|
2115 | At the time of this writing, the only OS-specific interface implemented |
|
|
2116 | is the Linux inotify interface (implementing kqueue support is left as an |
|
|
2117 | exercise for the reader. Note, however, that the author sees no way of |
|
|
2118 | implementing \f(CW\*(C`ev_stat\*(C'\fR semantics with kqueue, except as a hint). |
|
|
2119 | .PP |
|
|
2120 | \fI\s-1ABI\s0 Issues (Largefile Support)\fR |
|
|
2121 | .IX Subsection "ABI Issues (Largefile Support)" |
|
|
2122 | .PP |
|
|
2123 | Libev by default (unless the user overrides this) uses the default |
|
|
2124 | compilation environment, which means that on systems with large file |
|
|
2125 | support disabled by default, you get the 32 bit version of the stat |
|
|
2126 | structure. When using the library from programs that change the \s-1ABI\s0 to |
|
|
2127 | use 64 bit file offsets the programs will fail. In that case you have to |
|
|
2128 | compile libev with the same flags to get binary compatibility. This is |
|
|
2129 | obviously the case with any flags that change the \s-1ABI\s0, but the problem is |
|
|
2130 | most noticeably displayed with ev_stat and large file support. |
|
|
2131 | .PP |
|
|
2132 | The solution for this is to lobby your distribution maker to make large |
|
|
2133 | file interfaces available by default (as e.g. FreeBSD does) and not |
|
|
2134 | optional. Libev cannot simply switch on large file support because it has |
|
|
2135 | to exchange stat structures with application programs compiled using the |
|
|
2136 | default compilation environment. |
|
|
2137 | .PP |
|
|
2138 | \fIInotify and Kqueue\fR |
|
|
2139 | .IX Subsection "Inotify and Kqueue" |
|
|
2140 | .PP |
|
|
2141 | When \f(CW\*(C`inotify (7)\*(C'\fR support has been compiled into libev and present at |
|
|
2142 | runtime, it will be used to speed up change detection where possible. The |
|
|
2143 | inotify descriptor will be created lazily when the first \f(CW\*(C`ev_stat\*(C'\fR |
|
|
2144 | watcher is being started. |
|
|
2145 | .PP |
|
|
2146 | Inotify presence does not change the semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers |
|
|
2147 | except that changes might be detected earlier, and in some cases, to avoid |
|
|
2148 | making regular \f(CW\*(C`stat\*(C'\fR calls. Even in the presence of inotify support |
|
|
2149 | there are many cases where libev has to resort to regular \f(CW\*(C`stat\*(C'\fR polling, |
|
|
2150 | but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too |
|
|
2151 | many bugs), the path exists (i.e. stat succeeds), and the path resides on |
|
|
2152 | a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and |
|
|
2153 | xfs are fully working) libev usually gets away without polling. |
|
|
2154 | .PP |
|
|
2155 | There is no support for kqueue, as apparently it cannot be used to |
|
|
2156 | implement this functionality, due to the requirement of having a file |
|
|
2157 | descriptor open on the object at all times, and detecting renames, unlinks |
|
|
2158 | etc. is difficult. |
|
|
2159 | .PP |
|
|
2160 | \fI\f(CI\*(C`stat ()\*(C'\fI is a synchronous operation\fR |
|
|
2161 | .IX Subsection "stat () is a synchronous operation" |
|
|
2162 | .PP |
|
|
2163 | Libev doesn't normally do any kind of I/O itself, and so is not blocking |
|
|
2164 | the process. The exception are \f(CW\*(C`ev_stat\*(C'\fR watchers \- those call \f(CW\*(C`stat |
|
|
2165 | ()\*(C'\fR, which is a synchronous operation. |
|
|
2166 | .PP |
|
|
2167 | For local paths, this usually doesn't matter: unless the system is very |
|
|
2168 | busy or the intervals between stat's are large, a stat call will be fast, |
|
|
2169 | as the path data is usually in memory already (except when starting the |
|
|
2170 | watcher). |
|
|
2171 | .PP |
|
|
2172 | For networked file systems, calling \f(CW\*(C`stat ()\*(C'\fR can block an indefinite |
|
|
2173 | time due to network issues, and even under good conditions, a stat call |
|
|
2174 | often takes multiple milliseconds. |
|
|
2175 | .PP |
|
|
2176 | Therefore, it is best to avoid using \f(CW\*(C`ev_stat\*(C'\fR watchers on networked |
|
|
2177 | paths, although this is fully supported by libev. |
|
|
2178 | .PP |
|
|
2179 | \fIThe special problem of stat time resolution\fR |
|
|
2180 | .IX Subsection "The special problem of stat time resolution" |
|
|
2181 | .PP |
|
|
2182 | The \f(CW\*(C`stat ()\*(C'\fR system call only supports full-second resolution portably, |
|
|
2183 | and even on systems where the resolution is higher, most file systems |
|
|
2184 | still only support whole seconds. |
|
|
2185 | .PP |
|
|
2186 | That means that, if the time is the only thing that changes, you can |
|
|
2187 | easily miss updates: on the first update, \f(CW\*(C`ev_stat\*(C'\fR detects a change and |
|
|
2188 | calls your callback, which does something. When there is another update |
|
|
2189 | within the same second, \f(CW\*(C`ev_stat\*(C'\fR will be unable to detect unless the |
|
|
2190 | stat data does change in other ways (e.g. file size). |
|
|
2191 | .PP |
|
|
2192 | The solution to this is to delay acting on a change for slightly more |
|
|
2193 | than a second (or till slightly after the next full second boundary), using |
|
|
2194 | a roughly one-second-delay \f(CW\*(C`ev_timer\*(C'\fR (e.g. \f(CW\*(C`ev_timer_set (w, 0., 1.02); |
|
|
2195 | ev_timer_again (loop, w)\*(C'\fR). |
|
|
2196 | .PP |
|
|
2197 | The \f(CW.02\fR offset is added to work around small timing inconsistencies |
|
|
2198 | of some operating systems (where the second counter of the current time |
|
|
2199 | might be be delayed. One such system is the Linux kernel, where a call to |
|
|
2200 | \&\f(CW\*(C`gettimeofday\*(C'\fR might return a timestamp with a full second later than |
|
|
2201 | a subsequent \f(CW\*(C`time\*(C'\fR call \- if the equivalent of \f(CW\*(C`time ()\*(C'\fR is used to |
|
|
2202 | update file times then there will be a small window where the kernel uses |
|
|
2203 | the previous second to update file times but libev might already execute |
|
|
2204 | the timer callback). |
|
|
2205 | .PP |
|
|
2206 | \fIWatcher-Specific Functions and Data Members\fR |
|
|
2207 | .IX Subsection "Watcher-Specific Functions and Data Members" |
|
|
2208 | .IP "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 4 |
|
|
2209 | .IX Item "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" |
|
|
2210 | .PD 0 |
|
|
2211 | .IP "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" 4 |
|
|
2212 | .IX Item "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" |
|
|
2213 | .PD |
|
|
2214 | Configures the watcher to wait for status changes of the given |
|
|
2215 | \&\f(CW\*(C`path\*(C'\fR. The \f(CW\*(C`interval\*(C'\fR is a hint on how quickly a change is expected to |
|
|
2216 | be detected and should normally be specified as \f(CW0\fR to let libev choose |
|
|
2217 | a suitable value. The memory pointed to by \f(CW\*(C`path\*(C'\fR must point to the same |
|
|
2218 | path for as long as the watcher is active. |
|
|
2219 | .Sp |
|
|
2220 | The callback will receive an \f(CW\*(C`EV_STAT\*(C'\fR event when a change was detected, |
|
|
2221 | relative to the attributes at the time the watcher was started (or the |
|
|
2222 | last change was detected). |
|
|
2223 | .IP "ev_stat_stat (loop, ev_stat *)" 4 |
|
|
2224 | .IX Item "ev_stat_stat (loop, ev_stat *)" |
|
|
2225 | Updates the stat buffer immediately with new values. If you change the |
|
|
2226 | watched path in your callback, you could call this function to avoid |
|
|
2227 | detecting this change (while introducing a race condition if you are not |
|
|
2228 | the only one changing the path). Can also be useful simply to find out the |
|
|
2229 | new values. |
|
|
2230 | .IP "ev_statdata attr [read\-only]" 4 |
|
|
2231 | .IX Item "ev_statdata attr [read-only]" |
|
|
2232 | The most-recently detected attributes of the file. Although the type is |
|
|
2233 | \&\f(CW\*(C`ev_statdata\*(C'\fR, this is usually the (or one of the) \f(CW\*(C`struct stat\*(C'\fR types |
|
|
2234 | suitable for your system, but you can only rely on the POSIX-standardised |
|
|
2235 | members to be present. If the \f(CW\*(C`st_nlink\*(C'\fR member is \f(CW0\fR, then there was |
|
|
2236 | some error while \f(CW\*(C`stat\*(C'\fRing the file. |
|
|
2237 | .IP "ev_statdata prev [read\-only]" 4 |
|
|
2238 | .IX Item "ev_statdata prev [read-only]" |
|
|
2239 | The previous attributes of the file. The callback gets invoked whenever |
|
|
2240 | \&\f(CW\*(C`prev\*(C'\fR != \f(CW\*(C`attr\*(C'\fR, or, more precisely, one or more of these members |
|
|
2241 | 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, |
|
|
2242 | \&\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. |
|
|
2243 | .IP "ev_tstamp interval [read\-only]" 4 |
|
|
2244 | .IX Item "ev_tstamp interval [read-only]" |
|
|
2245 | The specified interval. |
|
|
2246 | .IP "const char *path [read\-only]" 4 |
|
|
2247 | .IX Item "const char *path [read-only]" |
|
|
2248 | The file system path that is being watched. |
|
|
2249 | .PP |
|
|
2250 | \fIExamples\fR |
|
|
2251 | .IX Subsection "Examples" |
|
|
2252 | .PP |
|
|
2253 | Example: Watch \f(CW\*(C`/etc/passwd\*(C'\fR for attribute changes. |
|
|
2254 | .PP |
|
|
2255 | .Vb 10 |
|
|
2256 | \& static void |
|
|
2257 | \& passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) |
|
|
2258 | \& { |
|
|
2259 | \& /* /etc/passwd changed in some way */ |
|
|
2260 | \& if (w\->attr.st_nlink) |
|
|
2261 | \& { |
|
|
2262 | \& printf ("passwd current size %ld\en", (long)w\->attr.st_size); |
|
|
2263 | \& printf ("passwd current atime %ld\en", (long)w\->attr.st_mtime); |
|
|
2264 | \& printf ("passwd current mtime %ld\en", (long)w\->attr.st_mtime); |
|
|
2265 | \& } |
|
|
2266 | \& else |
|
|
2267 | \& /* you shalt not abuse printf for puts */ |
|
|
2268 | \& puts ("wow, /etc/passwd is not there, expect problems. " |
|
|
2269 | \& "if this is windows, they already arrived\en"); |
|
|
2270 | \& } |
|
|
2271 | \& |
|
|
2272 | \& ... |
|
|
2273 | \& ev_stat passwd; |
|
|
2274 | \& |
|
|
2275 | \& ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.); |
|
|
2276 | \& ev_stat_start (loop, &passwd); |
|
|
2277 | .Ve |
|
|
2278 | .PP |
|
|
2279 | Example: Like above, but additionally use a one-second delay so we do not |
|
|
2280 | miss updates (however, frequent updates will delay processing, too, so |
|
|
2281 | one might do the work both on \f(CW\*(C`ev_stat\*(C'\fR callback invocation \fIand\fR on |
|
|
2282 | \&\f(CW\*(C`ev_timer\*(C'\fR callback invocation). |
|
|
2283 | .PP |
|
|
2284 | .Vb 2 |
|
|
2285 | \& static ev_stat passwd; |
|
|
2286 | \& static ev_timer timer; |
|
|
2287 | \& |
|
|
2288 | \& static void |
|
|
2289 | \& timer_cb (EV_P_ ev_timer *w, int revents) |
|
|
2290 | \& { |
|
|
2291 | \& ev_timer_stop (EV_A_ w); |
|
|
2292 | \& |
|
|
2293 | \& /* now it\*(Aqs one second after the most recent passwd change */ |
|
|
2294 | \& } |
|
|
2295 | \& |
|
|
2296 | \& static void |
|
|
2297 | \& stat_cb (EV_P_ ev_stat *w, int revents) |
|
|
2298 | \& { |
|
|
2299 | \& /* reset the one\-second timer */ |
|
|
2300 | \& ev_timer_again (EV_A_ &timer); |
|
|
2301 | \& } |
|
|
2302 | \& |
|
|
2303 | \& ... |
|
|
2304 | \& ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
|
|
2305 | \& ev_stat_start (loop, &passwd); |
|
|
2306 | \& ev_timer_init (&timer, timer_cb, 0., 1.02); |
|
|
2307 | .Ve |
788 | .ie n .Sh """ev_idle"" \- when you've got nothing better to do" |
2308 | .ie n .Sh """ev_idle"" \- when you've got nothing better to do..." |
789 | .el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do" |
2309 | .el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do..." |
790 | .IX Subsection "ev_idle - when you've got nothing better to do" |
2310 | .IX Subsection "ev_idle - when you've got nothing better to do..." |
791 | Idle watchers trigger events when there are no other events are pending |
2311 | Idle watchers trigger events when no other events of the same or higher |
792 | (prepare, check and other idle watchers do not count). That is, as long |
2312 | priority are pending (prepare, check and other idle watchers do not count |
793 | as your process is busy handling sockets or timeouts (or even signals, |
2313 | as receiving \*(L"events\*(R"). |
794 | imagine) it will not be triggered. But when your process is idle all idle |
2314 | .PP |
795 | watchers are being called again and again, once per event loop iteration \- |
2315 | That is, as long as your process is busy handling sockets or timeouts |
|
|
2316 | (or even signals, imagine) of the same or higher priority it will not be |
|
|
2317 | triggered. But when your process is idle (or only lower-priority watchers |
|
|
2318 | are pending), the idle watchers are being called once per event loop |
796 | until stopped, that is, or your process receives more events and becomes |
2319 | iteration \- until stopped, that is, or your process receives more events |
797 | busy. |
2320 | and becomes busy again with higher priority stuff. |
798 | .PP |
2321 | .PP |
799 | The most noteworthy effect is that as long as any idle watchers are |
2322 | The most noteworthy effect is that as long as any idle watchers are |
800 | active, the process will not block when waiting for new events. |
2323 | active, the process will not block when waiting for new events. |
801 | .PP |
2324 | .PP |
802 | Apart from keeping your process non-blocking (which is a useful |
2325 | Apart from keeping your process non-blocking (which is a useful |
803 | effect on its own sometimes), idle watchers are a good place to do |
2326 | effect on its own sometimes), idle watchers are a good place to do |
804 | \&\*(L"pseudo\-background processing\*(R", or delay processing stuff to after the |
2327 | \&\*(L"pseudo-background processing\*(R", or delay processing stuff to after the |
805 | event loop has handled all outstanding events. |
2328 | event loop has handled all outstanding events. |
|
|
2329 | .PP |
|
|
2330 | \fIWatcher-Specific Functions and Data Members\fR |
|
|
2331 | .IX Subsection "Watcher-Specific Functions and Data Members" |
806 | .IP "ev_idle_init (ev_signal *, callback)" 4 |
2332 | .IP "ev_idle_init (ev_signal *, callback)" 4 |
807 | .IX Item "ev_idle_init (ev_signal *, callback)" |
2333 | .IX Item "ev_idle_init (ev_signal *, callback)" |
808 | Initialises and configures the idle watcher \- it has no parameters of any |
2334 | Initialises and configures the idle watcher \- it has no parameters of any |
809 | kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless, |
2335 | kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless, |
