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129.\" ======================================================================== 124.\" ========================================================================
130.\" 125.\"
131.IX Title "EV 1" 126.IX Title "LIBEV 3"
132.TH EV 1 "2007-12-19" "perl v5.8.8" "User Contributed Perl Documentation" 127.TH LIBEV 3 "2012-05-06" "libev-4.11" "libev - high performance full featured event loop"
128.\" For nroff, turn off justification. Always turn off hyphenation; it makes
129.\" way too many mistakes in technical documents.
130.if n .ad l
131.nh
133.SH "NAME" 132.SH "NAME"
134libev \- a high performance full\-featured event loop written in C 133libev \- a high performance full\-featured event loop written in C
135.SH "SYNOPSIS" 134.SH "SYNOPSIS"
136.IX Header "SYNOPSIS" 135.IX Header "SYNOPSIS"
137.Vb 1 136.Vb 1
138\& #include <ev.h> 137\& #include <ev.h>
139.Ve 138.Ve
140.SH "EXAMPLE PROGRAM" 139.SS "\s-1EXAMPLE\s0 \s-1PROGRAM\s0"
141.IX Header "EXAMPLE PROGRAM" 140.IX Subsection "EXAMPLE PROGRAM"
142.Vb 1
143\& #include <ev.h>
144.Ve
145.PP
146.Vb 2 141.Vb 2
142\& // a single header file is required
143\& #include <ev.h>
144\&
145\& #include <stdio.h> // for puts
146\&
147\& // every watcher type has its own typedef\*(Aqd struct
148\& // with the name ev_TYPE
147\& ev_io stdin_watcher; 149\& ev_io stdin_watcher;
148\& ev_timer timeout_watcher; 150\& ev_timer timeout_watcher;
149.Ve 151\&
150.PP 152\& // all watcher callbacks have a similar signature
151.Vb 8
152\& /* called when data readable on stdin */ 153\& // this callback is called when data is readable on stdin
153\& static void 154\& static void
154\& stdin_cb (EV_P_ struct ev_io *w, int revents) 155\& stdin_cb (EV_P_ ev_io *w, int revents)
155\& { 156\& {
156\& /* puts ("stdin ready"); */ 157\& puts ("stdin ready");
157\& ev_io_stop (EV_A_ w); /* just a syntax example */ 158\& // for one\-shot events, one must manually stop the watcher
158\& ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */ 159\& // with its corresponding stop function.
160\& ev_io_stop (EV_A_ w);
161\&
162\& // this causes all nested ev_run\*(Aqs to stop iterating
163\& ev_break (EV_A_ EVBREAK_ALL);
159\& } 164\& }
160.Ve 165\&
161.PP 166\& // another callback, this time for a time\-out
162.Vb 6
163\& static void 167\& static void
164\& timeout_cb (EV_P_ struct ev_timer *w, int revents) 168\& timeout_cb (EV_P_ ev_timer *w, int revents)
165\& { 169\& {
166\& /* puts ("timeout"); */ 170\& puts ("timeout");
167\& ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */ 171\& // this causes the innermost ev_run to stop iterating
172\& ev_break (EV_A_ EVBREAK_ONE);
168\& } 173\& }
169.Ve 174\&
170.PP
171.Vb 4
172\& int 175\& int
173\& main (void) 176\& main (void)
174\& { 177\& {
175\& struct ev_loop *loop = ev_default_loop (0); 178\& // use the default event loop unless you have special needs
176.Ve 179\& struct ev_loop *loop = EV_DEFAULT;
177.PP 180\&
178.Vb 3
179\& /* initialise an io watcher, then start it */ 181\& // initialise an io watcher, then start it
182\& // this one will watch for stdin to become readable
180\& ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); 183\& ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
181\& ev_io_start (loop, &stdin_watcher); 184\& ev_io_start (loop, &stdin_watcher);
182.Ve 185\&
183.PP 186\& // initialise a timer watcher, then start it
184.Vb 3
185\& /* simple non-repeating 5.5 second timeout */ 187\& // simple non\-repeating 5.5 second timeout
186\& ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); 188\& ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
187\& ev_timer_start (loop, &timeout_watcher); 189\& ev_timer_start (loop, &timeout_watcher);
188.Ve 190\&
189.PP 191\& // now wait for events to arrive
190.Vb 2
191\& /* loop till timeout or data ready */
192\& ev_loop (loop, 0); 192\& ev_run (loop, 0);
193.Ve 193\&
194.PP 194\& // break was called, so exit
195.Vb 2
196\& return 0; 195\& return 0;
197\& } 196\& }
198.Ve 197.Ve
199.SH "DESCRIPTION" 198.SH "ABOUT THIS DOCUMENT"
200.IX Header "DESCRIPTION" 199.IX Header "ABOUT THIS DOCUMENT"
200This document documents the libev software package.
201.PP
201The newest version of this document is also available as a html-formatted 202The newest version of this document is also available as an html-formatted
202web page you might find easier to navigate when reading it for the first 203web page you might find easier to navigate when reading it for the first
203time: <http://cvs.schmorp.de/libev/ev.html>. 204time: <http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
204.PP 205.PP
206While this document tries to be as complete as possible in documenting
207libev, its usage and the rationale behind its design, it is not a tutorial
208on event-based programming, nor will it introduce event-based programming
209with libev.
210.PP
211Familiarity with event based programming techniques in general is assumed
212throughout this document.
213.SH "WHAT TO READ WHEN IN A HURRY"
214.IX Header "WHAT TO READ WHEN IN A HURRY"
215This manual tries to be very detailed, but unfortunately, this also makes
216it very long. If you just want to know the basics of libev, I suggest
217reading \*(L"\s-1ANATOMY\s0 \s-1OF\s0 A \s-1WATCHER\s0\*(R", then the \*(L"\s-1EXAMPLE\s0 \s-1PROGRAM\s0\*(R" above and
218look up the missing functions in \*(L"\s-1GLOBAL\s0 \s-1FUNCTIONS\s0\*(R" and the \f(CW\*(C`ev_io\*(C'\fR and
219\&\f(CW\*(C`ev_timer\*(C'\fR sections in \*(L"\s-1WATCHER\s0 \s-1TYPES\s0\*(R".
220.SH "ABOUT LIBEV"
221.IX Header "ABOUT LIBEV"
205Libev is an event loop: you register interest in certain events (such as a 222Libev is an event loop: you register interest in certain events (such as a
206file descriptor being readable or a timeout occuring), and it will manage 223file descriptor being readable or a timeout occurring), and it will manage
207these event sources and provide your program with events. 224these event sources and provide your program with events.
208.PP 225.PP
209To do this, it must take more or less complete control over your process 226To do this, it must take more or less complete control over your process
210(or thread) by executing the \fIevent loop\fR handler, and will then 227(or thread) by executing the \fIevent loop\fR handler, and will then
211communicate events via a callback mechanism. 228communicate events via a callback mechanism.
212.PP 229.PP
213You register interest in certain events by registering so-called \fIevent 230You register interest in certain events by registering so-called \fIevent
214watchers\fR, which are relatively small C structures you initialise with the 231watchers\fR, which are relatively small C structures you initialise with the
215details of the event, and then hand it over to libev by \fIstarting\fR the 232details of the event, and then hand it over to libev by \fIstarting\fR the
216watcher. 233watcher.
217.SH "FEATURES" 234.SS "\s-1FEATURES\s0"
218.IX Header "FEATURES" 235.IX Subsection "FEATURES"
219Libev supports \f(CW\*(C`select\*(C'\fR, \f(CW\*(C`poll\*(C'\fR, the Linux-specific \f(CW\*(C`epoll\*(C'\fR, the 236Libev supports \f(CW\*(C`select\*(C'\fR, \f(CW\*(C`poll\*(C'\fR, the Linux-specific \f(CW\*(C`epoll\*(C'\fR, the
220BSD-specific \f(CW\*(C`kqueue\*(C'\fR and the Solaris-specific event port mechanisms 237BSD-specific \f(CW\*(C`kqueue\*(C'\fR and the Solaris-specific event port mechanisms
221for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), the Linux \f(CW\*(C`inotify\*(C'\fR interface 238for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), the Linux \f(CW\*(C`inotify\*(C'\fR interface
222(for \f(CW\*(C`ev_stat\*(C'\fR), relative timers (\f(CW\*(C`ev_timer\*(C'\fR), absolute timers 239(for \f(CW\*(C`ev_stat\*(C'\fR), Linux eventfd/signalfd (for faster and cleaner
223with customised rescheduling (\f(CW\*(C`ev_periodic\*(C'\fR), synchronous signals 240inter-thread wakeup (\f(CW\*(C`ev_async\*(C'\fR)/signal handling (\f(CW\*(C`ev_signal\*(C'\fR)) relative
224(\f(CW\*(C`ev_signal\*(C'\fR), process status change events (\f(CW\*(C`ev_child\*(C'\fR), and event 241timers (\f(CW\*(C`ev_timer\*(C'\fR), absolute timers with customised rescheduling
225watchers dealing with the event loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR, 242(\f(CW\*(C`ev_periodic\*(C'\fR), synchronous signals (\f(CW\*(C`ev_signal\*(C'\fR), process status
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 243change events (\f(CW\*(C`ev_child\*(C'\fR), and event watchers dealing with the event
227file watchers (\f(CW\*(C`ev_stat\*(C'\fR) and even limited support for fork events 244loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR, \f(CW\*(C`ev_embed\*(C'\fR, \f(CW\*(C`ev_prepare\*(C'\fR and
228(\f(CW\*(C`ev_fork\*(C'\fR). 245\&\f(CW\*(C`ev_check\*(C'\fR watchers) as well as file watchers (\f(CW\*(C`ev_stat\*(C'\fR) and even
246limited support for fork events (\f(CW\*(C`ev_fork\*(C'\fR).
229.PP 247.PP
230It also is quite fast (see this 248It also is quite fast (see this
231benchmark comparing it to libevent 249benchmark <http://libev.schmorp.de/bench.html> comparing it to libevent
232for example). 250for example).
233.SH "CONVENTIONS" 251.SS "\s-1CONVENTIONS\s0"
234.IX Header "CONVENTIONS" 252.IX Subsection "CONVENTIONS"
235Libev is very configurable. In this manual the default configuration will 253Libev is very configurable. In this manual the default (and most common)
236be described, which supports multiple event loops. For more info about 254configuration will be described, which supports multiple event loops. For
237various configuration options please have a look at \fB\s-1EMBED\s0\fR section in 255more info about various configuration options please have a look at
238this manual. If libev was configured without support for multiple event 256\&\fB\s-1EMBED\s0\fR section in this manual. If libev was configured without support
239loops, then all functions taking an initial argument of name \f(CW\*(C`loop\*(C'\fR 257for multiple event loops, then all functions taking an initial argument of
240(which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR) will not have this argument. 258name \f(CW\*(C`loop\*(C'\fR (which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR) will not have
241.SH "TIME REPRESENTATION" 259this argument.
260.SS "\s-1TIME\s0 \s-1REPRESENTATION\s0"
242.IX Header "TIME REPRESENTATION" 261.IX Subsection "TIME REPRESENTATION"
243Libev represents time as a single floating point number, representing the 262Libev represents time as a single floating point number, representing
244(fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near 263the (fractional) number of seconds since the (\s-1POSIX\s0) epoch (in practice
245the beginning of 1970, details are complicated, don't ask). This type is 264somewhere near the beginning of 1970, details are complicated, don't
246called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use too. It usually aliases 265ask). This type is called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use
247to the \f(CW\*(C`double\*(C'\fR type in C, and when you need to do any calculations on 266too. It usually aliases to the \f(CW\*(C`double\*(C'\fR type in C. When you need to do
248it, you should treat it as some floatingpoint value. Unlike the name 267any calculations on it, you should treat it as some floating point value.
268.PP
249component \f(CW\*(C`stamp\*(C'\fR might indicate, it is also used for time differences 269Unlike the name component \f(CW\*(C`stamp\*(C'\fR might indicate, it is also used for
250throughout libev. 270time differences (e.g. delays) throughout libev.
271.SH "ERROR HANDLING"
272.IX Header "ERROR HANDLING"
273Libev knows three classes of errors: operating system errors, usage errors
274and internal errors (bugs).
275.PP
276When libev catches an operating system error it cannot handle (for example
277a system call indicating a condition libev cannot fix), it calls the callback
278set via \f(CW\*(C`ev_set_syserr_cb\*(C'\fR, which is supposed to fix the problem or
279abort. The default is to print a diagnostic message and to call \f(CW\*(C`abort
280()\*(C'\fR.
281.PP
282When libev detects a usage error such as a negative timer interval, then
283it will print a diagnostic message and abort (via the \f(CW\*(C`assert\*(C'\fR mechanism,
284so \f(CW\*(C`NDEBUG\*(C'\fR will disable this checking): these are programming errors in
285the libev caller and need to be fixed there.
286.PP
287Libev also has a few internal error-checking \f(CW\*(C`assert\*(C'\fRions, and also has
288extensive consistency checking code. These do not trigger under normal
289circumstances, as they indicate either a bug in libev or worse.
251.SH "GLOBAL FUNCTIONS" 290.SH "GLOBAL FUNCTIONS"
252.IX Header "GLOBAL FUNCTIONS" 291.IX Header "GLOBAL FUNCTIONS"
253These functions can be called anytime, even before initialising the 292These functions can be called anytime, even before initialising the
254library in any way. 293library in any way.
255.IP "ev_tstamp ev_time ()" 4 294.IP "ev_tstamp ev_time ()" 4
256.IX Item "ev_tstamp ev_time ()" 295.IX Item "ev_tstamp ev_time ()"
257Returns the current time as libev would use it. Please note that the 296Returns the current time as libev would use it. Please note that the
258\&\f(CW\*(C`ev_now\*(C'\fR function is usually faster and also often returns the timestamp 297\&\f(CW\*(C`ev_now\*(C'\fR function is usually faster and also often returns the timestamp
259you actually want to know. 298you actually want to know. Also interesting is the combination of
299\&\f(CW\*(C`ev_now_update\*(C'\fR and \f(CW\*(C`ev_now\*(C'\fR.
300.IP "ev_sleep (ev_tstamp interval)" 4
301.IX Item "ev_sleep (ev_tstamp interval)"
302Sleep for the given interval: The current thread will be blocked
303until either it is interrupted or the given time interval has
304passed (approximately \- it might return a bit earlier even if not
305interrupted). Returns immediately if \f(CW\*(C`interval <= 0\*(C'\fR.
306.Sp
307Basically this is a sub-second-resolution \f(CW\*(C`sleep ()\*(C'\fR.
308.Sp
309The range of the \f(CW\*(C`interval\*(C'\fR is limited \- libev only guarantees to work
310with sleep times of up to one day (\f(CW\*(C`interval <= 86400\*(C'\fR).
260.IP "int ev_version_major ()" 4 311.IP "int ev_version_major ()" 4
261.IX Item "int ev_version_major ()" 312.IX Item "int ev_version_major ()"
262.PD 0 313.PD 0
263.IP "int ev_version_minor ()" 4 314.IP "int ev_version_minor ()" 4
264.IX Item "int ev_version_minor ()" 315.IX Item "int ev_version_minor ()"
… …
276as this indicates an incompatible change. Minor versions are usually 327as this indicates an incompatible change. Minor versions are usually
277compatible to older versions, so a larger minor version alone is usually 328compatible to older versions, so a larger minor version alone is usually
278not a problem. 329not a problem.
279.Sp 330.Sp
280Example: Make sure we haven't accidentally been linked against the wrong 331Example: Make sure we haven't accidentally been linked against the wrong
281version. 332version (note, however, that this will not detect other \s-1ABI\s0 mismatches,
333such as \s-1LFS\s0 or reentrancy).
282.Sp 334.Sp
283.Vb 3 335.Vb 3
284\& assert (("libev version mismatch", 336\& assert (("libev version mismatch",
285\& ev_version_major () == EV_VERSION_MAJOR 337\& ev_version_major () == EV_VERSION_MAJOR
286\& && ev_version_minor () >= EV_VERSION_MINOR)); 338\& && ev_version_minor () >= EV_VERSION_MINOR));
287.Ve 339.Ve
288.IP "unsigned int ev_supported_backends ()" 4 340.IP "unsigned int ev_supported_backends ()" 4
289.IX Item "unsigned int ev_supported_backends ()" 341.IX Item "unsigned int ev_supported_backends ()"
290Return the set of all backends (i.e. their corresponding \f(CW\*(C`EV_BACKEND_*\*(C'\fR 342Return the set of all backends (i.e. their corresponding \f(CW\*(C`EV_BACKEND_*\*(C'\fR
291value) compiled into this binary of libev (independent of their 343value) compiled into this binary of libev (independent of their
… …
294.Sp 346.Sp
295Example: make sure we have the epoll method, because yeah this is cool and 347Example: make sure we have the epoll method, because yeah this is cool and
296a must have and can we have a torrent of it please!!!11 348a must have and can we have a torrent of it please!!!11
297.Sp 349.Sp
298.Vb 2 350.Vb 2
299\& assert (("sorry, no epoll, no sex", 351\& assert (("sorry, no epoll, no sex",
300\& ev_supported_backends () & EVBACKEND_EPOLL)); 352\& ev_supported_backends () & EVBACKEND_EPOLL));
301.Ve 353.Ve
302.IP "unsigned int ev_recommended_backends ()" 4 354.IP "unsigned int ev_recommended_backends ()" 4
303.IX Item "unsigned int ev_recommended_backends ()" 355.IX Item "unsigned int ev_recommended_backends ()"
304Return the set of all backends compiled into this binary of libev and also 356Return the set of all backends compiled into this binary of libev and
305recommended for this platform. This set is often smaller than the one 357also recommended for this platform, meaning it will work for most file
358descriptor types. This set is often smaller than the one returned by
306returned by \f(CW\*(C`ev_supported_backends\*(C'\fR, as for example kqueue is broken on 359\&\f(CW\*(C`ev_supported_backends\*(C'\fR, as for example kqueue is broken on most BSDs
307most BSDs and will not be autodetected unless you explicitly request it 360and will not be auto-detected unless you explicitly request it (assuming
308(assuming you know what you are doing). This is the set of backends that 361you know what you are doing). This is the set of backends that libev will
309libev will probe for if you specify no backends explicitly. 362probe for if you specify no backends explicitly.
310.IP "unsigned int ev_embeddable_backends ()" 4 363.IP "unsigned int ev_embeddable_backends ()" 4
311.IX Item "unsigned int ev_embeddable_backends ()" 364.IX Item "unsigned int ev_embeddable_backends ()"
312Returns the set of backends that are embeddable in other event loops. This 365Returns the set of backends that are embeddable in other event loops. This
313is the theoretical, all\-platform, value. To find which backends 366value is platform-specific but can include backends not available on the
314might be supported on the current system, you would need to look at 367current system. To find which embeddable backends might be supported on
315\&\f(CW\*(C`ev_embeddable_backends () & ev_supported_backends ()\*(C'\fR, likewise for 368the current system, you would need to look at \f(CW\*(C`ev_embeddable_backends ()
316recommended ones. 369& ev_supported_backends ()\*(C'\fR, likewise for recommended ones.
317.Sp 370.Sp
318See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info. 371See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info.
319.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4 372.IP "ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())" 4
320.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))" 373.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())"
321Sets the allocation function to use (the prototype is similar \- the 374Sets the allocation function to use (the prototype is similar \- the
322semantics is identical \- to the realloc C function). It is used to 375semantics are identical to the \f(CW\*(C`realloc\*(C'\fR C89/SuS/POSIX function). It is
323allocate and free memory (no surprises here). If it returns zero when 376used to allocate and free memory (no surprises here). If it returns zero
324memory needs to be allocated, the library might abort or take some 377when memory needs to be allocated (\f(CW\*(C`size != 0\*(C'\fR), the library might abort
325potentially destructive action. The default is your system realloc 378or take some potentially destructive action.
326function. 379.Sp
380Since some systems (at least OpenBSD and Darwin) fail to implement
381correct \f(CW\*(C`realloc\*(C'\fR semantics, libev will use a wrapper around the system
382\&\f(CW\*(C`realloc\*(C'\fR and \f(CW\*(C`free\*(C'\fR functions by default.
327.Sp 383.Sp
328You could override this function in high-availability programs to, say, 384You could override this function in high-availability programs to, say,
329free some memory if it cannot allocate memory, to use a special allocator, 385free some memory if it cannot allocate memory, to use a special allocator,
330or even to sleep a while and retry until some memory is available. 386or even to sleep a while and retry until some memory is available.
331.Sp 387.Sp
332Example: Replace the libev allocator with one that waits a bit and then 388Example: Replace the libev allocator with one that waits a bit and then
333retries). 389retries (example requires a standards-compliant \f(CW\*(C`realloc\*(C'\fR).
334.Sp 390.Sp
335.Vb 6 391.Vb 6
336\& static void * 392\& static void *
337\& persistent_realloc (void *ptr, size_t size) 393\& persistent_realloc (void *ptr, size_t size)
338\& { 394\& {
339\& for (;;) 395\& for (;;)
340\& { 396\& {
341\& void *newptr = realloc (ptr, size); 397\& void *newptr = realloc (ptr, size);
342.Ve 398\&
343.Sp
344.Vb 2
345\& if (newptr) 399\& if (newptr)
346\& return newptr; 400\& return newptr;
347.Ve 401\&
348.Sp
349.Vb 3
350\& sleep (60); 402\& sleep (60);
351\& } 403\& }
352\& } 404\& }
353.Ve 405\&
354.Sp
355.Vb 2
356\& ... 406\& ...
357\& ev_set_allocator (persistent_realloc); 407\& ev_set_allocator (persistent_realloc);
358.Ve 408.Ve
359.IP "ev_set_syserr_cb (void (*cb)(const char *msg));" 4 409.IP "ev_set_syserr_cb (void (*cb)(const char *msg) throw ())" 4
360.IX Item "ev_set_syserr_cb (void (*cb)(const char *msg));" 410.IX Item "ev_set_syserr_cb (void (*cb)(const char *msg) throw ())"
361Set the callback function to call on a retryable syscall error (such 411Set the callback function to call on a retryable system call error (such
362as failed select, poll, epoll_wait). The message is a printable string 412as failed select, poll, epoll_wait). The message is a printable string
363indicating the system call or subsystem causing the problem. If this 413indicating the system call or subsystem causing the problem. If this
364callback is set, then libev will expect it to remedy the sitution, no 414callback is set, then libev will expect it to remedy the situation, no
365matter what, when it returns. That is, libev will generally retry the 415matter what, when it returns. That is, libev will generally retry the
366requested operation, or, if the condition doesn't go away, do bad stuff 416requested operation, or, if the condition doesn't go away, do bad stuff
367(such as abort). 417(such as abort).
368.Sp 418.Sp
369Example: This is basically the same thing that libev does internally, too. 419Example: This is basically the same thing that libev does internally, too.
… …
373\& fatal_error (const char *msg) 423\& fatal_error (const char *msg)
374\& { 424\& {
375\& perror (msg); 425\& perror (msg);
376\& abort (); 426\& abort ();
377\& } 427\& }
378.Ve 428\&
379.Sp
380.Vb 2
381\& ... 429\& ...
382\& ev_set_syserr_cb (fatal_error); 430\& ev_set_syserr_cb (fatal_error);
383.Ve 431.Ve
432.IP "ev_feed_signal (int signum)" 4
433.IX Item "ev_feed_signal (int signum)"
434This function can be used to \*(L"simulate\*(R" a signal receive. It is completely
435safe to call this function at any time, from any context, including signal
436handlers or random threads.
437.Sp
438Its main use is to customise signal handling in your process, especially
439in the presence of threads. For example, you could block signals
440by default in all threads (and specifying \f(CW\*(C`EVFLAG_NOSIGMASK\*(C'\fR when
441creating any loops), and in one thread, use \f(CW\*(C`sigwait\*(C'\fR or any other
442mechanism to wait for signals, then \*(L"deliver\*(R" them to libev by calling
443\&\f(CW\*(C`ev_feed_signal\*(C'\fR.
384.SH "FUNCTIONS CONTROLLING THE EVENT LOOP" 444.SH "FUNCTIONS CONTROLLING EVENT LOOPS"
385.IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP" 445.IX Header "FUNCTIONS CONTROLLING EVENT LOOPS"
386An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR. The library knows two 446An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR (the \f(CW\*(C`struct\*(C'\fR is
387types of such loops, the \fIdefault\fR loop, which supports signals and child 447\&\fInot\fR optional in this case unless libev 3 compatibility is disabled, as
388events, and dynamically created loops which do not. 448libev 3 had an \f(CW\*(C`ev_loop\*(C'\fR function colliding with the struct name).
389.PP 449.PP
390If you use threads, a common model is to run the default event loop 450The library knows two types of such loops, the \fIdefault\fR loop, which
391in your main thread (or in a separate thread) and for each thread you 451supports child process events, and dynamically created event loops which
392create, you also create another event loop. Libev itself does no locking 452do not.
393whatsoever, so if you mix calls to the same event loop in different
394threads, make sure you lock (this is usually a bad idea, though, even if
395done correctly, because it's hideous and inefficient).
396.IP "struct ev_loop *ev_default_loop (unsigned int flags)" 4 453.IP "struct ev_loop *ev_default_loop (unsigned int flags)" 4
397.IX Item "struct ev_loop *ev_default_loop (unsigned int flags)" 454.IX Item "struct ev_loop *ev_default_loop (unsigned int flags)"
398This will initialise the default event loop if it hasn't been initialised 455This returns the \*(L"default\*(R" event loop object, which is what you should
399yet and return it. If the default loop could not be initialised, returns 456normally use when you just need \*(L"the event loop\*(R". Event loop objects and
400false. If it already was initialised it simply returns it (and ignores the 457the \f(CW\*(C`flags\*(C'\fR parameter are described in more detail in the entry for
401flags. If that is troubling you, check \f(CW\*(C`ev_backend ()\*(C'\fR afterwards). 458\&\f(CW\*(C`ev_loop_new\*(C'\fR.
459.Sp
460If the default loop is already initialised then this function simply
461returns it (and ignores the flags. If that is troubling you, check
462\&\f(CW\*(C`ev_backend ()\*(C'\fR afterwards). Otherwise it will create it with the given
463flags, which should almost always be \f(CW0\fR, unless the caller is also the
464one calling \f(CW\*(C`ev_run\*(C'\fR or otherwise qualifies as \*(L"the main program\*(R".
402.Sp 465.Sp
403If you don't know what event loop to use, use the one returned from this 466If you don't know what event loop to use, use the one returned from this
404function. 467function (or via the \f(CW\*(C`EV_DEFAULT\*(C'\fR macro).
468.Sp
469Note that this function is \fInot\fR thread-safe, so if you want to use it
470from multiple threads, you have to employ some kind of mutex (note also
471that this case is unlikely, as loops cannot be shared easily between
472threads anyway).
473.Sp
474The default loop is the only loop that can handle \f(CW\*(C`ev_child\*(C'\fR watchers,
475and to do this, it always registers a handler for \f(CW\*(C`SIGCHLD\*(C'\fR. If this is
476a problem for your application you can either create a dynamic loop with
477\&\f(CW\*(C`ev_loop_new\*(C'\fR which doesn't do that, or you can simply overwrite the
478\&\f(CW\*(C`SIGCHLD\*(C'\fR signal handler \fIafter\fR calling \f(CW\*(C`ev_default_init\*(C'\fR.
479.Sp
480Example: This is the most typical usage.
481.Sp
482.Vb 2
483\& if (!ev_default_loop (0))
484\& fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
485.Ve
486.Sp
487Example: Restrict libev to the select and poll backends, and do not allow
488environment settings to be taken into account:
489.Sp
490.Vb 1
491\& ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
492.Ve
493.IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4
494.IX Item "struct ev_loop *ev_loop_new (unsigned int flags)"
495This will create and initialise a new event loop object. If the loop
496could not be initialised, returns false.
497.Sp
498This function is thread-safe, and one common way to use libev with
499threads is indeed to create one loop per thread, and using the default
500loop in the \*(L"main\*(R" or \*(L"initial\*(R" thread.
405.Sp 501.Sp
406The flags argument can be used to specify special behaviour or specific 502The flags argument can be used to specify special behaviour or specific
407backends to use, and is usually specified as \f(CW0\fR (or \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). 503backends to use, and is usually specified as \f(CW0\fR (or \f(CW\*(C`EVFLAG_AUTO\*(C'\fR).
408.Sp 504.Sp
409The following flags are supported: 505The following flags are supported:
… …
414The default flags value. Use this if you have no clue (it's the right 510The default flags value. Use this if you have no clue (it's the right
415thing, believe me). 511thing, believe me).
416.ie n .IP """EVFLAG_NOENV""" 4 512.ie n .IP """EVFLAG_NOENV""" 4
417.el .IP "\f(CWEVFLAG_NOENV\fR" 4 513.el .IP "\f(CWEVFLAG_NOENV\fR" 4
418.IX Item "EVFLAG_NOENV" 514.IX Item "EVFLAG_NOENV"
419If this flag bit is ored into the flag value (or the program runs setuid 515If this flag bit is or'ed into the flag value (or the program runs setuid
420or setgid) then libev will \fInot\fR look at the environment variable 516or setgid) then libev will \fInot\fR look at the environment variable
421\&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will 517\&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will
422override the flags completely if it is found in the environment. This is 518override the flags completely if it is found in the environment. This is
423useful to try out specific backends to test their performance, or to work 519useful to try out specific backends to test their performance, or to work
424around bugs. 520around bugs.
425.ie n .IP """EVFLAG_FORKCHECK""" 4 521.ie n .IP """EVFLAG_FORKCHECK""" 4
426.el .IP "\f(CWEVFLAG_FORKCHECK\fR" 4 522.el .IP "\f(CWEVFLAG_FORKCHECK\fR" 4
427.IX Item "EVFLAG_FORKCHECK" 523.IX Item "EVFLAG_FORKCHECK"
428Instead of calling \f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR manually after 524Instead of calling \f(CW\*(C`ev_loop_fork\*(C'\fR manually after a fork, you can also
429a fork, you can also make libev check for a fork in each iteration by 525make libev check for a fork in each iteration by enabling this flag.
430enabling this flag.
431.Sp 526.Sp
432This works by calling \f(CW\*(C`getpid ()\*(C'\fR on every iteration of the loop, 527This works by calling \f(CW\*(C`getpid ()\*(C'\fR on every iteration of the loop,
433and thus this might slow down your event loop if you do a lot of loop 528and thus this might slow down your event loop if you do a lot of loop
434iterations and little real work, but is usually not noticeable (on my 529iterations and little real work, but is usually not noticeable (on my
435Linux system for example, \f(CW\*(C`getpid\*(C'\fR is actually a simple 5\-insn sequence 530GNU/Linux system for example, \f(CW\*(C`getpid\*(C'\fR is actually a simple 5\-insn sequence
436without a syscall and thus \fIvery\fR fast, but my Linux system also has 531without a system call and thus \fIvery\fR fast, but my GNU/Linux system also has
437\&\f(CW\*(C`pthread_atfork\*(C'\fR which is even faster). 532\&\f(CW\*(C`pthread_atfork\*(C'\fR which is even faster).
438.Sp 533.Sp
439The big advantage of this flag is that you can forget about fork (and 534The big advantage of this flag is that you can forget about fork (and
440forget about forgetting to tell libev about forking) when you use this 535forget about forgetting to tell libev about forking) when you use this
441flag. 536flag.
442.Sp 537.Sp
443This flag setting cannot be overriden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR 538This flag setting cannot be overridden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR
444environment variable. 539environment variable.
540.ie n .IP """EVFLAG_NOINOTIFY""" 4
541.el .IP "\f(CWEVFLAG_NOINOTIFY\fR" 4
542.IX Item "EVFLAG_NOINOTIFY"
543When this flag is specified, then libev will not attempt to use the
544\&\fIinotify\fR \s-1API\s0 for its \f(CW\*(C`ev_stat\*(C'\fR watchers. Apart from debugging and
545testing, this flag can be useful to conserve inotify file descriptors, as
546otherwise each loop using \f(CW\*(C`ev_stat\*(C'\fR watchers consumes one inotify handle.
547.ie n .IP """EVFLAG_SIGNALFD""" 4
548.el .IP "\f(CWEVFLAG_SIGNALFD\fR" 4
549.IX Item "EVFLAG_SIGNALFD"
550When this flag is specified, then libev will attempt to use the
551\&\fIsignalfd\fR \s-1API\s0 for its \f(CW\*(C`ev_signal\*(C'\fR (and \f(CW\*(C`ev_child\*(C'\fR) watchers. This \s-1API\s0
552delivers signals synchronously, which makes it both faster and might make
553it possible to get the queued signal data. It can also simplify signal
554handling with threads, as long as you properly block signals in your
555threads that are not interested in handling them.
556.Sp
557Signalfd will not be used by default as this changes your signal mask, and
558there are a lot of shoddy libraries and programs (glib's threadpool for
559example) that can't properly initialise their signal masks.
560.ie n .IP """EVFLAG_NOSIGMASK""" 4
561.el .IP "\f(CWEVFLAG_NOSIGMASK\fR" 4
562.IX Item "EVFLAG_NOSIGMASK"
563When this flag is specified, then libev will avoid to modify the signal
564mask. Specifically, this means you have to make sure signals are unblocked
565when you want to receive them.
566.Sp
567This behaviour is useful when you want to do your own signal handling, or
568want to handle signals only in specific threads and want to avoid libev
569unblocking the signals.
570.Sp
571It's also required by \s-1POSIX\s0 in a threaded program, as libev calls
572\&\f(CW\*(C`sigprocmask\*(C'\fR, whose behaviour is officially unspecified.
573.Sp
574This flag's behaviour will become the default in future versions of libev.
445.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4 575.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4
446.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4 576.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4
447.IX Item "EVBACKEND_SELECT (value 1, portable select backend)" 577.IX Item "EVBACKEND_SELECT (value 1, portable select backend)"
448This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as 578This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as
449libev tries to roll its own fd_set with no limits on the number of fds, 579libev tries to roll its own fd_set with no limits on the number of fds,
450but if that fails, expect a fairly low limit on the number of fds when 580but if that fails, expect a fairly low limit on the number of fds when
451using this backend. It doesn't scale too well (O(highest_fd)), but its usually 581using this backend. It doesn't scale too well (O(highest_fd)), but its
452the fastest backend for a low number of fds. 582usually the fastest backend for a low number of (low-numbered :) fds.
583.Sp
584To get good performance out of this backend you need a high amount of
585parallelism (most of the file descriptors should be busy). If you are
586writing a server, you should \f(CW\*(C`accept ()\*(C'\fR in a loop to accept as many
587connections as possible during one iteration. You might also want to have
588a look at \f(CW\*(C`ev_set_io_collect_interval ()\*(C'\fR to increase the amount of
589readiness notifications you get per iteration.
590.Sp
591This backend maps \f(CW\*(C`EV_READ\*(C'\fR to the \f(CW\*(C`readfds\*(C'\fR set and \f(CW\*(C`EV_WRITE\*(C'\fR to the
592\&\f(CW\*(C`writefds\*(C'\fR set (and to work around Microsoft Windows bugs, also onto the
593\&\f(CW\*(C`exceptfds\*(C'\fR set on that platform).
453.ie n .IP """EVBACKEND_POLL"" (value 2, poll backend, available everywhere except on windows)" 4 594.ie n .IP """EVBACKEND_POLL"" (value 2, poll backend, available everywhere except on windows)" 4
454.el .IP "\f(CWEVBACKEND_POLL\fR (value 2, poll backend, available everywhere except on windows)" 4 595.el .IP "\f(CWEVBACKEND_POLL\fR (value 2, poll backend, available everywhere except on windows)" 4
455.IX Item "EVBACKEND_POLL (value 2, poll backend, available everywhere except on windows)" 596.IX Item "EVBACKEND_POLL (value 2, poll backend, available everywhere except on windows)"
456And this is your standard \fIpoll\fR\|(2) backend. It's more complicated than 597And this is your standard \fIpoll\fR\|(2) backend. It's more complicated
457select, but handles sparse fds better and has no artificial limit on the 598than select, but handles sparse fds better and has no artificial
458number of fds you can use (except it will slow down considerably with a 599limit on the number of fds you can use (except it will slow down
459lot of inactive fds). It scales similarly to select, i.e. O(total_fds). 600considerably with a lot of inactive fds). It scales similarly to select,
601i.e. O(total_fds). See the entry for \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR, above, for
602performance tips.
603.Sp
604This backend maps \f(CW\*(C`EV_READ\*(C'\fR to \f(CW\*(C`POLLIN | POLLERR | POLLHUP\*(C'\fR, and
605\&\f(CW\*(C`EV_WRITE\*(C'\fR to \f(CW\*(C`POLLOUT | POLLERR | POLLHUP\*(C'\fR.
460.ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4 606.ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4
461.el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4 607.el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4
462.IX Item "EVBACKEND_EPOLL (value 4, Linux)" 608.IX Item "EVBACKEND_EPOLL (value 4, Linux)"
609Use the linux-specific \fIepoll\fR\|(7) interface (for both pre\- and post\-2.6.9
610kernels).
611.Sp
463For few fds, this backend is a bit little slower than poll and select, 612For few fds, this backend is a bit little slower than poll and select, but
464but it scales phenomenally better. While poll and select usually scale like 613it scales phenomenally better. While poll and select usually scale like
465O(total_fds) where n is the total number of fds (or the highest fd), epoll scales 614O(total_fds) where total_fds is the total number of fds (or the highest
466either O(1) or O(active_fds). 615fd), epoll scales either O(1) or O(active_fds).
467.Sp 616.Sp
617The epoll mechanism deserves honorable mention as the most misdesigned
618of the more advanced event mechanisms: mere annoyances include silently
619dropping file descriptors, requiring a system call per change per file
620descriptor (and unnecessary guessing of parameters), problems with dup,
621returning before the timeout value, resulting in additional iterations
622(and only giving 5ms accuracy while select on the same platform gives
6230.1ms) and so on. The biggest issue is fork races, however \- if a program
624forks then \fIboth\fR parent and child process have to recreate the epoll
625set, which can take considerable time (one syscall per file descriptor)
626and is of course hard to detect.
627.Sp
628Epoll is also notoriously buggy \- embedding epoll fds \fIshould\fR work,
629but of course \fIdoesn't\fR, and epoll just loves to report events for
630totally \fIdifferent\fR file descriptors (even already closed ones, so
631one cannot even remove them from the set) than registered in the set
632(especially on \s-1SMP\s0 systems). Libev tries to counter these spurious
633notifications by employing an additional generation counter and comparing
634that against the events to filter out spurious ones, recreating the set
635when required. Epoll also erroneously rounds down timeouts, but gives you
636no way to know when and by how much, so sometimes you have to busy-wait
637because epoll returns immediately despite a nonzero timeout. And last
638not least, it also refuses to work with some file descriptors which work
639perfectly fine with \f(CW\*(C`select\*(C'\fR (files, many character devices...).
640.Sp
641Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
642cobbled together in a hurry, no thought to design or interaction with
643others. Oh, the pain, will it ever stop...
644.Sp
468While stopping and starting an I/O watcher in the same iteration will 645While stopping, setting and starting an I/O watcher in the same iteration
469result in some caching, there is still a syscall per such incident 646will result in some caching, there is still a system call per such
470(because the fd could point to a different file description now), so its 647incident (because the same \fIfile descriptor\fR could point to a different
471best to avoid that. Also, \fIdup()\fRed file descriptors might not work very 648\&\fIfile description\fR now), so its best to avoid that. Also, \f(CW\*(C`dup ()\*(C'\fR'ed
472well if you register events for both fds. 649file descriptors might not work very well if you register events for both
650file descriptors.
473.Sp 651.Sp
474Please note that epoll sometimes generates spurious notifications, so you 652Best performance from this backend is achieved by not unregistering all
475need to use non-blocking I/O or other means to avoid blocking when no data 653watchers for a file descriptor until it has been closed, if possible,
476(or space) is available. 654i.e. keep at least one watcher active per fd at all times. Stopping and
655starting a watcher (without re-setting it) also usually doesn't cause
656extra overhead. A fork can both result in spurious notifications as well
657as in libev having to destroy and recreate the epoll object, which can
658take considerable time and thus should be avoided.
659.Sp
660All this means that, in practice, \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR can be as fast or
661faster than epoll for maybe up to a hundred file descriptors, depending on
662the usage. So sad.
663.Sp
664While nominally embeddable in other event loops, this feature is broken in
665all kernel versions tested so far.
666.Sp
667This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as
668\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
477.ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4 669.ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4
478.el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4 670.el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4
479.IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)" 671.IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)"
480Kqueue deserves special mention, as at the time of this writing, it 672Kqueue deserves special mention, as at the time of this writing, it
481was broken on all BSDs except NetBSD (usually it doesn't work with 673was broken on all BSDs except NetBSD (usually it doesn't work reliably
482anything but sockets and pipes, except on Darwin, where of course its 674with anything but sockets and pipes, except on Darwin, where of course
483completely useless). For this reason its not being \*(L"autodetected\*(R" 675it's completely useless). Unlike epoll, however, whose brokenness
676is by design, these kqueue bugs can (and eventually will) be fixed
677without \s-1API\s0 changes to existing programs. For this reason it's not being
484unless you explicitly specify it explicitly in the flags (i.e. using 678\&\*(L"auto-detected\*(R" unless you explicitly specify it in the flags (i.e. using
485\&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR). 679\&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR) or libev was compiled on a known-to-be-good (\-enough)
680system like NetBSD.
681.Sp
682You still can embed kqueue into a normal poll or select backend and use it
683only for sockets (after having made sure that sockets work with kqueue on
684the target platform). See \f(CW\*(C`ev_embed\*(C'\fR watchers for more info.
486.Sp 685.Sp
487It scales in the same way as the epoll backend, but the interface to the 686It scales in the same way as the epoll backend, but the interface to the
488kernel is more efficient (which says nothing about its actual speed, of 687kernel is more efficient (which says nothing about its actual speed, of
489course). While starting and stopping an I/O watcher does not cause an 688course). While stopping, setting and starting an I/O watcher does never
490extra syscall as with epoll, it still adds up to four event changes per 689cause an extra system call as with \f(CW\*(C`EVBACKEND_EPOLL\*(C'\fR, it still adds up to
491incident, so its best to avoid that. 690two event changes per incident. Support for \f(CW\*(C`fork ()\*(C'\fR is very bad (you
691might have to leak fd's on fork, but it's more sane than epoll) and it
692drops fds silently in similarly hard-to-detect cases
693.Sp
694This backend usually performs well under most conditions.
695.Sp
696While nominally embeddable in other event loops, this doesn't work
697everywhere, so you might need to test for this. And since it is broken
698almost everywhere, you should only use it when you have a lot of sockets
699(for which it usually works), by embedding it into another event loop
700(e.g. \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR (but \f(CW\*(C`poll\*(C'\fR is of course
701also broken on \s-1OS\s0 X)) and, did I mention it, using it only for sockets.
702.Sp
703This backend maps \f(CW\*(C`EV_READ\*(C'\fR into an \f(CW\*(C`EVFILT_READ\*(C'\fR kevent with
704\&\f(CW\*(C`NOTE_EOF\*(C'\fR, and \f(CW\*(C`EV_WRITE\*(C'\fR into an \f(CW\*(C`EVFILT_WRITE\*(C'\fR kevent with
705\&\f(CW\*(C`NOTE_EOF\*(C'\fR.
492.ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4 706.ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4
493.el .IP "\f(CWEVBACKEND_DEVPOLL\fR (value 16, Solaris 8)" 4 707.el .IP "\f(CWEVBACKEND_DEVPOLL\fR (value 16, Solaris 8)" 4
494.IX Item "EVBACKEND_DEVPOLL (value 16, Solaris 8)" 708.IX Item "EVBACKEND_DEVPOLL (value 16, Solaris 8)"
495This is not implemented yet (and might never be). 709This is not implemented yet (and might never be, unless you send me an
710implementation). According to reports, \f(CW\*(C`/dev/poll\*(C'\fR only supports sockets
711and is not embeddable, which would limit the usefulness of this backend
712immensely.
496.ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4 713.ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4
497.el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4 714.el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4
498.IX Item "EVBACKEND_PORT (value 32, Solaris 10)" 715.IX Item "EVBACKEND_PORT (value 32, Solaris 10)"
499This uses the Solaris 10 port mechanism. As with everything on Solaris, 716This uses the Solaris 10 event port mechanism. As with everything on Solaris,
500it's really slow, but it still scales very well (O(active_fds)). 717it's really slow, but it still scales very well (O(active_fds)).
501.Sp 718.Sp
502Please note that solaris ports can result in a lot of spurious 719While this backend scales well, it requires one system call per active
503notifications, so you need to use non-blocking I/O or other means to avoid 720file descriptor per loop iteration. For small and medium numbers of file
504blocking when no data (or space) is available. 721descriptors a \*(L"slow\*(R" \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR backend
722might perform better.
723.Sp
724On the positive side, this backend actually performed fully to
725specification in all tests and is fully embeddable, which is a rare feat
726among the OS-specific backends (I vastly prefer correctness over speed
727hacks).
728.Sp
729On the negative side, the interface is \fIbizarre\fR \- so bizarre that
730even sun itself gets it wrong in their code examples: The event polling
731function sometimes returns events to the caller even though an error
732occurred, but with no indication whether it has done so or not (yes, it's
733even documented that way) \- deadly for edge-triggered interfaces where you
734absolutely have to know whether an event occurred or not because you have
735to re-arm the watcher.
736.Sp
737Fortunately libev seems to be able to work around these idiocies.
738.Sp
739This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as
740\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
505.ie n .IP """EVBACKEND_ALL""" 4 741.ie n .IP """EVBACKEND_ALL""" 4
506.el .IP "\f(CWEVBACKEND_ALL\fR" 4 742.el .IP "\f(CWEVBACKEND_ALL\fR" 4
507.IX Item "EVBACKEND_ALL" 743.IX Item "EVBACKEND_ALL"
508Try all backends (even potentially broken ones that wouldn't be tried 744Try all backends (even potentially broken ones that wouldn't be tried
509with \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). Since this is a mask, you can do stuff such as 745with \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). Since this is a mask, you can do stuff such as
510\&\f(CW\*(C`EVBACKEND_ALL & ~EVBACKEND_KQUEUE\*(C'\fR. 746\&\f(CW\*(C`EVBACKEND_ALL & ~EVBACKEND_KQUEUE\*(C'\fR.
747.Sp
748It is definitely not recommended to use this flag, use whatever
749\&\f(CW\*(C`ev_recommended_backends ()\*(C'\fR returns, or simply do not specify a backend
750at all.
751.ie n .IP """EVBACKEND_MASK""" 4
752.el .IP "\f(CWEVBACKEND_MASK\fR" 4
753.IX Item "EVBACKEND_MASK"
754Not a backend at all, but a mask to select all backend bits from a
755\&\f(CW\*(C`flags\*(C'\fR value, in case you want to mask out any backends from a flags
756value (e.g. when modifying the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR environment variable).
511.RE 757.RE
512.RS 4 758.RS 4
513.Sp 759.Sp
514If one or more of these are ored into the flags value, then only these 760If one or more of the backend flags are or'ed into the flags value,
515backends will be tried (in the reverse order as given here). If none are 761then only these backends will be tried (in the reverse order as listed
516specified, most compiled-in backend will be tried, usually in reverse 762here). If none are specified, all backends in \f(CW\*(C`ev_recommended_backends
517order of their flag values :) 763()\*(C'\fR will be tried.
518.Sp 764.Sp
519The most typical usage is like this: 765Example: Try to create a event loop that uses epoll and nothing else.
