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129.\" ======================================================================== 132.\" ========================================================================
130.\" 133.\"
131.IX Title ""<STANDARD INPUT>" 1" 134.IX Title "EV 1"
132.TH "<STANDARD INPUT>" 1 "2007-11-24" "perl v5.8.8" "User Contributed Perl Documentation" 135.TH EV 1 "2008-01-28" "perl v5.10.0" "User Contributed Perl Documentation"
136.\" For nroff, turn off justification. Always turn off hyphenation; it makes
137.\" way too many mistakes in technical documents.
138.if n .ad l
139.nh
133.SH "NAME" 140.SH "NAME"
134libev \- a high performance full\-featured event loop written in C 141libev \- a high performance full\-featured event loop written in C
135.SH "SYNOPSIS" 142.SH "SYNOPSIS"
136.IX Header "SYNOPSIS" 143.IX Header "SYNOPSIS"
137.Vb 1 144.Vb 1
138\& #include <ev.h> 145\& #include <ev.h>
139.Ve 146.Ve
147.Sh "\s-1EXAMPLE\s0 \s-1PROGRAM\s0"
148.IX Subsection "EXAMPLE PROGRAM"
149.Vb 1
150\& #include <ev.h>
151\&
152\& ev_io stdin_watcher;
153\& ev_timer timeout_watcher;
154\&
155\& /* called when data readable on stdin */
156\& static void
157\& stdin_cb (EV_P_ struct ev_io *w, int revents)
158\& {
159\& /* puts ("stdin ready"); */
160\& ev_io_stop (EV_A_ w); /* just a syntax example */
161\& ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
162\& }
163\&
164\& static void
165\& timeout_cb (EV_P_ struct ev_timer *w, int revents)
166\& {
167\& /* puts ("timeout"); */
168\& ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
169\& }
170\&
171\& int
172\& main (void)
173\& {
174\& struct ev_loop *loop = ev_default_loop (0);
175\&
176\& /* initialise an io watcher, then start it */
177\& ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
178\& ev_io_start (loop, &stdin_watcher);
179\&
180\& /* simple non\-repeating 5.5 second timeout */
181\& ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
182\& ev_timer_start (loop, &timeout_watcher);
183\&
184\& /* loop till timeout or data ready */
185\& ev_loop (loop, 0);
186\&
187\& return 0;
188\& }
189.Ve
140.SH "DESCRIPTION" 190.SH "DESCRIPTION"
141.IX Header "DESCRIPTION" 191.IX Header "DESCRIPTION"
192The newest version of this document is also available as a html-formatted
193web page you might find easier to navigate when reading it for the first
194time: <http://cvs.schmorp.de/libev/ev.html>.
195.PP
142Libev is an event loop: you register interest in certain events (such as a 196Libev 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 197file descriptor being readable or a timeout occurring), and it will manage
144these event sources and provide your program with events. 198these event sources and provide your program with events.
145.PP 199.PP
146To do this, it must take more or less complete control over your process 200To 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 201(or thread) by executing the \fIevent loop\fR handler, and will then
148communicate events via a callback mechanism. 202communicate events via a callback mechanism.
149.PP 203.PP
150You register interest in certain events by registering so-called \fIevent 204You register interest in certain events by registering so-called \fIevent
151watchers\fR, which are relatively small C structures you initialise with the 205watchers\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 206details of the event, and then hand it over to libev by \fIstarting\fR the
153watcher. 207watcher.
154.SH "FEATURES" 208.Sh "\s-1FEATURES\s0"
155.IX Header "FEATURES" 209.IX Subsection "FEATURES"
156Libev supports select, poll, the linux-specific epoll and the bsd-specific 210Libev 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 211BSD-specific \f(CW\*(C`kqueue\*(C'\fR and the Solaris-specific event port mechanisms
158timers with customised rescheduling, signal events, process status change 212for 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 213(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 214with customised rescheduling (\f(CW\*(C`ev_periodic\*(C'\fR), synchronous signals
161fast (see this benchmark comparing 215(\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). 216watchers dealing with the event loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR,
217\&\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
218file watchers (\f(CW\*(C`ev_stat\*(C'\fR) and even limited support for fork events
219(\f(CW\*(C`ev_fork\*(C'\fR).
220.PP
221It also is quite fast (see this
222benchmark comparing it to libevent
223for example).
163.SH "CONVENTIONS" 224.Sh "\s-1CONVENTIONS\s0"
164.IX Header "CONVENTIONS" 225.IX Subsection "CONVENTIONS"
165Libev is very configurable. In this manual the default configuration 226Libev is very configurable. In this manual the default configuration will
166will be described, which supports multiple event loops. For more info 227be described, which supports multiple event loops. For more info about
167about various configuration options please have a look at the file 228various 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 229this manual. If libev was configured without support for multiple event
169support for multiple event loops, then all functions taking an initial 230loops, 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) 231(which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR) will not have this argument.
171will not have this argument. 232.Sh "\s-1TIME\s0 \s-1REPRESENTATION\s0"
172.SH "TIME REPRESENTATION"
173.IX Header "TIME REPRESENTATION" 233.IX Subsection "TIME REPRESENTATION"
174Libev represents time as a single floating point number, representing the 234Libev represents time as a single floating point number, representing the
175(fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near 235(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 236the 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 237called \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 238to 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. 239it, you should treat it as some floatingpoint value. Unlike the name
240component \f(CW\*(C`stamp\*(C'\fR might indicate, it is also used for time differences
241throughout libev.
180.SH "GLOBAL FUNCTIONS" 242.SH "GLOBAL FUNCTIONS"
181.IX Header "GLOBAL FUNCTIONS" 243.IX Header "GLOBAL FUNCTIONS"
182These functions can be called anytime, even before initialising the 244These functions can be called anytime, even before initialising the
183library in any way. 245library in any way.
184.IP "ev_tstamp ev_time ()" 4 246.IP "ev_tstamp ev_time ()" 4
185.IX Item "ev_tstamp ev_time ()" 247.IX Item "ev_tstamp ev_time ()"
186Returns the current time as libev would use it. Please note that the 248Returns 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 249\&\f(CW\*(C`ev_now\*(C'\fR function is usually faster and also often returns the timestamp
188you actually want to know. 250you actually want to know.
251.IP "ev_sleep (ev_tstamp interval)" 4
252.IX Item "ev_sleep (ev_tstamp interval)"
253Sleep for the given interval: The current thread will be blocked until
254either it is interrupted or the given time interval has passed. Basically
255this is a subsecond-resolution \f(CW\*(C`sleep ()\*(C'\fR.
189.IP "int ev_version_major ()" 4 256.IP "int ev_version_major ()" 4
190.IX Item "int ev_version_major ()" 257.IX Item "int ev_version_major ()"
191.PD 0 258.PD 0
192.IP "int ev_version_minor ()" 4 259.IP "int ev_version_minor ()" 4
193.IX Item "int ev_version_minor ()" 260.IX Item "int ev_version_minor ()"
194.PD 261.PD
195You can find out the major and minor version numbers of the library 262You 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 263you 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 264\&\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 265symbols \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. 266version of the library your program was compiled against.
200.Sp 267.Sp
268These version numbers refer to the \s-1ABI\s0 version of the library, not the
269release version.
270.Sp
201Usually, it's a good idea to terminate if the major versions mismatch, 271Usually, it's a good idea to terminate if the major versions mismatch,
202as this indicates an incompatible change. Minor versions are usually 272as this indicates an incompatible change. Minor versions are usually
203compatible to older versions, so a larger minor version alone is usually 273compatible to older versions, so a larger minor version alone is usually
204not a problem. 274not a problem.
205.Sp 275.Sp
206Example: make sure we haven't accidentally been linked against the wrong 276Example: Make sure we haven't accidentally been linked against the wrong
207version: 277version.
208.Sp 278.Sp
209.Vb 3 279.Vb 3
210\& assert (("libev version mismatch", 280\& assert (("libev version mismatch",
211\& ev_version_major () == EV_VERSION_MAJOR 281\& ev_version_major () == EV_VERSION_MAJOR
212\& && ev_version_minor () >= EV_VERSION_MINOR)); 282\& && ev_version_minor () >= EV_VERSION_MINOR));
… …
234(assuming you know what you are doing). This is the set of backends that 304(assuming you know what you are doing). This is the set of backends that
235libev will probe for if you specify no backends explicitly. 305libev will probe for if you specify no backends explicitly.
236.IP "unsigned int ev_embeddable_backends ()" 4 306.IP "unsigned int ev_embeddable_backends ()" 4
237.IX Item "unsigned int ev_embeddable_backends ()" 307.IX Item "unsigned int ev_embeddable_backends ()"
238Returns the set of backends that are embeddable in other event loops. This 308Returns the set of backends that are embeddable in other event loops. This
239is the theoretical, all\-platform, value. To find which backends 309is the theoretical, all-platform, value. To find which backends
240might be supported on the current system, you would need to look at 310might be supported on the current system, you would need to look at
241\&\f(CW\*(C`ev_embeddable_backends () & ev_supported_backends ()\*(C'\fR, likewise for 311\&\f(CW\*(C`ev_embeddable_backends () & ev_supported_backends ()\*(C'\fR, likewise for
242recommended ones. 312recommended ones.
243.Sp 313.Sp
244See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info. 314See 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))" 4 315.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4
246.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))" 316.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))"
247Sets the allocation function to use (the prototype is similar to the 317Sets the allocation function to use (the prototype is similar \- the
248realloc C function, the semantics are identical). It is used to allocate 318semantics is identical \- to the realloc C function). It is used to
249and free memory (no surprises here). If it returns zero when memory 319allocate and free memory (no surprises here). If it returns zero when
250needs to be allocated, the library might abort or take some potentially 320memory needs to be allocated, the library might abort or take some
251destructive action. The default is your system realloc function. 321potentially destructive action. The default is your system realloc
322function.
252.Sp 323.Sp
253You could override this function in high-availability programs to, say, 324You could override this function in high-availability programs to, say,
254free some memory if it cannot allocate memory, to use a special allocator, 325free 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. 326or even to sleep a while and retry until some memory is available.
256.Sp 327.Sp
257Example: replace the libev allocator with one that waits a bit and then 328Example: Replace the libev allocator with one that waits a bit and then
258retries: better than mine). 329retries).
259.Sp 330.Sp
260.Vb 6 331.Vb 6
261\& static void * 332\& static void *
262\& persistent_realloc (void *ptr, long size) 333\& persistent_realloc (void *ptr, size_t size)
263\& { 334\& {
264\& for (;;) 335\& for (;;)
265\& { 336\& {
266\& void *newptr = realloc (ptr, size); 337\& void *newptr = realloc (ptr, size);
267.Ve 338\&
268.Sp
269.Vb 2
270\& if (newptr) 339\& if (newptr)
271\& return newptr; 340\& return newptr;
272.Ve 341\&
273.Sp
274.Vb 3
275\& sleep (60); 342\& sleep (60);
276\& } 343\& }
277\& } 344\& }
278.Ve 345\&
279.Sp
280.Vb 2
281\& ... 346\& ...
282\& ev_set_allocator (persistent_realloc); 347\& ev_set_allocator (persistent_realloc);
283.Ve 348.Ve
284.IP "ev_set_syserr_cb (void (*cb)(const char *msg));" 4 349.IP "ev_set_syserr_cb (void (*cb)(const char *msg));" 4
285.IX Item "ev_set_syserr_cb (void (*cb)(const char *msg));" 350.IX Item "ev_set_syserr_cb (void (*cb)(const char *msg));"
… …
289callback is set, then libev will expect it to remedy the sitution, no 354callback is set, then libev will expect it to remedy the sitution, no
290matter what, when it returns. That is, libev will generally retry the 355matter what, when it returns. That is, libev will generally retry the
291requested operation, or, if the condition doesn't go away, do bad stuff 356requested operation, or, if the condition doesn't go away, do bad stuff
292(such as abort). 357(such as abort).
293.Sp 358.Sp
294Example: do the same thing as libev does internally: 359Example: This is basically the same thing that libev does internally, too.
295.Sp 360.Sp
296.Vb 6 361.Vb 6
297\& static void 362\& static void
298\& fatal_error (const char *msg) 363\& fatal_error (const char *msg)
299\& { 364\& {
300\& perror (msg); 365\& perror (msg);
301\& abort (); 366\& abort ();
302\& } 367\& }
303.Ve 368\&
304.Sp
305.Vb 2
306\& ... 369\& ...
307\& ev_set_syserr_cb (fatal_error); 370\& ev_set_syserr_cb (fatal_error);
308.Ve 371.Ve
309.SH "FUNCTIONS CONTROLLING THE EVENT LOOP" 372.SH "FUNCTIONS CONTROLLING THE EVENT LOOP"
310.IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP" 373.IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP"
… …
325false. If it already was initialised it simply returns it (and ignores the 388false. If it already was initialised it simply returns it (and ignores the
326flags. If that is troubling you, check \f(CW\*(C`ev_backend ()\*(C'\fR afterwards). 389flags. If that is troubling you, check \f(CW\*(C`ev_backend ()\*(C'\fR afterwards).
327.Sp 390.Sp
328If you don't know what event loop to use, use the one returned from this 391If you don't know what event loop to use, use the one returned from this
329function. 392function.
393.Sp
394The default loop is the only loop that can handle \f(CW\*(C`ev_signal\*(C'\fR and
395\&\f(CW\*(C`ev_child\*(C'\fR watchers, and to do this, it always registers a handler
396for \f(CW\*(C`SIGCHLD\*(C'\fR. If this is a problem for your app you can either
397create a dynamic loop with \f(CW\*(C`ev_loop_new\*(C'\fR that doesn't do that, or you
398can simply overwrite the \f(CW\*(C`SIGCHLD\*(C'\fR signal handler \fIafter\fR calling
399\&\f(CW\*(C`ev_default_init\*(C'\fR.
330.Sp 400.Sp
331The flags argument can be used to specify special behaviour or specific 401The flags argument can be used to specify special behaviour or specific
332backends to use, and is usually specified as \f(CW0\fR (or \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). 402backends to use, and is usually specified as \f(CW0\fR (or \f(CW\*(C`EVFLAG_AUTO\*(C'\fR).
333.Sp 403.Sp
334The following flags are supported: 404The following flags are supported:
… …
345or setgid) then libev will \fInot\fR look at the environment variable 415or 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 416\&\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 417override 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 418useful to try out specific backends to test their performance, or to work
349around bugs. 419around bugs.
420.ie n .IP """EVFLAG_FORKCHECK""" 4
421.el .IP "\f(CWEVFLAG_FORKCHECK\fR" 4
422.IX Item "EVFLAG_FORKCHECK"
423Instead of calling \f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR manually after
424a fork, you can also make libev check for a fork in each iteration by
425enabling this flag.
426.Sp
427This works by calling \f(CW\*(C`getpid ()\*(C'\fR on every iteration of the loop,
428and thus this might slow down your event loop if you do a lot of loop
429iterations and little real work, but is usually not noticeable (on my
430Linux system for example, \f(CW\*(C`getpid\*(C'\fR is actually a simple 5\-insn sequence
431without a syscall and thus \fIvery\fR fast, but my Linux system also has
432\&\f(CW\*(C`pthread_atfork\*(C'\fR which is even faster).
433.Sp
434The big advantage of this flag is that you can forget about fork (and
435forget about forgetting to tell libev about forking) when you use this
436flag.
437.Sp
438This flag setting cannot be overriden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR
439environment variable.
350.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4 440.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4
351.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4 441.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4
352.IX Item "EVBACKEND_SELECT (value 1, portable select backend)" 442.IX Item "EVBACKEND_SELECT (value 1, portable select backend)"
353This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as 443This 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, 444libev tries to roll its own fd_set with no limits on the number of fds,
355but if that fails, expect a fairly low limit on the number of fds when 445but if that fails, expect a fairly low limit on the number of fds when
356using this backend. It doesn't scale too well (O(highest_fd)), but its usually 446using this backend. It doesn't scale too well (O(highest_fd)), but its
357the fastest backend for a low number of fds. 447usually the fastest backend for a low number of (low-numbered :) fds.
448.Sp
449To get good performance out of this backend you need a high amount of
450parallelity (most of the file descriptors should be busy). If you are
451writing a server, you should \f(CW\*(C`accept ()\*(C'\fR in a loop to accept as many
452connections as possible during one iteration. You might also want to have
453a look at \f(CW\*(C`ev_set_io_collect_interval ()\*(C'\fR to increase the amount of
454readyness notifications you get per iteration.
358.ie n .IP """EVBACKEND_POLL"" (value 2, poll backend, available everywhere except on windows)" 4 455.ie n .IP """EVBACKEND_POLL"" (value 2, poll backend, available everywhere except on windows)" 4
359.el .IP "\f(CWEVBACKEND_POLL\fR (value 2, poll backend, available everywhere except on windows)" 4 456.el .IP "\f(CWEVBACKEND_POLL\fR (value 2, poll backend, available everywhere except on windows)" 4
360.IX Item "EVBACKEND_POLL (value 2, poll backend, available everywhere except on windows)" 457.IX Item "EVBACKEND_POLL (value 2, poll backend, available everywhere except on windows)"
361And this is your standard \fIpoll\fR\|(2) backend. It's more complicated than 458And this is your standard \fIpoll\fR\|(2) backend. It's more complicated
362select, but handles sparse fds better and has no artificial limit on the 459than select, but handles sparse fds better and has no artificial
363number of fds you can use (except it will slow down considerably with a 460limit on the number of fds you can use (except it will slow down
364lot of inactive fds). It scales similarly to select, i.e. O(total_fds). 461considerably with a lot of inactive fds). It scales similarly to select,
462i.e. O(total_fds). See the entry for \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR, above, for
463performance tips.
365.ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4 464.ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4
366.el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4 465.el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4
367.IX Item "EVBACKEND_EPOLL (value 4, Linux)" 466.IX Item "EVBACKEND_EPOLL (value 4, Linux)"
368For few fds, this backend is a bit little slower than poll and select, 467For 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 468but 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 469like O(total_fds) where n is the total number of fds (or the highest fd),
371either O(1) or O(active_fds). 470epoll scales either O(1) or O(active_fds). The epoll design has a number
471of shortcomings, such as silently dropping events in some hard-to-detect
472cases and rewiring a syscall per fd change, no fork support and bad
473support for dup.
