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Revision 1.34 by root, Thu Nov 29 12:21:21 2007 UTC vs.
Revision 1.44 by root, Sat Dec 8 15:30:26 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 "2007-11-29" "perl v5.8.8" "User Contributed Perl Documentation" 132.TH "<STANDARD INPUT>" 1 "2007-12-08" "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
… …
196\& return 0; 196\& return 0;
197\& } 197\& }
198.Ve 198.Ve
199.SH "DESCRIPTION" 199.SH "DESCRIPTION"
200.IX Header "DESCRIPTION" 200.IX Header "DESCRIPTION"
201The newest version of this document is also available as a html-formatted
202web page you might find easier to navigate when reading it for the first
203time: <http://cvs.schmorp.de/libev/ev.html>.
204.PP
201Libev is an event loop: you register interest in certain events (such as a 205Libev is an event loop: you register interest in certain events (such as a
202file descriptor being readable or a timeout occuring), and it will manage 206file descriptor being readable or a timeout occuring), and it will manage
203these event sources and provide your program with events. 207these event sources and provide your program with events.
204.PP 208.PP
205To do this, it must take more or less complete control over your process 209To do this, it must take more or less complete control over your process
… …
411or setgid) then libev will \fInot\fR look at the environment variable 415or setgid) then libev will \fInot\fR look at the environment variable
412\&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will 416\&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will
413override the flags completely if it is found in the environment. This is 417override the flags completely if it is found in the environment. This is
414useful to try out specific backends to test their performance, or to work 418useful to try out specific backends to test their performance, or to work
415around bugs. 419around bugs.
420.ie n .IP """EVFLAG_FORKCHECK""" 4
421.el .IP "\f(CWEVFLAG_FORKCHECK\fR" 4
422.IX Item "EVFLAG_FORKCHECK"
423Instead of calling \f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR manually after
424a fork, you can also make libev check for a fork in each iteration by
425enabling this flag.
426.Sp
427This works by calling \f(CW\*(C`getpid ()\*(C'\fR on every iteration of the loop,
428and thus this might slow down your event loop if you do a lot of loop
429iterations and little real work, but is usually not noticeable (on my
430Linux system for example, \f(CW\*(C`getpid\*(C'\fR is actually a simple 5\-insn sequence
431without a syscall and thus \fIvery\fR fast, but my Linux system also has
432\&\f(CW\*(C`pthread_atfork\*(C'\fR which is even faster).
433.Sp
434The big advantage of this flag is that you can forget about fork (and
435forget about forgetting to tell libev about forking) when you use this
436flag.
437.Sp
438This flag setting cannot be overriden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR
439environment variable.
416.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4 440.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4
417.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4 441.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4
418.IX Item "EVBACKEND_SELECT (value 1, portable select backend)" 442.IX Item "EVBACKEND_SELECT (value 1, portable select backend)"
419This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as 443This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as
420libev tries to roll its own fd_set with no limits on the number of fds, 444libev tries to roll its own fd_set with no limits on the number of fds,
… …
561.IP "ev_loop_fork (loop)" 4 585.IP "ev_loop_fork (loop)" 4
562.IX Item "ev_loop_fork (loop)" 586.IX Item "ev_loop_fork (loop)"
563Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by 587Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by
564\&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop 588\&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop
565after fork, and how you do this is entirely your own problem. 589after fork, and how you do this is entirely your own problem.
590.IP "unsigned int ev_loop_count (loop)" 4
591.IX Item "unsigned int ev_loop_count (loop)"
592Returns the count of loop iterations for the loop, which is identical to
593the number of times libev did poll for new events. It starts at \f(CW0\fR and
594happily wraps around with enough iterations.
595.Sp
596This value can sometimes be useful as a generation counter of sorts (it
597\&\*(L"ticks\*(R" the number of loop iterations), as it roughly corresponds with
598\&\f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR calls.
566.IP "unsigned int ev_backend (loop)" 4 599.IP "unsigned int ev_backend (loop)" 4
567.IX Item "unsigned int ev_backend (loop)" 600.IX Item "unsigned int ev_backend (loop)"
568Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in 601Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in
569use. 602use.
570.IP "ev_tstamp ev_now (loop)" 4 603.IP "ev_tstamp ev_now (loop)" 4
… …
856.IP "bool ev_is_pending (ev_TYPE *watcher)" 4 889.IP "bool ev_is_pending (ev_TYPE *watcher)" 4
857.IX Item "bool ev_is_pending (ev_TYPE *watcher)" 890.IX Item "bool ev_is_pending (ev_TYPE *watcher)"
858Returns a true value iff the watcher is pending, (i.e. it has outstanding 891Returns a true value iff the watcher is pending, (i.e. it has outstanding
859events but its callback has not yet been invoked). As long as a watcher 892events but its callback has not yet been invoked). As long as a watcher
860is pending (but not active) you must not call an init function on it (but 893is pending (but not active) you must not call an init function on it (but
861\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe) and you must make sure the watcher is available to 894\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe), you must not change its priority, and you must
862libev (e.g. you cnanot \f(CW\*(C`free ()\*(C'\fR it). 895make sure the watcher is available to libev (e.g. you cannot \f(CW\*(C`free ()\*(C'\fR
896it).
