[ViewVC] Diff of: cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.152 by root, Wed May 7 14:45:17 2008 UTC vs.
Revision 1.202 by root, Fri Oct 24 08:30:01 2008 UTC

 libev - a high performance full-featured event loop written in C
 =head1 SYNOPSIS
-  #include <ev.h>
+   #include <ev.h>
 =head2 EXAMPLE PROGRAM
-  // a single header file is required
+   // a single header file is required
-  #include <ev.h>
+   #include <ev.h>
-  // every watcher type has its own typedef'd struct
+   // every watcher type has its own typedef'd struct
-  // with the name ev_<type>
+   // with the name ev_TYPE
-  ev_io stdin_watcher;
+   ev_io stdin_watcher;
-  ev_timer timeout_watcher;
+   ev_timer timeout_watcher;
-  // all watcher callbacks have a similar signature
+   // all watcher callbacks have a similar signature
-  // this callback is called when data is readable on stdin
+   // this callback is called when data is readable on stdin
-  static void
+   static void
-  stdin_cb (EV_P_ struct ev_io *w, int revents)
+   stdin_cb (EV_P_ ev_io *w, int revents)
-  {
+   {
-    puts ("stdin ready");
+     puts ("stdin ready");
-    // for one-shot events, one must manually stop the watcher
+     // for one-shot events, one must manually stop the watcher
-    // with its corresponding stop function.
+     // with its corresponding stop function.
-    ev_io_stop (EV_A_ w);
+     ev_io_stop (EV_A_ w);
-    // this causes all nested ev_loop's to stop iterating
+     // this causes all nested ev_loop's to stop iterating
-    ev_unloop (EV_A_ EVUNLOOP_ALL);
+     ev_unloop (EV_A_ EVUNLOOP_ALL);
-  }
+   }
-  // another callback, this time for a time-out
+   // another callback, this time for a time-out
-  static void
+   static void
-  timeout_cb (EV_P_ struct ev_timer *w, int revents)
+   timeout_cb (EV_P_ ev_timer *w, int revents)
-  {
+   {
-    puts ("timeout");
+     puts ("timeout");
-    // this causes the innermost ev_loop to stop iterating
+     // this causes the innermost ev_loop to stop iterating
-    ev_unloop (EV_A_ EVUNLOOP_ONE);
+     ev_unloop (EV_A_ EVUNLOOP_ONE);
-  }
+   }
-  int
+   int
-  main (void)
+   main (void)
-  {
+   {
-    // use the default event loop unless you have special needs
+     // use the default event loop unless you have special needs
-    struct ev_loop *loop = ev_default_loop (0);
+     ev_loop *loop = ev_default_loop (0);
-    // initialise an io watcher, then start it
+     // initialise an io watcher, then start it
-    // this one will watch for stdin to become readable
+     // this one will watch for stdin to become readable
-    ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
+     ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
-    ev_io_start (loop, &stdin_watcher);
+     ev_io_start (loop, &stdin_watcher);
-    // initialise a timer watcher, then start it
+     // initialise a timer watcher, then start it
-    // simple non-repeating 5.5 second timeout
+     // simple non-repeating 5.5 second timeout
-    ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
+     ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
-    ev_timer_start (loop, &timeout_watcher);
+     ev_timer_start (loop, &timeout_watcher);
-    // now wait for events to arrive
+     // now wait for events to arrive
-    ev_loop (loop, 0);
+     ev_loop (loop, 0);
-    // unloop was called, so exit
+     // unloop was called, so exit
-    return 0;
+     return 0;
-  }
+   }
 =head1 DESCRIPTION
 The newest version of this document is also available as an 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>.
+time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
 Libev is an event loop: you register interest in certain events (such as a
 file descriptor being readable or a timeout occurring), and it will manage
 these event sources and provide your program with events.
 Libev is very configurable. In this manual the default (and most common)
 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
+name C<loop> (which is always of type C<ev_loop *>) will not have
 this argument.
 =head2 TIME REPRESENTATION
 Libev represents time as a single floating point number, representing the
 (fractional) number of seconds since the (POSIX) epoch (somewhere near
 the beginning of 1970, details are complicated, don't ask). This type is
 called C<ev_tstamp>, which is what you should use too. It usually aliases
 to the C<double> type in C, and when you need to do any calculations on
-it, you should treat it as some floatingpoint value. Unlike the name
+it, you should treat it as some floating point value. Unlike the name
 component C<stamp> might indicate, it is also used for time differences
 throughout libev.
+=head1 ERROR HANDLING
+Libev knows three classes of errors: operating system errors, usage errors
+and internal errors (bugs).
+When libev catches an operating system error it cannot handle (for example
+a system call indicating a condition libev cannot fix), it calls the callback
+set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
+abort. The default is to print a diagnostic message and to call C<abort
+()>.
+When libev detects a usage error such as a negative timer interval, then
+it will print a diagnostic message and abort (via the C<assert> mechanism,
+so C<NDEBUG> will disable this checking): these are programming errors in
+the libev caller and need to be fixed there.
+Libev also has a few internal error-checking C<assert>ions, and also has
+extensive consistency checking code. These do not trigger under normal
+circumstances, as they indicate either a bug in libev or worse.
 =head1 GLOBAL FUNCTIONS
 These functions can be called anytime, even before initialising the
 library in any way.
 =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 ()>.
+this is a sub-second-resolution C<sleep ()>.
 =item int ev_version_major ()
 =item int ev_version_minor ()
 not a problem.
 Example: Make sure we haven't accidentally been linked against the wrong
 version.
-  assert (("libev version mismatch",
+   assert (("libev version mismatch",
-           ev_version_major () == EV_VERSION_MAJOR
+            ev_version_major () == EV_VERSION_MAJOR
-           && ev_version_minor () >= EV_VERSION_MINOR));
+            && ev_version_minor () >= EV_VERSION_MINOR));
 =item unsigned int ev_supported_backends ()
 Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
 value) compiled into this binary of libev (independent of their
 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",
+   assert (("sorry, no epoll, no sex",
-           ev_supported_backends () & EVBACKEND_EPOLL));
+            ev_supported_backends () & EVBACKEND_EPOLL));
 =item unsigned int ev_recommended_backends ()
 Return the set of all backends compiled into this binary of libev and also
 recommended for this platform. This set is often smaller than the one
 returned by C<ev_supported_backends>, as for example kqueue is broken on
-most BSDs and will not be autodetected unless you explicitly request it
+most BSDs and will not be auto-detected unless you explicitly request it
 (assuming you know what you are doing). This is the set of backends that
 libev will probe for if you specify no backends explicitly.
 =item unsigned int ev_embeddable_backends ()
 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))
+=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
 Sets the allocation function to use (the prototype is similar - the
 semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
 used to allocate and free memory (no surprises here). If it returns zero
 when memory needs to be allocated (C<size != 0>), the library might abort
    }
    ...
    ev_set_allocator (persistent_realloc);
-=item ev_set_syserr_cb (void (*cb)(const char *msg));
+=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
-Set the callback function to call on a retryable syscall error (such
+Set the callback function to call on a retryable system call error (such
 as failed select, poll, epoll_wait). The message is a printable string
 indicating the system call or subsystem causing the problem. If this
-callback is set, then libev will expect it to remedy the sitution, no
+callback is set, then libev will expect it to remedy the situation, no
 matter what, when it returns. That is, libev will generally retry the
 requested operation, or, if the condition doesn't go away, do bad stuff
 (such as abort).
 Example: This is basically the same thing that libev does internally, too.
 =back
 =head1 FUNCTIONS CONTROLLING THE EVENT LOOP
-An event loop is described by a C<struct ev_loop *>. The library knows two
+An event loop is described by a C<struct ev_loop *> (the C<struct>
-types of such loops, the I<default> loop, which supports signals and child
+is I<not> optional in this case, as there is also an C<ev_loop>
-events, and dynamically created loops which do not.
+I<function>).
+The library knows two types of such loops, the I<default> loop, which
+supports signals and child events, and dynamically created loops which do
+not.
 =over 4
 =item struct ev_loop *ev_default_loop (unsigned int flags)
 from multiple threads, you have to lock (note also that this is unlikely,
 as loops cannot bes hared easily between threads anyway).
 The default loop is the only loop that can handle C<ev_signal> and
 C<ev_child> watchers, and to do this, it always registers a handler
-for C<SIGCHLD>. If this is a problem for your app you can either
+for C<SIGCHLD>. If this is a problem for your application you can either
 create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
 can simply overwrite the C<SIGCHLD> signal handler I<after> calling
 C<ev_default_init>.
 The flags argument can be used to specify special behaviour or specific
 The default flags value. Use this if you have no clue (it's the right
 thing, believe me).
