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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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9 | <meta name="created" content="Thu Nov 29 18:28:02 2007" /> |
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13 | <div class="pod"> |
13 | <div class="pod"> |
14 | <!-- INDEX START --> |
14 | <!-- INDEX START --> |
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333 | <p>Instead of calling <code>ev_default_fork</code> or <code>ev_loop_fork</code> manually after |
333 | <p>Instead of calling <code>ev_default_fork</code> or <code>ev_loop_fork</code> manually after |
334 | a fork, you can also make libev check for a fork in each iteration by |
334 | a fork, you can also make libev check for a fork in each iteration by |
335 | enabling this flag.</p> |
335 | enabling this flag.</p> |
336 | <p>This works by calling <code>getpid ()</code> on every iteration of the loop, |
336 | <p>This works by calling <code>getpid ()</code> on every iteration of the loop, |
337 | and thus this might slow down your event loop if you do a lot of loop |
337 | and thus this might slow down your event loop if you do a lot of loop |
338 | iterations and little real work, but is usually not noticable (on my |
338 | iterations and little real work, but is usually not noticeable (on my |
339 | Linux system for example, <code>getpid</code> is actually a simple 5-insn sequence |
339 | Linux system for example, <code>getpid</code> is actually a simple 5-insn sequence |
340 | without a syscall and thus <i>very</i> fast, but my Linux system also has |
340 | without a syscall and thus <i>very</i> fast, but my Linux system also has |
341 | <code>pthread_atfork</code> which is even faster).</p> |
341 | <code>pthread_atfork</code> which is even faster).</p> |
342 | <p>The big advantage of this flag is that you can forget about fork (and |
342 | <p>The big advantage of this flag is that you can forget about fork (and |
343 | forget about forgetting to tell libev about forking) when you use this |
343 | forget about forgetting to tell libev about forking) when you use this |
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481 | <dd> |
481 | <dd> |
482 | <p>Like <code>ev_default_fork</code>, but acts on an event loop created by |
482 | <p>Like <code>ev_default_fork</code>, but acts on an event loop created by |
483 | <code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop |
483 | <code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop |
484 | after fork, and how you do this is entirely your own problem.</p> |
484 | after fork, and how you do this is entirely your own problem.</p> |
485 | </dd> |
485 | </dd> |
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486 | <dt>unsigned int ev_loop_count (loop)</dt> |
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487 | <dd> |
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488 | <p>Returns the count of loop iterations for the loop, which is identical to |
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489 | the number of times libev did poll for new events. It starts at <code>0</code> and |
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490 | happily wraps around with enough iterations.</p> |
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491 | <p>This value can sometimes be useful as a generation counter of sorts (it |
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492 | "ticks" the number of loop iterations), as it roughly corresponds with |
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493 | <code>ev_prepare</code> and <code>ev_check</code> calls.</p> |
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494 | </dd> |
486 | <dt>unsigned int ev_backend (loop)</dt> |
495 | <dt>unsigned int ev_backend (loop)</dt> |
487 | <dd> |
496 | <dd> |
488 | <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in |
497 | <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in |
489 | use.</p> |
498 | use.</p> |
490 | </dd> |
499 | </dd> |
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769 | <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt> |
778 | <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt> |
770 | <dd> |
779 | <dd> |
771 | <p>Change the callback. You can change the callback at virtually any time |
780 | <p>Change the callback. You can change the callback at virtually any time |
772 | (modulo threads).</p> |
781 | (modulo threads).</p> |
773 | </dd> |
782 | </dd> |
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783 | <dt>ev_set_priority (ev_TYPE *watcher, priority)</dt> |
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784 | <dt>int ev_priority (ev_TYPE *watcher)</dt> |
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785 | <dd> |
