X-Git-Url: https://git.llucax.com/software/libev.git/blobdiff_plain/1260001bb124e3b8e60d559e1736ed3432c8cc6e..1e251ffd9e2bf720df7759c2eb3c807f5b0d474f:/ev.pod

diff --git a/ev.pod b/ev.pod
index 82febdd..ed0ac1b 100644
--- a/ev.pod
+++ b/ev.pod
@@ -6,6 +6,48 @@ libev - a high performance full-featured event loop written in C
 
   #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
@@ -23,23 +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
 
@@ -47,7 +95,8 @@ Libev represents time as a single floating point number, representing the
 (fractional) number of seconds since the (POSIX) epoch (somewhere near
 the beginning of 1970, details are complicated, don't ask). This type is
 called C<ev_tstamp>, which is what you should use too. It usually aliases
-to the double type in C.
+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
 
@@ -58,7 +107,9 @@ library in any way.
 
 =item ev_tstamp ev_time ()
 
-Returns the current time as libev would use it.
+Returns the current time as libev would use it. Please note that the
+C<ev_now> function is usually faster and also often returns the timestamp
+you actually want to know.
 
 =item int ev_version_major ()
 
@@ -75,18 +126,78 @@ 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.
+
+  assert (("libev version mismatch",
+           ev_version_major () == EV_VERSION_MAJOR
+           && ev_version_minor () >= EV_VERSION_MINOR));
+
+=item unsigned int ev_supported_backends ()
+
+Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
+value) compiled into this binary of libev (independent of their
+availability on the system you are running on). See C<ev_default_loop> for
+a description of the set values.
+
+Example: make sure we have the epoll method, because yeah this is cool and
+a must have and can we have a torrent of it please!!!11
+
+  assert (("sorry, no epoll, no sex",
+           ev_supported_backends () & EVBACKEND_EPOLL));
+
+=item unsigned int ev_recommended_backends ()
+
+Return the set of all backends compiled into this binary of libev and also
+recommended for this platform. This set is often smaller than the one
+returned by C<ev_supported_backends>, as for example kqueue is broken on
+most BSDs and will not be autodetected unless you explicitly request it
+(assuming you know what you are doing). This is the set of backends that
+libev will probe for if you specify no backends explicitly.
+
+=item unsigned int ev_embeddable_backends ()
+
+Returns the set of backends that are embeddable in other event loops. This
+is the theoretical, all-platform, value. To find which backends
+might be supported on the current system, you would need to look at
+C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
+recommended ones.
+
+See the description of C<ev_embed> watchers for more info.
+
 =item ev_set_allocator (void *(*cb)(void *ptr, long 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 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,
 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).
+
+   static void *
+   persistent_realloc (void *ptr, size_t size)
+   {
+     for (;;)
+       {
+         void *newptr = realloc (ptr, size);
+
+         if (newptr)
+           return newptr;
+
+         sleep (60);
+       }
+   }
+
+   ...
+   ev_set_allocator (persistent_realloc);
+
 =item ev_set_syserr_cb (void (*cb)(const char *msg));
 
 Set the callback function to call on a retryable syscall error (such
@@ -97,6 +208,18 @@ 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: This is basically the same thing that libev does internally, too.
+
+   static void
+   fatal_error (const char *msg)
+   {
+     perror (msg);
+     abort ();
+   }
+
+   ...
+   ev_set_syserr_cb (fatal_error);
+
 =back
 
 =head1 FUNCTIONS CONTROLLING THE EVENT LOOP
@@ -119,15 +242,15 @@ done correctly, because it's hideous and inefficient).
 This will initialise the default event loop if it hasn't been initialised
 yet and return it. If the default loop could not be initialised, returns
 false. If it already was initialised it simply returns it (and ignores the
-flags).
+flags. If that is troubling you, check C<ev_backend ()> afterwards).
 
 If you don't know what event loop to use, use the one returned from this
 function.
 
 The flags argument can be used to specify special behaviour or specific
-backends to use, and is usually specified as 0 (or EVFLAG_AUTO).
+backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
 
-It supports the following flags:
+The following flags are supported:
 
 =over 4
 
@@ -145,24 +268,115 @@ 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.
 
-=item C<EVMETHOD_SELECT>  (portable select backend)
+=item C<EVFLAG_FORKCHECK>
 
-=item C<EVMETHOD_POLL>    (poll backend, available everywhere except on windows)
+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.
 
-=item C<EVMETHOD_EPOLL>   (linux only)
+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).
 
-=item C<EVMETHOD_KQUEUE>  (some bsds only)
+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.
 
-=item C<EVMETHOD_DEVPOLL> (solaris 8 only)
+This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
+environment variable.
 