810 | believe me. |
2336 | believe me. |
|
|
2337 | .PP |
|
|
2338 | \fIExamples\fR |
|
|
2339 | .IX Subsection "Examples" |
|
|
2340 | .PP |
|
|
2341 | Example: Dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR watcher, start it, and in the |
|
|
2342 | callback, free it. Also, use no error checking, as usual. |
|
|
2343 | .PP |
|
|
2344 | .Vb 7 |
|
|
2345 | \& static void |
|
|
2346 | \& idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
|
|
2347 | \& { |
|
|
2348 | \& free (w); |
|
|
2349 | \& // now do something you wanted to do when the program has |
|
|
2350 | \& // no longer anything immediate to do. |
|
|
2351 | \& } |
|
|
2352 | \& |
|
|
2353 | \& ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
|
|
2354 | \& ev_idle_init (idle_watcher, idle_cb); |
|
|
2355 | \& ev_idle_start (loop, idle_cb); |
|
|
2356 | .Ve |
811 | .ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop" |
2357 | .ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop!" |
812 | .el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop" |
2358 | .el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!" |
813 | .IX Subsection "ev_prepare and ev_check - customise your event loop" |
2359 | .IX Subsection "ev_prepare and ev_check - customise your event loop!" |
814 | Prepare and check watchers are usually (but not always) used in tandem: |
2360 | Prepare and check watchers are usually (but not always) used in pairs: |
815 | prepare watchers get invoked before the process blocks and check watchers |
2361 | prepare watchers get invoked before the process blocks and check watchers |
816 | afterwards. |
2362 | afterwards. |
817 | .PP |
2363 | .PP |
|
|
2364 | You \fImust not\fR call \f(CW\*(C`ev_loop\*(C'\fR or similar functions that enter |
|
|
2365 | the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR |
|
|
2366 | watchers. Other loops than the current one are fine, however. The |
|
|
2367 | rationale behind this is that you do not need to check for recursion in |
|
|
2368 | those watchers, i.e. the sequence will always be \f(CW\*(C`ev_prepare\*(C'\fR, blocking, |
|
|
2369 | \&\f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each kind they will always be |
|
|
2370 | called in pairs bracketing the blocking call. |
|
|
2371 | .PP |
818 | Their main purpose is to integrate other event mechanisms into libev. This |
2372 | Their main purpose is to integrate other event mechanisms into libev and |
819 | could be used, for example, to track variable changes, implement your own |
2373 | their use is somewhat advanced. They could be used, for example, to track |
820 | watchers, integrate net-snmp or a coroutine library and lots more. |
2374 | variable changes, implement your own watchers, integrate net-snmp or a |
|
|
2375 | coroutine library and lots more. They are also occasionally useful if |
|
|
2376 | you cache some data and want to flush it before blocking (for example, |
|
|
2377 | in X programs you might want to do an \f(CW\*(C`XFlush ()\*(C'\fR in an \f(CW\*(C`ev_prepare\*(C'\fR |
|
|
2378 | watcher). |
821 | .PP |
2379 | .PP |
822 | This is done by examining in each prepare call which file descriptors need |
2380 | This is done by examining in each prepare call which file descriptors |
823 | to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for |
2381 | need to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers |
824 | them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries |
2382 | for them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many |
825 | provide just this functionality). Then, in the check watcher you check for |
2383 | libraries provide exactly this functionality). Then, in the check watcher, |
826 | any events that occured (by checking the pending status of all watchers |
2384 | you check for any events that occurred (by checking the pending status |
827 | and stopping them) and call back into the library. The I/O and timer |
2385 | of all watchers and stopping them) and call back into the library. The |
828 | callbacks will never actually be called (but must be valid nevertheless, |
2386 | I/O and timer callbacks will never actually be called (but must be valid |
829 | because you never know, you know?). |
2387 | nevertheless, because you never know, you know?). |
830 | .PP |
2388 | .PP |
831 | As another example, the Perl Coro module uses these hooks to integrate |
2389 | As another example, the Perl Coro module uses these hooks to integrate |
832 | coroutines into libev programs, by yielding to other active coroutines |
2390 | coroutines into libev programs, by yielding to other active coroutines |
833 | during each prepare and only letting the process block if no coroutines |
2391 | during each prepare and only letting the process block if no coroutines |
834 | are ready to run (it's actually more complicated: it only runs coroutines |
2392 | are ready to run (it's actually more complicated: it only runs coroutines |
835 | with priority higher than or equal to the event loop and one coroutine |
2393 | with priority higher than or equal to the event loop and one coroutine |
836 | of lower priority, but only once, using idle watchers to keep the event |
2394 | of lower priority, but only once, using idle watchers to keep the event |
837 | loop from blocking if lower-priority coroutines are active, thus mapping |
2395 | loop from blocking if lower-priority coroutines are active, thus mapping |
838 | low-priority coroutines to idle/background tasks). |
2396 | low-priority coroutines to idle/background tasks). |
|
|
2397 | .PP |
|
|
2398 | It is recommended to give \f(CW\*(C`ev_check\*(C'\fR watchers highest (\f(CW\*(C`EV_MAXPRI\*(C'\fR) |
|
|
2399 | priority, to ensure that they are being run before any other watchers |
|
|
2400 | after the poll (this doesn't matter for \f(CW\*(C`ev_prepare\*(C'\fR watchers). |
|
|
2401 | .PP |
|
|
2402 | Also, \f(CW\*(C`ev_check\*(C'\fR watchers (and \f(CW\*(C`ev_prepare\*(C'\fR watchers, too) should not |
|
|
2403 | activate (\*(L"feed\*(R") events into libev. While libev fully supports this, they |
|
|
2404 | might get executed before other \f(CW\*(C`ev_check\*(C'\fR watchers did their job. As |
|
|
2405 | \&\f(CW\*(C`ev_check\*(C'\fR watchers are often used to embed other (non-libev) event |
|
|
2406 | loops those other event loops might be in an unusable state until their |
|
|
2407 | \&\f(CW\*(C`ev_check\*(C'\fR watcher ran (always remind yourself to coexist peacefully with |
|
|
2408 | others). |
|
|
2409 | .PP |
|
|
2410 | \fIWatcher-Specific Functions and Data Members\fR |
|
|
2411 | .IX Subsection "Watcher-Specific Functions and Data Members" |
839 | .IP "ev_prepare_init (ev_prepare *, callback)" 4 |
2412 | .IP "ev_prepare_init (ev_prepare *, callback)" 4 |
840 | .IX Item "ev_prepare_init (ev_prepare *, callback)" |
2413 | .IX Item "ev_prepare_init (ev_prepare *, callback)" |
841 | .PD 0 |
2414 | .PD 0 |
842 | .IP "ev_check_init (ev_check *, callback)" 4 |
2415 | .IP "ev_check_init (ev_check *, callback)" 4 |
843 | .IX Item "ev_check_init (ev_check *, callback)" |
2416 | .IX Item "ev_check_init (ev_check *, callback)" |
844 | .PD |
2417 | .PD |
845 | Initialises and configures the prepare or check watcher \- they have no |
2418 | Initialises and configures the prepare or check watcher \- they have no |
846 | parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR |
2419 | parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR |
847 | macros, but using them is utterly, utterly and completely pointless. |
2420 | macros, but using them is utterly, utterly, utterly and completely |
|
|
2421 | pointless. |
|
|
2422 | .PP |
|
|
2423 | \fIExamples\fR |
|
|
2424 | .IX Subsection "Examples" |
|
|
2425 | .PP |
|
|
2426 | There are a number of principal ways to embed other event loops or modules |
|
|
2427 | into libev. Here are some ideas on how to include libadns into libev |
|
|
2428 | (there is a Perl module named \f(CW\*(C`EV::ADNS\*(C'\fR that does this, which you could |
|
|
2429 | use as a working example. Another Perl module named \f(CW\*(C`EV::Glib\*(C'\fR embeds a |
|
|
2430 | Glib main context into libev, and finally, \f(CW\*(C`Glib::EV\*(C'\fR embeds \s-1EV\s0 into the |
|
|
2431 | Glib event loop). |
|
|
2432 | .PP |
|
|
2433 | Method 1: Add \s-1IO\s0 watchers and a timeout watcher in a prepare handler, |
|
|
2434 | and in a check watcher, destroy them and call into libadns. What follows |
|
|
2435 | is pseudo-code only of course. This requires you to either use a low |
|
|
2436 | priority for the check watcher or use \f(CW\*(C`ev_clear_pending\*(C'\fR explicitly, as |
|
|
2437 | the callbacks for the IO/timeout watchers might not have been called yet. |
|
|
2438 | .PP |
|
|
2439 | .Vb 2 |
|
|
2440 | \& static ev_io iow [nfd]; |
|
|
2441 | \& static ev_timer tw; |
|
|
2442 | \& |
|
|
2443 | \& static void |
|
|
2444 | \& io_cb (struct ev_loop *loop, ev_io *w, int revents) |
|
|
2445 | \& { |
|
|
2446 | \& } |
|
|
2447 | \& |
|
|
2448 | \& // create io watchers for each fd and a timer before blocking |
|
|
2449 | \& static void |
|
|
2450 | \& adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents) |
|
|
2451 | \& { |
|
|
2452 | \& int timeout = 3600000; |
|
|
2453 | \& struct pollfd fds [nfd]; |
|
|
2454 | \& // actual code will need to loop here and realloc etc. |
|
|
2455 | \& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
|
|
2456 | \& |
|
|
2457 | \& /* the callback is illegal, but won\*(Aqt be called as we stop during check */ |
|
|
2458 | \& ev_timer_init (&tw, 0, timeout * 1e\-3); |
|
|
2459 | \& ev_timer_start (loop, &tw); |
|
|
2460 | \& |
|
|
2461 | \& // create one ev_io per pollfd |
|
|
2462 | \& for (int i = 0; i < nfd; ++i) |
|
|
2463 | \& { |
|
|
2464 | \& ev_io_init (iow + i, io_cb, fds [i].fd, |
|
|
2465 | \& ((fds [i].events & POLLIN ? EV_READ : 0) |
|
|
2466 | \& | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
|
|
2467 | \& |
|
|
2468 | \& fds [i].revents = 0; |
|
|
2469 | \& ev_io_start (loop, iow + i); |
|
|
2470 | \& } |
|
|
2471 | \& } |
|
|
2472 | \& |
|
|
2473 | \& // stop all watchers after blocking |
|
|
2474 | \& static void |
|
|
2475 | \& adns_check_cb (struct ev_loop *loop, ev_check *w, int revents) |
|
|
2476 | \& { |
|
|
2477 | \& ev_timer_stop (loop, &tw); |
|
|
2478 | \& |
|
|
2479 | \& for (int i = 0; i < nfd; ++i) |
|
|
2480 | \& { |
|
|
2481 | \& // set the relevant poll flags |
|
|
2482 | \& // could also call adns_processreadable etc. here |
|
|
2483 | \& struct pollfd *fd = fds + i; |
|
|
2484 | \& int revents = ev_clear_pending (iow + i); |
|
|
2485 | \& if (revents & EV_READ ) fd\->revents |= fd\->events & POLLIN; |
|
|
2486 | \& if (revents & EV_WRITE) fd\->revents |= fd\->events & POLLOUT; |
|
|
2487 | \& |
|
|
2488 | \& // now stop the watcher |
|
|
2489 | \& ev_io_stop (loop, iow + i); |
|
|
2490 | \& } |
|
|
2491 | \& |
|
|
2492 | \& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
|
|
2493 | \& } |
|
|
2494 | .Ve |
|
|
2495 | .PP |
|
|
2496 | Method 2: This would be just like method 1, but you run \f(CW\*(C`adns_afterpoll\*(C'\fR |
|
|
2497 | in the prepare watcher and would dispose of the check watcher. |
|
|
2498 | .PP |
|
|
2499 | Method 3: If the module to be embedded supports explicit event |
|
|
2500 | notification (libadns does), you can also make use of the actual watcher |
|
|
2501 | callbacks, and only destroy/create the watchers in the prepare watcher. |
|
|
2502 | .PP |
|
|
2503 | .Vb 5 |
|
|
2504 | \& static void |
|
|
2505 | \& timer_cb (EV_P_ ev_timer *w, int revents) |
|
|
2506 | \& { |
|
|
2507 | \& adns_state ads = (adns_state)w\->data; |
|
|
2508 | \& update_now (EV_A); |
|
|
2509 | \& |
|
|
2510 | \& adns_processtimeouts (ads, &tv_now); |
|
|
2511 | \& } |
|
|
2512 | \& |
|
|
2513 | \& static void |
|
|
2514 | \& io_cb (EV_P_ ev_io *w, int revents) |
|
|
2515 | \& { |
|
|
2516 | \& adns_state ads = (adns_state)w\->data; |
|
|
2517 | \& update_now (EV_A); |
|
|
2518 | \& |
|
|
2519 | \& if (revents & EV_READ ) adns_processreadable (ads, w\->fd, &tv_now); |
|
|
2520 | \& if (revents & EV_WRITE) adns_processwriteable (ads, w\->fd, &tv_now); |
|
|
2521 | \& } |
|
|
2522 | \& |
|
|
2523 | \& // do not ever call adns_afterpoll |
|
|
2524 | .Ve |
|
|
2525 | .PP |
|
|
2526 | Method 4: Do not use a prepare or check watcher because the module you |
|
|
2527 | want to embed is not flexible enough to support it. Instead, you can |
|
|
2528 | override their poll function. The drawback with this solution is that the |
|
|
2529 | main loop is now no longer controllable by \s-1EV\s0. The \f(CW\*(C`Glib::EV\*(C'\fR module uses |
|
|
2530 | this approach, effectively embedding \s-1EV\s0 as a client into the horrible |
|
|
2531 | libglib event loop. |
|
|
2532 | .PP |
|
|
2533 | .Vb 4 |
|
|
2534 | \& static gint |
|
|
2535 | \& event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
|
|
2536 | \& { |
|
|
2537 | \& int got_events = 0; |
|
|
2538 | \& |
|
|
2539 | \& for (n = 0; n < nfds; ++n) |
|
|
2540 | \& // create/start io watcher that sets the relevant bits in fds[n] and increment got_events |
|
|
2541 | \& |
|
|
2542 | \& if (timeout >= 0) |
|
|
2543 | \& // create/start timer |
|
|
2544 | \& |
|
|
2545 | \& // poll |
|
|
2546 | \& ev_loop (EV_A_ 0); |
|
|
2547 | \& |
|
|
2548 | \& // stop timer again |
|
|
2549 | \& if (timeout >= 0) |
|
|
2550 | \& ev_timer_stop (EV_A_ &to); |
|
|
2551 | \& |
|
|
2552 | \& // stop io watchers again \- their callbacks should have set |
|
|
2553 | \& for (n = 0; n < nfds; ++n) |
|
|
2554 | \& ev_io_stop (EV_A_ iow [n]); |
|
|
2555 | \& |
|
|
2556 | \& return got_events; |
|
|
2557 | \& } |
|
|
2558 | .Ve |
|
|
2559 | .ie n .Sh """ev_embed"" \- when one backend isn't enough..." |
|
|
2560 | .el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..." |
|
|
2561 | .IX Subsection "ev_embed - when one backend isn't enough..." |
|
|
2562 | This is a rather advanced watcher type that lets you embed one event loop |
|
|
2563 | into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded |
|
|
2564 | loop, other types of watchers might be handled in a delayed or incorrect |
|
|
2565 | fashion and must not be used). |
|
|
2566 | .PP |
|
|
2567 | There are primarily two reasons you would want that: work around bugs and |
|
|
2568 | prioritise I/O. |
|
|
2569 | .PP |
|
|
2570 | As an example for a bug workaround, the kqueue backend might only support |
|
|
2571 | sockets on some platform, so it is unusable as generic backend, but you |
|
|
2572 | still want to make use of it because you have many sockets and it scales |
|
|
2573 | so nicely. In this case, you would create a kqueue-based loop and embed |
|
|
