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4 | <head> |
4 | <head> |
5 | <title>libev</title> |
5 | <title>libev</title> |
6 | <meta name="description" content="Pod documentation for libev" /> |
6 | <meta name="description" content="Pod documentation for libev" /> |
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14 | <!-- INDEX START --> |
14 | <!-- INDEX START --> |
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185 | you actually want to know.</p> |
185 | you actually want to know.</p> |
186 | </dd> |
186 | </dd> |
187 | <dt>int ev_version_major ()</dt> |
187 | <dt>int ev_version_major ()</dt> |
188 | <dt>int ev_version_minor ()</dt> |
188 | <dt>int ev_version_minor ()</dt> |
189 | <dd> |
189 | <dd> |
190 | <p>You can find out the major and minor version numbers of the library |
190 | <p>You can find out the major and minor API/ABI version numbers of the library |
191 | you linked against by calling the functions <code>ev_version_major</code> and |
191 | you linked against by calling the functions <code>ev_version_major</code> and |
192 | <code>ev_version_minor</code>. If you want, you can compare against the global |
192 | <code>ev_version_minor</code>. If you want, you can compare against the global |
193 | symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the |
193 | symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the |
194 | version of the library your program was compiled against.</p> |
194 | version of the library your program was compiled against.</p> |
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195 | <p>These version numbers refer to the API and ABI version of the library, not |
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|
196 | the release version.</p> |
195 | <p>Usually, it's a good idea to terminate if the major versions mismatch, |
197 | <p>Usually, it's a good idea to terminate if the major versions mismatch, |
196 | as this indicates an incompatible change. Minor versions are usually |
198 | as this indicates an incompatible change. Minor versions are usually |
197 | compatible to older versions, so a larger minor version alone is usually |
199 | compatible to older versions, so a larger minor version alone is usually |
198 | not a problem.</p> |
200 | not a problem.</p> |
199 | <p>Example: Make sure we haven't accidentally been linked against the wrong |
201 | <p>Example: Make sure we haven't accidentally been linked against the wrong |
200 | version.</p> |
202 | version.</p> |
201 | <pre> assert (("libev version mismatch", |
203 | <pre> assert (("libev version mismatch", |
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529 | one iteration of the loop. This is useful if you are waiting for some |
531 | one iteration of the loop. This is useful if you are waiting for some |
530 | external event in conjunction with something not expressible using other |
532 | external event in conjunction with something not expressible using other |
531 | libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is |
533 | libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is |
532 | usually a better approach for this kind of thing.</p> |
534 | usually a better approach for this kind of thing.</p> |
533 | <p>Here are the gory details of what <code>ev_loop</code> does:</p> |
535 | <p>Here are the gory details of what <code>ev_loop</code> does:</p> |
|
|
536 | <pre> - Before the first iteration, call any pending watchers. |
534 | <pre> * If there are no active watchers (reference count is zero), return. |
537 | * If there are no active watchers (reference count is zero), return. |
535 | - Queue prepare watchers and then call all outstanding watchers. |
538 | - Queue all prepare watchers and then call all outstanding watchers. |
536 | - If we have been forked, recreate the kernel state. |
539 | - If we have been forked, recreate the kernel state. |
537 | - Update the kernel state with all outstanding changes. |
540 | - Update the kernel state with all outstanding changes. |
538 | - Update the "event loop time". |
541 | - Update the "event loop time". |
539 | - Calculate for how long to block. |
542 | - Calculate for how long to block. |
540 | - Block the process, waiting for any events. |
543 | - Block the process, waiting for any events. |
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769 | <dt>bool ev_is_pending (ev_TYPE *watcher)</dt> |
772 | <dt>bool ev_is_pending (ev_TYPE *watcher)</dt> |
770 | <dd> |
773 | <dd> |
771 | <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding |
774 | <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding |
772 | events but its callback has not yet been invoked). As long as a watcher |
775 | events but its callback has not yet been invoked). As long as a watcher |
773 | is pending (but not active) you must not call an init function on it (but |