-=item C<EVMETHOD_PORT>    (solaris 10 only)
+=item C<EVBACKEND_SELECT>  (value 1, portable select backend)
 
-If one or more of these are ored into the flags value, then only these
-backends will be tried (in the reverse order as given here). If one are
-specified, any backend will do.
+This is your standard select(2) backend. Not I<completely> standard, as
+libev tries to roll its own fd_set with no limits on the number of fds,
+but if that fails, expect a fairly low limit on the number of fds when
+using this backend. It doesn't scale too well (O(highest_fd)), but its usually
+the fastest backend for a low number of fds.
+
+=item C<EVBACKEND_POLL>    (value 2, poll backend, available everywhere except on windows)
+
+And this is your standard poll(2) backend. It's more complicated than
+select, but handles sparse fds better and has no artificial limit on the
+number of fds you can use (except it will slow down considerably with a
+lot of inactive fds). It scales similarly to select, i.e. O(total_fds).
+
+=item C<EVBACKEND_EPOLL>   (value 4, Linux)
+
+For few fds, this backend is a bit little slower than poll and select,
+but it scales phenomenally better. While poll and select usually scale like
+O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
+either O(1) or O(active_fds).
+
+While stopping and starting an I/O watcher in the same iteration will
+result in some caching, there is still a syscall per such incident
+(because the fd could point to a different file description now), so its
+best to avoid that. Also, dup()ed file descriptors might not work very
+well if you register events for both fds.
+
+Please note that epoll sometimes generates spurious notifications, so you
+need to use non-blocking I/O or other means to avoid blocking when no data
+(or space) is available.
+
+=item C<EVBACKEND_KQUEUE>  (value 8, most BSD clones)
+
+Kqueue deserves special mention, as at the time of this writing, it
+was broken on all BSDs except NetBSD (usually it doesn't work with
+anything but sockets and pipes, except on Darwin, where of course its
+completely useless). For this reason its not being "autodetected"
+unless you explicitly specify it explicitly in the flags (i.e. using
+C<EVBACKEND_KQUEUE>).
+
+It scales in the same way as the epoll backend, but the interface to the
+kernel is more efficient (which says nothing about its actual speed, of
+course). While starting and stopping an I/O watcher does not cause an
+extra syscall as with epoll, it still adds up to four event changes per
+incident, so its best to avoid that.
+
+=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
+
+This is not implemented yet (and might never be).
+
+=item C<EVBACKEND_PORT>    (value 32, Solaris 10)
+
+This uses the Solaris 10 port mechanism. As with everything on Solaris,
+it's really slow, but it still scales very well (O(active_fds)).
+
+Please note that solaris ports can result in a lot of spurious
+notifications, so you need to use non-blocking I/O or other means to avoid
+blocking when no data (or space) is available.
+
+=item C<EVBACKEND_ALL>
+
+Try all backends (even potentially broken ones that wouldn't be tried
+with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
+C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
 
 =back
 
+If one or more of these are ored into the flags value, then only these
+backends will be tried (in the reverse order as given here). If none are
+specified, most compiled-in backend will be tried, usually in reverse
+order of their flag values :)
+
+The most typical usage is like this:
+
+  if (!ev_default_loop (0))
+    fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
+
+Restrict libev to the select and poll backends, and do not allow
+environment settings to be taken into account:
+
+  ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
+
+Use whatever libev has to offer, but make sure that kqueue is used if
+available (warning, breaks stuff, best use only with your own private
+event loop and only if you know the OS supports your types of fds):
+
+  ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
+
 =item struct ev_loop *ev_loop_new (unsigned int flags)
 
 Similar to C<ev_default_loop>, but always creates a new event loop that is
@@ -170,11 +384,21 @@ 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.
+
+  struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
+  if (!epoller)
+    fatal ("no epoll found here, maybe it hides under your chair");
+
 =item ev_default_destroy ()
 
 Destroys the default loop again (frees all memory and kernel state
-etc.). This stops all registered event watchers (by not touching them in
-any way whatsoever, although you cannot rely on this :).
+etc.). None of the active event watchers will be stopped in the normal
+sense, so e.g. C<ev_is_active> might still return true. It is your
+responsibility to either stop all watchers cleanly yoursef I<before>
+calling this function, or cope with the fact afterwards (which is usually
+the easiest thing, youc na just ignore the watchers and/or C<free ()> them
+for example).
 
 =item ev_loop_destroy (loop)
 
@@ -188,9 +412,9 @@ one. Despite the name, you can call it anytime, but it makes most sense
 after forking, in either the parent or child process (or both, but that
 again makes little sense).
 
-You I<must> call this function after forking if and only if you want to
-use the event library in both processes. If you just fork+exec, you don't
-have to call it.
+You I<must> call this function in the child process after forking if and
+only if you want to use the event library in both processes. If you just
+fork+exec, you don't have to call it.
 
 The function itself is quite fast and it's usually not a problem to call
 it just in case after a fork. To make this easy, the function will fit in
@@ -198,24 +422,28 @@ quite nicely into a call to C<pthread_atfork>:
 
     pthread_atfork (0, 0, ev_default_fork);
 
+At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
+without calling this function, so if you force one of those backends you
+do not need to care.
+
 =item ev_loop_fork (loop)
 
 Like C<ev_default_fork>, but acts on an event loop created by
 C<ev_loop_new>. Yes, you have to call this on every allocated event loop
 after fork, and how you do this is entirely your own problem.
 
-=item unsigned int ev_method (loop)
+=item unsigned int ev_backend (loop)
 
-Returns one of the C<EVMETHOD_*> flags indicating the event backend in
+Returns one of the C<EVBACKEND_*> flags indicating the event backend in
 use.
 
 =item ev_tstamp ev_now (loop)
 
 Returns the current "event loop time", which is the time the event loop
-got events and started processing them. This timestamp does not change
-as long as callbacks are being processed, and this is also the base time
-used for relative timers. You can treat it as the timestamp of the event
-occuring (or more correctly, the mainloop finding out about it).
+received events and started processing them. This timestamp does not
+change as long as callbacks are being processed, and this is also the base
+time used for relative timers. You can treat it as the timestamp of the
+event occuring (or more correctly, libev finding out about it).
 
