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Revision 1.13 by root, Sat Nov 24 09:48:38 2007 UTC vs.
Revision 1.57 by root, Sat Dec 22 11:49:17 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 "2007-11-24" "perl v5.8.8" "User Contributed Perl Documentation" 132.TH EV 1 "2007-12-22" "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
185.IX Item "ev_tstamp ev_time ()" 256.IX Item "ev_tstamp ev_time ()"
186Returns the current time as libev would use it. Please note that the 257Returns the current time as libev would use it. Please note that the
187\&\f(CW\*(C`ev_now\*(C'\fR function is usually faster and also often returns the timestamp 258\&\f(CW\*(C`ev_now\*(C'\fR function is usually faster and also often returns the timestamp
188you actually want to know. 259you actually want to know.
260.IP "ev_sleep (ev_tstamp interval)" 4
261.IX Item "ev_sleep (ev_tstamp interval)"
262Sleep for the given interval: The current thread will be blocked until
263either it is interrupted or the given time interval has passed. Basically
264this is a subsecond-resolution \f(CW\*(C`sleep ()\*(C'\fR.
189.IP "int ev_version_major ()" 4 265.IP "int ev_version_major ()" 4
190.IX Item "int ev_version_major ()" 266.IX Item "int ev_version_major ()"
191.PD 0 267.PD 0
192.IP "int ev_version_minor ()" 4 268.IP "int ev_version_minor ()" 4
193.IX Item "int ev_version_minor ()" 269.IX Item "int ev_version_minor ()"
194.PD 270.PD
195You can find out the major and minor version numbers of the library 271You 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 272you 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 273\&\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 274symbols \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. 275version of the library your program was compiled against.
200.Sp 276.Sp
277These version numbers refer to the \s-1ABI\s0 version of the library, not the
278release version.
279.Sp
201Usually, it's a good idea to terminate if the major versions mismatch, 280Usually, it's a good idea to terminate if the major versions mismatch,
202as this indicates an incompatible change. Minor versions are usually 281as this indicates an incompatible change. Minor versions are usually
203compatible to older versions, so a larger minor version alone is usually 282compatible to older versions, so a larger minor version alone is usually
204not a problem. 283not a problem.
205.Sp 284.Sp
206Example: make sure we haven't accidentally been linked against the wrong 285Example: Make sure we haven't accidentally been linked against the wrong
207version: 286version.
208.Sp 287.Sp
209.Vb 3 288.Vb 3
210\& assert (("libev version mismatch", 289\& assert (("libev version mismatch",
211\& ev_version_major () == EV_VERSION_MAJOR 290\& ev_version_major () == EV_VERSION_MAJOR
212\& && ev_version_minor () >= EV_VERSION_MINOR)); 291\& && ev_version_minor () >= EV_VERSION_MINOR));
… …
242recommended ones. 321recommended ones.
243.Sp 322.Sp
244See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info. 323See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info.
245.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4 324.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4
246.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))" 325.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))"
247Sets the allocation function to use (the prototype is similar to the 326Sets the allocation function to use (the prototype is similar \- the
248realloc C function, the semantics are identical). It is used to allocate 327semantics is identical \- to the realloc C function). It is used to
249and free memory (no surprises here). If it returns zero when memory 328allocate and free memory (no surprises here). If it returns zero when
250needs to be allocated, the library might abort or take some potentially 329memory needs to be allocated, the library might abort or take some
251destructive action. The default is your system realloc function. 330potentially destructive action. The default is your system realloc
331function.
252.Sp 332.Sp
253You could override this function in high-availability programs to, say, 333You could override this function in high-availability programs to, say,
254free some memory if it cannot allocate memory, to use a special allocator, 334free some memory if it cannot allocate memory, to use a special allocator,
255or even to sleep a while and retry until some memory is available. 335or even to sleep a while and retry until some memory is available.
256.Sp 336.Sp
257Example: replace the libev allocator with one that waits a bit and then 337Example: Replace the libev allocator with one that waits a bit and then
258retries: better than mine). 338retries).
259.Sp 339.Sp
260.Vb 6 340.Vb 6
261\& static void * 341\& static void *
262\& persistent_realloc (void *ptr, long size) 342\& persistent_realloc (void *ptr, size_t size)
263\& { 343\& {
264\& for (;;) 344\& for (;;)
265\& { 345\& {
266\& void *newptr = realloc (ptr, size); 346\& void *newptr = realloc (ptr, size);
267.Ve 347.Ve
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289callback is set, then libev will expect it to remedy the sitution, no 369callback is set, then libev will expect it to remedy the sitution, no
290matter what, when it returns. That is, libev will generally retry the 370matter what, when it returns. That is, libev will generally retry the
291requested operation, or, if the condition doesn't go away, do bad stuff 371requested operation, or, if the condition doesn't go away, do bad stuff
292(such as abort). 372(such as abort).
293.Sp 373.Sp
294Example: do the same thing as libev does internally: 374Example: This is basically the same thing that libev does internally, too.
295.Sp 375.Sp
296.Vb 6 376.Vb 6
297\& static void 377\& static void
298\& fatal_error (const char *msg) 378\& fatal_error (const char *msg)
299\& { 379\& {
… …
345or setgid) then libev will \fInot\fR look at the environment variable 425or setgid) then libev will \fInot\fR look at the environment variable
346\&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will 426\&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will
347override the flags completely if it is found in the environment. This is 427override the flags completely if it is found in the environment. This is
348useful to try out specific backends to test their performance, or to work 428useful to try out specific backends to test their performance, or to work
349around bugs. 429around bugs.
430.ie n .IP """EVFLAG_FORKCHECK""" 4
431.el .IP "\f(CWEVFLAG_FORKCHECK\fR" 4
432.IX Item "EVFLAG_FORKCHECK"
433Instead of calling \f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR manually after
434a fork, you can also make libev check for a fork in each iteration by
435enabling this flag.
436.Sp
437This works by calling \f(CW\*(C`getpid ()\*(C'\fR on every iteration of the loop,
438and thus this might slow down your event loop if you do a lot of loop
439iterations and little real work, but is usually not noticeable (on my
440Linux system for example, \f(CW\*(C`getpid\*(C'\fR is actually a simple 5\-insn sequence
441without a syscall and thus \fIvery\fR fast, but my Linux system also has
442\&\f(CW\*(C`pthread_atfork\*(C'\fR which is even faster).
443.Sp
444The big advantage of this flag is that you can forget about fork (and
445forget about forgetting to tell libev about forking) when you use this
446flag.
447.Sp
448This flag setting cannot be overriden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR
449environment variable.
350.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4 450.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4
351.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4 451.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4
352.IX Item "EVBACKEND_SELECT (value 1, portable select backend)" 452.IX Item "EVBACKEND_SELECT (value 1, portable select backend)"
353This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as 453This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as
354libev tries to roll its own fd_set with no limits on the number of fds, 454libev tries to roll its own fd_set with no limits on the number of fds,
… …
364lot of inactive fds). It scales similarly to select, i.e. O(total_fds). 464lot of inactive fds). It scales similarly to select, i.e. O(total_fds).
365.ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4 465.ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4
366.el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4 466.el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4
367.IX Item "EVBACKEND_EPOLL (value 4, Linux)" 467.IX Item "EVBACKEND_EPOLL (value 4, Linux)"
368For few fds, this backend is a bit little slower than poll and select, 468For few fds, this backend is a bit little slower than poll and select,
369but it scales phenomenally better. While poll and select usually scale like 469but it scales phenomenally better. While poll and select usually scale
370O(total_fds) where n is the total number of fds (or the highest fd), epoll scales 470like O(total_fds) where n is the total number of fds (or the highest fd),
371either O(1) or O(active_fds). 471epoll scales either O(1) or O(active_fds). The epoll design has a number
472of shortcomings, such as silently dropping events in some hard-to-detect
473cases and rewiring a syscall per fd change, no fork support and bad
474support for dup:
372.Sp 475.Sp
373While stopping and starting an I/O watcher in the same iteration will 476While stopping, setting and starting an I/O watcher in the same iteration
374result in some caching, there is still a syscall per such incident 477will result in some caching, there is still a syscall per such incident
375(because the fd could point to a different file description now), so its 478(because the fd could point to a different file description now), so its
376best to avoid that. Also, \fIdup()\fRed file descriptors might not work very 479best to avoid that. Also, \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors might not work
377well if you register events for both fds. 480very well if you register events for both fds.
378.Sp 481.Sp
379Please note that epoll sometimes generates spurious notifications, so you 482Please note that epoll sometimes generates spurious notifications, so you
380need to use non-blocking I/O or other means to avoid blocking when no data 483need to use non-blocking I/O or other means to avoid blocking when no data
381(or space) is available. 484(or space) is available.
382.ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4 485.ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4
383.el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4 486.el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4
384.IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)" 487.IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)"
385Kqueue deserves special mention, as at the time of this writing, it 488Kqueue deserves special mention, as at the time of this writing, it
386was broken on all BSDs except NetBSD (usually it doesn't work with 489was broken on all BSDs except NetBSD (usually it doesn't work reliably
387anything but sockets and pipes, except on Darwin, where of course its 490with anything but sockets and pipes, except on Darwin, where of course
388completely useless). For this reason its not being \*(L"autodetected\*(R" 491it's completely useless). For this reason it's not being \*(L"autodetected\*(R"
389unless you explicitly specify it explicitly in the flags (i.e. using 492unless you explicitly specify it explicitly in the flags (i.e. using
390\&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR). 493\&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR) or libev was compiled on a known-to-be-good (\-enough)
494system like NetBSD.
495.Sp
496You still can embed kqueue into a normal poll or select backend and use it
497only for sockets (after having made sure that sockets work with kqueue on
498the target platform). See \f(CW\*(C`ev_embed\*(C'\fR watchers for more info.
391.Sp 499.Sp
392It scales in the same way as the epoll backend, but the interface to the 500It scales in the same way as the epoll backend, but the interface to the
393kernel is more efficient (which says nothing about its actual speed, of 501kernel is more efficient (which says nothing about its actual speed, of
394course). While starting and stopping an I/O watcher does not cause an 502course). While stopping, setting and starting an I/O watcher does never
395extra syscall as with epoll, it still adds up to four event changes per 503cause an extra syscall as with \f(CW\*(C`EVBACKEND_EPOLL\*(C'\fR, it still adds up to
396incident, so its best to avoid that. 504two event changes per incident, support for \f(CW\*(C`fork ()\*(C'\fR is very bad and it
505drops fds silently in similarly hard-to-detect cases.
397.ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4 506.ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4
398.el .IP "\f(CWEVBACKEND_DEVPOLL\fR (value 16, Solaris 8)" 4 507.el .IP "\f(CWEVBACKEND_DEVPOLL\fR (value 16, Solaris 8)" 4
399.IX Item "EVBACKEND_DEVPOLL (value 16, Solaris 8)" 508.IX Item "EVBACKEND_DEVPOLL (value 16, Solaris 8)"
400This is not implemented yet (and might never be). 509This is not implemented yet (and might never be).
401.ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4 510.ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4
402.el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4 511.el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4
403.IX Item "EVBACKEND_PORT (value 32, Solaris 10)" 512.IX Item "EVBACKEND_PORT (value 32, Solaris 10)"
404This uses the Solaris 10 port mechanism. As with everything on Solaris, 513This uses the Solaris 10 event port mechanism. As with everything on Solaris,
405it's really slow, but it still scales very well (O(active_fds)). 514it's really slow, but it still scales very well (O(active_fds)).
406.Sp 515.Sp
407Please note that solaris ports can result in a lot of spurious 516Please note that solaris event ports can deliver a lot of spurious
408notifications, so you need to use non-blocking I/O or other means to avoid 517notifications, so you need to use non-blocking I/O or other means to avoid
409blocking when no data (or space) is available. 518blocking when no data (or space) is available.
410.ie n .IP """EVBACKEND_ALL""" 4 519.ie n .IP """EVBACKEND_ALL""" 4
411.el .IP "\f(CWEVBACKEND_ALL\fR" 4 520.el .IP "\f(CWEVBACKEND_ALL\fR" 4
412.IX Item "EVBACKEND_ALL" 521.IX Item "EVBACKEND_ALL"
… …
448Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is 557Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is
449always distinct from the default loop. Unlike the default loop, it cannot 558always distinct from the default loop. Unlike the default loop, it cannot
450handle signal and child watchers, and attempts to do so will be greeted by 559handle signal and child watchers, and attempts to do so will be greeted by
451undefined behaviour (or a failed assertion if assertions are enabled). 560undefined behaviour (or a failed assertion if assertions are enabled).
452.Sp 561.Sp
453Example: try to create a event loop that uses epoll and nothing else. 562Example: Try to create a event loop that uses epoll and nothing else.
454.Sp 563.Sp
455.Vb 3 564.Vb 3
456\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); 565\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
457\& if (!epoller) 566\& if (!epoller)
458\& fatal ("no epoll found here, maybe it hides under your chair"); 567\& fatal ("no epoll found here, maybe it hides under your chair");
… …
462Destroys the default loop again (frees all memory and kernel state 571Destroys the default loop again (frees all memory and kernel state
463etc.). None of the active event watchers will be stopped in the normal 572etc.). None of the active event watchers will be stopped in the normal
464sense, so e.g. \f(CW\*(C`ev_is_active\*(C'\fR might still return true. It is your 573sense, so e.g. \f(CW\*(C`ev_is_active\*(C'\fR might still return true. It is your
465responsibility to either stop all watchers cleanly yoursef \fIbefore\fR 574responsibility to either stop all watchers cleanly yoursef \fIbefore\fR
466calling this function, or cope with the fact afterwards (which is usually 575calling this function, or cope with the fact afterwards (which is usually
467the easiest thing, youc na just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them 576the easiest thing, you can just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them
468for example). 577for example).
578.Sp
579Note that certain global state, such as signal state, will not be freed by
580this function, and related watchers (such as signal and child watchers)
581would need to be stopped manually.
582.Sp
583In general it is not advisable to call this function except in the
584rare occasion where you really need to free e.g. the signal handling
585pipe fds. If you need dynamically allocated loops it is better to use
586\&\f(CW\*(C`ev_loop_new\*(C'\fR and \f(CW\*(C`ev_loop_destroy\*(C'\fR).
469.IP "ev_loop_destroy (loop)" 4 587.IP "ev_loop_destroy (loop)" 4
470.IX Item "ev_loop_destroy (loop)" 588.IX Item "ev_loop_destroy (loop)"
471Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an 589Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an
472earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR. 590earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR.
