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Revision 1.9 by root, Fri Nov 23 16:17:12 2007 UTC vs.
Revision 1.54 by root, Fri Dec 21 04:38:45 2007 UTC

… …
126. ds Ae AE 126. ds Ae AE
127.\} 127.\}
128.rm #[ #] #H #V #F C 128.rm #[ #] #H #V #F C
129.\" ======================================================================== 129.\" ========================================================================
130.\" 130.\"
131.IX Title ""<STANDARD INPUT>" 1" 131.IX Title "EV 1"
132.TH "<STANDARD INPUT>" 1 "2007-11-23" "perl v5.8.8" "User Contributed Perl Documentation" 132.TH EV 1 "2007-12-21" "perl v5.8.8" "User Contributed Perl Documentation"
133.SH "NAME" 133.SH "NAME"
134libev \- a high performance full\-featured event loop written in C 134libev \- a high performance full\-featured event loop written in C
135.SH "SYNOPSIS" 135.SH "SYNOPSIS"
136.IX Header "SYNOPSIS" 136.IX Header "SYNOPSIS"
137.Vb 1 137.Vb 1
138\& #include <ev.h> 138\& #include <ev.h>
139.Ve 139.Ve
140.SH "EXAMPLE PROGRAM"
141.IX Header "EXAMPLE PROGRAM"
142.Vb 1
143\& #include <ev.h>
144.Ve
145.PP
146.Vb 2
147\& ev_io stdin_watcher;
148\& ev_timer timeout_watcher;
149.Ve
150.PP
151.Vb 8
152\& /* called when data readable on stdin */
153\& static void
154\& stdin_cb (EV_P_ struct ev_io *w, int revents)
155\& {
156\& /* puts ("stdin ready"); */
157\& ev_io_stop (EV_A_ w); /* just a syntax example */
158\& ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
159\& }
160.Ve
161.PP
162.Vb 6
163\& static void
164\& timeout_cb (EV_P_ struct ev_timer *w, int revents)
165\& {
166\& /* puts ("timeout"); */
167\& ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
168\& }
169.Ve
170.PP
171.Vb 4
172\& int
173\& main (void)
174\& {
175\& struct ev_loop *loop = ev_default_loop (0);
176.Ve
177.PP
178.Vb 3
179\& /* initialise an io watcher, then start it */
180\& ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
181\& ev_io_start (loop, &stdin_watcher);
182.Ve
183.PP
184.Vb 3
185\& /* simple non-repeating 5.5 second timeout */
186\& ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
187\& ev_timer_start (loop, &timeout_watcher);
188.Ve
189.PP
190.Vb 2
191\& /* loop till timeout or data ready */
192\& ev_loop (loop, 0);
193.Ve
194.PP
195.Vb 2
196\& return 0;
197\& }
198.Ve
140.SH "DESCRIPTION" 199.SH "DESCRIPTION"
141.IX Header "DESCRIPTION" 200.IX Header "DESCRIPTION"
201The newest version of this document is also available as a html-formatted
202web page you might find easier to navigate when reading it for the first
203time: <http://cvs.schmorp.de/libev/ev.html>.
204.PP
142Libev is an event loop: you register interest in certain events (such as a 205Libev is an event loop: you register interest in certain events (such as a
143file descriptor being readable or a timeout occuring), and it will manage 206file descriptor being readable or a timeout occurring), and it will manage
144these event sources and provide your program with events. 207these event sources and provide your program with events.
145.PP 208.PP
146To do this, it must take more or less complete control over your process 209To do this, it must take more or less complete control over your process
147(or thread) by executing the \fIevent loop\fR handler, and will then 210(or thread) by executing the \fIevent loop\fR handler, and will then
148communicate events via a callback mechanism. 211communicate events via a callback mechanism.
… …
151watchers\fR, which are relatively small C structures you initialise with the 214watchers\fR, which are relatively small C structures you initialise with the
152details of the event, and then hand it over to libev by \fIstarting\fR the 215details of the event, and then hand it over to libev by \fIstarting\fR the
153watcher. 216watcher.
154.SH "FEATURES" 217.SH "FEATURES"
155.IX Header "FEATURES" 218.IX Header "FEATURES"
156Libev supports select, poll, the linux-specific epoll and the bsd-specific 219Libev supports \f(CW\*(C`select\*(C'\fR, \f(CW\*(C`poll\*(C'\fR, the Linux-specific \f(CW\*(C`epoll\*(C'\fR, the
157kqueue mechanisms for file descriptor events, relative timers, absolute 220BSD-specific \f(CW\*(C`kqueue\*(C'\fR and the Solaris-specific event port mechanisms
158timers with customised rescheduling, signal events, process status change 221for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), the Linux \f(CW\*(C`inotify\*(C'\fR interface
159events (related to \s-1SIGCHLD\s0), and event watchers dealing with the event 222(for \f(CW\*(C`ev_stat\*(C'\fR), relative timers (\f(CW\*(C`ev_timer\*(C'\fR), absolute timers
160loop mechanism itself (idle, prepare and check watchers). It also is quite 223with customised rescheduling (\f(CW\*(C`ev_periodic\*(C'\fR), synchronous signals
161fast (see this benchmark comparing 224(\f(CW\*(C`ev_signal\*(C'\fR), process status change events (\f(CW\*(C`ev_child\*(C'\fR), and event
162it to libevent for example). 225watchers dealing with the event loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR,
226\&\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
227file watchers (\f(CW\*(C`ev_stat\*(C'\fR) and even limited support for fork events
228(\f(CW\*(C`ev_fork\*(C'\fR).
229.PP
230It also is quite fast (see this
231benchmark comparing it to libevent
232for example).
163.SH "CONVENTIONS" 233.SH "CONVENTIONS"
164.IX Header "CONVENTIONS" 234.IX Header "CONVENTIONS"
165Libev is very configurable. In this manual the default configuration 235Libev is very configurable. In this manual the default configuration will
166will be described, which supports multiple event loops. For more info 236be described, which supports multiple event loops. For more info about
167about various configuration options please have a look at the file 237various configuration options please have a look at \fB\s-1EMBED\s0\fR section in
168\&\fI\s-1README\s0.embed\fR in the libev distribution. If libev was configured without 238this manual. If libev was configured without support for multiple event
169support for multiple event loops, then all functions taking an initial 239loops, then all functions taking an initial argument of name \f(CW\*(C`loop\*(C'\fR
170argument of name \f(CW\*(C`loop\*(C'\fR (which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR) 240(which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR) will not have this argument.
171will not have this argument.
172.SH "TIME REPRESENTATION" 241.SH "TIME REPRESENTATION"
173.IX Header "TIME REPRESENTATION" 242.IX Header "TIME REPRESENTATION"
174Libev represents time as a single floating point number, representing the 243Libev represents time as a single floating point number, representing the
175(fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near 244(fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near
176the beginning of 1970, details are complicated, don't ask). This type is 245the beginning of 1970, details are complicated, don't ask). This type is
177called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use too. It usually aliases 246called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use too. It usually aliases
178to the \f(CW\*(C`double\*(C'\fR type in C, and when you need to do any calculations on 247to the \f(CW\*(C`double\*(C'\fR type in C, and when you need to do any calculations on
179it, you should treat it as such. 248it, you should treat it as some floatingpoint value. Unlike the name
249component \f(CW\*(C`stamp\*(C'\fR might indicate, it is also used for time differences
250throughout libev.
180.SH "GLOBAL FUNCTIONS" 251.SH "GLOBAL FUNCTIONS"
181.IX Header "GLOBAL FUNCTIONS" 252.IX Header "GLOBAL FUNCTIONS"
182These functions can be called anytime, even before initialising the 253These functions can be called anytime, even before initialising the
183library in any way. 254library in any way.
184.IP "ev_tstamp ev_time ()" 4 255.IP "ev_tstamp ev_time ()" 4
… …
190.IX Item "int ev_version_major ()" 261.IX Item "int ev_version_major ()"
191.PD 0 262.PD 0
192.IP "int ev_version_minor ()" 4 263.IP "int ev_version_minor ()" 4
193.IX Item "int ev_version_minor ()" 264.IX Item "int ev_version_minor ()"
194.PD 265.PD
195You can find out the major and minor version numbers of the library 266You can find out the major and minor \s-1ABI\s0 version numbers of the library
196you linked against by calling the functions \f(CW\*(C`ev_version_major\*(C'\fR and 267you linked against by calling the functions \f(CW\*(C`ev_version_major\*(C'\fR and
197\&\f(CW\*(C`ev_version_minor\*(C'\fR. If you want, you can compare against the global 268\&\f(CW\*(C`ev_version_minor\*(C'\fR. If you want, you can compare against the global
198symbols \f(CW\*(C`EV_VERSION_MAJOR\*(C'\fR and \f(CW\*(C`EV_VERSION_MINOR\*(C'\fR, which specify the 269symbols \f(CW\*(C`EV_VERSION_MAJOR\*(C'\fR and \f(CW\*(C`EV_VERSION_MINOR\*(C'\fR, which specify the
199version of the library your program was compiled against. 270version of the library your program was compiled against.
200.Sp 271.Sp
272These version numbers refer to the \s-1ABI\s0 version of the library, not the
273release version.
274.Sp
201Usually, it's a good idea to terminate if the major versions mismatch, 275Usually, it's a good idea to terminate if the major versions mismatch,
202as this indicates an incompatible change. Minor versions are usually 276as this indicates an incompatible change. Minor versions are usually
203compatible to older versions, so a larger minor version alone is usually 277compatible to older versions, so a larger minor version alone is usually
204not a problem. 278not a problem.
205.Sp 279.Sp
206Example: make sure we haven't accidentally been linked against the wrong 280Example: Make sure we haven't accidentally been linked against the wrong
207version: 281version.
208.Sp 282.Sp
209.Vb 3 283.Vb 3
210\& assert (("libev version mismatch", 284\& assert (("libev version mismatch",
211\& ev_version_major () == EV_VERSION_MAJOR 285\& ev_version_major () == EV_VERSION_MAJOR
212\& && ev_version_minor () >= EV_VERSION_MINOR)); 286\& && ev_version_minor () >= EV_VERSION_MINOR));
… …
231recommended for this platform. This set is often smaller than the one 305recommended for this platform. This set is often smaller than the one
232returned by \f(CW\*(C`ev_supported_backends\*(C'\fR, as for example kqueue is broken on 306returned by \f(CW\*(C`ev_supported_backends\*(C'\fR, as for example kqueue is broken on
233most BSDs and will not be autodetected unless you explicitly request it 307most BSDs and will not be autodetected unless you explicitly request it
234(assuming you know what you are doing). This is the set of backends that 308(assuming you know what you are doing). This is the set of backends that
235libev will probe for if you specify no backends explicitly. 309libev will probe for if you specify no backends explicitly.
310.IP "unsigned int ev_embeddable_backends ()" 4
311.IX Item "unsigned int ev_embeddable_backends ()"
312Returns the set of backends that are embeddable in other event loops. This
313is the theoretical, all\-platform, value. To find which backends
314might be supported on the current system, you would need to look at
315\&\f(CW\*(C`ev_embeddable_backends () & ev_supported_backends ()\*(C'\fR, likewise for
316recommended ones.
317.Sp
318See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info.
236.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4 319.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4
237.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))" 320.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))"
238Sets the allocation function to use (the prototype is similar to the 321Sets the allocation function to use (the prototype is similar \- the
239realloc C function, the semantics are identical). It is used to allocate 322semantics is identical \- to the realloc C function). It is used to
240and free memory (no surprises here). If it returns zero when memory 323allocate and free memory (no surprises here). If it returns zero when
241needs to be allocated, the library might abort or take some potentially 324memory needs to be allocated, the library might abort or take some
242destructive action. The default is your system realloc function. 325potentially destructive action. The default is your system realloc
326function.
243.Sp 327.Sp
244You could override this function in high-availability programs to, say, 328You could override this function in high-availability programs to, say,
245free some memory if it cannot allocate memory, to use a special allocator, 329free some memory if it cannot allocate memory, to use a special allocator,
246or even to sleep a while and retry until some memory is available. 330or even to sleep a while and retry until some memory is available.
247.Sp 331.Sp
248Example: replace the libev allocator with one that waits a bit and then 332Example: Replace the libev allocator with one that waits a bit and then
249retries: better than mine). 333retries).
250.Sp 334.Sp
251.Vb 6 335.Vb 6
252\& static void * 336\& static void *
253\& persistent_realloc (void *ptr, long size) 337\& persistent_realloc (void *ptr, size_t size)
254\& { 338\& {
255\& for (;;) 339\& for (;;)
256\& { 340\& {
257\& void *newptr = realloc (ptr, size); 341\& void *newptr = realloc (ptr, size);
258.Ve 342.Ve
… …
280callback is set, then libev will expect it to remedy the sitution, no 364callback is set, then libev will expect it to remedy the sitution, no
281matter what, when it returns. That is, libev will generally retry the 365matter what, when it returns. That is, libev will generally retry the
282requested operation, or, if the condition doesn't go away, do bad stuff 366requested operation, or, if the condition doesn't go away, do bad stuff
283(such as abort). 367(such as abort).
284.Sp 368.Sp
285Example: do the same thing as libev does internally: 369Example: This is basically the same thing that libev does internally, too.
286.Sp 370.Sp
287.Vb 6 371.Vb 6
288\& static void 372\& static void
289\& fatal_error (const char *msg) 373\& fatal_error (const char *msg)
290\& { 374\& {
… …
336or setgid) then libev will \fInot\fR look at the environment variable 420or setgid) then libev will \fInot\fR look at the environment variable
337\&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will 421\&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will
338override the flags completely if it is found in the environment. This is 422override the flags completely if it is found in the environment. This is
339useful to try out specific backends to test their performance, or to work 423useful to try out specific backends to test their performance, or to work
340around bugs. 424around bugs.
425.ie n .IP """EVFLAG_FORKCHECK""" 4
426.el .IP "\f(CWEVFLAG_FORKCHECK\fR" 4
427.IX Item "EVFLAG_FORKCHECK"
428Instead of calling \f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR manually after
429a fork, you can also make libev check for a fork in each iteration by
430enabling this flag.
431.Sp
432This works by calling \f(CW\*(C`getpid ()\*(C'\fR on every iteration of the loop,
433and thus this might slow down your event loop if you do a lot of loop
434iterations and little real work, but is usually not noticeable (on my
435Linux system for example, \f(CW\*(C`getpid\*(C'\fR is actually a simple 5\-insn sequence
436without a syscall and thus \fIvery\fR fast, but my Linux system also has
437\&\f(CW\*(C`pthread_atfork\*(C'\fR which is even faster).
438.Sp
439The big advantage of this flag is that you can forget about fork (and
440forget about forgetting to tell libev about forking) when you use this
441flag.
442.Sp
443This flag setting cannot be overriden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR
444environment variable.
341.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4 445.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4
342.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4 446.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4
343.IX Item "EVBACKEND_SELECT (value 1, portable select backend)" 447.IX Item "EVBACKEND_SELECT (value 1, portable select backend)"
344This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as 448This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as
345libev tries to roll its own fd_set with no limits on the number of fds, 449libev tries to roll its own fd_set with no limits on the number of fds,
… …
355lot of inactive fds). It scales similarly to select, i.e. O(total_fds). 459lot of inactive fds). It scales similarly to select, i.e. O(total_fds).