776 | is pending (but not active) you must not call an init function on it (but |
774 | <code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to |
777 | <code>ev_TYPE_set</code> is safe), you must not change its priority, and you must |
775 | libev (e.g. you cnanot <code>free ()</code> it).</p> |
778 | make sure the watcher is available to libev (e.g. you cannot <code>free ()</code> |
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|
779 | it).</p> |
776 | </dd> |
780 | </dd> |
777 | <dt>callback ev_cb (ev_TYPE *watcher)</dt> |
781 | <dt>callback ev_cb (ev_TYPE *watcher)</dt> |
778 | <dd> |
782 | <dd> |
779 | <p>Returns the callback currently set on the watcher.</p> |
783 | <p>Returns the callback currently set on the watcher.</p> |
780 | </dd> |
784 | </dd> |
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795 | invocation after new events have been received. This is useful, for |
799 | invocation after new events have been received. This is useful, for |
796 | example, to reduce latency after idling, or more often, to bind two |
800 | example, to reduce latency after idling, or more often, to bind two |
797 | watchers on the same event and make sure one is called first.</p> |
801 | watchers on the same event and make sure one is called first.</p> |
798 | <p>If you need to suppress invocation when higher priority events are pending |
802 | <p>If you need to suppress invocation when higher priority events are pending |
799 | you need to look at <code>ev_idle</code> watchers, which provide this functionality.</p> |
803 | you need to look at <code>ev_idle</code> watchers, which provide this functionality.</p> |
|
|
804 | <p>You <i>must not</i> change the priority of a watcher as long as it is active or |
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805 | pending.</p> |
800 | <p>The default priority used by watchers when no priority has been set is |
806 | <p>The default priority used by watchers when no priority has been set is |
801 | always <code>0</code>, which is supposed to not be too high and not be too low :).</p> |
807 | always <code>0</code>, which is supposed to not be too high and not be too low :).</p> |
802 | <p>Setting a priority outside the range of <code>EV_MINPRI</code> to <code>EV_MAXPRI</code> is |
808 | <p>Setting a priority outside the range of <code>EV_MINPRI</code> to <code>EV_MAXPRI</code> is |
803 | fine, as long as you do not mind that the priority value you query might |
809 | fine, as long as you do not mind that the priority value you query might |
804 | or might not have been adjusted to be within valid range.</p> |
810 | or might not have been adjusted to be within valid range.</p> |
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|
811 | </dd> |
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|
812 | <dt>ev_invoke (loop, ev_TYPE *watcher, int revents)</dt> |
|
|
813 | <dd> |
|
|
814 | <p>Invoke the <code>watcher</code> with the given <code>loop</code> and <code>revents</code>. Neither |
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815 | <code>loop</code> nor <code>revents</code> need to be valid as long as the watcher callback |
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816 | can deal with that fact.</p> |
|
|
817 | </dd> |
|
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818 | <dt>int ev_clear_pending (loop, ev_TYPE *watcher)</dt> |
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|
819 | <dd> |
|
|
820 | <p>If the watcher is pending, this function returns clears its pending status |
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|
821 | and returns its <code>revents</code> bitset (as if its callback was invoked). If the |
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822 | watcher isn't pending it does nothing and returns <code>0</code>.</p> |
805 | </dd> |
823 | </dd> |
806 | </dl> |
824 | </dl> |
807 | |
825 | |
808 | |
826 | |
809 | |
827 | |
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1081 | but on wallclock time (absolute time). You can tell a periodic watcher |
1099 | but on wallclock time (absolute time). You can tell a periodic watcher |
1082 | to trigger "at" some specific point in time. For example, if you tell a |
1100 | to trigger "at" some specific point in time. For example, if you tell a |
1083 | periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now () |
1101 | periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now () |
1084 | + 10.</code>) and then reset your system clock to the last year, then it will |
1102 | + 10.</code>) and then reset your system clock to the last year, then it will |
1085 | take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger |
1103 | take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger |
1086 | roughly 10 seconds later and of course not if you reset your system time |
