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131 | .IX Title ""<STANDARD INPUT>" 1" |
134 | .IX Title "LIBEV 3" |
132 | .TH "<STANDARD INPUT>" 1 "2007-11-23" "perl v5.8.8" "User Contributed Perl Documentation" |
135 | .TH LIBEV 3 "2008-06-19" "libev-3.43" "libev - high performance full featured event loop" |
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136 | .\" For nroff, turn off justification. Always turn off hyphenation; it makes |
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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 | \& // every watcher type has its own typedef\*(Aqd struct |
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154 | \& // with the name ev_<type> |
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155 | \& ev_io stdin_watcher; |
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156 | \& ev_timer timeout_watcher; |
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157 | \& |
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158 | \& // all watcher callbacks have a similar signature |
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159 | \& // this callback is called when data is readable on stdin |
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160 | \& static void |
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161 | \& stdin_cb (EV_P_ struct ev_io *w, int revents) |
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162 | \& { |
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163 | \& puts ("stdin ready"); |
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164 | \& // for one\-shot events, one must manually stop the watcher |
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165 | \& // with its corresponding stop function. |
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166 | \& ev_io_stop (EV_A_ w); |
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167 | \& |
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168 | \& // this causes all nested ev_loop\*(Aqs to stop iterating |
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169 | \& ev_unloop (EV_A_ EVUNLOOP_ALL); |
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170 | \& } |
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171 | \& |
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172 | \& // another callback, this time for a time\-out |
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173 | \& static void |
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174 | \& timeout_cb (EV_P_ struct ev_timer *w, int revents) |
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175 | \& { |
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176 | \& puts ("timeout"); |
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177 | \& // this causes the innermost ev_loop to stop iterating |
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178 | \& ev_unloop (EV_A_ EVUNLOOP_ONE); |
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179 | \& } |
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180 | \& |
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181 | \& int |
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182 | \& main (void) |
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183 | \& { |
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184 | \& // use the default event loop unless you have special needs |
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185 | \& struct ev_loop *loop = ev_default_loop (0); |
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186 | \& |
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187 | \& // initialise an io watcher, then start it |
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188 | \& // this one will watch for stdin to become readable |
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189 | \& ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
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190 | \& ev_io_start (loop, &stdin_watcher); |
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191 | \& |
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192 | \& // initialise a timer watcher, then start it |
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193 | \& // simple non\-repeating 5.5 second timeout |
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194 | \& ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
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195 | \& ev_timer_start (loop, &timeout_watcher); |
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196 | \& |
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197 | \& // now wait for events to arrive |
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198 | \& ev_loop (loop, 0); |
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199 | \& |
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200 | \& // unloop was called, so exit |
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201 | \& return 0; |
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202 | \& } |
139 | .Ve |
203 | .Ve |
140 | .SH "DESCRIPTION" |
204 | .SH "DESCRIPTION" |
141 | .IX Header "DESCRIPTION" |
205 | .IX Header "DESCRIPTION" |
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206 | The newest version of this document is also available as an html-formatted |
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207 | web page you might find easier to navigate when reading it for the first |
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208 | time: <http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
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209 | .PP |
142 | Libev is an event loop: you register interest in certain events (such as a |
210 | 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 |
211 | file descriptor being readable or a timeout occurring), and it will manage |
144 | these event sources and provide your program with events. |
212 | these event sources and provide your program with events. |
145 | .PP |
213 | .PP |
146 | To do this, it must take more or less complete control over your process |
214 | 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 |
215 | (or thread) by executing the \fIevent loop\fR handler, and will then |
148 | communicate events via a callback mechanism. |
216 | communicate events via a callback mechanism. |
149 | .PP |
217 | .PP |
150 | You register interest in certain events by registering so-called \fIevent |
218 | You register interest in certain events by registering so-called \fIevent |
151 | watchers\fR, which are relatively small C structures you initialise with the |
219 | 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 |
220 | details of the event, and then hand it over to libev by \fIstarting\fR the |
153 | watcher. |
221 | watcher. |
154 | .SH "FEATURES" |
222 | .Sh "\s-1FEATURES\s0" |
155 | .IX Header "FEATURES" |
223 | .IX Subsection "FEATURES" |
156 | Libev supports select, poll, the linux-specific epoll and the bsd-specific |
224 | 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 |
225 | 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 |
226 | 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 |
227 | (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 |
228 | with customised rescheduling (\f(CW\*(C`ev_periodic\*(C'\fR), synchronous signals |
161 | fast (see this benchmark comparing |
229 | (\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). |
230 | watchers dealing with the event loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR, |
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231 | \&\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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232 | file watchers (\f(CW\*(C`ev_stat\*(C'\fR) and even limited support for fork events |
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233 | (\f(CW\*(C`ev_fork\*(C'\fR). |
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234 | .PP |
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235 | It also is quite fast (see this |
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236 | benchmark comparing it to libevent |
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237 | for example). |
163 | .SH "CONVENTIONS" |
238 | .Sh "\s-1CONVENTIONS\s0" |
164 | .IX Header "CONVENTIONS" |
239 | .IX Subsection "CONVENTIONS" |
165 | Libev is very configurable. In this manual the default configuration |
240 | Libev is very configurable. In this manual the default (and most common) |
166 | will be described, which supports multiple event loops. For more info |
241 | configuration will be described, which supports multiple event loops. For |
167 | about various configuration options please have a look at the file |
242 | 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 |
243 | \&\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 |
244 | 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) |
245 | name \f(CW\*(C`loop\*(C'\fR (which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR) will not have |
171 | will not have this argument. |
246 | this argument. |
172 | .SH "TIME REPRESENTATION" |
247 | .Sh "\s-1TIME\s0 \s-1REPRESENTATION\s0" |
173 | .IX Header "TIME REPRESENTATION" |
248 | .IX Subsection "TIME REPRESENTATION" |
174 | Libev represents time as a single floating point number, representing the |
249 | Libev represents time as a single floating point number, representing the |
175 | (fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near |
250 | (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 |
251 | 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 |
252 | 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. |
253 | to the \f(CW\*(C`double\*(C'\fR type in C, and when you need to do any calculations on |
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254 | it, you should treat it as some floating point value. Unlike the name |
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255 | component \f(CW\*(C`stamp\*(C'\fR might indicate, it is also used for time differences |
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256 | throughout libev. |
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257 | .SH "ERROR HANDLING" |
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258 | .IX Header "ERROR HANDLING" |
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259 | Libev knows three classes of errors: operating system errors, usage errors |
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260 | and internal errors (bugs). |
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261 | .PP |
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262 | When libev catches an operating system error it cannot handle (for example |
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263 | a system call indicating a condition libev cannot fix), it calls the callback |
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264 | set via \f(CW\*(C`ev_set_syserr_cb\*(C'\fR, which is supposed to fix the problem or |
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265 | abort. The default is to print a diagnostic message and to call \f(CW\*(C`abort |
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266 | ()\*(C'\fR. |
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267 | .PP |
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268 | When libev detects a usage error such as a negative timer interval, then |
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269 | it will print a diagnostic message and abort (via the \f(CW\*(C`assert\*(C'\fR mechanism, |
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270 | so \f(CW\*(C`NDEBUG\*(C'\fR will disable this checking): these are programming errors in |
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271 | the libev caller and need to be fixed there. |
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272 | .PP |
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273 | Libev also has a few internal error-checking \f(CW\*(C`assert\*(C'\fRions, and also has |
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274 | extensive consistency checking code. These do not trigger under normal |
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275 | circumstances, as they indicate either a bug in libev or worse. |
179 | .SH "GLOBAL FUNCTIONS" |
276 | .SH "GLOBAL FUNCTIONS" |
180 | .IX Header "GLOBAL FUNCTIONS" |
277 | .IX Header "GLOBAL FUNCTIONS" |
181 | These functions can be called anytime, even before initialising the |
278 | These functions can be called anytime, even before initialising the |
182 | library in any way. |
279 | library in any way. |
183 | .IP "ev_tstamp ev_time ()" 4 |
280 | .IP "ev_tstamp ev_time ()" 4 |
184 | .IX Item "ev_tstamp ev_time ()" |
281 | .IX Item "ev_tstamp ev_time ()" |
185 | Returns the current time as libev would use it. Please note that the |
282 | 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 |
283 | \&\f(CW\*(C`ev_now\*(C'\fR function is usually faster and also often returns the timestamp |
187 | you actually want to know. |
284 | you actually want to know. |
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285 | .IP "ev_sleep (ev_tstamp interval)" 4 |
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286 | .IX Item "ev_sleep (ev_tstamp interval)" |
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287 | Sleep for the given interval: The current thread will be blocked until |
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288 | either it is interrupted or the given time interval has passed. Basically |
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289 | this is a sub-second-resolution \f(CW\*(C`sleep ()\*(C'\fR. |
188 | .IP "int ev_version_major ()" 4 |
290 | .IP "int ev_version_major ()" 4 |
189 | .IX Item "int ev_version_major ()" |
291 | .IX Item "int ev_version_major ()" |
190 | .PD 0 |
292 | .PD 0 |
191 | .IP "int ev_version_minor ()" 4 |
293 | .IP "int ev_version_minor ()" 4 |
192 | .IX Item "int ev_version_minor ()" |
294 | .IX Item "int ev_version_minor ()" |
193 | .PD |
295 | .PD |
194 | You can find out the major and minor version numbers of the library |
296 | 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 |
297 | 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 |
298 | \&\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 |
299 | 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. |
300 | version of the library your program was compiled against. |
199 | .Sp |
301 | .Sp |
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302 | These version numbers refer to the \s-1ABI\s0 version of the library, not the |
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303 | release version. |
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304 | .Sp |
200 | Usually, it's a good idea to terminate if the major versions mismatch, |
305 | Usually, it's a good idea to terminate if the major versions mismatch, |
201 | as this indicates an incompatible change. Minor versions are usually |
306 | as this indicates an incompatible change. Minor versions are usually |
202 | compatible to older versions, so a larger minor version alone is usually |
307 | compatible to older versions, so a larger minor version alone is usually |
203 | not a problem. |
308 | not a problem. |
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309 | .Sp |
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310 | Example: Make sure we haven't accidentally been linked against the wrong |
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311 | version. |
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312 | .Sp |
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313 | .Vb 3 |
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314 | \& assert (("libev version mismatch", |
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315 | \& ev_version_major () == EV_VERSION_MAJOR |
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316 | \& && ev_version_minor () >= EV_VERSION_MINOR)); |
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317 | .Ve |
204 | .IP "unsigned int ev_supported_backends ()" 4 |
318 | .IP "unsigned int ev_supported_backends ()" 4 |
205 | .IX Item "unsigned int ev_supported_backends ()" |
319 | .IX Item "unsigned int ev_supported_backends ()" |
206 | Return the set of all backends (i.e. their corresponding \f(CW\*(C`EV_BACKEND_*\*(C'\fR |
320 | Return the set of all backends (i.e. their corresponding \f(CW\*(C`EV_BACKEND_*\*(C'\fR |
207 | value) compiled into this binary of libev (independent of their |
321 | value) compiled into this binary of libev (independent of their |
208 | availability on the system you are running on). See \f(CW\*(C`ev_default_loop\*(C'\fR for |
322 | availability on the system you are running on). See \f(CW\*(C`ev_default_loop\*(C'\fR for |
209 | a description of the set values. |
323 | a description of the set values. |
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324 | .Sp |
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325 | Example: make sure we have the epoll method, because yeah this is cool and |
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326 | a must have and can we have a torrent of it please!!!11 |
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327 | .Sp |
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328 | .Vb 2 |
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329 | \& assert (("sorry, no epoll, no sex", |
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330 | \& ev_supported_backends () & EVBACKEND_EPOLL)); |
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331 | .Ve |
210 | .IP "unsigned int ev_recommended_backends ()" 4 |
332 | .IP "unsigned int ev_recommended_backends ()" 4 |
211 | .IX Item "unsigned int ev_recommended_backends ()" |
333 | .IX Item "unsigned int ev_recommended_backends ()" |
212 | Return the set of all backends compiled into this binary of libev and also |
334 | Return the set of all backends compiled into this binary of libev and also |
213 | recommended for this platform. This set is often smaller than the one |
335 | recommended for this platform. This set is often smaller than the one |
214 | returned by \f(CW\*(C`ev_supported_backends\*(C'\fR, as for example kqueue is broken on |
336 | returned by \f(CW\*(C`ev_supported_backends\*(C'\fR, as for example kqueue is broken on |
215 | most BSDs and will not be autodetected unless you explicitly request it |
337 | most BSDs and will not be auto-detected unless you explicitly request it |
216 | (assuming you know what you are doing). This is the set of backends that |
338 | (assuming you know what you are doing). This is the set of backends that |
217 | \&\f(CW\*(C`EVFLAG_AUTO\*(C'\fR will probe for. |
339 | libev will probe for if you specify no backends explicitly. |
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340 | .IP "unsigned int ev_embeddable_backends ()" 4 |
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341 | .IX Item "unsigned int ev_embeddable_backends ()" |
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342 | Returns the set of backends that are embeddable in other event loops. This |
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343 | is the theoretical, all-platform, value. To find which backends |
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344 | might be supported on the current system, you would need to look at |
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345 | \&\f(CW\*(C`ev_embeddable_backends () & ev_supported_backends ()\*(C'\fR, likewise for |
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346 | recommended ones. |
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347 | .Sp |
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348 | See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info. |
218 | .IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4 |
349 | .IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4 |
219 | .IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))" |
350 | .IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))" |
220 | Sets the allocation function to use (the prototype is similar to the |
351 | Sets the allocation function to use (the prototype is similar \- the |
221 | realloc C function, the semantics are identical). It is used to allocate |
352 | semantics are identical to the \f(CW\*(C`realloc\*(C'\fR C89/SuS/POSIX function). It is |
222 | and free memory (no surprises here). If it returns zero when memory |
353 | used to allocate and free memory (no surprises here). If it returns zero |
223 | needs to be allocated, the library might abort or take some potentially |
354 | when memory needs to be allocated (\f(CW\*(C`size != 0\*(C'\fR), the library might abort |
224 | destructive action. The default is your system realloc function. |
355 | or take some potentially destructive action. |
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356 | .Sp |
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357 | Since some systems (at least OpenBSD and Darwin) fail to implement |
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358 | correct \f(CW\*(C`realloc\*(C'\fR semantics, libev will use a wrapper around the system |
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359 | \&\f(CW\*(C`realloc\*(C'\fR and \f(CW\*(C`free\*(C'\fR functions by default. |
225 | .Sp |
360 | .Sp |
226 | You could override this function in high-availability programs to, say, |
361 | You could override this function in high-availability programs to, say, |
227 | free some memory if it cannot allocate memory, to use a special allocator, |
362 | free some memory if it cannot allocate memory, to use a special allocator, |
228 | or even to sleep a while and retry until some memory is available. |
363 | or even to sleep a while and retry until some memory is available. |
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364 | .Sp |
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365 | Example: Replace the libev allocator with one that waits a bit and then |
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366 | retries (example requires a standards-compliant \f(CW\*(C`realloc\*(C'\fR). |
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367 | .Sp |
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368 | .Vb 6 |
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369 | \& static void * |
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370 | \& persistent_realloc (void *ptr, size_t size) |
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371 | \& { |
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372 | \& for (;;) |
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373 | \& { |
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374 | \& void *newptr = realloc (ptr, size); |
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375 | \& |
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376 | \& if (newptr) |
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377 | \& return newptr; |
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378 | \& |
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379 | \& sleep (60); |
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380 | \& } |
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381 | \& } |
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382 | \& |
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383 | \& ... |
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384 | \& ev_set_allocator (persistent_realloc); |
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385 | .Ve |
229 | .IP "ev_set_syserr_cb (void (*cb)(const char *msg));" 4 |
386 | .IP "ev_set_syserr_cb (void (*cb)(const char *msg));" 4 |
230 | .IX Item "ev_set_syserr_cb (void (*cb)(const char *msg));" |
387 | .IX Item "ev_set_syserr_cb (void (*cb)(const char *msg));" |
231 | Set the callback function to call on a retryable syscall error (such |
388 | Set the callback function to call on a retryable system call error (such |
232 | as failed select, poll, epoll_wait). The message is a printable string |
389 | as failed select, poll, epoll_wait). The message is a printable string |
233 | indicating the system call or subsystem causing the problem. If this |
390 | indicating the system call or subsystem causing the problem. If this |
234 | callback is set, then libev will expect it to remedy the sitution, no |
391 | callback is set, then libev will expect it to remedy the situation, no |
235 | matter what, when it returns. That is, libev will generally retry the |
392 | matter what, when it returns. That is, libev will generally retry the |
236 | requested operation, or, if the condition doesn't go away, do bad stuff |
393 | requested operation, or, if the condition doesn't go away, do bad stuff |
237 | (such as abort). |
394 | (such as abort). |
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395 | .Sp |
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396 | Example: This is basically the same thing that libev does internally, too. |
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397 | .Sp |
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398 | .Vb 6 |
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399 | \& static void |
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400 | \& fatal_error (const char *msg) |
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401 | \& { |
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402 | \& perror (msg); |
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403 | \& abort (); |
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404 | \& } |
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405 | \& |
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406 | \& ... |
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407 | \& ev_set_syserr_cb (fatal_error); |
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408 | .Ve |
238 | .SH "FUNCTIONS CONTROLLING THE EVENT LOOP" |
409 | .SH "FUNCTIONS CONTROLLING THE EVENT LOOP" |
239 | .IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP" |
410 | .IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP" |
240 | An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR. The library knows two |
411 | An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR. The library knows two |
241 | types of such loops, the \fIdefault\fR loop, which supports signals and child |
412 | types of such loops, the \fIdefault\fR loop, which supports signals and child |
242 | events, and dynamically created loops which do not. |
413 | events, and dynamically created loops which do not. |
243 | .PP |
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244 | If you use threads, a common model is to run the default event loop |
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245 | in your main thread (or in a separate thread) and for each thread you |
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246 | create, you also create another event loop. Libev itself does no locking |
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247 | whatsoever, so if you mix calls to the same event loop in different |
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248 | threads, make sure you lock (this is usually a bad idea, though, even if |
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249 | done correctly, because it's hideous and inefficient). |
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250 | .IP "struct ev_loop *ev_default_loop (unsigned int flags)" 4 |
414 | .IP "struct ev_loop *ev_default_loop (unsigned int flags)" 4 |
251 | .IX Item "struct ev_loop *ev_default_loop (unsigned int flags)" |
415 | .IX Item "struct ev_loop *ev_default_loop (unsigned int flags)" |
252 | This will initialise the default event loop if it hasn't been initialised |
416 | This will initialise the default event loop if it hasn't been initialised |
253 | yet and return it. If the default loop could not be initialised, returns |
417 | yet and return it. If the default loop could not be initialised, returns |
254 | false. If it already was initialised it simply returns it (and ignores the |
418 | false. If it already was initialised it simply returns it (and ignores the |
255 | flags. If that is troubling you, check \f(CW\*(C`ev_backend ()\*(C'\fR afterwards). |
419 | flags. If that is troubling you, check \f(CW\*(C`ev_backend ()\*(C'\fR afterwards). |
256 | .Sp |
420 | .Sp |
257 | If you don't know what event loop to use, use the one returned from this |
421 | If you don't know what event loop to use, use the one returned from this |
258 | function. |
422 | function. |
259 | .Sp |
423 | .Sp |
|
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424 | Note that this function is \fInot\fR thread-safe, so if you want to use it |
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425 | from multiple threads, you have to lock (note also that this is unlikely, |
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426 | as loops cannot bes hared easily between threads anyway). |
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427 | .Sp |
|
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428 | The default loop is the only loop that can handle \f(CW\*(C`ev_signal\*(C'\fR and |
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429 | \&\f(CW\*(C`ev_child\*(C'\fR watchers, and to do this, it always registers a handler |
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430 | for \f(CW\*(C`SIGCHLD\*(C'\fR. If this is a problem for your application you can either |
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431 | create a dynamic loop with \f(CW\*(C`ev_loop_new\*(C'\fR that doesn't do that, or you |
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432 | can simply overwrite the \f(CW\*(C`SIGCHLD\*(C'\fR signal handler \fIafter\fR calling |
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433 | \&\f(CW\*(C`ev_default_init\*(C'\fR. |
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434 | .Sp |
260 | The flags argument can be used to specify special behaviour or specific |
435 | The flags argument can be used to specify special behaviour or specific |
261 | backends to use, and is usually specified as \f(CW0\fR (or \s-1EVFLAG_AUTO\s0). |
436 | backends to use, and is usually specified as \f(CW0\fR (or \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). |
262 | .Sp |
437 | .Sp |
263 | It supports the following flags: |
438 | The following flags are supported: |
264 | .RS 4 |
439 | .RS 4 |
265 | .ie n .IP """EVFLAG_AUTO""" 4 |
440 | .ie n .IP """EVFLAG_AUTO""" 4 |
266 | .el .IP "\f(CWEVFLAG_AUTO\fR" 4 |
441 | .el .IP "\f(CWEVFLAG_AUTO\fR" 4 |
267 | .IX Item "EVFLAG_AUTO" |
442 | .IX Item "EVFLAG_AUTO" |
268 | The default flags value. Use this if you have no clue (it's the right |
443 | The default flags value. Use this if you have no clue (it's the right |
269 | thing, believe me). |
444 | thing, believe me). |