372.Sp 474.Sp
373While stopping and starting an I/O watcher in the same iteration will 475While stopping, setting and starting an I/O watcher in the same iteration
374result in some caching, there is still a syscall per such incident 476will 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 477(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 478best to avoid that. Also, \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors might not work
377well if you register events for both fds. 479very well if you register events for both fds.
378.Sp 480.Sp
379Please note that epoll sometimes generates spurious notifications, so you 481Please 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 482need to use non-blocking I/O or other means to avoid blocking when no data
381(or space) is available. 483(or space) is available.
484.Sp
485Best performance from this backend is achieved by not unregistering all
486watchers for a file descriptor until it has been closed, if possible, i.e.
487keep at least one watcher active per fd at all times.
488.Sp
489While nominally embeddeble in other event loops, this feature is broken in
490all kernel versions tested so far.
382.ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4 491.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)" 4 492.el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4
384.IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)" 493.IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)"
385Kqueue deserves special mention, as at the time of this writing, it 494Kqueue deserves special mention, as at the time of this writing, it
386was broken on all BSDs except NetBSD (usually it doesn't work with 495was broken on all BSDs except NetBSD (usually it doesn't work reliably
387anything but sockets and pipes, except on Darwin, where of course its 496with anything but sockets and pipes, except on Darwin, where of course
388completely useless). For this reason its not being \*(L"autodetected\*(R" 497it'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 498unless you explicitly specify it explicitly in the flags (i.e. using
390\&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR). 499\&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR) or libev was compiled on a known-to-be-good (\-enough)
500system like NetBSD.
501.Sp
502You still can embed kqueue into a normal poll or select backend and use it
503only for sockets (after having made sure that sockets work with kqueue on
504the target platform). See \f(CW\*(C`ev_embed\*(C'\fR watchers for more info.
391.Sp 505.Sp
392It scales in the same way as the epoll backend, but the interface to the 506It 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 507kernel is more efficient (which says nothing about its actual speed, of
394course). While starting and stopping an I/O watcher does not cause an 508course). 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 509cause an extra syscall as with \f(CW\*(C`EVBACKEND_EPOLL\*(C'\fR, it still adds up to
396incident, so its best to avoid that. 510two event changes per incident, support for \f(CW\*(C`fork ()\*(C'\fR is very bad and it
511drops fds silently in similarly hard-to-detect cases.
512.Sp
513This backend usually performs well under most conditions.
514.Sp
515While nominally embeddable in other event loops, this doesn't work
516everywhere, so you might need to test for this. And since it is broken
517almost everywhere, you should only use it when you have a lot of sockets
518(for which it usually works), by embedding it into another event loop
519(e.g. \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR) and using it only for
520sockets.
397.ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4 521.ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4
398.el .IP "\f(CWEVBACKEND_DEVPOLL\fR (value 16, Solaris 8)" 4 522.el .IP "\f(CWEVBACKEND_DEVPOLL\fR (value 16, Solaris 8)" 4
399.IX Item "EVBACKEND_DEVPOLL (value 16, Solaris 8)" 523.IX Item "EVBACKEND_DEVPOLL (value 16, Solaris 8)"
400This is not implemented yet (and might never be). 524This is not implemented yet (and might never be, unless you send me an
525implementation). According to reports, \f(CW\*(C`/dev/poll\*(C'\fR only supports sockets
526and is not embeddable, which would limit the usefulness of this backend
527immensely.
401.ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4 528.ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4
402.el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4 529.el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4
403.IX Item "EVBACKEND_PORT (value 32, Solaris 10)" 530.IX Item "EVBACKEND_PORT (value 32, Solaris 10)"
404This uses the Solaris 10 port mechanism. As with everything on Solaris, 531This 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)). 532it's really slow, but it still scales very well (O(active_fds)).
406.Sp 533.Sp
407Please note that solaris ports can result in a lot of spurious 534Please 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 535notifications, so you need to use non-blocking I/O or other means to avoid
409blocking when no data (or space) is available. 536blocking when no data (or space) is available.
537.Sp
538While this backend scales well, it requires one system call per active
539file descriptor per loop iteration. For small and medium numbers of file
540descriptors a \*(L"slow\*(R" \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR backend
541might perform better.
542.Sp
543On the positive side, ignoring the spurious readyness notifications, this
544backend actually performed to specification in all tests and is fully
545embeddable, which is a rare feat among the OS-specific backends.
410.ie n .IP """EVBACKEND_ALL""" 4 546.ie n .IP """EVBACKEND_ALL""" 4
411.el .IP "\f(CWEVBACKEND_ALL\fR" 4 547.el .IP "\f(CWEVBACKEND_ALL\fR" 4
412.IX Item "EVBACKEND_ALL" 548.IX Item "EVBACKEND_ALL"
413Try all backends (even potentially broken ones that wouldn't be tried 549Try all backends (even potentially broken ones that wouldn't be tried
414with \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). Since this is a mask, you can do stuff such as 550with \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). Since this is a mask, you can do stuff such as
415\&\f(CW\*(C`EVBACKEND_ALL & ~EVBACKEND_KQUEUE\*(C'\fR. 551\&\f(CW\*(C`EVBACKEND_ALL & ~EVBACKEND_KQUEUE\*(C'\fR.
552.Sp
553It is definitely not recommended to use this flag.
416.RE 554.RE
417.RS 4 555.RS 4
418.Sp 556.Sp
419If one or more of these are ored into the flags value, then only these 557If one or more of these are ored into the flags value, then only these
420backends will be tried (in the reverse order as given here). If none are 558backends will be tried (in the reverse order as listed here). If none are
421specified, most compiled-in backend will be tried, usually in reverse 559specified, all backends in \f(CW\*(C`ev_recommended_backends ()\*(C'\fR will be tried.
422order of their flag values :)
423.Sp 560.Sp
424The most typical usage is like this: 561The most typical usage is like this:
425.Sp 562.Sp
426.Vb 2 563.Vb 2
427\& if (!ev_default_loop (0)) 564\& if (!ev_default_loop (0))
… …
448Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is 585Similar 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 586always 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 587handle signal and child watchers, and attempts to do so will be greeted by
451undefined behaviour (or a failed assertion if assertions are enabled). 588undefined behaviour (or a failed assertion if assertions are enabled).
452.Sp 589.Sp
453Example: try to create a event loop that uses epoll and nothing else. 590Example: Try to create a event loop that uses epoll and nothing else.
454.Sp 591.Sp
455.Vb 3 592.Vb 3
456\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); 593\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
457\& if (!epoller) 594\& if (!epoller)
458\& fatal ("no epoll found here, maybe it hides under your chair"); 595\& fatal ("no epoll found here, maybe it hides under your chair");
… …
462Destroys the default loop again (frees all memory and kernel state 599Destroys the default loop again (frees all memory and kernel state
463etc.). None of the active event watchers will be stopped in the normal 600etc.). 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 601sense, 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 602responsibility to either stop all watchers cleanly yoursef \fIbefore\fR
466calling this function, or cope with the fact afterwards (which is usually 603calling 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 604the easiest thing, you can just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them
468for example). 605for example).
606.Sp
607Note that certain global state, such as signal state, will not be freed by
608this function, and related watchers (such as signal and child watchers)
609would need to be stopped manually.
610.Sp
611In general it is not advisable to call this function except in the
612rare occasion where you really need to free e.g. the signal handling
613pipe fds. If you need dynamically allocated loops it is better to use
614\&\f(CW\*(C`ev_loop_new\*(C'\fR and \f(CW\*(C`ev_loop_destroy\*(C'\fR).
469.IP "ev_loop_destroy (loop)" 4 615.IP "ev_loop_destroy (loop)" 4
470.IX Item "ev_loop_destroy (loop)" 616.IX Item "ev_loop_destroy (loop)"
471Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an 617Like \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. 618earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR.
473.IP "ev_default_fork ()" 4 619.IP "ev_default_fork ()" 4
474.IX Item "ev_default_fork ()" 620.IX Item "ev_default_fork ()"
621This function sets a flag that causes subsequent \f(CW\*(C`ev_loop\*(C'\fR iterations
475This function reinitialises the kernel state for backends that have 622to reinitialise the kernel state for backends that have one. Despite the
476one. Despite the name, you can call it anytime, but it makes most sense 623name, you can call it anytime, but it makes most sense after forking, in
477after forking, in either the parent or child process (or both, but that 624the child process (or both child and parent, but that again makes little
478again makes little sense). 625sense). You \fImust\fR call it in the child before using any of the libev
626functions, and it will only take effect at the next \f(CW\*(C`ev_loop\*(C'\fR iteration.
479.Sp 627.Sp
480You \fImust\fR call this function in the child process after forking if and 628On the other hand, you only need to call this function in the child
481only if you want to use the event library in both processes. If you just 629process if and only if you want to use the event library in the child. If
482fork+exec, you don't have to call it. 630you just fork+exec, you don't have to call it at all.
483.Sp 631.Sp
484The function itself is quite fast and it's usually not a problem to call 632The function itself is quite fast and it's usually not a problem to call
485it just in case after a fork. To make this easy, the function will fit in 633it just in case after a fork. To make this easy, the function will fit in
486quite nicely into a call to \f(CW\*(C`pthread_atfork\*(C'\fR: 634quite nicely into a call to \f(CW\*(C`pthread_atfork\*(C'\fR:
487.Sp 635.Sp
488.Vb 1 636.Vb 1
489\& pthread_atfork (0, 0, ev_default_fork); 637\& pthread_atfork (0, 0, ev_default_fork);
490.Ve 638.Ve
491.Sp
492At the moment, \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and \f(CW\*(C`EVBACKEND_POLL\*(C'\fR are safe to use
493without calling this function, so if you force one of those backends you
494do not need to care.
495.IP "ev_loop_fork (loop)" 4 639.IP "ev_loop_fork (loop)" 4
496.IX Item "ev_loop_fork (loop)" 640.IX Item "ev_loop_fork (loop)"
497Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by 641Like \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 642\&\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. 643after fork, and how you do this is entirely your own problem.
644.IP "unsigned int ev_loop_count (loop)" 4
645.IX Item "unsigned int ev_loop_count (loop)"
646Returns the count of loop iterations for the loop, which is identical to
647the number of times libev did poll for new events. It starts at \f(CW0\fR and
648happily wraps around with enough iterations.
649.Sp
650This value can sometimes be useful as a generation counter of sorts (it
651\&\*(L"ticks\*(R" the number of loop iterations), as it roughly corresponds with
652\&\f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR calls.
500.IP "unsigned int ev_backend (loop)" 4 653.IP "unsigned int ev_backend (loop)" 4
501.IX Item "unsigned int ev_backend (loop)" 654.IX Item "unsigned int ev_backend (loop)"
502Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in 655Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in
503use. 656use.
504.IP "ev_tstamp ev_now (loop)" 4 657.IP "ev_tstamp ev_now (loop)" 4
505.IX Item "ev_tstamp ev_now (loop)" 658.IX Item "ev_tstamp ev_now (loop)"
506Returns the current \*(L"event loop time\*(R", which is the time the event loop 659Returns the current \*(L"event loop time\*(R", which is the time the event loop
507received events and started processing them. This timestamp does not 660received events and started processing them. This timestamp does not
508change as long as callbacks are being processed, and this is also the base 661change 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 662time used for relative timers. You can treat it as the timestamp of the
510event occuring (or more correctly, libev finding out about it). 663event occurring (or more correctly, libev finding out about it).
511.IP "ev_loop (loop, int flags)" 4 664.IP "ev_loop (loop, int flags)" 4
512.IX Item "ev_loop (loop, int flags)" 665.IX Item "ev_loop (loop, int flags)"
513Finally, this is it, the event handler. This function usually is called 666Finally, this is it, the event handler. This function usually is called
514after you initialised all your watchers and you want to start handling 667after you initialised all your watchers and you want to start handling
515events. 668events.
… …
535libev watchers. However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is 688libev 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. 689usually a better approach for this kind of thing.
537.Sp 690.Sp
538Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does: 691Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does:
539.Sp 692.Sp
540.Vb 18 693.Vb 10
541\& * If there are no active watchers (reference count is zero), return. 694\& \- Before the first iteration, call any pending watchers.
542\& - Queue prepare watchers and then call all outstanding watchers. 695\& * If EVFLAG_FORKCHECK was used, check for a fork.
696\& \- If a fork was detected, queue and call all fork watchers.
697\& \- Queue and call all prepare watchers.
543\& - If we have been forked, recreate the kernel state. 698\& \- If we have been forked, recreate the kernel state.
544\& - Update the kernel state with all outstanding changes. 699\& \- Update the kernel state with all outstanding changes.
545\& - Update the "event loop time". 700\& \- Update the "event loop time".
546\& - Calculate for how long to block. 701\& \- Calculate for how long to sleep or block, if at all
702\& (active idle watchers, EVLOOP_NONBLOCK or not having
703\& any active watchers at all will result in not sleeping).
704\& \- Sleep if the I/O and timer collect interval say so.
547\& - Block the process, waiting for any events. 705\& \- Block the process, waiting for any events.
548\& - Queue all outstanding I/O (fd) events. 706\& \- Queue all outstanding I/O (fd) events.
549\& - Update the "event loop time" and do time jump handling. 707\& \- Update the "event loop time" and do time jump handling.
550\& - Queue all outstanding timers. 708\& \- Queue all outstanding timers.
551\& - Queue all outstanding periodics. 709\& \- Queue all outstanding periodics.
552\& - If no events are pending now, queue all idle watchers. 710\& \- If no events are pending now, queue all idle watchers.
553\& - Queue all check watchers. 711\& \- Queue all check watchers.
554\& - Call all queued watchers in reverse order (i.e. check watchers first). 712\& \- Call all queued watchers in reverse order (i.e. check watchers first).
555\& Signals and child watchers are implemented as I/O watchers, and will 713\& Signals and child watchers are implemented as I/O watchers, and will
556\& be handled here by queueing them when their watcher gets executed. 714\& be handled here by queueing them when their watcher gets executed.
557\& - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 715\& \- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
558\& were used, return, otherwise continue with step *. 716\& were used, or there are no active watchers, return, otherwise
717\& continue with step *.
559.Ve 718.Ve
560.Sp 719.Sp
561Example: queue some jobs and then loop until no events are outsanding 720Example: Queue some jobs and then loop until no events are outstanding
562anymore. 721anymore.
563.Sp 722.Sp
564.Vb 4 723.Vb 4
565\& ... queue jobs here, make sure they register event watchers as long 724\& ... 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..) 725\& ... as they still have work to do (even an idle watcher will do..)
… …
571.IX Item "ev_unloop (loop, how)" 730.IX Item "ev_unloop (loop, how)"
572Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it 731Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it
573has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either 732has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either
574\&\f(CW\*(C`EVUNLOOP_ONE\*(C'\fR, which will make the innermost \f(CW\*(C`ev_loop\*(C'\fR call return, or 733\&\f(CW\*(C`EVUNLOOP_ONE\*(C'\fR, which will make the innermost \f(CW\*(C`ev_loop\*(C'\fR call return, or
575\&\f(CW\*(C`EVUNLOOP_ALL\*(C'\fR, which will make all nested \f(CW\*(C`ev_loop\*(C'\fR calls return. 734\&\f(CW\*(C`EVUNLOOP_ALL\*(C'\fR, which will make all nested \f(CW\*(C`ev_loop\*(C'\fR calls return.
735.Sp
736This \*(L"unloop state\*(R" will be cleared when entering \f(CW\*(C`ev_loop\*(C'\fR again.
576.IP "ev_ref (loop)" 4 737.IP "ev_ref (loop)" 4
577.IX Item "ev_ref (loop)" 738.IX Item "ev_ref (loop)"
578.PD 0 739.PD 0
579.IP "ev_unref (loop)" 4 740.IP "ev_unref (loop)" 4
580.IX Item "ev_unref (loop)" 741.IX Item "ev_unref (loop)"
… …
586returning, \fIev_unref()\fR after starting, and \fIev_ref()\fR before stopping it. For 747returning, \fIev_unref()\fR after starting, and \fIev_ref()\fR before stopping it. For
587example, libev itself uses this for its internal signal pipe: It is not 748example, libev itself uses this for its internal signal pipe: It is not
588visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if 749visible 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 750no 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 751way 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. 752libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR
753(but only if the watcher wasn't active before, or was active before,
754respectively).
592.Sp 755.Sp
593Example: create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR 756Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR
594running when nothing else is active. 757running when nothing else is active.
595.Sp 758.Sp
596.Vb 4 759.Vb 4
597\& struct dv_signal exitsig; 760\& struct ev_signal exitsig;
598\& ev_signal_init (&exitsig, sig_cb, SIGINT); 761\& ev_signal_init (&exitsig, sig_cb, SIGINT);
599\& ev_signal_start (myloop, &exitsig); 762\& ev_signal_start (loop, &exitsig);
600\& evf_unref (myloop); 763\& evf_unref (loop);
601.Ve 764.Ve
602.Sp 765.Sp
603Example: for some weird reason, unregister the above signal handler again. 766Example: For some weird reason, unregister the above signal handler again.
604.Sp 767.Sp
605.Vb 2 768.Vb 2
606\& ev_ref (myloop); 769\& ev_ref (loop);
607\& ev_signal_stop (myloop, &exitsig); 770\& ev_signal_stop (loop, &exitsig);
608.Ve 771.Ve
772.IP "ev_set_io_collect_interval (loop, ev_tstamp interval)" 4
773.IX Item "ev_set_io_collect_interval (loop, ev_tstamp interval)"
774.PD 0
775.IP "ev_set_timeout_collect_interval (loop, ev_tstamp interval)" 4
776.IX Item "ev_set_timeout_collect_interval (loop, ev_tstamp interval)"
777.PD
778These advanced functions influence the time that libev will spend waiting
779for events. Both are by default \f(CW0\fR, meaning that libev will try to
780invoke timer/periodic callbacks and I/O callbacks with minimum latency.
781.Sp
782Setting these to a higher value (the \f(CW\*(C`interval\*(C'\fR \fImust\fR be >= \f(CW0\fR)
783allows libev to delay invocation of I/O and timer/periodic callbacks to
784increase efficiency of loop iterations.
785.Sp
786The background is that sometimes your program runs just fast enough to
787handle one (or very few) event(s) per loop iteration. While this makes
788the program responsive, it also wastes a lot of \s-1CPU\s0 time to poll for new
789events, especially with backends like \f(CW\*(C`select ()\*(C'\fR which have a high
790overhead for the actual polling but can deliver many events at once.