 =item ev_loop (loop, int flags)
 
@@ -223,8 +451,14 @@ Finally, this is it, the event handler. This function usually is called
 after you initialised all your watchers and you want to start handling
 events.
 
-If the flags argument is specified as 0, it will not return until either
-no event watchers are active anymore or C<ev_unloop> was called.
+If the flags argument is specified as C<0>, it will not return until
+either no event watchers are active anymore or C<ev_unloop> was called.
+
+Please note that an explicit C<ev_unloop> is usually better than
+relying on all watchers to be stopped when deciding when a program has
+finished (especially in interactive programs), but having a program that
+automatically loops as long as it has to and no longer by virtue of
+relying on its watchers stopping correctly is a thing of beauty.
 
 A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
 those events and any outstanding ones, but will not block your process in
@@ -233,17 +467,45 @@ case there are no events and will return after one iteration of the loop.
 A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
 neccessary) and will handle those and any outstanding ones. It will block
 your process until at least one new event arrives, and will return after
-one iteration of the loop.
-
-This flags value could be used to implement alternative looping
-constructs, but the C<prepare> and C<check> watchers provide a better and
-more generic mechanism.
+one iteration of the loop. This is useful if you are waiting for some
+external event in conjunction with something not expressible using other
+libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
+usually a better approach for this kind of thing.
+
+Here are the gory details of what C<ev_loop> does:
+
+   * If there are no active watchers (reference count is zero), return.
+   - Queue prepare watchers and then call all outstanding watchers.
+   - If we have been forked, recreate the kernel state.
+   - Update the kernel state with all outstanding changes.
+   - Update the "event loop time".
+   - Calculate for how long to block.
+   - Block the process, waiting for any events.
+   - Queue all outstanding I/O (fd) events.
+   - Update the "event loop time" and do time jump handling.
+   - Queue all outstanding timers.
+   - Queue all outstanding periodics.
+   - If no events are pending now, queue all idle watchers.
+   - Queue all check watchers.
+   - Call all queued watchers in reverse order (i.e. check watchers first).
+     Signals and child watchers are implemented as I/O watchers, and will
+     be handled here by queueing them when their watcher gets executed.
+   - 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
+anymore.
+
+   ... queue jobs here, make sure they register event watchers as long
+   ... as they still have work to do (even an idle watcher will do..)
+   ev_loop (my_loop, 0);
+   ... jobs done. yeah!
 
 =item ev_unloop (loop, how)
 
 Can be used to make a call to C<ev_loop> return early (but only after it
 has processed all outstanding events). The C<how> argument must be either
-C<EVUNLOOP_ONCE>, which will make the innermost C<ev_loop> call return, or
+C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
 C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
 
 =item ev_ref (loop)
@@ -261,8 +523,22 @@ 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>.
 
+Example: Create a signal watcher, but keep it from keeping C<ev_loop>
+running when nothing else is active.
+
+  struct ev_signal exitsig;
+  ev_signal_init (&exitsig, sig_cb, SIGINT);
+  ev_signal_start (loop, &exitsig);
+  evf_unref (loop);
+
+Example: For some weird reason, unregister the above signal handler again.
+
+  ev_ref (loop);
+  ev_signal_stop (loop, &exitsig);
+
 =back
 
+
 =head1 ANATOMY OF A WATCHER
 
 A watcher is a structure that you create and register to record your
@@ -304,12 +580,7 @@ corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
 
 As long as your watcher is active (has been started but not stopped) you
 must not touch the values stored in it. Most specifically you must never
-reinitialise it or call its set method.
-
-You can check whether an event is active by calling the C<ev_is_active
-(watcher *)> macro. To see whether an event is outstanding (but the
-callback for it has not been called yet) you can use the C<ev_is_pending
-(watcher *)> macro.
+reinitialise it or call its C<set> macro.
 
 Each and every callback receives the event loop pointer as first, the
 registered watcher structure as second, and a bitset of received events as
@@ -344,6 +615,10 @@ 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.
 
+=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.
@@ -360,6 +635,15 @@ 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).
 
+=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
@@ -376,6 +660,85 @@ programs, though, so beware.
 