520.Sp 766.Sp
521.Vb 2 767.Vb 3
522\& if (!ev_default_loop (0)) 768\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
523\& fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); 769\& if (!epoller)
770\& fatal ("no epoll found here, maybe it hides under your chair");
524.Ve 771.Ve
525.Sp 772.Sp
526Restrict libev to the select and poll backends, and do not allow 773Example: Use whatever libev has to offer, but make sure that kqueue is
527environment settings to be taken into account: 774used if available.
528.Sp 775.Sp
529.Vb 1 776.Vb 1
530\& ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
531.Ve
532.Sp
533Use whatever libev has to offer, but make sure that kqueue is used if
534available (warning, breaks stuff, best use only with your own private
535event loop and only if you know the \s-1OS\s0 supports your types of fds):
536.Sp
537.Vb 1
538\& ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); 777\& struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
539.Ve 778.Ve
540.RE 779.RE
541.IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4
542.IX Item "struct ev_loop *ev_loop_new (unsigned int flags)"
543Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is
544always distinct from the default loop. Unlike the default loop, it cannot
545handle signal and child watchers, and attempts to do so will be greeted by
546undefined behaviour (or a failed assertion if assertions are enabled).
547.Sp
548Example: Try to create a event loop that uses epoll and nothing else.
549.Sp
550.Vb 3
551\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
552\& if (!epoller)
553\& fatal ("no epoll found here, maybe it hides under your chair");
554.Ve
555.IP "ev_default_destroy ()" 4 780.IP "ev_loop_destroy (loop)" 4
556.IX Item "ev_default_destroy ()" 781.IX Item "ev_loop_destroy (loop)"
557Destroys the default loop again (frees all memory and kernel state 782Destroys an event loop object (frees all memory and kernel state
558etc.). None of the active event watchers will be stopped in the normal 783etc.). None of the active event watchers will be stopped in the normal
559sense, so e.g. \f(CW\*(C`ev_is_active\*(C'\fR might still return true. It is your 784sense, so e.g. \f(CW\*(C`ev_is_active\*(C'\fR might still return true. It is your
560responsibility to either stop all watchers cleanly yoursef \fIbefore\fR 785responsibility to either stop all watchers cleanly yourself \fIbefore\fR
561calling this function, or cope with the fact afterwards (which is usually 786calling this function, or cope with the fact afterwards (which is usually
562the easiest thing, you can just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them 787the easiest thing, you can just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them
563for example). 788for example).
564.Sp 789.Sp
565Not that certain global state, such as signal state, will not be freed by 790Note that certain global state, such as signal state (and installed signal
566this function, and related watchers (such as signal and child watchers) 791handlers), will not be freed by this function, and related watchers (such
567would need to be stopped manually. 792as signal and child watchers) would need to be stopped manually.
568.Sp 793.Sp
569In general it is not advisable to call this function except in the 794This function is normally used on loop objects allocated by
570rare occasion where you really need to free e.g. the signal handling 795\&\f(CW\*(C`ev_loop_new\*(C'\fR, but it can also be used on the default loop returned by
571pipe fds. If you need dynamically allocated loops it is better to use 796\&\f(CW\*(C`ev_default_loop\*(C'\fR, in which case it is not thread-safe.
572\&\f(CW\*(C`ev_loop_new\*(C'\fR and \f(CW\*(C`ev_loop_destroy\*(C'\fR).
573.IP "ev_loop_destroy (loop)" 4
574.IX Item "ev_loop_destroy (loop)"
575Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an
576earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR.
577.IP "ev_default_fork ()" 4
578.IX Item "ev_default_fork ()"
579This function reinitialises the kernel state for backends that have
580one. Despite the name, you can call it anytime, but it makes most sense
581after forking, in either the parent or child process (or both, but that
582again makes little sense).
583.Sp 797.Sp
584You \fImust\fR call this function in the child process after forking if and 798Note that it is not advisable to call this function on the default loop
585only if you want to use the event library in both processes. If you just 799except in the rare occasion where you really need to free its resources.
586fork+exec, you don't have to call it. 800If you need dynamically allocated loops it is better to use \f(CW\*(C`ev_loop_new\*(C'\fR
587.Sp 801and \f(CW\*(C`ev_loop_destroy\*(C'\fR.
588The function itself is quite fast and it's usually not a problem to call
589it just in case after a fork. To make this easy, the function will fit in
590quite nicely into a call to \f(CW\*(C`pthread_atfork\*(C'\fR:
591.Sp
592.Vb 1
593\& pthread_atfork (0, 0, ev_default_fork);
594.Ve
595.Sp
596At the moment, \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and \f(CW\*(C`EVBACKEND_POLL\*(C'\fR are safe to use
597without calling this function, so if you force one of those backends you
598do not need to care.
599.IP "ev_loop_fork (loop)" 4 802.IP "ev_loop_fork (loop)" 4
600.IX Item "ev_loop_fork (loop)" 803.IX Item "ev_loop_fork (loop)"
601Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by 804This function sets a flag that causes subsequent \f(CW\*(C`ev_run\*(C'\fR iterations to
602\&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop 805reinitialise the kernel state for backends that have one. Despite the
603after fork, and how you do this is entirely your own problem. 806name, you can call it anytime, but it makes most sense after forking, in
807the child process. You \fImust\fR call it (or use \f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR) in the
808child before resuming or calling \f(CW\*(C`ev_run\*(C'\fR.
809.Sp
810Again, you \fIhave\fR to call it on \fIany\fR loop that you want to re-use after
811a fork, \fIeven if you do not plan to use the loop in the parent\fR. This is
812because some kernel interfaces *cough* \fIkqueue\fR *cough* do funny things
813during fork.
814.Sp
815On the other hand, you only need to call this function in the child
816process if and only if you want to use the event loop in the child. If
817you just fork+exec or create a new loop in the child, you don't have to
818call it at all (in fact, \f(CW\*(C`epoll\*(C'\fR is so badly broken that it makes a
819difference, but libev will usually detect this case on its own and do a
820costly reset of the backend).
821.Sp
822The function itself is quite fast and it's usually not a problem to call
823it just in case after a fork.
824.Sp
825Example: Automate calling \f(CW\*(C`ev_loop_fork\*(C'\fR on the default loop when
826using pthreads.
827.Sp
828.Vb 5
829\& static void
830\& post_fork_child (void)
831\& {
832\& ev_loop_fork (EV_DEFAULT);
833\& }
834\&
835\& ...
836\& pthread_atfork (0, 0, post_fork_child);
837.Ve
838.IP "int ev_is_default_loop (loop)" 4
839.IX Item "int ev_is_default_loop (loop)"
840Returns true when the given loop is, in fact, the default loop, and false
841otherwise.
604.IP "unsigned int ev_loop_count (loop)" 4 842.IP "unsigned int ev_iteration (loop)" 4
605.IX Item "unsigned int ev_loop_count (loop)" 843.IX Item "unsigned int ev_iteration (loop)"
606Returns the count of loop iterations for the loop, which is identical to 844Returns the current iteration count for the event loop, which is identical
607the number of times libev did poll for new events. It starts at \f(CW0\fR and 845to the number of times libev did poll for new events. It starts at \f(CW0\fR
608happily wraps around with enough iterations. 846and happily wraps around with enough iterations.
609.Sp 847.Sp
610This value can sometimes be useful as a generation counter of sorts (it 848This value can sometimes be useful as a generation counter of sorts (it
611\&\*(L"ticks\*(R" the number of loop iterations), as it roughly corresponds with 849\&\*(L"ticks\*(R" the number of loop iterations), as it roughly corresponds with
612\&\f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR calls. 850\&\f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR calls \- and is incremented between the
851prepare and check phases.
852.IP "unsigned int ev_depth (loop)" 4
853.IX Item "unsigned int ev_depth (loop)"
854Returns the number of times \f(CW\*(C`ev_run\*(C'\fR was entered minus the number of
855times \f(CW\*(C`ev_run\*(C'\fR was exited normally, in other words, the recursion depth.
856.Sp
857Outside \f(CW\*(C`ev_run\*(C'\fR, this number is zero. In a callback, this number is
858\&\f(CW1\fR, unless \f(CW\*(C`ev_run\*(C'\fR was invoked recursively (or from another thread),
859in which case it is higher.
860.Sp
861Leaving \f(CW\*(C`ev_run\*(C'\fR abnormally (setjmp/longjmp, cancelling the thread,
862throwing an exception etc.), doesn't count as \*(L"exit\*(R" \- consider this
863as a hint to avoid such ungentleman-like behaviour unless it's really
864convenient, in which case it is fully supported.
613.IP "unsigned int ev_backend (loop)" 4 865.IP "unsigned int ev_backend (loop)" 4
614.IX Item "unsigned int ev_backend (loop)" 866.IX Item "unsigned int ev_backend (loop)"
615Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in 867Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in
616use. 868use.
617.IP "ev_tstamp ev_now (loop)" 4 869.IP "ev_tstamp ev_now (loop)" 4
618.IX Item "ev_tstamp ev_now (loop)" 870.IX Item "ev_tstamp ev_now (loop)"
619Returns the current \*(L"event loop time\*(R", which is the time the event loop 871Returns the current \*(L"event loop time\*(R", which is the time the event loop
620received events and started processing them. This timestamp does not 872received events and started processing them. This timestamp does not
621change as long as callbacks are being processed, and this is also the base 873change as long as callbacks are being processed, and this is also the base
622time used for relative timers. You can treat it as the timestamp of the 874time used for relative timers. You can treat it as the timestamp of the
623event occuring (or more correctly, libev finding out about it). 875event occurring (or more correctly, libev finding out about it).
876.IP "ev_now_update (loop)" 4
877.IX Item "ev_now_update (loop)"
878Establishes the current time by querying the kernel, updating the time
879returned by \f(CW\*(C`ev_now ()\*(C'\fR in the progress. This is a costly operation and
880is usually done automatically within \f(CW\*(C`ev_run ()\*(C'\fR.
881.Sp
882This function is rarely useful, but when some event callback runs for a
883very long time without entering the event loop, updating libev's idea of
884the current time is a good idea.
885.Sp
886See also \*(L"The special problem of time updates\*(R" in the \f(CW\*(C`ev_timer\*(C'\fR section.
887.IP "ev_suspend (loop)" 4
888.IX Item "ev_suspend (loop)"
889.PD 0
890.IP "ev_resume (loop)" 4
891.IX Item "ev_resume (loop)"
892.PD
893These two functions suspend and resume an event loop, for use when the
894loop is not used for a while and timeouts should not be processed.
895.Sp
896A typical use case would be an interactive program such as a game: When
897the user presses \f(CW\*(C`^Z\*(C'\fR to suspend the game and resumes it an hour later it
898would be best to handle timeouts as if no time had actually passed while
899the program was suspended. This can be achieved by calling \f(CW\*(C`ev_suspend\*(C'\fR
900in your \f(CW\*(C`SIGTSTP\*(C'\fR handler, sending yourself a \f(CW\*(C`SIGSTOP\*(C'\fR and calling
901\&\f(CW\*(C`ev_resume\*(C'\fR directly afterwards to resume timer processing.
902.Sp
903Effectively, all \f(CW\*(C`ev_timer\*(C'\fR watchers will be delayed by the time spend
904between \f(CW\*(C`ev_suspend\*(C'\fR and \f(CW\*(C`ev_resume\*(C'\fR, and all \f(CW\*(C`ev_periodic\*(C'\fR watchers
905will be rescheduled (that is, they will lose any events that would have
906occurred while suspended).
907.Sp
908After calling \f(CW\*(C`ev_suspend\*(C'\fR you \fBmust not\fR call \fIany\fR function on the
909given loop other than \f(CW\*(C`ev_resume\*(C'\fR, and you \fBmust not\fR call \f(CW\*(C`ev_resume\*(C'\fR
910without a previous call to \f(CW\*(C`ev_suspend\*(C'\fR.
911.Sp
912Calling \f(CW\*(C`ev_suspend\*(C'\fR/\f(CW\*(C`ev_resume\*(C'\fR has the side effect of updating the
913event loop time (see \f(CW\*(C`ev_now_update\*(C'\fR).
624.IP "ev_loop (loop, int flags)" 4 914.IP "bool ev_run (loop, int flags)" 4
625.IX Item "ev_loop (loop, int flags)" 915.IX Item "bool ev_run (loop, int flags)"
626Finally, this is it, the event handler. This function usually is called 916Finally, this is it, the event handler. This function usually is called
627after you initialised all your watchers and you want to start handling 917after you have initialised all your watchers and you want to start
628events. 918handling events. It will ask the operating system for any new events, call
919the watcher callbacks, and then repeat the whole process indefinitely: This
920is why event loops are called \fIloops\fR.
629.Sp 921.Sp
630If the flags argument is specified as \f(CW0\fR, it will not return until 922If the flags argument is specified as \f(CW0\fR, it will keep handling events
631either no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called. 923until either no event watchers are active anymore or \f(CW\*(C`ev_break\*(C'\fR was
924called.
632.Sp 925.Sp
926The return value is false if there are no more active watchers (which
927usually means \*(L"all jobs done\*(R" or \*(L"deadlock\*(R"), and true in all other cases
928(which usually means " you should call \f(CW\*(C`ev_run\*(C'\fR again").
929.Sp
633Please note that an explicit \f(CW\*(C`ev_unloop\*(C'\fR is usually better than 930Please note that an explicit \f(CW\*(C`ev_break\*(C'\fR is usually better than
634relying on all watchers to be stopped when deciding when a program has 931relying on all watchers to be stopped when deciding when a program has
635finished (especially in interactive programs), but having a program that 932finished (especially in interactive programs), but having a program
636automatically loops as long as it has to and no longer by virtue of 933that automatically loops as long as it has to and no longer by virtue
637relying on its watchers stopping correctly is a thing of beauty. 934of relying on its watchers stopping correctly, that is truly a thing of
935beauty.
638.Sp 936.Sp
937This function is \fImostly\fR exception-safe \- you can break out of a
938\&\f(CW\*(C`ev_run\*(C'\fR call by calling \f(CW\*(C`longjmp\*(C'\fR in a callback, throwing a \*(C+
939exception and so on. This does not decrement the \f(CW\*(C`ev_depth\*(C'\fR value, nor
940will it clear any outstanding \f(CW\*(C`EVBREAK_ONE\*(C'\fR breaks.
941.Sp
639A flags value of \f(CW\*(C`EVLOOP_NONBLOCK\*(C'\fR will look for new events, will handle 942A flags value of \f(CW\*(C`EVRUN_NOWAIT\*(C'\fR will look for new events, will handle
640those events and any outstanding ones, but will not block your process in 943those events and any already outstanding ones, but will not wait and
641case there are no events and will return after one iteration of the loop. 944block your process in case there are no events and will return after one
945iteration of the loop. This is sometimes useful to poll and handle new
946events while doing lengthy calculations, to keep the program responsive.
642.Sp 947.Sp
643A flags value of \f(CW\*(C`EVLOOP_ONESHOT\*(C'\fR will look for new events (waiting if 948A flags value of \f(CW\*(C`EVRUN_ONCE\*(C'\fR will look for new events (waiting if
644neccessary) and will handle those and any outstanding ones. It will block 949necessary) and will handle those and any already outstanding ones. It
645your process until at least one new event arrives, and will return after 950will block your process until at least one new event arrives (which could
646one iteration of the loop. This is useful if you are waiting for some 951be an event internal to libev itself, so there is no guarantee that a
647external event in conjunction with something not expressible using other 952user-registered callback will be called), and will return after one
953iteration of the loop.
954.Sp
955This is useful if you are waiting for some external event in conjunction
956with something not expressible using other libev watchers (i.e. "roll your
648libev watchers. However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is 957own \f(CW\*(C`ev_run\*(C'\fR"). However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is
649usually a better approach for this kind of thing. 958usually a better approach for this kind of thing.
650.Sp 959.Sp
651Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does: 960Here are the gory details of what \f(CW\*(C`ev_run\*(C'\fR does (this is for your
961understanding, not a guarantee that things will work exactly like this in
962future versions):
652.Sp 963.Sp
653.Vb 19 964.Vb 10
965\& \- Increment loop depth.
966\& \- Reset the ev_break status.
654\& - Before the first iteration, call any pending watchers. 967\& \- Before the first iteration, call any pending watchers.
655\& * If there are no active watchers (reference count is zero), return. 968\& LOOP:
656\& - Queue all prepare watchers and then call all outstanding watchers. 969\& \- If EVFLAG_FORKCHECK was used, check for a fork.
970\& \- If a fork was detected (by any means), queue and call all fork watchers.
971\& \- Queue and call all prepare watchers.
972\& \- If ev_break was called, goto FINISH.
657\& - If we have been forked, recreate the kernel state. 973\& \- If we have been forked, detach and recreate the kernel state
974\& as to not disturb the other process.
658\& - Update the kernel state with all outstanding changes. 975\& \- Update the kernel state with all outstanding changes.
659\& - Update the "event loop time". 976\& \- Update the "event loop time" (ev_now ()).
660\& - Calculate for how long to block. 977\& \- Calculate for how long to sleep or block, if at all
978\& (active idle watchers, EVRUN_NOWAIT or not having
979\& any active watchers at all will result in not sleeping).
980\& \- Sleep if the I/O and timer collect interval say so.
981\& \- Increment loop iteration counter.
661\& - Block the process, waiting for any events. 982\& \- Block the process, waiting for any events.
662\& - Queue all outstanding I/O (fd) events. 983\& \- Queue all outstanding I/O (fd) events.
663\& - Update the "event loop time" and do time jump handling. 984\& \- Update the "event loop time" (ev_now ()), and do time jump adjustments.
664\& - Queue all outstanding timers. 985\& \- Queue all expired timers.
665\& - Queue all outstanding periodics. 986\& \- Queue all expired periodics.
666\& - If no events are pending now, queue all idle watchers. 987\& \- Queue all idle watchers with priority higher than that of pending events.
667\& - Queue all check watchers. 988\& \- Queue all check watchers.
668\& - Call all queued watchers in reverse order (i.e. check watchers first). 989\& \- Call all queued watchers in reverse order (i.e. check watchers first).
669\& Signals and child watchers are implemented as I/O watchers, and will 990\& Signals and child watchers are implemented as I/O watchers, and will
670\& be handled here by queueing them when their watcher gets executed. 991\& be handled here by queueing them when their watcher gets executed.
671\& - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 992\& \- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
672\& were used, return, otherwise continue with step *. 993\& were used, or there are no active watchers, goto FINISH, otherwise
994\& continue with step LOOP.
995\& FINISH:
996\& \- Reset the ev_break status iff it was EVBREAK_ONE.
997\& \- Decrement the loop depth.
998\& \- Return.
673.Ve 999.Ve
674.Sp 1000.Sp
675Example: Queue some jobs and then loop until no events are outsanding 1001Example: Queue some jobs and then loop until no events are outstanding
676anymore. 1002anymore.
677.Sp 1003.Sp
678.Vb 4 1004.Vb 4
679\& ... queue jobs here, make sure they register event watchers as long 1005\& ... queue jobs here, make sure they register event watchers as long
680\& ... as they still have work to do (even an idle watcher will do..) 1006\& ... as they still have work to do (even an idle watcher will do..)
681\& ev_loop (my_loop, 0); 1007\& ev_run (my_loop, 0);
682\& ... jobs done. yeah! 1008\& ... jobs done or somebody called break. yeah!
683.Ve 1009.Ve
684.IP "ev_unloop (loop, how)" 4 1010.IP "ev_break (loop, how)" 4
685.IX Item "ev_unloop (loop, how)" 1011.IX Item "ev_break (loop, how)"
686Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it 1012Can be used to make a call to \f(CW\*(C`ev_run\*(C'\fR return early (but only after it
687has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either 1013has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either
688\&\f(CW\*(C`EVUNLOOP_ONE\*(C'\fR, which will make the innermost \f(CW\*(C`ev_loop\*(C'\fR call return, or 1014\&\f(CW\*(C`EVBREAK_ONE\*(C'\fR, which will make the innermost \f(CW\*(C`ev_run\*(C'\fR call return, or
689\&\f(CW\*(C`EVUNLOOP_ALL\*(C'\fR, which will make all nested \f(CW\*(C`ev_loop\*(C'\fR calls return. 1015\&\f(CW\*(C`EVBREAK_ALL\*(C'\fR, which will make all nested \f(CW\*(C`ev_run\*(C'\fR calls return.
1016.Sp
1017This \*(L"break state\*(R" will be cleared on the next call to \f(CW\*(C`ev_run\*(C'\fR.
1018.Sp
1019It is safe to call \f(CW\*(C`ev_break\*(C'\fR from outside any \f(CW\*(C`ev_run\*(C'\fR calls, too, in
1020which case it will have no effect.
690.IP "ev_ref (loop)" 4 1021.IP "ev_ref (loop)" 4
691.IX Item "ev_ref (loop)" 1022.IX Item "ev_ref (loop)"
692.PD 0 1023.PD 0
693.IP "ev_unref (loop)" 4 1024.IP "ev_unref (loop)" 4
694.IX Item "ev_unref (loop)" 1025.IX Item "ev_unref (loop)"
695.PD 1026.PD
696Ref/unref can be used to add or remove a reference count on the event 1027Ref/unref can be used to add or remove a reference count on the event
697loop: Every watcher keeps one reference, and as long as the reference 1028loop: Every watcher keeps one reference, and as long as the reference
698count is nonzero, \f(CW\*(C`ev_loop\*(C'\fR will not return on its own. If you have 1029count is nonzero, \f(CW\*(C`ev_run\*(C'\fR will not return on its own.
699a watcher you never unregister that should not keep \f(CW\*(C`ev_loop\*(C'\fR from 1030.Sp
700returning, \fIev_unref()\fR after starting, and \fIev_ref()\fR before stopping it. For 1031This is useful when you have a watcher that you never intend to
1032unregister, but that nevertheless should not keep \f(CW\*(C`ev_run\*(C'\fR from
1033returning. In such a case, call \f(CW\*(C`ev_unref\*(C'\fR after starting, and \f(CW\*(C`ev_ref\*(C'\fR
1034before stopping it.
1035.Sp
701example, libev itself uses this for its internal signal pipe: It is not 1036As an example, libev itself uses this for its internal signal pipe: It
702visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if 1037is not visible to the libev user and should not keep \f(CW\*(C`ev_run\*(C'\fR from
703no event watchers registered by it are active. It is also an excellent 1038exiting if no event watchers registered by it are active. It is also an
704way to do this for generic recurring timers or from within third-party 1039excellent way to do this for generic recurring timers or from within
705libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR. 1040third-party libraries. Just remember to \fIunref after start\fR and \fIref
1041before stop\fR (but only if the watcher wasn't active before, or was active
1042before, respectively. Note also that libev might stop watchers itself
1043(e.g. non-repeating timers) in which case you have to \f(CW\*(C`ev_ref\*(C'\fR
1044in the callback).
706.Sp 1045.Sp
707Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR 1046Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_run\*(C'\fR
708running when nothing else is active. 1047running when nothing else is active.
709.Sp 1048.Sp
710.Vb 4 1049.Vb 4
711\& struct ev_signal exitsig; 1050\& ev_signal exitsig;
712\& ev_signal_init (&exitsig, sig_cb, SIGINT); 1051\& ev_signal_init (&exitsig, sig_cb, SIGINT);
713\& ev_signal_start (loop, &exitsig); 1052\& ev_signal_start (loop, &exitsig);
714\& evf_unref (loop); 1053\& ev_unref (loop);
715.Ve 1054.Ve
716.Sp 1055.Sp
717Example: For some weird reason, unregister the above signal handler again. 1056Example: For some weird reason, unregister the above signal handler again.
718.Sp 1057.Sp
719.Vb 2 1058.Vb 2
720\& ev_ref (loop); 1059\& ev_ref (loop);
721\& ev_signal_stop (loop, &exitsig); 1060\& ev_signal_stop (loop, &exitsig);
722.Ve 1061.Ve
1062.IP "ev_set_io_collect_interval (loop, ev_tstamp interval)" 4
1063.IX Item "ev_set_io_collect_interval (loop, ev_tstamp interval)"
1064.PD 0
1065.IP "ev_set_timeout_collect_interval (loop, ev_tstamp interval)" 4
1066.IX Item "ev_set_timeout_collect_interval (loop, ev_tstamp interval)"
1067.PD
1068These advanced functions influence the time that libev will spend waiting
1069for events. Both time intervals are by default \f(CW0\fR, meaning that libev
1070will try to invoke timer/periodic callbacks and I/O callbacks with minimum
1071latency.
1072.Sp
1073Setting these to a higher value (the \f(CW\*(C`interval\*(C'\fR \fImust\fR be >= \f(CW0\fR)
1074allows libev to delay invocation of I/O and timer/periodic callbacks
1075to increase efficiency of loop iterations (or to increase power-saving
1076opportunities).
1077.Sp
1078The idea is that sometimes your program runs just fast enough to handle
1079one (or very few) event(s) per loop iteration. While this makes the
1080program responsive, it also wastes a lot of \s-1CPU\s0 time to poll for new
1081events, especially with backends like \f(CW\*(C`select ()\*(C'\fR which have a high
1082overhead for the actual polling but can deliver many events at once.
1083.Sp
1084By setting a higher \fIio collect interval\fR you allow libev to spend more
1085time collecting I/O events, so you can handle more events per iteration,
1086at the cost of increasing latency. Timeouts (both \f(CW\*(C`ev_periodic\*(C'\fR and
1087\&\f(CW\*(C`ev_timer\*(C'\fR) will not be affected. Setting this to a non-null value will
1088introduce an additional \f(CW\*(C`ev_sleep ()\*(C'\fR call into most loop iterations. The
1089sleep time ensures that libev will not poll for I/O events more often then
1090once per this interval, on average (as long as the host time resolution is
1091good enough).
1092.Sp
1093Likewise, by setting a higher \fItimeout collect interval\fR you allow libev
1094to spend more time collecting timeouts, at the expense of increased
1095latency/jitter/inexactness (the watcher callback will be called
1096later). \f(CW\*(C`ev_io\*(C'\fR watchers will not be affected. Setting this to a non-null
1097value will not introduce any overhead in libev.
1098.Sp
1099Many (busy) programs can usually benefit by setting the I/O collect
1100interval to a value near \f(CW0.1\fR or so, which is often enough for
1101interactive servers (of course not for games), likewise for timeouts. It
1102usually doesn't make much sense to set it to a lower value than \f(CW0.01\fR,
1103as this approaches the timing granularity of most systems. Note that if
1104you do transactions with the outside world and you can't increase the
1105parallelity, then this setting will limit your transaction rate (if you
1106need to poll once per transaction and the I/O collect interval is 0.01,
1107then you can't do more than 100 transactions per second).
1108.Sp
1109Setting the \fItimeout collect interval\fR can improve the opportunity for
1110saving power, as the program will \*(L"bundle\*(R" timer callback invocations that
1111are \*(L"near\*(R" in time together, by delaying some, thus reducing the number of
1112times the process sleeps and wakes up again. Another useful technique to
1113reduce iterations/wake\-ups is to use \f(CW\*(C`ev_periodic\*(C'\fR watchers and make sure
1114they fire on, say, one-second boundaries only.
1115.Sp
1116Example: we only need 0.1s timeout granularity, and we wish not to poll
1117more often than 100 times per second:
1118.Sp
1119.Vb 2
1120\& ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
1121\& ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
1122.Ve
1123.IP "ev_invoke_pending (loop)" 4
1124.IX Item "ev_invoke_pending (loop)"
1125This call will simply invoke all pending watchers while resetting their
1126pending state. Normally, \f(CW\*(C`ev_run\*(C'\fR does this automatically when required,
1127but when overriding the invoke callback this call comes handy. This
1128function can be invoked from a watcher \- this can be useful for example
1129when you want to do some lengthy calculation and want to pass further
1130event handling to another thread (you still have to make sure only one
1131thread executes within \f(CW\*(C`ev_invoke_pending\*(C'\fR or \f(CW\*(C`ev_run\*(C'\fR of course).
1132.IP "int ev_pending_count (loop)" 4
1133.IX Item "int ev_pending_count (loop)"
1134Returns the number of pending watchers \- zero indicates that no watchers
1135are pending.
1136.IP "ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(\s-1EV_P\s0))" 4
1137.IX Item "ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))"
1138This overrides the invoke pending functionality of the loop: Instead of
1139invoking all pending watchers when there are any, \f(CW\*(C`ev_run\*(C'\fR will call
1140this callback instead. This is useful, for example, when you want to
1141invoke the actual watchers inside another context (another thread etc.).
1142.Sp
1143If you want to reset the callback, use \f(CW\*(C`ev_invoke_pending\*(C'\fR as new
1144callback.
1145.IP "ev_set_loop_release_cb (loop, void (*release)(\s-1EV_P\s0) throw (), void (*acquire)(\s-1EV_P\s0) throw ())" 4
1146.IX Item "ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())"
1147Sometimes you want to share the same loop between multiple threads. This
1148can be done relatively simply by putting mutex_lock/unlock calls around
1149each call to a libev function.
1150.Sp
1151However, \f(CW\*(C`ev_run\*(C'\fR can run an indefinite time, so it is not feasible
1152to wait for it to return. One way around this is to wake up the event
1153loop via \f(CW\*(C`ev_break\*(C'\fR and \f(CW\*(C`ev_async_send\*(C'\fR, another way is to set these
1154\&\fIrelease\fR and \fIacquire\fR callbacks on the loop.
1155.Sp
1156When set, then \f(CW\*(C`release\*(C'\fR will be called just before the thread is
1157suspended waiting for new events, and \f(CW\*(C`acquire\*(C'\fR is called just
1158afterwards.
1159.Sp
1160Ideally, \f(CW\*(C`release\*(C'\fR will just call your mutex_unlock function, and
1161\&\f(CW\*(C`acquire\*(C'\fR will just call the mutex_lock function again.
1162.Sp
1163While event loop modifications are allowed between invocations of
1164\&\f(CW\*(C`release\*(C'\fR and \f(CW\*(C`acquire\*(C'\fR (that's their only purpose after all), no
1165modifications done will affect the event loop, i.e. adding watchers will
1166have no effect on the set of file descriptors being watched, or the time
1167waited. Use an \f(CW\*(C`ev_async\*(C'\fR watcher to wake up \f(CW\*(C`ev_run\*(C'\fR when you want it
1168to take note of any changes you made.
1169.Sp
1170In theory, threads executing \f(CW\*(C`ev_run\*(C'\fR will be async-cancel safe between
1171invocations of \f(CW\*(C`release\*(C'\fR and \f(CW\*(C`acquire\*(C'\fR.
1172.Sp
1173See also the locking example in the \f(CW\*(C`THREADS\*(C'\fR section later in this
1174document.
1175.IP "ev_set_userdata (loop, void *data)" 4
1176.IX Item "ev_set_userdata (loop, void *data)"
1177.PD 0
1178.IP "void *ev_userdata (loop)" 4
1179.IX Item "void *ev_userdata (loop)"
1180.PD
1181Set and retrieve a single \f(CW\*(C`void *\*(C'\fR associated with a loop. When
1182\&\f(CW\*(C`ev_set_userdata\*(C'\fR has never been called, then \f(CW\*(C`ev_userdata\*(C'\fR returns
1183\&\f(CW0\fR.
1184.Sp
1185These two functions can be used to associate arbitrary data with a loop,
1186and are intended solely for the \f(CW\*(C`invoke_pending_cb\*(C'\fR, \f(CW\*(C`release\*(C'\fR and
1187\&\f(CW\*(C`acquire\*(C'\fR callbacks described above, but of course can be (ab\-)used for
1188any other purpose as well.
1189.IP "ev_verify (loop)" 4
1190.IX Item "ev_verify (loop)"
1191This function only does something when \f(CW\*(C`EV_VERIFY\*(C'\fR support has been
1192compiled in, which is the default for non-minimal builds. It tries to go
1193through all internal structures and checks them for validity. If anything
1194is found to be inconsistent, it will print an error message to standard
1195error and call \f(CW\*(C`abort ()\*(C'\fR.
1196.Sp
1197This can be used to catch bugs inside libev itself: under normal
1198circumstances, this function will never abort as of course libev keeps its
1199data structures consistent.
723.SH "ANATOMY OF A WATCHER" 1200.SH "ANATOMY OF A WATCHER"
724.IX Header "ANATOMY OF A WATCHER" 1201.IX Header "ANATOMY OF A WATCHER"
1202In the following description, uppercase \f(CW\*(C`TYPE\*(C'\fR in names stands for the
1203watcher type, e.g. \f(CW\*(C`ev_TYPE_start\*(C'\fR can mean \f(CW\*(C`ev_timer_start\*(C'\fR for timer
1204watchers and \f(CW\*(C`ev_io_start\*(C'\fR for I/O watchers.
1205.PP
725A watcher is a structure that you create and register to record your 1206A watcher is an opaque structure that you allocate and register to record
726interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to 1207your interest in some event. To make a concrete example, imagine you want
727become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that: 1208to wait for \s-1STDIN\s0 to become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher
1209for that:
728.PP 1210.PP
729.Vb 5 1211.Vb 5
730\& static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1212\& static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
731\& { 1213\& {
732\& ev_io_stop (w); 1214\& ev_io_stop (w);
733\& ev_unloop (loop, EVUNLOOP_ALL); 1215\& ev_break (loop, EVBREAK_ALL);
734\& } 1216\& }
735.Ve 1217\&
736.PP
737.Vb 6
738\& struct ev_loop *loop = ev_default_loop (0); 1218\& struct ev_loop *loop = ev_default_loop (0);
1219\&
739\& struct ev_io stdin_watcher; 1220\& ev_io stdin_watcher;
1221\&
740\& ev_init (&stdin_watcher, my_cb); 1222\& ev_init (&stdin_watcher, my_cb);
741\& ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); 1223\& ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
742\& ev_io_start (loop, &stdin_watcher); 1224\& ev_io_start (loop, &stdin_watcher);
1225\&
743\& ev_loop (loop, 0); 1226\& ev_run (loop, 0);
744.Ve 1227.Ve
745.PP 1228.PP
746As you can see, you are responsible for allocating the memory for your 1229As you can see, you are responsible for allocating the memory for your
747watcher structures (and it is usually a bad idea to do this on the stack, 1230watcher structures (and it is \fIusually\fR a bad idea to do this on the
748although this can sometimes be quite valid). 1231stack).
749.PP 1232.PP
1233Each watcher has an associated watcher structure (called \f(CW\*(C`struct ev_TYPE\*(C'\fR
1234or simply \f(CW\*(C`ev_TYPE\*(C'\fR, as typedefs are provided for all watcher structs).
1235.PP
750Each watcher structure must be initialised by a call to \f(CW\*(C`ev_init 1236Each watcher structure must be initialised by a call to \f(CW\*(C`ev_init (watcher
751(watcher *, callback)\*(C'\fR, which expects a callback to be provided. This 1237*, callback)\*(C'\fR, which expects a callback to be provided. This callback is
752callback gets invoked each time the event occurs (or, in the case of io 1238invoked each time the event occurs (or, in the case of I/O watchers, each
753watchers, each time the event loop detects that the file descriptor given 1239time the event loop detects that the file descriptor given is readable
754is readable and/or writable). 1240and/or writable).
755.PP 1241.PP
756Each watcher type has its own \f(CW\*(C`ev_<type>_set (watcher *, ...)\*(C'\fR macro 1242Each watcher type further has its own \f(CW\*(C`ev_TYPE_set (watcher *, ...)\*(C'\fR
757with arguments specific to this watcher type. There is also a macro 1243macro to configure it, with arguments specific to the watcher type. There
758to combine initialisation and setting in one call: \f(CW\*(C`ev_<type>_init 1244is also a macro to combine initialisation and setting in one call: \f(CW\*(C`ev_TYPE_init (watcher *, callback, ...)\*(C'\fR.
759(watcher *, callback, ...)\*(C'\fR.
760.PP 1245.PP
761To make the watcher actually watch out for events, you have to start it 1246To make the watcher actually watch out for events, you have to start it
762with a watcher-specific start function (\f(CW\*(C`ev_<type>_start (loop, watcher 1247with a watcher-specific start function (\f(CW\*(C`ev_TYPE_start (loop, watcher
763*)\*(C'\fR), and you can stop watching for events at any time by calling the 1248*)\*(C'\fR), and you can stop watching for events at any time by calling the
764corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR. 1249corresponding stop function (\f(CW\*(C`ev_TYPE_stop (loop, watcher *)\*(C'\fR.
765.PP 1250.PP
766As long as your watcher is active (has been started but not stopped) you 1251As long as your watcher is active (has been started but not stopped) you
767must not touch the values stored in it. Most specifically you must never 1252must not touch the values stored in it. Most specifically you must never
768reinitialise it or call its \f(CW\*(C`set\*(C'\fR macro. 1253reinitialise it or call its \f(CW\*(C`ev_TYPE_set\*(C'\fR macro.
769.PP 1254.PP
770Each and every callback receives the event loop pointer as first, the 1255Each and every callback receives the event loop pointer as first, the
771registered watcher structure as second, and a bitset of received events as 1256registered watcher structure as second, and a bitset of received events as
772third argument. 1257third argument.
773.PP 1258.PP
… …
782.el .IP "\f(CWEV_WRITE\fR" 4 1267.el .IP "\f(CWEV_WRITE\fR" 4
783.IX Item "EV_WRITE" 1268.IX Item "EV_WRITE"
784.PD 1269.PD
785The file descriptor in the \f(CW\*(C`ev_io\*(C'\fR watcher has become readable and/or 1270The file descriptor in the \f(CW\*(C`ev_io\*(C'\fR watcher has become readable and/or
786writable. 1271writable.
787.ie n .IP """EV_TIMEOUT""" 4 1272.ie n .IP """EV_TIMER""" 4
788.el .IP "\f(CWEV_TIMEOUT\fR" 4 1273.el .IP "\f(CWEV_TIMER\fR" 4
789.IX Item "EV_TIMEOUT" 1274.IX Item "EV_TIMER"
790The \f(CW\*(C`ev_timer\*(C'\fR watcher has timed out. 1275The \f(CW\*(C`ev_timer\*(C'\fR watcher has timed out.
791.ie n .IP """EV_PERIODIC""" 4 1276.ie n .IP """EV_PERIODIC""" 4
792.el .IP "\f(CWEV_PERIODIC\fR" 4 1277.el .IP "\f(CWEV_PERIODIC\fR" 4
793.IX Item "EV_PERIODIC" 1278.IX Item "EV_PERIODIC"
794The \f(CW\*(C`ev_periodic\*(C'\fR watcher has timed out. 1279The \f(CW\*(C`ev_periodic\*(C'\fR watcher has timed out.
… …
814.PD 0 1299.PD 0
815.ie n .IP """EV_CHECK""" 4 1300.ie n .IP """EV_CHECK""" 4
816.el .IP "\f(CWEV_CHECK\fR" 4 1301.el .IP "\f(CWEV_CHECK\fR" 4
817.IX Item "EV_CHECK" 1302.IX Item "EV_CHECK"
818.PD 1303.PD
819All \f(CW\*(C`ev_prepare\*(C'\fR watchers are invoked just \fIbefore\fR \f(CW\*(C`ev_loop\*(C'\fR starts 1304All \f(CW\*(C`ev_prepare\*(C'\fR watchers are invoked just \fIbefore\fR \f(CW\*(C`ev_run\*(C'\fR starts to
820to gather new events, and all \f(CW\*(C`ev_check\*(C'\fR watchers are invoked just after 1305gather new events, and all \f(CW\*(C`ev_check\*(C'\fR watchers are queued (not invoked)
821\&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any 1306just after \f(CW\*(C`ev_run\*(C'\fR has gathered them, but before it queues any callbacks
1307for any received events. That means \f(CW\*(C`ev_prepare\*(C'\fR watchers are the last
1308watchers invoked before the event loop sleeps or polls for new events, and
1309\&\f(CW\*(C`ev_check\*(C'\fR watchers will be invoked before any other watchers of the same
1310or lower priority within an event loop iteration.
1311.Sp
822received events. Callbacks of both watcher types can start and stop as 1312Callbacks of both watcher types can start and stop as many watchers as
823many watchers as they want, and all of them will be taken into account 1313they want, and all of them will be taken into account (for example, a
824(for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep 1314\&\f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep \f(CW\*(C`ev_run\*(C'\fR from
825\&\f(CW\*(C`ev_loop\*(C'\fR from blocking). 1315blocking).
826.ie n .IP """EV_EMBED""" 4 1316.ie n .IP """EV_EMBED""" 4
827.el .IP "\f(CWEV_EMBED\fR" 4 1317.el .IP "\f(CWEV_EMBED\fR" 4
828.IX Item "EV_EMBED" 1318.IX Item "EV_EMBED"
829The embedded event loop specified in the \f(CW\*(C`ev_embed\*(C'\fR watcher needs attention. 1319The embedded event loop specified in the \f(CW\*(C`ev_embed\*(C'\fR watcher needs attention.
830.ie n .IP """EV_FORK""" 4 1320.ie n .IP """EV_FORK""" 4
831.el .IP "\f(CWEV_FORK\fR" 4 1321.el .IP "\f(CWEV_FORK\fR" 4
832.IX Item "EV_FORK" 1322.IX Item "EV_FORK"
833The event loop has been resumed in the child process after fork (see 1323The event loop has been resumed in the child process after fork (see
834\&\f(CW\*(C`ev_fork\*(C'\fR). 1324\&\f(CW\*(C`ev_fork\*(C'\fR).
1325.ie n .IP """EV_CLEANUP""" 4
1326.el .IP "\f(CWEV_CLEANUP\fR" 4
1327.IX Item "EV_CLEANUP"
1328The event loop is about to be destroyed (see \f(CW\*(C`ev_cleanup\*(C'\fR).
1329.ie n .IP """EV_ASYNC""" 4
1330.el .IP "\f(CWEV_ASYNC\fR" 4
1331.IX Item "EV_ASYNC"
1332The given async watcher has been asynchronously notified (see \f(CW\*(C`ev_async\*(C'\fR).
1333.ie n .IP """EV_CUSTOM""" 4
1334.el .IP "\f(CWEV_CUSTOM\fR" 4
1335.IX Item "EV_CUSTOM"
1336Not ever sent (or otherwise used) by libev itself, but can be freely used
1337by libev users to signal watchers (e.g. via \f(CW\*(C`ev_feed_event\*(C'\fR).
835.ie n .IP """EV_ERROR""" 4 1338.ie n .IP """EV_ERROR""" 4
836.el .IP "\f(CWEV_ERROR\fR" 4 1339.el .IP "\f(CWEV_ERROR\fR" 4
837.IX Item "EV_ERROR" 1340.IX Item "EV_ERROR"
838An unspecified error has occured, the watcher has been stopped. This might 1341An unspecified error has occurred, the watcher has been stopped. This might
839happen because the watcher could not be properly started because libev 1342happen because the watcher could not be properly started because libev
840ran out of memory, a file descriptor was found to be closed or any other 1343ran out of memory, a file descriptor was found to be closed or any other
1344problem. Libev considers these application bugs.
1345.Sp
841problem. You best act on it by reporting the problem and somehow coping 1346You best act on it by reporting the problem and somehow coping with the
842with the watcher being stopped. 1347watcher being stopped. Note that well-written programs should not receive
1348an error ever, so when your watcher receives it, this usually indicates a
1349bug in your program.
843.Sp 1350.Sp
844Libev will usually signal a few \*(L"dummy\*(R" events together with an error, 1351Libev will usually signal a few \*(L"dummy\*(R" events together with an error, for
845for example it might indicate that a fd is readable or writable, and if 1352example it might indicate that a fd is readable or writable, and if your
846your callbacks is well-written it can just attempt the operation and cope 1353callbacks is well-written it can just attempt the operation and cope with
847with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded 1354the error from \fIread()\fR or \fIwrite()\fR. This will not work in multi-threaded
848programs, though, so beware. 1355programs, though, as the fd could already be closed and reused for another
1356thing, so beware.
849.Sh "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0" 1357.SS "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0"
850.IX Subsection "GENERIC WATCHER FUNCTIONS" 1358.IX Subsection "GENERIC WATCHER FUNCTIONS"
851In the following description, \f(CW\*(C`TYPE\*(C'\fR stands for the watcher type,
852e.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.
853.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4 1359.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4
854.el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4 1360.el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4
855.IX Item "ev_init (ev_TYPE *watcher, callback)" 1361.IX Item "ev_init (ev_TYPE *watcher, callback)"
856This macro initialises the generic portion of a watcher. The contents 1362This macro initialises the generic portion of a watcher. The contents
857of the watcher object can be arbitrary (so \f(CW\*(C`malloc\*(C'\fR will do). Only 1363of the watcher object can be arbitrary (so \f(CW\*(C`malloc\*(C'\fR will do). Only
… …
861which rolls both calls into one. 1367which rolls both calls into one.
862.Sp 1368.Sp
863You can reinitialise a watcher at any time as long as it has been stopped 1369You can reinitialise a watcher at any time as long as it has been stopped
864(or never started) and there are no pending events outstanding. 1370(or never started) and there are no pending events outstanding.
865.Sp 1371.Sp
866The callback is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher, 1372The callback is always of type \f(CW\*(C`void (*)(struct ev_loop *loop, ev_TYPE *watcher,
867int revents)\*(C'\fR. 1373int revents)\*(C'\fR.
1374.Sp
1375Example: Initialise an \f(CW\*(C`ev_io\*(C'\fR watcher in two steps.
1376.Sp
1377.Vb 3
1378\& ev_io w;
1379\& ev_init (&w, my_cb);
1380\& ev_io_set (&w, STDIN_FILENO, EV_READ);
1381.Ve
868.ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4 1382.ie n .IP """ev_TYPE_set"" (ev_TYPE *watcher, [args])" 4
869.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4 1383.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *watcher, [args])" 4
870.IX Item "ev_TYPE_set (ev_TYPE *, [args])" 1384.IX Item "ev_TYPE_set (ev_TYPE *watcher, [args])"
871This macro initialises the type-specific parts of a watcher. You need to 1385This macro initialises the type-specific parts of a watcher. You need to
872call \f(CW\*(C`ev_init\*(C'\fR at least once before you call this macro, but you can 1386call \f(CW\*(C`ev_init\*(C'\fR at least once before you call this macro, but you can
873call \f(CW\*(C`ev_TYPE_set\*(C'\fR any number of times. You must not, however, call this 1387call \f(CW\*(C`ev_TYPE_set\*(C'\fR any number of times. You must not, however, call this
874macro on a watcher that is active (it can be pending, however, which is a 1388macro on a watcher that is active (it can be pending, however, which is a
875difference to the \f(CW\*(C`ev_init\*(C'\fR macro). 1389difference to the \f(CW\*(C`ev_init\*(C'\fR macro).
876.Sp 1390.Sp
877Although some watcher types do not have type-specific arguments 1391Although some watcher types do not have type-specific arguments
878(e.g. \f(CW\*(C`ev_prepare\*(C'\fR) you still need to call its \f(CW\*(C`set\*(C'\fR macro. 1392(e.g. \f(CW\*(C`ev_prepare\*(C'\fR) you still need to call its \f(CW\*(C`set\*(C'\fR macro.
1393.Sp
1394See \f(CW\*(C`ev_init\*(C'\fR, above, for an example.