356.ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4 460.ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4
357.el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4 461.el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4
358.IX Item "EVBACKEND_EPOLL (value 4, Linux)" 462.IX Item "EVBACKEND_EPOLL (value 4, Linux)"
359For few fds, this backend is a bit little slower than poll and select, 463For few fds, this backend is a bit little slower than poll and select,
360but it scales phenomenally better. While poll and select usually scale like 464but it scales phenomenally better. While poll and select usually scale
361O(total_fds) where n is the total number of fds (or the highest fd), epoll scales 465like O(total_fds) where n is the total number of fds (or the highest fd),
362either O(1) or O(active_fds). 466epoll scales either O(1) or O(active_fds). The epoll design has a number
467of shortcomings, such as silently dropping events in some hard-to-detect
468cases and rewuiring a syscall per fd change, no fork support and bad
469support for dup:
363.Sp 470.Sp
364While stopping and starting an I/O watcher in the same iteration will 471While stopping, setting and starting an I/O watcher in the same iteration
365result in some caching, there is still a syscall per such incident 472will result in some caching, there is still a syscall per such incident
366(because the fd could point to a different file description now), so its 473(because the fd could point to a different file description now), so its
367best to avoid that. Also, \fIdup()\fRed file descriptors might not work very 474best to avoid that. Also, \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors might not work
368well if you register events for both fds. 475very well if you register events for both fds.
369.Sp 476.Sp
370Please note that epoll sometimes generates spurious notifications, so you 477Please note that epoll sometimes generates spurious notifications, so you
371need to use non-blocking I/O or other means to avoid blocking when no data 478need to use non-blocking I/O or other means to avoid blocking when no data
372(or space) is available. 479(or space) is available.
373.ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4 480.ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4
374.el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4 481.el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4
375.IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)" 482.IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)"
376Kqueue deserves special mention, as at the time of this writing, it 483Kqueue deserves special mention, as at the time of this writing, it
377was broken on all BSDs except NetBSD (usually it doesn't work with 484was broken on \fIall\fR BSDs (usually it doesn't work with anything but
378anything but sockets and pipes, except on Darwin, where of course its 485sockets and pipes, except on Darwin, where of course it's completely
486useless. On NetBSD, it seems to work for all the \s-1FD\s0 types I tested, so it
379completely useless). For this reason its not being \*(L"autodetected\*(R" 487is used by default there). For this reason it's not being \*(L"autodetected\*(R"
380unless you explicitly specify it explicitly in the flags (i.e. using 488unless you explicitly specify it explicitly in the flags (i.e. using
381\&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR). 489\&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR) or libev was compiled on a known-to-be-good (\-enough)
490system like NetBSD.
382.Sp 491.Sp
383It scales in the same way as the epoll backend, but the interface to the 492It scales in the same way as the epoll backend, but the interface to the
384kernel is more efficient (which says nothing about its actual speed, of 493kernel is more efficient (which says nothing about its actual speed,
385course). While starting and stopping an I/O watcher does not cause an 494of course). While stopping, setting and starting an I/O watcher does
386extra syscall as with epoll, it still adds up to four event changes per 495never cause an extra syscall as with epoll, it still adds up to two event
387incident, so its best to avoid that. 496changes per incident, support for \f(CW\*(C`fork ()\*(C'\fR is very bad and it drops fds
497silently in similarly hard-to-detetc cases.
388.ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4 498.ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4
389.el .IP "\f(CWEVBACKEND_DEVPOLL\fR (value 16, Solaris 8)" 4 499.el .IP "\f(CWEVBACKEND_DEVPOLL\fR (value 16, Solaris 8)" 4
390.IX Item "EVBACKEND_DEVPOLL (value 16, Solaris 8)" 500.IX Item "EVBACKEND_DEVPOLL (value 16, Solaris 8)"
391This is not implemented yet (and might never be). 501This is not implemented yet (and might never be).
392.ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4 502.ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4
393.el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4 503.el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4
394.IX Item "EVBACKEND_PORT (value 32, Solaris 10)" 504.IX Item "EVBACKEND_PORT (value 32, Solaris 10)"
395This uses the Solaris 10 port mechanism. As with everything on Solaris, 505This uses the Solaris 10 event port mechanism. As with everything on Solaris,
396it's really slow, but it still scales very well (O(active_fds)). 506it's really slow, but it still scales very well (O(active_fds)).
397.Sp 507.Sp
398Please note that solaris ports can result in a lot of spurious 508Please note that solaris event ports can deliver a lot of spurious
399notifications, so you need to use non-blocking I/O or other means to avoid 509notifications, so you need to use non-blocking I/O or other means to avoid
400blocking when no data (or space) is available. 510blocking when no data (or space) is available.
401.ie n .IP """EVBACKEND_ALL""" 4 511.ie n .IP """EVBACKEND_ALL""" 4
402.el .IP "\f(CWEVBACKEND_ALL\fR" 4 512.el .IP "\f(CWEVBACKEND_ALL\fR" 4
403.IX Item "EVBACKEND_ALL" 513.IX Item "EVBACKEND_ALL"
… …
439Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is 549Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is
440always distinct from the default loop. Unlike the default loop, it cannot 550always distinct from the default loop. Unlike the default loop, it cannot
441handle signal and child watchers, and attempts to do so will be greeted by 551handle signal and child watchers, and attempts to do so will be greeted by
442undefined behaviour (or a failed assertion if assertions are enabled). 552undefined behaviour (or a failed assertion if assertions are enabled).
443.Sp 553.Sp
444Example: try to create a event loop that uses epoll and nothing else. 554Example: Try to create a event loop that uses epoll and nothing else.
445.Sp 555.Sp
446.Vb 3 556.Vb 3
447\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); 557\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
448\& if (!epoller) 558\& if (!epoller)
449\& fatal ("no epoll found here, maybe it hides under your chair"); 559\& fatal ("no epoll found here, maybe it hides under your chair");
450.Ve 560.Ve
451.IP "ev_default_destroy ()" 4 561.IP "ev_default_destroy ()" 4
452.IX Item "ev_default_destroy ()" 562.IX Item "ev_default_destroy ()"
453Destroys the default loop again (frees all memory and kernel state 563Destroys the default loop again (frees all memory and kernel state
454etc.). This stops all registered event watchers (by not touching them in 564etc.). None of the active event watchers will be stopped in the normal
455any way whatsoever, although you cannot rely on this :). 565sense, so e.g. \f(CW\*(C`ev_is_active\*(C'\fR might still return true. It is your
566responsibility to either stop all watchers cleanly yoursef \fIbefore\fR
567calling this function, or cope with the fact afterwards (which is usually
568the easiest thing, you can just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them
569for example).
570.Sp
571Note that certain global state, such as signal state, will not be freed by
572this function, and related watchers (such as signal and child watchers)
573would need to be stopped manually.
574.Sp
575In general it is not advisable to call this function except in the
576rare occasion where you really need to free e.g. the signal handling
577pipe fds. If you need dynamically allocated loops it is better to use
578\&\f(CW\*(C`ev_loop_new\*(C'\fR and \f(CW\*(C`ev_loop_destroy\*(C'\fR).
456.IP "ev_loop_destroy (loop)" 4 579.IP "ev_loop_destroy (loop)" 4
457.IX Item "ev_loop_destroy (loop)" 580.IX Item "ev_loop_destroy (loop)"
458Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an 581Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an
459earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR. 582earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR.
460.IP "ev_default_fork ()" 4 583.IP "ev_default_fork ()" 4
… …
482.IP "ev_loop_fork (loop)" 4 605.IP "ev_loop_fork (loop)" 4
483.IX Item "ev_loop_fork (loop)" 606.IX Item "ev_loop_fork (loop)"
484Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by 607Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by
485\&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop 608\&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop
486after fork, and how you do this is entirely your own problem. 609after fork, and how you do this is entirely your own problem.
610.IP "unsigned int ev_loop_count (loop)" 4
611.IX Item "unsigned int ev_loop_count (loop)"
612Returns the count of loop iterations for the loop, which is identical to
613the number of times libev did poll for new events. It starts at \f(CW0\fR and
614happily wraps around with enough iterations.
615.Sp
616This value can sometimes be useful as a generation counter of sorts (it
617\&\*(L"ticks\*(R" the number of loop iterations), as it roughly corresponds with
618\&\f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR calls.
487.IP "unsigned int ev_backend (loop)" 4 619.IP "unsigned int ev_backend (loop)" 4
488.IX Item "unsigned int ev_backend (loop)" 620.IX Item "unsigned int ev_backend (loop)"
489Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in 621Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in
490use. 622use.
491.IP "ev_tstamp ev_now (loop)" 4 623.IP "ev_tstamp ev_now (loop)" 4
492.IX Item "ev_tstamp ev_now (loop)" 624.IX Item "ev_tstamp ev_now (loop)"
493Returns the current \*(L"event loop time\*(R", which is the time the event loop 625Returns the current \*(L"event loop time\*(R", which is the time the event loop
494received events and started processing them. This timestamp does not 626received events and started processing them. This timestamp does not
495change as long as callbacks are being processed, and this is also the base 627change as long as callbacks are being processed, and this is also the base
496time used for relative timers. You can treat it as the timestamp of the 628time used for relative timers. You can treat it as the timestamp of the
497event occuring (or more correctly, libev finding out about it). 629event occurring (or more correctly, libev finding out about it).
498.IP "ev_loop (loop, int flags)" 4 630.IP "ev_loop (loop, int flags)" 4
499.IX Item "ev_loop (loop, int flags)" 631.IX Item "ev_loop (loop, int flags)"
500Finally, this is it, the event handler. This function usually is called 632Finally, this is it, the event handler. This function usually is called
501after you initialised all your watchers and you want to start handling 633after you initialised all your watchers and you want to start handling
502events. 634events.
… …
522libev watchers. However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is 654libev watchers. However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is
523usually a better approach for this kind of thing. 655usually a better approach for this kind of thing.
524.Sp 656.Sp
525Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does: 657Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does:
526.Sp 658.Sp
527.Vb 18 659.Vb 19
660\& - Before the first iteration, call any pending watchers.
528\& * If there are no active watchers (reference count is zero), return. 661\& * If there are no active watchers (reference count is zero), return.
529\& - Queue prepare watchers and then call all outstanding watchers. 662\& - Queue all prepare watchers and then call all outstanding watchers.
530\& - If we have been forked, recreate the kernel state. 663\& - If we have been forked, recreate the kernel state.
531\& - Update the kernel state with all outstanding changes. 664\& - Update the kernel state with all outstanding changes.
532\& - Update the "event loop time". 665\& - Update the "event loop time".
533\& - Calculate for how long to block. 666\& - Calculate for how long to block.
534\& - Block the process, waiting for any events. 667\& - Block the process, waiting for any events.
… …
543\& be handled here by queueing them when their watcher gets executed. 676\& be handled here by queueing them when their watcher gets executed.
544\& - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 677\& - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
545\& were used, return, otherwise continue with step *. 678\& were used, return, otherwise continue with step *.
546.Ve 679.Ve
547.Sp 680.Sp
548Example: queue some jobs and then loop until no events are outsanding 681Example: Queue some jobs and then loop until no events are outsanding
549anymore. 682anymore.
550.Sp 683.Sp
551.Vb 4 684.Vb 4
552\& ... queue jobs here, make sure they register event watchers as long 685\& ... queue jobs here, make sure they register event watchers as long
553\& ... as they still have work to do (even an idle watcher will do..) 686\& ... as they still have work to do (even an idle watcher will do..)
… …
575visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if 708visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if
576no event watchers registered by it are active. It is also an excellent 709no event watchers registered by it are active. It is also an excellent
577way to do this for generic recurring timers or from within third-party 710way to do this for generic recurring timers or from within third-party
578libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR. 711libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR.
579.Sp 712.Sp
580Example: create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR 713Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR
581running when nothing else is active. 714running when nothing else is active.
582.Sp 715.Sp
583.Vb 4 716.Vb 4
584\& struct dv_signal exitsig; 717\& struct ev_signal exitsig;
585\& ev_signal_init (&exitsig, sig_cb, SIGINT); 718\& ev_signal_init (&exitsig, sig_cb, SIGINT);
586\& ev_signal_start (myloop, &exitsig); 719\& ev_signal_start (loop, &exitsig);
587\& evf_unref (myloop); 720\& evf_unref (loop);
588.Ve 721.Ve
589.Sp 722.Sp
590Example: for some weird reason, unregister the above signal handler again. 723Example: For some weird reason, unregister the above signal handler again.
591.Sp 724.Sp
592.Vb 2 725.Vb 2
593\& ev_ref (myloop); 726\& ev_ref (loop);
594\& ev_signal_stop (myloop, &exitsig); 727\& ev_signal_stop (loop, &exitsig);
595.Ve 728.Ve
596.SH "ANATOMY OF A WATCHER" 729.SH "ANATOMY OF A WATCHER"
597.IX Header "ANATOMY OF A WATCHER" 730.IX Header "ANATOMY OF A WATCHER"
598A watcher is a structure that you create and register to record your 731A watcher is a structure that you create and register to record your
599interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to 732interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to
… …
636*)\*(C'\fR), and you can stop watching for events at any time by calling the 769*)\*(C'\fR), and you can stop watching for events at any time by calling the
637corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR. 770corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR.
638.PP 771.PP
639As long as your watcher is active (has been started but not stopped) you 772As long as your watcher is active (has been started but not stopped) you
640must not touch the values stored in it. Most specifically you must never 773must not touch the values stored in it. Most specifically you must never
641reinitialise it or call its set macro. 774reinitialise it or call its \f(CW\*(C`set\*(C'\fR macro.
642.PP
643You can check whether an event is active by calling the \f(CW\*(C`ev_is_active
644(watcher *)\*(C'\fR macro. To see whether an event is outstanding (but the
645callback for it has not been called yet) you can use the \f(CW\*(C`ev_is_pending
646(watcher *)\*(C'\fR macro.
647.PP 775.PP
648Each and every callback receives the event loop pointer as first, the 776Each and every callback receives the event loop pointer as first, the
649registered watcher structure as second, and a bitset of received events as 777registered watcher structure as second, and a bitset of received events as
650third argument. 778third argument.
651.PP 779.PP
… …
676The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread. 804The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread.
677.ie n .IP """EV_CHILD""" 4 805.ie n .IP """EV_CHILD""" 4
678.el .IP "\f(CWEV_CHILD\fR" 4 806.el .IP "\f(CWEV_CHILD\fR" 4
679.IX Item "EV_CHILD" 807.IX Item "EV_CHILD"
680The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change. 808The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change.
809.ie n .IP """EV_STAT""" 4
810.el .IP "\f(CWEV_STAT\fR" 4
811.IX Item "EV_STAT"
812The path specified in the \f(CW\*(C`ev_stat\*(C'\fR watcher changed its attributes somehow.
681.ie n .IP """EV_IDLE""" 4 813.ie n .IP """EV_IDLE""" 4
682.el .IP "\f(CWEV_IDLE\fR" 4 814.el .IP "\f(CWEV_IDLE\fR" 4
683.IX Item "EV_IDLE" 815.IX Item "EV_IDLE"
684The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do. 816The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do.
685.ie n .IP """EV_PREPARE""" 4 817.ie n .IP """EV_PREPARE""" 4
… …
695\&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any 827\&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any
696received events. Callbacks of both watcher types can start and stop as 828received events. Callbacks of both watcher types can start and stop as
697many watchers as they want, and all of them will be taken into account 829many watchers as they want, and all of them will be taken into account
698(for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep 830(for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep
699\&\f(CW\*(C`ev_loop\*(C'\fR from blocking). 831\&\f(CW\*(C`ev_loop\*(C'\fR from blocking).
832.ie n .IP """EV_EMBED""" 4
833.el .IP "\f(CWEV_EMBED\fR" 4
834.IX Item "EV_EMBED"
835The embedded event loop specified in the \f(CW\*(C`ev_embed\*(C'\fR watcher needs attention.
836.ie n .IP """EV_FORK""" 4
837.el .IP "\f(CWEV_FORK\fR" 4
838.IX Item "EV_FORK"
839The event loop has been resumed in the child process after fork (see
840\&\f(CW\*(C`ev_fork\*(C'\fR).
