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Revision 1.43 by root, Sat Dec 8 14:27:38 2007 UTC vs.
Revision 1.50 by root, Wed Dec 12 17:55:05 2007 UTC

… …
127.\} 127.\}
128.rm #[ #] #H #V #F C 128.rm #[ #] #H #V #F C
129.\" ======================================================================== 129.\" ========================================================================
130.\" 130.\"
131.IX Title ""<STANDARD INPUT>" 1" 131.IX Title ""<STANDARD INPUT>" 1"
132.TH "<STANDARD INPUT>" 1 "2007-12-08" "perl v5.8.8" "User Contributed Perl Documentation" 132.TH "<STANDARD INPUT>" 1 "2007-12-12" "perl v5.8.8" "User Contributed Perl Documentation"
133.SH "NAME" 133.SH "NAME"
134libev \- a high performance full\-featured event loop written in C 134libev \- a high performance full\-featured event loop written in C
135.SH "SYNOPSIS" 135.SH "SYNOPSIS"
136.IX Header "SYNOPSIS" 136.IX Header "SYNOPSIS"
137.Vb 1 137.Vb 1
… …
259.IX Item "int ev_version_major ()" 259.IX Item "int ev_version_major ()"
260.PD 0 260.PD 0
261.IP "int ev_version_minor ()" 4 261.IP "int ev_version_minor ()" 4
262.IX Item "int ev_version_minor ()" 262.IX Item "int ev_version_minor ()"
263.PD 263.PD
264You can find out the major and minor version numbers of the library 264You can find out the major and minor \s-1ABI\s0 version numbers of the library
265you linked against by calling the functions \f(CW\*(C`ev_version_major\*(C'\fR and 265you linked against by calling the functions \f(CW\*(C`ev_version_major\*(C'\fR and
266\&\f(CW\*(C`ev_version_minor\*(C'\fR. If you want, you can compare against the global 266\&\f(CW\*(C`ev_version_minor\*(C'\fR. If you want, you can compare against the global
267symbols \f(CW\*(C`EV_VERSION_MAJOR\*(C'\fR and \f(CW\*(C`EV_VERSION_MINOR\*(C'\fR, which specify the 267symbols \f(CW\*(C`EV_VERSION_MAJOR\*(C'\fR and \f(CW\*(C`EV_VERSION_MINOR\*(C'\fR, which specify the
268version of the library your program was compiled against. 268version of the library your program was compiled against.
269.Sp 269.Sp
270These version numbers refer to the \s-1ABI\s0 version of the library, not the
271release version.
272.Sp
270Usually, it's a good idea to terminate if the major versions mismatch, 273Usually, it's a good idea to terminate if the major versions mismatch,
271as this indicates an incompatible change. Minor versions are usually 274as this indicates an incompatible change. Minor versions are usually
272compatible to older versions, so a larger minor version alone is usually 275compatible to older versions, so a larger minor version alone is usually
273not a problem. 276not a problem.
274.Sp 277.Sp
275Example: Make sure we haven't accidentally been linked against the wrong 278Example: Make sure we haven't accidentally been linked against the wrong
276version. 279version.
… …
634libev watchers. However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is 637libev watchers. However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is
635usually a better approach for this kind of thing. 638usually a better approach for this kind of thing.
636.Sp 639.Sp
637Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does: 640Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does:
638.Sp 641.Sp
639.Vb 18 642.Vb 19
643\& - Before the first iteration, call any pending watchers.
640\& * If there are no active watchers (reference count is zero), return. 644\& * If there are no active watchers (reference count is zero), return.
641\& - Queue prepare watchers and then call all outstanding watchers. 645\& - Queue all prepare watchers and then call all outstanding watchers.
642\& - If we have been forked, recreate the kernel state. 646\& - If we have been forked, recreate the kernel state.
643\& - Update the kernel state with all outstanding changes. 647\& - Update the kernel state with all outstanding changes.
644\& - Update the "event loop time". 648\& - Update the "event loop time".
645\& - Calculate for how long to block. 649\& - Calculate for how long to block.
646\& - Block the process, waiting for any events. 650\& - Block the process, waiting for any events.
