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129.\" ======================================================================== 124.\" ========================================================================
130.\" 125.\"
131.IX Title ""<STANDARD INPUT>" 1" 126.IX Title "LIBEV 3"
132.TH "<STANDARD INPUT>" 1 "2007-12-12" "perl v5.8.8" "User Contributed Perl Documentation" 127.TH LIBEV 3 "2013-06-07" "libev-4.15" "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 such. 267any calculations on it, you should treat it as some floating point value.
268.PP
269Unlike the name component \f(CW\*(C`stamp\*(C'\fR might indicate, it is also used for
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.
249.SH "GLOBAL FUNCTIONS" 290.SH "GLOBAL FUNCTIONS"
250.IX Header "GLOBAL FUNCTIONS" 291.IX Header "GLOBAL FUNCTIONS"
251These functions can be called anytime, even before initialising the 292These functions can be called anytime, even before initialising the
252library in any way. 293library in any way.
253.IP "ev_tstamp ev_time ()" 4 294.IP "ev_tstamp ev_time ()" 4
254.IX Item "ev_tstamp ev_time ()" 295.IX Item "ev_tstamp ev_time ()"
255Returns 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
256\&\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
257you 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).
258.IP "int ev_version_major ()" 4 311.IP "int ev_version_major ()" 4
259.IX Item "int ev_version_major ()" 312.IX Item "int ev_version_major ()"
260.PD 0 313.PD 0
261.IP "int ev_version_minor ()" 4 314.IP "int ev_version_minor ()" 4
262.IX Item "int ev_version_minor ()" 315.IX Item "int ev_version_minor ()"
… …
274as this indicates an incompatible change. Minor versions are usually 327as this indicates an incompatible change. Minor versions are usually
275compatible to older versions, so a larger minor version alone is usually 328compatible to older versions, so a larger minor version alone is usually
276not a problem. 329not a problem.
277.Sp 330.Sp
278Example: Make sure we haven't accidentally been linked against the wrong 331Example: Make sure we haven't accidentally been linked against the wrong
279version. 332version (note, however, that this will not detect other \s-1ABI\s0 mismatches,
333such as \s-1LFS\s0 or reentrancy).
280.Sp 334.Sp
281.Vb 3 335.Vb 3
282\& assert (("libev version mismatch", 336\& assert (("libev version mismatch",
283\& ev_version_major () == EV_VERSION_MAJOR 337\& ev_version_major () == EV_VERSION_MAJOR
284\& && ev_version_minor () >= EV_VERSION_MINOR)); 338\& && ev_version_minor () >= EV_VERSION_MINOR));
285.Ve 339.Ve
286.IP "unsigned int ev_supported_backends ()" 4 340.IP "unsigned int ev_supported_backends ()" 4
287.IX Item "unsigned int ev_supported_backends ()" 341.IX Item "unsigned int ev_supported_backends ()"
288Return 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
289value) compiled into this binary of libev (independent of their 343value) compiled into this binary of libev (independent of their
… …
292.Sp 346.Sp
293Example: 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
294a 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
295.Sp 349.Sp
296.Vb 2 350.Vb 2
297\& assert (("sorry, no epoll, no sex", 351\& assert (("sorry, no epoll, no sex",
298\& ev_supported_backends () & EVBACKEND_EPOLL)); 352\& ev_supported_backends () & EVBACKEND_EPOLL));
299.Ve 353.Ve
300.IP "unsigned int ev_recommended_backends ()" 4 354.IP "unsigned int ev_recommended_backends ()" 4
301.IX Item "unsigned int ev_recommended_backends ()" 355.IX Item "unsigned int ev_recommended_backends ()"
302Return 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
303recommended 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
304returned 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
305most BSDs and will not be autodetected unless you explicitly request it 360and will not be auto-detected unless you explicitly request it (assuming
306(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
307libev will probe for if you specify no backends explicitly. 362probe for if you specify no backends explicitly.
308.IP "unsigned int ev_embeddable_backends ()" 4 363.IP "unsigned int ev_embeddable_backends ()" 4
309.IX Item "unsigned int ev_embeddable_backends ()" 364.IX Item "unsigned int ev_embeddable_backends ()"
310Returns 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
311is the theoretical, all\-platform, value. To find which backends 366value is platform-specific but can include backends not available on the
312might be supported on the current system, you would need to look at 367current system. To find which embeddable backends might be supported on
313\&\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 ()
314recommended ones. 369& ev_supported_backends ()\*(C'\fR, likewise for recommended ones.
315.Sp 370.Sp
316See 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.
317.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4 372.IP "ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())" 4
318.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))" 373.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())"
319Sets the allocation function to use (the prototype is similar \- the 374Sets the allocation function to use (the prototype is similar \- the
320semantics 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
321allocate and free memory (no surprises here). If it returns zero when 376used to allocate and free memory (no surprises here). If it returns zero
322memory 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
323potentially destructive action. The default is your system realloc 378or take some potentially destructive action.
324function. 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.
325.Sp 383.Sp
326You could override this function in high-availability programs to, say, 384You could override this function in high-availability programs to, say,
327free 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,
328or 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.
329.Sp 387.Sp
330Example: 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
331retries). 389retries (example requires a standards-compliant \f(CW\*(C`realloc\*(C'\fR).
332.Sp 390.Sp
333.Vb 6 391.Vb 6
334\& static void * 392\& static void *
335\& persistent_realloc (void *ptr, size_t size) 393\& persistent_realloc (void *ptr, size_t size)
336\& { 394\& {
337\& for (;;) 395\& for (;;)
338\& { 396\& {
339\& void *newptr = realloc (ptr, size); 397\& void *newptr = realloc (ptr, size);
340.Ve 398\&
341.Sp
342.Vb 2
343\& if (newptr) 399\& if (newptr)
344\& return newptr; 400\& return newptr;
345.Ve 401\&
346.Sp
347.Vb 3
348\& sleep (60); 402\& sleep (60);
349\& } 403\& }
350\& } 404\& }
351.Ve 405\&
352.Sp
353.Vb 2
354\& ... 406\& ...
355\& ev_set_allocator (persistent_realloc); 407\& ev_set_allocator (persistent_realloc);
356.Ve 408.Ve
357.IP "ev_set_syserr_cb (void (*cb)(const char *msg));" 4 409.IP "ev_set_syserr_cb (void (*cb)(const char *msg) throw ())" 4
358.IX Item "ev_set_syserr_cb (void (*cb)(const char *msg));" 410.IX Item "ev_set_syserr_cb (void (*cb)(const char *msg) throw ())"
359Set the callback function to call on a retryable syscall error (such 411Set the callback function to call on a retryable system call error (such
360as failed select, poll, epoll_wait). The message is a printable string 412as failed select, poll, epoll_wait). The message is a printable string
361indicating the system call or subsystem causing the problem. If this 413indicating the system call or subsystem causing the problem. If this
362callback 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
363matter what, when it returns. That is, libev will generally retry the 415matter what, when it returns. That is, libev will generally retry the
364requested 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
365(such as abort). 417(such as abort).
366.Sp 418.Sp
367Example: This is basically the same thing that libev does internally, too. 419Example: This is basically the same thing that libev does internally, too.
… …
371\& fatal_error (const char *msg) 423\& fatal_error (const char *msg)
372\& { 424\& {
373\& perror (msg); 425\& perror (msg);
374\& abort (); 426\& abort ();
375\& } 427\& }
376.Ve 428\&
377.Sp
378.Vb 2
379\& ... 429\& ...
380\& ev_set_syserr_cb (fatal_error); 430\& ev_set_syserr_cb (fatal_error);
381.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.
382.SH "FUNCTIONS CONTROLLING THE EVENT LOOP" 444.SH "FUNCTIONS CONTROLLING EVENT LOOPS"
383.IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP" 445.IX Header "FUNCTIONS CONTROLLING EVENT LOOPS"
384An 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
385types 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
386events, and dynamically created loops which do not. 448libev 3 had an \f(CW\*(C`ev_loop\*(C'\fR function colliding with the struct name).
387.PP 449.PP
388If 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
389in your main thread (or in a separate thread) and for each thread you 451supports child process events, and dynamically created event loops which
390create, you also create another event loop. Libev itself does no locking 452do not.
391whatsoever, so if you mix calls to the same event loop in different
392threads, make sure you lock (this is usually a bad idea, though, even if
393done correctly, because it's hideous and inefficient).
394.IP "struct ev_loop *ev_default_loop (unsigned int flags)" 4 453.IP "struct ev_loop *ev_default_loop (unsigned int flags)" 4
395.IX Item "struct ev_loop *ev_default_loop (unsigned int flags)" 454.IX Item "struct ev_loop *ev_default_loop (unsigned int flags)"
396This 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
397yet 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
398false. 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
399flags. 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".
400.Sp 465.Sp
401If 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
402function. 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.
403.Sp 501.Sp
404The flags argument can be used to specify special behaviour or specific 502The flags argument can be used to specify special behaviour or specific
405backends 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).
406.Sp 504.Sp
407The following flags are supported: 505The following flags are supported:
… …
412The 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
413thing, believe me). 511thing, believe me).
414.ie n .IP """EVFLAG_NOENV""" 4 512.ie n .IP """EVFLAG_NOENV""" 4
415.el .IP "\f(CWEVFLAG_NOENV\fR" 4 513.el .IP "\f(CWEVFLAG_NOENV\fR" 4
416.IX Item "EVFLAG_NOENV" 514.IX Item "EVFLAG_NOENV"
417If 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
418or setgid) then libev will \fInot\fR look at the environment variable 516or setgid) then libev will \fInot\fR look at the environment variable
419\&\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
420override 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
421useful to try out specific backends to test their performance, or to work 519useful to try out specific backends to test their performance, to work
422around bugs. 520around bugs, or to make libev threadsafe (accessing environment variables
521cannot be done in a threadsafe way, but usually it works if no other
522thread modifies them).
423.ie n .IP """EVFLAG_FORKCHECK""" 4 523.ie n .IP """EVFLAG_FORKCHECK""" 4
424.el .IP "\f(CWEVFLAG_FORKCHECK\fR" 4 524.el .IP "\f(CWEVFLAG_FORKCHECK\fR" 4
425.IX Item "EVFLAG_FORKCHECK" 525.IX Item "EVFLAG_FORKCHECK"
426Instead of calling \f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR manually after 526Instead of calling \f(CW\*(C`ev_loop_fork\*(C'\fR manually after a fork, you can also
427a fork, you can also make libev check for a fork in each iteration by 527make libev check for a fork in each iteration by enabling this flag.
428enabling this flag.
429.Sp 528.Sp
430This works by calling \f(CW\*(C`getpid ()\*(C'\fR on every iteration of the loop, 529This works by calling \f(CW\*(C`getpid ()\*(C'\fR on every iteration of the loop,
431and thus this might slow down your event loop if you do a lot of loop 530and thus this might slow down your event loop if you do a lot of loop
432iterations and little real work, but is usually not noticeable (on my 531iterations and little real work, but is usually not noticeable (on my
433Linux system for example, \f(CW\*(C`getpid\*(C'\fR is actually a simple 5\-insn sequence 532GNU/Linux system for example, \f(CW\*(C`getpid\*(C'\fR is actually a simple 5\-insn sequence
434without a syscall and thus \fIvery\fR fast, but my Linux system also has 533without a system call and thus \fIvery\fR fast, but my GNU/Linux system also has
435\&\f(CW\*(C`pthread_atfork\*(C'\fR which is even faster). 534\&\f(CW\*(C`pthread_atfork\*(C'\fR which is even faster).
436.Sp 535.Sp
437The big advantage of this flag is that you can forget about fork (and 536The big advantage of this flag is that you can forget about fork (and
438forget about forgetting to tell libev about forking) when you use this 537forget about forgetting to tell libev about forking) when you use this
439flag. 538flag.
440.Sp 539.Sp
441This flag setting cannot be overriden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR 540This flag setting cannot be overridden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR
442environment variable. 541environment variable.
542.ie n .IP """EVFLAG_NOINOTIFY""" 4
543.el .IP "\f(CWEVFLAG_NOINOTIFY\fR" 4
544.IX Item "EVFLAG_NOINOTIFY"
545When this flag is specified, then libev will not attempt to use the
546\&\fIinotify\fR \s-1API\s0 for its \f(CW\*(C`ev_stat\*(C'\fR watchers. Apart from debugging and
547testing, this flag can be useful to conserve inotify file descriptors, as
548otherwise each loop using \f(CW\*(C`ev_stat\*(C'\fR watchers consumes one inotify handle.
549.ie n .IP """EVFLAG_SIGNALFD""" 4
550.el .IP "\f(CWEVFLAG_SIGNALFD\fR" 4
551.IX Item "EVFLAG_SIGNALFD"
552When this flag is specified, then libev will attempt to use the
553\&\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
554delivers signals synchronously, which makes it both faster and might make
555it possible to get the queued signal data. It can also simplify signal
556handling with threads, as long as you properly block signals in your
557threads that are not interested in handling them.
558.Sp
559Signalfd will not be used by default as this changes your signal mask, and
560there are a lot of shoddy libraries and programs (glib's threadpool for
561example) that can't properly initialise their signal masks.
562.ie n .IP """EVFLAG_NOSIGMASK""" 4
563.el .IP "\f(CWEVFLAG_NOSIGMASK\fR" 4
564.IX Item "EVFLAG_NOSIGMASK"
565When this flag is specified, then libev will avoid to modify the signal
566mask. Specifically, this means you have to make sure signals are unblocked
567when you want to receive them.
568.Sp
569This behaviour is useful when you want to do your own signal handling, or
570want to handle signals only in specific threads and want to avoid libev
571unblocking the signals.
572.Sp
573It's also required by \s-1POSIX\s0 in a threaded program, as libev calls
574\&\f(CW\*(C`sigprocmask\*(C'\fR, whose behaviour is officially unspecified.
575.Sp
576This flag's behaviour will become the default in future versions of libev.
443.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4 577.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4
444.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4 578.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4
445.IX Item "EVBACKEND_SELECT (value 1, portable select backend)" 579.IX Item "EVBACKEND_SELECT (value 1, portable select backend)"
446This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as 580This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as
447libev tries to roll its own fd_set with no limits on the number of fds, 581libev tries to roll its own fd_set with no limits on the number of fds,
448but if that fails, expect a fairly low limit on the number of fds when 582but if that fails, expect a fairly low limit on the number of fds when
449using this backend. It doesn't scale too well (O(highest_fd)), but its usually 583using this backend. It doesn't scale too well (O(highest_fd)), but its
450the fastest backend for a low number of fds. 584usually the fastest backend for a low number of (low-numbered :) fds.
585.Sp
586To get good performance out of this backend you need a high amount of
587parallelism (most of the file descriptors should be busy). If you are
588writing a server, you should \f(CW\*(C`accept ()\*(C'\fR in a loop to accept as many
589connections as possible during one iteration. You might also want to have
590a look at \f(CW\*(C`ev_set_io_collect_interval ()\*(C'\fR to increase the amount of
591readiness notifications you get per iteration.
592.Sp
593This 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
594\&\f(CW\*(C`writefds\*(C'\fR set (and to work around Microsoft Windows bugs, also onto the
595\&\f(CW\*(C`exceptfds\*(C'\fR set on that platform).
451.ie n .IP """EVBACKEND_POLL"" (value 2, poll backend, available everywhere except on windows)" 4 596.ie n .IP """EVBACKEND_POLL"" (value 2, poll backend, available everywhere except on windows)" 4
452.el .IP "\f(CWEVBACKEND_POLL\fR (value 2, poll backend, available everywhere except on windows)" 4 597.el .IP "\f(CWEVBACKEND_POLL\fR (value 2, poll backend, available everywhere except on windows)" 4
453.IX Item "EVBACKEND_POLL (value 2, poll backend, available everywhere except on windows)" 598.IX Item "EVBACKEND_POLL (value 2, poll backend, available everywhere except on windows)"
454And this is your standard \fIpoll\fR\|(2) backend. It's more complicated than 599And this is your standard \fIpoll\fR\|(2) backend. It's more complicated
455select, but handles sparse fds better and has no artificial limit on the 600than select, but handles sparse fds better and has no artificial
456number of fds you can use (except it will slow down considerably with a 601limit on the number of fds you can use (except it will slow down
457lot of inactive fds). It scales similarly to select, i.e. O(total_fds). 602considerably with a lot of inactive fds). It scales similarly to select,
603i.e. O(total_fds). See the entry for \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR, above, for
604performance tips.
605.Sp
606This backend maps \f(CW\*(C`EV_READ\*(C'\fR to \f(CW\*(C`POLLIN | POLLERR | POLLHUP\*(C'\fR, and
607\&\f(CW\*(C`EV_WRITE\*(C'\fR to \f(CW\*(C`POLLOUT | POLLERR | POLLHUP\*(C'\fR.
458.ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4 608.ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4
459.el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4 609.el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4
460.IX Item "EVBACKEND_EPOLL (value 4, Linux)" 610.IX Item "EVBACKEND_EPOLL (value 4, Linux)"
611Use the linux-specific \fIepoll\fR\|(7) interface (for both pre\- and post\-2.6.9
612kernels).
613.Sp
461For few fds, this backend is a bit little slower than poll and select, 614For few fds, this backend is a bit little slower than poll and select, but
462but it scales phenomenally better. While poll and select usually scale like 615it scales phenomenally better. While poll and select usually scale like
463O(total_fds) where n is the total number of fds (or the highest fd), epoll scales 616O(total_fds) where total_fds is the total number of fds (or the highest
464either O(1) or O(active_fds). 617fd), epoll scales either O(1) or O(active_fds).
465.Sp 618.Sp
619The epoll mechanism deserves honorable mention as the most misdesigned
620of the more advanced event mechanisms: mere annoyances include silently
621dropping file descriptors, requiring a system call per change per file
622descriptor (and unnecessary guessing of parameters), problems with dup,
623returning before the timeout value, resulting in additional iterations
624(and only giving 5ms accuracy while select on the same platform gives
6250.1ms) and so on. The biggest issue is fork races, however \- if a program
626forks then \fIboth\fR parent and child process have to recreate the epoll
627set, which can take considerable time (one syscall per file descriptor)
628and is of course hard to detect.
629.Sp
630Epoll is also notoriously buggy \- embedding epoll fds \fIshould\fR work,
631but of course \fIdoesn't\fR, and epoll just loves to report events for
632totally \fIdifferent\fR file descriptors (even already closed ones, so
633one cannot even remove them from the set) than registered in the set
634(especially on \s-1SMP\s0 systems). Libev tries to counter these spurious
635notifications by employing an additional generation counter and comparing
636that against the events to filter out spurious ones, recreating the set
637when required. Epoll also erroneously rounds down timeouts, but gives you
638no way to know when and by how much, so sometimes you have to busy-wait
639because epoll returns immediately despite a nonzero timeout. And last
640not least, it also refuses to work with some file descriptors which work
641perfectly fine with \f(CW\*(C`select\*(C'\fR (files, many character devices...).
642.Sp
643Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
644cobbled together in a hurry, no thought to design or interaction with
645others. Oh, the pain, will it ever stop...
646.Sp
466While stopping and starting an I/O watcher in the same iteration will 647While stopping, setting and starting an I/O watcher in the same iteration
467result in some caching, there is still a syscall per such incident 648will result in some caching, there is still a system call per such
468(because the fd could point to a different file description now), so its 649incident (because the same \fIfile descriptor\fR could point to a different
469best to avoid that. Also, \fIdup()\fRed file descriptors might not work very 650\&\fIfile description\fR now), so its best to avoid that. Also, \f(CW\*(C`dup ()\*(C'\fR'ed
470well if you register events for both fds. 651file descriptors might not work very well if you register events for both
652file descriptors.
471.Sp 653.Sp
472Please note that epoll sometimes generates spurious notifications, so you 654Best performance from this backend is achieved by not unregistering all
473need to use non-blocking I/O or other means to avoid blocking when no data 655watchers for a file descriptor until it has been closed, if possible,
474(or space) is available. 656i.e. keep at least one watcher active per fd at all times. Stopping and
657starting a watcher (without re-setting it) also usually doesn't cause
658extra overhead. A fork can both result in spurious notifications as well
659as in libev having to destroy and recreate the epoll object, which can
660take considerable time and thus should be avoided.
661.Sp
662All this means that, in practice, \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR can be as fast or
663faster than epoll for maybe up to a hundred file descriptors, depending on
664the usage. So sad.
665.Sp
666While nominally embeddable in other event loops, this feature is broken in
667all kernel versions tested so far.
668.Sp
669This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as
670\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
475.ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4 671.ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4
476.el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4 672.el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4
477.IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)" 673.IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)"
478Kqueue deserves special mention, as at the time of this writing, it 674Kqueue deserves special mention, as at the time of this writing, it
479was broken on all BSDs except NetBSD (usually it doesn't work with 675was broken on all BSDs except NetBSD (usually it doesn't work reliably
480anything but sockets and pipes, except on Darwin, where of course its 676with anything but sockets and pipes, except on Darwin, where of course
481completely useless). For this reason its not being \*(L"autodetected\*(R" 677it's completely useless). Unlike epoll, however, whose brokenness
678is by design, these kqueue bugs can (and eventually will) be fixed
679without \s-1API\s0 changes to existing programs. For this reason it's not being
482unless you explicitly specify it explicitly in the flags (i.e. using 680\&\*(L"auto-detected\*(R" unless you explicitly specify it in the flags (i.e. using
483\&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR). 681\&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR) or libev was compiled on a known-to-be-good (\-enough)
682system like NetBSD.
683.Sp
684You still can embed kqueue into a normal poll or select backend and use it
685only for sockets (after having made sure that sockets work with kqueue on
686the target platform). See \f(CW\*(C`ev_embed\*(C'\fR watchers for more info.
484.Sp 687.Sp
485It scales in the same way as the epoll backend, but the interface to the 688It scales in the same way as the epoll backend, but the interface to the
486kernel is more efficient (which says nothing about its actual speed, of 689kernel is more efficient (which says nothing about its actual speed, of
487course). While starting and stopping an I/O watcher does not cause an 690course). While stopping, setting and starting an I/O watcher does never
488extra syscall as with epoll, it still adds up to four event changes per 691cause an extra system call as with \f(CW\*(C`EVBACKEND_EPOLL\*(C'\fR, it still adds up to
489incident, so its best to avoid that. 692two event changes per incident. Support for \f(CW\*(C`fork ()\*(C'\fR is very bad (you
693might have to leak fd's on fork, but it's more sane than epoll) and it
694drops fds silently in similarly hard-to-detect cases.
695.Sp
696This backend usually performs well under most conditions.
697.Sp
698While nominally embeddable in other event loops, this doesn't work
699everywhere, so you might need to test for this. And since it is broken
700almost everywhere, you should only use it when you have a lot of sockets
701(for which it usually works), by embedding it into another event loop
702(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
703also broken on \s-1OS\s0 X)) and, did I mention it, using it only for sockets.
704.Sp
705This backend maps \f(CW\*(C`EV_READ\*(C'\fR into an \f(CW\*(C`EVFILT_READ\*(C'\fR kevent with
706\&\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
707\&\f(CW\*(C`NOTE_EOF\*(C'\fR.
490.ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4 708.ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4
491.el .IP "\f(CWEVBACKEND_DEVPOLL\fR (value 16, Solaris 8)" 4 709.el .IP "\f(CWEVBACKEND_DEVPOLL\fR (value 16, Solaris 8)" 4
492.IX Item "EVBACKEND_DEVPOLL (value 16, Solaris 8)" 710.IX Item "EVBACKEND_DEVPOLL (value 16, Solaris 8)"
493This is not implemented yet (and might never be). 711This is not implemented yet (and might never be, unless you send me an
712implementation). According to reports, \f(CW\*(C`/dev/poll\*(C'\fR only supports sockets
713and is not embeddable, which would limit the usefulness of this backend
714immensely.
494.ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4 715.ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4
495.el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4 716.el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4
496.IX Item "EVBACKEND_PORT (value 32, Solaris 10)" 717.IX Item "EVBACKEND_PORT (value 32, Solaris 10)"
497This uses the Solaris 10 port mechanism. As with everything on Solaris, 718This uses the Solaris 10 event port mechanism. As with everything on Solaris,
498it's really slow, but it still scales very well (O(active_fds)). 719it's really slow, but it still scales very well (O(active_fds)).
499.Sp 720.Sp
500Please note that solaris ports can result in a lot of spurious 721While this backend scales well, it requires one system call per active
501notifications, so you need to use non-blocking I/O or other means to avoid 722file descriptor per loop iteration. For small and medium numbers of file
502blocking when no data (or space) is available. 723descriptors a \*(L"slow\*(R" \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR backend
724might perform better.
725.Sp
726On the positive side, this backend actually performed fully to
727specification in all tests and is fully embeddable, which is a rare feat
728among the OS-specific backends (I vastly prefer correctness over speed
729hacks).
730.Sp
731On the negative side, the interface is \fIbizarre\fR \- so bizarre that
732even sun itself gets it wrong in their code examples: The event polling
733function sometimes returns events to the caller even though an error
734occurred, but with no indication whether it has done so or not (yes, it's
735even documented that way) \- deadly for edge-triggered interfaces where you
736absolutely have to know whether an event occurred or not because you have
737to re-arm the watcher.
738.Sp
739Fortunately libev seems to be able to work around these idiocies.
740.Sp
741This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as
742\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
503.ie n .IP """EVBACKEND_ALL""" 4 743.ie n .IP """EVBACKEND_ALL""" 4
504.el .IP "\f(CWEVBACKEND_ALL\fR" 4 744.el .IP "\f(CWEVBACKEND_ALL\fR" 4
505.IX Item "EVBACKEND_ALL" 745.IX Item "EVBACKEND_ALL"
506Try all backends (even potentially broken ones that wouldn't be tried 746Try all backends (even potentially broken ones that wouldn't be tried
507with \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). Since this is a mask, you can do stuff such as 747with \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). Since this is a mask, you can do stuff such as
508\&\f(CW\*(C`EVBACKEND_ALL & ~EVBACKEND_KQUEUE\*(C'\fR. 748\&\f(CW\*(C`EVBACKEND_ALL & ~EVBACKEND_KQUEUE\*(C'\fR.
749.Sp
750It is definitely not recommended to use this flag, use whatever
751\&\f(CW\*(C`ev_recommended_backends ()\*(C'\fR returns, or simply do not specify a backend
752at all.
753.ie n .IP """EVBACKEND_MASK""" 4
754.el .IP "\f(CWEVBACKEND_MASK\fR" 4
755.IX Item "EVBACKEND_MASK"
756Not a backend at all, but a mask to select all backend bits from a
757\&\f(CW\*(C`flags\*(C'\fR value, in case you want to mask out any backends from a flags
758value (e.g. when modifying the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR environment variable).
509.RE 759.RE
510.RS 4 760.RS 4
511.Sp 761.Sp
512If one or more of these are ored into the flags value, then only these 762If one or more of the backend flags are or'ed into the flags value,
513backends will be tried (in the reverse order as given here). If none are 763then only these backends will be tried (in the reverse order as listed
514specified, most compiled-in backend will be tried, usually in reverse 764here). If none are specified, all backends in \f(CW\*(C`ev_recommended_backends
515order of their flag values :) 765()\*(C'\fR will be tried.
516.Sp 766.Sp
517The most typical usage is like this: 767Example: Try to create a event loop that uses epoll and nothing else.
518.Sp 768.Sp
519.Vb 2 769.Vb 3
520\& if (!ev_default_loop (0)) 770\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
521\& fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); 771\& if (!epoller)
772\& fatal ("no epoll found here, maybe it hides under your chair");
522.Ve 773.Ve
523.Sp 774.Sp
524Restrict libev to the select and poll backends, and do not allow 775Example: Use whatever libev has to offer, but make sure that kqueue is
525environment settings to be taken into account: 776used if available.
526.Sp 777.Sp
527.Vb 1 778.Vb 1
528\& ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
529.Ve
530.Sp
531Use whatever libev has to offer, but make sure that kqueue is used if
532available (warning, breaks stuff, best use only with your own private
533event loop and only if you know the \s-1OS\s0 supports your types of fds):
534.Sp
535.Vb 1
536\& ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); 779\& struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
537.Ve 780.Ve
538.RE 781.RE
539.IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4
540.IX Item "struct ev_loop *ev_loop_new (unsigned int flags)"
541Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is
542always distinct from the default loop. Unlike the default loop, it cannot
543handle signal and child watchers, and attempts to do so will be greeted by
544undefined behaviour (or a failed assertion if assertions are enabled).
545.Sp
546Example: Try to create a event loop that uses epoll and nothing else.
547.Sp
548.Vb 3
549\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
550\& if (!epoller)
551\& fatal ("no epoll found here, maybe it hides under your chair");
552.Ve
553.IP "ev_default_destroy ()" 4 782.IP "ev_loop_destroy (loop)" 4
554.IX Item "ev_default_destroy ()" 783.IX Item "ev_loop_destroy (loop)"
555Destroys the default loop again (frees all memory and kernel state 784Destroys an event loop object (frees all memory and kernel state
556etc.). None of the active event watchers will be stopped in the normal 785etc.). None of the active event watchers will be stopped in the normal
557sense, so e.g. \f(CW\*(C`ev_is_active\*(C'\fR might still return true. It is your 786sense, so e.g. \f(CW\*(C`ev_is_active\*(C'\fR might still return true. It is your
558responsibility to either stop all watchers cleanly yoursef \fIbefore\fR 787responsibility to either stop all watchers cleanly yourself \fIbefore\fR
559calling this function, or cope with the fact afterwards (which is usually 788calling this function, or cope with the fact afterwards (which is usually
560the easiest thing, youc na just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them 789the easiest thing, you can just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them
561for example). 790for example).
562.IP "ev_loop_destroy (loop)" 4
563.IX Item "ev_loop_destroy (loop)"
564Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an
565earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR.
566.IP "ev_default_fork ()" 4
567.IX Item "ev_default_fork ()"
568This function reinitialises the kernel state for backends that have
569one. Despite the name, you can call it anytime, but it makes most sense
570after forking, in either the parent or child process (or both, but that
571again makes little sense).
572.Sp 791.Sp
573You \fImust\fR call this function in the child process after forking if and 792Note that certain global state, such as signal state (and installed signal
574only if you want to use the event library in both processes. If you just 793handlers), will not be freed by this function, and related watchers (such
575fork+exec, you don't have to call it. 794as signal and child watchers) would need to be stopped manually.
576.Sp 795.Sp
577The function itself is quite fast and it's usually not a problem to call 796This function is normally used on loop objects allocated by
578it just in case after a fork. To make this easy, the function will fit in 797\&\f(CW\*(C`ev_loop_new\*(C'\fR, but it can also be used on the default loop returned by
579quite nicely into a call to \f(CW\*(C`pthread_atfork\*(C'\fR: 798\&\f(CW\*(C`ev_default_loop\*(C'\fR, in which case it is not thread-safe.
580.Sp 799.Sp
581.Vb 1 800Note that it is not advisable to call this function on the default loop
582\& pthread_atfork (0, 0, ev_default_fork); 801except in the rare occasion where you really need to free its resources.
583.Ve 802If you need dynamically allocated loops it is better to use \f(CW\*(C`ev_loop_new\*(C'\fR
584.Sp 803and \f(CW\*(C`ev_loop_destroy\*(C'\fR.
585At the moment, \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and \f(CW\*(C`EVBACKEND_POLL\*(C'\fR are safe to use
586without calling this function, so if you force one of those backends you
587do not need to care.
588.IP "ev_loop_fork (loop)" 4 804.IP "ev_loop_fork (loop)" 4
589.IX Item "ev_loop_fork (loop)" 805.IX Item "ev_loop_fork (loop)"
590Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by 806This function sets a flag that causes subsequent \f(CW\*(C`ev_run\*(C'\fR iterations to
591\&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop 807reinitialise the kernel state for backends that have one. Despite the
592after fork, and how you do this is entirely your own problem. 808name, you can call it anytime, but it makes most sense after forking, in
809the child process. You \fImust\fR call it (or use \f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR) in the
810child before resuming or calling \f(CW\*(C`ev_run\*(C'\fR.
811.Sp
812Again, you \fIhave\fR to call it on \fIany\fR loop that you want to re-use after
813a fork, \fIeven if you do not plan to use the loop in the parent\fR. This is
814because some kernel interfaces *cough* \fIkqueue\fR *cough* do funny things
815during fork.
816.Sp
817On the other hand, you only need to call this function in the child
818process if and only if you want to use the event loop in the child. If
819you just fork+exec or create a new loop in the child, you don't have to
820call it at all (in fact, \f(CW\*(C`epoll\*(C'\fR is so badly broken that it makes a
821difference, but libev will usually detect this case on its own and do a
822costly reset of the backend).
823.Sp
824The function itself is quite fast and it's usually not a problem to call
825it just in case after a fork.
826.Sp
827Example: Automate calling \f(CW\*(C`ev_loop_fork\*(C'\fR on the default loop when
828using pthreads.
829.Sp
830.Vb 5
831\& static void
832\& post_fork_child (void)
833\& {
834\& ev_loop_fork (EV_DEFAULT);
835\& }
836\&
837\& ...
838\& pthread_atfork (0, 0, post_fork_child);
839.Ve
840.IP "int ev_is_default_loop (loop)" 4
841.IX Item "int ev_is_default_loop (loop)"
842Returns true when the given loop is, in fact, the default loop, and false
843otherwise.
593.IP "unsigned int ev_loop_count (loop)" 4 844.IP "unsigned int ev_iteration (loop)" 4
594.IX Item "unsigned int ev_loop_count (loop)" 845.IX Item "unsigned int ev_iteration (loop)"
595Returns the count of loop iterations for the loop, which is identical to 846Returns the current iteration count for the event loop, which is identical
596the number of times libev did poll for new events. It starts at \f(CW0\fR and 847to the number of times libev did poll for new events. It starts at \f(CW0\fR
597happily wraps around with enough iterations. 848and happily wraps around with enough iterations.
598.Sp 849.Sp
599This value can sometimes be useful as a generation counter of sorts (it 850This value can sometimes be useful as a generation counter of sorts (it
600\&\*(L"ticks\*(R" the number of loop iterations), as it roughly corresponds with 851\&\*(L"ticks\*(R" the number of loop iterations), as it roughly corresponds with
601\&\f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR calls. 852\&\f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR calls \- and is incremented between the
853prepare and check phases.
854.IP "unsigned int ev_depth (loop)" 4
855.IX Item "unsigned int ev_depth (loop)"
856Returns the number of times \f(CW\*(C`ev_run\*(C'\fR was entered minus the number of
857times \f(CW\*(C`ev_run\*(C'\fR was exited normally, in other words, the recursion depth.
858.Sp
859Outside \f(CW\*(C`ev_run\*(C'\fR, this number is zero. In a callback, this number is
860\&\f(CW1\fR, unless \f(CW\*(C`ev_run\*(C'\fR was invoked recursively (or from another thread),
861in which case it is higher.
862.Sp
863Leaving \f(CW\*(C`ev_run\*(C'\fR abnormally (setjmp/longjmp, cancelling the thread,
864throwing an exception etc.), doesn't count as \*(L"exit\*(R" \- consider this
865as a hint to avoid such ungentleman-like behaviour unless it's really
866convenient, in which case it is fully supported.
602.IP "unsigned int ev_backend (loop)" 4 867.IP "unsigned int ev_backend (loop)" 4
603.IX Item "unsigned int ev_backend (loop)" 868.IX Item "unsigned int ev_backend (loop)"
604Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in 869Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in
605use. 870use.
606.IP "ev_tstamp ev_now (loop)" 4 871.IP "ev_tstamp ev_now (loop)" 4
607.IX Item "ev_tstamp ev_now (loop)" 872.IX Item "ev_tstamp ev_now (loop)"
608Returns the current \*(L"event loop time\*(R", which is the time the event loop 873Returns the current \*(L"event loop time\*(R", which is the time the event loop
609received events and started processing them. This timestamp does not 874received events and started processing them. This timestamp does not
610change as long as callbacks are being processed, and this is also the base 875change as long as callbacks are being processed, and this is also the base
611time used for relative timers. You can treat it as the timestamp of the 876time used for relative timers. You can treat it as the timestamp of the
612event occuring (or more correctly, libev finding out about it). 877event occurring (or more correctly, libev finding out about it).
878.IP "ev_now_update (loop)" 4
879.IX Item "ev_now_update (loop)"
880Establishes the current time by querying the kernel, updating the time
881returned by \f(CW\*(C`ev_now ()\*(C'\fR in the progress. This is a costly operation and
882is usually done automatically within \f(CW\*(C`ev_run ()\*(C'\fR.
883.Sp
884This function is rarely useful, but when some event callback runs for a
885very long time without entering the event loop, updating libev's idea of
886the current time is a good idea.
887.Sp
888See also \*(L"The special problem of time updates\*(R" in the \f(CW\*(C`ev_timer\*(C'\fR section.
889.IP "ev_suspend (loop)" 4
890.IX Item "ev_suspend (loop)"
891.PD 0
892.IP "ev_resume (loop)" 4
893.IX Item "ev_resume (loop)"
894.PD
895These two functions suspend and resume an event loop, for use when the
896loop is not used for a while and timeouts should not be processed.
897.Sp
898A typical use case would be an interactive program such as a game: When
899the user presses \f(CW\*(C`^Z\*(C'\fR to suspend the game and resumes it an hour later it
900would be best to handle timeouts as if no time had actually passed while
901the program was suspended. This can be achieved by calling \f(CW\*(C`ev_suspend\*(C'\fR
902in your \f(CW\*(C`SIGTSTP\*(C'\fR handler, sending yourself a \f(CW\*(C`SIGSTOP\*(C'\fR and calling
903\&\f(CW\*(C`ev_resume\*(C'\fR directly afterwards to resume timer processing.
904.Sp
905Effectively, all \f(CW\*(C`ev_timer\*(C'\fR watchers will be delayed by the time spend
906between \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
907will be rescheduled (that is, they will lose any events that would have
908occurred while suspended).
909.Sp
910After calling \f(CW\*(C`ev_suspend\*(C'\fR you \fBmust not\fR call \fIany\fR function on the
911given loop other than \f(CW\*(C`ev_resume\*(C'\fR, and you \fBmust not\fR call \f(CW\*(C`ev_resume\*(C'\fR
912without a previous call to \f(CW\*(C`ev_suspend\*(C'\fR.
913.Sp
914Calling \f(CW\*(C`ev_suspend\*(C'\fR/\f(CW\*(C`ev_resume\*(C'\fR has the side effect of updating the
915event loop time (see \f(CW\*(C`ev_now_update\*(C'\fR).
613.IP "ev_loop (loop, int flags)" 4 916.IP "bool ev_run (loop, int flags)" 4
614.IX Item "ev_loop (loop, int flags)" 917.IX Item "bool ev_run (loop, int flags)"
615Finally, this is it, the event handler. This function usually is called 918Finally, this is it, the event handler. This function usually is called
616after you initialised all your watchers and you want to start handling 919after you have initialised all your watchers and you want to start
617events. 920handling events. It will ask the operating system for any new events, call
921the watcher callbacks, and then repeat the whole process indefinitely: This
922is why event loops are called \fIloops\fR.
618.Sp 923.Sp
619If the flags argument is specified as \f(CW0\fR, it will not return until 924If the flags argument is specified as \f(CW0\fR, it will keep handling events
620either no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called. 925until either no event watchers are active anymore or \f(CW\*(C`ev_break\*(C'\fR was
926called.
621.Sp 927.Sp
928The return value is false if there are no more active watchers (which
929usually means \*(L"all jobs done\*(R" or \*(L"deadlock\*(R"), and true in all other cases
930(which usually means " you should call \f(CW\*(C`ev_run\*(C'\fR again").
931.Sp
622Please note that an explicit \f(CW\*(C`ev_unloop\*(C'\fR is usually better than 932Please note that an explicit \f(CW\*(C`ev_break\*(C'\fR is usually better than
623relying on all watchers to be stopped when deciding when a program has 933relying on all watchers to be stopped when deciding when a program has
624finished (especially in interactive programs), but having a program that 934finished (especially in interactive programs), but having a program
625automatically loops as long as it has to and no longer by virtue of 935that automatically loops as long as it has to and no longer by virtue
626relying on its watchers stopping correctly is a thing of beauty. 936of relying on its watchers stopping correctly, that is truly a thing of
937beauty.
627.Sp 938.Sp
939This function is \fImostly\fR exception-safe \- you can break out of a
940\&\f(CW\*(C`ev_run\*(C'\fR call by calling \f(CW\*(C`longjmp\*(C'\fR in a callback, throwing a \*(C+
941exception and so on. This does not decrement the \f(CW\*(C`ev_depth\*(C'\fR value, nor
942will it clear any outstanding \f(CW\*(C`EVBREAK_ONE\*(C'\fR breaks.
943.Sp
628A flags value of \f(CW\*(C`EVLOOP_NONBLOCK\*(C'\fR will look for new events, will handle 944A flags value of \f(CW\*(C`EVRUN_NOWAIT\*(C'\fR will look for new events, will handle
629those events and any outstanding ones, but will not block your process in 945those events and any already outstanding ones, but will not wait and
630case there are no events and will return after one iteration of the loop. 946block your process in case there are no events and will return after one
947iteration of the loop. This is sometimes useful to poll and handle new
948events while doing lengthy calculations, to keep the program responsive.
631.Sp 949.Sp
632A flags value of \f(CW\*(C`EVLOOP_ONESHOT\*(C'\fR will look for new events (waiting if 950A flags value of \f(CW\*(C`EVRUN_ONCE\*(C'\fR will look for new events (waiting if
633neccessary) and will handle those and any outstanding ones. It will block 951necessary) and will handle those and any already outstanding ones. It
634your process until at least one new event arrives, and will return after 952will block your process until at least one new event arrives (which could
635one iteration of the loop. This is useful if you are waiting for some 953be an event internal to libev itself, so there is no guarantee that a
636external event in conjunction with something not expressible using other 954user-registered callback will be called), and will return after one
955iteration of the loop.
956.Sp
957This is useful if you are waiting for some external event in conjunction
958with something not expressible using other libev watchers (i.e. "roll your
637libev watchers. However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is 959own \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
638usually a better approach for this kind of thing. 960usually a better approach for this kind of thing.
639.Sp 961.Sp
640Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does: 962Here are the gory details of what \f(CW\*(C`ev_run\*(C'\fR does (this is for your
963understanding, not a guarantee that things will work exactly like this in
964future versions):
641.Sp 965.Sp
642.Vb 19 966.Vb 10
967\& \- Increment loop depth.
968\& \- Reset the ev_break status.
643\& - Before the first iteration, call any pending watchers. 969\& \- Before the first iteration, call any pending watchers.
644\& * If there are no active watchers (reference count is zero), return. 970\& LOOP:
645\& - Queue all prepare watchers and then call all outstanding watchers. 971\& \- If EVFLAG_FORKCHECK was used, check for a fork.
972\& \- If a fork was detected (by any means), queue and call all fork watchers.
973\& \- Queue and call all prepare watchers.
974\& \- If ev_break was called, goto FINISH.
646\& - If we have been forked, recreate the kernel state. 975\& \- If we have been forked, detach and recreate the kernel state
976\& as to not disturb the other process.
647\& - Update the kernel state with all outstanding changes. 977\& \- Update the kernel state with all outstanding changes.
648\& - Update the "event loop time". 978\& \- Update the "event loop time" (ev_now ()).
649\& - Calculate for how long to block. 979\& \- Calculate for how long to sleep or block, if at all
980\& (active idle watchers, EVRUN_NOWAIT or not having
981\& any active watchers at all will result in not sleeping).
982\& \- Sleep if the I/O and timer collect interval say so.
983\& \- Increment loop iteration counter.
650\& - Block the process, waiting for any events. 984\& \- Block the process, waiting for any events.
651\& - Queue all outstanding I/O (fd) events. 985\& \- Queue all outstanding I/O (fd) events.
652\& - Update the "event loop time" and do time jump handling. 986\& \- Update the "event loop time" (ev_now ()), and do time jump adjustments.
653\& - Queue all outstanding timers. 987\& \- Queue all expired timers.
654\& - Queue all outstanding periodics. 988\& \- Queue all expired periodics.
655\& - If no events are pending now, queue all idle watchers. 989\& \- Queue all idle watchers with priority higher than that of pending events.
656\& - Queue all check watchers. 990\& \- Queue all check watchers.
657\& - Call all queued watchers in reverse order (i.e. check watchers first). 991\& \- Call all queued watchers in reverse order (i.e. check watchers first).
658\& Signals and child watchers are implemented as I/O watchers, and will 992\& Signals and child watchers are implemented as I/O watchers, and will
659\& be handled here by queueing them when their watcher gets executed. 993\& be handled here by queueing them when their watcher gets executed.
