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Revision 1.1 by root, Tue Nov 13 03:11:57 2007 UTC vs.
Revision 1.56 by root, Sat Dec 22 05:47:57 2007 UTC

… …
126. ds Ae AE 126. ds Ae AE
127.\} 127.\}
128.rm #[ #] #H #V #F C 128.rm #[ #] #H #V #F C
129.\" ======================================================================== 129.\" ========================================================================
130.\" 130.\"
131.IX Title ""<STANDARD INPUT>" 1" 131.IX Title "EV 1"
132.TH "<STANDARD INPUT>" 1 "2007-11-13" "perl v5.8.8" "User Contributed Perl Documentation" 132.TH EV 1 "2007-12-22" "perl v5.8.8" "User Contributed Perl Documentation"
133.SH "NAME" 133.SH "NAME"
134libev \- a high performance full\-featured event loop written in C 134libev \- a high performance full\-featured event loop written in C
135.SH "SYNOPSIS" 135.SH "SYNOPSIS"
136.IX Header "SYNOPSIS" 136.IX Header "SYNOPSIS"
137.Vb 1 137.Vb 1
138\& #include <ev.h> 138\& #include <ev.h>
139.Ve 139.Ve
140.SH "EXAMPLE PROGRAM"
141.IX Header "EXAMPLE PROGRAM"
142.Vb 1
143\& #include <ev.h>
144.Ve
145.PP
146.Vb 2
147\& ev_io stdin_watcher;
148\& ev_timer timeout_watcher;
149.Ve
150.PP
151.Vb 8
152\& /* called when data readable on stdin */
153\& static void
154\& stdin_cb (EV_P_ struct ev_io *w, int revents)
155\& {
156\& /* puts ("stdin ready"); */
157\& ev_io_stop (EV_A_ w); /* just a syntax example */
158\& ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
159\& }
160.Ve
161.PP
162.Vb 6
163\& static void
164\& timeout_cb (EV_P_ struct ev_timer *w, int revents)
165\& {
166\& /* puts ("timeout"); */
167\& ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
168\& }
169.Ve
170.PP
171.Vb 4
172\& int
173\& main (void)
174\& {
175\& struct ev_loop *loop = ev_default_loop (0);
176.Ve
177.PP
178.Vb 3
179\& /* initialise an io watcher, then start it */
180\& ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
181\& ev_io_start (loop, &stdin_watcher);
182.Ve
183.PP
184.Vb 3
185\& /* simple non-repeating 5.5 second timeout */
186\& ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
187\& ev_timer_start (loop, &timeout_watcher);
188.Ve
189.PP
190.Vb 2
191\& /* loop till timeout or data ready */
192\& ev_loop (loop, 0);
193.Ve
194.PP
195.Vb 2
196\& return 0;
197\& }
198.Ve
140.SH "DESCRIPTION" 199.SH "DESCRIPTION"
141.IX Header "DESCRIPTION" 200.IX Header "DESCRIPTION"
201The newest version of this document is also available as a html-formatted
202web page you might find easier to navigate when reading it for the first
203time: <http://cvs.schmorp.de/libev/ev.html>.
204.PP
142Libev is an event loop: you register interest in certain events (such as a 205Libev is an event loop: you register interest in certain events (such as a
143file descriptor being readable or a timeout occuring), and it will manage 206file descriptor being readable or a timeout occurring), and it will manage
144these event sources and provide your program with events. 207these event sources and provide your program with events.
145.PP 208.PP
146To do this, it must take more or less complete control over your process 209To do this, it must take more or less complete control over your process
147(or thread) by executing the \fIevent loop\fR handler, and will then 210(or thread) by executing the \fIevent loop\fR handler, and will then
148communicate events via a callback mechanism. 211communicate events via a callback mechanism.
… …
151watchers\fR, which are relatively small C structures you initialise with the 214watchers\fR, which are relatively small C structures you initialise with the
152details of the event, and then hand it over to libev by \fIstarting\fR the 215details of the event, and then hand it over to libev by \fIstarting\fR the
153watcher. 216watcher.
154.SH "FEATURES" 217.SH "FEATURES"
155.IX Header "FEATURES" 218.IX Header "FEATURES"
156Libev supports select, poll, the linux-specific epoll and the bsd-specific 219Libev supports \f(CW\*(C`select\*(C'\fR, \f(CW\*(C`poll\*(C'\fR, the Linux-specific \f(CW\*(C`epoll\*(C'\fR, the
157kqueue mechanisms for file descriptor events, relative timers, absolute 220BSD-specific \f(CW\*(C`kqueue\*(C'\fR and the Solaris-specific event port mechanisms
158timers with customised rescheduling, signal events, process status change 221for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), the Linux \f(CW\*(C`inotify\*(C'\fR interface
159events (related to \s-1SIGCHLD\s0), and event watchers dealing with the event 222(for \f(CW\*(C`ev_stat\*(C'\fR), relative timers (\f(CW\*(C`ev_timer\*(C'\fR), absolute timers
160loop mechanism itself (idle, prepare and check watchers). It also is quite 223with customised rescheduling (\f(CW\*(C`ev_periodic\*(C'\fR), synchronous signals
161fast (see this benchmark comparing 224(\f(CW\*(C`ev_signal\*(C'\fR), process status change events (\f(CW\*(C`ev_child\*(C'\fR), and event
162it to libevent for example). 225watchers dealing with the event loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR,
226\&\f(CW\*(C`ev_embed\*(C'\fR, \f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR watchers) as well as
227file watchers (\f(CW\*(C`ev_stat\*(C'\fR) and even limited support for fork events
228(\f(CW\*(C`ev_fork\*(C'\fR).
229.PP
230It also is quite fast (see this
231benchmark comparing it to libevent
232for example).
163.SH "CONVENTIONS" 233.SH "CONVENTIONS"
164.IX Header "CONVENTIONS" 234.IX Header "CONVENTIONS"
165Libev is very configurable. In this manual the default configuration 235Libev is very configurable. In this manual the default configuration will
166will be described, which supports multiple event loops. For more info 236be described, which supports multiple event loops. For more info about
167about various configuration options please have a look at the file 237various configuration options please have a look at \fB\s-1EMBED\s0\fR section in
168\&\fI\s-1README\s0.embed\fR in the libev distribution. If libev was configured without 238this manual. If libev was configured without support for multiple event
169support for multiple event loops, then all functions taking an initial 239loops, then all functions taking an initial argument of name \f(CW\*(C`loop\*(C'\fR
170argument of name \f(CW\*(C`loop\*(C'\fR (which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR) 240(which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR) will not have this argument.
171will not have this argument.
172.SH "TIME REPRESENTATION" 241.SH "TIME REPRESENTATION"
173.IX Header "TIME REPRESENTATION" 242.IX Header "TIME REPRESENTATION"
174Libev represents time as a single floating point number, representing the 243Libev represents time as a single floating point number, representing the
175(fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near 244(fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near
176the beginning of 1970, details are complicated, don't ask). This type is 245the beginning of 1970, details are complicated, don't ask). This type is
177called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use too. It usually aliases 246called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use too. It usually aliases
178to the double type in C. 247to the \f(CW\*(C`double\*(C'\fR type in C, and when you need to do any calculations on
248it, you should treat it as some floatingpoint value. Unlike the name
249component \f(CW\*(C`stamp\*(C'\fR might indicate, it is also used for time differences
250throughout libev.
179.SH "GLOBAL FUNCTIONS" 251.SH "GLOBAL FUNCTIONS"
180.IX Header "GLOBAL FUNCTIONS" 252.IX Header "GLOBAL FUNCTIONS"
181These functions can be called anytime, even before initialising the 253These functions can be called anytime, even before initialising the
182library in any way. 254library in any way.
183.IP "ev_tstamp ev_time ()" 4 255.IP "ev_tstamp ev_time ()" 4
184.IX Item "ev_tstamp ev_time ()" 256.IX Item "ev_tstamp ev_time ()"
185Returns the current time as libev would use it. 257Returns the current time as libev would use it. Please note that the
258\&\f(CW\*(C`ev_now\*(C'\fR function is usually faster and also often returns the timestamp
259you actually want to know.
260.IP "void ev_sleep (ev_tstamp interval)" 4
261.IX Item "void ev_sleep (ev_tstamp interval)"
262Sleep for the given interval: The current thread will be blocked until
263either it is interrupted or the given time interval has passed. Basically
264this is a subsecond-resolution \f(CW\*(C`sleep ()\*(C'\fR.
186.IP "int ev_version_major ()" 4 265.IP "int ev_version_major ()" 4
187.IX Item "int ev_version_major ()" 266.IX Item "int ev_version_major ()"
188.PD 0 267.PD 0
189.IP "int ev_version_minor ()" 4 268.IP "int ev_version_minor ()" 4
190.IX Item "int ev_version_minor ()" 269.IX Item "int ev_version_minor ()"
191.PD 270.PD
192You can find out the major and minor version numbers of the library 271You can find out the major and minor \s-1ABI\s0 version numbers of the library
193you linked against by calling the functions \f(CW\*(C`ev_version_major\*(C'\fR and 272you linked against by calling the functions \f(CW\*(C`ev_version_major\*(C'\fR and
194\&\f(CW\*(C`ev_version_minor\*(C'\fR. If you want, you can compare against the global 273\&\f(CW\*(C`ev_version_minor\*(C'\fR. If you want, you can compare against the global
195symbols \f(CW\*(C`EV_VERSION_MAJOR\*(C'\fR and \f(CW\*(C`EV_VERSION_MINOR\*(C'\fR, which specify the 274symbols \f(CW\*(C`EV_VERSION_MAJOR\*(C'\fR and \f(CW\*(C`EV_VERSION_MINOR\*(C'\fR, which specify the
196version of the library your program was compiled against. 275version of the library your program was compiled against.
197.Sp 276.Sp
277These version numbers refer to the \s-1ABI\s0 version of the library, not the
278release version.
279.Sp
198Usually, it's a good idea to terminate if the major versions mismatch, 280Usually, it's a good idea to terminate if the major versions mismatch,
199as this indicates an incompatible change. Minor versions are usually 281as this indicates an incompatible change. Minor versions are usually
200compatible to older versions, so a larger minor version alone is usually 282compatible to older versions, so a larger minor version alone is usually
201not a problem. 283not a problem.
284.Sp
285Example: Make sure we haven't accidentally been linked against the wrong
286version.
287.Sp
288.Vb 3
289\& assert (("libev version mismatch",
290\& ev_version_major () == EV_VERSION_MAJOR
291\& && ev_version_minor () >= EV_VERSION_MINOR));
292.Ve
293.IP "unsigned int ev_supported_backends ()" 4
294.IX Item "unsigned int ev_supported_backends ()"
295Return the set of all backends (i.e. their corresponding \f(CW\*(C`EV_BACKEND_*\*(C'\fR
296value) compiled into this binary of libev (independent of their
297availability on the system you are running on). See \f(CW\*(C`ev_default_loop\*(C'\fR for
298a description of the set values.
299.Sp
300Example: make sure we have the epoll method, because yeah this is cool and
301a must have and can we have a torrent of it please!!!11
302.Sp
303.Vb 2
304\& assert (("sorry, no epoll, no sex",
305\& ev_supported_backends () & EVBACKEND_EPOLL));
306.Ve
307.IP "unsigned int ev_recommended_backends ()" 4
308.IX Item "unsigned int ev_recommended_backends ()"
309Return the set of all backends compiled into this binary of libev and also
310recommended for this platform. This set is often smaller than the one
311returned by \f(CW\*(C`ev_supported_backends\*(C'\fR, as for example kqueue is broken on
312most BSDs and will not be autodetected unless you explicitly request it
313(assuming you know what you are doing). This is the set of backends that
314libev will probe for if you specify no backends explicitly.
315.IP "unsigned int ev_embeddable_backends ()" 4
316.IX Item "unsigned int ev_embeddable_backends ()"
317Returns the set of backends that are embeddable in other event loops. This
318is the theoretical, all\-platform, value. To find which backends
319might be supported on the current system, you would need to look at
320\&\f(CW\*(C`ev_embeddable_backends () & ev_supported_backends ()\*(C'\fR, likewise for
321recommended ones.
322.Sp
323See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info.
202.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4 324.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4
203.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))" 325.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))"
204Sets the allocation function to use (the prototype is similar to the 326Sets the allocation function to use (the prototype is similar \- the
205realloc C function, the semantics are identical). It is used to allocate 327semantics is identical \- to the realloc C function). It is used to
206and free memory (no surprises here). If it returns zero when memory 328allocate and free memory (no surprises here). If it returns zero when
207needs to be allocated, the library might abort or take some potentially 329memory needs to be allocated, the library might abort or take some
208destructive action. The default is your system realloc function. 330potentially destructive action. The default is your system realloc
331function.
209.Sp 332.Sp
210You could override this function in high-availability programs to, say, 333You could override this function in high-availability programs to, say,
211free some memory if it cannot allocate memory, to use a special allocator, 334free some memory if it cannot allocate memory, to use a special allocator,
212or even to sleep a while and retry until some memory is available. 335or even to sleep a while and retry until some memory is available.
336.Sp
337Example: Replace the libev allocator with one that waits a bit and then
338retries).
339.Sp
340.Vb 6
341\& static void *
342\& persistent_realloc (void *ptr, size_t size)
343\& {
344\& for (;;)
345\& {
346\& void *newptr = realloc (ptr, size);
347.Ve
348.Sp
349.Vb 2
350\& if (newptr)
351\& return newptr;
352.Ve
353.Sp
354.Vb 3
355\& sleep (60);
356\& }
357\& }
358.Ve
359.Sp
360.Vb 2
361\& ...
362\& ev_set_allocator (persistent_realloc);
363.Ve
213.IP "ev_set_syserr_cb (void (*cb)(const char *msg));" 4 364.IP "ev_set_syserr_cb (void (*cb)(const char *msg));" 4
214.IX Item "ev_set_syserr_cb (void (*cb)(const char *msg));" 365.IX Item "ev_set_syserr_cb (void (*cb)(const char *msg));"
215Set the callback function to call on a retryable syscall error (such 366Set the callback function to call on a retryable syscall error (such
216as failed select, poll, epoll_wait). The message is a printable string 367as failed select, poll, epoll_wait). The message is a printable string
217indicating the system call or subsystem causing the problem. If this 368indicating the system call or subsystem causing the problem. If this
218callback is set, then libev will expect it to remedy the sitution, no 369callback is set, then libev will expect it to remedy the sitution, no
219matter what, when it returns. That is, libev will generally retry the 370matter what, when it returns. That is, libev will generally retry the
220requested operation, or, if the condition doesn't go away, do bad stuff 371requested operation, or, if the condition doesn't go away, do bad stuff
221(such as abort). 372(such as abort).
373.Sp
374Example: This is basically the same thing that libev does internally, too.
375.Sp
376.Vb 6
377\& static void
378\& fatal_error (const char *msg)
379\& {
380\& perror (msg);
381\& abort ();
382\& }
383.Ve
384.Sp
385.Vb 2
386\& ...
387\& ev_set_syserr_cb (fatal_error);
388.Ve
222.SH "FUNCTIONS CONTROLLING THE EVENT LOOP" 389.SH "FUNCTIONS CONTROLLING THE EVENT LOOP"
223.IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP" 390.IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP"
224An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR. The library knows two 391An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR. The library knows two
225types of such loops, the \fIdefault\fR loop, which supports signals and child 392types of such loops, the \fIdefault\fR loop, which supports signals and child
226events, and dynamically created loops which do not. 393events, and dynamically created loops which do not.
… …
234.IP "struct ev_loop *ev_default_loop (unsigned int flags)" 4 401.IP "struct ev_loop *ev_default_loop (unsigned int flags)" 4
235.IX Item "struct ev_loop *ev_default_loop (unsigned int flags)" 402.IX Item "struct ev_loop *ev_default_loop (unsigned int flags)"
236This will initialise the default event loop if it hasn't been initialised 403This will initialise the default event loop if it hasn't been initialised
237yet and return it. If the default loop could not be initialised, returns 404yet and return it. If the default loop could not be initialised, returns
238false. If it already was initialised it simply returns it (and ignores the 405false. If it already was initialised it simply returns it (and ignores the
239flags). 406flags. If that is troubling you, check \f(CW\*(C`ev_backend ()\*(C'\fR afterwards).
240.Sp 407.Sp
241If you don't know what event loop to use, use the one returned from this 408If you don't know what event loop to use, use the one returned from this
242function. 409function.
243.Sp 410.Sp
244The flags argument can be used to specify special behaviour or specific 411The flags argument can be used to specify special behaviour or specific
245backends to use, and is usually specified as 0 (or \s-1EVFLAG_AUTO\s0). 412backends to use, and is usually specified as \f(CW0\fR (or \f(CW\*(C`EVFLAG_AUTO\*(C'\fR).
