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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" /> |
7 | <meta name="inputfile" content="<standard input>" /> |
7 | <meta name="inputfile" content="<standard input>" /> |
8 | <meta name="outputfile" content="<standard output>" /> |
8 | <meta name="outputfile" content="<standard output>" /> |
9 | <meta name="created" content="Mon Nov 12 08:58:02 2007" /> |
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13 | <div class="pod"> |
13 | <div class="pod"> |
14 | <!-- INDEX START --> |
14 | <!-- INDEX START --> |
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26 | </ul> |
26 | </ul> |
27 | </li> |
27 | </li> |
28 | <li><a href="#WATCHER_TYPES">WATCHER TYPES</a> |
28 | <li><a href="#WATCHER_TYPES">WATCHER TYPES</a> |
29 | <ul><li><a href="#struct_ev_io_is_my_file_descriptor_r">struct ev_io - is my file descriptor readable or writable</a></li> |
29 | <ul><li><a href="#struct_ev_io_is_my_file_descriptor_r">struct ev_io - is my file descriptor readable or writable</a></li> |
30 | <li><a href="#struct_ev_timer_relative_and_optiona">struct ev_timer - relative and optionally recurring timeouts</a></li> |
30 | <li><a href="#struct_ev_timer_relative_and_optiona">struct ev_timer - relative and optionally recurring timeouts</a></li> |
31 | <li><a href="#ev_periodic">ev_periodic</a></li> |
31 | <li><a href="#ev_periodic_to_cron_or_not_to_cron_i">ev_periodic - to cron or not to cron it</a></li> |
32 | <li><a href="#ev_signal_signal_me_when_a_signal_ge">ev_signal - signal me when a signal gets signalled</a></li> |
32 | <li><a href="#ev_signal_signal_me_when_a_signal_ge">ev_signal - signal me when a signal gets signalled</a></li> |
33 | <li><a href="#ev_child_wait_for_pid_status_changes">ev_child - wait for pid status changes</a></li> |
33 | <li><a href="#ev_child_wait_for_pid_status_changes">ev_child - wait for pid status changes</a></li> |
34 | <li><a href="#ev_idle_when_you_ve_got_nothing_bett">ev_idle - when you've got nothing better to do</a></li> |
34 | <li><a href="#ev_idle_when_you_ve_got_nothing_bett">ev_idle - when you've got nothing better to do</a></li> |
35 | <li><a href="#prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</a></li> |
35 | <li><a href="#prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</a></li> |
36 | </ul> |
36 | </ul> |
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55 | </div> |
55 | </div> |
56 | <h1 id="DESCRIPTION">DESCRIPTION</h1><p><a href="#TOP" class="toplink">Top</a></p> |
56 | <h1 id="DESCRIPTION">DESCRIPTION</h1><p><a href="#TOP" class="toplink">Top</a></p> |
57 | <div id="DESCRIPTION_CONTENT"> |
57 | <div id="DESCRIPTION_CONTENT"> |
58 | <p>Libev is an event loop: you register interest in certain events (such as a |
58 | <p>Libev is an event loop: you register interest in certain events (such as a |
59 | file descriptor being readable or a timeout occuring), and it will manage |
59 | file descriptor being readable or a timeout occuring), and it will manage |
60 | these event sources and provide your program events.</p> |
60 | these event sources and provide your program with events.</p> |
61 | <p>To do this, it must take more or less complete control over your process |
61 | <p>To do this, it must take more or less complete control over your process |
62 | (or thread) by executing the <i>event loop</i> handler, and will then |
62 | (or thread) by executing the <i>event loop</i> handler, and will then |
63 | communicate events via a callback mechanism.</p> |
63 | communicate events via a callback mechanism.</p> |
64 | <p>You register interest in certain events by registering so-called <i>event |
64 | <p>You register interest in certain events by registering so-called <i>event |
65 | watchers</i>, which are relatively small C structures you initialise with the |
65 | watchers</i>, which are relatively small C structures you initialise with the |
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71 | <div id="FEATURES_CONTENT"> |
71 | <div id="FEATURES_CONTENT"> |
72 | <p>Libev supports select, poll, the linux-specific epoll and the bsd-specific |
72 | <p>Libev supports select, poll, the linux-specific epoll and the bsd-specific |
73 | kqueue mechanisms for file descriptor events, relative timers, absolute |
73 | kqueue mechanisms for file descriptor events, relative timers, absolute |
74 | timers with customised rescheduling, signal events, process status change |
74 | timers with customised rescheduling, signal events, process status change |
75 | events (related to SIGCHLD), and event watchers dealing with the event |
75 | events (related to SIGCHLD), and event watchers dealing with the event |
76 | loop mechanism itself (idle, prepare and check watchers).</p> |
76 | loop mechanism itself (idle, prepare and check watchers). It also is quite |
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77 | fast (see this <a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing |
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78 | it to libevent for example).</p> |
77 | |
79 | |
78 | </div> |
80 | </div> |
79 | <h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> |
81 | <h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> |
80 | <div id="CONVENTIONS_CONTENT"> |
