… | |
… | |
117 | |
117 | |
118 | =item int ev_version_major () |
118 | =item int ev_version_major () |
119 | |
119 | |
120 | =item int ev_version_minor () |
120 | =item int ev_version_minor () |
121 | |
121 | |
122 | You can find out the major and minor version numbers of the library |
122 | You can find out the major and minor ABI version numbers of the library |
123 | you linked against by calling the functions C<ev_version_major> and |
123 | you linked against by calling the functions C<ev_version_major> and |
124 | C<ev_version_minor>. If you want, you can compare against the global |
124 | C<ev_version_minor>. If you want, you can compare against the global |
125 | symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the |
125 | symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the |
126 | version of the library your program was compiled against. |
126 | version of the library your program was compiled against. |
127 | |
127 | |
|
|
128 | These version numbers refer to the ABI version of the library, not the |
|
|
129 | release version. |
|
|
130 | |
128 | Usually, it's a good idea to terminate if the major versions mismatch, |
131 | Usually, it's a good idea to terminate if the major versions mismatch, |
129 | as this indicates an incompatible change. Minor versions are usually |
132 | as this indicates an incompatible change. Minor versions are usually |
130 | compatible to older versions, so a larger minor version alone is usually |
133 | compatible to older versions, so a larger minor version alone is usually |
131 | not a problem. |
134 | not a problem. |
132 | |
135 | |
133 | Example: Make sure we haven't accidentally been linked against the wrong |
136 | Example: Make sure we haven't accidentally been linked against the wrong |
134 | version. |
137 | version. |
… | |
… | |
486 | libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is |
489 | libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is |
487 | usually a better approach for this kind of thing. |
490 | usually a better approach for this kind of thing. |
488 | |
491 | |
489 | Here are the gory details of what C<ev_loop> does: |
492 | Here are the gory details of what C<ev_loop> does: |
490 | |
493 | |
|
|
494 | - Before the first iteration, call any pending watchers. |
491 | * If there are no active watchers (reference count is zero), return. |
495 | * If there are no active watchers (reference count is zero), return. |
492 | - Queue prepare watchers and then call all outstanding watchers. |
496 | - Queue all prepare watchers and then call all outstanding watchers. |
493 | - If we have been forked, recreate the kernel state. |
497 | - If we have been forked, recreate the kernel state. |
494 | - Update the kernel state with all outstanding changes. |
498 | - Update the kernel state with all outstanding changes. |
495 | - Update the "event loop time". |
499 | - Update the "event loop time". |
496 | - Calculate for how long to block. |
500 | - Calculate for how long to block. |
497 | - Block the process, waiting for any events. |
501 | - Block the process, waiting for any events. |
… | |
… | |
907 | play around with an Xlib connection), then you have to seperately re-test |
911 | play around with an Xlib connection), then you have to seperately re-test |
908 | whether a file descriptor is really ready with a known-to-be good interface |
912 | whether a file descriptor is really ready with a known-to-be good interface |
909 | such as poll (fortunately in our Xlib example, Xlib already does this on |
913 | such as poll (fortunately in our Xlib example, Xlib already does this on |
910 | its own, so its quite safe to use). |
914 | its own, so its quite safe to use). |
911 | |
915 | |
|
|
916 | =head3 The special problem of disappearing file descriptors |
|
|
917 | |
|
|
918 | Some backends (e.g kqueue, epoll) need to be told about closing a file |
|
|
919 | descriptor (either by calling C<close> explicitly or by any other means, |
|
|
920 | such as C<dup>). The reason is that you register interest in some file |
|
|
921 | descriptor, but when it goes away, the operating system will silently drop |
|
|
922 | this interest. If another file descriptor with the same number then is |
|
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923 | registered with libev, there is no efficient way to see that this is, in |
|
|
924 | fact, a different file descriptor. |
|
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925 | |
|
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926 | To avoid having to explicitly tell libev about such cases, libev follows |
|
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927 | the following policy: Each time C<ev_io_set> is being called, libev |
|
|
928 | will assume that this is potentially a new file descriptor, otherwise |
|
|
929 | it is assumed that the file descriptor stays the same. That means that |
|
