=head1 FEATURES
-Libev supports C<select>, C<poll>, the linux-specific C<epoll>, the
-bsd-specific C<kqueue> and the solaris-specific event port mechanisms
-for file descriptor events (C<ev_io>), relative timers (C<ev_timer>),
-absolute timers with customised rescheduling (C<ev_periodic>), synchronous
-signals (C<ev_signal>), process status change events (C<ev_child>), and
-event watchers dealing with the event loop mechanism itself (C<ev_idle>,
+Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
+BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
+for file descriptor events (C<ev_io>), the Linux C<inotify> interface
+(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
+with customised rescheduling (C<ev_periodic>), synchronous signals
+(C<ev_signal>), process status change events (C<ev_child>), and event
+watchers dealing with the event loop mechanism itself (C<ev_idle>,
C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as
file watchers (C<ev_stat>) and even limited support for fork events
(C<ev_fork>).
See the description of C<ev_embed> watchers for more info.
-=item ev_set_allocator (void *(*cb)(void *ptr, size_t size))
+=item ev_set_allocator (void *(*cb)(void *ptr, long 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.
+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.
You could override this function in high-availability programs to, say,
free some memory if it cannot allocate memory, to use a special allocator,
useful to try out specific backends to test their performance, or to work
around bugs.
+=item C<EVFLAG_FORKCHECK>
+
+Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
+a fork, you can also make libev check for a fork in each iteration by
+enabling this flag.
+
+This works by calling C<getpid ()> 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, C<getpid> is actually a simple 5-insn sequence
+without a syscall and thus I<very> fast, but my Linux system also has
+C<pthread_atfork> which is even faster).
+
+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.
+
+This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
+environment variable.
+
=item C<EVBACKEND_SELECT> (value 1, portable select backend)
This is your standard select(2) backend. Not I<completely> standard, as
C<ev_TYPE_set> is safe) and you must make sure the watcher is available to
libev (e.g. you cnanot C<free ()> it).
-=item callback = ev_cb (ev_TYPE *watcher)
+=item callback ev_cb (ev_TYPE *watcher)
Returns the callback currently set on the watcher.
...
}
-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.
+
+Another common scenario is having some data structure with multiple
+watchers:
+
+ struct my_biggy
+ {
+ int some_data;
+ ev_timer t1;
+ ev_timer t2;
+ }
+
+In this case getting the pointer to C<my_biggy> is a bit more complicated,
+you need to use C<offsetof>:
+
+ #include <stddef.h>
+
+ 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));
+ }
+
+ 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));
+ }
=head1 WATCHER TYPES
This will act as if the timer timed out and restart it again if it is
repeating. The exact semantics are:
-If the timer is started but nonrepeating, stop it.
+If the timer is pending, its pending status is cleared.
+
+If the timer is started but nonrepeating, stop it (as if it timed out).
-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
+C<repeat> value), or reset the running timer to the C<repeat> value.
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 C<ev_timer> with C<after>=C<repeat>=C<60> 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 C<ev_timer> with a C<repeat> value of C<60> and then call
C<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.
+socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
+automatically restart it if need be.
-You can also ignore the C<after> value and C<ev_timer_start> altogether
-and only ever use the C<repeat> value:
+That means you can ignore the C<after> value and C<ev_timer_start>
+altogether and only ever use the C<repeat> value and C<ev_timer_again>:
ev_timer_init (timer, callback, 0., 5.);
ev_timer_again (loop, timer);
timer->again = 10.;
ev_timer_again (loop, timer);
-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.
=item ev_tstamp repeat [read-write]
otherwise always forced to be at least one) and all the other fields of
the stat buffer having unspecified contents.
+The path I<should> be absolute and I<must not> end in a slash. If it is
+relative and your working directory changes, the behaviour is undefined.
+
Since there is no standard to do this, the portable implementation simply
-calls C<stat (2)> regulalry on the path to see if it changed somehow. You
+calls C<stat (2)> 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 C<0> (highly recommended!) then a I<suitable,
unspecified default> value will be used (which you can expect to be around
as even with OS-supported change notifications, this can be
resource-intensive.
-At the time of this writing, no specific OS 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 C<ev_stat> 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.
=over 4
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 ()));
=back
-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.
static void
check_cb (EV_P_ ev_timer *w, int revents)
ev_check_start (EV_DEFAULT_ &check);
ev_loop (EV_DEFAULT_ 0);
-
=head1 EMBEDDING
Libev can (and often is) directly embedded into host
ev_win32.c required on win32 platforms only
- 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)
reserved for future expansion, works like the USE symbols above.
+=item EV_USE_INOTIFY
+
+If defined to be C<1>, libev will compile in support for the Linux inotify
+interface to speed up C<ev_stat> watchers. Its actual availability will
+be detected at runtime.
+
=item EV_H
The name of the F<ev.h> header file used to include it. The default if
C<ev_child> watchers use a small hash table to distribute workload by
pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
than enough. If you need to manage thousands of children you might want to
-increase this value.
+increase this value (I<must> be a power of two).
+
+=item EV_INOTIFY_HASHSIZE
+
+C<ev_staz> watchers use a small hash table to distribute workload by
+inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
+usually more than enough. If you need to manage thousands of C<ev_stat>
+watchers you might want to increase this value (I<must> be a power of
+two).
=item EV_COMMON
file.
The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
-that everybody includes and which overrides some autoconf choices:
+that everybody includes and which overrides some configure choices:
+ #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
#include "ev++.h"
=item Stopping check/prepare/idle watchers: O(1)
-=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))
+=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
=item Finding the next timer per loop iteration: O(1)
projects / software / libev.git / blobdiff