660\& - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 994\& \- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
661\& were used, return, otherwise continue with step *. 995\& were used, or there are no active watchers, goto FINISH, otherwise
996\& continue with step LOOP.
997\& FINISH:
998\& \- Reset the ev_break status iff it was EVBREAK_ONE.
999\& \- Decrement the loop depth.
1000\& \- Return.
662.Ve 1001.Ve
663.Sp 1002.Sp
664Example: Queue some jobs and then loop until no events are outsanding 1003Example: Queue some jobs and then loop until no events are outstanding
665anymore. 1004anymore.
666.Sp 1005.Sp
667.Vb 4 1006.Vb 4
668\& ... queue jobs here, make sure they register event watchers as long 1007\& ... queue jobs here, make sure they register event watchers as long
669\& ... as they still have work to do (even an idle watcher will do..) 1008\& ... as they still have work to do (even an idle watcher will do..)
670\& ev_loop (my_loop, 0); 1009\& ev_run (my_loop, 0);
671\& ... jobs done. yeah! 1010\& ... jobs done or somebody called break. yeah!
672.Ve 1011.Ve
673.IP "ev_unloop (loop, how)" 4 1012.IP "ev_break (loop, how)" 4
674.IX Item "ev_unloop (loop, how)" 1013.IX Item "ev_break (loop, how)"
675Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it 1014Can be used to make a call to \f(CW\*(C`ev_run\*(C'\fR return early (but only after it
676has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either 1015has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either
677\&\f(CW\*(C`EVUNLOOP_ONE\*(C'\fR, which will make the innermost \f(CW\*(C`ev_loop\*(C'\fR call return, or 1016\&\f(CW\*(C`EVBREAK_ONE\*(C'\fR, which will make the innermost \f(CW\*(C`ev_run\*(C'\fR call return, or
678\&\f(CW\*(C`EVUNLOOP_ALL\*(C'\fR, which will make all nested \f(CW\*(C`ev_loop\*(C'\fR calls return. 1017\&\f(CW\*(C`EVBREAK_ALL\*(C'\fR, which will make all nested \f(CW\*(C`ev_run\*(C'\fR calls return.
1018.Sp
1019This \*(L"break state\*(R" will be cleared on the next call to \f(CW\*(C`ev_run\*(C'\fR.
1020.Sp
1021It is safe to call \f(CW\*(C`ev_break\*(C'\fR from outside any \f(CW\*(C`ev_run\*(C'\fR calls, too, in
1022which case it will have no effect.
679.IP "ev_ref (loop)" 4 1023.IP "ev_ref (loop)" 4
680.IX Item "ev_ref (loop)" 1024.IX Item "ev_ref (loop)"
681.PD 0 1025.PD 0
682.IP "ev_unref (loop)" 4 1026.IP "ev_unref (loop)" 4
683.IX Item "ev_unref (loop)" 1027.IX Item "ev_unref (loop)"
684.PD 1028.PD
685Ref/unref can be used to add or remove a reference count on the event 1029Ref/unref can be used to add or remove a reference count on the event
686loop: Every watcher keeps one reference, and as long as the reference 1030loop: Every watcher keeps one reference, and as long as the reference
687count is nonzero, \f(CW\*(C`ev_loop\*(C'\fR will not return on its own. If you have 1031count is nonzero, \f(CW\*(C`ev_run\*(C'\fR will not return on its own.
688a watcher you never unregister that should not keep \f(CW\*(C`ev_loop\*(C'\fR from 1032.Sp
689returning, \fIev_unref()\fR after starting, and \fIev_ref()\fR before stopping it. For 1033This is useful when you have a watcher that you never intend to
1034unregister, but that nevertheless should not keep \f(CW\*(C`ev_run\*(C'\fR from
1035returning. In such a case, call \f(CW\*(C`ev_unref\*(C'\fR after starting, and \f(CW\*(C`ev_ref\*(C'\fR
1036before stopping it.
1037.Sp
690example, libev itself uses this for its internal signal pipe: It is not 1038As an example, libev itself uses this for its internal signal pipe: It
691visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if 1039is not visible to the libev user and should not keep \f(CW\*(C`ev_run\*(C'\fR from
692no event watchers registered by it are active. It is also an excellent 1040exiting if no event watchers registered by it are active. It is also an
693way to do this for generic recurring timers or from within third-party 1041excellent way to do this for generic recurring timers or from within
694libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR. 1042third-party libraries. Just remember to \fIunref after start\fR and \fIref
1043before stop\fR (but only if the watcher wasn't active before, or was active
1044before, respectively. Note also that libev might stop watchers itself
1045(e.g. non-repeating timers) in which case you have to \f(CW\*(C`ev_ref\*(C'\fR
1046in the callback).
695.Sp 1047.Sp
696Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR 1048Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_run\*(C'\fR
697running when nothing else is active. 1049running when nothing else is active.
698.Sp 1050.Sp
699.Vb 4 1051.Vb 4
700\& struct ev_signal exitsig; 1052\& ev_signal exitsig;
701\& ev_signal_init (&exitsig, sig_cb, SIGINT); 1053\& ev_signal_init (&exitsig, sig_cb, SIGINT);
702\& ev_signal_start (loop, &exitsig); 1054\& ev_signal_start (loop, &exitsig);
703\& evf_unref (loop); 1055\& ev_unref (loop);
704.Ve 1056.Ve
705.Sp 1057.Sp
706Example: For some weird reason, unregister the above signal handler again. 1058Example: For some weird reason, unregister the above signal handler again.
707.Sp 1059.Sp
708.Vb 2 1060.Vb 2
709\& ev_ref (loop); 1061\& ev_ref (loop);
710\& ev_signal_stop (loop, &exitsig); 1062\& ev_signal_stop (loop, &exitsig);
711.Ve 1063.Ve
1064.IP "ev_set_io_collect_interval (loop, ev_tstamp interval)" 4
1065.IX Item "ev_set_io_collect_interval (loop, ev_tstamp interval)"
1066.PD 0
1067.IP "ev_set_timeout_collect_interval (loop, ev_tstamp interval)" 4
1068.IX Item "ev_set_timeout_collect_interval (loop, ev_tstamp interval)"
1069.PD
1070These advanced functions influence the time that libev will spend waiting
1071for events. Both time intervals are by default \f(CW0\fR, meaning that libev
1072will try to invoke timer/periodic callbacks and I/O callbacks with minimum
1073latency.
1074.Sp
1075Setting these to a higher value (the \f(CW\*(C`interval\*(C'\fR \fImust\fR be >= \f(CW0\fR)
1076allows libev to delay invocation of I/O and timer/periodic callbacks
1077to increase efficiency of loop iterations (or to increase power-saving
1078opportunities).
1079.Sp
1080The idea is that sometimes your program runs just fast enough to handle
1081one (or very few) event(s) per loop iteration. While this makes the
1082program responsive, it also wastes a lot of \s-1CPU\s0 time to poll for new
1083events, especially with backends like \f(CW\*(C`select ()\*(C'\fR which have a high
1084overhead for the actual polling but can deliver many events at once.
1085.Sp
1086By setting a higher \fIio collect interval\fR you allow libev to spend more
1087time collecting I/O events, so you can handle more events per iteration,
1088at the cost of increasing latency. Timeouts (both \f(CW\*(C`ev_periodic\*(C'\fR and
1089\&\f(CW\*(C`ev_timer\*(C'\fR) will not be affected. Setting this to a non-null value will
1090introduce an additional \f(CW\*(C`ev_sleep ()\*(C'\fR call into most loop iterations. The
1091sleep time ensures that libev will not poll for I/O events more often then
1092once per this interval, on average (as long as the host time resolution is
1093good enough).
1094.Sp
1095Likewise, by setting a higher \fItimeout collect interval\fR you allow libev
1096to spend more time collecting timeouts, at the expense of increased
1097latency/jitter/inexactness (the watcher callback will be called
1098later). \f(CW\*(C`ev_io\*(C'\fR watchers will not be affected. Setting this to a non-null
1099value will not introduce any overhead in libev.
1100.Sp
1101Many (busy) programs can usually benefit by setting the I/O collect
1102interval to a value near \f(CW0.1\fR or so, which is often enough for
1103interactive servers (of course not for games), likewise for timeouts. It
1104usually doesn't make much sense to set it to a lower value than \f(CW0.01\fR,
1105as this approaches the timing granularity of most systems. Note that if
1106you do transactions with the outside world and you can't increase the
1107parallelity, then this setting will limit your transaction rate (if you
1108need to poll once per transaction and the I/O collect interval is 0.01,
1109then you can't do more than 100 transactions per second).
1110.Sp
1111Setting the \fItimeout collect interval\fR can improve the opportunity for
1112saving power, as the program will \*(L"bundle\*(R" timer callback invocations that
1113are \*(L"near\*(R" in time together, by delaying some, thus reducing the number of
1114times the process sleeps and wakes up again. Another useful technique to
1115reduce iterations/wake\-ups is to use \f(CW\*(C`ev_periodic\*(C'\fR watchers and make sure
1116they fire on, say, one-second boundaries only.
1117.Sp
1118Example: we only need 0.1s timeout granularity, and we wish not to poll
1119more often than 100 times per second:
1120.Sp
1121.Vb 2
1122\& ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
1123\& ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
1124.Ve
1125.IP "ev_invoke_pending (loop)" 4
1126.IX Item "ev_invoke_pending (loop)"
1127This call will simply invoke all pending watchers while resetting their
1128pending state. Normally, \f(CW\*(C`ev_run\*(C'\fR does this automatically when required,
1129but when overriding the invoke callback this call comes handy. This
1130function can be invoked from a watcher \- this can be useful for example
1131when you want to do some lengthy calculation and want to pass further
1132event handling to another thread (you still have to make sure only one
1133thread executes within \f(CW\*(C`ev_invoke_pending\*(C'\fR or \f(CW\*(C`ev_run\*(C'\fR of course).
1134.IP "int ev_pending_count (loop)" 4
1135.IX Item "int ev_pending_count (loop)"
1136Returns the number of pending watchers \- zero indicates that no watchers
1137are pending.
1138.IP "ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(\s-1EV_P\s0))" 4
1139.IX Item "ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))"
1140This overrides the invoke pending functionality of the loop: Instead of
1141invoking all pending watchers when there are any, \f(CW\*(C`ev_run\*(C'\fR will call
1142this callback instead. This is useful, for example, when you want to
1143invoke the actual watchers inside another context (another thread etc.).
1144.Sp
1145If you want to reset the callback, use \f(CW\*(C`ev_invoke_pending\*(C'\fR as new
1146callback.
1147.IP "ev_set_loop_release_cb (loop, void (*release)(\s-1EV_P\s0) throw (), void (*acquire)(\s-1EV_P\s0) throw ())" 4
1148.IX Item "ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())"
1149Sometimes you want to share the same loop between multiple threads. This
1150can be done relatively simply by putting mutex_lock/unlock calls around
1151each call to a libev function.
1152.Sp
1153However, \f(CW\*(C`ev_run\*(C'\fR can run an indefinite time, so it is not feasible
1154to wait for it to return. One way around this is to wake up the event
1155loop via \f(CW\*(C`ev_break\*(C'\fR and \f(CW\*(C`ev_async_send\*(C'\fR, another way is to set these
1156\&\fIrelease\fR and \fIacquire\fR callbacks on the loop.
1157.Sp
1158When set, then \f(CW\*(C`release\*(C'\fR will be called just before the thread is
1159suspended waiting for new events, and \f(CW\*(C`acquire\*(C'\fR is called just
1160afterwards.
1161.Sp
1162Ideally, \f(CW\*(C`release\*(C'\fR will just call your mutex_unlock function, and
1163\&\f(CW\*(C`acquire\*(C'\fR will just call the mutex_lock function again.
1164.Sp
1165While event loop modifications are allowed between invocations of
1166\&\f(CW\*(C`release\*(C'\fR and \f(CW\*(C`acquire\*(C'\fR (that's their only purpose after all), no
1167modifications done will affect the event loop, i.e. adding watchers will
1168have no effect on the set of file descriptors being watched, or the time
1169waited. Use an \f(CW\*(C`ev_async\*(C'\fR watcher to wake up \f(CW\*(C`ev_run\*(C'\fR when you want it
1170to take note of any changes you made.
1171.Sp
1172In theory, threads executing \f(CW\*(C`ev_run\*(C'\fR will be async-cancel safe between
1173invocations of \f(CW\*(C`release\*(C'\fR and \f(CW\*(C`acquire\*(C'\fR.
1174.Sp
1175See also the locking example in the \f(CW\*(C`THREADS\*(C'\fR section later in this
1176document.
1177.IP "ev_set_userdata (loop, void *data)" 4
1178.IX Item "ev_set_userdata (loop, void *data)"
1179.PD 0
1180.IP "void *ev_userdata (loop)" 4
1181.IX Item "void *ev_userdata (loop)"
1182.PD
1183Set and retrieve a single \f(CW\*(C`void *\*(C'\fR associated with a loop. When
1184\&\f(CW\*(C`ev_set_userdata\*(C'\fR has never been called, then \f(CW\*(C`ev_userdata\*(C'\fR returns
1185\&\f(CW0\fR.
1186.Sp
1187These two functions can be used to associate arbitrary data with a loop,
1188and are intended solely for the \f(CW\*(C`invoke_pending_cb\*(C'\fR, \f(CW\*(C`release\*(C'\fR and
1189\&\f(CW\*(C`acquire\*(C'\fR callbacks described above, but of course can be (ab\-)used for
1190any other purpose as well.
1191.IP "ev_verify (loop)" 4
1192.IX Item "ev_verify (loop)"
1193This function only does something when \f(CW\*(C`EV_VERIFY\*(C'\fR support has been
1194compiled in, which is the default for non-minimal builds. It tries to go
1195through all internal structures and checks them for validity. If anything
1196is found to be inconsistent, it will print an error message to standard
1197error and call \f(CW\*(C`abort ()\*(C'\fR.
1198.Sp
1199This can be used to catch bugs inside libev itself: under normal
1200circumstances, this function will never abort as of course libev keeps its
1201data structures consistent.
712.SH "ANATOMY OF A WATCHER" 1202.SH "ANATOMY OF A WATCHER"
713.IX Header "ANATOMY OF A WATCHER" 1203.IX Header "ANATOMY OF A WATCHER"
1204In the following description, uppercase \f(CW\*(C`TYPE\*(C'\fR in names stands for the
1205watcher type, e.g. \f(CW\*(C`ev_TYPE_start\*(C'\fR can mean \f(CW\*(C`ev_timer_start\*(C'\fR for timer
1206watchers and \f(CW\*(C`ev_io_start\*(C'\fR for I/O watchers.
1207.PP
714A watcher is a structure that you create and register to record your 1208A watcher is an opaque structure that you allocate and register to record
715interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to 1209your interest in some event. To make a concrete example, imagine you want
716become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that: 1210to wait for \s-1STDIN\s0 to become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher
1211for that:
717.PP 1212.PP
718.Vb 5 1213.Vb 5
719\& static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1214\& static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
720\& { 1215\& {
721\& ev_io_stop (w); 1216\& ev_io_stop (w);
722\& ev_unloop (loop, EVUNLOOP_ALL); 1217\& ev_break (loop, EVBREAK_ALL);
723\& } 1218\& }
724.Ve 1219\&
725.PP
726.Vb 6
727\& struct ev_loop *loop = ev_default_loop (0); 1220\& struct ev_loop *loop = ev_default_loop (0);
1221\&
728\& struct ev_io stdin_watcher; 1222\& ev_io stdin_watcher;
1223\&
729\& ev_init (&stdin_watcher, my_cb); 1224\& ev_init (&stdin_watcher, my_cb);
730\& ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); 1225\& ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
731\& ev_io_start (loop, &stdin_watcher); 1226\& ev_io_start (loop, &stdin_watcher);
1227\&
732\& ev_loop (loop, 0); 1228\& ev_run (loop, 0);
733.Ve 1229.Ve
734.PP 1230.PP
735As you can see, you are responsible for allocating the memory for your 1231As you can see, you are responsible for allocating the memory for your
736watcher structures (and it is usually a bad idea to do this on the stack, 1232watcher structures (and it is \fIusually\fR a bad idea to do this on the
737although this can sometimes be quite valid). 1233stack).
738.PP 1234.PP
1235Each watcher has an associated watcher structure (called \f(CW\*(C`struct ev_TYPE\*(C'\fR
1236or simply \f(CW\*(C`ev_TYPE\*(C'\fR, as typedefs are provided for all watcher structs).
1237.PP
739Each watcher structure must be initialised by a call to \f(CW\*(C`ev_init 1238Each watcher structure must be initialised by a call to \f(CW\*(C`ev_init (watcher
740(watcher *, callback)\*(C'\fR, which expects a callback to be provided. This 1239*, callback)\*(C'\fR, which expects a callback to be provided. This callback is
741callback gets invoked each time the event occurs (or, in the case of io 1240invoked each time the event occurs (or, in the case of I/O watchers, each
742watchers, each time the event loop detects that the file descriptor given 1241time the event loop detects that the file descriptor given is readable
743is readable and/or writable). 1242and/or writable).
744.PP 1243.PP
745Each watcher type has its own \f(CW\*(C`ev_<type>_set (watcher *, ...)\*(C'\fR macro 1244Each watcher type further has its own \f(CW\*(C`ev_TYPE_set (watcher *, ...)\*(C'\fR
746with arguments specific to this watcher type. There is also a macro 1245macro to configure it, with arguments specific to the watcher type. There
747to combine initialisation and setting in one call: \f(CW\*(C`ev_<type>_init 1246is also a macro to combine initialisation and setting in one call: \f(CW\*(C`ev_TYPE_init (watcher *, callback, ...)\*(C'\fR.
748(watcher *, callback, ...)\*(C'\fR.
749.PP 1247.PP
750To make the watcher actually watch out for events, you have to start it 1248To make the watcher actually watch out for events, you have to start it
751with a watcher-specific start function (\f(CW\*(C`ev_<type>_start (loop, watcher 1249with a watcher-specific start function (\f(CW\*(C`ev_TYPE_start (loop, watcher
752*)\*(C'\fR), and you can stop watching for events at any time by calling the 1250*)\*(C'\fR), and you can stop watching for events at any time by calling the
753corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR. 1251corresponding stop function (\f(CW\*(C`ev_TYPE_stop (loop, watcher *)\*(C'\fR.
754.PP 1252.PP
755As long as your watcher is active (has been started but not stopped) you 1253As long as your watcher is active (has been started but not stopped) you
756must not touch the values stored in it. Most specifically you must never 1254must not touch the values stored in it. Most specifically you must never
757reinitialise it or call its \f(CW\*(C`set\*(C'\fR macro. 1255reinitialise it or call its \f(CW\*(C`ev_TYPE_set\*(C'\fR macro.
758.PP 1256.PP
759Each and every callback receives the event loop pointer as first, the 1257Each and every callback receives the event loop pointer as first, the
760registered watcher structure as second, and a bitset of received events as 1258registered watcher structure as second, and a bitset of received events as
761third argument. 1259third argument.
762.PP 1260.PP
… …
771.el .IP "\f(CWEV_WRITE\fR" 4 1269.el .IP "\f(CWEV_WRITE\fR" 4
772.IX Item "EV_WRITE" 1270.IX Item "EV_WRITE"
773.PD 1271.PD
774The file descriptor in the \f(CW\*(C`ev_io\*(C'\fR watcher has become readable and/or 1272The file descriptor in the \f(CW\*(C`ev_io\*(C'\fR watcher has become readable and/or
775writable. 1273writable.
776.ie n .IP """EV_TIMEOUT""" 4 1274.ie n .IP """EV_TIMER""" 4
777.el .IP "\f(CWEV_TIMEOUT\fR" 4 1275.el .IP "\f(CWEV_TIMER\fR" 4
778.IX Item "EV_TIMEOUT" 1276.IX Item "EV_TIMER"
779The \f(CW\*(C`ev_timer\*(C'\fR watcher has timed out. 1277The \f(CW\*(C`ev_timer\*(C'\fR watcher has timed out.
780.ie n .IP """EV_PERIODIC""" 4 1278.ie n .IP """EV_PERIODIC""" 4
781.el .IP "\f(CWEV_PERIODIC\fR" 4 1279.el .IP "\f(CWEV_PERIODIC\fR" 4
782.IX Item "EV_PERIODIC" 1280.IX Item "EV_PERIODIC"
783The \f(CW\*(C`ev_periodic\*(C'\fR watcher has timed out. 1281The \f(CW\*(C`ev_periodic\*(C'\fR watcher has timed out.
… …
803.PD 0 1301.PD 0
804.ie n .IP """EV_CHECK""" 4 1302.ie n .IP """EV_CHECK""" 4
805.el .IP "\f(CWEV_CHECK\fR" 4 1303.el .IP "\f(CWEV_CHECK\fR" 4
806.IX Item "EV_CHECK" 1304.IX Item "EV_CHECK"
807.PD 1305.PD
808All \f(CW\*(C`ev_prepare\*(C'\fR watchers are invoked just \fIbefore\fR \f(CW\*(C`ev_loop\*(C'\fR starts 1306All \f(CW\*(C`ev_prepare\*(C'\fR watchers are invoked just \fIbefore\fR \f(CW\*(C`ev_run\*(C'\fR starts to
809to gather new events, and all \f(CW\*(C`ev_check\*(C'\fR watchers are invoked just after 1307gather new events, and all \f(CW\*(C`ev_check\*(C'\fR watchers are queued (not invoked)
810\&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any 1308just after \f(CW\*(C`ev_run\*(C'\fR has gathered them, but before it queues any callbacks
1309for any received events. That means \f(CW\*(C`ev_prepare\*(C'\fR watchers are the last
1310watchers invoked before the event loop sleeps or polls for new events, and
1311\&\f(CW\*(C`ev_check\*(C'\fR watchers will be invoked before any other watchers of the same
1312or lower priority within an event loop iteration.
1313.Sp
811received events. Callbacks of both watcher types can start and stop as 1314Callbacks of both watcher types can start and stop as many watchers as
812many watchers as they want, and all of them will be taken into account 1315they want, and all of them will be taken into account (for example, a
813(for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep 1316\&\f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep \f(CW\*(C`ev_run\*(C'\fR from
814\&\f(CW\*(C`ev_loop\*(C'\fR from blocking). 1317blocking).
815.ie n .IP """EV_EMBED""" 4 1318.ie n .IP """EV_EMBED""" 4
816.el .IP "\f(CWEV_EMBED\fR" 4 1319.el .IP "\f(CWEV_EMBED\fR" 4
817.IX Item "EV_EMBED" 1320.IX Item "EV_EMBED"
818The embedded event loop specified in the \f(CW\*(C`ev_embed\*(C'\fR watcher needs attention. 1321The embedded event loop specified in the \f(CW\*(C`ev_embed\*(C'\fR watcher needs attention.
819.ie n .IP """EV_FORK""" 4 1322.ie n .IP """EV_FORK""" 4
820.el .IP "\f(CWEV_FORK\fR" 4 1323.el .IP "\f(CWEV_FORK\fR" 4
821.IX Item "EV_FORK" 1324.IX Item "EV_FORK"
822The event loop has been resumed in the child process after fork (see 1325The event loop has been resumed in the child process after fork (see
823\&\f(CW\*(C`ev_fork\*(C'\fR). 1326\&\f(CW\*(C`ev_fork\*(C'\fR).
1327.ie n .IP """EV_CLEANUP""" 4
1328.el .IP "\f(CWEV_CLEANUP\fR" 4
1329.IX Item "EV_CLEANUP"
1330The event loop is about to be destroyed (see \f(CW\*(C`ev_cleanup\*(C'\fR).
1331.ie n .IP """EV_ASYNC""" 4
1332.el .IP "\f(CWEV_ASYNC\fR" 4
1333.IX Item "EV_ASYNC"
1334The given async watcher has been asynchronously notified (see \f(CW\*(C`ev_async\*(C'\fR).
1335.ie n .IP """EV_CUSTOM""" 4
1336.el .IP "\f(CWEV_CUSTOM\fR" 4
1337.IX Item "EV_CUSTOM"
1338Not ever sent (or otherwise used) by libev itself, but can be freely used
1339by libev users to signal watchers (e.g. via \f(CW\*(C`ev_feed_event\*(C'\fR).
824.ie n .IP """EV_ERROR""" 4 1340.ie n .IP """EV_ERROR""" 4
825.el .IP "\f(CWEV_ERROR\fR" 4 1341.el .IP "\f(CWEV_ERROR\fR" 4
826.IX Item "EV_ERROR" 1342.IX Item "EV_ERROR"
827An unspecified error has occured, the watcher has been stopped. This might 1343An unspecified error has occurred, the watcher has been stopped. This might
828happen because the watcher could not be properly started because libev 1344happen because the watcher could not be properly started because libev
829ran out of memory, a file descriptor was found to be closed or any other 1345ran out of memory, a file descriptor was found to be closed or any other
1346problem. Libev considers these application bugs.
1347.Sp
830problem. You best act on it by reporting the problem and somehow coping 1348You best act on it by reporting the problem and somehow coping with the
831with the watcher being stopped. 1349watcher being stopped. Note that well-written programs should not receive
1350an error ever, so when your watcher receives it, this usually indicates a
1351bug in your program.
832.Sp 1352.Sp
833Libev will usually signal a few \*(L"dummy\*(R" events together with an error, 1353Libev will usually signal a few \*(L"dummy\*(R" events together with an error, for
834for example it might indicate that a fd is readable or writable, and if 1354example it might indicate that a fd is readable or writable, and if your
835your callbacks is well-written it can just attempt the operation and cope 1355callbacks is well-written it can just attempt the operation and cope with
836with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded 1356the error from \fIread()\fR or \fIwrite()\fR. This will not work in multi-threaded
837programs, though, so beware. 1357programs, though, as the fd could already be closed and reused for another
1358thing, so beware.
838.Sh "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0" 1359.SS "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0"
839.IX Subsection "GENERIC WATCHER FUNCTIONS" 1360.IX Subsection "GENERIC WATCHER FUNCTIONS"
840In the following description, \f(CW\*(C`TYPE\*(C'\fR stands for the watcher type,
841e.g. \f(CW\*(C`timer\*(C'\fR for \f(CW\*(C`ev_timer\*(C'\fR watchers and \f(CW\*(C`io\*(C'\fR for \f(CW\*(C`ev_io\*(C'\fR watchers.
842.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4 1361.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4
843.el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4 1362.el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4
844.IX Item "ev_init (ev_TYPE *watcher, callback)" 1363.IX Item "ev_init (ev_TYPE *watcher, callback)"
845This macro initialises the generic portion of a watcher. The contents 1364This macro initialises the generic portion of a watcher. The contents
846of the watcher object can be arbitrary (so \f(CW\*(C`malloc\*(C'\fR will do). Only 1365of the watcher object can be arbitrary (so \f(CW\*(C`malloc\*(C'\fR will do). Only
… …
850which rolls both calls into one. 1369which rolls both calls into one.
851.Sp 1370.Sp
852You can reinitialise a watcher at any time as long as it has been stopped 1371You can reinitialise a watcher at any time as long as it has been stopped
853(or never started) and there are no pending events outstanding. 1372(or never started) and there are no pending events outstanding.
854.Sp 1373.Sp
855The callback is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher, 1374The callback is always of type \f(CW\*(C`void (*)(struct ev_loop *loop, ev_TYPE *watcher,
856int revents)\*(C'\fR. 1375int revents)\*(C'\fR.
1376.Sp
1377Example: Initialise an \f(CW\*(C`ev_io\*(C'\fR watcher in two steps.
1378.Sp
1379.Vb 3
1380\& ev_io w;
1381\& ev_init (&w, my_cb);
1382\& ev_io_set (&w, STDIN_FILENO, EV_READ);
1383.Ve
857.ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4 1384.ie n .IP """ev_TYPE_set"" (ev_TYPE *watcher, [args])" 4
858.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4 1385.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *watcher, [args])" 4
859.IX Item "ev_TYPE_set (ev_TYPE *, [args])" 1386.IX Item "ev_TYPE_set (ev_TYPE *watcher, [args])"
860This macro initialises the type-specific parts of a watcher. You need to 1387This macro initialises the type-specific parts of a watcher. You need to
861call \f(CW\*(C`ev_init\*(C'\fR at least once before you call this macro, but you can 1388call \f(CW\*(C`ev_init\*(C'\fR at least once before you call this macro, but you can
862call \f(CW\*(C`ev_TYPE_set\*(C'\fR any number of times. You must not, however, call this 1389call \f(CW\*(C`ev_TYPE_set\*(C'\fR any number of times. You must not, however, call this
863macro on a watcher that is active (it can be pending, however, which is a 1390macro on a watcher that is active (it can be pending, however, which is a
864difference to the \f(CW\*(C`ev_init\*(C'\fR macro). 1391difference to the \f(CW\*(C`ev_init\*(C'\fR macro).
865.Sp 1392.Sp
866Although some watcher types do not have type-specific arguments 1393Although some watcher types do not have type-specific arguments
867(e.g. \f(CW\*(C`ev_prepare\*(C'\fR) you still need to call its \f(CW\*(C`set\*(C'\fR macro. 1394(e.g. \f(CW\*(C`ev_prepare\*(C'\fR) you still need to call its \f(CW\*(C`set\*(C'\fR macro.
1395.Sp
1396See \f(CW\*(C`ev_init\*(C'\fR, above, for an example.
868.ie n .IP """ev_TYPE_init"" (ev_TYPE *watcher, callback, [args])" 4 1397.ie n .IP """ev_TYPE_init"" (ev_TYPE *watcher, callback, [args])" 4
869.el .IP "\f(CWev_TYPE_init\fR (ev_TYPE *watcher, callback, [args])" 4 1398.el .IP "\f(CWev_TYPE_init\fR (ev_TYPE *watcher, callback, [args])" 4
870.IX Item "ev_TYPE_init (ev_TYPE *watcher, callback, [args])" 1399.IX Item "ev_TYPE_init (ev_TYPE *watcher, callback, [args])"
871This convinience macro rolls both \f(CW\*(C`ev_init\*(C'\fR and \f(CW\*(C`ev_TYPE_set\*(C'\fR macro 1400This convenience macro rolls both \f(CW\*(C`ev_init\*(C'\fR and \f(CW\*(C`ev_TYPE_set\*(C'\fR macro
872calls into a single call. This is the most convinient method to initialise 1401calls into a single call. This is the most convenient method to initialise
873a watcher. The same limitations apply, of course. 1402a watcher. The same limitations apply, of course.
1403.Sp
1404Example: Initialise and set an \f(CW\*(C`ev_io\*(C'\fR watcher in one step.
1405.Sp
1406.Vb 1
1407\& ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1408.Ve
874.ie n .IP """ev_TYPE_start"" (loop *, ev_TYPE *watcher)" 4 1409.ie n .IP """ev_TYPE_start"" (loop, ev_TYPE *watcher)" 4
875.el .IP "\f(CWev_TYPE_start\fR (loop *, ev_TYPE *watcher)" 4 1410.el .IP "\f(CWev_TYPE_start\fR (loop, ev_TYPE *watcher)" 4
876.IX Item "ev_TYPE_start (loop *, ev_TYPE *watcher)" 1411.IX Item "ev_TYPE_start (loop, ev_TYPE *watcher)"
877Starts (activates) the given watcher. Only active watchers will receive 1412Starts (activates) the given watcher. Only active watchers will receive
878events. If the watcher is already active nothing will happen. 1413events. If the watcher is already active nothing will happen.
1414.Sp
1415Example: Start the \f(CW\*(C`ev_io\*(C'\fR watcher that is being abused as example in this
1416whole section.
1417.Sp
1418.Vb 1
1419\& ev_io_start (EV_DEFAULT_UC, &w);
1420.Ve
879.ie n .IP """ev_TYPE_stop"" (loop *, ev_TYPE *watcher)" 4 1421.ie n .IP """ev_TYPE_stop"" (loop, ev_TYPE *watcher)" 4
880.el .IP "\f(CWev_TYPE_stop\fR (loop *, ev_TYPE *watcher)" 4 1422.el .IP "\f(CWev_TYPE_stop\fR (loop, ev_TYPE *watcher)" 4
881.IX Item "ev_TYPE_stop (loop *, ev_TYPE *watcher)" 1423.IX Item "ev_TYPE_stop (loop, ev_TYPE *watcher)"
882Stops the given watcher again (if active) and clears the pending 1424Stops the given watcher if active, and clears the pending status (whether
1425the watcher was active or not).
1426.Sp
883status. It is possible that stopped watchers are pending (for example, 1427It is possible that stopped watchers are pending \- for example,
884non-repeating timers are being stopped when they become pending), but 1428non-repeating timers are being stopped when they become pending \- but
885\&\f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor pending. If 1429calling \f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor
886you want to free or reuse the memory used by the watcher it is therefore a 1430pending. If you want to free or reuse the memory used by the watcher it is
887good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function. 1431therefore a good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function.
888.IP "bool ev_is_active (ev_TYPE *watcher)" 4 1432.IP "bool ev_is_active (ev_TYPE *watcher)" 4
889.IX Item "bool ev_is_active (ev_TYPE *watcher)" 1433.IX Item "bool ev_is_active (ev_TYPE *watcher)"
890Returns a true value iff the watcher is active (i.e. it has been started 1434Returns a true value iff the watcher is active (i.e. it has been started
891and not yet been stopped). As long as a watcher is active you must not modify 1435and not yet been stopped). As long as a watcher is active you must not modify
892it. 1436it.
… …
899make sure the watcher is available to libev (e.g. you cannot \f(CW\*(C`free ()\*(C'\fR 1443make sure the watcher is available to libev (e.g. you cannot \f(CW\*(C`free ()\*(C'\fR
900it). 1444it).
901.IP "callback ev_cb (ev_TYPE *watcher)" 4 1445.IP "callback ev_cb (ev_TYPE *watcher)" 4
902.IX Item "callback ev_cb (ev_TYPE *watcher)" 1446.IX Item "callback ev_cb (ev_TYPE *watcher)"
903Returns the callback currently set on the watcher. 1447Returns the callback currently set on the watcher.
904.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4 1448.IP "ev_set_cb (ev_TYPE *watcher, callback)" 4
905.IX Item "ev_cb_set (ev_TYPE *watcher, callback)" 1449.IX Item "ev_set_cb (ev_TYPE *watcher, callback)"
906Change the callback. You can change the callback at virtually any time 1450Change the callback. You can change the callback at virtually any time
907(modulo threads). 1451(modulo threads).
908.IP "ev_set_priority (ev_TYPE *watcher, priority)" 4 1452.IP "ev_set_priority (ev_TYPE *watcher, int priority)" 4
909.IX Item "ev_set_priority (ev_TYPE *watcher, priority)" 1453.IX Item "ev_set_priority (ev_TYPE *watcher, int priority)"
910.PD 0 1454.PD 0
911.IP "int ev_priority (ev_TYPE *watcher)" 4 1455.IP "int ev_priority (ev_TYPE *watcher)" 4
912.IX Item "int ev_priority (ev_TYPE *watcher)" 1456.IX Item "int ev_priority (ev_TYPE *watcher)"
913.PD 1457.PD
914Set and query the priority of the watcher. The priority is a small 1458Set and query the priority of the watcher. The priority is a small
915integer between \f(CW\*(C`EV_MAXPRI\*(C'\fR (default: \f(CW2\fR) and \f(CW\*(C`EV_MINPRI\*(C'\fR 1459integer between \f(CW\*(C`EV_MAXPRI\*(C'\fR (default: \f(CW2\fR) and \f(CW\*(C`EV_MINPRI\*(C'\fR
916(default: \f(CW\*(C`\-2\*(C'\fR). Pending watchers with higher priority will be invoked 1460(default: \f(CW\*(C`\-2\*(C'\fR). Pending watchers with higher priority will be invoked
917before watchers with lower priority, but priority will not keep watchers 1461before watchers with lower priority, but priority will not keep watchers
918from being executed (except for \f(CW\*(C`ev_idle\*(C'\fR watchers). 1462from being executed (except for \f(CW\*(C`ev_idle\*(C'\fR watchers).
919.Sp 1463.Sp
920This means that priorities are \fIonly\fR used for ordering callback
921invocation after new events have been received. This is useful, for
922example, to reduce latency after idling, or more often, to bind two
923watchers on the same event and make sure one is called first.
924.Sp
925If you need to suppress invocation when higher priority events are pending 1464If you need to suppress invocation when higher priority events are pending
926you need to look at \f(CW\*(C`ev_idle\*(C'\fR watchers, which provide this functionality. 1465you need to look at \f(CW\*(C`ev_idle\*(C'\fR watchers, which provide this functionality.
927.Sp 1466.Sp
928You \fImust not\fR change the priority of a watcher as long as it is active or 1467You \fImust not\fR change the priority of a watcher as long as it is active or
929pending. 1468pending.
930.Sp 1469.Sp
1470Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR is
1471fine, as long as you do not mind that the priority value you query might
1472or might not have been clamped to the valid range.
1473.Sp
931The default priority used by watchers when no priority has been set is 1474The default priority used by watchers when no priority has been set is
932always \f(CW0\fR, which is supposed to not be too high and not be too low :). 1475always \f(CW0\fR, which is supposed to not be too high and not be too low :).
933.Sp 1476.Sp
934Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR is 1477See \*(L"\s-1WATCHER\s0 \s-1PRIORITY\s0 \s-1MODELS\s0\*(R", below, for a more thorough treatment of
935fine, as long as you do not mind that the priority value you query might 1478priorities.
936or might not have been adjusted to be within valid range.
937.IP "ev_invoke (loop, ev_TYPE *watcher, int revents)" 4 1479.IP "ev_invoke (loop, ev_TYPE *watcher, int revents)" 4
938.IX Item "ev_invoke (loop, ev_TYPE *watcher, int revents)" 1480.IX Item "ev_invoke (loop, ev_TYPE *watcher, int revents)"
939Invoke the \f(CW\*(C`watcher\*(C'\fR with the given \f(CW\*(C`loop\*(C'\fR and \f(CW\*(C`revents\*(C'\fR. Neither 1481Invoke the \f(CW\*(C`watcher\*(C'\fR with the given \f(CW\*(C`loop\*(C'\fR and \f(CW\*(C`revents\*(C'\fR. Neither
940\&\f(CW\*(C`loop\*(C'\fR nor \f(CW\*(C`revents\*(C'\fR need to be valid as long as the watcher callback 1482\&\f(CW\*(C`loop\*(C'\fR nor \f(CW\*(C`revents\*(C'\fR need to be valid as long as the watcher callback
941can deal with that fact. 1483can deal with that fact, as both are simply passed through to the
1484callback.
942.IP "int ev_clear_pending (loop, ev_TYPE *watcher)" 4 1485.IP "int ev_clear_pending (loop, ev_TYPE *watcher)" 4
943.IX Item "int ev_clear_pending (loop, ev_TYPE *watcher)" 1486.IX Item "int ev_clear_pending (loop, ev_TYPE *watcher)"
944If the watcher is pending, this function returns clears its pending status 1487If the watcher is pending, this function clears its pending status and
945and returns its \f(CW\*(C`revents\*(C'\fR bitset (as if its callback was invoked). If the 1488returns its \f(CW\*(C`revents\*(C'\fR bitset (as if its callback was invoked). If the
946watcher isn't pending it does nothing and returns \f(CW0\fR. 1489watcher isn't pending it does nothing and returns \f(CW0\fR.
947.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0" 1490.Sp
948.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER" 1491Sometimes it can be useful to \*(L"poll\*(R" a watcher instead of waiting for its
949Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change 1492callback to be invoked, which can be accomplished with this function.
950and read at any time, libev will completely ignore it. This can be used 1493.IP "ev_feed_event (loop, ev_TYPE *watcher, int revents)" 4
951to associate arbitrary data with your watcher. If you need more data and 1494.IX Item "ev_feed_event (loop, ev_TYPE *watcher, int revents)"
952don't want to allocate memory and store a pointer to it in that data 1495Feeds the given event set into the event loop, as if the specified event
953member, you can also \*(L"subclass\*(R" the watcher type and provide your own 1496had happened for the specified watcher (which must be a pointer to an
954data: 1497initialised but not necessarily started event watcher). Obviously you must
1498not free the watcher as long as it has pending events.
1499.Sp
1500Stopping the watcher, letting libev invoke it, or calling
1501\&\f(CW\*(C`ev_clear_pending\*(C'\fR will clear the pending event, even if the watcher was
1502not started in the first place.
1503.Sp
1504See also \f(CW\*(C`ev_feed_fd_event\*(C'\fR and \f(CW\*(C`ev_feed_signal_event\*(C'\fR for related
1505functions that do not need a watcher.
955.PP 1506.PP
1507See 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
1508\&\s-1OWN\s0 \s-1COMPOSITE\s0 \s-1WATCHERS\s0\*(R" idioms.
1509.SS "\s-1WATCHER\s0 \s-1STATES\s0"
1510.IX Subsection "WATCHER STATES"
1511There are various watcher states mentioned throughout this manual \-
1512active, pending and so on. In this section these states and the rules to
1513transition between them will be described in more detail \- and while these
1514rules might look complicated, they usually do \*(L"the right thing\*(R".
1515.IP "initialised" 4
1516.IX Item "initialised"
1517Before a watcher can be registered with the event loop it has to be
1518initialised. This can be done with a call to \f(CW\*(C`ev_TYPE_init\*(C'\fR, or calls to
1519\&\f(CW\*(C`ev_init\*(C'\fR followed by the watcher-specific \f(CW\*(C`ev_TYPE_set\*(C'\fR function.
1520.Sp
1521In this state it is simply some block of memory that is suitable for
1522use in an event loop. It can be moved around, freed, reused etc. at
1523will \- as long as you either keep the memory contents intact, or call
1524\&\f(CW\*(C`ev_TYPE_init\*(C'\fR again.
1525.IP "started/running/active" 4
1526.IX Item "started/running/active"
1527Once a watcher has been started with a call to \f(CW\*(C`ev_TYPE_start\*(C'\fR it becomes
1528property of the event loop, and is actively waiting for events. While in
1529this state it cannot be accessed (except in a few documented ways), moved,
1530freed or anything else \- the only legal thing is to keep a pointer to it,
1531and call libev functions on it that are documented to work on active watchers.
1532.IP "pending" 4
1533.IX Item "pending"
1534If a watcher is active and libev determines that an event it is interested
1535in has occurred (such as a timer expiring), it will become pending. It will
1536stay in this pending state until either it is stopped or its callback is
1537about to be invoked, so it is not normally pending inside the watcher
1538callback.
1539.Sp
1540The watcher might or might not be active while it is pending (for example,
1541an expired non-repeating timer can be pending but no longer active). If it
1542is stopped, it can be freely accessed (e.g. by calling \f(CW\*(C`ev_TYPE_set\*(C'\fR),
1543but it is still property of the event loop at this time, so cannot be
1544moved, freed or reused. And if it is active the rules described in the
1545previous item still apply.
1546.Sp
1547It is also possible to feed an event on a watcher that is not active (e.g.
1548via \f(CW\*(C`ev_feed_event\*(C'\fR), in which case it becomes pending without being
1549active.
1550.IP "stopped" 4
1551.IX Item "stopped"
1552A watcher can be stopped implicitly by libev (in which case it might still
1553be pending), or explicitly by calling its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function. The
1554latter will clear any pending state the watcher might be in, regardless
1555of whether it was active or not, so stopping a watcher explicitly before
1556freeing it is often a good idea.
1557.Sp
1558While stopped (and not pending) the watcher is essentially in the
1559initialised state, that is, it can be reused, moved, modified in any way
1560you wish (but when you trash the memory block, you need to \f(CW\*(C`ev_TYPE_init\*(C'\fR
1561it again).
1562.SS "\s-1WATCHER\s0 \s-1PRIORITY\s0 \s-1MODELS\s0"
1563.IX Subsection "WATCHER PRIORITY MODELS"
1564Many event loops support \fIwatcher priorities\fR, which are usually small
1565integers that influence the ordering of event callback invocation
1566between watchers in some way, all else being equal.
1567.PP
1568In libev, Watcher priorities can be set using \f(CW\*(C`ev_set_priority\*(C'\fR. See its
1569description for the more technical details such as the actual priority
1570range.
1571.PP
1572There are two common ways how these these priorities are being interpreted
1573by event loops:
1574.PP
1575In the more common lock-out model, higher priorities \*(L"lock out\*(R" invocation
1576of lower priority watchers, which means as long as higher priority
1577watchers receive events, lower priority watchers are not being invoked.
1578.PP
1579The less common only-for-ordering model uses priorities solely to order
1580callback invocation within a single event loop iteration: Higher priority
1581watchers are invoked before lower priority ones, but they all get invoked
1582before polling for new events.
