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98=head2 FEATURES 98=head2 FEATURES
99 99
100Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the 100Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
101BSD-specific C<kqueue> and the Solaris-specific event port mechanisms 101BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
102for file descriptor events (C<ev_io>), the Linux C<inotify> interface 102for file descriptor events (C<ev_io>), the Linux C<inotify> interface
103(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers 103(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
104with customised rescheduling (C<ev_periodic>), synchronous signals 104inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
105(C<ev_signal>), process status change events (C<ev_child>), and event 105timers (C<ev_timer>), absolute timers with customised rescheduling
106watchers dealing with the event loop mechanism itself (C<ev_idle>, 106(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
107C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as 107change events (C<ev_child>), and event watchers dealing with the event
108file watchers (C<ev_stat>) and even limited support for fork events 108loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
109(C<ev_fork>). 109C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
110limited support for fork events (C<ev_fork>).
110 111
111It also is quite fast (see this 112It also is quite fast (see this
112L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent 113L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
113for example). 114for example).
114 115
117Libev is very configurable. In this manual the default (and most common) 118Libev is very configurable. In this manual the default (and most common)
118configuration will be described, which supports multiple event loops. For 119configuration will be described, which supports multiple event loops. For
119more info about various configuration options please have a look at 120more info about various configuration options please have a look at
120B<EMBED> section in this manual. If libev was configured without support 121B<EMBED> section in this manual. If libev was configured without support
121for multiple event loops, then all functions taking an initial argument of 122for multiple event loops, then all functions taking an initial argument of
122name C<loop> (which is always of type C<ev_loop *>) will not have 123name C<loop> (which is always of type C<struct ev_loop *>) will not have
123this argument. 124this argument.
124 125
125=head2 TIME REPRESENTATION 126=head2 TIME REPRESENTATION
126 127
127Libev represents time as a single floating point number, representing 128Libev represents time as a single floating point number, representing
362flag. 363flag.
363 364
364This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> 365This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
365environment variable. 366environment variable.
366 367
368=item C<EVFLAG_NOINOTIFY>
369
370When this flag is specified, then libev will not attempt to use the
371I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and
372testing, this flag can be useful to conserve inotify file descriptors, as
373otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
374
375=item C<EVFLAG_SIGNALFD>
376
377When this flag is specified, then libev will attempt to use the
378I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API
379delivers signals synchronously, which makes is both faster and might make
380it possible to get the queued signal data.
381
382Signalfd will not be used by default as this changes your signal mask, and
383there are a lot of shoddy libraries and programs (glib's threadpool for
384example) that can't properly initialise their signal masks.
385
367=item C<EVBACKEND_SELECT> (value 1, portable select backend) 386=item C<EVBACKEND_SELECT> (value 1, portable select backend)
368 387
369This is your standard select(2) backend. Not I<completely> standard, as 388This is your standard select(2) backend. Not I<completely> standard, as
370libev tries to roll its own fd_set with no limits on the number of fds, 389libev tries to roll its own fd_set with no limits on the number of fds,
371but if that fails, expect a fairly low limit on the number of fds when 390but if that fails, expect a fairly low limit on the number of fds when
394 413
395This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and 414This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
396C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. 415C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
397 416
398=item C<EVBACKEND_EPOLL> (value 4, Linux) 417=item C<EVBACKEND_EPOLL> (value 4, Linux)
418
419Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
420kernels).
399 421
400For few fds, this backend is a bit little slower than poll and select, 422For few fds, this backend is a bit little slower than poll and select,
401but it scales phenomenally better. While poll and select usually scale 423but it scales phenomenally better. While poll and select usually scale
402like O(total_fds) where n is the total number of fds (or the highest fd), 424like O(total_fds) where n is the total number of fds (or the highest fd),
403epoll scales either O(1) or O(active_fds). 425epoll scales either O(1) or O(active_fds).
518 540
519It is definitely not recommended to use this flag. 541It is definitely not recommended to use this flag.
520 542
521=back 543=back
522 544
523If one or more of these are or'ed into the flags value, then only these 545If one or more of the backend flags are or'ed into the flags value,
524backends will be tried (in the reverse order as listed here). If none are 546then only these backends will be tried (in the reverse order as listed
525specified, all backends in C<ev_recommended_backends ()> will be tried. 547here). If none are specified, all backends in C<ev_recommended_backends
548()> will be tried.