246.Sp 413.Sp
247It supports the following flags: 414The following flags are supported:
248.RS 4 415.RS 4
249.ie n .IP """EVFLAG_AUTO""" 4 416.ie n .IP """EVFLAG_AUTO""" 4
250.el .IP "\f(CWEVFLAG_AUTO\fR" 4 417.el .IP "\f(CWEVFLAG_AUTO\fR" 4
251.IX Item "EVFLAG_AUTO" 418.IX Item "EVFLAG_AUTO"
252The default flags value. Use this if you have no clue (it's the right 419The default flags value. Use this if you have no clue (it's the right
… …
258or setgid) then libev will \fInot\fR look at the environment variable 425or setgid) then libev will \fInot\fR look at the environment variable
259\&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will 426\&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will
260override the flags completely if it is found in the environment. This is 427override the flags completely if it is found in the environment. This is
261useful to try out specific backends to test their performance, or to work 428useful to try out specific backends to test their performance, or to work
262around bugs. 429around bugs.
430.ie n .IP """EVFLAG_FORKCHECK""" 4
431.el .IP "\f(CWEVFLAG_FORKCHECK\fR" 4
432.IX Item "EVFLAG_FORKCHECK"
433Instead of calling \f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR manually after
434a fork, you can also make libev check for a fork in each iteration by
435enabling this flag.
436.Sp
437This works by calling \f(CW\*(C`getpid ()\*(C'\fR on every iteration of the loop,
438and thus this might slow down your event loop if you do a lot of loop
439iterations and little real work, but is usually not noticeable (on my
440Linux system for example, \f(CW\*(C`getpid\*(C'\fR is actually a simple 5\-insn sequence
441without a syscall and thus \fIvery\fR fast, but my Linux system also has
442\&\f(CW\*(C`pthread_atfork\*(C'\fR which is even faster).
443.Sp
444The big advantage of this flag is that you can forget about fork (and
445forget about forgetting to tell libev about forking) when you use this
446flag.
447.Sp
448This flag setting cannot be overriden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR
449environment variable.
263.ie n .IP """EVMETHOD_SELECT"" (portable select backend)" 4 450.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4
264.el .IP "\f(CWEVMETHOD_SELECT\fR (portable select backend)" 4 451.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4
265.IX Item "EVMETHOD_SELECT (portable select backend)" 452.IX Item "EVBACKEND_SELECT (value 1, portable select backend)"
266.PD 0 453This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as
454libev tries to roll its own fd_set with no limits on the number of fds,
455but if that fails, expect a fairly low limit on the number of fds when
456using this backend. It doesn't scale too well (O(highest_fd)), but its usually
457the fastest backend for a low number of fds.
267.ie n .IP """EVMETHOD_POLL"" (poll backend, available everywhere except on windows)" 4 458.ie n .IP """EVBACKEND_POLL"" (value 2, poll backend, available everywhere except on windows)" 4
268.el .IP "\f(CWEVMETHOD_POLL\fR (poll backend, available everywhere except on windows)" 4 459.el .IP "\f(CWEVBACKEND_POLL\fR (value 2, poll backend, available everywhere except on windows)" 4
269.IX Item "EVMETHOD_POLL (poll backend, available everywhere except on windows)" 460.IX Item "EVBACKEND_POLL (value 2, poll backend, available everywhere except on windows)"
461And this is your standard \fIpoll\fR\|(2) backend. It's more complicated than
462select, but handles sparse fds better and has no artificial limit on the
463number of fds you can use (except it will slow down considerably with a
464lot of inactive fds). It scales similarly to select, i.e. O(total_fds).
270.ie n .IP """EVMETHOD_EPOLL"" (linux only)" 4 465.ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4
271.el .IP "\f(CWEVMETHOD_EPOLL\fR (linux only)" 4 466.el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4
272.IX Item "EVMETHOD_EPOLL (linux only)" 467.IX Item "EVBACKEND_EPOLL (value 4, Linux)"
273.ie n .IP """EVMETHOD_KQUEUE"" (some bsds only)" 4 468For few fds, this backend is a bit little slower than poll and select,
274.el .IP "\f(CWEVMETHOD_KQUEUE\fR (some bsds only)" 4 469but it scales phenomenally better. While poll and select usually scale
275.IX Item "EVMETHOD_KQUEUE (some bsds only)" 470like O(total_fds) where n is the total number of fds (or the highest fd),
471epoll scales either O(1) or O(active_fds). The epoll design has a number
472of shortcomings, such as silently dropping events in some hard-to-detect
473cases and rewiring a syscall per fd change, no fork support and bad
474support for dup:
475.Sp
476While stopping, setting and starting an I/O watcher in the same iteration
477will result in some caching, there is still a syscall per such incident
478(because the fd could point to a different file description now), so its
479best to avoid that. Also, \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors might not work
480very well if you register events for both fds.
481.Sp
482Please note that epoll sometimes generates spurious notifications, so you
483need to use non-blocking I/O or other means to avoid blocking when no data
484(or space) is available.
485.ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4
486.el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4
487.IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)"
488Kqueue deserves special mention, as at the time of this writing, it
489was broken on \fIall\fR BSDs (usually it doesn't work with anything but
490sockets and pipes, except on Darwin, where of course it's completely
491useless. On NetBSD, it seems to work for all the \s-1FD\s0 types I tested, so it
492is used by default there). For this reason it's not being \*(L"autodetected\*(R"
493unless you explicitly specify it explicitly in the flags (i.e. using
494\&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR) or libev was compiled on a known-to-be-good (\-enough)
495system like NetBSD.
496.Sp
497It scales in the same way as the epoll backend, but the interface to the
498kernel is more efficient (which says nothing about its actual speed,
499of course). While stopping, setting and starting an I/O watcher does
500never cause an extra syscall as with epoll, it still adds up to two event
501changes per incident, support for \f(CW\*(C`fork ()\*(C'\fR is very bad and it drops fds
502silently in similarly hard-to-detetc cases.
276.ie n .IP """EVMETHOD_DEVPOLL"" (solaris 8 only)" 4 503.ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4
277.el .IP "\f(CWEVMETHOD_DEVPOLL\fR (solaris 8 only)" 4 504.el .IP "\f(CWEVBACKEND_DEVPOLL\fR (value 16, Solaris 8)" 4
278.IX Item "EVMETHOD_DEVPOLL (solaris 8 only)" 505.IX Item "EVBACKEND_DEVPOLL (value 16, Solaris 8)"
506This is not implemented yet (and might never be).
279.ie n .IP """EVMETHOD_PORT"" (solaris 10 only)" 4 507.ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4
280.el .IP "\f(CWEVMETHOD_PORT\fR (solaris 10 only)" 4 508.el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4
281.IX Item "EVMETHOD_PORT (solaris 10 only)" 509.IX Item "EVBACKEND_PORT (value 32, Solaris 10)"
282.PD 510This uses the Solaris 10 event port mechanism. As with everything on Solaris,
283If one or more of these are ored into the flags value, then only these 511it's really slow, but it still scales very well (O(active_fds)).
284backends will be tried (in the reverse order as given here). If one are 512.Sp
285specified, any backend will do. 513Please note that solaris event ports can deliver a lot of spurious
514notifications, so you need to use non-blocking I/O or other means to avoid
515blocking when no data (or space) is available.
516.ie n .IP """EVBACKEND_ALL""" 4
517.el .IP "\f(CWEVBACKEND_ALL\fR" 4
518.IX Item "EVBACKEND_ALL"
519Try all backends (even potentially broken ones that wouldn't be tried
520with \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). Since this is a mask, you can do stuff such as
521\&\f(CW\*(C`EVBACKEND_ALL & ~EVBACKEND_KQUEUE\*(C'\fR.
286.RE 522.RE
287.RS 4 523.RS 4
524.Sp
525If one or more of these are ored into the flags value, then only these
526backends will be tried (in the reverse order as given here). If none are
527specified, most compiled-in backend will be tried, usually in reverse
528order of their flag values :)
529.Sp
530The most typical usage is like this:
531.Sp
532.Vb 2
533\& if (!ev_default_loop (0))
534\& fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
535.Ve
536.Sp
537Restrict libev to the select and poll backends, and do not allow
538environment settings to be taken into account:
539.Sp
540.Vb 1
541\& ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
542.Ve
543.Sp
544Use whatever libev has to offer, but make sure that kqueue is used if
545available (warning, breaks stuff, best use only with your own private
546event loop and only if you know the \s-1OS\s0 supports your types of fds):
547.Sp
548.Vb 1
549\& ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
550.Ve
288.RE 551.RE
289.IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4 552.IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4
290.IX Item "struct ev_loop *ev_loop_new (unsigned int flags)" 553.IX Item "struct ev_loop *ev_loop_new (unsigned int flags)"
291Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is 554Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is
292always distinct from the default loop. Unlike the default loop, it cannot 555always distinct from the default loop. Unlike the default loop, it cannot
293handle signal and child watchers, and attempts to do so will be greeted by 556handle signal and child watchers, and attempts to do so will be greeted by
294undefined behaviour (or a failed assertion if assertions are enabled). 557undefined behaviour (or a failed assertion if assertions are enabled).
558.Sp
559Example: Try to create a event loop that uses epoll and nothing else.
560.Sp
561.Vb 3
562\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
563\& if (!epoller)
564\& fatal ("no epoll found here, maybe it hides under your chair");
565.Ve
295.IP "ev_default_destroy ()" 4 566.IP "ev_default_destroy ()" 4
296.IX Item "ev_default_destroy ()" 567.IX Item "ev_default_destroy ()"
297Destroys the default loop again (frees all memory and kernel state 568Destroys the default loop again (frees all memory and kernel state
298etc.). This stops all registered event watchers (by not touching them in 569etc.). None of the active event watchers will be stopped in the normal
299any way whatsoever, although you cannot rely on this :). 570sense, so e.g. \f(CW\*(C`ev_is_active\*(C'\fR might still return true. It is your
571responsibility to either stop all watchers cleanly yoursef \fIbefore\fR
572calling this function, or cope with the fact afterwards (which is usually
573the easiest thing, you can just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them
574for example).
575.Sp
576Note that certain global state, such as signal state, will not be freed by
577this function, and related watchers (such as signal and child watchers)
578would need to be stopped manually.
579.Sp
580In general it is not advisable to call this function except in the
581rare occasion where you really need to free e.g. the signal handling
582pipe fds. If you need dynamically allocated loops it is better to use
583\&\f(CW\*(C`ev_loop_new\*(C'\fR and \f(CW\*(C`ev_loop_destroy\*(C'\fR).
300.IP "ev_loop_destroy (loop)" 4 584.IP "ev_loop_destroy (loop)" 4
301.IX Item "ev_loop_destroy (loop)" 585.IX Item "ev_loop_destroy (loop)"
302Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an 586Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an
303earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR. 587earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR.
304.IP "ev_default_fork ()" 4 588.IP "ev_default_fork ()" 4
… …
306This function reinitialises the kernel state for backends that have 590This function reinitialises the kernel state for backends that have
307one. Despite the name, you can call it anytime, but it makes most sense 591one. Despite the name, you can call it anytime, but it makes most sense
308after forking, in either the parent or child process (or both, but that 592after forking, in either the parent or child process (or both, but that
309again makes little sense). 593again makes little sense).
310.Sp 594.Sp
311You \fImust\fR call this function after forking if and only if you want to 595You \fImust\fR call this function in the child process after forking if and
312use the event library in both processes. If you just fork+exec, you don't 596only if you want to use the event library in both processes. If you just
313have to call it. 597fork+exec, you don't have to call it.
314.Sp 598.Sp
315The function itself is quite fast and it's usually not a problem to call 599The function itself is quite fast and it's usually not a problem to call
316it just in case after a fork. To make this easy, the function will fit in 600it just in case after a fork. To make this easy, the function will fit in
317quite nicely into a call to \f(CW\*(C`pthread_atfork\*(C'\fR: 601quite nicely into a call to \f(CW\*(C`pthread_atfork\*(C'\fR:
318.Sp 602.Sp
319.Vb 1 603.Vb 1
320\& pthread_atfork (0, 0, ev_default_fork); 604\& pthread_atfork (0, 0, ev_default_fork);
321.Ve 605.Ve
606.Sp
607At the moment, \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and \f(CW\*(C`EVBACKEND_POLL\*(C'\fR are safe to use
608without calling this function, so if you force one of those backends you
609do not need to care.
322.IP "ev_loop_fork (loop)" 4 610.IP "ev_loop_fork (loop)" 4
323.IX Item "ev_loop_fork (loop)" 611.IX Item "ev_loop_fork (loop)"
324Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by 612Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by
325\&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop 613\&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop
326after fork, and how you do this is entirely your own problem. 614after fork, and how you do this is entirely your own problem.
615.IP "unsigned int ev_loop_count (loop)" 4
616.IX Item "unsigned int ev_loop_count (loop)"
617Returns the count of loop iterations for the loop, which is identical to
618the number of times libev did poll for new events. It starts at \f(CW0\fR and
619happily wraps around with enough iterations.
620.Sp
621This value can sometimes be useful as a generation counter of sorts (it
622\&\*(L"ticks\*(R" the number of loop iterations), as it roughly corresponds with
623\&\f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR calls.
327.IP "unsigned int ev_method (loop)" 4 624.IP "unsigned int ev_backend (loop)" 4
328.IX Item "unsigned int ev_method (loop)" 625.IX Item "unsigned int ev_backend (loop)"
329Returns one of the \f(CW\*(C`EVMETHOD_*\*(C'\fR flags indicating the event backend in 626Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in
330use. 627use.
331.IP "ev_tstamp ev_now (loop)" 4 628.IP "ev_tstamp ev_now (loop)" 4
332.IX Item "ev_tstamp ev_now (loop)" 629.IX Item "ev_tstamp ev_now (loop)"
333Returns the current \*(L"event loop time\*(R", which is the time the event loop 630Returns the current \*(L"event loop time\*(R", which is the time the event loop
334got events and started processing them. This timestamp does not change 631received events and started processing them. This timestamp does not
335as long as callbacks are being processed, and this is also the base time 632change as long as callbacks are being processed, and this is also the base
336used for relative timers. You can treat it as the timestamp of the event 633time used for relative timers. You can treat it as the timestamp of the
337occuring (or more correctly, the mainloop finding out about it). 634event occurring (or more correctly, libev finding out about it).
338.IP "ev_loop (loop, int flags)" 4 635.IP "ev_loop (loop, int flags)" 4
339.IX Item "ev_loop (loop, int flags)" 636.IX Item "ev_loop (loop, int flags)"
340Finally, this is it, the event handler. This function usually is called 637Finally, this is it, the event handler. This function usually is called
341after you initialised all your watchers and you want to start handling 638after you initialised all your watchers and you want to start handling
342events. 639events.
343.Sp 640.Sp
344If the flags argument is specified as 0, it will not return until either 641If the flags argument is specified as \f(CW0\fR, it will not return until
345no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called. 642either no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called.
643.Sp
644Please note that an explicit \f(CW\*(C`ev_unloop\*(C'\fR is usually better than
645relying on all watchers to be stopped when deciding when a program has
646finished (especially in interactive programs), but having a program that
647automatically loops as long as it has to and no longer by virtue of
648relying on its watchers stopping correctly is a thing of beauty.
346.Sp 649.Sp
347A flags value of \f(CW\*(C`EVLOOP_NONBLOCK\*(C'\fR will look for new events, will handle 650A flags value of \f(CW\*(C`EVLOOP_NONBLOCK\*(C'\fR will look for new events, will handle
348those events and any outstanding ones, but will not block your process in 651those events and any outstanding ones, but will not block your process in
349case there are no events and will return after one iteration of the loop. 652case there are no events and will return after one iteration of the loop.
350.Sp 653.Sp
351A flags value of \f(CW\*(C`EVLOOP_ONESHOT\*(C'\fR will look for new events (waiting if 654A flags value of \f(CW\*(C`EVLOOP_ONESHOT\*(C'\fR will look for new events (waiting if
352neccessary) and will handle those and any outstanding ones. It will block 655neccessary) and will handle those and any outstanding ones. It will block
353your process until at least one new event arrives, and will return after 656your process until at least one new event arrives, and will return after
354one iteration of the loop. 657one iteration of the loop. This is useful if you are waiting for some
658external event in conjunction with something not expressible using other
659libev watchers. However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is
660usually a better approach for this kind of thing.
355.Sp 661.Sp
356This flags value could be used to implement alternative looping 662Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does:
357constructs, but the \f(CW\*(C`prepare\*(C'\fR and \f(CW\*(C`check\*(C'\fR watchers provide a better and 663.Sp
358more generic mechanism. 664.Vb 19
665\& - Before the first iteration, call any pending watchers.
666\& * If there are no active watchers (reference count is zero), return.
667\& - Queue all prepare watchers and then call all outstanding watchers.
668\& - If we have been forked, recreate the kernel state.
669\& - Update the kernel state with all outstanding changes.
670\& - Update the "event loop time".
671\& - Calculate for how long to block.
672\& - Block the process, waiting for any events.
673\& - Queue all outstanding I/O (fd) events.
674\& - Update the "event loop time" and do time jump handling.
675\& - Queue all outstanding timers.
676\& - Queue all outstanding periodics.
677\& - If no events are pending now, queue all idle watchers.
678\& - Queue all check watchers.
679\& - Call all queued watchers in reverse order (i.e. check watchers first).
680\& Signals and child watchers are implemented as I/O watchers, and will
681\& be handled here by queueing them when their watcher gets executed.