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930 | you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the |
|
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931 | descriptor even if the file descriptor number itself did not change. |
|
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932 | |
|
|
933 | This is how one would do it normally anyway, the important point is that |
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934 | the libev application should not optimise around libev but should leave |
|
|
935 | optimisations to libev. |
|
|
936 | |
|
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937 | |
912 | =over 4 |
938 | =over 4 |
913 | |
939 | |
914 | =item ev_io_init (ev_io *, callback, int fd, int events) |
940 | =item ev_io_init (ev_io *, callback, int fd, int events) |
915 | |
941 | |
916 | =item ev_io_set (ev_io *, int fd, int events) |
942 | =item ev_io_set (ev_io *, int fd, int events) |
… | |
… | |
1073 | 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 |
1074 | 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 |
1075 | periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now () |
1101 | periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now () |
1076 | + 10.>) and then reset your system clock to the last year, then it will |
1102 | + 10.>) and then reset your system clock to the last year, then it will |
1077 | take a year to trigger the event (unlike an C<ev_timer>, which would trigger |
1103 | take a year to trigger the event (unlike an C<ev_timer>, which would trigger |
1078 | roughly 10 seconds later and of course not if you reset your system time |
1104 | roughly 10 seconds later). |
1079 | again). |
|
|
1080 | |
1105 | |
1081 | They can also be used to implement vastly more complex timers, such as |
1106 | They can also be used to implement vastly more complex timers, such as |
1082 | triggering an event on eahc midnight, local time. |
1107 | triggering an event on each midnight, local time or other, complicated, |
|
|
1108 | rules. |
1083 | |
1109 | |
1084 | As with timers, the callback is guarenteed to be invoked only when the |
1110 | As with timers, the callback is guarenteed to be invoked only when the |
1085 | time (C<at>) has been passed, but if multiple periodic timers become ready |
1111 | time (C<at>) has been passed, but if multiple periodic timers become ready |
1086 | during the same loop iteration then order of execution is undefined. |
1112 | during the same loop iteration then order of execution is undefined. |
1087 | |
1113 | |
… | |
… | |
1094 | Lots of arguments, lets sort it out... There are basically three modes of |
1120 | Lots of arguments, lets sort it out... There are basically three modes of |
1095 | operation, and we will explain them from simplest to complex: |
1121 | operation, and we will explain them from simplest to complex: |
1096 | |
1122 | |
1097 | =over 4 |
1123 | =over 4 |
1098 | |
1124 | |
1099 | =item * absolute timer (interval = reschedule_cb = 0) |
1125 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
1100 | |
1126 | |
1101 | In this configuration the watcher triggers an event at the wallclock time |
1127 | In this configuration the watcher triggers an event at the wallclock time |
1102 | C<at> and doesn't repeat. It will not adjust when a time jump occurs, |
1128 | C<at> and doesn't repeat. It will not adjust when a time jump occurs, |
1103 | that is, if it is to be run at January 1st 2011 then it will run when the |
1129 | that is, if it is to be run at January 1st 2011 then it will run when the |
1104 | system time reaches or surpasses this time. |
1130 | system time reaches or surpasses this time. |
1105 | |
1131 | |
1106 | =item * non-repeating interval timer (interval > 0, reschedule_cb = 0) |
1132 | =item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1107 | |
1133 | |
1108 | In this mode the watcher will always be scheduled to time out at the next |
1134 | In this mode the watcher will always be scheduled to time out at the next |
1109 | C<at + N * interval> time (for some integer N) and then repeat, regardless |
1135 | C<at + N * interval> time (for some integer N, which can also be negative) |
1110 | of any time jumps. |
1136 | and then repeat, regardless of any time jumps. |
1111 | |
1137 | |
1112 | This can be used to create timers that do not drift with respect to system |
1138 | This can be used to create timers that do not drift with respect to system |
1113 | time: |
1139 | time: |
1114 | |
1140 | |
1115 | ev_periodic_set (&periodic, 0., 3600., 0); |
1141 | ev_periodic_set (&periodic, 0., 3600., 0); |
… | |
… | |
1121 | |
1147 | |
1122 | Another way to think about it (for the mathematically inclined) is that |
1148 | Another way to think about it (for the mathematically inclined) is that |
1123 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1149 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1124 | time where C<time = at (mod interval)>, regardless of any time jumps. |