1104 | roughly 10 seconds later).</p> |
1087 | again).</p> |
|
|
1088 | <p>They can also be used to implement vastly more complex timers, such as |
1105 | <p>They can also be used to implement vastly more complex timers, such as |
1089 | triggering an event on eahc midnight, local time.</p> |
1106 | triggering an event on each midnight, local time or other, complicated, |
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|
1107 | rules.</p> |
1090 | <p>As with timers, the callback is guarenteed to be invoked only when the |
1108 | <p>As with timers, the callback is guarenteed to be invoked only when the |
1091 | time (<code>at</code>) has been passed, but if multiple periodic timers become ready |
1109 | time (<code>at</code>) has been passed, but if multiple periodic timers become ready |
1092 | during the same loop iteration then order of execution is undefined.</p> |
1110 | during the same loop iteration then order of execution is undefined.</p> |
1093 | <dl> |
1111 | <dl> |
1094 | <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> |
1112 | <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> |
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1096 | <dd> |
1114 | <dd> |
1097 | <p>Lots of arguments, lets sort it out... There are basically three modes of |
1115 | <p>Lots of arguments, lets sort it out... There are basically three modes of |
1098 | operation, and we will explain them from simplest to complex:</p> |
1116 | operation, and we will explain them from simplest to complex:</p> |
1099 | <p> |
1117 | <p> |
1100 | <dl> |
1118 | <dl> |
1101 | <dt>* absolute timer (interval = reschedule_cb = 0)</dt> |
1119 | <dt>* absolute timer (at = time, interval = reschedule_cb = 0)</dt> |
1102 | <dd> |
1120 | <dd> |
1103 | <p>In this configuration the watcher triggers an event at the wallclock time |
1121 | <p>In this configuration the watcher triggers an event at the wallclock time |
1104 | <code>at</code> and doesn't repeat. It will not adjust when a time jump occurs, |
1122 | <code>at</code> and doesn't repeat. It will not adjust when a time jump occurs, |
1105 | that is, if it is to be run at January 1st 2011 then it will run when the |
1123 | that is, if it is to be run at January 1st 2011 then it will run when the |
1106 | system time reaches or surpasses this time.</p> |
1124 | system time reaches or surpasses this time.</p> |
1107 | </dd> |
1125 | </dd> |
1108 | <dt>* non-repeating interval timer (interval > 0, reschedule_cb = 0)</dt> |
1126 | <dt>* non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)</dt> |
1109 | <dd> |
1127 | <dd> |
1110 | <p>In this mode the watcher will always be scheduled to time out at the next |
1128 | <p>In this mode the watcher will always be scheduled to time out at the next |
1111 | <code>at + N * interval</code> time (for some integer N) and then repeat, regardless |
1129 | <code>at + N * interval</code> time (for some integer N, which can also be negative) |
1112 | of any time jumps.</p> |
1130 | and then repeat, regardless of any time jumps.</p> |
1113 | <p>This can be used to create timers that do not drift with respect to system |
1131 | <p>This can be used to create timers that do not drift with respect to system |
1114 | time:</p> |
1132 | time:</p> |
1115 | <pre> ev_periodic_set (&periodic, 0., 3600., 0); |
1133 | <pre> ev_periodic_set (&periodic, 0., 3600., 0); |
1116 | |
1134 | |
1117 | </pre> |
1135 | </pre> |
… | |
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1120 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1138 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1121 | by 3600.</p> |
1139 | by 3600.</p> |
1122 | <p>Another way to think about it (for the mathematically inclined) is that |
1140 | <p>Another way to think about it (for the mathematically inclined) is that |
1123 | <code>ev_periodic</code> will try to run the callback in this mode at the next possible |
1141 | <code>ev_periodic</code> will try to run the callback in this mode at the next possible |
1124 | time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p> |
1142 | time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p> |
|
|
1143 | <p>For numerical stability it is preferable that the <code>at</code> value is near |
|
|
1144 | <code>ev_now ()</code> (the current time), but there is no range requirement for |
|
|
1145 | this value.</p> |
1125 | </dd> |
1146 | </dd> |
1126 | <dt>* manual reschedule mode (reschedule_cb = callback)</dt> |
1147 | <dt>* manual reschedule mode (at and interval ignored, reschedule_cb = callback)</dt> |
1127 | <dd> |
1148 | <dd> |
1128 | <p>In this mode the values for <code>interval</code> and <code>at</code> are both being |
1149 | <p>In this mode the values for <code>interval</code> and <code>at</code> are both being |
