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Revision 1.114 by root, Tue Jun 25 06:36:59 2019 UTC vs.
Revision 1.126 by root, Sat Jun 3 08:53:03 2023 UTC

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135.IX Title "LIBEV 3" 135.IX Title "LIBEV 3"
136.TH LIBEV 3 "2019-06-25" "libev-4.25" "libev - high performance full featured event loop" 136.TH LIBEV 3 "2023-05-15" "libev-4.33" "libev - high performance full featured event loop"
137.\" For nroff, turn off justification. Always turn off hyphenation; it makes 137.\" For nroff, turn off justification. Always turn off hyphenation; it makes
138.\" way too many mistakes in technical documents. 138.\" way too many mistakes in technical documents.
139.if n .ad l 139.if n .ad l
140.nh 140.nh
141.SH "NAME" 141.SH "NAME"
291When libev detects a usage error such as a negative timer interval, then 291When libev detects a usage error such as a negative timer interval, then
292it will print a diagnostic message and abort (via the \f(CW\*(C`assert\*(C'\fR mechanism, 292it will print a diagnostic message and abort (via the \f(CW\*(C`assert\*(C'\fR mechanism,
293so \f(CW\*(C`NDEBUG\*(C'\fR will disable this checking): these are programming errors in 293so \f(CW\*(C`NDEBUG\*(C'\fR will disable this checking): these are programming errors in
294the libev caller and need to be fixed there. 294the libev caller and need to be fixed there.
295.PP 295.PP
296Via the \f(CW\*(C`EV_FREQUENT\*(C'\fR macro you can compile in and/or enable extensive
297consistency checking code inside libev that can be used to check for
298internal inconsistencies, suually caused by application bugs.
299.PP
296Libev also has a few internal error-checking \f(CW\*(C`assert\*(C'\fRions, and also has 300Libev also has a few internal error-checking \f(CW\*(C`assert\*(C'\fRions. These do not
297extensive consistency checking code. These do not trigger under normal
298circumstances, as they indicate either a bug in libev or worse. 301trigger under normal circumstances, as they indicate either a bug in libev
302or worse.
299.SH "GLOBAL FUNCTIONS" 303.SH "GLOBAL FUNCTIONS"
300.IX Header "GLOBAL FUNCTIONS" 304.IX Header "GLOBAL FUNCTIONS"
301These functions can be called anytime, even before initialising the 305These functions can be called anytime, even before initialising the
302library in any way. 306library in any way.
303.IP "ev_tstamp ev_time ()" 4 307.IP "ev_tstamp ev_time ()" 4
602want to handle signals only in specific threads and want to avoid libev 606want to handle signals only in specific threads and want to avoid libev
603unblocking the signals. 607unblocking the signals.
604.Sp 608.Sp
605It's also required by \s-1POSIX\s0 in a threaded program, as libev calls 609It's also required by \s-1POSIX\s0 in a threaded program, as libev calls
606\&\f(CW\*(C`sigprocmask\*(C'\fR, whose behaviour is officially unspecified. 610\&\f(CW\*(C`sigprocmask\*(C'\fR, whose behaviour is officially unspecified.
611.ie n .IP """EVFLAG_NOTIMERFD""" 4
612.el .IP "\f(CWEVFLAG_NOTIMERFD\fR" 4
613.IX Item "EVFLAG_NOTIMERFD"
614When this flag is specified, the libev will avoid using a \f(CW\*(C`timerfd\*(C'\fR to
615detect time jumps. It will still be able to detect time jumps, but takes
616longer and has a lower accuracy in doing so, but saves a file descriptor
617per loop.
607.Sp 618.Sp
608This flag's behaviour will become the default in future versions of libev. 619The current implementation only tries to use a \f(CW\*(C`timerfd\*(C'\fR when the first
620\&\f(CW\*(C`ev_periodic\*(C'\fR watcher is started and falls back on other methods if it
621cannot be created, but this behaviour might change in the future.
609.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4 622.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4
610.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4 623.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4
611.IX Item "EVBACKEND_SELECT (value 1, portable select backend)" 624.IX Item "EVBACKEND_SELECT (value 1, portable select backend)"
612This is your standard \fBselect\fR\|(2) backend. Not \fIcompletely\fR standard, as 625This is your standard \fBselect\fR\|(2) backend. Not \fIcompletely\fR standard, as
613libev tries to roll its own fd_set with no limits on the number of fds, 626libev tries to roll its own fd_set with no limits on the number of fds,
788and is not embeddable, which would limit the usefulness of this backend 801and is not embeddable, which would limit the usefulness of this backend
789immensely. 802immensely.
