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… …
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 ""<STANDARD INPUT>" 1"
132.TH "<STANDARD INPUT>" 1 "2007-11-23" "perl v5.8.8" "User Contributed Perl Documentation" 132.TH "<STANDARD INPUT>" 1 "2007-12-09" "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 occuring), 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
… …
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 such.
179.SH "GLOBAL FUNCTIONS" 249.SH "GLOBAL FUNCTIONS"
180.IX Header "GLOBAL FUNCTIONS" 250.IX Header "GLOBAL FUNCTIONS"
181These functions can be called anytime, even before initialising the 251These functions can be called anytime, even before initialising the
182library in any way. 252library in any way.
183.IP "ev_tstamp ev_time ()" 4 253.IP "ev_tstamp ev_time ()" 4
… …
189.IX Item "int ev_version_major ()" 259.IX Item "int ev_version_major ()"
190.PD 0 260.PD 0
191.IP "int ev_version_minor ()" 4 261.IP "int ev_version_minor ()" 4
192.IX Item "int ev_version_minor ()" 262.IX Item "int ev_version_minor ()"
193.PD 263.PD
194You can find out the major and minor version numbers of the library 264You can find out the major and minor \s-1API/ABI\s0 version numbers of the library
195you linked against by calling the functions \f(CW\*(C`ev_version_major\*(C'\fR and 265you linked against by calling the functions \f(CW\*(C`ev_version_major\*(C'\fR and
196\&\f(CW\*(C`ev_version_minor\*(C'\fR. If you want, you can compare against the global 266\&\f(CW\*(C`ev_version_minor\*(C'\fR. If you want, you can compare against the global
197symbols \f(CW\*(C`EV_VERSION_MAJOR\*(C'\fR and \f(CW\*(C`EV_VERSION_MINOR\*(C'\fR, which specify the 267symbols \f(CW\*(C`EV_VERSION_MAJOR\*(C'\fR and \f(CW\*(C`EV_VERSION_MINOR\*(C'\fR, which specify the
198version of the library your program was compiled against. 268version of the library your program was compiled against.
199.Sp 269.Sp
270These version numbers refer to the \s-1API\s0 and \s-1ABI\s0 version of the library, not
271the release version.
272.Sp
200Usually, it's a good idea to terminate if the major versions mismatch, 273Usually, it's a good idea to terminate if the major versions mismatch,
201as this indicates an incompatible change. Minor versions are usually 274as this indicates an incompatible change. Minor versions are usually
202compatible to older versions, so a larger minor version alone is usually 275compatible to older versions, so a larger minor version alone is usually
203not a problem. 276not a problem.
277.Sp
278Example: Make sure we haven't accidentally been linked against the wrong
279version.
280.Sp
281.Vb 3
282\& assert (("libev version mismatch",
283\& ev_version_major () == EV_VERSION_MAJOR
284\& && ev_version_minor () >= EV_VERSION_MINOR));
285.Ve
204.IP "unsigned int ev_supported_backends ()" 4 286.IP "unsigned int ev_supported_backends ()" 4
205.IX Item "unsigned int ev_supported_backends ()" 287.IX Item "unsigned int ev_supported_backends ()"
206Return the set of all backends (i.e. their corresponding \f(CW\*(C`EV_BACKEND_*\*(C'\fR 288Return the set of all backends (i.e. their corresponding \f(CW\*(C`EV_BACKEND_*\*(C'\fR
207value) compiled into this binary of libev (independent of their 289value) compiled into this binary of libev (independent of their
208availability on the system you are running on). See \f(CW\*(C`ev_default_loop\*(C'\fR for 290availability on the system you are running on). See \f(CW\*(C`ev_default_loop\*(C'\fR for
209a description of the set values. 291a description of the set values.
292.Sp
293Example: make sure we have the epoll method, because yeah this is cool and
294a must have and can we have a torrent of it please!!!11
295.Sp
296.Vb 2
297\& assert (("sorry, no epoll, no sex",
298\& ev_supported_backends () & EVBACKEND_EPOLL));
299.Ve
210.IP "unsigned int ev_recommended_backends ()" 4 300.IP "unsigned int ev_recommended_backends ()" 4
211.IX Item "unsigned int ev_recommended_backends ()" 301.IX Item "unsigned int ev_recommended_backends ()"
212Return the set of all backends compiled into this binary of libev and also 302Return the set of all backends compiled into this binary of libev and also
213recommended for this platform. This set is often smaller than the one 303recommended for this platform. This set is often smaller than the one
214returned by \f(CW\*(C`ev_supported_backends\*(C'\fR, as for example kqueue is broken on 304returned by \f(CW\*(C`ev_supported_backends\*(C'\fR, as for example kqueue is broken on
215most BSDs and will not be autodetected unless you explicitly request it 305most BSDs and will not be autodetected unless you explicitly request it
216(assuming you know what you are doing). This is the set of backends that 306(assuming you know what you are doing). This is the set of backends that
217\&\f(CW\*(C`EVFLAG_AUTO\*(C'\fR will probe for. 307libev will probe for if you specify no backends explicitly.
308.IP "unsigned int ev_embeddable_backends ()" 4
309.IX Item "unsigned int ev_embeddable_backends ()"
310Returns the set of backends that are embeddable in other event loops. This
311is the theoretical, all\-platform, value. To find which backends
312might be supported on the current system, you would need to look at
313\&\f(CW\*(C`ev_embeddable_backends () & ev_supported_backends ()\*(C'\fR, likewise for
314recommended ones.
315.Sp
316See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info.
218.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4 317.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4
219.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))" 318.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))"
220Sets the allocation function to use (the prototype is similar to the 319Sets the allocation function to use (the prototype is similar \- the
221realloc C function, the semantics are identical). It is used to allocate 320semantics is identical \- to the realloc C function). It is used to
222and free memory (no surprises here). If it returns zero when memory 321allocate and free memory (no surprises here). If it returns zero when
223needs to be allocated, the library might abort or take some potentially 322memory needs to be allocated, the library might abort or take some
224destructive action. The default is your system realloc function. 323potentially destructive action. The default is your system realloc
324function.
225.Sp 325.Sp
226You could override this function in high-availability programs to, say, 326You could override this function in high-availability programs to, say,
227free some memory if it cannot allocate memory, to use a special allocator, 327free some memory if it cannot allocate memory, to use a special allocator,
228or even to sleep a while and retry until some memory is available. 328or even to sleep a while and retry until some memory is available.
329.Sp
330Example: Replace the libev allocator with one that waits a bit and then
331retries).
332.Sp
333.Vb 6
334\& static void *
335\& persistent_realloc (void *ptr, size_t size)
336\& {
337\& for (;;)
338\& {
339\& void *newptr = realloc (ptr, size);
340.Ve
341.Sp
342.Vb 2
343\& if (newptr)
344\& return newptr;
345.Ve
346.Sp
347.Vb 3
348\& sleep (60);
349\& }
350\& }
351.Ve
352.Sp
353.Vb 2
354\& ...
355\& ev_set_allocator (persistent_realloc);
356.Ve
229.IP "ev_set_syserr_cb (void (*cb)(const char *msg));" 4 357.IP "ev_set_syserr_cb (void (*cb)(const char *msg));" 4
230.IX Item "ev_set_syserr_cb (void (*cb)(const char *msg));" 358.IX Item "ev_set_syserr_cb (void (*cb)(const char *msg));"
231Set the callback function to call on a retryable syscall error (such 359Set the callback function to call on a retryable syscall error (such
232as failed select, poll, epoll_wait). The message is a printable string 360as failed select, poll, epoll_wait). The message is a printable string
233indicating the system call or subsystem causing the problem. If this 361indicating the system call or subsystem causing the problem. If this
234callback is set, then libev will expect it to remedy the sitution, no 362callback is set, then libev will expect it to remedy the sitution, no
235matter what, when it returns. That is, libev will generally retry the 363matter what, when it returns. That is, libev will generally retry the
236requested operation, or, if the condition doesn't go away, do bad stuff 364requested operation, or, if the condition doesn't go away, do bad stuff
237(such as abort). 365(such as abort).
366.Sp
367Example: This is basically the same thing that libev does internally, too.
368.Sp
369.Vb 6
370\& static void
371\& fatal_error (const char *msg)
372\& {
373\& perror (msg);
374\& abort ();
375\& }
376.Ve
377.Sp
378.Vb 2
379\& ...
380\& ev_set_syserr_cb (fatal_error);
381.Ve
238.SH "FUNCTIONS CONTROLLING THE EVENT LOOP" 382.SH "FUNCTIONS CONTROLLING THE EVENT LOOP"
239.IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP" 383.IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP"
240An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR. The library knows two 384An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR. The library knows two
241types of such loops, the \fIdefault\fR loop, which supports signals and child 385types of such loops, the \fIdefault\fR loop, which supports signals and child
242events, and dynamically created loops which do not. 386events, and dynamically created loops which do not.
… …
256.Sp 400.Sp
257If you don't know what event loop to use, use the one returned from this 401If you don't know what event loop to use, use the one returned from this
258function. 402function.
259.Sp 403.Sp
260The flags argument can be used to specify special behaviour or specific 404The flags argument can be used to specify special behaviour or specific
261backends to use, and is usually specified as \f(CW0\fR (or \s-1EVFLAG_AUTO\s0). 405backends to use, and is usually specified as \f(CW0\fR (or \f(CW\*(C`EVFLAG_AUTO\*(C'\fR).
262.Sp 406.Sp
263It supports the following flags: 407The following flags are supported:
264.RS 4 408.RS 4
265.ie n .IP """EVFLAG_AUTO""" 4 409.ie n .IP """EVFLAG_AUTO""" 4
266.el .IP "\f(CWEVFLAG_AUTO\fR" 4 410.el .IP "\f(CWEVFLAG_AUTO\fR" 4
267.IX Item "EVFLAG_AUTO" 411.IX Item "EVFLAG_AUTO"
268The default flags value. Use this if you have no clue (it's the right 412The default flags value. Use this if you have no clue (it's the right
… …
274or setgid) then libev will \fInot\fR look at the environment variable 418or setgid) then libev will \fInot\fR look at the environment variable
275\&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will 419\&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will
276override the flags completely if it is found in the environment. This is 420override the flags completely if it is found in the environment. This is
277useful to try out specific backends to test their performance, or to work 421useful to try out specific backends to test their performance, or to work
278around bugs. 422around bugs.
423.ie n .IP """EVFLAG_FORKCHECK""" 4
424.el .IP "\f(CWEVFLAG_FORKCHECK\fR" 4
425.IX Item "EVFLAG_FORKCHECK"
426Instead of calling \f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR manually after
427a fork, you can also make libev check for a fork in each iteration by
428enabling this flag.
429.Sp
430This works by calling \f(CW\*(C`getpid ()\*(C'\fR on every iteration of the loop,
431and thus this might slow down your event loop if you do a lot of loop
432iterations and little real work, but is usually not noticeable (on my
433Linux system for example, \f(CW\*(C`getpid\*(C'\fR is actually a simple 5\-insn sequence
434without a syscall and thus \fIvery\fR fast, but my Linux system also has
435\&\f(CW\*(C`pthread_atfork\*(C'\fR which is even faster).
436.Sp
437The big advantage of this flag is that you can forget about fork (and
438forget about forgetting to tell libev about forking) when you use this
439flag.
440.Sp
441This flag setting cannot be overriden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR
442environment variable.
279.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4 443.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4
280.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4 444.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4
281.IX Item "EVBACKEND_SELECT (value 1, portable select backend)" 445.IX Item "EVBACKEND_SELECT (value 1, portable select backend)"
282This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as 446This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as
283libev tries to roll its own fd_set with no limits on the number of fds, 447libev tries to roll its own fd_set with no limits on the number of fds,
… …
302While stopping and starting an I/O watcher in the same iteration will 466While stopping and starting an I/O watcher in the same iteration will
303result in some caching, there is still a syscall per such incident 467result in some caching, there is still a syscall per such incident
304(because the fd could point to a different file description now), so its 468(because the fd could point to a different file description now), so its
305best to avoid that. Also, \fIdup()\fRed file descriptors might not work very 469best to avoid that. Also, \fIdup()\fRed file descriptors might not work very
306well if you register events for both fds. 470well if you register events for both fds.
471.Sp
472Please note that epoll sometimes generates spurious notifications, so you
473need to use non-blocking I/O or other means to avoid blocking when no data
474(or space) is available.
307.ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4 475.ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4
308.el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4 476.el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4
309.IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)" 477.IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)"
310Kqueue deserves special mention, as at the time of this writing, it 478Kqueue deserves special mention, as at the time of this writing, it
311was broken on all BSDs except NetBSD (usually it doesn't work with 479was broken on all BSDs except NetBSD (usually it doesn't work with
312anything but sockets and pipes, except on Darwin, where of course its 480anything but sockets and pipes, except on Darwin, where of course its
313completely useless). For this reason its not being \*(L"autodetected\*(R" unless 481completely useless). For this reason its not being \*(L"autodetected\*(R"
314you explicitly specify the flags (i.e. you don't use \s-1EVFLAG_AUTO\s0). 482unless you explicitly specify it explicitly in the flags (i.e. using
483\&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR).
315.Sp 484.Sp
316It scales in the same way as the epoll backend, but the interface to the 485It scales in the same way as the epoll backend, but the interface to the
317kernel is more efficient (which says nothing about its actual speed, of 486kernel is more efficient (which says nothing about its actual speed, of
318course). While starting and stopping an I/O watcher does not cause an 487course). While starting and stopping an I/O watcher does not cause an
319extra syscall as with epoll, it still adds up to four event changes per 488extra syscall as with epoll, it still adds up to four event changes per
… …
325.ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4 494.ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4
326.el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4 495.el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4
327.IX Item "EVBACKEND_PORT (value 32, Solaris 10)" 496.IX Item "EVBACKEND_PORT (value 32, Solaris 10)"
328This uses the Solaris 10 port mechanism. As with everything on Solaris, 497This uses the Solaris 10 port mechanism. As with everything on Solaris,
329it's really slow, but it still scales very well (O(active_fds)). 498it's really slow, but it still scales very well (O(active_fds)).
499.Sp
500Please note that solaris ports can result in a lot of spurious
501notifications, so you need to use non-blocking I/O or other means to avoid
502blocking when no data (or space) is available.