82 | <div id="CONVENTIONS_CONTENT"> |
81 | <p>Libev is very configurable. In this manual the default configuration |
83 | <p>Libev is very configurable. In this manual the default configuration |
82 | will be described, which supports multiple event loops. For more info |
84 | will be described, which supports multiple event loops. For more info |
83 | about various configuraiton options please have a look at the file |
85 | about various configuration options please have a look at the file |
84 | <cite>README.embed</cite> in the libev distribution. If libev was configured without |
86 | <cite>README.embed</cite> in the libev distribution. If libev was configured without |
85 | support for multiple event loops, then all functions taking an initial |
87 | support for multiple event loops, then all functions taking an initial |
86 | argument of name <code>loop</code> (which is always of type <code>struct ev_loop *</code>) |
88 | argument of name <code>loop</code> (which is always of type <code>struct ev_loop *</code>) |
87 | will not have this argument.</p> |
89 | will not have this argument.</p> |
88 | |
90 | |
89 | </div> |
91 | </div> |
90 | <h1 id="TIME_AND_OTHER_GLOBAL_FUNCTIONS">TIME AND OTHER GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> |
92 | <h1 id="TIME_AND_OTHER_GLOBAL_FUNCTIONS">TIME AND OTHER GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> |
91 | <div id="TIME_AND_OTHER_GLOBAL_FUNCTIONS_CONT"> |
93 | <div id="TIME_AND_OTHER_GLOBAL_FUNCTIONS_CONT"> |
92 | <p>Libev represents time as a single floating point number. This type is |
94 | <p>Libev represents time as a single floating point number, representing the |
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95 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
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96 | the beginning of 1970, details are complicated, don't ask). This type is |
93 | called <code>ev_tstamp</code>, which is what you should use too. It usually aliases |
97 | called <code>ev_tstamp</code>, which is what you should use too. It usually aliases |
94 | to the double type in C.</p> |
98 | to the double type in C.</p> |
95 | <dl> |
99 | <dl> |
96 | <dt>ev_tstamp ev_time ()</dt> |
100 | <dt>ev_tstamp ev_time ()</dt> |
97 | <dd> |
101 | <dd> |
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111 | not a problem.</p> |
115 | not a problem.</p> |
112 | </dd> |
116 | </dd> |
113 | <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> |
117 | <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> |
114 | <dd> |
118 | <dd> |
115 | <p>Sets the allocation function to use (the prototype is similar to the |
119 | <p>Sets the allocation function to use (the prototype is similar to the |
116 | realloc function). It is used to allocate and free memory (no surprises |
120 | realloc C function, the semantics are identical). It is used to allocate |
117 | here). If it returns zero when memory needs to be allocated, the library |
121 | and free memory (no surprises here). If it returns zero when memory |
118 | might abort or take some potentially destructive action. The default is |
122 | needs to be allocated, the library might abort or take some potentially |
119 | your system realloc function.</p> |
123 | destructive action. The default is your system realloc function.</p> |
120 | <p>You could override this function in high-availability programs to, say, |
124 | <p>You could override this function in high-availability programs to, say, |
121 | free some memory if it cannot allocate memory, to use a special allocator, |
125 | free some memory if it cannot allocate memory, to use a special allocator, |
122 | or even to sleep a while and retry until some memory is available.</p> |
126 | or even to sleep a while and retry until some memory is available.</p> |
123 | </dd> |
127 | </dd> |
124 | <dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt> |
128 | <dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt> |
125 | <dd> |
129 | <dd> |
126 | <p>Set the callback function to call on a retryable syscall error (such |
130 | <p>Set the callback function to call on a retryable syscall error (such |
127 | as failed select, poll, epoll_wait). The message is a printable string |
131 | as failed select, poll, epoll_wait). The message is a printable string |
128 | indicating the system call or subsystem causing the problem. If this |
132 | indicating the system call or subsystem causing the problem. If this |
129 | callback is set, then libev will expect it to remedy the sitution, no |
133 | callback is set, then libev will expect it to remedy the sitution, no |
130 | matter what, when it returns. That is, libev will geenrally retry the |
134 | matter what, when it returns. That is, libev will generally retry the |
131 | requested operation, or, if the condition doesn't go away, do bad stuff |
135 | requested operation, or, if the condition doesn't go away, do bad stuff |
132 | (such as abort).</p> |
136 | (such as abort).</p> |
133 | </dd> |
137 | </dd> |
134 | </dl> |
138 | </dl> |
135 | |
139 | |
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139 | <p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two |
143 | <p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two |