700.ie n .IP """EV_ERROR""" 4 841.ie n .IP """EV_ERROR""" 4
701.el .IP "\f(CWEV_ERROR\fR" 4 842.el .IP "\f(CWEV_ERROR\fR" 4
702.IX Item "EV_ERROR" 843.IX Item "EV_ERROR"
703An unspecified error has occured, the watcher has been stopped. This might 844An unspecified error has occured, the watcher has been stopped. This might
704happen because the watcher could not be properly started because libev 845happen because the watcher could not be properly started because libev
… …
709Libev will usually signal a few \*(L"dummy\*(R" events together with an error, 850Libev will usually signal a few \*(L"dummy\*(R" events together with an error,
710for example it might indicate that a fd is readable or writable, and if 851for example it might indicate that a fd is readable or writable, and if
711your callbacks is well-written it can just attempt the operation and cope 852your callbacks is well-written it can just attempt the operation and cope
712with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded 853with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded
713programs, though, so beware. 854programs, though, so beware.
855.Sh "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0"
856.IX Subsection "GENERIC WATCHER FUNCTIONS"
857In the following description, \f(CW\*(C`TYPE\*(C'\fR stands for the watcher type,
858e.g. \f(CW\*(C`timer\*(C'\fR for \f(CW\*(C`ev_timer\*(C'\fR watchers and \f(CW\*(C`io\*(C'\fR for \f(CW\*(C`ev_io\*(C'\fR watchers.
859.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4
860.el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4
861.IX Item "ev_init (ev_TYPE *watcher, callback)"
862This macro initialises the generic portion of a watcher. The contents
863of the watcher object can be arbitrary (so \f(CW\*(C`malloc\*(C'\fR will do). Only
864the generic parts of the watcher are initialised, you \fIneed\fR to call
865the type-specific \f(CW\*(C`ev_TYPE_set\*(C'\fR macro afterwards to initialise the
866type-specific parts. For each type there is also a \f(CW\*(C`ev_TYPE_init\*(C'\fR macro
867which rolls both calls into one.
868.Sp
869You can reinitialise a watcher at any time as long as it has been stopped
870(or never started) and there are no pending events outstanding.
871.Sp
872The callback is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher,
873int revents)\*(C'\fR.
874.ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4
875.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4
876.IX Item "ev_TYPE_set (ev_TYPE *, [args])"
877This macro initialises the type-specific parts of a watcher. You need to
878call \f(CW\*(C`ev_init\*(C'\fR at least once before you call this macro, but you can
879call \f(CW\*(C`ev_TYPE_set\*(C'\fR any number of times. You must not, however, call this
880macro on a watcher that is active (it can be pending, however, which is a
881difference to the \f(CW\*(C`ev_init\*(C'\fR macro).
882.Sp
883Although some watcher types do not have type-specific arguments
884(e.g. \f(CW\*(C`ev_prepare\*(C'\fR) you still need to call its \f(CW\*(C`set\*(C'\fR macro.
885.ie n .IP """ev_TYPE_init"" (ev_TYPE *watcher, callback, [args])" 4
886.el .IP "\f(CWev_TYPE_init\fR (ev_TYPE *watcher, callback, [args])" 4
887.IX Item "ev_TYPE_init (ev_TYPE *watcher, callback, [args])"
888This convinience macro rolls both \f(CW\*(C`ev_init\*(C'\fR and \f(CW\*(C`ev_TYPE_set\*(C'\fR macro
889calls into a single call. This is the most convinient method to initialise
890a watcher. The same limitations apply, of course.
891.ie n .IP """ev_TYPE_start"" (loop *, ev_TYPE *watcher)" 4
892.el .IP "\f(CWev_TYPE_start\fR (loop *, ev_TYPE *watcher)" 4
893.IX Item "ev_TYPE_start (loop *, ev_TYPE *watcher)"
894Starts (activates) the given watcher. Only active watchers will receive
895events. If the watcher is already active nothing will happen.
896.ie n .IP """ev_TYPE_stop"" (loop *, ev_TYPE *watcher)" 4
897.el .IP "\f(CWev_TYPE_stop\fR (loop *, ev_TYPE *watcher)" 4
898.IX Item "ev_TYPE_stop (loop *, ev_TYPE *watcher)"
899Stops the given watcher again (if active) and clears the pending
900status. It is possible that stopped watchers are pending (for example,
901non-repeating timers are being stopped when they become pending), but
902\&\f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor pending. If
903you want to free or reuse the memory used by the watcher it is therefore a
904good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function.
905.IP "bool ev_is_active (ev_TYPE *watcher)" 4
906.IX Item "bool ev_is_active (ev_TYPE *watcher)"
907Returns a true value iff the watcher is active (i.e. it has been started
908and not yet been stopped). As long as a watcher is active you must not modify
909it.
910.IP "bool ev_is_pending (ev_TYPE *watcher)" 4
911.IX Item "bool ev_is_pending (ev_TYPE *watcher)"
912Returns a true value iff the watcher is pending, (i.e. it has outstanding
913events but its callback has not yet been invoked). As long as a watcher
914is pending (but not active) you must not call an init function on it (but
915\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe), you must not change its priority, and you must
916make sure the watcher is available to libev (e.g. you cannot \f(CW\*(C`free ()\*(C'\fR
917it).
918.IP "callback ev_cb (ev_TYPE *watcher)" 4
919.IX Item "callback ev_cb (ev_TYPE *watcher)"
920Returns the callback currently set on the watcher.
921.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4
922.IX Item "ev_cb_set (ev_TYPE *watcher, callback)"
923Change the callback. You can change the callback at virtually any time
924(modulo threads).
925.IP "ev_set_priority (ev_TYPE *watcher, priority)" 4
926.IX Item "ev_set_priority (ev_TYPE *watcher, priority)"
927.PD 0
928.IP "int ev_priority (ev_TYPE *watcher)" 4
929.IX Item "int ev_priority (ev_TYPE *watcher)"
930.PD
931Set and query the priority of the watcher. The priority is a small
932integer between \f(CW\*(C`EV_MAXPRI\*(C'\fR (default: \f(CW2\fR) and \f(CW\*(C`EV_MINPRI\*(C'\fR
933(default: \f(CW\*(C`\-2\*(C'\fR). Pending watchers with higher priority will be invoked
934before watchers with lower priority, but priority will not keep watchers
935from being executed (except for \f(CW\*(C`ev_idle\*(C'\fR watchers).
936.Sp
937This means that priorities are \fIonly\fR used for ordering callback
938invocation after new events have been received. This is useful, for
939example, to reduce latency after idling, or more often, to bind two
940watchers on the same event and make sure one is called first.
941.Sp
942If you need to suppress invocation when higher priority events are pending
943you need to look at \f(CW\*(C`ev_idle\*(C'\fR watchers, which provide this functionality.
944.Sp
945You \fImust not\fR change the priority of a watcher as long as it is active or
946pending.
947.Sp
948The default priority used by watchers when no priority has been set is
949always \f(CW0\fR, which is supposed to not be too high and not be too low :).
950.Sp
951Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR is
952fine, as long as you do not mind that the priority value you query might
953or might not have been adjusted to be within valid range.
954.IP "ev_invoke (loop, ev_TYPE *watcher, int revents)" 4
955.IX Item "ev_invoke (loop, ev_TYPE *watcher, int revents)"
956Invoke the \f(CW\*(C`watcher\*(C'\fR with the given \f(CW\*(C`loop\*(C'\fR and \f(CW\*(C`revents\*(C'\fR. Neither
957\&\f(CW\*(C`loop\*(C'\fR nor \f(CW\*(C`revents\*(C'\fR need to be valid as long as the watcher callback
958can deal with that fact.
959.IP "int ev_clear_pending (loop, ev_TYPE *watcher)" 4
960.IX Item "int ev_clear_pending (loop, ev_TYPE *watcher)"
961If the watcher is pending, this function returns clears its pending status
962and returns its \f(CW\*(C`revents\*(C'\fR bitset (as if its callback was invoked). If the
963watcher isn't pending it does nothing and returns \f(CW0\fR.
714.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0" 964.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0"
715.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER" 965.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER"
716Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change 966Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change
717and read at any time, libev will completely ignore it. This can be used 967and read at any time, libev will completely ignore it. This can be used
718to associate arbitrary data with your watcher. If you need more data and 968to associate arbitrary data with your watcher. If you need more data and
… …
739\& struct my_io *w = (struct my_io *)w_; 989\& struct my_io *w = (struct my_io *)w_;
740\& ... 990\& ...
741\& } 991\& }
742.Ve 992.Ve
743.PP 993.PP
744More interesting and less C\-conformant ways of catsing your callback type 994More interesting and less C\-conformant ways of casting your callback type
745have been omitted.... 995instead have been omitted.
996.PP
997Another common scenario is having some data structure with multiple
998watchers:
999.PP
1000.Vb 6
1001\& struct my_biggy
1002\& {
1003\& int some_data;
1004\& ev_timer t1;
1005\& ev_timer t2;
1006\& }
1007.Ve
1008.PP
1009In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more complicated,
1010you need to use \f(CW\*(C`offsetof\*(C'\fR:
1011.PP
1012.Vb 1
1013\& #include <stddef.h>
1014.Ve
1015.PP
1016.Vb 6
1017\& static void
1018\& t1_cb (EV_P_ struct ev_timer *w, int revents)
1019\& {
1020\& struct my_biggy big = (struct my_biggy *
1021\& (((char *)w) - offsetof (struct my_biggy, t1));
1022\& }
1023.Ve
1024.PP
1025.Vb 6
1026\& static void
1027\& t2_cb (EV_P_ struct ev_timer *w, int revents)
1028\& {
1029\& struct my_biggy big = (struct my_biggy *
1030\& (((char *)w) - offsetof (struct my_biggy, t2));
1031\& }
1032.Ve
746.SH "WATCHER TYPES" 1033.SH "WATCHER TYPES"
747.IX Header "WATCHER TYPES" 1034.IX Header "WATCHER TYPES"
748This section describes each watcher in detail, but will not repeat 1035This section describes each watcher in detail, but will not repeat
749information given in the last section. 1036information given in the last section. Any initialisation/set macros,
1037functions and members specific to the watcher type are explained.
1038.PP
1039Members are additionally marked with either \fI[read\-only]\fR, meaning that,
1040while the watcher is active, you can look at the member and expect some
1041sensible content, but you must not modify it (you can modify it while the
1042watcher is stopped to your hearts content), or \fI[read\-write]\fR, which
1043means you can expect it to have some sensible content while the watcher
1044is active, but you can also modify it. Modifying it may not do something
1045sensible or take immediate effect (or do anything at all), but libev will
1046not crash or malfunction in any way.
750.ie n .Sh """ev_io"" \- is this file descriptor readable or writable" 1047.ie n .Sh """ev_io"" \- is this file descriptor readable or writable?"
751.el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable" 1048.el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable?"
752.IX Subsection "ev_io - is this file descriptor readable or writable" 1049.IX Subsection "ev_io - is this file descriptor readable or writable?"
753I/O watchers check whether a file descriptor is readable or writable 1050I/O watchers check whether a file descriptor is readable or writable
754in each iteration of the event loop (This behaviour is called 1051in each iteration of the event loop, or, more precisely, when reading
755level-triggering because you keep receiving events as long as the 1052would not block the process and writing would at least be able to write
756condition persists. Remember you can stop the watcher if you don't want to 1053some data. This behaviour is called level-triggering because you keep
757act on the event and neither want to receive future events). 1054receiving events as long as the condition persists. Remember you can stop
1055the watcher if you don't want to act on the event and neither want to
1056receive future events.
758.PP 1057.PP
759In general you can register as many read and/or write event watchers per 1058In general you can register as many read and/or write event watchers per
760fd as you want (as long as you don't confuse yourself). Setting all file 1059fd as you want (as long as you don't confuse yourself). Setting all file
761descriptors to non-blocking mode is also usually a good idea (but not 1060descriptors to non-blocking mode is also usually a good idea (but not
762required if you know what you are doing). 1061required if you know what you are doing).
763.PP 1062.PP
764You have to be careful with dup'ed file descriptors, though. Some backends 1063You have to be careful with dup'ed file descriptors, though. Some backends
765(the linux epoll backend is a notable example) cannot handle dup'ed file 1064(the linux epoll backend is a notable example) cannot handle dup'ed file
766descriptors correctly if you register interest in two or more fds pointing 1065descriptors correctly if you register interest in two or more fds pointing
767to the same underlying file/socket etc. description (that is, they share 1066to the same underlying file/socket/etc. description (that is, they share
768the same underlying \*(L"file open\*(R"). 1067the same underlying \*(L"file open\*(R").
769.PP 1068.PP
770If you must do this, then force the use of a known-to-be-good backend 1069If you must do this, then force the use of a known-to-be-good backend
771(at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and 1070(at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and
772\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR). 1071\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR).
1072.PP
1073Another thing you have to watch out for is that it is quite easy to
1074receive \*(L"spurious\*(R" readyness notifications, that is your callback might
1075be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block
1076because there is no data. Not only are some backends known to create a
1077lot of those (for example solaris ports), it is very easy to get into
1078this situation even with a relatively standard program structure. Thus
1079it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning
1080\&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives.
1081.PP
1082If you cannot run the fd in non-blocking mode (for example you should not
1083play around with an Xlib connection), then you have to seperately re-test
1084whether a file descriptor is really ready with a known-to-be good interface
1085such as poll (fortunately in our Xlib example, Xlib already does this on
1086its own, so its quite safe to use).
1087.PP
1088\fIThe special problem of disappearing file descriptors\fR
1089.IX Subsection "The special problem of disappearing file descriptors"
1090.PP
1091Some backends (e.g. kqueue, epoll) need to be told about closing a file
1092descriptor (either by calling \f(CW\*(C`close\*(C'\fR explicitly or by any other means,
1093such as \f(CW\*(C`dup\*(C'\fR). The reason is that you register interest in some file
1094descriptor, but when it goes away, the operating system will silently drop
1095this interest. If another file descriptor with the same number then is
1096registered with libev, there is no efficient way to see that this is, in
1097fact, a different file descriptor.
1098.PP
1099To avoid having to explicitly tell libev about such cases, libev follows
1100the following policy: Each time \f(CW\*(C`ev_io_set\*(C'\fR is being called, libev
1101will assume that this is potentially a new file descriptor, otherwise
1102it is assumed that the file descriptor stays the same. That means that
1103you \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
1104descriptor even if the file descriptor number itself did not change.
1105.PP
1106This is how one would do it normally anyway, the important point is that
1107the libev application should not optimise around libev but should leave
1108optimisations to libev.
1109.PP
1110\fIThs special problem of dup'ed file descriptors\fR
1111.IX Subsection "Ths special problem of dup'ed file descriptors"
1112.PP
1113Some backends (e.g. epoll), cannot register events for file descriptors,
1114but only events for the underlying file descriptions. That menas when you
1115have \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors and register events for them, only one
1116file descriptor might actually receive events.
1117.PP
1118There is no workaorund possible except not registering events
1119for potentially \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors or to resort to
1120\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
1121.PP
1122\fIThe special problem of fork\fR
1123.IX Subsection "The special problem of fork"
1124.PP
1125Some backends (epoll, kqueue) do not support \f(CW\*(C`fork ()\*(C'\fR at all or exhibit
1126useless behaviour. Libev fully supports fork, but needs to be told about
1127it in the child.
1128.PP
1129To support fork in your programs, you either have to call
1130\&\f(CW\*(C`ev_default_fork ()\*(C'\fR or \f(CW\*(C`ev_loop_fork ()\*(C'\fR after a fork in the child,
1131enable \f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR, or resort to \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or
1132\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
1133.PP
1134\fIWatcher-Specific Functions\fR
1135.IX Subsection "Watcher-Specific Functions"
773.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4 1136.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4
774.IX Item "ev_io_init (ev_io *, callback, int fd, int events)" 1137.IX Item "ev_io_init (ev_io *, callback, int fd, int events)"
775.PD 0 1138.PD 0
776.IP "ev_io_set (ev_io *, int fd, int events)" 4 1139.IP "ev_io_set (ev_io *, int fd, int events)" 4
777.IX Item "ev_io_set (ev_io *, int fd, int events)" 1140.IX Item "ev_io_set (ev_io *, int fd, int events)"
778.PD 1141.PD
779Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The fd is the file descriptor to rceeive 1142Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to
780events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or \f(CW\*(C`EV_READ | 1143rceeive events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or
781EV_WRITE\*(C'\fR to receive the given events. 1144\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR to receive the given events.
