.\" ========================================================================
.\"
.IX Title ""<STANDARD INPUT>" 1"
-.TH "<STANDARD INPUT>" 1 "2007-11-27" "perl v5.8.8" "User Contributed Perl Documentation"
+.TH "<STANDARD INPUT>" 1 "2007-12-07" "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"
+The newest version of this document is also available as a html-formatted
+web page you might find easier to navigate when reading it for the first
+time: <http://cvs.schmorp.de/libev/ev.html>.
+.PP
Libev is an event loop: you register interest in certain events (such as a
file descriptor being readable or a timeout occuring), and it will manage
these event sources and provide your program with events.
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, 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.
+.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 \- the
+semantics is 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 *
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
override the flags completely if it is found in the environment. This is
useful to try out specific backends to test their performance, or to work
around bugs.
+.ie n .IP """EVFLAG_FORKCHECK""" 4
+.el .IP "\f(CWEVFLAG_FORKCHECK\fR" 4
+.IX Item "EVFLAG_FORKCHECK"
+Instead of calling \f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR manually after
+a fork, you can also make libev check for a fork in each iteration by
+enabling this flag.
+.Sp
+This works by calling \f(CW\*(C`getpid ()\*(C'\fR on every iteration of the loop,
+and thus this might slow down your event loop if you do a lot of loop
+iterations and little real work, but is usually not noticeable (on my
+Linux system for example, \f(CW\*(C`getpid\*(C'\fR is actually a simple 5\-insn sequence
+without a syscall and thus \fIvery\fR fast, but my Linux system also has
+\&\f(CW\*(C`pthread_atfork\*(C'\fR which is even faster).
+.Sp
+The big advantage of this flag is that you can forget about fork (and
+forget about forgetting to tell libev about forking) when you use this
+flag.
+.Sp
+This flag setting cannot be overriden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR
+environment variable.
.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4
.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4
.IX Item "EVBACKEND_SELECT (value 1, portable select backend)"
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);
Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by
\&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop
after fork, and how you do this is entirely your own problem.
+.IP "unsigned int ev_loop_count (loop)" 4
+.IX Item "unsigned int ev_loop_count (loop)"
+Returns the count of loop iterations for the loop, which is identical to
+the number of times libev did poll for new events. It starts at \f(CW0\fR and
+happily wraps around with enough iterations.
+.Sp
+This value can sometimes be useful as a generation counter of sorts (it
+\&\*(L"ticks\*(R" the number of loop iterations), as it roughly corresponds with
+\&\f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR calls.
.IP "unsigned int ev_backend (loop)" 4
.IX Item "unsigned int ev_backend (loop)"
Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in
\& 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)"
Change the callback. You can change the callback at virtually any time
(modulo threads).
+.IP "ev_set_priority (ev_TYPE *watcher, priority)" 4
+.IX Item "ev_set_priority (ev_TYPE *watcher, priority)"
+.PD 0
+.IP "int ev_priority (ev_TYPE *watcher)" 4
+.IX Item "int ev_priority (ev_TYPE *watcher)"
+.PD
+Set and query the priority of the watcher. The priority is a small
+integer between \f(CW\*(C`EV_MAXPRI\*(C'\fR (default: \f(CW2\fR) and \f(CW\*(C`EV_MINPRI\*(C'\fR
+(default: \f(CW\*(C`\-2\*(C'\fR). Pending watchers with higher priority will be invoked
+before watchers with lower priority, but priority will not keep watchers
+from being executed (except for \f(CW\*(C`ev_idle\*(C'\fR watchers).
+.Sp
+This means that priorities are \fIonly\fR used for ordering callback
+invocation after new events have been received. This is useful, for
+example, to reduce latency after idling, or more often, to bind two
+watchers on the same event and make sure one is called first.
+.Sp
+If you need to suppress invocation when higher priority events are pending
+you need to look at \f(CW\*(C`ev_idle\*(C'\fR watchers, which provide this functionality.
+.Sp
+The default priority used by watchers when no priority has been set is
+always \f(CW0\fR, which is supposed to not be too high and not be too low :).
+.Sp
+Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR is
+fine, as long as you do not mind that the priority value you query might
+or might not have been adjusted to be within valid range.
.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0"
.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER"
Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change
\& }
.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
.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
+whether 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 "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
This will act as if the timer timed out and restart it again if it is
repeating. The exact semantics are:
.Sp
-If the timer is started but nonrepeating, stop it.
+If the timer is pending, its pending status is cleared.
+.Sp
+If the timer is started but nonrepeating, stop it (as if it timed out).
.Sp
-If the timer is repeating, either start it if necessary (with the repeat
-value), or reset the running timer to the repeat value.
+If the timer is repeating, either start it if necessary (with the
+\&\f(CW\*(C`repeat\*(C'\fR value), or reset the running timer to the \f(CW\*(C`repeat\*(C'\fR 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 \f(CW\*(C`after\*(C'\fR=\f(CW\*(C`repeat\*(C'\fR=\f(CW60\fR and calling
+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 a \f(CW\*(C`repeat\*(C'\fR value of \f(CW60\fR and then call
\&\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.
+socket, you can \f(CW\*(C`ev_timer_stop\*(C'\fR the timer, and \f(CW\*(C`ev_timer_again\*(C'\fR 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:
+That means you can 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 and \f(CW\*(C`ev_timer_again\*(C'\fR:
.Sp
.Vb 8
\& ev_timer_init (timer, callback, 0., 5.);
\& 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.