270 | .ie n .IP """EVFLAG_NOENV""" 4 |
445 | .ie n .IP """EVFLAG_NOENV""" 4 |
271 | .el .IP "\f(CWEVFLAG_NOENV\fR" 4 |
446 | .el .IP "\f(CWEVFLAG_NOENV\fR" 4 |
272 | .IX Item "EVFLAG_NOENV" |
447 | .IX Item "EVFLAG_NOENV" |
273 | If this flag bit is ored into the flag value (or the program runs setuid |
448 | If this flag bit is or'ed into the flag value (or the program runs setuid |
274 | or setgid) then libev will \fInot\fR look at the environment variable |
449 | or setgid) then libev will \fInot\fR look at the environment variable |
275 | \&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will |
450 | \&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will |
276 | override the flags completely if it is found in the environment. This is |
451 | override the flags completely if it is found in the environment. This is |
277 | useful to try out specific backends to test their performance, or to work |
452 | useful to try out specific backends to test their performance, or to work |
278 | around bugs. |
453 | around bugs. |
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454 | .ie n .IP """EVFLAG_FORKCHECK""" 4 |
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455 | .el .IP "\f(CWEVFLAG_FORKCHECK\fR" 4 |
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456 | .IX Item "EVFLAG_FORKCHECK" |
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457 | Instead of calling \f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR manually after |
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458 | a fork, you can also make libev check for a fork in each iteration by |
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459 | enabling this flag. |
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460 | .Sp |
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461 | This works by calling \f(CW\*(C`getpid ()\*(C'\fR on every iteration of the loop, |
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462 | and thus this might slow down your event loop if you do a lot of loop |
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463 | iterations and little real work, but is usually not noticeable (on my |
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464 | GNU/Linux system for example, \f(CW\*(C`getpid\*(C'\fR is actually a simple 5\-insn sequence |
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465 | without a system call and thus \fIvery\fR fast, but my GNU/Linux system also has |
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466 | \&\f(CW\*(C`pthread_atfork\*(C'\fR which is even faster). |
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467 | .Sp |
|
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468 | The big advantage of this flag is that you can forget about fork (and |
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469 | forget about forgetting to tell libev about forking) when you use this |
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470 | flag. |
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471 | .Sp |
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472 | This flag setting cannot be overridden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR |
|
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473 | environment variable. |
279 | .ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4 |
474 | .ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4 |
280 | .el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4 |
475 | .el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4 |
281 | .IX Item "EVBACKEND_SELECT (value 1, portable select backend)" |
476 | .IX Item "EVBACKEND_SELECT (value 1, portable select backend)" |
282 | This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as |
477 | This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as |
283 | libev tries to roll its own fd_set with no limits on the number of fds, |
478 | libev tries to roll its own fd_set with no limits on the number of fds, |
284 | but if that fails, expect a fairly low limit on the number of fds when |
479 | but if that fails, expect a fairly low limit on the number of fds when |
285 | using this backend. It doesn't scale too well (O(highest_fd)), but its usually |
480 | using this backend. It doesn't scale too well (O(highest_fd)), but its |
286 | the fastest backend for a low number of fds. |
481 | usually the fastest backend for a low number of (low-numbered :) fds. |
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482 | .Sp |
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483 | To get good performance out of this backend you need a high amount of |
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484 | parallelism (most of the file descriptors should be busy). If you are |
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485 | writing a server, you should \f(CW\*(C`accept ()\*(C'\fR in a loop to accept as many |
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486 | connections as possible during one iteration. You might also want to have |
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487 | a look at \f(CW\*(C`ev_set_io_collect_interval ()\*(C'\fR to increase the amount of |
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488 | readiness notifications you get per iteration. |
287 | .ie n .IP """EVBACKEND_POLL"" (value 2, poll backend, available everywhere except on windows)" 4 |
489 | .ie n .IP """EVBACKEND_POLL"" (value 2, poll backend, available everywhere except on windows)" 4 |
288 | .el .IP "\f(CWEVBACKEND_POLL\fR (value 2, poll backend, available everywhere except on windows)" 4 |
490 | .el .IP "\f(CWEVBACKEND_POLL\fR (value 2, poll backend, available everywhere except on windows)" 4 |
289 | .IX Item "EVBACKEND_POLL (value 2, poll backend, available everywhere except on windows)" |
491 | .IX Item "EVBACKEND_POLL (value 2, poll backend, available everywhere except on windows)" |
290 | And this is your standard \fIpoll\fR\|(2) backend. It's more complicated than |
492 | And this is your standard \fIpoll\fR\|(2) backend. It's more complicated |
291 | select, but handles sparse fds better and has no artificial limit on the |
493 | than select, but handles sparse fds better and has no artificial |
292 | number of fds you can use (except it will slow down considerably with a |
494 | limit on the number of fds you can use (except it will slow down |
293 | lot of inactive fds). It scales similarly to select, i.e. O(total_fds). |
495 | considerably with a lot of inactive fds). It scales similarly to select, |
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496 | i.e. O(total_fds). See the entry for \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR, above, for |
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497 | performance tips. |
294 | .ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4 |
498 | .ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4 |
295 | .el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4 |
499 | .el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4 |
296 | .IX Item "EVBACKEND_EPOLL (value 4, Linux)" |
500 | .IX Item "EVBACKEND_EPOLL (value 4, Linux)" |
297 | For few fds, this backend is a bit little slower than poll and select, |
501 | For few fds, this backend is a bit little slower than poll and select, |
298 | but it scales phenomenally better. While poll and select usually scale like |
502 | but it scales phenomenally better. While poll and select usually scale |
299 | O(total_fds) where n is the total number of fds (or the highest fd), epoll scales |
503 | like O(total_fds) where n is the total number of fds (or the highest fd), |
300 | either O(1) or O(active_fds). |
504 | epoll scales either O(1) or O(active_fds). The epoll design has a number |
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505 | of shortcomings, such as silently dropping events in some hard-to-detect |
|
|
506 | cases and requiring a system call per fd change, no fork support and bad |
|
|
507 | support for dup. |
301 | .Sp |
508 | .Sp |
302 | While stopping and starting an I/O watcher in the same iteration will |
509 | While stopping, setting and starting an I/O watcher in the same iteration |
303 | result in some caching, there is still a syscall per such incident |
510 | will result in some caching, there is still a system call per such incident |
304 | (because the fd could point to a different file description now), so its |
511 | (because the fd could point to a different file description now), so its |
305 | best to avoid that. Also, \fIdup()\fRed file descriptors might not work very |
512 | best to avoid that. Also, \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors might not work |
306 | well if you register events for both fds. |
513 | very well if you register events for both fds. |
307 | .Sp |
514 | .Sp |
308 | Please note that epoll sometimes generates spurious notifications, so you |
515 | Please note that epoll sometimes generates spurious notifications, so you |
309 | need to use non-blocking I/O or other means to avoid blocking when no data |
516 | need to use non-blocking I/O or other means to avoid blocking when no data |
310 | (or space) is available. |
517 | (or space) is available. |
|
|
518 | .Sp |
|
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519 | Best performance from this backend is achieved by not unregistering all |
|
|
520 | watchers for a file descriptor until it has been closed, if possible, i.e. |
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521 | keep at least one watcher active per fd at all times. |
|
|
522 | .Sp |
|
|
523 | While nominally embeddable in other event loops, this feature is broken in |
|
|
524 | all kernel versions tested so far. |
311 | .ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4 |
525 | .ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4 |
312 | .el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4 |
526 | .el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4 |
313 | .IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)" |
527 | .IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)" |
314 | Kqueue deserves special mention, as at the time of this writing, it |
528 | Kqueue deserves special mention, as at the time of this writing, it |
315 | was broken on all BSDs except NetBSD (usually it doesn't work with |
529 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
316 | anything but sockets and pipes, except on Darwin, where of course its |
530 | with anything but sockets and pipes, except on Darwin, where of course |
317 | completely useless). For this reason its not being \*(L"autodetected\*(R" unless |
531 | it's completely useless). For this reason it's not being \*(L"auto-detected\*(R" |
318 | you explicitly specify the flags (i.e. you don't use \s-1EVFLAG_AUTO\s0). |
532 | unless you explicitly specify it explicitly in the flags (i.e. using |
|
|
533 | \&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR) or libev was compiled on a known-to-be-good (\-enough) |
|
|
534 | system like NetBSD. |
|
|
535 | .Sp |
|
|
536 | You still can embed kqueue into a normal poll or select backend and use it |
|
|
537 | only for sockets (after having made sure that sockets work with kqueue on |
|
|
538 | the target platform). See \f(CW\*(C`ev_embed\*(C'\fR watchers for more info. |
319 | .Sp |
539 | .Sp |
320 | It scales in the same way as the epoll backend, but the interface to the |
540 | It scales in the same way as the epoll backend, but the interface to the |
321 | kernel is more efficient (which says nothing about its actual speed, of |
541 | kernel is more efficient (which says nothing about its actual speed, of |
322 | course). While starting and stopping an I/O watcher does not cause an |
542 | course). While stopping, setting and starting an I/O watcher does never |
323 | extra syscall as with epoll, it still adds up to four event changes per |
543 | cause an extra system call as with \f(CW\*(C`EVBACKEND_EPOLL\*(C'\fR, it still adds up to |
324 | incident, so its best to avoid that. |
544 | two event changes per incident, support for \f(CW\*(C`fork ()\*(C'\fR is very bad and it |
|
|
545 | drops fds silently in similarly hard-to-detect cases. |
|
|
546 | .Sp |
|
|
547 | This backend usually performs well under most conditions. |
|
|
548 | .Sp |
|
|
549 | While nominally embeddable in other event loops, this doesn't work |
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|
550 | everywhere, so you might need to test for this. And since it is broken |
|
|
551 | almost everywhere, you should only use it when you have a lot of sockets |
|
|
552 | (for which it usually works), by embedding it into another event loop |
|
|
553 | (e.g. \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR) and using it only for |
|
|
554 | sockets. |
325 | .ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4 |
555 | .ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4 |
326 | .el .IP "\f(CWEVBACKEND_DEVPOLL\fR (value 16, Solaris 8)" 4 |
556 | .el .IP "\f(CWEVBACKEND_DEVPOLL\fR (value 16, Solaris 8)" 4 |
327 | .IX Item "EVBACKEND_DEVPOLL (value 16, Solaris 8)" |
557 | .IX Item "EVBACKEND_DEVPOLL (value 16, Solaris 8)" |
328 | This is not implemented yet (and might never be). |
558 | This is not implemented yet (and might never be, unless you send me an |
|
|
559 | implementation). According to reports, \f(CW\*(C`/dev/poll\*(C'\fR only supports sockets |
|
|
560 | and is not embeddable, which would limit the usefulness of this backend |
|
|
561 | immensely. |
329 | .ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4 |
562 | .ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4 |
330 | .el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4 |
563 | .el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4 |
331 | .IX Item "EVBACKEND_PORT (value 32, Solaris 10)" |
564 | .IX Item "EVBACKEND_PORT (value 32, Solaris 10)" |
332 | This uses the Solaris 10 port mechanism. As with everything on Solaris, |
565 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
333 | it's really slow, but it still scales very well (O(active_fds)). |
566 | it's really slow, but it still scales very well (O(active_fds)). |
334 | .Sp |
567 | .Sp |
335 | Please note that solaris ports can result in a lot of spurious |
568 | Please note that Solaris event ports can deliver a lot of spurious |
336 | notifications, so you need to use non-blocking I/O or other means to avoid |
569 | notifications, so you need to use non-blocking I/O or other means to avoid |
337 | blocking when no data (or space) is available. |
570 | blocking when no data (or space) is available. |
|
|
571 | .Sp |
|
|
572 | While this backend scales well, it requires one system call per active |
|
|
573 | file descriptor per loop iteration. For small and medium numbers of file |
|
|
574 | descriptors a \*(L"slow\*(R" \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR backend |
|
|
575 | might perform better. |
|
|
576 | .Sp |
|
|
577 | On the positive side, ignoring the spurious readiness notifications, this |
|
|
578 | backend actually performed to specification in all tests and is fully |
|
|
579 | embeddable, which is a rare feat among the OS-specific backends. |
338 | .ie n .IP """EVBACKEND_ALL""" 4 |
580 | .ie n .IP """EVBACKEND_ALL""" 4 |
339 | .el .IP "\f(CWEVBACKEND_ALL\fR" 4 |
581 | .el .IP "\f(CWEVBACKEND_ALL\fR" 4 |
340 | .IX Item "EVBACKEND_ALL" |
582 | .IX Item "EVBACKEND_ALL" |
341 | Try all backends (even potentially broken ones that wouldn't be tried |
583 | Try all backends (even potentially broken ones that wouldn't be tried |
342 | with \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). Since this is a mask, you can do stuff such as |
584 | with \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). Since this is a mask, you can do stuff such as |
343 | \&\f(CW\*(C`EVBACKEND_ALL & ~EVBACKEND_KQUEUE\*(C'\fR. |
585 | \&\f(CW\*(C`EVBACKEND_ALL & ~EVBACKEND_KQUEUE\*(C'\fR. |
|
|
586 | .Sp |
|
|
587 | It is definitely not recommended to use this flag. |
344 | .RE |
588 | .RE |
345 | .RS 4 |
589 | .RS 4 |
346 | .Sp |
590 | .Sp |
347 | If one or more of these are ored into the flags value, then only these |
591 | If one or more of these are or'ed into the flags value, then only these |
348 | backends will be tried (in the reverse order as given here). If none are |
592 | backends will be tried (in the reverse order as listed here). If none are |
349 | specified, most compiled-in backend will be tried, usually in reverse |
593 | specified, all backends in \f(CW\*(C`ev_recommended_backends ()\*(C'\fR will be tried. |
350 | order of their flag values :) |
594 | .Sp |
|
|
595 | The most typical usage is like this: |
|
|
596 | .Sp |
|
|
597 | .Vb 2 |
|
|
598 | \& if (!ev_default_loop (0)) |
|
|
599 | \& fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
|
|
600 | .Ve |
|
|
601 | .Sp |
|
|
602 | Restrict libev to the select and poll backends, and do not allow |
|
|
603 | environment settings to be taken into account: |
|
|
604 | .Sp |
|
|
605 | .Vb 1 |
|
|
606 | \& ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
|
|
607 | .Ve |
|
|
608 | .Sp |
|
|
609 | Use whatever libev has to offer, but make sure that kqueue is used if |
|
|
610 | available (warning, breaks stuff, best use only with your own private |
|
|
611 | event loop and only if you know the \s-1OS\s0 supports your types of fds): |
|
|
612 | .Sp |
|
|
613 | .Vb 1 |
|
|
614 | \& ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
615 | .Ve |
351 | .RE |
616 | .RE |
352 | .IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4 |
617 | .IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4 |
353 | .IX Item "struct ev_loop *ev_loop_new (unsigned int flags)" |
618 | .IX Item "struct ev_loop *ev_loop_new (unsigned int flags)" |
354 | Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is |
619 | Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is |
355 | always distinct from the default loop. Unlike the default loop, it cannot |
620 | always distinct from the default loop. Unlike the default loop, it cannot |
356 | handle signal and child watchers, and attempts to do so will be greeted by |
621 | handle signal and child watchers, and attempts to do so will be greeted by |
357 | undefined behaviour (or a failed assertion if assertions are enabled). |
622 | undefined behaviour (or a failed assertion if assertions are enabled). |
|
|
623 | .Sp |
|
|
624 | Note that this function \fIis\fR thread-safe, and the recommended way to use |
|
|
625 | libev with threads is indeed to create one loop per thread, and using the |
|
|
626 | default loop in the \*(L"main\*(R" or \*(L"initial\*(R" thread. |
|
|
627 | .Sp |
|
|
628 | Example: Try to create a event loop that uses epoll and nothing else. |
|
|
629 | .Sp |
|
|
630 | .Vb 3 |
|
|
631 | \& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
|
|
632 | \& if (!epoller) |
|
|
633 | \& fatal ("no epoll found here, maybe it hides under your chair"); |
|
|
634 | .Ve |
358 | .IP "ev_default_destroy ()" 4 |
635 | .IP "ev_default_destroy ()" 4 |
359 | .IX Item "ev_default_destroy ()" |
636 | .IX Item "ev_default_destroy ()" |
360 | Destroys the default loop again (frees all memory and kernel state |
637 | Destroys the default loop again (frees all memory and kernel state |
361 | etc.). This stops all registered event watchers (by not touching them in |
638 | etc.). None of the active event watchers will be stopped in the normal |
362 | any way whatsoever, although you cannot rely on this :). |
639 | sense, so e.g. \f(CW\*(C`ev_is_active\*(C'\fR might still return true. It is your |
|
|
640 | responsibility to either stop all watchers cleanly yourself \fIbefore\fR |
|
|
641 | calling this function, or cope with the fact afterwards (which is usually |
|
|
642 | the easiest thing, you can just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them |
|
|
643 | for example). |
|
|
644 | .Sp |
|
|
645 | Note that certain global state, such as signal state, will not be freed by |
|
|
646 | this function, and related watchers (such as signal and child watchers) |
|
|
647 | would need to be stopped manually. |
|
|
648 | .Sp |
|
|
649 | In general it is not advisable to call this function except in the |
|
|
650 | rare occasion where you really need to free e.g. the signal handling |
|
|
651 | pipe fds. If you need dynamically allocated loops it is better to use |
|
|
652 | \&\f(CW\*(C`ev_loop_new\*(C'\fR and \f(CW\*(C`ev_loop_destroy\*(C'\fR). |
363 | .IP "ev_loop_destroy (loop)" 4 |
653 | .IP "ev_loop_destroy (loop)" 4 |
364 | .IX Item "ev_loop_destroy (loop)" |
654 | .IX Item "ev_loop_destroy (loop)" |
365 | Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an |
655 | Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an |
366 | earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR. |
656 | earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR. |
367 | .IP "ev_default_fork ()" 4 |
657 | .IP "ev_default_fork ()" 4 |
368 | .IX Item "ev_default_fork ()" |
658 | .IX Item "ev_default_fork ()" |
|
|
659 | This function sets a flag that causes subsequent \f(CW\*(C`ev_loop\*(C'\fR iterations |
369 | This function reinitialises the kernel state for backends that have |
660 | to reinitialise the kernel state for backends that have one. Despite the |
370 | one. Despite the name, you can call it anytime, but it makes most sense |
661 | name, you can call it anytime, but it makes most sense after forking, in |
371 | after forking, in either the parent or child process (or both, but that |
662 | the child process (or both child and parent, but that again makes little |
372 | again makes little sense). |
663 | sense). You \fImust\fR call it in the child before using any of the libev |
|
|
664 | functions, and it will only take effect at the next \f(CW\*(C`ev_loop\*(C'\fR iteration. |
373 | .Sp |
665 | .Sp |
374 | You \fImust\fR call this function in the child process after forking if and |
666 | On the other hand, you only need to call this function in the child |
375 | only if you want to use the event library in both processes. If you just |
667 | process if and only if you want to use the event library in the child. If |
376 | fork+exec, you don't have to call it. |
668 | you just fork+exec, you don't have to call it at all. |
377 | .Sp |
669 | .Sp |
378 | The function itself is quite fast and it's usually not a problem to call |
670 | The function itself is quite fast and it's usually not a problem to call |
379 | it just in case after a fork. To make this easy, the function will fit in |
671 | it just in case after a fork. To make this easy, the function will fit in |
380 | quite nicely into a call to \f(CW\*(C`pthread_atfork\*(C'\fR: |
672 | quite nicely into a call to \f(CW\*(C`pthread_atfork\*(C'\fR: |
381 | .Sp |
673 | .Sp |
382 | .Vb 1 |
674 | .Vb 1 |
383 | \& pthread_atfork (0, 0, ev_default_fork); |
675 | \& pthread_atfork (0, 0, ev_default_fork); |
384 | .Ve |
676 | .Ve |
385 | .Sp |
|
|
386 | At the moment, \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and \f(CW\*(C`EVBACKEND_POLL\*(C'\fR are safe to use |
|
|
387 | without calling this function, so if you force one of those backends you |
|
|
388 | do not need to care. |
|
|
389 | .IP "ev_loop_fork (loop)" 4 |
677 | .IP "ev_loop_fork (loop)" 4 |
390 | .IX Item "ev_loop_fork (loop)" |
678 | .IX Item "ev_loop_fork (loop)" |
391 | Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by |
679 | Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by |
392 | \&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop |
680 | \&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop |
393 | after fork, and how you do this is entirely your own problem. |
681 | after fork, and how you do this is entirely your own problem. |
|
|
682 | .IP "int ev_is_default_loop (loop)" 4 |
|
|
683 | .IX Item "int ev_is_default_loop (loop)" |
|
|
684 | Returns true when the given loop actually is the default loop, false otherwise. |
|
|
685 | .IP "unsigned int ev_loop_count (loop)" 4 |
|
|
686 | .IX Item "unsigned int ev_loop_count (loop)" |
|
|
687 | Returns the count of loop iterations for the loop, which is identical to |
|
|
688 | the number of times libev did poll for new events. It starts at \f(CW0\fR and |
|
|
689 | happily wraps around with enough iterations. |
|
|
690 | .Sp |
|
|
691 | This value can sometimes be useful as a generation counter of sorts (it |
|
|
692 | \&\*(L"ticks\*(R" the number of loop iterations), as it roughly corresponds with |
|
|
693 | \&\f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR calls. |
394 | .IP "unsigned int ev_backend (loop)" 4 |
694 | .IP "unsigned int ev_backend (loop)" 4 |
395 | .IX Item "unsigned int ev_backend (loop)" |
695 | .IX Item "unsigned int ev_backend (loop)" |
396 | Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in |
696 | Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in |
397 | use. |
697 | use. |
398 | .IP "ev_tstamp ev_now (loop)" 4 |
698 | .IP "ev_tstamp ev_now (loop)" 4 |
399 | .IX Item "ev_tstamp ev_now (loop)" |
699 | .IX Item "ev_tstamp ev_now (loop)" |
400 | Returns the current \*(L"event loop time\*(R", which is the time the event loop |
700 | Returns the current \*(L"event loop time\*(R", which is the time the event loop |
401 | got events and started processing them. This timestamp does not change |
701 | received events and started processing them. This timestamp does not |
402 | as long as callbacks are being processed, and this is also the base time |
702 | change as long as callbacks are being processed, and this is also the base |
403 | used for relative timers. You can treat it as the timestamp of the event |
703 | time used for relative timers. You can treat it as the timestamp of the |
404 | occuring (or more correctly, the mainloop finding out about it). |
704 | event occurring (or more correctly, libev finding out about it). |
405 | .IP "ev_loop (loop, int flags)" 4 |
705 | .IP "ev_loop (loop, int flags)" 4 |
406 | .IX Item "ev_loop (loop, int flags)" |
706 | .IX Item "ev_loop (loop, int flags)" |
407 | Finally, this is it, the event handler. This function usually is called |
707 | Finally, this is it, the event handler. This function usually is called |
408 | after you initialised all your watchers and you want to start handling |
708 | after you initialised all your watchers and you want to start handling |
409 | events. |
709 | events. |
410 | .Sp |
710 | .Sp |
411 | If the flags argument is specified as 0, it will not return until either |
711 | If the flags argument is specified as \f(CW0\fR, it will not return until |
412 | no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called. |
712 | either no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called. |
|
|
713 | .Sp |
|
|
714 | Please note that an explicit \f(CW\*(C`ev_unloop\*(C'\fR is usually better than |
|
|
715 | relying on all watchers to be stopped when deciding when a program has |
|
|
716 | finished (especially in interactive programs), but having a program that |
|
|
717 | automatically loops as long as it has to and no longer by virtue of |
|
|
718 | relying on its watchers stopping correctly is a thing of beauty. |
413 | .Sp |
719 | .Sp |
414 | A flags value of \f(CW\*(C`EVLOOP_NONBLOCK\*(C'\fR will look for new events, will handle |
720 | A flags value of \f(CW\*(C`EVLOOP_NONBLOCK\*(C'\fR will look for new events, will handle |
415 | those events and any outstanding ones, but will not block your process in |
721 | those events and any outstanding ones, but will not block your process in |
416 | case there are no events and will return after one iteration of the loop. |
722 | case there are no events and will return after one iteration of the loop. |
417 | .Sp |
723 | .Sp |
418 | A flags value of \f(CW\*(C`EVLOOP_ONESHOT\*(C'\fR will look for new events (waiting if |
724 | A flags value of \f(CW\*(C`EVLOOP_ONESHOT\*(C'\fR will look for new events (waiting if |
419 | neccessary) and will handle those and any outstanding ones. It will block |
725 | necessary) and will handle those and any outstanding ones. It will block |
420 | your process until at least one new event arrives, and will return after |
726 | your process until at least one new event arrives, and will return after |
421 | one iteration of the loop. |
727 | one iteration of the loop. This is useful if you are waiting for some |
|
|
728 | external event in conjunction with something not expressible using other |
|
|
729 | libev watchers. However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is |
|
|
730 | usually a better approach for this kind of thing. |
422 | .Sp |
731 | .Sp |
423 | This flags value could be used to implement alternative looping |
|
|
424 | constructs, but the \f(CW\*(C`prepare\*(C'\fR and \f(CW\*(C`check\*(C'\fR watchers provide a better and |
|
|
425 | more generic mechanism. |
|
|
426 | .Sp |
|
|
427 | Here are the gory details of what ev_loop does: |
732 | Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does: |
428 | .Sp |
733 | .Sp |
429 | .Vb 15 |
734 | .Vb 10 |
430 | \& 1. If there are no active watchers (reference count is zero), return. |
735 | \& \- Before the first iteration, call any pending watchers. |
|
|
736 | \& * If EVFLAG_FORKCHECK was used, check for a fork. |
|
|
737 | \& \- If a fork was detected, queue and call all fork watchers. |
431 | \& 2. Queue and immediately call all prepare watchers. |
738 | \& \- Queue and call all prepare watchers. |
432 | \& 3. If we have been forked, recreate the kernel state. |
739 | \& \- If we have been forked, recreate the kernel state. |
433 | \& 4. Update the kernel state with all outstanding changes. |
740 | \& \- Update the kernel state with all outstanding changes. |
434 | \& 5. Update the "event loop time". |
741 | \& \- Update the "event loop time". |
435 | \& 6. Calculate for how long to block. |
742 | \& \- Calculate for how long to sleep or block, if at all |
|
|
743 | \& (active idle watchers, EVLOOP_NONBLOCK or not having |
|
|
744 | \& any active watchers at all will result in not sleeping). |
|
|
745 | \& \- Sleep if the I/O and timer collect interval say so. |
436 | \& 7. Block the process, waiting for events. |
746 | \& \- Block the process, waiting for any events. |
|
|
747 | \& \- Queue all outstanding I/O (fd) events. |
437 | \& 8. Update the "event loop time" and do time jump handling. |
748 | \& \- Update the "event loop time" and do time jump handling. |
438 | \& 9. Queue all outstanding timers. |
749 | \& \- Queue all outstanding timers. |
439 | \& 10. Queue all outstanding periodics. |
750 | \& \- Queue all outstanding periodics. |
440 | \& 11. If no events are pending now, queue all idle watchers. |
751 | \& \- If no events are pending now, queue all idle watchers. |
441 | \& 12. Queue all check watchers. |
752 | \& \- Queue all check watchers. |
442 | \& 13. Call all queued watchers in reverse order (i.e. check watchers first). |
