ViewVC Help
View File | Revision Log | Show Annotations | Download File
/cvs/libev/ev.html
(Generate patch)

Comparing libev/ev.html (file contents):
Revision 1.44 by root, Sat Nov 24 16:33:23 2007 UTC vs.
Revision 1.52 by root, Tue Nov 27 19:41:52 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="Sat Nov 24 17:33:21 2007" /> 9 <meta name="created" content="Tue Nov 27 20:38:24 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 -->
… …
31<ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</a></li> 31<ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</a></li>
32<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</a></li> 32<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</a></li>
33<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_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</a></li>
34<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_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</a></li>
35<li><a href="#code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</a></li> 35<li><a href="#code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</a></li>
36<li><a href="#code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</a></li>
36<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> 37<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>
37<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> 38<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>
38<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</a></li> 39<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</a></li>
40<li><a href="#code_ev_fork_code_the_audacity_to_re"><code>ev_fork</code> - the audacity to resume the event loop after a fork</a></li>
39</ul> 41</ul>
40</li> 42</li>
41<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> 43<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
42<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li> 44<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
43<li><a href="#C_SUPPORT">C++ SUPPORT</a></li> 45<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>
46<li><a href="#MACRO_MAGIC">MACRO MAGIC</a></li>
44<li><a href="#EMBEDDING">EMBEDDING</a> 47<li><a href="#EMBEDDING">EMBEDDING</a>
45<ul><li><a href="#FILESETS">FILESETS</a> 48<ul><li><a href="#FILESETS">FILESETS</a>
46<ul><li><a href="#CORE_EVENT_LOOP">CORE EVENT LOOP</a></li> 49<ul><li><a href="#CORE_EVENT_LOOP">CORE EVENT LOOP</a></li>
47<li><a href="#LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</a></li> 50<li><a href="#LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</a></li>
48<li><a href="#AUTOCONF_SUPPORT">AUTOCONF SUPPORT</a></li> 51<li><a href="#AUTOCONF_SUPPORT">AUTOCONF SUPPORT</a></li>
… …
50</li> 53</li>
51<li><a href="#PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</a></li> 54<li><a href="#PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</a></li>
52<li><a href="#EXAMPLES">EXAMPLES</a></li> 55<li><a href="#EXAMPLES">EXAMPLES</a></li>
53</ul> 56</ul>
54</li> 57</li>
58<li><a href="#COMPLEXITIES">COMPLEXITIES</a></li>
55<li><a href="#AUTHOR">AUTHOR</a> 59<li><a href="#AUTHOR">AUTHOR</a>
56</li> 60</li>
57</ul><hr /> 61</ul><hr />
58<!-- INDEX END --> 62<!-- INDEX END -->
59 63
… …
111(fractional) number of seconds since the (POSIX) epoch (somewhere near 115(fractional) number of seconds since the (POSIX) epoch (somewhere near
112the beginning of 1970, details are complicated, don't ask). This type is 116the beginning of 1970, details are complicated, don't ask). This type is
113called <code>ev_tstamp</code>, which is what you should use too. It usually aliases 117called <code>ev_tstamp</code>, which is what you should use too. It usually aliases
114to the <code>double</code> type in C, and when you need to do any calculations on 118to the <code>double</code> type in C, and when you need to do any calculations on
115it, you should treat it as such.</p> 119it, you should treat it as such.</p>
116
117
118
119
120 120
121</div> 121</div>
122<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 122<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
123<div id="GLOBAL_FUNCTIONS_CONTENT"> 123<div id="GLOBAL_FUNCTIONS_CONTENT">
124<p>These functions can be called anytime, even before initialising the 124<p>These functions can be called anytime, even before initialising the
… …
179might be supported on the current system, you would need to look at 179might be supported on the current system, you would need to look at
180<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for 180<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for
181recommended ones.</p> 181recommended ones.</p>
182 <p>See the description of <code>ev_embed</code> watchers for more info.</p> 182 <p>See the description of <code>ev_embed</code> watchers for more info.</p>
183 </dd> 183 </dd>
184 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> 184 <dt>ev_set_allocator (void *(*cb)(void *ptr, size_t size))</dt>
185 <dd> 185 <dd>
186 <p>Sets the allocation function to use (the prototype is similar to the 186 <p>Sets the allocation function to use (the prototype and semantics are
187realloc C function, the semantics are identical). It is used to allocate 187identical to the realloc C function). It is used to allocate and free
188and free memory (no surprises here). If it returns zero when memory 188memory (no surprises here). If it returns zero when memory needs to be
189needs to be allocated, the library might abort or take some potentially 189allocated, the library might abort or take some potentially destructive