330.ie n .IP """EVBACKEND_ALL""" 4 503.ie n .IP """EVBACKEND_ALL""" 4
331.el .IP "\f(CWEVBACKEND_ALL\fR" 4 504.el .IP "\f(CWEVBACKEND_ALL\fR" 4
332.IX Item "EVBACKEND_ALL" 505.IX Item "EVBACKEND_ALL"
333Try all backends (even potentially broken ones that wouldn't be tried 506Try all backends (even potentially broken ones that wouldn't be tried
334with \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). Since this is a mask, you can do stuff such as 507with \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). Since this is a mask, you can do stuff such as
… …
338.Sp 511.Sp
339If one or more of these are ored into the flags value, then only these 512If one or more of these are ored into the flags value, then only these
340backends will be tried (in the reverse order as given here). If none are 513backends will be tried (in the reverse order as given here). If none are
341specified, most compiled-in backend will be tried, usually in reverse 514specified, most compiled-in backend will be tried, usually in reverse
342order of their flag values :) 515order of their flag values :)
516.Sp
517The most typical usage is like this:
518.Sp
519.Vb 2
520\& if (!ev_default_loop (0))
521\& fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
522.Ve
523.Sp
524Restrict libev to the select and poll backends, and do not allow
525environment settings to be taken into account:
526.Sp
527.Vb 1
528\& ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
529.Ve
530.Sp
531Use whatever libev has to offer, but make sure that kqueue is used if
532available (warning, breaks stuff, best use only with your own private
533event loop and only if you know the \s-1OS\s0 supports your types of fds):
534.Sp
535.Vb 1
536\& ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
537.Ve
343.RE 538.RE
344.IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4 539.IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4
345.IX Item "struct ev_loop *ev_loop_new (unsigned int flags)" 540.IX Item "struct ev_loop *ev_loop_new (unsigned int flags)"
346Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is 541Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is
347always distinct from the default loop. Unlike the default loop, it cannot 542always distinct from the default loop. Unlike the default loop, it cannot
348handle signal and child watchers, and attempts to do so will be greeted by 543handle signal and child watchers, and attempts to do so will be greeted by
349undefined behaviour (or a failed assertion if assertions are enabled). 544undefined behaviour (or a failed assertion if assertions are enabled).
545.Sp
546Example: Try to create a event loop that uses epoll and nothing else.
547.Sp
548.Vb 3
549\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
550\& if (!epoller)
551\& fatal ("no epoll found here, maybe it hides under your chair");
552.Ve
350.IP "ev_default_destroy ()" 4 553.IP "ev_default_destroy ()" 4
351.IX Item "ev_default_destroy ()" 554.IX Item "ev_default_destroy ()"
352Destroys the default loop again (frees all memory and kernel state 555Destroys the default loop again (frees all memory and kernel state
353etc.). This stops all registered event watchers (by not touching them in 556etc.). None of the active event watchers will be stopped in the normal
354any way whatsoever, although you cannot rely on this :). 557sense, so e.g. \f(CW\*(C`ev_is_active\*(C'\fR might still return true. It is your
558responsibility to either stop all watchers cleanly yoursef \fIbefore\fR
559calling this function, or cope with the fact afterwards (which is usually
560the easiest thing, youc na just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them
561for example).
355.IP "ev_loop_destroy (loop)" 4 562.IP "ev_loop_destroy (loop)" 4
356.IX Item "ev_loop_destroy (loop)" 563.IX Item "ev_loop_destroy (loop)"
357Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an 564Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an
358earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR. 565earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR.
359.IP "ev_default_fork ()" 4 566.IP "ev_default_fork ()" 4
… …
381.IP "ev_loop_fork (loop)" 4 588.IP "ev_loop_fork (loop)" 4
382.IX Item "ev_loop_fork (loop)" 589.IX Item "ev_loop_fork (loop)"
383Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by 590Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by
384\&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop 591\&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop
385after fork, and how you do this is entirely your own problem. 592after fork, and how you do this is entirely your own problem.
593.IP "unsigned int ev_loop_count (loop)" 4
594.IX Item "unsigned int ev_loop_count (loop)"
595Returns the count of loop iterations for the loop, which is identical to
596the number of times libev did poll for new events. It starts at \f(CW0\fR and
597happily wraps around with enough iterations.
598.Sp
599This value can sometimes be useful as a generation counter of sorts (it
600\&\*(L"ticks\*(R" the number of loop iterations), as it roughly corresponds with
601\&\f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR calls.
386.IP "unsigned int ev_backend (loop)" 4 602.IP "unsigned int ev_backend (loop)" 4
387.IX Item "unsigned int ev_backend (loop)" 603.IX Item "unsigned int ev_backend (loop)"
388Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in 604Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in
389use. 605use.
390.IP "ev_tstamp ev_now (loop)" 4 606.IP "ev_tstamp ev_now (loop)" 4
391.IX Item "ev_tstamp ev_now (loop)" 607.IX Item "ev_tstamp ev_now (loop)"
392Returns the current \*(L"event loop time\*(R", which is the time the event loop 608Returns the current \*(L"event loop time\*(R", which is the time the event loop
393got events and started processing them. This timestamp does not change 609received events and started processing them. This timestamp does not
394as long as callbacks are being processed, and this is also the base time 610change as long as callbacks are being processed, and this is also the base
395used for relative timers. You can treat it as the timestamp of the event 611time used for relative timers. You can treat it as the timestamp of the
396occuring (or more correctly, the mainloop finding out about it). 612event occuring (or more correctly, libev finding out about it).
397.IP "ev_loop (loop, int flags)" 4 613.IP "ev_loop (loop, int flags)" 4
398.IX Item "ev_loop (loop, int flags)" 614.IX Item "ev_loop (loop, int flags)"
399Finally, this is it, the event handler. This function usually is called 615Finally, this is it, the event handler. This function usually is called
400after you initialised all your watchers and you want to start handling 616after you initialised all your watchers and you want to start handling
401events. 617events.
402.Sp 618.Sp
403If the flags argument is specified as 0, it will not return until either 619If the flags argument is specified as \f(CW0\fR, it will not return until
404no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called. 620either no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called.
621.Sp
622Please note that an explicit \f(CW\*(C`ev_unloop\*(C'\fR is usually better than
623relying on all watchers to be stopped when deciding when a program has
624finished (especially in interactive programs), but having a program that
625automatically loops as long as it has to and no longer by virtue of
626relying on its watchers stopping correctly is a thing of beauty.
405.Sp 627.Sp
406A flags value of \f(CW\*(C`EVLOOP_NONBLOCK\*(C'\fR will look for new events, will handle 628A flags value of \f(CW\*(C`EVLOOP_NONBLOCK\*(C'\fR will look for new events, will handle
407those events and any outstanding ones, but will not block your process in 629those events and any outstanding ones, but will not block your process in
408case there are no events and will return after one iteration of the loop. 630case there are no events and will return after one iteration of the loop.
409.Sp 631.Sp
410A flags value of \f(CW\*(C`EVLOOP_ONESHOT\*(C'\fR will look for new events (waiting if 632A flags value of \f(CW\*(C`EVLOOP_ONESHOT\*(C'\fR will look for new events (waiting if
411neccessary) and will handle those and any outstanding ones. It will block 633neccessary) and will handle those and any outstanding ones. It will block
412your process until at least one new event arrives, and will return after 634your process until at least one new event arrives, and will return after
413one iteration of the loop. 635one iteration of the loop. This is useful if you are waiting for some
636external event in conjunction with something not expressible using other
637libev watchers. However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is
638usually a better approach for this kind of thing.
414.Sp 639.Sp
415This flags value could be used to implement alternative looping
416constructs, but the \f(CW\*(C`prepare\*(C'\fR and \f(CW\*(C`check\*(C'\fR watchers provide a better and
417more generic mechanism.
418.Sp
419Here are the gory details of what ev_loop does: 640Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does:
420.Sp 641.Sp
421.Vb 15 642.Vb 19
643\& - Before the first iteration, call any pending watchers.
422\& 1. If there are no active watchers (reference count is zero), return. 644\& * If there are no active watchers (reference count is zero), return.
423\& 2. Queue and immediately call all prepare watchers. 645\& - Queue all prepare watchers and then call all outstanding watchers.
424\& 3. If we have been forked, recreate the kernel state. 646\& - If we have been forked, recreate the kernel state.
425\& 4. Update the kernel state with all outstanding changes. 647\& - Update the kernel state with all outstanding changes.
426\& 5. Update the "event loop time". 648\& - Update the "event loop time".
427\& 6. Calculate for how long to block. 649\& - Calculate for how long to block.
428\& 7. Block the process, waiting for events. 650\& - Block the process, waiting for any events.
651\& - Queue all outstanding I/O (fd) events.
429\& 8. Update the "event loop time" and do time jump handling. 652\& - Update the "event loop time" and do time jump handling.
430\& 9. Queue all outstanding timers. 653\& - Queue all outstanding timers.
431\& 10. Queue all outstanding periodics. 654\& - Queue all outstanding periodics.
432\& 11. If no events are pending now, queue all idle watchers. 655\& - If no events are pending now, queue all idle watchers.
433\& 12. Queue all check watchers. 656\& - Queue all check watchers.
434\& 13. Call all queued watchers in reverse order (i.e. check watchers first). 657\& - Call all queued watchers in reverse order (i.e. check watchers first).
658\& Signals and child watchers are implemented as I/O watchers, and will
659\& be handled here by queueing them when their watcher gets executed.
435\& 14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 660\& - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
436\& was used, return, otherwise continue with step #1. 661\& were used, return, otherwise continue with step *.
662.Ve
663.Sp
664Example: Queue some jobs and then loop until no events are outsanding
665anymore.
666.Sp
667.Vb 4
668\& ... queue jobs here, make sure they register event watchers as long
669\& ... as they still have work to do (even an idle watcher will do..)
670\& ev_loop (my_loop, 0);
671\& ... jobs done. yeah!
437.Ve 672.Ve
438.IP "ev_unloop (loop, how)" 4 673.IP "ev_unloop (loop, how)" 4
439.IX Item "ev_unloop (loop, how)" 674.IX Item "ev_unloop (loop, how)"
440Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it 675Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it
441has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either 676has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either
… …
455example, libev itself uses this for its internal signal pipe: It is not 690example, libev itself uses this for its internal signal pipe: It is not
456visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if 691visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if
457no event watchers registered by it are active. It is also an excellent 692no event watchers registered by it are active. It is also an excellent
458way to do this for generic recurring timers or from within third-party 693way to do this for generic recurring timers or from within third-party
459libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR. 694libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR.
695.Sp
696Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR
697running when nothing else is active.
698.Sp
699.Vb 4
700\& struct ev_signal exitsig;
701\& ev_signal_init (&exitsig, sig_cb, SIGINT);
702\& ev_signal_start (loop, &exitsig);
703\& evf_unref (loop);
704.Ve
705.Sp
706Example: For some weird reason, unregister the above signal handler again.
707.Sp
708.Vb 2
709\& ev_ref (loop);
710\& ev_signal_stop (loop, &exitsig);
711.Ve
460.SH "ANATOMY OF A WATCHER" 712.SH "ANATOMY OF A WATCHER"
461.IX Header "ANATOMY OF A WATCHER" 713.IX Header "ANATOMY OF A WATCHER"
462A watcher is a structure that you create and register to record your 714A watcher is a structure that you create and register to record your
463interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to 715interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to
464become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that: 716become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that:
… …
500*)\*(C'\fR), and you can stop watching for events at any time by calling the 752*)\*(C'\fR), and you can stop watching for events at any time by calling the
501corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR. 753corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR.
502.PP 754.PP
503As long as your watcher is active (has been started but not stopped) you 755As long as your watcher is active (has been started but not stopped) you
504must not touch the values stored in it. Most specifically you must never 756must not touch the values stored in it. Most specifically you must never
505reinitialise it or call its set macro. 757reinitialise it or call its \f(CW\*(C`set\*(C'\fR macro.
506.PP
507You can check whether an event is active by calling the \f(CW\*(C`ev_is_active
508(watcher *)\*(C'\fR macro. To see whether an event is outstanding (but the
509callback for it has not been called yet) you can use the \f(CW\*(C`ev_is_pending
510(watcher *)\*(C'\fR macro.
511.PP 758.PP
512Each and every callback receives the event loop pointer as first, the 759Each and every callback receives the event loop pointer as first, the
513registered watcher structure as second, and a bitset of received events as 760registered watcher structure as second, and a bitset of received events as
514third argument. 761third argument.
515.PP 762.PP
… …
540The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread. 787The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread.
541.ie n .IP """EV_CHILD""" 4 788.ie n .IP """EV_CHILD""" 4
542.el .IP "\f(CWEV_CHILD\fR" 4 789.el .IP "\f(CWEV_CHILD\fR" 4
543.IX Item "EV_CHILD" 790.IX Item "EV_CHILD"
544The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change. 791The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change.
792.ie n .IP """EV_STAT""" 4
793.el .IP "\f(CWEV_STAT\fR" 4
794.IX Item "EV_STAT"
795The path specified in the \f(CW\*(C`ev_stat\*(C'\fR watcher changed its attributes somehow.
545.ie n .IP """EV_IDLE""" 4 796.ie n .IP """EV_IDLE""" 4
546.el .IP "\f(CWEV_IDLE\fR" 4 797.el .IP "\f(CWEV_IDLE\fR" 4
547.IX Item "EV_IDLE" 798.IX Item "EV_IDLE"
548The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do. 799The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do.
549.ie n .IP """EV_PREPARE""" 4 800.ie n .IP """EV_PREPARE""" 4
… …
559\&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any 810\&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any
560received events. Callbacks of both watcher types can start and stop as 811received events. Callbacks of both watcher types can start and stop as
561many watchers as they want, and all of them will be taken into account 812many watchers as they want, and all of them will be taken into account
562(for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep 813(for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep
563\&\f(CW\*(C`ev_loop\*(C'\fR from blocking). 814\&\f(CW\*(C`ev_loop\*(C'\fR from blocking).
815.ie n .IP """EV_EMBED""" 4
816.el .IP "\f(CWEV_EMBED\fR" 4
817.IX Item "EV_EMBED"
818The embedded event loop specified in the \f(CW\*(C`ev_embed\*(C'\fR watcher needs attention.