753 | \& \- Call all queued watchers in reverse order (i.e. check watchers first). |
|
|
754 | \& Signals and child watchers are implemented as I/O watchers, and will |
|
|
755 | \& be handled here by queueing them when their watcher gets executed. |
443 | \& 14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
756 | \& \- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
444 | \& was used, return, otherwise continue with step #1. |
757 | \& were used, or there are no active watchers, return, otherwise |
|
|
758 | \& continue with step *. |
|
|
759 | .Ve |
|
|
760 | .Sp |
|
|
761 | Example: Queue some jobs and then loop until no events are outstanding |
|
|
762 | anymore. |
|
|
763 | .Sp |
|
|
764 | .Vb 4 |
|
|
765 | \& ... queue jobs here, make sure they register event watchers as long |
|
|
766 | \& ... as they still have work to do (even an idle watcher will do..) |
|
|
767 | \& ev_loop (my_loop, 0); |
|
|
768 | \& ... jobs done. yeah! |
445 | .Ve |
769 | .Ve |
446 | .IP "ev_unloop (loop, how)" 4 |
770 | .IP "ev_unloop (loop, how)" 4 |
447 | .IX Item "ev_unloop (loop, how)" |
771 | .IX Item "ev_unloop (loop, how)" |
448 | Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it |
772 | Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it |
449 | has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either |
773 | has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either |
450 | \&\f(CW\*(C`EVUNLOOP_ONE\*(C'\fR, which will make the innermost \f(CW\*(C`ev_loop\*(C'\fR call return, or |
774 | \&\f(CW\*(C`EVUNLOOP_ONE\*(C'\fR, which will make the innermost \f(CW\*(C`ev_loop\*(C'\fR call return, or |
451 | \&\f(CW\*(C`EVUNLOOP_ALL\*(C'\fR, which will make all nested \f(CW\*(C`ev_loop\*(C'\fR calls return. |
775 | \&\f(CW\*(C`EVUNLOOP_ALL\*(C'\fR, which will make all nested \f(CW\*(C`ev_loop\*(C'\fR calls return. |
|
|
776 | .Sp |
|
|
777 | This \*(L"unloop state\*(R" will be cleared when entering \f(CW\*(C`ev_loop\*(C'\fR again. |
452 | .IP "ev_ref (loop)" 4 |
778 | .IP "ev_ref (loop)" 4 |
453 | .IX Item "ev_ref (loop)" |
779 | .IX Item "ev_ref (loop)" |
454 | .PD 0 |
780 | .PD 0 |
455 | .IP "ev_unref (loop)" 4 |
781 | .IP "ev_unref (loop)" 4 |
456 | .IX Item "ev_unref (loop)" |
782 | .IX Item "ev_unref (loop)" |
… | |
… | |
462 | returning, \fIev_unref()\fR after starting, and \fIev_ref()\fR before stopping it. For |
788 | returning, \fIev_unref()\fR after starting, and \fIev_ref()\fR before stopping it. For |
463 | example, libev itself uses this for its internal signal pipe: It is not |
789 | example, libev itself uses this for its internal signal pipe: It is not |
464 | visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if |
790 | visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if |
465 | no event watchers registered by it are active. It is also an excellent |
791 | no event watchers registered by it are active. It is also an excellent |
466 | way to do this for generic recurring timers or from within third-party |
792 | way to do this for generic recurring timers or from within third-party |
467 | libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR. |
793 | libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR |
|
|
794 | (but only if the watcher wasn't active before, or was active before, |
|
|
795 | respectively). |
|
|
796 | .Sp |
|
|
797 | Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR |
|
|
798 | running when nothing else is active. |
|
|
799 | .Sp |
|
|
800 | .Vb 4 |
|
|
801 | \& struct ev_signal exitsig; |
|
|
802 | \& ev_signal_init (&exitsig, sig_cb, SIGINT); |
|
|
803 | \& ev_signal_start (loop, &exitsig); |
|
|
804 | \& evf_unref (loop); |
|
|
805 | .Ve |
|
|
806 | .Sp |
|
|
807 | Example: For some weird reason, unregister the above signal handler again. |
|
|
808 | .Sp |
|
|
809 | .Vb 2 |
|
|
810 | \& ev_ref (loop); |
|
|
811 | \& ev_signal_stop (loop, &exitsig); |
|
|
812 | .Ve |
|
|
813 | .IP "ev_set_io_collect_interval (loop, ev_tstamp interval)" 4 |
|
|
814 | .IX Item "ev_set_io_collect_interval (loop, ev_tstamp interval)" |
|
|
815 | .PD 0 |
|
|
816 | .IP "ev_set_timeout_collect_interval (loop, ev_tstamp interval)" 4 |
|
|
817 | .IX Item "ev_set_timeout_collect_interval (loop, ev_tstamp interval)" |
|
|
818 | .PD |
|
|
819 | These advanced functions influence the time that libev will spend waiting |
|
|
820 | for events. Both are by default \f(CW0\fR, meaning that libev will try to |
|
|
821 | invoke timer/periodic callbacks and I/O callbacks with minimum latency. |
|
|
822 | .Sp |
|
|
823 | Setting these to a higher value (the \f(CW\*(C`interval\*(C'\fR \fImust\fR be >= \f(CW0\fR) |
|
|
824 | allows libev to delay invocation of I/O and timer/periodic callbacks to |
|
|
825 | increase efficiency of loop iterations. |
|
|
826 | .Sp |
|
|
827 | The background is that sometimes your program runs just fast enough to |
|
|
828 | handle one (or very few) event(s) per loop iteration. While this makes |
|
|
829 | the program responsive, it also wastes a lot of \s-1CPU\s0 time to poll for new |
|
|
830 | events, especially with backends like \f(CW\*(C`select ()\*(C'\fR which have a high |
|
|
831 | overhead for the actual polling but can deliver many events at once. |
|
|
832 | .Sp |
|
|
833 | By setting a higher \fIio collect interval\fR you allow libev to spend more |
|
|
834 | time collecting I/O events, so you can handle more events per iteration, |
|
|
835 | at the cost of increasing latency. Timeouts (both \f(CW\*(C`ev_periodic\*(C'\fR and |
|
|
836 | \&\f(CW\*(C`ev_timer\*(C'\fR) will be not affected. Setting this to a non-null value will |
|
|
837 | introduce an additional \f(CW\*(C`ev_sleep ()\*(C'\fR call into most loop iterations. |
|
|
838 | .Sp |
|
|
839 | Likewise, by setting a higher \fItimeout collect interval\fR you allow libev |
|
|
840 | to spend more time collecting timeouts, at the expense of increased |
|
|
841 | latency (the watcher callback will be called later). \f(CW\*(C`ev_io\*(C'\fR watchers |
|
|
842 | will not be affected. Setting this to a non-null value will not introduce |
|
|
843 | any overhead in libev. |
|
|
844 | .Sp |
|
|
845 | Many (busy) programs can usually benefit by setting the I/O collect |
|
|
846 | interval to a value near \f(CW0.1\fR or so, which is often enough for |
|
|
847 | interactive servers (of course not for games), likewise for timeouts. It |
|
|
848 | usually doesn't make much sense to set it to a lower value than \f(CW0.01\fR, |
|
|
849 | as this approaches the timing granularity of most systems. |
|
|
850 | .IP "ev_loop_verify (loop)" 4 |
|
|
851 | .IX Item "ev_loop_verify (loop)" |
|
|
852 | This function only does something when \f(CW\*(C`EV_VERIFY\*(C'\fR support has been |
|
|
853 | compiled in. It tries to go through all internal structures and checks |
|
|
854 | them for validity. If anything is found to be inconsistent, it will print |
|
|
855 | an error message to standard error and call \f(CW\*(C`abort ()\*(C'\fR. |
|
|
856 | .Sp |
|
|
857 | This can be used to catch bugs inside libev itself: under normal |
|
|
858 | circumstances, this function will never abort as of course libev keeps its |
|
|
859 | data structures consistent. |
468 | .SH "ANATOMY OF A WATCHER" |
860 | .SH "ANATOMY OF A WATCHER" |
469 | .IX Header "ANATOMY OF A WATCHER" |
861 | .IX Header "ANATOMY OF A WATCHER" |
470 | A watcher is a structure that you create and register to record your |
862 | A watcher is a structure that you create and register to record your |
471 | interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to |
863 | interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to |
472 | become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that: |
864 | become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that: |
473 | .PP |
865 | .PP |
474 | .Vb 5 |
866 | .Vb 5 |
475 | \& static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
867 | \& static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
476 | \& { |
868 | \& { |
477 | \& ev_io_stop (w); |
869 | \& ev_io_stop (w); |
478 | \& ev_unloop (loop, EVUNLOOP_ALL); |
870 | \& ev_unloop (loop, EVUNLOOP_ALL); |
479 | \& } |
871 | \& } |
480 | .Ve |
872 | \& |
481 | .PP |
|
|
482 | .Vb 6 |
|
|
483 | \& struct ev_loop *loop = ev_default_loop (0); |
873 | \& struct ev_loop *loop = ev_default_loop (0); |
484 | \& struct ev_io stdin_watcher; |
874 | \& struct ev_io stdin_watcher; |
485 | \& ev_init (&stdin_watcher, my_cb); |
875 | \& ev_init (&stdin_watcher, my_cb); |
486 | \& ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
876 | \& ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
487 | \& ev_io_start (loop, &stdin_watcher); |
877 | \& ev_io_start (loop, &stdin_watcher); |
488 | \& ev_loop (loop, 0); |
878 | \& ev_loop (loop, 0); |
489 | .Ve |
879 | .Ve |
490 | .PP |
880 | .PP |
491 | As you can see, you are responsible for allocating the memory for your |
881 | As you can see, you are responsible for allocating the memory for your |
492 | watcher structures (and it is usually a bad idea to do this on the stack, |
882 | watcher structures (and it is usually a bad idea to do this on the stack, |
493 | although this can sometimes be quite valid). |
883 | although this can sometimes be quite valid). |
494 | .PP |
884 | .PP |
495 | Each watcher structure must be initialised by a call to \f(CW\*(C`ev_init |
885 | Each watcher structure must be initialised by a call to \f(CW\*(C`ev_init |
496 | (watcher *, callback)\*(C'\fR, which expects a callback to be provided. This |
886 | (watcher *, callback)\*(C'\fR, which expects a callback to be provided. This |
497 | callback gets invoked each time the event occurs (or, in the case of io |
887 | callback gets invoked each time the event occurs (or, in the case of I/O |
498 | watchers, each time the event loop detects that the file descriptor given |
888 | watchers, each time the event loop detects that the file descriptor given |
499 | is readable and/or writable). |
889 | is readable and/or writable). |
500 | .PP |
890 | .PP |
501 | Each watcher type has its own \f(CW\*(C`ev_<type>_set (watcher *, ...)\*(C'\fR macro |
891 | Each watcher type has its own \f(CW\*(C`ev_<type>_set (watcher *, ...)\*(C'\fR macro |
502 | with arguments specific to this watcher type. There is also a macro |
892 | with arguments specific to this watcher type. There is also a macro |
… | |
… | |
508 | *)\*(C'\fR), and you can stop watching for events at any time by calling the |
898 | *)\*(C'\fR), and you can stop watching for events at any time by calling the |
509 | corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR. |
899 | corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR. |
510 | .PP |
900 | .PP |
511 | As long as your watcher is active (has been started but not stopped) you |
901 | As long as your watcher is active (has been started but not stopped) you |
512 | must not touch the values stored in it. Most specifically you must never |
902 | must not touch the values stored in it. Most specifically you must never |
513 | reinitialise it or call its set macro. |
903 | reinitialise it or call its \f(CW\*(C`set\*(C'\fR macro. |
514 | .PP |
|
|
515 | You can check whether an event is active by calling the \f(CW\*(C`ev_is_active |
|
|
516 | (watcher *)\*(C'\fR macro. To see whether an event is outstanding (but the |
|
|
517 | callback for it has not been called yet) you can use the \f(CW\*(C`ev_is_pending |
|
|
518 | (watcher *)\*(C'\fR macro. |
|
|
519 | .PP |
904 | .PP |
520 | Each and every callback receives the event loop pointer as first, the |
905 | Each and every callback receives the event loop pointer as first, the |
521 | registered watcher structure as second, and a bitset of received events as |
906 | registered watcher structure as second, and a bitset of received events as |
522 | third argument. |
907 | third argument. |
523 | .PP |
908 | .PP |
… | |
… | |
548 | The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread. |
933 | The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread. |
549 | .ie n .IP """EV_CHILD""" 4 |
934 | .ie n .IP """EV_CHILD""" 4 |
550 | .el .IP "\f(CWEV_CHILD\fR" 4 |
935 | .el .IP "\f(CWEV_CHILD\fR" 4 |
551 | .IX Item "EV_CHILD" |
936 | .IX Item "EV_CHILD" |
552 | The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change. |
937 | The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change. |
|
|
938 | .ie n .IP """EV_STAT""" 4 |
|
|
939 | .el .IP "\f(CWEV_STAT\fR" 4 |
|
|
940 | .IX Item "EV_STAT" |
|
|
941 | The path specified in the \f(CW\*(C`ev_stat\*(C'\fR watcher changed its attributes somehow. |
553 | .ie n .IP """EV_IDLE""" 4 |
942 | .ie n .IP """EV_IDLE""" 4 |
554 | .el .IP "\f(CWEV_IDLE\fR" 4 |
943 | .el .IP "\f(CWEV_IDLE\fR" 4 |
555 | .IX Item "EV_IDLE" |
944 | .IX Item "EV_IDLE" |
556 | The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do. |
945 | The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do. |
557 | .ie n .IP """EV_PREPARE""" 4 |
946 | .ie n .IP """EV_PREPARE""" 4 |
… | |
… | |
567 | \&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any |
956 | \&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any |
568 | received events. Callbacks of both watcher types can start and stop as |
957 | received events. Callbacks of both watcher types can start and stop as |
569 | many watchers as they want, and all of them will be taken into account |
958 | many watchers as they want, and all of them will be taken into account |
570 | (for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep |
959 | (for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep |
571 | \&\f(CW\*(C`ev_loop\*(C'\fR from blocking). |
960 | \&\f(CW\*(C`ev_loop\*(C'\fR from blocking). |
|
|
961 | .ie n .IP """EV_EMBED""" 4 |
|
|
962 | .el .IP "\f(CWEV_EMBED\fR" 4 |
|
|
963 | .IX Item "EV_EMBED" |
|
|
964 | The embedded event loop specified in the \f(CW\*(C`ev_embed\*(C'\fR watcher needs attention. |
|
|
965 | .ie n .IP """EV_FORK""" 4 |
|
|
966 | .el .IP "\f(CWEV_FORK\fR" 4 |
|
|
967 | .IX Item "EV_FORK" |
|
|
968 | The event loop has been resumed in the child process after fork (see |
|
|
969 | \&\f(CW\*(C`ev_fork\*(C'\fR). |
|
|
970 | .ie n .IP """EV_ASYNC""" 4 |
|
|
971 | .el .IP "\f(CWEV_ASYNC\fR" 4 |
|
|
972 | .IX Item "EV_ASYNC" |
|
|
973 | The given async watcher has been asynchronously notified (see \f(CW\*(C`ev_async\*(C'\fR). |
572 | .ie n .IP """EV_ERROR""" 4 |
974 | .ie n .IP """EV_ERROR""" 4 |
573 | .el .IP "\f(CWEV_ERROR\fR" 4 |
975 | .el .IP "\f(CWEV_ERROR\fR" 4 |
574 | .IX Item "EV_ERROR" |
976 | .IX Item "EV_ERROR" |
575 | An unspecified error has occured, the watcher has been stopped. This might |
977 | An unspecified error has occurred, the watcher has been stopped. This might |
576 | happen because the watcher could not be properly started because libev |
978 | happen because the watcher could not be properly started because libev |
577 | ran out of memory, a file descriptor was found to be closed or any other |
979 | ran out of memory, a file descriptor was found to be closed or any other |
578 | problem. You best act on it by reporting the problem and somehow coping |
980 | problem. You best act on it by reporting the problem and somehow coping |
579 | with the watcher being stopped. |
981 | with the watcher being stopped. |
580 | .Sp |
982 | .Sp |
581 | Libev will usually signal a few \*(L"dummy\*(R" events together with an error, |
983 | Libev will usually signal a few \*(L"dummy\*(R" events together with an error, |
582 | for example it might indicate that a fd is readable or writable, and if |
984 | for example it might indicate that a fd is readable or writable, and if |
583 | your callbacks is well-written it can just attempt the operation and cope |
985 | your callbacks is well-written it can just attempt the operation and cope |
584 | with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded |
986 | with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multi-threaded |
585 | programs, though, so beware. |
987 | programs, though, so beware. |
|
|
988 | .Sh "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0" |
|
|
989 | .IX Subsection "GENERIC WATCHER FUNCTIONS" |
|
|
990 | In the following description, \f(CW\*(C`TYPE\*(C'\fR stands for the watcher type, |
|
|
991 | e.g. \f(CW\*(C`timer\*(C'\fR for \f(CW\*(C`ev_timer\*(C'\fR watchers and \f(CW\*(C`io\*(C'\fR for \f(CW\*(C`ev_io\*(C'\fR watchers. |
|
|
992 | .ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4 |
|
|
993 | .el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4 |
|
|
994 | .IX Item "ev_init (ev_TYPE *watcher, callback)" |
|
|
995 | This macro initialises the generic portion of a watcher. The contents |
|
|
996 | of the watcher object can be arbitrary (so \f(CW\*(C`malloc\*(C'\fR will do). Only |
|
|
997 | the generic parts of the watcher are initialised, you \fIneed\fR to call |
|
|
998 | the type-specific \f(CW\*(C`ev_TYPE_set\*(C'\fR macro afterwards to initialise the |
|
|
999 | type-specific parts. For each type there is also a \f(CW\*(C`ev_TYPE_init\*(C'\fR macro |
|
|
1000 | which rolls both calls into one. |
|
|
1001 | .Sp |
|
|
1002 | You can reinitialise a watcher at any time as long as it has been stopped |
|
|
1003 | (or never started) and there are no pending events outstanding. |
|
|
1004 | .Sp |
|
|
1005 | The callback is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher, |
|
|
1006 | int revents)\*(C'\fR. |
|
|
1007 | .ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4 |
|
|
1008 | .el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4 |
|
|
1009 | .IX Item "ev_TYPE_set (ev_TYPE *, [args])" |
|
|
1010 | This macro initialises the type-specific parts of a watcher. You need to |
|
|
1011 | call \f(CW\*(C`ev_init\*(C'\fR at least once before you call this macro, but you can |
|
|
1012 | call \f(CW\*(C`ev_TYPE_set\*(C'\fR any number of times. You must not, however, call this |
|
|
1013 | macro on a watcher that is active (it can be pending, however, which is a |
|
|
1014 | difference to the \f(CW\*(C`ev_init\*(C'\fR macro). |
|
|
1015 | .Sp |
|
|
1016 | Although some watcher types do not have type-specific arguments |
|
|
1017 | (e.g. \f(CW\*(C`ev_prepare\*(C'\fR) you still need to call its \f(CW\*(C`set\*(C'\fR macro. |
|
|
1018 | .ie n .IP """ev_TYPE_init"" (ev_TYPE *watcher, callback, [args])" 4 |
|
|
1019 | .el .IP "\f(CWev_TYPE_init\fR (ev_TYPE *watcher, callback, [args])" 4 |
|
|
1020 | .IX Item "ev_TYPE_init (ev_TYPE *watcher, callback, [args])" |
|
|
1021 | This convenience macro rolls both \f(CW\*(C`ev_init\*(C'\fR and \f(CW\*(C`ev_TYPE_set\*(C'\fR macro |
|
|
1022 | calls into a single call. This is the most convenient method to initialise |
|
|
1023 | a watcher. The same limitations apply, of course. |
|
|
1024 | .ie n .IP """ev_TYPE_start"" (loop *, ev_TYPE *watcher)" 4 |
|
|
1025 | .el .IP "\f(CWev_TYPE_start\fR (loop *, ev_TYPE *watcher)" 4 |
|
|
1026 | .IX Item "ev_TYPE_start (loop *, ev_TYPE *watcher)" |
|
|
1027 | Starts (activates) the given watcher. Only active watchers will receive |
|
|
1028 | events. If the watcher is already active nothing will happen. |
|
|
1029 | .ie n .IP """ev_TYPE_stop"" (loop *, ev_TYPE *watcher)" 4 |
|
|
1030 | .el .IP "\f(CWev_TYPE_stop\fR (loop *, ev_TYPE *watcher)" 4 |
|
|
1031 | .IX Item "ev_TYPE_stop (loop *, ev_TYPE *watcher)" |
|
|
1032 | Stops the given watcher again (if active) and clears the pending |
|
|
1033 | status. It is possible that stopped watchers are pending (for example, |
|
|
1034 | non-repeating timers are being stopped when they become pending), but |
|
|
1035 | \&\f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor pending. If |
|
|
1036 | you want to free or reuse the memory used by the watcher it is therefore a |
|
|
1037 | good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function. |
|
|
1038 | .IP "bool ev_is_active (ev_TYPE *watcher)" 4 |
|
|
1039 | .IX Item "bool ev_is_active (ev_TYPE *watcher)" |
|
|
1040 | Returns a true value iff the watcher is active (i.e. it has been started |
|
|
1041 | and not yet been stopped). As long as a watcher is active you must not modify |
|
|
1042 | it. |
|
|
1043 | .IP "bool ev_is_pending (ev_TYPE *watcher)" 4 |
|
|
1044 | .IX Item "bool ev_is_pending (ev_TYPE *watcher)" |
|
|
1045 | Returns a true value iff the watcher is pending, (i.e. it has outstanding |
|
|
1046 | events but its callback has not yet been invoked). As long as a watcher |
|
|
1047 | is pending (but not active) you must not call an init function on it (but |
|
|
1048 | \&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe), you must not change its priority, and you must |
|
|
1049 | make sure the watcher is available to libev (e.g. you cannot \f(CW\*(C`free ()\*(C'\fR |
|
|
1050 | it). |
|
|
1051 | .IP "callback ev_cb (ev_TYPE *watcher)" 4 |
|
|
1052 | .IX Item "callback ev_cb (ev_TYPE *watcher)" |
|
|
1053 | Returns the callback currently set on the watcher. |
|
|
1054 | .IP "ev_cb_set (ev_TYPE *watcher, callback)" 4 |
|
|
1055 | .IX Item "ev_cb_set (ev_TYPE *watcher, callback)" |
|
|
1056 | Change the callback. You can change the callback at virtually any time |
|
|
1057 | (modulo threads). |
|
|
1058 | .IP "ev_set_priority (ev_TYPE *watcher, priority)" 4 |
|
|
1059 | .IX Item "ev_set_priority (ev_TYPE *watcher, priority)" |
|
|
1060 | .PD 0 |
|
|
1061 | .IP "int ev_priority (ev_TYPE *watcher)" 4 |
|
|
1062 | .IX Item "int ev_priority (ev_TYPE *watcher)" |
|
|
1063 | .PD |
|
|
1064 | Set and query the priority of the watcher. The priority is a small |
|
|
1065 | integer between \f(CW\*(C`EV_MAXPRI\*(C'\fR (default: \f(CW2\fR) and \f(CW\*(C`EV_MINPRI\*(C'\fR |
|
|
1066 | (default: \f(CW\*(C`\-2\*(C'\fR). Pending watchers with higher priority will be invoked |
|
|
1067 | before watchers with lower priority, but priority will not keep watchers |
|
|
1068 | from being executed (except for \f(CW\*(C`ev_idle\*(C'\fR watchers). |
|
|
1069 | .Sp |
|
|
1070 | This means that priorities are \fIonly\fR used for ordering callback |
|
|
1071 | invocation after new events have been received. This is useful, for |
|
|
1072 | example, to reduce latency after idling, or more often, to bind two |
|
|
1073 | watchers on the same event and make sure one is called first. |
|
|
1074 | .Sp |
|
|
1075 | If you need to suppress invocation when higher priority events are pending |
|
|
1076 | you need to look at \f(CW\*(C`ev_idle\*(C'\fR watchers, which provide this functionality. |
|
|
1077 | .Sp |
|
|
1078 | You \fImust not\fR change the priority of a watcher as long as it is active or |
|
|
1079 | pending. |
|
|
1080 | .Sp |
|
|
1081 | The default priority used by watchers when no priority has been set is |
|
|
1082 | always \f(CW0\fR, which is supposed to not be too high and not be too low :). |
|
|
1083 | .Sp |
|
|
1084 | Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR is |
|
|
1085 | fine, as long as you do not mind that the priority value you query might |
|
|
1086 | or might not have been adjusted to be within valid range. |
|
|
1087 | .IP "ev_invoke (loop, ev_TYPE *watcher, int revents)" 4 |
|
|
1088 | .IX Item "ev_invoke (loop, ev_TYPE *watcher, int revents)" |
|
|
1089 | 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 |
|
|
1090 | \&\f(CW\*(C`loop\*(C'\fR nor \f(CW\*(C`revents\*(C'\fR need to be valid as long as the watcher callback |
|
|
1091 | can deal with that fact. |
|
|
1092 | .IP "int ev_clear_pending (loop, ev_TYPE *watcher)" 4 |
|
|
1093 | .IX Item "int ev_clear_pending (loop, ev_TYPE *watcher)" |
|
|
1094 | If the watcher is pending, this function returns clears its pending status |
|
|
1095 | and returns its \f(CW\*(C`revents\*(C'\fR bitset (as if its callback was invoked). If the |
|
|
1096 | watcher isn't pending it does nothing and returns \f(CW0\fR. |
586 | .Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0" |
1097 | .Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0" |
587 | .IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER" |
1098 | .IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER" |
588 | Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change |
1099 | Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change |
589 | and read at any time, libev will completely ignore it. This can be used |
1100 | and read at any time, libev will completely ignore it. This can be used |
590 | to associate arbitrary data with your watcher. If you need more data and |
1101 | to associate arbitrary data with your watcher. If you need more data and |
591 | don't want to allocate memory and store a pointer to it in that data |
1102 | don't want to allocate memory and store a pointer to it in that data |
592 | member, you can also \*(L"subclass\*(R" the watcher type and provide your own |
1103 | member, you can also \*(L"subclass\*(R" the watcher type and provide your own |
593 | data: |
1104 | data: |
594 | .PP |
1105 | .PP |
595 | .Vb 7 |
1106 | .Vb 7 |
596 | \& struct my_io |
1107 | \& struct my_io |
597 | \& { |
1108 | \& { |
598 | \& struct ev_io io; |
1109 | \& struct ev_io io; |
599 | \& int otherfd; |
1110 | \& int otherfd; |
600 | \& void *somedata; |
1111 | \& void *somedata; |
601 | \& struct whatever *mostinteresting; |
1112 | \& struct whatever *mostinteresting; |
602 | \& } |
1113 | \& } |
603 | .Ve |
1114 | .Ve |
604 | .PP |
1115 | .PP |
605 | And since your callback will be called with a pointer to the watcher, you |
1116 | And since your callback will be called with a pointer to the watcher, you |
606 | can cast it back to your own type: |
1117 | can cast it back to your own type: |
607 | .PP |
1118 | .PP |
608 | .Vb 5 |
1119 | .Vb 5 |
609 | \& static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) |
1120 | \& static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) |
610 | \& { |
1121 | \& { |
611 | \& struct my_io *w = (struct my_io *)w_; |
1122 | \& struct my_io *w = (struct my_io *)w_; |
612 | \& ... |
1123 | \& ... |
613 | \& } |
1124 | \& } |
614 | .Ve |
1125 | .Ve |
615 | .PP |
1126 | .PP |
616 | More interesting and less C\-conformant ways of catsing your callback type |
1127 | More interesting and less C\-conformant ways of casting your callback type |
617 | have been omitted.... |
1128 | instead have been omitted. |
|
|
1129 | .PP |
|
|
1130 | Another common scenario is having some data structure with multiple |
|
|
1131 | watchers: |
|
|
1132 | .PP |
|
|
1133 | .Vb 6 |
|
|
1134 | \& struct my_biggy |
|
|
1135 | \& { |
|
|
1136 | \& int some_data; |
|
|
1137 | \& ev_timer t1; |
|
|
1138 | \& ev_timer t2; |
|
|
1139 | \& } |
|
|
1140 | .Ve |
|
|
1141 | .PP |
|
|
1142 | In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more complicated, |
|
|
1143 | you need to use \f(CW\*(C`offsetof\*(C'\fR: |
|
|
1144 | .PP |
|
|
1145 | .Vb 1 |
|
|
1146 | \& #include <stddef.h> |
|
|
1147 | \& |
|
|
1148 | \& static void |
|
|
1149 | \& t1_cb (EV_P_ struct ev_timer *w, int revents) |
|
|
1150 | \& { |
|
|
1151 | \& struct my_biggy big = (struct my_biggy * |
|
|
1152 | \& (((char *)w) \- offsetof (struct my_biggy, t1)); |
|
|
1153 | \& } |
|
|
1154 | \& |
|
|
1155 | \& static void |
|
|
1156 | \& t2_cb (EV_P_ struct ev_timer *w, int revents) |
|
|
1157 | \& { |
|
|
1158 | \& struct my_biggy big = (struct my_biggy * |
|
|
1159 | \& (((char *)w) \- offsetof (struct my_biggy, t2)); |
|
|
1160 | \& } |
|
|
1161 | .Ve |
618 | .SH "WATCHER TYPES" |
1162 | .SH "WATCHER TYPES" |
619 | .IX Header "WATCHER TYPES" |
1163 | .IX Header "WATCHER TYPES" |
620 | This section describes each watcher in detail, but will not repeat |
1164 | This section describes each watcher in detail, but will not repeat |
621 | information given in the last section. |
1165 | information given in the last section. Any initialisation/set macros, |
|
|
1166 | functions and members specific to the watcher type are explained. |
|
|
1167 | .PP |
|
|
1168 | Members are additionally marked with either \fI[read\-only]\fR, meaning that, |
|
|
1169 | while the watcher is active, you can look at the member and expect some |
|
|
1170 | sensible content, but you must not modify it (you can modify it while the |
|
|
1171 | watcher is stopped to your hearts content), or \fI[read\-write]\fR, which |
|
|
1172 | means you can expect it to have some sensible content while the watcher |
|
|
1173 | is active, but you can also modify it. Modifying it may not do something |
|
|
1174 | sensible or take immediate effect (or do anything at all), but libev will |
|
|
1175 | not crash or malfunction in any way. |
622 | .ie n .Sh """ev_io"" \- is this file descriptor readable or writable" |
1176 | .ie n .Sh """ev_io"" \- is this file descriptor readable or writable?" |
623 | .el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable" |
1177 | .el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable?" |
624 | .IX Subsection "ev_io - is this file descriptor readable or writable" |
1178 | .IX Subsection "ev_io - is this file descriptor readable or writable?" |
625 | I/O watchers check whether a file descriptor is readable or writable |
1179 | I/O watchers check whether a file descriptor is readable or writable |
626 | in each iteration of the event loop (This behaviour is called |
1180 | in each iteration of the event loop, or, more precisely, when reading |
627 | level-triggering because you keep receiving events as long as the |
1181 | would not block the process and writing would at least be able to write |
628 | condition persists. Remember you can stop the watcher if you don't want to |
1182 | some data. This behaviour is called level-triggering because you keep |
629 | act on the event and neither want to receive future events). |
1183 | receiving events as long as the condition persists. Remember you can stop |
|
|
1184 | the watcher if you don't want to act on the event and neither want to |
|
|
1185 | receive future events. |
630 | .PP |
1186 | .PP |
631 | In general you can register as many read and/or write event watchers per |
1187 | In general you can register as many read and/or write event watchers per |
632 | fd as you want (as long as you don't confuse yourself). Setting all file |
1188 | fd as you want (as long as you don't confuse yourself). Setting all file |
633 | descriptors to non-blocking mode is also usually a good idea (but not |
1189 | descriptors to non-blocking mode is also usually a good idea (but not |
634 | required if you know what you are doing). |
1190 | required if you know what you are doing). |
635 | .PP |
1191 | .PP |
636 | You have to be careful with dup'ed file descriptors, though. Some backends |
|
|
637 | (the linux epoll backend is a notable example) cannot handle dup'ed file |
|
|
638 | descriptors correctly if you register interest in two or more fds pointing |
|
|
639 | to the same underlying file/socket etc. description (that is, they share |
|
|
640 | the same underlying \*(L"file open\*(R"). |
|
|
641 | .PP |
|
|
642 | If you must do this, then force the use of a known-to-be-good backend |
1192 | If you must do this, then force the use of a known-to-be-good backend |