2574 | it into your default loop (which might use e.g. poll). Overall operation |
|
|
2575 | will be a bit slower because first libev has to call \f(CW\*(C`poll\*(C'\fR and then |
|
|
2576 | \&\f(CW\*(C`kevent\*(C'\fR, but at least you can use both mechanisms for what they are |
|
|
2577 | best: \f(CW\*(C`kqueue\*(C'\fR for scalable sockets and \f(CW\*(C`poll\*(C'\fR if you want it to work :) |
|
|
2578 | .PP |
|
|
2579 | As for prioritising I/O: under rare circumstances you have the case where |
|
|
2580 | some fds have to be watched and handled very quickly (with low latency), |
|
|
2581 | and even priorities and idle watchers might have too much overhead. In |
|
|
2582 | this case you would put all the high priority stuff in one loop and all |
|
|
2583 | the rest in a second one, and embed the second one in the first. |
|
|
2584 | .PP |
|
|
2585 | As long as the watcher is active, the callback will be invoked every |
|
|
2586 | time there might be events pending in the embedded loop. The callback |
|
|
2587 | must then call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single |
|
|
2588 | sweep and invoke their callbacks (the callback doesn't need to invoke the |
|
|
2589 | \&\f(CW\*(C`ev_embed_sweep\*(C'\fR function directly, it could also start an idle watcher |
|
|
2590 | to give the embedded loop strictly lower priority for example). |
|
|
2591 | .PP |
|
|
2592 | You can also set the callback to \f(CW0\fR, in which case the embed watcher |
|
|
2593 | will automatically execute the embedded loop sweep whenever necessary. |
|
|
2594 | .PP |
|
|
2595 | Fork detection will be handled transparently while the \f(CW\*(C`ev_embed\*(C'\fR watcher |
|
|
2596 | is active, i.e., the embedded loop will automatically be forked when the |
|
|
2597 | embedding loop forks. In other cases, the user is responsible for calling |
|
|
2598 | \&\f(CW\*(C`ev_loop_fork\*(C'\fR on the embedded loop. |
|
|
2599 | .PP |
|
|
2600 | Unfortunately, not all backends are embeddable: only the ones returned by |
|
|
2601 | \&\f(CW\*(C`ev_embeddable_backends\*(C'\fR are, which, unfortunately, does not include any |
|
|
2602 | portable one. |
|
|
2603 | .PP |
|
|
2604 | So when you want to use this feature you will always have to be prepared |
|
|
2605 | that you cannot get an embeddable loop. The recommended way to get around |
|
|
2606 | this is to have a separate variables for your embeddable loop, try to |
|
|
2607 | create it, and if that fails, use the normal loop for everything. |
|
|
2608 | .PP |
|
|
2609 | \fI\f(CI\*(C`ev_embed\*(C'\fI and fork\fR |
|
|
2610 | .IX Subsection "ev_embed and fork" |
|
|
2611 | .PP |
|
|
2612 | While the \f(CW\*(C`ev_embed\*(C'\fR watcher is running, forks in the embedding loop will |
|
|
2613 | automatically be applied to the embedded loop as well, so no special |
|
|
2614 | fork handling is required in that case. When the watcher is not running, |
|
|
2615 | however, it is still the task of the libev user to call \f(CW\*(C`ev_loop_fork ()\*(C'\fR |
|
|
2616 | as applicable. |
|
|
2617 | .PP |
|
|
2618 | \fIWatcher-Specific Functions and Data Members\fR |
|
|
2619 | .IX Subsection "Watcher-Specific Functions and Data Members" |
|
|
2620 | .IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4 |
|
|
2621 | .IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" |
|
|
2622 | .PD 0 |
|
|
2623 | .IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4 |
|
|
2624 | .IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" |
|
|
2625 | .PD |
|
|
2626 | Configures the watcher to embed the given loop, which must be |
|
|
2627 | embeddable. If the callback is \f(CW0\fR, then \f(CW\*(C`ev_embed_sweep\*(C'\fR will be |
|
|
2628 | invoked automatically, otherwise it is the responsibility of the callback |
|
|
2629 | to invoke it (it will continue to be called until the sweep has been done, |
|
|
2630 | if you do not want that, you need to temporarily stop the embed watcher). |
|
|
2631 | .IP "ev_embed_sweep (loop, ev_embed *)" 4 |
|
|
2632 | .IX Item "ev_embed_sweep (loop, ev_embed *)" |
|
|
2633 | Make a single, non-blocking sweep over the embedded loop. This works |
|
|
2634 | similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most |
|
|
2635 | appropriate way for embedded loops. |
|
|
2636 | .IP "struct ev_loop *other [read\-only]" 4 |
|
|
2637 | .IX Item "struct ev_loop *other [read-only]" |
|
|
2638 | The embedded event loop. |
|
|
2639 | .PP |
|
|
2640 | \fIExamples\fR |
|
|
2641 | .IX Subsection "Examples" |
|
|
2642 | .PP |
|
|
2643 | Example: Try to get an embeddable event loop and embed it into the default |
|
|
2644 | event loop. If that is not possible, use the default loop. The default |
|
|
2645 | loop is stored in \f(CW\*(C`loop_hi\*(C'\fR, while the embeddable loop is stored in |
|
|
2646 | \&\f(CW\*(C`loop_lo\*(C'\fR (which is \f(CW\*(C`loop_hi\*(C'\fR in the case no embeddable loop can be |
|
|
2647 | used). |
|
|
2648 | .PP |
|
|
2649 | .Vb 3 |
|
|
2650 | \& struct ev_loop *loop_hi = ev_default_init (0); |
|
|
2651 | \& struct ev_loop *loop_lo = 0; |
|
|
2652 | \& ev_embed embed; |
|
|
2653 | \& |
|
|
2654 | \& // see if there is a chance of getting one that works |
|
|
2655 | \& // (remember that a flags value of 0 means autodetection) |
|
|
2656 | \& loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
|
|
2657 | \& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
|
|
2658 | \& : 0; |
|
|
2659 | \& |
|
|
2660 | \& // if we got one, then embed it, otherwise default to loop_hi |
|
|
2661 | \& if (loop_lo) |
|
|
2662 | \& { |
|
|
2663 | \& ev_embed_init (&embed, 0, loop_lo); |
|
|
2664 | \& ev_embed_start (loop_hi, &embed); |
|
|
2665 | \& } |
|
|
2666 | \& else |
|
|
2667 | \& loop_lo = loop_hi; |
|
|
2668 | .Ve |
|
|
2669 | .PP |
|
|
2670 | Example: Check if kqueue is available but not recommended and create |
|
|
2671 | a kqueue backend for use with sockets (which usually work with any |
|
|
2672 | kqueue implementation). Store the kqueue/socket\-only event loop in |
|
|
2673 | \&\f(CW\*(C`loop_socket\*(C'\fR. (One might optionally use \f(CW\*(C`EVFLAG_NOENV\*(C'\fR, too). |
|
|
2674 | .PP |
|
|
2675 | .Vb 3 |
|
|
2676 | \& struct ev_loop *loop = ev_default_init (0); |
|
|
2677 | \& struct ev_loop *loop_socket = 0; |
|
|
2678 | \& ev_embed embed; |
|
|
2679 | \& |
|
|
2680 | \& if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
|
|
2681 | \& if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
|
|
2682 | \& { |
|
|
2683 | \& ev_embed_init (&embed, 0, loop_socket); |
|
|
2684 | \& ev_embed_start (loop, &embed); |
|
|
2685 | \& } |
|
|
2686 | \& |
|
|
2687 | \& if (!loop_socket) |
|
|
2688 | \& loop_socket = loop; |
|
|
2689 | \& |
|
|
2690 | \& // now use loop_socket for all sockets, and loop for everything else |
|
|
2691 | .Ve |
|
|
2692 | .ie n .Sh """ev_fork"" \- the audacity to resume the event loop after a fork" |
|
|
2693 | .el .Sh "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork" |
|
|
2694 | .IX Subsection "ev_fork - the audacity to resume the event loop after a fork" |
|
|
2695 | Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because |
|
|
2696 | whoever is a good citizen cared to tell libev about it by calling |
|
|
2697 | \&\f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the |
|
|
2698 | event loop blocks next and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called, |
|
|
2699 | and only in the child after the fork. If whoever good citizen calling |
|
|
2700 | \&\f(CW\*(C`ev_default_fork\*(C'\fR cheats and calls it in the wrong process, the fork |
|
|
2701 | handlers will be invoked, too, of course. |
|
|
2702 | .PP |
|
|
2703 | \fIWatcher-Specific Functions and Data Members\fR |
|
|
2704 | .IX Subsection "Watcher-Specific Functions and Data Members" |
|
|
2705 | .IP "ev_fork_init (ev_signal *, callback)" 4 |
|
|
2706 | .IX Item "ev_fork_init (ev_signal *, callback)" |
|
|
2707 | Initialises and configures the fork watcher \- it has no parameters of any |
|
|
2708 | kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless, |
|
|
2709 | believe me. |
|
|
2710 | .ie n .Sh """ev_async"" \- how to wake up another event loop" |
|
|
2711 | .el .Sh "\f(CWev_async\fP \- how to wake up another event loop" |
|
|
2712 | .IX Subsection "ev_async - how to wake up another event loop" |
|
|
2713 | In general, you cannot use an \f(CW\*(C`ev_loop\*(C'\fR from multiple threads or other |
|
|
2714 | asynchronous sources such as signal handlers (as opposed to multiple event |
|
|
2715 | loops \- those are of course safe to use in different threads). |
|
|
2716 | .PP |
|
|
2717 | Sometimes, however, you need to wake up another event loop you do not |
|
|
2718 | control, for example because it belongs to another thread. This is what |
|
|
2719 | \&\f(CW\*(C`ev_async\*(C'\fR watchers do: as long as the \f(CW\*(C`ev_async\*(C'\fR watcher is active, you |
|
|
2720 | can signal it by calling \f(CW\*(C`ev_async_send\*(C'\fR, which is thread\- and signal |
|
|
2721 | safe. |
|
|
2722 | .PP |
|
|
2723 | This functionality is very similar to \f(CW\*(C`ev_signal\*(C'\fR watchers, as signals, |
|
|
2724 | too, are asynchronous in nature, and signals, too, will be compressed |
|
|
2725 | (i.e. the number of callback invocations may be less than the number of |
|
|
2726 | \&\f(CW\*(C`ev_async_sent\*(C'\fR calls). |
|
|
2727 | .PP |
|
|
2728 | Unlike \f(CW\*(C`ev_signal\*(C'\fR watchers, \f(CW\*(C`ev_async\*(C'\fR works with any event loop, not |
|
|
2729 | just the default loop. |
|
|
2730 | .PP |
|
|
2731 | \fIQueueing\fR |
|
|
2732 | .IX Subsection "Queueing" |
|
|
2733 | .PP |
|
|
2734 | \&\f(CW\*(C`ev_async\*(C'\fR does not support queueing of data in any way. The reason |
|
|
2735 | is that the author does not know of a simple (or any) algorithm for a |
|
|
2736 | multiple-writer-single-reader queue that works in all cases and doesn't |
|
|
2737 | need elaborate support such as pthreads. |
|
|
2738 | .PP |
|
|
2739 | That means that if you want to queue data, you have to provide your own |
|
|
2740 | queue. But at least I can tell you how to implement locking around your |
|
|
2741 | queue: |
|
|
2742 | .IP "queueing from a signal handler context" 4 |
|
|
2743 | .IX Item "queueing from a signal handler context" |
|
|
2744 | To implement race-free queueing, you simply add to the queue in the signal |
|
|
2745 | handler but you block the signal handler in the watcher callback. Here is |
|
|
2746 | an example that does that for some fictitious \s-1SIGUSR1\s0 handler: |
|
|
2747 | .Sp |
|
|
2748 | .Vb 1 |
|
|
2749 | \& static ev_async mysig; |
|
|
2750 | \& |
|
|
2751 | \& static void |
|
|
2752 | \& sigusr1_handler (void) |
|
|
2753 | \& { |
|
|
2754 | \& sometype data; |
|
|
2755 | \& |
|
|
2756 | \& // no locking etc. |
|
|
2757 | \& queue_put (data); |
|
|
2758 | \& ev_async_send (EV_DEFAULT_ &mysig); |
|
|
2759 | \& } |
|
|
2760 | \& |
|
|
2761 | \& static void |
|
|
2762 | \& mysig_cb (EV_P_ ev_async *w, int revents) |
|
|
2763 | \& { |
|
|
2764 | \& sometype data; |
|
|
2765 | \& sigset_t block, prev; |
|
|
2766 | \& |
|
|
2767 | \& sigemptyset (&block); |
|
|
2768 | \& sigaddset (&block, SIGUSR1); |
|
|
2769 | \& sigprocmask (SIG_BLOCK, &block, &prev); |
|
|
2770 | \& |
|
|
2771 | \& while (queue_get (&data)) |
|
|
2772 | \& process (data); |
|
|
2773 | \& |
|
|
2774 | \& if (sigismember (&prev, SIGUSR1) |
|
|
2775 | \& sigprocmask (SIG_UNBLOCK, &block, 0); |
|
|
2776 | \& } |
|
|
2777 | .Ve |
|
|
2778 | .Sp |
|
|
2779 | (Note: pthreads in theory requires you to use \f(CW\*(C`pthread_setmask\*(C'\fR |
|
|
2780 | instead of \f(CW\*(C`sigprocmask\*(C'\fR when you use threads, but libev doesn't do it |
|
|
2781 | either...). |
|
|
2782 | .IP "queueing from a thread context" 4 |
|
|
2783 | .IX Item "queueing from a thread context" |
|
|
2784 | The strategy for threads is different, as you cannot (easily) block |
|
|
2785 | threads but you can easily preempt them, so to queue safely you need to |
|
|
2786 | employ a traditional mutex lock, such as in this pthread example: |
|
|
2787 | .Sp |
|
|
2788 | .Vb 2 |
|
|
2789 | \& static ev_async mysig; |
|
|
2790 | \& static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER; |
|
|
2791 | \& |
|
|
2792 | \& static void |
|
|
2793 | \& otherthread (void) |
|
|
2794 | \& { |
|
|
2795 | \& // only need to lock the actual queueing operation |
|
|
2796 | \& pthread_mutex_lock (&mymutex); |
|
|
2797 | \& queue_put (data); |
|
|
2798 | \& pthread_mutex_unlock (&mymutex); |
|
|
2799 | \& |
|
|
2800 | \& ev_async_send (EV_DEFAULT_ &mysig); |
|
|
2801 | \& } |
|
|
2802 | \& |
|
|
2803 | \& static void |
|
|
2804 | \& mysig_cb (EV_P_ ev_async *w, int revents) |
|
|
2805 | \& { |
|
|
2806 | \& pthread_mutex_lock (&mymutex); |
|
|
2807 | \& |
|
|
2808 | \& while (queue_get (&data)) |
|
|
2809 | \& process (data); |
|
|
2810 | \& |
|
|
2811 | \& pthread_mutex_unlock (&mymutex); |
|
|
2812 | \& } |
|
|
2813 | .Ve |
|
|
2814 | .PP |
|
|
2815 | \fIWatcher-Specific Functions and Data Members\fR |
|
|
2816 | .IX Subsection "Watcher-Specific Functions and Data Members" |
|
|
2817 | .IP "ev_async_init (ev_async *, callback)" 4 |
|
|
2818 | .IX Item "ev_async_init (ev_async *, callback)" |
|
|
2819 | Initialises and configures the async watcher \- it has no parameters of any |
|
|
2820 | kind. There is a \f(CW\*(C`ev_async_set\*(C'\fR macro, but using it is utterly pointless, |
|
|
2821 | trust me. |
|
|
2822 | .IP "ev_async_send (loop, ev_async *)" 4 |
|
|
2823 | .IX Item "ev_async_send (loop, ev_async *)" |
|
|
2824 | Sends/signals/activates the given \f(CW\*(C`ev_async\*(C'\fR watcher, that is, feeds |
|
|
2825 | an \f(CW\*(C`EV_ASYNC\*(C'\fR event on the watcher into the event loop. Unlike |
|
|
2826 | \&\f(CW\*(C`ev_feed_event\*(C'\fR, this call is safe to do from other threads, signal or |
|
|
2827 | similar contexts (see the discussion of \f(CW\*(C`EV_ATOMIC_T\*(C'\fR in the embedding |
|
|
2828 | section below on what exactly this means). |
|
|
2829 | .Sp |
|
|
2830 | This call incurs the overhead of a system call only once per loop iteration, |
|
|
2831 | so while the overhead might be noticeable, it doesn't apply to repeated |
|
|
2832 | calls to \f(CW\*(C`ev_async_send\*(C'\fR. |
|
|
2833 | .IP "bool = ev_async_pending (ev_async *)" 4 |
|
|
2834 | .IX Item "bool = ev_async_pending (ev_async *)" |
|
|
2835 | Returns a non-zero value when \f(CW\*(C`ev_async_send\*(C'\fR has been called on the |
|
|
2836 | watcher but the event has not yet been processed (or even noted) by the |
|
|
2837 | event loop. |
|
|
2838 | .Sp |
|
|
2839 | \&\f(CW\*(C`ev_async_send\*(C'\fR sets a flag in the watcher and wakes up the loop. When |