473.IP "ev_default_fork ()" 4 591.IP "ev_default_fork ()" 4
… …
495.IP "ev_loop_fork (loop)" 4 613.IP "ev_loop_fork (loop)" 4
496.IX Item "ev_loop_fork (loop)" 614.IX Item "ev_loop_fork (loop)"
497Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by 615Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by
498\&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop 616\&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop
499after fork, and how you do this is entirely your own problem. 617after fork, and how you do this is entirely your own problem.
618.IP "unsigned int ev_loop_count (loop)" 4
619.IX Item "unsigned int ev_loop_count (loop)"
620Returns the count of loop iterations for the loop, which is identical to
621the number of times libev did poll for new events. It starts at \f(CW0\fR and
622happily wraps around with enough iterations.
623.Sp
624This value can sometimes be useful as a generation counter of sorts (it
625\&\*(L"ticks\*(R" the number of loop iterations), as it roughly corresponds with
626\&\f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR calls.
500.IP "unsigned int ev_backend (loop)" 4 627.IP "unsigned int ev_backend (loop)" 4
501.IX Item "unsigned int ev_backend (loop)" 628.IX Item "unsigned int ev_backend (loop)"
502Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in 629Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in
503use. 630use.
504.IP "ev_tstamp ev_now (loop)" 4 631.IP "ev_tstamp ev_now (loop)" 4
505.IX Item "ev_tstamp ev_now (loop)" 632.IX Item "ev_tstamp ev_now (loop)"
506Returns the current \*(L"event loop time\*(R", which is the time the event loop 633Returns the current \*(L"event loop time\*(R", which is the time the event loop
507received events and started processing them. This timestamp does not 634received events and started processing them. This timestamp does not
508change as long as callbacks are being processed, and this is also the base 635change as long as callbacks are being processed, and this is also the base
509time used for relative timers. You can treat it as the timestamp of the 636time used for relative timers. You can treat it as the timestamp of the
510event occuring (or more correctly, libev finding out about it). 637event occurring (or more correctly, libev finding out about it).
511.IP "ev_loop (loop, int flags)" 4 638.IP "ev_loop (loop, int flags)" 4
512.IX Item "ev_loop (loop, int flags)" 639.IX Item "ev_loop (loop, int flags)"
513Finally, this is it, the event handler. This function usually is called 640Finally, this is it, the event handler. This function usually is called
514after you initialised all your watchers and you want to start handling 641after you initialised all your watchers and you want to start handling
515events. 642events.
… …
535libev watchers. However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is 662libev watchers. However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is
536usually a better approach for this kind of thing. 663usually a better approach for this kind of thing.
537.Sp 664.Sp
538Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does: 665Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does:
539.Sp 666.Sp
540.Vb 18 667.Vb 19
668\& - Before the first iteration, call any pending watchers.
541\& * If there are no active watchers (reference count is zero), return. 669\& * If there are no active watchers (reference count is zero), return.
542\& - Queue prepare watchers and then call all outstanding watchers. 670\& - Queue all prepare watchers and then call all outstanding watchers.
543\& - If we have been forked, recreate the kernel state. 671\& - If we have been forked, recreate the kernel state.
544\& - Update the kernel state with all outstanding changes. 672\& - Update the kernel state with all outstanding changes.
545\& - Update the "event loop time". 673\& - Update the "event loop time".
546\& - Calculate for how long to block. 674\& - Calculate for how long to block.
547\& - Block the process, waiting for any events. 675\& - Block the process, waiting for any events.
… …
556\& be handled here by queueing them when their watcher gets executed. 684\& be handled here by queueing them when their watcher gets executed.
557\& - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 685\& - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
558\& were used, return, otherwise continue with step *. 686\& were used, return, otherwise continue with step *.
559.Ve 687.Ve
560.Sp 688.Sp
561Example: queue some jobs and then loop until no events are outsanding 689Example: Queue some jobs and then loop until no events are outsanding
562anymore. 690anymore.
563.Sp 691.Sp
564.Vb 4 692.Vb 4
565\& ... queue jobs here, make sure they register event watchers as long 693\& ... queue jobs here, make sure they register event watchers as long
566\& ... as they still have work to do (even an idle watcher will do..) 694\& ... as they still have work to do (even an idle watcher will do..)
… …
588visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if 716visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if
589no event watchers registered by it are active. It is also an excellent 717no event watchers registered by it are active. It is also an excellent
590way to do this for generic recurring timers or from within third-party 718way to do this for generic recurring timers or from within third-party
591libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR. 719libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR.
592.Sp 720.Sp
593Example: create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR 721Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR
594running when nothing else is active. 722running when nothing else is active.
595.Sp 723.Sp
596.Vb 4 724.Vb 4
597\& struct dv_signal exitsig; 725\& struct ev_signal exitsig;
598\& ev_signal_init (&exitsig, sig_cb, SIGINT); 726\& ev_signal_init (&exitsig, sig_cb, SIGINT);
599\& ev_signal_start (myloop, &exitsig); 727\& ev_signal_start (loop, &exitsig);
600\& evf_unref (myloop); 728\& evf_unref (loop);
601.Ve 729.Ve
602.Sp 730.Sp
603Example: for some weird reason, unregister the above signal handler again. 731Example: For some weird reason, unregister the above signal handler again.
604.Sp 732.Sp
605.Vb 2 733.Vb 2
606\& ev_ref (myloop); 734\& ev_ref (loop);
607\& ev_signal_stop (myloop, &exitsig); 735\& ev_signal_stop (loop, &exitsig);
608.Ve 736.Ve
737.IP "ev_set_io_collect_interval (loop, ev_tstamp interval)" 4
738.IX Item "ev_set_io_collect_interval (loop, ev_tstamp interval)"
739.PD 0
740.IP "ev_set_timeout_collect_interval (loop, ev_tstamp interval)" 4
741.IX Item "ev_set_timeout_collect_interval (loop, ev_tstamp interval)"
742.PD
743These advanced functions influence the time that libev will spend waiting
744for events. Both are by default \f(CW0\fR, meaning that libev will try to
745invoke timer/periodic callbacks and I/O callbacks with minimum latency.
746.Sp
747Setting these to a higher value (the \f(CW\*(C`interval\*(C'\fR \fImust\fR be >= \f(CW0\fR)
748allows libev to delay invocation of I/O and timer/periodic callbacks to
749increase efficiency of loop iterations.
750.Sp
751The background is that sometimes your program runs just fast enough to
752handle one (or very few) event(s) per loop iteration. While this makes
753the program responsive, it also wastes a lot of \s-1CPU\s0 time to poll for new
754events, especially with backends like \f(CW\*(C`select ()\*(C'\fR which have a high
755overhead for the actual polling but can deliver many events at once.
756.Sp
757By setting a higher \fIio collect interval\fR you allow libev to spend more
758time collecting I/O events, so you can handle more events per iteration,
759at the cost of increasing latency. Timeouts (both \f(CW\*(C`ev_periodic\*(C'\fR and
760\&\f(CW\*(C`ev_timer\*(C'\fR) will be not affected. Setting this to a non-null bvalue will
761introduce an additional \f(CW\*(C`ev_sleep ()\*(C'\fR call into most loop iterations.
762.Sp
763Likewise, by setting a higher \fItimeout collect interval\fR you allow libev
764to spend more time collecting timeouts, at the expense of increased
765latency (the watcher callback will be called later). \f(CW\*(C`ev_io\*(C'\fR watchers
766will not be affected. Setting this to a non-null value will not introduce
767any overhead in libev.
768.Sp
769Many (busy) programs can usually benefit by setting the io collect
770interval to a value near \f(CW0.1\fR or so, which is often enough for
771interactive servers (of course not for games), likewise for timeouts. It
772usually doesn't make much sense to set it to a lower value than \f(CW0.01\fR,
773as this approsaches the timing granularity of most systems.
609.SH "ANATOMY OF A WATCHER" 774.SH "ANATOMY OF A WATCHER"
610.IX Header "ANATOMY OF A WATCHER" 775.IX Header "ANATOMY OF A WATCHER"
611A watcher is a structure that you create and register to record your 776A watcher is a structure that you create and register to record your
612interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to 777interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to
613become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that: 778become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that:
… …
684The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread. 849The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread.
685.ie n .IP """EV_CHILD""" 4 850.ie n .IP """EV_CHILD""" 4
686.el .IP "\f(CWEV_CHILD\fR" 4 851.el .IP "\f(CWEV_CHILD\fR" 4
687.IX Item "EV_CHILD" 852.IX Item "EV_CHILD"
688The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change. 853The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change.
854.ie n .IP """EV_STAT""" 4
855.el .IP "\f(CWEV_STAT\fR" 4
856.IX Item "EV_STAT"
857The path specified in the \f(CW\*(C`ev_stat\*(C'\fR watcher changed its attributes somehow.
689.ie n .IP """EV_IDLE""" 4 858.ie n .IP """EV_IDLE""" 4
690.el .IP "\f(CWEV_IDLE\fR" 4 859.el .IP "\f(CWEV_IDLE\fR" 4
691.IX Item "EV_IDLE" 860.IX Item "EV_IDLE"
692The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do. 861The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do.
693.ie n .IP """EV_PREPARE""" 4 862.ie n .IP """EV_PREPARE""" 4
… …
703\&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any 872\&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any
704received events. Callbacks of both watcher types can start and stop as 873received events. Callbacks of both watcher types can start and stop as
705many watchers as they want, and all of them will be taken into account 874many watchers as they want, and all of them will be taken into account
706(for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep 875(for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep
707\&\f(CW\*(C`ev_loop\*(C'\fR from blocking). 876\&\f(CW\*(C`ev_loop\*(C'\fR from blocking).
877.ie n .IP """EV_EMBED""" 4
878.el .IP "\f(CWEV_EMBED\fR" 4
879.IX Item "EV_EMBED"
880The embedded event loop specified in the \f(CW\*(C`ev_embed\*(C'\fR watcher needs attention.
881.ie n .IP """EV_FORK""" 4
882.el .IP "\f(CWEV_FORK\fR" 4
883.IX Item "EV_FORK"
884The event loop has been resumed in the child process after fork (see
885\&\f(CW\*(C`ev_fork\*(C'\fR).
708.ie n .IP """EV_ERROR""" 4 886.ie n .IP """EV_ERROR""" 4
709.el .IP "\f(CWEV_ERROR\fR" 4 887.el .IP "\f(CWEV_ERROR\fR" 4
710.IX Item "EV_ERROR" 888.IX Item "EV_ERROR"
711An unspecified error has occured, the watcher has been stopped. This might 889An unspecified error has occured, the watcher has been stopped. This might
712happen because the watcher could not be properly started because libev 890happen because the watcher could not be properly started because libev
… …
717Libev will usually signal a few \*(L"dummy\*(R" events together with an error, 895Libev will usually signal a few \*(L"dummy\*(R" events together with an error,
718for example it might indicate that a fd is readable or writable, and if 896for example it might indicate that a fd is readable or writable, and if
719your callbacks is well-written it can just attempt the operation and cope 897your callbacks is well-written it can just attempt the operation and cope
720with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded 898with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded
721programs, though, so beware. 899programs, though, so beware.
722.Sh "\s-1SUMMARY\s0 \s-1OF\s0 \s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0" 900.Sh "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0"
723.IX Subsection "SUMMARY OF GENERIC WATCHER FUNCTIONS" 901.IX Subsection "GENERIC WATCHER FUNCTIONS"
724In the following description, \f(CW\*(C`TYPE\*(C'\fR stands for the watcher type, 902In the following description, \f(CW\*(C`TYPE\*(C'\fR stands for the watcher type,
725e.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. 903e.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.
726.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4 904.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4
727.el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4 905.el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4
728.IX Item "ev_init (ev_TYPE *watcher, callback)" 906.IX Item "ev_init (ev_TYPE *watcher, callback)"
… …
734which rolls both calls into one. 912which rolls both calls into one.
735.Sp 913.Sp
736You can reinitialise a watcher at any time as long as it has been stopped 914You can reinitialise a watcher at any time as long as it has been stopped
737(or never started) and there are no pending events outstanding. 915(or never started) and there are no pending events outstanding.
738.Sp 916.Sp
739The callbakc is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher, 917The callback is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher,
740int revents)\*(C'\fR. 918int revents)\*(C'\fR.
741.ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4 919.ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4
742.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4 920.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4
743.IX Item "ev_TYPE_set (ev_TYPE *, [args])" 921.IX Item "ev_TYPE_set (ev_TYPE *, [args])"
744This macro initialises the type-specific parts of a watcher. You need to 922This macro initialises the type-specific parts of a watcher. You need to
… …
777.IP "bool ev_is_pending (ev_TYPE *watcher)" 4 955.IP "bool ev_is_pending (ev_TYPE *watcher)" 4
778.IX Item "bool ev_is_pending (ev_TYPE *watcher)" 956.IX Item "bool ev_is_pending (ev_TYPE *watcher)"
779Returns a true value iff the watcher is pending, (i.e. it has outstanding 957Returns a true value iff the watcher is pending, (i.e. it has outstanding
780events but its callback has not yet been invoked). As long as a watcher 958events but its callback has not yet been invoked). As long as a watcher
781is pending (but not active) you must not call an init function on it (but 959is pending (but not active) you must not call an init function on it (but
782\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe) and you must make sure the watcher is available to 960\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe), you must not change its priority, and you must
783libev (e.g. you cnanot \f(CW\*(C`free ()\*(C'\fR it). 961make sure the watcher is available to libev (e.g. you cannot \f(CW\*(C`free ()\*(C'\fR
962it).
784.IP "callback = ev_cb (ev_TYPE *watcher)" 4 963.IP "callback ev_cb (ev_TYPE *watcher)" 4
785.IX Item "callback = ev_cb (ev_TYPE *watcher)" 964.IX Item "callback ev_cb (ev_TYPE *watcher)"
786Returns the callback currently set on the watcher. 965Returns the callback currently set on the watcher.
787.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4 966.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4
788.IX Item "ev_cb_set (ev_TYPE *watcher, callback)" 967.IX Item "ev_cb_set (ev_TYPE *watcher, callback)"
789Change the callback. You can change the callback at virtually any time 968Change the callback. You can change the callback at virtually any time
790(modulo threads). 969(modulo threads).
970.IP "ev_set_priority (ev_TYPE *watcher, priority)" 4
971.IX Item "ev_set_priority (ev_TYPE *watcher, priority)"
972.PD 0
973.IP "int ev_priority (ev_TYPE *watcher)" 4
974.IX Item "int ev_priority (ev_TYPE *watcher)"
975.PD
976Set and query the priority of the watcher. The priority is a small
977integer between \f(CW\*(C`EV_MAXPRI\*(C'\fR (default: \f(CW2\fR) and \f(CW\*(C`EV_MINPRI\*(C'\fR
978(default: \f(CW\*(C`\-2\*(C'\fR). Pending watchers with higher priority will be invoked
979before watchers with lower priority, but priority will not keep watchers
980from being executed (except for \f(CW\*(C`ev_idle\*(C'\fR watchers).
