experimental, and likely broken, inotify support

[software/libev.git] / ev.pod

diff --git a/ev.pod b/ev.pod
index 05bac9896ea08f8e6c9e49c1b1abe0d87cf4d183..241fadeb0d8583805516d7e54bc4e3041fe3dde5 100644 (file)
--- a/ev.pod
+++ b/ev.pod
@@ -6,6 +6,48 @@ libev - a high performance full-featured event loop written in C
 
   #include <ev.h>
 
 
   #include <ev.h>
 

+=head1 EXAMPLE PROGRAM
+
+  #include <ev.h>
+
+  ev_io stdin_watcher;
+  ev_timer timeout_watcher;
+
+  /* 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 */
+  }
+
+  static void
+  timeout_cb (EV_P_ struct ev_timer *w, int revents)
+  {
+    /* puts ("timeout"); */
+    ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
+  }
+
+  int
+  main (void)
+  {
+    struct ev_loop *loop = ev_default_loop (0);
+
+    /* 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);
+
+    /* simple non-repeating 5.5 second timeout */
+    ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
+    ev_timer_start (loop, &timeout_watcher);
+
+    /* loop till timeout or data ready */
+    ev_loop (loop, 0);
+
+    return 0;
+  }
+

 =head1 DESCRIPTION
 
 Libev is an event loop: you register interest in certain events (such as a
 =head1 DESCRIPTION
 
 Libev is an event loop: you register interest in certain events (such as a


@@ -23,23 +65,28 @@ watcher.
 
 =head1 FEATURES
 
 
 =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>), 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
 
 
 =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
 
 
 =head1 TIME REPRESENTATION
 


@@ -50,7 +97,6 @@ called C<ev_tstamp>, which is what you should use too. It usually aliases
 to the C<double> type in C, and when you need to do any calculations on
 it, you should treat it as such.
 
 to the C<double> type in C, and when you need to do any calculations on
 it, you should treat it as such.
 

-

 =head1 GLOBAL FUNCTIONS
 
 These functions can be called anytime, even before initialising the
 =head1 GLOBAL FUNCTIONS
 
 These functions can be called anytime, even before initialising the


@@ -79,8 +125,8 @@ 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.
 
 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
 
   assert (("libev version mismatch",
            ev_version_major () == EV_VERSION_MAJOR


@@ -118,23 +164,23 @@ recommended ones.
 
 See the description of C<ev_embed> watchers for more info.
 
 
 See the description of C<ev_embed> watchers for more info.
 

-=item ev_set_allocator (void *(*cb)(void *ptr, long size))
+=item ev_set_allocator (void *(*cb)(void *ptr, size_t 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.
+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.

 
 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.
 
 
 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 *
 
    static void *

-   persistent_realloc (void *ptr, long size)
+   persistent_realloc (void *ptr, size_t size)

    {
      for (;;)
        {
    {
      for (;;)
        {


@@ -160,7 +206,7 @@ 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).
 
 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)
 
    static void
    fatal_error (const char *msg)


@@ -316,7 +362,7 @@ 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).
 
 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)
 
   struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
   if (!epoller)


@@ -425,7 +471,7 @@ 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 *.
 
    - 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
 anymore.
 
    ... queue jobs here, make sure they register event watchers as long


@@ -455,21 +501,22 @@ 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>.
 
 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.
 
 running when nothing else is active.
 

-  struct dv_signal exitsig;
+  struct ev_signal exitsig;

   ev_signal_init (&exitsig, sig_cb, SIGINT);
   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
 
 
 =back
 

+

 =head1 ANATOMY OF A WATCHER
 
 A watcher is a structure that you create and register to record your
 =head1 ANATOMY OF A WATCHER
 
 A watcher is a structure that you create and register to record your


@@ -546,6 +593,10 @@ The signal specified in the C<ev_signal> watcher has been received by a thread.
 
 The pid specified in the C<ev_child> watcher has received a status change.
 
 
 The pid specified in the C<ev_child> watcher has received a status change.
 

