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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" /> |
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14 | <!-- INDEX START --> |
14 | <!-- INDEX START --> |
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119 | </pre> |
119 | </pre> |
120 | |
120 | |
121 | </div> |
121 | </div> |
122 | <h1 id="DESCRIPTION">DESCRIPTION</h1> |
122 | <h1 id="DESCRIPTION">DESCRIPTION</h1> |
123 | <div id="DESCRIPTION_CONTENT"> |
123 | <div id="DESCRIPTION_CONTENT"> |
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124 | <p>The newest version of this document is also available as a html-formatted |
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125 | web page you might find easier to navigate when reading it for the first |
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126 | time: <a href="http://cvs.schmorp.de/libev/ev.html">http://cvs.schmorp.de/libev/ev.html</a>.</p> |
124 | <p>Libev is an event loop: you register interest in certain events (such as a |
127 | <p>Libev is an event loop: you register interest in certain events (such as a |
125 | file descriptor being readable or a timeout occuring), and it will manage |
128 | file descriptor being readable or a timeout occuring), and it will manage |
126 | these event sources and provide your program with events.</p> |
129 | these event sources and provide your program with events.</p> |
127 | <p>To do this, it must take more or less complete control over your process |
130 | <p>To do this, it must take more or less complete control over your process |
128 | (or thread) by executing the <i>event loop</i> handler, and will then |
131 | (or thread) by executing the <i>event loop</i> handler, and will then |
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526 | one iteration of the loop. This is useful if you are waiting for some |
529 | one iteration of the loop. This is useful if you are waiting for some |
527 | external event in conjunction with something not expressible using other |
530 | external event in conjunction with something not expressible using other |
528 | libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is |
531 | libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is |
529 | usually a better approach for this kind of thing.</p> |
532 | usually a better approach for this kind of thing.</p> |
530 | <p>Here are the gory details of what <code>ev_loop</code> does:</p> |
533 | <p>Here are the gory details of what <code>ev_loop</code> does:</p> |
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|
534 | <pre> - Before the first iteration, call any pending watchers. |
531 | <pre> * If there are no active watchers (reference count is zero), return. |
535 | * If there are no active watchers (reference count is zero), return. |
532 | - Queue prepare watchers and then call all outstanding watchers. |
536 | - Queue all prepare watchers and then call all outstanding watchers. |
533 | - If we have been forked, recreate the kernel state. |
537 | - If we have been forked, recreate the kernel state. |
534 | - Update the kernel state with all outstanding changes. |
538 | - Update the kernel state with all outstanding changes. |
535 | - Update the "event loop time". |
539 | - Update the "event loop time". |
536 | - Calculate for how long to block. |
540 | - Calculate for how long to block. |
537 | - Block the process, waiting for any events. |
541 | - Block the process, waiting for any events. |
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766 | <dt>bool ev_is_pending (ev_TYPE *watcher)</dt> |
770 | <dt>bool ev_is_pending (ev_TYPE *watcher)</dt> |
767 | <dd> |
771 | <dd> |
768 | <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding |
772 | <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding |
769 | events but its callback has not yet been invoked). As long as a watcher |
773 | events but its callback has not yet been invoked). As long as a watcher |
770 | is pending (but not active) you must not call an init function on it (but |
774 | is pending (but not active) you must not call an init function on it (but |
771 | <code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to |
775 | <code>ev_TYPE_set</code> is safe), you must not change its priority, and you must |
772 | libev (e.g. you cnanot <code>free ()</code> it).</p> |
776 | make sure the watcher is available to libev (e.g. you cannot <code>free ()</code> |
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777 | it).</p> |
773 | </dd> |
778 | </dd> |
774 | <dt>callback ev_cb (ev_TYPE *watcher)</dt> |
779 | <dt>callback ev_cb (ev_TYPE *watcher)</dt> |
775 | <dd> |
780 | <dd> |
776 | <p>Returns the callback currently set on the watcher.</p> |
781 | <p>Returns the callback currently set on the watcher.</p> |
777 | </dd> |
782 | </dd> |
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792 | invocation after new events have been received. This is useful, for |
797 | invocation after new events have been received. This is useful, for |
793 | example, to reduce latency after idling, or more often, to bind two |
798 | example, to reduce latency after idling, or more often, to bind two |
794 | watchers on the same event and make sure one is called first.</p> |
799 | watchers on the same event and make sure one is called first.</p> |
795 | <p>If you need to suppress invocation when higher priority events are pending |
800 | <p>If you need to suppress invocation when higher priority events are pending |
796 | you need to look at <code>ev_idle</code> watchers, which provide this functionality.</p> |