682\& - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
683\& were used, return, otherwise continue with step *.
684.Ve
685.Sp
686Example: Queue some jobs and then loop until no events are outsanding
687anymore.
688.Sp
689.Vb 4
690\& ... queue jobs here, make sure they register event watchers as long
691\& ... as they still have work to do (even an idle watcher will do..)
692\& ev_loop (my_loop, 0);
693\& ... jobs done. yeah!
694.Ve
359.IP "ev_unloop (loop, how)" 4 695.IP "ev_unloop (loop, how)" 4
360.IX Item "ev_unloop (loop, how)" 696.IX Item "ev_unloop (loop, how)"
361Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it 697Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it
362has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either 698has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either
363\&\f(CW\*(C`EVUNLOOP_ONE\*(C'\fR, which will make the innermost \f(CW\*(C`ev_loop\*(C'\fR call return, or 699\&\f(CW\*(C`EVUNLOOP_ONE\*(C'\fR, which will make the innermost \f(CW\*(C`ev_loop\*(C'\fR call return, or
… …
376example, libev itself uses this for its internal signal pipe: It is not 712example, libev itself uses this for its internal signal pipe: It is not
377visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if 713visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if
378no event watchers registered by it are active. It is also an excellent 714no event watchers registered by it are active. It is also an excellent
379way to do this for generic recurring timers or from within third-party 715way to do this for generic recurring timers or from within third-party
380libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR. 716libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR.
717.Sp
718Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR
719running when nothing else is active.
720.Sp
721.Vb 4
722\& struct ev_signal exitsig;
723\& ev_signal_init (&exitsig, sig_cb, SIGINT);
724\& ev_signal_start (loop, &exitsig);
725\& evf_unref (loop);
726.Ve
727.Sp
728Example: For some weird reason, unregister the above signal handler again.
729.Sp
730.Vb 2
731\& ev_ref (loop);
732\& ev_signal_stop (loop, &exitsig);
733.Ve
734.IP "ev_set_io_collect_interval (ev_tstamp interval)" 4
735.IX Item "ev_set_io_collect_interval (ev_tstamp interval)"
736.PD 0
737.IP "ev_set_timeout_collect_interval (ev_tstamp interval)" 4
738.IX Item "ev_set_timeout_collect_interval (ev_tstamp interval)"
739.PD
740These advanced functions influence the time that libev will spend waiting
741for events. Both are by default \f(CW0\fR, meaning that libev will try to
742invoke timer/periodic callbacks and I/O callbacks with minimum latency.
743.Sp
744Setting these to a higher value (the \f(CW\*(C`interval\*(C'\fR \fImust\fR be >= \f(CW0\fR)
745allows libev to delay invocation of I/O and timer/periodic callbacks to
746increase efficiency of loop iterations.
747.Sp
748The background is that sometimes your program runs just fast enough to
749handle one (or very few) event(s) per loop iteration. While this makes
750the program responsive, it also wastes a lot of \s-1CPU\s0 time to poll for new
751events, especially with backends like \f(CW\*(C`select ()\*(C'\fR which have a high
752overhead for the actual polling but can deliver many events at once.
753.Sp
754By setting a higher \fIio collect interval\fR you allow libev to spend more
755time collecting I/O events, so you can handle more events per iteration,
756at the cost of increasing latency. Timeouts (both \f(CW\*(C`ev_periodic\*(C'\fR and
757\&\f(CW\*(C`ev_timer\*(C'\fR) will be not affected.
758.Sp
759Likewise, by setting a higher \fItimeout collect interval\fR you allow libev
760to spend more time collecting timeouts, at the expense of increased
761latency (the watcher callback will be called later). \f(CW\*(C`ev_io\*(C'\fR watchers
762will not be affected.
763.Sp
764Many programs can usually benefit by setting the io collect interval to
765a value near \f(CW0.1\fR or so, which is often enough for interactive servers
766(of course not for games), likewise for timeouts. It usually doesn't make
767much sense to set it to a lower value than \f(CW0.01\fR, as this approsaches
768the timing granularity of most systems.
381.SH "ANATOMY OF A WATCHER" 769.SH "ANATOMY OF A WATCHER"
382.IX Header "ANATOMY OF A WATCHER" 770.IX Header "ANATOMY OF A WATCHER"
383A watcher is a structure that you create and register to record your 771A watcher is a structure that you create and register to record your
384interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to 772interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to
385become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that: 773become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that:
… …
421*)\*(C'\fR), and you can stop watching for events at any time by calling the 809*)\*(C'\fR), and you can stop watching for events at any time by calling the
422corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR. 810corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR.
423.PP 811.PP
424As long as your watcher is active (has been started but not stopped) you 812As long as your watcher is active (has been started but not stopped) you
425must not touch the values stored in it. Most specifically you must never 813must not touch the values stored in it. Most specifically you must never
426reinitialise it or call its set method. 814reinitialise it or call its \f(CW\*(C`set\*(C'\fR macro.
427.PP
428You can check whether an event is active by calling the \f(CW\*(C`ev_is_active
429(watcher *)\*(C'\fR macro. To see whether an event is outstanding (but the
430callback for it has not been called yet) you can use the \f(CW\*(C`ev_is_pending
431(watcher *)\*(C'\fR macro.
432.PP 815.PP
433Each and every callback receives the event loop pointer as first, the 816Each and every callback receives the event loop pointer as first, the
434registered watcher structure as second, and a bitset of received events as 817registered watcher structure as second, and a bitset of received events as
435third argument. 818third argument.
436.PP 819.PP
… …
461The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread. 844The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread.
462.ie n .IP """EV_CHILD""" 4 845.ie n .IP """EV_CHILD""" 4
463.el .IP "\f(CWEV_CHILD\fR" 4 846.el .IP "\f(CWEV_CHILD\fR" 4
464.IX Item "EV_CHILD" 847.IX Item "EV_CHILD"
465The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change. 848The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change.
849.ie n .IP """EV_STAT""" 4
850.el .IP "\f(CWEV_STAT\fR" 4
851.IX Item "EV_STAT"
852The path specified in the \f(CW\*(C`ev_stat\*(C'\fR watcher changed its attributes somehow.
466.ie n .IP """EV_IDLE""" 4 853.ie n .IP """EV_IDLE""" 4
467.el .IP "\f(CWEV_IDLE\fR" 4 854.el .IP "\f(CWEV_IDLE\fR" 4
468.IX Item "EV_IDLE" 855.IX Item "EV_IDLE"
469The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do. 856The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do.
470.ie n .IP """EV_PREPARE""" 4 857.ie n .IP """EV_PREPARE""" 4
… …
480\&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any 867\&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any
481received events. Callbacks of both watcher types can start and stop as 868received events. Callbacks of both watcher types can start and stop as
482many watchers as they want, and all of them will be taken into account 869many watchers as they want, and all of them will be taken into account
483(for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep 870(for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep
484\&\f(CW\*(C`ev_loop\*(C'\fR from blocking). 871\&\f(CW\*(C`ev_loop\*(C'\fR from blocking).
872.ie n .IP """EV_EMBED""" 4
873.el .IP "\f(CWEV_EMBED\fR" 4
874.IX Item "EV_EMBED"
875The embedded event loop specified in the \f(CW\*(C`ev_embed\*(C'\fR watcher needs attention.
876.ie n .IP """EV_FORK""" 4
877.el .IP "\f(CWEV_FORK\fR" 4
878.IX Item "EV_FORK"
879The event loop has been resumed in the child process after fork (see
880\&\f(CW\*(C`ev_fork\*(C'\fR).
485.ie n .IP """EV_ERROR""" 4 881.ie n .IP """EV_ERROR""" 4
486.el .IP "\f(CWEV_ERROR\fR" 4 882.el .IP "\f(CWEV_ERROR\fR" 4
487.IX Item "EV_ERROR" 883.IX Item "EV_ERROR"
488An unspecified error has occured, the watcher has been stopped. This might 884An unspecified error has occured, the watcher has been stopped. This might
489happen because the watcher could not be properly started because libev 885happen because the watcher could not be properly started because libev
… …
494Libev will usually signal a few \*(L"dummy\*(R" events together with an error, 890Libev will usually signal a few \*(L"dummy\*(R" events together with an error,
495for example it might indicate that a fd is readable or writable, and if 891for example it might indicate that a fd is readable or writable, and if
496your callbacks is well-written it can just attempt the operation and cope 892your callbacks is well-written it can just attempt the operation and cope
497with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded 893with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded
498programs, though, so beware. 894programs, though, so beware.
895.Sh "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0"
896.IX Subsection "GENERIC WATCHER FUNCTIONS"
897In the following description, \f(CW\*(C`TYPE\*(C'\fR stands for the watcher type,
898e.g. \f(CW\*(C`timer\*(C'\fR for \f(CW\*(C`ev_timer\*(C'\fR watchers and \f(CW\*(C`io\*(C'\fR for \f(CW\*(C`ev_io\*(C'\fR watchers.
899.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4
900.el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4
901.IX Item "ev_init (ev_TYPE *watcher, callback)"
902This macro initialises the generic portion of a watcher. The contents
903of the watcher object can be arbitrary (so \f(CW\*(C`malloc\*(C'\fR will do). Only
904the generic parts of the watcher are initialised, you \fIneed\fR to call
905the type-specific \f(CW\*(C`ev_TYPE_set\*(C'\fR macro afterwards to initialise the
906type-specific parts. For each type there is also a \f(CW\*(C`ev_TYPE_init\*(C'\fR macro
907which rolls both calls into one.
908.Sp
909You can reinitialise a watcher at any time as long as it has been stopped
910(or never started) and there are no pending events outstanding.
911.Sp
912The callback is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher,
913int revents)\*(C'\fR.
914.ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4
915.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4
916.IX Item "ev_TYPE_set (ev_TYPE *, [args])"
917This macro initialises the type-specific parts of a watcher. You need to
918call \f(CW\*(C`ev_init\*(C'\fR at least once before you call this macro, but you can
919call \f(CW\*(C`ev_TYPE_set\*(C'\fR any number of times. You must not, however, call this
920macro on a watcher that is active (it can be pending, however, which is a
921difference to the \f(CW\*(C`ev_init\*(C'\fR macro).
922.Sp
923Although some watcher types do not have type-specific arguments
924(e.g. \f(CW\*(C`ev_prepare\*(C'\fR) you still need to call its \f(CW\*(C`set\*(C'\fR macro.
925.ie n .IP """ev_TYPE_init"" (ev_TYPE *watcher, callback, [args])" 4
926.el .IP "\f(CWev_TYPE_init\fR (ev_TYPE *watcher, callback, [args])" 4
927.IX Item "ev_TYPE_init (ev_TYPE *watcher, callback, [args])"
928This convinience macro rolls both \f(CW\*(C`ev_init\*(C'\fR and \f(CW\*(C`ev_TYPE_set\*(C'\fR macro
929calls into a single call. This is the most convinient method to initialise
930a watcher. The same limitations apply, of course.
931.ie n .IP """ev_TYPE_start"" (loop *, ev_TYPE *watcher)" 4
932.el .IP "\f(CWev_TYPE_start\fR (loop *, ev_TYPE *watcher)" 4
933.IX Item "ev_TYPE_start (loop *, ev_TYPE *watcher)"
934Starts (activates) the given watcher. Only active watchers will receive
935events. If the watcher is already active nothing will happen.
936.ie n .IP """ev_TYPE_stop"" (loop *, ev_TYPE *watcher)" 4
937.el .IP "\f(CWev_TYPE_stop\fR (loop *, ev_TYPE *watcher)" 4
938.IX Item "ev_TYPE_stop (loop *, ev_TYPE *watcher)"
939Stops the given watcher again (if active) and clears the pending
940status. It is possible that stopped watchers are pending (for example,
941non-repeating timers are being stopped when they become pending), but
942\&\f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor pending. If
943you want to free or reuse the memory used by the watcher it is therefore a
944good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function.
945.IP "bool ev_is_active (ev_TYPE *watcher)" 4
946.IX Item "bool ev_is_active (ev_TYPE *watcher)"
947Returns a true value iff the watcher is active (i.e. it has been started
948and not yet been stopped). As long as a watcher is active you must not modify
949it.
950.IP "bool ev_is_pending (ev_TYPE *watcher)" 4
951.IX Item "bool ev_is_pending (ev_TYPE *watcher)"
952Returns a true value iff the watcher is pending, (i.e. it has outstanding
953events but its callback has not yet been invoked). As long as a watcher
954is pending (but not active) you must not call an init function on it (but
955\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe), you must not change its priority, and you must
956make sure the watcher is available to libev (e.g. you cannot \f(CW\*(C`free ()\*(C'\fR
957it).
958.IP "callback ev_cb (ev_TYPE *watcher)" 4
959.IX Item "callback ev_cb (ev_TYPE *watcher)"
960Returns the callback currently set on the watcher.
961.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4
962.IX Item "ev_cb_set (ev_TYPE *watcher, callback)"
963Change the callback. You can change the callback at virtually any time
964(modulo threads).
965.IP "ev_set_priority (ev_TYPE *watcher, priority)" 4
966.IX Item "ev_set_priority (ev_TYPE *watcher, priority)"
967.PD 0
968.IP "int ev_priority (ev_TYPE *watcher)" 4
969.IX Item "int ev_priority (ev_TYPE *watcher)"
970.PD
971Set and query the priority of the watcher. The priority is a small
972integer between \f(CW\*(C`EV_MAXPRI\*(C'\fR (default: \f(CW2\fR) and \f(CW\*(C`EV_MINPRI\*(C'\fR
973(default: \f(CW\*(C`\-2\*(C'\fR). Pending watchers with higher priority will be invoked
974before watchers with lower priority, but priority will not keep watchers
975from being executed (except for \f(CW\*(C`ev_idle\*(C'\fR watchers).
976.Sp
977This means that priorities are \fIonly\fR used for ordering callback
978invocation after new events have been received. This is useful, for
979example, to reduce latency after idling, or more often, to bind two
980watchers on the same event and make sure one is called first.
981.Sp
982If you need to suppress invocation when higher priority events are pending
983you need to look at \f(CW\*(C`ev_idle\*(C'\fR watchers, which provide this functionality.
984.Sp
985You \fImust not\fR change the priority of a watcher as long as it is active or
986pending.
987.Sp
988The default priority used by watchers when no priority has been set is
989always \f(CW0\fR, which is supposed to not be too high and not be too low :).
990.Sp
991Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR is
992fine, as long as you do not mind that the priority value you query might
993or might not have been adjusted to be within valid range.
994.IP "ev_invoke (loop, ev_TYPE *watcher, int revents)" 4
995.IX Item "ev_invoke (loop, ev_TYPE *watcher, int revents)"
996Invoke the \f(CW\*(C`watcher\*(C'\fR with the given \f(CW\*(C`loop\*(C'\fR and \f(CW\*(C`revents\*(C'\fR. Neither
997\&\f(CW\*(C`loop\*(C'\fR nor \f(CW\*(C`revents\*(C'\fR need to be valid as long as the watcher callback
998can deal with that fact.
999.IP "int ev_clear_pending (loop, ev_TYPE *watcher)" 4
1000.IX Item "int ev_clear_pending (loop, ev_TYPE *watcher)"
1001If the watcher is pending, this function returns clears its pending status
1002and returns its \f(CW\*(C`revents\*(C'\fR bitset (as if its callback was invoked). If the
1003watcher isn't pending it does nothing and returns \f(CW0\fR.
499.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0" 1004.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0"
500.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER" 1005.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER"
501Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change 1006Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change
502and read at any time, libev will completely ignore it. This can be used 1007and read at any time, libev will completely ignore it. This can be used
503to associate arbitrary data with your watcher. If you need more data and 1008to associate arbitrary data with your watcher. If you need more data and
… …
524\& struct my_io *w = (struct my_io *)w_; 1029\& struct my_io *w = (struct my_io *)w_;
525\& ... 1030\& ...
526\& } 1031\& }
527.Ve 1032.Ve
528.PP 1033.PP
529More interesting and less C\-conformant ways of catsing your callback type 1034More interesting and less C\-conformant ways of casting your callback type
530have been omitted.... 1035instead have been omitted.
1036.PP
1037Another common scenario is having some data structure with multiple
1038watchers:
1039.PP
1040.Vb 6
1041\& struct my_biggy
1042\& {
1043\& int some_data;
1044\& ev_timer t1;
1045\& ev_timer t2;
1046\& }
1047.Ve
1048.PP
1049In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more complicated,
1050you need to use \f(CW\*(C`offsetof\*(C'\fR:
1051.PP
1052.Vb 1
1053\& #include <stddef.h>
1054.Ve
1055.PP
1056.Vb 6
1057\& static void
1058\& t1_cb (EV_P_ struct ev_timer *w, int revents)
1059\& {
1060\& struct my_biggy big = (struct my_biggy *
1061\& (((char *)w) - offsetof (struct my_biggy, t1));
1062\& }
1063.Ve
1064.PP
1065.Vb 6
1066\& static void
1067\& t2_cb (EV_P_ struct ev_timer *w, int revents)
1068\& {
1069\& struct my_biggy big = (struct my_biggy *
1070\& (((char *)w) - offsetof (struct my_biggy, t2));
1071\& }
1072.Ve
531.SH "WATCHER TYPES" 1073.SH "WATCHER TYPES"
532.IX Header "WATCHER TYPES" 1074.IX Header "WATCHER TYPES"
533This section describes each watcher in detail, but will not repeat 1075This section describes each watcher in detail, but will not repeat
534information given in the last section. 1076information given in the last section. Any initialisation/set macros,
1077functions and members specific to the watcher type are explained.