1583.PP
1584Libev uses the second (only-for-ordering) model for all its watchers
1585except for idle watchers (which use the lock-out model).
1586.PP
1587The rationale behind this is that implementing the lock-out model for
1588watchers is not well supported by most kernel interfaces, and most event
1589libraries will just poll for the same events again and again as long as
1590their callbacks have not been executed, which is very inefficient in the
1591common case of one high-priority watcher locking out a mass of lower
1592priority ones.
1593.PP
1594Static (ordering) priorities are most useful when you have two or more
1595watchers handling the same resource: a typical usage example is having an
1596\&\f(CW\*(C`ev_io\*(C'\fR watcher to receive data, and an associated \f(CW\*(C`ev_timer\*(C'\fR to handle
1597timeouts. Under load, data might be received while the program handles
1598other jobs, but since timers normally get invoked first, the timeout
1599handler will be executed before checking for data. In that case, giving
1600the timer a lower priority than the I/O watcher ensures that I/O will be
1601handled first even under adverse conditions (which is usually, but not
1602always, what you want).
1603.PP
1604Since idle watchers use the \*(L"lock-out\*(R" model, meaning that idle watchers
1605will only be executed when no same or higher priority watchers have
1606received events, they can be used to implement the \*(L"lock-out\*(R" model when
1607required.
1608.PP
1609For example, to emulate how many other event libraries handle priorities,
1610you can associate an \f(CW\*(C`ev_idle\*(C'\fR watcher to each such watcher, and in
1611the normal watcher callback, you just start the idle watcher. The real
1612processing is done in the idle watcher callback. This causes libev to
1613continuously poll and process kernel event data for the watcher, but when
1614the lock-out case is known to be rare (which in turn is rare :), this is
1615workable.
1616.PP
1617Usually, however, the lock-out model implemented that way will perform
1618miserably under the type of load it was designed to handle. In that case,
1619it might be preferable to stop the real watcher before starting the
1620idle watcher, so the kernel will not have to process the event in case
1621the actual processing will be delayed for considerable time.
1622.PP
1623Here is an example of an I/O watcher that should run at a strictly lower
1624priority than the default, and which should only process data when no
1625other events are pending:
1626.PP
956.Vb 7 1627.Vb 2
957\& struct my_io 1628\& ev_idle idle; // actual processing watcher
958\& { 1629\& ev_io io; // actual event watcher
959\& struct ev_io io; 1630\&
960\& int otherfd;
961\& void *somedata;
962\& struct whatever *mostinteresting;
963\& }
964.Ve
965.PP
966And since your callback will be called with a pointer to the watcher, you
967can cast it back to your own type:
968.PP
969.Vb 5
970\& static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
971\& {
972\& struct my_io *w = (struct my_io *)w_;
973\& ...
974\& }
975.Ve
976.PP
977More interesting and less C\-conformant ways of casting your callback type
978instead have been omitted.
979.PP
980Another common scenario is having some data structure with multiple
981watchers:
982.PP
983.Vb 6
984\& struct my_biggy
985\& {
986\& int some_data;
987\& ev_timer t1;
988\& ev_timer t2;
989\& }
990.Ve
991.PP
992In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more complicated,
993you need to use \f(CW\*(C`offsetof\*(C'\fR:
994.PP
995.Vb 1
996\& #include <stddef.h>
997.Ve
998.PP
999.Vb 6
1000\& static void 1631\& static void
1001\& t1_cb (EV_P_ struct ev_timer *w, int revents) 1632\& io_cb (EV_P_ ev_io *w, int revents)
1002\& { 1633\& {
1003\& struct my_biggy big = (struct my_biggy * 1634\& // stop the I/O watcher, we received the event, but
1004\& (((char *)w) - offsetof (struct my_biggy, t1)); 1635\& // are not yet ready to handle it.
1636\& ev_io_stop (EV_A_ w);
1637\&
1638\& // start the idle watcher to handle the actual event.
1639\& // it will not be executed as long as other watchers
1640\& // with the default priority are receiving events.
1641\& ev_idle_start (EV_A_ &idle);
1005\& } 1642\& }
1006.Ve 1643\&
1007.PP
1008.Vb 6
1009\& static void 1644\& static void
1010\& t2_cb (EV_P_ struct ev_timer *w, int revents) 1645\& idle_cb (EV_P_ ev_idle *w, int revents)
1011\& { 1646\& {
1012\& struct my_biggy big = (struct my_biggy * 1647\& // actual processing
1013\& (((char *)w) - offsetof (struct my_biggy, t2)); 1648\& read (STDIN_FILENO, ...);
1649\&
1650\& // have to start the I/O watcher again, as
1651\& // we have handled the event
1652\& ev_io_start (EV_P_ &io);
1014\& } 1653\& }
1654\&
1655\& // initialisation
1656\& ev_idle_init (&idle, idle_cb);
1657\& ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
1658\& ev_io_start (EV_DEFAULT_ &io);
1015.Ve 1659.Ve
1660.PP
1661In the \*(L"real\*(R" world, it might also be beneficial to start a timer, so that
1662low-priority connections can not be locked out forever under load. This
1663enables your program to keep a lower latency for important connections
1664during short periods of high load, while not completely locking out less
1665important ones.
1016.SH "WATCHER TYPES" 1666.SH "WATCHER TYPES"
1017.IX Header "WATCHER TYPES" 1667.IX Header "WATCHER TYPES"
1018This section describes each watcher in detail, but will not repeat 1668This section describes each watcher in detail, but will not repeat
1019information given in the last section. Any initialisation/set macros, 1669information given in the last section. Any initialisation/set macros,
1020functions and members specific to the watcher type are explained. 1670functions and members specific to the watcher type are explained.
… …
1025watcher is stopped to your hearts content), or \fI[read\-write]\fR, which 1675watcher is stopped to your hearts content), or \fI[read\-write]\fR, which
1026means you can expect it to have some sensible content while the watcher 1676means you can expect it to have some sensible content while the watcher
1027is active, but you can also modify it. Modifying it may not do something 1677is active, but you can also modify it. Modifying it may not do something
1028sensible or take immediate effect (or do anything at all), but libev will 1678sensible or take immediate effect (or do anything at all), but libev will
1029not crash or malfunction in any way. 1679not crash or malfunction in any way.
1030.ie n .Sh """ev_io"" \- is this file descriptor readable or writable?" 1680.ie n .SS """ev_io"" \- is this file descriptor readable or writable?"
1031.el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable?" 1681.el .SS "\f(CWev_io\fP \- is this file descriptor readable or writable?"
1032.IX Subsection "ev_io - is this file descriptor readable or writable?" 1682.IX Subsection "ev_io - is this file descriptor readable or writable?"
1033I/O watchers check whether a file descriptor is readable or writable 1683I/O watchers check whether a file descriptor is readable or writable
1034in each iteration of the event loop, or, more precisely, when reading 1684in each iteration of the event loop, or, more precisely, when reading
1035would not block the process and writing would at least be able to write 1685would not block the process and writing would at least be able to write
1036some data. This behaviour is called level-triggering because you keep 1686some data. This behaviour is called level-triggering because you keep
… …
1041In general you can register as many read and/or write event watchers per 1691In general you can register as many read and/or write event watchers per
1042fd as you want (as long as you don't confuse yourself). Setting all file 1692fd as you want (as long as you don't confuse yourself). Setting all file
1043descriptors to non-blocking mode is also usually a good idea (but not 1693descriptors to non-blocking mode is also usually a good idea (but not
1044required if you know what you are doing). 1694required if you know what you are doing).
1045.PP 1695.PP
1046You have to be careful with dup'ed file descriptors, though. Some backends
1047(the linux epoll backend is a notable example) cannot handle dup'ed file
1048descriptors correctly if you register interest in two or more fds pointing
1049to the same underlying file/socket/etc. description (that is, they share
1050the same underlying \*(L"file open\*(R").
1051.PP
1052If you must do this, then force the use of a known-to-be-good backend
1053(at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and
1054\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR).
1055.PP
1056Another thing you have to watch out for is that it is quite easy to 1696Another thing you have to watch out for is that it is quite easy to
1057receive \*(L"spurious\*(R" readyness notifications, that is your callback might 1697receive \*(L"spurious\*(R" readiness notifications, that is, your callback might
1058be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block 1698be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block
1059because there is no data. Not only are some backends known to create a 1699because there is no data. It is very easy to get into this situation even
1060lot of those (for example solaris ports), it is very easy to get into 1700with a relatively standard program structure. Thus it is best to always
1061this situation even with a relatively standard program structure. Thus 1701use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning \f(CW\*(C`EAGAIN\*(C'\fR is far
1062it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning
1063\&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives. 1702preferable to a program hanging until some data arrives.
1064.PP 1703.PP
1065If you cannot run the fd in non-blocking mode (for example you should not 1704If you cannot run the fd in non-blocking mode (for example you should
1066play around with an Xlib connection), then you have to seperately re-test 1705not play around with an Xlib connection), then you have to separately
1067whether a file descriptor is really ready with a known-to-be good interface 1706re-test whether a file descriptor is really ready with a known-to-be good
1068such as poll (fortunately in our Xlib example, Xlib already does this on 1707interface such as poll (fortunately in the case of Xlib, it already does
1069its own, so its quite safe to use). 1708this on its own, so its quite safe to use). Some people additionally
1709use \f(CW\*(C`SIGALRM\*(C'\fR and an interval timer, just to be sure you won't block
1710indefinitely.
1711.PP
1712But really, best use non-blocking mode.
1070.PP 1713.PP
1071\fIThe special problem of disappearing file descriptors\fR 1714\fIThe special problem of disappearing file descriptors\fR
1072.IX Subsection "The special problem of disappearing file descriptors" 1715.IX Subsection "The special problem of disappearing file descriptors"
1073.PP 1716.PP
1074Some backends (e.g kqueue, epoll) need to be told about closing a file 1717Some backends (e.g. kqueue, epoll) need to be told about closing a file
1075descriptor (either by calling \f(CW\*(C`close\*(C'\fR explicitly or by any other means, 1718descriptor (either due to calling \f(CW\*(C`close\*(C'\fR explicitly or any other means,
1076such as \f(CW\*(C`dup\*(C'\fR). The reason is that you register interest in some file 1719such as \f(CW\*(C`dup2\*(C'\fR). The reason is that you register interest in some file
1077descriptor, but when it goes away, the operating system will silently drop 1720descriptor, but when it goes away, the operating system will silently drop
1078this interest. If another file descriptor with the same number then is 1721this interest. If another file descriptor with the same number then is
1079registered with libev, there is no efficient way to see that this is, in 1722registered with libev, there is no efficient way to see that this is, in
1080fact, a different file descriptor. 1723fact, a different file descriptor.
1081.PP 1724.PP
… …
1087descriptor even if the file descriptor number itself did not change. 1730descriptor even if the file descriptor number itself did not change.
1088.PP 1731.PP
1089This is how one would do it normally anyway, the important point is that 1732This is how one would do it normally anyway, the important point is that
1090the libev application should not optimise around libev but should leave 1733the libev application should not optimise around libev but should leave
1091optimisations to libev. 1734optimisations to libev.
1735.PP
1736\fIThe special problem of dup'ed file descriptors\fR
1737.IX Subsection "The special problem of dup'ed file descriptors"
1738.PP
1739Some backends (e.g. epoll), cannot register events for file descriptors,
1740but only events for the underlying file descriptions. That means when you
1741have \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors or weirder constellations, and register
1742events for them, only one file descriptor might actually receive events.
1743.PP
1744There is no workaround possible except not registering events
1745for potentially \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors, or to resort to
1746\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
1747.PP
1748\fIThe special problem of files\fR
1749.IX Subsection "The special problem of files"
1750.PP
1751Many people try to use \f(CW\*(C`select\*(C'\fR (or libev) on file descriptors
1752representing files, and expect it to become ready when their program
1753doesn't block on disk accesses (which can take a long time on their own).
1754.PP
1755However, this cannot ever work in the \*(L"expected\*(R" way \- you get a readiness
1756notification as soon as the kernel knows whether and how much data is
1757there, and in the case of open files, that's always the case, so you
1758always get a readiness notification instantly, and your read (or possibly
1759write) will still block on the disk I/O.
1760.PP
1761Another way to view it is that in the case of sockets, pipes, character
1762devices and so on, there is another party (the sender) that delivers data
1763on its own, but in the case of files, there is no such thing: the disk
1764will not send data on its own, simply because it doesn't know what you
1765wish to read \- you would first have to request some data.
1766.PP
1767Since files are typically not-so-well supported by advanced notification
1768mechanism, libev tries hard to emulate \s-1POSIX\s0 behaviour with respect
1769to files, even though you should not use it. The reason for this is
1770convenience: sometimes you want to watch \s-1STDIN\s0 or \s-1STDOUT\s0, which is
1771usually a tty, often a pipe, but also sometimes files or special devices
1772(for example, \f(CW\*(C`epoll\*(C'\fR on Linux works with \fI/dev/random\fR but not with
1773\&\fI/dev/urandom\fR), and even though the file might better be served with
1774asynchronous I/O instead of with non-blocking I/O, it is still useful when
1775it \*(L"just works\*(R" instead of freezing.
1776.PP
1777So avoid file descriptors pointing to files when you know it (e.g. use
1778libeio), but use them when it is convenient, e.g. for \s-1STDIN/STDOUT\s0, or
1779when you rarely read from a file instead of from a socket, and want to
1780reuse the same code path.
1781.PP
1782\fIThe special problem of fork\fR
1783.IX Subsection "The special problem of fork"
1784.PP
1785Some backends (epoll, kqueue) do not support \f(CW\*(C`fork ()\*(C'\fR at all or exhibit
1786useless behaviour. Libev fully supports fork, but needs to be told about
1787it in the child if you want to continue to use it in the child.
1788.PP
1789To support fork in your child processes, you have to call \f(CW\*(C`ev_loop_fork
1790()\*(C'\fR after a fork in the child, enable \f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR, or resort to
1791\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
1792.PP
1793\fIThe special problem of \s-1SIGPIPE\s0\fR
1794.IX Subsection "The special problem of SIGPIPE"
1795.PP
1796While not really specific to libev, it is easy to forget about \f(CW\*(C`SIGPIPE\*(C'\fR:
1797when writing to a pipe whose other end has been closed, your program gets
1798sent a \s-1SIGPIPE\s0, which, by default, aborts your program. For most programs
1799this is sensible behaviour, for daemons, this is usually undesirable.
1800.PP
1801So when you encounter spurious, unexplained daemon exits, make sure you
1802ignore \s-1SIGPIPE\s0 (and maybe make sure you log the exit status of your daemon
1803somewhere, as that would have given you a big clue).
1804.PP
1805\fIThe special problem of \fIaccept()\fIing when you can't\fR
1806.IX Subsection "The special problem of accept()ing when you can't"
1807.PP
1808Many implementations of the \s-1POSIX\s0 \f(CW\*(C`accept\*(C'\fR function (for example,
1809found in post\-2004 Linux) have the peculiar behaviour of not removing a
1810connection from the pending queue in all error cases.
1811.PP
1812For example, larger servers often run out of file descriptors (because
1813of resource limits), causing \f(CW\*(C`accept\*(C'\fR to fail with \f(CW\*(C`ENFILE\*(C'\fR but not
1814rejecting the connection, leading to libev signalling readiness on
1815the next iteration again (the connection still exists after all), and
1816typically causing the program to loop at 100% \s-1CPU\s0 usage.
1817.PP
1818Unfortunately, the set of errors that cause this issue differs between
1819operating systems, there is usually little the app can do to remedy the
1820situation, and no known thread-safe method of removing the connection to
1821cope with overload is known (to me).
1822.PP
1823One of the easiest ways to handle this situation is to just ignore it
1824\&\- when the program encounters an overload, it will just loop until the
1825situation is over. While this is a form of busy waiting, no \s-1OS\s0 offers an
1826event-based way to handle this situation, so it's the best one can do.
1827.PP
1828A better way to handle the situation is to log any errors other than
1829\&\f(CW\*(C`EAGAIN\*(C'\fR and \f(CW\*(C`EWOULDBLOCK\*(C'\fR, making sure not to flood the log with such
1830messages, and continue as usual, which at least gives the user an idea of
1831what could be wrong (\*(L"raise the ulimit!\*(R"). For extra points one could stop
1832the \f(CW\*(C`ev_io\*(C'\fR watcher on the listening fd \*(L"for a while\*(R", which reduces \s-1CPU\s0
1833usage.
1834.PP
1835If your program is single-threaded, then you could also keep a dummy file
1836descriptor for overload situations (e.g. by opening \fI/dev/null\fR), and
1837when 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,
1838close that fd, and create a new dummy fd. This will gracefully refuse
1839clients under typical overload conditions.
1840.PP
1841The last way to handle it is to simply log the error and \f(CW\*(C`exit\*(C'\fR, as
1842is often done with \f(CW\*(C`malloc\*(C'\fR failures, but this results in an easy
1843opportunity for a DoS attack.
1092.PP 1844.PP
1093\fIWatcher-Specific Functions\fR 1845\fIWatcher-Specific Functions\fR
1094.IX Subsection "Watcher-Specific Functions" 1846.IX Subsection "Watcher-Specific Functions"
1095.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4 1847.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4
1096.IX Item "ev_io_init (ev_io *, callback, int fd, int events)" 1848.IX Item "ev_io_init (ev_io *, callback, int fd, int events)"
1097.PD 0 1849.PD 0
1098.IP "ev_io_set (ev_io *, int fd, int events)" 4 1850.IP "ev_io_set (ev_io *, int fd, int events)" 4
1099.IX Item "ev_io_set (ev_io *, int fd, int events)" 1851.IX Item "ev_io_set (ev_io *, int fd, int events)"
1100.PD 1852.PD
1101Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to 1853Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to
1102rceeive events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or 1854receive 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
1103\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR to receive the given events. 1855\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR, to express the desire to receive the given events.
1104.IP "int fd [read\-only]" 4 1856.IP "int fd [read\-only]" 4
1105.IX Item "int fd [read-only]" 1857.IX Item "int fd [read-only]"
1106The file descriptor being watched. 1858The file descriptor being watched.
1107.IP "int events [read\-only]" 4 1859.IP "int events [read\-only]" 4
1108.IX Item "int events [read-only]" 1860.IX Item "int events [read-only]"
1109The events being watched. 1861The events being watched.
1110.PP 1862.PP
1863\fIExamples\fR
1864.IX Subsection "Examples"
1865.PP
1111Example: Call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well 1866Example: Call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well
1112readable, but only once. Since it is likely line\-buffered, you could 1867readable, but only once. Since it is likely line-buffered, you could
1113attempt to read a whole line in the callback. 1868attempt to read a whole line in the callback.
1114.PP 1869.PP
1115.Vb 6 1870.Vb 6
1116\& static void 1871\& static void
1117\& stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1872\& stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1118\& { 1873\& {
1119\& ev_io_stop (loop, w); 1874\& ev_io_stop (loop, w);
1120\& .. read from stdin here (or from w->fd) and haqndle any I/O errors 1875\& .. read from stdin here (or from w\->fd) and handle any I/O errors
1121\& } 1876\& }
1122.Ve 1877\&
1123.PP
1124.Vb 6
1125\& ... 1878\& ...
1126\& struct ev_loop *loop = ev_default_init (0); 1879\& struct ev_loop *loop = ev_default_init (0);
1127\& struct ev_io stdin_readable; 1880\& ev_io stdin_readable;
1128\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); 1881\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1129\& ev_io_start (loop, &stdin_readable); 1882\& ev_io_start (loop, &stdin_readable);
1130\& ev_loop (loop, 0); 1883\& ev_run (loop, 0);
1131.Ve 1884.Ve
1132.ie n .Sh """ev_timer"" \- relative and optionally repeating timeouts" 1885.ie n .SS """ev_timer"" \- relative and optionally repeating timeouts"
1133.el .Sh "\f(CWev_timer\fP \- relative and optionally repeating timeouts" 1886.el .SS "\f(CWev_timer\fP \- relative and optionally repeating timeouts"
1134.IX Subsection "ev_timer - relative and optionally repeating timeouts" 1887.IX Subsection "ev_timer - relative and optionally repeating timeouts"
1135Timer watchers are simple relative timers that generate an event after a 1888Timer watchers are simple relative timers that generate an event after a
1136given time, and optionally repeating in regular intervals after that. 1889given time, and optionally repeating in regular intervals after that.
1137.PP 1890.PP
1138The timers are based on real time, that is, if you register an event that 1891The timers are based on real time, that is, if you register an event that
1139times out after an hour and you reset your system clock to last years 1892times out after an hour and you reset your system clock to January last
1140time, it will still time out after (roughly) and hour. \*(L"Roughly\*(R" because 1893year, it will still time out after (roughly) one hour. \*(L"Roughly\*(R" because
1141detecting time jumps is hard, and some inaccuracies are unavoidable (the 1894detecting time jumps is hard, and some inaccuracies are unavoidable (the
1142monotonic clock option helps a lot here). 1895monotonic clock option helps a lot here).
1896.PP
1897The callback is guaranteed to be invoked only \fIafter\fR its timeout has
1898passed (not \fIat\fR, so on systems with very low-resolution clocks this
1899might introduce a small delay, see \*(L"the special problem of being too
1900early\*(R", below). If multiple timers become ready during the same loop
1901iteration then the ones with earlier time-out values are invoked before
1902ones of the same priority with later time-out values (but this is no
1903longer true when a callback calls \f(CW\*(C`ev_run\*(C'\fR recursively).
1904.PP
1905\fIBe smart about timeouts\fR
1906.IX Subsection "Be smart about timeouts"
1907.PP
1908Many real-world problems involve some kind of timeout, usually for error
1909recovery. A typical example is an \s-1HTTP\s0 request \- if the other side hangs,
1910you want to raise some error after a while.
1911.PP
1912What follows are some ways to handle this problem, from obvious and
1913inefficient to smart and efficient.
1914.PP
1915In the following, a 60 second activity timeout is assumed \- a timeout that
1916gets reset to 60 seconds each time there is activity (e.g. each time some
1917data or other life sign was received).
1918.IP "1. Use a timer and stop, reinitialise and start it on activity." 4
1919.IX Item "1. Use a timer and stop, reinitialise and start it on activity."
1920This is the most obvious, but not the most simple way: In the beginning,
1921start the watcher:
1922.Sp
1923.Vb 2
1924\& ev_timer_init (timer, callback, 60., 0.);
1925\& ev_timer_start (loop, timer);
1926.Ve
1927.Sp
1928Then, each time there is some activity, \f(CW\*(C`ev_timer_stop\*(C'\fR it, initialise it
1929and start it again:
1930.Sp
1931.Vb 3
1932\& ev_timer_stop (loop, timer);
1933\& ev_timer_set (timer, 60., 0.);
1934\& ev_timer_start (loop, timer);
1935.Ve
1936.Sp
1937This is relatively simple to implement, but means that each time there is
1938some activity, libev will first have to remove the timer from its internal
1939data structure and then add it again. Libev tries to be fast, but it's
1940still not a constant-time operation.
1941.ie n .IP "2. Use a timer and re-start it with ""ev_timer_again"" inactivity." 4
1942.el .IP "2. Use a timer and re-start it with \f(CWev_timer_again\fR inactivity." 4
1943.IX Item "2. Use a timer and re-start it with ev_timer_again inactivity."
1944This is the easiest way, and involves using \f(CW\*(C`ev_timer_again\*(C'\fR instead of
1945\&\f(CW\*(C`ev_timer_start\*(C'\fR.
1946.Sp
1947To implement this, configure an \f(CW\*(C`ev_timer\*(C'\fR with a \f(CW\*(C`repeat\*(C'\fR value
1948of \f(CW60\fR and then call \f(CW\*(C`ev_timer_again\*(C'\fR at start and each time you
1949successfully read or write some data. If you go into an idle state where
1950you do not expect data to travel on the socket, you can \f(CW\*(C`ev_timer_stop\*(C'\fR
1951the timer, and \f(CW\*(C`ev_timer_again\*(C'\fR will automatically restart it if need be.
1952.Sp
1953That means you can ignore both the \f(CW\*(C`ev_timer_start\*(C'\fR function and the
1954\&\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
1955member and \f(CW\*(C`ev_timer_again\*(C'\fR.
1956.Sp
1957At start:
1958.Sp
1959.Vb 3
1960\& ev_init (timer, callback);
1961\& timer\->repeat = 60.;
1962\& ev_timer_again (loop, timer);
1963.Ve
1964.Sp
1965Each time there is some activity:
1966.Sp
1967.Vb 1
1968\& ev_timer_again (loop, timer);
1969.Ve
1970.Sp
1971It is even possible to change the time-out on the fly, regardless of
1972whether the watcher is active or not:
1973.Sp
1974.Vb 2
1975\& timer\->repeat = 30.;
1976\& ev_timer_again (loop, timer);
1977.Ve
1978.Sp
1979This is slightly more efficient then stopping/starting the timer each time
1980you want to modify its timeout value, as libev does not have to completely
1981remove and re-insert the timer from/into its internal data structure.
1982.Sp
1983It is, however, even simpler than the \*(L"obvious\*(R" way to do it.
1984.IP "3. Let the timer time out, but then re-arm it as required." 4
1985.IX Item "3. Let the timer time out, but then re-arm it as required."
1986This method is more tricky, but usually most efficient: Most timeouts are
1987relatively long compared to the intervals between other activity \- in
1988our example, within 60 seconds, there are usually many I/O events with
1989associated activity resets.
1990.Sp
1991In this case, it would be more efficient to leave the \f(CW\*(C`ev_timer\*(C'\fR alone,
1992but remember the time of last activity, and check for a real timeout only
1993within the callback:
1994.Sp
1995.Vb 3
1996\& ev_tstamp timeout = 60.;
1997\& ev_tstamp last_activity; // time of last activity
1998\& ev_timer timer;
1999\&
2000\& static void
2001\& callback (EV_P_ ev_timer *w, int revents)
2002\& {
2003\& // calculate when the timeout would happen
2004\& ev_tstamp after = last_activity \- ev_now (EV_A) + timeout;
2005\&
2006\& // if negative, it means we the timeout already occurred
2007\& if (after < 0.)
2008\& {
2009\& // timeout occurred, take action
2010\& }
2011\& else
2012\& {
2013\& // callback was invoked, but there was some recent
2014\& // activity. simply restart the timer to time out
2015\& // after "after" seconds, which is the earliest time
2016\& // the timeout can occur.
2017\& ev_timer_set (w, after, 0.);
2018\& ev_timer_start (EV_A_ w);
2019\& }
2020\& }
2021.Ve
2022.Sp
2023To summarise the callback: first calculate in how many seconds the
2024timeout will occur (by calculating the absolute time when it would occur,
2025\&\f(CW\*(C`last_activity + timeout\*(C'\fR, and subtracting the current time, \f(CW\*(C`ev_now
2026(EV_A)\*(C'\fR from that).
2027.Sp
2028If this value is negative, then we are already past the timeout, i.e. we
2029timed out, and need to do whatever is needed in this case.
2030.Sp
2031Otherwise, we now the earliest time at which the timeout would trigger,
2032and simply start the timer with this timeout value.
2033.Sp
2034In other words, each time the callback is invoked it will check whether
2035the timeout occurred. If not, it will simply reschedule itself to check
2036again at the earliest time it could time out. Rinse. Repeat.
2037.Sp
2038This scheme causes more callback invocations (about one every 60 seconds
2039minus half the average time between activity), but virtually no calls to
2040libev to change the timeout.
2041.Sp
2042To start the machinery, simply initialise the watcher and set
2043\&\f(CW\*(C`last_activity\*(C'\fR to the current time (meaning there was some activity just
2044now), then call the callback, which will \*(L"do the right thing\*(R" and start
2045the timer:
2046.Sp
2047.Vb 3
2048\& last_activity = ev_now (EV_A);
2049\& ev_init (&timer, callback);
2050\& callback (EV_A_ &timer, 0);
2051.Ve
2052.Sp
2053When there is some activity, simply store the current time in
2054\&\f(CW\*(C`last_activity\*(C'\fR, no libev calls at all:
2055.Sp
2056.Vb 2
2057\& if (activity detected)
2058\& last_activity = ev_now (EV_A);
2059.Ve
2060.Sp
2061When your timeout value changes, then the timeout can be changed by simply
2062providing a new value, stopping the timer and calling the callback, which
2063will again do the right thing (for example, time out immediately :).
2064.Sp
2065.Vb 3
2066\& timeout = new_value;
2067\& ev_timer_stop (EV_A_ &timer);
2068\& callback (EV_A_ &timer, 0);
2069.Ve
2070.Sp
2071This technique is slightly more complex, but in most cases where the
2072time-out is unlikely to be triggered, much more efficient.
2073.IP "4. Wee, just use a double-linked list for your timeouts." 4
2074.IX Item "4. Wee, just use a double-linked list for your timeouts."
2075If there is not one request, but many thousands (millions...), all
2076employing some kind of timeout with the same timeout value, then one can
2077do even better:
2078.Sp
2079When starting the timeout, calculate the timeout value and put the timeout
2080at the \fIend\fR of the list.
2081.Sp
2082Then use an \f(CW\*(C`ev_timer\*(C'\fR to fire when the timeout at the \fIbeginning\fR of
2083the list is expected to fire (for example, using the technique #3).
2084.Sp
2085When there is some activity, remove the timer from the list, recalculate
2086the timeout, append it to the end of the list again, and make sure to
2087update the \f(CW\*(C`ev_timer\*(C'\fR if it was taken from the beginning of the list.
2088.Sp
2089This way, one can manage an unlimited number of timeouts in O(1) time for
2090starting, stopping and updating the timers, at the expense of a major
2091complication, and having to use a constant timeout. The constant timeout
2092ensures that the list stays sorted.
2093.PP
2094So which method the best?
2095.PP
2096Method #2 is a simple no-brain-required solution that is adequate in most
2097situations. Method #3 requires a bit more thinking, but handles many cases
2098better, and isn't very complicated either. In most case, choosing either
2099one is fine, with #3 being better in typical situations.
2100.PP
2101Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
2102rather complicated, but extremely efficient, something that really pays
2103off after the first million or so of active timers, i.e. it's usually
2104overkill :)
2105.PP
2106\fIThe special problem of being too early\fR
2107.IX Subsection "The special problem of being too early"
2108.PP
2109If you ask a timer to call your callback after three seconds, then
2110you expect it to be invoked after three seconds \- but of course, this
2111cannot be guaranteed to infinite precision. Less obviously, it cannot be
2112guaranteed to any precision by libev \- imagine somebody suspending the
2113process with a \s-1STOP\s0 signal for a few hours for example.
2114.PP
2115So, libev tries to invoke your callback as soon as possible \fIafter\fR the
2116delay has occurred, but cannot guarantee this.
2117.PP
2118A less obvious failure mode is calling your callback too early: many event
2119loops compare timestamps with a \*(L"elapsed delay >= requested delay\*(R", but
2120this can cause your callback to be invoked much earlier than you would
2121expect.
2122.PP
2123To see why, imagine a system with a clock that only offers full second
2124resolution (think windows if you can't come up with a broken enough \s-1OS\s0
2125yourself). If you schedule a one-second timer at the time 500.9, then the
2126event loop will schedule your timeout to elapse at a system time of 500
2127(500.9 truncated to the resolution) + 1, or 501.
2128.PP
2129If an event library looks at the timeout 0.1s later, it will see \*(L"501 >=
2130501\*(R" and invoke the callback 0.1s after it was started, even though a
2131one-second delay was requested \- this is being \*(L"too early\*(R", despite best
2132intentions.
2133.PP
2134This is the reason why libev will never invoke the callback if the elapsed
2135delay equals the requested delay, but only when the elapsed delay is
2136larger than the requested delay. In the example above, libev would only invoke
2137the callback at system time 502, or 1.1s after the timer was started.
2138.PP
2139So, while libev cannot guarantee that your callback will be invoked
2140exactly when requested, it \fIcan\fR and \fIdoes\fR guarantee that the requested
2141delay has actually elapsed, or in other words, it always errs on the \*(L"too
2142late\*(R" side of things.
2143.PP
2144\fIThe special problem of time updates\fR
2145.IX Subsection "The special problem of time updates"
2146.PP
2147Establishing the current time is a costly operation (it usually takes
2148at least one system call): \s-1EV\s0 therefore updates its idea of the current
2149time only before and after \f(CW\*(C`ev_run\*(C'\fR collects new events, which causes a
2150growing difference between \f(CW\*(C`ev_now ()\*(C'\fR and \f(CW\*(C`ev_time ()\*(C'\fR when handling
2151lots of events in one iteration.
1143.PP 2152.PP
1144The relative timeouts are calculated relative to the \f(CW\*(C`ev_now ()\*(C'\fR 2153The relative timeouts are calculated relative to the \f(CW\*(C`ev_now ()\*(C'\fR
1145time. This is usually the right thing as this timestamp refers to the time 2154time. This is usually the right thing as this timestamp refers to the time
1146of the event triggering whatever timeout you are modifying/starting. If 2155of the event triggering whatever timeout you are modifying/starting. If
1147you suspect event processing to be delayed and you \fIneed\fR to base the timeout 2156you suspect event processing to be delayed and you \fIneed\fR to base the
1148on the current time, use something like this to adjust for this: 2157timeout on the current time, use something like this to adjust for this:
1149.PP 2158.PP
1150.Vb 1 2159.Vb 1
1151\& ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); 2160\& ev_timer_set (&timer, after + ev_now () \- ev_time (), 0.);
1152.Ve 2161.Ve
1153.PP 2162.PP
1154The callback is guarenteed to be invoked only when its timeout has passed, 2163If the event loop is suspended for a long time, you can also force an
1155but if multiple timers become ready during the same loop iteration then 2164update of the time returned by \f(CW\*(C`ev_now ()\*(C'\fR by calling \f(CW\*(C`ev_now_update
1156order of execution is undefined. 2165()\*(C'\fR.
2166.PP
2167\fIThe special problem of unsynchronised clocks\fR
2168.IX Subsection "The special problem of unsynchronised clocks"
2169.PP
2170Modern systems have a variety of clocks \- libev itself uses the normal
2171\&\*(L"wall clock\*(R" clock and, if available, the monotonic clock (to avoid time
2172jumps).
2173.PP
2174Neither of these clocks is synchronised with each other or any other clock
2175on the system, so \f(CW\*(C`ev_time ()\*(C'\fR might return a considerably different time
2176than \f(CW\*(C`gettimeofday ()\*(C'\fR or \f(CW\*(C`time ()\*(C'\fR. On a GNU/Linux system, for example,
2177a call to \f(CW\*(C`gettimeofday\*(C'\fR might return a second count that is one higher
2178than a directly following call to \f(CW\*(C`time\*(C'\fR.
2179.PP
2180The moral of this is to only compare libev-related timestamps with
2181\&\f(CW\*(C`ev_time ()\*(C'\fR and \f(CW\*(C`ev_now ()\*(C'\fR, at least if you want better precision than
2182a second or so.
2183.PP
2184One more problem arises due to this lack of synchronisation: if libev uses
2185the system monotonic clock and you compare timestamps from \f(CW\*(C`ev_time\*(C'\fR
2186or \f(CW\*(C`ev_now\*(C'\fR from when you started your timer and when your callback is
2187invoked, you will find that sometimes the callback is a bit \*(L"early\*(R".
2188.PP
2189This is because \f(CW\*(C`ev_timer\*(C'\fRs work in real time, not wall clock time, so
2190libev makes sure your callback is not invoked before the delay happened,
2191\&\fImeasured according to the real time\fR, not the system clock.
2192.PP
2193If your timeouts are based on a physical timescale (e.g. \*(L"time out this
2194connection after 100 seconds\*(R") then this shouldn't bother you as it is
2195exactly the right behaviour.
2196.PP
2197If you want to compare wall clock/system timestamps to your timers, then
2198you need to use \f(CW\*(C`ev_periodic\*(C'\fRs, as these are based on the wall clock
2199time, where your comparisons will always generate correct results.
2200.PP
2201\fIThe special problems of suspended animation\fR
2202.IX Subsection "The special problems of suspended animation"
2203.PP
2204When you leave the server world it is quite customary to hit machines that
2205can suspend/hibernate \- what happens to the clocks during such a suspend?
2206.PP
2207Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
2208all processes, while the clocks (\f(CW\*(C`times\*(C'\fR, \f(CW\*(C`CLOCK_MONOTONIC\*(C'\fR) continue
2209to run until the system is suspended, but they will not advance while the
2210system is suspended. That means, on resume, it will be as if the program
2211was frozen for a few seconds, but the suspend time will not be counted
2212towards \f(CW\*(C`ev_timer\*(C'\fR when a monotonic clock source is used. The real time
2213clock advanced as expected, but if it is used as sole clocksource, then a
2214long suspend would be detected as a time jump by libev, and timers would
2215be adjusted accordingly.
2216.PP
2217I would not be surprised to see different behaviour in different between
2218operating systems, \s-1OS\s0 versions or even different hardware.
2219.PP
2220The other form of suspend (job control, or sending a \s-1SIGSTOP\s0) will see a
2221time jump in the monotonic clocks and the realtime clock. If the program
2222is suspended for a very long time, and monotonic clock sources are in use,
2223then you can expect \f(CW\*(C`ev_timer\*(C'\fRs to expire as the full suspension time
2224will be counted towards the timers. When no monotonic clock source is in
2225use, then libev will again assume a timejump and adjust accordingly.
2226.PP
2227It might be beneficial for this latter case to call \f(CW\*(C`ev_suspend\*(C'\fR
2228and \f(CW\*(C`ev_resume\*(C'\fR in code that handles \f(CW\*(C`SIGTSTP\*(C'\fR, to at least get
2229deterministic behaviour in this case (you can do nothing against
2230\&\f(CW\*(C`SIGSTOP\*(C'\fR).
1157.PP 2231.PP
1158\fIWatcher-Specific Functions and Data Members\fR 2232\fIWatcher-Specific Functions and Data Members\fR
1159.IX Subsection "Watcher-Specific Functions and Data Members" 2233.IX Subsection "Watcher-Specific Functions and Data Members"
1160.IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4 2234.IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4
1161.IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 2235.IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)"
1162.PD 0 2236.PD 0
1163.IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4 2237.IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4
1164.IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 2238.IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)"
1165.PD 2239.PD
1166Configure the timer to trigger after \f(CW\*(C`after\*(C'\fR seconds. If \f(CW\*(C`repeat\*(C'\fR is 2240Configure the timer to trigger after \f(CW\*(C`after\*(C'\fR seconds. If \f(CW\*(C`repeat\*(C'\fR
1167\&\f(CW0.\fR, then it will automatically be stopped. If it is positive, then the 2241is \f(CW0.\fR, then it will automatically be stopped once the timeout is
1168timer will automatically be configured to trigger again \f(CW\*(C`repeat\*(C'\fR seconds 2242reached. If it is positive, then the timer will automatically be
1169later, again, and again, until stopped manually. 2243configured to trigger again \f(CW\*(C`repeat\*(C'\fR seconds later, again, and again,
2244until stopped manually.
1170.Sp 2245.Sp
1171The timer itself will do a best-effort at avoiding drift, that is, if you 2246The timer itself will do a best-effort at avoiding drift, that is, if
1172configure a timer to trigger every 10 seconds, then it will trigger at 2247you configure a timer to trigger every 10 seconds, then it will normally
1173exactly 10 second intervals. If, however, your program cannot keep up with 2248trigger at exactly 10 second intervals. If, however, your program cannot
1174the timer (because it takes longer than those 10 seconds to do stuff) the 2249keep up with the timer (because it takes longer than those 10 seconds to
1175timer will not fire more than once per event loop iteration. 2250do stuff) the timer will not fire more than once per event loop iteration.
1176.IP "ev_timer_again (loop)" 4 2251.IP "ev_timer_again (loop, ev_timer *)" 4
1177.IX Item "ev_timer_again (loop)" 2252.IX Item "ev_timer_again (loop, ev_timer *)"
1178This will act as if the timer timed out and restart it again if it is 2253This will act as if the timer timed out, and restarts it again if it is
1179repeating. The exact semantics are: 2254repeating. It basically works like calling \f(CW\*(C`ev_timer_stop\*(C'\fR, updating the
2255timeout to the \f(CW\*(C`repeat\*(C'\fR value and calling \f(CW\*(C`ev_timer_start\*(C'\fR.
1180.Sp 2256.Sp
2257The exact semantics are as in the following rules, all of which will be
2258applied to the watcher:
2259.RS 4
1181If the timer is pending, its pending status is cleared. 2260.IP "If the timer is pending, the pending status is always cleared." 4
1182.Sp 2261.IX Item "If the timer is pending, the pending status is always cleared."
2262.PD 0
1183If the timer is started but nonrepeating, stop it (as if it timed out). 2263.IP "If the timer is started but non-repeating, stop it (as if it timed out, without invoking it)." 4
2264.IX Item "If the timer is started but non-repeating, stop it (as if it timed out, without invoking it)."
2265.ie n .IP "If the timer is repeating, make the ""repeat"" value the new timeout and start the timer, if necessary." 4
2266.el .IP "If the timer is repeating, make the \f(CWrepeat\fR value the new timeout and start the timer, if necessary." 4
2267.IX Item "If the timer is repeating, make the repeat value the new timeout and start the timer, if necessary."
2268.RE
2269.RS 4
2270.PD
1184.Sp 2271.Sp
1185If the timer is repeating, either start it if necessary (with the 2272This sounds a bit complicated, see \*(L"Be smart about timeouts\*(R", above, for a
1186\&\f(CW\*(C`repeat\*(C'\fR value), or reset the running timer to the \f(CW\*(C`repeat\*(C'\fR value. 2273usage example.
2274.RE
2275.IP "ev_tstamp ev_timer_remaining (loop, ev_timer *)" 4
2276.IX Item "ev_tstamp ev_timer_remaining (loop, ev_timer *)"
2277Returns the remaining time until a timer fires. If the timer is active,
2278then this time is relative to the current event loop time, otherwise it's
2279the timeout value currently configured.
1187.Sp 2280.Sp
1188This sounds a bit complicated, but here is a useful and typical 2281That is, after an \f(CW\*(C`ev_timer_set (w, 5, 7)\*(C'\fR, \f(CW\*(C`ev_timer_remaining\*(C'\fR returns
1189example: Imagine you have a tcp connection and you want a so-called idle 2282\&\f(CW5\fR. When the timer is started and one second passes, \f(CW\*(C`ev_timer_remaining\*(C'\fR
1190timeout, that is, you want to be called when there have been, say, 60 2283will return \f(CW4\fR. When the timer expires and is restarted, it will return
1191seconds of inactivity on the socket. The easiest way to do this is to 2284roughly \f(CW7\fR (likely slightly less as callback invocation takes some time,
1192configure an \f(CW\*(C`ev_timer\*(C'\fR with a \f(CW\*(C`repeat\*(C'\fR value of \f(CW60\fR and then call 2285too), and so on.
1193\&\f(CW\*(C`ev_timer_again\*(C'\fR each time you successfully read or write some data. If
1194you go into an idle state where you do not expect data to travel on the
1195socket, you can \f(CW\*(C`ev_timer_stop\*(C'\fR the timer, and \f(CW\*(C`ev_timer_again\*(C'\fR will
1196automatically restart it if need be.
1197.Sp
1198That means you can ignore the \f(CW\*(C`after\*(C'\fR value and \f(CW\*(C`ev_timer_start\*(C'\fR
1199altogether and only ever use the \f(CW\*(C`repeat\*(C'\fR value and \f(CW\*(C`ev_timer_again\*(C'\fR:
1200.Sp
1201.Vb 8
1202\& ev_timer_init (timer, callback, 0., 5.);
1203\& ev_timer_again (loop, timer);
1204\& ...
1205\& timer->again = 17.;
1206\& ev_timer_again (loop, timer);
1207\& ...
1208\& timer->again = 10.;
1209\& ev_timer_again (loop, timer);
1210.Ve
1211.Sp
1212This is more slightly efficient then stopping/starting the timer each time
1213you want to modify its timeout value.
1214.IP "ev_tstamp repeat [read\-write]" 4 2286.IP "ev_tstamp repeat [read\-write]" 4
1215.IX Item "ev_tstamp repeat [read-write]" 2287.IX Item "ev_tstamp repeat [read-write]"
1216The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out 2288The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out
1217or \f(CW\*(C`ev_timer_again\*(C'\fR is called and determines the next timeout (if any), 2289or \f(CW\*(C`ev_timer_again\*(C'\fR is called, and determines the next timeout (if any),
1218which is also when any modifications are taken into account. 2290which is also when any modifications are taken into account.
1219.PP 2291.PP
2292\fIExamples\fR
2293.IX Subsection "Examples"
2294.PP
1220Example: Create a timer that fires after 60 seconds. 2295Example: Create a timer that fires after 60 seconds.