190destructive action. The default is your system realloc function.</p> 190action. The default is your system realloc function.</p>
191 <p>You could override this function in high-availability programs to, say, 191 <p>You could override this function in high-availability programs to, say,
192free some memory if it cannot allocate memory, to use a special allocator, 192free some memory if it cannot allocate memory, to use a special allocator,
193or even to sleep a while and retry until some memory is available.</p> 193or even to sleep a while and retry until some memory is available.</p>
194 <p>Example: replace the libev allocator with one that waits a bit and then 194 <p>Example: replace the libev allocator with one that waits a bit and then
195retries: better than mine).</p> 195retries: better than mine).</p>
196<pre> static void * 196<pre> static void *
197 persistent_realloc (void *ptr, long size) 197 persistent_realloc (void *ptr, size_t size)
198 { 198 {
199 for (;;) 199 for (;;)
200 { 200 {
201 void *newptr = realloc (ptr, size); 201 void *newptr = realloc (ptr, size);
202 202
… …
585 </dd> 585 </dd>
586 <dt><code>EV_CHILD</code></dt> 586 <dt><code>EV_CHILD</code></dt>
587 <dd> 587 <dd>
588 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p> 588 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>
589 </dd> 589 </dd>
590 <dt><code>EV_STAT</code></dt>
591 <dd>
592 <p>The path specified in the <code>ev_stat</code> watcher changed its attributes somehow.</p>
593 </dd>
590 <dt><code>EV_IDLE</code></dt> 594 <dt><code>EV_IDLE</code></dt>
591 <dd> 595 <dd>
592 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p> 596 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>
593 </dd> 597 </dd>
594 <dt><code>EV_PREPARE</code></dt> 598 <dt><code>EV_PREPARE</code></dt>
… …
599<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any 603<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any
600received events. Callbacks of both watcher types can start and stop as 604received events. Callbacks of both watcher types can start and stop as
601many watchers as they want, and all of them will be taken into account 605many watchers as they want, and all of them will be taken into account
602(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep 606(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
603<code>ev_loop</code> from blocking).</p> 607<code>ev_loop</code> from blocking).</p>
608 </dd>
609 <dt><code>EV_EMBED</code></dt>
610 <dd>
611 <p>The embedded event loop specified in the <code>ev_embed</code> watcher needs attention.</p>
612 </dd>
613 <dt><code>EV_FORK</code></dt>
614 <dd>
615 <p>The event loop has been resumed in the child process after fork (see
616<code>ev_fork</code>).</p>
604 </dd> 617 </dd>
605 <dt><code>EV_ERROR</code></dt> 618 <dt><code>EV_ERROR</code></dt>
606 <dd> 619 <dd>
607 <p>An unspecified error has occured, the watcher has been stopped. This might 620 <p>An unspecified error has occured, the watcher has been stopped. This might
608happen because the watcher could not be properly started because libev 621happen because the watcher could not be properly started because libev
… …
731 744
732</div> 745</div>
733<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> 746<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p>
734<div id="WATCHER_TYPES_CONTENT"> 747<div id="WATCHER_TYPES_CONTENT">
735<p>This section describes each watcher in detail, but will not repeat 748<p>This section describes each watcher in detail, but will not repeat
736information given in the last section.</p> 749information given in the last section. Any initialisation/set macros,
750functions and members specific to the watcher type are explained.</p>
751<p>Members are additionally marked with either <i>[read-only]</i>, meaning that,
752while the watcher is active, you can look at the member and expect some
753sensible content, but you must not modify it (you can modify it while the
754watcher is stopped to your hearts content), or <i>[read-write]</i>, which
755means you can expect it to have some sensible content while the watcher
756is active, but you can also modify it. Modifying it may not do something
757sensible or take immediate effect (or do anything at all), but libev will
758not crash or malfunction in any way.</p>
737 759
738 760
739 761
740 762
741 763
… …
780 <dd> 802 <dd>
781 <p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to 803 <p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to
782rceeive events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or 804rceeive events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or
783<code>EV_READ | EV_WRITE</code> to receive the given events.</p> 805<code>EV_READ | EV_WRITE</code> to receive the given events.</p>
784 </dd> 806 </dd>
807 <dt>int fd [read-only]</dt>
808 <dd>
809 <p>The file descriptor being watched.</p>
810 </dd>
811 <dt>int events [read-only]</dt>
812 <dd>
813 <p>The events being watched.</p>
814 </dd>
785</dl> 815</dl>
786<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well 816<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
787readable, but only once. Since it is likely line-buffered, you could 817readable, but only once. Since it is likely line-buffered, you could
788attempt to read a whole line in the callback:</p> 818attempt to read a whole line in the callback:</p>
789<pre> static void 819<pre> static void
… …
846repeating. The exact semantics are:</p> 876repeating. The exact semantics are:</p>