801 | you need to look at <code>ev_idle</code> watchers, which provide this functionality.</p> |
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802 | <p>You <i>must not</i> change the priority of a watcher as long as it is active or |
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803 | pending.</p> |
797 | <p>The default priority used by watchers when no priority has been set is |
804 | <p>The default priority used by watchers when no priority has been set is |
798 | always <code>0</code>, which is supposed to not be too high and not be too low :).</p> |
805 | always <code>0</code>, which is supposed to not be too high and not be too low :).</p> |
799 | <p>Setting a priority outside the range of <code>EV_MINPRI</code> to <code>EV_MAXPRI</code> is |
806 | <p>Setting a priority outside the range of <code>EV_MINPRI</code> to <code>EV_MAXPRI</code> is |
800 | fine, as long as you do not mind that the priority value you query might |
807 | fine, as long as you do not mind that the priority value you query might |
801 | or might not have been adjusted to be within valid range.</p> |
808 | or might not have been adjusted to be within valid range.</p> |
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809 | </dd> |
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810 | <dt>ev_invoke (loop, ev_TYPE *watcher, int revents)</dt> |
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811 | <dd> |
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812 | <p>Invoke the <code>watcher</code> with the given <code>loop</code> and <code>revents</code>. Neither |
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813 | <code>loop</code> nor <code>revents</code> need to be valid as long as the watcher callback |
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814 | can deal with that fact.</p> |
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815 | </dd> |
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816 | <dt>int ev_clear_pending (loop, ev_TYPE *watcher)</dt> |
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817 | <dd> |
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818 | <p>If the watcher is pending, this function returns clears its pending status |
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819 | and returns its <code>revents</code> bitset (as if its callback was invoked). If the |
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820 | watcher isn't pending it does nothing and returns <code>0</code>.</p> |
802 | </dd> |
821 | </dd> |
803 | </dl> |
822 | </dl> |
804 | |
823 | |
805 | |
824 | |
806 | |
825 | |
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917 | this situation even with a relatively standard program structure. Thus |
936 | this situation even with a relatively standard program structure. Thus |
918 | it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning |
937 | it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning |
919 | <code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p> |
938 | <code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p> |
920 | <p>If you cannot run the fd in non-blocking mode (for example you should not |
939 | <p>If you cannot run the fd in non-blocking mode (for example you should not |
921 | play around with an Xlib connection), then you have to seperately re-test |
940 | play around with an Xlib connection), then you have to seperately re-test |
922 | wether a file descriptor is really ready with a known-to-be good interface |
941 | whether a file descriptor is really ready with a known-to-be good interface |
923 | such as poll (fortunately in our Xlib example, Xlib already does this on |
942 | such as poll (fortunately in our Xlib example, Xlib already does this on |
924 | its own, so its quite safe to use).</p> |
943 | its own, so its quite safe to use).</p> |
925 | <dl> |
944 | <dl> |
926 | <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> |
945 | <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> |
927 | <dt>ev_io_set (ev_io *, int fd, int events)</dt> |
946 | <dt>ev_io_set (ev_io *, int fd, int events)</dt> |
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1078 | but on wallclock time (absolute time). You can tell a periodic watcher |
1097 | but on wallclock time (absolute time). You can tell a periodic watcher |
1079 | to trigger "at" some specific point in time. For example, if you tell a |
1098 | to trigger "at" some specific point in time. For example, if you tell a |
1080 | periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now () |
1099 | periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now () |
1081 | + 10.</code>) and then reset your system clock to the last year, then it will |
1100 | + 10.</code>) and then reset your system clock to the last year, then it will |
1082 | take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger |
1101 | take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger |
1083 | roughly 10 seconds later and of course not if you reset your system time |
1102 | roughly 10 seconds later).</p> |
1084 | again).</p> |
|
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1085 | <p>They can also be used to implement vastly more complex timers, such as |
1103 | <p>They can also be used to implement vastly more complex timers, such as |
1086 | triggering an event on eahc midnight, local time.</p> |
1104 | triggering an event on each midnight, local time or other, complicated, |
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1105 | rules.</p> |
1087 | <p>As with timers, the callback is guarenteed to be invoked only when the |
1106 | <p>As with timers, the callback is guarenteed to be invoked only when the |