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786 | <p>Set and query the priority of the watcher. The priority is a small |
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787 | integer between <code>EV_MAXPRI</code> (default: <code>2</code>) and <code>EV_MINPRI</code> |
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788 | (default: <code>-2</code>). Pending watchers with higher priority will be invoked |
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789 | before watchers with lower priority, but priority will not keep watchers |
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790 | from being executed (except for <code>ev_idle</code> watchers).</p> |
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791 | <p>This means that priorities are <i>only</i> used for ordering callback |
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792 | invocation after new events have been received. This is useful, for |
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793 | example, to reduce latency after idling, or more often, to bind two |
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794 | watchers on the same event and make sure one is called first.</p> |
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795 | <p>If you need to suppress invocation when higher priority events are pending |
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796 | you need to look at <code>ev_idle</code> watchers, which provide this functionality.</p> |
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797 | <p>The default priority used by watchers when no priority has been set is |
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798 | always <code>0</code>, which is supposed to not be too high and not be too low :).</p> |
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799 | <p>Setting a priority outside the range of <code>EV_MINPRI</code> to <code>EV_MAXPRI</code> is |
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800 | fine, as long as you do not mind that the priority value you query might |
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801 | or might not have been adjusted to be within valid range.</p> |
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802 | </dd> |
774 | </dl> |
803 | </dl> |
775 | |
804 | |
776 | |
805 | |
777 | |
806 | |
778 | |
807 | |
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888 | this situation even with a relatively standard program structure. Thus |
917 | this situation even with a relatively standard program structure. Thus |
889 | it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning |
918 | it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning |
890 | <code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p> |
919 | <code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p> |
891 | <p>If you cannot run the fd in non-blocking mode (for example you should not |
920 | <p>If you cannot run the fd in non-blocking mode (for example you should not |
892 | play around with an Xlib connection), then you have to seperately re-test |
921 | play around with an Xlib connection), then you have to seperately re-test |
893 | wether a file descriptor is really ready with a known-to-be good interface |
922 | whether a file descriptor is really ready with a known-to-be good interface |
894 | such as poll (fortunately in our Xlib example, Xlib already does this on |
923 | such as poll (fortunately in our Xlib example, Xlib already does this on |
895 | its own, so its quite safe to use).</p> |
924 | its own, so its quite safe to use).</p> |
896 | <dl> |
925 | <dl> |
897 | <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> |
926 | <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> |
898 | <dt>ev_io_set (ev_io *, int fd, int events)</dt> |
927 | <dt>ev_io_set (ev_io *, int fd, int events)</dt> |
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1358 | </pre> |
1387 | </pre> |
1359 | |
1388 | |
1360 | </div> |
1389 | </div> |
1361 | <h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2> |
1390 | <h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2> |
1362 | <div id="code_ev_idle_code_when_you_ve_got_no-2"> |
1391 | <div id="code_ev_idle_code_when_you_ve_got_no-2"> |
1363 | <p>Idle watchers trigger events when there are no other events are pending |
1392 | <p>Idle watchers trigger events when no other events of the same or higher |
1364 | (prepare, check and other idle watchers do not count). That is, as long |
1393 | priority are pending (prepare, check and other idle watchers do not |
1365 | as your process is busy handling sockets or timeouts (or even signals, |
1394 | count).</p> |
1366 | imagine) it will not be triggered. But when your process is idle all idle |