879.ie n .IP """ev_TYPE_init"" (ev_TYPE *watcher, callback, [args])" 4 1395.ie n .IP """ev_TYPE_init"" (ev_TYPE *watcher, callback, [args])" 4
880.el .IP "\f(CWev_TYPE_init\fR (ev_TYPE *watcher, callback, [args])" 4 1396.el .IP "\f(CWev_TYPE_init\fR (ev_TYPE *watcher, callback, [args])" 4
881.IX Item "ev_TYPE_init (ev_TYPE *watcher, callback, [args])" 1397.IX Item "ev_TYPE_init (ev_TYPE *watcher, callback, [args])"
882This convinience macro rolls both \f(CW\*(C`ev_init\*(C'\fR and \f(CW\*(C`ev_TYPE_set\*(C'\fR macro 1398This convenience macro rolls both \f(CW\*(C`ev_init\*(C'\fR and \f(CW\*(C`ev_TYPE_set\*(C'\fR macro
883calls into a single call. This is the most convinient method to initialise 1399calls into a single call. This is the most convenient method to initialise
884a watcher. The same limitations apply, of course. 1400a watcher. The same limitations apply, of course.
1401.Sp
1402Example: Initialise and set an \f(CW\*(C`ev_io\*(C'\fR watcher in one step.
1403.Sp
1404.Vb 1
1405\& ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1406.Ve
885.ie n .IP """ev_TYPE_start"" (loop *, ev_TYPE *watcher)" 4 1407.ie n .IP """ev_TYPE_start"" (loop, ev_TYPE *watcher)" 4
886.el .IP "\f(CWev_TYPE_start\fR (loop *, ev_TYPE *watcher)" 4 1408.el .IP "\f(CWev_TYPE_start\fR (loop, ev_TYPE *watcher)" 4
887.IX Item "ev_TYPE_start (loop *, ev_TYPE *watcher)" 1409.IX Item "ev_TYPE_start (loop, ev_TYPE *watcher)"
888Starts (activates) the given watcher. Only active watchers will receive 1410Starts (activates) the given watcher. Only active watchers will receive
889events. If the watcher is already active nothing will happen. 1411events. If the watcher is already active nothing will happen.
1412.Sp
1413Example: Start the \f(CW\*(C`ev_io\*(C'\fR watcher that is being abused as example in this
1414whole section.
1415.Sp
1416.Vb 1
1417\& ev_io_start (EV_DEFAULT_UC, &w);
1418.Ve
890.ie n .IP """ev_TYPE_stop"" (loop *, ev_TYPE *watcher)" 4 1419.ie n .IP """ev_TYPE_stop"" (loop, ev_TYPE *watcher)" 4
891.el .IP "\f(CWev_TYPE_stop\fR (loop *, ev_TYPE *watcher)" 4 1420.el .IP "\f(CWev_TYPE_stop\fR (loop, ev_TYPE *watcher)" 4
892.IX Item "ev_TYPE_stop (loop *, ev_TYPE *watcher)" 1421.IX Item "ev_TYPE_stop (loop, ev_TYPE *watcher)"
893Stops the given watcher again (if active) and clears the pending 1422Stops the given watcher if active, and clears the pending status (whether
1423the watcher was active or not).
1424.Sp
894status. It is possible that stopped watchers are pending (for example, 1425It is possible that stopped watchers are pending \- for example,
895non-repeating timers are being stopped when they become pending), but 1426non-repeating timers are being stopped when they become pending \- but
896\&\f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor pending. If 1427calling \f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor
897you want to free or reuse the memory used by the watcher it is therefore a 1428pending. If you want to free or reuse the memory used by the watcher it is
898good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function. 1429therefore a good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function.
899.IP "bool ev_is_active (ev_TYPE *watcher)" 4 1430.IP "bool ev_is_active (ev_TYPE *watcher)" 4
900.IX Item "bool ev_is_active (ev_TYPE *watcher)" 1431.IX Item "bool ev_is_active (ev_TYPE *watcher)"
901Returns a true value iff the watcher is active (i.e. it has been started 1432Returns a true value iff the watcher is active (i.e. it has been started
902and not yet been stopped). As long as a watcher is active you must not modify 1433and not yet been stopped). As long as a watcher is active you must not modify
903it. 1434it.
… …
910make sure the watcher is available to libev (e.g. you cannot \f(CW\*(C`free ()\*(C'\fR 1441make sure the watcher is available to libev (e.g. you cannot \f(CW\*(C`free ()\*(C'\fR
911it). 1442it).
912.IP "callback ev_cb (ev_TYPE *watcher)" 4 1443.IP "callback ev_cb (ev_TYPE *watcher)" 4
913.IX Item "callback ev_cb (ev_TYPE *watcher)" 1444.IX Item "callback ev_cb (ev_TYPE *watcher)"
914Returns the callback currently set on the watcher. 1445Returns the callback currently set on the watcher.
915.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4 1446.IP "ev_set_cb (ev_TYPE *watcher, callback)" 4
916.IX Item "ev_cb_set (ev_TYPE *watcher, callback)" 1447.IX Item "ev_set_cb (ev_TYPE *watcher, callback)"
917Change the callback. You can change the callback at virtually any time 1448Change the callback. You can change the callback at virtually any time
918(modulo threads). 1449(modulo threads).
919.IP "ev_set_priority (ev_TYPE *watcher, priority)" 4 1450.IP "ev_set_priority (ev_TYPE *watcher, int priority)" 4
920.IX Item "ev_set_priority (ev_TYPE *watcher, priority)" 1451.IX Item "ev_set_priority (ev_TYPE *watcher, int priority)"
921.PD 0 1452.PD 0
922.IP "int ev_priority (ev_TYPE *watcher)" 4 1453.IP "int ev_priority (ev_TYPE *watcher)" 4
923.IX Item "int ev_priority (ev_TYPE *watcher)" 1454.IX Item "int ev_priority (ev_TYPE *watcher)"
924.PD 1455.PD
925Set and query the priority of the watcher. The priority is a small 1456Set and query the priority of the watcher. The priority is a small
926integer between \f(CW\*(C`EV_MAXPRI\*(C'\fR (default: \f(CW2\fR) and \f(CW\*(C`EV_MINPRI\*(C'\fR 1457integer between \f(CW\*(C`EV_MAXPRI\*(C'\fR (default: \f(CW2\fR) and \f(CW\*(C`EV_MINPRI\*(C'\fR
927(default: \f(CW\*(C`\-2\*(C'\fR). Pending watchers with higher priority will be invoked 1458(default: \f(CW\*(C`\-2\*(C'\fR). Pending watchers with higher priority will be invoked
928before watchers with lower priority, but priority will not keep watchers 1459before watchers with lower priority, but priority will not keep watchers
929from being executed (except for \f(CW\*(C`ev_idle\*(C'\fR watchers). 1460from being executed (except for \f(CW\*(C`ev_idle\*(C'\fR watchers).
930.Sp 1461.Sp
931This means that priorities are \fIonly\fR used for ordering callback
932invocation after new events have been received. This is useful, for
933example, to reduce latency after idling, or more often, to bind two
934watchers on the same event and make sure one is called first.
935.Sp
936If you need to suppress invocation when higher priority events are pending 1462If you need to suppress invocation when higher priority events are pending
937you need to look at \f(CW\*(C`ev_idle\*(C'\fR watchers, which provide this functionality. 1463you need to look at \f(CW\*(C`ev_idle\*(C'\fR watchers, which provide this functionality.
938.Sp 1464.Sp
939You \fImust not\fR change the priority of a watcher as long as it is active or 1465You \fImust not\fR change the priority of a watcher as long as it is active or
940pending. 1466pending.
941.Sp 1467.Sp
1468Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR is
1469fine, as long as you do not mind that the priority value you query might
1470or might not have been clamped to the valid range.
1471.Sp
942The default priority used by watchers when no priority has been set is 1472The default priority used by watchers when no priority has been set is
943always \f(CW0\fR, which is supposed to not be too high and not be too low :). 1473always \f(CW0\fR, which is supposed to not be too high and not be too low :).
944.Sp 1474.Sp
945Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR is 1475See \*(L"\s-1WATCHER\s0 \s-1PRIORITY\s0 \s-1MODELS\s0\*(R", below, for a more thorough treatment of
946fine, as long as you do not mind that the priority value you query might 1476priorities.
947or might not have been adjusted to be within valid range.
948.IP "ev_invoke (loop, ev_TYPE *watcher, int revents)" 4 1477.IP "ev_invoke (loop, ev_TYPE *watcher, int revents)" 4
949.IX Item "ev_invoke (loop, ev_TYPE *watcher, int revents)" 1478.IX Item "ev_invoke (loop, ev_TYPE *watcher, int revents)"
950Invoke the \f(CW\*(C`watcher\*(C'\fR with the given \f(CW\*(C`loop\*(C'\fR and \f(CW\*(C`revents\*(C'\fR. Neither 1479Invoke the \f(CW\*(C`watcher\*(C'\fR with the given \f(CW\*(C`loop\*(C'\fR and \f(CW\*(C`revents\*(C'\fR. Neither
951\&\f(CW\*(C`loop\*(C'\fR nor \f(CW\*(C`revents\*(C'\fR need to be valid as long as the watcher callback 1480\&\f(CW\*(C`loop\*(C'\fR nor \f(CW\*(C`revents\*(C'\fR need to be valid as long as the watcher callback
952can deal with that fact. 1481can deal with that fact, as both are simply passed through to the
1482callback.
953.IP "int ev_clear_pending (loop, ev_TYPE *watcher)" 4 1483.IP "int ev_clear_pending (loop, ev_TYPE *watcher)" 4
954.IX Item "int ev_clear_pending (loop, ev_TYPE *watcher)" 1484.IX Item "int ev_clear_pending (loop, ev_TYPE *watcher)"
955If the watcher is pending, this function returns clears its pending status 1485If the watcher is pending, this function clears its pending status and
956and returns its \f(CW\*(C`revents\*(C'\fR bitset (as if its callback was invoked). If the 1486returns its \f(CW\*(C`revents\*(C'\fR bitset (as if its callback was invoked). If the
957watcher isn't pending it does nothing and returns \f(CW0\fR. 1487watcher isn't pending it does nothing and returns \f(CW0\fR.
958.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0" 1488.Sp
959.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER" 1489Sometimes it can be useful to \*(L"poll\*(R" a watcher instead of waiting for its
960Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change 1490callback to be invoked, which can be accomplished with this function.
961and read at any time, libev will completely ignore it. This can be used 1491.IP "ev_feed_event (loop, ev_TYPE *watcher, int revents)" 4
962to associate arbitrary data with your watcher. If you need more data and 1492.IX Item "ev_feed_event (loop, ev_TYPE *watcher, int revents)"
963don't want to allocate memory and store a pointer to it in that data 1493Feeds the given event set into the event loop, as if the specified event
964member, you can also \*(L"subclass\*(R" the watcher type and provide your own 1494had happened for the specified watcher (which must be a pointer to an
965data: 1495initialised but not necessarily started event watcher). Obviously you must
1496not free the watcher as long as it has pending events.
1497.Sp
1498Stopping the watcher, letting libev invoke it, or calling
1499\&\f(CW\*(C`ev_clear_pending\*(C'\fR will clear the pending event, even if the watcher was
1500not started in the first place.
1501.Sp
1502See also \f(CW\*(C`ev_feed_fd_event\*(C'\fR and \f(CW\*(C`ev_feed_signal_event\*(C'\fR for related
1503functions that do not need a watcher.
966.PP 1504.PP
1505See also the \*(L"\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0\*(R" and \*(L"\s-1BUILDING\s0 \s-1YOUR\s0
1506\&\s-1OWN\s0 \s-1COMPOSITE\s0 \s-1WATCHERS\s0\*(R" idioms.
1507.SS "\s-1WATCHER\s0 \s-1STATES\s0"
1508.IX Subsection "WATCHER STATES"
1509There are various watcher states mentioned throughout this manual \-
1510active, pending and so on. In this section these states and the rules to
1511transition between them will be described in more detail \- and while these
1512rules might look complicated, they usually do \*(L"the right thing\*(R".
1513.IP "initialiased" 4
1514.IX Item "initialiased"
1515Before a watcher can be registered with the event loop it has to be
1516initialised. This can be done with a call to \f(CW\*(C`ev_TYPE_init\*(C'\fR, or calls to
1517\&\f(CW\*(C`ev_init\*(C'\fR followed by the watcher-specific \f(CW\*(C`ev_TYPE_set\*(C'\fR function.
1518.Sp
1519In this state it is simply some block of memory that is suitable for
1520use in an event loop. It can be moved around, freed, reused etc. at
1521will \- as long as you either keep the memory contents intact, or call
1522\&\f(CW\*(C`ev_TYPE_init\*(C'\fR again.
1523.IP "started/running/active" 4
1524.IX Item "started/running/active"
1525Once a watcher has been started with a call to \f(CW\*(C`ev_TYPE_start\*(C'\fR it becomes
1526property of the event loop, and is actively waiting for events. While in
1527this state it cannot be accessed (except in a few documented ways), moved,
1528freed or anything else \- the only legal thing is to keep a pointer to it,
1529and call libev functions on it that are documented to work on active watchers.
1530.IP "pending" 4
1531.IX Item "pending"
1532If a watcher is active and libev determines that an event it is interested
1533in has occurred (such as a timer expiring), it will become pending. It will
1534stay in this pending state until either it is stopped or its callback is
1535about to be invoked, so it is not normally pending inside the watcher
1536callback.
1537.Sp
1538The watcher might or might not be active while it is pending (for example,
1539an expired non-repeating timer can be pending but no longer active). If it
1540is stopped, it can be freely accessed (e.g. by calling \f(CW\*(C`ev_TYPE_set\*(C'\fR),
1541but it is still property of the event loop at this time, so cannot be
1542moved, freed or reused. And if it is active the rules described in the
1543previous item still apply.
1544.Sp
1545It is also possible to feed an event on a watcher that is not active (e.g.
1546via \f(CW\*(C`ev_feed_event\*(C'\fR), in which case it becomes pending without being
1547active.
1548.IP "stopped" 4
1549.IX Item "stopped"
1550A watcher can be stopped implicitly by libev (in which case it might still
1551be pending), or explicitly by calling its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function. The
1552latter will clear any pending state the watcher might be in, regardless
1553of whether it was active or not, so stopping a watcher explicitly before
1554freeing it is often a good idea.
1555.Sp
1556While stopped (and not pending) the watcher is essentially in the
1557initialised state, that is, it can be reused, moved, modified in any way
1558you wish (but when you trash the memory block, you need to \f(CW\*(C`ev_TYPE_init\*(C'\fR
1559it again).
1560.SS "\s-1WATCHER\s0 \s-1PRIORITY\s0 \s-1MODELS\s0"
1561.IX Subsection "WATCHER PRIORITY MODELS"
1562Many event loops support \fIwatcher priorities\fR, which are usually small
1563integers that influence the ordering of event callback invocation
1564between watchers in some way, all else being equal.
1565.PP
1566In libev, Watcher priorities can be set using \f(CW\*(C`ev_set_priority\*(C'\fR. See its
1567description for the more technical details such as the actual priority
1568range.
1569.PP
1570There are two common ways how these these priorities are being interpreted
1571by event loops:
1572.PP
1573In the more common lock-out model, higher priorities \*(L"lock out\*(R" invocation
1574of lower priority watchers, which means as long as higher priority
1575watchers receive events, lower priority watchers are not being invoked.
1576.PP
1577The less common only-for-ordering model uses priorities solely to order
1578callback invocation within a single event loop iteration: Higher priority
1579watchers are invoked before lower priority ones, but they all get invoked
1580before polling for new events.
1581.PP
1582Libev uses the second (only-for-ordering) model for all its watchers
1583except for idle watchers (which use the lock-out model).
1584.PP
1585The rationale behind this is that implementing the lock-out model for
1586watchers is not well supported by most kernel interfaces, and most event
1587libraries will just poll for the same events again and again as long as
1588their callbacks have not been executed, which is very inefficient in the
1589common case of one high-priority watcher locking out a mass of lower
1590priority ones.
1591.PP
1592Static (ordering) priorities are most useful when you have two or more
1593watchers handling the same resource: a typical usage example is having an
1594\&\f(CW\*(C`ev_io\*(C'\fR watcher to receive data, and an associated \f(CW\*(C`ev_timer\*(C'\fR to handle
1595timeouts. Under load, data might be received while the program handles
1596other jobs, but since timers normally get invoked first, the timeout
1597handler will be executed before checking for data. In that case, giving
1598the timer a lower priority than the I/O watcher ensures that I/O will be
1599handled first even under adverse conditions (which is usually, but not
1600always, what you want).
1601.PP
1602Since idle watchers use the \*(L"lock-out\*(R" model, meaning that idle watchers
1603will only be executed when no same or higher priority watchers have
1604received events, they can be used to implement the \*(L"lock-out\*(R" model when
1605required.
1606.PP
1607For example, to emulate how many other event libraries handle priorities,
1608you can associate an \f(CW\*(C`ev_idle\*(C'\fR watcher to each such watcher, and in
1609the normal watcher callback, you just start the idle watcher. The real
1610processing is done in the idle watcher callback. This causes libev to
1611continuously poll and process kernel event data for the watcher, but when
1612the lock-out case is known to be rare (which in turn is rare :), this is
1613workable.
1614.PP
1615Usually, however, the lock-out model implemented that way will perform
1616miserably under the type of load it was designed to handle. In that case,
1617it might be preferable to stop the real watcher before starting the
1618idle watcher, so the kernel will not have to process the event in case
1619the actual processing will be delayed for considerable time.
1620.PP
1621Here is an example of an I/O watcher that should run at a strictly lower
1622priority than the default, and which should only process data when no
1623other events are pending:
1624.PP
967.Vb 7 1625.Vb 2
968\& struct my_io 1626\& ev_idle idle; // actual processing watcher
969\& { 1627\& ev_io io; // actual event watcher
970\& struct ev_io io; 1628\&
971\& int otherfd;
972\& void *somedata;
973\& struct whatever *mostinteresting;
974\& }
975.Ve
976.PP
977And since your callback will be called with a pointer to the watcher, you
978can cast it back to your own type:
979.PP
980.Vb 5
981\& static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
982\& {
983\& struct my_io *w = (struct my_io *)w_;
984\& ...
985\& }
986.Ve
987.PP
988More interesting and less C\-conformant ways of casting your callback type
989instead have been omitted.
990.PP
991Another common scenario is having some data structure with multiple
992watchers:
993.PP
994.Vb 6
995\& struct my_biggy
996\& {
997\& int some_data;
998\& ev_timer t1;
999\& ev_timer t2;
1000\& }
1001.Ve
1002.PP
1003In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more complicated,
1004you need to use \f(CW\*(C`offsetof\*(C'\fR:
1005.PP
1006.Vb 1
1007\& #include <stddef.h>
1008.Ve
1009.PP
1010.Vb 6
1011\& static void 1629\& static void
1012\& t1_cb (EV_P_ struct ev_timer *w, int revents) 1630\& io_cb (EV_P_ ev_io *w, int revents)
1013\& { 1631\& {
1014\& struct my_biggy big = (struct my_biggy * 1632\& // stop the I/O watcher, we received the event, but
1015\& (((char *)w) - offsetof (struct my_biggy, t1)); 1633\& // are not yet ready to handle it.
1634\& ev_io_stop (EV_A_ w);
1635\&
1636\& // start the idle watcher to handle the actual event.
1637\& // it will not be executed as long as other watchers
1638\& // with the default priority are receiving events.
1639\& ev_idle_start (EV_A_ &idle);
1016\& } 1640\& }
1017.Ve 1641\&
1018.PP
1019.Vb 6
1020\& static void 1642\& static void
1021\& t2_cb (EV_P_ struct ev_timer *w, int revents) 1643\& idle_cb (EV_P_ ev_idle *w, int revents)
1022\& { 1644\& {
1023\& struct my_biggy big = (struct my_biggy * 1645\& // actual processing
1024\& (((char *)w) - offsetof (struct my_biggy, t2)); 1646\& read (STDIN_FILENO, ...);
1647\&
1648\& // have to start the I/O watcher again, as
1649\& // we have handled the event
1650\& ev_io_start (EV_P_ &io);
1025\& } 1651\& }
1652\&
1653\& // initialisation
1654\& ev_idle_init (&idle, idle_cb);
1655\& ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
1656\& ev_io_start (EV_DEFAULT_ &io);
1026.Ve 1657.Ve
1658.PP
1659In the \*(L"real\*(R" world, it might also be beneficial to start a timer, so that
1660low-priority connections can not be locked out forever under load. This
1661enables your program to keep a lower latency for important connections
1662during short periods of high load, while not completely locking out less
1663important ones.
1027.SH "WATCHER TYPES" 1664.SH "WATCHER TYPES"
1028.IX Header "WATCHER TYPES" 1665.IX Header "WATCHER TYPES"
1029This section describes each watcher in detail, but will not repeat 1666This section describes each watcher in detail, but will not repeat
1030information given in the last section. Any initialisation/set macros, 1667information given in the last section. Any initialisation/set macros,
1031functions and members specific to the watcher type are explained. 1668functions and members specific to the watcher type are explained.
… …
1036watcher is stopped to your hearts content), or \fI[read\-write]\fR, which 1673watcher is stopped to your hearts content), or \fI[read\-write]\fR, which
1037means you can expect it to have some sensible content while the watcher 1674means you can expect it to have some sensible content while the watcher
1038is active, but you can also modify it. Modifying it may not do something 1675is active, but you can also modify it. Modifying it may not do something
1039sensible or take immediate effect (or do anything at all), but libev will 1676sensible or take immediate effect (or do anything at all), but libev will
1040not crash or malfunction in any way. 1677not crash or malfunction in any way.
1041.ie n .Sh """ev_io"" \- is this file descriptor readable or writable?" 1678.ie n .SS """ev_io"" \- is this file descriptor readable or writable?"
1042.el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable?" 1679.el .SS "\f(CWev_io\fP \- is this file descriptor readable or writable?"
1043.IX Subsection "ev_io - is this file descriptor readable or writable?" 1680.IX Subsection "ev_io - is this file descriptor readable or writable?"
1044I/O watchers check whether a file descriptor is readable or writable 1681I/O watchers check whether a file descriptor is readable or writable
1045in each iteration of the event loop, or, more precisely, when reading 1682in each iteration of the event loop, or, more precisely, when reading
1046would not block the process and writing would at least be able to write 1683would not block the process and writing would at least be able to write
1047some data. This behaviour is called level-triggering because you keep 1684some data. This behaviour is called level-triggering because you keep
… …
1052In general you can register as many read and/or write event watchers per 1689In general you can register as many read and/or write event watchers per
1053fd as you want (as long as you don't confuse yourself). Setting all file 1690fd as you want (as long as you don't confuse yourself). Setting all file
1054descriptors to non-blocking mode is also usually a good idea (but not 1691descriptors to non-blocking mode is also usually a good idea (but not
1055required if you know what you are doing). 1692required if you know what you are doing).
1056.PP 1693.PP
1057You have to be careful with dup'ed file descriptors, though. Some backends
1058(the linux epoll backend is a notable example) cannot handle dup'ed file
1059descriptors correctly if you register interest in two or more fds pointing
1060to the same underlying file/socket/etc. description (that is, they share
1061the same underlying \*(L"file open\*(R").
1062.PP
1063If you must do this, then force the use of a known-to-be-good backend
1064(at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and
1065\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR).
1066.PP
1067Another thing you have to watch out for is that it is quite easy to 1694Another thing you have to watch out for is that it is quite easy to
1068receive \*(L"spurious\*(R" readyness notifications, that is your callback might 1695receive \*(L"spurious\*(R" readiness notifications, that is, your callback might
1069be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block 1696be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block
1070because there is no data. Not only are some backends known to create a 1697because there is no data. It is very easy to get into this situation even
1071lot of those (for example solaris ports), it is very easy to get into 1698with a relatively standard program structure. Thus it is best to always
1072this situation even with a relatively standard program structure. Thus 1699use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning \f(CW\*(C`EAGAIN\*(C'\fR is far
1073it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning
1074\&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives. 1700preferable to a program hanging until some data arrives.
1075.PP 1701.PP
1076If you cannot run the fd in non-blocking mode (for example you should not 1702If you cannot run the fd in non-blocking mode (for example you should
1077play around with an Xlib connection), then you have to seperately re-test 1703not play around with an Xlib connection), then you have to separately
1078whether a file descriptor is really ready with a known-to-be good interface 1704re-test whether a file descriptor is really ready with a known-to-be good
1079such as poll (fortunately in our Xlib example, Xlib already does this on 1705interface such as poll (fortunately in the case of Xlib, it already does
1080its own, so its quite safe to use). 1706this on its own, so its quite safe to use). Some people additionally
1707use \f(CW\*(C`SIGALRM\*(C'\fR and an interval timer, just to be sure you won't block
1708indefinitely.
1709.PP
1710But really, best use non-blocking mode.
1081.PP 1711.PP
1082\fIThe special problem of disappearing file descriptors\fR 1712\fIThe special problem of disappearing file descriptors\fR
1083.IX Subsection "The special problem of disappearing file descriptors" 1713.IX Subsection "The special problem of disappearing file descriptors"
1084.PP 1714.PP
1085Some backends (e.g kqueue, epoll) need to be told about closing a file 1715Some backends (e.g. kqueue, epoll) need to be told about closing a file
1086descriptor (either by calling \f(CW\*(C`close\*(C'\fR explicitly or by any other means, 1716descriptor (either due to calling \f(CW\*(C`close\*(C'\fR explicitly or any other means,
1087such as \f(CW\*(C`dup\*(C'\fR). The reason is that you register interest in some file 1717such as \f(CW\*(C`dup2\*(C'\fR). The reason is that you register interest in some file
1088descriptor, but when it goes away, the operating system will silently drop 1718descriptor, but when it goes away, the operating system will silently drop
1089this interest. If another file descriptor with the same number then is 1719this interest. If another file descriptor with the same number then is
1090registered with libev, there is no efficient way to see that this is, in 1720registered with libev, there is no efficient way to see that this is, in
1091fact, a different file descriptor. 1721fact, a different file descriptor.
1092.PP 1722.PP
… …
1098descriptor even if the file descriptor number itself did not change. 1728descriptor even if the file descriptor number itself did not change.
1099.PP 1729.PP
1100This is how one would do it normally anyway, the important point is that 1730This is how one would do it normally anyway, the important point is that
1101the libev application should not optimise around libev but should leave 1731the libev application should not optimise around libev but should leave
1102optimisations to libev. 1732optimisations to libev.
1733.PP
1734\fIThe special problem of dup'ed file descriptors\fR
1735.IX Subsection "The special problem of dup'ed file descriptors"
1736.PP
1737Some backends (e.g. epoll), cannot register events for file descriptors,
1738but only events for the underlying file descriptions. That means when you
1739have \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors or weirder constellations, and register
1740events for them, only one file descriptor might actually receive events.
1741.PP
1742There is no workaround possible except not registering events
1743for potentially \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors, or to resort to
1744\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
1745.PP
1746\fIThe special problem of files\fR
1747.IX Subsection "The special problem of files"
1748.PP
1749Many people try to use \f(CW\*(C`select\*(C'\fR (or libev) on file descriptors
1750representing files, and expect it to become ready when their program
1751doesn't block on disk accesses (which can take a long time on their own).
1752.PP
1753However, this cannot ever work in the \*(L"expected\*(R" way \- you get a readiness
1754notification as soon as the kernel knows whether and how much data is
1755there, and in the case of open files, that's always the case, so you
1756always get a readiness notification instantly, and your read (or possibly
1757write) will still block on the disk I/O.
1758.PP
1759Another way to view it is that in the case of sockets, pipes, character
1760devices and so on, there is another party (the sender) that delivers data
1761on its own, but in the case of files, there is no such thing: the disk
1762will not send data on its own, simply because it doesn't know what you
1763wish to read \- you would first have to request some data.
1764.PP
1765Since files are typically not-so-well supported by advanced notification
1766mechanism, libev tries hard to emulate \s-1POSIX\s0 behaviour with respect
1767to files, even though you should not use it. The reason for this is
1768convenience: sometimes you want to watch \s-1STDIN\s0 or \s-1STDOUT\s0, which is
1769usually a tty, often a pipe, but also sometimes files or special devices
1770(for example, \f(CW\*(C`epoll\*(C'\fR on Linux works with \fI/dev/random\fR but not with
1771\&\fI/dev/urandom\fR), and even though the file might better be served with
1772asynchronous I/O instead of with non-blocking I/O, it is still useful when
1773it \*(L"just works\*(R" instead of freezing.
1774.PP
1775So avoid file descriptors pointing to files when you know it (e.g. use
1776libeio), but use them when it is convenient, e.g. for \s-1STDIN/STDOUT\s0, or
1777when you rarely read from a file instead of from a socket, and want to
1778reuse the same code path.
1779.PP
1780\fIThe special problem of fork\fR
1781.IX Subsection "The special problem of fork"
1782.PP
1783Some backends (epoll, kqueue) do not support \f(CW\*(C`fork ()\*(C'\fR at all or exhibit
1784useless behaviour. Libev fully supports fork, but needs to be told about
1785it in the child if you want to continue to use it in the child.
1786.PP
1787To support fork in your child processes, you have to call \f(CW\*(C`ev_loop_fork
1788()\*(C'\fR after a fork in the child, enable \f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR, or resort to
1789\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
1790.PP
1791\fIThe special problem of \s-1SIGPIPE\s0\fR
1792.IX Subsection "The special problem of SIGPIPE"
1793.PP
1794While not really specific to libev, it is easy to forget about \f(CW\*(C`SIGPIPE\*(C'\fR:
1795when writing to a pipe whose other end has been closed, your program gets
1796sent a \s-1SIGPIPE\s0, which, by default, aborts your program. For most programs
1797this is sensible behaviour, for daemons, this is usually undesirable.
1798.PP
1799So when you encounter spurious, unexplained daemon exits, make sure you
1800ignore \s-1SIGPIPE\s0 (and maybe make sure you log the exit status of your daemon
1801somewhere, as that would have given you a big clue).
1802.PP
1803\fIThe special problem of \fIaccept()\fIing when you can't\fR
1804.IX Subsection "The special problem of accept()ing when you can't"
1805.PP
1806Many implementations of the \s-1POSIX\s0 \f(CW\*(C`accept\*(C'\fR function (for example,
1807found in post\-2004 Linux) have the peculiar behaviour of not removing a
1808connection from the pending queue in all error cases.
1809.PP
1810For example, larger servers often run out of file descriptors (because
1811of resource limits), causing \f(CW\*(C`accept\*(C'\fR to fail with \f(CW\*(C`ENFILE\*(C'\fR but not
1812rejecting the connection, leading to libev signalling readiness on
1813the next iteration again (the connection still exists after all), and
1814typically causing the program to loop at 100% \s-1CPU\s0 usage.
1815.PP
1816Unfortunately, the set of errors that cause this issue differs between
1817operating systems, there is usually little the app can do to remedy the
1818situation, and no known thread-safe method of removing the connection to
1819cope with overload is known (to me).
1820.PP
1821One of the easiest ways to handle this situation is to just ignore it
1822\&\- when the program encounters an overload, it will just loop until the
1823situation is over. While this is a form of busy waiting, no \s-1OS\s0 offers an
1824event-based way to handle this situation, so it's the best one can do.
1825.PP
1826A better way to handle the situation is to log any errors other than
1827\&\f(CW\*(C`EAGAIN\*(C'\fR and \f(CW\*(C`EWOULDBLOCK\*(C'\fR, making sure not to flood the log with such
1828messages, and continue as usual, which at least gives the user an idea of
1829what could be wrong (\*(L"raise the ulimit!\*(R"). For extra points one could stop
1830the \f(CW\*(C`ev_io\*(C'\fR watcher on the listening fd \*(L"for a while\*(R", which reduces \s-1CPU\s0
1831usage.
1832.PP
1833If your program is single-threaded, then you could also keep a dummy file
1834descriptor for overload situations (e.g. by opening \fI/dev/null\fR), and
1835when you run into \f(CW\*(C`ENFILE\*(C'\fR or \f(CW\*(C`EMFILE\*(C'\fR, close it, run \f(CW\*(C`accept\*(C'\fR,
1836close that fd, and create a new dummy fd. This will gracefully refuse
1837clients under typical overload conditions.
1838.PP
1839The last way to handle it is to simply log the error and \f(CW\*(C`exit\*(C'\fR, as
1840is often done with \f(CW\*(C`malloc\*(C'\fR failures, but this results in an easy
1841opportunity for a DoS attack.
1103.PP 1842.PP
1104\fIWatcher-Specific Functions\fR 1843\fIWatcher-Specific Functions\fR
1105.IX Subsection "Watcher-Specific Functions" 1844.IX Subsection "Watcher-Specific Functions"
1106.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4 1845.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4
1107.IX Item "ev_io_init (ev_io *, callback, int fd, int events)" 1846.IX Item "ev_io_init (ev_io *, callback, int fd, int events)"
1108.PD 0 1847.PD 0
1109.IP "ev_io_set (ev_io *, int fd, int events)" 4 1848.IP "ev_io_set (ev_io *, int fd, int events)" 4
1110.IX Item "ev_io_set (ev_io *, int fd, int events)" 1849.IX Item "ev_io_set (ev_io *, int fd, int events)"
1111.PD 1850.PD
1112Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to 1851Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to
1113rceeive events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or 1852receive events for and \f(CW\*(C`events\*(C'\fR is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or
1114\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR to receive the given events. 1853\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR, to express the desire to receive the given events.
1115.IP "int fd [read\-only]" 4 1854.IP "int fd [read\-only]" 4
1116.IX Item "int fd [read-only]" 1855.IX Item "int fd [read-only]"
1117The file descriptor being watched. 1856The file descriptor being watched.
1118.IP "int events [read\-only]" 4 1857.IP "int events [read\-only]" 4
1119.IX Item "int events [read-only]" 1858.IX Item "int events [read-only]"
1120The events being watched. 1859The events being watched.
1121.PP 1860.PP
1861\fIExamples\fR
1862.IX Subsection "Examples"
1863.PP
1122Example: Call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well 1864Example: Call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well
1123readable, but only once. Since it is likely line\-buffered, you could 1865readable, but only once. Since it is likely line-buffered, you could
1124attempt to read a whole line in the callback. 1866attempt to read a whole line in the callback.
1125.PP 1867.PP
1126.Vb 6 1868.Vb 6
1127\& static void 1869\& static void
1128\& stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1870\& stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1129\& { 1871\& {
1130\& ev_io_stop (loop, w); 1872\& ev_io_stop (loop, w);
1131\& .. read from stdin here (or from w->fd) and haqndle any I/O errors 1873\& .. read from stdin here (or from w\->fd) and handle any I/O errors
1132\& } 1874\& }
1133.Ve 1875\&
1134.PP
1135.Vb 6
1136\& ... 1876\& ...
1137\& struct ev_loop *loop = ev_default_init (0); 1877\& struct ev_loop *loop = ev_default_init (0);
1138\& struct ev_io stdin_readable; 1878\& ev_io stdin_readable;
1139\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); 1879\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1140\& ev_io_start (loop, &stdin_readable); 1880\& ev_io_start (loop, &stdin_readable);
1141\& ev_loop (loop, 0); 1881\& ev_run (loop, 0);
1142.Ve 1882.Ve
1143.ie n .Sh """ev_timer"" \- relative and optionally repeating timeouts" 1883.ie n .SS """ev_timer"" \- relative and optionally repeating timeouts"
1144.el .Sh "\f(CWev_timer\fP \- relative and optionally repeating timeouts" 1884.el .SS "\f(CWev_timer\fP \- relative and optionally repeating timeouts"
1145.IX Subsection "ev_timer - relative and optionally repeating timeouts" 1885.IX Subsection "ev_timer - relative and optionally repeating timeouts"
1146Timer watchers are simple relative timers that generate an event after a 1886Timer watchers are simple relative timers that generate an event after a
1147given time, and optionally repeating in regular intervals after that. 1887given time, and optionally repeating in regular intervals after that.
1148.PP 1888.PP
1149The timers are based on real time, that is, if you register an event that 1889The timers are based on real time, that is, if you register an event that
1150times out after an hour and you reset your system clock to last years 1890times out after an hour and you reset your system clock to January last
1151time, it will still time out after (roughly) and hour. \*(L"Roughly\*(R" because 1891year, it will still time out after (roughly) one hour. \*(L"Roughly\*(R" because
1152detecting time jumps is hard, and some inaccuracies are unavoidable (the 1892detecting time jumps is hard, and some inaccuracies are unavoidable (the
1153monotonic clock option helps a lot here). 1893monotonic clock option helps a lot here).
1894.PP
1895The callback is guaranteed to be invoked only \fIafter\fR its timeout has
1896passed (not \fIat\fR, so on systems with very low-resolution clocks this
1897might introduce a small delay, see \*(L"the special problem of being too
1898early\*(R", below). If multiple timers become ready during the same loop
1899iteration then the ones with earlier time-out values are invoked before
1900ones of the same priority with later time-out values (but this is no
1901longer true when a callback calls \f(CW\*(C`ev_run\*(C'\fR recursively).
1902.PP
1903\fIBe smart about timeouts\fR
1904.IX Subsection "Be smart about timeouts"
1905.PP
1906Many real-world problems involve some kind of timeout, usually for error
1907recovery. A typical example is an \s-1HTTP\s0 request \- if the other side hangs,
1908you want to raise some error after a while.
1909.PP
1910What follows are some ways to handle this problem, from obvious and
1911inefficient to smart and efficient.
1912.PP
1913In the following, a 60 second activity timeout is assumed \- a timeout that
1914gets reset to 60 seconds each time there is activity (e.g. each time some
1915data or other life sign was received).
1916.IP "1. Use a timer and stop, reinitialise and start it on activity." 4
1917.IX Item "1. Use a timer and stop, reinitialise and start it on activity."
1918This is the most obvious, but not the most simple way: In the beginning,
1919start the watcher:
1920.Sp
1921.Vb 2
1922\& ev_timer_init (timer, callback, 60., 0.);
1923\& ev_timer_start (loop, timer);
1924.Ve
1925.Sp
1926Then, each time there is some activity, \f(CW\*(C`ev_timer_stop\*(C'\fR it, initialise it
1927and start it again:
1928.Sp
1929.Vb 3
1930\& ev_timer_stop (loop, timer);
1931\& ev_timer_set (timer, 60., 0.);
1932\& ev_timer_start (loop, timer);
1933.Ve
1934.Sp
1935This is relatively simple to implement, but means that each time there is
1936some activity, libev will first have to remove the timer from its internal
1937data structure and then add it again. Libev tries to be fast, but it's
1938still not a constant-time operation.
1939.ie n .IP "2. Use a timer and re-start it with ""ev_timer_again"" inactivity." 4
1940.el .IP "2. Use a timer and re-start it with \f(CWev_timer_again\fR inactivity." 4
1941.IX Item "2. Use a timer and re-start it with ev_timer_again inactivity."
1942This is the easiest way, and involves using \f(CW\*(C`ev_timer_again\*(C'\fR instead of
1943\&\f(CW\*(C`ev_timer_start\*(C'\fR.
1944.Sp
1945To implement this, configure an \f(CW\*(C`ev_timer\*(C'\fR with a \f(CW\*(C`repeat\*(C'\fR value
1946of \f(CW60\fR and then call \f(CW\*(C`ev_timer_again\*(C'\fR at start and each time you
1947successfully read or write some data. If you go into an idle state where
1948you do not expect data to travel on the socket, you can \f(CW\*(C`ev_timer_stop\*(C'\fR
1949the timer, and \f(CW\*(C`ev_timer_again\*(C'\fR will automatically restart it if need be.
1950.Sp
1951That means you can ignore both the \f(CW\*(C`ev_timer_start\*(C'\fR function and the
1952\&\f(CW\*(C`after\*(C'\fR argument to \f(CW\*(C`ev_timer_set\*(C'\fR, and only ever use the \f(CW\*(C`repeat\*(C'\fR
1953member and \f(CW\*(C`ev_timer_again\*(C'\fR.
1954.Sp
1955At start:
1956.Sp
1957.Vb 3
1958\& ev_init (timer, callback);
1959\& timer\->repeat = 60.;
1960\& ev_timer_again (loop, timer);
1961.Ve
1962.Sp
1963Each time there is some activity:
1964.Sp
1965.Vb 1
1966\& ev_timer_again (loop, timer);
1967.Ve
1968.Sp
1969It is even possible to change the time-out on the fly, regardless of
1970whether the watcher is active or not:
1971.Sp
1972.Vb 2
1973\& timer\->repeat = 30.;
1974\& ev_timer_again (loop, timer);
1975.Ve
1976.Sp
1977This is slightly more efficient then stopping/starting the timer each time
1978you want to modify its timeout value, as libev does not have to completely
1979remove and re-insert the timer from/into its internal data structure.
1980.Sp
1981It is, however, even simpler than the \*(L"obvious\*(R" way to do it.
1982.IP "3. Let the timer time out, but then re-arm it as required." 4
1983.IX Item "3. Let the timer time out, but then re-arm it as required."
1984This method is more tricky, but usually most efficient: Most timeouts are
1985relatively long compared to the intervals between other activity \- in
1986our example, within 60 seconds, there are usually many I/O events with
1987associated activity resets.
1988.Sp
1989In this case, it would be more efficient to leave the \f(CW\*(C`ev_timer\*(C'\fR alone,
1990but remember the time of last activity, and check for a real timeout only
1991within the callback:
1992.Sp
1993.Vb 3
1994\& ev_tstamp timeout = 60.;
1995\& ev_tstamp last_activity; // time of last activity
1996\& ev_timer timer;
1997\&
1998\& static void
1999\& callback (EV_P_ ev_timer *w, int revents)
2000\& {
2001\& // calculate when the timeout would happen
2002\& ev_tstamp after = last_activity \- ev_now (EV_A) + timeout;
2003\&
2004\& // if negative, it means we the timeout already occurred
2005\& if (after < 0.)
2006\& {
2007\& // timeout occurred, take action
2008\& }
2009\& else
2010\& {
2011\& // callback was invoked, but there was some recent
2012\& // activity. simply restart the timer to time out
2013\& // after "after" seconds, which is the earliest time
2014\& // the timeout can occur.
2015\& ev_timer_set (w, after, 0.);
2016\& ev_timer_start (EV_A_ w);
2017\& }
2018\& }
2019.Ve
2020.Sp
2021To summarise the callback: first calculate in how many seconds the
2022timeout will occur (by calculating the absolute time when it would occur,
2023\&\f(CW\*(C`last_activity + timeout\*(C'\fR, and subtracting the current time, \f(CW\*(C`ev_now
2024(EV_A)\*(C'\fR from that).
2025.Sp
2026If this value is negative, then we are already past the timeout, i.e. we
2027timed out, and need to do whatever is needed in this case.
2028.Sp
2029Otherwise, we now the earliest time at which the timeout would trigger,
2030and simply start the timer with this timeout value.
2031.Sp
2032In other words, each time the callback is invoked it will check whether
2033the timeout occurred. If not, it will simply reschedule itself to check
2034again at the earliest time it could time out. Rinse. Repeat.
2035.Sp
2036This scheme causes more callback invocations (about one every 60 seconds
2037minus half the average time between activity), but virtually no calls to
2038libev to change the timeout.
2039.Sp
2040To start the machinery, simply initialise the watcher and set
2041\&\f(CW\*(C`last_activity\*(C'\fR to the current time (meaning there was some activity just
2042now), then call the callback, which will \*(L"do the right thing\*(R" and start
2043the timer:
2044.Sp
2045.Vb 3
2046\& last_activity = ev_now (EV_A);
2047\& ev_init (&timer, callback);
2048\& callback (EV_A_ &timer, 0);
2049.Ve
2050.Sp
2051When there is some activity, simply store the current time in
2052\&\f(CW\*(C`last_activity\*(C'\fR, no libev calls at all:
2053.Sp
2054.Vb 2
2055\& if (activity detected)
2056\& last_activity = ev_now (EV_A);
2057.Ve
2058.Sp
2059When your timeout value changes, then the timeout can be changed by simply
2060providing a new value, stopping the timer and calling the callback, which
2061will again do the right thing (for example, time out immediately :).
2062.Sp
2063.Vb 3
2064\& timeout = new_value;
2065\& ev_timer_stop (EV_A_ &timer);
2066\& callback (EV_A_ &timer, 0);
2067.Ve
2068.Sp
2069This technique is slightly more complex, but in most cases where the
2070time-out is unlikely to be triggered, much more efficient.
2071.IP "4. Wee, just use a double-linked list for your timeouts." 4
2072.IX Item "4. Wee, just use a double-linked list for your timeouts."
2073If there is not one request, but many thousands (millions...), all
2074employing some kind of timeout with the same timeout value, then one can
2075do even better:
2076.Sp
2077When starting the timeout, calculate the timeout value and put the timeout
2078at the \fIend\fR of the list.
2079.Sp
2080Then use an \f(CW\*(C`ev_timer\*(C'\fR to fire when the timeout at the \fIbeginning\fR of
2081the list is expected to fire (for example, using the technique #3).
2082.Sp
2083When there is some activity, remove the timer from the list, recalculate
2084the timeout, append it to the end of the list again, and make sure to
2085update the \f(CW\*(C`ev_timer\*(C'\fR if it was taken from the beginning of the list.
2086.Sp
2087This way, one can manage an unlimited number of timeouts in O(1) time for
2088starting, stopping and updating the timers, at the expense of a major
2089complication, and having to use a constant timeout. The constant timeout
2090ensures that the list stays sorted.
2091.PP
2092So which method the best?
2093.PP
2094Method #2 is a simple no-brain-required solution that is adequate in most
2095situations. Method #3 requires a bit more thinking, but handles many cases
2096better, and isn't very complicated either. In most case, choosing either
2097one is fine, with #3 being better in typical situations.
2098.PP
2099Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
2100rather complicated, but extremely efficient, something that really pays
2101off after the first million or so of active timers, i.e. it's usually
2102overkill :)
2103.PP
2104\fIThe special problem of being too early\fR
2105.IX Subsection "The special problem of being too early"
2106.PP
2107If you ask a timer to call your callback after three seconds, then
2108you expect it to be invoked after three seconds \- but of course, this
2109cannot be guaranteed to infinite precision. Less obviously, it cannot be
2110guaranteed to any precision by libev \- imagine somebody suspending the
2111process with a \s-1STOP\s0 signal for a few hours for example.
2112.PP
2113So, libev tries to invoke your callback as soon as possible \fIafter\fR the
2114delay has occurred, but cannot guarantee this.
2115.PP
2116A less obvious failure mode is calling your callback too early: many event
2117loops compare timestamps with a \*(L"elapsed delay >= requested delay\*(R", but
2118this can cause your callback to be invoked much earlier than you would
2119expect.
2120.PP
2121To see why, imagine a system with a clock that only offers full second
2122resolution (think windows if you can't come up with a broken enough \s-1OS\s0
2123yourself). If you schedule a one-second timer at the time 500.9, then the
2124event loop will schedule your timeout to elapse at a system time of 500
2125(500.9 truncated to the resolution) + 1, or 501.
2126.PP
2127If an event library looks at the timeout 0.1s later, it will see \*(L"501 >=
2128501\*(R" and invoke the callback 0.1s after it was started, even though a
2129one-second delay was requested \- this is being \*(L"too early\*(R", despite best
2130intentions.
2131.PP
2132This is the reason why libev will never invoke the callback if the elapsed
2133delay equals the requested delay, but only when the elapsed delay is
2134larger than the requested delay. In the example above, libev would only invoke
2135the callback at system time 502, or 1.1s after the timer was started.
2136.PP
2137So, while libev cannot guarantee that your callback will be invoked
2138exactly when requested, it \fIcan\fR and \fIdoes\fR guarantee that the requested
2139delay has actually elapsed, or in other words, it always errs on the \*(L"too
2140late\*(R" side of things.
2141.PP
2142\fIThe special problem of time updates\fR
2143.IX Subsection "The special problem of time updates"
2144.PP
2145Establishing the current time is a costly operation (it usually takes
2146at least one system call): \s-1EV\s0 therefore updates its idea of the current
2147time only before and after \f(CW\*(C`ev_run\*(C'\fR collects new events, which causes a
2148growing difference between \f(CW\*(C`ev_now ()\*(C'\fR and \f(CW\*(C`ev_time ()\*(C'\fR when handling
2149lots of events in one iteration.