1221.PP 2296.PP
1222.Vb 5 2297.Vb 5
1223\& static void 2298\& static void
1224\& one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 2299\& one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1225\& { 2300\& {
1226\& .. one minute over, w is actually stopped right here 2301\& .. one minute over, w is actually stopped right here
1227\& } 2302\& }
1228.Ve 2303\&
1229.PP
1230.Vb 3
1231\& struct ev_timer mytimer; 2304\& ev_timer mytimer;
1232\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.); 2305\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1233\& ev_timer_start (loop, &mytimer); 2306\& ev_timer_start (loop, &mytimer);
1234.Ve 2307.Ve
1235.PP 2308.PP
1236Example: Create a timeout timer that times out after 10 seconds of 2309Example: Create a timeout timer that times out after 10 seconds of
1237inactivity. 2310inactivity.
1238.PP 2311.PP
1239.Vb 5 2312.Vb 5
1240\& static void 2313\& static void
1241\& timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 2314\& timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1242\& { 2315\& {
1243\& .. ten seconds without any activity 2316\& .. ten seconds without any activity
1244\& } 2317\& }
1245.Ve 2318\&
1246.PP
1247.Vb 4
1248\& struct ev_timer mytimer; 2319\& ev_timer mytimer;
1249\& ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ 2320\& ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1250\& ev_timer_again (&mytimer); /* start timer */ 2321\& ev_timer_again (&mytimer); /* start timer */
1251\& ev_loop (loop, 0); 2322\& ev_run (loop, 0);
1252.Ve 2323\&
1253.PP
1254.Vb 3
1255\& // and in some piece of code that gets executed on any "activity": 2324\& // and in some piece of code that gets executed on any "activity":
1256\& // reset the timeout to start ticking again at 10 seconds 2325\& // reset the timeout to start ticking again at 10 seconds
1257\& ev_timer_again (&mytimer); 2326\& ev_timer_again (&mytimer);
1258.Ve 2327.Ve
1259.ie n .Sh """ev_periodic"" \- to cron or not to cron?" 2328.ie n .SS """ev_periodic"" \- to cron or not to cron?"
1260.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron?" 2329.el .SS "\f(CWev_periodic\fP \- to cron or not to cron?"
1261.IX Subsection "ev_periodic - to cron or not to cron?" 2330.IX Subsection "ev_periodic - to cron or not to cron?"
1262Periodic watchers are also timers of a kind, but they are very versatile 2331Periodic watchers are also timers of a kind, but they are very versatile
1263(and unfortunately a bit complex). 2332(and unfortunately a bit complex).
1264.PP 2333.PP
1265Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time) 2334Unlike \f(CW\*(C`ev_timer\*(C'\fR, periodic watchers are not based on real time (or
1266but on wallclock time (absolute time). You can tell a periodic watcher 2335relative time, the physical time that passes) but on wall clock time
1267to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a 2336(absolute time, the thing you can read on your calender or clock). The
1268periodic watcher to trigger in 10 seconds (by specifiying e.g. \f(CW\*(C`ev_now () 2337difference is that wall clock time can run faster or slower than real
1269+ 10.\*(C'\fR) and then reset your system clock to the last year, then it will 2338time, and time jumps are not uncommon (e.g. when you adjust your
1270take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger 2339wrist-watch).
1271roughly 10 seconds later).
1272.PP 2340.PP
1273They can also be used to implement vastly more complex timers, such as 2341You can tell a periodic watcher to trigger after some specific point
1274triggering an event on each midnight, local time or other, complicated, 2342in time: for example, if you tell a periodic watcher to trigger \*(L"in 10
1275rules. 2343seconds\*(R" (by specifying e.g. \f(CW\*(C`ev_now () + 10.\*(C'\fR, that is, an absolute time
2344not a delay) and then reset your system clock to January of the previous
2345year, then it will take a year or more to trigger the event (unlike an
2346\&\f(CW\*(C`ev_timer\*(C'\fR, which would still trigger roughly 10 seconds after starting
2347it, as it uses a relative timeout).
1276.PP 2348.PP
2349\&\f(CW\*(C`ev_periodic\*(C'\fR watchers can also be used to implement vastly more complex
2350timers, such as triggering an event on each \*(L"midnight, local time\*(R", or
2351other complicated rules. This cannot be done with \f(CW\*(C`ev_timer\*(C'\fR watchers, as
2352those cannot react to time jumps.
2353.PP
1277As with timers, the callback is guarenteed to be invoked only when the 2354As with timers, the callback is guaranteed to be invoked only when the
1278time (\f(CW\*(C`at\*(C'\fR) has been passed, but if multiple periodic timers become ready 2355point in time where it is supposed to trigger has passed. If multiple
1279during the same loop iteration then order of execution is undefined. 2356timers become ready during the same loop iteration then the ones with
2357earlier time-out values are invoked before ones with later time-out values
2358(but this is no longer true when a callback calls \f(CW\*(C`ev_run\*(C'\fR recursively).
1280.PP 2359.PP
1281\fIWatcher-Specific Functions and Data Members\fR 2360\fIWatcher-Specific Functions and Data Members\fR
1282.IX Subsection "Watcher-Specific Functions and Data Members" 2361.IX Subsection "Watcher-Specific Functions and Data Members"
1283.IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4 2362.IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)" 4
1284.IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 2363.IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)"
1285.PD 0 2364.PD 0
1286.IP "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 4 2365.IP "ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)" 4
1287.IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 2366.IX Item "ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)"
1288.PD 2367.PD
1289Lots of arguments, lets sort it out... There are basically three modes of 2368Lots of arguments, let's sort it out... There are basically three modes of
1290operation, and we will explain them from simplest to complex: 2369operation, and we will explain them from simplest to most complex:
1291.RS 4 2370.RS 4
2371.IP "\(bu" 4
1292.IP "* absolute timer (at = time, interval = reschedule_cb = 0)" 4 2372absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1293.IX Item "absolute timer (at = time, interval = reschedule_cb = 0)" 2373.Sp
1294In this configuration the watcher triggers an event at the wallclock time 2374In this configuration the watcher triggers an event after the wall clock
1295\&\f(CW\*(C`at\*(C'\fR and doesn't repeat. It will not adjust when a time jump occurs, 2375time \f(CW\*(C`offset\*(C'\fR has passed. It will not repeat and will not adjust when a
1296that is, if it is to be run at January 1st 2011 then it will run when the 2376time jump occurs, that is, if it is to be run at January 1st 2011 then it
1297system time reaches or surpasses this time. 2377will be stopped and invoked when the system clock reaches or surpasses
1298.IP "* non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)" 4 2378this point in time.
1299.IX Item "non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)" 2379.IP "\(bu" 4
2380repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
2381.Sp
1300In this mode the watcher will always be scheduled to time out at the next 2382In this mode the watcher will always be scheduled to time out at the next
1301\&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N, which can also be negative) 2383\&\f(CW\*(C`offset + N * interval\*(C'\fR time (for some integer N, which can also be
1302and then repeat, regardless of any time jumps. 2384negative) and then repeat, regardless of any time jumps. The \f(CW\*(C`offset\*(C'\fR
2385argument is merely an offset into the \f(CW\*(C`interval\*(C'\fR periods.
1303.Sp 2386.Sp
1304This can be used to create timers that do not drift with respect to system 2387This can be used to create timers that do not drift with respect to the
1305time: 2388system clock, for example, here is an \f(CW\*(C`ev_periodic\*(C'\fR that triggers each
2389hour, on the hour (with respect to \s-1UTC\s0):
1306.Sp 2390.Sp
1307.Vb 1 2391.Vb 1
1308\& ev_periodic_set (&periodic, 0., 3600., 0); 2392\& ev_periodic_set (&periodic, 0., 3600., 0);
1309.Ve 2393.Ve
1310.Sp 2394.Sp
1311This doesn't mean there will always be 3600 seconds in between triggers, 2395This doesn't mean there will always be 3600 seconds in between triggers,
1312but only that the the callback will be called when the system time shows a 2396but only that the callback will be called when the system time shows a
1313full hour (\s-1UTC\s0), or more correctly, when the system time is evenly divisible 2397full hour (\s-1UTC\s0), or more correctly, when the system time is evenly divisible
1314by 3600. 2398by 3600.
1315.Sp 2399.Sp
1316Another way to think about it (for the mathematically inclined) is that 2400Another way to think about it (for the mathematically inclined) is that
1317\&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible 2401\&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible
1318time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps. 2402time where \f(CW\*(C`time = offset (mod interval)\*(C'\fR, regardless of any time jumps.
1319.Sp 2403.Sp
1320For numerical stability it is preferable that the \f(CW\*(C`at\*(C'\fR value is near 2404The \f(CW\*(C`interval\*(C'\fR \fI\s-1MUST\s0\fR be positive, and for numerical stability, the
1321\&\f(CW\*(C`ev_now ()\*(C'\fR (the current time), but there is no range requirement for 2405interval value should be higher than \f(CW\*(C`1/8192\*(C'\fR (which is around 100
1322this value. 2406microseconds) and \f(CW\*(C`offset\*(C'\fR should be higher than \f(CW0\fR and should have
2407at most a similar magnitude as the current time (say, within a factor of
2408ten). Typical values for offset are, in fact, \f(CW0\fR or something between
2409\&\f(CW0\fR and \f(CW\*(C`interval\*(C'\fR, which is also the recommended range.
2410.Sp
2411Note also that there is an upper limit to how often a timer can fire (\s-1CPU\s0
2412speed for example), so if \f(CW\*(C`interval\*(C'\fR is very small then timing stability
2413will of course deteriorate. Libev itself tries to be exact to be about one
2414millisecond (if the \s-1OS\s0 supports it and the machine is fast enough).
2415.IP "\(bu" 4
1323.IP "* manual reschedule mode (at and interval ignored, reschedule_cb = callback)" 4 2416manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1324.IX Item "manual reschedule mode (at and interval ignored, reschedule_cb = callback)" 2417.Sp
1325In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR are both being 2418In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`offset\*(C'\fR are both being
1326ignored. Instead, each time the periodic watcher gets scheduled, the 2419ignored. Instead, each time the periodic watcher gets scheduled, the
1327reschedule callback will be called with the watcher as first, and the 2420reschedule callback will be called with the watcher as first, and the
1328current time as second argument. 2421current time as second argument.
1329.Sp 2422.Sp
1330\&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher, 2423\&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher, ever,
1331ever, or make any event loop modifications\fR. If you need to stop it, 2424or make \s-1ANY\s0 other event loop modifications whatsoever, unless explicitly
1332return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop it afterwards (e.g. by 2425allowed by documentation here\fR.
2426.Sp
2427If you need to stop it, return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop
1333starting an \f(CW\*(C`ev_prepare\*(C'\fR watcher, which is legal). 2428it afterwards (e.g. by starting an \f(CW\*(C`ev_prepare\*(C'\fR watcher, which is the
2429only event loop modification you are allowed to do).
1334.Sp 2430.Sp
1335Its prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 2431The callback prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(ev_periodic
1336ev_tstamp now)\*(C'\fR, e.g.: 2432*w, ev_tstamp now)\*(C'\fR, e.g.:
1337.Sp 2433.Sp
1338.Vb 4 2434.Vb 5
2435\& static ev_tstamp
1339\& static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 2436\& my_rescheduler (ev_periodic *w, ev_tstamp now)
1340\& { 2437\& {
1341\& return now + 60.; 2438\& return now + 60.;
1342\& } 2439\& }
1343.Ve 2440.Ve
1344.Sp 2441.Sp
1345It must return the next time to trigger, based on the passed time value 2442It must return the next time to trigger, based on the passed time value
1346(that is, the lowest time value larger than to the second argument). It 2443(that is, the lowest time value larger than to the second argument). It
1347will usually be called just before the callback will be triggered, but 2444will usually be called just before the callback will be triggered, but
1348might be called at other times, too. 2445might be called at other times, too.
1349.Sp 2446.Sp
1350\&\s-1NOTE:\s0 \fIThis callback must always return a time that is later than the 2447\&\s-1NOTE:\s0 \fIThis callback must always return a time that is higher than or
1351passed \f(CI\*(C`now\*(C'\fI value\fR. Not even \f(CW\*(C`now\*(C'\fR itself will do, it \fImust\fR be larger. 2448equal to the passed \f(CI\*(C`now\*(C'\fI value\fR.
1352.Sp 2449.Sp
1353This can be used to create very complex timers, such as a timer that 2450This can be used to create very complex timers, such as a timer that
1354triggers on each midnight, local time. To do this, you would calculate the 2451triggers on \*(L"next midnight, local time\*(R". To do this, you would calculate the
1355next midnight after \f(CW\*(C`now\*(C'\fR and return the timestamp value for this. How 2452next midnight after \f(CW\*(C`now\*(C'\fR and return the timestamp value for this. How
1356you do this is, again, up to you (but it is not trivial, which is the main 2453you do this is, again, up to you (but it is not trivial, which is the main
1357reason I omitted it as an example). 2454reason I omitted it as an example).
1358.RE 2455.RE
1359.RS 4 2456.RS 4
… …
1362.IX Item "ev_periodic_again (loop, ev_periodic *)" 2459.IX Item "ev_periodic_again (loop, ev_periodic *)"
1363Simply stops and restarts the periodic watcher again. This is only useful 2460Simply stops and restarts the periodic watcher again. This is only useful
1364when you changed some parameters or the reschedule callback would return 2461when you changed some parameters or the reschedule callback would return
1365a different time than the last time it was called (e.g. in a crond like 2462a different time than the last time it was called (e.g. in a crond like
1366program when the crontabs have changed). 2463program when the crontabs have changed).
2464.IP "ev_tstamp ev_periodic_at (ev_periodic *)" 4
2465.IX Item "ev_tstamp ev_periodic_at (ev_periodic *)"
2466When active, returns the absolute time that the watcher is supposed
2467to trigger next. This is not the same as the \f(CW\*(C`offset\*(C'\fR argument to
2468\&\f(CW\*(C`ev_periodic_set\*(C'\fR, but indeed works even in interval and manual
2469rescheduling modes.
1367.IP "ev_tstamp offset [read\-write]" 4 2470.IP "ev_tstamp offset [read\-write]" 4
1368.IX Item "ev_tstamp offset [read-write]" 2471.IX Item "ev_tstamp offset [read-write]"
1369When repeating, this contains the offset value, otherwise this is the 2472When repeating, this contains the offset value, otherwise this is the
1370absolute point in time (the \f(CW\*(C`at\*(C'\fR value passed to \f(CW\*(C`ev_periodic_set\*(C'\fR). 2473absolute point in time (the \f(CW\*(C`offset\*(C'\fR value passed to \f(CW\*(C`ev_periodic_set\*(C'\fR,
2474although libev might modify this value for better numerical stability).
1371.Sp 2475.Sp
1372Can be modified any time, but changes only take effect when the periodic 2476Can be modified any time, but changes only take effect when the periodic
1373timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called. 2477timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
1374.IP "ev_tstamp interval [read\-write]" 4 2478.IP "ev_tstamp interval [read\-write]" 4
1375.IX Item "ev_tstamp interval [read-write]" 2479.IX Item "ev_tstamp interval [read-write]"
1376The current interval value. Can be modified any time, but changes only 2480The current interval value. Can be modified any time, but changes only
1377take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being 2481take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being
1378called. 2482called.
1379.IP "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read\-write]" 4 2483.IP "ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read\-write]" 4
1380.IX Item "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]" 2484.IX Item "ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]"
1381The current reschedule callback, or \f(CW0\fR, if this functionality is 2485The current reschedule callback, or \f(CW0\fR, if this functionality is
1382switched off. Can be changed any time, but changes only take effect when 2486switched off. Can be changed any time, but changes only take effect when
1383the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called. 2487the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
1384.PP 2488.PP
2489\fIExamples\fR
2490.IX Subsection "Examples"
2491.PP
1385Example: Call a callback every hour, or, more precisely, whenever the 2492Example: Call a callback every hour, or, more precisely, whenever the
1386system clock is divisible by 3600. The callback invocation times have 2493system time is divisible by 3600. The callback invocation times have
1387potentially a lot of jittering, but good long-term stability. 2494potentially a lot of jitter, but good long-term stability.
1388.PP 2495.PP
1389.Vb 5 2496.Vb 5
1390\& static void 2497\& static void
1391\& clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) 2498\& clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1392\& { 2499\& {
1393\& ... its now a full hour (UTC, or TAI or whatever your clock follows) 2500\& ... its now a full hour (UTC, or TAI or whatever your clock follows)
1394\& } 2501\& }
1395.Ve 2502\&
1396.PP
1397.Vb 3
1398\& struct ev_periodic hourly_tick; 2503\& ev_periodic hourly_tick;
1399\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); 2504\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1400\& ev_periodic_start (loop, &hourly_tick); 2505\& ev_periodic_start (loop, &hourly_tick);
1401.Ve 2506.Ve
1402.PP 2507.PP
1403Example: The same as above, but use a reschedule callback to do it: 2508Example: The same as above, but use a reschedule callback to do it:
1404.PP 2509.PP
1405.Vb 1 2510.Vb 1
1406\& #include <math.h> 2511\& #include <math.h>
1407.Ve 2512\&
1408.PP
1409.Vb 5
1410\& static ev_tstamp 2513\& static ev_tstamp
1411\& my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) 2514\& my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1412\& { 2515\& {
1413\& return fmod (now, 3600.) + 3600.; 2516\& return now + (3600. \- fmod (now, 3600.));
1414\& } 2517\& }
1415.Ve 2518\&
1416.PP
1417.Vb 1
1418\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); 2519\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1419.Ve 2520.Ve
1420.PP 2521.PP
1421Example: Call a callback every hour, starting now: 2522Example: Call a callback every hour, starting now:
1422.PP 2523.PP
1423.Vb 4 2524.Vb 4
1424\& struct ev_periodic hourly_tick; 2525\& ev_periodic hourly_tick;
1425\& ev_periodic_init (&hourly_tick, clock_cb, 2526\& ev_periodic_init (&hourly_tick, clock_cb,
1426\& fmod (ev_now (loop), 3600.), 3600., 0); 2527\& fmod (ev_now (loop), 3600.), 3600., 0);
1427\& ev_periodic_start (loop, &hourly_tick); 2528\& ev_periodic_start (loop, &hourly_tick);
1428.Ve 2529.Ve
1429.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled!" 2530.ie n .SS """ev_signal"" \- signal me when a signal gets signalled!"
1430.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled!" 2531.el .SS "\f(CWev_signal\fP \- signal me when a signal gets signalled!"
1431.IX Subsection "ev_signal - signal me when a signal gets signalled!" 2532.IX Subsection "ev_signal - signal me when a signal gets signalled!"
1432Signal watchers will trigger an event when the process receives a specific 2533Signal watchers will trigger an event when the process receives a specific
1433signal one or more times. Even though signals are very asynchronous, libev 2534signal one or more times. Even though signals are very asynchronous, libev
1434will try it's best to deliver signals synchronously, i.e. as part of the 2535will try its best to deliver signals synchronously, i.e. as part of the
1435normal event processing, like any other event. 2536normal event processing, like any other event.
1436.PP 2537.PP
2538If you want signals to be delivered truly asynchronously, just use
2539\&\f(CW\*(C`sigaction\*(C'\fR as you would do without libev and forget about sharing
2540the signal. You can even use \f(CW\*(C`ev_async\*(C'\fR from a signal handler to
2541synchronously wake up an event loop.
2542.PP
1437You can configure as many watchers as you like per signal. Only when the 2543You can configure as many watchers as you like for the same signal, but
2544only within the same loop, i.e. you can watch for \f(CW\*(C`SIGINT\*(C'\fR in your
2545default loop and for \f(CW\*(C`SIGIO\*(C'\fR in another loop, but you cannot watch for
2546\&\f(CW\*(C`SIGINT\*(C'\fR in both the default loop and another loop at the same time. At
2547the moment, \f(CW\*(C`SIGCHLD\*(C'\fR is permanently tied to the default loop.
2548.PP
1438first watcher gets started will libev actually register a signal watcher 2549When the first watcher gets started will libev actually register something
1439with the kernel (thus it coexists with your own signal handlers as long 2550with the kernel (thus it coexists with your own signal handlers as long as
1440as you don't register any with libev). Similarly, when the last signal 2551you don't register any with libev for the same signal).
1441watcher for a signal is stopped libev will reset the signal handler to 2552.PP
1442\&\s-1SIG_DFL\s0 (regardless of what it was set to before). 2553If possible and supported, libev will install its handlers with
2554\&\f(CW\*(C`SA_RESTART\*(C'\fR (or equivalent) behaviour enabled, so system calls should
2555not be unduly interrupted. If you have a problem with system calls getting
2556interrupted by signals you can block all signals in an \f(CW\*(C`ev_check\*(C'\fR watcher
2557and unblock them in an \f(CW\*(C`ev_prepare\*(C'\fR watcher.
2558.PP
2559\fIThe special problem of inheritance over fork/execve/pthread_create\fR
2560.IX Subsection "The special problem of inheritance over fork/execve/pthread_create"
2561.PP
2562Both the signal mask (\f(CW\*(C`sigprocmask\*(C'\fR) and the signal disposition
2563(\f(CW\*(C`sigaction\*(C'\fR) are unspecified after starting a signal watcher (and after
2564stopping it again), that is, libev might or might not block the signal,
2565and might or might not set or restore the installed signal handler (but
2566see \f(CW\*(C`EVFLAG_NOSIGMASK\*(C'\fR).
2567.PP
2568While this does not matter for the signal disposition (libev never
2569sets signals to \f(CW\*(C`SIG_IGN\*(C'\fR, so handlers will be reset to \f(CW\*(C`SIG_DFL\*(C'\fR on
2570\&\f(CW\*(C`execve\*(C'\fR), this matters for the signal mask: many programs do not expect
2571certain signals to be blocked.
2572.PP
2573This means that before calling \f(CW\*(C`exec\*(C'\fR (from the child) you should reset
2574the signal mask to whatever \*(L"default\*(R" you expect (all clear is a good
2575choice usually).
2576.PP
2577The simplest way to ensure that the signal mask is reset in the child is
2578to install a fork handler with \f(CW\*(C`pthread_atfork\*(C'\fR that resets it. That will
2579catch fork calls done by libraries (such as the libc) as well.
2580.PP
2581In current versions of libev, the signal will not be blocked indefinitely
2582unless you use the \f(CW\*(C`signalfd\*(C'\fR \s-1API\s0 (\f(CW\*(C`EV_SIGNALFD\*(C'\fR). While this reduces
2583the window of opportunity for problems, it will not go away, as libev
2584\&\fIhas\fR to modify the signal mask, at least temporarily.
2585.PP
2586So I can't stress this enough: \fIIf you do not reset your signal mask when
2587you expect it to be empty, you have a race condition in your code\fR. This
2588is not a libev-specific thing, this is true for most event libraries.
2589.PP
2590\fIThe special problem of threads signal handling\fR
2591.IX Subsection "The special problem of threads signal handling"
2592.PP
2593\&\s-1POSIX\s0 threads has problematic signal handling semantics, specifically,
2594a lot of functionality (sigfd, sigwait etc.) only really works if all
2595threads in a process block signals, which is hard to achieve.
2596.PP
2597When you want to use sigwait (or mix libev signal handling with your own
2598for the same signals), you can tackle this problem by globally blocking
2599all signals before creating any threads (or creating them with a fully set
2600sigprocmask) and also specifying the \f(CW\*(C`EVFLAG_NOSIGMASK\*(C'\fR when creating
2601loops. Then designate one thread as \*(L"signal receiver thread\*(R" which handles
2602these signals. You can pass on any signals that libev might be interested
2603in by calling \f(CW\*(C`ev_feed_signal\*(C'\fR.
1443.PP 2604.PP
1444\fIWatcher-Specific Functions and Data Members\fR 2605\fIWatcher-Specific Functions and Data Members\fR
1445.IX Subsection "Watcher-Specific Functions and Data Members" 2606.IX Subsection "Watcher-Specific Functions and Data Members"
1446.IP "ev_signal_init (ev_signal *, callback, int signum)" 4 2607.IP "ev_signal_init (ev_signal *, callback, int signum)" 4
1447.IX Item "ev_signal_init (ev_signal *, callback, int signum)" 2608.IX Item "ev_signal_init (ev_signal *, callback, int signum)"
… …
1452Configures the watcher to trigger on the given signal number (usually one 2613Configures the watcher to trigger on the given signal number (usually one
1453of the \f(CW\*(C`SIGxxx\*(C'\fR constants). 2614of the \f(CW\*(C`SIGxxx\*(C'\fR constants).
1454.IP "int signum [read\-only]" 4 2615.IP "int signum [read\-only]" 4
1455.IX Item "int signum [read-only]" 2616.IX Item "int signum [read-only]"
1456The signal the watcher watches out for. 2617The signal the watcher watches out for.
2618.PP
2619\fIExamples\fR
2620.IX Subsection "Examples"
2621.PP
2622Example: Try to exit cleanly on \s-1SIGINT\s0.
2623.PP
2624.Vb 5
2625\& static void
2626\& sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2627\& {
2628\& ev_break (loop, EVBREAK_ALL);
2629\& }
2630\&
2631\& ev_signal signal_watcher;
2632\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2633\& ev_signal_start (loop, &signal_watcher);
2634.Ve
1457.ie n .Sh """ev_child"" \- watch out for process status changes" 2635.ie n .SS """ev_child"" \- watch out for process status changes"
1458.el .Sh "\f(CWev_child\fP \- watch out for process status changes" 2636.el .SS "\f(CWev_child\fP \- watch out for process status changes"
1459.IX Subsection "ev_child - watch out for process status changes" 2637.IX Subsection "ev_child - watch out for process status changes"
1460Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to 2638Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to
1461some child status changes (most typically when a child of yours dies). 2639some child status changes (most typically when a child of yours dies or
2640exits). It is permissible to install a child watcher \fIafter\fR the child
2641has been forked (which implies it might have already exited), as long
2642as the event loop isn't entered (or is continued from a watcher), i.e.,
2643forking and then immediately registering a watcher for the child is fine,
2644but forking and registering a watcher a few event loop iterations later or
2645in the next callback invocation is not.
2646.PP
2647Only the default event loop is capable of handling signals, and therefore
2648you can only register child watchers in the default event loop.
2649.PP
2650Due to some design glitches inside libev, child watchers will always be
2651handled at maximum priority (their priority is set to \f(CW\*(C`EV_MAXPRI\*(C'\fR by
2652libev)
2653.PP
2654\fIProcess Interaction\fR
2655.IX Subsection "Process Interaction"
2656.PP
2657Libev grabs \f(CW\*(C`SIGCHLD\*(C'\fR as soon as the default event loop is
2658initialised. This is necessary to guarantee proper behaviour even if the
2659first child watcher is started after the child exits. The occurrence
2660of \f(CW\*(C`SIGCHLD\*(C'\fR is recorded asynchronously, but child reaping is done
2661synchronously as part of the event loop processing. Libev always reaps all
2662children, even ones not watched.
2663.PP
2664\fIOverriding the Built-In Processing\fR
2665.IX Subsection "Overriding the Built-In Processing"
2666.PP
2667Libev offers no special support for overriding the built-in child
2668processing, but if your application collides with libev's default child
2669handler, you can override it easily by installing your own handler for
2670\&\f(CW\*(C`SIGCHLD\*(C'\fR after initialising the default loop, and making sure the
2671default loop never gets destroyed. You are encouraged, however, to use an
2672event-based approach to child reaping and thus use libev's support for
2673that, so other libev users can use \f(CW\*(C`ev_child\*(C'\fR watchers freely.
2674.PP
2675\fIStopping the Child Watcher\fR
2676.IX Subsection "Stopping the Child Watcher"
2677.PP
2678Currently, the child watcher never gets stopped, even when the
2679child terminates, so normally one needs to stop the watcher in the
2680callback. Future versions of libev might stop the watcher automatically
2681when a child exit is detected (calling \f(CW\*(C`ev_child_stop\*(C'\fR twice is not a
2682problem).
1462.PP 2683.PP
1463\fIWatcher-Specific Functions and Data Members\fR 2684\fIWatcher-Specific Functions and Data Members\fR
1464.IX Subsection "Watcher-Specific Functions and Data Members" 2685.IX Subsection "Watcher-Specific Functions and Data Members"
1465.IP "ev_child_init (ev_child *, callback, int pid)" 4 2686.IP "ev_child_init (ev_child *, callback, int pid, int trace)" 4
1466.IX Item "ev_child_init (ev_child *, callback, int pid)" 2687.IX Item "ev_child_init (ev_child *, callback, int pid, int trace)"
1467.PD 0 2688.PD 0
1468.IP "ev_child_set (ev_child *, int pid)" 4 2689.IP "ev_child_set (ev_child *, int pid, int trace)" 4
1469.IX Item "ev_child_set (ev_child *, int pid)" 2690.IX Item "ev_child_set (ev_child *, int pid, int trace)"
1470.PD 2691.PD
1471Configures the watcher to wait for status changes of process \f(CW\*(C`pid\*(C'\fR (or 2692Configures the watcher to wait for status changes of process \f(CW\*(C`pid\*(C'\fR (or
1472\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look 2693\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look
1473at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see 2694at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see
1474the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems 2695the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems
1475\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the 2696\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the
1476process causing the status change. 2697process causing the status change. \f(CW\*(C`trace\*(C'\fR must be either \f(CW0\fR (only
2698activate the watcher when the process terminates) or \f(CW1\fR (additionally
2699activate the watcher when the process is stopped or continued).
1477.IP "int pid [read\-only]" 4 2700.IP "int pid [read\-only]" 4
1478.IX Item "int pid [read-only]" 2701.IX Item "int pid [read-only]"
1479The process id this watcher watches out for, or \f(CW0\fR, meaning any process id. 2702The process id this watcher watches out for, or \f(CW0\fR, meaning any process id.
1480.IP "int rpid [read\-write]" 4 2703.IP "int rpid [read\-write]" 4
1481.IX Item "int rpid [read-write]" 2704.IX Item "int rpid [read-write]"
… …
1483.IP "int rstatus [read\-write]" 4 2706.IP "int rstatus [read\-write]" 4
1484.IX Item "int rstatus [read-write]" 2707.IX Item "int rstatus [read-write]"
1485The process exit/trace status caused by \f(CW\*(C`rpid\*(C'\fR (see your systems 2708The process exit/trace status caused by \f(CW\*(C`rpid\*(C'\fR (see your systems
1486\&\f(CW\*(C`waitpid\*(C'\fR and \f(CW\*(C`sys/wait.h\*(C'\fR documentation for details). 2709\&\f(CW\*(C`waitpid\*(C'\fR and \f(CW\*(C`sys/wait.h\*(C'\fR documentation for details).
1487.PP 2710.PP
1488Example: Try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0. 2711\fIExamples\fR
2712.IX Subsection "Examples"
1489.PP 2713.PP
2714Example: \f(CW\*(C`fork()\*(C'\fR a new process and install a child handler to wait for
2715its completion.
2716.PP
1490.Vb 5 2717.Vb 1
2718\& ev_child cw;
2719\&
1491\& static void 2720\& static void
1492\& sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 2721\& child_cb (EV_P_ ev_child *w, int revents)
1493\& { 2722\& {
1494\& ev_unloop (loop, EVUNLOOP_ALL); 2723\& ev_child_stop (EV_A_ w);
2724\& printf ("process %d exited with status %x\en", w\->rpid, w\->rstatus);
1495\& } 2725\& }
2726\&
2727\& pid_t pid = fork ();
2728\&
2729\& if (pid < 0)
2730\& // error
2731\& else if (pid == 0)
2732\& {
2733\& // the forked child executes here
2734\& exit (1);
2735\& }
2736\& else
2737\& {
2738\& ev_child_init (&cw, child_cb, pid, 0);
2739\& ev_child_start (EV_DEFAULT_ &cw);
2740\& }
1496.Ve 2741.Ve
1497.PP
1498.Vb 3
1499\& struct ev_signal signal_watcher;
1500\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1501\& ev_signal_start (loop, &sigint_cb);
1502.Ve
1503.ie n .Sh """ev_stat"" \- did the file attributes just change?" 2742.ie n .SS """ev_stat"" \- did the file attributes just change?"
1504.el .Sh "\f(CWev_stat\fP \- did the file attributes just change?" 2743.el .SS "\f(CWev_stat\fP \- did the file attributes just change?"
1505.IX Subsection "ev_stat - did the file attributes just change?" 2744.IX Subsection "ev_stat - did the file attributes just change?"
1506This watches a filesystem path for attribute changes. That is, it calls 2745This watches a file system path for attribute changes. That is, it calls
1507\&\f(CW\*(C`stat\*(C'\fR regularly (or when the \s-1OS\s0 says it changed) and sees if it changed 2746\&\f(CW\*(C`stat\*(C'\fR on that path in regular intervals (or when the \s-1OS\s0 says it changed)
1508compared to the last time, invoking the callback if it did. 2747and sees if it changed compared to the last time, invoking the callback
2748if it did. Starting the watcher \f(CW\*(C`stat\*(C'\fR's the file, so only changes that
2749happen after the watcher has been started will be reported.
1509.PP 2750.PP
1510The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does 2751The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does
1511not exist\*(R" is a status change like any other. The condition \*(L"path does 2752not exist\*(R" is a status change like any other. The condition \*(L"path does not
1512not exist\*(R" is signified by the \f(CW\*(C`st_nlink\*(C'\fR field being zero (which is 2753exist\*(R" (or more correctly \*(L"path cannot be stat'ed\*(R") is signified by the
1513otherwise always forced to be at least one) and all the other fields of 2754\&\f(CW\*(C`st_nlink\*(C'\fR field being zero (which is otherwise always forced to be at
1514the stat buffer having unspecified contents. 2755least one) and all the other fields of the stat buffer having unspecified
2756contents.
1515.PP 2757.PP
1516The path \fIshould\fR be absolute and \fImust not\fR end in a slash. If it is 2758The path \fImust not\fR end in a slash or contain special components such as
2759\&\f(CW\*(C`.\*(C'\fR or \f(CW\*(C`..\*(C'\fR. The path \fIshould\fR be absolute: If it is relative and
1517relative and your working directory changes, the behaviour is undefined. 2760your working directory changes, then the behaviour is undefined.
1518.PP 2761.PP
1519Since there is no standard to do this, the portable implementation simply 2762Since there is no portable change notification interface available, the
1520calls \f(CW\*(C`stat (2)\*(C'\fR regularly on the path to see if it changed somehow. You 2763portable implementation simply calls \f(CWstat(2)\fR regularly on the path
1521can specify a recommended polling interval for this case. If you specify 2764to see if it changed somehow. You can specify a recommended polling
1522a polling interval of \f(CW0\fR (highly recommended!) then a \fIsuitable, 2765interval for this case. If you specify a polling interval of \f(CW0\fR (highly
1523unspecified default\fR value will be used (which you can expect to be around 2766recommended!) then a \fIsuitable, unspecified default\fR value will be used
1524five seconds, although this might change dynamically). Libev will also 2767(which you can expect to be around five seconds, although this might
1525impose a minimum interval which is currently around \f(CW0.1\fR, but thats 2768change dynamically). Libev will also impose a minimum interval which is
1526usually overkill. 2769currently around \f(CW0.1\fR, but that's usually overkill.
1527.PP 2770.PP
1528This watcher type is not meant for massive numbers of stat watchers, 2771This watcher type is not meant for massive numbers of stat watchers,
1529as even with OS-supported change notifications, this can be 2772as even with OS-supported change notifications, this can be
1530resource\-intensive. 2773resource-intensive.
1531.PP 2774.PP
1532At the time of this writing, only the Linux inotify interface is 2775At the time of this writing, the only OS-specific interface implemented
1533implemented (implementing kqueue support is left as an exercise for the 2776is the Linux inotify interface (implementing kqueue support is left as an
1534reader). Inotify will be used to give hints only and should not change the 2777exercise for the reader. Note, however, that the author sees no way of
1535semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers, which means that libev sometimes needs 2778implementing \f(CW\*(C`ev_stat\*(C'\fR semantics with kqueue, except as a hint).
1536to fall back to regular polling again even with inotify, but changes are 2779.PP
1537usually detected immediately, and if the file exists there will be no 2780\fI\s-1ABI\s0 Issues (Largefile Support)\fR
1538polling. 2781.IX Subsection "ABI Issues (Largefile Support)"
2782.PP
2783Libev by default (unless the user overrides this) uses the default
2784compilation environment, which means that on systems with large file
2785support disabled by default, you get the 32 bit version of the stat
2786structure. When using the library from programs that change the \s-1ABI\s0 to
2787use 64 bit file offsets the programs will fail. In that case you have to
2788compile libev with the same flags to get binary compatibility. This is
2789obviously the case with any flags that change the \s-1ABI\s0, but the problem is
2790most noticeably displayed with ev_stat and large file support.
2791.PP
2792The solution for this is to lobby your distribution maker to make large
2793file interfaces available by default (as e.g. FreeBSD does) and not
2794optional. Libev cannot simply switch on large file support because it has
2795to exchange stat structures with application programs compiled using the
2796default compilation environment.
2797.PP
2798\fIInotify and Kqueue\fR
2799.IX Subsection "Inotify and Kqueue"
2800.PP
2801When \f(CW\*(C`inotify (7)\*(C'\fR support has been compiled into libev and present at
2802runtime, it will be used to speed up change detection where possible. The
2803inotify descriptor will be created lazily when the first \f(CW\*(C`ev_stat\*(C'\fR
2804watcher is being started.
2805.PP
2806Inotify presence does not change the semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers
2807except that changes might be detected earlier, and in some cases, to avoid
2808making regular \f(CW\*(C`stat\*(C'\fR calls. Even in the presence of inotify support
2809there are many cases where libev has to resort to regular \f(CW\*(C`stat\*(C'\fR polling,
2810but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
2811many bugs), the path exists (i.e. stat succeeds), and the path resides on
2812a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
2813xfs are fully working) libev usually gets away without polling.
2814.PP
2815There is no support for kqueue, as apparently it cannot be used to
2816implement this functionality, due to the requirement of having a file
2817descriptor open on the object at all times, and detecting renames, unlinks
2818etc. is difficult.
2819.PP
2820\fI\f(CI\*(C`stat ()\*(C'\fI is a synchronous operation\fR
2821.IX Subsection "stat () is a synchronous operation"
2822.PP
2823Libev doesn't normally do any kind of I/O itself, and so is not blocking
2824the process. The exception are \f(CW\*(C`ev_stat\*(C'\fR watchers \- those call \f(CW\*(C`stat
2825()\*(C'\fR, which is a synchronous operation.
2826.PP
2827For local paths, this usually doesn't matter: unless the system is very
2828busy or the intervals between stat's are large, a stat call will be fast,
2829as the path data is usually in memory already (except when starting the
2830watcher).
2831.PP
2832For networked file systems, calling \f(CW\*(C`stat ()\*(C'\fR can block an indefinite
2833time due to network issues, and even under good conditions, a stat call
2834often takes multiple milliseconds.
2835.PP
2836Therefore, it is best to avoid using \f(CW\*(C`ev_stat\*(C'\fR watchers on networked
2837paths, although this is fully supported by libev.
2838.PP
2839\fIThe special problem of stat time resolution\fR
2840.IX Subsection "The special problem of stat time resolution"
2841.PP
2842The \f(CW\*(C`stat ()\*(C'\fR system call only supports full-second resolution portably,
2843and even on systems where the resolution is higher, most file systems
2844still only support whole seconds.
2845.PP
2846That means that, if the time is the only thing that changes, you can
2847easily miss updates: on the first update, \f(CW\*(C`ev_stat\*(C'\fR detects a change and
2848calls your callback, which does something. When there is another update
2849within the same second, \f(CW\*(C`ev_stat\*(C'\fR will be unable to detect unless the
2850stat data does change in other ways (e.g. file size).
2851.PP
2852The solution to this is to delay acting on a change for slightly more
2853than a second (or till slightly after the next full second boundary), using
2854a roughly one-second-delay \f(CW\*(C`ev_timer\*(C'\fR (e.g. \f(CW\*(C`ev_timer_set (w, 0., 1.02);
2855ev_timer_again (loop, w)\*(C'\fR).
2856.PP
2857The \f(CW.02\fR offset is added to work around small timing inconsistencies
2858of some operating systems (where the second counter of the current time
2859might be be delayed. One such system is the Linux kernel, where a call to
2860\&\f(CW\*(C`gettimeofday\*(C'\fR might return a timestamp with a full second later than
2861a subsequent \f(CW\*(C`time\*(C'\fR call \- if the equivalent of \f(CW\*(C`time ()\*(C'\fR is used to
2862update file times then there will be a small window where the kernel uses
2863the previous second to update file times but libev might already execute
2864the timer callback).
1539.PP 2865.PP
1540\fIWatcher-Specific Functions and Data Members\fR 2866\fIWatcher-Specific Functions and Data Members\fR
1541.IX Subsection "Watcher-Specific Functions and Data Members" 2867.IX Subsection "Watcher-Specific Functions and Data Members"
1542.IP "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 4 2868.IP "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 4
1543.IX Item "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 2869.IX Item "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)"
… …
1549\&\f(CW\*(C`path\*(C'\fR. The \f(CW\*(C`interval\*(C'\fR is a hint on how quickly a change is expected to 2875\&\f(CW\*(C`path\*(C'\fR. The \f(CW\*(C`interval\*(C'\fR is a hint on how quickly a change is expected to
1550be detected and should normally be specified as \f(CW0\fR to let libev choose 2876be detected and should normally be specified as \f(CW0\fR to let libev choose
1551a suitable value. The memory pointed to by \f(CW\*(C`path\*(C'\fR must point to the same 2877a suitable value. The memory pointed to by \f(CW\*(C`path\*(C'\fR must point to the same
1552path for as long as the watcher is active. 2878path for as long as the watcher is active.
1553.Sp 2879.Sp
1554The callback will be receive \f(CW\*(C`EV_STAT\*(C'\fR when a change was detected, 2880The callback will receive an \f(CW\*(C`EV_STAT\*(C'\fR event when a change was detected,
1555relative to the attributes at the time the watcher was started (or the 2881relative to the attributes at the time the watcher was started (or the
1556last change was detected). 2882last change was detected).
1557.IP "ev_stat_stat (ev_stat *)" 4 2883.IP "ev_stat_stat (loop, ev_stat *)" 4
1558.IX Item "ev_stat_stat (ev_stat *)" 2884.IX Item "ev_stat_stat (loop, ev_stat *)"
1559Updates the stat buffer immediately with new values. If you change the 2885Updates the stat buffer immediately with new values. If you change the
1560watched path in your callback, you could call this fucntion to avoid 2886watched path in your callback, you could call this function to avoid
1561detecting this change (while introducing a race condition). Can also be 2887detecting this change (while introducing a race condition if you are not
1562useful simply to find out the new values. 2888the only one changing the path). Can also be useful simply to find out the
2889new values.
1563.IP "ev_statdata attr [read\-only]" 4 2890.IP "ev_statdata attr [read\-only]" 4
1564.IX Item "ev_statdata attr [read-only]" 2891.IX Item "ev_statdata attr [read-only]"
1565The most-recently detected attributes of the file. Although the type is of 2892The most-recently detected attributes of the file. Although the type is
1566\&\f(CW\*(C`ev_statdata\*(C'\fR, this is usually the (or one of the) \f(CW\*(C`struct stat\*(C'\fR types 2893\&\f(CW\*(C`ev_statdata\*(C'\fR, this is usually the (or one of the) \f(CW\*(C`struct stat\*(C'\fR types
2894suitable for your system, but you can only rely on the POSIX-standardised
1567suitable for your system. If the \f(CW\*(C`st_nlink\*(C'\fR member is \f(CW0\fR, then there 2895members to be present. If the \f(CW\*(C`st_nlink\*(C'\fR member is \f(CW0\fR, then there was
1568was some error while \f(CW\*(C`stat\*(C'\fRing the file. 2896some error while \f(CW\*(C`stat\*(C'\fRing the file.
1569.IP "ev_statdata prev [read\-only]" 4 2897.IP "ev_statdata prev [read\-only]" 4
1570.IX Item "ev_statdata prev [read-only]" 2898.IX Item "ev_statdata prev [read-only]"
1571The previous attributes of the file. The callback gets invoked whenever 2899The previous attributes of the file. The callback gets invoked whenever
1572\&\f(CW\*(C`prev\*(C'\fR != \f(CW\*(C`attr\*(C'\fR. 2900\&\f(CW\*(C`prev\*(C'\fR != \f(CW\*(C`attr\*(C'\fR, or, more precisely, one or more of these members
2901differ: \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,
2902\&\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.