+=item C<EV_STAT>
+
+The path specified in the C<ev_stat> watcher changed its attributes somehow.
+

 =item C<EV_IDLE>
 
 The C<ev_idle> watcher has determined that you have nothing better to do.
 =item C<EV_IDLE>
 
 The C<ev_idle> watcher has determined that you have nothing better to do.


@@ -562,6 +613,15 @@ many watchers as they want, and all of them will be taken into account
 (for example, a C<ev_prepare> watcher might start an idle watcher to keep
 C<ev_loop> from blocking).
 
 (for example, a C<ev_prepare> watcher might start an idle watcher to keep
 C<ev_loop> from blocking).
 

+=item C<EV_EMBED>
+
+The embedded event loop specified in the C<ev_embed> watcher needs attention.
+
+=item C<EV_FORK>
+
+The event loop has been resumed in the child process after fork (see
+C<ev_fork>).
+

 =item C<EV_ERROR>
 
 An unspecified error has occured, the watcher has been stopped. This might
 =item C<EV_ERROR>
 
 An unspecified error has occured, the watcher has been stopped. This might


@@ -578,7 +638,7 @@ programs, though, so beware.
 
 =back
 
 
 =back
 

-=head2 SUMMARY OF GENERIC WATCHER FUNCTIONS
+=head2 GENERIC WATCHER FUNCTIONS

 
 In the following description, C<TYPE> stands for the watcher type,
 e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
 
 In the following description, C<TYPE> stands for the watcher type,
 e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.


@@ -597,7 +657,7 @@ which rolls both calls into one.
 You can reinitialise a watcher at any time as long as it has been stopped
 (or never started) and there are no pending events outstanding.
 
 You can reinitialise a watcher at any time as long as it has been stopped
 (or never started) and there are no pending events outstanding.
 

-The callbakc is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
+The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,

 int revents)>.
 
 =item C<ev_TYPE_set> (ev_TYPE *, [args])
 int revents)>.
 
 =item C<ev_TYPE_set> (ev_TYPE *, [args])


@@ -645,7 +705,7 @@ 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).
 
 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.
 
 
 Returns the callback currently set on the watcher.
 


@@ -683,23 +743,64 @@ 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
 
 This section describes each watcher in detail, but will not repeat
 
 
 =head1 WATCHER TYPES
 
 This section describes each watcher in detail, but will not repeat

-information given in the last section.
+information given in the last section. Any initialisation/set macros,
+functions and members specific to the watcher type are explained.
+
+Members are additionally marked with either I<[read-only]>, meaning that,
+while the watcher is active, you can look at the member and expect some
+sensible content, but you must not modify it (you can modify it while the
+watcher is stopped to your hearts content), or I<[read-write]>, which
+means you can expect it to have some sensible content while the watcher
+is active, but you can also modify it. Modifying it may not do something
+sensible or take immediate effect (or do anything at all), but libev will
+not crash or malfunction in any way.

 
 
 
 

-=head2 C<ev_io> - is this file descriptor readable or writable
+=head2 C<ev_io> - is this file descriptor readable or writable?

 
 I/O watchers check whether a file descriptor is readable or writable
 
 I/O watchers check whether a file descriptor is readable or writable

-in each iteration of the event loop (This behaviour is called
-level-triggering because you keep receiving events as long as the
-condition persists. Remember you can stop the watcher if you don't want to
-act on the event and neither want to receive future events).
+in each iteration of the event loop, or, more precisely, when reading
+would not block the process and writing would at least be able to write
+some data. This behaviour is called level-triggering because you keep
+receiving events as long as the condition persists. Remember you can stop
+the watcher if you don't want to act on the event and neither want to
+receive future events.

 
 In general you can register as many read and/or write event watchers per
 fd as you want (as long as you don't confuse yourself). Setting all file
 
 In general you can register as many read and/or write event watchers per
 fd as you want (as long as you don't confuse yourself). Setting all file


@@ -709,39 +810,51 @@ required if you know what you are doing).
 You have to be careful with dup'ed file descriptors, though. Some backends
 (the linux epoll backend is a notable example) cannot handle dup'ed file
 descriptors correctly if you register interest in two or more fds pointing
 You have to be careful with dup'ed file descriptors, though. Some backends
 (the linux epoll backend is a notable example) cannot handle dup'ed file
 descriptors correctly if you register interest in two or more fds pointing

-to the same underlying file/socket etc. description (that is, they share
+to the same underlying file/socket/etc. description (that is, they share

 the same underlying "file open").
 