 =item C<EVFLAG_NOENV>
-If this flag bit is ored into the flag value (or the program runs setuid
+If this flag bit is or'ed into the flag value (or the program runs setuid
 or setgid) then libev will I<not> look at the environment variable
 C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
 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.
 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
 GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
-without a syscall and thus I<very> fast, but my GNU/Linux system also has
+without a system call and thus I<very> fast, but my GNU/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>
+This flag setting cannot be overridden 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
 but if that fails, expect a fairly low limit on the number of fds when
 using this backend. It doesn't scale too well (O(highest_fd)), but its
 usually the fastest backend for a low number of (low-numbered :) fds.
 To get good performance out of this backend you need a high amount of
-parallelity (most of the file descriptors should be busy). If you are
+parallelism (most of the file descriptors should be busy). If you are
 writing a server, you should C<accept ()> in a loop to accept as many
 connections as possible during one iteration. You might also want to have
 a look at C<ev_set_io_collect_interval ()> to increase the amount of
-readyness notifications you get per iteration.
+readiness notifications you get per iteration.
+This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
+C<writefds> set (and to work around Microsoft Windows bugs, also onto the
+C<exceptfds> set on that platform).
 =item C<EVBACKEND_POLL>    (value 2, poll backend, available everywhere except on windows)
 And this is your standard poll(2) backend. It's more complicated
 than select, but handles sparse fds better and has no artificial
 limit on the number of fds you can use (except it will slow down
 considerably with a lot of inactive fds). It scales similarly to select,
 i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
 performance tips.
+This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
+C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
 =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). The epoll design has a number
 of shortcomings, such as silently dropping events in some hard-to-detect
-cases and requiring a syscall per fd change, no fork support and bad
+cases and requiring a system call 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
+will result in some caching, there is still a system call per such incident
 (because the fd could point to a different file description now), so its
 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
 (or space) is available.
 Best performance from this backend is achieved by not unregistering all
-watchers for a file descriptor until it has been closed, if possible, i.e.
+watchers for a file descriptor until it has been closed, if possible,
-keep at least one watcher active per fd at all times.
+i.e. keep at least one watcher active per fd at all times. Stopping and
+starting a watcher (without re-setting it) also usually doesn't cause
+extra overhead.
-While nominally embeddeble in other event loops, this feature is broken in
+While nominally embeddable in other event loops, this feature is broken in
 all kernel versions tested so far.
+This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
+C<EVBACKEND_POLL>.
 =item C<EVBACKEND_KQUEUE>  (value 8, most BSD clones)
-Kqueue deserves special mention, as at the time of this writing, it
+Kqueue deserves special mention, as at the time of this writing, it was
-was broken on all BSDs except NetBSD (usually it doesn't work reliably
+broken on all BSDs except NetBSD (usually it doesn't work reliably with
-with anything but sockets and pipes, except on Darwin, where of course
+anything but sockets and pipes, except on Darwin, where of course it's
-it's completely useless). For this reason it's not being "autodetected"
+completely useless). For this reason it's not being "auto-detected" unless
-unless you explicitly specify it explicitly in the flags (i.e. using
+you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or
-C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
+libev was compiled on a known-to-be-good (-enough) system like NetBSD.
-system like NetBSD.
 You still can embed kqueue into a normal poll or select backend and use it
 only for sockets (after having made sure that sockets work with kqueue on
 the target platform). See C<ev_embed> watchers for more info.
 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 stopping, setting and starting an I/O watcher does never
-cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
+cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
-two event changes per incident, support for C<fork ()> is very bad and it
+two event changes per incident. Support for C<fork ()> is very bad and it
 drops fds silently in similarly hard-to-detect cases.
 This backend usually performs well under most conditions.
 While nominally embeddable in other event loops, this doesn't work
 everywhere, so you might need to test for this. And since it is broken
 almost everywhere, you should only use it when you have a lot of sockets
 (for which it usually works), by embedding it into another event loop
-(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
+(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
-sockets.
+using it only for sockets.
+This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
+C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
+C<NOTE_EOF>.
 =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
 This is not implemented yet (and might never be, unless you send me an
 implementation). According to reports, C</dev/poll> only supports sockets
 =item C<EVBACKEND_PORT>    (value 32, Solaris 10)
 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)).
-Please note that solaris event ports can deliver 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.
 While this backend scales well, it requires one system call per active
 file descriptor per loop iteration. For small and medium numbers of file
 descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
 might perform better.
-On the positive side, ignoring the spurious readyness notifications, this
+On the positive side, with the exception of the spurious readiness
-backend actually performed to specification in all tests and is fully
+notifications, this backend actually performed fully to specification
-embeddable, which is a rare feat among the OS-specific backends.
+in all tests and is fully embeddable, which is a rare feat among the
+OS-specific backends.
+This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
+C<EVBACKEND_POLL>.
 =item C<EVBACKEND_ALL>
 Try all backends (even potentially broken ones that wouldn't be tried
 with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
 It is definitely not recommended to use this flag.
 =back
-If one or more of these are ored into the flags value, then only these
+If one or more of these are or'ed into the flags value, then only these
 backends will be tried (in the reverse order as listed here). If none are
 specified, all backends in C<ev_recommended_backends ()> will be tried.
-The most typical usage is like this:
+Example: This is the most typical usage.
-  if (!ev_default_loop (0))
+   if (!ev_default_loop (0))
-    fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
+     fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
-Restrict libev to the select and poll backends, and do not allow
+Example: Restrict libev to the select and poll backends, and do not allow
 environment settings to be taken into account:
-  ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
+   ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
-Use whatever libev has to offer, but make sure that kqueue is used if
+Example: Use whatever libev has to offer, but make sure that kqueue is
-available (warning, breaks stuff, best use only with your own private
+used if available (warning, breaks stuff, best use only with your own
-event loop and only if you know the OS supports your types of fds):
+private event loop and only if you know the OS supports your types of
+fds):
-  ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
+   ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
 =item struct ev_loop *ev_loop_new (unsigned int flags)
 Similar to C<ev_default_loop>, but always creates a new event loop that is
 always distinct from the default loop. Unlike the default loop, it cannot
 libev with threads is indeed to create one loop per thread, and using the
 default loop in the "main" or "initial" thread.
 Example: Try to create a event loop that uses epoll and nothing else.
-  struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
+   struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
-  if (!epoller)
+   if (!epoller)
-    fatal ("no epoll found here, maybe it hides under your chair");
+     fatal ("no epoll found here, maybe it hides under your chair");
 =item ev_default_destroy ()
 Destroys the default loop again (frees all memory and kernel state
 etc.). 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>
+responsibility to either stop all watchers cleanly yourself I<before>
 calling this function, or cope with the fact afterwards (which is usually
 the easiest thing, you can just ignore the watchers and/or C<free ()> them
 for example).
 Note that certain global state, such as signal state, will not be freed by
 =item ev_loop_fork (loop)
 Like C<ev_default_fork>, but acts on an event loop created by
 C<ev_loop_new>. Yes, you have to call this on every allocated event loop
-after fork, and how you do this is entirely your own problem.
+after fork that you want to re-use in the child, and how you do this is
+entirely your own problem.
 =item int ev_is_default_loop (loop)
-Returns true when the given loop actually is the default loop, false otherwise.
+Returns true when the given loop is, in fact, the default loop, and false
+otherwise.
 =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
 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 occurring (or more correctly, libev finding out about it).
+=item ev_now_update (loop)
+Establishes the current time by querying the kernel, updating the time
+returned by C<ev_now ()> in the progress. This is a costly operation and
+is usually done automatically within C<ev_loop ()>.
+This function is rarely useful, but when some event callback runs for a
+very long time without entering the event loop, updating libev's idea of
+the current time is a good idea.
+See also "The special problem of time updates" in the C<ev_timer> section.
 =item ev_loop (loop, int flags)
 Finally, this is it, the event handler. This function usually is called
 after you initialised all your watchers and you want to start handling
 events.
 If the flags argument is specified as 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
+finished (especially in interactive programs), but having a program
-automatically loops as long as it has to and no longer by virtue of
+that automatically loops as long as it has to and no longer by virtue
-relying on its watchers stopping correctly is a thing of beauty.
+of relying on its watchers stopping correctly, that is truly 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
+those events and any already outstanding ones, but will not block your
-case there are no events and will return after one iteration of the loop.
+process in case there are no events and will return after one iteration of
+the loop.
 A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
-neccessary) and will handle those and any outstanding ones. It will block
+necessary) and will handle those and any already outstanding ones. It
-your process until at least one new event arrives, and will return after
+will block your process until at least one new event arrives (which could
-one iteration of the loop. This is useful if you are waiting for some
+be an event internal to libev itself, so there is no guarentee that a
-external event in conjunction with something not expressible using other
+user-registered callback will be called), and will return after one
+iteration of the loop.