|
|
2840 | the loop iterates next and checks for the watcher to have become active, |
|
|
2841 | it will reset the flag again. \f(CW\*(C`ev_async_pending\*(C'\fR can be used to very |
|
|
2842 | quickly check whether invoking the loop might be a good idea. |
|
|
2843 | .Sp |
|
|
2844 | Not that this does \fInot\fR check whether the watcher itself is pending, only |
|
|
2845 | whether it has been requested to make this watcher pending. |
848 | .SH "OTHER FUNCTIONS" |
2846 | .SH "OTHER FUNCTIONS" |
849 | .IX Header "OTHER FUNCTIONS" |
2847 | .IX Header "OTHER FUNCTIONS" |
850 | There are some other functions of possible interest. Described. Here. Now. |
2848 | There are some other functions of possible interest. Described. Here. Now. |
851 | .IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4 |
2849 | .IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4 |
852 | .IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" |
2850 | .IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" |
853 | This function combines a simple timer and an I/O watcher, calls your |
2851 | This function combines a simple timer and an I/O watcher, calls your |
854 | callback on whichever event happens first and automatically stop both |
2852 | callback on whichever event happens first and automatically stops both |
855 | watchers. This is useful if you want to wait for a single event on an fd |
2853 | watchers. This is useful if you want to wait for a single event on an fd |
856 | or timeout without having to allocate/configure/start/stop/free one or |
2854 | or timeout without having to allocate/configure/start/stop/free one or |
857 | more watchers yourself. |
2855 | more watchers yourself. |
858 | .Sp |
2856 | .Sp |
859 | If \f(CW\*(C`fd\*(C'\fR is less than 0, then no I/O watcher will be started and events |
2857 | If \f(CW\*(C`fd\*(C'\fR is less than 0, then no I/O watcher will be started and the |
860 | is being ignored. Otherwise, an \f(CW\*(C`ev_io\*(C'\fR watcher for the given \f(CW\*(C`fd\*(C'\fR and |
2858 | \&\f(CW\*(C`events\*(C'\fR argument is being ignored. Otherwise, an \f(CW\*(C`ev_io\*(C'\fR watcher for |
861 | \&\f(CW\*(C`events\*(C'\fR set will be craeted and started. |
2859 | the given \f(CW\*(C`fd\*(C'\fR and \f(CW\*(C`events\*(C'\fR set will be created and started. |
862 | .Sp |
2860 | .Sp |
863 | If \f(CW\*(C`timeout\*(C'\fR is less than 0, then no timeout watcher will be |
2861 | If \f(CW\*(C`timeout\*(C'\fR is less than 0, then no timeout watcher will be |
864 | started. Otherwise an \f(CW\*(C`ev_timer\*(C'\fR watcher with after = \f(CW\*(C`timeout\*(C'\fR (and |
2862 | started. Otherwise an \f(CW\*(C`ev_timer\*(C'\fR watcher with after = \f(CW\*(C`timeout\*(C'\fR (and |
865 | repeat = 0) will be started. While \f(CW0\fR is a valid timeout, it is of |
2863 | repeat = 0) will be started. \f(CW0\fR is a valid timeout. |
866 | dubious value. |
|
|
867 | .Sp |
2864 | .Sp |
868 | The callback has the type \f(CW\*(C`void (*cb)(int revents, void *arg)\*(C'\fR and gets |
2865 | The callback has the type \f(CW\*(C`void (*cb)(int revents, void *arg)\*(C'\fR and gets |
869 | passed an \f(CW\*(C`revents\*(C'\fR set like normal event callbacks (a combination of |
2866 | passed an \f(CW\*(C`revents\*(C'\fR set like normal event callbacks (a combination of |
870 | \&\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 |
2867 | \&\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 |
871 | value passed to \f(CW\*(C`ev_once\*(C'\fR: |
2868 | value passed to \f(CW\*(C`ev_once\*(C'\fR. Note that it is possible to receive \fIboth\fR |
|
|
2869 | a timeout and an io event at the same time \- you probably should give io |
|
|
2870 | events precedence. |
|
|
2871 | .Sp |
|
|
2872 | Example: wait up to ten seconds for data to appear on \s-1STDIN_FILENO\s0. |
872 | .Sp |
2873 | .Sp |
873 | .Vb 7 |
2874 | .Vb 7 |
874 | \& static void stdin_ready (int revents, void *arg) |
2875 | \& static void stdin_ready (int revents, void *arg) |
875 | \& { |
2876 | \& { |
876 | \& if (revents & EV_TIMEOUT) |
|
|
877 | \& /* doh, nothing entered */; |
|
|
878 | \& else if (revents & EV_READ) |
2877 | \& if (revents & EV_READ) |
879 | \& /* stdin might have data for us, joy! */; |
2878 | \& /* stdin might have data for us, joy! */; |
|
|
2879 | \& else if (revents & EV_TIMEOUT) |
|
|
2880 | \& /* doh, nothing entered */; |
880 | \& } |
2881 | \& } |
881 | .Ve |
2882 | \& |
882 | .Sp |
|
|
883 | .Vb 1 |
|
|
884 | \& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2883 | \& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
885 | .Ve |
2884 | .Ve |
886 | .IP "ev_feed_event (loop, watcher, int events)" 4 |
2885 | .IP "ev_feed_event (struct ev_loop *, watcher *, int revents)" 4 |
887 | .IX Item "ev_feed_event (loop, watcher, int events)" |
2886 | .IX Item "ev_feed_event (struct ev_loop *, watcher *, int revents)" |
888 | Feeds the given event set into the event loop, as if the specified event |
2887 | Feeds the given event set into the event loop, as if the specified event |
889 | had happened for the specified watcher (which must be a pointer to an |
2888 | had happened for the specified watcher (which must be a pointer to an |
890 | initialised but not necessarily started event watcher). |
2889 | initialised but not necessarily started event watcher). |
891 | .IP "ev_feed_fd_event (loop, int fd, int revents)" 4 |
2890 | .IP "ev_feed_fd_event (struct ev_loop *, int fd, int revents)" 4 |
892 | .IX Item "ev_feed_fd_event (loop, int fd, int revents)" |
2891 | .IX Item "ev_feed_fd_event (struct ev_loop *, int fd, int revents)" |
893 | Feed an event on the given fd, as if a file descriptor backend detected |
2892 | Feed an event on the given fd, as if a file descriptor backend detected |
894 | the given events it. |
2893 | the given events it. |
895 | .IP "ev_feed_signal_event (loop, int signum)" 4 |
2894 | .IP "ev_feed_signal_event (struct ev_loop *loop, int signum)" 4 |
896 | .IX Item "ev_feed_signal_event (loop, int signum)" |
2895 | .IX Item "ev_feed_signal_event (struct ev_loop *loop, int signum)" |
897 | Feed an event as if the given signal occured (loop must be the default loop!). |
2896 | Feed an event as if the given signal occurred (\f(CW\*(C`loop\*(C'\fR must be the default |
|
|
2897 | loop!). |
898 | .SH "LIBEVENT EMULATION" |
2898 | .SH "LIBEVENT EMULATION" |
899 | .IX Header "LIBEVENT EMULATION" |
2899 | .IX Header "LIBEVENT EMULATION" |
900 | Libev offers a compatibility emulation layer for libevent. It cannot |
2900 | Libev offers a compatibility emulation layer for libevent. It cannot |
901 | emulate the internals of libevent, so here are some usage hints: |
2901 | emulate the internals of libevent, so here are some usage hints: |
|
|
2902 | .IP "\(bu" 4 |
902 | .IP "* Use it by including <event.h>, as usual." 4 |
2903 | Use it by including <event.h>, as usual. |
903 | .IX Item "Use it by including <event.h>, as usual." |
2904 | .IP "\(bu" 4 |
904 | .PD 0 |
2905 | The following members are fully supported: ev_base, ev_callback, |
905 | .IP "* The following members are fully supported: ev_base, ev_callback, ev_arg, ev_fd, ev_res, ev_events." 4 |
2906 | ev_arg, ev_fd, ev_res, ev_events. |
906 | .IX Item "The following members are fully supported: ev_base, ev_callback, ev_arg, ev_fd, ev_res, ev_events." |
2907 | .IP "\(bu" 4 |
907 | .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 |
2908 | Avoid using ev_flags and the EVLIST_*\-macros, while it is |
908 | .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)." |
2909 | maintained by libev, it does not work exactly the same way as in libevent (consider |
909 | .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 |
2910 | it a private \s-1API\s0). |
910 | .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." |
2911 | .IP "\(bu" 4 |
|
|
2912 | Priorities are not currently supported. Initialising priorities |
|
|
2913 | will fail and all watchers will have the same priority, even though there |
|
|
2914 | is an ev_pri field. |
|
|
2915 | .IP "\(bu" 4 |
|
|
2916 | In libevent, the last base created gets the signals, in libev, the |
|
|
2917 | first base created (== the default loop) gets the signals. |
|
|
2918 | .IP "\(bu" 4 |
911 | .IP "* Other members are not supported." 4 |
2919 | Other members are not supported. |
912 | .IX Item "Other members are not supported." |
2920 | .IP "\(bu" 4 |
913 | .IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4 |
2921 | The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need |
914 | .IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library." |
2922 | to use the libev header file and library. |
915 | .PD |
|
|
916 | .SH "\*(C+ SUPPORT" |
2923 | .SH "\*(C+ SUPPORT" |
917 | .IX Header " SUPPORT" |
2924 | .IX Header " SUPPORT" |
918 | \&\s-1TBD\s0. |
2925 | Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow |
|
|
2926 | you to use some convenience methods to start/stop watchers and also change |
|
|
2927 | the callback model to a model using method callbacks on objects. |
|
|
2928 | .PP |
|
|
2929 | To use it, |
|
|
2930 | .PP |
|
|
2931 | .Vb 1 |
|
|
2932 | \& #include <ev++.h> |
|
|
2933 | .Ve |
|
|
2934 | .PP |
|
|
2935 | This automatically includes \fIev.h\fR and puts all of its definitions (many |
|
|
2936 | of them macros) into the global namespace. All \*(C+ specific things are |
|
|
2937 | put into the \f(CW\*(C`ev\*(C'\fR namespace. It should support all the same embedding |
|
|
2938 | options as \fIev.h\fR, most notably \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. |
|
|
2939 | .PP |
|
|
2940 | Care has been taken to keep the overhead low. The only data member the \*(C+ |
|
|
2941 | classes add (compared to plain C\-style watchers) is the event loop pointer |
|
|
2942 | that the watcher is associated with (or no additional members at all if |
|
|
2943 | you disable \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR when embedding libev). |
|
|
2944 | .PP |
|
|
2945 | Currently, functions, and static and non-static member functions can be |
|
|
2946 | used as callbacks. Other types should be easy to add as long as they only |
|
|
2947 | need one additional pointer for context. If you need support for other |
|
|
2948 | types of functors please contact the author (preferably after implementing |
|
|
2949 | it). |
|
|
2950 | .PP |
|
|
2951 | Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace: |
|
|
2952 | .ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4 |
|
|
2953 | .el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4 |
|
|
2954 | .IX Item "ev::READ, ev::WRITE etc." |
|
|
2955 | These are just enum values with the same values as the \f(CW\*(C`EV_READ\*(C'\fR etc. |
|
|
2956 | macros from \fIev.h\fR. |
|
|
2957 | .ie n .IP """ev::tstamp""\fR, \f(CW""ev::now""" 4 |
|
|
2958 | .el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4 |
|
|
2959 | .IX Item "ev::tstamp, ev::now" |
|
|
2960 | Aliases to the same types/functions as with the \f(CW\*(C`ev_\*(C'\fR prefix. |
|
|
2961 | .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 |
|
|
2962 | .el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4 |
|
|
2963 | .IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc." |
|
|
2964 | For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of |
|
|
2965 | the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR |
|
|
2966 | which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro |
|
|
2967 | defines by many implementations. |
|
|
2968 | .Sp |
|
|
2969 | All of those classes have these methods: |
|
|
2970 | .RS 4 |
|
|
2971 | .IP "ev::TYPE::TYPE ()" 4 |
|
|
2972 | .IX Item "ev::TYPE::TYPE ()" |
|
|
2973 | .PD 0 |
|
|
2974 | .IP "ev::TYPE::TYPE (struct ev_loop *)" 4 |
|
|
2975 | .IX Item "ev::TYPE::TYPE (struct ev_loop *)" |
|
|
2976 | .IP "ev::TYPE::~TYPE" 4 |
|
|
2977 | .IX Item "ev::TYPE::~TYPE" |
|
|
2978 | .PD |
|
|
2979 | The constructor (optionally) takes an event loop to associate the watcher |
|
|
2980 | with. If it is omitted, it will use \f(CW\*(C`EV_DEFAULT\*(C'\fR. |
|
|
2981 | .Sp |
|
|
2982 | The constructor calls \f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the |
|
|
2983 | \&\f(CW\*(C`set\*(C'\fR method before starting it. |
|
|
2984 | .Sp |
|
|
2985 | It will not set a callback, however: You have to call the templated \f(CW\*(C`set\*(C'\fR |
|
|
2986 | method to set a callback before you can start the watcher. |
|
|
2987 | .Sp |
|
|
2988 | (The reason why you have to use a method is a limitation in \*(C+ which does |
|
|
2989 | not allow explicit template arguments for constructors). |
|
|
2990 | .Sp |
|
|
2991 | The destructor automatically stops the watcher if it is active. |
|
|
2992 | .IP "w\->set<class, &class::method> (object *)" 4 |
|
|
2993 | .IX Item "w->set<class, &class::method> (object *)" |
|
|
2994 | This method sets the callback method to call. The method has to have a |
|
|
2995 | signature of \f(CW\*(C`void (*)(ev_TYPE &, int)\*(C'\fR, it receives the watcher as |
|
|
2996 | first argument and the \f(CW\*(C`revents\*(C'\fR as second. The object must be given as |
|
|
2997 | parameter and is stored in the \f(CW\*(C`data\*(C'\fR member of the watcher. |
|
|
2998 | .Sp |
|
|
2999 | This method synthesizes efficient thunking code to call your method from |
|
|
3000 | the C callback that libev requires. If your compiler can inline your |
|
|
3001 | callback (i.e. it is visible to it at the place of the \f(CW\*(C`set\*(C'\fR call and |
|
|
3002 | your compiler is good :), then the method will be fully inlined into the |
|
|
3003 | thunking function, making it as fast as a direct C callback. |
|
|
3004 | .Sp |
|
|
3005 | Example: simple class declaration and watcher initialisation |
|
|
3006 | .Sp |
|
|
3007 | .Vb 4 |
|
|
3008 | \& struct myclass |
|
|
3009 | \& { |
|
|
3010 | \& void io_cb (ev::io &w, int revents) { } |
|
|
3011 | \& } |
|
|
3012 | \& |
|
|
3013 | \& myclass obj; |
|
|
3014 | \& ev::io iow; |
|
|
3015 | \& iow.set <myclass, &myclass::io_cb> (&obj); |
|
|
3016 | .Ve |
|
|
3017 | .IP "w\->set (object *)" 4 |
|
|
3018 | .IX Item "w->set (object *)" |
|
|
3019 | This is an \fBexperimental\fR feature that might go away in a future version. |
|
|
3020 | .Sp |
|
|
3021 | This is a variation of a method callback \- leaving out the method to call |
|
|
3022 | will default the method to \f(CW\*(C`operator ()\*(C'\fR, which makes it possible to use |
|
|
3023 | functor objects without having to manually specify the \f(CW\*(C`operator ()\*(C'\fR all |
|
|
3024 | the time. Incidentally, you can then also leave out the template argument |
|
|
3025 | list. |
|
|
3026 | .Sp |
|
|