819.ie n .IP """EV_FORK""" 4
820.el .IP "\f(CWEV_FORK\fR" 4
821.IX Item "EV_FORK"
822The event loop has been resumed in the child process after fork (see
823\&\f(CW\*(C`ev_fork\*(C'\fR).
564.ie n .IP """EV_ERROR""" 4 824.ie n .IP """EV_ERROR""" 4
565.el .IP "\f(CWEV_ERROR\fR" 4 825.el .IP "\f(CWEV_ERROR\fR" 4
566.IX Item "EV_ERROR" 826.IX Item "EV_ERROR"
567An unspecified error has occured, the watcher has been stopped. This might 827An unspecified error has occured, the watcher has been stopped. This might
568happen because the watcher could not be properly started because libev 828happen because the watcher could not be properly started because libev
… …
573Libev will usually signal a few \*(L"dummy\*(R" events together with an error, 833Libev will usually signal a few \*(L"dummy\*(R" events together with an error,
574for example it might indicate that a fd is readable or writable, and if 834for example it might indicate that a fd is readable or writable, and if
575your callbacks is well-written it can just attempt the operation and cope 835your callbacks is well-written it can just attempt the operation and cope
576with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded 836with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded
577programs, though, so beware. 837programs, though, so beware.
838.Sh "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0"
839.IX Subsection "GENERIC WATCHER FUNCTIONS"
840In the following description, \f(CW\*(C`TYPE\*(C'\fR stands for the watcher type,
841e.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.
842.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4
843.el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4
844.IX Item "ev_init (ev_TYPE *watcher, callback)"
845This macro initialises the generic portion of a watcher. The contents
846of the watcher object can be arbitrary (so \f(CW\*(C`malloc\*(C'\fR will do). Only
847the generic parts of the watcher are initialised, you \fIneed\fR to call
848the type-specific \f(CW\*(C`ev_TYPE_set\*(C'\fR macro afterwards to initialise the
849type-specific parts. For each type there is also a \f(CW\*(C`ev_TYPE_init\*(C'\fR macro
850which rolls both calls into one.
851.Sp
852You can reinitialise a watcher at any time as long as it has been stopped
853(or never started) and there are no pending events outstanding.
854.Sp
855The callback is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher,
856int revents)\*(C'\fR.
857.ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4
858.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4
859.IX Item "ev_TYPE_set (ev_TYPE *, [args])"
860This macro initialises the type-specific parts of a watcher. You need to
861call \f(CW\*(C`ev_init\*(C'\fR at least once before you call this macro, but you can
862call \f(CW\*(C`ev_TYPE_set\*(C'\fR any number of times. You must not, however, call this
863macro on a watcher that is active (it can be pending, however, which is a
864difference to the \f(CW\*(C`ev_init\*(C'\fR macro).
865.Sp
866Although some watcher types do not have type-specific arguments
867(e.g. \f(CW\*(C`ev_prepare\*(C'\fR) you still need to call its \f(CW\*(C`set\*(C'\fR macro.
868.ie n .IP """ev_TYPE_init"" (ev_TYPE *watcher, callback, [args])" 4
869.el .IP "\f(CWev_TYPE_init\fR (ev_TYPE *watcher, callback, [args])" 4
870.IX Item "ev_TYPE_init (ev_TYPE *watcher, callback, [args])"
871This convinience macro rolls both \f(CW\*(C`ev_init\*(C'\fR and \f(CW\*(C`ev_TYPE_set\*(C'\fR macro
872calls into a single call. This is the most convinient method to initialise
873a watcher. The same limitations apply, of course.
874.ie n .IP """ev_TYPE_start"" (loop *, ev_TYPE *watcher)" 4
875.el .IP "\f(CWev_TYPE_start\fR (loop *, ev_TYPE *watcher)" 4
876.IX Item "ev_TYPE_start (loop *, ev_TYPE *watcher)"
877Starts (activates) the given watcher. Only active watchers will receive
878events. If the watcher is already active nothing will happen.
879.ie n .IP """ev_TYPE_stop"" (loop *, ev_TYPE *watcher)" 4
880.el .IP "\f(CWev_TYPE_stop\fR (loop *, ev_TYPE *watcher)" 4
881.IX Item "ev_TYPE_stop (loop *, ev_TYPE *watcher)"
882Stops the given watcher again (if active) and clears the pending
883status. It is possible that stopped watchers are pending (for example,
884non-repeating timers are being stopped when they become pending), but
885\&\f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor pending. If
886you want to free or reuse the memory used by the watcher it is therefore a
887good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function.
888.IP "bool ev_is_active (ev_TYPE *watcher)" 4
889.IX Item "bool ev_is_active (ev_TYPE *watcher)"
890Returns a true value iff the watcher is active (i.e. it has been started
891and not yet been stopped). As long as a watcher is active you must not modify
892it.
893.IP "bool ev_is_pending (ev_TYPE *watcher)" 4
894.IX Item "bool ev_is_pending (ev_TYPE *watcher)"
895Returns a true value iff the watcher is pending, (i.e. it has outstanding
896events but its callback has not yet been invoked). As long as a watcher
897is pending (but not active) you must not call an init function on it (but
898\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe), you must not change its priority, and you must
899make sure the watcher is available to libev (e.g. you cannot \f(CW\*(C`free ()\*(C'\fR
900it).
901.IP "callback ev_cb (ev_TYPE *watcher)" 4
902.IX Item "callback ev_cb (ev_TYPE *watcher)"
903Returns the callback currently set on the watcher.
904.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4
905.IX Item "ev_cb_set (ev_TYPE *watcher, callback)"
906Change the callback. You can change the callback at virtually any time
907(modulo threads).
908.IP "ev_set_priority (ev_TYPE *watcher, priority)" 4
909.IX Item "ev_set_priority (ev_TYPE *watcher, priority)"
910.PD 0
911.IP "int ev_priority (ev_TYPE *watcher)" 4
912.IX Item "int ev_priority (ev_TYPE *watcher)"
913.PD
914Set and query the priority of the watcher. The priority is a small
915integer between \f(CW\*(C`EV_MAXPRI\*(C'\fR (default: \f(CW2\fR) and \f(CW\*(C`EV_MINPRI\*(C'\fR
916(default: \f(CW\*(C`\-2\*(C'\fR). Pending watchers with higher priority will be invoked
917before watchers with lower priority, but priority will not keep watchers
918from being executed (except for \f(CW\*(C`ev_idle\*(C'\fR watchers).
919.Sp
920This means that priorities are \fIonly\fR used for ordering callback
921invocation after new events have been received. This is useful, for
922example, to reduce latency after idling, or more often, to bind two
923watchers on the same event and make sure one is called first.
924.Sp
925If you need to suppress invocation when higher priority events are pending
926you need to look at \f(CW\*(C`ev_idle\*(C'\fR watchers, which provide this functionality.
927.Sp
928You \fImust not\fR change the priority of a watcher as long as it is active or
929pending.
930.Sp
931The default priority used by watchers when no priority has been set is
932always \f(CW0\fR, which is supposed to not be too high and not be too low :).
933.Sp
934Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR is
935fine, as long as you do not mind that the priority value you query might
936or might not have been adjusted to be within valid range.
937.IP "ev_invoke (loop, ev_TYPE *watcher, int revents)" 4
938.IX Item "ev_invoke (loop, ev_TYPE *watcher, int revents)"
939Invoke the \f(CW\*(C`watcher\*(C'\fR with the given \f(CW\*(C`loop\*(C'\fR and \f(CW\*(C`revents\*(C'\fR. Neither
940\&\f(CW\*(C`loop\*(C'\fR nor \f(CW\*(C`revents\*(C'\fR need to be valid as long as the watcher callback
941can deal with that fact.
942.IP "int ev_clear_pending (loop, ev_TYPE *watcher)" 4
943.IX Item "int ev_clear_pending (loop, ev_TYPE *watcher)"
944If the watcher is pending, this function returns clears its pending status
945and returns its \f(CW\*(C`revents\*(C'\fR bitset (as if its callback was invoked). If the
946watcher isn't pending it does nothing and returns \f(CW0\fR.
578.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0" 947.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0"
579.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER" 948.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER"
580Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change 949Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change
581and read at any time, libev will completely ignore it. This can be used 950and read at any time, libev will completely ignore it. This can be used
582to associate arbitrary data with your watcher. If you need more data and 951to associate arbitrary data with your watcher. If you need more data and
… …
603\& struct my_io *w = (struct my_io *)w_; 972\& struct my_io *w = (struct my_io *)w_;
604\& ... 973\& ...
605\& } 974\& }
606.Ve 975.Ve
607.PP 976.PP
608More interesting and less C\-conformant ways of catsing your callback type 977More interesting and less C\-conformant ways of casting your callback type
609have been omitted.... 978instead have been omitted.
979.PP
980Another common scenario is having some data structure with multiple
981watchers:
982.PP
983.Vb 6
984\& struct my_biggy
985\& {
986\& int some_data;
987\& ev_timer t1;
988\& ev_timer t2;
989\& }
990.Ve
991.PP
992In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more complicated,
993you need to use \f(CW\*(C`offsetof\*(C'\fR:
994.PP
995.Vb 1
996\& #include <stddef.h>
997.Ve
998.PP
999.Vb 6
1000\& static void
1001\& t1_cb (EV_P_ struct ev_timer *w, int revents)
1002\& {
1003\& struct my_biggy big = (struct my_biggy *
1004\& (((char *)w) - offsetof (struct my_biggy, t1));
1005\& }
1006.Ve
1007.PP
1008.Vb 6
1009\& static void
1010\& t2_cb (EV_P_ struct ev_timer *w, int revents)
1011\& {
1012\& struct my_biggy big = (struct my_biggy *
1013\& (((char *)w) - offsetof (struct my_biggy, t2));
1014\& }
1015.Ve
610.SH "WATCHER TYPES" 1016.SH "WATCHER TYPES"
611.IX Header "WATCHER TYPES" 1017.IX Header "WATCHER TYPES"
612This section describes each watcher in detail, but will not repeat 1018This section describes each watcher in detail, but will not repeat
613information given in the last section. 1019information given in the last section. Any initialisation/set macros,
1020functions and members specific to the watcher type are explained.
1021.PP
1022Members are additionally marked with either \fI[read\-only]\fR, meaning that,
1023while the watcher is active, you can look at the member and expect some
1024sensible content, but you must not modify it (you can modify it while the
1025watcher is stopped to your hearts content), or \fI[read\-write]\fR, which
1026means you can expect it to have some sensible content while the watcher
1027is active, but you can also modify it. Modifying it may not do something
1028sensible or take immediate effect (or do anything at all), but libev will
1029not crash or malfunction in any way.
614.ie n .Sh """ev_io"" \- is this file descriptor readable or writable" 1030.ie n .Sh """ev_io"" \- is this file descriptor readable or writable?"
615.el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable" 1031.el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable?"
616.IX Subsection "ev_io - is this file descriptor readable or writable" 1032.IX Subsection "ev_io - is this file descriptor readable or writable?"
617I/O watchers check whether a file descriptor is readable or writable 1033I/O watchers check whether a file descriptor is readable or writable
618in each iteration of the event loop (This behaviour is called 1034in each iteration of the event loop, or, more precisely, when reading
619level-triggering because you keep receiving events as long as the 1035would not block the process and writing would at least be able to write
620condition persists. Remember you can stop the watcher if you don't want to 1036some data. This behaviour is called level-triggering because you keep
621act on the event and neither want to receive future events). 1037receiving events as long as the condition persists. Remember you can stop
1038the watcher if you don't want to act on the event and neither want to
1039receive future events.
622.PP 1040.PP
623In general you can register as many read and/or write event watchers per 1041In general you can register as many read and/or write event watchers per
624fd as you want (as long as you don't confuse yourself). Setting all file 1042fd as you want (as long as you don't confuse yourself). Setting all file
625descriptors to non-blocking mode is also usually a good idea (but not 1043descriptors to non-blocking mode is also usually a good idea (but not
626required if you know what you are doing). 1044required if you know what you are doing).
627.PP 1045.PP
628You have to be careful with dup'ed file descriptors, though. Some backends 1046You have to be careful with dup'ed file descriptors, though. Some backends
629(the linux epoll backend is a notable example) cannot handle dup'ed file 1047(the linux epoll backend is a notable example) cannot handle dup'ed file
630descriptors correctly if you register interest in two or more fds pointing 1048descriptors correctly if you register interest in two or more fds pointing
631to the same underlying file/socket etc. description (that is, they share 1049to the same underlying file/socket/etc. description (that is, they share
632the same underlying \*(L"file open\*(R"). 1050the same underlying \*(L"file open\*(R").
633.PP 1051.PP
634If you must do this, then force the use of a known-to-be-good backend 1052If you must do this, then force the use of a known-to-be-good backend
635(at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and 1053(at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and
636\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR). 1054\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR).
1055.PP
1056Another thing you have to watch out for is that it is quite easy to
1057receive \*(L"spurious\*(R" readyness notifications, that is your callback might
1058be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block
1059because there is no data. Not only are some backends known to create a
1060lot of those (for example solaris ports), it is very easy to get into
1061this situation even with a relatively standard program structure. Thus
1062it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning
1063\&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives.
1064.PP
1065If you cannot run the fd in non-blocking mode (for example you should not
1066play around with an Xlib connection), then you have to seperately re-test
1067whether a file descriptor is really ready with a known-to-be good interface
1068such as poll (fortunately in our Xlib example, Xlib already does this on
1069its own, so its quite safe to use).
637.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4 1070.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4
638.IX Item "ev_io_init (ev_io *, callback, int fd, int events)" 1071.IX Item "ev_io_init (ev_io *, callback, int fd, int events)"
639.PD 0 1072.PD 0
640.IP "ev_io_set (ev_io *, int fd, int events)" 4 1073.IP "ev_io_set (ev_io *, int fd, int events)" 4
641.IX Item "ev_io_set (ev_io *, int fd, int events)" 1074.IX Item "ev_io_set (ev_io *, int fd, int events)"
642.PD 1075.PD
643Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The fd is the file descriptor to rceeive 1076Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to
644events 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 | 1077rceeive events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or
645EV_WRITE\*(C'\fR to receive the given events. 1078\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR to receive the given events.
1079.IP "int fd [read\-only]" 4
1080.IX Item "int fd [read-only]"
1081The file descriptor being watched.
