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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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14 | <!-- INDEX START --> |
14 | <!-- INDEX START --> |
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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 | |
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113 | not a problem.</p> |
115 | not a problem.</p> |
114 | </dd> |
116 | </dd> |
115 | <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> |
117 | <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> |
116 | <dd> |
118 | <dd> |
117 | <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 |
118 | 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 |
119 | 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 |
120 | might abort or take some potentially destructive action. The default is |
122 | needs to be allocated, the library might abort or take some potentially |
121 | your system realloc function.</p> |
123 | destructive action. The default is your system realloc function.</p> |
122 | <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, |
123 | 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, |
124 | 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> |
125 | </dd> |
127 | </dd> |
126 | <dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt> |
128 | <dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt> |
127 | <dd> |
129 | <dd> |
128 | <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 |
129 | 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 |
130 | indicating the system call or subsystem causing the problem. If this |
132 | indicating the system call or subsystem causing the problem. If this |
131 | 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 |
132 | 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 |
133 | 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 |
134 | (such as abort).</p> |
136 | (such as abort).</p> |
135 | </dd> |
137 | </dd> |
136 | </dl> |
138 | </dl> |
137 | |
139 | |
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141 | <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 |
142 | 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 |
143 | events, and dynamically created loops which do not.</p> |
145 | events, and dynamically created loops which do not.</p> |
144 | <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 |
145 | 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 |
146 | 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 |
147 | 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 |
148 | 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> |
149 | <dl> |
152 | <dl> |
150 | <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt> |
153 | <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt> |
151 | <dd> |
154 | <dd> |
152 | <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 |
153 | 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 |
154 | 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 |
155 | flags).</p> |
158 | flags).</p> |
156 | <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 |
157 | function.</p> |
160 | function.</p> |
158 | <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 |
159 | 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> |
160 | <p>It supports the following flags:</p> |
163 | <p>It supports the following flags:</p> |
161 | <p> |
164 | <p> |
162 | <dl> |
165 | <dl> |
163 | <dt>EVFLAG_AUTO</dt> |
166 | <dt>EVFLAG_AUTO</dt> |
164 | <dd> |
167 | <dd> |
165 | <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 |
166 | thing, believe me).</p> |
169 | thing, believe me).</p> |
167 | </dd> |
170 | </dd> |
168 | <dt>EVFLAG_NOENV</dt> |
171 | <dt>EVFLAG_NOENV</dt> |
169 | <dd> |
172 | <dd> |
170 | <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 |
171 | 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 |
172 | 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 |
173 | 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 |
174 | bugs.</p> |
178 | around bugs.</p> |
175 | </dd> |
179 | </dd> |
176 | <dt>EVMETHOD_SELECT portable select backend</dt> |
180 | <dt>EVMETHOD_SELECT portable select backend</dt> |
177 | <dt>EVMETHOD_POLL poll backend (everywhere except windows)</dt> |
181 | <dt>EVMETHOD_POLL poll backend (everywhere except windows)</dt> |
178 | <dt>EVMETHOD_EPOLL linux only</dt> |
182 | <dt>EVMETHOD_EPOLL linux only</dt> |
179 | <dt>EVMETHOD_KQUEUE some bsds only</dt> |
183 | <dt>EVMETHOD_KQUEUE some bsds only</dt> |
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427 | <p>I/O watchers check whether a file descriptor is readable or writable |
431 | <p>I/O watchers check whether a file descriptor is readable or writable |
428 | in each iteration of the event loop (This behaviour is called |
432 | in each iteration of the event loop (This behaviour is called |
429 | level-triggering because you keep receiving events as long as the |
433 | level-triggering because you keep receiving events as long as the |
430 | 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 |
431 | 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> |
432 | <dl> |
447 | <dl> |
433 | <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> |
434 | <dt>ev_io_set (ev_io *, int fd, int events)</dt> |
449 | <dt>ev_io_set (ev_io *, int fd, int events)</dt> |
435 | <dd> |
450 | <dd> |
436 | <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 |