+This is useful if you are waiting for some external event in conjunction
+with something not expressible using other libev watchers (i.e. "roll your
-libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
+own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
 usually a better approach for this kind of thing.
 Here are the gory details of what C<ev_loop> does:
    - Before the first iteration, call any pending watchers.
    * If EVFLAG_FORKCHECK was used, check for a fork.
-   - If a fork was detected, queue and call all fork watchers.
+   - If a fork was detected (by any means), queue and call all fork watchers.
    - Queue and call all prepare watchers.
-   - If we have been forked, recreate the kernel state.
+   - If we have been forked, detach and recreate the kernel state
+     as to not disturb the other process.
    - Update the kernel state with all outstanding changes.
-   - Update the "event loop time".
+   - Update the "event loop time" (ev_now ()).
    - Calculate for how long to sleep or block, if at all
      (active idle watchers, EVLOOP_NONBLOCK or not having
      any active watchers at all will result in not sleeping).
    - Sleep if the I/O and timer collect interval say so.
    - Block the process, waiting for any events.
    - Queue all outstanding I/O (fd) events.
-   - Update the "event loop time" and do time jump handling.
+   - Update the "event loop time" (ev_now ()), and do time jump adjustments.
-   - Queue all outstanding timers.
+   - Queue all expired timers.
-   - Queue all outstanding periodics.
+   - Queue all expired periodics.
-   - If no events are pending now, queue all idle watchers.
+   - Unless any events are pending now, queue all idle watchers.
    - Queue all check watchers.
    - Call all queued watchers in reverse order (i.e. check watchers first).
      Signals and child watchers are implemented as I/O watchers, and will
      be handled here by queueing them when their watcher gets executed.
    - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
 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!
+   ... jobs done or somebody called unloop. yeah!
 =item ev_unloop (loop, how)
 Can be used to make a call to C<ev_loop> return early (but only after it
 has processed all outstanding events). The C<how> argument must be either
 C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
 C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
 This "unloop state" will be cleared when entering C<ev_loop> again.
+It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
 =item ev_ref (loop)
 =item ev_unref (loop)
 Ref/unref can be used to add or remove a reference count on the event
 loop: Every watcher keeps one reference, and as long as the reference
-count is nonzero, C<ev_loop> will not return on its own. If you have
+count is nonzero, C<ev_loop> will not return on its own.
-a watcher you never unregister that should not keep C<ev_loop> from
+If you have a watcher you never unregister that should not keep C<ev_loop>
-returning, ev_unref() after starting, and ev_ref() before stopping it. For
+from returning, call ev_unref() after starting, and ev_ref() before
+stopping it.
-example, libev itself uses this for its internal signal pipe: It is not
+As an example, libev itself uses this for its internal signal pipe: It is
-visible to the libev user and should not keep C<ev_loop> from exiting if
+not visible to the libev user and should not keep C<ev_loop> from exiting
-no event watchers registered by it are active. It is also an excellent
+if 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>
 (but only if the watcher wasn't active before, or was active before,
 respectively).
 Example: Create a signal watcher, but keep it from keeping C<ev_loop>
 running when nothing else is active.
-  struct ev_signal exitsig;
+   ev_signal exitsig;
-  ev_signal_init (&exitsig, sig_cb, SIGINT);
+   ev_signal_init (&exitsig, sig_cb, SIGINT);
-  ev_signal_start (loop, &exitsig);
+   ev_signal_start (loop, &exitsig);
-  evf_unref (loop);
+   evf_unref (loop);
 Example: For some weird reason, unregister the above signal handler again.
-  ev_ref (loop);
+   ev_ref (loop);
-  ev_signal_stop (loop, &exitsig);
+   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
+for events. Both time intervals are by default C<0>, meaning that libev
-invoke timer/periodic callbacks and I/O callbacks with minimum latency.
+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
+allows libev to delay invocation of I/O and timer/periodic callbacks
-increase efficiency of loop iterations.
+to increase efficiency of loop iterations (or to increase power-saving
+opportunities).
-The background is that sometimes your program runs just fast enough to
+The idea is that sometimes your program runs just fast enough to handle
-handle one (or very few) event(s) per loop iteration. While this makes
+one (or very few) event(s) per loop iteration. While this makes the
-the program responsive, it also wastes a lot of CPU time to poll for new
+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.
 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,
 C<ev_timer>) will be not affected. Setting this to a non-null value will
 introduce an additional C<ev_sleep ()> call into most loop iterations.
 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
+latency/jitter/inexactness (the watcher callback will be called
-will not be affected. Setting this to a non-null value will not introduce
+later). C<ev_io> watchers will not be affected. Setting this to a non-null
-any overhead in libev.
+value will not introduce any overhead in libev.
-Many (busy) programs can usually benefit by setting the io collect
+Many (busy) programs can usually benefit by setting the I/O 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.
+as this approaches the timing granularity of most systems.
+Setting the I<timeout collect interval> can improve the opportunity for
+saving power, as the program will "bundle" timer callback invocations that
+are "near" in time together, by delaying some, thus reducing the number of
+times the process sleeps and wakes up again. Another useful technique to
+reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
+they fire on, say, one-second boundaries only.
+=item ev_loop_verify (loop)
+This function only does something when C<EV_VERIFY> support has been
+compiled in, which is the default for non-minimal builds. It tries to go
+through all internal structures and checks them for validity. If anything
+is found to be inconsistent, it will print an error message to standard
+error and call C<abort ()>.
+This can be used to catch bugs inside libev itself: under normal
+circumstances, this function will never abort as of course libev keeps its
+data structures consistent.
 =back
 =head1 ANATOMY OF A WATCHER
+In the following description, uppercase C<TYPE> in names stands for the
+watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
+watchers and C<ev_io_start> for I/O watchers.
 A watcher is a structure that you create and register to record your
 interest in some event. For instance, if you want to wait for STDIN to
 become readable, you would create an C<ev_io> watcher for that:
-  static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
+   static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
-  {
+   {
-    ev_io_stop (w);
+     ev_io_stop (w);
-    ev_unloop (loop, EVUNLOOP_ALL);
+     ev_unloop (loop, EVUNLOOP_ALL);
-  }
+   }
-  struct ev_loop *loop = ev_default_loop (0);
+   struct ev_loop *loop = ev_default_loop (0);
-  struct ev_io stdin_watcher;
+   ev_io stdin_watcher;
-  ev_init (&stdin_watcher, my_cb);
+   ev_init (&stdin_watcher, my_cb);
-  ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
+   ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
-  ev_io_start (loop, &stdin_watcher);
+   ev_io_start (loop, &stdin_watcher);
-  ev_loop (loop, 0);
+   ev_loop (loop, 0);
 As you can see, you are responsible for allocating the memory for your
-watcher structures (and it is usually a bad idea to do this on the stack,
+watcher structures (and it is I<usually> a bad idea to do this on the
-although this can sometimes be quite valid).
+stack).
+Each watcher has an associated watcher structure (called C<struct ev_TYPE>
+or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
 Each watcher structure must be initialised by a call to C<ev_init
 (watcher *, callback)>, which expects a callback to be provided. This
-callback gets invoked each time the event occurs (or, in the case of io
+callback gets invoked each time the event occurs (or, in the case of I/O
 watchers, each time the event loop detects that the file descriptor given
 is readable and/or writable).
-Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro
+Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
-with arguments specific to this watcher type. There is also a macro
+macro to configure it, with arguments specific to the watcher type. There
-to combine initialisation and setting in one call: C<< ev_<type>_init
+is also a macro to combine initialisation and setting in one call: C<<
-(watcher *, callback, ...) >>.
+ev_TYPE_init (watcher *, callback, ...) >>.
 To make the watcher actually watch out for events, you have to start it
-with a watcher-specific start function (C<< ev_<type>_start (loop, watcher
+with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
 *) >>), and you can stop watching for events at any time by calling the
-corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
+corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
 As long as your watcher is active (has been started but not stopped) you
 must not touch the values stored in it. Most specifically you must never
-reinitialise it or call its C<set> macro.
+reinitialise it or call its C<ev_TYPE_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
 third argument.
 The given async watcher has been asynchronously notified (see C<ev_async>).
 =item C<EV_ERROR>
-An unspecified error has occured, the watcher has been stopped. This might
+An unspecified error has occurred, the watcher has been stopped. This might
 happen because the watcher could not be properly started because libev
 ran out of memory, a file descriptor was found to be closed or any other
+problem. Libev considers these application bugs.
-problem. You best act on it by reporting the problem and somehow coping
+You best act on it by reporting the problem and somehow coping with the
-with the watcher being stopped.
+watcher being stopped. Note that well-written programs should not receive
+an error ever, so when your watcher receives it, this usually indicates a
+bug in your program.