1150 | time where C<time = at (mod interval)>, regardless of any time jumps. |
1125 | |
1151 | |
|
|
1152 | For numerical stability it is preferable that the C<at> value is near |
|
|
1153 | C<ev_now ()> (the current time), but there is no range requirement for |
|
|
1154 | this value. |
|
|
1155 | |
1126 | =item * manual reschedule mode (reschedule_cb = callback) |
1156 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
1127 | |
1157 | |
1128 | In this mode the values for C<interval> and C<at> are both being |
1158 | In this mode the values for C<interval> and C<at> are both being |
1129 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1159 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1130 | reschedule callback will be called with the watcher as first, and the |
1160 | reschedule callback will be called with the watcher as first, and the |
1131 | current time as second argument. |
1161 | current time as second argument. |
1132 | |
1162 | |
1133 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
1163 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
1134 | ever, or make any event loop modifications>. If you need to stop it, |
1164 | ever, or make any event loop modifications>. If you need to stop it, |
1135 | return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by |
1165 | return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by |
1136 | starting a prepare watcher). |
1166 | starting an C<ev_prepare> watcher, which is legal). |
1137 | |
1167 | |
1138 | Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w, |
1168 | Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w, |
1139 | ev_tstamp now)>, e.g.: |
1169 | ev_tstamp now)>, e.g.: |
1140 | |
1170 | |
1141 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1171 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
… | |
… | |
1163 | |
1193 | |
1164 | Simply stops and restarts the periodic watcher again. This is only useful |
1194 | Simply stops and restarts the periodic watcher again. This is only useful |
1165 | when you changed some parameters or the reschedule callback would return |
1195 | when you changed some parameters or the reschedule callback would return |
1166 | a different time than the last time it was called (e.g. in a crond like |
1196 | a different time than the last time it was called (e.g. in a crond like |
1167 | program when the crontabs have changed). |
1197 | program when the crontabs have changed). |
|
|
1198 | |
|
|
1199 | =item ev_tstamp offset [read-write] |
|
|
1200 | |
|
|
1201 | When repeating, this contains the offset value, otherwise this is the |
|
|
1202 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
|
|
1203 | |
|
|
1204 | Can be modified any time, but changes only take effect when the periodic |
|
|
1205 | timer fires or C<ev_periodic_again> is being called. |
1168 | |
1206 | |
1169 | =item ev_tstamp interval [read-write] |
1207 | =item ev_tstamp interval [read-write] |
1170 | |
1208 | |
1171 | The current interval value. Can be modified any time, but changes only |
1209 | The current interval value. Can be modified any time, but changes only |
1172 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
1210 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
… | |
… | |
1481 | with priority higher than or equal to the event loop and one coroutine |
1519 | with priority higher than or equal to the event loop and one coroutine |
1482 | of lower priority, but only once, using idle watchers to keep the event |
1520 | of lower priority, but only once, using idle watchers to keep the event |
1483 | loop from blocking if lower-priority coroutines are active, thus mapping |
1521 | loop from blocking if lower-priority coroutines are active, thus mapping |
1484 | low-priority coroutines to idle/background tasks). |
1522 | low-priority coroutines to idle/background tasks). |
1485 | |
1523 | |
|
|
1524 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
|
|
1525 | priority, to ensure that they are being run before any other watchers |
|
|
1526 | after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, |
|
|
1527 | too) should not activate ("feed") events into libev. While libev fully |
|
|
1528 | supports this, they will be called before other C<ev_check> watchers did |
|
|
1529 | their job. As C<ev_check> watchers are often used to embed other event |
|
|
1530 | loops those other event loops might be in an unusable state until their |
|
|
1531 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
|
|
1532 | others). |
|
|
1533 | |
1486 | =over 4 |
1534 | =over 4 |
1487 | |
1535 | |
1488 | =item ev_prepare_init (ev_prepare *, callback) |
1536 | =item ev_prepare_init (ev_prepare *, callback) |
1489 | |
1537 | |
1490 | =item ev_check_init (ev_check *, callback) |
1538 | =item ev_check_init (ev_check *, callback) |