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Revision 1.115 by root, Wed Jun 26 00:01:46 2019 UTC vs.
Revision 1.120 by root, Wed Jan 22 13:33:44 2020 UTC

… …
131.\} 131.\}
132.rm #[ #] #H #V #F C 132.rm #[ #] #H #V #F C
133.\" ======================================================================== 133.\" ========================================================================
134.\" 134.\"
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 "2020-01-22" "libev-4.31" "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"
… …
606want 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
607unblocking the signals. 607unblocking the signals.
608.Sp 608.Sp
609It'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
610\&\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.
611.Sp 618.Sp
612This 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.
613.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4 622.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4
614.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
615.IX Item "EVBACKEND_SELECT (value 1, portable select backend)" 624.IX Item "EVBACKEND_SELECT (value 1, portable select backend)"
616This 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
617libev 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,
… …
1340with 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
1341*)\*(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
1342corresponding 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.
1343.PP 1352.PP
1344As 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
1345must not touch the values stored in it. Most specifically you must never 1354must not touch the values stored in it except when explicitly documented
1346reinitialise 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.
1347.PP 1357.PP
1348Each and every callback receives the event loop pointer as first, the 1358Each and every callback receives the event loop pointer as first, the
1349registered watcher structure as second, and a bitset of received events as 1359registered watcher structure as second, and a bitset of received events as
1350third argument. 1360third argument.
1351.PP 1361.PP
… …
1654.IX Subsection "WATCHER PRIORITY MODELS" 1664.IX Subsection "WATCHER PRIORITY MODELS"
1655Many event loops support \fIwatcher priorities\fR, which are usually small 1665Many event loops support \fIwatcher priorities\fR, which are usually small
1656integers that influence the ordering of event callback invocation 1666integers that influence the ordering of event callback invocation
1657between watchers in some way, all else being equal. 1667between watchers in some way, all else being equal.
1658.PP 1668.PP
1659In libev, Watcher priorities can be set using \f(CW\*(C`ev_set_priority\*(C'\fR. See its 1669In libev, watcher priorities can be set using \f(CW\*(C`ev_set_priority\*(C'\fR. See its
1660description for the more technical details such as the actual priority 1670description for the more technical details such as the actual priority
1661range. 1671range.
1662.PP 1672.PP
1663There are two common ways how these these priorities are being interpreted 1673There are two common ways how these these priorities are being interpreted
1664by event loops: 1674by event loops:
… …
1758.IX Header "WATCHER TYPES" 1768.IX Header "WATCHER TYPES"
1759This section describes each watcher in detail, but will not repeat 1769This section describes each watcher in detail, but will not repeat
1760information given in the last section. Any initialisation/set macros, 1770information given in the last section. Any initialisation/set macros,
1761functions and members specific to the watcher type are explained. 1771functions and members specific to the watcher type are explained.
1762.PP 1772.PP
1763Members are additionally marked with either \fI[read\-only]\fR, meaning that, 1773Most members are additionally marked with either \fI[read\-only]\fR, meaning
1764while the watcher is active, you can look at the member and expect some 1774that, while the watcher is active, you can look at the member and expect
1765sensible content, but you must not modify it (you can modify it while the 1775some sensible content, but you must not modify it (you can modify it while
1766watcher is stopped to your hearts content), or \fI[read\-write]\fR, which 1776the watcher is stopped to your hearts content), or \fI[read\-write]\fR, which
1767means you can expect it to have some sensible content while the watcher 1777means you can expect it to have some sensible content while the watcher
1768is active, but you can also modify it. Modifying it may not do something 1778is active, but you can also modify it. Modifying it may not do something
1769sensible or take immediate effect (or do anything at all), but libev will 1779sensible or take immediate effect (or do anything at all), but libev will
1770not crash or malfunction in any way. 1780not crash or malfunction in any way.
1781.PP
1782In any case, the documentation for each member will explain what the
1783effects are, and if there are any additional access restrictions.
1771.ie n .SS """ev_io"" \- is this file descriptor readable or writable?" 1784.ie n .SS """ev_io"" \- is this file descriptor readable or writable?"
1772.el .SS "\f(CWev_io\fP \- is this file descriptor readable or writable?" 1785.el .SS "\f(CWev_io\fP \- is this file descriptor readable or writable?"
1773.IX Subsection "ev_io - is this file descriptor readable or writable?" 1786.IX Subsection "ev_io - is this file descriptor readable or writable?"
1774I/O watchers check whether a file descriptor is readable or writable 1787I/O watchers check whether a file descriptor is readable or writable
1775in each iteration of the event loop, or, more precisely, when reading 1788in each iteration of the event loop, or, more precisely, when reading
… …
1871reuse the same code path. 1884reuse the same code path.
1872.PP 1885.PP
1873\fIThe special problem of fork\fR 1886\fIThe special problem of fork\fR
1874.IX Subsection "The special problem of fork" 1887.IX Subsection "The special problem of fork"
1875.PP 1888.PP
1876Some backends (epoll, kqueue, probably linuxaio) do not support \f(CW\*(C`fork ()\*(C'\fR 1889Some backends (epoll, kqueue, linuxaio, iouring) do not support \f(CW\*(C`fork ()\*(C'\fR
1877at all or exhibit useless behaviour. Libev fully supports fork, but needs 1890at all or exhibit useless behaviour. Libev fully supports fork, but needs
1878to be told about it in the child if you want to continue to use it in the 1891to be told about it in the child if you want to continue to use it in the
1879child. 1892child.
1880.PP 1893.PP
1881To support fork in your child processes, you have to call \f(CW\*(C`ev_loop_fork 1894To support fork in your child processes, you have to call \f(CW\*(C`ev_loop_fork
… …
1941.PD 0 1954.PD 0
1942.IP "ev_io_set (ev_io *, int fd, int events)" 4 1955.IP "ev_io_set (ev_io *, int fd, int events)" 4
1943.IX Item "ev_io_set (ev_io *, int fd, int events)" 1956.IX Item "ev_io_set (ev_io *, int fd, int events)"
1944.PD 1957.PD
1945Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to 1958Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to
1946receive 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 1959receive 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
1947\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR, to express the desire to receive the given events. 1960\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR or \f(CW0\fR, to express the desire to receive the given
1961events.
1962.Sp
1963Note that setting the \f(CW\*(C`events\*(C'\fR to \f(CW0\fR and starting the watcher is
1964supported, but not specially optimized \- if your program sometimes happens
1965to generate this combination this is fine, but if it is easy to avoid
1966starting an io watcher watching for no events you should do so.
1967.IP "ev_io_modify (ev_io *, int events)" 4
1968.IX Item "ev_io_modify (ev_io *, int events)"
1969Similar to \f(CW\*(C`ev_io_set\*(C'\fR, but only changes the event mask. Using this might
1970be faster with some backends, as libev can assume that the \f(CW\*(C`fd\*(C'\fR still
1971refers to the same underlying file description, something it cannot do
1972when using \f(CW\*(C`ev_io_set\*(C'\fR.
1948.IP "int fd [read\-only]" 4 1973.IP "int fd [no\-modify]" 4
1949.IX Item "int fd [read-only]" 1974.IX Item "int fd [no-modify]"
1950The file descriptor being watched. 1975The file descriptor being watched. While it can be read at any time, you
1976must not modify this member even when the watcher is stopped \- always use
1977\&\f(CW\*(C`ev_io_set\*(C'\fR for that.
1951.IP "int events [read\-only]" 4 1978.IP "int events [no\-modify]" 4
1952.IX Item "int events [read-only]" 1979.IX Item "int events [no-modify]"
1953The events being watched. 1980The set of events the fd is being watched for, among other flags. Remember
1981that this is a bit set \- to test for \f(CW\*(C`EV_READ\*(C'\fR, use \f(CW\*(C`w\->events &
1982EV_READ\*(C'\fR, and similarly for \f(CW\*(C`EV_WRITE\*(C'\fR.
1983.Sp
1984As with \f(CW\*(C`fd\*(C'\fR, you must not modify this member even when the watcher is
1985stopped, always use \f(CW\*(C`ev_io_set\*(C'\fR or \f(CW\*(C`ev_io_modify\*(C'\fR for that.
1954.PP 1986.PP
1955\fIExamples\fR 1987\fIExamples\fR
1956.IX Subsection "Examples" 1988.IX Subsection "Examples"
1957.PP 1989.PP
1958Example: Call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well 1990Example: Call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well
… …
4386gets automatically stopped and restarted when reconfiguring it with this 4418gets automatically stopped and restarted when reconfiguring it with this
4387method. 4419method.
4388.Sp 4420.Sp
4389For \f(CW\*(C`ev::embed\*(C'\fR watchers this method is called \f(CW\*(C`set_embed\*(C'\fR, to avoid 4421For \f(CW\*(C`ev::embed\*(C'\fR watchers this method is called \f(CW\*(C`set_embed\*(C'\fR, to avoid
4390clashing with the \f(CW\*(C`set (loop)\*(C'\fR method. 4422clashing with the \f(CW\*(C`set (loop)\*(C'\fR method.
4423.Sp
4424For \f(CW\*(C`ev::io\*(C'\fR watchers there is an additional \f(CW\*(C`set\*(C'\fR method that acepts a
4425new event mask only, and internally calls \f(CW\*(C`ev_io_modfify\*(C'\fR.
4391.IP "w\->start ()" 4 4426.IP "w\->start ()" 4
4392.IX Item "w->start ()" 4427.IX Item "w->start ()"
4393Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the 4428Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the
4394constructor already stores the event loop. 4429constructor already stores the event loop.
4395.IP "w\->start ([arguments])" 4 4430.IP "w\->start ([arguments])" 4
… …
4624\& 4659\&
4625\& ev_select.c only when select backend is enabled 4660\& ev_select.c only when select backend is enabled
4626\& ev_poll.c only when poll backend is enabled 4661\& ev_poll.c only when poll backend is enabled
4627\& ev_epoll.c only when the epoll backend is enabled 4662\& ev_epoll.c only when the epoll backend is enabled
4628\& ev_linuxaio.c only when the linux aio backend is enabled 4663\& ev_linuxaio.c only when the linux aio backend is enabled
4664\& ev_iouring.c only when the linux io_uring backend is enabled
4629\& ev_kqueue.c only when the kqueue backend is enabled 4665\& ev_kqueue.c only when the kqueue backend is enabled
4630\& ev_port.c only when the solaris port backend is enabled 4666\& ev_port.c only when the solaris port backend is enabled
4631.Ve 4667.Ve
4632.PP 4668.PP
4633\&\fIev.c\fR includes the backend files directly when enabled, so you only need 4669\&\fIev.c\fR includes the backend files directly when enabled, so you only need
… …
4746higher, as it simplifies linking (no need for \f(CW\*(C`\-lrt\*(C'\fR). 4782higher, as it simplifies linking (no need for \f(CW\*(C`\-lrt\*(C'\fR).
4747.IP "\s-1EV_USE_NANOSLEEP\s0" 4 4783.IP "\s-1EV_USE_NANOSLEEP\s0" 4
4748.IX Item "EV_USE_NANOSLEEP" 4784.IX Item "EV_USE_NANOSLEEP"
4749If defined to be \f(CW1\fR, libev will assume that \f(CW\*(C`nanosleep ()\*(C'\fR is available 4785If defined to be \f(CW1\fR, libev will assume that \f(CW\*(C`nanosleep ()\*(C'\fR is available
4750and will use it for delays. Otherwise it will use \f(CW\*(C`select ()\*(C'\fR. 4786and will use it for delays. Otherwise it will use \f(CW\*(C`select ()\*(C'\fR.
4787.IP "\s-1EV_USE_EVENTFD\s0" 4
4788.IX Item "EV_USE_EVENTFD"
4789If defined to be \f(CW1\fR, then libev will assume that \f(CW\*(C`eventfd ()\*(C'\fR is
4790available and will probe for kernel support at runtime. This will improve
4791\&\f(CW\*(C`ev_signal\*(C'\fR and \f(CW\*(C`ev_async\*(C'\fR performance and reduce resource consumption.
4792If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
47932.7 or newer, otherwise disabled.
4794.IP "\s-1EV_USE_SIGNALFD\s0" 4
4795.IX Item "EV_USE_SIGNALFD"
4796If defined to be \f(CW1\fR, then libev will assume that \f(CW\*(C`signalfd ()\*(C'\fR is
4797available and will probe for kernel support at runtime. This enables
4798the use of \s-1EVFLAG_SIGNALFD\s0 for faster and simpler signal handling. If
4799undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
48002.7 or newer, otherwise disabled.
4801.IP "\s-1EV_USE_TIMERFD\s0" 4
4802.IX Item "EV_USE_TIMERFD"
4803If defined to be \f(CW1\fR, then libev will assume that \f(CW\*(C`timerfd ()\*(C'\fR is
4804available and will probe for kernel support at runtime. This allows
4805libev to detect time jumps accurately. If undefined, it will be enabled
4806if the headers indicate GNU/Linux + Glibc 2.8 or newer and define
4807\&\f(CW\*(C`TFD_TIMER_CANCEL_ON_SET\*(C'\fR, otherwise disabled.
4751.IP "\s-1EV_USE_EVENTFD\s0" 4 4808.IP "\s-1EV_USE_EVENTFD\s0" 4
4752.IX Item "EV_USE_EVENTFD" 4809.IX Item "EV_USE_EVENTFD"
4753If defined to be \f(CW1\fR, then libev will assume that \f(CW\*(C`eventfd ()\*(C'\fR is 4810If defined to be \f(CW1\fR, then libev will assume that \f(CW\*(C`eventfd ()\*(C'\fR is
4754available and will probe for kernel support at runtime. This will improve 4811available and will probe for kernel support at runtime. This will improve
4755\&\f(CW\*(C`ev_signal\*(C'\fR and \f(CW\*(C`ev_async\*(C'\fR performance and reduce resource consumption. 4812\&\f(CW\*(C`ev_signal\*(C'\fR and \f(CW\*(C`ev_async\*(C'\fR performance and reduce resource consumption.
… …
4816otherwise another method will be used as fallback. This is the preferred 4873otherwise another method will be used as fallback. This is the preferred
4817backend for GNU/Linux systems. If undefined, it will be enabled if the 4874backend for GNU/Linux systems. If undefined, it will be enabled if the
4818headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. 4875headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
4819.IP "\s-1EV_USE_LINUXAIO\s0" 4 4876.IP "\s-1EV_USE_LINUXAIO\s0" 4
4820.IX Item "EV_USE_LINUXAIO" 4877.IX Item "EV_USE_LINUXAIO"
4878If defined to be \f(CW1\fR, libev will compile in support for the Linux aio
4879backend (\f(CW\*(C`EV_USE_EPOLL\*(C'\fR must also be enabled). If undefined, it will be
4880enabled on linux, otherwise disabled.
4881.IP "\s-1EV_USE_IOURING\s0" 4
4882.IX Item "EV_USE_IOURING"
4821If defined to be \f(CW1\fR, libev will compile in support for the Linux 4883If defined to be \f(CW1\fR, libev will compile in support for the Linux
4822aio backend. Due to it's currenbt limitations it has to be requested 4884io_uring backend (\f(CW\*(C`EV_USE_EPOLL\*(C'\fR must also be enabled). Due to it's
4823explicitly. If undefined, it will be enabled on linux, otherwise 4885current limitations it has to be requested explicitly. If undefined, it
4824disabled. 4886will be enabled on linux, otherwise disabled.
4825.IP "\s-1EV_USE_KQUEUE\s0" 4 4887.IP "\s-1EV_USE_KQUEUE\s0" 4
4826.IX Item "EV_USE_KQUEUE" 4888.IX Item "EV_USE_KQUEUE"
4827If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style 4889If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style
4828\&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime, 4890\&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime,
4829otherwise another method will be used as fallback. This is the preferred 4891otherwise another method will be used as fallback. This is the preferred

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