1154.PP 2150.PP
1155The relative timeouts are calculated relative to the \f(CW\*(C`ev_now ()\*(C'\fR 2151The relative timeouts are calculated relative to the \f(CW\*(C`ev_now ()\*(C'\fR
1156time. This is usually the right thing as this timestamp refers to the time 2152time. This is usually the right thing as this timestamp refers to the time
1157of the event triggering whatever timeout you are modifying/starting. If 2153of the event triggering whatever timeout you are modifying/starting. If
1158you suspect event processing to be delayed and you \fIneed\fR to base the timeout 2154you suspect event processing to be delayed and you \fIneed\fR to base the
1159on the current time, use something like this to adjust for this: 2155timeout on the current time, use something like this to adjust for this:
1160.PP 2156.PP
1161.Vb 1 2157.Vb 1
1162\& ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); 2158\& ev_timer_set (&timer, after + ev_now () \- ev_time (), 0.);
1163.Ve 2159.Ve
1164.PP 2160.PP
1165The callback is guarenteed to be invoked only when its timeout has passed, 2161If the event loop is suspended for a long time, you can also force an
1166but if multiple timers become ready during the same loop iteration then 2162update of the time returned by \f(CW\*(C`ev_now ()\*(C'\fR by calling \f(CW\*(C`ev_now_update
1167order of execution is undefined. 2163()\*(C'\fR.
2164.PP
2165\fIThe special problem of unsynchronised clocks\fR
2166.IX Subsection "The special problem of unsynchronised clocks"
2167.PP
2168Modern systems have a variety of clocks \- libev itself uses the normal
2169\&\*(L"wall clock\*(R" clock and, if available, the monotonic clock (to avoid time
2170jumps).
2171.PP
2172Neither of these clocks is synchronised with each other or any other clock
2173on the system, so \f(CW\*(C`ev_time ()\*(C'\fR might return a considerably different time
2174than \f(CW\*(C`gettimeofday ()\*(C'\fR or \f(CW\*(C`time ()\*(C'\fR. On a GNU/Linux system, for example,
2175a call to \f(CW\*(C`gettimeofday\*(C'\fR might return a second count that is one higher
2176than a directly following call to \f(CW\*(C`time\*(C'\fR.
2177.PP
2178The moral of this is to only compare libev-related timestamps with
2179\&\f(CW\*(C`ev_time ()\*(C'\fR and \f(CW\*(C`ev_now ()\*(C'\fR, at least if you want better precision than
2180a second or so.
2181.PP
2182One more problem arises due to this lack of synchronisation: if libev uses
2183the system monotonic clock and you compare timestamps from \f(CW\*(C`ev_time\*(C'\fR
2184or \f(CW\*(C`ev_now\*(C'\fR from when you started your timer and when your callback is
2185invoked, you will find that sometimes the callback is a bit \*(L"early\*(R".
2186.PP
2187This is because \f(CW\*(C`ev_timer\*(C'\fRs work in real time, not wall clock time, so
2188libev makes sure your callback is not invoked before the delay happened,
2189\&\fImeasured according to the real time\fR, not the system clock.
2190.PP
2191If your timeouts are based on a physical timescale (e.g. \*(L"time out this
2192connection after 100 seconds\*(R") then this shouldn't bother you as it is
2193exactly the right behaviour.
2194.PP
2195If you want to compare wall clock/system timestamps to your timers, then
2196you need to use \f(CW\*(C`ev_periodic\*(C'\fRs, as these are based on the wall clock
2197time, where your comparisons will always generate correct results.
2198.PP
2199\fIThe special problems of suspended animation\fR
2200.IX Subsection "The special problems of suspended animation"
2201.PP
2202When you leave the server world it is quite customary to hit machines that
2203can suspend/hibernate \- what happens to the clocks during such a suspend?
2204.PP
2205Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
2206all processes, while the clocks (\f(CW\*(C`times\*(C'\fR, \f(CW\*(C`CLOCK_MONOTONIC\*(C'\fR) continue
2207to run until the system is suspended, but they will not advance while the
2208system is suspended. That means, on resume, it will be as if the program
2209was frozen for a few seconds, but the suspend time will not be counted
2210towards \f(CW\*(C`ev_timer\*(C'\fR when a monotonic clock source is used. The real time
2211clock advanced as expected, but if it is used as sole clocksource, then a
2212long suspend would be detected as a time jump by libev, and timers would
2213be adjusted accordingly.
2214.PP
2215I would not be surprised to see different behaviour in different between
2216operating systems, \s-1OS\s0 versions or even different hardware.
2217.PP
2218The other form of suspend (job control, or sending a \s-1SIGSTOP\s0) will see a
2219time jump in the monotonic clocks and the realtime clock. If the program
2220is suspended for a very long time, and monotonic clock sources are in use,
2221then you can expect \f(CW\*(C`ev_timer\*(C'\fRs to expire as the full suspension time
2222will be counted towards the timers. When no monotonic clock source is in
2223use, then libev will again assume a timejump and adjust accordingly.
2224.PP
2225It might be beneficial for this latter case to call \f(CW\*(C`ev_suspend\*(C'\fR
2226and \f(CW\*(C`ev_resume\*(C'\fR in code that handles \f(CW\*(C`SIGTSTP\*(C'\fR, to at least get
2227deterministic behaviour in this case (you can do nothing against
2228\&\f(CW\*(C`SIGSTOP\*(C'\fR).
1168.PP 2229.PP
1169\fIWatcher-Specific Functions and Data Members\fR 2230\fIWatcher-Specific Functions and Data Members\fR
1170.IX Subsection "Watcher-Specific Functions and Data Members" 2231.IX Subsection "Watcher-Specific Functions and Data Members"
1171.IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4 2232.IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4
1172.IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 2233.IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)"
1173.PD 0 2234.PD 0
1174.IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4 2235.IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4
1175.IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 2236.IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)"
1176.PD 2237.PD
1177Configure the timer to trigger after \f(CW\*(C`after\*(C'\fR seconds. If \f(CW\*(C`repeat\*(C'\fR is 2238Configure the timer to trigger after \f(CW\*(C`after\*(C'\fR seconds. If \f(CW\*(C`repeat\*(C'\fR
1178\&\f(CW0.\fR, then it will automatically be stopped. If it is positive, then the 2239is \f(CW0.\fR, then it will automatically be stopped once the timeout is
1179timer will automatically be configured to trigger again \f(CW\*(C`repeat\*(C'\fR seconds 2240reached. If it is positive, then the timer will automatically be
1180later, again, and again, until stopped manually. 2241configured to trigger again \f(CW\*(C`repeat\*(C'\fR seconds later, again, and again,
2242until stopped manually.
1181.Sp 2243.Sp
1182The timer itself will do a best-effort at avoiding drift, that is, if you 2244The timer itself will do a best-effort at avoiding drift, that is, if
1183configure a timer to trigger every 10 seconds, then it will trigger at 2245you configure a timer to trigger every 10 seconds, then it will normally
1184exactly 10 second intervals. If, however, your program cannot keep up with 2246trigger at exactly 10 second intervals. If, however, your program cannot
1185the timer (because it takes longer than those 10 seconds to do stuff) the 2247keep up with the timer (because it takes longer than those 10 seconds to
1186timer will not fire more than once per event loop iteration. 2248do stuff) the timer will not fire more than once per event loop iteration.
1187.IP "ev_timer_again (loop)" 4 2249.IP "ev_timer_again (loop, ev_timer *)" 4
1188.IX Item "ev_timer_again (loop)" 2250.IX Item "ev_timer_again (loop, ev_timer *)"
1189This will act as if the timer timed out and restart it again if it is 2251This will act as if the timer timed out, and restarts it again if it is
1190repeating. The exact semantics are: 2252repeating. It basically works like calling \f(CW\*(C`ev_timer_stop\*(C'\fR, updating the
2253timeout to the \f(CW\*(C`repeat\*(C'\fR value and calling \f(CW\*(C`ev_timer_start\*(C'\fR.
1191.Sp 2254.Sp
2255The exact semantics are as in the following rules, all of which will be
2256applied to the watcher:
2257.RS 4
1192If the timer is pending, its pending status is cleared. 2258.IP "If the timer is pending, the pending status is always cleared." 4
1193.Sp 2259.IX Item "If the timer is pending, the pending status is always cleared."
2260.PD 0
1194If the timer is started but nonrepeating, stop it (as if it timed out). 2261.IP "If the timer is started but non-repeating, stop it (as if it timed out, without invoking it)." 4
2262.IX Item "If the timer is started but non-repeating, stop it (as if it timed out, without invoking it)."
2263.ie n .IP "If the timer is repeating, make the ""repeat"" value the new timeout and start the timer, if necessary." 4
2264.el .IP "If the timer is repeating, make the \f(CWrepeat\fR value the new timeout and start the timer, if necessary." 4
2265.IX Item "If the timer is repeating, make the repeat value the new timeout and start the timer, if necessary."
2266.RE
2267.RS 4
2268.PD
1195.Sp 2269.Sp
1196If the timer is repeating, either start it if necessary (with the 2270This sounds a bit complicated, see \*(L"Be smart about timeouts\*(R", above, for a
1197\&\f(CW\*(C`repeat\*(C'\fR value), or reset the running timer to the \f(CW\*(C`repeat\*(C'\fR value. 2271usage example.
2272.RE
2273.IP "ev_tstamp ev_timer_remaining (loop, ev_timer *)" 4
2274.IX Item "ev_tstamp ev_timer_remaining (loop, ev_timer *)"
2275Returns the remaining time until a timer fires. If the timer is active,
2276then this time is relative to the current event loop time, otherwise it's
2277the timeout value currently configured.
1198.Sp 2278.Sp
1199This sounds a bit complicated, but here is a useful and typical 2279That is, after an \f(CW\*(C`ev_timer_set (w, 5, 7)\*(C'\fR, \f(CW\*(C`ev_timer_remaining\*(C'\fR returns
1200example: Imagine you have a tcp connection and you want a so-called idle 2280\&\f(CW5\fR. When the timer is started and one second passes, \f(CW\*(C`ev_timer_remaining\*(C'\fR
1201timeout, that is, you want to be called when there have been, say, 60 2281will return \f(CW4\fR. When the timer expires and is restarted, it will return
1202seconds of inactivity on the socket. The easiest way to do this is to 2282roughly \f(CW7\fR (likely slightly less as callback invocation takes some time,
1203configure an \f(CW\*(C`ev_timer\*(C'\fR with a \f(CW\*(C`repeat\*(C'\fR value of \f(CW60\fR and then call 2283too), and so on.
1204\&\f(CW\*(C`ev_timer_again\*(C'\fR each time you successfully read or write some data. If
1205you go into an idle state where you do not expect data to travel on the
1206socket, you can \f(CW\*(C`ev_timer_stop\*(C'\fR the timer, and \f(CW\*(C`ev_timer_again\*(C'\fR will
1207automatically restart it if need be.
1208.Sp
1209That means you can ignore the \f(CW\*(C`after\*(C'\fR value and \f(CW\*(C`ev_timer_start\*(C'\fR
1210altogether and only ever use the \f(CW\*(C`repeat\*(C'\fR value and \f(CW\*(C`ev_timer_again\*(C'\fR:
1211.Sp
1212.Vb 8
1213\& ev_timer_init (timer, callback, 0., 5.);
1214\& ev_timer_again (loop, timer);
1215\& ...
1216\& timer->again = 17.;
1217\& ev_timer_again (loop, timer);
1218\& ...
1219\& timer->again = 10.;
1220\& ev_timer_again (loop, timer);
1221.Ve
1222.Sp
1223This is more slightly efficient then stopping/starting the timer each time
1224you want to modify its timeout value.
1225.IP "ev_tstamp repeat [read\-write]" 4 2284.IP "ev_tstamp repeat [read\-write]" 4
1226.IX Item "ev_tstamp repeat [read-write]" 2285.IX Item "ev_tstamp repeat [read-write]"
1227The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out 2286The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out
1228or \f(CW\*(C`ev_timer_again\*(C'\fR is called and determines the next timeout (if any), 2287or \f(CW\*(C`ev_timer_again\*(C'\fR is called, and determines the next timeout (if any),
1229which is also when any modifications are taken into account. 2288which is also when any modifications are taken into account.
1230.PP 2289.PP
2290\fIExamples\fR
2291.IX Subsection "Examples"
2292.PP
1231Example: Create a timer that fires after 60 seconds. 2293Example: Create a timer that fires after 60 seconds.
1232.PP 2294.PP
1233.Vb 5 2295.Vb 5
1234\& static void 2296\& static void
1235\& one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 2297\& one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1236\& { 2298\& {
1237\& .. one minute over, w is actually stopped right here 2299\& .. one minute over, w is actually stopped right here
1238\& } 2300\& }
1239.Ve 2301\&
1240.PP
1241.Vb 3
1242\& struct ev_timer mytimer; 2302\& ev_timer mytimer;
1243\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.); 2303\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1244\& ev_timer_start (loop, &mytimer); 2304\& ev_timer_start (loop, &mytimer);
1245.Ve 2305.Ve
1246.PP 2306.PP
1247Example: Create a timeout timer that times out after 10 seconds of 2307Example: Create a timeout timer that times out after 10 seconds of
1248inactivity. 2308inactivity.
1249.PP 2309.PP
1250.Vb 5 2310.Vb 5
1251\& static void 2311\& static void
1252\& timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 2312\& timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1253\& { 2313\& {
1254\& .. ten seconds without any activity 2314\& .. ten seconds without any activity
1255\& } 2315\& }
1256.Ve 2316\&
1257.PP
1258.Vb 4
1259\& struct ev_timer mytimer; 2317\& ev_timer mytimer;
1260\& ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ 2318\& ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1261\& ev_timer_again (&mytimer); /* start timer */ 2319\& ev_timer_again (&mytimer); /* start timer */
1262\& ev_loop (loop, 0); 2320\& ev_run (loop, 0);
1263.Ve 2321\&
1264.PP
1265.Vb 3
1266\& // and in some piece of code that gets executed on any "activity": 2322\& // and in some piece of code that gets executed on any "activity":
1267\& // reset the timeout to start ticking again at 10 seconds 2323\& // reset the timeout to start ticking again at 10 seconds
1268\& ev_timer_again (&mytimer); 2324\& ev_timer_again (&mytimer);
1269.Ve 2325.Ve
1270.ie n .Sh """ev_periodic"" \- to cron or not to cron?" 2326.ie n .SS """ev_periodic"" \- to cron or not to cron?"
1271.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron?" 2327.el .SS "\f(CWev_periodic\fP \- to cron or not to cron?"
1272.IX Subsection "ev_periodic - to cron or not to cron?" 2328.IX Subsection "ev_periodic - to cron or not to cron?"
1273Periodic watchers are also timers of a kind, but they are very versatile 2329Periodic watchers are also timers of a kind, but they are very versatile
1274(and unfortunately a bit complex). 2330(and unfortunately a bit complex).
1275.PP 2331.PP
1276Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time) 2332Unlike \f(CW\*(C`ev_timer\*(C'\fR, periodic watchers are not based on real time (or
1277but on wallclock time (absolute time). You can tell a periodic watcher 2333relative time, the physical time that passes) but on wall clock time
1278to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a 2334(absolute time, the thing you can read on your calender or clock). The
1279periodic watcher to trigger in 10 seconds (by specifiying e.g. \f(CW\*(C`ev_now () 2335difference is that wall clock time can run faster or slower than real
1280+ 10.\*(C'\fR) and then reset your system clock to the last year, then it will 2336time, and time jumps are not uncommon (e.g. when you adjust your
1281take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger 2337wrist-watch).
1282roughly 10 seconds later).
1283.PP 2338.PP
1284They can also be used to implement vastly more complex timers, such as 2339You can tell a periodic watcher to trigger after some specific point
1285triggering an event on each midnight, local time or other, complicated, 2340in time: for example, if you tell a periodic watcher to trigger \*(L"in 10
1286rules. 2341seconds\*(R" (by specifying e.g. \f(CW\*(C`ev_now () + 10.\*(C'\fR, that is, an absolute time
2342not a delay) and then reset your system clock to January of the previous
2343year, then it will take a year or more to trigger the event (unlike an
2344\&\f(CW\*(C`ev_timer\*(C'\fR, which would still trigger roughly 10 seconds after starting
2345it, as it uses a relative timeout).
1287.PP 2346.PP
2347\&\f(CW\*(C`ev_periodic\*(C'\fR watchers can also be used to implement vastly more complex
2348timers, such as triggering an event on each \*(L"midnight, local time\*(R", or
2349other complicated rules. This cannot be done with \f(CW\*(C`ev_timer\*(C'\fR watchers, as
2350those cannot react to time jumps.
2351.PP
1288As with timers, the callback is guarenteed to be invoked only when the 2352As with timers, the callback is guaranteed to be invoked only when the
1289time (\f(CW\*(C`at\*(C'\fR) has been passed, but if multiple periodic timers become ready 2353point in time where it is supposed to trigger has passed. If multiple
1290during the same loop iteration then order of execution is undefined. 2354timers become ready during the same loop iteration then the ones with
2355earlier time-out values are invoked before ones with later time-out values
2356(but this is no longer true when a callback calls \f(CW\*(C`ev_run\*(C'\fR recursively).
1291.PP 2357.PP
1292\fIWatcher-Specific Functions and Data Members\fR 2358\fIWatcher-Specific Functions and Data Members\fR
1293.IX Subsection "Watcher-Specific Functions and Data Members" 2359.IX Subsection "Watcher-Specific Functions and Data Members"
1294.IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4 2360.IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)" 4
1295.IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 2361.IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)"
1296.PD 0 2362.PD 0
1297.IP "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 4 2363.IP "ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)" 4
1298.IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 2364.IX Item "ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)"
1299.PD 2365.PD
1300Lots of arguments, lets sort it out... There are basically three modes of 2366Lots of arguments, let's sort it out... There are basically three modes of
1301operation, and we will explain them from simplest to complex: 2367operation, and we will explain them from simplest to most complex:
1302.RS 4 2368.RS 4
2369.IP "\(bu" 4
1303.IP "* absolute timer (at = time, interval = reschedule_cb = 0)" 4 2370absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1304.IX Item "absolute timer (at = time, interval = reschedule_cb = 0)" 2371.Sp
1305In this configuration the watcher triggers an event at the wallclock time 2372In this configuration the watcher triggers an event after the wall clock
1306\&\f(CW\*(C`at\*(C'\fR and doesn't repeat. It will not adjust when a time jump occurs, 2373time \f(CW\*(C`offset\*(C'\fR has passed. It will not repeat and will not adjust when a
1307that is, if it is to be run at January 1st 2011 then it will run when the 2374time jump occurs, that is, if it is to be run at January 1st 2011 then it
1308system time reaches or surpasses this time. 2375will be stopped and invoked when the system clock reaches or surpasses
1309.IP "* non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)" 4 2376this point in time.
1310.IX Item "non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)" 2377.IP "\(bu" 4
2378repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
2379.Sp
1311In this mode the watcher will always be scheduled to time out at the next 2380In this mode the watcher will always be scheduled to time out at the next
1312\&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N, which can also be negative) 2381\&\f(CW\*(C`offset + N * interval\*(C'\fR time (for some integer N, which can also be
1313and then repeat, regardless of any time jumps. 2382negative) and then repeat, regardless of any time jumps. The \f(CW\*(C`offset\*(C'\fR
2383argument is merely an offset into the \f(CW\*(C`interval\*(C'\fR periods.
1314.Sp 2384.Sp
1315This can be used to create timers that do not drift with respect to system 2385This can be used to create timers that do not drift with respect to the
1316time: 2386system clock, for example, here is an \f(CW\*(C`ev_periodic\*(C'\fR that triggers each
2387hour, on the hour (with respect to \s-1UTC\s0):
1317.Sp 2388.Sp
1318.Vb 1 2389.Vb 1
1319\& ev_periodic_set (&periodic, 0., 3600., 0); 2390\& ev_periodic_set (&periodic, 0., 3600., 0);
1320.Ve 2391.Ve
1321.Sp 2392.Sp
1322This doesn't mean there will always be 3600 seconds in between triggers, 2393This doesn't mean there will always be 3600 seconds in between triggers,
1323but only that the the callback will be called when the system time shows a 2394but only that the callback will be called when the system time shows a
1324full hour (\s-1UTC\s0), or more correctly, when the system time is evenly divisible 2395full hour (\s-1UTC\s0), or more correctly, when the system time is evenly divisible
1325by 3600. 2396by 3600.
1326.Sp 2397.Sp
1327Another way to think about it (for the mathematically inclined) is that 2398Another way to think about it (for the mathematically inclined) is that
1328\&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible 2399\&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible
1329time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps. 2400time where \f(CW\*(C`time = offset (mod interval)\*(C'\fR, regardless of any time jumps.
1330.Sp 2401.Sp
1331For numerical stability it is preferable that the \f(CW\*(C`at\*(C'\fR value is near 2402The \f(CW\*(C`interval\*(C'\fR \fI\s-1MUST\s0\fR be positive, and for numerical stability, the
1332\&\f(CW\*(C`ev_now ()\*(C'\fR (the current time), but there is no range requirement for 2403interval value should be higher than \f(CW\*(C`1/8192\*(C'\fR (which is around 100
1333this value. 2404microseconds) and \f(CW\*(C`offset\*(C'\fR should be higher than \f(CW0\fR and should have
2405at most a similar magnitude as the current time (say, within a factor of
2406ten). Typical values for offset are, in fact, \f(CW0\fR or something between
2407\&\f(CW0\fR and \f(CW\*(C`interval\*(C'\fR, which is also the recommended range.
2408.Sp
2409Note also that there is an upper limit to how often a timer can fire (\s-1CPU\s0
2410speed for example), so if \f(CW\*(C`interval\*(C'\fR is very small then timing stability
2411will of course deteriorate. Libev itself tries to be exact to be about one
2412millisecond (if the \s-1OS\s0 supports it and the machine is fast enough).
2413.IP "\(bu" 4
1334.IP "* manual reschedule mode (at and interval ignored, reschedule_cb = callback)" 4 2414manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1335.IX Item "manual reschedule mode (at and interval ignored, reschedule_cb = callback)" 2415.Sp
1336In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR are both being 2416In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`offset\*(C'\fR are both being
1337ignored. Instead, each time the periodic watcher gets scheduled, the 2417ignored. Instead, each time the periodic watcher gets scheduled, the
1338reschedule callback will be called with the watcher as first, and the 2418reschedule callback will be called with the watcher as first, and the
1339current time as second argument. 2419current time as second argument.
1340.Sp 2420.Sp
1341\&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher, 2421\&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher, ever,
1342ever, or make any event loop modifications\fR. If you need to stop it, 2422or make \s-1ANY\s0 other event loop modifications whatsoever, unless explicitly
1343return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop it afterwards (e.g. by 2423allowed by documentation here\fR.
2424.Sp
2425If you need to stop it, return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop
1344starting an \f(CW\*(C`ev_prepare\*(C'\fR watcher, which is legal). 2426it afterwards (e.g. by starting an \f(CW\*(C`ev_prepare\*(C'\fR watcher, which is the
2427only event loop modification you are allowed to do).
1345.Sp 2428.Sp
1346Its prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 2429The callback prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(ev_periodic
1347ev_tstamp now)\*(C'\fR, e.g.: 2430*w, ev_tstamp now)\*(C'\fR, e.g.:
1348.Sp 2431.Sp
1349.Vb 4 2432.Vb 5
2433\& static ev_tstamp
1350\& static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 2434\& my_rescheduler (ev_periodic *w, ev_tstamp now)
1351\& { 2435\& {
1352\& return now + 60.; 2436\& return now + 60.;
1353\& } 2437\& }
1354.Ve 2438.Ve
1355.Sp 2439.Sp
1356It must return the next time to trigger, based on the passed time value 2440It must return the next time to trigger, based on the passed time value
1357(that is, the lowest time value larger than to the second argument). It 2441(that is, the lowest time value larger than to the second argument). It
1358will usually be called just before the callback will be triggered, but 2442will usually be called just before the callback will be triggered, but
1359might be called at other times, too. 2443might be called at other times, too.
1360.Sp 2444.Sp
1361\&\s-1NOTE:\s0 \fIThis callback must always return a time that is later than the 2445\&\s-1NOTE:\s0 \fIThis callback must always return a time that is higher than or
1362passed \f(CI\*(C`now\*(C'\fI value\fR. Not even \f(CW\*(C`now\*(C'\fR itself will do, it \fImust\fR be larger. 2446equal to the passed \f(CI\*(C`now\*(C'\fI value\fR.
1363.Sp 2447.Sp
1364This can be used to create very complex timers, such as a timer that 2448This can be used to create very complex timers, such as a timer that
1365triggers on each midnight, local time. To do this, you would calculate the 2449triggers on \*(L"next midnight, local time\*(R". To do this, you would calculate the
1366next midnight after \f(CW\*(C`now\*(C'\fR and return the timestamp value for this. How 2450next midnight after \f(CW\*(C`now\*(C'\fR and return the timestamp value for this. How
1367you do this is, again, up to you (but it is not trivial, which is the main 2451you do this is, again, up to you (but it is not trivial, which is the main
1368reason I omitted it as an example). 2452reason I omitted it as an example).
1369.RE 2453.RE
1370.RS 4 2454.RS 4
… …
1373.IX Item "ev_periodic_again (loop, ev_periodic *)" 2457.IX Item "ev_periodic_again (loop, ev_periodic *)"
1374Simply stops and restarts the periodic watcher again. This is only useful 2458Simply stops and restarts the periodic watcher again. This is only useful
1375when you changed some parameters or the reschedule callback would return 2459when you changed some parameters or the reschedule callback would return
1376a different time than the last time it was called (e.g. in a crond like 2460a different time than the last time it was called (e.g. in a crond like
1377program when the crontabs have changed). 2461program when the crontabs have changed).
2462.IP "ev_tstamp ev_periodic_at (ev_periodic *)" 4
2463.IX Item "ev_tstamp ev_periodic_at (ev_periodic *)"
2464When active, returns the absolute time that the watcher is supposed
2465to trigger next. This is not the same as the \f(CW\*(C`offset\*(C'\fR argument to
2466\&\f(CW\*(C`ev_periodic_set\*(C'\fR, but indeed works even in interval and manual
2467rescheduling modes.
1378.IP "ev_tstamp offset [read\-write]" 4 2468.IP "ev_tstamp offset [read\-write]" 4
1379.IX Item "ev_tstamp offset [read-write]" 2469.IX Item "ev_tstamp offset [read-write]"
1380When repeating, this contains the offset value, otherwise this is the 2470When repeating, this contains the offset value, otherwise this is the
1381absolute point in time (the \f(CW\*(C`at\*(C'\fR value passed to \f(CW\*(C`ev_periodic_set\*(C'\fR). 2471absolute point in time (the \f(CW\*(C`offset\*(C'\fR value passed to \f(CW\*(C`ev_periodic_set\*(C'\fR,
2472although libev might modify this value for better numerical stability).
1382.Sp 2473.Sp
1383Can be modified any time, but changes only take effect when the periodic 2474Can be modified any time, but changes only take effect when the periodic
1384timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called. 2475timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
1385.IP "ev_tstamp interval [read\-write]" 4 2476.IP "ev_tstamp interval [read\-write]" 4
1386.IX Item "ev_tstamp interval [read-write]" 2477.IX Item "ev_tstamp interval [read-write]"
1387The current interval value. Can be modified any time, but changes only 2478The current interval value. Can be modified any time, but changes only
1388take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being 2479take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being
1389called. 2480called.
1390.IP "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read\-write]" 4 2481.IP "ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read\-write]" 4
1391.IX Item "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]" 2482.IX Item "ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]"
1392The current reschedule callback, or \f(CW0\fR, if this functionality is 2483The current reschedule callback, or \f(CW0\fR, if this functionality is
1393switched off. Can be changed any time, but changes only take effect when 2484switched off. Can be changed any time, but changes only take effect when
1394the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called. 2485the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
1395.IP "ev_tstamp at [read\-only]" 4 2486.PP
1396.IX Item "ev_tstamp at [read-only]" 2487\fIExamples\fR
1397When active, contains the absolute time that the watcher is supposed to 2488.IX Subsection "Examples"
1398trigger next.
1399.PP 2489.PP
1400Example: Call a callback every hour, or, more precisely, whenever the 2490Example: Call a callback every hour, or, more precisely, whenever the
1401system clock is divisible by 3600. The callback invocation times have 2491system time is divisible by 3600. The callback invocation times have
1402potentially a lot of jittering, but good long-term stability. 2492potentially a lot of jitter, but good long-term stability.
1403.PP 2493.PP
1404.Vb 5 2494.Vb 5
1405\& static void 2495\& static void
1406\& clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) 2496\& clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1407\& { 2497\& {
1408\& ... its now a full hour (UTC, or TAI or whatever your clock follows) 2498\& ... its now a full hour (UTC, or TAI or whatever your clock follows)
1409\& } 2499\& }
1410.Ve 2500\&
1411.PP
1412.Vb 3
1413\& struct ev_periodic hourly_tick; 2501\& ev_periodic hourly_tick;
1414\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); 2502\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1415\& ev_periodic_start (loop, &hourly_tick); 2503\& ev_periodic_start (loop, &hourly_tick);
1416.Ve 2504.Ve
1417.PP 2505.PP
1418Example: The same as above, but use a reschedule callback to do it: 2506Example: The same as above, but use a reschedule callback to do it:
1419.PP 2507.PP
1420.Vb 1 2508.Vb 1
1421\& #include <math.h> 2509\& #include <math.h>
1422.Ve 2510\&
1423.PP
1424.Vb 5
1425\& static ev_tstamp 2511\& static ev_tstamp
1426\& my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) 2512\& my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1427\& { 2513\& {
1428\& return fmod (now, 3600.) + 3600.; 2514\& return now + (3600. \- fmod (now, 3600.));
1429\& } 2515\& }
1430.Ve 2516\&
1431.PP
1432.Vb 1
1433\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); 2517\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1434.Ve 2518.Ve
1435.PP 2519.PP
1436Example: Call a callback every hour, starting now: 2520Example: Call a callback every hour, starting now:
1437.PP 2521.PP
1438.Vb 4 2522.Vb 4
1439\& struct ev_periodic hourly_tick; 2523\& ev_periodic hourly_tick;
1440\& ev_periodic_init (&hourly_tick, clock_cb, 2524\& ev_periodic_init (&hourly_tick, clock_cb,
1441\& fmod (ev_now (loop), 3600.), 3600., 0); 2525\& fmod (ev_now (loop), 3600.), 3600., 0);
1442\& ev_periodic_start (loop, &hourly_tick); 2526\& ev_periodic_start (loop, &hourly_tick);
1443.Ve 2527.Ve
1444.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled!" 2528.ie n .SS """ev_signal"" \- signal me when a signal gets signalled!"
1445.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled!" 2529.el .SS "\f(CWev_signal\fP \- signal me when a signal gets signalled!"
1446.IX Subsection "ev_signal - signal me when a signal gets signalled!" 2530.IX Subsection "ev_signal - signal me when a signal gets signalled!"
1447Signal watchers will trigger an event when the process receives a specific 2531Signal watchers will trigger an event when the process receives a specific
1448signal one or more times. Even though signals are very asynchronous, libev 2532signal one or more times. Even though signals are very asynchronous, libev
1449will try it's best to deliver signals synchronously, i.e. as part of the 2533will try its best to deliver signals synchronously, i.e. as part of the
1450normal event processing, like any other event. 2534normal event processing, like any other event.
1451.PP 2535.PP
2536If you want signals to be delivered truly asynchronously, just use
2537\&\f(CW\*(C`sigaction\*(C'\fR as you would do without libev and forget about sharing
2538the signal. You can even use \f(CW\*(C`ev_async\*(C'\fR from a signal handler to
2539synchronously wake up an event loop.
2540.PP
1452You can configure as many watchers as you like per signal. Only when the 2541You can configure as many watchers as you like for the same signal, but
2542only within the same loop, i.e. you can watch for \f(CW\*(C`SIGINT\*(C'\fR in your
2543default loop and for \f(CW\*(C`SIGIO\*(C'\fR in another loop, but you cannot watch for
2544\&\f(CW\*(C`SIGINT\*(C'\fR in both the default loop and another loop at the same time. At
2545the moment, \f(CW\*(C`SIGCHLD\*(C'\fR is permanently tied to the default loop.
2546.PP
1453first watcher gets started will libev actually register a signal watcher 2547When the first watcher gets started will libev actually register something
1454with the kernel (thus it coexists with your own signal handlers as long 2548with the kernel (thus it coexists with your own signal handlers as long as
1455as you don't register any with libev). Similarly, when the last signal 2549you don't register any with libev for the same signal).
1456watcher for a signal is stopped libev will reset the signal handler to 2550.PP
1457\&\s-1SIG_DFL\s0 (regardless of what it was set to before). 2551If possible and supported, libev will install its handlers with
2552\&\f(CW\*(C`SA_RESTART\*(C'\fR (or equivalent) behaviour enabled, so system calls should
2553not be unduly interrupted. If you have a problem with system calls getting
2554interrupted by signals you can block all signals in an \f(CW\*(C`ev_check\*(C'\fR watcher
2555and unblock them in an \f(CW\*(C`ev_prepare\*(C'\fR watcher.
2556.PP
2557\fIThe special problem of inheritance over fork/execve/pthread_create\fR
2558.IX Subsection "The special problem of inheritance over fork/execve/pthread_create"
2559.PP
2560Both the signal mask (\f(CW\*(C`sigprocmask\*(C'\fR) and the signal disposition
2561(\f(CW\*(C`sigaction\*(C'\fR) are unspecified after starting a signal watcher (and after
2562stopping it again), that is, libev might or might not block the signal,
2563and might or might not set or restore the installed signal handler (but
2564see \f(CW\*(C`EVFLAG_NOSIGMASK\*(C'\fR).
2565.PP
2566While this does not matter for the signal disposition (libev never
2567sets signals to \f(CW\*(C`SIG_IGN\*(C'\fR, so handlers will be reset to \f(CW\*(C`SIG_DFL\*(C'\fR on
2568\&\f(CW\*(C`execve\*(C'\fR), this matters for the signal mask: many programs do not expect
2569certain signals to be blocked.
2570.PP
2571This means that before calling \f(CW\*(C`exec\*(C'\fR (from the child) you should reset
2572the signal mask to whatever \*(L"default\*(R" you expect (all clear is a good
2573choice usually).
2574.PP
2575The simplest way to ensure that the signal mask is reset in the child is
2576to install a fork handler with \f(CW\*(C`pthread_atfork\*(C'\fR that resets it. That will
2577catch fork calls done by libraries (such as the libc) as well.
2578.PP
2579In current versions of libev, the signal will not be blocked indefinitely
2580unless you use the \f(CW\*(C`signalfd\*(C'\fR \s-1API\s0 (\f(CW\*(C`EV_SIGNALFD\*(C'\fR). While this reduces
2581the window of opportunity for problems, it will not go away, as libev
2582\&\fIhas\fR to modify the signal mask, at least temporarily.
2583.PP
2584So I can't stress this enough: \fIIf you do not reset your signal mask when
2585you expect it to be empty, you have a race condition in your code\fR. This
2586is not a libev-specific thing, this is true for most event libraries.
2587.PP
2588\fIThe special problem of threads signal handling\fR
2589.IX Subsection "The special problem of threads signal handling"
2590.PP
2591\&\s-1POSIX\s0 threads has problematic signal handling semantics, specifically,
2592a lot of functionality (sigfd, sigwait etc.) only really works if all
2593threads in a process block signals, which is hard to achieve.
2594.PP
2595When you want to use sigwait (or mix libev signal handling with your own
2596for the same signals), you can tackle this problem by globally blocking
2597all signals before creating any threads (or creating them with a fully set
2598sigprocmask) and also specifying the \f(CW\*(C`EVFLAG_NOSIGMASK\*(C'\fR when creating
2599loops. Then designate one thread as \*(L"signal receiver thread\*(R" which handles
2600these signals. You can pass on any signals that libev might be interested
2601in by calling \f(CW\*(C`ev_feed_signal\*(C'\fR.
1458.PP 2602.PP
1459\fIWatcher-Specific Functions and Data Members\fR 2603\fIWatcher-Specific Functions and Data Members\fR
1460.IX Subsection "Watcher-Specific Functions and Data Members" 2604.IX Subsection "Watcher-Specific Functions and Data Members"
1461.IP "ev_signal_init (ev_signal *, callback, int signum)" 4 2605.IP "ev_signal_init (ev_signal *, callback, int signum)" 4
1462.IX Item "ev_signal_init (ev_signal *, callback, int signum)" 2606.IX Item "ev_signal_init (ev_signal *, callback, int signum)"
… …
1467Configures the watcher to trigger on the given signal number (usually one 2611Configures the watcher to trigger on the given signal number (usually one
1468of the \f(CW\*(C`SIGxxx\*(C'\fR constants). 2612of the \f(CW\*(C`SIGxxx\*(C'\fR constants).
1469.IP "int signum [read\-only]" 4 2613.IP "int signum [read\-only]" 4
1470.IX Item "int signum [read-only]" 2614.IX Item "int signum [read-only]"
1471The signal the watcher watches out for. 2615The signal the watcher watches out for.
2616.PP
2617\fIExamples\fR
2618.IX Subsection "Examples"
2619.PP
2620Example: Try to exit cleanly on \s-1SIGINT\s0.
2621.PP
2622.Vb 5
2623\& static void
2624\& sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2625\& {
2626\& ev_break (loop, EVBREAK_ALL);
2627\& }
2628\&
2629\& ev_signal signal_watcher;
2630\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2631\& ev_signal_start (loop, &signal_watcher);
2632.Ve
1472.ie n .Sh """ev_child"" \- watch out for process status changes" 2633.ie n .SS """ev_child"" \- watch out for process status changes"
1473.el .Sh "\f(CWev_child\fP \- watch out for process status changes" 2634.el .SS "\f(CWev_child\fP \- watch out for process status changes"
1474.IX Subsection "ev_child - watch out for process status changes" 2635.IX Subsection "ev_child - watch out for process status changes"
1475Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to 2636Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to
1476some child status changes (most typically when a child of yours dies). 2637some child status changes (most typically when a child of yours dies or
2638exits). It is permissible to install a child watcher \fIafter\fR the child
2639has been forked (which implies it might have already exited), as long
2640as the event loop isn't entered (or is continued from a watcher), i.e.,
2641forking and then immediately registering a watcher for the child is fine,
2642but forking and registering a watcher a few event loop iterations later or
2643in the next callback invocation is not.
2644.PP
2645Only the default event loop is capable of handling signals, and therefore
2646you can only register child watchers in the default event loop.
2647.PP
2648Due to some design glitches inside libev, child watchers will always be
2649handled at maximum priority (their priority is set to \f(CW\*(C`EV_MAXPRI\*(C'\fR by
2650libev)
2651.PP
2652\fIProcess Interaction\fR
2653.IX Subsection "Process Interaction"
2654.PP
2655Libev grabs \f(CW\*(C`SIGCHLD\*(C'\fR as soon as the default event loop is
2656initialised. This is necessary to guarantee proper behaviour even if the
2657first child watcher is started after the child exits. The occurrence
2658of \f(CW\*(C`SIGCHLD\*(C'\fR is recorded asynchronously, but child reaping is done
2659synchronously as part of the event loop processing. Libev always reaps all
2660children, even ones not watched.
2661.PP
2662\fIOverriding the Built-In Processing\fR
2663.IX Subsection "Overriding the Built-In Processing"
2664.PP
2665Libev offers no special support for overriding the built-in child
2666processing, but if your application collides with libev's default child
2667handler, you can override it easily by installing your own handler for
2668\&\f(CW\*(C`SIGCHLD\*(C'\fR after initialising the default loop, and making sure the
2669default loop never gets destroyed. You are encouraged, however, to use an
2670event-based approach to child reaping and thus use libev's support for
2671that, so other libev users can use \f(CW\*(C`ev_child\*(C'\fR watchers freely.
2672.PP
2673\fIStopping the Child Watcher\fR
2674.IX Subsection "Stopping the Child Watcher"
2675.PP
2676Currently, the child watcher never gets stopped, even when the
2677child terminates, so normally one needs to stop the watcher in the
2678callback. Future versions of libev might stop the watcher automatically
2679when a child exit is detected (calling \f(CW\*(C`ev_child_stop\*(C'\fR twice is not a
2680problem).
1477.PP 2681.PP
1478\fIWatcher-Specific Functions and Data Members\fR 2682\fIWatcher-Specific Functions and Data Members\fR
1479.IX Subsection "Watcher-Specific Functions and Data Members" 2683.IX Subsection "Watcher-Specific Functions and Data Members"
1480.IP "ev_child_init (ev_child *, callback, int pid)" 4 2684.IP "ev_child_init (ev_child *, callback, int pid, int trace)" 4
1481.IX Item "ev_child_init (ev_child *, callback, int pid)" 2685.IX Item "ev_child_init (ev_child *, callback, int pid, int trace)"
1482.PD 0 2686.PD 0
1483.IP "ev_child_set (ev_child *, int pid)" 4 2687.IP "ev_child_set (ev_child *, int pid, int trace)" 4
1484.IX Item "ev_child_set (ev_child *, int pid)" 2688.IX Item "ev_child_set (ev_child *, int pid, int trace)"
1485.PD 2689.PD
1486Configures the watcher to wait for status changes of process \f(CW\*(C`pid\*(C'\fR (or 2690Configures the watcher to wait for status changes of process \f(CW\*(C`pid\*(C'\fR (or
1487\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look 2691\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look
1488at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see 2692at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see
1489the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems 2693the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems
1490\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the 2694\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the
1491process causing the status change. 2695process causing the status change. \f(CW\*(C`trace\*(C'\fR must be either \f(CW0\fR (only
2696activate the watcher when the process terminates) or \f(CW1\fR (additionally
2697activate the watcher when the process is stopped or continued).
1492.IP "int pid [read\-only]" 4 2698.IP "int pid [read\-only]" 4
1493.IX Item "int pid [read-only]" 2699.IX Item "int pid [read-only]"
1494The process id this watcher watches out for, or \f(CW0\fR, meaning any process id. 2700The process id this watcher watches out for, or \f(CW0\fR, meaning any process id.
1495.IP "int rpid [read\-write]" 4 2701.IP "int rpid [read\-write]" 4
1496.IX Item "int rpid [read-write]" 2702.IX Item "int rpid [read-write]"
… …
1498.IP "int rstatus [read\-write]" 4 2704.IP "int rstatus [read\-write]" 4
1499.IX Item "int rstatus [read-write]" 2705.IX Item "int rstatus [read-write]"
1500The process exit/trace status caused by \f(CW\*(C`rpid\*(C'\fR (see your systems 2706The process exit/trace status caused by \f(CW\*(C`rpid\*(C'\fR (see your systems
1501\&\f(CW\*(C`waitpid\*(C'\fR and \f(CW\*(C`sys/wait.h\*(C'\fR documentation for details). 2707\&\f(CW\*(C`waitpid\*(C'\fR and \f(CW\*(C`sys/wait.h\*(C'\fR documentation for details).
1502.PP 2708.PP
1503Example: Try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0. 2709\fIExamples\fR
2710.IX Subsection "Examples"
1504.PP 2711.PP
2712Example: \f(CW\*(C`fork()\*(C'\fR a new process and install a child handler to wait for
2713its completion.
2714.PP
1505.Vb 5 2715.Vb 1
2716\& ev_child cw;
2717\&
1506\& static void 2718\& static void
1507\& sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 2719\& child_cb (EV_P_ ev_child *w, int revents)
1508\& { 2720\& {
1509\& ev_unloop (loop, EVUNLOOP_ALL); 2721\& ev_child_stop (EV_A_ w);
2722\& printf ("process %d exited with status %x\en", w\->rpid, w\->rstatus);
1510\& } 2723\& }
2724\&
2725\& pid_t pid = fork ();
2726\&
2727\& if (pid < 0)
2728\& // error
2729\& else if (pid == 0)
2730\& {
2731\& // the forked child executes here
2732\& exit (1);
2733\& }
2734\& else
2735\& {
2736\& ev_child_init (&cw, child_cb, pid, 0);
2737\& ev_child_start (EV_DEFAULT_ &cw);
2738\& }
1511.Ve 2739.Ve
1512.PP
1513.Vb 3
1514\& struct ev_signal signal_watcher;
1515\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1516\& ev_signal_start (loop, &sigint_cb);
1517.Ve
1518.ie n .Sh """ev_stat"" \- did the file attributes just change?" 2740.ie n .SS """ev_stat"" \- did the file attributes just change?"
1519.el .Sh "\f(CWev_stat\fP \- did the file attributes just change?" 2741.el .SS "\f(CWev_stat\fP \- did the file attributes just change?"
1520.IX Subsection "ev_stat - did the file attributes just change?" 2742.IX Subsection "ev_stat - did the file attributes just change?"
1521This watches a filesystem path for attribute changes. That is, it calls 2743This watches a file system path for attribute changes. That is, it calls
1522\&\f(CW\*(C`stat\*(C'\fR regularly (or when the \s-1OS\s0 says it changed) and sees if it changed 2744\&\f(CW\*(C`stat\*(C'\fR on that path in regular intervals (or when the \s-1OS\s0 says it changed)
1523compared to the last time, invoking the callback if it did. 2745and sees if it changed compared to the last time, invoking the callback if
2746it did.
1524.PP 2747.PP
1525The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does 2748The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does
1526not exist\*(R" is a status change like any other. The condition \*(L"path does 2749not exist\*(R" is a status change like any other. The condition \*(L"path does not
1527not exist\*(R" is signified by the \f(CW\*(C`st_nlink\*(C'\fR field being zero (which is 2750exist\*(R" (or more correctly \*(L"path cannot be stat'ed\*(R") is signified by the
1528otherwise always forced to be at least one) and all the other fields of 2751\&\f(CW\*(C`st_nlink\*(C'\fR field being zero (which is otherwise always forced to be at
1529the stat buffer having unspecified contents. 2752least one) and all the other fields of the stat buffer having unspecified
2753contents.
1530.PP 2754.PP
1531The path \fIshould\fR be absolute and \fImust not\fR end in a slash. If it is 2755The path \fImust not\fR end in a slash or contain special components such as
2756\&\f(CW\*(C`.\*(C'\fR or \f(CW\*(C`..\*(C'\fR. The path \fIshould\fR be absolute: If it is relative and
1532relative and your working directory changes, the behaviour is undefined. 2757your working directory changes, then the behaviour is undefined.
1533.PP 2758.PP
1534Since there is no standard to do this, the portable implementation simply 2759Since there is no portable change notification interface available, the
1535calls \f(CW\*(C`stat (2)\*(C'\fR regularly on the path to see if it changed somehow. You 2760portable implementation simply calls \f(CWstat(2)\fR regularly on the path
1536can specify a recommended polling interval for this case. If you specify 2761to see if it changed somehow. You can specify a recommended polling
1537a polling interval of \f(CW0\fR (highly recommended!) then a \fIsuitable, 2762interval for this case. If you specify a polling interval of \f(CW0\fR (highly
1538unspecified default\fR value will be used (which you can expect to be around 2763recommended!) then a \fIsuitable, unspecified default\fR value will be used
1539five seconds, although this might change dynamically). Libev will also 2764(which you can expect to be around five seconds, although this might
1540impose a minimum interval which is currently around \f(CW0.1\fR, but thats 2765change dynamically). Libev will also impose a minimum interval which is
1541usually overkill. 2766currently around \f(CW0.1\fR, but that's usually overkill.