526 549
527Example: This is the most typical usage. 550Example: This is the most typical usage.
528 551
529 if (!ev_default_loop (0)) 552 if (!ev_default_loop (0))
530 fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); 553 fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
573as signal and child watchers) would need to be stopped manually. 596as signal and child watchers) would need to be stopped manually.
574 597
575In general it is not advisable to call this function except in the 598In general it is not advisable to call this function except in the
576rare occasion where you really need to free e.g. the signal handling 599rare occasion where you really need to free e.g. the signal handling
577pipe fds. If you need dynamically allocated loops it is better to use 600pipe fds. If you need dynamically allocated loops it is better to use
578C<ev_loop_new> and C<ev_loop_destroy>). 601C<ev_loop_new> and C<ev_loop_destroy>.
579 602
580=item ev_loop_destroy (loop) 603=item ev_loop_destroy (loop)
581 604
582Like C<ev_default_destroy>, but destroys an event loop created by an 605Like C<ev_default_destroy>, but destroys an event loop created by an
583earlier call to C<ev_loop_new>. 606earlier call to C<ev_loop_new>.
687event loop time (see C<ev_now_update>). 710event loop time (see C<ev_now_update>).
688 711
689=item ev_loop (loop, int flags) 712=item ev_loop (loop, int flags)
690 713
691Finally, this is it, the event handler. This function usually is called 714Finally, this is it, the event handler. This function usually is called
692after you initialised all your watchers and you want to start handling 715after you have initialised all your watchers and you want to start
693events. 716handling events.
694 717
695If the flags argument is specified as C<0>, it will not return until 718If the flags argument is specified as C<0>, it will not return until
696either no event watchers are active anymore or C<ev_unloop> was called. 719either no event watchers are active anymore or C<ev_unloop> was called.
697 720
698Please note that an explicit C<ev_unloop> is usually better than 721Please note that an explicit C<ev_unloop> is usually better than
772 795
773Ref/unref can be used to add or remove a reference count on the event 796Ref/unref can be used to add or remove a reference count on the event
774loop: Every watcher keeps one reference, and as long as the reference 797loop: Every watcher keeps one reference, and as long as the reference
775count is nonzero, C<ev_loop> will not return on its own. 798count is nonzero, C<ev_loop> will not return on its own.
776 799
777If you have a watcher you never unregister that should not keep C<ev_loop> 800This is useful when you have a watcher that you never intend to
778from returning, call ev_unref() after starting, and ev_ref() before 801unregister, but that nevertheless should not keep C<ev_loop> from
802returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
779stopping it. 803before stopping it.
780 804
781As an example, libev itself uses this for its internal signal pipe: It 805As an example, libev itself uses this for its internal signal pipe: It
782is not visible to the libev user and should not keep C<ev_loop> from 806is not visible to the libev user and should not keep C<ev_loop> from
783exiting if no event watchers registered by it are active. It is also an 807exiting if no event watchers registered by it are active. It is also an
784excellent way to do this for generic recurring timers or from within 808excellent way to do this for generic recurring timers or from within
862 886
863This call will simply invoke all pending watchers while resetting their 887This call will simply invoke all pending watchers while resetting their
864pending state. Normally, C<ev_loop> does this automatically when required, 888pending state. Normally, C<ev_loop> does this automatically when required,
865but when overriding the invoke callback this call comes handy. 889but when overriding the invoke callback this call comes handy.
866 890
891=item int ev_pending_count (loop)
892
893Returns the number of pending watchers - zero indicates that no watchers
894are pending.
895
867=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P)) 896=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
868 897
869This overrides the invoke pending functionality of the loop: Instead of 898This overrides the invoke pending functionality of the loop: Instead of
870invoking all pending watchers when there are any, C<ev_loop> will call 899invoking all pending watchers when there are any, C<ev_loop> will call
871this callback instead. This is useful, for example, when you want to 900this callback instead. This is useful, for example, when you want to
894 923
895While event loop modifications are allowed between invocations of 924While event loop modifications are allowed between invocations of
896C<release> and C<acquire> (that's their only purpose after all), no 925C<release> and C<acquire> (that's their only purpose after all), no
897modifications done will affect the event loop, i.e. adding watchers will 926modifications done will affect the event loop, i.e. adding watchers will
898have no effect on the set of file descriptors being watched, or the time 927have no effect on the set of file descriptors being watched, or the time
899waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it 928waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it
900to take note of any changes you made. 929to take note of any changes you made.