-Libev will usually signal a few "dummy" events together with an error,
+Libev will usually signal a few "dummy" events together with an error, for
-for example it might indicate that a fd is readable or writable, and if
+example it might indicate that a fd is readable or writable, and if your
-your callbacks is well-written it can just attempt the operation and cope
+callbacks is well-written it can just attempt the operation and cope with
-with the error from read() or write(). This will not work in multithreaded
+the error from read() or write(). This will not work in multi-threaded
-programs, though, so beware.
+programs, though, as the fd could already be closed and reused for another
+thing, so beware.
 =back
 =head2 GENERIC WATCHER FUNCTIONS
-In the following description, C<TYPE> stands for the watcher type,
-e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
 =over 4
 =item C<ev_init> (ev_TYPE *watcher, callback)
 which rolls both calls into one.
 You can reinitialise a watcher at any time as long as it has been stopped
 (or never started) and there are no pending events outstanding.
-The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
+The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
 int revents)>.
+Example: Initialise an C<ev_io> watcher in two steps.
+   ev_io w;
+   ev_init (&w, my_cb);
+   ev_io_set (&w, STDIN_FILENO, EV_READ);
 =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
 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.
+See C<ev_init>, above, for an example.
 =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
-This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
+This convenience 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
+calls into a single call. This is the most convenient method to initialise
 a watcher. The same limitations apply, of course.
+Example: Initialise and set an C<ev_io> watcher in one step.
+   ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
 =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.
+Example: Start the C<ev_io> watcher that is being abused as example in this
+whole section.
+   ev_io_start (EV_DEFAULT_UC, &w);
 =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
-Stops the given watcher again (if active) and clears the pending
+Stops the given watcher if active, and clears the pending status (whether
+the watcher was active or not).
-status. It is possible that stopped watchers are pending (for example,
+It is possible that stopped watchers are pending - for example,
-non-repeating timers are being stopped when they become pending), but
+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
+calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
-you want to free or reuse the memory used by the watcher it is therefore a
+pending. If you want to free or reuse the memory used by the watcher it is
-good idea to always call its C<ev_TYPE_stop> function.
+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
 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.
+or might not have been clamped to the 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.
+can deal with that fact, as both are simply passed through to the
+callback.
 =item int ev_clear_pending (loop, ev_TYPE *watcher)
-If the watcher is pending, this function returns clears its pending status
+If the watcher is pending, this function clears its pending status and
-and returns its C<revents> bitset (as if its callback was invoked). If the
+returns its C<revents> bitset (as if its callback was invoked). If the
 watcher isn't pending it does nothing and returns C<0>.
+Sometimes it can be useful to "poll" a watcher instead of waiting for its
+callback to be invoked, which can be accomplished with this function.
 =back
 =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
 Each watcher has, by default, a member C<void *data> that you can change
-and read at any time, libev will completely ignore it. This can be used
+and read at any time: libev will completely ignore it. This can be used
 to associate arbitrary data with your watcher. If you need more data and
 don't want to allocate memory and store a pointer to it in that data
 member, you can also "subclass" the watcher type and provide your own
 data:
-  struct my_io
+   struct my_io
-  {
+   {
-    struct ev_io io;
+     ev_io io;
-    int otherfd;
+     int otherfd;
-    void *somedata;
+     void *somedata;
-    struct whatever *mostinteresting;
+     struct whatever *mostinteresting;
-  }
+   };
+   ...
+   struct my_io w;
+   ev_io_init (&w.io, my_cb, fd, EV_READ);
 And since your callback will be called with a pointer to the watcher, you
 can cast it back to your own type:
-  static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
+   static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
-  {
+   {
-    struct my_io *w = (struct my_io *)w_;
+     struct my_io *w = (struct my_io *)w_;
-    ...
+     ...
-  }
+   }
 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
+Another common scenario is to use some data structure with multiple
-watchers:
+embedded watchers:
-  struct my_biggy
+   struct my_biggy
-  {
+   {
-    int some_data;
+     int some_data;
-    ev_timer t1;
+     ev_timer t1;
-    ev_timer t2;
+     ev_timer t2;
-  }
+   }
-In this case getting the pointer to C<my_biggy> is a bit more complicated,
+In this case getting the pointer to C<my_biggy> is a bit more
-you need to use C<offsetof>:
+complicated: Either you store the address of your C<my_biggy> struct
+in the C<data> member of the watcher (for woozies), or you need to use
+some pointer arithmetic using C<offsetof> inside your watchers (for real
+programmers):
-  #include <stddef.h>
+   #include <stddef.h>
-  static void
+   static void
-  t1_cb (EV_P_ struct ev_timer *w, int revents)
+   t1_cb (EV_P_ ev_timer *w, int revents)
-  {
+   {
-    struct my_biggy big = (struct my_biggy *
+     struct my_biggy big = (struct my_biggy *
-      (((char *)w) - offsetof (struct my_biggy, t1));
+       (((char *)w) - offsetof (struct my_biggy, t1));
-  }
+   }
-  static void
+   static void
-  t2_cb (EV_P_ struct ev_timer *w, int revents)
+   t2_cb (EV_P_ ev_timer *w, int revents)
-  {
+   {
-    struct my_biggy big = (struct my_biggy *
+     struct my_biggy big = (struct my_biggy *
-      (((char *)w) - offsetof (struct my_biggy, t2));
+       (((char *)w) - offsetof (struct my_biggy, t2));
-  }
+   }
 =head1 WATCHER TYPES
 This section describes each watcher in detail, but will not repeat
 In general you can register as many read and/or write event watchers per
 fd as you want (as long as you don't confuse yourself). Setting all file
 descriptors to non-blocking mode is also usually a good idea (but not
 required if you know what you are doing).
-If you must do this, then force the use of a known-to-be-good backend
+If you cannot use non-blocking mode, then force the use of a
-(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
+known-to-be-good backend (at the time of this writing, this includes only
-C<EVBACKEND_POLL>).
+C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
 Another thing you have to watch out for is that it is quite easy to
-receive "spurious" readyness notifications, that is your callback might
+receive "spurious" readiness notifications, that is your callback might
 be called with C<EV_READ> but a subsequent C<read>(2) will actually block
 because there is no data. Not only are some backends known to create a
-lot of those (for example solaris ports), it is very easy to get into
+lot of those (for example Solaris ports), it is very easy to get into
 this situation even with a relatively standard program structure. Thus
 it is best to always use non-blocking I/O: An extra C<read>(2) returning
 C<EAGAIN> is far preferable to a program hanging until some data arrives.
-If you cannot run the fd in non-blocking mode (for example you should not
+If you cannot run the fd in non-blocking mode (for example you should
-play around with an Xlib connection), then you have to seperately re-test
+not play around with an Xlib connection), then you have to separately
-whether a file descriptor is really ready with a known-to-be good interface
+re-test whether a file descriptor is really ready with a known-to-be good
-such as poll (fortunately in our Xlib example, Xlib already does this on
+interface such as poll (fortunately in our Xlib example, Xlib already
-its own, so its quite safe to use).
+does this on its own, so its quite safe to use). Some people additionally
+use C<SIGALRM> and an interval timer, just to be sure you won't block
+indefinitely.
+But really, best use non-blocking mode.
 =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,
+descriptor (either due to calling C<close> explicitly or any other means,
-such as C<dup>). The reason is that you register interest in some file
+such as C<dup2>). 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.
 enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
 C<EVBACKEND_POLL>.
 =head3 The special problem of SIGPIPE
-While not really specific to libev, it is easy to forget about SIGPIPE:
+While not really specific to libev, it is easy to forget about C<SIGPIPE>:
-when reading from a pipe whose other end has been closed, your program
+when writing to a pipe whose other end has been closed, your program gets
-gets send a SIGPIPE, which, by default, aborts your program. For most
+sent a SIGPIPE, which, by default, aborts your program. For most programs
-programs this is sensible behaviour, for daemons, this is usually
+this is sensible behaviour, for daemons, this is usually undesirable.
-undesirable.
 So when you encounter spurious, unexplained daemon exits, make sure you
 ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
 somewhere, as that would have given you a big clue).
 =item ev_io_init (ev_io *, callback, int fd, int events)
 =item ev_io_set (ev_io *, int fd, int events)
 Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
-rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
+receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
-C<EV_READ | EV_WRITE> to receive the given events.
+C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
 =item int fd [read-only]
 The file descriptor being watched.
 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
+   static void
-  stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
+   stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
-  {
+   {
-     ev_io_stop (loop, w);
+      ev_io_stop (loop, w);
-    .. read from stdin here (or from w->fd) and haqndle any I/O errors
+     .. read from stdin here (or from w->fd) and handle any I/O errors
-  }
+   }
-  ...
+   ...