… …
1061If you cannot run the fd in non-blocking mode (for example you should not 1065If you cannot run the fd in non-blocking mode (for example you should not
1062play around with an Xlib connection), then you have to seperately re-test 1066play around with an Xlib connection), then you have to seperately re-test
1063whether a file descriptor is really ready with a known-to-be good interface 1067whether a file descriptor is really ready with a known-to-be good interface
1064such as poll (fortunately in our Xlib example, Xlib already does this on 1068such as poll (fortunately in our Xlib example, Xlib already does this on
1065its own, so its quite safe to use). 1069its own, so its quite safe to use).
1070.PP
1071\fIThe special problem of disappearing file descriptors\fR
1072.IX Subsection "The special problem of disappearing file descriptors"
1073.PP
1074Some backends (e.g kqueue, epoll) need to be told about closing a file
1075descriptor (either by calling \f(CW\*(C`close\*(C'\fR explicitly or by any other means,
1076such as \f(CW\*(C`dup\*(C'\fR). The reason is that you register interest in some file
1077descriptor, but when it goes away, the operating system will silently drop
1078this interest. If another file descriptor with the same number then is
1079registered with libev, there is no efficient way to see that this is, in
1080fact, a different file descriptor.
1081.PP
1082To avoid having to explicitly tell libev about such cases, libev follows
1083the following policy: Each time \f(CW\*(C`ev_io_set\*(C'\fR is being called, libev
1084will assume that this is potentially a new file descriptor, otherwise
1085it is assumed that the file descriptor stays the same. That means that
1086you \fIhave\fR to call \f(CW\*(C`ev_io_set\*(C'\fR (or \f(CW\*(C`ev_io_init\*(C'\fR) when you change the
1087descriptor even if the file descriptor number itself did not change.
1088.PP
1089This is how one would do it normally anyway, the important point is that
1090the libev application should not optimise around libev but should leave
1091optimisations to libev.
1092.PP
1093\fIWatcher-Specific Functions\fR
1094.IX Subsection "Watcher-Specific Functions"
1066.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4 1095.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4
1067.IX Item "ev_io_init (ev_io *, callback, int fd, int events)" 1096.IX Item "ev_io_init (ev_io *, callback, int fd, int events)"
1068.PD 0 1097.PD 0
1069.IP "ev_io_set (ev_io *, int fd, int events)" 4 1098.IP "ev_io_set (ev_io *, int fd, int events)" 4
1070.IX Item "ev_io_set (ev_io *, int fd, int events)" 1099.IX Item "ev_io_set (ev_io *, int fd, int events)"
… …
1123.Ve 1152.Ve
1124.PP 1153.PP
1125The callback is guarenteed to be invoked only when its timeout has passed, 1154The callback is guarenteed to be invoked only when its timeout has passed,
1126but if multiple timers become ready during the same loop iteration then 1155but if multiple timers become ready during the same loop iteration then
1127order of execution is undefined. 1156order of execution is undefined.
1157.PP
1158\fIWatcher-Specific Functions and Data Members\fR
1159.IX Subsection "Watcher-Specific Functions and Data Members"
1128.IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4 1160.IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4
1129.IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 1161.IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)"
1130.PD 0 1162.PD 0
1131.IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4 1163.IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4
1132.IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 1164.IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)"
… …
1234but on wallclock time (absolute time). You can tell a periodic watcher 1266but on wallclock time (absolute time). You can tell a periodic watcher
1235to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a 1267to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a
1236periodic watcher to trigger in 10 seconds (by specifiying e.g. \f(CW\*(C`ev_now () 1268periodic watcher to trigger in 10 seconds (by specifiying e.g. \f(CW\*(C`ev_now ()
1237+ 10.\*(C'\fR) and then reset your system clock to the last year, then it will 1269+ 10.\*(C'\fR) and then reset your system clock to the last year, then it will
1238take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger 1270take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger
1239roughly 10 seconds later and of course not if you reset your system time 1271roughly 10 seconds later).
1240again).
1241.PP 1272.PP
1242They can also be used to implement vastly more complex timers, such as 1273They can also be used to implement vastly more complex timers, such as
1243triggering an event on eahc midnight, local time. 1274triggering an event on each midnight, local time or other, complicated,
1275rules.
1244.PP 1276.PP
1245As with timers, the callback is guarenteed to be invoked only when the 1277As with timers, the callback is guarenteed to be invoked only when the
1246time (\f(CW\*(C`at\*(C'\fR) has been passed, but if multiple periodic timers become ready 1278time (\f(CW\*(C`at\*(C'\fR) has been passed, but if multiple periodic timers become ready
1247during the same loop iteration then order of execution is undefined. 1279during the same loop iteration then order of execution is undefined.