 =back
 
+=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.
+
+=over 4
+
+=item C<ev_init> (ev_TYPE *watcher, callback)
+
+This macro initialises the generic portion of a watcher. The contents
+of the watcher object can be arbitrary (so C<malloc> will do). Only
+the generic parts of the watcher are initialised, you I<need> to call
+the type-specific C<ev_TYPE_set> macro afterwards to initialise the
+type-specific parts. For each type there is also a C<ev_TYPE_init> macro
+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.
+
+The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
+int revents)>.
+
+=item C<ev_TYPE_set> (ev_TYPE *, [args])
+
+This macro initialises the type-specific parts of a watcher. You need to
+call C<ev_init> at least once before you call this macro, but you can
+call C<ev_TYPE_set> any number of times. You must not, however, call this
+macro on a watcher that is active (it can be pending, however, which is a
+difference to the C<ev_init> macro).
+
+Although some watcher types do not have type-specific arguments
+(e.g. C<ev_prepare>) you still need to call its C<set> macro.
+
+=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
+
+This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
+calls into a single call. This is the most convinient method to initialise
+a watcher. The same limitations apply, of course.
+
+=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
+
+Starts (activates) the given watcher. Only active watchers will receive
+events. If the watcher is already active nothing will happen.
+
+=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
+
+Stops the given watcher again (if active) and clears the pending
+status. It is possible that stopped watchers are pending (for example,
+non-repeating timers are being stopped when they become pending), but
+C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If
+you want to free or reuse the memory used by the watcher it is therefore a
+good idea to always call its C<ev_TYPE_stop> function.
+
+=item bool ev_is_active (ev_TYPE *watcher)
+
+Returns a true value iff the watcher is active (i.e. it has been started
+and not yet been stopped). As long as a watcher is active you must not modify
+it.
+
+=item bool ev_is_pending (ev_TYPE *watcher)
+
+Returns a true value iff the watcher is pending, (i.e. it has outstanding
+events but its callback has not yet been invoked). As long as a watcher
+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)
+
+Returns the callback currently set on the watcher.
+
+=item ev_cb_set (ev_TYPE *watcher, callback)
+
+Change the callback. You can change the callback at virtually any time
+(modulo threads).
+
+=back
+
+
 =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
 
 Each watcher has, by default, a member C<void *data> that you can change
@@ -402,24 +765,66 @@ 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
-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.
 
-=head2 C<ev_io> - is this file descriptor readable or writable
+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.
 
-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 general you can register as many read and/or write event watchers oer
+=head2 C<ev_io> - is this file descriptor readable or writable?
+
+I/O watchers check whether a file descriptor is readable or writable
+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
 descriptors to non-blocking mode is also usually a good idea (but not
 required if you know what you are doing).
@@ -427,11 +832,27 @@ 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
-to the same file/socket etc. description.
+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 EVMETHOD_SELECT and
-EVMETHOD_POLL).
+(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
 
@@ -439,31 +860,62 @@ EVMETHOD_POLL).
 
 =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.
+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
 
-=head2 C<ev_timer> - relative and optionally recurring timeouts
+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.
+
+  static void
+  stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
+  {
+     ev_io_stop (loop, w);
+    .. read from stdin here (or from w->fd) and haqndle any I/O errors
+  }
+
+  ...
+  struct ev_loop *loop = ev_default_init (0);
+  struct ev_io stdin_readable;
+  ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
+  ev_io_start (loop, &stdin_readable);
+  ev_loop (loop, 0);
+
+
+=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.
 
 The timers are based on real time, that is, if you register an event that
-times out after an hour and youreset your system clock to last years
+times out after an hour and you reset your system clock to last years
 time, it will still time out after (roughly) and hour. "Roughly" because
-detecting time jumps is hard, and soem inaccuracies are unavoidable (the
+detecting time jumps is hard, and some inaccuracies are unavoidable (the
 monotonic clock option helps a lot here).
 
 The relative timeouts are calculated relative to the C<ev_now ()>
 time. This is usually the right thing as this timestamp refers to the time
-of the event triggering whatever timeout you are modifying/starting.  If
-you suspect event processing to be delayed and you *need* to base the timeout
-ion the current time, use something like this to adjust for this:
+of the event triggering whatever timeout you are modifying/starting. If
+you suspect event processing to be delayed and you I<need> to base the timeout
+on the current time, use something like this to adjust for this:
 
    ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
 
+The callback is guarenteed to be invoked only when its timeout has passed,
+but if multiple timers become ready during the same loop iteration then
+order of execution is undefined.
+
 =over 4
 
 =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
@@ -478,7 +930,7 @@ later, again, and again, until stopped manually.
 The timer itself will do a best-effort at avoiding drift, that is, if you
 configure a timer to trigger every 10 seconds, then it will trigger at
 exactly 10 second intervals. If, however, your program cannot keep up with
-the timer (ecause it takes longer than those 10 seconds to do stuff) the
+the timer (because it takes longer than those 10 seconds to do stuff) the
 timer will not fire more than once per event loop iteration.
 
 =item ev_timer_again (loop)
@@ -486,23 +938,78 @@ timer will not fire more than once per event loop iteration.
 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 repeating, either start it if necessary (with the repeat
-value), or reset the running timer to the repeat value.
+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
+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 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.
+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 C<ev_timer_stop> the timer, and C<ev_timer_again> will
+automatically restart it if need be.
+
+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 = 17.;
+   ev_timer_again (loop, timer);
+   ...
+   timer->again = 10.;
+   ev_timer_again (loop, timer);
+
+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]
+
+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
 
-=head2 C<ev_periodic> - to cron or not to cron
+Example: Create a timer that fires after 60 seconds.
+
+  static void
+  one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
+  {
+    .. one minute over, w is actually stopped right here
+  }
+
+  struct ev_timer 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
+inactivity.
+
+  static void
+  timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
+  {
+    .. ten seconds without any activity
+  }
+
+  struct ev_timer mytimer;
+  ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
+  ev_timer_again (&mytimer); /* start timer */
+  ev_loop (loop, 0);
+
+  // and in some piece of code that gets executed on any "activity":
+  // reset the timeout to start ticking again at 10 seconds
+  ev_timer_again (&mytimer);
+
+
+=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).
@@ -510,7 +1017,7 @@ Periodic watchers are also timers of a kind, but they are very versatile
 Unlike C<ev_timer>'s, they are not based on real time (or relative time)
 but on wallclock time (absolute time). You can tell a periodic watcher
 to trigger "at" some specific point in time. For example, if you tell a
-periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()
+periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
 + 10.>) and then reset your system clock to the last year, then it will
 take a year to trigger the event (unlike an C<ev_timer>, which would trigger
 roughly 10 seconds later and of course not if you reset your system time
@@ -519,6 +1026,10 @@ again).
 They can also be used to implement vastly more complex timers, such as
 triggering an event on eahc midnight, local time.
 