901 930
902In theory, threads executing C<ev_loop> will be async-cancel safe between 931In theory, threads executing C<ev_loop> will be async-cancel safe between
903invocations of C<release> and C<acquire>. 932invocations of C<release> and C<acquire>.
904 933
1101 1130
1102 ev_io w; 1131 ev_io w;
1103 ev_init (&w, my_cb); 1132 ev_init (&w, my_cb);
1104 ev_io_set (&w, STDIN_FILENO, EV_READ); 1133 ev_io_set (&w, STDIN_FILENO, EV_READ);
1105 1134
1106=item C<ev_TYPE_set> (ev_TYPE *, [args]) 1135=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1107 1136
1108This macro initialises the type-specific parts of a watcher. You need to 1137This macro initialises the type-specific parts of a watcher. You need to
1109call C<ev_init> at least once before you call this macro, but you can 1138call C<ev_init> at least once before you call this macro, but you can
1110call C<ev_TYPE_set> any number of times. You must not, however, call this 1139call C<ev_TYPE_set> any number of times. You must not, however, call this
1111macro on a watcher that is active (it can be pending, however, which is a 1140macro on a watcher that is active (it can be pending, however, which is a
1124 1153
1125Example: Initialise and set an C<ev_io> watcher in one step. 1154Example: Initialise and set an C<ev_io> watcher in one step.
1126 1155
1127 ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); 1156 ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1128 1157
1129=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) 1158=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1130 1159
1131Starts (activates) the given watcher. Only active watchers will receive 1160Starts (activates) the given watcher. Only active watchers will receive
1132events. If the watcher is already active nothing will happen. 1161events. If the watcher is already active nothing will happen.
1133 1162
1134Example: Start the C<ev_io> watcher that is being abused as example in this 1163Example: Start the C<ev_io> watcher that is being abused as example in this
1135whole section. 1164whole section.
1136 1165
1137 ev_io_start (EV_DEFAULT_UC, &w); 1166 ev_io_start (EV_DEFAULT_UC, &w);
1138 1167
1139=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) 1168=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1140 1169
1141Stops the given watcher if active, and clears the pending status (whether 1170Stops the given watcher if active, and clears the pending status (whether
1142the watcher was active or not). 1171the watcher was active or not).
1143 1172
1144It is possible that stopped watchers are pending - for example, 1173It is possible that stopped watchers are pending - for example,
1169=item ev_cb_set (ev_TYPE *watcher, callback) 1198=item ev_cb_set (ev_TYPE *watcher, callback)
1170 1199
1171Change the callback. You can change the callback at virtually any time 1200Change the callback. You can change the callback at virtually any time
1172(modulo threads). 1201(modulo threads).
1173 1202
1174=item ev_set_priority (ev_TYPE *watcher, priority) 1203=item ev_set_priority (ev_TYPE *watcher, int priority)
1175 1204
1176=item int ev_priority (ev_TYPE *watcher) 1205=item int ev_priority (ev_TYPE *watcher)
1177 1206
1178Set and query the priority of the watcher. The priority is a small 1207Set and query the priority of the watcher. The priority is a small
1179integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> 1208integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1210returns its C<revents> bitset (as if its callback was invoked). If the 1239returns its C<revents> bitset (as if its callback was invoked). If the
1211watcher isn't pending it does nothing and returns C<0>. 1240watcher isn't pending it does nothing and returns C<0>.
1212 1241
1213Sometimes it can be useful to "poll" a watcher instead of waiting for its 1242Sometimes it can be useful to "poll" a watcher instead of waiting for its
1214callback to be invoked, which can be accomplished with this function. 1243callback to be invoked, which can be accomplished with this function.
1244
1245=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
1246
1247Feeds the given event set into the event loop, as if the specified event
1248had happened for the specified watcher (which must be a pointer to an
1249initialised but not necessarily started event watcher). Obviously you must
1250not free the watcher as long as it has pending events.
1251
1252Stopping the watcher, letting libev invoke it, or calling
1253C<ev_clear_pending> will clear the pending event, even if the watcher was
1254not started in the first place.
1255
1256See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1257functions that do not need a watcher.
