.\" ========================================================================
.\"
.IX Title ""<STANDARD INPUT>" 1"
-.TH "<STANDARD INPUT>" 1 "2007-11-27" "perl v5.8.8" "User Contributed Perl Documentation"
+.TH "<STANDARD INPUT>" 1 "2007-11-29" "perl v5.8.8" "User Contributed Perl Documentation"
.SH "NAME"
libev \- a high performance full\-featured event loop written in C
.SH "SYNOPSIS"
watcher.
.SH "FEATURES"
.IX Header "FEATURES"
-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), 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,
+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).
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,
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 noticable (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)"
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
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
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
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 wether 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
\&\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
.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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