782.Sp 1145.IP "int fd [read\-only]" 4
783Please note that most of the more scalable backend mechanisms (for example 1146.IX Item "int fd [read-only]"
784epoll and solaris ports) can result in spurious readyness notifications 1147The file descriptor being watched.
785for file descriptors, so you practically need to use non-blocking I/O (and 1148.IP "int events [read\-only]" 4
786treat callback invocation as hint only), or retest separately with a safe 1149.IX Item "int events [read-only]"
787interface before doing I/O (XLib can do this), or force the use of either 1150The events being watched.
788\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR, which don't suffer from this
789problem. Also note that it is quite easy to have your callback invoked
790when the readyness condition is no longer valid even when employing
791typical ways of handling events, so its a good idea to use non-blocking
792I/O unconditionally.
793.PP 1151.PP
794Example: call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well 1152Example: Call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well
795readable, but only once. Since it is likely line\-buffered, you could 1153readable, but only once. Since it is likely line\-buffered, you could
796attempt to read a whole line in the callback: 1154attempt to read a whole line in the callback.
797.PP 1155.PP
798.Vb 6 1156.Vb 6
799\& static void 1157\& static void
800\& stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1158\& stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
801\& { 1159\& {
… …
810\& struct ev_io stdin_readable; 1168\& struct ev_io stdin_readable;
811\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); 1169\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
812\& ev_io_start (loop, &stdin_readable); 1170\& ev_io_start (loop, &stdin_readable);
813\& ev_loop (loop, 0); 1171\& ev_loop (loop, 0);
814.Ve 1172.Ve
815.ie n .Sh """ev_timer"" \- relative and optionally recurring timeouts" 1173.ie n .Sh """ev_timer"" \- relative and optionally repeating timeouts"
816.el .Sh "\f(CWev_timer\fP \- relative and optionally recurring timeouts" 1174.el .Sh "\f(CWev_timer\fP \- relative and optionally repeating timeouts"
817.IX Subsection "ev_timer - relative and optionally recurring timeouts" 1175.IX Subsection "ev_timer - relative and optionally repeating timeouts"
818Timer watchers are simple relative timers that generate an event after a 1176Timer watchers are simple relative timers that generate an event after a
819given time, and optionally repeating in regular intervals after that. 1177given time, and optionally repeating in regular intervals after that.
820.PP 1178.PP
821The timers are based on real time, that is, if you register an event that 1179The timers are based on real time, that is, if you register an event that
822times out after an hour and you reset your system clock to last years 1180times out after an hour and you reset your system clock to last years
… …
835.Ve 1193.Ve
836.PP 1194.PP
837The callback is guarenteed to be invoked only when its timeout has passed, 1195The callback is guarenteed to be invoked only when its timeout has passed,
838but if multiple timers become ready during the same loop iteration then 1196but if multiple timers become ready during the same loop iteration then
839order of execution is undefined. 1197order of execution is undefined.
1198.PP
1199\fIWatcher-Specific Functions and Data Members\fR
1200.IX Subsection "Watcher-Specific Functions and Data Members"
840.IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4 1201.IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4
841.IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 1202.IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)"
842.PD 0 1203.PD 0
843.IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4 1204.IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4
844.IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 1205.IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)"
… …
856.IP "ev_timer_again (loop)" 4 1217.IP "ev_timer_again (loop)" 4
857.IX Item "ev_timer_again (loop)" 1218.IX Item "ev_timer_again (loop)"
858This will act as if the timer timed out and restart it again if it is 1219This will act as if the timer timed out and restart it again if it is
859repeating. The exact semantics are: 1220repeating. The exact semantics are:
860.Sp 1221.Sp
1222If the timer is pending, its pending status is cleared.
1223.Sp
861If the timer is started but nonrepeating, stop it. 1224If the timer is started but nonrepeating, stop it (as if it timed out).
862.Sp 1225.Sp
863If the timer is repeating, either start it if necessary (with the repeat 1226If the timer is repeating, either start it if necessary (with the
864value), or reset the running timer to the repeat value. 1227\&\f(CW\*(C`repeat\*(C'\fR value), or reset the running timer to the \f(CW\*(C`repeat\*(C'\fR value.
865.Sp 1228.Sp
866This sounds a bit complicated, but here is a useful and typical 1229This sounds a bit complicated, but here is a useful and typical
867example: Imagine you have a tcp connection and you want a so-called idle 1230example: Imagine you have a tcp connection and you want a so-called idle
868timeout, that is, you want to be called when there have been, say, 60 1231timeout, that is, you want to be called when there have been, say, 60
869seconds of inactivity on the socket. The easiest way to do this is to 1232seconds of inactivity on the socket. The easiest way to do this is to
870configure an \f(CW\*(C`ev_timer\*(C'\fR with after=repeat=60 and calling ev_timer_again each 1233configure an \f(CW\*(C`ev_timer\*(C'\fR with a \f(CW\*(C`repeat\*(C'\fR value of \f(CW60\fR and then call
871time you successfully read or write some data. If you go into an idle 1234\&\f(CW\*(C`ev_timer_again\*(C'\fR each time you successfully read or write some data. If
872state where you do not expect data to travel on the socket, you can stop 1235you go into an idle state where you do not expect data to travel on the
873the timer, and again will automatically restart it if need be. 1236socket, you can \f(CW\*(C`ev_timer_stop\*(C'\fR the timer, and \f(CW\*(C`ev_timer_again\*(C'\fR will
1237automatically restart it if need be.
1238.Sp
1239That means you can ignore the \f(CW\*(C`after\*(C'\fR value and \f(CW\*(C`ev_timer_start\*(C'\fR
1240altogether and only ever use the \f(CW\*(C`repeat\*(C'\fR value and \f(CW\*(C`ev_timer_again\*(C'\fR:
1241.Sp
1242.Vb 8
1243\& ev_timer_init (timer, callback, 0., 5.);
1244\& ev_timer_again (loop, timer);
1245\& ...
1246\& timer->again = 17.;
1247\& ev_timer_again (loop, timer);
1248\& ...
1249\& timer->again = 10.;
1250\& ev_timer_again (loop, timer);
1251.Ve
1252.Sp
1253This is more slightly efficient then stopping/starting the timer each time
1254you want to modify its timeout value.
1255.IP "ev_tstamp repeat [read\-write]" 4
1256.IX Item "ev_tstamp repeat [read-write]"
1257The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out
1258or \f(CW\*(C`ev_timer_again\*(C'\fR is called and determines the next timeout (if any),
1259which is also when any modifications are taken into account.
874.PP 1260.PP
875Example: create a timer that fires after 60 seconds. 1261Example: Create a timer that fires after 60 seconds.
876.PP 1262.PP
877.Vb 5 1263.Vb 5
878\& static void 1264\& static void
879\& one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1265\& one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
880\& { 1266\& {
… …
886\& struct ev_timer mytimer; 1272\& struct ev_timer mytimer;
887\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.); 1273\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
888\& ev_timer_start (loop, &mytimer); 1274\& ev_timer_start (loop, &mytimer);
889.Ve 1275.Ve
890.PP 1276.PP
891Example: create a timeout timer that times out after 10 seconds of 1277Example: Create a timeout timer that times out after 10 seconds of
892inactivity. 1278inactivity.
893.PP 1279.PP
894.Vb 5 1280.Vb 5
895\& static void 1281\& static void
896\& timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1282\& timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
… …
909.Vb 3 1295.Vb 3
910\& // and in some piece of code that gets executed on any "activity": 1296\& // and in some piece of code that gets executed on any "activity":
911\& // reset the timeout to start ticking again at 10 seconds 1297\& // reset the timeout to start ticking again at 10 seconds
912\& ev_timer_again (&mytimer); 1298\& ev_timer_again (&mytimer);
913.Ve 1299.Ve
914.ie n .Sh """ev_periodic"" \- to cron or not to cron" 1300.ie n .Sh """ev_periodic"" \- to cron or not to cron?"
915.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron" 1301.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron?"
916.IX Subsection "ev_periodic - to cron or not to cron" 1302.IX Subsection "ev_periodic - to cron or not to cron?"
917Periodic watchers are also timers of a kind, but they are very versatile 1303Periodic watchers are also timers of a kind, but they are very versatile
918(and unfortunately a bit complex). 1304(and unfortunately a bit complex).
919.PP 1305.PP
920Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time) 1306Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time)
921but on wallclock time (absolute time). You can tell a periodic watcher 1307but on wallclock time (absolute time). You can tell a periodic watcher
922to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a 1308to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a
923periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now () 1309periodic watcher to trigger in 10 seconds (by specifiying e.g. \f(CW\*(C`ev_now ()
924+ 10.>) and then reset your system clock to the last year, then it will 1310+ 10.\*(C'\fR) and then reset your system clock to the last year, then it will
925take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger 1311take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger
926roughly 10 seconds later and of course not if you reset your system time 1312roughly 10 seconds later).
927again).
928.PP 1313.PP
929They can also be used to implement vastly more complex timers, such as 1314They can also be used to implement vastly more complex timers, such as
930triggering an event on eahc midnight, local time. 1315triggering an event on each midnight, local time or other, complicated,
1316rules.
931.PP 1317.PP
932As with timers, the callback is guarenteed to be invoked only when the 1318As with timers, the callback is guarenteed to be invoked only when the
933time (\f(CW\*(C`at\*(C'\fR) has been passed, but if multiple periodic timers become ready 1319time (\f(CW\*(C`at\*(C'\fR) has been passed, but if multiple periodic timers become ready
934during the same loop iteration then order of execution is undefined. 1320during the same loop iteration then order of execution is undefined.
1321.PP
1322\fIWatcher-Specific Functions and Data Members\fR
1323.IX Subsection "Watcher-Specific Functions and Data Members"
935.IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4 1324.IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4
936.IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 1325.IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)"
937.PD 0 1326.PD 0
938.IP "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 4 1327.IP "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 4
939.IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 1328.IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)"
940.PD 1329.PD
941Lots of arguments, lets sort it out... There are basically three modes of 1330Lots of arguments, lets sort it out... There are basically three modes of
942operation, and we will explain them from simplest to complex: 1331operation, and we will explain them from simplest to complex:
943.RS 4 1332.RS 4
944.IP "* absolute timer (interval = reschedule_cb = 0)" 4 1333.IP "* absolute timer (at = time, interval = reschedule_cb = 0)" 4
945.IX Item "absolute timer (interval = reschedule_cb = 0)" 1334.IX Item "absolute timer (at = time, interval = reschedule_cb = 0)"
946In this configuration the watcher triggers an event at the wallclock time 1335In this configuration the watcher triggers an event at the wallclock time
947\&\f(CW\*(C`at\*(C'\fR and doesn't repeat. It will not adjust when a time jump occurs, 1336\&\f(CW\*(C`at\*(C'\fR and doesn't repeat. It will not adjust when a time jump occurs,
948that is, if it is to be run at January 1st 2011 then it will run when the 1337that is, if it is to be run at January 1st 2011 then it will run when the
949system time reaches or surpasses this time. 1338system time reaches or surpasses this time.
950.IP "* non-repeating interval timer (interval > 0, reschedule_cb = 0)" 4 1339.IP "* non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)" 4
951.IX Item "non-repeating interval timer (interval > 0, reschedule_cb = 0)" 1340.IX Item "non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)"
952In this mode the watcher will always be scheduled to time out at the next 1341In this mode the watcher will always be scheduled to time out at the next
953\&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N) and then repeat, regardless 1342\&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N, which can also be negative)
954of any time jumps. 1343and then repeat, regardless of any time jumps.
955.Sp 1344.Sp
956This can be used to create timers that do not drift with respect to system 1345This can be used to create timers that do not drift with respect to system
957time: 1346time:
958.Sp 1347.Sp
959.Vb 1 1348.Vb 1
… …
966by 3600. 1355by 3600.
967.Sp 1356.Sp
968Another way to think about it (for the mathematically inclined) is that 1357Another way to think about it (for the mathematically inclined) is that
969\&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible 1358\&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible
970time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps. 1359time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps.
1360.Sp
1361For numerical stability it is preferable that the \f(CW\*(C`at\*(C'\fR value is near
1362\&\f(CW\*(C`ev_now ()\*(C'\fR (the current time), but there is no range requirement for
1363this value.
971.IP "* manual reschedule mode (reschedule_cb = callback)" 4 1364.IP "* manual reschedule mode (at and interval ignored, reschedule_cb = callback)" 4
972.IX Item "manual reschedule mode (reschedule_cb = callback)" 1365.IX Item "manual reschedule mode (at and interval ignored, reschedule_cb = callback)"
973In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR are both being 1366In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR are both being
974ignored. Instead, each time the periodic watcher gets scheduled, the 1367ignored. Instead, each time the periodic watcher gets scheduled, the
975reschedule callback will be called with the watcher as first, and the 1368reschedule callback will be called with the watcher as first, and the
976current time as second argument. 1369current time as second argument.
977.Sp 1370.Sp
978\&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher, 1371\&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher,
979ever, or make any event loop modifications\fR. If you need to stop it, 1372ever, or make any event loop modifications\fR. If you need to stop it,
980return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop it afterwards (e.g. by 1373return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop it afterwards (e.g. by
981starting a prepare watcher). 1374starting an \f(CW\*(C`ev_prepare\*(C'\fR watcher, which is legal).
982.Sp 1375.Sp
983Its prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 1376Its prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
984ev_tstamp now)\*(C'\fR, e.g.: 1377ev_tstamp now)\*(C'\fR, e.g.:
985.Sp 1378.Sp
986.Vb 4 1379.Vb 4
… …
1010.IX Item "ev_periodic_again (loop, ev_periodic *)" 1403.IX Item "ev_periodic_again (loop, ev_periodic *)"
1011Simply stops and restarts the periodic watcher again. This is only useful 1404Simply stops and restarts the periodic watcher again. This is only useful
1012when you changed some parameters or the reschedule callback would return 1405when you changed some parameters or the reschedule callback would return
1013a different time than the last time it was called (e.g. in a crond like 1406a different time than the last time it was called (e.g. in a crond like
1014program when the crontabs have changed). 1407program when the crontabs have changed).
1408.IP "ev_tstamp offset [read\-write]" 4
1409.IX Item "ev_tstamp offset [read-write]"
1410When repeating, this contains the offset value, otherwise this is the
1411absolute point in time (the \f(CW\*(C`at\*(C'\fR value passed to \f(CW\*(C`ev_periodic_set\*(C'\fR).
1412.Sp
1413Can be modified any time, but changes only take effect when the periodic
1414timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
1415.IP "ev_tstamp interval [read\-write]" 4
1416.IX Item "ev_tstamp interval [read-write]"
1417The current interval value. Can be modified any time, but changes only
1418take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being
1419called.
1420.IP "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read\-write]" 4
1421.IX Item "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]"
1422The current reschedule callback, or \f(CW0\fR, if this functionality is
1423switched off. Can be changed any time, but changes only take effect when
1424the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
1425.IP "ev_tstamp at [read\-only]" 4
1426.IX Item "ev_tstamp at [read-only]"
1427When active, contains the absolute time that the watcher is supposed to
1428trigger next.
1015.PP 1429.PP
1016Example: call a callback every hour, or, more precisely, whenever the 1430Example: Call a callback every hour, or, more precisely, whenever the
1017system clock is divisible by 3600. The callback invocation times have 1431system clock is divisible by 3600. The callback invocation times have
1018potentially a lot of jittering, but good long-term stability. 1432potentially a lot of jittering, but good long-term stability.