1082.IP "int events [read\-only]" 4
1083.IX Item "int events [read-only]"
1084The events being watched.
1085.PP
1086Example: Call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well
1087readable, but only once. Since it is likely line\-buffered, you could
1088attempt to read a whole line in the callback.
1089.PP
1090.Vb 6
1091\& static void
1092\& stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1093\& {
1094\& ev_io_stop (loop, w);
1095\& .. read from stdin here (or from w->fd) and haqndle any I/O errors
1096\& }
1097.Ve
1098.PP
1099.Vb 6
1100\& ...
1101\& struct ev_loop *loop = ev_default_init (0);
1102\& struct ev_io stdin_readable;
1103\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1104\& ev_io_start (loop, &stdin_readable);
1105\& ev_loop (loop, 0);
1106.Ve
646.ie n .Sh """ev_timer"" \- relative and optionally recurring timeouts" 1107.ie n .Sh """ev_timer"" \- relative and optionally repeating timeouts"
647.el .Sh "\f(CWev_timer\fP \- relative and optionally recurring timeouts" 1108.el .Sh "\f(CWev_timer\fP \- relative and optionally repeating timeouts"
648.IX Subsection "ev_timer - relative and optionally recurring timeouts" 1109.IX Subsection "ev_timer - relative and optionally repeating timeouts"
649Timer watchers are simple relative timers that generate an event after a 1110Timer watchers are simple relative timers that generate an event after a
650given time, and optionally repeating in regular intervals after that. 1111given time, and optionally repeating in regular intervals after that.
651.PP 1112.PP
652The timers are based on real time, that is, if you register an event that 1113The timers are based on real time, that is, if you register an event that
653times out after an hour and you reset your system clock to last years 1114times out after an hour and you reset your system clock to last years
… …
687.IP "ev_timer_again (loop)" 4 1148.IP "ev_timer_again (loop)" 4
688.IX Item "ev_timer_again (loop)" 1149.IX Item "ev_timer_again (loop)"
689This will act as if the timer timed out and restart it again if it is 1150This will act as if the timer timed out and restart it again if it is
690repeating. The exact semantics are: 1151repeating. The exact semantics are:
691.Sp 1152.Sp
1153If the timer is pending, its pending status is cleared.
1154.Sp
692If the timer is started but nonrepeating, stop it. 1155If the timer is started but nonrepeating, stop it (as if it timed out).
693.Sp 1156.Sp
694If the timer is repeating, either start it if necessary (with the repeat 1157If the timer is repeating, either start it if necessary (with the
695value), or reset the running timer to the repeat value. 1158\&\f(CW\*(C`repeat\*(C'\fR value), or reset the running timer to the \f(CW\*(C`repeat\*(C'\fR value.
696.Sp 1159.Sp
697This sounds a bit complicated, but here is a useful and typical 1160This sounds a bit complicated, but here is a useful and typical
698example: Imagine you have a tcp connection and you want a so-called idle 1161example: Imagine you have a tcp connection and you want a so-called idle
699timeout, that is, you want to be called when there have been, say, 60 1162timeout, that is, you want to be called when there have been, say, 60
700seconds of inactivity on the socket. The easiest way to do this is to 1163seconds of inactivity on the socket. The easiest way to do this is to
701configure an \f(CW\*(C`ev_timer\*(C'\fR with after=repeat=60 and calling ev_timer_again each 1164configure an \f(CW\*(C`ev_timer\*(C'\fR with a \f(CW\*(C`repeat\*(C'\fR value of \f(CW60\fR and then call
702time you successfully read or write some data. If you go into an idle 1165\&\f(CW\*(C`ev_timer_again\*(C'\fR each time you successfully read or write some data. If
703state where you do not expect data to travel on the socket, you can stop 1166you go into an idle state where you do not expect data to travel on the
704the timer, and again will automatically restart it if need be. 1167socket, you can \f(CW\*(C`ev_timer_stop\*(C'\fR the timer, and \f(CW\*(C`ev_timer_again\*(C'\fR will
1168automatically restart it if need be.
1169.Sp
1170That means you can ignore the \f(CW\*(C`after\*(C'\fR value and \f(CW\*(C`ev_timer_start\*(C'\fR
1171altogether and only ever use the \f(CW\*(C`repeat\*(C'\fR value and \f(CW\*(C`ev_timer_again\*(C'\fR:
1172.Sp
1173.Vb 8
1174\& ev_timer_init (timer, callback, 0., 5.);
1175\& ev_timer_again (loop, timer);
1176\& ...
1177\& timer->again = 17.;
1178\& ev_timer_again (loop, timer);
1179\& ...
1180\& timer->again = 10.;
1181\& ev_timer_again (loop, timer);
1182.Ve
1183.Sp
1184This is more slightly efficient then stopping/starting the timer each time
1185you want to modify its timeout value.
1186.IP "ev_tstamp repeat [read\-write]" 4
1187.IX Item "ev_tstamp repeat [read-write]"
1188The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out
1189or \f(CW\*(C`ev_timer_again\*(C'\fR is called and determines the next timeout (if any),
1190which is also when any modifications are taken into account.
1191.PP
1192Example: Create a timer that fires after 60 seconds.
1193.PP
1194.Vb 5
1195\& static void
1196\& one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1197\& {
1198\& .. one minute over, w is actually stopped right here
1199\& }
1200.Ve
1201.PP
1202.Vb 3
1203\& struct ev_timer mytimer;
1204\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1205\& ev_timer_start (loop, &mytimer);
1206.Ve
1207.PP
1208Example: Create a timeout timer that times out after 10 seconds of
1209inactivity.
1210.PP
1211.Vb 5
1212\& static void
1213\& timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1214\& {
1215\& .. ten seconds without any activity
1216\& }
1217.Ve
1218.PP
1219.Vb 4
1220\& struct ev_timer mytimer;
1221\& ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1222\& ev_timer_again (&mytimer); /* start timer */
1223\& ev_loop (loop, 0);
1224.Ve
1225.PP
1226.Vb 3
1227\& // and in some piece of code that gets executed on any "activity":
1228\& // reset the timeout to start ticking again at 10 seconds
1229\& ev_timer_again (&mytimer);
1230.Ve
705.ie n .Sh """ev_periodic"" \- to cron or not to cron" 1231.ie n .Sh """ev_periodic"" \- to cron or not to cron?"
706.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron" 1232.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron?"
707.IX Subsection "ev_periodic - to cron or not to cron" 1233.IX Subsection "ev_periodic - to cron or not to cron?"
708Periodic watchers are also timers of a kind, but they are very versatile 1234Periodic watchers are also timers of a kind, but they are very versatile
709(and unfortunately a bit complex). 1235(and unfortunately a bit complex).
710.PP 1236.PP
711Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time) 1237Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time)
712but on wallclock time (absolute time). You can tell a periodic watcher 1238but on wallclock time (absolute time). You can tell a periodic watcher
713to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a 1239to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a
714periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now () 1240periodic watcher to trigger in 10 seconds (by specifiying e.g. \f(CW\*(C`ev_now ()
715+ 10.>) and then reset your system clock to the last year, then it will 1241+ 10.\*(C'\fR) and then reset your system clock to the last year, then it will
716take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger 1242take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger
717roughly 10 seconds later and of course not if you reset your system time 1243roughly 10 seconds later).
718again).
719.PP 1244.PP
720They can also be used to implement vastly more complex timers, such as 1245They can also be used to implement vastly more complex timers, such as
721triggering an event on eahc midnight, local time. 1246triggering an event on each midnight, local time or other, complicated,
1247rules.
722.PP 1248.PP
723As with timers, the callback is guarenteed to be invoked only when the 1249As with timers, the callback is guarenteed to be invoked only when the
724time (\f(CW\*(C`at\*(C'\fR) has been passed, but if multiple periodic timers become ready 1250time (\f(CW\*(C`at\*(C'\fR) has been passed, but if multiple periodic timers become ready
725during the same loop iteration then order of execution is undefined. 1251during the same loop iteration then order of execution is undefined.
726.IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4 1252.IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4
… …
730.IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 1256.IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)"
731.PD 1257.PD
732Lots of arguments, lets sort it out... There are basically three modes of 1258Lots of arguments, lets sort it out... There are basically three modes of
733operation, and we will explain them from simplest to complex: 1259operation, and we will explain them from simplest to complex:
734.RS 4 1260.RS 4
735.IP "* absolute timer (interval = reschedule_cb = 0)" 4 1261.IP "* absolute timer (at = time, interval = reschedule_cb = 0)" 4
736.IX Item "absolute timer (interval = reschedule_cb = 0)" 1262.IX Item "absolute timer (at = time, interval = reschedule_cb = 0)"
737In this configuration the watcher triggers an event at the wallclock time 1263In this configuration the watcher triggers an event at the wallclock time
738\&\f(CW\*(C`at\*(C'\fR and doesn't repeat. It will not adjust when a time jump occurs, 1264\&\f(CW\*(C`at\*(C'\fR and doesn't repeat. It will not adjust when a time jump occurs,
739that is, if it is to be run at January 1st 2011 then it will run when the 1265that is, if it is to be run at January 1st 2011 then it will run when the
740system time reaches or surpasses this time. 1266system time reaches or surpasses this time.
741.IP "* non-repeating interval timer (interval > 0, reschedule_cb = 0)" 4 1267.IP "* non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)" 4
742.IX Item "non-repeating interval timer (interval > 0, reschedule_cb = 0)" 1268.IX Item "non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)"
743In this mode the watcher will always be scheduled to time out at the next 1269In this mode the watcher will always be scheduled to time out at the next
744\&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N) and then repeat, regardless 1270\&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N, which can also be negative)
745of any time jumps. 1271and then repeat, regardless of any time jumps.
746.Sp 1272.Sp
747This can be used to create timers that do not drift with respect to system 1273This can be used to create timers that do not drift with respect to system
748time: 1274time:
749.Sp 1275.Sp
750.Vb 1 1276.Vb 1
… …
757by 3600. 1283by 3600.
758.Sp 1284.Sp
759Another way to think about it (for the mathematically inclined) is that 1285Another way to think about it (for the mathematically inclined) is that
760\&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible 1286\&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible
761time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps. 1287time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps.
1288.Sp
1289For numerical stability it is preferable that the \f(CW\*(C`at\*(C'\fR value is near
1290\&\f(CW\*(C`ev_now ()\*(C'\fR (the current time), but there is no range requirement for
1291this value.
762.IP "* manual reschedule mode (reschedule_cb = callback)" 4 1292.IP "* manual reschedule mode (at and interval ignored, reschedule_cb = callback)" 4
763.IX Item "manual reschedule mode (reschedule_cb = callback)" 1293.IX Item "manual reschedule mode (at and interval ignored, reschedule_cb = callback)"
764In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR are both being 1294In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR are both being
765ignored. Instead, each time the periodic watcher gets scheduled, the 1295ignored. Instead, each time the periodic watcher gets scheduled, the
766reschedule callback will be called with the watcher as first, and the 1296reschedule callback will be called with the watcher as first, and the
767current time as second argument. 1297current time as second argument.
768.Sp 1298.Sp
769\&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher, 1299\&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher,
770ever, or make any event loop modifications\fR. If you need to stop it, 1300ever, or make any event loop modifications\fR. If you need to stop it,
771return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop it afterwards (e.g. by 1301return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop it afterwards (e.g. by
772starting a prepare watcher). 1302starting an \f(CW\*(C`ev_prepare\*(C'\fR watcher, which is legal).
773.Sp 1303.Sp
774Its prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 1304Its prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
775ev_tstamp now)\*(C'\fR, e.g.: 1305ev_tstamp now)\*(C'\fR, e.g.:
776.Sp 1306.Sp
777.Vb 4 1307.Vb 4
… …
801.IX Item "ev_periodic_again (loop, ev_periodic *)" 1331.IX Item "ev_periodic_again (loop, ev_periodic *)"
802Simply stops and restarts the periodic watcher again. This is only useful 1332Simply stops and restarts the periodic watcher again. This is only useful
803when you changed some parameters or the reschedule callback would return 1333when you changed some parameters or the reschedule callback would return
804a different time than the last time it was called (e.g. in a crond like 1334a different time than the last time it was called (e.g. in a crond like
805program when the crontabs have changed). 1335program when the crontabs have changed).
1336.IP "ev_tstamp offset [read\-write]" 4
1337.IX Item "ev_tstamp offset [read-write]"
1338When repeating, this contains the offset value, otherwise this is the
1339absolute point in time (the \f(CW\*(C`at\*(C'\fR value passed to \f(CW\*(C`ev_periodic_set\*(C'\fR).
1340.Sp
1341Can be modified any time, but changes only take effect when the periodic
1342timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
1343.IP "ev_tstamp interval [read\-write]" 4
1344.IX Item "ev_tstamp interval [read-write]"
1345The current interval value. Can be modified any time, but changes only
1346take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being
1347called.
1348.IP "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read\-write]" 4
1349.IX Item "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]"
1350The current reschedule callback, or \f(CW0\fR, if this functionality is
1351switched off. Can be changed any time, but changes only take effect when
1352the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
1353.PP
1354Example: Call a callback every hour, or, more precisely, whenever the
1355system clock is divisible by 3600. The callback invocation times have
1356potentially a lot of jittering, but good long-term stability.
1357.PP
1358.Vb 5
1359\& static void
1360\& clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1361\& {
1362\& ... its now a full hour (UTC, or TAI or whatever your clock follows)
1363\& }
1364.Ve
1365.PP
1366.Vb 3
1367\& struct ev_periodic hourly_tick;
1368\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1369\& ev_periodic_start (loop, &hourly_tick);
1370.Ve
1371.PP
1372Example: The same as above, but use a reschedule callback to do it:
1373.PP
1374.Vb 1
1375\& #include <math.h>
1376.Ve
1377.PP
1378.Vb 5
1379\& static ev_tstamp
1380\& my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1381\& {
1382\& return fmod (now, 3600.) + 3600.;
1383\& }
1384.Ve
1385.PP
1386.Vb 1
1387\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1388.Ve
1389.PP
1390Example: Call a callback every hour, starting now:
1391.PP
1392.Vb 4
1393\& struct ev_periodic hourly_tick;
1394\& ev_periodic_init (&hourly_tick, clock_cb,
1395\& fmod (ev_now (loop), 3600.), 3600., 0);
1396\& ev_periodic_start (loop, &hourly_tick);
1397.Ve
806.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled" 1398.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled!"
