*** empty log message ***

[software/libev.git] / ev.pod

diff --git a/ev.pod b/ev.pod
index cc478bd5fe6848984dfc050dca81f00a8f9ec98c..26d837bab7765a16bfc65778a93d4c0dfd7196a5 100644 (file)
--- a/ev.pod
+++ b/ev.pod
@@ -6,10 +6,56 @@ libev - a high performance full-featured event loop written in C
 
   #include <ev.h>
 
 
   #include <ev.h>
 

+=head1 EXAMPLE PROGRAM
+
+  #include <ev.h>
+
+  ev_io stdin_watcher;
+  ev_timer timeout_watcher;
+
+  /* called when data readable on stdin */
+  static void
+  stdin_cb (EV_P_ struct ev_io *w, int revents)
+  {
+    /* puts ("stdin ready"); */
+    ev_io_stop (EV_A_ w); /* just a syntax example */
+    ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
+  }
+
+  static void
+  timeout_cb (EV_P_ struct ev_timer *w, int revents)
+  {
+    /* puts ("timeout"); */
+    ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
+  }
+
+  int
+  main (void)
+  {
+    struct ev_loop *loop = ev_default_loop (0);
+
+    /* initialise an io watcher, then start it */
+    ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
+    ev_io_start (loop, &stdin_watcher);
+
+    /* simple non-repeating 5.5 second timeout */
+    ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
+    ev_timer_start (loop, &timeout_watcher);
+
+    /* loop till timeout or data ready */
+    ev_loop (loop, 0);
+
+    return 0;
+  }
+

 =head1 DESCRIPTION
 
 =head1 DESCRIPTION
 

+The newest version of this document is also available as a html-formatted
+web page you might find easier to navigate when reading it for the first
+time: L<http://cvs.schmorp.de/libev/ev.html>.
+

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

-file descriptor being readable or a timeout occuring), and it will manage
+file descriptor being readable or a timeout occurring), and it will manage

 these event sources and provide your program with events.
 
 To do this, it must take more or less complete control over your process
 these event sources and provide your program with events.
 
 To do this, it must take more or less complete control over your process


@@ -23,23 +69,29 @@ watcher.
 
 =head1 FEATURES
 
 
 =head1 FEATURES
 

-Libev supports select, poll, the linux-specific epoll and the bsd-specific
-kqueue mechanisms for file descriptor events, relative timers, absolute
-timers with customised rescheduling, signal events, process status change
-events (related to SIGCHLD), and event watchers dealing with the event
-loop mechanism itself (idle, prepare and check watchers). It also is quite
-fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing
-it to libevent for example).
+Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
+BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
+for file descriptor events (C<ev_io>), 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
 
 
 =head1 CONVENTIONS
 

-Libev is very configurable. In this manual the default configuration
-will be described, which supports multiple event loops. For more info
-about various configuration options please have a look at the file
-F<README.embed> in the libev distribution. If libev was configured without
-support for multiple event loops, then all functions taking an initial
-argument of name C<loop> (which is always of type C<struct ev_loop *>)
-will not have this argument.
+Libev is very configurable. In this manual the default configuration will
+be described, which supports multiple event loops. For more info about
+various configuration options please have a look at B<EMBED> section in
+this manual. If libev was configured without support for multiple event
+loops, then all functions taking an initial argument of name C<loop>
+(which is always of type C<struct ev_loop *>) will not have this argument.

 
 =head1 TIME REPRESENTATION
 
 
 =head1 TIME REPRESENTATION
 


@@ -48,8 +100,9 @@ Libev represents time as a single floating point number, representing the
 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 C<double> type in C, and when you need to do any calculations on
 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 C<double> type in C, and when you need to do any calculations on

-it, you should treat it as such.
-
+it, you should treat it as some floatingpoint value. Unlike the name
+component C<stamp> might indicate, it is also used for time differences
+throughout libev.

 
 =head1 GLOBAL FUNCTIONS
 
 
 =head1 GLOBAL FUNCTIONS
 


@@ -64,23 +117,32 @@ 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.
 
 C<ev_now> function is usually faster and also often returns the timestamp
 you actually want to know.
 

+=item ev_sleep (ev_tstamp interval)
+
+Sleep for the given interval: The current thread will be blocked until
+either it is interrupted or the given time interval has passed. Basically
+this is a subsecond-resolution C<sleep ()>.
+

 =item int ev_version_major ()
 
 =item int ev_version_minor ()
 
 =item int ev_version_major ()
 
 =item int ev_version_minor ()
 

-You can find out the major and minor version numbers of the library
+You can find out the major and minor ABI version numbers of the library

 you linked against by calling the functions C<ev_version_major> and
 C<ev_version_minor>. If you want, you can compare against the global
 symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
 version of the library your program was compiled against.
 
 you linked against by calling the functions C<ev_version_major> and
 C<ev_version_minor>. If you want, you can compare against the global
 symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
 version of the library your program was compiled against.
 

+These version numbers refer to the ABI version of the library, not the
+release version.
+

 Usually, it's a good idea to terminate if the major versions mismatch,
 Usually, it's a good idea to terminate if the major versions mismatch,

-as this indicates an incompatible change.  Minor versions are usually
+as this indicates an incompatible change. Minor versions are usually

 compatible to older versions, so a larger minor version alone is usually
 not a problem.
 
 compatible to older versions, so a larger minor version alone is usually
 not a problem.
 

-Example: make sure we haven't accidentally been linked against the wrong
-version:
+Example: Make sure we haven't accidentally been linked against the wrong
+version.

 
   assert (("libev version mismatch",
            ev_version_major () == EV_VERSION_MAJOR
 
   assert (("libev version mismatch",
            ev_version_major () == EV_VERSION_MAJOR


@@ -120,21 +182,22 @@ See the description of C<ev_embed> watchers for more info.
 
 =item ev_set_allocator (void *(*cb)(void *ptr, long size))
 
 
 =item ev_set_allocator (void *(*cb)(void *ptr, 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.
 
 
 You could override this function in high-availability programs to, say,
 free some memory if it cannot allocate memory, to use a special allocator,
 or even to sleep a while and retry until some memory is available.
 

-Example: replace the libev allocator with one that waits a bit and then
-retries: better than mine).
+Example: Replace the libev allocator with one that waits a bit and then
+retries).

 
    static void *
 
    static void *

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

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


@@ -160,7 +223,7 @@ matter what, when it returns. That is, libev will generally retry the
 requested operation, or, if the condition doesn't go away, do bad stuff
 (such as abort).
 
 requested operation, or, if the condition doesn't go away, do bad stuff
 (such as abort).
 

