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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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13 | <div class="pod"> |
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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326 | <code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will |
329 | <code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will |
327 | 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 |
328 | 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 |
329 | around bugs.</p> |
332 | around bugs.</p> |
330 | </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> |
331 | <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt> |
351 | <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt> |
332 | <dd> |
352 | <dd> |
333 | <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 |
334 | 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, |
335 | 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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463 | <dt>ev_loop_fork (loop)</dt> |
483 | <dt>ev_loop_fork (loop)</dt> |
464 | <dd> |
484 | <dd> |
465 | <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 |
466 | <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 |
467 | 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> |
468 | </dd> |
497 | </dd> |
469 | <dt>unsigned int ev_backend (loop)</dt> |
498 | <dt>unsigned int ev_backend (loop)</dt> |
470 | <dd> |
499 | <dd> |
471 | <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 |
472 | use.</p> |
501 | use.</p> |
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752 | <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt> |
781 | <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt> |
753 | <dd> |
782 | <dd> |
754 | <p>Change the callback. You can change the callback at virtually any time |
783 | <p>Change the callback. You can change the callback at virtually any time |
755 | (modulo threads).</p> |
784 | (modulo threads).</p> |
756 | </dd> |
785 | </dd> |
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786 | <dt>ev_set_priority (ev_TYPE *watcher, priority)</dt> |
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787 | <dt>int ev_priority (ev_TYPE *watcher)</dt> |
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788 | <dd> |
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789 | <p>Set and query the priority of the watcher. The priority is a small |
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790 | integer between <code>EV_MAXPRI</code> (default: <code>2</code>) and <code>EV_MINPRI</code> |
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791 | (default: <code>-2</code>). Pending watchers with higher priority will be invoked |
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792 | before watchers with lower priority, but priority will not keep watchers |
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793 | from being executed (except for <code>ev_idle</code> watchers).</p> |
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794 | <p>This means that priorities are <i>only</i> used for ordering callback |
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795 | invocation after new events have been received. This is useful, for |
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796 | example, to reduce latency after idling, or more often, to bind two |
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797 | watchers on the same event and make sure one is called first.</p> |
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798 | <p>If you need to suppress invocation when higher priority events are pending |
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799 | you need to look at <code>ev_idle</code> watchers, which provide this functionality.</p> |
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|
800 | <p>The default priority used by watchers when no priority has been set is |
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|
801 | always <code>0</code>, which is supposed to not be too high and not be too low :).</p> |
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|
802 | <p>Setting a priority outside the range of <code>EV_MINPRI</code> to <code>EV_MAXPRI</code> is |
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|
803 | fine, as long as you do not mind that the priority value you query might |
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804 | or might not have been adjusted to be within valid range.</p> |