807.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled" 1399.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled!"
808.IX Subsection "ev_signal - signal me when a signal gets signalled" 1400.IX Subsection "ev_signal - signal me when a signal gets signalled!"
809Signal watchers will trigger an event when the process receives a specific 1401Signal watchers will trigger an event when the process receives a specific
810signal one or more times. Even though signals are very asynchronous, libev 1402signal one or more times. Even though signals are very asynchronous, libev
811will try it's best to deliver signals synchronously, i.e. as part of the 1403will try it's best to deliver signals synchronously, i.e. as part of the
812normal event processing, like any other event. 1404normal event processing, like any other event.
813.PP 1405.PP
… …
823.IP "ev_signal_set (ev_signal *, int signum)" 4 1415.IP "ev_signal_set (ev_signal *, int signum)" 4
824.IX Item "ev_signal_set (ev_signal *, int signum)" 1416.IX Item "ev_signal_set (ev_signal *, int signum)"
825.PD 1417.PD
826Configures the watcher to trigger on the given signal number (usually one 1418Configures the watcher to trigger on the given signal number (usually one
827of the \f(CW\*(C`SIGxxx\*(C'\fR constants). 1419of the \f(CW\*(C`SIGxxx\*(C'\fR constants).
1420.IP "int signum [read\-only]" 4
1421.IX Item "int signum [read-only]"
1422The signal the watcher watches out for.
828.ie n .Sh """ev_child"" \- wait for pid status changes" 1423.ie n .Sh """ev_child"" \- watch out for process status changes"
829.el .Sh "\f(CWev_child\fP \- wait for pid status changes" 1424.el .Sh "\f(CWev_child\fP \- watch out for process status changes"
830.IX Subsection "ev_child - wait for pid status changes" 1425.IX Subsection "ev_child - watch out for process status changes"
831Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to 1426Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to
832some child status changes (most typically when a child of yours dies). 1427some child status changes (most typically when a child of yours dies).
833.IP "ev_child_init (ev_child *, callback, int pid)" 4 1428.IP "ev_child_init (ev_child *, callback, int pid)" 4
834.IX Item "ev_child_init (ev_child *, callback, int pid)" 1429.IX Item "ev_child_init (ev_child *, callback, int pid)"
835.PD 0 1430.PD 0
… …
840\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look 1435\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look
841at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see 1436at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see
842the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems 1437the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems
843\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the 1438\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the
844process causing the status change. 1439process causing the status change.
1440.IP "int pid [read\-only]" 4
1441.IX Item "int pid [read-only]"
1442The process id this watcher watches out for, or \f(CW0\fR, meaning any process id.
1443.IP "int rpid [read\-write]" 4
1444.IX Item "int rpid [read-write]"
1445The process id that detected a status change.
1446.IP "int rstatus [read\-write]" 4
1447.IX Item "int rstatus [read-write]"
1448The process exit/trace status caused by \f(CW\*(C`rpid\*(C'\fR (see your systems
1449\&\f(CW\*(C`waitpid\*(C'\fR and \f(CW\*(C`sys/wait.h\*(C'\fR documentation for details).
1450.PP
1451Example: Try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0.
1452.PP
1453.Vb 5
1454\& static void
1455\& sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1456\& {
1457\& ev_unloop (loop, EVUNLOOP_ALL);
1458\& }
1459.Ve
1460.PP
1461.Vb 3
1462\& struct ev_signal signal_watcher;
1463\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1464\& ev_signal_start (loop, &sigint_cb);
1465.Ve
1466.ie n .Sh """ev_stat"" \- did the file attributes just change?"
1467.el .Sh "\f(CWev_stat\fP \- did the file attributes just change?"
1468.IX Subsection "ev_stat - did the file attributes just change?"
1469This watches a filesystem path for attribute changes. That is, it calls
1470\&\f(CW\*(C`stat\*(C'\fR regularly (or when the \s-1OS\s0 says it changed) and sees if it changed
1471compared to the last time, invoking the callback if it did.
1472.PP
1473The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does
1474not exist\*(R" is a status change like any other. The condition \*(L"path does
1475not exist\*(R" is signified by the \f(CW\*(C`st_nlink\*(C'\fR field being zero (which is
1476otherwise always forced to be at least one) and all the other fields of
1477the stat buffer having unspecified contents.
1478.PP
1479The path \fIshould\fR be absolute and \fImust not\fR end in a slash. If it is
1480relative and your working directory changes, the behaviour is undefined.
1481.PP
1482Since there is no standard to do this, the portable implementation simply
1483calls \f(CW\*(C`stat (2)\*(C'\fR regularly on the path to see if it changed somehow. You
1484can specify a recommended polling interval for this case. If you specify
1485a polling interval of \f(CW0\fR (highly recommended!) then a \fIsuitable,
1486unspecified default\fR value will be used (which you can expect to be around
1487five seconds, although this might change dynamically). Libev will also
1488impose a minimum interval which is currently around \f(CW0.1\fR, but thats
1489usually overkill.
1490.PP
1491This watcher type is not meant for massive numbers of stat watchers,
1492as even with OS-supported change notifications, this can be
1493resource\-intensive.
1494.PP
1495At the time of this writing, only the Linux inotify interface is
1496implemented (implementing kqueue support is left as an exercise for the
1497reader). Inotify will be used to give hints only and should not change the
1498semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers, which means that libev sometimes needs
1499to fall back to regular polling again even with inotify, but changes are
1500usually detected immediately, and if the file exists there will be no
1501polling.
1502.IP "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 4
1503.IX Item "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)"
1504.PD 0
1505.IP "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" 4
1506.IX Item "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)"
1507.PD
1508Configures the watcher to wait for status changes of the given
1509\&\f(CW\*(C`path\*(C'\fR. The \f(CW\*(C`interval\*(C'\fR is a hint on how quickly a change is expected to
1510be detected and should normally be specified as \f(CW0\fR to let libev choose
1511a suitable value. The memory pointed to by \f(CW\*(C`path\*(C'\fR must point to the same
1512path for as long as the watcher is active.
1513.Sp
1514The callback will be receive \f(CW\*(C`EV_STAT\*(C'\fR when a change was detected,
1515relative to the attributes at the time the watcher was started (or the
1516last change was detected).
1517.IP "ev_stat_stat (ev_stat *)" 4
1518.IX Item "ev_stat_stat (ev_stat *)"
1519Updates the stat buffer immediately with new values. If you change the
1520watched path in your callback, you could call this fucntion to avoid
1521detecting this change (while introducing a race condition). Can also be
1522useful simply to find out the new values.
1523.IP "ev_statdata attr [read\-only]" 4
1524.IX Item "ev_statdata attr [read-only]"
1525The most-recently detected attributes of the file. Although the type is of
1526\&\f(CW\*(C`ev_statdata\*(C'\fR, this is usually the (or one of the) \f(CW\*(C`struct stat\*(C'\fR types
1527suitable for your system. If the \f(CW\*(C`st_nlink\*(C'\fR member is \f(CW0\fR, then there
1528was some error while \f(CW\*(C`stat\*(C'\fRing the file.
1529.IP "ev_statdata prev [read\-only]" 4
1530.IX Item "ev_statdata prev [read-only]"
1531The previous attributes of the file. The callback gets invoked whenever
1532\&\f(CW\*(C`prev\*(C'\fR != \f(CW\*(C`attr\*(C'\fR.
1533.IP "ev_tstamp interval [read\-only]" 4
1534.IX Item "ev_tstamp interval [read-only]"
1535The specified interval.
1536.IP "const char *path [read\-only]" 4
1537.IX Item "const char *path [read-only]"
1538The filesystem path that is being watched.
1539.PP
1540Example: Watch \f(CW\*(C`/etc/passwd\*(C'\fR for attribute changes.
1541.PP
1542.Vb 15
1543\& static void
1544\& passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1545\& {
1546\& /* /etc/passwd changed in some way */
1547\& if (w->attr.st_nlink)
1548\& {
1549\& printf ("passwd current size %ld\en", (long)w->attr.st_size);
1550\& printf ("passwd current atime %ld\en", (long)w->attr.st_mtime);
1551\& printf ("passwd current mtime %ld\en", (long)w->attr.st_mtime);
1552\& }
1553\& else
1554\& /* you shalt not abuse printf for puts */
1555\& puts ("wow, /etc/passwd is not there, expect problems. "
1556\& "if this is windows, they already arrived\en");
1557\& }
1558.Ve
1559.PP
1560.Vb 2
1561\& ...
1562\& ev_stat passwd;
1563.Ve
1564.PP
1565.Vb 2
1566\& ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
1567\& ev_stat_start (loop, &passwd);
1568.Ve
845.ie n .Sh """ev_idle"" \- when you've got nothing better to do" 1569.ie n .Sh """ev_idle"" \- when you've got nothing better to do..."
846.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do" 1570.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do..."
847.IX Subsection "ev_idle - when you've got nothing better to do" 1571.IX Subsection "ev_idle - when you've got nothing better to do..."
848Idle watchers trigger events when there are no other events are pending 1572Idle watchers trigger events when no other events of the same or higher
849(prepare, check and other idle watchers do not count). That is, as long 1573priority are pending (prepare, check and other idle watchers do not
850as your process is busy handling sockets or timeouts (or even signals, 1574count).
851imagine) it will not be triggered. But when your process is idle all idle 1575.PP
852watchers are being called again and again, once per event loop iteration \- 1576That is, as long as your process is busy handling sockets or timeouts
1577(or even signals, imagine) of the same or higher priority it will not be
1578triggered. But when your process is idle (or only lower-priority watchers
1579are pending), the idle watchers are being called once per event loop
853until stopped, that is, or your process receives more events and becomes 1580iteration \- until stopped, that is, or your process receives more events
854busy. 1581and becomes busy again with higher priority stuff.
855.PP 1582.PP
856The most noteworthy effect is that as long as any idle watchers are 1583The most noteworthy effect is that as long as any idle watchers are
857active, the process will not block when waiting for new events. 1584active, the process will not block when waiting for new events.
858.PP 1585.PP
859Apart from keeping your process non-blocking (which is a useful 1586Apart from keeping your process non-blocking (which is a useful
… …
863.IP "ev_idle_init (ev_signal *, callback)" 4 1590.IP "ev_idle_init (ev_signal *, callback)" 4
864.IX Item "ev_idle_init (ev_signal *, callback)" 1591.IX Item "ev_idle_init (ev_signal *, callback)"
865Initialises and configures the idle watcher \- it has no parameters of any 1592Initialises and configures the idle watcher \- it has no parameters of any
866kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless, 1593kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless,
867believe me. 1594believe me.
1595.PP
1596Example: Dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR watcher, start it, and in the
1597callback, free it. Also, use no error checking, as usual.
1598.PP
1599.Vb 7
1600\& static void
1601\& idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1602\& {
1603\& free (w);
1604\& // now do something you wanted to do when the program has
1605\& // no longer asnything immediate to do.
1606\& }
1607.Ve
1608.PP
1609.Vb 3
1610\& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1611\& ev_idle_init (idle_watcher, idle_cb);
1612\& ev_idle_start (loop, idle_cb);
1613.Ve
868.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop" 1614.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop!"
869.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop" 1615.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!"
870.IX Subsection "ev_prepare and ev_check - customise your event loop" 1616.IX Subsection "ev_prepare and ev_check - customise your event loop!"
871Prepare and check watchers are usually (but not always) used in tandem: 1617Prepare and check watchers are usually (but not always) used in tandem:
872prepare watchers get invoked before the process blocks and check watchers 1618prepare watchers get invoked before the process blocks and check watchers
873afterwards. 1619afterwards.
874.PP 1620.PP
1621You \fImust not\fR call \f(CW\*(C`ev_loop\*(C'\fR or similar functions that enter
1622the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR
1623watchers. Other loops than the current one are fine, however. The
1624rationale behind this is that you do not need to check for recursion in
1625those watchers, i.e. the sequence will always be \f(CW\*(C`ev_prepare\*(C'\fR, blocking,
1626\&\f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each kind they will always be
1627called in pairs bracketing the blocking call.
1628.PP
875Their main purpose is to integrate other event mechanisms into libev. This 1629Their main purpose is to integrate other event mechanisms into libev and
876could be used, for example, to track variable changes, implement your own 1630their use is somewhat advanced. This could be used, for example, to track
877watchers, integrate net-snmp or a coroutine library and lots more. 1631variable changes, implement your own watchers, integrate net-snmp or a
1632coroutine library and lots more. They are also occasionally useful if
1633you cache some data and want to flush it before blocking (for example,
1634in X programs you might want to do an \f(CW\*(C`XFlush ()\*(C'\fR in an \f(CW\*(C`ev_prepare\*(C'\fR
1635watcher).
878.PP 1636.PP
879This is done by examining in each prepare call which file descriptors need 1637This is done by examining in each prepare call which file descriptors need
880to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for 1638to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for
881them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries 1639them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries
882provide just this functionality). Then, in the check watcher you check for 1640provide just this functionality). Then, in the check watcher you check for
… …
891are ready to run (it's actually more complicated: it only runs coroutines 1649are ready to run (it's actually more complicated: it only runs coroutines
892with priority higher than or equal to the event loop and one coroutine 1650with priority higher than or equal to the event loop and one coroutine
893of lower priority, but only once, using idle watchers to keep the event 1651of lower priority, but only once, using idle watchers to keep the event
894loop from blocking if lower-priority coroutines are active, thus mapping 1652loop from blocking if lower-priority coroutines are active, thus mapping
895low-priority coroutines to idle/background tasks). 1653low-priority coroutines to idle/background tasks).
1654.PP
1655It is recommended to give \f(CW\*(C`ev_check\*(C'\fR watchers highest (\f(CW\*(C`EV_MAXPRI\*(C'\fR)
1656priority, to ensure that they are being run before any other watchers
1657after the poll. Also, \f(CW\*(C`ev_check\*(C'\fR watchers (and \f(CW\*(C`ev_prepare\*(C'\fR watchers,
1658too) should not activate (\*(L"feed\*(R") events into libev. While libev fully
1659supports this, they will be called before other \f(CW\*(C`ev_check\*(C'\fR watchers did
1660their job. As \f(CW\*(C`ev_check\*(C'\fR watchers are often used to embed other event
1661loops those other event loops might be in an unusable state until their
1662\&\f(CW\*(C`ev_check\*(C'\fR watcher ran (always remind yourself to coexist peacefully with
1663others).