-Example: do the same thing as libev does internally:
+Example: This is basically the same thing that libev does internally, too.

 
    static void
    fatal_error (const char *msg)
 
    static void
    fatal_error (const char *msg)


@@ -220,6 +283,26 @@ 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.
 
 useful to try out specific backends to test their performance, or to work
 around bugs.
 

+=item C<EVFLAG_FORKCHECK>
+
+Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
+a fork, you can also make libev check for a fork in each iteration by
+enabling this flag.
+
+This works by calling C<getpid ()> on every iteration of the loop,
+and thus this might slow down your event loop if you do a lot of loop
+iterations and little real work, but is usually not noticeable (on my
+Linux system for example, C<getpid> is actually a simple 5-insn sequence
+without a syscall and thus I<very> fast, but my Linux system also has
+C<pthread_atfork> which is even faster).
+
+The big advantage of this flag is that you can forget about fork (and
+forget about forgetting to tell libev about forking) when you use this
+flag.
+
+This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
+environment variable.
+

 =item C<EVBACKEND_SELECT>  (value 1, portable select backend)
 
 This is your standard select(2) backend. Not I<completely> standard, as
 =item C<EVBACKEND_SELECT>  (value 1, portable select backend)
 
 This is your standard select(2) backend. Not I<completely> standard, as


@@ -238,15 +321,18 @@ 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,
 =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
+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). The epoll design has a number
+of shortcomings, such as silently dropping events in some hard-to-detect
+cases and rewiring a syscall per fd change, no fork support and bad
+support for dup:
+
+While stopping, setting 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
 (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.
+best to avoid that. Also, C<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
 
 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


@@ -255,17 +341,20 @@ need to use non-blocking I/O or other means to avoid blocking when no data
 =item C<EVBACKEND_KQUEUE>  (value 8, most BSD clones)
 
 Kqueue deserves special mention, as at the time of this writing, it
 =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"
+was broken on I<all> BSDs (usually it doesn't work with anything but
+sockets and pipes, except on Darwin, where of course it's completely
+useless. On NetBSD, it seems to work for all the FD types I tested, so it
+is used by default there). For this reason it's not being "autodetected"

 unless you explicitly specify it explicitly in the flags (i.e. using
 unless you explicitly specify it explicitly in the flags (i.e. using

-C<EVBACKEND_KQUEUE>).
+C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
+system like NetBSD.

 
 It scales in the same way as the epoll backend, but the interface to the
 
 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.
+kernel is more efficient (which says nothing about its actual speed,
+of course). While stopping, setting and starting an I/O watcher does
+never cause an extra syscall as with epoll, it still adds up to two event
+changes per incident, support for C<fork ()> is very bad and it drops fds
+silently in similarly hard-to-detetc cases.

 
 =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
 
 
 =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
 


@@ -273,10 +362,10 @@ This is not implemented yet (and might never be).
 
 =item C<EVBACKEND_PORT>    (value 32, Solaris 10)
 
 
 =item C<EVBACKEND_PORT>    (value 32, Solaris 10)
 

-This uses the Solaris 10 port mechanism. As with everything on Solaris,
+This uses the Solaris 10 event port mechanism. As with everything on Solaris,

 it's really slow, but it still scales very well (O(active_fds)).
 
 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
+Please note that solaris event ports can deliver 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.
 
 notifications, so you need to use non-blocking I/O or other means to avoid
 blocking when no data (or space) is available.
 


@@ -316,7 +405,7 @@ always distinct from the default loop. Unlike the default loop, it cannot
 handle signal and child watchers, and attempts to do so will be greeted by
 undefined behaviour (or a failed assertion if assertions are enabled).
 
 handle signal and child watchers, and attempts to do so will be greeted by
 undefined behaviour (or a failed assertion if assertions are enabled).
 

-Example: try to create a event loop that uses epoll and nothing else.
+Example: Try to create a event loop that uses epoll and nothing else.

 
   struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
   if (!epoller)
 
   struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
   if (!epoller)


@@ -329,9 +418,18 @@ 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
 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
+the easiest thing, you can just ignore the watchers and/or C<free ()> them

 for example).
 
 for example).
 

+Note that certain global state, such as signal state, will not be freed by
+this function, and related watchers (such as signal and child watchers)
+would need to be stopped manually.
+
+In general it is not advisable to call this function except in the
+rare occasion where you really need to free e.g. the signal handling
+pipe fds. If you need dynamically allocated loops it is better to use
+C<ev_loop_new> and C<ev_loop_destroy>).
+

 =item ev_loop_destroy (loop)
 
 Like C<ev_default_destroy>, but destroys an event loop created by an
 =item ev_loop_destroy (loop)
 
 Like C<ev_default_destroy>, but destroys an event loop created by an


@@ -364,6 +462,16 @@ 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.
 
 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_loop_count (loop)
+
+Returns the count of loop iterations for the loop, which is identical to
+the number of times libev did poll for new events. It starts at C<0> and
+happily wraps around with enough iterations.
+
+This value can sometimes be useful as a generation counter of sorts (it
+"ticks" the number of loop iterations), as it roughly corresponds with
+C<ev_prepare> and C<ev_check> calls.
+

 =item unsigned int ev_backend (loop)
 
 Returns one of the C<EVBACKEND_*> flags indicating the event backend in
 =item unsigned int ev_backend (loop)
 
 Returns one of the C<EVBACKEND_*> flags indicating the event backend in


@@ -375,7 +483,7 @@ Returns the current "event loop time", which is the time the event loop
 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
 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).
+event occurring (or more correctly, libev finding out about it).

 
 =item ev_loop (loop, int flags)
 
 
 =item ev_loop (loop, int flags)
 


@@ -406,8 +514,9 @@ usually a better approach for this kind of thing.
 
 Here are the gory details of what C<ev_loop> does:
 
 
 Here are the gory details of what C<ev_loop> does:
 

+   - Before the first iteration, call any pending watchers.

    * If there are no active watchers (reference count is zero), return.
    * If there are no active watchers (reference count is zero), return.

-   - Queue prepare watchers and then call all outstanding watchers.
+   - Queue all 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".
    - If we have been forked, recreate the kernel state.
    - Update the kernel state with all outstanding changes.
    - Update the "event loop time".


@@ -425,7 +534,7 @@ Here are the gory details of what C<ev_loop> does:
    - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
      were used, return, otherwise continue with step *.
 
    - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
      were used, return, otherwise continue with step *.
 

-Example: queue some jobs and then loop until no events are outsanding
+Example: Queue some jobs and then loop until no events are outsanding

 anymore.
 
    ... queue jobs here, make sure they register event watchers as long
 anymore.
 
