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Revision 1.35 by root, Fri Nov 23 16:17:12 2007 UTC vs.
Revision 1.36 by root, Sat Nov 24 06:23:27 2007 UTC

… …
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" />
7 <meta name="inputfile" content="&lt;standard input&gt;" /> 7 <meta name="inputfile" content="&lt;standard input&gt;" />
8 <meta name="outputfile" content="&lt;standard output&gt;" /> 8 <meta name="outputfile" content="&lt;standard output&gt;" />
9 <meta name="created" content="Fri Nov 23 17:17:04 2007" /> 9 <meta name="created" content="Sat Nov 24 05:58:35 2007" />
10 <meta name="generator" content="Pod::Xhtml 1.57" /> 10 <meta name="generator" content="Pod::Xhtml 1.57" />
11<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head> 11<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head>
12<body> 12<body>
13<div class="pod"> 13<div class="pod">
14<!-- INDEX START --> 14<!-- INDEX START -->
… …
32<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</a></li> 32<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</a></li>
33<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</a></li> 33<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</a></li>
34<li><a href="#code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</a></li> 34<li><a href="#code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</a></li>
35<li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</a></li> 35<li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</a></li>
36<li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</a></li> 36<li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</a></li>
37<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough</a></li>
37</ul> 38</ul>
38</li> 39</li>
39<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> 40<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
40<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li> 41<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
41<li><a href="#C_SUPPORT">C++ SUPPORT</a></li> 42<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>
… …
156recommended for this platform. This set is often smaller than the one 157recommended for this platform. This set is often smaller than the one
157returned by <code>ev_supported_backends</code>, as for example kqueue is broken on 158returned by <code>ev_supported_backends</code>, as for example kqueue is broken on
158most BSDs and will not be autodetected unless you explicitly request it 159most BSDs and will not be autodetected unless you explicitly request it
159(assuming you know what you are doing). This is the set of backends that 160(assuming you know what you are doing). This is the set of backends that
160libev will probe for if you specify no backends explicitly.</p> 161libev will probe for if you specify no backends explicitly.</p>
162 </dd>
163 <dt>unsigned int ev_embeddable_backends ()</dt>
164 <dd>
165 <p>Returns the set of backends that are embeddable in other event loops. This
166is the theoretical, all-platform, value. To find which backends
167might be supported on the current system, you would need to look at
168<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for
169recommended ones.</p>
170 <p>See the description of <code>ev_embed</code> watchers for more info.</p>
161 </dd> 171 </dd>
162 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> 172 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
163 <dd> 173 <dd>
164 <p>Sets the allocation function to use (the prototype is similar to the 174 <p>Sets the allocation function to use (the prototype is similar to the
165realloc C function, the semantics are identical). It is used to allocate 175realloc C function, the semantics are identical). It is used to allocate
… …
931 <p>Configures the watcher to trigger on the given signal number (usually one 941 <p>Configures the watcher to trigger on the given signal number (usually one
932of the <code>SIGxxx</code> constants).</p> 942of the <code>SIGxxx</code> constants).</p>
933 </dd> 943 </dd>
934</dl> 944</dl>
935 945
946
947
948
949
936</div> 950</div>
937<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2> 951<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2>
938<div id="code_ev_child_code_wait_for_pid_stat-2"> 952<div id="code_ev_child_code_wait_for_pid_stat-2">
939<p>Child watchers trigger when your process receives a SIGCHLD in response to 953<p>Child watchers trigger when your process receives a SIGCHLD in response to
940some child status changes (most typically when a child of yours dies).</p> 954some child status changes (most typically when a child of yours dies).</p>
… …
1013<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2> 1027<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2>
1014<div id="code_ev_prepare_code_and_code_ev_che-2"> 1028<div id="code_ev_prepare_code_and_code_ev_che-2">
1015<p>Prepare and check watchers are usually (but not always) used in tandem: 1029<p>Prepare and check watchers are usually (but not always) used in tandem:
1016prepare watchers get invoked before the process blocks and check watchers 1030prepare watchers get invoked before the process blocks and check watchers
1017afterwards.</p> 1031afterwards.</p>
1018<p>Their main purpose is to integrate other event mechanisms into libev. This 1032<p>Their main purpose is to integrate other event mechanisms into libev and
1019could be used, for example, to track variable changes, implement your own 1033their use is somewhat advanced. This could be used, for example, to track
1020watchers, integrate net-snmp or a coroutine library and lots more.</p> 1034variable changes, implement your own watchers, integrate net-snmp or a
1035coroutine library and lots more.</p>
1021<p>This is done by examining in each prepare call which file descriptors need 1036<p>This is done by examining in each prepare call which file descriptors need
1022to be watched by the other library, registering <code>ev_io</code> watchers for 1037to be watched by the other library, registering <code>ev_io</code> watchers for
1023them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries 1038them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
1024provide just this functionality). Then, in the check watcher you check for 1039provide just this functionality). Then, in the check watcher you check for
1025any events that occured (by checking the pending status of all watchers 1040any events that occured (by checking the pending status of all watchers
… …
1042parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 1057parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
1043macros, but using them is utterly, utterly and completely pointless.</p> 1058macros, but using them is utterly, utterly and completely pointless.</p>
1044 </dd> 1059 </dd>
1045</dl> 1060</dl>
1046<p>Example: *TODO*.</p> 1061<p>Example: *TODO*.</p>
1062
1063
1064
1065
1066
1067</div>
1068<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough</h2>
1069<div id="code_ev_embed_code_when_one_backend_-2">
1070<p>This is a rather advanced watcher type that lets you embed one event loop
1071into another.</p>
1072<p>There are primarily two reasons you would want that: work around bugs and
1073prioritise I/O.</p>
1074<p>As an example for a bug workaround, the kqueue backend might only support
1075sockets on some platform, so it is unusable as generic backend, but you
1076still want to make use of it because you have many sockets and it scales
1077so nicely. In this case, you would create a kqueue-based loop and embed it
1078into your default loop (which might use e.g. poll). Overall operation will
1079be a bit slower because first libev has to poll and then call kevent, but
1080at least you can use both at what they are best.</p>
1081<p>As for prioritising I/O: rarely you have the case where some fds have
1082to be watched and handled very quickly (with low latency), and even
1083priorities and idle watchers might have too much overhead. In this case
1084you would put all the high priority stuff in one loop and all the rest in
1085a second one, and embed the second one in the first.</p>
1086<p>As long as the watcher is started it will automatically handle events. The
1087callback will be invoked whenever some events have been handled. You can
1088set the callback to <code>0</code> to avoid having to specify one if you are not
1089interested in that.</p>
1090<p>Also, there have not currently been made special provisions for forking:
1091when you fork, you not only have to call <code>ev_loop_fork</code> on both loops,
1092but you will also have to stop and restart any <code>ev_embed</code> watchers
1093yourself.</p>
1094<p>Unfortunately, not all backends are embeddable, only the ones returned by
1095<code>ev_embeddable_backends</code> are, which, unfortunately, does not include any
1096portable one.</p>
1097<p>So when you want to use this feature you will always have to be prepared
1098that you cannot get an embeddable loop. The recommended way to get around
1099this is to have a separate variables for your embeddable loop, try to
1100create it, and if that fails, use the normal loop for everything:</p>
1101<pre> struct ev_loop *loop_hi = ev_default_init (0);
1102 struct ev_loop *loop_lo = 0;
1103 struct ev_embed embed;
1104
1105 // see if there is a chance of getting one that works
1106 // (remember that a flags value of 0 means autodetection)
1107 loop_lo = ev_embeddable_backends () &amp; ev_recommended_backends ()
1108 ? ev_loop_new (ev_embeddable_backends () &amp; ev_recommended_backends ())
1109 : 0;
1110
1111 // if we got one, then embed it, otherwise default to loop_hi
1112 if (loop_lo)
1113 {
1114 ev_embed_init (&amp;embed, 0, loop_lo);
1115 ev_embed_start (loop_hi, &amp;embed);
1116 }
1117 else
1118 loop_lo = loop_hi;
1119
1120</pre>
1121<dl>
1122 <dt>ev_embed_init (ev_embed *, callback, struct ev_loop *loop)</dt>
1123 <dt>ev_embed_set (ev_embed *, callback, struct ev_loop *loop)</dt>
1124 <dd>
1125 <p>Configures the watcher to embed the given loop, which must be embeddable.</p>
1126 </dd>
1127</dl>
1047 1128
1048 1129
1049 1130
1050 1131
1051 1132

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