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… | |
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 | |
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128 | These version numbers refer to the ABI version of the library, not the |
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129 | release version. |
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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. |
… | |
… | |
908 | 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 |
909 | 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 |
910 | 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 |
911 | its own, so its quite safe to use). |
914 | its own, so its quite safe to use). |
912 | |
915 | |
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916 | =head3 The special problem of disappearing file descriptors |
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917 | |
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918 | Some backends (e.g kqueue, epoll) need to be told about closing a file |
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919 | descriptor (either by calling C<close> explicitly or by any other means, |
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920 | such as C<dup>). The reason is that you register interest in some file |
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921 | descriptor, but when it goes away, the operating system will silently drop |
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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 |
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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 |
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928 | will assume that this is potentially a new file descriptor, otherwise |
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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 | |
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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 |
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935 | optimisations to libev. |
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936 | |
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937 | |
913 | =over 4 |
938 | =over 4 |
914 | |
939 | |
915 | =item ev_io_init (ev_io *, callback, int fd, int events) |
940 | =item ev_io_init (ev_io *, callback, int fd, int events) |
916 | |
941 | |
917 | =item ev_io_set (ev_io *, int fd, int events) |
942 | =item ev_io_set (ev_io *, int fd, int events) |
… | |
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1074 | 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 |
1075 | 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 |
1076 | 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 () |
1077 | + 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 |
1078 | 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 |
1079 | roughly 10 seconds later and of course not if you reset your system time |
1104 | roughly 10 seconds later). |
1080 | again). |
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1081 | |
1105 | |
1082 | 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 |
1083 | triggering an event on eahc midnight, local time. |
1107 | triggering an event on each midnight, local time or other, complicated, |
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1108 | rules. |
1084 | |
1109 | |
1085 | 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 |
1086 | 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 |
1087 | during the same loop iteration then order of execution is undefined. |
1112 | during the same loop iteration then order of execution is undefined. |
1088 | |
1113 | |
… | |
… | |
1095 | 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 |
1096 | operation, and we will explain them from simplest to complex: |
1121 | operation, and we will explain them from simplest to complex: |
1097 | |
1122 | |
1098 | =over 4 |
1123 | =over 4 |
1099 | |
1124 | |
1100 | =item * absolute timer (interval = reschedule_cb = 0) |
1125 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
1101 | |
1126 | |
1102 | 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 |
1103 | 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, |
1104 | 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 |
1105 | system time reaches or surpasses this time. |
1130 | system time reaches or surpasses this time. |
1106 | |
1131 | |
1107 | =item * non-repeating interval timer (interval > 0, reschedule_cb = 0) |
1132 | =item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1108 | |
1133 | |
1109 | 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 |
1110 | 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) |
1111 | of any time jumps. |
1136 | and then repeat, regardless of any time jumps. |
1112 | |
1137 | |
1113 | 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 |
1114 | time: |
1139 | time: |
1115 | |
1140 | |
1116 | ev_periodic_set (&periodic, 0., 3600., 0); |
1141 | ev_periodic_set (&periodic, 0., 3600., 0); |
… | |
… | |
1122 | |
1147 | |
1123 | 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 |
1124 | 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 |
1125 | 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. |
1126 | |
1151 | |
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1152 | For numerical stability it is preferable that the C<at> value is near |
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1153 | C<ev_now ()> (the current time), but there is no range requirement for |
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1154 | this value. |
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1155 | |
1127 | =item * manual reschedule mode (reschedule_cb = callback) |
1156 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
1128 | |
1157 | |
1129 | 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 |
1130 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1159 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1131 | 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 |
1132 | current time as second argument. |
1161 | current time as second argument. |
1133 | |
1162 | |
1134 | 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, |
1135 | 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, |
1136 | 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 |
1137 | starting a prepare watcher). |
1166 | starting an C<ev_prepare> watcher, which is legal). |
1138 | |
1167 | |
1139 | 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, |
1140 | ev_tstamp now)>, e.g.: |
1169 | ev_tstamp now)>, e.g.: |
1141 | |
1170 | |
1142 | 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) |
… | |
… | |
1164 | |
1193 | |
1165 | 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 |
1166 | when you changed some parameters or the reschedule callback would return |
1195 | when you changed some parameters or the reschedule callback would return |
1167 | 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 |
1168 | program when the crontabs have changed). |
1197 | program when the crontabs have changed). |
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1198 | |
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1199 | =item ev_tstamp offset [read-write] |
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1200 | |
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1201 | When repeating, this contains the offset value, otherwise this is the |
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1202 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
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1203 | |
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1204 | Can be modified any time, but changes only take effect when the periodic |
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1205 | timer fires or C<ev_periodic_again> is being called. |
1169 | |
1206 | |
1170 | =item ev_tstamp interval [read-write] |
1207 | =item ev_tstamp interval [read-write] |
1171 | |
1208 | |
1172 | 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 |
1173 | 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 |