790.ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4 803.ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4
791.el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4 804.el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4
792.IX Item "EVBACKEND_PORT (value 32, Solaris 10)" 805.IX Item "EVBACKEND_PORT (value 32, Solaris 10)"
793This uses the Solaris 10 event port mechanism. As with everything on Solaris, 806This uses the Solaris 10 event port mechanism. As with everything on
794it's really slow, but it still scales very well (O(active_fds)). 807Solaris, it's really slow, but it still scales very well (O(active_fds)).
795.Sp 808.Sp
796While this backend scales well, it requires one system call per active 809While this backend scales well, it requires one system call per active
797file descriptor per loop iteration. For small and medium numbers of file 810file descriptor per loop iteration. For small and medium numbers of file
798descriptors a \*(L"slow\*(R" \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR backend 811descriptors a \*(L"slow\*(R" \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR backend
799might perform better. 812might perform better.
1074\& \- Queue all expired timers. 1087\& \- Queue all expired timers.
1075\& \- Queue all expired periodics. 1088\& \- Queue all expired periodics.
1076\& \- Queue all idle watchers with priority higher than that of pending events. 1089\& \- Queue all idle watchers with priority higher than that of pending events.
1077\& \- Queue all check watchers. 1090\& \- Queue all check watchers.
1078\& \- Call all queued watchers in reverse order (i.e. check watchers first). 1091\& \- Call all queued watchers in reverse order (i.e. check watchers first).
1079\& Signals and child watchers are implemented as I/O watchers, and will 1092\& Signals, async and child watchers are implemented as I/O watchers, and
1080\& be handled here by queueing them when their watcher gets executed. 1093\& will be handled here by queueing them when their watcher gets executed.
1081\& \- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT 1094\& \- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
1082\& were used, or there are no active watchers, goto FINISH, otherwise 1095\& were used, or there are no active watchers, goto FINISH, otherwise
1083\& continue with step LOOP. 1096\& continue with step LOOP.
1084\& FINISH: 1097\& FINISH:
1085\& \- Reset the ev_break status iff it was EVBREAK_ONE. 1098\& \- Reset the ev_break status iff it was EVBREAK_ONE.
1336with a watcher-specific start function (\f(CW\*(C`ev_TYPE_start (loop, watcher 1349with a watcher-specific start function (\f(CW\*(C`ev_TYPE_start (loop, watcher
1337*)\*(C'\fR), and you can stop watching for events at any time by calling the 1350*)\*(C'\fR), and you can stop watching for events at any time by calling the
1338corresponding stop function (\f(CW\*(C`ev_TYPE_stop (loop, watcher *)\*(C'\fR. 1351corresponding stop function (\f(CW\*(C`ev_TYPE_stop (loop, watcher *)\*(C'\fR.
1339.PP 1352.PP
1340As long as your watcher is active (has been started but not stopped) you 1353As long as your watcher is active (has been started but not stopped) you
1341must not touch the values stored in it. Most specifically you must never 1354must not touch the values stored in it except when explicitly documented
1342reinitialise it or call its \f(CW\*(C`ev_TYPE_set\*(C'\fR macro. 1355otherwise. Most specifically you must never reinitialise it or call its
1356\&\f(CW\*(C`ev_TYPE_set\*(C'\fR macro.
1343.PP 1357.PP
1344Each and every callback receives the event loop pointer as first, the 1358Each and every callback receives the event loop pointer as first, the
1345registered watcher structure as second, and a bitset of received events as 1359registered watcher structure as second, and a bitset of received events as
1346third argument. 1360third argument.
1347.PP 1361.PP
1518therefore a good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function. 1532therefore a good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function.
1519.IP "bool ev_is_active (ev_TYPE *watcher)" 4 1533.IP "bool ev_is_active (ev_TYPE *watcher)" 4
1520.IX Item "bool ev_is_active (ev_TYPE *watcher)" 1534.IX Item "bool ev_is_active (ev_TYPE *watcher)"
1521Returns a true value iff the watcher is active (i.e. it has been started 1535Returns a true value iff the watcher is active (i.e. it has been started
1522and not yet been stopped). As long as a watcher is active you must not modify 1536and not yet been stopped). As long as a watcher is active you must not modify
1523it. 1537it unless documented otherwise.
1538.Sp
1539Obviously, it is safe to call this on an active watcher, or actually any
1540watcher that is initialised.