1088 | time (<code>at</code>) has been passed, but if multiple periodic timers become ready |
1107 | time (<code>at</code>) has been passed, but if multiple periodic timers become ready |
1089 | during the same loop iteration then order of execution is undefined.</p> |
1108 | during the same loop iteration then order of execution is undefined.</p> |
1090 | <dl> |
1109 | <dl> |
1091 | <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> |
1110 | <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> |
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1093 | <dd> |
1112 | <dd> |
1094 | <p>Lots of arguments, lets sort it out... There are basically three modes of |
1113 | <p>Lots of arguments, lets sort it out... There are basically three modes of |
1095 | operation, and we will explain them from simplest to complex:</p> |
1114 | operation, and we will explain them from simplest to complex:</p> |
1096 | <p> |
1115 | <p> |
1097 | <dl> |
1116 | <dl> |
1098 | <dt>* absolute timer (interval = reschedule_cb = 0)</dt> |
1117 | <dt>* absolute timer (at = time, interval = reschedule_cb = 0)</dt> |
1099 | <dd> |
1118 | <dd> |
1100 | <p>In this configuration the watcher triggers an event at the wallclock time |
1119 | <p>In this configuration the watcher triggers an event at the wallclock time |
1101 | <code>at</code> and doesn't repeat. It will not adjust when a time jump occurs, |
1120 | <code>at</code> and doesn't repeat. It will not adjust when a time jump occurs, |
1102 | that is, if it is to be run at January 1st 2011 then it will run when the |
1121 | that is, if it is to be run at January 1st 2011 then it will run when the |
1103 | system time reaches or surpasses this time.</p> |
1122 | system time reaches or surpasses this time.</p> |
1104 | </dd> |
1123 | </dd> |
1105 | <dt>* non-repeating interval timer (interval > 0, reschedule_cb = 0)</dt> |
1124 | <dt>* non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)</dt> |
1106 | <dd> |
1125 | <dd> |
1107 | <p>In this mode the watcher will always be scheduled to time out at the next |
1126 | <p>In this mode the watcher will always be scheduled to time out at the next |
1108 | <code>at + N * interval</code> time (for some integer N) and then repeat, regardless |
1127 | <code>at + N * interval</code> time (for some integer N, which can also be negative) |
1109 | of any time jumps.</p> |
1128 | and then repeat, regardless of any time jumps.</p> |
1110 | <p>This can be used to create timers that do not drift with respect to system |
1129 | <p>This can be used to create timers that do not drift with respect to system |
1111 | time:</p> |
1130 | time:</p> |
1112 | <pre> ev_periodic_set (&periodic, 0., 3600., 0); |
1131 | <pre> ev_periodic_set (&periodic, 0., 3600., 0); |
1113 | |
1132 | |
1114 | </pre> |
1133 | </pre> |
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1117 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1136 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1118 | by 3600.</p> |
1137 | by 3600.</p> |
1119 | <p>Another way to think about it (for the mathematically inclined) is that |
1138 | <p>Another way to think about it (for the mathematically inclined) is that |
1120 | <code>ev_periodic</code> will try to run the callback in this mode at the next possible |
1139 | <code>ev_periodic</code> will try to run the callback in this mode at the next possible |
1121 | time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p> |
1140 | time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p> |
|
|
1141 | <p>For numerical stability it is preferable that the <code>at</code> value is near |
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|
1142 | <code>ev_now ()</code> (the current time), but there is no range requirement for |
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|
1143 | this value.</p> |
1122 | </dd> |
1144 | </dd> |
1123 | <dt>* manual reschedule mode (reschedule_cb = callback)</dt> |
1145 | <dt>* manual reschedule mode (at and interval ignored, reschedule_cb = callback)</dt> |
1124 | <dd> |
1146 | <dd> |
1125 | <p>In this mode the values for <code>interval</code> and <code>at</code> are both being |
1147 | <p>In this mode the values for <code>interval</code> and <code>at</code> are both being |
1126 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1148 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1127 | reschedule callback will be called with the watcher as first, and the |
1149 | reschedule callback will be called with the watcher as first, and the |
1128 | current time as second argument.</p> |
1150 | current time as second argument.</p> |
1129 | <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher, |
1151 | <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher, |
1130 | ever, or make any event loop modifications</i>. If you need to stop it, |
1152 | ever, or make any event loop modifications</i>. If you need to stop it, |
1131 | return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by |
1153 | return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by |
1132 | starting a prepare watcher).</p> |
1154 | starting an <code>ev_prepare</code> watcher, which is legal).</p> |
1133 | <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, |
1155 | <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, |
1134 | ev_tstamp now)</code>, e.g.:</p> |
1156 | ev_tstamp now)</code>, e.g.:</p> |
1135 | <pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1157 | <pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1136 | { |
1158 | { |
1137 | return now + 60.; |
1159 | return now + 60.; |