981.Sp
982This means that priorities are \fIonly\fR used for ordering callback
983invocation after new events have been received. This is useful, for
984example, to reduce latency after idling, or more often, to bind two
985watchers on the same event and make sure one is called first.
986.Sp
987If you need to suppress invocation when higher priority events are pending
988you need to look at \f(CW\*(C`ev_idle\*(C'\fR watchers, which provide this functionality.
989.Sp
990You \fImust not\fR change the priority of a watcher as long as it is active or
991pending.
992.Sp
993The default priority used by watchers when no priority has been set is
994always \f(CW0\fR, which is supposed to not be too high and not be too low :).
995.Sp
996Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR is
997fine, as long as you do not mind that the priority value you query might
998or might not have been adjusted to be within valid range.
999.IP "ev_invoke (loop, ev_TYPE *watcher, int revents)" 4
1000.IX Item "ev_invoke (loop, ev_TYPE *watcher, int revents)"
1001Invoke the \f(CW\*(C`watcher\*(C'\fR with the given \f(CW\*(C`loop\*(C'\fR and \f(CW\*(C`revents\*(C'\fR. Neither
1002\&\f(CW\*(C`loop\*(C'\fR nor \f(CW\*(C`revents\*(C'\fR need to be valid as long as the watcher callback
1003can deal with that fact.
1004.IP "int ev_clear_pending (loop, ev_TYPE *watcher)" 4
1005.IX Item "int ev_clear_pending (loop, ev_TYPE *watcher)"
1006If the watcher is pending, this function returns clears its pending status
1007and returns its \f(CW\*(C`revents\*(C'\fR bitset (as if its callback was invoked). If the
1008watcher isn't pending it does nothing and returns \f(CW0\fR.
791.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0" 1009.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0"
792.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER" 1010.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER"
793Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change 1011Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change
794and read at any time, libev will completely ignore it. This can be used 1012and read at any time, libev will completely ignore it. This can be used
795to associate arbitrary data with your watcher. If you need more data and 1013to associate arbitrary data with your watcher. If you need more data and
… …
816\& struct my_io *w = (struct my_io *)w_; 1034\& struct my_io *w = (struct my_io *)w_;
817\& ... 1035\& ...
818\& } 1036\& }
819.Ve 1037.Ve
820.PP 1038.PP
821More interesting and less C\-conformant ways of catsing your callback type 1039More interesting and less C\-conformant ways of casting your callback type
822have been omitted.... 1040instead have been omitted.
1041.PP
1042Another common scenario is having some data structure with multiple
1043watchers:
1044.PP
1045.Vb 6
1046\& struct my_biggy
1047\& {
1048\& int some_data;
1049\& ev_timer t1;
1050\& ev_timer t2;
1051\& }
1052.Ve
1053.PP
1054In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more complicated,
1055you need to use \f(CW\*(C`offsetof\*(C'\fR:
1056.PP
1057.Vb 1
1058\& #include <stddef.h>
1059.Ve
1060.PP
1061.Vb 6
1062\& static void
1063\& t1_cb (EV_P_ struct ev_timer *w, int revents)
1064\& {
1065\& struct my_biggy big = (struct my_biggy *
1066\& (((char *)w) - offsetof (struct my_biggy, t1));
1067\& }
1068.Ve
1069.PP
1070.Vb 6
1071\& static void
1072\& t2_cb (EV_P_ struct ev_timer *w, int revents)
1073\& {
1074\& struct my_biggy big = (struct my_biggy *
1075\& (((char *)w) - offsetof (struct my_biggy, t2));
1076\& }
1077.Ve
823.SH "WATCHER TYPES" 1078.SH "WATCHER TYPES"
824.IX Header "WATCHER TYPES" 1079.IX Header "WATCHER TYPES"
825This section describes each watcher in detail, but will not repeat 1080This section describes each watcher in detail, but will not repeat
826information given in the last section. 1081information given in the last section. Any initialisation/set macros,
1082functions and members specific to the watcher type are explained.
1083.PP
1084Members are additionally marked with either \fI[read\-only]\fR, meaning that,
1085while the watcher is active, you can look at the member and expect some
1086sensible content, but you must not modify it (you can modify it while the
1087watcher is stopped to your hearts content), or \fI[read\-write]\fR, which
1088means you can expect it to have some sensible content while the watcher
1089is active, but you can also modify it. Modifying it may not do something
1090sensible or take immediate effect (or do anything at all), but libev will
1091not crash or malfunction in any way.
827.ie n .Sh """ev_io"" \- is this file descriptor readable or writable" 1092.ie n .Sh """ev_io"" \- is this file descriptor readable or writable?"
828.el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable" 1093.el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable?"
829.IX Subsection "ev_io - is this file descriptor readable or writable" 1094.IX Subsection "ev_io - is this file descriptor readable or writable?"
830I/O watchers check whether a file descriptor is readable or writable 1095I/O watchers check whether a file descriptor is readable or writable
831in each iteration of the event loop (This behaviour is called 1096in each iteration of the event loop, or, more precisely, when reading
832level-triggering because you keep receiving events as long as the 1097would not block the process and writing would at least be able to write
833condition persists. Remember you can stop the watcher if you don't want to 1098some data. This behaviour is called level-triggering because you keep
834act on the event and neither want to receive future events). 1099receiving events as long as the condition persists. Remember you can stop
1100the watcher if you don't want to act on the event and neither want to
1101receive future events.
835.PP 1102.PP
836In general you can register as many read and/or write event watchers per 1103In general you can register as many read and/or write event watchers per
837fd as you want (as long as you don't confuse yourself). Setting all file 1104fd as you want (as long as you don't confuse yourself). Setting all file
838descriptors to non-blocking mode is also usually a good idea (but not 1105descriptors to non-blocking mode is also usually a good idea (but not
839required if you know what you are doing). 1106required if you know what you are doing).
840.PP 1107.PP
841You have to be careful with dup'ed file descriptors, though. Some backends 1108You have to be careful with dup'ed file descriptors, though. Some backends
842(the linux epoll backend is a notable example) cannot handle dup'ed file 1109(the linux epoll backend is a notable example) cannot handle dup'ed file
843descriptors correctly if you register interest in two or more fds pointing 1110descriptors correctly if you register interest in two or more fds pointing
844to the same underlying file/socket etc. description (that is, they share 1111to the same underlying file/socket/etc. description (that is, they share
845the same underlying \*(L"file open\*(R"). 1112the same underlying \*(L"file open\*(R").
846.PP 1113.PP
847If you must do this, then force the use of a known-to-be-good backend 1114If you must do this, then force the use of a known-to-be-good backend
848(at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and 1115(at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and
849\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR). 1116\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR).
1117.PP
1118Another thing you have to watch out for is that it is quite easy to
1119receive \*(L"spurious\*(R" readyness notifications, that is your callback might
1120be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block
1121because there is no data. Not only are some backends known to create a
1122lot of those (for example solaris ports), it is very easy to get into
1123this situation even with a relatively standard program structure. Thus
1124it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning
1125\&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives.
1126.PP
1127If you cannot run the fd in non-blocking mode (for example you should not
1128play around with an Xlib connection), then you have to seperately re-test
1129whether a file descriptor is really ready with a known-to-be good interface
1130such as poll (fortunately in our Xlib example, Xlib already does this on
1131its own, so its quite safe to use).
1132.PP
1133\fIThe special problem of disappearing file descriptors\fR
1134.IX Subsection "The special problem of disappearing file descriptors"
1135.PP
1136Some backends (e.g. kqueue, epoll) need to be told about closing a file
1137descriptor (either by calling \f(CW\*(C`close\*(C'\fR explicitly or by any other means,
1138such as \f(CW\*(C`dup\*(C'\fR). The reason is that you register interest in some file
1139descriptor, but when it goes away, the operating system will silently drop
1140this interest. If another file descriptor with the same number then is
1141registered with libev, there is no efficient way to see that this is, in
1142fact, a different file descriptor.
1143.PP
1144To avoid having to explicitly tell libev about such cases, libev follows
1145the following policy: Each time \f(CW\*(C`ev_io_set\*(C'\fR is being called, libev
1146will assume that this is potentially a new file descriptor, otherwise
1147it is assumed that the file descriptor stays the same. That means that
1148you \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
1149descriptor even if the file descriptor number itself did not change.
1150.PP
1151This is how one would do it normally anyway, the important point is that
1152the libev application should not optimise around libev but should leave
1153optimisations to libev.
1154.PP
1155\fIThe special problem of dup'ed file descriptors\fR
1156.IX Subsection "The special problem of dup'ed file descriptors"
1157.PP
1158Some backends (e.g. epoll), cannot register events for file descriptors,
1159but only events for the underlying file descriptions. That menas when you
1160have \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors and register events for them, only one
1161file descriptor might actually receive events.
1162.PP
1163There is no workaorund possible except not registering events
1164for potentially \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors or to resort to
1165\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
1166.PP
1167\fIThe special problem of fork\fR
1168.IX Subsection "The special problem of fork"
1169.PP
1170Some backends (epoll, kqueue) do not support \f(CW\*(C`fork ()\*(C'\fR at all or exhibit
1171useless behaviour. Libev fully supports fork, but needs to be told about
1172it in the child.
1173.PP
1174To support fork in your programs, you either have to call
1175\&\f(CW\*(C`ev_default_fork ()\*(C'\fR or \f(CW\*(C`ev_loop_fork ()\*(C'\fR after a fork in the child,
1176enable \f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR, or resort to \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or
1177\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
1178.PP
1179\fIWatcher-Specific Functions\fR
1180.IX Subsection "Watcher-Specific Functions"
850.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4 1181.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4
851.IX Item "ev_io_init (ev_io *, callback, int fd, int events)" 1182.IX Item "ev_io_init (ev_io *, callback, int fd, int events)"
852.PD 0 1183.PD 0
853.IP "ev_io_set (ev_io *, int fd, int events)" 4 1184.IP "ev_io_set (ev_io *, int fd, int events)" 4
854.IX Item "ev_io_set (ev_io *, int fd, int events)" 1185.IX Item "ev_io_set (ev_io *, int fd, int events)"
855.PD 1186.PD
856Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The fd is the file descriptor to rceeive 1187Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to
857events 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 | 1188rceeive events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or
858EV_WRITE\*(C'\fR to receive the given events. 1189\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR to receive the given events.
859.Sp 1190.IP "int fd [read\-only]" 4
860Please note that most of the more scalable backend mechanisms (for example 1191.IX Item "int fd [read-only]"
861epoll and solaris ports) can result in spurious readyness notifications 1192The file descriptor being watched.
862for file descriptors, so you practically need to use non-blocking I/O (and 1193.IP "int events [read\-only]" 4
863treat callback invocation as hint only), or retest separately with a safe 1194.IX Item "int events [read-only]"
864interface before doing I/O (XLib can do this), or force the use of either 1195The events being watched.
865\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR, which don't suffer from this
866problem. Also note that it is quite easy to have your callback invoked
867when the readyness condition is no longer valid even when employing
868typical ways of handling events, so its a good idea to use non-blocking
869I/O unconditionally.
870.PP 1196.PP
871Example: call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well 1197Example: Call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well
872readable, but only once. Since it is likely line\-buffered, you could 1198readable, but only once. Since it is likely line\-buffered, you could
873attempt to read a whole line in the callback: 1199attempt to read a whole line in the callback.
874.PP 1200.PP
875.Vb 6 1201.Vb 6
876\& static void 1202\& static void
877\& stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1203\& stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
878\& { 1204\& {
… …
887\& struct ev_io stdin_readable; 1213\& struct ev_io stdin_readable;
888\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); 1214\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
889\& ev_io_start (loop, &stdin_readable); 1215\& ev_io_start (loop, &stdin_readable);
890\& ev_loop (loop, 0); 1216\& ev_loop (loop, 0);
891.Ve 1217.Ve
892.ie n .Sh """ev_timer"" \- relative and optionally recurring timeouts" 1218.ie n .Sh """ev_timer"" \- relative and optionally repeating timeouts"
893.el .Sh "\f(CWev_timer\fP \- relative and optionally recurring timeouts" 1219.el .Sh "\f(CWev_timer\fP \- relative and optionally repeating timeouts"
894.IX Subsection "ev_timer - relative and optionally recurring timeouts" 1220.IX Subsection "ev_timer - relative and optionally repeating timeouts"
895Timer watchers are simple relative timers that generate an event after a 1221Timer watchers are simple relative timers that generate an event after a
896given time, and optionally repeating in regular intervals after that. 1222given time, and optionally repeating in regular intervals after that.
897.PP 1223.PP
898The timers are based on real time, that is, if you register an event that 1224The timers are based on real time, that is, if you register an event that
899times out after an hour and you reset your system clock to last years 1225times out after an hour and you reset your system clock to last years
… …
912.Ve 1238.Ve
913.PP 1239.PP
914The callback is guarenteed to be invoked only when its timeout has passed, 1240The callback is guarenteed to be invoked only when its timeout has passed,
915but if multiple timers become ready during the same loop iteration then 1241but if multiple timers become ready during the same loop iteration then
916order of execution is undefined. 1242order of execution is undefined.
1243.PP
1244\fIWatcher-Specific Functions and Data Members\fR
1245.IX Subsection "Watcher-Specific Functions and Data Members"
917.IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4 1246.IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4
918.IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 1247.IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)"
919.PD 0 1248.PD 0
920.IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4 1249.IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4
921.IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 1250.IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)"
… …
933.IP "ev_timer_again (loop)" 4 1262.IP "ev_timer_again (loop)" 4
934.IX Item "ev_timer_again (loop)" 1263.IX Item "ev_timer_again (loop)"
935This will act as if the timer timed out and restart it again if it is 1264This will act as if the timer timed out and restart it again if it is
936repeating. The exact semantics are: 1265repeating. The exact semantics are:
937.Sp 1266.Sp
1267If the timer is pending, its pending status is cleared.
1268.Sp
938If the timer is started but nonrepeating, stop it. 1269If the timer is started but nonrepeating, stop it (as if it timed out).
939.Sp 1270.Sp
940If the timer is repeating, either start it if necessary (with the repeat 1271If the timer is repeating, either start it if necessary (with the
941value), or reset the running timer to the repeat value. 1272\&\f(CW\*(C`repeat\*(C'\fR value), or reset the running timer to the \f(CW\*(C`repeat\*(C'\fR value.
