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.\" ======================================================================== |
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.\" |
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.IX Title "LIBEV 3" |
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.TH LIBEV 3 "2009-07-15" "libev-3.7" "libev - high performance full featured event loop" |
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.\" For nroff, turn off justification. Always turn off hyphenation; it makes |
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.\" way too many mistakes in technical documents. |
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.if n .ad l |
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1.1 |
.SH "NAME" |
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libev \- a high performance full\-featured event loop written in C |
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.SH "SYNOPSIS" |
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.IX Header "SYNOPSIS" |
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.Vb 1 |
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\& #include <ev.h> |
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1.28 |
.Ve |
139 |
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1.79 |
.SS "\s-1EXAMPLE\s0 \s-1PROGRAM\s0" |
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.IX Subsection "EXAMPLE PROGRAM" |
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.Vb 2 |
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\& // a single header file is required |
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\& #include <ev.h> |
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\& |
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\& #include <stdio.h> // for puts |
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\& |
147 |
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\& // every watcher type has its own typedef\*(Aqd struct |
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\& // with the name ev_TYPE |
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\& ev_io stdin_watcher; |
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\& ev_timer timeout_watcher; |
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\& |
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\& // all watcher callbacks have a similar signature |
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\& // this callback is called when data is readable on stdin |
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\& static void |
155 |
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\& stdin_cb (EV_P_ ev_io *w, int revents) |
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\& { |
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\& puts ("stdin ready"); |
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\& // for one\-shot events, one must manually stop the watcher |
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\& // with its corresponding stop function. |
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\& ev_io_stop (EV_A_ w); |
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\& |
162 |
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\& // this causes all nested ev_loop\*(Aqs to stop iterating |
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\& ev_unloop (EV_A_ EVUNLOOP_ALL); |
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\& } |
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\& |
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\& // another callback, this time for a time\-out |
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\& static void |
168 |
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\& timeout_cb (EV_P_ ev_timer *w, int revents) |
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\& { |
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\& puts ("timeout"); |
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\& // this causes the innermost ev_loop to stop iterating |
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\& ev_unloop (EV_A_ EVUNLOOP_ONE); |
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\& } |
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\& |
175 |
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\& int |
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\& main (void) |
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\& { |
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\& // use the default event loop unless you have special needs |
179 |
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\& struct ev_loop *loop = ev_default_loop (0); |
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\& |
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\& // initialise an io watcher, then start it |
182 |
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\& // this one will watch for stdin to become readable |
183 |
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\& ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
184 |
|
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\& ev_io_start (loop, &stdin_watcher); |
185 |
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\& |
186 |
|
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\& // initialise a timer watcher, then start it |
187 |
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\& // simple non\-repeating 5.5 second timeout |
188 |
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\& ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
189 |
|
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\& ev_timer_start (loop, &timeout_watcher); |
190 |
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\& |
191 |
|
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\& // now wait for events to arrive |
192 |
|
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\& ev_loop (loop, 0); |
193 |
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\& |
194 |
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\& // unloop was called, so exit |
195 |
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\& return 0; |
196 |
|
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\& } |
197 |
root |
1.27 |
.Ve |
198 |
root |
1.78 |
.SH "ABOUT THIS DOCUMENT" |
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.IX Header "ABOUT THIS DOCUMENT" |
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This document documents the libev software package. |
201 |
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.PP |
202 |
root |
1.61 |
The newest version of this document is also available as an html-formatted |
203 |
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1.39 |
web page you might find easier to navigate when reading it for the first |
204 |
root |
1.66 |
time: <http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
205 |
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1.39 |
.PP |
206 |
root |
1.78 |
While this document tries to be as complete as possible in documenting |
207 |
|
|
libev, its usage and the rationale behind its design, it is not a tutorial |
208 |
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|
on event-based programming, nor will it introduce event-based programming |
209 |
|
|
with libev. |
210 |
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.PP |
211 |
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Familarity with event based programming techniques in general is assumed |
212 |
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throughout this document. |
213 |
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|
.SH "ABOUT LIBEV" |
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.IX Header "ABOUT LIBEV" |
215 |
root |
1.1 |
Libev is an event loop: you register interest in certain events (such as a |
216 |
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1.54 |
file descriptor being readable or a timeout occurring), and it will manage |
217 |
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1.1 |
these event sources and provide your program with events. |
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.PP |
219 |
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To do this, it must take more or less complete control over your process |
220 |
|
|
(or thread) by executing the \fIevent loop\fR handler, and will then |
221 |
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communicate events via a callback mechanism. |
222 |
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.PP |
223 |
|
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You register interest in certain events by registering so-called \fIevent |
224 |
|
|
watchers\fR, which are relatively small C structures you initialise with the |
225 |
|
|
details of the event, and then hand it over to libev by \fIstarting\fR the |
226 |
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watcher. |
227 |
root |
1.79 |
.SS "\s-1FEATURES\s0" |
228 |
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1.59 |
.IX Subsection "FEATURES" |
229 |
root |
1.31 |
Libev supports \f(CW\*(C`select\*(C'\fR, \f(CW\*(C`poll\*(C'\fR, the Linux-specific \f(CW\*(C`epoll\*(C'\fR, the |
230 |
|
|
BSD-specific \f(CW\*(C`kqueue\*(C'\fR and the Solaris-specific event port mechanisms |
231 |
|
|
for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), the Linux \f(CW\*(C`inotify\*(C'\fR interface |
232 |
|
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(for \f(CW\*(C`ev_stat\*(C'\fR), relative timers (\f(CW\*(C`ev_timer\*(C'\fR), absolute timers |
233 |
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with customised rescheduling (\f(CW\*(C`ev_periodic\*(C'\fR), synchronous signals |
234 |
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(\f(CW\*(C`ev_signal\*(C'\fR), process status change events (\f(CW\*(C`ev_child\*(C'\fR), and event |
235 |
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watchers dealing with the event loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR, |
236 |
root |
1.28 |
\&\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 |
237 |
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|
file watchers (\f(CW\*(C`ev_stat\*(C'\fR) and even limited support for fork events |
238 |
|
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(\f(CW\*(C`ev_fork\*(C'\fR). |
239 |
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.PP |
240 |
|
|
It also is quite fast (see this |
241 |
root |
1.79 |
<benchmark> comparing it to libevent |
242 |
root |
1.28 |
for example). |
243 |
root |
1.79 |
.SS "\s-1CONVENTIONS\s0" |
244 |
root |
1.59 |
.IX Subsection "CONVENTIONS" |
245 |
root |
1.61 |
Libev is very configurable. In this manual the default (and most common) |
246 |
|
|
configuration will be described, which supports multiple event loops. For |
247 |
|
|
more info about various configuration options please have a look at |
248 |
|
|
\&\fB\s-1EMBED\s0\fR section in this manual. If libev was configured without support |
249 |
|
|
for multiple event loops, then all functions taking an initial argument of |
250 |
root |
1.73 |
name \f(CW\*(C`loop\*(C'\fR (which is always of type \f(CW\*(C`ev_loop *\*(C'\fR) will not have |
251 |
root |
1.61 |
this argument. |
252 |
root |
1.79 |
.SS "\s-1TIME\s0 \s-1REPRESENTATION\s0" |
253 |
root |
1.59 |
.IX Subsection "TIME REPRESENTATION" |
254 |
root |
1.78 |
Libev represents time as a single floating point number, representing |
255 |
|
|
the (fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere |
256 |
|
|
near the beginning of 1970, details are complicated, don't ask). This |
257 |
|
|
type is called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use too. It usually |
258 |
|
|
aliases to the \f(CW\*(C`double\*(C'\fR type in C. When you need to do any calculations |
259 |
|
|
on it, you should treat it as some floating point value. Unlike the name |
260 |
root |
1.52 |
component \f(CW\*(C`stamp\*(C'\fR might indicate, it is also used for time differences |
261 |
|
|
throughout libev. |
262 |
root |
1.67 |
.SH "ERROR HANDLING" |
263 |
|
|
.IX Header "ERROR HANDLING" |
264 |
|
|
Libev knows three classes of errors: operating system errors, usage errors |
265 |
|
|
and internal errors (bugs). |
266 |
|
|
.PP |
267 |
|
|
When libev catches an operating system error it cannot handle (for example |
268 |
root |
1.68 |
a system call indicating a condition libev cannot fix), it calls the callback |
269 |
root |
1.67 |
set via \f(CW\*(C`ev_set_syserr_cb\*(C'\fR, which is supposed to fix the problem or |
270 |
|
|
abort. The default is to print a diagnostic message and to call \f(CW\*(C`abort |
271 |
|
|
()\*(C'\fR. |
272 |
|
|
.PP |
273 |
|
|
When libev detects a usage error such as a negative timer interval, then |
274 |
|
|
it will print a diagnostic message and abort (via the \f(CW\*(C`assert\*(C'\fR mechanism, |
275 |
|
|
so \f(CW\*(C`NDEBUG\*(C'\fR will disable this checking): these are programming errors in |
276 |
|
|
the libev caller and need to be fixed there. |
277 |
|
|
.PP |
278 |
|
|
Libev also has a few internal error-checking \f(CW\*(C`assert\*(C'\fRions, and also has |
279 |
|
|
extensive consistency checking code. These do not trigger under normal |
280 |
|
|
circumstances, as they indicate either a bug in libev or worse. |
281 |
root |
1.1 |
.SH "GLOBAL FUNCTIONS" |
282 |
|
|
.IX Header "GLOBAL FUNCTIONS" |
283 |
|
|
These functions can be called anytime, even before initialising the |
284 |
|
|
library in any way. |
285 |
|
|
.IP "ev_tstamp ev_time ()" 4 |
286 |
|
|
.IX Item "ev_tstamp ev_time ()" |
287 |
root |
1.2 |
Returns the current time as libev would use it. Please note that the |
288 |
|
|
\&\f(CW\*(C`ev_now\*(C'\fR function is usually faster and also often returns the timestamp |
289 |
|
|
you actually want to know. |
290 |
root |
1.57 |
.IP "ev_sleep (ev_tstamp interval)" 4 |
291 |
|
|
.IX Item "ev_sleep (ev_tstamp interval)" |
292 |
root |
1.56 |
Sleep for the given interval: The current thread will be blocked until |
293 |
|
|
either it is interrupted or the given time interval has passed. Basically |
294 |
root |
1.68 |
this is a sub-second-resolution \f(CW\*(C`sleep ()\*(C'\fR. |
295 |
root |
1.1 |
.IP "int ev_version_major ()" 4 |
296 |
|
|
.IX Item "int ev_version_major ()" |
297 |
|
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.PD 0 |
298 |
|
|
.IP "int ev_version_minor ()" 4 |
299 |
|
|
.IX Item "int ev_version_minor ()" |
300 |
|
|
.PD |
301 |
root |
1.48 |
You can find out the major and minor \s-1ABI\s0 version numbers of the library |
302 |
root |
1.1 |
you linked against by calling the functions \f(CW\*(C`ev_version_major\*(C'\fR and |
303 |
|
|
\&\f(CW\*(C`ev_version_minor\*(C'\fR. If you want, you can compare against the global |
304 |
|
|
symbols \f(CW\*(C`EV_VERSION_MAJOR\*(C'\fR and \f(CW\*(C`EV_VERSION_MINOR\*(C'\fR, which specify the |
305 |
|
|
version of the library your program was compiled against. |
306 |
|
|
.Sp |
307 |
root |
1.48 |
These version numbers refer to the \s-1ABI\s0 version of the library, not the |
308 |
|
|
release version. |
309 |
root |
1.47 |
.Sp |
310 |
root |
1.1 |
Usually, it's a good idea to terminate if the major versions mismatch, |
311 |
root |
1.47 |
as this indicates an incompatible change. Minor versions are usually |
312 |
root |
1.1 |
compatible to older versions, so a larger minor version alone is usually |
313 |
|
|
not a problem. |
314 |
root |
1.9 |
.Sp |
315 |
root |
1.28 |
Example: Make sure we haven't accidentally been linked against the wrong |
316 |
|
|
version. |
317 |
root |
1.9 |
.Sp |
318 |
|
|
.Vb 3 |
319 |
root |
1.68 |
\& assert (("libev version mismatch", |
320 |
|
|
\& ev_version_major () == EV_VERSION_MAJOR |
321 |
|
|
\& && ev_version_minor () >= EV_VERSION_MINOR)); |
322 |
root |
1.9 |
.Ve |
323 |
root |
1.6 |
.IP "unsigned int ev_supported_backends ()" 4 |
324 |
|
|
.IX Item "unsigned int ev_supported_backends ()" |
325 |
|
|
Return the set of all backends (i.e. their corresponding \f(CW\*(C`EV_BACKEND_*\*(C'\fR |
326 |
|
|
value) compiled into this binary of libev (independent of their |
327 |
|
|
availability on the system you are running on). See \f(CW\*(C`ev_default_loop\*(C'\fR for |
328 |
|
|
a description of the set values. |
329 |
root |
1.9 |
.Sp |
330 |
|
|
Example: make sure we have the epoll method, because yeah this is cool and |
331 |
|
|
a must have and can we have a torrent of it please!!!11 |
332 |
|
|
.Sp |
333 |
|
|
.Vb 2 |
334 |
root |
1.68 |
\& assert (("sorry, no epoll, no sex", |
335 |
|
|
\& ev_supported_backends () & EVBACKEND_EPOLL)); |
336 |
root |
1.9 |
.Ve |
337 |
root |
1.6 |
.IP "unsigned int ev_recommended_backends ()" 4 |
338 |
|
|
.IX Item "unsigned int ev_recommended_backends ()" |
339 |
|
|
Return the set of all backends compiled into this binary of libev and also |
340 |
|
|
recommended for this platform. This set is often smaller than the one |
341 |
|
|
returned by \f(CW\*(C`ev_supported_backends\*(C'\fR, as for example kqueue is broken on |
342 |
root |
1.68 |
most BSDs and will not be auto-detected unless you explicitly request it |
343 |
root |
1.6 |
(assuming you know what you are doing). This is the set of backends that |
344 |
root |
1.8 |
libev will probe for if you specify no backends explicitly. |
345 |
root |
1.10 |
.IP "unsigned int ev_embeddable_backends ()" 4 |
346 |
|
|
.IX Item "unsigned int ev_embeddable_backends ()" |
347 |
|
|
Returns the set of backends that are embeddable in other event loops. This |
348 |
root |
1.60 |
is the theoretical, all-platform, value. To find which backends |
349 |
root |
1.10 |
might be supported on the current system, you would need to look at |
350 |
|
|
\&\f(CW\*(C`ev_embeddable_backends () & ev_supported_backends ()\*(C'\fR, likewise for |
351 |
|
|
recommended ones. |
352 |
|
|
.Sp |
353 |
|
|
See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info. |
354 |
root |
1.71 |
.IP "ev_set_allocator (void *(*cb)(void *ptr, long size)) [\s-1NOT\s0 \s-1REENTRANT\s0]" 4 |
355 |
|
|
.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]" |
356 |
root |
1.32 |
Sets the allocation function to use (the prototype is similar \- the |
357 |
root |
1.64 |
semantics are identical to the \f(CW\*(C`realloc\*(C'\fR C89/SuS/POSIX function). It is |
358 |
|
|
used to allocate and free memory (no surprises here). If it returns zero |
359 |
|
|
when memory needs to be allocated (\f(CW\*(C`size != 0\*(C'\fR), the library might abort |
360 |
|
|
or take some potentially destructive action. |
361 |
|
|
.Sp |
362 |
|
|
Since some systems (at least OpenBSD and Darwin) fail to implement |
363 |
|
|
correct \f(CW\*(C`realloc\*(C'\fR semantics, libev will use a wrapper around the system |
364 |
|
|
\&\f(CW\*(C`realloc\*(C'\fR and \f(CW\*(C`free\*(C'\fR functions by default. |
365 |
root |
1.1 |
.Sp |
366 |
|
|
You could override this function in high-availability programs to, say, |
367 |
|
|
free some memory if it cannot allocate memory, to use a special allocator, |
368 |
|
|
or even to sleep a while and retry until some memory is available. |
369 |
root |
1.9 |
.Sp |
370 |
root |
1.28 |
Example: Replace the libev allocator with one that waits a bit and then |
371 |
root |
1.64 |
retries (example requires a standards-compliant \f(CW\*(C`realloc\*(C'\fR). |
372 |
root |
1.9 |
.Sp |
373 |
|
|
.Vb 6 |
374 |
|
|
\& static void * |
375 |
root |
1.26 |
\& persistent_realloc (void *ptr, size_t size) |
376 |
root |
1.9 |
\& { |
377 |
|
|
\& for (;;) |
378 |
|
|
\& { |
379 |
|
|
\& void *newptr = realloc (ptr, size); |
380 |
root |
1.60 |
\& |
381 |
root |
1.9 |
\& if (newptr) |
382 |
|
|
\& return newptr; |
383 |
root |
1.60 |
\& |
384 |
root |
1.9 |
\& sleep (60); |
385 |
|
|
\& } |
386 |
|
|
\& } |
387 |
root |
1.60 |
\& |
388 |
root |
1.9 |
\& ... |
389 |
|
|
\& ev_set_allocator (persistent_realloc); |
390 |
|
|
.Ve |
391 |
root |
1.71 |
.IP "ev_set_syserr_cb (void (*cb)(const char *msg)); [\s-1NOT\s0 \s-1REENTRANT\s0]" 4 |
392 |
|
|
.IX Item "ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]" |
393 |
root |
1.68 |
Set the callback function to call on a retryable system call error (such |
394 |
root |
1.1 |
as failed select, poll, epoll_wait). The message is a printable string |
395 |
|
|
indicating the system call or subsystem causing the problem. If this |
396 |
root |
1.68 |
callback is set, then libev will expect it to remedy the situation, no |
397 |
root |
1.1 |
matter what, when it returns. That is, libev will generally retry the |
398 |
|
|
requested operation, or, if the condition doesn't go away, do bad stuff |
399 |
|
|
(such as abort). |
400 |
root |
1.9 |
.Sp |
401 |
root |
1.28 |
Example: This is basically the same thing that libev does internally, too. |
402 |
root |
1.9 |
.Sp |
403 |
|
|
.Vb 6 |
404 |
|
|
\& static void |
405 |
|
|
\& fatal_error (const char *msg) |
406 |
|
|
\& { |
407 |
|
|
\& perror (msg); |
408 |
|
|
\& abort (); |
409 |
|
|
\& } |
410 |
root |
1.60 |
\& |
411 |
root |
1.9 |
\& ... |
412 |
|
|
\& ev_set_syserr_cb (fatal_error); |
413 |
|
|
.Ve |
414 |
root |
1.1 |
.SH "FUNCTIONS CONTROLLING THE EVENT LOOP" |
415 |
|
|
.IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP" |
416 |
root |
1.73 |
An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR (the \f(CW\*(C`struct\*(C'\fR |
417 |
|
|
is \fInot\fR optional in this case, as there is also an \f(CW\*(C`ev_loop\*(C'\fR |
418 |
|
|
\&\fIfunction\fR). |
419 |
|
|
.PP |
420 |
|
|
The library knows two types of such loops, the \fIdefault\fR loop, which |
421 |
|
|
supports signals and child events, and dynamically created loops which do |
422 |
|
|
not. |
423 |
root |
1.1 |
.IP "struct ev_loop *ev_default_loop (unsigned int flags)" 4 |
424 |
|
|
.IX Item "struct ev_loop *ev_default_loop (unsigned int flags)" |
425 |
|
|
This will initialise the default event loop if it hasn't been initialised |
426 |
|
|
yet and return it. If the default loop could not be initialised, returns |
427 |
|
|
false. If it already was initialised it simply returns it (and ignores the |
428 |
root |
1.6 |
flags. If that is troubling you, check \f(CW\*(C`ev_backend ()\*(C'\fR afterwards). |
429 |
root |
1.1 |
.Sp |
430 |
|
|
If you don't know what event loop to use, use the one returned from this |
431 |
|
|
function. |
432 |
|
|
.Sp |
433 |
root |
1.63 |
Note that this function is \fInot\fR thread-safe, so if you want to use it |
434 |
|
|
from multiple threads, you have to lock (note also that this is unlikely, |
435 |
root |
1.73 |
as loops cannot be shared easily between threads anyway). |
436 |
root |
1.63 |
.Sp |
437 |
root |
1.60 |
The default loop is the only loop that can handle \f(CW\*(C`ev_signal\*(C'\fR and |
438 |
|
|
\&\f(CW\*(C`ev_child\*(C'\fR watchers, and to do this, it always registers a handler |
439 |
root |
1.68 |
for \f(CW\*(C`SIGCHLD\*(C'\fR. If this is a problem for your application you can either |
440 |
root |
1.60 |
create a dynamic loop with \f(CW\*(C`ev_loop_new\*(C'\fR that doesn't do that, or you |
441 |
|
|
can simply overwrite the \f(CW\*(C`SIGCHLD\*(C'\fR signal handler \fIafter\fR calling |
442 |
|
|
\&\f(CW\*(C`ev_default_init\*(C'\fR. |
443 |
|
|
.Sp |
444 |
root |
1.1 |
The flags argument can be used to specify special behaviour or specific |
445 |
root |
1.8 |
backends to use, and is usually specified as \f(CW0\fR (or \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). |
446 |
root |
1.1 |
.Sp |
447 |
root |
1.8 |
The following flags are supported: |
448 |
root |
1.1 |
.RS 4 |
449 |
|
|
.ie n .IP """EVFLAG_AUTO""" 4 |
450 |
|
|
.el .IP "\f(CWEVFLAG_AUTO\fR" 4 |
451 |
|
|
.IX Item "EVFLAG_AUTO" |
452 |
|
|
The default flags value. Use this if you have no clue (it's the right |
453 |
|
|
thing, believe me). |
454 |
|
|
.ie n .IP """EVFLAG_NOENV""" 4 |
455 |
|
|
.el .IP "\f(CWEVFLAG_NOENV\fR" 4 |
456 |
|
|
.IX Item "EVFLAG_NOENV" |
457 |
root |
1.68 |
If this flag bit is or'ed into the flag value (or the program runs setuid |
458 |
root |
1.1 |
or setgid) then libev will \fInot\fR look at the environment variable |
459 |
|
|
\&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will |
460 |
|
|
override the flags completely if it is found in the environment. This is |
461 |
|
|
useful to try out specific backends to test their performance, or to work |
462 |
|
|
around bugs. |
463 |
root |
1.35 |
.ie n .IP """EVFLAG_FORKCHECK""" 4 |
464 |
|
|
.el .IP "\f(CWEVFLAG_FORKCHECK\fR" 4 |
465 |
|
|
.IX Item "EVFLAG_FORKCHECK" |
466 |
|
|
Instead of calling \f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR manually after |
467 |
|
|
a fork, you can also make libev check for a fork in each iteration by |
468 |
|
|
enabling this flag. |
469 |
|
|
.Sp |
470 |
|
|
This works by calling \f(CW\*(C`getpid ()\*(C'\fR on every iteration of the loop, |
471 |
|
|
and thus this might slow down your event loop if you do a lot of loop |
472 |
root |
1.37 |
iterations and little real work, but is usually not noticeable (on my |
473 |
root |
1.61 |
GNU/Linux system for example, \f(CW\*(C`getpid\*(C'\fR is actually a simple 5\-insn sequence |
474 |
root |
1.68 |
without a system call and thus \fIvery\fR fast, but my GNU/Linux system also has |
475 |
root |
1.35 |
\&\f(CW\*(C`pthread_atfork\*(C'\fR which is even faster). |
476 |
|
|
.Sp |
477 |
|
|
The big advantage of this flag is that you can forget about fork (and |
478 |
|
|
forget about forgetting to tell libev about forking) when you use this |
479 |
|
|
flag. |
480 |
|
|
.Sp |
481 |
root |
1.68 |
This flag setting cannot be overridden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR |
482 |
root |
1.35 |
environment variable. |
483 |
root |
1.6 |
.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4 |
484 |
|
|
.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4 |
485 |
|
|
.IX Item "EVBACKEND_SELECT (value 1, portable select backend)" |
486 |
root |
1.3 |
This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as |
487 |
|
|
libev tries to roll its own fd_set with no limits on the number of fds, |
488 |
|
|
but if that fails, expect a fairly low limit on the number of fds when |
489 |
root |
1.58 |
using this backend. It doesn't scale too well (O(highest_fd)), but its |
490 |
root |
1.60 |
usually the fastest backend for a low number of (low-numbered :) fds. |
491 |
root |
1.58 |
.Sp |
492 |
|
|
To get good performance out of this backend you need a high amount of |
493 |
root |
1.68 |
parallelism (most of the file descriptors should be busy). If you are |
494 |
root |
1.58 |
writing a server, you should \f(CW\*(C`accept ()\*(C'\fR in a loop to accept as many |
495 |
|
|
connections as possible during one iteration. You might also want to have |
496 |
|
|
a look at \f(CW\*(C`ev_set_io_collect_interval ()\*(C'\fR to increase the amount of |
497 |
root |
1.67 |
readiness notifications you get per iteration. |
498 |
root |
1.71 |
.Sp |
499 |
|
|
This backend maps \f(CW\*(C`EV_READ\*(C'\fR to the \f(CW\*(C`readfds\*(C'\fR set and \f(CW\*(C`EV_WRITE\*(C'\fR to the |
500 |
|
|
\&\f(CW\*(C`writefds\*(C'\fR set (and to work around Microsoft Windows bugs, also onto the |
501 |
|
|
\&\f(CW\*(C`exceptfds\*(C'\fR set on that platform). |
502 |
root |
1.6 |
.ie n .IP """EVBACKEND_POLL"" (value 2, poll backend, available everywhere except on windows)" 4 |
503 |
|
|
.el .IP "\f(CWEVBACKEND_POLL\fR (value 2, poll backend, available everywhere except on windows)" 4 |
504 |
|
|
.IX Item "EVBACKEND_POLL (value 2, poll backend, available everywhere except on windows)" |
505 |
root |
1.58 |
And this is your standard \fIpoll\fR\|(2) backend. It's more complicated |
506 |
|
|
than select, but handles sparse fds better and has no artificial |
507 |
|
|
limit on the number of fds you can use (except it will slow down |
508 |
|
|
considerably with a lot of inactive fds). It scales similarly to select, |
509 |
|
|
i.e. O(total_fds). See the entry for \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR, above, for |
510 |
|
|
performance tips. |
511 |
root |
1.71 |
.Sp |
512 |
|
|
This backend maps \f(CW\*(C`EV_READ\*(C'\fR to \f(CW\*(C`POLLIN | POLLERR | POLLHUP\*(C'\fR, and |
513 |
|
|
\&\f(CW\*(C`EV_WRITE\*(C'\fR to \f(CW\*(C`POLLOUT | POLLERR | POLLHUP\*(C'\fR. |
514 |
root |
1.6 |
.ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4 |
515 |
|
|
.el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4 |
516 |
|
|
.IX Item "EVBACKEND_EPOLL (value 4, Linux)" |
517 |
root |
1.3 |
For few fds, this backend is a bit little slower than poll and select, |
518 |
root |
1.54 |
but it scales phenomenally better. While poll and select usually scale |
519 |
|
|
like O(total_fds) where n is the total number of fds (or the highest fd), |
520 |
root |
1.73 |
epoll scales either O(1) or O(active_fds). |
521 |
|
|
.Sp |
522 |
|
|
The epoll mechanism deserves honorable mention as the most misdesigned |
523 |
|
|
of the more advanced event mechanisms: mere annoyances include silently |
524 |
|
|
dropping file descriptors, requiring a system call per change per file |
525 |
|
|
descriptor (and unnecessary guessing of parameters), problems with dup and |
526 |
|
|
so on. The biggest issue is fork races, however \- if a program forks then |
527 |
|
|
\&\fIboth\fR parent and child process have to recreate the epoll set, which can |
528 |
|
|
take considerable time (one syscall per file descriptor) and is of course |
529 |
|
|
hard to detect. |
530 |
|
|
.Sp |
531 |
|
|
Epoll is also notoriously buggy \- embedding epoll fds \fIshould\fR work, but |
532 |
|
|
of course \fIdoesn't\fR, and epoll just loves to report events for totally |
533 |
|
|
\&\fIdifferent\fR file descriptors (even already closed ones, so one cannot |
534 |
|
|
even remove them from the set) than registered in the set (especially |
535 |
|
|
on \s-1SMP\s0 systems). Libev tries to counter these spurious notifications by |
536 |
|
|
employing an additional generation counter and comparing that against the |
537 |
|
|
events to filter out spurious ones, recreating the set when required. |
538 |
root |
1.3 |
.Sp |
539 |
root |
1.54 |
While stopping, setting and starting an I/O watcher in the same iteration |
540 |
root |
1.73 |
will result in some caching, there is still a system call per such |
541 |
|
|
incident (because the same \fIfile descriptor\fR could point to a different |
542 |
|
|
\&\fIfile description\fR now), so its best to avoid that. Also, \f(CW\*(C`dup ()\*(C'\fR'ed |
543 |
|
|
file descriptors might not work very well if you register events for both |
544 |
|
|
file descriptors. |
545 |
root |
1.58 |
.Sp |
546 |
|
|
Best performance from this backend is achieved by not unregistering all |
547 |
root |
1.71 |
watchers for a file descriptor until it has been closed, if possible, |
548 |
|
|
i.e. keep at least one watcher active per fd at all times. Stopping and |
549 |
|
|
starting a watcher (without re-setting it) also usually doesn't cause |
550 |
root |
1.73 |
extra overhead. A fork can both result in spurious notifications as well |
551 |
|
|
as in libev having to destroy and recreate the epoll object, which can |
552 |
|
|
take considerable time and thus should be avoided. |
553 |
root |
1.58 |
.Sp |
554 |
root |
1.74 |
All this means that, in practice, \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR can be as fast or |
555 |
|
|
faster than epoll for maybe up to a hundred file descriptors, depending on |
556 |
|
|
the usage. So sad. |
557 |
|
|
.Sp |
558 |
root |
1.68 |
While nominally embeddable in other event loops, this feature is broken in |
559 |
root |
1.58 |
all kernel versions tested so far. |
560 |
root |
1.71 |
.Sp |
561 |
|
|
This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as |
562 |
|
|
\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
563 |
root |
1.6 |
.ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4 |
564 |
|
|
.el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4 |
565 |
|
|
.IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)" |
566 |
root |
1.73 |
Kqueue deserves special mention, as at the time of this writing, it |
567 |
|
|
was broken on all BSDs except NetBSD (usually it doesn't work reliably |
568 |
|
|
with anything but sockets and pipes, except on Darwin, where of course |
569 |
|
|
it's completely useless). Unlike epoll, however, whose brokenness |
570 |
|
|
is by design, these kqueue bugs can (and eventually will) be fixed |
571 |
|
|
without \s-1API\s0 changes to existing programs. For this reason it's not being |
572 |
|
|
\&\*(L"auto-detected\*(R" unless you explicitly specify it in the flags (i.e. using |
573 |
|
|
\&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR) or libev was compiled on a known-to-be-good (\-enough) |
574 |
|
|
system like NetBSD. |
575 |
root |
1.3 |
.Sp |
576 |
root |
1.57 |
You still can embed kqueue into a normal poll or select backend and use it |
577 |
|
|
only for sockets (after having made sure that sockets work with kqueue on |
578 |
|
|
the target platform). See \f(CW\*(C`ev_embed\*(C'\fR watchers for more info. |
579 |
|
|
.Sp |
580 |
root |
1.3 |
It scales in the same way as the epoll backend, but the interface to the |
581 |
root |
1.57 |
kernel is more efficient (which says nothing about its actual speed, of |
582 |
|
|
course). While stopping, setting and starting an I/O watcher does never |
583 |
root |
1.68 |
cause an extra system call as with \f(CW\*(C`EVBACKEND_EPOLL\*(C'\fR, it still adds up to |
584 |
root |
1.73 |
two event changes per incident. Support for \f(CW\*(C`fork ()\*(C'\fR is very bad (but |
585 |
|
|
sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
586 |
|
|
cases |
587 |
root |
1.58 |
.Sp |
588 |
|
|
This backend usually performs well under most conditions. |
589 |
|
|
.Sp |
590 |
|
|
While nominally embeddable in other event loops, this doesn't work |
591 |
|
|
everywhere, so you might need to test for this. And since it is broken |
592 |
|
|
almost everywhere, you should only use it when you have a lot of sockets |
593 |
|
|
(for which it usually works), by embedding it into another event loop |
594 |
root |
1.75 |
(e.g. \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR (but \f(CW\*(C`poll\*(C'\fR is of course |
595 |
|
|
also broken on \s-1OS\s0 X)) and, did I mention it, using it only for sockets. |
596 |
root |
1.71 |
.Sp |
597 |
|
|