140 | types of such loops, the <i>default</i> loop, which supports signals and child |
144 | types of such loops, the <i>default</i> loop, which supports signals and child |
141 | events, and dynamically created loops which do not.</p> |
145 | events, and dynamically created loops which do not.</p> |
142 | <p>If you use threads, a common model is to run the default event loop |
146 | <p>If you use threads, a common model is to run the default event loop |
143 | in your main thread (or in a separate thrad) and for each thread you |
147 | in your main thread (or in a separate thrad) and for each thread you |
144 | create, you also create another event loop. Libev itself does no lockign |
148 | create, you also create another event loop. Libev itself does no locking |
145 | whatsoever, so if you mix calls to different event loops, make sure you |
149 | whatsoever, so if you mix calls to the same event loop in different |
146 | lock (this is usually a bad idea, though, even if done right).</p> |
150 | threads, make sure you lock (this is usually a bad idea, though, even if |
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151 | done correctly, because its hideous and inefficient).</p> |
147 | <dl> |
152 | <dl> |
148 | <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt> |
153 | <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt> |
149 | <dd> |
154 | <dd> |
150 | <p>This will initialise the default event loop if it hasn't been initialised |
155 | <p>This will initialise the default event loop if it hasn't been initialised |
151 | yet and return it. If the default loop could not be initialised, returns |
156 | yet and return it. If the default loop could not be initialised, returns |
152 | false. If it already was initialised it simply returns it (and ignores the |
157 | false. If it already was initialised it simply returns it (and ignores the |
153 | flags).</p> |
158 | flags).</p> |
154 | <p>If you don't know what event loop to use, use the one returned from this |
159 | <p>If you don't know what event loop to use, use the one returned from this |
155 | function.</p> |
160 | function.</p> |
156 | <p>The flags argument can be used to specify special behaviour or specific |
161 | <p>The flags argument can be used to specify special behaviour or specific |
157 | backends to use, and is usually specified as 0 (or EVFLAG_AUTO)</p> |
162 | backends to use, and is usually specified as 0 (or EVFLAG_AUTO).</p> |
158 | <p>It supports the following flags:</p> |
163 | <p>It supports the following flags:</p> |
159 | <p> |
164 | <p> |
160 | <dl> |
165 | <dl> |
161 | <dt>EVFLAG_AUTO</dt> |
166 | <dt>EVFLAG_AUTO</dt> |
162 | <dd> |
167 | <dd> |
163 | <p>The default flags value. Use this if you have no clue (its the right |
168 | <p>The default flags value. Use this if you have no clue (its the right |
164 | thing, believe me).</p> |
169 | thing, believe me).</p> |
165 | </dd> |
170 | </dd> |
166 | <dt>EVFLAG_NOENV</dt> |
171 | <dt>EVFLAG_NOENV</dt> |
167 | <dd> |
172 | <dd> |
168 | <p>If this flag bit is ored into the flag value then libev will <i>not</i> look |
173 | <p>If this flag bit is ored into the flag value (or the program runs setuid |
169 | at the environment variable <code>LIBEV_FLAGS</code>. Otherwise (the default), this |
174 | or setgid) then libev will <i>not</i> look at the environment variable |
170 | environment variable will override the flags completely. This is useful |
175 | <code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will |
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176 | override the flags completely if it is found in the environment. This is |
171 | to try out specific backends to tets their performance, or to work around |
177 | useful to try out specific backends to test their performance, or to work |
172 | bugs.</p> |
178 | around bugs.</p> |
173 | </dd> |
179 | </dd> |
174 | <dt>EVMETHOD_SELECT portable select backend</dt> |
180 | <dt>EVMETHOD_SELECT portable select backend</dt> |
175 | <dt>EVMETHOD_POLL poll backend (everywhere except windows)</dt> |
181 | <dt>EVMETHOD_POLL poll backend (everywhere except windows)</dt> |
176 | <dt>EVMETHOD_EPOLL linux only</dt> |
182 | <dt>EVMETHOD_EPOLL linux only</dt> |
177 | <dt>EVMETHOD_KQUEUE some bsds only</dt> |
183 | <dt>EVMETHOD_KQUEUE some bsds only</dt> |
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314 | *)</code>), and you can stop watching for events at any time by calling the |
320 | *)</code>), and you can stop watching for events at any time by calling the |
315 | corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p> |
321 | corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p> |
316 | <p>As long as your watcher is active (has been started but not stopped) you |
322 | <p>As long as your watcher is active (has been started but not stopped) you |
317 | must not touch the values stored in it. Most specifically you must never |
323 | must not touch the values stored in it. Most specifically you must never |
318 | reinitialise it or call its set method.</p> |
324 | reinitialise it or call its set method.</p> |
319 | <p>You cna check wether an event is active by calling the <code>ev_is_active |
