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Revision 1.43 by root, Sat Dec 8 14:27:38 2007 UTC vs.
Revision 1.48 by root, Sun Dec 9 19:47:29 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 "2007-12-09" "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.
… …
1234but on wallclock time (absolute time). You can tell a periodic watcher 1238but 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 1239to 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 () 1240periodic 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 1241+ 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 1242take 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 1243roughly 10 seconds later).
1240again).
1241.PP 1244.PP
1242They can also be used to implement vastly more complex timers, such as 1245They can also be used to implement vastly more complex timers, such as
1243triggering an event on eahc midnight, local time. 1246triggering an event on each midnight, local time or other, complicated,
1247rules.
1244.PP 1248.PP
1245As with timers, the callback is guarenteed to be invoked only when the 1249As 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 1250time (\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. 1251during the same loop iteration then order of execution is undefined.
1248.IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4 1252.IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4
… …
1252.IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 1256.IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)"
1253.PD 1257.PD
1254Lots of arguments, lets sort it out... There are basically three modes of 1258Lots of arguments, lets sort it out... There are basically three modes of
1255operation, and we will explain them from simplest to complex: 1259operation, and we will explain them from simplest to complex:
1256.RS 4 1260.RS 4
1257.IP "* absolute timer (interval = reschedule_cb = 0)" 4 1261.IP "* absolute timer (at = time, interval = reschedule_cb = 0)" 4
1258.IX Item "absolute timer (interval = reschedule_cb = 0)" 1262.IX Item "absolute timer (at = time, interval = reschedule_cb = 0)"
1259In this configuration the watcher triggers an event at the wallclock time 1263In 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, 1264\&\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 1265that is, if it is to be run at January 1st 2011 then it will run when the
1262system time reaches or surpasses this time. 1266system time reaches or surpasses this time.
1263.IP "* non-repeating interval timer (interval > 0, reschedule_cb = 0)" 4 1267.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)" 1268.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 1269In 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 1270\&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N, which can also be negative)
1267of any time jumps. 1271and then repeat, regardless of any time jumps.
1268.Sp 1272.Sp
1269This can be used to create timers that do not drift with respect to system 1273This can be used to create timers that do not drift with respect to system
1270time: 1274time:
1271.Sp 1275.Sp
1272.Vb 1 1276.Vb 1
… …
1279by 3600. 1283by 3600.
1280.Sp 1284.Sp
1281Another way to think about it (for the mathematically inclined) is that 1285Another 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 1286\&\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. 1287time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps.
1288.Sp
1289For numerical stability it is preferable that the \f(CW\*(C`at\*(C'\fR value is near
1290\&\f(CW\*(C`ev_now ()\*(C'\fR (the current time), but there is no range requirement for
1291this value.
1284.IP "* manual reschedule mode (reschedule_cb = callback)" 4 1292.IP "* manual reschedule mode (at and interval ignored, reschedule_cb = callback)" 4
1285.IX Item "manual reschedule mode (reschedule_cb = callback)" 1293.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 1294In 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 1295ignored. Instead, each time the periodic watcher gets scheduled, the
1288reschedule callback will be called with the watcher as first, and the 1296reschedule callback will be called with the watcher as first, and the
1289current time as second argument. 1297current time as second argument.
1290.Sp 1298.Sp
1291\&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher, 1299\&\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, 1300ever, 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 1301return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop it afterwards (e.g. by
1294starting a prepare watcher). 1302starting an \f(CW\*(C`ev_prepare\*(C'\fR watcher, which is legal).
1295.Sp 1303.Sp
1296Its prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 1304Its prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
1297ev_tstamp now)\*(C'\fR, e.g.: 1305ev_tstamp now)\*(C'\fR, e.g.:
1298.Sp 1306.Sp
1299.Vb 4 1307.Vb 4
… …
1323.IX Item "ev_periodic_again (loop, ev_periodic *)" 1331.IX Item "ev_periodic_again (loop, ev_periodic *)"
1324Simply stops and restarts the periodic watcher again. This is only useful 1332Simply stops and restarts the periodic watcher again. This is only useful
1325when you changed some parameters or the reschedule callback would return 1333when 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 1334a different time than the last time it was called (e.g. in a crond like
1327program when the crontabs have changed). 1335program when the crontabs have changed).
1336.IP "ev_tstamp offset [read\-write]" 4
1337.IX Item "ev_tstamp offset [read-write]"
1338When repeating, this contains the offset value, otherwise this is the
1339absolute point in time (the \f(CW\*(C`at\*(C'\fR value passed to \f(CW\*(C`ev_periodic_set\*(C'\fR).
1340.Sp
1341Can be modified any time, but changes only take effect when the periodic
1342timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
1328.IP "ev_tstamp interval [read\-write]" 4 1343.IP "ev_tstamp interval [read\-write]" 4
1329.IX Item "ev_tstamp interval [read-write]" 1344.IX Item "ev_tstamp interval [read-write]"
1330The current interval value. Can be modified any time, but changes only 1345The 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 1346take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being
1332called. 1347called.
… …
1634are ready to run (it's actually more complicated: it only runs coroutines 1649are 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 1650with 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 1651of lower priority, but only once, using idle watchers to keep the event
1637loop from blocking if lower-priority coroutines are active, thus mapping 1652loop from blocking if lower-priority coroutines are active, thus mapping
1638low-priority coroutines to idle/background tasks). 1653low-priority coroutines to idle/background tasks).
1654.PP
1655It is recommended to give \f(CW\*(C`ev_check\*(C'\fR watchers highest (\f(CW\*(C`EV_MAXPRI\*(C'\fR)
1656priority, to ensure that they are being run before any other watchers
1657after the poll. Also, \f(CW\*(C`ev_check\*(C'\fR watchers (and \f(CW\*(C`ev_prepare\*(C'\fR watchers,
1658too) should not activate (\*(L"feed\*(R") events into libev. While libev fully
1659supports this, they will be called before other \f(CW\*(C`ev_check\*(C'\fR watchers did
1660their job. As \f(CW\*(C`ev_check\*(C'\fR watchers are often used to embed other event
1661loops those other event loops might be in an unusable state until their
1662\&\f(CW\*(C`ev_check\*(C'\fR watcher ran (always remind yourself to coexist peacefully with
1663others).
1639.IP "ev_prepare_init (ev_prepare *, callback)" 4 1664.IP "ev_prepare_init (ev_prepare *, callback)" 4
1640.IX Item "ev_prepare_init (ev_prepare *, callback)" 1665.IX Item "ev_prepare_init (ev_prepare *, callback)"
1641.PD 0 1666.PD 0
1642.IP "ev_check_init (ev_check *, callback)" 4 1667.IP "ev_check_init (ev_check *, callback)" 4
1643.IX Item "ev_check_init (ev_check *, callback)" 1668.IX Item "ev_check_init (ev_check *, callback)"
1644.PD 1669.PD
1645Initialises and configures the prepare or check watcher \- they have no 1670Initialises 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 1671parameters 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. 1672macros, but using them is utterly, utterly and completely pointless.
1648.PP 1673.PP
1649Example: To include a library such as adns, you would add \s-1IO\s0 watchers 1674There 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 1675into libev. Here are some ideas on how to include libadns into libev
1676(there is a Perl module named \f(CW\*(C`EV::ADNS\*(C'\fR that does this, which you could
1677use for an actually working example. Another Perl module named \f(CW\*(C`EV::Glib\*(C'\fR
1678embeds a Glib main context into libev, and finally, \f(CW\*(C`Glib::EV\*(C'\fR embeds \s-1EV\s0
1679into the Glib event loop).
1680.PP
1681Method 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 1682and in a check watcher, destroy them and call into libadns. What follows
1652pseudo-code only of course: 1683is pseudo-code only of course. This requires you to either use a low
1684priority for the check watcher or use \f(CW\*(C`ev_clear_pending\*(C'\fR explicitly, as
1685the callbacks for the IO/timeout watchers might not have been called yet.
1653.PP 1686.PP
1654.Vb 2 1687.Vb 2
1655\& static ev_io iow [nfd]; 1688\& static ev_io iow [nfd];
1656\& static ev_timer tw; 1689\& static ev_timer tw;
1657.Ve 1690.Ve
1658.PP 1691.PP
1659.Vb 9 1692.Vb 4
1660\& static void 1693\& static void
1661\& io_cb (ev_loop *loop, ev_io *w, int revents) 1694\& io_cb (ev_loop *loop, ev_io *w, int revents)
1662\& { 1695\& {
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\& } 1696\& }
1669.Ve 1697.Ve
1670.PP 1698.PP
1671.Vb 8 1699.Vb 8
1672\& // create io watchers for each fd and a timer before blocking 1700\& // create io watchers for each fd and a timer before blocking
… …
1684\& ev_timer_init (&tw, 0, timeout * 1e-3); 1712\& ev_timer_init (&tw, 0, timeout * 1e-3);
1685\& ev_timer_start (loop, &tw); 1713\& ev_timer_start (loop, &tw);
1686.Ve 1714.Ve
1687.PP 1715.PP
1688.Vb 6 1716.Vb 6
1689\& // create on ev_io per pollfd 1717\& // create one ev_io per pollfd
1690\& for (int i = 0; i < nfd; ++i) 1718\& for (int i = 0; i < nfd; ++i)
1691\& { 1719\& {
1692\& ev_io_init (iow + i, io_cb, fds [i].fd, 1720\& ev_io_init (iow + i, io_cb, fds [i].fd,
1693\& ((fds [i].events & POLLIN ? EV_READ : 0) 1721\& ((fds [i].events & POLLIN ? EV_READ : 0)
1694\& | (fds [i].events & POLLOUT ? EV_WRITE : 0))); 1722\& | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1695.Ve 1723.Ve
1696.PP 1724.PP
1697.Vb 5 1725.Vb 4
1698\& fds [i].revents = 0; 1726\& fds [i].revents = 0;
1699\& iow [i].data = fds + i;
1700\& ev_io_start (loop, iow + i); 1727\& ev_io_start (loop, iow + i);
1701\& } 1728\& }
1702\& } 1729\& }
1703.Ve 1730.Ve
1704.PP 1731.PP
… …
1708\& adns_check_cb (ev_loop *loop, ev_check *w, int revents) 1735\& adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1709\& { 1736\& {
1710\& ev_timer_stop (loop, &tw); 1737\& ev_timer_stop (loop, &tw);
1711.Ve 1738.Ve
1712.PP 1739.PP
1713.Vb 2 1740.Vb 8
1714\& for (int i = 0; i < nfd; ++i) 1741\& for (int i = 0; i < nfd; ++i)
1742\& {
1743\& // set the relevant poll flags
1744\& // could also call adns_processreadable etc. here
1745\& struct pollfd *fd = fds + i;
1746\& int revents = ev_clear_pending (iow + i);
1747\& if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1748\& if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1749.Ve
1750.PP
1751.Vb 3
1752\& // now stop the watcher
1715\& ev_io_stop (loop, iow + i); 1753\& ev_io_stop (loop, iow + i);
1754\& }
1716.Ve 1755.Ve
1717.PP 1756.PP
1718.Vb 2 1757.Vb 2
1719\& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); 1758\& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1759\& }
1760.Ve
1761.PP
1762Method 2: This would be just like method 1, but you run \f(CW\*(C`adns_afterpoll\*(C'\fR
1763in the prepare watcher and would dispose of the check watcher.
1764.PP
1765Method 3: If the module to be embedded supports explicit event
1766notification (adns does), you can also make use of the actual watcher
1767callbacks, and only destroy/create the watchers in the prepare watcher.
1768.PP
1769.Vb 5
1770\& static void
1771\& timer_cb (EV_P_ ev_timer *w, int revents)
1772\& {
1773\& adns_state ads = (adns_state)w->data;
1774\& update_now (EV_A);
1775.Ve
1776.PP
1777.Vb 2
1778\& adns_processtimeouts (ads, &tv_now);
1779\& }
1780.Ve
1781.PP
1782.Vb 5
1783\& static void
1784\& io_cb (EV_P_ ev_io *w, int revents)
1785\& {
1786\& adns_state ads = (adns_state)w->data;
1787\& update_now (EV_A);
1788.Ve
1789.PP
1790.Vb 3
1791\& if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1792\& if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1793\& }
1794.Ve
1795.PP
1796.Vb 1
1797\& // do not ever call adns_afterpoll
1798.Ve
1799.PP
1800Method 4: Do not use a prepare or check watcher because the module you
1801want to embed is too inflexible to support it. Instead, youc na override
1802their poll function. The drawback with this solution is that the main
1803loop is now no longer controllable by \s-1EV\s0. The \f(CW\*(C`Glib::EV\*(C'\fR module does
1804this.
1805.PP
1806.Vb 4
1807\& static gint
1808\& event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1809\& {
1810\& int got_events = 0;
1811.Ve
1812.PP
1813.Vb 2
1814\& for (n = 0; n < nfds; ++n)
1815\& // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1816.Ve
1817.PP
1818.Vb 2
1819\& if (timeout >= 0)
1820\& // create/start timer
1821.Ve
1822.PP
1823.Vb 2
1824\& // poll
1825\& ev_loop (EV_A_ 0);
1826.Ve
1827.PP
1828.Vb 3
1829\& // stop timer again
1830\& if (timeout >= 0)
1831\& ev_timer_stop (EV_A_ &to);
1832.Ve
1833.PP
1834.Vb 3
1835\& // stop io watchers again - their callbacks should have set
1836\& for (n = 0; n < nfds; ++n)
1837\& ev_io_stop (EV_A_ iow [n]);
1838.Ve
1839.PP
1840.Vb 2
1841\& return got_events;
1720\& } 1842\& }
1721.Ve 1843.Ve
1722.ie n .Sh """ev_embed"" \- when one backend isn't enough..." 1844.ie n .Sh """ev_embed"" \- when one backend isn't enough..."
1723.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..." 1845.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..."
1724.IX Subsection "ev_embed - when one backend isn't enough..." 1846.IX Subsection "ev_embed - when one backend isn't enough..."

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