    ... queue jobs here, make sure they register event watchers as long


@@ -455,18 +564,52 @@ no event watchers registered by it are active. It is also an excellent
 way to do this for generic recurring timers or from within third-party
 libraries. Just remember to I<unref after start> and I<ref before stop>.
 
 way to do this for generic recurring timers or from within third-party
 libraries. Just remember to I<unref after start> and I<ref before stop>.
 

-Example: create a signal watcher, but keep it from keeping C<ev_loop>
+Example: Create a signal watcher, but keep it from keeping C<ev_loop>

 running when nothing else is active.
 
 running when nothing else is active.
 

-  struct dv_signal exitsig;
+  struct ev_signal exitsig;

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

-  ev_signal_start (myloop, &exitsig);
-  evf_unref (myloop);
+  ev_signal_start (loop, &exitsig);
+  evf_unref (loop);
+
+Example: For some weird reason, unregister the above signal handler again.
+
+  ev_ref (loop);
+  ev_signal_stop (loop, &exitsig);
+
+=item ev_set_io_collect_interval (loop, ev_tstamp interval)
+
+=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
+
+These advanced functions influence the time that libev will spend waiting
+for events. Both are by default C<0>, meaning that libev will try to
+invoke timer/periodic callbacks and I/O callbacks with minimum latency.
+
+Setting these to a higher value (the C<interval> I<must> be >= C<0>)
+allows libev to delay invocation of I/O and timer/periodic callbacks to
+increase efficiency of loop iterations.

 
 

-Example: for some weird reason, unregister the above signal handler again.
+The background is that sometimes your program runs just fast enough to
+handle one (or very few) event(s) per loop iteration. While this makes
+the program responsive, it also wastes a lot of CPU time to poll for new
+events, especially with backends like C<select ()> which have a high
+overhead for the actual polling but can deliver many events at once.

 
 

-  ev_ref (myloop);
-  ev_signal_stop (myloop, &exitsig);
+By setting a higher I<io collect interval> you allow libev to spend more
+time collecting I/O events, so you can handle more events per iteration,
+at the cost of increasing latency. Timeouts (both C<ev_periodic> and
+C<ev_timer>) will be not affected.
+
+Likewise, by setting a higher I<timeout collect interval> you allow libev
+to spend more time collecting timeouts, at the expense of increased
+latency (the watcher callback will be called later). C<ev_io> watchers
+will not be affected.
+
+Many (busy) programs can usually benefit by setting the io collect
+interval to a value near C<0.1> or so, which is often enough for
+interactive servers (of course not for games), likewise for timeouts. It
+usually doesn't make much sense to set it to a lower value than C<0.01>,
+as this approsaches the timing granularity of most systems.

 
 =back
 
 
 =back
 


@@ -567,6 +710,15 @@ many watchers as they want, and all of them will be taken into account
 (for example, a C<ev_prepare> watcher might start an idle watcher to keep
 C<ev_loop> from blocking).
 
 (for example, a C<ev_prepare> watcher might start an idle watcher to keep
 C<ev_loop> from blocking).
 

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

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


@@ -647,10 +799,11 @@ it.
 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
 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).
+C<ev_TYPE_set> is safe), you must not change its priority, and you must
+make sure the watcher is available to libev (e.g. you cannot C<free ()>
+it).

 
 

-=item callback = ev_cb (ev_TYPE *watcher)
+=item callback ev_cb (ev_TYPE *watcher)

 
 Returns the callback currently set on the watcher.
 
 
 Returns the callback currently set on the watcher.
 


@@ -659,6 +812,46 @@ Returns the callback currently set on the watcher.
 Change the callback. You can change the callback at virtually any time
 (modulo threads).
 
 Change the callback. You can change the callback at virtually any time
 (modulo threads).
 

+=item ev_set_priority (ev_TYPE *watcher, priority)
+
+=item int ev_priority (ev_TYPE *watcher)
+
+Set and query the priority of the watcher. The priority is a small
+integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
+(default: C<-2>). Pending watchers with higher priority will be invoked
+before watchers with lower priority, but priority will not keep watchers
+from being executed (except for C<ev_idle> watchers).
+
+This means that priorities are I<only> used for ordering callback
+invocation after new events have been received. This is useful, for
+example, to reduce latency after idling, or more often, to bind two
+watchers on the same event and make sure one is called first.
+
+If you need to suppress invocation when higher priority events are pending
+you need to look at C<ev_idle> watchers, which provide this functionality.
+
+You I<must not> change the priority of a watcher as long as it is active or
+pending.
+
+The default priority used by watchers when no priority has been set is
+always C<0>, which is supposed to not be too high and not be too low :).
+
+Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
+fine, as long as you do not mind that the priority value you query might
+or might not have been adjusted to be within valid range.
+
+=item ev_invoke (loop, ev_TYPE *watcher, int revents)
+
+Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
+C<loop> nor C<revents> need to be valid as long as the watcher callback
+can deal with that fact.
+
+=item int ev_clear_pending (loop, ev_TYPE *watcher)
+
+If the watcher is pending, this function returns clears its pending status
+and returns its C<revents> bitset (as if its callback was invoked). If the
+watcher isn't pending it does nothing and returns C<0>.
+

 =back
 
 
 =back
 
 


@@ -688,8 +881,37 @@ can cast it back to your own type:
     ...
   }
 
     ...
   }
 

-More interesting and less C-conformant ways of catsing your callback type
-have been omitted....
+More interesting and less C-conformant ways of casting your callback type
+instead have been omitted.
+
+Another common scenario is having some data structure with multiple
+watchers:
+
+  struct my_biggy
+  {
+    int some_data;
+    ev_timer t1;
+    ev_timer t2;
+  }
+
+In this case getting the pointer to C<my_biggy> is a bit more complicated,
+you need to use C<offsetof>:
+
+  #include <stddef.h>
+
+  static void
+  t1_cb (EV_P_ struct ev_timer *w, int revents)
+  {
+    struct my_biggy big = (struct my_biggy *
+      (((char *)w) - offsetof (struct my_biggy, t1));
+  }
+
+  static void
+  t2_cb (EV_P_ struct ev_timer *w, int revents)
+  {
+    struct my_biggy big = (struct my_biggy *
+      (((char *)w) - offsetof (struct my_biggy, t2));
+  }

 
 
 =head1 WATCHER TYPES
 
 
 =head1 WATCHER TYPES


@@ -744,10 +966,56 @@ 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
 
 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
+whether 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).
 
 such as poll (fortunately in our Xlib example, Xlib already does this on
 its own, so its quite safe to use).
 