847 <p>If the timer is started but nonrepeating, stop it.</p> 877 <p>If the timer is started but nonrepeating, stop it.</p>
848 <p>If the timer is repeating, either start it if necessary (with the repeat 878 <p>If the timer is repeating, either start it if necessary (with the repeat
849value), or reset the running timer to the repeat value.</p> 879value), or reset the running timer to the repeat value.</p>
850 <p>This sounds a bit complicated, but here is a useful and typical 880 <p>This sounds a bit complicated, but here is a useful and typical
851example: Imagine you have a tcp connection and you want a so-called idle 881example: Imagine you have a tcp connection and you want a so-called
852timeout, that is, you want to be called when there have been, say, 60 882idle timeout, that is, you want to be called when there have been,
853seconds of inactivity on the socket. The easiest way to do this is to 883say, 60 seconds of inactivity on the socket. The easiest way to do
854configure an <code>ev_timer</code> with after=repeat=60 and calling ev_timer_again each 884this is to configure an <code>ev_timer</code> with <code>after</code>=<code>repeat</code>=<code>60</code> and calling
855time you successfully read or write some data. If you go into an idle 885<code>ev_timer_again</code> each time you successfully read or write some data. If
856state where you do not expect data to travel on the socket, you can stop 886you go into an idle state where you do not expect data to travel on the
857the timer, and again will automatically restart it if need be.</p> 887socket, you can stop the timer, and again will automatically restart it if
888need be.</p>
889 <p>You can also ignore the <code>after</code> value and <code>ev_timer_start</code> altogether
890and only ever use the <code>repeat</code> value:</p>
891<pre> ev_timer_init (timer, callback, 0., 5.);
892 ev_timer_again (loop, timer);
893 ...
894 timer-&gt;again = 17.;
895 ev_timer_again (loop, timer);
896 ...
897 timer-&gt;again = 10.;
898 ev_timer_again (loop, timer);
899
900</pre>
901 <p>This is more efficient then stopping/starting the timer eahc time you want
902to modify its timeout value.</p>
903 </dd>
904 <dt>ev_tstamp repeat [read-write]</dt>
905 <dd>
906 <p>The current <code>repeat</code> value. Will be used each time the watcher times out
907or <code>ev_timer_again</code> is called and determines the next timeout (if any),
908which is also when any modifications are taken into account.</p>
858 </dd> 909 </dd>
859</dl> 910</dl>
860<p>Example: create a timer that fires after 60 seconds.</p> 911<p>Example: create a timer that fires after 60 seconds.</p>
861<pre> static void 912<pre> static void
862 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 913 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
… …
980 <p>Simply stops and restarts the periodic watcher again. This is only useful 1031 <p>Simply stops and restarts the periodic watcher again. This is only useful
981when you changed some parameters or the reschedule callback would return 1032when you changed some parameters or the reschedule callback would return
982a different time than the last time it was called (e.g. in a crond like 1033a different time than the last time it was called (e.g. in a crond like
983program when the crontabs have changed).</p> 1034program when the crontabs have changed).</p>
984 </dd> 1035 </dd>
1036 <dt>ev_tstamp interval [read-write]</dt>
1037 <dd>
1038 <p>The current interval value. Can be modified any time, but changes only
1039take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
1040called.</p>
1041 </dd>
1042 <dt>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]</dt>
1043 <dd>
1044 <p>The current reschedule callback, or <code>0</code>, if this functionality is
1045switched off. Can be changed any time, but changes only take effect when
1046the periodic timer fires or <code>ev_periodic_again</code> is being called.</p>
1047 </dd>
985</dl> 1048</dl>
986<p>Example: call a callback every hour, or, more precisely, whenever the 1049<p>Example: call a callback every hour, or, more precisely, whenever the
987system clock is divisible by 3600. The callback invocation times have 1050system clock is divisible by 3600. The callback invocation times have
988potentially a lot of jittering, but good long-term stability.</p> 1051potentially a lot of jittering, but good long-term stability.</p>
989<pre> static void 1052<pre> static void
… …
1038 <dt>ev_signal_set (ev_signal *, int signum)</dt> 1101 <dt>ev_signal_set (ev_signal *, int signum)</dt>
1039 <dd> 1102 <dd>
1040 <p>Configures the watcher to trigger on the given signal number (usually one 1103 <p>Configures the watcher to trigger on the given signal number (usually one
1041of the <code>SIGxxx</code> constants).</p> 1104of the <code>SIGxxx</code> constants).</p>
1042 </dd> 1105 </dd>
1106 <dt>int signum [read-only]</dt>
1107 <dd>
1108 <p>The signal the watcher watches out for.</p>
1109 </dd>
1043</dl> 1110</dl>
1044 1111
1045 1112
1046 1113
1047 1114
… …
1060at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see 1127at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see
1061the status word (use the macros from <code>sys/wait.h</code> and see your systems 1128the status word (use the macros from <code>sys/wait.h</code> and see your systems
1062<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the 1129<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