1129 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1150 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1130 | reschedule callback will be called with the watcher as first, and the |
1151 | reschedule callback will be called with the watcher as first, and the |
1131 | current time as second argument.</p> |
1152 | current time as second argument.</p> |
1132 | <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher, |
1153 | <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher, |
1133 | ever, or make any event loop modifications</i>. If you need to stop it, |
1154 | ever, or make any event loop modifications</i>. If you need to stop it, |
1134 | return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by |
1155 | return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by |
1135 | starting a prepare watcher).</p> |
1156 | starting an <code>ev_prepare</code> watcher, which is legal).</p> |
1136 | <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, |
1157 | <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, |
1137 | ev_tstamp now)</code>, e.g.:</p> |
1158 | ev_tstamp now)</code>, e.g.:</p> |
1138 | <pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1159 | <pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1139 | { |
1160 | { |
1140 | return now + 60.; |
1161 | return now + 60.; |
… | |
… | |
1160 | <dd> |
1181 | <dd> |
1161 | <p>Simply stops and restarts the periodic watcher again. This is only useful |
1182 | <p>Simply stops and restarts the periodic watcher again. This is only useful |
1162 | when you changed some parameters or the reschedule callback would return |
1183 | when you changed some parameters or the reschedule callback would return |
1163 | a different time than the last time it was called (e.g. in a crond like |
1184 | a different time than the last time it was called (e.g. in a crond like |
1164 | program when the crontabs have changed).</p> |
1185 | program when the crontabs have changed).</p> |
|
|
1186 | </dd> |
|
|
1187 | <dt>ev_tstamp offset [read-write]</dt> |
|
|
1188 | <dd> |
|
|
1189 | <p>When repeating, this contains the offset value, otherwise this is the |
|
|
1190 | absolute point in time (the <code>at</code> value passed to <code>ev_periodic_set</code>).</p> |
|
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1191 | <p>Can be modified any time, but changes only take effect when the periodic |
|
|
1192 | timer fires or <code>ev_periodic_again</code> is being called.</p> |
1165 | </dd> |
1193 | </dd> |
1166 | <dt>ev_tstamp interval [read-write]</dt> |
1194 | <dt>ev_tstamp interval [read-write]</dt> |
1167 | <dd> |
1195 | <dd> |
1168 | <p>The current interval value. Can be modified any time, but changes only |
1196 | <p>The current interval value. Can be modified any time, but changes only |
1169 | take effect when the periodic timer fires or <code>ev_periodic_again</code> is being |
1197 | take effect when the periodic timer fires or <code>ev_periodic_again</code> is being |
… | |
… | |
1468 | are ready to run (it's actually more complicated: it only runs coroutines |
1496 | are ready to run (it's actually more complicated: it only runs coroutines |
1469 | with priority higher than or equal to the event loop and one coroutine |
1497 | with priority higher than or equal to the event loop and one coroutine |
1470 | of lower priority, but only once, using idle watchers to keep the event |
1498 | of lower priority, but only once, using idle watchers to keep the event |
1471 | loop from blocking if lower-priority coroutines are active, thus mapping |
1499 | loop from blocking if lower-priority coroutines are active, thus mapping |
1472 | low-priority coroutines to idle/background tasks).</p> |
1500 | low-priority coroutines to idle/background tasks).</p> |
|
|
1501 | <p>It is recommended to give <code>ev_check</code> watchers highest (<code>EV_MAXPRI</code>) |
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1502 | priority, to ensure that they are being run before any other watchers |
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1503 | after the poll. Also, <code>ev_check</code> watchers (and <code>ev_prepare</code> watchers, |
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|
1504 | too) should not activate ("feed") events into libev. While libev fully |
|
|
1505 | supports this, they will be called before other <code>ev_check</code> watchers did |
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|
1506 | their job. As <code>ev_check</code> watchers are often used to embed other event |
|
|
1507 | loops those other event loops might be in an unusable state until their |
|
|
1508 | <code>ev_check</code> watcher ran (always remind yourself to coexist peacefully with |
|
|
1509 | others).</p> |
1473 | <dl> |
1510 | <dl> |
1474 | <dt>ev_prepare_init (ev_prepare *, callback)</dt> |
