.\" ========================================================================
.\"
.IX Title ""<STANDARD INPUT>" 1"
-.TH "<STANDARD INPUT>" 1 "2007-11-27" "perl v5.8.8" "User Contributed Perl Documentation"
+.TH "<STANDARD INPUT>" 1 "2007-11-28" "perl v5.8.8" "User Contributed Perl Documentation"
.SH "NAME"
libev \- a high performance full\-featured event loop written in C
.SH "SYNOPSIS"
.Vb 1
\& #include <ev.h>
.Ve
+.SH "EXAMPLE PROGRAM"
+.IX Header "EXAMPLE PROGRAM"
+.Vb 1
+\& #include <ev.h>
+.Ve
+.PP
+.Vb 2
+\& 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
watcher.
.SH "FEATURES"
.IX Header "FEATURES"
-Libev supports select, poll, the linux-specific epoll and the bsd-specific
-kqueue mechanisms for file descriptor events, relative timers, absolute
-timers with customised rescheduling, signal events, process status change
-events (related to \s-1SIGCHLD\s0), and event watchers dealing with the event
-loop mechanism itself (idle, prepare and check watchers). It also is quite
-fast (see this benchmark comparing
-it to libevent for example).
+Libev supports \f(CW\*(C`select\*(C'\fR, \f(CW\*(C`poll\*(C'\fR, the Linux-specific \f(CW\*(C`epoll\*(C'\fR, the
+BSD-specific \f(CW\*(C`kqueue\*(C'\fR and the Solaris-specific event port mechanisms
+for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), the Linux \f(CW\*(C`inotify\*(C'\fR interface
+(for \f(CW\*(C`ev_stat\*(C'\fR), relative timers (\f(CW\*(C`ev_timer\*(C'\fR), absolute timers
+with customised rescheduling (\f(CW\*(C`ev_periodic\*(C'\fR), synchronous signals
+(\f(CW\*(C`ev_signal\*(C'\fR), process status change events (\f(CW\*(C`ev_child\*(C'\fR), and event
+watchers dealing with the event loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR,
+\&\f(CW\*(C`ev_embed\*(C'\fR, \f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR watchers) as well as
+file watchers (\f(CW\*(C`ev_stat\*(C'\fR) and even limited support for fork events
+(\f(CW\*(C`ev_fork\*(C'\fR).
+.PP
+It also is quite fast (see this
+benchmark comparing it to libevent
+for example).
.SH "CONVENTIONS"
.IX Header "CONVENTIONS"
-Libev is very configurable. In this manual the default configuration
-will be described, which supports multiple event loops. For more info
-about various configuration options please have a look at the file
-\&\fI\s-1README\s0.embed\fR in the libev distribution. If libev was configured without
-support for multiple event loops, then all functions taking an initial
-argument of name \f(CW\*(C`loop\*(C'\fR (which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR)
-will not have this argument.
+Libev is very configurable. In this manual the default configuration will
+be described, which supports multiple event loops. For more info about
+various configuration options please have a look at \fB\s-1EMBED\s0\fR section in
+this manual. If libev was configured without support for multiple event
+loops, then all functions taking an initial argument of name \f(CW\*(C`loop\*(C'\fR
+(which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR) will not have this argument.
.SH "TIME REPRESENTATION"
.IX Header "TIME REPRESENTATION"
Libev represents time as a single floating point number, representing the
compatible to older versions, so a larger minor version alone is usually
not a problem.
.Sp
-Example: make sure we haven't accidentally been linked against the wrong
-version:
+Example: Make sure we haven't accidentally been linked against the wrong
+version.
.Sp
.Vb 3
\& assert (("libev version mismatch",
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,
or even to sleep a while and retry until some memory is available.
.Sp
-Example: replace the libev allocator with one that waits a bit and then
-retries: better than mine).
+Example: Replace the libev allocator with one that waits a bit and then
+retries).
.Sp
.Vb 6
\& static void *
-\& persistent_realloc (void *ptr, long size)
+\& persistent_realloc (void *ptr, size_t size)
\& {
\& for (;;)
\& {
requested operation, or, if the condition doesn't go away, do bad stuff
(such as abort).
.Sp
-Example: do the same thing as libev does internally:
+Example: This is basically the same thing that libev does internally, too.
.Sp
.Vb 6
\& static void
handle signal and child watchers, and attempts to do so will be greeted by
undefined behaviour (or a failed assertion if assertions are enabled).
.Sp
-Example: try to create a event loop that uses epoll and nothing else.
+Example: Try to create a event loop that uses epoll and nothing else.
.Sp
.Vb 3
\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
\& were used, return, otherwise continue with step *.
.Ve
.Sp
-Example: queue some jobs and then loop until no events are outsanding
+Example: Queue some jobs and then loop until no events are outsanding
anymore.
.Sp
.Vb 4
way to do this for generic recurring timers or from within third-party
libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR.
.Sp
-Example: create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR
+Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR
running when nothing else is active.
.Sp
.Vb 4
-\& struct dv_signal exitsig;
+\& struct ev_signal exitsig;
\& ev_signal_init (&exitsig, sig_cb, SIGINT);
-\& ev_signal_start (myloop, &exitsig);
-\& evf_unref (myloop);
+\& ev_signal_start (loop, &exitsig);
+\& evf_unref (loop);
.Ve
.Sp
-Example: for some weird reason, unregister the above signal handler again.