1542.PP 2767.PP
1543This watcher type is not meant for massive numbers of stat watchers, 2768This watcher type is not meant for massive numbers of stat watchers,
1544as even with OS-supported change notifications, this can be 2769as even with OS-supported change notifications, this can be
1545resource\-intensive. 2770resource-intensive.
1546.PP 2771.PP
1547At the time of this writing, only the Linux inotify interface is 2772At the time of this writing, the only OS-specific interface implemented
1548implemented (implementing kqueue support is left as an exercise for the 2773is the Linux inotify interface (implementing kqueue support is left as an
1549reader). Inotify will be used to give hints only and should not change the 2774exercise for the reader. Note, however, that the author sees no way of
1550semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers, which means that libev sometimes needs 2775implementing \f(CW\*(C`ev_stat\*(C'\fR semantics with kqueue, except as a hint).
1551to fall back to regular polling again even with inotify, but changes are 2776.PP
1552usually detected immediately, and if the file exists there will be no 2777\fI\s-1ABI\s0 Issues (Largefile Support)\fR
1553polling. 2778.IX Subsection "ABI Issues (Largefile Support)"
2779.PP
2780Libev by default (unless the user overrides this) uses the default
2781compilation environment, which means that on systems with large file
2782support disabled by default, you get the 32 bit version of the stat
2783structure. When using the library from programs that change the \s-1ABI\s0 to
2784use 64 bit file offsets the programs will fail. In that case you have to
2785compile libev with the same flags to get binary compatibility. This is
2786obviously the case with any flags that change the \s-1ABI\s0, but the problem is
2787most noticeably displayed with ev_stat and large file support.
2788.PP
2789The solution for this is to lobby your distribution maker to make large
2790file interfaces available by default (as e.g. FreeBSD does) and not
2791optional. Libev cannot simply switch on large file support because it has
2792to exchange stat structures with application programs compiled using the
2793default compilation environment.
2794.PP
2795\fIInotify and Kqueue\fR
2796.IX Subsection "Inotify and Kqueue"
2797.PP
2798When \f(CW\*(C`inotify (7)\*(C'\fR support has been compiled into libev and present at
2799runtime, it will be used to speed up change detection where possible. The
2800inotify descriptor will be created lazily when the first \f(CW\*(C`ev_stat\*(C'\fR
2801watcher is being started.
2802.PP
2803Inotify presence does not change the semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers
2804except that changes might be detected earlier, and in some cases, to avoid
2805making regular \f(CW\*(C`stat\*(C'\fR calls. Even in the presence of inotify support
2806there are many cases where libev has to resort to regular \f(CW\*(C`stat\*(C'\fR polling,
2807but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
2808many bugs), the path exists (i.e. stat succeeds), and the path resides on
2809a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
2810xfs are fully working) libev usually gets away without polling.
2811.PP
2812There is no support for kqueue, as apparently it cannot be used to
2813implement this functionality, due to the requirement of having a file
2814descriptor open on the object at all times, and detecting renames, unlinks
2815etc. is difficult.
2816.PP
2817\fI\f(CI\*(C`stat ()\*(C'\fI is a synchronous operation\fR
2818.IX Subsection "stat () is a synchronous operation"
2819.PP
2820Libev doesn't normally do any kind of I/O itself, and so is not blocking
2821the process. The exception are \f(CW\*(C`ev_stat\*(C'\fR watchers \- those call \f(CW\*(C`stat
2822()\*(C'\fR, which is a synchronous operation.
2823.PP
2824For local paths, this usually doesn't matter: unless the system is very
2825busy or the intervals between stat's are large, a stat call will be fast,
2826as the path data is usually in memory already (except when starting the
2827watcher).
2828.PP
2829For networked file systems, calling \f(CW\*(C`stat ()\*(C'\fR can block an indefinite
2830time due to network issues, and even under good conditions, a stat call
2831often takes multiple milliseconds.
2832.PP
2833Therefore, it is best to avoid using \f(CW\*(C`ev_stat\*(C'\fR watchers on networked
2834paths, although this is fully supported by libev.
2835.PP
2836\fIThe special problem of stat time resolution\fR
2837.IX Subsection "The special problem of stat time resolution"
2838.PP
2839The \f(CW\*(C`stat ()\*(C'\fR system call only supports full-second resolution portably,
2840and even on systems where the resolution is higher, most file systems
2841still only support whole seconds.
2842.PP
2843That means that, if the time is the only thing that changes, you can
2844easily miss updates: on the first update, \f(CW\*(C`ev_stat\*(C'\fR detects a change and
2845calls your callback, which does something. When there is another update
2846within the same second, \f(CW\*(C`ev_stat\*(C'\fR will be unable to detect unless the
2847stat data does change in other ways (e.g. file size).
2848.PP
2849The solution to this is to delay acting on a change for slightly more
2850than a second (or till slightly after the next full second boundary), using
2851a roughly one-second-delay \f(CW\*(C`ev_timer\*(C'\fR (e.g. \f(CW\*(C`ev_timer_set (w, 0., 1.02);
2852ev_timer_again (loop, w)\*(C'\fR).
2853.PP
2854The \f(CW.02\fR offset is added to work around small timing inconsistencies
2855of some operating systems (where the second counter of the current time
2856might be be delayed. One such system is the Linux kernel, where a call to
2857\&\f(CW\*(C`gettimeofday\*(C'\fR might return a timestamp with a full second later than
2858a subsequent \f(CW\*(C`time\*(C'\fR call \- if the equivalent of \f(CW\*(C`time ()\*(C'\fR is used to
2859update file times then there will be a small window where the kernel uses
2860the previous second to update file times but libev might already execute
2861the timer callback).
1554.PP 2862.PP
1555\fIWatcher-Specific Functions and Data Members\fR 2863\fIWatcher-Specific Functions and Data Members\fR
1556.IX Subsection "Watcher-Specific Functions and Data Members" 2864.IX Subsection "Watcher-Specific Functions and Data Members"
1557.IP "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 4 2865.IP "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 4
1558.IX Item "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 2866.IX Item "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)"
… …
1564\&\f(CW\*(C`path\*(C'\fR. The \f(CW\*(C`interval\*(C'\fR is a hint on how quickly a change is expected to 2872\&\f(CW\*(C`path\*(C'\fR. The \f(CW\*(C`interval\*(C'\fR is a hint on how quickly a change is expected to
1565be detected and should normally be specified as \f(CW0\fR to let libev choose 2873be detected and should normally be specified as \f(CW0\fR to let libev choose
1566a suitable value. The memory pointed to by \f(CW\*(C`path\*(C'\fR must point to the same 2874a suitable value. The memory pointed to by \f(CW\*(C`path\*(C'\fR must point to the same
1567path for as long as the watcher is active. 2875path for as long as the watcher is active.
1568.Sp 2876.Sp
1569The callback will be receive \f(CW\*(C`EV_STAT\*(C'\fR when a change was detected, 2877The callback will receive an \f(CW\*(C`EV_STAT\*(C'\fR event when a change was detected,
1570relative to the attributes at the time the watcher was started (or the 2878relative to the attributes at the time the watcher was started (or the
1571last change was detected). 2879last change was detected).
1572.IP "ev_stat_stat (ev_stat *)" 4 2880.IP "ev_stat_stat (loop, ev_stat *)" 4
1573.IX Item "ev_stat_stat (ev_stat *)" 2881.IX Item "ev_stat_stat (loop, ev_stat *)"
1574Updates the stat buffer immediately with new values. If you change the 2882Updates the stat buffer immediately with new values. If you change the
1575watched path in your callback, you could call this fucntion to avoid 2883watched path in your callback, you could call this function to avoid
1576detecting this change (while introducing a race condition). Can also be 2884detecting this change (while introducing a race condition if you are not
1577useful simply to find out the new values. 2885the only one changing the path). Can also be useful simply to find out the
2886new values.
1578.IP "ev_statdata attr [read\-only]" 4 2887.IP "ev_statdata attr [read\-only]" 4
1579.IX Item "ev_statdata attr [read-only]" 2888.IX Item "ev_statdata attr [read-only]"
1580The most-recently detected attributes of the file. Although the type is of 2889The most-recently detected attributes of the file. Although the type is
1581\&\f(CW\*(C`ev_statdata\*(C'\fR, this is usually the (or one of the) \f(CW\*(C`struct stat\*(C'\fR types 2890\&\f(CW\*(C`ev_statdata\*(C'\fR, this is usually the (or one of the) \f(CW\*(C`struct stat\*(C'\fR types
2891suitable for your system, but you can only rely on the POSIX-standardised
1582suitable for your system. If the \f(CW\*(C`st_nlink\*(C'\fR member is \f(CW0\fR, then there 2892members to be present. If the \f(CW\*(C`st_nlink\*(C'\fR member is \f(CW0\fR, then there was
1583was some error while \f(CW\*(C`stat\*(C'\fRing the file. 2893some error while \f(CW\*(C`stat\*(C'\fRing the file.
1584.IP "ev_statdata prev [read\-only]" 4 2894.IP "ev_statdata prev [read\-only]" 4
1585.IX Item "ev_statdata prev [read-only]" 2895.IX Item "ev_statdata prev [read-only]"
1586The previous attributes of the file. The callback gets invoked whenever 2896The previous attributes of the file. The callback gets invoked whenever
1587\&\f(CW\*(C`prev\*(C'\fR != \f(CW\*(C`attr\*(C'\fR. 2897\&\f(CW\*(C`prev\*(C'\fR != \f(CW\*(C`attr\*(C'\fR, or, more precisely, one or more of these members
2898differ: \f(CW\*(C`st_dev\*(C'\fR, \f(CW\*(C`st_ino\*(C'\fR, \f(CW\*(C`st_mode\*(C'\fR, \f(CW\*(C`st_nlink\*(C'\fR, \f(CW\*(C`st_uid\*(C'\fR,
2899\&\f(CW\*(C`st_gid\*(C'\fR, \f(CW\*(C`st_rdev\*(C'\fR, \f(CW\*(C`st_size\*(C'\fR, \f(CW\*(C`st_atime\*(C'\fR, \f(CW\*(C`st_mtime\*(C'\fR, \f(CW\*(C`st_ctime\*(C'\fR.
1588.IP "ev_tstamp interval [read\-only]" 4 2900.IP "ev_tstamp interval [read\-only]" 4
1589.IX Item "ev_tstamp interval [read-only]" 2901.IX Item "ev_tstamp interval [read-only]"
1590The specified interval. 2902The specified interval.
1591.IP "const char *path [read\-only]" 4 2903.IP "const char *path [read\-only]" 4
1592.IX Item "const char *path [read-only]" 2904.IX Item "const char *path [read-only]"
1593The filesystem path that is being watched. 2905The file system path that is being watched.
2906.PP
2907\fIExamples\fR
2908.IX Subsection "Examples"
1594.PP 2909.PP
1595Example: Watch \f(CW\*(C`/etc/passwd\*(C'\fR for attribute changes. 2910Example: Watch \f(CW\*(C`/etc/passwd\*(C'\fR for attribute changes.
1596.PP 2911.PP
1597.Vb 15 2912.Vb 10
1598\& static void 2913\& static void
1599\& passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) 2914\& passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1600\& { 2915\& {
1601\& /* /etc/passwd changed in some way */ 2916\& /* /etc/passwd changed in some way */
1602\& if (w->attr.st_nlink) 2917\& if (w\->attr.st_nlink)
1603\& { 2918\& {
1604\& printf ("passwd current size %ld\en", (long)w->attr.st_size); 2919\& printf ("passwd current size %ld\en", (long)w\->attr.st_size);
1605\& printf ("passwd current atime %ld\en", (long)w->attr.st_mtime); 2920\& printf ("passwd current atime %ld\en", (long)w\->attr.st_mtime);
1606\& printf ("passwd current mtime %ld\en", (long)w->attr.st_mtime); 2921\& printf ("passwd current mtime %ld\en", (long)w\->attr.st_mtime);
1607\& } 2922\& }
1608\& else 2923\& else
1609\& /* you shalt not abuse printf for puts */ 2924\& /* you shalt not abuse printf for puts */
1610\& puts ("wow, /etc/passwd is not there, expect problems. " 2925\& puts ("wow, /etc/passwd is not there, expect problems. "
1611\& "if this is windows, they already arrived\en"); 2926\& "if this is windows, they already arrived\en");
1612\& } 2927\& }
2928\&
2929\& ...
2930\& ev_stat passwd;
2931\&
2932\& ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
2933\& ev_stat_start (loop, &passwd);
1613.Ve 2934.Ve
2935.PP
2936Example: Like above, but additionally use a one-second delay so we do not
2937miss updates (however, frequent updates will delay processing, too, so
2938one might do the work both on \f(CW\*(C`ev_stat\*(C'\fR callback invocation \fIand\fR on
2939\&\f(CW\*(C`ev_timer\*(C'\fR callback invocation).
1614.PP 2940.PP
1615.Vb 2 2941.Vb 2
2942\& static ev_stat passwd;
2943\& static ev_timer timer;
2944\&
2945\& static void
2946\& timer_cb (EV_P_ ev_timer *w, int revents)
2947\& {
2948\& ev_timer_stop (EV_A_ w);
2949\&
2950\& /* now it\*(Aqs one second after the most recent passwd change */
2951\& }
2952\&
2953\& static void
2954\& stat_cb (EV_P_ ev_stat *w, int revents)
2955\& {
2956\& /* reset the one\-second timer */
2957\& ev_timer_again (EV_A_ &timer);
2958\& }
2959\&
1616\& ... 2960\& ...
1617\& ev_stat passwd;
1618.Ve
1619.PP
1620.Vb 2
1621\& ev_stat_init (&passwd, passwd_cb, "/etc/passwd"); 2961\& ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1622\& ev_stat_start (loop, &passwd); 2962\& ev_stat_start (loop, &passwd);
2963\& ev_timer_init (&timer, timer_cb, 0., 1.02);
1623.Ve 2964.Ve
1624.ie n .Sh """ev_idle"" \- when you've got nothing better to do..." 2965.ie n .SS """ev_idle"" \- when you've got nothing better to do..."
1625.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do..." 2966.el .SS "\f(CWev_idle\fP \- when you've got nothing better to do..."
1626.IX Subsection "ev_idle - when you've got nothing better to do..." 2967.IX Subsection "ev_idle - when you've got nothing better to do..."
1627Idle watchers trigger events when no other events of the same or higher 2968Idle watchers trigger events when no other events of the same or higher
1628priority are pending (prepare, check and other idle watchers do not 2969priority are pending (prepare, check and other idle watchers do not count
1629count). 2970as receiving \*(L"events\*(R").
1630.PP 2971.PP
1631That is, as long as your process is busy handling sockets or timeouts 2972That is, as long as your process is busy handling sockets or timeouts
1632(or even signals, imagine) of the same or higher priority it will not be 2973(or even signals, imagine) of the same or higher priority it will not be
1633triggered. But when your process is idle (or only lower-priority watchers 2974triggered. But when your process is idle (or only lower-priority watchers
1634are pending), the idle watchers are being called once per event loop 2975are pending), the idle watchers are being called once per event loop
… …
1638The most noteworthy effect is that as long as any idle watchers are 2979The most noteworthy effect is that as long as any idle watchers are
1639active, the process will not block when waiting for new events. 2980active, the process will not block when waiting for new events.
1640.PP 2981.PP
1641Apart from keeping your process non-blocking (which is a useful 2982Apart from keeping your process non-blocking (which is a useful
1642effect on its own sometimes), idle watchers are a good place to do 2983effect on its own sometimes), idle watchers are a good place to do
1643\&\*(L"pseudo\-background processing\*(R", or delay processing stuff to after the 2984\&\*(L"pseudo-background processing\*(R", or delay processing stuff to after the
1644event loop has handled all outstanding events. 2985event loop has handled all outstanding events.
2986.PP
2987\fIAbusing an \f(CI\*(C`ev_idle\*(C'\fI watcher for its side-effect\fR
2988.IX Subsection "Abusing an ev_idle watcher for its side-effect"
2989.PP
2990As long as there is at least one active idle watcher, libev will never
2991sleep unnecessarily. Or in other words, it will loop as fast as possible.
2992For this to work, the idle watcher doesn't need to be invoked at all \- the
2993lowest priority will do.
2994.PP
2995This mode of operation can be useful together with an \f(CW\*(C`ev_check\*(C'\fR watcher,
2996to do something on each event loop iteration \- for example to balance load
2997between different connections.
2998.PP
2999See \*(L"Abusing an ev_check watcher for its side-effect\*(R" for a longer
3000example.
1645.PP 3001.PP
1646\fIWatcher-Specific Functions and Data Members\fR 3002\fIWatcher-Specific Functions and Data Members\fR
1647.IX Subsection "Watcher-Specific Functions and Data Members" 3003.IX Subsection "Watcher-Specific Functions and Data Members"
1648.IP "ev_idle_init (ev_signal *, callback)" 4 3004.IP "ev_idle_init (ev_idle *, callback)" 4
1649.IX Item "ev_idle_init (ev_signal *, callback)" 3005.IX Item "ev_idle_init (ev_idle *, callback)"
1650Initialises and configures the idle watcher \- it has no parameters of any 3006Initialises and configures the idle watcher \- it has no parameters of any
1651kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless, 3007kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless,
1652believe me. 3008believe me.
1653.PP 3009.PP
3010\fIExamples\fR
3011.IX Subsection "Examples"
3012.PP
1654Example: Dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR watcher, start it, and in the 3013Example: Dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR watcher, start it, and in the
1655callback, free it. Also, use no error checking, as usual. 3014callback, free it. Also, use no error checking, as usual.
1656.PP 3015.PP
1657.Vb 7 3016.Vb 5
1658\& static void 3017\& static void
1659\& idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 3018\& idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1660\& { 3019\& {
3020\& // stop the watcher
3021\& ev_idle_stop (loop, w);
3022\&
3023\& // now we can free it
1661\& free (w); 3024\& free (w);
3025\&
1662\& // now do something you wanted to do when the program has 3026\& // now do something you wanted to do when the program has
1663\& // no longer asnything immediate to do. 3027\& // no longer anything immediate to do.
1664\& } 3028\& }
1665.Ve 3029\&
1666.PP
1667.Vb 3
1668\& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); 3030\& ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1669\& ev_idle_init (idle_watcher, idle_cb); 3031\& ev_idle_init (idle_watcher, idle_cb);
1670\& ev_idle_start (loop, idle_cb); 3032\& ev_idle_start (loop, idle_watcher);
1671.Ve 3033.Ve
1672.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop!" 3034.ie n .SS """ev_prepare"" and ""ev_check"" \- customise your event loop!"
1673.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!" 3035.el .SS "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!"
1674.IX Subsection "ev_prepare and ev_check - customise your event loop!" 3036.IX Subsection "ev_prepare and ev_check - customise your event loop!"
1675Prepare and check watchers are usually (but not always) used in tandem: 3037Prepare and check watchers are often (but not always) used in pairs:
1676prepare watchers get invoked before the process blocks and check watchers 3038prepare watchers get invoked before the process blocks and check watchers
1677afterwards. 3039afterwards.
1678.PP 3040.PP
1679You \fImust not\fR call \f(CW\*(C`ev_loop\*(C'\fR or similar functions that enter 3041You \fImust not\fR call \f(CW\*(C`ev_run\*(C'\fR or similar functions that enter
1680the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR 3042the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR
1681watchers. Other loops than the current one are fine, however. The 3043watchers. Other loops than the current one are fine, however. The
1682rationale behind this is that you do not need to check for recursion in 3044rationale behind this is that you do not need to check for recursion in
1683those watchers, i.e. the sequence will always be \f(CW\*(C`ev_prepare\*(C'\fR, blocking, 3045those watchers, i.e. the sequence will always be \f(CW\*(C`ev_prepare\*(C'\fR, blocking,
1684\&\f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each kind they will always be 3046\&\f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each kind they will always be
1685called in pairs bracketing the blocking call. 3047called in pairs bracketing the blocking call.
1686.PP 3048.PP
1687Their main purpose is to integrate other event mechanisms into libev and 3049Their main purpose is to integrate other event mechanisms into libev and
1688their use is somewhat advanced. This could be used, for example, to track 3050their use is somewhat advanced. They could be used, for example, to track
1689variable changes, implement your own watchers, integrate net-snmp or a 3051variable changes, implement your own watchers, integrate net-snmp or a
1690coroutine library and lots more. They are also occasionally useful if 3052coroutine library and lots more. They are also occasionally useful if
1691you cache some data and want to flush it before blocking (for example, 3053you cache some data and want to flush it before blocking (for example,
1692in X programs you might want to do an \f(CW\*(C`XFlush ()\*(C'\fR in an \f(CW\*(C`ev_prepare\*(C'\fR 3054in X programs you might want to do an \f(CW\*(C`XFlush ()\*(C'\fR in an \f(CW\*(C`ev_prepare\*(C'\fR
1693watcher). 3055watcher).
1694.PP 3056.PP
1695This is done by examining in each prepare call which file descriptors need 3057This is done by examining in each prepare call which file descriptors
1696to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for 3058need to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers
1697them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries 3059for them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many
1698provide just this functionality). Then, in the check watcher you check for 3060libraries provide exactly this functionality). Then, in the check watcher,
1699any events that occured (by checking the pending status of all watchers 3061you check for any events that occurred (by checking the pending status
1700and stopping them) and call back into the library. The I/O and timer 3062of all watchers and stopping them) and call back into the library. The
1701callbacks will never actually be called (but must be valid nevertheless, 3063I/O and timer callbacks will never actually be called (but must be valid
1702because you never know, you know?). 3064nevertheless, because you never know, you know?).
1703.PP 3065.PP
1704As another example, the Perl Coro module uses these hooks to integrate 3066As another example, the Perl Coro module uses these hooks to integrate
1705coroutines into libev programs, by yielding to other active coroutines 3067coroutines into libev programs, by yielding to other active coroutines
1706during each prepare and only letting the process block if no coroutines 3068during each prepare and only letting the process block if no coroutines
1707are ready to run (it's actually more complicated: it only runs coroutines 3069are ready to run (it's actually more complicated: it only runs coroutines
1708with priority higher than or equal to the event loop and one coroutine 3070with priority higher than or equal to the event loop and one coroutine
1709of lower priority, but only once, using idle watchers to keep the event 3071of lower priority, but only once, using idle watchers to keep the event
1710loop from blocking if lower-priority coroutines are active, thus mapping 3072loop from blocking if lower-priority coroutines are active, thus mapping
1711low-priority coroutines to idle/background tasks). 3073low-priority coroutines to idle/background tasks).
1712.PP 3074.PP
1713It is recommended to give \f(CW\*(C`ev_check\*(C'\fR watchers highest (\f(CW\*(C`EV_MAXPRI\*(C'\fR) 3075When used for this purpose, it is recommended to give \f(CW\*(C`ev_check\*(C'\fR watchers
1714priority, to ensure that they are being run before any other watchers 3076highest (\f(CW\*(C`EV_MAXPRI\*(C'\fR) priority, to ensure that they are being run before
3077any other watchers after the poll (this doesn't matter for \f(CW\*(C`ev_prepare\*(C'\fR
3078watchers).
3079.PP
1715after the poll. Also, \f(CW\*(C`ev_check\*(C'\fR watchers (and \f(CW\*(C`ev_prepare\*(C'\fR watchers, 3080Also, \f(CW\*(C`ev_check\*(C'\fR watchers (and \f(CW\*(C`ev_prepare\*(C'\fR watchers, too) should not
1716too) should not activate (\*(L"feed\*(R") events into libev. While libev fully 3081activate (\*(L"feed\*(R") events into libev. While libev fully supports this, they
1717supports this, they will be called before other \f(CW\*(C`ev_check\*(C'\fR watchers did 3082might get executed before other \f(CW\*(C`ev_check\*(C'\fR watchers did their job. As
1718their job. As \f(CW\*(C`ev_check\*(C'\fR watchers are often used to embed other event 3083\&\f(CW\*(C`ev_check\*(C'\fR watchers are often used to embed other (non-libev) event
1719loops those other event loops might be in an unusable state until their 3084loops those other event loops might be in an unusable state until their
1720\&\f(CW\*(C`ev_check\*(C'\fR watcher ran (always remind yourself to coexist peacefully with 3085\&\f(CW\*(C`ev_check\*(C'\fR watcher ran (always remind yourself to coexist peacefully with
1721others). 3086others).
3087.PP
3088\fIAbusing an \f(CI\*(C`ev_check\*(C'\fI watcher for its side-effect\fR
3089.IX Subsection "Abusing an ev_check watcher for its side-effect"
3090.PP
3091\&\f(CW\*(C`ev_check\*(C'\fR (and less often also \f(CW\*(C`ev_prepare\*(C'\fR) watchers can also be
3092useful because they are called once per event loop iteration. For
3093example, if you want to handle a large number of connections fairly, you
3094normally only do a bit of work for each active connection, and if there
3095is more work to do, you wait for the next event loop iteration, so other
3096connections have a chance of making progress.
3097.PP
3098Using an \f(CW\*(C`ev_check\*(C'\fR watcher is almost enough: it will be called on the
3099next event loop iteration. However, that isn't as soon as possible \-
3100without external events, your \f(CW\*(C`ev_check\*(C'\fR watcher will not be invoked.
3101.PP
3102This is where \f(CW\*(C`ev_idle\*(C'\fR watchers come in handy \- all you need is a
3103single global idle watcher that is active as long as you have one active
3104\&\f(CW\*(C`ev_check\*(C'\fR watcher. The \f(CW\*(C`ev_idle\*(C'\fR watcher makes sure the event loop
3105will not sleep, and the \f(CW\*(C`ev_check\*(C'\fR watcher makes sure a callback gets
3106invoked. Neither watcher alone can do that.
1722.PP 3107.PP
1723\fIWatcher-Specific Functions and Data Members\fR 3108\fIWatcher-Specific Functions and Data Members\fR
1724.IX Subsection "Watcher-Specific Functions and Data Members" 3109.IX Subsection "Watcher-Specific Functions and Data Members"
1725.IP "ev_prepare_init (ev_prepare *, callback)" 4 3110.IP "ev_prepare_init (ev_prepare *, callback)" 4
1726.IX Item "ev_prepare_init (ev_prepare *, callback)" 3111.IX Item "ev_prepare_init (ev_prepare *, callback)"
… …
1728.IP "ev_check_init (ev_check *, callback)" 4 3113.IP "ev_check_init (ev_check *, callback)" 4
1729.IX Item "ev_check_init (ev_check *, callback)" 3114.IX Item "ev_check_init (ev_check *, callback)"
1730.PD 3115.PD
1731Initialises and configures the prepare or check watcher \- they have no 3116Initialises and configures the prepare or check watcher \- they have no
1732parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR 3117parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR
1733macros, but using them is utterly, utterly and completely pointless. 3118macros, but using them is utterly, utterly, utterly and completely
3119pointless.
3120.PP
3121\fIExamples\fR
3122.IX Subsection "Examples"
1734.PP 3123.PP
1735There are a number of principal ways to embed other event loops or modules 3124There are a number of principal ways to embed other event loops or modules
1736into libev. Here are some ideas on how to include libadns into libev 3125into libev. Here are some ideas on how to include libadns into libev
1737(there is a Perl module named \f(CW\*(C`EV::ADNS\*(C'\fR that does this, which you could 3126(there is a Perl module named \f(CW\*(C`EV::ADNS\*(C'\fR that does this, which you could
1738use for an actually working example. Another Perl module named \f(CW\*(C`EV::Glib\*(C'\fR 3127use as a working example. Another Perl module named \f(CW\*(C`EV::Glib\*(C'\fR embeds a
1739embeds a Glib main context into libev, and finally, \f(CW\*(C`Glib::EV\*(C'\fR embeds \s-1EV\s0 3128Glib main context into libev, and finally, \f(CW\*(C`Glib::EV\*(C'\fR embeds \s-1EV\s0 into the
1740into the Glib event loop). 3129Glib event loop).
1741.PP 3130.PP
1742Method 1: Add \s-1IO\s0 watchers and a timeout watcher in a prepare handler, 3131Method 1: Add \s-1IO\s0 watchers and a timeout watcher in a prepare handler,
1743and in a check watcher, destroy them and call into libadns. What follows 3132and in a check watcher, destroy them and call into libadns. What follows
1744is pseudo-code only of course. This requires you to either use a low 3133is pseudo-code only of course. This requires you to either use a low
1745priority for the check watcher or use \f(CW\*(C`ev_clear_pending\*(C'\fR explicitly, as 3134priority for the check watcher or use \f(CW\*(C`ev_clear_pending\*(C'\fR explicitly, as
1746the callbacks for the IO/timeout watchers might not have been called yet. 3135the callbacks for the IO/timeout watchers might not have been called yet.
1747.PP 3136.PP
1748.Vb 2 3137.Vb 2
1749\& static ev_io iow [nfd]; 3138\& static ev_io iow [nfd];
1750\& static ev_timer tw; 3139\& static ev_timer tw;
1751.Ve 3140\&
1752.PP
1753.Vb 4
1754\& static void 3141\& static void
1755\& io_cb (ev_loop *loop, ev_io *w, int revents) 3142\& io_cb (struct ev_loop *loop, ev_io *w, int revents)
1756\& { 3143\& {
1757\& } 3144\& }
1758.Ve 3145\&
1759.PP
1760.Vb 8
1761\& // create io watchers for each fd and a timer before blocking 3146\& // create io watchers for each fd and a timer before blocking
1762\& static void 3147\& static void
1763\& adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) 3148\& adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1764\& { 3149\& {
1765\& int timeout = 3600000; 3150\& int timeout = 3600000;
1766\& struct pollfd fds [nfd]; 3151\& struct pollfd fds [nfd];
1767\& // actual code will need to loop here and realloc etc. 3152\& // actual code will need to loop here and realloc etc.
1768\& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); 3153\& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1769.Ve 3154\&
1770.PP
1771.Vb 3
1772\& /* the callback is illegal, but won't be called as we stop during check */ 3155\& /* the callback is illegal, but won\*(Aqt be called as we stop during check */
1773\& ev_timer_init (&tw, 0, timeout * 1e-3); 3156\& ev_timer_init (&tw, 0, timeout * 1e\-3, 0.);
1774\& ev_timer_start (loop, &tw); 3157\& ev_timer_start (loop, &tw);
1775.Ve 3158\&
1776.PP
1777.Vb 6
1778\& // create one ev_io per pollfd 3159\& // create one ev_io per pollfd
1779\& for (int i = 0; i < nfd; ++i) 3160\& for (int i = 0; i < nfd; ++i)
1780\& { 3161\& {
1781\& ev_io_init (iow + i, io_cb, fds [i].fd, 3162\& ev_io_init (iow + i, io_cb, fds [i].fd,
1782\& ((fds [i].events & POLLIN ? EV_READ : 0) 3163\& ((fds [i].events & POLLIN ? EV_READ : 0)
1783\& | (fds [i].events & POLLOUT ? EV_WRITE : 0))); 3164\& | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1784.Ve 3165\&
1785.PP
1786.Vb 4
1787\& fds [i].revents = 0; 3166\& fds [i].revents = 0;
1788\& ev_io_start (loop, iow + i); 3167\& ev_io_start (loop, iow + i);
1789\& } 3168\& }
1790\& } 3169\& }
1791.Ve 3170\&
1792.PP
1793.Vb 5
1794\& // stop all watchers after blocking 3171\& // stop all watchers after blocking
1795\& static void 3172\& static void
1796\& adns_check_cb (ev_loop *loop, ev_check *w, int revents) 3173\& adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1797\& { 3174\& {
1798\& ev_timer_stop (loop, &tw); 3175\& ev_timer_stop (loop, &tw);
1799.Ve 3176\&
1800.PP
1801.Vb 8
1802\& for (int i = 0; i < nfd; ++i) 3177\& for (int i = 0; i < nfd; ++i)
1803\& { 3178\& {
1804\& // set the relevant poll flags 3179\& // set the relevant poll flags
1805\& // could also call adns_processreadable etc. here 3180\& // could also call adns_processreadable etc. here
1806\& struct pollfd *fd = fds + i; 3181\& struct pollfd *fd = fds + i;
1807\& int revents = ev_clear_pending (iow + i); 3182\& int revents = ev_clear_pending (iow + i);
1808\& if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; 3183\& if (revents & EV_READ ) fd\->revents |= fd\->events & POLLIN;
1809\& if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; 3184\& if (revents & EV_WRITE) fd\->revents |= fd\->events & POLLOUT;
1810.Ve 3185\&
1811.PP
1812.Vb 3
1813\& // now stop the watcher 3186\& // now stop the watcher
1814\& ev_io_stop (loop, iow + i); 3187\& ev_io_stop (loop, iow + i);
1815\& } 3188\& }
1816.Ve 3189\&
1817.PP
1818.Vb 2
1819\& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); 3190\& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1820\& } 3191\& }
1821.Ve 3192.Ve
1822.PP 3193.PP
1823Method 2: This would be just like method 1, but you run \f(CW\*(C`adns_afterpoll\*(C'\fR 3194Method 2: This would be just like method 1, but you run \f(CW\*(C`adns_afterpoll\*(C'\fR
1824in the prepare watcher and would dispose of the check watcher. 3195in the prepare watcher and would dispose of the check watcher.
1825.PP 3196.PP
1826Method 3: If the module to be embedded supports explicit event 3197Method 3: If the module to be embedded supports explicit event
1827notification (adns does), you can also make use of the actual watcher 3198notification (libadns does), you can also make use of the actual watcher
1828callbacks, and only destroy/create the watchers in the prepare watcher. 3199callbacks, and only destroy/create the watchers in the prepare watcher.
1829.PP 3200.PP
1830.Vb 5 3201.Vb 5
1831\& static void 3202\& static void
1832\& timer_cb (EV_P_ ev_timer *w, int revents) 3203\& timer_cb (EV_P_ ev_timer *w, int revents)
1833\& { 3204\& {
1834\& adns_state ads = (adns_state)w->data; 3205\& adns_state ads = (adns_state)w\->data;
1835\& update_now (EV_A); 3206\& update_now (EV_A);
1836.Ve 3207\&
1837.PP
1838.Vb 2
1839\& adns_processtimeouts (ads, &tv_now); 3208\& adns_processtimeouts (ads, &tv_now);
1840\& } 3209\& }
1841.Ve 3210\&
1842.PP
1843.Vb 5
1844\& static void 3211\& static void
1845\& io_cb (EV_P_ ev_io *w, int revents) 3212\& io_cb (EV_P_ ev_io *w, int revents)
1846\& { 3213\& {
1847\& adns_state ads = (adns_state)w->data; 3214\& adns_state ads = (adns_state)w\->data;
1848\& update_now (EV_A); 3215\& update_now (EV_A);
1849.Ve 3216\&
1850.PP
1851.Vb 3
1852\& if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now); 3217\& if (revents & EV_READ ) adns_processreadable (ads, w\->fd, &tv_now);
1853\& if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now); 3218\& if (revents & EV_WRITE) adns_processwriteable (ads, w\->fd, &tv_now);
1854\& } 3219\& }
1855.Ve 3220\&
1856.PP
1857.Vb 1
1858\& // do not ever call adns_afterpoll 3221\& // do not ever call adns_afterpoll
1859.Ve 3222.Ve
1860.PP 3223.PP
1861Method 4: Do not use a prepare or check watcher because the module you 3224Method 4: Do not use a prepare or check watcher because the module you
1862want to embed is too inflexible to support it. Instead, youc na override 3225want to embed is not flexible enough to support it. Instead, you can
1863their poll function. The drawback with this solution is that the main 3226override their poll function. The drawback with this solution is that the
1864loop is now no longer controllable by \s-1EV\s0. The \f(CW\*(C`Glib::EV\*(C'\fR module does 3227main loop is now no longer controllable by \s-1EV\s0. The \f(CW\*(C`Glib::EV\*(C'\fR module uses
1865this. 3228this approach, effectively embedding \s-1EV\s0 as a client into the horrible
3229libglib event loop.
1866.PP 3230.PP
1867.Vb 4 3231.Vb 4
1868\& static gint 3232\& static gint
1869\& event_poll_func (GPollFD *fds, guint nfds, gint timeout) 3233\& event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1870\& { 3234\& {
1871\& int got_events = 0; 3235\& int got_events = 0;
1872.Ve 3236\&
1873.PP
1874.Vb 2
1875\& for (n = 0; n < nfds; ++n) 3237\& for (n = 0; n < nfds; ++n)
1876\& // create/start io watcher that sets the relevant bits in fds[n] and increment got_events 3238\& // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1877.Ve 3239\&
1878.PP
1879.Vb 2
1880\& if (timeout >= 0) 3240\& if (timeout >= 0)
1881\& // create/start timer 3241\& // create/start timer
1882.Ve 3242\&
1883.PP
1884.Vb 2
1885\& // poll 3243\& // poll
1886\& ev_loop (EV_A_ 0); 3244\& ev_run (EV_A_ 0);
1887.Ve 3245\&
1888.PP
1889.Vb 3
1890\& // stop timer again 3246\& // stop timer again
1891\& if (timeout >= 0) 3247\& if (timeout >= 0)
1892\& ev_timer_stop (EV_A_ &to); 3248\& ev_timer_stop (EV_A_ &to);
1893.Ve 3249\&
1894.PP
1895.Vb 3
1896\& // stop io watchers again - their callbacks should have set 3250\& // stop io watchers again \- their callbacks should have set
1897\& for (n = 0; n < nfds; ++n) 3251\& for (n = 0; n < nfds; ++n)
1898\& ev_io_stop (EV_A_ iow [n]); 3252\& ev_io_stop (EV_A_ iow [n]);
1899.Ve 3253\&
1900.PP
1901.Vb 2
1902\& return got_events; 3254\& return got_events;
1903\& } 3255\& }
1904.Ve 3256.Ve
1905.ie n .Sh """ev_embed"" \- when one backend isn't enough..." 3257.ie n .SS """ev_embed"" \- when one backend isn't enough..."
1906.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..." 3258.el .SS "\f(CWev_embed\fP \- when one backend isn't enough..."
1907.IX Subsection "ev_embed - when one backend isn't enough..." 3259.IX Subsection "ev_embed - when one backend isn't enough..."
1908This is a rather advanced watcher type that lets you embed one event loop 3260This is a rather advanced watcher type that lets you embed one event loop
1909into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded 3261into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded
1910loop, other types of watchers might be handled in a delayed or incorrect 3262loop, other types of watchers might be handled in a delayed or incorrect
1911fashion and must not be used). 3263fashion and must not be used).
… …
1914prioritise I/O. 3266prioritise I/O.
1915.PP 3267.PP
1916As an example for a bug workaround, the kqueue backend might only support 3268As an example for a bug workaround, the kqueue backend might only support
1917sockets on some platform, so it is unusable as generic backend, but you 3269sockets on some platform, so it is unusable as generic backend, but you
1918still want to make use of it because you have many sockets and it scales 3270still want to make use of it because you have many sockets and it scales
1919so nicely. In this case, you would create a kqueue-based loop and embed it 3271so nicely. In this case, you would create a kqueue-based loop and embed
1920into your default loop (which might use e.g. poll). Overall operation will 3272it into your default loop (which might use e.g. poll). Overall operation
1921be a bit slower because first libev has to poll and then call kevent, but 3273will be a bit slower because first libev has to call \f(CW\*(C`poll\*(C'\fR and then
1922at least you can use both at what they are best. 3274\&\f(CW\*(C`kevent\*(C'\fR, but at least you can use both mechanisms for what they are
3275best: \f(CW\*(C`kqueue\*(C'\fR for scalable sockets and \f(CW\*(C`poll\*(C'\fR if you want it to work :)
1923.PP 3276.PP
1924As for prioritising I/O: rarely you have the case where some fds have 3277As for prioritising I/O: under rare circumstances you have the case where
1925to be watched and handled very quickly (with low latency), and even 3278some fds have to be watched and handled very quickly (with low latency),
1926priorities and idle watchers might have too much overhead. In this case 3279and even priorities and idle watchers might have too much overhead. In
1927you would put all the high priority stuff in one loop and all the rest in 3280this case you would put all the high priority stuff in one loop and all
1928a second one, and embed the second one in the first. 3281the rest in a second one, and embed the second one in the first.
1929.PP 3282.PP
1930As long as the watcher is active, the callback will be invoked every time 3283As long as the watcher is active, the callback will be invoked every
1931there might be events pending in the embedded loop. The callback must then 3284time there might be events pending in the embedded loop. The callback
1932call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single sweep and invoke 3285must then call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single
1933their callbacks (you could also start an idle watcher to give the embedded 3286sweep and invoke their callbacks (the callback doesn't need to invoke the
1934loop strictly lower priority for example). You can also set the callback 3287\&\f(CW\*(C`ev_embed_sweep\*(C'\fR function directly, it could also start an idle watcher
1935to \f(CW0\fR, in which case the embed watcher will automatically execute the 3288to give the embedded loop strictly lower priority for example).
1936embedded loop sweep.
1937.PP 3289.PP
1938As long as the watcher is started it will automatically handle events. The 3290You can also set the callback to \f(CW0\fR, in which case the embed watcher
1939callback will be invoked whenever some events have been handled. You can 3291will automatically execute the embedded loop sweep whenever necessary.
1940set the callback to \f(CW0\fR to avoid having to specify one if you are not
1941interested in that.
1942.PP 3292.PP
1943Also, there have not currently been made special provisions for forking: 3293Fork detection will be handled transparently while the \f(CW\*(C`ev_embed\*(C'\fR watcher
1944when you fork, you not only have to call \f(CW\*(C`ev_loop_fork\*(C'\fR on both loops, 3294is active, i.e., the embedded loop will automatically be forked when the
1945but you will also have to stop and restart any \f(CW\*(C`ev_embed\*(C'\fR watchers 3295embedding loop forks. In other cases, the user is responsible for calling
1946yourself. 3296\&\f(CW\*(C`ev_loop_fork\*(C'\fR on the embedded loop.
1947.PP 3297.PP
1948Unfortunately, not all backends are embeddable, only the ones returned by 3298Unfortunately, not all backends are embeddable: only the ones returned by
1949\&\f(CW\*(C`ev_embeddable_backends\*(C'\fR are, which, unfortunately, does not include any 3299\&\f(CW\*(C`ev_embeddable_backends\*(C'\fR are, which, unfortunately, does not include any
1950portable one. 3300portable one.
1951.PP 3301.PP
1952So when you want to use this feature you will always have to be prepared 3302So when you want to use this feature you will always have to be prepared
1953that you cannot get an embeddable loop. The recommended way to get around 3303that you cannot get an embeddable loop. The recommended way to get around
1954this is to have a separate variables for your embeddable loop, try to 3304this is to have a separate variables for your embeddable loop, try to
1955create it, and if that fails, use the normal loop for everything: 3305create it, and if that fails, use the normal loop for everything.
1956.PP 3306.PP
1957.Vb 3 3307\fI\f(CI\*(C`ev_embed\*(C'\fI and fork\fR
1958\& struct ev_loop *loop_hi = ev_default_init (0); 3308.IX Subsection "ev_embed and fork"
1959\& struct ev_loop *loop_lo = 0;
1960\& struct ev_embed embed;
1961.Ve
1962.PP 3309.PP
1963.Vb 5 3310While the \f(CW\*(C`ev_embed\*(C'\fR watcher is running, forks in the embedding loop will
1964\& // see if there is a chance of getting one that works 3311automatically be applied to the embedded loop as well, so no special
1965\& // (remember that a flags value of 0 means autodetection) 3312fork handling is required in that case. When the watcher is not running,
1966\& loop_lo = ev_embeddable_backends () & ev_recommended_backends () 3313however, it is still the task of the libev user to call \f(CW\*(C`ev_loop_fork ()\*(C'\fR
1967\& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) 3314as applicable.
1968\& : 0;
1969.Ve
1970.PP
1971.Vb 8
1972\& // if we got one, then embed it, otherwise default to loop_hi
1973\& if (loop_lo)
1974\& {
1975\& ev_embed_init (&embed, 0, loop_lo);
1976\& ev_embed_start (loop_hi, &embed);
1977\& }
1978\& else
1979\& loop_lo = loop_hi;
1980.Ve
1981.PP 3315.PP
1982\fIWatcher-Specific Functions and Data Members\fR 3316\fIWatcher-Specific Functions and Data Members\fR
1983.IX Subsection "Watcher-Specific Functions and Data Members" 3317.IX Subsection "Watcher-Specific Functions and Data Members"
1984.IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4 3318.IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
1985.IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 3319.IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)"
… …
1989.PD 3323.PD
1990Configures the watcher to embed the given loop, which must be 3324Configures the watcher to embed the given loop, which must be
1991embeddable. If the callback is \f(CW0\fR, then \f(CW\*(C`ev_embed_sweep\*(C'\fR will be 3325embeddable. If the callback is \f(CW0\fR, then \f(CW\*(C`ev_embed_sweep\*(C'\fR will be
1992invoked automatically, otherwise it is the responsibility of the callback 3326invoked automatically, otherwise it is the responsibility of the callback
1993to invoke it (it will continue to be called until the sweep has been done, 3327to invoke it (it will continue to be called until the sweep has been done,
1994if you do not want thta, you need to temporarily stop the embed watcher). 3328if you do not want that, you need to temporarily stop the embed watcher).
1995.IP "ev_embed_sweep (loop, ev_embed *)" 4 3329.IP "ev_embed_sweep (loop, ev_embed *)" 4
1996.IX Item "ev_embed_sweep (loop, ev_embed *)" 3330.IX Item "ev_embed_sweep (loop, ev_embed *)"
1997Make a single, non-blocking sweep over the embedded loop. This works 3331Make a single, non-blocking sweep over the embedded loop. This works
1998similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most 3332similarly to \f(CW\*(C`ev_run (embedded_loop, EVRUN_NOWAIT)\*(C'\fR, but in the most
1999apropriate way for embedded loops. 3333appropriate way for embedded loops.
2000.IP "struct ev_loop *loop [read\-only]" 4 3334.IP "struct ev_loop *other [read\-only]" 4
2001.IX Item "struct ev_loop *loop [read-only]" 3335.IX Item "struct ev_loop *other [read-only]"
2002The embedded event loop. 3336The embedded event loop.
3337.PP
3338\fIExamples\fR
3339.IX Subsection "Examples"
3340.PP
3341Example: Try to get an embeddable event loop and embed it into the default
3342event loop. If that is not possible, use the default loop. The default
3343loop is stored in \f(CW\*(C`loop_hi\*(C'\fR, while the embeddable loop is stored in
3344\&\f(CW\*(C`loop_lo\*(C'\fR (which is \f(CW\*(C`loop_hi\*(C'\fR in the case no embeddable loop can be
3345used).
3346.PP
3347.Vb 3
3348\& struct ev_loop *loop_hi = ev_default_init (0);
3349\& struct ev_loop *loop_lo = 0;
3350\& ev_embed embed;
3351\&
3352\& // see if there is a chance of getting one that works
3353\& // (remember that a flags value of 0 means autodetection)
3354\& loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
3355\& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
3356\& : 0;
3357\&
3358\& // if we got one, then embed it, otherwise default to loop_hi
3359\& if (loop_lo)
3360\& {
3361\& ev_embed_init (&embed, 0, loop_lo);
3362\& ev_embed_start (loop_hi, &embed);
3363\& }
3364\& else
3365\& loop_lo = loop_hi;
3366.Ve
3367.PP
3368Example: Check if kqueue is available but not recommended and create
3369a kqueue backend for use with sockets (which usually work with any
3370kqueue implementation). Store the kqueue/socket\-only event loop in
3371\&\f(CW\*(C`loop_socket\*(C'\fR. (One might optionally use \f(CW\*(C`EVFLAG_NOENV\*(C'\fR, too).