1215 1258
1216=back 1259=back
1217 1260
1218 1261
1219=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER 1262=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1750 1793
1751If the event loop is suspended for a long time, you can also force an 1794If the event loop is suspended for a long time, you can also force an
1752update of the time returned by C<ev_now ()> by calling C<ev_now_update 1795update of the time returned by C<ev_now ()> by calling C<ev_now_update
1753()>. 1796()>.
1754 1797
1798=head3 The special problems of suspended animation
1799
1800When you leave the server world it is quite customary to hit machines that
1801can suspend/hibernate - what happens to the clocks during such a suspend?
1802
1803Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
1804all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
1805to run until the system is suspended, but they will not advance while the
1806system is suspended. That means, on resume, it will be as if the program
1807was frozen for a few seconds, but the suspend time will not be counted
1808towards C<ev_timer> when a monotonic clock source is used. The real time
1809clock advanced as expected, but if it is used as sole clocksource, then a
1810long suspend would be detected as a time jump by libev, and timers would
1811be adjusted accordingly.
1812
1813I would not be surprised to see different behaviour in different between
1814operating systems, OS versions or even different hardware.
1815
1816The other form of suspend (job control, or sending a SIGSTOP) will see a
1817time jump in the monotonic clocks and the realtime clock. If the program
1818is suspended for a very long time, and monotonic clock sources are in use,
1819then you can expect C<ev_timer>s to expire as the full suspension time
1820will be counted towards the timers. When no monotonic clock source is in
1821use, then libev will again assume a timejump and adjust accordingly.
1822
1823It might be beneficial for this latter case to call C<ev_suspend>
1824and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
1825deterministic behaviour in this case (you can do nothing against
1826C<SIGSTOP>).
1827
1755=head3 Watcher-Specific Functions and Data Members 1828=head3 Watcher-Specific Functions and Data Members
1756 1829
1757=over 4 1830=over 4
1758 1831
1759=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) 1832=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1784If the timer is repeating, either start it if necessary (with the 1857If the timer is repeating, either start it if necessary (with the
1785C<repeat> value), or reset the running timer to the C<repeat> value. 1858C<repeat> value), or reset the running timer to the C<repeat> value.
1786 1859
1787This sounds a bit complicated, see L<Be smart about timeouts>, above, for a 1860This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1788usage example. 1861usage example.
1862
1863=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1864
1865Returns the remaining time until a timer fires. If the timer is active,
1866then this time is relative to the current event loop time, otherwise it's
1867the timeout value currently configured.
1868
1869That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1870C<5>. When the timer is started and one second passes, C<ev_timer_remain>
1871will return C<4>. When the timer expires and is restarted, it will return
1872roughly C<7> (likely slightly less as callback invocation takes some time,
1873too), and so on.
1789 1874
1790=item ev_tstamp repeat [read-write] 1875=item ev_tstamp repeat [read-write]
1791 1876
1792The current C<repeat> value. Will be used each time the watcher times out 1877The current C<repeat> value. Will be used each time the watcher times out
1793or C<ev_timer_again> is called, and determines the next timeout (if any), 1878or C<ev_timer_again> is called, and determines the next timeout (if any),
2029Signal watchers will trigger an event when the process receives a specific 2114Signal watchers will trigger an event when the process receives a specific
2030signal one or more times. Even though signals are very asynchronous, libev 2115signal one or more times. Even though signals are very asynchronous, libev
2031will try it's best to deliver signals synchronously, i.e. as part of the 2116will try it's best to deliver signals synchronously, i.e. as part of the
2032normal event processing, like any other event. 2117normal event processing, like any other event.
2033 2118
2034If you want signals asynchronously, just use C<sigaction> as you would 2119If you want signals to be delivered truly asynchronously, just use
2035do without libev and forget about sharing the signal. You can even use 2120C<sigaction> as you would do without libev and forget about sharing
2036C<ev_async> from a signal handler to synchronously wake up an event loop. 2121the signal. You can even use C<ev_async> from a signal handler to
2122synchronously wake up an event loop.
2037 2123
2038You can configure as many watchers as you like per signal. Only when the 2124You can configure as many watchers as you like for the same signal, but
2125only within the same loop, i.e. you can watch for C<SIGINT> in your
2126default loop and for C<SIGIO> in another loop, but you cannot watch for
2127C<SIGINT> in both the default loop and another loop at the same time. At
2128the moment, C<SIGCHLD> is permanently tied to the default loop.