1511 | <dt>ev_prepare_init (ev_prepare *, callback)</dt> |
1475 | <dt>ev_check_init (ev_check *, callback)</dt> |
1512 | <dt>ev_check_init (ev_check *, callback)</dt> |
1476 | <dd> |
1513 | <dd> |
1477 | <p>Initialises and configures the prepare or check watcher - they have no |
1514 | <p>Initialises and configures the prepare or check watcher - they have no |
1478 | parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> |
1515 | parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> |
1479 | macros, but using them is utterly, utterly and completely pointless.</p> |
1516 | macros, but using them is utterly, utterly and completely pointless.</p> |
1480 | </dd> |
1517 | </dd> |
1481 | </dl> |
1518 | </dl> |
1482 | <p>Example: To include a library such as adns, you would add IO watchers |
1519 | <p>There are a number of principal ways to embed other event loops or modules |
1483 | and a timeout watcher in a prepare handler, as required by libadns, and |
1520 | into libev. Here are some ideas on how to include libadns into libev |
|
|
1521 | (there is a Perl module named <code>EV::ADNS</code> that does this, which you could |
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|
1522 | use for an actually working example. Another Perl module named <code>EV::Glib</code> |
|
|
1523 | embeds a Glib main context into libev, and finally, <code>Glib::EV</code> embeds EV |
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|
1524 | into the Glib event loop).</p> |
|
|
1525 | <p>Method 1: Add IO watchers and a timeout watcher in a prepare handler, |
1484 | in a check watcher, destroy them and call into libadns. What follows is |
1526 | and in a check watcher, destroy them and call into libadns. What follows |
1485 | pseudo-code only of course:</p> |
1527 | is pseudo-code only of course. This requires you to either use a low |
|
|
1528 | priority for the check watcher or use <code>ev_clear_pending</code> explicitly, as |
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1529 | the callbacks for the IO/timeout watchers might not have been called yet.</p> |
1486 | <pre> static ev_io iow [nfd]; |
1530 | <pre> static ev_io iow [nfd]; |
1487 | static ev_timer tw; |
1531 | static ev_timer tw; |
1488 | |
1532 | |
1489 | static void |
1533 | static void |
1490 | io_cb (ev_loop *loop, ev_io *w, int revents) |
1534 | io_cb (ev_loop *loop, ev_io *w, int revents) |
1491 | { |
1535 | { |
1492 | // set the relevant poll flags |
|
|
1493 | // could also call adns_processreadable etc. here |
|
|
1494 | struct pollfd *fd = (struct pollfd *)w->data; |
|
|
1495 | if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; |
|
|
1496 | if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; |
|
|
1497 | } |
1536 | } |
1498 | |
1537 | |
1499 | // create io watchers for each fd and a timer before blocking |
1538 | // create io watchers for each fd and a timer before blocking |
1500 | static void |
1539 | static void |
1501 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
1540 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
… | |
… | |
1507 | |
1546 | |
1508 | /* the callback is illegal, but won't be called as we stop during check */ |
1547 | /* the callback is illegal, but won't be called as we stop during check */ |
1509 | ev_timer_init (&tw, 0, timeout * 1e-3); |
1548 | ev_timer_init (&tw, 0, timeout * 1e-3); |
1510 | ev_timer_start (loop, &tw); |
1549 | ev_timer_start (loop, &tw); |
1511 | |
1550 | |
1512 | // create on ev_io per pollfd |
1551 | // create one ev_io per pollfd |
1513 | for (int i = 0; i < nfd; ++i) |
1552 | for (int i = 0; i < nfd; ++i) |
1514 | { |
1553 | { |
1515 | ev_io_init (iow + i, io_cb, fds [i].fd, |
1554 | ev_io_init (iow + i, io_cb, fds [i].fd, |
1516 | ((fds [i].events & POLLIN ? EV_READ : 0) |
1555 | ((fds [i].events & POLLIN ? EV_READ : 0) |
1517 | | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
1556 | | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
1518 | |
1557 | |
1519 | fds [i].revents = 0; |
1558 | fds [i].revents = 0; |
1520 | iow [i].data = fds + i; |
|
|
1521 | ev_io_start (loop, iow + i); |
1559 | ev_io_start (loop, iow + i); |
1522 | } |
1560 | } |
1523 | } |
1561 | } |
1524 | |
1562 | |
1525 | // stop all watchers after blocking |
1563 | // stop all watchers after blocking |
… | |
… | |
1527 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
1565 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
1528 | { |
1566 | { |
1529 | ev_timer_stop (loop, &tw); |
1567 | ev_timer_stop (loop, &tw); |
1530 | |
1568 | |
1531 | for (int i = 0; i < nfd; ++i) |
1569 | for (int i = 0; i < nfd; ++i) |
|
|
1570 | { |
|
|
1571 | // set the relevant poll flags |
|
|
1572 | // could also call adns_processreadable etc. here |
|
|
1573 | struct pollfd *fd = fds + i; |
|
|
1574 | int revents = ev_clear_pending (iow + i); |