+=head3 The special problem of disappearing file descriptors
+
+Some backends (e.g. kqueue, epoll) need to be told about closing a file
+descriptor (either by calling C<close> explicitly or by any other means,
+such as C<dup>). The reason is that you register interest in some file
+descriptor, but when it goes away, the operating system will silently drop
+this interest. If another file descriptor with the same number then is
+registered with libev, there is no efficient way to see that this is, in
+fact, a different file descriptor.
+
+To avoid having to explicitly tell libev about such cases, libev follows
+the following policy:  Each time C<ev_io_set> is being called, libev
+will assume that this is potentially a new file descriptor, otherwise
+it is assumed that the file descriptor stays the same. That means that
+you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
+descriptor even if the file descriptor number itself did not change.
+
+This is how one would do it normally anyway, the important point is that
+the libev application should not optimise around libev but should leave
+optimisations to libev.
+
+=head3 The special problem of dup'ed file descriptors
+
+Some backends (e.g. epoll), cannot register events for file descriptors,
+but only events for the underlying file descriptions. That menas when you
+have C<dup ()>'ed file descriptors and register events for them, only one
+file descriptor might actually receive events.
+
+There is no workaorund possible except not registering events
+for potentially C<dup ()>'ed file descriptors or to resort to
+C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
+
+=head3 The special problem of fork
+
+Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
+useless behaviour. Libev fully supports fork, but needs to be told about
+it in the child.
+
+To support fork in your programs, you either have to call
+C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
+enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
+C<EVBACKEND_POLL>.
+
+
+=head3 Watcher-Specific Functions
+

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


@@ -768,9 +1036,9 @@ The events being watched.
 
 =back
 
 
 =back
 

-Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well
+Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well

 readable, but only once. Since it is likely line-buffered, you could
 readable, but only once. Since it is likely line-buffered, you could

-attempt to read a whole line in the callback:
+attempt to read a whole line in the callback.

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


@@ -810,6 +1078,8 @@ 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.
 
 but if multiple timers become ready during the same loop iteration then
 order of execution is undefined.
 

+=head3 Watcher-Specific Functions and Data Members
+

 =over 4
 
 =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
 =over 4
 
 =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)


@@ -832,23 +1102,25 @@ 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:
 
 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
 
 This sounds a bit complicated, but here is a useful and typical

-example: Imagine you have a tcp connection and you want a so-called
-idle timeout, that is, you want to be called when there have been,
-say, 60 seconds of inactivity on the socket. The easiest way to do
-this is to configure an C<ev_timer> with C<after>=C<repeat>=C<60> and calling
+example: Imagine you have a tcp connection and you want a so-called idle
+timeout, that is, you want to be called when there have been, say, 60
+seconds of inactivity on the socket. The easiest way to do this is to
+configure an C<ev_timer> with a C<repeat> value of C<60> and then call

 C<ev_timer_again> each time you successfully read or write some data. If
 you go into an idle state where you do not expect data to travel on the
 C<ev_timer_again> each time you successfully read or write some data. If
 you go into an idle state where you do not expect data to travel on the

-socket, you can stop the timer, and again will automatically restart it if
-need be.
+socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
+automatically restart it if need be.

 
 

-You can also ignore the C<after> value and C<ev_timer_start> altogether
-and only ever use the C<repeat> value:
+That means you can ignore the C<after> value and C<ev_timer_start>
+altogether and only ever use the C<repeat> value and C<ev_timer_again>:

 
    ev_timer_init (timer, callback, 0., 5.);
    ev_timer_again (loop, timer);
 
    ev_timer_init (timer, callback, 0., 5.);
    ev_timer_again (loop, timer);


@@ -859,8 +1131,8 @@ and only ever use the C<repeat> value:
    timer->again = 10.;
    ev_timer_again (loop, timer);
 
    timer->again = 10.;
    ev_timer_again (loop, timer);
 

-This is more efficient then stopping/starting the timer eahc time you want
-to modify its timeout value.
+This is more slightly efficient then stopping/starting the timer each time
+you want to modify its timeout value.

 
 =item ev_tstamp repeat [read-write]
 
 
 =item ev_tstamp repeat [read-write]
 


@@ -870,7 +1142,7 @@ which is also when any modifications are taken into account.
 
 =back
 
 
 =back
 

-Example: create a timer that fires after 60 seconds.
+Example: Create a timer that fires after 60 seconds.

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


@@ -882,7 +1154,7 @@ Example: create a timer that fires after 60 seconds.
   ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
   ev_timer_start (loop, &mytimer);
 
   ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
   ev_timer_start (loop, &mytimer);
 

-Example: create a timeout timer that times out after 10 seconds of
+Example: Create a timeout timer that times out after 10 seconds of

 inactivity.
 
   static void
 inactivity.
 
   static void


@@ -912,16 +1184,18 @@ 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 ()
 + 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
 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
-again).
+roughly 10 seconds later).

 
 They can also be used to implement vastly more complex timers, such as
 
 They can also be used to implement vastly more complex timers, such as

-triggering an event on eahc midnight, local time.
+triggering an event on each midnight, local time or other, complicated,
+rules.

 
 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.
 
 
 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.
 

+=head3 Watcher-Specific Functions and Data Members
+

 =over 4
 
 =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
 =over 4
 
 =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)


@@ -933,18 +1207,18 @@ operation, and we will explain them from simplest to complex:
 
 =over 4
 
 
 =over 4
 

-=item * absolute timer (interval = reschedule_cb = 0)
+=item * absolute timer (at = time, interval = reschedule_cb = 0)

 
 In this configuration the watcher triggers an event at the wallclock time
 C<at> and doesn't repeat. It will not adjust when a time jump occurs,
 that is, if it is to be run at January 1st 2011 then it will run when the
 system time reaches or surpasses this time.
 
 
 In this configuration the watcher triggers an event at the wallclock time
 C<at> and doesn't repeat. It will not adjust when a time jump occurs,
 that is, if it is to be run at January 1st 2011 then it will run when the
 system time reaches or surpasses this time.
 

-=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)
+=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)

 
 In this mode the watcher will always be scheduled to time out at the next
 
 In this mode the watcher will always be scheduled to time out at the next

-C<at + N * interval> time (for some integer N) and then repeat, regardless
-of any time jumps.
+C<at + N * interval> time (for some integer N, which can also be negative)
+and then repeat, regardless of any time jumps.

 
 This can be used to create timers that do not drift with respect to system
 time:
 
 This can be used to create timers that do not drift with respect to system
 time:


@@ -960,7 +1234,11 @@ Another way to think about it (for the mathematically inclined) is that
 C<ev_periodic> will try to run the callback in this mode at the next possible
 time where C<time = at (mod interval)>, regardless of any time jumps.
 
 C<ev_periodic> will try to run the callback in this mode at the next possible
 time where C<time = at (mod interval)>, regardless of any time jumps.
 