1573.IP "ev_tstamp interval [read\-only]" 4 2903.IP "ev_tstamp interval [read\-only]" 4
1574.IX Item "ev_tstamp interval [read-only]" 2904.IX Item "ev_tstamp interval [read-only]"
1575The specified interval. 2905The specified interval.
1576.IP "const char *path [read\-only]" 4 2906.IP "const char *path [read\-only]" 4
1577.IX Item "const char *path [read-only]" 2907.IX Item "const char *path [read-only]"
1578The filesystem path that is being watched. 2908The file system path that is being watched.
2909.PP
2910\fIExamples\fR
2911.IX Subsection "Examples"
1579.PP 2912.PP
1580Example: Watch \f(CW\*(C`/etc/passwd\*(C'\fR for attribute changes. 2913Example: Watch \f(CW\*(C`/etc/passwd\*(C'\fR for attribute changes.
1581.PP 2914.PP
1582.Vb 15 2915.Vb 10
1583\& static void 2916\& static void
1584\& passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) 2917\& passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1585\& { 2918\& {
1586\& /* /etc/passwd changed in some way */ 2919\& /* /etc/passwd changed in some way */
1587\& if (w->attr.st_nlink) 2920\& if (w\->attr.st_nlink)
1588\& { 2921\& {
1589\& printf ("passwd current size %ld\en", (long)w->attr.st_size); 2922\& printf ("passwd current size %ld\en", (long)w\->attr.st_size);
1590\& printf ("passwd current atime %ld\en", (long)w->attr.st_mtime); 2923\& printf ("passwd current atime %ld\en", (long)w\->attr.st_mtime);
1591\& printf ("passwd current mtime %ld\en", (long)w->attr.st_mtime); 2924\& printf ("passwd current mtime %ld\en", (long)w\->attr.st_mtime);
1592\& } 2925\& }
1593\& else 2926\& else
1594\& /* you shalt not abuse printf for puts */ 2927\& /* you shalt not abuse printf for puts */
1595\& puts ("wow, /etc/passwd is not there, expect problems. " 2928\& puts ("wow, /etc/passwd is not there, expect problems. "
1596\& "if this is windows, they already arrived\en"); 2929\& "if this is windows, they already arrived\en");
1597\& } 2930\& }
2931\&
2932\& ...
2933\& ev_stat passwd;
2934\&
2935\& ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
2936\& ev_stat_start (loop, &passwd);
1598.Ve 2937.Ve
2938.PP
2939Example: Like above, but additionally use a one-second delay so we do not
2940miss updates (however, frequent updates will delay processing, too, so
2941one might do the work both on \f(CW\*(C`ev_stat\*(C'\fR callback invocation \fIand\fR on
2942\&\f(CW\*(C`ev_timer\*(C'\fR callback invocation).
1599.PP 2943.PP
1600.Vb 2 2944.Vb 2
2945\& static ev_stat passwd;
2946\& static ev_timer timer;
2947\&
2948\& static void
2949\& timer_cb (EV_P_ ev_timer *w, int revents)
2950\& {
2951\& ev_timer_stop (EV_A_ w);
2952\&
2953\& /* now it\*(Aqs one second after the most recent passwd change */
2954\& }
2955\&
2956\& static void
2957\& stat_cb (EV_P_ ev_stat *w, int revents)
2958\& {
2959\& /* reset the one\-second timer */
2960\& ev_timer_again (EV_A_ &timer);
2961\& }
2962\&
1601\& ... 2963\& ...
1602\& ev_stat passwd;
1603.Ve
1604.PP
1605.Vb 2
1606\& ev_stat_init (&passwd, passwd_cb, "/etc/passwd"); 2964\& ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1607\& ev_stat_start (loop, &passwd); 2965\& ev_stat_start (loop, &passwd);
2966\& ev_timer_init (&timer, timer_cb, 0., 1.02);
1608.Ve 2967.Ve
1609.ie n .Sh """ev_idle"" \- when you've got nothing better to do..." 2968.ie n .SS """ev_idle"" \- when you've got nothing better to do..."
1610.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do..." 2969.el .SS "\f(CWev_idle\fP \- when you've got nothing better to do..."
1611.IX Subsection "ev_idle - when you've got nothing better to do..." 2970.IX Subsection "ev_idle - when you've got nothing better to do..."
1612Idle watchers trigger events when no other events of the same or higher 2971Idle watchers trigger events when no other events of the same or higher
1613priority are pending (prepare, check and other idle watchers do not 2972priority are pending (prepare, check and other idle watchers do not count
1614count). 2973as receiving \*(L"events\*(R").
1615.PP 2974.PP
1616That is, as long as your process is busy handling sockets or timeouts 2975That is, as long as your process is busy handling sockets or timeouts
1617(or even signals, imagine) of the same or higher priority it will not be 2976(or even signals, imagine) of the same or higher priority it will not be
1618triggered. But when your process is idle (or only lower-priority watchers 2977triggered. But when your process is idle (or only lower-priority watchers
1619are pending), the idle watchers are being called once per event loop 2978are pending), the idle watchers are being called once per event loop
… …
1623The most noteworthy effect is that as long as any idle watchers are 2982The most noteworthy effect is that as long as any idle watchers are
1624active, the process will not block when waiting for new events. 2983active, the process will not block when waiting for new events.
1625.PP 2984.PP
1626Apart from keeping your process non-blocking (which is a useful 2985Apart from keeping your process non-blocking (which is a useful
1627effect on its own sometimes), idle watchers are a good place to do 2986effect on its own sometimes), idle watchers are a good place to do
1628\&\*(L"pseudo\-background processing\*(R", or delay processing stuff to after the 2987\&\*(L"pseudo-background processing\*(R", or delay processing stuff to after the
1629event loop has handled all outstanding events. 2988event loop has handled all outstanding events.
2989.PP
2990\fIAbusing an \f(CI\*(C`ev_idle\*(C'\fI watcher for its side-effect\fR
2991.IX Subsection "Abusing an ev_idle watcher for its side-effect"
2992.PP
2993As long as there is at least one active idle watcher, libev will never
2994sleep unnecessarily. Or in other words, it will loop as fast as possible.
2995For this to work, the idle watcher doesn't need to be invoked at all \- the
2996lowest priority will do.
2997.PP
2998This mode of operation can be useful together with an \f(CW\*(C`ev_check\*(C'\fR watcher,
2999to do something on each event loop iteration \- for example to balance load
3000between different connections.
3001.PP
3002See \*(L"Abusing an ev_check watcher for its side-effect\*(R" for a longer
3003example.
1630.PP 3004.PP
1631\fIWatcher-Specific Functions and Data Members\fR 3005\fIWatcher-Specific Functions and Data Members\fR
1632.IX Subsection "Watcher-Specific Functions and Data Members" 3006.IX Subsection "Watcher-Specific Functions and Data Members"
1633.IP "ev_idle_init (ev_signal *, callback)" 4 3007.IP "ev_idle_init (ev_idle *, callback)" 4
1634.IX Item "ev_idle_init (ev_signal *, callback)" 3008.IX Item "ev_idle_init (ev_idle *, callback)"
1635Initialises and configures the idle watcher \- it has no parameters of any 3009Initialises and configures the idle watcher \- it has no parameters of any
1636kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless, 3010kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless,
1637believe me. 3011believe me.
1638.PP 3012.PP
3013\fIExamples\fR
3014.IX Subsection "Examples"
3015.PP
1639Example: Dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR watcher, start it, and in the 3016Example: Dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR watcher, start it, and in the
1640callback, free it. Also, use no error checking, as usual. 3017callback, free it. Also, use no error checking, as usual.
1641.PP 3018.PP
1642.Vb 7 3019.Vb 5
1643\& static void 3020\& static void
1644\& idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 3021\& idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1645\& { 3022\& {
3023\& // stop the watcher
3024\& ev_idle_stop (loop, w);
3025\&
3026\& // now we can free it
1646\& free (w); 3027\& free (w);
3028\&
1647\& // now do something you wanted to do when the program has 3029\& // now do something you wanted to do when the program has
1648\& // no longer asnything immediate to do. 3030\& // no longer anything immediate to do.
1649\& } 3031\& }
1650.Ve 3032\&
1651.PP
1652.Vb 3
1653\& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); 3033\& ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1654\& ev_idle_init (idle_watcher, idle_cb); 3034\& ev_idle_init (idle_watcher, idle_cb);
1655\& ev_idle_start (loop, idle_cb); 3035\& ev_idle_start (loop, idle_watcher);
1656.Ve 3036.Ve
1657.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop!" 3037.ie n .SS """ev_prepare"" and ""ev_check"" \- customise your event loop!"
1658.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!" 3038.el .SS "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!"
1659.IX Subsection "ev_prepare and ev_check - customise your event loop!" 3039.IX Subsection "ev_prepare and ev_check - customise your event loop!"
1660Prepare and check watchers are usually (but not always) used in tandem: 3040Prepare and check watchers are often (but not always) used in pairs:
1661prepare watchers get invoked before the process blocks and check watchers 3041prepare watchers get invoked before the process blocks and check watchers
1662afterwards. 3042afterwards.
1663.PP 3043.PP
1664You \fImust not\fR call \f(CW\*(C`ev_loop\*(C'\fR or similar functions that enter 3044You \fImust not\fR call \f(CW\*(C`ev_run\*(C'\fR or similar functions that enter
1665the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR 3045the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR
1666watchers. Other loops than the current one are fine, however. The 3046watchers. Other loops than the current one are fine, however. The
1667rationale behind this is that you do not need to check for recursion in 3047rationale behind this is that you do not need to check for recursion in
1668those watchers, i.e. the sequence will always be \f(CW\*(C`ev_prepare\*(C'\fR, blocking, 3048those watchers, i.e. the sequence will always be \f(CW\*(C`ev_prepare\*(C'\fR, blocking,
1669\&\f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each kind they will always be 3049\&\f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each kind they will always be
1670called in pairs bracketing the blocking call. 3050called in pairs bracketing the blocking call.
1671.PP 3051.PP
1672Their main purpose is to integrate other event mechanisms into libev and 3052Their main purpose is to integrate other event mechanisms into libev and
1673their use is somewhat advanced. This could be used, for example, to track 3053their use is somewhat advanced. They could be used, for example, to track
1674variable changes, implement your own watchers, integrate net-snmp or a 3054variable changes, implement your own watchers, integrate net-snmp or a
1675coroutine library and lots more. They are also occasionally useful if 3055coroutine library and lots more. They are also occasionally useful if
1676you cache some data and want to flush it before blocking (for example, 3056you cache some data and want to flush it before blocking (for example,
1677in X programs you might want to do an \f(CW\*(C`XFlush ()\*(C'\fR in an \f(CW\*(C`ev_prepare\*(C'\fR 3057in X programs you might want to do an \f(CW\*(C`XFlush ()\*(C'\fR in an \f(CW\*(C`ev_prepare\*(C'\fR
1678watcher). 3058watcher).
1679.PP 3059.PP
1680This is done by examining in each prepare call which file descriptors need 3060This is done by examining in each prepare call which file descriptors
1681to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for 3061need to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers
1682them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries 3062for them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many
1683provide just this functionality). Then, in the check watcher you check for 3063libraries provide exactly this functionality). Then, in the check watcher,
1684any events that occured (by checking the pending status of all watchers 3064you check for any events that occurred (by checking the pending status
1685and stopping them) and call back into the library. The I/O and timer 3065of all watchers and stopping them) and call back into the library. The
1686callbacks will never actually be called (but must be valid nevertheless, 3066I/O and timer callbacks will never actually be called (but must be valid
1687because you never know, you know?). 3067nevertheless, because you never know, you know?).
1688.PP 3068.PP
1689As another example, the Perl Coro module uses these hooks to integrate 3069As another example, the Perl Coro module uses these hooks to integrate
1690coroutines into libev programs, by yielding to other active coroutines 3070coroutines into libev programs, by yielding to other active coroutines
1691during each prepare and only letting the process block if no coroutines 3071during each prepare and only letting the process block if no coroutines
1692are ready to run (it's actually more complicated: it only runs coroutines 3072are ready to run (it's actually more complicated: it only runs coroutines
1693with priority higher than or equal to the event loop and one coroutine 3073with priority higher than or equal to the event loop and one coroutine
1694of lower priority, but only once, using idle watchers to keep the event 3074of lower priority, but only once, using idle watchers to keep the event
1695loop from blocking if lower-priority coroutines are active, thus mapping 3075loop from blocking if lower-priority coroutines are active, thus mapping
1696low-priority coroutines to idle/background tasks). 3076low-priority coroutines to idle/background tasks).
1697.PP 3077.PP
1698It is recommended to give \f(CW\*(C`ev_check\*(C'\fR watchers highest (\f(CW\*(C`EV_MAXPRI\*(C'\fR) 3078When used for this purpose, it is recommended to give \f(CW\*(C`ev_check\*(C'\fR watchers
1699priority, to ensure that they are being run before any other watchers 3079highest (\f(CW\*(C`EV_MAXPRI\*(C'\fR) priority, to ensure that they are being run before
3080any other watchers after the poll (this doesn't matter for \f(CW\*(C`ev_prepare\*(C'\fR
3081watchers).
3082.PP
1700after the poll. Also, \f(CW\*(C`ev_check\*(C'\fR watchers (and \f(CW\*(C`ev_prepare\*(C'\fR watchers, 3083Also, \f(CW\*(C`ev_check\*(C'\fR watchers (and \f(CW\*(C`ev_prepare\*(C'\fR watchers, too) should not
1701too) should not activate (\*(L"feed\*(R") events into libev. While libev fully 3084activate (\*(L"feed\*(R") events into libev. While libev fully supports this, they
1702supports this, they will be called before other \f(CW\*(C`ev_check\*(C'\fR watchers did 3085might get executed before other \f(CW\*(C`ev_check\*(C'\fR watchers did their job. As
1703their job. As \f(CW\*(C`ev_check\*(C'\fR watchers are often used to embed other event 3086\&\f(CW\*(C`ev_check\*(C'\fR watchers are often used to embed other (non-libev) event
1704loops those other event loops might be in an unusable state until their 3087loops those other event loops might be in an unusable state until their
1705\&\f(CW\*(C`ev_check\*(C'\fR watcher ran (always remind yourself to coexist peacefully with 3088\&\f(CW\*(C`ev_check\*(C'\fR watcher ran (always remind yourself to coexist peacefully with
1706others). 3089others).
3090.PP
3091\fIAbusing an \f(CI\*(C`ev_check\*(C'\fI watcher for its side-effect\fR
3092.IX Subsection "Abusing an ev_check watcher for its side-effect"
3093.PP
3094\&\f(CW\*(C`ev_check\*(C'\fR (and less often also \f(CW\*(C`ev_prepare\*(C'\fR) watchers can also be
3095useful because they are called once per event loop iteration. For
3096example, if you want to handle a large number of connections fairly, you
3097normally only do a bit of work for each active connection, and if there
3098is more work to do, you wait for the next event loop iteration, so other
3099connections have a chance of making progress.
3100.PP
3101Using an \f(CW\*(C`ev_check\*(C'\fR watcher is almost enough: it will be called on the
3102next event loop iteration. However, that isn't as soon as possible \-
3103without external events, your \f(CW\*(C`ev_check\*(C'\fR watcher will not be invoked.
3104.PP
3105This is where \f(CW\*(C`ev_idle\*(C'\fR watchers come in handy \- all you need is a
3106single global idle watcher that is active as long as you have one active
3107\&\f(CW\*(C`ev_check\*(C'\fR watcher. The \f(CW\*(C`ev_idle\*(C'\fR watcher makes sure the event loop
3108will not sleep, and the \f(CW\*(C`ev_check\*(C'\fR watcher makes sure a callback gets
3109invoked. Neither watcher alone can do that.
1707.PP 3110.PP
1708\fIWatcher-Specific Functions and Data Members\fR 3111\fIWatcher-Specific Functions and Data Members\fR
1709.IX Subsection "Watcher-Specific Functions and Data Members" 3112.IX Subsection "Watcher-Specific Functions and Data Members"
1710.IP "ev_prepare_init (ev_prepare *, callback)" 4 3113.IP "ev_prepare_init (ev_prepare *, callback)" 4
1711.IX Item "ev_prepare_init (ev_prepare *, callback)" 3114.IX Item "ev_prepare_init (ev_prepare *, callback)"
… …
1713.IP "ev_check_init (ev_check *, callback)" 4 3116.IP "ev_check_init (ev_check *, callback)" 4
1714.IX Item "ev_check_init (ev_check *, callback)" 3117.IX Item "ev_check_init (ev_check *, callback)"
1715.PD 3118.PD
1716Initialises and configures the prepare or check watcher \- they have no 3119Initialises and configures the prepare or check watcher \- they have no
1717parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR 3120parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR
1718macros, but using them is utterly, utterly and completely pointless. 3121macros, but using them is utterly, utterly, utterly and completely
3122pointless.
3123.PP
3124\fIExamples\fR
3125.IX Subsection "Examples"
1719.PP 3126.PP
1720There are a number of principal ways to embed other event loops or modules 3127There are a number of principal ways to embed other event loops or modules
1721into libev. Here are some ideas on how to include libadns into libev 3128into libev. Here are some ideas on how to include libadns into libev
1722(there is a Perl module named \f(CW\*(C`EV::ADNS\*(C'\fR that does this, which you could 3129(there is a Perl module named \f(CW\*(C`EV::ADNS\*(C'\fR that does this, which you could
1723use for an actually working example. Another Perl module named \f(CW\*(C`EV::Glib\*(C'\fR 3130use as a working example. Another Perl module named \f(CW\*(C`EV::Glib\*(C'\fR embeds a
1724embeds a Glib main context into libev, and finally, \f(CW\*(C`Glib::EV\*(C'\fR embeds \s-1EV\s0 3131Glib main context into libev, and finally, \f(CW\*(C`Glib::EV\*(C'\fR embeds \s-1EV\s0 into the
1725into the Glib event loop). 3132Glib event loop).
1726.PP 3133.PP
1727Method 1: Add \s-1IO\s0 watchers and a timeout watcher in a prepare handler, 3134Method 1: Add \s-1IO\s0 watchers and a timeout watcher in a prepare handler,
1728and in a check watcher, destroy them and call into libadns. What follows 3135and in a check watcher, destroy them and call into libadns. What follows
1729is pseudo-code only of course. This requires you to either use a low 3136is pseudo-code only of course. This requires you to either use a low
1730priority for the check watcher or use \f(CW\*(C`ev_clear_pending\*(C'\fR explicitly, as 3137priority for the check watcher or use \f(CW\*(C`ev_clear_pending\*(C'\fR explicitly, as
1731the callbacks for the IO/timeout watchers might not have been called yet. 3138the callbacks for the IO/timeout watchers might not have been called yet.
1732.PP 3139.PP
1733.Vb 2 3140.Vb 2
1734\& static ev_io iow [nfd]; 3141\& static ev_io iow [nfd];
1735\& static ev_timer tw; 3142\& static ev_timer tw;
1736.Ve 3143\&
1737.PP
1738.Vb 4
1739\& static void 3144\& static void
1740\& io_cb (ev_loop *loop, ev_io *w, int revents) 3145\& io_cb (struct ev_loop *loop, ev_io *w, int revents)
1741\& { 3146\& {
1742\& } 3147\& }
1743.Ve 3148\&
1744.PP
1745.Vb 8
1746\& // create io watchers for each fd and a timer before blocking 3149\& // create io watchers for each fd and a timer before blocking
1747\& static void 3150\& static void
1748\& adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) 3151\& adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1749\& { 3152\& {
1750\& int timeout = 3600000; 3153\& int timeout = 3600000;
1751\& struct pollfd fds [nfd]; 3154\& struct pollfd fds [nfd];
1752\& // actual code will need to loop here and realloc etc. 3155\& // actual code will need to loop here and realloc etc.
1753\& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); 3156\& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1754.Ve 3157\&
1755.PP
1756.Vb 3
1757\& /* the callback is illegal, but won't be called as we stop during check */ 3158\& /* the callback is illegal, but won\*(Aqt be called as we stop during check */
1758\& ev_timer_init (&tw, 0, timeout * 1e-3); 3159\& ev_timer_init (&tw, 0, timeout * 1e\-3, 0.);
1759\& ev_timer_start (loop, &tw); 3160\& ev_timer_start (loop, &tw);
1760.Ve 3161\&
1761.PP
1762.Vb 6
1763\& // create one ev_io per pollfd 3162\& // create one ev_io per pollfd
1764\& for (int i = 0; i < nfd; ++i) 3163\& for (int i = 0; i < nfd; ++i)
1765\& { 3164\& {
1766\& ev_io_init (iow + i, io_cb, fds [i].fd, 3165\& ev_io_init (iow + i, io_cb, fds [i].fd,
1767\& ((fds [i].events & POLLIN ? EV_READ : 0) 3166\& ((fds [i].events & POLLIN ? EV_READ : 0)
1768\& | (fds [i].events & POLLOUT ? EV_WRITE : 0))); 3167\& | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1769.Ve 3168\&
1770.PP
1771.Vb 4
1772\& fds [i].revents = 0; 3169\& fds [i].revents = 0;
1773\& ev_io_start (loop, iow + i); 3170\& ev_io_start (loop, iow + i);
1774\& } 3171\& }
1775\& } 3172\& }
1776.Ve 3173\&
1777.PP
1778.Vb 5
1779\& // stop all watchers after blocking 3174\& // stop all watchers after blocking
1780\& static void 3175\& static void
1781\& adns_check_cb (ev_loop *loop, ev_check *w, int revents) 3176\& adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1782\& { 3177\& {
1783\& ev_timer_stop (loop, &tw); 3178\& ev_timer_stop (loop, &tw);
1784.Ve 3179\&
1785.PP
1786.Vb 8
1787\& for (int i = 0; i < nfd; ++i) 3180\& for (int i = 0; i < nfd; ++i)
1788\& { 3181\& {
1789\& // set the relevant poll flags 3182\& // set the relevant poll flags
1790\& // could also call adns_processreadable etc. here 3183\& // could also call adns_processreadable etc. here
1791\& struct pollfd *fd = fds + i; 3184\& struct pollfd *fd = fds + i;
1792\& int revents = ev_clear_pending (iow + i); 3185\& int revents = ev_clear_pending (iow + i);
1793\& if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; 3186\& if (revents & EV_READ ) fd\->revents |= fd\->events & POLLIN;
1794\& if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; 3187\& if (revents & EV_WRITE) fd\->revents |= fd\->events & POLLOUT;
1795.Ve 3188\&
1796.PP
1797.Vb 3
1798\& // now stop the watcher 3189\& // now stop the watcher
1799\& ev_io_stop (loop, iow + i); 3190\& ev_io_stop (loop, iow + i);
1800\& } 3191\& }
1801.Ve 3192\&
1802.PP
1803.Vb 2
1804\& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); 3193\& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1805\& } 3194\& }
1806.Ve 3195.Ve
1807.PP 3196.PP
1808Method 2: This would be just like method 1, but you run \f(CW\*(C`adns_afterpoll\*(C'\fR 3197Method 2: This would be just like method 1, but you run \f(CW\*(C`adns_afterpoll\*(C'\fR
1809in the prepare watcher and would dispose of the check watcher. 3198in the prepare watcher and would dispose of the check watcher.
1810.PP 3199.PP
1811Method 3: If the module to be embedded supports explicit event 3200Method 3: If the module to be embedded supports explicit event
1812notification (adns does), you can also make use of the actual watcher 3201notification (libadns does), you can also make use of the actual watcher
1813callbacks, and only destroy/create the watchers in the prepare watcher. 3202callbacks, and only destroy/create the watchers in the prepare watcher.
1814.PP 3203.PP
1815.Vb 5 3204.Vb 5
1816\& static void 3205\& static void
1817\& timer_cb (EV_P_ ev_timer *w, int revents) 3206\& timer_cb (EV_P_ ev_timer *w, int revents)
1818\& { 3207\& {
1819\& adns_state ads = (adns_state)w->data; 3208\& adns_state ads = (adns_state)w\->data;
1820\& update_now (EV_A); 3209\& update_now (EV_A);
1821.Ve 3210\&
1822.PP
1823.Vb 2
1824\& adns_processtimeouts (ads, &tv_now); 3211\& adns_processtimeouts (ads, &tv_now);
1825\& } 3212\& }
1826.Ve 3213\&
1827.PP
1828.Vb 5
1829\& static void 3214\& static void
1830\& io_cb (EV_P_ ev_io *w, int revents) 3215\& io_cb (EV_P_ ev_io *w, int revents)
1831\& { 3216\& {
1832\& adns_state ads = (adns_state)w->data; 3217\& adns_state ads = (adns_state)w\->data;
1833\& update_now (EV_A); 3218\& update_now (EV_A);
1834.Ve 3219\&
1835.PP
1836.Vb 3
1837\& if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now); 3220\& if (revents & EV_READ ) adns_processreadable (ads, w\->fd, &tv_now);
1838\& if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now); 3221\& if (revents & EV_WRITE) adns_processwriteable (ads, w\->fd, &tv_now);
1839\& } 3222\& }
1840.Ve 3223\&
1841.PP
1842.Vb 1
1843\& // do not ever call adns_afterpoll 3224\& // do not ever call adns_afterpoll
1844.Ve 3225.Ve
1845.PP 3226.PP
1846Method 4: Do not use a prepare or check watcher because the module you 3227Method 4: Do not use a prepare or check watcher because the module you
1847want to embed is too inflexible to support it. Instead, youc na override 3228want to embed is not flexible enough to support it. Instead, you can
1848their poll function. The drawback with this solution is that the main 3229override their poll function. The drawback with this solution is that the
1849loop is now no longer controllable by \s-1EV\s0. The \f(CW\*(C`Glib::EV\*(C'\fR module does 3230main loop is now no longer controllable by \s-1EV\s0. The \f(CW\*(C`Glib::EV\*(C'\fR module uses
1850this. 3231this approach, effectively embedding \s-1EV\s0 as a client into the horrible
3232libglib event loop.
1851.PP 3233.PP
1852.Vb 4 3234.Vb 4
1853\& static gint 3235\& static gint
1854\& event_poll_func (GPollFD *fds, guint nfds, gint timeout) 3236\& event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1855\& { 3237\& {
1856\& int got_events = 0; 3238\& int got_events = 0;
1857.Ve 3239\&
1858.PP
1859.Vb 2
1860\& for (n = 0; n < nfds; ++n) 3240\& for (n = 0; n < nfds; ++n)
1861\& // create/start io watcher that sets the relevant bits in fds[n] and increment got_events 3241\& // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1862.Ve 3242\&
1863.PP
1864.Vb 2
1865\& if (timeout >= 0) 3243\& if (timeout >= 0)
1866\& // create/start timer 3244\& // create/start timer
1867.Ve 3245\&
1868.PP
1869.Vb 2
1870\& // poll 3246\& // poll
1871\& ev_loop (EV_A_ 0); 3247\& ev_run (EV_A_ 0);
1872.Ve 3248\&
1873.PP
1874.Vb 3
1875\& // stop timer again 3249\& // stop timer again
1876\& if (timeout >= 0) 3250\& if (timeout >= 0)
1877\& ev_timer_stop (EV_A_ &to); 3251\& ev_timer_stop (EV_A_ &to);
1878.Ve 3252\&
1879.PP
1880.Vb 3
1881\& // stop io watchers again - their callbacks should have set 3253\& // stop io watchers again \- their callbacks should have set
1882\& for (n = 0; n < nfds; ++n) 3254\& for (n = 0; n < nfds; ++n)
1883\& ev_io_stop (EV_A_ iow [n]); 3255\& ev_io_stop (EV_A_ iow [n]);
1884.Ve 3256\&
1885.PP
1886.Vb 2
1887\& return got_events; 3257\& return got_events;
1888\& } 3258\& }
1889.Ve 3259.Ve
1890.ie n .Sh """ev_embed"" \- when one backend isn't enough..." 3260.ie n .SS """ev_embed"" \- when one backend isn't enough..."
1891.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..." 3261.el .SS "\f(CWev_embed\fP \- when one backend isn't enough..."
1892.IX Subsection "ev_embed - when one backend isn't enough..." 3262.IX Subsection "ev_embed - when one backend isn't enough..."
1893This is a rather advanced watcher type that lets you embed one event loop 3263This is a rather advanced watcher type that lets you embed one event loop
1894into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded 3264into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded
1895loop, other types of watchers might be handled in a delayed or incorrect 3265loop, other types of watchers might be handled in a delayed or incorrect
1896fashion and must not be used). 3266fashion and must not be used).
… …
1899prioritise I/O. 3269prioritise I/O.
1900.PP 3270.PP
1901As an example for a bug workaround, the kqueue backend might only support 3271As an example for a bug workaround, the kqueue backend might only support
1902sockets on some platform, so it is unusable as generic backend, but you 3272sockets on some platform, so it is unusable as generic backend, but you
1903still want to make use of it because you have many sockets and it scales 3273still want to make use of it because you have many sockets and it scales
1904so nicely. In this case, you would create a kqueue-based loop and embed it 3274so nicely. In this case, you would create a kqueue-based loop and embed
1905into your default loop (which might use e.g. poll). Overall operation will 3275it into your default loop (which might use e.g. poll). Overall operation
1906be a bit slower because first libev has to poll and then call kevent, but 3276will be a bit slower because first libev has to call \f(CW\*(C`poll\*(C'\fR and then
1907at least you can use both at what they are best. 3277\&\f(CW\*(C`kevent\*(C'\fR, but at least you can use both mechanisms for what they are
3278best: \f(CW\*(C`kqueue\*(C'\fR for scalable sockets and \f(CW\*(C`poll\*(C'\fR if you want it to work :)
1908.PP 3279.PP
1909As for prioritising I/O: rarely you have the case where some fds have 3280As for prioritising I/O: under rare circumstances you have the case where
1910to be watched and handled very quickly (with low latency), and even 3281some fds have to be watched and handled very quickly (with low latency),
1911priorities and idle watchers might have too much overhead. In this case 3282and even priorities and idle watchers might have too much overhead. In
1912you would put all the high priority stuff in one loop and all the rest in 3283this case you would put all the high priority stuff in one loop and all
1913a second one, and embed the second one in the first. 3284the rest in a second one, and embed the second one in the first.
1914.PP 3285.PP
1915As long as the watcher is active, the callback will be invoked every time 3286As long as the watcher is active, the callback will be invoked every
1916there might be events pending in the embedded loop. The callback must then 3287time there might be events pending in the embedded loop. The callback
1917call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single sweep and invoke 3288must then call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single
1918their callbacks (you could also start an idle watcher to give the embedded 3289sweep and invoke their callbacks (the callback doesn't need to invoke the
1919loop strictly lower priority for example). You can also set the callback 3290\&\f(CW\*(C`ev_embed_sweep\*(C'\fR function directly, it could also start an idle watcher
1920to \f(CW0\fR, in which case the embed watcher will automatically execute the 3291to give the embedded loop strictly lower priority for example).
1921embedded loop sweep.
1922.PP 3292.PP
1923As long as the watcher is started it will automatically handle events. The 3293You can also set the callback to \f(CW0\fR, in which case the embed watcher
1924callback will be invoked whenever some events have been handled. You can 3294will automatically execute the embedded loop sweep whenever necessary.
1925set the callback to \f(CW0\fR to avoid having to specify one if you are not
1926interested in that.
1927.PP 3295.PP
1928Also, there have not currently been made special provisions for forking: 3296Fork detection will be handled transparently while the \f(CW\*(C`ev_embed\*(C'\fR watcher
1929when you fork, you not only have to call \f(CW\*(C`ev_loop_fork\*(C'\fR on both loops, 3297is active, i.e., the embedded loop will automatically be forked when the
1930but you will also have to stop and restart any \f(CW\*(C`ev_embed\*(C'\fR watchers 3298embedding loop forks. In other cases, the user is responsible for calling
1931yourself. 3299\&\f(CW\*(C`ev_loop_fork\*(C'\fR on the embedded loop.
1932.PP 3300.PP
1933Unfortunately, not all backends are embeddable, only the ones returned by 3301Unfortunately, not all backends are embeddable: only the ones returned by
1934\&\f(CW\*(C`ev_embeddable_backends\*(C'\fR are, which, unfortunately, does not include any 3302\&\f(CW\*(C`ev_embeddable_backends\*(C'\fR are, which, unfortunately, does not include any
1935portable one. 3303portable one.
1936.PP 3304.PP
1937So when you want to use this feature you will always have to be prepared 3305So when you want to use this feature you will always have to be prepared
1938that you cannot get an embeddable loop. The recommended way to get around 3306that you cannot get an embeddable loop. The recommended way to get around
1939this is to have a separate variables for your embeddable loop, try to 3307this is to have a separate variables for your embeddable loop, try to
1940create it, and if that fails, use the normal loop for everything: 3308create it, and if that fails, use the normal loop for everything.
1941.PP 3309.PP
1942.Vb 3 3310\fI\f(CI\*(C`ev_embed\*(C'\fI and fork\fR
1943\& struct ev_loop *loop_hi = ev_default_init (0); 3311.IX Subsection "ev_embed and fork"
1944\& struct ev_loop *loop_lo = 0;
1945\& struct ev_embed embed;
1946.Ve
1947.PP 3312.PP
1948.Vb 5 3313While the \f(CW\*(C`ev_embed\*(C'\fR watcher is running, forks in the embedding loop will
1949\& // see if there is a chance of getting one that works 3314automatically be applied to the embedded loop as well, so no special
1950\& // (remember that a flags value of 0 means autodetection) 3315fork handling is required in that case. When the watcher is not running,
1951\& loop_lo = ev_embeddable_backends () & ev_recommended_backends () 3316however, it is still the task of the libev user to call \f(CW\*(C`ev_loop_fork ()\*(C'\fR
1952\& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) 3317as applicable.
1953\& : 0;
1954.Ve
1955.PP
1956.Vb 8
1957\& // if we got one, then embed it, otherwise default to loop_hi
1958\& if (loop_lo)
1959\& {
1960\& ev_embed_init (&embed, 0, loop_lo);
1961\& ev_embed_start (loop_hi, &embed);
1962\& }
1963\& else
1964\& loop_lo = loop_hi;
1965.Ve
1966.PP 3318.PP
1967\fIWatcher-Specific Functions and Data Members\fR 3319\fIWatcher-Specific Functions and Data Members\fR
1968.IX Subsection "Watcher-Specific Functions and Data Members" 3320.IX Subsection "Watcher-Specific Functions and Data Members"
1969.IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4 3321.IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
1970.IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 3322.IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)"
1971.PD 0 3323.PD 0
1972.IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4 3324.IP "ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)" 4
1973.IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 3325.IX Item "ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)"
1974.PD 3326.PD
1975Configures the watcher to embed the given loop, which must be 3327Configures the watcher to embed the given loop, which must be
1976embeddable. If the callback is \f(CW0\fR, then \f(CW\*(C`ev_embed_sweep\*(C'\fR will be 3328embeddable. If the callback is \f(CW0\fR, then \f(CW\*(C`ev_embed_sweep\*(C'\fR will be
1977invoked automatically, otherwise it is the responsibility of the callback 3329invoked automatically, otherwise it is the responsibility of the callback
1978to invoke it (it will continue to be called until the sweep has been done, 3330to invoke it (it will continue to be called until the sweep has been done,
1979if you do not want thta, you need to temporarily stop the embed watcher). 3331if you do not want that, you need to temporarily stop the embed watcher).
1980.IP "ev_embed_sweep (loop, ev_embed *)" 4 3332.IP "ev_embed_sweep (loop, ev_embed *)" 4
1981.IX Item "ev_embed_sweep (loop, ev_embed *)" 3333.IX Item "ev_embed_sweep (loop, ev_embed *)"
1982Make a single, non-blocking sweep over the embedded loop. This works 3334Make a single, non-blocking sweep over the embedded loop. This works
1983similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most 3335similarly to \f(CW\*(C`ev_run (embedded_loop, EVRUN_NOWAIT)\*(C'\fR, but in the most
1984apropriate way for embedded loops. 3336appropriate way for embedded loops.
1985.IP "struct ev_loop *loop [read\-only]" 4 3337.IP "struct ev_loop *other [read\-only]" 4
1986.IX Item "struct ev_loop *loop [read-only]" 3338.IX Item "struct ev_loop *other [read-only]"
1987The embedded event loop. 3339The embedded event loop.
3340.PP
3341\fIExamples\fR
3342.IX Subsection "Examples"
3343.PP
3344Example: Try to get an embeddable event loop and embed it into the default
3345event loop. If that is not possible, use the default loop. The default
3346loop is stored in \f(CW\*(C`loop_hi\*(C'\fR, while the embeddable loop is stored in
3347\&\f(CW\*(C`loop_lo\*(C'\fR (which is \f(CW\*(C`loop_hi\*(C'\fR in the case no embeddable loop can be
3348used).
3349.PP
3350.Vb 3
3351\& struct ev_loop *loop_hi = ev_default_init (0);
3352\& struct ev_loop *loop_lo = 0;
3353\& ev_embed embed;
3354\&
3355\& // see if there is a chance of getting one that works
3356\& // (remember that a flags value of 0 means autodetection)
3357\& loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
3358\& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
3359\& : 0;
3360\&
3361\& // if we got one, then embed it, otherwise default to loop_hi
3362\& if (loop_lo)
3363\& {
3364\& ev_embed_init (&embed, 0, loop_lo);
3365\& ev_embed_start (loop_hi, &embed);
3366\& }
3367\& else
3368\& loop_lo = loop_hi;
3369.Ve
3370.PP
3371Example: Check if kqueue is available but not recommended and create
3372a kqueue backend for use with sockets (which usually work with any
3373kqueue implementation). Store the kqueue/socket\-only event loop in
3374\&\f(CW\*(C`loop_socket\*(C'\fR. (One might optionally use \f(CW\*(C`EVFLAG_NOENV\*(C'\fR, too).
3375.PP
3376.Vb 3
3377\& struct ev_loop *loop = ev_default_init (0);
3378\& struct ev_loop *loop_socket = 0;
3379\& ev_embed embed;
3380\&
3381\& if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
3382\& if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
3383\& {
3384\& ev_embed_init (&embed, 0, loop_socket);
3385\& ev_embed_start (loop, &embed);
3386\& }
3387\&
3388\& if (!loop_socket)
3389\& loop_socket = loop;
3390\&
3391\& // now use loop_socket for all sockets, and loop for everything else
3392.Ve
1988.ie n .Sh """ev_fork"" \- the audacity to resume the event loop after a fork" 3393.ie n .SS """ev_fork"" \- the audacity to resume the event loop after a fork"
1989.el .Sh "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork" 3394.el .SS "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork"
1990.IX Subsection "ev_fork - the audacity to resume the event loop after a fork" 3395.IX Subsection "ev_fork - the audacity to resume the event loop after a fork"
1991Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because 3396Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because
1992whoever is a good citizen cared to tell libev about it by calling 3397whoever is a good citizen cared to tell libev about it by calling
1993\&\f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the 3398\&\f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the event loop blocks next
1994event loop blocks next and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called, 3399and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called, and only in the child
1995and only in the child after the fork. If whoever good citizen calling 3400after the fork. If whoever good citizen calling \f(CW\*(C`ev_default_fork\*(C'\fR cheats
1996\&\f(CW\*(C`ev_default_fork\*(C'\fR cheats and calls it in the wrong process, the fork 3401and calls it in the wrong process, the fork handlers will be invoked, too,
1997handlers will be invoked, too, of course. 3402of course.
3403.PP
3404\fIThe special problem of life after fork \- how is it possible?\fR
3405.IX Subsection "The special problem of life after fork - how is it possible?"
3406.PP
3407Most uses of \f(CW\*(C`fork()\*(C'\fR consist of forking, then some simple calls to set
3408up/change the process environment, followed by a call to \f(CW\*(C`exec()\*(C'\fR. This
3409sequence should be handled by libev without any problems.
3410.PP
3411This changes when the application actually wants to do event handling
3412in the child, or both parent in child, in effect \*(L"continuing\*(R" after the
3413fork.
3414.PP
3415The default mode of operation (for libev, with application help to detect
3416forks) is to duplicate all the state in the child, as would be expected
3417when \fIeither\fR the parent \fIor\fR the child process continues.
3418.PP
3419When both processes want to continue using libev, then this is usually the
3420wrong result. In that case, usually one process (typically the parent) is
3421supposed to continue with all watchers in place as before, while the other
3422process typically wants to start fresh, i.e. without any active watchers.
3423.PP
3424The cleanest and most efficient way to achieve that with libev is to
3425simply create a new event loop, which of course will be \*(L"empty\*(R", and
3426use that for new watchers. This has the advantage of not touching more
3427memory than necessary, and thus avoiding the copy-on-write, and the
3428disadvantage of having to use multiple event loops (which do not support
3429signal watchers).
3430.PP
3431When this is not possible, or you want to use the default loop for
3432other reasons, then in the process that wants to start \*(L"fresh\*(R", call
3433\&\f(CW\*(C`ev_loop_destroy (EV_DEFAULT)\*(C'\fR followed by \f(CW\*(C`ev_default_loop (...)\*(C'\fR.
3434Destroying the default loop will \*(L"orphan\*(R" (not stop) all registered
3435watchers, so you have to be careful not to execute code that modifies
3436those watchers. Note also that in that case, you have to re-register any
3437signal watchers.
1998.PP 3438.PP
1999\fIWatcher-Specific Functions and Data Members\fR 3439\fIWatcher-Specific Functions and Data Members\fR
2000.IX Subsection "Watcher-Specific Functions and Data Members" 3440.IX Subsection "Watcher-Specific Functions and Data Members"
2001.IP "ev_fork_init (ev_signal *, callback)" 4 3441.IP "ev_fork_init (ev_fork *, callback)" 4
2002.IX Item "ev_fork_init (ev_signal *, callback)" 3442.IX Item "ev_fork_init (ev_fork *, callback)"
2003Initialises and configures the fork watcher \- it has no parameters of any 3443Initialises and configures the fork watcher \- it has no parameters of any
2004kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless, 3444kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless,
2005believe me. 3445really.
3446.ie n .SS """ev_cleanup"" \- even the best things end"
3447.el .SS "\f(CWev_cleanup\fP \- even the best things end"
3448.IX Subsection "ev_cleanup - even the best things end"
3449Cleanup watchers are called just before the event loop is being destroyed
3450by a call to \f(CW\*(C`ev_loop_destroy\*(C'\fR.
3451.PP
3452While there is no guarantee that the event loop gets destroyed, cleanup
3453watchers provide a convenient method to install cleanup hooks for your
3454program, worker threads and so on \- you just to make sure to destroy the
3455loop when you want them to be invoked.
3456.PP
3457Cleanup watchers are invoked in the same way as any other watcher. Unlike
3458all other watchers, they do not keep a reference to the event loop (which
3459makes a lot of sense if you think about it). Like all other watchers, you
3460can call libev functions in the callback, except \f(CW\*(C`ev_cleanup_start\*(C'\fR.
3461.PP
3462\fIWatcher-Specific Functions and Data Members\fR
3463.IX Subsection "Watcher-Specific Functions and Data Members"
3464.IP "ev_cleanup_init (ev_cleanup *, callback)" 4
3465.IX Item "ev_cleanup_init (ev_cleanup *, callback)"
3466Initialises and configures the cleanup watcher \- it has no parameters of
3467any kind. There is a \f(CW\*(C`ev_cleanup_set\*(C'\fR macro, but using it is utterly
3468pointless, I assure you.
3469.PP
3470Example: Register an atexit handler to destroy the default loop, so any
3471cleanup functions are called.
3472.PP
3473.Vb 5
3474\& static void
3475\& program_exits (void)
3476\& {
3477\& ev_loop_destroy (EV_DEFAULT_UC);
3478\& }
3479\&
3480\& ...
3481\& atexit (program_exits);
3482.Ve
3483.ie n .SS """ev_async"" \- how to wake up an event loop"
3484.el .SS "\f(CWev_async\fP \- how to wake up an event loop"
3485.IX Subsection "ev_async - how to wake up an event loop"
3486In general, you cannot use an \f(CW\*(C`ev_loop\*(C'\fR from multiple threads or other
3487asynchronous sources such as signal handlers (as opposed to multiple event
3488loops \- those are of course safe to use in different threads).
3489.PP
3490Sometimes, however, you need to wake up an event loop you do not control,
3491for example because it belongs to another thread. This is what \f(CW\*(C`ev_async\*(C'\fR
3492watchers do: as long as the \f(CW\*(C`ev_async\*(C'\fR watcher is active, you can signal
3493it by calling \f(CW\*(C`ev_async_send\*(C'\fR, which is thread\- and signal safe.