896.IP "ev_prepare_init (ev_prepare *, callback)" 4 1664.IP "ev_prepare_init (ev_prepare *, callback)" 4
897.IX Item "ev_prepare_init (ev_prepare *, callback)" 1665.IX Item "ev_prepare_init (ev_prepare *, callback)"
898.PD 0 1666.PD 0
899.IP "ev_check_init (ev_check *, callback)" 4 1667.IP "ev_check_init (ev_check *, callback)" 4
900.IX Item "ev_check_init (ev_check *, callback)" 1668.IX Item "ev_check_init (ev_check *, callback)"
901.PD 1669.PD
902Initialises and configures the prepare or check watcher \- they have no 1670Initialises and configures the prepare or check watcher \- they have no
903parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR 1671parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR
904macros, but using them is utterly, utterly and completely pointless. 1672macros, but using them is utterly, utterly and completely pointless.
1673.PP
1674There are a number of principal ways to embed other event loops or modules
1675into libev. Here are some ideas on how to include libadns into libev
1676(there is a Perl module named \f(CW\*(C`EV::ADNS\*(C'\fR that does this, which you could
1677use for an actually working example. Another Perl module named \f(CW\*(C`EV::Glib\*(C'\fR
1678embeds a Glib main context into libev, and finally, \f(CW\*(C`Glib::EV\*(C'\fR embeds \s-1EV\s0
1679into the Glib event loop).
1680.PP
1681Method 1: Add \s-1IO\s0 watchers and a timeout watcher in a prepare handler,
1682and in a check watcher, destroy them and call into libadns. What follows
1683is pseudo-code only of course. This requires you to either use a low
1684priority for the check watcher or use \f(CW\*(C`ev_clear_pending\*(C'\fR explicitly, as
1685the callbacks for the IO/timeout watchers might not have been called yet.
1686.PP
1687.Vb 2
1688\& static ev_io iow [nfd];
1689\& static ev_timer tw;
1690.Ve
1691.PP
1692.Vb 4
1693\& static void
1694\& io_cb (ev_loop *loop, ev_io *w, int revents)
1695\& {
1696\& }
1697.Ve
1698.PP
1699.Vb 8
1700\& // create io watchers for each fd and a timer before blocking
1701\& static void
1702\& adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1703\& {
1704\& int timeout = 3600000;
1705\& struct pollfd fds [nfd];
1706\& // actual code will need to loop here and realloc etc.
1707\& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1708.Ve
1709.PP
1710.Vb 3
1711\& /* the callback is illegal, but won't be called as we stop during check */
1712\& ev_timer_init (&tw, 0, timeout * 1e-3);
1713\& ev_timer_start (loop, &tw);
1714.Ve
1715.PP
1716.Vb 6
1717\& // create one ev_io per pollfd
1718\& for (int i = 0; i < nfd; ++i)
1719\& {
1720\& ev_io_init (iow + i, io_cb, fds [i].fd,
1721\& ((fds [i].events & POLLIN ? EV_READ : 0)
1722\& | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1723.Ve
1724.PP
1725.Vb 4
1726\& fds [i].revents = 0;
1727\& ev_io_start (loop, iow + i);
1728\& }
1729\& }
1730.Ve
1731.PP
1732.Vb 5
1733\& // stop all watchers after blocking
1734\& static void
1735\& adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1736\& {
1737\& ev_timer_stop (loop, &tw);
1738.Ve
1739.PP
1740.Vb 8
1741\& for (int i = 0; i < nfd; ++i)
1742\& {
1743\& // set the relevant poll flags
1744\& // could also call adns_processreadable etc. here
1745\& struct pollfd *fd = fds + i;
1746\& int revents = ev_clear_pending (iow + i);
1747\& if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1748\& if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1749.Ve
1750.PP
1751.Vb 3
1752\& // now stop the watcher
1753\& ev_io_stop (loop, iow + i);
1754\& }
1755.Ve
1756.PP
1757.Vb 2
1758\& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1759\& }
1760.Ve
1761.PP
1762Method 2: This would be just like method 1, but you run \f(CW\*(C`adns_afterpoll\*(C'\fR
1763in the prepare watcher and would dispose of the check watcher.
1764.PP
1765Method 3: If the module to be embedded supports explicit event
1766notification (adns does), you can also make use of the actual watcher
1767callbacks, and only destroy/create the watchers in the prepare watcher.
1768.PP
1769.Vb 5
1770\& static void
1771\& timer_cb (EV_P_ ev_timer *w, int revents)
1772\& {
1773\& adns_state ads = (adns_state)w->data;
1774\& update_now (EV_A);
1775.Ve
1776.PP
1777.Vb 2
1778\& adns_processtimeouts (ads, &tv_now);
1779\& }
1780.Ve
1781.PP
1782.Vb 5
1783\& static void
1784\& io_cb (EV_P_ ev_io *w, int revents)
1785\& {
1786\& adns_state ads = (adns_state)w->data;
1787\& update_now (EV_A);
1788.Ve
1789.PP
1790.Vb 3
1791\& if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1792\& if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1793\& }
1794.Ve
1795.PP
1796.Vb 1
1797\& // do not ever call adns_afterpoll
1798.Ve
1799.PP
1800Method 4: Do not use a prepare or check watcher because the module you
1801want to embed is too inflexible to support it. Instead, youc na override
1802their poll function. The drawback with this solution is that the main
1803loop is now no longer controllable by \s-1EV\s0. The \f(CW\*(C`Glib::EV\*(C'\fR module does
1804this.
1805.PP
1806.Vb 4
1807\& static gint
1808\& event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1809\& {
1810\& int got_events = 0;
1811.Ve
1812.PP
1813.Vb 2
1814\& for (n = 0; n < nfds; ++n)
1815\& // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1816.Ve
1817.PP
1818.Vb 2
1819\& if (timeout >= 0)
1820\& // create/start timer
1821.Ve
1822.PP
1823.Vb 2
1824\& // poll
1825\& ev_loop (EV_A_ 0);
1826.Ve
1827.PP
1828.Vb 3
1829\& // stop timer again
1830\& if (timeout >= 0)
1831\& ev_timer_stop (EV_A_ &to);
1832.Ve
1833.PP
1834.Vb 3
1835\& // stop io watchers again - their callbacks should have set
1836\& for (n = 0; n < nfds; ++n)
1837\& ev_io_stop (EV_A_ iow [n]);
1838.Ve
1839.PP
1840.Vb 2
1841\& return got_events;
1842\& }
1843.Ve
1844.ie n .Sh """ev_embed"" \- when one backend isn't enough..."
1845.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..."
1846.IX Subsection "ev_embed - when one backend isn't enough..."
1847This is a rather advanced watcher type that lets you embed one event loop
1848into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded
1849loop, other types of watchers might be handled in a delayed or incorrect
1850fashion and must not be used).
1851.PP
1852There are primarily two reasons you would want that: work around bugs and
1853prioritise I/O.
1854.PP
1855As an example for a bug workaround, the kqueue backend might only support
1856sockets on some platform, so it is unusable as generic backend, but you
1857still want to make use of it because you have many sockets and it scales
1858so nicely. In this case, you would create a kqueue-based loop and embed it
1859into your default loop (which might use e.g. poll). Overall operation will
1860be a bit slower because first libev has to poll and then call kevent, but
1861at least you can use both at what they are best.
1862.PP
1863As for prioritising I/O: rarely you have the case where some fds have
1864to be watched and handled very quickly (with low latency), and even
1865priorities and idle watchers might have too much overhead. In this case
1866you would put all the high priority stuff in one loop and all the rest in
1867a second one, and embed the second one in the first.
1868.PP
1869As long as the watcher is active, the callback will be invoked every time
1870there might be events pending in the embedded loop. The callback must then
1871call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single sweep and invoke
1872their callbacks (you could also start an idle watcher to give the embedded
1873loop strictly lower priority for example). You can also set the callback
1874to \f(CW0\fR, in which case the embed watcher will automatically execute the
1875embedded loop sweep.
1876.PP
1877As long as the watcher is started it will automatically handle events. The
1878callback will be invoked whenever some events have been handled. You can
1879set the callback to \f(CW0\fR to avoid having to specify one if you are not
1880interested in that.
1881.PP
1882Also, there have not currently been made special provisions for forking:
1883when you fork, you not only have to call \f(CW\*(C`ev_loop_fork\*(C'\fR on both loops,
1884but you will also have to stop and restart any \f(CW\*(C`ev_embed\*(C'\fR watchers
1885yourself.
1886.PP
1887Unfortunately, not all backends are embeddable, only the ones returned by
1888\&\f(CW\*(C`ev_embeddable_backends\*(C'\fR are, which, unfortunately, does not include any
1889portable one.
1890.PP
1891So when you want to use this feature you will always have to be prepared
1892that you cannot get an embeddable loop. The recommended way to get around
1893this is to have a separate variables for your embeddable loop, try to
1894create it, and if that fails, use the normal loop for everything:
1895.PP
1896.Vb 3
1897\& struct ev_loop *loop_hi = ev_default_init (0);
1898\& struct ev_loop *loop_lo = 0;
1899\& struct ev_embed embed;
1900.Ve
1901.PP
1902.Vb 5
1903\& // see if there is a chance of getting one that works
1904\& // (remember that a flags value of 0 means autodetection)
1905\& loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1906\& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1907\& : 0;
1908.Ve
1909.PP
1910.Vb 8
1911\& // if we got one, then embed it, otherwise default to loop_hi
1912\& if (loop_lo)
1913\& {
1914\& ev_embed_init (&embed, 0, loop_lo);
1915\& ev_embed_start (loop_hi, &embed);
1916\& }
1917\& else
1918\& loop_lo = loop_hi;
1919.Ve
1920.IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
1921.IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)"
1922.PD 0
1923.IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
1924.IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)"
1925.PD
1926Configures the watcher to embed the given loop, which must be
1927embeddable. If the callback is \f(CW0\fR, then \f(CW\*(C`ev_embed_sweep\*(C'\fR will be
1928invoked automatically, otherwise it is the responsibility of the callback
1929to invoke it (it will continue to be called until the sweep has been done,
1930if you do not want thta, you need to temporarily stop the embed watcher).
1931.IP "ev_embed_sweep (loop, ev_embed *)" 4
1932.IX Item "ev_embed_sweep (loop, ev_embed *)"
1933Make a single, non-blocking sweep over the embedded loop. This works
1934similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most
1935apropriate way for embedded loops.
1936.IP "struct ev_loop *loop [read\-only]" 4
1937.IX Item "struct ev_loop *loop [read-only]"
1938The embedded event loop.
1939.ie n .Sh """ev_fork"" \- the audacity to resume the event loop after a fork"
1940.el .Sh "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork"
1941.IX Subsection "ev_fork - the audacity to resume the event loop after a fork"
1942Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because
1943whoever is a good citizen cared to tell libev about it by calling
1944\&\f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the
1945event loop blocks next and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called,
1946and only in the child after the fork. If whoever good citizen calling
1947\&\f(CW\*(C`ev_default_fork\*(C'\fR cheats and calls it in the wrong process, the fork
1948handlers will be invoked, too, of course.
1949.IP "ev_fork_init (ev_signal *, callback)" 4
1950.IX Item "ev_fork_init (ev_signal *, callback)"
1951Initialises and configures the fork watcher \- it has no parameters of any
1952kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless,
1953believe me.
905.SH "OTHER FUNCTIONS" 1954.SH "OTHER FUNCTIONS"
906.IX Header "OTHER FUNCTIONS" 1955.IX Header "OTHER FUNCTIONS"
907There are some other functions of possible interest. Described. Here. Now. 1956There are some other functions of possible interest. Described. Here. Now.
908.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4 1957.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4
909.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 1958.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)"
… …
938.Ve 1987.Ve
939.Sp 1988.Sp
940.Vb 1 1989.Vb 1
941\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); 1990\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
942.Ve 1991.Ve
943.IP "ev_feed_event (loop, watcher, int events)" 4 1992.IP "ev_feed_event (ev_loop *, watcher *, int revents)" 4
944.IX Item "ev_feed_event (loop, watcher, int events)" 1993.IX Item "ev_feed_event (ev_loop *, watcher *, int revents)"
945Feeds the given event set into the event loop, as if the specified event 1994Feeds the given event set into the event loop, as if the specified event
946had happened for the specified watcher (which must be a pointer to an 1995had happened for the specified watcher (which must be a pointer to an
947initialised but not necessarily started event watcher). 1996initialised but not necessarily started event watcher).
948.IP "ev_feed_fd_event (loop, int fd, int revents)" 4 1997.IP "ev_feed_fd_event (ev_loop *, int fd, int revents)" 4
949.IX Item "ev_feed_fd_event (loop, int fd, int revents)" 1998.IX Item "ev_feed_fd_event (ev_loop *, int fd, int revents)"
950Feed an event on the given fd, as if a file descriptor backend detected 1999Feed an event on the given fd, as if a file descriptor backend detected
951the given events it. 2000the given events it.
952.IP "ev_feed_signal_event (loop, int signum)" 4 2001.IP "ev_feed_signal_event (ev_loop *loop, int signum)" 4
953.IX Item "ev_feed_signal_event (loop, int signum)" 2002.IX Item "ev_feed_signal_event (ev_loop *loop, int signum)"
954Feed an event as if the given signal occured (loop must be the default loop!). 2003Feed an event as if the given signal occured (\f(CW\*(C`loop\*(C'\fR must be the default
2004loop!).
955.SH "LIBEVENT EMULATION" 2005.SH "LIBEVENT EMULATION"
956.IX Header "LIBEVENT EMULATION" 2006.IX Header "LIBEVENT EMULATION"
957Libev offers a compatibility emulation layer for libevent. It cannot 2007Libev offers a compatibility emulation layer for libevent. It cannot
958emulate the internals of libevent, so here are some usage hints: 2008emulate the internals of libevent, so here are some usage hints:
959.IP "* Use it by including <event.h>, as usual." 4 2009.IP "* Use it by including <event.h>, as usual." 4
… …
970.IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4 2020.IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4
971.IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library." 2021.IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library."