-=item * manual reschedule mode (reschedule_cb = callback)
+For numerical stability it is preferable that the C<at> value is near
+C<ev_now ()> (the current time), but there is no range requirement for
+this value.
+
+=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)

 
 In this mode the values for C<interval> and C<at> are both being
 ignored. Instead, each time the periodic watcher gets scheduled, the
 
 In this mode the values for C<interval> and C<at> are both being
 ignored. Instead, each time the periodic watcher gets scheduled, the


@@ -970,7 +1248,7 @@ current time as second argument.
 NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
 ever, or make any event loop modifications>. If you need to stop it,
 return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
 NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
 ever, or make any event loop modifications>. If you need to stop it,
 return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by

-starting a prepare watcher).
+starting an C<ev_prepare> watcher, which is legal).

 
 Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
 ev_tstamp now)>, e.g.:
 
 Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
 ev_tstamp now)>, e.g.:


@@ -1003,6 +1281,14 @@ when you changed some parameters or the reschedule callback would return
 a different time than the last time it was called (e.g. in a crond like
 program when the crontabs have changed).
 
 a different time than the last time it was called (e.g. in a crond like
 program when the crontabs have changed).
 

+=item ev_tstamp offset [read-write]
+
+When repeating, this contains the offset value, otherwise this is the
+absolute point in time (the C<at> value passed to C<ev_periodic_set>).
+
+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 interval [read-write]
 
 The current interval value. Can be modified any time, but changes only
 =item ev_tstamp interval [read-write]
 
 The current interval value. Can be modified any time, but changes only


@@ -1015,9 +1301,14 @@ 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.
 
 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.
 

+=item ev_tstamp at [read-only]
+
+When active, contains the absolute time that the watcher is supposed to
+trigger next.
+

 =back
 
 =back
 

-Example: call a callback every hour, or, more precisely, whenever the
+Example: Call a callback every hour, or, more precisely, whenever the

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


@@ -1031,7 +1322,7 @@ potentially a lot of jittering, but good long-term stability.
   ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
   ev_periodic_start (loop, &hourly_tick);
 
   ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
   ev_periodic_start (loop, &hourly_tick);
 

-Example: the same as above, but use a reschedule callback to do it:
+Example: The same as above, but use a reschedule callback to do it:

 
   #include <math.h>
 
 
   #include <math.h>
 


@@ -1043,7 +1334,7 @@ Example: the same as above, but use a reschedule callback to do it:
 
   ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
 
 
   ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
 

-Example: call a callback every hour, starting now:
+Example: Call a callback every hour, starting now:

 
   struct ev_periodic hourly_tick;
   ev_periodic_init (&hourly_tick, clock_cb,
 
   struct ev_periodic hourly_tick;
   ev_periodic_init (&hourly_tick, clock_cb,


@@ -1065,6 +1356,8 @@ as you don't register any with libev). Similarly, when the last signal
 watcher for a signal is stopped libev will reset the signal handler to
 SIG_DFL (regardless of what it was set to before).
 
 watcher for a signal is stopped libev will reset the signal handler to
 SIG_DFL (regardless of what it was set to before).
 

+=head3 Watcher-Specific Functions and Data Members
+

 =over 4
 
 =item ev_signal_init (ev_signal *, callback, int signum)
 =over 4
 
 =item ev_signal_init (ev_signal *, callback, int signum)


@@ -1086,6 +1379,8 @@ The signal the watcher watches out for.
 Child watchers trigger when your process receives a SIGCHLD in response to
 some child status changes (most typically when a child of yours dies).
 
 Child watchers trigger when your process receives a SIGCHLD in response to
 some child status changes (most typically when a child of yours dies).
 

+=head3 Watcher-Specific Functions and Data Members
+

 =over 4
 
 =item ev_child_init (ev_child *, callback, int pid)
 =over 4
 
 =item ev_child_init (ev_child *, callback, int pid)


@@ -1114,7 +1409,7 @@ C<waitpid> and C<sys/wait.h> documentation for details).
 
 =back
 
 
 =back
 

-Example: try to exit cleanly on SIGINT and SIGTERM.
+Example: Try to exit cleanly on SIGINT and SIGTERM.

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


@@ -1139,8 +1434,11 @@ 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.
 
 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
 Since there is no standard to do this, the portable implementation simply

-calls C<stat (2)> regulalry on the path to see if it changed somehow. You
+calls C<stat (2)> regularly on the path to see if it changed somehow. You

 can specify a recommended polling interval for this case. If you specify
 a polling interval of C<0> (highly recommended!) then a I<suitable,
 unspecified default> value will be used (which you can expect to be around
 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


@@ -1152,8 +1450,15 @@ This watcher type is not meant for massive numbers of stat watchers,
 as even with OS-supported change notifications, this can be
 resource-intensive.
 
 as even with OS-supported change notifications, this can be
 resource-intensive.
 

-At the time of this writing, no specific OS backends are implemented, but
-if demand increases, at least a kqueue and inotify backend will be added.
+At the time of this writing, only the Linux inotify interface is
+implemented (implementing kqueue support is left as an exercise for the
+reader). Inotify will be used to give hints only and should not change the
+semantics of C<ev_stat> watchers, which means that libev sometimes needs
+to fall back to regular polling again even with inotify, but changes are
+usually detected immediately, and if the file exists there will be no
+polling.
+
+=head3 Watcher-Specific Functions and Data Members

 
 =over 4
 
 
 =over 4
 


@@ -1227,13 +1532,16 @@ Example: Watch C</etc/passwd> for attribute changes.
 
 =head2 C<ev_idle> - when you've got nothing better to do...
 
 
 =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
-as your process is busy handling sockets or timeouts (or even signals,
-imagine) it will not be triggered. But when your process is idle all idle
-watchers are being called again and again, once per event loop iteration -
-until stopped, that is, or your process receives more events and becomes
-busy.
+Idle watchers trigger events when no other events of the same or higher
+priority are pending (prepare, check and other idle watchers do not
+count).
+
+That is, as long as your process is busy handling sockets or timeouts
+(or even signals, imagine) of the same or higher priority it will not be
+triggered. But when your process is idle (or only lower-priority watchers
+are pending), the idle watchers are being called once per event loop
+iteration - until stopped, that is, or your process receives more events
+and becomes busy again with higher priority stuff.

 
 The most noteworthy effect is that as long as any idle watchers are
 active, the process will not block when waiting for new events.
 
 The most noteworthy effect is that as long as any idle watchers are
 active, the process will not block when waiting for new events.


@@ -1243,6 +1551,8 @@ effect on its own sometimes), idle watchers are a good place to do
 "pseudo-background processing", or delay processing stuff to after the
 event loop has handled all outstanding events.
 