643 | (at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and |
1193 | (at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and |
644 | \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR). |
1194 | \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR). |
|
|
1195 | .PP |
|
|
1196 | Another thing you have to watch out for is that it is quite easy to |
|
|
1197 | receive \*(L"spurious\*(R" readiness notifications, that is your callback might |
|
|
1198 | be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block |
|
|
1199 | because there is no data. Not only are some backends known to create a |
|
|
1200 | lot of those (for example Solaris ports), it is very easy to get into |
|
|
1201 | this situation even with a relatively standard program structure. Thus |
|
|
1202 | it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning |
|
|
1203 | \&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives. |
|
|
1204 | .PP |
|
|
1205 | If you cannot run the fd in non-blocking mode (for example you should not |
|
|
1206 | play around with an Xlib connection), then you have to separately re-test |
|
|
1207 | whether a file descriptor is really ready with a known-to-be good interface |
|
|
1208 | such as poll (fortunately in our Xlib example, Xlib already does this on |
|
|
1209 | its own, so its quite safe to use). |
|
|
1210 | .PP |
|
|
1211 | \fIThe special problem of disappearing file descriptors\fR |
|
|
1212 | .IX Subsection "The special problem of disappearing file descriptors" |
|
|
1213 | .PP |
|
|
1214 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
|
|
1215 | descriptor (either by calling \f(CW\*(C`close\*(C'\fR explicitly or by any other means, |
|
|
1216 | such as \f(CW\*(C`dup\*(C'\fR). The reason is that you register interest in some file |
|
|
1217 | descriptor, but when it goes away, the operating system will silently drop |
|
|
1218 | this interest. If another file descriptor with the same number then is |
|
|
1219 | registered with libev, there is no efficient way to see that this is, in |
|
|
1220 | fact, a different file descriptor. |
|
|
1221 | .PP |
|
|
1222 | To avoid having to explicitly tell libev about such cases, libev follows |
|
|
1223 | the following policy: Each time \f(CW\*(C`ev_io_set\*(C'\fR is being called, libev |
|
|
1224 | will assume that this is potentially a new file descriptor, otherwise |
|
|
1225 | it is assumed that the file descriptor stays the same. That means that |
|
|
1226 | 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 |
|
|
1227 | descriptor even if the file descriptor number itself did not change. |
|
|
1228 | .PP |
|
|
1229 | This is how one would do it normally anyway, the important point is that |
|
|
1230 | the libev application should not optimise around libev but should leave |
|
|
1231 | optimisations to libev. |
|
|
1232 | .PP |
|
|
1233 | \fIThe special problem of dup'ed file descriptors\fR |
|
|
1234 | .IX Subsection "The special problem of dup'ed file descriptors" |
|
|
1235 | .PP |
|
|
1236 | Some backends (e.g. epoll), cannot register events for file descriptors, |
|
|
1237 | but only events for the underlying file descriptions. That means when you |
|
|
1238 | have \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors or weirder constellations, and register |
|
|
1239 | events for them, only one file descriptor might actually receive events. |
|
|
1240 | .PP |
|
|
1241 | There is no workaround possible except not registering events |
|
|
1242 | for potentially \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors, or to resort to |
|
|
1243 | \&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
|
|
1244 | .PP |
|
|
1245 | \fIThe special problem of fork\fR |
|
|
1246 | .IX Subsection "The special problem of fork" |
|
|
1247 | .PP |
|
|
1248 | Some backends (epoll, kqueue) do not support \f(CW\*(C`fork ()\*(C'\fR at all or exhibit |
|
|
1249 | useless behaviour. Libev fully supports fork, but needs to be told about |
|
|
1250 | it in the child. |
|
|
1251 | .PP |
|
|
1252 | To support fork in your programs, you either have to call |
|
|
1253 | \&\f(CW\*(C`ev_default_fork ()\*(C'\fR or \f(CW\*(C`ev_loop_fork ()\*(C'\fR after a fork in the child, |
|
|
1254 | enable \f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR, or resort to \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or |
|
|
1255 | \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
|
|
1256 | .PP |
|
|
1257 | \fIThe special problem of \s-1SIGPIPE\s0\fR |
|
|
1258 | .IX Subsection "The special problem of SIGPIPE" |
|
|
1259 | .PP |
|
|
1260 | While not really specific to libev, it is easy to forget about \s-1SIGPIPE:\s0 |
|
|
1261 | when reading from a pipe whose other end has been closed, your program |
|
|
1262 | gets send a \s-1SIGPIPE\s0, which, by default, aborts your program. For most |
|
|
1263 | programs this is sensible behaviour, for daemons, this is usually |
|
|
1264 | undesirable. |
|
|
1265 | .PP |
|
|
1266 | So when you encounter spurious, unexplained daemon exits, make sure you |
|
|
1267 | ignore \s-1SIGPIPE\s0 (and maybe make sure you log the exit status of your daemon |
|
|
1268 | somewhere, as that would have given you a big clue). |
|
|
1269 | .PP |
|
|
1270 | \fIWatcher-Specific Functions\fR |
|
|
1271 | .IX Subsection "Watcher-Specific Functions" |
645 | .IP "ev_io_init (ev_io *, callback, int fd, int events)" 4 |
1272 | .IP "ev_io_init (ev_io *, callback, int fd, int events)" 4 |
646 | .IX Item "ev_io_init (ev_io *, callback, int fd, int events)" |
1273 | .IX Item "ev_io_init (ev_io *, callback, int fd, int events)" |
647 | .PD 0 |
1274 | .PD 0 |
648 | .IP "ev_io_set (ev_io *, int fd, int events)" 4 |
1275 | .IP "ev_io_set (ev_io *, int fd, int events)" 4 |
649 | .IX Item "ev_io_set (ev_io *, int fd, int events)" |
1276 | .IX Item "ev_io_set (ev_io *, int fd, int events)" |
650 | .PD |
1277 | .PD |
651 | Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The fd is the file descriptor to rceeive |
1278 | Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to |
652 | 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 | |
1279 | receive events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or |
653 | EV_WRITE\*(C'\fR to receive the given events. |
1280 | \&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR to receive the given events. |
654 | .Sp |
1281 | .IP "int fd [read\-only]" 4 |
655 | Please note that most of the more scalable backend mechanisms (for example |
1282 | .IX Item "int fd [read-only]" |
656 | epoll and solaris ports) can result in spurious readyness notifications |
1283 | The file descriptor being watched. |
657 | for file descriptors, so you practically need to use non-blocking I/O (and |
1284 | .IP "int events [read\-only]" 4 |
658 | treat callback invocation as hint only), or retest separately with a safe |
1285 | .IX Item "int events [read-only]" |
659 | interface before doing I/O (XLib can do this), or force the use of either |
1286 | The events being watched. |
660 | \&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR, which don't suffer from this |
1287 | .PP |
661 | problem. Also note that it is quite easy to have your callback invoked |
1288 | \fIExamples\fR |
662 | when the readyness condition is no longer valid even when employing |
1289 | .IX Subsection "Examples" |
663 | typical ways of handling events, so its a good idea to use non-blocking |
1290 | .PP |
664 | I/O unconditionally. |
1291 | Example: Call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well |
|
|
1292 | readable, but only once. Since it is likely line-buffered, you could |
|
|
1293 | attempt to read a whole line in the callback. |
|
|
1294 | .PP |
|
|
1295 | .Vb 6 |
|
|
1296 | \& static void |
|
|
1297 | \& stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
|
|
1298 | \& { |
|
|
1299 | \& ev_io_stop (loop, w); |
|
|
1300 | \& .. read from stdin here (or from w\->fd) and haqndle any I/O errors |
|
|
1301 | \& } |
|
|
1302 | \& |
|
|
1303 | \& ... |
|
|
1304 | \& struct ev_loop *loop = ev_default_init (0); |
|
|
1305 | \& struct ev_io stdin_readable; |
|
|
1306 | \& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
|
|
1307 | \& ev_io_start (loop, &stdin_readable); |
|
|
1308 | \& ev_loop (loop, 0); |
|
|
1309 | .Ve |
665 | .ie n .Sh """ev_timer"" \- relative and optionally recurring timeouts" |
1310 | .ie n .Sh """ev_timer"" \- relative and optionally repeating timeouts" |
666 | .el .Sh "\f(CWev_timer\fP \- relative and optionally recurring timeouts" |
1311 | .el .Sh "\f(CWev_timer\fP \- relative and optionally repeating timeouts" |
667 | .IX Subsection "ev_timer - relative and optionally recurring timeouts" |
1312 | .IX Subsection "ev_timer - relative and optionally repeating timeouts" |
668 | Timer watchers are simple relative timers that generate an event after a |
1313 | Timer watchers are simple relative timers that generate an event after a |
669 | given time, and optionally repeating in regular intervals after that. |
1314 | given time, and optionally repeating in regular intervals after that. |
670 | .PP |
1315 | .PP |
671 | The timers are based on real time, that is, if you register an event that |
1316 | The timers are based on real time, that is, if you register an event that |
672 | times out after an hour and you reset your system clock to last years |
1317 | times out after an hour and you reset your system clock to January last |
673 | time, it will still time out after (roughly) and hour. \*(L"Roughly\*(R" because |
1318 | year, it will still time out after (roughly) and hour. \*(L"Roughly\*(R" because |
674 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1319 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
675 | monotonic clock option helps a lot here). |
1320 | monotonic clock option helps a lot here). |
676 | .PP |
1321 | .PP |
677 | The relative timeouts are calculated relative to the \f(CW\*(C`ev_now ()\*(C'\fR |
1322 | The relative timeouts are calculated relative to the \f(CW\*(C`ev_now ()\*(C'\fR |
678 | time. This is usually the right thing as this timestamp refers to the time |
1323 | time. This is usually the right thing as this timestamp refers to the time |
679 | of the event triggering whatever timeout you are modifying/starting. If |
1324 | of the event triggering whatever timeout you are modifying/starting. If |
680 | you suspect event processing to be delayed and you \fIneed\fR to base the timeout |
1325 | you suspect event processing to be delayed and you \fIneed\fR to base the timeout |
681 | on the current time, use something like this to adjust for this: |
1326 | on the current time, use something like this to adjust for this: |
682 | .PP |
1327 | .PP |
683 | .Vb 1 |
1328 | .Vb 1 |
684 | \& ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1329 | \& ev_timer_set (&timer, after + ev_now () \- ev_time (), 0.); |
685 | .Ve |
1330 | .Ve |
686 | .PP |
1331 | .PP |
687 | The callback is guarenteed to be invoked only when its timeout has passed, |
1332 | The callback is guaranteed to be invoked only after its timeout has passed, |
688 | but if multiple timers become ready during the same loop iteration then |
1333 | but if multiple timers become ready during the same loop iteration then |
689 | order of execution is undefined. |
1334 | order of execution is undefined. |
|
|
1335 | .PP |
|
|
1336 | \fIWatcher-Specific Functions and Data Members\fR |
|
|
1337 | .IX Subsection "Watcher-Specific Functions and Data Members" |
690 | .IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4 |
1338 | .IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4 |
691 | .IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" |
1339 | .IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" |
692 | .PD 0 |
1340 | .PD 0 |
693 | .IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4 |
1341 | .IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4 |
694 | .IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" |
1342 | .IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" |
695 | .PD |
1343 | .PD |
696 | Configure the timer to trigger after \f(CW\*(C`after\*(C'\fR seconds. If \f(CW\*(C`repeat\*(C'\fR is |
1344 | Configure the timer to trigger after \f(CW\*(C`after\*(C'\fR seconds. If \f(CW\*(C`repeat\*(C'\fR |
697 | \&\f(CW0.\fR, then it will automatically be stopped. If it is positive, then the |
1345 | is \f(CW0.\fR, then it will automatically be stopped once the timeout is |
698 | timer will automatically be configured to trigger again \f(CW\*(C`repeat\*(C'\fR seconds |
1346 | reached. If it is positive, then the timer will automatically be |
699 | later, again, and again, until stopped manually. |
1347 | configured to trigger again \f(CW\*(C`repeat\*(C'\fR seconds later, again, and again, |
|
|
1348 | until stopped manually. |
700 | .Sp |
1349 | .Sp |
701 | The timer itself will do a best-effort at avoiding drift, that is, if you |
1350 | The timer itself will do a best-effort at avoiding drift, that is, if |
702 | configure a timer to trigger every 10 seconds, then it will trigger at |
1351 | you configure a timer to trigger every 10 seconds, then it will normally |
703 | exactly 10 second intervals. If, however, your program cannot keep up with |
1352 | trigger at exactly 10 second intervals. If, however, your program cannot |
704 | the timer (because it takes longer than those 10 seconds to do stuff) the |
1353 | keep up with the timer (because it takes longer than those 10 seconds to |
705 | timer will not fire more than once per event loop iteration. |
1354 | do stuff) the timer will not fire more than once per event loop iteration. |
706 | .IP "ev_timer_again (loop)" 4 |
1355 | .IP "ev_timer_again (loop, ev_timer *)" 4 |
707 | .IX Item "ev_timer_again (loop)" |
1356 | .IX Item "ev_timer_again (loop, ev_timer *)" |
708 | This will act as if the timer timed out and restart it again if it is |
1357 | This will act as if the timer timed out and restart it again if it is |
709 | repeating. The exact semantics are: |
1358 | repeating. The exact semantics are: |
710 | .Sp |
1359 | .Sp |
|
|
1360 | If the timer is pending, its pending status is cleared. |
|
|
1361 | .Sp |
711 | If the timer is started but nonrepeating, stop it. |
1362 | If the timer is started but non-repeating, stop it (as if it timed out). |
712 | .Sp |
1363 | .Sp |
713 | If the timer is repeating, either start it if necessary (with the repeat |
1364 | If the timer is repeating, either start it if necessary (with the |
714 | value), or reset the running timer to the repeat value. |
1365 | \&\f(CW\*(C`repeat\*(C'\fR value), or reset the running timer to the \f(CW\*(C`repeat\*(C'\fR value. |
715 | .Sp |
1366 | .Sp |
716 | This sounds a bit complicated, but here is a useful and typical |
1367 | This sounds a bit complicated, but here is a useful and typical |
717 | example: Imagine you have a tcp connection and you want a so-called idle |
1368 | example: Imagine you have a \s-1TCP\s0 connection and you want a so-called idle |
718 | timeout, that is, you want to be called when there have been, say, 60 |
1369 | timeout, that is, you want to be called when there have been, say, 60 |
719 | seconds of inactivity on the socket. The easiest way to do this is to |
1370 | seconds of inactivity on the socket. The easiest way to do this is to |
720 | configure an \f(CW\*(C`ev_timer\*(C'\fR with after=repeat=60 and calling ev_timer_again each |
1371 | configure an \f(CW\*(C`ev_timer\*(C'\fR with a \f(CW\*(C`repeat\*(C'\fR value of \f(CW60\fR and then call |
721 | time you successfully read or write some data. If you go into an idle |
1372 | \&\f(CW\*(C`ev_timer_again\*(C'\fR each time you successfully read or write some data. If |
722 | state where you do not expect data to travel on the socket, you can stop |
1373 | you go into an idle state where you do not expect data to travel on the |
723 | the timer, and again will automatically restart it if need be. |
1374 | socket, you can \f(CW\*(C`ev_timer_stop\*(C'\fR the timer, and \f(CW\*(C`ev_timer_again\*(C'\fR will |
|
|
1375 | automatically restart it if need be. |
|
|
1376 | .Sp |
|
|
1377 | That means you can ignore the \f(CW\*(C`after\*(C'\fR value and \f(CW\*(C`ev_timer_start\*(C'\fR |
|
|
1378 | altogether and only ever use the \f(CW\*(C`repeat\*(C'\fR value and \f(CW\*(C`ev_timer_again\*(C'\fR: |
|
|
1379 | .Sp |
|
|
1380 | .Vb 8 |
|
|
1381 | \& ev_timer_init (timer, callback, 0., 5.); |
|
|
1382 | \& ev_timer_again (loop, timer); |
|
|
1383 | \& ... |
|
|
1384 | \& timer\->again = 17.; |
|
|
1385 | \& ev_timer_again (loop, timer); |
|
|
1386 | \& ... |
|
|
1387 | \& timer\->again = 10.; |
|
|
1388 | \& ev_timer_again (loop, timer); |
|
|
1389 | .Ve |
|
|
1390 | .Sp |
|
|
1391 | This is more slightly efficient then stopping/starting the timer each time |
|
|
1392 | you want to modify its timeout value. |
|
|
1393 | .IP "ev_tstamp repeat [read\-write]" 4 |
|
|
1394 | .IX Item "ev_tstamp repeat [read-write]" |
|
|
1395 | The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out |
|
|
1396 | or \f(CW\*(C`ev_timer_again\*(C'\fR is called and determines the next timeout (if any), |
|
|
1397 | which is also when any modifications are taken into account. |
|
|
1398 | .PP |
|
|
1399 | \fIExamples\fR |
|
|
1400 | .IX Subsection "Examples" |
|
|
1401 | .PP |
|
|
1402 | Example: Create a timer that fires after 60 seconds. |
|
|
1403 | .PP |
|
|
1404 | .Vb 5 |
|
|
1405 | \& static void |
|
|
1406 | \& one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
|
|
1407 | \& { |
|
|
1408 | \& .. one minute over, w is actually stopped right here |
|
|
1409 | \& } |
|
|
1410 | \& |
|
|
1411 | \& struct ev_timer mytimer; |
|
|
1412 | \& ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
|
|
1413 | \& ev_timer_start (loop, &mytimer); |
|
|
1414 | .Ve |
|
|
1415 | .PP |
|
|
1416 | Example: Create a timeout timer that times out after 10 seconds of |
|
|
1417 | inactivity. |
|
|
1418 | .PP |
|
|
1419 | .Vb 5 |
|
|
1420 | \& static void |
|
|
1421 | \& timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
|
|
1422 | \& { |
|
|
1423 | \& .. ten seconds without any activity |
|
|
1424 | \& } |
|
|
1425 | \& |
|
|
1426 | \& struct ev_timer mytimer; |
|
|
1427 | \& ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
|
|
1428 | \& ev_timer_again (&mytimer); /* start timer */ |
|
|
1429 | \& ev_loop (loop, 0); |
|
|
1430 | \& |
|
|
1431 | \& // and in some piece of code that gets executed on any "activity": |
|
|
1432 | \& // reset the timeout to start ticking again at 10 seconds |
|
|
1433 | \& ev_timer_again (&mytimer); |
|
|
1434 | .Ve |
724 | .ie n .Sh """ev_periodic"" \- to cron or not to cron" |
1435 | .ie n .Sh """ev_periodic"" \- to cron or not to cron?" |
725 | .el .Sh "\f(CWev_periodic\fP \- to cron or not to cron" |
1436 | .el .Sh "\f(CWev_periodic\fP \- to cron or not to cron?" |
726 | .IX Subsection "ev_periodic - to cron or not to cron" |
1437 | .IX Subsection "ev_periodic - to cron or not to cron?" |
727 | Periodic watchers are also timers of a kind, but they are very versatile |
1438 | Periodic watchers are also timers of a kind, but they are very versatile |
728 | (and unfortunately a bit complex). |
1439 | (and unfortunately a bit complex). |
729 | .PP |
1440 | .PP |
730 | Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time) |
1441 | Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time) |
731 | but on wallclock time (absolute time). You can tell a periodic watcher |
1442 | but on wall clock time (absolute time). You can tell a periodic watcher |
732 | to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a |
1443 | to trigger after some specific point in time. For example, if you tell a |
733 | periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now () |
1444 | periodic watcher to trigger in 10 seconds (by specifying e.g. \f(CW\*(C`ev_now () |
734 | + 10.>) and then reset your system clock to the last year, then it will |
1445 | + 10.\*(C'\fR, that is, an absolute time not a delay) and then reset your system |
|
|
1446 | clock to January of the previous year, then it will take more than year |
735 | take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger |
1447 | to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would still trigger |
736 | roughly 10 seconds later and of course not if you reset your system time |
1448 | roughly 10 seconds later as it uses a relative timeout). |
737 | again). |
|
|
738 | .PP |
1449 | .PP |
739 | They can also be used to implement vastly more complex timers, such as |
1450 | \&\f(CW\*(C`ev_periodic\*(C'\fRs can also be used to implement vastly more complex timers, |
740 | triggering an event on eahc midnight, local time. |
1451 | such as triggering an event on each \*(L"midnight, local time\*(R", or other |
|
|
1452 | complicated, rules. |
741 | .PP |
1453 | .PP |
742 | As with timers, the callback is guarenteed to be invoked only when the |
1454 | As with timers, the callback is guaranteed to be invoked only when the |
743 | time (\f(CW\*(C`at\*(C'\fR) has been passed, but if multiple periodic timers become ready |
1455 | time (\f(CW\*(C`at\*(C'\fR) has passed, but if multiple periodic timers become ready |
744 | during the same loop iteration then order of execution is undefined. |
1456 | during the same loop iteration then order of execution is undefined. |
|
|
1457 | .PP |
|
|
1458 | \fIWatcher-Specific Functions and Data Members\fR |
|
|
1459 | .IX Subsection "Watcher-Specific Functions and Data Members" |
745 | .IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4 |
1460 | .IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4 |
746 | .IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" |
1461 | .IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" |
747 | .PD 0 |
1462 | .PD 0 |
748 | .IP "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 4 |
1463 | .IP "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 4 |
749 | .IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" |
1464 | .IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" |
750 | .PD |
1465 | .PD |
751 | Lots of arguments, lets sort it out... There are basically three modes of |
1466 | Lots of arguments, lets sort it out... There are basically three modes of |
752 | operation, and we will explain them from simplest to complex: |
1467 | operation, and we will explain them from simplest to complex: |
753 | .RS 4 |
1468 | .RS 4 |
|
|
1469 | .IP "\(bu" 4 |
754 | .IP "* absolute timer (interval = reschedule_cb = 0)" 4 |
1470 | absolute timer (at = time, interval = reschedule_cb = 0) |
755 | .IX Item "absolute timer (interval = reschedule_cb = 0)" |
1471 | .Sp |
756 | In this configuration the watcher triggers an event at the wallclock time |
1472 | In this configuration the watcher triggers an event after the wall clock |
757 | \&\f(CW\*(C`at\*(C'\fR and doesn't repeat. It will not adjust when a time jump occurs, |
1473 | time \f(CW\*(C`at\*(C'\fR has passed and doesn't repeat. It will not adjust when a time |
758 | that is, if it is to be run at January 1st 2011 then it will run when the |
1474 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
759 | system time reaches or surpasses this time. |
1475 | run when the system time reaches or surpasses this time. |
|
|
1476 | .IP "\(bu" 4 |
760 | .IP "* non-repeating interval timer (interval > 0, reschedule_cb = 0)" 4 |
1477 | repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
761 | .IX Item "non-repeating interval timer (interval > 0, reschedule_cb = 0)" |
1478 | .Sp |
762 | In this mode the watcher will always be scheduled to time out at the next |
1479 | In this mode the watcher will always be scheduled to time out at the next |
763 | \&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N) and then repeat, regardless |
1480 | \&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N, which can also be negative) |
764 | of any time jumps. |
1481 | and then repeat, regardless of any time jumps. |
765 | .Sp |
1482 | .Sp |
766 | This can be used to create timers that do not drift with respect to system |
1483 | This can be used to create timers that do not drift with respect to system |
767 | time: |
1484 | time, for example, here is a \f(CW\*(C`ev_periodic\*(C'\fR that triggers each hour, on |
|
|
1485 | the hour: |
768 | .Sp |
1486 | .Sp |
769 | .Vb 1 |
1487 | .Vb 1 |
770 | \& ev_periodic_set (&periodic, 0., 3600., 0); |
1488 | \& ev_periodic_set (&periodic, 0., 3600., 0); |
771 | .Ve |
1489 | .Ve |
772 | .Sp |
1490 | .Sp |
773 | This doesn't mean there will always be 3600 seconds in between triggers, |
1491 | This doesn't mean there will always be 3600 seconds in between triggers, |
774 | but only that the the callback will be called when the system time shows a |
1492 | but only that the callback will be called when the system time shows a |
775 | full hour (\s-1UTC\s0), or more correctly, when the system time is evenly divisible |
1493 | full hour (\s-1UTC\s0), or more correctly, when the system time is evenly divisible |
776 | by 3600. |
1494 | by 3600. |
777 | .Sp |
1495 | .Sp |
778 | Another way to think about it (for the mathematically inclined) is that |
1496 | Another way to think about it (for the mathematically inclined) is that |
779 | \&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible |
1497 | \&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible |
780 | time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps. |
1498 | time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps. |
781 | .IP "* manual reschedule mode (reschedule_cb = callback)" 4 |
1499 | .Sp |
782 | .IX Item "manual reschedule mode (reschedule_cb = callback)" |
1500 | For numerical stability it is preferable that the \f(CW\*(C`at\*(C'\fR value is near |
|
|
1501 | \&\f(CW\*(C`ev_now ()\*(C'\fR (the current time), but there is no range requirement for |
|
|
1502 | this value, and in fact is often specified as zero. |
|
|
1503 | .Sp |
|
|
1504 | Note also that there is an upper limit to how often a timer can fire (\s-1CPU\s0 |
|
|
1505 | speed for example), so if \f(CW\*(C`interval\*(C'\fR is very small then timing stability |
|
|
1506 | will of course deteriorate. Libev itself tries to be exact to be about one |
|
|
1507 | millisecond (if the \s-1OS\s0 supports it and the machine is fast enough). |
|
|
1508 | .IP "\(bu" 4 |
|
|
1509 | manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
|
|
1510 | .Sp |
783 | In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR are both being |
1511 | In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR are both being |
784 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1512 | ignored. Instead, each time the periodic watcher gets scheduled, the |
785 | reschedule callback will be called with the watcher as first, and the |
1513 | reschedule callback will be called with the watcher as first, and the |
786 | current time as second argument. |
1514 | current time as second argument. |
787 | .Sp |
1515 | .Sp |
788 | \&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher, |
1516 | \&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher, |
789 | ever, or make any event loop modifications\fR. If you need to stop it, |
1517 | ever, or make \s-1ANY\s0 event loop modifications whatsoever\fR. |
790 | return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop it afterwards (e.g. by |
|
|
791 | starting a prepare watcher). |
|
|
792 | .Sp |
1518 | .Sp |
|
|
1519 | If you need to stop it, return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop |
|
|
1520 | it afterwards (e.g. by starting an \f(CW\*(C`ev_prepare\*(C'\fR watcher, which is the |
|
|
1521 | only event loop modification you are allowed to do). |
|
|
1522 | .Sp |
793 | Its prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic *w, |
1523 | The callback prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic |
794 | ev_tstamp now)\*(C'\fR, e.g.: |
1524 | *w, ev_tstamp now)\*(C'\fR, e.g.: |
795 | .Sp |
1525 | .Sp |
796 | .Vb 4 |
1526 | .Vb 4 |
797 | \& static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1527 | \& static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
798 | \& { |
1528 | \& { |
799 | \& return now + 60.; |
1529 | \& return now + 60.; |
… | |
… | |
803 | It must return the next time to trigger, based on the passed time value |
1533 | It must return the next time to trigger, based on the passed time value |
804 | (that is, the lowest time value larger than to the second argument). It |
1534 | (that is, the lowest time value larger than to the second argument). It |
805 | will usually be called just before the callback will be triggered, but |
1535 | will usually be called just before the callback will be triggered, but |
806 | might be called at other times, too. |
1536 | might be called at other times, too. |
807 | .Sp |
1537 | .Sp |
808 | \&\s-1NOTE:\s0 \fIThis callback must always return a time that is later than the |
1538 | \&\s-1NOTE:\s0 \fIThis callback must always return a time that is higher than or |
809 | 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. |
1539 | equal to the passed \f(CI\*(C`now\*(C'\fI value\fR. |
810 | .Sp |
1540 | .Sp |
811 | This can be used to create very complex timers, such as a timer that |
1541 | This can be used to create very complex timers, such as a timer that |
812 | triggers on each midnight, local time. To do this, you would calculate the |
1542 | triggers on \*(L"next midnight, local time\*(R". To do this, you would calculate the |
813 | next midnight after \f(CW\*(C`now\*(C'\fR and return the timestamp value for this. How |
1543 | next midnight after \f(CW\*(C`now\*(C'\fR and return the timestamp value for this. How |
814 | you do this is, again, up to you (but it is not trivial, which is the main |
1544 | you do this is, again, up to you (but it is not trivial, which is the main |
815 | reason I omitted it as an example). |
1545 | reason I omitted it as an example). |
816 | .RE |
1546 | .RE |
817 | .RS 4 |
1547 | .RS 4 |
… | |
… | |
820 | .IX Item "ev_periodic_again (loop, ev_periodic *)" |
1550 | .IX Item "ev_periodic_again (loop, ev_periodic *)" |
821 | Simply stops and restarts the periodic watcher again. This is only useful |
1551 | Simply stops and restarts the periodic watcher again. This is only useful |
822 | when you changed some parameters or the reschedule callback would return |
1552 | when you changed some parameters or the reschedule callback would return |
823 | a different time than the last time it was called (e.g. in a crond like |
1553 | a different time than the last time it was called (e.g. in a crond like |
824 | program when the crontabs have changed). |
1554 | program when the crontabs have changed). |
|
|
1555 | .IP "ev_tstamp ev_periodic_at (ev_periodic *)" 4 |
|
|
1556 | .IX Item "ev_tstamp ev_periodic_at (ev_periodic *)" |
|
|
1557 | When active, returns the absolute time that the watcher is supposed to |
|
|
1558 | trigger next. |
|
|