 If you must do this, then force the use of a known-to-be-good backend
 (at the time of this writing, this includes only C<EVBACKEND_SELECT> and
 C<EVBACKEND_POLL>).
 
 the same underlying "file open").
 
 If you must do this, then force the use of a known-to-be-good backend
 (at the time of this writing, this includes only C<EVBACKEND_SELECT> and
 C<EVBACKEND_POLL>).
 

+Another thing you have to watch out for is that it is quite easy to
+receive "spurious" readyness notifications, that is your callback might
+be called with C<EV_READ> but a subsequent C<read>(2) will actually block
+because there is no data. Not only are some backends known to create a
+lot of those (for example solaris ports), it is very easy to get into
+this situation even with a relatively standard program structure. Thus
+it is best to always use non-blocking I/O: An extra C<read>(2) returning
+C<EAGAIN> is far preferable to a program hanging until some data arrives.
+
+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
+such as poll (fortunately in our Xlib example, Xlib already does this on
+its own, so its quite safe to use).
+

 =over 4
 
 =item ev_io_init (ev_io *, callback, int fd, int events)
 
 =item ev_io_set (ev_io *, int fd, int events)
 
 =over 4
 
 =item ev_io_init (ev_io *, callback, int fd, int events)
 
 =item ev_io_set (ev_io *, int fd, int events)
 

-Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive
-events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ |
-EV_WRITE> to receive the given events.
-
-Please note that most of the more scalable backend mechanisms (for example
-epoll and solaris ports) can result in spurious readyness notifications
-for file descriptors, so you practically need to use non-blocking I/O (and
-treat callback invocation as hint only), or retest separately with a safe
-interface before doing I/O (XLib can do this), or force the use of either
-C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>, which don't suffer from this
-problem. Also note that it is quite easy to have your callback invoked
-when the readyness condition is no longer valid even when employing
-typical ways of handling events, so its a good idea to use non-blocking
-I/O unconditionally.
+Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
+rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
+C<EV_READ | EV_WRITE> to receive the given events.
+
+=item int fd [read-only]
+
+The file descriptor being watched.
+
+=item int events [read-only]
+
+The events being watched.

 
 =back
 
 
 =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
 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)
 
   static void
   stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)


@@ -758,7 +871,7 @@ attempt to read a whole line in the callback:
   ev_loop (loop, 0);
 
 
   ev_loop (loop, 0);
 
 

-=head2 C<ev_timer> - relative and optionally recurring timeouts
+=head2 C<ev_timer> - relative and optionally repeating timeouts

 
 Timer watchers are simple relative timers that generate an event after a
 given time, and optionally repeating in regular intervals after that.
 
 Timer watchers are simple relative timers that generate an event after a
 given time, and optionally repeating in regular intervals after that.


@@ -809,17 +922,39 @@ If the timer is repeating, either start it if necessary (with the repeat
 value), or reset the running timer to the repeat value.
 
 This sounds a bit complicated, but here is a useful and typical
 value), or reset the running timer to the 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 after=repeat=60 and calling 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.
+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
+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.
+
+You can also ignore the C<after> value and C<ev_timer_start> altogether
+and only ever use the C<repeat> value:
+
+   ev_timer_init (timer, callback, 0., 5.);
+   ev_timer_again (loop, timer);
+   ...
+   timer->again = 17.;
+   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.
+
+=item ev_tstamp repeat [read-write]
+
+The current C<repeat> value. Will be used each time the watcher times out
+or C<ev_timer_again> is called and determines the next timeout (if any),
+which is also when any modifications are taken into account.

 
 =back
 
 
 =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)
 
   static void
   one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)


@@ -831,7 +966,7 @@ Example: create a timer that fires after 60 seconds.
   ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
   ev_timer_start (loop, &mytimer);
 
   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
 inactivity.
 
   static void


@@ -850,7 +985,7 @@ inactivity.
   ev_timer_again (&mytimer);
 
 
   ev_timer_again (&mytimer);
 
 

-=head2 C<ev_periodic> - to cron or not to cron
+=head2 C<ev_periodic> - to cron or not to cron?