-  struct ev_loop *loop = ev_default_init (0);
+   struct ev_loop *loop = ev_default_init (0);
-  struct ev_io stdin_readable;
+   ev_io stdin_readable;
-  ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
+   ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
-  ev_io_start (loop, &stdin_readable);
+   ev_io_start (loop, &stdin_readable);
-  ev_loop (loop, 0);
+   ev_loop (loop, 0);
 =head2 C<ev_timer> - relative and optionally repeating timeouts
 Timer watchers are simple relative timers that generate an event after a
 given time, and optionally repeating in regular intervals after that.
 The timers are based on real time, that is, if you register an event that
-times out after an hour and you reset your system clock to last years
+times out after an hour and you reset your system clock to January last
-time, it will still time out after (roughly) and hour. "Roughly" because
+year, it will still time out after (roughly) one hour. "Roughly" because
 detecting time jumps is hard, and some inaccuracies are unavoidable (the
 monotonic clock option helps a lot here).
+The callback is guaranteed to be invoked only I<after> its timeout has
+passed, but if multiple timers become ready during the same loop iteration
+then order of execution is undefined.
+=head3 Be smart about timeouts
+Many real-world problems involve some kind of timeout, usually for error
+recovery. A typical example is an HTTP request - if the other side hangs,
+you want to raise some error after a while.
+What follows are some ways to handle this problem, from obvious and
+inefficient to smart and efficient.
+In the following, a 60 second activity timeout is assumed - a timeout that
+gets reset to 60 seconds each time there is activity (e.g. each time some
+data or other life sign was received).
+=over 4
+=item 1. Use a timer and stop, reinitialise and start it on activity.
+This is the most obvious, but not the most simple way: In the beginning,
+start the watcher:
+   ev_timer_init (timer, callback, 60., 0.);
+   ev_timer_start (loop, timer);
+Then, each time there is some activity, C<ev_timer_stop> it, initialise it
+and start it again:
+   ev_timer_stop (loop, timer);
+   ev_timer_set (timer, 60., 0.);
+   ev_timer_start (loop, timer);
+This is relatively simple to implement, but means that each time there is
+some activity, libev will first have to remove the timer from its internal
+data structure and then add it again. Libev tries to be fast, but it's
+still not a constant-time operation.
+=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
+This is the easiest way, and involves using C<ev_timer_again> instead of
+C<ev_timer_start>.
+To implement this, configure an C<ev_timer> with a C<repeat> value
+of C<60> and then call C<ev_timer_again> at start and each time you
+successfully read or write some data. If you go into an idle state where
+you do not expect data to travel on the socket, you can C<ev_timer_stop>
+the timer, and C<ev_timer_again> will automatically restart it if need be.
+That means you can ignore both the C<ev_timer_start> function and the
+C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
+member and C<ev_timer_again>.
+At start:
+   ev_timer_init (timer, callback);
+   timer->repeat = 60.;
+   ev_timer_again (loop, timer);
+Each time there is some activity:
+   ev_timer_again (loop, timer);
+It is even possible to change the time-out on the fly, regardless of
+whether the watcher is active or not:
+   timer->repeat = 30.;
+   ev_timer_again (loop, timer);
+This is slightly more efficient then stopping/starting the timer each time
+you want to modify its timeout value, as libev does not have to completely
+remove and re-insert the timer from/into its internal data structure.
+It is, however, even simpler than the "obvious" way to do it.
+=item 3. Let the timer time out, but then re-arm it as required.
+This method is more tricky, but usually most efficient: Most timeouts are
+relatively long compared to the intervals between other activity - in
+our example, within 60 seconds, there are usually many I/O events with
+associated activity resets.
+In this case, it would be more efficient to leave the C<ev_timer> alone,
+but remember the time of last activity, and check for a real timeout only
+within the callback:
+   ev_tstamp last_activity; // time of last activity
+   static void
+   callback (EV_P_ ev_timer *w, int revents)
+   {
+     ev_tstamp now     = ev_now (EV_A);
+     ev_tstamp timeout = last_activity + 60.;
+     // if last_activity + 60. is older than now, we did time out
+     if (timeout < now)
+       {
+         // timeout occured, take action
+       }
+     else
+       {
+         // callback was invoked, but there was some activity, re-arm
+         // the watcher to fire in last_activity + 60, which is
+         // guaranteed to be in the future, so "again" is positive:
+         w->again = timeout - now;
+         ev_timer_again (EV_A_ w);
+       }
+   }
+To summarise the callback: first calculate the real timeout (defined
+as "60 seconds after the last activity"), then check if that time has
+been reached, which means something I<did>, in fact, time out. Otherwise
+the callback was invoked too early (C<timeout> is in the future), so
+re-schedule the timer to fire at that future time, to see if maybe we have
+a timeout then.
+Note how C<ev_timer_again> is used, taking advantage of the
+C<ev_timer_again> optimisation when the timer is already running.
+This scheme causes more callback invocations (about one every 60 seconds
+minus half the average time between activity), but virtually no calls to
+libev to change the timeout.
+To start the timer, simply initialise the watcher and set C<last_activity>
+to the current time (meaning we just have some activity :), then call the
+callback, which will "do the right thing" and start the timer:
+   ev_timer_init (timer, callback);
+   last_activity = ev_now (loop);
+   callback (loop, timer, EV_TIMEOUT);
+And when there is some activity, simply store the current time in
+C<last_activity>, no libev calls at all:
+   last_actiivty = ev_now (loop);
+This technique is slightly more complex, but in most cases where the
+time-out is unlikely to be triggered, much more efficient.
+Changing the timeout is trivial as well (if it isn't hard-coded in the
+callback :) - just change the timeout and invoke the callback, which will
+fix things for you.
+=item 4. Wee, just use a double-linked list for your timeouts.
+If there is not one request, but many thousands (millions...), all
+employing some kind of timeout with the same timeout value, then one can
+do even better:
+When starting the timeout, calculate the timeout value and put the timeout
+at the I<end> of the list.
+Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
+the list is expected to fire (for example, using the technique #3).
+When there is some activity, remove the timer from the list, recalculate
+the timeout, append it to the end of the list again, and make sure to
+update the C<ev_timer> if it was taken from the beginning of the list.
+This way, one can manage an unlimited number of timeouts in O(1) time for
+starting, stopping and updating the timers, at the expense of a major
+complication, and having to use a constant timeout. The constant timeout
+ensures that the list stays sorted.
+=back
+So which method the best?
+Method #2 is a simple no-brain-required solution that is adequate in most
+situations. Method #3 requires a bit more thinking, but handles many cases
+better, and isn't very complicated either. In most case, choosing either
+one is fine, with #3 being better in typical situations.
+Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
+rather complicated, but extremely efficient, something that really pays
+off after the first million or so of active timers, i.e. it's usually
+overkill :)
+=head3 The special problem of time updates
+Establishing the current time is a costly operation (it usually takes at
+least two system calls): EV therefore updates its idea of the current
+time only before and after C<ev_loop> collects new events, which causes a
+growing difference between C<ev_now ()> and C<ev_time ()> when handling
+lots of events in one iteration.
 The relative timeouts are calculated relative to the C<ev_now ()>
 time. This is usually the right thing as this timestamp refers to the time
 of the event triggering whatever timeout you are modifying/starting. If
-you suspect event processing to be delayed and you I<need> to base the timeout
+you suspect event processing to be delayed and you I<need> to base the
-on the current time, use something like this to adjust for this:
+timeout on the current time, use something like this to adjust for this:
    ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
-The callback is guarenteed to be invoked only when its timeout has passed,
+If the event loop is suspended for a long time, you can also force an
-but if multiple timers become ready during the same loop iteration then
+update of the time returned by C<ev_now ()> by calling C<ev_now_update
-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)
 =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
-Configure the timer to trigger after C<after> seconds. If C<repeat> is
+Configure the timer to trigger after C<after> seconds. If C<repeat>
-C<0.>, then it will automatically be stopped. If it is positive, then the
+is C<0.>, then it will automatically be stopped once the timeout is
-timer will automatically be configured to trigger again C<repeat> seconds
+reached. If it is positive, then the timer will automatically be
-later, again, and again, until stopped manually.
+configured to trigger again C<repeat> seconds later, again, and again,
+until stopped manually.
-The timer itself will do a best-effort at avoiding drift, that is, if you
+The timer itself will do a best-effort at avoiding drift, that is, if
-configure a timer to trigger every 10 seconds, then it will trigger at
+you configure a timer to trigger every 10 seconds, then it will normally
-exactly 10 second intervals. If, however, your program cannot keep up with
+trigger at exactly 10 second intervals. If, however, your program cannot
-the timer (because it takes longer than those 10 seconds to do stuff) the
+keep up with the timer (because it takes longer than those 10 seconds to
-timer will not fire more than once per event loop iteration.
+do stuff) the timer will not fire more than once per event loop iteration.
 =item ev_timer_again (loop, ev_timer *)
 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 pending, its pending status is cleared.