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1157 | <dd> |
1179 | <dd> |
1158 | <p>Simply stops and restarts the periodic watcher again. This is only useful |
1180 | <p>Simply stops and restarts the periodic watcher again. This is only useful |
1159 | when you changed some parameters or the reschedule callback would return |
1181 | when you changed some parameters or the reschedule callback would return |
1160 | a different time than the last time it was called (e.g. in a crond like |
1182 | a different time than the last time it was called (e.g. in a crond like |
1161 | program when the crontabs have changed).</p> |
1183 | program when the crontabs have changed).</p> |
|
|
1184 | </dd> |
|
|
1185 | <dt>ev_tstamp offset [read-write]</dt> |
|
|
1186 | <dd> |
|
|
1187 | <p>When repeating, this contains the offset value, otherwise this is the |
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|
1188 | absolute point in time (the <code>at</code> value passed to <code>ev_periodic_set</code>).</p> |
|
|
1189 | <p>Can be modified any time, but changes only take effect when the periodic |
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1190 | timer fires or <code>ev_periodic_again</code> is being called.</p> |
1162 | </dd> |
1191 | </dd> |
1163 | <dt>ev_tstamp interval [read-write]</dt> |
1192 | <dt>ev_tstamp interval [read-write]</dt> |
1164 | <dd> |
1193 | <dd> |
1165 | <p>The current interval value. Can be modified any time, but changes only |
1194 | <p>The current interval value. Can be modified any time, but changes only |
1166 | take effect when the periodic timer fires or <code>ev_periodic_again</code> is being |
1195 | take effect when the periodic timer fires or <code>ev_periodic_again</code> is being |
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1465 | are ready to run (it's actually more complicated: it only runs coroutines |
1494 | are ready to run (it's actually more complicated: it only runs coroutines |
1466 | with priority higher than or equal to the event loop and one coroutine |
1495 | with priority higher than or equal to the event loop and one coroutine |
1467 | of lower priority, but only once, using idle watchers to keep the event |
1496 | of lower priority, but only once, using idle watchers to keep the event |
1468 | loop from blocking if lower-priority coroutines are active, thus mapping |
1497 | loop from blocking if lower-priority coroutines are active, thus mapping |
1469 | low-priority coroutines to idle/background tasks).</p> |
1498 | low-priority coroutines to idle/background tasks).</p> |
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1499 | <p>It is recommended to give <code>ev_check</code> watchers highest (<code>EV_MAXPRI</code>) |
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1500 | priority, to ensure that they are being run before any other watchers |
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1501 | after the poll. Also, <code>ev_check</code> watchers (and <code>ev_prepare</code> watchers, |
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1502 | too) should not activate ("feed") events into libev. While libev fully |
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1503 | supports this, they will be called before other <code>ev_check</code> watchers did |
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|
1504 | their job. As <code>ev_check</code> watchers are often used to embed other event |
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1505 | loops those other event loops might be in an unusable state until their |
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1506 | <code>ev_check</code> watcher ran (always remind yourself to coexist peacefully with |
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1507 | others).</p> |
1470 | <dl> |
1508 | <dl> |
1471 | <dt>ev_prepare_init (ev_prepare *, callback)</dt> |
1509 | <dt>ev_prepare_init (ev_prepare *, callback)</dt> |
1472 | <dt>ev_check_init (ev_check *, callback)</dt> |
1510 | <dt>ev_check_init (ev_check *, callback)</dt> |
1473 | <dd> |
1511 | <dd> |
1474 | <p>Initialises and configures the prepare or check watcher - they have no |
1512 | <p>Initialises and configures the prepare or check watcher - they have no |
1475 | parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> |
1513 | parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> |
1476 | macros, but using them is utterly, utterly and completely pointless.</p> |
1514 | macros, but using them is utterly, utterly and completely pointless.</p> |
1477 | </dd> |
1515 | </dd> |
1478 | </dl> |
1516 | </dl> |
1479 | <p>Example: To include a library such as adns, you would add IO watchers |
1517 | <p>There are a number of principal ways to embed other event loops or modules |
1480 | and a timeout watcher in a prepare handler, as required by libadns, and |
1518 | into libev. Here are some ideas on how to include libadns into libev |
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|
1519 | (there is a Perl module named <code>EV::ADNS</code> that does this, which you could |
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1520 | use for an actually working example. Another Perl module named <code>EV::Glib</code> |
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1521 | embeds a Glib main context into libev, and finally, <code>Glib::EV</code> embeds EV |
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|
1522 | into the Glib event loop).</p> |
|
|
1523 | <p>Method 1: Add IO watchers and a timeout watcher in a prepare handler, |
1481 | in a check watcher, destroy them and call into libadns. What follows is |