325 | <p>You cna check whether an event is active by calling the <code>ev_is_active |
320 | (watcher *)</code> macro. To see wether an event is outstanding (but the |
326 | (watcher *)</code> macro. To see whether an event is outstanding (but the |
321 | callback for it has not been called yet) you cna use the <code>ev_is_pending |
327 | callback for it has not been called yet) you cna use the <code>ev_is_pending |
322 | (watcher *)</code> macro.</p> |
328 | (watcher *)</code> macro.</p> |
323 | <p>Each and every callback receives the event loop pointer as first, the |
329 | <p>Each and every callback receives the event loop pointer as first, the |
324 | registered watcher structure as second, and a bitset of received events as |
330 | registered watcher structure as second, and a bitset of received events as |
325 | third argument.</p> |
331 | third argument.</p> |
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420 | information given in the last section.</p> |
426 | information given in the last section.</p> |
421 | |
427 | |
422 | </div> |
428 | </div> |
423 | <h2 id="struct_ev_io_is_my_file_descriptor_r">struct ev_io - is my file descriptor readable or writable</h2> |
429 | <h2 id="struct_ev_io_is_my_file_descriptor_r">struct ev_io - is my file descriptor readable or writable</h2> |
424 | <div id="struct_ev_io_is_my_file_descriptor_r-2"> |
430 | <div id="struct_ev_io_is_my_file_descriptor_r-2"> |
425 | <p>I/O watchers check wether a file descriptor is readable or writable |
431 | <p>I/O watchers check whether a file descriptor is readable or writable |
426 | in each iteration of the event loop (This behaviour is called |
432 | in each iteration of the event loop (This behaviour is called |
427 | level-triggering because you keep receiving events as long as the |
433 | level-triggering because you keep receiving events as long as the |
428 | condition persists. Remember you cna stop the watcher if you don't want to |
434 | condition persists. Remember you cna stop the watcher if you don't want to |
429 | act on the event and neither want to receive future events).</p> |
435 | act on the event and neither want to receive future events).</p> |
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436 | <p>In general you can register as many read and/or write event watchers oer |
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437 | fd as you want (as long as you don't confuse yourself). Setting all file |
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438 | descriptors to non-blocking mode is also usually a good idea (but not |
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439 | required if you know what you are doing).</p> |
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440 | <p>You have to be careful with dup'ed file descriptors, though. Some backends |
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441 | (the linux epoll backend is a notable example) cannot handle dup'ed file |
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442 | descriptors correctly if you register interest in two or more fds pointing |
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443 | to the same file/socket etc. description.</p> |
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444 | <p>If you must do this, then force the use of a known-to-be-good backend |
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445 | (at the time of this writing, this includes only EVMETHOD_SELECT and |
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446 | EVMETHOD_POLL).</p> |
430 | <dl> |
447 | <dl> |
431 | <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> |
448 | <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> |
432 | <dt>ev_io_set (ev_io *, int fd, int events)</dt> |
449 | <dt>ev_io_set (ev_io *, int fd, int events)</dt> |
433 | <dd> |
450 | <dd> |
434 | <p>Configures an ev_io watcher. The fd is the file descriptor to rceeive |
451 | <p>Configures an ev_io watcher. The fd is the file descriptor to rceeive |
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478 | the timer, and again will automatically restart it if need be.</p> |
495 | the timer, and again will automatically restart it if need be.</p> |
479 | </dd> |
496 | </dd> |
480 | </dl> |
497 | </dl> |
481 | |
498 | |
482 | </div> |
499 | </div> |
483 | <h2 id="ev_periodic">ev_periodic</h2> |
500 | <h2 id="ev_periodic_to_cron_or_not_to_cron_i">ev_periodic - to cron or not to cron it</h2> |
484 | <div id="ev_periodic_CONTENT"> |
501 | <div id="ev_periodic_to_cron_or_not_to_cron_i-2"> |
485 | <p>Periodic watchers are also timers of a kind, but they are very versatile |
502 | <p>Periodic watchers are also timers of a kind, but they are very versatile |
486 | (and unfortunately a bit complex).</p> |
503 | (and unfortunately a bit complex).</p> |
487 | <p>Unlike ev_timer's, they are not based on real time (or relative time) |
504 | <p>Unlike ev_timer's, they are not based on real time (or relative time) |
488 | but on wallclock time (absolute time). You can tell a periodic watcher |
505 | but on wallclock time (absolute time). You can tell a periodic watcher |
489 | to trigger "at" some specific point in time. For example, if you tell a |
506 | to trigger "at" some specific point in time. For example, if you tell a |