2129
2039first watcher gets started will libev actually register a signal handler 2130When the first watcher gets started will libev actually register something
2040with the kernel (thus it coexists with your own signal handlers as long as 2131with the kernel (thus it coexists with your own signal handlers as long as
2041you don't register any with libev for the same signal). Similarly, when 2132you don't register any with libev for the same signal).
2042the last signal watcher for a signal is stopped, libev will reset the
2043signal handler to SIG_DFL (regardless of what it was set to before).
2044 2133
2045If possible and supported, libev will install its handlers with 2134If possible and supported, libev will install its handlers with
2046C<SA_RESTART> behaviour enabled, so system calls should not be unduly 2135C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2047interrupted. If you have a problem with system calls getting interrupted by 2136not be unduly interrupted. If you have a problem with system calls getting
2048signals you can block all signals in an C<ev_check> watcher and unblock 2137interrupted by signals you can block all signals in an C<ev_check> watcher
2049them in an C<ev_prepare> watcher. 2138and unblock them in an C<ev_prepare> watcher.
2139
2140=head3 The special problem of inheritance over fork/execve/pthread_create
2141
2142Both the signal mask (C<sigprocmask>) and the signal disposition
2143(C<sigaction>) are unspecified after starting a signal watcher (and after
2144stopping it again), that is, libev might or might not block the signal,
2145and might or might not set or restore the installed signal handler.
2146
2147While this does not matter for the signal disposition (libev never
2148sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2149C<execve>), this matters for the signal mask: many programs do not expect
2150certain signals to be blocked.
2151
2152This means that before calling C<exec> (from the child) you should reset
2153the signal mask to whatever "default" you expect (all clear is a good
2154choice usually).
2155
2156The simplest way to ensure that the signal mask is reset in the child is
2157to install a fork handler with C<pthread_atfork> that resets it. That will
2158catch fork calls done by libraries (such as the libc) as well.
2159
2160In current versions of libev, the signal will not be blocked indefinitely
2161unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
2162the window of opportunity for problems, it will not go away, as libev
2163I<has> to modify the signal mask, at least temporarily.
2164
2165So I can't stress this enough I<if you do not reset your signal mask
2166when you expect it to be empty, you have a race condition in your
2167program>. This is not a libev-specific thing, this is true for most event
2168libraries.
2050 2169
2051=head3 Watcher-Specific Functions and Data Members 2170=head3 Watcher-Specific Functions and Data Members
2052 2171
2053=over 4 2172=over 4
2054 2173
2099libev) 2218libev)
2100 2219
2101=head3 Process Interaction 2220=head3 Process Interaction
2102 2221
2103Libev grabs C<SIGCHLD> as soon as the default event loop is 2222Libev grabs C<SIGCHLD> as soon as the default event loop is
2104initialised. This is necessary to guarantee proper behaviour even if 2223initialised. This is necessary to guarantee proper behaviour even if the
2105the first child watcher is started after the child exits. The occurrence 2224first child watcher is started after the child exits. The occurrence
2106of C<SIGCHLD> is recorded asynchronously, but child reaping is done 2225of C<SIGCHLD> is recorded asynchronously, but child reaping is done
2107synchronously as part of the event loop processing. Libev always reaps all 2226synchronously as part of the event loop processing. Libev always reaps all
2108children, even ones not watched. 2227children, even ones not watched.
2109 2228
2110=head3 Overriding the Built-In Processing 2229=head3 Overriding the Built-In Processing
2120=head3 Stopping the Child Watcher 2239=head3 Stopping the Child Watcher
2121 2240
2122Currently, the child watcher never gets stopped, even when the 2241Currently, the child watcher never gets stopped, even when the
2123child terminates, so normally one needs to stop the watcher in the 2242child terminates, so normally one needs to stop the watcher in the
2124callback. Future versions of libev might stop the watcher automatically 2243callback. Future versions of libev might stop the watcher automatically
2125when a child exit is detected. 2244when a child exit is detected (calling C<ev_child_stop> twice is not a
2245problem).
2126 2246
2127=head3 Watcher-Specific Functions and Data Members 2247=head3 Watcher-Specific Functions and Data Members
2128 2248
2129=over 4 2249=over 4
2130 2250
2870=head3 Queueing 2990=head3 Queueing
2871 2991
2872C<ev_async> does not support queueing of data in any way. The reason 2992C<ev_async> does not support queueing of data in any way. The reason
2873is that the author does not know of a simple (or any) algorithm for a 2993is that the author does not know of a simple (or any) algorithm for a
2874multiple-writer-single-reader queue that works in all cases and doesn't 2994multiple-writer-single-reader queue that works in all cases and doesn't
2875need elaborate support such as pthreads. 2995need elaborate support such as pthreads or unportable memory access
2996semantics.