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|
805 | </dd> |
757 | </dl> |
806 | </dl> |
758 | |
807 | |
759 | |
808 | |
760 | |
809 | |
761 | |
810 | |
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871 | this situation even with a relatively standard program structure. Thus |
920 | this situation even with a relatively standard program structure. Thus |
872 | it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning |
921 | it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning |
873 | <code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p> |
922 | <code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p> |
874 | <p>If you cannot run the fd in non-blocking mode (for example you should not |
923 | <p>If you cannot run the fd in non-blocking mode (for example you should not |
875 | play around with an Xlib connection), then you have to seperately re-test |
924 | play around with an Xlib connection), then you have to seperately re-test |
876 | wether a file descriptor is really ready with a known-to-be good interface |
925 | whether a file descriptor is really ready with a known-to-be good interface |
877 | such as poll (fortunately in our Xlib example, Xlib already does this on |
926 | such as poll (fortunately in our Xlib example, Xlib already does this on |
878 | its own, so its quite safe to use).</p> |
927 | its own, so its quite safe to use).</p> |
879 | <dl> |
928 | <dl> |
880 | <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> |
929 | <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> |
881 | <dt>ev_io_set (ev_io *, int fd, int events)</dt> |
930 | <dt>ev_io_set (ev_io *, int fd, int events)</dt> |
… | |
… | |
952 | </dd> |
1001 | </dd> |
953 | <dt>ev_timer_again (loop)</dt> |
1002 | <dt>ev_timer_again (loop)</dt> |
954 | <dd> |
1003 | <dd> |
955 | <p>This will act as if the timer timed out and restart it again if it is |
1004 | <p>This will act as if the timer timed out and restart it again if it is |
956 | repeating. The exact semantics are:</p> |
1005 | repeating. The exact semantics are:</p> |
|
|
1006 | <p>If the timer is pending, its pending status is cleared.</p> |
957 | <p>If the timer is started but nonrepeating, stop it.</p> |
1007 | <p>If the timer is started but nonrepeating, stop it (as if it timed out).</p> |
958 | <p>If the timer is repeating, either start it if necessary (with the repeat |
1008 | <p>If the timer is repeating, either start it if necessary (with the |
959 | value), or reset the running timer to the repeat value.</p> |
1009 | <code>repeat</code> value), or reset the running timer to the <code>repeat</code> value.</p> |
960 | <p>This sounds a bit complicated, but here is a useful and typical |
1010 | <p>This sounds a bit complicated, but here is a useful and typical |
961 | example: Imagine you have a tcp connection and you want a so-called |
1011 | example: Imagine you have a tcp connection and you want a so-called idle |
962 | idle timeout, that is, you want to be called when there have been, |
1012 | timeout, that is, you want to be called when there have been, say, 60 |
963 | say, 60 seconds of inactivity on the socket. The easiest way to do |
1013 | seconds of inactivity on the socket. The easiest way to do this is to |
964 | this is to configure an <code>ev_timer</code> with <code>after</code>=<code>repeat</code>=<code>60</code> and calling |
1014 | configure an <code>ev_timer</code> with a <code>repeat</code> value of <code>60</code> and then call |
965 | <code>ev_timer_again</code> each time you successfully read or write some data. If |
1015 | <code>ev_timer_again</code> each time you successfully read or write some data. If |
966 | you go into an idle state where you do not expect data to travel on the |
1016 | you go into an idle state where you do not expect data to travel on the |
967 | socket, you can stop the timer, and again will automatically restart it if |
1017 | socket, you can <code>ev_timer_stop</code> the timer, and <code>ev_timer_again</code> will |
968 | need be.</p> |
1018 | automatically restart it if need be.</p> |
969 | <p>You can also ignore the <code>after</code> value and <code>ev_timer_start</code> altogether |
1019 | <p>That means you can ignore the <code>after</code> value and <code>ev_timer_start</code> |
970 | and only ever use the <code>repeat</code> value:</p> |
1020 | altogether and only ever use the <code>repeat</code> value and <code>ev_timer_again</code>:</p> |