3494.PP
3495This functionality is very similar to \f(CW\*(C`ev_signal\*(C'\fR watchers, as signals,
3496too, are asynchronous in nature, and signals, too, will be compressed
3497(i.e. the number of callback invocations may be less than the number of
3498\&\f(CW\*(C`ev_async_send\*(C'\fR calls). In fact, you could use signal watchers as a kind
3499of \*(L"global async watchers\*(R" by using a watcher on an otherwise unused
3500signal, and \f(CW\*(C`ev_feed_signal\*(C'\fR to signal this watcher from another thread,
3501even without knowing which loop owns the signal.
3502.PP
3503\fIQueueing\fR
3504.IX Subsection "Queueing"
3505.PP
3506\&\f(CW\*(C`ev_async\*(C'\fR does not support queueing of data in any way. The reason
3507is that the author does not know of a simple (or any) algorithm for a
3508multiple-writer-single-reader queue that works in all cases and doesn't
3509need elaborate support such as pthreads or unportable memory access
3510semantics.
3511.PP
3512That means that if you want to queue data, you have to provide your own
3513queue. But at least I can tell you how to implement locking around your
3514queue:
3515.IP "queueing from a signal handler context" 4
3516.IX Item "queueing from a signal handler context"
3517To implement race-free queueing, you simply add to the queue in the signal
3518handler but you block the signal handler in the watcher callback. Here is
3519an example that does that for some fictitious \s-1SIGUSR1\s0 handler:
3520.Sp
3521.Vb 1
3522\& static ev_async mysig;
3523\&
3524\& static void
3525\& sigusr1_handler (void)
3526\& {
3527\& sometype data;
3528\&
3529\& // no locking etc.
3530\& queue_put (data);
3531\& ev_async_send (EV_DEFAULT_ &mysig);
3532\& }
3533\&
3534\& static void
3535\& mysig_cb (EV_P_ ev_async *w, int revents)
3536\& {
3537\& sometype data;
3538\& sigset_t block, prev;
3539\&
3540\& sigemptyset (&block);
3541\& sigaddset (&block, SIGUSR1);
3542\& sigprocmask (SIG_BLOCK, &block, &prev);
3543\&
3544\& while (queue_get (&data))
3545\& process (data);
3546\&
3547\& if (sigismember (&prev, SIGUSR1)
3548\& sigprocmask (SIG_UNBLOCK, &block, 0);
3549\& }
3550.Ve
3551.Sp
3552(Note: pthreads in theory requires you to use \f(CW\*(C`pthread_setmask\*(C'\fR
3553instead of \f(CW\*(C`sigprocmask\*(C'\fR when you use threads, but libev doesn't do it
3554either...).
3555.IP "queueing from a thread context" 4
3556.IX Item "queueing from a thread context"
3557The strategy for threads is different, as you cannot (easily) block
3558threads but you can easily preempt them, so to queue safely you need to
3559employ a traditional mutex lock, such as in this pthread example:
3560.Sp
3561.Vb 2
3562\& static ev_async mysig;
3563\& static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
3564\&
3565\& static void
3566\& otherthread (void)
3567\& {
3568\& // only need to lock the actual queueing operation
3569\& pthread_mutex_lock (&mymutex);
3570\& queue_put (data);
3571\& pthread_mutex_unlock (&mymutex);
3572\&
3573\& ev_async_send (EV_DEFAULT_ &mysig);
3574\& }
3575\&
3576\& static void
3577\& mysig_cb (EV_P_ ev_async *w, int revents)
3578\& {
3579\& pthread_mutex_lock (&mymutex);
3580\&
3581\& while (queue_get (&data))
3582\& process (data);
3583\&
3584\& pthread_mutex_unlock (&mymutex);
3585\& }
3586.Ve
3587.PP
3588\fIWatcher-Specific Functions and Data Members\fR
3589.IX Subsection "Watcher-Specific Functions and Data Members"
3590.IP "ev_async_init (ev_async *, callback)" 4
3591.IX Item "ev_async_init (ev_async *, callback)"
3592Initialises and configures the async watcher \- it has no parameters of any
3593kind. There is a \f(CW\*(C`ev_async_set\*(C'\fR macro, but using it is utterly pointless,
3594trust me.
3595.IP "ev_async_send (loop, ev_async *)" 4
3596.IX Item "ev_async_send (loop, ev_async *)"
3597Sends/signals/activates the given \f(CW\*(C`ev_async\*(C'\fR watcher, that is, feeds
3598an \f(CW\*(C`EV_ASYNC\*(C'\fR event on the watcher into the event loop, and instantly
3599returns.
3600.Sp
3601Unlike \f(CW\*(C`ev_feed_event\*(C'\fR, this call is safe to do from other threads,
3602signal or similar contexts (see the discussion of \f(CW\*(C`EV_ATOMIC_T\*(C'\fR in the
3603embedding section below on what exactly this means).
3604.Sp
3605Note that, as with other watchers in libev, multiple events might get
3606compressed into a single callback invocation (another way to look at
3607this is that \f(CW\*(C`ev_async\*(C'\fR watchers are level-triggered: they are set on
3608\&\f(CW\*(C`ev_async_send\*(C'\fR, reset when the event loop detects that).
3609.Sp
3610This call incurs the overhead of at most one extra system call per event
3611loop iteration, if the event loop is blocked, and no syscall at all if
3612the event loop (or your program) is processing events. That means that
3613repeated calls are basically free (there is no need to avoid calls for
3614performance reasons) and that the overhead becomes smaller (typically
3615zero) under load.
3616.IP "bool = ev_async_pending (ev_async *)" 4
3617.IX Item "bool = ev_async_pending (ev_async *)"
3618Returns a non-zero value when \f(CW\*(C`ev_async_send\*(C'\fR has been called on the
3619watcher but the event has not yet been processed (or even noted) by the
3620event loop.
3621.Sp
3622\&\f(CW\*(C`ev_async_send\*(C'\fR sets a flag in the watcher and wakes up the loop. When
3623the loop iterates next and checks for the watcher to have become active,
3624it will reset the flag again. \f(CW\*(C`ev_async_pending\*(C'\fR can be used to very
3625quickly check whether invoking the loop might be a good idea.
3626.Sp
3627Not that this does \fInot\fR check whether the watcher itself is pending,
3628only whether it has been requested to make this watcher pending: there
3629is a time window between the event loop checking and resetting the async
3630notification, and the callback being invoked.
2006.SH "OTHER FUNCTIONS" 3631.SH "OTHER FUNCTIONS"
2007.IX Header "OTHER FUNCTIONS" 3632.IX Header "OTHER FUNCTIONS"
2008There are some other functions of possible interest. Described. Here. Now. 3633There are some other functions of possible interest. Described. Here. Now.
2009.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4 3634.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4
2010.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 3635.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)"
2011This function combines a simple timer and an I/O watcher, calls your 3636This function combines a simple timer and an I/O watcher, calls your
2012callback on whichever event happens first and automatically stop both 3637callback on whichever event happens first and automatically stops both
2013watchers. This is useful if you want to wait for a single event on an fd 3638watchers. This is useful if you want to wait for a single event on an fd
2014or timeout without having to allocate/configure/start/stop/free one or 3639or timeout without having to allocate/configure/start/stop/free one or
2015more watchers yourself. 3640more watchers yourself.
2016.Sp 3641.Sp
2017If \f(CW\*(C`fd\*(C'\fR is less than 0, then no I/O watcher will be started and events 3642If \f(CW\*(C`fd\*(C'\fR is less than 0, then no I/O watcher will be started and the
2018is being ignored. Otherwise, an \f(CW\*(C`ev_io\*(C'\fR watcher for the given \f(CW\*(C`fd\*(C'\fR and 3643\&\f(CW\*(C`events\*(C'\fR argument is being ignored. Otherwise, an \f(CW\*(C`ev_io\*(C'\fR watcher for
2019\&\f(CW\*(C`events\*(C'\fR set will be craeted and started. 3644the given \f(CW\*(C`fd\*(C'\fR and \f(CW\*(C`events\*(C'\fR set will be created and started.
2020.Sp 3645.Sp
2021If \f(CW\*(C`timeout\*(C'\fR is less than 0, then no timeout watcher will be 3646If \f(CW\*(C`timeout\*(C'\fR is less than 0, then no timeout watcher will be
2022started. Otherwise an \f(CW\*(C`ev_timer\*(C'\fR watcher with after = \f(CW\*(C`timeout\*(C'\fR (and 3647started. Otherwise an \f(CW\*(C`ev_timer\*(C'\fR watcher with after = \f(CW\*(C`timeout\*(C'\fR (and
2023repeat = 0) will be started. While \f(CW0\fR is a valid timeout, it is of 3648repeat = 0) will be started. \f(CW0\fR is a valid timeout.
2024dubious value.
2025.Sp 3649.Sp
2026The callback has the type \f(CW\*(C`void (*cb)(int revents, void *arg)\*(C'\fR and gets 3650The callback has the type \f(CW\*(C`void (*cb)(int revents, void *arg)\*(C'\fR and is
2027passed an \f(CW\*(C`revents\*(C'\fR set like normal event callbacks (a combination of 3651passed an \f(CW\*(C`revents\*(C'\fR set like normal event callbacks (a combination of
2028\&\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 3652\&\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
2029value passed to \f(CW\*(C`ev_once\*(C'\fR: 3653value passed to \f(CW\*(C`ev_once\*(C'\fR. Note that it is possible to receive \fIboth\fR
3654a timeout and an io event at the same time \- you probably should give io
3655events precedence.
3656.Sp
3657Example: wait up to ten seconds for data to appear on \s-1STDIN_FILENO\s0.
2030.Sp 3658.Sp
2031.Vb 7 3659.Vb 7
2032\& static void stdin_ready (int revents, void *arg) 3660\& static void stdin_ready (int revents, void *arg)
3661\& {
3662\& if (revents & EV_READ)
3663\& /* stdin might have data for us, joy! */;
3664\& else if (revents & EV_TIMER)
3665\& /* doh, nothing entered */;
3666\& }
3667\&
3668\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3669.Ve
3670.IP "ev_feed_fd_event (loop, int fd, int revents)" 4
3671.IX Item "ev_feed_fd_event (loop, int fd, int revents)"
3672Feed an event on the given fd, as if a file descriptor backend detected
3673the given events.
3674.IP "ev_feed_signal_event (loop, int signum)" 4
3675.IX Item "ev_feed_signal_event (loop, int signum)"
3676Feed an event as if the given signal occurred. See also \f(CW\*(C`ev_feed_signal\*(C'\fR,
3677which is async-safe.
3678.SH "COMMON OR USEFUL IDIOMS (OR BOTH)"
3679.IX Header "COMMON OR USEFUL IDIOMS (OR BOTH)"
3680This section explains some common idioms that are not immediately
3681obvious. Note that examples are sprinkled over the whole manual, and this
3682section only contains stuff that wouldn't fit anywhere else.
3683.SS "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0"
3684.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER"
3685Each watcher has, by default, a \f(CW\*(C`void *data\*(C'\fR member that you can read
3686or modify at any time: libev will completely ignore it. This can be used
3687to associate arbitrary data with your watcher. If you need more data and
3688don't want to allocate memory separately and store a pointer to it in that
3689data member, you can also \*(L"subclass\*(R" the watcher type and provide your own
3690data:
3691.PP
3692.Vb 7
3693\& struct my_io
3694\& {
3695\& ev_io io;
3696\& int otherfd;
3697\& void *somedata;
3698\& struct whatever *mostinteresting;
3699\& };
3700\&
3701\& ...
3702\& struct my_io w;
3703\& ev_io_init (&w.io, my_cb, fd, EV_READ);
3704.Ve
3705.PP
3706And since your callback will be called with a pointer to the watcher, you
3707can cast it back to your own type:
3708.PP
3709.Vb 5
3710\& static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
3711\& {
3712\& struct my_io *w = (struct my_io *)w_;
3713\& ...
3714\& }
3715.Ve
3716.PP
3717More interesting and less C\-conformant ways of casting your callback
3718function type instead have been omitted.
3719.SS "\s-1BUILDING\s0 \s-1YOUR\s0 \s-1OWN\s0 \s-1COMPOSITE\s0 \s-1WATCHERS\s0"
3720.IX Subsection "BUILDING YOUR OWN COMPOSITE WATCHERS"
3721Another common scenario is to use some data structure with multiple
3722embedded watchers, in effect creating your own watcher that combines
3723multiple libev event sources into one \*(L"super-watcher\*(R":
3724.PP
3725.Vb 6
3726\& struct my_biggy
3727\& {
3728\& int some_data;
3729\& ev_timer t1;
3730\& ev_timer t2;
3731\& }
3732.Ve
3733.PP
3734In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more
3735complicated: Either you store the address of your \f(CW\*(C`my_biggy\*(C'\fR struct in
3736the \f(CW\*(C`data\*(C'\fR member of the watcher (for woozies or \*(C+ coders), or you need
3737to use some pointer arithmetic using \f(CW\*(C`offsetof\*(C'\fR inside your watchers (for
3738real programmers):
3739.PP
3740.Vb 1
3741\& #include <stddef.h>
3742\&
3743\& static void
3744\& t1_cb (EV_P_ ev_timer *w, int revents)
3745\& {
3746\& struct my_biggy big = (struct my_biggy *)
3747\& (((char *)w) \- offsetof (struct my_biggy, t1));
3748\& }
3749\&
3750\& static void
3751\& t2_cb (EV_P_ ev_timer *w, int revents)
3752\& {
3753\& struct my_biggy big = (struct my_biggy *)
3754\& (((char *)w) \- offsetof (struct my_biggy, t2));
3755\& }
3756.Ve
3757.SS "\s-1AVOIDING\s0 \s-1FINISHING\s0 \s-1BEFORE\s0 \s-1RETURNING\s0"
3758.IX Subsection "AVOIDING FINISHING BEFORE RETURNING"
3759Often you have structures like this in event-based programs:
3760.PP
3761.Vb 4
3762\& callback ()
2033\& { 3763\& {
2034\& if (revents & EV_TIMEOUT) 3764\& free (request);
2035\& /* doh, nothing entered */;
2036\& else if (revents & EV_READ)
2037\& /* stdin might have data for us, joy! */;
2038\& } 3765\& }
3766\&
3767\& request = start_new_request (..., callback);
2039.Ve 3768.Ve
2040.Sp 3769.PP
3770The intent is to start some \*(L"lengthy\*(R" operation. The \f(CW\*(C`request\*(C'\fR could be
3771used to cancel the operation, or do other things with it.
3772.PP
3773It's not uncommon to have code paths in \f(CW\*(C`start_new_request\*(C'\fR that
3774immediately invoke the callback, for example, to report errors. Or you add
3775some caching layer that finds that it can skip the lengthy aspects of the
3776operation and simply invoke the callback with the result.
3777.PP
3778The problem here is that this will happen \fIbefore\fR \f(CW\*(C`start_new_request\*(C'\fR
3779has returned, so \f(CW\*(C`request\*(C'\fR is not set.
3780.PP
3781Even if you pass the request by some safer means to the callback, you
3782might want to do something to the request after starting it, such as
3783canceling it, which probably isn't working so well when the callback has
3784already been invoked.
3785.PP
3786A common way around all these issues is to make sure that
3787\&\f(CW\*(C`start_new_request\*(C'\fR \fIalways\fR returns before the callback is invoked. If
3788\&\f(CW\*(C`start_new_request\*(C'\fR immediately knows the result, it can artificially
3789delay invoking the callback by using a \f(CW\*(C`prepare\*(C'\fR or \f(CW\*(C`idle\*(C'\fR watcher for
3790example, or more sneakily, by reusing an existing (stopped) watcher and
3791pushing it into the pending queue:
3792.PP
2041.Vb 1 3793.Vb 2
2042\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); 3794\& ev_set_cb (watcher, callback);
3795\& ev_feed_event (EV_A_ watcher, 0);
2043.Ve 3796.Ve
2044.IP "ev_feed_event (ev_loop *, watcher *, int revents)" 4 3797.PP
2045.IX Item "ev_feed_event (ev_loop *, watcher *, int revents)" 3798This way, \f(CW\*(C`start_new_request\*(C'\fR can safely return before the callback is
2046Feeds the given event set into the event loop, as if the specified event 3799invoked, while not delaying callback invocation too much.
2047had happened for the specified watcher (which must be a pointer to an 3800.SS "\s-1MODEL/NESTED\s0 \s-1EVENT\s0 \s-1LOOP\s0 \s-1INVOCATIONS\s0 \s-1AND\s0 \s-1EXIT\s0 \s-1CONDITIONS\s0"
2048initialised but not necessarily started event watcher). 3801.IX Subsection "MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS"
2049.IP "ev_feed_fd_event (ev_loop *, int fd, int revents)" 4 3802Often (especially in \s-1GUI\s0 toolkits) there are places where you have
2050.IX Item "ev_feed_fd_event (ev_loop *, int fd, int revents)" 3803\&\fImodal\fR interaction, which is most easily implemented by recursively
2051Feed an event on the given fd, as if a file descriptor backend detected 3804invoking \f(CW\*(C`ev_run\*(C'\fR.
2052the given events it. 3805.PP
2053.IP "ev_feed_signal_event (ev_loop *loop, int signum)" 4 3806This brings the problem of exiting \- a callback might want to finish the
2054.IX Item "ev_feed_signal_event (ev_loop *loop, int signum)" 3807main \f(CW\*(C`ev_run\*(C'\fR call, but not the nested one (e.g. user clicked \*(L"Quit\*(R", but
2055Feed an event as if the given signal occured (\f(CW\*(C`loop\*(C'\fR must be the default 3808a modal \*(L"Are you sure?\*(R" dialog is still waiting), or just the nested one
2056loop!). 3809and not the main one (e.g. user clocked \*(L"Ok\*(R" in a modal dialog), or some
3810other combination: In these cases, a simple \f(CW\*(C`ev_break\*(C'\fR will not work.
3811.PP
3812The solution is to maintain \*(L"break this loop\*(R" variable for each \f(CW\*(C`ev_run\*(C'\fR
3813invocation, and use a loop around \f(CW\*(C`ev_run\*(C'\fR until the condition is
3814triggered, using \f(CW\*(C`EVRUN_ONCE\*(C'\fR:
3815.PP
3816.Vb 2
3817\& // main loop
3818\& int exit_main_loop = 0;
3819\&
3820\& while (!exit_main_loop)
3821\& ev_run (EV_DEFAULT_ EVRUN_ONCE);
3822\&
3823\& // in a modal watcher
3824\& int exit_nested_loop = 0;
3825\&
3826\& while (!exit_nested_loop)
3827\& ev_run (EV_A_ EVRUN_ONCE);
3828.Ve
3829.PP
3830To exit from any of these loops, just set the corresponding exit variable:
3831.PP
3832.Vb 2
3833\& // exit modal loop
3834\& exit_nested_loop = 1;
3835\&
3836\& // exit main program, after modal loop is finished
3837\& exit_main_loop = 1;
3838\&
3839\& // exit both
3840\& exit_main_loop = exit_nested_loop = 1;
3841.Ve
3842.SS "\s-1THREAD\s0 \s-1LOCKING\s0 \s-1EXAMPLE\s0"
3843.IX Subsection "THREAD LOCKING EXAMPLE"
3844Here is a fictitious example of how to run an event loop in a different
3845thread from where callbacks are being invoked and watchers are
3846created/added/removed.
3847.PP
3848For a real-world example, see the \f(CW\*(C`EV::Loop::Async\*(C'\fR perl module,
3849which uses exactly this technique (which is suited for many high-level
3850languages).
3851.PP
3852The example uses a pthread mutex to protect the loop data, a condition
3853variable to wait for callback invocations, an async watcher to notify the
3854event loop thread and an unspecified mechanism to wake up the main thread.
3855.PP
3856First, you need to associate some data with the event loop:
3857.PP
3858.Vb 6
3859\& typedef struct {
3860\& mutex_t lock; /* global loop lock */
3861\& ev_async async_w;
3862\& thread_t tid;
3863\& cond_t invoke_cv;
3864\& } userdata;
3865\&
3866\& void prepare_loop (EV_P)
3867\& {
3868\& // for simplicity, we use a static userdata struct.
3869\& static userdata u;
3870\&
3871\& ev_async_init (&u\->async_w, async_cb);
3872\& ev_async_start (EV_A_ &u\->async_w);
3873\&
3874\& pthread_mutex_init (&u\->lock, 0);
3875\& pthread_cond_init (&u\->invoke_cv, 0);
3876\&
3877\& // now associate this with the loop
3878\& ev_set_userdata (EV_A_ u);
3879\& ev_set_invoke_pending_cb (EV_A_ l_invoke);
3880\& ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
3881\&
3882\& // then create the thread running ev_run
3883\& pthread_create (&u\->tid, 0, l_run, EV_A);
3884\& }
3885.Ve
3886.PP
3887The callback for the \f(CW\*(C`ev_async\*(C'\fR watcher does nothing: the watcher is used
3888solely to wake up the event loop so it takes notice of any new watchers
3889that might have been added:
3890.PP
3891.Vb 5
3892\& static void
3893\& async_cb (EV_P_ ev_async *w, int revents)
3894\& {
3895\& // just used for the side effects
3896\& }
3897.Ve
3898.PP
3899The \f(CW\*(C`l_release\*(C'\fR and \f(CW\*(C`l_acquire\*(C'\fR callbacks simply unlock/lock the mutex
3900protecting the loop data, respectively.
3901.PP
3902.Vb 6
3903\& static void
3904\& l_release (EV_P)
3905\& {
3906\& userdata *u = ev_userdata (EV_A);
3907\& pthread_mutex_unlock (&u\->lock);
3908\& }
3909\&
3910\& static void
3911\& l_acquire (EV_P)
3912\& {
3913\& userdata *u = ev_userdata (EV_A);
3914\& pthread_mutex_lock (&u\->lock);
3915\& }
3916.Ve
3917.PP
3918The event loop thread first acquires the mutex, and then jumps straight
3919into \f(CW\*(C`ev_run\*(C'\fR:
3920.PP
3921.Vb 4
3922\& void *
3923\& l_run (void *thr_arg)
3924\& {
3925\& struct ev_loop *loop = (struct ev_loop *)thr_arg;
3926\&
3927\& l_acquire (EV_A);
3928\& pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
3929\& ev_run (EV_A_ 0);
3930\& l_release (EV_A);
3931\&
3932\& return 0;
3933\& }
3934.Ve
3935.PP
3936Instead of invoking all pending watchers, the \f(CW\*(C`l_invoke\*(C'\fR callback will
3937signal the main thread via some unspecified mechanism (signals? pipe
3938writes? \f(CW\*(C`Async::Interrupt\*(C'\fR?) and then waits until all pending watchers
3939have been called (in a while loop because a) spurious wakeups are possible
3940and b) skipping inter-thread-communication when there are no pending
3941watchers is very beneficial):
3942.PP
3943.Vb 4
3944\& static void
3945\& l_invoke (EV_P)
3946\& {
3947\& userdata *u = ev_userdata (EV_A);
3948\&
3949\& while (ev_pending_count (EV_A))
3950\& {
3951\& wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
3952\& pthread_cond_wait (&u\->invoke_cv, &u\->lock);
3953\& }
3954\& }
3955.Ve
3956.PP
3957Now, whenever the main thread gets told to invoke pending watchers, it
3958will grab the lock, call \f(CW\*(C`ev_invoke_pending\*(C'\fR and then signal the loop
3959thread to continue:
3960.PP
3961.Vb 4
3962\& static void
3963\& real_invoke_pending (EV_P)
3964\& {
3965\& userdata *u = ev_userdata (EV_A);
3966\&
3967\& pthread_mutex_lock (&u\->lock);
3968\& ev_invoke_pending (EV_A);
3969\& pthread_cond_signal (&u\->invoke_cv);
3970\& pthread_mutex_unlock (&u\->lock);
3971\& }
3972.Ve
3973.PP
3974Whenever you want to start/stop a watcher or do other modifications to an
3975event loop, you will now have to lock:
3976.PP
3977.Vb 2
3978\& ev_timer timeout_watcher;
3979\& userdata *u = ev_userdata (EV_A);
3980\&
3981\& ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
3982\&
3983\& pthread_mutex_lock (&u\->lock);
3984\& ev_timer_start (EV_A_ &timeout_watcher);
3985\& ev_async_send (EV_A_ &u\->async_w);
3986\& pthread_mutex_unlock (&u\->lock);
3987.Ve
3988.PP
3989Note that sending the \f(CW\*(C`ev_async\*(C'\fR watcher is required because otherwise
3990an event loop currently blocking in the kernel will have no knowledge
3991about the newly added timer. By waking up the loop it will pick up any new
3992watchers in the next event loop iteration.
3993.SS "\s-1THREADS\s0, \s-1COROUTINES\s0, \s-1CONTINUATIONS\s0, \s-1QUEUES\s0... \s-1INSTEAD\s0 \s-1OF\s0 \s-1CALLBACKS\s0"
3994.IX Subsection "THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS"
3995While the overhead of a callback that e.g. schedules a thread is small, it
3996is still an overhead. If you embed libev, and your main usage is with some
3997kind of threads or coroutines, you might want to customise libev so that
3998doesn't need callbacks anymore.
3999.PP
4000Imagine you have coroutines that you can switch to using a function
4001\&\f(CW\*(C`switch_to (coro)\*(C'\fR, that libev runs in a coroutine called \f(CW\*(C`libev_coro\*(C'\fR
4002and that due to some magic, the currently active coroutine is stored in a
4003global called \f(CW\*(C`current_coro\*(C'\fR. Then you can build your own \*(L"wait for libev
4004event\*(R" primitive by changing \f(CW\*(C`EV_CB_DECLARE\*(C'\fR and \f(CW\*(C`EV_CB_INVOKE\*(C'\fR (note
4005the differing \f(CW\*(C`;\*(C'\fR conventions):
4006.PP
4007.Vb 2
4008\& #define EV_CB_DECLARE(type) struct my_coro *cb;
4009\& #define EV_CB_INVOKE(watcher) switch_to ((watcher)\->cb)
4010.Ve
4011.PP
4012That means instead of having a C callback function, you store the
4013coroutine to switch to in each watcher, and instead of having libev call
4014your callback, you instead have it switch to that coroutine.
4015.PP
4016A coroutine might now wait for an event with a function called
4017\&\f(CW\*(C`wait_for_event\*(C'\fR. (the watcher needs to be started, as always, but it doesn't
4018matter when, or whether the watcher is active or not when this function is
4019called):
4020.PP
4021.Vb 6
4022\& void
4023\& wait_for_event (ev_watcher *w)
4024\& {
4025\& ev_set_cb (w, current_coro);
4026\& switch_to (libev_coro);
4027\& }
4028.Ve
4029.PP
4030That basically suspends the coroutine inside \f(CW\*(C`wait_for_event\*(C'\fR and
4031continues the libev coroutine, which, when appropriate, switches back to
4032this or any other coroutine.
4033.PP
4034You can do similar tricks if you have, say, threads with an event queue \-
4035instead of storing a coroutine, you store the queue object and instead of
4036switching to a coroutine, you push the watcher onto the queue and notify
4037any waiters.
4038.PP
4039To embed libev, see \*(L"\s-1EMBEDDING\s0\*(R", but in short, it's easiest to create two
4040files, \fImy_ev.h\fR and \fImy_ev.c\fR that include the respective libev files:
4041.PP
4042.Vb 4
4043\& // my_ev.h
4044\& #define EV_CB_DECLARE(type) struct my_coro *cb;
4045\& #define EV_CB_INVOKE(watcher) switch_to ((watcher)\->cb);
4046\& #include "../libev/ev.h"
4047\&
4048\& // my_ev.c
4049\& #define EV_H "my_ev.h"
4050\& #include "../libev/ev.c"
4051.Ve
4052.PP
4053And then use \fImy_ev.h\fR when you would normally use \fIev.h\fR, and compile
4054\&\fImy_ev.c\fR into your project. When properly specifying include paths, you
4055can even use \fIev.h\fR as header file name directly.
2057.SH "LIBEVENT EMULATION" 4056.SH "LIBEVENT EMULATION"
2058.IX Header "LIBEVENT EMULATION" 4057.IX Header "LIBEVENT EMULATION"
2059Libev offers a compatibility emulation layer for libevent. It cannot 4058Libev offers a compatibility emulation layer for libevent. It cannot
2060emulate the internals of libevent, so here are some usage hints: 4059emulate the internals of libevent, so here are some usage hints:
4060.IP "\(bu" 4
4061Only the libevent\-1.4.1\-beta \s-1API\s0 is being emulated.
4062.Sp
4063This was the newest libevent version available when libev was implemented,
4064and is still mostly unchanged in 2010.
4065.IP "\(bu" 4
2061.IP "* Use it by including <event.h>, as usual." 4 4066Use it by including <event.h>, as usual.
2062.IX Item "Use it by including <event.h>, as usual." 4067.IP "\(bu" 4
2063.PD 0 4068The following members are fully supported: ev_base, ev_callback,
2064.IP "* The following members are fully supported: ev_base, ev_callback, ev_arg, ev_fd, ev_res, ev_events." 4 4069ev_arg, ev_fd, ev_res, ev_events.
2065.IX Item "The following members are fully supported: ev_base, ev_callback, ev_arg, ev_fd, ev_res, ev_events." 4070.IP "\(bu" 4
2066.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 4071Avoid using ev_flags and the EVLIST_*\-macros, while it is
2067.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)." 4072maintained by libev, it does not work exactly the same way as in libevent (consider
2068.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 4073it a private \s-1API\s0).
2069.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." 4074.IP "\(bu" 4
4075Priorities are not currently supported. Initialising priorities
4076will fail and all watchers will have the same priority, even though there
4077is an ev_pri field.
4078.IP "\(bu" 4
4079In libevent, the last base created gets the signals, in libev, the
4080base that registered the signal gets the signals.
4081.IP "\(bu" 4
2070.IP "* Other members are not supported." 4 4082Other members are not supported.
2071.IX Item "Other members are not supported." 4083.IP "\(bu" 4
2072.IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4 4084The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need
2073.IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library." 4085to use the libev header file and library.
2074.PD
2075.SH "\*(C+ SUPPORT" 4086.SH "\*(C+ SUPPORT"
2076.IX Header " SUPPORT" 4087.IX Header " SUPPORT"
4088.SS "C \s-1API\s0"
4089.IX Subsection "C API"
4090The normal C \s-1API\s0 should work fine when used from \*(C+: both ev.h and the
4091libev sources can be compiled as \*(C+. Therefore, code that uses the C \s-1API\s0
4092will work fine.
4093.PP
4094Proper exception specifications might have to be added to callbacks passed
4095to libev: exceptions may be thrown only from watcher callbacks, all
4096other callbacks (allocator, syserr, loop acquire/release and periodic
4097reschedule callbacks) must not throw exceptions, and might need a \f(CW\*(C`throw
4098()\*(C'\fR specification. If you have code that needs to be compiled as both C
4099and \*(C+ you can use the \f(CW\*(C`EV_THROW\*(C'\fR macro for this:
4100.PP
4101.Vb 6
4102\& static void
4103\& fatal_error (const char *msg) EV_THROW
4104\& {
4105\& perror (msg);
4106\& abort ();
4107\& }
4108\&
4109\& ...
4110\& ev_set_syserr_cb (fatal_error);
4111.Ve
4112.PP
4113The only \s-1API\s0 functions that can currently throw exceptions are \f(CW\*(C`ev_run\*(C'\fR,
4114\&\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
4115because it runs cleanup watchers).
4116.PP
4117Throwing exceptions in watcher callbacks is only supported if libev itself
4118is compiled with a \*(C+ compiler or your C and \*(C+ environments allow
4119throwing exceptions through C libraries (most do).
4120.SS "\*(C+ \s-1API\s0"
4121.IX Subsection " API"
2077Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow 4122Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow
2078you to use some convinience methods to start/stop watchers and also change 4123you to use some convenience methods to start/stop watchers and also change
2079the callback model to a model using method callbacks on objects. 4124the callback model to a model using method callbacks on objects.
2080.PP 4125.PP
2081To use it, 4126To use it,
2082.PP 4127.PP
2083.Vb 1 4128.Vb 1
2084\& #include <ev++.h> 4129\& #include <ev++.h>
2085.Ve 4130.Ve
2086.PP 4131.PP
2087This automatically includes \fIev.h\fR and puts all of its definitions (many 4132This automatically includes \fIev.h\fR and puts all of its definitions (many
2088of them macros) into the global namespace. All \*(C+ specific things are 4133of them macros) into the global namespace. All \*(C+ specific things are
2089put into the \f(CW\*(C`ev\*(C'\fR namespace. It should support all the same embedding 4134put into the \f(CW\*(C`ev\*(C'\fR namespace. It should support all the same embedding
… …
2092Care has been taken to keep the overhead low. The only data member the \*(C+ 4137Care has been taken to keep the overhead low. The only data member the \*(C+
2093classes add (compared to plain C\-style watchers) is the event loop pointer 4138classes add (compared to plain C\-style watchers) is the event loop pointer
2094that the watcher is associated with (or no additional members at all if 4139that the watcher is associated with (or no additional members at all if
2095you disable \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR when embedding libev). 4140you disable \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR when embedding libev).
2096.PP 4141.PP
2097Currently, functions, and static and non-static member functions can be 4142Currently, functions, static and non-static member functions and classes
2098used as callbacks. Other types should be easy to add as long as they only 4143with \f(CW\*(C`operator ()\*(C'\fR can be used as callbacks. Other types should be easy
2099need one additional pointer for context. If you need support for other 4144to add as long as they only need one additional pointer for context. If
2100types of functors please contact the author (preferably after implementing 4145you need support for other types of functors please contact the author
2101it). 4146(preferably after implementing it).
4147.PP
4148For all this to work, your \*(C+ compiler either has to use the same calling
4149conventions as your C compiler (for static member functions), or you have
4150to embed libev and compile libev itself as \*(C+.
2102.PP 4151.PP
2103Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace: 4152Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace:
2104.ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4 4153.ie n .IP """ev::READ"", ""ev::WRITE"" etc." 4
2105.el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4 4154.el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4
2106.IX Item "ev::READ, ev::WRITE etc." 4155.IX Item "ev::READ, ev::WRITE etc."
2107These are just enum values with the same values as the \f(CW\*(C`EV_READ\*(C'\fR etc. 4156These are just enum values with the same values as the \f(CW\*(C`EV_READ\*(C'\fR etc.
2108macros from \fIev.h\fR. 4157macros from \fIev.h\fR.
2109.ie n .IP """ev::tstamp""\fR, \f(CW""ev::now""" 4 4158.ie n .IP """ev::tstamp"", ""ev::now""" 4
2110.el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4 4159.el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4
2111.IX Item "ev::tstamp, ev::now" 4160.IX Item "ev::tstamp, ev::now"
2112Aliases to the same types/functions as with the \f(CW\*(C`ev_\*(C'\fR prefix. 4161Aliases to the same types/functions as with the \f(CW\*(C`ev_\*(C'\fR prefix.
2113.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 4162.ie n .IP """ev::io"", ""ev::timer"", ""ev::periodic"", ""ev::idle"", ""ev::sig"" etc." 4
2114.el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4 4163.el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4
2115.IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc." 4164.IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc."
2116For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of 4165For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of
2117the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR 4166the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR
2118which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro 4167which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro
2119defines by many implementations. 4168defined by many implementations.
2120.Sp 4169.Sp
2121All of those classes have these methods: 4170All of those classes have these methods:
2122.RS 4 4171.RS 4
2123.IP "ev::TYPE::TYPE ()" 4 4172.IP "ev::TYPE::TYPE ()" 4
2124.IX Item "ev::TYPE::TYPE ()" 4173.IX Item "ev::TYPE::TYPE ()"
2125.PD 0 4174.PD 0
2126.IP "ev::TYPE::TYPE (struct ev_loop *)" 4 4175.IP "ev::TYPE::TYPE (loop)" 4
2127.IX Item "ev::TYPE::TYPE (struct ev_loop *)" 4176.IX Item "ev::TYPE::TYPE (loop)"
2128.IP "ev::TYPE::~TYPE" 4 4177.IP "ev::TYPE::~TYPE" 4
2129.IX Item "ev::TYPE::~TYPE" 4178.IX Item "ev::TYPE::~TYPE"
2130.PD 4179.PD
2131The constructor (optionally) takes an event loop to associate the watcher 4180The constructor (optionally) takes an event loop to associate the watcher
2132with. If it is omitted, it will use \f(CW\*(C`EV_DEFAULT\*(C'\fR. 4181with. If it is omitted, it will use \f(CW\*(C`EV_DEFAULT\*(C'\fR.
… …
2155thunking function, making it as fast as a direct C callback. 4204thunking function, making it as fast as a direct C callback.
2156.Sp 4205.Sp
2157Example: simple class declaration and watcher initialisation 4206Example: simple class declaration and watcher initialisation
2158.Sp 4207.Sp
2159.Vb 4 4208.Vb 4
2160\& struct myclass 4209\& struct myclass
2161\& { 4210\& {
2162\& void io_cb (ev::io &w, int revents) { } 4211\& void io_cb (ev::io &w, int revents) { }
2163\& } 4212\& }
2164.Ve 4213\&
2165.Sp
2166.Vb 3
2167\& myclass obj; 4214\& myclass obj;
2168\& ev::io iow; 4215\& ev::io iow;
2169\& iow.set <myclass, &myclass::io_cb> (&obj); 4216\& iow.set <myclass, &myclass::io_cb> (&obj);
4217.Ve
4218.IP "w\->set (object *)" 4
4219.IX Item "w->set (object *)"
4220This is a variation of a method callback \- leaving out the method to call
4221will default the method to \f(CW\*(C`operator ()\*(C'\fR, which makes it possible to use
4222functor objects without having to manually specify the \f(CW\*(C`operator ()\*(C'\fR all
4223the time. Incidentally, you can then also leave out the template argument
4224list.
4225.Sp
4226The \f(CW\*(C`operator ()\*(C'\fR method prototype must be \f(CW\*(C`void operator ()(watcher &w,
4227int revents)\*(C'\fR.
4228.Sp
4229See the method\-\f(CW\*(C`set\*(C'\fR above for more details.
4230.Sp
4231Example: use a functor object as callback.
4232.Sp
4233.Vb 7
4234\& struct myfunctor
4235\& {
4236\& void operator() (ev::io &w, int revents)
4237\& {
4238\& ...
4239\& }
4240\& }
4241\&
4242\& myfunctor f;
4243\&
4244\& ev::io w;
4245\& w.set (&f);
2170.Ve 4246.Ve
2171.IP "w\->set<function> (void *data = 0)" 4 4247.IP "w\->set<function> (void *data = 0)" 4
2172.IX Item "w->set<function> (void *data = 0)" 4248.IX Item "w->set<function> (void *data = 0)"
2173Also sets a callback, but uses a static method or plain function as 4249Also sets a callback, but uses a static method or plain function as
2174callback. The optional \f(CW\*(C`data\*(C'\fR argument will be stored in the watcher's 4250callback. The optional \f(CW\*(C`data\*(C'\fR argument will be stored in the watcher's
… …
2176.Sp 4252.Sp
2177The prototype of the \f(CW\*(C`function\*(C'\fR must be \f(CW\*(C`void (*)(ev::TYPE &w, int)\*(C'\fR. 4253The prototype of the \f(CW\*(C`function\*(C'\fR must be \f(CW\*(C`void (*)(ev::TYPE &w, int)\*(C'\fR.
2178.Sp 4254.Sp
2179See the method\-\f(CW\*(C`set\*(C'\fR above for more details. 4255See the method\-\f(CW\*(C`set\*(C'\fR above for more details.
2180.Sp 4256.Sp
2181Example: 4257Example: Use a plain function as callback.
2182.Sp 4258.Sp
2183.Vb 2 4259.Vb 2
2184\& static void io_cb (ev::io &w, int revents) { } 4260\& static void io_cb (ev::io &w, int revents) { }
2185\& iow.set <io_cb> (); 4261\& iow.set <io_cb> ();
2186.Ve 4262.Ve
2187.IP "w\->set (struct ev_loop *)" 4 4263.IP "w\->set (loop)" 4
2188.IX Item "w->set (struct ev_loop *)" 4264.IX Item "w->set (loop)"
2189Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only 4265Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only
2190do this when the watcher is inactive (and not pending either). 4266do this when the watcher is inactive (and not pending either).
2191.IP "w\->set ([args])" 4 4267.IP "w\->set ([arguments])" 4
2192.IX Item "w->set ([args])" 4268.IX Item "w->set ([arguments])"
2193Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same args. Must be 4269Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR (except for \f(CW\*(C`ev::embed\*(C'\fR watchers>),
4270with the same arguments. Either this method or a suitable start method
2194called at least once. Unlike the C counterpart, an active watcher gets 4271must be called at least once. Unlike the C counterpart, an active watcher
2195automatically stopped and restarted when reconfiguring it with this 4272gets automatically stopped and restarted when reconfiguring it with this
2196method. 4273method.
4274.Sp
4275For \f(CW\*(C`ev::embed\*(C'\fR watchers this method is called \f(CW\*(C`set_embed\*(C'\fR, to avoid
4276clashing with the \f(CW\*(C`set (loop)\*(C'\fR method.
2197.IP "w\->start ()" 4 4277.IP "w\->start ()" 4
2198.IX Item "w->start ()" 4278.IX Item "w->start ()"
2199Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the 4279Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the
2200constructor already stores the event loop. 4280constructor already stores the event loop.
4281.IP "w\->start ([arguments])" 4
4282.IX Item "w->start ([arguments])"
4283Instead of calling \f(CW\*(C`set\*(C'\fR and \f(CW\*(C`start\*(C'\fR methods separately, it is often
4284convenient to wrap them in one call. Uses the same type of arguments as
4285the configure \f(CW\*(C`set\*(C'\fR method of the watcher.
2201.IP "w\->stop ()" 4 4286.IP "w\->stop ()" 4
2202.IX Item "w->stop ()" 4287.IX Item "w->stop ()"
2203Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument. 4288Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument.
2204.ie n .IP "w\->again () ""ev::timer""\fR, \f(CW""ev::periodic"" only" 4 4289.ie n .IP "w\->again () (""ev::timer"", ""ev::periodic"" only)" 4
2205.el .IP "w\->again () \f(CWev::timer\fR, \f(CWev::periodic\fR only" 4 4290.el .IP "w\->again () (\f(CWev::timer\fR, \f(CWev::periodic\fR only)" 4
2206.IX Item "w->again () ev::timer, ev::periodic only" 4291.IX Item "w->again () (ev::timer, ev::periodic only)"
2207For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding 4292For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding
2208\&\f(CW\*(C`ev_TYPE_again\*(C'\fR function. 4293\&\f(CW\*(C`ev_TYPE_again\*(C'\fR function.
2209.ie n .IP "w\->sweep () ""ev::embed"" only" 4 4294.ie n .IP "w\->sweep () (""ev::embed"" only)" 4
2210.el .IP "w\->sweep () \f(CWev::embed\fR only" 4 4295.el .IP "w\->sweep () (\f(CWev::embed\fR only)" 4
2211.IX Item "w->sweep () ev::embed only" 4296.IX Item "w->sweep () (ev::embed only)"
2212Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR. 4297Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR.
2213.ie n .IP "w\->update () ""ev::stat"" only" 4 4298.ie n .IP "w\->update () (""ev::stat"" only)" 4
2214.el .IP "w\->update () \f(CWev::stat\fR only" 4 4299.el .IP "w\->update () (\f(CWev::stat\fR only)" 4
2215.IX Item "w->update () ev::stat only" 4300.IX Item "w->update () (ev::stat only)"
2216Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR. 4301Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR.
2217.RE 4302.RE
2218.RS 4 4303.RS 4
2219.RE 4304.RE
2220.PP 4305.PP
2221Example: Define a class with an \s-1IO\s0 and idle watcher, start one of them in 4306Example: Define a class with two I/O and idle watchers, start the I/O
2222the constructor. 4307watchers in the constructor.