 "pseudo-background processing", or delay processing stuff to after the
 event loop has handled all outstanding events.
 

+=head3 Watcher-Specific Functions and Data Members
+

 =over 4
 
 =item ev_idle_init (ev_signal *, callback)
 =over 4
 
 =item ev_idle_init (ev_signal *, callback)


@@ -1253,8 +1563,8 @@ believe me.
 
 =back
 
 
 =back
 

-Example: dynamically allocate an C<ev_idle>, start it, and in the
-callback, free it. Alos, use no error checking, as usual.
+Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
+callback, free it. Also, use no error checking, as usual.

 
   static void
   idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
 
   static void
   idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)


@@ -1309,6 +1619,18 @@ 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).
 
 loop from blocking if lower-priority coroutines are active, thus mapping
 low-priority coroutines to idle/background tasks).
 

+It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
+priority, to ensure that they are being run before any other watchers
+after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
+too) should not activate ("feed") events into libev. While libev fully
+supports this, they will be called before other C<ev_check> watchers did
+their job. As C<ev_check> watchers are often used to embed other event
+loops those other event loops might be in an unusable state until their
+C<ev_check> watcher ran (always remind yourself to coexist peacefully with
+others).
+
+=head3 Watcher-Specific Functions and Data Members
+

 =over 4
 
 =item ev_prepare_init (ev_prepare *, callback)
 =over 4
 
 =item ev_prepare_init (ev_prepare *, callback)


@@ -1321,10 +1643,18 @@ macros, but using them is utterly, utterly and completely pointless.
 
 =back
 
 
 =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:
+There are a number of principal ways to embed other event loops or modules
+into libev. Here are some ideas on how to include libadns into libev
+(there is a Perl module named C<EV::ADNS> that does this, which you could
+use for an actually working example. Another Perl module named C<EV::Glib>
+embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
+into the Glib event loop).
+
+Method 1: Add IO watchers and a timeout watcher in a prepare handler,
+and in a check watcher, destroy them and call into libadns. What follows
+is pseudo-code only of course. This requires you to either use a low
+priority for the check watcher or use C<ev_clear_pending> explicitly, as
+the callbacks for the IO/timeout watchers might not have been called yet.

 
   static ev_io iow [nfd];
   static ev_timer tw;
 
   static ev_io iow [nfd];
   static ev_timer tw;


@@ -1332,18 +1662,14 @@ pseudo-code only of course:
   static void
   io_cb (ev_loop *loop, ev_io *w, int revents)
   {
   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)
   {
   }
 
   // create io watchers for each fd and a timer before blocking
   static void
   adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
   {

-    int timeout = 3600000;truct pollfd fds [nfd];
+    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 ()));
 
     // actual code will need to loop here and realloc etc.
     adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
 


@@ -1351,7 +1677,7 @@ pseudo-code only of course:
     ev_timer_init (&tw, 0, timeout * 1e-3);
     ev_timer_start (loop, &tw);
 
     ev_timer_init (&tw, 0, timeout * 1e-3);
     ev_timer_start (loop, &tw);
 

-    // create on ev_io per pollfd
+    // create one ev_io per pollfd

     for (int i = 0; i < nfd; ++i)
       {
         ev_io_init (iow + i, io_cb, fds [i].fd,
     for (int i = 0; i < nfd; ++i)
       {
         ev_io_init (iow + i, io_cb, fds [i].fd,


@@ -1359,7 +1685,6 @@ pseudo-code only of course:
            | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
 
         fds [i].revents = 0;
            | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
 
         fds [i].revents = 0;

-        iow [i].data = fds + i;

         ev_io_start (loop, iow + i);
       }
   }
         ev_io_start (loop, iow + i);
       }
   }


@@ -1371,18 +1696,87 @@ pseudo-code only of course:
     ev_timer_stop (loop, &tw);
 
     for (int i = 0; i < nfd; ++i)
     ev_timer_stop (loop, &tw);
 
     for (int i = 0; i < nfd; ++i)

-      ev_io_stop (loop, iow + i);
+      {
+        // set the relevant poll flags
+        // could also call adns_processreadable etc. here
+        struct pollfd *fd = fds + i;
+        int revents = ev_clear_pending (iow + i);
+        if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
+        if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
+
+        // now stop the watcher
+        ev_io_stop (loop, iow + i);
+      }

 
     adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
   }
 
 
     adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
   }
 

+Method 2: This would be just like method 1, but you run C<adns_afterpoll>
+in the prepare watcher and would dispose of the check watcher.
+
+Method 3: If the module to be embedded supports explicit event
+notification (adns does), you can also make use of the actual watcher
+callbacks, and only destroy/create the watchers in the prepare watcher.
+
+  static void
+  timer_cb (EV_P_ ev_timer *w, int revents)
+  {
+    adns_state ads = (adns_state)w->data;
+    update_now (EV_A);
+
+    adns_processtimeouts (ads, &tv_now);
+  }
+
+  static void
+  io_cb (EV_P_ ev_io *w, int revents)
+  {
+    adns_state ads = (adns_state)w->data;
+    update_now (EV_A);
+
+    if (revents & EV_READ ) adns_processreadable  (ads, w->fd, &tv_now);
+    if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
+  }
+
+  // do not ever call adns_afterpoll
+
+Method 4: Do not use a prepare or check watcher because the module you
+want to embed is too inflexible to support it. Instead, youc na override
+their poll function.  The drawback with this solution is that the main
+loop is now no longer controllable by EV. The C<Glib::EV> module does
+this.
+
+  static gint
+  event_poll_func (GPollFD *fds, guint nfds, gint timeout)
+  {
+    int got_events = 0;
+
+    for (n = 0; n < nfds; ++n)
+      // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
+
+    if (timeout >= 0)
+      // create/start timer
+
+    // poll
+    ev_loop (EV_A_ 0);
+
+    // stop timer again
+    if (timeout >= 0)
+      ev_timer_stop (EV_A_ &to);
+
+    // stop io watchers again - their callbacks should have set
+    for (n = 0; n < nfds; ++n)
+      ev_io_stop (EV_A_ iow [n]);
+
+    return got_events;
+  }
+

 
 =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
 
 =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).
+fashion and must not be used). (See portability notes, below).

 
 There are primarily two reasons you would want that: work around bugs and
 prioritise I/O.
 
 There are primarily two reasons you would want that: work around bugs and
 prioritise I/O.