2876 2997
2877That means that if you want to queue data, you have to provide your own 2998That means that if you want to queue data, you have to provide your own
2878queue. But at least I can tell you how to implement locking around your 2999queue. But at least I can tell you how to implement locking around your
2879queue: 3000queue:
2880 3001
3038 /* doh, nothing entered */; 3159 /* doh, nothing entered */;
3039 } 3160 }
3040 3161
3041 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); 3162 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3042 3163
3043=item ev_feed_event (struct ev_loop *, watcher *, int revents)
3044
3045Feeds the given event set into the event loop, as if the specified event
3046had happened for the specified watcher (which must be a pointer to an
3047initialised but not necessarily started event watcher).
3048
3049=item ev_feed_fd_event (struct ev_loop *, int fd, int revents) 3164=item ev_feed_fd_event (loop, int fd, int revents)
3050 3165
3051Feed an event on the given fd, as if a file descriptor backend detected 3166Feed an event on the given fd, as if a file descriptor backend detected
3052the given events it. 3167the given events it.
3053 3168
3054=item ev_feed_signal_event (struct ev_loop *loop, int signum) 3169=item ev_feed_signal_event (loop, int signum)
3055 3170
3056Feed an event as if the given signal occurred (C<loop> must be the default 3171Feed an event as if the given signal occurred (C<loop> must be the default
3057loop!). 3172loop!).
3058 3173
3059=back 3174=back
3139 3254
3140=over 4 3255=over 4
3141 3256
3142=item ev::TYPE::TYPE () 3257=item ev::TYPE::TYPE ()
3143 3258
3144=item ev::TYPE::TYPE (struct ev_loop *) 3259=item ev::TYPE::TYPE (loop)
3145 3260
3146=item ev::TYPE::~TYPE 3261=item ev::TYPE::~TYPE
3147 3262
3148The constructor (optionally) takes an event loop to associate the watcher 3263The constructor (optionally) takes an event loop to associate the watcher
3149with. If it is omitted, it will use C<EV_DEFAULT>. 3264with. If it is omitted, it will use C<EV_DEFAULT>.
3226Example: Use a plain function as callback. 3341Example: Use a plain function as callback.
3227 3342
3228 static void io_cb (ev::io &w, int revents) { } 3343 static void io_cb (ev::io &w, int revents) { }
3229 iow.set <io_cb> (); 3344 iow.set <io_cb> ();
3230 3345
3231=item w->set (struct ev_loop *) 3346=item w->set (loop)
3232 3347
3233Associates a different C<struct ev_loop> with this watcher. You can only 3348Associates a different C<struct ev_loop> with this watcher. You can only
3234do this when the watcher is inactive (and not pending either). 3349do this when the watcher is inactive (and not pending either).
3235 3350
3236=item w->set ([arguments]) 3351=item w->set ([arguments])
3333=item Ocaml 3448=item Ocaml
3334 3449
3335Erkki Seppala has written Ocaml bindings for libev, to be found at 3450Erkki Seppala has written Ocaml bindings for libev, to be found at
3336L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. 3451L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
3337 3452
3453=item Lua
3454
3455Brian Maher has written a partial interface to libev
3456for lua (only C<ev_io> and C<ev_timer>), to be found at
3457L<http://github.com/brimworks/lua-ev>.
3458
3338=back 3459=back
3339 3460
3340 3461
3341=head1 MACRO MAGIC 3462=head1 MACRO MAGIC
3342 3463
3508keeps libev from including F<config.h>, and it also defines dummy 3629keeps libev from including F<config.h>, and it also defines dummy
3509implementations for some libevent functions (such as logging, which is not 3630implementations for some libevent functions (such as logging, which is not
3510supported). It will also not define any of the structs usually found in 3631supported). It will also not define any of the structs usually found in
3511F<event.h> that are not directly supported by the libev core alone. 3632F<event.h> that are not directly supported by the libev core alone.