|
|
1575 | if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; |
|
|
1576 | if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; |
|
|
1577 | |
|
|
1578 | // now stop the watcher |
1532 | ev_io_stop (loop, iow + i); |
1579 | ev_io_stop (loop, iow + i); |
|
|
1580 | } |
1533 | |
1581 | |
1534 | adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
1582 | adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
|
|
1583 | } |
|
|
1584 | |
|
|
1585 | </pre> |
|
|
1586 | <p>Method 2: This would be just like method 1, but you run <code>adns_afterpoll</code> |
|
|
1587 | in the prepare watcher and would dispose of the check watcher.</p> |
|
|
1588 | <p>Method 3: If the module to be embedded supports explicit event |
|
|
1589 | notification (adns does), you can also make use of the actual watcher |
|
|
1590 | callbacks, and only destroy/create the watchers in the prepare watcher.</p> |
|
|
1591 | <pre> static void |
|
|
1592 | timer_cb (EV_P_ ev_timer *w, int revents) |
|
|
1593 | { |
|
|
1594 | adns_state ads = (adns_state)w->data; |
|
|
1595 | update_now (EV_A); |
|
|
1596 | |
|
|
1597 | adns_processtimeouts (ads, &tv_now); |
|
|
1598 | } |
|
|
1599 | |
|
|
1600 | static void |
|
|
1601 | io_cb (EV_P_ ev_io *w, int revents) |
|
|
1602 | { |
|
|
1603 | adns_state ads = (adns_state)w->data; |
|
|
1604 | update_now (EV_A); |
|
|
1605 | |
|
|
1606 | if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now); |
|
|
1607 | if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now); |
|
|
1608 | } |
|
|
1609 | |
|
|
1610 | // do not ever call adns_afterpoll |
|
|
1611 | |
|
|
1612 | </pre> |
|
|
1613 | <p>Method 4: Do not use a prepare or check watcher because the module you |
|
|
1614 | want to embed is too inflexible to support it. Instead, youc na override |
|
|
1615 | their poll function. The drawback with this solution is that the main |
|
|
1616 | loop is now no longer controllable by EV. The <code>Glib::EV</code> module does |
|
|
1617 | this.</p> |
|
|
1618 | <pre> static gint |
|
|
1619 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
|
|
1620 | { |
|
|
1621 | int got_events = 0; |
|
|
1622 | |
|
|
1623 | for (n = 0; n < nfds; ++n) |
|
|
1624 | // create/start io watcher that sets the relevant bits in fds[n] and increment got_events |
|
|
1625 | |
|
|
1626 | if (timeout >= 0) |
|
|
1627 | // create/start timer |
|
|
1628 | |
|
|
1629 | // poll |
|
|
1630 | ev_loop (EV_A_ 0); |
|
|
1631 | |
|
|
1632 | // stop timer again |
|
|
1633 | if (timeout >= 0) |
|
|
1634 | ev_timer_stop (EV_A_ &to); |
|
|
1635 | |
|
|
1636 | // stop io watchers again - their callbacks should have set |
|
|
1637 | for (n = 0; n < nfds; ++n) |
|
|
1638 | ev_io_stop (EV_A_ iow [n]); |
|
|
1639 | |
|
|
1640 | return got_events; |
1535 | } |
1641 | } |
1536 | |
1642 | |
1537 | |
1643 | |
1538 | |
1644 | |
1539 | |
1645 | |
… | |
… | |
1736 | the callback model to a model using method callbacks on objects.</p> |
1842 | the callback model to a model using method callbacks on objects.</p> |
1737 | <p>To use it,</p> |
1843 | <p>To use it,</p> |
1738 | <pre> #include <ev++.h> |
1844 | <pre> #include <ev++.h> |
1739 | |
1845 | |
1740 | </pre> |
1846 | </pre> |
1741 | <p>(it is not installed by default). This automatically includes <cite>ev.h</cite> |
1847 | <p>This automatically includes <cite>ev.h</cite> and puts all of its definitions (many |
1742 | and puts all of its definitions (many of them macros) into the global |
1848 | of them macros) into the global namespace. All C++ specific things are |
1743 | namespace. All C++ specific things are put into the <code>ev</code> namespace.</p> |
1849 | put into the <code>ev</code> namespace. It should support all the same embedding |
1744 | <p>It should support all the same embedding options as <cite>ev.h</cite>, most notably |
1850 | options as <cite>ev.h</cite>, most notably <code>EV_MULTIPLICITY</code>.</p> |
1745 | <code>EV_MULTIPLICITY</code>.</p> |
1851 | <p>Care has been taken to keep the overhead low. The only data member the C++ |
|
|
1852 | classes add (compared to plain C-style watchers) is the event loop pointer |
|
|
1853 | that the watcher is associated with (or no additional members at all if |
|
|
1854 | you disable <code>EV_MULTIPLICITY</code> when embedding libev).</p> |
|
|
1855 | <p>Currently, functions, and static and non-static member functions can be |
|
|
1856 | used as callbacks. Other types should be easy to add as long as they only |
|
|
1857 | need one additional pointer for context. If you need support for other |
|
|
1858 | types of functors please contact the author (preferably after implementing |
|
|
1859 | it).</p> |
1746 | <p>Here is a list of things available in the <code>ev</code> namespace:</p> |
1860 | <p>Here is a list of things available in the <code>ev</code> namespace:</p> |