971 | <pre> ev_timer_init (timer, callback, 0., 5.); |
1021 | <pre> ev_timer_init (timer, callback, 0., 5.); |
972 | ev_timer_again (loop, timer); |
1022 | ev_timer_again (loop, timer); |
973 | ... |
1023 | ... |
974 | timer->again = 17.; |
1024 | timer->again = 17.; |
975 | ev_timer_again (loop, timer); |
1025 | ev_timer_again (loop, timer); |
976 | ... |
1026 | ... |
977 | timer->again = 10.; |
1027 | timer->again = 10.; |
978 | ev_timer_again (loop, timer); |
1028 | ev_timer_again (loop, timer); |
979 | |
1029 | |
980 | </pre> |
1030 | </pre> |
981 | <p>This is more efficient then stopping/starting the timer eahc time you want |
1031 | <p>This is more slightly efficient then stopping/starting the timer each time |
982 | to modify its timeout value.</p> |
1032 | you want to modify its timeout value.</p> |
983 | </dd> |
1033 | </dd> |
984 | <dt>ev_tstamp repeat [read-write]</dt> |
1034 | <dt>ev_tstamp repeat [read-write]</dt> |
985 | <dd> |
1035 | <dd> |
986 | <p>The current <code>repeat</code> value. Will be used each time the watcher times out |
1036 | <p>The current <code>repeat</code> value. Will be used each time the watcher times out |
987 | or <code>ev_timer_again</code> is called and determines the next timeout (if any), |
1037 | or <code>ev_timer_again</code> is called and determines the next timeout (if any), |
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1248 | <p>The path does not need to exist: changing from "path exists" to "path does |
1298 | <p>The path does not need to exist: changing from "path exists" to "path does |
1249 | not exist" is a status change like any other. The condition "path does |
1299 | not exist" is a status change like any other. The condition "path does |
1250 | not exist" is signified by the <code>st_nlink</code> field being zero (which is |
1300 | not exist" is signified by the <code>st_nlink</code> field being zero (which is |
1251 | otherwise always forced to be at least one) and all the other fields of |
1301 | otherwise always forced to be at least one) and all the other fields of |
1252 | the stat buffer having unspecified contents.</p> |
1302 | the stat buffer having unspecified contents.</p> |
|
|
1303 | <p>The path <i>should</i> be absolute and <i>must not</i> end in a slash. If it is |
|
|
1304 | relative and your working directory changes, the behaviour is undefined.</p> |
1253 | <p>Since there is no standard to do this, the portable implementation simply |
1305 | <p>Since there is no standard to do this, the portable implementation simply |
1254 | calls <code>stat (2)</code> regularly on the path to see if it changed somehow. You |
1306 | calls <code>stat (2)</code> regularly on the path to see if it changed somehow. You |
1255 | can specify a recommended polling interval for this case. If you specify |
1307 | can specify a recommended polling interval for this case. If you specify |
1256 | a polling interval of <code>0</code> (highly recommended!) then a <i>suitable, |
1308 | a polling interval of <code>0</code> (highly recommended!) then a <i>suitable, |
1257 | unspecified default</i> value will be used (which you can expect to be around |
1309 | unspecified default</i> value will be used (which you can expect to be around |
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1338 | </pre> |
1390 | </pre> |
1339 | |
1391 | |
1340 | </div> |
1392 | </div> |
1341 | <h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2> |
1393 | <h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2> |
1342 | <div id="code_ev_idle_code_when_you_ve_got_no-2"> |
1394 | <div id="code_ev_idle_code_when_you_ve_got_no-2"> |
1343 | <p>Idle watchers trigger events when there are no other events are pending |
1395 | <p>Idle watchers trigger events when no other events of the same or higher |
1344 | (prepare, check and other idle watchers do not count). That is, as long |
1396 | priority are pending (prepare, check and other idle watchers do not |
1345 | as your process is busy handling sockets or timeouts (or even signals, |
1397 | count).</p> |
1346 | imagine) it will not be triggered. But when your process is idle all idle |
1398 | <p>That is, as long as your process is busy handling sockets or timeouts |
1347 | watchers are being called again and again, once per event loop iteration - |
1399 | (or even signals, imagine) of the same or higher priority it will not be |
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1400 | triggered. But when your process is idle (or only lower-priority watchers |
|
|
