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118Libev is very configurable. In this manual the default (and most common) 118Libev is very configurable. In this manual the default (and most common)
119configuration will be described, which supports multiple event loops. For 119configuration will be described, which supports multiple event loops. For
120more info about various configuration options please have a look at 120more info about various configuration options please have a look at
121B<EMBED> section in this manual. If libev was configured without support 121B<EMBED> section in this manual. If libev was configured without support
122for multiple event loops, then all functions taking an initial argument of 122for multiple event loops, then all functions taking an initial argument of
123name 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
124this argument. 124this argument.
125 125
126=head2 TIME REPRESENTATION 126=head2 TIME REPRESENTATION
127 127
128Libev represents time as a single floating point number, representing 128Libev represents time as a single floating point number, representing
410 410
411This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and 411This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
412C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. 412C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
413 413
414=item C<EVBACKEND_EPOLL> (value 4, Linux) 414=item C<EVBACKEND_EPOLL> (value 4, Linux)
415
416Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
417kernels).
415 418
416For few fds, this backend is a bit little slower than poll and select, 419For few fds, this backend is a bit little slower than poll and select,
417but it scales phenomenally better. While poll and select usually scale 420but it scales phenomenally better. While poll and select usually scale
418like O(total_fds) where n is the total number of fds (or the highest fd), 421like O(total_fds) where n is the total number of fds (or the highest fd),
419epoll scales either O(1) or O(active_fds). 422epoll scales either O(1) or O(active_fds).
789 792
790Ref/unref can be used to add or remove a reference count on the event 793Ref/unref can be used to add or remove a reference count on the event
791loop: Every watcher keeps one reference, and as long as the reference 794loop: Every watcher keeps one reference, and as long as the reference
792count is nonzero, C<ev_loop> will not return on its own. 795count is nonzero, C<ev_loop> will not return on its own.
793 796
794If you have a watcher you never unregister that should not keep C<ev_loop> 797This is useful when you have a watcher that you never intend to
795from returning, call ev_unref() after starting, and ev_ref() before 798unregister, but that nevertheless should not keep C<ev_loop> from
799returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
796stopping it. 800before stopping it.
797 801
798As an example, libev itself uses this for its internal signal pipe: It 802As an example, libev itself uses this for its internal signal pipe: It
799is not visible to the libev user and should not keep C<ev_loop> from 803is not visible to the libev user and should not keep C<ev_loop> from
800exiting if no event watchers registered by it are active. It is also an 804exiting if no event watchers registered by it are active. It is also an
801excellent way to do this for generic recurring timers or from within 805excellent way to do this for generic recurring timers or from within
916 920
917While event loop modifications are allowed between invocations of 921While event loop modifications are allowed between invocations of
918C<release> and C<acquire> (that's their only purpose after all), no 922C<release> and C<acquire> (that's their only purpose after all), no
919modifications done will affect the event loop, i.e. adding watchers will 923modifications done will affect the event loop, i.e. adding watchers will
920have no effect on the set of file descriptors being watched, or the time 924have no effect on the set of file descriptors being watched, or the time
921waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it 925waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it
922to take note of any changes you made. 926to take note of any changes you made.
923 927
924In theory, threads executing C<ev_loop> will be async-cancel safe between 928In theory, threads executing C<ev_loop> will be async-cancel safe between
925invocations of C<release> and C<acquire>. 929invocations of C<release> and C<acquire>.
926 930
1123 1127
1124 ev_io w; 1128 ev_io w;
1125 ev_init (&w, my_cb); 1129 ev_init (&w, my_cb);
1126 ev_io_set (&w, STDIN_FILENO, EV_READ); 1130 ev_io_set (&w, STDIN_FILENO, EV_READ);
1127 1131
1128=item C<ev_TYPE_set> (ev_TYPE *, [args]) 1132=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1129 1133
1130This macro initialises the type-specific parts of a watcher. You need to 1134This macro initialises the type-specific parts of a watcher. You need to
1131call C<ev_init> at least once before you call this macro, but you can 1135call C<ev_init> at least once before you call this macro, but you can
1132call C<ev_TYPE_set> any number of times. You must not, however, call this 1136call C<ev_TYPE_set> any number of times. You must not, however, call this
1133macro on a watcher that is active (it can be pending, however, which is a 1137macro on a watcher that is active (it can be pending, however, which is a
1146 1150
1147Example: Initialise and set an C<ev_io> watcher in one step. 1151Example: Initialise and set an C<ev_io> watcher in one step.
1148 1152
1149 ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); 1153 ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1150 1154
1151=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) 1155=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1152 1156
1153Starts (activates) the given watcher. Only active watchers will receive 1157Starts (activates) the given watcher. Only active watchers will receive
1154events. If the watcher is already active nothing will happen. 1158events. If the watcher is already active nothing will happen.
1155 1159
1156Example: Start the C<ev_io> watcher that is being abused as example in this 1160Example: Start the C<ev_io> watcher that is being abused as example in this
1157whole section. 1161whole section.
1158 1162
1159 ev_io_start (EV_DEFAULT_UC, &w); 1163 ev_io_start (EV_DEFAULT_UC, &w);
1160 1164
1161=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) 1165=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1162 1166
1163Stops the given watcher if active, and clears the pending status (whether 1167Stops the given watcher if active, and clears the pending status (whether
1164the watcher was active or not). 1168the watcher was active or not).
1165 1169
1166It is possible that stopped watchers are pending - for example, 1170It is possible that stopped watchers are pending - for example,
1191=item ev_cb_set (ev_TYPE *watcher, callback) 1195=item ev_cb_set (ev_TYPE *watcher, callback)
1192 1196
1193Change the callback. You can change the callback at virtually any time 1197Change the callback. You can change the callback at virtually any time
1194(modulo threads). 1198(modulo threads).
1195 1199
1196=item ev_set_priority (ev_TYPE *watcher, priority) 1200=item ev_set_priority (ev_TYPE *watcher, int priority)
1197 1201
1198=item int ev_priority (ev_TYPE *watcher) 1202=item int ev_priority (ev_TYPE *watcher)
1199 1203
1200Set and query the priority of the watcher. The priority is a small 1204Set and query the priority of the watcher. The priority is a small
1201integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> 1205integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1232returns its C<revents> bitset (as if its callback was invoked). If the 1236returns its C<revents> bitset (as if its callback was invoked). If the
1233watcher isn't pending it does nothing and returns C<0>. 1237watcher isn't pending it does nothing and returns C<0>.
1234 1238
1235Sometimes it can be useful to "poll" a watcher instead of waiting for its 1239Sometimes it can be useful to "poll" a watcher instead of waiting for its
1236callback to be invoked, which can be accomplished with this function. 1240callback to be invoked, which can be accomplished with this function.
1241
1242=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
1243
1244Feeds the given event set into the event loop, as if the specified event
1245had happened for the specified watcher (which must be a pointer to an
1246initialised but not necessarily started event watcher). Obviously you must
1247not free the watcher as long as it has pending events.
1248
1249Stopping the watcher, letting libev invoke it, or calling
1250C<ev_clear_pending> will clear the pending event, even if the watcher was
1251not started in the first place.
1252
1253See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1254functions that do not need a watcher.
1237 1255
1238=back 1256=back
1239 1257
1240 1258
1241=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER 1259=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1837C<repeat> value), or reset the running timer to the C<repeat> value. 1855C<repeat> value), or reset the running timer to the C<repeat> value.
1838 1856
1839This sounds a bit complicated, see L<Be smart about timeouts>, above, for a 1857This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1840usage example. 1858usage example.
1841 1859
1842=item ev_timer_remaining (loop, ev_timer *) 1860=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1843 1861
1844Returns the remaining time until a timer fires. If the timer is active, 1862Returns the remaining time until a timer fires. If the timer is active,
1845then this time is relative to the current event loop time, otherwise it's 1863then this time is relative to the current event loop time, otherwise it's
1846the timeout value currently configured. 1864the timeout value currently configured.
1847 1865
2136to install a fork handler with C<pthread_atfork> that resets it. That will 2154to install a fork handler with C<pthread_atfork> that resets it. That will
2137catch fork calls done by libraries (such as the libc) as well. 2155catch fork calls done by libraries (such as the libc) as well.
2138 2156
2139In current versions of libev, you can also ensure that the signal mask is 2157In current versions of libev, you can also ensure that the signal mask is
2140not blocking any signals (except temporarily, so thread users watch out) 2158not blocking any signals (except temporarily, so thread users watch out)
2141by specifying the C<EVFLAG_NOSIGNALFD> when creating the event loop. This 2159by specifying the C<EVFLAG_NOSIGFD> when creating the event loop. This
2142is not guaranteed for future versions, however. 2160is not guaranteed for future versions, however.
2143 2161
2144=head3 Watcher-Specific Functions and Data Members 2162=head3 Watcher-Specific Functions and Data Members
2145 2163
2146=over 4 2164=over 4
2964=head3 Queueing 2982=head3 Queueing
2965 2983
2966C<ev_async> does not support queueing of data in any way. The reason 2984C<ev_async> does not support queueing of data in any way. The reason
2967is that the author does not know of a simple (or any) algorithm for a 2985is that the author does not know of a simple (or any) algorithm for a
2968multiple-writer-single-reader queue that works in all cases and doesn't 2986multiple-writer-single-reader queue that works in all cases and doesn't
2969need elaborate support such as pthreads. 2987need elaborate support such as pthreads or unportable memory access
2988semantics.
2970 2989
2971That means that if you want to queue data, you have to provide your own 2990That means that if you want to queue data, you have to provide your own
2972queue. But at least I can tell you how to implement locking around your 2991queue. But at least I can tell you how to implement locking around your
2973queue: 2992queue:
2974 2993
3132 /* doh, nothing entered */; 3151 /* doh, nothing entered */;
3133 } 3152 }
3134 3153
3135 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); 3154 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3136 3155
3137=item ev_feed_event (struct ev_loop *, watcher *, int revents)
3138
3139Feeds the given event set into the event loop, as if the specified event
3140had happened for the specified watcher (which must be a pointer to an
3141initialised but not necessarily started event watcher).
3142
3143=item ev_feed_fd_event (struct ev_loop *, int fd, int revents) 3156=item ev_feed_fd_event (loop, int fd, int revents)
3144 3157
3145Feed an event on the given fd, as if a file descriptor backend detected 3158Feed an event on the given fd, as if a file descriptor backend detected
3146the given events it. 3159the given events it.
3147 3160
3148=item ev_feed_signal_event (struct ev_loop *loop, int signum) 3161=item ev_feed_signal_event (loop, int signum)
3149 3162
3150Feed an event as if the given signal occurred (C<loop> must be the default 3163Feed an event as if the given signal occurred (C<loop> must be the default
3151loop!). 3164loop!).
3152 3165
3153=back 3166=back
3233 3246
3234=over 4 3247=over 4
3235 3248
3236=item ev::TYPE::TYPE () 3249=item ev::TYPE::TYPE ()
3237 3250
3238=item ev::TYPE::TYPE (struct ev_loop *) 3251=item ev::TYPE::TYPE (loop)
3239 3252
3240=item ev::TYPE::~TYPE 3253=item ev::TYPE::~TYPE
3241 3254
3242The constructor (optionally) takes an event loop to associate the watcher 3255The constructor (optionally) takes an event loop to associate the watcher
3243with. If it is omitted, it will use C<EV_DEFAULT>. 3256with. If it is omitted, it will use C<EV_DEFAULT>.
3320Example: Use a plain function as callback. 3333Example: Use a plain function as callback.
3321 3334
3322 static void io_cb (ev::io &w, int revents) { } 3335 static void io_cb (ev::io &w, int revents) { }
3323 iow.set <io_cb> (); 3336 iow.set <io_cb> ();
3324 3337
3325=item w->set (struct ev_loop *) 3338=item w->set (loop)
3326 3339
3327Associates a different C<struct ev_loop> with this watcher. You can only 3340Associates a different C<struct ev_loop> with this watcher. You can only
3328do this when the watcher is inactive (and not pending either). 3341do this when the watcher is inactive (and not pending either).
3329 3342
3330=item w->set ([arguments]) 3343=item w->set ([arguments])

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