This backend maps \f(CW\*(C`EV_READ\*(C'\fR into an \f(CW\*(C`EVFILT_READ\*(C'\fR kevent with |
598 |
|
|
\&\f(CW\*(C`NOTE_EOF\*(C'\fR, and \f(CW\*(C`EV_WRITE\*(C'\fR into an \f(CW\*(C`EVFILT_WRITE\*(C'\fR kevent with |
599 |
|
|
\&\f(CW\*(C`NOTE_EOF\*(C'\fR. |
600 |
root |
1.6 |
.ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4 |
601 |
|
|
.el .IP "\f(CWEVBACKEND_DEVPOLL\fR (value 16, Solaris 8)" 4 |
602 |
|
|
.IX Item "EVBACKEND_DEVPOLL (value 16, Solaris 8)" |
603 |
root |
1.58 |
This is not implemented yet (and might never be, unless you send me an |
604 |
|
|
implementation). According to reports, \f(CW\*(C`/dev/poll\*(C'\fR only supports sockets |
605 |
|
|
and is not embeddable, which would limit the usefulness of this backend |
606 |
|
|
immensely. |
607 |
root |
1.6 |
.ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4 |
608 |
|
|
.el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4 |
609 |
|
|
.IX Item "EVBACKEND_PORT (value 32, Solaris 10)" |
610 |
root |
1.54 |
This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
611 |
root |
1.3 |
it's really slow, but it still scales very well (O(active_fds)). |
612 |
root |
1.7 |
.Sp |
613 |
root |
1.68 |
Please note that Solaris event ports can deliver a lot of spurious |
614 |
root |
1.7 |
notifications, so you need to use non-blocking I/O or other means to avoid |
615 |
|
|
blocking when no data (or space) is available. |
616 |
root |
1.58 |
.Sp |
617 |
|
|
While this backend scales well, it requires one system call per active |
618 |
|
|
file descriptor per loop iteration. For small and medium numbers of file |
619 |
|
|
descriptors a \*(L"slow\*(R" \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR backend |
620 |
|
|
might perform better. |
621 |
root |
1.60 |
.Sp |
622 |
root |
1.71 |
On the positive side, with the exception of the spurious readiness |
623 |
|
|
notifications, this backend actually performed fully to specification |
624 |
|
|
in all tests and is fully embeddable, which is a rare feat among the |
625 |
root |
1.73 |
OS-specific backends (I vastly prefer correctness over speed hacks). |
626 |
root |
1.71 |
.Sp |
627 |
|
|
This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as |
628 |
|
|
\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
629 |
root |
1.6 |
.ie n .IP """EVBACKEND_ALL""" 4 |
630 |
|
|
.el .IP "\f(CWEVBACKEND_ALL\fR" 4 |
631 |
|
|
.IX Item "EVBACKEND_ALL" |
632 |
root |
1.4 |
Try all backends (even potentially broken ones that wouldn't be tried |
633 |
|
|
with \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). Since this is a mask, you can do stuff such as |
634 |
root |
1.6 |
\&\f(CW\*(C`EVBACKEND_ALL & ~EVBACKEND_KQUEUE\*(C'\fR. |
635 |
root |
1.58 |
.Sp |
636 |
|
|
It is definitely not recommended to use this flag. |
637 |
root |
1.1 |
.RE |
638 |
|
|
.RS 4 |
639 |
root |
1.3 |
.Sp |
640 |
root |
1.68 |
If one or more of these are or'ed into the flags value, then only these |
641 |
root |
1.60 |
backends will be tried (in the reverse order as listed here). If none are |
642 |
|
|
specified, all backends in \f(CW\*(C`ev_recommended_backends ()\*(C'\fR will be tried. |
643 |
root |
1.8 |
.Sp |
644 |
root |
1.71 |
Example: This is the most typical usage. |
645 |
root |
1.8 |
.Sp |
646 |
|
|
.Vb 2 |
647 |
root |
1.68 |
\& if (!ev_default_loop (0)) |
648 |
|
|
\& fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
649 |
root |
1.8 |
.Ve |
650 |
|
|
.Sp |
651 |
root |
1.71 |
Example: Restrict libev to the select and poll backends, and do not allow |
652 |
root |
1.8 |
environment settings to be taken into account: |
653 |
|
|
.Sp |
654 |
|
|
.Vb 1 |
655 |
root |
1.68 |
\& ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
656 |
root |
1.8 |
.Ve |
657 |
|
|
.Sp |
658 |
root |
1.71 |
Example: Use whatever libev has to offer, but make sure that kqueue is |
659 |
|
|
used if available (warning, breaks stuff, best use only with your own |
660 |
|
|
private event loop and only if you know the \s-1OS\s0 supports your types of |
661 |
|
|
fds): |
662 |
root |
1.8 |
.Sp |
663 |
|
|
.Vb 1 |
664 |
root |
1.68 |
\& ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
665 |
root |
1.8 |
.Ve |
666 |
root |
1.1 |
.RE |
667 |
|
|
.IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4 |
668 |
|
|
.IX Item "struct ev_loop *ev_loop_new (unsigned int flags)" |
669 |
|
|
Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is |
670 |
|
|
always distinct from the default loop. Unlike the default loop, it cannot |
671 |
|
|
handle signal and child watchers, and attempts to do so will be greeted by |
672 |
|
|
undefined behaviour (or a failed assertion if assertions are enabled). |
673 |
root |
1.9 |
.Sp |
674 |
root |
1.63 |
Note that this function \fIis\fR thread-safe, and the recommended way to use |
675 |
|
|
libev with threads is indeed to create one loop per thread, and using the |
676 |
|
|
default loop in the \*(L"main\*(R" or \*(L"initial\*(R" thread. |
677 |
|
|
.Sp |
678 |
root |
1.28 |
Example: Try to create a event loop that uses epoll and nothing else. |
679 |
root |
1.9 |
.Sp |
680 |
|
|
.Vb 3 |
681 |
root |
1.68 |
\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
682 |
|
|
\& if (!epoller) |
683 |
|
|
\& fatal ("no epoll found here, maybe it hides under your chair"); |
684 |
root |
1.9 |
.Ve |
685 |
root |
1.1 |
.IP "ev_default_destroy ()" 4 |
686 |
|
|
.IX Item "ev_default_destroy ()" |
687 |
|
|
Destroys the default loop again (frees all memory and kernel state |
688 |
root |
1.12 |
etc.). None of the active event watchers will be stopped in the normal |
689 |
|
|
sense, so e.g. \f(CW\*(C`ev_is_active\*(C'\fR might still return true. It is your |
690 |
root |
1.68 |
responsibility to either stop all watchers cleanly yourself \fIbefore\fR |
691 |
root |
1.12 |
calling this function, or cope with the fact afterwards (which is usually |
692 |
root |
1.52 |
the easiest thing, you can just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them |
693 |
root |
1.12 |
for example). |
694 |
root |
1.52 |
.Sp |
695 |
root |
1.73 |
Note that certain global state, such as signal state (and installed signal |
696 |
|
|
handlers), will not be freed by this function, and related watchers (such |
697 |
|
|
as signal and child watchers) would need to be stopped manually. |
698 |
root |
1.52 |
.Sp |
699 |
|
|
In general it is not advisable to call this function except in the |
700 |
|
|
rare occasion where you really need to free e.g. the signal handling |
701 |
|
|
pipe fds. If you need dynamically allocated loops it is better to use |
702 |
|
|
\&\f(CW\*(C`ev_loop_new\*(C'\fR and \f(CW\*(C`ev_loop_destroy\*(C'\fR). |
703 |
root |
1.1 |
.IP "ev_loop_destroy (loop)" 4 |
704 |
|
|
.IX Item "ev_loop_destroy (loop)" |
705 |
|
|
Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an |
706 |
|
|
earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR. |
707 |
|
|
.IP "ev_default_fork ()" 4 |
708 |
|
|
.IX Item "ev_default_fork ()" |
709 |
root |
1.60 |
This function sets a flag that causes subsequent \f(CW\*(C`ev_loop\*(C'\fR iterations |
710 |
|
|
to reinitialise the kernel state for backends that have one. Despite the |
711 |
|
|
name, you can call it anytime, but it makes most sense after forking, in |
712 |
|
|
the child process (or both child and parent, but that again makes little |
713 |
|
|
sense). You \fImust\fR call it in the child before using any of the libev |
714 |
|
|
functions, and it will only take effect at the next \f(CW\*(C`ev_loop\*(C'\fR iteration. |
715 |
|
|
.Sp |
716 |
|
|
On the other hand, you only need to call this function in the child |
717 |
|
|
process if and only if you want to use the event library in the child. If |
718 |
|
|
you just fork+exec, you don't have to call it at all. |
719 |
root |
1.1 |
.Sp |
720 |
|
|
The function itself is quite fast and it's usually not a problem to call |
721 |
|
|
it just in case after a fork. To make this easy, the function will fit in |
722 |
|
|
quite nicely into a call to \f(CW\*(C`pthread_atfork\*(C'\fR: |
723 |
|
|
.Sp |
724 |
|
|
.Vb 1 |
725 |
|
|
\& pthread_atfork (0, 0, ev_default_fork); |
726 |
|
|
.Ve |
727 |
|
|
.IP "ev_loop_fork (loop)" 4 |
728 |
|
|
.IX Item "ev_loop_fork (loop)" |
729 |
|
|
Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by |
730 |
|
|
\&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop |
731 |
root |
1.71 |
after fork that you want to re-use in the child, and how you do this is |
732 |
|
|
entirely your own problem. |
733 |
root |
1.61 |
.IP "int ev_is_default_loop (loop)" 4 |
734 |
|
|
.IX Item "int ev_is_default_loop (loop)" |
735 |
root |
1.71 |
Returns true when the given loop is, in fact, the default loop, and false |
736 |
|
|
otherwise. |
737 |
root |
1.37 |
.IP "unsigned int ev_loop_count (loop)" 4 |
738 |
|
|
.IX Item "unsigned int ev_loop_count (loop)" |
739 |
|
|
Returns the count of loop iterations for the loop, which is identical to |
740 |
|
|
the number of times libev did poll for new events. It starts at \f(CW0\fR and |
741 |
|
|
happily wraps around with enough iterations. |
742 |
|
|
.Sp |
743 |
|
|
This value can sometimes be useful as a generation counter of sorts (it |
744 |
|
|
\&\*(L"ticks\*(R" the number of loop iterations), as it roughly corresponds with |
745 |
|
|
\&\f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR calls. |
746 |
root |
1.79 |
.IP "unsigned int ev_loop_depth (loop)" 4 |
747 |
|
|
.IX Item "unsigned int ev_loop_depth (loop)" |
748 |
|
|
Returns the number of times \f(CW\*(C`ev_loop\*(C'\fR was entered minus the number of |
749 |
|
|
times \f(CW\*(C`ev_loop\*(C'\fR was exited, in other words, the recursion depth. |
750 |
|
|
.Sp |
751 |
|
|
Outside \f(CW\*(C`ev_loop\*(C'\fR, this number is zero. In a callback, this number is |
752 |
|
|
\&\f(CW1\fR, unless \f(CW\*(C`ev_loop\*(C'\fR was invoked recursively (or from another thread), |
753 |
|
|
in which case it is higher. |
754 |
|
|
.Sp |
755 |
|
|
Leaving \f(CW\*(C`ev_loop\*(C'\fR abnormally (setjmp/longjmp, cancelling the thread |
756 |
|
|
etc.), doesn't count as exit. |
757 |
root |
1.6 |
.IP "unsigned int ev_backend (loop)" 4 |
758 |
|
|
.IX Item "unsigned int ev_backend (loop)" |
759 |
|
|
Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in |
760 |
root |
1.1 |
use. |
761 |
|
|
.IP "ev_tstamp ev_now (loop)" 4 |
762 |
|
|
.IX Item "ev_tstamp ev_now (loop)" |
763 |
|
|
Returns the current \*(L"event loop time\*(R", which is the time the event loop |
764 |
root |
1.9 |
received events and started processing them. This timestamp does not |
765 |
|
|
change as long as callbacks are being processed, and this is also the base |
766 |
|
|
time used for relative timers. You can treat it as the timestamp of the |
767 |
root |
1.54 |
event occurring (or more correctly, libev finding out about it). |
768 |
root |
1.71 |
.IP "ev_now_update (loop)" 4 |
769 |
|
|
.IX Item "ev_now_update (loop)" |
770 |
|
|
Establishes the current time by querying the kernel, updating the time |
771 |
|
|
returned by \f(CW\*(C`ev_now ()\*(C'\fR in the progress. This is a costly operation and |
772 |
|
|
is usually done automatically within \f(CW\*(C`ev_loop ()\*(C'\fR. |
773 |
|
|
.Sp |
774 |
|
|
This function is rarely useful, but when some event callback runs for a |
775 |
|
|
very long time without entering the event loop, updating libev's idea of |
776 |
|
|
the current time is a good idea. |
777 |
|
|
.Sp |
778 |
|
|
See also \*(L"The special problem of time updates\*(R" in the \f(CW\*(C`ev_timer\*(C'\fR section. |
779 |
root |
1.78 |
.IP "ev_suspend (loop)" 4 |
780 |
|
|
.IX Item "ev_suspend (loop)" |
781 |
|
|
.PD 0 |
782 |
|
|
.IP "ev_resume (loop)" 4 |
783 |
|
|
.IX Item "ev_resume (loop)" |
784 |
|
|
.PD |
785 |
|
|
These two functions suspend and resume a loop, for use when the loop is |
786 |
|
|
not used for a while and timeouts should not be processed. |
787 |
|
|
.Sp |
788 |
|
|
A typical use case would be an interactive program such as a game: When |
789 |
|
|
the user presses \f(CW\*(C`^Z\*(C'\fR to suspend the game and resumes it an hour later it |
790 |
|
|
would be best to handle timeouts as if no time had actually passed while |
791 |
|
|
the program was suspended. This can be achieved by calling \f(CW\*(C`ev_suspend\*(C'\fR |
792 |
|
|
in your \f(CW\*(C`SIGTSTP\*(C'\fR handler, sending yourself a \f(CW\*(C`SIGSTOP\*(C'\fR and calling |
793 |
|
|
\&\f(CW\*(C`ev_resume\*(C'\fR directly afterwards to resume timer processing. |
794 |
|
|
.Sp |
795 |
|
|
Effectively, all \f(CW\*(C`ev_timer\*(C'\fR watchers will be delayed by the time spend |
796 |
|
|
between \f(CW\*(C`ev_suspend\*(C'\fR and \f(CW\*(C`ev_resume\*(C'\fR, and all \f(CW\*(C`ev_periodic\*(C'\fR watchers |
797 |
|
|
will be rescheduled (that is, they will lose any events that would have |
798 |
|
|
occured while suspended). |
799 |
|
|
.Sp |
800 |
|
|
After calling \f(CW\*(C`ev_suspend\*(C'\fR you \fBmust not\fR call \fIany\fR function on the |
801 |
|
|
given loop other than \f(CW\*(C`ev_resume\*(C'\fR, and you \fBmust not\fR call \f(CW\*(C`ev_resume\*(C'\fR |
802 |
|
|
without a previous call to \f(CW\*(C`ev_suspend\*(C'\fR. |
803 |
|
|
.Sp |
804 |
|
|
Calling \f(CW\*(C`ev_suspend\*(C'\fR/\f(CW\*(C`ev_resume\*(C'\fR has the side effect of updating the |
805 |
|
|
event loop time (see \f(CW\*(C`ev_now_update\*(C'\fR). |
806 |
root |
1.1 |
.IP "ev_loop (loop, int flags)" 4 |
807 |
|
|
.IX Item "ev_loop (loop, int flags)" |
808 |
|
|
Finally, this is it, the event handler. This function usually is called |
809 |
|
|
after you initialised all your watchers and you want to start handling |
810 |
|
|
events. |
811 |
|
|
.Sp |
812 |
root |
1.8 |
If the flags argument is specified as \f(CW0\fR, it will not return until |
813 |
|
|
either no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called. |
814 |
root |
1.1 |
.Sp |
815 |
root |
1.9 |
Please note that an explicit \f(CW\*(C`ev_unloop\*(C'\fR is usually better than |
816 |
|
|
relying on all watchers to be stopped when deciding when a program has |
817 |
root |
1.71 |
finished (especially in interactive programs), but having a program |
818 |
|
|
that automatically loops as long as it has to and no longer by virtue |
819 |
|
|
of relying on its watchers stopping correctly, that is truly a thing of |
820 |
|
|
beauty. |
821 |
root |
1.9 |
.Sp |
822 |
root |
1.1 |
A flags value of \f(CW\*(C`EVLOOP_NONBLOCK\*(C'\fR will look for new events, will handle |
823 |
root |
1.71 |
those events and any already outstanding ones, but will not block your |
824 |
|
|
process in case there are no events and will return after one iteration of |
825 |
|
|
the loop. |
826 |
root |
1.1 |
.Sp |
827 |
|
|
A flags value of \f(CW\*(C`EVLOOP_ONESHOT\*(C'\fR will look for new events (waiting if |
828 |
root |
1.71 |
necessary) and will handle those and any already outstanding ones. It |
829 |
|
|
will block your process until at least one new event arrives (which could |
830 |
root |
1.73 |
be an event internal to libev itself, so there is no guarantee that a |
831 |
root |
1.71 |
user-registered callback will be called), and will return after one |
832 |
|
|
iteration of the loop. |
833 |
|
|
.Sp |
834 |
|
|
This is useful if you are waiting for some external event in conjunction |
835 |
|
|
with something not expressible using other libev watchers (i.e. "roll your |
836 |
|
|
own \f(CW\*(C`ev_loop\*(C'\fR"). However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is |
837 |
root |
1.8 |
usually a better approach for this kind of thing. |
838 |
|
|
.Sp |
839 |
|
|
Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does: |
840 |
|
|
.Sp |
841 |
root |
1.60 |
.Vb 10 |
842 |
|
|
\& \- Before the first iteration, call any pending watchers. |
843 |
|
|
\& * If EVFLAG_FORKCHECK was used, check for a fork. |
844 |
root |
1.71 |
\& \- If a fork was detected (by any means), queue and call all fork watchers. |
845 |
root |
1.60 |
\& \- Queue and call all prepare watchers. |
846 |
root |
1.71 |
\& \- If we have been forked, detach and recreate the kernel state |
847 |
|
|
\& as to not disturb the other process. |
848 |
root |
1.60 |
\& \- Update the kernel state with all outstanding changes. |
849 |
root |
1.71 |
\& \- Update the "event loop time" (ev_now ()). |
850 |
root |
1.60 |
\& \- Calculate for how long to sleep or block, if at all |
851 |
|
|
\& (active idle watchers, EVLOOP_NONBLOCK or not having |
852 |
|
|
\& any active watchers at all will result in not sleeping). |
853 |
|
|
\& \- Sleep if the I/O and timer collect interval say so. |
854 |
|
|
\& \- Block the process, waiting for any events. |
855 |
|
|
\& \- Queue all outstanding I/O (fd) events. |
856 |
root |
1.71 |
\& \- Update the "event loop time" (ev_now ()), and do time jump adjustments. |
857 |
|
|
\& \- Queue all expired timers. |
858 |
|
|
\& \- Queue all expired periodics. |
859 |
|
|
\& \- Unless any events are pending now, queue all idle watchers. |
860 |
root |
1.60 |
\& \- Queue all check watchers. |
861 |
|
|
\& \- Call all queued watchers in reverse order (i.e. check watchers first). |
862 |
root |
1.8 |
\& Signals and child watchers are implemented as I/O watchers, and will |
863 |
|
|
\& be handled here by queueing them when their watcher gets executed. |
864 |
root |
1.60 |
\& \- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
865 |
|
|
\& were used, or there are no active watchers, return, otherwise |
866 |
|
|
\& continue with step *. |
867 |
root |
1.2 |
.Ve |
868 |
root |
1.9 |
.Sp |
869 |
root |
1.60 |
Example: Queue some jobs and then loop until no events are outstanding |
870 |
root |
1.9 |
anymore. |
871 |
|
|
.Sp |
872 |
|
|
.Vb 4 |
873 |
|
|
\& ... queue jobs here, make sure they register event watchers as long |
874 |
|
|
\& ... as they still have work to do (even an idle watcher will do..) |
875 |
|
|
\& ev_loop (my_loop, 0); |
876 |
root |
1.71 |
\& ... jobs done or somebody called unloop. yeah! |
877 |
root |
1.9 |
.Ve |
878 |
root |
1.1 |
.IP "ev_unloop (loop, how)" 4 |
879 |
|
|
.IX Item "ev_unloop (loop, how)" |
880 |
|
|
Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it |
881 |
|
|
has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either |
882 |
|
|
\&\f(CW\*(C`EVUNLOOP_ONE\*(C'\fR, which will make the innermost \f(CW\*(C`ev_loop\*(C'\fR call return, or |
883 |
|
|
\&\f(CW\*(C`EVUNLOOP_ALL\*(C'\fR, which will make all nested \f(CW\*(C`ev_loop\*(C'\fR calls return. |
884 |
root |
1.60 |
.Sp |
885 |
|
|
This \*(L"unloop state\*(R" will be cleared when entering \f(CW\*(C`ev_loop\*(C'\fR again. |
886 |
root |
1.72 |
.Sp |
887 |
|
|
It is safe to call \f(CW\*(C`ev_unloop\*(C'\fR from otuside any \f(CW\*(C`ev_loop\*(C'\fR calls. |
888 |
root |
1.1 |
.IP "ev_ref (loop)" 4 |
889 |
|
|
.IX Item "ev_ref (loop)" |
890 |
|
|
.PD 0 |
891 |
|
|
.IP "ev_unref (loop)" 4 |
892 |
|
|
.IX Item "ev_unref (loop)" |
893 |
|
|
.PD |
894 |
|
|
Ref/unref can be used to add or remove a reference count on the event |
895 |
|
|
loop: Every watcher keeps one reference, and as long as the reference |
896 |
root |
1.71 |
count is nonzero, \f(CW\*(C`ev_loop\*(C'\fR will not return on its own. |
897 |
|
|
.Sp |
898 |
|
|
If you have a watcher you never unregister that should not keep \f(CW\*(C`ev_loop\*(C'\fR |
899 |
|
|
from returning, call \fIev_unref()\fR after starting, and \fIev_ref()\fR before |
900 |
|
|
stopping it. |
901 |
|
|
.Sp |
902 |
root |
1.78 |
As an example, libev itself uses this for its internal signal pipe: It |
903 |
|
|
is not visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from |
904 |
|
|
exiting if no event watchers registered by it are active. It is also an |
905 |
|
|
excellent way to do this for generic recurring timers or from within |
906 |
|
|
third-party libraries. Just remember to \fIunref after start\fR and \fIref |
907 |
|
|
before stop\fR (but only if the watcher wasn't active before, or was active |
908 |
|
|
before, respectively. Note also that libev might stop watchers itself |
909 |
|
|
(e.g. non-repeating timers) in which case you have to \f(CW\*(C`ev_ref\*(C'\fR |
910 |
|
|
in the callback). |
911 |
root |
1.9 |
.Sp |
912 |
root |
1.28 |
Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR |
913 |
root |
1.9 |
running when nothing else is active. |
914 |
|
|
.Sp |
915 |
|
|
.Vb 4 |
916 |
root |
1.73 |
\& ev_signal exitsig; |
917 |
root |
1.68 |
\& ev_signal_init (&exitsig, sig_cb, SIGINT); |
918 |
|
|
\& ev_signal_start (loop, &exitsig); |
919 |
|
|
\& evf_unref (loop); |
920 |
root |
1.9 |
.Ve |
921 |
|
|
.Sp |
922 |
root |
1.28 |
Example: For some weird reason, unregister the above signal handler again. |
923 |
root |
1.9 |
.Sp |
924 |
|
|
.Vb 2 |
925 |
root |
1.68 |
\& ev_ref (loop); |
926 |
|
|
\& ev_signal_stop (loop, &exitsig); |
927 |
root |
1.9 |
.Ve |
928 |
root |
1.57 |
.IP "ev_set_io_collect_interval (loop, ev_tstamp interval)" 4 |
929 |
|
|
.IX Item "ev_set_io_collect_interval (loop, ev_tstamp interval)" |
930 |
root |
1.56 |
.PD 0 |
931 |
root |
1.57 |
.IP "ev_set_timeout_collect_interval (loop, ev_tstamp interval)" 4 |
932 |
|
|
.IX Item "ev_set_timeout_collect_interval (loop, ev_tstamp interval)" |
933 |
root |
1.56 |
.PD |
934 |
|
|
These advanced functions influence the time that libev will spend waiting |
935 |
root |
1.71 |
for events. Both time intervals are by default \f(CW0\fR, meaning that libev |
936 |
|
|
will try to invoke timer/periodic callbacks and I/O callbacks with minimum |
937 |
|
|
latency. |
938 |
root |
1.56 |
.Sp |
939 |
|
|
Setting these to a higher value (the \f(CW\*(C`interval\*(C'\fR \fImust\fR be >= \f(CW0\fR) |
940 |
root |
1.71 |
allows libev to delay invocation of I/O and timer/periodic callbacks |
941 |
|
|
to increase efficiency of loop iterations (or to increase power-saving |
942 |
|
|
opportunities). |
943 |
|
|
.Sp |
944 |
|
|
The idea is that sometimes your program runs just fast enough to handle |
945 |
|
|
one (or very few) event(s) per loop iteration. While this makes the |
946 |
|
|
program responsive, it also wastes a lot of \s-1CPU\s0 time to poll for new |
947 |
root |
1.56 |
events, especially with backends like \f(CW\*(C`select ()\*(C'\fR which have a high |
948 |
|
|
overhead for the actual polling but can deliver many events at once. |
949 |
|
|
.Sp |
950 |
|
|
By setting a higher \fIio collect interval\fR you allow libev to spend more |
951 |
|
|
time collecting I/O events, so you can handle more events per iteration, |
952 |
|
|
at the cost of increasing latency. Timeouts (both \f(CW\*(C`ev_periodic\*(C'\fR and |
953 |
root |
1.58 |
\&\f(CW\*(C`ev_timer\*(C'\fR) will be not affected. Setting this to a non-null value will |
954 |
root |
1.79 |
introduce an additional \f(CW\*(C`ev_sleep ()\*(C'\fR call into most loop iterations. The |
955 |
|
|
sleep time ensures that libev will not poll for I/O events more often then |
956 |
|
|
once per this interval, on average. |
957 |
root |
1.56 |
.Sp |
958 |
|
|
Likewise, by setting a higher \fItimeout collect interval\fR you allow libev |
959 |
|
|
to spend more time collecting timeouts, at the expense of increased |
960 |
root |
1.71 |
latency/jitter/inexactness (the watcher callback will be called |
961 |
|
|
later). \f(CW\*(C`ev_io\*(C'\fR watchers will not be affected. Setting this to a non-null |
962 |
|
|
value will not introduce any overhead in libev. |
963 |
root |
1.56 |
.Sp |
964 |
root |
1.68 |
Many (busy) programs can usually benefit by setting the I/O collect |
965 |
root |
1.57 |
interval to a value near \f(CW0.1\fR or so, which is often enough for |
966 |
|
|
interactive servers (of course not for games), likewise for timeouts. It |
967 |
|
|
usually doesn't make much sense to set it to a lower value than \f(CW0.01\fR, |
968 |
root |
1.79 |
as this approaches the timing granularity of most systems. Note that if |
969 |
|
|
you do transactions with the outside world and you can't increase the |
970 |
|
|
parallelity, then this setting will limit your transaction rate (if you |
971 |
|
|
need to poll once per transaction and the I/O collect interval is 0.01, |
972 |
|
|
then you can't do more than 100 transations per second). |
973 |
root |
1.71 |
.Sp |
974 |
|
|
Setting the \fItimeout collect interval\fR can improve the opportunity for |
975 |
|
|
saving power, as the program will \*(L"bundle\*(R" timer callback invocations that |
976 |
|
|
are \*(L"near\*(R" in time together, by delaying some, thus reducing the number of |
977 |
|
|
times the process sleeps and wakes up again. Another useful technique to |
978 |
|
|
reduce iterations/wake\-ups is to use \f(CW\*(C`ev_periodic\*(C'\fR watchers and make sure |
979 |
|
|
they fire on, say, one-second boundaries only. |
980 |
root |
1.79 |
.Sp |
981 |
|
|
Example: we only need 0.1s timeout granularity, and we wish not to poll |
982 |
|
|
more often than 100 times per second: |
983 |
|
|
.Sp |
984 |
|
|
.Vb 2 |
985 |
|
|
\& ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1); |
986 |
|
|
\& ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
987 |
|
|
.Ve |
988 |
|
|
.IP "ev_invoke_pending (loop)" 4 |
989 |
|
|
.IX Item "ev_invoke_pending (loop)" |
990 |
|
|
This call will simply invoke all pending watchers while resetting their |
991 |
|
|
pending state. Normally, \f(CW\*(C`ev_loop\*(C'\fR does this automatically when required, |
992 |
|
|
but when overriding the invoke callback this call comes handy. |
993 |
|
|
.IP "int ev_pending_count (loop)" 4 |
994 |
|
|
.IX Item "int ev_pending_count (loop)" |
995 |
|
|
Returns the number of pending watchers \- zero indicates that no watchers |
996 |
|
|
are pending. |
997 |
|
|
.IP "ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(\s-1EV_P\s0))" 4 |
998 |
|
|
.IX Item "ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))" |
999 |
|
|
This overrides the invoke pending functionality of the loop: Instead of |
1000 |
|
|
invoking all pending watchers when there are any, \f(CW\*(C`ev_loop\*(C'\fR will call |
1001 |
|
|
this callback instead. This is useful, for example, when you want to |
1002 |
|
|
invoke the actual watchers inside another context (another thread etc.). |
1003 |
|
|
.Sp |
1004 |
|
|
If you want to reset the callback, use \f(CW\*(C`ev_invoke_pending\*(C'\fR as new |
1005 |
|
|
callback. |
1006 |
|
|
.IP "ev_set_loop_release_cb (loop, void (*release)(\s-1EV_P\s0), void (*acquire)(\s-1EV_P\s0))" 4 |
1007 |
|
|
.IX Item "ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))" |
1008 |
|
|
Sometimes you want to share the same loop between multiple threads. This |
1009 |
|
|
can be done relatively simply by putting mutex_lock/unlock calls around |
1010 |
|
|
each call to a libev function. |
1011 |
|
|
.Sp |
1012 |
|
|
However, \f(CW\*(C`ev_loop\*(C'\fR can run an indefinite time, so it is not feasible to |
1013 |
|
|
wait for it to return. One way around this is to wake up the loop via |
1014 |
|
|
\&\f(CW\*(C`ev_unloop\*(C'\fR and \f(CW\*(C`av_async_send\*(C'\fR, another way is to set these \fIrelease\fR |
1015 |
|
|
and \fIacquire\fR callbacks on the loop. |
1016 |
|
|
.Sp |
1017 |
|
|
When set, then \f(CW\*(C`release\*(C'\fR will be called just before the thread is |
1018 |
|
|
suspended waiting for new events, and \f(CW\*(C`acquire\*(C'\fR is called just |
1019 |
|
|
afterwards. |
1020 |
|
|
.Sp |
1021 |
|
|
Ideally, \f(CW\*(C`release\*(C'\fR will just call your mutex_unlock function, and |
1022 |
|
|
\&\f(CW\*(C`acquire\*(C'\fR will just call the mutex_lock function again. |
1023 |
|
|
.Sp |
1024 |
|
|
While event loop modifications are allowed between invocations of |
1025 |
|
|
\&\f(CW\*(C`release\*(C'\fR and \f(CW\*(C`acquire\*(C'\fR (that's their only purpose after all), no |
1026 |
|
|
modifications done will affect the event loop, i.e. adding watchers will |
1027 |
|
|
have no effect on the set of file descriptors being watched, or the time |
1028 |
|
|
waited. USe an \f(CW\*(C`ev_async\*(C'\fR watcher to wake up \f(CW\*(C`ev_loop\*(C'\fR when you want it |
1029 |
|
|
to take note of any changes you made. |
1030 |
|
|
.Sp |
1031 |
|
|
In theory, threads executing \f(CW\*(C`ev_loop\*(C'\fR will be async-cancel safe between |
1032 |
|
|
invocations of \f(CW\*(C`release\*(C'\fR and \f(CW\*(C`acquire\*(C'\fR. |
1033 |
|
|
.Sp |
1034 |
|
|
See also the locking example in the \f(CW\*(C`THREADS\*(C'\fR section later in this |
1035 |
|
|
document. |
1036 |
|
|
.IP "ev_set_userdata (loop, void *data)" 4 |
1037 |
|
|
.IX Item "ev_set_userdata (loop, void *data)" |
1038 |
|
|
.PD 0 |
1039 |
|
|
.IP "ev_userdata (loop)" 4 |
1040 |
|
|
.IX Item "ev_userdata (loop)" |
1041 |
|
|
.PD |
1042 |
|
|
Set and retrieve a single \f(CW\*(C`void *\*(C'\fR associated with a loop. When |
1043 |
|
|
\&\f(CW\*(C`ev_set_userdata\*(C'\fR has never been called, then \f(CW\*(C`ev_userdata\*(C'\fR returns |
1044 |
|
|
\&\f(CW0.\fR |
1045 |
|
|
.Sp |
1046 |
|
|
These two functions can be used to associate arbitrary data with a loop, |
1047 |
|
|
and are intended solely for the \f(CW\*(C`invoke_pending_cb\*(C'\fR, \f(CW\*(C`release\*(C'\fR and |
1048 |
|
|
\&\f(CW\*(C`acquire\*(C'\fR callbacks described above, but of course can be (ab\-)used for |
1049 |
|
|
any other purpose as well. |
1050 |
root |
1.67 |
.IP "ev_loop_verify (loop)" 4 |
1051 |
|
|
.IX Item "ev_loop_verify (loop)" |
1052 |
|
|
This function only does something when \f(CW\*(C`EV_VERIFY\*(C'\fR support has been |
1053 |
root |
1.73 |
compiled in, which is the default for non-minimal builds. It tries to go |
1054 |
root |
1.71 |
through all internal structures and checks them for validity. If anything |
1055 |
|
|
is found to be inconsistent, it will print an error message to standard |
1056 |
|
|
error and call \f(CW\*(C`abort ()\*(C'\fR. |
1057 |
root |
1.67 |
.Sp |
1058 |
|
|
This can be used to catch bugs inside libev itself: under normal |
1059 |
|
|
circumstances, this function will never abort as of course libev keeps its |
1060 |
|
|
data structures consistent. |
1061 |
root |
1.1 |
.SH "ANATOMY OF A WATCHER" |
1062 |
|
|
.IX Header "ANATOMY OF A WATCHER" |
1063 |
root |
1.73 |
In the following description, uppercase \f(CW\*(C`TYPE\*(C'\fR in names stands for the |
1064 |
|
|
watcher type, e.g. \f(CW\*(C`ev_TYPE_start\*(C'\fR can mean \f(CW\*(C`ev_timer_start\*(C'\fR for timer |
1065 |
|
|
watchers and \f(CW\*(C`ev_io_start\*(C'\fR for I/O watchers. |
1066 |
|
|
.PP |
1067 |
root |
1.1 |
A watcher is a structure that you create and register to record your |
1068 |
|
|
interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to |
1069 |
|
|
become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that: |
1070 |
|
|
.PP |
1071 |
|
|
.Vb 5 |
1072 |
root |
1.73 |
\& static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
1073 |
root |
1.68 |
\& { |
1074 |
|
|
\& ev_io_stop (w); |
1075 |
|
|
\& ev_unloop (loop, EVUNLOOP_ALL); |
1076 |
|
|
\& } |
1077 |
|
|
\& |
1078 |
|
|
\& struct ev_loop *loop = ev_default_loop (0); |
1079 |
root |
1.73 |
\& |
1080 |
|
|
\& ev_io stdin_watcher; |
1081 |
|
|
\& |
1082 |
root |
1.68 |
\& ev_init (&stdin_watcher, my_cb); |
1083 |
|
|
\& ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
1084 |
|
|
\& ev_io_start (loop, &stdin_watcher); |
1085 |
root |
1.73 |
\& |
1086 |
root |
1.68 |
\& ev_loop (loop, 0); |
1087 |
root |
1.1 |
.Ve |
1088 |
|
|
.PP |
1089 |
|
|
As you can see, you are responsible for allocating the memory for your |
1090 |
root |
1.73 |
watcher structures (and it is \fIusually\fR a bad idea to do this on the |
1091 |
|
|
stack). |
1092 |
|
|
.PP |
1093 |
|
|
Each watcher has an associated watcher structure (called \f(CW\*(C`struct ev_TYPE\*(C'\fR |
1094 |
|
|
or simply \f(CW\*(C`ev_TYPE\*(C'\fR, as typedefs are provided for all watcher structs). |
1095 |
root |
1.1 |
.PP |
1096 |
|
|
Each watcher structure must be initialised by a call to \f(CW\*(C`ev_init |
1097 |
|
|
(watcher *, callback)\*(C'\fR, which expects a callback to be provided. This |
1098 |
root |
1.68 |
callback gets invoked each time the event occurs (or, in the case of I/O |
1099 |
root |
1.1 |
watchers, each time the event loop detects that the file descriptor given |
1100 |
|
|
is readable and/or writable). |
1101 |
|
|
.PP |
1102 |
root |
1.73 |
Each watcher type further has its own \f(CW\*(C`ev_TYPE_set (watcher *, ...)\*(C'\fR |
1103 |
|
|
macro to configure it, with arguments specific to the watcher type. There |
1104 |
|
|
is also a macro to combine initialisation and setting in one call: \f(CW\*(C`ev_TYPE_init (watcher *, callback, ...)\*(C'\fR. |
1105 |
root |
1.1 |
.PP |
1106 |
|
|
To make the watcher actually watch out for events, you have to start it |
1107 |
root |
1.73 |
with a watcher-specific start function (\f(CW\*(C`ev_TYPE_start (loop, watcher |
1108 |
root |
1.1 |
*)\*(C'\fR), and you can stop watching for events at any time by calling the |
1109 |
root |
1.73 |
corresponding stop function (\f(CW\*(C`ev_TYPE_stop (loop, watcher *)\*(C'\fR. |
1110 |
root |
1.1 |
.PP |
1111 |
|
|
As long as your watcher is active (has been started but not stopped) you |
1112 |
|
|
must not touch the values stored in it. Most specifically you must never |
1113 |
root |
1.73 |
reinitialise it or call its \f(CW\*(C`ev_TYPE_set\*(C'\fR macro. |
1114 |
root |
1.1 |
.PP |
1115 |
|
|
Each and every callback receives the event loop pointer as first, the |
1116 |
|
|
registered watcher structure as second, and a bitset of received events as |
1117 |
|
|
third argument. |
1118 |
|
|
.PP |
1119 |
|
|
The received events usually include a single bit per event type received |
1120 |
|
|
(you can receive multiple events at the same time). The possible bit masks |
1121 |
|
|
are: |
1122 |
|
|
.ie n .IP """EV_READ""" 4 |
1123 |
|
|
.el .IP "\f(CWEV_READ\fR" 4 |
1124 |
|
|
.IX Item "EV_READ" |
1125 |
|
|
.PD 0 |
1126 |
|
|
.ie n .IP """EV_WRITE""" 4 |
1127 |
|
|
.el .IP "\f(CWEV_WRITE\fR" 4 |
1128 |
|
|
.IX Item "EV_WRITE" |
1129 |
|
|
.PD |
1130 |
|
|
The file descriptor in the \f(CW\*(C`ev_io\*(C'\fR watcher has become readable and/or |
1131 |
|
|
writable. |
1132 |
|
|
.ie n .IP """EV_TIMEOUT""" 4 |
1133 |
|
|
.el .IP "\f(CWEV_TIMEOUT\fR" 4 |
1134 |
|
|
.IX Item "EV_TIMEOUT" |
1135 |
|
|
The \f(CW\*(C`ev_timer\*(C'\fR watcher has timed out. |
1136 |
|
|
.ie n .IP """EV_PERIODIC""" 4 |
1137 |
|
|
.el .IP "\f(CWEV_PERIODIC\fR" 4 |
1138 |
|
|
.IX Item "EV_PERIODIC" |
1139 |
