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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="Wed Nov 28 12:27:27 2007" /> |
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14 | <!-- INDEX START --> |
14 | <!-- INDEX START --> |
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133 | watcher.</p> |
133 | watcher.</p> |
134 | |
134 | |
135 | </div> |
135 | </div> |
136 | <h1 id="FEATURES">FEATURES</h1> |
136 | <h1 id="FEATURES">FEATURES</h1> |
137 | <div id="FEATURES_CONTENT"> |
137 | <div id="FEATURES_CONTENT"> |
138 | <p>Libev supports <code>select</code>, <code>poll</code>, the linux-specific <code>epoll</code>, the |
138 | <p>Libev supports <code>select</code>, <code>poll</code>, the Linux-specific <code>epoll</code>, the |
139 | bsd-specific <code>kqueue</code> and the solaris-specific event port mechanisms |
139 | BSD-specific <code>kqueue</code> and the Solaris-specific event port mechanisms |
140 | for file descriptor events (<code>ev_io</code>), relative timers (<code>ev_timer</code>), |
140 | for file descriptor events (<code>ev_io</code>), the Linux <code>inotify</code> interface |
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141 | (for <code>ev_stat</code>), relative timers (<code>ev_timer</code>), absolute timers |
141 | absolute timers with customised rescheduling (<code>ev_periodic</code>), synchronous |
142 | with customised rescheduling (<code>ev_periodic</code>), synchronous signals |
142 | signals (<code>ev_signal</code>), process status change events (<code>ev_child</code>), and |
143 | (<code>ev_signal</code>), process status change events (<code>ev_child</code>), and event |
143 | event watchers dealing with the event loop mechanism itself (<code>ev_idle</code>, |
144 | watchers dealing with the event loop mechanism itself (<code>ev_idle</code>, |
144 | <code>ev_embed</code>, <code>ev_prepare</code> and <code>ev_check</code> watchers) as well as |
145 | <code>ev_embed</code>, <code>ev_prepare</code> and <code>ev_check</code> watchers) as well as |
145 | file watchers (<code>ev_stat</code>) and even limited support for fork events |
146 | file watchers (<code>ev_stat</code>) and even limited support for fork events |
146 | (<code>ev_fork</code>).</p> |
147 | (<code>ev_fork</code>).</p> |
147 | <p>It also is quite fast (see this |
148 | <p>It also is quite fast (see this |
148 | <a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it to libevent |
149 | <a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it to libevent |
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229 | might be supported on the current system, you would need to look at |
230 | might be supported on the current system, you would need to look at |
230 | <code>ev_embeddable_backends () & ev_supported_backends ()</code>, likewise for |
231 | <code>ev_embeddable_backends () & ev_supported_backends ()</code>, likewise for |
231 | recommended ones.</p> |
232 | recommended ones.</p> |
232 | <p>See the description of <code>ev_embed</code> watchers for more info.</p> |
233 | <p>See the description of <code>ev_embed</code> watchers for more info.</p> |
233 | </dd> |
234 | </dd> |
234 | <dt>ev_set_allocator (void *(*cb)(void *ptr, size_t size))</dt> |
235 | <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> |
235 | <dd> |
236 | <dd> |
236 | <p>Sets the allocation function to use (the prototype and semantics are |
237 | <p>Sets the allocation function to use (the prototype is similar - the |
237 | identical to the realloc C function). It is used to allocate and free |
238 | semantics is identical - to the realloc C function). It is used to |
238 | memory (no surprises here). If it returns zero when memory needs to be |
239 | allocate and free memory (no surprises here). If it returns zero when |
239 | allocated, the library might abort or take some potentially destructive |
240 | memory needs to be allocated, the library might abort or take some |
240 | action. The default is your system realloc function.</p> |
241 | potentially destructive action. The default is your system realloc |
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242 | function.</p> |
241 | <p>You could override this function in high-availability programs to, say, |
243 | <p>You could override this function in high-availability programs to, say, |
242 | free some memory if it cannot allocate memory, to use a special allocator, |
244 | free some memory if it cannot allocate memory, to use a special allocator, |
243 | or even to sleep a while and retry until some memory is available.</p> |
245 | or even to sleep a while and retry until some memory is available.</p> |
244 | <p>Example: Replace the libev allocator with one that waits a bit and then |
246 | <p>Example: Replace the libev allocator with one that waits a bit and then |
245 | retries).</p> |
247 | retries).</p> |
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950 | </dd> |
952 | </dd> |
951 | <dt>ev_timer_again (loop)</dt> |
953 | <dt>ev_timer_again (loop)</dt> |
952 | <dd> |
954 | <dd> |
953 | <p>This will act as if the timer timed out and restart it again if it is |
955 | <p>This will act as if the timer timed out and restart it again if it is |
954 | repeating. The exact semantics are:</p> |
956 | repeating. The exact semantics are:</p> |
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957 | <p>If the timer is pending, its pending status is cleared.</p> |
955 | <p>If the timer is started but nonrepeating, stop it.</p> |
