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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="Tue Nov 27 21:29:04 2007" /> |
9 | <meta name="created" content="Thu Nov 29 13:21:20 2007" /> |
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12 | <body> |
12 | <body> |
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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741 | events but its callback has not yet been invoked). As long as a watcher |
743 | events but its callback has not yet been invoked). As long as a watcher |
742 | is pending (but not active) you must not call an init function on it (but |
744 | is pending (but not active) you must not call an init function on it (but |
743 | <code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to |
745 | <code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to |
744 | libev (e.g. you cnanot <code>free ()</code> it).</p> |
746 | libev (e.g. you cnanot <code>free ()</code> it).</p> |
745 | </dd> |
747 | </dd> |
746 | <dt>callback = ev_cb (ev_TYPE *watcher)</dt> |
748 | <dt>callback ev_cb (ev_TYPE *watcher)</dt> |
747 | <dd> |
749 | <dd> |
748 | <p>Returns the callback currently set on the watcher.</p> |
750 | <p>Returns the callback currently set on the watcher.</p> |
749 | </dd> |
751 | </dd> |
750 | <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt> |
752 | <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt> |
751 | <dd> |
753 | <dd> |
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783 | struct my_io *w = (struct my_io *)w_; |
785 | struct my_io *w = (struct my_io *)w_; |
784 | ... |
786 | ... |
785 | } |
787 | } |
786 | |
788 | |
787 | </pre> |
789 | </pre> |
788 | <p>More interesting and less C-conformant ways of catsing your callback type |
790 | <p>More interesting and less C-conformant ways of casting your callback type |
789 | have been omitted....</p> |
791 | instead have been omitted.</p> |
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792 | <p>Another common scenario is having some data structure with multiple |
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793 | watchers:</p> |
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794 | <pre> struct my_biggy |
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795 | { |
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796 | int some_data; |
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797 | ev_timer t1; |
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798 | ev_timer t2; |
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799 | } |
790 | |
800 | |
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801 | </pre> |
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802 | <p>In this case getting the pointer to <code>my_biggy</code> is a bit more complicated, |
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803 | you need to use <code>offsetof</code>:</p> |
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804 | <pre> #include <stddef.h> |
791 | |
805 | |
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806 | static void |
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807 | t1_cb (EV_P_ struct ev_timer *w, int revents) |
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808 | { |
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809 | struct my_biggy big = (struct my_biggy * |
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810 | (((char *)w) - offsetof (struct my_biggy, t1)); |
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811 | } |
792 | |
812 | |
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813 | static void |
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814 | t2_cb (EV_P_ struct ev_timer *w, int revents) |
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815 | { |
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816 | struct my_biggy big = (struct my_biggy * |
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817 | (((char *)w) - offsetof (struct my_biggy, t2)); |
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818 | } |
793 | |
819 | |
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820 | |
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821 | |
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822 | |
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823 | </pre> |
794 | |
824 | |
795 | </div> |
825 | </div> |
796 | <h1 id="WATCHER_TYPES">WATCHER TYPES</h1> |
826 | <h1 id="WATCHER_TYPES">WATCHER TYPES</h1> |
797 | <div id="WATCHER_TYPES_CONTENT"> |
827 | <div id="WATCHER_TYPES_CONTENT"> |
798 | <p>This section describes each watcher in detail, but will not repeat |
828 | <p>This section describes each watcher in detail, but will not repeat |
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… | |
922 | </dd> |
952 | </dd> |
923 | <dt>ev_timer_again (loop)</dt> |
953 | <dt>ev_timer_again (loop)</dt> |
924 | <dd> |
954 | <dd> |
925 | <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 |
926 | 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> |
927 | <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> |
928 | <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 |
929 | 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> |
930 | <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 |
931 | 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 |
932 | 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 |
933 | 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 |
934 | 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 |
935 | <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 |
936 | 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 |
937 | 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 |
938 | need be.</p> |
969 | automatically restart it if need be.</p> |
939 | <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> |
940 | 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> |
941 | <pre> ev_timer_init (timer, callback, 0., 5.); |
972 | <pre> ev_timer_init (timer, callback, 0., 5.); |
942 | ev_timer_again (loop, timer); |
973 | ev_timer_again (loop, timer); |
943 | ... |
974 | ... |
944 | timer->again = 17.; |
975 | timer->again = 17.; |
945 | ev_timer_again (loop, timer); |
976 | ev_timer_again (loop, timer); |
946 | ... |
977 | ... |
947 | timer->again = 10.; |
978 | timer->again = 10.; |
948 | ev_timer_again (loop, timer); |
979 | ev_timer_again (loop, timer); |
949 | |
980 | |
950 | </pre> |
981 | </pre> |
951 | <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 |
952 | to modify its timeout value.</p> |
983 | you want to modify its timeout value.</p> |
953 | </dd> |
984 | </dd> |
954 | <dt>ev_tstamp repeat [read-write]</dt> |
985 | <dt>ev_tstamp repeat [read-write]</dt> |
955 | <dd> |
986 | <dd> |
956 | <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 |
957 | 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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1218 | <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 |
1219 | 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 |
1220 | 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 |
1221 | 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 |
1222 | 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> |
1223 | <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 |