2223.PP 4308.PP
2224.Vb 4 4309.Vb 5
2225\& class myclass 4310\& class myclass
2226\& { 4311\& {
2227\& ev_io io; void io_cb (ev::io &w, int revents); 4312\& ev::io io ; void io_cb (ev::io &w, int revents);
4313\& ev::io io2 ; void io2_cb (ev::io &w, int revents);
2228\& ev_idle idle void idle_cb (ev::idle &w, int revents); 4314\& ev::idle idle; void idle_cb (ev::idle &w, int revents);
2229.Ve 4315\&
2230.PP
2231.Vb 2
2232\& myclass (); 4316\& myclass (int fd)
2233\& }
2234.Ve
2235.PP
2236.Vb 4
2237\& myclass::myclass (int fd)
2238\& { 4317\& {
2239\& io .set <myclass, &myclass::io_cb > (this); 4318\& io .set <myclass, &myclass::io_cb > (this);
4319\& io2 .set <myclass, &myclass::io2_cb > (this);
2240\& idle.set <myclass, &myclass::idle_cb> (this); 4320\& idle.set <myclass, &myclass::idle_cb> (this);
2241.Ve 4321\&
2242.PP 4322\& io.set (fd, ev::WRITE); // configure the watcher
2243.Vb 2 4323\& io.start (); // start it whenever convenient
2244\& io.start (fd, ev::READ); 4324\&
4325\& io2.start (fd, ev::READ); // set + start in one call
4326\& }
2245\& } 4327\& };
2246.Ve 4328.Ve
4329.SH "OTHER LANGUAGE BINDINGS"
4330.IX Header "OTHER LANGUAGE BINDINGS"
4331Libev does not offer other language bindings itself, but bindings for a
4332number of languages exist in the form of third-party packages. If you know
4333any interesting language binding in addition to the ones listed here, drop
4334me a note.
4335.IP "Perl" 4
4336.IX Item "Perl"
4337The \s-1EV\s0 module implements the full libev \s-1API\s0 and is actually used to test
4338libev. \s-1EV\s0 is developed together with libev. Apart from the \s-1EV\s0 core module,
4339there are additional modules that implement libev-compatible interfaces
4340to \f(CW\*(C`libadns\*(C'\fR (\f(CW\*(C`EV::ADNS\*(C'\fR, but \f(CW\*(C`AnyEvent::DNS\*(C'\fR is preferred nowadays),
4341\&\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
4342and \f(CW\*(C`EV::Glib\*(C'\fR).
4343.Sp
4344It can be found and installed via \s-1CPAN\s0, its homepage is at
4345<http://software.schmorp.de/pkg/EV>.
4346.IP "Python" 4
4347.IX Item "Python"
4348Python bindings can be found at <http://code.google.com/p/pyev/>. It
4349seems to be quite complete and well-documented.
4350.IP "Ruby" 4
4351.IX Item "Ruby"
4352Tony Arcieri has written a ruby extension that offers access to a subset
4353of the libev \s-1API\s0 and adds file handle abstractions, asynchronous \s-1DNS\s0 and
4354more on top of it. It can be found via gem servers. Its homepage is at
4355<http://rev.rubyforge.org/>.
4356.Sp
4357Roger Pack reports that using the link order \f(CW\*(C`\-lws2_32 \-lmsvcrt\-ruby\-190\*(C'\fR
4358makes rev work even on mingw.
4359.IP "Haskell" 4
4360.IX Item "Haskell"
4361A haskell binding to libev is available at
4362http://hackage.haskell.org/cgi\-bin/hackage\-scripts/package/hlibev <http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
4363.IP "D" 4
4364.IX Item "D"
4365Leandro Lucarella has written a D language binding (\fIev.d\fR) for libev, to
4366be found at <http://www.llucax.com.ar/proj/ev.d/index.html>.
4367.IP "Ocaml" 4
4368.IX Item "Ocaml"
4369Erkki Seppala has written Ocaml bindings for libev, to be found at
4370http://modeemi.cs.tut.fi/~flux/software/ocaml\-ev/ <http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
4371.IP "Lua" 4
4372.IX Item "Lua"
4373Brian Maher has written a partial interface to libev for lua (at the
4374time of this writing, only \f(CW\*(C`ev_io\*(C'\fR and \f(CW\*(C`ev_timer\*(C'\fR), to be found at
4375http://github.com/brimworks/lua\-ev <http://github.com/brimworks/lua-ev>.
4376.IP "Javascript" 4
4377.IX Item "Javascript"
4378Node.js (<http://nodejs.org>) uses libev as the underlying event library.
4379.IP "Others" 4
4380.IX Item "Others"
4381There are others, and I stopped counting.
2247.SH "MACRO MAGIC" 4382.SH "MACRO MAGIC"
2248.IX Header "MACRO MAGIC" 4383.IX Header "MACRO MAGIC"
2249Libev can be compiled with a variety of options, the most fundemantal is 4384Libev can be compiled with a variety of options, the most fundamental
2250\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most) functions and 4385of which is \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most)
2251callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument. 4386functions and callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument.
2252.PP 4387.PP
2253To make it easier to write programs that cope with either variant, the 4388To make it easier to write programs that cope with either variant, the
2254following macros are defined: 4389following macros are defined:
2255.ie n .IP """EV_A""\fR, \f(CW""EV_A_""" 4 4390.ie n .IP """EV_A"", ""EV_A_""" 4
2256.el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4 4391.el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4
2257.IX Item "EV_A, EV_A_" 4392.IX Item "EV_A, EV_A_"
2258This provides the loop \fIargument\fR for functions, if one is required (\*(L"ev 4393This provides the loop \fIargument\fR for functions, if one is required (\*(L"ev
2259loop argument\*(R"). The \f(CW\*(C`EV_A\*(C'\fR form is used when this is the sole argument, 4394loop argument\*(R"). The \f(CW\*(C`EV_A\*(C'\fR form is used when this is the sole argument,
2260\&\f(CW\*(C`EV_A_\*(C'\fR is used when other arguments are following. Example: 4395\&\f(CW\*(C`EV_A_\*(C'\fR is used when other arguments are following. Example:
2261.Sp 4396.Sp
2262.Vb 3 4397.Vb 3
2263\& ev_unref (EV_A); 4398\& ev_unref (EV_A);
2264\& ev_timer_add (EV_A_ watcher); 4399\& ev_timer_add (EV_A_ watcher);
2265\& ev_loop (EV_A_ 0); 4400\& ev_run (EV_A_ 0);
2266.Ve 4401.Ve
2267.Sp 4402.Sp
2268It assumes the variable \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR is in scope, 4403It assumes the variable \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR is in scope,
2269which is often provided by the following macro. 4404which is often provided by the following macro.
2270.ie n .IP """EV_P""\fR, \f(CW""EV_P_""" 4 4405.ie n .IP """EV_P"", ""EV_P_""" 4
2271.el .IP "\f(CWEV_P\fR, \f(CWEV_P_\fR" 4 4406.el .IP "\f(CWEV_P\fR, \f(CWEV_P_\fR" 4
2272.IX Item "EV_P, EV_P_" 4407.IX Item "EV_P, EV_P_"
2273This provides the loop \fIparameter\fR for functions, if one is required (\*(L"ev 4408This provides the loop \fIparameter\fR for functions, if one is required (\*(L"ev
2274loop parameter\*(R"). The \f(CW\*(C`EV_P\*(C'\fR form is used when this is the sole parameter, 4409loop parameter\*(R"). The \f(CW\*(C`EV_P\*(C'\fR form is used when this is the sole parameter,
2275\&\f(CW\*(C`EV_P_\*(C'\fR is used when other parameters are following. Example: 4410\&\f(CW\*(C`EV_P_\*(C'\fR is used when other parameters are following. Example:
2276.Sp 4411.Sp
2277.Vb 2 4412.Vb 2
2278\& // this is how ev_unref is being declared 4413\& // this is how ev_unref is being declared
2279\& static void ev_unref (EV_P); 4414\& static void ev_unref (EV_P);
2280.Ve 4415\&
2281.Sp
2282.Vb 2
2283\& // this is how you can declare your typical callback 4416\& // this is how you can declare your typical callback
2284\& static void cb (EV_P_ ev_timer *w, int revents) 4417\& static void cb (EV_P_ ev_timer *w, int revents)
2285.Ve 4418.Ve
2286.Sp 4419.Sp
2287It declares a parameter \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR, quite 4420It declares a parameter \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR, quite
2288suitable for use with \f(CW\*(C`EV_A\*(C'\fR. 4421suitable for use with \f(CW\*(C`EV_A\*(C'\fR.
2289.ie n .IP """EV_DEFAULT""\fR, \f(CW""EV_DEFAULT_""" 4 4422.ie n .IP """EV_DEFAULT"", ""EV_DEFAULT_""" 4
2290.el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4 4423.el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4
2291.IX Item "EV_DEFAULT, EV_DEFAULT_" 4424.IX Item "EV_DEFAULT, EV_DEFAULT_"
2292Similar to the other two macros, this gives you the value of the default 4425Similar to the other two macros, this gives you the value of the default
2293loop, if multiple loops are supported (\*(L"ev loop default\*(R"). 4426loop, if multiple loops are supported (\*(L"ev loop default\*(R"). The default loop
4427will be initialised if it isn't already initialised.
4428.Sp
4429For non-multiplicity builds, these macros do nothing, so you always have
4430to initialise the loop somewhere.
4431.ie n .IP """EV_DEFAULT_UC"", ""EV_DEFAULT_UC_""" 4
4432.el .IP "\f(CWEV_DEFAULT_UC\fR, \f(CWEV_DEFAULT_UC_\fR" 4
4433.IX Item "EV_DEFAULT_UC, EV_DEFAULT_UC_"
4434Usage identical to \f(CW\*(C`EV_DEFAULT\*(C'\fR and \f(CW\*(C`EV_DEFAULT_\*(C'\fR, but requires that the
4435default loop has been initialised (\f(CW\*(C`UC\*(C'\fR == unchecked). Their behaviour
4436is undefined when the default loop has not been initialised by a previous
4437execution of \f(CW\*(C`EV_DEFAULT\*(C'\fR, \f(CW\*(C`EV_DEFAULT_\*(C'\fR or \f(CW\*(C`ev_default_init (...)\*(C'\fR.
4438.Sp
4439It is often prudent to use \f(CW\*(C`EV_DEFAULT\*(C'\fR when initialising the first
4440watcher in a function but use \f(CW\*(C`EV_DEFAULT_UC\*(C'\fR afterwards.
2294.PP 4441.PP
2295Example: Declare and initialise a check watcher, utilising the above 4442Example: Declare and initialise a check watcher, utilising the above
2296macros so it will work regardless of whether multiple loops are supported 4443macros so it will work regardless of whether multiple loops are supported
2297or not. 4444or not.
2298.PP 4445.PP
2299.Vb 5 4446.Vb 5
2300\& static void 4447\& static void
2301\& check_cb (EV_P_ ev_timer *w, int revents) 4448\& check_cb (EV_P_ ev_timer *w, int revents)
2302\& { 4449\& {
2303\& ev_check_stop (EV_A_ w); 4450\& ev_check_stop (EV_A_ w);
2304\& } 4451\& }
2305.Ve 4452\&
2306.PP
2307.Vb 4
2308\& ev_check check; 4453\& ev_check check;
2309\& ev_check_init (&check, check_cb); 4454\& ev_check_init (&check, check_cb);
2310\& ev_check_start (EV_DEFAULT_ &check); 4455\& ev_check_start (EV_DEFAULT_ &check);
2311\& ev_loop (EV_DEFAULT_ 0); 4456\& ev_run (EV_DEFAULT_ 0);
2312.Ve 4457.Ve
2313.SH "EMBEDDING" 4458.SH "EMBEDDING"
2314.IX Header "EMBEDDING" 4459.IX Header "EMBEDDING"
2315Libev can (and often is) directly embedded into host 4460Libev can (and often is) directly embedded into host
2316applications. Examples of applications that embed it include the Deliantra 4461applications. Examples of applications that embed it include the Deliantra
2317Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe) 4462Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe)
2318and rxvt\-unicode. 4463and rxvt-unicode.
2319.PP 4464.PP
2320The goal is to enable you to just copy the neecssary files into your 4465The goal is to enable you to just copy the necessary files into your
2321source directory without having to change even a single line in them, so 4466source directory without having to change even a single line in them, so
2322you can easily upgrade by simply copying (or having a checked-out copy of 4467you can easily upgrade by simply copying (or having a checked-out copy of
2323libev somewhere in your source tree). 4468libev somewhere in your source tree).
2324.Sh "\s-1FILESETS\s0" 4469.SS "\s-1FILESETS\s0"
2325.IX Subsection "FILESETS" 4470.IX Subsection "FILESETS"
2326Depending on what features you need you need to include one or more sets of files 4471Depending on what features you need you need to include one or more sets of files
2327in your app. 4472in your application.
2328.PP 4473.PP
2329\fI\s-1CORE\s0 \s-1EVENT\s0 \s-1LOOP\s0\fR 4474\fI\s-1CORE\s0 \s-1EVENT\s0 \s-1LOOP\s0\fR
2330.IX Subsection "CORE EVENT LOOP" 4475.IX Subsection "CORE EVENT LOOP"
2331.PP 4476.PP
2332To include only the libev core (all the \f(CW\*(C`ev_*\*(C'\fR functions), with manual 4477To include only the libev core (all the \f(CW\*(C`ev_*\*(C'\fR functions), with manual
2333configuration (no autoconf): 4478configuration (no autoconf):
2334.PP 4479.PP
2335.Vb 2 4480.Vb 2
2336\& #define EV_STANDALONE 1 4481\& #define EV_STANDALONE 1
2337\& #include "ev.c" 4482\& #include "ev.c"
2338.Ve 4483.Ve
2339.PP 4484.PP
2340This will automatically include \fIev.h\fR, too, and should be done in a 4485This will automatically include \fIev.h\fR, too, and should be done in a
2341single C source file only to provide the function implementations. To use 4486single C source file only to provide the function implementations. To use
2342it, do the same for \fIev.h\fR in all files wishing to use this \s-1API\s0 (best 4487it, do the same for \fIev.h\fR in all files wishing to use this \s-1API\s0 (best
2343done by writing a wrapper around \fIev.h\fR that you can include instead and 4488done by writing a wrapper around \fIev.h\fR that you can include instead and
2344where you can put other configuration options): 4489where you can put other configuration options):
2345.PP 4490.PP
2346.Vb 2 4491.Vb 2
2347\& #define EV_STANDALONE 1 4492\& #define EV_STANDALONE 1
2348\& #include "ev.h" 4493\& #include "ev.h"
2349.Ve 4494.Ve
2350.PP 4495.PP
2351Both header files and implementation files can be compiled with a \*(C+ 4496Both header files and implementation files can be compiled with a \*(C+
2352compiler (at least, thats a stated goal, and breakage will be treated 4497compiler (at least, that's a stated goal, and breakage will be treated
2353as a bug). 4498as a bug).
2354.PP 4499.PP
2355You need the following files in your source tree, or in a directory 4500You need the following files in your source tree, or in a directory
2356in your include path (e.g. in libev/ when using \-Ilibev): 4501in your include path (e.g. in libev/ when using \-Ilibev):
2357.PP 4502.PP
2358.Vb 4 4503.Vb 4
2359\& ev.h 4504\& ev.h
2360\& ev.c 4505\& ev.c
2361\& ev_vars.h 4506\& ev_vars.h
2362\& ev_wrap.h 4507\& ev_wrap.h
2363.Ve 4508\&
2364.PP
2365.Vb 1
2366\& ev_win32.c required on win32 platforms only 4509\& ev_win32.c required on win32 platforms only
2367.Ve 4510\&
2368.PP
2369.Vb 5
2370\& ev_select.c only when select backend is enabled (which is enabled by default) 4511\& ev_select.c only when select backend is enabled (which is enabled by default)
2371\& ev_poll.c only when poll backend is enabled (disabled by default) 4512\& ev_poll.c only when poll backend is enabled (disabled by default)
2372\& ev_epoll.c only when the epoll backend is enabled (disabled by default) 4513\& ev_epoll.c only when the epoll backend is enabled (disabled by default)
2373\& ev_kqueue.c only when the kqueue backend is enabled (disabled by default) 4514\& ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2374\& ev_port.c only when the solaris port backend is enabled (disabled by default) 4515\& ev_port.c only when the solaris port backend is enabled (disabled by default)
2375.Ve 4516.Ve
2376.PP 4517.PP
2377\&\fIev.c\fR includes the backend files directly when enabled, so you only need 4518\&\fIev.c\fR includes the backend files directly when enabled, so you only need
2378to compile this single file. 4519to compile this single file.
2379.PP 4520.PP
… …
2381.IX Subsection "LIBEVENT COMPATIBILITY API" 4522.IX Subsection "LIBEVENT COMPATIBILITY API"
2382.PP 4523.PP
2383To include the libevent compatibility \s-1API\s0, also include: 4524To include the libevent compatibility \s-1API\s0, also include:
2384.PP 4525.PP
2385.Vb 1 4526.Vb 1
2386\& #include "event.c" 4527\& #include "event.c"
2387.Ve 4528.Ve
2388.PP 4529.PP
2389in the file including \fIev.c\fR, and: 4530in the file including \fIev.c\fR, and:
2390.PP 4531.PP
2391.Vb 1 4532.Vb 1
2392\& #include "event.h" 4533\& #include "event.h"
2393.Ve 4534.Ve
2394.PP 4535.PP
2395in the files that want to use the libevent \s-1API\s0. This also includes \fIev.h\fR. 4536in the files that want to use the libevent \s-1API\s0. This also includes \fIev.h\fR.
2396.PP 4537.PP
2397You need the following additional files for this: 4538You need the following additional files for this:
2398.PP 4539.PP
2399.Vb 2 4540.Vb 2
2400\& event.h 4541\& event.h
2401\& event.c 4542\& event.c
2402.Ve 4543.Ve
2403.PP 4544.PP
2404\fI\s-1AUTOCONF\s0 \s-1SUPPORT\s0\fR 4545\fI\s-1AUTOCONF\s0 \s-1SUPPORT\s0\fR
2405.IX Subsection "AUTOCONF SUPPORT" 4546.IX Subsection "AUTOCONF SUPPORT"
2406.PP 4547.PP
2407Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your config in 4548Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your configuration in
2408whatever way you want, you can also \f(CW\*(C`m4_include([libev.m4])\*(C'\fR in your 4549whatever way you want, you can also \f(CW\*(C`m4_include([libev.m4])\*(C'\fR in your
2409\&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR undefined. \fIev.c\fR will then 4550\&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR undefined. \fIev.c\fR will then
2410include \fIconfig.h\fR and configure itself accordingly. 4551include \fIconfig.h\fR and configure itself accordingly.
2411.PP 4552.PP
2412For this of course you need the m4 file: 4553For this of course you need the m4 file:
2413.PP 4554.PP
2414.Vb 1 4555.Vb 1
2415\& libev.m4 4556\& libev.m4
2416.Ve 4557.Ve
2417.Sh "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0" 4558.SS "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0"
2418.IX Subsection "PREPROCESSOR SYMBOLS/MACROS" 4559.IX Subsection "PREPROCESSOR SYMBOLS/MACROS"
2419Libev can be configured via a variety of preprocessor symbols you have to define 4560Libev can be configured via a variety of preprocessor symbols you have to
2420before including any of its files. The default is not to build for multiplicity 4561define before including (or compiling) any of its files. The default in
2421and only include the select backend. 4562the absence of autoconf is documented for every option.
4563.PP
4564Symbols marked with \*(L"(h)\*(R" do not change the \s-1ABI\s0, and can have different
4565values when compiling libev vs. including \fIev.h\fR, so it is permissible
4566to redefine them before including \fIev.h\fR without breaking compatibility
4567to a compiled library. All other symbols change the \s-1ABI\s0, which means all
4568users of libev and the libev code itself must be compiled with compatible
4569settings.
4570.IP "\s-1EV_COMPAT3\s0 (h)" 4
4571.IX Item "EV_COMPAT3 (h)"
4572Backwards compatibility is a major concern for libev. This is why this
4573release of libev comes with wrappers for the functions and symbols that
4574have been renamed between libev version 3 and 4.
4575.Sp
4576You can disable these wrappers (to test compatibility with future
4577versions) by defining \f(CW\*(C`EV_COMPAT3\*(C'\fR to \f(CW0\fR when compiling your
4578sources. This has the additional advantage that you can drop the \f(CW\*(C`struct\*(C'\fR
4579from \f(CW\*(C`struct ev_loop\*(C'\fR declarations, as libev will provide an \f(CW\*(C`ev_loop\*(C'\fR
4580typedef in that case.
4581.Sp
4582In some future version, the default for \f(CW\*(C`EV_COMPAT3\*(C'\fR will become \f(CW0\fR,
4583and in some even more future version the compatibility code will be
4584removed completely.
2422.IP "\s-1EV_STANDALONE\s0" 4 4585.IP "\s-1EV_STANDALONE\s0 (h)" 4
2423.IX Item "EV_STANDALONE" 4586.IX Item "EV_STANDALONE (h)"
2424Must always be \f(CW1\fR if you do not use autoconf configuration, which 4587Must always be \f(CW1\fR if you do not use autoconf configuration, which
2425keeps libev from including \fIconfig.h\fR, and it also defines dummy 4588keeps libev from including \fIconfig.h\fR, and it also defines dummy
2426implementations for some libevent functions (such as logging, which is not 4589implementations for some libevent functions (such as logging, which is not
2427supported). It will also not define any of the structs usually found in 4590supported). It will also not define any of the structs usually found in
2428\&\fIevent.h\fR that are not directly supported by the libev core alone. 4591\&\fIevent.h\fR that are not directly supported by the libev core alone.
4592.Sp
4593In standalone mode, libev will still try to automatically deduce the
4594configuration, but has to be more conservative.
4595.IP "\s-1EV_USE_FLOOR\s0" 4
4596.IX Item "EV_USE_FLOOR"
4597If defined to be \f(CW1\fR, libev will use the \f(CW\*(C`floor ()\*(C'\fR function for its
4598periodic reschedule calculations, otherwise libev will fall back on a
4599portable (slower) implementation. If you enable this, you usually have to
4600link against libm or something equivalent. Enabling this when the \f(CW\*(C`floor\*(C'\fR
4601function is not available will fail, so the safe default is to not enable
4602this.
2429.IP "\s-1EV_USE_MONOTONIC\s0" 4 4603.IP "\s-1EV_USE_MONOTONIC\s0" 4
2430.IX Item "EV_USE_MONOTONIC" 4604.IX Item "EV_USE_MONOTONIC"
2431If defined to be \f(CW1\fR, libev will try to detect the availability of the 4605If defined to be \f(CW1\fR, libev will try to detect the availability of the
2432monotonic clock option at both compiletime and runtime. Otherwise no use 4606monotonic clock option at both compile time and runtime. Otherwise no
2433of the monotonic clock option will be attempted. If you enable this, you 4607use of the monotonic clock option will be attempted. If you enable this,
2434usually have to link against librt or something similar. Enabling it when 4608you usually have to link against librt or something similar. Enabling it
2435the functionality isn't available is safe, though, althoguh you have 4609when the functionality isn't available is safe, though, although you have
2436to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR 4610to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR
2437function is hiding in (often \fI\-lrt\fR). 4611function is hiding in (often \fI\-lrt\fR). See also \f(CW\*(C`EV_USE_CLOCK_SYSCALL\*(C'\fR.
2438.IP "\s-1EV_USE_REALTIME\s0" 4 4612.IP "\s-1EV_USE_REALTIME\s0" 4
2439.IX Item "EV_USE_REALTIME" 4613.IX Item "EV_USE_REALTIME"
2440If defined to be \f(CW1\fR, libev will try to detect the availability of the 4614If defined to be \f(CW1\fR, libev will try to detect the availability of the
2441realtime clock option at compiletime (and assume its availability at 4615real-time clock option at compile time (and assume its availability
2442runtime if successful). Otherwise no use of the realtime clock option will 4616at runtime if successful). Otherwise no use of the real-time clock
2443be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get 4617option will be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR
2444(CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See tzhe note about libraries 4618by \f(CW\*(C`clock_get (CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect
2445in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though. 4619correctness. See the note about libraries in the description of
4620\&\f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though. Defaults to the opposite value of
4621\&\f(CW\*(C`EV_USE_CLOCK_SYSCALL\*(C'\fR.
4622.IP "\s-1EV_USE_CLOCK_SYSCALL\s0" 4
4623.IX Item "EV_USE_CLOCK_SYSCALL"
4624If defined to be \f(CW1\fR, libev will try to use a direct syscall instead
4625of calling the system-provided \f(CW\*(C`clock_gettime\*(C'\fR function. This option
4626exists 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
4627unconditionally pulls in \f(CW\*(C`libpthread\*(C'\fR, slowing down single-threaded
4628programs needlessly. Using a direct syscall is slightly slower (in
4629theory), because no optimised vdso implementation can be used, but avoids
4630the pthread dependency. Defaults to \f(CW1\fR on GNU/Linux with glibc 2.x or
4631higher, as it simplifies linking (no need for \f(CW\*(C`\-lrt\*(C'\fR).
4632.IP "\s-1EV_USE_NANOSLEEP\s0" 4
4633.IX Item "EV_USE_NANOSLEEP"
4634If defined to be \f(CW1\fR, libev will assume that \f(CW\*(C`nanosleep ()\*(C'\fR is available
4635and will use it for delays. Otherwise it will use \f(CW\*(C`select ()\*(C'\fR.
4636.IP "\s-1EV_USE_EVENTFD\s0" 4
4637.IX Item "EV_USE_EVENTFD"
4638If defined to be \f(CW1\fR, then libev will assume that \f(CW\*(C`eventfd ()\*(C'\fR is
4639available and will probe for kernel support at runtime. This will improve
4640\&\f(CW\*(C`ev_signal\*(C'\fR and \f(CW\*(C`ev_async\*(C'\fR performance and reduce resource consumption.
4641If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
46422.7 or newer, otherwise disabled.
2446.IP "\s-1EV_USE_SELECT\s0" 4 4643.IP "\s-1EV_USE_SELECT\s0" 4
2447.IX Item "EV_USE_SELECT" 4644.IX Item "EV_USE_SELECT"
2448If undefined or defined to be \f(CW1\fR, libev will compile in support for the 4645If undefined or defined to be \f(CW1\fR, libev will compile in support for the
2449\&\f(CW\*(C`select\*(C'\fR(2) backend. No attempt at autodetection will be done: if no 4646\&\f(CW\*(C`select\*(C'\fR(2) backend. No attempt at auto-detection will be done: if no
2450other method takes over, select will be it. Otherwise the select backend 4647other method takes over, select will be it. Otherwise the select backend
2451will not be compiled in. 4648will not be compiled in.
2452.IP "\s-1EV_SELECT_USE_FD_SET\s0" 4 4649.IP "\s-1EV_SELECT_USE_FD_SET\s0" 4
2453.IX Item "EV_SELECT_USE_FD_SET" 4650.IX Item "EV_SELECT_USE_FD_SET"
2454If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR 4651If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR
2455structure. This is useful if libev doesn't compile due to a missing 4652structure. This is useful if libev doesn't compile due to a missing
2456\&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it misguesses the bitset layout on 4653\&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it mis-guesses the bitset layout
2457exotic systems. This usually limits the range of file descriptors to some 4654on exotic systems. This usually limits the range of file descriptors to
2458low limit such as 1024 or might have other limitations (winsocket only 4655some low limit such as 1024 or might have other limitations (winsocket
2459allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation, might 4656only allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation,
2460influence the size of the \f(CW\*(C`fd_set\*(C'\fR used. 4657configures the maximum size of the \f(CW\*(C`fd_set\*(C'\fR.
2461.IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4 4658.IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4
2462.IX Item "EV_SELECT_IS_WINSOCKET" 4659.IX Item "EV_SELECT_IS_WINSOCKET"
2463When defined to \f(CW1\fR, the select backend will assume that 4660When defined to \f(CW1\fR, the select backend will assume that
2464select/socket/connect etc. don't understand file descriptors but 4661select/socket/connect etc. don't understand file descriptors but
2465wants osf handles on win32 (this is the case when the select to 4662wants osf handles on win32 (this is the case when the select to
2466be used is the winsock select). This means that it will call 4663be used is the winsock select). This means that it will call
2467\&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise, 4664\&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise,
2468it is assumed that all these functions actually work on fds, even 4665it is assumed that all these functions actually work on fds, even
2469on win32. Should not be defined on non\-win32 platforms. 4666on win32. Should not be defined on non\-win32 platforms.
4667.IP "\s-1EV_FD_TO_WIN32_HANDLE\s0(fd)" 4
4668.IX Item "EV_FD_TO_WIN32_HANDLE(fd)"
4669If \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR is enabled, then libev needs a way to map
4670file descriptors to socket handles. When not defining this symbol (the
4671default), then libev will call \f(CW\*(C`_get_osfhandle\*(C'\fR, which is usually
4672correct. In some cases, programs use their own file descriptor management,
4673in which case they can provide this function to map fds to socket handles.
4674.IP "\s-1EV_WIN32_HANDLE_TO_FD\s0(handle)" 4
4675.IX Item "EV_WIN32_HANDLE_TO_FD(handle)"
4676If \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR then libev maps handles to file descriptors
4677using the standard \f(CW\*(C`_open_osfhandle\*(C'\fR function. For programs implementing
4678their own fd to handle mapping, overwriting this function makes it easier
4679to do so. This can be done by defining this macro to an appropriate value.
4680.IP "\s-1EV_WIN32_CLOSE_FD\s0(fd)" 4
4681.IX Item "EV_WIN32_CLOSE_FD(fd)"
4682If programs implement their own fd to handle mapping on win32, then this
4683macro can be used to override the \f(CW\*(C`close\*(C'\fR function, useful to unregister
4684file descriptors again. Note that the replacement function has to close
4685the underlying \s-1OS\s0 handle.
4686.IP "\s-1EV_USE_WSASOCKET\s0" 4
4687.IX Item "EV_USE_WSASOCKET"
4688If defined to be \f(CW1\fR, libev will use \f(CW\*(C`WSASocket\*(C'\fR to create its internal
4689communication socket, which works better in some environments. Otherwise,
4690the normal \f(CW\*(C`socket\*(C'\fR function will be used, which works better in other
4691environments.
2470.IP "\s-1EV_USE_POLL\s0" 4 4692.IP "\s-1EV_USE_POLL\s0" 4
2471.IX Item "EV_USE_POLL" 4693.IX Item "EV_USE_POLL"
2472If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2) 4694If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2)
2473backend. Otherwise it will be enabled on non\-win32 platforms. It 4695backend. Otherwise it will be enabled on non\-win32 platforms. It
2474takes precedence over select. 4696takes precedence over select.
2475.IP "\s-1EV_USE_EPOLL\s0" 4 4697.IP "\s-1EV_USE_EPOLL\s0" 4
2476.IX Item "EV_USE_EPOLL" 4698.IX Item "EV_USE_EPOLL"
2477If defined to be \f(CW1\fR, libev will compile in support for the Linux 4699If defined to be \f(CW1\fR, libev will compile in support for the Linux
2478\&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime, 4700\&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime,
2479otherwise another method will be used as fallback. This is the 4701otherwise another method will be used as fallback. This is the preferred
2480preferred backend for GNU/Linux systems. 4702backend for GNU/Linux systems. If undefined, it will be enabled if the
4703headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2481.IP "\s-1EV_USE_KQUEUE\s0" 4 4704.IP "\s-1EV_USE_KQUEUE\s0" 4
2482.IX Item "EV_USE_KQUEUE" 4705.IX Item "EV_USE_KQUEUE"
2483If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style 4706If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style
2484\&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime, 4707\&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime,
2485otherwise another method will be used as fallback. This is the preferred 4708otherwise another method will be used as fallback. This is the preferred
… …
249510 port style backend. Its availability will be detected at runtime, 471810 port style backend. Its availability will be detected at runtime,
2496otherwise another method will be used as fallback. This is the preferred 4719otherwise another method will be used as fallback. This is the preferred
2497backend for Solaris 10 systems. 4720backend for Solaris 10 systems.
2498.IP "\s-1EV_USE_DEVPOLL\s0" 4 4721.IP "\s-1EV_USE_DEVPOLL\s0" 4
2499.IX Item "EV_USE_DEVPOLL" 4722.IX Item "EV_USE_DEVPOLL"
2500reserved for future expansion, works like the \s-1USE\s0 symbols above. 4723Reserved for future expansion, works like the \s-1USE\s0 symbols above.
2501.IP "\s-1EV_USE_INOTIFY\s0" 4 4724.IP "\s-1EV_USE_INOTIFY\s0" 4
2502.IX Item "EV_USE_INOTIFY" 4725.IX Item "EV_USE_INOTIFY"
2503If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify 4726If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify
2504interface to speed up \f(CW\*(C`ev_stat\*(C'\fR watchers. Its actual availability will 4727interface to speed up \f(CW\*(C`ev_stat\*(C'\fR watchers. Its actual availability will
2505be detected at runtime. 4728be detected at runtime. If undefined, it will be enabled if the headers
4729indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
4730.IP "\s-1EV_NO_SMP\s0" 4
4731.IX Item "EV_NO_SMP"
4732If defined to be \f(CW1\fR, libev will assume that memory is always coherent
4733between threads, that is, threads can be used, but threads never run on
4734different cpus (or different cpu cores). This reduces dependencies
4735and makes libev faster.
4736.IP "\s-1EV_NO_THREADS\s0" 4
4737.IX Item "EV_NO_THREADS"
4738If defined to be \f(CW1\fR, libev will assume that it will never be called from
4739different threads (that includes signal handlers), which is a stronger
4740assumption than \f(CW\*(C`EV_NO_SMP\*(C'\fR, above. This reduces dependencies and makes
4741libev faster.
4742.IP "\s-1EV_ATOMIC_T\s0" 4
4743.IX Item "EV_ATOMIC_T"
4744Libev requires an integer type (suitable for storing \f(CW0\fR or \f(CW1\fR) whose
4745access is atomic with respect to other threads or signal contexts. No
4746such type is easily found in the C language, so you can provide your own
4747type that you know is safe for your purposes. It is used both for signal
4748handler \*(L"locking\*(R" as well as for signal and thread safety in \f(CW\*(C`ev_async\*(C'\fR
4749watchers.
4750.Sp
4751In the absence of this define, libev will use \f(CW\*(C`sig_atomic_t volatile\*(C'\fR
4752(from \fIsignal.h\fR), which is usually good enough on most platforms.
2506.IP "\s-1EV_H\s0" 4 4753.IP "\s-1EV_H\s0 (h)" 4
2507.IX Item "EV_H" 4754.IX Item "EV_H (h)"
2508The name of the \fIev.h\fR header file used to include it. The default if 4755The name of the \fIev.h\fR header file used to include it. The default if
2509undefined is \f(CW\*(C`<ev.h>\*(C'\fR in \fIevent.h\fR and \f(CW"ev.h"\fR in \fIev.c\fR. This 4756undefined is \f(CW"ev.h"\fR in \fIevent.h\fR, \fIev.c\fR and \fIev++.h\fR. This can be
2510can be used to virtually rename the \fIev.h\fR header file in case of conflicts. 4757used to virtually rename the \fIev.h\fR header file in case of conflicts.
2511.IP "\s-1EV_CONFIG_H\s0" 4 4758.IP "\s-1EV_CONFIG_H\s0 (h)" 4
2512.IX Item "EV_CONFIG_H" 4759.IX Item "EV_CONFIG_H (h)"
2513If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override 4760If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override
2514\&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to 4761\&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to
2515\&\f(CW\*(C`EV_H\*(C'\fR, above. 4762\&\f(CW\*(C`EV_H\*(C'\fR, above.
2516.IP "\s-1EV_EVENT_H\s0" 4 4763.IP "\s-1EV_EVENT_H\s0 (h)" 4
2517.IX Item "EV_EVENT_H" 4764.IX Item "EV_EVENT_H (h)"
2518Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea 4765Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea
2519of how the \fIevent.h\fR header can be found. 4766of how the \fIevent.h\fR header can be found, the default is \f(CW"event.h"\fR.
2520.IP "\s-1EV_PROTOTYPES\s0" 4 4767.IP "\s-1EV_PROTOTYPES\s0 (h)" 4
2521.IX Item "EV_PROTOTYPES" 4768.IX Item "EV_PROTOTYPES (h)"
2522If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function 4769If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function
2523prototypes, but still define all the structs and other symbols. This is 4770prototypes, but still define all the structs and other symbols. This is
2524occasionally useful if you want to provide your own wrapper functions 4771occasionally useful if you want to provide your own wrapper functions
2525around libev functions. 4772around libev functions.
2526.IP "\s-1EV_MULTIPLICITY\s0" 4 4773.IP "\s-1EV_MULTIPLICITY\s0" 4
… …
2528If undefined or defined to \f(CW1\fR, then all event-loop-specific functions 4775If undefined or defined to \f(CW1\fR, then all event-loop-specific functions
2529will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create 4776will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create
2530additional independent event loops. Otherwise there will be no support 4777additional independent event loops. Otherwise there will be no support
2531for multiple event loops and there is no first event loop pointer 4778for multiple event loops and there is no first event loop pointer
2532argument. Instead, all functions act on the single default loop. 4779argument. Instead, all functions act on the single default loop.
4780.Sp
4781Note that \f(CW\*(C`EV_DEFAULT\*(C'\fR and \f(CW\*(C`EV_DEFAULT_\*(C'\fR will no longer provide a
4782default loop when multiplicity is switched off \- you always have to
4783initialise the loop manually in this case.
2533.IP "\s-1EV_MINPRI\s0" 4 4784.IP "\s-1EV_MINPRI\s0" 4
2534.IX Item "EV_MINPRI" 4785.IX Item "EV_MINPRI"
2535.PD 0 4786.PD 0
2536.IP "\s-1EV_MAXPRI\s0" 4 4787.IP "\s-1EV_MAXPRI\s0" 4
2537.IX Item "EV_MAXPRI" 4788.IX Item "EV_MAXPRI"
… …
2544When doing priority-based operations, libev usually has to linearly search 4795When doing priority-based operations, libev usually has to linearly search
2545all the priorities, so having many of them (hundreds) uses a lot of space 4796all the priorities, so having many of them (hundreds) uses a lot of space
2546and time, so using the defaults of five priorities (\-2 .. +2) is usually 4797and time, so using the defaults of five priorities (\-2 .. +2) is usually
2547fine. 4798fine.
2548.Sp 4799.Sp
2549If your embedding app does not need any priorities, defining these both to 4800If your embedding application does not need any priorities, defining these
2550\&\f(CW0\fR will save some memory and cpu. 4801both to \f(CW0\fR will save some memory and \s-1CPU\s0.
2551.IP "\s-1EV_PERIODIC_ENABLE\s0" 4 4802.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
2552.IX Item "EV_PERIODIC_ENABLE" 4803.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."
2553If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If 4804If undefined or defined to be \f(CW1\fR (and the platform supports it), then
2554defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of 4805the respective watcher type is supported. If defined to be \f(CW0\fR, then it
2555code. 4806is not. Disabling watcher types mainly saves code size.
2556.IP "\s-1EV_IDLE_ENABLE\s0" 4
2557.IX Item "EV_IDLE_ENABLE"
2558If undefined or defined to be \f(CW1\fR, then idle watchers are supported. If
2559defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
2560code.
2561.IP "\s-1EV_EMBED_ENABLE\s0" 4
2562.IX Item "EV_EMBED_ENABLE"
2563If undefined or defined to be \f(CW1\fR, then embed watchers are supported. If
2564defined to be \f(CW0\fR, then they are not.
2565.IP "\s-1EV_STAT_ENABLE\s0" 4 4807.IP "\s-1EV_FEATURES\s0" 4
2566.IX Item "EV_STAT_ENABLE" 4808.IX Item "EV_FEATURES"
2567If undefined or defined to be \f(CW1\fR, then stat watchers are supported. If
2568defined to be \f(CW0\fR, then they are not.
2569.IP "\s-1EV_FORK_ENABLE\s0" 4
2570.IX Item "EV_FORK_ENABLE"
2571If undefined or defined to be \f(CW1\fR, then fork watchers are supported. If
2572defined to be \f(CW0\fR, then they are not.
2573.IP "\s-1EV_MINIMAL\s0" 4
2574.IX Item "EV_MINIMAL"
2575If you need to shave off some kilobytes of code at the expense of some 4809If you need to shave off some kilobytes of code at the expense of some
2576speed, define this symbol to \f(CW1\fR. Currently only used for gcc to override 4810speed (but with the full \s-1API\s0), you can define this symbol to request
2577some inlining decisions, saves roughly 30% codesize of amd64. 4811certain subsets of functionality. The default is to enable all features
4812that can be enabled on the platform.
4813.Sp
4814A typical way to use this symbol is to define it to \f(CW0\fR (or to a bitset
4815with some broad features you want) and then selectively re-enable
4816additional parts you want, for example if you want everything minimal,
4817but multiple event loop support, async and child watchers and the poll
4818backend, use this:
4819.Sp
4820.Vb 5
4821\& #define EV_FEATURES 0
4822\& #define EV_MULTIPLICITY 1
4823\& #define EV_USE_POLL 1
4824\& #define EV_CHILD_ENABLE 1
4825\& #define EV_ASYNC_ENABLE 1
4826.Ve
4827.Sp
4828The actual value is a bitset, it can be a combination of the following
4829values (by default, all of these are enabled):
4830.RS 4
4831.ie n .IP "1 \- faster/larger code" 4
4832.el .IP "\f(CW1\fR \- faster/larger code" 4
4833.IX Item "1 - faster/larger code"
4834Use larger code to speed up some operations.
4835.Sp
4836Currently this is used to override some inlining decisions (enlarging the
4837code size by roughly 30% on amd64).
4838.Sp
4839When optimising for size, use of compiler flags such as \f(CW\*(C`\-Os\*(C'\fR with
4840gcc is recommended, as well as \f(CW\*(C`\-DNDEBUG\*(C'\fR, as libev contains a number of
4841assertions.
4842.Sp
4843The default is off when \f(CW\*(C`_\|_OPTIMIZE_SIZE_\|_\*(C'\fR is defined by your compiler
4844(e.g. gcc with \f(CW\*(C`\-Os\*(C'\fR).
4845.ie n .IP "2 \- faster/larger data structures" 4
4846.el .IP "\f(CW2\fR \- faster/larger data structures" 4
4847.IX Item "2 - faster/larger data structures"
4848Replaces the small 2\-heap for timer management by a faster 4\-heap, larger
4849hash table sizes and so on. This will usually further increase code size
4850and can additionally have an effect on the size of data structures at
4851runtime.
4852.Sp
4853The default is off when \f(CW\*(C`_\|_OPTIMIZE_SIZE_\|_\*(C'\fR is defined by your compiler
4854(e.g. gcc with \f(CW\*(C`\-Os\*(C'\fR).
4855.ie n .IP "4 \- full \s-1API\s0 configuration" 4
4856.el .IP "\f(CW4\fR \- full \s-1API\s0 configuration" 4
4857.IX Item "4 - full API configuration"
4858This enables priorities (sets \f(CW\*(C`EV_MAXPRI\*(C'\fR=2 and \f(CW\*(C`EV_MINPRI\*(C'\fR=\-2), and
4859enables multiplicity (\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR=1).
4860.ie n .IP "8 \- full \s-1API\s0" 4
4861.el .IP "\f(CW8\fR \- full \s-1API\s0" 4
4862.IX Item "8 - full API"
4863This enables a lot of the \*(L"lesser used\*(R" \s-1API\s0 functions. See \f(CW\*(C`ev.h\*(C'\fR for
4864details on which parts of the \s-1API\s0 are still available without this
4865feature, and do not complain if this subset changes over time.
4866.ie n .IP "16 \- enable all optional watcher types" 4
4867.el .IP "\f(CW16\fR \- enable all optional watcher types" 4
4868.IX Item "16 - enable all optional watcher types"
4869Enables all optional watcher types. If you want to selectively enable
4870only some watcher types other than I/O and timers (e.g. prepare,
4871embed, async, child...) you can enable them manually by defining
4872\&\f(CW\*(C`EV_watchertype_ENABLE\*(C'\fR to \f(CW1\fR instead.
4873.ie n .IP "32 \- enable all backends" 4
4874.el .IP "\f(CW32\fR \- enable all backends" 4
4875.IX Item "32 - enable all backends"
4876This enables all backends \- without this feature, you need to enable at
4877least one backend manually (\f(CW\*(C`EV_USE_SELECT\*(C'\fR is a good choice).
4878.ie n .IP "64 \- enable OS-specific ""helper"" APIs" 4
4879.el .IP "\f(CW64\fR \- enable OS-specific ``helper'' APIs" 4
4880.IX Item "64 - enable OS-specific helper APIs"
4881Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
4882default.
4883.RE
4884.RS 4
4885.Sp
4886Compiling with \f(CW\*(C`gcc \-Os \-DEV_STANDALONE \-DEV_USE_EPOLL=1 \-DEV_FEATURES=0\*(C'\fR
4887reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
4888code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
4889watchers, timers and monotonic clock support.
4890.Sp
4891With an intelligent-enough linker (gcc+binutils are intelligent enough
4892when you use \f(CW\*(C`\-Wl,\-\-gc\-sections \-ffunction\-sections\*(C'\fR) functions unused by
4893your program might be left out as well \- a binary starting a timer and an
4894I/O watcher then might come out at only 5Kb.