958 | <p>If the timer is started but nonrepeating, stop it (as if it timed out).</p> |
956 | <p>If the timer is repeating, either start it if necessary (with the repeat |
959 | <p>If the timer is repeating, either start it if necessary (with the |
957 | value), or reset the running timer to the repeat value.</p> |
960 | <code>repeat</code> value), or reset the running timer to the <code>repeat</code> value.</p> |
958 | <p>This sounds a bit complicated, but here is a useful and typical |
961 | <p>This sounds a bit complicated, but here is a useful and typical |
959 | example: Imagine you have a tcp connection and you want a so-called |
962 | example: Imagine you have a tcp connection and you want a so-called idle |
960 | idle timeout, that is, you want to be called when there have been, |
963 | timeout, that is, you want to be called when there have been, say, 60 |
961 | say, 60 seconds of inactivity on the socket. The easiest way to do |
964 | seconds of inactivity on the socket. The easiest way to do this is to |
962 | this is to configure an <code>ev_timer</code> with <code>after</code>=<code>repeat</code>=<code>60</code> and calling |
965 | configure an <code>ev_timer</code> with a <code>repeat</code> value of <code>60</code> and then call |
963 | <code>ev_timer_again</code> each time you successfully read or write some data. If |
966 | <code>ev_timer_again</code> each time you successfully read or write some data. If |
964 | you go into an idle state where you do not expect data to travel on the |
967 | you go into an idle state where you do not expect data to travel on the |
965 | socket, you can stop the timer, and again will automatically restart it if |
968 | socket, you can <code>ev_timer_stop</code> the timer, and <code>ev_timer_again</code> will |
966 | need be.</p> |
969 | automatically restart it if need be.</p> |
967 | <p>You can also ignore the <code>after</code> value and <code>ev_timer_start</code> altogether |
970 | <p>That means you can ignore the <code>after</code> value and <code>ev_timer_start</code> |
968 | and only ever use the <code>repeat</code> value:</p> |
971 | altogether and only ever use the <code>repeat</code> value and <code>ev_timer_again</code>:</p> |
969 | <pre> ev_timer_init (timer, callback, 0., 5.); |
972 | <pre> ev_timer_init (timer, callback, 0., 5.); |
970 | ev_timer_again (loop, timer); |
973 | ev_timer_again (loop, timer); |
971 | ... |
974 | ... |
972 | timer->again = 17.; |
975 | timer->again = 17.; |
973 | ev_timer_again (loop, timer); |
976 | ev_timer_again (loop, timer); |
974 | ... |
977 | ... |
975 | timer->again = 10.; |
978 | timer->again = 10.; |
976 | ev_timer_again (loop, timer); |
979 | ev_timer_again (loop, timer); |
977 | |
980 | |
978 | </pre> |
981 | </pre> |
979 | <p>This is more efficient then stopping/starting the timer eahc time you want |
982 | <p>This is more slightly efficient then stopping/starting the timer each time |
980 | to modify its timeout value.</p> |
983 | you want to modify its timeout value.</p> |
981 | </dd> |
984 | </dd> |
982 | <dt>ev_tstamp repeat [read-write]</dt> |
985 | <dt>ev_tstamp repeat [read-write]</dt> |
983 | <dd> |
986 | <dd> |
984 | <p>The current <code>repeat</code> value. Will be used each time the watcher times out |
987 | <p>The current <code>repeat</code> value. Will be used each time the watcher times out |
985 | or <code>ev_timer_again</code> is called and determines the next timeout (if any), |
988 | or <code>ev_timer_again</code> is called and determines the next timeout (if any), |
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1246 | <p>The path does not need to exist: changing from "path exists" to "path does |
1249 | <p>The path does not need to exist: changing from "path exists" to "path does |
1247 | not exist" is a status change like any other. The condition "path does |
1250 | not exist" is a status change like any other. The condition "path does |
1248 | not exist" is signified by the <code>st_nlink</code> field being zero (which is |
1251 | not exist" is signified by the <code>st_nlink</code> field being zero (which is |
1249 | otherwise always forced to be at least one) and all the other fields of |
1252 | otherwise always forced to be at least one) and all the other fields of |
1250 | the stat buffer having unspecified contents.</p> |
1253 | the stat buffer having unspecified contents.</p> |
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1254 | <p>The path <i>should</i> be absolute and <i>must not</i> end in a slash. If it is |
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1255 | relative and your working directory changes, the behaviour is undefined.</p> |
1251 | <p>Since there is no standard to do this, the portable implementation simply |
1256 | <p>Since there is no standard to do this, the portable implementation simply |
1252 | calls <code>stat (2)</code> regularly on the path to see if it changed somehow. You |
1257 | calls <code>stat (2)</code> regularly on the path to see if it changed somehow. You |
1253 | can specify a recommended polling interval for this case. If you specify |
1258 | can specify a recommended polling interval for this case. If you specify |
1254 | a polling interval of <code>0</code> (highly recommended!) then a <i>suitable, |
1259 | a polling interval of <code>0</code> (highly recommended!) then a <i>suitable, |
1255 | unspecified default</i> value will be used (which you can expect to be around |
1260 | unspecified default</i> value will be used (which you can expect to be around |