1019.PP 1433.PP
1020.Vb 5 1434.Vb 5
1021\& static void 1435\& static void
… …
1029\& struct ev_periodic hourly_tick; 1443\& struct ev_periodic hourly_tick;
1030\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); 1444\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1031\& ev_periodic_start (loop, &hourly_tick); 1445\& ev_periodic_start (loop, &hourly_tick);
1032.Ve 1446.Ve
1033.PP 1447.PP
1034Example: the same as above, but use a reschedule callback to do it: 1448Example: The same as above, but use a reschedule callback to do it:
1035.PP 1449.PP
1036.Vb 1 1450.Vb 1
1037\& #include <math.h> 1451\& #include <math.h>
1038.Ve 1452.Ve
1039.PP 1453.PP
… …
1047.PP 1461.PP
1048.Vb 1 1462.Vb 1
1049\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); 1463\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1050.Ve 1464.Ve
1051.PP 1465.PP
1052Example: call a callback every hour, starting now: 1466Example: Call a callback every hour, starting now:
1053.PP 1467.PP
1054.Vb 4 1468.Vb 4
1055\& struct ev_periodic hourly_tick; 1469\& struct ev_periodic hourly_tick;
1056\& ev_periodic_init (&hourly_tick, clock_cb, 1470\& ev_periodic_init (&hourly_tick, clock_cb,
1057\& fmod (ev_now (loop), 3600.), 3600., 0); 1471\& fmod (ev_now (loop), 3600.), 3600., 0);
1058\& ev_periodic_start (loop, &hourly_tick); 1472\& ev_periodic_start (loop, &hourly_tick);
1059.Ve 1473.Ve
1060.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled" 1474.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled!"
1061.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled" 1475.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled!"
1062.IX Subsection "ev_signal - signal me when a signal gets signalled" 1476.IX Subsection "ev_signal - signal me when a signal gets signalled!"
1063Signal watchers will trigger an event when the process receives a specific 1477Signal watchers will trigger an event when the process receives a specific
1064signal one or more times. Even though signals are very asynchronous, libev 1478signal one or more times. Even though signals are very asynchronous, libev
1065will try it's best to deliver signals synchronously, i.e. as part of the 1479will try it's best to deliver signals synchronously, i.e. as part of the
1066normal event processing, like any other event. 1480normal event processing, like any other event.
1067.PP 1481.PP
… …
1069first watcher gets started will libev actually register a signal watcher 1483first watcher gets started will libev actually register a signal watcher
1070with the kernel (thus it coexists with your own signal handlers as long 1484with the kernel (thus it coexists with your own signal handlers as long
1071as you don't register any with libev). Similarly, when the last signal 1485as you don't register any with libev). Similarly, when the last signal
1072watcher for a signal is stopped libev will reset the signal handler to 1486watcher for a signal is stopped libev will reset the signal handler to
1073\&\s-1SIG_DFL\s0 (regardless of what it was set to before). 1487\&\s-1SIG_DFL\s0 (regardless of what it was set to before).
1488.PP
1489\fIWatcher-Specific Functions and Data Members\fR
1490.IX Subsection "Watcher-Specific Functions and Data Members"
1074.IP "ev_signal_init (ev_signal *, callback, int signum)" 4 1491.IP "ev_signal_init (ev_signal *, callback, int signum)" 4
1075.IX Item "ev_signal_init (ev_signal *, callback, int signum)" 1492.IX Item "ev_signal_init (ev_signal *, callback, int signum)"
1076.PD 0 1493.PD 0
1077.IP "ev_signal_set (ev_signal *, int signum)" 4 1494.IP "ev_signal_set (ev_signal *, int signum)" 4
1078.IX Item "ev_signal_set (ev_signal *, int signum)" 1495.IX Item "ev_signal_set (ev_signal *, int signum)"
1079.PD 1496.PD
1080Configures the watcher to trigger on the given signal number (usually one 1497Configures the watcher to trigger on the given signal number (usually one
1081of the \f(CW\*(C`SIGxxx\*(C'\fR constants). 1498of the \f(CW\*(C`SIGxxx\*(C'\fR constants).
1499.IP "int signum [read\-only]" 4
1500.IX Item "int signum [read-only]"
1501The signal the watcher watches out for.
1082.ie n .Sh """ev_child"" \- wait for pid status changes" 1502.ie n .Sh """ev_child"" \- watch out for process status changes"
1083.el .Sh "\f(CWev_child\fP \- wait for pid status changes" 1503.el .Sh "\f(CWev_child\fP \- watch out for process status changes"
1084.IX Subsection "ev_child - wait for pid status changes" 1504.IX Subsection "ev_child - watch out for process status changes"
1085Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to 1505Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to
1086some child status changes (most typically when a child of yours dies). 1506some child status changes (most typically when a child of yours dies).
1507.PP
1508\fIWatcher-Specific Functions and Data Members\fR
1509.IX Subsection "Watcher-Specific Functions and Data Members"
1087.IP "ev_child_init (ev_child *, callback, int pid)" 4 1510.IP "ev_child_init (ev_child *, callback, int pid)" 4
1088.IX Item "ev_child_init (ev_child *, callback, int pid)" 1511.IX Item "ev_child_init (ev_child *, callback, int pid)"
1089.PD 0 1512.PD 0
1090.IP "ev_child_set (ev_child *, int pid)" 4 1513.IP "ev_child_set (ev_child *, int pid)" 4
1091.IX Item "ev_child_set (ev_child *, int pid)" 1514.IX Item "ev_child_set (ev_child *, int pid)"
… …
1094\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look 1517\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look
1095at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see 1518at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see
1096the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems 1519the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems
1097\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the 1520\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the
1098process causing the status change. 1521process causing the status change.
1522.IP "int pid [read\-only]" 4
1523.IX Item "int pid [read-only]"
1524The process id this watcher watches out for, or \f(CW0\fR, meaning any process id.
1525.IP "int rpid [read\-write]" 4
1526.IX Item "int rpid [read-write]"
1527The process id that detected a status change.
1528.IP "int rstatus [read\-write]" 4
1529.IX Item "int rstatus [read-write]"
1530The process exit/trace status caused by \f(CW\*(C`rpid\*(C'\fR (see your systems
1531\&\f(CW\*(C`waitpid\*(C'\fR and \f(CW\*(C`sys/wait.h\*(C'\fR documentation for details).
1099.PP 1532.PP
1100Example: try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0. 1533Example: Try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0.
1101.PP 1534.PP
1102.Vb 5 1535.Vb 5
1103\& static void 1536\& static void
1104\& sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1537\& sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1105\& { 1538\& {
… …
1110.Vb 3 1543.Vb 3
1111\& struct ev_signal signal_watcher; 1544\& struct ev_signal signal_watcher;
1112\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT); 1545\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1113\& ev_signal_start (loop, &sigint_cb); 1546\& ev_signal_start (loop, &sigint_cb);
1114.Ve 1547.Ve
1548.ie n .Sh """ev_stat"" \- did the file attributes just change?"
1549.el .Sh "\f(CWev_stat\fP \- did the file attributes just change?"
1550.IX Subsection "ev_stat - did the file attributes just change?"
1551This watches a filesystem path for attribute changes. That is, it calls
1552\&\f(CW\*(C`stat\*(C'\fR regularly (or when the \s-1OS\s0 says it changed) and sees if it changed
1553compared to the last time, invoking the callback if it did.
1554.PP
1555The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does
1556not exist\*(R" is a status change like any other. The condition \*(L"path does
1557not exist\*(R" is signified by the \f(CW\*(C`st_nlink\*(C'\fR field being zero (which is
1558otherwise always forced to be at least one) and all the other fields of
1559the stat buffer having unspecified contents.
1560.PP
1561The path \fIshould\fR be absolute and \fImust not\fR end in a slash. If it is
1562relative and your working directory changes, the behaviour is undefined.
1563.PP
1564Since there is no standard to do this, the portable implementation simply
1565calls \f(CW\*(C`stat (2)\*(C'\fR regularly on the path to see if it changed somehow. You
1566can specify a recommended polling interval for this case. If you specify
1567a polling interval of \f(CW0\fR (highly recommended!) then a \fIsuitable,
1568unspecified default\fR value will be used (which you can expect to be around
1569five seconds, although this might change dynamically). Libev will also
1570impose a minimum interval which is currently around \f(CW0.1\fR, but thats
1571usually overkill.
1572.PP
1573This watcher type is not meant for massive numbers of stat watchers,
1574as even with OS-supported change notifications, this can be
1575resource\-intensive.
1576.PP
1577At the time of this writing, only the Linux inotify interface is
1578implemented (implementing kqueue support is left as an exercise for the
1579reader). Inotify will be used to give hints only and should not change the
1580semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers, which means that libev sometimes needs
1581to fall back to regular polling again even with inotify, but changes are
1582usually detected immediately, and if the file exists there will be no
1583polling.
1584.PP
1585\fIWatcher-Specific Functions and Data Members\fR
1586.IX Subsection "Watcher-Specific Functions and Data Members"
1587.IP "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 4
1588.IX Item "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)"
1589.PD 0
1590.IP "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" 4
1591.IX Item "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)"
1592.PD
1593Configures the watcher to wait for status changes of the given
1594\&\f(CW\*(C`path\*(C'\fR. The \f(CW\*(C`interval\*(C'\fR is a hint on how quickly a change is expected to
1595be detected and should normally be specified as \f(CW0\fR to let libev choose
1596a suitable value. The memory pointed to by \f(CW\*(C`path\*(C'\fR must point to the same
1597path for as long as the watcher is active.
1598.Sp
1599The callback will be receive \f(CW\*(C`EV_STAT\*(C'\fR when a change was detected,
1600relative to the attributes at the time the watcher was started (or the
1601last change was detected).
1602.IP "ev_stat_stat (ev_stat *)" 4
1603.IX Item "ev_stat_stat (ev_stat *)"
1604Updates the stat buffer immediately with new values. If you change the
1605watched path in your callback, you could call this fucntion to avoid
1606detecting this change (while introducing a race condition). Can also be
1607useful simply to find out the new values.
1608.IP "ev_statdata attr [read\-only]" 4
1609.IX Item "ev_statdata attr [read-only]"
1610The most-recently detected attributes of the file. Although the type is of
1611\&\f(CW\*(C`ev_statdata\*(C'\fR, this is usually the (or one of the) \f(CW\*(C`struct stat\*(C'\fR types
1612suitable for your system. If the \f(CW\*(C`st_nlink\*(C'\fR member is \f(CW0\fR, then there
1613was some error while \f(CW\*(C`stat\*(C'\fRing the file.
1614.IP "ev_statdata prev [read\-only]" 4
1615.IX Item "ev_statdata prev [read-only]"
1616The previous attributes of the file. The callback gets invoked whenever
1617\&\f(CW\*(C`prev\*(C'\fR != \f(CW\*(C`attr\*(C'\fR.
1618.IP "ev_tstamp interval [read\-only]" 4
1619.IX Item "ev_tstamp interval [read-only]"
1620The specified interval.
1621.IP "const char *path [read\-only]" 4
1622.IX Item "const char *path [read-only]"
1623The filesystem path that is being watched.
1624.PP
1625Example: Watch \f(CW\*(C`/etc/passwd\*(C'\fR for attribute changes.
1626.PP
1627.Vb 15
1628\& static void
1629\& passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1630\& {
1631\& /* /etc/passwd changed in some way */
1632\& if (w->attr.st_nlink)
1633\& {
1634\& printf ("passwd current size %ld\en", (long)w->attr.st_size);
1635\& printf ("passwd current atime %ld\en", (long)w->attr.st_mtime);
1636\& printf ("passwd current mtime %ld\en", (long)w->attr.st_mtime);
1637\& }
1638\& else
1639\& /* you shalt not abuse printf for puts */
1640\& puts ("wow, /etc/passwd is not there, expect problems. "
1641\& "if this is windows, they already arrived\en");
1642\& }
1643.Ve
1644.PP
1645.Vb 2
1646\& ...
1647\& ev_stat passwd;
1648.Ve
1649.PP
1650.Vb 2
1651\& ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
1652\& ev_stat_start (loop, &passwd);
1653.Ve
1115.ie n .Sh """ev_idle"" \- when you've got nothing better to do" 1654.ie n .Sh """ev_idle"" \- when you've got nothing better to do..."
1116.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do" 1655.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do..."
1117.IX Subsection "ev_idle - when you've got nothing better to do" 1656.IX Subsection "ev_idle - when you've got nothing better to do..."
1118Idle watchers trigger events when there are no other events are pending 1657Idle watchers trigger events when no other events of the same or higher
1119(prepare, check and other idle watchers do not count). That is, as long 1658priority are pending (prepare, check and other idle watchers do not
1120as your process is busy handling sockets or timeouts (or even signals, 1659count).
1121imagine) it will not be triggered. But when your process is idle all idle 1660.PP
1122watchers are being called again and again, once per event loop iteration \- 1661That is, as long as your process is busy handling sockets or timeouts
1662(or even signals, imagine) of the same or higher priority it will not be
1663triggered. But when your process is idle (or only lower-priority watchers
1664are pending), the idle watchers are being called once per event loop
1123until stopped, that is, or your process receives more events and becomes 1665iteration \- until stopped, that is, or your process receives more events
1124busy. 1666and becomes busy again with higher priority stuff.
1125.PP 1667.PP
1126The most noteworthy effect is that as long as any idle watchers are 1668The most noteworthy effect is that as long as any idle watchers are
1127active, the process will not block when waiting for new events. 1669active, the process will not block when waiting for new events.
1128.PP 1670.PP
1129Apart from keeping your process non-blocking (which is a useful 1671Apart from keeping your process non-blocking (which is a useful
1130effect on its own sometimes), idle watchers are a good place to do 1672effect on its own sometimes), idle watchers are a good place to do
1131\&\*(L"pseudo\-background processing\*(R", or delay processing stuff to after the 1673\&\*(L"pseudo\-background processing\*(R", or delay processing stuff to after the
1132event loop has handled all outstanding events. 1674event loop has handled all outstanding events.
1675.PP
1676\fIWatcher-Specific Functions and Data Members\fR
1677.IX Subsection "Watcher-Specific Functions and Data Members"
1133.IP "ev_idle_init (ev_signal *, callback)" 4 1678.IP "ev_idle_init (ev_signal *, callback)" 4
1134.IX Item "ev_idle_init (ev_signal *, callback)" 1679.IX Item "ev_idle_init (ev_signal *, callback)"
1135Initialises and configures the idle watcher \- it has no parameters of any 1680Initialises and configures the idle watcher \- it has no parameters of any
1136kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless, 1681kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless,
1137believe me. 1682believe me.
1138.PP 1683.PP
1139Example: dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR, start it, and in the 1684Example: Dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR watcher, start it, and in the
1140callback, free it. Alos, use no error checking, as usual. 1685callback, free it. Also, use no error checking, as usual.
1141.PP 1686.PP
1142.Vb 7 1687.Vb 7
1143\& static void 1688\& static void
1144\& idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1689\& idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1145\& { 1690\& {
… …
1152.Vb 3 1697.Vb 3
1153\& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); 1698\& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1154\& ev_idle_init (idle_watcher, idle_cb); 1699\& ev_idle_init (idle_watcher, idle_cb);
1155\& ev_idle_start (loop, idle_cb); 1700\& ev_idle_start (loop, idle_cb);
1156.Ve 1701.Ve
1157.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop" 1702.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop!"
1158.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop" 1703.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!"
1159.IX Subsection "ev_prepare and ev_check - customise your event loop" 1704.IX Subsection "ev_prepare and ev_check - customise your event loop!"
1160Prepare and check watchers are usually (but not always) used in tandem: 1705Prepare and check watchers are usually (but not always) used in tandem:
1161prepare watchers get invoked before the process blocks and check watchers 1706prepare watchers get invoked before the process blocks and check watchers
1162afterwards. 1707afterwards.
1163.PP 1708.PP
1709You \fImust not\fR call \f(CW\*(C`ev_loop\*(C'\fR or similar functions that enter
1710the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR
1711watchers. Other loops than the current one are fine, however. The
1712rationale behind this is that you do not need to check for recursion in
1713those watchers, i.e. the sequence will always be \f(CW\*(C`ev_prepare\*(C'\fR, blocking,
1714\&\f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each kind they will always be
1715called in pairs bracketing the blocking call.