1747 | <dl> |
1861 | <dl> |
1748 | <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt> |
1862 | <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt> |
1749 | <dd> |
1863 | <dd> |
1750 | <p>These are just enum values with the same values as the <code>EV_READ</code> etc. |
1864 | <p>These are just enum values with the same values as the <code>EV_READ</code> etc. |
… | |
… | |
1761 | which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro |
1875 | which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro |
1762 | defines by many implementations.</p> |
1876 | defines by many implementations.</p> |
1763 | <p>All of those classes have these methods:</p> |
1877 | <p>All of those classes have these methods:</p> |
1764 | <p> |
1878 | <p> |
1765 | <dl> |
1879 | <dl> |
1766 | <dt>ev::TYPE::TYPE (object *, object::method *)</dt> |
1880 | <dt>ev::TYPE::TYPE ()</dt> |
1767 | <dt>ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)</dt> |
1881 | <dt>ev::TYPE::TYPE (struct ev_loop *)</dt> |
1768 | <dt>ev::TYPE::~TYPE</dt> |
1882 | <dt>ev::TYPE::~TYPE</dt> |
1769 | <dd> |
1883 | <dd> |
1770 | <p>The constructor takes a pointer to an object and a method pointer to |
1884 | <p>The constructor (optionally) takes an event loop to associate the watcher |
1771 | the event handler callback to call in this class. The constructor calls |
1885 | with. If it is omitted, it will use <code>EV_DEFAULT</code>.</p> |
1772 | <code>ev_init</code> for you, which means you have to call the <code>set</code> method |
1886 | <p>The constructor calls <code>ev_init</code> for you, which means you have to call the |
1773 | before starting it. If you do not specify a loop then the constructor |
1887 | <code>set</code> method before starting it.</p> |
1774 | automatically associates the default loop with this watcher.</p> |
1888 | <p>It will not set a callback, however: You have to call the templated <code>set</code> |
|
|
1889 | method to set a callback before you can start the watcher.</p> |
|
|
1890 | <p>(The reason why you have to use a method is a limitation in C++ which does |
|
|
1891 | not allow explicit template arguments for constructors).</p> |
1775 | <p>The destructor automatically stops the watcher if it is active.</p> |
1892 | <p>The destructor automatically stops the watcher if it is active.</p> |
|
|
1893 | </dd> |
|
|
1894 | <dt>w->set<class, &class::method> (object *)</dt> |
|
|
1895 | <dd> |
|
|
1896 | <p>This method sets the callback method to call. The method has to have a |
|
|
1897 | signature of <code>void (*)(ev_TYPE &, int)</code>, it receives the watcher as |
|
|
1898 | first argument and the <code>revents</code> as second. The object must be given as |
|
|
1899 | parameter and is stored in the <code>data</code> member of the watcher.</p> |
|
|
1900 | <p>This method synthesizes efficient thunking code to call your method from |
|
|
1901 | the C callback that libev requires. If your compiler can inline your |
|
|
1902 | callback (i.e. it is visible to it at the place of the <code>set</code> call and |
|
|
1903 | your compiler is good :), then the method will be fully inlined into the |
|
|
1904 | thunking function, making it as fast as a direct C callback.</p> |
|
|
1905 | <p>Example: simple class declaration and watcher initialisation</p> |
|
|
1906 | <pre> struct myclass |
|
|
1907 | { |
|
|
1908 | void io_cb (ev::io &w, int revents) { } |
|
|
1909 | } |
|
|
1910 | |
|
|
1911 | myclass obj; |
|
|
1912 | ev::io iow; |
|
|
1913 | iow.set <myclass, &myclass::io_cb> (&obj); |
|
|
1914 | |
|
|
1915 | </pre> |
|
|
1916 | </dd> |
|
|
1917 | <dt>w->set<function> (void *data = 0)</dt> |
|
|
1918 | <dd> |
|
|
1919 | <p>Also sets a callback, but uses a static method or plain function as |
|
|
1920 | callback. The optional <code>data</code> argument will be stored in the watcher's |
|
|
1921 | <code>data</code> member and is free for you to use.</p> |
|
|
1922 | <p>The prototype of the <code>function</code> must be <code>void (*)(ev::TYPE &w, int)</code>.</p> |
|
|
1923 | <p>See the method-<code>set</code> above for more details.</p> |
|
|
1924 | <p>Example:</p> |
|
|
1925 | <pre> static void io_cb (ev::io &w, int revents) { } |
|
|
1926 | iow.set <io_cb> (); |
|
|
1927 | |
|
|
1928 | </pre> |
1776 | </dd> |
1929 | </dd> |
1777 | <dt>w->set (struct ev_loop *)</dt> |
1930 | <dt>w->set (struct ev_loop *)</dt> |
1778 | <dd> |
1931 | <dd> |
1779 | <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only |
1932 | <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only |
1780 | do this when the watcher is inactive (and not pending either).</p> |
1933 | do this when the watcher is inactive (and not pending either).</p> |
1781 | </dd> |
1934 | </dd> |
1782 | <dt>w->set ([args])</dt> |
1935 | <dt>w->set ([args])</dt> |
1783 | <dd> |
1936 | <dd> |