|
|
The \f(CW\*(C`ev_periodic\*(C'\fR watcher has timed out. |
1140 |
|
|
.ie n .IP """EV_SIGNAL""" 4 |
1141 |
|
|
.el .IP "\f(CWEV_SIGNAL\fR" 4 |
1142 |
|
|
.IX Item "EV_SIGNAL" |
1143 |
|
|
The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread. |
1144 |
|
|
.ie n .IP """EV_CHILD""" 4 |
1145 |
|
|
.el .IP "\f(CWEV_CHILD\fR" 4 |
1146 |
|
|
.IX Item "EV_CHILD" |
1147 |
|
|
The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change. |
1148 |
root |
1.22 |
.ie n .IP """EV_STAT""" 4 |
1149 |
|
|
.el .IP "\f(CWEV_STAT\fR" 4 |
1150 |
|
|
.IX Item "EV_STAT" |
1151 |
|
|
The path specified in the \f(CW\*(C`ev_stat\*(C'\fR watcher changed its attributes somehow. |
1152 |
root |
1.1 |
.ie n .IP """EV_IDLE""" 4 |
1153 |
|
|
.el .IP "\f(CWEV_IDLE\fR" 4 |
1154 |
|
|
.IX Item "EV_IDLE" |
1155 |
|
|
The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do. |
1156 |
|
|
.ie n .IP """EV_PREPARE""" 4 |
1157 |
|
|
.el .IP "\f(CWEV_PREPARE\fR" 4 |
1158 |
|
|
.IX Item "EV_PREPARE" |
1159 |
|
|
.PD 0 |
1160 |
|
|
.ie n .IP """EV_CHECK""" 4 |
1161 |
|
|
.el .IP "\f(CWEV_CHECK\fR" 4 |
1162 |
|
|
.IX Item "EV_CHECK" |
1163 |
|
|
.PD |
1164 |
|
|
All \f(CW\*(C`ev_prepare\*(C'\fR watchers are invoked just \fIbefore\fR \f(CW\*(C`ev_loop\*(C'\fR starts |
1165 |
|
|
to gather new events, and all \f(CW\*(C`ev_check\*(C'\fR watchers are invoked just after |
1166 |
|
|
\&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any |
1167 |
|
|
received events. Callbacks of both watcher types can start and stop as |
1168 |
|
|
many watchers as they want, and all of them will be taken into account |
1169 |
|
|
(for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep |
1170 |
|
|
\&\f(CW\*(C`ev_loop\*(C'\fR from blocking). |
1171 |
root |
1.24 |
.ie n .IP """EV_EMBED""" 4 |
1172 |
|
|
.el .IP "\f(CWEV_EMBED\fR" 4 |
1173 |
|
|
.IX Item "EV_EMBED" |
1174 |
|
|
The embedded event loop specified in the \f(CW\*(C`ev_embed\*(C'\fR watcher needs attention. |
1175 |
|
|
.ie n .IP """EV_FORK""" 4 |
1176 |
|
|
.el .IP "\f(CWEV_FORK\fR" 4 |
1177 |
|
|
.IX Item "EV_FORK" |
1178 |
|
|
The event loop has been resumed in the child process after fork (see |
1179 |
|
|
\&\f(CW\*(C`ev_fork\*(C'\fR). |
1180 |
root |
1.61 |
.ie n .IP """EV_ASYNC""" 4 |
1181 |
|
|
.el .IP "\f(CWEV_ASYNC\fR" 4 |
1182 |
|
|
.IX Item "EV_ASYNC" |
1183 |
|
|
The given async watcher has been asynchronously notified (see \f(CW\*(C`ev_async\*(C'\fR). |
1184 |
root |
1.78 |
.ie n .IP """EV_CUSTOM""" 4 |
1185 |
|
|
.el .IP "\f(CWEV_CUSTOM\fR" 4 |
1186 |
|
|
.IX Item "EV_CUSTOM" |
1187 |
|
|
Not ever sent (or otherwise used) by libev itself, but can be freely used |
1188 |
|
|
by libev users to signal watchers (e.g. via \f(CW\*(C`ev_feed_event\*(C'\fR). |
1189 |
root |
1.1 |
.ie n .IP """EV_ERROR""" 4 |
1190 |
|
|
.el .IP "\f(CWEV_ERROR\fR" 4 |
1191 |
|
|
.IX Item "EV_ERROR" |
1192 |
root |
1.68 |
An unspecified error has occurred, the watcher has been stopped. This might |
1193 |
root |
1.1 |
happen because the watcher could not be properly started because libev |
1194 |
|
|
ran out of memory, a file descriptor was found to be closed or any other |
1195 |
root |
1.73 |
problem. Libev considers these application bugs. |
1196 |
|
|
.Sp |
1197 |
|
|
You best act on it by reporting the problem and somehow coping with the |
1198 |
|
|
watcher being stopped. Note that well-written programs should not receive |
1199 |
|
|
an error ever, so when your watcher receives it, this usually indicates a |
1200 |
|
|
bug in your program. |
1201 |
root |
1.1 |
.Sp |
1202 |
root |
1.71 |
Libev will usually signal a few \*(L"dummy\*(R" events together with an error, for |
1203 |
|
|
example it might indicate that a fd is readable or writable, and if your |
1204 |
|
|
callbacks is well-written it can just attempt the operation and cope with |
1205 |
|
|
the error from \fIread()\fR or \fIwrite()\fR. This will not work in multi-threaded |
1206 |
|
|
programs, though, as the fd could already be closed and reused for another |
1207 |
|
|
thing, so beware. |
1208 |
root |
1.79 |
.SS "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0" |
1209 |
root |
1.17 |
.IX Subsection "GENERIC WATCHER FUNCTIONS" |
1210 |
root |
1.11 |
.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4 |
1211 |
|
|
.el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4 |
1212 |
|
|
.IX Item "ev_init (ev_TYPE *watcher, callback)" |
1213 |
|
|
This macro initialises the generic portion of a watcher. The contents |
1214 |
|
|
of the watcher object can be arbitrary (so \f(CW\*(C`malloc\*(C'\fR will do). Only |
1215 |
|
|
the generic parts of the watcher are initialised, you \fIneed\fR to call |
1216 |
|
|
the type-specific \f(CW\*(C`ev_TYPE_set\*(C'\fR macro afterwards to initialise the |
1217 |
|
|
type-specific parts. For each type there is also a \f(CW\*(C`ev_TYPE_init\*(C'\fR macro |
1218 |
|
|
which rolls both calls into one. |
1219 |
|
|
.Sp |
1220 |
|
|
You can reinitialise a watcher at any time as long as it has been stopped |
1221 |
|
|
(or never started) and there are no pending events outstanding. |
1222 |
|
|
.Sp |
1223 |
root |
1.73 |
The callback is always of type \f(CW\*(C`void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
1224 |
root |
1.11 |
int revents)\*(C'\fR. |
1225 |
root |
1.71 |
.Sp |
1226 |
|
|
Example: Initialise an \f(CW\*(C`ev_io\*(C'\fR watcher in two steps. |
1227 |
|
|
.Sp |
1228 |
|
|
.Vb 3 |
1229 |
|
|
\& ev_io w; |
1230 |
|
|
\& ev_init (&w, my_cb); |
1231 |
|
|
\& ev_io_set (&w, STDIN_FILENO, EV_READ); |
1232 |
|
|
.Ve |
1233 |
root |
1.11 |
.ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4 |
1234 |
|
|
.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4 |
1235 |
|
|
.IX Item "ev_TYPE_set (ev_TYPE *, [args])" |
1236 |
|
|
This macro initialises the type-specific parts of a watcher. You need to |
1237 |
|
|
call \f(CW\*(C`ev_init\*(C'\fR at least once before you call this macro, but you can |
1238 |
|
|
call \f(CW\*(C`ev_TYPE_set\*(C'\fR any number of times. You must not, however, call this |
1239 |
|
|
macro on a watcher that is active (it can be pending, however, which is a |
1240 |
|
|
difference to the \f(CW\*(C`ev_init\*(C'\fR macro). |
1241 |
|
|
.Sp |
1242 |
|
|
Although some watcher types do not have type-specific arguments |
1243 |
|
|
(e.g. \f(CW\*(C`ev_prepare\*(C'\fR) you still need to call its \f(CW\*(C`set\*(C'\fR macro. |
1244 |
root |
1.71 |
.Sp |
1245 |
|
|
See \f(CW\*(C`ev_init\*(C'\fR, above, for an example. |
1246 |
root |
1.11 |
.ie n .IP """ev_TYPE_init"" (ev_TYPE *watcher, callback, [args])" 4 |
1247 |
|
|
.el .IP "\f(CWev_TYPE_init\fR (ev_TYPE *watcher, callback, [args])" 4 |
1248 |
|
|
.IX Item "ev_TYPE_init (ev_TYPE *watcher, callback, [args])" |
1249 |
root |
1.68 |
This convenience macro rolls both \f(CW\*(C`ev_init\*(C'\fR and \f(CW\*(C`ev_TYPE_set\*(C'\fR macro |
1250 |
|
|
calls into a single call. This is the most convenient method to initialise |
1251 |
root |
1.11 |
a watcher. The same limitations apply, of course. |
1252 |
root |
1.71 |
.Sp |
1253 |
|
|
Example: Initialise and set an \f(CW\*(C`ev_io\*(C'\fR watcher in one step. |
1254 |
|
|
.Sp |
1255 |
|
|
.Vb 1 |
1256 |
|
|
\& ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
1257 |
|
|
.Ve |
1258 |
root |
1.11 |
.ie n .IP """ev_TYPE_start"" (loop *, ev_TYPE *watcher)" 4 |
1259 |
|
|
.el .IP "\f(CWev_TYPE_start\fR (loop *, ev_TYPE *watcher)" 4 |
1260 |
|
|
.IX Item "ev_TYPE_start (loop *, ev_TYPE *watcher)" |
1261 |
|
|
Starts (activates) the given watcher. Only active watchers will receive |
1262 |
|
|
events. If the watcher is already active nothing will happen. |
1263 |
root |
1.71 |
.Sp |
1264 |
|
|
Example: Start the \f(CW\*(C`ev_io\*(C'\fR watcher that is being abused as example in this |
1265 |
|
|
whole section. |
1266 |
|
|
.Sp |
1267 |
|
|
.Vb 1 |
1268 |
|
|
\& ev_io_start (EV_DEFAULT_UC, &w); |
1269 |
|
|
.Ve |
1270 |
root |
1.11 |
.ie n .IP """ev_TYPE_stop"" (loop *, ev_TYPE *watcher)" 4 |
1271 |
|
|
.el .IP "\f(CWev_TYPE_stop\fR (loop *, ev_TYPE *watcher)" 4 |
1272 |
|
|
.IX Item "ev_TYPE_stop (loop *, ev_TYPE *watcher)" |
1273 |
root |
1.72 |
Stops the given watcher if active, and clears the pending status (whether |
1274 |
|
|
the watcher was active or not). |
1275 |
|
|
.Sp |
1276 |
|
|
It is possible that stopped watchers are pending \- for example, |
1277 |
|
|
non-repeating timers are being stopped when they become pending \- but |
1278 |
|
|
calling \f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor |
1279 |
|
|
pending. If you want to free or reuse the memory used by the watcher it is |
1280 |
|
|
therefore a good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function. |
1281 |
root |
1.11 |
.IP "bool ev_is_active (ev_TYPE *watcher)" 4 |
1282 |
|
|
.IX Item "bool ev_is_active (ev_TYPE *watcher)" |
1283 |
|
|
Returns a true value iff the watcher is active (i.e. it has been started |
1284 |
|
|
and not yet been stopped). As long as a watcher is active you must not modify |
1285 |
|
|
it. |
1286 |
|
|
.IP "bool ev_is_pending (ev_TYPE *watcher)" 4 |
1287 |
|
|
.IX Item "bool ev_is_pending (ev_TYPE *watcher)" |
1288 |
|
|
Returns a true value iff the watcher is pending, (i.e. it has outstanding |
1289 |
|
|
events but its callback has not yet been invoked). As long as a watcher |
1290 |
|
|
is pending (but not active) you must not call an init function on it (but |
1291 |
root |
1.43 |
\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe), you must not change its priority, and you must |
1292 |
|
|
make sure the watcher is available to libev (e.g. you cannot \f(CW\*(C`free ()\*(C'\fR |
1293 |
|
|
it). |
1294 |
root |
1.29 |
.IP "callback ev_cb (ev_TYPE *watcher)" 4 |
1295 |
|
|
.IX Item "callback ev_cb (ev_TYPE *watcher)" |
1296 |
root |
1.11 |
Returns the callback currently set on the watcher. |
1297 |
|
|
.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4 |
1298 |
|
|
.IX Item "ev_cb_set (ev_TYPE *watcher, callback)" |
1299 |
|
|
Change the callback. You can change the callback at virtually any time |
1300 |
|
|
(modulo threads). |
1301 |
root |
1.37 |
.IP "ev_set_priority (ev_TYPE *watcher, priority)" 4 |
1302 |
|
|
.IX Item "ev_set_priority (ev_TYPE *watcher, priority)" |
1303 |
|
|
.PD 0 |
1304 |
|
|
.IP "int ev_priority (ev_TYPE *watcher)" 4 |
1305 |
|
|
.IX Item "int ev_priority (ev_TYPE *watcher)" |
1306 |
|
|
.PD |
1307 |
|
|
Set and query the priority of the watcher. The priority is a small |
1308 |
|
|
integer between \f(CW\*(C`EV_MAXPRI\*(C'\fR (default: \f(CW2\fR) and \f(CW\*(C`EV_MINPRI\*(C'\fR |
1309 |
|
|
(default: \f(CW\*(C`\-2\*(C'\fR). Pending watchers with higher priority will be invoked |
1310 |
|
|
before watchers with lower priority, but priority will not keep watchers |
1311 |
|
|
from being executed (except for \f(CW\*(C`ev_idle\*(C'\fR watchers). |
1312 |
|
|
.Sp |
1313 |
|
|
If you need to suppress invocation when higher priority events are pending |
1314 |
|
|
you need to look at \f(CW\*(C`ev_idle\*(C'\fR watchers, which provide this functionality. |
1315 |
|
|
.Sp |
1316 |
root |
1.43 |
You \fImust not\fR change the priority of a watcher as long as it is active or |
1317 |
|
|
pending. |
1318 |
|
|
.Sp |
1319 |
root |
1.78 |
Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR is |
1320 |
|
|
fine, as long as you do not mind that the priority value you query might |
1321 |
|
|
or might not have been clamped to the valid range. |
1322 |
|
|
.Sp |
1323 |
root |
1.37 |
The default priority used by watchers when no priority has been set is |
1324 |
|
|
always \f(CW0\fR, which is supposed to not be too high and not be too low :). |
1325 |
|
|
.Sp |
1326 |
root |
1.78 |
See \*(L"\s-1WATCHER\s0 \s-1PRIORITY\s0 \s-1MODELS\s0\*(R", below, for a more thorough treatment of |
1327 |
|
|
priorities. |
1328 |
root |
1.43 |
.IP "ev_invoke (loop, ev_TYPE *watcher, int revents)" 4 |
1329 |
|
|
.IX Item "ev_invoke (loop, ev_TYPE *watcher, int revents)" |
1330 |
|
|
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 |
1331 |
|
|
\&\f(CW\*(C`loop\*(C'\fR nor \f(CW\*(C`revents\*(C'\fR need to be valid as long as the watcher callback |
1332 |
root |
1.71 |
can deal with that fact, as both are simply passed through to the |
1333 |
|
|
callback. |
1334 |
root |
1.43 |
.IP "int ev_clear_pending (loop, ev_TYPE *watcher)" 4 |
1335 |
|
|
.IX Item "int ev_clear_pending (loop, ev_TYPE *watcher)" |
1336 |
root |
1.71 |
If the watcher is pending, this function clears its pending status and |
1337 |
|
|
returns its \f(CW\*(C`revents\*(C'\fR bitset (as if its callback was invoked). If the |
1338 |
root |
1.43 |
watcher isn't pending it does nothing and returns \f(CW0\fR. |
1339 |
root |
1.71 |
.Sp |
1340 |
|
|
Sometimes it can be useful to \*(L"poll\*(R" a watcher instead of waiting for its |
1341 |
|
|
callback to be invoked, which can be accomplished with this function. |
1342 |
root |
1.79 |
.SS "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0" |
1343 |
root |
1.1 |
.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER" |
1344 |
|
|
Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change |
1345 |
root |
1.71 |
and read at any time: libev will completely ignore it. This can be used |
1346 |
root |
1.1 |
to associate arbitrary data with your watcher. If you need more data and |
1347 |
|
|
don't want to allocate memory and store a pointer to it in that data |
1348 |
|
|
member, you can also \*(L"subclass\*(R" the watcher type and provide your own |
1349 |
|
|
data: |
1350 |
|
|
.PP |
1351 |
|
|
.Vb 7 |
1352 |
root |
1.68 |
\& struct my_io |
1353 |
|
|
\& { |
1354 |
root |
1.73 |
\& ev_io io; |
1355 |
root |
1.68 |
\& int otherfd; |
1356 |
|
|
\& void *somedata; |
1357 |
|
|
\& struct whatever *mostinteresting; |
1358 |
root |
1.71 |
\& }; |
1359 |
|
|
\& |
1360 |
|
|
\& ... |
1361 |
|
|
\& struct my_io w; |
1362 |
|
|
\& ev_io_init (&w.io, my_cb, fd, EV_READ); |
1363 |
root |
1.1 |
.Ve |
1364 |
|
|
.PP |
1365 |
|
|
And since your callback will be called with a pointer to the watcher, you |
1366 |
|
|
can cast it back to your own type: |
1367 |
|
|
.PP |
1368 |
|
|
.Vb 5 |
1369 |
root |
1.73 |
\& static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
1370 |
root |
1.68 |
\& { |
1371 |
|
|
\& struct my_io *w = (struct my_io *)w_; |
1372 |
|
|
\& ... |
1373 |
|
|
\& } |
1374 |
root |
1.1 |
.Ve |
1375 |
|
|
.PP |
1376 |
root |
1.29 |
More interesting and less C\-conformant ways of casting your callback type |
1377 |
|
|
instead have been omitted. |
1378 |
|
|
.PP |
1379 |
root |
1.71 |
Another common scenario is to use some data structure with multiple |
1380 |
|
|
embedded watchers: |
1381 |
root |
1.29 |
.PP |
1382 |
|
|
.Vb 6 |
1383 |
root |
1.68 |
\& struct my_biggy |
1384 |
|
|
\& { |
1385 |
|
|
\& int some_data; |
1386 |
|
|
\& ev_timer t1; |
1387 |
|
|
\& ev_timer t2; |
1388 |
|
|
\& } |
1389 |
root |
1.29 |
.Ve |
1390 |
|
|
.PP |
1391 |
root |
1.71 |
In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more |
1392 |
|
|
complicated: Either you store the address of your \f(CW\*(C`my_biggy\*(C'\fR struct |
1393 |
|
|
in the \f(CW\*(C`data\*(C'\fR member of the watcher (for woozies), or you need to use |
1394 |
|
|
some pointer arithmetic using \f(CW\*(C`offsetof\*(C'\fR inside your watchers (for real |
1395 |
|
|
programmers): |
1396 |
root |
1.29 |
.PP |
1397 |
|
|
.Vb 1 |
1398 |
root |
1.68 |
\& #include <stddef.h> |
1399 |
root |
1.60 |
\& |
1400 |
root |
1.68 |
\& static void |
1401 |
root |
1.73 |
\& t1_cb (EV_P_ ev_timer *w, int revents) |
1402 |
root |
1.68 |
\& { |
1403 |
root |
1.79 |
\& struct my_biggy big = (struct my_biggy *) |
1404 |
root |
1.68 |
\& (((char *)w) \- offsetof (struct my_biggy, t1)); |
1405 |
|
|
\& } |
1406 |
|
|
\& |
1407 |
|
|
\& static void |
1408 |
root |
1.73 |
\& t2_cb (EV_P_ ev_timer *w, int revents) |
1409 |
root |
1.68 |
\& { |
1410 |
root |
1.79 |
\& struct my_biggy big = (struct my_biggy *) |
1411 |
root |
1.68 |
\& (((char *)w) \- offsetof (struct my_biggy, t2)); |
1412 |
|
|
\& } |
1413 |
root |
1.29 |
.Ve |
1414 |
root |
1.79 |
.SS "\s-1WATCHER\s0 \s-1PRIORITY\s0 \s-1MODELS\s0" |
1415 |
root |
1.78 |
.IX Subsection "WATCHER PRIORITY MODELS" |
1416 |
|
|
Many event loops support \fIwatcher priorities\fR, which are usually small |
1417 |
|
|
integers that influence the ordering of event callback invocation |
1418 |
|
|
between watchers in some way, all else being equal. |
1419 |
|
|
.PP |
1420 |
|
|
In libev, Watcher priorities can be set using \f(CW\*(C`ev_set_priority\*(C'\fR. See its |
1421 |
|
|
description for the more technical details such as the actual priority |
1422 |
|
|
range. |
1423 |
|
|
.PP |
1424 |
|
|
There are two common ways how these these priorities are being interpreted |
1425 |
|
|
by event loops: |
1426 |
|
|
.PP |
1427 |
|
|
In the more common lock-out model, higher priorities \*(L"lock out\*(R" invocation |
1428 |
|
|
of lower priority watchers, which means as long as higher priority |
1429 |
|
|
watchers receive events, lower priority watchers are not being invoked. |
1430 |
|
|
.PP |
1431 |
|
|
The less common only-for-ordering model uses priorities solely to order |
1432 |
|
|
callback invocation within a single event loop iteration: Higher priority |
1433 |
|
|
watchers are invoked before lower priority ones, but they all get invoked |
1434 |
|
|
before polling for new events. |
1435 |
|
|
.PP |
1436 |
|
|
Libev uses the second (only-for-ordering) model for all its watchers |
1437 |
|
|
except for idle watchers (which use the lock-out model). |
1438 |
|
|
.PP |
1439 |
|
|
The rationale behind this is that implementing the lock-out model for |
1440 |
|
|
watchers is not well supported by most kernel interfaces, and most event |
1441 |
|
|
libraries will just poll for the same events again and again as long as |
1442 |
|
|
their callbacks have not been executed, which is very inefficient in the |
1443 |
|
|
common case of one high-priority watcher locking out a mass of lower |
1444 |
|
|
priority ones. |
1445 |
|
|
.PP |
1446 |
|
|
Static (ordering) priorities are most useful when you have two or more |
1447 |
|
|
watchers handling the same resource: a typical usage example is having an |
1448 |
|
|
\&\f(CW\*(C`ev_io\*(C'\fR watcher to receive data, and an associated \f(CW\*(C`ev_timer\*(C'\fR to handle |
1449 |
|
|
timeouts. Under load, data might be received while the program handles |
1450 |
|
|
other jobs, but since timers normally get invoked first, the timeout |
1451 |
|
|
handler will be executed before checking for data. In that case, giving |
1452 |
|
|
the timer a lower priority than the I/O watcher ensures that I/O will be |
1453 |
|
|
handled first even under adverse conditions (which is usually, but not |
1454 |
|
|
always, what you want). |
1455 |
|
|
.PP |
1456 |
|
|
Since idle watchers use the \*(L"lock-out\*(R" model, meaning that idle watchers |
1457 |
|
|
will only be executed when no same or higher priority watchers have |
1458 |
|
|
received events, they can be used to implement the \*(L"lock-out\*(R" model when |
1459 |
|
|
required. |
1460 |
|
|
.PP |
1461 |
|
|
For example, to emulate how many other event libraries handle priorities, |
1462 |
|
|
you can associate an \f(CW\*(C`ev_idle\*(C'\fR watcher to each such watcher, and in |
1463 |
|
|
the normal watcher callback, you just start the idle watcher. The real |
1464 |
|
|
processing is done in the idle watcher callback. This causes libev to |
1465 |
|
|
continously poll and process kernel event data for the watcher, but when |
1466 |
|
|
the lock-out case is known to be rare (which in turn is rare :), this is |
1467 |
|
|
workable. |
1468 |
|
|
.PP |
1469 |
|
|
Usually, however, the lock-out model implemented that way will perform |
1470 |
|
|
miserably under the type of load it was designed to handle. In that case, |
1471 |
|
|
it might be preferable to stop the real watcher before starting the |
1472 |
|
|
idle watcher, so the kernel will not have to process the event in case |
1473 |
|
|
the actual processing will be delayed for considerable time. |
1474 |
|
|
.PP |
1475 |
|
|
Here is an example of an I/O watcher that should run at a strictly lower |
1476 |
|
|
priority than the default, and which should only process data when no |
1477 |
|
|
other events are pending: |
1478 |
|
|
.PP |
1479 |
|
|
.Vb 2 |
1480 |
|
|
\& ev_idle idle; // actual processing watcher |
1481 |
|
|
\& ev_io io; // actual event watcher |
1482 |
|
|
\& |
1483 |
|
|
\& static void |
1484 |
|
|
\& io_cb (EV_P_ ev_io *w, int revents) |
1485 |
|
|
\& { |
1486 |
|
|
\& // stop the I/O watcher, we received the event, but |
1487 |
|
|
\& // are not yet ready to handle it. |
1488 |
|
|
\& ev_io_stop (EV_A_ w); |
1489 |
|
|
\& |
1490 |
|
|
\& // start the idle watcher to ahndle the actual event. |
1491 |
|
|
\& // it will not be executed as long as other watchers |
1492 |
|
|
\& // with the default priority are receiving events. |
1493 |
|
|
\& ev_idle_start (EV_A_ &idle); |
1494 |
|
|
\& } |
1495 |
|
|
\& |
1496 |
|
|
\& static void |
1497 |
root |
1.79 |
\& idle_cb (EV_P_ ev_idle *w, int revents) |
1498 |
root |
1.78 |
\& { |
1499 |
|
|
\& // actual processing |
1500 |
|
|
\& read (STDIN_FILENO, ...); |
1501 |
|
|
\& |
1502 |
|
|
\& // have to start the I/O watcher again, as |
1503 |
|
|
\& // we have handled the event |
1504 |
|
|
\& ev_io_start (EV_P_ &io); |
1505 |
|
|
\& } |
1506 |
|
|
\& |
1507 |
|
|
\& // initialisation |
1508 |
|
|
\& ev_idle_init (&idle, idle_cb); |
1509 |
|
|
\& ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ); |
1510 |
|
|
\& ev_io_start (EV_DEFAULT_ &io); |
1511 |
|
|
.Ve |
1512 |
|
|
.PP |
1513 |
|
|
In the \*(L"real\*(R" world, it might also be beneficial to start a timer, so that |
1514 |
|
|
low-priority connections can not be locked out forever under load. This |
1515 |
|
|
enables your program to keep a lower latency for important connections |
1516 |
|
|
during short periods of high load, while not completely locking out less |
1517 |
|
|
important ones. |
1518 |
root |
1.1 |
.SH "WATCHER TYPES" |
1519 |
|
|
.IX Header "WATCHER TYPES" |
1520 |
|
|
This section describes each watcher in detail, but will not repeat |
1521 |
root |
1.22 |
information given in the last section. Any initialisation/set macros, |
1522 |
|
|
functions and members specific to the watcher type are explained. |
1523 |
|
|
.PP |
1524 |
|
|
Members are additionally marked with either \fI[read\-only]\fR, meaning that, |
1525 |
|
|
while the watcher is active, you can look at the member and expect some |
1526 |
|
|
sensible content, but you must not modify it (you can modify it while the |
1527 |
|
|
watcher is stopped to your hearts content), or \fI[read\-write]\fR, which |
1528 |
|
|
means you can expect it to have some sensible content while the watcher |
1529 |
|
|
is active, but you can also modify it. Modifying it may not do something |
1530 |
|
|
sensible or take immediate effect (or do anything at all), but libev will |
1531 |
|
|
not crash or malfunction in any way. |
1532 |
root |
1.79 |
.ie n .SS """ev_io"" \- is this file descriptor readable or writable?" |
1533 |
|
|
.el .SS "\f(CWev_io\fP \- is this file descriptor readable or writable?" |
1534 |
root |
1.17 |
.IX Subsection "ev_io - is this file descriptor readable or writable?" |
1535 |
root |
1.1 |
I/O watchers check whether a file descriptor is readable or writable |
1536 |
root |
1.17 |
in each iteration of the event loop, or, more precisely, when reading |
1537 |
|
|
would not block the process and writing would at least be able to write |
1538 |
|
|
some data. This behaviour is called level-triggering because you keep |
1539 |
|
|
receiving events as long as the condition persists. Remember you can stop |
1540 |
|
|
the watcher if you don't want to act on the event and neither want to |
1541 |
|
|
receive future events. |
1542 |
root |
1.1 |
.PP |
1543 |
|
|
In general you can register as many read and/or write event watchers per |
1544 |
|
|
fd as you want (as long as you don't confuse yourself). Setting all file |
1545 |
|
|
descriptors to non-blocking mode is also usually a good idea (but not |
1546 |
|
|
required if you know what you are doing). |
1547 |
|
|
.PP |
1548 |
root |
1.71 |
If you cannot use non-blocking mode, then force the use of a |
1549 |
|
|
known-to-be-good backend (at the time of this writing, this includes only |
1550 |
root |
1.78 |
\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and \f(CW\*(C`EVBACKEND_POLL\*(C'\fR). The same applies to file |
1551 |
|
|
descriptors for which non-blocking operation makes no sense (such as |
1552 |
|
|
files) \- libev doesn't guarentee any specific behaviour in that case. |
1553 |
root |
1.17 |
.PP |
1554 |
|
|
Another thing you have to watch out for is that it is quite easy to |
1555 |
root |
1.67 |
receive \*(L"spurious\*(R" readiness notifications, that is your callback might |
1556 |
root |
1.17 |
be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block |
1557 |
|
|
because there is no data. Not only are some backends known to create a |
1558 |
root |
1.68 |
lot of those (for example Solaris ports), it is very easy to get into |
1559 |
root |
1.17 |
this situation even with a relatively standard program structure. Thus |
1560 |
|
|
it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning |
1561 |
|
|
\&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives. |
1562 |
|
|
.PP |
1563 |
root |
1.71 |
If you cannot run the fd in non-blocking mode (for example you should |
1564 |
|
|
not play around with an Xlib connection), then you have to separately |
1565 |
|
|
re-test whether a file descriptor is really ready with a known-to-be good |
1566 |
|
|
interface such as poll (fortunately in our Xlib example, Xlib already |
1567 |
|
|
does this on its own, so its quite safe to use). Some people additionally |
1568 |
|
|
use \f(CW\*(C`SIGALRM\*(C'\fR and an interval timer, just to be sure you won't block |
1569 |
|
|
indefinitely. |
1570 |
|
|
.PP |
1571 |
|
|
But really, best use non-blocking mode. |
1572 |
root |
1.49 |
.PP |
1573 |
|
|
\fIThe special problem of disappearing file descriptors\fR |
1574 |
|
|
.IX Subsection "The special problem of disappearing file descriptors" |
1575 |
|
|
.PP |
1576 |
root |
1.54 |
Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1577 |
root |
1.71 |
descriptor (either due to calling \f(CW\*(C`close\*(C'\fR explicitly or any other means, |
1578 |
|
|
such as \f(CW\*(C`dup2\*(C'\fR). The reason is that you register interest in some file |
1579 |
root |
1.49 |
descriptor, but when it goes away, the operating system will silently drop |
1580 |
|
|
this interest. If another file descriptor with the same number then is |
1581 |
|
|
registered with libev, there is no efficient way to see that this is, in |
1582 |
|
|
fact, a different file descriptor. |
1583 |
|
|
.PP |
1584 |
|
|
To avoid having to explicitly tell libev about such cases, libev follows |
1585 |
|
|
the following policy: Each time \f(CW\*(C`ev_io_set\*(C'\fR is being called, libev |
1586 |
|
|
will assume that this is potentially a new file descriptor, otherwise |
1587 |
|
|
it is assumed that the file descriptor stays the same. That means that |
1588 |
|
|
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 |
1589 |
|
|
descriptor even if the file descriptor number itself did not change. |
1590 |
|
|
.PP |
1591 |
|
|
This is how one would do it normally anyway, the important point is that |
1592 |
|
|
the libev application should not optimise around libev but should leave |
1593 |
|
|
optimisations to libev. |
1594 |
root |
1.50 |
.PP |
1595 |
root |
1.55 |
\fIThe special problem of dup'ed file descriptors\fR |
1596 |
|
|
.IX Subsection "The special problem of dup'ed file descriptors" |
1597 |
root |
1.54 |
.PP |
1598 |
|
|
Some backends (e.g. epoll), cannot register events for file descriptors, |
1599 |
root |
1.59 |
but only events for the underlying file descriptions. That means when you |
1600 |
|
|
have \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors or weirder constellations, and register |
1601 |
|
|
events for them, only one file descriptor might actually receive events. |
1602 |
root |
1.54 |
.PP |
1603 |
root |
1.59 |
There is no workaround possible except not registering events |
1604 |
|
|
for potentially \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors, or to resort to |
1605 |
root |
1.54 |
\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
1606 |
|
|
.PP |
1607 |
|
|
\fIThe special problem of fork\fR |
1608 |
|
|
.IX Subsection "The special problem of fork" |
1609 |
|
|
.PP |
1610 |
|
|
Some backends (epoll, kqueue) do not support \f(CW\*(C`fork ()\*(C'\fR at all or exhibit |
1611 |
|
|
useless behaviour. Libev fully supports fork, but needs to be told about |
1612 |
|
|
it in the child. |
1613 |
|
|
.PP |
1614 |
|
|
To support fork in your programs, you either have to call |
1615 |
|
|
\&\f(CW\*(C`ev_default_fork ()\*(C'\fR or \f(CW\*(C`ev_loop_fork ()\*(C'\fR after a fork in the child, |
1616 |
|
|
enable \f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR, or resort to \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or |
1617 |
|
|
\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
1618 |
|
|
.PP |
1619 |
root |
1.63 |
\fIThe special problem of \s-1SIGPIPE\s0\fR |
1620 |
|
|
.IX Subsection "The special problem of SIGPIPE" |
1621 |
|
|
.PP |
1622 |
root |
1.71 |
While not really specific to libev, it is easy to forget about \f(CW\*(C`SIGPIPE\*(C'\fR: |
1623 |
|
|
when writing to a pipe whose other end has been closed, your program gets |
1624 |
|
|
sent a \s-1SIGPIPE\s0, which, by default, aborts your program. For most programs |
1625 |
|
|
this is sensible behaviour, for daemons, this is usually undesirable. |
1626 |
root |
1.63 |
.PP |
1627 |
|
|
So when you encounter spurious, unexplained daemon exits, make sure you |
1628 |
|
|
ignore \s-1SIGPIPE\s0 (and maybe make sure you log the exit status of your daemon |
1629 |
|
|
somewhere, as that would have given you a big clue). |
1630 |
|
|
.PP |
1631 |
root |
1.50 |
\fIWatcher-Specific Functions\fR |
1632 |
|
|
.IX Subsection "Watcher-Specific Functions" |
1633 |
root |
1.1 |
.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4 |
1634 |
|
|
.IX Item "ev_io_init (ev_io *, callback, int fd, int events)" |
1635 |
|
|
.PD 0 |
1636 |
|
|
.IP "ev_io_set (ev_io *, int fd, int events)" 4 |
1637 |
|
|
.IX Item "ev_io_set (ev_io *, int fd, int events)" |
1638 |
|
|
.PD |
1639 |
root |
1.17 |
Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to |
1640 |
root |
1.71 |
receive events for and \f(CW\*(C`events\*(C'\fR is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or |
1641 |
|
|
\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR, to express the desire to receive the given events. |
1642 |
root |
1.22 |
.IP "int fd [read\-only]" 4 |
1643 |
|
|
.IX Item "int fd [read-only]" |
1644 |
|
|
The file descriptor being watched. |
1645 |
|
|
.IP "int events [read\-only]" 4 |
1646 |
|
|
.IX Item "int events [read-only]" |
1647 |
|
|
The events being watched. |
1648 |
root |
1.9 |
.PP |
1649 |
root |
1.60 |
\fIExamples\fR |
1650 |
|
|
.IX Subsection "Examples" |
1651 |
|
|
.PP |
1652 |
root |
1.28 |
Example: Call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well |
1653 |
root |
1.60 |
readable, but only once. Since it is likely line-buffered, you could |
1654 |
root |
1.28 |
attempt to read a whole line in the callback. |
1655 |
root |
1.9 |
.PP |
1656 |
|
|
.Vb 6 |
1657 |
root |
1.68 |
\& static void |
1658 |
root |
1.73 |
\& stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents) |
1659 |
root |
1.68 |
\& { |
1660 |
|
|
\& ev_io_stop (loop, w); |
1661 |
root |
1.71 |
\& .. read from stdin here (or from w\->fd) and handle any I/O errors |
1662 |
root |
1.68 |
\& } |
1663 |
|
|
\& |
1664 |
|
|
\& ... |
1665 |
|
|
\& struct ev_loop *loop = ev_default_init (0); |
1666 |
root |
1.73 |
\& ev_io stdin_readable; |
1667 |
root |
1.68 |
\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1668 |
|
|
\& ev_io_start (loop, &stdin_readable); |
1669 |
|
|
\& ev_loop (loop, 0); |
1670 |
root |
1.9 |
.Ve |
1671 |
root |
1.79 |
.ie n .SS """ev_timer"" \- relative and optionally repeating timeouts" |
1672 |
|
|
.el .SS "\f(CWev_timer\fP \- relative and optionally repeating timeouts" |
1673 |
root |
1.17 |
.IX Subsection "ev_timer - relative and optionally repeating timeouts" |
1674 |
root |
1.1 |
Timer watchers are simple relative timers that generate an event after a |
1675 |
|
|
given time, and optionally repeating in regular intervals after that. |
1676 |
|
|
.PP |
1677 |
|
|
The timers are based on real time, that is, if you register an event that |
1678 |
root |
1.68 |
times out after an hour and you reset your system clock to January last |
1679 |
root |
1.71 |
year, it will still time out after (roughly) one hour. \*(L"Roughly\*(R" because |
1680 |
root |
1.2 |
detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1681 |
root |
1.1 |
monotonic clock option helps a lot here). |
1682 |
|
|
.PP |
1683 |
root |
1.71 |
The callback is guaranteed to be invoked only \fIafter\fR its timeout has |
1684 |
root |
1.78 |
passed (not \fIat\fR, so on systems with very low-resolution clocks this |
1685 |
|
|
might introduce a small delay). If multiple timers become ready during the |
1686 |
|
|
same loop iteration then the ones with earlier time-out values are invoked |
1687 |
root |
1.79 |
before ones of the same priority with later time-out values (but this is |
1688 |
|
|
no longer true when a callback calls \f(CW\*(C`ev_loop\*(C'\fR recursively). |
1689 |
root |
1.71 |
.PP |
1690 |
root |
1.73 |
\fIBe smart about timeouts\fR |
1691 |
|
|
.IX Subsection "Be smart about timeouts" |
1692 |
|
|
.PP |
1693 |
|
|
Many real-world problems involve some kind of timeout, usually for error |
1694 |
|
|
recovery. A typical example is an \s-1HTTP\s0 request \- if the other side hangs, |
1695 |
|
|
you want to raise some error after a while. |
1696 |
|
|
.PP |
1697 |
|
|
What follows are some ways to handle this problem, from obvious and |
1698 |
|
|
inefficient to smart and efficient. |
1699 |
|
|
.PP |
1700 |
|
|
In the following, a 60 second activity timeout is assumed \- a timeout that |
1701 |
|
|
gets reset to 60 seconds each time there is activity (e.g. each time some |