1401 | are pending), the idle watchers are being called once per event loop |
1348 | until stopped, that is, or your process receives more events and becomes |
1402 | iteration - until stopped, that is, or your process receives more events |
1349 | busy.</p> |
1403 | and becomes busy again with higher priority stuff.</p> |
1350 | <p>The most noteworthy effect is that as long as any idle watchers are |
1404 | <p>The most noteworthy effect is that as long as any idle watchers are |
1351 | active, the process will not block when waiting for new events.</p> |
1405 | active, the process will not block when waiting for new events.</p> |
1352 | <p>Apart from keeping your process non-blocking (which is a useful |
1406 | <p>Apart from keeping your process non-blocking (which is a useful |
1353 | effect on its own sometimes), idle watchers are a good place to do |
1407 | effect on its own sometimes), idle watchers are a good place to do |
1354 | "pseudo-background processing", or delay processing stuff to after the |
1408 | "pseudo-background processing", or delay processing stuff to after the |
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… | |
1444 | |
1498 | |
1445 | // create io watchers for each fd and a timer before blocking |
1499 | // create io watchers for each fd and a timer before blocking |
1446 | static void |
1500 | static void |
1447 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
1501 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
1448 | { |
1502 | { |
1449 | int timeout = 3600000;truct pollfd fds [nfd]; |
1503 | int timeout = 3600000; |
|
|
1504 | struct pollfd fds [nfd]; |
1450 | // actual code will need to loop here and realloc etc. |
1505 | // actual code will need to loop here and realloc etc. |
1451 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
1506 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
1452 | |
1507 | |
1453 | /* the callback is illegal, but won't be called as we stop during check */ |
1508 | /* the callback is illegal, but won't be called as we stop during check */ |
1454 | ev_timer_init (&tw, 0, timeout * 1e-3); |
1509 | ev_timer_init (&tw, 0, timeout * 1e-3); |
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1780 | |
1835 | |
1781 | </div> |
1836 | </div> |
1782 | <h1 id="MACRO_MAGIC">MACRO MAGIC</h1> |
1837 | <h1 id="MACRO_MAGIC">MACRO MAGIC</h1> |
1783 | <div id="MACRO_MAGIC_CONTENT"> |
1838 | <div id="MACRO_MAGIC_CONTENT"> |
1784 | <p>Libev can be compiled with a variety of options, the most fundemantal is |
1839 | <p>Libev can be compiled with a variety of options, the most fundemantal is |
1785 | <code>EV_MULTIPLICITY</code>. This option determines wether (most) functions and |
1840 | <code>EV_MULTIPLICITY</code>. This option determines whether (most) functions and |
1786 | callbacks have an initial <code>struct ev_loop *</code> argument.</p> |
1841 | callbacks have an initial <code>struct ev_loop *</code> argument.</p> |
1787 | <p>To make it easier to write programs that cope with either variant, the |
1842 | <p>To make it easier to write programs that cope with either variant, the |
1788 | following macros are defined:</p> |
1843 | following macros are defined:</p> |
1789 | <dl> |
1844 | <dl> |
1790 | <dt><code>EV_A</code>, <code>EV_A_</code></dt> |
1845 | <dt><code>EV_A</code>, <code>EV_A_</code></dt> |
… | |
… | |
1819 | <dd> |
1874 | <dd> |
1820 | <p>Similar to the other two macros, this gives you the value of the default |
1875 | <p>Similar to the other two macros, this gives you the value of the default |
1821 | loop, if multiple loops are supported ("ev loop default").</p> |
1876 | loop, if multiple loops are supported ("ev loop default").</p> |
1822 | </dd> |
1877 | </dd> |
1823 | </dl> |
1878 | </dl> |
1824 | <p>Example: Declare and initialise a check watcher, working regardless of |
1879 | <p>Example: Declare and initialise a check watcher, utilising the above |
1825 | wether multiple loops are supported or not.</p> |
1880 | macros so it will work regardless of whether multiple loops are supported |
|
|
1881 | or not.</p> |
1826 | <pre> static void |
1882 | <pre> static void |
1827 | check_cb (EV_P_ ev_timer *w, int revents) |
1883 | check_cb (EV_P_ ev_timer *w, int revents) |
1828 | { |
1884 | { |
1829 | ev_check_stop (EV_A_ w); |
1885 | ev_check_stop (EV_A_ w); |
1830 | } |
1886 | } |
1831 | |
1887 | |
1832 | ev_check check; |
1888 | ev_check check; |
1833 | ev_check_init (&check, check_cb); |
1889 | ev_check_init (&check, check_cb); |