+This is more slightly efficient then stopping/starting the timer each 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.
+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
otherwise always forced to be at least one) and all the other fields of
the stat buffer having unspecified contents.
.PP
+The path \fIshould\fR be absolute and \fImust not\fR end in a slash. If it is
+relative and your working directory changes, the behaviour is undefined.
+.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
.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,
-imagine) it will not be triggered. But when your process is idle all idle
-watchers are being called again and again, once per event loop iteration \-
-until stopped, that is, or your process receives more events and becomes
-busy.
+Idle watchers trigger events when no other events of the same or higher
+priority are pending (prepare, check and other idle watchers do not
+count).
+.PP
+That is, as long as your process is busy handling sockets or timeouts
+(or even signals, imagine) of the same or higher priority it will not be
+triggered. But when your process is idle (or only lower-priority watchers
+are pending), the idle watchers are being called once per event loop
+iteration \- until stopped, that is, or your process receives more events
+and becomes busy again with higher priority stuff.
.PP
The most noteworthy effect is that as long as any idle watchers are
active, the process will not block when waiting for new events.
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
\& }
.Ve
.PP
-.Vb 7
+.Vb 8
\& // 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];
+\& int timeout = 3600000;
+\& struct pollfd fds [nfd];
\& // actual code will need to loop here and realloc etc.
\& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
.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
+\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (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
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.
+Example: Declare and initialise a check watcher, utilising the above
+macros so it will work regardless of whether multiple loops are supported
+or not.
.PP
.Vb 5
\& static void
.Ve
.PP
.Vb 5
-\& ev_select.c only when select backend is enabled (which is by default)
+\& ev_select.c only when select backend is enabled (which is enabled 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)
.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
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_MINPRI\s0" 4
+.IX Item "EV_MINPRI"
+.PD 0
+.IP "\s-1EV_MAXPRI\s0" 4
+.IX Item "EV_MAXPRI"
+.PD
+The range of allowed priorities. \f(CW\*(C`EV_MINPRI\*(C'\fR must be smaller or equal to
+\&\f(CW\*(C`EV_MAXPRI\*(C'\fR, but otherwise there are no non-obvious limitations. You can
+provide for more priorities by overriding those symbols (usually defined
+to be \f(CW\*(C`\-2\*(C'\fR and \f(CW2\fR, respectively).
+.Sp
+When doing priority-based operations, libev usually has to linearly search
+all the priorities, so having many of them (hundreds) uses a lot of space
+and time, so using the defaults of five priorities (\-2 .. +2) is usually
+fine.
+.Sp
+If your embedding app does not need any priorities, defining these both to
+\&\f(CW0\fR will save some memory and cpu.
.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_IDLE_ENABLE\s0" 4
+.IX Item "EV_IDLE_ENABLE"
+If undefined or defined to be \f(CW1\fR, then idle watchers 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
\&\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.
+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
file.
.Sp
The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file
-that everybody includes and which overrides some autoconf choices:
+that everybody includes and which overrides some configure choices:
.Sp
-.Vb 4
+.Vb 9
+\& #define EV_MINIMAL 1
\& #define EV_USE_POLL 0
\& #define EV_MULTIPLICITY 0
-\& #define EV_PERIODICS 0
+\& #define EV_PERIODIC_ENABLE 0
+\& #define EV_STAT_ENABLE 0
+\& #define EV_FORK_ENABLE 0
\& #define EV_CONFIG_H <config.h>
+\& #define EV_MINPRI 0
+\& #define EV_MAXPRI 0
.Ve
.Sp
.Vb 1
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.
+.Sp
+All of the following are about amortised time: If an array needs to be
+extended, libev needs to realloc and move the whole array, but this
+happens asymptotically never with higher number of elements, so O(1) might
+mean it might do a lengthy realloc operation in rare cases, but on average
+it is much faster and asymptotically approaches constant time.
.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
+This means that, when you have a watcher that triggers in one hour and
+there are 100 watchers that would trigger before that then inserting will
+have to skip those 100 watchers.
.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)"
+That means that for changing a timer costs less than removing/adding them
+as only the relative motion in the event queue has to be paid for.
.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))"
+These just add the watcher into an array or at the head of a list.
+=item Stopping check/prepare/idle watchers: O(1)
+.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))"
+These watchers are stored in lists then need to be walked to find the
+correct watcher to remove. The lists are usually short (you don't usually
+have many watchers waiting for the same fd or signal).
.IP "Finding the next timer per loop iteration: O(1)" 4
.IX Item "Finding the next timer per loop iteration: O(1)"
+.PD 0
.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)"
+.PD
+A change means an I/O watcher gets started or stopped, which requires
+libev to recalculate its status (and possibly tell the kernel).
.IP "Activating one watcher: O(1)" 4
.IX Item "Activating one watcher: O(1)"
+.PD 0
+.IP "Priority handling: O(number_of_priorities)" 4
+.IX Item "Priority handling: O(number_of_priorities)"
+.PD
+Priorities are implemented by allocating some space for each
+priority. When doing priority-based operations, libev usually has to
+linearly search all the priorities.
.RE
.RS 4
-.PD
.SH "AUTHOR"
.IX Header "AUTHOR"
Marc Lehmann <libev@schmorp.de>.
projects / software / libev.git / blobdiff