3027 | The \f(CW\*(C`operator ()\*(C'\fR method prototype must be \f(CW\*(C`void operator ()(watcher &w, |
|
|
3028 | int revents)\*(C'\fR. |
|
|
3029 | .Sp |
|
|
3030 | See the method\-\f(CW\*(C`set\*(C'\fR above for more details. |
|
|
3031 | .Sp |
|
|
3032 | Example: use a functor object as callback. |
|
|
3033 | .Sp |
|
|
3034 | .Vb 7 |
|
|
3035 | \& struct myfunctor |
|
|
3036 | \& { |
|
|
3037 | \& void operator() (ev::io &w, int revents) |
|
|
3038 | \& { |
|
|
3039 | \& ... |
|
|
3040 | \& } |
|
|
3041 | \& } |
|
|
3042 | \& |
|
|
3043 | \& myfunctor f; |
|
|
3044 | \& |
|
|
3045 | \& ev::io w; |
|
|
3046 | \& w.set (&f); |
|
|
3047 | .Ve |
|
|
3048 | .IP "w\->set<function> (void *data = 0)" 4 |
|
|
3049 | .IX Item "w->set<function> (void *data = 0)" |
|
|
3050 | Also sets a callback, but uses a static method or plain function as |
|
|
3051 | callback. The optional \f(CW\*(C`data\*(C'\fR argument will be stored in the watcher's |
|
|
3052 | \&\f(CW\*(C`data\*(C'\fR member and is free for you to use. |
|
|
3053 | .Sp |
|
|
3054 | The prototype of the \f(CW\*(C`function\*(C'\fR must be \f(CW\*(C`void (*)(ev::TYPE &w, int)\*(C'\fR. |
|
|
3055 | .Sp |
|
|
3056 | See the method\-\f(CW\*(C`set\*(C'\fR above for more details. |
|
|
3057 | .Sp |
|
|
3058 | Example: Use a plain function as callback. |
|
|
3059 | .Sp |
|
|
3060 | .Vb 2 |
|
|
3061 | \& static void io_cb (ev::io &w, int revents) { } |
|
|
3062 | \& iow.set <io_cb> (); |
|
|
3063 | .Ve |
|
|
3064 | .IP "w\->set (struct ev_loop *)" 4 |
|
|
3065 | .IX Item "w->set (struct ev_loop *)" |
|
|
3066 | Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only |
|
|
3067 | do this when the watcher is inactive (and not pending either). |
|
|
3068 | .IP "w\->set ([arguments])" 4 |
|
|
3069 | .IX Item "w->set ([arguments])" |
|
|
3070 | Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same arguments. Must be |
|
|
3071 | called at least once. Unlike the C counterpart, an active watcher gets |
|
|
3072 | automatically stopped and restarted when reconfiguring it with this |
|
|
3073 | method. |
|
|
3074 | .IP "w\->start ()" 4 |
|
|
3075 | .IX Item "w->start ()" |
|
|
3076 | Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the |
|
|
3077 | constructor already stores the event loop. |
|
|
3078 | .IP "w\->stop ()" 4 |
|
|
3079 | .IX Item "w->stop ()" |
|
|
3080 | Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument. |
|
|
3081 | .ie n .IP "w\->again () (""ev::timer""\fR, \f(CW""ev::periodic"" only)" 4 |
|
|
3082 | .el .IP "w\->again () (\f(CWev::timer\fR, \f(CWev::periodic\fR only)" 4 |
|
|
3083 | .IX Item "w->again () (ev::timer, ev::periodic only)" |
|
|
3084 | For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding |
|
|
3085 | \&\f(CW\*(C`ev_TYPE_again\*(C'\fR function. |
|
|
3086 | .ie n .IP "w\->sweep () (""ev::embed"" only)" 4 |
|
|
3087 | .el .IP "w\->sweep () (\f(CWev::embed\fR only)" 4 |
|
|
3088 | .IX Item "w->sweep () (ev::embed only)" |
|
|
3089 | Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR. |
|
|
3090 | .ie n .IP "w\->update () (""ev::stat"" only)" 4 |
|
|
3091 | .el .IP "w\->update () (\f(CWev::stat\fR only)" 4 |
|
|
3092 | .IX Item "w->update () (ev::stat only)" |
|
|
3093 | Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR. |
|
|
3094 | .RE |
|
|
3095 | .RS 4 |
|
|
3096 | .RE |
|
|
3097 | .PP |
|
|
3098 | Example: Define a class with an \s-1IO\s0 and idle watcher, start one of them in |
|
|
3099 | the constructor. |
|
|
3100 | .PP |
|
|
3101 | .Vb 4 |
|
|
3102 | \& class myclass |
|
|
3103 | \& { |
|
|
3104 | \& ev::io io ; void io_cb (ev::io &w, int revents); |
|
|
3105 | \& ev::idle idle; void idle_cb (ev::idle &w, int revents); |
|
|
3106 | \& |
|
|
3107 | \& myclass (int fd) |
|
|
3108 | \& { |
|
|
3109 | \& io .set <myclass, &myclass::io_cb > (this); |
|
|
3110 | \& idle.set <myclass, &myclass::idle_cb> (this); |
|
|
3111 | \& |
|
|
3112 | \& io.start (fd, ev::READ); |
|
|
3113 | \& } |
|
|
3114 | \& }; |
|
|
3115 | .Ve |
|
|
3116 | .SH "OTHER LANGUAGE BINDINGS" |
|
|
3117 | .IX Header "OTHER LANGUAGE BINDINGS" |
|
|
3118 | Libev does not offer other language bindings itself, but bindings for a |
|
|
3119 | number of languages exist in the form of third-party packages. If you know |
|
|
3120 | any interesting language binding in addition to the ones listed here, drop |
|
|
3121 | me a note. |
|
|
3122 | .IP "Perl" 4 |
|
|
3123 | .IX Item "Perl" |
|
|
3124 | The \s-1EV\s0 module implements the full libev \s-1API\s0 and is actually used to test |
|
|
3125 | libev. \s-1EV\s0 is developed together with libev. Apart from the \s-1EV\s0 core module, |
|
|
3126 | there are additional modules that implement libev-compatible interfaces |
|
|
3127 | 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), |
|
|
3128 | \&\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 |
|
|
3129 | and \f(CW\*(C`EV::Glib\*(C'\fR). |
|
|
3130 | .Sp |
|
|
3131 | It can be found and installed via \s-1CPAN\s0, its homepage is at |
|
|
3132 | <http://software.schmorp.de/pkg/EV>. |
|
|
3133 | .IP "Python" 4 |
|
|
3134 | .IX Item "Python" |
|
|
3135 | Python bindings can be found at <http://code.google.com/p/pyev/>. It |
|
|
3136 | seems to be quite complete and well-documented. Note, however, that the |
|
|
3137 | patch they require for libev is outright dangerous as it breaks the \s-1ABI\s0 |
|
|
3138 | for everybody else, and therefore, should never be applied in an installed |
|
|
3139 | libev (if python requires an incompatible \s-1ABI\s0 then it needs to embed |
|
|
3140 | libev). |
|
|
3141 | .IP "Ruby" 4 |
|
|
3142 | .IX Item "Ruby" |
|
|
3143 | Tony Arcieri has written a ruby extension that offers access to a subset |
|
|
3144 | of the libev \s-1API\s0 and adds file handle abstractions, asynchronous \s-1DNS\s0 and |
|
|
3145 | more on top of it. It can be found via gem servers. Its homepage is at |
|
|
3146 | <http://rev.rubyforge.org/>. |
|
|
3147 | .Sp |
|
|
3148 | Roger Pack reports that using the link order \f(CW\*(C`\-lws2_32 \-lmsvcrt\-ruby\-190\*(C'\fR |
|
|
3149 | makes rev work even on mingw. |
|
|
3150 | .IP "D" 4 |
|
|
3151 | .IX Item "D" |
|
|
3152 | Leandro Lucarella has written a D language binding (\fIev.d\fR) for libev, to |
|
|
3153 | be found at <http://proj.llucax.com.ar/wiki/evd>. |
|
|
3154 | .IP "Ocaml" 4 |
|
|
3155 | .IX Item "Ocaml" |
|
|
3156 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
|
|
3157 | <http://modeemi.cs.tut.fi/~flux/software/ocaml\-ev/>. |
|
|
3158 | .SH "MACRO MAGIC" |
|
|
3159 | .IX Header "MACRO MAGIC" |
|
|
3160 | Libev can be compiled with a variety of options, the most fundamental |
|
|
3161 | of which is \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most) |
|
|
3162 | functions and callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument. |
|
|
3163 | .PP |
|
|
3164 | To make it easier to write programs that cope with either variant, the |
|
|
3165 | following macros are defined: |
|
|
3166 | .ie n .IP """EV_A""\fR, \f(CW""EV_A_""" 4 |
|
|
3167 | .el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4 |
|
|
3168 | .IX Item "EV_A, EV_A_" |
|
|
3169 | This provides the loop \fIargument\fR for functions, if one is required (\*(L"ev |
|
|
3170 | loop argument\*(R"). The \f(CW\*(C`EV_A\*(C'\fR form is used when this is the sole argument, |
|
|
3171 | \&\f(CW\*(C`EV_A_\*(C'\fR is used when other arguments are following. Example: |
|
|
3172 | .Sp |
|
|
3173 | .Vb 3 |
|
|
3174 | \& ev_unref (EV_A); |
|
|
3175 | \& ev_timer_add (EV_A_ watcher); |
|
|
3176 | \& ev_loop (EV_A_ 0); |
|
|
3177 | .Ve |
|
|
3178 | .Sp |
|
|
3179 | It assumes the variable \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR is in scope, |
|
|
3180 | which is often provided by the following macro. |
|
|
3181 | .ie n .IP """EV_P""\fR, \f(CW""EV_P_""" 4 |
|
|
3182 | .el .IP "\f(CWEV_P\fR, \f(CWEV_P_\fR" 4 |
|
|
3183 | .IX Item "EV_P, EV_P_" |
|
|
3184 | This provides the loop \fIparameter\fR for functions, if one is required (\*(L"ev |
|
|
3185 | loop parameter\*(R"). The \f(CW\*(C`EV_P\*(C'\fR form is used when this is the sole parameter, |
|
|
3186 | \&\f(CW\*(C`EV_P_\*(C'\fR is used when other parameters are following. Example: |
|
|
3187 | .Sp |
|
|
3188 | .Vb 2 |
|
|
3189 | \& // this is how ev_unref is being declared |
|
|
3190 | \& static void ev_unref (EV_P); |
|
|
3191 | \& |
|
|
3192 | \& // this is how you can declare your typical callback |
|
|
3193 | \& static void cb (EV_P_ ev_timer *w, int revents) |
|
|
3194 | .Ve |
|
|
3195 | .Sp |
|
|
3196 | It declares a parameter \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR, quite |
|
|
3197 | suitable for use with \f(CW\*(C`EV_A\*(C'\fR. |
|
|
3198 | .ie n .IP """EV_DEFAULT""\fR, \f(CW""EV_DEFAULT_""" 4 |
|
|
3199 | .el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4 |
|
|
3200 | .IX Item "EV_DEFAULT, EV_DEFAULT_" |
|
|
3201 | Similar to the other two macros, this gives you the value of the default |
|
|
3202 | loop, if multiple loops are supported (\*(L"ev loop default\*(R"). |
|
|
3203 | .ie n .IP """EV_DEFAULT_UC""\fR, \f(CW""EV_DEFAULT_UC_""" 4 |
|
|
3204 | .el .IP "\f(CWEV_DEFAULT_UC\fR, \f(CWEV_DEFAULT_UC_\fR" 4 |
|
|
3205 | .IX Item "EV_DEFAULT_UC, EV_DEFAULT_UC_" |
|
|
3206 | Usage identical to \f(CW\*(C`EV_DEFAULT\*(C'\fR and \f(CW\*(C`EV_DEFAULT_\*(C'\fR, but requires that the |
|
|
3207 | default loop has been initialised (\f(CW\*(C`UC\*(C'\fR == unchecked). Their behaviour |
|
|
3208 | is undefined when the default loop has not been initialised by a previous |
|
|
3209 | 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. |
|
|
3210 | .Sp |
|
|
3211 | It is often prudent to use \f(CW\*(C`EV_DEFAULT\*(C'\fR when initialising the first |
|
|
3212 | watcher in a function but use \f(CW\*(C`EV_DEFAULT_UC\*(C'\fR afterwards. |
|
|
3213 | .PP |
|
|
3214 | Example: Declare and initialise a check watcher, utilising the above |
|
|
3215 | macros so it will work regardless of whether multiple loops are supported |
|
|
3216 | or not. |
|
|
3217 | .PP |
|
|
3218 | .Vb 5 |
|
|
3219 | \& static void |
|
|
3220 | \& check_cb (EV_P_ ev_timer *w, int revents) |
|
|
3221 | \& { |
|
|
3222 | \& ev_check_stop (EV_A_ w); |
|
|
3223 | \& } |
|
|
3224 | \& |
|
|
3225 | \& ev_check check; |
|
|
3226 | \& ev_check_init (&check, check_cb); |
|
|
3227 | \& ev_check_start (EV_DEFAULT_ &check); |
|
|
3228 | \& ev_loop (EV_DEFAULT_ 0); |
|
|
3229 | .Ve |
|
|
3230 | .SH "EMBEDDING" |
|
|
3231 | .IX Header "EMBEDDING" |
|
|
3232 | Libev can (and often is) directly embedded into host |
|
|
3233 | applications. Examples of applications that embed it include the Deliantra |
|
|
3234 | Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe) |
|
|
3235 | and rxvt-unicode. |
|
|
3236 | .PP |
|
|
3237 | The goal is to enable you to just copy the necessary files into your |
|
|
3238 | source directory without having to change even a single line in them, so |
|
|
3239 | you can easily upgrade by simply copying (or having a checked-out copy of |
|
|
3240 | libev somewhere in your source tree). |
|
|
3241 | .Sh "\s-1FILESETS\s0" |
|
|
3242 | .IX Subsection "FILESETS" |
|
|
3243 | Depending on what features you need you need to include one or more sets of files |
|
|
3244 | in your application. |
|
|
3245 | .PP |
|
|
3246 | \fI\s-1CORE\s0 \s-1EVENT\s0 \s-1LOOP\s0\fR |
|
|
3247 | .IX Subsection "CORE EVENT LOOP" |
|
|
3248 | .PP |
|
|
3249 | To include only the libev core (all the \f(CW\*(C`ev_*\*(C'\fR functions), with manual |
|
|
3250 | configuration (no autoconf): |
|
|
3251 | .PP |
|
|
3252 | .Vb 2 |
|
|
3253 | \& #define EV_STANDALONE 1 |
|
|
3254 | \& #include "ev.c" |
|
|
3255 | .Ve |
|
|
3256 | .PP |
|
|
3257 | This will automatically include \fIev.h\fR, too, and should be done in a |
|
|
3258 | single C source file only to provide the function implementations. To use |
|
|
3259 | it, do the same for \fIev.h\fR in all files wishing to use this \s-1API\s0 (best |
|
|
3260 | done by writing a wrapper around \fIev.h\fR that you can include instead and |
|
|
3261 | where you can put other configuration options): |
|
|
3262 | .PP |
|
|
3263 | .Vb 2 |
|
|
3264 | \& #define EV_STANDALONE 1 |
|
|
3265 | \& #include "ev.h" |
|
|
3266 | .Ve |
|
|
3267 | .PP |
|
|
3268 | Both header files and implementation files can be compiled with a \*(C+ |
|
|
3269 | compiler (at least, that's a stated goal, and breakage will be treated |
|
|
3270 | as a bug). |
|
|
3271 | .PP |
|
|
3272 | You need the following files in your source tree, or in a directory |
|
|
3273 | in your include path (e.g. in libev/ when using \-Ilibev): |
|
|
3274 | .PP |
|
|
3275 | .Vb 4 |
|
|
3276 | \& ev.h |
|
|
3277 | \& ev.c |
|
|
3278 | \& ev_vars.h |
|
|
3279 | \& ev_wrap.h |
|
|
3280 | \& |
|
|
3281 | \& ev_win32.c required on win32 platforms only |
|
|
3282 | \& |
|
|
3283 | \& ev_select.c only when select backend is enabled (which is enabled by default) |
|
|
3284 | \& ev_poll.c only when poll backend is enabled (disabled by default) |
|
|
3285 | \& ev_epoll.c only when the epoll backend is enabled (disabled by default) |
|
|
3286 | \& ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
|
|
3287 | \& ev_port.c only when the solaris port backend is enabled (disabled by default) |
|
|
3288 | .Ve |
|
|
3289 | .PP |
|
|
3290 | \&\fIev.c\fR includes the backend files directly when enabled, so you only need |
|
|
3291 | to compile this single file. |
|
|
3292 | .PP |
|
|
3293 | \fI\s-1LIBEVENT\s0 \s-1COMPATIBILITY\s0 \s-1API\s0\fR |
|
|
3294 | .IX Subsection "LIBEVENT COMPATIBILITY API" |
|
|
3295 | .PP |
|
|
3296 | To include the libevent compatibility \s-1API\s0, also include: |
|
|
3297 | .PP |
|
|
3298 | .Vb 1 |
|
|
3299 | \& #include "event.c" |
|
|
3300 | .Ve |
|
|
3301 | .PP |
|
|
3302 | in the file including \fIev.c\fR, and: |
|
|
3303 | .PP |
|
|
3304 | .Vb 1 |
|
|
3305 | \& #include "event.h" |
|
|
3306 | .Ve |
|
|
3307 | .PP |
|
|
3308 | in the files that want to use the libevent \s-1API\s0. This also includes \fIev.h\fR. |
|
|
3309 | .PP |
|
|
3310 | You need the following additional files for this: |
|
|
3311 | .PP |
|
|
3312 | .Vb 2 |
|
|
3313 | \& event.h |
|
|
3314 | \& event.c |
|
|
3315 | .Ve |
|
|
3316 | .PP |
|
|
3317 | \fI\s-1AUTOCONF\s0 \s-1SUPPORT\s0\fR |
|
|
3318 | .IX Subsection "AUTOCONF SUPPORT" |
|
|
3319 | .PP |
|
|
3320 | Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your configuration in |
|
|
3321 | whatever way you want, you can also \f(CW\*(C`m4_include([libev.m4])\*(C'\fR in your |
|
|
3322 | \&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR undefined. \fIev.c\fR will then |
|
|
3323 | include \fIconfig.h\fR and configure itself accordingly. |
|
|
3324 | .PP |
|
|
3325 | For this of course you need the m4 file: |