972.PD 2022.PD
973.SH "\*(C+ SUPPORT" 2023.SH "\*(C+ SUPPORT"
974.IX Header " SUPPORT" 2024.IX Header " SUPPORT"
975\&\s-1TBD\s0. 2025Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow
2026you to use some convinience methods to start/stop watchers and also change
2027the callback model to a model using method callbacks on objects.
2028.PP
2029To use it,
2030.PP
2031.Vb 1
2032\& #include <ev++.h>
2033.Ve
2034.PP
2035This automatically includes \fIev.h\fR and puts all of its definitions (many
2036of them macros) into the global namespace. All \*(C+ specific things are
2037put into the \f(CW\*(C`ev\*(C'\fR namespace. It should support all the same embedding
2038options as \fIev.h\fR, most notably \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR.
2039.PP
2040Care has been taken to keep the overhead low. The only data member the \*(C+
2041classes add (compared to plain C\-style watchers) is the event loop pointer
2042that the watcher is associated with (or no additional members at all if
2043you disable \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR when embedding libev).
2044.PP
2045Currently, functions, and static and non-static member functions can be
2046used as callbacks. Other types should be easy to add as long as they only
2047need one additional pointer for context. If you need support for other
2048types of functors please contact the author (preferably after implementing
2049it).
2050.PP
2051Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace:
2052.ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4
2053.el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4
2054.IX Item "ev::READ, ev::WRITE etc."
2055These are just enum values with the same values as the \f(CW\*(C`EV_READ\*(C'\fR etc.
2056macros from \fIev.h\fR.
2057.ie n .IP """ev::tstamp""\fR, \f(CW""ev::now""" 4
2058.el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4
2059.IX Item "ev::tstamp, ev::now"
2060Aliases to the same types/functions as with the \f(CW\*(C`ev_\*(C'\fR prefix.
2061.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
2062.el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4
2063.IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc."
2064For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of
2065the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR
2066which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro
2067defines by many implementations.
2068.Sp
2069All of those classes have these methods:
2070.RS 4
2071.IP "ev::TYPE::TYPE ()" 4
2072.IX Item "ev::TYPE::TYPE ()"
2073.PD 0
2074.IP "ev::TYPE::TYPE (struct ev_loop *)" 4
2075.IX Item "ev::TYPE::TYPE (struct ev_loop *)"
2076.IP "ev::TYPE::~TYPE" 4
2077.IX Item "ev::TYPE::~TYPE"
2078.PD
2079The constructor (optionally) takes an event loop to associate the watcher
2080with. If it is omitted, it will use \f(CW\*(C`EV_DEFAULT\*(C'\fR.
2081.Sp
2082The constructor calls \f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the
2083\&\f(CW\*(C`set\*(C'\fR method before starting it.
2084.Sp
2085It will not set a callback, however: You have to call the templated \f(CW\*(C`set\*(C'\fR
2086method to set a callback before you can start the watcher.
2087.Sp
2088(The reason why you have to use a method is a limitation in \*(C+ which does
2089not allow explicit template arguments for constructors).
2090.Sp
2091The destructor automatically stops the watcher if it is active.
2092.IP "w\->set<class, &class::method> (object *)" 4
2093.IX Item "w->set<class, &class::method> (object *)"
2094This method sets the callback method to call. The method has to have a
2095signature of \f(CW\*(C`void (*)(ev_TYPE &, int)\*(C'\fR, it receives the watcher as
2096first argument and the \f(CW\*(C`revents\*(C'\fR as second. The object must be given as
2097parameter and is stored in the \f(CW\*(C`data\*(C'\fR member of the watcher.
2098.Sp
2099This method synthesizes efficient thunking code to call your method from
2100the C callback that libev requires. If your compiler can inline your
2101callback (i.e. it is visible to it at the place of the \f(CW\*(C`set\*(C'\fR call and
2102your compiler is good :), then the method will be fully inlined into the
2103thunking function, making it as fast as a direct C callback.
2104.Sp
2105Example: simple class declaration and watcher initialisation
2106.Sp
2107.Vb 4
2108\& struct myclass
2109\& {
2110\& void io_cb (ev::io &w, int revents) { }
2111\& }
2112.Ve
2113.Sp
2114.Vb 3
2115\& myclass obj;
2116\& ev::io iow;
2117\& iow.set <myclass, &myclass::io_cb> (&obj);
2118.Ve
2119.IP "w\->set<function> (void *data = 0)" 4
2120.IX Item "w->set<function> (void *data = 0)"
2121Also sets a callback, but uses a static method or plain function as
2122callback. The optional \f(CW\*(C`data\*(C'\fR argument will be stored in the watcher's
2123\&\f(CW\*(C`data\*(C'\fR member and is free for you to use.
2124.Sp
2125The prototype of the \f(CW\*(C`function\*(C'\fR must be \f(CW\*(C`void (*)(ev::TYPE &w, int)\*(C'\fR.
2126.Sp
2127See the method\-\f(CW\*(C`set\*(C'\fR above for more details.
2128.Sp
2129Example:
2130.Sp
2131.Vb 2
2132\& static void io_cb (ev::io &w, int revents) { }
2133\& iow.set <io_cb> ();
2134.Ve
2135.IP "w\->set (struct ev_loop *)" 4
2136.IX Item "w->set (struct ev_loop *)"
2137Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only
2138do this when the watcher is inactive (and not pending either).
2139.IP "w\->set ([args])" 4
2140.IX Item "w->set ([args])"
2141Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same args. Must be
2142called at least once. Unlike the C counterpart, an active watcher gets
2143automatically stopped and restarted when reconfiguring it with this
2144method.
2145.IP "w\->start ()" 4
2146.IX Item "w->start ()"
2147Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the
2148constructor already stores the event loop.
2149.IP "w\->stop ()" 4
2150.IX Item "w->stop ()"
2151Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument.
2152.ie n .IP "w\->again () ""ev::timer""\fR, \f(CW""ev::periodic"" only" 4
2153.el .IP "w\->again () \f(CWev::timer\fR, \f(CWev::periodic\fR only" 4
2154.IX Item "w->again () ev::timer, ev::periodic only"
2155For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding
2156\&\f(CW\*(C`ev_TYPE_again\*(C'\fR function.
2157.ie n .IP "w\->sweep () ""ev::embed"" only" 4
2158.el .IP "w\->sweep () \f(CWev::embed\fR only" 4
2159.IX Item "w->sweep () ev::embed only"
2160Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR.
2161.ie n .IP "w\->update () ""ev::stat"" only" 4
2162.el .IP "w\->update () \f(CWev::stat\fR only" 4
2163.IX Item "w->update () ev::stat only"
2164Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR.
2165.RE
2166.RS 4
2167.RE
2168.PP
2169Example: Define a class with an \s-1IO\s0 and idle watcher, start one of them in
2170the constructor.
2171.PP
2172.Vb 4
2173\& class myclass
2174\& {
2175\& ev_io io; void io_cb (ev::io &w, int revents);
2176\& ev_idle idle void idle_cb (ev::idle &w, int revents);
2177.Ve
2178.PP
2179.Vb 2
2180\& myclass ();
2181\& }
2182.Ve
2183.PP
2184.Vb 4
2185\& myclass::myclass (int fd)
2186\& {
2187\& io .set <myclass, &myclass::io_cb > (this);
2188\& idle.set <myclass, &myclass::idle_cb> (this);
2189.Ve
2190.PP
2191.Vb 2
2192\& io.start (fd, ev::READ);
2193\& }
2194.Ve
2195.SH "MACRO MAGIC"
2196.IX Header "MACRO MAGIC"
2197Libev can be compiled with a variety of options, the most fundemantal is
2198\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most) functions and
2199callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument.
2200.PP
2201To make it easier to write programs that cope with either variant, the
2202following macros are defined:
2203.ie n .IP """EV_A""\fR, \f(CW""EV_A_""" 4
2204.el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4
2205.IX Item "EV_A, EV_A_"
2206This provides the loop \fIargument\fR for functions, if one is required (\*(L"ev
2207loop argument\*(R"). The \f(CW\*(C`EV_A\*(C'\fR form is used when this is the sole argument,
2208\&\f(CW\*(C`EV_A_\*(C'\fR is used when other arguments are following. Example:
2209.Sp
2210.Vb 3
2211\& ev_unref (EV_A);
2212\& ev_timer_add (EV_A_ watcher);
2213\& ev_loop (EV_A_ 0);
2214.Ve
2215.Sp
2216It assumes the variable \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR is in scope,
2217which is often provided by the following macro.
2218.ie n .IP """EV_P""\fR, \f(CW""EV_P_""" 4
2219.el .IP "\f(CWEV_P\fR, \f(CWEV_P_\fR" 4
2220.IX Item "EV_P, EV_P_"
2221This provides the loop \fIparameter\fR for functions, if one is required (\*(L"ev
2222loop parameter\*(R"). The \f(CW\*(C`EV_P\*(C'\fR form is used when this is the sole parameter,
2223\&\f(CW\*(C`EV_P_\*(C'\fR is used when other parameters are following. Example:
2224.Sp
2225.Vb 2
2226\& // this is how ev_unref is being declared
2227\& static void ev_unref (EV_P);
2228.Ve
2229.Sp
2230.Vb 2
2231\& // this is how you can declare your typical callback
2232\& static void cb (EV_P_ ev_timer *w, int revents)
2233.Ve
2234.Sp
2235It declares a parameter \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR, quite
2236suitable for use with \f(CW\*(C`EV_A\*(C'\fR.
2237.ie n .IP """EV_DEFAULT""\fR, \f(CW""EV_DEFAULT_""" 4
2238.el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4
2239.IX Item "EV_DEFAULT, EV_DEFAULT_"
2240Similar to the other two macros, this gives you the value of the default
2241loop, if multiple loops are supported (\*(L"ev loop default\*(R").
2242.PP
2243Example: Declare and initialise a check watcher, utilising the above
2244macros so it will work regardless of whether multiple loops are supported
2245or not.
2246.PP
2247.Vb 5
2248\& static void
2249\& check_cb (EV_P_ ev_timer *w, int revents)
2250\& {
2251\& ev_check_stop (EV_A_ w);
2252\& }
2253.Ve
2254.PP
2255.Vb 4
2256\& ev_check check;
2257\& ev_check_init (&check, check_cb);
2258\& ev_check_start (EV_DEFAULT_ &check);
2259\& ev_loop (EV_DEFAULT_ 0);
2260.Ve
2261.SH "EMBEDDING"
2262.IX Header "EMBEDDING"
2263Libev can (and often is) directly embedded into host
2264applications. Examples of applications that embed it include the Deliantra
2265Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe)
2266and rxvt\-unicode.
2267.PP
2268The goal is to enable you to just copy the neecssary files into your
2269source directory without having to change even a single line in them, so
2270you can easily upgrade by simply copying (or having a checked-out copy of
2271libev somewhere in your source tree).
2272.Sh "\s-1FILESETS\s0"
2273.IX Subsection "FILESETS"
2274Depending on what features you need you need to include one or more sets of files
2275in your app.
2276.PP
2277\fI\s-1CORE\s0 \s-1EVENT\s0 \s-1LOOP\s0\fR
2278.IX Subsection "CORE EVENT LOOP"
2279.PP
2280To include only the libev core (all the \f(CW\*(C`ev_*\*(C'\fR functions), with manual
2281configuration (no autoconf):
2282.PP
2283.Vb 2
2284\& #define EV_STANDALONE 1
2285\& #include "ev.c"
2286.Ve
2287.PP
2288This will automatically include \fIev.h\fR, too, and should be done in a
2289single C source file only to provide the function implementations. To use
2290it, do the same for \fIev.h\fR in all files wishing to use this \s-1API\s0 (best
2291done by writing a wrapper around \fIev.h\fR that you can include instead and
2292where you can put other configuration options):
2293.PP
2294.Vb 2
2295\& #define EV_STANDALONE 1
2296\& #include "ev.h"
2297.Ve
2298.PP
2299Both header files and implementation files can be compiled with a \*(C+
2300compiler (at least, thats a stated goal, and breakage will be treated
2301as a bug).
2302.PP
2303You need the following files in your source tree, or in a directory
2304in your include path (e.g. in libev/ when using \-Ilibev):
2305.PP
2306.Vb 4
2307\& ev.h
2308\& ev.c
2309\& ev_vars.h
2310\& ev_wrap.h
2311.Ve
2312.PP
2313.Vb 1
2314\& ev_win32.c required on win32 platforms only
2315.Ve
2316.PP
2317.Vb 5
2318\& ev_select.c only when select backend is enabled (which is enabled by default)
2319\& ev_poll.c only when poll backend is enabled (disabled by default)
2320\& ev_epoll.c only when the epoll backend is enabled (disabled by default)
2321\& ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2322\& ev_port.c only when the solaris port backend is enabled (disabled by default)
2323.Ve
2324.PP
2325\&\fIev.c\fR includes the backend files directly when enabled, so you only need
2326to compile this single file.
2327.PP
2328\fI\s-1LIBEVENT\s0 \s-1COMPATIBILITY\s0 \s-1API\s0\fR
2329.IX Subsection "LIBEVENT COMPATIBILITY API"
2330.PP
2331To include the libevent compatibility \s-1API\s0, also include:
2332.PP
2333.Vb 1
2334\& #include "event.c"
2335.Ve
2336.PP
2337in the file including \fIev.c\fR, and:
2338.PP
2339.Vb 1
2340\& #include "event.h"
2341.Ve
2342.PP
2343in the files that want to use the libevent \s-1API\s0. This also includes \fIev.h\fR.
2344.PP
2345You need the following additional files for this:
2346.PP
2347.Vb 2
2348\& event.h
2349\& event.c
2350.Ve
2351.PP
2352\fI\s-1AUTOCONF\s0 \s-1SUPPORT\s0\fR
2353.IX Subsection "AUTOCONF SUPPORT"
2354.PP
2355Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your config in
2356whatever way you want, you can also \f(CW\*(C`m4_include([libev.m4])\*(C'\fR in your
2357\&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR undefined. \fIev.c\fR will then
2358include \fIconfig.h\fR and configure itself accordingly.
2359.PP
2360For this of course you need the m4 file:
2361.PP
2362.Vb 1
2363\& libev.m4
2364.Ve
2365.Sh "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0"
2366.IX Subsection "PREPROCESSOR SYMBOLS/MACROS"
2367Libev can be configured via a variety of preprocessor symbols you have to define
2368before including any of its files. The default is not to build for multiplicity
2369and only include the select backend.