1716.PP
1164Their main purpose is to integrate other event mechanisms into libev. This 1717Their main purpose is to integrate other event mechanisms into libev and
1165could be used, for example, to track variable changes, implement your own 1718their use is somewhat advanced. This could be used, for example, to track
1166watchers, integrate net-snmp or a coroutine library and lots more. 1719variable changes, implement your own watchers, integrate net-snmp or a
1720coroutine library and lots more. They are also occasionally useful if
1721you cache some data and want to flush it before blocking (for example,
1722in X programs you might want to do an \f(CW\*(C`XFlush ()\*(C'\fR in an \f(CW\*(C`ev_prepare\*(C'\fR
1723watcher).
1167.PP 1724.PP
1168This is done by examining in each prepare call which file descriptors need 1725This is done by examining in each prepare call which file descriptors need
1169to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for 1726to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for
1170them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries 1727them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries
1171provide just this functionality). Then, in the check watcher you check for 1728provide just this functionality). Then, in the check watcher you check for
… …
1180are ready to run (it's actually more complicated: it only runs coroutines 1737are ready to run (it's actually more complicated: it only runs coroutines
1181with priority higher than or equal to the event loop and one coroutine 1738with priority higher than or equal to the event loop and one coroutine
1182of lower priority, but only once, using idle watchers to keep the event 1739of lower priority, but only once, using idle watchers to keep the event
1183loop from blocking if lower-priority coroutines are active, thus mapping 1740loop from blocking if lower-priority coroutines are active, thus mapping
1184low-priority coroutines to idle/background tasks). 1741low-priority coroutines to idle/background tasks).
1742.PP
1743It is recommended to give \f(CW\*(C`ev_check\*(C'\fR watchers highest (\f(CW\*(C`EV_MAXPRI\*(C'\fR)
1744priority, to ensure that they are being run before any other watchers
1745after the poll. Also, \f(CW\*(C`ev_check\*(C'\fR watchers (and \f(CW\*(C`ev_prepare\*(C'\fR watchers,
1746too) should not activate (\*(L"feed\*(R") events into libev. While libev fully
1747supports this, they will be called before other \f(CW\*(C`ev_check\*(C'\fR watchers did
1748their job. As \f(CW\*(C`ev_check\*(C'\fR watchers are often used to embed other event
1749loops those other event loops might be in an unusable state until their
1750\&\f(CW\*(C`ev_check\*(C'\fR watcher ran (always remind yourself to coexist peacefully with
1751others).
1752.PP
1753\fIWatcher-Specific Functions and Data Members\fR
1754.IX Subsection "Watcher-Specific Functions and Data Members"
1185.IP "ev_prepare_init (ev_prepare *, callback)" 4 1755.IP "ev_prepare_init (ev_prepare *, callback)" 4
1186.IX Item "ev_prepare_init (ev_prepare *, callback)" 1756.IX Item "ev_prepare_init (ev_prepare *, callback)"
1187.PD 0 1757.PD 0
1188.IP "ev_check_init (ev_check *, callback)" 4 1758.IP "ev_check_init (ev_check *, callback)" 4
1189.IX Item "ev_check_init (ev_check *, callback)" 1759.IX Item "ev_check_init (ev_check *, callback)"
1190.PD 1760.PD
1191Initialises and configures the prepare or check watcher \- they have no 1761Initialises and configures the prepare or check watcher \- they have no
1192parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR 1762parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR
1193macros, but using them is utterly, utterly and completely pointless. 1763macros, but using them is utterly, utterly and completely pointless.
1194.PP 1764.PP
1195Example: *TODO*. 1765There are a number of principal ways to embed other event loops or modules
1766into libev. Here are some ideas on how to include libadns into libev
1767(there is a Perl module named \f(CW\*(C`EV::ADNS\*(C'\fR that does this, which you could
1768use for an actually working example. Another Perl module named \f(CW\*(C`EV::Glib\*(C'\fR
1769embeds a Glib main context into libev, and finally, \f(CW\*(C`Glib::EV\*(C'\fR embeds \s-1EV\s0
1770into the Glib event loop).
1771.PP
1772Method 1: Add \s-1IO\s0 watchers and a timeout watcher in a prepare handler,
1773and in a check watcher, destroy them and call into libadns. What follows
1774is pseudo-code only of course. This requires you to either use a low
1775priority for the check watcher or use \f(CW\*(C`ev_clear_pending\*(C'\fR explicitly, as
1776the callbacks for the IO/timeout watchers might not have been called yet.
1777.PP
1778.Vb 2
1779\& static ev_io iow [nfd];
1780\& static ev_timer tw;
1781.Ve
1782.PP
1783.Vb 4
1784\& static void
1785\& io_cb (ev_loop *loop, ev_io *w, int revents)
1786\& {
1787\& }
1788.Ve
1789.PP
1790.Vb 8
1791\& // create io watchers for each fd and a timer before blocking
1792\& static void
1793\& adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1794\& {
1795\& int timeout = 3600000;
1796\& struct pollfd fds [nfd];
1797\& // actual code will need to loop here and realloc etc.
1798\& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1799.Ve
1800.PP
1801.Vb 3
1802\& /* the callback is illegal, but won't be called as we stop during check */
1803\& ev_timer_init (&tw, 0, timeout * 1e-3);
1804\& ev_timer_start (loop, &tw);
1805.Ve
1806.PP
1807.Vb 6
1808\& // create one ev_io per pollfd
1809\& for (int i = 0; i < nfd; ++i)
1810\& {
1811\& ev_io_init (iow + i, io_cb, fds [i].fd,
1812\& ((fds [i].events & POLLIN ? EV_READ : 0)
1813\& | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1814.Ve
1815.PP
1816.Vb 4
1817\& fds [i].revents = 0;
1818\& ev_io_start (loop, iow + i);
1819\& }
1820\& }
1821.Ve
1822.PP
1823.Vb 5
1824\& // stop all watchers after blocking
1825\& static void
1826\& adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1827\& {
1828\& ev_timer_stop (loop, &tw);
1829.Ve
1830.PP
1831.Vb 8
1832\& for (int i = 0; i < nfd; ++i)
1833\& {
1834\& // set the relevant poll flags
1835\& // could also call adns_processreadable etc. here
1836\& struct pollfd *fd = fds + i;
1837\& int revents = ev_clear_pending (iow + i);
1838\& if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1839\& if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1840.Ve
1841.PP
1842.Vb 3
1843\& // now stop the watcher
1844\& ev_io_stop (loop, iow + i);
1845\& }
1846.Ve
1847.PP
1848.Vb 2
1849\& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1850\& }
1851.Ve
1852.PP
1853Method 2: This would be just like method 1, but you run \f(CW\*(C`adns_afterpoll\*(C'\fR
1854in the prepare watcher and would dispose of the check watcher.
1855.PP
1856Method 3: If the module to be embedded supports explicit event
1857notification (adns does), you can also make use of the actual watcher
1858callbacks, and only destroy/create the watchers in the prepare watcher.
1859.PP
1860.Vb 5
1861\& static void
1862\& timer_cb (EV_P_ ev_timer *w, int revents)
1863\& {
1864\& adns_state ads = (adns_state)w->data;
1865\& update_now (EV_A);
1866.Ve
1867.PP
1868.Vb 2
1869\& adns_processtimeouts (ads, &tv_now);
1870\& }
1871.Ve
1872.PP
1873.Vb 5
1874\& static void
1875\& io_cb (EV_P_ ev_io *w, int revents)
1876\& {
1877\& adns_state ads = (adns_state)w->data;
1878\& update_now (EV_A);
1879.Ve
1880.PP
1881.Vb 3
1882\& if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1883\& if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1884\& }
1885.Ve
1886.PP
1887.Vb 1
1888\& // do not ever call adns_afterpoll
1889.Ve
1890.PP
1891Method 4: Do not use a prepare or check watcher because the module you
1892want to embed is too inflexible to support it. Instead, youc na override
1893their poll function. The drawback with this solution is that the main
1894loop is now no longer controllable by \s-1EV\s0. The \f(CW\*(C`Glib::EV\*(C'\fR module does
1895this.
1896.PP
1897.Vb 4
1898\& static gint
1899\& event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1900\& {
1901\& int got_events = 0;
1902.Ve
1903.PP
1904.Vb 2
1905\& for (n = 0; n < nfds; ++n)
1906\& // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1907.Ve
1908.PP
1909.Vb 2
1910\& if (timeout >= 0)
1911\& // create/start timer
1912.Ve
1913.PP
1914.Vb 2
1915\& // poll
1916\& ev_loop (EV_A_ 0);
1917.Ve
1918.PP
1919.Vb 3
1920\& // stop timer again
1921\& if (timeout >= 0)
1922\& ev_timer_stop (EV_A_ &to);
1923.Ve
1924.PP
1925.Vb 3
1926\& // stop io watchers again - their callbacks should have set
1927\& for (n = 0; n < nfds; ++n)
1928\& ev_io_stop (EV_A_ iow [n]);
1929.Ve
1930.PP
1931.Vb 2
1932\& return got_events;
1933\& }
1934.Ve
1935.ie n .Sh """ev_embed"" \- when one backend isn't enough..."
1936.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..."
1937.IX Subsection "ev_embed - when one backend isn't enough..."
1938This is a rather advanced watcher type that lets you embed one event loop
1939into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded
1940loop, other types of watchers might be handled in a delayed or incorrect
1941fashion and must not be used). (See portability notes, below).
1942.PP
1943There are primarily two reasons you would want that: work around bugs and
1944prioritise I/O.
1945.PP
1946As an example for a bug workaround, the kqueue backend might only support
1947sockets on some platform, so it is unusable as generic backend, but you
1948still want to make use of it because you have many sockets and it scales
1949so nicely. In this case, you would create a kqueue-based loop and embed it
1950into your default loop (which might use e.g. poll). Overall operation will
1951be a bit slower because first libev has to poll and then call kevent, but
1952at least you can use both at what they are best.
1953.PP
1954As for prioritising I/O: rarely you have the case where some fds have
1955to be watched and handled very quickly (with low latency), and even
1956priorities and idle watchers might have too much overhead. In this case
1957you would put all the high priority stuff in one loop and all the rest in
1958a second one, and embed the second one in the first.
1959.PP
1960As long as the watcher is active, the callback will be invoked every time
1961there might be events pending in the embedded loop. The callback must then
1962call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single sweep and invoke
1963their callbacks (you could also start an idle watcher to give the embedded
1964loop strictly lower priority for example). You can also set the callback
1965to \f(CW0\fR, in which case the embed watcher will automatically execute the
1966embedded loop sweep.
1967.PP
1968As long as the watcher is started it will automatically handle events. The
1969callback will be invoked whenever some events have been handled. You can
1970set the callback to \f(CW0\fR to avoid having to specify one if you are not
1971interested in that.
1972.PP
1973Also, there have not currently been made special provisions for forking:
1974when you fork, you not only have to call \f(CW\*(C`ev_loop_fork\*(C'\fR on both loops,
1975but you will also have to stop and restart any \f(CW\*(C`ev_embed\*(C'\fR watchers
1976yourself.
1977.PP
1978Unfortunately, not all backends are embeddable, only the ones returned by
1979\&\f(CW\*(C`ev_embeddable_backends\*(C'\fR are, which, unfortunately, does not include any
1980portable one.
1981.PP
1982So when you want to use this feature you will always have to be prepared
1983that you cannot get an embeddable loop. The recommended way to get around
1984this is to have a separate variables for your embeddable loop, try to
1985create it, and if that fails, use the normal loop for everything:
1986.PP
1987.Vb 3
1988\& struct ev_loop *loop_hi = ev_default_init (0);
1989\& struct ev_loop *loop_lo = 0;
1990\& struct ev_embed embed;
1991.Ve
1992.PP
1993.Vb 5
1994\& // see if there is a chance of getting one that works
1995\& // (remember that a flags value of 0 means autodetection)
1996\& loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1997\& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1998\& : 0;
1999.Ve
2000.PP
2001.Vb 8
2002\& // if we got one, then embed it, otherwise default to loop_hi
2003\& if (loop_lo)
2004\& {
2005\& ev_embed_init (&embed, 0, loop_lo);
2006\& ev_embed_start (loop_hi, &embed);
2007\& }
2008\& else
2009\& loop_lo = loop_hi;
2010.Ve
2011.Sh "Portability notes"
2012.IX Subsection "Portability notes"
2013Kqueue is nominally embeddable, but this is broken on all BSDs that I
2014tried, in various ways. Usually the embedded event loop will simply never
2015receive events, sometimes it will only trigger a few times, sometimes in a
2016loop. Epoll is also nominally embeddable, but many Linux kernel versions
2017will always eport the epoll fd as ready, even when no events are pending.
2018.PP
2019While libev allows embedding these backends (they are contained in
2020\&\f(CW\*(C`ev_embeddable_backends ()\*(C'\fR), take extreme care that it will actually
2021work.
2022.PP
2023When in doubt, create a dynamic event loop forced to use sockets (this
2024usually works) and possibly another thread and a pipe or so to report to
2025your main event loop.
2026.PP
2027\fIWatcher-Specific Functions and Data Members\fR
2028.IX Subsection "Watcher-Specific Functions and Data Members"
2029.IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
2030.IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)"
2031.PD 0
2032.IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
2033.IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)"
2034.PD
2035Configures the watcher to embed the given loop, which must be
2036embeddable. If the callback is \f(CW0\fR, then \f(CW\*(C`ev_embed_sweep\*(C'\fR will be
2037invoked automatically, otherwise it is the responsibility of the callback
2038to invoke it (it will continue to be called until the sweep has been done,
2039if you do not want thta, you need to temporarily stop the embed watcher).
2040.IP "ev_embed_sweep (loop, ev_embed *)" 4
2041.IX Item "ev_embed_sweep (loop, ev_embed *)"
2042Make a single, non-blocking sweep over the embedded loop. This works
2043similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most
2044apropriate way for embedded loops.
2045.IP "struct ev_loop *other [read\-only]" 4
2046.IX Item "struct ev_loop *other [read-only]"
2047The embedded event loop.
2048.ie n .Sh """ev_fork"" \- the audacity to resume the event loop after a fork"
2049.el .Sh "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork"
2050.IX Subsection "ev_fork - the audacity to resume the event loop after a fork"
2051Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because
2052whoever is a good citizen cared to tell libev about it by calling
2053\&\f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the
2054event loop blocks next and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called,
2055and only in the child after the fork. If whoever good citizen calling
2056\&\f(CW\*(C`ev_default_fork\*(C'\fR cheats and calls it in the wrong process, the fork
2057handlers will be invoked, too, of course.
2058.PP
2059\fIWatcher-Specific Functions and Data Members\fR
2060.IX Subsection "Watcher-Specific Functions and Data Members"
2061.IP "ev_fork_init (ev_signal *, callback)" 4
2062.IX Item "ev_fork_init (ev_signal *, callback)"
2063Initialises and configures the fork watcher \- it has no parameters of any
2064kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless,
2065believe me.
1196.SH "OTHER FUNCTIONS" 2066.SH "OTHER FUNCTIONS"
1197.IX Header "OTHER FUNCTIONS" 2067.IX Header "OTHER FUNCTIONS"
1198There are some other functions of possible interest. Described. Here. Now. 2068There are some other functions of possible interest. Described. Here. Now.
1199.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4 2069.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4
1200.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 2070.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)"
… …
1229.Ve 2099.Ve
1230.Sp 2100.Sp
1231.Vb 1 2101.Vb 1
1232\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); 2102\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1233.Ve 2103.Ve
1234.IP "ev_feed_event (loop, watcher, int events)" 4 2104.IP "ev_feed_event (ev_loop *, watcher *, int revents)" 4
1235.IX Item "ev_feed_event (loop, watcher, int events)" 2105.IX Item "ev_feed_event (ev_loop *, watcher *, int revents)"
1236Feeds the given event set into the event loop, as if the specified event 2106Feeds the given event set into the event loop, as if the specified event
1237had happened for the specified watcher (which must be a pointer to an 2107had happened for the specified watcher (which must be a pointer to an
1238initialised but not necessarily started event watcher). 2108initialised but not necessarily started event watcher).