@@ -1447,6 +1841,24 @@ create it, and if that fails, use the normal loop for everything:
   else
     loop_lo = loop_hi;
 
   else
     loop_lo = loop_hi;
 

+=head2 Portability notes
+
+Kqueue is nominally embeddable, but this is broken on all BSDs that I
+tried, in various ways. Usually the embedded event loop will simply never
+receive events, sometimes it will only trigger a few times, sometimes in a
+loop. Epoll is also nominally embeddable, but many Linux kernel versions
+will always eport the epoll fd as ready, even when no events are pending.
+
+While libev allows embedding these backends (they are contained in
+C<ev_embeddable_backends ()>), take extreme care that it will actually
+work.
+
+When in doubt, create a dynamic event loop forced to use sockets (this
+usually works) and possibly another thread and a pipe or so to report to
+your main event loop.
+
+=head3 Watcher-Specific Functions and Data Members
+

 =over 4
 
 =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
 =over 4
 
 =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)


@@ -1465,13 +1877,36 @@ Make a single, non-blocking sweep over the embedded loop. This works
 similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
 apropriate way for embedded loops.
 
 similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
 apropriate way for embedded loops.
 

-=item struct ev_loop *loop [read-only]
+=item struct ev_loop *other [read-only]

 
 The embedded event loop.
 
 =back
 
 
 
 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.
+
+=head3 Watcher-Specific Functions and Data Members
+
+=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.
 =head1 OTHER FUNCTIONS
 
 There are some other functions of possible interest. Described. Here. Now.


@@ -1566,12 +2001,21 @@ To use it,
    
   #include <ev++.h>
 
    
   #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.
+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>.
+
+Care has been taken to keep the overhead low. The only data member the C++
+classes add (compared to plain C-style watchers) is the event loop pointer
+that the watcher is associated with (or no additional members at all if
+you disable C<EV_MULTIPLICITY> when embedding libev).

 
 

-It should support all the same embedding options as F<ev.h>, most notably
-C<EV_MULTIPLICITY>.
+Currently, functions, and static and non-static member functions can be
+used as callbacks. Other types should be easy to add as long as they only
+need one additional pointer for context. If you need support for other
+types of functors please contact the author (preferably after implementing
+it).

 
 Here is a list of things available in the C<ev> namespace:
 
 
 Here is a list of things available in the C<ev> namespace:
 


@@ -1597,20 +2041,65 @@ All of those classes have these methods:
 
 =over 4
 
 
 =over 4
 

-=item ev::TYPE::TYPE (object *, object::method *)
+=item ev::TYPE::TYPE ()

 
 

-=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)
+=item ev::TYPE::TYPE (struct ev_loop *)

 
 =item ev::TYPE::~TYPE
 
 
 =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 constructor (optionally) takes an event loop to associate the watcher
+with. If it is omitted, it will use C<EV_DEFAULT>.
+
+The constructor calls C<ev_init> for you, which means you have to call the
+C<set> method before starting it.
+
+It will not set a callback, however: You have to call the templated C<set>
+method to set a callback before you can start the watcher.
+
+(The reason why you have to use a method is a limitation in C++ which does
+not allow explicit template arguments for constructors).

 
 The destructor automatically stops the watcher if it is active.
 
 
 The destructor automatically stops the watcher if it is active.
 

+=item w->set<class, &class::method> (object *)
+
+This method sets the callback method to call. The method has to have a
+signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
+first argument and the C<revents> as second. The object must be given as
+parameter and is stored in the C<data> member of the watcher.
+
+This method synthesizes efficient thunking code to call your method from
+the C callback that libev requires. If your compiler can inline your
+callback (i.e. it is visible to it at the place of the C<set> call and
+your compiler is good :), then the method will be fully inlined into the
+thunking function, making it as fast as a direct C callback.
+
+Example: simple class declaration and watcher initialisation
+
+  struct myclass
+  {
+    void io_cb (ev::io &w, int revents) { }
+  }
+
+  myclass obj;
+  ev::io iow;
+  iow.set <myclass, &myclass::io_cb> (&obj);
+
+=item w->set<function> (void *data = 0)
+
+Also sets a callback, but uses a static method or plain function as
+callback. The optional C<data> argument will be stored in the watcher's
+C<data> member and is free for you to use.
+
+The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
+
+See the method-C<set> above for more details.
+
+Example:
+
+  static void io_cb (ev::io &w, int revents) { }
+  iow.set <io_cb> ();
+

 =item w->set (struct ev_loop *)
 
 Associates a different C<struct ev_loop> with this watcher. You can only
 =item w->set (struct ev_loop *)
 
 Associates a different C<struct ev_loop> with this watcher. You can only


@@ -1619,27 +2108,32 @@ 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
 =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.
+called at least once. Unlike the C counterpart, an active watcher gets
+automatically stopped and restarted when reconfiguring it with this
+method.

 
 =item w->start ()
 
 
 =item w->start ()
 

-Starts the watcher. Note that there is no C<loop> argument as the
-constructor already takes the loop.
+Starts the watcher. Note that there is no C<loop> argument, as the
+constructor already stores the event loop.

 
 =item w->stop ()
 
 Stops the watcher if it is active. Again, no C<loop> argument.
 
 
 =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
+=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.
 
 
 For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
 C<ev_TYPE_again> function.
 

-=item w->sweep ()       C<ev::embed> only
+=item w->sweep () (C<ev::embed> only)

 
 Invokes C<ev_embed_sweep>.
 
 
 Invokes C<ev_embed_sweep>.
 

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

 =back
 
 =back
 =back
 
 =back


@@ -1656,12 +2150,75 @@ the constructor.
   }
 
   myclass::myclass (int fd)
   }
 
   myclass::myclass (int fd)

-  : io   (this, &myclass::io_cb),
-    idle (this, &myclass::idle_cb)

   {
   {

+    io  .set <myclass, &myclass::io_cb  > (this);
+    idle.set <myclass, &myclass::idle_cb> (this);
+

     io.start (fd, ev::READ);
   }
 
     io.start (fd, ev::READ);
   }
 

+
+=head1 MACRO MAGIC
+
+Libev can be compiled with a variety of options, the most fundamantal
+of which is C<EV_MULTIPLICITY>. This option determines whether (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 whether multiple loops are supported
+or not.
+
+  static void
+  check_cb (EV_P_ ev_timer *w, int revents)
+  {
+    ev_check_stop (EV_A_ w);
+  }
+
+  ev_check check;
+  ev_check_init (&check, check_cb);
+  ev_check_start (EV_DEFAULT_ &check);
+  ev_loop (EV_DEFAULT_ 0);
+

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


@@ -1669,7 +2226,7 @@ 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.
 
 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
+The goal is to enable you to just copy the necessary 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).
 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).