1280.PP
1281\fIWatcher-Specific Functions and Data Members\fR
1282.IX Subsection "Watcher-Specific Functions and Data Members"
1248.IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4 1283.IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4
1249.IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 1284.IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)"
1250.PD 0 1285.PD 0
1251.IP "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 4 1286.IP "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 4
1252.IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 1287.IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)"
1253.PD 1288.PD
1254Lots of arguments, lets sort it out... There are basically three modes of 1289Lots of arguments, lets sort it out... There are basically three modes of
1255operation, and we will explain them from simplest to complex: 1290operation, and we will explain them from simplest to complex:
1256.RS 4 1291.RS 4
1257.IP "* absolute timer (interval = reschedule_cb = 0)" 4 1292.IP "* absolute timer (at = time, interval = reschedule_cb = 0)" 4
1258.IX Item "absolute timer (interval = reschedule_cb = 0)" 1293.IX Item "absolute timer (at = time, interval = reschedule_cb = 0)"
1259In this configuration the watcher triggers an event at the wallclock time 1294In this configuration the watcher triggers an event at the wallclock time
1260\&\f(CW\*(C`at\*(C'\fR and doesn't repeat. It will not adjust when a time jump occurs, 1295\&\f(CW\*(C`at\*(C'\fR and doesn't repeat. It will not adjust when a time jump occurs,
1261that is, if it is to be run at January 1st 2011 then it will run when the 1296that is, if it is to be run at January 1st 2011 then it will run when the
1262system time reaches or surpasses this time. 1297system time reaches or surpasses this time.
1263.IP "* non-repeating interval timer (interval > 0, reschedule_cb = 0)" 4 1298.IP "* non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)" 4
1264.IX Item "non-repeating interval timer (interval > 0, reschedule_cb = 0)" 1299.IX Item "non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)"
1265In this mode the watcher will always be scheduled to time out at the next 1300In this mode the watcher will always be scheduled to time out at the next
1266\&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N) and then repeat, regardless 1301\&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N, which can also be negative)
1267of any time jumps. 1302and then repeat, regardless of any time jumps.
1268.Sp 1303.Sp
1269This can be used to create timers that do not drift with respect to system 1304This can be used to create timers that do not drift with respect to system
1270time: 1305time:
1271.Sp 1306.Sp
1272.Vb 1 1307.Vb 1
… …
1279by 3600. 1314by 3600.
1280.Sp 1315.Sp
1281Another way to think about it (for the mathematically inclined) is that 1316Another way to think about it (for the mathematically inclined) is that
1282\&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible 1317\&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible
1283time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps. 1318time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps.
1319.Sp
1320For numerical stability it is preferable that the \f(CW\*(C`at\*(C'\fR value is near
1321\&\f(CW\*(C`ev_now ()\*(C'\fR (the current time), but there is no range requirement for
1322this value.
1284.IP "* manual reschedule mode (reschedule_cb = callback)" 4 1323.IP "* manual reschedule mode (at and interval ignored, reschedule_cb = callback)" 4
1285.IX Item "manual reschedule mode (reschedule_cb = callback)" 1324.IX Item "manual reschedule mode (at and interval ignored, reschedule_cb = callback)"
1286In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR are both being 1325In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR are both being
1287ignored. Instead, each time the periodic watcher gets scheduled, the 1326ignored. Instead, each time the periodic watcher gets scheduled, the
1288reschedule callback will be called with the watcher as first, and the 1327reschedule callback will be called with the watcher as first, and the
1289current time as second argument. 1328current time as second argument.
1290.Sp 1329.Sp
1291\&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher, 1330\&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher,
1292ever, or make any event loop modifications\fR. If you need to stop it, 1331ever, or make any event loop modifications\fR. If you need to stop it,
1293return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop it afterwards (e.g. by 1332return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop it afterwards (e.g. by
1294starting a prepare watcher). 1333starting an \f(CW\*(C`ev_prepare\*(C'\fR watcher, which is legal).