942.Sp 1273.Sp
943This sounds a bit complicated, but here is a useful and typical 1274This sounds a bit complicated, but here is a useful and typical
944example: Imagine you have a tcp connection and you want a so-called idle 1275example: Imagine you have a tcp connection and you want a so-called idle
945timeout, that is, you want to be called when there have been, say, 60 1276timeout, that is, you want to be called when there have been, say, 60
946seconds of inactivity on the socket. The easiest way to do this is to 1277seconds of inactivity on the socket. The easiest way to do this is to
947configure an \f(CW\*(C`ev_timer\*(C'\fR with after=repeat=60 and calling ev_timer_again each 1278configure an \f(CW\*(C`ev_timer\*(C'\fR with a \f(CW\*(C`repeat\*(C'\fR value of \f(CW60\fR and then call
948time you successfully read or write some data. If you go into an idle 1279\&\f(CW\*(C`ev_timer_again\*(C'\fR each time you successfully read or write some data. If
949state where you do not expect data to travel on the socket, you can stop 1280you go into an idle state where you do not expect data to travel on the
950the timer, and again will automatically restart it if need be. 1281socket, you can \f(CW\*(C`ev_timer_stop\*(C'\fR the timer, and \f(CW\*(C`ev_timer_again\*(C'\fR will
1282automatically restart it if need be.
1283.Sp
1284That means you can ignore the \f(CW\*(C`after\*(C'\fR value and \f(CW\*(C`ev_timer_start\*(C'\fR
1285altogether and only ever use the \f(CW\*(C`repeat\*(C'\fR value and \f(CW\*(C`ev_timer_again\*(C'\fR:
1286.Sp
1287.Vb 8
1288\& ev_timer_init (timer, callback, 0., 5.);
1289\& ev_timer_again (loop, timer);
1290\& ...
1291\& timer->again = 17.;
1292\& ev_timer_again (loop, timer);
1293\& ...
1294\& timer->again = 10.;
1295\& ev_timer_again (loop, timer);
1296.Ve
1297.Sp
1298This is more slightly efficient then stopping/starting the timer each time
1299you want to modify its timeout value.
1300.IP "ev_tstamp repeat [read\-write]" 4
1301.IX Item "ev_tstamp repeat [read-write]"
1302The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out
1303or \f(CW\*(C`ev_timer_again\*(C'\fR is called and determines the next timeout (if any),
1304which is also when any modifications are taken into account.
951.PP 1305.PP
952Example: create a timer that fires after 60 seconds. 1306Example: Create a timer that fires after 60 seconds.
953.PP 1307.PP
954.Vb 5 1308.Vb 5
955\& static void 1309\& static void
956\& one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1310\& one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
957\& { 1311\& {
… …
963\& struct ev_timer mytimer; 1317\& struct ev_timer mytimer;
964\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.); 1318\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
965\& ev_timer_start (loop, &mytimer); 1319\& ev_timer_start (loop, &mytimer);
966.Ve 1320.Ve
967.PP 1321.PP
968Example: create a timeout timer that times out after 10 seconds of 1322Example: Create a timeout timer that times out after 10 seconds of
969inactivity. 1323inactivity.
970.PP 1324.PP
971.Vb 5 1325.Vb 5
972\& static void 1326\& static void
973\& timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1327\& timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
… …
986.Vb 3 1340.Vb 3
987\& // and in some piece of code that gets executed on any "activity": 1341\& // and in some piece of code that gets executed on any "activity":
988\& // reset the timeout to start ticking again at 10 seconds 1342\& // reset the timeout to start ticking again at 10 seconds
989\& ev_timer_again (&mytimer); 1343\& ev_timer_again (&mytimer);
990.Ve 1344.Ve
991.ie n .Sh """ev_periodic"" \- to cron or not to cron" 1345.ie n .Sh """ev_periodic"" \- to cron or not to cron?"
992.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron" 1346.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron?"
993.IX Subsection "ev_periodic - to cron or not to cron" 1347.IX Subsection "ev_periodic - to cron or not to cron?"
994Periodic watchers are also timers of a kind, but they are very versatile 1348Periodic watchers are also timers of a kind, but they are very versatile
995(and unfortunately a bit complex). 1349(and unfortunately a bit complex).
996.PP 1350.PP
997Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time) 1351Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time)
998but on wallclock time (absolute time). You can tell a periodic watcher 1352but on wallclock time (absolute time). You can tell a periodic watcher
999to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a 1353to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a
1000periodic watcher to trigger in 10 seconds (by specifiying e.g. \f(CW\*(C`ev_now () 1354periodic watcher to trigger in 10 seconds (by specifiying e.g. \f(CW\*(C`ev_now ()
1001+ 10.\*(C'\fR) and then reset your system clock to the last year, then it will 1355+ 10.\*(C'\fR) and then reset your system clock to the last year, then it will
1002take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger 1356take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger
1003roughly 10 seconds later and of course not if you reset your system time 1357roughly 10 seconds later).
1004again).
1005.PP 1358.PP
1006They can also be used to implement vastly more complex timers, such as 1359They can also be used to implement vastly more complex timers, such as
1007triggering an event on eahc midnight, local time. 1360triggering an event on each midnight, local time or other, complicated,
1361rules.
1008.PP 1362.PP
1009As with timers, the callback is guarenteed to be invoked only when the 1363As with timers, the callback is guarenteed to be invoked only when the
1010time (\f(CW\*(C`at\*(C'\fR) has been passed, but if multiple periodic timers become ready 1364time (\f(CW\*(C`at\*(C'\fR) has been passed, but if multiple periodic timers become ready
1011during the same loop iteration then order of execution is undefined. 1365during the same loop iteration then order of execution is undefined.
1366.PP
1367\fIWatcher-Specific Functions and Data Members\fR
1368.IX Subsection "Watcher-Specific Functions and Data Members"
1012.IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4 1369.IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4
1013.IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 1370.IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)"
1014.PD 0 1371.PD 0
1015.IP "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 4 1372.IP "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 4
1016.IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 1373.IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)"
1017.PD 1374.PD
1018Lots of arguments, lets sort it out... There are basically three modes of 1375Lots of arguments, lets sort it out... There are basically three modes of
1019operation, and we will explain them from simplest to complex: 1376operation, and we will explain them from simplest to complex:
1020.RS 4 1377.RS 4
1021.IP "* absolute timer (interval = reschedule_cb = 0)" 4 1378.IP "* absolute timer (at = time, interval = reschedule_cb = 0)" 4
1022.IX Item "absolute timer (interval = reschedule_cb = 0)" 1379.IX Item "absolute timer (at = time, interval = reschedule_cb = 0)"
1023In this configuration the watcher triggers an event at the wallclock time 1380In this configuration the watcher triggers an event at the wallclock time
1024\&\f(CW\*(C`at\*(C'\fR and doesn't repeat. It will not adjust when a time jump occurs, 1381\&\f(CW\*(C`at\*(C'\fR and doesn't repeat. It will not adjust when a time jump occurs,
1025that is, if it is to be run at January 1st 2011 then it will run when the 1382that is, if it is to be run at January 1st 2011 then it will run when the
1026system time reaches or surpasses this time. 1383system time reaches or surpasses this time.
1027.IP "* non-repeating interval timer (interval > 0, reschedule_cb = 0)" 4 1384.IP "* non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)" 4
1028.IX Item "non-repeating interval timer (interval > 0, reschedule_cb = 0)" 1385.IX Item "non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)"
1029In this mode the watcher will always be scheduled to time out at the next 1386In this mode the watcher will always be scheduled to time out at the next
1030\&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N) and then repeat, regardless 1387\&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N, which can also be negative)
1031of any time jumps. 1388and then repeat, regardless of any time jumps.
1032.Sp 1389.Sp
1033This can be used to create timers that do not drift with respect to system 1390This can be used to create timers that do not drift with respect to system
1034time: 1391time:
1035.Sp 1392.Sp
1036.Vb 1 1393.Vb 1
… …
1043by 3600. 1400by 3600.
1044.Sp 1401.Sp
1045Another way to think about it (for the mathematically inclined) is that 1402Another way to think about it (for the mathematically inclined) is that
1046\&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible 1403\&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible
1047time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps. 1404time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps.
1405.Sp
1406For numerical stability it is preferable that the \f(CW\*(C`at\*(C'\fR value is near
1407\&\f(CW\*(C`ev_now ()\*(C'\fR (the current time), but there is no range requirement for
1408this value.
1048.IP "* manual reschedule mode (reschedule_cb = callback)" 4 1409.IP "* manual reschedule mode (at and interval ignored, reschedule_cb = callback)" 4
1049.IX Item "manual reschedule mode (reschedule_cb = callback)" 1410.IX Item "manual reschedule mode (at and interval ignored, reschedule_cb = callback)"
1050In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR are both being 1411In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR are both being
1051ignored. Instead, each time the periodic watcher gets scheduled, the 1412ignored. Instead, each time the periodic watcher gets scheduled, the
1052reschedule callback will be called with the watcher as first, and the 1413reschedule callback will be called with the watcher as first, and the
1053current time as second argument. 1414current time as second argument.
1054.Sp 1415.Sp
1055\&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher, 1416\&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher,
1056ever, or make any event loop modifications\fR. If you need to stop it, 1417ever, or make any event loop modifications\fR. If you need to stop it,
1057return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop it afterwards (e.g. by 1418return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop it afterwards (e.g. by
1058starting a prepare watcher). 1419starting an \f(CW\*(C`ev_prepare\*(C'\fR watcher, which is legal).
1059.Sp 1420.Sp
1060Its prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 1421Its prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
1061ev_tstamp now)\*(C'\fR, e.g.: 1422ev_tstamp now)\*(C'\fR, e.g.:
1062.Sp 1423.Sp
1063.Vb 4 1424.Vb 4
… …
1087.IX Item "ev_periodic_again (loop, ev_periodic *)" 1448.IX Item "ev_periodic_again (loop, ev_periodic *)"
1088Simply stops and restarts the periodic watcher again. This is only useful 1449Simply stops and restarts the periodic watcher again. This is only useful
1089when you changed some parameters or the reschedule callback would return 1450when you changed some parameters or the reschedule callback would return
1090a different time than the last time it was called (e.g. in a crond like 1451a different time than the last time it was called (e.g. in a crond like
1091program when the crontabs have changed). 1452program when the crontabs have changed).
1453.IP "ev_tstamp offset [read\-write]" 4
1454.IX Item "ev_tstamp offset [read-write]"
1455When repeating, this contains the offset value, otherwise this is the
1456absolute point in time (the \f(CW\*(C`at\*(C'\fR value passed to \f(CW\*(C`ev_periodic_set\*(C'\fR).
1457.Sp
1458Can be modified any time, but changes only take effect when the periodic
1459timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
1460.IP "ev_tstamp interval [read\-write]" 4
1461.IX Item "ev_tstamp interval [read-write]"
1462The current interval value. Can be modified any time, but changes only
1463take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being
1464called.
1465.IP "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read\-write]" 4
1466.IX Item "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]"
1467The current reschedule callback, or \f(CW0\fR, if this functionality is
1468switched off. Can be changed any time, but changes only take effect when
1469the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
1470.IP "ev_tstamp at [read\-only]" 4
1471.IX Item "ev_tstamp at [read-only]"
1472When active, contains the absolute time that the watcher is supposed to
1473trigger next.
1092.PP 1474.PP
1093Example: call a callback every hour, or, more precisely, whenever the 1475Example: Call a callback every hour, or, more precisely, whenever the
1094system clock is divisible by 3600. The callback invocation times have 1476system clock is divisible by 3600. The callback invocation times have
1095potentially a lot of jittering, but good long-term stability. 1477potentially a lot of jittering, but good long-term stability.
1096.PP 1478.PP
1097.Vb 5 1479.Vb 5
1098\& static void 1480\& static void
… …
1106\& struct ev_periodic hourly_tick; 1488\& struct ev_periodic hourly_tick;
1107\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); 1489\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1108\& ev_periodic_start (loop, &hourly_tick); 1490\& ev_periodic_start (loop, &hourly_tick);
1109.Ve 1491.Ve
1110.PP 1492.PP
1111Example: the same as above, but use a reschedule callback to do it: 1493Example: The same as above, but use a reschedule callback to do it:
1112.PP 1494.PP
1113.Vb 1 1495.Vb 1
1114\& #include <math.h> 1496\& #include <math.h>
1115.Ve 1497.Ve
1116.PP 1498.PP
… …
1124.PP 1506.PP
1125.Vb 1 1507.Vb 1
1126\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); 1508\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1127.Ve 1509.Ve
1128.PP 1510.PP
1129Example: call a callback every hour, starting now: 1511Example: Call a callback every hour, starting now:
1130.PP 1512.PP
1131.Vb 4 1513.Vb 4
1132\& struct ev_periodic hourly_tick; 1514\& struct ev_periodic hourly_tick;
1133\& ev_periodic_init (&hourly_tick, clock_cb, 1515\& ev_periodic_init (&hourly_tick, clock_cb,
1134\& fmod (ev_now (loop), 3600.), 3600., 0); 1516\& fmod (ev_now (loop), 3600.), 3600., 0);
1135\& ev_periodic_start (loop, &hourly_tick); 1517\& ev_periodic_start (loop, &hourly_tick);
1136.Ve 1518.Ve
1137.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled" 1519.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled!"
1138.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled" 1520.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled!"
1139.IX Subsection "ev_signal - signal me when a signal gets signalled" 1521.IX Subsection "ev_signal - signal me when a signal gets signalled!"
1140Signal watchers will trigger an event when the process receives a specific 1522Signal watchers will trigger an event when the process receives a specific
1141signal one or more times. Even though signals are very asynchronous, libev 1523signal one or more times. Even though signals are very asynchronous, libev
1142will try it's best to deliver signals synchronously, i.e. as part of the 1524will try it's best to deliver signals synchronously, i.e. as part of the
1143normal event processing, like any other event. 1525normal event processing, like any other event.
1144.PP 1526.PP
… …
1146first watcher gets started will libev actually register a signal watcher 1528first watcher gets started will libev actually register a signal watcher
1147with the kernel (thus it coexists with your own signal handlers as long 1529with the kernel (thus it coexists with your own signal handlers as long
1148as you don't register any with libev). Similarly, when the last signal 1530as you don't register any with libev). Similarly, when the last signal
1149watcher for a signal is stopped libev will reset the signal handler to 1531watcher for a signal is stopped libev will reset the signal handler to
1150\&\s-1SIG_DFL\s0 (regardless of what it was set to before). 1532\&\s-1SIG_DFL\s0 (regardless of what it was set to before).