1702 |
|
|
data or other life sign was received). |
1703 |
|
|
.IP "1. Use a timer and stop, reinitialise and start it on activity." 4 |
1704 |
|
|
.IX Item "1. Use a timer and stop, reinitialise and start it on activity." |
1705 |
|
|
This is the most obvious, but not the most simple way: In the beginning, |
1706 |
|
|
start the watcher: |
1707 |
|
|
.Sp |
1708 |
|
|
.Vb 2 |
1709 |
|
|
\& ev_timer_init (timer, callback, 60., 0.); |
1710 |
|
|
\& ev_timer_start (loop, timer); |
1711 |
|
|
.Ve |
1712 |
|
|
.Sp |
1713 |
|
|
Then, each time there is some activity, \f(CW\*(C`ev_timer_stop\*(C'\fR it, initialise it |
1714 |
|
|
and start it again: |
1715 |
|
|
.Sp |
1716 |
|
|
.Vb 3 |
1717 |
|
|
\& ev_timer_stop (loop, timer); |
1718 |
|
|
\& ev_timer_set (timer, 60., 0.); |
1719 |
|
|
\& ev_timer_start (loop, timer); |
1720 |
|
|
.Ve |
1721 |
|
|
.Sp |
1722 |
|
|
This is relatively simple to implement, but means that each time there is |
1723 |
|
|
some activity, libev will first have to remove the timer from its internal |
1724 |
|
|
data structure and then add it again. Libev tries to be fast, but it's |
1725 |
|
|
still not a constant-time operation. |
1726 |
|
|
.ie n .IP "2. Use a timer and re-start it with ""ev_timer_again"" inactivity." 4 |
1727 |
|
|
.el .IP "2. Use a timer and re-start it with \f(CWev_timer_again\fR inactivity." 4 |
1728 |
|
|
.IX Item "2. Use a timer and re-start it with ev_timer_again inactivity." |
1729 |
|
|
This is the easiest way, and involves using \f(CW\*(C`ev_timer_again\*(C'\fR instead of |
1730 |
|
|
\&\f(CW\*(C`ev_timer_start\*(C'\fR. |
1731 |
|
|
.Sp |
1732 |
|
|
To implement this, configure an \f(CW\*(C`ev_timer\*(C'\fR with a \f(CW\*(C`repeat\*(C'\fR value |
1733 |
|
|
of \f(CW60\fR and then call \f(CW\*(C`ev_timer_again\*(C'\fR at start and each time you |
1734 |
|
|
successfully read or write some data. If you go into an idle state where |
1735 |
|
|
you do not expect data to travel on the socket, you can \f(CW\*(C`ev_timer_stop\*(C'\fR |
1736 |
|
|
the timer, and \f(CW\*(C`ev_timer_again\*(C'\fR will automatically restart it if need be. |
1737 |
|
|
.Sp |
1738 |
|
|
That means you can ignore both the \f(CW\*(C`ev_timer_start\*(C'\fR function and the |
1739 |
|
|
\&\f(CW\*(C`after\*(C'\fR argument to \f(CW\*(C`ev_timer_set\*(C'\fR, and only ever use the \f(CW\*(C`repeat\*(C'\fR |
1740 |
|
|
member and \f(CW\*(C`ev_timer_again\*(C'\fR. |
1741 |
|
|
.Sp |
1742 |
|
|
At start: |
1743 |
|
|
.Sp |
1744 |
|
|
.Vb 3 |
1745 |
root |
1.79 |
\& ev_init (timer, callback); |
1746 |
root |
1.73 |
\& timer\->repeat = 60.; |
1747 |
|
|
\& ev_timer_again (loop, timer); |
1748 |
|
|
.Ve |
1749 |
|
|
.Sp |
1750 |
|
|
Each time there is some activity: |
1751 |
|
|
.Sp |
1752 |
|
|
.Vb 1 |
1753 |
|
|
\& ev_timer_again (loop, timer); |
1754 |
|
|
.Ve |
1755 |
|
|
.Sp |
1756 |
|
|
It is even possible to change the time-out on the fly, regardless of |
1757 |
|
|
whether the watcher is active or not: |
1758 |
|
|
.Sp |
1759 |
|
|
.Vb 2 |
1760 |
|
|
\& timer\->repeat = 30.; |
1761 |
|
|
\& ev_timer_again (loop, timer); |
1762 |
|
|
.Ve |
1763 |
|
|
.Sp |
1764 |
|
|
This is slightly more efficient then stopping/starting the timer each time |
1765 |
|
|
you want to modify its timeout value, as libev does not have to completely |
1766 |
|
|
remove and re-insert the timer from/into its internal data structure. |
1767 |
|
|
.Sp |
1768 |
|
|
It is, however, even simpler than the \*(L"obvious\*(R" way to do it. |
1769 |
|
|
.IP "3. Let the timer time out, but then re-arm it as required." 4 |
1770 |
|
|
.IX Item "3. Let the timer time out, but then re-arm it as required." |
1771 |
|
|
This method is more tricky, but usually most efficient: Most timeouts are |
1772 |
|
|
relatively long compared to the intervals between other activity \- in |
1773 |
|
|
our example, within 60 seconds, there are usually many I/O events with |
1774 |
|
|
associated activity resets. |
1775 |
|
|
.Sp |
1776 |
|
|
In this case, it would be more efficient to leave the \f(CW\*(C`ev_timer\*(C'\fR alone, |
1777 |
|
|
but remember the time of last activity, and check for a real timeout only |
1778 |
|
|
within the callback: |
1779 |
|
|
.Sp |
1780 |
|
|
.Vb 1 |
1781 |
|
|
\& ev_tstamp last_activity; // time of last activity |
1782 |
|
|
\& |
1783 |
|
|
\& static void |
1784 |
|
|
\& callback (EV_P_ ev_timer *w, int revents) |
1785 |
|
|
\& { |
1786 |
|
|
\& ev_tstamp now = ev_now (EV_A); |
1787 |
|
|
\& ev_tstamp timeout = last_activity + 60.; |
1788 |
|
|
\& |
1789 |
|
|
\& // if last_activity + 60. is older than now, we did time out |
1790 |
|
|
\& if (timeout < now) |
1791 |
|
|
\& { |
1792 |
|
|
\& // timeout occured, take action |
1793 |
|
|
\& } |
1794 |
|
|
\& else |
1795 |
|
|
\& { |
1796 |
|
|
\& // callback was invoked, but there was some activity, re\-arm |
1797 |
|
|
\& // the watcher to fire in last_activity + 60, which is |
1798 |
|
|
\& // guaranteed to be in the future, so "again" is positive: |
1799 |
root |
1.74 |
\& w\->repeat = timeout \- now; |
1800 |
root |
1.73 |
\& ev_timer_again (EV_A_ w); |
1801 |
|
|
\& } |
1802 |
|
|
\& } |
1803 |
|
|
.Ve |
1804 |
|
|
.Sp |
1805 |
|
|
To summarise the callback: first calculate the real timeout (defined |
1806 |
|
|
as \*(L"60 seconds after the last activity\*(R"), then check if that time has |
1807 |
|
|
been reached, which means something \fIdid\fR, in fact, time out. Otherwise |
1808 |
|
|
the callback was invoked too early (\f(CW\*(C`timeout\*(C'\fR is in the future), so |
1809 |
|
|
re-schedule the timer to fire at that future time, to see if maybe we have |
1810 |
|
|
a timeout then. |
1811 |
|
|
.Sp |
1812 |
|
|
Note how \f(CW\*(C`ev_timer_again\*(C'\fR is used, taking advantage of the |
1813 |
|
|
\&\f(CW\*(C`ev_timer_again\*(C'\fR optimisation when the timer is already running. |
1814 |
|
|
.Sp |
1815 |
|
|
This scheme causes more callback invocations (about one every 60 seconds |
1816 |
|
|
minus half the average time between activity), but virtually no calls to |
1817 |
|
|
libev to change the timeout. |
1818 |
|
|
.Sp |
1819 |
|
|
To start the timer, simply initialise the watcher and set \f(CW\*(C`last_activity\*(C'\fR |
1820 |
|
|
to the current time (meaning we just have some activity :), then call the |
1821 |
|
|
callback, which will \*(L"do the right thing\*(R" and start the timer: |
1822 |
|
|
.Sp |
1823 |
|
|
.Vb 3 |
1824 |
root |
1.79 |
\& ev_init (timer, callback); |
1825 |
root |
1.73 |
\& last_activity = ev_now (loop); |
1826 |
|
|
\& callback (loop, timer, EV_TIMEOUT); |
1827 |
|
|
.Ve |
1828 |
|
|
.Sp |
1829 |
|
|
And when there is some activity, simply store the current time in |
1830 |
|
|
\&\f(CW\*(C`last_activity\*(C'\fR, no libev calls at all: |
1831 |
|
|
.Sp |
1832 |
|
|
.Vb 1 |
1833 |
|
|
\& last_actiivty = ev_now (loop); |
1834 |
|
|
.Ve |
1835 |
|
|
.Sp |
1836 |
|
|
This technique is slightly more complex, but in most cases where the |
1837 |
|
|
time-out is unlikely to be triggered, much more efficient. |
1838 |
|
|
.Sp |
1839 |
|
|
Changing the timeout is trivial as well (if it isn't hard-coded in the |
1840 |
|
|
callback :) \- just change the timeout and invoke the callback, which will |
1841 |
|
|
fix things for you. |
1842 |
|
|
.IP "4. Wee, just use a double-linked list for your timeouts." 4 |
1843 |
|
|
.IX Item "4. Wee, just use a double-linked list for your timeouts." |
1844 |
|
|
If there is not one request, but many thousands (millions...), all |
1845 |
|
|
employing some kind of timeout with the same timeout value, then one can |
1846 |
|
|
do even better: |
1847 |
|
|
.Sp |
1848 |
|
|
When starting the timeout, calculate the timeout value and put the timeout |
1849 |
|
|
at the \fIend\fR of the list. |
1850 |
|
|
.Sp |
1851 |
|
|
Then use an \f(CW\*(C`ev_timer\*(C'\fR to fire when the timeout at the \fIbeginning\fR of |
1852 |
|
|
the list is expected to fire (for example, using the technique #3). |
1853 |
|
|
.Sp |
1854 |
|
|
When there is some activity, remove the timer from the list, recalculate |
1855 |
|
|
the timeout, append it to the end of the list again, and make sure to |
1856 |
|
|
update the \f(CW\*(C`ev_timer\*(C'\fR if it was taken from the beginning of the list. |
1857 |
|
|
.Sp |
1858 |
|
|
This way, one can manage an unlimited number of timeouts in O(1) time for |
1859 |
|
|
starting, stopping and updating the timers, at the expense of a major |
1860 |
|
|
complication, and having to use a constant timeout. The constant timeout |
1861 |
|
|
ensures that the list stays sorted. |
1862 |
|
|
.PP |
1863 |
|
|
So which method the best? |
1864 |
|
|
.PP |
1865 |
|
|
Method #2 is a simple no-brain-required solution that is adequate in most |
1866 |
|
|
situations. Method #3 requires a bit more thinking, but handles many cases |
1867 |
|
|
better, and isn't very complicated either. In most case, choosing either |
1868 |
|
|
one is fine, with #3 being better in typical situations. |
1869 |
|
|
.PP |
1870 |
|
|
Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1871 |
|
|
rather complicated, but extremely efficient, something that really pays |
1872 |
|
|
off after the first million or so of active timers, i.e. it's usually |
1873 |
|
|
overkill :) |
1874 |
|
|
.PP |
1875 |
root |
1.71 |
\fIThe special problem of time updates\fR |
1876 |
|
|
.IX Subsection "The special problem of time updates" |
1877 |
|
|
.PP |
1878 |
|
|
Establishing the current time is a costly operation (it usually takes at |
1879 |
|
|
least two system calls): \s-1EV\s0 therefore updates its idea of the current |
1880 |
|
|
time only before and after \f(CW\*(C`ev_loop\*(C'\fR collects new events, which causes a |
1881 |
|
|
growing difference between \f(CW\*(C`ev_now ()\*(C'\fR and \f(CW\*(C`ev_time ()\*(C'\fR when handling |
1882 |
|
|
lots of events in one iteration. |
1883 |
|
|
.PP |
1884 |
root |
1.1 |
The relative timeouts are calculated relative to the \f(CW\*(C`ev_now ()\*(C'\fR |
1885 |
|
|
time. This is usually the right thing as this timestamp refers to the time |
1886 |
root |
1.2 |
of the event triggering whatever timeout you are modifying/starting. If |
1887 |
root |
1.71 |
you suspect event processing to be delayed and you \fIneed\fR to base the |
1888 |
|
|
timeout on the current time, use something like this to adjust for this: |
1889 |
root |
1.1 |
.PP |
1890 |
|
|
.Vb 1 |
1891 |
root |
1.60 |
\& ev_timer_set (&timer, after + ev_now () \- ev_time (), 0.); |
1892 |
root |
1.1 |
.Ve |
1893 |
root |
1.2 |
.PP |
1894 |
root |
1.71 |
If the event loop is suspended for a long time, you can also force an |
1895 |
|
|
update of the time returned by \f(CW\*(C`ev_now ()\*(C'\fR by calling \f(CW\*(C`ev_now_update |
1896 |
|
|
()\*(C'\fR. |
1897 |
root |
1.50 |
.PP |
1898 |
root |
1.79 |
\fIThe special problems of suspended animation\fR |
1899 |
|
|
.IX Subsection "The special problems of suspended animation" |
1900 |
|
|
.PP |
1901 |
|
|
When you leave the server world it is quite customary to hit machines that |
1902 |
|
|
can suspend/hibernate \- what happens to the clocks during such a suspend? |
1903 |
|
|
.PP |
1904 |
|
|
Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes |
1905 |
|
|
all processes, while the clocks (\f(CW\*(C`times\*(C'\fR, \f(CW\*(C`CLOCK_MONOTONIC\*(C'\fR) continue |
1906 |
|
|
to run until the system is suspended, but they will not advance while the |
1907 |
|
|
system is suspended. That means, on resume, it will be as if the program |
1908 |
|
|
was frozen for a few seconds, but the suspend time will not be counted |
1909 |
|
|
towards \f(CW\*(C`ev_timer\*(C'\fR when a monotonic clock source is used. The real time |
1910 |
|
|
clock advanced as expected, but if it is used as sole clocksource, then a |
1911 |
|
|
long suspend would be detected as a time jump by libev, and timers would |
1912 |
|
|
be adjusted accordingly. |
1913 |
|
|
.PP |
1914 |
|
|
I would not be surprised to see different behaviour in different between |
1915 |
|
|
operating systems, \s-1OS\s0 versions or even different hardware. |
1916 |
|
|
.PP |
1917 |
|
|
The other form of suspend (job control, or sending a \s-1SIGSTOP\s0) will see a |
1918 |
|
|
time jump in the monotonic clocks and the realtime clock. If the program |
1919 |
|
|
is suspended for a very long time, and monotonic clock sources are in use, |
1920 |
|
|
then you can expect \f(CW\*(C`ev_timer\*(C'\fRs to expire as the full suspension time |
1921 |
|
|
will be counted towards the timers. When no monotonic clock source is in |
1922 |
|
|
use, then libev will again assume a timejump and adjust accordingly. |
1923 |
|
|
.PP |
1924 |
|
|
It might be beneficial for this latter case to call \f(CW\*(C`ev_suspend\*(C'\fR |
1925 |
|
|
and \f(CW\*(C`ev_resume\*(C'\fR in code that handles \f(CW\*(C`SIGTSTP\*(C'\fR, to at least get |
1926 |
|
|
deterministic behaviour in this case (you can do nothing against |
1927 |
|
|
\&\f(CW\*(C`SIGSTOP\*(C'\fR). |
1928 |
|
|
.PP |
1929 |
root |
1.50 |
\fIWatcher-Specific Functions and Data Members\fR |
1930 |
|
|
.IX Subsection "Watcher-Specific Functions and Data Members" |
1931 |
root |
1.1 |
.IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4 |
1932 |
|
|
.IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" |
1933 |
|
|
.PD 0 |
1934 |
|
|
.IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4 |
1935 |
|
|
.IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" |
1936 |
|
|
.PD |
1937 |
root |
1.67 |
Configure the timer to trigger after \f(CW\*(C`after\*(C'\fR seconds. If \f(CW\*(C`repeat\*(C'\fR |
1938 |
|
|
is \f(CW0.\fR, then it will automatically be stopped once the timeout is |
1939 |
|
|
reached. If it is positive, then the timer will automatically be |
1940 |
|
|
configured to trigger again \f(CW\*(C`repeat\*(C'\fR seconds later, again, and again, |
1941 |
|
|
until stopped manually. |
1942 |
|
|
.Sp |
1943 |
|
|
The timer itself will do a best-effort at avoiding drift, that is, if |
1944 |
|
|
you configure a timer to trigger every 10 seconds, then it will normally |
1945 |
|
|
trigger at exactly 10 second intervals. If, however, your program cannot |
1946 |
|
|
keep up with the timer (because it takes longer than those 10 seconds to |
1947 |
|
|
do stuff) the timer will not fire more than once per event loop iteration. |
1948 |
root |
1.61 |
.IP "ev_timer_again (loop, ev_timer *)" 4 |
1949 |
|
|
.IX Item "ev_timer_again (loop, ev_timer *)" |
1950 |
root |
1.1 |
This will act as if the timer timed out and restart it again if it is |
1951 |
|
|
repeating. The exact semantics are: |
1952 |
|
|
.Sp |
1953 |
root |
1.34 |
If the timer is pending, its pending status is cleared. |
1954 |
root |
1.1 |
.Sp |
1955 |
root |
1.68 |
If the timer is started but non-repeating, stop it (as if it timed out). |
1956 |
root |
1.34 |
.Sp |
1957 |
|
|
If the timer is repeating, either start it if necessary (with the |
1958 |
|
|
\&\f(CW\*(C`repeat\*(C'\fR value), or reset the running timer to the \f(CW\*(C`repeat\*(C'\fR value. |
1959 |
root |
1.1 |
.Sp |
1960 |
root |
1.73 |
This sounds a bit complicated, see \*(L"Be smart about timeouts\*(R", above, for a |
1961 |
|
|
usage example. |
1962 |
root |
1.79 |
.IP "ev_timer_remaining (loop, ev_timer *)" 4 |
1963 |
|
|
.IX Item "ev_timer_remaining (loop, ev_timer *)" |
1964 |
|
|
Returns the remaining time until a timer fires. If the timer is active, |
1965 |
|
|
then this time is relative to the current event loop time, otherwise it's |
1966 |
|
|
the timeout value currently configured. |
1967 |
|
|
.Sp |
1968 |
|
|
That is, after an \f(CW\*(C`ev_timer_set (w, 5, 7)\*(C'\fR, \f(CW\*(C`ev_timer_remaining\*(C'\fR returns |
1969 |
|
|
\&\f(CW5\fR. When the timer is started and one second passes, \f(CW\*(C`ev_timer_remain\*(C'\fR |
1970 |
|
|
will return \f(CW4\fR. When the timer expires and is restarted, it will return |
1971 |
|
|
roughly \f(CW7\fR (likely slightly less as callback invocation takes some time, |
1972 |
|
|
too), and so on. |
1973 |
root |
1.22 |
.IP "ev_tstamp repeat [read\-write]" 4 |
1974 |
|
|
.IX Item "ev_tstamp repeat [read-write]" |
1975 |
|
|
The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out |
1976 |
root |
1.71 |
or \f(CW\*(C`ev_timer_again\*(C'\fR is called, and determines the next timeout (if any), |
1977 |
root |
1.22 |
which is also when any modifications are taken into account. |
1978 |
root |
1.9 |
.PP |
1979 |
root |
1.60 |
\fIExamples\fR |
1980 |
|
|
.IX Subsection "Examples" |
1981 |
|
|
.PP |
1982 |
root |
1.28 |
Example: Create a timer that fires after 60 seconds. |
1983 |
root |
1.9 |
.PP |
1984 |
|
|
.Vb 5 |
1985 |
root |
1.68 |
\& static void |
1986 |
root |
1.73 |
\& one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1987 |
root |
1.68 |
\& { |
1988 |
|
|
\& .. one minute over, w is actually stopped right here |
1989 |
|
|
\& } |
1990 |
|
|
\& |
1991 |
root |
1.73 |
\& ev_timer mytimer; |
1992 |
root |
1.68 |
\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1993 |
|
|
\& ev_timer_start (loop, &mytimer); |
1994 |
root |
1.9 |
.Ve |
1995 |
|
|
.PP |
1996 |
root |
1.28 |
Example: Create a timeout timer that times out after 10 seconds of |
1997 |
root |
1.9 |
inactivity. |
1998 |
|
|
.PP |
1999 |
|
|
.Vb 5 |
2000 |
root |
1.68 |
\& static void |
2001 |
root |
1.73 |
\& timeout_cb (struct ev_loop *loop, ev_timer *w, int revents) |
2002 |
root |
1.68 |
\& { |
2003 |
|
|
\& .. ten seconds without any activity |
2004 |
|
|
\& } |
2005 |
|
|
\& |
2006 |
root |
1.73 |
\& ev_timer mytimer; |
2007 |
root |
1.68 |
\& ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
2008 |
|
|
\& ev_timer_again (&mytimer); /* start timer */ |
2009 |
|
|
\& ev_loop (loop, 0); |
2010 |
|
|
\& |
2011 |
|
|
\& // and in some piece of code that gets executed on any "activity": |
2012 |
|
|
\& // reset the timeout to start ticking again at 10 seconds |
2013 |
|
|
\& ev_timer_again (&mytimer); |
2014 |
root |
1.9 |
.Ve |
2015 |
root |
1.79 |
.ie n .SS """ev_periodic"" \- to cron or not to cron?" |
2016 |
|
|
.el .SS "\f(CWev_periodic\fP \- to cron or not to cron?" |
2017 |
root |
1.17 |
.IX Subsection "ev_periodic - to cron or not to cron?" |
2018 |
root |
1.1 |
Periodic watchers are also timers of a kind, but they are very versatile |
2019 |
|
|
(and unfortunately a bit complex). |
2020 |
|
|
.PP |
2021 |
root |
1.78 |
Unlike \f(CW\*(C`ev_timer\*(C'\fR, periodic watchers are not based on real time (or |
2022 |
|
|
relative time, the physical time that passes) but on wall clock time |
2023 |
|
|
(absolute time, the thing you can read on your calender or clock). The |
2024 |
|
|
difference is that wall clock time can run faster or slower than real |
2025 |
|
|
time, and time jumps are not uncommon (e.g. when you adjust your |
2026 |
|
|
wrist-watch). |
2027 |
|
|
.PP |
2028 |
|
|
You can tell a periodic watcher to trigger after some specific point |
2029 |
|
|
in time: for example, if you tell a periodic watcher to trigger \*(L"in 10 |
2030 |
|
|
seconds\*(R" (by specifying e.g. \f(CW\*(C`ev_now () + 10.\*(C'\fR, that is, an absolute time |
2031 |
|
|
not a delay) and then reset your system clock to January of the previous |
2032 |
|
|
year, then it will take a year or more to trigger the event (unlike an |
2033 |
|
|
\&\f(CW\*(C`ev_timer\*(C'\fR, which would still trigger roughly 10 seconds after starting |
2034 |
|
|
it, as it uses a relative timeout). |
2035 |
|
|
.PP |
2036 |
|
|
\&\f(CW\*(C`ev_periodic\*(C'\fR watchers can also be used to implement vastly more complex |
2037 |
|
|
timers, such as triggering an event on each \*(L"midnight, local time\*(R", or |
2038 |
|
|
other complicated rules. This cannot be done with \f(CW\*(C`ev_timer\*(C'\fR watchers, as |
2039 |
|
|
those cannot react to time jumps. |
2040 |
root |
1.2 |
.PP |
2041 |
root |
1.68 |
As with timers, the callback is guaranteed to be invoked only when the |
2042 |
root |
1.78 |
point in time where it is supposed to trigger has passed. If multiple |
2043 |
|
|
timers become ready during the same loop iteration then the ones with |
2044 |
|
|
earlier time-out values are invoked before ones with later time-out values |
2045 |
|
|
(but this is no longer true when a callback calls \f(CW\*(C`ev_loop\*(C'\fR recursively). |
2046 |
root |
1.50 |
.PP |
2047 |
|
|
\fIWatcher-Specific Functions and Data Members\fR |
2048 |
|
|
.IX Subsection "Watcher-Specific Functions and Data Members" |
2049 |
root |
1.78 |
.IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)" 4 |
2050 |
|
|
.IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)" |
2051 |
root |
1.1 |
.PD 0 |
2052 |
root |
1.78 |
.IP "ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)" 4 |
2053 |
|
|
.IX Item "ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)" |
2054 |
root |
1.1 |
.PD |
2055 |
root |
1.78 |
Lots of arguments, let's sort it out... There are basically three modes of |
2056 |
root |
1.71 |
operation, and we will explain them from simplest to most complex: |
2057 |
root |
1.1 |
.RS 4 |
2058 |
root |
1.60 |
.IP "\(bu" 4 |
2059 |
root |
1.78 |
absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0) |
2060 |
root |
1.60 |
.Sp |
2061 |
root |
1.68 |
In this configuration the watcher triggers an event after the wall clock |
2062 |
root |
1.78 |
time \f(CW\*(C`offset\*(C'\fR has passed. It will not repeat and will not adjust when a |
2063 |
|
|
time jump occurs, that is, if it is to be run at January 1st 2011 then it |
2064 |
|
|
will be stopped and invoked when the system clock reaches or surpasses |
2065 |
|
|
this point in time. |
2066 |
root |
1.60 |
.IP "\(bu" 4 |
2067 |
root |
1.78 |
repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0) |
2068 |
root |
1.60 |
.Sp |
2069 |
root |
1.1 |
In this mode the watcher will always be scheduled to time out at the next |
2070 |
root |
1.78 |
\&\f(CW\*(C`offset + N * interval\*(C'\fR time (for some integer N, which can also be |
2071 |
|
|
negative) and then repeat, regardless of any time jumps. The \f(CW\*(C`offset\*(C'\fR |
2072 |
|
|
argument is merely an offset into the \f(CW\*(C`interval\*(C'\fR periods. |
2073 |
root |
1.1 |
.Sp |
2074 |
root |
1.71 |
This can be used to create timers that do not drift with respect to the |
2075 |
root |
1.78 |
system clock, for example, here is an \f(CW\*(C`ev_periodic\*(C'\fR that triggers each |
2076 |
|
|
hour, on the hour (with respect to \s-1UTC\s0): |
2077 |
root |
1.1 |
.Sp |
2078 |
|
|
.Vb 1 |
2079 |
|
|
\& ev_periodic_set (&periodic, 0., 3600., 0); |
2080 |
|
|
.Ve |
2081 |
|
|
.Sp |
2082 |
|
|
This doesn't mean there will always be 3600 seconds in between triggers, |
2083 |
root |
1.68 |
but only that the callback will be called when the system time shows a |
2084 |
root |
1.1 |
full hour (\s-1UTC\s0), or more correctly, when the system time is evenly divisible |
2085 |
|
|
by 3600. |
2086 |
|
|
.Sp |
2087 |
|
|
Another way to think about it (for the mathematically inclined) is that |
2088 |
|
|
\&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible |
2089 |
root |
1.78 |
time where \f(CW\*(C`time = offset (mod interval)\*(C'\fR, regardless of any time jumps. |
2090 |
root |
1.46 |
.Sp |
2091 |
root |
1.78 |
For numerical stability it is preferable that the \f(CW\*(C`offset\*(C'\fR value is near |
2092 |
root |
1.46 |
\&\f(CW\*(C`ev_now ()\*(C'\fR (the current time), but there is no range requirement for |
2093 |
root |
1.67 |
this value, and in fact is often specified as zero. |
2094 |
|
|
.Sp |
2095 |
root |
1.68 |
Note also that there is an upper limit to how often a timer can fire (\s-1CPU\s0 |
2096 |
root |
1.67 |
speed for example), so if \f(CW\*(C`interval\*(C'\fR is very small then timing stability |
2097 |
root |
1.68 |
will of course deteriorate. Libev itself tries to be exact to be about one |
2098 |
root |
1.67 |
millisecond (if the \s-1OS\s0 supports it and the machine is fast enough). |
2099 |
root |
1.60 |
.IP "\(bu" 4 |
2100 |
root |
1.78 |
manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback) |
2101 |
root |
1.60 |
.Sp |
2102 |
root |
1.78 |
In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`offset\*(C'\fR are both being |
2103 |
root |
1.1 |
ignored. Instead, each time the periodic watcher gets scheduled, the |
2104 |
|
|
reschedule callback will be called with the watcher as first, and the |
2105 |
|
|
current time as second argument. |
2106 |
|
|
.Sp |
2107 |
root |
1.78 |
\&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher, ever, |
2108 |
|
|
or make \s-1ANY\s0 other event loop modifications whatsoever, unless explicitly |
2109 |
|
|
allowed by documentation here\fR. |
2110 |
root |
1.67 |
.Sp |
2111 |
|
|
If you need to stop it, return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop |
2112 |
|
|
it afterwards (e.g. by starting an \f(CW\*(C`ev_prepare\*(C'\fR watcher, which is the |
2113 |
|
|
only event loop modification you are allowed to do). |
2114 |
root |
1.1 |
.Sp |
2115 |
root |
1.73 |
The callback prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(ev_periodic |
2116 |
root |
1.67 |
*w, ev_tstamp now)\*(C'\fR, e.g.: |
2117 |
root |
1.1 |
.Sp |
2118 |
root |
1.73 |
.Vb 5 |
2119 |
|
|
\& static ev_tstamp |
2120 |
|
|
\& my_rescheduler (ev_periodic *w, ev_tstamp now) |
2121 |
root |
1.1 |
\& { |
2122 |
|
|
\& return now + 60.; |
2123 |
|
|
\& } |
2124 |
|
|
.Ve |
2125 |
|
|
.Sp |
2126 |
|
|
It must return the next time to trigger, based on the passed time value |
2127 |
|
|
(that is, the lowest time value larger than to the second argument). It |
2128 |
|
|
will usually be called just before the callback will be triggered, but |
2129 |
|
|
might be called at other times, too. |
2130 |
|
|
.Sp |
2131 |
root |
1.67 |
\&\s-1NOTE:\s0 \fIThis callback must always return a time that is higher than or |
2132 |
|
|
equal to the passed \f(CI\*(C`now\*(C'\fI value\fR. |
2133 |
root |
1.1 |
.Sp |
2134 |
|
|
This can be used to create very complex timers, such as a timer that |
2135 |
root |
1.67 |
triggers on \*(L"next midnight, local time\*(R". To do this, you would calculate the |
2136 |
root |
1.1 |
next midnight after \f(CW\*(C`now\*(C'\fR and return the timestamp value for this. How |
2137 |
|
|
you do this is, again, up to you (but it is not trivial, which is the main |
2138 |
|
|
reason I omitted it as an example). |
2139 |
|
|
.RE |
2140 |
|
|
.RS 4 |
2141 |
|
|
.RE |
2142 |
|
|
.IP "ev_periodic_again (loop, ev_periodic *)" 4 |
2143 |
|
|
.IX Item "ev_periodic_again (loop, ev_periodic *)" |
2144 |
|
|
Simply stops and restarts the periodic watcher again. This is only useful |
2145 |
|
|
when you changed some parameters or the reschedule callback would return |
2146 |
|
|
a different time than the last time it was called (e.g. in a crond like |
2147 |
|
|
program when the crontabs have changed). |
2148 |
root |
1.65 |
.IP "ev_tstamp ev_periodic_at (ev_periodic *)" 4 |
2149 |
|
|
.IX Item "ev_tstamp ev_periodic_at (ev_periodic *)" |
2150 |
root |
1.78 |
When active, returns the absolute time that the watcher is supposed |
2151 |
|
|
to trigger next. This is not the same as the \f(CW\*(C`offset\*(C'\fR argument to |
2152 |
|
|
\&\f(CW\*(C`ev_periodic_set\*(C'\fR, but indeed works even in interval and manual |
2153 |
|
|
rescheduling modes. |
2154 |
root |
1.46 |
.IP "ev_tstamp offset [read\-write]" 4 |
2155 |
|
|
.IX Item "ev_tstamp offset [read-write]" |
2156 |
|
|
When repeating, this contains the offset value, otherwise this is the |
2157 |
root |
1.78 |
absolute point in time (the \f(CW\*(C`offset\*(C'\fR value passed to \f(CW\*(C`ev_periodic_set\*(C'\fR, |
2158 |
|
|
although libev might modify this value for better numerical stability). |
2159 |
root |
1.46 |
.Sp |
2160 |
|
|
Can be modified any time, but changes only take effect when the periodic |
2161 |
|
|
timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called. |
2162 |
root |
1.22 |
.IP "ev_tstamp interval [read\-write]" 4 |
2163 |
|
|
.IX Item "ev_tstamp interval [read-write]" |
2164 |
|
|
The current interval value. Can be modified any time, but changes only |
2165 |
|
|
take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being |
2166 |
|
|
called. |
2167 |
root |
1.73 |
.IP "ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read\-write]" 4 |
2168 |
|
|
.IX Item "ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]" |
2169 |
root |
1.22 |
The current reschedule callback, or \f(CW0\fR, if this functionality is |
2170 |
|
|
switched off. Can be changed any time, but changes only take effect when |
2171 |
|
|
the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called. |
2172 |
root |
1.9 |
.PP |
2173 |
root |
1.60 |
\fIExamples\fR |
2174 |
|
|
.IX Subsection "Examples" |
2175 |
|
|
.PP |
2176 |
root |
1.28 |
Example: Call a callback every hour, or, more precisely, whenever the |
2177 |
root |
1.71 |
system time is divisible by 3600. The callback invocation times have |
2178 |
root |
1.68 |
potentially a lot of jitter, but good long-term stability. |
2179 |
root |
1.9 |
.PP |
2180 |
|
|
.Vb 5 |
2181 |
root |
1.68 |
\& static void |
2182 |
root |
1.73 |
\& clock_cb (struct ev_loop *loop, ev_io *w, int revents) |
2183 |
root |
1.68 |
\& { |
2184 |
|
|
\& ... its now a full hour (UTC, or TAI or whatever your clock follows) |
2185 |
|
|
\& } |
2186 |
|
|
\& |
2187 |
root |
1.73 |
\& ev_periodic hourly_tick; |
2188 |
root |
1.68 |
\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
2189 |
|
|
\& ev_periodic_start (loop, &hourly_tick); |
2190 |
root |
1.9 |
.Ve |
2191 |
|
|
.PP |
2192 |
root |
1.28 |
Example: The same as above, but use a reschedule callback to do it: |
2193 |
root |
1.9 |
.PP |
2194 |
|
|
.Vb 1 |
2195 |
root |
1.68 |
\& #include <math.h> |
2196 |
root |
1.60 |
\& |
2197 |
root |
1.68 |
\& static ev_tstamp |
2198 |
root |
1.73 |
\& my_scheduler_cb (ev_periodic *w, ev_tstamp now) |
2199 |
root |
1.68 |
\& { |
2200 |
root |
1.71 |
\& return now + (3600. \- fmod (now, 3600.)); |
2201 |
root |
1.68 |
\& } |
2202 |
root |
1.60 |
\& |
2203 |
root |
1.68 |
\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
2204 |
root |
1.9 |
.Ve |
2205 |
|
|
.PP |
2206 |
root |
1.28 |
Example: Call a callback every hour, starting now: |
2207 |
root |
1.9 |
.PP |
2208 |
|
|
.Vb 4 |
2209 |
root |
1.73 |
\& ev_periodic hourly_tick; |
2210 |
root |
1.68 |
\& ev_periodic_init (&hourly_tick, clock_cb, |
2211 |
|
|
\& fmod (ev_now (loop), 3600.), 3600., 0); |
2212 |
|
|
\& ev_periodic_start (loop, &hourly_tick); |
2213 |
root |
1.9 |
.Ve |
2214 |
root |
1.79 |
.ie n .SS """ev_signal"" \- signal me when a signal gets signalled!" |
2215 |
|
|
.el .SS "\f(CWev_signal\fP \- signal me when a signal gets signalled!" |
2216 |
root |
1.17 |
.IX Subsection "ev_signal - signal me when a signal gets signalled!" |
2217 |
root |
1.1 |
Signal watchers will trigger an event when the process receives a specific |
2218 |
|
|
signal one or more times. Even though signals are very asynchronous, libev |
2219 |
|
|
will try it's best to deliver signals synchronously, i.e. as part of the |
2220 |
|
|
normal event processing, like any other event. |
2221 |
|
|
.PP |
2222 |
root |
1.71 |
If you want signals asynchronously, just use \f(CW\*(C`sigaction\*(C'\fR as you would |
2223 |
|
|
do without libev and forget about sharing the signal. You can even use |
2224 |
|
|
\&\f(CW\*(C`ev_async\*(C'\fR from a signal handler to synchronously wake up an event loop. |
2225 |
|
|
.PP |
2226 |
root |
1.1 |
You can configure as many watchers as you like per signal. Only when the |
2227 |
root |
1.71 |
first watcher gets started will libev actually register a signal handler |
2228 |
|
|
with the kernel (thus it coexists with your own signal handlers as long as |
2229 |
|
|
you don't register any with libev for the same signal). Similarly, when |
2230 |
|
|
the last signal watcher for a signal is stopped, libev will reset the |
2231 |
|
|
signal handler to \s-1SIG_DFL\s0 (regardless of what it was set to before). |
2232 |
root |
1.50 |
.PP |
2233 |
root |
1.61 |
If possible and supported, libev will install its handlers with |
2234 |
root |
1.68 |
\&\f(CW\*(C`SA_RESTART\*(C'\fR behaviour enabled, so system calls should not be unduly |
2235 |
|
|
interrupted. If you have a problem with system calls getting interrupted by |
2236 |
root |
1.61 |
signals you can block all signals in an \f(CW\*(C`ev_check\*(C'\fR watcher and unblock |
2237 |
|
|
them in an \f(CW\*(C`ev_prepare\*(C'\fR watcher. |
2238 |
|
|
.PP |
2239 |
root |
1.50 |
\fIWatcher-Specific Functions and Data Members\fR |
2240 |
|
|
.IX Subsection "Watcher-Specific Functions and Data Members" |
2241 |
root |
1.1 |
.IP "ev_signal_init (ev_signal *, callback, int signum)" 4 |
2242 |
|
|
.IX Item "ev_signal_init (ev_signal *, callback, int signum)" |
2243 |
|
|
.PD 0 |
2244 |
|
|
.IP "ev_signal_set (ev_signal *, int signum)" 4 |
2245 |
|
|
.IX Item "ev_signal_set (ev_signal *, int signum)" |
2246 |
|
|
.PD |
2247 |
|
|
Configures the watcher to trigger on the given signal number (usually one |
2248 |
|
|
of the \f(CW\*(C`SIGxxx\*(C'\fR constants). |
2249 |
root |
1.22 |
.IP "int signum [read\-only]" 4 |
2250 |
|
|
.IX Item "int signum [read-only]" |
2251 |
|
|
The signal the watcher watches out for. |
2252 |
root |
1.61 |
.PP |
2253 |
|
|
\fIExamples\fR |
2254 |
|
|
.IX Subsection "Examples" |
2255 |
|
|
.PP |
2256 |
root |
1.72 |
Example: Try to exit cleanly on \s-1SIGINT\s0. |
2257 |
root |
1.61 |
.PP |
2258 |
|
|
.Vb 5 |
2259 |
root |
1.68 |
\& static void |
2260 |
root |
1.73 |
\& sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
2261 |
root |
1.68 |
\& { |
2262 |
|
|
\& ev_unloop (loop, EVUNLOOP_ALL); |
2263 |
|
|
\& } |
2264 |
|
|
\& |
2265 |
root |
1.73 |
\& ev_signal signal_watcher; |
2266 |
root |
1.68 |
\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
2267 |
root |
1.72 |
\& ev_signal_start (loop, &signal_watcher); |
2268 |
root |
1.61 |
.Ve |
2269 |
root |
1.79 |
.ie n .SS """ev_child"" \- watch out for process status changes" |
2270 |
|
|
.el .SS "\f(CWev_child\fP \- watch out for process status changes" |
2271 |
root |
1.17 |
.IX Subsection "ev_child - watch out for process status changes" |
2272 |
root |
1.1 |
Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to |
2273 |
root |
1.71 |
some child status changes (most typically when a child of yours dies or |
2274 |
|
|
exits). It is permissible to install a child watcher \fIafter\fR the child |