1524 | and in a check watcher, destroy them and call into libadns. What follows |
1482 | pseudo-code only of course:</p> |
1525 | is pseudo-code only of course. This requires you to either use a low |
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1526 | priority for the check watcher or use <code>ev_clear_pending</code> explicitly, as |
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1527 | the callbacks for the IO/timeout watchers might not have been called yet.</p> |
1483 | <pre> static ev_io iow [nfd]; |
1528 | <pre> static ev_io iow [nfd]; |
1484 | static ev_timer tw; |
1529 | static ev_timer tw; |
1485 | |
1530 | |
1486 | static void |
1531 | static void |
1487 | io_cb (ev_loop *loop, ev_io *w, int revents) |
1532 | io_cb (ev_loop *loop, ev_io *w, int revents) |
1488 | { |
1533 | { |
1489 | // set the relevant poll flags |
|
|
1490 | // could also call adns_processreadable etc. here |
|
|
1491 | struct pollfd *fd = (struct pollfd *)w->data; |
|
|
1492 | if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; |
|
|
1493 | if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; |
|
|
1494 | } |
1534 | } |
1495 | |
1535 | |
1496 | // create io watchers for each fd and a timer before blocking |
1536 | // create io watchers for each fd and a timer before blocking |
1497 | static void |
1537 | static void |
1498 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
1538 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
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… | |
1504 | |
1544 | |
1505 | /* the callback is illegal, but won't be called as we stop during check */ |
1545 | /* the callback is illegal, but won't be called as we stop during check */ |
1506 | ev_timer_init (&tw, 0, timeout * 1e-3); |
1546 | ev_timer_init (&tw, 0, timeout * 1e-3); |
1507 | ev_timer_start (loop, &tw); |
1547 | ev_timer_start (loop, &tw); |
1508 | |
1548 | |
1509 | // create on ev_io per pollfd |
1549 | // create one ev_io per pollfd |
1510 | for (int i = 0; i < nfd; ++i) |
1550 | for (int i = 0; i < nfd; ++i) |
1511 | { |
1551 | { |
1512 | ev_io_init (iow + i, io_cb, fds [i].fd, |
1552 | ev_io_init (iow + i, io_cb, fds [i].fd, |
1513 | ((fds [i].events & POLLIN ? EV_READ : 0) |
1553 | ((fds [i].events & POLLIN ? EV_READ : 0) |
1514 | | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
1554 | | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
1515 | |
1555 | |
1516 | fds [i].revents = 0; |
1556 | fds [i].revents = 0; |
1517 | iow [i].data = fds + i; |
|
|
1518 | ev_io_start (loop, iow + i); |
1557 | ev_io_start (loop, iow + i); |
1519 | } |
1558 | } |
1520 | } |
1559 | } |
1521 | |
1560 | |
1522 | // stop all watchers after blocking |
1561 | // stop all watchers after blocking |
… | |
… | |
1524 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
1563 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
1525 | { |
1564 | { |
1526 | ev_timer_stop (loop, &tw); |
1565 | ev_timer_stop (loop, &tw); |
1527 | |
1566 | |
1528 | for (int i = 0; i < nfd; ++i) |
1567 | for (int i = 0; i < nfd; ++i) |
|
|
1568 | { |
|
|
1569 | // set the relevant poll flags |
|
|
1570 | // could also call adns_processreadable etc. here |
|
|
1571 | struct pollfd *fd = fds + i; |
|
|
1572 | int revents = ev_clear_pending (iow + i); |
|
|
1573 | if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; |
|
|
1574 | if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; |
|
|
1575 | |
|
|
1576 | // now stop the watcher |
1529 | ev_io_stop (loop, iow + i); |
1577 | ev_io_stop (loop, iow + i); |
|
|
1578 | } |
1530 | |
1579 | |
1531 | adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
1580 | adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
|
|
1581 | } |
|
|
1582 | |
|
|
1583 | </pre> |
|
|
1584 | <p>Method 2: This would be just like method 1, but you run <code>adns_afterpoll</code> |
|
|
1585 | in the prepare watcher and would dispose of the check watcher.</p> |
|
|
1586 | <p>Method 3: If the module to be embedded supports explicit event |
|
|
1587 | notification (adns does), you can also make use of the actual watcher |
|
|
1588 | callbacks, and only destroy/create the watchers in the prepare watcher.</p> |
|
|
1589 | <pre> static void |
|
|
1590 | timer_cb (EV_P_ ev_timer *w, int revents) |
|
|
1591 | { |
|
|
1592 | adns_state ads = (adns_state)w->data; |
|
|
1593 | update_now (EV_A); |
|
|
1594 | |
|
|
1595 | adns_processtimeouts (ads, &tv_now); |
|
|
1596 | } |
|
|
1597 | |
|
|
1598 | static void |
|
|
1599 | io_cb (EV_P_ ev_io *w, int revents) |
|
|
1600 | { |
|
|
1601 | adns_state ads = (adns_state)w->data; |
|
|
1602 | update_now (EV_A); |
|
|
1603 | |
|
|
1604 | if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now); |
|
|
1605 | if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now); |
|
|
1606 | } |
|
|
1607 | |
|
|
1608 | // do not ever call adns_afterpoll |
|
|
1609 | |
|
|
1610 | </pre> |
|
|
1611 | <p>Method 4: Do not use a prepare or check watcher because the module you |
|
|
1612 | want to embed is too inflexible to support it. Instead, youc na override |
|
|
1613 | their poll function. The drawback with this solution is that the main |
|
|
1614 | loop is now no longer controllable by EV. The <code>Glib::EV</code> module does |
|
|
1615 | this.</p> |
|
|
1616 | <pre> static gint |
|
|
1617 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
|
|
1618 | { |
|
|
1619 | int got_events = 0; |
|
|
1620 | |
|
|
1621 | for (n = 0; n < nfds; ++n) |
|
|
1622 | // create/start io watcher that sets the relevant bits in fds[n] and increment got_events |
|
|
1623 | |
|
|
1624 | if (timeout >= 0) |
|
|
1625 | // create/start timer |