791.Sp
792By setting a higher \fIio collect interval\fR you allow libev to spend more
793time collecting I/O events, so you can handle more events per iteration,
794at the cost of increasing latency. Timeouts (both \f(CW\*(C`ev_periodic\*(C'\fR and
795\&\f(CW\*(C`ev_timer\*(C'\fR) will be not affected. Setting this to a non-null value will
796introduce an additional \f(CW\*(C`ev_sleep ()\*(C'\fR call into most loop iterations.
797.Sp
798Likewise, by setting a higher \fItimeout collect interval\fR you allow libev
799to spend more time collecting timeouts, at the expense of increased
800latency (the watcher callback will be called later). \f(CW\*(C`ev_io\*(C'\fR watchers
801will not be affected. Setting this to a non-null value will not introduce
802any overhead in libev.
803.Sp
804Many (busy) programs can usually benefit by setting the io collect
805interval to a value near \f(CW0.1\fR or so, which is often enough for
806interactive servers (of course not for games), likewise for timeouts. It
807usually doesn't make much sense to set it to a lower value than \f(CW0.01\fR,
808as this approsaches the timing granularity of most systems.
609.SH "ANATOMY OF A WATCHER" 809.SH "ANATOMY OF A WATCHER"
610.IX Header "ANATOMY OF A WATCHER" 810.IX Header "ANATOMY OF A WATCHER"
611A watcher is a structure that you create and register to record your 811A 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 812interest 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: 813become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that:
… …
616\& static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) 816\& static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
617\& { 817\& {
618\& ev_io_stop (w); 818\& ev_io_stop (w);
619\& ev_unloop (loop, EVUNLOOP_ALL); 819\& ev_unloop (loop, EVUNLOOP_ALL);
620\& } 820\& }
621.Ve 821\&
622.PP
623.Vb 6
624\& struct ev_loop *loop = ev_default_loop (0); 822\& struct ev_loop *loop = ev_default_loop (0);
625\& struct ev_io stdin_watcher; 823\& struct ev_io stdin_watcher;
626\& ev_init (&stdin_watcher, my_cb); 824\& ev_init (&stdin_watcher, my_cb);
627\& ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); 825\& ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
628\& ev_io_start (loop, &stdin_watcher); 826\& ev_io_start (loop, &stdin_watcher);
… …
684The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread. 882The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread.
685.ie n .IP """EV_CHILD""" 4 883.ie n .IP """EV_CHILD""" 4
686.el .IP "\f(CWEV_CHILD\fR" 4 884.el .IP "\f(CWEV_CHILD\fR" 4
687.IX Item "EV_CHILD" 885.IX Item "EV_CHILD"
688The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change. 886The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change.
887.ie n .IP """EV_STAT""" 4
888.el .IP "\f(CWEV_STAT\fR" 4
889.IX Item "EV_STAT"
890The path specified in the \f(CW\*(C`ev_stat\*(C'\fR watcher changed its attributes somehow.
689.ie n .IP """EV_IDLE""" 4 891.ie n .IP """EV_IDLE""" 4
690.el .IP "\f(CWEV_IDLE\fR" 4 892.el .IP "\f(CWEV_IDLE\fR" 4
691.IX Item "EV_IDLE" 893.IX Item "EV_IDLE"
692The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do. 894The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do.
693.ie n .IP """EV_PREPARE""" 4 895.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 905\&\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 906received 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 907many 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 908(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). 909\&\f(CW\*(C`ev_loop\*(C'\fR from blocking).
910.ie n .IP """EV_EMBED""" 4
911.el .IP "\f(CWEV_EMBED\fR" 4
912.IX Item "EV_EMBED"
913The embedded event loop specified in the \f(CW\*(C`ev_embed\*(C'\fR watcher needs attention.
914.ie n .IP """EV_FORK""" 4
915.el .IP "\f(CWEV_FORK\fR" 4
916.IX Item "EV_FORK"
917The event loop has been resumed in the child process after fork (see
918\&\f(CW\*(C`ev_fork\*(C'\fR).
708.ie n .IP """EV_ERROR""" 4 919.ie n .IP """EV_ERROR""" 4
709.el .IP "\f(CWEV_ERROR\fR" 4 920.el .IP "\f(CWEV_ERROR\fR" 4
710.IX Item "EV_ERROR" 921.IX Item "EV_ERROR"
711An unspecified error has occured, the watcher has been stopped. This might 922An unspecified error has occured, the watcher has been stopped. This might
712happen because the watcher could not be properly started because libev 923happen because the watcher could not be properly started because libev
… …
777.IP "bool ev_is_pending (ev_TYPE *watcher)" 4 988.IP "bool ev_is_pending (ev_TYPE *watcher)" 4
778.IX Item "bool ev_is_pending (ev_TYPE *watcher)" 989.IX Item "bool ev_is_pending (ev_TYPE *watcher)"
779Returns a true value iff the watcher is pending, (i.e. it has outstanding 990Returns 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 991events 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 992is 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 993\&\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). 994make sure the watcher is available to libev (e.g. you cannot \f(CW\*(C`free ()\*(C'\fR
995it).
784.IP "callback = ev_cb (ev_TYPE *watcher)" 4 996.IP "callback ev_cb (ev_TYPE *watcher)" 4
785.IX Item "callback = ev_cb (ev_TYPE *watcher)" 997.IX Item "callback ev_cb (ev_TYPE *watcher)"
786Returns the callback currently set on the watcher. 998Returns the callback currently set on the watcher.
787.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4 999.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4
788.IX Item "ev_cb_set (ev_TYPE *watcher, callback)" 1000.IX Item "ev_cb_set (ev_TYPE *watcher, callback)"
789Change the callback. You can change the callback at virtually any time 1001Change the callback. You can change the callback at virtually any time
790(modulo threads). 1002(modulo threads).
1003.IP "ev_set_priority (ev_TYPE *watcher, priority)" 4
1004.IX Item "ev_set_priority (ev_TYPE *watcher, priority)"
1005.PD 0
1006.IP "int ev_priority (ev_TYPE *watcher)" 4
1007.IX Item "int ev_priority (ev_TYPE *watcher)"
1008.PD
1009Set and query the priority of the watcher. The priority is a small
1010integer between \f(CW\*(C`EV_MAXPRI\*(C'\fR (default: \f(CW2\fR) and \f(CW\*(C`EV_MINPRI\*(C'\fR
1011(default: \f(CW\*(C`\-2\*(C'\fR). Pending watchers with higher priority will be invoked
1012before watchers with lower priority, but priority will not keep watchers
1013from being executed (except for \f(CW\*(C`ev_idle\*(C'\fR watchers).
1014.Sp
1015This means that priorities are \fIonly\fR used for ordering callback
1016invocation after new events have been received. This is useful, for
1017example, to reduce latency after idling, or more often, to bind two
1018watchers on the same event and make sure one is called first.
1019.Sp
1020If you need to suppress invocation when higher priority events are pending
1021you need to look at \f(CW\*(C`ev_idle\*(C'\fR watchers, which provide this functionality.
1022.Sp
1023You \fImust not\fR change the priority of a watcher as long as it is active or
1024pending.
1025.Sp
1026The default priority used by watchers when no priority has been set is
1027always \f(CW0\fR, which is supposed to not be too high and not be too low :).
1028.Sp
1029Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR is
1030fine, as long as you do not mind that the priority value you query might
1031or might not have been adjusted to be within valid range.
1032.IP "ev_invoke (loop, ev_TYPE *watcher, int revents)" 4
1033.IX Item "ev_invoke (loop, ev_TYPE *watcher, int revents)"
1034Invoke the \f(CW\*(C`watcher\*(C'\fR with the given \f(CW\*(C`loop\*(C'\fR and \f(CW\*(C`revents\*(C'\fR. Neither
1035\&\f(CW\*(C`loop\*(C'\fR nor \f(CW\*(C`revents\*(C'\fR need to be valid as long as the watcher callback
1036can deal with that fact.
1037.IP "int ev_clear_pending (loop, ev_TYPE *watcher)" 4
1038.IX Item "int ev_clear_pending (loop, ev_TYPE *watcher)"
1039If the watcher is pending, this function returns clears its pending status
1040and returns its \f(CW\*(C`revents\*(C'\fR bitset (as if its callback was invoked). If the
1041watcher 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" 1042.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" 1043.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 1044Each 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 1045and 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 1046to associate arbitrary data with your watcher. If you need more data and
… …
816\& struct my_io *w = (struct my_io *)w_; 1067\& struct my_io *w = (struct my_io *)w_;
817\& ... 1068\& ...
818\& } 1069\& }
819.Ve 1070.Ve
820.PP 1071.PP
821More interesting and less C\-conformant ways of catsing your callback type 1072More interesting and less C\-conformant ways of casting your callback type
822have been omitted.... 1073instead have been omitted.
1074.PP
1075Another common scenario is having some data structure with multiple
1076watchers:
1077.PP
1078.Vb 6
1079\& struct my_biggy
1080\& {
1081\& int some_data;
1082\& ev_timer t1;
1083\& ev_timer t2;
1084\& }
1085.Ve
1086.PP
1087In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more complicated,
1088you need to use \f(CW\*(C`offsetof\*(C'\fR:
1089.PP
1090.Vb 1
1091\& #include <stddef.h>
1092\&
1093\& static void
1094\& t1_cb (EV_P_ struct ev_timer *w, int revents)
1095\& {
1096\& struct my_biggy big = (struct my_biggy *
1097\& (((char *)w) \- offsetof (struct my_biggy, t1));
1098\& }
1099\&
1100\& static void
1101\& t2_cb (EV_P_ struct ev_timer *w, int revents)
1102\& {
1103\& struct my_biggy big = (struct my_biggy *
1104\& (((char *)w) \- offsetof (struct my_biggy, t2));
1105\& }
1106.Ve
823.SH "WATCHER TYPES" 1107.SH "WATCHER TYPES"
824.IX Header "WATCHER TYPES" 1108.IX Header "WATCHER TYPES"
825This section describes each watcher in detail, but will not repeat 1109This section describes each watcher in detail, but will not repeat
826information given in the last section. 1110information given in the last section. Any initialisation/set macros,
1111functions and members specific to the watcher type are explained.
1112.PP
1113Members are additionally marked with either \fI[read\-only]\fR, meaning that,
1114while the watcher is active, you can look at the member and expect some
1115sensible content, but you must not modify it (you can modify it while the
1116watcher is stopped to your hearts content), or \fI[read\-write]\fR, which
1117means you can expect it to have some sensible content while the watcher
1118is active, but you can also modify it. Modifying it may not do something
1119sensible or take immediate effect (or do anything at all), but libev will
1120not crash or malfunction in any way.
827.ie n .Sh """ev_io"" \- is this file descriptor readable or writable?" 1121.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?" 1122.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?" 1123.IX Subsection "ev_io - is this file descriptor readable or writable?"
830I/O watchers check whether a file descriptor is readable or writable 1124I/O watchers check whether a file descriptor is readable or writable
831in each iteration of the event loop, or, more precisely, when reading 1125in each iteration of the event loop, or, more precisely, when reading
… …
838In general you can register as many read and/or write event watchers per 1132In general you can register as many read and/or write event watchers per
839fd as you want (as long as you don't confuse yourself). Setting all file 1133fd as you want (as long as you don't confuse yourself). Setting all file
840descriptors to non-blocking mode is also usually a good idea (but not 1134descriptors to non-blocking mode is also usually a good idea (but not
841required if you know what you are doing). 1135required if you know what you are doing).
842.PP 1136.PP
843You have to be careful with dup'ed file descriptors, though. Some backends
844(the linux epoll backend is a notable example) cannot handle dup'ed file
845descriptors correctly if you register interest in two or more fds pointing
846to the same underlying file/socket/etc. description (that is, they share
847the same underlying \*(L"file open\*(R").
848.PP
849If you must do this, then force the use of a known-to-be-good backend 1137If you must do this, then force the use of a known-to-be-good backend
850(at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and 1138(at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and
851\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR). 1139\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR).
852.PP 1140.PP
853Another thing you have to watch out for is that it is quite easy to 1141Another thing you have to watch out for is that it is quite easy to
… …
859it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning 1147it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning
860\&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives. 1148\&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives.
861.PP 1149.PP
862If you cannot run the fd in non-blocking mode (for example you should not 1150If you cannot run the fd in non-blocking mode (for example you should not
863play around with an Xlib connection), then you have to seperately re-test 1151play around with an Xlib connection), then you have to seperately re-test
864wether a file descriptor is really ready with a known-to-be good interface 1152whether a file descriptor is really ready with a known-to-be good interface
865such as poll (fortunately in our Xlib example, Xlib already does this on 1153such as poll (fortunately in our Xlib example, Xlib already does this on
866its own, so its quite safe to use). 1154its own, so its quite safe to use).
1155.PP
1156\fIThe special problem of disappearing file descriptors\fR
1157.IX Subsection "The special problem of disappearing file descriptors"
1158.PP
1159Some backends (e.g. kqueue, epoll) need to be told about closing a file
1160descriptor (either by calling \f(CW\*(C`close\*(C'\fR explicitly or by any other means,
1161such as \f(CW\*(C`dup\*(C'\fR). The reason is that you register interest in some file
1162descriptor, but when it goes away, the operating system will silently drop
1163this interest. If another file descriptor with the same number then is
1164registered with libev, there is no efficient way to see that this is, in
1165fact, a different file descriptor.
1166.PP
1167To avoid having to explicitly tell libev about such cases, libev follows
1168the following policy: Each time \f(CW\*(C`ev_io_set\*(C'\fR is being called, libev
1169will assume that this is potentially a new file descriptor, otherwise
1170it is assumed that the file descriptor stays the same. That means that
1171you \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
1172descriptor even if the file descriptor number itself did not change.
1173.PP
1174This is how one would do it normally anyway, the important point is that
1175the libev application should not optimise around libev but should leave
1176optimisations to libev.
1177.PP
1178\fIThe special problem of dup'ed file descriptors\fR
1179.IX Subsection "The special problem of dup'ed file descriptors"
1180.PP
1181Some backends (e.g. epoll), cannot register events for file descriptors,
1182but only events for the underlying file descriptions. That means when you
1183have \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors or weirder constellations, and register
1184events for them, only one file descriptor might actually receive events.
1185.PP
1186There is no workaround possible except not registering events
1187for potentially \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors, or to resort to
1188\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
1189.PP
1190\fIThe special problem of fork\fR
1191.IX Subsection "The special problem of fork"
1192.PP
1193Some backends (epoll, kqueue) do not support \f(CW\*(C`fork ()\*(C'\fR at all or exhibit
1194useless behaviour. Libev fully supports fork, but needs to be told about
1195it in the child.
1196.PP
1197To support fork in your programs, you either have to call
1198\&\f(CW\*(C`ev_default_fork ()\*(C'\fR or \f(CW\*(C`ev_loop_fork ()\*(C'\fR after a fork in the child,
1199enable \f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR, or resort to \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or
1200\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
1201.PP
1202\fIWatcher-Specific Functions\fR
1203.IX Subsection "Watcher-Specific Functions"
867.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4 1204.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4
868.IX Item "ev_io_init (ev_io *, callback, int fd, int events)" 1205.IX Item "ev_io_init (ev_io *, callback, int fd, int events)"
869.PD 0 1206.PD 0
870.IP "ev_io_set (ev_io *, int fd, int events)" 4 1207.IP "ev_io_set (ev_io *, int fd, int events)" 4
871.IX Item "ev_io_set (ev_io *, int fd, int events)" 1208.IX Item "ev_io_set (ev_io *, int fd, int events)"
872.PD 1209.PD
873Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to 1210Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to
874rceeive events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or 1211rceeive events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or
875\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR to receive the given events. 1212\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR to receive the given events.
1213.IP "int fd [read\-only]" 4
1214.IX Item "int fd [read-only]"
1215The file descriptor being watched.
1216.IP "int events [read\-only]" 4
1217.IX Item "int events [read-only]"
1218The events being watched.
876.PP 1219.PP
1220\fIExamples\fR
1221.IX Subsection "Examples"
1222.PP
877Example: call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well 1223Example: Call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well
878readable, but only once. Since it is likely line\-buffered, you could 1224readable, but only once. Since it is likely line-buffered, you could
879attempt to read a whole line in the callback: 1225attempt to read a whole line in the callback.
880.PP 1226.PP
881.Vb 6 1227.Vb 6
882\& static void 1228\& static void
883\& stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1229\& stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
884\& { 1230\& {
885\& ev_io_stop (loop, w); 1231\& ev_io_stop (loop, w);
886\& .. read from stdin here (or from w->fd) and haqndle any I/O errors 1232\& .. read from stdin here (or from w\->fd) and haqndle any I/O errors
887\& } 1233\& }
888.Ve 1234\&
889.PP
890.Vb 6
891\& ... 1235\& ...
892\& struct ev_loop *loop = ev_default_init (0); 1236\& struct ev_loop *loop = ev_default_init (0);
893\& struct ev_io stdin_readable; 1237\& struct ev_io stdin_readable;
894\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); 1238\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
895\& ev_io_start (loop, &stdin_readable); 1239\& ev_io_start (loop, &stdin_readable);
… …
912of the event triggering whatever timeout you are modifying/starting. If 1256of the event triggering whatever timeout you are modifying/starting. If
913you suspect event processing to be delayed and you \fIneed\fR to base the timeout 1257you suspect event processing to be delayed and you \fIneed\fR to base the timeout
914on the current time, use something like this to adjust for this: 1258on the current time, use something like this to adjust for this:
915.PP 1259.PP
916.Vb 1 1260.Vb 1
917\& ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); 1261\& ev_timer_set (&timer, after + ev_now () \- ev_time (), 0.);
918.Ve 1262.Ve
919.PP 1263.PP
920The callback is guarenteed to be invoked only when its timeout has passed, 1264The callback is guarenteed to be invoked only when its timeout has passed,
921but if multiple timers become ready during the same loop iteration then 1265but if multiple timers become ready during the same loop iteration then
922order of execution is undefined. 1266order of execution is undefined.