863.IP "callback ev_cb (ev_TYPE *watcher)" 4 897.IP "callback ev_cb (ev_TYPE *watcher)" 4
864.IX Item "callback ev_cb (ev_TYPE *watcher)" 898.IX Item "callback ev_cb (ev_TYPE *watcher)"
865Returns the callback currently set on the watcher. 899Returns the callback currently set on the watcher.
866.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4 900.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4
867.IX Item "ev_cb_set (ev_TYPE *watcher, callback)" 901.IX Item "ev_cb_set (ev_TYPE *watcher, callback)"
868Change the callback. You can change the callback at virtually any time 902Change the callback. You can change the callback at virtually any time
869(modulo threads). 903(modulo threads).
904.IP "ev_set_priority (ev_TYPE *watcher, priority)" 4
905.IX Item "ev_set_priority (ev_TYPE *watcher, priority)"
906.PD 0
907.IP "int ev_priority (ev_TYPE *watcher)" 4
908.IX Item "int ev_priority (ev_TYPE *watcher)"
909.PD
910Set and query the priority of the watcher. The priority is a small
911integer between \f(CW\*(C`EV_MAXPRI\*(C'\fR (default: \f(CW2\fR) and \f(CW\*(C`EV_MINPRI\*(C'\fR
912(default: \f(CW\*(C`\-2\*(C'\fR). Pending watchers with higher priority will be invoked
913before watchers with lower priority, but priority will not keep watchers
914from being executed (except for \f(CW\*(C`ev_idle\*(C'\fR watchers).
915.Sp
916This means that priorities are \fIonly\fR used for ordering callback
917invocation after new events have been received. This is useful, for
918example, to reduce latency after idling, or more often, to bind two
919watchers on the same event and make sure one is called first.
920.Sp
921If you need to suppress invocation when higher priority events are pending
922you need to look at \f(CW\*(C`ev_idle\*(C'\fR watchers, which provide this functionality.
923.Sp
924You \fImust not\fR change the priority of a watcher as long as it is active or
925pending.
926.Sp
927The default priority used by watchers when no priority has been set is
928always \f(CW0\fR, which is supposed to not be too high and not be too low :).
929.Sp
930Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR is
931fine, as long as you do not mind that the priority value you query might
932or might not have been adjusted to be within valid range.
933.IP "ev_invoke (loop, ev_TYPE *watcher, int revents)" 4
934.IX Item "ev_invoke (loop, ev_TYPE *watcher, int revents)"
935Invoke the \f(CW\*(C`watcher\*(C'\fR with the given \f(CW\*(C`loop\*(C'\fR and \f(CW\*(C`revents\*(C'\fR. Neither
936\&\f(CW\*(C`loop\*(C'\fR nor \f(CW\*(C`revents\*(C'\fR need to be valid as long as the watcher callback
937can deal with that fact.
938.IP "int ev_clear_pending (loop, ev_TYPE *watcher)" 4
939.IX Item "int ev_clear_pending (loop, ev_TYPE *watcher)"
940If the watcher is pending, this function returns clears its pending status
941and returns its \f(CW\*(C`revents\*(C'\fR bitset (as if its callback was invoked). If the
942watcher isn't pending it does nothing and returns \f(CW0\fR.
870.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0" 943.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0"
871.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER" 944.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER"
872Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change 945Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change
873and read at any time, libev will completely ignore it. This can be used 946and read at any time, libev will completely ignore it. This can be used
874to associate arbitrary data with your watcher. If you need more data and 947to associate arbitrary data with your watcher. If you need more data and
… …
985it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning 1058it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning
986\&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives. 1059\&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives.
987.PP 1060.PP
988If you cannot run the fd in non-blocking mode (for example you should not 1061If you cannot run the fd in non-blocking mode (for example you should not
989play around with an Xlib connection), then you have to seperately re-test 1062play around with an Xlib connection), then you have to seperately re-test
990wether a file descriptor is really ready with a known-to-be good interface 1063whether a file descriptor is really ready with a known-to-be good interface
991such as poll (fortunately in our Xlib example, Xlib already does this on 1064such as poll (fortunately in our Xlib example, Xlib already does this on
992its own, so its quite safe to use). 1065its own, so its quite safe to use).