+As with timers, the callback is guarenteed to be invoked only when the
+time (C<at>) has been passed, but if multiple periodic timers become ready
+during the same loop iteration then order of execution is undefined.
+
 =over 4
 
 =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
@@ -528,7 +1039,6 @@ triggering an event on eahc midnight, local time.
 Lots of arguments, lets sort it out... There are basically three modes of
 operation, and we will explain them from simplest to complex:
 
-
 =over 4
 
 =item * absolute timer (interval = reschedule_cb = 0)
@@ -584,12 +1094,13 @@ will usually be called just before the callback will be triggered, but
 might be called at other times, too.
 
 NOTE: I<< This callback must always return a time that is later than the
-passed C<now> value >>. Not even C<now> itself will do, it must be larger.
+passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.
 
 This can be used to create very complex timers, such as a timer that
 triggers on each midnight, local time. To do this, you would calculate the
-next midnight after C<now> and return the timestamp value for this. How you do this
-is, again, up to you (but it is not trivial).
+next midnight after C<now> and return the timestamp value for this. How
+you do this is, again, up to you (but it is not trivial, which is the main
+reason I omitted it as an example).
 
 =back
 
@@ -600,9 +1111,55 @@ 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).
 
+=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
 
-=head2 C<ev_signal> - signal me when a signal gets signalled
+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.
+
+  static void
+  clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
+  {
+    ... its now a full hour (UTC, or TAI or whatever your clock follows)
+  }
+
+  struct ev_periodic 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:
+
+  #include <math.h>
+
+  static ev_tstamp
+  my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
+  {
+    return fmod (now, 3600.) + 3600.;
+  }
+
+  ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
+
+Example: Call a callback every hour, starting now:
+
+  struct ev_periodic hourly_tick;
+  ev_periodic_init (&hourly_tick, clock_cb,
+                    fmod (ev_now (loop), 3600.), 3600., 0);
+  ev_periodic_start (loop, &hourly_tick);
+  
+
+=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
@@ -625,9 +1182,14 @@ 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).
 
+=item int signum [read-only]
+
+The signal the watcher watches out for.
+
 =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).
@@ -645,9 +1207,141 @@ 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.
 
+=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
+
+Example: Try to exit cleanly on SIGINT and SIGTERM.
+
+  static void
+  sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
+  {
+    ev_unloop (loop, EVUNLOOP_ALL);
+  }
+
+  struct ev_signal signal_watcher;
+  ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
+  ev_signal_start (loop, &sigint_cb);
+
+
+=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.
+
+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)> 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
+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, 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
+
+=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
 
-=head2 C<ev_idle> - when you've got nothing better to do
+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
@@ -675,15 +1369,43 @@ believe me.
 
 =back
 
-=head2 C<ev_prepare> and C<ev_check> - customise your event loop
+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)
+  {
+    free (w);
+    // now do something you wanted to do when the program has
+    // no longer asnything immediate to do.
+  }
+
+  struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
+  ev_idle_init (idle_watcher, idle_cb);
+  ev_idle_start (loop, idle_cb);
+
+
+=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
+prepare watchers get invoked before the process blocks and check watchers
 afterwards.
 
-Their main purpose is to integrate other event mechanisms into libev. This
-could be used, for example, to track variable changes, implement your own
-watchers, integrate net-snmp or a coroutine library and lots more.
+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
+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
@@ -691,17 +1413,17 @@ them and starting an C<ev_timer> watcher for any timeouts (many libraries
 provide just this functionality). Then, in the check watcher you check for
 any events that occured (by checking the pending status of all watchers
 and stopping them) and call back into the library. The I/O and timer
-callbacks will never actually be called (but must be valid neverthelles,
+callbacks will never actually be called (but must be valid nevertheless,
 because you never know, you know?).
 
 As another example, the Perl Coro module uses these hooks to integrate
 coroutines into libev programs, by yielding to other active coroutines
 during each prepare and only letting the process block if no coroutines
-are ready to run (its actually more complicated, it only runs coroutines
-with priority higher than the event loop and one lower priority once,
-using idle watchers to keep the event loop from blocking if lower-priority
-coroutines exist, thus mapping low-priority coroutines to idle/background
-tasks).
+are ready to run (it's actually more complicated: it only runs coroutines
+with priority higher than or equal to the event loop and one coroutine
+of lower priority, but only once, using idle watchers to keep the event
+loop from blocking if lower-priority coroutines are active, thus mapping
+low-priority coroutines to idle/background tasks).
 
 =over 4
 
@@ -715,6 +1437,179 @@ macros, but using them is utterly, utterly and completely pointless.
 