1295.Sp 1334.Sp
1296Its prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 1335Its prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
1297ev_tstamp now)\*(C'\fR, e.g.: 1336ev_tstamp now)\*(C'\fR, e.g.:
1298.Sp 1337.Sp
1299.Vb 4 1338.Vb 4
… …
1323.IX Item "ev_periodic_again (loop, ev_periodic *)" 1362.IX Item "ev_periodic_again (loop, ev_periodic *)"
1324Simply stops and restarts the periodic watcher again. This is only useful 1363Simply stops and restarts the periodic watcher again. This is only useful
1325when you changed some parameters or the reschedule callback would return 1364when you changed some parameters or the reschedule callback would return
1326a different time than the last time it was called (e.g. in a crond like 1365a different time than the last time it was called (e.g. in a crond like
1327program when the crontabs have changed). 1366program when the crontabs have changed).
1367.IP "ev_tstamp offset [read\-write]" 4
1368.IX Item "ev_tstamp offset [read-write]"
1369When repeating, this contains the offset value, otherwise this is the
1370absolute point in time (the \f(CW\*(C`at\*(C'\fR value passed to \f(CW\*(C`ev_periodic_set\*(C'\fR).
1371.Sp
1372Can be modified any time, but changes only take effect when the periodic
1373timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
1328.IP "ev_tstamp interval [read\-write]" 4 1374.IP "ev_tstamp interval [read\-write]" 4
1329.IX Item "ev_tstamp interval [read-write]" 1375.IX Item "ev_tstamp interval [read-write]"
1330The current interval value. Can be modified any time, but changes only 1376The current interval value. Can be modified any time, but changes only
1331take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being 1377take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being
1332called. 1378called.
… …
1392first watcher gets started will libev actually register a signal watcher 1438first watcher gets started will libev actually register a signal watcher
1393with the kernel (thus it coexists with your own signal handlers as long 1439with the kernel (thus it coexists with your own signal handlers as long
1394as you don't register any with libev). Similarly, when the last signal 1440as you don't register any with libev). Similarly, when the last signal
1395watcher for a signal is stopped libev will reset the signal handler to 1441watcher for a signal is stopped libev will reset the signal handler to
1396\&\s-1SIG_DFL\s0 (regardless of what it was set to before). 1442\&\s-1SIG_DFL\s0 (regardless of what it was set to before).
1443.PP
1444\fIWatcher-Specific Functions and Data Members\fR
1445.IX Subsection "Watcher-Specific Functions and Data Members"
1397.IP "ev_signal_init (ev_signal *, callback, int signum)" 4 1446.IP "ev_signal_init (ev_signal *, callback, int signum)" 4
1398.IX Item "ev_signal_init (ev_signal *, callback, int signum)" 1447.IX Item "ev_signal_init (ev_signal *, callback, int signum)"
1399.PD 0 1448.PD 0
1400.IP "ev_signal_set (ev_signal *, int signum)" 4 1449.IP "ev_signal_set (ev_signal *, int signum)" 4
1401.IX Item "ev_signal_set (ev_signal *, int signum)" 1450.IX Item "ev_signal_set (ev_signal *, int signum)"
… …
1408.ie n .Sh """ev_child"" \- watch out for process status changes" 1457.ie n .Sh """ev_child"" \- watch out for process status changes"
1409.el .Sh "\f(CWev_child\fP \- watch out for process status changes" 1458.el .Sh "\f(CWev_child\fP \- watch out for process status changes"
1410.IX Subsection "ev_child - watch out for process status changes" 1459.IX Subsection "ev_child - watch out for process status changes"
1411Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to 1460Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to
1412some child status changes (most typically when a child of yours dies). 1461some child status changes (most typically when a child of yours dies).
1462.PP
1463\fIWatcher-Specific Functions and Data Members\fR
1464.IX Subsection "Watcher-Specific Functions and Data Members"
1413.IP "ev_child_init (ev_child *, callback, int pid)" 4 1465.IP "ev_child_init (ev_child *, callback, int pid)" 4
1414.IX Item "ev_child_init (ev_child *, callback, int pid)" 1466.IX Item "ev_child_init (ev_child *, callback, int pid)"
1415.PD 0 1467.PD 0
1416.IP "ev_child_set (ev_child *, int pid)" 4 1468.IP "ev_child_set (ev_child *, int pid)" 4
1417.IX Item "ev_child_set (ev_child *, int pid)" 1469.IX Item "ev_child_set (ev_child *, int pid)"
… …
1482reader). Inotify will be used to give hints only and should not change the 1534reader). Inotify will be used to give hints only and should not change the
1483semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers, which means that libev sometimes needs 1535semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers, which means that libev sometimes needs
1484to fall back to regular polling again even with inotify, but changes are 1536to fall back to regular polling again even with inotify, but changes are
1485usually detected immediately, and if the file exists there will be no 1537usually detected immediately, and if the file exists there will be no
1486polling. 1538polling.