993.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4 1066.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4
994.IX Item "ev_io_init (ev_io *, callback, int fd, int events)" 1067.IX Item "ev_io_init (ev_io *, callback, int fd, int events)"
995.PD 0 1068.PD 0
… …
1479\& ev_stat_start (loop, &passwd); 1552\& ev_stat_start (loop, &passwd);
1480.Ve 1553.Ve
1481.ie n .Sh """ev_idle"" \- when you've got nothing better to do..." 1554.ie n .Sh """ev_idle"" \- when you've got nothing better to do..."
1482.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do..." 1555.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do..."
1483.IX Subsection "ev_idle - when you've got nothing better to do..." 1556.IX Subsection "ev_idle - when you've got nothing better to do..."
1484Idle watchers trigger events when there are no other events are pending 1557Idle watchers trigger events when no other events of the same or higher
1485(prepare, check and other idle watchers do not count). That is, as long 1558priority are pending (prepare, check and other idle watchers do not
1486as your process is busy handling sockets or timeouts (or even signals, 1559count).
1487imagine) it will not be triggered. But when your process is idle all idle 1560.PP
1488watchers are being called again and again, once per event loop iteration \- 1561That is, as long as your process is busy handling sockets or timeouts
1562(or even signals, imagine) of the same or higher priority it will not be
1563triggered. But when your process is idle (or only lower-priority watchers
1564are pending), the idle watchers are being called once per event loop
1489until stopped, that is, or your process receives more events and becomes 1565iteration \- until stopped, that is, or your process receives more events
1490busy. 1566and becomes busy again with higher priority stuff.
1491.PP 1567.PP
1492The most noteworthy effect is that as long as any idle watchers are 1568The most noteworthy effect is that as long as any idle watchers are
1493active, the process will not block when waiting for new events. 1569active, the process will not block when waiting for new events.
1494.PP 1570.PP
1495Apart from keeping your process non-blocking (which is a useful 1571Apart from keeping your process non-blocking (which is a useful
… …
1568.PD 1644.PD
1569Initialises and configures the prepare or check watcher \- they have no 1645Initialises and configures the prepare or check watcher \- they have no
1570parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR 1646parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR
1571macros, but using them is utterly, utterly and completely pointless. 1647macros, but using them is utterly, utterly and completely pointless.
1572.PP 1648.PP
1573Example: To include a library such as adns, you would add \s-1IO\s0 watchers 1649There are a number of principal ways to embed other event loops or modules
1574and a timeout watcher in a prepare handler, as required by libadns, and 1650into libev. Here are some ideas on how to include libadns into libev
1651(there is a Perl module named \f(CW\*(C`EV::ADNS\*(C'\fR that does this, which you could
1652use for an actually working example. Another Perl module named \f(CW\*(C`EV::Glib\*(C'\fR
1653embeds a Glib main context into libev, and finally, \f(CW\*(C`Glib::EV\*(C'\fR embeds \s-1EV\s0
1654into the Glib event loop).
1655.PP
1656Method 1: Add \s-1IO\s0 watchers and a timeout watcher in a prepare handler,
1575in a check watcher, destroy them and call into libadns. What follows is 1657and in a check watcher, destroy them and call into libadns. What follows
1576pseudo-code only of course: 1658is pseudo-code only of course. This requires you to either use a low
1659priority for the check watcher or use \f(CW\*(C`ev_clear_pending\*(C'\fR explicitly, as
1660the callbacks for the IO/timeout watchers might not have been called yet.
1577.PP 1661.PP
1578.Vb 2 1662.Vb 2
1579\& static ev_io iow [nfd]; 1663\& static ev_io iow [nfd];
1580\& static ev_timer tw; 1664\& static ev_timer tw;
1581.Ve 1665.Ve
1582.PP 1666.PP
1583.Vb 9 1667.Vb 4
1584\& static void 1668\& static void
1585\& io_cb (ev_loop *loop, ev_io *w, int revents) 1669\& io_cb (ev_loop *loop, ev_io *w, int revents)
1586\& { 1670\& {
1587\& // set the relevant poll flags
1588\& // could also call adns_processreadable etc. here
1589\& struct pollfd *fd = (struct pollfd *)w->data;
1590\& if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1591\& if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1592\& } 1671\& }
1593.Ve 1672.Ve
1594.PP 1673.PP
1595.Vb 7 1674.Vb 8
1596\& // create io watchers for each fd and a timer before blocking 1675\& // create io watchers for each fd and a timer before blocking
1597\& static void 1676\& static void
1598\& adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) 1677\& adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1599\& { 1678\& {
1600\& int timeout = 3600000;truct pollfd fds [nfd]; 1679\& int timeout = 3600000;
1680\& struct pollfd fds [nfd];
1601\& // actual code will need to loop here and realloc etc. 1681\& // actual code will need to loop here and realloc etc.