 
 Periodic watchers are also timers of a kind, but they are very versatile
 (and unfortunately a bit complex).
 
 Periodic watchers are also timers of a kind, but they are very versatile
 (and unfortunately a bit complex).


@@ -952,9 +1087,21 @@ when you changed some parameters or the reschedule callback would return
 a different time than the last time it was called (e.g. in a crond like
 program when the crontabs have changed).
 
 a different time than the last time it was called (e.g. in a crond like
 program when the crontabs have changed).
 

+=item ev_tstamp interval [read-write]
+
+The current interval value. Can be modified any time, but changes only
+take effect when the periodic timer fires or C<ev_periodic_again> is being
+called.
+
+=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
+
+The current reschedule callback, or C<0>, if this functionality is
+switched off. Can be changed any time, but changes only take effect when
+the periodic timer fires or C<ev_periodic_again> is being called.
+

 =back
 
 =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.
 
 system clock is divisible by 3600. The callback invocation times have
 potentially a lot of jittering, but good long-term stability.
 


@@ -968,7 +1115,7 @@ 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);
 
   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>
 
 
   #include <math.h>
 


@@ -980,7 +1127,7 @@ 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);
 
 
   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,
 
   struct ev_periodic hourly_tick;
   ev_periodic_init (&hourly_tick, clock_cb,


@@ -988,7 +1135,7 @@ Example: call a callback every hour, starting now:
   ev_periodic_start (loop, &hourly_tick);
   
 
   ev_periodic_start (loop, &hourly_tick);
   
 

-=head2 C<ev_signal> - signal me when a signal gets signalled
+=head2 C<ev_signal> - signal me when a signal gets signalled!

 
 Signal watchers will trigger an event when the process receives a specific
 signal one or more times. Even though signals are very asynchronous, libev
 
 Signal watchers will trigger an event when the process receives a specific
 signal one or more times. Even though signals are very asynchronous, libev


@@ -1011,10 +1158,14 @@ SIG_DFL (regardless of what it was set to before).
 Configures the watcher to trigger on the given signal number (usually one
 of the C<SIGxxx> constants).
 
 Configures the watcher to trigger on the given signal number (usually one
 of the C<SIGxxx> constants).
 

+=item int signum [read-only]
+
+The signal the watcher watches out for.
+

 =back
 
 
 =back
 
 

-=head2 C<ev_child> - wait for pid status changes
+=head2 C<ev_child> - watch out for process status changes

 
 Child watchers trigger when your process receives a SIGCHLD in response to
 some child status changes (most typically when a child of yours dies).
 
 Child watchers trigger when your process receives a SIGCHLD in response to
 some child status changes (most typically when a child of yours dies).


@@ -1032,9 +1183,22 @@ the status word (use the macros from C<sys/wait.h> and see your systems
 C<waitpid> documentation). The C<rpid> member contains the pid of the
 process causing the status change.
 
 C<waitpid> documentation). The C<rpid> member contains the pid of the
 process causing the status change.
 

+=item int pid [read-only]
+
+The process id this watcher watches out for, or C<0>, meaning any process id.
+
+=item int rpid [read-write]
+
+The process id that detected a status change.
+
+=item int rstatus [read-write]
+
+The process exit/trace status caused by C<rpid> (see your systems
+C<waitpid> and C<sys/wait.h> documentation for details).
+

 =back
 
 =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)
 
   static void
   sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)


@@ -1047,7 +1211,105 @@ Example: try to exit cleanly on SIGINT and SIGTERM.
   ev_signal_start (loop, &sigint_cb);
 
 
   ev_signal_start (loop, &sigint_cb);
 
 