|
|
3326 | .PP |
|
|
3327 | .Vb 1 |
|
|
3328 | \& libev.m4 |
|
|
3329 | .Ve |
|
|
3330 | .Sh "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0" |
|
|
3331 | .IX Subsection "PREPROCESSOR SYMBOLS/MACROS" |
|
|
3332 | Libev can be configured via a variety of preprocessor symbols you have to |
|
|
3333 | define before including any of its files. The default in the absence of |
|
|
3334 | autoconf is documented for every option. |
|
|
3335 | .IP "\s-1EV_STANDALONE\s0" 4 |
|
|
3336 | .IX Item "EV_STANDALONE" |
|
|
3337 | Must always be \f(CW1\fR if you do not use autoconf configuration, which |
|
|
3338 | keeps libev from including \fIconfig.h\fR, and it also defines dummy |
|
|
3339 | implementations for some libevent functions (such as logging, which is not |
|
|
3340 | supported). It will also not define any of the structs usually found in |
|
|
3341 | \&\fIevent.h\fR that are not directly supported by the libev core alone. |
|
|
3342 | .Sp |
|
|
3343 | In stanbdalone mode, libev will still try to automatically deduce the |
|
|
3344 | configuration, but has to be more conservative. |
|
|
3345 | .IP "\s-1EV_USE_MONOTONIC\s0" 4 |
|
|
3346 | .IX Item "EV_USE_MONOTONIC" |
|
|
3347 | If defined to be \f(CW1\fR, libev will try to detect the availability of the |
|
|
3348 | monotonic clock option at both compile time and runtime. Otherwise no |
|
|
3349 | use of the monotonic clock option will be attempted. If you enable this, |
|
|
3350 | you usually have to link against librt or something similar. Enabling it |
|
|
3351 | when the functionality isn't available is safe, though, although you have |
|
|
3352 | to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR |
|
|
3353 | function is hiding in (often \fI\-lrt\fR). See also \f(CW\*(C`EV_USE_CLOCK_SYSCALL\*(C'\fR. |
|
|
3354 | .IP "\s-1EV_USE_REALTIME\s0" 4 |
|
|
3355 | .IX Item "EV_USE_REALTIME" |
|
|
3356 | If defined to be \f(CW1\fR, libev will try to detect the availability of the |
|
|
3357 | real-time clock option at compile time (and assume its availability at |
|
|
3358 | runtime if successful). Otherwise no use of the real-time clock option will |
|
|
3359 | be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get |
|
|
3360 | (CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See the |
|
|
3361 | note about libraries in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though. |
|
|
3362 | .IP "\s-1EV_USE_CLOCK_SYSCALL\s0" 4 |
|
|
3363 | .IX Item "EV_USE_CLOCK_SYSCALL" |
|
|
3364 | If defined to be \f(CW1\fR, libev will try to use a direct syscall instead |
|
|
3365 | of calling the system-provided \f(CW\*(C`clock_gettime\*(C'\fR function. This option |
|
|
3366 | 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 |
|
|
3367 | unconditionally pulls in \f(CW\*(C`libpthread\*(C'\fR, slowing down single-threaded |
|
|
3368 | programs needlessly. Using a direct syscall is slightly slower (in |
|
|
3369 | theory), because no optimised vdso implementation can be used, but avoids |
|
|
3370 | the pthread dependency. Defaults to \f(CW1\fR on GNU/Linux with glibc 2.x or |
|
|
3371 | higher, as it simplifies linking (no need for \f(CW\*(C`\-lrt\*(C'\fR). |
|
|
3372 | .IP "\s-1EV_USE_NANOSLEEP\s0" 4 |
|
|
3373 | .IX Item "EV_USE_NANOSLEEP" |
|
|
3374 | If defined to be \f(CW1\fR, libev will assume that \f(CW\*(C`nanosleep ()\*(C'\fR is available |
|
|
3375 | and will use it for delays. Otherwise it will use \f(CW\*(C`select ()\*(C'\fR. |
|
|
3376 | .IP "\s-1EV_USE_EVENTFD\s0" 4 |
|
|
3377 | .IX Item "EV_USE_EVENTFD" |
|
|
3378 | If defined to be \f(CW1\fR, then libev will assume that \f(CW\*(C`eventfd ()\*(C'\fR is |
|
|
3379 | available and will probe for kernel support at runtime. This will improve |
|
|
3380 | \&\f(CW\*(C`ev_signal\*(C'\fR and \f(CW\*(C`ev_async\*(C'\fR performance and reduce resource consumption. |
|
|
3381 | If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
|
|
3382 | 2.7 or newer, otherwise disabled. |
|
|
3383 | .IP "\s-1EV_USE_SELECT\s0" 4 |
|
|
3384 | .IX Item "EV_USE_SELECT" |
|
|
3385 | If undefined or defined to be \f(CW1\fR, libev will compile in support for the |
|
|
3386 | \&\f(CW\*(C`select\*(C'\fR(2) backend. No attempt at auto-detection will be done: if no |
|
|
3387 | other method takes over, select will be it. Otherwise the select backend |
|
|
3388 | will not be compiled in. |
|
|
3389 | .IP "\s-1EV_SELECT_USE_FD_SET\s0" 4 |
|
|
3390 | .IX Item "EV_SELECT_USE_FD_SET" |
|
|
3391 | If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR |
|
|
3392 | structure. This is useful if libev doesn't compile due to a missing |
|
|
3393 | \&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it mis-guesses the bitset layout |
|
|
3394 | on exotic systems. This usually limits the range of file descriptors to |
|
|
3395 | some low limit such as 1024 or might have other limitations (winsocket |
|
|
3396 | only allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation, |
|
|
3397 | configures the maximum size of the \f(CW\*(C`fd_set\*(C'\fR. |
|
|
3398 | .IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4 |
|
|
3399 | .IX Item "EV_SELECT_IS_WINSOCKET" |
|
|
3400 | When defined to \f(CW1\fR, the select backend will assume that |
|
|
3401 | select/socket/connect etc. don't understand file descriptors but |
|
|
3402 | wants osf handles on win32 (this is the case when the select to |
|
|
3403 | be used is the winsock select). This means that it will call |
|
|
3404 | \&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise, |
|
|
3405 | it is assumed that all these functions actually work on fds, even |
|
|
3406 | on win32. Should not be defined on non\-win32 platforms. |
|
|
3407 | .IP "\s-1EV_FD_TO_WIN32_HANDLE\s0" 4 |
|
|
3408 | .IX Item "EV_FD_TO_WIN32_HANDLE" |
|
|
3409 | If \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR is enabled, then libev needs a way to map |
|
|
3410 | file descriptors to socket handles. When not defining this symbol (the |
|
|
3411 | default), then libev will call \f(CW\*(C`_get_osfhandle\*(C'\fR, which is usually |
|
|
3412 | correct. In some cases, programs use their own file descriptor management, |
|
|
3413 | in which case they can provide this function to map fds to socket handles. |
|
|
3414 | .IP "\s-1EV_USE_POLL\s0" 4 |
|
|
3415 | .IX Item "EV_USE_POLL" |
|
|
3416 | If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2) |
|
|
3417 | backend. Otherwise it will be enabled on non\-win32 platforms. It |
|
|
3418 | takes precedence over select. |
|
|
3419 | .IP "\s-1EV_USE_EPOLL\s0" 4 |
|
|
3420 | .IX Item "EV_USE_EPOLL" |
|
|
3421 | If defined to be \f(CW1\fR, libev will compile in support for the Linux |
|
|
3422 | \&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime, |
|
|
3423 | otherwise another method will be used as fallback. This is the preferred |
|
|
3424 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
|
|
3425 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
|
|
3426 | .IP "\s-1EV_USE_KQUEUE\s0" 4 |
|
|
3427 | .IX Item "EV_USE_KQUEUE" |
|
|
3428 | If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style |
|
|
3429 | \&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime, |
|
|
3430 | otherwise another method will be used as fallback. This is the preferred |
|
|
3431 | backend for \s-1BSD\s0 and BSD-like systems, although on most BSDs kqueue only |
|
|
3432 | supports some types of fds correctly (the only platform we found that |
|
|
3433 | supports ptys for example was NetBSD), so kqueue might be compiled in, but |
|
|
3434 | not be used unless explicitly requested. The best way to use it is to find |
|
|
3435 | out whether kqueue supports your type of fd properly and use an embedded |
|
|
3436 | kqueue loop. |
|
|
3437 | .IP "\s-1EV_USE_PORT\s0" 4 |
|
|
3438 | .IX Item "EV_USE_PORT" |
|
|
3439 | If defined to be \f(CW1\fR, libev will compile in support for the Solaris |
|
|
3440 | 10 port style backend. Its availability will be detected at runtime, |
|
|
3441 | otherwise another method will be used as fallback. This is the preferred |
|
|
3442 | backend for Solaris 10 systems. |
|
|
3443 | .IP "\s-1EV_USE_DEVPOLL\s0" 4 |
|
|
3444 | .IX Item "EV_USE_DEVPOLL" |
|
|
3445 | Reserved for future expansion, works like the \s-1USE\s0 symbols above. |
|
|
3446 | .IP "\s-1EV_USE_INOTIFY\s0" 4 |
|
|
3447 | .IX Item "EV_USE_INOTIFY" |
|
|
3448 | If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify |
|
|
3449 | interface to speed up \f(CW\*(C`ev_stat\*(C'\fR watchers. Its actual availability will |
|
|
3450 | be detected at runtime. If undefined, it will be enabled if the headers |
|
|
3451 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
|
|
3452 | .IP "\s-1EV_ATOMIC_T\s0" 4 |
|
|
3453 | .IX Item "EV_ATOMIC_T" |
|
|
3454 | Libev requires an integer type (suitable for storing \f(CW0\fR or \f(CW1\fR) whose |
|
|
3455 | access is atomic with respect to other threads or signal contexts. No such |
|
|
3456 | type is easily found in the C language, so you can provide your own type |
|
|
3457 | that you know is safe for your purposes. It is used both for signal handler \*(L"locking\*(R" |
|
|
3458 | as well as for signal and thread safety in \f(CW\*(C`ev_async\*(C'\fR watchers. |
|
|
3459 | .Sp |
|
|
3460 | In the absence of this define, libev will use \f(CW\*(C`sig_atomic_t volatile\*(C'\fR |
|
|
3461 | (from \fIsignal.h\fR), which is usually good enough on most platforms. |
|
|
3462 | .IP "\s-1EV_H\s0" 4 |
|
|
3463 | .IX Item "EV_H" |
|
|
3464 | The name of the \fIev.h\fR header file used to include it. The default if |
|
|
3465 | undefined is \f(CW"ev.h"\fR in \fIevent.h\fR, \fIev.c\fR and \fIev++.h\fR. This can be |
|
|
3466 | used to virtually rename the \fIev.h\fR header file in case of conflicts. |
|
|
3467 | .IP "\s-1EV_CONFIG_H\s0" 4 |
|
|
3468 | .IX Item "EV_CONFIG_H" |
|
|
3469 | If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override |
|
|
3470 | \&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to |
|
|
3471 | \&\f(CW\*(C`EV_H\*(C'\fR, above. |
|
|
3472 | .IP "\s-1EV_EVENT_H\s0" 4 |
|
|
3473 | .IX Item "EV_EVENT_H" |
|
|
3474 | Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea |
|
|
3475 | of how the \fIevent.h\fR header can be found, the default is \f(CW"event.h"\fR. |
|
|
3476 | .IP "\s-1EV_PROTOTYPES\s0" 4 |
|
|
3477 | .IX Item "EV_PROTOTYPES" |
|
|
3478 | If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function |
|
|
3479 | prototypes, but still define all the structs and other symbols. This is |
|
|
3480 | occasionally useful if you want to provide your own wrapper functions |
|
|
3481 | around libev functions. |
|
|
3482 | .IP "\s-1EV_MULTIPLICITY\s0" 4 |
|
|
3483 | .IX Item "EV_MULTIPLICITY" |
|
|
3484 | If undefined or defined to \f(CW1\fR, then all event-loop-specific functions |
|
|
3485 | will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create |
|
|
3486 | additional independent event loops. Otherwise there will be no support |
|
|
3487 | for multiple event loops and there is no first event loop pointer |
|
|
3488 | argument. Instead, all functions act on the single default loop. |
|
|
3489 | .IP "\s-1EV_MINPRI\s0" 4 |
|
|
3490 | .IX Item "EV_MINPRI" |
|
|
3491 | .PD 0 |
|
|
3492 | .IP "\s-1EV_MAXPRI\s0" 4 |
|
|
3493 | .IX Item "EV_MAXPRI" |
|
|
3494 | .PD |
|
|
3495 | The range of allowed priorities. \f(CW\*(C`EV_MINPRI\*(C'\fR must be smaller or equal to |
|
|
3496 | \&\f(CW\*(C`EV_MAXPRI\*(C'\fR, but otherwise there are no non-obvious limitations. You can |
|
|
3497 | provide for more priorities by overriding those symbols (usually defined |
|
|
3498 | to be \f(CW\*(C`\-2\*(C'\fR and \f(CW2\fR, respectively). |
|
|
3499 | .Sp |
|
|
3500 | When doing priority-based operations, libev usually has to linearly search |
|
|
3501 | all the priorities, so having many of them (hundreds) uses a lot of space |
|
|
3502 | and time, so using the defaults of five priorities (\-2 .. +2) is usually |
|
|
3503 | fine. |
|
|
3504 | .Sp |
|
|
3505 | If your embedding application does not need any priorities, defining these |
|
|
3506 | both to \f(CW0\fR will save some memory and \s-1CPU\s0. |
|
|
3507 | .IP "\s-1EV_PERIODIC_ENABLE\s0" 4 |
|
|
3508 | .IX Item "EV_PERIODIC_ENABLE" |
|
|
3509 | If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If |
|
|
3510 | defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of |
|
|
3511 | code. |
|
|
3512 | .IP "\s-1EV_IDLE_ENABLE\s0" 4 |
|
|
3513 | .IX Item "EV_IDLE_ENABLE" |
|
|
3514 | If undefined or defined to be \f(CW1\fR, then idle watchers are supported. If |
|
|
3515 | defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of |
|
|
3516 | code. |
|
|
3517 | .IP "\s-1EV_EMBED_ENABLE\s0" 4 |
|
|
3518 | .IX Item "EV_EMBED_ENABLE" |
|
|
3519 | If undefined or defined to be \f(CW1\fR, then embed watchers are supported. If |
|
|
3520 | defined to be \f(CW0\fR, then they are not. Embed watchers rely on most other |
|
|
3521 | watcher types, which therefore must not be disabled. |
|
|
3522 | .IP "\s-1EV_STAT_ENABLE\s0" 4 |
|
|
3523 | .IX Item "EV_STAT_ENABLE" |
|
|
3524 | If undefined or defined to be \f(CW1\fR, then stat watchers are supported. If |
|
|
3525 | defined to be \f(CW0\fR, then they are not. |
|
|
3526 | .IP "\s-1EV_FORK_ENABLE\s0" 4 |
|
|
3527 | .IX Item "EV_FORK_ENABLE" |
|
|
3528 | If undefined or defined to be \f(CW1\fR, then fork watchers are supported. If |
|
|
3529 | defined to be \f(CW0\fR, then they are not. |
|
|
3530 | .IP "\s-1EV_ASYNC_ENABLE\s0" 4 |
|
|
3531 | .IX Item "EV_ASYNC_ENABLE" |
|
|
3532 | If undefined or defined to be \f(CW1\fR, then async watchers are supported. If |
|
|
3533 | defined to be \f(CW0\fR, then they are not. |
|
|
3534 | .IP "\s-1EV_MINIMAL\s0" 4 |
|
|
3535 | .IX Item "EV_MINIMAL" |
|
|
3536 | If you need to shave off some kilobytes of code at the expense of some |
|
|
3537 | speed, define this symbol to \f(CW1\fR. Currently this is used to override some |
|
|
3538 | inlining decisions, saves roughly 30% code size on amd64. It also selects a |
|
|
3539 | much smaller 2\-heap for timer management over the default 4\-heap. |
|
|
3540 | .IP "\s-1EV_PID_HASHSIZE\s0" 4 |
|
|
3541 | .IX Item "EV_PID_HASHSIZE" |
|
|
3542 | \&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by |
|
|
3543 | pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), usually more |
|
|
3544 | than enough. If you need to manage thousands of children you might want to |
|
|
3545 | increase this value (\fImust\fR be a power of two). |
|
|
3546 | .IP "\s-1EV_INOTIFY_HASHSIZE\s0" 4 |
|
|
3547 | .IX Item "EV_INOTIFY_HASHSIZE" |
|
|
3548 | \&\f(CW\*(C`ev_stat\*(C'\fR watchers use a small hash table to distribute workload by |