1524.IP "bool ev_is_pending (ev_TYPE *watcher)" 4 1541.IP "bool ev_is_pending (ev_TYPE *watcher)" 4
1525.IX Item "bool ev_is_pending (ev_TYPE *watcher)" 1542.IX Item "bool ev_is_pending (ev_TYPE *watcher)"
1526Returns a true value iff the watcher is pending, (i.e. it has outstanding 1543Returns a true value iff the watcher is pending, (i.e. it has outstanding
1527events but its callback has not yet been invoked). As long as a watcher 1544events but its callback has not yet been invoked). As long as a watcher
1528is pending (but not active) you must not call an init function on it (but 1545is pending (but not active) you must not call an init function on it (but
1529\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe), you must not change its priority, and you must 1546\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe), you must not change its priority, and you must
1530make sure the watcher is available to libev (e.g. you cannot \f(CW\*(C`free ()\*(C'\fR 1547make sure the watcher is available to libev (e.g. you cannot \f(CW\*(C`free ()\*(C'\fR
1531it). 1548it).
1549.Sp
1550It is safe to call this on any watcher in any state as long as it is
1551initialised.
1532.IP "callback ev_cb (ev_TYPE *watcher)" 4 1552.IP "callback ev_cb (ev_TYPE *watcher)" 4
1533.IX Item "callback ev_cb (ev_TYPE *watcher)" 1553.IX Item "callback ev_cb (ev_TYPE *watcher)"
1534Returns the callback currently set on the watcher. 1554Returns the callback currently set on the watcher.
1535.IP "ev_set_cb (ev_TYPE *watcher, callback)" 4 1555.IP "ev_set_cb (ev_TYPE *watcher, callback)" 4
1536.IX Item "ev_set_cb (ev_TYPE *watcher, callback)" 1556.IX Item "ev_set_cb (ev_TYPE *watcher, callback)"
1549from being executed (except for \f(CW\*(C`ev_idle\*(C'\fR watchers). 1569from being executed (except for \f(CW\*(C`ev_idle\*(C'\fR watchers).
1550.Sp 1570.Sp
1551If you need to suppress invocation when higher priority events are pending 1571If you need to suppress invocation when higher priority events are pending
1552you need to look at \f(CW\*(C`ev_idle\*(C'\fR watchers, which provide this functionality. 1572you need to look at \f(CW\*(C`ev_idle\*(C'\fR watchers, which provide this functionality.
1553.Sp 1573.Sp
1554You \fImust not\fR change the priority of a watcher as long as it is active or 1574You \fImust not\fR change the priority of a watcher as long as it is active
1555pending. 1575or pending. Reading the priority with \f(CW\*(C`ev_priority\*(C'\fR is fine in any state.
1556.Sp 1576.Sp
1557Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR is 1577Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR is
1558fine, as long as you do not mind that the priority value you query might 1578fine, as long as you do not mind that the priority value you query might
1559or might not have been clamped to the valid range. 1579or might not have been clamped to the valid range.
1560.Sp 1580.Sp
1579callback to be invoked, which can be accomplished with this function. 1599callback to be invoked, which can be accomplished with this function.
1580.IP "ev_feed_event (loop, ev_TYPE *watcher, int revents)" 4 1600.IP "ev_feed_event (loop, ev_TYPE *watcher, int revents)" 4
1581.IX Item "ev_feed_event (loop, ev_TYPE *watcher, int revents)" 1601.IX Item "ev_feed_event (loop, ev_TYPE *watcher, int revents)"
1582Feeds the given event set into the event loop, as if the specified event 1602Feeds the given event set into the event loop, as if the specified event
1583had happened for the specified watcher (which must be a pointer to an 1603had happened for the specified watcher (which must be a pointer to an
1584initialised but not necessarily started event watcher). Obviously you must 1604initialised but not necessarily started event watcher, though it can be
1585not free the watcher as long as it has pending events. 1605active). Obviously you must not free the watcher as long as it has pending
1606events.
1586.Sp 1607.Sp
1587Stopping the watcher, letting libev invoke it, or calling 1608Stopping the watcher, letting libev invoke it, or calling
1588\&\f(CW\*(C`ev_clear_pending\*(C'\fR will clear the pending event, even if the watcher was 1609\&\f(CW\*(C`ev_clear_pending\*(C'\fR will clear the pending event, even if the watcher was
1589not started in the first place. 1610not started in the first place.
1590.Sp 1611.Sp
1611\&\f(CW\*(C`ev_TYPE_init\*(C'\fR again. 1632\&\f(CW\*(C`ev_TYPE_init\*(C'\fR again.
1612.IP "started/running/active" 4 1633.IP "started/running/active" 4
1613.IX Item "started/running/active" 1634.IX Item "started/running/active"
1614Once a watcher has been started with a call to \f(CW\*(C`ev_TYPE_start\*(C'\fR it becomes 1635Once a watcher has been started with a call to \f(CW\*(C`ev_TYPE_start\*(C'\fR it becomes
1615property of the event loop, and is actively waiting for events. While in 1636property of the event loop, and is actively waiting for events. While in
1616this state it cannot be accessed (except in a few documented ways), moved, 1637this state it cannot be accessed (except in a few documented ways, such as
1617freed or anything else \- the only legal thing is to keep a pointer to it, 1638stoping it), moved, freed or anything else \- the only legal thing is to
1618and call libev functions on it that are documented to work on active watchers. 1639keep a pointer to it, and call libev functions on it that are documented
1640to work on active watchers.
1641.Sp
1642As a rule of thumb, before accessing a member or calling any function on
1643a watcher, it should be stopped (or freshly initialised). If that is not
1644convenient, you can check the documentation for that function or member to
1645see if it is safe to use on an active watcher.
1619.IP "pending" 4 1646.IP "pending" 4
1620.IX Item "pending" 1647.IX Item "pending"
1621If a watcher is active and libev determines that an event it is interested 1648If a watcher is active and libev determines that an event it is interested
1622in has occurred (such as a timer expiring), it will become pending. It will 1649in has occurred (such as a timer expiring), it will become pending. It
1623stay in this pending state until either it is stopped or its callback is 1650will stay in this pending state until either it is explicitly stopped or
1624about to be invoked, so it is not normally pending inside the watcher 1651its callback is about to be invoked, so it is not normally pending inside
1625callback. 1652the watcher callback.
1626.Sp 1653.Sp
1627The watcher might or might not be active while it is pending (for example, 1654Generally, the watcher might or might not be active while it is pending
1628an expired non-repeating timer can be pending but no longer active). If it 1655(for example, an expired non-repeating timer can be pending but no longer
1629is stopped, it can be freely accessed (e.g. by calling \f(CW\*(C`ev_TYPE_set\*(C'\fR), 1656active). If it is pending but not active, it can be freely accessed (e.g.
1630but it is still property of the event loop at this time, so cannot be 1657by calling \f(CW\*(C`ev_TYPE_set\*(C'\fR), but it is still property of the event loop at
1631moved, freed or reused. And if it is active the rules described in the 1658this time, so cannot be moved, freed or reused. And if it is active the
1632previous item still apply. 1659rules described in the previous item still apply.
1660.Sp
1661Explicitly stopping a watcher will also clear the pending state
1662unconditionally, so it is safe to stop a watcher and then free it.
1633.Sp 1663.Sp
1634It is also possible to feed an event on a watcher that is not active (e.g. 1664It is also possible to feed an event on a watcher that is not active (e.g.
1635via \f(CW\*(C`ev_feed_event\*(C'\fR), in which case it becomes pending without being 1665via \f(CW\*(C`ev_feed_event\*(C'\fR), in which case it becomes pending without being
1636active. 1666active.
1637.IP "stopped" 4 1667.IP "stopped" 4
1650.IX Subsection "WATCHER PRIORITY MODELS" 1680.IX Subsection "WATCHER PRIORITY MODELS"
1651Many event loops support \fIwatcher priorities\fR, which are usually small 1681Many event loops support \fIwatcher priorities\fR, which are usually small
1652integers that influence the ordering of event callback invocation 1682integers that influence the ordering of event callback invocation
1653between watchers in some way, all else being equal. 1683between watchers in some way, all else being equal.
1654.PP 1684.PP
1655In libev, Watcher priorities can be set using \f(CW\*(C`ev_set_priority\*(C'\fR. See its 1685In libev, watcher priorities can be set using \f(CW\*(C`ev_set_priority\*(C'\fR. See its
1656description for the more technical details such as the actual priority 1686description for the more technical details such as the actual priority
1657range. 1687range.
1658.PP 1688.PP
1659There are two common ways how these these priorities are being interpreted 1689There are two common ways how these these priorities are being interpreted
1660by event loops: 1690by event loops:
1754.IX Header "WATCHER TYPES" 1784.IX Header "WATCHER TYPES"
1755This section describes each watcher in detail, but will not repeat 1785This section describes each watcher in detail, but will not repeat
1756information given in the last section. Any initialisation/set macros, 1786information given in the last section. Any initialisation/set macros,
1757functions and members specific to the watcher type are explained. 1787functions and members specific to the watcher type are explained.
1758.PP 1788.PP
1759Members are additionally marked with either \fI[read\-only]\fR, meaning that, 1789Most members are additionally marked with either \fI[read\-only]\fR, meaning
1760while the watcher is active, you can look at the member and expect some 1790that, while the watcher is active, you can look at the member and expect
1761sensible content, but you must not modify it (you can modify it while the 1791some sensible content, but you must not modify it (you can modify it while
1762watcher is stopped to your hearts content), or \fI[read\-write]\fR, which 1792the watcher is stopped to your hearts content), or \fI[read\-write]\fR, which
1763means you can expect it to have some sensible content while the watcher 1793means you can expect it to have some sensible content while the watcher is
1764is active, but you can also modify it. Modifying it may not do something 1794active, but you can also modify it (within the same thread as the event
1795loop, i.e. without creating data races). Modifying it may not do something
1765sensible or take immediate effect (or do anything at all), but libev will 1796sensible or take immediate effect (or do anything at all), but libev will
1766not crash or malfunction in any way. 1797not crash or malfunction in any way.
1798.PP
1799In any case, the documentation for each member will explain what the
1800effects are, and if there are any additional access restrictions.
1767.ie n .SS """ev_io"" \- is this file descriptor readable or writable?" 1801.ie n .SS """ev_io"" \- is this file descriptor readable or writable?"
1768.el .SS "\f(CWev_io\fP \- is this file descriptor readable or writable?" 1802.el .SS "\f(CWev_io\fP \- is this file descriptor readable or writable?"
1769.IX Subsection "ev_io - is this file descriptor readable or writable?" 1803.IX Subsection "ev_io - is this file descriptor readable or writable?"
1770I/O watchers check whether a file descriptor is readable or writable 1804I/O watchers check whether a file descriptor is readable or writable
1771in each iteration of the event loop, or, more precisely, when reading 1805in each iteration of the event loop, or, more precisely, when reading
1867reuse the same code path. 1901reuse the same code path.
1868.PP 1902.PP
1869\fIThe special problem of fork\fR 1903\fIThe special problem of fork\fR
1870.IX Subsection "The special problem of fork" 1904.IX Subsection "The special problem of fork"
1871.PP 1905.PP
1872Some backends (epoll, kqueue, probably linuxaio) do not support \f(CW\*(C`fork ()\*(C'\fR 1906Some backends (epoll, kqueue, linuxaio, iouring) do not support \f(CW\*(C`fork ()\*(C'\fR
1873at all or exhibit useless behaviour. Libev fully supports fork, but needs 1907at all or exhibit useless behaviour. Libev fully supports fork, but needs
1874to be told about it in the child if you want to continue to use it in the 1908to be told about it in the child if you want to continue to use it in the
1875child. 1909child.
1876.PP 1910.PP
1877To support fork in your child processes, you have to call \f(CW\*(C`ev_loop_fork 1911To support fork in your child processes, you have to call \f(CW\*(C`ev_loop_fork
1937.PD 0 1971.PD 0
1938.IP "ev_io_set (ev_io *, int fd, int events)" 4 1972.IP "ev_io_set (ev_io *, int fd, int events)" 4
1939.IX Item "ev_io_set (ev_io *, int fd, int events)" 1973.IX Item "ev_io_set (ev_io *, int fd, int events)"
1940.PD 1974.PD
1941Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to 1975Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to
1942receive events for and \f(CW\*(C`events\*(C'\fR is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or 1976receive events for and \f(CW\*(C`events\*(C'\fR is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR, both
1943\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR, to express the desire to receive the given events. 1977\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR or \f(CW0\fR, to express the desire to receive the given
1978events.
1979.Sp
1980Note that setting the \f(CW\*(C`events\*(C'\fR to \f(CW0\fR and starting the watcher is
1981supported, but not specially optimized \- if your program sometimes happens
1982to generate this combination this is fine, but if it is easy to avoid
1983starting an io watcher watching for no events you should do so.
1984.IP "ev_io_modify (ev_io *, int events)" 4
1985.IX Item "ev_io_modify (ev_io *, int events)"
1986Similar to \f(CW\*(C`ev_io_set\*(C'\fR, but only changes the requested events. Using this
1987might be faster with some backends, as libev can assume that the \f(CW\*(C`fd\*(C'\fR
1988still refers to the same underlying file description, something it cannot
1989do when using \f(CW\*(C`ev_io_set\*(C'\fR.
1944.IP "int fd [read\-only]" 4 1990.IP "int fd [no\-modify]" 4
1945.IX Item "int fd [read-only]" 1991.IX Item "int fd [no-modify]"
1946The file descriptor being watched. 1992The file descriptor being watched. While it can be read at any time, you
1993must not modify this member even when the watcher is stopped \- always use
1994\&\f(CW\*(C`ev_io_set\*(C'\fR for that.
1947.IP "int events [read\-only]" 4 1995.IP "int events [no\-modify]" 4
1948.IX Item "int events [read-only]" 1996.IX Item "int events [no-modify]"
1949The events being watched. 1997The set of events the fd is being watched for, among other flags. Remember
1998that this is a bit set \- to test for \f(CW\*(C`EV_READ\*(C'\fR, use \f(CW\*(C`w\->events &
1999EV_READ\*(C'\fR, and similarly for \f(CW\*(C`EV_WRITE\*(C'\fR.
2000.Sp
2001As with \f(CW\*(C`fd\*(C'\fR, you must not modify this member even when the watcher is
2002stopped, always use \f(CW\*(C`ev_io_set\*(C'\fR or \f(CW\*(C`ev_io_modify\*(C'\fR for that.
1950.PP 2003.PP
1951\fIExamples\fR 2004\fIExamples\fR
1952.IX Subsection "Examples" 2005.IX Subsection "Examples"
1953.PP 2006.PP
1954Example: Call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well 2007Example: Call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well
3965.PP 4018.PP
3966First, you need to associate some data with the event loop: 4019First, you need to associate some data with the event loop:
3967.PP 4020.PP
3968.Vb 6 4021.Vb 6
3969\& typedef struct { 4022\& typedef struct {
3970\& mutex_t lock; /* global loop lock */ 4023\& pthread_mutex_t lock; /* global loop lock */
4024\& pthread_t tid;
4025\& pthread_cond_t invoke_cv;
3971\& ev_async async_w; 4026\& ev_async async_w;
3972\& thread_t tid;
3973\& cond_t invoke_cv;
3974\& } userdata; 4027\& } userdata;
3975\& 4028\&
3976\& void prepare_loop (EV_P) 4029\& void prepare_loop (EV_P)
3977\& { 4030\& {
3978\& // for simplicity, we use a static userdata struct. 4031\& // for simplicity, we use a static userdata struct.
3979\& static userdata u; 4032\& static userdata u;
3980\& 4033\&
3981\& ev_async_init (&u\->async_w, async_cb); 4034\& ev_async_init (&u.async_w, async_cb);
3982\& ev_async_start (EV_A_ &u\->async_w); 4035\& ev_async_start (EV_A_ &u.async_w);
3983\& 4036\&
3984\& pthread_mutex_init (&u\->lock, 0); 4037\& pthread_mutex_init (&u.lock, 0);
3985\& pthread_cond_init (&u\->invoke_cv, 0); 4038\& pthread_cond_init (&u.invoke_cv, 0);
3986\& 4039\&
3987\& // now associate this with the loop 4040\& // now associate this with the loop
3988\& ev_set_userdata (EV_A_ u); 4041\& ev_set_userdata (EV_A_ &u);
3989\& ev_set_invoke_pending_cb (EV_A_ l_invoke); 4042\& ev_set_invoke_pending_cb (EV_A_ l_invoke);
3990\& ev_set_loop_release_cb (EV_A_ l_release, l_acquire); 4043\& ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
3991\& 4044\&
3992\& // then create the thread running ev_run 4045\& // then create the thread running ev_run
3993\& pthread_create (&u\->tid, 0, l_run, EV_A); 4046\& pthread_create (&u.tid, 0, l_run, EV_A);
3994\& } 4047\& }
3995.Ve 4048.Ve
3996.PP 4049.PP
3997The callback for the \f(CW\*(C`ev_async\*(C'\fR watcher does nothing: the watcher is used 4050The callback for the \f(CW\*(C`ev_async\*(C'\fR watcher does nothing: the watcher is used
3998solely to wake up the event loop so it takes notice of any new watchers 4051solely to wake up the event loop so it takes notice of any new watchers
4382gets automatically stopped and restarted when reconfiguring it with this 4435gets automatically stopped and restarted when reconfiguring it with this
4383method. 4436method.
4384.Sp 4437.Sp
4385For \f(CW\*(C`ev::embed\*(C'\fR watchers this method is called \f(CW\*(C`set_embed\*(C'\fR, to avoid 4438For \f(CW\*(C`ev::embed\*(C'\fR watchers this method is called \f(CW\*(C`set_embed\*(C'\fR, to avoid
4386clashing with the \f(CW\*(C`set (loop)\*(C'\fR method. 4439clashing with the \f(CW\*(C`set (loop)\*(C'\fR method.
4440.Sp
4441For \f(CW\*(C`ev::io\*(C'\fR watchers there is an additional \f(CW\*(C`set\*(C'\fR method that acepts a
4442new event mask only, and internally calls \f(CW\*(C`ev_io_modify\*(C'\fR.
4387.IP "w\->start ()" 4 4443.IP "w\->start ()" 4
4388.IX Item "w->start ()" 4444.IX Item "w->start ()"
4389Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the 4445Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the
4390constructor already stores the event loop. 4446constructor already stores the event loop.
4391.IP "w\->start ([arguments])" 4 4447.IP "w\->start ([arguments])" 4
4620\& 4676\&
4621\& ev_select.c only when select backend is enabled 4677\& ev_select.c only when select backend is enabled
4622\& ev_poll.c only when poll backend is enabled 4678\& ev_poll.c only when poll backend is enabled
4623\& ev_epoll.c only when the epoll backend is enabled 4679\& ev_epoll.c only when the epoll backend is enabled
4624\& ev_linuxaio.c only when the linux aio backend is enabled 4680\& ev_linuxaio.c only when the linux aio backend is enabled
4681\& ev_iouring.c only when the linux io_uring backend is enabled
4625\& ev_kqueue.c only when the kqueue backend is enabled 4682\& ev_kqueue.c only when the kqueue backend is enabled
4626\& ev_port.c only when the solaris port backend is enabled 4683\& ev_port.c only when the solaris port backend is enabled
4627.Ve 4684.Ve
4628.PP 4685.PP
4629\&\fIev.c\fR includes the backend files directly when enabled, so you only need 4686\&\fIev.c\fR includes the backend files directly when enabled, so you only need
4742higher, as it simplifies linking (no need for \f(CW\*(C`\-lrt\*(C'\fR). 4799higher, as it simplifies linking (no need for \f(CW\*(C`\-lrt\*(C'\fR).
4743.IP "\s-1EV_USE_NANOSLEEP\s0" 4 4800.IP "\s-1EV_USE_NANOSLEEP\s0" 4
4744.IX Item "EV_USE_NANOSLEEP" 4801.IX Item "EV_USE_NANOSLEEP"
4745If defined to be \f(CW1\fR, libev will assume that \f(CW\*(C`nanosleep ()\*(C'\fR is available 4802If defined to be \f(CW1\fR, libev will assume that \f(CW\*(C`nanosleep ()\*(C'\fR is available
4746and will use it for delays. Otherwise it will use \f(CW\*(C`select ()\*(C'\fR. 4803and will use it for delays. Otherwise it will use \f(CW\*(C`select ()\*(C'\fR.
4804.IP "\s-1EV_USE_EVENTFD\s0" 4
4805.IX Item "EV_USE_EVENTFD"
4806If defined to be \f(CW1\fR, then libev will assume that \f(CW\*(C`eventfd ()\*(C'\fR is
4807available and will probe for kernel support at runtime. This will improve
4808\&\f(CW\*(C`ev_signal\*(C'\fR and \f(CW\*(C`ev_async\*(C'\fR performance and reduce resource consumption.
4809If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
48102.7 or newer, otherwise disabled.
4811.IP "\s-1EV_USE_SIGNALFD\s0" 4
4812.IX Item "EV_USE_SIGNALFD"
4813If defined to be \f(CW1\fR, then libev will assume that \f(CW\*(C`signalfd ()\*(C'\fR is
4814available and will probe for kernel support at runtime. This enables
4815the use of \s-1EVFLAG_SIGNALFD\s0 for faster and simpler signal handling. If
4816undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
48172.7 or newer, otherwise disabled.
4818.IP "\s-1EV_USE_TIMERFD\s0" 4
4819.IX Item "EV_USE_TIMERFD"
4820If defined to be \f(CW1\fR, then libev will assume that \f(CW\*(C`timerfd ()\*(C'\fR is
4821available and will probe for kernel support at runtime. This allows
4822libev to detect time jumps accurately. If undefined, it will be enabled
4823if the headers indicate GNU/Linux + Glibc 2.8 or newer and define
4824\&\f(CW\*(C`TFD_TIMER_CANCEL_ON_SET\*(C'\fR, otherwise disabled.
4747.IP "\s-1EV_USE_EVENTFD\s0" 4 4825.IP "\s-1EV_USE_EVENTFD\s0" 4
4748.IX Item "EV_USE_EVENTFD" 4826.IX Item "EV_USE_EVENTFD"
4749If defined to be \f(CW1\fR, then libev will assume that \f(CW\*(C`eventfd ()\*(C'\fR is 4827If defined to be \f(CW1\fR, then libev will assume that \f(CW\*(C`eventfd ()\*(C'\fR is
4750available and will probe for kernel support at runtime. This will improve 4828available and will probe for kernel support at runtime. This will improve
4751\&\f(CW\*(C`ev_signal\*(C'\fR and \f(CW\*(C`ev_async\*(C'\fR performance and reduce resource consumption. 4829\&\f(CW\*(C`ev_signal\*(C'\fR and \f(CW\*(C`ev_async\*(C'\fR performance and reduce resource consumption.
4812otherwise another method will be used as fallback. This is the preferred 4890otherwise another method will be used as fallback. This is the preferred
4813backend for GNU/Linux systems. If undefined, it will be enabled if the 4891backend for GNU/Linux systems. If undefined, it will be enabled if the
4814headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. 4892headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
4815.IP "\s-1EV_USE_LINUXAIO\s0" 4 4893.IP "\s-1EV_USE_LINUXAIO\s0" 4
4816.IX Item "EV_USE_LINUXAIO" 4894.IX Item "EV_USE_LINUXAIO"
4895If defined to be \f(CW1\fR, libev will compile in support for the Linux aio
4896backend (\f(CW\*(C`EV_USE_EPOLL\*(C'\fR must also be enabled). If undefined, it will be
4897enabled on linux, otherwise disabled.
4898.IP "\s-1EV_USE_IOURING\s0" 4
4899.IX Item "EV_USE_IOURING"
4817If defined to be \f(CW1\fR, libev will compile in support for the Linux 4900If defined to be \f(CW1\fR, libev will compile in support for the Linux
4818aio backend. Due to it's currenbt limitations it has to be requested 4901io_uring backend (\f(CW\*(C`EV_USE_EPOLL\*(C'\fR must also be enabled). Due to it's
4819explicitly. If undefined, it will be enabled on linux, otherwise 4902current limitations it has to be requested explicitly. If undefined, it
4820disabled. 4903will be enabled on linux, otherwise disabled.
4821.IP "\s-1EV_USE_KQUEUE\s0" 4 4904.IP "\s-1EV_USE_KQUEUE\s0" 4
4822.IX Item "EV_USE_KQUEUE" 4905.IX Item "EV_USE_KQUEUE"
4823If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style 4906If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style
4824\&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime, 4907\&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime,
4825otherwise another method will be used as fallback. This is the preferred 4908otherwise another method will be used as fallback. This is the preferred
5081in. If set to \f(CW1\fR, then verification code will be compiled in, but not 5164in. If set to \f(CW1\fR, then verification code will be compiled in, but not
5082called. If set to \f(CW2\fR, then the internal verification code will be 5165called. If set to \f(CW2\fR, then the internal verification code will be
5083called once per loop, which can slow down libev. If set to \f(CW3\fR, then the 5166called once per loop, which can slow down libev. If set to \f(CW3\fR, then the
5084verification code will be called very frequently, which will slow down 5167verification code will be called very frequently, which will slow down
5085libev considerably. 5168libev considerably.
5169.Sp
5170Verification errors are reported via C's \f(CW\*(C`assert\*(C'\fR mechanism, so if you
5171disable that (e.g. by defining \f(CW\*(C`NDEBUG\*(C'\fR) then no errors will be reported.
5086.Sp 5172.Sp
5087The default is \f(CW1\fR, unless \f(CW\*(C`EV_FEATURES\*(C'\fR overrides it, in which case it 5173The default is \f(CW1\fR, unless \f(CW\*(C`EV_FEATURES\*(C'\fR overrides it, in which case it
5088will be \f(CW0\fR. 5174will be \f(CW0\fR.
5089.IP "\s-1EV_COMMON\s0" 4 5175.IP "\s-1EV_COMMON\s0" 4
5090.IX Item "EV_COMMON" 5176.IX Item "EV_COMMON"

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