1395 | <p>That is, as long as your process is busy handling sockets or timeouts |
1367 | watchers are being called again and again, once per event loop iteration - |
1396 | (or even signals, imagine) of the same or higher priority it will not be |
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1397 | triggered. But when your process is idle (or only lower-priority watchers |
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1398 | are pending), the idle watchers are being called once per event loop |
1368 | until stopped, that is, or your process receives more events and becomes |
1399 | iteration - until stopped, that is, or your process receives more events |
1369 | busy.</p> |
1400 | and becomes busy again with higher priority stuff.</p> |
1370 | <p>The most noteworthy effect is that as long as any idle watchers are |
1401 | <p>The most noteworthy effect is that as long as any idle watchers are |
1371 | active, the process will not block when waiting for new events.</p> |
1402 | active, the process will not block when waiting for new events.</p> |
1372 | <p>Apart from keeping your process non-blocking (which is a useful |
1403 | <p>Apart from keeping your process non-blocking (which is a useful |
1373 | effect on its own sometimes), idle watchers are a good place to do |
1404 | effect on its own sometimes), idle watchers are a good place to do |
1374 | "pseudo-background processing", or delay processing stuff to after the |
1405 | "pseudo-background processing", or delay processing stuff to after the |
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1464 | |
1495 | |
1465 | // create io watchers for each fd and a timer before blocking |
1496 | // create io watchers for each fd and a timer before blocking |
1466 | static void |
1497 | static void |
1467 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
1498 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
1468 | { |
1499 | { |
1469 | int timeout = 3600000;truct pollfd fds [nfd]; |
1500 | int timeout = 3600000; |
|
|
1501 | struct pollfd fds [nfd]; |
1470 | // actual code will need to loop here and realloc etc. |
1502 | // actual code will need to loop here and realloc etc. |
1471 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
1503 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
1472 | |
1504 | |
1473 | /* the callback is illegal, but won't be called as we stop during check */ |
1505 | /* the callback is illegal, but won't be called as we stop during check */ |
1474 | ev_timer_init (&tw, 0, timeout * 1e-3); |
1506 | ev_timer_init (&tw, 0, timeout * 1e-3); |
… | |
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1800 | |
1832 | |
1801 | </div> |
1833 | </div> |
1802 | <h1 id="MACRO_MAGIC">MACRO MAGIC</h1> |
1834 | <h1 id="MACRO_MAGIC">MACRO MAGIC</h1> |
1803 | <div id="MACRO_MAGIC_CONTENT"> |
1835 | <div id="MACRO_MAGIC_CONTENT"> |
1804 | <p>Libev can be compiled with a variety of options, the most fundemantal is |
1836 | <p>Libev can be compiled with a variety of options, the most fundemantal is |
1805 | <code>EV_MULTIPLICITY</code>. This option determines wether (most) functions and |
1837 | <code>EV_MULTIPLICITY</code>. This option determines whether (most) functions and |
1806 | callbacks have an initial <code>struct ev_loop *</code> argument.</p> |
1838 | callbacks have an initial <code>struct ev_loop *</code> argument.</p> |
1807 | <p>To make it easier to write programs that cope with either variant, the |
1839 | <p>To make it easier to write programs that cope with either variant, the |
1808 | following macros are defined:</p> |
1840 | following macros are defined:</p> |
1809 | <dl> |
1841 | <dl> |
1810 | <dt><code>EV_A</code>, <code>EV_A_</code></dt> |
1842 | <dt><code>EV_A</code>, <code>EV_A_</code></dt> |
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1839 | <dd> |
1871 | <dd> |
1840 | <p>Similar to the other two macros, this gives you the value of the default |
1872 | <p>Similar to the other two macros, this gives you the value of the default |
1841 | loop, if multiple loops are supported ("ev loop default").</p> |
1873 | loop, if multiple loops are supported ("ev loop default").</p> |
1842 | </dd> |
1874 | </dd> |
1843 | </dl> |
1875 | </dl> |
1844 | <p>Example: Declare and initialise a check watcher, working regardless of |
1876 | <p>Example: Declare and initialise a check watcher, utilising the above |
1845 | wether multiple loops are supported or not.</p> |
1877 | macros so it will work regardless of whether multiple loops are supported |
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|
1878 | or not.</p> |
1846 | <pre> static void |
1879 | <pre> static void |
1847 | check_cb (EV_P_ ev_timer *w, int revents) |
1880 | check_cb (EV_P_ ev_timer *w, int revents) |
1848 | { |
1881 | { |
1849 | ev_check_stop (EV_A_ w); |