1834 | ev_check_start (EV_DEFAULT_ &check); |
1890 | ev_check_start (EV_DEFAULT_ &check); |
1835 | ev_loop (EV_DEFAULT_ 0); |
1891 | ev_loop (EV_DEFAULT_ 0); |
1836 | |
|
|
1837 | |
|
|
1838 | |
|
|
1839 | |
1892 | |
1840 | </pre> |
1893 | </pre> |
1841 | |
1894 | |
1842 | </div> |
1895 | </div> |
1843 | <h1 id="EMBEDDING">EMBEDDING</h1> |
1896 | <h1 id="EMBEDDING">EMBEDDING</h1> |
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1885 | ev_vars.h |
1938 | ev_vars.h |
1886 | ev_wrap.h |
1939 | ev_wrap.h |
1887 | |
1940 | |
1888 | ev_win32.c required on win32 platforms only |
1941 | ev_win32.c required on win32 platforms only |
1889 | |
1942 | |
1890 | ev_select.c only when select backend is enabled (which is by default) |
1943 | ev_select.c only when select backend is enabled (which is enabled by default) |
1891 | ev_poll.c only when poll backend is enabled (disabled by default) |
1944 | ev_poll.c only when poll backend is enabled (disabled by default) |
1892 | ev_epoll.c only when the epoll backend is enabled (disabled by default) |
1945 | ev_epoll.c only when the epoll backend is enabled (disabled by default) |
1893 | ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
1946 | ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
1894 | ev_port.c only when the solaris port backend is enabled (disabled by default) |
1947 | ev_port.c only when the solaris port backend is enabled (disabled by default) |
1895 | |
1948 | |
… | |
… | |
2060 | will have the <code>struct ev_loop *</code> as first argument, and you can create |
2113 | will have the <code>struct ev_loop *</code> as first argument, and you can create |
2061 | additional independent event loops. Otherwise there will be no support |
2114 | additional independent event loops. Otherwise there will be no support |
2062 | for multiple event loops and there is no first event loop pointer |
2115 | for multiple event loops and there is no first event loop pointer |
2063 | argument. Instead, all functions act on the single default loop.</p> |
2116 | argument. Instead, all functions act on the single default loop.</p> |
2064 | </dd> |
2117 | </dd> |
|
|
2118 | <dt>EV_MINPRI</dt> |
|
|
2119 | <dt>EV_MAXPRI</dt> |
|
|
2120 | <dd> |
|
|
2121 | <p>The range of allowed priorities. <code>EV_MINPRI</code> must be smaller or equal to |
|
|
2122 | <code>EV_MAXPRI</code>, but otherwise there are no non-obvious limitations. You can |
|
|
2123 | provide for more priorities by overriding those symbols (usually defined |
|
|
2124 | to be <code>-2</code> and <code>2</code>, respectively).</p> |
|
|
2125 | <p>When doing priority-based operations, libev usually has to linearly search |
|
|
2126 | all the priorities, so having many of them (hundreds) uses a lot of space |
|
|
2127 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
|
|
2128 | fine.</p> |
|
|
2129 | <p>If your embedding app does not need any priorities, defining these both to |
|
|
2130 | <code>0</code> will save some memory and cpu.</p> |
|
|
2131 | </dd> |
2065 | <dt>EV_PERIODIC_ENABLE</dt> |
2132 | <dt>EV_PERIODIC_ENABLE</dt> |
2066 | <dd> |
2133 | <dd> |
2067 | <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If |
2134 | <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If |
|
|
2135 | defined to be <code>0</code>, then they are not. Disabling them saves a few kB of |
|
|
2136 | code.</p> |
|
|
2137 | </dd> |
|
|
2138 | <dt>EV_IDLE_ENABLE</dt> |
|
|
2139 | <dd> |
|
|
2140 | <p>If undefined or defined to be <code>1</code>, then idle watchers are supported. If |
2068 | defined to be <code>0</code>, then they are not. Disabling them saves a few kB of |
2141 | defined to be <code>0</code>, then they are not. Disabling them saves a few kB of |
2069 | code.</p> |
2142 | code.</p> |
2070 | </dd> |
2143 | </dd> |
2071 | <dt>EV_EMBED_ENABLE</dt> |
2144 | <dt>EV_EMBED_ENABLE</dt> |
2072 | <dd> |
2145 | <dd> |
… | |
… | |
2137 | the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public |
2210 | the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public |
2138 | interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file |
2211 | interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file |
2139 | will be compiled. It is pretty complex because it provides its own header |
2212 | will be compiled. It is pretty complex because it provides its own header |
2140 | file.</p> |
2213 | file.</p> |
2141 | <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file |
2214 | <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file |