1078.PP
1079Members are additionally marked with either \fI[read\-only]\fR, meaning that,
1080while the watcher is active, you can look at the member and expect some
1081sensible content, but you must not modify it (you can modify it while the
1082watcher is stopped to your hearts content), or \fI[read\-write]\fR, which
1083means you can expect it to have some sensible content while the watcher
1084is active, but you can also modify it. Modifying it may not do something
1085sensible or take immediate effect (or do anything at all), but libev will
1086not crash or malfunction in any way.
535.ie n .Sh """ev_io"" \- is this file descriptor readable or writable" 1087.ie n .Sh """ev_io"" \- is this file descriptor readable or writable?"
536.el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable" 1088.el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable?"
537.IX Subsection "ev_io - is this file descriptor readable or writable" 1089.IX Subsection "ev_io - is this file descriptor readable or writable?"
538I/O watchers check whether a file descriptor is readable or writable 1090I/O watchers check whether a file descriptor is readable or writable
539in each iteration of the event loop (This behaviour is called 1091in each iteration of the event loop, or, more precisely, when reading
540level-triggering because you keep receiving events as long as the 1092would not block the process and writing would at least be able to write
541condition persists. Remember you can stop the watcher if you don't want to 1093some data. This behaviour is called level-triggering because you keep
542act on the event and neither want to receive future events). 1094receiving events as long as the condition persists. Remember you can stop
1095the watcher if you don't want to act on the event and neither want to
1096receive future events.
543.PP 1097.PP
544In general you can register as many read and/or write event watchers per 1098In general you can register as many read and/or write event watchers per
545fd as you want (as long as you don't confuse yourself). Setting all file 1099fd as you want (as long as you don't confuse yourself). Setting all file
546descriptors to non-blocking mode is also usually a good idea (but not 1100descriptors to non-blocking mode is also usually a good idea (but not
547required if you know what you are doing). 1101required if you know what you are doing).
548.PP 1102.PP
549You have to be careful with dup'ed file descriptors, though. Some backends 1103You have to be careful with dup'ed file descriptors, though. Some backends
550(the linux epoll backend is a notable example) cannot handle dup'ed file 1104(the linux epoll backend is a notable example) cannot handle dup'ed file
551descriptors correctly if you register interest in two or more fds pointing 1105descriptors correctly if you register interest in two or more fds pointing
552to the same underlying file/socket etc. description (that is, they share 1106to the same underlying file/socket/etc. description (that is, they share
553the same underlying \*(L"file open\*(R"). 1107the same underlying \*(L"file open\*(R").
554.PP 1108.PP
555If you must do this, then force the use of a known-to-be-good backend 1109If you must do this, then force the use of a known-to-be-good backend
556(at the time of this writing, this includes only \s-1EVMETHOD_SELECT\s0 and 1110(at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and
557\&\s-1EVMETHOD_POLL\s0). 1111\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR).
1112.PP
1113Another thing you have to watch out for is that it is quite easy to
1114receive \*(L"spurious\*(R" readyness notifications, that is your callback might
1115be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block
1116because there is no data. Not only are some backends known to create a
1117lot of those (for example solaris ports), it is very easy to get into
1118this situation even with a relatively standard program structure. Thus
1119it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning
1120\&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives.
1121.PP
1122If you cannot run the fd in non-blocking mode (for example you should not
1123play around with an Xlib connection), then you have to seperately re-test
1124whether a file descriptor is really ready with a known-to-be good interface
1125such as poll (fortunately in our Xlib example, Xlib already does this on
1126its own, so its quite safe to use).
1127.PP
1128\fIThe special problem of disappearing file descriptors\fR
1129.IX Subsection "The special problem of disappearing file descriptors"
1130.PP
1131Some backends (e.g. kqueue, epoll) need to be told about closing a file
1132descriptor (either by calling \f(CW\*(C`close\*(C'\fR explicitly or by any other means,
1133such as \f(CW\*(C`dup\*(C'\fR). The reason is that you register interest in some file
1134descriptor, but when it goes away, the operating system will silently drop
1135this interest. If another file descriptor with the same number then is
1136registered with libev, there is no efficient way to see that this is, in
1137fact, a different file descriptor.
1138.PP
1139To avoid having to explicitly tell libev about such cases, libev follows
1140the following policy: Each time \f(CW\*(C`ev_io_set\*(C'\fR is being called, libev
1141will assume that this is potentially a new file descriptor, otherwise
1142it is assumed that the file descriptor stays the same. That means that
1143you \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
1144descriptor even if the file descriptor number itself did not change.
1145.PP
1146This is how one would do it normally anyway, the important point is that
1147the libev application should not optimise around libev but should leave
1148optimisations to libev.
1149.PP
1150\fIThe special problem of dup'ed file descriptors\fR
1151.IX Subsection "The special problem of dup'ed file descriptors"
1152.PP
1153Some backends (e.g. epoll), cannot register events for file descriptors,
1154but only events for the underlying file descriptions. That menas when you
1155have \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors and register events for them, only one
1156file descriptor might actually receive events.
1157.PP
1158There is no workaorund possible except not registering events
1159for potentially \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors or to resort to
1160\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
1161.PP
1162\fIThe special problem of fork\fR
1163.IX Subsection "The special problem of fork"
1164.PP
1165Some backends (epoll, kqueue) do not support \f(CW\*(C`fork ()\*(C'\fR at all or exhibit
1166useless behaviour. Libev fully supports fork, but needs to be told about
1167it in the child.
1168.PP
1169To support fork in your programs, you either have to call
1170\&\f(CW\*(C`ev_default_fork ()\*(C'\fR or \f(CW\*(C`ev_loop_fork ()\*(C'\fR after a fork in the child,
1171enable \f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR, or resort to \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or
1172\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
1173.PP
1174\fIWatcher-Specific Functions\fR
1175.IX Subsection "Watcher-Specific Functions"
558.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4 1176.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4
559.IX Item "ev_io_init (ev_io *, callback, int fd, int events)" 1177.IX Item "ev_io_init (ev_io *, callback, int fd, int events)"
560.PD 0 1178.PD 0
561.IP "ev_io_set (ev_io *, int fd, int events)" 4 1179.IP "ev_io_set (ev_io *, int fd, int events)" 4
562.IX Item "ev_io_set (ev_io *, int fd, int events)" 1180.IX Item "ev_io_set (ev_io *, int fd, int events)"
563.PD 1181.PD
564Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The fd is the file descriptor to rceeive 1182Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to
565events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or \f(CW\*(C`EV_READ | 1183rceeive events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or
566EV_WRITE\*(C'\fR to receive the given events. 1184\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR to receive the given events.
1185.IP "int fd [read\-only]" 4
1186.IX Item "int fd [read-only]"
1187The file descriptor being watched.
1188.IP "int events [read\-only]" 4
1189.IX Item "int events [read-only]"
1190The events being watched.
1191.PP
1192Example: Call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well
1193readable, but only once. Since it is likely line\-buffered, you could
1194attempt to read a whole line in the callback.
1195.PP
1196.Vb 6
1197\& static void
1198\& stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1199\& {
1200\& ev_io_stop (loop, w);
1201\& .. read from stdin here (or from w->fd) and haqndle any I/O errors
1202\& }
1203.Ve
1204.PP
1205.Vb 6
1206\& ...
1207\& struct ev_loop *loop = ev_default_init (0);
1208\& struct ev_io stdin_readable;
1209\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1210\& ev_io_start (loop, &stdin_readable);
1211\& ev_loop (loop, 0);
1212.Ve
567.ie n .Sh """ev_timer"" \- relative and optionally recurring timeouts" 1213.ie n .Sh """ev_timer"" \- relative and optionally repeating timeouts"
568.el .Sh "\f(CWev_timer\fP \- relative and optionally recurring timeouts" 1214.el .Sh "\f(CWev_timer\fP \- relative and optionally repeating timeouts"
569.IX Subsection "ev_timer - relative and optionally recurring timeouts" 1215.IX Subsection "ev_timer - relative and optionally repeating timeouts"
570Timer watchers are simple relative timers that generate an event after a 1216Timer watchers are simple relative timers that generate an event after a
571given time, and optionally repeating in regular intervals after that. 1217given time, and optionally repeating in regular intervals after that.
572.PP 1218.PP
573The timers are based on real time, that is, if you register an event that 1219The timers are based on real time, that is, if you register an event that
574times out after an hour and you reset your system clock to last years 1220times out after an hour and you reset your system clock to last years
575time, it will still time out after (roughly) and hour. \*(L"Roughly\*(R" because 1221time, it will still time out after (roughly) and hour. \*(L"Roughly\*(R" because
576detecting time jumps is hard, and soem inaccuracies are unavoidable (the 1222detecting time jumps is hard, and some inaccuracies are unavoidable (the
577monotonic clock option helps a lot here). 1223monotonic clock option helps a lot here).
578.PP 1224.PP
579The relative timeouts are calculated relative to the \f(CW\*(C`ev_now ()\*(C'\fR 1225The relative timeouts are calculated relative to the \f(CW\*(C`ev_now ()\*(C'\fR
580time. This is usually the right thing as this timestamp refers to the time 1226time. This is usually the right thing as this timestamp refers to the time
581of the event triggering whatever timeout you are modifying/starting. If 1227of the event triggering whatever timeout you are modifying/starting. If
582you suspect event processing to be delayed and you *need* to base the timeout 1228you suspect event processing to be delayed and you \fIneed\fR to base the timeout
583on the current time, use something like this to adjust for this: 1229on the current time, use something like this to adjust for this:
584.PP 1230.PP
585.Vb 1 1231.Vb 1
586\& ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); 1232\& ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
587.Ve 1233.Ve
1234.PP
1235The callback is guarenteed to be invoked only when its timeout has passed,
1236but if multiple timers become ready during the same loop iteration then
1237order of execution is undefined.
1238.PP
1239\fIWatcher-Specific Functions and Data Members\fR
1240.IX Subsection "Watcher-Specific Functions and Data Members"
588.IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4 1241.IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4
589.IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 1242.IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)"
590.PD 0 1243.PD 0
591.IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4 1244.IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4
592.IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 1245.IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)"
… …
604.IP "ev_timer_again (loop)" 4 1257.IP "ev_timer_again (loop)" 4
605.IX Item "ev_timer_again (loop)" 1258.IX Item "ev_timer_again (loop)"
606This will act as if the timer timed out and restart it again if it is 1259This will act as if the timer timed out and restart it again if it is
607repeating. The exact semantics are: 1260repeating. The exact semantics are:
608.Sp 1261.Sp
1262If the timer is pending, its pending status is cleared.
1263.Sp
609If the timer is started but nonrepeating, stop it. 1264If the timer is started but nonrepeating, stop it (as if it timed out).
610.Sp 1265.Sp
611If the timer is repeating, either start it if necessary (with the repeat 1266If the timer is repeating, either start it if necessary (with the
612value), or reset the running timer to the repeat value. 1267\&\f(CW\*(C`repeat\*(C'\fR value), or reset the running timer to the \f(CW\*(C`repeat\*(C'\fR value.
613.Sp 1268.Sp
614This sounds a bit complicated, but here is a useful and typical 1269This sounds a bit complicated, but here is a useful and typical
615example: Imagine you have a tcp connection and you want a so-called idle 1270example: Imagine you have a tcp connection and you want a so-called idle
616timeout, that is, you want to be called when there have been, say, 60 1271timeout, that is, you want to be called when there have been, say, 60
617seconds of inactivity on the socket. The easiest way to do this is to 1272seconds of inactivity on the socket. The easiest way to do this is to
618configure an \f(CW\*(C`ev_timer\*(C'\fR with after=repeat=60 and calling ev_timer_again each 1273configure an \f(CW\*(C`ev_timer\*(C'\fR with a \f(CW\*(C`repeat\*(C'\fR value of \f(CW60\fR and then call
619time you successfully read or write some data. If you go into an idle 1274\&\f(CW\*(C`ev_timer_again\*(C'\fR each time you successfully read or write some data. If
620state where you do not expect data to travel on the socket, you can stop 1275you go into an idle state where you do not expect data to travel on the
621the timer, and again will automatically restart it if need be. 1276socket, you can \f(CW\*(C`ev_timer_stop\*(C'\fR the timer, and \f(CW\*(C`ev_timer_again\*(C'\fR will
1277automatically restart it if need be.
1278.Sp
1279That means you can ignore the \f(CW\*(C`after\*(C'\fR value and \f(CW\*(C`ev_timer_start\*(C'\fR
1280altogether and only ever use the \f(CW\*(C`repeat\*(C'\fR value and \f(CW\*(C`ev_timer_again\*(C'\fR:
1281.Sp
1282.Vb 8
1283\& ev_timer_init (timer, callback, 0., 5.);
1284\& ev_timer_again (loop, timer);
1285\& ...
1286\& timer->again = 17.;
1287\& ev_timer_again (loop, timer);
1288\& ...
1289\& timer->again = 10.;
1290\& ev_timer_again (loop, timer);
1291.Ve
1292.Sp
1293This is more slightly efficient then stopping/starting the timer each time
1294you want to modify its timeout value.
1295.IP "ev_tstamp repeat [read\-write]" 4
1296.IX Item "ev_tstamp repeat [read-write]"
1297The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out
1298or \f(CW\*(C`ev_timer_again\*(C'\fR is called and determines the next timeout (if any),
1299which is also when any modifications are taken into account.
1300.PP
1301Example: Create a timer that fires after 60 seconds.
1302.PP
1303.Vb 5
1304\& static void
1305\& one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1306\& {
1307\& .. one minute over, w is actually stopped right here
1308\& }
1309.Ve
1310.PP
1311.Vb 3
1312\& struct ev_timer mytimer;
1313\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1314\& ev_timer_start (loop, &mytimer);
1315.Ve
1316.PP
1317Example: Create a timeout timer that times out after 10 seconds of
1318inactivity.
1319.PP
1320.Vb 5
1321\& static void
1322\& timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1323\& {
1324\& .. ten seconds without any activity
1325\& }
1326.Ve
1327.PP
1328.Vb 4
1329\& struct ev_timer mytimer;
1330\& ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1331\& ev_timer_again (&mytimer); /* start timer */
1332\& ev_loop (loop, 0);
1333.Ve
1334.PP
1335.Vb 3
1336\& // and in some piece of code that gets executed on any "activity":
1337\& // reset the timeout to start ticking again at 10 seconds
1338\& ev_timer_again (&mytimer);
1339.Ve
622.ie n .Sh """ev_periodic"" \- to cron or not to cron" 1340.ie n .Sh """ev_periodic"" \- to cron or not to cron?"
623.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron" 1341.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron?"
624.IX Subsection "ev_periodic - to cron or not to cron" 1342.IX Subsection "ev_periodic - to cron or not to cron?"
625Periodic watchers are also timers of a kind, but they are very versatile 1343Periodic watchers are also timers of a kind, but they are very versatile
626(and unfortunately a bit complex). 1344(and unfortunately a bit complex).
627.PP 1345.PP
628Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time) 1346Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time)
629but on wallclock time (absolute time). You can tell a periodic watcher 1347but on wallclock time (absolute time). You can tell a periodic watcher
630to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a 1348to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a
631periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now () 1349periodic watcher to trigger in 10 seconds (by specifiying e.g. \f(CW\*(C`ev_now ()
632+ 10.>) and then reset your system clock to the last year, then it will 1350+ 10.\*(C'\fR) and then reset your system clock to the last year, then it will
633take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger 1351take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger
634roughly 10 seconds later and of course not if you reset your system time 1352roughly 10 seconds later).
635again).
636.PP 1353.PP
637They can also be used to implement vastly more complex timers, such as 1354They can also be used to implement vastly more complex timers, such as
638triggering an event on eahc midnight, local time. 1355triggering an event on each midnight, local time or other, complicated,
1356rules.
1357.PP
1358As with timers, the callback is guarenteed to be invoked only when the
1359time (\f(CW\*(C`at\*(C'\fR) has been passed, but if multiple periodic timers become ready
1360during the same loop iteration then order of execution is undefined.