-If the timer is started but nonrepeating, stop it (as if it timed out).
+If the timer is started but non-repeating, 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, see "Be smart about timeouts", above, for a
-example: Imagine you have a tcp connection and you want a so-called idle
+usage example.
-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
-socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
-automatically restart it if need be.
-That means you can ignore the C<after> value and C<ev_timer_start>
-altogether and only ever use the C<repeat> value and C<ev_timer_again>:
-   ev_timer_init (timer, callback, 0., 5.);
-   ev_timer_again (loop, timer);
-   ...
-   timer->again = 17.;
-   ev_timer_again (loop, timer);
-   ...
-   timer->again = 10.;
-   ev_timer_again (loop, timer);
-This is more slightly efficient then stopping/starting the timer each time
-you want to modify its timeout value.
 =item ev_tstamp repeat [read-write]
 The current C<repeat> value. Will be used each time the watcher times out
-or C<ev_timer_again> is called and determines the next timeout (if any),
+or C<ev_timer_again> is called, and determines the next timeout (if any),
 which is also when any modifications are taken into account.
 =back
 =head3 Examples
 Example: Create a timer that fires after 60 seconds.
-  static void
+   static void
-  one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
+   one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
-  {
+   {
-    .. one minute over, w is actually stopped right here
+     .. one minute over, w is actually stopped right here
-  }
+   }
-  struct ev_timer mytimer;
+   ev_timer mytimer;
-  ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
+   ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
-  ev_timer_start (loop, &mytimer);
+   ev_timer_start (loop, &mytimer);
 Example: Create a timeout timer that times out after 10 seconds of
 inactivity.
-  static void
+   static void
-  timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
+   timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
-  {
+   {
-    .. ten seconds without any activity
+     .. ten seconds without any activity
-  }
+   }
-  struct ev_timer mytimer;
+   ev_timer mytimer;
-  ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
+   ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
-  ev_timer_again (&mytimer); /* start timer */
+   ev_timer_again (&mytimer); /* start timer */
-  ev_loop (loop, 0);
+   ev_loop (loop, 0);
-  // and in some piece of code that gets executed on any "activity":
+   // and in some piece of code that gets executed on any "activity":
-  // reset the timeout to start ticking again at 10 seconds
+   // reset the timeout to start ticking again at 10 seconds
-  ev_timer_again (&mytimer);
+   ev_timer_again (&mytimer);
 =head2 C<ev_periodic> - to cron or not to cron?
 Periodic watchers are also timers of a kind, but they are very versatile
 (and unfortunately a bit complex).
 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
+but on wall clock time (absolute time). You can tell a periodic watcher
-to trigger "at" some specific point in time. For example, if you tell a
+to trigger after 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 specifying e.g. C<ev_now ()
-+ 10.>) and then reset your system clock to the last year, then it will
++ 10.>, that is, an absolute time not a delay) and then reset your system
+clock to January of the previous year, then it will take more than year
-take a year to trigger the event (unlike an C<ev_timer>, which would trigger
+to trigger the event (unlike an C<ev_timer>, which would still trigger
-roughly 10 seconds later).
+roughly 10 seconds later as it uses a relative timeout).
-They can also be used to implement vastly more complex timers, such as
+C<ev_periodic>s can also be used to implement vastly more complex timers,
-triggering an event on each midnight, local time or other, complicated,
+such as triggering an event on each "midnight, local time", or other
-rules.
+complicated rules.
-As with timers, the callback is guarenteed to be invoked only when the
+As with timers, the callback is guaranteed to be invoked only when the
-time (C<at>) has been passed, but if multiple periodic timers become ready
+time (C<at>) has passed, but if multiple periodic timers become ready
-during the same loop iteration then order of execution is undefined.
+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)
 =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
 Lots of arguments, lets sort it out... There are basically three modes of
-operation, and we will explain them from simplest to complex:
+operation, and we will explain them from simplest to most complex:
 =over 4
 =item * absolute timer (at = time, interval = reschedule_cb = 0)
-In this configuration the watcher triggers an event at the wallclock time
+In this configuration the watcher triggers an event after the wall clock
-C<at> and doesn't repeat. It will not adjust when a time jump occurs,
+time C<at> has passed. It will not repeat and will not adjust when a time
-that is, if it is to be run at January 1st 2011 then it will run when the
+jump occurs, that is, if it is to be run at January 1st 2011 then it will
-system time reaches or surpasses this time.
+only run when the system clock reaches or surpasses this time.
 =item * 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
 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
+This can be used to create timers that do not drift with respect to the
-time:
+system clock, for example, here is a C<ev_periodic> that triggers each
+hour, on the hour:
    ev_periodic_set (&periodic, 0., 3600., 0);
 This doesn't mean there will always be 3600 seconds in between triggers,
-but only that the the callback will be called when the system time shows a
+but only that the callback will be called when the system time shows a
 full hour (UTC), or more correctly, when the system time is evenly divisible
 by 3600.
 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.
 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.
+this value, and in fact is often specified as zero.
+Note also that there is an upper limit to how often a timer can fire (CPU
+speed for example), so if C<interval> is very small then timing stability
+will of course deteriorate. Libev itself tries to be exact to be about one
+millisecond (if the OS supports it and the machine is fast enough).
 =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
 reschedule callback will be called with the watcher as first, and the
 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,
+ever, or make ANY event loop modifications whatsoever>.
-return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
-starting an C<ev_prepare> watcher, which is legal).
+If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
+it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
+only event loop modification you are allowed to do).
-Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
+The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
-ev_tstamp now)>, e.g.:
+*w, ev_tstamp now)>, e.g.:
+   static ev_tstamp
-   static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
+   my_rescheduler (ev_periodic *w, ev_tstamp now)
    {
      return now + 60.;
    }
 It must return the next time to trigger, based on the passed time value
 (that is, the lowest time value larger than to the second argument). It
 will usually be called just before the callback will be triggered, but
 might be called at other times, too.
-NOTE: I<< This callback must always return a time that is later than the
+NOTE: I<< This callback must always return a time that is higher than or
-passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.
+equal to the passed C<now> value >>.
 This can be used to create very complex timers, such as a timer that
-triggers on each midnight, local time. To do this, you would calculate the
+triggers on "next midnight, local time". To do this, you would calculate the
 next midnight after C<now> and return the timestamp value for this. How
 you do this is, again, up to you (but it is not trivial, which is the main
 reason I omitted it as an example).
 =back
 The current interval value. Can be modified any time, but changes only
 take effect when the periodic timer fires or C<ev_periodic_again> is being
 called.
-=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
+=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
 The current reschedule callback, or C<0>, if this functionality is
 switched off. Can be changed any time, but changes only take effect when
 the periodic timer fires or C<ev_periodic_again> is being called.
 =back
 =head3 Examples
 Example: Call a callback every hour, or, more precisely, whenever the
-system clock is divisible by 3600. The callback invocation times have
+system time is divisible by 3600. The callback invocation times have
-potentially a lot of jittering, but good long-term stability.
+potentially a lot of jitter, but good long-term stability.
-  static void
+   static void
-  clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
+   clock_cb (struct ev_loop *loop, ev_io *w, int revents)
-  {
+   {
-    ... its now a full hour (UTC, or TAI or whatever your clock follows)
+     ... its now a full hour (UTC, or TAI or whatever your clock follows)
-  }
+   }
-  struct ev_periodic hourly_tick;
+   ev_periodic hourly_tick;
-  ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
+   ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
-  ev_periodic_start (loop, &hourly_tick);
+   ev_periodic_start (loop, &hourly_tick);
 Example: The same as above, but use a reschedule callback to do it:
-  #include <math.h>
+   #include <math.h>
-  static ev_tstamp
+   static ev_tstamp
-  my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
+   my_scheduler_cb (ev_periodic *w, ev_tstamp now)
-  {
+   {
-    return fmod (now, 3600.) + 3600.;
+     return now + (3600. - fmod (now, 3600.));
-  }
+   }
-  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:
-  struct ev_periodic hourly_tick;
+   ev_periodic hourly_tick;
-  ev_periodic_init (&hourly_tick, clock_cb,
+   ev_periodic_init (&hourly_tick, clock_cb,
-                    fmod (ev_now (loop), 3600.), 3600., 0);
+                     fmod (ev_now (loop), 3600.), 3600., 0);
-  ev_periodic_start (loop, &hourly_tick);
+   ev_periodic_start (loop, &hourly_tick);
 =head2 C<ev_signal> - signal me when a signal gets signalled!
 Signal watchers will trigger an event when the process receives a specific
 signal one or more times. Even though signals are very asynchronous, libev
 will try it's best to deliver signals synchronously, i.e. as part of the
 normal event processing, like any other event.