1267.PP
1268\fIWatcher-Specific Functions and Data Members\fR
1269.IX Subsection "Watcher-Specific Functions and Data Members"
923.IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4 1270.IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4
924.IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 1271.IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)"
925.PD 0 1272.PD 0
926.IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4 1273.IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4
927.IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 1274.IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)"
… …
939.IP "ev_timer_again (loop)" 4 1286.IP "ev_timer_again (loop)" 4
940.IX Item "ev_timer_again (loop)" 1287.IX Item "ev_timer_again (loop)"
941This will act as if the timer timed out and restart it again if it is 1288This will act as if the timer timed out and restart it again if it is
942repeating. The exact semantics are: 1289repeating. The exact semantics are:
943.Sp 1290.Sp
1291If the timer is pending, its pending status is cleared.
1292.Sp
944If the timer is started but nonrepeating, stop it. 1293If the timer is started but nonrepeating, stop it (as if it timed out).
945.Sp 1294.Sp
946If the timer is repeating, either start it if necessary (with the repeat 1295If the timer is repeating, either start it if necessary (with the
947value), or reset the running timer to the repeat value. 1296\&\f(CW\*(C`repeat\*(C'\fR value), or reset the running timer to the \f(CW\*(C`repeat\*(C'\fR value.
948.Sp 1297.Sp
949This sounds a bit complicated, but here is a useful and typical 1298This sounds a bit complicated, but here is a useful and typical
950example: Imagine you have a tcp connection and you want a so-called idle 1299example: Imagine you have a tcp connection and you want a so-called idle
951timeout, that is, you want to be called when there have been, say, 60 1300timeout, that is, you want to be called when there have been, say, 60
952seconds of inactivity on the socket. The easiest way to do this is to 1301seconds of inactivity on the socket. The easiest way to do this is to
953configure an \f(CW\*(C`ev_timer\*(C'\fR with after=repeat=60 and calling ev_timer_again each 1302configure an \f(CW\*(C`ev_timer\*(C'\fR with a \f(CW\*(C`repeat\*(C'\fR value of \f(CW60\fR and then call
954time you successfully read or write some data. If you go into an idle 1303\&\f(CW\*(C`ev_timer_again\*(C'\fR each time you successfully read or write some data. If
955state where you do not expect data to travel on the socket, you can stop 1304you go into an idle state where you do not expect data to travel on the
956the timer, and again will automatically restart it if need be. 1305socket, you can \f(CW\*(C`ev_timer_stop\*(C'\fR the timer, and \f(CW\*(C`ev_timer_again\*(C'\fR will
1306automatically restart it if need be.
1307.Sp
1308That means you can ignore the \f(CW\*(C`after\*(C'\fR value and \f(CW\*(C`ev_timer_start\*(C'\fR
1309altogether and only ever use the \f(CW\*(C`repeat\*(C'\fR value and \f(CW\*(C`ev_timer_again\*(C'\fR:
1310.Sp
1311.Vb 8
1312\& ev_timer_init (timer, callback, 0., 5.);
1313\& ev_timer_again (loop, timer);
1314\& ...
1315\& timer\->again = 17.;
1316\& ev_timer_again (loop, timer);
1317\& ...
1318\& timer\->again = 10.;
1319\& ev_timer_again (loop, timer);
1320.Ve
1321.Sp
1322This is more slightly efficient then stopping/starting the timer each time
1323you want to modify its timeout value.
1324.IP "ev_tstamp repeat [read\-write]" 4
1325.IX Item "ev_tstamp repeat [read-write]"
1326The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out
1327or \f(CW\*(C`ev_timer_again\*(C'\fR is called and determines the next timeout (if any),
1328which is also when any modifications are taken into account.
957.PP 1329.PP
1330\fIExamples\fR
1331.IX Subsection "Examples"
1332.PP
958Example: create a timer that fires after 60 seconds. 1333Example: Create a timer that fires after 60 seconds.
959.PP 1334.PP
960.Vb 5 1335.Vb 5
961\& static void 1336\& static void
962\& one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1337\& one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
963\& { 1338\& {
964\& .. one minute over, w is actually stopped right here 1339\& .. one minute over, w is actually stopped right here
965\& } 1340\& }
966.Ve 1341\&
967.PP
968.Vb 3
969\& struct ev_timer mytimer; 1342\& struct ev_timer mytimer;
970\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.); 1343\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
971\& ev_timer_start (loop, &mytimer); 1344\& ev_timer_start (loop, &mytimer);
972.Ve 1345.Ve
973.PP 1346.PP
974Example: create a timeout timer that times out after 10 seconds of 1347Example: Create a timeout timer that times out after 10 seconds of
975inactivity. 1348inactivity.
976.PP 1349.PP
977.Vb 5 1350.Vb 5
978\& static void 1351\& static void
979\& timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1352\& timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
980\& { 1353\& {
981\& .. ten seconds without any activity 1354\& .. ten seconds without any activity
982\& } 1355\& }
983.Ve 1356\&
984.PP
985.Vb 4
986\& struct ev_timer mytimer; 1357\& struct ev_timer mytimer;
987\& ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ 1358\& ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
988\& ev_timer_again (&mytimer); /* start timer */ 1359\& ev_timer_again (&mytimer); /* start timer */
989\& ev_loop (loop, 0); 1360\& ev_loop (loop, 0);
990.Ve 1361\&
991.PP
992.Vb 3
993\& // and in some piece of code that gets executed on any "activity": 1362\& // and in some piece of code that gets executed on any "activity":
994\& // reset the timeout to start ticking again at 10 seconds 1363\& // reset the timeout to start ticking again at 10 seconds
995\& ev_timer_again (&mytimer); 1364\& ev_timer_again (&mytimer);
996.Ve 1365.Ve
997.ie n .Sh """ev_periodic"" \- to cron or not to cron?" 1366.ie n .Sh """ev_periodic"" \- to cron or not to cron?"
… …
1004but on wallclock time (absolute time). You can tell a periodic watcher 1373but on wallclock time (absolute time). You can tell a periodic watcher
1005to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a 1374to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a
1006periodic watcher to trigger in 10 seconds (by specifiying e.g. \f(CW\*(C`ev_now () 1375periodic watcher to trigger in 10 seconds (by specifiying e.g. \f(CW\*(C`ev_now ()
1007+ 10.\*(C'\fR) and then reset your system clock to the last year, then it will 1376+ 10.\*(C'\fR) and then reset your system clock to the last year, then it will
1008take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger 1377take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger
1009roughly 10 seconds later and of course not if you reset your system time 1378roughly 10 seconds later).
1010again).
1011.PP 1379.PP
1012They can also be used to implement vastly more complex timers, such as 1380They can also be used to implement vastly more complex timers, such as
1013triggering an event on eahc midnight, local time. 1381triggering an event on each midnight, local time or other, complicated,
1382rules.
1014.PP 1383.PP
1015As with timers, the callback is guarenteed to be invoked only when the 1384As with timers, the callback is guarenteed to be invoked only when the
1016time (\f(CW\*(C`at\*(C'\fR) has been passed, but if multiple periodic timers become ready 1385time (\f(CW\*(C`at\*(C'\fR) has been passed, but if multiple periodic timers become ready
1017during the same loop iteration then order of execution is undefined. 1386during the same loop iteration then order of execution is undefined.
1387.PP
1388\fIWatcher-Specific Functions and Data Members\fR
1389.IX Subsection "Watcher-Specific Functions and Data Members"
1018.IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4 1390.IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4
1019.IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 1391.IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)"
1020.PD 0 1392.PD 0
1021.IP "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 4 1393.IP "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 4
1022.IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 1394.IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)"
1023.PD 1395.PD
1024Lots of arguments, lets sort it out... There are basically three modes of 1396Lots of arguments, lets sort it out... There are basically three modes of
1025operation, and we will explain them from simplest to complex: 1397operation, and we will explain them from simplest to complex:
1026.RS 4 1398.RS 4
1399.IP "\(bu" 4
1027.IP "* absolute timer (interval = reschedule_cb = 0)" 4 1400absolute timer (at = time, interval = reschedule_cb = 0)
1028.IX Item "absolute timer (interval = reschedule_cb = 0)" 1401.Sp
1029In this configuration the watcher triggers an event at the wallclock time 1402In this configuration the watcher triggers an event at the wallclock time
1030\&\f(CW\*(C`at\*(C'\fR and doesn't repeat. It will not adjust when a time jump occurs, 1403\&\f(CW\*(C`at\*(C'\fR and doesn't repeat. It will not adjust when a time jump occurs,
1031that is, if it is to be run at January 1st 2011 then it will run when the 1404that is, if it is to be run at January 1st 2011 then it will run when the
1032system time reaches or surpasses this time. 1405system time reaches or surpasses this time.
1406.IP "\(bu" 4
1033.IP "* non-repeating interval timer (interval > 0, reschedule_cb = 0)" 4 1407non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1034.IX Item "non-repeating interval timer (interval > 0, reschedule_cb = 0)" 1408.Sp
1035In this mode the watcher will always be scheduled to time out at the next 1409In this mode the watcher will always be scheduled to time out at the next
1036\&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N) and then repeat, regardless 1410\&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N, which can also be negative)
1037of any time jumps. 1411and then repeat, regardless of any time jumps.
1038.Sp 1412.Sp
1039This can be used to create timers that do not drift with respect to system 1413This can be used to create timers that do not drift with respect to system
1040time: 1414time:
1041.Sp 1415.Sp
1042.Vb 1 1416.Vb 1
… …
1049by 3600. 1423by 3600.
1050.Sp 1424.Sp
1051Another way to think about it (for the mathematically inclined) is that 1425Another way to think about it (for the mathematically inclined) is that
1052\&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible 1426\&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible
1053time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps. 1427time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps.
1054.IP "* manual reschedule mode (reschedule_cb = callback)" 4 1428.Sp
1055.IX Item "manual reschedule mode (reschedule_cb = callback)" 1429For numerical stability it is preferable that the \f(CW\*(C`at\*(C'\fR value is near
1430\&\f(CW\*(C`ev_now ()\*(C'\fR (the current time), but there is no range requirement for
1431this value.
1432.IP "\(bu" 4
1433manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1434.Sp
1056In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR are both being 1435In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR are both being
1057ignored. Instead, each time the periodic watcher gets scheduled, the 1436ignored. Instead, each time the periodic watcher gets scheduled, the
1058reschedule callback will be called with the watcher as first, and the 1437reschedule callback will be called with the watcher as first, and the
1059current time as second argument. 1438current time as second argument.
1060.Sp 1439.Sp
1061\&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher, 1440\&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher,
1062ever, or make any event loop modifications\fR. If you need to stop it, 1441ever, or make any event loop modifications\fR. If you need to stop it,
1063return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop it afterwards (e.g. by 1442return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop it afterwards (e.g. by
1064starting a prepare watcher). 1443starting an \f(CW\*(C`ev_prepare\*(C'\fR watcher, which is legal).
1065.Sp 1444.Sp
1066Its prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 1445Its prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
1067ev_tstamp now)\*(C'\fR, e.g.: 1446ev_tstamp now)\*(C'\fR, e.g.:
1068.Sp 1447.Sp
1069.Vb 4 1448.Vb 4
… …
1093.IX Item "ev_periodic_again (loop, ev_periodic *)" 1472.IX Item "ev_periodic_again (loop, ev_periodic *)"
1094Simply stops and restarts the periodic watcher again. This is only useful 1473Simply stops and restarts the periodic watcher again. This is only useful
1095when you changed some parameters or the reschedule callback would return 1474when you changed some parameters or the reschedule callback would return
1096a different time than the last time it was called (e.g. in a crond like 1475a different time than the last time it was called (e.g. in a crond like
1097program when the crontabs have changed). 1476program when the crontabs have changed).
1477.IP "ev_tstamp offset [read\-write]" 4
1478.IX Item "ev_tstamp offset [read-write]"
1479When repeating, this contains the offset value, otherwise this is the
1480absolute point in time (the \f(CW\*(C`at\*(C'\fR value passed to \f(CW\*(C`ev_periodic_set\*(C'\fR).
1481.Sp
1482Can be modified any time, but changes only take effect when the periodic
1483timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
1484.IP "ev_tstamp interval [read\-write]" 4
1485.IX Item "ev_tstamp interval [read-write]"
1486The current interval value. Can be modified any time, but changes only
1487take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being
1488called.
1489.IP "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read\-write]" 4
1490.IX Item "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]"
1491The current reschedule callback, or \f(CW0\fR, if this functionality is
1492switched off. Can be changed any time, but changes only take effect when
1493the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
1494.IP "ev_tstamp at [read\-only]" 4
1495.IX Item "ev_tstamp at [read-only]"
1496When active, contains the absolute time that the watcher is supposed to
1497trigger next.
1098.PP 1498.PP
1499\fIExamples\fR
1500.IX Subsection "Examples"
1501.PP
1099Example: call a callback every hour, or, more precisely, whenever the 1502Example: Call a callback every hour, or, more precisely, whenever the
1100system clock is divisible by 3600. The callback invocation times have 1503system clock is divisible by 3600. The callback invocation times have
1101potentially a lot of jittering, but good long-term stability. 1504potentially a lot of jittering, but good long-term stability.
1102.PP 1505.PP
1103.Vb 5 1506.Vb 5
1104\& static void 1507\& static void
1105\& clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1508\& clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1106\& { 1509\& {
1107\& ... its now a full hour (UTC, or TAI or whatever your clock follows) 1510\& ... its now a full hour (UTC, or TAI or whatever your clock follows)
1108\& } 1511\& }
1109.Ve 1512\&
1110.PP
1111.Vb 3
1112\& struct ev_periodic hourly_tick; 1513\& struct ev_periodic hourly_tick;
1113\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); 1514\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1114\& ev_periodic_start (loop, &hourly_tick); 1515\& ev_periodic_start (loop, &hourly_tick);
1115.Ve 1516.Ve
1116.PP 1517.PP
1117Example: the same as above, but use a reschedule callback to do it: 1518Example: The same as above, but use a reschedule callback to do it:
1118.PP 1519.PP
1119.Vb 1 1520.Vb 1
1120\& #include <math.h> 1521\& #include <math.h>
1121.Ve 1522\&
1122.PP
1123.Vb 5
1124\& static ev_tstamp 1523\& static ev_tstamp
1125\& my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) 1524\& my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1126\& { 1525\& {
1127\& return fmod (now, 3600.) + 3600.; 1526\& return fmod (now, 3600.) + 3600.;
1128\& } 1527\& }
1129.Ve 1528\&
1130.PP
1131.Vb 1
1132\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); 1529\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1133.Ve 1530.Ve
1134.PP 1531.PP
1135Example: call a callback every hour, starting now: 1532Example: Call a callback every hour, starting now:
1136.PP 1533.PP
1137.Vb 4 1534.Vb 4
1138\& struct ev_periodic hourly_tick; 1535\& struct ev_periodic hourly_tick;
1139\& ev_periodic_init (&hourly_tick, clock_cb, 1536\& ev_periodic_init (&hourly_tick, clock_cb,
1140\& fmod (ev_now (loop), 3600.), 3600., 0); 1537\& fmod (ev_now (loop), 3600.), 3600., 0);
… …
1152first watcher gets started will libev actually register a signal watcher 1549first watcher gets started will libev actually register a signal watcher
1153with the kernel (thus it coexists with your own signal handlers as long 1550with the kernel (thus it coexists with your own signal handlers as long
1154as you don't register any with libev). Similarly, when the last signal 1551as you don't register any with libev). Similarly, when the last signal
1155watcher for a signal is stopped libev will reset the signal handler to 1552watcher for a signal is stopped libev will reset the signal handler to
1156\&\s-1SIG_DFL\s0 (regardless of what it was set to before). 1553\&\s-1SIG_DFL\s0 (regardless of what it was set to before).
1554.PP
1555\fIWatcher-Specific Functions and Data Members\fR
1556.IX Subsection "Watcher-Specific Functions and Data Members"
1157.IP "ev_signal_init (ev_signal *, callback, int signum)" 4 1557.IP "ev_signal_init (ev_signal *, callback, int signum)" 4
1158.IX Item "ev_signal_init (ev_signal *, callback, int signum)" 1558.IX Item "ev_signal_init (ev_signal *, callback, int signum)"
1159.PD 0 1559.PD 0
1160.IP "ev_signal_set (ev_signal *, int signum)" 4 1560.IP "ev_signal_set (ev_signal *, int signum)" 4
1161.IX Item "ev_signal_set (ev_signal *, int signum)" 1561.IX Item "ev_signal_set (ev_signal *, int signum)"
1162.PD 1562.PD
1163Configures the watcher to trigger on the given signal number (usually one 1563Configures the watcher to trigger on the given signal number (usually one
1164of the \f(CW\*(C`SIGxxx\*(C'\fR constants). 1564of the \f(CW\*(C`SIGxxx\*(C'\fR constants).
1565.IP "int signum [read\-only]" 4
1566.IX Item "int signum [read-only]"
1567The signal the watcher watches out for.
1165.ie n .Sh """ev_child"" \- watch out for process status changes" 1568.ie n .Sh """ev_child"" \- watch out for process status changes"
1166.el .Sh "\f(CWev_child\fP \- watch out for process status changes" 1569.el .Sh "\f(CWev_child\fP \- watch out for process status changes"
1167.IX Subsection "ev_child - watch out for process status changes" 1570.IX Subsection "ev_child - watch out for process status changes"
1168Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to 1571Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to
1169some child status changes (most typically when a child of yours dies). 1572some child status changes (most typically when a child of yours dies).
1573.PP
1574\fIWatcher-Specific Functions and Data Members\fR
1575.IX Subsection "Watcher-Specific Functions and Data Members"
1170.IP "ev_child_init (ev_child *, callback, int pid)" 4 1576.IP "ev_child_init (ev_child *, callback, int pid, int trace)" 4
1171.IX Item "ev_child_init (ev_child *, callback, int pid)" 1577.IX Item "ev_child_init (ev_child *, callback, int pid, int trace)"
1172.PD 0 1578.PD 0
1173.IP "ev_child_set (ev_child *, int pid)" 4 1579.IP "ev_child_set (ev_child *, int pid, int trace)" 4
1174.IX Item "ev_child_set (ev_child *, int pid)" 1580.IX Item "ev_child_set (ev_child *, int pid, int trace)"
1175.PD 1581.PD
1176Configures the watcher to wait for status changes of process \f(CW\*(C`pid\*(C'\fR (or 1582Configures the watcher to wait for status changes of process \f(CW\*(C`pid\*(C'\fR (or
1177\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look 1583\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look
1178at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see 1584at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see
1179the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems 1585the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems
1180\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the 1586\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the
1181process causing the status change. 1587process causing the status change. \f(CW\*(C`trace\*(C'\fR must be either \f(CW0\fR (only
1588activate the watcher when the process terminates) or \f(CW1\fR (additionally
1589activate the watcher when the process is stopped or continued).