1361.PP
1362\fIWatcher-Specific Functions and Data Members\fR
1363.IX Subsection "Watcher-Specific Functions and Data Members"
639.IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4 1364.IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4
640.IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 1365.IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)"
641.PD 0 1366.PD 0
642.IP "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 4 1367.IP "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 4
643.IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 1368.IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)"
644.PD 1369.PD
645Lots of arguments, lets sort it out... There are basically three modes of 1370Lots of arguments, lets sort it out... There are basically three modes of
646operation, and we will explain them from simplest to complex: 1371operation, and we will explain them from simplest to complex:
647.RS 4 1372.RS 4
648.IP "* absolute timer (interval = reschedule_cb = 0)" 4 1373.IP "* absolute timer (at = time, interval = reschedule_cb = 0)" 4
649.IX Item "absolute timer (interval = reschedule_cb = 0)" 1374.IX Item "absolute timer (at = time, interval = reschedule_cb = 0)"
650In this configuration the watcher triggers an event at the wallclock time 1375In this configuration the watcher triggers an event at the wallclock time
651\&\f(CW\*(C`at\*(C'\fR and doesn't repeat. It will not adjust when a time jump occurs, 1376\&\f(CW\*(C`at\*(C'\fR and doesn't repeat. It will not adjust when a time jump occurs,
652that is, if it is to be run at January 1st 2011 then it will run when the 1377that is, if it is to be run at January 1st 2011 then it will run when the
653system time reaches or surpasses this time. 1378system time reaches or surpasses this time.
654.IP "* non-repeating interval timer (interval > 0, reschedule_cb = 0)" 4 1379.IP "* non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)" 4
655.IX Item "non-repeating interval timer (interval > 0, reschedule_cb = 0)" 1380.IX Item "non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)"
656In this mode the watcher will always be scheduled to time out at the next 1381In this mode the watcher will always be scheduled to time out at the next
657\&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N) and then repeat, regardless 1382\&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N, which can also be negative)
658of any time jumps. 1383and then repeat, regardless of any time jumps.
659.Sp 1384.Sp
660This can be used to create timers that do not drift with respect to system 1385This can be used to create timers that do not drift with respect to system
661time: 1386time:
662.Sp 1387.Sp
663.Vb 1 1388.Vb 1
… …
670by 3600. 1395by 3600.
671.Sp 1396.Sp
672Another way to think about it (for the mathematically inclined) is that 1397Another way to think about it (for the mathematically inclined) is that
673\&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible 1398\&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible
674time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps. 1399time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps.
1400.Sp
1401For numerical stability it is preferable that the \f(CW\*(C`at\*(C'\fR value is near
1402\&\f(CW\*(C`ev_now ()\*(C'\fR (the current time), but there is no range requirement for
1403this value.
675.IP "* manual reschedule mode (reschedule_cb = callback)" 4 1404.IP "* manual reschedule mode (at and interval ignored, reschedule_cb = callback)" 4
676.IX Item "manual reschedule mode (reschedule_cb = callback)" 1405.IX Item "manual reschedule mode (at and interval ignored, reschedule_cb = callback)"
677In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR are both being 1406In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR are both being
678ignored. Instead, each time the periodic watcher gets scheduled, the 1407ignored. Instead, each time the periodic watcher gets scheduled, the
679reschedule callback will be called with the watcher as first, and the 1408reschedule callback will be called with the watcher as first, and the
680current time as second argument. 1409current time as second argument.
681.Sp 1410.Sp
682\&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher, 1411\&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher,
683ever, or make any event loop modifications\fR. If you need to stop it, 1412ever, or make any event loop modifications\fR. If you need to stop it,
684return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop it afterwards (e.g. by 1413return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop it afterwards (e.g. by
685starting a prepare watcher). 1414starting an \f(CW\*(C`ev_prepare\*(C'\fR watcher, which is legal).
686.Sp 1415.Sp
687Its prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 1416Its prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
688ev_tstamp now)\*(C'\fR, e.g.: 1417ev_tstamp now)\*(C'\fR, e.g.:
689.Sp 1418.Sp
690.Vb 4 1419.Vb 4
… …
714.IX Item "ev_periodic_again (loop, ev_periodic *)" 1443.IX Item "ev_periodic_again (loop, ev_periodic *)"
715Simply stops and restarts the periodic watcher again. This is only useful 1444Simply stops and restarts the periodic watcher again. This is only useful
716when you changed some parameters or the reschedule callback would return 1445when you changed some parameters or the reschedule callback would return
717a different time than the last time it was called (e.g. in a crond like 1446a different time than the last time it was called (e.g. in a crond like
718program when the crontabs have changed). 1447program when the crontabs have changed).
1448.IP "ev_tstamp offset [read\-write]" 4
1449.IX Item "ev_tstamp offset [read-write]"
1450When repeating, this contains the offset value, otherwise this is the
1451absolute point in time (the \f(CW\*(C`at\*(C'\fR value passed to \f(CW\*(C`ev_periodic_set\*(C'\fR).
1452.Sp
1453Can be modified any time, but changes only take effect when the periodic
1454timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
1455.IP "ev_tstamp interval [read\-write]" 4
1456.IX Item "ev_tstamp interval [read-write]"
1457The current interval value. Can be modified any time, but changes only
1458take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being
1459called.
1460.IP "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read\-write]" 4
1461.IX Item "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]"
1462The current reschedule callback, or \f(CW0\fR, if this functionality is
1463switched off. Can be changed any time, but changes only take effect when
1464the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
1465.IP "ev_tstamp at [read\-only]" 4
1466.IX Item "ev_tstamp at [read-only]"
1467When active, contains the absolute time that the watcher is supposed to
1468trigger next.
1469.PP
1470Example: Call a callback every hour, or, more precisely, whenever the
1471system clock is divisible by 3600. The callback invocation times have
1472potentially a lot of jittering, but good long-term stability.
1473.PP
1474.Vb 5
1475\& static void
1476\& clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1477\& {
1478\& ... its now a full hour (UTC, or TAI or whatever your clock follows)
1479\& }
1480.Ve
1481.PP
1482.Vb 3
1483\& struct ev_periodic hourly_tick;
1484\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1485\& ev_periodic_start (loop, &hourly_tick);
1486.Ve
1487.PP
1488Example: The same as above, but use a reschedule callback to do it:
1489.PP
1490.Vb 1
1491\& #include <math.h>
1492.Ve
1493.PP
1494.Vb 5
1495\& static ev_tstamp
1496\& my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1497\& {
1498\& return fmod (now, 3600.) + 3600.;
1499\& }
1500.Ve
1501.PP
1502.Vb 1
1503\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1504.Ve
1505.PP
1506Example: Call a callback every hour, starting now:
1507.PP
1508.Vb 4
1509\& struct ev_periodic hourly_tick;
1510\& ev_periodic_init (&hourly_tick, clock_cb,
1511\& fmod (ev_now (loop), 3600.), 3600., 0);
1512\& ev_periodic_start (loop, &hourly_tick);
1513.Ve
719.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled" 1514.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled!"
720.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled" 1515.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled!"
721.IX Subsection "ev_signal - signal me when a signal gets signalled" 1516.IX Subsection "ev_signal - signal me when a signal gets signalled!"
722Signal watchers will trigger an event when the process receives a specific 1517Signal watchers will trigger an event when the process receives a specific
723signal one or more times. Even though signals are very asynchronous, libev 1518signal one or more times. Even though signals are very asynchronous, libev
724will try it's best to deliver signals synchronously, i.e. as part of the 1519will try it's best to deliver signals synchronously, i.e. as part of the
725normal event processing, like any other event. 1520normal event processing, like any other event.
726.PP 1521.PP
… …
728first watcher gets started will libev actually register a signal watcher 1523first watcher gets started will libev actually register a signal watcher
729with the kernel (thus it coexists with your own signal handlers as long 1524with the kernel (thus it coexists with your own signal handlers as long
730as you don't register any with libev). Similarly, when the last signal 1525as you don't register any with libev). Similarly, when the last signal
731watcher for a signal is stopped libev will reset the signal handler to 1526watcher for a signal is stopped libev will reset the signal handler to
732\&\s-1SIG_DFL\s0 (regardless of what it was set to before). 1527\&\s-1SIG_DFL\s0 (regardless of what it was set to before).
1528.PP
1529\fIWatcher-Specific Functions and Data Members\fR
1530.IX Subsection "Watcher-Specific Functions and Data Members"
733.IP "ev_signal_init (ev_signal *, callback, int signum)" 4 1531.IP "ev_signal_init (ev_signal *, callback, int signum)" 4
734.IX Item "ev_signal_init (ev_signal *, callback, int signum)" 1532.IX Item "ev_signal_init (ev_signal *, callback, int signum)"
735.PD 0 1533.PD 0
736.IP "ev_signal_set (ev_signal *, int signum)" 4 1534.IP "ev_signal_set (ev_signal *, int signum)" 4
737.IX Item "ev_signal_set (ev_signal *, int signum)" 1535.IX Item "ev_signal_set (ev_signal *, int signum)"
738.PD 1536.PD
739Configures the watcher to trigger on the given signal number (usually one 1537Configures the watcher to trigger on the given signal number (usually one
740of the \f(CW\*(C`SIGxxx\*(C'\fR constants). 1538of the \f(CW\*(C`SIGxxx\*(C'\fR constants).
1539.IP "int signum [read\-only]" 4
1540.IX Item "int signum [read-only]"
1541The signal the watcher watches out for.
741.ie n .Sh """ev_child"" \- wait for pid status changes" 1542.ie n .Sh """ev_child"" \- watch out for process status changes"
742.el .Sh "\f(CWev_child\fP \- wait for pid status changes" 1543.el .Sh "\f(CWev_child\fP \- watch out for process status changes"
743.IX Subsection "ev_child - wait for pid status changes" 1544.IX Subsection "ev_child - watch out for process status changes"
744Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to 1545Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to
745some child status changes (most typically when a child of yours dies). 1546some child status changes (most typically when a child of yours dies).
1547.PP
1548\fIWatcher-Specific Functions and Data Members\fR
1549.IX Subsection "Watcher-Specific Functions and Data Members"
746.IP "ev_child_init (ev_child *, callback, int pid)" 4 1550.IP "ev_child_init (ev_child *, callback, int pid)" 4
747.IX Item "ev_child_init (ev_child *, callback, int pid)" 1551.IX Item "ev_child_init (ev_child *, callback, int pid)"
748.PD 0 1552.PD 0
749.IP "ev_child_set (ev_child *, int pid)" 4 1553.IP "ev_child_set (ev_child *, int pid)" 4
750.IX Item "ev_child_set (ev_child *, int pid)" 1554.IX Item "ev_child_set (ev_child *, int pid)"
… …
753\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look 1557\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look
754at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see 1558at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see
755the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems 1559the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems
756\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the 1560\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the
757process causing the status change. 1561process causing the status change.
1562.IP "int pid [read\-only]" 4
1563.IX Item "int pid [read-only]"
1564The process id this watcher watches out for, or \f(CW0\fR, meaning any process id.
1565.IP "int rpid [read\-write]" 4
1566.IX Item "int rpid [read-write]"
1567The process id that detected a status change.
1568.IP "int rstatus [read\-write]" 4
1569.IX Item "int rstatus [read-write]"
1570The process exit/trace status caused by \f(CW\*(C`rpid\*(C'\fR (see your systems
1571\&\f(CW\*(C`waitpid\*(C'\fR and \f(CW\*(C`sys/wait.h\*(C'\fR documentation for details).
1572.PP
1573Example: Try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0.
1574.PP
1575.Vb 5
1576\& static void
1577\& sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1578\& {
1579\& ev_unloop (loop, EVUNLOOP_ALL);
1580\& }
1581.Ve
1582.PP
1583.Vb 3
1584\& struct ev_signal signal_watcher;
1585\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1586\& ev_signal_start (loop, &sigint_cb);
1587.Ve
1588.ie n .Sh """ev_stat"" \- did the file attributes just change?"
1589.el .Sh "\f(CWev_stat\fP \- did the file attributes just change?"
1590.IX Subsection "ev_stat - did the file attributes just change?"
1591This watches a filesystem path for attribute changes. That is, it calls
1592\&\f(CW\*(C`stat\*(C'\fR regularly (or when the \s-1OS\s0 says it changed) and sees if it changed
1593compared to the last time, invoking the callback if it did.
1594.PP
1595The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does
1596not exist\*(R" is a status change like any other. The condition \*(L"path does
1597not exist\*(R" is signified by the \f(CW\*(C`st_nlink\*(C'\fR field being zero (which is
1598otherwise always forced to be at least one) and all the other fields of
1599the stat buffer having unspecified contents.
1600.PP
1601The path \fIshould\fR be absolute and \fImust not\fR end in a slash. If it is
1602relative and your working directory changes, the behaviour is undefined.
1603.PP
1604Since there is no standard to do this, the portable implementation simply
1605calls \f(CW\*(C`stat (2)\*(C'\fR regularly on the path to see if it changed somehow. You
1606can specify a recommended polling interval for this case. If you specify
1607a polling interval of \f(CW0\fR (highly recommended!) then a \fIsuitable,
1608unspecified default\fR value will be used (which you can expect to be around
1609five seconds, although this might change dynamically). Libev will also
1610impose a minimum interval which is currently around \f(CW0.1\fR, but thats
1611usually overkill.
1612.PP
1613This watcher type is not meant for massive numbers of stat watchers,
1614as even with OS-supported change notifications, this can be
1615resource\-intensive.
1616.PP
1617At the time of this writing, only the Linux inotify interface is
1618implemented (implementing kqueue support is left as an exercise for the
1619reader). Inotify will be used to give hints only and should not change the
1620semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers, which means that libev sometimes needs
1621to fall back to regular polling again even with inotify, but changes are
1622usually detected immediately, and if the file exists there will be no
1623polling.
1624.PP
1625\fIWatcher-Specific Functions and Data Members\fR
1626.IX Subsection "Watcher-Specific Functions and Data Members"
1627.IP "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 4
1628.IX Item "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)"
1629.PD 0
1630.IP "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" 4
1631.IX Item "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)"
1632.PD
1633Configures the watcher to wait for status changes of the given
1634\&\f(CW\*(C`path\*(C'\fR. The \f(CW\*(C`interval\*(C'\fR is a hint on how quickly a change is expected to
1635be detected and should normally be specified as \f(CW0\fR to let libev choose
1636a suitable value. The memory pointed to by \f(CW\*(C`path\*(C'\fR must point to the same
1637path for as long as the watcher is active.
1638.Sp
1639The callback will be receive \f(CW\*(C`EV_STAT\*(C'\fR when a change was detected,
1640relative to the attributes at the time the watcher was started (or the
1641last change was detected).
1642.IP "ev_stat_stat (ev_stat *)" 4
1643.IX Item "ev_stat_stat (ev_stat *)"
1644Updates the stat buffer immediately with new values. If you change the
1645watched path in your callback, you could call this fucntion to avoid
1646detecting this change (while introducing a race condition). Can also be
1647useful simply to find out the new values.
1648.IP "ev_statdata attr [read\-only]" 4
1649.IX Item "ev_statdata attr [read-only]"
1650The most-recently detected attributes of the file. Although the type is of
1651\&\f(CW\*(C`ev_statdata\*(C'\fR, this is usually the (or one of the) \f(CW\*(C`struct stat\*(C'\fR types
1652suitable for your system. If the \f(CW\*(C`st_nlink\*(C'\fR member is \f(CW0\fR, then there
1653was some error while \f(CW\*(C`stat\*(C'\fRing the file.
1654.IP "ev_statdata prev [read\-only]" 4
1655.IX Item "ev_statdata prev [read-only]"
1656The previous attributes of the file. The callback gets invoked whenever
1657\&\f(CW\*(C`prev\*(C'\fR != \f(CW\*(C`attr\*(C'\fR.
1658.IP "ev_tstamp interval [read\-only]" 4
1659.IX Item "ev_tstamp interval [read-only]"
1660The specified interval.
1661.IP "const char *path [read\-only]" 4
1662.IX Item "const char *path [read-only]"
1663The filesystem path that is being watched.
1664.PP
1665Example: Watch \f(CW\*(C`/etc/passwd\*(C'\fR for attribute changes.
1666.PP
1667.Vb 15
1668\& static void
1669\& passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1670\& {
1671\& /* /etc/passwd changed in some way */
1672\& if (w->attr.st_nlink)
1673\& {
1674\& printf ("passwd current size %ld\en", (long)w->attr.st_size);
1675\& printf ("passwd current atime %ld\en", (long)w->attr.st_mtime);
1676\& printf ("passwd current mtime %ld\en", (long)w->attr.st_mtime);
1677\& }
1678\& else
1679\& /* you shalt not abuse printf for puts */
1680\& puts ("wow, /etc/passwd is not there, expect problems. "
1681\& "if this is windows, they already arrived\en");
1682\& }
1683.Ve
1684.PP
1685.Vb 2
1686\& ...
1687\& ev_stat passwd;
1688.Ve
1689.PP
1690.Vb 2
1691\& ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
1692\& ev_stat_start (loop, &passwd);
1693.Ve
758.ie n .Sh """ev_idle"" \- when you've got nothing better to do" 1694.ie n .Sh """ev_idle"" \- when you've got nothing better to do..."
759.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do" 1695.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do..."
760.IX Subsection "ev_idle - when you've got nothing better to do" 1696.IX Subsection "ev_idle - when you've got nothing better to do..."
761Idle watchers trigger events when there are no other events are pending 1697Idle watchers trigger events when no other events of the same or higher
762(prepare, check and other idle watchers do not count). That is, as long 1698priority are pending (prepare, check and other idle watchers do not
763as your process is busy handling sockets or timeouts (or even signals, 1699count).