|
|
3549 | inotify watch id. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), |
|
|
3550 | usually more than enough. If you need to manage thousands of \f(CW\*(C`ev_stat\*(C'\fR |
|
|
3551 | watchers you might want to increase this value (\fImust\fR be a power of |
|
|
3552 | two). |
|
|
3553 | .IP "\s-1EV_USE_4HEAP\s0" 4 |
|
|
3554 | .IX Item "EV_USE_4HEAP" |
|
|
3555 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
|
|
3556 | timer and periodics heaps, libev uses a 4\-heap when this symbol is defined |
|
|
3557 | to \f(CW1\fR. The 4\-heap uses more complicated (longer) code but has noticeably |
|
|
3558 | faster performance with many (thousands) of watchers. |
|
|
3559 | .Sp |
|
|
3560 | The default is \f(CW1\fR unless \f(CW\*(C`EV_MINIMAL\*(C'\fR is set in which case it is \f(CW0\fR |
|
|
3561 | (disabled). |
|
|
3562 | .IP "\s-1EV_HEAP_CACHE_AT\s0" 4 |
|
|
3563 | .IX Item "EV_HEAP_CACHE_AT" |
|
|
3564 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
|
|
3565 | timer and periodics heaps, libev can cache the timestamp (\fIat\fR) within |
|
|
3566 | the heap structure (selected by defining \f(CW\*(C`EV_HEAP_CACHE_AT\*(C'\fR to \f(CW1\fR), |
|
|
3567 | which uses 8\-12 bytes more per watcher and a few hundred bytes more code, |
|
|
3568 | but avoids random read accesses on heap changes. This improves performance |
|
|
3569 | noticeably with many (hundreds) of watchers. |
|
|
3570 | .Sp |
|
|
3571 | The default is \f(CW1\fR unless \f(CW\*(C`EV_MINIMAL\*(C'\fR is set in which case it is \f(CW0\fR |
|
|
3572 | (disabled). |
|
|
3573 | .IP "\s-1EV_VERIFY\s0" 4 |
|
|
3574 | .IX Item "EV_VERIFY" |
|
|
3575 | Controls how much internal verification (see \f(CW\*(C`ev_loop_verify ()\*(C'\fR) will |
|
|
3576 | be done: If set to \f(CW0\fR, no internal verification code will be compiled |
|
|
3577 | in. If set to \f(CW1\fR, then verification code will be compiled in, but not |
|
|
3578 | called. If set to \f(CW2\fR, then the internal verification code will be |
|
|
3579 | called once per loop, which can slow down libev. If set to \f(CW3\fR, then the |
|
|
3580 | verification code will be called very frequently, which will slow down |
|
|
3581 | libev considerably. |
|
|
3582 | .Sp |
|
|
3583 | The default is \f(CW1\fR, unless \f(CW\*(C`EV_MINIMAL\*(C'\fR is set, in which case it will be |
|
|
3584 | \&\f(CW0\fR. |
|
|
3585 | .IP "\s-1EV_COMMON\s0" 4 |
|
|
3586 | .IX Item "EV_COMMON" |
|
|
3587 | By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining |
|
|
3588 | this macro to a something else you can include more and other types of |
|
|
3589 | members. You have to define it each time you include one of the files, |
|
|
3590 | though, and it must be identical each time. |
|
|
3591 | .Sp |
|
|
3592 | For example, the perl \s-1EV\s0 module uses something like this: |
|
|
3593 | .Sp |
|
|
3594 | .Vb 3 |
|
|
3595 | \& #define EV_COMMON \e |
|
|
3596 | \& SV *self; /* contains this struct */ \e |
|
|
3597 | \& SV *cb_sv, *fh /* note no trailing ";" */ |
|
|
3598 | .Ve |
|
|
3599 | .IP "\s-1EV_CB_DECLARE\s0 (type)" 4 |
|
|
3600 | .IX Item "EV_CB_DECLARE (type)" |
|
|
3601 | .PD 0 |
|
|
3602 | .IP "\s-1EV_CB_INVOKE\s0 (watcher, revents)" 4 |
|
|
3603 | .IX Item "EV_CB_INVOKE (watcher, revents)" |
|
|
3604 | .IP "ev_set_cb (ev, cb)" 4 |
|
|
3605 | .IX Item "ev_set_cb (ev, cb)" |
|
|
3606 | .PD |
|
|
3607 | Can be used to change the callback member declaration in each watcher, |
|
|
3608 | and the way callbacks are invoked and set. Must expand to a struct member |
|
|
3609 | definition and a statement, respectively. See the \fIev.h\fR header file for |
|
|
3610 | their default definitions. One possible use for overriding these is to |
|
|
3611 | avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use |
|
|
3612 | method calls instead of plain function calls in \*(C+. |
|
|
3613 | .Sh "\s-1EXPORTED\s0 \s-1API\s0 \s-1SYMBOLS\s0" |
|
|
3614 | .IX Subsection "EXPORTED API SYMBOLS" |
|
|
3615 | If you need to re-export the \s-1API\s0 (e.g. via a \s-1DLL\s0) and you need a list of |
|
|
3616 | exported symbols, you can use the provided \fISymbol.*\fR files which list |
|
|
3617 | all public symbols, one per line: |
|
|
3618 | .PP |
|
|
3619 | .Vb 2 |
|
|
3620 | \& Symbols.ev for libev proper |
|
|
3621 | \& Symbols.event for the libevent emulation |
|
|
3622 | .Ve |
|
|
3623 | .PP |
|
|
3624 | This can also be used to rename all public symbols to avoid clashes with |
|
|
3625 | multiple versions of libev linked together (which is obviously bad in |
|
|
3626 | itself, but sometimes it is inconvenient to avoid this). |
|
|
3627 | .PP |
|
|
3628 | A sed command like this will create wrapper \f(CW\*(C`#define\*(C'\fR's that you need to |
|
|
3629 | include before including \fIev.h\fR: |
|
|
3630 | .PP |
|
|
3631 | .Vb 1 |
|
|
3632 | \& <Symbols.ev sed \-e "s/.*/#define & myprefix_&/" >wrap.h |
|
|
3633 | .Ve |
|
|
3634 | .PP |
|
|
3635 | This would create a file \fIwrap.h\fR which essentially looks like this: |
|
|
3636 | .PP |
|
|
3637 | .Vb 4 |
|
|
3638 | \& #define ev_backend myprefix_ev_backend |
|
|
3639 | \& #define ev_check_start myprefix_ev_check_start |
|
|
3640 | \& #define ev_check_stop myprefix_ev_check_stop |
|
|
3641 | \& ... |
|
|
3642 | .Ve |
|
|
3643 | .Sh "\s-1EXAMPLES\s0" |
|
|
3644 | .IX Subsection "EXAMPLES" |
|
|
3645 | For a real-world example of a program the includes libev |
|
|
3646 | verbatim, you can have a look at the \s-1EV\s0 perl module |
|
|
3647 | (<http://software.schmorp.de/pkg/EV.html>). It has the libev files in |
|
|
3648 | the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public |
|
|
3649 | interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file |
|
|
3650 | will be compiled. It is pretty complex because it provides its own header |
|
|
3651 | file. |
|
|
3652 | .PP |
|
|
3653 | The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file |
|
|
3654 | that everybody includes and which overrides some configure choices: |
|
|
3655 | .PP |
|
|
3656 | .Vb 9 |
|
|
3657 | \& #define EV_MINIMAL 1 |
|
|
3658 | \& #define EV_USE_POLL 0 |
|
|
3659 | \& #define EV_MULTIPLICITY 0 |
|
|
3660 | \& #define EV_PERIODIC_ENABLE 0 |
|
|
3661 | \& #define EV_STAT_ENABLE 0 |
|
|
3662 | \& #define EV_FORK_ENABLE 0 |
|
|
3663 | \& #define EV_CONFIG_H <config.h> |
|
|
3664 | \& #define EV_MINPRI 0 |
|
|
3665 | \& #define EV_MAXPRI 0 |
|
|
3666 | \& |
|
|
3667 | \& #include "ev++.h" |
|
|
3668 | .Ve |
|
|
3669 | .PP |
|
|
3670 | And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled: |
|
|
3671 | .PP |
|
|
3672 | .Vb 2 |
|
|
3673 | \& #include "ev_cpp.h" |
|
|
3674 | \& #include "ev.c" |
|
|
3675 | .Ve |
|
|
3676 | .SH "INTERACTION WITH OTHER PROGRAMS OR LIBRARIES" |
|
|
3677 | .IX Header "INTERACTION WITH OTHER PROGRAMS OR LIBRARIES" |
|
|
3678 | .Sh "\s-1THREADS\s0 \s-1AND\s0 \s-1COROUTINES\s0" |
|
|
3679 | .IX Subsection "THREADS AND COROUTINES" |
|
|
3680 | \fI\s-1THREADS\s0\fR |
|
|
3681 | .IX Subsection "THREADS" |
|
|
3682 | .PP |
|
|
3683 | All libev functions are reentrant and thread-safe unless explicitly |
|
|
3684 | documented otherwise, but libev implements no locking itself. This means |
|
|
3685 | that you can use as many loops as you want in parallel, as long as there |
|
|
3686 | are no concurrent calls into any libev function with the same loop |
|
|
3687 | parameter (\f(CW\*(C`ev_default_*\*(C'\fR calls have an implicit default loop parameter, |
|
|
3688 | of course): libev guarantees that different event loops share no data |
|
|
3689 | structures that need any locking. |
|
|
3690 | .PP |
|
|
3691 | Or to put it differently: calls with different loop parameters can be done |
|
|
3692 | concurrently from multiple threads, calls with the same loop parameter |
|
|
3693 | must be done serially (but can be done from different threads, as long as |
|
|
3694 | only one thread ever is inside a call at any point in time, e.g. by using |
|
|
3695 | a mutex per loop). |
|
|
3696 | .PP |
|
|
3697 | Specifically to support threads (and signal handlers), libev implements |
|
|
3698 | so-called \f(CW\*(C`ev_async\*(C'\fR watchers, which allow some limited form of |
|
|
3699 | concurrency on the same event loop, namely waking it up \*(L"from the |
|
|
3700 | outside\*(R". |
|
|
3701 | .PP |
|
|
3702 | If you want to know which design (one loop, locking, or multiple loops |
|
|
3703 | without or something else still) is best for your problem, then I cannot |
|
|
3704 | help you, but here is some generic advice: |
|
|
3705 | .IP "\(bu" 4 |
|
|
3706 | most applications have a main thread: use the default libev loop |
|
|
3707 | in that thread, or create a separate thread running only the default loop. |
|
|
3708 | .Sp |
|
|
3709 | This helps integrating other libraries or software modules that use libev |
|
|
3710 | themselves and don't care/know about threading. |
|
|
3711 | .IP "\(bu" 4 |
|
|
3712 | one loop per thread is usually a good model. |
|
|
3713 | .Sp |
|
|
3714 | Doing this is almost never wrong, sometimes a better-performance model |
|
|
3715 | exists, but it is always a good start. |
|
|
3716 | .IP "\(bu" 4 |
|
|
3717 | other models exist, such as the leader/follower pattern, where one |
|
|
3718 | loop is handed through multiple threads in a kind of round-robin fashion. |
|
|
3719 | .Sp |
|
|
3720 | Choosing a model is hard \- look around, learn, know that usually you can do |
|
|
3721 | better than you currently do :\-) |
|
|
3722 | .IP "\(bu" 4 |
|
|
3723 | often you need to talk to some other thread which blocks in the |
|
|
3724 | event loop. |
|
|
3725 | .Sp |
|
|
3726 | \&\f(CW\*(C`ev_async\*(C'\fR watchers can be used to wake them up from other threads safely |
|
|
3727 | (or from signal contexts...). |
|
|
3728 | .Sp |
|
|
3729 | An example use would be to communicate signals or other events that only |
|
|
3730 | work in the default loop by registering the signal watcher with the |
|
|
3731 | default loop and triggering an \f(CW\*(C`ev_async\*(C'\fR watcher from the default loop |
|
|
3732 | watcher callback into the event loop interested in the signal. |
|
|
3733 | .PP |
|
|
3734 | \fI\s-1COROUTINES\s0\fR |
|
|
3735 | .IX Subsection "COROUTINES" |
|
|
3736 | .PP |
|
|
3737 | Libev is very accommodating to coroutines (\*(L"cooperative threads\*(R"): |
|
|
3738 | libev fully supports nesting calls to its functions from different |
|
|
3739 | coroutines (e.g. you can call \f(CW\*(C`ev_loop\*(C'\fR on the same loop from two |
|
|
3740 | different coroutines, and switch freely between both coroutines running the |
|
|
3741 | loop, as long as you don't confuse yourself). The only exception is that |
|
|
3742 | you must not do this from \f(CW\*(C`ev_periodic\*(C'\fR reschedule callbacks. |
|
|
3743 | .PP |
|
|
3744 | Care has been taken to ensure that libev does not keep local state inside |
|
|
3745 | \&\f(CW\*(C`ev_loop\*(C'\fR, and other calls do not usually allow for coroutine switches as |
|
|
3746 | they do not call any callbacks. |
|
|
3747 | .Sh "\s-1COMPILER\s0 \s-1WARNINGS\s0" |
|
|
3748 | .IX Subsection "COMPILER WARNINGS" |
|
|
3749 | Depending on your compiler and compiler settings, you might get no or a |
|
|
3750 | lot of warnings when compiling libev code. Some people are apparently |
|
|
3751 | scared by this. |
|
|
3752 | .PP |
|
|
3753 | However, these are unavoidable for many reasons. For one, each compiler |
|
|
3754 | has different warnings, and each user has different tastes regarding |
|
|
3755 | warning options. \*(L"Warn-free\*(R" code therefore cannot be a goal except when |
|
|
3756 | targeting a specific compiler and compiler-version. |
|
|
3757 | .PP |
|
|
3758 | Another reason is that some compiler warnings require elaborate |
|
|
3759 | workarounds, or other changes to the code that make it less clear and less |
|
|
3760 | maintainable. |
|
|
3761 | .PP |
|
|
3762 | And of course, some compiler warnings are just plain stupid, or simply |
|
|
3763 | wrong (because they don't actually warn about the condition their message |
|
|
3764 | seems to warn about). For example, certain older gcc versions had some |
|
|
3765 | warnings that resulted an extreme number of false positives. These have |
|
|
3766 | been fixed, but some people still insist on making code warn-free with |
|
|
3767 | such buggy versions. |
|
|
3768 | .PP |
|
|
3769 | While libev is written to generate as few warnings as possible, |
|
|
3770 | \&\*(L"warn-free\*(R" code is not a goal, and it is recommended not to build libev |
|
|
3771 | with any compiler warnings enabled unless you are prepared to cope with |
|
|
3772 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
3773 | warnings, not errors, or proof of bugs. |
|
|
3774 | .Sh "\s-1VALGRIND\s0" |
|
|
3775 | .IX Subsection "VALGRIND" |
|
|
3776 | Valgrind has a special section here because it is a popular tool that is |
|
|
3777 | highly useful. Unfortunately, valgrind reports are very hard to interpret. |
|
|
3778 | .PP |
|
|
3779 | If you think you found a bug (memory leak, uninitialised data access etc.) |
|
|
3780 | in libev, then check twice: If valgrind reports something like: |
|
|
3781 | .PP |
|
|
3782 | .Vb 3 |
|
|
3783 | \& ==2274== definitely lost: 0 bytes in 0 blocks. |
|
|
3784 | \& ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
3785 | \& ==2274== still reachable: 256 bytes in 1 blocks. |
|
|
3786 | .Ve |
|
|
3787 | .PP |
|
|
3788 | Then there is no memory leak, just as memory accounted to global variables |
|
|
3789 | is not a memleak \- the memory is still being referenced, and didn't leak. |
|
|
3790 | .PP |
|
|
3791 | Similarly, under some circumstances, valgrind might report kernel bugs |
|
|
3792 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
|
|
3793 | although an acceptable workaround has been found here), or it might be |
|
|
3794 | confused. |
|
|
3795 | .PP |
|
|
3796 | Keep in mind that valgrind is a very good tool, but only a tool. Don't |
|
|
3797 | make it into some kind of religion. |
|
|
3798 | .PP |
|
|
3799 | If you are unsure about something, feel free to contact the mailing list |
|
|
3800 | with the full valgrind report and an explanation on why you think this |
|
|
3801 | is a bug in libev (best check the archives, too :). However, don't be |
|
|
3802 | annoyed when you get a brisk \*(L"this is no bug\*(R" answer and take the chance |
|
|
3803 | of learning how to interpret valgrind properly. |
|
|
3804 | .PP |
|
|
3805 | If you need, for some reason, empty reports from valgrind for your project |
|
|
3806 | I suggest using suppression lists. |
|
|
3807 | .SH "PORTABILITY NOTES" |
|
|
3808 | .IX Header "PORTABILITY NOTES" |
|
|