1533.PP
1534\fIWatcher-Specific Functions and Data Members\fR
1535.IX Subsection "Watcher-Specific Functions and Data Members"
1151.IP "ev_signal_init (ev_signal *, callback, int signum)" 4 1536.IP "ev_signal_init (ev_signal *, callback, int signum)" 4
1152.IX Item "ev_signal_init (ev_signal *, callback, int signum)" 1537.IX Item "ev_signal_init (ev_signal *, callback, int signum)"
1153.PD 0 1538.PD 0
1154.IP "ev_signal_set (ev_signal *, int signum)" 4 1539.IP "ev_signal_set (ev_signal *, int signum)" 4
1155.IX Item "ev_signal_set (ev_signal *, int signum)" 1540.IX Item "ev_signal_set (ev_signal *, int signum)"
1156.PD 1541.PD
1157Configures the watcher to trigger on the given signal number (usually one 1542Configures the watcher to trigger on the given signal number (usually one
1158of the \f(CW\*(C`SIGxxx\*(C'\fR constants). 1543of the \f(CW\*(C`SIGxxx\*(C'\fR constants).
1544.IP "int signum [read\-only]" 4
1545.IX Item "int signum [read-only]"
1546The signal the watcher watches out for.
1159.ie n .Sh """ev_child"" \- wait for pid status changes" 1547.ie n .Sh """ev_child"" \- watch out for process status changes"
1160.el .Sh "\f(CWev_child\fP \- wait for pid status changes" 1548.el .Sh "\f(CWev_child\fP \- watch out for process status changes"
1161.IX Subsection "ev_child - wait for pid status changes" 1549.IX Subsection "ev_child - watch out for process status changes"
1162Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to 1550Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to
1163some child status changes (most typically when a child of yours dies). 1551some child status changes (most typically when a child of yours dies).
1552.PP
1553\fIWatcher-Specific Functions and Data Members\fR
1554.IX Subsection "Watcher-Specific Functions and Data Members"
1164.IP "ev_child_init (ev_child *, callback, int pid)" 4 1555.IP "ev_child_init (ev_child *, callback, int pid)" 4
1165.IX Item "ev_child_init (ev_child *, callback, int pid)" 1556.IX Item "ev_child_init (ev_child *, callback, int pid)"
1166.PD 0 1557.PD 0
1167.IP "ev_child_set (ev_child *, int pid)" 4 1558.IP "ev_child_set (ev_child *, int pid)" 4
1168.IX Item "ev_child_set (ev_child *, int pid)" 1559.IX Item "ev_child_set (ev_child *, int pid)"
… …
1171\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look 1562\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look
1172at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see 1563at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see
1173the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems 1564the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems
1174\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the 1565\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the
1175process causing the status change. 1566process causing the status change.
1567.IP "int pid [read\-only]" 4
1568.IX Item "int pid [read-only]"
1569The process id this watcher watches out for, or \f(CW0\fR, meaning any process id.
1570.IP "int rpid [read\-write]" 4
1571.IX Item "int rpid [read-write]"
1572The process id that detected a status change.
1573.IP "int rstatus [read\-write]" 4
1574.IX Item "int rstatus [read-write]"
1575The process exit/trace status caused by \f(CW\*(C`rpid\*(C'\fR (see your systems
1576\&\f(CW\*(C`waitpid\*(C'\fR and \f(CW\*(C`sys/wait.h\*(C'\fR documentation for details).
1176.PP 1577.PP
1177Example: try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0. 1578Example: Try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0.
1178.PP 1579.PP
1179.Vb 5 1580.Vb 5
1180\& static void 1581\& static void
1181\& sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1582\& sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1182\& { 1583\& {
… …
1187.Vb 3 1588.Vb 3
1188\& struct ev_signal signal_watcher; 1589\& struct ev_signal signal_watcher;
1189\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT); 1590\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1190\& ev_signal_start (loop, &sigint_cb); 1591\& ev_signal_start (loop, &sigint_cb);
1191.Ve 1592.Ve
1593.ie n .Sh """ev_stat"" \- did the file attributes just change?"
1594.el .Sh "\f(CWev_stat\fP \- did the file attributes just change?"
1595.IX Subsection "ev_stat - did the file attributes just change?"
1596This watches a filesystem path for attribute changes. That is, it calls
1597\&\f(CW\*(C`stat\*(C'\fR regularly (or when the \s-1OS\s0 says it changed) and sees if it changed
1598compared to the last time, invoking the callback if it did.
1599.PP
1600The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does
1601not exist\*(R" is a status change like any other. The condition \*(L"path does
1602not exist\*(R" is signified by the \f(CW\*(C`st_nlink\*(C'\fR field being zero (which is
1603otherwise always forced to be at least one) and all the other fields of
1604the stat buffer having unspecified contents.
1605.PP
1606The path \fIshould\fR be absolute and \fImust not\fR end in a slash. If it is
1607relative and your working directory changes, the behaviour is undefined.
1608.PP
1609Since there is no standard to do this, the portable implementation simply
1610calls \f(CW\*(C`stat (2)\*(C'\fR regularly on the path to see if it changed somehow. You
1611can specify a recommended polling interval for this case. If you specify
1612a polling interval of \f(CW0\fR (highly recommended!) then a \fIsuitable,
1613unspecified default\fR value will be used (which you can expect to be around
1614five seconds, although this might change dynamically). Libev will also
1615impose a minimum interval which is currently around \f(CW0.1\fR, but thats
1616usually overkill.
1617.PP
1618This watcher type is not meant for massive numbers of stat watchers,
1619as even with OS-supported change notifications, this can be
1620resource\-intensive.
1621.PP
1622At the time of this writing, only the Linux inotify interface is
1623implemented (implementing kqueue support is left as an exercise for the
1624reader). Inotify will be used to give hints only and should not change the
1625semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers, which means that libev sometimes needs
1626to fall back to regular polling again even with inotify, but changes are
1627usually detected immediately, and if the file exists there will be no
1628polling.
1629.PP
1630\fIWatcher-Specific Functions and Data Members\fR
1631.IX Subsection "Watcher-Specific Functions and Data Members"
1632.IP "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 4
1633.IX Item "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)"
1634.PD 0
1635.IP "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" 4
1636.IX Item "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)"
1637.PD
1638Configures the watcher to wait for status changes of the given
1639\&\f(CW\*(C`path\*(C'\fR. The \f(CW\*(C`interval\*(C'\fR is a hint on how quickly a change is expected to
1640be detected and should normally be specified as \f(CW0\fR to let libev choose
1641a suitable value. The memory pointed to by \f(CW\*(C`path\*(C'\fR must point to the same
1642path for as long as the watcher is active.
1643.Sp
1644The callback will be receive \f(CW\*(C`EV_STAT\*(C'\fR when a change was detected,
1645relative to the attributes at the time the watcher was started (or the
1646last change was detected).
1647.IP "ev_stat_stat (ev_stat *)" 4
1648.IX Item "ev_stat_stat (ev_stat *)"
1649Updates the stat buffer immediately with new values. If you change the
1650watched path in your callback, you could call this fucntion to avoid
1651detecting this change (while introducing a race condition). Can also be
1652useful simply to find out the new values.
1653.IP "ev_statdata attr [read\-only]" 4
1654.IX Item "ev_statdata attr [read-only]"
1655The most-recently detected attributes of the file. Although the type is of
1656\&\f(CW\*(C`ev_statdata\*(C'\fR, this is usually the (or one of the) \f(CW\*(C`struct stat\*(C'\fR types
1657suitable for your system. If the \f(CW\*(C`st_nlink\*(C'\fR member is \f(CW0\fR, then there
1658was some error while \f(CW\*(C`stat\*(C'\fRing the file.
1659.IP "ev_statdata prev [read\-only]" 4
1660.IX Item "ev_statdata prev [read-only]"
1661The previous attributes of the file. The callback gets invoked whenever
1662\&\f(CW\*(C`prev\*(C'\fR != \f(CW\*(C`attr\*(C'\fR.
1663.IP "ev_tstamp interval [read\-only]" 4
1664.IX Item "ev_tstamp interval [read-only]"
1665The specified interval.
1666.IP "const char *path [read\-only]" 4
1667.IX Item "const char *path [read-only]"
1668The filesystem path that is being watched.
1669.PP
1670Example: Watch \f(CW\*(C`/etc/passwd\*(C'\fR for attribute changes.
1671.PP
1672.Vb 15
1673\& static void
1674\& passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1675\& {
1676\& /* /etc/passwd changed in some way */
1677\& if (w->attr.st_nlink)
1678\& {
1679\& printf ("passwd current size %ld\en", (long)w->attr.st_size);
1680\& printf ("passwd current atime %ld\en", (long)w->attr.st_mtime);
1681\& printf ("passwd current mtime %ld\en", (long)w->attr.st_mtime);
1682\& }
1683\& else
1684\& /* you shalt not abuse printf for puts */
1685\& puts ("wow, /etc/passwd is not there, expect problems. "
1686\& "if this is windows, they already arrived\en");
1687\& }
1688.Ve
1689.PP
1690.Vb 2
1691\& ...
1692\& ev_stat passwd;
1693.Ve
1694.PP
1695.Vb 2
1696\& ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
1697\& ev_stat_start (loop, &passwd);
1698.Ve
1192.ie n .Sh """ev_idle"" \- when you've got nothing better to do" 1699.ie n .Sh """ev_idle"" \- when you've got nothing better to do..."
1193.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do" 1700.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do..."
1194.IX Subsection "ev_idle - when you've got nothing better to do" 1701.IX Subsection "ev_idle - when you've got nothing better to do..."
1195Idle watchers trigger events when there are no other events are pending 1702Idle watchers trigger events when no other events of the same or higher
1196(prepare, check and other idle watchers do not count). That is, as long 1703priority are pending (prepare, check and other idle watchers do not
1197as your process is busy handling sockets or timeouts (or even signals, 1704count).
1198imagine) it will not be triggered. But when your process is idle all idle 1705.PP
1199watchers are being called again and again, once per event loop iteration \- 1706That is, as long as your process is busy handling sockets or timeouts
1707(or even signals, imagine) of the same or higher priority it will not be
1708triggered. But when your process is idle (or only lower-priority watchers
1709are pending), the idle watchers are being called once per event loop
1200until stopped, that is, or your process receives more events and becomes 1710iteration \- until stopped, that is, or your process receives more events
1201busy. 1711and becomes busy again with higher priority stuff.
1202.PP 1712.PP
1203The most noteworthy effect is that as long as any idle watchers are 1713The most noteworthy effect is that as long as any idle watchers are
1204active, the process will not block when waiting for new events. 1714active, the process will not block when waiting for new events.
1205.PP 1715.PP
1206Apart from keeping your process non-blocking (which is a useful 1716Apart from keeping your process non-blocking (which is a useful
1207effect on its own sometimes), idle watchers are a good place to do 1717effect on its own sometimes), idle watchers are a good place to do
1208\&\*(L"pseudo\-background processing\*(R", or delay processing stuff to after the 1718\&\*(L"pseudo\-background processing\*(R", or delay processing stuff to after the
1209event loop has handled all outstanding events. 1719event loop has handled all outstanding events.
1720.PP
1721\fIWatcher-Specific Functions and Data Members\fR
1722.IX Subsection "Watcher-Specific Functions and Data Members"
1210.IP "ev_idle_init (ev_signal *, callback)" 4 1723.IP "ev_idle_init (ev_signal *, callback)" 4
1211.IX Item "ev_idle_init (ev_signal *, callback)" 1724.IX Item "ev_idle_init (ev_signal *, callback)"
1212Initialises and configures the idle watcher \- it has no parameters of any 1725Initialises and configures the idle watcher \- it has no parameters of any
1213kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless, 1726kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless,
1214believe me. 1727believe me.
1215.PP 1728.PP
1216Example: dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR, start it, and in the 1729Example: Dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR watcher, start it, and in the
1217callback, free it. Alos, use no error checking, as usual. 1730callback, free it. Also, use no error checking, as usual.
1218.PP 1731.PP
1219.Vb 7 1732.Vb 7
1220\& static void 1733\& static void
1221\& idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1734\& idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1222\& { 1735\& {
… …
1229.Vb 3 1742.Vb 3
1230\& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); 1743\& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1231\& ev_idle_init (idle_watcher, idle_cb); 1744\& ev_idle_init (idle_watcher, idle_cb);
1232\& ev_idle_start (loop, idle_cb); 1745\& ev_idle_start (loop, idle_cb);
1233.Ve 1746.Ve
1234.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop" 1747.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop!"
1235.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop" 1748.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!"
1236.IX Subsection "ev_prepare and ev_check - customise your event loop" 1749.IX Subsection "ev_prepare and ev_check - customise your event loop!"
1237Prepare and check watchers are usually (but not always) used in tandem: 1750Prepare and check watchers are usually (but not always) used in tandem:
1238prepare watchers get invoked before the process blocks and check watchers 1751prepare watchers get invoked before the process blocks and check watchers
1239afterwards. 1752afterwards.
1240.PP 1753.PP
1754You \fImust not\fR call \f(CW\*(C`ev_loop\*(C'\fR or similar functions that enter
1755the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR
1756watchers. Other loops than the current one are fine, however. The
1757rationale behind this is that you do not need to check for recursion in
1758those watchers, i.e. the sequence will always be \f(CW\*(C`ev_prepare\*(C'\fR, blocking,
1759\&\f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each kind they will always be
1760called in pairs bracketing the blocking call.
1761.PP
1241Their main purpose is to integrate other event mechanisms into libev and 1762Their main purpose is to integrate other event mechanisms into libev and
1242their use is somewhat advanced. This could be used, for example, to track 1763their use is somewhat advanced. This could be used, for example, to track
1243variable changes, implement your own watchers, integrate net-snmp or a 1764variable changes, implement your own watchers, integrate net-snmp or a
1244coroutine library and lots more. 1765coroutine library and lots more. They are also occasionally useful if
1766you cache some data and want to flush it before blocking (for example,
1767in X programs you might want to do an \f(CW\*(C`XFlush ()\*(C'\fR in an \f(CW\*(C`ev_prepare\*(C'\fR
1768watcher).