764imagine) it will not be triggered. But when your process is idle all idle 1700.PP
765watchers are being called again and again, once per event loop iteration \- 1701That is, as long as your process is busy handling sockets or timeouts
1702(or even signals, imagine) of the same or higher priority it will not be
1703triggered. But when your process is idle (or only lower-priority watchers
1704are pending), the idle watchers are being called once per event loop
766until stopped, that is, or your process receives more events and becomes 1705iteration \- until stopped, that is, or your process receives more events
767busy. 1706and becomes busy again with higher priority stuff.
768.PP 1707.PP
769The most noteworthy effect is that as long as any idle watchers are 1708The most noteworthy effect is that as long as any idle watchers are
770active, the process will not block when waiting for new events. 1709active, the process will not block when waiting for new events.
771.PP 1710.PP
772Apart from keeping your process non-blocking (which is a useful 1711Apart from keeping your process non-blocking (which is a useful
773effect on its own sometimes), idle watchers are a good place to do 1712effect on its own sometimes), idle watchers are a good place to do
774\&\*(L"pseudo\-background processing\*(R", or delay processing stuff to after the 1713\&\*(L"pseudo\-background processing\*(R", or delay processing stuff to after the
775event loop has handled all outstanding events. 1714event loop has handled all outstanding events.
1715.PP
1716\fIWatcher-Specific Functions and Data Members\fR
1717.IX Subsection "Watcher-Specific Functions and Data Members"
776.IP "ev_idle_init (ev_signal *, callback)" 4 1718.IP "ev_idle_init (ev_signal *, callback)" 4
777.IX Item "ev_idle_init (ev_signal *, callback)" 1719.IX Item "ev_idle_init (ev_signal *, callback)"
778Initialises and configures the idle watcher \- it has no parameters of any 1720Initialises and configures the idle watcher \- it has no parameters of any
779kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless, 1721kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless,
780believe me. 1722believe me.
1723.PP
1724Example: Dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR watcher, start it, and in the
1725callback, free it. Also, use no error checking, as usual.
1726.PP
1727.Vb 7
1728\& static void
1729\& idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1730\& {
1731\& free (w);
1732\& // now do something you wanted to do when the program has
1733\& // no longer asnything immediate to do.
1734\& }
1735.Ve
1736.PP
1737.Vb 3
1738\& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1739\& ev_idle_init (idle_watcher, idle_cb);
1740\& ev_idle_start (loop, idle_cb);
1741.Ve
781.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop" 1742.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop!"
782.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop" 1743.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!"
783.IX Subsection "ev_prepare and ev_check - customise your event loop" 1744.IX Subsection "ev_prepare and ev_check - customise your event loop!"
784Prepare and check watchers are usually (but not always) used in tandem: 1745Prepare and check watchers are usually (but not always) used in tandem:
785prepare watchers get invoked before the process blocks and check watchers 1746prepare watchers get invoked before the process blocks and check watchers
786afterwards. 1747afterwards.
787.PP 1748.PP
1749You \fImust not\fR call \f(CW\*(C`ev_loop\*(C'\fR or similar functions that enter
1750the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR
1751watchers. Other loops than the current one are fine, however. The
1752rationale behind this is that you do not need to check for recursion in
1753those watchers, i.e. the sequence will always be \f(CW\*(C`ev_prepare\*(C'\fR, blocking,
1754\&\f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each kind they will always be
1755called in pairs bracketing the blocking call.
1756.PP
788Their main purpose is to integrate other event mechanisms into libev. This 1757Their main purpose is to integrate other event mechanisms into libev and
789could be used, for example, to track variable changes, implement your own 1758their use is somewhat advanced. This could be used, for example, to track
790watchers, integrate net-snmp or a coroutine library and lots more. 1759variable changes, implement your own watchers, integrate net-snmp or a
1760coroutine library and lots more. They are also occasionally useful if
1761you cache some data and want to flush it before blocking (for example,
1762in X programs you might want to do an \f(CW\*(C`XFlush ()\*(C'\fR in an \f(CW\*(C`ev_prepare\*(C'\fR
1763watcher).
791.PP 1764.PP
792This is done by examining in each prepare call which file descriptors need 1765This is done by examining in each prepare call which file descriptors need
793to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for 1766to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for
794them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries 1767them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries
795provide just this functionality). Then, in the check watcher you check for 1768provide just this functionality). Then, in the check watcher you check for
… …
804are ready to run (it's actually more complicated: it only runs coroutines 1777are ready to run (it's actually more complicated: it only runs coroutines
805with priority higher than or equal to the event loop and one coroutine 1778with priority higher than or equal to the event loop and one coroutine
806of lower priority, but only once, using idle watchers to keep the event 1779of lower priority, but only once, using idle watchers to keep the event
807loop from blocking if lower-priority coroutines are active, thus mapping 1780loop from blocking if lower-priority coroutines are active, thus mapping
808low-priority coroutines to idle/background tasks). 1781low-priority coroutines to idle/background tasks).
1782.PP
1783It is recommended to give \f(CW\*(C`ev_check\*(C'\fR watchers highest (\f(CW\*(C`EV_MAXPRI\*(C'\fR)
1784priority, to ensure that they are being run before any other watchers
1785after the poll. Also, \f(CW\*(C`ev_check\*(C'\fR watchers (and \f(CW\*(C`ev_prepare\*(C'\fR watchers,
1786too) should not activate (\*(L"feed\*(R") events into libev. While libev fully
1787supports this, they will be called before other \f(CW\*(C`ev_check\*(C'\fR watchers did
1788their job. As \f(CW\*(C`ev_check\*(C'\fR watchers are often used to embed other event
1789loops those other event loops might be in an unusable state until their
1790\&\f(CW\*(C`ev_check\*(C'\fR watcher ran (always remind yourself to coexist peacefully with
1791others).
1792.PP
1793\fIWatcher-Specific Functions and Data Members\fR
1794.IX Subsection "Watcher-Specific Functions and Data Members"
809.IP "ev_prepare_init (ev_prepare *, callback)" 4 1795.IP "ev_prepare_init (ev_prepare *, callback)" 4
810.IX Item "ev_prepare_init (ev_prepare *, callback)" 1796.IX Item "ev_prepare_init (ev_prepare *, callback)"
811.PD 0 1797.PD 0
812.IP "ev_check_init (ev_check *, callback)" 4 1798.IP "ev_check_init (ev_check *, callback)" 4
813.IX Item "ev_check_init (ev_check *, callback)" 1799.IX Item "ev_check_init (ev_check *, callback)"
814.PD 1800.PD
815Initialises and configures the prepare or check watcher \- they have no 1801Initialises and configures the prepare or check watcher \- they have no
816parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR 1802parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR
817macros, but using them is utterly, utterly and completely pointless. 1803macros, but using them is utterly, utterly and completely pointless.
1804.PP
1805There are a number of principal ways to embed other event loops or modules
1806into libev. Here are some ideas on how to include libadns into libev
1807(there is a Perl module named \f(CW\*(C`EV::ADNS\*(C'\fR that does this, which you could
1808use for an actually working example. Another Perl module named \f(CW\*(C`EV::Glib\*(C'\fR
1809embeds a Glib main context into libev, and finally, \f(CW\*(C`Glib::EV\*(C'\fR embeds \s-1EV\s0
1810into the Glib event loop).
1811.PP
1812Method 1: Add \s-1IO\s0 watchers and a timeout watcher in a prepare handler,
1813and in a check watcher, destroy them and call into libadns. What follows
1814is pseudo-code only of course. This requires you to either use a low
1815priority for the check watcher or use \f(CW\*(C`ev_clear_pending\*(C'\fR explicitly, as
1816the callbacks for the IO/timeout watchers might not have been called yet.
1817.PP
1818.Vb 2
1819\& static ev_io iow [nfd];
1820\& static ev_timer tw;
1821.Ve
1822.PP
1823.Vb 4
1824\& static void
1825\& io_cb (ev_loop *loop, ev_io *w, int revents)
1826\& {
1827\& }
1828.Ve
1829.PP
1830.Vb 8
1831\& // create io watchers for each fd and a timer before blocking
1832\& static void
1833\& adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1834\& {
1835\& int timeout = 3600000;
1836\& struct pollfd fds [nfd];
1837\& // actual code will need to loop here and realloc etc.
1838\& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1839.Ve
1840.PP
1841.Vb 3
1842\& /* the callback is illegal, but won't be called as we stop during check */
1843\& ev_timer_init (&tw, 0, timeout * 1e-3);
1844\& ev_timer_start (loop, &tw);
1845.Ve
1846.PP
1847.Vb 6
1848\& // create one ev_io per pollfd
1849\& for (int i = 0; i < nfd; ++i)
1850\& {
1851\& ev_io_init (iow + i, io_cb, fds [i].fd,
1852\& ((fds [i].events & POLLIN ? EV_READ : 0)
1853\& | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1854.Ve
1855.PP
1856.Vb 4
1857\& fds [i].revents = 0;
1858\& ev_io_start (loop, iow + i);
1859\& }
1860\& }
1861.Ve
1862.PP
1863.Vb 5
1864\& // stop all watchers after blocking
1865\& static void
1866\& adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1867\& {
1868\& ev_timer_stop (loop, &tw);
1869.Ve
1870.PP
1871.Vb 8
1872\& for (int i = 0; i < nfd; ++i)
1873\& {
1874\& // set the relevant poll flags
1875\& // could also call adns_processreadable etc. here
1876\& struct pollfd *fd = fds + i;
1877\& int revents = ev_clear_pending (iow + i);
1878\& if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1879\& if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1880.Ve
1881.PP
1882.Vb 3
1883\& // now stop the watcher
1884\& ev_io_stop (loop, iow + i);
1885\& }
1886.Ve
1887.PP
1888.Vb 2
1889\& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1890\& }
1891.Ve
1892.PP
1893Method 2: This would be just like method 1, but you run \f(CW\*(C`adns_afterpoll\*(C'\fR
1894in the prepare watcher and would dispose of the check watcher.
1895.PP
1896Method 3: If the module to be embedded supports explicit event
1897notification (adns does), you can also make use of the actual watcher
1898callbacks, and only destroy/create the watchers in the prepare watcher.
1899.PP
1900.Vb 5
1901\& static void
1902\& timer_cb (EV_P_ ev_timer *w, int revents)
1903\& {
1904\& adns_state ads = (adns_state)w->data;
1905\& update_now (EV_A);
1906.Ve
1907.PP
1908.Vb 2
1909\& adns_processtimeouts (ads, &tv_now);
1910\& }
1911.Ve
1912.PP
1913.Vb 5
1914\& static void
1915\& io_cb (EV_P_ ev_io *w, int revents)
1916\& {
1917\& adns_state ads = (adns_state)w->data;
1918\& update_now (EV_A);
1919.Ve
1920.PP
1921.Vb 3
1922\& if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1923\& if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1924\& }
1925.Ve
1926.PP
1927.Vb 1
1928\& // do not ever call adns_afterpoll
1929.Ve
1930.PP
1931Method 4: Do not use a prepare or check watcher because the module you
1932want to embed is too inflexible to support it. Instead, youc na override
1933their poll function. The drawback with this solution is that the main
1934loop is now no longer controllable by \s-1EV\s0. The \f(CW\*(C`Glib::EV\*(C'\fR module does
1935this.
1936.PP
1937.Vb 4
1938\& static gint
1939\& event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1940\& {
1941\& int got_events = 0;
1942.Ve
1943.PP
1944.Vb 2
1945\& for (n = 0; n < nfds; ++n)
1946\& // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1947.Ve
1948.PP
1949.Vb 2
1950\& if (timeout >= 0)
1951\& // create/start timer
1952.Ve
1953.PP
1954.Vb 2
1955\& // poll
1956\& ev_loop (EV_A_ 0);
1957.Ve
1958.PP
1959.Vb 3
1960\& // stop timer again
1961\& if (timeout >= 0)
1962\& ev_timer_stop (EV_A_ &to);
1963.Ve
1964.PP
1965.Vb 3
1966\& // stop io watchers again - their callbacks should have set
1967\& for (n = 0; n < nfds; ++n)
1968\& ev_io_stop (EV_A_ iow [n]);
1969.Ve
1970.PP
1971.Vb 2
1972\& return got_events;
1973\& }
1974.Ve
1975.ie n .Sh """ev_embed"" \- when one backend isn't enough..."
1976.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..."
1977.IX Subsection "ev_embed - when one backend isn't enough..."
1978This is a rather advanced watcher type that lets you embed one event loop
1979into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded
1980loop, other types of watchers might be handled in a delayed or incorrect
1981fashion and must not be used). (See portability notes, below).
1982.PP
1983There are primarily two reasons you would want that: work around bugs and
1984prioritise I/O.
1985.PP
1986As an example for a bug workaround, the kqueue backend might only support
1987sockets on some platform, so it is unusable as generic backend, but you
1988still want to make use of it because you have many sockets and it scales
1989so nicely. In this case, you would create a kqueue-based loop and embed it
1990into your default loop (which might use e.g. poll). Overall operation will
1991be a bit slower because first libev has to poll and then call kevent, but
1992at least you can use both at what they are best.
1993.PP
1994As for prioritising I/O: rarely you have the case where some fds have
1995to be watched and handled very quickly (with low latency), and even
1996priorities and idle watchers might have too much overhead. In this case
1997you would put all the high priority stuff in one loop and all the rest in
1998a second one, and embed the second one in the first.
1999.PP
2000As long as the watcher is active, the callback will be invoked every time
2001there might be events pending in the embedded loop. The callback must then
2002call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single sweep and invoke
2003their callbacks (you could also start an idle watcher to give the embedded
2004loop strictly lower priority for example). You can also set the callback
2005to \f(CW0\fR, in which case the embed watcher will automatically execute the
2006embedded loop sweep.
2007.PP
2008As long as the watcher is started it will automatically handle events. The
2009callback will be invoked whenever some events have been handled. You can
2010set the callback to \f(CW0\fR to avoid having to specify one if you are not
2011interested in that.
2012.PP
2013Also, there have not currently been made special provisions for forking:
2014when you fork, you not only have to call \f(CW\*(C`ev_loop_fork\*(C'\fR on both loops,
2015but you will also have to stop and restart any \f(CW\*(C`ev_embed\*(C'\fR watchers
2016yourself.
2017.PP
2018Unfortunately, not all backends are embeddable, only the ones returned by
2019\&\f(CW\*(C`ev_embeddable_backends\*(C'\fR are, which, unfortunately, does not include any
2020portable one.
2021.PP
2022So when you want to use this feature you will always have to be prepared
2023that you cannot get an embeddable loop. The recommended way to get around
2024this is to have a separate variables for your embeddable loop, try to
2025create it, and if that fails, use the normal loop for everything:
2026.PP
2027.Vb 3
2028\& struct ev_loop *loop_hi = ev_default_init (0);
2029\& struct ev_loop *loop_lo = 0;
2030\& struct ev_embed embed;
2031.Ve
2032.PP
2033.Vb 5
2034\& // see if there is a chance of getting one that works
2035\& // (remember that a flags value of 0 means autodetection)
2036\& loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2037\& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2038\& : 0;
2039.Ve
2040.PP
2041.Vb 8
2042\& // if we got one, then embed it, otherwise default to loop_hi
2043\& if (loop_lo)
2044\& {
2045\& ev_embed_init (&embed, 0, loop_lo);
2046\& ev_embed_start (loop_hi, &embed);
2047\& }
2048\& else
2049\& loop_lo = loop_hi;
2050.Ve
2051.Sh "Portability notes"
2052.IX Subsection "Portability notes"
2053Kqueue is nominally embeddable, but this is broken on all BSDs that I
2054tried, in various ways. Usually the embedded event loop will simply never
2055receive events, sometimes it will only trigger a few times, sometimes in a
2056loop. Epoll is also nominally embeddable, but many Linux kernel versions
2057will always eport the epoll fd as ready, even when no events are pending.
2058.PP
2059While libev allows embedding these backends (they are contained in
2060\&\f(CW\*(C`ev_embeddable_backends ()\*(C'\fR), take extreme care that it will actually
2061work.
2062.PP
2063When in doubt, create a dynamic event loop forced to use sockets (this
2064usually works) and possibly another thread and a pipe or so to report to
2065your main event loop.
2066.PP
2067\fIWatcher-Specific Functions and Data Members\fR
2068.IX Subsection "Watcher-Specific Functions and Data Members"
2069.IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
2070.IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)"
2071.PD 0
2072.IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
2073.IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)"
2074.PD
2075Configures the watcher to embed the given loop, which must be
2076embeddable. If the callback is \f(CW0\fR, then \f(CW\*(C`ev_embed_sweep\*(C'\fR will be
2077invoked automatically, otherwise it is the responsibility of the callback
2078to invoke it (it will continue to be called until the sweep has been done,
2079if you do not want thta, you need to temporarily stop the embed watcher).
2080.IP "ev_embed_sweep (loop, ev_embed *)" 4
2081.IX Item "ev_embed_sweep (loop, ev_embed *)"
2082Make a single, non-blocking sweep over the embedded loop. This works
2083similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most
2084apropriate way for embedded loops.