1590.IP "int pid [read\-only]" 4
1591.IX Item "int pid [read-only]"
1592The process id this watcher watches out for, or \f(CW0\fR, meaning any process id.
1593.IP "int rpid [read\-write]" 4
1594.IX Item "int rpid [read-write]"
1595The process id that detected a status change.
1596.IP "int rstatus [read\-write]" 4
1597.IX Item "int rstatus [read-write]"
1598The process exit/trace status caused by \f(CW\*(C`rpid\*(C'\fR (see your systems
1599\&\f(CW\*(C`waitpid\*(C'\fR and \f(CW\*(C`sys/wait.h\*(C'\fR documentation for details).
1182.PP 1600.PP
1601\fIExamples\fR
1602.IX Subsection "Examples"
1603.PP
1183Example: try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0. 1604Example: Try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0.
1184.PP 1605.PP
1185.Vb 5 1606.Vb 5
1186\& static void 1607\& static void
1187\& sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1608\& sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1188\& { 1609\& {
1189\& ev_unloop (loop, EVUNLOOP_ALL); 1610\& ev_unloop (loop, EVUNLOOP_ALL);
1190\& } 1611\& }
1191.Ve 1612\&
1192.PP
1193.Vb 3
1194\& struct ev_signal signal_watcher; 1613\& struct ev_signal signal_watcher;
1195\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT); 1614\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1196\& ev_signal_start (loop, &sigint_cb); 1615\& ev_signal_start (loop, &sigint_cb);
1197.Ve 1616.Ve
1617.ie n .Sh """ev_stat"" \- did the file attributes just change?"
1618.el .Sh "\f(CWev_stat\fP \- did the file attributes just change?"
1619.IX Subsection "ev_stat - did the file attributes just change?"
1620This watches a filesystem path for attribute changes. That is, it calls
1621\&\f(CW\*(C`stat\*(C'\fR regularly (or when the \s-1OS\s0 says it changed) and sees if it changed
1622compared to the last time, invoking the callback if it did.
1623.PP
1624The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does
1625not exist\*(R" is a status change like any other. The condition \*(L"path does
1626not exist\*(R" is signified by the \f(CW\*(C`st_nlink\*(C'\fR field being zero (which is
1627otherwise always forced to be at least one) and all the other fields of
1628the stat buffer having unspecified contents.
1629.PP
1630The path \fIshould\fR be absolute and \fImust not\fR end in a slash. If it is
1631relative and your working directory changes, the behaviour is undefined.
1632.PP
1633Since there is no standard to do this, the portable implementation simply
1634calls \f(CW\*(C`stat (2)\*(C'\fR regularly on the path to see if it changed somehow. You
1635can specify a recommended polling interval for this case. If you specify
1636a polling interval of \f(CW0\fR (highly recommended!) then a \fIsuitable,
1637unspecified default\fR value will be used (which you can expect to be around
1638five seconds, although this might change dynamically). Libev will also
1639impose a minimum interval which is currently around \f(CW0.1\fR, but thats
1640usually overkill.
1641.PP
1642This watcher type is not meant for massive numbers of stat watchers,
1643as even with OS-supported change notifications, this can be
1644resource-intensive.
1645.PP
1646At the time of this writing, only the Linux inotify interface is
1647implemented (implementing kqueue support is left as an exercise for the
1648reader). Inotify will be used to give hints only and should not change the
1649semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers, which means that libev sometimes needs
1650to fall back to regular polling again even with inotify, but changes are
1651usually detected immediately, and if the file exists there will be no
1652polling.
1653.PP
1654\fIInotify\fR
1655.IX Subsection "Inotify"
1656.PP
1657When \f(CW\*(C`inotify (7)\*(C'\fR support has been compiled into libev (generally only
1658available on Linux) and present at runtime, it will be used to speed up
1659change detection where possible. The inotify descriptor will be created lazily
1660when the first \f(CW\*(C`ev_stat\*(C'\fR watcher is being started.
1661.PP
1662Inotify presense does not change the semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers
1663except that changes might be detected earlier, and in some cases, to avoid
1664making regular \f(CW\*(C`stat\*(C'\fR calls. Even in the presense of inotify support
1665there are many cases where libev has to resort to regular \f(CW\*(C`stat\*(C'\fR polling.
1666.PP
1667(There is no support for kqueue, as apparently it cannot be used to
1668implement this functionality, due to the requirement of having a file
1669descriptor open on the object at all times).
1670.PP
1671\fIThe special problem of stat time resolution\fR
1672.IX Subsection "The special problem of stat time resolution"
1673.PP
1674The \f(CW\*(C`stat ()\*(C'\fR syscall only supports full-second resolution portably, and
1675even on systems where the resolution is higher, many filesystems still
1676only support whole seconds.
1677.PP
1678That means that, if the time is the only thing that changes, you might
1679miss updates: on the first update, \f(CW\*(C`ev_stat\*(C'\fR detects a change and calls
1680your callback, which does something. When there is another update within
1681the same second, \f(CW\*(C`ev_stat\*(C'\fR will be unable to detect it.
1682.PP
1683The solution to this is to delay acting on a change for a second (or till
1684the next second boundary), using a roughly one-second delay \f(CW\*(C`ev_timer\*(C'\fR
1685(\f(CW\*(C`ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)\*(C'\fR). The \f(CW.01\fR
1686is added to work around small timing inconsistencies of some operating
1687systems.
1688.PP
1689\fIWatcher-Specific Functions and Data Members\fR
1690.IX Subsection "Watcher-Specific Functions and Data Members"
1691.IP "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 4
1692.IX Item "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)"
1693.PD 0
1694.IP "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" 4
1695.IX Item "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)"
1696.PD
1697Configures the watcher to wait for status changes of the given
1698\&\f(CW\*(C`path\*(C'\fR. The \f(CW\*(C`interval\*(C'\fR is a hint on how quickly a change is expected to
1699be detected and should normally be specified as \f(CW0\fR to let libev choose
1700a suitable value. The memory pointed to by \f(CW\*(C`path\*(C'\fR must point to the same
1701path for as long as the watcher is active.
1702.Sp
1703The callback will be receive \f(CW\*(C`EV_STAT\*(C'\fR when a change was detected,
1704relative to the attributes at the time the watcher was started (or the
1705last change was detected).
1706.IP "ev_stat_stat (ev_stat *)" 4
1707.IX Item "ev_stat_stat (ev_stat *)"
1708Updates the stat buffer immediately with new values. If you change the
1709watched path in your callback, you could call this fucntion to avoid
1710detecting this change (while introducing a race condition). Can also be
1711useful simply to find out the new values.
1712.IP "ev_statdata attr [read\-only]" 4
1713.IX Item "ev_statdata attr [read-only]"
1714The most-recently detected attributes of the file. Although the type is of
1715\&\f(CW\*(C`ev_statdata\*(C'\fR, this is usually the (or one of the) \f(CW\*(C`struct stat\*(C'\fR types
1716suitable for your system. If the \f(CW\*(C`st_nlink\*(C'\fR member is \f(CW0\fR, then there
1717was some error while \f(CW\*(C`stat\*(C'\fRing the file.
1718.IP "ev_statdata prev [read\-only]" 4
1719.IX Item "ev_statdata prev [read-only]"
1720The previous attributes of the file. The callback gets invoked whenever
1721\&\f(CW\*(C`prev\*(C'\fR != \f(CW\*(C`attr\*(C'\fR.
1722.IP "ev_tstamp interval [read\-only]" 4
1723.IX Item "ev_tstamp interval [read-only]"
1724The specified interval.
1725.IP "const char *path [read\-only]" 4
1726.IX Item "const char *path [read-only]"
1727The filesystem path that is being watched.
1728.PP
1729\fIExamples\fR
1730.IX Subsection "Examples"
1731.PP
1732Example: Watch \f(CW\*(C`/etc/passwd\*(C'\fR for attribute changes.
1733.PP
1734.Vb 10
1735\& static void
1736\& passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1737\& {
1738\& /* /etc/passwd changed in some way */
1739\& if (w\->attr.st_nlink)
1740\& {
1741\& printf ("passwd current size %ld\en", (long)w\->attr.st_size);
1742\& printf ("passwd current atime %ld\en", (long)w\->attr.st_mtime);
1743\& printf ("passwd current mtime %ld\en", (long)w\->attr.st_mtime);
1744\& }
1745\& else
1746\& /* you shalt not abuse printf for puts */
1747\& puts ("wow, /etc/passwd is not there, expect problems. "
1748\& "if this is windows, they already arrived\en");
1749\& }
1750\&
1751\& ...
1752\& ev_stat passwd;
1753\&
1754\& ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1755\& ev_stat_start (loop, &passwd);
1756.Ve
1757.PP
1758Example: Like above, but additionally use a one-second delay so we do not
1759miss updates (however, frequent updates will delay processing, too, so
1760one might do the work both on \f(CW\*(C`ev_stat\*(C'\fR callback invocation \fIand\fR on
1761\&\f(CW\*(C`ev_timer\*(C'\fR callback invocation).
1762.PP
1763.Vb 2
1764\& static ev_stat passwd;
1765\& static ev_timer timer;
1766\&
1767\& static void
1768\& timer_cb (EV_P_ ev_timer *w, int revents)
1769\& {
1770\& ev_timer_stop (EV_A_ w);
1771\&
1772\& /* now it\*(Aqs one second after the most recent passwd change */
1773\& }
1774\&
1775\& static void
1776\& stat_cb (EV_P_ ev_stat *w, int revents)
1777\& {
1778\& /* reset the one\-second timer */
1779\& ev_timer_again (EV_A_ &timer);
1780\& }
1781\&
1782\& ...
1783\& ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1784\& ev_stat_start (loop, &passwd);
1785\& ev_timer_init (&timer, timer_cb, 0., 1.01);
1786.Ve
1198.ie n .Sh """ev_idle"" \- when you've got nothing better to do..." 1787.ie n .Sh """ev_idle"" \- when you've got nothing better to do..."
1199.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do..." 1788.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do..."
1200.IX Subsection "ev_idle - when you've got nothing better to do..." 1789.IX Subsection "ev_idle - when you've got nothing better to do..."
1201Idle watchers trigger events when there are no other events are pending 1790Idle watchers trigger events when no other events of the same or higher
1202(prepare, check and other idle watchers do not count). That is, as long 1791priority are pending (prepare, check and other idle watchers do not
1203as your process is busy handling sockets or timeouts (or even signals, 1792count).
1204imagine) it will not be triggered. But when your process is idle all idle 1793.PP
1205watchers are being called again and again, once per event loop iteration \- 1794That is, as long as your process is busy handling sockets or timeouts
1795(or even signals, imagine) of the same or higher priority it will not be
1796triggered. But when your process is idle (or only lower-priority watchers
1797are pending), the idle watchers are being called once per event loop
1206until stopped, that is, or your process receives more events and becomes 1798iteration \- until stopped, that is, or your process receives more events
1207busy. 1799and becomes busy again with higher priority stuff.
1208.PP 1800.PP
1209The most noteworthy effect is that as long as any idle watchers are 1801The most noteworthy effect is that as long as any idle watchers are
1210active, the process will not block when waiting for new events. 1802active, the process will not block when waiting for new events.
1211.PP 1803.PP
1212Apart from keeping your process non-blocking (which is a useful 1804Apart from keeping your process non-blocking (which is a useful
1213effect on its own sometimes), idle watchers are a good place to do 1805effect on its own sometimes), idle watchers are a good place to do
1214\&\*(L"pseudo\-background processing\*(R", or delay processing stuff to after the 1806\&\*(L"pseudo-background processing\*(R", or delay processing stuff to after the
1215event loop has handled all outstanding events. 1807event loop has handled all outstanding events.
1808.PP
1809\fIWatcher-Specific Functions and Data Members\fR
1810.IX Subsection "Watcher-Specific Functions and Data Members"
1216.IP "ev_idle_init (ev_signal *, callback)" 4 1811.IP "ev_idle_init (ev_signal *, callback)" 4
1217.IX Item "ev_idle_init (ev_signal *, callback)" 1812.IX Item "ev_idle_init (ev_signal *, callback)"
1218Initialises and configures the idle watcher \- it has no parameters of any 1813Initialises and configures the idle watcher \- it has no parameters of any
1219kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless, 1814kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless,
1220believe me. 1815believe me.
1221.PP 1816.PP
1817\fIExamples\fR
1818.IX Subsection "Examples"
1819.PP
1222Example: dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR, start it, and in the 1820Example: Dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR watcher, start it, and in the
1223callback, free it. Alos, use no error checking, as usual. 1821callback, free it. Also, use no error checking, as usual.
1224.PP 1822.PP
1225.Vb 7 1823.Vb 7
1226\& static void 1824\& static void
1227\& idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1825\& idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1228\& { 1826\& {
1229\& free (w); 1827\& free (w);
1230\& // now do something you wanted to do when the program has 1828\& // now do something you wanted to do when the program has
1231\& // no longer asnything immediate to do. 1829\& // no longer anything immediate to do.
1232\& } 1830\& }
1233.Ve 1831\&
1234.PP
1235.Vb 3
1236\& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); 1832\& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1237\& ev_idle_init (idle_watcher, idle_cb); 1833\& ev_idle_init (idle_watcher, idle_cb);
1238\& ev_idle_start (loop, idle_cb); 1834\& ev_idle_start (loop, idle_cb);
1239.Ve 1835.Ve
1240.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop!" 1836.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop!"
… …
1242.IX Subsection "ev_prepare and ev_check - customise your event loop!" 1838.IX Subsection "ev_prepare and ev_check - customise your event loop!"
1243Prepare and check watchers are usually (but not always) used in tandem: 1839Prepare and check watchers are usually (but not always) used in tandem:
1244prepare watchers get invoked before the process blocks and check watchers 1840prepare watchers get invoked before the process blocks and check watchers
1245afterwards. 1841afterwards.
1246.PP 1842.PP
1843You \fImust not\fR call \f(CW\*(C`ev_loop\*(C'\fR or similar functions that enter
1844the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR
1845watchers. Other loops than the current one are fine, however. The
1846rationale behind this is that you do not need to check for recursion in
1847those watchers, i.e. the sequence will always be \f(CW\*(C`ev_prepare\*(C'\fR, blocking,
1848\&\f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each kind they will always be
1849called in pairs bracketing the blocking call.
1850.PP
1247Their main purpose is to integrate other event mechanisms into libev and 1851Their main purpose is to integrate other event mechanisms into libev and
1248their use is somewhat advanced. This could be used, for example, to track 1852their use is somewhat advanced. This could be used, for example, to track
1249variable changes, implement your own watchers, integrate net-snmp or a 1853variable changes, implement your own watchers, integrate net-snmp or a
1250coroutine library and lots more. 1854coroutine library and lots more. They are also occasionally useful if
1855you cache some data and want to flush it before blocking (for example,
1856in X programs you might want to do an \f(CW\*(C`XFlush ()\*(C'\fR in an \f(CW\*(C`ev_prepare\*(C'\fR
1857watcher).
1251.PP 1858.PP
1252This is done by examining in each prepare call which file descriptors need 1859This is done by examining in each prepare call which file descriptors need
1253to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for 1860to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for
1254them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries 1861them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries
1255provide just this functionality). Then, in the check watcher you check for 1862provide just this functionality). Then, in the check watcher you check for
… …
1264are ready to run (it's actually more complicated: it only runs coroutines 1871are ready to run (it's actually more complicated: it only runs coroutines
1265with priority higher than or equal to the event loop and one coroutine 1872with priority higher than or equal to the event loop and one coroutine
1266of lower priority, but only once, using idle watchers to keep the event 1873of lower priority, but only once, using idle watchers to keep the event
1267loop from blocking if lower-priority coroutines are active, thus mapping 1874loop from blocking if lower-priority coroutines are active, thus mapping
1268low-priority coroutines to idle/background tasks). 1875low-priority coroutines to idle/background tasks).
1876.PP
1877It is recommended to give \f(CW\*(C`ev_check\*(C'\fR watchers highest (\f(CW\*(C`EV_MAXPRI\*(C'\fR)
1878priority, to ensure that they are being run before any other watchers
1879after the poll. Also, \f(CW\*(C`ev_check\*(C'\fR watchers (and \f(CW\*(C`ev_prepare\*(C'\fR watchers,
1880too) should not activate (\*(L"feed\*(R") events into libev. While libev fully
1881supports this, they will be called before other \f(CW\*(C`ev_check\*(C'\fR watchers
1882did their job. As \f(CW\*(C`ev_check\*(C'\fR watchers are often used to embed other
1883(non-libev) event loops those other event loops might be in an unusable
1884state until their \f(CW\*(C`ev_check\*(C'\fR watcher ran (always remind yourself to
1885coexist peacefully with others).
1886.PP
1887\fIWatcher-Specific Functions and Data Members\fR
1888.IX Subsection "Watcher-Specific Functions and Data Members"
1269.IP "ev_prepare_init (ev_prepare *, callback)" 4 1889.IP "ev_prepare_init (ev_prepare *, callback)" 4
1270.IX Item "ev_prepare_init (ev_prepare *, callback)" 1890.IX Item "ev_prepare_init (ev_prepare *, callback)"
1271.PD 0 1891.PD 0
1272.IP "ev_check_init (ev_check *, callback)" 4 1892.IP "ev_check_init (ev_check *, callback)" 4
1273.IX Item "ev_check_init (ev_check *, callback)" 1893.IX Item "ev_check_init (ev_check *, callback)"
1274.PD 1894.PD
1275Initialises and configures the prepare or check watcher \- they have no 1895Initialises and configures the prepare or check watcher \- they have no
1276parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR 1896parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR
1277macros, but using them is utterly, utterly and completely pointless. 1897macros, but using them is utterly, utterly and completely pointless.