1559 | .IP "ev_tstamp offset [read\-write]" 4 |
|
|
1560 | .IX Item "ev_tstamp offset [read-write]" |
|
|
1561 | When repeating, this contains the offset value, otherwise this is the |
|
|
1562 | absolute point in time (the \f(CW\*(C`at\*(C'\fR value passed to \f(CW\*(C`ev_periodic_set\*(C'\fR). |
|
|
1563 | .Sp |
|
|
1564 | Can be modified any time, but changes only take effect when the periodic |
|
|
1565 | timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called. |
|
|
1566 | .IP "ev_tstamp interval [read\-write]" 4 |
|
|
1567 | .IX Item "ev_tstamp interval [read-write]" |
|
|
1568 | The current interval value. Can be modified any time, but changes only |
|
|
1569 | take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being |
|
|
1570 | called. |
|
|
1571 | .IP "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read\-write]" 4 |
|
|
1572 | .IX Item "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]" |
|
|
1573 | The current reschedule callback, or \f(CW0\fR, if this functionality is |
|
|
1574 | switched off. Can be changed any time, but changes only take effect when |
|
|
1575 | the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called. |
|
|
1576 | .PP |
|
|
1577 | \fIExamples\fR |
|
|
1578 | .IX Subsection "Examples" |
|
|
1579 | .PP |
|
|
1580 | Example: Call a callback every hour, or, more precisely, whenever the |
|
|
1581 | system clock is divisible by 3600. The callback invocation times have |
|
|
1582 | potentially a lot of jitter, but good long-term stability. |
|
|
1583 | .PP |
|
|
1584 | .Vb 5 |
|
|
1585 | \& static void |
|
|
1586 | \& clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
|
|
1587 | \& { |
|
|
1588 | \& ... its now a full hour (UTC, or TAI or whatever your clock follows) |
|
|
1589 | \& } |
|
|
1590 | \& |
|
|
1591 | \& struct ev_periodic hourly_tick; |
|
|
1592 | \& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
|
|
1593 | \& ev_periodic_start (loop, &hourly_tick); |
|
|
1594 | .Ve |
|
|
1595 | .PP |
|
|
1596 | Example: The same as above, but use a reschedule callback to do it: |
|
|
1597 | .PP |
|
|
1598 | .Vb 1 |
|
|
1599 | \& #include <math.h> |
|
|
1600 | \& |
|
|
1601 | \& static ev_tstamp |
|
|
1602 | \& my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
|
|
1603 | \& { |
|
|
1604 | \& return fmod (now, 3600.) + 3600.; |
|
|
1605 | \& } |
|
|
1606 | \& |
|
|
1607 | \& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
|
|
1608 | .Ve |
|
|
1609 | .PP |
|
|
1610 | Example: Call a callback every hour, starting now: |
|
|
1611 | .PP |
|
|
1612 | .Vb 4 |
|
|
1613 | \& struct ev_periodic hourly_tick; |
|
|
1614 | \& ev_periodic_init (&hourly_tick, clock_cb, |
|
|
1615 | \& fmod (ev_now (loop), 3600.), 3600., 0); |
|
|
1616 | \& ev_periodic_start (loop, &hourly_tick); |
|
|
1617 | .Ve |
825 | .ie n .Sh """ev_signal"" \- signal me when a signal gets signalled" |
1618 | .ie n .Sh """ev_signal"" \- signal me when a signal gets signalled!" |
826 | .el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled" |
1619 | .el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled!" |
827 | .IX Subsection "ev_signal - signal me when a signal gets signalled" |
1620 | .IX Subsection "ev_signal - signal me when a signal gets signalled!" |
828 | Signal watchers will trigger an event when the process receives a specific |
1621 | Signal watchers will trigger an event when the process receives a specific |
829 | signal one or more times. Even though signals are very asynchronous, libev |
1622 | signal one or more times. Even though signals are very asynchronous, libev |
830 | will try it's best to deliver signals synchronously, i.e. as part of the |
1623 | will try it's best to deliver signals synchronously, i.e. as part of the |
831 | normal event processing, like any other event. |
1624 | normal event processing, like any other event. |
832 | .PP |
1625 | .PP |
… | |
… | |
834 | first watcher gets started will libev actually register a signal watcher |
1627 | first watcher gets started will libev actually register a signal watcher |
835 | with the kernel (thus it coexists with your own signal handlers as long |
1628 | with the kernel (thus it coexists with your own signal handlers as long |
836 | as you don't register any with libev). Similarly, when the last signal |
1629 | as you don't register any with libev). Similarly, when the last signal |
837 | watcher for a signal is stopped libev will reset the signal handler to |
1630 | watcher for a signal is stopped libev will reset the signal handler to |
838 | \&\s-1SIG_DFL\s0 (regardless of what it was set to before). |
1631 | \&\s-1SIG_DFL\s0 (regardless of what it was set to before). |
|
|
1632 | .PP |
|
|
1633 | If possible and supported, libev will install its handlers with |
|
|
1634 | \&\f(CW\*(C`SA_RESTART\*(C'\fR behaviour enabled, so system calls should not be unduly |
|
|
1635 | interrupted. If you have a problem with system calls getting interrupted by |
|
|
1636 | signals you can block all signals in an \f(CW\*(C`ev_check\*(C'\fR watcher and unblock |
|
|
1637 | them in an \f(CW\*(C`ev_prepare\*(C'\fR watcher. |
|
|
1638 | .PP |
|
|
1639 | \fIWatcher-Specific Functions and Data Members\fR |
|
|
1640 | .IX Subsection "Watcher-Specific Functions and Data Members" |
839 | .IP "ev_signal_init (ev_signal *, callback, int signum)" 4 |
1641 | .IP "ev_signal_init (ev_signal *, callback, int signum)" 4 |
840 | .IX Item "ev_signal_init (ev_signal *, callback, int signum)" |
1642 | .IX Item "ev_signal_init (ev_signal *, callback, int signum)" |
841 | .PD 0 |
1643 | .PD 0 |
842 | .IP "ev_signal_set (ev_signal *, int signum)" 4 |
1644 | .IP "ev_signal_set (ev_signal *, int signum)" 4 |
843 | .IX Item "ev_signal_set (ev_signal *, int signum)" |
1645 | .IX Item "ev_signal_set (ev_signal *, int signum)" |
844 | .PD |
1646 | .PD |
845 | Configures the watcher to trigger on the given signal number (usually one |
1647 | Configures the watcher to trigger on the given signal number (usually one |
846 | of the \f(CW\*(C`SIGxxx\*(C'\fR constants). |
1648 | of the \f(CW\*(C`SIGxxx\*(C'\fR constants). |
|
|
1649 | .IP "int signum [read\-only]" 4 |
|
|
1650 | .IX Item "int signum [read-only]" |
|
|
1651 | The signal the watcher watches out for. |
|
|
1652 | .PP |
|
|
1653 | \fIExamples\fR |
|
|
1654 | .IX Subsection "Examples" |
|
|
1655 | .PP |
|
|
1656 | Example: Try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0. |
|
|
1657 | .PP |
|
|
1658 | .Vb 5 |
|
|
1659 | \& static void |
|
|
1660 | \& sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
|
|
1661 | \& { |
|
|
1662 | \& ev_unloop (loop, EVUNLOOP_ALL); |
|
|
1663 | \& } |
|
|
1664 | \& |
|
|
1665 | \& struct ev_signal signal_watcher; |
|
|
1666 | \& ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
|
|
1667 | \& ev_signal_start (loop, &sigint_cb); |
|
|
1668 | .Ve |
847 | .ie n .Sh """ev_child"" \- wait for pid status changes" |
1669 | .ie n .Sh """ev_child"" \- watch out for process status changes" |
848 | .el .Sh "\f(CWev_child\fP \- wait for pid status changes" |
1670 | .el .Sh "\f(CWev_child\fP \- watch out for process status changes" |
849 | .IX Subsection "ev_child - wait for pid status changes" |
1671 | .IX Subsection "ev_child - watch out for process status changes" |
850 | Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to |
1672 | Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to |
851 | some child status changes (most typically when a child of yours dies). |
1673 | some child status changes (most typically when a child of yours dies). It |
|
|
1674 | is permissible to install a child watcher \fIafter\fR the child has been |
|
|
1675 | forked (which implies it might have already exited), as long as the event |
|
|
1676 | loop isn't entered (or is continued from a watcher). |
|
|
1677 | .PP |
|
|
1678 | Only the default event loop is capable of handling signals, and therefore |
|
|
1679 | you can only register child watchers in the default event loop. |
|
|
1680 | .PP |
|
|
1681 | \fIProcess Interaction\fR |
|
|
1682 | .IX Subsection "Process Interaction" |
|
|
1683 | .PP |
|
|
1684 | Libev grabs \f(CW\*(C`SIGCHLD\*(C'\fR as soon as the default event loop is |
|
|
1685 | initialised. This is necessary to guarantee proper behaviour even if |
|
|
1686 | the first child watcher is started after the child exits. The occurrence |
|
|
1687 | of \f(CW\*(C`SIGCHLD\*(C'\fR is recorded asynchronously, but child reaping is done |
|
|
1688 | synchronously as part of the event loop processing. Libev always reaps all |
|
|
1689 | children, even ones not watched. |
|
|
1690 | .PP |
|
|
1691 | \fIOverriding the Built-In Processing\fR |
|
|
1692 | .IX Subsection "Overriding the Built-In Processing" |
|
|
1693 | .PP |
|
|
1694 | Libev offers no special support for overriding the built-in child |
|
|
1695 | processing, but if your application collides with libev's default child |
|
|
1696 | handler, you can override it easily by installing your own handler for |
|
|
1697 | \&\f(CW\*(C`SIGCHLD\*(C'\fR after initialising the default loop, and making sure the |
|
|
1698 | default loop never gets destroyed. You are encouraged, however, to use an |
|
|
1699 | event-based approach to child reaping and thus use libev's support for |
|
|
1700 | that, so other libev users can use \f(CW\*(C`ev_child\*(C'\fR watchers freely. |
|
|
1701 | .PP |
|
|
1702 | \fIWatcher-Specific Functions and Data Members\fR |
|
|
1703 | .IX Subsection "Watcher-Specific Functions and Data Members" |
852 | .IP "ev_child_init (ev_child *, callback, int pid)" 4 |
1704 | .IP "ev_child_init (ev_child *, callback, int pid, int trace)" 4 |
853 | .IX Item "ev_child_init (ev_child *, callback, int pid)" |
1705 | .IX Item "ev_child_init (ev_child *, callback, int pid, int trace)" |
854 | .PD 0 |
1706 | .PD 0 |
855 | .IP "ev_child_set (ev_child *, int pid)" 4 |
1707 | .IP "ev_child_set (ev_child *, int pid, int trace)" 4 |
856 | .IX Item "ev_child_set (ev_child *, int pid)" |
1708 | .IX Item "ev_child_set (ev_child *, int pid, int trace)" |
857 | .PD |
1709 | .PD |
858 | Configures the watcher to wait for status changes of process \f(CW\*(C`pid\*(C'\fR (or |
1710 | Configures the watcher to wait for status changes of process \f(CW\*(C`pid\*(C'\fR (or |
859 | \&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look |
1711 | \&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look |
860 | at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see |
1712 | at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see |
861 | the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems |
1713 | the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems |
862 | \&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the |
1714 | \&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the |
863 | process causing the status change. |
1715 | process causing the status change. \f(CW\*(C`trace\*(C'\fR must be either \f(CW0\fR (only |
|
|
1716 | activate the watcher when the process terminates) or \f(CW1\fR (additionally |
|
|
1717 | activate the watcher when the process is stopped or continued). |
|
|
1718 | .IP "int pid [read\-only]" 4 |
|
|
1719 | .IX Item "int pid [read-only]" |
|
|
1720 | The process id this watcher watches out for, or \f(CW0\fR, meaning any process id. |
|
|
1721 | .IP "int rpid [read\-write]" 4 |
|
|
1722 | .IX Item "int rpid [read-write]" |
|
|
1723 | The process id that detected a status change. |
|
|
1724 | .IP "int rstatus [read\-write]" 4 |
|
|
1725 | .IX Item "int rstatus [read-write]" |
|
|
1726 | The process exit/trace status caused by \f(CW\*(C`rpid\*(C'\fR (see your systems |
|
|
1727 | \&\f(CW\*(C`waitpid\*(C'\fR and \f(CW\*(C`sys/wait.h\*(C'\fR documentation for details). |
|
|
1728 | .PP |
|
|
1729 | \fIExamples\fR |
|
|
1730 | .IX Subsection "Examples" |
|
|
1731 | .PP |
|
|
1732 | Example: \f(CW\*(C`fork()\*(C'\fR a new process and install a child handler to wait for |
|
|
1733 | its completion. |
|
|
1734 | .PP |
|
|
1735 | .Vb 1 |
|
|
1736 | \& ev_child cw; |
|
|
1737 | \& |
|
|
1738 | \& static void |
|
|
1739 | \& child_cb (EV_P_ struct ev_child *w, int revents) |
|
|
1740 | \& { |
|
|
1741 | \& ev_child_stop (EV_A_ w); |
|
|
1742 | \& printf ("process %d exited with status %x\en", w\->rpid, w\->rstatus); |
|
|
1743 | \& } |
|
|
1744 | \& |
|
|
1745 | \& pid_t pid = fork (); |
|
|
1746 | \& |
|
|
1747 | \& if (pid < 0) |
|
|
1748 | \& // error |
|
|
1749 | \& else if (pid == 0) |
|
|
1750 | \& { |
|
|
1751 | \& // the forked child executes here |
|
|
1752 | \& exit (1); |
|
|
1753 | \& } |
|
|
1754 | \& else |
|
|
1755 | \& { |
|
|
1756 | \& ev_child_init (&cw, child_cb, pid, 0); |
|
|
1757 | \& ev_child_start (EV_DEFAULT_ &cw); |
|
|
1758 | \& } |
|
|
1759 | .Ve |
|
|
1760 | .ie n .Sh """ev_stat"" \- did the file attributes just change?" |
|
|
1761 | .el .Sh "\f(CWev_stat\fP \- did the file attributes just change?" |
|
|
1762 | .IX Subsection "ev_stat - did the file attributes just change?" |
|
|
1763 | This watches a file system path for attribute changes. That is, it calls |
|
|
1764 | \&\f(CW\*(C`stat\*(C'\fR regularly (or when the \s-1OS\s0 says it changed) and sees if it changed |
|
|
1765 | compared to the last time, invoking the callback if it did. |
|
|
1766 | .PP |
|
|
1767 | The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does |
|
|
1768 | not exist\*(R" is a status change like any other. The condition \*(L"path does |
|
|
1769 | not exist\*(R" is signified by the \f(CW\*(C`st_nlink\*(C'\fR field being zero (which is |
|
|
1770 | otherwise always forced to be at least one) and all the other fields of |
|
|
1771 | the stat buffer having unspecified contents. |
|
|
1772 | .PP |
|
|
1773 | The path \fIshould\fR be absolute and \fImust not\fR end in a slash. If it is |
|
|
1774 | relative and your working directory changes, the behaviour is undefined. |
|
|
1775 | .PP |
|
|
1776 | Since there is no standard to do this, the portable implementation simply |
|
|
1777 | calls \f(CW\*(C`stat (2)\*(C'\fR regularly on the path to see if it changed somehow. You |
|
|
1778 | can specify a recommended polling interval for this case. If you specify |
|
|
1779 | a polling interval of \f(CW0\fR (highly recommended!) then a \fIsuitable, |
|
|
1780 | unspecified default\fR value will be used (which you can expect to be around |
|
|
1781 | five seconds, although this might change dynamically). Libev will also |
|
|
1782 | impose a minimum interval which is currently around \f(CW0.1\fR, but thats |
|
|
1783 | usually overkill. |
|
|
1784 | .PP |
|
|
1785 | This watcher type is not meant for massive numbers of stat watchers, |
|
|
1786 | as even with OS-supported change notifications, this can be |
|
|
1787 | resource-intensive. |
|
|
1788 | .PP |
|
|
1789 | At the time of this writing, only the Linux inotify interface is |
|
|
1790 | implemented (implementing kqueue support is left as an exercise for the |
|
|
1791 | reader, note, however, that the author sees no way of implementing ev_stat |
|
|
1792 | semantics with kqueue). Inotify will be used to give hints only and should |
|
|
1793 | not change the semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers, which means that libev |
|
|
1794 | sometimes needs to fall back to regular polling again even with inotify, |
|
|
1795 | but changes are usually detected immediately, and if the file exists there |
|
|
1796 | will be no polling. |
|
|
1797 | .PP |
|
|
1798 | \fI\s-1ABI\s0 Issues (Largefile Support)\fR |
|
|
1799 | .IX Subsection "ABI Issues (Largefile Support)" |
|
|
1800 | .PP |
|
|
1801 | Libev by default (unless the user overrides this) uses the default |
|
|
1802 | compilation environment, which means that on systems with large file |
|
|
1803 | support disabled by default, you get the 32 bit version of the stat |
|
|
1804 | structure. When using the library from programs that change the \s-1ABI\s0 to |
|
|
1805 | use 64 bit file offsets the programs will fail. In that case you have to |
|
|
1806 | compile libev with the same flags to get binary compatibility. This is |
|
|
1807 | obviously the case with any flags that change the \s-1ABI\s0, but the problem is |
|
|
1808 | most noticeably disabled with ev_stat and large file support. |
|
|
1809 | .PP |
|
|
1810 | The solution for this is to lobby your distribution maker to make large |
|
|
1811 | file interfaces available by default (as e.g. FreeBSD does) and not |
|
|
1812 | optional. Libev cannot simply switch on large file support because it has |
|
|
1813 | to exchange stat structures with application programs compiled using the |
|
|
1814 | default compilation environment. |
|
|
1815 | .PP |
|
|
1816 | \fIInotify\fR |
|
|
1817 | .IX Subsection "Inotify" |
|
|
1818 | .PP |
|
|
1819 | When \f(CW\*(C`inotify (7)\*(C'\fR support has been compiled into libev (generally only |
|
|
1820 | available on Linux) and present at runtime, it will be used to speed up |
|
|
1821 | change detection where possible. The inotify descriptor will be created lazily |
|
|
1822 | when the first \f(CW\*(C`ev_stat\*(C'\fR watcher is being started. |
|
|
1823 | .PP |
|
|
1824 | Inotify presence does not change the semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers |
|
|
1825 | except that changes might be detected earlier, and in some cases, to avoid |
|
|
1826 | making regular \f(CW\*(C`stat\*(C'\fR calls. Even in the presence of inotify support |
|
|
1827 | there are many cases where libev has to resort to regular \f(CW\*(C`stat\*(C'\fR polling. |
|
|
1828 | .PP |
|
|
1829 | (There is no support for kqueue, as apparently it cannot be used to |
|
|
1830 | implement this functionality, due to the requirement of having a file |
|
|
1831 | descriptor open on the object at all times). |
|
|
1832 | .PP |
|
|
1833 | \fIThe special problem of stat time resolution\fR |
|
|
1834 | .IX Subsection "The special problem of stat time resolution" |
|
|
1835 | .PP |
|
|
1836 | The \f(CW\*(C`stat ()\*(C'\fR system call only supports full-second resolution portably, and |
|
|
1837 | even on systems where the resolution is higher, many file systems still |
|
|
1838 | only support whole seconds. |
|
|
1839 | .PP |
|
|
1840 | That means that, if the time is the only thing that changes, you can |
|
|
1841 | easily miss updates: on the first update, \f(CW\*(C`ev_stat\*(C'\fR detects a change and |
|
|
1842 | calls your callback, which does something. When there is another update |
|
|
1843 | within the same second, \f(CW\*(C`ev_stat\*(C'\fR will be unable to detect it as the stat |
|
|
1844 | data does not change. |
|
|
1845 | .PP |
|
|
1846 | The solution to this is to delay acting on a change for slightly more |
|
|
1847 | than a second (or till slightly after the next full second boundary), using |
|
|
1848 | a roughly one-second-delay \f(CW\*(C`ev_timer\*(C'\fR (e.g. \f(CW\*(C`ev_timer_set (w, 0., 1.02); |
|
|
1849 | ev_timer_again (loop, w)\*(C'\fR). |
|
|
1850 | .PP |
|
|
1851 | The \f(CW.02\fR offset is added to work around small timing inconsistencies |
|
|
1852 | of some operating systems (where the second counter of the current time |
|
|
1853 | might be be delayed. One such system is the Linux kernel, where a call to |
|
|
1854 | \&\f(CW\*(C`gettimeofday\*(C'\fR might return a timestamp with a full second later than |
|
|
1855 | a subsequent \f(CW\*(C`time\*(C'\fR call \- if the equivalent of \f(CW\*(C`time ()\*(C'\fR is used to |
|
|
1856 | update file times then there will be a small window where the kernel uses |
|
|
1857 | the previous second to update file times but libev might already execute |
|
|
1858 | the timer callback). |
|
|
1859 | .PP |
|
|
1860 | \fIWatcher-Specific Functions and Data Members\fR |
|
|
1861 | .IX Subsection "Watcher-Specific Functions and Data Members" |
|
|
1862 | .IP "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 4 |
|
|
1863 | .IX Item "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" |
|
|
1864 | .PD 0 |
|
|
1865 | .IP "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" 4 |
|
|
1866 | .IX Item "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" |
|
|
1867 | .PD |
|
|
1868 | Configures the watcher to wait for status changes of the given |
|
|
1869 | \&\f(CW\*(C`path\*(C'\fR. The \f(CW\*(C`interval\*(C'\fR is a hint on how quickly a change is expected to |
|
|
1870 | be detected and should normally be specified as \f(CW0\fR to let libev choose |
|
|
1871 | a suitable value. The memory pointed to by \f(CW\*(C`path\*(C'\fR must point to the same |
|
|
1872 | path for as long as the watcher is active. |
|
|
1873 | .Sp |
|
|
1874 | The callback will receive \f(CW\*(C`EV_STAT\*(C'\fR when a change was detected, relative |
|
|
1875 | to the attributes at the time the watcher was started (or the last change |
|
|
1876 | was detected). |
|
|
1877 | .IP "ev_stat_stat (loop, ev_stat *)" 4 |
|
|
1878 | .IX Item "ev_stat_stat (loop, ev_stat *)" |
|
|
1879 | Updates the stat buffer immediately with new values. If you change the |
|
|
1880 | watched path in your callback, you could call this function to avoid |
|
|
1881 | detecting this change (while introducing a race condition if you are not |
|
|
1882 | the only one changing the path). Can also be useful simply to find out the |
|
|
1883 | new values. |
|
|
1884 | .IP "ev_statdata attr [read\-only]" 4 |
|
|
1885 | .IX Item "ev_statdata attr [read-only]" |
|
|
1886 | The most-recently detected attributes of the file. Although the type is |
|
|
1887 | \&\f(CW\*(C`ev_statdata\*(C'\fR, this is usually the (or one of the) \f(CW\*(C`struct stat\*(C'\fR types |
|
|
1888 | suitable for your system, but you can only rely on the POSIX-standardised |
|
|
1889 | members to be present. If the \f(CW\*(C`st_nlink\*(C'\fR member is \f(CW0\fR, then there was |
|
|
1890 | some error while \f(CW\*(C`stat\*(C'\fRing the file. |
|
|
1891 | .IP "ev_statdata prev [read\-only]" 4 |
|
|
1892 | .IX Item "ev_statdata prev [read-only]" |
|
|
1893 | The previous attributes of the file. The callback gets invoked whenever |
|
|
1894 | \&\f(CW\*(C`prev\*(C'\fR != \f(CW\*(C`attr\*(C'\fR, or, more precisely, one or more of these members |
|
|
1895 | 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, |
|
|
1896 | \&\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. |
|
|
1897 | .IP "ev_tstamp interval [read\-only]" 4 |
|
|
1898 | .IX Item "ev_tstamp interval [read-only]" |
|
|
1899 | The specified interval. |
|
|
1900 | .IP "const char *path [read\-only]" 4 |
|
|
1901 | .IX Item "const char *path [read-only]" |
|
|
1902 | The file system path that is being watched. |
|
|
1903 | .PP |
|
|
1904 | \fIExamples\fR |
|
|
1905 | .IX Subsection "Examples" |
|
|
1906 | .PP |
|
|
1907 | Example: Watch \f(CW\*(C`/etc/passwd\*(C'\fR for attribute changes. |
|
|
1908 | .PP |
|
|
1909 | .Vb 10 |
|
|
1910 | \& static void |
|
|
1911 | \& passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) |
|
|
1912 | \& { |
|
|
1913 | \& /* /etc/passwd changed in some way */ |
|
|
1914 | \& if (w\->attr.st_nlink) |
|
|
1915 | \& { |
|
|
1916 | \& printf ("passwd current size %ld\en", (long)w\->attr.st_size); |
|
|
1917 | \& printf ("passwd current atime %ld\en", (long)w\->attr.st_mtime); |
|
|
1918 | \& printf ("passwd current mtime %ld\en", (long)w\->attr.st_mtime); |
|
|
1919 | \& } |
|
|
1920 | \& else |
|
|
1921 | \& /* you shalt not abuse printf for puts */ |
|
|
1922 | \& puts ("wow, /etc/passwd is not there, expect problems. " |
|
|
1923 | \& "if this is windows, they already arrived\en"); |
|
|
1924 | \& } |
|
|
1925 | \& |
|
|
1926 | \& ... |
|
|
1927 | \& ev_stat passwd; |
|
|
1928 | \& |
|
|
1929 | \& ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.); |
|
|
1930 | \& ev_stat_start (loop, &passwd); |
|
|
1931 | .Ve |
|
|
1932 | .PP |
|
|
1933 | Example: Like above, but additionally use a one-second delay so we do not |
|
|
1934 | miss updates (however, frequent updates will delay processing, too, so |
|
|
1935 | one might do the work both on \f(CW\*(C`ev_stat\*(C'\fR callback invocation \fIand\fR on |
|
|
1936 | \&\f(CW\*(C`ev_timer\*(C'\fR callback invocation). |
|
|
1937 | .PP |
|
|
1938 | .Vb 2 |
|
|
1939 | \& static ev_stat passwd; |
|
|
1940 | \& static ev_timer timer; |
|
|
1941 | \& |
|
|
1942 | \& static void |
|
|
1943 | \& timer_cb (EV_P_ ev_timer *w, int revents) |
|
|
1944 | \& { |
|
|
1945 | \& ev_timer_stop (EV_A_ w); |
|
|
1946 | \& |
|
|
1947 | \& /* now it\*(Aqs one second after the most recent passwd change */ |
|
|
1948 | \& } |
|
|
1949 | \& |
|
|
1950 | \& static void |
|
|
1951 | \& stat_cb (EV_P_ ev_stat *w, int revents) |
|
|
1952 | \& { |
|
|
1953 | \& /* reset the one\-second timer */ |
|
|
1954 | \& ev_timer_again (EV_A_ &timer); |
|
|
1955 | \& } |
|
|
1956 | \& |
|
|
1957 | \& ... |
|
|
1958 | \& ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
|
|
1959 | \& ev_stat_start (loop, &passwd); |
|
|
1960 | \& ev_timer_init (&timer, timer_cb, 0., 1.02); |
|
|
1961 | .Ve |
864 | .ie n .Sh """ev_idle"" \- when you've got nothing better to do" |
1962 | .ie n .Sh """ev_idle"" \- when you've got nothing better to do..." |
865 | .el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do" |
1963 | .el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do..." |
866 | .IX Subsection "ev_idle - when you've got nothing better to do" |
1964 | .IX Subsection "ev_idle - when you've got nothing better to do..." |
867 | Idle watchers trigger events when there are no other events are pending |
1965 | Idle watchers trigger events when no other events of the same or higher |
868 | (prepare, check and other idle watchers do not count). That is, as long |
1966 | priority are pending (prepare, check and other idle watchers do not |
869 | as your process is busy handling sockets or timeouts (or even signals, |
1967 | count). |
870 | imagine) it will not be triggered. But when your process is idle all idle |
1968 | .PP |
871 | watchers are being called again and again, once per event loop iteration \- |
1969 | That is, as long as your process is busy handling sockets or timeouts |
|
|
1970 | (or even signals, imagine) of the same or higher priority it will not be |
|
|
1971 | triggered. But when your process is idle (or only lower-priority watchers |
|
|
1972 | are pending), the idle watchers are being called once per event loop |
872 | until stopped, that is, or your process receives more events and becomes |
1973 | iteration \- until stopped, that is, or your process receives more events |
873 | busy. |
1974 | and becomes busy again with higher priority stuff. |
874 | .PP |
1975 | .PP |
875 | The most noteworthy effect is that as long as any idle watchers are |
1976 | The most noteworthy effect is that as long as any idle watchers are |
876 | active, the process will not block when waiting for new events. |
1977 | active, the process will not block when waiting for new events. |
877 | .PP |
1978 | .PP |
878 | Apart from keeping your process non-blocking (which is a useful |
1979 | Apart from keeping your process non-blocking (which is a useful |
879 | effect on its own sometimes), idle watchers are a good place to do |
1980 | effect on its own sometimes), idle watchers are a good place to do |
880 | \&\*(L"pseudo\-background processing\*(R", or delay processing stuff to after the |
1981 | \&\*(L"pseudo-background processing\*(R", or delay processing stuff to after the |
881 | event loop has handled all outstanding events. |
1982 | event loop has handled all outstanding events. |
|
|
1983 | .PP |
|
|
1984 | \fIWatcher-Specific Functions and Data Members\fR |
|
|
1985 | .IX Subsection "Watcher-Specific Functions and Data Members" |
882 | .IP "ev_idle_init (ev_signal *, callback)" 4 |
1986 | .IP "ev_idle_init (ev_signal *, callback)" 4 |
883 | .IX Item "ev_idle_init (ev_signal *, callback)" |
1987 | .IX Item "ev_idle_init (ev_signal *, callback)" |
884 | Initialises and configures the idle watcher \- it has no parameters of any |
1988 | Initialises and configures the idle watcher \- it has no parameters of any |
885 | kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless, |
1989 | kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless, |
886 | believe me. |
1990 | believe me. |
|
|
1991 | .PP |
|
|
1992 | \fIExamples\fR |
|
|
1993 | .IX Subsection "Examples" |
|
|
1994 | .PP |
|
|
1995 | Example: Dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR watcher, start it, and in the |
|
|
1996 | callback, free it. Also, use no error checking, as usual. |
|
|
1997 | .PP |
|
|
1998 | .Vb 7 |
|
|
1999 | \& static void |
|
|
2000 | \& idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
|
|
2001 | \& { |
|
|
2002 | \& free (w); |
|
|
2003 | \& // now do something you wanted to do when the program has |
|
|
2004 | \& // no longer anything immediate to do. |
|
|
2005 | \& } |
|
|
2006 | \& |
|
|
2007 | \& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
|
|
2008 | \& ev_idle_init (idle_watcher, idle_cb); |
|
|
2009 | \& ev_idle_start (loop, idle_cb); |
|
|
2010 | .Ve |
887 | .ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop" |
2011 | .ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop!" |
888 | .el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop" |
2012 | .el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!" |
889 | .IX Subsection "ev_prepare and ev_check - customise your event loop" |
2013 | .IX Subsection "ev_prepare and ev_check - customise your event loop!" |
890 | Prepare and check watchers are usually (but not always) used in tandem: |
2014 | Prepare and check watchers are usually (but not always) used in tandem: |
891 | prepare watchers get invoked before the process blocks and check watchers |
2015 | prepare watchers get invoked before the process blocks and check watchers |
892 | afterwards. |
2016 | afterwards. |
893 | .PP |
2017 | .PP |
|
|
2018 | You \fImust not\fR call \f(CW\*(C`ev_loop\*(C'\fR or similar functions that enter |
|
|
2019 | the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR |
|
|
2020 | watchers. Other loops than the current one are fine, however. The |
|
|
2021 | rationale behind this is that you do not need to check for recursion in |
|
|
2022 | those watchers, i.e. the sequence will always be \f(CW\*(C`ev_prepare\*(C'\fR, blocking, |
|
|
2023 | \&\f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each kind they will always be |
|
|
2024 | called in pairs bracketing the blocking call. |
|
|
2025 | .PP |
894 | Their main purpose is to integrate other event mechanisms into libev. This |
2026 | Their main purpose is to integrate other event mechanisms into libev and |
895 | could be used, for example, to track variable changes, implement your own |
2027 | their use is somewhat advanced. This could be used, for example, to track |
896 | watchers, integrate net-snmp or a coroutine library and lots more. |
2028 | variable changes, implement your own watchers, integrate net-snmp or a |
|
|
2029 | coroutine library and lots more. They are also occasionally useful if |
|
|