1882 | ev_check_stop (EV_A_ w); |
1850 | } |
1883 | } |
1851 | |
1884 | |
1852 | ev_check check; |
1885 | ev_check check; |
1853 | ev_check_init (&check, check_cb); |
1886 | ev_check_init (&check, check_cb); |
1854 | ev_check_start (EV_DEFAULT_ &check); |
1887 | ev_check_start (EV_DEFAULT_ &check); |
1855 | ev_loop (EV_DEFAULT_ 0); |
1888 | ev_loop (EV_DEFAULT_ 0); |
1856 | |
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1857 | |
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1858 | |
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|
1859 | |
1889 | |
1860 | </pre> |
1890 | </pre> |
1861 | |
1891 | |
1862 | </div> |
1892 | </div> |
1863 | <h1 id="EMBEDDING">EMBEDDING</h1> |
1893 | <h1 id="EMBEDDING">EMBEDDING</h1> |
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1905 | ev_vars.h |
1935 | ev_vars.h |
1906 | ev_wrap.h |
1936 | ev_wrap.h |
1907 | |
1937 | |
1908 | ev_win32.c required on win32 platforms only |
1938 | ev_win32.c required on win32 platforms only |
1909 | |
1939 | |
1910 | ev_select.c only when select backend is enabled (which is by default) |
1940 | ev_select.c only when select backend is enabled (which is enabled by default) |
1911 | ev_poll.c only when poll backend is enabled (disabled by default) |
1941 | ev_poll.c only when poll backend is enabled (disabled by default) |
1912 | ev_epoll.c only when the epoll backend is enabled (disabled by default) |
1942 | ev_epoll.c only when the epoll backend is enabled (disabled by default) |
1913 | ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
1943 | ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
1914 | ev_port.c only when the solaris port backend is enabled (disabled by default) |
1944 | ev_port.c only when the solaris port backend is enabled (disabled by default) |
1915 | |
1945 | |
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2083 | argument. Instead, all functions act on the single default loop.</p> |
2113 | argument. Instead, all functions act on the single default loop.</p> |
2084 | </dd> |
2114 | </dd> |
2085 | <dt>EV_PERIODIC_ENABLE</dt> |
2115 | <dt>EV_PERIODIC_ENABLE</dt> |
2086 | <dd> |
2116 | <dd> |
2087 | <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If |
2117 | <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If |
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2118 | defined to be <code>0</code>, then they are not. Disabling them saves a few kB of |
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2119 | code.</p> |
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2120 | </dd> |
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|
2121 | <dt>EV_IDLE_ENABLE</dt> |
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|
2122 | <dd> |
|
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2123 | <p>If undefined or defined to be <code>1</code>, then idle watchers are supported. If |
2088 | defined to be <code>0</code>, then they are not. Disabling them saves a few kB of |
2124 | defined to be <code>0</code>, then they are not. Disabling them saves a few kB of |
2089 | code.</p> |
2125 | code.</p> |
2090 | </dd> |
2126 | </dd> |
2091 | <dt>EV_EMBED_ENABLE</dt> |
2127 | <dt>EV_EMBED_ENABLE</dt> |
2092 | <dd> |
2128 | <dd> |
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2157 | the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public |
2193 | the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public |
2158 | interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file |
2194 | interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file |
2159 | will be compiled. It is pretty complex because it provides its own header |
2195 | will be compiled. It is pretty complex because it provides its own header |
2160 | file.</p> |
2196 | file.</p> |
2161 | <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file |
2197 | <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file |
2162 | that everybody includes and which overrides some autoconf choices:</p> |
2198 | that everybody includes and which overrides some configure choices:</p> |
|
|
2199 | <pre> #define EV_MINIMAL 1 |
2163 | <pre> #define EV_USE_POLL 0 |
2200 | #define EV_USE_POLL 0 |
2164 | #define EV_MULTIPLICITY 0 |
2201 | #define EV_MULTIPLICITY 0 |
2165 | #define EV_PERIODICS 0 |
2202 | #define EV_PERIODIC_ENABLE 0 |
|
|
2203 | #define EV_STAT_ENABLE 0 |
|
|
2204 | #define EV_FORK_ENABLE 0 |
2166 | #define EV_CONFIG_H <config.h> |
2205 | #define EV_CONFIG_H <config.h> |
|
|
2206 | #define EV_MINPRI 0 |
|
|
2207 | #define EV_MAXPRI 0 |
2167 | |
2208 | |
2168 | #include "ev++.h" |
2209 | #include "ev++.h" |
2169 | |
2210 | |
2170 | </pre> |
2211 | </pre> |
2171 | <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p> |
2212 | <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p> |