1278.PP 1898.PP
1279Example: *TODO*. 1899\fIExamples\fR
1900.IX Subsection "Examples"
1901.PP
1902There are a number of principal ways to embed other event loops or modules
1903into libev. Here are some ideas on how to include libadns into libev
1904(there is a Perl module named \f(CW\*(C`EV::ADNS\*(C'\fR that does this, which you could
1905use for an actually working example. Another Perl module named \f(CW\*(C`EV::Glib\*(C'\fR
1906embeds a Glib main context into libev, and finally, \f(CW\*(C`Glib::EV\*(C'\fR embeds \s-1EV\s0
1907into the Glib event loop).
1908.PP
1909Method 1: Add \s-1IO\s0 watchers and a timeout watcher in a prepare handler,
1910and in a check watcher, destroy them and call into libadns. What follows
1911is pseudo-code only of course. This requires you to either use a low
1912priority for the check watcher or use \f(CW\*(C`ev_clear_pending\*(C'\fR explicitly, as
1913the callbacks for the IO/timeout watchers might not have been called yet.
1914.PP
1915.Vb 2
1916\& static ev_io iow [nfd];
1917\& static ev_timer tw;
1918\&
1919\& static void
1920\& io_cb (ev_loop *loop, ev_io *w, int revents)
1921\& {
1922\& }
1923\&
1924\& // create io watchers for each fd and a timer before blocking
1925\& static void
1926\& adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1927\& {
1928\& int timeout = 3600000;
1929\& struct pollfd fds [nfd];
1930\& // actual code will need to loop here and realloc etc.
1931\& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1932\&
1933\& /* the callback is illegal, but won\*(Aqt be called as we stop during check */
1934\& ev_timer_init (&tw, 0, timeout * 1e\-3);
1935\& ev_timer_start (loop, &tw);
1936\&
1937\& // create one ev_io per pollfd
1938\& for (int i = 0; i < nfd; ++i)
1939\& {
1940\& ev_io_init (iow + i, io_cb, fds [i].fd,
1941\& ((fds [i].events & POLLIN ? EV_READ : 0)
1942\& | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1943\&
1944\& fds [i].revents = 0;
1945\& ev_io_start (loop, iow + i);
1946\& }
1947\& }
1948\&
1949\& // stop all watchers after blocking
1950\& static void
1951\& adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1952\& {
1953\& ev_timer_stop (loop, &tw);
1954\&
1955\& for (int i = 0; i < nfd; ++i)
1956\& {
1957\& // set the relevant poll flags
1958\& // could also call adns_processreadable etc. here
1959\& struct pollfd *fd = fds + i;
1960\& int revents = ev_clear_pending (iow + i);
1961\& if (revents & EV_READ ) fd\->revents |= fd\->events & POLLIN;
1962\& if (revents & EV_WRITE) fd\->revents |= fd\->events & POLLOUT;
1963\&
1964\& // now stop the watcher
1965\& ev_io_stop (loop, iow + i);
1966\& }
1967\&
1968\& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1969\& }
1970.Ve
1971.PP
1972Method 2: This would be just like method 1, but you run \f(CW\*(C`adns_afterpoll\*(C'\fR
1973in the prepare watcher and would dispose of the check watcher.
1974.PP
1975Method 3: If the module to be embedded supports explicit event
1976notification (adns does), you can also make use of the actual watcher
1977callbacks, and only destroy/create the watchers in the prepare watcher.
1978.PP
1979.Vb 5
1980\& static void
1981\& timer_cb (EV_P_ ev_timer *w, int revents)
1982\& {
1983\& adns_state ads = (adns_state)w\->data;
1984\& update_now (EV_A);
1985\&
1986\& adns_processtimeouts (ads, &tv_now);
1987\& }
1988\&
1989\& static void
1990\& io_cb (EV_P_ ev_io *w, int revents)
1991\& {
1992\& adns_state ads = (adns_state)w\->data;
1993\& update_now (EV_A);
1994\&
1995\& if (revents & EV_READ ) adns_processreadable (ads, w\->fd, &tv_now);
1996\& if (revents & EV_WRITE) adns_processwriteable (ads, w\->fd, &tv_now);
1997\& }
1998\&
1999\& // do not ever call adns_afterpoll
2000.Ve
2001.PP
2002Method 4: Do not use a prepare or check watcher because the module you
2003want to embed is too inflexible to support it. Instead, youc na override
2004their poll function. The drawback with this solution is that the main
2005loop is now no longer controllable by \s-1EV\s0. The \f(CW\*(C`Glib::EV\*(C'\fR module does
2006this.
2007.PP
2008.Vb 4
2009\& static gint
2010\& event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2011\& {
2012\& int got_events = 0;
2013\&
2014\& for (n = 0; n < nfds; ++n)
2015\& // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
2016\&
2017\& if (timeout >= 0)
2018\& // create/start timer
2019\&
2020\& // poll
2021\& ev_loop (EV_A_ 0);
2022\&
2023\& // stop timer again
2024\& if (timeout >= 0)
2025\& ev_timer_stop (EV_A_ &to);
2026\&
2027\& // stop io watchers again \- their callbacks should have set
2028\& for (n = 0; n < nfds; ++n)
2029\& ev_io_stop (EV_A_ iow [n]);
2030\&
2031\& return got_events;
2032\& }
2033.Ve
1280.ie n .Sh """ev_embed"" \- when one backend isn't enough..." 2034.ie n .Sh """ev_embed"" \- when one backend isn't enough..."
1281.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..." 2035.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..."
1282.IX Subsection "ev_embed - when one backend isn't enough..." 2036.IX Subsection "ev_embed - when one backend isn't enough..."
1283This is a rather advanced watcher type that lets you embed one event loop 2037This is a rather advanced watcher type that lets you embed one event loop
1284into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded 2038into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded
… …
1325portable one. 2079portable one.
1326.PP 2080.PP
1327So when you want to use this feature you will always have to be prepared 2081So when you want to use this feature you will always have to be prepared
1328that you cannot get an embeddable loop. The recommended way to get around 2082that you cannot get an embeddable loop. The recommended way to get around
1329this is to have a separate variables for your embeddable loop, try to 2083this is to have a separate variables for your embeddable loop, try to
1330create it, and if that fails, use the normal loop for everything: 2084create it, and if that fails, use the normal loop for everything.
1331.PP 2085.PP
1332.Vb 3 2086\fIWatcher-Specific Functions and Data Members\fR
1333\& struct ev_loop *loop_hi = ev_default_init (0); 2087.IX Subsection "Watcher-Specific Functions and Data Members"
1334\& struct ev_loop *loop_lo = 0;
1335\& struct ev_embed embed;
1336.Ve
1337.PP
1338.Vb 5
1339\& // see if there is a chance of getting one that works
1340\& // (remember that a flags value of 0 means autodetection)
1341\& loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1342\& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1343\& : 0;
1344.Ve
1345.PP
1346.Vb 8
1347\& // if we got one, then embed it, otherwise default to loop_hi
1348\& if (loop_lo)
1349\& {
1350\& ev_embed_init (&embed, 0, loop_lo);
1351\& ev_embed_start (loop_hi, &embed);
1352\& }
1353\& else
1354\& loop_lo = loop_hi;
1355.Ve
1356.IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4 2088.IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
1357.IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 2089.IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)"
1358.PD 0 2090.PD 0
1359.IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4 2091.IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
1360.IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 2092.IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)"
… …
1367.IP "ev_embed_sweep (loop, ev_embed *)" 4 2099.IP "ev_embed_sweep (loop, ev_embed *)" 4
1368.IX Item "ev_embed_sweep (loop, ev_embed *)" 2100.IX Item "ev_embed_sweep (loop, ev_embed *)"
1369Make a single, non-blocking sweep over the embedded loop. This works 2101Make a single, non-blocking sweep over the embedded loop. This works
1370similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most 2102similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most
1371apropriate way for embedded loops. 2103apropriate way for embedded loops.
2104.IP "struct ev_loop *other [read\-only]" 4
2105.IX Item "struct ev_loop *other [read-only]"
2106The embedded event loop.
2107.PP
2108\fIExamples\fR
2109.IX Subsection "Examples"
2110.PP
2111Example: Try to get an embeddable event loop and embed it into the default
2112event loop. If that is not possible, use the default loop. The default
2113loop is stored in \f(CW\*(C`loop_hi\*(C'\fR, while the mebeddable loop is stored in
2114\&\f(CW\*(C`loop_lo\*(C'\fR (which is \f(CW\*(C`loop_hi\*(C'\fR in the acse no embeddable loop can be
2115used).
2116.PP
2117.Vb 3
2118\& struct ev_loop *loop_hi = ev_default_init (0);
2119\& struct ev_loop *loop_lo = 0;
2120\& struct ev_embed embed;
2121\&
2122\& // see if there is a chance of getting one that works
2123\& // (remember that a flags value of 0 means autodetection)
2124\& loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2125\& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2126\& : 0;
2127\&
2128\& // if we got one, then embed it, otherwise default to loop_hi
2129\& if (loop_lo)
2130\& {
2131\& ev_embed_init (&embed, 0, loop_lo);
2132\& ev_embed_start (loop_hi, &embed);
2133\& }
2134\& else
2135\& loop_lo = loop_hi;
2136.Ve
2137.PP
2138Example: Check if kqueue is available but not recommended and create
2139a kqueue backend for use with sockets (which usually work with any
2140kqueue implementation). Store the kqueue/socket\-only event loop in
2141\&\f(CW\*(C`loop_socket\*(C'\fR. (One might optionally use \f(CW\*(C`EVFLAG_NOENV\*(C'\fR, too).
2142.PP
2143.Vb 3
2144\& struct ev_loop *loop = ev_default_init (0);
2145\& struct ev_loop *loop_socket = 0;
2146\& struct ev_embed embed;
2147\&
2148\& if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2149\& if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2150\& {
2151\& ev_embed_init (&embed, 0, loop_socket);
2152\& ev_embed_start (loop, &embed);
2153\& }
2154\&
2155\& if (!loop_socket)
2156\& loop_socket = loop;
2157\&
2158\& // now use loop_socket for all sockets, and loop for everything else
2159.Ve
2160.ie n .Sh """ev_fork"" \- the audacity to resume the event loop after a fork"
2161.el .Sh "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork"
2162.IX Subsection "ev_fork - the audacity to resume the event loop after a fork"
2163Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because
2164whoever is a good citizen cared to tell libev about it by calling
2165\&\f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the
2166event loop blocks next and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called,
2167and only in the child after the fork. If whoever good citizen calling
2168\&\f(CW\*(C`ev_default_fork\*(C'\fR cheats and calls it in the wrong process, the fork
2169handlers will be invoked, too, of course.
2170.PP
2171\fIWatcher-Specific Functions and Data Members\fR
2172.IX Subsection "Watcher-Specific Functions and Data Members"
2173.IP "ev_fork_init (ev_signal *, callback)" 4
2174.IX Item "ev_fork_init (ev_signal *, callback)"
2175Initialises and configures the fork watcher \- it has no parameters of any
2176kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless,
2177believe me.
1372.SH "OTHER FUNCTIONS" 2178.SH "OTHER FUNCTIONS"
1373.IX Header "OTHER FUNCTIONS" 2179.IX Header "OTHER FUNCTIONS"
1374There are some other functions of possible interest. Described. Here. Now. 2180There are some other functions of possible interest. Described. Here. Now.
1375.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4 2181.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4
1376.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 2182.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)"
… …
1400\& if (revents & EV_TIMEOUT) 2206\& if (revents & EV_TIMEOUT)
1401\& /* doh, nothing entered */; 2207\& /* doh, nothing entered */;
1402\& else if (revents & EV_READ) 2208\& else if (revents & EV_READ)
1403\& /* stdin might have data for us, joy! */; 2209\& /* stdin might have data for us, joy! */;
1404\& } 2210\& }
1405.Ve 2211\&
1406.Sp
1407.Vb 1
1408\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); 2212\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1409.Ve 2213.Ve
1410.IP "ev_feed_event (ev_loop *, watcher *, int revents)" 4 2214.IP "ev_feed_event (ev_loop *, watcher *, int revents)" 4
1411.IX Item "ev_feed_event (ev_loop *, watcher *, int revents)" 2215.IX Item "ev_feed_event (ev_loop *, watcher *, int revents)"
1412Feeds the given event set into the event loop, as if the specified event 2216Feeds the given event set into the event loop, as if the specified event
… …
1422loop!). 2226loop!).
1423.SH "LIBEVENT EMULATION" 2227.SH "LIBEVENT EMULATION"
1424.IX Header "LIBEVENT EMULATION" 2228.IX Header "LIBEVENT EMULATION"
1425Libev offers a compatibility emulation layer for libevent. It cannot 2229Libev offers a compatibility emulation layer for libevent. It cannot
1426emulate the internals of libevent, so here are some usage hints: 2230emulate the internals of libevent, so here are some usage hints:
2231.IP "\(bu" 4
1427.IP "* Use it by including <event.h>, as usual." 4 2232Use it by including <event.h>, as usual.
1428.IX Item "Use it by including <event.h>, as usual." 2233.IP "\(bu" 4
1429.PD 0 2234The following members are fully supported: ev_base, ev_callback,
1430.IP "* The following members are fully supported: ev_base, ev_callback, ev_arg, ev_fd, ev_res, ev_events." 4 2235ev_arg, ev_fd, ev_res, ev_events.
1431.IX Item "The following members are fully supported: ev_base, ev_callback, ev_arg, ev_fd, ev_res, ev_events." 2236.IP "\(bu" 4
1432.IP "* Avoid using ev_flags and the EVLIST_*\-macros, while it is maintained by libev, it does not work exactly the same way as in libevent (consider it a private \s-1API\s0)." 4 2237Avoid using ev_flags and the EVLIST_*\-macros, while it is
1433.IX Item "Avoid using ev_flags and the EVLIST_*-macros, while it is maintained by libev, it does not work exactly the same way as in libevent (consider it a private API)." 2238maintained by libev, it does not work exactly the same way as in libevent (consider
1434.IP "* Priorities are not currently supported. Initialising priorities will fail and all watchers will have the same priority, even though there is an ev_pri field." 4 2239it a private \s-1API\s0).
1435.IX Item "Priorities are not currently supported. Initialising priorities will fail and all watchers will have the same priority, even though there is an ev_pri field." 2240.IP "\(bu" 4
2241Priorities are not currently supported. Initialising priorities
2242will fail and all watchers will have the same priority, even though there
2243is an ev_pri field.
2244.IP "\(bu" 4
1436.IP "* Other members are not supported." 4 2245Other members are not supported.
1437.IX Item "Other members are not supported." 2246.IP "\(bu" 4
1438.IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4 2247The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need
1439.IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library." 2248to use the libev header file and library.
1440.PD
1441.SH "\*(C+ SUPPORT" 2249.SH "\*(C+ SUPPORT"
1442.IX Header " SUPPORT" 2250.IX Header " SUPPORT"
1443Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow 2251Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow
1444you to use some convinience methods to start/stop watchers and also change 2252you to use some convinience methods to start/stop watchers and also change
1445the callback model to a model using method callbacks on objects. 2253the callback model to a model using method callbacks on objects.
… …
1448.PP 2256.PP
1449.Vb 1 2257.Vb 1
1450\& #include <ev++.h> 2258\& #include <ev++.h>
1451.Ve 2259.Ve
1452.PP 2260.PP
1453(it is not installed by default). This automatically includes \fIev.h\fR 2261This automatically includes \fIev.h\fR and puts all of its definitions (many
1454and puts all of its definitions (many of them macros) into the global 2262of them macros) into the global namespace. All \*(C+ specific things are
1455namespace. All \*(C+ specific things are put into the \f(CW\*(C`ev\*(C'\fR namespace. 2263put into the \f(CW\*(C`ev\*(C'\fR namespace. It should support all the same embedding
2264options as \fIev.h\fR, most notably \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR.
1456.PP 2265.PP
1457It should support all the same embedding options as \fIev.h\fR, most notably 2266Care has been taken to keep the overhead low. The only data member the \*(C+
1458\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. 2267classes add (compared to plain C\-style watchers) is the event loop pointer
2268that the watcher is associated with (or no additional members at all if
2269you disable \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR when embedding libev).
2270.PP
2271Currently, functions, and static and non-static member functions can be
2272used as callbacks. Other types should be easy to add as long as they only
2273need one additional pointer for context. If you need support for other
2274types of functors please contact the author (preferably after implementing
2275it).
1459.PP 2276.PP
1460Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace: 2277Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace:
1461.ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4 2278.ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4
1462.el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4 2279.el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4
1463.IX Item "ev::READ, ev::WRITE etc." 2280.IX Item "ev::READ, ev::WRITE etc."
… …
1475which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro 2292which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro
1476defines by many implementations. 2293defines by many implementations.
1477.Sp 2294.Sp
1478All of those classes have these methods: 2295All of those classes have these methods:
1479.RS 4 2296.RS 4
1480.IP "ev::TYPE::TYPE (object *, object::method *)" 4 2297.IP "ev::TYPE::TYPE ()" 4
1481.IX Item "ev::TYPE::TYPE (object *, object::method *)" 2298.IX Item "ev::TYPE::TYPE ()"
1482.PD 0 2299.PD 0
1483.IP "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)" 4 2300.IP "ev::TYPE::TYPE (struct ev_loop *)" 4
1484.IX Item "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)" 2301.IX Item "ev::TYPE::TYPE (struct ev_loop *)"
1485.IP "ev::TYPE::~TYPE" 4 2302.IP "ev::TYPE::~TYPE" 4
1486.IX Item "ev::TYPE::~TYPE" 2303.IX Item "ev::TYPE::~TYPE"
1487.PD 2304.PD
1488The constructor takes a pointer to an object and a method pointer to 2305The constructor (optionally) takes an event loop to associate the watcher
1489the event handler callback to call in this class. The constructor calls 2306with. If it is omitted, it will use \f(CW\*(C`EV_DEFAULT\*(C'\fR.
1490\&\f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the \f(CW\*(C`set\*(C'\fR method 2307.Sp
1491before starting it. If you do not specify a loop then the constructor 2308The constructor calls \f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the
1492automatically associates the default loop with this watcher. 2309\&\f(CW\*(C`set\*(C'\fR method before starting it.
2310.Sp
2311It will not set a callback, however: You have to call the templated \f(CW\*(C`set\*(C'\fR
2312method to set a callback before you can start the watcher.
2313.Sp
2314(The reason why you have to use a method is a limitation in \*(C+ which does
2315not allow explicit template arguments for constructors).