2275 |
|
|
has been forked (which implies it might have already exited), as long |
2276 |
|
|
as the event loop isn't entered (or is continued from a watcher), i.e., |
2277 |
|
|
forking and then immediately registering a watcher for the child is fine, |
2278 |
root |
1.79 |
but forking and registering a watcher a few event loop iterations later or |
2279 |
|
|
in the next callback invocation is not. |
2280 |
root |
1.61 |
.PP |
2281 |
|
|
Only the default event loop is capable of handling signals, and therefore |
2282 |
root |
1.68 |
you can only register child watchers in the default event loop. |
2283 |
root |
1.61 |
.PP |
2284 |
root |
1.79 |
Due to some design glitches inside libev, child watchers will always be |
2285 |
|
|
handled at maximum priority (their priority is set to \f(CW\*(C`EV_MAXPRI\*(C'\fR by |
2286 |
|
|
libev) |
2287 |
|
|
.PP |
2288 |
root |
1.61 |
\fIProcess Interaction\fR |
2289 |
|
|
.IX Subsection "Process Interaction" |
2290 |
|
|
.PP |
2291 |
|
|
Libev grabs \f(CW\*(C`SIGCHLD\*(C'\fR as soon as the default event loop is |
2292 |
|
|
initialised. This is necessary to guarantee proper behaviour even if |
2293 |
root |
1.68 |
the first child watcher is started after the child exits. The occurrence |
2294 |
root |
1.61 |
of \f(CW\*(C`SIGCHLD\*(C'\fR is recorded asynchronously, but child reaping is done |
2295 |
|
|
synchronously as part of the event loop processing. Libev always reaps all |
2296 |
|
|
children, even ones not watched. |
2297 |
|
|
.PP |
2298 |
|
|
\fIOverriding the Built-In Processing\fR |
2299 |
|
|
.IX Subsection "Overriding the Built-In Processing" |
2300 |
|
|
.PP |
2301 |
|
|
Libev offers no special support for overriding the built-in child |
2302 |
|
|
processing, but if your application collides with libev's default child |
2303 |
|
|
handler, you can override it easily by installing your own handler for |
2304 |
|
|
\&\f(CW\*(C`SIGCHLD\*(C'\fR after initialising the default loop, and making sure the |
2305 |
|
|
default loop never gets destroyed. You are encouraged, however, to use an |
2306 |
|
|
event-based approach to child reaping and thus use libev's support for |
2307 |
|
|
that, so other libev users can use \f(CW\*(C`ev_child\*(C'\fR watchers freely. |
2308 |
root |
1.50 |
.PP |
2309 |
root |
1.71 |
\fIStopping the Child Watcher\fR |
2310 |
|
|
.IX Subsection "Stopping the Child Watcher" |
2311 |
|
|
.PP |
2312 |
|
|
Currently, the child watcher never gets stopped, even when the |
2313 |
|
|
child terminates, so normally one needs to stop the watcher in the |
2314 |
|
|
callback. Future versions of libev might stop the watcher automatically |
2315 |
|
|
when a child exit is detected. |
2316 |
|
|
.PP |
2317 |
root |
1.50 |
\fIWatcher-Specific Functions and Data Members\fR |
2318 |
|
|
.IX Subsection "Watcher-Specific Functions and Data Members" |
2319 |
root |
1.60 |
.IP "ev_child_init (ev_child *, callback, int pid, int trace)" 4 |
2320 |
|
|
.IX Item "ev_child_init (ev_child *, callback, int pid, int trace)" |
2321 |
root |
1.1 |
.PD 0 |
2322 |
root |
1.60 |
.IP "ev_child_set (ev_child *, int pid, int trace)" 4 |
2323 |
|
|
.IX Item "ev_child_set (ev_child *, int pid, int trace)" |
2324 |
root |
1.1 |
.PD |
2325 |
|
|
Configures the watcher to wait for status changes of process \f(CW\*(C`pid\*(C'\fR (or |
2326 |
|
|
\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look |
2327 |
|
|
at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see |
2328 |
|
|
the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems |
2329 |
|
|
\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the |
2330 |
root |
1.60 |
process causing the status change. \f(CW\*(C`trace\*(C'\fR must be either \f(CW0\fR (only |
2331 |
|
|
activate the watcher when the process terminates) or \f(CW1\fR (additionally |
2332 |
|
|
activate the watcher when the process is stopped or continued). |
2333 |
root |
1.22 |
.IP "int pid [read\-only]" 4 |
2334 |
|
|
.IX Item "int pid [read-only]" |
2335 |
|
|
The process id this watcher watches out for, or \f(CW0\fR, meaning any process id. |
2336 |
|
|
.IP "int rpid [read\-write]" 4 |
2337 |
|
|
.IX Item "int rpid [read-write]" |
2338 |
|
|
The process id that detected a status change. |
2339 |
|
|
.IP "int rstatus [read\-write]" 4 |
2340 |
|
|
.IX Item "int rstatus [read-write]" |
2341 |
|
|
The process exit/trace status caused by \f(CW\*(C`rpid\*(C'\fR (see your systems |
2342 |
|
|
\&\f(CW\*(C`waitpid\*(C'\fR and \f(CW\*(C`sys/wait.h\*(C'\fR documentation for details). |
2343 |
root |
1.9 |
.PP |
2344 |
root |
1.60 |
\fIExamples\fR |
2345 |
|
|
.IX Subsection "Examples" |
2346 |
|
|
.PP |
2347 |
root |
1.61 |
Example: \f(CW\*(C`fork()\*(C'\fR a new process and install a child handler to wait for |
2348 |
|
|
its completion. |
2349 |
root |
1.9 |
.PP |
2350 |
root |
1.61 |
.Vb 1 |
2351 |
root |
1.68 |
\& ev_child cw; |
2352 |
root |
1.61 |
\& |
2353 |
root |
1.68 |
\& static void |
2354 |
root |
1.73 |
\& child_cb (EV_P_ ev_child *w, int revents) |
2355 |
root |
1.68 |
\& { |
2356 |
|
|
\& ev_child_stop (EV_A_ w); |
2357 |
|
|
\& printf ("process %d exited with status %x\en", w\->rpid, w\->rstatus); |
2358 |
|
|
\& } |
2359 |
|
|
\& |
2360 |
|
|
\& pid_t pid = fork (); |
2361 |
|
|
\& |
2362 |
|
|
\& if (pid < 0) |
2363 |
|
|
\& // error |
2364 |
|
|
\& else if (pid == 0) |
2365 |
|
|
\& { |
2366 |
|
|
\& // the forked child executes here |
2367 |
|
|
\& exit (1); |
2368 |
|
|
\& } |
2369 |
|
|
\& else |
2370 |
|
|
\& { |
2371 |
|
|
\& ev_child_init (&cw, child_cb, pid, 0); |
2372 |
|
|
\& ev_child_start (EV_DEFAULT_ &cw); |
2373 |
|
|
\& } |
2374 |
root |
1.9 |
.Ve |
2375 |
root |
1.79 |
.ie n .SS """ev_stat"" \- did the file attributes just change?" |
2376 |
|
|
.el .SS "\f(CWev_stat\fP \- did the file attributes just change?" |
2377 |
root |
1.22 |
.IX Subsection "ev_stat - did the file attributes just change?" |
2378 |
root |
1.68 |
This watches a file system path for attribute changes. That is, it calls |
2379 |
root |
1.73 |
\&\f(CW\*(C`stat\*(C'\fR on that path in regular intervals (or when the \s-1OS\s0 says it changed) |
2380 |
|
|
and sees if it changed compared to the last time, invoking the callback if |
2381 |
|
|
it did. |
2382 |
root |
1.22 |
.PP |
2383 |
|
|
The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does |
2384 |
root |
1.74 |
not exist\*(R" is a status change like any other. The condition \*(L"path does not |
2385 |
|
|
exist\*(R" (or more correctly \*(L"path cannot be stat'ed\*(R") is signified by the |
2386 |
|
|
\&\f(CW\*(C`st_nlink\*(C'\fR field being zero (which is otherwise always forced to be at |
2387 |
|
|
least one) and all the other fields of the stat buffer having unspecified |
2388 |
|
|
contents. |
2389 |
root |
1.22 |
.PP |
2390 |
root |
1.73 |
The path \fImust not\fR end in a slash or contain special components such as |
2391 |
|
|
\&\f(CW\*(C`.\*(C'\fR or \f(CW\*(C`..\*(C'\fR. The path \fIshould\fR be absolute: If it is relative and |
2392 |
|
|
your working directory changes, then the behaviour is undefined. |
2393 |
|
|
.PP |
2394 |
|
|
Since there is no portable change notification interface available, the |
2395 |
|
|
portable implementation simply calls \f(CWstat(2)\fR regularly on the path |
2396 |
|
|
to see if it changed somehow. You can specify a recommended polling |
2397 |
|
|
interval for this case. If you specify a polling interval of \f(CW0\fR (highly |
2398 |
|
|
recommended!) then a \fIsuitable, unspecified default\fR value will be used |
2399 |
|
|
(which you can expect to be around five seconds, although this might |
2400 |
|
|
change dynamically). Libev will also impose a minimum interval which is |
2401 |
|
|
currently around \f(CW0.1\fR, but that's usually overkill. |
2402 |
root |
1.22 |
.PP |
2403 |
|
|
This watcher type is not meant for massive numbers of stat watchers, |
2404 |
|
|
as even with OS-supported change notifications, this can be |
2405 |
root |
1.60 |
resource-intensive. |
2406 |
root |
1.22 |
.PP |
2407 |
root |
1.71 |
At the time of this writing, the only OS-specific interface implemented |
2408 |
root |
1.74 |
is the Linux inotify interface (implementing kqueue support is left as an |
2409 |
|
|
exercise for the reader. Note, however, that the author sees no way of |
2410 |
|
|
implementing \f(CW\*(C`ev_stat\*(C'\fR semantics with kqueue, except as a hint). |
2411 |
root |
1.50 |
.PP |
2412 |
root |
1.63 |
\fI\s-1ABI\s0 Issues (Largefile Support)\fR |
2413 |
|
|
.IX Subsection "ABI Issues (Largefile Support)" |
2414 |
|
|
.PP |
2415 |
|
|
Libev by default (unless the user overrides this) uses the default |
2416 |
root |
1.69 |
compilation environment, which means that on systems with large file |
2417 |
|
|
support disabled by default, you get the 32 bit version of the stat |
2418 |
root |
1.63 |
structure. When using the library from programs that change the \s-1ABI\s0 to |
2419 |
|
|
use 64 bit file offsets the programs will fail. In that case you have to |
2420 |
|
|
compile libev with the same flags to get binary compatibility. This is |
2421 |
|
|
obviously the case with any flags that change the \s-1ABI\s0, but the problem is |
2422 |
root |
1.73 |
most noticeably displayed with ev_stat and large file support. |
2423 |
root |
1.69 |
.PP |
2424 |
|
|
The solution for this is to lobby your distribution maker to make large |
2425 |
|
|
file interfaces available by default (as e.g. FreeBSD does) and not |
2426 |
|
|
optional. Libev cannot simply switch on large file support because it has |
2427 |
|
|
to exchange stat structures with application programs compiled using the |
2428 |
|
|
default compilation environment. |
2429 |
root |
1.63 |
.PP |
2430 |
root |
1.71 |
\fIInotify and Kqueue\fR |
2431 |
|
|
.IX Subsection "Inotify and Kqueue" |
2432 |
root |
1.59 |
.PP |
2433 |
root |
1.74 |
When \f(CW\*(C`inotify (7)\*(C'\fR support has been compiled into libev and present at |
2434 |
|
|
runtime, it will be used to speed up change detection where possible. The |
2435 |
|
|
inotify descriptor will be created lazily when the first \f(CW\*(C`ev_stat\*(C'\fR |
2436 |
|
|
watcher is being started. |
2437 |
root |
1.59 |
.PP |
2438 |
root |
1.65 |
Inotify presence does not change the semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers |
2439 |
root |
1.59 |
except that changes might be detected earlier, and in some cases, to avoid |
2440 |
root |
1.65 |
making regular \f(CW\*(C`stat\*(C'\fR calls. Even in the presence of inotify support |
2441 |
root |
1.71 |
there are many cases where libev has to resort to regular \f(CW\*(C`stat\*(C'\fR polling, |
2442 |
root |
1.74 |
but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too |
2443 |
|
|
many bugs), the path exists (i.e. stat succeeds), and the path resides on |
2444 |
|
|
a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and |
2445 |
|
|
xfs are fully working) libev usually gets away without polling. |
2446 |
root |
1.59 |
.PP |
2447 |
root |
1.71 |
There is no support for kqueue, as apparently it cannot be used to |
2448 |
root |
1.59 |
implement this functionality, due to the requirement of having a file |
2449 |
root |
1.71 |
descriptor open on the object at all times, and detecting renames, unlinks |
2450 |
|
|
etc. is difficult. |
2451 |
root |
1.59 |
.PP |
2452 |
root |
1.74 |
\fI\f(CI\*(C`stat ()\*(C'\fI is a synchronous operation\fR |
2453 |
|
|
.IX Subsection "stat () is a synchronous operation" |
2454 |
|
|
.PP |
2455 |
|
|
Libev doesn't normally do any kind of I/O itself, and so is not blocking |
2456 |
|
|
the process. The exception are \f(CW\*(C`ev_stat\*(C'\fR watchers \- those call \f(CW\*(C`stat |
2457 |
|
|
()\*(C'\fR, which is a synchronous operation. |
2458 |
|
|
.PP |
2459 |
|
|
For local paths, this usually doesn't matter: unless the system is very |
2460 |
|
|
busy or the intervals between stat's are large, a stat call will be fast, |
2461 |
root |
1.75 |
as the path data is usually in memory already (except when starting the |
2462 |
root |
1.74 |
watcher). |
2463 |
|
|
.PP |
2464 |
|
|
For networked file systems, calling \f(CW\*(C`stat ()\*(C'\fR can block an indefinite |
2465 |
|
|
time due to network issues, and even under good conditions, a stat call |
2466 |
|
|
often takes multiple milliseconds. |
2467 |
|
|
.PP |
2468 |
|
|
Therefore, it is best to avoid using \f(CW\*(C`ev_stat\*(C'\fR watchers on networked |
2469 |
|
|
paths, although this is fully supported by libev. |
2470 |
|
|
.PP |
2471 |
root |
1.59 |
\fIThe special problem of stat time resolution\fR |
2472 |
|
|
.IX Subsection "The special problem of stat time resolution" |
2473 |
|
|
.PP |
2474 |
root |
1.73 |
The \f(CW\*(C`stat ()\*(C'\fR system call only supports full-second resolution portably, |
2475 |
|
|
and even on systems where the resolution is higher, most file systems |
2476 |
|
|
still only support whole seconds. |
2477 |
root |
1.59 |
.PP |
2478 |
root |
1.65 |
That means that, if the time is the only thing that changes, you can |
2479 |
|
|
easily miss updates: on the first update, \f(CW\*(C`ev_stat\*(C'\fR detects a change and |
2480 |
|
|
calls your callback, which does something. When there is another update |
2481 |
root |
1.71 |
within the same second, \f(CW\*(C`ev_stat\*(C'\fR will be unable to detect unless the |
2482 |
|
|
stat data does change in other ways (e.g. file size). |
2483 |
root |
1.65 |
.PP |
2484 |
|
|
The solution to this is to delay acting on a change for slightly more |
2485 |
root |
1.67 |
than a second (or till slightly after the next full second boundary), using |
2486 |
root |
1.65 |
a roughly one-second-delay \f(CW\*(C`ev_timer\*(C'\fR (e.g. \f(CW\*(C`ev_timer_set (w, 0., 1.02); |
2487 |
|
|
ev_timer_again (loop, w)\*(C'\fR). |
2488 |
|
|
.PP |
2489 |
|
|
The \f(CW.02\fR offset is added to work around small timing inconsistencies |
2490 |
|
|
of some operating systems (where the second counter of the current time |
2491 |
|
|
might be be delayed. One such system is the Linux kernel, where a call to |
2492 |
|
|
\&\f(CW\*(C`gettimeofday\*(C'\fR might return a timestamp with a full second later than |
2493 |
|
|
a subsequent \f(CW\*(C`time\*(C'\fR call \- if the equivalent of \f(CW\*(C`time ()\*(C'\fR is used to |
2494 |
|
|
update file times then there will be a small window where the kernel uses |
2495 |
|
|
the previous second to update file times but libev might already execute |
2496 |
|
|
the timer callback). |
2497 |
root |
1.59 |
.PP |
2498 |
root |
1.50 |
\fIWatcher-Specific Functions and Data Members\fR |
2499 |
|
|
.IX Subsection "Watcher-Specific Functions and Data Members" |
2500 |
root |
1.22 |
.IP "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 4 |
2501 |
|
|
.IX Item "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" |
2502 |
|
|
.PD 0 |
2503 |
|
|
.IP "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" 4 |
2504 |
|
|
.IX Item "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" |
2505 |
|
|
.PD |
2506 |
|
|
Configures the watcher to wait for status changes of the given |
2507 |
|
|
\&\f(CW\*(C`path\*(C'\fR. The \f(CW\*(C`interval\*(C'\fR is a hint on how quickly a change is expected to |
2508 |
|
|
be detected and should normally be specified as \f(CW0\fR to let libev choose |
2509 |
|
|
a suitable value. The memory pointed to by \f(CW\*(C`path\*(C'\fR must point to the same |
2510 |
|
|
path for as long as the watcher is active. |
2511 |
|
|
.Sp |
2512 |
root |
1.71 |
The callback will receive an \f(CW\*(C`EV_STAT\*(C'\fR event when a change was detected, |
2513 |
|
|
relative to the attributes at the time the watcher was started (or the |
2514 |
|
|
last change was detected). |
2515 |
root |
1.61 |
.IP "ev_stat_stat (loop, ev_stat *)" 4 |
2516 |
|
|
.IX Item "ev_stat_stat (loop, ev_stat *)" |
2517 |
root |
1.22 |
Updates the stat buffer immediately with new values. If you change the |
2518 |
root |
1.65 |
watched path in your callback, you could call this function to avoid |
2519 |
|
|
detecting this change (while introducing a race condition if you are not |
2520 |
|
|
the only one changing the path). Can also be useful simply to find out the |
2521 |
|
|
new values. |
2522 |
root |
1.22 |
.IP "ev_statdata attr [read\-only]" 4 |
2523 |
|
|
.IX Item "ev_statdata attr [read-only]" |
2524 |
root |
1.65 |
The most-recently detected attributes of the file. Although the type is |
2525 |
root |
1.22 |
\&\f(CW\*(C`ev_statdata\*(C'\fR, this is usually the (or one of the) \f(CW\*(C`struct stat\*(C'\fR types |
2526 |
root |
1.65 |
suitable for your system, but you can only rely on the POSIX-standardised |
2527 |
|
|
members to be present. If the \f(CW\*(C`st_nlink\*(C'\fR member is \f(CW0\fR, then there was |
2528 |
|
|
some error while \f(CW\*(C`stat\*(C'\fRing the file. |
2529 |
root |
1.22 |
.IP "ev_statdata prev [read\-only]" 4 |
2530 |
|
|
.IX Item "ev_statdata prev [read-only]" |
2531 |
|
|
The previous attributes of the file. The callback gets invoked whenever |
2532 |
root |
1.65 |
\&\f(CW\*(C`prev\*(C'\fR != \f(CW\*(C`attr\*(C'\fR, or, more precisely, one or more of these members |
2533 |
|
|
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, |
2534 |
|
|
\&\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. |
2535 |
root |
1.22 |
.IP "ev_tstamp interval [read\-only]" 4 |
2536 |
|
|
.IX Item "ev_tstamp interval [read-only]" |
2537 |
|
|
The specified interval. |
2538 |
|
|
.IP "const char *path [read\-only]" 4 |
2539 |
|
|
.IX Item "const char *path [read-only]" |
2540 |
root |
1.68 |
The file system path that is being watched. |
2541 |
root |
1.22 |
.PP |
2542 |
root |
1.59 |
\fIExamples\fR |
2543 |
|
|
.IX Subsection "Examples" |
2544 |
|
|
.PP |
2545 |
root |
1.22 |
Example: Watch \f(CW\*(C`/etc/passwd\*(C'\fR for attribute changes. |
2546 |
|
|
.PP |
2547 |
root |
1.60 |
.Vb 10 |
2548 |
root |
1.68 |
\& static void |
2549 |
|
|
\& passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) |
2550 |
|
|
\& { |
2551 |
|
|
\& /* /etc/passwd changed in some way */ |
2552 |
|
|
\& if (w\->attr.st_nlink) |
2553 |
|
|
\& { |
2554 |
|
|
\& printf ("passwd current size %ld\en", (long)w\->attr.st_size); |
2555 |
|
|
\& printf ("passwd current atime %ld\en", (long)w\->attr.st_mtime); |
2556 |
|
|
\& printf ("passwd current mtime %ld\en", (long)w\->attr.st_mtime); |
2557 |
|
|
\& } |
2558 |
|
|
\& else |
2559 |
|
|
\& /* you shalt not abuse printf for puts */ |
2560 |
|
|
\& puts ("wow, /etc/passwd is not there, expect problems. " |
2561 |
|
|
\& "if this is windows, they already arrived\en"); |
2562 |
|
|
\& } |
2563 |
root |
1.60 |
\& |
2564 |
root |
1.68 |
\& ... |
2565 |
|
|
\& ev_stat passwd; |
2566 |
root |
1.60 |
\& |
2567 |
root |
1.68 |
\& ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.); |
2568 |
|
|
\& ev_stat_start (loop, &passwd); |
2569 |
root |
1.22 |
.Ve |
2570 |
root |
1.59 |
.PP |
2571 |
|
|
Example: Like above, but additionally use a one-second delay so we do not |
2572 |
|
|
miss updates (however, frequent updates will delay processing, too, so |
2573 |
|
|
one might do the work both on \f(CW\*(C`ev_stat\*(C'\fR callback invocation \fIand\fR on |
2574 |
|
|
\&\f(CW\*(C`ev_timer\*(C'\fR callback invocation). |
2575 |
|
|
.PP |
2576 |
|
|
.Vb 2 |
2577 |
root |
1.68 |
\& static ev_stat passwd; |
2578 |
|
|
\& static ev_timer timer; |
2579 |
root |
1.60 |
\& |
2580 |
root |
1.68 |
\& static void |
2581 |
|
|
\& timer_cb (EV_P_ ev_timer *w, int revents) |
2582 |
|
|
\& { |
2583 |
|
|
\& ev_timer_stop (EV_A_ w); |
2584 |
|
|
\& |
2585 |
|
|
\& /* now it\*(Aqs one second after the most recent passwd change */ |
2586 |
|
|
\& } |
2587 |
|
|
\& |
2588 |
|
|
\& static void |
2589 |
|
|
\& stat_cb (EV_P_ ev_stat *w, int revents) |
2590 |
|
|
\& { |
2591 |
|
|
\& /* reset the one\-second timer */ |
2592 |
|
|
\& ev_timer_again (EV_A_ &timer); |
2593 |
|
|
\& } |
2594 |
|
|
\& |
2595 |
|
|
\& ... |
2596 |
|
|
\& ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
2597 |
|
|
\& ev_stat_start (loop, &passwd); |
2598 |
|
|
\& ev_timer_init (&timer, timer_cb, 0., 1.02); |
2599 |
root |
1.59 |
.Ve |
2600 |
root |
1.79 |
.ie n .SS """ev_idle"" \- when you've got nothing better to do..." |
2601 |
|
|
.el .SS "\f(CWev_idle\fP \- when you've got nothing better to do..." |
2602 |
root |
1.17 |
.IX Subsection "ev_idle - when you've got nothing better to do..." |
2603 |
root |
1.37 |
Idle watchers trigger events when no other events of the same or higher |
2604 |
root |
1.71 |
priority are pending (prepare, check and other idle watchers do not count |
2605 |
|
|
as receiving \*(L"events\*(R"). |
2606 |
root |
1.37 |
.PP |
2607 |
|
|
That is, as long as your process is busy handling sockets or timeouts |
2608 |
|
|
(or even signals, imagine) of the same or higher priority it will not be |
2609 |
|
|
triggered. But when your process is idle (or only lower-priority watchers |
2610 |
|
|
are pending), the idle watchers are being called once per event loop |
2611 |
|
|
iteration \- until stopped, that is, or your process receives more events |
2612 |
|
|
and becomes busy again with higher priority stuff. |
2613 |
root |
1.1 |
.PP |
2614 |
|
|
The most noteworthy effect is that as long as any idle watchers are |
2615 |
|
|
active, the process will not block when waiting for new events. |
2616 |
|
|
.PP |
2617 |
|
|
Apart from keeping your process non-blocking (which is a useful |
2618 |
|
|
effect on its own sometimes), idle watchers are a good place to do |
2619 |
root |
1.60 |
\&\*(L"pseudo-background processing\*(R", or delay processing stuff to after the |
2620 |
root |
1.1 |
event loop has handled all outstanding events. |
2621 |
root |
1.50 |
.PP |
2622 |
|
|
\fIWatcher-Specific Functions and Data Members\fR |
2623 |
|
|
.IX Subsection "Watcher-Specific Functions and Data Members" |
2624 |
root |
1.78 |
.IP "ev_idle_init (ev_idle *, callback)" 4 |
2625 |
|
|
.IX Item "ev_idle_init (ev_idle *, callback)" |
2626 |
root |
1.1 |
Initialises and configures the idle watcher \- it has no parameters of any |
2627 |
|
|
kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless, |
2628 |
|
|
believe me. |
2629 |
root |
1.9 |
.PP |
2630 |
root |
1.60 |
\fIExamples\fR |
2631 |
|
|
.IX Subsection "Examples" |
2632 |
|
|
.PP |
2633 |
root |
1.28 |
Example: Dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR watcher, start it, and in the |
2634 |
|
|
callback, free it. Also, use no error checking, as usual. |
2635 |
root |
1.9 |
.PP |
2636 |
|
|
.Vb 7 |
2637 |
root |
1.68 |
\& static void |
2638 |
root |
1.73 |
\& idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
2639 |
root |
1.68 |
\& { |
2640 |
|
|
\& free (w); |
2641 |
|
|
\& // now do something you wanted to do when the program has |
2642 |
|
|
\& // no longer anything immediate to do. |
2643 |
|
|
\& } |
2644 |
|
|
\& |
2645 |
root |
1.73 |
\& ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2646 |
root |
1.68 |
\& ev_idle_init (idle_watcher, idle_cb); |
2647 |
root |
1.79 |
\& ev_idle_start (loop, idle_watcher); |
2648 |
root |
1.9 |
.Ve |
2649 |
root |
1.79 |
.ie n .SS """ev_prepare"" and ""ev_check"" \- customise your event loop!" |
2650 |
|
|
.el .SS "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!" |
2651 |
root |
1.17 |
.IX Subsection "ev_prepare and ev_check - customise your event loop!" |
2652 |
root |
1.71 |
Prepare and check watchers are usually (but not always) used in pairs: |
2653 |
root |
1.1 |
prepare watchers get invoked before the process blocks and check watchers |
2654 |
|
|
afterwards. |
2655 |
|
|
.PP |
2656 |
root |
1.20 |
You \fImust not\fR call \f(CW\*(C`ev_loop\*(C'\fR or similar functions that enter |
2657 |
|
|
the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR |
2658 |
|
|
watchers. Other loops than the current one are fine, however. The |
2659 |
|
|
rationale behind this is that you do not need to check for recursion in |
2660 |
|
|
those watchers, i.e. the sequence will always be \f(CW\*(C`ev_prepare\*(C'\fR, blocking, |
2661 |
|
|
\&\f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each kind they will always be |
2662 |
|
|
called in pairs bracketing the blocking call. |
2663 |
|
|
.PP |
2664 |
root |
1.10 |
Their main purpose is to integrate other event mechanisms into libev and |
2665 |
root |
1.71 |
their use is somewhat advanced. They could be used, for example, to track |
2666 |
root |
1.10 |
variable changes, implement your own watchers, integrate net-snmp or a |
2667 |
root |
1.20 |
coroutine library and lots more. They are also occasionally useful if |
2668 |
|
|
you cache some data and want to flush it before blocking (for example, |
2669 |
|
|
in X programs you might want to do an \f(CW\*(C`XFlush ()\*(C'\fR in an \f(CW\*(C`ev_prepare\*(C'\fR |
2670 |
|
|
watcher). |
2671 |
root |
1.1 |
.PP |
2672 |
root |
1.71 |
This is done by examining in each prepare call which file descriptors |
2673 |
|
|
need to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers |
2674 |
|
|
for them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many |
2675 |
|
|
libraries provide exactly this functionality). Then, in the check watcher, |
2676 |
|
|
you check for any events that occurred (by checking the pending status |
2677 |
|
|
of all watchers and stopping them) and call back into the library. The |
2678 |
|
|
I/O and timer callbacks will never actually be called (but must be valid |
2679 |
|
|
nevertheless, because you never know, you know?). |
2680 |
root |
1.1 |
.PP |
2681 |
|
|
As another example, the Perl Coro module uses these hooks to integrate |
2682 |
|
|
coroutines into libev programs, by yielding to other active coroutines |
2683 |
|
|
during each prepare and only letting the process block if no coroutines |
2684 |
|
|
are ready to run (it's actually more complicated: it only runs coroutines |
2685 |
|
|
with priority higher than or equal to the event loop and one coroutine |
2686 |
|
|
of lower priority, but only once, using idle watchers to keep the event |
2687 |
|
|
loop from blocking if lower-priority coroutines are active, thus mapping |
2688 |
|
|
low-priority coroutines to idle/background tasks). |
2689 |
root |
1.45 |
.PP |
2690 |
|
|
It is recommended to give \f(CW\*(C`ev_check\*(C'\fR watchers highest (\f(CW\*(C`EV_MAXPRI\*(C'\fR) |
2691 |
|
|
priority, to ensure that they are being run before any other watchers |
2692 |
root |
1.71 |
after the poll (this doesn't matter for \f(CW\*(C`ev_prepare\*(C'\fR watchers). |
2693 |
|
|
.PP |
2694 |
|
|
Also, \f(CW\*(C`ev_check\*(C'\fR watchers (and \f(CW\*(C`ev_prepare\*(C'\fR watchers, too) should not |
2695 |
|
|
activate (\*(L"feed\*(R") events into libev. While libev fully supports this, they |
2696 |
|
|
might get executed before other \f(CW\*(C`ev_check\*(C'\fR watchers did their job. As |
2697 |
|
|
\&\f(CW\*(C`ev_check\*(C'\fR watchers are often used to embed other (non-libev) event |
2698 |
|
|
loops those other event loops might be in an unusable state until their |
2699 |
|
|
\&\f(CW\*(C`ev_check\*(C'\fR watcher ran (always remind yourself to coexist peacefully with |
2700 |
|
|
others). |
2701 |
root |
1.50 |
.PP |
2702 |
|
|
\fIWatcher-Specific Functions and Data Members\fR |
2703 |
|
|
.IX Subsection "Watcher-Specific Functions and Data Members" |
2704 |
root |
1.1 |
.IP "ev_prepare_init (ev_prepare *, callback)" 4 |
2705 |
|
|
.IX Item "ev_prepare_init (ev_prepare *, callback)" |
2706 |
|
|
.PD 0 |
2707 |
|
|
.IP "ev_check_init (ev_check *, callback)" 4 |
2708 |
|
|
.IX Item "ev_check_init (ev_check *, callback)" |
2709 |
|
|
.PD |
2710 |
|
|
Initialises and configures the prepare or check watcher \- they have no |
2711 |
|
|
parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR |
2712 |
root |
1.71 |
macros, but using them is utterly, utterly, utterly and completely |
2713 |
|
|
pointless. |
2714 |
root |
1.9 |
.PP |
2715 |
root |
1.60 |
\fIExamples\fR |
2716 |
|
|
.IX Subsection "Examples" |
2717 |
|
|
.PP |
2718 |
root |
1.44 |
There are a number of principal ways to embed other event loops or modules |
2719 |
|
|
into libev. Here are some ideas on how to include libadns into libev |
2720 |
|
|
(there is a Perl module named \f(CW\*(C`EV::ADNS\*(C'\fR that does this, which you could |
2721 |
root |
1.65 |
use as a working example. Another Perl module named \f(CW\*(C`EV::Glib\*(C'\fR embeds a |
2722 |
|
|
Glib main context into libev, and finally, \f(CW\*(C`Glib::EV\*(C'\fR embeds \s-1EV\s0 into the |
2723 |
|
|
Glib event loop). |
2724 |
root |
1.44 |
.PP |
2725 |
|
|
Method 1: Add \s-1IO\s0 watchers and a timeout watcher in a prepare handler, |
2726 |
|
|
and in a check watcher, destroy them and call into libadns. What follows |
2727 |
|
|
is pseudo-code only of course. This requires you to either use a low |
2728 |
|
|
priority for the check watcher or use \f(CW\*(C`ev_clear_pending\*(C'\fR explicitly, as |
2729 |
|
|
the callbacks for the IO/timeout watchers might not have been called yet. |
2730 |
root |
1.20 |
.PP |
2731 |
|
|
.Vb 2 |
2732 |
root |
1.68 |
\& static ev_io iow [nfd]; |
2733 |
|
|
\& static ev_timer tw; |
2734 |
|
|
\& |
2735 |
|
|
\& static void |
2736 |
root |
1.73 |
\& io_cb (struct ev_loop *loop, ev_io *w, int revents) |
2737 |
root |
1.68 |
\& { |
2738 |
|
|
\& } |
2739 |
|
|
\& |
2740 |
|
|
\& // create io watchers for each fd and a timer before blocking |
2741 |
|
|
\& static void |
2742 |
root |
1.73 |
\& adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents) |
2743 |
root |
1.68 |
\& { |
2744 |
|
|
\& int timeout = 3600000; |
2745 |
|
|
\& struct pollfd fds [nfd]; |
2746 |
|
|
\& // actual code will need to loop here and realloc etc. |
2747 |
|
|
\& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2748 |
|
|
\& |
2749 |
|
|
\& /* the callback is illegal, but won\*(Aqt be called as we stop during check */ |
2750 |
root |
1.79 |
\& ev_timer_init (&tw, 0, timeout * 1e\-3, 0.); |
2751 |
root |
1.68 |
\& ev_timer_start (loop, &tw); |
2752 |
root |
1.60 |
\& |
2753 |
root |
1.68 |
\& // create one ev_io per pollfd |
2754 |
|
|
\& for (int i = 0; i < nfd; ++i) |
2755 |
|
|
\& { |
2756 |
|
|
\& ev_io_init (iow + i, io_cb, fds [i].fd, |
2757 |
|
|
\& ((fds [i].events & POLLIN ? EV_READ : 0) |
2758 |
|
|
\& | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
2759 |
|
|
\& |
2760 |
|
|
\& fds [i].revents = 0; |
2761 |
|
|
\& ev_io_start (loop, iow + i); |
2762 |
|
|
\& } |
2763 |
|
|
\& } |
2764 |
|
|
\& |
2765 |
|
|
\& // stop all watchers after blocking |
2766 |
|
|
\& static void |
2767 |
root |
1.73 |
\& adns_check_cb (struct ev_loop *loop, ev_check *w, int revents) |
2768 |
root |
1.68 |
\& { |
2769 |
|
|
\& ev_timer_stop (loop, &tw); |
2770 |
|
|
\& |
2771 |
|
|
\& for (int i = 0; i < nfd; ++i) |
2772 |
|
|
\& { |
2773 |
|
|
\& // set the relevant poll flags |
2774 |
|
|
\& // could also call adns_processreadable etc. here |
2775 |
|
|
\& struct pollfd *fd = fds + i; |
2776 |
|
|
\& int revents = ev_clear_pending (iow + i); |
2777 |
|
|
\& if (revents & EV_READ ) fd\->revents |= fd\->events & POLLIN; |
2778 |
|
|
\& if (revents & EV_WRITE) fd\->revents |= fd\->events & POLLOUT; |
2779 |
root |
1.60 |
\& |
2780 |
root |
1.68 |
\& // now stop the watcher |
2781 |
|
|
\& ev_io_stop (loop, iow + i); |
2782 |
|
|
\& } |
2783 |
|
|
\& |
2784 |
|
|
\& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
2785 |
|
|
\& } |
2786 |
root |
1.20 |
.Ve |
2787 |
root |
1.44 |
.PP |
2788 |
|
|
Method 2: This would be just like method 1, but you run \f(CW\*(C`adns_afterpoll\*(C'\fR |
2789 |
|
|
in the prepare watcher and would dispose of the check watcher. |
2790 |
|
|
.PP |
2791 |
|
|
Method 3: If the module to be embedded supports explicit event |
2792 |
root |
1.68 |
notification (libadns does), you can also make use of the actual watcher |
2793 |
root |
1.44 |
callbacks, and only destroy/create the watchers in the prepare watcher. |
2794 |
|
|
.PP |
2795 |
|
|
.Vb 5 |
2796 |
root |
1.68 |
\& static void |
2797 |
|
|
\& timer_cb (EV_P_ ev_timer *w, int revents) |
2798 |
|
|
\& { |
2799 |
|
|
\& adns_state ads = (adns_state)w\->data; |
2800 |
|
|
\& update_now (EV_A); |
2801 |
|
|
\& |
2802 |
|
|
\& adns_processtimeouts (ads, &tv_now); |
2803 |
|
|
\& } |
2804 |
|
|
\& |
2805 |
|
|
\& static void |
2806 |
|
|
\& io_cb (EV_P_ ev_io *w, int revents) |
2807 |
|
|
\& { |
2808 |
|
|
\& adns_state ads = (adns_state)w\->data; |
2809 |
|
|
\& update_now (EV_A); |
2810 |
root |
1.60 |
\& |
2811 |
root |
1.68 |
\& if (revents & EV_READ ) adns_processreadable (ads, w\->fd, &tv_now); |
2812 |
|
|
\& if (revents & EV_WRITE) adns_processwriteable (ads, w\->fd, &tv_now); |
2813 |
|
|
\& } |
2814 |
|
|
\& |
2815 |
|
|
\& // do not ever call adns_afterpoll |
2816 |
root |
1.44 |
.Ve |
2817 |
|
|
.PP |
2818 |
|
|
Method 4: Do not use a prepare or check watcher because the module you |
2819 |
root |
1.71 |
want to embed is not flexible enough to support it. Instead, you can |
2820 |
|
|
override their poll function. The drawback with this solution is that the |
2821 |
|
|
main loop is now no longer controllable by \s-1EV\s0. The \f(CW\*(C`Glib::EV\*(C'\fR module uses |
2822 |
|
|
this approach, effectively embedding \s-1EV\s0 as a client into the horrible |
2823 |
|
|
libglib event loop. |
2824 |
root |
1.44 |
.PP |
2825 |
|
|
.Vb 4 |
2826 |
root |
1.68 |
\& static gint |
2827 |
|
|
\& event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
2828 |
|
|
\& { |
2829 |
|
|
\& int got_events = 0; |
2830 |
|
|
\& |
2831 |
|
|
\& for (n = 0; n < nfds; ++n) |
2832 |
|
|
\& // create/start io watcher that sets the relevant bits in fds[n] and increment got_events |
2833 |
|
|
\& |
2834 |
|
|
\& if (timeout >= 0) |
2835 |
|
|
\& // create/start timer |
2836 |
|
|
\& |
2837 |
|
|
\& // poll |
2838 |
|
|
\& ev_loop (EV_A_ 0); |
2839 |
|
|
\& |
2840 |
|
|
\& // stop timer again |
2841 |
|
|
\& if (timeout >= 0) |
2842 |
|
|
\& ev_timer_stop (EV_A_ &to); |
2843 |
root |
1.60 |
\& |
2844 |
root |
1.68 |
\& // stop io watchers again \- their callbacks should have set |
2845 |
|
|
\& for (n = 0; n < nfds; ++n) |
2846 |
|
|
\& ev_io_stop (EV_A_ iow [n]); |
2847 |
|
|
\& |
2848 |
|
|
\& return got_events; |
2849 |
|
|
\& } |
2850 |
root |
1.44 |
.Ve |
2851 |
root |
1.79 |
.ie n .SS """ev_embed"" \- when one backend isn't enough..." |
2852 |
|
|
.el .SS "\f(CWev_embed\fP \- when one backend isn't enough..." |
2853 |