3372.PP
3373.Vb 3
3374\& struct ev_loop *loop = ev_default_init (0);
3375\& struct ev_loop *loop_socket = 0;
3376\& ev_embed embed;
3377\&
3378\& if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
3379\& if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
3380\& {
3381\& ev_embed_init (&embed, 0, loop_socket);
3382\& ev_embed_start (loop, &embed);
3383\& }
3384\&
3385\& if (!loop_socket)
3386\& loop_socket = loop;
3387\&
3388\& // now use loop_socket for all sockets, and loop for everything else
3389.Ve
2003.ie n .Sh """ev_fork"" \- the audacity to resume the event loop after a fork" 3390.ie n .SS """ev_fork"" \- the audacity to resume the event loop after a fork"
2004.el .Sh "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork" 3391.el .SS "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork"
2005.IX Subsection "ev_fork - the audacity to resume the event loop after a fork" 3392.IX Subsection "ev_fork - the audacity to resume the event loop after a fork"
2006Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because 3393Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because
2007whoever is a good citizen cared to tell libev about it by calling 3394whoever is a good citizen cared to tell libev about it by calling
2008\&\f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the 3395\&\f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the
2009event loop blocks next and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called, 3396event loop blocks next and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called,
2010and only in the child after the fork. If whoever good citizen calling 3397and only in the child after the fork. If whoever good citizen calling
2011\&\f(CW\*(C`ev_default_fork\*(C'\fR cheats and calls it in the wrong process, the fork 3398\&\f(CW\*(C`ev_default_fork\*(C'\fR cheats and calls it in the wrong process, the fork
2012handlers will be invoked, too, of course. 3399handlers will be invoked, too, of course.
2013.PP 3400.PP
3401\fIThe special problem of life after fork \- how is it possible?\fR
3402.IX Subsection "The special problem of life after fork - how is it possible?"
3403.PP
3404Most uses of \f(CW\*(C`fork()\*(C'\fR consist of forking, then some simple calls to set
3405up/change the process environment, followed by a call to \f(CW\*(C`exec()\*(C'\fR. This
3406sequence should be handled by libev without any problems.
3407.PP
3408This changes when the application actually wants to do event handling
3409in the child, or both parent in child, in effect \*(L"continuing\*(R" after the
3410fork.
3411.PP
3412The default mode of operation (for libev, with application help to detect
3413forks) is to duplicate all the state in the child, as would be expected
3414when \fIeither\fR the parent \fIor\fR the child process continues.
3415.PP
3416When both processes want to continue using libev, then this is usually the
3417wrong result. In that case, usually one process (typically the parent) is
3418supposed to continue with all watchers in place as before, while the other
3419process typically wants to start fresh, i.e. without any active watchers.
3420.PP
3421The cleanest and most efficient way to achieve that with libev is to
3422simply create a new event loop, which of course will be \*(L"empty\*(R", and
3423use that for new watchers. This has the advantage of not touching more
3424memory than necessary, and thus avoiding the copy-on-write, and the
3425disadvantage of having to use multiple event loops (which do not support
3426signal watchers).
3427.PP
3428When this is not possible, or you want to use the default loop for
3429other reasons, then in the process that wants to start \*(L"fresh\*(R", call
3430\&\f(CW\*(C`ev_loop_destroy (EV_DEFAULT)\*(C'\fR followed by \f(CW\*(C`ev_default_loop (...)\*(C'\fR.
3431Destroying the default loop will \*(L"orphan\*(R" (not stop) all registered
3432watchers, so you have to be careful not to execute code that modifies
3433those watchers. Note also that in that case, you have to re-register any
3434signal watchers.
3435.PP
2014\fIWatcher-Specific Functions and Data Members\fR 3436\fIWatcher-Specific Functions and Data Members\fR
2015.IX Subsection "Watcher-Specific Functions and Data Members" 3437.IX Subsection "Watcher-Specific Functions and Data Members"
2016.IP "ev_fork_init (ev_signal *, callback)" 4 3438.IP "ev_fork_init (ev_fork *, callback)" 4
2017.IX Item "ev_fork_init (ev_signal *, callback)" 3439.IX Item "ev_fork_init (ev_fork *, callback)"
2018Initialises and configures the fork watcher \- it has no parameters of any 3440Initialises and configures the fork watcher \- it has no parameters of any
2019kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless, 3441kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless,
2020believe me. 3442really.
3443.ie n .SS """ev_cleanup"" \- even the best things end"
3444.el .SS "\f(CWev_cleanup\fP \- even the best things end"
3445.IX Subsection "ev_cleanup - even the best things end"
3446Cleanup watchers are called just before the event loop is being destroyed
3447by a call to \f(CW\*(C`ev_loop_destroy\*(C'\fR.
3448.PP
3449While there is no guarantee that the event loop gets destroyed, cleanup
3450watchers provide a convenient method to install cleanup hooks for your
3451program, worker threads and so on \- you just to make sure to destroy the
3452loop when you want them to be invoked.
3453.PP
3454Cleanup watchers are invoked in the same way as any other watcher. Unlike
3455all other watchers, they do not keep a reference to the event loop (which
3456makes a lot of sense if you think about it). Like all other watchers, you
3457can call libev functions in the callback, except \f(CW\*(C`ev_cleanup_start\*(C'\fR.
3458.PP
3459\fIWatcher-Specific Functions and Data Members\fR
3460.IX Subsection "Watcher-Specific Functions and Data Members"
3461.IP "ev_cleanup_init (ev_cleanup *, callback)" 4
3462.IX Item "ev_cleanup_init (ev_cleanup *, callback)"
3463Initialises and configures the cleanup watcher \- it has no parameters of
3464any kind. There is a \f(CW\*(C`ev_cleanup_set\*(C'\fR macro, but using it is utterly
3465pointless, I assure you.
3466.PP
3467Example: Register an atexit handler to destroy the default loop, so any
3468cleanup functions are called.
3469.PP
3470.Vb 5
3471\& static void
3472\& program_exits (void)
3473\& {
3474\& ev_loop_destroy (EV_DEFAULT_UC);
3475\& }
3476\&
3477\& ...
3478\& atexit (program_exits);
3479.Ve
3480.ie n .SS """ev_async"" \- how to wake up an event loop"
3481.el .SS "\f(CWev_async\fP \- how to wake up an event loop"
3482.IX Subsection "ev_async - how to wake up an event loop"
3483In general, you cannot use an \f(CW\*(C`ev_loop\*(C'\fR from multiple threads or other
3484asynchronous sources such as signal handlers (as opposed to multiple event
3485loops \- those are of course safe to use in different threads).
3486.PP
3487Sometimes, however, you need to wake up an event loop you do not control,
3488for example because it belongs to another thread. This is what \f(CW\*(C`ev_async\*(C'\fR
3489watchers do: as long as the \f(CW\*(C`ev_async\*(C'\fR watcher is active, you can signal
3490it by calling \f(CW\*(C`ev_async_send\*(C'\fR, which is thread\- and signal safe.
3491.PP
3492This functionality is very similar to \f(CW\*(C`ev_signal\*(C'\fR watchers, as signals,
3493too, are asynchronous in nature, and signals, too, will be compressed
3494(i.e. the number of callback invocations may be less than the number of
3495\&\f(CW\*(C`ev_async_send\*(C'\fR calls). In fact, you could use signal watchers as a kind
3496of \*(L"global async watchers\*(R" by using a watcher on an otherwise unused
3497signal, and \f(CW\*(C`ev_feed_signal\*(C'\fR to signal this watcher from another thread,
3498even without knowing which loop owns the signal.
3499.PP
3500\fIQueueing\fR
3501.IX Subsection "Queueing"
3502.PP
3503\&\f(CW\*(C`ev_async\*(C'\fR does not support queueing of data in any way. The reason
3504is that the author does not know of a simple (or any) algorithm for a
3505multiple-writer-single-reader queue that works in all cases and doesn't
3506need elaborate support such as pthreads or unportable memory access
3507semantics.
3508.PP
3509That means that if you want to queue data, you have to provide your own
3510queue. But at least I can tell you how to implement locking around your
3511queue:
3512.IP "queueing from a signal handler context" 4
3513.IX Item "queueing from a signal handler context"
3514To implement race-free queueing, you simply add to the queue in the signal
3515handler but you block the signal handler in the watcher callback. Here is
3516an example that does that for some fictitious \s-1SIGUSR1\s0 handler:
3517.Sp
3518.Vb 1
3519\& static ev_async mysig;
3520\&
3521\& static void
3522\& sigusr1_handler (void)
3523\& {
3524\& sometype data;
3525\&
3526\& // no locking etc.
3527\& queue_put (data);
3528\& ev_async_send (EV_DEFAULT_ &mysig);
3529\& }
3530\&
3531\& static void
3532\& mysig_cb (EV_P_ ev_async *w, int revents)
3533\& {
3534\& sometype data;
3535\& sigset_t block, prev;
3536\&
3537\& sigemptyset (&block);
3538\& sigaddset (&block, SIGUSR1);
3539\& sigprocmask (SIG_BLOCK, &block, &prev);
3540\&
3541\& while (queue_get (&data))
3542\& process (data);
3543\&
3544\& if (sigismember (&prev, SIGUSR1)
3545\& sigprocmask (SIG_UNBLOCK, &block, 0);
3546\& }
3547.Ve
3548.Sp
3549(Note: pthreads in theory requires you to use \f(CW\*(C`pthread_setmask\*(C'\fR
3550instead of \f(CW\*(C`sigprocmask\*(C'\fR when you use threads, but libev doesn't do it
3551either...).
3552.IP "queueing from a thread context" 4
3553.IX Item "queueing from a thread context"
3554The strategy for threads is different, as you cannot (easily) block
3555threads but you can easily preempt them, so to queue safely you need to
3556employ a traditional mutex lock, such as in this pthread example:
3557.Sp
3558.Vb 2
3559\& static ev_async mysig;
3560\& static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
3561\&
3562\& static void
3563\& otherthread (void)
3564\& {
3565\& // only need to lock the actual queueing operation
3566\& pthread_mutex_lock (&mymutex);
3567\& queue_put (data);
3568\& pthread_mutex_unlock (&mymutex);
3569\&
3570\& ev_async_send (EV_DEFAULT_ &mysig);
3571\& }
3572\&
3573\& static void
3574\& mysig_cb (EV_P_ ev_async *w, int revents)
3575\& {
3576\& pthread_mutex_lock (&mymutex);
3577\&
3578\& while (queue_get (&data))
3579\& process (data);
3580\&
3581\& pthread_mutex_unlock (&mymutex);
3582\& }
3583.Ve
3584.PP
3585\fIWatcher-Specific Functions and Data Members\fR
3586.IX Subsection "Watcher-Specific Functions and Data Members"
3587.IP "ev_async_init (ev_async *, callback)" 4
3588.IX Item "ev_async_init (ev_async *, callback)"
3589Initialises and configures the async watcher \- it has no parameters of any
3590kind. There is a \f(CW\*(C`ev_async_set\*(C'\fR macro, but using it is utterly pointless,
3591trust me.
3592.IP "ev_async_send (loop, ev_async *)" 4
3593.IX Item "ev_async_send (loop, ev_async *)"
3594Sends/signals/activates the given \f(CW\*(C`ev_async\*(C'\fR watcher, that is, feeds
3595an \f(CW\*(C`EV_ASYNC\*(C'\fR event on the watcher into the event loop, and instantly
3596returns.
3597.Sp
3598Unlike \f(CW\*(C`ev_feed_event\*(C'\fR, this call is safe to do from other threads,
3599signal or similar contexts (see the discussion of \f(CW\*(C`EV_ATOMIC_T\*(C'\fR in the
3600embedding section below on what exactly this means).
3601.Sp
3602Note that, as with other watchers in libev, multiple events might get
3603compressed into a single callback invocation (another way to look at
3604this is that \f(CW\*(C`ev_async\*(C'\fR watchers are level-triggered: they are set on
3605\&\f(CW\*(C`ev_async_send\*(C'\fR, reset when the event loop detects that).
3606.Sp
3607This call incurs the overhead of at most one extra system call per event
3608loop iteration, if the event loop is blocked, and no syscall at all if
3609the event loop (or your program) is processing events. That means that
3610repeated calls are basically free (there is no need to avoid calls for
3611performance reasons) and that the overhead becomes smaller (typically
3612zero) under load.
3613.IP "bool = ev_async_pending (ev_async *)" 4
3614.IX Item "bool = ev_async_pending (ev_async *)"
3615Returns a non-zero value when \f(CW\*(C`ev_async_send\*(C'\fR has been called on the
3616watcher but the event has not yet been processed (or even noted) by the
3617event loop.
3618.Sp
3619\&\f(CW\*(C`ev_async_send\*(C'\fR sets a flag in the watcher and wakes up the loop. When
3620the loop iterates next and checks for the watcher to have become active,
3621it will reset the flag again. \f(CW\*(C`ev_async_pending\*(C'\fR can be used to very
3622quickly check whether invoking the loop might be a good idea.
3623.Sp
3624Not that this does \fInot\fR check whether the watcher itself is pending,
3625only whether it has been requested to make this watcher pending: there
3626is a time window between the event loop checking and resetting the async
3627notification, and the callback being invoked.
2021.SH "OTHER FUNCTIONS" 3628.SH "OTHER FUNCTIONS"
2022.IX Header "OTHER FUNCTIONS" 3629.IX Header "OTHER FUNCTIONS"
2023There are some other functions of possible interest. Described. Here. Now. 3630There are some other functions of possible interest. Described. Here. Now.
2024.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4 3631.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4
2025.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 3632.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)"
2026This function combines a simple timer and an I/O watcher, calls your 3633This function combines a simple timer and an I/O watcher, calls your
2027callback on whichever event happens first and automatically stop both 3634callback on whichever event happens first and automatically stops both
2028watchers. This is useful if you want to wait for a single event on an fd 3635watchers. This is useful if you want to wait for a single event on an fd
2029or timeout without having to allocate/configure/start/stop/free one or 3636or timeout without having to allocate/configure/start/stop/free one or
2030more watchers yourself. 3637more watchers yourself.
2031.Sp 3638.Sp
2032If \f(CW\*(C`fd\*(C'\fR is less than 0, then no I/O watcher will be started and events 3639If \f(CW\*(C`fd\*(C'\fR is less than 0, then no I/O watcher will be started and the
2033is being ignored. Otherwise, an \f(CW\*(C`ev_io\*(C'\fR watcher for the given \f(CW\*(C`fd\*(C'\fR and 3640\&\f(CW\*(C`events\*(C'\fR argument is being ignored. Otherwise, an \f(CW\*(C`ev_io\*(C'\fR watcher for
2034\&\f(CW\*(C`events\*(C'\fR set will be craeted and started. 3641the given \f(CW\*(C`fd\*(C'\fR and \f(CW\*(C`events\*(C'\fR set will be created and started.
2035.Sp 3642.Sp
2036If \f(CW\*(C`timeout\*(C'\fR is less than 0, then no timeout watcher will be 3643If \f(CW\*(C`timeout\*(C'\fR is less than 0, then no timeout watcher will be
2037started. Otherwise an \f(CW\*(C`ev_timer\*(C'\fR watcher with after = \f(CW\*(C`timeout\*(C'\fR (and 3644started. Otherwise an \f(CW\*(C`ev_timer\*(C'\fR watcher with after = \f(CW\*(C`timeout\*(C'\fR (and
2038repeat = 0) will be started. While \f(CW0\fR is a valid timeout, it is of 3645repeat = 0) will be started. \f(CW0\fR is a valid timeout.
2039dubious value.
2040.Sp 3646.Sp
2041The callback has the type \f(CW\*(C`void (*cb)(int revents, void *arg)\*(C'\fR and gets 3647The callback has the type \f(CW\*(C`void (*cb)(int revents, void *arg)\*(C'\fR and is
2042passed an \f(CW\*(C`revents\*(C'\fR set like normal event callbacks (a combination of 3648passed an \f(CW\*(C`revents\*(C'\fR set like normal event callbacks (a combination of
2043\&\f(CW\*(C`EV_ERROR\*(C'\fR, \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or \f(CW\*(C`EV_TIMEOUT\*(C'\fR) and the \f(CW\*(C`arg\*(C'\fR 3649\&\f(CW\*(C`EV_ERROR\*(C'\fR, \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or \f(CW\*(C`EV_TIMER\*(C'\fR) and the \f(CW\*(C`arg\*(C'\fR
2044value passed to \f(CW\*(C`ev_once\*(C'\fR: 3650value passed to \f(CW\*(C`ev_once\*(C'\fR. Note that it is possible to receive \fIboth\fR
3651a timeout and an io event at the same time \- you probably should give io
3652events precedence.
3653.Sp
3654Example: wait up to ten seconds for data to appear on \s-1STDIN_FILENO\s0.
2045.Sp 3655.Sp
2046.Vb 7 3656.Vb 7
2047\& static void stdin_ready (int revents, void *arg) 3657\& static void stdin_ready (int revents, void *arg)
3658\& {
3659\& if (revents & EV_READ)
3660\& /* stdin might have data for us, joy! */;
3661\& else if (revents & EV_TIMER)
3662\& /* doh, nothing entered */;
3663\& }
3664\&
3665\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3666.Ve
3667.IP "ev_feed_fd_event (loop, int fd, int revents)" 4
3668.IX Item "ev_feed_fd_event (loop, int fd, int revents)"
3669Feed an event on the given fd, as if a file descriptor backend detected
3670the given events.
3671.IP "ev_feed_signal_event (loop, int signum)" 4
3672.IX Item "ev_feed_signal_event (loop, int signum)"
3673Feed an event as if the given signal occurred. See also \f(CW\*(C`ev_feed_signal\*(C'\fR,
3674which is async-safe.
3675.SH "COMMON OR USEFUL IDIOMS (OR BOTH)"
3676.IX Header "COMMON OR USEFUL IDIOMS (OR BOTH)"
3677This section explains some common idioms that are not immediately
3678obvious. Note that examples are sprinkled over the whole manual, and this
3679section only contains stuff that wouldn't fit anywhere else.
3680.SS "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0"
3681.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER"
3682Each watcher has, by default, a \f(CW\*(C`void *data\*(C'\fR member that you can read
3683or modify at any time: libev will completely ignore it. This can be used
3684to associate arbitrary data with your watcher. If you need more data and
3685don't want to allocate memory separately and store a pointer to it in that
3686data member, you can also \*(L"subclass\*(R" the watcher type and provide your own
3687data:
3688.PP
3689.Vb 7
3690\& struct my_io
3691\& {
3692\& ev_io io;
3693\& int otherfd;
3694\& void *somedata;
3695\& struct whatever *mostinteresting;
3696\& };
3697\&
3698\& ...
3699\& struct my_io w;
3700\& ev_io_init (&w.io, my_cb, fd, EV_READ);
3701.Ve
3702.PP
3703And since your callback will be called with a pointer to the watcher, you
3704can cast it back to your own type:
3705.PP
3706.Vb 5
3707\& static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
3708\& {
3709\& struct my_io *w = (struct my_io *)w_;
3710\& ...
3711\& }
3712.Ve
3713.PP
3714More interesting and less C\-conformant ways of casting your callback
3715function type instead have been omitted.
3716.SS "\s-1BUILDING\s0 \s-1YOUR\s0 \s-1OWN\s0 \s-1COMPOSITE\s0 \s-1WATCHERS\s0"
3717.IX Subsection "BUILDING YOUR OWN COMPOSITE WATCHERS"
3718Another common scenario is to use some data structure with multiple
3719embedded watchers, in effect creating your own watcher that combines
3720multiple libev event sources into one \*(L"super-watcher\*(R":
3721.PP
3722.Vb 6
3723\& struct my_biggy
3724\& {
3725\& int some_data;
3726\& ev_timer t1;
3727\& ev_timer t2;
3728\& }
3729.Ve
3730.PP
3731In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more
3732complicated: Either you store the address of your \f(CW\*(C`my_biggy\*(C'\fR struct in
3733the \f(CW\*(C`data\*(C'\fR member of the watcher (for woozies or \*(C+ coders), or you need
3734to use some pointer arithmetic using \f(CW\*(C`offsetof\*(C'\fR inside your watchers (for
3735real programmers):
3736.PP
3737.Vb 1
3738\& #include <stddef.h>
3739\&
3740\& static void
3741\& t1_cb (EV_P_ ev_timer *w, int revents)
3742\& {
3743\& struct my_biggy big = (struct my_biggy *)
3744\& (((char *)w) \- offsetof (struct my_biggy, t1));
3745\& }
3746\&
3747\& static void
3748\& t2_cb (EV_P_ ev_timer *w, int revents)
3749\& {
3750\& struct my_biggy big = (struct my_biggy *)
3751\& (((char *)w) \- offsetof (struct my_biggy, t2));
3752\& }
3753.Ve
3754.SS "\s-1AVOIDING\s0 \s-1FINISHING\s0 \s-1BEFORE\s0 \s-1RETURNING\s0"
3755.IX Subsection "AVOIDING FINISHING BEFORE RETURNING"
3756Often you have structures like this in event-based programs:
3757.PP
3758.Vb 4
3759\& callback ()
2048\& { 3760\& {
2049\& if (revents & EV_TIMEOUT) 3761\& free (request);
2050\& /* doh, nothing entered */;
2051\& else if (revents & EV_READ)
2052\& /* stdin might have data for us, joy! */;
2053\& } 3762\& }
3763\&
3764\& request = start_new_request (..., callback);
2054.Ve 3765.Ve
2055.Sp 3766.PP
3767The intent is to start some \*(L"lengthy\*(R" operation. The \f(CW\*(C`request\*(C'\fR could be
3768used to cancel the operation, or do other things with it.
3769.PP
3770It's not uncommon to have code paths in \f(CW\*(C`start_new_request\*(C'\fR that
3771immediately invoke the callback, for example, to report errors. Or you add
3772some caching layer that finds that it can skip the lengthy aspects of the
3773operation and simply invoke the callback with the result.
3774.PP
3775The problem here is that this will happen \fIbefore\fR \f(CW\*(C`start_new_request\*(C'\fR
3776has returned, so \f(CW\*(C`request\*(C'\fR is not set.
3777.PP
3778Even if you pass the request by some safer means to the callback, you
3779might want to do something to the request after starting it, such as
3780canceling it, which probably isn't working so well when the callback has
3781already been invoked.
3782.PP
3783A common way around all these issues is to make sure that
3784\&\f(CW\*(C`start_new_request\*(C'\fR \fIalways\fR returns before the callback is invoked. If
3785\&\f(CW\*(C`start_new_request\*(C'\fR immediately knows the result, it can artificially
3786delay invoking the callback by e.g. using a \f(CW\*(C`prepare\*(C'\fR or \f(CW\*(C`idle\*(C'\fR watcher
3787for example, or more sneakily, by reusing an existing (stopped) watcher
3788and pushing it into the pending queue:
3789.PP
2056.Vb 1 3790.Vb 2
2057\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); 3791\& ev_set_cb (watcher, callback);
3792\& ev_feed_event (EV_A_ watcher, 0);
2058.Ve 3793.Ve
2059.IP "ev_feed_event (ev_loop *, watcher *, int revents)" 4 3794.PP
2060.IX Item "ev_feed_event (ev_loop *, watcher *, int revents)" 3795This way, \f(CW\*(C`start_new_request\*(C'\fR can safely return before the callback is
2061Feeds the given event set into the event loop, as if the specified event 3796invoked, while not delaying callback invocation too much.
2062had happened for the specified watcher (which must be a pointer to an 3797.SS "\s-1MODEL/NESTED\s0 \s-1EVENT\s0 \s-1LOOP\s0 \s-1INVOCATIONS\s0 \s-1AND\s0 \s-1EXIT\s0 \s-1CONDITIONS\s0"
2063initialised but not necessarily started event watcher). 3798.IX Subsection "MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS"
2064.IP "ev_feed_fd_event (ev_loop *, int fd, int revents)" 4 3799Often (especially in \s-1GUI\s0 toolkits) there are places where you have
2065.IX Item "ev_feed_fd_event (ev_loop *, int fd, int revents)" 3800\&\fImodal\fR interaction, which is most easily implemented by recursively
2066Feed an event on the given fd, as if a file descriptor backend detected 3801invoking \f(CW\*(C`ev_run\*(C'\fR.
2067the given events it. 3802.PP
2068.IP "ev_feed_signal_event (ev_loop *loop, int signum)" 4 3803This brings the problem of exiting \- a callback might want to finish the
2069.IX Item "ev_feed_signal_event (ev_loop *loop, int signum)" 3804main \f(CW\*(C`ev_run\*(C'\fR call, but not the nested one (e.g. user clicked \*(L"Quit\*(R", but
2070Feed an event as if the given signal occured (\f(CW\*(C`loop\*(C'\fR must be the default 3805a modal \*(L"Are you sure?\*(R" dialog is still waiting), or just the nested one
2071loop!). 3806and not the main one (e.g. user clocked \*(L"Ok\*(R" in a modal dialog), or some
3807other combination: In these cases, \f(CW\*(C`ev_break\*(C'\fR will not work alone.
3808.PP
3809The solution is to maintain \*(L"break this loop\*(R" variable for each \f(CW\*(C`ev_run\*(C'\fR
3810invocation, and use a loop around \f(CW\*(C`ev_run\*(C'\fR until the condition is
3811triggered, using \f(CW\*(C`EVRUN_ONCE\*(C'\fR:
3812.PP
3813.Vb 2
3814\& // main loop
3815\& int exit_main_loop = 0;
3816\&
3817\& while (!exit_main_loop)
3818\& ev_run (EV_DEFAULT_ EVRUN_ONCE);
3819\&
3820\& // in a modal watcher
3821\& int exit_nested_loop = 0;
3822\&
3823\& while (!exit_nested_loop)
3824\& ev_run (EV_A_ EVRUN_ONCE);
3825.Ve
3826.PP
3827To exit from any of these loops, just set the corresponding exit variable:
3828.PP
3829.Vb 2
3830\& // exit modal loop
3831\& exit_nested_loop = 1;
3832\&
3833\& // exit main program, after modal loop is finished
3834\& exit_main_loop = 1;
3835\&
3836\& // exit both
3837\& exit_main_loop = exit_nested_loop = 1;
3838.Ve
3839.SS "\s-1THREAD\s0 \s-1LOCKING\s0 \s-1EXAMPLE\s0"
3840.IX Subsection "THREAD LOCKING EXAMPLE"
3841Here is a fictitious example of how to run an event loop in a different
3842thread from where callbacks are being invoked and watchers are
3843created/added/removed.
3844.PP
3845For a real-world example, see the \f(CW\*(C`EV::Loop::Async\*(C'\fR perl module,
3846which uses exactly this technique (which is suited for many high-level
3847languages).
3848.PP
3849The example uses a pthread mutex to protect the loop data, a condition
3850variable to wait for callback invocations, an async watcher to notify the
3851event loop thread and an unspecified mechanism to wake up the main thread.
3852.PP
3853First, you need to associate some data with the event loop:
3854.PP
3855.Vb 6
3856\& typedef struct {
3857\& mutex_t lock; /* global loop lock */
3858\& ev_async async_w;
3859\& thread_t tid;
3860\& cond_t invoke_cv;
3861\& } userdata;
3862\&
3863\& void prepare_loop (EV_P)
3864\& {
3865\& // for simplicity, we use a static userdata struct.
3866\& static userdata u;
3867\&
3868\& ev_async_init (&u\->async_w, async_cb);
3869\& ev_async_start (EV_A_ &u\->async_w);
3870\&
3871\& pthread_mutex_init (&u\->lock, 0);
3872\& pthread_cond_init (&u\->invoke_cv, 0);
3873\&
3874\& // now associate this with the loop
3875\& ev_set_userdata (EV_A_ u);
3876\& ev_set_invoke_pending_cb (EV_A_ l_invoke);
3877\& ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
3878\&
3879\& // then create the thread running ev_run
3880\& pthread_create (&u\->tid, 0, l_run, EV_A);
3881\& }
3882.Ve
3883.PP
3884The callback for the \f(CW\*(C`ev_async\*(C'\fR watcher does nothing: the watcher is used
3885solely to wake up the event loop so it takes notice of any new watchers
3886that might have been added:
3887.PP
3888.Vb 5
3889\& static void
3890\& async_cb (EV_P_ ev_async *w, int revents)
3891\& {
3892\& // just used for the side effects
3893\& }
3894.Ve
3895.PP
3896The \f(CW\*(C`l_release\*(C'\fR and \f(CW\*(C`l_acquire\*(C'\fR callbacks simply unlock/lock the mutex
3897protecting the loop data, respectively.
3898.PP
3899.Vb 6
3900\& static void
3901\& l_release (EV_P)
3902\& {
3903\& userdata *u = ev_userdata (EV_A);
3904\& pthread_mutex_unlock (&u\->lock);
3905\& }
3906\&
3907\& static void
3908\& l_acquire (EV_P)
3909\& {
3910\& userdata *u = ev_userdata (EV_A);
3911\& pthread_mutex_lock (&u\->lock);
3912\& }
3913.Ve
3914.PP
3915The event loop thread first acquires the mutex, and then jumps straight
3916into \f(CW\*(C`ev_run\*(C'\fR:
3917.PP
3918.Vb 4
3919\& void *
3920\& l_run (void *thr_arg)
3921\& {
3922\& struct ev_loop *loop = (struct ev_loop *)thr_arg;
3923\&
3924\& l_acquire (EV_A);
3925\& pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
3926\& ev_run (EV_A_ 0);
3927\& l_release (EV_A);
3928\&
3929\& return 0;
3930\& }
3931.Ve
3932.PP
3933Instead of invoking all pending watchers, the \f(CW\*(C`l_invoke\*(C'\fR callback will
3934signal the main thread via some unspecified mechanism (signals? pipe
3935writes? \f(CW\*(C`Async::Interrupt\*(C'\fR?) and then waits until all pending watchers
3936have been called (in a while loop because a) spurious wakeups are possible
3937and b) skipping inter-thread-communication when there are no pending
3938watchers is very beneficial):
3939.PP
3940.Vb 4
3941\& static void
3942\& l_invoke (EV_P)
3943\& {
3944\& userdata *u = ev_userdata (EV_A);
3945\&
3946\& while (ev_pending_count (EV_A))
3947\& {
3948\& wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
3949\& pthread_cond_wait (&u\->invoke_cv, &u\->lock);
3950\& }
3951\& }
3952.Ve
3953.PP
3954Now, whenever the main thread gets told to invoke pending watchers, it
3955will grab the lock, call \f(CW\*(C`ev_invoke_pending\*(C'\fR and then signal the loop
3956thread to continue:
3957.PP
3958.Vb 4
3959\& static void
3960\& real_invoke_pending (EV_P)
3961\& {
3962\& userdata *u = ev_userdata (EV_A);
3963\&
3964\& pthread_mutex_lock (&u\->lock);
3965\& ev_invoke_pending (EV_A);
3966\& pthread_cond_signal (&u\->invoke_cv);
3967\& pthread_mutex_unlock (&u\->lock);
3968\& }
3969.Ve
3970.PP
3971Whenever you want to start/stop a watcher or do other modifications to an
3972event loop, you will now have to lock:
3973.PP
3974.Vb 2
3975\& ev_timer timeout_watcher;
3976\& userdata *u = ev_userdata (EV_A);
3977\&
3978\& ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
3979\&
3980\& pthread_mutex_lock (&u\->lock);
3981\& ev_timer_start (EV_A_ &timeout_watcher);
3982\& ev_async_send (EV_A_ &u\->async_w);
3983\& pthread_mutex_unlock (&u\->lock);
3984.Ve
3985.PP
3986Note that sending the \f(CW\*(C`ev_async\*(C'\fR watcher is required because otherwise
3987an event loop currently blocking in the kernel will have no knowledge
3988about the newly added timer. By waking up the loop it will pick up any new
3989watchers in the next event loop iteration.
3990.SS "\s-1THREADS\s0, \s-1COROUTINES\s0, \s-1CONTINUATIONS\s0, \s-1QUEUES\s0... \s-1INSTEAD\s0 \s-1OF\s0 \s-1CALLBACKS\s0"
3991.IX Subsection "THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS"
3992While the overhead of a callback that e.g. schedules a thread is small, it
3993is still an overhead. If you embed libev, and your main usage is with some
3994kind of threads or coroutines, you might want to customise libev so that
3995doesn't need callbacks anymore.
3996.PP
3997Imagine you have coroutines that you can switch to using a function
3998\&\f(CW\*(C`switch_to (coro)\*(C'\fR, that libev runs in a coroutine called \f(CW\*(C`libev_coro\*(C'\fR
3999and that due to some magic, the currently active coroutine is stored in a
4000global called \f(CW\*(C`current_coro\*(C'\fR. Then you can build your own \*(L"wait for libev
4001event\*(R" primitive by changing \f(CW\*(C`EV_CB_DECLARE\*(C'\fR and \f(CW\*(C`EV_CB_INVOKE\*(C'\fR (note
4002the differing \f(CW\*(C`;\*(C'\fR conventions):
4003.PP
4004.Vb 2
4005\& #define EV_CB_DECLARE(type) struct my_coro *cb;
4006\& #define EV_CB_INVOKE(watcher) switch_to ((watcher)\->cb)
4007.Ve
4008.PP
4009That means instead of having a C callback function, you store the
4010coroutine to switch to in each watcher, and instead of having libev call
4011your callback, you instead have it switch to that coroutine.
4012.PP
4013A coroutine might now wait for an event with a function called
4014\&\f(CW\*(C`wait_for_event\*(C'\fR. (the watcher needs to be started, as always, but it doesn't
4015matter when, or whether the watcher is active or not when this function is
4016called):
4017.PP
4018.Vb 6
4019\& void
4020\& wait_for_event (ev_watcher *w)
4021\& {
4022\& ev_set_cb (w, current_coro);
4023\& switch_to (libev_coro);
4024\& }
4025.Ve
4026.PP
4027That basically suspends the coroutine inside \f(CW\*(C`wait_for_event\*(C'\fR and
4028continues the libev coroutine, which, when appropriate, switches back to
4029this or any other coroutine.
4030.PP
4031You can do similar tricks if you have, say, threads with an event queue \-
4032instead of storing a coroutine, you store the queue object and instead of
4033switching to a coroutine, you push the watcher onto the queue and notify
4034any waiters.
4035.PP
4036To embed libev, see \*(L"\s-1EMBEDDING\s0\*(R", but in short, it's easiest to create two
4037files, \fImy_ev.h\fR and \fImy_ev.c\fR that include the respective libev files:
4038.PP
4039.Vb 4
4040\& // my_ev.h
4041\& #define EV_CB_DECLARE(type) struct my_coro *cb;
4042\& #define EV_CB_INVOKE(watcher) switch_to ((watcher)\->cb);
4043\& #include "../libev/ev.h"
4044\&
4045\& // my_ev.c
4046\& #define EV_H "my_ev.h"
4047\& #include "../libev/ev.c"
4048.Ve
4049.PP
4050And then use \fImy_ev.h\fR when you would normally use \fIev.h\fR, and compile
4051\&\fImy_ev.c\fR into your project. When properly specifying include paths, you
4052can even use \fIev.h\fR as header file name directly.
2072.SH "LIBEVENT EMULATION" 4053.SH "LIBEVENT EMULATION"
2073.IX Header "LIBEVENT EMULATION" 4054.IX Header "LIBEVENT EMULATION"
2074Libev offers a compatibility emulation layer for libevent. It cannot 4055Libev offers a compatibility emulation layer for libevent. It cannot
2075emulate the internals of libevent, so here are some usage hints: 4056emulate the internals of libevent, so here are some usage hints:
4057.IP "\(bu" 4
4058Only the libevent\-1.4.1\-beta \s-1API\s0 is being emulated.
4059.Sp
4060This was the newest libevent version available when libev was implemented,
4061and is still mostly unchanged in 2010.
4062.IP "\(bu" 4
2076.IP "* Use it by including <event.h>, as usual." 4 4063Use it by including <event.h>, as usual.
2077.IX Item "Use it by including <event.h>, as usual." 4064.IP "\(bu" 4
2078.PD 0 4065The following members are fully supported: ev_base, ev_callback,
2079.IP "* The following members are fully supported: ev_base, ev_callback, ev_arg, ev_fd, ev_res, ev_events." 4 4066ev_arg, ev_fd, ev_res, ev_events.
2080.IX Item "The following members are fully supported: ev_base, ev_callback, ev_arg, ev_fd, ev_res, ev_events." 4067.IP "\(bu" 4
2081.IP "* Avoid using ev_flags and the EVLIST_*\-macros, while it is maintained by libev, it does not work exactly the same way as in libevent (consider it a private \s-1API\s0)." 4 4068Avoid using ev_flags and the EVLIST_*\-macros, while it is
2082.IX Item "Avoid using ev_flags and the EVLIST_*-macros, while it is maintained by libev, it does not work exactly the same way as in libevent (consider it a private API)." 4069maintained by libev, it does not work exactly the same way as in libevent (consider
2083.IP "* Priorities are not currently supported. Initialising priorities will fail and all watchers will have the same priority, even though there is an ev_pri field." 4 4070it a private \s-1API\s0).
2084.IX Item "Priorities are not currently supported. Initialising priorities will fail and all watchers will have the same priority, even though there is an ev_pri field." 4071.IP "\(bu" 4
4072Priorities are not currently supported. Initialising priorities
4073will fail and all watchers will have the same priority, even though there
4074is an ev_pri field.
4075.IP "\(bu" 4
4076In libevent, the last base created gets the signals, in libev, the
4077base that registered the signal gets the signals.
4078.IP "\(bu" 4
2085.IP "* Other members are not supported." 4 4079Other members are not supported.
2086.IX Item "Other members are not supported." 4080.IP "\(bu" 4
2087.IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4 4081The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need
2088.IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library." 4082to use the libev header file and library.
2089.PD
2090.SH "\*(C+ SUPPORT" 4083.SH "\*(C+ SUPPORT"
2091.IX Header " SUPPORT" 4084.IX Header " SUPPORT"
4085.SS "C \s-1API\s0"
4086.IX Subsection "C API"
4087The normal C \s-1API\s0 should work fine when used from \*(C+: both ev.h and the
4088libev sources can be compiled as \*(C+. Therefore, code that uses the C \s-1API\s0
4089will work fine.
4090.PP
4091Proper exception specifications might have to be added to callbacks passed
4092to libev: exceptions may be thrown only from watcher callbacks, all
4093other callbacks (allocator, syserr, loop acquire/release and periodioc
4094reschedule callbacks) must not throw exceptions, and might need a \f(CW\*(C`throw
4095()\*(C'\fR specification. If you have code that needs to be compiled as both C
4096and \*(C+ you can use the \f(CW\*(C`EV_THROW\*(C'\fR macro for this:
4097.PP
4098.Vb 6
4099\& static void
4100\& fatal_error (const char *msg) EV_THROW
4101\& {
4102\& perror (msg);
4103\& abort ();
4104\& }
4105\&
4106\& ...
4107\& ev_set_syserr_cb (fatal_error);
4108.Ve
4109.PP
4110The only \s-1API\s0 functions that can currently throw exceptions are \f(CW\*(C`ev_run\*(C'\fR,
4111\&\f(CW\*(C`ev_invoke\*(C'\fR, \f(CW\*(C`ev_invoke_pending\*(C'\fR and \f(CW\*(C`ev_loop_destroy\*(C'\fR (the latter
4112because it runs cleanup watchers).
4113.PP
4114Throwing exceptions in watcher callbacks is only supported if libev itself
4115is compiled with a \*(C+ compiler or your C and \*(C+ environments allow
4116throwing exceptions through C libraries (most do).
4117.SS "\*(C+ \s-1API\s0"
4118.IX Subsection " API"
2092Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow 4119Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow
2093you to use some convinience methods to start/stop watchers and also change 4120you to use some convenience methods to start/stop watchers and also change
2094the callback model to a model using method callbacks on objects. 4121the callback model to a model using method callbacks on objects.
2095.PP 4122.PP
2096To use it, 4123To use it,
2097.PP 4124.PP
2098.Vb 1 4125.Vb 1
2099\& #include <ev++.h> 4126\& #include <ev++.h>
2100.Ve 4127.Ve
2101.PP 4128.PP
2102This automatically includes \fIev.h\fR and puts all of its definitions (many 4129This automatically includes \fIev.h\fR and puts all of its definitions (many
2103of them macros) into the global namespace. All \*(C+ specific things are 4130of them macros) into the global namespace. All \*(C+ specific things are
2104put into the \f(CW\*(C`ev\*(C'\fR namespace. It should support all the same embedding 4131put into the \f(CW\*(C`ev\*(C'\fR namespace. It should support all the same embedding
… …
2107Care has been taken to keep the overhead low. The only data member the \*(C+ 4134Care has been taken to keep the overhead low. The only data member the \*(C+
2108classes add (compared to plain C\-style watchers) is the event loop pointer 4135classes add (compared to plain C\-style watchers) is the event loop pointer
2109that the watcher is associated with (or no additional members at all if 4136that the watcher is associated with (or no additional members at all if
2110you disable \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR when embedding libev). 4137you disable \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR when embedding libev).
2111.PP 4138.PP
2112Currently, functions, and static and non-static member functions can be 4139Currently, functions, static and non-static member functions and classes
2113used as callbacks. Other types should be easy to add as long as they only 4140with \f(CW\*(C`operator ()\*(C'\fR can be used as callbacks. Other types should be easy
2114need one additional pointer for context. If you need support for other 4141to add as long as they only need one additional pointer for context. If
2115types of functors please contact the author (preferably after implementing 4142you need support for other types of functors please contact the author
2116it). 4143(preferably after implementing it).
4144.PP
4145For all this to work, your \*(C+ compiler either has to use the same calling
4146conventions as your C compiler (for static member functions), or you have
4147to embed libev and compile libev itself as \*(C+.
2117.PP 4148.PP
2118Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace: 4149Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace:
2119.ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4 4150.ie n .IP """ev::READ"", ""ev::WRITE"" etc." 4
2120.el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4 4151.el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4
2121.IX Item "ev::READ, ev::WRITE etc." 4152.IX Item "ev::READ, ev::WRITE etc."
2122These are just enum values with the same values as the \f(CW\*(C`EV_READ\*(C'\fR etc. 4153These are just enum values with the same values as the \f(CW\*(C`EV_READ\*(C'\fR etc.
2123macros from \fIev.h\fR. 4154macros from \fIev.h\fR.
2124.ie n .IP """ev::tstamp""\fR, \f(CW""ev::now""" 4 4155.ie n .IP """ev::tstamp"", ""ev::now""" 4
2125.el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4 4156.el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4
2126.IX Item "ev::tstamp, ev::now" 4157.IX Item "ev::tstamp, ev::now"
2127Aliases to the same types/functions as with the \f(CW\*(C`ev_\*(C'\fR prefix. 4158Aliases to the same types/functions as with the \f(CW\*(C`ev_\*(C'\fR prefix.
2128.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 4159.ie n .IP """ev::io"", ""ev::timer"", ""ev::periodic"", ""ev::idle"", ""ev::sig"" etc." 4
2129.el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4 4160.el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4
2130.IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc." 4161.IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc."
2131For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of 4162For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of
2132the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR 4163the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR
2133which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro 4164which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro
2134defines by many implementations. 4165defined by many implementations.
2135.Sp 4166.Sp
2136All of those classes have these methods: 4167All of those classes have these methods:
2137.RS 4 4168.RS 4
2138.IP "ev::TYPE::TYPE ()" 4 4169.IP "ev::TYPE::TYPE ()" 4
2139.IX Item "ev::TYPE::TYPE ()" 4170.IX Item "ev::TYPE::TYPE ()"
2140.PD 0 4171.PD 0
2141.IP "ev::TYPE::TYPE (struct ev_loop *)" 4 4172.IP "ev::TYPE::TYPE (loop)" 4
2142.IX Item "ev::TYPE::TYPE (struct ev_loop *)" 4173.IX Item "ev::TYPE::TYPE (loop)"
2143.IP "ev::TYPE::~TYPE" 4 4174.IP "ev::TYPE::~TYPE" 4
2144.IX Item "ev::TYPE::~TYPE" 4175.IX Item "ev::TYPE::~TYPE"
2145.PD 4176.PD
2146The constructor (optionally) takes an event loop to associate the watcher 4177The constructor (optionally) takes an event loop to associate the watcher
2147with. If it is omitted, it will use \f(CW\*(C`EV_DEFAULT\*(C'\fR. 4178with. If it is omitted, it will use \f(CW\*(C`EV_DEFAULT\*(C'\fR.
… …
2170thunking function, making it as fast as a direct C callback. 4201thunking function, making it as fast as a direct C callback.
2171.Sp 4202.Sp
2172Example: simple class declaration and watcher initialisation 4203Example: simple class declaration and watcher initialisation
2173.Sp 4204.Sp
2174.Vb 4 4205.Vb 4
2175\& struct myclass 4206\& struct myclass
2176\& { 4207\& {
2177\& void io_cb (ev::io &w, int revents) { } 4208\& void io_cb (ev::io &w, int revents) { }
2178\& } 4209\& }
2179.Ve 4210\&
2180.Sp
2181.Vb 3
2182\& myclass obj; 4211\& myclass obj;
2183\& ev::io iow; 4212\& ev::io iow;
2184\& iow.set <myclass, &myclass::io_cb> (&obj); 4213\& iow.set <myclass, &myclass::io_cb> (&obj);
4214.Ve
4215.IP "w\->set (object *)" 4
4216.IX Item "w->set (object *)"
4217This is a variation of a method callback \- leaving out the method to call
4218will default the method to \f(CW\*(C`operator ()\*(C'\fR, which makes it possible to use
4219functor objects without having to manually specify the \f(CW\*(C`operator ()\*(C'\fR all
4220the time. Incidentally, you can then also leave out the template argument
4221list.
4222.Sp
4223The \f(CW\*(C`operator ()\*(C'\fR method prototype must be \f(CW\*(C`void operator ()(watcher &w,
4224int revents)\*(C'\fR.
4225.Sp
4226See the method\-\f(CW\*(C`set\*(C'\fR above for more details.
4227.Sp
4228Example: use a functor object as callback.
4229.Sp
4230.Vb 7
4231\& struct myfunctor
4232\& {
4233\& void operator() (ev::io &w, int revents)
4234\& {
4235\& ...
4236\& }
4237\& }
4238\&
4239\& myfunctor f;
4240\&
4241\& ev::io w;
4242\& w.set (&f);
2185.Ve 4243.Ve
2186.IP "w\->set<function> (void *data = 0)" 4 4244.IP "w\->set<function> (void *data = 0)" 4
2187.IX Item "w->set<function> (void *data = 0)" 4245.IX Item "w->set<function> (void *data = 0)"
2188Also sets a callback, but uses a static method or plain function as 4246Also sets a callback, but uses a static method or plain function as
2189callback. The optional \f(CW\*(C`data\*(C'\fR argument will be stored in the watcher's 4247callback. The optional \f(CW\*(C`data\*(C'\fR argument will be stored in the watcher's
… …
2191.Sp 4249.Sp
2192The prototype of the \f(CW\*(C`function\*(C'\fR must be \f(CW\*(C`void (*)(ev::TYPE &w, int)\*(C'\fR. 4250The prototype of the \f(CW\*(C`function\*(C'\fR must be \f(CW\*(C`void (*)(ev::TYPE &w, int)\*(C'\fR.
2193.Sp 4251.Sp
2194See the method\-\f(CW\*(C`set\*(C'\fR above for more details. 4252See the method\-\f(CW\*(C`set\*(C'\fR above for more details.
2195.Sp 4253.Sp
2196Example: 4254Example: Use a plain function as callback.