2030 | you cache some data and want to flush it before blocking (for example, |
|
|
2031 | in X programs you might want to do an \f(CW\*(C`XFlush ()\*(C'\fR in an \f(CW\*(C`ev_prepare\*(C'\fR |
|
|
2032 | watcher). |
897 | .PP |
2033 | .PP |
898 | This is done by examining in each prepare call which file descriptors need |
2034 | This is done by examining in each prepare call which file descriptors need |
899 | to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for |
2035 | to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for |
900 | them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries |
2036 | them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries |
901 | provide just this functionality). Then, in the check watcher you check for |
2037 | provide just this functionality). Then, in the check watcher you check for |
902 | any events that occured (by checking the pending status of all watchers |
2038 | any events that occurred (by checking the pending status of all watchers |
903 | and stopping them) and call back into the library. The I/O and timer |
2039 | and stopping them) and call back into the library. The I/O and timer |
904 | callbacks will never actually be called (but must be valid nevertheless, |
2040 | callbacks will never actually be called (but must be valid nevertheless, |
905 | because you never know, you know?). |
2041 | because you never know, you know?). |
906 | .PP |
2042 | .PP |
907 | As another example, the Perl Coro module uses these hooks to integrate |
2043 | As another example, the Perl Coro module uses these hooks to integrate |
… | |
… | |
910 | are ready to run (it's actually more complicated: it only runs coroutines |
2046 | are ready to run (it's actually more complicated: it only runs coroutines |
911 | with priority higher than or equal to the event loop and one coroutine |
2047 | with priority higher than or equal to the event loop and one coroutine |
912 | of lower priority, but only once, using idle watchers to keep the event |
2048 | of lower priority, but only once, using idle watchers to keep the event |
913 | loop from blocking if lower-priority coroutines are active, thus mapping |
2049 | loop from blocking if lower-priority coroutines are active, thus mapping |
914 | low-priority coroutines to idle/background tasks). |
2050 | low-priority coroutines to idle/background tasks). |
|
|
2051 | .PP |
|
|
2052 | It is recommended to give \f(CW\*(C`ev_check\*(C'\fR watchers highest (\f(CW\*(C`EV_MAXPRI\*(C'\fR) |
|
|
2053 | priority, to ensure that they are being run before any other watchers |
|
|
2054 | after the poll. Also, \f(CW\*(C`ev_check\*(C'\fR watchers (and \f(CW\*(C`ev_prepare\*(C'\fR watchers, |
|
|
2055 | too) should not activate (\*(L"feed\*(R") events into libev. While libev fully |
|
|
2056 | supports this, they might get executed before other \f(CW\*(C`ev_check\*(C'\fR watchers |
|
|
2057 | did their job. As \f(CW\*(C`ev_check\*(C'\fR watchers are often used to embed other |
|
|
2058 | (non-libev) event loops those other event loops might be in an unusable |
|
|
2059 | state until their \f(CW\*(C`ev_check\*(C'\fR watcher ran (always remind yourself to |
|
|
2060 | coexist peacefully with others). |
|
|
2061 | .PP |
|
|
2062 | \fIWatcher-Specific Functions and Data Members\fR |
|
|
2063 | .IX Subsection "Watcher-Specific Functions and Data Members" |
915 | .IP "ev_prepare_init (ev_prepare *, callback)" 4 |
2064 | .IP "ev_prepare_init (ev_prepare *, callback)" 4 |
916 | .IX Item "ev_prepare_init (ev_prepare *, callback)" |
2065 | .IX Item "ev_prepare_init (ev_prepare *, callback)" |
917 | .PD 0 |
2066 | .PD 0 |
918 | .IP "ev_check_init (ev_check *, callback)" 4 |
2067 | .IP "ev_check_init (ev_check *, callback)" 4 |
919 | .IX Item "ev_check_init (ev_check *, callback)" |
2068 | .IX Item "ev_check_init (ev_check *, callback)" |
920 | .PD |
2069 | .PD |
921 | Initialises and configures the prepare or check watcher \- they have no |
2070 | Initialises and configures the prepare or check watcher \- they have no |
922 | parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR |
2071 | parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR |
923 | macros, but using them is utterly, utterly and completely pointless. |
2072 | macros, but using them is utterly, utterly and completely pointless. |
|
|
2073 | .PP |
|
|
2074 | \fIExamples\fR |
|
|
2075 | .IX Subsection "Examples" |
|
|
2076 | .PP |
|
|
2077 | There are a number of principal ways to embed other event loops or modules |
|
|
2078 | into libev. Here are some ideas on how to include libadns into libev |
|
|
2079 | (there is a Perl module named \f(CW\*(C`EV::ADNS\*(C'\fR that does this, which you could |
|
|
2080 | use as a working example. Another Perl module named \f(CW\*(C`EV::Glib\*(C'\fR embeds a |
|
|
2081 | Glib main context into libev, and finally, \f(CW\*(C`Glib::EV\*(C'\fR embeds \s-1EV\s0 into the |
|
|
2082 | Glib event loop). |
|
|
2083 | .PP |
|
|
2084 | Method 1: Add \s-1IO\s0 watchers and a timeout watcher in a prepare handler, |
|
|
2085 | and in a check watcher, destroy them and call into libadns. What follows |
|
|
2086 | is pseudo-code only of course. This requires you to either use a low |
|
|
2087 | priority for the check watcher or use \f(CW\*(C`ev_clear_pending\*(C'\fR explicitly, as |
|
|
2088 | the callbacks for the IO/timeout watchers might not have been called yet. |
|
|
2089 | .PP |
|
|
2090 | .Vb 2 |
|
|
2091 | \& static ev_io iow [nfd]; |
|
|
2092 | \& static ev_timer tw; |
|
|
2093 | \& |
|
|
2094 | \& static void |
|
|
2095 | \& io_cb (ev_loop *loop, ev_io *w, int revents) |
|
|
2096 | \& { |
|
|
2097 | \& } |
|
|
2098 | \& |
|
|
2099 | \& // create io watchers for each fd and a timer before blocking |
|
|
2100 | \& static void |
|
|
2101 | \& adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
|
|
2102 | \& { |
|
|
2103 | \& int timeout = 3600000; |
|
|
2104 | \& struct pollfd fds [nfd]; |
|
|
2105 | \& // actual code will need to loop here and realloc etc. |
|
|
2106 | \& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
|
|
2107 | \& |
|
|
2108 | \& /* the callback is illegal, but won\*(Aqt be called as we stop during check */ |
|
|
2109 | \& ev_timer_init (&tw, 0, timeout * 1e\-3); |
|
|
2110 | \& ev_timer_start (loop, &tw); |
|
|
2111 | \& |
|
|
2112 | \& // create one ev_io per pollfd |
|
|
2113 | \& for (int i = 0; i < nfd; ++i) |
|
|
2114 | \& { |
|
|
2115 | \& ev_io_init (iow + i, io_cb, fds [i].fd, |
|
|
2116 | \& ((fds [i].events & POLLIN ? EV_READ : 0) |
|
|
2117 | \& | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
|
|
2118 | \& |
|
|
2119 | \& fds [i].revents = 0; |
|
|
2120 | \& ev_io_start (loop, iow + i); |
|
|
2121 | \& } |
|
|
2122 | \& } |
|
|
2123 | \& |
|
|
2124 | \& // stop all watchers after blocking |
|
|
2125 | \& static void |
|
|
2126 | \& adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
|
|
2127 | \& { |
|
|
2128 | \& ev_timer_stop (loop, &tw); |
|
|
2129 | \& |
|
|
2130 | \& for (int i = 0; i < nfd; ++i) |
|
|
2131 | \& { |
|
|
2132 | \& // set the relevant poll flags |
|
|
2133 | \& // could also call adns_processreadable etc. here |
|
|
2134 | \& struct pollfd *fd = fds + i; |
|
|
2135 | \& int revents = ev_clear_pending (iow + i); |
|
|
2136 | \& if (revents & EV_READ ) fd\->revents |= fd\->events & POLLIN; |
|
|
2137 | \& if (revents & EV_WRITE) fd\->revents |= fd\->events & POLLOUT; |
|
|
2138 | \& |
|
|
2139 | \& // now stop the watcher |
|
|
2140 | \& ev_io_stop (loop, iow + i); |
|
|
2141 | \& } |
|
|
2142 | \& |
|
|
2143 | \& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
|
|
2144 | \& } |
|
|
2145 | .Ve |
|
|
2146 | .PP |
|
|
2147 | Method 2: This would be just like method 1, but you run \f(CW\*(C`adns_afterpoll\*(C'\fR |
|
|
2148 | in the prepare watcher and would dispose of the check watcher. |
|
|
2149 | .PP |
|
|
2150 | Method 3: If the module to be embedded supports explicit event |
|
|
2151 | notification (libadns does), you can also make use of the actual watcher |
|
|
2152 | callbacks, and only destroy/create the watchers in the prepare watcher. |
|
|
2153 | .PP |
|
|
2154 | .Vb 5 |
|
|
2155 | \& static void |
|
|
2156 | \& timer_cb (EV_P_ ev_timer *w, int revents) |
|
|
2157 | \& { |
|
|
2158 | \& adns_state ads = (adns_state)w\->data; |
|
|
2159 | \& update_now (EV_A); |
|
|
2160 | \& |
|
|
2161 | \& adns_processtimeouts (ads, &tv_now); |
|
|
2162 | \& } |
|
|
2163 | \& |
|
|
2164 | \& static void |
|
|
2165 | \& io_cb (EV_P_ ev_io *w, int revents) |
|
|
2166 | \& { |
|
|
2167 | \& adns_state ads = (adns_state)w\->data; |
|
|
2168 | \& update_now (EV_A); |
|
|
2169 | \& |
|
|
2170 | \& if (revents & EV_READ ) adns_processreadable (ads, w\->fd, &tv_now); |
|
|
2171 | \& if (revents & EV_WRITE) adns_processwriteable (ads, w\->fd, &tv_now); |
|
|
2172 | \& } |
|
|
2173 | \& |
|
|
2174 | \& // do not ever call adns_afterpoll |
|
|
2175 | .Ve |
|
|
2176 | .PP |
|
|
2177 | Method 4: Do not use a prepare or check watcher because the module you |
|
|
2178 | want to embed is too inflexible to support it. Instead, you can override |
|
|
2179 | their poll function. The drawback with this solution is that the main |
|
|
2180 | loop is now no longer controllable by \s-1EV\s0. The \f(CW\*(C`Glib::EV\*(C'\fR module does |
|
|
2181 | this. |
|
|
2182 | .PP |
|
|
2183 | .Vb 4 |
|
|
2184 | \& static gint |
|
|
2185 | \& event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
|
|
2186 | \& { |
|
|
2187 | \& int got_events = 0; |
|
|
2188 | \& |
|
|
2189 | \& for (n = 0; n < nfds; ++n) |
|
|
2190 | \& // create/start io watcher that sets the relevant bits in fds[n] and increment got_events |
|
|
2191 | \& |
|
|
2192 | \& if (timeout >= 0) |
|
|
2193 | \& // create/start timer |
|
|
2194 | \& |
|
|
2195 | \& // poll |
|
|
2196 | \& ev_loop (EV_A_ 0); |
|
|
2197 | \& |
|
|
2198 | \& // stop timer again |
|
|
2199 | \& if (timeout >= 0) |
|
|
2200 | \& ev_timer_stop (EV_A_ &to); |
|
|
2201 | \& |
|
|
2202 | \& // stop io watchers again \- their callbacks should have set |
|
|
2203 | \& for (n = 0; n < nfds; ++n) |
|
|
2204 | \& ev_io_stop (EV_A_ iow [n]); |
|
|
2205 | \& |
|
|
2206 | \& return got_events; |
|
|
2207 | \& } |
|
|
2208 | .Ve |
|
|
2209 | .ie n .Sh """ev_embed"" \- when one backend isn't enough..." |
|
|
2210 | .el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..." |
|
|
2211 | .IX Subsection "ev_embed - when one backend isn't enough..." |
|
|
2212 | This is a rather advanced watcher type that lets you embed one event loop |
|
|
2213 | into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded |
|
|
2214 | loop, other types of watchers might be handled in a delayed or incorrect |
|
|
2215 | fashion and must not be used). |
|
|
2216 | .PP |
|
|
2217 | There are primarily two reasons you would want that: work around bugs and |
|
|
2218 | prioritise I/O. |
|
|
2219 | .PP |
|
|
2220 | As an example for a bug workaround, the kqueue backend might only support |
|
|
2221 | sockets on some platform, so it is unusable as generic backend, but you |
|
|
2222 | still want to make use of it because you have many sockets and it scales |
|
|
2223 | so nicely. In this case, you would create a kqueue-based loop and embed it |
|
|
2224 | into your default loop (which might use e.g. poll). Overall operation will |
|
|
2225 | be a bit slower because first libev has to poll and then call kevent, but |
|
|
2226 | at least you can use both at what they are best. |
|
|
2227 | .PP |
|
|
2228 | As for prioritising I/O: rarely you have the case where some fds have |
|
|
2229 | to be watched and handled very quickly (with low latency), and even |
|
|
2230 | priorities and idle watchers might have too much overhead. In this case |
|
|
2231 | you would put all the high priority stuff in one loop and all the rest in |
|
|
2232 | a second one, and embed the second one in the first. |
|
|
2233 | .PP |
|
|
2234 | As long as the watcher is active, the callback will be invoked every time |
|
|
2235 | there might be events pending in the embedded loop. The callback must then |
|
|
2236 | call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single sweep and invoke |
|
|
2237 | their callbacks (you could also start an idle watcher to give the embedded |
|
|
2238 | loop strictly lower priority for example). You can also set the callback |
|
|
2239 | to \f(CW0\fR, in which case the embed watcher will automatically execute the |
|
|
2240 | embedded loop sweep. |
|
|
2241 | .PP |
|
|
2242 | As long as the watcher is started it will automatically handle events. The |
|
|
2243 | callback will be invoked whenever some events have been handled. You can |
|
|
2244 | set the callback to \f(CW0\fR to avoid having to specify one if you are not |
|
|
2245 | interested in that. |
|
|
2246 | .PP |
|
|
2247 | Also, there have not currently been made special provisions for forking: |
|
|
2248 | when you fork, you not only have to call \f(CW\*(C`ev_loop_fork\*(C'\fR on both loops, |
|
|
2249 | but you will also have to stop and restart any \f(CW\*(C`ev_embed\*(C'\fR watchers |
|
|
2250 | yourself. |
|
|
2251 | .PP |
|
|
2252 | Unfortunately, not all backends are embeddable, only the ones returned by |
|
|
2253 | \&\f(CW\*(C`ev_embeddable_backends\*(C'\fR are, which, unfortunately, does not include any |
|
|
2254 | portable one. |
|
|
2255 | .PP |
|
|
2256 | So when you want to use this feature you will always have to be prepared |
|
|
2257 | that you cannot get an embeddable loop. The recommended way to get around |
|
|
2258 | this is to have a separate variables for your embeddable loop, try to |
|
|
2259 | create it, and if that fails, use the normal loop for everything. |
|
|
2260 | .PP |
|
|
2261 | \fIWatcher-Specific Functions and Data Members\fR |
|
|
2262 | .IX Subsection "Watcher-Specific Functions and Data Members" |
|
|
2263 | .IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4 |
|
|
2264 | .IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" |
|
|
2265 | .PD 0 |
|
|
2266 | .IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4 |
|
|
2267 | .IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" |
|
|
2268 | .PD |
|
|
2269 | Configures the watcher to embed the given loop, which must be |
|
|
2270 | embeddable. If the callback is \f(CW0\fR, then \f(CW\*(C`ev_embed_sweep\*(C'\fR will be |
|
|
2271 | invoked automatically, otherwise it is the responsibility of the callback |
|
|
2272 | to invoke it (it will continue to be called until the sweep has been done, |
|
|
2273 | if you do not want that, you need to temporarily stop the embed watcher). |
|
|
2274 | .IP "ev_embed_sweep (loop, ev_embed *)" 4 |
|
|
2275 | .IX Item "ev_embed_sweep (loop, ev_embed *)" |
|
|
2276 | Make a single, non-blocking sweep over the embedded loop. This works |
|
|
2277 | similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most |
|
|
2278 | appropriate way for embedded loops. |
|
|
2279 | .IP "struct ev_loop *other [read\-only]" 4 |
|
|
2280 | .IX Item "struct ev_loop *other [read-only]" |
|
|
2281 | The embedded event loop. |
|
|
2282 | .PP |
|
|
2283 | \fIExamples\fR |
|
|
2284 | .IX Subsection "Examples" |
|
|
2285 | .PP |
|
|
2286 | Example: Try to get an embeddable event loop and embed it into the default |
|
|
2287 | event loop. If that is not possible, use the default loop. The default |
|
|
2288 | loop is stored in \f(CW\*(C`loop_hi\*(C'\fR, while the embeddable loop is stored in |
|
|
2289 | \&\f(CW\*(C`loop_lo\*(C'\fR (which is \f(CW\*(C`loop_hi\*(C'\fR in the case no embeddable loop can be |
|
|
2290 | used). |
|
|
2291 | .PP |
|
|
2292 | .Vb 3 |
|
|
2293 | \& struct ev_loop *loop_hi = ev_default_init (0); |
|
|
2294 | \& struct ev_loop *loop_lo = 0; |
|
|
2295 | \& struct ev_embed embed; |
|
|
2296 | \& |
|
|
2297 | \& // see if there is a chance of getting one that works |
|
|
2298 | \& // (remember that a flags value of 0 means autodetection) |
|
|
2299 | \& loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
|
|
2300 | \& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
|
|
2301 | \& : 0; |
|
|
2302 | \& |
|
|
2303 | \& // if we got one, then embed it, otherwise default to loop_hi |
|
|
2304 | \& if (loop_lo) |
|
|
2305 | \& { |
|
|
2306 | \& ev_embed_init (&embed, 0, loop_lo); |
|
|
2307 | \& ev_embed_start (loop_hi, &embed); |
|
|
2308 | \& } |
|
|
2309 | \& else |
|
|
2310 | \& loop_lo = loop_hi; |
|
|
2311 | .Ve |
|
|
2312 | .PP |
|
|
2313 | Example: Check if kqueue is available but not recommended and create |
|
|
2314 | a kqueue backend for use with sockets (which usually work with any |
|
|
2315 | kqueue implementation). Store the kqueue/socket\-only event loop in |
|
|
2316 | \&\f(CW\*(C`loop_socket\*(C'\fR. (One might optionally use \f(CW\*(C`EVFLAG_NOENV\*(C'\fR, too). |
|
|
2317 | .PP |
|
|
2318 | .Vb 3 |
|
|
2319 | \& struct ev_loop *loop = ev_default_init (0); |
|
|
2320 | \& struct ev_loop *loop_socket = 0; |
|
|
2321 | \& struct ev_embed embed; |
|
|
2322 | \& |
|
|
2323 | \& if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
|
|
2324 | \& if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
|
|
2325 | \& { |
|
|
2326 | \& ev_embed_init (&embed, 0, loop_socket); |
|
|
2327 | \& ev_embed_start (loop, &embed); |
|
|
2328 | \& } |
|
|
2329 | \& |
|
|
2330 | \& if (!loop_socket) |
|
|
2331 | \& loop_socket = loop; |
|
|
2332 | \& |
|
|
2333 | \& // now use loop_socket for all sockets, and loop for everything else |
|
|
2334 | .Ve |
|
|
2335 | .ie n .Sh """ev_fork"" \- the audacity to resume the event loop after a fork" |
|
|
2336 | .el .Sh "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork" |
|
|
2337 | .IX Subsection "ev_fork - the audacity to resume the event loop after a fork" |
|
|
2338 | Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because |
|
|
2339 | whoever is a good citizen cared to tell libev about it by calling |
|
|
2340 | \&\f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the |
|
|
2341 | event loop blocks next and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called, |
|
|
2342 | and only in the child after the fork. If whoever good citizen calling |
|
|
2343 | \&\f(CW\*(C`ev_default_fork\*(C'\fR cheats and calls it in the wrong process, the fork |
|
|
2344 | handlers will be invoked, too, of course. |
|
|
2345 | .PP |
|
|
2346 | \fIWatcher-Specific Functions and Data Members\fR |
|
|
2347 | .IX Subsection "Watcher-Specific Functions and Data Members" |
|
|
2348 | .IP "ev_fork_init (ev_signal *, callback)" 4 |
|
|
2349 | .IX Item "ev_fork_init (ev_signal *, callback)" |
|
|
2350 | Initialises and configures the fork watcher \- it has no parameters of any |
|
|
2351 | kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless, |
|
|
2352 | believe me. |
|
|
2353 | .ie n .Sh """ev_async"" \- how to wake up another event loop" |
|
|
2354 | .el .Sh "\f(CWev_async\fP \- how to wake up another event loop" |
|
|
2355 | .IX Subsection "ev_async - how to wake up another event loop" |
|
|
2356 | In general, you cannot use an \f(CW\*(C`ev_loop\*(C'\fR from multiple threads or other |
|
|
2357 | asynchronous sources such as signal handlers (as opposed to multiple event |
|
|
2358 | loops \- those are of course safe to use in different threads). |
|
|
2359 | .PP |
|
|
2360 | Sometimes, however, you need to wake up another event loop you do not |
|
|
2361 | control, for example because it belongs to another thread. This is what |
|
|
2362 | \&\f(CW\*(C`ev_async\*(C'\fR watchers do: as long as the \f(CW\*(C`ev_async\*(C'\fR watcher is active, you |
|
|
2363 | can signal it by calling \f(CW\*(C`ev_async_send\*(C'\fR, which is thread\- and signal |
|
|
2364 | safe. |
|
|
2365 | .PP |
|
|
2366 | This functionality is very similar to \f(CW\*(C`ev_signal\*(C'\fR watchers, as signals, |
|
|
2367 | too, are asynchronous in nature, and signals, too, will be compressed |
|
|
2368 | (i.e. the number of callback invocations may be less than the number of |
|
|
2369 | \&\f(CW\*(C`ev_async_sent\*(C'\fR calls). |
|
|
2370 | .PP |
|
|
2371 | Unlike \f(CW\*(C`ev_signal\*(C'\fR watchers, \f(CW\*(C`ev_async\*(C'\fR works with any event loop, not |
|
|
2372 | just the default loop. |
|
|
2373 | .PP |
|
|
2374 | \fIQueueing\fR |
|
|
2375 | .IX Subsection "Queueing" |
|
|
2376 | .PP |
|
|
2377 | \&\f(CW\*(C`ev_async\*(C'\fR does not support queueing of data in any way. The reason |
|
|
2378 | is that the author does not know of a simple (or any) algorithm for a |
|
|
2379 | multiple-writer-single-reader queue that works in all cases and doesn't |
|
|
2380 | need elaborate support such as pthreads. |
|
|
2381 | .PP |
|
|
2382 | That means that if you want to queue data, you have to provide your own |
|
|
2383 | queue. But at least I can tell you would implement locking around your |
|
|
2384 | queue: |
|
|
2385 | .IP "queueing from a signal handler context" 4 |
|
|
2386 | .IX Item "queueing from a signal handler context" |
|
|
2387 | To implement race-free queueing, you simply add to the queue in the signal |
|
|
2388 | handler but you block the signal handler in the watcher callback. Here is an example that does that for |
|
|
2389 | some fictitious \s-1SIGUSR1\s0 handler: |
|
|
2390 | .Sp |
|
|
2391 | .Vb 1 |
|
|
2392 | \& static ev_async mysig; |
|
|
2393 | \& |
|
|
2394 | \& static void |
|
|
2395 | \& sigusr1_handler (void) |
|
|
2396 | \& { |
|
|
2397 | \& sometype data; |
|
|
2398 | \& |
|
|
2399 | \& // no locking etc. |
|
|
2400 | \& queue_put (data); |
|
|
2401 | \& ev_async_send (EV_DEFAULT_ &mysig); |
|
|
2402 | \& } |
|
|
2403 | \& |
|
|
2404 | \& static void |
|
|
2405 | \& mysig_cb (EV_P_ ev_async *w, int revents) |
|
|
2406 | \& { |
|
|
2407 | \& sometype data; |
|
|
2408 | \& sigset_t block, prev; |
|
|
2409 | \& |
|
|
2410 | \& sigemptyset (&block); |
|
|
2411 | \& sigaddset (&block, SIGUSR1); |
|
|
2412 | \& sigprocmask (SIG_BLOCK, &block, &prev); |
|
|
2413 | \& |
|
|
2414 | \& while (queue_get (&data)) |
|
|
2415 | \& process (data); |
|
|
2416 | \& |
|
|
2417 | \& if (sigismember (&prev, SIGUSR1) |
|
|
2418 | \& sigprocmask (SIG_UNBLOCK, &block, 0); |
|
|
2419 | \& } |
|
|
2420 | .Ve |
|
|
2421 | .Sp |
|
|
2422 | (Note: pthreads in theory requires you to use \f(CW\*(C`pthread_setmask\*(C'\fR |
|
|
2423 | instead of \f(CW\*(C`sigprocmask\*(C'\fR when you use threads, but libev doesn't do it |
|
|
2424 | either...). |
|
|
2425 | .IP "queueing from a thread context" 4 |
|
|
2426 | .IX Item "queueing from a thread context" |
|
|
2427 | The strategy for threads is different, as you cannot (easily) block |
|
|
2428 | threads but you can easily preempt them, so to queue safely you need to |
|
|
2429 | employ a traditional mutex lock, such as in this pthread example: |
|
|
2430 | .Sp |
|
|
2431 | .Vb 2 |
|
|
2432 | \& static ev_async mysig; |
|
|
2433 | \& static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER; |
|
|
2434 | \& |
|
|
2435 | \& static void |
|
|
2436 | \& otherthread (void) |
|
|
2437 | \& { |
|
|
2438 | \& // only need to lock the actual queueing operation |
|
|
2439 | \& pthread_mutex_lock (&mymutex); |
|
|
2440 | \& queue_put (data); |
|
|
2441 | \& pthread_mutex_unlock (&mymutex); |
|
|
2442 | \& |
|
|
2443 | \& ev_async_send (EV_DEFAULT_ &mysig); |
|
|
2444 | \& } |
|
|
2445 | \& |
|
|
2446 | \& static void |
|
|
2447 | \& mysig_cb (EV_P_ ev_async *w, int revents) |
|
|
2448 | \& { |
|
|
2449 | \& pthread_mutex_lock (&mymutex); |
|
|
2450 | \& |
|
|
2451 | \& while (queue_get (&data)) |
|
|
2452 | \& process (data); |
|
|
2453 | \& |
|
|
2454 | \& pthread_mutex_unlock (&mymutex); |
|
|
2455 | \& } |
|
|
2456 | .Ve |
|
|
2457 | .PP |
|
|
2458 | \fIWatcher-Specific Functions and Data Members\fR |
|
|
2459 | .IX Subsection "Watcher-Specific Functions and Data Members" |
|
|
2460 | .IP "ev_async_init (ev_async *, callback)" 4 |
|
|
2461 | .IX Item "ev_async_init (ev_async *, callback)" |
|
|
2462 | Initialises and configures the async watcher \- it has no parameters of any |
|
|
2463 | kind. There is a \f(CW\*(C`ev_asynd_set\*(C'\fR macro, but using it is utterly pointless, |
|
|
2464 | believe me. |
|
|
2465 | .IP "ev_async_send (loop, ev_async *)" 4 |
|
|
2466 | .IX Item "ev_async_send (loop, ev_async *)" |
|
|
2467 | Sends/signals/activates the given \f(CW\*(C`ev_async\*(C'\fR watcher, that is, feeds |
|
|
2468 | an \f(CW\*(C`EV_ASYNC\*(C'\fR event on the watcher into the event loop. Unlike |
|
|
2469 | \&\f(CW\*(C`ev_feed_event\*(C'\fR, this call is safe to do in other threads, signal or |
|
|
2470 | similar contexts (see the discussion of \f(CW\*(C`EV_ATOMIC_T\*(C'\fR in the embedding |
|
|
2471 | section below on what exactly this means). |
|
|
2472 | .Sp |
|
|
2473 | This call incurs the overhead of a system call only once per loop iteration, |
|
|
2474 | so while the overhead might be noticeable, it doesn't apply to repeated |
|
|
2475 | calls to \f(CW\*(C`ev_async_send\*(C'\fR. |
|
|
2476 | .IP "bool = ev_async_pending (ev_async *)" 4 |
|
|
2477 | .IX Item "bool = ev_async_pending (ev_async *)" |
|
|
2478 | Returns a non-zero value when \f(CW\*(C`ev_async_send\*(C'\fR has been called on the |
|
|
2479 | watcher but the event has not yet been processed (or even noted) by the |
|
|
2480 | event loop. |
|
|
2481 | .Sp |
|
|
2482 | \&\f(CW\*(C`ev_async_send\*(C'\fR sets a flag in the watcher and wakes up the loop. When |
|
|
2483 | the loop iterates next and checks for the watcher to have become active, |
|
|
2484 | it will reset the flag again. \f(CW\*(C`ev_async_pending\*(C'\fR can be used to very |
|
|
2485 | quickly check whether invoking the loop might be a good idea. |
|
|
2486 | .Sp |
|
|
2487 | Not that this does \fInot\fR check whether the watcher itself is pending, only |
|
|
2488 | whether it has been requested to make this watcher pending. |
924 | .SH "OTHER FUNCTIONS" |
2489 | .SH "OTHER FUNCTIONS" |
925 | .IX Header "OTHER FUNCTIONS" |
2490 | .IX Header "OTHER FUNCTIONS" |
926 | There are some other functions of possible interest. Described. Here. Now. |
2491 | There are some other functions of possible interest. Described. Here. Now. |
927 | .IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4 |
2492 | .IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4 |
928 | .IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" |
2493 | .IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" |
… | |
… | |
932 | or timeout without having to allocate/configure/start/stop/free one or |
2497 | or timeout without having to allocate/configure/start/stop/free one or |
933 | more watchers yourself. |
2498 | more watchers yourself. |
934 | .Sp |
2499 | .Sp |
935 | If \f(CW\*(C`fd\*(C'\fR is less than 0, then no I/O watcher will be started and events |
2500 | If \f(CW\*(C`fd\*(C'\fR is less than 0, then no I/O watcher will be started and events |
936 | is being ignored. Otherwise, an \f(CW\*(C`ev_io\*(C'\fR watcher for the given \f(CW\*(C`fd\*(C'\fR and |
2501 | is being ignored. Otherwise, an \f(CW\*(C`ev_io\*(C'\fR watcher for the given \f(CW\*(C`fd\*(C'\fR and |
937 | \&\f(CW\*(C`events\*(C'\fR set will be craeted and started. |
2502 | \&\f(CW\*(C`events\*(C'\fR set will be created and started. |
938 | .Sp |
2503 | .Sp |
939 | If \f(CW\*(C`timeout\*(C'\fR is less than 0, then no timeout watcher will be |
2504 | If \f(CW\*(C`timeout\*(C'\fR is less than 0, then no timeout watcher will be |
940 | started. Otherwise an \f(CW\*(C`ev_timer\*(C'\fR watcher with after = \f(CW\*(C`timeout\*(C'\fR (and |
2505 | started. Otherwise an \f(CW\*(C`ev_timer\*(C'\fR watcher with after = \f(CW\*(C`timeout\*(C'\fR (and |
941 | repeat = 0) will be started. While \f(CW0\fR is a valid timeout, it is of |
2506 | repeat = 0) will be started. While \f(CW0\fR is a valid timeout, it is of |
942 | dubious value. |
2507 | dubious value. |
… | |
… | |
945 | passed an \f(CW\*(C`revents\*(C'\fR set like normal event callbacks (a combination of |
2510 | passed an \f(CW\*(C`revents\*(C'\fR set like normal event callbacks (a combination of |
946 | \&\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 |
2511 | \&\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 |
947 | value passed to \f(CW\*(C`ev_once\*(C'\fR: |
2512 | value passed to \f(CW\*(C`ev_once\*(C'\fR: |
948 | .Sp |
2513 | .Sp |
949 | .Vb 7 |
2514 | .Vb 7 |
950 | \& static void stdin_ready (int revents, void *arg) |
2515 | \& static void stdin_ready (int revents, void *arg) |
951 | \& { |
2516 | \& { |
952 | \& if (revents & EV_TIMEOUT) |
2517 | \& if (revents & EV_TIMEOUT) |
953 | \& /* doh, nothing entered */; |
2518 | \& /* doh, nothing entered */; |
954 | \& else if (revents & EV_READ) |
2519 | \& else if (revents & EV_READ) |
955 | \& /* stdin might have data for us, joy! */; |
2520 | \& /* stdin might have data for us, joy! */; |
956 | \& } |
2521 | \& } |
957 | .Ve |
2522 | \& |
958 | .Sp |
|
|
959 | .Vb 1 |
|
|
960 | \& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2523 | \& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
961 | .Ve |
2524 | .Ve |
962 | .IP "ev_feed_event (loop, watcher, int events)" 4 |
2525 | .IP "ev_feed_event (ev_loop *, watcher *, int revents)" 4 |
963 | .IX Item "ev_feed_event (loop, watcher, int events)" |
2526 | .IX Item "ev_feed_event (ev_loop *, watcher *, int revents)" |
964 | Feeds the given event set into the event loop, as if the specified event |
2527 | Feeds the given event set into the event loop, as if the specified event |
965 | had happened for the specified watcher (which must be a pointer to an |
2528 | had happened for the specified watcher (which must be a pointer to an |
966 | initialised but not necessarily started event watcher). |
2529 | initialised but not necessarily started event watcher). |
967 | .IP "ev_feed_fd_event (loop, int fd, int revents)" 4 |
2530 | .IP "ev_feed_fd_event (ev_loop *, int fd, int revents)" 4 |
968 | .IX Item "ev_feed_fd_event (loop, int fd, int revents)" |
2531 | .IX Item "ev_feed_fd_event (ev_loop *, int fd, int revents)" |
969 | Feed an event on the given fd, as if a file descriptor backend detected |
2532 | Feed an event on the given fd, as if a file descriptor backend detected |
970 | the given events it. |
2533 | the given events it. |
971 | .IP "ev_feed_signal_event (loop, int signum)" 4 |
2534 | .IP "ev_feed_signal_event (ev_loop *loop, int signum)" 4 |
972 | .IX Item "ev_feed_signal_event (loop, int signum)" |
2535 | .IX Item "ev_feed_signal_event (ev_loop *loop, int signum)" |
973 | Feed an event as if the given signal occured (loop must be the default loop!). |
2536 | Feed an event as if the given signal occurred (\f(CW\*(C`loop\*(C'\fR must be the default |
|
|
2537 | loop!). |
974 | .SH "LIBEVENT EMULATION" |
2538 | .SH "LIBEVENT EMULATION" |
975 | .IX Header "LIBEVENT EMULATION" |
2539 | .IX Header "LIBEVENT EMULATION" |
976 | Libev offers a compatibility emulation layer for libevent. It cannot |
2540 | Libev offers a compatibility emulation layer for libevent. It cannot |
977 | emulate the internals of libevent, so here are some usage hints: |