3809 | .Sh "\s-1WIN32\s0 \s-1PLATFORM\s0 \s-1LIMITATIONS\s0 \s-1AND\s0 \s-1WORKAROUNDS\s0" |
|
|
3810 | .IX Subsection "WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS" |
|
|
3811 | Win32 doesn't support any of the standards (e.g. \s-1POSIX\s0) that libev |
|
|
3812 | requires, and its I/O model is fundamentally incompatible with the \s-1POSIX\s0 |
|
|
3813 | model. Libev still offers limited functionality on this platform in |
|
|
3814 | the form of the \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR backend, and only supports socket |
|
|
3815 | descriptors. This only applies when using Win32 natively, not when using |
|
|
3816 | e.g. cygwin. |
|
|
3817 | .PP |
|
|
3818 | Lifting these limitations would basically require the full |
|
|
3819 | re-implementation of the I/O system. If you are into these kinds of |
|
|
3820 | things, then note that glib does exactly that for you in a very portable |
|
|
3821 | way (note also that glib is the slowest event library known to man). |
|
|
3822 | .PP |
|
|
3823 | There is no supported compilation method available on windows except |
|
|
3824 | embedding it into other applications. |
|
|
3825 | .PP |
|
|
3826 | Not a libev limitation but worth mentioning: windows apparently doesn't |
|
|
3827 | accept large writes: instead of resulting in a partial write, windows will |
|
|
3828 | either accept everything or return \f(CW\*(C`ENOBUFS\*(C'\fR if the buffer is too large, |
|
|
3829 | so make sure you only write small amounts into your sockets (less than a |
|
|
3830 | megabyte seems safe, but this apparently depends on the amount of memory |
|
|
3831 | available). |
|
|
3832 | .PP |
|
|
3833 | Due to the many, low, and arbitrary limits on the win32 platform and |
|
|
3834 | the abysmal performance of winsockets, using a large number of sockets |
|
|
3835 | is not recommended (and not reasonable). If your program needs to use |
|
|
3836 | more than a hundred or so sockets, then likely it needs to use a totally |
|
|
3837 | different implementation for windows, as libev offers the \s-1POSIX\s0 readiness |
|
|
3838 | notification model, which cannot be implemented efficiently on windows |
|
|
3839 | (Microsoft monopoly games). |
|
|
3840 | .PP |
|
|
3841 | A typical way to use libev under windows is to embed it (see the embedding |
|
|
3842 | section for details) and use the following \fIevwrap.h\fR header file instead |
|
|
3843 | of \fIev.h\fR: |
|
|
3844 | .PP |
|
|
3845 | .Vb 2 |
|
|
3846 | \& #define EV_STANDALONE /* keeps ev from requiring config.h */ |
|
|
3847 | \& #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
|
|
3848 | \& |
|
|
3849 | \& #include "ev.h" |
|
|
3850 | .Ve |
|
|
3851 | .PP |
|
|
3852 | And compile the following \fIevwrap.c\fR file into your project (make sure |
|
|
3853 | you do \fInot\fR compile the \fIev.c\fR or any other embedded source files!): |
|
|
3854 | .PP |
|
|
3855 | .Vb 2 |
|
|
3856 | \& #include "evwrap.h" |
|
|
3857 | \& #include "ev.c" |
|
|
3858 | .Ve |
|
|
3859 | .IP "The winsocket select function" 4 |
|
|
3860 | .IX Item "The winsocket select function" |
|
|
3861 | The winsocket \f(CW\*(C`select\*(C'\fR function doesn't follow \s-1POSIX\s0 in that it |
|
|
3862 | requires socket \fIhandles\fR and not socket \fIfile descriptors\fR (it is |
|
|
3863 | also extremely buggy). This makes select very inefficient, and also |
|
|
3864 | requires a mapping from file descriptors to socket handles (the Microsoft |
|
|
3865 | C runtime provides the function \f(CW\*(C`_open_osfhandle\*(C'\fR for this). See the |
|
|
3866 | discussion of the \f(CW\*(C`EV_SELECT_USE_FD_SET\*(C'\fR, \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR and |
|
|
3867 | \&\f(CW\*(C`EV_FD_TO_WIN32_HANDLE\*(C'\fR preprocessor symbols for more info. |
|
|
3868 | .Sp |
|
|
3869 | The configuration for a \*(L"naked\*(R" win32 using the Microsoft runtime |
|
|
3870 | libraries and raw winsocket select is: |
|
|
3871 | .Sp |
|
|
3872 | .Vb 2 |
|
|
3873 | \& #define EV_USE_SELECT 1 |
|
|
3874 | \& #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
|
|
3875 | .Ve |
|
|
3876 | .Sp |
|
|
3877 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
|
|
3878 | complexity in the O(nA\*^X) range when using win32. |
|
|
3879 | .IP "Limited number of file descriptors" 4 |
|
|
3880 | .IX Item "Limited number of file descriptors" |
|
|
3881 | Windows has numerous arbitrary (and low) limits on things. |
|
|
3882 | .Sp |
|
|
3883 | Early versions of winsocket's select only supported waiting for a maximum |
|
|
3884 | of \f(CW64\fR handles (probably owning to the fact that all windows kernels |
|
|
3885 | can only wait for \f(CW64\fR things at the same time internally; Microsoft |
|
|
3886 | recommends spawning a chain of threads and wait for 63 handles and the |
|
|
3887 | previous thread in each. Great). |
|
|
3888 | .Sp |
|
|
3889 | Newer versions support more handles, but you need to define \f(CW\*(C`FD_SETSIZE\*(C'\fR |
|
|
3890 | to some high number (e.g. \f(CW2048\fR) before compiling the winsocket select |
|
|
3891 | call (which might be in libev or elsewhere, for example, perl does its own |
|
|
3892 | select emulation on windows). |
|
|
3893 | .Sp |
|
|
3894 | Another limit is the number of file descriptors in the Microsoft runtime |
|
|
3895 | libraries, which by default is \f(CW64\fR (there must be a hidden \fI64\fR fetish |
|
|
3896 | or something like this inside Microsoft). You can increase this by calling |
|
|
3897 | \&\f(CW\*(C`_setmaxstdio\*(C'\fR, which can increase this limit to \f(CW2048\fR (another |
|
|
3898 | arbitrary limit), but is broken in many versions of the Microsoft runtime |
|
|
3899 | libraries. |
|
|
3900 | .Sp |
|
|
3901 | This might get you to about \f(CW512\fR or \f(CW2048\fR sockets (depending on |
|
|
3902 | windows version and/or the phase of the moon). To get more, you need to |
|
|
3903 | wrap all I/O functions and provide your own fd management, but the cost of |
|
|
3904 | calling select (O(nA\*^X)) will likely make this unworkable. |
|
|
3905 | .Sh "\s-1PORTABILITY\s0 \s-1REQUIREMENTS\s0" |
|
|
3906 | .IX Subsection "PORTABILITY REQUIREMENTS" |
|
|
3907 | In addition to a working ISO-C implementation and of course the |
|
|
3908 | backend-specific APIs, libev relies on a few additional extensions: |
|
|
3909 | .ie n .IP """void (*)(ev_watcher_type *, int revents)""\fR must have compatible calling conventions regardless of \f(CW""ev_watcher_type *""." 4 |
|
|
3910 | .el .IP "\f(CWvoid (*)(ev_watcher_type *, int revents)\fR must have compatible calling conventions regardless of \f(CWev_watcher_type *\fR." 4 |
|
|
3911 | .IX Item "void (*)(ev_watcher_type *, int revents) must have compatible calling conventions regardless of ev_watcher_type *." |
|
|
3912 | Libev assumes not only that all watcher pointers have the same internal |
|
|
3913 | structure (guaranteed by \s-1POSIX\s0 but not by \s-1ISO\s0 C for example), but it also |
|
|
3914 | assumes that the same (machine) code can be used to call any watcher |
|
|
3915 | callback: The watcher callbacks have different type signatures, but libev |
|
|
3916 | calls them using an \f(CW\*(C`ev_watcher *\*(C'\fR internally. |
|
|
3917 | .ie n .IP """sig_atomic_t volatile"" must be thread-atomic as well" 4 |
|
|
3918 | .el .IP "\f(CWsig_atomic_t volatile\fR must be thread-atomic as well" 4 |
|
|
3919 | .IX Item "sig_atomic_t volatile must be thread-atomic as well" |
|
|
3920 | The type \f(CW\*(C`sig_atomic_t volatile\*(C'\fR (or whatever is defined as |
|
|
3921 | \&\f(CW\*(C`EV_ATOMIC_T\*(C'\fR) must be atomic with respect to accesses from different |
|
|
3922 | threads. This is not part of the specification for \f(CW\*(C`sig_atomic_t\*(C'\fR, but is |
|
|
3923 | believed to be sufficiently portable. |
|
|
3924 | .ie n .IP """sigprocmask"" must work in a threaded environment" 4 |
|
|
3925 | .el .IP "\f(CWsigprocmask\fR must work in a threaded environment" 4 |
|
|
3926 | .IX Item "sigprocmask must work in a threaded environment" |
|
|
3927 | Libev uses \f(CW\*(C`sigprocmask\*(C'\fR to temporarily block signals. This is not |
|
|
3928 | allowed in a threaded program (\f(CW\*(C`pthread_sigmask\*(C'\fR has to be used). Typical |
|
|
3929 | pthread implementations will either allow \f(CW\*(C`sigprocmask\*(C'\fR in the \*(L"main |
|
|
3930 | thread\*(R" or will block signals process-wide, both behaviours would |
|
|
3931 | be compatible with libev. Interaction between \f(CW\*(C`sigprocmask\*(C'\fR and |
|
|
3932 | \&\f(CW\*(C`pthread_sigmask\*(C'\fR could complicate things, however. |
|
|
3933 | .Sp |
|
|
3934 | The most portable way to handle signals is to block signals in all threads |
|
|
3935 | except the initial one, and run the default loop in the initial thread as |
|
|
3936 | well. |
|
|
3937 | .ie n .IP """long"" must be large enough for common memory allocation sizes" 4 |
|
|
3938 | .el .IP "\f(CWlong\fR must be large enough for common memory allocation sizes" 4 |
|
|
3939 | .IX Item "long must be large enough for common memory allocation sizes" |
|
|
3940 | To improve portability and simplify its \s-1API\s0, libev uses \f(CW\*(C`long\*(C'\fR internally |
|
|
3941 | instead of \f(CW\*(C`size_t\*(C'\fR when allocating its data structures. On non-POSIX |
|
|
3942 | systems (Microsoft...) this might be unexpectedly low, but is still at |
|
|
3943 | least 31 bits everywhere, which is enough for hundreds of millions of |
|
|
3944 | watchers. |
|
|
3945 | .ie n .IP """double"" must hold a time value in seconds with enough accuracy" 4 |
|
|
3946 | .el .IP "\f(CWdouble\fR must hold a time value in seconds with enough accuracy" 4 |
|
|
3947 | .IX Item "double must hold a time value in seconds with enough accuracy" |
|
|
3948 | The type \f(CW\*(C`double\*(C'\fR is used to represent timestamps. It is required to |
|
|
3949 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
|
|
3950 | enough for at least into the year 4000. This requirement is fulfilled by |
|
|
3951 | implementations implementing \s-1IEEE\s0 754 (basically all existing ones). |
|
|
3952 | .PP |
|
|
3953 | If you know of other additional requirements drop me a note. |
|
|
3954 | .SH "ALGORITHMIC COMPLEXITIES" |
|
|
3955 | .IX Header "ALGORITHMIC COMPLEXITIES" |
|
|
3956 | In this section the complexities of (many of) the algorithms used inside |
|
|
3957 | libev will be documented. For complexity discussions about backends see |
|
|
3958 | the documentation for \f(CW\*(C`ev_default_init\*(C'\fR. |
|
|
3959 | .PP |
|
|
3960 | All of the following are about amortised time: If an array needs to be |
|
|
3961 | extended, libev needs to realloc and move the whole array, but this |
|
|
3962 | happens asymptotically rarer with higher number of elements, so O(1) might |
|
|
3963 | mean that libev does a lengthy realloc operation in rare cases, but on |
|
|
3964 | average it is much faster and asymptotically approaches constant time. |
|
|
3965 | .IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4 |
|
|
3966 | .IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" |
|
|
3967 | This means that, when you have a watcher that triggers in one hour and |
|
|
3968 | there are 100 watchers that would trigger before that, then inserting will |
|
|
3969 | have to skip roughly seven (\f(CW\*(C`ld 100\*(C'\fR) of these watchers. |
|
|
3970 | .IP "Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)" 4 |
|
|
3971 | .IX Item "Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)" |
|
|
3972 | That means that changing a timer costs less than removing/adding them, |
|
|
3973 | as only the relative motion in the event queue has to be paid for. |
|
|
3974 | .IP "Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)" 4 |
|
|
3975 | .IX Item "Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)" |
|
|
3976 | These just add the watcher into an array or at the head of a list. |
|
|
3977 | .IP "Stopping check/prepare/idle/fork/async watchers: O(1)" 4 |
|
|
3978 | .IX Item "Stopping check/prepare/idle/fork/async watchers: O(1)" |
|
|
3979 | .PD 0 |
|
|
3980 | .IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4 |
|
|
3981 | .IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))" |
|
|
3982 | .PD |
|
|
3983 | These watchers are stored in lists, so they need to be walked to find the |
|
|
3984 | correct watcher to remove. The lists are usually short (you don't usually |
|
|
3985 | have many watchers waiting for the same fd or signal: one is typical, two |
|
|
3986 | is rare). |
|
|
3987 | .IP "Finding the next timer in each loop iteration: O(1)" 4 |
|
|
3988 | .IX Item "Finding the next timer in each loop iteration: O(1)" |
|
|
3989 | By virtue of using a binary or 4\-heap, the next timer is always found at a |
|
|
3990 | fixed position in the storage array. |
|
|
3991 | .IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4 |
|
|
3992 | .IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" |
|
|
3993 | A change means an I/O watcher gets started or stopped, which requires |
|
|
3994 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
3995 | on backend and whether \f(CW\*(C`ev_io_set\*(C'\fR was used). |
|
|
3996 | .IP "Activating one watcher (putting it into the pending state): O(1)" 4 |
|
|
3997 | .IX Item "Activating one watcher (putting it into the pending state): O(1)" |
|
|
3998 | .PD 0 |
|
|
3999 | .IP "Priority handling: O(number_of_priorities)" 4 |
|
|
4000 | .IX Item "Priority handling: O(number_of_priorities)" |
|
|
4001 | .PD |
|
|
4002 | Priorities are implemented by allocating some space for each |
|
|
4003 | priority. When doing priority-based operations, libev usually has to |
|
|
4004 | linearly search all the priorities, but starting/stopping and activating |
|
|
4005 | watchers becomes O(1) with respect to priority handling. |
|
|
4006 | .IP "Sending an ev_async: O(1)" 4 |
|
|
4007 | .IX Item "Sending an ev_async: O(1)" |
|
|
4008 | .PD 0 |
|
|
4009 | .IP "Processing ev_async_send: O(number_of_async_watchers)" 4 |
|
|
4010 | .IX Item "Processing ev_async_send: O(number_of_async_watchers)" |
|
|
4011 | .IP "Processing signals: O(max_signal_number)" 4 |
|
|
4012 | .IX Item "Processing signals: O(max_signal_number)" |
|
|
4013 | .PD |
|
|
4014 | Sending involves a system call \fIiff\fR there were no other \f(CW\*(C`ev_async_send\*(C'\fR |
|
|
4015 | calls in the current loop iteration. Checking for async and signal events |
|
|
4016 | involves iterating over all running async watchers or all signal numbers. |
919 | .SH "AUTHOR" |
4017 | .SH "AUTHOR" |
920 | .IX Header "AUTHOR" |
4018 | .IX Header "AUTHOR" |
921 | Marc Lehmann <libev@schmorp.de>. |
4019 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |