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4 | <head> |
4 | <head> |
5 | <title>libev</title> |
5 | <title>libev</title> |
6 | <meta name="description" content="Pod documentation for libev" /> |
6 | <meta name="description" content="Pod documentation for libev" /> |
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14 | <!-- INDEX START --> |
14 | <!-- INDEX START --> |
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119 | </pre> |
119 | </pre> |
120 | |
120 | |
121 | </div> |
121 | </div> |
122 | <h1 id="DESCRIPTION">DESCRIPTION</h1> |
122 | <h1 id="DESCRIPTION">DESCRIPTION</h1> |
123 | <div id="DESCRIPTION_CONTENT"> |
123 | <div id="DESCRIPTION_CONTENT"> |
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124 | <p>The newest version of this document is also available as a html-formatted |
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125 | web page you might find easier to navigate when reading it for the first |
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126 | time: <a href="http://cvs.schmorp.de/libev/ev.html">http://cvs.schmorp.de/libev/ev.html</a>.</p> |
124 | <p>Libev is an event loop: you register interest in certain events (such as a |
127 | <p>Libev is an event loop: you register interest in certain events (such as a |
125 | file descriptor being readable or a timeout occuring), and it will manage |
128 | file descriptor being readable or a timeout occuring), and it will manage |
126 | these event sources and provide your program with events.</p> |
129 | these event sources and provide your program with events.</p> |
127 | <p>To do this, it must take more or less complete control over your process |
130 | <p>To do this, it must take more or less complete control over your process |
128 | (or thread) by executing the <i>event loop</i> handler, and will then |
131 | (or thread) by executing the <i>event loop</i> handler, and will then |
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133 | watcher.</p> |
136 | watcher.</p> |
134 | |
137 | |
135 | </div> |
138 | </div> |
136 | <h1 id="FEATURES">FEATURES</h1> |
139 | <h1 id="FEATURES">FEATURES</h1> |
137 | <div id="FEATURES_CONTENT"> |
140 | <div id="FEATURES_CONTENT"> |
138 | <p>Libev supports <code>select</code>, <code>poll</code>, the linux-specific <code>epoll</code>, the |
141 | <p>Libev supports <code>select</code>, <code>poll</code>, the Linux-specific <code>epoll</code>, the |
139 | bsd-specific <code>kqueue</code> and the solaris-specific event port mechanisms |
142 | BSD-specific <code>kqueue</code> and the Solaris-specific event port mechanisms |
140 | for file descriptor events (<code>ev_io</code>), relative timers (<code>ev_timer</code>), |
143 | for file descriptor events (<code>ev_io</code>), the Linux <code>inotify</code> interface |
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144 | (for <code>ev_stat</code>), relative timers (<code>ev_timer</code>), absolute timers |
141 | absolute timers with customised rescheduling (<code>ev_periodic</code>), synchronous |
145 | with customised rescheduling (<code>ev_periodic</code>), synchronous signals |
142 | signals (<code>ev_signal</code>), process status change events (<code>ev_child</code>), and |
146 | (<code>ev_signal</code>), process status change events (<code>ev_child</code>), and event |
143 | event watchers dealing with the event loop mechanism itself (<code>ev_idle</code>, |
147 | watchers dealing with the event loop mechanism itself (<code>ev_idle</code>, |
144 | <code>ev_embed</code>, <code>ev_prepare</code> and <code>ev_check</code> watchers) as well as |
148 | <code>ev_embed</code>, <code>ev_prepare</code> and <code>ev_check</code> watchers) as well as |
145 | file watchers (<code>ev_stat</code>) and even limited support for fork events |
149 | file watchers (<code>ev_stat</code>) and even limited support for fork events |
146 | (<code>ev_fork</code>).</p> |
150 | (<code>ev_fork</code>).</p> |
147 | <p>It also is quite fast (see this |
151 | <p>It also is quite fast (see this |
148 | <a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it to libevent |
152 | <a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it to libevent |
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229 | might be supported on the current system, you would need to look at |
233 | might be supported on the current system, you would need to look at |
230 | <code>ev_embeddable_backends () & ev_supported_backends ()</code>, likewise for |
234 | <code>ev_embeddable_backends () & ev_supported_backends ()</code>, likewise for |
231 | recommended ones.</p> |
235 | recommended ones.</p> |
232 | <p>See the description of <code>ev_embed</code> watchers for more info.</p> |
236 | <p>See the description of <code>ev_embed</code> watchers for more info.</p> |
233 | </dd> |
237 | </dd> |
234 | <dt>ev_set_allocator (void *(*cb)(void *ptr, size_t size))</dt> |
238 | <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> |
235 | <dd> |
239 | <dd> |
236 | <p>Sets the allocation function to use (the prototype and semantics are |
240 | <p>Sets the allocation function to use (the prototype is similar - the |
237 | identical to the realloc C function). It is used to allocate and free |
241 | semantics is identical - to the realloc C function). It is used to |
238 | memory (no surprises here). If it returns zero when memory needs to be |
242 | allocate and free memory (no surprises here). If it returns zero when |
239 | allocated, the library might abort or take some potentially destructive |
243 | memory needs to be allocated, the library might abort or take some |
240 | action. The default is your system realloc function.</p> |
244 | potentially destructive action. The default is your system realloc |
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245 | function.</p> |
241 | <p>You could override this function in high-availability programs to, say, |
246 | <p>You could override this function in high-availability programs to, say, |
242 | free some memory if it cannot allocate memory, to use a special allocator, |
247 | free some memory if it cannot allocate memory, to use a special allocator, |
243 | or even to sleep a while and retry until some memory is available.</p> |
248 | or even to sleep a while and retry until some memory is available.</p> |
244 | <p>Example: Replace the libev allocator with one that waits a bit and then |
249 | <p>Example: Replace the libev allocator with one that waits a bit and then |
245 | retries).</p> |
250 | retries).</p> |
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324 | <code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will |
329 | <code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will |
325 | override the flags completely if it is found in the environment. This is |
330 | override the flags completely if it is found in the environment. This is |
326 | useful to try out specific backends to test their performance, or to work |
331 | useful to try out specific backends to test their performance, or to work |
327 | around bugs.</p> |
332 | around bugs.</p> |
328 | </dd> |
333 | </dd> |
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334 | <dt><code>EVFLAG_FORKCHECK</code></dt> |
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335 | <dd> |
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336 | <p>Instead of calling <code>ev_default_fork</code> or <code>ev_loop_fork</code> manually after |
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337 | a fork, you can also make libev check for a fork in each iteration by |
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338 | enabling this flag.</p> |
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339 | <p>This works by calling <code>getpid ()</code> on every iteration of the loop, |
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340 | and thus this might slow down your event loop if you do a lot of loop |
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341 | iterations and little real work, but is usually not noticeable (on my |
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342 | Linux system for example, <code>getpid</code> is actually a simple 5-insn sequence |
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343 | without a syscall and thus <i>very</i> fast, but my Linux system also has |
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344 | <code>pthread_atfork</code> which is even faster).</p> |
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345 | <p>The big advantage of this flag is that you can forget about fork (and |
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346 | forget about forgetting to tell libev about forking) when you use this |
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347 | flag.</p> |
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348 | <p>This flag setting cannot be overriden or specified in the <code>LIBEV_FLAGS</code> |
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349 | environment variable.</p> |
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350 | </dd> |
329 | <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt> |
351 | <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt> |
330 | <dd> |
352 | <dd> |
331 | <p>This is your standard select(2) backend. Not <i>completely</i> standard, as |
353 | <p>This is your standard select(2) backend. Not <i>completely</i> standard, as |
332 | libev tries to roll its own fd_set with no limits on the number of fds, |
354 | libev tries to roll its own fd_set with no limits on the number of fds, |
333 | but if that fails, expect a fairly low limit on the number of fds when |
355 | but if that fails, expect a fairly low limit on the number of fds when |
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461 | <dt>ev_loop_fork (loop)</dt> |
483 | <dt>ev_loop_fork (loop)</dt> |
462 | <dd> |
484 | <dd> |
463 | <p>Like <code>ev_default_fork</code>, but acts on an event loop created by |
485 | <p>Like <code>ev_default_fork</code>, but acts on an event loop created by |
464 | <code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop |
486 | <code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop |
465 | after fork, and how you do this is entirely your own problem.</p> |
487 | after fork, and how you do this is entirely your own problem.</p> |
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488 | </dd> |
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489 | <dt>unsigned int ev_loop_count (loop)</dt> |
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490 | <dd> |
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491 | <p>Returns the count of loop iterations for the loop, which is identical to |
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492 | the number of times libev did poll for new events. It starts at <code>0</code> and |
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493 | happily wraps around with enough iterations.</p> |
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494 | <p>This value can sometimes be useful as a generation counter of sorts (it |
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495 | "ticks" the number of loop iterations), as it roughly corresponds with |
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496 | <code>ev_prepare</code> and <code>ev_check</code> calls.</p> |
466 | </dd> |
497 | </dd> |
467 | <dt>unsigned int ev_backend (loop)</dt> |
498 | <dt>unsigned int ev_backend (loop)</dt> |
468 | <dd> |
499 | <dd> |
469 | <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in |
500 | <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in |
470 | use.</p> |
501 | use.</p> |
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498 | one iteration of the loop. This is useful if you are waiting for some |
529 | one iteration of the loop. This is useful if you are waiting for some |
499 | external event in conjunction with something not expressible using other |
530 | external event in conjunction with something not expressible using other |
500 | libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is |
531 | libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is |
501 | usually a better approach for this kind of thing.</p> |
532 | usually a better approach for this kind of thing.</p> |
502 | <p>Here are the gory details of what <code>ev_loop</code> does:</p> |
533 | <p>Here are the gory details of what <code>ev_loop</code> does:</p> |
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534 | <pre> - Before the first iteration, call any pending watchers. |
503 | <pre> * If there are no active watchers (reference count is zero), return. |
535 | * If there are no active watchers (reference count is zero), return. |
504 | - Queue prepare watchers and then call all outstanding watchers. |
536 | - Queue all prepare watchers and then call all outstanding watchers. |
505 | - If we have been forked, recreate the kernel state. |
537 | - If we have been forked, recreate the kernel state. |
506 | - Update the kernel state with all outstanding changes. |
538 | - Update the kernel state with all outstanding changes. |
507 | - Update the "event loop time". |
539 | - Update the "event loop time". |
508 | - Calculate for how long to block. |
540 | - Calculate for how long to block. |
509 | - Block the process, waiting for any events. |
541 | - Block the process, waiting for any events. |
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738 | <dt>bool ev_is_pending (ev_TYPE *watcher)</dt> |
770 | <dt>bool ev_is_pending (ev_TYPE *watcher)</dt> |
739 | <dd> |
771 | <dd> |
740 | <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding |
772 | <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding |
741 | events but its callback has not yet been invoked). As long as a watcher |
773 | events but its callback has not yet been invoked). As long as a watcher |
742 | is pending (but not active) you must not call an init function on it (but |
774 | is pending (but not active) you must not call an init function on it (but |
743 | <code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to |
775 | <code>ev_TYPE_set</code> is safe), you must not change its priority, and you must |
744 | libev (e.g. you cnanot <code>free ()</code> it).</p> |
776 | make sure the watcher is available to libev (e.g. you cannot <code>free ()</code> |
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777 | it).</p> |
745 | </dd> |
778 | </dd> |
746 | <dt>callback ev_cb (ev_TYPE *watcher)</dt> |
779 | <dt>callback ev_cb (ev_TYPE *watcher)</dt> |
747 | <dd> |
780 | <dd> |
748 | <p>Returns the callback currently set on the watcher.</p> |
781 | <p>Returns the callback currently set on the watcher.</p> |
749 | </dd> |
782 | </dd> |
750 | <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt> |
783 | <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt> |
751 | <dd> |
784 | <dd> |
752 | <p>Change the callback. You can change the callback at virtually any time |
785 | <p>Change the callback. You can change the callback at virtually any time |
753 | (modulo threads).</p> |
786 | (modulo threads).</p> |
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787 | </dd> |
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788 | <dt>ev_set_priority (ev_TYPE *watcher, priority)</dt> |
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789 | <dt>int ev_priority (ev_TYPE *watcher)</dt> |
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790 | <dd> |
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791 | <p>Set and query the priority of the watcher. The priority is a small |
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792 | integer between <code>EV_MAXPRI</code> (default: <code>2</code>) and <code>EV_MINPRI</code> |
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793 | (default: <code>-2</code>). Pending watchers with higher priority will be invoked |
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794 | before watchers with lower priority, but priority will not keep watchers |
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795 | from being executed (except for <code>ev_idle</code> watchers).</p> |
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796 | <p>This means that priorities are <i>only</i> used for ordering callback |
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797 | invocation after new events have been received. This is useful, for |
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798 | example, to reduce latency after idling, or more often, to bind two |
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799 | watchers on the same event and make sure one is called first.</p> |
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800 | <p>If you need to suppress invocation when higher priority events are pending |
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801 | you need to look at <code>ev_idle</code> watchers, which provide this functionality.</p> |
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802 | <p>You <i>must not</i> change the priority of a watcher as long as it is active or |
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803 | pending.</p> |
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804 | <p>The default priority used by watchers when no priority has been set is |
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805 | always <code>0</code>, which is supposed to not be too high and not be too low :).</p> |
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806 | <p>Setting a priority outside the range of <code>EV_MINPRI</code> to <code>EV_MAXPRI</code> is |
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807 | fine, as long as you do not mind that the priority value you query might |
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808 | or might not have been adjusted to be within valid range.</p> |
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809 | </dd> |
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810 | <dt>ev_invoke (loop, ev_TYPE *watcher, int revents)</dt> |
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811 | <dd> |
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812 | <p>Invoke the <code>watcher</code> with the given <code>loop</code> and <code>revents</code>. Neither |
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813 | <code>loop</code> nor <code>revents</code> need to be valid as long as the watcher callback |
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814 | can deal with that fact.</p> |
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815 | </dd> |
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816 | <dt>int ev_clear_pending (loop, ev_TYPE *watcher)</dt> |
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817 | <dd> |
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|
818 | <p>If the watcher is pending, this function returns clears its pending status |
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819 | and returns its <code>revents</code> bitset (as if its callback was invoked). If the |
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820 | watcher isn't pending it does nothing and returns <code>0</code>.</p> |
754 | </dd> |
821 | </dd> |
755 | </dl> |
822 | </dl> |
756 | |
823 | |
757 | |
824 | |
758 | |
825 | |
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869 | this situation even with a relatively standard program structure. Thus |
936 | this situation even with a relatively standard program structure. Thus |
870 | it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning |
937 | it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning |
871 | <code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p> |
938 | <code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p> |
872 | <p>If you cannot run the fd in non-blocking mode (for example you should not |
939 | <p>If you cannot run the fd in non-blocking mode (for example you should not |
873 | play around with an Xlib connection), then you have to seperately re-test |
940 | play around with an Xlib connection), then you have to seperately re-test |
874 | wether a file descriptor is really ready with a known-to-be good interface |
941 | whether a file descriptor is really ready with a known-to-be good interface |
875 | such as poll (fortunately in our Xlib example, Xlib already does this on |
942 | such as poll (fortunately in our Xlib example, Xlib already does this on |
876 | its own, so its quite safe to use).</p> |
943 | its own, so its quite safe to use).</p> |
877 | <dl> |
944 | <dl> |
878 | <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> |
945 | <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> |
879 | <dt>ev_io_set (ev_io *, int fd, int events)</dt> |
946 | <dt>ev_io_set (ev_io *, int fd, int events)</dt> |
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950 | </dd> |
1017 | </dd> |
951 | <dt>ev_timer_again (loop)</dt> |
1018 | <dt>ev_timer_again (loop)</dt> |
952 | <dd> |
1019 | <dd> |
953 | <p>This will act as if the timer timed out and restart it again if it is |
1020 | <p>This will act as if the timer timed out and restart it again if it is |
954 | repeating. The exact semantics are:</p> |
1021 | repeating. The exact semantics are:</p> |
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|
1022 | <p>If the timer is pending, its pending status is cleared.</p> |
955 | <p>If the timer is started but nonrepeating, stop it.</p> |
1023 | <p>If the timer is started but nonrepeating, stop it (as if it timed out).</p> |
956 | <p>If the timer is repeating, either start it if necessary (with the repeat |
1024 | <p>If the timer is repeating, either start it if necessary (with the |
957 | value), or reset the running timer to the repeat value.</p> |
1025 | <code>repeat</code> value), or reset the running timer to the <code>repeat</code> value.</p> |
958 | <p>This sounds a bit complicated, but here is a useful and typical |
1026 | <p>This sounds a bit complicated, but here is a useful and typical |
959 | example: Imagine you have a tcp connection and you want a so-called |
1027 | example: Imagine you have a tcp connection and you want a so-called idle |
960 | idle timeout, that is, you want to be called when there have been, |
1028 | timeout, that is, you want to be called when there have been, say, 60 |
961 | say, 60 seconds of inactivity on the socket. The easiest way to do |
1029 | seconds of inactivity on the socket. The easiest way to do this is to |
962 | this is to configure an <code>ev_timer</code> with <code>after</code>=<code>repeat</code>=<code>60</code> and calling |
1030 | configure an <code>ev_timer</code> with a <code>repeat</code> value of <code>60</code> and then call |
963 | <code>ev_timer_again</code> each time you successfully read or write some data. If |
1031 | <code>ev_timer_again</code> each time you successfully read or write some data. If |
964 | you go into an idle state where you do not expect data to travel on the |
1032 | you go into an idle state where you do not expect data to travel on the |
965 | socket, you can stop the timer, and again will automatically restart it if |
1033 | socket, you can <code>ev_timer_stop</code> the timer, and <code>ev_timer_again</code> will |
966 | need be.</p> |
1034 | automatically restart it if need be.</p> |
967 | <p>You can also ignore the <code>after</code> value and <code>ev_timer_start</code> altogether |
1035 | <p>That means you can ignore the <code>after</code> value and <code>ev_timer_start</code> |
968 | and only ever use the <code>repeat</code> value:</p> |
1036 | altogether and only ever use the <code>repeat</code> value and <code>ev_timer_again</code>:</p> |
969 | <pre> ev_timer_init (timer, callback, 0., 5.); |
1037 | <pre> ev_timer_init (timer, callback, 0., 5.); |
970 | ev_timer_again (loop, timer); |
1038 | ev_timer_again (loop, timer); |
971 | ... |
1039 | ... |
972 | timer->again = 17.; |
1040 | timer->again = 17.; |
973 | ev_timer_again (loop, timer); |
1041 | ev_timer_again (loop, timer); |
974 | ... |
1042 | ... |
975 | timer->again = 10.; |
1043 | timer->again = 10.; |
976 | ev_timer_again (loop, timer); |
1044 | ev_timer_again (loop, timer); |
977 | |
1045 | |
978 | </pre> |
1046 | </pre> |
979 | <p>This is more efficient then stopping/starting the timer eahc time you want |
1047 | <p>This is more slightly efficient then stopping/starting the timer each time |
980 | to modify its timeout value.</p> |
1048 | you want to modify its timeout value.</p> |
981 | </dd> |
1049 | </dd> |
982 | <dt>ev_tstamp repeat [read-write]</dt> |
1050 | <dt>ev_tstamp repeat [read-write]</dt> |
983 | <dd> |
1051 | <dd> |
984 | <p>The current <code>repeat</code> value. Will be used each time the watcher times out |
1052 | <p>The current <code>repeat</code> value. Will be used each time the watcher times out |
985 | or <code>ev_timer_again</code> is called and determines the next timeout (if any), |
1053 | or <code>ev_timer_again</code> is called and determines the next timeout (if any), |
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1246 | <p>The path does not need to exist: changing from "path exists" to "path does |
1314 | <p>The path does not need to exist: changing from "path exists" to "path does |
1247 | not exist" is a status change like any other. The condition "path does |
1315 | not exist" is a status change like any other. The condition "path does |
1248 | not exist" is signified by the <code>st_nlink</code> field being zero (which is |
1316 | not exist" is signified by the <code>st_nlink</code> field being zero (which is |
1249 | otherwise always forced to be at least one) and all the other fields of |
1317 | otherwise always forced to be at least one) and all the other fields of |
1250 | the stat buffer having unspecified contents.</p> |
1318 | the stat buffer having unspecified contents.</p> |
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1319 | <p>The path <i>should</i> be absolute and <i>must not</i> end in a slash. If it is |
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1320 | relative and your working directory changes, the behaviour is undefined.</p> |
1251 | <p>Since there is no standard to do this, the portable implementation simply |
1321 | <p>Since there is no standard to do this, the portable implementation simply |
1252 | calls <code>stat (2)</code> regulalry on the path to see if it changed somehow. You |
1322 | calls <code>stat (2)</code> regularly on the path to see if it changed somehow. You |
1253 | can specify a recommended polling interval for this case. If you specify |
1323 | can specify a recommended polling interval for this case. If you specify |
1254 | a polling interval of <code>0</code> (highly recommended!) then a <i>suitable, |
1324 | a polling interval of <code>0</code> (highly recommended!) then a <i>suitable, |
1255 | unspecified default</i> value will be used (which you can expect to be around |
1325 | unspecified default</i> value will be used (which you can expect to be around |
1256 | five seconds, although this might change dynamically). Libev will also |
1326 | five seconds, although this might change dynamically). Libev will also |
1257 | impose a minimum interval which is currently around <code>0.1</code>, but thats |
1327 | impose a minimum interval which is currently around <code>0.1</code>, but thats |
1258 | usually overkill.</p> |
1328 | usually overkill.</p> |
1259 | <p>This watcher type is not meant for massive numbers of stat watchers, |
1329 | <p>This watcher type is not meant for massive numbers of stat watchers, |
1260 | as even with OS-supported change notifications, this can be |
1330 | as even with OS-supported change notifications, this can be |
1261 | resource-intensive.</p> |
1331 | resource-intensive.</p> |
1262 | <p>At the time of this writing, no specific OS backends are implemented, but |
1332 | <p>At the time of this writing, only the Linux inotify interface is |
1263 | if demand increases, at least a kqueue and inotify backend will be added.</p> |
1333 | implemented (implementing kqueue support is left as an exercise for the |
|
|
1334 | reader). Inotify will be used to give hints only and should not change the |
|
|
1335 | semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs |
|
|
1336 | to fall back to regular polling again even with inotify, but changes are |
|
|
1337 | usually detected immediately, and if the file exists there will be no |
|
|
1338 | polling.</p> |
1264 | <dl> |
1339 | <dl> |
1265 | <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt> |
1340 | <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt> |
1266 | <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt> |
1341 | <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt> |
1267 | <dd> |
1342 | <dd> |
1268 | <p>Configures the watcher to wait for status changes of the given |
1343 | <p>Configures the watcher to wait for status changes of the given |
… | |
… | |
1331 | </pre> |
1406 | </pre> |
1332 | |
1407 | |
1333 | </div> |
1408 | </div> |
1334 | <h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2> |
1409 | <h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2> |
1335 | <div id="code_ev_idle_code_when_you_ve_got_no-2"> |
1410 | <div id="code_ev_idle_code_when_you_ve_got_no-2"> |
1336 | <p>Idle watchers trigger events when there are no other events are pending |
1411 | <p>Idle watchers trigger events when no other events of the same or higher |
1337 | (prepare, check and other idle watchers do not count). That is, as long |
1412 | priority are pending (prepare, check and other idle watchers do not |
1338 | as your process is busy handling sockets or timeouts (or even signals, |
1413 | count).</p> |
1339 | imagine) it will not be triggered. But when your process is idle all idle |
1414 | <p>That is, as long as your process is busy handling sockets or timeouts |
1340 | watchers are being called again and again, once per event loop iteration - |
1415 | (or even signals, imagine) of the same or higher priority it will not be |
|
|
1416 | triggered. But when your process is idle (or only lower-priority watchers |
|
|
1417 | are pending), the idle watchers are being called once per event loop |
1341 | until stopped, that is, or your process receives more events and becomes |
1418 | iteration - until stopped, that is, or your process receives more events |
1342 | busy.</p> |
1419 | and becomes busy again with higher priority stuff.</p> |
1343 | <p>The most noteworthy effect is that as long as any idle watchers are |
1420 | <p>The most noteworthy effect is that as long as any idle watchers are |
1344 | active, the process will not block when waiting for new events.</p> |
1421 | active, the process will not block when waiting for new events.</p> |
1345 | <p>Apart from keeping your process non-blocking (which is a useful |
1422 | <p>Apart from keeping your process non-blocking (which is a useful |
1346 | effect on its own sometimes), idle watchers are a good place to do |
1423 | effect on its own sometimes), idle watchers are a good place to do |
1347 | "pseudo-background processing", or delay processing stuff to after the |
1424 | "pseudo-background processing", or delay processing stuff to after the |
… | |
… | |
1407 | are ready to run (it's actually more complicated: it only runs coroutines |
1484 | are ready to run (it's actually more complicated: it only runs coroutines |
1408 | with priority higher than or equal to the event loop and one coroutine |
1485 | with priority higher than or equal to the event loop and one coroutine |
1409 | of lower priority, but only once, using idle watchers to keep the event |
1486 | of lower priority, but only once, using idle watchers to keep the event |
1410 | loop from blocking if lower-priority coroutines are active, thus mapping |
1487 | loop from blocking if lower-priority coroutines are active, thus mapping |
1411 | low-priority coroutines to idle/background tasks).</p> |
1488 | low-priority coroutines to idle/background tasks).</p> |
|
|
1489 | <p>It is recommended to give <code>ev_check</code> watchers highest (<code>EV_MAXPRI</code>) |
|
|
1490 | priority, to ensure that they are being run before any other watchers |
|
|
1491 | after the poll. Also, <code>ev_check</code> watchers (and <code>ev_prepare</code> watchers, |
|
|
1492 | too) should not activate ("feed") events into libev. While libev fully |
|
|
1493 | supports this, they will be called before other <code>ev_check</code> watchers did |
|
|
1494 | their job. As <code>ev_check</code> watchers are often used to embed other event |
|
|
1495 | loops those other event loops might be in an unusable state until their |
|
|
1496 | <code>ev_check</code> watcher ran (always remind yourself to coexist peacefully with |
|
|
1497 | others).</p> |
1412 | <dl> |
1498 | <dl> |
1413 | <dt>ev_prepare_init (ev_prepare *, callback)</dt> |
1499 | <dt>ev_prepare_init (ev_prepare *, callback)</dt> |
1414 | <dt>ev_check_init (ev_check *, callback)</dt> |
1500 | <dt>ev_check_init (ev_check *, callback)</dt> |
1415 | <dd> |
1501 | <dd> |
1416 | <p>Initialises and configures the prepare or check watcher - they have no |
1502 | <p>Initialises and configures the prepare or check watcher - they have no |
1417 | parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> |
1503 | parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> |
1418 | macros, but using them is utterly, utterly and completely pointless.</p> |
1504 | macros, but using them is utterly, utterly and completely pointless.</p> |
1419 | </dd> |
1505 | </dd> |
1420 | </dl> |
1506 | </dl> |
1421 | <p>Example: To include a library such as adns, you would add IO watchers |
1507 | <p>There are a number of principal ways to embed other event loops or modules |
1422 | and a timeout watcher in a prepare handler, as required by libadns, and |
1508 | into libev. Here are some ideas on how to include libadns into libev |
|
|
1509 | (there is a Perl module named <code>EV::ADNS</code> that does this, which you could |
|
|
1510 | use for an actually working example. Another Perl module named <code>EV::Glib</code> |
|
|
1511 | embeds a Glib main context into libev, and finally, <code>Glib::EV</code> embeds EV |
|
|
1512 | into the Glib event loop).</p> |
|
|
1513 | <p>Method 1: Add IO watchers and a timeout watcher in a prepare handler, |
1423 | in a check watcher, destroy them and call into libadns. What follows is |
1514 | and in a check watcher, destroy them and call into libadns. What follows |
1424 | pseudo-code only of course:</p> |
1515 | is pseudo-code only of course. This requires you to either use a low |
|
|
1516 | priority for the check watcher or use <code>ev_clear_pending</code> explicitly, as |
|
|
1517 | the callbacks for the IO/timeout watchers might not have been called yet.</p> |
1425 | <pre> static ev_io iow [nfd]; |
1518 | <pre> static ev_io iow [nfd]; |
1426 | static ev_timer tw; |
1519 | static ev_timer tw; |
1427 | |
1520 | |
1428 | static void |
1521 | static void |
1429 | io_cb (ev_loop *loop, ev_io *w, int revents) |
1522 | io_cb (ev_loop *loop, ev_io *w, int revents) |
1430 | { |
1523 | { |
1431 | // set the relevant poll flags |
|
|
1432 | // could also call adns_processreadable etc. here |
|
|
1433 | struct pollfd *fd = (struct pollfd *)w->data; |
|
|
1434 | if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; |
|
|
1435 | if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; |
|
|
1436 | } |
1524 | } |
1437 | |
1525 | |
1438 | // create io watchers for each fd and a timer before blocking |
1526 | // create io watchers for each fd and a timer before blocking |
1439 | static void |
1527 | static void |
1440 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
1528 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
1441 | { |
1529 | { |
1442 | int timeout = 3600000;truct pollfd fds [nfd]; |
1530 | int timeout = 3600000; |
|
|
1531 | struct pollfd fds [nfd]; |
1443 | // actual code will need to loop here and realloc etc. |
1532 | // actual code will need to loop here and realloc etc. |
1444 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
1533 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
1445 | |
1534 | |
1446 | /* the callback is illegal, but won't be called as we stop during check */ |
1535 | /* the callback is illegal, but won't be called as we stop during check */ |
1447 | ev_timer_init (&tw, 0, timeout * 1e-3); |
1536 | ev_timer_init (&tw, 0, timeout * 1e-3); |
1448 | ev_timer_start (loop, &tw); |
1537 | ev_timer_start (loop, &tw); |
1449 | |
1538 | |
1450 | // create on ev_io per pollfd |
1539 | // create one ev_io per pollfd |
1451 | for (int i = 0; i < nfd; ++i) |
1540 | for (int i = 0; i < nfd; ++i) |
1452 | { |
1541 | { |
1453 | ev_io_init (iow + i, io_cb, fds [i].fd, |
1542 | ev_io_init (iow + i, io_cb, fds [i].fd, |
1454 | ((fds [i].events & POLLIN ? EV_READ : 0) |
1543 | ((fds [i].events & POLLIN ? EV_READ : 0) |
1455 | | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
1544 | | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
1456 | |
1545 | |
1457 | fds [i].revents = 0; |
1546 | fds [i].revents = 0; |
1458 | iow [i].data = fds + i; |
|
|
1459 | ev_io_start (loop, iow + i); |
1547 | ev_io_start (loop, iow + i); |
1460 | } |
1548 | } |
1461 | } |
1549 | } |
1462 | |
1550 | |
1463 | // stop all watchers after blocking |
1551 | // stop all watchers after blocking |
… | |
… | |
1465 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
1553 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
1466 | { |
1554 | { |
1467 | ev_timer_stop (loop, &tw); |
1555 | ev_timer_stop (loop, &tw); |
1468 | |
1556 | |
1469 | for (int i = 0; i < nfd; ++i) |
1557 | for (int i = 0; i < nfd; ++i) |
|
|
1558 | { |
|
|
1559 | // set the relevant poll flags |
|
|
1560 | // could also call adns_processreadable etc. here |
|
|
1561 | struct pollfd *fd = fds + i; |
|
|
1562 | int revents = ev_clear_pending (iow + i); |
|
|
1563 | if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; |
|
|
1564 | if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; |
|
|
1565 | |
|
|
1566 | // now stop the watcher |
1470 | ev_io_stop (loop, iow + i); |
1567 | ev_io_stop (loop, iow + i); |
|
|
1568 | } |
1471 | |
1569 | |
1472 | adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
1570 | adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
|
|
1571 | } |
|
|
1572 | |
|
|
1573 | </pre> |
|
|
1574 | <p>Method 2: This would be just like method 1, but you run <code>adns_afterpoll</code> |
|
|
1575 | in the prepare watcher and would dispose of the check watcher.</p> |
|
|
1576 | <p>Method 3: If the module to be embedded supports explicit event |
|
|
1577 | notification (adns does), you can also make use of the actual watcher |
|
|
1578 | callbacks, and only destroy/create the watchers in the prepare watcher.</p> |
|
|
1579 | <pre> static void |
|
|
1580 | timer_cb (EV_P_ ev_timer *w, int revents) |
|
|
1581 | { |
|
|
1582 | adns_state ads = (adns_state)w->data; |
|
|
1583 | update_now (EV_A); |
|
|
1584 | |
|
|
1585 | adns_processtimeouts (ads, &tv_now); |
|
|
1586 | } |
|
|
1587 | |
|
|
1588 | static void |
|
|
1589 | io_cb (EV_P_ ev_io *w, int revents) |
|
|
1590 | { |
|
|
1591 | adns_state ads = (adns_state)w->data; |
|
|
1592 | update_now (EV_A); |
|
|
1593 | |
|
|
1594 | if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now); |
|
|
1595 | if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now); |
|
|
1596 | } |
|
|
1597 | |
|
|
1598 | // do not ever call adns_afterpoll |
|
|
1599 | |
|
|
1600 | </pre> |
|
|
1601 | <p>Method 4: Do not use a prepare or check watcher because the module you |
|
|
1602 | want to embed is too inflexible to support it. Instead, youc na override |
|
|
1603 | their poll function. The drawback with this solution is that the main |
|
|
1604 | loop is now no longer controllable by EV. The <code>Glib::EV</code> module does |
|
|
1605 | this.</p> |
|
|
1606 | <pre> static gint |
|
|
1607 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
|
|
1608 | { |
|
|
1609 | int got_events = 0; |
|
|
1610 | |
|
|
1611 | for (n = 0; n < nfds; ++n) |
|
|
1612 | // create/start io watcher that sets the relevant bits in fds[n] and increment got_events |
|
|
1613 | |
|
|
1614 | if (timeout >= 0) |
|
|
1615 | // create/start timer |
|
|
1616 | |
|
|
1617 | // poll |
|
|
1618 | ev_loop (EV_A_ 0); |
|
|
1619 | |
|
|
1620 | // stop timer again |
|
|
1621 | if (timeout >= 0) |
|
|
1622 | ev_timer_stop (EV_A_ &to); |
|
|
1623 | |
|
|
1624 | // stop io watchers again - their callbacks should have set |
|
|
1625 | for (n = 0; n < nfds; ++n) |
|
|
1626 | ev_io_stop (EV_A_ iow [n]); |
|
|
1627 | |
|
|
1628 | return got_events; |
1473 | } |
1629 | } |
1474 | |
1630 | |
1475 | |
1631 | |
1476 | |
1632 | |
1477 | |
1633 | |
… | |
… | |
1674 | the callback model to a model using method callbacks on objects.</p> |
1830 | the callback model to a model using method callbacks on objects.</p> |
1675 | <p>To use it,</p> |
1831 | <p>To use it,</p> |
1676 | <pre> #include <ev++.h> |
1832 | <pre> #include <ev++.h> |
1677 | |
1833 | |
1678 | </pre> |
1834 | </pre> |
1679 | <p>(it is not installed by default). This automatically includes <cite>ev.h</cite> |
1835 | <p>This automatically includes <cite>ev.h</cite> and puts all of its definitions (many |
1680 | and puts all of its definitions (many of them macros) into the global |
1836 | of them macros) into the global namespace. All C++ specific things are |
1681 | namespace. All C++ specific things are put into the <code>ev</code> namespace.</p> |
1837 | put into the <code>ev</code> namespace. It should support all the same embedding |
1682 | <p>It should support all the same embedding options as <cite>ev.h</cite>, most notably |
1838 | options as <cite>ev.h</cite>, most notably <code>EV_MULTIPLICITY</code>.</p> |
1683 | <code>EV_MULTIPLICITY</code>.</p> |
1839 | <p>Care has been taken to keep the overhead low. The only data member the C++ |
|
|
1840 | classes add (compared to plain C-style watchers) is the event loop pointer |
|
|
1841 | that the watcher is associated with (or no additional members at all if |
|
|
1842 | you disable <code>EV_MULTIPLICITY</code> when embedding libev).</p> |
|
|
1843 | <p>Currently, functions, and static and non-static member functions can be |
|
|
1844 | used as callbacks. Other types should be easy to add as long as they only |
|
|
1845 | need one additional pointer for context. If you need support for other |
|
|
1846 | types of functors please contact the author (preferably after implementing |
|
|
1847 | it).</p> |
1684 | <p>Here is a list of things available in the <code>ev</code> namespace:</p> |
1848 | <p>Here is a list of things available in the <code>ev</code> namespace:</p> |
1685 | <dl> |
1849 | <dl> |
1686 | <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt> |
1850 | <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt> |
1687 | <dd> |
1851 | <dd> |
1688 | <p>These are just enum values with the same values as the <code>EV_READ</code> etc. |
1852 | <p>These are just enum values with the same values as the <code>EV_READ</code> etc. |
… | |
… | |
1699 | which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro |
1863 | which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro |
1700 | defines by many implementations.</p> |
1864 | defines by many implementations.</p> |
1701 | <p>All of those classes have these methods:</p> |
1865 | <p>All of those classes have these methods:</p> |
1702 | <p> |
1866 | <p> |
1703 | <dl> |
1867 | <dl> |
1704 | <dt>ev::TYPE::TYPE (object *, object::method *)</dt> |
1868 | <dt>ev::TYPE::TYPE ()</dt> |
1705 | <dt>ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)</dt> |
1869 | <dt>ev::TYPE::TYPE (struct ev_loop *)</dt> |
1706 | <dt>ev::TYPE::~TYPE</dt> |
1870 | <dt>ev::TYPE::~TYPE</dt> |
1707 | <dd> |
1871 | <dd> |
1708 | <p>The constructor takes a pointer to an object and a method pointer to |
1872 | <p>The constructor (optionally) takes an event loop to associate the watcher |
1709 | the event handler callback to call in this class. The constructor calls |
1873 | with. If it is omitted, it will use <code>EV_DEFAULT</code>.</p> |
1710 | <code>ev_init</code> for you, which means you have to call the <code>set</code> method |
1874 | <p>The constructor calls <code>ev_init</code> for you, which means you have to call the |
1711 | before starting it. If you do not specify a loop then the constructor |
1875 | <code>set</code> method before starting it.</p> |
1712 | automatically associates the default loop with this watcher.</p> |
1876 | <p>It will not set a callback, however: You have to call the templated <code>set</code> |
|
|
1877 | method to set a callback before you can start the watcher.</p> |
|
|
1878 | <p>(The reason why you have to use a method is a limitation in C++ which does |
|
|
1879 | not allow explicit template arguments for constructors).</p> |
1713 | <p>The destructor automatically stops the watcher if it is active.</p> |
1880 | <p>The destructor automatically stops the watcher if it is active.</p> |
|
|
1881 | </dd> |
|
|
1882 | <dt>w->set<class, &class::method> (object *)</dt> |
|
|
1883 | <dd> |
|
|
1884 | <p>This method sets the callback method to call. The method has to have a |
|
|
1885 | signature of <code>void (*)(ev_TYPE &, int)</code>, it receives the watcher as |
|
|
1886 | first argument and the <code>revents</code> as second. The object must be given as |
|
|
1887 | parameter and is stored in the <code>data</code> member of the watcher.</p> |
|
|
1888 | <p>This method synthesizes efficient thunking code to call your method from |
|
|
1889 | the C callback that libev requires. If your compiler can inline your |
|
|
1890 | callback (i.e. it is visible to it at the place of the <code>set</code> call and |
|
|
1891 | your compiler is good :), then the method will be fully inlined into the |
|
|
1892 | thunking function, making it as fast as a direct C callback.</p> |
|
|
1893 | <p>Example: simple class declaration and watcher initialisation</p> |
|
|
1894 | <pre> struct myclass |
|
|
1895 | { |
|
|
1896 | void io_cb (ev::io &w, int revents) { } |
|
|
1897 | } |
|
|
1898 | |
|
|
1899 | myclass obj; |
|
|
1900 | ev::io iow; |
|
|
1901 | iow.set <myclass, &myclass::io_cb> (&obj); |
|
|
1902 | |
|
|
1903 | </pre> |
|
|
1904 | </dd> |
|
|
1905 | <dt>w->set<function> (void *data = 0)</dt> |
|
|
1906 | <dd> |
|
|
1907 | <p>Also sets a callback, but uses a static method or plain function as |
|
|
1908 | callback. The optional <code>data</code> argument will be stored in the watcher's |
|
|
1909 | <code>data</code> member and is free for you to use.</p> |
|
|
1910 | <p>The prototype of the <code>function</code> must be <code>void (*)(ev::TYPE &w, int)</code>.</p> |
|
|
1911 | <p>See the method-<code>set</code> above for more details.</p> |
|
|
1912 | <p>Example:</p> |
|
|
1913 | <pre> static void io_cb (ev::io &w, int revents) { } |
|
|
1914 | iow.set <io_cb> (); |
|
|
1915 | |
|
|
1916 | </pre> |
1714 | </dd> |
1917 | </dd> |
1715 | <dt>w->set (struct ev_loop *)</dt> |
1918 | <dt>w->set (struct ev_loop *)</dt> |
1716 | <dd> |
1919 | <dd> |
1717 | <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only |
1920 | <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only |
1718 | do this when the watcher is inactive (and not pending either).</p> |
1921 | do this when the watcher is inactive (and not pending either).</p> |
1719 | </dd> |
1922 | </dd> |
1720 | <dt>w->set ([args])</dt> |
1923 | <dt>w->set ([args])</dt> |
1721 | <dd> |
1924 | <dd> |
1722 | <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be |
1925 | <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be |
1723 | called at least once. Unlike the C counterpart, an active watcher gets |
1926 | called at least once. Unlike the C counterpart, an active watcher gets |
1724 | automatically stopped and restarted.</p> |
1927 | automatically stopped and restarted when reconfiguring it with this |
|
|
1928 | method.</p> |
1725 | </dd> |
1929 | </dd> |
1726 | <dt>w->start ()</dt> |
1930 | <dt>w->start ()</dt> |
1727 | <dd> |
1931 | <dd> |
1728 | <p>Starts the watcher. Note that there is no <code>loop</code> argument as the |
1932 | <p>Starts the watcher. Note that there is no <code>loop</code> argument, as the |
1729 | constructor already takes the loop.</p> |
1933 | constructor already stores the event loop.</p> |
1730 | </dd> |
1934 | </dd> |
1731 | <dt>w->stop ()</dt> |
1935 | <dt>w->stop ()</dt> |
1732 | <dd> |
1936 | <dd> |
1733 | <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p> |
1937 | <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p> |
1734 | </dd> |
1938 | </dd> |
… | |
… | |
1758 | |
1962 | |
1759 | myclass (); |
1963 | myclass (); |
1760 | } |
1964 | } |
1761 | |
1965 | |
1762 | myclass::myclass (int fd) |
1966 | myclass::myclass (int fd) |
1763 | : io (this, &myclass::io_cb), |
|
|
1764 | idle (this, &myclass::idle_cb) |
|
|
1765 | { |
1967 | { |
|
|
1968 | io .set <myclass, &myclass::io_cb > (this); |
|
|
1969 | idle.set <myclass, &myclass::idle_cb> (this); |
|
|
1970 | |
1766 | io.start (fd, ev::READ); |
1971 | io.start (fd, ev::READ); |
1767 | } |
1972 | } |
1768 | |
1973 | |
1769 | |
1974 | |
1770 | |
1975 | |
… | |
… | |
1773 | |
1978 | |
1774 | </div> |
1979 | </div> |
1775 | <h1 id="MACRO_MAGIC">MACRO MAGIC</h1> |
1980 | <h1 id="MACRO_MAGIC">MACRO MAGIC</h1> |
1776 | <div id="MACRO_MAGIC_CONTENT"> |
1981 | <div id="MACRO_MAGIC_CONTENT"> |
1777 | <p>Libev can be compiled with a variety of options, the most fundemantal is |
1982 | <p>Libev can be compiled with a variety of options, the most fundemantal is |
1778 | <code>EV_MULTIPLICITY</code>. This option determines wether (most) functions and |
1983 | <code>EV_MULTIPLICITY</code>. This option determines whether (most) functions and |
1779 | callbacks have an initial <code>struct ev_loop *</code> argument.</p> |
1984 | callbacks have an initial <code>struct ev_loop *</code> argument.</p> |
1780 | <p>To make it easier to write programs that cope with either variant, the |
1985 | <p>To make it easier to write programs that cope with either variant, the |
1781 | following macros are defined:</p> |
1986 | following macros are defined:</p> |
1782 | <dl> |
1987 | <dl> |
1783 | <dt><code>EV_A</code>, <code>EV_A_</code></dt> |
1988 | <dt><code>EV_A</code>, <code>EV_A_</code></dt> |
… | |
… | |
1812 | <dd> |
2017 | <dd> |
1813 | <p>Similar to the other two macros, this gives you the value of the default |
2018 | <p>Similar to the other two macros, this gives you the value of the default |
1814 | loop, if multiple loops are supported ("ev loop default").</p> |
2019 | loop, if multiple loops are supported ("ev loop default").</p> |
1815 | </dd> |
2020 | </dd> |
1816 | </dl> |
2021 | </dl> |
1817 | <p>Example: Declare and initialise a check watcher, working regardless of |
2022 | <p>Example: Declare and initialise a check watcher, utilising the above |
1818 | wether multiple loops are supported or not.</p> |
2023 | macros so it will work regardless of whether multiple loops are supported |
|
|
2024 | or not.</p> |
1819 | <pre> static void |
2025 | <pre> static void |
1820 | check_cb (EV_P_ ev_timer *w, int revents) |
2026 | check_cb (EV_P_ ev_timer *w, int revents) |
1821 | { |
2027 | { |
1822 | ev_check_stop (EV_A_ w); |
2028 | ev_check_stop (EV_A_ w); |
1823 | } |
2029 | } |
1824 | |
2030 | |
1825 | ev_check check; |
2031 | ev_check check; |
1826 | ev_check_init (&check, check_cb); |
2032 | ev_check_init (&check, check_cb); |
1827 | ev_check_start (EV_DEFAULT_ &check); |
2033 | ev_check_start (EV_DEFAULT_ &check); |
1828 | ev_loop (EV_DEFAULT_ 0); |
2034 | ev_loop (EV_DEFAULT_ 0); |
1829 | |
|
|
1830 | |
|
|
1831 | |
|
|
1832 | |
2035 | |
1833 | </pre> |
2036 | </pre> |
1834 | |
2037 | |
1835 | </div> |
2038 | </div> |
1836 | <h1 id="EMBEDDING">EMBEDDING</h1> |
2039 | <h1 id="EMBEDDING">EMBEDDING</h1> |
… | |
… | |
1878 | ev_vars.h |
2081 | ev_vars.h |
1879 | ev_wrap.h |
2082 | ev_wrap.h |
1880 | |
2083 | |
1881 | ev_win32.c required on win32 platforms only |
2084 | ev_win32.c required on win32 platforms only |
1882 | |
2085 | |
1883 | ev_select.c only when select backend is enabled (which is by default) |
2086 | ev_select.c only when select backend is enabled (which is enabled by default) |
1884 | ev_poll.c only when poll backend is enabled (disabled by default) |
2087 | ev_poll.c only when poll backend is enabled (disabled by default) |
1885 | ev_epoll.c only when the epoll backend is enabled (disabled by default) |
2088 | ev_epoll.c only when the epoll backend is enabled (disabled by default) |
1886 | ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
2089 | ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
1887 | ev_port.c only when the solaris port backend is enabled (disabled by default) |
2090 | ev_port.c only when the solaris port backend is enabled (disabled by default) |
1888 | |
2091 | |
… | |
… | |
2015 | </dd> |
2218 | </dd> |
2016 | <dt>EV_USE_DEVPOLL</dt> |
2219 | <dt>EV_USE_DEVPOLL</dt> |
2017 | <dd> |
2220 | <dd> |
2018 | <p>reserved for future expansion, works like the USE symbols above.</p> |
2221 | <p>reserved for future expansion, works like the USE symbols above.</p> |
2019 | </dd> |
2222 | </dd> |
|
|
2223 | <dt>EV_USE_INOTIFY</dt> |
|
|
2224 | <dd> |
|
|
2225 | <p>If defined to be <code>1</code>, libev will compile in support for the Linux inotify |
|
|
2226 | interface to speed up <code>ev_stat</code> watchers. Its actual availability will |
|
|
2227 | be detected at runtime.</p> |
|
|
2228 | </dd> |
2020 | <dt>EV_H</dt> |
2229 | <dt>EV_H</dt> |
2021 | <dd> |
2230 | <dd> |
2022 | <p>The name of the <cite>ev.h</cite> header file used to include it. The default if |
2231 | <p>The name of the <cite>ev.h</cite> header file used to include it. The default if |
2023 | undefined is <code><ev.h></code> in <cite>event.h</cite> and <code>"ev.h"</code> in <cite>ev.c</cite>. This |
2232 | undefined is <code><ev.h></code> in <cite>event.h</cite> and <code>"ev.h"</code> in <cite>ev.c</cite>. This |
2024 | can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p> |
2233 | can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p> |
… | |
… | |
2047 | will have the <code>struct ev_loop *</code> as first argument, and you can create |
2256 | will have the <code>struct ev_loop *</code> as first argument, and you can create |
2048 | additional independent event loops. Otherwise there will be no support |
2257 | additional independent event loops. Otherwise there will be no support |
2049 | for multiple event loops and there is no first event loop pointer |
2258 | for multiple event loops and there is no first event loop pointer |
2050 | argument. Instead, all functions act on the single default loop.</p> |
2259 | argument. Instead, all functions act on the single default loop.</p> |
2051 | </dd> |
2260 | </dd> |
|
|
2261 | <dt>EV_MINPRI</dt> |
|
|
2262 | <dt>EV_MAXPRI</dt> |
|
|
2263 | <dd> |
|
|
2264 | <p>The range of allowed priorities. <code>EV_MINPRI</code> must be smaller or equal to |
|
|
2265 | <code>EV_MAXPRI</code>, but otherwise there are no non-obvious limitations. You can |
|
|
2266 | provide for more priorities by overriding those symbols (usually defined |
|
|
2267 | to be <code>-2</code> and <code>2</code>, respectively).</p> |
|
|
2268 | <p>When doing priority-based operations, libev usually has to linearly search |
|
|
2269 | all the priorities, so having many of them (hundreds) uses a lot of space |
|
|
2270 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
|
|
2271 | fine.</p> |
|
|
2272 | <p>If your embedding app does not need any priorities, defining these both to |
|
|
2273 | <code>0</code> will save some memory and cpu.</p> |