1493.Sp 2316.Sp
1494The destructor automatically stops the watcher if it is active. 2317The destructor automatically stops the watcher if it is active.
2318.IP "w\->set<class, &class::method> (object *)" 4
2319.IX Item "w->set<class, &class::method> (object *)"
2320This method sets the callback method to call. The method has to have a
2321signature of \f(CW\*(C`void (*)(ev_TYPE &, int)\*(C'\fR, it receives the watcher as
2322first argument and the \f(CW\*(C`revents\*(C'\fR as second. The object must be given as
2323parameter and is stored in the \f(CW\*(C`data\*(C'\fR member of the watcher.
2324.Sp
2325This method synthesizes efficient thunking code to call your method from
2326the C callback that libev requires. If your compiler can inline your
2327callback (i.e. it is visible to it at the place of the \f(CW\*(C`set\*(C'\fR call and
2328your compiler is good :), then the method will be fully inlined into the
2329thunking function, making it as fast as a direct C callback.
2330.Sp
2331Example: simple class declaration and watcher initialisation
2332.Sp
2333.Vb 4
2334\& struct myclass
2335\& {
2336\& void io_cb (ev::io &w, int revents) { }
2337\& }
2338\&
2339\& myclass obj;
2340\& ev::io iow;
2341\& iow.set <myclass, &myclass::io_cb> (&obj);
2342.Ve
2343.IP "w\->set<function> (void *data = 0)" 4
2344.IX Item "w->set<function> (void *data = 0)"
2345Also sets a callback, but uses a static method or plain function as
2346callback. The optional \f(CW\*(C`data\*(C'\fR argument will be stored in the watcher's
2347\&\f(CW\*(C`data\*(C'\fR member and is free for you to use.
2348.Sp
2349The prototype of the \f(CW\*(C`function\*(C'\fR must be \f(CW\*(C`void (*)(ev::TYPE &w, int)\*(C'\fR.
2350.Sp
2351See the method\-\f(CW\*(C`set\*(C'\fR above for more details.
2352.Sp
2353Example:
2354.Sp
2355.Vb 2
2356\& static void io_cb (ev::io &w, int revents) { }
2357\& iow.set <io_cb> ();
2358.Ve
1495.IP "w\->set (struct ev_loop *)" 4 2359.IP "w\->set (struct ev_loop *)" 4
1496.IX Item "w->set (struct ev_loop *)" 2360.IX Item "w->set (struct ev_loop *)"
1497Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only 2361Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only
1498do this when the watcher is inactive (and not pending either). 2362do this when the watcher is inactive (and not pending either).
1499.IP "w\->set ([args])" 4 2363.IP "w\->set ([args])" 4
1500.IX Item "w->set ([args])" 2364.IX Item "w->set ([args])"
1501Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same args. Must be 2365Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same args. Must be
1502called at least once. Unlike the C counterpart, an active watcher gets 2366called at least once. Unlike the C counterpart, an active watcher gets
1503automatically stopped and restarted. 2367automatically stopped and restarted when reconfiguring it with this
2368method.
1504.IP "w\->start ()" 4 2369.IP "w\->start ()" 4
1505.IX Item "w->start ()" 2370.IX Item "w->start ()"
1506Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument as the 2371Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the
1507constructor already takes the loop. 2372constructor already stores the event loop.
1508.IP "w\->stop ()" 4 2373.IP "w\->stop ()" 4
1509.IX Item "w->stop ()" 2374.IX Item "w->stop ()"
1510Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument. 2375Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument.
1511.ie n .IP "w\->again () ""ev::timer""\fR, \f(CW""ev::periodic"" only" 4 2376.ie n .IP "w\->again () (""ev::timer""\fR, \f(CW""ev::periodic"" only)" 4
1512.el .IP "w\->again () \f(CWev::timer\fR, \f(CWev::periodic\fR only" 4 2377.el .IP "w\->again () (\f(CWev::timer\fR, \f(CWev::periodic\fR only)" 4
1513.IX Item "w->again () ev::timer, ev::periodic only" 2378.IX Item "w->again () (ev::timer, ev::periodic only)"
1514For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding 2379For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding
1515\&\f(CW\*(C`ev_TYPE_again\*(C'\fR function. 2380\&\f(CW\*(C`ev_TYPE_again\*(C'\fR function.
1516.ie n .IP "w\->sweep () ""ev::embed"" only" 4 2381.ie n .IP "w\->sweep () (""ev::embed"" only)" 4
1517.el .IP "w\->sweep () \f(CWev::embed\fR only" 4 2382.el .IP "w\->sweep () (\f(CWev::embed\fR only)" 4
1518.IX Item "w->sweep () ev::embed only" 2383.IX Item "w->sweep () (ev::embed only)"
1519Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR. 2384Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR.
2385.ie n .IP "w\->update () (""ev::stat"" only)" 4
2386.el .IP "w\->update () (\f(CWev::stat\fR only)" 4
2387.IX Item "w->update () (ev::stat only)"
2388Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR.
1520.RE 2389.RE
1521.RS 4 2390.RS 4
1522.RE 2391.RE
1523.PP 2392.PP
1524Example: Define a class with an \s-1IO\s0 and idle watcher, start one of them in 2393Example: Define a class with an \s-1IO\s0 and idle watcher, start one of them in
1525the constructor. 2394the constructor.
1526.PP 2395.PP
1527.Vb 4 2396.Vb 4
1528\& class myclass 2397\& class myclass
1529\& { 2398\& {
1530\& ev_io io; void io_cb (ev::io &w, int revents); 2399\& ev::io io; void io_cb (ev::io &w, int revents);
1531\& ev_idle idle void idle_cb (ev::idle &w, int revents); 2400\& ev:idle idle void idle_cb (ev::idle &w, int revents);
2401\&
2402\& myclass (int fd)
2403\& {
2404\& io .set <myclass, &myclass::io_cb > (this);
2405\& idle.set <myclass, &myclass::idle_cb> (this);
2406\&
2407\& io.start (fd, ev::READ);
2408\& }
2409\& };
1532.Ve 2410.Ve
2411.SH "MACRO MAGIC"
2412.IX Header "MACRO MAGIC"
2413Libev can be compiled with a variety of options, the most fundamantal
2414of which is \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most)
2415functions and callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument.
1533.PP 2416.PP
2417To make it easier to write programs that cope with either variant, the
2418following macros are defined:
2419.ie n .IP """EV_A""\fR, \f(CW""EV_A_""" 4
2420.el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4
2421.IX Item "EV_A, EV_A_"
2422This provides the loop \fIargument\fR for functions, if one is required (\*(L"ev
2423loop argument\*(R"). The \f(CW\*(C`EV_A\*(C'\fR form is used when this is the sole argument,
2424\&\f(CW\*(C`EV_A_\*(C'\fR is used when other arguments are following. Example:
2425.Sp
2426.Vb 3
2427\& ev_unref (EV_A);
2428\& ev_timer_add (EV_A_ watcher);
2429\& ev_loop (EV_A_ 0);
2430.Ve
2431.Sp
2432It assumes the variable \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR is in scope,
2433which is often provided by the following macro.
2434.ie n .IP """EV_P""\fR, \f(CW""EV_P_""" 4
2435.el .IP "\f(CWEV_P\fR, \f(CWEV_P_\fR" 4
2436.IX Item "EV_P, EV_P_"
2437This provides the loop \fIparameter\fR for functions, if one is required (\*(L"ev
2438loop parameter\*(R"). The \f(CW\*(C`EV_P\*(C'\fR form is used when this is the sole parameter,
2439\&\f(CW\*(C`EV_P_\*(C'\fR is used when other parameters are following. Example:
2440.Sp
1534.Vb 2 2441.Vb 2
1535\& myclass (); 2442\& // this is how ev_unref is being declared
2443\& static void ev_unref (EV_P);
2444\&
2445\& // this is how you can declare your typical callback
2446\& static void cb (EV_P_ ev_timer *w, int revents)
2447.Ve
2448.Sp
2449It declares a parameter \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR, quite
2450suitable for use with \f(CW\*(C`EV_A\*(C'\fR.
2451.ie n .IP """EV_DEFAULT""\fR, \f(CW""EV_DEFAULT_""" 4
2452.el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4
2453.IX Item "EV_DEFAULT, EV_DEFAULT_"
2454Similar to the other two macros, this gives you the value of the default
2455loop, if multiple loops are supported (\*(L"ev loop default\*(R").
2456.PP
2457Example: Declare and initialise a check watcher, utilising the above
2458macros so it will work regardless of whether multiple loops are supported
2459or not.
2460.PP
2461.Vb 5
2462\& static void
2463\& check_cb (EV_P_ ev_timer *w, int revents)
2464\& {
2465\& ev_check_stop (EV_A_ w);
1536\& } 2466\& }
1537.Ve 2467\&
1538.PP 2468\& ev_check check;
1539.Vb 6 2469\& ev_check_init (&check, check_cb);
1540\& myclass::myclass (int fd) 2470\& ev_check_start (EV_DEFAULT_ &check);
1541\& : io (this, &myclass::io_cb), 2471\& ev_loop (EV_DEFAULT_ 0);
1542\& idle (this, &myclass::idle_cb)
1543\& {
1544\& io.start (fd, ev::READ);
1545\& }
1546.Ve 2472.Ve
1547.SH "EMBEDDING" 2473.SH "EMBEDDING"
1548.IX Header "EMBEDDING" 2474.IX Header "EMBEDDING"
1549Libev can (and often is) directly embedded into host 2475Libev can (and often is) directly embedded into host
1550applications. Examples of applications that embed it include the Deliantra 2476applications. Examples of applications that embed it include the Deliantra
1551Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe) 2477Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe)
1552and rxvt\-unicode. 2478and rxvt-unicode.
1553.PP 2479.PP
1554The goal is to enable you to just copy the neecssary files into your 2480The goal is to enable you to just copy the necessary files into your
1555source directory without having to change even a single line in them, so 2481source directory without having to change even a single line in them, so
1556you can easily upgrade by simply copying (or having a checked-out copy of 2482you can easily upgrade by simply copying (or having a checked-out copy of
1557libev somewhere in your source tree). 2483libev somewhere in your source tree).
1558.Sh "\s-1FILESETS\s0" 2484.Sh "\s-1FILESETS\s0"
1559.IX Subsection "FILESETS" 2485.IX Subsection "FILESETS"
… …
1592.Vb 4 2518.Vb 4
1593\& ev.h 2519\& ev.h
1594\& ev.c 2520\& ev.c
1595\& ev_vars.h 2521\& ev_vars.h
1596\& ev_wrap.h 2522\& ev_wrap.h
1597.Ve 2523\&
1598.PP
1599.Vb 1
1600\& ev_win32.c required on win32 platforms only 2524\& ev_win32.c required on win32 platforms only
1601.Ve 2525\&
1602.PP
1603.Vb 5
1604\& ev_select.c only when select backend is enabled (which is is by default) 2526\& ev_select.c only when select backend is enabled (which is enabled by default)
1605\& ev_poll.c only when poll backend is enabled (disabled by default) 2527\& ev_poll.c only when poll backend is enabled (disabled by default)
1606\& ev_epoll.c only when the epoll backend is enabled (disabled by default) 2528\& ev_epoll.c only when the epoll backend is enabled (disabled by default)
1607\& ev_kqueue.c only when the kqueue backend is enabled (disabled by default) 2529\& ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1608\& ev_port.c only when the solaris port backend is enabled (disabled by default) 2530\& ev_port.c only when the solaris port backend is enabled (disabled by default)
1609.Ve 2531.Ve
1610.PP 2532.PP
1611\&\fIev.c\fR includes the backend files directly when enabled, so you only need 2533\&\fIev.c\fR includes the backend files directly when enabled, so you only need
1612to compile a single file. 2534to compile this single file.
1613.PP 2535.PP
1614\fI\s-1LIBEVENT\s0 \s-1COMPATIBILITY\s0 \s-1API\s0\fR 2536\fI\s-1LIBEVENT\s0 \s-1COMPATIBILITY\s0 \s-1API\s0\fR
1615.IX Subsection "LIBEVENT COMPATIBILITY API" 2537.IX Subsection "LIBEVENT COMPATIBILITY API"
1616.PP 2538.PP
1617To include the libevent compatibility \s-1API\s0, also include: 2539To include the libevent compatibility \s-1API\s0, also include:
… …
1638\fI\s-1AUTOCONF\s0 \s-1SUPPORT\s0\fR 2560\fI\s-1AUTOCONF\s0 \s-1SUPPORT\s0\fR
1639.IX Subsection "AUTOCONF SUPPORT" 2561.IX Subsection "AUTOCONF SUPPORT"
1640.PP 2562.PP
1641Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your config in 2563Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your config in
1642whatever way you want, you can also \f(CW\*(C`m4_include([libev.m4])\*(C'\fR in your 2564whatever way you want, you can also \f(CW\*(C`m4_include([libev.m4])\*(C'\fR in your
1643\&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR off. \fIev.c\fR will then include 2565\&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR undefined. \fIev.c\fR will then
1644\&\fIconfig.h\fR and configure itself accordingly. 2566include \fIconfig.h\fR and configure itself accordingly.
1645.PP 2567.PP
1646For this of course you need the m4 file: 2568For this of course you need the m4 file:
1647.PP 2569.PP
1648.Vb 1 2570.Vb 1
1649\& libev.m4 2571\& libev.m4
… …
1664.IX Item "EV_USE_MONOTONIC" 2586.IX Item "EV_USE_MONOTONIC"
1665If defined to be \f(CW1\fR, libev will try to detect the availability of the 2587If defined to be \f(CW1\fR, libev will try to detect the availability of the
1666monotonic clock option at both compiletime and runtime. Otherwise no use 2588monotonic clock option at both compiletime and runtime. Otherwise no use
1667of the monotonic clock option will be attempted. If you enable this, you 2589of the monotonic clock option will be attempted. If you enable this, you
1668usually have to link against librt or something similar. Enabling it when 2590usually have to link against librt or something similar. Enabling it when
1669the functionality isn't available is safe, though, althoguh you have 2591the functionality isn't available is safe, though, although you have
1670to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR 2592to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR
1671function is hiding in (often \fI\-lrt\fR). 2593function is hiding in (often \fI\-lrt\fR).
1672.IP "\s-1EV_USE_REALTIME\s0" 4 2594.IP "\s-1EV_USE_REALTIME\s0" 4
1673.IX Item "EV_USE_REALTIME" 2595.IX Item "EV_USE_REALTIME"
1674If defined to be \f(CW1\fR, libev will try to detect the availability of the 2596If defined to be \f(CW1\fR, libev will try to detect the availability of the
1675realtime clock option at compiletime (and assume its availability at 2597realtime clock option at compiletime (and assume its availability at
1676runtime if successful). Otherwise no use of the realtime clock option will 2598runtime if successful). Otherwise no use of the realtime clock option will
1677be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get 2599be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get
1678(CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See tzhe note about libraries 2600(CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See the
1679in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though. 2601note about libraries in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though.
2602.IP "\s-1EV_USE_NANOSLEEP\s0" 4
2603.IX Item "EV_USE_NANOSLEEP"
2604If defined to be \f(CW1\fR, libev will assume that \f(CW\*(C`nanosleep ()\*(C'\fR is available
2605and will use it for delays. Otherwise it will use \f(CW\*(C`select ()\*(C'\fR.
1680.IP "\s-1EV_USE_SELECT\s0" 4 2606.IP "\s-1EV_USE_SELECT\s0" 4
1681.IX Item "EV_USE_SELECT" 2607.IX Item "EV_USE_SELECT"
1682If undefined or defined to be \f(CW1\fR, libev will compile in support for the 2608If undefined or defined to be \f(CW1\fR, libev will compile in support for the
1683\&\f(CW\*(C`select\*(C'\fR(2) backend. No attempt at autodetection will be done: if no 2609\&\f(CW\*(C`select\*(C'\fR(2) backend. No attempt at autodetection will be done: if no
1684other method takes over, select will be it. Otherwise the select backend 2610other method takes over, select will be it. Otherwise the select backend
… …
1699wants osf handles on win32 (this is the case when the select to 2625wants osf handles on win32 (this is the case when the select to
1700be used is the winsock select). This means that it will call 2626be used is the winsock select). This means that it will call
1701\&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise, 2627\&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise,
1702it is assumed that all these functions actually work on fds, even 2628it is assumed that all these functions actually work on fds, even
1703on win32. Should not be defined on non\-win32 platforms. 2629on win32. Should not be defined on non\-win32 platforms.
2630.IP "\s-1EV_FD_TO_WIN32_HANDLE\s0" 4
2631.IX Item "EV_FD_TO_WIN32_HANDLE"
2632If \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR is enabled, then libev needs a way to map
2633file descriptors to socket handles. When not defining this symbol (the
2634default), then libev will call \f(CW\*(C`_get_osfhandle\*(C'\fR, which is usually
2635correct. In some cases, programs use their own file descriptor management,
2636in which case they can provide this function to map fds to socket handles.
1704.IP "\s-1EV_USE_POLL\s0" 4 2637.IP "\s-1EV_USE_POLL\s0" 4
1705.IX Item "EV_USE_POLL" 2638.IX Item "EV_USE_POLL"
1706If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2) 2639If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2)
1707backend. Otherwise it will be enabled on non\-win32 platforms. It 2640backend. Otherwise it will be enabled on non\-win32 platforms. It
1708takes precedence over select. 2641takes precedence over select.
… …
1730otherwise another method will be used as fallback. This is the preferred 2663otherwise another method will be used as fallback. This is the preferred
1731backend for Solaris 10 systems. 2664backend for Solaris 10 systems.
1732.IP "\s-1EV_USE_DEVPOLL\s0" 4 2665.IP "\s-1EV_USE_DEVPOLL\s0" 4
1733.IX Item "EV_USE_DEVPOLL" 2666.IX Item "EV_USE_DEVPOLL"
1734reserved for future expansion, works like the \s-1USE\s0 symbols above. 2667reserved for future expansion, works like the \s-1USE\s0 symbols above.
2668.IP "\s-1EV_USE_INOTIFY\s0" 4
2669.IX Item "EV_USE_INOTIFY"
2670If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify
2671interface to speed up \f(CW\*(C`ev_stat\*(C'\fR watchers. Its actual availability will
2672be detected at runtime.
