document c++ api

[software/libev.git] / ev.pod

diff --git a/ev.pod b/ev.pod
index db6934a2ad66cc454e6d2c6df71238374cf7ffee..5440be5d550f9dfcc75920231c1843e29d243bfb 100644 (file)
--- a/ev.pod
+++ b/ev.pod
@@ -47,7 +47,9 @@ 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
 (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
 
 
 =head1 GLOBAL FUNCTIONS
 


@@ -77,6 +79,13 @@ 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:
+
+  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_*>
 =item unsigned int ev_supported_backends ()
 
 Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>


@@ -84,6 +93,12 @@ 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.
 
 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
 =item unsigned int ev_recommended_backends ()
 
 Return the set of all backends compiled into this binary of libev and also


@@ -93,6 +108,16 @@ 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.
 
 (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
 =item ev_set_allocator (void *(*cb)(void *ptr, long size))
 
 Sets the allocation function to use (the prototype is similar to the


@@ -105,6 +130,26 @@ 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.
 
 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).
+
+   static void *
+   persistent_realloc (void *ptr, long 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
 =item ev_set_syserr_cb (void (*cb)(const char *msg));
 
 Set the callback function to call on a retryable syscall error (such


@@ -115,6 +160,18 @@ 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).
 
 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:
+
+   static void
+   fatal_error (const char *msg)
+   {
+     perror (msg);
+     abort ();
+   }
+
+   ...
+   ev_set_syserr_cb (fatal_error);
+

 =back
 
 =head1 FUNCTIONS CONTROLLING THE EVENT LOOP
 =back
 
 =head1 FUNCTIONS CONTROLLING THE EVENT LOOP


@@ -259,11 +316,21 @@ 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).
 
 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
 =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)
 
 
 =item ev_loop_destroy (loop)
 


@@ -305,10 +372,10 @@ use.
 =item ev_tstamp ev_now (loop)
 
 Returns the current "event loop time", which is the time the event loop
 =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)
 
 
 =item ev_loop (loop, int flags)
 


@@ -319,6 +386,12 @@ events.
 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.
 
 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
 case there are no events and will return after one iteration of the loop.
 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
 case there are no events and will return after one iteration of the loop.


@@ -352,6 +425,14 @@ 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
+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
 =item ev_unloop (loop, how)
 
 Can be used to make a call to C<ev_loop> return early (but only after it


@@ -374,6 +455,19 @@ 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>
+running when nothing else is active.
+
+  struct dv_signal exitsig;
+  ev_signal_init (&exitsig, sig_cb, SIGINT);
+  ev_signal_start (myloop, &exitsig);
+  evf_unref (myloop);
+
+Example: for some weird reason, unregister the above signal handler again.
+
+  ev_ref (myloop);
+  ev_signal_stop (myloop, &exitsig);
+

 =back
 
 =head1 ANATOMY OF A WATCHER
 =back
 
 =head1 ANATOMY OF A WATCHER


@@ -417,12 +511,7 @@ 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
 
 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 macro.
-
-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
 
 Each and every callback receives the event loop pointer as first, the
 registered watcher structure as second, and a bitset of received events as


@@ -489,6 +578,85 @@ programs, though, so beware.
 
 =back
 
 
 =back
 

+=head2 SUMMARY OF 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 callbakc 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
 =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
 
 Each watcher has, by default, a member C<void *data> that you can change


@@ -524,6 +692,7 @@ have been omitted....
 This section describes each watcher in detail, but will not repeat
 information given in the last section.
 
 This section describes each watcher in detail, but will not repeat
 information given in the last section.
 

+

 =head2 C<ev_io> - is this file descriptor readable or writable
 
 I/O watchers check whether a file descriptor is 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


@@ -570,6 +739,25 @@ I/O unconditionally.
 
 =back
 
 
 =back
 

+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 recurring timeouts
 
 Timer watchers are simple relative timers that generate an event after a
 =head2 C<ev_timer> - relative and optionally recurring timeouts
 
 Timer watchers are simple relative timers that generate an event after a


@@ -631,6 +819,37 @@ the timer, and again will automatically restart it if need be.
 
 =back
 
 
 =back
 

+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
 =head2 C<ev_periodic> - to cron or not to cron
 
 Periodic watchers are also timers of a kind, but they are very versatile


@@ -639,7 +858,7 @@ 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
 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
 + 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


@@ -735,6 +954,40 @@ program when the crontabs have changed).
 
 =back
 
 
 =back
 

+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
 =head2 C<ev_signal> - signal me when a signal gets signalled
 
 Signal watchers will trigger an event when the process receives a specific


@@ -760,6 +1013,7 @@ of the C<SIGxxx> constants).
 
 =back
 
 
 =back
 

+

 =head2 C<ev_child> - wait for pid status changes
 
 Child watchers trigger when your process receives a SIGCHLD in response to
 =head2 C<ev_child> - wait for pid status changes
 
 Child watchers trigger when your process receives a SIGCHLD in response to


@@ -780,6 +1034,19 @@ process causing the status change.
 
 =back
 
 
 =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_idle> - when you've got nothing better to do
 
 Idle watchers trigger events when there are no other events are pending
 =head2 C<ev_idle> - when you've got nothing better to do
 
 Idle watchers trigger events when there are no other events are pending


@@ -808,15 +1075,32 @@ 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.
+
+  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
 afterwards.
 
 =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.
 

-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.
+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.

 
 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


@@ -848,6 +1132,100 @@ macros, but using them is utterly, utterly and completely pointless.
 
 =back
 
 
 =back
 

+Example: *TODO*.
+
+
+=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.
+
+=back
+
+

 =head1 OTHER FUNCTIONS
 
 There are some other functions of possible interest. Described. Here. Now.
 =head1 OTHER FUNCTIONS
 
 There are some other functions of possible interest. Described. Here. Now.


@@ -886,23 +1264,25 @@ value passed to C<ev_once>:
 
   ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
 
 
   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).
 
 
 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.
 
 
 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 (loop must be the default loop!).
+Feed an event as if the given signal occured (C<loop> must be the default
+loop!).

 
 =back
 
 
 =back
 

+

 =head1 LIBEVENT EMULATION
 
 Libev offers a compatibility emulation layer for libevent. It cannot
 =head1 LIBEVENT EMULATION
 
 Libev offers a compatibility emulation layer for libevent. It cannot


@@ -932,7 +1312,109 @@ to use the libev header file and library.
 
 =head1 C++ SUPPORT
 
 
 =head1 C++ SUPPORT
 

-TBD.
+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>.
+
+=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 AUTHOR
 
 
 =head1 AUTHOR