X-Git-Url: https://git.llucax.com/software/libev.git/blobdiff_plain/bd14babf134e551f28f49193bf20705933c772c8..e53306e99926168d590f09e39ec05ad229799811:/ev.pod

diff --git a/ev.pod b/ev.pod
index 43db80f..fbb7ff3 100644
--- a/ev.pod
+++ b/ev.pod
@@ -4,10 +4,12 @@ libev - a high performance full-featured event loop written in C
 
 =head1 SYNOPSIS
 
-  /* this is the only header you need */
   #include <ev.h>
 
-  /* what follows is a fully working example program */
+=head1 EXAMPLE PROGRAM
+
+  #include <ev.h>
+
   ev_io stdin_watcher;
   ev_timer timeout_watcher;
 
@@ -63,23 +65,29 @@ watcher.
 
 =head1 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 SIGCHLD), and event watchers dealing with the event
-loop mechanism itself (idle, prepare and check watchers). It also is quite
-fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing
-it to libevent for example).
+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>).
+
+It also is quite fast (see this
+L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
+for example).
 
 =head1 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
-F<README.embed> in the libev distribution. If libev was configured without
-support for multiple event loops, then all functions taking an initial
-argument of name C<loop> (which is always of type C<struct ev_loop *>)
-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 B<EMBED> section in
+this manual. If libev was configured without support for multiple event
+loops, then all functions taking an initial argument of name C<loop>
+(which is always of type C<struct ev_loop *>) will not have this argument.
 
 =head1 TIME REPRESENTATION
 
@@ -118,8 +126,8 @@ as this indicates an incompatible change.  Minor versions are usually
 compatible to older versions, so a larger minor version alone is usually
 not a problem.
 
-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.
 
   assert (("libev version mismatch",
            ev_version_major () == EV_VERSION_MAJOR
@@ -169,8 +177,8 @@ 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.
 
-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).
 
    static void *
    persistent_realloc (void *ptr, size_t size)
@@ -199,7 +207,7 @@ matter what, when it returns. That is, libev will generally retry the
 requested operation, or, if the condition doesn't go away, do bad stuff
 (such as abort).
 
-Example: do the same thing as libev does internally:
+Example: This is basically the same thing that libev does internally, too.
 
    static void
    fatal_error (const char *msg)
@@ -355,7 +363,7 @@ always distinct from the default loop. Unlike the default loop, it cannot
 handle signal and child watchers, and attempts to do so will be greeted by
 undefined behaviour (or a failed assertion if assertions are enabled).
 
-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.
 
   struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
   if (!epoller)
@@ -464,7 +472,7 @@ Here are the gory details of what C<ev_loop> does:
    - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
      were used, return, otherwise continue with step *.
 
-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.
 
    ... queue jobs here, make sure they register event watchers as long
@@ -494,18 +502,18 @@ no event watchers registered by it are active. It is also an excellent
 way to do this for generic recurring timers or from within third-party
 libraries. Just remember to I<unref after start> and I<ref before stop>.
 
-Example: create a signal watcher, but keep it from keeping C<ev_loop>
+Example: Create a signal watcher, but keep it from keeping C<ev_loop>
 running when nothing else is active.
 
-  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);
 
-Example: for some weird reason, unregister the above signal handler again.
+Example: For some weird reason, unregister the above signal handler again.
 
-  ev_ref (myloop);
-  ev_signal_stop (myloop, &exitsig);
+  ev_ref (loop);
+  ev_signal_stop (loop, &exitsig);
 
 =back
 
@@ -698,7 +706,7 @@ is pending (but not active) you must not call an init function on it (but
 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.
 
@@ -736,8 +744,37 @@ can cast it back to your own type:
     ...
   }
 
-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
@@ -816,9 +853,9 @@ The events being watched.
 
 =back
 
-Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well
+Example: Call C<stdin_readable_cb> when STDIN_FILENO 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.
 
   static void
   stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
@@ -918,7 +955,7 @@ which is also when any modifications are taken into account.
 
 =back
 
-Example: create a timer that fires after 60 seconds.
+Example: Create a timer that fires after 60 seconds.
 
   static void
   one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
@@ -930,7 +967,7 @@ Example: create a timer that fires after 60 seconds.
   ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
   ev_timer_start (loop, &mytimer);
 
-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.
 
   static void
@@ -1065,7 +1102,7 @@ the periodic timer fires or C<ev_periodic_again> is being called.
 
 =back
 
-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.
 
@@ -1079,7 +1116,7 @@ potentially a lot of jittering, but good long-term stability.
   ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
   ev_periodic_start (loop, &hourly_tick);
 
-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:
 
   #include <math.h>
 
@@ -1091,7 +1128,7 @@ Example: the same as above, but use a reschedule callback to do it:
 
   ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
 
-Example: call a callback every hour, starting now:
+Example: Call a callback every hour, starting now:
 
   struct ev_periodic hourly_tick;
   ev_periodic_init (&hourly_tick, clock_cb,
@@ -1162,7 +1199,7 @@ C<waitpid> and C<sys/wait.h> documentation for details).
 
 =back
 
-Example: try to exit cleanly on SIGINT and SIGTERM.
+Example: Try to exit cleanly on SIGINT and SIGTERM.
 
   static void
   sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
@@ -1188,7 +1225,7 @@ otherwise always forced to be at least one) and all the other fields of
 the stat buffer having unspecified contents.
 
 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
@@ -1200,8 +1237,13 @@ This watcher type is not meant for massive numbers of stat watchers,
 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
 
@@ -1301,8 +1343,8 @@ believe me.
 
 =back
 
-Example: dynamically allocate an C<ev_idle>, start it, and in the
-callback, free it. Alos, use no error checking, as usual.
+Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
+callback, free it. Also, use no error checking, as usual.
 
   static void
   idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
@@ -1980,6 +2022,12 @@ backend for Solaris 10 systems.
 
 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
@@ -2044,7 +2092,15 @@ some inlining decisions, saves roughly 30% codesize of amd64.
 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
 
@@ -2114,7 +2170,7 @@ documentation for C<ev_default_init>.
 
 =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)