+Example: For some weird reason, unregister the above signal handler again.
.Sp
.Vb 2
-\& ev_ref (myloop);
-\& ev_signal_stop (myloop, &exitsig);
+\& ev_ref (loop);
+\& ev_signal_stop (loop, &exitsig);
.Ve
.SH "ANATOMY OF A WATCHER"
.IX Header "ANATOMY OF A WATCHER"
is pending (but not active) you must not call an init function on it (but
\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe) and you must make sure the watcher is available to
libev (e.g. you cnanot \f(CW\*(C`free ()\*(C'\fR it).
-.IP "callback = ev_cb (ev_TYPE *watcher)" 4
-.IX Item "callback = ev_cb (ev_TYPE *watcher)"
+.IP "callback ev_cb (ev_TYPE *watcher)" 4
+.IX Item "callback ev_cb (ev_TYPE *watcher)"
Returns the callback currently set on the watcher.
.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4
.IX Item "ev_cb_set (ev_TYPE *watcher, callback)"
\& }
.Ve
.PP
-More interesting and less C\-conformant ways of catsing your callback type
-have been omitted....
+More interesting and less C\-conformant ways of casting your callback type
+instead have been omitted.
+.PP
+Another common scenario is having some data structure with multiple
+watchers:
+.PP
+.Vb 6
+\& struct my_biggy
+\& {
+\& int some_data;
+\& ev_timer t1;
+\& ev_timer t2;
+\& }
+.Ve
+.PP
+In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more complicated,
+you need to use \f(CW\*(C`offsetof\*(C'\fR:
+.PP
+.Vb 1
+\& #include <stddef.h>
+.Ve
+.PP
+.Vb 6
+\& static void
+\& t1_cb (EV_P_ struct ev_timer *w, int revents)
+\& {
+\& struct my_biggy big = (struct my_biggy *
+\& (((char *)w) - offsetof (struct my_biggy, t1));
+\& }
+.Ve
+.PP
+.Vb 6
+\& static void
+\& t2_cb (EV_P_ struct ev_timer *w, int revents)
+\& {
+\& struct my_biggy big = (struct my_biggy *
+\& (((char *)w) - offsetof (struct my_biggy, t2));
+\& }
+.Ve
.SH "WATCHER TYPES"
.IX Header "WATCHER TYPES"
This section describes each watcher in detail, but will not repeat
.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
+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
-attempt to read a whole line in the callback:
+attempt to read a whole line in the callback.
.PP
.Vb 6
\& static void
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.
+Example: Create a timer that fires after 60 seconds.
.PP
.Vb 5
\& static void
\& ev_timer_start (loop, &mytimer);
.Ve
.PP
-Example: create a timeout timer that times out after 10 seconds of
+Example: Create a timeout timer that times out after 10 seconds of
inactivity.
.PP
.Vb 5
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
+Example: Call a callback every hour, or, more precisely, whenever the
system clock is divisible by 3600. The callback invocation times have
potentially a lot of jittering, but good long-term stability.
.PP
\& ev_periodic_start (loop, &hourly_tick);
.Ve
.PP
-Example: the same as above, but use a reschedule callback to do it:
+Example: The same as above, but use a reschedule callback to do it:
.PP
.Vb 1
\& #include <math.h>
\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
.Ve
.PP
-Example: call a callback every hour, starting now:
+Example: Call a callback every hour, starting now:
.PP
.Vb 4
\& struct ev_periodic hourly_tick;
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.
+Example: Try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0.
.PP
.Vb 5
\& static void
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
+calls \f(CW\*(C`stat (2)\*(C'\fR regularly 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
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.
+At the time of this writing, only the Linux inotify interface is
+implemented (implementing kqueue support is left as an exercise for the
+reader). Inotify will be used to give hints only and should not change the
+semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers, which means that libev sometimes needs
+to fall back to regular polling again even with inotify, but changes are
+usually detected immediately, and if the file exists there will be no
+polling.
.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
kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless,
believe me.
.PP
-Example: dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR, start it, and in the
-callback, free it. Alos, use no error checking, as usual.
+Example: Dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR watcher, start it, and in the
+callback, free it. Also, use no error checking, as usual.
.PP
.Vb 7
\& static void
.IP "\s-1EV_USE_DEVPOLL\s0" 4
.IX Item "EV_USE_DEVPOLL"
reserved for future expansion, works like the \s-1USE\s0 symbols above.
+.IP "\s-1EV_USE_INOTIFY\s0" 4
+.IX Item "EV_USE_INOTIFY"
+If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify
+interface to speed up \f(CW\*(C`ev_stat\*(C'\fR watchers. Its actual availability will
+be detected at runtime.
.IP "\s-1EV_H\s0" 4
.IX Item "EV_H"
The name of the \fIev.h\fR header file used to include it. The default if
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 (\fImust\fR be a power of two).
+.IP "\s-1EV_INOTIFY_HASHSIZE\s0" 4
+.IX Item "EV_INOTIFY_HASHSIZE"
+\&\f(CW\*(C`ev_staz\*(C'\fR watchers use a small hash table to distribute workload by
+inotify watch id. 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 \f(CW\*(C`ev_stat\*(C'\fR
+watchers you might want to increase this value (\fImust\fR be a power of
+two).
.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
.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 "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4
+.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))"
.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
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