1539.PP
1540\fIWatcher-Specific Functions and Data Members\fR
1541.IX Subsection "Watcher-Specific Functions and Data Members"
1487.IP "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 4 1542.IP "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 4
1488.IX Item "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 1543.IX Item "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)"
1489.PD 0 1544.PD 0
1490.IP "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" 4 1545.IP "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" 4
1491.IX Item "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" 1546.IX Item "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)"
… …
1570.PP 1625.PP
1571Apart from keeping your process non-blocking (which is a useful 1626Apart from keeping your process non-blocking (which is a useful
1572effect on its own sometimes), idle watchers are a good place to do 1627effect on its own sometimes), idle watchers are a good place to do
1573\&\*(L"pseudo\-background processing\*(R", or delay processing stuff to after the 1628\&\*(L"pseudo\-background processing\*(R", or delay processing stuff to after the
1574event loop has handled all outstanding events. 1629event loop has handled all outstanding events.
1630.PP
1631\fIWatcher-Specific Functions and Data Members\fR
1632.IX Subsection "Watcher-Specific Functions and Data Members"
1575.IP "ev_idle_init (ev_signal *, callback)" 4 1633.IP "ev_idle_init (ev_signal *, callback)" 4
1576.IX Item "ev_idle_init (ev_signal *, callback)" 1634.IX Item "ev_idle_init (ev_signal *, callback)"
1577Initialises and configures the idle watcher \- it has no parameters of any 1635Initialises and configures the idle watcher \- it has no parameters of any
1578kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless, 1636kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless,
1579believe me. 1637believe me.
… …
1634are ready to run (it's actually more complicated: it only runs coroutines 1692are ready to run (it's actually more complicated: it only runs coroutines
1635with priority higher than or equal to the event loop and one coroutine 1693with priority higher than or equal to the event loop and one coroutine
1636of lower priority, but only once, using idle watchers to keep the event 1694of lower priority, but only once, using idle watchers to keep the event
1637loop from blocking if lower-priority coroutines are active, thus mapping 1695loop from blocking if lower-priority coroutines are active, thus mapping
1638low-priority coroutines to idle/background tasks). 1696low-priority coroutines to idle/background tasks).
1697.PP
1698It is recommended to give \f(CW\*(C`ev_check\*(C'\fR watchers highest (\f(CW\*(C`EV_MAXPRI\*(C'\fR)
1699priority, to ensure that they are being run before any other watchers
1700after the poll. Also, \f(CW\*(C`ev_check\*(C'\fR watchers (and \f(CW\*(C`ev_prepare\*(C'\fR watchers,
1701too) should not activate (\*(L"feed\*(R") events into libev. While libev fully
1702supports this, they will be called before other \f(CW\*(C`ev_check\*(C'\fR watchers did
1703their job. As \f(CW\*(C`ev_check\*(C'\fR watchers are often used to embed other event
1704loops those other event loops might be in an unusable state until their
1705\&\f(CW\*(C`ev_check\*(C'\fR watcher ran (always remind yourself to coexist peacefully with
1706others).
1707.PP
1708\fIWatcher-Specific Functions and Data Members\fR
1709.IX Subsection "Watcher-Specific Functions and Data Members"
1639.IP "ev_prepare_init (ev_prepare *, callback)" 4 1710.IP "ev_prepare_init (ev_prepare *, callback)" 4
1640.IX Item "ev_prepare_init (ev_prepare *, callback)" 1711.IX Item "ev_prepare_init (ev_prepare *, callback)"
1641.PD 0 1712.PD 0
1642.IP "ev_check_init (ev_check *, callback)" 4 1713.IP "ev_check_init (ev_check *, callback)" 4
1643.IX Item "ev_check_init (ev_check *, callback)" 1714.IX Item "ev_check_init (ev_check *, callback)"
1644.PD 1715.PD
1645Initialises and configures the prepare or check watcher \- they have no 1716Initialises and configures the prepare or check watcher \- they have no
1646parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR 1717parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR
1647macros, but using them is utterly, utterly and completely pointless. 1718macros, but using them is utterly, utterly and completely pointless.