1224 | calls <code>stat (2)</code> regulalry 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 |
1225 | 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 |
1226 | 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, |
1227 | 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 |
1228 | five seconds, although this might change dynamically). Libev will also |
1261 | five seconds, although this might change dynamically). Libev will also |
1229 | impose a minimum interval which is currently around <code>0.1</code>, but thats |
1262 | impose a minimum interval which is currently around <code>0.1</code>, but thats |
1230 | usually overkill.</p> |
1263 | usually overkill.</p> |
1231 | <p>This watcher type is not meant for massive numbers of stat watchers, |
1264 | <p>This watcher type is not meant for massive numbers of stat watchers, |
1232 | as even with OS-supported change notifications, this can be |
1265 | as even with OS-supported change notifications, this can be |
1233 | resource-intensive.</p> |
1266 | resource-intensive.</p> |
1234 | <p>At the time of this writing, no specific OS backends are implemented, but |
1267 | <p>At the time of this writing, only the Linux inotify interface is |
1235 | if demand increases, at least a kqueue and inotify backend will be added.</p> |
1268 | implemented (implementing kqueue support is left as an exercise for the |
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1269 | reader). Inotify will be used to give hints only and should not change the |
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1270 | semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs |
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1271 | to fall back to regular polling again even with inotify, but changes are |
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1272 | usually detected immediately, and if the file exists there will be no |
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1273 | polling.</p> |
1236 | <dl> |
1274 | <dl> |
1237 | <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt> |
1275 | <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt> |
1238 | <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt> |
1276 | <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt> |
1239 | <dd> |
1277 | <dd> |
1240 | <p>Configures the watcher to wait for status changes of the given |
1278 | <p>Configures the watcher to wait for status changes of the given |
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… | |
1987 | </dd> |
2025 | </dd> |
1988 | <dt>EV_USE_DEVPOLL</dt> |
2026 | <dt>EV_USE_DEVPOLL</dt> |
1989 | <dd> |
2027 | <dd> |
1990 | <p>reserved for future expansion, works like the USE symbols above.</p> |
2028 | <p>reserved for future expansion, works like the USE symbols above.</p> |
1991 | </dd> |
2029 | </dd> |
|
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2030 | <dt>EV_USE_INOTIFY</dt> |
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2031 | <dd> |
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2032 | <p>If defined to be <code>1</code>, libev will compile in support for the Linux inotify |
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2033 | interface to speed up <code>ev_stat</code> watchers. Its actual availability will |
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2034 | be detected at runtime.</p> |
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2035 | </dd> |
1992 | <dt>EV_H</dt> |
2036 | <dt>EV_H</dt> |
1993 | <dd> |
2037 | <dd> |
1994 | <p>The name of the <cite>ev.h</cite> header file used to include it. The default if |
2038 | <p>The name of the <cite>ev.h</cite> header file used to include it. The default if |
1995 | undefined is <code><ev.h></code> in <cite>event.h</cite> and <code>"ev.h"</code> in <cite>ev.c</cite>. This |
2039 | undefined is <code><ev.h></code> in <cite>event.h</cite> and <code>"ev.h"</code> in <cite>ev.c</cite>. This |
1996 | can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p> |
2040 | can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p> |
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2051 | <dt>EV_PID_HASHSIZE</dt> |
2095 | <dt>EV_PID_HASHSIZE</dt> |
2052 | <dd> |
2096 | <dd> |
2053 | <p><code>ev_child</code> watchers use a small hash table to distribute workload by |
2097 | <p><code>ev_child</code> watchers use a small hash table to distribute workload by |
2054 | pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more |
2098 | pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more |
2055 | than enough. If you need to manage thousands of children you might want to |
2099 | than enough. If you need to manage thousands of children you might want to |
2056 | increase this value.</p> |
2100 | increase this value (<i>must</i> be a power of two).</p> |
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2101 | </dd> |
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2102 | <dt>EV_INOTIFY_HASHSIZE</dt> |
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2103 | <dd> |
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2104 | <p><code>ev_staz</code> watchers use a small hash table to distribute workload by |
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2105 | inotify watch id. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), |
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2106 | usually more than enough. If you need to manage thousands of <code>ev_stat</code> |
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2107 | watchers you might want to increase this value (<i>must</i> be a power of |
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2108 | two).</p> |
2057 | </dd> |
2109 | </dd> |
2058 | <dt>EV_COMMON</dt> |
2110 | <dt>EV_COMMON</dt> |
2059 | <dd> |
2111 | <dd> |
2060 | <p>By default, all watchers have a <code>void *data</code> member. By redefining |
2112 | <p>By default, all watchers have a <code>void *data</code> member. By redefining |
2061 | this macro to a something else you can include more and other types of |
2113 | this macro to a something else you can include more and other types of |
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… | |
2118 | <dl> |
2170 | <dl> |
2119 | <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> |
2171 | <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> |
2120 | <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt> |
2172 | <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt> |
2121 | <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> |
2173 | <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> |
2122 | <dt>Stopping check/prepare/idle watchers: O(1)</dt> |
2174 | <dt>Stopping check/prepare/idle watchers: O(1)</dt> |
2123 | <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))</dt> |
2175 | <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt> |
2124 | <dt>Finding the next timer per loop iteration: O(1)</dt> |
2176 | <dt>Finding the next timer per loop iteration: O(1)</dt> |
2125 | <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt> |
2177 | <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt> |
2126 | <dt>Activating one watcher: O(1)</dt> |
2178 | <dt>Activating one watcher: O(1)</dt> |
2127 | </dl> |
2179 | </dl> |
2128 | </p> |
2180 | </p> |