1602\& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); 1682\& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1603.Ve 1683.Ve
1604.PP 1684.PP
1605.Vb 3 1685.Vb 3
… …
1607\& ev_timer_init (&tw, 0, timeout * 1e-3); 1687\& ev_timer_init (&tw, 0, timeout * 1e-3);
1608\& ev_timer_start (loop, &tw); 1688\& ev_timer_start (loop, &tw);
1609.Ve 1689.Ve
1610.PP 1690.PP
1611.Vb 6 1691.Vb 6
1612\& // create on ev_io per pollfd 1692\& // create one ev_io per pollfd
1613\& for (int i = 0; i < nfd; ++i) 1693\& for (int i = 0; i < nfd; ++i)
1614\& { 1694\& {
1615\& ev_io_init (iow + i, io_cb, fds [i].fd, 1695\& ev_io_init (iow + i, io_cb, fds [i].fd,
1616\& ((fds [i].events & POLLIN ? EV_READ : 0) 1696\& ((fds [i].events & POLLIN ? EV_READ : 0)
1617\& | (fds [i].events & POLLOUT ? EV_WRITE : 0))); 1697\& | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1618.Ve 1698.Ve
1619.PP 1699.PP
1620.Vb 5 1700.Vb 4
1621\& fds [i].revents = 0; 1701\& fds [i].revents = 0;
1622\& iow [i].data = fds + i;
1623\& ev_io_start (loop, iow + i); 1702\& ev_io_start (loop, iow + i);
1624\& } 1703\& }
1625\& } 1704\& }
1626.Ve 1705.Ve
1627.PP 1706.PP
… …
1631\& adns_check_cb (ev_loop *loop, ev_check *w, int revents) 1710\& adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1632\& { 1711\& {
1633\& ev_timer_stop (loop, &tw); 1712\& ev_timer_stop (loop, &tw);
1634.Ve 1713.Ve
1635.PP 1714.PP
1636.Vb 2 1715.Vb 8
1637\& for (int i = 0; i < nfd; ++i) 1716\& for (int i = 0; i < nfd; ++i)
1717\& {
1718\& // set the relevant poll flags
1719\& // could also call adns_processreadable etc. here
1720\& struct pollfd *fd = fds + i;
1721\& int revents = ev_clear_pending (iow + i);
1722\& if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1723\& if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1724.Ve
1725.PP
1726.Vb 3
1727\& // now stop the watcher
1638\& ev_io_stop (loop, iow + i); 1728\& ev_io_stop (loop, iow + i);
1729\& }
1639.Ve 1730.Ve
1640.PP 1731.PP
1641.Vb 2 1732.Vb 2
1642\& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); 1733\& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1734\& }
1735.Ve
1736.PP
1737Method 2: This would be just like method 1, but you run \f(CW\*(C`adns_afterpoll\*(C'\fR
1738in the prepare watcher and would dispose of the check watcher.
1739.PP
1740Method 3: If the module to be embedded supports explicit event
1741notification (adns does), you can also make use of the actual watcher
1742callbacks, and only destroy/create the watchers in the prepare watcher.
1743.PP
1744.Vb 5
1745\& static void
1746\& timer_cb (EV_P_ ev_timer *w, int revents)
1747\& {
1748\& adns_state ads = (adns_state)w->data;
1749\& update_now (EV_A);
1750.Ve
1751.PP
1752.Vb 2
1753\& adns_processtimeouts (ads, &tv_now);
1754\& }
1755.Ve
1756.PP
1757.Vb 5
1758\& static void
1759\& io_cb (EV_P_ ev_io *w, int revents)
1760\& {
1761\& adns_state ads = (adns_state)w->data;
1762\& update_now (EV_A);
1763.Ve
1764.PP
1765.Vb 3
1766\& if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1767\& if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1768\& }
1769.Ve
1770.PP
1771.Vb 1
1772\& // do not ever call adns_afterpoll
1773.Ve
1774.PP
1775Method 4: Do not use a prepare or check watcher because the module you
1776want to embed is too inflexible to support it. Instead, youc na override
1777their poll function. The drawback with this solution is that the main
1778loop is now no longer controllable by \s-1EV\s0. The \f(CW\*(C`Glib::EV\*(C'\fR module does
1779this.
1780.PP
1781.Vb 4
1782\& static gint
1783\& event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1784\& {
1785\& int got_events = 0;
1786.Ve
1787.PP
1788.Vb 2
1789\& for (n = 0; n < nfds; ++n)
1790\& // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1791.Ve
1792.PP
1793.Vb 2
1794\& if (timeout >= 0)
1795\& // create/start timer
1796.Ve
1797.PP
1798.Vb 2
1799\& // poll
1800\& ev_loop (EV_A_ 0);
1801.Ve
1802.PP
1803.Vb 3
1804\& // stop timer again
1805\& if (timeout >= 0)
1806\& ev_timer_stop (EV_A_ &to);
1807.Ve
1808.PP
1809.Vb 3
1810\& // stop io watchers again - their callbacks should have set
1811\& for (n = 0; n < nfds; ++n)
1812\& ev_io_stop (EV_A_ iow [n]);
1813.Ve
1814.PP
1815.Vb 2
1816\& return got_events;
1643\& } 1817\& }
1644.Ve 1818.Ve
1645.ie n .Sh """ev_embed"" \- when one backend isn't enough..." 1819.ie n .Sh """ev_embed"" \- when one backend isn't enough..."
1646.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..." 1820.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..."
1647.IX Subsection "ev_embed - when one backend isn't enough..." 1821.IX Subsection "ev_embed - when one backend isn't enough..."
… …
1831.PP 2005.PP
1832.Vb 1 2006.Vb 1
1833\& #include <ev++.h> 2007\& #include <ev++.h>
1834.Ve 2008.Ve
1835.PP 2009.PP
1836(it is not installed by default). This automatically includes \fIev.h\fR 2010This automatically includes \fIev.h\fR and puts all of its definitions (many
1837and puts all of its definitions (many of them macros) into the global 2011of them macros) into the global namespace. All \*(C+ specific things are
1838namespace. All \*(C+ specific things are put into the \f(CW\*(C`ev\*(C'\fR namespace. 2012put into the \f(CW\*(C`ev\*(C'\fR namespace. It should support all the same embedding
2013options as \fIev.h\fR, most notably \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR.
1839.PP 2014.PP
1840It should support all the same embedding options as \fIev.h\fR, most notably 2015Care has been taken to keep the overhead low. The only data member the \*(C+
1841\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. 2016classes add (compared to plain C\-style watchers) is the event loop pointer
2017that the watcher is associated with (or no additional members at all if
2018you disable \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR when embedding libev).
2019.PP
2020Currently, functions, and static and non-static member functions can be
2021used as callbacks. Other types should be easy to add as long as they only
2022need one additional pointer for context. If you need support for other
2023types of functors please contact the author (preferably after implementing
2024it).
1842.PP 2025.PP
1843Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace: 2026Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace:
1844.ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4 2027.ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4
1845.el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4 2028.el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4
1846.IX Item "ev::READ, ev::WRITE etc." 2029.IX Item "ev::READ, ev::WRITE etc."
… …
1858which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro 2041which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro
1859defines by many implementations. 2042defines by many implementations.
1860.Sp 2043.Sp
1861All of those classes have these methods: 2044All of those classes have these methods:
1862.RS 4 2045.RS 4
1863.IP "ev::TYPE::TYPE (object *, object::method *)" 4 2046.IP "ev::TYPE::TYPE ()" 4
1864.IX Item "ev::TYPE::TYPE (object *, object::method *)" 2047.IX Item "ev::TYPE::TYPE ()"
1865.PD 0 2048.PD 0
1866.IP "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)" 4 2049.IP "ev::TYPE::TYPE (struct ev_loop *)" 4
1867.IX Item "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)" 2050.IX Item "ev::TYPE::TYPE (struct ev_loop *)"
1868.IP "ev::TYPE::~TYPE" 4 2051.IP "ev::TYPE::~TYPE" 4
1869.IX Item "ev::TYPE::~TYPE" 2052.IX Item "ev::TYPE::~TYPE"
1870.PD 2053.PD
1871The constructor takes a pointer to an object and a method pointer to 2054The constructor (optionally) takes an event loop to associate the watcher
1872the event handler callback to call in this class. The constructor calls 2055with. If it is omitted, it will use \f(CW\*(C`EV_DEFAULT\*(C'\fR.
1873\&\f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the \f(CW\*(C`set\*(C'\fR method 2056.Sp
1874before starting it. If you do not specify a loop then the constructor 2057The constructor calls \f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the
1875automatically associates the default loop with this watcher. 2058\&\f(CW\*(C`set\*(C'\fR method before starting it.
2059.Sp
2060It will not set a callback, however: You have to call the templated \f(CW\*(C`set\*(C'\fR
2061method to set a callback before you can start the watcher.
2062.Sp
2063(The reason why you have to use a method is a limitation in \*(C+ which does
2064not allow explicit template arguments for constructors).
1876.Sp 2065.Sp
1877The destructor automatically stops the watcher if it is active. 2066The destructor automatically stops the watcher if it is active.
2067.IP "w\->set<class, &class::method> (object *)" 4
2068.IX Item "w->set<class, &class::method> (object *)"
2069This method sets the callback method to call. The method has to have a
2070signature of \f(CW\*(C`void (*)(ev_TYPE &, int)\*(C'\fR, it receives the watcher as
2071first argument and the \f(CW\*(C`revents\*(C'\fR as second. The object must be given as
2072parameter and is stored in the \f(CW\*(C`data\*(C'\fR member of the watcher.
2073.Sp
2074This method synthesizes efficient thunking code to call your method from
2075the C callback that libev requires. If your compiler can inline your
2076callback (i.e. it is visible to it at the place of the \f(CW\*(C`set\*(C'\fR call and
2077your compiler is good :), then the method will be fully inlined into the
2078thunking function, making it as fast as a direct C callback.
2079.Sp
2080Example: simple class declaration and watcher initialisation
2081.Sp
2082.Vb 4
2083\& struct myclass
2084\& {
2085\& void io_cb (ev::io &w, int revents) { }
2086\& }
2087.Ve
2088.Sp
2089.Vb 3
2090\& myclass obj;
2091\& ev::io iow;
2092\& iow.set <myclass, &myclass::io_cb> (&obj);
2093.Ve
2094.IP "w\->set<function> (void *data = 0)" 4
2095.IX Item "w->set<function> (void *data = 0)"
2096Also sets a callback, but uses a static method or plain function as
2097callback. The optional \f(CW\*(C`data\*(C'\fR argument will be stored in the watcher's
2098\&\f(CW\*(C`data\*(C'\fR member and is free for you to use.
2099.Sp
2100The prototype of the \f(CW\*(C`function\*(C'\fR must be \f(CW\*(C`void (*)(ev::TYPE &w, int)\*(C'\fR.
2101.Sp
2102See the method\-\f(CW\*(C`set\*(C'\fR above for more details.
2103.Sp
2104Example:
2105.Sp
2106.Vb 2
2107\& static void io_cb (ev::io &w, int revents) { }
2108\& iow.set <io_cb> ();
2109.Ve
1878.IP "w\->set (struct ev_loop *)" 4 2110.IP "w\->set (struct ev_loop *)" 4
1879.IX Item "w->set (struct ev_loop *)" 2111.IX Item "w->set (struct ev_loop *)"
1880Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only 2112Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only
1881do this when the watcher is inactive (and not pending either). 2113do this when the watcher is inactive (and not pending either).
1882.IP "w\->set ([args])" 4 2114.IP "w\->set ([args])" 4
1883.IX Item "w->set ([args])" 2115.IX Item "w->set ([args])"
1884Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same args. Must be 2116Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same args. Must be
1885called at least once. Unlike the C counterpart, an active watcher gets 2117called at least once. Unlike the C counterpart, an active watcher gets
1886automatically stopped and restarted. 2118automatically stopped and restarted when reconfiguring it with this
2119method.
1887.IP "w\->start ()" 4 2120.IP "w\->start ()" 4
1888.IX Item "w->start ()" 2121.IX Item "w->start ()"
1889Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument as the 2122Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the
1890constructor already takes the loop. 2123constructor already stores the event loop.
1891.IP "w\->stop ()" 4 2124.IP "w\->stop ()" 4
1892.IX Item "w->stop ()" 2125.IX Item "w->stop ()"
1893Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument. 2126Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument.
1894.ie n .IP "w\->again () ""ev::timer""\fR, \f(CW""ev::periodic"" only" 4 2127.ie n .IP "w\->again () ""ev::timer""\fR, \f(CW""ev::periodic"" only" 4
1895.el .IP "w\->again () \f(CWev::timer\fR, \f(CWev::periodic\fR only" 4 2128.el .IP "w\->again () \f(CWev::timer\fR, \f(CWev::periodic\fR only" 4
… …
1921.Vb 2 2154.Vb 2
1922\& myclass (); 2155\& myclass ();
1923\& } 2156\& }
1924.Ve 2157.Ve
1925.PP 2158.PP
1926.Vb 6 2159.Vb 4
1927\& myclass::myclass (int fd) 2160\& myclass::myclass (int fd)
1928\& : io (this, &myclass::io_cb),
1929\& idle (this, &myclass::idle_cb)
1930\& { 2161\& {
2162\& io .set <myclass, &myclass::io_cb > (this);
2163\& idle.set <myclass, &myclass::idle_cb> (this);
2164.Ve
2165.PP
2166.Vb 2
1931\& io.start (fd, ev::READ); 2167\& io.start (fd, ev::READ);
1932\& } 2168\& }
1933.Ve 2169.Ve
1934.SH "MACRO MAGIC" 2170.SH "MACRO MAGIC"
1935.IX Header "MACRO MAGIC" 2171.IX Header "MACRO MAGIC"
1936Libev can be compiled with a variety of options, the most fundemantal is 2172Libev can be compiled with a variety of options, the most fundemantal is
1937\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines wether (most) functions and 2173\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most) functions and
1938callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument. 2174callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument.
1939.PP 2175.PP
1940To make it easier to write programs that cope with either variant, the 2176To make it easier to write programs that cope with either variant, the
1941following macros are defined: 2177following macros are defined:
1942.ie n .IP """EV_A""\fR, \f(CW""EV_A_""" 4 2178.ie n .IP """EV_A""\fR, \f(CW""EV_A_""" 4
… …
1977.el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4 2213.el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4
1978.IX Item "EV_DEFAULT, EV_DEFAULT_" 2214.IX Item "EV_DEFAULT, EV_DEFAULT_"
1979Similar to the other two macros, this gives you the value of the default 2215Similar to the other two macros, this gives you the value of the default
1980loop, if multiple loops are supported (\*(L"ev loop default\*(R"). 2216loop, if multiple loops are supported (\*(L"ev loop default\*(R").
1981.PP 2217.PP
1982Example: Declare and initialise a check watcher, working regardless of 2218Example: Declare and initialise a check watcher, utilising the above
1983wether multiple loops are supported or not. 2219macros so it will work regardless of whether multiple loops are supported
2220or not.
1984.PP 2221.PP
1985.Vb 5 2222.Vb 5
1986\& static void 2223\& static void
1987\& check_cb (EV_P_ ev_timer *w, int revents) 2224\& check_cb (EV_P_ ev_timer *w, int revents)
1988\& { 2225\& {
… …
2051.Vb 1 2288.Vb 1
2052\& ev_win32.c required on win32 platforms only 2289\& ev_win32.c required on win32 platforms only
2053.Ve 2290.Ve
2054.PP 2291.PP
2055.Vb 5 2292.Vb 5
2056\& ev_select.c only when select backend is enabled (which is by default) 2293\& ev_select.c only when select backend is enabled (which is enabled by default)
2057\& ev_poll.c only when poll backend is enabled (disabled by default) 2294\& ev_poll.c only when poll backend is enabled (disabled by default)
2058\& ev_epoll.c only when the epoll backend is enabled (disabled by default) 2295\& ev_epoll.c only when the epoll backend is enabled (disabled by default)
2059\& ev_kqueue.c only when the kqueue backend is enabled (disabled by default) 2296\& ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2060\& ev_port.c only when the solaris port backend is enabled (disabled by default) 2297\& ev_port.c only when the solaris port backend is enabled (disabled by default)
2061.Ve 2298.Ve
… …
2214If undefined or defined to \f(CW1\fR, then all event-loop-specific functions 2451If undefined or defined to \f(CW1\fR, then all event-loop-specific functions
2215will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create 2452will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create
2216additional independent event loops. Otherwise there will be no support 2453additional independent event loops. Otherwise there will be no support
2217for multiple event loops and there is no first event loop pointer 2454for multiple event loops and there is no first event loop pointer
2218argument. Instead, all functions act on the single default loop. 2455argument. Instead, all functions act on the single default loop.
2456.IP "\s-1EV_MINPRI\s0" 4
2457.IX Item "EV_MINPRI"
2458.PD 0
2459.IP "\s-1EV_MAXPRI\s0" 4
2460.IX Item "EV_MAXPRI"
2461.PD
2462The range of allowed priorities. \f(CW\*(C`EV_MINPRI\*(C'\fR must be smaller or equal to
2463\&\f(CW\*(C`EV_MAXPRI\*(C'\fR, but otherwise there are no non-obvious limitations. You can
2464provide for more priorities by overriding those symbols (usually defined
2465to be \f(CW\*(C`\-2\*(C'\fR and \f(CW2\fR, respectively).
2466.Sp
2467When doing priority-based operations, libev usually has to linearly search
2468all the priorities, so having many of them (hundreds) uses a lot of space
2469and time, so using the defaults of five priorities (\-2 .. +2) is usually
2470fine.
2471.Sp
2472If your embedding app does not need any priorities, defining these both to
2473\&\f(CW0\fR will save some memory and cpu.
2219.IP "\s-1EV_PERIODIC_ENABLE\s0" 4 2474.IP "\s-1EV_PERIODIC_ENABLE\s0" 4
2220.IX Item "EV_PERIODIC_ENABLE" 2475.IX Item "EV_PERIODIC_ENABLE"
2221If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If 2476If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If
2477defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
2478code.
2479.IP "\s-1EV_IDLE_ENABLE\s0" 4
2480.IX Item "EV_IDLE_ENABLE"
2481If undefined or defined to be \f(CW1\fR, then idle watchers are supported. If
2222defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of 2482defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
2223code. 2483code.
2224.IP "\s-1EV_EMBED_ENABLE\s0" 4 2484.IP "\s-1EV_EMBED_ENABLE\s0" 4
2225.IX Item "EV_EMBED_ENABLE" 2485.IX Item "EV_EMBED_ENABLE"
2226If undefined or defined to be \f(CW1\fR, then embed watchers are supported. If 2486If undefined or defined to be \f(CW1\fR, then embed watchers are supported. If
… …
2288interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file 2548interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file
2289will be compiled. It is pretty complex because it provides its own header 2549will be compiled. It is pretty complex because it provides its own header
2290file. 2550file.
2291.Sp 2551.Sp
2292The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file 2552The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file
2293that everybody includes and which overrides some autoconf choices: 2553that everybody includes and which overrides some configure choices:
2294.Sp 2554.Sp
2295.Vb 4 2555.Vb 9
2556\& #define EV_MINIMAL 1
2296\& #define EV_USE_POLL 0 2557\& #define EV_USE_POLL 0
2297\& #define EV_MULTIPLICITY 0 2558\& #define EV_MULTIPLICITY 0
2298\& #define EV_PERIODICS 0 2559\& #define EV_PERIODIC_ENABLE 0
2560\& #define EV_STAT_ENABLE 0
2561\& #define EV_FORK_ENABLE 0
2299\& #define EV_CONFIG_H <config.h> 2562\& #define EV_CONFIG_H <config.h>
2563\& #define EV_MINPRI 0
2564\& #define EV_MAXPRI 0
2300.Ve 2565.Ve
2301.Sp 2566.Sp
2302.Vb 1 2567.Vb 1
2303\& #include "ev++.h" 2568\& #include "ev++.h"
2304.Ve 2569.Ve
… …
2312.SH "COMPLEXITIES" 2577.SH "COMPLEXITIES"
2313.IX Header "COMPLEXITIES" 2578.IX Header "COMPLEXITIES"
2314In this section the complexities of (many of) the algorithms used inside 2579In this section the complexities of (many of) the algorithms used inside
2315libev will be explained. For complexity discussions about backends see the 2580libev will be explained. For complexity discussions about backends see the
2316documentation for \f(CW\*(C`ev_default_init\*(C'\fR. 2581documentation for \f(CW\*(C`ev_default_init\*(C'\fR.
2582.Sp
2583All of the following are about amortised time: If an array needs to be
2584extended, libev needs to realloc and move the whole array, but this
2585happens asymptotically never with higher number of elements, so O(1) might
2586mean it might do a lengthy realloc operation in rare cases, but on average
2587it is much faster and asymptotically approaches constant time.
2317.RS 4 2588.RS 4
2318.IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4 2589.IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4
2319.IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 2590.IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)"
2320.PD 0 2591This means that, when you have a watcher that triggers in one hour and
2592there are 100 watchers that would trigger before that then inserting will
2593have to skip those 100 watchers.
2321.IP "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)" 4 2594.IP "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)" 4
2322.IX Item "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)" 2595.IX Item "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)"
2596That means that for changing a timer costs less than removing/adding them
2597as only the relative motion in the event queue has to be paid for.
2323.IP "Starting io/check/prepare/idle/signal/child watchers: O(1)" 4 2598.IP "Starting io/check/prepare/idle/signal/child watchers: O(1)" 4
2324.IX Item "Starting io/check/prepare/idle/signal/child watchers: O(1)" 2599.IX Item "Starting io/check/prepare/idle/signal/child watchers: O(1)"
2325.IP "Stopping check/prepare/idle watchers: O(1)" 4 2600These just add the watcher into an array or at the head of a list.
2326.IX Item "Stopping check/prepare/idle watchers: O(1)" 2601=item Stopping check/prepare/idle watchers: O(1)
2327.IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4 2602.IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4
2328.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))" 2603.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))"
2604These watchers are stored in lists then need to be walked to find the
2605correct watcher to remove. The lists are usually short (you don't usually
2606have many watchers waiting for the same fd or signal).
2329.IP "Finding the next timer per loop iteration: O(1)" 4 2607.IP "Finding the next timer per loop iteration: O(1)" 4
2330.IX Item "Finding the next timer per loop iteration: O(1)" 2608.IX Item "Finding the next timer per loop iteration: O(1)"
2609.PD 0
2331.IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4 2610.IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4
2332.IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 2611.IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)"
2612.PD
2613A change means an I/O watcher gets started or stopped, which requires
2614libev to recalculate its status (and possibly tell the kernel).
2333.IP "Activating one watcher: O(1)" 4 2615.IP "Activating one watcher: O(1)" 4
2334.IX Item "Activating one watcher: O(1)" 2616.IX Item "Activating one watcher: O(1)"
2617.PD 0
2618.IP "Priority handling: O(number_of_priorities)" 4
2619.IX Item "Priority handling: O(number_of_priorities)"
2620.PD
2621Priorities are implemented by allocating some space for each
2622priority. When doing priority-based operations, libev usually has to
2623linearly search all the priorities.
2335.RE 2624.RE
2336.RS 4 2625.RS 4
2337.PD
2338.SH "AUTHOR" 2626.SH "AUTHOR"
2339.IX Header "AUTHOR" 2627.IX Header "AUTHOR"
2340Marc Lehmann <libev@schmorp.de>. 2628Marc Lehmann <libev@schmorp.de>.

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