4895.RE
4896.IP "\s-1EV_API_STATIC\s0" 4
4897.IX Item "EV_API_STATIC"
4898If this symbol is defined (by default it is not), then all identifiers
4899will have static linkage. This means that libev will not export any
4900identifiers, and you cannot link against libev anymore. This can be useful
4901when you embed libev, only want to use libev functions in a single file,
4902and do not want its identifiers to be visible.
4903.Sp
4904To use this, define \f(CW\*(C`EV_API_STATIC\*(C'\fR and include \fIev.c\fR in the file that
4905wants to use libev.
4906.Sp
4907This option only works when libev is compiled with a C compiler, as \*(C+
4908doesn't support the required declaration syntax.
4909.IP "\s-1EV_AVOID_STDIO\s0" 4
4910.IX Item "EV_AVOID_STDIO"
4911If this is set to \f(CW1\fR at compiletime, then libev will avoid using stdio
4912functions (printf, scanf, perror etc.). This will increase the code size
4913somewhat, but if your program doesn't otherwise depend on stdio and your
4914libc allows it, this avoids linking in the stdio library which is quite
4915big.
4916.Sp
4917Note that error messages might become less precise when this option is
4918enabled.
4919.IP "\s-1EV_NSIG\s0" 4
4920.IX Item "EV_NSIG"
4921The highest supported signal number, +1 (or, the number of
4922signals): Normally, libev tries to deduce the maximum number of signals
4923automatically, but sometimes this fails, in which case it can be
4924specified. Also, using a lower number than detected (\f(CW32\fR should be
4925good for about any system in existence) can save some memory, as libev
4926statically allocates some 12\-24 bytes per signal number.
2578.IP "\s-1EV_PID_HASHSIZE\s0" 4 4927.IP "\s-1EV_PID_HASHSIZE\s0" 4
2579.IX Item "EV_PID_HASHSIZE" 4928.IX Item "EV_PID_HASHSIZE"
2580\&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by 4929\&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by
2581pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), usually more 4930pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_FEATURES\*(C'\fR disabled),
2582than enough. If you need to manage thousands of children you might want to 4931usually more than enough. If you need to manage thousands of children you
2583increase this value (\fImust\fR be a power of two). 4932might want to increase this value (\fImust\fR be a power of two).
2584.IP "\s-1EV_INOTIFY_HASHSIZE\s0" 4 4933.IP "\s-1EV_INOTIFY_HASHSIZE\s0" 4
2585.IX Item "EV_INOTIFY_HASHSIZE" 4934.IX Item "EV_INOTIFY_HASHSIZE"
2586\&\f(CW\*(C`ev_staz\*(C'\fR watchers use a small hash table to distribute workload by 4935\&\f(CW\*(C`ev_stat\*(C'\fR watchers use a small hash table to distribute workload by
2587inotify watch id. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), 4936inotify watch id. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_FEATURES\*(C'\fR
2588usually more than enough. If you need to manage thousands of \f(CW\*(C`ev_stat\*(C'\fR 4937disabled), usually more than enough. If you need to manage thousands of
2589watchers you might want to increase this value (\fImust\fR be a power of 4938\&\f(CW\*(C`ev_stat\*(C'\fR watchers you might want to increase this value (\fImust\fR be a
2590two). 4939power of two).
4940.IP "\s-1EV_USE_4HEAP\s0" 4
4941.IX Item "EV_USE_4HEAP"
4942Heaps are not very cache-efficient. To improve the cache-efficiency of the
4943timer and periodics heaps, libev uses a 4\-heap when this symbol is defined
4944to \f(CW1\fR. The 4\-heap uses more complicated (longer) code but has noticeably
4945faster performance with many (thousands) of watchers.
4946.Sp
4947The default is \f(CW1\fR, unless \f(CW\*(C`EV_FEATURES\*(C'\fR overrides it, in which case it
4948will be \f(CW0\fR.
4949.IP "\s-1EV_HEAP_CACHE_AT\s0" 4
4950.IX Item "EV_HEAP_CACHE_AT"
4951Heaps are not very cache-efficient. To improve the cache-efficiency of the
4952timer and periodics heaps, libev can cache the timestamp (\fIat\fR) within
4953the heap structure (selected by defining \f(CW\*(C`EV_HEAP_CACHE_AT\*(C'\fR to \f(CW1\fR),
4954which uses 8\-12 bytes more per watcher and a few hundred bytes more code,
4955but avoids random read accesses on heap changes. This improves performance
4956noticeably with many (hundreds) of watchers.
4957.Sp
4958The default is \f(CW1\fR, unless \f(CW\*(C`EV_FEATURES\*(C'\fR overrides it, in which case it
4959will be \f(CW0\fR.
4960.IP "\s-1EV_VERIFY\s0" 4
4961.IX Item "EV_VERIFY"
4962Controls how much internal verification (see \f(CW\*(C`ev_verify ()\*(C'\fR) will
4963be done: If set to \f(CW0\fR, no internal verification code will be compiled
4964in. If set to \f(CW1\fR, then verification code will be compiled in, but not
4965called. If set to \f(CW2\fR, then the internal verification code will be
4966called once per loop, which can slow down libev. If set to \f(CW3\fR, then the
4967verification code will be called very frequently, which will slow down
4968libev considerably.
4969.Sp
4970The default is \f(CW1\fR, unless \f(CW\*(C`EV_FEATURES\*(C'\fR overrides it, in which case it
4971will be \f(CW0\fR.
2591.IP "\s-1EV_COMMON\s0" 4 4972.IP "\s-1EV_COMMON\s0" 4
2592.IX Item "EV_COMMON" 4973.IX Item "EV_COMMON"
2593By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining 4974By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining
2594this macro to a something else you can include more and other types of 4975this macro to something else you can include more and other types of
2595members. You have to define it each time you include one of the files, 4976members. You have to define it each time you include one of the files,
2596though, and it must be identical each time. 4977though, and it must be identical each time.
2597.Sp 4978.Sp
2598For example, the perl \s-1EV\s0 module uses something like this: 4979For example, the perl \s-1EV\s0 module uses something like this:
2599.Sp 4980.Sp
2600.Vb 3 4981.Vb 3
2601\& #define EV_COMMON \e 4982\& #define EV_COMMON \e
2602\& SV *self; /* contains this struct */ \e 4983\& SV *self; /* contains this struct */ \e
2603\& SV *cb_sv, *fh /* note no trailing ";" */ 4984\& SV *cb_sv, *fh /* note no trailing ";" */
2604.Ve 4985.Ve
2605.IP "\s-1EV_CB_DECLARE\s0 (type)" 4 4986.IP "\s-1EV_CB_DECLARE\s0 (type)" 4
2606.IX Item "EV_CB_DECLARE (type)" 4987.IX Item "EV_CB_DECLARE (type)"
2607.PD 0 4988.PD 0
2608.IP "\s-1EV_CB_INVOKE\s0 (watcher, revents)" 4 4989.IP "\s-1EV_CB_INVOKE\s0 (watcher, revents)" 4
… …
2610.IP "ev_set_cb (ev, cb)" 4 4991.IP "ev_set_cb (ev, cb)" 4
2611.IX Item "ev_set_cb (ev, cb)" 4992.IX Item "ev_set_cb (ev, cb)"
2612.PD 4993.PD
2613Can be used to change the callback member declaration in each watcher, 4994Can be used to change the callback member declaration in each watcher,
2614and the way callbacks are invoked and set. Must expand to a struct member 4995and the way callbacks are invoked and set. Must expand to a struct member
2615definition and a statement, respectively. See the \fIev.v\fR header file for 4996definition and a statement, respectively. See the \fIev.h\fR header file for
2616their default definitions. One possible use for overriding these is to 4997their default definitions. One possible use for overriding these is to
2617avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use 4998avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use
2618method calls instead of plain function calls in \*(C+. 4999method calls instead of plain function calls in \*(C+.
5000.SS "\s-1EXPORTED\s0 \s-1API\s0 \s-1SYMBOLS\s0"
5001.IX Subsection "EXPORTED API SYMBOLS"
5002If you need to re-export the \s-1API\s0 (e.g. via a \s-1DLL\s0) and you need a list of
5003exported symbols, you can use the provided \fISymbol.*\fR files which list
5004all public symbols, one per line:
5005.PP
5006.Vb 2
5007\& Symbols.ev for libev proper
5008\& Symbols.event for the libevent emulation
5009.Ve
5010.PP
5011This can also be used to rename all public symbols to avoid clashes with
5012multiple versions of libev linked together (which is obviously bad in
5013itself, but sometimes it is inconvenient to avoid this).
5014.PP
5015A sed command like this will create wrapper \f(CW\*(C`#define\*(C'\fR's that you need to
5016include before including \fIev.h\fR:
5017.PP
5018.Vb 1
5019\& <Symbols.ev sed \-e "s/.*/#define & myprefix_&/" >wrap.h
5020.Ve
5021.PP
5022This would create a file \fIwrap.h\fR which essentially looks like this:
5023.PP
5024.Vb 4
5025\& #define ev_backend myprefix_ev_backend
5026\& #define ev_check_start myprefix_ev_check_start
5027\& #define ev_check_stop myprefix_ev_check_stop
5028\& ...
5029.Ve
2619.Sh "\s-1EXAMPLES\s0" 5030.SS "\s-1EXAMPLES\s0"
2620.IX Subsection "EXAMPLES" 5031.IX Subsection "EXAMPLES"
2621For a real-world example of a program the includes libev 5032For a real-world example of a program the includes libev
2622verbatim, you can have a look at the \s-1EV\s0 perl module 5033verbatim, you can have a look at the \s-1EV\s0 perl module
2623(<http://software.schmorp.de/pkg/EV.html>). It has the libev files in 5034(<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
2624the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public 5035the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public
2625interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file 5036interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file
2626will be compiled. It is pretty complex because it provides its own header 5037will be compiled. It is pretty complex because it provides its own header
2627file. 5038file.
2628.Sp 5039.PP
2629The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file 5040The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file
2630that everybody includes and which overrides some configure choices: 5041that everybody includes and which overrides some configure choices:
2631.Sp 5042.PP
2632.Vb 9 5043.Vb 8
2633\& #define EV_MINIMAL 1 5044\& #define EV_FEATURES 8
2634\& #define EV_USE_POLL 0 5045\& #define EV_USE_SELECT 1
2635\& #define EV_MULTIPLICITY 0
2636\& #define EV_PERIODIC_ENABLE 0 5046\& #define EV_PREPARE_ENABLE 1
5047\& #define EV_IDLE_ENABLE 1
2637\& #define EV_STAT_ENABLE 0 5048\& #define EV_SIGNAL_ENABLE 1
2638\& #define EV_FORK_ENABLE 0 5049\& #define EV_CHILD_ENABLE 1
5050\& #define EV_USE_STDEXCEPT 0
2639\& #define EV_CONFIG_H <config.h> 5051\& #define EV_CONFIG_H <config.h>
2640\& #define EV_MINPRI 0 5052\&
2641\& #define EV_MAXPRI 0
2642.Ve
2643.Sp
2644.Vb 1
2645\& #include "ev++.h" 5053\& #include "ev++.h"
2646.Ve 5054.Ve
2647.Sp 5055.PP
2648And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled: 5056And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled:
2649.Sp 5057.PP
2650.Vb 2 5058.Vb 2
2651\& #include "ev_cpp.h" 5059\& #include "ev_cpp.h"
2652\& #include "ev.c" 5060\& #include "ev.c"
2653.Ve 5061.Ve
5062.SH "INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT"
5063.IX Header "INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT"
5064.SS "\s-1THREADS\s0 \s-1AND\s0 \s-1COROUTINES\s0"
5065.IX Subsection "THREADS AND COROUTINES"
5066\fI\s-1THREADS\s0\fR
5067.IX Subsection "THREADS"
5068.PP
5069All libev functions are reentrant and thread-safe unless explicitly
5070documented otherwise, but libev implements no locking itself. This means
5071that you can use as many loops as you want in parallel, as long as there
5072are no concurrent calls into any libev function with the same loop
5073parameter (\f(CW\*(C`ev_default_*\*(C'\fR calls have an implicit default loop parameter,
5074of course): libev guarantees that different event loops share no data
5075structures that need any locking.
5076.PP
5077Or to put it differently: calls with different loop parameters can be done
5078concurrently from multiple threads, calls with the same loop parameter
5079must be done serially (but can be done from different threads, as long as
5080only one thread ever is inside a call at any point in time, e.g. by using
5081a mutex per loop).
5082.PP
5083Specifically to support threads (and signal handlers), libev implements
5084so-called \f(CW\*(C`ev_async\*(C'\fR watchers, which allow some limited form of
5085concurrency on the same event loop, namely waking it up \*(L"from the
5086outside\*(R".
5087.PP
5088If you want to know which design (one loop, locking, or multiple loops
5089without or something else still) is best for your problem, then I cannot
5090help you, but here is some generic advice:
5091.IP "\(bu" 4
5092most applications have a main thread: use the default libev loop
5093in that thread, or create a separate thread running only the default loop.
5094.Sp
5095This helps integrating other libraries or software modules that use libev
5096themselves and don't care/know about threading.
5097.IP "\(bu" 4
5098one loop per thread is usually a good model.
5099.Sp
5100Doing this is almost never wrong, sometimes a better-performance model
5101exists, but it is always a good start.
5102.IP "\(bu" 4
5103other models exist, such as the leader/follower pattern, where one
5104loop is handed through multiple threads in a kind of round-robin fashion.
5105.Sp
5106Choosing a model is hard \- look around, learn, know that usually you can do
5107better than you currently do :\-)
5108.IP "\(bu" 4
5109often you need to talk to some other thread which blocks in the
5110event loop.
5111.Sp
5112\&\f(CW\*(C`ev_async\*(C'\fR watchers can be used to wake them up from other threads safely
5113(or from signal contexts...).
5114.Sp
5115An example use would be to communicate signals or other events that only
5116work in the default loop by registering the signal watcher with the
5117default loop and triggering an \f(CW\*(C`ev_async\*(C'\fR watcher from the default loop
5118watcher callback into the event loop interested in the signal.
5119.PP
5120See also \*(L"\s-1THREAD\s0 \s-1LOCKING\s0 \s-1EXAMPLE\s0\*(R".
5121.PP
5122\fI\s-1COROUTINES\s0\fR
5123.IX Subsection "COROUTINES"
5124.PP
5125Libev is very accommodating to coroutines (\*(L"cooperative threads\*(R"):
5126libev fully supports nesting calls to its functions from different
5127coroutines (e.g. you can call \f(CW\*(C`ev_run\*(C'\fR on the same loop from two
5128different coroutines, and switch freely between both coroutines running
5129the loop, as long as you don't confuse yourself). The only exception is
5130that you must not do this from \f(CW\*(C`ev_periodic\*(C'\fR reschedule callbacks.
5131.PP
5132Care has been taken to ensure that libev does not keep local state inside
5133\&\f(CW\*(C`ev_run\*(C'\fR, and other calls do not usually allow for coroutine switches as
5134they do not call any callbacks.
5135.SS "\s-1COMPILER\s0 \s-1WARNINGS\s0"
5136.IX Subsection "COMPILER WARNINGS"
5137Depending on your compiler and compiler settings, you might get no or a
5138lot of warnings when compiling libev code. Some people are apparently
5139scared by this.
5140.PP
5141However, these are unavoidable for many reasons. For one, each compiler
5142has different warnings, and each user has different tastes regarding
5143warning options. \*(L"Warn-free\*(R" code therefore cannot be a goal except when
5144targeting a specific compiler and compiler-version.
5145.PP
5146Another reason is that some compiler warnings require elaborate
5147workarounds, or other changes to the code that make it less clear and less
5148maintainable.
5149.PP
5150And of course, some compiler warnings are just plain stupid, or simply
5151wrong (because they don't actually warn about the condition their message
5152seems to warn about). For example, certain older gcc versions had some
5153warnings that resulted in an extreme number of false positives. These have
5154been fixed, but some people still insist on making code warn-free with
5155such buggy versions.
5156.PP
5157While libev is written to generate as few warnings as possible,
5158\&\*(L"warn-free\*(R" code is not a goal, and it is recommended not to build libev
5159with any compiler warnings enabled unless you are prepared to cope with
5160them (e.g. by ignoring them). Remember that warnings are just that:
5161warnings, not errors, or proof of bugs.
5162.SS "\s-1VALGRIND\s0"
5163.IX Subsection "VALGRIND"
5164Valgrind has a special section here because it is a popular tool that is
5165highly useful. Unfortunately, valgrind reports are very hard to interpret.
5166.PP
5167If you think you found a bug (memory leak, uninitialised data access etc.)
5168in libev, then check twice: If valgrind reports something like:
5169.PP
5170.Vb 3
5171\& ==2274== definitely lost: 0 bytes in 0 blocks.
5172\& ==2274== possibly lost: 0 bytes in 0 blocks.
5173\& ==2274== still reachable: 256 bytes in 1 blocks.
5174.Ve
5175.PP
5176Then there is no memory leak, just as memory accounted to global variables
5177is not a memleak \- the memory is still being referenced, and didn't leak.
5178.PP
5179Similarly, under some circumstances, valgrind might report kernel bugs
5180as if it were a bug in libev (e.g. in realloc or in the poll backend,
5181although an acceptable workaround has been found here), or it might be
5182confused.
5183.PP
5184Keep in mind that valgrind is a very good tool, but only a tool. Don't
5185make it into some kind of religion.
5186.PP
5187If you are unsure about something, feel free to contact the mailing list
5188with the full valgrind report and an explanation on why you think this
5189is a bug in libev (best check the archives, too :). However, don't be
5190annoyed when you get a brisk \*(L"this is no bug\*(R" answer and take the chance
5191of learning how to interpret valgrind properly.
5192.PP
5193If you need, for some reason, empty reports from valgrind for your project
5194I suggest using suppression lists.
5195.SH "PORTABILITY NOTES"
5196.IX Header "PORTABILITY NOTES"
5197.SS "\s-1GNU/LINUX\s0 32 \s-1BIT\s0 \s-1LIMITATIONS\s0"
5198.IX Subsection "GNU/LINUX 32 BIT LIMITATIONS"
5199GNU/Linux is the only common platform that supports 64 bit file/large file
5200interfaces but \fIdisables\fR them by default.
5201.PP
5202That means that libev compiled in the default environment doesn't support
5203files larger than 2GiB or so, which mainly affects \f(CW\*(C`ev_stat\*(C'\fR watchers.
5204.PP
5205Unfortunately, many programs try to work around this GNU/Linux issue
5206by enabling the large file \s-1API\s0, which makes them incompatible with the
5207standard libev compiled for their system.
5208.PP
5209Likewise, libev cannot enable the large file \s-1API\s0 itself as this would
5210suddenly make it incompatible to the default compile time environment,
5211i.e. all programs not using special compile switches.
5212.SS "\s-1OS/X\s0 \s-1AND\s0 \s-1DARWIN\s0 \s-1BUGS\s0"
5213.IX Subsection "OS/X AND DARWIN BUGS"
5214The whole thing is a bug if you ask me \- basically any system interface
5215you touch is broken, whether it is locales, poll, kqueue or even the
5216OpenGL drivers.
5217.PP
5218\fI\f(CI\*(C`kqueue\*(C'\fI is buggy\fR
5219.IX Subsection "kqueue is buggy"
5220.PP
5221The kqueue syscall is broken in all known versions \- most versions support
5222only sockets, many support pipes.
5223.PP
5224Libev tries to work around this by not using \f(CW\*(C`kqueue\*(C'\fR by default on this
5225rotten platform, but of course you can still ask for it when creating a
5226loop \- embedding a socket-only kqueue loop into a select-based one is
5227probably going to work well.
5228.PP
5229\fI\f(CI\*(C`poll\*(C'\fI is buggy\fR
5230.IX Subsection "poll is buggy"
5231.PP
5232Instead of fixing \f(CW\*(C`kqueue\*(C'\fR, Apple replaced their (working) \f(CW\*(C`poll\*(C'\fR
5233implementation by something calling \f(CW\*(C`kqueue\*(C'\fR internally around the 10.5.6
5234release, so now \f(CW\*(C`kqueue\*(C'\fR \fIand\fR \f(CW\*(C`poll\*(C'\fR are broken.
5235.PP
5236Libev tries to work around this by not using \f(CW\*(C`poll\*(C'\fR by default on
5237this rotten platform, but of course you can still ask for it when creating
5238a loop.
5239.PP
5240\fI\f(CI\*(C`select\*(C'\fI is buggy\fR
5241.IX Subsection "select is buggy"
5242.PP
5243All that's left is \f(CW\*(C`select\*(C'\fR, and of course Apple found a way to fuck this
5244one up as well: On \s-1OS/X\s0, \f(CW\*(C`select\*(C'\fR actively limits the number of file
5245descriptors you can pass in to 1024 \- your program suddenly crashes when
5246you use more.
5247.PP
5248There is an undocumented \*(L"workaround\*(R" for this \- defining
5249\&\f(CW\*(C`_DARWIN_UNLIMITED_SELECT\*(C'\fR, which libev tries to use, so select \fIshould\fR
5250work on \s-1OS/X\s0.
5251.SS "\s-1SOLARIS\s0 \s-1PROBLEMS\s0 \s-1AND\s0 \s-1WORKAROUNDS\s0"
5252.IX Subsection "SOLARIS PROBLEMS AND WORKAROUNDS"
5253\fI\f(CI\*(C`errno\*(C'\fI reentrancy\fR
5254.IX Subsection "errno reentrancy"
5255.PP
5256The default compile environment on Solaris is unfortunately so
5257thread-unsafe that you can't even use components/libraries compiled
5258without \f(CW\*(C`\-D_REENTRANT\*(C'\fR in a threaded program, which, of course, isn't
5259defined by default. A valid, if stupid, implementation choice.
5260.PP
5261If you want to use libev in threaded environments you have to make sure
5262it's compiled with \f(CW\*(C`_REENTRANT\*(C'\fR defined.
5263.PP
5264\fIEvent port backend\fR
5265.IX Subsection "Event port backend"
5266.PP
5267The scalable event interface for Solaris is called \*(L"event
5268ports\*(R". Unfortunately, this mechanism is very buggy in all major
5269releases. If you run into high \s-1CPU\s0 usage, your program freezes or you get
5270a large number of spurious wakeups, make sure you have all the relevant
5271and latest kernel patches applied. No, I don't know which ones, but there
5272are multiple ones to apply, and afterwards, event ports actually work
5273great.
5274.PP
5275If you can't get it to work, you can try running the program by setting
5276the environment variable \f(CW\*(C`LIBEV_FLAGS=3\*(C'\fR to only allow \f(CW\*(C`poll\*(C'\fR and
5277\&\f(CW\*(C`select\*(C'\fR backends.
5278.SS "\s-1AIX\s0 \s-1POLL\s0 \s-1BUG\s0"
5279.IX Subsection "AIX POLL BUG"
5280\&\s-1AIX\s0 unfortunately has a broken \f(CW\*(C`poll.h\*(C'\fR header. Libev works around
5281this by trying to avoid the poll backend altogether (i.e. it's not even
5282compiled in), which normally isn't a big problem as \f(CW\*(C`select\*(C'\fR works fine
5283with large bitsets on \s-1AIX\s0, and \s-1AIX\s0 is dead anyway.
5284.SS "\s-1WIN32\s0 \s-1PLATFORM\s0 \s-1LIMITATIONS\s0 \s-1AND\s0 \s-1WORKAROUNDS\s0"
5285.IX Subsection "WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS"
5286\fIGeneral issues\fR
5287.IX Subsection "General issues"
5288.PP
5289Win32 doesn't support any of the standards (e.g. \s-1POSIX\s0) that libev
5290requires, and its I/O model is fundamentally incompatible with the \s-1POSIX\s0
5291model. Libev still offers limited functionality on this platform in
5292the form of the \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR backend, and only supports socket
5293descriptors. This only applies when using Win32 natively, not when using
5294e.g. cygwin. Actually, it only applies to the microsofts own compilers,
5295as every compiler comes with a slightly differently broken/incompatible
5296environment.
5297.PP
5298Lifting these limitations would basically require the full
5299re-implementation of the I/O system. If you are into this kind of thing,
5300then note that glib does exactly that for you in a very portable way (note
5301also that glib is the slowest event library known to man).
5302.PP
5303There is no supported compilation method available on windows except
5304embedding it into other applications.
5305.PP
5306Sensible signal handling is officially unsupported by Microsoft \- libev
5307tries its best, but under most conditions, signals will simply not work.
5308.PP
5309Not a libev limitation but worth mentioning: windows apparently doesn't
5310accept large writes: instead of resulting in a partial write, windows will
5311either accept everything or return \f(CW\*(C`ENOBUFS\*(C'\fR if the buffer is too large,
5312so make sure you only write small amounts into your sockets (less than a
5313megabyte seems safe, but this apparently depends on the amount of memory
5314available).
5315.PP
5316Due to the many, low, and arbitrary limits on the win32 platform and
5317the abysmal performance of winsockets, using a large number of sockets
5318is not recommended (and not reasonable). If your program needs to use
5319more than a hundred or so sockets, then likely it needs to use a totally
5320different implementation for windows, as libev offers the \s-1POSIX\s0 readiness
5321notification model, which cannot be implemented efficiently on windows
5322(due to Microsoft monopoly games).
5323.PP
5324A typical way to use libev under windows is to embed it (see the embedding
5325section for details) and use the following \fIevwrap.h\fR header file instead
5326of \fIev.h\fR:
5327.PP
5328.Vb 2
5329\& #define EV_STANDALONE /* keeps ev from requiring config.h */
5330\& #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
5331\&
5332\& #include "ev.h"
5333.Ve
5334.PP
5335And compile the following \fIevwrap.c\fR file into your project (make sure
5336you do \fInot\fR compile the \fIev.c\fR or any other embedded source files!):
5337.PP
5338.Vb 2
5339\& #include "evwrap.h"
5340\& #include "ev.c"
5341.Ve
5342.PP
5343\fIThe winsocket \f(CI\*(C`select\*(C'\fI function\fR
5344.IX Subsection "The winsocket select function"
5345.PP
5346The winsocket \f(CW\*(C`select\*(C'\fR function doesn't follow \s-1POSIX\s0 in that it
5347requires socket \fIhandles\fR and not socket \fIfile descriptors\fR (it is
5348also extremely buggy). This makes select very inefficient, and also
5349requires a mapping from file descriptors to socket handles (the Microsoft
5350C runtime provides the function \f(CW\*(C`_open_osfhandle\*(C'\fR for this). See the
5351discussion of the \f(CW\*(C`EV_SELECT_USE_FD_SET\*(C'\fR, \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR and
5352\&\f(CW\*(C`EV_FD_TO_WIN32_HANDLE\*(C'\fR preprocessor symbols for more info.
5353.PP
5354The configuration for a \*(L"naked\*(R" win32 using the Microsoft runtime
5355libraries and raw winsocket select is:
5356.PP
5357.Vb 2
5358\& #define EV_USE_SELECT 1
5359\& #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
5360.Ve
5361.PP
5362Note that winsockets handling of fd sets is O(n), so you can easily get a
5363complexity in the O(nA\*^X) range when using win32.
5364.PP
5365\fILimited number of file descriptors\fR
5366.IX Subsection "Limited number of file descriptors"
5367.PP
5368Windows has numerous arbitrary (and low) limits on things.
5369.PP
5370Early versions of winsocket's select only supported waiting for a maximum
5371of \f(CW64\fR handles (probably owning to the fact that all windows kernels
5372can only wait for \f(CW64\fR things at the same time internally; Microsoft
5373recommends spawning a chain of threads and wait for 63 handles and the
5374previous thread in each. Sounds great!).
5375.PP
5376Newer versions support more handles, but you need to define \f(CW\*(C`FD_SETSIZE\*(C'\fR
5377to some high number (e.g. \f(CW2048\fR) before compiling the winsocket select
5378call (which might be in libev or elsewhere, for example, perl and many
5379other interpreters do their own select emulation on windows).
5380.PP
5381Another limit is the number of file descriptors in the Microsoft runtime
5382libraries, which by default is \f(CW64\fR (there must be a hidden \fI64\fR
5383fetish or something like this inside Microsoft). You can increase this
5384by calling \f(CW\*(C`_setmaxstdio\*(C'\fR, which can increase this limit to \f(CW2048\fR
5385(another arbitrary limit), but is broken in many versions of the Microsoft
5386runtime libraries. This might get you to about \f(CW512\fR or \f(CW2048\fR sockets
5387(depending on windows version and/or the phase of the moon). To get more,
5388you need to wrap all I/O functions and provide your own fd management, but
5389the cost of calling select (O(nA\*^X)) will likely make this unworkable.
5390.SS "\s-1PORTABILITY\s0 \s-1REQUIREMENTS\s0"
5391.IX Subsection "PORTABILITY REQUIREMENTS"
5392In addition to a working ISO-C implementation and of course the
5393backend-specific APIs, libev relies on a few additional extensions:
5394.ie n .IP """void (*)(ev_watcher_type *, int revents)"" must have compatible calling conventions regardless of ""ev_watcher_type *""." 4
5395.el .IP "\f(CWvoid (*)(ev_watcher_type *, int revents)\fR must have compatible calling conventions regardless of \f(CWev_watcher_type *\fR." 4
5396.IX Item "void (*)(ev_watcher_type *, int revents) must have compatible calling conventions regardless of ev_watcher_type *."
5397Libev assumes not only that all watcher pointers have the same internal
5398structure (guaranteed by \s-1POSIX\s0 but not by \s-1ISO\s0 C for example), but it also
5399assumes that the same (machine) code can be used to call any watcher
5400callback: The watcher callbacks have different type signatures, but libev
5401calls them using an \f(CW\*(C`ev_watcher *\*(C'\fR internally.
5402.IP "pointer accesses must be thread-atomic" 4
5403.IX Item "pointer accesses must be thread-atomic"
5404Accessing a pointer value must be atomic, it must both be readable and
5405writable in one piece \- this is the case on all current architectures.
5406.ie n .IP """sig_atomic_t volatile"" must be thread-atomic as well" 4
5407.el .IP "\f(CWsig_atomic_t volatile\fR must be thread-atomic as well" 4
5408.IX Item "sig_atomic_t volatile must be thread-atomic as well"
5409The type \f(CW\*(C`sig_atomic_t volatile\*(C'\fR (or whatever is defined as
5410\&\f(CW\*(C`EV_ATOMIC_T\*(C'\fR) must be atomic with respect to accesses from different
5411threads. This is not part of the specification for \f(CW\*(C`sig_atomic_t\*(C'\fR, but is
5412believed to be sufficiently portable.
5413.ie n .IP """sigprocmask"" must work in a threaded environment" 4
5414.el .IP "\f(CWsigprocmask\fR must work in a threaded environment" 4
5415.IX Item "sigprocmask must work in a threaded environment"
5416Libev uses \f(CW\*(C`sigprocmask\*(C'\fR to temporarily block signals. This is not
5417allowed in a threaded program (\f(CW\*(C`pthread_sigmask\*(C'\fR has to be used). Typical
5418pthread implementations will either allow \f(CW\*(C`sigprocmask\*(C'\fR in the \*(L"main
5419thread\*(R" or will block signals process-wide, both behaviours would
5420be compatible with libev. Interaction between \f(CW\*(C`sigprocmask\*(C'\fR and
5421\&\f(CW\*(C`pthread_sigmask\*(C'\fR could complicate things, however.
5422.Sp
5423The most portable way to handle signals is to block signals in all threads
5424except the initial one, and run the signal handling loop in the initial
5425thread as well.
5426.ie n .IP """long"" must be large enough for common memory allocation sizes" 4
5427.el .IP "\f(CWlong\fR must be large enough for common memory allocation sizes" 4
5428.IX Item "long must be large enough for common memory allocation sizes"
5429To improve portability and simplify its \s-1API\s0, libev uses \f(CW\*(C`long\*(C'\fR internally
5430instead of \f(CW\*(C`size_t\*(C'\fR when allocating its data structures. On non-POSIX
5431systems (Microsoft...) this might be unexpectedly low, but is still at
5432least 31 bits everywhere, which is enough for hundreds of millions of
5433watchers.
5434.ie n .IP """double"" must hold a time value in seconds with enough accuracy" 4
5435.el .IP "\f(CWdouble\fR must hold a time value in seconds with enough accuracy" 4
5436.IX Item "double must hold a time value in seconds with enough accuracy"
5437The type \f(CW\*(C`double\*(C'\fR is used to represent timestamps. It is required to
5438have at least 51 bits of mantissa (and 9 bits of exponent), which is
5439good enough for at least into the year 4000 with millisecond accuracy
5440(the design goal for libev). This requirement is overfulfilled by
5441implementations using \s-1IEEE\s0 754, which is basically all existing ones.
5442.Sp
5443With \s-1IEEE\s0 754 doubles, you get microsecond accuracy until at least the
5444year 2255 (and millisecond accuracy till the year 287396 \- by then, libev
5445is either obsolete or somebody patched it to use \f(CW\*(C`long double\*(C'\fR or
5446something like that, just kidding).
5447.PP
5448If you know of other additional requirements drop me a note.
2654.SH "COMPLEXITIES" 5449.SH "ALGORITHMIC COMPLEXITIES"
2655.IX Header "COMPLEXITIES" 5450.IX Header "ALGORITHMIC COMPLEXITIES"
2656In this section the complexities of (many of) the algorithms used inside 5451In this section the complexities of (many of) the algorithms used inside
2657libev will be explained. For complexity discussions about backends see the 5452libev will be documented. For complexity discussions about backends see
2658documentation for \f(CW\*(C`ev_default_init\*(C'\fR. 5453the documentation for \f(CW\*(C`ev_default_init\*(C'\fR.
2659.Sp 5454.PP
2660All of the following are about amortised time: If an array needs to be 5455All of the following are about amortised time: If an array needs to be
2661extended, libev needs to realloc and move the whole array, but this 5456extended, libev needs to realloc and move the whole array, but this
2662happens asymptotically never with higher number of elements, so O(1) might 5457happens asymptotically rarer with higher number of elements, so O(1) might
2663mean it might do a lengthy realloc operation in rare cases, but on average 5458mean that libev does a lengthy realloc operation in rare cases, but on
2664it is much faster and asymptotically approaches constant time. 5459average it is much faster and asymptotically approaches constant time.
2665.RS 4
2666.IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4 5460.IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4
2667.IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 5461.IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)"
2668This means that, when you have a watcher that triggers in one hour and 5462This means that, when you have a watcher that triggers in one hour and
2669there are 100 watchers that would trigger before that then inserting will 5463there are 100 watchers that would trigger before that, then inserting will
2670have to skip those 100 watchers. 5464have to skip roughly seven (\f(CW\*(C`ld 100\*(C'\fR) of these watchers.
2671.IP "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)" 4 5465.IP "Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)" 4
2672.IX Item "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)" 5466.IX Item "Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)"
2673That means that for changing a timer costs less than removing/adding them 5467That means that changing a timer costs less than removing/adding them,
2674as only the relative motion in the event queue has to be paid for. 5468as only the relative motion in the event queue has to be paid for.
2675.IP "Starting io/check/prepare/idle/signal/child watchers: O(1)" 4 5469.IP "Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)" 4
2676.IX Item "Starting io/check/prepare/idle/signal/child watchers: O(1)" 5470.IX Item "Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)"
2677These just add the watcher into an array or at the head of a list. 5471These just add the watcher into an array or at the head of a list.
5472.IP "Stopping check/prepare/idle/fork/async watchers: O(1)" 4
2678=item Stopping check/prepare/idle watchers: O(1) 5473.IX Item "Stopping check/prepare/idle/fork/async watchers: O(1)"
5474.PD 0
2679.IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4 5475.IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4
2680.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))" 5476.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))"
5477.PD
2681These watchers are stored in lists then need to be walked to find the 5478These watchers are stored in lists, so they need to be walked to find the
2682correct watcher to remove. The lists are usually short (you don't usually 5479correct watcher to remove. The lists are usually short (you don't usually
2683have many watchers waiting for the same fd or signal). 5480have many watchers waiting for the same fd or signal: one is typical, two
5481is rare).
2684.IP "Finding the next timer per loop iteration: O(1)" 4 5482.IP "Finding the next timer in each loop iteration: O(1)" 4
2685.IX Item "Finding the next timer per loop iteration: O(1)" 5483.IX Item "Finding the next timer in each loop iteration: O(1)"
2686.PD 0 5484By virtue of using a binary or 4\-heap, the next timer is always found at a
5485fixed position in the storage array.
2687.IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4 5486.IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4
2688.IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 5487.IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)"
2689.PD
2690A change means an I/O watcher gets started or stopped, which requires 5488A change means an I/O watcher gets started or stopped, which requires
2691libev to recalculate its status (and possibly tell the kernel). 5489libev to recalculate its status (and possibly tell the kernel, depending
2692.IP "Activating one watcher: O(1)" 4 5490on backend and whether \f(CW\*(C`ev_io_set\*(C'\fR was used).
2693.IX Item "Activating one watcher: O(1)" 5491.IP "Activating one watcher (putting it into the pending state): O(1)" 4
5492.IX Item "Activating one watcher (putting it into the pending state): O(1)"
2694.PD 0 5493.PD 0
2695.IP "Priority handling: O(number_of_priorities)" 4 5494.IP "Priority handling: O(number_of_priorities)" 4
2696.IX Item "Priority handling: O(number_of_priorities)" 5495.IX Item "Priority handling: O(number_of_priorities)"
2697.PD 5496.PD
2698Priorities are implemented by allocating some space for each 5497Priorities are implemented by allocating some space for each
2699priority. When doing priority-based operations, libev usually has to 5498priority. When doing priority-based operations, libev usually has to
2700linearly search all the priorities. 5499linearly search all the priorities, but starting/stopping and activating
2701.RE 5500watchers becomes O(1) with respect to priority handling.
2702.RS 4 5501.IP "Sending an ev_async: O(1)" 4
5502.IX Item "Sending an ev_async: O(1)"
5503.PD 0
5504.IP "Processing ev_async_send: O(number_of_async_watchers)" 4
5505.IX Item "Processing ev_async_send: O(number_of_async_watchers)"
5506.IP "Processing signals: O(max_signal_number)" 4
5507.IX Item "Processing signals: O(max_signal_number)"
5508.PD
5509Sending involves a system call \fIiff\fR there were no other \f(CW\*(C`ev_async_send\*(C'\fR
5510calls in the current loop iteration and the loop is currently
5511blocked. Checking for async and signal events involves iterating over all
5512running async watchers or all signal numbers.
5513.SH "PORTING FROM LIBEV 3.X TO 4.X"
5514.IX Header "PORTING FROM LIBEV 3.X TO 4.X"
5515The major version 4 introduced some incompatible changes to the \s-1API\s0.
5516.PP
5517At the moment, the \f(CW\*(C`ev.h\*(C'\fR header file provides compatibility definitions
5518for all changes, so most programs should still compile. The compatibility
5519layer might be removed in later versions of libev, so better update to the
5520new \s-1API\s0 early than late.
5521.ie n .IP """EV_COMPAT3"" backwards compatibility mechanism" 4
5522.el .IP "\f(CWEV_COMPAT3\fR backwards compatibility mechanism" 4
5523.IX Item "EV_COMPAT3 backwards compatibility mechanism"
5524The backward compatibility mechanism can be controlled by
5525\&\f(CW\*(C`EV_COMPAT3\*(C'\fR. See \*(L"\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0\*(R" in the \*(L"\s-1EMBEDDING\s0\*(R"
5526section.
5527.ie n .IP """ev_default_destroy"" and ""ev_default_fork"" have been removed" 4
5528.el .IP "\f(CWev_default_destroy\fR and \f(CWev_default_fork\fR have been removed" 4
5529.IX Item "ev_default_destroy and ev_default_fork have been removed"
5530These calls can be replaced easily by their \f(CW\*(C`ev_loop_xxx\*(C'\fR counterparts:
5531.Sp
5532.Vb 2
5533\& ev_loop_destroy (EV_DEFAULT_UC);
5534\& ev_loop_fork (EV_DEFAULT);
5535.Ve
5536.IP "function/symbol renames" 4
5537.IX Item "function/symbol renames"
5538A number of functions and symbols have been renamed:
5539.Sp
5540.Vb 3
5541\& ev_loop => ev_run
5542\& EVLOOP_NONBLOCK => EVRUN_NOWAIT
5543\& EVLOOP_ONESHOT => EVRUN_ONCE
5544\&
5545\& ev_unloop => ev_break
5546\& EVUNLOOP_CANCEL => EVBREAK_CANCEL
5547\& EVUNLOOP_ONE => EVBREAK_ONE
5548\& EVUNLOOP_ALL => EVBREAK_ALL
5549\&
5550\& EV_TIMEOUT => EV_TIMER
5551\&
5552\& ev_loop_count => ev_iteration
5553\& ev_loop_depth => ev_depth
5554\& ev_loop_verify => ev_verify
5555.Ve
5556.Sp
5557Most functions working on \f(CW\*(C`struct ev_loop\*(C'\fR objects don't have an
5558\&\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
5559associated constants have been renamed to not collide with the \f(CW\*(C`struct
5560ev_loop\*(C'\fR anymore and \f(CW\*(C`EV_TIMER\*(C'\fR now follows the same naming scheme
5561as all other watcher types. Note that \f(CW\*(C`ev_loop_fork\*(C'\fR is still called
5562\&\f(CW\*(C`ev_loop_fork\*(C'\fR because it would otherwise clash with the \f(CW\*(C`ev_fork\*(C'\fR
5563typedef.
5564.ie n .IP """EV_MINIMAL"" mechanism replaced by ""EV_FEATURES""" 4
5565.el .IP "\f(CWEV_MINIMAL\fR mechanism replaced by \f(CWEV_FEATURES\fR" 4
5566.IX Item "EV_MINIMAL mechanism replaced by EV_FEATURES"
5567The preprocessor symbol \f(CW\*(C`EV_MINIMAL\*(C'\fR has been replaced by a different
5568mechanism, \f(CW\*(C`EV_FEATURES\*(C'\fR. Programs using \f(CW\*(C`EV_MINIMAL\*(C'\fR usually compile
5569and work, but the library code will of course be larger.
5570.SH "GLOSSARY"
5571.IX Header "GLOSSARY"
5572.IP "active" 4
5573.IX Item "active"
5574A watcher is active as long as it has been started and not yet stopped.
5575See \*(L"\s-1WATCHER\s0 \s-1STATES\s0\*(R" for details.
5576.IP "application" 4
5577.IX Item "application"
5578In this document, an application is whatever is using libev.
5579.IP "backend" 4
5580.IX Item "backend"
5581The part of the code dealing with the operating system interfaces.
5582.IP "callback" 4
5583.IX Item "callback"
5584The address of a function that is called when some event has been
5585detected. Callbacks are being passed the event loop, the watcher that
5586received the event, and the actual event bitset.
5587.IP "callback/watcher invocation" 4
5588.IX Item "callback/watcher invocation"
5589The act of calling the callback associated with a watcher.
5590.IP "event" 4
5591.IX Item "event"
5592A change of state of some external event, such as data now being available
5593for reading on a file descriptor, time having passed or simply not having
5594any other events happening anymore.
5595.Sp
5596In libev, events are represented as single bits (such as \f(CW\*(C`EV_READ\*(C'\fR or
5597\&\f(CW\*(C`EV_TIMER\*(C'\fR).
5598.IP "event library" 4
5599.IX Item "event library"
5600A software package implementing an event model and loop.
5601.IP "event loop" 4
5602.IX Item "event loop"
5603An entity that handles and processes external events and converts them
5604into callback invocations.
5605.IP "event model" 4
5606.IX Item "event model"
5607The model used to describe how an event loop handles and processes
5608watchers and events.
5609.IP "pending" 4
5610.IX Item "pending"
5611A watcher is pending as soon as the corresponding event has been
5612detected. See \*(L"\s-1WATCHER\s0 \s-1STATES\s0\*(R" for details.
5613.IP "real time" 4
5614.IX Item "real time"
5615The physical time that is observed. It is apparently strictly monotonic :)
5616.IP "wall-clock time" 4
5617.IX Item "wall-clock time"
5618The time and date as shown on clocks. Unlike real time, it can actually
5619be wrong and jump forwards and backwards, e.g. when you adjust your
5620clock.
5621.IP "watcher" 4
5622.IX Item "watcher"
5623A data structure that describes interest in certain events. Watchers need
5624to be started (attached to an event loop) before they can receive events.
2703.SH "AUTHOR" 5625.SH "AUTHOR"
2704.IX Header "AUTHOR" 5626.IX Header "AUTHOR"
2705Marc Lehmann <libev@schmorp.de>. 5627Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
5628Magnusson and Emanuele Giaquinta, and minor corrections by many others.

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