root |
1.17 |
.IX Subsection "ev_embed - when one backend isn't enough..." |
2854 |
root |
1.10 |
This is a rather advanced watcher type that lets you embed one event loop |
2855 |
root |
1.11 |
into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded |
2856 |
|
|
loop, other types of watchers might be handled in a delayed or incorrect |
2857 |
root |
1.57 |
fashion and must not be used). |
2858 |
root |
1.10 |
.PP |
2859 |
|
|
There are primarily two reasons you would want that: work around bugs and |
2860 |
|
|
prioritise I/O. |
2861 |
|
|
.PP |
2862 |
|
|
As an example for a bug workaround, the kqueue backend might only support |
2863 |
|
|
sockets on some platform, so it is unusable as generic backend, but you |
2864 |
|
|
still want to make use of it because you have many sockets and it scales |
2865 |
root |
1.71 |
so nicely. In this case, you would create a kqueue-based loop and embed |
2866 |
|
|
it into your default loop (which might use e.g. poll). Overall operation |
2867 |
|
|
will be a bit slower because first libev has to call \f(CW\*(C`poll\*(C'\fR and then |
2868 |
|
|
\&\f(CW\*(C`kevent\*(C'\fR, but at least you can use both mechanisms for what they are |
2869 |
|
|
best: \f(CW\*(C`kqueue\*(C'\fR for scalable sockets and \f(CW\*(C`poll\*(C'\fR if you want it to work :) |
2870 |
|
|
.PP |
2871 |
|
|
As for prioritising I/O: under rare circumstances you have the case where |
2872 |
|
|
some fds have to be watched and handled very quickly (with low latency), |
2873 |
|
|
and even priorities and idle watchers might have too much overhead. In |
2874 |
|
|
this case you would put all the high priority stuff in one loop and all |
2875 |
|
|
the rest in a second one, and embed the second one in the first. |
2876 |
root |
1.10 |
.PP |
2877 |
root |
1.75 |
As long as the watcher is active, the callback will be invoked every |
2878 |
|
|
time there might be events pending in the embedded loop. The callback |
2879 |
|
|
must then call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single |
2880 |
|
|
sweep and invoke their callbacks (the callback doesn't need to invoke the |
2881 |
|
|
\&\f(CW\*(C`ev_embed_sweep\*(C'\fR function directly, it could also start an idle watcher |
2882 |
|
|
to give the embedded loop strictly lower priority for example). |
2883 |
|
|
.PP |
2884 |
|
|
You can also set the callback to \f(CW0\fR, in which case the embed watcher |
2885 |
|
|
will automatically execute the embedded loop sweep whenever necessary. |
2886 |
|
|
.PP |
2887 |
|
|
Fork detection will be handled transparently while the \f(CW\*(C`ev_embed\*(C'\fR watcher |
2888 |
|
|
is active, i.e., the embedded loop will automatically be forked when the |
2889 |
|
|
embedding loop forks. In other cases, the user is responsible for calling |
2890 |
|
|
\&\f(CW\*(C`ev_loop_fork\*(C'\fR on the embedded loop. |
2891 |
root |
1.10 |
.PP |
2892 |
root |
1.71 |
Unfortunately, not all backends are embeddable: only the ones returned by |
2893 |
root |
1.10 |
\&\f(CW\*(C`ev_embeddable_backends\*(C'\fR are, which, unfortunately, does not include any |
2894 |
|
|
portable one. |
2895 |
|
|
.PP |
2896 |
|
|
So when you want to use this feature you will always have to be prepared |
2897 |
|
|
that you cannot get an embeddable loop. The recommended way to get around |
2898 |
|
|
this is to have a separate variables for your embeddable loop, try to |
2899 |
root |
1.60 |
create it, and if that fails, use the normal loop for everything. |
2900 |
root |
1.50 |
.PP |
2901 |
root |
1.71 |
\fI\f(CI\*(C`ev_embed\*(C'\fI and fork\fR |
2902 |
|
|
.IX Subsection "ev_embed and fork" |
2903 |
|
|
.PP |
2904 |
|
|
While the \f(CW\*(C`ev_embed\*(C'\fR watcher is running, forks in the embedding loop will |
2905 |
|
|
automatically be applied to the embedded loop as well, so no special |
2906 |
|
|
fork handling is required in that case. When the watcher is not running, |
2907 |
|
|
however, it is still the task of the libev user to call \f(CW\*(C`ev_loop_fork ()\*(C'\fR |
2908 |
|
|
as applicable. |
2909 |
|
|
.PP |
2910 |
root |
1.50 |
\fIWatcher-Specific Functions and Data Members\fR |
2911 |
|
|
.IX Subsection "Watcher-Specific Functions and Data Members" |
2912 |
root |
1.11 |
.IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4 |
2913 |
|
|
.IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" |
2914 |
root |
1.10 |
.PD 0 |
2915 |
root |
1.11 |
.IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4 |
2916 |
|
|
.IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" |
2917 |
root |
1.10 |
.PD |
2918 |
root |
1.11 |
Configures the watcher to embed the given loop, which must be |
2919 |
|
|
embeddable. If the callback is \f(CW0\fR, then \f(CW\*(C`ev_embed_sweep\*(C'\fR will be |
2920 |
|
|
invoked automatically, otherwise it is the responsibility of the callback |
2921 |
|
|
to invoke it (it will continue to be called until the sweep has been done, |
2922 |
root |
1.68 |
if you do not want that, you need to temporarily stop the embed watcher). |
2923 |
root |
1.11 |
.IP "ev_embed_sweep (loop, ev_embed *)" 4 |
2924 |
|
|
.IX Item "ev_embed_sweep (loop, ev_embed *)" |
2925 |
|
|
Make a single, non-blocking sweep over the embedded loop. This works |
2926 |
|
|
similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most |
2927 |
root |
1.68 |
appropriate way for embedded loops. |
2928 |
root |
1.54 |
.IP "struct ev_loop *other [read\-only]" 4 |
2929 |
|
|
.IX Item "struct ev_loop *other [read-only]" |
2930 |
root |
1.22 |
The embedded event loop. |
2931 |
root |
1.60 |
.PP |
2932 |
|
|
\fIExamples\fR |
2933 |
|
|
.IX Subsection "Examples" |
2934 |
|
|
.PP |
2935 |
|
|
Example: Try to get an embeddable event loop and embed it into the default |
2936 |
|
|
event loop. If that is not possible, use the default loop. The default |
2937 |
root |
1.68 |
loop is stored in \f(CW\*(C`loop_hi\*(C'\fR, while the embeddable loop is stored in |
2938 |
|
|
\&\f(CW\*(C`loop_lo\*(C'\fR (which is \f(CW\*(C`loop_hi\*(C'\fR in the case no embeddable loop can be |
2939 |
root |
1.60 |
used). |
2940 |
|
|
.PP |
2941 |
|
|
.Vb 3 |
2942 |
root |
1.68 |
\& struct ev_loop *loop_hi = ev_default_init (0); |
2943 |
|
|
\& struct ev_loop *loop_lo = 0; |
2944 |
root |
1.73 |
\& ev_embed embed; |
2945 |
root |
1.68 |
\& |
2946 |
|
|
\& // see if there is a chance of getting one that works |
2947 |
|
|
\& // (remember that a flags value of 0 means autodetection) |
2948 |
|
|
\& loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2949 |
|
|
\& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
2950 |
|
|
\& : 0; |
2951 |
|
|
\& |
2952 |
|
|
\& // if we got one, then embed it, otherwise default to loop_hi |
2953 |
|
|
\& if (loop_lo) |
2954 |
|
|
\& { |
2955 |
|
|
\& ev_embed_init (&embed, 0, loop_lo); |
2956 |
|
|
\& ev_embed_start (loop_hi, &embed); |
2957 |
|
|
\& } |
2958 |
|
|
\& else |
2959 |
|
|
\& loop_lo = loop_hi; |
2960 |
root |
1.60 |
.Ve |
2961 |
|
|
.PP |
2962 |
|
|
Example: Check if kqueue is available but not recommended and create |
2963 |
|
|
a kqueue backend for use with sockets (which usually work with any |
2964 |
|
|
kqueue implementation). Store the kqueue/socket\-only event loop in |
2965 |
|
|
\&\f(CW\*(C`loop_socket\*(C'\fR. (One might optionally use \f(CW\*(C`EVFLAG_NOENV\*(C'\fR, too). |
2966 |
|
|
.PP |
2967 |
|
|
.Vb 3 |
2968 |
root |
1.68 |
\& struct ev_loop *loop = ev_default_init (0); |
2969 |
|
|
\& struct ev_loop *loop_socket = 0; |
2970 |
root |
1.73 |
\& ev_embed embed; |
2971 |
root |
1.68 |
\& |
2972 |
|
|
\& if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2973 |
|
|
\& if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2974 |
|
|
\& { |
2975 |
|
|
\& ev_embed_init (&embed, 0, loop_socket); |
2976 |
|
|
\& ev_embed_start (loop, &embed); |
2977 |
|
|
\& } |
2978 |
root |
1.60 |
\& |
2979 |
root |
1.68 |
\& if (!loop_socket) |
2980 |
|
|
\& loop_socket = loop; |
2981 |
root |
1.60 |
\& |
2982 |
root |
1.68 |
\& // now use loop_socket for all sockets, and loop for everything else |
2983 |
root |
1.60 |
.Ve |
2984 |
root |
1.79 |
.ie n .SS """ev_fork"" \- the audacity to resume the event loop after a fork" |
2985 |
|
|
.el .SS "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork" |
2986 |
root |
1.24 |
.IX Subsection "ev_fork - the audacity to resume the event loop after a fork" |
2987 |
|
|
Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because |
2988 |
|
|
whoever is a good citizen cared to tell libev about it by calling |
2989 |
|
|
\&\f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the |
2990 |
|
|
event loop blocks next and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called, |
2991 |
|
|
and only in the child after the fork. If whoever good citizen calling |
2992 |
|
|
\&\f(CW\*(C`ev_default_fork\*(C'\fR cheats and calls it in the wrong process, the fork |
2993 |
|
|
handlers will be invoked, too, of course. |
2994 |
root |
1.51 |
.PP |
2995 |
root |
1.78 |
\fIThe special problem of life after fork \- how is it possible?\fR |
2996 |
|
|
.IX Subsection "The special problem of life after fork - how is it possible?" |
2997 |
|
|
.PP |
2998 |
|
|
Most uses of \f(CW\*(C`fork()\*(C'\fR consist of forking, then some simple calls to ste |
2999 |
|
|
up/change the process environment, followed by a call to \f(CW\*(C`exec()\*(C'\fR. This |
3000 |
|
|
sequence should be handled by libev without any problems. |
3001 |
|
|
.PP |
3002 |
|
|
This changes when the application actually wants to do event handling |
3003 |
|
|
in the child, or both parent in child, in effect \*(L"continuing\*(R" after the |
3004 |
|
|
fork. |
3005 |
|
|
.PP |
3006 |
|
|
The default mode of operation (for libev, with application help to detect |
3007 |
|
|
forks) is to duplicate all the state in the child, as would be expected |
3008 |
|
|
when \fIeither\fR the parent \fIor\fR the child process continues. |
3009 |
|
|
.PP |
3010 |
|
|
When both processes want to continue using libev, then this is usually the |
3011 |
|
|
wrong result. In that case, usually one process (typically the parent) is |
3012 |
|
|
supposed to continue with all watchers in place as before, while the other |
3013 |
|
|
process typically wants to start fresh, i.e. without any active watchers. |
3014 |
|
|
.PP |
3015 |
|
|
The cleanest and most efficient way to achieve that with libev is to |
3016 |
|
|
simply create a new event loop, which of course will be \*(L"empty\*(R", and |
3017 |
|
|
use that for new watchers. This has the advantage of not touching more |
3018 |
|
|
memory than necessary, and thus avoiding the copy-on-write, and the |
3019 |
|
|
disadvantage of having to use multiple event loops (which do not support |
3020 |
|
|
signal watchers). |
3021 |
|
|
.PP |
3022 |
|
|
When this is not possible, or you want to use the default loop for |
3023 |
|
|
other reasons, then in the process that wants to start \*(L"fresh\*(R", call |
3024 |
|
|
\&\f(CW\*(C`ev_default_destroy ()\*(C'\fR followed by \f(CW\*(C`ev_default_loop (...)\*(C'\fR. Destroying |
3025 |
|
|
the default loop will \*(L"orphan\*(R" (not stop) all registered watchers, so you |
3026 |
|
|
have to be careful not to execute code that modifies those watchers. Note |
3027 |
|
|
also that in that case, you have to re-register any signal watchers. |
3028 |
|
|
.PP |
3029 |
root |
1.51 |
\fIWatcher-Specific Functions and Data Members\fR |
3030 |
|
|
.IX Subsection "Watcher-Specific Functions and Data Members" |
3031 |
root |
1.24 |
.IP "ev_fork_init (ev_signal *, callback)" 4 |
3032 |
|
|
.IX Item "ev_fork_init (ev_signal *, callback)" |
3033 |
|
|
Initialises and configures the fork watcher \- it has no parameters of any |
3034 |
|
|
kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless, |
3035 |
|
|
believe me. |
3036 |
root |
1.79 |
.ie n .SS """ev_async"" \- how to wake up another event loop" |
3037 |
|
|
.el .SS "\f(CWev_async\fP \- how to wake up another event loop" |
3038 |
root |
1.61 |
.IX Subsection "ev_async - how to wake up another event loop" |
3039 |
|
|
In general, you cannot use an \f(CW\*(C`ev_loop\*(C'\fR from multiple threads or other |
3040 |
|
|
asynchronous sources such as signal handlers (as opposed to multiple event |
3041 |
|
|
loops \- those are of course safe to use in different threads). |
3042 |
|
|
.PP |
3043 |
|
|
Sometimes, however, you need to wake up another event loop you do not |
3044 |
|
|
control, for example because it belongs to another thread. This is what |
3045 |
|
|
\&\f(CW\*(C`ev_async\*(C'\fR watchers do: as long as the \f(CW\*(C`ev_async\*(C'\fR watcher is active, you |
3046 |
|
|
can signal it by calling \f(CW\*(C`ev_async_send\*(C'\fR, which is thread\- and signal |
3047 |
|
|
safe. |
3048 |
|
|
.PP |
3049 |
|
|
This functionality is very similar to \f(CW\*(C`ev_signal\*(C'\fR watchers, as signals, |
3050 |
|
|
too, are asynchronous in nature, and signals, too, will be compressed |
3051 |
|
|
(i.e. the number of callback invocations may be less than the number of |
3052 |
|
|
\&\f(CW\*(C`ev_async_sent\*(C'\fR calls). |
3053 |
|
|
.PP |
3054 |
|
|
Unlike \f(CW\*(C`ev_signal\*(C'\fR watchers, \f(CW\*(C`ev_async\*(C'\fR works with any event loop, not |
3055 |
|
|
just the default loop. |
3056 |
|
|
.PP |
3057 |
|
|
\fIQueueing\fR |
3058 |
|
|
.IX Subsection "Queueing" |
3059 |
|
|
.PP |
3060 |
|
|
\&\f(CW\*(C`ev_async\*(C'\fR does not support queueing of data in any way. The reason |
3061 |
|
|
is that the author does not know of a simple (or any) algorithm for a |
3062 |
|
|
multiple-writer-single-reader queue that works in all cases and doesn't |
3063 |
|
|
need elaborate support such as pthreads. |
3064 |
|
|
.PP |
3065 |
|
|
That means that if you want to queue data, you have to provide your own |
3066 |
root |
1.71 |
queue. But at least I can tell you how to implement locking around your |
3067 |
root |
1.61 |
queue: |
3068 |
|
|
.IP "queueing from a signal handler context" 4 |
3069 |
|
|
.IX Item "queueing from a signal handler context" |
3070 |
|
|
To implement race-free queueing, you simply add to the queue in the signal |
3071 |
root |
1.72 |
handler but you block the signal handler in the watcher callback. Here is |
3072 |
|
|
an example that does that for some fictitious \s-1SIGUSR1\s0 handler: |
3073 |
root |
1.61 |
.Sp |
3074 |
|
|
.Vb 1 |
3075 |
|
|
\& static ev_async mysig; |
3076 |
|
|
\& |
3077 |
|
|
\& static void |
3078 |
|
|
\& sigusr1_handler (void) |
3079 |
|
|
\& { |
3080 |
|
|
\& sometype data; |
3081 |
|
|
\& |
3082 |
|
|
\& // no locking etc. |
3083 |
|
|
\& queue_put (data); |
3084 |
|
|
\& ev_async_send (EV_DEFAULT_ &mysig); |
3085 |
|
|
\& } |
3086 |
|
|
\& |
3087 |
|
|
\& static void |
3088 |
|
|
\& mysig_cb (EV_P_ ev_async *w, int revents) |
3089 |
|
|
\& { |
3090 |
|
|
\& sometype data; |
3091 |
|
|
\& sigset_t block, prev; |
3092 |
|
|
\& |
3093 |
|
|
\& sigemptyset (&block); |
3094 |
|
|
\& sigaddset (&block, SIGUSR1); |
3095 |
|
|
\& sigprocmask (SIG_BLOCK, &block, &prev); |
3096 |
|
|
\& |
3097 |
|
|
\& while (queue_get (&data)) |
3098 |
|
|
\& process (data); |
3099 |
|
|
\& |
3100 |
|
|
\& if (sigismember (&prev, SIGUSR1) |
3101 |
|
|
\& sigprocmask (SIG_UNBLOCK, &block, 0); |
3102 |
|
|
\& } |
3103 |
|
|
.Ve |
3104 |
|
|
.Sp |
3105 |
|
|
(Note: pthreads in theory requires you to use \f(CW\*(C`pthread_setmask\*(C'\fR |
3106 |
|
|
instead of \f(CW\*(C`sigprocmask\*(C'\fR when you use threads, but libev doesn't do it |
3107 |
|
|
either...). |
3108 |
|
|
.IP "queueing from a thread context" 4 |
3109 |
|
|
.IX Item "queueing from a thread context" |
3110 |
|
|
The strategy for threads is different, as you cannot (easily) block |
3111 |
|
|
threads but you can easily preempt them, so to queue safely you need to |
3112 |
|
|
employ a traditional mutex lock, such as in this pthread example: |
3113 |
|
|
.Sp |
3114 |
|
|
.Vb 2 |
3115 |
|
|
\& static ev_async mysig; |
3116 |
|
|
\& static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER; |
3117 |
|
|
\& |
3118 |
|
|
\& static void |
3119 |
|
|
\& otherthread (void) |
3120 |
|
|
\& { |
3121 |
|
|
\& // only need to lock the actual queueing operation |
3122 |
|
|
\& pthread_mutex_lock (&mymutex); |
3123 |
|
|
\& queue_put (data); |
3124 |
|
|
\& pthread_mutex_unlock (&mymutex); |
3125 |
|
|
\& |
3126 |
|
|
\& ev_async_send (EV_DEFAULT_ &mysig); |
3127 |
|
|
\& } |
3128 |
|
|
\& |
3129 |
|
|
\& static void |
3130 |
|
|
\& mysig_cb (EV_P_ ev_async *w, int revents) |
3131 |
|
|
\& { |
3132 |
|
|
\& pthread_mutex_lock (&mymutex); |
3133 |
|
|
\& |
3134 |
|
|
\& while (queue_get (&data)) |
3135 |
|
|
\& process (data); |
3136 |
|
|
\& |
3137 |
|
|
\& pthread_mutex_unlock (&mymutex); |
3138 |
|
|
\& } |
3139 |
|
|
.Ve |
3140 |
|
|
.PP |
3141 |
|
|
\fIWatcher-Specific Functions and Data Members\fR |
3142 |
|
|
.IX Subsection "Watcher-Specific Functions and Data Members" |
3143 |
|
|
.IP "ev_async_init (ev_async *, callback)" 4 |
3144 |
|
|
.IX Item "ev_async_init (ev_async *, callback)" |
3145 |
|
|
Initialises and configures the async watcher \- it has no parameters of any |
3146 |
root |
1.73 |
kind. There is a \f(CW\*(C`ev_async_set\*(C'\fR macro, but using it is utterly pointless, |
3147 |
root |
1.71 |
trust me. |
3148 |
root |
1.61 |
.IP "ev_async_send (loop, ev_async *)" 4 |
3149 |
|
|
.IX Item "ev_async_send (loop, ev_async *)" |
3150 |
|
|
Sends/signals/activates the given \f(CW\*(C`ev_async\*(C'\fR watcher, that is, feeds |
3151 |
|
|
an \f(CW\*(C`EV_ASYNC\*(C'\fR event on the watcher into the event loop. Unlike |
3152 |
root |
1.71 |
\&\f(CW\*(C`ev_feed_event\*(C'\fR, this call is safe to do from other threads, signal or |
3153 |
root |
1.68 |
similar contexts (see the discussion of \f(CW\*(C`EV_ATOMIC_T\*(C'\fR in the embedding |
3154 |
root |
1.61 |
section below on what exactly this means). |
3155 |
|
|
.Sp |
3156 |
root |
1.78 |
Note that, as with other watchers in libev, multiple events might get |
3157 |
|
|
compressed into a single callback invocation (another way to look at this |
3158 |
|
|
is that \f(CW\*(C`ev_async\*(C'\fR watchers are level-triggered, set on \f(CW\*(C`ev_async_send\*(C'\fR, |
3159 |
|
|
reset when the event loop detects that). |
3160 |
|
|
.Sp |
3161 |
|
|
This call incurs the overhead of a system call only once per event loop |
3162 |
|
|
iteration, so while the overhead might be noticeable, it doesn't apply to |
3163 |
|
|
repeated calls to \f(CW\*(C`ev_async_send\*(C'\fR for the same event loop. |
3164 |
root |
1.63 |
.IP "bool = ev_async_pending (ev_async *)" 4 |
3165 |
|
|
.IX Item "bool = ev_async_pending (ev_async *)" |
3166 |
|
|
Returns a non-zero value when \f(CW\*(C`ev_async_send\*(C'\fR has been called on the |
3167 |
|
|
watcher but the event has not yet been processed (or even noted) by the |
3168 |
|
|
event loop. |
3169 |
|
|
.Sp |
3170 |
|
|
\&\f(CW\*(C`ev_async_send\*(C'\fR sets a flag in the watcher and wakes up the loop. When |
3171 |
|
|
the loop iterates next and checks for the watcher to have become active, |
3172 |
|
|
it will reset the flag again. \f(CW\*(C`ev_async_pending\*(C'\fR can be used to very |
3173 |
root |
1.68 |
quickly check whether invoking the loop might be a good idea. |
3174 |
root |
1.63 |
.Sp |
3175 |
root |
1.78 |
Not that this does \fInot\fR check whether the watcher itself is pending, |
3176 |
|
|
only whether it has been requested to make this watcher pending: there |
3177 |
|
|
is a time window between the event loop checking and resetting the async |
3178 |
|
|
notification, and the callback being invoked. |
3179 |
root |
1.1 |
.SH "OTHER FUNCTIONS" |
3180 |
|
|
.IX Header "OTHER FUNCTIONS" |
3181 |
|
|
There are some other functions of possible interest. Described. Here. Now. |
3182 |
|
|
.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4 |
3183 |
|
|
.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" |
3184 |
|
|
This function combines a simple timer and an I/O watcher, calls your |
3185 |
root |
1.72 |
callback on whichever event happens first and automatically stops both |
3186 |
root |
1.1 |
watchers. This is useful if you want to wait for a single event on an fd |
3187 |
|
|
or timeout without having to allocate/configure/start/stop/free one or |
3188 |
|
|
more watchers yourself. |
3189 |
|
|
.Sp |
3190 |
root |
1.72 |
If \f(CW\*(C`fd\*(C'\fR is less than 0, then no I/O watcher will be started and the |
3191 |
|
|
\&\f(CW\*(C`events\*(C'\fR argument is being ignored. Otherwise, an \f(CW\*(C`ev_io\*(C'\fR watcher for |
3192 |
|
|
the given \f(CW\*(C`fd\*(C'\fR and \f(CW\*(C`events\*(C'\fR set will be created and started. |
3193 |
root |
1.1 |
.Sp |
3194 |
|
|
If \f(CW\*(C`timeout\*(C'\fR is less than 0, then no timeout watcher will be |
3195 |
|
|
started. Otherwise an \f(CW\*(C`ev_timer\*(C'\fR watcher with after = \f(CW\*(C`timeout\*(C'\fR (and |
3196 |
root |
1.72 |
repeat = 0) will be started. \f(CW0\fR is a valid timeout. |
3197 |
root |
1.1 |
.Sp |
3198 |
|
|
The callback has the type \f(CW\*(C`void (*cb)(int revents, void *arg)\*(C'\fR and gets |
3199 |
|
|
passed an \f(CW\*(C`revents\*(C'\fR set like normal event callbacks (a combination of |
3200 |
|
|
\&\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 |
3201 |
root |
1.72 |
value passed to \f(CW\*(C`ev_once\*(C'\fR. Note that it is possible to receive \fIboth\fR |
3202 |
|
|
a timeout and an io event at the same time \- you probably should give io |
3203 |
|
|
events precedence. |
3204 |
|
|
.Sp |
3205 |
|
|
Example: wait up to ten seconds for data to appear on \s-1STDIN_FILENO\s0. |
3206 |
root |
1.1 |
.Sp |
3207 |
|
|
.Vb 7 |
3208 |
root |
1.68 |
\& static void stdin_ready (int revents, void *arg) |
3209 |
|
|
\& { |
3210 |
root |
1.72 |
\& if (revents & EV_READ) |
3211 |
|
|
\& /* stdin might have data for us, joy! */; |
3212 |
|
|
\& else if (revents & EV_TIMEOUT) |
3213 |
root |
1.68 |
\& /* doh, nothing entered */; |
3214 |
|
|
\& } |
3215 |
root |
1.60 |
\& |
3216 |
root |
1.68 |
\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3217 |
root |
1.1 |
.Ve |
3218 |
root |
1.73 |
.IP "ev_feed_event (struct ev_loop *, watcher *, int revents)" 4 |
3219 |
|
|
.IX Item "ev_feed_event (struct ev_loop *, watcher *, int revents)" |
3220 |
root |
1.1 |
Feeds the given event set into the event loop, as if the specified event |
3221 |
|
|
had happened for the specified watcher (which must be a pointer to an |
3222 |
|
|
initialised but not necessarily started event watcher). |
3223 |
root |
1.73 |
.IP "ev_feed_fd_event (struct ev_loop *, int fd, int revents)" 4 |
3224 |
|
|
.IX Item "ev_feed_fd_event (struct ev_loop *, int fd, int revents)" |
3225 |
root |
1.1 |
Feed an event on the given fd, as if a file descriptor backend detected |
3226 |
|
|
the given events it. |
3227 |
root |
1.73 |
.IP "ev_feed_signal_event (struct ev_loop *loop, int signum)" 4 |
3228 |
|
|
.IX Item "ev_feed_signal_event (struct ev_loop *loop, int signum)" |
3229 |
root |
1.68 |
Feed an event as if the given signal occurred (\f(CW\*(C`loop\*(C'\fR must be the default |
3230 |
root |
1.11 |
loop!). |
3231 |
root |
1.1 |
.SH "LIBEVENT EMULATION" |
3232 |
|
|
.IX Header "LIBEVENT EMULATION" |
3233 |
|
|
Libev offers a compatibility emulation layer for libevent. It cannot |
3234 |
|
|
emulate the internals of libevent, so here are some usage hints: |
3235 |
root |
1.60 |
.IP "\(bu" 4 |
3236 |
|
|
Use it by including <event.h>, as usual. |
3237 |
|
|
.IP "\(bu" 4 |
3238 |
|
|
The following members are fully supported: ev_base, ev_callback, |
3239 |
|
|
ev_arg, ev_fd, ev_res, ev_events. |
3240 |
|
|
.IP "\(bu" 4 |
3241 |
|
|
Avoid using ev_flags and the EVLIST_*\-macros, while it is |
3242 |
|
|
maintained by libev, it does not work exactly the same way as in libevent (consider |
3243 |
|
|
it a private \s-1API\s0). |
3244 |
|
|
.IP "\(bu" 4 |
3245 |
|
|
Priorities are not currently supported. Initialising priorities |
3246 |
|
|
will fail and all watchers will have the same priority, even though there |
3247 |
|
|
is an ev_pri field. |
3248 |
|
|
.IP "\(bu" 4 |
3249 |
root |
1.64 |
In libevent, the last base created gets the signals, in libev, the |
3250 |
|
|
first base created (== the default loop) gets the signals. |
3251 |
|
|
.IP "\(bu" 4 |
3252 |
root |
1.60 |
Other members are not supported. |
3253 |
|
|
.IP "\(bu" 4 |
3254 |
|
|
The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need |
3255 |
|
|
to use the libev header file and library. |
3256 |
root |
1.1 |
.SH "\*(C+ SUPPORT" |
3257 |
|
|
.IX Header " SUPPORT" |
3258 |
root |
1.13 |
Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow |
3259 |
root |
1.68 |
you to use some convenience methods to start/stop watchers and also change |
3260 |
root |
1.13 |
the callback model to a model using method callbacks on objects. |
3261 |
|
|
.PP |
3262 |
|
|
To use it, |
3263 |
|
|
.PP |
3264 |
|
|
.Vb 1 |
3265 |
root |
1.68 |
\& #include <ev++.h> |
3266 |
root |
1.13 |
.Ve |
3267 |
|
|
.PP |
3268 |
root |
1.41 |
This automatically includes \fIev.h\fR and puts all of its definitions (many |
3269 |
|
|
of them macros) into the global namespace. All \*(C+ specific things are |
3270 |
|
|
put into the \f(CW\*(C`ev\*(C'\fR namespace. It should support all the same embedding |
3271 |
|
|
options as \fIev.h\fR, most notably \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. |
3272 |
|
|
.PP |
3273 |
root |
1.42 |
Care has been taken to keep the overhead low. The only data member the \*(C+ |
3274 |
|
|
classes add (compared to plain C\-style watchers) is the event loop pointer |
3275 |
|
|
that the watcher is associated with (or no additional members at all if |
3276 |
|
|
you disable \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR when embedding libev). |
3277 |
root |
1.41 |
.PP |
3278 |
root |
1.42 |
Currently, functions, and static and non-static member functions can be |
3279 |
root |
1.41 |
used as callbacks. Other types should be easy to add as long as they only |
3280 |
|
|
need one additional pointer for context. If you need support for other |
3281 |
|
|
types of functors please contact the author (preferably after implementing |
3282 |
|
|
it). |
3283 |
root |
1.13 |
.PP |
3284 |
|
|
Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace: |
3285 |
root |
1.79 |
.ie n .IP """ev::READ"", ""ev::WRITE"" etc." 4 |
3286 |
root |
1.13 |
.el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4 |
3287 |
|
|
.IX Item "ev::READ, ev::WRITE etc." |
3288 |
|
|
These are just enum values with the same values as the \f(CW\*(C`EV_READ\*(C'\fR etc. |
3289 |
|
|
macros from \fIev.h\fR. |
3290 |
root |
1.79 |
.ie n .IP """ev::tstamp"", ""ev::now""" 4 |
3291 |
root |
1.13 |
.el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4 |
3292 |
|
|
.IX Item "ev::tstamp, ev::now" |
3293 |
|
|
Aliases to the same types/functions as with the \f(CW\*(C`ev_\*(C'\fR prefix. |
3294 |
root |
1.79 |
.ie n .IP """ev::io"", ""ev::timer"", ""ev::periodic"", ""ev::idle"", ""ev::sig"" etc." 4 |
3295 |
root |
1.13 |
.el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4 |
3296 |
|
|
.IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc." |
3297 |
|
|
For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of |
3298 |
|
|
the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR |
3299 |
|
|
which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro |
3300 |
|
|
defines by many implementations. |
3301 |
|
|
.Sp |
3302 |
|
|
All of those classes have these methods: |
3303 |
|
|
.RS 4 |
3304 |
root |
1.41 |
.IP "ev::TYPE::TYPE ()" 4 |
3305 |
|
|
.IX Item "ev::TYPE::TYPE ()" |
3306 |
root |
1.13 |
.PD 0 |
3307 |
root |
1.41 |
.IP "ev::TYPE::TYPE (struct ev_loop *)" 4 |
3308 |
|
|
.IX Item "ev::TYPE::TYPE (struct ev_loop *)" |
3309 |
root |
1.13 |
.IP "ev::TYPE::~TYPE" 4 |
3310 |
|
|
.IX Item "ev::TYPE::~TYPE" |
3311 |
|
|
.PD |
3312 |
root |
1.41 |
The constructor (optionally) takes an event loop to associate the watcher |
3313 |
|
|
with. If it is omitted, it will use \f(CW\*(C`EV_DEFAULT\*(C'\fR. |
3314 |
|
|
.Sp |
3315 |
|
|
The constructor calls \f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the |
3316 |
|
|
\&\f(CW\*(C`set\*(C'\fR method before starting it. |
3317 |
|
|
.Sp |
3318 |
|
|
It will not set a callback, however: You have to call the templated \f(CW\*(C`set\*(C'\fR |
3319 |
|
|
method to set a callback before you can start the watcher. |
3320 |
|
|
.Sp |
3321 |
|
|
(The reason why you have to use a method is a limitation in \*(C+ which does |
3322 |
|
|
not allow explicit template arguments for constructors). |
3323 |
root |
1.13 |
.Sp |
3324 |
|
|
The destructor automatically stops the watcher if it is active. |
3325 |
root |
1.41 |
.IP "w\->set<class, &class::method> (object *)" 4 |
3326 |
|
|
.IX Item "w->set<class, &class::method> (object *)" |
3327 |
|
|
This method sets the callback method to call. The method has to have a |
3328 |
|
|
signature of \f(CW\*(C`void (*)(ev_TYPE &, int)\*(C'\fR, it receives the watcher as |
3329 |
|
|
first argument and the \f(CW\*(C`revents\*(C'\fR as second. The object must be given as |
3330 |
|
|
parameter and is stored in the \f(CW\*(C`data\*(C'\fR member of the watcher. |
3331 |
|
|
.Sp |
3332 |
|
|
This method synthesizes efficient thunking code to call your method from |
3333 |
|
|
the C callback that libev requires. If your compiler can inline your |
3334 |
|
|
callback (i.e. it is visible to it at the place of the \f(CW\*(C`set\*(C'\fR call and |
3335 |
|
|
your compiler is good :), then the method will be fully inlined into the |
3336 |
|
|
thunking function, making it as fast as a direct C callback. |
3337 |
|
|
.Sp |
3338 |
|
|
Example: simple class declaration and watcher initialisation |
3339 |
|
|
.Sp |
3340 |
|
|
.Vb 4 |
3341 |
root |
1.68 |
\& struct myclass |
3342 |
|
|
\& { |
3343 |
|
|
\& void io_cb (ev::io &w, int revents) { } |
3344 |
|
|
\& } |
3345 |
|
|
\& |
3346 |
|
|
\& myclass obj; |
3347 |
|
|
\& ev::io iow; |
3348 |
|
|
\& iow.set <myclass, &myclass::io_cb> (&obj); |
3349 |
root |
1.41 |
.Ve |
3350 |
root |
1.75 |
.IP "w\->set (object *)" 4 |
3351 |
|
|
.IX Item "w->set (object *)" |
3352 |
|
|
This is an \fBexperimental\fR feature that might go away in a future version. |
3353 |
|
|
.Sp |
3354 |
|
|
This is a variation of a method callback \- leaving out the method to call |
3355 |
|
|
will default the method to \f(CW\*(C`operator ()\*(C'\fR, which makes it possible to use |
3356 |
|
|
functor objects without having to manually specify the \f(CW\*(C`operator ()\*(C'\fR all |
3357 |
|
|
the time. Incidentally, you can then also leave out the template argument |
3358 |
|
|
list. |
3359 |
|
|
.Sp |
3360 |
|
|
The \f(CW\*(C`operator ()\*(C'\fR method prototype must be \f(CW\*(C`void operator ()(watcher &w, |
3361 |
|
|
int revents)\*(C'\fR. |
3362 |
|
|
.Sp |
3363 |
|
|
See the method\-\f(CW\*(C`set\*(C'\fR above for more details. |
3364 |
|
|
.Sp |
3365 |
|
|
Example: use a functor object as callback. |
3366 |
|
|
.Sp |
3367 |
|
|
.Vb 7 |
3368 |
|
|
\& struct myfunctor |
3369 |
|
|
\& { |
3370 |
|
|
\& void operator() (ev::io &w, int revents) |
3371 |
|
|
\& { |
3372 |
|
|
\& ... |
3373 |
|
|
\& } |
3374 |
|
|
\& } |
3375 |
|
|
\& |
3376 |
|
|
\& myfunctor f; |
3377 |
|
|
\& |
3378 |
|
|
\& ev::io w; |
3379 |
|
|
\& w.set (&f); |
3380 |
|
|
.Ve |
3381 |
root |
1.43 |
.IP "w\->set<function> (void *data = 0)" 4 |
3382 |
|
|
.IX Item "w->set<function> (void *data = 0)" |
3383 |
root |
1.41 |
Also sets a callback, but uses a static method or plain function as |
3384 |
|
|
callback. The optional \f(CW\*(C`data\*(C'\fR argument will be stored in the watcher's |
3385 |
|
|
\&\f(CW\*(C`data\*(C'\fR member and is free for you to use. |
3386 |
|
|
.Sp |
3387 |
root |
1.43 |
The prototype of the \f(CW\*(C`function\*(C'\fR must be \f(CW\*(C`void (*)(ev::TYPE &w, int)\*(C'\fR. |
3388 |
|
|
.Sp |
3389 |
root |
1.41 |
See the method\-\f(CW\*(C`set\*(C'\fR above for more details. |
3390 |
root |
1.43 |
.Sp |
3391 |
root |
1.71 |
Example: Use a plain function as callback. |
3392 |
root |
1.43 |
.Sp |
3393 |
|
|
.Vb 2 |
3394 |
root |
1.68 |
\& static void io_cb (ev::io &w, int revents) { } |
3395 |
|
|
\& iow.set <io_cb> (); |
3396 |
root |
1.43 |
.Ve |
3397 |
root |
1.13 |
.IP "w\->set (struct ev_loop *)" 4 |
3398 |
|
|
.IX Item "w->set (struct ev_loop *)" |
3399 |
|
|
Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only |
3400 |
|
|
do this when the watcher is inactive (and not pending either). |
3401 |
root |
1.68 |
.IP "w\->set ([arguments])" 4 |
3402 |
|
|
.IX Item "w->set ([arguments])" |
3403 |
|
|
Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same arguments. Must be |
3404 |
root |
1.41 |
called at least once. Unlike the C counterpart, an active watcher gets |
3405 |
|
|
automatically stopped and restarted when reconfiguring it with this |
3406 |
|
|
method. |
3407 |
root |
1.13 |
.IP "w\->start ()" 4 |
3408 |
|
|
.IX Item "w->start ()" |
3409 |
root |
1.41 |
Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the |
3410 |
|
|
constructor already stores the event loop. |
3411 |
root |
1.13 |
.IP "w\->stop ()" 4 |
3412 |
|
|
.IX Item "w->stop ()" |
3413 |
|
|
Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument. |
3414 |
root |
1.79 |
.ie n .IP "w\->again () (""ev::timer"", ""ev::periodic"" only)" 4 |
3415 |
root |
1.52 |
.el .IP "w\->again () (\f(CWev::timer\fR, \f(CWev::periodic\fR only)" 4 |
3416 |
|
|
.IX Item "w->again () (ev::timer, ev::periodic only)" |
3417 |
root |
1.13 |
For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding |
3418 |
|
|
\&\f(CW\*(C`ev_TYPE_again\*(C'\fR function. |
3419 |
root |
1.52 |
.ie n .IP "w\->sweep () (""ev::embed"" only)" 4 |
3420 |
|
|
.el .IP "w\->sweep () (\f(CWev::embed\fR only)" 4 |
3421 |
|
|
.IX Item "w->sweep () (ev::embed only)" |
3422 |
root |
1.13 |
Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR. |
3423 |
root |
1.52 |
.ie n .IP "w\->update () (""ev::stat"" only)" 4 |
3424 |
|
|
.el .IP "w\->update () (\f(CWev::stat\fR only)" 4 |
3425 |
|
|
.IX Item "w->update () (ev::stat only)" |
3426 |
root |
1.23 |
Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR. |
3427 |
root |
1.13 |
.RE |
3428 |
|
|
.RS 4 |
3429 |
|
|
.RE |
3430 |
|
|
.PP |
3431 |
|
|
Example: Define a class with an \s-1IO\s0 and idle watcher, start one of them in |
3432 |
|
|
the constructor. |
3433 |
|
|
.PP |
3434 |
|
|
.Vb 4 |
3435 |