3512 3633
3513In stanbdalone mode, libev will still try to automatically deduce the 3634In standalone mode, libev will still try to automatically deduce the
3514configuration, but has to be more conservative. 3635configuration, but has to be more conservative.
3515 3636
3516=item EV_USE_MONOTONIC 3637=item EV_USE_MONOTONIC
3517 3638
3518If defined to be C<1>, libev will try to detect the availability of the 3639If defined to be C<1>, libev will try to detect the availability of the
3583be used is the winsock select). This means that it will call 3704be used is the winsock select). This means that it will call
3584C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, 3705C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3585it is assumed that all these functions actually work on fds, even 3706it is assumed that all these functions actually work on fds, even
3586on win32. Should not be defined on non-win32 platforms. 3707on win32. Should not be defined on non-win32 platforms.
3587 3708
3588=item EV_FD_TO_WIN32_HANDLE 3709=item EV_FD_TO_WIN32_HANDLE(fd)
3589 3710
3590If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map 3711If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3591file descriptors to socket handles. When not defining this symbol (the 3712file descriptors to socket handles. When not defining this symbol (the
3592default), then libev will call C<_get_osfhandle>, which is usually 3713default), then libev will call C<_get_osfhandle>, which is usually
3593correct. In some cases, programs use their own file descriptor management, 3714correct. In some cases, programs use their own file descriptor management,
3594in which case they can provide this function to map fds to socket handles. 3715in which case they can provide this function to map fds to socket handles.
3716
3717=item EV_WIN32_HANDLE_TO_FD(handle)
3718
3719If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
3720using the standard C<_open_osfhandle> function. For programs implementing
3721their own fd to handle mapping, overwriting this function makes it easier
3722to do so. This can be done by defining this macro to an appropriate value.
3723
3724=item EV_WIN32_CLOSE_FD(fd)
3725
3726If programs implement their own fd to handle mapping on win32, then this
3727macro can be used to override the C<close> function, useful to unregister
3728file descriptors again. Note that the replacement function has to close
3729the underlying OS handle.
3595 3730
3596=item EV_USE_POLL 3731=item EV_USE_POLL
3597 3732
3598If defined to be C<1>, libev will compile in support for the C<poll>(2) 3733If defined to be C<1>, libev will compile in support for the C<poll>(2)
3599backend. Otherwise it will be enabled on non-win32 platforms. It 3734backend. Otherwise it will be enabled on non-win32 platforms. It
3745Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to 3880Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
3746provide a bare-bones event library. See C<ev.h> for details on what parts 3881provide a bare-bones event library. See C<ev.h> for details on what parts
3747of the API are still available, and do not complain if this subset changes 3882of the API are still available, and do not complain if this subset changes
3748over time. 3883over time.
3749 3884
3885=item EV_NSIG
3886
3887The highest supported signal number, +1 (or, the number of
3888signals): Normally, libev tries to deduce the maximum number of signals
3889automatically, but sometimes this fails, in which case it can be
3890specified. Also, using a lower number than detected (C<32> should be
3891good for about any system in existance) can save some memory, as libev
3892statically allocates some 12-24 bytes per signal number.
3893
3750=item EV_PID_HASHSIZE 3894=item EV_PID_HASHSIZE
3751 3895
3752C<ev_child> watchers use a small hash table to distribute workload by 3896C<ev_child> watchers use a small hash table to distribute workload by
3753pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more 3897pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
3754than enough. If you need to manage thousands of children you might want to 3898than enough. If you need to manage thousands of children you might want to
3998protecting the loop data, respectively. 4142protecting the loop data, respectively.