1063process causing the status change.</p> 1130process causing the status change.</p>
1064 </dd> 1131 </dd>
1132 <dt>int pid [read-only]</dt>
1133 <dd>
1134 <p>The process id this watcher watches out for, or <code>0</code>, meaning any process id.</p>
1135 </dd>
1136 <dt>int rpid [read-write]</dt>
1137 <dd>
1138 <p>The process id that detected a status change.</p>
1139 </dd>
1140 <dt>int rstatus [read-write]</dt>
1141 <dd>
1142 <p>The process exit/trace status caused by <code>rpid</code> (see your systems
1143<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p>
1144 </dd>
1065</dl> 1145</dl>
1066<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p> 1146<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p>
1067<pre> static void 1147<pre> static void
1068 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1148 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1069 { 1149 {
… …
1071 } 1151 }
1072 1152
1073 struct ev_signal signal_watcher; 1153 struct ev_signal signal_watcher;
1074 ev_signal_init (&amp;signal_watcher, sigint_cb, SIGINT); 1154 ev_signal_init (&amp;signal_watcher, sigint_cb, SIGINT);
1075 ev_signal_start (loop, &amp;sigint_cb); 1155 ev_signal_start (loop, &amp;sigint_cb);
1156
1157
1158
1159
1160</pre>
1161
1162</div>
1163<h2 id="code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</h2>
1164<div id="code_ev_stat_code_did_the_file_attri-2">
1165<p>This watches a filesystem path for attribute changes. That is, it calls
1166<code>stat</code> regularly (or when the OS says it changed) and sees if it changed
1167compared to the last time, invoking the callback if it did.</p>
1168<p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does
1169not exist&quot; is a status change like any other. The condition &quot;path does
1170not exist&quot; is signified by the <code>st_nlink</code> field being zero (which is
1171otherwise always forced to be at least one) and all the other fields of
1172the stat buffer having unspecified contents.</p>
1173<p>Since there is no standard to do this, the portable implementation simply
1174calls <code>stat (2)</code> regulalry on the path to see if it changed somehow. You
1175can specify a recommended polling interval for this case. If you specify
1176a polling interval of <code>0</code> (highly recommended!) then a <i>suitable,
1177unspecified default</i> value will be used (which you can expect to be around
1178five seconds, although this might change dynamically). Libev will also
1179impose a minimum interval which is currently around <code>0.1</code>, but thats
1180usually overkill.</p>
1181<p>This watcher type is not meant for massive numbers of stat watchers,
1182as even with OS-supported change notifications, this can be
1183resource-intensive.</p>
1184<p>At the time of this writing, no specific OS backends are implemented, but
1185if demand increases, at least a kqueue and inotify backend will be added.</p>
1186<dl>
1187 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt>
1188 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt>
1189 <dd>
1190 <p>Configures the watcher to wait for status changes of the given
1191<code>path</code>. The <code>interval</code> is a hint on how quickly a change is expected to
1192be detected and should normally be specified as <code>0</code> to let libev choose
1193a suitable value. The memory pointed to by <code>path</code> must point to the same
1194path for as long as the watcher is active.</p>
1195 <p>The callback will be receive <code>EV_STAT</code> when a change was detected,
1196relative to the attributes at the time the watcher was started (or the
1197last change was detected).</p>
1198 </dd>
1199 <dt>ev_stat_stat (ev_stat *)</dt>
1200 <dd>
1201 <p>Updates the stat buffer immediately with new values. If you change the
1202watched path in your callback, you could call this fucntion to avoid
1203detecting this change (while introducing a race condition). Can also be
1204useful simply to find out the new values.</p>
1205 </dd>
1206 <dt>ev_statdata attr [read-only]</dt>
1207 <dd>
1208 <p>The most-recently detected attributes of the file. Although the type is of
1209<code>ev_statdata</code>, this is usually the (or one of the) <code>struct stat</code> types
1210suitable for your system. If the <code>st_nlink</code> member is <code>0</code>, then there
1211was some error while <code>stat</code>ing the file.</p>
1212 </dd>
1213 <dt>ev_statdata prev [read-only]</dt>
1214 <dd>
1215 <p>The previous attributes of the file. The callback gets invoked whenever
1216<code>prev</code> != <code>attr</code>.</p>
1217 </dd>
1218 <dt>ev_tstamp interval [read-only]</dt>
1219 <dd>
1220 <p>The specified interval.</p>
1221 </dd>
1222 <dt>const char *path [read-only]</dt>
1223 <dd>
1224 <p>The filesystem path that is being watched.</p>
1225 </dd>
1226</dl>
1227<p>Example: Watch <code>/etc/passwd</code> for attribute changes.</p>
1228<pre> static void
1229 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1230 {
1231 /* /etc/passwd changed in some way */
1232 if (w-&gt;attr.st_nlink)
1233 {
1234 printf (&quot;passwd current size %ld\n&quot;, (long)w-&gt;attr.st_size);
1235 printf (&quot;passwd current atime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1236 printf (&quot;passwd current mtime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1237 }
1238 else
1239 /* you shalt not abuse printf for puts */
1240 puts (&quot;wow, /etc/passwd is not there, expect problems. &quot;
1241 &quot;if this is windows, they already arrived\n&quot;);
1242 }
1243
1244 ...