2370.IP "\s-1EV_STANDALONE\s0" 4
2371.IX Item "EV_STANDALONE"
2372Must always be \f(CW1\fR if you do not use autoconf configuration, which
2373keeps libev from including \fIconfig.h\fR, and it also defines dummy
2374implementations for some libevent functions (such as logging, which is not
2375supported). It will also not define any of the structs usually found in
2376\&\fIevent.h\fR that are not directly supported by the libev core alone.
2377.IP "\s-1EV_USE_MONOTONIC\s0" 4
2378.IX Item "EV_USE_MONOTONIC"
2379If defined to be \f(CW1\fR, libev will try to detect the availability of the
2380monotonic clock option at both compiletime and runtime. Otherwise no use
2381of the monotonic clock option will be attempted. If you enable this, you
2382usually have to link against librt or something similar. Enabling it when
2383the functionality isn't available is safe, though, althoguh you have
2384to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR
2385function is hiding in (often \fI\-lrt\fR).
2386.IP "\s-1EV_USE_REALTIME\s0" 4
2387.IX Item "EV_USE_REALTIME"
2388If defined to be \f(CW1\fR, libev will try to detect the availability of the
2389realtime clock option at compiletime (and assume its availability at
2390runtime if successful). Otherwise no use of the realtime clock option will
2391be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get
2392(CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See tzhe note about libraries
2393in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though.
2394.IP "\s-1EV_USE_SELECT\s0" 4
2395.IX Item "EV_USE_SELECT"
2396If undefined or defined to be \f(CW1\fR, libev will compile in support for the
2397\&\f(CW\*(C`select\*(C'\fR(2) backend. No attempt at autodetection will be done: if no
2398other method takes over, select will be it. Otherwise the select backend
2399will not be compiled in.
2400.IP "\s-1EV_SELECT_USE_FD_SET\s0" 4
2401.IX Item "EV_SELECT_USE_FD_SET"
2402If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR
2403structure. This is useful if libev doesn't compile due to a missing
2404\&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it misguesses the bitset layout on
2405exotic systems. This usually limits the range of file descriptors to some
2406low limit such as 1024 or might have other limitations (winsocket only
2407allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation, might
2408influence the size of the \f(CW\*(C`fd_set\*(C'\fR used.
2409.IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4
2410.IX Item "EV_SELECT_IS_WINSOCKET"
2411When defined to \f(CW1\fR, the select backend will assume that
2412select/socket/connect etc. don't understand file descriptors but
2413wants osf handles on win32 (this is the case when the select to
2414be used is the winsock select). This means that it will call
2415\&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise,
2416it is assumed that all these functions actually work on fds, even
2417on win32. Should not be defined on non\-win32 platforms.
2418.IP "\s-1EV_USE_POLL\s0" 4
2419.IX Item "EV_USE_POLL"
2420If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2)
2421backend. Otherwise it will be enabled on non\-win32 platforms. It
2422takes precedence over select.
2423.IP "\s-1EV_USE_EPOLL\s0" 4
2424.IX Item "EV_USE_EPOLL"
2425If defined to be \f(CW1\fR, libev will compile in support for the Linux
2426\&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime,
2427otherwise another method will be used as fallback. This is the
2428preferred backend for GNU/Linux systems.
2429.IP "\s-1EV_USE_KQUEUE\s0" 4
2430.IX Item "EV_USE_KQUEUE"
2431If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style
2432\&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime,
2433otherwise another method will be used as fallback. This is the preferred
2434backend for \s-1BSD\s0 and BSD-like systems, although on most BSDs kqueue only
2435supports some types of fds correctly (the only platform we found that
2436supports ptys for example was NetBSD), so kqueue might be compiled in, but
2437not be used unless explicitly requested. The best way to use it is to find
2438out whether kqueue supports your type of fd properly and use an embedded
2439kqueue loop.
2440.IP "\s-1EV_USE_PORT\s0" 4
2441.IX Item "EV_USE_PORT"
2442If defined to be \f(CW1\fR, libev will compile in support for the Solaris
244310 port style backend. Its availability will be detected at runtime,
2444otherwise another method will be used as fallback. This is the preferred
2445backend for Solaris 10 systems.
2446.IP "\s-1EV_USE_DEVPOLL\s0" 4
2447.IX Item "EV_USE_DEVPOLL"
2448reserved for future expansion, works like the \s-1USE\s0 symbols above.
2449.IP "\s-1EV_USE_INOTIFY\s0" 4
2450.IX Item "EV_USE_INOTIFY"
2451If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify
2452interface to speed up \f(CW\*(C`ev_stat\*(C'\fR watchers. Its actual availability will
2453be detected at runtime.
2454.IP "\s-1EV_H\s0" 4
2455.IX Item "EV_H"
2456The name of the \fIev.h\fR header file used to include it. The default if
2457undefined is \f(CW\*(C`<ev.h>\*(C'\fR in \fIevent.h\fR and \f(CW"ev.h"\fR in \fIev.c\fR. This
2458can be used to virtually rename the \fIev.h\fR header file in case of conflicts.
2459.IP "\s-1EV_CONFIG_H\s0" 4
2460.IX Item "EV_CONFIG_H"
2461If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override
2462\&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to
2463\&\f(CW\*(C`EV_H\*(C'\fR, above.
2464.IP "\s-1EV_EVENT_H\s0" 4
2465.IX Item "EV_EVENT_H"
2466Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea
2467of how the \fIevent.h\fR header can be found.
2468.IP "\s-1EV_PROTOTYPES\s0" 4
2469.IX Item "EV_PROTOTYPES"
2470If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function
2471prototypes, but still define all the structs and other symbols. This is
2472occasionally useful if you want to provide your own wrapper functions
2473around libev functions.
2474.IP "\s-1EV_MULTIPLICITY\s0" 4
2475.IX Item "EV_MULTIPLICITY"
2476If undefined or defined to \f(CW1\fR, then all event-loop-specific functions
2477will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create
2478additional independent event loops. Otherwise there will be no support
2479for multiple event loops and there is no first event loop pointer
2480argument. Instead, all functions act on the single default loop.
2481.IP "\s-1EV_MINPRI\s0" 4
2482.IX Item "EV_MINPRI"
2483.PD 0
2484.IP "\s-1EV_MAXPRI\s0" 4
2485.IX Item "EV_MAXPRI"
2486.PD
2487The range of allowed priorities. \f(CW\*(C`EV_MINPRI\*(C'\fR must be smaller or equal to
2488\&\f(CW\*(C`EV_MAXPRI\*(C'\fR, but otherwise there are no non-obvious limitations. You can
2489provide for more priorities by overriding those symbols (usually defined
2490to be \f(CW\*(C`\-2\*(C'\fR and \f(CW2\fR, respectively).
2491.Sp
2492When doing priority-based operations, libev usually has to linearly search
2493all the priorities, so having many of them (hundreds) uses a lot of space
2494and time, so using the defaults of five priorities (\-2 .. +2) is usually
2495fine.
2496.Sp
2497If your embedding app does not need any priorities, defining these both to
2498\&\f(CW0\fR will save some memory and cpu.
2499.IP "\s-1EV_PERIODIC_ENABLE\s0" 4
2500.IX Item "EV_PERIODIC_ENABLE"
2501If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If
2502defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
2503code.
2504.IP "\s-1EV_IDLE_ENABLE\s0" 4
2505.IX Item "EV_IDLE_ENABLE"
2506If undefined or defined to be \f(CW1\fR, then idle watchers are supported. If
2507defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
2508code.
2509.IP "\s-1EV_EMBED_ENABLE\s0" 4
2510.IX Item "EV_EMBED_ENABLE"
2511If undefined or defined to be \f(CW1\fR, then embed watchers are supported. If
2512defined to be \f(CW0\fR, then they are not.
2513.IP "\s-1EV_STAT_ENABLE\s0" 4
2514.IX Item "EV_STAT_ENABLE"
2515If undefined or defined to be \f(CW1\fR, then stat watchers are supported. If
2516defined to be \f(CW0\fR, then they are not.
2517.IP "\s-1EV_FORK_ENABLE\s0" 4
2518.IX Item "EV_FORK_ENABLE"
2519If undefined or defined to be \f(CW1\fR, then fork watchers are supported. If
2520defined to be \f(CW0\fR, then they are not.
2521.IP "\s-1EV_MINIMAL\s0" 4
2522.IX Item "EV_MINIMAL"
2523If you need to shave off some kilobytes of code at the expense of some
2524speed, define this symbol to \f(CW1\fR. Currently only used for gcc to override
2525some inlining decisions, saves roughly 30% codesize of amd64.
2526.IP "\s-1EV_PID_HASHSIZE\s0" 4
2527.IX Item "EV_PID_HASHSIZE"
2528\&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by
2529pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), usually more
2530than enough. If you need to manage thousands of children you might want to
2531increase this value (\fImust\fR be a power of two).
2532.IP "\s-1EV_INOTIFY_HASHSIZE\s0" 4
2533.IX Item "EV_INOTIFY_HASHSIZE"
2534\&\f(CW\*(C`ev_staz\*(C'\fR watchers use a small hash table to distribute workload by
2535inotify watch id. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR),
2536usually more than enough. If you need to manage thousands of \f(CW\*(C`ev_stat\*(C'\fR
2537watchers you might want to increase this value (\fImust\fR be a power of
2538two).
2539.IP "\s-1EV_COMMON\s0" 4
2540.IX Item "EV_COMMON"
2541By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining
2542this macro to a something else you can include more and other types of
2543members. You have to define it each time you include one of the files,
2544though, and it must be identical each time.
2545.Sp
2546For example, the perl \s-1EV\s0 module uses something like this:
2547.Sp
2548.Vb 3
2549\& #define EV_COMMON \e
2550\& SV *self; /* contains this struct */ \e
2551\& SV *cb_sv, *fh /* note no trailing ";" */
2552.Ve
2553.IP "\s-1EV_CB_DECLARE\s0 (type)" 4
2554.IX Item "EV_CB_DECLARE (type)"
2555.PD 0
2556.IP "\s-1EV_CB_INVOKE\s0 (watcher, revents)" 4
2557.IX Item "EV_CB_INVOKE (watcher, revents)"
2558.IP "ev_set_cb (ev, cb)" 4
2559.IX Item "ev_set_cb (ev, cb)"
2560.PD
2561Can be used to change the callback member declaration in each watcher,
2562and the way callbacks are invoked and set. Must expand to a struct member
2563definition and a statement, respectively. See the \fIev.v\fR header file for
2564their default definitions. One possible use for overriding these is to
2565avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use
2566method calls instead of plain function calls in \*(C+.
2567.Sh "\s-1EXAMPLES\s0"
2568.IX Subsection "EXAMPLES"
2569For a real-world example of a program the includes libev
2570verbatim, you can have a look at the \s-1EV\s0 perl module
2571(<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
2572the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public
2573interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file
2574will be compiled. It is pretty complex because it provides its own header
2575file.
2576.Sp
2577The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file
2578that everybody includes and which overrides some configure choices:
2579.Sp
2580.Vb 9
2581\& #define EV_MINIMAL 1
2582\& #define EV_USE_POLL 0
2583\& #define EV_MULTIPLICITY 0
2584\& #define EV_PERIODIC_ENABLE 0
2585\& #define EV_STAT_ENABLE 0
2586\& #define EV_FORK_ENABLE 0
2587\& #define EV_CONFIG_H <config.h>
2588\& #define EV_MINPRI 0
2589\& #define EV_MAXPRI 0
2590.Ve
2591.Sp
2592.Vb 1
2593\& #include "ev++.h"
2594.Ve
2595.Sp
2596And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled:
2597.Sp
2598.Vb 2
2599\& #include "ev_cpp.h"
2600\& #include "ev.c"
2601.Ve
2602.SH "COMPLEXITIES"
2603.IX Header "COMPLEXITIES"
2604In this section the complexities of (many of) the algorithms used inside
2605libev will be explained. For complexity discussions about backends see the
2606documentation for \f(CW\*(C`ev_default_init\*(C'\fR.
2607.Sp
2608All of the following are about amortised time: If an array needs to be
2609extended, libev needs to realloc and move the whole array, but this
2610happens asymptotically never with higher number of elements, so O(1) might
2611mean it might do a lengthy realloc operation in rare cases, but on average
2612it is much faster and asymptotically approaches constant time.
2613.RS 4
2614.IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4
2615.IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)"
2616This means that, when you have a watcher that triggers in one hour and
2617there are 100 watchers that would trigger before that then inserting will
2618have to skip those 100 watchers.
2619.IP "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)" 4
2620.IX Item "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)"
2621That means that for changing a timer costs less than removing/adding them
2622as only the relative motion in the event queue has to be paid for.
2623.IP "Starting io/check/prepare/idle/signal/child watchers: O(1)" 4
2624.IX Item "Starting io/check/prepare/idle/signal/child watchers: O(1)"
2625These just add the watcher into an array or at the head of a list.
2626=item Stopping check/prepare/idle watchers: O(1)
2627.IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4
2628.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))"
2629These watchers are stored in lists then need to be walked to find the
2630correct watcher to remove. The lists are usually short (you don't usually
2631have many watchers waiting for the same fd or signal).
2632.IP "Finding the next timer per loop iteration: O(1)" 4
2633.IX Item "Finding the next timer per loop iteration: O(1)"
2634.PD 0
2635.IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4
2636.IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)"
2637.PD
2638A change means an I/O watcher gets started or stopped, which requires
2639libev to recalculate its status (and possibly tell the kernel).
2640.IP "Activating one watcher: O(1)" 4
2641.IX Item "Activating one watcher: O(1)"
2642.PD 0
2643.IP "Priority handling: O(number_of_priorities)" 4
2644.IX Item "Priority handling: O(number_of_priorities)"
2645.PD
2646Priorities are implemented by allocating some space for each
2647priority. When doing priority-based operations, libev usually has to
2648linearly search all the priorities.
2649.RE
2650.RS 4
976.SH "AUTHOR" 2651.SH "AUTHOR"
977.IX Header "AUTHOR" 2652.IX Header "AUTHOR"
978Marc Lehmann <libev@schmorp.de>. 2653Marc Lehmann <libev@schmorp.de>.

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