+If you want signals asynchronously, just use C<sigaction> as you would
+do without libev and forget about sharing the signal. You can even use
+C<ev_async> from a signal handler to synchronously wake up an event loop.
 You can configure as many watchers as you like per signal. Only when the
-first watcher gets started will libev actually register a signal watcher
+first watcher gets started will libev actually register a signal handler
-with the kernel (thus it coexists with your own signal handlers as long
+with the kernel (thus it coexists with your own signal handlers as long as
-as you don't register any with libev). Similarly, when the last signal
+you don't register any with libev for the same signal). Similarly, when
-watcher for a signal is stopped libev will reset the signal handler to
+the last signal watcher for a signal is stopped, libev will reset the
-SIG_DFL (regardless of what it was set to before).
+signal handler to SIG_DFL (regardless of what it was set to before).
 If possible and supported, libev will install its handlers with
-C<SA_RESTART> behaviour enabled, so syscalls should not be unduly
+C<SA_RESTART> behaviour enabled, so system calls should not be unduly
-interrupted. If you have a problem with syscalls getting interrupted by
+interrupted. If you have a problem with system calls getting interrupted by
 signals you can block all signals in an C<ev_check> watcher and unblock
 them in an C<ev_prepare> watcher.
 =head3 Watcher-Specific Functions and Data Members
 =back
 =head3 Examples
-Example: Try to exit cleanly on SIGINT and SIGTERM.
+Example: Try to exit cleanly on SIGINT.
-  static void
+   static void
-  sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
+   sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
-  {
+   {
-    ev_unloop (loop, EVUNLOOP_ALL);
+     ev_unloop (loop, EVUNLOOP_ALL);
-  }
+   }
-  struct ev_signal signal_watcher;
+   ev_signal signal_watcher;
-  ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
+   ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
-  ev_signal_start (loop, &sigint_cb);
+   ev_signal_start (loop, &signal_watcher);
 =head2 C<ev_child> - watch out for process status changes
 Child watchers trigger when your process receives a SIGCHLD in response to
-some child status changes (most typically when a child of yours dies). It
+some child status changes (most typically when a child of yours dies or
-is permissible to install a child watcher I<after> the child has been
+exits). It is permissible to install a child watcher I<after> the child
-forked (which implies it might have already exited), as long as the event
+has been forked (which implies it might have already exited), as long
-loop isn't entered (or is continued from a watcher).
+as the event loop isn't entered (or is continued from a watcher), i.e.,
+forking and then immediately registering a watcher for the child is fine,
+but forking and registering a watcher a few event loop iterations later is
+not.
 Only the default event loop is capable of handling signals, and therefore
-you can only rgeister child watchers in the default event loop.
+you can only register child watchers in the default event loop.
 =head3 Process Interaction
 Libev grabs C<SIGCHLD> as soon as the default event loop is
 initialised. This is necessary to guarantee proper behaviour even if
-the first child watcher is started after the child exits. The occurance
+the first child watcher is started after the child exits. The occurrence
 of C<SIGCHLD> is recorded asynchronously, but child reaping is done
 synchronously as part of the event loop processing. Libev always reaps all
 children, even ones not watched.
 =head3 Overriding the Built-In Processing
 handler, you can override it easily by installing your own handler for
 C<SIGCHLD> after initialising the default loop, and making sure the
 default loop never gets destroyed. You are encouraged, however, to use an
 event-based approach to child reaping and thus use libev's support for
 that, so other libev users can use C<ev_child> watchers freely.
+=head3 Stopping the Child Watcher
+Currently, the child watcher never gets stopped, even when the
+child terminates, so normally one needs to stop the watcher in the
+callback. Future versions of libev might stop the watcher automatically
+when a child exit is detected.
 =head3 Watcher-Specific Functions and Data Members
 =over 4
 =head3 Examples
 Example: C<fork()> a new process and install a child handler to wait for
 its completion.
-  ev_child cw;
+   ev_child cw;
-  static void
+   static void
-  child_cb (EV_P_ struct ev_child *w, int revents)
+   child_cb (EV_P_ ev_child *w, int revents)
-  {
+   {
-    ev_child_stop (EV_A_ w);
+     ev_child_stop (EV_A_ w);
-    printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
+     printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
-  }
+   }
-  pid_t pid = fork ();
+   pid_t pid = fork ();
-  if (pid < 0)
+   if (pid < 0)
-    // error
+     // error
-  else if (pid == 0)
+   else if (pid == 0)
-    {
+     {
-      // the forked child executes here
+       // the forked child executes here
-      exit (1);
+       exit (1);
-    }
+     }
-  else
+   else
-    {
+     {
-      ev_child_init (&cw, child_cb, pid, 0);
+       ev_child_init (&cw, child_cb, pid, 0);
-      ev_child_start (EV_DEFAULT_ &cw);
+       ev_child_start (EV_DEFAULT_ &cw);
-    }
+     }
 =head2 C<ev_stat> - did the file attributes just change?
-This watches a filesystem path for attribute changes. That is, it calls
+This watches a file system path for attribute changes. That is, it calls
 C<stat> regularly (or when the OS says it changed) and sees if it changed
 compared to the last time, invoking the callback if it did.
 The path does not need to exist: changing from "path exists" to "path does
 not exist" is a status change like any other. The condition "path does
 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 kernel interface to do this, the portable
-calls C<stat (2)> regularly on the path to see if it changed somehow. You
+implementation simply calls C<stat (2)> regularly on the path to see if
-can specify a recommended polling interval for this case. If you specify
+it changed somehow. You can specify a recommended polling interval for
-a polling interval of C<0> (highly recommended!) then a I<suitable,
+this case. If you specify a polling interval of C<0> (highly recommended!)
-unspecified default> value will be used (which you can expect to be around
+then a I<suitable, unspecified default> value will be used (which
-five seconds, although this might change dynamically). Libev will also
+you can expect to be around five seconds, although this might change
-impose a minimum interval which is currently around C<0.1>, but thats
+dynamically). Libev will also impose a minimum interval which is currently
-usually overkill.
+around C<0.1>, but thats usually overkill.
 This watcher type is not meant for massive numbers of stat watchers,
 as even with OS-supported change notifications, this can be
 resource-intensive.
-At the time of this writing, only the Linux inotify interface is
+At the time of this writing, the only OS-specific interface implemented
-implemented (implementing kqueue support is left as an exercise for the
+is the Linux inotify interface (implementing kqueue support is left as
-reader, note, however, that the author sees no way of implementing ev_stat
+an exercise for the reader. Note, however, that the author sees no way
-semantics with kqueue). Inotify will be used to give hints only and should
+of implementing C<ev_stat> semantics with kqueue).
-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 ABI Issues (Largefile Support)
 Libev by default (unless the user overrides this) uses the default
-compilation environment, which means that on systems with optionally
+compilation environment, which means that on systems with large file
-disabled large file support, you get the 32 bit version of the stat
+support disabled by default, you get the 32 bit version of the stat
 structure. When using the library from programs that change the ABI to
 use 64 bit file offsets the programs will fail. In that case you have to
 compile libev with the same flags to get binary compatibility. This is
 obviously the case with any flags that change the ABI, but the problem is
-most noticably with ev_stat and largefile support.
+most noticeably disabled with ev_stat and large file support.
-=head3 Inotify
+The solution for this is to lobby your distribution maker to make large
+file interfaces available by default (as e.g. FreeBSD does) and not
+optional. Libev cannot simply switch on large file support because it has
+to exchange stat structures with application programs compiled using the
+default compilation environment.
+=head3 Inotify and Kqueue
-When C<inotify (7)> support has been compiled into libev (generally only
+When C<inotify (7)> support has been compiled into libev (generally
+only available with Linux 2.6.25 or above due to bugs in earlier
-available on Linux) and present at runtime, it will be used to speed up
+implementations) and present at runtime, it will be used to speed up
-change detection where possible. The inotify descriptor will be created lazily
+change detection where possible. The inotify descriptor will be created
-when the first C<ev_stat> watcher is being started.
+lazily when the first C<ev_stat> watcher is being started.
 Inotify presence does not change the semantics of C<ev_stat> watchers
 except that changes might be detected earlier, and in some cases, to avoid
 making regular C<stat> calls. Even in the presence of inotify support
-there are many cases where libev has to resort to regular C<stat> polling.
+there are many cases where libev has to resort to regular C<stat> polling,
+but as long as the path exists, libev usually gets away without polling.
-(There is no support for kqueue, as apparently it cannot be used to
+There is no support for kqueue, as apparently it cannot be used to
 implement this functionality, due to the requirement of having a file
-descriptor open on the object at all times).
+descriptor open on the object at all times, and detecting renames, unlinks
+etc. is difficult.
 =head3 The special problem of stat time resolution
-The C<stat ()> syscall only supports full-second resolution portably, and
+The C<stat ()> system call only supports full-second resolution portably, and
-even on systems where the resolution is higher, many filesystems still
+even on systems where the resolution is higher, most file systems still
 only support whole seconds.