|
|
1626 | |
|
|
1627 | // poll |
|
|
1628 | ev_loop (EV_A_ 0); |
|
|
1629 | |
|
|
1630 | // stop timer again |
|
|
1631 | if (timeout >= 0) |
|
|
1632 | ev_timer_stop (EV_A_ &to); |
|
|
1633 | |
|
|
1634 | // stop io watchers again - their callbacks should have set |
|
|
1635 | for (n = 0; n < nfds; ++n) |
|
|
1636 | ev_io_stop (EV_A_ iow [n]); |
|
|
1637 | |
|
|
1638 | return got_events; |
1532 | } |
1639 | } |
1533 | |
1640 | |
1534 | |
1641 | |
1535 | |
1642 | |
1536 | |
1643 | |
… | |
… | |
1733 | the callback model to a model using method callbacks on objects.</p> |
1840 | the callback model to a model using method callbacks on objects.</p> |
1734 | <p>To use it,</p> |
1841 | <p>To use it,</p> |
1735 | <pre> #include <ev++.h> |
1842 | <pre> #include <ev++.h> |
1736 | |
1843 | |
1737 | </pre> |
1844 | </pre> |
1738 | <p>(it is not installed by default). This automatically includes <cite>ev.h</cite> |
1845 | <p>This automatically includes <cite>ev.h</cite> and puts all of its definitions (many |
1739 | and puts all of its definitions (many of them macros) into the global |
1846 | of them macros) into the global namespace. All C++ specific things are |
1740 | namespace. All C++ specific things are put into the <code>ev</code> namespace.</p> |
1847 | put into the <code>ev</code> namespace. It should support all the same embedding |
1741 | <p>It should support all the same embedding options as <cite>ev.h</cite>, most notably |
1848 | options as <cite>ev.h</cite>, most notably <code>EV_MULTIPLICITY</code>.</p> |
1742 | <code>EV_MULTIPLICITY</code>.</p> |
1849 | <p>Care has been taken to keep the overhead low. The only data member the C++ |
|
|
1850 | classes add (compared to plain C-style watchers) is the event loop pointer |
|
|
1851 | that the watcher is associated with (or no additional members at all if |
|
|
1852 | you disable <code>EV_MULTIPLICITY</code> when embedding libev).</p> |
|
|
1853 | <p>Currently, functions, and static and non-static member functions can be |
|
|
1854 | used as callbacks. Other types should be easy to add as long as they only |
|
|
1855 | need one additional pointer for context. If you need support for other |
|
|
1856 | types of functors please contact the author (preferably after implementing |
|
|
1857 | it).</p> |
1743 | <p>Here is a list of things available in the <code>ev</code> namespace:</p> |
1858 | <p>Here is a list of things available in the <code>ev</code> namespace:</p> |
1744 | <dl> |
1859 | <dl> |
1745 | <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt> |
1860 | <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt> |
1746 | <dd> |
1861 | <dd> |
1747 | <p>These are just enum values with the same values as the <code>EV_READ</code> etc. |
1862 | <p>These are just enum values with the same values as the <code>EV_READ</code> etc. |
… | |
… | |
1758 | which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro |
1873 | which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro |
1759 | defines by many implementations.</p> |
1874 | defines by many implementations.</p> |
1760 | <p>All of those classes have these methods:</p> |
1875 | <p>All of those classes have these methods:</p> |
1761 | <p> |
1876 | <p> |
1762 | <dl> |
1877 | <dl> |
1763 | <dt>ev::TYPE::TYPE (object *, object::method *)</dt> |
1878 | <dt>ev::TYPE::TYPE ()</dt> |
1764 | <dt>ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)</dt> |
1879 | <dt>ev::TYPE::TYPE (struct ev_loop *)</dt> |
1765 | <dt>ev::TYPE::~TYPE</dt> |
1880 | <dt>ev::TYPE::~TYPE</dt> |
1766 | <dd> |
1881 | <dd> |
1767 | <p>The constructor takes a pointer to an object and a method pointer to |
1882 | <p>The constructor (optionally) takes an event loop to associate the watcher |
1768 | the event handler callback to call in this class. The constructor calls |
1883 | with. If it is omitted, it will use <code>EV_DEFAULT</code>.</p> |
1769 | <code>ev_init</code> for you, which means you have to call the <code>set</code> method |
1884 | <p>The constructor calls <code>ev_init</code> for you, which means you have to call the |
1770 | before starting it. If you do not specify a loop then the constructor |
1885 | <code>set</code> method before starting it.</p> |
1771 | automatically associates the default loop with this watcher.</p> |
1886 | <p>It will not set a callback, however: You have to call the templated <code>set</code> |
|
|
1887 | method to set a callback before you can start the watcher.</p> |
|
|
1888 | <p>(The reason why you have to use a method is a limitation in C++ which does |
|
|
1889 | not allow explicit template arguments for constructors).</p> |
1772 | <p>The destructor automatically stops the watcher if it is active.</p> |
1890 | <p>The destructor automatically stops the watcher if it is active.</p> |
|
|
1891 | </dd> |
|
|
1892 | <dt>w->set<class, &class::method> (object *)</dt> |
|
|
1893 | <dd> |
|
|
1894 | <p>This method sets the callback method to call. The method has to have a |
|
|
1895 | signature of <code>void (*)(ev_TYPE &, int)</code>, it receives the watcher as |
|
|
1896 | first argument and the <code>revents</code> as second. The object must be given as |
|
|
1897 | parameter and is stored in the <code>data</code> member of the watcher.</p> |
|
|
1898 | <p>This method synthesizes efficient thunking code to call your method from |
|
|
1899 | the C callback that libev requires. If your compiler can inline your |
|
|
1900 | callback (i.e. it is visible to it at the place of the <code>set</code> call and |
|
|
1901 | your compiler is good :), then the method will be fully inlined into the |
|
|