1245.PP 1769.PP
1246This is done by examining in each prepare call which file descriptors need 1770This is done by examining in each prepare call which file descriptors need
1247to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for 1771to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for
1248them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries 1772them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries
1249provide just this functionality). Then, in the check watcher you check for 1773provide just this functionality). Then, in the check watcher you check for
… …
1258are ready to run (it's actually more complicated: it only runs coroutines 1782are ready to run (it's actually more complicated: it only runs coroutines
1259with priority higher than or equal to the event loop and one coroutine 1783with priority higher than or equal to the event loop and one coroutine
1260of lower priority, but only once, using idle watchers to keep the event 1784of lower priority, but only once, using idle watchers to keep the event
1261loop from blocking if lower-priority coroutines are active, thus mapping 1785loop from blocking if lower-priority coroutines are active, thus mapping
1262low-priority coroutines to idle/background tasks). 1786low-priority coroutines to idle/background tasks).
1787.PP
1788It is recommended to give \f(CW\*(C`ev_check\*(C'\fR watchers highest (\f(CW\*(C`EV_MAXPRI\*(C'\fR)
1789priority, to ensure that they are being run before any other watchers
1790after the poll. Also, \f(CW\*(C`ev_check\*(C'\fR watchers (and \f(CW\*(C`ev_prepare\*(C'\fR watchers,
1791too) should not activate (\*(L"feed\*(R") events into libev. While libev fully
1792supports this, they will be called before other \f(CW\*(C`ev_check\*(C'\fR watchers
1793did their job. As \f(CW\*(C`ev_check\*(C'\fR watchers are often used to embed other
1794(non\-libev) event loops those other event loops might be in an unusable
1795state until their \f(CW\*(C`ev_check\*(C'\fR watcher ran (always remind yourself to
1796coexist peacefully with others).
1797.PP
1798\fIWatcher-Specific Functions and Data Members\fR
1799.IX Subsection "Watcher-Specific Functions and Data Members"
1263.IP "ev_prepare_init (ev_prepare *, callback)" 4 1800.IP "ev_prepare_init (ev_prepare *, callback)" 4
1264.IX Item "ev_prepare_init (ev_prepare *, callback)" 1801.IX Item "ev_prepare_init (ev_prepare *, callback)"
1265.PD 0 1802.PD 0
1266.IP "ev_check_init (ev_check *, callback)" 4 1803.IP "ev_check_init (ev_check *, callback)" 4
1267.IX Item "ev_check_init (ev_check *, callback)" 1804.IX Item "ev_check_init (ev_check *, callback)"
1268.PD 1805.PD
1269Initialises and configures the prepare or check watcher \- they have no 1806Initialises and configures the prepare or check watcher \- they have no
1270parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR 1807parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR
1271macros, but using them is utterly, utterly and completely pointless. 1808macros, but using them is utterly, utterly and completely pointless.
1272.PP 1809.PP
1273Example: *TODO*. 1810There are a number of principal ways to embed other event loops or modules
1811into libev. Here are some ideas on how to include libadns into libev
1812(there is a Perl module named \f(CW\*(C`EV::ADNS\*(C'\fR that does this, which you could
1813use for an actually working example. Another Perl module named \f(CW\*(C`EV::Glib\*(C'\fR
1814embeds a Glib main context into libev, and finally, \f(CW\*(C`Glib::EV\*(C'\fR embeds \s-1EV\s0
1815into the Glib event loop).
1816.PP
1817Method 1: Add \s-1IO\s0 watchers and a timeout watcher in a prepare handler,
1818and in a check watcher, destroy them and call into libadns. What follows
1819is pseudo-code only of course. This requires you to either use a low
1820priority for the check watcher or use \f(CW\*(C`ev_clear_pending\*(C'\fR explicitly, as
1821the callbacks for the IO/timeout watchers might not have been called yet.
1822.PP
1823.Vb 2
1824\& static ev_io iow [nfd];
1825\& static ev_timer tw;
1826.Ve
1827.PP
1828.Vb 4
1829\& static void
1830\& io_cb (ev_loop *loop, ev_io *w, int revents)
1831\& {
1832\& }
1833.Ve
1834.PP
1835.Vb 8
1836\& // create io watchers for each fd and a timer before blocking
1837\& static void
1838\& adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1839\& {
1840\& int timeout = 3600000;
1841\& struct pollfd fds [nfd];
1842\& // actual code will need to loop here and realloc etc.
1843\& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1844.Ve
1845.PP
1846.Vb 3
1847\& /* the callback is illegal, but won't be called as we stop during check */
1848\& ev_timer_init (&tw, 0, timeout * 1e-3);
1849\& ev_timer_start (loop, &tw);
1850.Ve
1851.PP
1852.Vb 6
1853\& // create one ev_io per pollfd
1854\& for (int i = 0; i < nfd; ++i)
1855\& {
1856\& ev_io_init (iow + i, io_cb, fds [i].fd,
1857\& ((fds [i].events & POLLIN ? EV_READ : 0)
1858\& | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1859.Ve
1860.PP
1861.Vb 4
1862\& fds [i].revents = 0;
1863\& ev_io_start (loop, iow + i);
1864\& }
1865\& }
1866.Ve
1867.PP
1868.Vb 5
1869\& // stop all watchers after blocking
1870\& static void
1871\& adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1872\& {
1873\& ev_timer_stop (loop, &tw);
1874.Ve
1875.PP
1876.Vb 8
1877\& for (int i = 0; i < nfd; ++i)
1878\& {
1879\& // set the relevant poll flags
1880\& // could also call adns_processreadable etc. here
1881\& struct pollfd *fd = fds + i;
1882\& int revents = ev_clear_pending (iow + i);
1883\& if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1884\& if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1885.Ve
1886.PP
1887.Vb 3
1888\& // now stop the watcher
1889\& ev_io_stop (loop, iow + i);
1890\& }
1891.Ve
1892.PP
1893.Vb 2
1894\& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1895\& }
1896.Ve
1897.PP
1898Method 2: This would be just like method 1, but you run \f(CW\*(C`adns_afterpoll\*(C'\fR
1899in the prepare watcher and would dispose of the check watcher.
1900.PP
1901Method 3: If the module to be embedded supports explicit event
1902notification (adns does), you can also make use of the actual watcher
1903callbacks, and only destroy/create the watchers in the prepare watcher.
1904.PP
1905.Vb 5
1906\& static void
1907\& timer_cb (EV_P_ ev_timer *w, int revents)
1908\& {
1909\& adns_state ads = (adns_state)w->data;
1910\& update_now (EV_A);
1911.Ve
1912.PP
1913.Vb 2
1914\& adns_processtimeouts (ads, &tv_now);
1915\& }
1916.Ve
1917.PP
1918.Vb 5
1919\& static void
1920\& io_cb (EV_P_ ev_io *w, int revents)
1921\& {
1922\& adns_state ads = (adns_state)w->data;
1923\& update_now (EV_A);
1924.Ve
1925.PP
1926.Vb 3
1927\& if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1928\& if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1929\& }
1930.Ve
1931.PP
1932.Vb 1
1933\& // do not ever call adns_afterpoll
1934.Ve
1935.PP
1936Method 4: Do not use a prepare or check watcher because the module you
1937want to embed is too inflexible to support it. Instead, youc na override
1938their poll function. The drawback with this solution is that the main
1939loop is now no longer controllable by \s-1EV\s0. The \f(CW\*(C`Glib::EV\*(C'\fR module does
1940this.
1941.PP
1942.Vb 4
1943\& static gint
1944\& event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1945\& {
1946\& int got_events = 0;
1947.Ve
1948.PP
1949.Vb 2
1950\& for (n = 0; n < nfds; ++n)
1951\& // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1952.Ve
1953.PP
1954.Vb 2
1955\& if (timeout >= 0)
1956\& // create/start timer
1957.Ve
1958.PP
1959.Vb 2
1960\& // poll
1961\& ev_loop (EV_A_ 0);
1962.Ve
1963.PP
1964.Vb 3
1965\& // stop timer again
1966\& if (timeout >= 0)
1967\& ev_timer_stop (EV_A_ &to);
1968.Ve
1969.PP
1970.Vb 3
1971\& // stop io watchers again - their callbacks should have set
1972\& for (n = 0; n < nfds; ++n)
1973\& ev_io_stop (EV_A_ iow [n]);
1974.Ve
1975.PP
1976.Vb 2
1977\& return got_events;
1978\& }
1979.Ve
1274.ie n .Sh """ev_embed"" \- when one backend isn't enough" 1980.ie n .Sh """ev_embed"" \- when one backend isn't enough..."
1275.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough" 1981.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..."
1276.IX Subsection "ev_embed - when one backend isn't enough" 1982.IX Subsection "ev_embed - when one backend isn't enough..."
1277This is a rather advanced watcher type that lets you embed one event loop 1983This is a rather advanced watcher type that lets you embed one event loop
1278into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded 1984into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded
1279loop, other types of watchers might be handled in a delayed or incorrect 1985loop, other types of watchers might be handled in a delayed or incorrect
1280fashion and must not be used). 1986fashion and must not be used).
1281.PP 1987.PP
… …
1345\& ev_embed_start (loop_hi, &embed); 2051\& ev_embed_start (loop_hi, &embed);
1346\& } 2052\& }
1347\& else 2053\& else
1348\& loop_lo = loop_hi; 2054\& loop_lo = loop_hi;
1349.Ve 2055.Ve
2056.PP
2057\fIWatcher-Specific Functions and Data Members\fR
2058.IX Subsection "Watcher-Specific Functions and Data Members"
1350.IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4 2059.IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
1351.IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 2060.IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)"
1352.PD 0 2061.PD 0
1353.IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4 2062.IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
1354.IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 2063.IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)"
… …
1361.IP "ev_embed_sweep (loop, ev_embed *)" 4 2070.IP "ev_embed_sweep (loop, ev_embed *)" 4
1362.IX Item "ev_embed_sweep (loop, ev_embed *)" 2071.IX Item "ev_embed_sweep (loop, ev_embed *)"
1363Make a single, non-blocking sweep over the embedded loop. This works 2072Make a single, non-blocking sweep over the embedded loop. This works
1364similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most 2073similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most
1365apropriate way for embedded loops. 2074apropriate way for embedded loops.
2075.IP "struct ev_loop *other [read\-only]" 4
2076.IX Item "struct ev_loop *other [read-only]"
2077The embedded event loop.
2078.ie n .Sh """ev_fork"" \- the audacity to resume the event loop after a fork"
2079.el .Sh "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork"
2080.IX Subsection "ev_fork - the audacity to resume the event loop after a fork"
2081Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because
2082whoever is a good citizen cared to tell libev about it by calling
2083\&\f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the
2084event loop blocks next and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called,
2085and only in the child after the fork. If whoever good citizen calling
2086\&\f(CW\*(C`ev_default_fork\*(C'\fR cheats and calls it in the wrong process, the fork
2087handlers will be invoked, too, of course.
2088.PP
2089\fIWatcher-Specific Functions and Data Members\fR
2090.IX Subsection "Watcher-Specific Functions and Data Members"
2091.IP "ev_fork_init (ev_signal *, callback)" 4
2092.IX Item "ev_fork_init (ev_signal *, callback)"
2093Initialises and configures the fork watcher \- it has no parameters of any
2094kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless,
2095believe me.
1366.SH "OTHER FUNCTIONS" 2096.SH "OTHER FUNCTIONS"
1367.IX Header "OTHER FUNCTIONS" 2097.IX Header "OTHER FUNCTIONS"
1368There are some other functions of possible interest. Described. Here. Now. 2098There are some other functions of possible interest. Described. Here. Now.
1369.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4 2099.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4
1370.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 2100.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)"
… …
1442.PP 2172.PP
1443.Vb 1 2173.Vb 1
1444\& #include <ev++.h> 2174\& #include <ev++.h>
1445.Ve 2175.Ve
1446.PP 2176.PP
1447(it is not installed by default). This automatically includes \fIev.h\fR 2177This automatically includes \fIev.h\fR and puts all of its definitions (many
1448and puts all of its definitions (many of them macros) into the global 2178of them macros) into the global namespace. All \*(C+ specific things are
1449namespace. All \*(C+ specific things are put into the \f(CW\*(C`ev\*(C'\fR namespace. 2179put into the \f(CW\*(C`ev\*(C'\fR namespace. It should support all the same embedding
2180options as \fIev.h\fR, most notably \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR.
1450.PP 2181.PP
1451It should support all the same embedding options as \fIev.h\fR, most notably 2182Care has been taken to keep the overhead low. The only data member the \*(C+
1452\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. 2183classes add (compared to plain C\-style watchers) is the event loop pointer
2184that the watcher is associated with (or no additional members at all if
2185you disable \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR when embedding libev).
2186.PP
2187Currently, functions, and static and non-static member functions can be
2188used as callbacks. Other types should be easy to add as long as they only
2189need one additional pointer for context. If you need support for other
2190types of functors please contact the author (preferably after implementing
2191it).
1453.PP 2192.PP
1454Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace: 2193Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace:
1455.ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4 2194.ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4
1456.el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4 2195.el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4
1457.IX Item "ev::READ, ev::WRITE etc." 2196.IX Item "ev::READ, ev::WRITE etc."
… …
1469which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro 2208which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro
1470defines by many implementations. 2209defines by many implementations.
1471.Sp 2210.Sp
1472All of those classes have these methods: 2211All of those classes have these methods:
1473.RS 4 2212.RS 4
1474.IP "ev::TYPE::TYPE (object *, object::method *)" 4 2213.IP "ev::TYPE::TYPE ()" 4
1475.IX Item "ev::TYPE::TYPE (object *, object::method *)" 2214.IX Item "ev::TYPE::TYPE ()"
1476.PD 0 2215.PD 0
1477.IP "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)" 4 2216.IP "ev::TYPE::TYPE (struct ev_loop *)" 4
1478.IX Item "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)" 2217.IX Item "ev::TYPE::TYPE (struct ev_loop *)"
1479.IP "ev::TYPE::~TYPE" 4 2218.IP "ev::TYPE::~TYPE" 4
1480.IX Item "ev::TYPE::~TYPE" 2219.IX Item "ev::TYPE::~TYPE"
1481.PD 2220.PD
1482The constructor takes a pointer to an object and a method pointer to 2221The constructor (optionally) takes an event loop to associate the watcher
1483the event handler callback to call in this class. The constructor calls 2222with. If it is omitted, it will use \f(CW\*(C`EV_DEFAULT\*(C'\fR.
1484\&\f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the \f(CW\*(C`set\*(C'\fR method 2223.Sp
1485before starting it. If you do not specify a loop then the constructor 2224The constructor calls \f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the
1486automatically associates the default loop with this watcher. 2225\&\f(CW\*(C`set\*(C'\fR method before starting it.