1245 ev_stat passwd;
1246
1247 ev_stat_init (&amp;passwd, passwd_cb, &quot;/etc/passwd&quot;);
1248 ev_stat_start (loop, &amp;passwd);
1076 1249
1077 1250
1078 1251
1079 1252
1080</pre> 1253</pre>
… …
1126<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</h2> 1299<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</h2>
1127<div id="code_ev_prepare_code_and_code_ev_che-2"> 1300<div id="code_ev_prepare_code_and_code_ev_che-2">
1128<p>Prepare and check watchers are usually (but not always) used in tandem: 1301<p>Prepare and check watchers are usually (but not always) used in tandem:
1129prepare watchers get invoked before the process blocks and check watchers 1302prepare watchers get invoked before the process blocks and check watchers
1130afterwards.</p> 1303afterwards.</p>
1304<p>You <i>must not</i> call <code>ev_loop</code> or similar functions that enter
1305the current event loop from either <code>ev_prepare</code> or <code>ev_check</code>
1306watchers. Other loops than the current one are fine, however. The
1307rationale behind this is that you do not need to check for recursion in
1308those watchers, i.e. the sequence will always be <code>ev_prepare</code>, blocking,
1309<code>ev_check</code> so if you have one watcher of each kind they will always be
1310called in pairs bracketing the blocking call.</p>
1131<p>Their main purpose is to integrate other event mechanisms into libev and 1311<p>Their main purpose is to integrate other event mechanisms into libev and
1132their use is somewhat advanced. This could be used, for example, to track 1312their use is somewhat advanced. This could be used, for example, to track
1133variable changes, implement your own watchers, integrate net-snmp or a 1313variable changes, implement your own watchers, integrate net-snmp or a
1134coroutine library and lots more.</p> 1314coroutine library and lots more. They are also occasionally useful if
1315you cache some data and want to flush it before blocking (for example,
1316in X programs you might want to do an <code>XFlush ()</code> in an <code>ev_prepare</code>
1317watcher).</p>
1135<p>This is done by examining in each prepare call which file descriptors need 1318<p>This is done by examining in each prepare call which file descriptors need
1136to be watched by the other library, registering <code>ev_io</code> watchers for 1319to be watched by the other library, registering <code>ev_io</code> watchers for
1137them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries 1320them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
1138provide just this functionality). Then, in the check watcher you check for 1321provide just this functionality). Then, in the check watcher you check for
1139any events that occured (by checking the pending status of all watchers 1322any events that occured (by checking the pending status of all watchers
… …
1155 <p>Initialises and configures the prepare or check watcher - they have no 1338 <p>Initialises and configures the prepare or check watcher - they have no
1156parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 1339parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
1157macros, but using them is utterly, utterly and completely pointless.</p> 1340macros, but using them is utterly, utterly and completely pointless.</p>
1158 </dd> 1341 </dd>
1159</dl> 1342</dl>
1160<p>Example: *TODO*.</p> 1343<p>Example: To include a library such as adns, you would add IO watchers
1344and a timeout watcher in a prepare handler, as required by libadns, and
1345in a check watcher, destroy them and call into libadns. What follows is
1346pseudo-code only of course:</p>
1347<pre> static ev_io iow [nfd];
1348 static ev_timer tw;
1161 1349
1350 static void
1351 io_cb (ev_loop *loop, ev_io *w, int revents)
1352 {
1353 // set the relevant poll flags
1354 // could also call adns_processreadable etc. here
1355 struct pollfd *fd = (struct pollfd *)w-&gt;data;
1356 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1357 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1358 }
1162 1359
1360 // create io watchers for each fd and a timer before blocking
1361 static void
1362 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1363 {
1364 int timeout = 3600000;truct pollfd fds [nfd];
1365 // actual code will need to loop here and realloc etc.