2142 | that everybody includes and which overrides some autoconf choices:</p> |
2215 | that everybody includes and which overrides some configure choices:</p> |
|
|
2216 | <pre> #define EV_MINIMAL 1 |
2143 | <pre> #define EV_USE_POLL 0 |
2217 | #define EV_USE_POLL 0 |
2144 | #define EV_MULTIPLICITY 0 |
2218 | #define EV_MULTIPLICITY 0 |
2145 | #define EV_PERIODICS 0 |
2219 | #define EV_PERIODIC_ENABLE 0 |
|
|
2220 | #define EV_STAT_ENABLE 0 |
|
|
2221 | #define EV_FORK_ENABLE 0 |
2146 | #define EV_CONFIG_H <config.h> |
2222 | #define EV_CONFIG_H <config.h> |
|
|
2223 | #define EV_MINPRI 0 |
|
|
2224 | #define EV_MAXPRI 0 |
2147 | |
2225 | |
2148 | #include "ev++.h" |
2226 | #include "ev++.h" |
2149 | |
2227 | |
2150 | </pre> |
2228 | </pre> |
2151 | <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p> |
2229 | <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p> |
… | |
… | |
2161 | <h1 id="COMPLEXITIES">COMPLEXITIES</h1> |
2239 | <h1 id="COMPLEXITIES">COMPLEXITIES</h1> |
2162 | <div id="COMPLEXITIES_CONTENT"> |
2240 | <div id="COMPLEXITIES_CONTENT"> |
2163 | <p>In this section the complexities of (many of) the algorithms used inside |
2241 | <p>In this section the complexities of (many of) the algorithms used inside |
2164 | libev will be explained. For complexity discussions about backends see the |
2242 | libev will be explained. For complexity discussions about backends see the |
2165 | documentation for <code>ev_default_init</code>.</p> |
2243 | documentation for <code>ev_default_init</code>.</p> |
|
|
2244 | <p>All of the following are about amortised time: If an array needs to be |
|
|
2245 | extended, libev needs to realloc and move the whole array, but this |
|
|
2246 | happens asymptotically never with higher number of elements, so O(1) might |
|
|
2247 | mean it might do a lengthy realloc operation in rare cases, but on average |
|
|
2248 | it is much faster and asymptotically approaches constant time.</p> |
2166 | <p> |
2249 | <p> |
2167 | <dl> |
2250 | <dl> |
2168 | <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> |
2251 | <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> |
|
|
2252 | <dd> |
|
|
2253 | <p>This means that, when you have a watcher that triggers in one hour and |
|
|
2254 | there are 100 watchers that would trigger before that then inserting will |
|
|
2255 | have to skip those 100 watchers.</p> |
|
|
2256 | </dd> |
2169 | <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt> |
2257 | <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt> |
|
|
2258 | <dd> |
|
|
2259 | <p>That means that for changing a timer costs less than removing/adding them |
|
|
2260 | as only the relative motion in the event queue has to be paid for.</p> |
|
|
2261 | </dd> |
2170 | <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> |
2262 | <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> |
|
|
2263 | <dd> |
|
|
2264 | <p>These just add the watcher into an array or at the head of a list. |
2171 | <dt>Stopping check/prepare/idle watchers: O(1)</dt> |
2265 | =item Stopping check/prepare/idle watchers: O(1)</p> |
|
|
2266 | </dd> |
2172 | <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt> |
2267 | <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt> |
|
|
2268 | <dd> |
|
|
2269 | <p>These watchers are stored in lists then need to be walked to find the |
|
|
2270 | correct watcher to remove. The lists are usually short (you don't usually |
|
|
2271 | have many watchers waiting for the same fd or signal).</p> |
|
|
2272 | </dd> |
2173 | <dt>Finding the next timer per loop iteration: O(1)</dt> |
2273 | <dt>Finding the next timer per loop iteration: O(1)</dt> |
2174 | <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt> |
2274 | <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt> |
|
|
2275 | <dd> |
|
|
2276 | <p>A change means an I/O watcher gets started or stopped, which requires |
|
|
2277 | libev to recalculate its status (and possibly tell the kernel).</p> |
|
|
2278 | </dd> |
2175 | <dt>Activating one watcher: O(1)</dt> |
2279 | <dt>Activating one watcher: O(1)</dt> |
|
|
2280 | <dt>Priority handling: O(number_of_priorities)</dt> |
|
|
2281 | <dd> |
|
|
2282 | <p>Priorities are implemented by allocating some space for each |
|
|
2283 | priority. When doing priority-based operations, libev usually has to |
|
|
2284 | linearly search all the priorities.</p> |
|
|
2285 | </dd> |
2176 | </dl> |
2286 | </dl> |
2177 | </p> |
2287 | </p> |
2178 | |
2288 | |
2179 | |
2289 | |
2180 | |
2290 | |