2085.IP "struct ev_loop *other [read\-only]" 4
2086.IX Item "struct ev_loop *other [read-only]"
2087The embedded event loop.
2088.ie n .Sh """ev_fork"" \- the audacity to resume the event loop after a fork"
2089.el .Sh "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork"
2090.IX Subsection "ev_fork - the audacity to resume the event loop after a fork"
2091Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because
2092whoever is a good citizen cared to tell libev about it by calling
2093\&\f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the
2094event loop blocks next and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called,
2095and only in the child after the fork. If whoever good citizen calling
2096\&\f(CW\*(C`ev_default_fork\*(C'\fR cheats and calls it in the wrong process, the fork
2097handlers will be invoked, too, of course.
2098.PP
2099\fIWatcher-Specific Functions and Data Members\fR
2100.IX Subsection "Watcher-Specific Functions and Data Members"
2101.IP "ev_fork_init (ev_signal *, callback)" 4
2102.IX Item "ev_fork_init (ev_signal *, callback)"
2103Initialises and configures the fork watcher \- it has no parameters of any
2104kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless,
2105believe me.
818.SH "OTHER FUNCTIONS" 2106.SH "OTHER FUNCTIONS"
819.IX Header "OTHER FUNCTIONS" 2107.IX Header "OTHER FUNCTIONS"
820There are some other functions of possible interest. Described. Here. Now. 2108There are some other functions of possible interest. Described. Here. Now.
821.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4 2109.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4
822.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 2110.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)"
… …
851.Ve 2139.Ve
852.Sp 2140.Sp
853.Vb 1 2141.Vb 1
854\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); 2142\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
855.Ve 2143.Ve
856.IP "ev_feed_event (loop, watcher, int events)" 4 2144.IP "ev_feed_event (ev_loop *, watcher *, int revents)" 4
857.IX Item "ev_feed_event (loop, watcher, int events)" 2145.IX Item "ev_feed_event (ev_loop *, watcher *, int revents)"
858Feeds the given event set into the event loop, as if the specified event 2146Feeds the given event set into the event loop, as if the specified event
859had happened for the specified watcher (which must be a pointer to an 2147had happened for the specified watcher (which must be a pointer to an
860initialised but not necessarily started event watcher). 2148initialised but not necessarily started event watcher).
861.IP "ev_feed_fd_event (loop, int fd, int revents)" 4 2149.IP "ev_feed_fd_event (ev_loop *, int fd, int revents)" 4
862.IX Item "ev_feed_fd_event (loop, int fd, int revents)" 2150.IX Item "ev_feed_fd_event (ev_loop *, int fd, int revents)"
863Feed an event on the given fd, as if a file descriptor backend detected 2151Feed an event on the given fd, as if a file descriptor backend detected
864the given events it. 2152the given events it.
865.IP "ev_feed_signal_event (loop, int signum)" 4 2153.IP "ev_feed_signal_event (ev_loop *loop, int signum)" 4
866.IX Item "ev_feed_signal_event (loop, int signum)" 2154.IX Item "ev_feed_signal_event (ev_loop *loop, int signum)"
867Feed an event as if the given signal occured (loop must be the default loop!). 2155Feed an event as if the given signal occured (\f(CW\*(C`loop\*(C'\fR must be the default
2156loop!).
868.SH "LIBEVENT EMULATION" 2157.SH "LIBEVENT EMULATION"
869.IX Header "LIBEVENT EMULATION" 2158.IX Header "LIBEVENT EMULATION"
870Libev offers a compatibility emulation layer for libevent. It cannot 2159Libev offers a compatibility emulation layer for libevent. It cannot
871emulate the internals of libevent, so here are some usage hints: 2160emulate the internals of libevent, so here are some usage hints:
872.IP "* Use it by including <event.h>, as usual." 4 2161.IP "* Use it by including <event.h>, as usual." 4
… …
883.IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4 2172.IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4
884.IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library." 2173.IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library."
885.PD 2174.PD
886.SH "\*(C+ SUPPORT" 2175.SH "\*(C+ SUPPORT"
887.IX Header " SUPPORT" 2176.IX Header " SUPPORT"
888\&\s-1TBD\s0. 2177Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow
2178you to use some convinience methods to start/stop watchers and also change
2179the callback model to a model using method callbacks on objects.
2180.PP
2181To use it,
2182.PP
2183.Vb 1
2184\& #include <ev++.h>
2185.Ve
2186.PP
2187This automatically includes \fIev.h\fR and puts all of its definitions (many
2188of them macros) into the global namespace. All \*(C+ specific things are
2189put into the \f(CW\*(C`ev\*(C'\fR namespace. It should support all the same embedding
2190options as \fIev.h\fR, most notably \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR.
2191.PP
2192Care has been taken to keep the overhead low. The only data member the \*(C+
2193classes add (compared to plain C\-style watchers) is the event loop pointer
2194that the watcher is associated with (or no additional members at all if
2195you disable \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR when embedding libev).
2196.PP
2197Currently, functions, and static and non-static member functions can be
2198used as callbacks. Other types should be easy to add as long as they only
2199need one additional pointer for context. If you need support for other
2200types of functors please contact the author (preferably after implementing
2201it).
2202.PP
2203Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace:
2204.ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4
2205.el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4
2206.IX Item "ev::READ, ev::WRITE etc."
2207These are just enum values with the same values as the \f(CW\*(C`EV_READ\*(C'\fR etc.
2208macros from \fIev.h\fR.
2209.ie n .IP """ev::tstamp""\fR, \f(CW""ev::now""" 4
2210.el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4
2211.IX Item "ev::tstamp, ev::now"
2212Aliases to the same types/functions as with the \f(CW\*(C`ev_\*(C'\fR prefix.
2213.ie n .IP """ev::io""\fR, \f(CW""ev::timer""\fR, \f(CW""ev::periodic""\fR, \f(CW""ev::idle""\fR, \f(CW""ev::sig"" etc." 4
2214.el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4
2215.IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc."
2216For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of
2217the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR
2218which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro
2219defines by many implementations.
2220.Sp
2221All of those classes have these methods:
2222.RS 4
2223.IP "ev::TYPE::TYPE ()" 4
2224.IX Item "ev::TYPE::TYPE ()"
2225.PD 0
2226.IP "ev::TYPE::TYPE (struct ev_loop *)" 4
2227.IX Item "ev::TYPE::TYPE (struct ev_loop *)"
2228.IP "ev::TYPE::~TYPE" 4
2229.IX Item "ev::TYPE::~TYPE"
2230.PD
2231The constructor (optionally) takes an event loop to associate the watcher
2232with. If it is omitted, it will use \f(CW\*(C`EV_DEFAULT\*(C'\fR.
2233.Sp
2234The constructor calls \f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the
2235\&\f(CW\*(C`set\*(C'\fR method before starting it.
2236.Sp
2237It will not set a callback, however: You have to call the templated \f(CW\*(C`set\*(C'\fR
2238method to set a callback before you can start the watcher.
2239.Sp
2240(The reason why you have to use a method is a limitation in \*(C+ which does
2241not allow explicit template arguments for constructors).
2242.Sp
2243The destructor automatically stops the watcher if it is active.
2244.IP "w\->set<class, &class::method> (object *)" 4
2245.IX Item "w->set<class, &class::method> (object *)"
2246This method sets the callback method to call. The method has to have a
2247signature of \f(CW\*(C`void (*)(ev_TYPE &, int)\*(C'\fR, it receives the watcher as
2248first argument and the \f(CW\*(C`revents\*(C'\fR as second. The object must be given as
2249parameter and is stored in the \f(CW\*(C`data\*(C'\fR member of the watcher.
2250.Sp
2251This method synthesizes efficient thunking code to call your method from
2252the C callback that libev requires. If your compiler can inline your
2253callback (i.e. it is visible to it at the place of the \f(CW\*(C`set\*(C'\fR call and
2254your compiler is good :), then the method will be fully inlined into the
2255thunking function, making it as fast as a direct C callback.
2256.Sp
2257Example: simple class declaration and watcher initialisation
2258.Sp
2259.Vb 4
2260\& struct myclass
2261\& {
2262\& void io_cb (ev::io &w, int revents) { }
2263\& }
2264.Ve
2265.Sp
2266.Vb 3
2267\& myclass obj;
2268\& ev::io iow;
2269\& iow.set <myclass, &myclass::io_cb> (&obj);
2270.Ve
2271.IP "w\->set<function> (void *data = 0)" 4
2272.IX Item "w->set<function> (void *data = 0)"
2273Also sets a callback, but uses a static method or plain function as
2274callback. The optional \f(CW\*(C`data\*(C'\fR argument will be stored in the watcher's
2275\&\f(CW\*(C`data\*(C'\fR member and is free for you to use.
2276.Sp
2277The prototype of the \f(CW\*(C`function\*(C'\fR must be \f(CW\*(C`void (*)(ev::TYPE &w, int)\*(C'\fR.
2278.Sp
2279See the method\-\f(CW\*(C`set\*(C'\fR above for more details.
2280.Sp
2281Example:
2282.Sp
2283.Vb 2
2284\& static void io_cb (ev::io &w, int revents) { }
2285\& iow.set <io_cb> ();
2286.Ve
2287.IP "w\->set (struct ev_loop *)" 4
2288.IX Item "w->set (struct ev_loop *)"
2289Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only
2290do this when the watcher is inactive (and not pending either).
2291.IP "w\->set ([args])" 4
2292.IX Item "w->set ([args])"
2293Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same args. Must be
2294called at least once. Unlike the C counterpart, an active watcher gets
2295automatically stopped and restarted when reconfiguring it with this
2296method.
2297.IP "w\->start ()" 4
2298.IX Item "w->start ()"
2299Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the
2300constructor already stores the event loop.
2301.IP "w\->stop ()" 4
2302.IX Item "w->stop ()"
2303Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument.
2304.ie n .IP "w\->again () (""ev::timer""\fR, \f(CW""ev::periodic"" only)" 4
2305.el .IP "w\->again () (\f(CWev::timer\fR, \f(CWev::periodic\fR only)" 4
2306.IX Item "w->again () (ev::timer, ev::periodic only)"
2307For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding
2308\&\f(CW\*(C`ev_TYPE_again\*(C'\fR function.
2309.ie n .IP "w\->sweep () (""ev::embed"" only)" 4
2310.el .IP "w\->sweep () (\f(CWev::embed\fR only)" 4
2311.IX Item "w->sweep () (ev::embed only)"
2312Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR.
2313.ie n .IP "w\->update () (""ev::stat"" only)" 4
2314.el .IP "w\->update () (\f(CWev::stat\fR only)" 4
2315.IX Item "w->update () (ev::stat only)"
2316Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR.
2317.RE
2318.RS 4
2319.RE
2320.PP
2321Example: Define a class with an \s-1IO\s0 and idle watcher, start one of them in
2322the constructor.
2323.PP
2324.Vb 4
2325\& class myclass
2326\& {
2327\& ev_io io; void io_cb (ev::io &w, int revents);
2328\& ev_idle idle void idle_cb (ev::idle &w, int revents);
2329.Ve
2330.PP
2331.Vb 2
2332\& myclass ();
2333\& }
2334.Ve
2335.PP
2336.Vb 4
2337\& myclass::myclass (int fd)
2338\& {
2339\& io .set <myclass, &myclass::io_cb > (this);
2340\& idle.set <myclass, &myclass::idle_cb> (this);
2341.Ve
2342.PP
2343.Vb 2
2344\& io.start (fd, ev::READ);
2345\& }
2346.Ve
2347.SH "MACRO MAGIC"
2348.IX Header "MACRO MAGIC"
2349Libev can be compiled with a variety of options, the most fundamantal
2350of which is \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most)
2351functions and callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument.
2352.PP
2353To make it easier to write programs that cope with either variant, the
2354following macros are defined:
2355.ie n .IP """EV_A""\fR, \f(CW""EV_A_""" 4
2356.el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4
2357.IX Item "EV_A, EV_A_"
2358This provides the loop \fIargument\fR for functions, if one is required (\*(L"ev
2359loop argument\*(R"). The \f(CW\*(C`EV_A\*(C'\fR form is used when this is the sole argument,
2360\&\f(CW\*(C`EV_A_\*(C'\fR is used when other arguments are following. Example:
2361.Sp
2362.Vb 3
2363\& ev_unref (EV_A);
2364\& ev_timer_add (EV_A_ watcher);
2365\& ev_loop (EV_A_ 0);
2366.Ve
2367.Sp
2368It assumes the variable \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR is in scope,
2369which is often provided by the following macro.
2370.ie n .IP """EV_P""\fR, \f(CW""EV_P_""" 4
2371.el .IP "\f(CWEV_P\fR, \f(CWEV_P_\fR" 4
2372.IX Item "EV_P, EV_P_"
2373This provides the loop \fIparameter\fR for functions, if one is required (\*(L"ev
2374loop parameter\*(R"). The \f(CW\*(C`EV_P\*(C'\fR form is used when this is the sole parameter,
2375\&\f(CW\*(C`EV_P_\*(C'\fR is used when other parameters are following. Example:
2376.Sp
2377.Vb 2
2378\& // this is how ev_unref is being declared
2379\& static void ev_unref (EV_P);
2380.Ve
2381.Sp
2382.Vb 2
2383\& // this is how you can declare your typical callback
2384\& static void cb (EV_P_ ev_timer *w, int revents)
2385.Ve
2386.Sp
2387It declares a parameter \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR, quite
2388suitable for use with \f(CW\*(C`EV_A\*(C'\fR.
2389.ie n .IP """EV_DEFAULT""\fR, \f(CW""EV_DEFAULT_""" 4
2390.el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4
2391.IX Item "EV_DEFAULT, EV_DEFAULT_"
2392Similar to the other two macros, this gives you the value of the default
2393loop, if multiple loops are supported (\*(L"ev loop default\*(R").
2394.PP
2395Example: Declare and initialise a check watcher, utilising the above
2396macros so it will work regardless of whether multiple loops are supported
2397or not.
2398.PP
2399.Vb 5
2400\& static void
2401\& check_cb (EV_P_ ev_timer *w, int revents)
2402\& {
2403\& ev_check_stop (EV_A_ w);
2404\& }
2405.Ve
2406.PP
2407.Vb 4
2408\& ev_check check;
2409\& ev_check_init (&check, check_cb);
2410\& ev_check_start (EV_DEFAULT_ &check);
2411\& ev_loop (EV_DEFAULT_ 0);
2412.Ve
2413.SH "EMBEDDING"
2414.IX Header "EMBEDDING"
2415Libev can (and often is) directly embedded into host
2416applications. Examples of applications that embed it include the Deliantra
2417Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe)
2418and rxvt\-unicode.
2419.PP
2420The goal is to enable you to just copy the necessary files into your
2421source directory without having to change even a single line in them, so
2422you can easily upgrade by simply copying (or having a checked-out copy of
2423libev somewhere in your source tree).
2424.Sh "\s-1FILESETS\s0"
2425.IX Subsection "FILESETS"
2426Depending on what features you need you need to include one or more sets of files
2427in your app.
2428.PP
2429\fI\s-1CORE\s0 \s-1EVENT\s0 \s-1LOOP\s0\fR
2430.IX Subsection "CORE EVENT LOOP"
2431.PP
2432To include only the libev core (all the \f(CW\*(C`ev_*\*(C'\fR functions), with manual
2433configuration (no autoconf):
2434.PP
2435.Vb 2
2436\& #define EV_STANDALONE 1
2437\& #include "ev.c"
2438.Ve
2439.PP
2440This will automatically include \fIev.h\fR, too, and should be done in a
2441single C source file only to provide the function implementations. To use
2442it, do the same for \fIev.h\fR in all files wishing to use this \s-1API\s0 (best
2443done by writing a wrapper around \fIev.h\fR that you can include instead and
2444where you can put other configuration options):
2445.PP
2446.Vb 2
2447\& #define EV_STANDALONE 1
2448\& #include "ev.h"
2449.Ve
2450.PP
2451Both header files and implementation files can be compiled with a \*(C+
2452compiler (at least, thats a stated goal, and breakage will be treated
2453as a bug).
2454.PP
2455You need the following files in your source tree, or in a directory
2456in your include path (e.g. in libev/ when using \-Ilibev):
2457.PP
2458.Vb 4
2459\& ev.h
2460\& ev.c
2461\& ev_vars.h
2462\& ev_wrap.h
2463.Ve
2464.PP
2465.Vb 1
2466\& ev_win32.c required on win32 platforms only
2467.Ve
2468.PP
2469.Vb 5
2470\& ev_select.c only when select backend is enabled (which is enabled by default)
2471\& ev_poll.c only when poll backend is enabled (disabled by default)
2472\& ev_epoll.c only when the epoll backend is enabled (disabled by default)
2473\& ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2474\& ev_port.c only when the solaris port backend is enabled (disabled by default)
2475.Ve
2476.PP
2477\&\fIev.c\fR includes the backend files directly when enabled, so you only need
2478to compile this single file.