root |
1.68 |
\& class myclass |
3436 |
|
|
\& { |
3437 |
root |
1.71 |
\& ev::io io ; void io_cb (ev::io &w, int revents); |
3438 |
|
|
\& ev::idle idle; void idle_cb (ev::idle &w, int revents); |
3439 |
root |
1.68 |
\& |
3440 |
|
|
\& myclass (int fd) |
3441 |
|
|
\& { |
3442 |
|
|
\& io .set <myclass, &myclass::io_cb > (this); |
3443 |
|
|
\& idle.set <myclass, &myclass::idle_cb> (this); |
3444 |
|
|
\& |
3445 |
|
|
\& io.start (fd, ev::READ); |
3446 |
|
|
\& } |
3447 |
|
|
\& }; |
3448 |
root |
1.13 |
.Ve |
3449 |
root |
1.62 |
.SH "OTHER LANGUAGE BINDINGS" |
3450 |
|
|
.IX Header "OTHER LANGUAGE BINDINGS" |
3451 |
|
|
Libev does not offer other language bindings itself, but bindings for a |
3452 |
root |
1.68 |
number of languages exist in the form of third-party packages. If you know |
3453 |
root |
1.62 |
any interesting language binding in addition to the ones listed here, drop |
3454 |
|
|
me a note. |
3455 |
|
|
.IP "Perl" 4 |
3456 |
|
|
.IX Item "Perl" |
3457 |
|
|
The \s-1EV\s0 module implements the full libev \s-1API\s0 and is actually used to test |
3458 |
|
|
libev. \s-1EV\s0 is developed together with libev. Apart from the \s-1EV\s0 core module, |
3459 |
|
|
there are additional modules that implement libev-compatible interfaces |
3460 |
root |
1.71 |
to \f(CW\*(C`libadns\*(C'\fR (\f(CW\*(C`EV::ADNS\*(C'\fR, but \f(CW\*(C`AnyEvent::DNS\*(C'\fR is preferred nowadays), |
3461 |
|
|
\&\f(CW\*(C`Net::SNMP\*(C'\fR (\f(CW\*(C`Net::SNMP::EV\*(C'\fR) and the \f(CW\*(C`libglib\*(C'\fR event core (\f(CW\*(C`Glib::EV\*(C'\fR |
3462 |
|
|
and \f(CW\*(C`EV::Glib\*(C'\fR). |
3463 |
root |
1.62 |
.Sp |
3464 |
root |
1.68 |
It can be found and installed via \s-1CPAN\s0, its homepage is at |
3465 |
root |
1.62 |
<http://software.schmorp.de/pkg/EV>. |
3466 |
root |
1.68 |
.IP "Python" 4 |
3467 |
|
|
.IX Item "Python" |
3468 |
|
|
Python bindings can be found at <http://code.google.com/p/pyev/>. It |
3469 |
root |
1.78 |
seems to be quite complete and well-documented. |
3470 |
root |
1.62 |
.IP "Ruby" 4 |
3471 |
|
|
.IX Item "Ruby" |
3472 |
|
|
Tony Arcieri has written a ruby extension that offers access to a subset |
3473 |
root |
1.68 |
of the libev \s-1API\s0 and adds file handle abstractions, asynchronous \s-1DNS\s0 and |
3474 |
root |
1.62 |
more on top of it. It can be found via gem servers. Its homepage is at |
3475 |
|
|
<http://rev.rubyforge.org/>. |
3476 |
root |
1.75 |
.Sp |
3477 |
|
|
Roger Pack reports that using the link order \f(CW\*(C`\-lws2_32 \-lmsvcrt\-ruby\-190\*(C'\fR |
3478 |
|
|
makes rev work even on mingw. |
3479 |
root |
1.78 |
.IP "Haskell" 4 |
3480 |
|
|
.IX Item "Haskell" |
3481 |
|
|
A haskell binding to libev is available at |
3482 |
|
|
<http://hackage.haskell.org/cgi\-bin/hackage\-scripts/package/hlibev>. |
3483 |
root |
1.62 |
.IP "D" 4 |
3484 |
|
|
.IX Item "D" |
3485 |
|
|
Leandro Lucarella has written a D language binding (\fIev.d\fR) for libev, to |
3486 |
root |
1.71 |
be found at <http://proj.llucax.com.ar/wiki/evd>. |
3487 |
root |
1.73 |
.IP "Ocaml" 4 |
3488 |
|
|
.IX Item "Ocaml" |
3489 |
|
|
Erkki Seppala has written Ocaml bindings for libev, to be found at |
3490 |
|
|
<http://modeemi.cs.tut.fi/~flux/software/ocaml\-ev/>. |
3491 |
root |
1.24 |
.SH "MACRO MAGIC" |
3492 |
|
|
.IX Header "MACRO MAGIC" |
3493 |
root |
1.68 |
Libev can be compiled with a variety of options, the most fundamental |
3494 |
root |
1.52 |
of which is \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most) |
3495 |
|
|
functions and callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument. |
3496 |
root |
1.24 |
.PP |
3497 |
|
|
To make it easier to write programs that cope with either variant, the |
3498 |
|
|
following macros are defined: |
3499 |
root |
1.79 |
.ie n .IP """EV_A"", ""EV_A_""" 4 |
3500 |
root |
1.24 |
.el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4 |
3501 |
|
|
.IX Item "EV_A, EV_A_" |
3502 |
|
|
This provides the loop \fIargument\fR for functions, if one is required (\*(L"ev |
3503 |
|
|
loop argument\*(R"). The \f(CW\*(C`EV_A\*(C'\fR form is used when this is the sole argument, |
3504 |
|
|
\&\f(CW\*(C`EV_A_\*(C'\fR is used when other arguments are following. Example: |
3505 |
|
|
.Sp |
3506 |
|
|
.Vb 3 |
3507 |
root |
1.68 |
\& ev_unref (EV_A); |
3508 |
|
|
\& ev_timer_add (EV_A_ watcher); |
3509 |
|
|
\& ev_loop (EV_A_ 0); |
3510 |
root |
1.24 |
.Ve |
3511 |
|
|
.Sp |
3512 |
|
|
It assumes the variable \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR is in scope, |
3513 |
|
|
which is often provided by the following macro. |
3514 |
root |
1.79 |
.ie n .IP """EV_P"", ""EV_P_""" 4 |
3515 |
root |
1.24 |
.el .IP "\f(CWEV_P\fR, \f(CWEV_P_\fR" 4 |
3516 |
|
|
.IX Item "EV_P, EV_P_" |
3517 |
|
|
This provides the loop \fIparameter\fR for functions, if one is required (\*(L"ev |
3518 |
|
|
loop parameter\*(R"). The \f(CW\*(C`EV_P\*(C'\fR form is used when this is the sole parameter, |
3519 |
|
|
\&\f(CW\*(C`EV_P_\*(C'\fR is used when other parameters are following. Example: |
3520 |
|
|
.Sp |
3521 |
|
|
.Vb 2 |
3522 |
root |
1.68 |
\& // this is how ev_unref is being declared |
3523 |
|
|
\& static void ev_unref (EV_P); |
3524 |
root |
1.60 |
\& |
3525 |
root |
1.68 |
\& // this is how you can declare your typical callback |
3526 |
|
|
\& static void cb (EV_P_ ev_timer *w, int revents) |
3527 |
root |
1.24 |
.Ve |
3528 |
|
|
.Sp |
3529 |
|
|
It declares a parameter \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR, quite |
3530 |
|
|
suitable for use with \f(CW\*(C`EV_A\*(C'\fR. |
3531 |
root |
1.79 |
.ie n .IP """EV_DEFAULT"", ""EV_DEFAULT_""" 4 |
3532 |
root |
1.24 |
.el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4 |
3533 |
|
|
.IX Item "EV_DEFAULT, EV_DEFAULT_" |
3534 |
|
|
Similar to the other two macros, this gives you the value of the default |
3535 |
|
|
loop, if multiple loops are supported (\*(L"ev loop default\*(R"). |
3536 |
root |
1.79 |
.ie n .IP """EV_DEFAULT_UC"", ""EV_DEFAULT_UC_""" 4 |
3537 |
root |
1.64 |
.el .IP "\f(CWEV_DEFAULT_UC\fR, \f(CWEV_DEFAULT_UC_\fR" 4 |
3538 |
|
|
.IX Item "EV_DEFAULT_UC, EV_DEFAULT_UC_" |
3539 |
|
|
Usage identical to \f(CW\*(C`EV_DEFAULT\*(C'\fR and \f(CW\*(C`EV_DEFAULT_\*(C'\fR, but requires that the |
3540 |
|
|
default loop has been initialised (\f(CW\*(C`UC\*(C'\fR == unchecked). Their behaviour |
3541 |
|
|
is undefined when the default loop has not been initialised by a previous |
3542 |
|
|
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. |
3543 |
|
|
.Sp |
3544 |
|
|
It is often prudent to use \f(CW\*(C`EV_DEFAULT\*(C'\fR when initialising the first |
3545 |
|
|
watcher in a function but use \f(CW\*(C`EV_DEFAULT_UC\*(C'\fR afterwards. |
3546 |
root |
1.24 |
.PP |
3547 |
root |
1.36 |
Example: Declare and initialise a check watcher, utilising the above |
3548 |
root |
1.38 |
macros so it will work regardless of whether multiple loops are supported |
3549 |
root |
1.36 |
or not. |
3550 |
root |
1.24 |
.PP |
3551 |
|
|
.Vb 5 |
3552 |
root |
1.68 |
\& static void |
3553 |
|
|
\& check_cb (EV_P_ ev_timer *w, int revents) |
3554 |
|
|
\& { |
3555 |
|
|
\& ev_check_stop (EV_A_ w); |
3556 |
|
|
\& } |
3557 |
|
|
\& |
3558 |
|
|
\& ev_check check; |
3559 |
|
|
\& ev_check_init (&check, check_cb); |
3560 |
|
|
\& ev_check_start (EV_DEFAULT_ &check); |
3561 |
|
|
\& ev_loop (EV_DEFAULT_ 0); |
3562 |
root |
1.24 |
.Ve |
3563 |
root |
1.14 |
.SH "EMBEDDING" |
3564 |
|
|
.IX Header "EMBEDDING" |
3565 |
|
|
Libev can (and often is) directly embedded into host |
3566 |
|
|
applications. Examples of applications that embed it include the Deliantra |
3567 |
|
|
Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe) |
3568 |
root |
1.60 |
and rxvt-unicode. |
3569 |
root |
1.14 |
.PP |
3570 |
root |
1.54 |
The goal is to enable you to just copy the necessary files into your |
3571 |
root |
1.14 |
source directory without having to change even a single line in them, so |
3572 |
|
|
you can easily upgrade by simply copying (or having a checked-out copy of |
3573 |
|
|
libev somewhere in your source tree). |
3574 |
root |
1.79 |
.SS "\s-1FILESETS\s0" |
3575 |
root |
1.14 |
.IX Subsection "FILESETS" |
3576 |
|
|
Depending on what features you need you need to include one or more sets of files |
3577 |
root |
1.68 |
in your application. |
3578 |
root |
1.14 |
.PP |
3579 |
|
|
\fI\s-1CORE\s0 \s-1EVENT\s0 \s-1LOOP\s0\fR |
3580 |
|
|
.IX Subsection "CORE EVENT LOOP" |
3581 |
|
|
.PP |
3582 |
|
|
To include only the libev core (all the \f(CW\*(C`ev_*\*(C'\fR functions), with manual |
3583 |
|
|
configuration (no autoconf): |
3584 |
|
|
.PP |
3585 |
|
|
.Vb 2 |
3586 |
root |
1.68 |
\& #define EV_STANDALONE 1 |
3587 |
|
|
\& #include "ev.c" |
3588 |
root |
1.14 |
.Ve |
3589 |
|
|
.PP |
3590 |
|
|
This will automatically include \fIev.h\fR, too, and should be done in a |
3591 |
|
|
single C source file only to provide the function implementations. To use |
3592 |
|
|
it, do the same for \fIev.h\fR in all files wishing to use this \s-1API\s0 (best |
3593 |
|
|
done by writing a wrapper around \fIev.h\fR that you can include instead and |
3594 |
|
|
where you can put other configuration options): |
3595 |
|
|
.PP |
3596 |
|
|
.Vb 2 |
3597 |
root |
1.68 |
\& #define EV_STANDALONE 1 |
3598 |
|
|
\& #include "ev.h" |
3599 |
root |
1.14 |
.Ve |
3600 |
|
|
.PP |
3601 |
|
|
Both header files and implementation files can be compiled with a \*(C+ |
3602 |
root |
1.73 |
compiler (at least, that's a stated goal, and breakage will be treated |
3603 |
root |
1.14 |
as a bug). |
3604 |
|
|
.PP |
3605 |
|
|
You need the following files in your source tree, or in a directory |
3606 |
|
|
in your include path (e.g. in libev/ when using \-Ilibev): |
3607 |
|
|
.PP |
3608 |
|
|
.Vb 4 |
3609 |
root |
1.68 |
\& ev.h |
3610 |
|
|
\& ev.c |
3611 |
|
|
\& ev_vars.h |
3612 |
|
|
\& ev_wrap.h |
3613 |
|
|
\& |
3614 |
|
|
\& ev_win32.c required on win32 platforms only |
3615 |
|
|
\& |
3616 |
|
|
\& ev_select.c only when select backend is enabled (which is enabled by default) |
3617 |
|
|
\& ev_poll.c only when poll backend is enabled (disabled by default) |
3618 |
|
|
\& ev_epoll.c only when the epoll backend is enabled (disabled by default) |
3619 |
|
|
\& ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
3620 |
|
|
\& ev_port.c only when the solaris port backend is enabled (disabled by default) |
3621 |
root |
1.14 |
.Ve |
3622 |
|
|
.PP |
3623 |
|
|
\&\fIev.c\fR includes the backend files directly when enabled, so you only need |
3624 |
root |
1.18 |
to compile this single file. |
3625 |
root |
1.14 |
.PP |
3626 |
|
|
\fI\s-1LIBEVENT\s0 \s-1COMPATIBILITY\s0 \s-1API\s0\fR |
3627 |
|
|
.IX Subsection "LIBEVENT COMPATIBILITY API" |
3628 |
|
|
.PP |
3629 |
|
|
To include the libevent compatibility \s-1API\s0, also include: |
3630 |
|
|
.PP |
3631 |
|
|
.Vb 1 |
3632 |
root |
1.68 |
\& #include "event.c" |
3633 |
root |
1.14 |
.Ve |
3634 |
|
|
.PP |
3635 |
|
|
in the file including \fIev.c\fR, and: |
3636 |
|
|
.PP |
3637 |
|
|
.Vb 1 |
3638 |
root |
1.68 |
\& #include "event.h" |
3639 |
root |
1.14 |
.Ve |
3640 |
|
|
.PP |
3641 |
|
|
in the files that want to use the libevent \s-1API\s0. This also includes \fIev.h\fR. |
3642 |
|
|
.PP |
3643 |
|
|
You need the following additional files for this: |
3644 |
|
|
.PP |
3645 |
|
|
.Vb 2 |
3646 |
root |
1.68 |
\& event.h |
3647 |
|
|
\& event.c |
3648 |
root |
1.14 |
.Ve |
3649 |
|
|
.PP |
3650 |
|
|
\fI\s-1AUTOCONF\s0 \s-1SUPPORT\s0\fR |
3651 |
|
|
.IX Subsection "AUTOCONF SUPPORT" |
3652 |
|
|
.PP |
3653 |
root |
1.68 |
Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your configuration in |
3654 |
root |
1.14 |
whatever way you want, you can also \f(CW\*(C`m4_include([libev.m4])\*(C'\fR in your |
3655 |
root |
1.18 |
\&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR undefined. \fIev.c\fR will then |
3656 |
|
|
include \fIconfig.h\fR and configure itself accordingly. |
3657 |
root |
1.14 |
.PP |
3658 |
|
|
For this of course you need the m4 file: |
3659 |
|
|
.PP |
3660 |
|
|
.Vb 1 |
3661 |
root |
1.68 |
\& libev.m4 |
3662 |
root |
1.14 |
.Ve |
3663 |
root |
1.79 |
.SS "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0" |
3664 |
root |
1.14 |
.IX Subsection "PREPROCESSOR SYMBOLS/MACROS" |
3665 |
root |
1.64 |
Libev can be configured via a variety of preprocessor symbols you have to |
3666 |
root |
1.68 |
define before including any of its files. The default in the absence of |
3667 |
root |
1.71 |
autoconf is documented for every option. |
3668 |
root |
1.14 |
.IP "\s-1EV_STANDALONE\s0" 4 |
3669 |
|
|
.IX Item "EV_STANDALONE" |
3670 |
|
|
Must always be \f(CW1\fR if you do not use autoconf configuration, which |
3671 |
|
|
keeps libev from including \fIconfig.h\fR, and it also defines dummy |
3672 |
|
|
implementations for some libevent functions (such as logging, which is not |
3673 |
|
|
supported). It will also not define any of the structs usually found in |
3674 |
|
|
\&\fIevent.h\fR that are not directly supported by the libev core alone. |
3675 |
root |
1.75 |
.Sp |
3676 |
|
|
In stanbdalone mode, libev will still try to automatically deduce the |
3677 |
|
|
configuration, but has to be more conservative. |
3678 |
root |
1.14 |
.IP "\s-1EV_USE_MONOTONIC\s0" 4 |
3679 |
|
|
.IX Item "EV_USE_MONOTONIC" |
3680 |
|
|
If defined to be \f(CW1\fR, libev will try to detect the availability of the |
3681 |
root |
1.75 |
monotonic clock option at both compile time and runtime. Otherwise no |
3682 |
|
|
use of the monotonic clock option will be attempted. If you enable this, |
3683 |
|
|
you usually have to link against librt or something similar. Enabling it |
3684 |
|
|
when the functionality isn't available is safe, though, although you have |
3685 |
root |
1.14 |
to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR |
3686 |
root |
1.75 |
function is hiding in (often \fI\-lrt\fR). See also \f(CW\*(C`EV_USE_CLOCK_SYSCALL\*(C'\fR. |
3687 |
root |
1.14 |
.IP "\s-1EV_USE_REALTIME\s0" 4 |
3688 |
|
|
.IX Item "EV_USE_REALTIME" |
3689 |
|
|
If defined to be \f(CW1\fR, libev will try to detect the availability of the |
3690 |
root |
1.77 |
real-time clock option at compile time (and assume its availability |
3691 |
|
|
at runtime if successful). Otherwise no use of the real-time clock |
3692 |
|
|
option will be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR |
3693 |
|
|
by \f(CW\*(C`clock_get (CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect |
3694 |
|
|
correctness. See the note about libraries in the description of |
3695 |
|
|
\&\f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though. Defaults to the opposite value of |
3696 |
|
|
\&\f(CW\*(C`EV_USE_CLOCK_SYSCALL\*(C'\fR. |
3697 |
root |
1.75 |
.IP "\s-1EV_USE_CLOCK_SYSCALL\s0" 4 |
3698 |
|
|
.IX Item "EV_USE_CLOCK_SYSCALL" |
3699 |
|
|
If defined to be \f(CW1\fR, libev will try to use a direct syscall instead |
3700 |
|
|
of calling the system-provided \f(CW\*(C`clock_gettime\*(C'\fR function. This option |
3701 |
|
|
exists because on GNU/Linux, \f(CW\*(C`clock_gettime\*(C'\fR is in \f(CW\*(C`librt\*(C'\fR, but \f(CW\*(C`librt\*(C'\fR |
3702 |
|
|
unconditionally pulls in \f(CW\*(C`libpthread\*(C'\fR, slowing down single-threaded |
3703 |
|
|
programs needlessly. Using a direct syscall is slightly slower (in |
3704 |
|
|
theory), because no optimised vdso implementation can be used, but avoids |
3705 |
|
|
the pthread dependency. Defaults to \f(CW1\fR on GNU/Linux with glibc 2.x or |
3706 |
|
|
higher, as it simplifies linking (no need for \f(CW\*(C`\-lrt\*(C'\fR). |
3707 |
root |
1.56 |
.IP "\s-1EV_USE_NANOSLEEP\s0" 4 |
3708 |
|
|
.IX Item "EV_USE_NANOSLEEP" |
3709 |
|
|
If defined to be \f(CW1\fR, libev will assume that \f(CW\*(C`nanosleep ()\*(C'\fR is available |
3710 |
|
|
and will use it for delays. Otherwise it will use \f(CW\*(C`select ()\*(C'\fR. |
3711 |
root |
1.64 |
.IP "\s-1EV_USE_EVENTFD\s0" 4 |
3712 |
|
|
.IX Item "EV_USE_EVENTFD" |
3713 |
|
|
If defined to be \f(CW1\fR, then libev will assume that \f(CW\*(C`eventfd ()\*(C'\fR is |
3714 |
|
|
available and will probe for kernel support at runtime. This will improve |
3715 |
|
|
\&\f(CW\*(C`ev_signal\*(C'\fR and \f(CW\*(C`ev_async\*(C'\fR performance and reduce resource consumption. |
3716 |
|
|
If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
3717 |
|
|
2.7 or newer, otherwise disabled. |
3718 |
root |
1.14 |
.IP "\s-1EV_USE_SELECT\s0" 4 |
3719 |
|
|
.IX Item "EV_USE_SELECT" |
3720 |
|
|
If undefined or defined to be \f(CW1\fR, libev will compile in support for the |
3721 |
root |
1.68 |
\&\f(CW\*(C`select\*(C'\fR(2) backend. No attempt at auto-detection will be done: if no |
3722 |
root |
1.14 |
other method takes over, select will be it. Otherwise the select backend |
3723 |
|
|
will not be compiled in. |
3724 |
|
|
.IP "\s-1EV_SELECT_USE_FD_SET\s0" 4 |
3725 |
|
|
.IX Item "EV_SELECT_USE_FD_SET" |
3726 |
|
|
If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR |
3727 |
|
|
structure. This is useful if libev doesn't compile due to a missing |
3728 |
root |
1.75 |
\&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it mis-guesses the bitset layout |
3729 |
|
|
on exotic systems. This usually limits the range of file descriptors to |
3730 |
|
|
some low limit such as 1024 or might have other limitations (winsocket |
3731 |
|
|
only allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation, |
3732 |
|
|
configures the maximum size of the \f(CW\*(C`fd_set\*(C'\fR. |
3733 |
root |
1.14 |
.IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4 |
3734 |
|
|
.IX Item "EV_SELECT_IS_WINSOCKET" |
3735 |
|
|
When defined to \f(CW1\fR, the select backend will assume that |
3736 |
|
|
select/socket/connect etc. don't understand file descriptors but |
3737 |
|
|
wants osf handles on win32 (this is the case when the select to |
3738 |
|
|
be used is the winsock select). This means that it will call |
3739 |
|
|
\&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise, |
3740 |
|
|
it is assumed that all these functions actually work on fds, even |
3741 |
|
|
on win32. Should not be defined on non\-win32 platforms. |
3742 |
root |
1.60 |
.IP "\s-1EV_FD_TO_WIN32_HANDLE\s0" 4 |
3743 |
|
|
.IX Item "EV_FD_TO_WIN32_HANDLE" |
3744 |
|
|
If \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR is enabled, then libev needs a way to map |
3745 |
|
|
file descriptors to socket handles. When not defining this symbol (the |
3746 |
|
|
default), then libev will call \f(CW\*(C`_get_osfhandle\*(C'\fR, which is usually |
3747 |
|
|
correct. In some cases, programs use their own file descriptor management, |
3748 |
|
|
in which case they can provide this function to map fds to socket handles. |
3749 |
root |
1.14 |
.IP "\s-1EV_USE_POLL\s0" 4 |
3750 |
|
|
.IX Item "EV_USE_POLL" |
3751 |
|
|
If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2) |
3752 |
|
|
backend. Otherwise it will be enabled on non\-win32 platforms. It |
3753 |
|
|
takes precedence over select. |
3754 |
|
|
.IP "\s-1EV_USE_EPOLL\s0" 4 |
3755 |
|
|
.IX Item "EV_USE_EPOLL" |
3756 |
|
|
If defined to be \f(CW1\fR, libev will compile in support for the Linux |
3757 |
|
|
\&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime, |
3758 |
root |
1.64 |
otherwise another method will be used as fallback. This is the preferred |
3759 |
|
|
backend for GNU/Linux systems. If undefined, it will be enabled if the |
3760 |
|
|
headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
3761 |
root |
1.14 |
.IP "\s-1EV_USE_KQUEUE\s0" 4 |
3762 |
|
|
.IX Item "EV_USE_KQUEUE" |
3763 |
|
|
If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style |
3764 |
|
|
\&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime, |
3765 |
|
|
otherwise another method will be used as fallback. This is the preferred |
3766 |
|
|
backend for \s-1BSD\s0 and BSD-like systems, although on most BSDs kqueue only |
3767 |
|
|
supports some types of fds correctly (the only platform we found that |
3768 |
|
|
supports ptys for example was NetBSD), so kqueue might be compiled in, but |
3769 |
|
|
not be used unless explicitly requested. The best way to use it is to find |
3770 |
root |
1.16 |
out whether kqueue supports your type of fd properly and use an embedded |
3771 |
root |
1.14 |
kqueue loop. |
3772 |
|
|
.IP "\s-1EV_USE_PORT\s0" 4 |
3773 |
|
|
.IX Item "EV_USE_PORT" |
3774 |
|
|
If defined to be \f(CW1\fR, libev will compile in support for the Solaris |
3775 |
|
|
10 port style backend. Its availability will be detected at runtime, |
3776 |
|
|
otherwise another method will be used as fallback. This is the preferred |
3777 |
|
|
backend for Solaris 10 systems. |
3778 |
|
|
.IP "\s-1EV_USE_DEVPOLL\s0" 4 |
3779 |
|
|
.IX Item "EV_USE_DEVPOLL" |
3780 |
root |
1.68 |
Reserved for future expansion, works like the \s-1USE\s0 symbols above. |
3781 |
root |
1.30 |
.IP "\s-1EV_USE_INOTIFY\s0" 4 |
3782 |
|
|
.IX Item "EV_USE_INOTIFY" |
3783 |
|
|
If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify |
3784 |
|
|
interface to speed up \f(CW\*(C`ev_stat\*(C'\fR watchers. Its actual availability will |
3785 |
root |
1.64 |
be detected at runtime. If undefined, it will be enabled if the headers |
3786 |
|
|
indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
3787 |
root |
1.61 |
.IP "\s-1EV_ATOMIC_T\s0" 4 |
3788 |
|
|
.IX Item "EV_ATOMIC_T" |
3789 |
|
|
Libev requires an integer type (suitable for storing \f(CW0\fR or \f(CW1\fR) whose |
3790 |
|
|
access is atomic with respect to other threads or signal contexts. No such |
3791 |
|
|
type is easily found in the C language, so you can provide your own type |
3792 |
|
|
that you know is safe for your purposes. It is used both for signal handler \*(L"locking\*(R" |
3793 |
|
|
as well as for signal and thread safety in \f(CW\*(C`ev_async\*(C'\fR watchers. |
3794 |
|
|
.Sp |
3795 |
root |
1.68 |
In the absence of this define, libev will use \f(CW\*(C`sig_atomic_t volatile\*(C'\fR |
3796 |
root |
1.61 |
(from \fIsignal.h\fR), which is usually good enough on most platforms. |
3797 |
root |
1.14 |
.IP "\s-1EV_H\s0" 4 |
3798 |
|
|
.IX Item "EV_H" |
3799 |
|
|
The name of the \fIev.h\fR header file used to include it. The default if |
3800 |
root |
1.60 |
undefined is \f(CW"ev.h"\fR in \fIevent.h\fR, \fIev.c\fR and \fIev++.h\fR. This can be |
3801 |
|
|
used to virtually rename the \fIev.h\fR header file in case of conflicts. |
3802 |
root |
1.14 |
.IP "\s-1EV_CONFIG_H\s0" 4 |
3803 |
|
|
.IX Item "EV_CONFIG_H" |
3804 |
|
|
If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override |
3805 |
|
|
\&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to |
3806 |
|
|
\&\f(CW\*(C`EV_H\*(C'\fR, above. |
3807 |
|
|
.IP "\s-1EV_EVENT_H\s0" 4 |
3808 |
|
|
.IX Item "EV_EVENT_H" |
3809 |
|
|
Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea |
3810 |
root |
1.60 |
of how the \fIevent.h\fR header can be found, the default is \f(CW"event.h"\fR. |
3811 |
root |
1.14 |
.IP "\s-1EV_PROTOTYPES\s0" 4 |
3812 |
|
|
.IX Item "EV_PROTOTYPES" |
3813 |
|
|
If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function |
3814 |
|
|
prototypes, but still define all the structs and other symbols. This is |
3815 |
|
|
occasionally useful if you want to provide your own wrapper functions |
3816 |
|
|
around libev functions. |
3817 |
|
|
.IP "\s-1EV_MULTIPLICITY\s0" 4 |
3818 |
|
|
.IX Item "EV_MULTIPLICITY" |
3819 |
|
|
If undefined or defined to \f(CW1\fR, then all event-loop-specific functions |
3820 |
|
|
will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create |
3821 |
|
|
additional independent event loops. Otherwise there will be no support |
3822 |
|
|
for multiple event loops and there is no first event loop pointer |
3823 |
|
|
argument. Instead, all functions act on the single default loop. |
3824 |
root |
1.39 |
.IP "\s-1EV_MINPRI\s0" 4 |
3825 |
|
|
.IX Item "EV_MINPRI" |
3826 |
|
|
.PD 0 |
3827 |
|
|
.IP "\s-1EV_MAXPRI\s0" 4 |
3828 |
|
|
.IX Item "EV_MAXPRI" |
3829 |
|
|
.PD |
3830 |
|
|
The range of allowed priorities. \f(CW\*(C`EV_MINPRI\*(C'\fR must be smaller or equal to |
3831 |
|
|
\&\f(CW\*(C`EV_MAXPRI\*(C'\fR, but otherwise there are no non-obvious limitations. You can |
3832 |
|
|
provide for more priorities by overriding those symbols (usually defined |
3833 |
|
|
to be \f(CW\*(C`\-2\*(C'\fR and \f(CW2\fR, respectively). |
3834 |
|
|
.Sp |
3835 |
|
|
When doing priority-based operations, libev usually has to linearly search |
3836 |
|
|
all the priorities, so having many of them (hundreds) uses a lot of space |
3837 |
|
|
and time, so using the defaults of five priorities (\-2 .. +2) is usually |
3838 |
|
|
fine. |
3839 |
|
|
.Sp |
3840 |
root |
1.71 |
If your embedding application does not need any priorities, defining these |
3841 |
|
|
both to \f(CW0\fR will save some memory and \s-1CPU\s0. |
3842 |
root |
1.22 |
.IP "\s-1EV_PERIODIC_ENABLE\s0" 4 |
3843 |
|
|
.IX Item "EV_PERIODIC_ENABLE" |
3844 |
|
|
If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If |
3845 |
|
|
defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of |
3846 |
|
|
code. |
3847 |
root |
1.37 |
.IP "\s-1EV_IDLE_ENABLE\s0" 4 |
3848 |
|
|
.IX Item "EV_IDLE_ENABLE" |
3849 |
|
|
If undefined or defined to be \f(CW1\fR, then idle watchers are supported. If |
3850 |
|
|
defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of |
3851 |
|
|
code. |
3852 |
root |
1.22 |
.IP "\s-1EV_EMBED_ENABLE\s0" 4 |
3853 |
|
|
.IX Item "EV_EMBED_ENABLE" |
3854 |
|
|
If undefined or defined to be \f(CW1\fR, then embed watchers are supported. If |
3855 |
root |
1.71 |
defined to be \f(CW0\fR, then they are not. Embed watchers rely on most other |
3856 |
|
|
watcher types, which therefore must not be disabled. |
3857 |
root |
1.22 |
.IP "\s-1EV_STAT_ENABLE\s0" 4 |
3858 |
|
|
.IX Item "EV_STAT_ENABLE" |
3859 |
|
|
If undefined or defined to be \f(CW1\fR, then stat watchers are supported. If |
3860 |
|
|
defined to be \f(CW0\fR, then they are not. |
3861 |
root |
1.24 |
.IP "\s-1EV_FORK_ENABLE\s0" 4 |
3862 |
|
|
.IX Item "EV_FORK_ENABLE" |
3863 |
|
|
If undefined or defined to be \f(CW1\fR, then fork watchers are supported. If |
3864 |
|
|
defined to be \f(CW0\fR, then they are not. |
3865 |
root |
1.61 |
.IP "\s-1EV_ASYNC_ENABLE\s0" 4 |
3866 |
|
|
.IX Item "EV_ASYNC_ENABLE" |
3867 |
|
|
If undefined or defined to be \f(CW1\fR, then async watchers are supported. If |
3868 |
|
|
defined to be \f(CW0\fR, then they are not. |
3869 |
root |
1.22 |
.IP "\s-1EV_MINIMAL\s0" 4 |
3870 |
|
|
.IX Item "EV_MINIMAL" |
3871 |
|
|
If you need to shave off some kilobytes of code at the expense of some |
3872 |
root |
1.79 |
speed (but with the full \s-1API\s0), define this symbol to \f(CW1\fR. Currently this |
3873 |
|
|
is used to override some inlining decisions, saves roughly 30% code size |
3874 |
|
|
on amd64. It also selects a much smaller 2\-heap for timer management over |
3875 |
|
|
the default 4\-heap. |
3876 |
|
|
.Sp |
3877 |
|
|
You can save even more by disabling watcher types you do not need |
3878 |
|
|
and setting \f(CW\*(C`EV_MAXPRI\*(C'\fR == \f(CW\*(C`EV_MINPRI\*(C'\fR. Also, disabling \f(CW\*(C`assert\*(C'\fR |
3879 |
|
|
(\f(CW\*(C`\-DNDEBUG\*(C'\fR) will usually reduce code size a lot. |
3880 |
|
|
.Sp |
3881 |
|
|
Defining \f(CW\*(C`EV_MINIMAL\*(C'\fR to \f(CW2\fR will additionally reduce the core \s-1API\s0 to |
3882 |
|
|
provide a bare-bones event library. See \f(CW\*(C`ev.h\*(C'\fR for details on what parts |
3883 |
|
|
of the \s-1API\s0 are still available, and do not complain if this subset changes |
3884 |
|
|
over time. |
3885 |
root |
1.25 |
.IP "\s-1EV_PID_HASHSIZE\s0" 4 |
3886 |
|
|
.IX Item "EV_PID_HASHSIZE" |
3887 |
|
|
\&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by |
3888 |
|
|
pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), usually more |
3889 |
|
|
than enough. If you need to manage thousands of children you might want to |
3890 |
root |
1.30 |
increase this value (\fImust\fR be a power of two). |
3891 |
|
|
.IP "\s-1EV_INOTIFY_HASHSIZE\s0" 4 |
3892 |
|
|
.IX Item "EV_INOTIFY_HASHSIZE" |
3893 |
root |
1.59 |
\&\f(CW\*(C`ev_stat\*(C'\fR watchers use a small hash table to distribute workload by |
3894 |
root |
1.30 |
inotify watch id. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), |
3895 |
|
|
usually more than enough. If you need to manage thousands of \f(CW\*(C`ev_stat\*(C'\fR |
3896 |
|
|
watchers you might want to increase this value (\fImust\fR be a power of |
3897 |
|
|
two). |
3898 |
root |
1.65 |
.IP "\s-1EV_USE_4HEAP\s0" 4 |
3899 |
|
|
.IX Item "EV_USE_4HEAP" |
3900 |
|
|
Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3901 |
root |
1.71 |
timer and periodics heaps, libev uses a 4\-heap when this symbol is defined |
3902 |
|
|
to \f(CW1\fR. The 4\-heap uses more complicated (longer) code but has noticeably |
3903 |
|
|
faster performance with many (thousands) of watchers. |
3904 |
root |
1.65 |
.Sp |
3905 |
|
|
The default is \f(CW1\fR unless \f(CW\*(C`EV_MINIMAL\*(C'\fR is set in which case it is \f(CW0\fR |
3906 |
|
|
(disabled). |
3907 |
|
|
.IP "\s-1EV_HEAP_CACHE_AT\s0" 4 |
3908 |
|
|
.IX Item "EV_HEAP_CACHE_AT" |
3909 |
|
|
Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3910 |
root |
1.71 |
timer and periodics heaps, libev can cache the timestamp (\fIat\fR) within |
3911 |
root |
1.65 |
the heap structure (selected by defining \f(CW\*(C`EV_HEAP_CACHE_AT\*(C'\fR to \f(CW1\fR), |
3912 |
|
|
which uses 8\-12 bytes more per watcher and a few hundred bytes more code, |
3913 |
root |
1.67 |
but avoids random read accesses on heap changes. This improves performance |
3914 |
root |
1.71 |
noticeably with many (hundreds) of watchers. |
3915 |
root |
1.65 |
.Sp |
3916 |
|
|
The default is \f(CW1\fR unless \f(CW\*(C`EV_MINIMAL\*(C'\fR is set in which case it is \f(CW0\fR |
3917 |
|
|
(disabled). |
3918 |
root |
1.67 |
.IP "\s-1EV_VERIFY\s0" 4 |
3919 |
|
|
.IX Item "EV_VERIFY" |
3920 |
|
|
Controls how much internal verification (see \f(CW\*(C`ev_loop_verify ()\*(C'\fR) will |
3921 |
|
|
be done: If set to \f(CW0\fR, no internal verification code will be compiled |
3922 |
|
|
in. If set to \f(CW1\fR, then verification code will be compiled in, but not |
3923 |
|
|
called. If set to \f(CW2\fR, then the internal verification code will be |
3924 |
|
|
called once per loop, which can slow down libev. If set to \f(CW3\fR, then the |
3925 |
|
|
verification code will be called very frequently, which will slow down |
3926 |
|
|
libev considerably. |
3927 |
|
|
.Sp |
3928 |
|
|
The default is \f(CW1\fR, unless \f(CW\*(C`EV_MINIMAL\*(C'\fR is set, in which case it will be |
3929 |
root |
1.71 |
\&\f(CW0\fR. |
3930 |
root |
1.14 |
.IP "\s-1EV_COMMON\s0" 4 |
3931 |
|
|
.IX Item "EV_COMMON" |
3932 |
|
|
By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining |
3933 |
|
|
this macro to a something else you can include more and other types of |
3934 |
|
|
members. You have to define it each time you include one of the files, |
3935 |
|
|
though, and it must be identical each time. |
3936 |
|
|
.Sp |
3937 |
|
|
For example, the perl \s-1EV\s0 module uses something like this: |
3938 |
|
|
.Sp |
3939 |
|
|
.Vb 3 |
3940 |
root |
1.68 |
\& #define EV_COMMON \e |
3941 |
|
|
\& SV *self; /* contains this struct */ \e |
3942 |
|
|
\& SV *cb_sv, *fh /* note no trailing ";" */ |
3943 |
root |
1.14 |
.Ve |
3944 |
root |
1.19 |
.IP "\s-1EV_CB_DECLARE\s0 (type)" 4 |
3945 |
|
|
.IX Item "EV_CB_DECLARE (type)" |
3946 |
root |
1.14 |
.PD 0 |
3947 |
root |
1.19 |
.IP "\s-1EV_CB_INVOKE\s0 (watcher, revents)" 4 |
3948 |
|
|
.IX Item "EV_CB_INVOKE (watcher, revents)" |
3949 |
|
|
.IP "ev_set_cb (ev, cb)" 4 |
3950 |
|
|
.IX Item "ev_set_cb (ev, cb)" |
3951 |
root |
1.14 |
.PD |
3952 |
|
|
Can be used to change the callback member declaration in each watcher, |
3953 |
|
|
and the way callbacks are invoked and set. Must expand to a struct member |
3954 |
root |
1.54 |
definition and a statement, respectively. See the \fIev.h\fR header file for |
3955 |
root |
1.14 |
their default definitions. One possible use for overriding these is to |
3956 |
root |
1.19 |
avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use |
3957 |
|
|
method calls instead of plain function calls in \*(C+. |
3958 |
root |
1.79 |
.SS "\s-1EXPORTED\s0 \s-1API\s0 \s-1SYMBOLS\s0" |
3959 |
root |
1.53 |
.IX Subsection "EXPORTED API SYMBOLS" |
3960 |
root |
1.68 |
If you need to re-export the \s-1API\s0 (e.g. via a \s-1DLL\s0) and you need a list of |
3961 |
root |
1.53 |
exported symbols, you can use the provided \fISymbol.*\fR files which list |
3962 |
|
|
all public symbols, one per line: |
3963 |
root |
1.60 |
.PP |
3964 |
root |
1.53 |
.Vb 2 |
3965 |
root |
1.68 |
\& Symbols.ev for libev proper |
3966 |
|
|
\& Symbols.event for the libevent emulation |
3967 |
root |
1.53 |
.Ve |
3968 |
root |
1.60 |
.PP |
3969 |
root |
1.53 |
This can also be used to rename all public symbols to avoid clashes with |
3970 |
|
|
multiple versions of libev linked together (which is obviously bad in |
3971 |
root |
1.68 |
itself, but sometimes it is inconvenient to avoid this). |
3972 |
root |
1.60 |
.PP |
3973 |
root |
1.54 |
A sed command like this will create wrapper \f(CW\*(C`#define\*(C'\fR's that you need to |
3974 |
root |
1.53 |
include before including \fIev.h\fR: |
3975 |
root |
1.60 |
.PP |
3976 |
root |
1.53 |
.Vb 1 |
3977 |
root |
1.60 |
\& <Symbols.ev sed \-e "s/.*/#define & myprefix_&/" >wrap.h |
3978 |
root |
1.53 |
.Ve |
3979 |
root |
1.60 |
.PP |
3980 |
root |
1.53 |
This would create a file \fIwrap.h\fR which essentially looks like this: |
3981 |
root |
1.60 |
.PP |
3982 |
root |
1.53 |
.Vb 4 |
3983 |
|
|
\& #define ev_backend myprefix_ev_backend |
3984 |
|
|
\& #define ev_check_start myprefix_ev_check_start |
3985 |
|
|
\& #define ev_check_stop myprefix_ev_check_stop |
3986 |
|
|
\& ... |
3987 |
|
|
.Ve |
3988 |
root |
1.79 |
.SS "\s-1EXAMPLES\s0" |
3989 |
root |
1.14 |
.IX Subsection "EXAMPLES" |
3990 |
|
|
For a real-world example of a program the includes libev |
3991 |
|
|
verbatim, you can have a look at the \s-1EV\s0 perl module |
3992 |
|
|
(<http://software.schmorp.de/pkg/EV.html>). It has the libev files in |
3993 |
|
|
the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public |
3994 |
|
|
interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file |
3995 |
|
|