2226.Sp
2227It will not set a callback, however: You have to call the templated \f(CW\*(C`set\*(C'\fR
2228method to set a callback before you can start the watcher.
2229.Sp
2230(The reason why you have to use a method is a limitation in \*(C+ which does
2231not allow explicit template arguments for constructors).
1487.Sp 2232.Sp
1488The destructor automatically stops the watcher if it is active. 2233The destructor automatically stops the watcher if it is active.
2234.IP "w\->set<class, &class::method> (object *)" 4
2235.IX Item "w->set<class, &class::method> (object *)"
2236This method sets the callback method to call. The method has to have a
2237signature of \f(CW\*(C`void (*)(ev_TYPE &, int)\*(C'\fR, it receives the watcher as
2238first argument and the \f(CW\*(C`revents\*(C'\fR as second. The object must be given as
2239parameter and is stored in the \f(CW\*(C`data\*(C'\fR member of the watcher.
2240.Sp
2241This method synthesizes efficient thunking code to call your method from
2242the C callback that libev requires. If your compiler can inline your
2243callback (i.e. it is visible to it at the place of the \f(CW\*(C`set\*(C'\fR call and
2244your compiler is good :), then the method will be fully inlined into the
2245thunking function, making it as fast as a direct C callback.
2246.Sp
2247Example: simple class declaration and watcher initialisation
2248.Sp
2249.Vb 4
2250\& struct myclass
2251\& {
2252\& void io_cb (ev::io &w, int revents) { }
2253\& }
2254.Ve
2255.Sp
2256.Vb 3
2257\& myclass obj;
2258\& ev::io iow;
2259\& iow.set <myclass, &myclass::io_cb> (&obj);
2260.Ve
2261.IP "w\->set<function> (void *data = 0)" 4
2262.IX Item "w->set<function> (void *data = 0)"
2263Also sets a callback, but uses a static method or plain function as
2264callback. The optional \f(CW\*(C`data\*(C'\fR argument will be stored in the watcher's
2265\&\f(CW\*(C`data\*(C'\fR member and is free for you to use.
2266.Sp
2267The prototype of the \f(CW\*(C`function\*(C'\fR must be \f(CW\*(C`void (*)(ev::TYPE &w, int)\*(C'\fR.
2268.Sp
2269See the method\-\f(CW\*(C`set\*(C'\fR above for more details.
2270.Sp
2271Example:
2272.Sp
2273.Vb 2
2274\& static void io_cb (ev::io &w, int revents) { }
2275\& iow.set <io_cb> ();
2276.Ve
1489.IP "w\->set (struct ev_loop *)" 4 2277.IP "w\->set (struct ev_loop *)" 4
1490.IX Item "w->set (struct ev_loop *)" 2278.IX Item "w->set (struct ev_loop *)"
1491Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only 2279Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only
1492do this when the watcher is inactive (and not pending either). 2280do this when the watcher is inactive (and not pending either).
1493.IP "w\->set ([args])" 4 2281.IP "w\->set ([args])" 4
1494.IX Item "w->set ([args])" 2282.IX Item "w->set ([args])"
1495Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same args. Must be 2283Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same args. Must be
1496called at least once. Unlike the C counterpart, an active watcher gets 2284called at least once. Unlike the C counterpart, an active watcher gets
1497automatically stopped and restarted. 2285automatically stopped and restarted when reconfiguring it with this
2286method.
1498.IP "w\->start ()" 4 2287.IP "w\->start ()" 4
1499.IX Item "w->start ()" 2288.IX Item "w->start ()"
1500Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument as the 2289Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the
1501constructor already takes the loop. 2290constructor already stores the event loop.
1502.IP "w\->stop ()" 4 2291.IP "w\->stop ()" 4
1503.IX Item "w->stop ()" 2292.IX Item "w->stop ()"
1504Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument. 2293Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument.
1505.ie n .IP "w\->again () ""ev::timer""\fR, \f(CW""ev::periodic"" only" 4 2294.ie n .IP "w\->again () (""ev::timer""\fR, \f(CW""ev::periodic"" only)" 4
1506.el .IP "w\->again () \f(CWev::timer\fR, \f(CWev::periodic\fR only" 4 2295.el .IP "w\->again () (\f(CWev::timer\fR, \f(CWev::periodic\fR only)" 4
1507.IX Item "w->again () ev::timer, ev::periodic only" 2296.IX Item "w->again () (ev::timer, ev::periodic only)"
1508For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding 2297For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding
1509\&\f(CW\*(C`ev_TYPE_again\*(C'\fR function. 2298\&\f(CW\*(C`ev_TYPE_again\*(C'\fR function.
1510.ie n .IP "w\->sweep () ""ev::embed"" only" 4 2299.ie n .IP "w\->sweep () (""ev::embed"" only)" 4
1511.el .IP "w\->sweep () \f(CWev::embed\fR only" 4 2300.el .IP "w\->sweep () (\f(CWev::embed\fR only)" 4
1512.IX Item "w->sweep () ev::embed only" 2301.IX Item "w->sweep () (ev::embed only)"
1513Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR. 2302Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR.
2303.ie n .IP "w\->update () (""ev::stat"" only)" 4
2304.el .IP "w\->update () (\f(CWev::stat\fR only)" 4
2305.IX Item "w->update () (ev::stat only)"
2306Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR.
1514.RE 2307.RE
1515.RS 4 2308.RS 4
1516.RE 2309.RE
1517.PP 2310.PP
1518Example: Define a class with an \s-1IO\s0 and idle watcher, start one of them in 2311Example: Define a class with an \s-1IO\s0 and idle watcher, start one of them in
… …
1528.Vb 2 2321.Vb 2
1529\& myclass (); 2322\& myclass ();
1530\& } 2323\& }
1531.Ve 2324.Ve
1532.PP 2325.PP
1533.Vb 6 2326.Vb 4
1534\& myclass::myclass (int fd) 2327\& myclass::myclass (int fd)
1535\& : io (this, &myclass::io_cb),
1536\& idle (this, &myclass::idle_cb)
1537\& { 2328\& {
2329\& io .set <myclass, &myclass::io_cb > (this);
2330\& idle.set <myclass, &myclass::idle_cb> (this);
2331.Ve
2332.PP
2333.Vb 2
1538\& io.start (fd, ev::READ); 2334\& io.start (fd, ev::READ);
1539\& } 2335\& }
1540.Ve 2336.Ve
2337.SH "MACRO MAGIC"
2338.IX Header "MACRO MAGIC"
2339Libev can be compiled with a variety of options, the most fundamantal
2340of which is \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most)
2341functions and callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument.
2342.PP
2343To make it easier to write programs that cope with either variant, the
2344following macros are defined:
2345.ie n .IP """EV_A""\fR, \f(CW""EV_A_""" 4
2346.el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4
2347.IX Item "EV_A, EV_A_"
2348This provides the loop \fIargument\fR for functions, if one is required (\*(L"ev
2349loop argument\*(R"). The \f(CW\*(C`EV_A\*(C'\fR form is used when this is the sole argument,
2350\&\f(CW\*(C`EV_A_\*(C'\fR is used when other arguments are following. Example:
2351.Sp
2352.Vb 3
2353\& ev_unref (EV_A);
2354\& ev_timer_add (EV_A_ watcher);
2355\& ev_loop (EV_A_ 0);
2356.Ve
2357.Sp
2358It assumes the variable \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR is in scope,
2359which is often provided by the following macro.
2360.ie n .IP """EV_P""\fR, \f(CW""EV_P_""" 4
2361.el .IP "\f(CWEV_P\fR, \f(CWEV_P_\fR" 4
2362.IX Item "EV_P, EV_P_"
2363This provides the loop \fIparameter\fR for functions, if one is required (\*(L"ev
2364loop parameter\*(R"). The \f(CW\*(C`EV_P\*(C'\fR form is used when this is the sole parameter,
2365\&\f(CW\*(C`EV_P_\*(C'\fR is used when other parameters are following. Example:
2366.Sp
2367.Vb 2
2368\& // this is how ev_unref is being declared
2369\& static void ev_unref (EV_P);
2370.Ve
2371.Sp
2372.Vb 2
2373\& // this is how you can declare your typical callback
2374\& static void cb (EV_P_ ev_timer *w, int revents)
2375.Ve
2376.Sp
2377It declares a parameter \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR, quite
2378suitable for use with \f(CW\*(C`EV_A\*(C'\fR.
2379.ie n .IP """EV_DEFAULT""\fR, \f(CW""EV_DEFAULT_""" 4
2380.el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4
2381.IX Item "EV_DEFAULT, EV_DEFAULT_"
2382Similar to the other two macros, this gives you the value of the default
2383loop, if multiple loops are supported (\*(L"ev loop default\*(R").
2384.PP
2385Example: Declare and initialise a check watcher, utilising the above
2386macros so it will work regardless of whether multiple loops are supported
2387or not.
2388.PP
2389.Vb 5
2390\& static void
2391\& check_cb (EV_P_ ev_timer *w, int revents)
2392\& {
2393\& ev_check_stop (EV_A_ w);
2394\& }
2395.Ve
2396.PP
2397.Vb 4
2398\& ev_check check;
2399\& ev_check_init (&check, check_cb);
2400\& ev_check_start (EV_DEFAULT_ &check);
2401\& ev_loop (EV_DEFAULT_ 0);
2402.Ve
2403.SH "EMBEDDING"
2404.IX Header "EMBEDDING"
2405Libev can (and often is) directly embedded into host
2406applications. Examples of applications that embed it include the Deliantra
2407Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe)
2408and rxvt\-unicode.
2409.PP
2410The goal is to enable you to just copy the necessary files into your
2411source directory without having to change even a single line in them, so
2412you can easily upgrade by simply copying (or having a checked-out copy of
2413libev somewhere in your source tree).
2414.Sh "\s-1FILESETS\s0"
2415.IX Subsection "FILESETS"
2416Depending on what features you need you need to include one or more sets of files
2417in your app.
2418.PP
2419\fI\s-1CORE\s0 \s-1EVENT\s0 \s-1LOOP\s0\fR
2420.IX Subsection "CORE EVENT LOOP"
2421.PP
2422To include only the libev core (all the \f(CW\*(C`ev_*\*(C'\fR functions), with manual
2423configuration (no autoconf):
2424.PP
2425.Vb 2
2426\& #define EV_STANDALONE 1
2427\& #include "ev.c"
2428.Ve
2429.PP
2430This will automatically include \fIev.h\fR, too, and should be done in a
2431single C source file only to provide the function implementations. To use
2432it, do the same for \fIev.h\fR in all files wishing to use this \s-1API\s0 (best
2433done by writing a wrapper around \fIev.h\fR that you can include instead and
2434where you can put other configuration options):
2435.PP
2436.Vb 2
2437\& #define EV_STANDALONE 1
2438\& #include "ev.h"
2439.Ve
2440.PP
2441Both header files and implementation files can be compiled with a \*(C+
2442compiler (at least, thats a stated goal, and breakage will be treated
2443as a bug).
2444.PP
2445You need the following files in your source tree, or in a directory
2446in your include path (e.g. in libev/ when using \-Ilibev):
2447.PP
2448.Vb 4
2449\& ev.h
2450\& ev.c
2451\& ev_vars.h
2452\& ev_wrap.h
2453.Ve
2454.PP
2455.Vb 1
2456\& ev_win32.c required on win32 platforms only
2457.Ve
2458.PP
2459.Vb 5
2460\& ev_select.c only when select backend is enabled (which is enabled by default)
2461\& ev_poll.c only when poll backend is enabled (disabled by default)
2462\& ev_epoll.c only when the epoll backend is enabled (disabled by default)
2463\& ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2464\& ev_port.c only when the solaris port backend is enabled (disabled by default)
2465.Ve
2466.PP
2467\&\fIev.c\fR includes the backend files directly when enabled, so you only need
2468to compile this single file.
2469.PP
2470\fI\s-1LIBEVENT\s0 \s-1COMPATIBILITY\s0 \s-1API\s0\fR
2471.IX Subsection "LIBEVENT COMPATIBILITY API"
2472.PP
2473To include the libevent compatibility \s-1API\s0, also include:
2474.PP
2475.Vb 1
2476\& #include "event.c"
2477.Ve
2478.PP
2479in the file including \fIev.c\fR, and:
2480.PP
2481.Vb 1
2482\& #include "event.h"
2483.Ve
2484.PP
2485in the files that want to use the libevent \s-1API\s0. This also includes \fIev.h\fR.
2486.PP
2487You need the following additional files for this:
2488.PP
2489.Vb 2
2490\& event.h
2491\& event.c
2492.Ve
2493.PP
2494\fI\s-1AUTOCONF\s0 \s-1SUPPORT\s0\fR
2495.IX Subsection "AUTOCONF SUPPORT"
2496.PP
2497Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your config in
2498whatever way you want, you can also \f(CW\*(C`m4_include([libev.m4])\*(C'\fR in your
2499\&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR undefined. \fIev.c\fR will then
2500include \fIconfig.h\fR and configure itself accordingly.
2501.PP
2502For this of course you need the m4 file:
2503.PP
2504.Vb 1
2505\& libev.m4
2506.Ve
2507.Sh "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0"
2508.IX Subsection "PREPROCESSOR SYMBOLS/MACROS"
2509Libev can be configured via a variety of preprocessor symbols you have to define
2510before including any of its files. The default is not to build for multiplicity
2511and only include the select backend.
2512.IP "\s-1EV_STANDALONE\s0" 4
2513.IX Item "EV_STANDALONE"
2514Must always be \f(CW1\fR if you do not use autoconf configuration, which
2515keeps libev from including \fIconfig.h\fR, and it also defines dummy
2516implementations for some libevent functions (such as logging, which is not
2517supported). It will also not define any of the structs usually found in
2518\&\fIevent.h\fR that are not directly supported by the libev core alone.
2519.IP "\s-1EV_USE_MONOTONIC\s0" 4
2520.IX Item "EV_USE_MONOTONIC"
2521If defined to be \f(CW1\fR, libev will try to detect the availability of the
2522monotonic clock option at both compiletime and runtime. Otherwise no use
2523of the monotonic clock option will be attempted. If you enable this, you
2524usually have to link against librt or something similar. Enabling it when
2525the functionality isn't available is safe, though, although you have
2526to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR
2527function is hiding in (often \fI\-lrt\fR).
2528.IP "\s-1EV_USE_REALTIME\s0" 4
2529.IX Item "EV_USE_REALTIME"
2530If defined to be \f(CW1\fR, libev will try to detect the availability of the
2531realtime clock option at compiletime (and assume its availability at
2532runtime if successful). Otherwise no use of the realtime clock option will
2533be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get
2534(CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See the
2535note about libraries in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though.