 =back
 
+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;
+    struct 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...
+
+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
+loop, other types of watchers might be handled in a delayed or incorrect
+fashion and must not be used).
+
+There are primarily two reasons you would want that: work around bugs and
+prioritise I/O.
+
+As an example for a bug workaround, the kqueue backend might only support
+sockets on some platform, so it is unusable as generic backend, but you
+still want to make use of it because you have many sockets and it scales
+so nicely. In this case, you would create a kqueue-based loop and embed it
+into your default loop (which might use e.g. poll). Overall operation will
+be a bit slower because first libev has to poll and then call kevent, but
+at least you can use both at what they are best.
+
+As for prioritising I/O: rarely you have the case where some fds have
+to be watched and handled very quickly (with low latency), and even
+priorities and idle watchers might have too much overhead. In this case
+you would put all the high priority stuff in one loop and all the rest in
+a second one, and embed the second one in the first.
+
+As long as the watcher is active, the callback will be invoked every time
+there might be events pending in the embedded loop. The callback must then
+call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
+their callbacks (you could also start an idle watcher to give the embedded
+loop strictly lower priority for example). You can also set the callback
+to C<0>, in which case the embed watcher will automatically execute the
+embedded loop sweep.
+
+As long as the watcher is started it will automatically handle events. The
+callback will be invoked whenever some events have been handled. You can
+set the callback to C<0> to avoid having to specify one if you are not
+interested in that.
+
+Also, there have not currently been made special provisions for forking:
+when you fork, you not only have to call C<ev_loop_fork> on both loops,
+but you will also have to stop and restart any C<ev_embed> watchers
+yourself.
+
+Unfortunately, not all backends are embeddable, only the ones returned by
+C<ev_embeddable_backends> are, which, unfortunately, does not include any
+portable one.
+
+So when you want to use this feature you will always have to be prepared
+that you cannot get an embeddable loop. The recommended way to get around
+this is to have a separate variables for your embeddable loop, try to
+create it, and if that fails, use the normal loop for everything:
+
+  struct ev_loop *loop_hi = ev_default_init (0);
+  struct ev_loop *loop_lo = 0;
+  struct ev_embed embed;
+  
+  // see if there is a chance of getting one that works
+  // (remember that a flags value of 0 means autodetection)
+  loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
+    ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
+    : 0;
+
+  // if we got one, then embed it, otherwise default to loop_hi
+  if (loop_lo)
+    {
+      ev_embed_init (&embed, 0, loop_lo);
+      ev_embed_start (loop_hi, &embed);
+    }
+  else
+    loop_lo = loop_hi;
+
+=over 4
+
+=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
+
+=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
+
+Configures the watcher to embed the given loop, which must be
+embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
+invoked automatically, otherwise it is the responsibility of the callback
+to invoke it (it will continue to be called until the sweep has been done,
+if you do not want thta, you need to temporarily stop the embed watcher).
+
+=item ev_embed_sweep (loop, ev_embed *)
+
+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.
+
+=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
+
+
 =head1 OTHER FUNCTIONS
 
 There are some other functions of possible interest. Described. Here. Now.
@@ -726,7 +1621,7 @@ There are some other functions of possible interest. Described. Here. Now.
 This function combines a simple timer and an I/O watcher, calls your
 callback on whichever event happens first and automatically stop both
 watchers. This is useful if you want to wait for a single event on an fd
-or timeout without havign to allocate/configure/start/stop/free one or
+or timeout without having to allocate/configure/start/stop/free one or
 more watchers yourself.
 
 If C<fd> is less than 0, then no I/O watcher will be started and events
@@ -739,7 +1634,7 @@ repeat = 0) will be started. While C<0> is a valid timeout, it is of
 dubious value.
 
 The callback has the type C<void (*cb)(int revents, void *arg)> and gets
-passed an events set like normal event callbacks (with a combination of
+passed an C<revents> set like normal event callbacks (a combination of
 C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
 value passed to C<ev_once>:
 
@@ -753,23 +1648,571 @@ value passed to C<ev_once>:
 
   ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
 
-=item ev_feed_event (loop, watcher, int events)
+=item ev_feed_event (ev_loop *, watcher *, int revents)
 
 Feeds the given event set into the event loop, as if the specified event
 had happened for the specified watcher (which must be a pointer to an
 initialised but not necessarily started event watcher).
 
-=item ev_feed_fd_event (loop, int fd, int revents)
+=item ev_feed_fd_event (ev_loop *, int fd, int revents)
 
 Feed an event on the given fd, as if a file descriptor backend detected
 the given events it.
 