1735.IP "\s-1EV_H\s0" 4 2673.IP "\s-1EV_H\s0" 4
1736.IX Item "EV_H" 2674.IX Item "EV_H"
1737The name of the \fIev.h\fR header file used to include it. The default if 2675The name of the \fIev.h\fR header file used to include it. The default if
1738undefined is \f(CW\*(C`<ev.h>\*(C'\fR in \fIevent.h\fR and \f(CW"ev.h"\fR in \fIev.c\fR. This 2676undefined is \f(CW"ev.h"\fR in \fIevent.h\fR, \fIev.c\fR and \fIev++.h\fR. This can be
1739can be used to virtually rename the \fIev.h\fR header file in case of conflicts. 2677used to virtually rename the \fIev.h\fR header file in case of conflicts.
1740.IP "\s-1EV_CONFIG_H\s0" 4 2678.IP "\s-1EV_CONFIG_H\s0" 4
1741.IX Item "EV_CONFIG_H" 2679.IX Item "EV_CONFIG_H"
1742If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override 2680If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override
1743\&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to 2681\&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to
1744\&\f(CW\*(C`EV_H\*(C'\fR, above. 2682\&\f(CW\*(C`EV_H\*(C'\fR, above.
1745.IP "\s-1EV_EVENT_H\s0" 4 2683.IP "\s-1EV_EVENT_H\s0" 4
1746.IX Item "EV_EVENT_H" 2684.IX Item "EV_EVENT_H"
1747Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea 2685Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea
1748of how the \fIevent.h\fR header can be found. 2686of how the \fIevent.h\fR header can be found, the default is \f(CW"event.h"\fR.
1749.IP "\s-1EV_PROTOTYPES\s0" 4 2687.IP "\s-1EV_PROTOTYPES\s0" 4
1750.IX Item "EV_PROTOTYPES" 2688.IX Item "EV_PROTOTYPES"
1751If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function 2689If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function
1752prototypes, but still define all the structs and other symbols. This is 2690prototypes, but still define all the structs and other symbols. This is
1753occasionally useful if you want to provide your own wrapper functions 2691occasionally useful if you want to provide your own wrapper functions
… …
1757If undefined or defined to \f(CW1\fR, then all event-loop-specific functions 2695If undefined or defined to \f(CW1\fR, then all event-loop-specific functions
1758will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create 2696will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create
1759additional independent event loops. Otherwise there will be no support 2697additional independent event loops. Otherwise there will be no support
1760for multiple event loops and there is no first event loop pointer 2698for multiple event loops and there is no first event loop pointer
1761argument. Instead, all functions act on the single default loop. 2699argument. Instead, all functions act on the single default loop.
2700.IP "\s-1EV_MINPRI\s0" 4
2701.IX Item "EV_MINPRI"
2702.PD 0
2703.IP "\s-1EV_MAXPRI\s0" 4
2704.IX Item "EV_MAXPRI"
2705.PD
2706The range of allowed priorities. \f(CW\*(C`EV_MINPRI\*(C'\fR must be smaller or equal to
2707\&\f(CW\*(C`EV_MAXPRI\*(C'\fR, but otherwise there are no non-obvious limitations. You can
2708provide for more priorities by overriding those symbols (usually defined
2709to be \f(CW\*(C`\-2\*(C'\fR and \f(CW2\fR, respectively).
2710.Sp
2711When doing priority-based operations, libev usually has to linearly search
2712all the priorities, so having many of them (hundreds) uses a lot of space
2713and time, so using the defaults of five priorities (\-2 .. +2) is usually
2714fine.
2715.Sp
2716If your embedding app does not need any priorities, defining these both to
2717\&\f(CW0\fR will save some memory and cpu.
1762.IP "\s-1EV_PERIODICS\s0" 4 2718.IP "\s-1EV_PERIODIC_ENABLE\s0" 4
1763.IX Item "EV_PERIODICS" 2719.IX Item "EV_PERIODIC_ENABLE"
1764If undefined or defined to be \f(CW1\fR, then periodic timers are supported, 2720If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If
1765otherwise not. This saves a few kb of code. 2721defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
2722code.
2723.IP "\s-1EV_IDLE_ENABLE\s0" 4
2724.IX Item "EV_IDLE_ENABLE"
2725If undefined or defined to be \f(CW1\fR, then idle watchers are supported. If
2726defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
2727code.
2728.IP "\s-1EV_EMBED_ENABLE\s0" 4
2729.IX Item "EV_EMBED_ENABLE"
2730If undefined or defined to be \f(CW1\fR, then embed watchers are supported. If
2731defined to be \f(CW0\fR, then they are not.
2732.IP "\s-1EV_STAT_ENABLE\s0" 4
2733.IX Item "EV_STAT_ENABLE"
2734If undefined or defined to be \f(CW1\fR, then stat watchers are supported. If
2735defined to be \f(CW0\fR, then they are not.
2736.IP "\s-1EV_FORK_ENABLE\s0" 4
2737.IX Item "EV_FORK_ENABLE"
2738If undefined or defined to be \f(CW1\fR, then fork watchers are supported. If
2739defined to be \f(CW0\fR, then they are not.
2740.IP "\s-1EV_MINIMAL\s0" 4
2741.IX Item "EV_MINIMAL"
2742If you need to shave off some kilobytes of code at the expense of some
2743speed, define this symbol to \f(CW1\fR. Currently only used for gcc to override
2744some inlining decisions, saves roughly 30% codesize of amd64.
2745.IP "\s-1EV_PID_HASHSIZE\s0" 4
2746.IX Item "EV_PID_HASHSIZE"
2747\&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by
2748pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), usually more
2749than enough. If you need to manage thousands of children you might want to
2750increase this value (\fImust\fR be a power of two).
2751.IP "\s-1EV_INOTIFY_HASHSIZE\s0" 4
2752.IX Item "EV_INOTIFY_HASHSIZE"
2753\&\f(CW\*(C`ev_stat\*(C'\fR watchers use a small hash table to distribute workload by
2754inotify watch id. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR),
2755usually more than enough. If you need to manage thousands of \f(CW\*(C`ev_stat\*(C'\fR
2756watchers you might want to increase this value (\fImust\fR be a power of
2757two).
1766.IP "\s-1EV_COMMON\s0" 4 2758.IP "\s-1EV_COMMON\s0" 4
1767.IX Item "EV_COMMON" 2759.IX Item "EV_COMMON"
1768By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining 2760By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining
1769this macro to a something else you can include more and other types of 2761this macro to a something else you can include more and other types of
1770members. You have to define it each time you include one of the files, 2762members. You have to define it each time you include one of the files,
… …
1775.Vb 3 2767.Vb 3
1776\& #define EV_COMMON \e 2768\& #define EV_COMMON \e
1777\& SV *self; /* contains this struct */ \e 2769\& SV *self; /* contains this struct */ \e
1778\& SV *cb_sv, *fh /* note no trailing ";" */ 2770\& SV *cb_sv, *fh /* note no trailing ";" */
1779.Ve 2771.Ve
1780.IP "\s-1EV_CB_DECLARE\s0(type)" 4 2772.IP "\s-1EV_CB_DECLARE\s0 (type)" 4
1781.IX Item "EV_CB_DECLARE(type)" 2773.IX Item "EV_CB_DECLARE (type)"
1782.PD 0 2774.PD 0
1783.IP "\s-1EV_CB_INVOKE\s0(watcher,revents)" 4 2775.IP "\s-1EV_CB_INVOKE\s0 (watcher, revents)" 4
1784.IX Item "EV_CB_INVOKE(watcher,revents)" 2776.IX Item "EV_CB_INVOKE (watcher, revents)"
1785.IP "ev_set_cb(ev,cb)" 4 2777.IP "ev_set_cb (ev, cb)" 4
1786.IX Item "ev_set_cb(ev,cb)" 2778.IX Item "ev_set_cb (ev, cb)"
1787.PD 2779.PD
1788Can be used to change the callback member declaration in each watcher, 2780Can be used to change the callback member declaration in each watcher,
1789and the way callbacks are invoked and set. Must expand to a struct member 2781and the way callbacks are invoked and set. Must expand to a struct member
1790definition and a statement, respectively. See the \fIev.v\fR header file for 2782definition and a statement, respectively. See the \fIev.h\fR header file for
1791their default definitions. One possible use for overriding these is to 2783their default definitions. One possible use for overriding these is to
1792avoid the ev_loop pointer as first argument in all cases, or to use method 2784avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use
1793calls instead of plain function calls in \*(C+. 2785method calls instead of plain function calls in \*(C+.
2786.Sh "\s-1EXPORTED\s0 \s-1API\s0 \s-1SYMBOLS\s0"
2787.IX Subsection "EXPORTED API SYMBOLS"
2788If you need to re-export the \s-1API\s0 (e.g. via a dll) and you need a list of
2789exported symbols, you can use the provided \fISymbol.*\fR files which list
2790all public symbols, one per line:
2791.PP
2792.Vb 2
2793\& Symbols.ev for libev proper
2794\& Symbols.event for the libevent emulation
2795.Ve
2796.PP
2797This can also be used to rename all public symbols to avoid clashes with
2798multiple versions of libev linked together (which is obviously bad in
2799itself, but sometimes it is inconvinient to avoid this).
2800.PP
2801A sed command like this will create wrapper \f(CW\*(C`#define\*(C'\fR's that you need to
2802include before including \fIev.h\fR:
2803.PP
2804.Vb 1
2805\& <Symbols.ev sed \-e "s/.*/#define & myprefix_&/" >wrap.h
2806.Ve
2807.PP
2808This would create a file \fIwrap.h\fR which essentially looks like this:
2809.PP
2810.Vb 4
2811\& #define ev_backend myprefix_ev_backend
2812\& #define ev_check_start myprefix_ev_check_start
2813\& #define ev_check_stop myprefix_ev_check_stop
2814\& ...
2815.Ve
1794.Sh "\s-1EXAMPLES\s0" 2816.Sh "\s-1EXAMPLES\s0"
1795.IX Subsection "EXAMPLES" 2817.IX Subsection "EXAMPLES"
1796For a real-world example of a program the includes libev 2818For a real-world example of a program the includes libev
1797verbatim, you can have a look at the \s-1EV\s0 perl module 2819verbatim, you can have a look at the \s-1EV\s0 perl module
1798(<http://software.schmorp.de/pkg/EV.html>). It has the libev files in 2820(<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
1799the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public 2821the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public
1800interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file 2822interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file
1801will be compiled. It is pretty complex because it provides its own header 2823will be compiled. It is pretty complex because it provides its own header
1802file. 2824file.
1803.Sp 2825.PP
1804The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file 2826The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file
1805that everybody includes and which overrides some autoconf choices: 2827that everybody includes and which overrides some configure choices:
1806.Sp 2828.PP
1807.Vb 4 2829.Vb 9
2830\& #define EV_MINIMAL 1
1808\& #define EV_USE_POLL 0 2831\& #define EV_USE_POLL 0
1809\& #define EV_MULTIPLICITY 0 2832\& #define EV_MULTIPLICITY 0
1810\& #define EV_PERIODICS 0 2833\& #define EV_PERIODIC_ENABLE 0
2834\& #define EV_STAT_ENABLE 0
2835\& #define EV_FORK_ENABLE 0
1811\& #define EV_CONFIG_H <config.h> 2836\& #define EV_CONFIG_H <config.h>
1812.Ve 2837\& #define EV_MINPRI 0
1813.Sp 2838\& #define EV_MAXPRI 0
1814.Vb 1 2839\&
1815\& #include "ev++.h" 2840\& #include "ev++.h"
1816.Ve 2841.Ve
1817.Sp 2842.PP
1818And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled: 2843And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled:
1819.Sp 2844.PP
1820.Vb 2 2845.Vb 2
1821\& #include "ev_cpp.h" 2846\& #include "ev_cpp.h"
1822\& #include "ev.c" 2847\& #include "ev.c"
1823.Ve 2848.Ve
2849.SH "COMPLEXITIES"
2850.IX Header "COMPLEXITIES"
2851In this section the complexities of (many of) the algorithms used inside
2852libev will be explained. For complexity discussions about backends see the
2853documentation for \f(CW\*(C`ev_default_init\*(C'\fR.
2854.PP
2855All of the following are about amortised time: If an array needs to be
2856extended, libev needs to realloc and move the whole array, but this
2857happens asymptotically never with higher number of elements, so O(1) might
2858mean it might do a lengthy realloc operation in rare cases, but on average
2859it is much faster and asymptotically approaches constant time.
2860.IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4
2861.IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)"
2862This means that, when you have a watcher that triggers in one hour and
2863there are 100 watchers that would trigger before that then inserting will
2864have to skip roughly seven (\f(CW\*(C`ld 100\*(C'\fR) of these watchers.
2865.IP "Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)" 4
2866.IX Item "Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)"
2867That means that changing a timer costs less than removing/adding them
2868as only the relative motion in the event queue has to be paid for.
2869.IP "Starting io/check/prepare/idle/signal/child watchers: O(1)" 4
2870.IX Item "Starting io/check/prepare/idle/signal/child watchers: O(1)"
2871These just add the watcher into an array or at the head of a list.
2872.IP "Stopping check/prepare/idle watchers: O(1)" 4
2873.IX Item "Stopping check/prepare/idle watchers: O(1)"
2874.PD 0
2875.IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4
2876.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))"
2877.PD
2878These watchers are stored in lists then need to be walked to find the
2879correct watcher to remove. The lists are usually short (you don't usually
2880have many watchers waiting for the same fd or signal).
2881.IP "Finding the next timer in each loop iteration: O(1)" 4
2882.IX Item "Finding the next timer in each loop iteration: O(1)"
2883By virtue of using a binary heap, the next timer is always found at the
2884beginning of the storage array.
2885.IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4
2886.IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)"
2887A change means an I/O watcher gets started or stopped, which requires
2888libev to recalculate its status (and possibly tell the kernel, depending
2889on backend and wether \f(CW\*(C`ev_io_set\*(C'\fR was used).
2890.IP "Activating one watcher (putting it into the pending state): O(1)" 4
2891.IX Item "Activating one watcher (putting it into the pending state): O(1)"
2892.PD 0
2893.IP "Priority handling: O(number_of_priorities)" 4
2894.IX Item "Priority handling: O(number_of_priorities)"
2895.PD
2896Priorities are implemented by allocating some space for each
2897priority. When doing priority-based operations, libev usually has to
2898linearly search all the priorities, but starting/stopping and activating
2899watchers becomes O(1) w.r.t. prioritiy handling.
2900.SH "Win32 platform limitations and workarounds"
2901.IX Header "Win32 platform limitations and workarounds"
2902Win32 doesn't support any of the standards (e.g. \s-1POSIX\s0) that libev
2903requires, and its I/O model is fundamentally incompatible with the \s-1POSIX\s0
2904model. Libev still offers limited functionality on this platform in
2905the form of the \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR backend, and only supports socket
2906descriptors. This only applies when using Win32 natively, not when using
2907e.g. cygwin.
2908.PP
2909There is no supported compilation method available on windows except
2910embedding it into other applications.
2911.PP
2912Due to the many, low, and arbitrary limits on the win32 platform and the
2913abysmal performance of winsockets, using a large number of sockets is not
2914recommended (and not reasonable). If your program needs to use more than
2915a hundred or so sockets, then likely it needs to use a totally different
2916implementation for windows, as libev offers the \s-1POSIX\s0 model, which cannot
2917be implemented efficiently on windows (microsoft monopoly games).
2918.IP "The winsocket select function" 4
2919.IX Item "The winsocket select function"
2920The winsocket \f(CW\*(C`select\*(C'\fR function doesn't follow \s-1POSIX\s0 in that it requires
2921socket \fIhandles\fR and not socket \fIfile descriptors\fR. This makes select
2922very inefficient, and also requires a mapping from file descriptors
2923to socket handles. See the discussion of the \f(CW\*(C`EV_SELECT_USE_FD_SET\*(C'\fR,
2924\&\f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR and \f(CW\*(C`EV_FD_TO_WIN32_HANDLE\*(C'\fR preprocessor
2925symbols for more info.
2926.Sp
2927The configuration for a \*(L"naked\*(R" win32 using the microsoft runtime
2928libraries and raw winsocket select is:
2929.Sp
2930.Vb 2
2931\& #define EV_USE_SELECT 1
2932\& #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
2933.Ve
2934.Sp
2935Note that winsockets handling of fd sets is O(n), so you can easily get a
2936complexity in the O(nA\*^X) range when using win32.
2937.IP "Limited number of file descriptors" 4
2938.IX Item "Limited number of file descriptors"
2939Windows has numerous arbitrary (and low) limits on things. Early versions
2940of winsocket's select only supported waiting for a max. of \f(CW64\fR handles
2941(probably owning to the fact that all windows kernels can only wait for
2942\&\f(CW64\fR things at the same time internally; microsoft recommends spawning a
2943chain of threads and wait for 63 handles and the previous thread in each).
2944.Sp
2945Newer versions support more handles, but you need to define \f(CW\*(C`FD_SETSIZE\*(C'\fR
2946to some high number (e.g. \f(CW2048\fR) before compiling the winsocket select
2947call (which might be in libev or elsewhere, for example, perl does its own
2948select emulation on windows).
2949.Sp
2950Another limit is the number of file descriptors in the microsoft runtime
2951libraries, which by default is \f(CW64\fR (there must be a hidden \fI64\fR fetish
2952or something like this inside microsoft). You can increase this by calling
2953\&\f(CW\*(C`_setmaxstdio\*(C'\fR, which can increase this limit to \f(CW2048\fR (another
2954arbitrary limit), but is broken in many versions of the microsoft runtime
2955libraries.
2956.Sp
2957This might get you to about \f(CW512\fR or \f(CW2048\fR sockets (depending on
2958windows version and/or the phase of the moon). To get more, you need to
2959wrap all I/O functions and provide your own fd management, but the cost of
2960calling select (O(nA\*^X)) will likely make this unworkable.
1824.SH "AUTHOR" 2961.SH "AUTHOR"
1825.IX Header "AUTHOR" 2962.IX Header "AUTHOR"
1826Marc Lehmann <libev@schmorp.de>. 2963Marc Lehmann <libev@schmorp.de>.
2964.SH "POD ERRORS"
2965.IX Header "POD ERRORS"
2966Hey! \fBThe above document had some coding errors, which are explained below:\fR
2967.IP "Around line 2686:" 4
2968.IX Item "Around line 2686:"
2969You forgot a '=back' before '=head2'

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