1648.PP 1719.PP
1649Example: To include a library such as adns, you would add \s-1IO\s0 watchers 1720There are a number of principal ways to embed other event loops or modules
1650and a timeout watcher in a prepare handler, as required by libadns, and 1721into libev. Here are some ideas on how to include libadns into libev
1722(there is a Perl module named \f(CW\*(C`EV::ADNS\*(C'\fR that does this, which you could
1723use for an actually working example. Another Perl module named \f(CW\*(C`EV::Glib\*(C'\fR
1724embeds a Glib main context into libev, and finally, \f(CW\*(C`Glib::EV\*(C'\fR embeds \s-1EV\s0
1725into the Glib event loop).
1726.PP
1727Method 1: Add \s-1IO\s0 watchers and a timeout watcher in a prepare handler,
1651in a check watcher, destroy them and call into libadns. What follows is 1728and in a check watcher, destroy them and call into libadns. What follows
1652pseudo-code only of course: 1729is pseudo-code only of course. This requires you to either use a low
1730priority for the check watcher or use \f(CW\*(C`ev_clear_pending\*(C'\fR explicitly, as
1731the callbacks for the IO/timeout watchers might not have been called yet.
1653.PP 1732.PP
1654.Vb 2 1733.Vb 2
1655\& static ev_io iow [nfd]; 1734\& static ev_io iow [nfd];
1656\& static ev_timer tw; 1735\& static ev_timer tw;
1657.Ve 1736.Ve
1658.PP 1737.PP
1659.Vb 9 1738.Vb 4
1660\& static void 1739\& static void
1661\& io_cb (ev_loop *loop, ev_io *w, int revents) 1740\& io_cb (ev_loop *loop, ev_io *w, int revents)
1662\& { 1741\& {
1663\& // set the relevant poll flags
1664\& // could also call adns_processreadable etc. here
1665\& struct pollfd *fd = (struct pollfd *)w->data;
1666\& if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1667\& if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1668\& } 1742\& }
1669.Ve 1743.Ve
1670.PP 1744.PP
1671.Vb 8 1745.Vb 8
1672\& // create io watchers for each fd and a timer before blocking 1746\& // create io watchers for each fd and a timer before blocking
… …
1684\& ev_timer_init (&tw, 0, timeout * 1e-3); 1758\& ev_timer_init (&tw, 0, timeout * 1e-3);
1685\& ev_timer_start (loop, &tw); 1759\& ev_timer_start (loop, &tw);
1686.Ve 1760.Ve
1687.PP 1761.PP
1688.Vb 6 1762.Vb 6
1689\& // create on ev_io per pollfd 1763\& // create one ev_io per pollfd
1690\& for (int i = 0; i < nfd; ++i) 1764\& for (int i = 0; i < nfd; ++i)
1691\& { 1765\& {
1692\& ev_io_init (iow + i, io_cb, fds [i].fd, 1766\& ev_io_init (iow + i, io_cb, fds [i].fd,
1693\& ((fds [i].events & POLLIN ? EV_READ : 0) 1767\& ((fds [i].events & POLLIN ? EV_READ : 0)
1694\& | (fds [i].events & POLLOUT ? EV_WRITE : 0))); 1768\& | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1695.Ve 1769.Ve
1696.PP 1770.PP
1697.Vb 5 1771.Vb 4
1698\& fds [i].revents = 0; 1772\& fds [i].revents = 0;
1699\& iow [i].data = fds + i;
1700\& ev_io_start (loop, iow + i); 1773\& ev_io_start (loop, iow + i);
1701\& } 1774\& }
1702\& } 1775\& }
1703.Ve 1776.Ve
1704.PP 1777.PP
… …
1708\& adns_check_cb (ev_loop *loop, ev_check *w, int revents) 1781\& adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1709\& { 1782\& {
1710\& ev_timer_stop (loop, &tw); 1783\& ev_timer_stop (loop, &tw);
1711.Ve 1784.Ve
1712.PP 1785.PP
1713.Vb 2 1786.Vb 8
1714\& for (int i = 0; i < nfd; ++i) 1787\& for (int i = 0; i < nfd; ++i)
1788\& {
1789\& // set the relevant poll flags
1790\& // could also call adns_processreadable etc. here
1791\& struct pollfd *fd = fds + i;
1792\& int revents = ev_clear_pending (iow + i);
1793\& if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1794\& if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1795.Ve
1796.PP
1797.Vb 3
1798\& // now stop the watcher
1715\& ev_io_stop (loop, iow + i); 1799\& ev_io_stop (loop, iow + i);
1800\& }
1716.Ve 1801.Ve
1717.PP 1802.PP
1718.Vb 2 1803.Vb 2
1719\& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); 1804\& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1805\& }
1806.Ve
1807.PP
1808Method 2: This would be just like method 1, but you run \f(CW\*(C`adns_afterpoll\*(C'\fR
1809in the prepare watcher and would dispose of the check watcher.