2479.PP
2480\fI\s-1LIBEVENT\s0 \s-1COMPATIBILITY\s0 \s-1API\s0\fR
2481.IX Subsection "LIBEVENT COMPATIBILITY API"
2482.PP
2483To include the libevent compatibility \s-1API\s0, also include:
2484.PP
2485.Vb 1
2486\& #include "event.c"
2487.Ve
2488.PP
2489in the file including \fIev.c\fR, and:
2490.PP
2491.Vb 1
2492\& #include "event.h"
2493.Ve
2494.PP
2495in the files that want to use the libevent \s-1API\s0. This also includes \fIev.h\fR.
2496.PP
2497You need the following additional files for this:
2498.PP
2499.Vb 2
2500\& event.h
2501\& event.c
2502.Ve
2503.PP
2504\fI\s-1AUTOCONF\s0 \s-1SUPPORT\s0\fR
2505.IX Subsection "AUTOCONF SUPPORT"
2506.PP
2507Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your config in
2508whatever way you want, you can also \f(CW\*(C`m4_include([libev.m4])\*(C'\fR in your
2509\&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR undefined. \fIev.c\fR will then
2510include \fIconfig.h\fR and configure itself accordingly.
2511.PP
2512For this of course you need the m4 file:
2513.PP
2514.Vb 1
2515\& libev.m4
2516.Ve
2517.Sh "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0"
2518.IX Subsection "PREPROCESSOR SYMBOLS/MACROS"
2519Libev can be configured via a variety of preprocessor symbols you have to define
2520before including any of its files. The default is not to build for multiplicity
2521and only include the select backend.
2522.IP "\s-1EV_STANDALONE\s0" 4
2523.IX Item "EV_STANDALONE"
2524Must always be \f(CW1\fR if you do not use autoconf configuration, which
2525keeps libev from including \fIconfig.h\fR, and it also defines dummy
2526implementations for some libevent functions (such as logging, which is not
2527supported). It will also not define any of the structs usually found in
2528\&\fIevent.h\fR that are not directly supported by the libev core alone.
2529.IP "\s-1EV_USE_MONOTONIC\s0" 4
2530.IX Item "EV_USE_MONOTONIC"
2531If defined to be \f(CW1\fR, libev will try to detect the availability of the
2532monotonic clock option at both compiletime and runtime. Otherwise no use
2533of the monotonic clock option will be attempted. If you enable this, you
2534usually have to link against librt or something similar. Enabling it when
2535the functionality isn't available is safe, though, although you have
2536to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR
2537function is hiding in (often \fI\-lrt\fR).
2538.IP "\s-1EV_USE_REALTIME\s0" 4
2539.IX Item "EV_USE_REALTIME"
2540If defined to be \f(CW1\fR, libev will try to detect the availability of the
2541realtime clock option at compiletime (and assume its availability at
2542runtime if successful). Otherwise no use of the realtime clock option will
2543be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get
2544(CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See the
2545note about libraries in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though.
2546.IP "\s-1EV_USE_NANOSLEEP\s0" 4
2547.IX Item "EV_USE_NANOSLEEP"
2548If defined to be \f(CW1\fR, libev will assume that \f(CW\*(C`nanosleep ()\*(C'\fR is available
2549and will use it for delays. Otherwise it will use \f(CW\*(C`select ()\*(C'\fR.
2550.IP "\s-1EV_USE_SELECT\s0" 4
2551.IX Item "EV_USE_SELECT"
2552If undefined or defined to be \f(CW1\fR, libev will compile in support for the
2553\&\f(CW\*(C`select\*(C'\fR(2) backend. No attempt at autodetection will be done: if no
2554other method takes over, select will be it. Otherwise the select backend
2555will not be compiled in.
2556.IP "\s-1EV_SELECT_USE_FD_SET\s0" 4
2557.IX Item "EV_SELECT_USE_FD_SET"
2558If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR
2559structure. This is useful if libev doesn't compile due to a missing
2560\&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it misguesses the bitset layout on
2561exotic systems. This usually limits the range of file descriptors to some
2562low limit such as 1024 or might have other limitations (winsocket only
2563allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation, might
2564influence the size of the \f(CW\*(C`fd_set\*(C'\fR used.
2565.IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4
2566.IX Item "EV_SELECT_IS_WINSOCKET"
2567When defined to \f(CW1\fR, the select backend will assume that
2568select/socket/connect etc. don't understand file descriptors but
2569wants osf handles on win32 (this is the case when the select to
2570be used is the winsock select). This means that it will call
2571\&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise,
2572it is assumed that all these functions actually work on fds, even
2573on win32. Should not be defined on non\-win32 platforms.
2574.IP "\s-1EV_USE_POLL\s0" 4
2575.IX Item "EV_USE_POLL"
2576If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2)
2577backend. Otherwise it will be enabled on non\-win32 platforms. It
2578takes precedence over select.
2579.IP "\s-1EV_USE_EPOLL\s0" 4
2580.IX Item "EV_USE_EPOLL"
2581If defined to be \f(CW1\fR, libev will compile in support for the Linux
2582\&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime,
2583otherwise another method will be used as fallback. This is the
2584preferred backend for GNU/Linux systems.
2585.IP "\s-1EV_USE_KQUEUE\s0" 4
2586.IX Item "EV_USE_KQUEUE"
2587If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style
2588\&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime,
2589otherwise another method will be used as fallback. This is the preferred
2590backend for \s-1BSD\s0 and BSD-like systems, although on most BSDs kqueue only
2591supports some types of fds correctly (the only platform we found that
2592supports ptys for example was NetBSD), so kqueue might be compiled in, but
2593not be used unless explicitly requested. The best way to use it is to find
2594out whether kqueue supports your type of fd properly and use an embedded
2595kqueue loop.
2596.IP "\s-1EV_USE_PORT\s0" 4
2597.IX Item "EV_USE_PORT"
2598If defined to be \f(CW1\fR, libev will compile in support for the Solaris
259910 port style backend. Its availability will be detected at runtime,
2600otherwise another method will be used as fallback. This is the preferred
2601backend for Solaris 10 systems.
2602.IP "\s-1EV_USE_DEVPOLL\s0" 4
2603.IX Item "EV_USE_DEVPOLL"
2604reserved for future expansion, works like the \s-1USE\s0 symbols above.
2605.IP "\s-1EV_USE_INOTIFY\s0" 4
2606.IX Item "EV_USE_INOTIFY"
2607If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify
2608interface to speed up \f(CW\*(C`ev_stat\*(C'\fR watchers. Its actual availability will
2609be detected at runtime.
2610.IP "\s-1EV_H\s0" 4
2611.IX Item "EV_H"
2612The name of the \fIev.h\fR header file used to include it. The default if
2613undefined is \f(CW\*(C`<ev.h>\*(C'\fR in \fIevent.h\fR and \f(CW"ev.h"\fR in \fIev.c\fR. This
2614can be used to virtually rename the \fIev.h\fR header file in case of conflicts.
2615.IP "\s-1EV_CONFIG_H\s0" 4
2616.IX Item "EV_CONFIG_H"
2617If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override
2618\&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to
2619\&\f(CW\*(C`EV_H\*(C'\fR, above.
2620.IP "\s-1EV_EVENT_H\s0" 4
2621.IX Item "EV_EVENT_H"
2622Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea
2623of how the \fIevent.h\fR header can be found.
2624.IP "\s-1EV_PROTOTYPES\s0" 4
2625.IX Item "EV_PROTOTYPES"
2626If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function
2627prototypes, but still define all the structs and other symbols. This is
2628occasionally useful if you want to provide your own wrapper functions
2629around libev functions.
2630.IP "\s-1EV_MULTIPLICITY\s0" 4
2631.IX Item "EV_MULTIPLICITY"
2632If undefined or defined to \f(CW1\fR, then all event-loop-specific functions
2633will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create
2634additional independent event loops. Otherwise there will be no support
2635for multiple event loops and there is no first event loop pointer
2636argument. Instead, all functions act on the single default loop.
2637.IP "\s-1EV_MINPRI\s0" 4
2638.IX Item "EV_MINPRI"
2639.PD 0
2640.IP "\s-1EV_MAXPRI\s0" 4
2641.IX Item "EV_MAXPRI"
2642.PD
2643The range of allowed priorities. \f(CW\*(C`EV_MINPRI\*(C'\fR must be smaller or equal to
2644\&\f(CW\*(C`EV_MAXPRI\*(C'\fR, but otherwise there are no non-obvious limitations. You can
2645provide for more priorities by overriding those symbols (usually defined
2646to be \f(CW\*(C`\-2\*(C'\fR and \f(CW2\fR, respectively).
2647.Sp
2648When doing priority-based operations, libev usually has to linearly search
2649all the priorities, so having many of them (hundreds) uses a lot of space
2650and time, so using the defaults of five priorities (\-2 .. +2) is usually
2651fine.
2652.Sp
2653If your embedding app does not need any priorities, defining these both to
2654\&\f(CW0\fR will save some memory and cpu.
2655.IP "\s-1EV_PERIODIC_ENABLE\s0" 4
2656.IX Item "EV_PERIODIC_ENABLE"
2657If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If
2658defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
2659code.
2660.IP "\s-1EV_IDLE_ENABLE\s0" 4
2661.IX Item "EV_IDLE_ENABLE"
2662If undefined or defined to be \f(CW1\fR, then idle watchers are supported. If
2663defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
2664code.
2665.IP "\s-1EV_EMBED_ENABLE\s0" 4
2666.IX Item "EV_EMBED_ENABLE"
2667If undefined or defined to be \f(CW1\fR, then embed watchers are supported. If
2668defined to be \f(CW0\fR, then they are not.
2669.IP "\s-1EV_STAT_ENABLE\s0" 4
2670.IX Item "EV_STAT_ENABLE"
2671If undefined or defined to be \f(CW1\fR, then stat watchers are supported. If
2672defined to be \f(CW0\fR, then they are not.
2673.IP "\s-1EV_FORK_ENABLE\s0" 4
2674.IX Item "EV_FORK_ENABLE"
2675If undefined or defined to be \f(CW1\fR, then fork watchers are supported. If
2676defined to be \f(CW0\fR, then they are not.
2677.IP "\s-1EV_MINIMAL\s0" 4
2678.IX Item "EV_MINIMAL"
2679If you need to shave off some kilobytes of code at the expense of some
2680speed, define this symbol to \f(CW1\fR. Currently only used for gcc to override
2681some inlining decisions, saves roughly 30% codesize of amd64.
2682.IP "\s-1EV_PID_HASHSIZE\s0" 4
2683.IX Item "EV_PID_HASHSIZE"
2684\&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by
2685pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), usually more
2686than enough. If you need to manage thousands of children you might want to
2687increase this value (\fImust\fR be a power of two).
2688.IP "\s-1EV_INOTIFY_HASHSIZE\s0" 4
2689.IX Item "EV_INOTIFY_HASHSIZE"
2690\&\f(CW\*(C`ev_staz\*(C'\fR watchers use a small hash table to distribute workload by
2691inotify watch id. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR),
2692usually more than enough. If you need to manage thousands of \f(CW\*(C`ev_stat\*(C'\fR
2693watchers you might want to increase this value (\fImust\fR be a power of
2694two).
2695.IP "\s-1EV_COMMON\s0" 4
2696.IX Item "EV_COMMON"
2697By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining
2698this macro to a something else you can include more and other types of
2699members. You have to define it each time you include one of the files,
2700though, and it must be identical each time.
2701.Sp
2702For example, the perl \s-1EV\s0 module uses something like this:
2703.Sp
2704.Vb 3
2705\& #define EV_COMMON \e
2706\& SV *self; /* contains this struct */ \e
2707\& SV *cb_sv, *fh /* note no trailing ";" */
2708.Ve
2709.IP "\s-1EV_CB_DECLARE\s0 (type)" 4
2710.IX Item "EV_CB_DECLARE (type)"
2711.PD 0
2712.IP "\s-1EV_CB_INVOKE\s0 (watcher, revents)" 4
2713.IX Item "EV_CB_INVOKE (watcher, revents)"
2714.IP "ev_set_cb (ev, cb)" 4
2715.IX Item "ev_set_cb (ev, cb)"
2716.PD
2717Can be used to change the callback member declaration in each watcher,
2718and the way callbacks are invoked and set. Must expand to a struct member
2719definition and a statement, respectively. See the \fIev.h\fR header file for
2720their default definitions. One possible use for overriding these is to
2721avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use
2722method calls instead of plain function calls in \*(C+.
2723.Sh "\s-1EXPORTED\s0 \s-1API\s0 \s-1SYMBOLS\s0"
2724.IX Subsection "EXPORTED API SYMBOLS"
2725If you need to re-export the \s-1API\s0 (e.g. via a dll) and you need a list of
2726exported symbols, you can use the provided \fISymbol.*\fR files which list
2727all public symbols, one per line:
2728.Sp
2729.Vb 2
2730\& Symbols.ev for libev proper
2731\& Symbols.event for the libevent emulation
2732.Ve
2733.Sp
2734This can also be used to rename all public symbols to avoid clashes with
2735multiple versions of libev linked together (which is obviously bad in
2736itself, but sometimes it is inconvinient to avoid this).
2737.Sp
2738A sed command like this will create wrapper \f(CW\*(C`#define\*(C'\fR's that you need to
2739include before including \fIev.h\fR:
2740.Sp
2741.Vb 1
2742\& <Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
2743.Ve
2744.Sp
2745This would create a file \fIwrap.h\fR which essentially looks like this:
2746.Sp
2747.Vb 4
2748\& #define ev_backend myprefix_ev_backend
2749\& #define ev_check_start myprefix_ev_check_start
2750\& #define ev_check_stop myprefix_ev_check_stop
2751\& ...
2752.Ve
2753.Sh "\s-1EXAMPLES\s0"
2754.IX Subsection "EXAMPLES"
2755For a real-world example of a program the includes libev
2756verbatim, you can have a look at the \s-1EV\s0 perl module
2757(<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
2758the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public
2759interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file
2760will be compiled. It is pretty complex because it provides its own header
2761file.
2762.Sp
2763The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file
2764that everybody includes and which overrides some configure choices:
2765.Sp
2766.Vb 9
2767\& #define EV_MINIMAL 1
2768\& #define EV_USE_POLL 0
2769\& #define EV_MULTIPLICITY 0
2770\& #define EV_PERIODIC_ENABLE 0
2771\& #define EV_STAT_ENABLE 0
2772\& #define EV_FORK_ENABLE 0
2773\& #define EV_CONFIG_H <config.h>
2774\& #define EV_MINPRI 0
2775\& #define EV_MAXPRI 0
2776.Ve
2777.Sp
2778.Vb 1
2779\& #include "ev++.h"
2780.Ve
2781.Sp
2782And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled:
2783.Sp
2784.Vb 2
2785\& #include "ev_cpp.h"
2786\& #include "ev.c"
2787.Ve
2788.SH "COMPLEXITIES"
2789.IX Header "COMPLEXITIES"
2790In this section the complexities of (many of) the algorithms used inside
2791libev will be explained. For complexity discussions about backends see the
2792documentation for \f(CW\*(C`ev_default_init\*(C'\fR.
2793.Sp
2794All of the following are about amortised time: If an array needs to be
2795extended, libev needs to realloc and move the whole array, but this
2796happens asymptotically never with higher number of elements, so O(1) might
2797mean it might do a lengthy realloc operation in rare cases, but on average
2798it is much faster and asymptotically approaches constant time.
2799.RS 4
2800.IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4
2801.IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)"
2802This means that, when you have a watcher that triggers in one hour and
2803there are 100 watchers that would trigger before that then inserting will
2804have to skip those 100 watchers.
2805.IP "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)" 4
2806.IX Item "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)"
2807That means that for changing a timer costs less than removing/adding them
2808as only the relative motion in the event queue has to be paid for.
2809.IP "Starting io/check/prepare/idle/signal/child watchers: O(1)" 4
2810.IX Item "Starting io/check/prepare/idle/signal/child watchers: O(1)"
2811These just add the watcher into an array or at the head of a list.
2812=item Stopping check/prepare/idle watchers: O(1)
2813.IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4
2814.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))"
2815These watchers are stored in lists then need to be walked to find the
2816correct watcher to remove. The lists are usually short (you don't usually
2817have many watchers waiting for the same fd or signal).
2818.IP "Finding the next timer per loop iteration: O(1)" 4
2819.IX Item "Finding the next timer per loop iteration: O(1)"
2820.PD 0
2821.IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4
2822.IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)"
2823.PD
2824A change means an I/O watcher gets started or stopped, which requires
2825libev to recalculate its status (and possibly tell the kernel).
2826.IP "Activating one watcher: O(1)" 4
2827.IX Item "Activating one watcher: O(1)"
2828.PD 0
2829.IP "Priority handling: O(number_of_priorities)" 4
2830.IX Item "Priority handling: O(number_of_priorities)"
2831.PD
2832Priorities are implemented by allocating some space for each
2833priority. When doing priority-based operations, libev usually has to
2834linearly search all the priorities.
2835.RE
2836.RS 4
889.SH "AUTHOR" 2837.SH "AUTHOR"
890.IX Header "AUTHOR" 2838.IX Header "AUTHOR"
891Marc Lehmann <libev@schmorp.de>. 2839Marc Lehmann <libev@schmorp.de>.

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