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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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13 | <div class="pod"> |
13 | <div class="pod"> |
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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323 | or setgid) then libev will <i>not</i> look at the environment variable |
325 | or setgid) then libev will <i>not</i> look at the environment variable |
324 | <code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will |
326 | <code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will |
325 | override the flags completely if it is found in the environment. This is |
327 | override the flags completely if it is found in the environment. This is |
326 | useful to try out specific backends to test their performance, or to work |
328 | useful to try out specific backends to test their performance, or to work |
327 | around bugs.</p> |
329 | around bugs.</p> |
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330 | </dd> |
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331 | <dt><code>EVFLAG_FORKCHECK</code></dt> |
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332 | <dd> |
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333 | <p>Instead of calling <code>ev_default_fork</code> or <code>ev_loop_fork</code> manually after |
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334 | a fork, you can also make libev check for a fork in each iteration by |
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335 | enabling this flag.</p> |
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336 | <p>This works by calling <code>getpid ()</code> on every iteration of the loop, |
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337 | and thus this might slow down your event loop if you do a lot of loop |
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338 | iterations and little real work, but is usually not noticable (on my |
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339 | Linux system for example, <code>getpid</code> is actually a simple 5-insn sequence |
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340 | without a syscall and thus <i>very</i> fast, but my Linux system also has |
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341 | <code>pthread_atfork</code> which is even faster).</p> |
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342 | <p>The big advantage of this flag is that you can forget about fork (and |
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343 | forget about forgetting to tell libev about forking) when you use this |
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344 | flag.</p> |
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345 | <p>This flag setting cannot be overriden or specified in the <code>LIBEV_FLAGS</code> |
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346 | environment variable.</p> |
328 | </dd> |
347 | </dd> |
329 | <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt> |
348 | <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt> |
330 | <dd> |
349 | <dd> |
331 | <p>This is your standard select(2) backend. Not <i>completely</i> standard, as |
350 | <p>This is your standard select(2) backend. Not <i>completely</i> standard, as |
332 | libev tries to roll its own fd_set with no limits on the number of fds, |
351 | libev tries to roll its own fd_set with no limits on the number of fds, |
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950 | </dd> |
969 | </dd> |
951 | <dt>ev_timer_again (loop)</dt> |
970 | <dt>ev_timer_again (loop)</dt> |
952 | <dd> |
971 | <dd> |
953 | <p>This will act as if the timer timed out and restart it again if it is |
972 | <p>This will act as if the timer timed out and restart it again if it is |
954 | repeating. The exact semantics are:</p> |
973 | repeating. The exact semantics are:</p> |
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974 | <p>If the timer is pending, its pending status is cleared.</p> |
955 | <p>If the timer is started but nonrepeating, stop it.</p> |
975 | <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 |
976 | <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> |
977 | <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 |
978 | <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 |
979 | 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, |
980 | 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 |
981 | 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 |
982 | 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 |
983 | <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 |
984 | 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 |
985 | socket, you can <code>ev_timer_stop</code> the timer, and <code>ev_timer_again</code> will |
966 | need be.</p> |
986 | 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 |
987 | <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> |
988 | 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.); |
989 | <pre> ev_timer_init (timer, callback, 0., 5.); |
970 | ev_timer_again (loop, timer); |
990 | ev_timer_again (loop, timer); |
971 | ... |
991 | ... |
972 | timer->again = 17.; |
992 | timer->again = 17.; |
973 | ev_timer_again (loop, timer); |
993 | ev_timer_again (loop, timer); |
974 | ... |
994 | ... |
975 | timer->again = 10.; |
995 | timer->again = 10.; |
976 | ev_timer_again (loop, timer); |
996 | ev_timer_again (loop, timer); |
977 | |
997 | |
978 | </pre> |
998 | </pre> |
979 | <p>This is more efficient then stopping/starting the timer eahc time you want |
999 | <p>This is more slightly efficient then stopping/starting the timer each time |
980 | to modify its timeout value.</p> |
1000 | you want to modify its timeout value.</p> |
981 | </dd> |
1001 | </dd> |
982 | <dt>ev_tstamp repeat [read-write]</dt> |
1002 | <dt>ev_tstamp repeat [read-write]</dt> |
983 | <dd> |
1003 | <dd> |
984 | <p>The current <code>repeat</code> value. Will be used each time the watcher times out |
1004 | <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), |
1005 | 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 |
1266 | <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 |
1267 | 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 |
1268 | 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 |
1269 | otherwise always forced to be at least one) and all the other fields of |
1250 | the stat buffer having unspecified contents.</p> |
1270 | the stat buffer having unspecified contents.</p> |
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1271 | <p>The path <i>should</i> be absolute and <i>must not</i> end in a slash. If it is |
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1272 | 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 |
1273 | <p>Since there is no standard to do this, the portable implementation simply |
1252 | calls <code>stat (2)</code> regulalry on the path to see if it changed somehow. You |
1274 | 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 |