will be compiled. It is pretty complex because it provides its own header |
3996 |
|
|
file. |
3997 |
root |
1.60 |
.PP |
3998 |
root |
1.14 |
The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file |
3999 |
root |
1.36 |
that everybody includes and which overrides some configure choices: |
4000 |
root |
1.60 |
.PP |
4001 |
root |
1.36 |
.Vb 9 |
4002 |
root |
1.68 |
\& #define EV_MINIMAL 1 |
4003 |
|
|
\& #define EV_USE_POLL 0 |
4004 |
|
|
\& #define EV_MULTIPLICITY 0 |
4005 |
|
|
\& #define EV_PERIODIC_ENABLE 0 |
4006 |
|
|
\& #define EV_STAT_ENABLE 0 |
4007 |
|
|
\& #define EV_FORK_ENABLE 0 |
4008 |
|
|
\& #define EV_CONFIG_H <config.h> |
4009 |
|
|
\& #define EV_MINPRI 0 |
4010 |
|
|
\& #define EV_MAXPRI 0 |
4011 |
root |
1.60 |
\& |
4012 |
root |
1.68 |
\& #include "ev++.h" |
4013 |
root |
1.14 |
.Ve |
4014 |
root |
1.60 |
.PP |
4015 |
root |
1.14 |
And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled: |
4016 |
root |
1.60 |
.PP |
4017 |
root |
1.14 |
.Vb 2 |
4018 |
root |
1.68 |
\& #include "ev_cpp.h" |
4019 |
|
|
\& #include "ev.c" |
4020 |
root |
1.14 |
.Ve |
4021 |
root |
1.72 |
.SH "INTERACTION WITH OTHER PROGRAMS OR LIBRARIES" |
4022 |
|
|
.IX Header "INTERACTION WITH OTHER PROGRAMS OR LIBRARIES" |
4023 |
root |
1.79 |
.SS "\s-1THREADS\s0 \s-1AND\s0 \s-1COROUTINES\s0" |
4024 |
root |
1.72 |
.IX Subsection "THREADS AND COROUTINES" |
4025 |
|
|
\fI\s-1THREADS\s0\fR |
4026 |
root |
1.64 |
.IX Subsection "THREADS" |
4027 |
root |
1.72 |
.PP |
4028 |
root |
1.71 |
All libev functions are reentrant and thread-safe unless explicitly |
4029 |
root |
1.72 |
documented otherwise, but libev implements no locking itself. This means |
4030 |
|
|
that you can use as many loops as you want in parallel, as long as there |
4031 |
|
|
are no concurrent calls into any libev function with the same loop |
4032 |
|
|
parameter (\f(CW\*(C`ev_default_*\*(C'\fR calls have an implicit default loop parameter, |
4033 |
|
|
of course): libev guarantees that different event loops share no data |
4034 |
root |
1.71 |
structures that need any locking. |
4035 |
|
|
.PP |
4036 |
|
|
Or to put it differently: calls with different loop parameters can be done |
4037 |
|
|
concurrently from multiple threads, calls with the same loop parameter |
4038 |
|
|
must be done serially (but can be done from different threads, as long as |
4039 |
|
|
only one thread ever is inside a call at any point in time, e.g. by using |
4040 |
|
|
a mutex per loop). |
4041 |
|
|
.PP |
4042 |
|
|
Specifically to support threads (and signal handlers), libev implements |
4043 |
|
|
so-called \f(CW\*(C`ev_async\*(C'\fR watchers, which allow some limited form of |
4044 |
|
|
concurrency on the same event loop, namely waking it up \*(L"from the |
4045 |
|
|
outside\*(R". |
4046 |
root |
1.64 |
.PP |
4047 |
root |
1.70 |
If you want to know which design (one loop, locking, or multiple loops |
4048 |
|
|
without or something else still) is best for your problem, then I cannot |
4049 |
root |
1.71 |
help you, but here is some generic advice: |
4050 |
root |
1.64 |
.IP "\(bu" 4 |
4051 |
|
|
most applications have a main thread: use the default libev loop |
4052 |
root |
1.68 |
in that thread, or create a separate thread running only the default loop. |
4053 |
root |
1.64 |
.Sp |
4054 |
|
|
This helps integrating other libraries or software modules that use libev |
4055 |
|
|
themselves and don't care/know about threading. |
4056 |
|
|
.IP "\(bu" 4 |
4057 |
|
|
one loop per thread is usually a good model. |
4058 |
|
|
.Sp |
4059 |
|
|
Doing this is almost never wrong, sometimes a better-performance model |
4060 |
|
|
exists, but it is always a good start. |
4061 |
|
|
.IP "\(bu" 4 |
4062 |
|
|
other models exist, such as the leader/follower pattern, where one |
4063 |
root |
1.68 |
loop is handed through multiple threads in a kind of round-robin fashion. |
4064 |
root |
1.64 |
.Sp |
4065 |
root |
1.68 |
Choosing a model is hard \- look around, learn, know that usually you can do |
4066 |
root |
1.64 |
better than you currently do :\-) |
4067 |
|
|
.IP "\(bu" 4 |
4068 |
|
|
often you need to talk to some other thread which blocks in the |
4069 |
root |
1.71 |
event loop. |
4070 |
|
|
.Sp |
4071 |
|
|
\&\f(CW\*(C`ev_async\*(C'\fR watchers can be used to wake them up from other threads safely |
4072 |
|
|
(or from signal contexts...). |
4073 |
|
|
.Sp |
4074 |
|
|
An example use would be to communicate signals or other events that only |
4075 |
|
|
work in the default loop by registering the signal watcher with the |
4076 |
|
|
default loop and triggering an \f(CW\*(C`ev_async\*(C'\fR watcher from the default loop |
4077 |
|
|
watcher callback into the event loop interested in the signal. |
4078 |
root |
1.72 |
.PP |
4079 |
root |
1.79 |
\s-1THREAD\s0 \s-1LOCKING\s0 \s-1EXAMPLE\s0 |
4080 |
|
|
.IX Subsection "THREAD LOCKING EXAMPLE" |
4081 |
|
|
.PP |
4082 |
|
|
Here is a fictitious example of how to run an event loop in a different |
4083 |
|
|
thread than where callbacks are being invoked and watchers are |
4084 |
|
|
created/added/removed. |
4085 |
|
|
.PP |
4086 |
|
|
For a real-world example, see the \f(CW\*(C`EV::Loop::Async\*(C'\fR perl module, |
4087 |
|
|
which uses exactly this technique (which is suited for many high-level |
4088 |
|
|
languages). |
4089 |
|
|
.PP |
4090 |
|
|
The example uses a pthread mutex to protect the loop data, a condition |
4091 |
|
|
variable to wait for callback invocations, an async watcher to notify the |
4092 |
|
|
event loop thread and an unspecified mechanism to wake up the main thread. |
4093 |
|
|
.PP |
4094 |
|
|
First, you need to associate some data with the event loop: |
4095 |
|
|
.PP |
4096 |
|
|
.Vb 6 |
4097 |
|
|
\& typedef struct { |
4098 |
|
|
\& mutex_t lock; /* global loop lock */ |
4099 |
|
|
\& ev_async async_w; |
4100 |
|
|
\& thread_t tid; |
4101 |
|
|
\& cond_t invoke_cv; |
4102 |
|
|
\& } userdata; |
4103 |
|
|
\& |
4104 |
|
|
\& void prepare_loop (EV_P) |
4105 |
|
|
\& { |
4106 |
|
|
\& // for simplicity, we use a static userdata struct. |
4107 |
|
|
\& static userdata u; |
4108 |
|
|
\& |
4109 |
|
|
\& ev_async_init (&u\->async_w, async_cb); |
4110 |
|
|
\& ev_async_start (EV_A_ &u\->async_w); |
4111 |
|
|
\& |
4112 |
|
|
\& pthread_mutex_init (&u\->lock, 0); |
4113 |
|
|
\& pthread_cond_init (&u\->invoke_cv, 0); |
4114 |
|
|
\& |
4115 |
|
|
\& // now associate this with the loop |
4116 |
|
|
\& ev_set_userdata (EV_A_ u); |
4117 |
|
|
\& ev_set_invoke_pending_cb (EV_A_ l_invoke); |
4118 |
|
|
\& ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
4119 |
|
|
\& |
4120 |
|
|
\& // then create the thread running ev_loop |
4121 |
|
|
\& pthread_create (&u\->tid, 0, l_run, EV_A); |
4122 |
|
|
\& } |
4123 |
|
|
.Ve |
4124 |
|
|
.PP |
4125 |
|
|
The callback for the \f(CW\*(C`ev_async\*(C'\fR watcher does nothing: the watcher is used |
4126 |
|
|
solely to wake up the event loop so it takes notice of any new watchers |
4127 |
|
|
that might have been added: |
4128 |
|
|
.PP |
4129 |
|
|
.Vb 5 |
4130 |
|
|
\& static void |
4131 |
|
|
\& async_cb (EV_P_ ev_async *w, int revents) |
4132 |
|
|
\& { |
4133 |
|
|
\& // just used for the side effects |
4134 |
|
|
\& } |
4135 |
|
|
.Ve |
4136 |
|
|
.PP |
4137 |
|
|
The \f(CW\*(C`l_release\*(C'\fR and \f(CW\*(C`l_acquire\*(C'\fR callbacks simply unlock/lock the mutex |
4138 |
|
|
protecting the loop data, respectively. |
4139 |
|
|
.PP |
4140 |
|
|
.Vb 6 |
4141 |
|
|
\& static void |
4142 |
|
|
\& l_release (EV_P) |
4143 |
|
|
\& { |
4144 |
|
|
\& userdata *u = ev_userdata (EV_A); |
4145 |
|
|
\& pthread_mutex_unlock (&u\->lock); |
4146 |
|
|
\& } |
4147 |
|
|
\& |
4148 |
|
|
\& static void |
4149 |
|
|
\& l_acquire (EV_P) |
4150 |
|
|
\& { |
4151 |
|
|
\& userdata *u = ev_userdata (EV_A); |
4152 |
|
|
\& pthread_mutex_lock (&u\->lock); |
4153 |
|
|
\& } |
4154 |
|
|
.Ve |
4155 |
|
|
.PP |
4156 |
|
|
The event loop thread first acquires the mutex, and then jumps straight |
4157 |
|
|
into \f(CW\*(C`ev_loop\*(C'\fR: |
4158 |
|
|
.PP |
4159 |
|
|
.Vb 4 |
4160 |
|
|
\& void * |
4161 |
|
|
\& l_run (void *thr_arg) |
4162 |
|
|
\& { |
4163 |
|
|
\& struct ev_loop *loop = (struct ev_loop *)thr_arg; |
4164 |
|
|
\& |
4165 |
|
|
\& l_acquire (EV_A); |
4166 |
|
|
\& pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
4167 |
|
|
\& ev_loop (EV_A_ 0); |
4168 |
|
|
\& l_release (EV_A); |
4169 |
|
|
\& |
4170 |
|
|
\& return 0; |
4171 |
|
|
\& } |
4172 |
|
|
.Ve |
4173 |
|
|
.PP |
4174 |
|
|
Instead of invoking all pending watchers, the \f(CW\*(C`l_invoke\*(C'\fR callback will |
4175 |
|
|
signal the main thread via some unspecified mechanism (signals? pipe |
4176 |
|
|
writes? \f(CW\*(C`Async::Interrupt\*(C'\fR?) and then waits until all pending watchers |
4177 |
|
|
have been called (in a while loop because a) spurious wakeups are possible |
4178 |
|
|
and b) skipping inter-thread-communication when there are no pending |
4179 |
|
|
watchers is very beneficial): |
4180 |
|
|
.PP |
4181 |
|
|
.Vb 4 |
4182 |
|
|
\& static void |
4183 |
|
|
\& l_invoke (EV_P) |
4184 |
|
|
\& { |
4185 |
|
|
\& userdata *u = ev_userdata (EV_A); |
4186 |
|
|
\& |
4187 |
|
|
\& while (ev_pending_count (EV_A)) |
4188 |
|
|
\& { |
4189 |
|
|
\& wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
4190 |
|
|
\& pthread_cond_wait (&u\->invoke_cv, &u\->lock); |
4191 |
|
|
\& } |
4192 |
|
|
\& } |
4193 |
|
|
.Ve |
4194 |
|
|
.PP |
4195 |
|
|
Now, whenever the main thread gets told to invoke pending watchers, it |
4196 |
|
|
will grab the lock, call \f(CW\*(C`ev_invoke_pending\*(C'\fR and then signal the loop |
4197 |
|
|
thread to continue: |
4198 |
|
|
.PP |
4199 |
|
|
.Vb 4 |
4200 |
|
|
\& static void |
4201 |
|
|
\& real_invoke_pending (EV_P) |
4202 |
|
|
\& { |
4203 |
|
|
\& userdata *u = ev_userdata (EV_A); |
4204 |
|
|
\& |
4205 |
|
|
\& pthread_mutex_lock (&u\->lock); |
4206 |
|
|
\& ev_invoke_pending (EV_A); |
4207 |
|
|
\& pthread_cond_signal (&u\->invoke_cv); |
4208 |
|
|
\& pthread_mutex_unlock (&u\->lock); |
4209 |
|
|
\& } |
4210 |
|
|
.Ve |
4211 |
|
|
.PP |
4212 |
|
|
Whenever you want to start/stop a watcher or do other modifications to an |
4213 |
|
|
event loop, you will now have to lock: |
4214 |
|
|
.PP |
4215 |
|
|
.Vb 2 |
4216 |
|
|
\& ev_timer timeout_watcher; |
4217 |
|
|
\& userdata *u = ev_userdata (EV_A); |
4218 |
|
|
\& |
4219 |
|
|
\& ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
4220 |
|
|
\& |
4221 |
|
|
\& pthread_mutex_lock (&u\->lock); |
4222 |
|
|
\& ev_timer_start (EV_A_ &timeout_watcher); |
4223 |
|
|
\& ev_async_send (EV_A_ &u\->async_w); |
4224 |
|
|
\& pthread_mutex_unlock (&u\->lock); |
4225 |
|
|
.Ve |
4226 |
|
|
.PP |
4227 |
|
|
Note that sending the \f(CW\*(C`ev_async\*(C'\fR watcher is required because otherwise |
4228 |
|
|
an event loop currently blocking in the kernel will have no knowledge |
4229 |
|
|
about the newly added timer. By waking up the loop it will pick up any new |
4230 |
|
|
watchers in the next event loop iteration. |
4231 |
|
|
.PP |
4232 |
root |
1.72 |
\fI\s-1COROUTINES\s0\fR |
4233 |
root |
1.64 |
.IX Subsection "COROUTINES" |
4234 |
root |
1.72 |
.PP |
4235 |
|
|
Libev is very accommodating to coroutines (\*(L"cooperative threads\*(R"): |
4236 |
|
|
libev fully supports nesting calls to its functions from different |
4237 |
root |
1.64 |
coroutines (e.g. you can call \f(CW\*(C`ev_loop\*(C'\fR on the same loop from two |
4238 |
root |
1.79 |
different coroutines, and switch freely between both coroutines running |
4239 |
|
|
the loop, as long as you don't confuse yourself). The only exception is |
4240 |
|
|
that you must not do this from \f(CW\*(C`ev_periodic\*(C'\fR reschedule callbacks. |
4241 |
root |
1.64 |
.PP |
4242 |
root |
1.71 |
Care has been taken to ensure that libev does not keep local state inside |
4243 |
root |
1.72 |
\&\f(CW\*(C`ev_loop\*(C'\fR, and other calls do not usually allow for coroutine switches as |
4244 |
root |
1.73 |
they do not call any callbacks. |
4245 |
root |
1.79 |
.SS "\s-1COMPILER\s0 \s-1WARNINGS\s0" |
4246 |
root |
1.72 |
.IX Subsection "COMPILER WARNINGS" |
4247 |
|
|
Depending on your compiler and compiler settings, you might get no or a |
4248 |
|
|
lot of warnings when compiling libev code. Some people are apparently |
4249 |
|
|
scared by this. |
4250 |
|
|
.PP |
4251 |
|
|
However, these are unavoidable for many reasons. For one, each compiler |
4252 |
|
|
has different warnings, and each user has different tastes regarding |
4253 |
|
|
warning options. \*(L"Warn-free\*(R" code therefore cannot be a goal except when |
4254 |
|
|
targeting a specific compiler and compiler-version. |
4255 |
|
|
.PP |
4256 |
|
|
Another reason is that some compiler warnings require elaborate |
4257 |
|
|
workarounds, or other changes to the code that make it less clear and less |
4258 |
|
|
maintainable. |
4259 |
|
|
.PP |
4260 |
|
|
And of course, some compiler warnings are just plain stupid, or simply |
4261 |
|
|
wrong (because they don't actually warn about the condition their message |
4262 |
|
|
seems to warn about). For example, certain older gcc versions had some |
4263 |
|
|
warnings that resulted an extreme number of false positives. These have |
4264 |
|
|
been fixed, but some people still insist on making code warn-free with |
4265 |
|
|
such buggy versions. |
4266 |
|
|
.PP |
4267 |
|
|
While libev is written to generate as few warnings as possible, |
4268 |
|
|
\&\*(L"warn-free\*(R" code is not a goal, and it is recommended not to build libev |
4269 |
|
|
with any compiler warnings enabled unless you are prepared to cope with |
4270 |
|
|
them (e.g. by ignoring them). Remember that warnings are just that: |
4271 |
|
|
warnings, not errors, or proof of bugs. |
4272 |
root |
1.79 |
.SS "\s-1VALGRIND\s0" |
4273 |
root |
1.72 |
.IX Subsection "VALGRIND" |
4274 |
|
|
Valgrind has a special section here because it is a popular tool that is |
4275 |
|
|
highly useful. Unfortunately, valgrind reports are very hard to interpret. |
4276 |
|
|
.PP |
4277 |
|
|
If you think you found a bug (memory leak, uninitialised data access etc.) |
4278 |
|
|
in libev, then check twice: If valgrind reports something like: |
4279 |
|
|
.PP |
4280 |
|
|
.Vb 3 |
4281 |
|
|
\& ==2274== definitely lost: 0 bytes in 0 blocks. |
4282 |
|
|
\& ==2274== possibly lost: 0 bytes in 0 blocks. |
4283 |
|
|
\& ==2274== still reachable: 256 bytes in 1 blocks. |
4284 |
|
|
.Ve |
4285 |
|
|
.PP |
4286 |
|
|
Then there is no memory leak, just as memory accounted to global variables |
4287 |
root |
1.73 |
is not a memleak \- the memory is still being referenced, and didn't leak. |
4288 |
root |
1.72 |
.PP |
4289 |
|
|
Similarly, under some circumstances, valgrind might report kernel bugs |
4290 |
|
|
as if it were a bug in libev (e.g. in realloc or in the poll backend, |
4291 |
|
|
although an acceptable workaround has been found here), or it might be |
4292 |
|
|
confused. |
4293 |
|
|
.PP |
4294 |
|
|
Keep in mind that valgrind is a very good tool, but only a tool. Don't |
4295 |
|
|
make it into some kind of religion. |
4296 |
|
|
.PP |
4297 |
|
|
If you are unsure about something, feel free to contact the mailing list |
4298 |
|
|
with the full valgrind report and an explanation on why you think this |
4299 |
|
|
is a bug in libev (best check the archives, too :). However, don't be |
4300 |
|
|
annoyed when you get a brisk \*(L"this is no bug\*(R" answer and take the chance |
4301 |
|
|
of learning how to interpret valgrind properly. |
4302 |
root |
1.60 |
.PP |
4303 |
root |
1.72 |
If you need, for some reason, empty reports from valgrind for your project |
4304 |
|
|
I suggest using suppression lists. |
4305 |
|
|
.SH "PORTABILITY NOTES" |
4306 |
|
|
.IX Header "PORTABILITY NOTES" |
4307 |
root |
1.79 |
.SS "\s-1WIN32\s0 \s-1PLATFORM\s0 \s-1LIMITATIONS\s0 \s-1AND\s0 \s-1WORKAROUNDS\s0" |
4308 |
root |
1.72 |
.IX Subsection "WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS" |
4309 |
root |
1.60 |
Win32 doesn't support any of the standards (e.g. \s-1POSIX\s0) that libev |
4310 |
|
|
requires, and its I/O model is fundamentally incompatible with the \s-1POSIX\s0 |
4311 |
|
|
model. Libev still offers limited functionality on this platform in |
4312 |
|
|
the form of the \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR backend, and only supports socket |
4313 |
|
|
descriptors. This only applies when using Win32 natively, not when using |
4314 |
|
|
e.g. cygwin. |
4315 |
|
|
.PP |
4316 |
root |
1.65 |
Lifting these limitations would basically require the full |
4317 |
|
|
re-implementation of the I/O system. If you are into these kinds of |
4318 |
|
|
things, then note that glib does exactly that for you in a very portable |
4319 |
|
|
way (note also that glib is the slowest event library known to man). |
4320 |
|
|
.PP |
4321 |
root |
1.60 |
There is no supported compilation method available on windows except |
4322 |
|
|
embedding it into other applications. |
4323 |
|
|
.PP |
4324 |
root |
1.78 |
Sensible signal handling is officially unsupported by Microsoft \- libev |
4325 |
|
|
tries its best, but under most conditions, signals will simply not work. |
4326 |
|
|
.PP |
4327 |
root |
1.68 |
Not a libev limitation but worth mentioning: windows apparently doesn't |
4328 |
|
|
accept large writes: instead of resulting in a partial write, windows will |
4329 |
|
|
either accept everything or return \f(CW\*(C`ENOBUFS\*(C'\fR if the buffer is too large, |
4330 |
|
|
so make sure you only write small amounts into your sockets (less than a |
4331 |
root |
1.71 |
megabyte seems safe, but this apparently depends on the amount of memory |
4332 |
root |
1.68 |
available). |
4333 |
|
|
.PP |
4334 |
root |
1.65 |
Due to the many, low, and arbitrary limits on the win32 platform and |
4335 |
|
|
the abysmal performance of winsockets, using a large number of sockets |
4336 |
|
|
is not recommended (and not reasonable). If your program needs to use |
4337 |
|
|
more than a hundred or so sockets, then likely it needs to use a totally |
4338 |
root |
1.67 |
different implementation for windows, as libev offers the \s-1POSIX\s0 readiness |
4339 |
root |
1.65 |
notification model, which cannot be implemented efficiently on windows |
4340 |
root |
1.78 |
(due to Microsoft monopoly games). |
4341 |
root |
1.68 |
.PP |
4342 |
|
|
A typical way to use libev under windows is to embed it (see the embedding |
4343 |
|
|
section for details) and use the following \fIevwrap.h\fR header file instead |
4344 |
|
|
of \fIev.h\fR: |
4345 |
|
|
.PP |
4346 |
|
|
.Vb 2 |
4347 |
|
|
\& #define EV_STANDALONE /* keeps ev from requiring config.h */ |
4348 |
|
|
\& #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
4349 |
|
|
\& |
4350 |
|
|
\& #include "ev.h" |
4351 |
|
|
.Ve |
4352 |
|
|
.PP |
4353 |
|
|
And compile the following \fIevwrap.c\fR file into your project (make sure |
4354 |
root |
1.71 |
you do \fInot\fR compile the \fIev.c\fR or any other embedded source files!): |
4355 |
root |
1.68 |
.PP |
4356 |
|
|
.Vb 2 |
4357 |
|
|
\& #include "evwrap.h" |
4358 |
|
|
\& #include "ev.c" |
4359 |
|
|
.Ve |
4360 |
root |
1.60 |
.IP "The winsocket select function" 4 |
4361 |
|
|
.IX Item "The winsocket select function" |
4362 |
root |
1.67 |
The winsocket \f(CW\*(C`select\*(C'\fR function doesn't follow \s-1POSIX\s0 in that it |
4363 |
|
|
requires socket \fIhandles\fR and not socket \fIfile descriptors\fR (it is |
4364 |
|
|
also extremely buggy). This makes select very inefficient, and also |
4365 |
root |
1.68 |
requires a mapping from file descriptors to socket handles (the Microsoft |
4366 |
|
|
C runtime provides the function \f(CW\*(C`_open_osfhandle\*(C'\fR for this). See the |
4367 |
root |
1.67 |
discussion of the \f(CW\*(C`EV_SELECT_USE_FD_SET\*(C'\fR, \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR and |
4368 |
|
|
\&\f(CW\*(C`EV_FD_TO_WIN32_HANDLE\*(C'\fR preprocessor symbols for more info. |
4369 |
root |
1.60 |
.Sp |
4370 |
root |
1.68 |
The configuration for a \*(L"naked\*(R" win32 using the Microsoft runtime |
4371 |
root |
1.60 |
libraries and raw winsocket select is: |
4372 |
|
|
.Sp |
4373 |
|
|
.Vb 2 |
4374 |
root |
1.68 |
\& #define EV_USE_SELECT 1 |
4375 |
|
|
\& #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
4376 |
root |
1.60 |
.Ve |
4377 |
|
|
.Sp |
4378 |
|
|
Note that winsockets handling of fd sets is O(n), so you can easily get a |
4379 |
|
|
complexity in the O(nA\*^X) range when using win32. |
4380 |
|
|
.IP "Limited number of file descriptors" 4 |
4381 |
|
|
.IX Item "Limited number of file descriptors" |
4382 |
root |
1.65 |
Windows has numerous arbitrary (and low) limits on things. |
4383 |
|
|
.Sp |
4384 |
|
|
Early versions of winsocket's select only supported waiting for a maximum |
4385 |
|
|
of \f(CW64\fR handles (probably owning to the fact that all windows kernels |
4386 |
root |
1.68 |
can only wait for \f(CW64\fR things at the same time internally; Microsoft |
4387 |
root |
1.65 |
recommends spawning a chain of threads and wait for 63 handles and the |
4388 |
root |
1.78 |
previous thread in each. Sounds great!). |
4389 |
root |
1.60 |
.Sp |
4390 |
|
|
Newer versions support more handles, but you need to define \f(CW\*(C`FD_SETSIZE\*(C'\fR |
4391 |
|
|
to some high number (e.g. \f(CW2048\fR) before compiling the winsocket select |
4392 |
root |
1.78 |
call (which might be in libev or elsewhere, for example, perl and many |
4393 |
|
|
other interpreters do their own select emulation on windows). |
4394 |
root |
1.60 |
.Sp |
4395 |
root |
1.68 |
Another limit is the number of file descriptors in the Microsoft runtime |
4396 |
root |
1.78 |
libraries, which by default is \f(CW64\fR (there must be a hidden \fI64\fR |
4397 |
|
|
fetish or something like this inside Microsoft). You can increase this |
4398 |
|
|
by calling \f(CW\*(C`_setmaxstdio\*(C'\fR, which can increase this limit to \f(CW2048\fR |
4399 |
|
|
(another arbitrary limit), but is broken in many versions of the Microsoft |
4400 |
|
|
runtime libraries. This might get you to about \f(CW512\fR or \f(CW2048\fR sockets |
4401 |
|
|
(depending on windows version and/or the phase of the moon). To get more, |
4402 |
|
|
you need to wrap all I/O functions and provide your own fd management, but |
4403 |
|
|
the cost of calling select (O(nA\*^X)) will likely make this unworkable. |
4404 |
root |
1.79 |
.SS "\s-1PORTABILITY\s0 \s-1REQUIREMENTS\s0" |
4405 |
root |
1.72 |
.IX Subsection "PORTABILITY REQUIREMENTS" |
4406 |
|
|
In addition to a working ISO-C implementation and of course the |
4407 |
|
|
backend-specific APIs, libev relies on a few additional extensions: |
4408 |
root |
1.79 |
.ie n .IP """void (*)(ev_watcher_type *, int revents)"" must have compatible calling conventions regardless of ""ev_watcher_type *""." 4 |
4409 |
root |
1.68 |
.el .IP "\f(CWvoid (*)(ev_watcher_type *, int revents)\fR must have compatible calling conventions regardless of \f(CWev_watcher_type *\fR." 4 |
4410 |
|
|
.IX Item "void (*)(ev_watcher_type *, int revents) must have compatible calling conventions regardless of ev_watcher_type *." |
4411 |
|
|
Libev assumes not only that all watcher pointers have the same internal |
4412 |
|
|
structure (guaranteed by \s-1POSIX\s0 but not by \s-1ISO\s0 C for example), but it also |
4413 |
|
|
assumes that the same (machine) code can be used to call any watcher |
4414 |
|
|
callback: The watcher callbacks have different type signatures, but libev |
4415 |
|
|
calls them using an \f(CW\*(C`ev_watcher *\*(C'\fR internally. |
4416 |
root |
1.65 |
.ie n .IP """sig_atomic_t volatile"" must be thread-atomic as well" 4 |
4417 |
|
|
.el .IP "\f(CWsig_atomic_t volatile\fR must be thread-atomic as well" 4 |
4418 |
|
|
.IX Item "sig_atomic_t volatile must be thread-atomic as well" |
4419 |
|
|
The type \f(CW\*(C`sig_atomic_t volatile\*(C'\fR (or whatever is defined as |
4420 |
root |
1.71 |
\&\f(CW\*(C`EV_ATOMIC_T\*(C'\fR) must be atomic with respect to accesses from different |
4421 |
root |
1.65 |
threads. This is not part of the specification for \f(CW\*(C`sig_atomic_t\*(C'\fR, but is |
4422 |
|
|
believed to be sufficiently portable. |
4423 |
|
|
.ie n .IP """sigprocmask"" must work in a threaded environment" 4 |
4424 |
|
|
.el .IP "\f(CWsigprocmask\fR must work in a threaded environment" 4 |
4425 |
|
|
.IX Item "sigprocmask must work in a threaded environment" |
4426 |
|
|
Libev uses \f(CW\*(C`sigprocmask\*(C'\fR to temporarily block signals. This is not |
4427 |
|
|
allowed in a threaded program (\f(CW\*(C`pthread_sigmask\*(C'\fR has to be used). Typical |
4428 |
|
|
pthread implementations will either allow \f(CW\*(C`sigprocmask\*(C'\fR in the \*(L"main |
4429 |
|
|
thread\*(R" or will block signals process-wide, both behaviours would |
4430 |
|
|
be compatible with libev. Interaction between \f(CW\*(C`sigprocmask\*(C'\fR and |
4431 |
|
|
\&\f(CW\*(C`pthread_sigmask\*(C'\fR could complicate things, however. |
4432 |
|
|
.Sp |
4433 |
|
|
The most portable way to handle signals is to block signals in all threads |
4434 |
|
|
except the initial one, and run the default loop in the initial thread as |
4435 |
|
|
well. |
4436 |
|
|
.ie n .IP """long"" must be large enough for common memory allocation sizes" 4 |
4437 |
|
|
.el .IP "\f(CWlong\fR must be large enough for common memory allocation sizes" 4 |
4438 |
|
|
.IX Item "long must be large enough for common memory allocation sizes" |
4439 |
root |
1.72 |
To improve portability and simplify its \s-1API\s0, libev uses \f(CW\*(C`long\*(C'\fR internally |
4440 |
|
|
instead of \f(CW\*(C`size_t\*(C'\fR when allocating its data structures. On non-POSIX |
4441 |
|
|
systems (Microsoft...) this might be unexpectedly low, but is still at |
4442 |
|
|
least 31 bits everywhere, which is enough for hundreds of millions of |
4443 |
|
|
watchers. |
4444 |
root |
1.65 |
.ie n .IP """double"" must hold a time value in seconds with enough accuracy" 4 |
4445 |
|
|
.el .IP "\f(CWdouble\fR must hold a time value in seconds with enough accuracy" 4 |
4446 |
|
|
.IX Item "double must hold a time value in seconds with enough accuracy" |
4447 |
|
|
The type \f(CW\*(C`double\*(C'\fR is used to represent timestamps. It is required to |
4448 |
|
|
have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
4449 |
|
|
enough for at least into the year 4000. This requirement is fulfilled by |
4450 |
root |
1.79 |
implementations implementing \s-1IEEE\s0 754, which is basically all existing |
4451 |
|
|
ones. With \s-1IEEE\s0 754 doubles, you get microsecond accuracy until at least |
4452 |
|
|
2200. |
4453 |
root |
1.65 |
.PP |
4454 |
|
|
If you know of other additional requirements drop me a note. |
4455 |
root |
1.72 |
.SH "ALGORITHMIC COMPLEXITIES" |
4456 |
|
|
.IX Header "ALGORITHMIC COMPLEXITIES" |
4457 |
|
|
In this section the complexities of (many of) the algorithms used inside |
4458 |
|
|
libev will be documented. For complexity discussions about backends see |
4459 |
|
|
the documentation for \f(CW\*(C`ev_default_init\*(C'\fR. |
4460 |
root |
1.67 |
.PP |
4461 |
root |
1.72 |
All of the following are about amortised time: If an array needs to be |
4462 |
|
|
extended, libev needs to realloc and move the whole array, but this |
4463 |
|
|
happens asymptotically rarer with higher number of elements, so O(1) might |
4464 |
|
|
mean that libev does a lengthy realloc operation in rare cases, but on |
4465 |
|
|
average it is much faster and asymptotically approaches constant time. |
4466 |
|
|
.IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4 |
4467 |
|
|
.IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" |
4468 |
|
|
This means that, when you have a watcher that triggers in one hour and |
4469 |
|
|
there are 100 watchers that would trigger before that, then inserting will |
4470 |
|
|
have to skip roughly seven (\f(CW\*(C`ld 100\*(C'\fR) of these watchers. |
4471 |
|
|
.IP "Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)" 4 |
4472 |
|
|
.IX Item "Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)" |
4473 |
|
|
That means that changing a timer costs less than removing/adding them, |
4474 |
|
|
as only the relative motion in the event queue has to be paid for. |
4475 |
|
|
.IP "Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)" 4 |
4476 |
|
|
.IX Item "Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)" |
4477 |
|
|
These just add the watcher into an array or at the head of a list. |
4478 |
|
|
.IP "Stopping check/prepare/idle/fork/async watchers: O(1)" 4 |
4479 |
|
|
.IX Item "Stopping check/prepare/idle/fork/async watchers: O(1)" |
4480 |
|
|
.PD 0 |
4481 |
|
|
.IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4 |
4482 |
|
|
.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))" |
4483 |
|
|
.PD |
4484 |
|
|
These watchers are stored in lists, so they need to be walked to find the |
4485 |
|
|
correct watcher to remove. The lists are usually short (you don't usually |
4486 |
|
|
have many watchers waiting for the same fd or signal: one is typical, two |
4487 |
|
|
is rare). |
4488 |
|
|
.IP "Finding the next timer in each loop iteration: O(1)" 4 |
4489 |
|
|
.IX Item "Finding the next timer in each loop iteration: O(1)" |
4490 |
|
|
By virtue of using a binary or 4\-heap, the next timer is always found at a |
4491 |
|
|
fixed position in the storage array. |
4492 |
|
|
.IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4 |
4493 |
|
|
.IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" |
4494 |
|
|
A change means an I/O watcher gets started or stopped, which requires |
4495 |
|
|
libev to recalculate its status (and possibly tell the kernel, depending |
4496 |
|
|
on backend and whether \f(CW\*(C`ev_io_set\*(C'\fR was used). |
4497 |
|
|
.IP "Activating one watcher (putting it into the pending state): O(1)" 4 |
4498 |
|
|
.IX Item "Activating one watcher (putting it into the pending state): O(1)" |
4499 |
|
|
.PD 0 |
4500 |
|
|
.IP "Priority handling: O(number_of_priorities)" 4 |
4501 |
|
|
.IX Item "Priority handling: O(number_of_priorities)" |
4502 |
|
|
.PD |
4503 |
|
|
Priorities are implemented by allocating some space for each |
4504 |
|
|
priority. When doing priority-based operations, libev usually has to |
4505 |
|
|
linearly search all the priorities, but starting/stopping and activating |
4506 |
|
|
watchers becomes O(1) with respect to priority handling. |
4507 |
|
|
.IP "Sending an ev_async: O(1)" 4 |
4508 |
|
|
.IX Item "Sending an ev_async: O(1)" |
4509 |
|
|
.PD 0 |
4510 |
|
|
.IP "Processing ev_async_send: O(number_of_async_watchers)" 4 |
4511 |
|
|
.IX Item "Processing ev_async_send: O(number_of_async_watchers)" |
4512 |
|
|
.IP "Processing signals: O(max_signal_number)" 4 |
4513 |
|
|
.IX Item "Processing signals: O(max_signal_number)" |
4514 |
|
|
.PD |
4515 |
|
|
Sending involves a system call \fIiff\fR there were no other \f(CW\*(C`ev_async_send\*(C'\fR |
4516 |
|
|
calls in the current loop iteration. Checking for async and signal events |
4517 |
|
|
involves iterating over all running async watchers or all signal numbers. |
4518 |
root |
1.78 |
.SH "GLOSSARY" |
4519 |
|
|
.IX Header "GLOSSARY" |
4520 |
|
|
.IP "active" 4 |
4521 |
|
|
.IX Item "active" |
4522 |
|
|
A watcher is active as long as it has been started (has been attached to |
4523 |
|
|
an event loop) but not yet stopped (disassociated from the event loop). |
4524 |
|
|
.IP "application" 4 |
4525 |
|
|
.IX Item "application" |
4526 |
|
|
In this document, an application is whatever is using libev. |
4527 |
|
|
.IP "callback" 4 |
4528 |
|
|
.IX Item "callback" |
4529 |
|
|
The address of a function that is called when some event has been |
4530 |
|
|
detected. Callbacks are being passed the event loop, the watcher that |
4531 |
|
|
received the event, and the actual event bitset. |
4532 |
|
|
.IP "callback invocation" 4 |
4533 |
|
|
.IX Item "callback invocation" |
4534 |
|
|
The act of calling the callback associated with a watcher. |
4535 |
|
|
.IP "event" 4 |
4536 |
|
|
.IX Item "event" |
4537 |
|
|
A change of state of some external event, such as data now being available |
4538 |
|
|
for reading on a file descriptor, time having passed or simply not having |
4539 |
|
|
any other events happening anymore. |
4540 |
|
|
.Sp |
4541 |
|
|
In libev, events are represented as single bits (such as \f(CW\*(C`EV_READ\*(C'\fR or |
4542 |
|
|
\&\f(CW\*(C`EV_TIMEOUT\*(C'\fR). |
4543 |
|
|
.IP "event library" 4 |
4544 |
|
|
.IX Item "event library" |
4545 |
|
|
A software package implementing an event model and loop. |
4546 |
|
|
.IP "event loop" 4 |
4547 |
|
|
.IX Item "event loop" |
4548 |
|
|
An entity that handles and processes external events and converts them |
4549 |
|
|
into callback invocations. |
4550 |
|
|
.IP "event model" 4 |
4551 |
|
|
.IX Item "event model" |
4552 |
|
|
The model used to describe how an event loop handles and processes |
4553 |
|
|
watchers and events. |
4554 |
|
|
.IP "pending" 4 |
4555 |
|
|
.IX Item "pending" |
4556 |
|
|
A watcher is pending as soon as the corresponding event has been detected, |
4557 |
|
|
and stops being pending as soon as the watcher will be invoked or its |
4558 |
|
|
pending status is explicitly cleared by the application. |
4559 |
|
|
.Sp |
4560 |
|
|
A watcher can be pending, but not active. Stopping a watcher also clears |
4561 |
|
|
its pending status. |
4562 |
|
|
.IP "real time" 4 |
4563 |
|
|
.IX Item "real time" |
4564 |
|
|
The physical time that is observed. It is apparently strictly monotonic :) |
4565 |
|
|
.IP "wall-clock time" 4 |
4566 |
|
|
.IX Item "wall-clock time" |
4567 |
|
|
The time and date as shown on clocks. Unlike real time, it can actually |
4568 |
|
|
be wrong and jump forwards and backwards, e.g. when the you adjust your |
4569 |
|
|
clock. |
4570 |
|
|
.IP "watcher" 4 |
4571 |
|
|
.IX Item "watcher" |
4572 |
|
|
A data structure that describes interest in certain events. Watchers need |
4573 |
|
|
to be started (attached to an event loop) before they can receive events. |
4574 |
|
|
.IP "watcher invocation" 4 |
4575 |
|
|
.IX Item "watcher invocation" |
4576 |
|
|
The act of calling the callback associated with a watcher. |
4577 |
root |
1.1 |
.SH "AUTHOR" |
4578 |
|
|
.IX Header "AUTHOR" |
4579 |
root |
1.73 |
Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |