.\" ========================================================================
.\"
.IX Title ""<STANDARD INPUT>" 1"
-.TH "<STANDARD INPUT>" 1 "2007-11-24" "perl v5.8.8" "User Contributed Perl Documentation"
+.TH "<STANDARD INPUT>" 1 "2007-11-27" "perl v5.8.8" "User Contributed Perl Documentation"
.SH "NAME"
libev \- a high performance full\-featured event loop written in C
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
-.Vb 1
+.Vb 2
+\& /* this is the only header you need */
\& #include <ev.h>
.Ve
+.PP
+.Vb 3
+\& /* what follows is a fully working example program */
+\& ev_io stdin_watcher;
+\& ev_timer timeout_watcher;
+.Ve
+.PP
+.Vb 8
+\& /* called when data readable on stdin */
+\& static void
+\& stdin_cb (EV_P_ struct ev_io *w, int revents)
+\& {
+\& /* puts ("stdin ready"); */
+\& ev_io_stop (EV_A_ w); /* just a syntax example */
+\& ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
+\& }
+.Ve
+.PP
+.Vb 6
+\& static void
+\& timeout_cb (EV_P_ struct ev_timer *w, int revents)
+\& {
+\& /* puts ("timeout"); */
+\& ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
+\& }
+.Ve
+.PP
+.Vb 4
+\& int
+\& main (void)
+\& {
+\& struct ev_loop *loop = ev_default_loop (0);
+.Ve
+.PP
+.Vb 3
+\& /* initialise an io watcher, then start it */
+\& ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
+\& ev_io_start (loop, &stdin_watcher);
+.Ve
+.PP
+.Vb 3
+\& /* simple non-repeating 5.5 second timeout */
+\& ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
+\& ev_timer_start (loop, &timeout_watcher);
+.Ve
+.PP
+.Vb 2
+\& /* loop till timeout or data ready */
+\& ev_loop (loop, 0);
+.Ve
+.PP
+.Vb 2
+\& return 0;
+\& }
+.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
Libev is an event loop: you register interest in certain events (such as a
recommended ones.
.Sp
See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info.
-.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4
-.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))"
-Sets the allocation function to use (the prototype is similar to the
-realloc C function, the semantics are identical). It is used to allocate
-and free memory (no surprises here). If it returns zero when memory
-needs to be allocated, the library might abort or take some potentially
-destructive action. The default is your system realloc function.
+.IP "ev_set_allocator (void *(*cb)(void *ptr, size_t size))" 4
+.IX Item "ev_set_allocator (void *(*cb)(void *ptr, size_t size))"
+Sets the allocation function to use (the prototype and semantics are
+identical to the realloc C function). It is used to allocate and free
+memory (no surprises here). If it returns zero when memory needs to be
+allocated, the library might abort or take some potentially destructive
+action. The default is your system realloc function.
.Sp
You could override this function in high-availability programs to, say,
free some memory if it cannot allocate memory, to use a special allocator,
.Sp
.Vb 6
\& static void *
-\& persistent_realloc (void *ptr, long size)
+\& persistent_realloc (void *ptr, size_t size)
\& {
\& for (;;)
\& {
.el .IP "\f(CWEV_CHILD\fR" 4
.IX Item "EV_CHILD"
The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change.
+.ie n .IP """EV_STAT""" 4
+.el .IP "\f(CWEV_STAT\fR" 4
+.IX Item "EV_STAT"
+The path specified in the \f(CW\*(C`ev_stat\*(C'\fR watcher changed its attributes somehow.
.ie n .IP """EV_IDLE""" 4
.el .IP "\f(CWEV_IDLE\fR" 4
.IX Item "EV_IDLE"
many watchers as they want, and all of them will be taken into account
(for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep
\&\f(CW\*(C`ev_loop\*(C'\fR from blocking).
+.ie n .IP """EV_EMBED""" 4
+.el .IP "\f(CWEV_EMBED\fR" 4
+.IX Item "EV_EMBED"
+The embedded event loop specified in the \f(CW\*(C`ev_embed\*(C'\fR watcher needs attention.
+.ie n .IP """EV_FORK""" 4
+.el .IP "\f(CWEV_FORK\fR" 4
+.IX Item "EV_FORK"
+The event loop has been resumed in the child process after fork (see
+\&\f(CW\*(C`ev_fork\*(C'\fR).
.ie n .IP """EV_ERROR""" 4
.el .IP "\f(CWEV_ERROR\fR" 4
.IX Item "EV_ERROR"
your callbacks is well-written it can just attempt the operation and cope
with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded
programs, though, so beware.
-.Sh "\s-1SUMMARY\s0 \s-1OF\s0 \s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0"
-.IX Subsection "SUMMARY OF GENERIC WATCHER FUNCTIONS"
+.Sh "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0"
+.IX Subsection "GENERIC WATCHER FUNCTIONS"
In the following description, \f(CW\*(C`TYPE\*(C'\fR stands for the watcher type,
e.g. \f(CW\*(C`timer\*(C'\fR for \f(CW\*(C`ev_timer\*(C'\fR watchers and \f(CW\*(C`io\*(C'\fR for \f(CW\*(C`ev_io\*(C'\fR watchers.
.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4
You can reinitialise a watcher at any time as long as it has been stopped
(or never started) and there are no pending events outstanding.
.Sp
-The callbakc is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher,
+The callback is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher,
int revents)\*(C'\fR.
.ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4
.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4
.SH "WATCHER TYPES"
.IX Header "WATCHER TYPES"
This section describes each watcher in detail, but will not repeat
-information given in the last section.
-.ie n .Sh """ev_io"" \- is this file descriptor readable or writable"
-.el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable"
-.IX Subsection "ev_io - is this file descriptor readable or writable"
+information given in the last section. Any initialisation/set macros,
+functions and members specific to the watcher type are explained.
+.PP
+Members are additionally marked with either \fI[read\-only]\fR, meaning that,
+while the watcher is active, you can look at the member and expect some
+sensible content, but you must not modify it (you can modify it while the
+watcher is stopped to your hearts content), or \fI[read\-write]\fR, which
+means you can expect it to have some sensible content while the watcher
+is active, but you can also modify it. Modifying it may not do something
+sensible or take immediate effect (or do anything at all), but libev will
+not crash or malfunction in any way.
+.ie n .Sh """ev_io"" \- is this file descriptor readable or writable?"
+.el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable?"
+.IX Subsection "ev_io - is this file descriptor readable or writable?"
I/O watchers check whether a file descriptor is readable or writable
-in each iteration of the event loop (This behaviour is called
-level-triggering because you keep receiving events as long as the
-condition persists. Remember you can stop the watcher if you don't want to
-act on the event and neither want to receive future events).
+in each iteration of the event loop, or, more precisely, when reading
+would not block the process and writing would at least be able to write
+some data. This behaviour is called level-triggering because you keep
+receiving events as long as the condition persists. Remember you can stop
+the watcher if you don't want to act on the event and neither want to
+receive future events.
.PP
In general you can register as many read and/or write event watchers per
fd as you want (as long as you don't confuse yourself). Setting all file
You have to be careful with dup'ed file descriptors, though. Some backends
(the linux epoll backend is a notable example) cannot handle dup'ed file
descriptors correctly if you register interest in two or more fds pointing
-to the same underlying file/socket etc. description (that is, they share
+to the same underlying file/socket/etc. description (that is, they share
the same underlying \*(L"file open\*(R").
.PP
If you must do this, then force the use of a known-to-be-good backend
(at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and
\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR).
+.PP
+Another thing you have to watch out for is that it is quite easy to
+receive \*(L"spurious\*(R" readyness notifications, that is your callback might
+be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block
+because there is no data. Not only are some backends known to create a
+lot of those (for example solaris ports), it is very easy to get into
+this situation even with a relatively standard program structure. Thus
+it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning
+\&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives.
+.PP
+If you cannot run the fd in non-blocking mode (for example you should not
+play around with an Xlib connection), then you have to seperately re-test
+wether a file descriptor is really ready with a known-to-be good interface
+such as poll (fortunately in our Xlib example, Xlib already does this on
+its own, so its quite safe to use).
.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4
.IX Item "ev_io_init (ev_io *, callback, int fd, int events)"
.PD 0
.IP "ev_io_set (ev_io *, int fd, int events)" 4
.IX Item "ev_io_set (ev_io *, int fd, int events)"
.PD
-Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The fd is the file descriptor to rceeive
-events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or \f(CW\*(C`EV_READ |
-EV_WRITE\*(C'\fR to receive the given events.
-.Sp
-Please note that most of the more scalable backend mechanisms (for example
-epoll and solaris ports) can result in spurious readyness notifications
-for file descriptors, so you practically need to use non-blocking I/O (and
-treat callback invocation as hint only), or retest separately with a safe
-interface before doing I/O (XLib can do this), or force the use of either
-\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR, which don't suffer from this
-problem. Also note that it is quite easy to have your callback invoked
-when the readyness condition is no longer valid even when employing
-typical ways of handling events, so its a good idea to use non-blocking
-I/O unconditionally.
+Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to
+rceeive events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or
+\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR to receive the given events.
+.IP "int fd [read\-only]" 4
+.IX Item "int fd [read-only]"
+The file descriptor being watched.
+.IP "int events [read\-only]" 4
+.IX Item "int events [read-only]"
+The events being watched.
.PP
Example: call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well
readable, but only once. Since it is likely line\-buffered, you could
\& ev_io_start (loop, &stdin_readable);
\& ev_loop (loop, 0);
.Ve
-.ie n .Sh """ev_timer"" \- relative and optionally recurring timeouts"
-.el .Sh "\f(CWev_timer\fP \- relative and optionally recurring timeouts"
-.IX Subsection "ev_timer - relative and optionally recurring timeouts"
+.ie n .Sh """ev_timer"" \- relative and optionally repeating timeouts"
+.el .Sh "\f(CWev_timer\fP \- relative and optionally repeating timeouts"
+.IX Subsection "ev_timer - relative and optionally repeating timeouts"
Timer watchers are simple relative timers that generate an event after a
given time, and optionally repeating in regular intervals after that.
.PP
value), or reset the running timer to the repeat value.
.Sp
This sounds a bit complicated, but here is a useful and typical
-example: Imagine you have a tcp connection and you want a so-called idle
-timeout, that is, you want to be called when there have been, say, 60
-seconds of inactivity on the socket. The easiest way to do this is to
-configure an \f(CW\*(C`ev_timer\*(C'\fR with after=repeat=60 and calling ev_timer_again each
-time you successfully read or write some data. If you go into an idle
-state where you do not expect data to travel on the socket, you can stop
-the timer, and again will automatically restart it if need be.
+example: Imagine you have a tcp connection and you want a so-called
+idle timeout, that is, you want to be called when there have been,
+say, 60 seconds of inactivity on the socket. The easiest way to do
+this is to configure an \f(CW\*(C`ev_timer\*(C'\fR with \f(CW\*(C`after\*(C'\fR=\f(CW\*(C`repeat\*(C'\fR=\f(CW60\fR and calling
+\&\f(CW\*(C`ev_timer_again\*(C'\fR each time you successfully read or write some data. If
+you go into an idle state where you do not expect data to travel on the
+socket, you can stop the timer, and again will automatically restart it if
+need be.
+.Sp
+You can also ignore the \f(CW\*(C`after\*(C'\fR value and \f(CW\*(C`ev_timer_start\*(C'\fR altogether
+and only ever use the \f(CW\*(C`repeat\*(C'\fR value:
+.Sp
+.Vb 8
+\& ev_timer_init (timer, callback, 0., 5.);
+\& ev_timer_again (loop, timer);
+\& ...
+\& timer->again = 17.;
+\& ev_timer_again (loop, timer);
+\& ...
+\& timer->again = 10.;
+\& ev_timer_again (loop, timer);
+.Ve
+.Sp
+This is more efficient then stopping/starting the timer eahc time you want
+to modify its timeout value.
+.IP "ev_tstamp repeat [read\-write]" 4
+.IX Item "ev_tstamp repeat [read-write]"
+The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out
+or \f(CW\*(C`ev_timer_again\*(C'\fR is called and determines the next timeout (if any),
+which is also when any modifications are taken into account.
.PP
Example: create a timer that fires after 60 seconds.
.PP
\& // reset the timeout to start ticking again at 10 seconds
\& ev_timer_again (&mytimer);
.Ve
-.ie n .Sh """ev_periodic"" \- to cron or not to cron"
-.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron"
-.IX Subsection "ev_periodic - to cron or not to cron"
+.ie n .Sh """ev_periodic"" \- to cron or not to cron?"
+.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron?"
+.IX Subsection "ev_periodic - to cron or not to cron?"
Periodic watchers are also timers of a kind, but they are very versatile
(and unfortunately a bit complex).
.PP
when you changed some parameters or the reschedule callback would return
a different time than the last time it was called (e.g. in a crond like
program when the crontabs have changed).
+.IP "ev_tstamp interval [read\-write]" 4
+.IX Item "ev_tstamp interval [read-write]"
+The current interval value. Can be modified any time, but changes only
+take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being
+called.
+.IP "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read\-write]" 4
+.IX Item "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]"
+The current reschedule callback, or \f(CW0\fR, if this functionality is
+switched off. Can be changed any time, but changes only take effect when
+the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
.PP
Example: call a callback every hour, or, more precisely, whenever the
system clock is divisible by 3600. The callback invocation times have
\& fmod (ev_now (loop), 3600.), 3600., 0);
\& ev_periodic_start (loop, &hourly_tick);
.Ve
-.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled"
-.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled"
-.IX Subsection "ev_signal - signal me when a signal gets signalled"
+.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled!"
+.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled!"
+.IX Subsection "ev_signal - signal me when a signal gets signalled!"
Signal watchers will trigger an event when the process receives a specific
signal one or more times. Even though signals are very asynchronous, libev
will try it's best to deliver signals synchronously, i.e. as part of the
.PD
Configures the watcher to trigger on the given signal number (usually one
of the \f(CW\*(C`SIGxxx\*(C'\fR constants).
-.ie n .Sh """ev_child"" \- wait for pid status changes"
-.el .Sh "\f(CWev_child\fP \- wait for pid status changes"
-.IX Subsection "ev_child - wait for pid status changes"
+.IP "int signum [read\-only]" 4
+.IX Item "int signum [read-only]"
+The signal the watcher watches out for.
+.ie n .Sh """ev_child"" \- watch out for process status changes"
+.el .Sh "\f(CWev_child\fP \- watch out for process status changes"
+.IX Subsection "ev_child - watch out for process status changes"
Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to
some child status changes (most typically when a child of yours dies).
.IP "ev_child_init (ev_child *, callback, int pid)" 4
the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems
\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the
process causing the status change.
+.IP "int pid [read\-only]" 4
+.IX Item "int pid [read-only]"
+The process id this watcher watches out for, or \f(CW0\fR, meaning any process id.
+.IP "int rpid [read\-write]" 4
+.IX Item "int rpid [read-write]"
+The process id that detected a status change.
+.IP "int rstatus [read\-write]" 4
+.IX Item "int rstatus [read-write]"
+The process exit/trace status caused by \f(CW\*(C`rpid\*(C'\fR (see your systems
+\&\f(CW\*(C`waitpid\*(C'\fR and \f(CW\*(C`sys/wait.h\*(C'\fR documentation for details).
.PP
Example: try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0.
.PP
\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
\& ev_signal_start (loop, &sigint_cb);
.Ve
-.ie n .Sh """ev_idle"" \- when you've got nothing better to do"
-.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do"
-.IX Subsection "ev_idle - when you've got nothing better to do"
+.ie n .Sh """ev_stat"" \- did the file attributes just change?"
+.el .Sh "\f(CWev_stat\fP \- did the file attributes just change?"
+.IX Subsection "ev_stat - did the file attributes just change?"
+This watches a filesystem path for attribute changes. That is, it calls
+\&\f(CW\*(C`stat\*(C'\fR regularly (or when the \s-1OS\s0 says it changed) and sees if it changed
+compared to the last time, invoking the callback if it did.
+.PP
+The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does
+not exist\*(R" is a status change like any other. The condition \*(L"path does
+not exist\*(R" is signified by the \f(CW\*(C`st_nlink\*(C'\fR field being zero (which is
+otherwise always forced to be at least one) and all the other fields of
+the stat buffer having unspecified contents.
+.PP
+Since there is no standard to do this, the portable implementation simply
+calls \f(CW\*(C`stat (2)\*(C'\fR regulalry on the path to see if it changed somehow. You
+can specify a recommended polling interval for this case. If you specify
+a polling interval of \f(CW0\fR (highly recommended!) then a \fIsuitable,
+unspecified default\fR value will be used (which you can expect to be around
+five seconds, although this might change dynamically). Libev will also
+impose a minimum interval which is currently around \f(CW0.1\fR, but thats
+usually overkill.
+.PP
+This watcher type is not meant for massive numbers of stat watchers,
+as even with OS-supported change notifications, this can be
+resource\-intensive.
+.PP
+At the time of this writing, no specific \s-1OS\s0 backends are implemented, but
+if demand increases, at least a kqueue and inotify backend will be added.
+.IP "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 4
+.IX Item "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)"
+.PD 0
+.IP "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" 4
+.IX Item "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)"
+.PD
+Configures the watcher to wait for status changes of the given
+\&\f(CW\*(C`path\*(C'\fR. The \f(CW\*(C`interval\*(C'\fR is a hint on how quickly a change is expected to
+be detected and should normally be specified as \f(CW0\fR to let libev choose
+a suitable value. The memory pointed to by \f(CW\*(C`path\*(C'\fR must point to the same
+path for as long as the watcher is active.
+.Sp
+The callback will be receive \f(CW\*(C`EV_STAT\*(C'\fR when a change was detected,
+relative to the attributes at the time the watcher was started (or the
+last change was detected).
+.IP "ev_stat_stat (ev_stat *)" 4
+.IX Item "ev_stat_stat (ev_stat *)"
+Updates the stat buffer immediately with new values. If you change the
+watched path in your callback, you could call this fucntion to avoid
+detecting this change (while introducing a race condition). Can also be
+useful simply to find out the new values.
+.IP "ev_statdata attr [read\-only]" 4
+.IX Item "ev_statdata attr [read-only]"
+The most-recently detected attributes of the file. Although the type is of
+\&\f(CW\*(C`ev_statdata\*(C'\fR, this is usually the (or one of the) \f(CW\*(C`struct stat\*(C'\fR types
+suitable for your system. If the \f(CW\*(C`st_nlink\*(C'\fR member is \f(CW0\fR, then there
+was some error while \f(CW\*(C`stat\*(C'\fRing the file.
+.IP "ev_statdata prev [read\-only]" 4
+.IX Item "ev_statdata prev [read-only]"
+The previous attributes of the file. The callback gets invoked whenever
+\&\f(CW\*(C`prev\*(C'\fR != \f(CW\*(C`attr\*(C'\fR.
+.IP "ev_tstamp interval [read\-only]" 4
+.IX Item "ev_tstamp interval [read-only]"
+The specified interval.
+.IP "const char *path [read\-only]" 4
+.IX Item "const char *path [read-only]"
+The filesystem path that is being watched.
+.PP
+Example: Watch \f(CW\*(C`/etc/passwd\*(C'\fR for attribute changes.
+.PP
+.Vb 15
+\& static void
+\& passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
+\& {
+\& /* /etc/passwd changed in some way */
+\& if (w->attr.st_nlink)
+\& {
+\& printf ("passwd current size %ld\en", (long)w->attr.st_size);
+\& printf ("passwd current atime %ld\en", (long)w->attr.st_mtime);
+\& printf ("passwd current mtime %ld\en", (long)w->attr.st_mtime);
+\& }
+\& else
+\& /* you shalt not abuse printf for puts */
+\& puts ("wow, /etc/passwd is not there, expect problems. "
+\& "if this is windows, they already arrived\en");
+\& }
+.Ve
+.PP
+.Vb 2
+\& ...
+\& ev_stat passwd;
+.Ve
+.PP
+.Vb 2
+\& ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
+\& ev_stat_start (loop, &passwd);
+.Ve
+.ie n .Sh """ev_idle"" \- when you've got nothing better to do..."
+.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do..."
+.IX Subsection "ev_idle - when you've got nothing better to do..."
Idle watchers trigger events when there are no other events are pending
(prepare, check and other idle watchers do not count). That is, as long
as your process is busy handling sockets or timeouts (or even signals,
\& ev_idle_init (idle_watcher, idle_cb);
\& ev_idle_start (loop, idle_cb);
.Ve
-.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop"
-.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop"
-.IX Subsection "ev_prepare and ev_check - customise your event loop"
+.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop!"
+.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!"
+.IX Subsection "ev_prepare and ev_check - customise your event loop!"
Prepare and check watchers are usually (but not always) used in tandem:
prepare watchers get invoked before the process blocks and check watchers
afterwards.
.PP
+You \fImust not\fR call \f(CW\*(C`ev_loop\*(C'\fR or similar functions that enter
+the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR
+watchers. Other loops than the current one are fine, however. The
+rationale behind this is that you do not need to check for recursion in
+those watchers, i.e. the sequence will always be \f(CW\*(C`ev_prepare\*(C'\fR, blocking,
+\&\f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each kind they will always be
+called in pairs bracketing the blocking call.
+.PP
Their main purpose is to integrate other event mechanisms into libev and
their use is somewhat advanced. This could be used, for example, to track
variable changes, implement your own watchers, integrate net-snmp or a
-coroutine library and lots more.
+coroutine library and lots more. They are also occasionally useful if
+you cache some data and want to flush it before blocking (for example,
+in X programs you might want to do an \f(CW\*(C`XFlush ()\*(C'\fR in an \f(CW\*(C`ev_prepare\*(C'\fR
+watcher).
.PP
This is done by examining in each prepare call which file descriptors need
to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for
parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR
macros, but using them is utterly, utterly and completely pointless.
.PP
-Example: *TODO*.
-.ie n .Sh """ev_embed"" \- when one backend isn't enough"
-.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough"
-.IX Subsection "ev_embed - when one backend isn't enough"
+Example: To include a library such as adns, you would add \s-1IO\s0 watchers
+and a timeout watcher in a prepare handler, as required by libadns, and
+in a check watcher, destroy them and call into libadns. What follows is
+pseudo-code only of course:
+.PP
+.Vb 2
+\& static ev_io iow [nfd];
+\& static ev_timer tw;
+.Ve
+.PP
+.Vb 9
+\& static void
+\& io_cb (ev_loop *loop, ev_io *w, int revents)
+\& {
+\& // set the relevant poll flags
+\& // could also call adns_processreadable etc. here
+\& struct pollfd *fd = (struct pollfd *)w->data;
+\& if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
+\& if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
+\& }
+.Ve
+.PP
+.Vb 7
+\& // create io watchers for each fd and a timer before blocking
+\& static void
+\& adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
+\& {
+\& int timeout = 3600000;truct pollfd fds [nfd];
+\& // actual code will need to loop here and realloc etc.
+\& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
+.Ve
+.PP
+.Vb 3
+\& /* the callback is illegal, but won't be called as we stop during check */
+\& ev_timer_init (&tw, 0, timeout * 1e-3);
+\& ev_timer_start (loop, &tw);
+.Ve
+.PP
+.Vb 6
+\& // create on ev_io per pollfd
+\& for (int i = 0; i < nfd; ++i)
+\& {
+\& ev_io_init (iow + i, io_cb, fds [i].fd,
+\& ((fds [i].events & POLLIN ? EV_READ : 0)
+\& | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
+.Ve
+.PP
+.Vb 5
+\& fds [i].revents = 0;
+\& iow [i].data = fds + i;
+\& ev_io_start (loop, iow + i);
+\& }
+\& }
+.Ve
+.PP
+.Vb 5
+\& // stop all watchers after blocking
+\& static void
+\& adns_check_cb (ev_loop *loop, ev_check *w, int revents)
+\& {
+\& ev_timer_stop (loop, &tw);
+.Ve
+.PP
+.Vb 2
+\& for (int i = 0; i < nfd; ++i)
+\& ev_io_stop (loop, iow + i);
+.Ve
+.PP
+.Vb 2
+\& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
+\& }
+.Ve
+.ie n .Sh """ev_embed"" \- when one backend isn't enough..."
+.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..."
+.IX Subsection "ev_embed - when one backend isn't enough..."
This is a rather advanced watcher type that lets you embed one event loop
into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded
loop, other types of watchers might be handled in a delayed or incorrect
Make a single, non-blocking sweep over the embedded loop. This works
similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most
apropriate way for embedded loops.
+.IP "struct ev_loop *loop [read\-only]" 4
+.IX Item "struct ev_loop *loop [read-only]"
+The embedded event loop.
+.ie n .Sh """ev_fork"" \- the audacity to resume the event loop after a fork"
+.el .Sh "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork"
+.IX Subsection "ev_fork - the audacity to resume the event loop after a fork"
+Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because
+whoever is a good citizen cared to tell libev about it by calling
+\&\f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the
+event loop blocks next and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called,
+and only in the child after the fork. If whoever good citizen calling
+\&\f(CW\*(C`ev_default_fork\*(C'\fR cheats and calls it in the wrong process, the fork
+handlers will be invoked, too, of course.
+.IP "ev_fork_init (ev_signal *, callback)" 4
+.IX Item "ev_fork_init (ev_signal *, callback)"
+Initialises and configures the fork watcher \- it has no parameters of any
+kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless,
+believe me.
.SH "OTHER FUNCTIONS"
.IX Header "OTHER FUNCTIONS"
There are some other functions of possible interest. Described. Here. Now.
.el .IP "w\->sweep () \f(CWev::embed\fR only" 4
.IX Item "w->sweep () ev::embed only"
Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR.
+.ie n .IP "w\->update () ""ev::stat"" only" 4
+.el .IP "w\->update () \f(CWev::stat\fR only" 4
+.IX Item "w->update () ev::stat only"
+Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR.
.RE
.RS 4
.RE
\& io.start (fd, ev::READ);
\& }
.Ve
+.SH "MACRO MAGIC"
+.IX Header "MACRO MAGIC"
+Libev can be compiled with a variety of options, the most fundemantal is
+\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines wether (most) functions and
+callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument.
+.PP
+To make it easier to write programs that cope with either variant, the
+following macros are defined:
+.ie n .IP """EV_A""\fR, \f(CW""EV_A_""" 4
+.el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4
+.IX Item "EV_A, EV_A_"
+This provides the loop \fIargument\fR for functions, if one is required (\*(L"ev
+loop argument\*(R"). The \f(CW\*(C`EV_A\*(C'\fR form is used when this is the sole argument,
+\&\f(CW\*(C`EV_A_\*(C'\fR is used when other arguments are following. Example:
+.Sp
+.Vb 3
+\& ev_unref (EV_A);
+\& ev_timer_add (EV_A_ watcher);
+\& ev_loop (EV_A_ 0);
+.Ve
+.Sp
+It assumes the variable \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR is in scope,
+which is often provided by the following macro.
+.ie n .IP """EV_P""\fR, \f(CW""EV_P_""" 4
+.el .IP "\f(CWEV_P\fR, \f(CWEV_P_\fR" 4
+.IX Item "EV_P, EV_P_"
+This provides the loop \fIparameter\fR for functions, if one is required (\*(L"ev
+loop parameter\*(R"). The \f(CW\*(C`EV_P\*(C'\fR form is used when this is the sole parameter,
+\&\f(CW\*(C`EV_P_\*(C'\fR is used when other parameters are following. Example:
+.Sp
+.Vb 2
+\& // this is how ev_unref is being declared
+\& static void ev_unref (EV_P);
+.Ve
+.Sp
+.Vb 2
+\& // this is how you can declare your typical callback
+\& static void cb (EV_P_ ev_timer *w, int revents)
+.Ve
+.Sp
+It declares a parameter \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR, quite
+suitable for use with \f(CW\*(C`EV_A\*(C'\fR.
+.ie n .IP """EV_DEFAULT""\fR, \f(CW""EV_DEFAULT_""" 4
+.el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4
+.IX Item "EV_DEFAULT, EV_DEFAULT_"
+Similar to the other two macros, this gives you the value of the default
+loop, if multiple loops are supported (\*(L"ev loop default\*(R").
+.PP
+Example: Declare and initialise a check watcher, working regardless of
+wether multiple loops are supported or not.
+.PP
+.Vb 5
+\& static void
+\& check_cb (EV_P_ ev_timer *w, int revents)
+\& {
+\& ev_check_stop (EV_A_ w);
+\& }
+.Ve
+.PP
+.Vb 4
+\& ev_check check;
+\& ev_check_init (&check, check_cb);
+\& ev_check_start (EV_DEFAULT_ &check);
+\& ev_loop (EV_DEFAULT_ 0);
+.Ve
.SH "EMBEDDING"
.IX Header "EMBEDDING"
Libev can (and often is) directly embedded into host
.Ve
.PP
.Vb 5
-\& ev_select.c only when select backend is enabled (which is is by default)
+\& ev_select.c only when select backend is enabled (which is by default)
\& ev_poll.c only when poll backend is enabled (disabled by default)
\& ev_epoll.c only when the epoll backend is enabled (disabled by default)
\& ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
.Ve
.PP
\&\fIev.c\fR includes the backend files directly when enabled, so you only need
-to compile a single file.
+to compile this single file.
.PP
\fI\s-1LIBEVENT\s0 \s-1COMPATIBILITY\s0 \s-1API\s0\fR
.IX Subsection "LIBEVENT COMPATIBILITY API"
.PP
Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your config in
whatever way you want, you can also \f(CW\*(C`m4_include([libev.m4])\*(C'\fR in your
-\&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR off. \fIev.c\fR will then include
-\&\fIconfig.h\fR and configure itself accordingly.
+\&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR undefined. \fIev.c\fR will then
+include \fIconfig.h\fR and configure itself accordingly.
.PP
For this of course you need the m4 file:
.PP
additional independent event loops. Otherwise there will be no support
for multiple event loops and there is no first event loop pointer
argument. Instead, all functions act on the single default loop.
-.IP "\s-1EV_PERIODICS\s0" 4
-.IX Item "EV_PERIODICS"
-If undefined or defined to be \f(CW1\fR, then periodic timers are supported,
-otherwise not. This saves a few kb of code.
+.IP "\s-1EV_PERIODIC_ENABLE\s0" 4
+.IX Item "EV_PERIODIC_ENABLE"
+If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If
+defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
+code.
+.IP "\s-1EV_EMBED_ENABLE\s0" 4
+.IX Item "EV_EMBED_ENABLE"
+If undefined or defined to be \f(CW1\fR, then embed watchers are supported. If
+defined to be \f(CW0\fR, then they are not.
+.IP "\s-1EV_STAT_ENABLE\s0" 4
+.IX Item "EV_STAT_ENABLE"
+If undefined or defined to be \f(CW1\fR, then stat watchers are supported. If
+defined to be \f(CW0\fR, then they are not.
+.IP "\s-1EV_FORK_ENABLE\s0" 4
+.IX Item "EV_FORK_ENABLE"
+If undefined or defined to be \f(CW1\fR, then fork watchers are supported. If
+defined to be \f(CW0\fR, then they are not.
+.IP "\s-1EV_MINIMAL\s0" 4
+.IX Item "EV_MINIMAL"
+If you need to shave off some kilobytes of code at the expense of some
+speed, define this symbol to \f(CW1\fR. Currently only used for gcc to override
+some inlining decisions, saves roughly 30% codesize of amd64.
+.IP "\s-1EV_PID_HASHSIZE\s0" 4
+.IX Item "EV_PID_HASHSIZE"
+\&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by
+pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), usually more
+than enough. If you need to manage thousands of children you might want to
+increase this value.
.IP "\s-1EV_COMMON\s0" 4
.IX Item "EV_COMMON"
By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining
\& SV *self; /* contains this struct */ \e
\& SV *cb_sv, *fh /* note no trailing ";" */
.Ve
-.IP "\s-1EV_CB_DECLARE\s0(type)" 4
-.IX Item "EV_CB_DECLARE(type)"
+.IP "\s-1EV_CB_DECLARE\s0 (type)" 4
+.IX Item "EV_CB_DECLARE (type)"
.PD 0
-.IP "\s-1EV_CB_INVOKE\s0(watcher,revents)" 4
-.IX Item "EV_CB_INVOKE(watcher,revents)"
-.IP "ev_set_cb(ev,cb)" 4
-.IX Item "ev_set_cb(ev,cb)"
+.IP "\s-1EV_CB_INVOKE\s0 (watcher, revents)" 4
+.IX Item "EV_CB_INVOKE (watcher, revents)"
+.IP "ev_set_cb (ev, cb)" 4
+.IX Item "ev_set_cb (ev, cb)"
.PD
Can be used to change the callback member declaration in each watcher,
and the way callbacks are invoked and set. Must expand to a struct member
definition and a statement, respectively. See the \fIev.v\fR header file for
their default definitions. One possible use for overriding these is to
-avoid the ev_loop pointer as first argument in all cases, or to use method
-calls instead of plain function calls in \*(C+.
+avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use
+method calls instead of plain function calls in \*(C+.
.Sh "\s-1EXAMPLES\s0"
.IX Subsection "EXAMPLES"
For a real-world example of a program the includes libev
\& #include "ev_cpp.h"
\& #include "ev.c"
.Ve
+.SH "COMPLEXITIES"
+.IX Header "COMPLEXITIES"
+In this section the complexities of (many of) the algorithms used inside
+libev will be explained. For complexity discussions about backends see the
+documentation for \f(CW\*(C`ev_default_init\*(C'\fR.
+.RS 4
+.IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4
+.IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)"
+.PD 0
+.IP "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)" 4
+.IX Item "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)"
+.IP "Starting io/check/prepare/idle/signal/child watchers: O(1)" 4
+.IX Item "Starting io/check/prepare/idle/signal/child watchers: O(1)"
+.IP "Stopping check/prepare/idle watchers: O(1)" 4
+.IX Item "Stopping check/prepare/idle watchers: O(1)"
+.IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))" 4
+.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))"
+.IP "Finding the next timer per loop iteration: O(1)" 4
+.IX Item "Finding the next timer per loop iteration: O(1)"
+.IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4
+.IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)"
+.IP "Activating one watcher: O(1)" 4
+.IX Item "Activating one watcher: O(1)"
+.RE
+.RS 4
+.PD
.SH "AUTHOR"
.IX Header "AUTHOR"
Marc Lehmann <libev@schmorp.de>.
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