-=head2 C<ev_idle> - when you've got nothing better to do
+=head2 C<ev_stat> - did the file attributes just change?
+
+This watches a filesystem path for attribute changes. That is, it calls
+C<stat> regularly (or when the OS says it changed) and sees if it changed
+compared to the last time, invoking the callback if it did.
+
+The path does not need to exist: changing from "path exists" to "path does
+not exist" is a status change like any other. The condition "path does
+not exist" is signified by the C<st_nlink> field being zero (which is
+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
+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
+five seconds, although this might change dynamically). Libev will also
+impose a minimum interval which is currently around C<0.1>, but thats
+usually overkill.
+
+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.
+
+=over 4
+
+=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
+
+=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
+
+Configures the watcher to wait for status changes of the given
+C<path>. The C<interval> is a hint on how quickly a change is expected to
+be detected and should normally be specified as C<0> to let libev choose
+a suitable value. The memory pointed to by C<path> must point to the same
+path for as long as the watcher is active.
+
+The callback will be receive C<EV_STAT> when a change was detected,
+relative to the attributes at the time the watcher was started (or the
+last change was detected).
+
+=item ev_stat_stat (ev_stat *)
+
+Updates the stat buffer immediately with new values. If you change the
+watched path in your callback, you could call this fucntion to avoid
+detecting this change (while introducing a race condition). Can also be
+useful simply to find out the new values.
+
+=item ev_statdata attr [read-only]
+
+The most-recently detected attributes of the file. Although the type is of
+C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
+suitable for your system. If the C<st_nlink> member is C<0>, then there
+was some error while C<stat>ing the file.
+
+=item ev_statdata prev [read-only]
+
+The previous attributes of the file. The callback gets invoked whenever
+C<prev> != C<attr>.
+
+=item ev_tstamp interval [read-only]
+
+The specified interval.
+
+=item const char *path [read-only]
+
+The filesystem path that is being watched.
+
+=back
+
+Example: Watch C</etc/passwd> for attribute changes.
+
+  static void
+  passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
+  {
+    /* /etc/passwd changed in some way */
+    if (w->attr.st_nlink)
+      {
+        printf ("passwd current size  %ld\n", (long)w->attr.st_size);
+        printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
+        printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
+      }
+    else
+      /* you shalt not abuse printf for puts */
+      puts ("wow, /etc/passwd is not there, expect problems. "
+            "if this is windows, they already arrived\n");
+  }
+
+  ...
+  ev_stat passwd;
+
+  ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
+  ev_stat_start (loop, &passwd);
+
+
+=head2 C<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
 
 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


@@ -1075,8 +1337,8 @@ believe me.
 
 =back
 
 
 =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)
 
   static void
   idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)


@@ -1091,16 +1353,27 @@ callback, free it. Alos, use no error checking, as usual.
   ev_idle_start (loop, idle_cb);
 
 
   ev_idle_start (loop, idle_cb);
 
 

-=head2 C<ev_prepare> and C<ev_check> - customise your event loop
+=head2 C<ev_prepare> and C<ev_check> - customise your event loop!

 
 Prepare and check watchers are usually (but not always) used in tandem:
 prepare watchers get invoked before the process blocks and check watchers
 afterwards.
 
 
 Prepare and check watchers are usually (but not always) used in tandem:
 prepare watchers get invoked before the process blocks and check watchers
 afterwards.
 

+You I<must not> call C<ev_loop> or similar functions that enter
+the current event loop from either C<ev_prepare> or C<ev_check>
+watchers. Other loops than the current one are fine, however. The
+rationale behind this is that you do not need to check for recursion in
+those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
+C<ev_check> so if you have one watcher of each kind they will always be
+called in pairs bracketing the blocking call.
+

 Their main purpose is to integrate other event mechanisms into libev and
 their use is somewhat advanced. This could be used, for example, to track
 variable changes, implement your own watchers, integrate net-snmp or a
 Their main purpose is to integrate other event mechanisms into libev and
 their use is somewhat advanced. This could be used, for example, to track
 variable changes, implement your own watchers, integrate net-snmp or a

-coroutine library and lots more.
+coroutine library and lots more. They are also occasionally useful if
+you cache some data and want to flush it before blocking (for example,
+in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
+watcher).