1810.PP
1811Method 3: If the module to be embedded supports explicit event
1812notification (adns does), you can also make use of the actual watcher
1813callbacks, and only destroy/create the watchers in the prepare watcher.
1814.PP
1815.Vb 5
1816\& static void
1817\& timer_cb (EV_P_ ev_timer *w, int revents)
1818\& {
1819\& adns_state ads = (adns_state)w->data;
1820\& update_now (EV_A);
1821.Ve
1822.PP
1823.Vb 2
1824\& adns_processtimeouts (ads, &tv_now);
1825\& }
1826.Ve
1827.PP
1828.Vb 5
1829\& static void
1830\& io_cb (EV_P_ ev_io *w, int revents)
1831\& {
1832\& adns_state ads = (adns_state)w->data;
1833\& update_now (EV_A);
1834.Ve
1835.PP
1836.Vb 3
1837\& if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1838\& if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1839\& }
1840.Ve
1841.PP
1842.Vb 1
1843\& // do not ever call adns_afterpoll
1844.Ve
1845.PP
1846Method 4: Do not use a prepare or check watcher because the module you
1847want to embed is too inflexible to support it. Instead, youc na override
1848their poll function. The drawback with this solution is that the main
1849loop is now no longer controllable by \s-1EV\s0. The \f(CW\*(C`Glib::EV\*(C'\fR module does
1850this.
1851.PP
1852.Vb 4
1853\& static gint
1854\& event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1855\& {
1856\& int got_events = 0;
1857.Ve
1858.PP
1859.Vb 2
1860\& for (n = 0; n < nfds; ++n)
1861\& // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1862.Ve
1863.PP
1864.Vb 2
1865\& if (timeout >= 0)
1866\& // create/start timer
1867.Ve
1868.PP
1869.Vb 2
1870\& // poll
1871\& ev_loop (EV_A_ 0);
1872.Ve
1873.PP
1874.Vb 3
1875\& // stop timer again
1876\& if (timeout >= 0)
1877\& ev_timer_stop (EV_A_ &to);
1878.Ve
1879.PP
1880.Vb 3
1881\& // stop io watchers again - their callbacks should have set
1882\& for (n = 0; n < nfds; ++n)
1883\& ev_io_stop (EV_A_ iow [n]);
1884.Ve
1885.PP
1886.Vb 2
1887\& return got_events;
1720\& } 1888\& }
1721.Ve 1889.Ve
1722.ie n .Sh """ev_embed"" \- when one backend isn't enough..." 1890.ie n .Sh """ev_embed"" \- when one backend isn't enough..."
1723.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..." 1891.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..."
1724.IX Subsection "ev_embed - when one backend isn't enough..." 1892.IX Subsection "ev_embed - when one backend isn't enough..."
… …
1793\& ev_embed_start (loop_hi, &embed); 1961\& ev_embed_start (loop_hi, &embed);
1794\& } 1962\& }
1795\& else 1963\& else
1796\& loop_lo = loop_hi; 1964\& loop_lo = loop_hi;
1797.Ve 1965.Ve
1966.PP
1967\fIWatcher-Specific Functions and Data Members\fR
1968.IX Subsection "Watcher-Specific Functions and Data Members"
1798.IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4 1969.IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
1799.IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 1970.IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)"
1800.PD 0 1971.PD 0
1801.IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4 1972.IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
1802.IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 1973.IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)"

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