|
|
2274 | </dd> |
2052 | <dt>EV_PERIODIC_ENABLE</dt> |
2275 | <dt>EV_PERIODIC_ENABLE</dt> |
2053 | <dd> |
2276 | <dd> |
2054 | <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If |
2277 | <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If |
2055 | defined to be <code>0</code>, then they are not. Disabling them saves a few kB of |
2278 | defined to be <code>0</code>, then they are not. Disabling them saves a few kB of |
2056 | code.</p> |
2279 | code.</p> |
2057 | </dd> |
2280 | </dd> |
|
|
2281 | <dt>EV_IDLE_ENABLE</dt> |
|
|
2282 | <dd> |
|
|
2283 | <p>If undefined or defined to be <code>1</code>, then idle watchers are supported. If |
|
|
2284 | defined to be <code>0</code>, then they are not. Disabling them saves a few kB of |
|
|
2285 | code.</p> |
|
|
2286 | </dd> |
2058 | <dt>EV_EMBED_ENABLE</dt> |
2287 | <dt>EV_EMBED_ENABLE</dt> |
2059 | <dd> |
2288 | <dd> |
2060 | <p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If |
2289 | <p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If |
2061 | defined to be <code>0</code>, then they are not.</p> |
2290 | defined to be <code>0</code>, then they are not.</p> |
2062 | </dd> |
2291 | </dd> |
… | |
… | |
2079 | <dt>EV_PID_HASHSIZE</dt> |
2308 | <dt>EV_PID_HASHSIZE</dt> |
2080 | <dd> |
2309 | <dd> |
2081 | <p><code>ev_child</code> watchers use a small hash table to distribute workload by |
2310 | <p><code>ev_child</code> watchers use a small hash table to distribute workload by |
2082 | pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more |
2311 | pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more |
2083 | than enough. If you need to manage thousands of children you might want to |
2312 | than enough. If you need to manage thousands of children you might want to |
2084 | increase this value.</p> |
2313 | increase this value (<i>must</i> be a power of two).</p> |
|
|
2314 | </dd> |
|
|
2315 | <dt>EV_INOTIFY_HASHSIZE</dt> |
|
|
2316 | <dd> |
|
|
2317 | <p><code>ev_staz</code> watchers use a small hash table to distribute workload by |
|
|
2318 | inotify watch id. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), |
|
|
2319 | usually more than enough. If you need to manage thousands of <code>ev_stat</code> |
|
|
2320 | watchers you might want to increase this value (<i>must</i> be a power of |
|
|
2321 | two).</p> |
2085 | </dd> |
2322 | </dd> |
2086 | <dt>EV_COMMON</dt> |
2323 | <dt>EV_COMMON</dt> |
2087 | <dd> |
2324 | <dd> |
2088 | <p>By default, all watchers have a <code>void *data</code> member. By redefining |
2325 | <p>By default, all watchers have a <code>void *data</code> member. By redefining |
2089 | this macro to a something else you can include more and other types of |
2326 | this macro to a something else you can include more and other types of |
… | |
… | |
2116 | the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public |
2353 | the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public |
2117 | interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file |
2354 | interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file |
2118 | will be compiled. It is pretty complex because it provides its own header |
2355 | will be compiled. It is pretty complex because it provides its own header |
2119 | file.</p> |
2356 | file.</p> |
2120 | <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file |
2357 | <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file |
2121 | that everybody includes and which overrides some autoconf choices:</p> |
2358 | that everybody includes and which overrides some configure choices:</p> |
|
|
2359 | <pre> #define EV_MINIMAL 1 |
2122 | <pre> #define EV_USE_POLL 0 |
2360 | #define EV_USE_POLL 0 |
2123 | #define EV_MULTIPLICITY 0 |
2361 | #define EV_MULTIPLICITY 0 |
2124 | #define EV_PERIODICS 0 |
2362 | #define EV_PERIODIC_ENABLE 0 |
|
|
2363 | #define EV_STAT_ENABLE 0 |
|
|
2364 | #define EV_FORK_ENABLE 0 |
2125 | #define EV_CONFIG_H <config.h> |
2365 | #define EV_CONFIG_H <config.h> |
|
|
2366 | #define EV_MINPRI 0 |
|
|
2367 | #define EV_MAXPRI 0 |
2126 | |
2368 | |
2127 | #include "ev++.h" |
2369 | #include "ev++.h" |
2128 | |
2370 | |
2129 | </pre> |
2371 | </pre> |
2130 | <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p> |
2372 | <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p> |
… | |
… | |
2140 | <h1 id="COMPLEXITIES">COMPLEXITIES</h1> |
2382 | <h1 id="COMPLEXITIES">COMPLEXITIES</h1> |
2141 | <div id="COMPLEXITIES_CONTENT"> |
2383 | <div id="COMPLEXITIES_CONTENT"> |
2142 | <p>In this section the complexities of (many of) the algorithms used inside |
2384 | <p>In this section the complexities of (many of) the algorithms used inside |
2143 | libev will be explained. For complexity discussions about backends see the |
2385 | libev will be explained. For complexity discussions about backends see the |
2144 | documentation for <code>ev_default_init</code>.</p> |
2386 | documentation for <code>ev_default_init</code>.</p> |
|
|
2387 | <p>All of the following are about amortised time: If an array needs to be |
|
|
2388 | extended, libev needs to realloc and move the whole array, but this |
|
|
2389 | happens asymptotically never with higher number of elements, so O(1) might |
|
|
2390 | mean it might do a lengthy realloc operation in rare cases, but on average |
|
|
2391 | it is much faster and asymptotically approaches constant time.</p> |
2145 | <p> |
2392 | <p> |
2146 | <dl> |
2393 | <dl> |
2147 | <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> |
2394 | <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> |
|
|
2395 | <dd> |
|
|
2396 | <p>This means that, when you have a watcher that triggers in one hour and |
|
|
2397 | there are 100 watchers that would trigger before that then inserting will |
|
|
2398 | have to skip those 100 watchers.</p> |
|
|
2399 | </dd> |
2148 | <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt> |
2400 | <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt> |
|
|
2401 | <dd> |
|
|
2402 | <p>That means that for changing a timer costs less than removing/adding them |
|
|
2403 | as only the relative motion in the event queue has to be paid for.</p> |
|
|
2404 | </dd> |
2149 | <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> |
2405 | <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> |
|
|
2406 | <dd> |
|
|
2407 | <p>These just add the watcher into an array or at the head of a list. |
2150 | <dt>Stopping check/prepare/idle watchers: O(1)</dt> |
2408 | =item Stopping check/prepare/idle watchers: O(1)</p> |
|
|
2409 | </dd> |
2151 | <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))</dt> |
2410 | <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt> |
|
|
2411 | <dd> |
|
|
2412 | <p>These watchers are stored in lists then need to be walked to find the |
|
|
2413 | correct watcher to remove. The lists are usually short (you don't usually |
|
|
2414 | have many watchers waiting for the same fd or signal).</p> |
|
|
2415 | </dd> |
2152 | <dt>Finding the next timer per loop iteration: O(1)</dt> |
2416 | <dt>Finding the next timer per loop iteration: O(1)</dt> |
2153 | <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt> |
2417 | <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt> |
|
|
2418 | <dd> |
|
|
2419 | <p>A change means an I/O watcher gets started or stopped, which requires |
|
|
2420 | libev to recalculate its status (and possibly tell the kernel).</p> |
|
|
2421 | </dd> |
2154 | <dt>Activating one watcher: O(1)</dt> |
2422 | <dt>Activating one watcher: O(1)</dt> |
|
|
2423 | <dt>Priority handling: O(number_of_priorities)</dt> |
|
|
2424 | <dd> |
|
|
2425 | <p>Priorities are implemented by allocating some space for each |
|
|
2426 | priority. When doing priority-based operations, libev usually has to |
|
|
2427 | linearly search all the priorities.</p> |
|
|
2428 | </dd> |
2155 | </dl> |
2429 | </dl> |
2156 | </p> |
2430 | </p> |
2157 | |
2431 | |
2158 | |
2432 | |
2159 | |
2433 | |