 
 This is done by examining in each prepare call which file descriptors need
 to be watched by the other library, registering C<ev_io> watchers for
 
 This is done by examining in each prepare call which file descriptors need
 to be watched by the other library, registering C<ev_io> watchers for


@@ -1132,10 +1405,63 @@ macros, but using them is utterly, utterly and completely pointless.
 
 =back
 
 
 =back
 

-Example: *TODO*.
+Example: To include a library such as adns, you would add IO watchers
+and a timeout watcher in a prepare handler, as required by libadns, and
+in a check watcher, destroy them and call into libadns. What follows is
+pseudo-code only of course:
+
+  static ev_io iow [nfd];
+  static ev_timer tw;
+
+  static void
+  io_cb (ev_loop *loop, ev_io *w, int revents)
+  {
+    // set the relevant poll flags
+    // could also call adns_processreadable etc. here
+    struct pollfd *fd = (struct pollfd *)w->data;
+    if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
+    if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
+  }
+
+  // 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];
+    // actual code will need to loop here and realloc etc.
+    adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
+
+    /* the callback is illegal, but won't be called as we stop during check */
+    ev_timer_init (&tw, 0, timeout * 1e-3);
+    ev_timer_start (loop, &tw);
+
+    // create on ev_io per pollfd
+    for (int i = 0; i < nfd; ++i)
+      {
+        ev_io_init (iow + i, io_cb, fds [i].fd,
+          ((fds [i].events & POLLIN ? EV_READ : 0)
+           | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
+
+        fds [i].revents = 0;
+        iow [i].data = fds + i;
+        ev_io_start (loop, iow + i);
+      }
+  }
+
+  // stop all watchers after blocking
+  static void
+  adns_check_cb (ev_loop *loop, ev_check *w, int revents)
+  {
+    ev_timer_stop (loop, &tw);
+
+    for (int i = 0; i < nfd; ++i)
+      ev_io_stop (loop, iow + i);
+
+    adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
+  }

 
 
 
 

-=head2 C<ev_embed> - when one backend isn't enough
+=head2 C<ev_embed> - when one backend isn't enough...

 
 This is a rather advanced watcher type that lets you embed one event loop
 into another (currently only C<ev_io> events are supported in the embedded
 
 This is a rather advanced watcher type that lets you embed one event loop
 into another (currently only C<ev_io> events are supported in the embedded


@@ -1223,6 +1549,31 @@ Make a single, non-blocking sweep over the embedded loop. This works
 similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
 apropriate way for embedded loops.
 
 similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
 apropriate way for embedded loops.
 

+=item struct ev_loop *loop [read-only]
+
+The embedded event loop.
+
+=back
+
+
+=head2 C<ev_fork> - the audacity to resume the event loop after a fork
+
+Fork watchers are called when a C<fork ()> was detected (usually because
+whoever is a good citizen cared to tell libev about it by calling
+C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
+event loop blocks next and before C<ev_check> watchers are being called,
+and only in the child after the fork. If whoever good citizen calling
+C<ev_default_fork> cheats and calls it in the wrong process, the fork
+handlers will be invoked, too, of course.
+
+=over 4
+
+=item ev_fork_init (ev_signal *, callback)
+
+Initialises and configures the fork watcher - it has no parameters of any
+kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
+believe me.
+

 =back
 
 
 =back
 
 


@@ -1394,6 +1745,10 @@ C<ev_TYPE_again> function.
 
 Invokes C<ev_embed_sweep>.
 
 
 Invokes C<ev_embed_sweep>.
 