1239.IP "ev_feed_fd_event (loop, int fd, int revents)" 4 2109.IP "ev_feed_fd_event (ev_loop *, int fd, int revents)" 4
1240.IX Item "ev_feed_fd_event (loop, int fd, int revents)" 2110.IX Item "ev_feed_fd_event (ev_loop *, int fd, int revents)"
1241Feed an event on the given fd, as if a file descriptor backend detected 2111Feed an event on the given fd, as if a file descriptor backend detected
1242the given events it. 2112the given events it.
1243.IP "ev_feed_signal_event (loop, int signum)" 4 2113.IP "ev_feed_signal_event (ev_loop *loop, int signum)" 4
1244.IX Item "ev_feed_signal_event (loop, int signum)" 2114.IX Item "ev_feed_signal_event (ev_loop *loop, int signum)"
1245Feed an event as if the given signal occured (loop must be the default loop!). 2115Feed an event as if the given signal occured (\f(CW\*(C`loop\*(C'\fR must be the default
2116loop!).
1246.SH "LIBEVENT EMULATION" 2117.SH "LIBEVENT EMULATION"
1247.IX Header "LIBEVENT EMULATION" 2118.IX Header "LIBEVENT EMULATION"
1248Libev offers a compatibility emulation layer for libevent. It cannot 2119Libev offers a compatibility emulation layer for libevent. It cannot
1249emulate the internals of libevent, so here are some usage hints: 2120emulate the internals of libevent, so here are some usage hints:
1250.IP "* Use it by including <event.h>, as usual." 4 2121.IP "* Use it by including <event.h>, as usual." 4
… …
1261.IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4 2132.IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4
1262.IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library." 2133.IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library."
1263.PD 2134.PD
1264.SH "\*(C+ SUPPORT" 2135.SH "\*(C+ SUPPORT"
1265.IX Header " SUPPORT" 2136.IX Header " SUPPORT"
1266\&\s-1TBD\s0. 2137Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow
2138you to use some convinience methods to start/stop watchers and also change
2139the callback model to a model using method callbacks on objects.
2140.PP
2141To use it,
2142.PP
2143.Vb 1
2144\& #include <ev++.h>
2145.Ve
2146.PP
2147This automatically includes \fIev.h\fR and puts all of its definitions (many
2148of them macros) into the global namespace. All \*(C+ specific things are
2149put into the \f(CW\*(C`ev\*(C'\fR namespace. It should support all the same embedding
2150options as \fIev.h\fR, most notably \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR.
2151.PP
2152Care has been taken to keep the overhead low. The only data member the \*(C+
2153classes add (compared to plain C\-style watchers) is the event loop pointer
2154that the watcher is associated with (or no additional members at all if
2155you disable \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR when embedding libev).
2156.PP
2157Currently, functions, and static and non-static member functions can be
2158used as callbacks. Other types should be easy to add as long as they only
2159need one additional pointer for context. If you need support for other
2160types of functors please contact the author (preferably after implementing
2161it).
2162.PP
2163Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace:
2164.ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4
2165.el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4
2166.IX Item "ev::READ, ev::WRITE etc."
2167These are just enum values with the same values as the \f(CW\*(C`EV_READ\*(C'\fR etc.
2168macros from \fIev.h\fR.
2169.ie n .IP """ev::tstamp""\fR, \f(CW""ev::now""" 4
2170.el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4
2171.IX Item "ev::tstamp, ev::now"
2172Aliases to the same types/functions as with the \f(CW\*(C`ev_\*(C'\fR prefix.
2173.ie n .IP """ev::io""\fR, \f(CW""ev::timer""\fR, \f(CW""ev::periodic""\fR, \f(CW""ev::idle""\fR, \f(CW""ev::sig"" etc." 4
2174.el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4
2175.IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc."
2176For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of
2177the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR
2178which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro
2179defines by many implementations.
2180.Sp
2181All of those classes have these methods:
2182.RS 4
2183.IP "ev::TYPE::TYPE ()" 4
2184.IX Item "ev::TYPE::TYPE ()"
2185.PD 0
2186.IP "ev::TYPE::TYPE (struct ev_loop *)" 4
2187.IX Item "ev::TYPE::TYPE (struct ev_loop *)"
2188.IP "ev::TYPE::~TYPE" 4
2189.IX Item "ev::TYPE::~TYPE"
2190.PD
2191The constructor (optionally) takes an event loop to associate the watcher
2192with. If it is omitted, it will use \f(CW\*(C`EV_DEFAULT\*(C'\fR.
2193.Sp
2194The constructor calls \f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the
2195\&\f(CW\*(C`set\*(C'\fR method before starting it.
2196.Sp
2197It will not set a callback, however: You have to call the templated \f(CW\*(C`set\*(C'\fR
2198method to set a callback before you can start the watcher.
2199.Sp
2200(The reason why you have to use a method is a limitation in \*(C+ which does
2201not allow explicit template arguments for constructors).
2202.Sp
2203The destructor automatically stops the watcher if it is active.
2204.IP "w\->set<class, &class::method> (object *)" 4
2205.IX Item "w->set<class, &class::method> (object *)"
2206This method sets the callback method to call. The method has to have a
2207signature of \f(CW\*(C`void (*)(ev_TYPE &, int)\*(C'\fR, it receives the watcher as
2208first argument and the \f(CW\*(C`revents\*(C'\fR as second. The object must be given as
2209parameter and is stored in the \f(CW\*(C`data\*(C'\fR member of the watcher.
2210.Sp
2211This method synthesizes efficient thunking code to call your method from
2212the C callback that libev requires. If your compiler can inline your
2213callback (i.e. it is visible to it at the place of the \f(CW\*(C`set\*(C'\fR call and
2214your compiler is good :), then the method will be fully inlined into the
2215thunking function, making it as fast as a direct C callback.
2216.Sp
2217Example: simple class declaration and watcher initialisation
2218.Sp
2219.Vb 4
2220\& struct myclass
2221\& {
2222\& void io_cb (ev::io &w, int revents) { }
2223\& }
2224.Ve
2225.Sp
2226.Vb 3
2227\& myclass obj;
2228\& ev::io iow;
2229\& iow.set <myclass, &myclass::io_cb> (&obj);
2230.Ve
2231.IP "w\->set<function> (void *data = 0)" 4
2232.IX Item "w->set<function> (void *data = 0)"
2233Also sets a callback, but uses a static method or plain function as
2234callback. The optional \f(CW\*(C`data\*(C'\fR argument will be stored in the watcher's
2235\&\f(CW\*(C`data\*(C'\fR member and is free for you to use.
2236.Sp
2237The prototype of the \f(CW\*(C`function\*(C'\fR must be \f(CW\*(C`void (*)(ev::TYPE &w, int)\*(C'\fR.
2238.Sp
2239See the method\-\f(CW\*(C`set\*(C'\fR above for more details.
2240.Sp
2241Example:
2242.Sp
2243.Vb 2
2244\& static void io_cb (ev::io &w, int revents) { }
2245\& iow.set <io_cb> ();
2246.Ve
2247.IP "w\->set (struct ev_loop *)" 4
2248.IX Item "w->set (struct ev_loop *)"
2249Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only
2250do this when the watcher is inactive (and not pending either).
2251.IP "w\->set ([args])" 4
2252.IX Item "w->set ([args])"
2253Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same args. Must be
2254called at least once. Unlike the C counterpart, an active watcher gets
2255automatically stopped and restarted when reconfiguring it with this
2256method.
2257.IP "w\->start ()" 4
2258.IX Item "w->start ()"
2259Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the
2260constructor already stores the event loop.
2261.IP "w\->stop ()" 4
2262.IX Item "w->stop ()"
2263Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument.
2264.ie n .IP "w\->again () (""ev::timer""\fR, \f(CW""ev::periodic"" only)" 4
2265.el .IP "w\->again () (\f(CWev::timer\fR, \f(CWev::periodic\fR only)" 4
2266.IX Item "w->again () (ev::timer, ev::periodic only)"
2267For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding
2268\&\f(CW\*(C`ev_TYPE_again\*(C'\fR function.
2269.ie n .IP "w\->sweep () (""ev::embed"" only)" 4
2270.el .IP "w\->sweep () (\f(CWev::embed\fR only)" 4
2271.IX Item "w->sweep () (ev::embed only)"
2272Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR.
2273.ie n .IP "w\->update () (""ev::stat"" only)" 4
2274.el .IP "w\->update () (\f(CWev::stat\fR only)" 4
2275.IX Item "w->update () (ev::stat only)"
2276Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR.
2277.RE
2278.RS 4
2279.RE
2280.PP
2281Example: Define a class with an \s-1IO\s0 and idle watcher, start one of them in
2282the constructor.
2283.PP
2284.Vb 4
2285\& class myclass
2286\& {
2287\& ev_io io; void io_cb (ev::io &w, int revents);
2288\& ev_idle idle void idle_cb (ev::idle &w, int revents);
2289.Ve
2290.PP
2291.Vb 2
2292\& myclass ();
2293\& }
2294.Ve
2295.PP
2296.Vb 4
2297\& myclass::myclass (int fd)
2298\& {
2299\& io .set <myclass, &myclass::io_cb > (this);
2300\& idle.set <myclass, &myclass::idle_cb> (this);
2301.Ve
2302.PP
2303.Vb 2
2304\& io.start (fd, ev::READ);
2305\& }
2306.Ve
2307.SH "MACRO MAGIC"
2308.IX Header "MACRO MAGIC"
2309Libev can be compiled with a variety of options, the most fundamantal
2310of which is \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most)
2311functions and callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument.
2312.PP
2313To make it easier to write programs that cope with either variant, the
2314following macros are defined:
2315.ie n .IP """EV_A""\fR, \f(CW""EV_A_""" 4
2316.el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4
2317.IX Item "EV_A, EV_A_"
2318This provides the loop \fIargument\fR for functions, if one is required (\*(L"ev
2319loop argument\*(R"). The \f(CW\*(C`EV_A\*(C'\fR form is used when this is the sole argument,
2320\&\f(CW\*(C`EV_A_\*(C'\fR is used when other arguments are following. Example:
2321.Sp
2322.Vb 3
2323\& ev_unref (EV_A);
2324\& ev_timer_add (EV_A_ watcher);
2325\& ev_loop (EV_A_ 0);
2326.Ve
2327.Sp
2328It assumes the variable \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR is in scope,
2329which is often provided by the following macro.
2330.ie n .IP """EV_P""\fR, \f(CW""EV_P_""" 4
2331.el .IP "\f(CWEV_P\fR, \f(CWEV_P_\fR" 4
2332.IX Item "EV_P, EV_P_"
2333This provides the loop \fIparameter\fR for functions, if one is required (\*(L"ev
2334loop parameter\*(R"). The \f(CW\*(C`EV_P\*(C'\fR form is used when this is the sole parameter,
2335\&\f(CW\*(C`EV_P_\*(C'\fR is used when other parameters are following. Example:
2336.Sp
2337.Vb 2
2338\& // this is how ev_unref is being declared
2339\& static void ev_unref (EV_P);
2340.Ve
2341.Sp
2342.Vb 2
2343\& // this is how you can declare your typical callback
2344\& static void cb (EV_P_ ev_timer *w, int revents)
2345.Ve
2346.Sp
2347It declares a parameter \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR, quite
2348suitable for use with \f(CW\*(C`EV_A\*(C'\fR.
2349.ie n .IP """EV_DEFAULT""\fR, \f(CW""EV_DEFAULT_""" 4
2350.el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4
2351.IX Item "EV_DEFAULT, EV_DEFAULT_"
2352Similar to the other two macros, this gives you the value of the default
2353loop, if multiple loops are supported (\*(L"ev loop default\*(R").
2354.PP
2355Example: Declare and initialise a check watcher, utilising the above
2356macros so it will work regardless of whether multiple loops are supported
2357or not.
2358.PP
2359.Vb 5
2360\& static void
2361\& check_cb (EV_P_ ev_timer *w, int revents)
2362\& {
2363\& ev_check_stop (EV_A_ w);
2364\& }
2365.Ve
2366.PP
2367.Vb 4
2368\& ev_check check;
2369\& ev_check_init (&check, check_cb);
2370\& ev_check_start (EV_DEFAULT_ &check);
2371\& ev_loop (EV_DEFAULT_ 0);
2372.Ve
2373.SH "EMBEDDING"
2374.IX Header "EMBEDDING"
2375Libev can (and often is) directly embedded into host
2376applications. Examples of applications that embed it include the Deliantra
2377Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe)
2378and rxvt\-unicode.
2379.PP
2380The goal is to enable you to just copy the necessary files into your
2381source directory without having to change even a single line in them, so
2382you can easily upgrade by simply copying (or having a checked-out copy of
2383libev somewhere in your source tree).
2384.Sh "\s-1FILESETS\s0"
2385.IX Subsection "FILESETS"
2386Depending on what features you need you need to include one or more sets of files
2387in your app.
2388.PP
2389\fI\s-1CORE\s0 \s-1EVENT\s0 \s-1LOOP\s0\fR
2390.IX Subsection "CORE EVENT LOOP"
2391.PP
2392To include only the libev core (all the \f(CW\*(C`ev_*\*(C'\fR functions), with manual
2393configuration (no autoconf):
2394.PP
2395.Vb 2
2396\& #define EV_STANDALONE 1
2397\& #include "ev.c"
2398.Ve
2399.PP
2400This will automatically include \fIev.h\fR, too, and should be done in a
2401single C source file only to provide the function implementations. To use
2402it, do the same for \fIev.h\fR in all files wishing to use this \s-1API\s0 (best
2403done by writing a wrapper around \fIev.h\fR that you can include instead and
2404where you can put other configuration options):
2405.PP
2406.Vb 2
2407\& #define EV_STANDALONE 1
2408\& #include "ev.h"
2409.Ve
2410.PP
2411Both header files and implementation files can be compiled with a \*(C+
2412compiler (at least, thats a stated goal, and breakage will be treated
2413as a bug).
2414.PP
2415You need the following files in your source tree, or in a directory
2416in your include path (e.g. in libev/ when using \-Ilibev):
2417.PP
2418.Vb 4
2419\& ev.h
2420\& ev.c
2421\& ev_vars.h
2422\& ev_wrap.h
2423.Ve
2424.PP
2425.Vb 1
2426\& ev_win32.c required on win32 platforms only
2427.Ve
2428.PP
2429.Vb 5
2430\& ev_select.c only when select backend is enabled (which is enabled by default)
2431\& ev_poll.c only when poll backend is enabled (disabled by default)
2432\& ev_epoll.c only when the epoll backend is enabled (disabled by default)
2433\& ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2434\& ev_port.c only when the solaris port backend is enabled (disabled by default)
2435.Ve
2436.PP
2437\&\fIev.c\fR includes the backend files directly when enabled, so you only need
2438to compile this single file.
2439.PP
2440\fI\s-1LIBEVENT\s0 \s-1COMPATIBILITY\s0 \s-1API\s0\fR
2441.IX Subsection "LIBEVENT COMPATIBILITY API"
2442.PP
2443To include the libevent compatibility \s-1API\s0, also include:
2444.PP
2445.Vb 1
2446\& #include "event.c"
2447.Ve
2448.PP
2449in the file including \fIev.c\fR, and:
2450.PP
2451.Vb 1
2452\& #include "event.h"
2453.Ve
2454.PP
2455in the files that want to use the libevent \s-1API\s0. This also includes \fIev.h\fR.
2456.PP
2457You need the following additional files for this:
2458.PP
2459.Vb 2
2460\& event.h
2461\& event.c
2462.Ve
2463.PP
2464\fI\s-1AUTOCONF\s0 \s-1SUPPORT\s0\fR
2465.IX Subsection "AUTOCONF SUPPORT"
2466.PP
2467Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your config in
2468whatever way you want, you can also \f(CW\*(C`m4_include([libev.m4])\*(C'\fR in your
2469\&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR undefined. \fIev.c\fR will then
2470include \fIconfig.h\fR and configure itself accordingly.