1902 | thunking function, making it as fast as a direct C callback.</p> |
|
|
1903 | <p>Example: simple class declaration and watcher initialisation</p> |
|
|
1904 | <pre> struct myclass |
|
|
1905 | { |
|
|
1906 | void io_cb (ev::io &w, int revents) { } |
|
|
1907 | } |
|
|
1908 | |
|
|
1909 | myclass obj; |
|
|
1910 | ev::io iow; |
|
|
1911 | iow.set <myclass, &myclass::io_cb> (&obj); |
|
|
1912 | |
|
|
1913 | </pre> |
|
|
1914 | </dd> |
|
|
1915 | <dt>w->set<function> (void *data = 0)</dt> |
|
|
1916 | <dd> |
|
|
1917 | <p>Also sets a callback, but uses a static method or plain function as |
|
|
1918 | callback. The optional <code>data</code> argument will be stored in the watcher's |
|
|
1919 | <code>data</code> member and is free for you to use.</p> |
|
|
1920 | <p>The prototype of the <code>function</code> must be <code>void (*)(ev::TYPE &w, int)</code>.</p> |
|
|
1921 | <p>See the method-<code>set</code> above for more details.</p> |
|
|
1922 | <p>Example:</p> |
|
|
1923 | <pre> static void io_cb (ev::io &w, int revents) { } |
|
|
1924 | iow.set <io_cb> (); |
|
|
1925 | |
|
|
1926 | </pre> |
1773 | </dd> |
1927 | </dd> |
1774 | <dt>w->set (struct ev_loop *)</dt> |
1928 | <dt>w->set (struct ev_loop *)</dt> |
1775 | <dd> |
1929 | <dd> |
1776 | <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only |
1930 | <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only |
1777 | do this when the watcher is inactive (and not pending either).</p> |
1931 | do this when the watcher is inactive (and not pending either).</p> |
1778 | </dd> |
1932 | </dd> |
1779 | <dt>w->set ([args])</dt> |
1933 | <dt>w->set ([args])</dt> |
1780 | <dd> |
1934 | <dd> |
1781 | <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be |
1935 | <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be |
1782 | called at least once. Unlike the C counterpart, an active watcher gets |
1936 | called at least once. Unlike the C counterpart, an active watcher gets |
1783 | automatically stopped and restarted.</p> |
1937 | automatically stopped and restarted when reconfiguring it with this |
|
|
1938 | method.</p> |
1784 | </dd> |
1939 | </dd> |
1785 | <dt>w->start ()</dt> |
1940 | <dt>w->start ()</dt> |
1786 | <dd> |
1941 | <dd> |
1787 | <p>Starts the watcher. Note that there is no <code>loop</code> argument as the |
1942 | <p>Starts the watcher. Note that there is no <code>loop</code> argument, as the |
1788 | constructor already takes the loop.</p> |
1943 | constructor already stores the event loop.</p> |
1789 | </dd> |
1944 | </dd> |
1790 | <dt>w->stop ()</dt> |
1945 | <dt>w->stop ()</dt> |
1791 | <dd> |
1946 | <dd> |
1792 | <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p> |
1947 | <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p> |
1793 | </dd> |
1948 | </dd> |
… | |
… | |
1817 | |
1972 | |
1818 | myclass (); |
1973 | myclass (); |
1819 | } |
1974 | } |
1820 | |
1975 | |
1821 | myclass::myclass (int fd) |
1976 | myclass::myclass (int fd) |
1822 | : io (this, &myclass::io_cb), |
|
|
1823 | idle (this, &myclass::idle_cb) |
|
|
1824 | { |
1977 | { |
|
|
1978 | io .set <myclass, &myclass::io_cb > (this); |
|
|
1979 | idle.set <myclass, &myclass::idle_cb> (this); |
|
|
1980 | |
1825 | io.start (fd, ev::READ); |
1981 | io.start (fd, ev::READ); |
1826 | } |
1982 | } |
1827 | |
1983 | |
1828 | |
1984 | |
1829 | |
1985 | |
… | |
… | |
1832 | |
1988 | |
1833 | </div> |
1989 | </div> |
1834 | <h1 id="MACRO_MAGIC">MACRO MAGIC</h1> |
1990 | <h1 id="MACRO_MAGIC">MACRO MAGIC</h1> |
1835 | <div id="MACRO_MAGIC_CONTENT"> |
1991 | <div id="MACRO_MAGIC_CONTENT"> |
1836 | <p>Libev can be compiled with a variety of options, the most fundemantal is |
1992 | <p>Libev can be compiled with a variety of options, the most fundemantal is |
1837 | <code>EV_MULTIPLICITY</code>. This option determines wether (most) functions and |
1993 | <code>EV_MULTIPLICITY</code>. This option determines whether (most) functions and |
1838 | callbacks have an initial <code>struct ev_loop *</code> argument.</p> |
1994 | callbacks have an initial <code>struct ev_loop *</code> argument.</p> |
1839 | <p>To make it easier to write programs that cope with either variant, the |
1995 | <p>To make it easier to write programs that cope with either variant, the |
1840 | following macros are defined:</p> |
1996 | following macros are defined:</p> |
1841 | <dl> |
1997 | <dl> |
1842 | <dt><code>EV_A</code>, <code>EV_A_</code></dt> |
1998 | <dt><code>EV_A</code>, <code>EV_A_</code></dt> |
… | |
… | |
1872 | <p>Similar to the other two macros, this gives you the value of the default |
2028 | <p>Similar to the other two macros, this gives you the value of the default |
1873 | loop, if multiple loops are supported ("ev loop default").</p> |
2029 | loop, if multiple loops are supported ("ev loop default").</p> |
1874 | </dd> |
2030 | </dd> |
1875 | </dl> |
2031 | </dl> |
1876 | <p>Example: Declare and initialise a check watcher, utilising the above |
2032 | <p>Example: Declare and initialise a check watcher, utilising the above |
1877 | macros so it will work regardless of wether multiple loops are supported |
2033 | macros so it will work regardless of whether multiple loops are supported |
1878 | or not.</p> |
2034 | or not.</p> |
1879 | <pre> static void |
2035 | <pre> static void |
1880 | check_cb (EV_P_ ev_timer *w, int revents) |
2036 | check_cb (EV_P_ ev_timer *w, int revents) |
1881 | { |
2037 | { |
1882 | ev_check_stop (EV_A_ w); |
2038 | ev_check_stop (EV_A_ w); |
… | |
… | |
2109 | <p>If undefined or defined to <code>1</code>, then all event-loop-specific functions |
2265 | <p>If undefined or defined to <code>1</code>, then all event-loop-specific functions |