+=item w->update ()      C<ev::stat> only
+
+Invokes C<ev_stat_stat>.
+

 =back
 
 =back
 =back
 
 =back


@@ -1416,6 +1771,68 @@ the constructor.
     io.start (fd, ev::READ);
   }
 
     io.start (fd, ev::READ);
   }
 

+
+=head1 MACRO MAGIC
+
+Libev can be compiled with a variety of options, the most fundemantal is
+C<EV_MULTIPLICITY>. This option determines wether (most) functions and
+callbacks have an initial C<struct ev_loop *> argument.
+
+To make it easier to write programs that cope with either variant, the
+following macros are defined:
+
+=over 4
+
+=item C<EV_A>, C<EV_A_>
+
+This provides the loop I<argument> for functions, if one is required ("ev
+loop argument"). The C<EV_A> form is used when this is the sole argument,
+C<EV_A_> is used when other arguments are following. Example:
+
+  ev_unref (EV_A);
+  ev_timer_add (EV_A_ watcher);
+  ev_loop (EV_A_ 0);
+
+It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
+which is often provided by the following macro.
+
+=item C<EV_P>, C<EV_P_>
+
+This provides the loop I<parameter> for functions, if one is required ("ev
+loop parameter"). The C<EV_P> form is used when this is the sole parameter,
+C<EV_P_> is used when other parameters are following. Example:
+
+  // this is how ev_unref is being declared
+  static void ev_unref (EV_P);
+
+  // this is how you can declare your typical callback
+  static void cb (EV_P_ ev_timer *w, int revents)
+
+It declares a parameter C<loop> of type C<struct ev_loop *>, quite
+suitable for use with C<EV_A>.
+
+=item C<EV_DEFAULT>, C<EV_DEFAULT_>
+
+Similar to the other two macros, this gives you the value of the default
+loop, if multiple loops are supported ("ev loop default").
+
+=back
+
+Example: Declare and initialise a check watcher, working regardless of
+wether multiple loops are supported or not.
+
+  static void
+  check_cb (EV_P_ ev_timer *w, int revents)
+  {
+    ev_check_stop (EV_A_ w);
+  }
+
+  ev_check check;
+  ev_check_init (&check, check_cb);
+  ev_check_start (EV_DEFAULT_ &check);
+  ev_loop (EV_DEFAULT_ 0);
+
+

 =head1 EMBEDDING
 
 Libev can (and often is) directly embedded into host
 =head1 EMBEDDING
 
 Libev can (and often is) directly embedded into host


@@ -1464,14 +1881,14 @@ in your include path (e.g. in libev/ when using -Ilibev):
 
   ev_win32.c      required on win32 platforms only
 
 
   ev_win32.c      required on win32 platforms only
 

-  ev_select.c     only when select backend is enabled (which is is by default)
+  ev_select.c     only when select backend is enabled (which is 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)
   ev_port.c       only when the solaris port backend is enabled (disabled by default)
 
 F<ev.c> includes the backend files directly when enabled, so you only need
   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)
   ev_port.c       only when the solaris port backend is enabled (disabled by default)
 
 F<ev.c> includes the backend files directly when enabled, so you only need

-to compile a single file.
+to compile this single file.

 
 =head3 LIBEVENT COMPATIBILITY API
 
 
 =head3 LIBEVENT COMPATIBILITY API
 


@@ -1494,8 +1911,8 @@ You need the following additional files for this:
 
 Instead of using C<EV_STANDALONE=1> and providing your config in
 whatever way you want, you can also C<m4_include([libev.m4])> in your
 
 Instead of using C<EV_STANDALONE=1> and providing your config in
 whatever way you want, you can also C<m4_include([libev.m4])> in your

-F<configure.ac> and leave C<EV_STANDALONE> off. F<ev.c> will then include
-F<config.h> and configure itself accordingly.
+F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
+include F<config.h> and configure itself accordingly.

 
 For this of course you need the m4 file:
 
 
 For this of course you need the m4 file:
 


@@ -1585,7 +2002,7 @@ backend for BSD and BSD-like systems, although on most BSDs kqueue only
 supports some types of fds correctly (the only platform we found that
 supports ptys for example was NetBSD), so kqueue might be compiled in, but
 not be used unless explicitly requested. The best way to use it is to find
 supports some types of fds correctly (the only platform we found that
 supports ptys for example was NetBSD), so kqueue might be compiled in, but
 not be used unless explicitly requested. The best way to use it is to find

-out wether kqueue supports your type of fd properly and use an embedded
+out whether kqueue supports your type of fd properly and use an embedded

 kqueue loop.
 
 =item EV_USE_PORT
 kqueue loop.
 
 =item EV_USE_PORT


@@ -1599,6 +2016,12 @@ backend for Solaris 10 systems.
 
 reserved for future expansion, works like the USE symbols above.
 