@@ -1710,7 +2267,7 @@ in your include path (e.g. in libev/ when using -Ilibev):
 
   ev_win32.c      required on win32 platforms only
 
 
   ev_win32.c      required on win32 platforms only
 

-  ev_select.c     only when select backend is enabled (which is by default)
+  ev_select.c     only when select backend is enabled (which is enabled by default)

   ev_poll.c       only when poll backend is enabled (disabled by default)
   ev_epoll.c      only when the epoll backend is enabled (disabled by default)
   ev_kqueue.c     only when the kqueue backend is enabled (disabled by default)
   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)


@@ -1769,7 +2326,7 @@ 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
 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
+the functionality isn't available is safe, though, although you have

 to make sure you link against any libraries where the C<clock_gettime>
 function is hiding in (often F<-lrt>).
 
 to make sure you link against any libraries where the C<clock_gettime>
 function is hiding in (often F<-lrt>).
 


@@ -1779,8 +2336,13 @@ 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
 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.
+(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
+note about libraries in the description of C<EV_USE_MONOTONIC>, though.
+
+=item EV_USE_NANOSLEEP
+
+If defined to be C<1>, libev will assume that C<nanosleep ()> is available
+and will use it for delays. Otherwise it will use C<select ()>.

 
 =item EV_USE_SELECT
 
 
 =item EV_USE_SELECT
 


@@ -1845,6 +2407,12 @@ backend for Solaris 10 systems.
 
 reserved for future expansion, works like the USE symbols above.
 
 
 reserved for future expansion, works like the USE symbols above.
 

+=item EV_USE_INOTIFY
+
+If defined to be C<1>, libev will compile in support for the Linux inotify
+interface to speed up C<ev_stat> watchers. Its actual availability will
+be detected at runtime.
+

 =item EV_H
 
 The name of the F<ev.h> header file used to include it. The default if
 =item EV_H
 
 The name of the F<ev.h> header file used to include it. The default if


@@ -1877,12 +2445,35 @@ additional independent event loops. Otherwise there will be no support
 for multiple event loops and there is no first event loop pointer
 argument. Instead, all functions act on the single default loop.
 
 for multiple event loops and there is no first event loop pointer
 argument. Instead, all functions act on the single default loop.
 

+=item EV_MINPRI
+
+=item EV_MAXPRI
+
+The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
+C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
+provide for more priorities by overriding those symbols (usually defined
+to be C<-2> and C<2>, respectively).
+
+When doing priority-based operations, libev usually has to linearly search
+all the priorities, so having many of them (hundreds) uses a lot of space
+and time, so using the defaults of five priorities (-2 .. +2) is usually
+fine.
+
+If your embedding app does not need any priorities, defining these both to
+C<0> will save some memory and cpu.
+

 =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_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_IDLE_ENABLE
+
+If undefined or defined to be C<1>, then idle watchers 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
 =item EV_EMBED_ENABLE
 
 If undefined or defined to be C<1>, then embed watchers are supported. If


@@ -1893,12 +2484,32 @@ defined to be C<0>, then they are not.
 If undefined or defined to be C<1>, then stat watchers are supported. If
 defined to be C<0>, then they are not.
 
 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_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
 =item EV_COMMON
 
 By default, all watchers have a C<void *data> member. By redefining


@@ -1920,11 +2531,36 @@ For example, the perl EV module uses something like this:
 
 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
 
 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
+definition and a statement, respectively. See the F<ev.h> 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++.
 
 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 EXPORTED API SYMBOLS
+
+If you need to re-export the API (e.g. via a dll) and you need a list of
+exported symbols, you can use the provided F<Symbol.*> files which list
+all public symbols, one per line:
+
+  Symbols.ev      for libev proper
+  Symbols.event   for the libevent emulation
+
+This can also be used to rename all public symbols to avoid clashes with
+multiple versions of libev linked together (which is obviously bad in
+itself, but sometimes it is inconvinient to avoid this).
+
+A sed command like this will create wrapper C<#define>'s that you need to
+include before including F<ev.h>:
+
+   <Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
+
+This would create a file F<wrap.h> which essentially looks like this:
+
+   #define ev_backend     myprefix_ev_backend
+   #define ev_check_start myprefix_ev_check_start
+   #define ev_check_stop  myprefix_ev_check_stop
+   ...
+

 =head2 EXAMPLES
 
 For a real-world example of a program the includes libev
 =head2 EXAMPLES
 
 For a real-world example of a program the includes libev


@@ -1936,12 +2572,17 @@ 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
 file.
 
 The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file

-that everybody includes and which overrides some autoconf choices:
+that everybody includes and which overrides some configure choices:

 
 

+  #define EV_MINIMAL 1

   #define EV_USE_POLL 0
   #define EV_MULTIPLICITY 0
   #define EV_USE_POLL 0
   #define EV_MULTIPLICITY 0

-  #define EV_PERIODICS 0
+  #define EV_PERIODIC_ENABLE 0
+  #define EV_STAT_ENABLE 0
+  #define EV_FORK_ENABLE 0

   #define EV_CONFIG_H <config.h>
   #define EV_CONFIG_H <config.h>

+  #define EV_MINPRI 0
+  #define EV_MAXPRI 0

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


@@ -1957,24 +2598,51 @@ 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>.
 
 libev will be explained. For complexity discussions about backends see the
 documentation for C<ev_default_init>.
 

+All of the following are about amortised time: If an array needs to be
+extended, libev needs to realloc and move the whole array, but this
+happens asymptotically never with higher number of elements, so O(1) might
+mean it might do a lengthy realloc operation in rare cases, but on average
+it is much faster and asymptotically approaches constant time.
+

 =over 4
 
 =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
 
 =over 4
 
 =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
 

+This means that, when you have a watcher that triggers in one hour and
+there are 100 watchers that would trigger before that then inserting will
+have to skip those 100 watchers.
+

 =item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
 
 =item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
 

+That means that for changing a timer costs less than removing/adding them
+as only the relative motion in the event queue has to be paid for.
+

 =item Starting io/check/prepare/idle/signal/child watchers: O(1)
 
 =item Starting io/check/prepare/idle/signal/child watchers: O(1)
 

+These just add the watcher into an array or at the head of a list.

 =item Stopping check/prepare/idle 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 % 16))
+=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
+
+These watchers are stored in lists then need to be walked to find the
+correct watcher to remove. The lists are usually short (you don't usually
+have many watchers waiting for the same fd or signal).

 
 =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 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)
 

+A change means an I/O watcher gets started or stopped, which requires
+libev to recalculate its status (and possibly tell the kernel).
+

 =item Activating one watcher: O(1)
 
 =item Activating one watcher: O(1)
 

+=item Priority handling: O(number_of_priorities)
+
+Priorities are implemented by allocating some space for each
+priority. When doing priority-based operations, libev usually has to
+linearly search all the priorities.
+

 =back
 
 
 =back