2541 | emulate the internals of libevent, so here are some usage hints: |
|
|
2542 | .IP "\(bu" 4 |
978 | .IP "* Use it by including <event.h>, as usual." 4 |
2543 | Use it by including <event.h>, as usual. |
979 | .IX Item "Use it by including <event.h>, as usual." |
2544 | .IP "\(bu" 4 |
980 | .PD 0 |
2545 | The following members are fully supported: ev_base, ev_callback, |
981 | .IP "* The following members are fully supported: ev_base, ev_callback, ev_arg, ev_fd, ev_res, ev_events." 4 |
2546 | ev_arg, ev_fd, ev_res, ev_events. |
982 | .IX Item "The following members are fully supported: ev_base, ev_callback, ev_arg, ev_fd, ev_res, ev_events." |
2547 | .IP "\(bu" 4 |
983 | .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 |
2548 | Avoid using ev_flags and the EVLIST_*\-macros, while it is |
984 | .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)." |
2549 | maintained by libev, it does not work exactly the same way as in libevent (consider |
985 | .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 |
2550 | it a private \s-1API\s0). |
986 | .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." |
2551 | .IP "\(bu" 4 |
|
|
2552 | Priorities are not currently supported. Initialising priorities |
|
|
2553 | will fail and all watchers will have the same priority, even though there |
|
|
2554 | is an ev_pri field. |
|
|
2555 | .IP "\(bu" 4 |
|
|
2556 | In libevent, the last base created gets the signals, in libev, the |
|
|
2557 | first base created (== the default loop) gets the signals. |
|
|
2558 | .IP "\(bu" 4 |
987 | .IP "* Other members are not supported." 4 |
2559 | Other members are not supported. |
988 | .IX Item "Other members are not supported." |
2560 | .IP "\(bu" 4 |
989 | .IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4 |
2561 | The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need |
990 | .IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library." |
2562 | to use the libev header file and library. |
991 | .PD |
|
|
992 | .SH "\*(C+ SUPPORT" |
2563 | .SH "\*(C+ SUPPORT" |
993 | .IX Header " SUPPORT" |
2564 | .IX Header " SUPPORT" |
994 | \&\s-1TBD\s0. |
2565 | Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow |
|
|
2566 | you to use some convenience methods to start/stop watchers and also change |
|
|
2567 | the callback model to a model using method callbacks on objects. |
|
|
2568 | .PP |
|
|
2569 | To use it, |
|
|
2570 | .PP |
|
|
2571 | .Vb 1 |
|
|
2572 | \& #include <ev++.h> |
|
|
2573 | .Ve |
|
|
2574 | .PP |
|
|
2575 | This automatically includes \fIev.h\fR and puts all of its definitions (many |
|
|
2576 | of them macros) into the global namespace. All \*(C+ specific things are |
|
|
2577 | put into the \f(CW\*(C`ev\*(C'\fR namespace. It should support all the same embedding |
|
|
2578 | options as \fIev.h\fR, most notably \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. |
|
|
2579 | .PP |
|
|
2580 | Care has been taken to keep the overhead low. The only data member the \*(C+ |
|
|
2581 | classes add (compared to plain C\-style watchers) is the event loop pointer |
|
|
2582 | that the watcher is associated with (or no additional members at all if |
|
|
2583 | you disable \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR when embedding libev). |
|
|
2584 | .PP |
|
|
2585 | Currently, functions, and static and non-static member functions can be |
|
|
2586 | used as callbacks. Other types should be easy to add as long as they only |
|
|
2587 | need one additional pointer for context. If you need support for other |
|
|
2588 | types of functors please contact the author (preferably after implementing |
|
|
2589 | it). |
|
|
2590 | .PP |
|
|
2591 | Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace: |
|
|
2592 | .ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4 |
|
|
2593 | .el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4 |
|
|
2594 | .IX Item "ev::READ, ev::WRITE etc." |
|
|
2595 | These are just enum values with the same values as the \f(CW\*(C`EV_READ\*(C'\fR etc. |
|
|
2596 | macros from \fIev.h\fR. |
|
|
2597 | .ie n .IP """ev::tstamp""\fR, \f(CW""ev::now""" 4 |
|
|
2598 | .el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4 |
|
|
2599 | .IX Item "ev::tstamp, ev::now" |
|
|
2600 | Aliases to the same types/functions as with the \f(CW\*(C`ev_\*(C'\fR prefix. |
|
|
2601 | .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 |
|
|
2602 | .el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4 |
|
|
2603 | .IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc." |
|
|
2604 | For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of |
|
|
2605 | the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR |
|
|
2606 | which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro |
|
|
2607 | defines by many implementations. |
|
|
2608 | .Sp |
|
|
2609 | All of those classes have these methods: |
|
|
2610 | .RS 4 |
|
|
2611 | .IP "ev::TYPE::TYPE ()" 4 |
|
|
2612 | .IX Item "ev::TYPE::TYPE ()" |
|
|
2613 | .PD 0 |
|
|
2614 | .IP "ev::TYPE::TYPE (struct ev_loop *)" 4 |
|
|
2615 | .IX Item "ev::TYPE::TYPE (struct ev_loop *)" |
|
|
2616 | .IP "ev::TYPE::~TYPE" 4 |
|
|
2617 | .IX Item "ev::TYPE::~TYPE" |
|
|
2618 | .PD |
|
|
2619 | The constructor (optionally) takes an event loop to associate the watcher |
|
|
2620 | with. If it is omitted, it will use \f(CW\*(C`EV_DEFAULT\*(C'\fR. |
|
|
2621 | .Sp |
|
|
2622 | The constructor calls \f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the |
|
|
2623 | \&\f(CW\*(C`set\*(C'\fR method before starting it. |
|
|
2624 | .Sp |
|
|
2625 | It will not set a callback, however: You have to call the templated \f(CW\*(C`set\*(C'\fR |
|
|
2626 | method to set a callback before you can start the watcher. |
|
|
2627 | .Sp |
|
|
2628 | (The reason why you have to use a method is a limitation in \*(C+ which does |
|
|
2629 | not allow explicit template arguments for constructors). |
|
|
2630 | .Sp |
|
|
2631 | The destructor automatically stops the watcher if it is active. |
|
|
2632 | .IP "w\->set<class, &class::method> (object *)" 4 |
|
|
2633 | .IX Item "w->set<class, &class::method> (object *)" |
|
|
2634 | This method sets the callback method to call. The method has to have a |
|
|
2635 | signature of \f(CW\*(C`void (*)(ev_TYPE &, int)\*(C'\fR, it receives the watcher as |
|
|
2636 | first argument and the \f(CW\*(C`revents\*(C'\fR as second. The object must be given as |
|
|
2637 | parameter and is stored in the \f(CW\*(C`data\*(C'\fR member of the watcher. |
|
|
2638 | .Sp |
|
|
2639 | This method synthesizes efficient thunking code to call your method from |
|
|
2640 | the C callback that libev requires. If your compiler can inline your |
|
|
2641 | callback (i.e. it is visible to it at the place of the \f(CW\*(C`set\*(C'\fR call and |
|
|
2642 | your compiler is good :), then the method will be fully inlined into the |
|
|
2643 | thunking function, making it as fast as a direct C callback. |
|
|
2644 | .Sp |
|
|
2645 | Example: simple class declaration and watcher initialisation |
|
|
2646 | .Sp |
|
|
2647 | .Vb 4 |
|
|
2648 | \& struct myclass |
|
|
2649 | \& { |
|
|
2650 | \& void io_cb (ev::io &w, int revents) { } |
|
|
2651 | \& } |
|
|
2652 | \& |
|
|
2653 | \& myclass obj; |
|
|
2654 | \& ev::io iow; |
|
|
2655 | \& iow.set <myclass, &myclass::io_cb> (&obj); |
|
|
2656 | .Ve |
|
|
2657 | .IP "w\->set<function> (void *data = 0)" 4 |
|
|
2658 | .IX Item "w->set<function> (void *data = 0)" |
|
|
2659 | Also sets a callback, but uses a static method or plain function as |
|
|
2660 | callback. The optional \f(CW\*(C`data\*(C'\fR argument will be stored in the watcher's |
|
|
2661 | \&\f(CW\*(C`data\*(C'\fR member and is free for you to use. |
|
|
2662 | .Sp |
|
|
2663 | The prototype of the \f(CW\*(C`function\*(C'\fR must be \f(CW\*(C`void (*)(ev::TYPE &w, int)\*(C'\fR. |
|
|
2664 | .Sp |
|
|
2665 | See the method\-\f(CW\*(C`set\*(C'\fR above for more details. |
|
|
2666 | .Sp |
|
|
2667 | Example: |
|
|
2668 | .Sp |
|
|
2669 | .Vb 2 |
|
|
2670 | \& static void io_cb (ev::io &w, int revents) { } |
|
|
2671 | \& iow.set <io_cb> (); |
|
|
2672 | .Ve |
|
|
2673 | .IP "w\->set (struct ev_loop *)" 4 |
|
|
2674 | .IX Item "w->set (struct ev_loop *)" |
|
|
2675 | Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only |
|
|
2676 | do this when the watcher is inactive (and not pending either). |
|
|
2677 | .IP "w\->set ([arguments])" 4 |
|
|
2678 | .IX Item "w->set ([arguments])" |
|
|
2679 | Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same arguments. Must be |
|
|
2680 | called at least once. Unlike the C counterpart, an active watcher gets |
|
|
2681 | automatically stopped and restarted when reconfiguring it with this |
|
|
2682 | method. |
|
|
2683 | .IP "w\->start ()" 4 |
|
|
2684 | .IX Item "w->start ()" |
|
|
2685 | Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the |
|
|
2686 | constructor already stores the event loop. |
|
|
2687 | .IP "w\->stop ()" 4 |
|
|
2688 | .IX Item "w->stop ()" |
|
|
2689 | Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument. |
|
|
2690 | .ie n .IP "w\->again () (""ev::timer""\fR, \f(CW""ev::periodic"" only)" 4 |
|
|
2691 | .el .IP "w\->again () (\f(CWev::timer\fR, \f(CWev::periodic\fR only)" 4 |
|
|
2692 | .IX Item "w->again () (ev::timer, ev::periodic only)" |
|
|
2693 | For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding |
|
|
2694 | \&\f(CW\*(C`ev_TYPE_again\*(C'\fR function. |
|
|
2695 | .ie n .IP "w\->sweep () (""ev::embed"" only)" 4 |
|
|
2696 | .el .IP "w\->sweep () (\f(CWev::embed\fR only)" 4 |
|
|
2697 | .IX Item "w->sweep () (ev::embed only)" |
|
|
2698 | Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR. |
|
|
2699 | .ie n .IP "w\->update () (""ev::stat"" only)" 4 |
|
|
2700 | .el .IP "w\->update () (\f(CWev::stat\fR only)" 4 |
|
|
2701 | .IX Item "w->update () (ev::stat only)" |
|
|
2702 | Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR. |
|
|
2703 | .RE |
|
|
2704 | .RS 4 |
|
|
2705 | .RE |
|
|
2706 | .PP |
|
|
2707 | Example: Define a class with an \s-1IO\s0 and idle watcher, start one of them in |
|
|
2708 | the constructor. |
|
|
2709 | .PP |
|
|
2710 | .Vb 4 |
|
|
2711 | \& class myclass |
|
|
2712 | \& { |
|
|
2713 | \& ev::io io; void io_cb (ev::io &w, int revents); |
|
|
2714 | \& ev:idle idle void idle_cb (ev::idle &w, int revents); |
|
|
2715 | \& |
|
|
2716 | \& myclass (int fd) |
|
|
2717 | \& { |
|
|
2718 | \& io .set <myclass, &myclass::io_cb > (this); |
|
|
2719 | \& idle.set <myclass, &myclass::idle_cb> (this); |
|
|
2720 | \& |
|
|
2721 | \& io.start (fd, ev::READ); |
|
|
2722 | \& } |
|
|
2723 | \& }; |
|
|
2724 | .Ve |
|
|
2725 | .SH "OTHER LANGUAGE BINDINGS" |
|
|
2726 | .IX Header "OTHER LANGUAGE BINDINGS" |
|
|
2727 | Libev does not offer other language bindings itself, but bindings for a |
|
|
2728 | number of languages exist in the form of third-party packages. If you know |
|
|
2729 | any interesting language binding in addition to the ones listed here, drop |
|
|
2730 | me a note. |
|
|
2731 | .IP "Perl" 4 |
|
|
2732 | .IX Item "Perl" |
|
|
2733 | The \s-1EV\s0 module implements the full libev \s-1API\s0 and is actually used to test |
|
|
2734 | libev. \s-1EV\s0 is developed together with libev. Apart from the \s-1EV\s0 core module, |
|
|
2735 | there are additional modules that implement libev-compatible interfaces |
|
|
2736 | to \f(CW\*(C`libadns\*(C'\fR (\f(CW\*(C`EV::ADNS\*(C'\fR), \f(CW\*(C`Net::SNMP\*(C'\fR (\f(CW\*(C`Net::SNMP::EV\*(C'\fR) and the |
|
|
2737 | \&\f(CW\*(C`libglib\*(C'\fR event core (\f(CW\*(C`Glib::EV\*(C'\fR and \f(CW\*(C`EV::Glib\*(C'\fR). |
|
|
2738 | .Sp |
|
|
2739 | It can be found and installed via \s-1CPAN\s0, its homepage is at |
|
|
2740 | <http://software.schmorp.de/pkg/EV>. |
|
|
2741 | .IP "Python" 4 |
|
|
2742 | .IX Item "Python" |
|
|
2743 | Python bindings can be found at <http://code.google.com/p/pyev/>. It |
|
|
2744 | seems to be quite complete and well-documented. Note, however, that the |
|
|
2745 | patch they require for libev is outright dangerous as it breaks the \s-1ABI\s0 |
|
|
2746 | for everybody else, and therefore, should never be applied in an installed |
|
|
2747 | libev (if python requires an incompatible \s-1ABI\s0 then it needs to embed |
|
|
2748 | libev). |
|
|
2749 | .IP "Ruby" 4 |
|
|
2750 | .IX Item "Ruby" |
|
|
2751 | Tony Arcieri has written a ruby extension that offers access to a subset |
|
|
2752 | of the libev \s-1API\s0 and adds file handle abstractions, asynchronous \s-1DNS\s0 and |
|
|
2753 | more on top of it. It can be found via gem servers. Its homepage is at |
|
|
2754 | <http://rev.rubyforge.org/>. |
|
|
2755 | .IP "D" 4 |
|
|
2756 | .IX Item "D" |
|
|
2757 | Leandro Lucarella has written a D language binding (\fIev.d\fR) for libev, to |
|
|
2758 | be found at <http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>. |
|
|
2759 | .SH "MACRO MAGIC" |
|
|
2760 | .IX Header "MACRO MAGIC" |
|
|
2761 | Libev can be compiled with a variety of options, the most fundamental |
|
|
2762 | of which is \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most) |
|
|
2763 | functions and callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument. |
|
|
2764 | .PP |
|
|
2765 | To make it easier to write programs that cope with either variant, the |
|
|
2766 | following macros are defined: |
|
|
2767 | .ie n .IP """EV_A""\fR, \f(CW""EV_A_""" 4 |
|
|
2768 | .el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4 |
|
|
2769 | .IX Item "EV_A, EV_A_" |
|
|
2770 | This provides the loop \fIargument\fR for functions, if one is required (\*(L"ev |
|
|
2771 | loop argument\*(R"). The \f(CW\*(C`EV_A\*(C'\fR form is used when this is the sole argument, |
|
|
2772 | \&\f(CW\*(C`EV_A_\*(C'\fR is used when other arguments are following. Example: |
|
|
2773 | .Sp |
|
|
2774 | .Vb 3 |
|
|
2775 | \& ev_unref (EV_A); |
|
|
2776 | \& ev_timer_add (EV_A_ watcher); |
|
|
2777 | \& ev_loop (EV_A_ 0); |
|
|
2778 | .Ve |
|
|
2779 | .Sp |
|
|
2780 | It assumes the variable \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR is in scope, |
|
|
2781 | which is often provided by the following macro. |
|
|
2782 | .ie n .IP """EV_P""\fR, \f(CW""EV_P_""" 4 |
|
|
2783 | .el .IP "\f(CWEV_P\fR, \f(CWEV_P_\fR" 4 |
|
|
2784 | .IX Item "EV_P, EV_P_" |
|
|
2785 | This provides the loop \fIparameter\fR for functions, if one is required (\*(L"ev |
|
|
2786 | loop parameter\*(R"). The \f(CW\*(C`EV_P\*(C'\fR form is used when this is the sole parameter, |
|
|
2787 | \&\f(CW\*(C`EV_P_\*(C'\fR is used when other parameters are following. Example: |
|
|
2788 | .Sp |
|
|
2789 | .Vb 2 |
|
|
2790 | \& // this is how ev_unref is being declared |
|
|
2791 | \& static void ev_unref (EV_P); |
|
|
2792 | \& |
|
|
2793 | \& // this is how you can declare your typical callback |
|
|
2794 | \& static void cb (EV_P_ ev_timer *w, int revents) |
|
|
2795 | .Ve |
|
|
2796 | .Sp |
|
|
2797 | It declares a parameter \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR, quite |
|
|
2798 | suitable for use with \f(CW\*(C`EV_A\*(C'\fR. |
|
|
2799 | .ie n .IP """EV_DEFAULT""\fR, \f(CW""EV_DEFAULT_""" 4 |
|
|
2800 | .el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4 |
|
|
2801 | .IX Item "EV_DEFAULT, EV_DEFAULT_" |
|
|
2802 | Similar to the other two macros, this gives you the value of the default |
|
|
2803 | loop, if multiple loops are supported (\*(L"ev loop default\*(R"). |
|
|
2804 | .ie n .IP """EV_DEFAULT_UC""\fR, \f(CW""EV_DEFAULT_UC_""" 4 |
|
|
2805 | .el .IP "\f(CWEV_DEFAULT_UC\fR, \f(CWEV_DEFAULT_UC_\fR" 4 |
|
|
2806 | .IX Item "EV_DEFAULT_UC, EV_DEFAULT_UC_" |
|
|
2807 | Usage identical to \f(CW\*(C`EV_DEFAULT\*(C'\fR and \f(CW\*(C`EV_DEFAULT_\*(C'\fR, but requires that the |
|
|
2808 | default loop has been initialised (\f(CW\*(C`UC\*(C'\fR == unchecked). Their behaviour |
|
|
2809 | is undefined when the default loop has not been initialised by a previous |
|
|
2810 | 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. |
|
|
2811 | .Sp |
|
|
2812 | It is often prudent to use \f(CW\*(C`EV_DEFAULT\*(C'\fR when initialising the first |
|
|
2813 | watcher in a function but use \f(CW\*(C`EV_DEFAULT_UC\*(C'\fR afterwards. |
|
|
2814 | .PP |
|
|
2815 | Example: Declare and initialise a check watcher, utilising the above |
|
|
2816 | macros so it will work regardless of whether multiple loops are supported |
|
|
2817 | or not. |
|
|
2818 | .PP |
|
|
2819 | .Vb 5 |
|
|
2820 | \& static void |
|
|
2821 | \& check_cb (EV_P_ ev_timer *w, int revents) |
|
|
2822 | \& { |
|
|
2823 | \& ev_check_stop (EV_A_ w); |
|
|
2824 | \& } |
|
|
2825 | \& |
|
|
2826 | \& ev_check check; |
|
|
2827 | \& ev_check_init (&check, check_cb); |
|
|
2828 | \& ev_check_start (EV_DEFAULT_ &check); |
|
|
2829 | \& ev_loop (EV_DEFAULT_ 0); |
|
|
2830 | .Ve |
|
|
2831 | .SH "EMBEDDING" |
|
|
2832 | .IX Header "EMBEDDING" |
|
|
2833 | Libev can (and often is) directly embedded into host |
|
|
2834 | applications. Examples of applications that embed it include the Deliantra |
|
|
2835 | Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe) |
|
|
2836 | and rxvt-unicode. |
|
|
2837 | .PP |
|
|
2838 | The goal is to enable you to just copy the necessary files into your |
|
|
2839 | source directory without having to change even a single line in them, so |
|
|
2840 | you can easily upgrade by simply copying (or having a checked-out copy of |
|
|
2841 | libev somewhere in your source tree). |
|
|
2842 | .Sh "\s-1FILESETS\s0" |
|
|
2843 | .IX Subsection "FILESETS" |
|
|
2844 | Depending on what features you need you need to include one or more sets of files |
|
|
2845 | in your application. |
|
|
2846 | .PP |
|
|
2847 | \fI\s-1CORE\s0 \s-1EVENT\s0 \s-1LOOP\s0\fR |
|
|
2848 | .IX Subsection "CORE EVENT LOOP" |
|
|
2849 | .PP |
|
|
2850 | To include only the libev core (all the \f(CW\*(C`ev_*\*(C'\fR functions), with manual |
|
|
2851 | configuration (no autoconf): |
|
|
2852 | .PP |
|
|
2853 | .Vb 2 |
|
|
2854 | \& #define EV_STANDALONE 1 |
|
|
2855 | \& #include "ev.c" |
|
|
2856 | .Ve |
|
|
2857 | .PP |
|
|
2858 | This will automatically include \fIev.h\fR, too, and should be done in a |
|
|
2859 | single C source file only to provide the function implementations. To use |
|
|
2860 | it, do the same for \fIev.h\fR in all files wishing to use this \s-1API\s0 (best |
|
|
2861 | done by writing a wrapper around \fIev.h\fR that you can include instead and |
|
|
2862 | where you can put other configuration options): |
|
|
2863 | .PP |
|
|
2864 | .Vb 2 |
|
|
2865 | \& #define EV_STANDALONE 1 |
|
|
2866 | \& #include "ev.h" |
|
|
2867 | .Ve |
|
|
2868 | .PP |
|
|
2869 | Both header files and implementation files can be compiled with a \*(C+ |
|
|
2870 | compiler (at least, thats a stated goal, and breakage will be treated |
|
|
2871 | as a bug). |
|
|
2872 | .PP |
|
|
2873 | You need the following files in your source tree, or in a directory |
|
|
2874 | in your include path (e.g. in libev/ when using \-Ilibev): |
|
|
2875 | .PP |
|
|
2876 | .Vb 4 |
|
|
2877 | \& ev.h |
|
|
2878 | \& ev.c |
|
|
2879 | \& ev_vars.h |
|
|
2880 | \& ev_wrap.h |
|
|
2881 | \& |
|
|
2882 | \& ev_win32.c required on win32 platforms only |
|
|
2883 | \& |
|
|
2884 | \& ev_select.c only when select backend is enabled (which is enabled by default) |
|
|
2885 | \& ev_poll.c only when poll backend is enabled (disabled by default) |
|
|
2886 | \& ev_epoll.c only when the epoll backend is enabled (disabled by default) |
|
|
2887 | \& ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
|
|
2888 | \& ev_port.c only when the solaris port backend is enabled (disabled by default) |
|
|
2889 | .Ve |
|
|
2890 | .PP |
|
|
2891 | \&\fIev.c\fR includes the backend files directly when enabled, so you only need |
|
|
2892 | to compile this single file. |
|
|
2893 | .PP |
|
|
2894 | \fI\s-1LIBEVENT\s0 \s-1COMPATIBILITY\s0 \s-1API\s0\fR |
|
|
2895 | .IX Subsection "LIBEVENT COMPATIBILITY API" |
|
|
2896 | .PP |
|
|
2897 | To include the libevent compatibility \s-1API\s0, also include: |
|
|
2898 | .PP |
|
|
2899 | .Vb 1 |
|
|
2900 | \& #include "event.c" |
|
|
2901 | .Ve |
|
|
2902 | .PP |
|
|
2903 | in the file including \fIev.c\fR, and: |
|
|
2904 | .PP |
|
|
2905 | .Vb 1 |
|
|
2906 | \& #include "event.h" |
|
|
2907 | .Ve |
|
|
2908 | .PP |
|
|
2909 | in the files that want to use the libevent \s-1API\s0. This also includes \fIev.h\fR. |
|
|
2910 | .PP |
|
|
2911 | You need the following additional files for this: |
|
|
2912 | .PP |
|
|
2913 | .Vb 2 |
|
|
2914 | \& event.h |
|
|
2915 | \& event.c |
|
|
2916 | .Ve |
|
|
2917 | .PP |
|
|
2918 | \fI\s-1AUTOCONF\s0 \s-1SUPPORT\s0\fR |
|
|
2919 | .IX Subsection "AUTOCONF SUPPORT" |
|
|
2920 | .PP |
|
|
2921 | Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your configuration in |
|
|
2922 | whatever way you want, you can also \f(CW\*(C`m4_include([libev.m4])\*(C'\fR in your |
|
|
2923 | \&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR undefined. \fIev.c\fR will then |
|
|
2924 | include \fIconfig.h\fR and configure itself accordingly. |
|
|
2925 | .PP |
|
|
2926 | For this of course you need the m4 file: |
|
|
2927 | .PP |
|
|
2928 | .Vb 1 |
|
|
2929 | \& libev.m4 |
|
|
2930 | .Ve |
|
|
2931 | .Sh "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0" |
|
|
2932 | .IX Subsection "PREPROCESSOR SYMBOLS/MACROS" |
|
|
2933 | Libev can be configured via a variety of preprocessor symbols you have to |
|
|
2934 | define before including any of its files. The default in the absence of |
|
|
2935 | autoconf is noted for every option. |
|
|
2936 | .IP "\s-1EV_STANDALONE\s0" 4 |
|
|
2937 | .IX Item "EV_STANDALONE" |
|
|
2938 | Must always be \f(CW1\fR if you do not use autoconf configuration, which |
|
|
2939 | keeps libev from including \fIconfig.h\fR, and it also defines dummy |
|
|
2940 | implementations for some libevent functions (such as logging, which is not |
|
|
2941 | supported). It will also not define any of the structs usually found in |
|
|
2942 | \&\fIevent.h\fR that are not directly supported by the libev core alone. |
|
|
2943 | .IP "\s-1EV_USE_MONOTONIC\s0" 4 |
|
|
2944 | .IX Item "EV_USE_MONOTONIC" |
|
|
2945 | If defined to be \f(CW1\fR, libev will try to detect the availability of the |
|
|
2946 | monotonic clock option at both compile time and runtime. Otherwise no use |
|
|
2947 | of the monotonic clock option will be attempted. If you enable this, you |
|
|
2948 | usually have to link against librt or something similar. Enabling it when |
|
|
2949 | the functionality isn't available is safe, though, although you have |
|
|
2950 | to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR |
|
|
2951 | function is hiding in (often \fI\-lrt\fR). |
|
|
2952 | .IP "\s-1EV_USE_REALTIME\s0" 4 |
|
|
2953 | .IX Item "EV_USE_REALTIME" |
|
|
2954 | If defined to be \f(CW1\fR, libev will try to detect the availability of the |
|
|
2955 | real-time clock option at compile time (and assume its availability at |
|
|
2956 | runtime if successful). Otherwise no use of the real-time clock option will |
|
|
2957 | be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get |
|
|
2958 | (CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See the |
|
|
2959 | note about libraries in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though. |
|
|
2960 | .IP "\s-1EV_USE_NANOSLEEP\s0" 4 |
|
|
2961 | .IX Item "EV_USE_NANOSLEEP" |
|
|
2962 | If defined to be \f(CW1\fR, libev will assume that \f(CW\*(C`nanosleep ()\*(C'\fR is available |
|
|
2963 | and will use it for delays. Otherwise it will use \f(CW\*(C`select ()\*(C'\fR. |
|
|
2964 | .IP "\s-1EV_USE_EVENTFD\s0" 4 |
|
|
2965 | .IX Item "EV_USE_EVENTFD" |
|
|
2966 | If defined to be \f(CW1\fR, then libev will assume that \f(CW\*(C`eventfd ()\*(C'\fR is |
|
|
2967 | available and will probe for kernel support at runtime. This will improve |
|
|
2968 | \&\f(CW\*(C`ev_signal\*(C'\fR and \f(CW\*(C`ev_async\*(C'\fR performance and reduce resource consumption. |
|
|
2969 | If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
|
|
2970 | 2.7 or newer, otherwise disabled. |
|
|
2971 | .IP "\s-1EV_USE_SELECT\s0" 4 |
|
|
2972 | .IX Item "EV_USE_SELECT" |
|
|
2973 | If undefined or defined to be \f(CW1\fR, libev will compile in support for the |
|
|
2974 | \&\f(CW\*(C`select\*(C'\fR(2) backend. No attempt at auto-detection will be done: if no |
|
|
2975 | other method takes over, select will be it. Otherwise the select backend |
|
|
2976 | will not be compiled in. |
|
|
2977 | .IP "\s-1EV_SELECT_USE_FD_SET\s0" 4 |
|
|
2978 | .IX Item "EV_SELECT_USE_FD_SET" |
|
|
2979 | If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR |
|
|
2980 | structure. This is useful if libev doesn't compile due to a missing |
|
|
2981 | \&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it mis-guesses the bitset layout on |
|
|
2982 | exotic systems. This usually limits the range of file descriptors to some |
|
|
2983 | low limit such as 1024 or might have other limitations (winsocket only |
|
|
2984 | allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation, might |
|
|
2985 | influence the size of the \f(CW\*(C`fd_set\*(C'\fR used. |
|
|
2986 | .IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4 |
|
|
2987 | .IX Item "EV_SELECT_IS_WINSOCKET" |
|
|
2988 | When defined to \f(CW1\fR, the select backend will assume that |
|
|
2989 | select/socket/connect etc. don't understand file descriptors but |
|
|
2990 | wants osf handles on win32 (this is the case when the select to |
|
|
2991 | be used is the winsock select). This means that it will call |
|
|
2992 | \&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise, |
|
|
2993 | it is assumed that all these functions actually work on fds, even |
|
|
2994 | on win32. Should not be defined on non\-win32 platforms. |
|
|
2995 | .IP "\s-1EV_FD_TO_WIN32_HANDLE\s0" 4 |
|
|
2996 | .IX Item "EV_FD_TO_WIN32_HANDLE" |
|
|
2997 | If \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR is enabled, then libev needs a way to map |
|
|
2998 | file descriptors to socket handles. When not defining this symbol (the |
|
|
2999 | default), then libev will call \f(CW\*(C`_get_osfhandle\*(C'\fR, which is usually |
|
|
3000 | correct. In some cases, programs use their own file descriptor management, |
|
|
3001 | in which case they can provide this function to map fds to socket handles. |
|
|
3002 | .IP "\s-1EV_USE_POLL\s0" 4 |
|
|
3003 | .IX Item "EV_USE_POLL" |
|
|
3004 | If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2) |
|
|
3005 | backend. Otherwise it will be enabled on non\-win32 platforms. It |
|
|
3006 | takes precedence over select. |
|
|
3007 | .IP "\s-1EV_USE_EPOLL\s0" 4 |
|
|
3008 | .IX Item "EV_USE_EPOLL" |
|
|
3009 | If defined to be \f(CW1\fR, libev will compile in support for the Linux |
|
|
3010 | \&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime, |
|
|
3011 | otherwise another method will be used as fallback. This is the preferred |
|
|
3012 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
|
|
3013 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
|
|
3014 | .IP "\s-1EV_USE_KQUEUE\s0" 4 |
|
|
3015 | .IX Item "EV_USE_KQUEUE" |
|
|
3016 | If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style |
|
|
3017 | \&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime, |
|
|
3018 | otherwise another method will be used as fallback. This is the preferred |
|
|
3019 | backend for \s-1BSD\s0 and BSD-like systems, although on most BSDs kqueue only |
|
|
3020 | supports some types of fds correctly (the only platform we found that |
|
|
3021 | supports ptys for example was NetBSD), so kqueue might be compiled in, but |
|
|
3022 | not be used unless explicitly requested. The best way to use it is to find |
|
|
3023 | out whether kqueue supports your type of fd properly and use an embedded |
|
|
3024 | kqueue loop. |
|
|
3025 | .IP "\s-1EV_USE_PORT\s0" 4 |
|
|
3026 | .IX Item "EV_USE_PORT" |
|
|
3027 | If defined to be \f(CW1\fR, libev will compile in support for the Solaris |
|
|
3028 | 10 port style backend. Its availability will be detected at runtime, |
|
|
3029 | otherwise another method will be used as fallback. This is the preferred |
|
|
3030 | backend for Solaris 10 systems. |
|
|
3031 | .IP "\s-1EV_USE_DEVPOLL\s0" 4 |
|
|
3032 | .IX Item "EV_USE_DEVPOLL" |
|
|
3033 | Reserved for future expansion, works like the \s-1USE\s0 symbols above. |
|
|
3034 | .IP "\s-1EV_USE_INOTIFY\s0" 4 |
|
|
3035 | .IX Item "EV_USE_INOTIFY" |
|
|
3036 | If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify |
|
|
3037 | interface to speed up \f(CW\*(C`ev_stat\*(C'\fR watchers. Its actual availability will |
|
|
3038 | be detected at runtime. If undefined, it will be enabled if the headers |
|
|
3039 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
|
|
3040 | .IP "\s-1EV_ATOMIC_T\s0" 4 |
|
|
3041 | .IX Item "EV_ATOMIC_T" |
|
|
3042 | Libev requires an integer type (suitable for storing \f(CW0\fR or \f(CW1\fR) whose |
|
|
3043 | access is atomic with respect to other threads or signal contexts. No such |
|
|
3044 | type is easily found in the C language, so you can provide your own type |
|
|
3045 | that you know is safe for your purposes. It is used both for signal handler \*(L"locking\*(R" |
|
|
3046 | as well as for signal and thread safety in \f(CW\*(C`ev_async\*(C'\fR watchers. |
|
|
3047 | .Sp |
|
|
3048 | In the absence of this define, libev will use \f(CW\*(C`sig_atomic_t volatile\*(C'\fR |
|
|
3049 | (from \fIsignal.h\fR), which is usually good enough on most platforms. |
|
|
3050 | .IP "\s-1EV_H\s0" 4 |
|
|
3051 | .IX Item "EV_H" |
|
|
3052 | The name of the \fIev.h\fR header file used to include it. The default if |
|
|
3053 | undefined is \f(CW"ev.h"\fR in \fIevent.h\fR, \fIev.c\fR and \fIev++.h\fR. This can be |
|
|
3054 | used to virtually rename the \fIev.h\fR header file in case of conflicts. |
|
|
3055 | .IP "\s-1EV_CONFIG_H\s0" 4 |
|
|
3056 | .IX Item "EV_CONFIG_H" |
|
|
3057 | If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override |
|
|
3058 | \&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to |
|
|
3059 | \&\f(CW\*(C`EV_H\*(C'\fR, above. |
|
|
3060 | .IP "\s-1EV_EVENT_H\s0" 4 |
|
|
3061 | .IX Item "EV_EVENT_H" |
|
|
3062 | Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea |
|
|
3063 | of how the \fIevent.h\fR header can be found, the default is \f(CW"event.h"\fR. |
|
|
3064 | .IP "\s-1EV_PROTOTYPES\s0" 4 |
|
|
3065 | .IX Item "EV_PROTOTYPES" |
|
|
3066 | If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function |
|
|
3067 | prototypes, but still define all the structs and other symbols. This is |
|
|
3068 | occasionally useful if you want to provide your own wrapper functions |
|
|
3069 | around libev functions. |
|
|
3070 | .IP "\s-1EV_MULTIPLICITY\s0" 4 |
|
|
3071 | .IX Item "EV_MULTIPLICITY" |
|
|
3072 | If undefined or defined to \f(CW1\fR, then all event-loop-specific functions |
|
|
3073 | will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create |
|
|