2197.Sp 4255.Sp
2198.Vb 2 4256.Vb 2
2199\& static void io_cb (ev::io &w, int revents) { } 4257\& static void io_cb (ev::io &w, int revents) { }
2200\& iow.set <io_cb> (); 4258\& iow.set <io_cb> ();
2201.Ve 4259.Ve
2202.IP "w\->set (struct ev_loop *)" 4 4260.IP "w\->set (loop)" 4
2203.IX Item "w->set (struct ev_loop *)" 4261.IX Item "w->set (loop)"
2204Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only 4262Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only
2205do this when the watcher is inactive (and not pending either). 4263do this when the watcher is inactive (and not pending either).
2206.IP "w\->set ([args])" 4 4264.IP "w\->set ([arguments])" 4
2207.IX Item "w->set ([args])" 4265.IX Item "w->set ([arguments])"
2208Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same args. Must be 4266Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same arguments. Either this
2209called at least once. Unlike the C counterpart, an active watcher gets 4267method or a suitable start method must be called at least once. Unlike the
2210automatically stopped and restarted when reconfiguring it with this 4268C counterpart, an active watcher gets automatically stopped and restarted
2211method. 4269when reconfiguring it with this method.
2212.IP "w\->start ()" 4 4270.IP "w\->start ()" 4
2213.IX Item "w->start ()" 4271.IX Item "w->start ()"
2214Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the 4272Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the
2215constructor already stores the event loop. 4273constructor already stores the event loop.
4274.IP "w\->start ([arguments])" 4
4275.IX Item "w->start ([arguments])"
4276Instead of calling \f(CW\*(C`set\*(C'\fR and \f(CW\*(C`start\*(C'\fR methods separately, it is often
4277convenient to wrap them in one call. Uses the same type of arguments as
4278the configure \f(CW\*(C`set\*(C'\fR method of the watcher.
2216.IP "w\->stop ()" 4 4279.IP "w\->stop ()" 4
2217.IX Item "w->stop ()" 4280.IX Item "w->stop ()"
2218Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument. 4281Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument.
2219.ie n .IP "w\->again () (""ev::timer""\fR, \f(CW""ev::periodic"" only)" 4 4282.ie n .IP "w\->again () (""ev::timer"", ""ev::periodic"" only)" 4
2220.el .IP "w\->again () (\f(CWev::timer\fR, \f(CWev::periodic\fR only)" 4 4283.el .IP "w\->again () (\f(CWev::timer\fR, \f(CWev::periodic\fR only)" 4
2221.IX Item "w->again () (ev::timer, ev::periodic only)" 4284.IX Item "w->again () (ev::timer, ev::periodic only)"
2222For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding 4285For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding
2223\&\f(CW\*(C`ev_TYPE_again\*(C'\fR function. 4286\&\f(CW\*(C`ev_TYPE_again\*(C'\fR function.
2224.ie n .IP "w\->sweep () (""ev::embed"" only)" 4 4287.ie n .IP "w\->sweep () (""ev::embed"" only)" 4
… …
2231Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR. 4294Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR.
2232.RE 4295.RE
2233.RS 4 4296.RS 4
2234.RE 4297.RE
2235.PP 4298.PP
2236Example: Define a class with an \s-1IO\s0 and idle watcher, start one of them in 4299Example: Define a class with two I/O and idle watchers, start the I/O
2237the constructor. 4300watchers in the constructor.
2238.PP 4301.PP
2239.Vb 4 4302.Vb 5
2240\& class myclass 4303\& class myclass
2241\& { 4304\& {
2242\& ev_io io; void io_cb (ev::io &w, int revents); 4305\& ev::io io ; void io_cb (ev::io &w, int revents);
4306\& ev::io io2 ; void io2_cb (ev::io &w, int revents);
2243\& ev_idle idle void idle_cb (ev::idle &w, int revents); 4307\& ev::idle idle; void idle_cb (ev::idle &w, int revents);
2244.Ve 4308\&
2245.PP
2246.Vb 2
2247\& myclass (); 4309\& myclass (int fd)
2248\& }
2249.Ve
2250.PP
2251.Vb 4
2252\& myclass::myclass (int fd)
2253\& { 4310\& {
2254\& io .set <myclass, &myclass::io_cb > (this); 4311\& io .set <myclass, &myclass::io_cb > (this);
4312\& io2 .set <myclass, &myclass::io2_cb > (this);
2255\& idle.set <myclass, &myclass::idle_cb> (this); 4313\& idle.set <myclass, &myclass::idle_cb> (this);
2256.Ve 4314\&
2257.PP 4315\& io.set (fd, ev::WRITE); // configure the watcher
2258.Vb 2 4316\& io.start (); // start it whenever convenient
2259\& io.start (fd, ev::READ); 4317\&
4318\& io2.start (fd, ev::READ); // set + start in one call
4319\& }
2260\& } 4320\& };
2261.Ve 4321.Ve
4322.SH "OTHER LANGUAGE BINDINGS"
4323.IX Header "OTHER LANGUAGE BINDINGS"
4324Libev does not offer other language bindings itself, but bindings for a
4325number of languages exist in the form of third-party packages. If you know
4326any interesting language binding in addition to the ones listed here, drop
4327me a note.
4328.IP "Perl" 4
4329.IX Item "Perl"
4330The \s-1EV\s0 module implements the full libev \s-1API\s0 and is actually used to test
4331libev. \s-1EV\s0 is developed together with libev. Apart from the \s-1EV\s0 core module,
4332there are additional modules that implement libev-compatible interfaces
4333to \f(CW\*(C`libadns\*(C'\fR (\f(CW\*(C`EV::ADNS\*(C'\fR, but \f(CW\*(C`AnyEvent::DNS\*(C'\fR is preferred nowadays),
4334\&\f(CW\*(C`Net::SNMP\*(C'\fR (\f(CW\*(C`Net::SNMP::EV\*(C'\fR) and the \f(CW\*(C`libglib\*(C'\fR event core (\f(CW\*(C`Glib::EV\*(C'\fR
4335and \f(CW\*(C`EV::Glib\*(C'\fR).
4336.Sp
4337It can be found and installed via \s-1CPAN\s0, its homepage is at
4338<http://software.schmorp.de/pkg/EV>.
4339.IP "Python" 4
4340.IX Item "Python"
4341Python bindings can be found at <http://code.google.com/p/pyev/>. It
4342seems to be quite complete and well-documented.
4343.IP "Ruby" 4
4344.IX Item "Ruby"
4345Tony Arcieri has written a ruby extension that offers access to a subset
4346of the libev \s-1API\s0 and adds file handle abstractions, asynchronous \s-1DNS\s0 and
4347more on top of it. It can be found via gem servers. Its homepage is at
4348<http://rev.rubyforge.org/>.
4349.Sp
4350Roger Pack reports that using the link order \f(CW\*(C`\-lws2_32 \-lmsvcrt\-ruby\-190\*(C'\fR
4351makes rev work even on mingw.
4352.IP "Haskell" 4
4353.IX Item "Haskell"
4354A haskell binding to libev is available at
4355http://hackage.haskell.org/cgi\-bin/hackage\-scripts/package/hlibev <http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
4356.IP "D" 4
4357.IX Item "D"
4358Leandro Lucarella has written a D language binding (\fIev.d\fR) for libev, to
4359be found at <http://www.llucax.com.ar/proj/ev.d/index.html>.
4360.IP "Ocaml" 4
4361.IX Item "Ocaml"
4362Erkki Seppala has written Ocaml bindings for libev, to be found at
4363http://modeemi.cs.tut.fi/~flux/software/ocaml\-ev/ <http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
4364.IP "Lua" 4
4365.IX Item "Lua"
4366Brian Maher has written a partial interface to libev for lua (at the
4367time of this writing, only \f(CW\*(C`ev_io\*(C'\fR and \f(CW\*(C`ev_timer\*(C'\fR), to be found at
4368http://github.com/brimworks/lua\-ev <http://github.com/brimworks/lua-ev>.
2262.SH "MACRO MAGIC" 4369.SH "MACRO MAGIC"
2263.IX Header "MACRO MAGIC" 4370.IX Header "MACRO MAGIC"
2264Libev can be compiled with a variety of options, the most fundamantal 4371Libev can be compiled with a variety of options, the most fundamental
2265of which is \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most) 4372of which is \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most)
2266functions and callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument. 4373functions and callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument.
2267.PP 4374.PP
2268To make it easier to write programs that cope with either variant, the 4375To make it easier to write programs that cope with either variant, the
2269following macros are defined: 4376following macros are defined:
2270.ie n .IP """EV_A""\fR, \f(CW""EV_A_""" 4 4377.ie n .IP """EV_A"", ""EV_A_""" 4
2271.el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4 4378.el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4
2272.IX Item "EV_A, EV_A_" 4379.IX Item "EV_A, EV_A_"
2273This provides the loop \fIargument\fR for functions, if one is required (\*(L"ev 4380This provides the loop \fIargument\fR for functions, if one is required (\*(L"ev
2274loop argument\*(R"). The \f(CW\*(C`EV_A\*(C'\fR form is used when this is the sole argument, 4381loop argument\*(R"). The \f(CW\*(C`EV_A\*(C'\fR form is used when this is the sole argument,
2275\&\f(CW\*(C`EV_A_\*(C'\fR is used when other arguments are following. Example: 4382\&\f(CW\*(C`EV_A_\*(C'\fR is used when other arguments are following. Example:
2276.Sp 4383.Sp
2277.Vb 3 4384.Vb 3
2278\& ev_unref (EV_A); 4385\& ev_unref (EV_A);
2279\& ev_timer_add (EV_A_ watcher); 4386\& ev_timer_add (EV_A_ watcher);
2280\& ev_loop (EV_A_ 0); 4387\& ev_run (EV_A_ 0);
2281.Ve 4388.Ve
2282.Sp 4389.Sp
2283It assumes the variable \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR is in scope, 4390It assumes the variable \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR is in scope,
2284which is often provided by the following macro. 4391which is often provided by the following macro.
2285.ie n .IP """EV_P""\fR, \f(CW""EV_P_""" 4 4392.ie n .IP """EV_P"", ""EV_P_""" 4
2286.el .IP "\f(CWEV_P\fR, \f(CWEV_P_\fR" 4 4393.el .IP "\f(CWEV_P\fR, \f(CWEV_P_\fR" 4
2287.IX Item "EV_P, EV_P_" 4394.IX Item "EV_P, EV_P_"
2288This provides the loop \fIparameter\fR for functions, if one is required (\*(L"ev 4395This provides the loop \fIparameter\fR for functions, if one is required (\*(L"ev
2289loop parameter\*(R"). The \f(CW\*(C`EV_P\*(C'\fR form is used when this is the sole parameter, 4396loop parameter\*(R"). The \f(CW\*(C`EV_P\*(C'\fR form is used when this is the sole parameter,
2290\&\f(CW\*(C`EV_P_\*(C'\fR is used when other parameters are following. Example: 4397\&\f(CW\*(C`EV_P_\*(C'\fR is used when other parameters are following. Example:
2291.Sp 4398.Sp
2292.Vb 2 4399.Vb 2
2293\& // this is how ev_unref is being declared 4400\& // this is how ev_unref is being declared
2294\& static void ev_unref (EV_P); 4401\& static void ev_unref (EV_P);
2295.Ve 4402\&
2296.Sp
2297.Vb 2
2298\& // this is how you can declare your typical callback 4403\& // this is how you can declare your typical callback
2299\& static void cb (EV_P_ ev_timer *w, int revents) 4404\& static void cb (EV_P_ ev_timer *w, int revents)
2300.Ve 4405.Ve
2301.Sp 4406.Sp
2302It declares a parameter \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR, quite 4407It declares a parameter \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR, quite
2303suitable for use with \f(CW\*(C`EV_A\*(C'\fR. 4408suitable for use with \f(CW\*(C`EV_A\*(C'\fR.
2304.ie n .IP """EV_DEFAULT""\fR, \f(CW""EV_DEFAULT_""" 4 4409.ie n .IP """EV_DEFAULT"", ""EV_DEFAULT_""" 4
2305.el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4 4410.el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4
2306.IX Item "EV_DEFAULT, EV_DEFAULT_" 4411.IX Item "EV_DEFAULT, EV_DEFAULT_"
2307Similar to the other two macros, this gives you the value of the default 4412Similar to the other two macros, this gives you the value of the default
2308loop, if multiple loops are supported (\*(L"ev loop default\*(R"). 4413loop, if multiple loops are supported (\*(L"ev loop default\*(R"). The default loop
4414will be initialised if it isn't already initialised.
4415.Sp
4416For non-multiplicity builds, these macros do nothing, so you always have
4417to initialise the loop somewhere.
4418.ie n .IP """EV_DEFAULT_UC"", ""EV_DEFAULT_UC_""" 4
4419.el .IP "\f(CWEV_DEFAULT_UC\fR, \f(CWEV_DEFAULT_UC_\fR" 4
4420.IX Item "EV_DEFAULT_UC, EV_DEFAULT_UC_"
4421Usage identical to \f(CW\*(C`EV_DEFAULT\*(C'\fR and \f(CW\*(C`EV_DEFAULT_\*(C'\fR, but requires that the
4422default loop has been initialised (\f(CW\*(C`UC\*(C'\fR == unchecked). Their behaviour
4423is undefined when the default loop has not been initialised by a previous
4424execution of \f(CW\*(C`EV_DEFAULT\*(C'\fR, \f(CW\*(C`EV_DEFAULT_\*(C'\fR or \f(CW\*(C`ev_default_init (...)\*(C'\fR.
4425.Sp
4426It is often prudent to use \f(CW\*(C`EV_DEFAULT\*(C'\fR when initialising the first
4427watcher in a function but use \f(CW\*(C`EV_DEFAULT_UC\*(C'\fR afterwards.
2309.PP 4428.PP
2310Example: Declare and initialise a check watcher, utilising the above 4429Example: Declare and initialise a check watcher, utilising the above
2311macros so it will work regardless of whether multiple loops are supported 4430macros so it will work regardless of whether multiple loops are supported
2312or not. 4431or not.
2313.PP 4432.PP
2314.Vb 5 4433.Vb 5
2315\& static void 4434\& static void
2316\& check_cb (EV_P_ ev_timer *w, int revents) 4435\& check_cb (EV_P_ ev_timer *w, int revents)
2317\& { 4436\& {
2318\& ev_check_stop (EV_A_ w); 4437\& ev_check_stop (EV_A_ w);
2319\& } 4438\& }
2320.Ve 4439\&
2321.PP
2322.Vb 4
2323\& ev_check check; 4440\& ev_check check;
2324\& ev_check_init (&check, check_cb); 4441\& ev_check_init (&check, check_cb);
2325\& ev_check_start (EV_DEFAULT_ &check); 4442\& ev_check_start (EV_DEFAULT_ &check);
2326\& ev_loop (EV_DEFAULT_ 0); 4443\& ev_run (EV_DEFAULT_ 0);
2327.Ve 4444.Ve
2328.SH "EMBEDDING" 4445.SH "EMBEDDING"
2329.IX Header "EMBEDDING" 4446.IX Header "EMBEDDING"
2330Libev can (and often is) directly embedded into host 4447Libev can (and often is) directly embedded into host
2331applications. Examples of applications that embed it include the Deliantra 4448applications. Examples of applications that embed it include the Deliantra
2332Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe) 4449Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe)
2333and rxvt\-unicode. 4450and rxvt-unicode.
2334.PP 4451.PP
2335The goal is to enable you to just copy the neecssary files into your 4452The goal is to enable you to just copy the necessary files into your
2336source directory without having to change even a single line in them, so 4453source directory without having to change even a single line in them, so
2337you can easily upgrade by simply copying (or having a checked-out copy of 4454you can easily upgrade by simply copying (or having a checked-out copy of
2338libev somewhere in your source tree). 4455libev somewhere in your source tree).
2339.Sh "\s-1FILESETS\s0" 4456.SS "\s-1FILESETS\s0"
2340.IX Subsection "FILESETS" 4457.IX Subsection "FILESETS"
2341Depending on what features you need you need to include one or more sets of files 4458Depending on what features you need you need to include one or more sets of files
2342in your app. 4459in your application.
2343.PP 4460.PP
2344\fI\s-1CORE\s0 \s-1EVENT\s0 \s-1LOOP\s0\fR 4461\fI\s-1CORE\s0 \s-1EVENT\s0 \s-1LOOP\s0\fR
2345.IX Subsection "CORE EVENT LOOP" 4462.IX Subsection "CORE EVENT LOOP"
2346.PP 4463.PP
2347To include only the libev core (all the \f(CW\*(C`ev_*\*(C'\fR functions), with manual 4464To include only the libev core (all the \f(CW\*(C`ev_*\*(C'\fR functions), with manual
2348configuration (no autoconf): 4465configuration (no autoconf):
2349.PP 4466.PP
2350.Vb 2 4467.Vb 2
2351\& #define EV_STANDALONE 1 4468\& #define EV_STANDALONE 1
2352\& #include "ev.c" 4469\& #include "ev.c"
2353.Ve 4470.Ve
2354.PP 4471.PP
2355This will automatically include \fIev.h\fR, too, and should be done in a 4472This will automatically include \fIev.h\fR, too, and should be done in a
2356single C source file only to provide the function implementations. To use 4473single C source file only to provide the function implementations. To use
2357it, do the same for \fIev.h\fR in all files wishing to use this \s-1API\s0 (best 4474it, do the same for \fIev.h\fR in all files wishing to use this \s-1API\s0 (best
2358done by writing a wrapper around \fIev.h\fR that you can include instead and 4475done by writing a wrapper around \fIev.h\fR that you can include instead and
2359where you can put other configuration options): 4476where you can put other configuration options):
2360.PP 4477.PP
2361.Vb 2 4478.Vb 2
2362\& #define EV_STANDALONE 1 4479\& #define EV_STANDALONE 1
2363\& #include "ev.h" 4480\& #include "ev.h"
2364.Ve 4481.Ve
2365.PP 4482.PP
2366Both header files and implementation files can be compiled with a \*(C+ 4483Both header files and implementation files can be compiled with a \*(C+
2367compiler (at least, thats a stated goal, and breakage will be treated 4484compiler (at least, that's a stated goal, and breakage will be treated
2368as a bug). 4485as a bug).
2369.PP 4486.PP
2370You need the following files in your source tree, or in a directory 4487You need the following files in your source tree, or in a directory
2371in your include path (e.g. in libev/ when using \-Ilibev): 4488in your include path (e.g. in libev/ when using \-Ilibev):
2372.PP 4489.PP
2373.Vb 4 4490.Vb 4
2374\& ev.h 4491\& ev.h
2375\& ev.c 4492\& ev.c
2376\& ev_vars.h 4493\& ev_vars.h
2377\& ev_wrap.h 4494\& ev_wrap.h
2378.Ve 4495\&
2379.PP
2380.Vb 1
2381\& ev_win32.c required on win32 platforms only 4496\& ev_win32.c required on win32 platforms only
2382.Ve 4497\&
2383.PP
2384.Vb 5
2385\& ev_select.c only when select backend is enabled (which is enabled by default) 4498\& ev_select.c only when select backend is enabled (which is enabled by default)
2386\& ev_poll.c only when poll backend is enabled (disabled by default) 4499\& ev_poll.c only when poll backend is enabled (disabled by default)
2387\& ev_epoll.c only when the epoll backend is enabled (disabled by default) 4500\& ev_epoll.c only when the epoll backend is enabled (disabled by default)
2388\& ev_kqueue.c only when the kqueue backend is enabled (disabled by default) 4501\& ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2389\& ev_port.c only when the solaris port backend is enabled (disabled by default) 4502\& ev_port.c only when the solaris port backend is enabled (disabled by default)
2390.Ve 4503.Ve
2391.PP 4504.PP
2392\&\fIev.c\fR includes the backend files directly when enabled, so you only need 4505\&\fIev.c\fR includes the backend files directly when enabled, so you only need
2393to compile this single file. 4506to compile this single file.
2394.PP 4507.PP
… …
2396.IX Subsection "LIBEVENT COMPATIBILITY API" 4509.IX Subsection "LIBEVENT COMPATIBILITY API"
2397.PP 4510.PP
2398To include the libevent compatibility \s-1API\s0, also include: 4511To include the libevent compatibility \s-1API\s0, also include:
2399.PP 4512.PP
2400.Vb 1 4513.Vb 1
2401\& #include "event.c" 4514\& #include "event.c"
2402.Ve 4515.Ve
2403.PP 4516.PP
2404in the file including \fIev.c\fR, and: 4517in the file including \fIev.c\fR, and:
2405.PP 4518.PP
2406.Vb 1 4519.Vb 1
2407\& #include "event.h" 4520\& #include "event.h"
2408.Ve 4521.Ve
2409.PP 4522.PP
2410in the files that want to use the libevent \s-1API\s0. This also includes \fIev.h\fR. 4523in the files that want to use the libevent \s-1API\s0. This also includes \fIev.h\fR.
2411.PP 4524.PP
2412You need the following additional files for this: 4525You need the following additional files for this:
2413.PP 4526.PP
2414.Vb 2 4527.Vb 2
2415\& event.h 4528\& event.h
2416\& event.c 4529\& event.c
2417.Ve 4530.Ve
2418.PP 4531.PP
2419\fI\s-1AUTOCONF\s0 \s-1SUPPORT\s0\fR 4532\fI\s-1AUTOCONF\s0 \s-1SUPPORT\s0\fR
2420.IX Subsection "AUTOCONF SUPPORT" 4533.IX Subsection "AUTOCONF SUPPORT"
2421.PP 4534.PP
2422Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your config in 4535Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your configuration in
2423whatever way you want, you can also \f(CW\*(C`m4_include([libev.m4])\*(C'\fR in your 4536whatever way you want, you can also \f(CW\*(C`m4_include([libev.m4])\*(C'\fR in your
2424\&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR undefined. \fIev.c\fR will then 4537\&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR undefined. \fIev.c\fR will then
2425include \fIconfig.h\fR and configure itself accordingly. 4538include \fIconfig.h\fR and configure itself accordingly.
2426.PP 4539.PP
2427For this of course you need the m4 file: 4540For this of course you need the m4 file:
2428.PP 4541.PP
2429.Vb 1 4542.Vb 1
2430\& libev.m4 4543\& libev.m4
2431.Ve 4544.Ve
2432.Sh "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0" 4545.SS "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0"
2433.IX Subsection "PREPROCESSOR SYMBOLS/MACROS" 4546.IX Subsection "PREPROCESSOR SYMBOLS/MACROS"
2434Libev can be configured via a variety of preprocessor symbols you have to define 4547Libev can be configured via a variety of preprocessor symbols you have to
2435before including any of its files. The default is not to build for multiplicity 4548define before including (or compiling) any of its files. The default in
2436and only include the select backend. 4549the absence of autoconf is documented for every option.
4550.PP
4551Symbols marked with \*(L"(h)\*(R" do not change the \s-1ABI\s0, and can have different
4552values when compiling libev vs. including \fIev.h\fR, so it is permissible
4553to redefine them before including \fIev.h\fR without breaking compatibility
4554to a compiled library. All other symbols change the \s-1ABI\s0, which means all
4555users of libev and the libev code itself must be compiled with compatible
4556settings.
4557.IP "\s-1EV_COMPAT3\s0 (h)" 4
4558.IX Item "EV_COMPAT3 (h)"
4559Backwards compatibility is a major concern for libev. This is why this
4560release of libev comes with wrappers for the functions and symbols that
4561have been renamed between libev version 3 and 4.
4562.Sp
4563You can disable these wrappers (to test compatibility with future
4564versions) by defining \f(CW\*(C`EV_COMPAT3\*(C'\fR to \f(CW0\fR when compiling your
4565sources. This has the additional advantage that you can drop the \f(CW\*(C`struct\*(C'\fR
4566from \f(CW\*(C`struct ev_loop\*(C'\fR declarations, as libev will provide an \f(CW\*(C`ev_loop\*(C'\fR
4567typedef in that case.
4568.Sp
4569In some future version, the default for \f(CW\*(C`EV_COMPAT3\*(C'\fR will become \f(CW0\fR,
4570and in some even more future version the compatibility code will be
4571removed completely.
2437.IP "\s-1EV_STANDALONE\s0" 4 4572.IP "\s-1EV_STANDALONE\s0 (h)" 4
2438.IX Item "EV_STANDALONE" 4573.IX Item "EV_STANDALONE (h)"
2439Must always be \f(CW1\fR if you do not use autoconf configuration, which 4574Must always be \f(CW1\fR if you do not use autoconf configuration, which
2440keeps libev from including \fIconfig.h\fR, and it also defines dummy 4575keeps libev from including \fIconfig.h\fR, and it also defines dummy
2441implementations for some libevent functions (such as logging, which is not 4576implementations for some libevent functions (such as logging, which is not
2442supported). It will also not define any of the structs usually found in 4577supported). It will also not define any of the structs usually found in
2443\&\fIevent.h\fR that are not directly supported by the libev core alone. 4578\&\fIevent.h\fR that are not directly supported by the libev core alone.
4579.Sp
4580In standalone mode, libev will still try to automatically deduce the
4581configuration, but has to be more conservative.
4582.IP "\s-1EV_USE_FLOOR\s0" 4
4583.IX Item "EV_USE_FLOOR"
4584If defined to be \f(CW1\fR, libev will use the \f(CW\*(C`floor ()\*(C'\fR function for its
4585periodic reschedule calculations, otherwise libev will fall back on a
4586portable (slower) implementation. If you enable this, you usually have to
4587link against libm or something equivalent. Enabling this when the \f(CW\*(C`floor\*(C'\fR
4588function is not available will fail, so the safe default is to not enable
4589this.
2444.IP "\s-1EV_USE_MONOTONIC\s0" 4 4590.IP "\s-1EV_USE_MONOTONIC\s0" 4
2445.IX Item "EV_USE_MONOTONIC" 4591.IX Item "EV_USE_MONOTONIC"
2446If defined to be \f(CW1\fR, libev will try to detect the availability of the 4592If defined to be \f(CW1\fR, libev will try to detect the availability of the
2447monotonic clock option at both compiletime and runtime. Otherwise no use 4593monotonic clock option at both compile time and runtime. Otherwise no
2448of the monotonic clock option will be attempted. If you enable this, you 4594use of the monotonic clock option will be attempted. If you enable this,
2449usually have to link against librt or something similar. Enabling it when 4595you usually have to link against librt or something similar. Enabling it
2450the functionality isn't available is safe, though, althoguh you have 4596when the functionality isn't available is safe, though, although you have
2451to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR 4597to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR
2452function is hiding in (often \fI\-lrt\fR). 4598function is hiding in (often \fI\-lrt\fR). See also \f(CW\*(C`EV_USE_CLOCK_SYSCALL\*(C'\fR.
2453.IP "\s-1EV_USE_REALTIME\s0" 4 4599.IP "\s-1EV_USE_REALTIME\s0" 4
2454.IX Item "EV_USE_REALTIME" 4600.IX Item "EV_USE_REALTIME"
2455If defined to be \f(CW1\fR, libev will try to detect the availability of the 4601If defined to be \f(CW1\fR, libev will try to detect the availability of the
2456realtime clock option at compiletime (and assume its availability at 4602real-time clock option at compile time (and assume its availability
2457runtime if successful). Otherwise no use of the realtime clock option will 4603at runtime if successful). Otherwise no use of the real-time clock
2458be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get 4604option will be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR
2459(CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See tzhe note about libraries 4605by \f(CW\*(C`clock_get (CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect
2460in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though. 4606correctness. See the note about libraries in the description of
4607\&\f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though. Defaults to the opposite value of
4608\&\f(CW\*(C`EV_USE_CLOCK_SYSCALL\*(C'\fR.
4609.IP "\s-1EV_USE_CLOCK_SYSCALL\s0" 4
4610.IX Item "EV_USE_CLOCK_SYSCALL"
4611If defined to be \f(CW1\fR, libev will try to use a direct syscall instead
4612of calling the system-provided \f(CW\*(C`clock_gettime\*(C'\fR function. This option
4613exists because on GNU/Linux, \f(CW\*(C`clock_gettime\*(C'\fR is in \f(CW\*(C`librt\*(C'\fR, but \f(CW\*(C`librt\*(C'\fR
4614unconditionally pulls in \f(CW\*(C`libpthread\*(C'\fR, slowing down single-threaded
4615programs needlessly. Using a direct syscall is slightly slower (in
4616theory), because no optimised vdso implementation can be used, but avoids
4617the pthread dependency. Defaults to \f(CW1\fR on GNU/Linux with glibc 2.x or
4618higher, as it simplifies linking (no need for \f(CW\*(C`\-lrt\*(C'\fR).
4619.IP "\s-1EV_USE_NANOSLEEP\s0" 4
4620.IX Item "EV_USE_NANOSLEEP"
4621If defined to be \f(CW1\fR, libev will assume that \f(CW\*(C`nanosleep ()\*(C'\fR is available
4622and will use it for delays. Otherwise it will use \f(CW\*(C`select ()\*(C'\fR.
4623.IP "\s-1EV_USE_EVENTFD\s0" 4
4624.IX Item "EV_USE_EVENTFD"
4625If defined to be \f(CW1\fR, then libev will assume that \f(CW\*(C`eventfd ()\*(C'\fR is
4626available and will probe for kernel support at runtime. This will improve
4627\&\f(CW\*(C`ev_signal\*(C'\fR and \f(CW\*(C`ev_async\*(C'\fR performance and reduce resource consumption.
4628If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
46292.7 or newer, otherwise disabled.
2461.IP "\s-1EV_USE_SELECT\s0" 4 4630.IP "\s-1EV_USE_SELECT\s0" 4
2462.IX Item "EV_USE_SELECT" 4631.IX Item "EV_USE_SELECT"
2463If undefined or defined to be \f(CW1\fR, libev will compile in support for the 4632If undefined or defined to be \f(CW1\fR, libev will compile in support for the
2464\&\f(CW\*(C`select\*(C'\fR(2) backend. No attempt at autodetection will be done: if no 4633\&\f(CW\*(C`select\*(C'\fR(2) backend. No attempt at auto-detection will be done: if no
2465other method takes over, select will be it. Otherwise the select backend 4634other method takes over, select will be it. Otherwise the select backend
2466will not be compiled in. 4635will not be compiled in.
2467.IP "\s-1EV_SELECT_USE_FD_SET\s0" 4 4636.IP "\s-1EV_SELECT_USE_FD_SET\s0" 4
2468.IX Item "EV_SELECT_USE_FD_SET" 4637.IX Item "EV_SELECT_USE_FD_SET"
2469If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR 4638If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR
2470structure. This is useful if libev doesn't compile due to a missing 4639structure. This is useful if libev doesn't compile due to a missing
2471\&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it misguesses the bitset layout on 4640\&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it mis-guesses the bitset layout
2472exotic systems. This usually limits the range of file descriptors to some 4641on exotic systems. This usually limits the range of file descriptors to
2473low limit such as 1024 or might have other limitations (winsocket only 4642some low limit such as 1024 or might have other limitations (winsocket
2474allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation, might 4643only allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation,
2475influence the size of the \f(CW\*(C`fd_set\*(C'\fR used. 4644configures the maximum size of the \f(CW\*(C`fd_set\*(C'\fR.
2476.IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4 4645.IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4
2477.IX Item "EV_SELECT_IS_WINSOCKET" 4646.IX Item "EV_SELECT_IS_WINSOCKET"
2478When defined to \f(CW1\fR, the select backend will assume that 4647When defined to \f(CW1\fR, the select backend will assume that
2479select/socket/connect etc. don't understand file descriptors but 4648select/socket/connect etc. don't understand file descriptors but
2480wants osf handles on win32 (this is the case when the select to 4649wants osf handles on win32 (this is the case when the select to
2481be used is the winsock select). This means that it will call 4650be used is the winsock select). This means that it will call
2482\&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise, 4651\&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise,
2483it is assumed that all these functions actually work on fds, even 4652it is assumed that all these functions actually work on fds, even
2484on win32. Should not be defined on non\-win32 platforms. 4653on win32. Should not be defined on non\-win32 platforms.
4654.IP "\s-1EV_FD_TO_WIN32_HANDLE\s0(fd)" 4
4655.IX Item "EV_FD_TO_WIN32_HANDLE(fd)"
4656If \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR is enabled, then libev needs a way to map
4657file descriptors to socket handles. When not defining this symbol (the
4658default), then libev will call \f(CW\*(C`_get_osfhandle\*(C'\fR, which is usually
4659correct. In some cases, programs use their own file descriptor management,
4660in which case they can provide this function to map fds to socket handles.
4661.IP "\s-1EV_WIN32_HANDLE_TO_FD\s0(handle)" 4
4662.IX Item "EV_WIN32_HANDLE_TO_FD(handle)"
4663If \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR then libev maps handles to file descriptors
4664using the standard \f(CW\*(C`_open_osfhandle\*(C'\fR function. For programs implementing
4665their own fd to handle mapping, overwriting this function makes it easier
4666to do so. This can be done by defining this macro to an appropriate value.
4667.IP "\s-1EV_WIN32_CLOSE_FD\s0(fd)" 4
4668.IX Item "EV_WIN32_CLOSE_FD(fd)"
4669If programs implement their own fd to handle mapping on win32, then this
4670macro can be used to override the \f(CW\*(C`close\*(C'\fR function, useful to unregister
4671file descriptors again. Note that the replacement function has to close
4672the underlying \s-1OS\s0 handle.
2485.IP "\s-1EV_USE_POLL\s0" 4 4673.IP "\s-1EV_USE_POLL\s0" 4
2486.IX Item "EV_USE_POLL" 4674.IX Item "EV_USE_POLL"
2487If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2) 4675If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2)
2488backend. Otherwise it will be enabled on non\-win32 platforms. It 4676backend. Otherwise it will be enabled on non\-win32 platforms. It
2489takes precedence over select. 4677takes precedence over select.
2490.IP "\s-1EV_USE_EPOLL\s0" 4 4678.IP "\s-1EV_USE_EPOLL\s0" 4
2491.IX Item "EV_USE_EPOLL" 4679.IX Item "EV_USE_EPOLL"
2492If defined to be \f(CW1\fR, libev will compile in support for the Linux 4680If defined to be \f(CW1\fR, libev will compile in support for the Linux
2493\&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime, 4681\&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime,
2494otherwise another method will be used as fallback. This is the 4682otherwise another method will be used as fallback. This is the preferred
2495preferred backend for GNU/Linux systems. 4683backend for GNU/Linux systems. If undefined, it will be enabled if the
4684headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2496.IP "\s-1EV_USE_KQUEUE\s0" 4 4685.IP "\s-1EV_USE_KQUEUE\s0" 4
2497.IX Item "EV_USE_KQUEUE" 4686.IX Item "EV_USE_KQUEUE"
2498If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style 4687If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style
2499\&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime, 4688\&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime,
2500otherwise another method will be used as fallback. This is the preferred 4689otherwise another method will be used as fallback. This is the preferred
… …
251010 port style backend. Its availability will be detected at runtime, 469910 port style backend. Its availability will be detected at runtime,
2511otherwise another method will be used as fallback. This is the preferred 4700otherwise another method will be used as fallback. This is the preferred
2512backend for Solaris 10 systems. 4701backend for Solaris 10 systems.
2513.IP "\s-1EV_USE_DEVPOLL\s0" 4 4702.IP "\s-1EV_USE_DEVPOLL\s0" 4
2514.IX Item "EV_USE_DEVPOLL" 4703.IX Item "EV_USE_DEVPOLL"
2515reserved for future expansion, works like the \s-1USE\s0 symbols above. 4704Reserved for future expansion, works like the \s-1USE\s0 symbols above.
2516.IP "\s-1EV_USE_INOTIFY\s0" 4 4705.IP "\s-1EV_USE_INOTIFY\s0" 4
2517.IX Item "EV_USE_INOTIFY" 4706.IX Item "EV_USE_INOTIFY"
2518If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify 4707If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify
2519interface to speed up \f(CW\*(C`ev_stat\*(C'\fR watchers. Its actual availability will 4708interface to speed up \f(CW\*(C`ev_stat\*(C'\fR watchers. Its actual availability will
2520be detected at runtime. 4709be detected at runtime. If undefined, it will be enabled if the headers
4710indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
4711.IP "\s-1EV_NO_SMP\s0" 4
4712.IX Item "EV_NO_SMP"
4713If defined to be \f(CW1\fR, libev will assume that memory is always coherent
4714between threads, that is, threads can be used, but threads never run on
4715different cpus (or different cpu cores). This reduces dependencies
4716and makes libev faster.
4717.IP "\s-1EV_NO_THREADS\s0" 4
4718.IX Item "EV_NO_THREADS"
4719If defined to be \f(CW1\fR, libev will assume that it will never be called
4720from different threads, which is a stronger assumption than \f(CW\*(C`EV_NO_SMP\*(C'\fR,
4721above. This reduces dependencies and makes libev faster.
4722.IP "\s-1EV_ATOMIC_T\s0" 4
4723.IX Item "EV_ATOMIC_T"
4724Libev requires an integer type (suitable for storing \f(CW0\fR or \f(CW1\fR) whose
4725access is atomic and serialised with respect to other threads or signal
4726contexts. No such type is easily found in the C language, so you can
4727provide your own type that you know is safe for your purposes. It is used
4728both for signal handler \*(L"locking\*(R" as well as for signal and thread safety
4729in \f(CW\*(C`ev_async\*(C'\fR watchers.
4730.Sp
4731In the absence of this define, libev will use \f(CW\*(C`sig_atomic_t volatile\*(C'\fR
4732(from \fIsignal.h\fR), which is usually good enough on most platforms,
4733although strictly speaking using a type that also implies a memory fence
4734is required.
2521.IP "\s-1EV_H\s0" 4 4735.IP "\s-1EV_H\s0 (h)" 4
2522.IX Item "EV_H" 4736.IX Item "EV_H (h)"
2523The name of the \fIev.h\fR header file used to include it. The default if 4737The name of the \fIev.h\fR header file used to include it. The default if
2524undefined is \f(CW\*(C`<ev.h>\*(C'\fR in \fIevent.h\fR and \f(CW"ev.h"\fR in \fIev.c\fR. This 4738undefined is \f(CW"ev.h"\fR in \fIevent.h\fR, \fIev.c\fR and \fIev++.h\fR. This can be
2525can be used to virtually rename the \fIev.h\fR header file in case of conflicts. 4739used to virtually rename the \fIev.h\fR header file in case of conflicts.
2526.IP "\s-1EV_CONFIG_H\s0" 4 4740.IP "\s-1EV_CONFIG_H\s0 (h)" 4
2527.IX Item "EV_CONFIG_H" 4741.IX Item "EV_CONFIG_H (h)"
2528If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override 4742If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override
2529\&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to 4743\&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to
2530\&\f(CW\*(C`EV_H\*(C'\fR, above. 4744\&\f(CW\*(C`EV_H\*(C'\fR, above.
2531.IP "\s-1EV_EVENT_H\s0" 4 4745.IP "\s-1EV_EVENT_H\s0 (h)" 4
2532.IX Item "EV_EVENT_H" 4746.IX Item "EV_EVENT_H (h)"
2533Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea 4747Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea
2534of how the \fIevent.h\fR header can be found. 4748of how the \fIevent.h\fR header can be found, the default is \f(CW"event.h"\fR.
2535.IP "\s-1EV_PROTOTYPES\s0" 4 4749.IP "\s-1EV_PROTOTYPES\s0 (h)" 4
2536.IX Item "EV_PROTOTYPES" 4750.IX Item "EV_PROTOTYPES (h)"
2537If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function 4751If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function
2538prototypes, but still define all the structs and other symbols. This is 4752prototypes, but still define all the structs and other symbols. This is
2539occasionally useful if you want to provide your own wrapper functions 4753occasionally useful if you want to provide your own wrapper functions
2540around libev functions. 4754around libev functions.
2541.IP "\s-1EV_MULTIPLICITY\s0" 4 4755.IP "\s-1EV_MULTIPLICITY\s0" 4
… …
2543If undefined or defined to \f(CW1\fR, then all event-loop-specific functions 4757If undefined or defined to \f(CW1\fR, then all event-loop-specific functions
2544will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create 4758will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create
2545additional independent event loops. Otherwise there will be no support 4759additional independent event loops. Otherwise there will be no support
2546for multiple event loops and there is no first event loop pointer 4760for multiple event loops and there is no first event loop pointer
2547argument. Instead, all functions act on the single default loop. 4761argument. Instead, all functions act on the single default loop.
4762.Sp
4763Note that \f(CW\*(C`EV_DEFAULT\*(C'\fR and \f(CW\*(C`EV_DEFAULT_\*(C'\fR will no longer provide a
4764default loop when multiplicity is switched off \- you always have to
4765initialise the loop manually in this case.
2548.IP "\s-1EV_MINPRI\s0" 4 4766.IP "\s-1EV_MINPRI\s0" 4
2549.IX Item "EV_MINPRI" 4767.IX Item "EV_MINPRI"
2550.PD 0 4768.PD 0
2551.IP "\s-1EV_MAXPRI\s0" 4 4769.IP "\s-1EV_MAXPRI\s0" 4
2552.IX Item "EV_MAXPRI" 4770.IX Item "EV_MAXPRI"
… …
2559When doing priority-based operations, libev usually has to linearly search 4777When doing priority-based operations, libev usually has to linearly search
2560all the priorities, so having many of them (hundreds) uses a lot of space 4778all the priorities, so having many of them (hundreds) uses a lot of space
2561and time, so using the defaults of five priorities (\-2 .. +2) is usually 4779and time, so using the defaults of five priorities (\-2 .. +2) is usually
2562fine. 4780fine.
2563.Sp 4781.Sp
2564If your embedding app does not need any priorities, defining these both to 4782If your embedding application does not need any priorities, defining these
2565\&\f(CW0\fR will save some memory and cpu. 4783both to \f(CW0\fR will save some memory and \s-1CPU\s0.
2566.IP "\s-1EV_PERIODIC_ENABLE\s0" 4 4784.IP "\s-1EV_PERIODIC_ENABLE\s0, \s-1EV_IDLE_ENABLE\s0, \s-1EV_EMBED_ENABLE\s0, \s-1EV_STAT_ENABLE\s0, \s-1EV_PREPARE_ENABLE\s0, \s-1EV_CHECK_ENABLE\s0, \s-1EV_FORK_ENABLE\s0, \s-1EV_SIGNAL_ENABLE\s0, \s-1EV_ASYNC_ENABLE\s0, \s-1EV_CHILD_ENABLE\s0." 4
2567.IX Item "EV_PERIODIC_ENABLE" 4785.IX Item "EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE, EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE, EV_ASYNC_ENABLE, EV_CHILD_ENABLE."
2568If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If 4786If undefined or defined to be \f(CW1\fR (and the platform supports it), then
2569defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of 4787the respective watcher type is supported. If defined to be \f(CW0\fR, then it
2570code. 4788is not. Disabling watcher types mainly saves code size.
2571.IP "\s-1EV_IDLE_ENABLE\s0" 4
2572.IX Item "EV_IDLE_ENABLE"
2573If undefined or defined to be \f(CW1\fR, then idle watchers are supported. If
2574defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
2575code.
2576.IP "\s-1EV_EMBED_ENABLE\s0" 4
2577.IX Item "EV_EMBED_ENABLE"
2578If undefined or defined to be \f(CW1\fR, then embed watchers are supported. If
2579defined to be \f(CW0\fR, then they are not.
2580.IP "\s-1EV_STAT_ENABLE\s0" 4 4789.IP "\s-1EV_FEATURES\s0" 4
2581.IX Item "EV_STAT_ENABLE" 4790.IX Item "EV_FEATURES"
2582If undefined or defined to be \f(CW1\fR, then stat watchers are supported. If
2583defined to be \f(CW0\fR, then they are not.
2584.IP "\s-1EV_FORK_ENABLE\s0" 4
2585.IX Item "EV_FORK_ENABLE"
2586If undefined or defined to be \f(CW1\fR, then fork watchers are supported. If
2587defined to be \f(CW0\fR, then they are not.
2588.IP "\s-1EV_MINIMAL\s0" 4
2589.IX Item "EV_MINIMAL"
2590If you need to shave off some kilobytes of code at the expense of some 4791If you need to shave off some kilobytes of code at the expense of some
2591speed, define this symbol to \f(CW1\fR. Currently only used for gcc to override 4792speed (but with the full \s-1API\s0), you can define this symbol to request
2592some inlining decisions, saves roughly 30% codesize of amd64. 4793certain subsets of functionality. The default is to enable all features
4794that can be enabled on the platform.
4795.Sp
4796A typical way to use this symbol is to define it to \f(CW0\fR (or to a bitset
4797with some broad features you want) and then selectively re-enable
4798additional parts you want, for example if you want everything minimal,
4799but multiple event loop support, async and child watchers and the poll
4800backend, use this:
4801.Sp
4802.Vb 5
4803\& #define EV_FEATURES 0
4804\& #define EV_MULTIPLICITY 1
4805\& #define EV_USE_POLL 1
4806\& #define EV_CHILD_ENABLE 1
4807\& #define EV_ASYNC_ENABLE 1
4808.Ve
4809.Sp
4810The actual value is a bitset, it can be a combination of the following
4811values (by default, all of these are enabled):
4812.RS 4
4813.ie n .IP "1 \- faster/larger code" 4
4814.el .IP "\f(CW1\fR \- faster/larger code" 4
4815.IX Item "1 - faster/larger code"
4816Use larger code to speed up some operations.
4817.Sp
4818Currently this is used to override some inlining decisions (enlarging the
4819code size by roughly 30% on amd64).
4820.Sp
4821When optimising for size, use of compiler flags such as \f(CW\*(C`\-Os\*(C'\fR with
4822gcc is recommended, as well as \f(CW\*(C`\-DNDEBUG\*(C'\fR, as libev contains a number of
4823assertions.
4824.Sp
4825The default is off when \f(CW\*(C`_\|_OPTIMIZE_SIZE_\|_\*(C'\fR is defined by your compiler
4826(e.g. gcc with \f(CW\*(C`\-Os\*(C'\fR).
4827.ie n .IP "2 \- faster/larger data structures" 4
4828.el .IP "\f(CW2\fR \- faster/larger data structures" 4
4829.IX Item "2 - faster/larger data structures"
4830Replaces the small 2\-heap for timer management by a faster 4\-heap, larger
4831hash table sizes and so on. This will usually further increase code size
4832and can additionally have an effect on the size of data structures at
4833runtime.
4834.Sp
4835The default is off when \f(CW\*(C`_\|_OPTIMIZE_SIZE_\|_\*(C'\fR is defined by your compiler
4836(e.g. gcc with \f(CW\*(C`\-Os\*(C'\fR).
4837.ie n .IP "4 \- full \s-1API\s0 configuration" 4
4838.el .IP "\f(CW4\fR \- full \s-1API\s0 configuration" 4
4839.IX Item "4 - full API configuration"
4840This enables priorities (sets \f(CW\*(C`EV_MAXPRI\*(C'\fR=2 and \f(CW\*(C`EV_MINPRI\*(C'\fR=\-2), and
4841enables multiplicity (\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR=1).
4842.ie n .IP "8 \- full \s-1API\s0" 4
4843.el .IP "\f(CW8\fR \- full \s-1API\s0" 4
4844.IX Item "8 - full API"
4845This enables a lot of the \*(L"lesser used\*(R" \s-1API\s0 functions. See \f(CW\*(C`ev.h\*(C'\fR for
4846details on which parts of the \s-1API\s0 are still available without this
4847feature, and do not complain if this subset changes over time.