2536.IP "\s-1EV_USE_NANOSLEEP\s0" 4
2537.IX Item "EV_USE_NANOSLEEP"
2538If defined to be \f(CW1\fR, libev will assume that \f(CW\*(C`nanosleep ()\*(C'\fR is available
2539and will use it for delays. Otherwise it will use \f(CW\*(C`select ()\*(C'\fR.
2540.IP "\s-1EV_USE_SELECT\s0" 4
2541.IX Item "EV_USE_SELECT"
2542If undefined or defined to be \f(CW1\fR, libev will compile in support for the
2543\&\f(CW\*(C`select\*(C'\fR(2) backend. No attempt at autodetection will be done: if no
2544other method takes over, select will be it. Otherwise the select backend
2545will not be compiled in.
2546.IP "\s-1EV_SELECT_USE_FD_SET\s0" 4
2547.IX Item "EV_SELECT_USE_FD_SET"
2548If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR
2549structure. This is useful if libev doesn't compile due to a missing
2550\&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it misguesses the bitset layout on
2551exotic systems. This usually limits the range of file descriptors to some
2552low limit such as 1024 or might have other limitations (winsocket only
2553allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation, might
2554influence the size of the \f(CW\*(C`fd_set\*(C'\fR used.
2555.IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4
2556.IX Item "EV_SELECT_IS_WINSOCKET"
2557When defined to \f(CW1\fR, the select backend will assume that
2558select/socket/connect etc. don't understand file descriptors but
2559wants osf handles on win32 (this is the case when the select to
2560be used is the winsock select). This means that it will call
2561\&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise,
2562it is assumed that all these functions actually work on fds, even
2563on win32. Should not be defined on non\-win32 platforms.
2564.IP "\s-1EV_USE_POLL\s0" 4
2565.IX Item "EV_USE_POLL"
2566If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2)
2567backend. Otherwise it will be enabled on non\-win32 platforms. It
2568takes precedence over select.
2569.IP "\s-1EV_USE_EPOLL\s0" 4
2570.IX Item "EV_USE_EPOLL"
2571If defined to be \f(CW1\fR, libev will compile in support for the Linux
2572\&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime,
2573otherwise another method will be used as fallback. This is the
2574preferred backend for GNU/Linux systems.
2575.IP "\s-1EV_USE_KQUEUE\s0" 4
2576.IX Item "EV_USE_KQUEUE"
2577If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style
2578\&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime,
2579otherwise another method will be used as fallback. This is the preferred
2580backend for \s-1BSD\s0 and BSD-like systems, although on most BSDs kqueue only
2581supports some types of fds correctly (the only platform we found that
2582supports ptys for example was NetBSD), so kqueue might be compiled in, but
2583not be used unless explicitly requested. The best way to use it is to find
2584out whether kqueue supports your type of fd properly and use an embedded
2585kqueue loop.
2586.IP "\s-1EV_USE_PORT\s0" 4
2587.IX Item "EV_USE_PORT"
2588If defined to be \f(CW1\fR, libev will compile in support for the Solaris
258910 port style backend. Its availability will be detected at runtime,
2590otherwise another method will be used as fallback. This is the preferred
2591backend for Solaris 10 systems.
2592.IP "\s-1EV_USE_DEVPOLL\s0" 4
2593.IX Item "EV_USE_DEVPOLL"
2594reserved for future expansion, works like the \s-1USE\s0 symbols above.
2595.IP "\s-1EV_USE_INOTIFY\s0" 4
2596.IX Item "EV_USE_INOTIFY"
2597If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify
2598interface to speed up \f(CW\*(C`ev_stat\*(C'\fR watchers. Its actual availability will
2599be detected at runtime.
2600.IP "\s-1EV_H\s0" 4
2601.IX Item "EV_H"
2602The name of the \fIev.h\fR header file used to include it. The default if
2603undefined is \f(CW\*(C`<ev.h>\*(C'\fR in \fIevent.h\fR and \f(CW"ev.h"\fR in \fIev.c\fR. This
2604can be used to virtually rename the \fIev.h\fR header file in case of conflicts.
2605.IP "\s-1EV_CONFIG_H\s0" 4
2606.IX Item "EV_CONFIG_H"
2607If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override
2608\&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to
2609\&\f(CW\*(C`EV_H\*(C'\fR, above.
2610.IP "\s-1EV_EVENT_H\s0" 4
2611.IX Item "EV_EVENT_H"
2612Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea
2613of how the \fIevent.h\fR header can be found.
2614.IP "\s-1EV_PROTOTYPES\s0" 4
2615.IX Item "EV_PROTOTYPES"
2616If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function
2617prototypes, but still define all the structs and other symbols. This is
2618occasionally useful if you want to provide your own wrapper functions
2619around libev functions.
2620.IP "\s-1EV_MULTIPLICITY\s0" 4
2621.IX Item "EV_MULTIPLICITY"
2622If undefined or defined to \f(CW1\fR, then all event-loop-specific functions
2623will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create
2624additional independent event loops. Otherwise there will be no support
2625for multiple event loops and there is no first event loop pointer
2626argument. Instead, all functions act on the single default loop.
2627.IP "\s-1EV_MINPRI\s0" 4
2628.IX Item "EV_MINPRI"
2629.PD 0
2630.IP "\s-1EV_MAXPRI\s0" 4
2631.IX Item "EV_MAXPRI"
2632.PD
2633The range of allowed priorities. \f(CW\*(C`EV_MINPRI\*(C'\fR must be smaller or equal to
2634\&\f(CW\*(C`EV_MAXPRI\*(C'\fR, but otherwise there are no non-obvious limitations. You can
2635provide for more priorities by overriding those symbols (usually defined
2636to be \f(CW\*(C`\-2\*(C'\fR and \f(CW2\fR, respectively).
2637.Sp
2638When doing priority-based operations, libev usually has to linearly search
2639all the priorities, so having many of them (hundreds) uses a lot of space
2640and time, so using the defaults of five priorities (\-2 .. +2) is usually
2641fine.
2642.Sp
2643If your embedding app does not need any priorities, defining these both to
2644\&\f(CW0\fR will save some memory and cpu.
2645.IP "\s-1EV_PERIODIC_ENABLE\s0" 4
2646.IX Item "EV_PERIODIC_ENABLE"
2647If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If
2648defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
2649code.
2650.IP "\s-1EV_IDLE_ENABLE\s0" 4
2651.IX Item "EV_IDLE_ENABLE"
2652If undefined or defined to be \f(CW1\fR, then idle watchers are supported. If
2653defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
2654code.
2655.IP "\s-1EV_EMBED_ENABLE\s0" 4
2656.IX Item "EV_EMBED_ENABLE"
2657If undefined or defined to be \f(CW1\fR, then embed watchers are supported. If
2658defined to be \f(CW0\fR, then they are not.
2659.IP "\s-1EV_STAT_ENABLE\s0" 4
2660.IX Item "EV_STAT_ENABLE"
2661If undefined or defined to be \f(CW1\fR, then stat watchers are supported. If
2662defined to be \f(CW0\fR, then they are not.
2663.IP "\s-1EV_FORK_ENABLE\s0" 4
2664.IX Item "EV_FORK_ENABLE"
2665If undefined or defined to be \f(CW1\fR, then fork watchers are supported. If
2666defined to be \f(CW0\fR, then they are not.
2667.IP "\s-1EV_MINIMAL\s0" 4
2668.IX Item "EV_MINIMAL"
2669If you need to shave off some kilobytes of code at the expense of some
2670speed, define this symbol to \f(CW1\fR. Currently only used for gcc to override
2671some inlining decisions, saves roughly 30% codesize of amd64.
2672.IP "\s-1EV_PID_HASHSIZE\s0" 4
2673.IX Item "EV_PID_HASHSIZE"
2674\&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by
2675pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), usually more
2676than enough. If you need to manage thousands of children you might want to
2677increase this value (\fImust\fR be a power of two).
2678.IP "\s-1EV_INOTIFY_HASHSIZE\s0" 4
2679.IX Item "EV_INOTIFY_HASHSIZE"
2680\&\f(CW\*(C`ev_staz\*(C'\fR watchers use a small hash table to distribute workload by
2681inotify watch id. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR),
2682usually more than enough. If you need to manage thousands of \f(CW\*(C`ev_stat\*(C'\fR
2683watchers you might want to increase this value (\fImust\fR be a power of
2684two).
2685.IP "\s-1EV_COMMON\s0" 4
2686.IX Item "EV_COMMON"
2687By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining
2688this macro to a something else you can include more and other types of
2689members. You have to define it each time you include one of the files,
2690though, and it must be identical each time.
2691.Sp
2692For example, the perl \s-1EV\s0 module uses something like this:
2693.Sp
2694.Vb 3
2695\& #define EV_COMMON \e
2696\& SV *self; /* contains this struct */ \e
2697\& SV *cb_sv, *fh /* note no trailing ";" */
2698.Ve
2699.IP "\s-1EV_CB_DECLARE\s0 (type)" 4
2700.IX Item "EV_CB_DECLARE (type)"
2701.PD 0
2702.IP "\s-1EV_CB_INVOKE\s0 (watcher, revents)" 4
2703.IX Item "EV_CB_INVOKE (watcher, revents)"
2704.IP "ev_set_cb (ev, cb)" 4
2705.IX Item "ev_set_cb (ev, cb)"
2706.PD
2707Can be used to change the callback member declaration in each watcher,
2708and the way callbacks are invoked and set. Must expand to a struct member
2709definition and a statement, respectively. See the \fIev.h\fR header file for
2710their default definitions. One possible use for overriding these is to
2711avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use
2712method calls instead of plain function calls in \*(C+.
2713.Sh "\s-1EXPORTED\s0 \s-1API\s0 \s-1SYMBOLS\s0"
2714.IX Subsection "EXPORTED API SYMBOLS"
2715If you need to re-export the \s-1API\s0 (e.g. via a dll) and you need a list of
2716exported symbols, you can use the provided \fISymbol.*\fR files which list
2717all public symbols, one per line:
2718.Sp
2719.Vb 2
2720\& Symbols.ev for libev proper
2721\& Symbols.event for the libevent emulation
2722.Ve
2723.Sp
2724This can also be used to rename all public symbols to avoid clashes with
2725multiple versions of libev linked together (which is obviously bad in
2726itself, but sometimes it is inconvinient to avoid this).
2727.Sp
2728A sed command like this will create wrapper \f(CW\*(C`#define\*(C'\fR's that you need to
2729include before including \fIev.h\fR:
2730.Sp
2731.Vb 1
2732\& <Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
2733.Ve
2734.Sp
2735This would create a file \fIwrap.h\fR which essentially looks like this:
2736.Sp
2737.Vb 4
2738\& #define ev_backend myprefix_ev_backend
2739\& #define ev_check_start myprefix_ev_check_start
2740\& #define ev_check_stop myprefix_ev_check_stop
2741\& ...
2742.Ve
2743.Sh "\s-1EXAMPLES\s0"
2744.IX Subsection "EXAMPLES"
2745For a real-world example of a program the includes libev
2746verbatim, you can have a look at the \s-1EV\s0 perl module
2747(<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
2748the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public
2749interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file
2750will be compiled. It is pretty complex because it provides its own header
2751file.
2752.Sp
2753The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file
2754that everybody includes and which overrides some configure choices:
2755.Sp
2756.Vb 9
2757\& #define EV_MINIMAL 1
2758\& #define EV_USE_POLL 0
2759\& #define EV_MULTIPLICITY 0
2760\& #define EV_PERIODIC_ENABLE 0
2761\& #define EV_STAT_ENABLE 0
2762\& #define EV_FORK_ENABLE 0
2763\& #define EV_CONFIG_H <config.h>
2764\& #define EV_MINPRI 0
2765\& #define EV_MAXPRI 0
2766.Ve
2767.Sp
2768.Vb 1
2769\& #include "ev++.h"
2770.Ve
2771.Sp
2772And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled:
2773.Sp
2774.Vb 2
2775\& #include "ev_cpp.h"
2776\& #include "ev.c"
2777.Ve
2778.SH "COMPLEXITIES"
2779.IX Header "COMPLEXITIES"
2780In this section the complexities of (many of) the algorithms used inside
2781libev will be explained. For complexity discussions about backends see the
2782documentation for \f(CW\*(C`ev_default_init\*(C'\fR.
2783.Sp
2784All of the following are about amortised time: If an array needs to be
2785extended, libev needs to realloc and move the whole array, but this
2786happens asymptotically never with higher number of elements, so O(1) might
2787mean it might do a lengthy realloc operation in rare cases, but on average
2788it is much faster and asymptotically approaches constant time.
2789.RS 4
2790.IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4
2791.IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)"
2792This means that, when you have a watcher that triggers in one hour and
2793there are 100 watchers that would trigger before that then inserting will
2794have to skip those 100 watchers.
2795.IP "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)" 4
2796.IX Item "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)"
2797That means that for changing a timer costs less than removing/adding them
2798as only the relative motion in the event queue has to be paid for.
2799.IP "Starting io/check/prepare/idle/signal/child watchers: O(1)" 4
2800.IX Item "Starting io/check/prepare/idle/signal/child watchers: O(1)"
2801These just add the watcher into an array or at the head of a list.
2802=item Stopping check/prepare/idle watchers: O(1)
2803.IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4
2804.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))"
2805These watchers are stored in lists then need to be walked to find the
2806correct watcher to remove. The lists are usually short (you don't usually
2807have many watchers waiting for the same fd or signal).
2808.IP "Finding the next timer per loop iteration: O(1)" 4
2809.IX Item "Finding the next timer per loop iteration: O(1)"
2810.PD 0
2811.IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4
2812.IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)"
2813.PD
2814A change means an I/O watcher gets started or stopped, which requires
2815libev to recalculate its status (and possibly tell the kernel).
2816.IP "Activating one watcher: O(1)" 4
2817.IX Item "Activating one watcher: O(1)"
2818.PD 0
2819.IP "Priority handling: O(number_of_priorities)" 4
2820.IX Item "Priority handling: O(number_of_priorities)"
2821.PD
2822Priorities are implemented by allocating some space for each
2823priority. When doing priority-based operations, libev usually has to
2824linearly search all the priorities.
2825.RE
2826.RS 4
1541.SH "AUTHOR" 2827.SH "AUTHOR"
1542.IX Header "AUTHOR" 2828.IX Header "AUTHOR"
1543Marc Lehmann <libev@schmorp.de>. 2829Marc Lehmann <libev@schmorp.de>.

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