2471.PP
2472For this of course you need the m4 file:
2473.PP
2474.Vb 1
2475\& libev.m4
2476.Ve
2477.Sh "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0"
2478.IX Subsection "PREPROCESSOR SYMBOLS/MACROS"
2479Libev can be configured via a variety of preprocessor symbols you have to define
2480before including any of its files. The default is not to build for multiplicity
2481and only include the select backend.
2482.IP "\s-1EV_STANDALONE\s0" 4
2483.IX Item "EV_STANDALONE"
2484Must always be \f(CW1\fR if you do not use autoconf configuration, which
2485keeps libev from including \fIconfig.h\fR, and it also defines dummy
2486implementations for some libevent functions (such as logging, which is not
2487supported). It will also not define any of the structs usually found in
2488\&\fIevent.h\fR that are not directly supported by the libev core alone.
2489.IP "\s-1EV_USE_MONOTONIC\s0" 4
2490.IX Item "EV_USE_MONOTONIC"
2491If defined to be \f(CW1\fR, libev will try to detect the availability of the
2492monotonic clock option at both compiletime and runtime. Otherwise no use
2493of the monotonic clock option will be attempted. If you enable this, you
2494usually have to link against librt or something similar. Enabling it when
2495the functionality isn't available is safe, though, although you have
2496to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR
2497function is hiding in (often \fI\-lrt\fR).
2498.IP "\s-1EV_USE_REALTIME\s0" 4
2499.IX Item "EV_USE_REALTIME"
2500If defined to be \f(CW1\fR, libev will try to detect the availability of the
2501realtime clock option at compiletime (and assume its availability at
2502runtime if successful). Otherwise no use of the realtime clock option will
2503be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get
2504(CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See the
2505note about libraries in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though.
2506.IP "\s-1EV_USE_SELECT\s0" 4
2507.IX Item "EV_USE_SELECT"
2508If undefined or defined to be \f(CW1\fR, libev will compile in support for the
2509\&\f(CW\*(C`select\*(C'\fR(2) backend. No attempt at autodetection will be done: if no
2510other method takes over, select will be it. Otherwise the select backend
2511will not be compiled in.
2512.IP "\s-1EV_SELECT_USE_FD_SET\s0" 4
2513.IX Item "EV_SELECT_USE_FD_SET"
2514If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR
2515structure. This is useful if libev doesn't compile due to a missing
2516\&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it misguesses the bitset layout on
2517exotic systems. This usually limits the range of file descriptors to some
2518low limit such as 1024 or might have other limitations (winsocket only
2519allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation, might
2520influence the size of the \f(CW\*(C`fd_set\*(C'\fR used.
2521.IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4
2522.IX Item "EV_SELECT_IS_WINSOCKET"
2523When defined to \f(CW1\fR, the select backend will assume that
2524select/socket/connect etc. don't understand file descriptors but
2525wants osf handles on win32 (this is the case when the select to
2526be used is the winsock select). This means that it will call
2527\&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise,
2528it is assumed that all these functions actually work on fds, even
2529on win32. Should not be defined on non\-win32 platforms.
2530.IP "\s-1EV_USE_POLL\s0" 4
2531.IX Item "EV_USE_POLL"
2532If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2)
2533backend. Otherwise it will be enabled on non\-win32 platforms. It
2534takes precedence over select.
2535.IP "\s-1EV_USE_EPOLL\s0" 4
2536.IX Item "EV_USE_EPOLL"
2537If defined to be \f(CW1\fR, libev will compile in support for the Linux
2538\&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime,
2539otherwise another method will be used as fallback. This is the
2540preferred backend for GNU/Linux systems.
2541.IP "\s-1EV_USE_KQUEUE\s0" 4
2542.IX Item "EV_USE_KQUEUE"
2543If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style
2544\&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime,
2545otherwise another method will be used as fallback. This is the preferred
2546backend for \s-1BSD\s0 and BSD-like systems, although on most BSDs kqueue only
2547supports some types of fds correctly (the only platform we found that
2548supports ptys for example was NetBSD), so kqueue might be compiled in, but
2549not be used unless explicitly requested. The best way to use it is to find
2550out whether kqueue supports your type of fd properly and use an embedded
2551kqueue loop.
2552.IP "\s-1EV_USE_PORT\s0" 4
2553.IX Item "EV_USE_PORT"
2554If defined to be \f(CW1\fR, libev will compile in support for the Solaris
255510 port style backend. Its availability will be detected at runtime,
2556otherwise another method will be used as fallback. This is the preferred
2557backend for Solaris 10 systems.
2558.IP "\s-1EV_USE_DEVPOLL\s0" 4
2559.IX Item "EV_USE_DEVPOLL"
2560reserved for future expansion, works like the \s-1USE\s0 symbols above.
2561.IP "\s-1EV_USE_INOTIFY\s0" 4
2562.IX Item "EV_USE_INOTIFY"
2563If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify
2564interface to speed up \f(CW\*(C`ev_stat\*(C'\fR watchers. Its actual availability will
2565be detected at runtime.
2566.IP "\s-1EV_H\s0" 4
2567.IX Item "EV_H"
2568The name of the \fIev.h\fR header file used to include it. The default if
2569undefined is \f(CW\*(C`<ev.h>\*(C'\fR in \fIevent.h\fR and \f(CW"ev.h"\fR in \fIev.c\fR. This
2570can be used to virtually rename the \fIev.h\fR header file in case of conflicts.
2571.IP "\s-1EV_CONFIG_H\s0" 4
2572.IX Item "EV_CONFIG_H"
2573If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override
2574\&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to
2575\&\f(CW\*(C`EV_H\*(C'\fR, above.
2576.IP "\s-1EV_EVENT_H\s0" 4
2577.IX Item "EV_EVENT_H"
2578Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea
2579of how the \fIevent.h\fR header can be found.
2580.IP "\s-1EV_PROTOTYPES\s0" 4
2581.IX Item "EV_PROTOTYPES"
2582If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function
2583prototypes, but still define all the structs and other symbols. This is
2584occasionally useful if you want to provide your own wrapper functions
2585around libev functions.
2586.IP "\s-1EV_MULTIPLICITY\s0" 4
2587.IX Item "EV_MULTIPLICITY"
2588If undefined or defined to \f(CW1\fR, then all event-loop-specific functions
2589will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create
2590additional independent event loops. Otherwise there will be no support
2591for multiple event loops and there is no first event loop pointer
2592argument. Instead, all functions act on the single default loop.
2593.IP "\s-1EV_MINPRI\s0" 4
2594.IX Item "EV_MINPRI"
2595.PD 0
2596.IP "\s-1EV_MAXPRI\s0" 4
2597.IX Item "EV_MAXPRI"
2598.PD
2599The range of allowed priorities. \f(CW\*(C`EV_MINPRI\*(C'\fR must be smaller or equal to
2600\&\f(CW\*(C`EV_MAXPRI\*(C'\fR, but otherwise there are no non-obvious limitations. You can
2601provide for more priorities by overriding those symbols (usually defined
2602to be \f(CW\*(C`\-2\*(C'\fR and \f(CW2\fR, respectively).
2603.Sp
2604When doing priority-based operations, libev usually has to linearly search
2605all the priorities, so having many of them (hundreds) uses a lot of space
2606and time, so using the defaults of five priorities (\-2 .. +2) is usually
2607fine.
2608.Sp
2609If your embedding app does not need any priorities, defining these both to
2610\&\f(CW0\fR will save some memory and cpu.
2611.IP "\s-1EV_PERIODIC_ENABLE\s0" 4
2612.IX Item "EV_PERIODIC_ENABLE"
2613If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If
2614defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
2615code.
2616.IP "\s-1EV_IDLE_ENABLE\s0" 4
2617.IX Item "EV_IDLE_ENABLE"
2618If undefined or defined to be \f(CW1\fR, then idle watchers are supported. If
2619defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
2620code.
2621.IP "\s-1EV_EMBED_ENABLE\s0" 4
2622.IX Item "EV_EMBED_ENABLE"
2623If undefined or defined to be \f(CW1\fR, then embed watchers are supported. If
2624defined to be \f(CW0\fR, then they are not.
2625.IP "\s-1EV_STAT_ENABLE\s0" 4
2626.IX Item "EV_STAT_ENABLE"
2627If undefined or defined to be \f(CW1\fR, then stat watchers are supported. If
2628defined to be \f(CW0\fR, then they are not.
2629.IP "\s-1EV_FORK_ENABLE\s0" 4
2630.IX Item "EV_FORK_ENABLE"
2631If undefined or defined to be \f(CW1\fR, then fork watchers are supported. If
2632defined to be \f(CW0\fR, then they are not.
2633.IP "\s-1EV_MINIMAL\s0" 4
2634.IX Item "EV_MINIMAL"
2635If you need to shave off some kilobytes of code at the expense of some
2636speed, define this symbol to \f(CW1\fR. Currently only used for gcc to override
2637some inlining decisions, saves roughly 30% codesize of amd64.
2638.IP "\s-1EV_PID_HASHSIZE\s0" 4
2639.IX Item "EV_PID_HASHSIZE"
2640\&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by
2641pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), usually more
2642than enough. If you need to manage thousands of children you might want to
2643increase this value (\fImust\fR be a power of two).
2644.IP "\s-1EV_INOTIFY_HASHSIZE\s0" 4
2645.IX Item "EV_INOTIFY_HASHSIZE"
2646\&\f(CW\*(C`ev_staz\*(C'\fR watchers use a small hash table to distribute workload by
2647inotify watch id. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR),
2648usually more than enough. If you need to manage thousands of \f(CW\*(C`ev_stat\*(C'\fR
2649watchers you might want to increase this value (\fImust\fR be a power of
2650two).
2651.IP "\s-1EV_COMMON\s0" 4
2652.IX Item "EV_COMMON"
2653By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining
2654this macro to a something else you can include more and other types of
2655members. You have to define it each time you include one of the files,
2656though, and it must be identical each time.
2657.Sp
2658For example, the perl \s-1EV\s0 module uses something like this:
2659.Sp
2660.Vb 3
2661\& #define EV_COMMON \e
2662\& SV *self; /* contains this struct */ \e
2663\& SV *cb_sv, *fh /* note no trailing ";" */
2664.Ve
2665.IP "\s-1EV_CB_DECLARE\s0 (type)" 4
2666.IX Item "EV_CB_DECLARE (type)"
2667.PD 0
2668.IP "\s-1EV_CB_INVOKE\s0 (watcher, revents)" 4
2669.IX Item "EV_CB_INVOKE (watcher, revents)"
2670.IP "ev_set_cb (ev, cb)" 4
2671.IX Item "ev_set_cb (ev, cb)"
2672.PD
2673Can be used to change the callback member declaration in each watcher,
2674and the way callbacks are invoked and set. Must expand to a struct member
2675definition and a statement, respectively. See the \fIev.h\fR header file for
2676their default definitions. One possible use for overriding these is to
2677avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use
2678method calls instead of plain function calls in \*(C+.
2679.Sh "\s-1EXPORTED\s0 \s-1API\s0 \s-1SYMBOLS\s0"
2680.IX Subsection "EXPORTED API SYMBOLS"
2681If you need to re-export the \s-1API\s0 (e.g. via a dll) and you need a list of
2682exported symbols, you can use the provided \fISymbol.*\fR files which list
2683all public symbols, one per line:
2684.Sp
2685.Vb 2
2686\& Symbols.ev for libev proper
2687\& Symbols.event for the libevent emulation
2688.Ve
2689.Sp
2690This can also be used to rename all public symbols to avoid clashes with
2691multiple versions of libev linked together (which is obviously bad in
2692itself, but sometimes it is inconvinient to avoid this).
2693.Sp
2694A sed command like this will create wrapper \f(CW\*(C`#define\*(C'\fR's that you need to
2695include before including \fIev.h\fR:
2696.Sp
2697.Vb 1
2698\& <Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
2699.Ve
2700.Sp
2701This would create a file \fIwrap.h\fR which essentially looks like this:
2702.Sp
2703.Vb 4
2704\& #define ev_backend myprefix_ev_backend
2705\& #define ev_check_start myprefix_ev_check_start
2706\& #define ev_check_stop myprefix_ev_check_stop
2707\& ...
2708.Ve
2709.Sh "\s-1EXAMPLES\s0"
2710.IX Subsection "EXAMPLES"
2711For a real-world example of a program the includes libev
2712verbatim, you can have a look at the \s-1EV\s0 perl module
2713(<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
2714the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public
2715interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file
2716will be compiled. It is pretty complex because it provides its own header
2717file.
2718.Sp
2719The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file
2720that everybody includes and which overrides some configure choices:
2721.Sp
2722.Vb 9
2723\& #define EV_MINIMAL 1
2724\& #define EV_USE_POLL 0
2725\& #define EV_MULTIPLICITY 0
2726\& #define EV_PERIODIC_ENABLE 0
2727\& #define EV_STAT_ENABLE 0
2728\& #define EV_FORK_ENABLE 0
2729\& #define EV_CONFIG_H <config.h>
2730\& #define EV_MINPRI 0
2731\& #define EV_MAXPRI 0
2732.Ve
2733.Sp
2734.Vb 1
2735\& #include "ev++.h"
2736.Ve
2737.Sp
2738And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled:
2739.Sp
2740.Vb 2
2741\& #include "ev_cpp.h"
2742\& #include "ev.c"
2743.Ve
2744.SH "COMPLEXITIES"
2745.IX Header "COMPLEXITIES"
2746In this section the complexities of (many of) the algorithms used inside
2747libev will be explained. For complexity discussions about backends see the
2748documentation for \f(CW\*(C`ev_default_init\*(C'\fR.
2749.Sp
2750All of the following are about amortised time: If an array needs to be
2751extended, libev needs to realloc and move the whole array, but this
2752happens asymptotically never with higher number of elements, so O(1) might
2753mean it might do a lengthy realloc operation in rare cases, but on average
2754it is much faster and asymptotically approaches constant time.
2755.RS 4
2756.IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4
2757.IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)"
2758This means that, when you have a watcher that triggers in one hour and
2759there are 100 watchers that would trigger before that then inserting will
2760have to skip those 100 watchers.
2761.IP "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)" 4
2762.IX Item "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)"
2763That means that for changing a timer costs less than removing/adding them
2764as only the relative motion in the event queue has to be paid for.
2765.IP "Starting io/check/prepare/idle/signal/child watchers: O(1)" 4
2766.IX Item "Starting io/check/prepare/idle/signal/child watchers: O(1)"
2767These just add the watcher into an array or at the head of a list.
2768=item Stopping check/prepare/idle watchers: O(1)
2769.IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4
2770.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))"
2771These watchers are stored in lists then need to be walked to find the
2772correct watcher to remove. The lists are usually short (you don't usually
2773have many watchers waiting for the same fd or signal).
2774.IP "Finding the next timer per loop iteration: O(1)" 4
2775.IX Item "Finding the next timer per loop iteration: O(1)"
2776.PD 0
2777.IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4
2778.IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)"
2779.PD
2780A change means an I/O watcher gets started or stopped, which requires
2781libev to recalculate its status (and possibly tell the kernel).
2782.IP "Activating one watcher: O(1)" 4
2783.IX Item "Activating one watcher: O(1)"
2784.PD 0
2785.IP "Priority handling: O(number_of_priorities)" 4
2786.IX Item "Priority handling: O(number_of_priorities)"
2787.PD
2788Priorities are implemented by allocating some space for each
2789priority. When doing priority-based operations, libev usually has to
2790linearly search all the priorities.
2791.RE
2792.RS 4
1267.SH "AUTHOR" 2793.SH "AUTHOR"
1268.IX Header "AUTHOR" 2794.IX Header "AUTHOR"
1269Marc Lehmann <libev@schmorp.de>. 2795Marc Lehmann <libev@schmorp.de>.

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