3999 4143
4000 static void 4144 static void
4001 l_release (EV_P) 4145 l_release (EV_P)
4002 { 4146 {
4003 udat *u = ev_userdata (EV_A); 4147 userdata *u = ev_userdata (EV_A);
4004 pthread_mutex_unlock (&u->lock); 4148 pthread_mutex_unlock (&u->lock);
4005 } 4149 }
4006 4150
4007 static void 4151 static void
4008 l_acquire (EV_P) 4152 l_acquire (EV_P)
4009 { 4153 {
4010 udat *u = ev_userdata (EV_A); 4154 userdata *u = ev_userdata (EV_A);
4011 pthread_mutex_lock (&u->lock); 4155 pthread_mutex_lock (&u->lock);
4012 } 4156 }
4013 4157
4014The event loop thread first acquires the mutex, and then jumps straight 4158The event loop thread first acquires the mutex, and then jumps straight
4015into C<ev_loop>: 4159into C<ev_loop>:
4028 } 4172 }
4029 4173
4030Instead of invoking all pending watchers, the C<l_invoke> callback will 4174Instead of invoking all pending watchers, the C<l_invoke> callback will
4031signal the main thread via some unspecified mechanism (signals? pipe 4175signal the main thread via some unspecified mechanism (signals? pipe
4032writes? C<Async::Interrupt>?) and then waits until all pending watchers 4176writes? C<Async::Interrupt>?) and then waits until all pending watchers
4033have been called: 4177have been called (in a while loop because a) spurious wakeups are possible
4178and b) skipping inter-thread-communication when there are no pending
4179watchers is very beneficial):
4034 4180
4035 static void 4181 static void
4036 l_invoke (EV_P) 4182 l_invoke (EV_P)
4037 { 4183 {
4038 udat *u = ev_userdata (EV_A); 4184 userdata *u = ev_userdata (EV_A);
4039 4185
4186 while (ev_pending_count (EV_A))
4187 {
4040 wake_up_other_thread_in_some_magic_or_not_so_magic_way (); 4188 wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4041
4042 pthread_cond_wait (&u->invoke_cv, &u->lock); 4189 pthread_cond_wait (&u->invoke_cv, &u->lock);
4190 }
4043 } 4191 }
4044 4192
4045Now, whenever the main thread gets told to invoke pending watchers, it 4193Now, whenever the main thread gets told to invoke pending watchers, it
4046will grab the lock, call C<ev_invoke_pending> and then signal the loop 4194will grab the lock, call C<ev_invoke_pending> and then signal the loop
4047thread to continue: 4195thread to continue:
4048 4196
4049 static void 4197 static void
4050 real_invoke_pending (EV_P) 4198 real_invoke_pending (EV_P)
4051 { 4199 {
4052 udat *u = ev_userdata (EV_A); 4200 userdata *u = ev_userdata (EV_A);
4053 4201
4054 pthread_mutex_lock (&u->lock); 4202 pthread_mutex_lock (&u->lock);
4055 ev_invoke_pending (EV_A); 4203 ev_invoke_pending (EV_A);
4056 pthread_cond_signal (&u->invoke_cv); 4204 pthread_cond_signal (&u->invoke_cv);
4057 pthread_mutex_unlock (&u->lock); 4205 pthread_mutex_unlock (&u->lock);
4059 4207
4060Whenever you want to start/stop a watcher or do other modifications to an 4208Whenever you want to start/stop a watcher or do other modifications to an
4061event loop, you will now have to lock: 4209event loop, you will now have to lock:
4062 4210
4063 ev_timer timeout_watcher; 4211 ev_timer timeout_watcher;
4064 udat *u = ev_userdata (EV_A); 4212 userdata *u = ev_userdata (EV_A);
4065 4213
4066 ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); 4214 ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4067 4215
4068 pthread_mutex_lock (&u->lock); 4216 pthread_mutex_lock (&u->lock);
4069 ev_timer_start (EV_A_ &timeout_watcher); 4217 ev_timer_start (EV_A_ &timeout_watcher);
4078=head3 COROUTINES 4226=head3 COROUTINES
4079 4227
4080Libev is very accommodating to coroutines ("cooperative threads"): 4228Libev is very accommodating to coroutines ("cooperative threads"):
4081libev fully supports nesting calls to its functions from different 4229libev fully supports nesting calls to its functions from different
4082coroutines (e.g. you can call C<ev_loop> on the same loop from two 4230coroutines (e.g. you can call C<ev_loop> on the same loop from two
4083different coroutines, and switch freely between both coroutines running the 4231different coroutines, and switch freely between both coroutines running
4084loop, as long as you don't confuse yourself). The only exception is that 4232the loop, as long as you don't confuse yourself). The only exception is
4085you must not do this from C<ev_periodic> reschedule callbacks. 4233that you must not do this from C<ev_periodic> reschedule callbacks.
4086 4234
4087Care has been taken to ensure that libev does not keep local state inside 4235Care has been taken to ensure that libev does not keep local state inside
4088C<ev_loop>, and other calls do not usually allow for coroutine switches as 4236C<ev_loop>, and other calls do not usually allow for coroutine switches as
4089they do not call any callbacks. 4237they do not call any callbacks.
4090 4238

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