1366 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ()));
1163 1367
1368 /* the callback is illegal, but won't be called as we stop during check */
1369 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
1370 ev_timer_start (loop, &amp;tw);
1164 1371
1372 // create on ev_io per pollfd
1373 for (int i = 0; i &lt; nfd; ++i)
1374 {
1375 ev_io_init (iow + i, io_cb, fds [i].fd,
1376 ((fds [i].events &amp; POLLIN ? EV_READ : 0)
1377 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0)));
1378
1379 fds [i].revents = 0;
1380 iow [i].data = fds + i;
1381 ev_io_start (loop, iow + i);
1382 }
1383 }
1384
1385 // stop all watchers after blocking
1386 static void
1387 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1388 {
1389 ev_timer_stop (loop, &amp;tw);
1390
1391 for (int i = 0; i &lt; nfd; ++i)
1392 ev_io_stop (loop, iow + i);
1393
1394 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1395 }
1396
1397
1398
1399
1400</pre>
1165 1401
1166</div> 1402</div>
1167<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</h2> 1403<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</h2>
1168<div id="code_ev_embed_code_when_one_backend_-2"> 1404<div id="code_ev_embed_code_when_one_backend_-2">
1169<p>This is a rather advanced watcher type that lets you embed one event loop 1405<p>This is a rather advanced watcher type that lets you embed one event loop
… …
1239 <dt>ev_embed_sweep (loop, ev_embed *)</dt> 1475 <dt>ev_embed_sweep (loop, ev_embed *)</dt>
1240 <dd> 1476 <dd>
1241 <p>Make a single, non-blocking sweep over the embedded loop. This works 1477 <p>Make a single, non-blocking sweep over the embedded loop. This works
1242similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most 1478similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most
1243apropriate way for embedded loops.</p> 1479apropriate way for embedded loops.</p>
1480 </dd>
1481 <dt>struct ev_loop *loop [read-only]</dt>
1482 <dd>
1483 <p>The embedded event loop.</p>
1484 </dd>
1485</dl>
1486
1487
1488
1489
1490
1491</div>
1492<h2 id="code_ev_fork_code_the_audacity_to_re"><code>ev_fork</code> - the audacity to resume the event loop after a fork</h2>
1493<div id="code_ev_fork_code_the_audacity_to_re-2">
1494<p>Fork watchers are called when a <code>fork ()</code> was detected (usually because
1495whoever is a good citizen cared to tell libev about it by calling
1496<code>ev_default_fork</code> or <code>ev_loop_fork</code>). The invocation is done before the
1497event loop blocks next and before <code>ev_check</code> watchers are being called,
1498and only in the child after the fork. If whoever good citizen calling
1499<code>ev_default_fork</code> cheats and calls it in the wrong process, the fork
1500handlers will be invoked, too, of course.</p>
1501<dl>
1502 <dt>ev_fork_init (ev_signal *, callback)</dt>
1503 <dd>
1504 <p>Initialises and configures the fork watcher - it has no parameters of any
1505kind. There is a <code>ev_fork_set</code> macro, but using it is utterly pointless,
1506believe me.</p>
1244 </dd> 1507 </dd>
1245</dl> 1508</dl>
1246 1509
1247 1510
1248 1511
… …
1398 </dd> 1661 </dd>
1399 <dt>w-&gt;sweep () <code>ev::embed</code> only</dt> 1662 <dt>w-&gt;sweep () <code>ev::embed</code> only</dt>
1400 <dd> 1663 <dd>
1401 <p>Invokes <code>ev_embed_sweep</code>.</p> 1664 <p>Invokes <code>ev_embed_sweep</code>.</p>
1402 </dd> 1665 </dd>
1666 <dt>w-&gt;update () <code>ev::stat</code> only</dt>
1667 <dd>
1668 <p>Invokes <code>ev_stat_stat</code>.</p>
1669 </dd>
1403 </dl> 1670 </dl>
1404 </p> 1671 </p>
1405 </dd> 1672 </dd>
1406</dl> 1673</dl>
1407<p>Example: Define a class with an IO and idle watcher, start one of them in 1674<p>Example: Define a class with an IO and idle watcher, start one of them in
… …
1418 : io (this, &amp;myclass::io_cb), 1685 : io (this, &amp;myclass::io_cb),
1419 idle (this, &amp;myclass::idle_cb) 1686 idle (this, &amp;myclass::idle_cb)
1420 { 1687 {
1421 io.start (fd, ev::READ); 1688 io.start (fd, ev::READ);
1422 } 1689 }
1690
1691
1692
1693
1694</pre>
1695
1696</div>
1697<h1 id="MACRO_MAGIC">MACRO MAGIC</h1><p><a href="#TOP" class="toplink">Top</a></p>
1698<div id="MACRO_MAGIC_CONTENT">