1784 | <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be |
1937 | <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be |
1785 | called at least once. Unlike the C counterpart, an active watcher gets |
1938 | called at least once. Unlike the C counterpart, an active watcher gets |
1786 | automatically stopped and restarted.</p> |
1939 | automatically stopped and restarted when reconfiguring it with this |
|
|
1940 | method.</p> |
1787 | </dd> |
1941 | </dd> |
1788 | <dt>w->start ()</dt> |
1942 | <dt>w->start ()</dt> |
1789 | <dd> |
1943 | <dd> |
1790 | <p>Starts the watcher. Note that there is no <code>loop</code> argument as the |
1944 | <p>Starts the watcher. Note that there is no <code>loop</code> argument, as the |
1791 | constructor already takes the loop.</p> |
1945 | constructor already stores the event loop.</p> |
1792 | </dd> |
1946 | </dd> |
1793 | <dt>w->stop ()</dt> |
1947 | <dt>w->stop ()</dt> |
1794 | <dd> |
1948 | <dd> |
1795 | <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p> |
1949 | <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p> |
1796 | </dd> |
1950 | </dd> |
… | |
… | |
1820 | |
1974 | |
1821 | myclass (); |
1975 | myclass (); |
1822 | } |
1976 | } |
1823 | |
1977 | |
1824 | myclass::myclass (int fd) |
1978 | myclass::myclass (int fd) |
1825 | : io (this, &myclass::io_cb), |
|
|
1826 | idle (this, &myclass::idle_cb) |
|
|
1827 | { |
1979 | { |
|
|
1980 | io .set <myclass, &myclass::io_cb > (this); |
|
|
1981 | idle.set <myclass, &myclass::idle_cb> (this); |
|
|
1982 | |
1828 | io.start (fd, ev::READ); |
1983 | io.start (fd, ev::READ); |
1829 | } |
1984 | } |
1830 | |
1985 | |
1831 | |
1986 | |
1832 | |
1987 | |
… | |
… | |
2239 | <h1 id="COMPLEXITIES">COMPLEXITIES</h1> |
2394 | <h1 id="COMPLEXITIES">COMPLEXITIES</h1> |
2240 | <div id="COMPLEXITIES_CONTENT"> |
2395 | <div id="COMPLEXITIES_CONTENT"> |
2241 | <p>In this section the complexities of (many of) the algorithms used inside |
2396 | <p>In this section the complexities of (many of) the algorithms used inside |
2242 | libev will be explained. For complexity discussions about backends see the |
2397 | libev will be explained. For complexity discussions about backends see the |
2243 | documentation for <code>ev_default_init</code>.</p> |
2398 | documentation for <code>ev_default_init</code>.</p> |
|
|
2399 | <p>All of the following are about amortised time: If an array needs to be |
|
|
2400 | extended, libev needs to realloc and move the whole array, but this |
|
|
2401 | happens asymptotically never with higher number of elements, so O(1) might |
|
|
2402 | mean it might do a lengthy realloc operation in rare cases, but on average |
|
|
2403 | it is much faster and asymptotically approaches constant time.</p> |
2244 | <p> |
2404 | <p> |
2245 | <dl> |
2405 | <dl> |
2246 | <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> |
2406 | <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> |
2247 | <dd> |
2407 | <dd> |
2248 | <p>This means that, when you have a watcher that triggers in one hour and |
2408 | <p>This means that, when you have a watcher that triggers in one hour and |
… | |
… | |
2254 | <p>That means that for changing a timer costs less than removing/adding them |
2414 | <p>That means that for changing a timer costs less than removing/adding them |
2255 | as only the relative motion in the event queue has to be paid for.</p> |
2415 | as only the relative motion in the event queue has to be paid for.</p> |
2256 | </dd> |
2416 | </dd> |
2257 | <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> |
2417 | <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> |
2258 | <dd> |
2418 | <dd> |
2259 | <p>These just add the watcher into an array or at the head of a list. If |
2419 | <p>These just add the watcher into an array or at the head of a list. |
2260 | the array needs to be extended libev needs to realloc and move the whole |
|
|
2261 | array, but this happen asymptotically less and less with more watchers, |
|
|
2262 | thus amortised O(1).</p> |
|
|
2263 | </dd> |
|
|
2264 | <dt>Stopping check/prepare/idle watchers: O(1)</dt> |
2420 | =item Stopping check/prepare/idle watchers: O(1)</p> |
|
|
2421 | </dd> |
2265 | <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt> |
2422 | <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt> |
2266 | <dd> |
2423 | <dd> |
2267 | <p>These watchers are stored in lists then need to be walked to find the |
2424 | <p>These watchers are stored in lists then need to be walked to find the |
2268 | correct watcher to remove. The lists are usually short (you don't usually |
2425 | correct watcher to remove. The lists are usually short (you don't usually |
2269 | have many watchers waiting for the same fd or signal).</p> |
2426 | have many watchers waiting for the same fd or signal).</p> |