3074 | additional independent event loops. Otherwise there will be no support |
|
|
3075 | for multiple event loops and there is no first event loop pointer |
|
|
3076 | argument. Instead, all functions act on the single default loop. |
|
|
3077 | .IP "\s-1EV_MINPRI\s0" 4 |
|
|
3078 | .IX Item "EV_MINPRI" |
|
|
3079 | .PD 0 |
|
|
3080 | .IP "\s-1EV_MAXPRI\s0" 4 |
|
|
3081 | .IX Item "EV_MAXPRI" |
|
|
3082 | .PD |
|
|
3083 | The range of allowed priorities. \f(CW\*(C`EV_MINPRI\*(C'\fR must be smaller or equal to |
|
|
3084 | \&\f(CW\*(C`EV_MAXPRI\*(C'\fR, but otherwise there are no non-obvious limitations. You can |
|
|
3085 | provide for more priorities by overriding those symbols (usually defined |
|
|
3086 | to be \f(CW\*(C`\-2\*(C'\fR and \f(CW2\fR, respectively). |
|
|
3087 | .Sp |
|
|
3088 | When doing priority-based operations, libev usually has to linearly search |
|
|
3089 | all the priorities, so having many of them (hundreds) uses a lot of space |
|
|
3090 | and time, so using the defaults of five priorities (\-2 .. +2) is usually |
|
|
3091 | fine. |
|
|
3092 | .Sp |
|
|
3093 | If your embedding application does not need any priorities, defining these both to |
|
|
3094 | \&\f(CW0\fR will save some memory and \s-1CPU\s0. |
|
|
3095 | .IP "\s-1EV_PERIODIC_ENABLE\s0" 4 |
|
|
3096 | .IX Item "EV_PERIODIC_ENABLE" |
|
|
3097 | If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If |
|
|
3098 | defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of |
|
|
3099 | code. |
|
|
3100 | .IP "\s-1EV_IDLE_ENABLE\s0" 4 |
|
|
3101 | .IX Item "EV_IDLE_ENABLE" |
|
|
3102 | If undefined or defined to be \f(CW1\fR, then idle watchers are supported. If |
|
|
3103 | defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of |
|
|
3104 | code. |
|
|
3105 | .IP "\s-1EV_EMBED_ENABLE\s0" 4 |
|
|
3106 | .IX Item "EV_EMBED_ENABLE" |
|
|
3107 | If undefined or defined to be \f(CW1\fR, then embed watchers are supported. If |
|
|
3108 | defined to be \f(CW0\fR, then they are not. |
|
|
3109 | .IP "\s-1EV_STAT_ENABLE\s0" 4 |
|
|
3110 | .IX Item "EV_STAT_ENABLE" |
|
|
3111 | If undefined or defined to be \f(CW1\fR, then stat watchers are supported. If |
|
|
3112 | defined to be \f(CW0\fR, then they are not. |
|
|
3113 | .IP "\s-1EV_FORK_ENABLE\s0" 4 |
|
|
3114 | .IX Item "EV_FORK_ENABLE" |
|
|
3115 | If undefined or defined to be \f(CW1\fR, then fork watchers are supported. If |
|
|
3116 | defined to be \f(CW0\fR, then they are not. |
|
|
3117 | .IP "\s-1EV_ASYNC_ENABLE\s0" 4 |
|
|
3118 | .IX Item "EV_ASYNC_ENABLE" |
|
|
3119 | If undefined or defined to be \f(CW1\fR, then async watchers are supported. If |
|
|
3120 | defined to be \f(CW0\fR, then they are not. |
|
|
3121 | .IP "\s-1EV_MINIMAL\s0" 4 |
|
|
3122 | .IX Item "EV_MINIMAL" |
|
|
3123 | If you need to shave off some kilobytes of code at the expense of some |
|
|
3124 | speed, define this symbol to \f(CW1\fR. Currently this is used to override some |
|
|
3125 | inlining decisions, saves roughly 30% code size on amd64. It also selects a |
|
|
3126 | much smaller 2\-heap for timer management over the default 4\-heap. |
|
|
3127 | .IP "\s-1EV_PID_HASHSIZE\s0" 4 |
|
|
3128 | .IX Item "EV_PID_HASHSIZE" |
|
|
3129 | \&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by |
|
|
3130 | pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), usually more |
|
|
3131 | than enough. If you need to manage thousands of children you might want to |
|
|
3132 | increase this value (\fImust\fR be a power of two). |
|
|
3133 | .IP "\s-1EV_INOTIFY_HASHSIZE\s0" 4 |
|
|
3134 | .IX Item "EV_INOTIFY_HASHSIZE" |
|
|
3135 | \&\f(CW\*(C`ev_stat\*(C'\fR watchers use a small hash table to distribute workload by |
|
|
3136 | inotify watch id. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), |
|
|
3137 | usually more than enough. If you need to manage thousands of \f(CW\*(C`ev_stat\*(C'\fR |
|
|
3138 | watchers you might want to increase this value (\fImust\fR be a power of |
|
|
3139 | two). |
|
|
3140 | .IP "\s-1EV_USE_4HEAP\s0" 4 |
|
|
3141 | .IX Item "EV_USE_4HEAP" |
|
|
3142 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
|
|
3143 | timer and periodics heap, libev uses a 4\-heap when this symbol is defined |
|
|
3144 | to \f(CW1\fR. The 4\-heap uses more complicated (longer) code but has |
|
|
3145 | noticeably faster performance with many (thousands) of watchers. |
|
|
3146 | .Sp |
|
|
3147 | The default is \f(CW1\fR unless \f(CW\*(C`EV_MINIMAL\*(C'\fR is set in which case it is \f(CW0\fR |
|
|
3148 | (disabled). |
|
|
3149 | .IP "\s-1EV_HEAP_CACHE_AT\s0" 4 |
|
|
3150 | .IX Item "EV_HEAP_CACHE_AT" |
|
|
3151 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
|
|
3152 | timer and periodics heap, libev can cache the timestamp (\fIat\fR) within |
|
|
3153 | the heap structure (selected by defining \f(CW\*(C`EV_HEAP_CACHE_AT\*(C'\fR to \f(CW1\fR), |
|
|
3154 | which uses 8\-12 bytes more per watcher and a few hundred bytes more code, |
|
|
3155 | but avoids random read accesses on heap changes. This improves performance |
|
|
3156 | noticeably with with many (hundreds) of watchers. |
|
|
3157 | .Sp |
|
|
3158 | The default is \f(CW1\fR unless \f(CW\*(C`EV_MINIMAL\*(C'\fR is set in which case it is \f(CW0\fR |
|
|
3159 | (disabled). |
|
|
3160 | .IP "\s-1EV_VERIFY\s0" 4 |
|
|
3161 | .IX Item "EV_VERIFY" |
|
|
3162 | Controls how much internal verification (see \f(CW\*(C`ev_loop_verify ()\*(C'\fR) will |
|
|
3163 | be done: If set to \f(CW0\fR, no internal verification code will be compiled |
|
|
3164 | in. If set to \f(CW1\fR, then verification code will be compiled in, but not |
|
|
3165 | called. If set to \f(CW2\fR, then the internal verification code will be |
|
|
3166 | called once per loop, which can slow down libev. If set to \f(CW3\fR, then the |
|
|
3167 | verification code will be called very frequently, which will slow down |
|
|
3168 | libev considerably. |
|
|
3169 | .Sp |
|
|
3170 | The default is \f(CW1\fR, unless \f(CW\*(C`EV_MINIMAL\*(C'\fR is set, in which case it will be |
|
|
3171 | \&\f(CW0.\fR |
|
|
3172 | .IP "\s-1EV_COMMON\s0" 4 |
|
|
3173 | .IX Item "EV_COMMON" |
|
|
3174 | By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining |
|
|
3175 | this macro to a something else you can include more and other types of |
|
|
3176 | members. You have to define it each time you include one of the files, |
|
|
3177 | though, and it must be identical each time. |
|
|
3178 | .Sp |
|
|
3179 | For example, the perl \s-1EV\s0 module uses something like this: |
|
|
3180 | .Sp |
|
|
3181 | .Vb 3 |
|
|
3182 | \& #define EV_COMMON \e |
|
|
3183 | \& SV *self; /* contains this struct */ \e |
|
|
3184 | \& SV *cb_sv, *fh /* note no trailing ";" */ |
|
|
3185 | .Ve |
|
|
3186 | .IP "\s-1EV_CB_DECLARE\s0 (type)" 4 |
|
|
3187 | .IX Item "EV_CB_DECLARE (type)" |
|
|
3188 | .PD 0 |
|
|
3189 | .IP "\s-1EV_CB_INVOKE\s0 (watcher, revents)" 4 |
|
|
3190 | .IX Item "EV_CB_INVOKE (watcher, revents)" |
|
|
3191 | .IP "ev_set_cb (ev, cb)" 4 |
|
|
3192 | .IX Item "ev_set_cb (ev, cb)" |
|
|
3193 | .PD |
|
|
3194 | Can be used to change the callback member declaration in each watcher, |
|
|
3195 | and the way callbacks are invoked and set. Must expand to a struct member |
|
|
3196 | definition and a statement, respectively. See the \fIev.h\fR header file for |
|
|
3197 | their default definitions. One possible use for overriding these is to |
|
|
3198 | avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use |
|
|
3199 | method calls instead of plain function calls in \*(C+. |
|
|
3200 | .Sh "\s-1EXPORTED\s0 \s-1API\s0 \s-1SYMBOLS\s0" |
|
|
3201 | .IX Subsection "EXPORTED API SYMBOLS" |
|
|
3202 | If you need to re-export the \s-1API\s0 (e.g. via a \s-1DLL\s0) and you need a list of |
|
|
3203 | exported symbols, you can use the provided \fISymbol.*\fR files which list |
|
|
3204 | all public symbols, one per line: |
|
|
3205 | .PP |
|
|
3206 | .Vb 2 |
|
|
3207 | \& Symbols.ev for libev proper |
|
|
3208 | \& Symbols.event for the libevent emulation |
|
|
3209 | .Ve |
|
|
3210 | .PP |
|
|
3211 | This can also be used to rename all public symbols to avoid clashes with |
|
|
3212 | multiple versions of libev linked together (which is obviously bad in |
|
|
3213 | itself, but sometimes it is inconvenient to avoid this). |
|
|
3214 | .PP |
|
|
3215 | A sed command like this will create wrapper \f(CW\*(C`#define\*(C'\fR's that you need to |
|
|
3216 | include before including \fIev.h\fR: |
|
|
3217 | .PP |
|
|
3218 | .Vb 1 |
|
|
3219 | \& <Symbols.ev sed \-e "s/.*/#define & myprefix_&/" >wrap.h |
|
|
3220 | .Ve |
|
|
3221 | .PP |
|
|
3222 | This would create a file \fIwrap.h\fR which essentially looks like this: |
|
|
3223 | .PP |
|
|
3224 | .Vb 4 |
|
|
3225 | \& #define ev_backend myprefix_ev_backend |
|
|
3226 | \& #define ev_check_start myprefix_ev_check_start |
|
|
3227 | \& #define ev_check_stop myprefix_ev_check_stop |
|
|
3228 | \& ... |
|
|
3229 | .Ve |
|
|
3230 | .Sh "\s-1EXAMPLES\s0" |
|
|
3231 | .IX Subsection "EXAMPLES" |
|
|
3232 | For a real-world example of a program the includes libev |
|
|
3233 | verbatim, you can have a look at the \s-1EV\s0 perl module |
|
|
3234 | (<http://software.schmorp.de/pkg/EV.html>). It has the libev files in |
|
|
3235 | the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public |
|
|
3236 | interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file |
|
|
3237 | will be compiled. It is pretty complex because it provides its own header |
|
|
3238 | file. |
|
|
3239 | .PP |
|
|
3240 | The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file |
|
|
3241 | that everybody includes and which overrides some configure choices: |
|
|
3242 | .PP |
|
|
3243 | .Vb 9 |
|
|
3244 | \& #define EV_MINIMAL 1 |
|
|
3245 | \& #define EV_USE_POLL 0 |
|
|
3246 | \& #define EV_MULTIPLICITY 0 |
|
|
3247 | \& #define EV_PERIODIC_ENABLE 0 |
|
|
3248 | \& #define EV_STAT_ENABLE 0 |
|
|
3249 | \& #define EV_FORK_ENABLE 0 |
|
|
3250 | \& #define EV_CONFIG_H <config.h> |
|
|
3251 | \& #define EV_MINPRI 0 |
|
|
3252 | \& #define EV_MAXPRI 0 |
|
|
3253 | \& |
|
|
3254 | \& #include "ev++.h" |
|
|
3255 | .Ve |
|
|
3256 | .PP |
|
|
3257 | And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled: |
|
|
3258 | .PP |
|
|
3259 | .Vb 2 |
|
|
3260 | \& #include "ev_cpp.h" |
|
|
3261 | \& #include "ev.c" |
|
|
3262 | .Ve |
|
|
3263 | .SH "THREADS AND COROUTINES" |
|
|
3264 | .IX Header "THREADS AND COROUTINES" |
|
|
3265 | .Sh "\s-1THREADS\s0" |
|
|
3266 | .IX Subsection "THREADS" |
|
|
3267 | Libev itself is completely thread-safe, but it uses no locking. This |
|
|
3268 | means that you can use as many loops as you want in parallel, as long as |
|
|
3269 | only one thread ever calls into one libev function with the same loop |
|
|
3270 | parameter. |
|
|
3271 | .PP |
|
|
3272 | Or put differently: calls with different loop parameters can be done in |
|
|
3273 | parallel from multiple threads, calls with the same loop parameter must be |
|
|
3274 | done serially (but can be done from different threads, as long as only one |
|
|
3275 | thread ever is inside a call at any point in time, e.g. by using a mutex |
|
|
3276 | per loop). |
|
|
3277 | .PP |
|
|
3278 | If you want to know which design is best for your problem, then I cannot |
|
|
3279 | help you but by giving some generic advice: |
|
|
3280 | .IP "\(bu" 4 |
|
|
3281 | most applications have a main thread: use the default libev loop |
|
|
3282 | in that thread, or create a separate thread running only the default loop. |
|
|
3283 | .Sp |
|
|
3284 | This helps integrating other libraries or software modules that use libev |
|
|
3285 | themselves and don't care/know about threading. |
|
|
3286 | .IP "\(bu" 4 |
|
|
3287 | one loop per thread is usually a good model. |
|
|
3288 | .Sp |
|
|
3289 | Doing this is almost never wrong, sometimes a better-performance model |
|
|
3290 | exists, but it is always a good start. |
|
|
3291 | .IP "\(bu" 4 |
|
|
3292 | other models exist, such as the leader/follower pattern, where one |
|
|
3293 | loop is handed through multiple threads in a kind of round-robin fashion. |
|
|
3294 | .Sp |
|
|
3295 | Choosing a model is hard \- look around, learn, know that usually you can do |
|
|
3296 | better than you currently do :\-) |
|
|
3297 | .IP "\(bu" 4 |
|
|
3298 | often you need to talk to some other thread which blocks in the |
|
|
3299 | event loop \- \f(CW\*(C`ev_async\*(C'\fR watchers can be used to wake them up from other |
|
|
3300 | threads safely (or from signal contexts...). |
|
|
3301 | .Sh "\s-1COROUTINES\s0" |
|
|
3302 | .IX Subsection "COROUTINES" |
|
|
3303 | Libev is much more accommodating to coroutines (\*(L"cooperative threads\*(R"): |
|
|
3304 | libev fully supports nesting calls to it's functions from different |
|
|
3305 | coroutines (e.g. you can call \f(CW\*(C`ev_loop\*(C'\fR on the same loop from two |
|
|
3306 | different coroutines and switch freely between both coroutines running the |
|
|
3307 | loop, as long as you don't confuse yourself). The only exception is that |
|
|
3308 | you must not do this from \f(CW\*(C`ev_periodic\*(C'\fR reschedule callbacks. |
|
|
3309 | .PP |
|
|
3310 | Care has been invested into making sure that libev does not keep local |
|
|
3311 | state inside \f(CW\*(C`ev_loop\*(C'\fR, and other calls do not usually allow coroutine |
|
|
3312 | switches. |
|
|
3313 | .SH "COMPLEXITIES" |
|
|
3314 | .IX Header "COMPLEXITIES" |
|
|
3315 | In this section the complexities of (many of) the algorithms used inside |
|
|
3316 | libev will be explained. For complexity discussions about backends see the |
|
|
3317 | documentation for \f(CW\*(C`ev_default_init\*(C'\fR. |
|
|
3318 | .PP |
|
|
3319 | All of the following are about amortised time: If an array needs to be |
|
|
3320 | extended, libev needs to realloc and move the whole array, but this |
|
|
3321 | happens asymptotically never with higher number of elements, so O(1) might |
|
|
3322 | mean it might do a lengthy realloc operation in rare cases, but on average |
|
|
3323 | it is much faster and asymptotically approaches constant time. |
|
|
3324 | .IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4 |
|
|
3325 | .IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" |
|
|
3326 | This means that, when you have a watcher that triggers in one hour and |
|
|
3327 | there are 100 watchers that would trigger before that then inserting will |
|
|
3328 | have to skip roughly seven (\f(CW\*(C`ld 100\*(C'\fR) of these watchers. |
|
|
3329 | .IP "Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)" 4 |
|
|
3330 | .IX Item "Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)" |
|
|
3331 | That means that changing a timer costs less than removing/adding them |
|
|
3332 | as only the relative motion in the event queue has to be paid for. |
|
|
3333 | .IP "Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)" 4 |
|
|
3334 | .IX Item "Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)" |
|
|
3335 | These just add the watcher into an array or at the head of a list. |
|
|
3336 | .IP "Stopping check/prepare/idle/fork/async watchers: O(1)" 4 |
|
|
3337 | .IX Item "Stopping check/prepare/idle/fork/async watchers: O(1)" |
|
|
3338 | .PD 0 |
|
|
3339 | .IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4 |
|
|
3340 | .IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))" |
|
|
3341 | .PD |
|
|
3342 | These watchers are stored in lists then need to be walked to find the |
|
|
3343 | correct watcher to remove. The lists are usually short (you don't usually |
|
|
3344 | have many watchers waiting for the same fd or signal). |
|
|
3345 | .IP "Finding the next timer in each loop iteration: O(1)" 4 |
|
|
3346 | .IX Item "Finding the next timer in each loop iteration: O(1)" |
|
|
3347 | By virtue of using a binary or 4\-heap, the next timer is always found at a |
|
|
3348 | fixed position in the storage array. |
|
|
3349 | .IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4 |
|
|
3350 | .IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" |
|
|
3351 | A change means an I/O watcher gets started or stopped, which requires |
|
|
3352 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
3353 | on backend and whether \f(CW\*(C`ev_io_set\*(C'\fR was used). |
|
|
3354 | .IP "Activating one watcher (putting it into the pending state): O(1)" 4 |
|
|
3355 | .IX Item "Activating one watcher (putting it into the pending state): O(1)" |
|
|
3356 | .PD 0 |
|
|
3357 | .IP "Priority handling: O(number_of_priorities)" 4 |
|
|
3358 | .IX Item "Priority handling: O(number_of_priorities)" |
|
|
3359 | .PD |
|
|
3360 | Priorities are implemented by allocating some space for each |
|
|
3361 | priority. When doing priority-based operations, libev usually has to |
|
|
3362 | linearly search all the priorities, but starting/stopping and activating |
|
|
3363 | watchers becomes O(1) w.r.t. priority handling. |
|
|
3364 | .IP "Sending an ev_async: O(1)" 4 |
|
|
3365 | .IX Item "Sending an ev_async: O(1)" |
|
|
3366 | .PD 0 |
|
|
3367 | .IP "Processing ev_async_send: O(number_of_async_watchers)" 4 |
|
|
3368 | .IX Item "Processing ev_async_send: O(number_of_async_watchers)" |
|
|
3369 | .IP "Processing signals: O(max_signal_number)" 4 |
|
|
3370 | .IX Item "Processing signals: O(max_signal_number)" |
|
|
3371 | .PD |
|
|
3372 | Sending involves a system call \fIiff\fR there were no other \f(CW\*(C`ev_async_send\*(C'\fR |
|
|
3373 | calls in the current loop iteration. Checking for async and signal events |
|
|
3374 | involves iterating over all running async watchers or all signal numbers. |
|
|
3375 | .SH "WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS" |
|
|
3376 | .IX Header "WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS" |
|
|
3377 | Win32 doesn't support any of the standards (e.g. \s-1POSIX\s0) that libev |
|
|
3378 | requires, and its I/O model is fundamentally incompatible with the \s-1POSIX\s0 |
|
|
3379 | model. Libev still offers limited functionality on this platform in |
|
|
3380 | the form of the \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR backend, and only supports socket |
|
|
3381 | descriptors. This only applies when using Win32 natively, not when using |
|
|
3382 | e.g. cygwin. |
|
|
3383 | .PP |
|
|
3384 | Lifting these limitations would basically require the full |
|
|
3385 | re-implementation of the I/O system. If you are into these kinds of |
|
|
3386 | things, then note that glib does exactly that for you in a very portable |
|
|
3387 | way (note also that glib is the slowest event library known to man). |
|
|
3388 | .PP |
|
|
3389 | There is no supported compilation method available on windows except |
|
|
3390 | embedding it into other applications. |
|
|
3391 | .PP |
|
|
3392 | Not a libev limitation but worth mentioning: windows apparently doesn't |
|
|
3393 | accept large writes: instead of resulting in a partial write, windows will |
|
|
3394 | either accept everything or return \f(CW\*(C`ENOBUFS\*(C'\fR if the buffer is too large, |
|
|
3395 | so make sure you only write small amounts into your sockets (less than a |
|
|
3396 | megabyte seems safe, but thsi apparently depends on the amount of memory |
|
|
3397 | available). |
|
|
3398 | .PP |
|
|
3399 | Due to the many, low, and arbitrary limits on the win32 platform and |
|
|
3400 | the abysmal performance of winsockets, using a large number of sockets |
|
|
3401 | is not recommended (and not reasonable). If your program needs to use |
|
|
3402 | more than a hundred or so sockets, then likely it needs to use a totally |
|
|
3403 | different implementation for windows, as libev offers the \s-1POSIX\s0 readiness |
|
|
3404 | notification model, which cannot be implemented efficiently on windows |
|
|
3405 | (Microsoft monopoly games). |
|
|
3406 | .PP |
|
|
3407 | A typical way to use libev under windows is to embed it (see the embedding |
|
|
3408 | section for details) and use the following \fIevwrap.h\fR header file instead |
|
|
3409 | of \fIev.h\fR: |
|
|
3410 | .PP |
|
|
3411 | .Vb 2 |
|
|
3412 | \& #define EV_STANDALONE /* keeps ev from requiring config.h */ |
|
|
3413 | \& #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
|
|
3414 | \& |
|
|
3415 | \& #include "ev.h" |
|
|
3416 | .Ve |
|
|
3417 | .PP |
|
|
3418 | And compile the following \fIevwrap.c\fR file into your project (make sure |
|
|
3419 | you do \fInot\fR compile the \fIev.c\fR or any other embedded soruce files!): |
|
|
3420 | .PP |
|
|
3421 | .Vb 2 |
|
|
3422 | \& #include "evwrap.h" |
|
|
3423 | \& #include "ev.c" |
|
|
3424 | .Ve |
|
|
3425 | .IP "The winsocket select function" 4 |
|
|
3426 | .IX Item "The winsocket select function" |
|
|
3427 | The winsocket \f(CW\*(C`select\*(C'\fR function doesn't follow \s-1POSIX\s0 in that it |
|
|
3428 | requires socket \fIhandles\fR and not socket \fIfile descriptors\fR (it is |
|
|
3429 | also extremely buggy). This makes select very inefficient, and also |
|
|
3430 | requires a mapping from file descriptors to socket handles (the Microsoft |
|
|
3431 | C runtime provides the function \f(CW\*(C`_open_osfhandle\*(C'\fR for this). See the |
|
|
3432 | discussion of the \f(CW\*(C`EV_SELECT_USE_FD_SET\*(C'\fR, \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR and |
|
|
3433 | \&\f(CW\*(C`EV_FD_TO_WIN32_HANDLE\*(C'\fR preprocessor symbols for more info. |
|
|
3434 | .Sp |
|
|
3435 | The configuration for a \*(L"naked\*(R" win32 using the Microsoft runtime |
|
|
3436 | libraries and raw winsocket select is: |
|
|
3437 | .Sp |
|
|
3438 | .Vb 2 |
|
|
3439 | \& #define EV_USE_SELECT 1 |
|
|
3440 | \& #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
|
|
3441 | .Ve |
|
|
3442 | .Sp |
|
|
3443 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
|
|
3444 | complexity in the O(nA\*^X) range when using win32. |
|
|
3445 | .IP "Limited number of file descriptors" 4 |
|
|
3446 | .IX Item "Limited number of file descriptors" |
|
|
3447 | Windows has numerous arbitrary (and low) limits on things. |
|
|
3448 | .Sp |
|
|
3449 | Early versions of winsocket's select only supported waiting for a maximum |
|
|
3450 | of \f(CW64\fR handles (probably owning to the fact that all windows kernels |
|
|
3451 | can only wait for \f(CW64\fR things at the same time internally; Microsoft |
|
|
3452 | recommends spawning a chain of threads and wait for 63 handles and the |
|
|
3453 | previous thread in each. Great). |
|
|
3454 | .Sp |
|
|
3455 | Newer versions support more handles, but you need to define \f(CW\*(C`FD_SETSIZE\*(C'\fR |
|
|
3456 | to some high number (e.g. \f(CW2048\fR) before compiling the winsocket select |
|
|
3457 | call (which might be in libev or elsewhere, for example, perl does its own |
|
|
3458 | select emulation on windows). |
|
|
3459 | .Sp |
|
|
3460 | Another limit is the number of file descriptors in the Microsoft runtime |
|
|
3461 | libraries, which by default is \f(CW64\fR (there must be a hidden \fI64\fR fetish |
|
|
3462 | or something like this inside Microsoft). You can increase this by calling |
|
|
3463 | \&\f(CW\*(C`_setmaxstdio\*(C'\fR, which can increase this limit to \f(CW2048\fR (another |
|
|
3464 | arbitrary limit), but is broken in many versions of the Microsoft runtime |
|
|
3465 | libraries. |
|
|
3466 | .Sp |
|
|
3467 | This might get you to about \f(CW512\fR or \f(CW2048\fR sockets (depending on |
|
|
3468 | windows version and/or the phase of the moon). To get more, you need to |
|
|
3469 | wrap all I/O functions and provide your own fd management, but the cost of |
|
|
3470 | calling select (O(nA\*^X)) will likely make this unworkable. |
|
|
3471 | .SH "PORTABILITY REQUIREMENTS" |
|
|
3472 | .IX Header "PORTABILITY REQUIREMENTS" |
|
|
3473 | In addition to a working ISO-C implementation, libev relies on a few |
|
|
3474 | additional extensions: |
|
|
3475 | .ie n .IP """void (*)(ev_watcher_type *, int revents)""\fR must have compatible calling conventions regardless of \f(CW""ev_watcher_type *""." 4 |
|
|
3476 | .el .IP "\f(CWvoid (*)(ev_watcher_type *, int revents)\fR must have compatible calling conventions regardless of \f(CWev_watcher_type *\fR." 4 |
|
|
3477 | .IX Item "void (*)(ev_watcher_type *, int revents) must have compatible calling conventions regardless of ev_watcher_type *." |
|
|
3478 | Libev assumes not only that all watcher pointers have the same internal |
|
|
3479 | structure (guaranteed by \s-1POSIX\s0 but not by \s-1ISO\s0 C for example), but it also |
|
|
3480 | assumes that the same (machine) code can be used to call any watcher |
|
|
3481 | callback: The watcher callbacks have different type signatures, but libev |
|
|
3482 | calls them using an \f(CW\*(C`ev_watcher *\*(C'\fR internally. |
|
|
3483 | .ie n .IP """sig_atomic_t volatile"" must be thread-atomic as well" 4 |
|
|
3484 | .el .IP "\f(CWsig_atomic_t volatile\fR must be thread-atomic as well" 4 |
|
|
3485 | .IX Item "sig_atomic_t volatile must be thread-atomic as well" |
|
|
3486 | The type \f(CW\*(C`sig_atomic_t volatile\*(C'\fR (or whatever is defined as |
|
|
3487 | \&\f(CW\*(C`EV_ATOMIC_T\*(C'\fR) must be atomic w.r.t. accesses from different |
|
|
3488 | threads. This is not part of the specification for \f(CW\*(C`sig_atomic_t\*(C'\fR, but is |
|
|
3489 | believed to be sufficiently portable. |
|
|
3490 | .ie n .IP """sigprocmask"" must work in a threaded environment" 4 |
|
|
3491 | .el .IP "\f(CWsigprocmask\fR must work in a threaded environment" 4 |
|
|
3492 | .IX Item "sigprocmask must work in a threaded environment" |
|
|
3493 | Libev uses \f(CW\*(C`sigprocmask\*(C'\fR to temporarily block signals. This is not |
|
|
3494 | allowed in a threaded program (\f(CW\*(C`pthread_sigmask\*(C'\fR has to be used). Typical |
|
|
3495 | pthread implementations will either allow \f(CW\*(C`sigprocmask\*(C'\fR in the \*(L"main |
|
|
3496 | thread\*(R" or will block signals process-wide, both behaviours would |
|
|
3497 | be compatible with libev. Interaction between \f(CW\*(C`sigprocmask\*(C'\fR and |
|
|
3498 | \&\f(CW\*(C`pthread_sigmask\*(C'\fR could complicate things, however. |
|
|
3499 | .Sp |
|
|
3500 | The most portable way to handle signals is to block signals in all threads |
|
|
3501 | except the initial one, and run the default loop in the initial thread as |
|
|
3502 | well. |
|
|
3503 | .ie n .IP """long"" must be large enough for common memory allocation sizes" 4 |
|
|
3504 | .el .IP "\f(CWlong\fR must be large enough for common memory allocation sizes" 4 |
|
|
3505 | .IX Item "long must be large enough for common memory allocation sizes" |
|
|
3506 | To improve portability and simplify using libev, libev uses \f(CW\*(C`long\*(C'\fR |
|
|
3507 | internally instead of \f(CW\*(C`size_t\*(C'\fR when allocating its data structures. On |
|
|
3508 | non-POSIX systems (Microsoft...) this might be unexpectedly low, but |
|
|
3509 | is still at least 31 bits everywhere, which is enough for hundreds of |
|
|
3510 | millions of watchers. |
|
|
3511 | .ie n .IP """double"" must hold a time value in seconds with enough accuracy" 4 |
|
|
3512 | .el .IP "\f(CWdouble\fR must hold a time value in seconds with enough accuracy" 4 |
|
|
3513 | .IX Item "double must hold a time value in seconds with enough accuracy" |
|
|
3514 | The type \f(CW\*(C`double\*(C'\fR is used to represent timestamps. It is required to |
|
|
3515 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
|
|
3516 | enough for at least into the year 4000. This requirement is fulfilled by |
|
|
3517 | implementations implementing \s-1IEEE\s0 754 (basically all existing ones). |
|
|
3518 | .PP |
|
|
3519 | If you know of other additional requirements drop me a note. |
|
|
3520 | .SH "COMPILER WARNINGS" |
|
|
3521 | .IX Header "COMPILER WARNINGS" |
|
|
3522 | Depending on your compiler and compiler settings, you might get no or a |
|
|
3523 | lot of warnings when compiling libev code. Some people are apparently |
|
|
3524 | scared by this. |
|
|
3525 | .PP |
|
|
3526 | However, these are unavoidable for many reasons. For one, each compiler |
|
|
3527 | has different warnings, and each user has different tastes regarding |
|
|
3528 | warning options. \*(L"Warn-free\*(R" code therefore cannot be a goal except when |
|
|
3529 | targeting a specific compiler and compiler-version. |
|
|
3530 | .PP |
|
|
3531 | Another reason is that some compiler warnings require elaborate |
|
|
3532 | workarounds, or other changes to the code that make it less clear and less |
|
|
3533 | maintainable. |
|
|
3534 | .PP |
|
|
3535 | And of course, some compiler warnings are just plain stupid, or simply |
|
|
3536 | wrong (because they don't actually warn about the condition their message |
|
|
3537 | seems to warn about). |
|
|
3538 | .PP |
|
|
3539 | While libev is written to generate as few warnings as possible, |
|
|
3540 | \&\*(L"warn-free\*(R" code is not a goal, and it is recommended not to build libev |
|
|
3541 | with any compiler warnings enabled unless you are prepared to cope with |
|
|
3542 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
3543 | warnings, not errors, or proof of bugs. |
|
|
3544 | .SH "VALGRIND" |
|
|
3545 | .IX Header "VALGRIND" |
|
|
3546 | Valgrind has a special section here because it is a popular tool that is |
|
|
3547 | highly useful, but valgrind reports are very hard to interpret. |
|
|
3548 | .PP |
|
|
3549 | If you think you found a bug (memory leak, uninitialised data access etc.) |
|
|
3550 | in libev, then check twice: If valgrind reports something like: |
|
|
3551 | .PP |
|
|
3552 | .Vb 3 |
|
|
3553 | \& ==2274== definitely lost: 0 bytes in 0 blocks. |
|
|
3554 | \& ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
3555 | \& ==2274== still reachable: 256 bytes in 1 blocks. |
|
|
3556 | .Ve |
|
|
3557 | .PP |
|
|
3558 | Then there is no memory leak. Similarly, under some circumstances, |
|
|
3559 | valgrind might report kernel bugs as if it were a bug in libev, or it |
|
|
3560 | might be confused (it is a very good tool, but only a tool). |
|
|
3561 | .PP |
|
|
3562 | If you are unsure about something, feel free to contact the mailing list |
|
|
3563 | with the full valgrind report and an explanation on why you think this is |
|
|
3564 | a bug in libev. However, don't be annoyed when you get a brisk \*(L"this is |
|
|
3565 | no bug\*(R" answer and take the chance of learning how to interpret valgrind |
|
|
3566 | properly. |
|
|
3567 | .PP |
|
|
3568 | If you need, for some reason, empty reports from valgrind for your project |
|
|
3569 | I suggest using suppression lists. |
995 | .SH "AUTHOR" |
3570 | .SH "AUTHOR" |
996 | .IX Header "AUTHOR" |
3571 | .IX Header "AUTHOR" |
997 | Marc Lehmann <libev@schmorp.de>. |
3572 | Marc Lehmann <libev@schmorp.de>. |
|
|
3573 | .SH "POD ERRORS" |
|
|
3574 | .IX Header "POD ERRORS" |
|
|
3575 | Hey! \fBThe above document had some coding errors, which are explained below:\fR |
|
|
3576 | .IP "Around line 3122:" 4 |
|
|
3577 | .IX Item "Around line 3122:" |
|
|
3578 | You forgot a '=back' before '=head2' |