1699<p>Libev can be compiled with a variety of options, the most fundemantal is
1700<code>EV_MULTIPLICITY</code>. This option determines wether (most) functions and
1701callbacks have an initial <code>struct ev_loop *</code> argument.</p>
1702<p>To make it easier to write programs that cope with either variant, the
1703following macros are defined:</p>
1704<dl>
1705 <dt><code>EV_A</code>, <code>EV_A_</code></dt>
1706 <dd>
1707 <p>This provides the loop <i>argument</i> for functions, if one is required (&quot;ev
1708loop argument&quot;). The <code>EV_A</code> form is used when this is the sole argument,
1709<code>EV_A_</code> is used when other arguments are following. Example:</p>
1710<pre> ev_unref (EV_A);
1711 ev_timer_add (EV_A_ watcher);
1712 ev_loop (EV_A_ 0);
1713
1714</pre>
1715 <p>It assumes the variable <code>loop</code> of type <code>struct ev_loop *</code> is in scope,
1716which is often provided by the following macro.</p>
1717 </dd>
1718 <dt><code>EV_P</code>, <code>EV_P_</code></dt>
1719 <dd>
1720 <p>This provides the loop <i>parameter</i> for functions, if one is required (&quot;ev
1721loop parameter&quot;). The <code>EV_P</code> form is used when this is the sole parameter,
1722<code>EV_P_</code> is used when other parameters are following. Example:</p>
1723<pre> // this is how ev_unref is being declared
1724 static void ev_unref (EV_P);
1725
1726 // this is how you can declare your typical callback
1727 static void cb (EV_P_ ev_timer *w, int revents)
1728
1729</pre>
1730 <p>It declares a parameter <code>loop</code> of type <code>struct ev_loop *</code>, quite
1731suitable for use with <code>EV_A</code>.</p>
1732 </dd>
1733 <dt><code>EV_DEFAULT</code>, <code>EV_DEFAULT_</code></dt>
1734 <dd>
1735 <p>Similar to the other two macros, this gives you the value of the default
1736loop, if multiple loops are supported (&quot;ev loop default&quot;).</p>
1737 </dd>
1738</dl>
1739<p>Example: Declare and initialise a check watcher, working regardless of
1740wether multiple loops are supported or not.</p>
1741<pre> static void
1742 check_cb (EV_P_ ev_timer *w, int revents)
1743 {
1744 ev_check_stop (EV_A_ w);
1745 }
1746
1747 ev_check check;
1748 ev_check_init (&amp;check, check_cb);
1749 ev_check_start (EV_DEFAULT_ &amp;check);
1750 ev_loop (EV_DEFAULT_ 0);
1751
1752
1753
1423 1754
1424</pre> 1755</pre>
1425 1756
1426</div> 1757</div>
1427<h1 id="EMBEDDING">EMBEDDING</h1><p><a href="#TOP" class="toplink">Top</a></p> 1758<h1 id="EMBEDDING">EMBEDDING</h1><p><a href="#TOP" class="toplink">Top</a></p>
… …
1638will have the <code>struct ev_loop *</code> as first argument, and you can create 1969will have the <code>struct ev_loop *</code> as first argument, and you can create
1639additional independent event loops. Otherwise there will be no support 1970additional independent event loops. Otherwise there will be no support
1640for multiple event loops and there is no first event loop pointer 1971for multiple event loops and there is no first event loop pointer
1641argument. Instead, all functions act on the single default loop.</p> 1972argument. Instead, all functions act on the single default loop.</p>
1642 </dd> 1973 </dd>
1643 <dt>EV_PERIODICS</dt> 1974 <dt>EV_PERIODIC_ENABLE</dt>
1644 <dd> 1975 <dd>
1645 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported, 1976 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
1646otherwise not. This saves a few kb of code.</p> 1977defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
1978code.</p>
1979 </dd>
1980 <dt>EV_EMBED_ENABLE</dt>
1981 <dd>
1982 <p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If
1983defined to be <code>0</code>, then they are not.</p>
1984 </dd>
1985 <dt>EV_STAT_ENABLE</dt>
1986 <dd>
1987 <p>If undefined or defined to be <code>1</code>, then stat watchers are supported. If
1988defined to be <code>0</code>, then they are not.</p>
1989 </dd>
1990 <dt>EV_FORK_ENABLE</dt>
1991 <dd>
1992 <p>If undefined or defined to be <code>1</code>, then fork watchers are supported. If
1993defined to be <code>0</code>, then they are not.</p>
1994 </dd>
1995 <dt>EV_MINIMAL</dt>
1996 <dd>
1997 <p>If you need to shave off some kilobytes of code at the expense of some