-=item ev_feed_signal_event (loop, int signum)
+=item ev_feed_signal_event (ev_loop *loop, int signum)
+
+Feed an event as if the given signal occured (C<loop> must be the default
+loop!).
+
+=back
+
+
+=head1 LIBEVENT EMULATION
+
+Libev offers a compatibility emulation layer for libevent. It cannot
+emulate the internals of libevent, so here are some usage hints:
+
+=over 4
+
+=item * Use it by including <event.h>, as usual.
+
+=item * The following members are fully supported: ev_base, ev_callback,
+ev_arg, ev_fd, ev_res, ev_events.
+
+=item * Avoid using ev_flags and the EVLIST_*-macros, while it is
+maintained by libev, it does not work exactly the same way as in libevent (consider
+it a private API).
+
+=item * Priorities are not currently supported. Initialising priorities
+will fail and all watchers will have the same priority, even though there
+is an ev_pri field.
+
+=item * Other members are not supported.
+
+=item * The libev emulation is I<not> ABI compatible to libevent, you need
+to use the libev header file and library.
+
+=back
+
+=head1 C++ SUPPORT
+
+Libev comes with some simplistic wrapper classes for C++ that mainly allow
+you to use some convinience methods to start/stop watchers and also change
+the callback model to a model using method callbacks on objects.
+
+To use it,
+   
+  #include <ev++.h>
+
+(it is not installed by default). This automatically includes F<ev.h>
+and puts all of its definitions (many of them macros) into the global
+namespace. All C++ specific things are put into the C<ev> namespace.
+
+It should support all the same embedding options as F<ev.h>, most notably
+C<EV_MULTIPLICITY>.
+
+Here is a list of things available in the C<ev> namespace:
+
+=over 4
+
+=item C<ev::READ>, C<ev::WRITE> etc.
+
+These are just enum values with the same values as the C<EV_READ> etc.
+macros from F<ev.h>.
+
+=item C<ev::tstamp>, C<ev::now>
+
+Aliases to the same types/functions as with the C<ev_> prefix.
+
+=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
+
+For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
+the same name in the C<ev> namespace, with the exception of C<ev_signal>
+which is called C<ev::sig> to avoid clashes with the C<signal> macro
+defines by many implementations.
+
+All of those classes have these methods:
+
+=over 4
+
+=item ev::TYPE::TYPE (object *, object::method *)
+
+=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)
+
+=item ev::TYPE::~TYPE
+
+The constructor takes a pointer to an object and a method pointer to
+the event handler callback to call in this class. The constructor calls
+C<ev_init> for you, which means you have to call the C<set> method
+before starting it. If you do not specify a loop then the constructor
+automatically associates the default loop with this watcher.
+
+The destructor automatically stops the watcher if it is active.
+
+=item w->set (struct ev_loop *)
+
+Associates a different C<struct ev_loop> with this watcher. You can only
+do this when the watcher is inactive (and not pending either).
+
+=item w->set ([args])
+
+Basically the same as C<ev_TYPE_set>, with the same args. Must be
+called at least once.  Unlike the C counterpart, an active watcher gets
+automatically stopped and restarted.
+
+=item w->start ()
+
+Starts the watcher. Note that there is no C<loop> argument as the
+constructor already takes the loop.
+
+=item w->stop ()
+
+Stops the watcher if it is active. Again, no C<loop> argument.
+
+=item w->again ()       C<ev::timer>, C<ev::periodic> only
+
+For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
+C<ev_TYPE_again> function.
+
+=item w->sweep ()       C<ev::embed> only
+
+Invokes C<ev_embed_sweep>.
+
+=item w->update ()      C<ev::stat> only
+
+Invokes C<ev_stat_stat>.
 
-Feed an event as if the given signal occured (loop must be the default loop!).
+=back
 