4848.ie n .IP "16 \- enable all optional watcher types" 4
4849.el .IP "\f(CW16\fR \- enable all optional watcher types" 4
4850.IX Item "16 - enable all optional watcher types"
4851Enables all optional watcher types. If you want to selectively enable
4852only some watcher types other than I/O and timers (e.g. prepare,
4853embed, async, child...) you can enable them manually by defining
4854\&\f(CW\*(C`EV_watchertype_ENABLE\*(C'\fR to \f(CW1\fR instead.
4855.ie n .IP "32 \- enable all backends" 4
4856.el .IP "\f(CW32\fR \- enable all backends" 4
4857.IX Item "32 - enable all backends"
4858This enables all backends \- without this feature, you need to enable at
4859least one backend manually (\f(CW\*(C`EV_USE_SELECT\*(C'\fR is a good choice).
4860.ie n .IP "64 \- enable OS-specific ""helper"" APIs" 4
4861.el .IP "\f(CW64\fR \- enable OS-specific ``helper'' APIs" 4
4862.IX Item "64 - enable OS-specific helper APIs"
4863Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
4864default.
4865.RE
4866.RS 4
4867.Sp
4868Compiling with \f(CW\*(C`gcc \-Os \-DEV_STANDALONE \-DEV_USE_EPOLL=1 \-DEV_FEATURES=0\*(C'\fR
4869reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
4870code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
4871watchers, timers and monotonic clock support.
4872.Sp
4873With an intelligent-enough linker (gcc+binutils are intelligent enough
4874when you use \f(CW\*(C`\-Wl,\-\-gc\-sections \-ffunction\-sections\*(C'\fR) functions unused by
4875your program might be left out as well \- a binary starting a timer and an
4876I/O watcher then might come out at only 5Kb.
4877.RE
4878.IP "\s-1EV_API_STATIC\s0" 4
4879.IX Item "EV_API_STATIC"
4880If this symbol is defined (by default it is not), then all identifiers
4881will have static linkage. This means that libev will not export any
4882identifiers, and you cannot link against libev anymore. This can be useful
4883when you embed libev, only want to use libev functions in a single file,
4884and do not want its identifiers to be visible.
4885.Sp
4886To use this, define \f(CW\*(C`EV_API_STATIC\*(C'\fR and include \fIev.c\fR in the file that
4887wants to use libev.
4888.Sp
4889This option only works when libev is compiled with a C compiler, as \*(C+
4890doesn't support the required declaration syntax.
4891.IP "\s-1EV_AVOID_STDIO\s0" 4
4892.IX Item "EV_AVOID_STDIO"
4893If this is set to \f(CW1\fR at compiletime, then libev will avoid using stdio
4894functions (printf, scanf, perror etc.). This will increase the code size
4895somewhat, but if your program doesn't otherwise depend on stdio and your
4896libc allows it, this avoids linking in the stdio library which is quite
4897big.
4898.Sp
4899Note that error messages might become less precise when this option is
4900enabled.
4901.IP "\s-1EV_NSIG\s0" 4
4902.IX Item "EV_NSIG"
4903The highest supported signal number, +1 (or, the number of
4904signals): Normally, libev tries to deduce the maximum number of signals
4905automatically, but sometimes this fails, in which case it can be
4906specified. Also, using a lower number than detected (\f(CW32\fR should be
4907good for about any system in existence) can save some memory, as libev
4908statically allocates some 12\-24 bytes per signal number.
2593.IP "\s-1EV_PID_HASHSIZE\s0" 4 4909.IP "\s-1EV_PID_HASHSIZE\s0" 4
2594.IX Item "EV_PID_HASHSIZE" 4910.IX Item "EV_PID_HASHSIZE"
2595\&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by 4911\&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by
2596pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), usually more 4912pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_FEATURES\*(C'\fR disabled),
2597than enough. If you need to manage thousands of children you might want to 4913usually more than enough. If you need to manage thousands of children you
2598increase this value (\fImust\fR be a power of two). 4914might want to increase this value (\fImust\fR be a power of two).
2599.IP "\s-1EV_INOTIFY_HASHSIZE\s0" 4 4915.IP "\s-1EV_INOTIFY_HASHSIZE\s0" 4
2600.IX Item "EV_INOTIFY_HASHSIZE" 4916.IX Item "EV_INOTIFY_HASHSIZE"
2601\&\f(CW\*(C`ev_staz\*(C'\fR watchers use a small hash table to distribute workload by 4917\&\f(CW\*(C`ev_stat\*(C'\fR watchers use a small hash table to distribute workload by
2602inotify watch id. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), 4918inotify watch id. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_FEATURES\*(C'\fR
2603usually more than enough. If you need to manage thousands of \f(CW\*(C`ev_stat\*(C'\fR 4919disabled), usually more than enough. If you need to manage thousands of
2604watchers you might want to increase this value (\fImust\fR be a power of 4920\&\f(CW\*(C`ev_stat\*(C'\fR watchers you might want to increase this value (\fImust\fR be a
2605two). 4921power of two).
4922.IP "\s-1EV_USE_4HEAP\s0" 4
4923.IX Item "EV_USE_4HEAP"
4924Heaps are not very cache-efficient. To improve the cache-efficiency of the
4925timer and periodics heaps, libev uses a 4\-heap when this symbol is defined
4926to \f(CW1\fR. The 4\-heap uses more complicated (longer) code but has noticeably
4927faster performance with many (thousands) of watchers.
4928.Sp
4929The default is \f(CW1\fR, unless \f(CW\*(C`EV_FEATURES\*(C'\fR overrides it, in which case it
4930will be \f(CW0\fR.
4931.IP "\s-1EV_HEAP_CACHE_AT\s0" 4
4932.IX Item "EV_HEAP_CACHE_AT"
4933Heaps are not very cache-efficient. To improve the cache-efficiency of the
4934timer and periodics heaps, libev can cache the timestamp (\fIat\fR) within
4935the heap structure (selected by defining \f(CW\*(C`EV_HEAP_CACHE_AT\*(C'\fR to \f(CW1\fR),
4936which uses 8\-12 bytes more per watcher and a few hundred bytes more code,
4937but avoids random read accesses on heap changes. This improves performance
4938noticeably with many (hundreds) of watchers.
4939.Sp
4940The default is \f(CW1\fR, unless \f(CW\*(C`EV_FEATURES\*(C'\fR overrides it, in which case it
4941will be \f(CW0\fR.
4942.IP "\s-1EV_VERIFY\s0" 4
4943.IX Item "EV_VERIFY"
4944Controls how much internal verification (see \f(CW\*(C`ev_verify ()\*(C'\fR) will
4945be done: If set to \f(CW0\fR, no internal verification code will be compiled
4946in. If set to \f(CW1\fR, then verification code will be compiled in, but not
4947called. If set to \f(CW2\fR, then the internal verification code will be
4948called once per loop, which can slow down libev. If set to \f(CW3\fR, then the
4949verification code will be called very frequently, which will slow down
4950libev considerably.
4951.Sp
4952The default is \f(CW1\fR, unless \f(CW\*(C`EV_FEATURES\*(C'\fR overrides it, in which case it
4953will be \f(CW0\fR.
2606.IP "\s-1EV_COMMON\s0" 4 4954.IP "\s-1EV_COMMON\s0" 4
2607.IX Item "EV_COMMON" 4955.IX Item "EV_COMMON"
2608By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining 4956By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining
2609this macro to a something else you can include more and other types of 4957this macro to something else you can include more and other types of
2610members. You have to define it each time you include one of the files, 4958members. You have to define it each time you include one of the files,
2611though, and it must be identical each time. 4959though, and it must be identical each time.
2612.Sp 4960.Sp
2613For example, the perl \s-1EV\s0 module uses something like this: 4961For example, the perl \s-1EV\s0 module uses something like this:
2614.Sp 4962.Sp
2615.Vb 3 4963.Vb 3
2616\& #define EV_COMMON \e 4964\& #define EV_COMMON \e
2617\& SV *self; /* contains this struct */ \e 4965\& SV *self; /* contains this struct */ \e
2618\& SV *cb_sv, *fh /* note no trailing ";" */ 4966\& SV *cb_sv, *fh /* note no trailing ";" */
2619.Ve 4967.Ve
2620.IP "\s-1EV_CB_DECLARE\s0 (type)" 4 4968.IP "\s-1EV_CB_DECLARE\s0 (type)" 4
2621.IX Item "EV_CB_DECLARE (type)" 4969.IX Item "EV_CB_DECLARE (type)"
2622.PD 0 4970.PD 0
2623.IP "\s-1EV_CB_INVOKE\s0 (watcher, revents)" 4 4971.IP "\s-1EV_CB_INVOKE\s0 (watcher, revents)" 4
… …
2625.IP "ev_set_cb (ev, cb)" 4 4973.IP "ev_set_cb (ev, cb)" 4
2626.IX Item "ev_set_cb (ev, cb)" 4974.IX Item "ev_set_cb (ev, cb)"
2627.PD 4975.PD
2628Can be used to change the callback member declaration in each watcher, 4976Can be used to change the callback member declaration in each watcher,
2629and the way callbacks are invoked and set. Must expand to a struct member 4977and the way callbacks are invoked and set. Must expand to a struct member
2630definition and a statement, respectively. See the \fIev.v\fR header file for 4978definition and a statement, respectively. See the \fIev.h\fR header file for
2631their default definitions. One possible use for overriding these is to 4979their default definitions. One possible use for overriding these is to
2632avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use 4980avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use
2633method calls instead of plain function calls in \*(C+. 4981method calls instead of plain function calls in \*(C+.
2634.Sh "\s-1EXPORTED\s0 \s-1API\s0 \s-1SYMBOLS\s0" 4982.SS "\s-1EXPORTED\s0 \s-1API\s0 \s-1SYMBOLS\s0"
2635.IX Subsection "EXPORTED API SYMBOLS" 4983.IX Subsection "EXPORTED API SYMBOLS"
2636If you need to re-export the \s-1API\s0 (e.g. via a dll) and you need a list of 4984If you need to re-export the \s-1API\s0 (e.g. via a \s-1DLL\s0) and you need a list of
2637exported symbols, you can use the provided \fISymbol.*\fR files which list 4985exported symbols, you can use the provided \fISymbol.*\fR files which list
2638all public symbols, one per line: 4986all public symbols, one per line:
2639.Sp 4987.PP
2640.Vb 2 4988.Vb 2
2641\& Symbols.ev for libev proper 4989\& Symbols.ev for libev proper
2642\& Symbols.event for the libevent emulation 4990\& Symbols.event for the libevent emulation
2643.Ve 4991.Ve
2644.Sp 4992.PP
2645This can also be used to rename all public symbols to avoid clashes with 4993This can also be used to rename all public symbols to avoid clashes with
2646multiple versions of libev linked together (which is obviously bad in 4994multiple versions of libev linked together (which is obviously bad in
2647itself, but sometimes it is inconvinient to avoid this). 4995itself, but sometimes it is inconvenient to avoid this).
2648.Sp 4996.PP
2649A sed comamnd like this will create wrapper \f(CW\*(C`#define\*(C'\fR's that you need to 4997A sed command like this will create wrapper \f(CW\*(C`#define\*(C'\fR's that you need to
2650include before including \fIev.h\fR: 4998include before including \fIev.h\fR:
2651.Sp 4999.PP
2652.Vb 1 5000.Vb 1
2653\& <Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h 5001\& <Symbols.ev sed \-e "s/.*/#define & myprefix_&/" >wrap.h
2654.Ve 5002.Ve
2655.Sp 5003.PP
2656This would create a file \fIwrap.h\fR which essentially looks like this: 5004This would create a file \fIwrap.h\fR which essentially looks like this:
2657.Sp 5005.PP
2658.Vb 4 5006.Vb 4
2659\& #define ev_backend myprefix_ev_backend 5007\& #define ev_backend myprefix_ev_backend
2660\& #define ev_check_start myprefix_ev_check_start 5008\& #define ev_check_start myprefix_ev_check_start
2661\& #define ev_check_stop myprefix_ev_check_stop 5009\& #define ev_check_stop myprefix_ev_check_stop
2662\& ... 5010\& ...
2663.Ve 5011.Ve
2664.Sh "\s-1EXAMPLES\s0" 5012.SS "\s-1EXAMPLES\s0"
2665.IX Subsection "EXAMPLES" 5013.IX Subsection "EXAMPLES"
2666For a real-world example of a program the includes libev 5014For a real-world example of a program the includes libev
2667verbatim, you can have a look at the \s-1EV\s0 perl module 5015verbatim, you can have a look at the \s-1EV\s0 perl module
2668(<http://software.schmorp.de/pkg/EV.html>). It has the libev files in 5016(<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
2669the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public 5017the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public
2670interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file 5018interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file
2671will be compiled. It is pretty complex because it provides its own header 5019will be compiled. It is pretty complex because it provides its own header
2672file. 5020file.
2673.Sp 5021.PP
2674The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file 5022The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file
2675that everybody includes and which overrides some configure choices: 5023that everybody includes and which overrides some configure choices:
2676.Sp 5024.PP
2677.Vb 9 5025.Vb 8
2678\& #define EV_MINIMAL 1 5026\& #define EV_FEATURES 8
2679\& #define EV_USE_POLL 0 5027\& #define EV_USE_SELECT 1
2680\& #define EV_MULTIPLICITY 0
2681\& #define EV_PERIODIC_ENABLE 0 5028\& #define EV_PREPARE_ENABLE 1
5029\& #define EV_IDLE_ENABLE 1
2682\& #define EV_STAT_ENABLE 0 5030\& #define EV_SIGNAL_ENABLE 1
2683\& #define EV_FORK_ENABLE 0 5031\& #define EV_CHILD_ENABLE 1
5032\& #define EV_USE_STDEXCEPT 0
2684\& #define EV_CONFIG_H <config.h> 5033\& #define EV_CONFIG_H <config.h>
2685\& #define EV_MINPRI 0 5034\&
2686\& #define EV_MAXPRI 0
2687.Ve
2688.Sp
2689.Vb 1
2690\& #include "ev++.h" 5035\& #include "ev++.h"
2691.Ve 5036.Ve
2692.Sp 5037.PP
2693And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled: 5038And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled:
2694.Sp 5039.PP
2695.Vb 2 5040.Vb 2
2696\& #include "ev_cpp.h" 5041\& #include "ev_cpp.h"
2697\& #include "ev.c" 5042\& #include "ev.c"
2698.Ve 5043.Ve
5044.SH "INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT"
5045.IX Header "INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT"
5046.SS "\s-1THREADS\s0 \s-1AND\s0 \s-1COROUTINES\s0"
5047.IX Subsection "THREADS AND COROUTINES"
5048\fI\s-1THREADS\s0\fR
5049.IX Subsection "THREADS"
5050.PP
5051All libev functions are reentrant and thread-safe unless explicitly
5052documented otherwise, but libev implements no locking itself. This means
5053that you can use as many loops as you want in parallel, as long as there
5054are no concurrent calls into any libev function with the same loop
5055parameter (\f(CW\*(C`ev_default_*\*(C'\fR calls have an implicit default loop parameter,
5056of course): libev guarantees that different event loops share no data
5057structures that need any locking.
5058.PP
5059Or to put it differently: calls with different loop parameters can be done
5060concurrently from multiple threads, calls with the same loop parameter
5061must be done serially (but can be done from different threads, as long as
5062only one thread ever is inside a call at any point in time, e.g. by using
5063a mutex per loop).
5064.PP
5065Specifically to support threads (and signal handlers), libev implements
5066so-called \f(CW\*(C`ev_async\*(C'\fR watchers, which allow some limited form of
5067concurrency on the same event loop, namely waking it up \*(L"from the
5068outside\*(R".
5069.PP
5070If you want to know which design (one loop, locking, or multiple loops
5071without or something else still) is best for your problem, then I cannot
5072help you, but here is some generic advice:
5073.IP "\(bu" 4
5074most applications have a main thread: use the default libev loop
5075in that thread, or create a separate thread running only the default loop.
5076.Sp
5077This helps integrating other libraries or software modules that use libev
5078themselves and don't care/know about threading.
5079.IP "\(bu" 4
5080one loop per thread is usually a good model.
5081.Sp
5082Doing this is almost never wrong, sometimes a better-performance model
5083exists, but it is always a good start.
5084.IP "\(bu" 4
5085other models exist, such as the leader/follower pattern, where one
5086loop is handed through multiple threads in a kind of round-robin fashion.
5087.Sp
5088Choosing a model is hard \- look around, learn, know that usually you can do
5089better than you currently do :\-)
5090.IP "\(bu" 4
5091often you need to talk to some other thread which blocks in the
5092event loop.
5093.Sp
5094\&\f(CW\*(C`ev_async\*(C'\fR watchers can be used to wake them up from other threads safely
5095(or from signal contexts...).
5096.Sp
5097An example use would be to communicate signals or other events that only
5098work in the default loop by registering the signal watcher with the
5099default loop and triggering an \f(CW\*(C`ev_async\*(C'\fR watcher from the default loop
5100watcher callback into the event loop interested in the signal.
5101.PP
5102See also \*(L"\s-1THREAD\s0 \s-1LOCKING\s0 \s-1EXAMPLE\s0\*(R".
5103.PP
5104\fI\s-1COROUTINES\s0\fR
5105.IX Subsection "COROUTINES"
5106.PP
5107Libev is very accommodating to coroutines (\*(L"cooperative threads\*(R"):
5108libev fully supports nesting calls to its functions from different
5109coroutines (e.g. you can call \f(CW\*(C`ev_run\*(C'\fR on the same loop from two
5110different coroutines, and switch freely between both coroutines running
5111the loop, as long as you don't confuse yourself). The only exception is
5112that you must not do this from \f(CW\*(C`ev_periodic\*(C'\fR reschedule callbacks.
5113.PP
5114Care has been taken to ensure that libev does not keep local state inside
5115\&\f(CW\*(C`ev_run\*(C'\fR, and other calls do not usually allow for coroutine switches as
5116they do not call any callbacks.
5117.SS "\s-1COMPILER\s0 \s-1WARNINGS\s0"
5118.IX Subsection "COMPILER WARNINGS"
5119Depending on your compiler and compiler settings, you might get no or a
5120lot of warnings when compiling libev code. Some people are apparently
5121scared by this.
5122.PP
5123However, these are unavoidable for many reasons. For one, each compiler
5124has different warnings, and each user has different tastes regarding
5125warning options. \*(L"Warn-free\*(R" code therefore cannot be a goal except when
5126targeting a specific compiler and compiler-version.
5127.PP
5128Another reason is that some compiler warnings require elaborate
5129workarounds, or other changes to the code that make it less clear and less
5130maintainable.
5131.PP
5132And of course, some compiler warnings are just plain stupid, or simply
5133wrong (because they don't actually warn about the condition their message
5134seems to warn about). For example, certain older gcc versions had some
5135warnings that resulted in an extreme number of false positives. These have
5136been fixed, but some people still insist on making code warn-free with
5137such buggy versions.
5138.PP
5139While libev is written to generate as few warnings as possible,
5140\&\*(L"warn-free\*(R" code is not a goal, and it is recommended not to build libev
5141with any compiler warnings enabled unless you are prepared to cope with
5142them (e.g. by ignoring them). Remember that warnings are just that:
5143warnings, not errors, or proof of bugs.
5144.SS "\s-1VALGRIND\s0"
5145.IX Subsection "VALGRIND"
5146Valgrind has a special section here because it is a popular tool that is
5147highly useful. Unfortunately, valgrind reports are very hard to interpret.
5148.PP
5149If you think you found a bug (memory leak, uninitialised data access etc.)
5150in libev, then check twice: If valgrind reports something like:
5151.PP
5152.Vb 3
5153\& ==2274== definitely lost: 0 bytes in 0 blocks.
5154\& ==2274== possibly lost: 0 bytes in 0 blocks.
5155\& ==2274== still reachable: 256 bytes in 1 blocks.
5156.Ve
5157.PP
5158Then there is no memory leak, just as memory accounted to global variables
5159is not a memleak \- the memory is still being referenced, and didn't leak.
5160.PP
5161Similarly, under some circumstances, valgrind might report kernel bugs
5162as if it were a bug in libev (e.g. in realloc or in the poll backend,
5163although an acceptable workaround has been found here), or it might be
5164confused.
5165.PP
5166Keep in mind that valgrind is a very good tool, but only a tool. Don't
5167make it into some kind of religion.
5168.PP
5169If you are unsure about something, feel free to contact the mailing list
5170with the full valgrind report and an explanation on why you think this
5171is a bug in libev (best check the archives, too :). However, don't be
5172annoyed when you get a brisk \*(L"this is no bug\*(R" answer and take the chance
5173of learning how to interpret valgrind properly.
5174.PP
5175If you need, for some reason, empty reports from valgrind for your project
5176I suggest using suppression lists.
5177.SH "PORTABILITY NOTES"
5178.IX Header "PORTABILITY NOTES"
5179.SS "\s-1GNU/LINUX\s0 32 \s-1BIT\s0 \s-1LIMITATIONS\s0"
5180.IX Subsection "GNU/LINUX 32 BIT LIMITATIONS"
5181GNU/Linux is the only common platform that supports 64 bit file/large file
5182interfaces but \fIdisables\fR them by default.
5183.PP
5184That means that libev compiled in the default environment doesn't support
5185files larger than 2GiB or so, which mainly affects \f(CW\*(C`ev_stat\*(C'\fR watchers.
5186.PP
5187Unfortunately, many programs try to work around this GNU/Linux issue
5188by enabling the large file \s-1API\s0, which makes them incompatible with the
5189standard libev compiled for their system.
5190.PP
5191Likewise, libev cannot enable the large file \s-1API\s0 itself as this would
5192suddenly make it incompatible to the default compile time environment,
5193i.e. all programs not using special compile switches.
5194.SS "\s-1OS/X\s0 \s-1AND\s0 \s-1DARWIN\s0 \s-1BUGS\s0"
5195.IX Subsection "OS/X AND DARWIN BUGS"
5196The whole thing is a bug if you ask me \- basically any system interface
5197you touch is broken, whether it is locales, poll, kqueue or even the
5198OpenGL drivers.
5199.PP
5200\fI\f(CI\*(C`kqueue\*(C'\fI is buggy\fR
5201.IX Subsection "kqueue is buggy"
5202.PP
5203The kqueue syscall is broken in all known versions \- most versions support
5204only sockets, many support pipes.
5205.PP
5206Libev tries to work around this by not using \f(CW\*(C`kqueue\*(C'\fR by default on this
5207rotten platform, but of course you can still ask for it when creating a
5208loop \- embedding a socket-only kqueue loop into a select-based one is
5209probably going to work well.
5210.PP
5211\fI\f(CI\*(C`poll\*(C'\fI is buggy\fR
5212.IX Subsection "poll is buggy"
5213.PP
5214Instead of fixing \f(CW\*(C`kqueue\*(C'\fR, Apple replaced their (working) \f(CW\*(C`poll\*(C'\fR
5215implementation by something calling \f(CW\*(C`kqueue\*(C'\fR internally around the 10.5.6
5216release, so now \f(CW\*(C`kqueue\*(C'\fR \fIand\fR \f(CW\*(C`poll\*(C'\fR are broken.
5217.PP
5218Libev tries to work around this by not using \f(CW\*(C`poll\*(C'\fR by default on
5219this rotten platform, but of course you can still ask for it when creating
5220a loop.
5221.PP
5222\fI\f(CI\*(C`select\*(C'\fI is buggy\fR
5223.IX Subsection "select is buggy"
5224.PP
5225All that's left is \f(CW\*(C`select\*(C'\fR, and of course Apple found a way to fuck this
5226one up as well: On \s-1OS/X\s0, \f(CW\*(C`select\*(C'\fR actively limits the number of file
5227descriptors you can pass in to 1024 \- your program suddenly crashes when
5228you use more.
5229.PP
5230There is an undocumented \*(L"workaround\*(R" for this \- defining
5231\&\f(CW\*(C`_DARWIN_UNLIMITED_SELECT\*(C'\fR, which libev tries to use, so select \fIshould\fR
5232work on \s-1OS/X\s0.
5233.SS "\s-1SOLARIS\s0 \s-1PROBLEMS\s0 \s-1AND\s0 \s-1WORKAROUNDS\s0"
5234.IX Subsection "SOLARIS PROBLEMS AND WORKAROUNDS"
5235\fI\f(CI\*(C`errno\*(C'\fI reentrancy\fR
5236.IX Subsection "errno reentrancy"
5237.PP
5238The default compile environment on Solaris is unfortunately so
5239thread-unsafe that you can't even use components/libraries compiled
5240without \f(CW\*(C`\-D_REENTRANT\*(C'\fR in a threaded program, which, of course, isn't
5241defined by default. A valid, if stupid, implementation choice.
5242.PP
5243If you want to use libev in threaded environments you have to make sure
5244it's compiled with \f(CW\*(C`_REENTRANT\*(C'\fR defined.
5245.PP
5246\fIEvent port backend\fR
5247.IX Subsection "Event port backend"
5248.PP
5249The scalable event interface for Solaris is called \*(L"event
5250ports\*(R". Unfortunately, this mechanism is very buggy in all major
5251releases. If you run into high \s-1CPU\s0 usage, your program freezes or you get
5252a large number of spurious wakeups, make sure you have all the relevant
5253and latest kernel patches applied. No, I don't know which ones, but there
5254are multiple ones to apply, and afterwards, event ports actually work
5255great.
5256.PP
5257If you can't get it to work, you can try running the program by setting
5258the environment variable \f(CW\*(C`LIBEV_FLAGS=3\*(C'\fR to only allow \f(CW\*(C`poll\*(C'\fR and
5259\&\f(CW\*(C`select\*(C'\fR backends.
5260.SS "\s-1AIX\s0 \s-1POLL\s0 \s-1BUG\s0"
5261.IX Subsection "AIX POLL BUG"
5262\&\s-1AIX\s0 unfortunately has a broken \f(CW\*(C`poll.h\*(C'\fR header. Libev works around
5263this by trying to avoid the poll backend altogether (i.e. it's not even
5264compiled in), which normally isn't a big problem as \f(CW\*(C`select\*(C'\fR works fine
5265with large bitsets on \s-1AIX\s0, and \s-1AIX\s0 is dead anyway.
5266.SS "\s-1WIN32\s0 \s-1PLATFORM\s0 \s-1LIMITATIONS\s0 \s-1AND\s0 \s-1WORKAROUNDS\s0"
5267.IX Subsection "WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS"
5268\fIGeneral issues\fR
5269.IX Subsection "General issues"
5270.PP
5271Win32 doesn't support any of the standards (e.g. \s-1POSIX\s0) that libev
5272requires, and its I/O model is fundamentally incompatible with the \s-1POSIX\s0
5273model. Libev still offers limited functionality on this platform in
5274the form of the \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR backend, and only supports socket
5275descriptors. This only applies when using Win32 natively, not when using
5276e.g. cygwin. Actually, it only applies to the microsofts own compilers,
5277as every compiler comes with a slightly differently broken/incompatible
5278environment.
5279.PP
5280Lifting these limitations would basically require the full
5281re-implementation of the I/O system. If you are into this kind of thing,
5282then note that glib does exactly that for you in a very portable way (note
5283also that glib is the slowest event library known to man).
5284.PP
5285There is no supported compilation method available on windows except
5286embedding it into other applications.
5287.PP
5288Sensible signal handling is officially unsupported by Microsoft \- libev
5289tries its best, but under most conditions, signals will simply not work.
5290.PP
5291Not a libev limitation but worth mentioning: windows apparently doesn't
5292accept large writes: instead of resulting in a partial write, windows will
5293either accept everything or return \f(CW\*(C`ENOBUFS\*(C'\fR if the buffer is too large,
5294so make sure you only write small amounts into your sockets (less than a
5295megabyte seems safe, but this apparently depends on the amount of memory
5296available).
5297.PP
5298Due to the many, low, and arbitrary limits on the win32 platform and
5299the abysmal performance of winsockets, using a large number of sockets
5300is not recommended (and not reasonable). If your program needs to use
5301more than a hundred or so sockets, then likely it needs to use a totally
5302different implementation for windows, as libev offers the \s-1POSIX\s0 readiness
5303notification model, which cannot be implemented efficiently on windows
5304(due to Microsoft monopoly games).
5305.PP
5306A typical way to use libev under windows is to embed it (see the embedding
5307section for details) and use the following \fIevwrap.h\fR header file instead
5308of \fIev.h\fR:
5309.PP
5310.Vb 2
5311\& #define EV_STANDALONE /* keeps ev from requiring config.h */
5312\& #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
5313\&
5314\& #include "ev.h"
5315.Ve
5316.PP
5317And compile the following \fIevwrap.c\fR file into your project (make sure
5318you do \fInot\fR compile the \fIev.c\fR or any other embedded source files!):
5319.PP
5320.Vb 2
5321\& #include "evwrap.h"
5322\& #include "ev.c"
5323.Ve
5324.PP
5325\fIThe winsocket \f(CI\*(C`select\*(C'\fI function\fR
5326.IX Subsection "The winsocket select function"
5327.PP
5328The winsocket \f(CW\*(C`select\*(C'\fR function doesn't follow \s-1POSIX\s0 in that it
5329requires socket \fIhandles\fR and not socket \fIfile descriptors\fR (it is
5330also extremely buggy). This makes select very inefficient, and also
5331requires a mapping from file descriptors to socket handles (the Microsoft
5332C runtime provides the function \f(CW\*(C`_open_osfhandle\*(C'\fR for this). See the
5333discussion of the \f(CW\*(C`EV_SELECT_USE_FD_SET\*(C'\fR, \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR and
5334\&\f(CW\*(C`EV_FD_TO_WIN32_HANDLE\*(C'\fR preprocessor symbols for more info.
5335.PP
5336The configuration for a \*(L"naked\*(R" win32 using the Microsoft runtime
5337libraries and raw winsocket select is:
5338.PP
5339.Vb 2
5340\& #define EV_USE_SELECT 1
5341\& #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
5342.Ve
5343.PP
5344Note that winsockets handling of fd sets is O(n), so you can easily get a
5345complexity in the O(nA\*^X) range when using win32.
5346.PP
5347\fILimited number of file descriptors\fR
5348.IX Subsection "Limited number of file descriptors"
5349.PP
5350Windows has numerous arbitrary (and low) limits on things.
5351.PP
5352Early versions of winsocket's select only supported waiting for a maximum
5353of \f(CW64\fR handles (probably owning to the fact that all windows kernels
5354can only wait for \f(CW64\fR things at the same time internally; Microsoft
5355recommends spawning a chain of threads and wait for 63 handles and the
5356previous thread in each. Sounds great!).
5357.PP
5358Newer versions support more handles, but you need to define \f(CW\*(C`FD_SETSIZE\*(C'\fR
5359to some high number (e.g. \f(CW2048\fR) before compiling the winsocket select
5360call (which might be in libev or elsewhere, for example, perl and many
5361other interpreters do their own select emulation on windows).
5362.PP
5363Another limit is the number of file descriptors in the Microsoft runtime
5364libraries, which by default is \f(CW64\fR (there must be a hidden \fI64\fR
5365fetish or something like this inside Microsoft). You can increase this
5366by calling \f(CW\*(C`_setmaxstdio\*(C'\fR, which can increase this limit to \f(CW2048\fR
5367(another arbitrary limit), but is broken in many versions of the Microsoft
5368runtime libraries. This might get you to about \f(CW512\fR or \f(CW2048\fR sockets
5369(depending on windows version and/or the phase of the moon). To get more,
5370you need to wrap all I/O functions and provide your own fd management, but
5371the cost of calling select (O(nA\*^X)) will likely make this unworkable.
5372.SS "\s-1PORTABILITY\s0 \s-1REQUIREMENTS\s0"
5373.IX Subsection "PORTABILITY REQUIREMENTS"
5374In addition to a working ISO-C implementation and of course the
5375backend-specific APIs, libev relies on a few additional extensions:
5376.ie n .IP """void (*)(ev_watcher_type *, int revents)"" must have compatible calling conventions regardless of ""ev_watcher_type *""." 4
5377.el .IP "\f(CWvoid (*)(ev_watcher_type *, int revents)\fR must have compatible calling conventions regardless of \f(CWev_watcher_type *\fR." 4
5378.IX Item "void (*)(ev_watcher_type *, int revents) must have compatible calling conventions regardless of ev_watcher_type *."
5379Libev assumes not only that all watcher pointers have the same internal
5380structure (guaranteed by \s-1POSIX\s0 but not by \s-1ISO\s0 C for example), but it also
5381assumes that the same (machine) code can be used to call any watcher
5382callback: The watcher callbacks have different type signatures, but libev
5383calls them using an \f(CW\*(C`ev_watcher *\*(C'\fR internally.
5384.IP "pointer accesses must be thread-atomic" 4
5385.IX Item "pointer accesses must be thread-atomic"
5386Accessing a pointer value must be atomic, it must both be readable and
5387writable in one piece \- this is the case on all current architectures.
5388.ie n .IP """sig_atomic_t volatile"" must be thread-atomic as well" 4
5389.el .IP "\f(CWsig_atomic_t volatile\fR must be thread-atomic as well" 4
5390.IX Item "sig_atomic_t volatile must be thread-atomic as well"
5391The type \f(CW\*(C`sig_atomic_t volatile\*(C'\fR (or whatever is defined as
5392\&\f(CW\*(C`EV_ATOMIC_T\*(C'\fR) must be atomic with respect to accesses from different
5393threads. This is not part of the specification for \f(CW\*(C`sig_atomic_t\*(C'\fR, but is
5394believed to be sufficiently portable.
5395.ie n .IP """sigprocmask"" must work in a threaded environment" 4
5396.el .IP "\f(CWsigprocmask\fR must work in a threaded environment" 4
5397.IX Item "sigprocmask must work in a threaded environment"
5398Libev uses \f(CW\*(C`sigprocmask\*(C'\fR to temporarily block signals. This is not
5399allowed in a threaded program (\f(CW\*(C`pthread_sigmask\*(C'\fR has to be used). Typical
5400pthread implementations will either allow \f(CW\*(C`sigprocmask\*(C'\fR in the \*(L"main
5401thread\*(R" or will block signals process-wide, both behaviours would
5402be compatible with libev. Interaction between \f(CW\*(C`sigprocmask\*(C'\fR and
5403\&\f(CW\*(C`pthread_sigmask\*(C'\fR could complicate things, however.
5404.Sp
5405The most portable way to handle signals is to block signals in all threads
5406except the initial one, and run the default loop in the initial thread as
5407well.
5408.ie n .IP """long"" must be large enough for common memory allocation sizes" 4
5409.el .IP "\f(CWlong\fR must be large enough for common memory allocation sizes" 4
5410.IX Item "long must be large enough for common memory allocation sizes"
5411To improve portability and simplify its \s-1API\s0, libev uses \f(CW\*(C`long\*(C'\fR internally
5412instead of \f(CW\*(C`size_t\*(C'\fR when allocating its data structures. On non-POSIX
5413systems (Microsoft...) this might be unexpectedly low, but is still at
5414least 31 bits everywhere, which is enough for hundreds of millions of
5415watchers.
5416.ie n .IP """double"" must hold a time value in seconds with enough accuracy" 4
5417.el .IP "\f(CWdouble\fR must hold a time value in seconds with enough accuracy" 4
5418.IX Item "double must hold a time value in seconds with enough accuracy"
5419The type \f(CW\*(C`double\*(C'\fR is used to represent timestamps. It is required to
5420have at least 51 bits of mantissa (and 9 bits of exponent), which is
5421good enough for at least into the year 4000 with millisecond accuracy
5422(the design goal for libev). This requirement is overfulfilled by
5423implementations using \s-1IEEE\s0 754, which is basically all existing ones.
5424.Sp
5425With \s-1IEEE\s0 754 doubles, you get microsecond accuracy until at least the
5426year 2255 (and millisecond accuracy till the year 287396 \- by then, libev
5427is either obsolete or somebody patched it to use \f(CW\*(C`long double\*(C'\fR or
5428something like that, just kidding).
5429.PP
5430If you know of other additional requirements drop me a note.
2699.SH "COMPLEXITIES" 5431.SH "ALGORITHMIC COMPLEXITIES"
2700.IX Header "COMPLEXITIES" 5432.IX Header "ALGORITHMIC COMPLEXITIES"
2701In this section the complexities of (many of) the algorithms used inside 5433In this section the complexities of (many of) the algorithms used inside
2702libev will be explained. For complexity discussions about backends see the 5434libev will be documented. For complexity discussions about backends see
2703documentation for \f(CW\*(C`ev_default_init\*(C'\fR. 5435the documentation for \f(CW\*(C`ev_default_init\*(C'\fR.
2704.Sp 5436.PP
2705All of the following are about amortised time: If an array needs to be 5437All of the following are about amortised time: If an array needs to be
2706extended, libev needs to realloc and move the whole array, but this 5438extended, libev needs to realloc and move the whole array, but this
2707happens asymptotically never with higher number of elements, so O(1) might 5439happens asymptotically rarer with higher number of elements, so O(1) might
2708mean it might do a lengthy realloc operation in rare cases, but on average 5440mean that libev does a lengthy realloc operation in rare cases, but on
2709it is much faster and asymptotically approaches constant time. 5441average it is much faster and asymptotically approaches constant time.
2710.RS 4
2711.IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4 5442.IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4
2712.IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 5443.IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)"
2713This means that, when you have a watcher that triggers in one hour and 5444This means that, when you have a watcher that triggers in one hour and
2714there are 100 watchers that would trigger before that then inserting will 5445there are 100 watchers that would trigger before that, then inserting will
2715have to skip those 100 watchers. 5446have to skip roughly seven (\f(CW\*(C`ld 100\*(C'\fR) of these watchers.
2716.IP "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)" 4 5447.IP "Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)" 4
2717.IX Item "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)" 5448.IX Item "Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)"
2718That means that for changing a timer costs less than removing/adding them 5449That means that changing a timer costs less than removing/adding them,
2719as only the relative motion in the event queue has to be paid for. 5450as only the relative motion in the event queue has to be paid for.
2720.IP "Starting io/check/prepare/idle/signal/child watchers: O(1)" 4 5451.IP "Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)" 4
2721.IX Item "Starting io/check/prepare/idle/signal/child watchers: O(1)" 5452.IX Item "Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)"
2722These just add the watcher into an array or at the head of a list. 5453These just add the watcher into an array or at the head of a list.
5454.IP "Stopping check/prepare/idle/fork/async watchers: O(1)" 4
2723=item Stopping check/prepare/idle watchers: O(1) 5455.IX Item "Stopping check/prepare/idle/fork/async watchers: O(1)"
5456.PD 0
2724.IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4 5457.IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4
2725.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))" 5458.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))"
5459.PD
2726These watchers are stored in lists then need to be walked to find the 5460These watchers are stored in lists, so they need to be walked to find the
2727correct watcher to remove. The lists are usually short (you don't usually 5461correct watcher to remove. The lists are usually short (you don't usually
2728have many watchers waiting for the same fd or signal). 5462have many watchers waiting for the same fd or signal: one is typical, two
5463is rare).
2729.IP "Finding the next timer per loop iteration: O(1)" 4 5464.IP "Finding the next timer in each loop iteration: O(1)" 4
2730.IX Item "Finding the next timer per loop iteration: O(1)" 5465.IX Item "Finding the next timer in each loop iteration: O(1)"
2731.PD 0 5466By virtue of using a binary or 4\-heap, the next timer is always found at a
5467fixed position in the storage array.
2732.IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4 5468.IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4
2733.IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 5469.IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)"
2734.PD
2735A change means an I/O watcher gets started or stopped, which requires 5470A change means an I/O watcher gets started or stopped, which requires
2736libev to recalculate its status (and possibly tell the kernel). 5471libev to recalculate its status (and possibly tell the kernel, depending
2737.IP "Activating one watcher: O(1)" 4 5472on backend and whether \f(CW\*(C`ev_io_set\*(C'\fR was used).
2738.IX Item "Activating one watcher: O(1)" 5473.IP "Activating one watcher (putting it into the pending state): O(1)" 4
5474.IX Item "Activating one watcher (putting it into the pending state): O(1)"
2739.PD 0 5475.PD 0
2740.IP "Priority handling: O(number_of_priorities)" 4 5476.IP "Priority handling: O(number_of_priorities)" 4
2741.IX Item "Priority handling: O(number_of_priorities)" 5477.IX Item "Priority handling: O(number_of_priorities)"
2742.PD 5478.PD
2743Priorities are implemented by allocating some space for each 5479Priorities are implemented by allocating some space for each
2744priority. When doing priority-based operations, libev usually has to 5480priority. When doing priority-based operations, libev usually has to
2745linearly search all the priorities. 5481linearly search all the priorities, but starting/stopping and activating
2746.RE 5482watchers becomes O(1) with respect to priority handling.
2747.RS 4 5483.IP "Sending an ev_async: O(1)" 4
5484.IX Item "Sending an ev_async: O(1)"
5485.PD 0
5486.IP "Processing ev_async_send: O(number_of_async_watchers)" 4
5487.IX Item "Processing ev_async_send: O(number_of_async_watchers)"
5488.IP "Processing signals: O(max_signal_number)" 4
5489.IX Item "Processing signals: O(max_signal_number)"
5490.PD
5491Sending involves a system call \fIiff\fR there were no other \f(CW\*(C`ev_async_send\*(C'\fR
5492calls in the current loop iteration and the loop is currently
5493blocked. Checking for async and signal events involves iterating over all
5494running async watchers or all signal numbers.
5495.SH "PORTING FROM LIBEV 3.X TO 4.X"
5496.IX Header "PORTING FROM LIBEV 3.X TO 4.X"
5497The major version 4 introduced some incompatible changes to the \s-1API\s0.
5498.PP
5499At the moment, the \f(CW\*(C`ev.h\*(C'\fR header file provides compatibility definitions
5500for all changes, so most programs should still compile. The compatibility
5501layer might be removed in later versions of libev, so better update to the
5502new \s-1API\s0 early than late.
5503.ie n .IP """EV_COMPAT3"" backwards compatibility mechanism" 4
5504.el .IP "\f(CWEV_COMPAT3\fR backwards compatibility mechanism" 4
5505.IX Item "EV_COMPAT3 backwards compatibility mechanism"
5506The backward compatibility mechanism can be controlled by
5507\&\f(CW\*(C`EV_COMPAT3\*(C'\fR. See \*(L"\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0\*(R" in the \*(L"\s-1EMBEDDING\s0\*(R"
5508section.
5509.ie n .IP """ev_default_destroy"" and ""ev_default_fork"" have been removed" 4
5510.el .IP "\f(CWev_default_destroy\fR and \f(CWev_default_fork\fR have been removed" 4
5511.IX Item "ev_default_destroy and ev_default_fork have been removed"
5512These calls can be replaced easily by their \f(CW\*(C`ev_loop_xxx\*(C'\fR counterparts:
5513.Sp
5514.Vb 2
5515\& ev_loop_destroy (EV_DEFAULT_UC);
5516\& ev_loop_fork (EV_DEFAULT);
5517.Ve
5518.IP "function/symbol renames" 4
5519.IX Item "function/symbol renames"
5520A number of functions and symbols have been renamed:
5521.Sp
5522.Vb 3
5523\& ev_loop => ev_run
5524\& EVLOOP_NONBLOCK => EVRUN_NOWAIT
5525\& EVLOOP_ONESHOT => EVRUN_ONCE
5526\&
5527\& ev_unloop => ev_break
5528\& EVUNLOOP_CANCEL => EVBREAK_CANCEL
5529\& EVUNLOOP_ONE => EVBREAK_ONE
5530\& EVUNLOOP_ALL => EVBREAK_ALL
5531\&
5532\& EV_TIMEOUT => EV_TIMER
5533\&
5534\& ev_loop_count => ev_iteration
5535\& ev_loop_depth => ev_depth
5536\& ev_loop_verify => ev_verify
5537.Ve
5538.Sp
5539Most functions working on \f(CW\*(C`struct ev_loop\*(C'\fR objects don't have an
5540\&\f(CW\*(C`ev_loop_\*(C'\fR prefix, so it was removed; \f(CW\*(C`ev_loop\*(C'\fR, \f(CW\*(C`ev_unloop\*(C'\fR and
5541associated constants have been renamed to not collide with the \f(CW\*(C`struct
5542ev_loop\*(C'\fR anymore and \f(CW\*(C`EV_TIMER\*(C'\fR now follows the same naming scheme
5543as all other watcher types. Note that \f(CW\*(C`ev_loop_fork\*(C'\fR is still called
5544\&\f(CW\*(C`ev_loop_fork\*(C'\fR because it would otherwise clash with the \f(CW\*(C`ev_fork\*(C'\fR
5545typedef.
5546.ie n .IP """EV_MINIMAL"" mechanism replaced by ""EV_FEATURES""" 4
5547.el .IP "\f(CWEV_MINIMAL\fR mechanism replaced by \f(CWEV_FEATURES\fR" 4
5548.IX Item "EV_MINIMAL mechanism replaced by EV_FEATURES"
5549The preprocessor symbol \f(CW\*(C`EV_MINIMAL\*(C'\fR has been replaced by a different
5550mechanism, \f(CW\*(C`EV_FEATURES\*(C'\fR. Programs using \f(CW\*(C`EV_MINIMAL\*(C'\fR usually compile
5551and work, but the library code will of course be larger.
5552.SH "GLOSSARY"
5553.IX Header "GLOSSARY"
5554.IP "active" 4
5555.IX Item "active"
5556A watcher is active as long as it has been started and not yet stopped.
5557See \*(L"\s-1WATCHER\s0 \s-1STATES\s0\*(R" for details.
5558.IP "application" 4
5559.IX Item "application"
5560In this document, an application is whatever is using libev.
5561.IP "backend" 4
5562.IX Item "backend"
5563The part of the code dealing with the operating system interfaces.
5564.IP "callback" 4
5565.IX Item "callback"
5566The address of a function that is called when some event has been
5567detected. Callbacks are being passed the event loop, the watcher that
5568received the event, and the actual event bitset.
5569.IP "callback/watcher invocation" 4
5570.IX Item "callback/watcher invocation"
5571The act of calling the callback associated with a watcher.
5572.IP "event" 4
5573.IX Item "event"
5574A change of state of some external event, such as data now being available
5575for reading on a file descriptor, time having passed or simply not having
5576any other events happening anymore.
5577.Sp
5578In libev, events are represented as single bits (such as \f(CW\*(C`EV_READ\*(C'\fR or
5579\&\f(CW\*(C`EV_TIMER\*(C'\fR).
5580.IP "event library" 4
5581.IX Item "event library"
5582A software package implementing an event model and loop.
5583.IP "event loop" 4
5584.IX Item "event loop"
5585An entity that handles and processes external events and converts them
5586into callback invocations.
5587.IP "event model" 4
5588.IX Item "event model"
5589The model used to describe how an event loop handles and processes
5590watchers and events.
5591.IP "pending" 4
5592.IX Item "pending"
5593A watcher is pending as soon as the corresponding event has been
5594detected. See \*(L"\s-1WATCHER\s0 \s-1STATES\s0\*(R" for details.
5595.IP "real time" 4
5596.IX Item "real time"
5597The physical time that is observed. It is apparently strictly monotonic :)
5598.IP "wall-clock time" 4
5599.IX Item "wall-clock time"
5600The time and date as shown on clocks. Unlike real time, it can actually
5601be wrong and jump forwards and backwards, e.g. when you adjust your
5602clock.
5603.IP "watcher" 4
5604.IX Item "watcher"
5605A data structure that describes interest in certain events. Watchers need
5606to be started (attached to an event loop) before they can receive events.
2748.SH "AUTHOR" 5607.SH "AUTHOR"
2749.IX Header "AUTHOR" 5608.IX Header "AUTHOR"
2750Marc Lehmann <libev@schmorp.de>. 5609Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
5610Magnusson and Emanuele Giaquinta, and minor corrections by many others.

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