1998speed, define this symbol to <code>1</code>. Currently only used for gcc to override
1999some inlining decisions, saves roughly 30% codesize of amd64.</p>
2000 </dd>
2001 <dt>EV_PID_HASHSIZE</dt>
2002 <dd>
2003 <p><code>ev_child</code> watchers use a small hash table to distribute workload by
2004pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more
2005than enough. If you need to manage thousands of children you might want to
2006increase this value.</p>
1647 </dd> 2007 </dd>
1648 <dt>EV_COMMON</dt> 2008 <dt>EV_COMMON</dt>
1649 <dd> 2009 <dd>
1650 <p>By default, all watchers have a <code>void *data</code> member. By redefining 2010 <p>By default, all watchers have a <code>void *data</code> member. By redefining
1651this macro to a something else you can include more and other types of 2011this macro to a something else you can include more and other types of
… …
1656 SV *self; /* contains this struct */ \ 2016 SV *self; /* contains this struct */ \
1657 SV *cb_sv, *fh /* note no trailing &quot;;&quot; */ 2017 SV *cb_sv, *fh /* note no trailing &quot;;&quot; */
1658 2018
1659</pre> 2019</pre>
1660 </dd> 2020 </dd>
1661 <dt>EV_CB_DECLARE(type)</dt> 2021 <dt>EV_CB_DECLARE (type)</dt>
1662 <dt>EV_CB_INVOKE(watcher,revents)</dt> 2022 <dt>EV_CB_INVOKE (watcher, revents)</dt>
1663 <dt>ev_set_cb(ev,cb)</dt> 2023 <dt>ev_set_cb (ev, cb)</dt>
1664 <dd> 2024 <dd>
1665 <p>Can be used to change the callback member declaration in each watcher, 2025 <p>Can be used to change the callback member declaration in each watcher,
1666and the way callbacks are invoked and set. Must expand to a struct member 2026and the way callbacks are invoked and set. Must expand to a struct member
1667definition and a statement, respectively. See the <cite>ev.v</cite> header file for 2027definition and a statement, respectively. See the <cite>ev.v</cite> header file for
1668their default definitions. One possible use for overriding these is to 2028their default definitions. One possible use for overriding these is to
1669avoid the ev_loop pointer as first argument in all cases, or to use method 2029avoid the <code>struct ev_loop *</code> as first argument in all cases, or to use
1670calls instead of plain function calls in C++.</p> 2030method calls instead of plain function calls in C++.</p>
1671 2031
1672</div> 2032</div>
1673<h2 id="EXAMPLES">EXAMPLES</h2> 2033<h2 id="EXAMPLES">EXAMPLES</h2>
1674<div id="EXAMPLES_CONTENT"> 2034<div id="EXAMPLES_CONTENT">
1675 <p>For a real-world example of a program the includes libev 2035 <p>For a real-world example of a program the includes libev
… …
1691</pre> 2051</pre>
1692 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p> 2052 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
1693<pre> #include &quot;ev_cpp.h&quot; 2053<pre> #include &quot;ev_cpp.h&quot;
1694 #include &quot;ev.c&quot; 2054 #include &quot;ev.c&quot;
1695 2055
2056
2057
2058
1696</pre> 2059</pre>
2060
2061</div>
2062<h1 id="COMPLEXITIES">COMPLEXITIES</h1><p><a href="#TOP" class="toplink">Top</a></p>
2063<div id="COMPLEXITIES_CONTENT">
2064 <p>In this section the complexities of (many of) the algorithms used inside
2065libev will be explained. For complexity discussions about backends see the
2066documentation for <code>ev_default_init</code>.</p>
2067 <p>
2068 <dl>
2069 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
2070 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
2071 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
2072 <dt>Stopping check/prepare/idle watchers: O(1)</dt>
2073 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))</dt>
2074 <dt>Finding the next timer per loop iteration: O(1)</dt>
2075 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
2076 <dt>Activating one watcher: O(1)</dt>
2077 </dl>
2078 </p>
2079
2080
2081
2082
1697 2083
1698</div> 2084</div>
1699<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 2085<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>
1700<div id="AUTHOR_CONTENT"> 2086<div id="AUTHOR_CONTENT">
1701 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 2087 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>

Diff Legend

– Removed lines
+ Added lines
< Changed lines
> Changed lines