 
 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
 =item EV_H
 
 The name of the F<ev.h> header file used to include it. The default if


@@ -1631,10 +2054,47 @@ 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.
 
 for multiple event loops and there is no first event loop pointer
 argument. Instead, all functions act on the single default loop.
 

-=item EV_PERIODICS
+=item EV_PERIODIC_ENABLE
+
+If undefined or defined to be C<1>, then periodic timers are supported. If
+defined to be C<0>, then they are not. Disabling them saves a few kB of
+code.
+
+=item EV_EMBED_ENABLE
+
+If undefined or defined to be C<1>, then embed watchers are supported. If
+defined to be C<0>, then they are not.
+
+=item EV_STAT_ENABLE

 
 

-If undefined or defined to be C<1>, then periodic timers are supported,
-otherwise not. This saves a few kb of code.
+If undefined or defined to be C<1>, then stat watchers are supported. If
+defined to be C<0>, then they are not.
+
+=item EV_FORK_ENABLE
+
+If undefined or defined to be C<1>, then fork watchers are supported. If
+defined to be C<0>, then they are not.
+
+=item EV_MINIMAL
+
+If you need to shave off some kilobytes of code at the expense of some
+speed, define this symbol to C<1>. Currently only used for gcc to override
+some inlining decisions, saves roughly 30% codesize of amd64.
+
+=item EV_PID_HASHSIZE
+
+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 (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
 
 
 =item EV_COMMON
 


@@ -1649,18 +2109,18 @@ For example, the perl EV module uses something like this:
     SV *self; /* contains this struct */  \
     SV *cb_sv, *fh /* note no trailing ";" */
 
     SV *self; /* contains this struct */  \
     SV *cb_sv, *fh /* note no trailing ";" */
 

-=item EV_CB_DECLARE(type)
+=item EV_CB_DECLARE (type)

 
 

-=item EV_CB_INVOKE(watcher,revents)
+=item EV_CB_INVOKE (watcher, revents)

 
 

-=item ev_set_cb(ev,cb)
+=item ev_set_cb (ev, cb)

 
 Can be used to change the callback member declaration in each watcher,
 and the way callbacks are invoked and set. Must expand to a struct member
 definition and a statement, respectively. See the F<ev.v> header file for
 their default definitions. One possible use for overriding these is to
 
 Can be used to change the callback member declaration in each watcher,
 and the way callbacks are invoked and set. Must expand to a struct member
 definition and a statement, respectively. See the F<ev.v> header file for
 their default definitions. One possible use for overriding these is to

-avoid the ev_loop pointer as first argument in all cases, or to use method
-calls instead of plain function calls in C++.
+avoid the C<struct ev_loop *> as first argument in all cases, or to use
+method calls instead of plain function calls in C++.

 
 =head2 EXAMPLES
 
 
 =head2 EXAMPLES
 


@@ -1675,21 +2135,44 @@ 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:
 
 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:
 

-   #define EV_USE_POLL 0
-   #define EV_MULTIPLICITY 0
-   #define EV_PERIODICS 0
-   #define EV_CONFIG_H <config.h>
+  #define EV_USE_POLL 0
+  #define EV_MULTIPLICITY 0
+  #define EV_PERIODICS 0
+  #define EV_CONFIG_H <config.h>

 
 

-   #include "ev++.h"
+  #include "ev++.h"

 
 And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
 
 
 And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
 

-   #include "rxvttoolkit.h"
+  #include "ev_cpp.h"
+  #include "ev.c"
+
+
+=head1 COMPLEXITIES

 
 

-   /* darwin has problems with its header files in C++, requiring this namespace juggling */
-   using namespace ev;
+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 C<ev_default_init>.

 
 

-   #include "ev.c"
+=over 4
+
+=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
+
+=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
+
+=item Starting io/check/prepare/idle/signal/child watchers: O(1)
+
+=item Stopping check/prepare/idle watchers: O(1)
+
+=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)
+
+=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
+
+=item Activating one watcher: O(1)
+
+=back

 
 
 =head1 AUTHOR
 
 
 =head1 AUTHOR