2110 | will have the <code>struct ev_loop *</code> as first argument, and you can create |
2266 | will have the <code>struct ev_loop *</code> as first argument, and you can create |
2111 | additional independent event loops. Otherwise there will be no support |
2267 | additional independent event loops. Otherwise there will be no support |
2112 | for multiple event loops and there is no first event loop pointer |
2268 | for multiple event loops and there is no first event loop pointer |
2113 | argument. Instead, all functions act on the single default loop.</p> |
2269 | argument. Instead, all functions act on the single default loop.</p> |
|
|
2270 | </dd> |
|
|
2271 | <dt>EV_MINPRI</dt> |
|
|
2272 | <dt>EV_MAXPRI</dt> |
|
|
2273 | <dd> |
|
|
2274 | <p>The range of allowed priorities. <code>EV_MINPRI</code> must be smaller or equal to |
|
|
2275 | <code>EV_MAXPRI</code>, but otherwise there are no non-obvious limitations. You can |
|
|
2276 | provide for more priorities by overriding those symbols (usually defined |
|
|
2277 | to be <code>-2</code> and <code>2</code>, respectively).</p> |
|
|
2278 | <p>When doing priority-based operations, libev usually has to linearly search |
|
|
2279 | all the priorities, so having many of them (hundreds) uses a lot of space |
|
|
2280 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
|
|
2281 | fine.</p> |
|
|
2282 | <p>If your embedding app does not need any priorities, defining these both to |
|
|
2283 | <code>0</code> will save some memory and cpu.</p> |
2114 | </dd> |
2284 | </dd> |
2115 | <dt>EV_PERIODIC_ENABLE</dt> |
2285 | <dt>EV_PERIODIC_ENABLE</dt> |
2116 | <dd> |
2286 | <dd> |
2117 | <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If |
2287 | <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If |
2118 | defined to be <code>0</code>, then they are not. Disabling them saves a few kB of |
2288 | defined to be <code>0</code>, then they are not. Disabling them saves a few kB of |
… | |
… | |
2222 | <h1 id="COMPLEXITIES">COMPLEXITIES</h1> |
2392 | <h1 id="COMPLEXITIES">COMPLEXITIES</h1> |
2223 | <div id="COMPLEXITIES_CONTENT"> |
2393 | <div id="COMPLEXITIES_CONTENT"> |
2224 | <p>In this section the complexities of (many of) the algorithms used inside |
2394 | <p>In this section the complexities of (many of) the algorithms used inside |
2225 | libev will be explained. For complexity discussions about backends see the |
2395 | libev will be explained. For complexity discussions about backends see the |
2226 | documentation for <code>ev_default_init</code>.</p> |
2396 | documentation for <code>ev_default_init</code>.</p> |
|
|
2397 | <p>All of the following are about amortised time: If an array needs to be |
|
|
2398 | extended, libev needs to realloc and move the whole array, but this |
|
|
2399 | happens asymptotically never with higher number of elements, so O(1) might |
|
|
2400 | mean it might do a lengthy realloc operation in rare cases, but on average |
|
|
2401 | it is much faster and asymptotically approaches constant time.</p> |
2227 | <p> |
2402 | <p> |
2228 | <dl> |
2403 | <dl> |
2229 | <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> |
2404 | <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> |
|
|
2405 | <dd> |
|
|
2406 | <p>This means that, when you have a watcher that triggers in one hour and |
|
|
2407 | there are 100 watchers that would trigger before that then inserting will |
|
|
2408 | have to skip those 100 watchers.</p> |
|
|
2409 | </dd> |
2230 | <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt> |
2410 | <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt> |
|
|
2411 | <dd> |
|
|
2412 | <p>That means that for changing a timer costs less than removing/adding them |
|
|
2413 | as only the relative motion in the event queue has to be paid for.</p> |
|
|
2414 | </dd> |
2231 | <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> |
2415 | <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> |
|
|
2416 | <dd> |
|
|
2417 | <p>These just add the watcher into an array or at the head of a list. |
2232 | <dt>Stopping check/prepare/idle watchers: O(1)</dt> |
2418 | =item Stopping check/prepare/idle watchers: O(1)</p> |
|
|
2419 | </dd> |
2233 | <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt> |
2420 | <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt> |
|
|
2421 | <dd> |
|
|
2422 | <p>These watchers are stored in lists then need to be walked to find the |
|
|
2423 | correct watcher to remove. The lists are usually short (you don't usually |
|
|
2424 | have many watchers waiting for the same fd or signal).</p> |
|
|
2425 | </dd> |
2234 | <dt>Finding the next timer per loop iteration: O(1)</dt> |
2426 | <dt>Finding the next timer per loop iteration: O(1)</dt> |
2235 | <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt> |
2427 | <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt> |
|
|
2428 | <dd> |
|
|
2429 | <p>A change means an I/O watcher gets started or stopped, which requires |
|
|
2430 | libev to recalculate its status (and possibly tell the kernel).</p> |
|
|
2431 | </dd> |
2236 | <dt>Activating one watcher: O(1)</dt> |
2432 | <dt>Activating one watcher: O(1)</dt> |
|
|
2433 | <dt>Priority handling: O(number_of_priorities)</dt> |
|
|
2434 | <dd> |
|
|
2435 | <p>Priorities are implemented by allocating some space for each |
|
|
2436 | priority. When doing priority-based operations, libev usually has to |
|
|
2437 | linearly search all the priorities.</p> |
|
|
2438 | </dd> |
2237 | </dl> |
2439 | </dl> |
2238 | </p> |
2440 | </p> |
2239 | |
2441 | |
2240 | |
2442 | |
2241 | |
2443 | |