 =back
 
+Example: Define a class with an IO and idle watcher, start one of them in
+the constructor.
+
+  class myclass
+  {
+    ev_io   io;   void io_cb   (ev::io   &w, int revents);
+    ev_idle idle  void idle_cb (ev::idle &w, int revents);
+
+    myclass ();
+  }
+
+  myclass::myclass (int fd)
+  : io   (this, &myclass::io_cb),
+    idle (this, &myclass::idle_cb)
+  {
+    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, 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_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
+applications. Examples of applications that embed it include the Deliantra
+Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
+and rxvt-unicode.
+
+The goal is to enable you to just copy the neecssary files into your
+source directory without having to change even a single line in them, so
+you can easily upgrade by simply copying (or having a checked-out copy of
+libev somewhere in your source tree).
+
+=head2 FILESETS
+
+Depending on what features you need you need to include one or more sets of files
+in your app.
+
+=head3 CORE EVENT LOOP
+
+To include only the libev core (all the C<ev_*> functions), with manual
+configuration (no autoconf):
+
+  #define EV_STANDALONE 1
+  #include "ev.c"
+
+This will automatically include F<ev.h>, too, and should be done in a
+single C source file only to provide the function implementations. To use
+it, do the same for F<ev.h> in all files wishing to use this API (best
+done by writing a wrapper around F<ev.h> that you can include instead and
+where you can put other configuration options):
+
+  #define EV_STANDALONE 1
+  #include "ev.h"
+
+Both header files and implementation files can be compiled with a C++
+compiler (at least, thats a stated goal, and breakage will be treated
+as a bug).
+
+You need the following files in your source tree, or in a directory
+in your include path (e.g. in libev/ when using -Ilibev):
+
+  ev.h
+  ev.c
+  ev_vars.h
+  ev_wrap.h
+
+  ev_win32.c      required on win32 platforms only
+
+  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)
+  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 this single file.
+
+=head3 LIBEVENT COMPATIBILITY API
+
+To include the libevent compatibility API, also include:
+
+  #include "event.c"
+
+in the file including F<ev.c>, and:
+
+  #include "event.h"
+
+in the files that want to use the libevent API. This also includes F<ev.h>.
+
+You need the following additional files for this:
+
+  event.h
+  event.c
+
+=head3 AUTOCONF SUPPORT
+
+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> undefined. F<ev.c> will then
+include F<config.h> and configure itself accordingly.
+
+For this of course you need the m4 file:
+
+  libev.m4
+
+=head2 PREPROCESSOR SYMBOLS/MACROS
+
+Libev can be configured via a variety of preprocessor symbols you have to define
+before including any of its files. The default is not to build for multiplicity
+and only include the select backend.
+
+=over 4
+
+=item EV_STANDALONE
+
+Must always be C<1> if you do not use autoconf configuration, which
+keeps libev from including F<config.h>, and it also defines dummy
+implementations for some libevent functions (such as logging, which is not
+supported). It will also not define any of the structs usually found in
+F<event.h> that are not directly supported by the libev core alone.
+
+=item EV_USE_MONOTONIC
+
+If defined to be C<1>, libev will try to detect the availability of the
+monotonic clock option at both compiletime and runtime. Otherwise no use
+of the monotonic clock option will be attempted. If you enable this, you
+usually have to link against librt or something similar. Enabling it when
+the functionality isn't available is safe, though, althoguh you have
+to make sure you link against any libraries where the C<clock_gettime>
+function is hiding in (often F<-lrt>).
+
+=item EV_USE_REALTIME
+
+If defined to be C<1>, libev will try to detect the availability of the
+realtime clock option at compiletime (and assume its availability at
+runtime if successful). Otherwise no use of the realtime clock option will
+be attempted. This effectively replaces C<gettimeofday> by C<clock_get
+(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries
+in the description of C<EV_USE_MONOTONIC>, though.
+
+=item EV_USE_SELECT
+
+If undefined or defined to be C<1>, libev will compile in support for the
+C<select>(2) backend. No attempt at autodetection will be done: if no
+other method takes over, select will be it. Otherwise the select backend
+will not be compiled in.
+
+=item EV_SELECT_USE_FD_SET
+
+If defined to C<1>, then the select backend will use the system C<fd_set>
+structure. This is useful if libev doesn't compile due to a missing
+C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on
+exotic systems. This usually limits the range of file descriptors to some
+low limit such as 1024 or might have other limitations (winsocket only
+allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
+influence the size of the C<fd_set> used.
+
+=item EV_SELECT_IS_WINSOCKET
+
+When defined to C<1>, the select backend will assume that
+select/socket/connect etc. don't understand file descriptors but
+wants osf handles on win32 (this is the case when the select to
+be used is the winsock select). This means that it will call
+C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
+it is assumed that all these functions actually work on fds, even
+on win32. Should not be defined on non-win32 platforms.
+
+=item EV_USE_POLL
+
+If defined to be C<1>, libev will compile in support for the C<poll>(2)
+backend. Otherwise it will be enabled on non-win32 platforms. It
+takes precedence over select.
+
+=item EV_USE_EPOLL
+
+If defined to be C<1>, libev will compile in support for the Linux
+C<epoll>(7) backend. Its availability will be detected at runtime,
+otherwise another method will be used as fallback. This is the
+preferred backend for GNU/Linux systems.
+
+=item EV_USE_KQUEUE
+
+If defined to be C<1>, libev will compile in support for the BSD style
+C<kqueue>(2) backend. Its actual availability will be detected at runtime,
+otherwise another method will be used as fallback. This is the preferred
+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
+out whether kqueue supports your type of fd properly and use an embedded
+kqueue loop.
+
+=item EV_USE_PORT
+
+If defined to be C<1>, libev will compile in support for the Solaris
+10 port style backend. Its availability will be detected at runtime,
+otherwise another method will be used as fallback. This is the preferred
+backend for Solaris 10 systems.
+
+=item EV_USE_DEVPOLL
+
+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
+undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
+can be used to virtually rename the F<ev.h> header file in case of conflicts.
+
+=item EV_CONFIG_H
+
+If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
+F<ev.c>'s idea of where to find the F<config.h> file, similarly to
+C<EV_H>, above.
+
+=item EV_EVENT_H
+
+Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
+of how the F<event.h> header can be found.
+
+=item EV_PROTOTYPES
+
+If defined to be C<0>, then F<ev.h> will not define any function
+prototypes, but still define all the structs and other symbols. This is
+occasionally useful if you want to provide your own wrapper functions
+around libev functions.
+
+=item EV_MULTIPLICITY
+
+If undefined or defined to C<1>, then all event-loop-specific functions
+will have the C<struct ev_loop *> as first argument, and you can create
+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.
+
+=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 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
+
+By default, all watchers have a C<void *data> member. By redefining
+this macro to a something else you can include more and other types of
+members. You have to define it each time you include one of the files,
+though, and it must be identical each time.
+
+For example, the perl EV module uses something like this:
+
+  #define EV_COMMON                       \
+    SV *self; /* contains this struct */  \
+    SV *cb_sv, *fh /* note no trailing ";" */
+
+=item EV_CB_DECLARE (type)
+
+=item EV_CB_INVOKE (watcher, revents)
+
+=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
+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
+
+For a real-world example of a program the includes libev
+verbatim, you can have a look at the EV perl module
+(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
+the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public
+interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
+will be compiled. It is pretty complex because it provides its own header
+file.
+
+The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
+that everybody includes and which overrides some configure choices:
+
+  #define EV_MINIMAL 1
+  #define EV_USE_POLL 0
+  #define EV_MULTIPLICITY 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"
+
+And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
+
+  #include "ev_cpp.h"
+  #include "ev.c"
+
+
+=head1 COMPLEXITIES
+
+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>.
+
+=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
 
 Marc Lehmann <libev@schmorp.de>.