1275 | 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, |
1276 | 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 |
1277 | unspecified default</i> value will be used (which you can expect to be around |
1256 | five seconds, although this might change dynamically). Libev will also |
1278 | five seconds, although this might change dynamically). Libev will also |
1257 | impose a minimum interval which is currently around <code>0.1</code>, but thats |
1279 | impose a minimum interval which is currently around <code>0.1</code>, but thats |
1258 | usually overkill.</p> |
1280 | usually overkill.</p> |
1259 | <p>This watcher type is not meant for massive numbers of stat watchers, |
1281 | <p>This watcher type is not meant for massive numbers of stat watchers, |
1260 | as even with OS-supported change notifications, this can be |
1282 | as even with OS-supported change notifications, this can be |
1261 | resource-intensive.</p> |
1283 | resource-intensive.</p> |
1262 | <p>At the time of this writing, no specific OS backends are implemented, but |
1284 | <p>At the time of this writing, only the Linux inotify interface is |
1263 | if demand increases, at least a kqueue and inotify backend will be added.</p> |
1285 | implemented (implementing kqueue support is left as an exercise for the |
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1286 | reader). Inotify will be used to give hints only and should not change the |
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1287 | semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs |
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1288 | to fall back to regular polling again even with inotify, but changes are |
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1289 | usually detected immediately, and if the file exists there will be no |
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1290 | polling.</p> |
1264 | <dl> |
1291 | <dl> |
1265 | <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt> |
1292 | <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt> |
1266 | <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt> |
1293 | <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt> |
1267 | <dd> |
1294 | <dd> |
1268 | <p>Configures the watcher to wait for status changes of the given |
1295 | <p>Configures the watcher to wait for status changes of the given |
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2015 | </dd> |
2042 | </dd> |
2016 | <dt>EV_USE_DEVPOLL</dt> |
2043 | <dt>EV_USE_DEVPOLL</dt> |
2017 | <dd> |
2044 | <dd> |
2018 | <p>reserved for future expansion, works like the USE symbols above.</p> |
2045 | <p>reserved for future expansion, works like the USE symbols above.</p> |
2019 | </dd> |
2046 | </dd> |
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2047 | <dt>EV_USE_INOTIFY</dt> |
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2048 | <dd> |
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2049 | <p>If defined to be <code>1</code>, libev will compile in support for the Linux inotify |
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2050 | interface to speed up <code>ev_stat</code> watchers. Its actual availability will |
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2051 | be detected at runtime.</p> |
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2052 | </dd> |
2020 | <dt>EV_H</dt> |
2053 | <dt>EV_H</dt> |
2021 | <dd> |
2054 | <dd> |
2022 | <p>The name of the <cite>ev.h</cite> header file used to include it. The default if |
2055 | <p>The name of the <cite>ev.h</cite> header file used to include it. The default if |
2023 | undefined is <code><ev.h></code> in <cite>event.h</cite> and <code>"ev.h"</code> in <cite>ev.c</cite>. This |
2056 | undefined is <code><ev.h></code> in <cite>event.h</cite> and <code>"ev.h"</code> in <cite>ev.c</cite>. This |
2024 | can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p> |
2057 | can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p> |
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2079 | <dt>EV_PID_HASHSIZE</dt> |
2112 | <dt>EV_PID_HASHSIZE</dt> |
2080 | <dd> |
2113 | <dd> |
2081 | <p><code>ev_child</code> watchers use a small hash table to distribute workload by |
2114 | <p><code>ev_child</code> watchers use a small hash table to distribute workload by |
2082 | pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more |
2115 | pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more |
2083 | than enough. If you need to manage thousands of children you might want to |
2116 | than enough. If you need to manage thousands of children you might want to |
2084 | increase this value.</p> |
2117 | increase this value (<i>must</i> be a power of two).</p> |
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2118 | </dd> |
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2119 | <dt>EV_INOTIFY_HASHSIZE</dt> |
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2120 | <dd> |
|
|
2121 | <p><code>ev_staz</code> watchers use a small hash table to distribute workload by |
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2122 | inotify watch id. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), |
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2123 | usually more than enough. If you need to manage thousands of <code>ev_stat</code> |
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2124 | watchers you might want to increase this value (<i>must</i> be a power of |
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2125 | two).</p> |
2085 | </dd> |
2126 | </dd> |
2086 | <dt>EV_COMMON</dt> |
2127 | <dt>EV_COMMON</dt> |
2087 | <dd> |
2128 | <dd> |
2088 | <p>By default, all watchers have a <code>void *data</code> member. By redefining |
2129 | <p>By default, all watchers have a <code>void *data</code> member. By redefining |
2089 | this macro to a something else you can include more and other types of |
2130 | this macro to a something else you can include more and other types of |
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2146 | <dl> |
2187 | <dl> |
2147 | <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> |
2188 | <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> |
2148 | <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt> |
2189 | <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt> |
2149 | <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> |
2190 | <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> |
2150 | <dt>Stopping check/prepare/idle watchers: O(1)</dt> |
2191 | <dt>Stopping check/prepare/idle watchers: O(1)</dt> |
2151 | <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))</dt> |
2192 | <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt> |
2152 | <dt>Finding the next timer per loop iteration: O(1)</dt> |
2193 | <dt>Finding the next timer per loop iteration: O(1)</dt> |
2153 | <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt> |
2194 | <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt> |
2154 | <dt>Activating one watcher: O(1)</dt> |
2195 | <dt>Activating one watcher: O(1)</dt> |
2155 | </dl> |
2196 | </dl> |
2156 | </p> |
2197 | </p> |