 That means that, if the time is the only thing that changes, you can
 easily miss updates: on the first update, C<ev_stat> detects a change and
 calls your callback, which does something. When there is another update
-within the same second, C<ev_stat> will be unable to detect it as the stat
+within the same second, C<ev_stat> will be unable to detect unless the
-data does not change.
+stat data does change in other ways (e.g. file size).
 The solution to this is to delay acting on a change for slightly more
-than second (or till slightly after the next full second boundary), using
+than a second (or till slightly after the next full second boundary), using
 a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
 ev_timer_again (loop, w)>).
 The C<.02> offset is added to work around small timing inconsistencies
 of some operating systems (where the second counter of the current time
 C<path>. The C<interval> is a hint on how quickly a change is expected to
 be detected and should normally be specified as C<0> to let libev choose
 a suitable value. The memory pointed to by C<path> must point to the same
 path for as long as the watcher is active.
-The callback will receive C<EV_STAT> when a change was detected, relative
+The callback will receive an C<EV_STAT> event when a change was detected,
-to the attributes at the time the watcher was started (or the last change
+relative to the attributes at the time the watcher was started (or the
-was detected).
+last change was detected).
 =item ev_stat_stat (loop, ev_stat *)
 Updates the stat buffer immediately with new values. If you change the
 watched path in your callback, you could call this function to avoid
 The specified interval.
 =item const char *path [read-only]
-The filesystem path that is being watched.
+The file system path that is being watched.
 =back
 =head3 Examples
 Example: Watch C</etc/passwd> for attribute changes.
-  static void
+   static void
-  passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
+   passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
-  {
+   {
-    /* /etc/passwd changed in some way */
+     /* /etc/passwd changed in some way */
-    if (w->attr.st_nlink)
+     if (w->attr.st_nlink)
-      {
+       {
-        printf ("passwd current size  %ld\n", (long)w->attr.st_size);
+         printf ("passwd current size  %ld\n", (long)w->attr.st_size);
-        printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
+         printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
-        printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
+         printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
-      }
+       }
-    else
+     else
-      /* you shalt not abuse printf for puts */
+       /* you shalt not abuse printf for puts */
-      puts ("wow, /etc/passwd is not there, expect problems. "
+       puts ("wow, /etc/passwd is not there, expect problems. "
-            "if this is windows, they already arrived\n");
+             "if this is windows, they already arrived\n");
-  }
+   }
-  ...
+   ...
-  ev_stat passwd;
+   ev_stat passwd;
-  ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
+   ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
-  ev_stat_start (loop, &passwd);
+   ev_stat_start (loop, &passwd);
 Example: Like above, but additionally use a one-second delay so we do not
 miss updates (however, frequent updates will delay processing, too, so
 one might do the work both on C<ev_stat> callback invocation I<and> on
 C<ev_timer> callback invocation).
-  static ev_stat passwd;
+   static ev_stat passwd;
-  static ev_timer timer;
+   static ev_timer timer;
-  static void
+   static void
-  timer_cb (EV_P_ ev_timer *w, int revents)
+   timer_cb (EV_P_ ev_timer *w, int revents)
-  {
+   {
-    ev_timer_stop (EV_A_ w);
+     ev_timer_stop (EV_A_ w);
-    /* now it's one second after the most recent passwd change */
+     /* now it's one second after the most recent passwd change */
-  }
+   }
-  static void
+   static void
-  stat_cb (EV_P_ ev_stat *w, int revents)
+   stat_cb (EV_P_ ev_stat *w, int revents)
-  {
+   {
-    /* reset the one-second timer */
+     /* reset the one-second timer */
-    ev_timer_again (EV_A_ &timer);
+     ev_timer_again (EV_A_ &timer);
-  }
+   }
-  ...
+   ...
-  ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
+   ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
-  ev_stat_start (loop, &passwd);
+   ev_stat_start (loop, &passwd);
-  ev_timer_init (&timer, timer_cb, 0., 1.02);
+   ev_timer_init (&timer, timer_cb, 0., 1.02);
 =head2 C<ev_idle> - when you've got nothing better to do...
 Idle watchers trigger events when no other events of the same or higher
-priority are pending (prepare, check and other idle watchers do not
+priority are pending (prepare, check and other idle watchers do not count
-count).
+as receiving "events").
 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
 =head3 Examples
 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
+   static void
-  idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
+   idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
-  {
+   {
-    free (w);
+     free (w);
-    // now do something you wanted to do when the program has
+     // now do something you wanted to do when the program has
-    // no longer anything immediate to do.
+     // no longer anything immediate to do.
-  }
+   }
-  struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
+   ev_idle *idle_watcher = malloc (sizeof (ev_idle));
-  ev_idle_init (idle_watcher, idle_cb);
+   ev_idle_init (idle_watcher, idle_cb);
-  ev_idle_start (loop, 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 and check watchers are usually (but not always) used in pairs:
 prepare watchers get invoked before the process blocks and check watchers
 afterwards.
 You I<must not> call C<ev_loop> or similar functions that enter
 the current event loop from either C<ev_prepare> or C<ev_check>
 those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
 C<ev_check> so if you have one watcher of each kind they will always be
 called in pairs bracketing the blocking call.
 Their main purpose is to integrate other event mechanisms into libev and
-their use is somewhat advanced. This could be used, for example, to track
+their use is somewhat advanced. They could be used, for example, to track
 variable changes, implement your own watchers, integrate net-snmp or a
 coroutine library and lots more. They are also occasionally useful if
 you cache some data and want to flush it before blocking (for example,
 in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
 watcher).
-This is done by examining in each prepare call which file descriptors need
+This is done by examining in each prepare call which file descriptors
-to be watched by the other library, registering C<ev_io> watchers for
+need to be watched by the other library, registering C<ev_io> watchers
-them and starting an C<ev_timer> watcher for any timeouts (many libraries
+for them and starting an C<ev_timer> watcher for any timeouts (many
-provide just this functionality). Then, in the check watcher you check for
+libraries provide exactly this functionality). Then, in the check watcher,
-any events that occured (by checking the pending status of all watchers
+you check for any events that occurred (by checking the pending status
-and stopping them) and call back into the library. The I/O and timer
+of all watchers and stopping them) and call back into the library. The
-callbacks will never actually be called (but must be valid nevertheless,
+I/O and timer callbacks will never actually be called (but must be valid
-because you never know, you know?).
+nevertheless, because you never know, you know?).
 As another example, the Perl Coro module uses these hooks to integrate
 coroutines into libev programs, by yielding to other active coroutines
 during each prepare and only letting the process block if no coroutines
 are ready to run (it's actually more complicated: it only runs coroutines
 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 (this doesn't matter for C<ev_prepare> watchers).
-after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
+Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
-too) should not activate ("feed") events into libev. While libev fully
+activate ("feed") events into libev. While libev fully supports this, they
-supports this, they might get executed before other C<ev_check> watchers
+might get executed before other C<ev_check> watchers did their job. As
-did their job. As C<ev_check> watchers are often used to embed other
+C<ev_check> watchers are often used to embed other (non-libev) event
-(non-libev) event loops those other event loops might be in an unusable
+loops those other event loops might be in an unusable state until their
-state until their C<ev_check> watcher ran (always remind yourself to
+C<ev_check> watcher ran (always remind yourself to coexist peacefully with
-coexist peacefully with others).
+others).
 =head3 Watcher-Specific Functions and Data Members
 =over 4
 =item ev_check_init (ev_check *, callback)
 Initialises and configures the prepare or check watcher - they have no
 parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
-macros, but using them is utterly, utterly and completely pointless.
+macros, but using them is utterly, utterly, utterly and completely
+pointless.
 =back
 =head3 Examples
 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_io iow [nfd];
-  static ev_timer tw;
+   static ev_timer tw;
-  static void
+   static void
-  io_cb (ev_loop *loop, ev_io *w, int revents)
+   io_cb (struct ev_loop *loop, ev_io *w, int revents)
-  {
+   {
-  }
+   }
-  // create io watchers for each fd and a timer before blocking
+   // create io watchers for each fd and a timer before blocking
-  static void
+   static void
-  adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
+   adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
-  {
+   {
-    int timeout = 3600000;
+     int timeout = 3600000;
-    struct pollfd fds [nfd];
+     struct pollfd fds [nfd];
-    // actual code will need to loop here and realloc etc.
+     // actual code will need to loop here and realloc etc.
-    adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
+     adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
-    /* the callback is illegal, but won't be called as we stop during check */
+     /* the callback is illegal, but won't be called as we stop during check */
-    ev_timer_init (&tw, 0, timeout * 1e-3);
+     ev_timer_init (&tw, 0, timeout * 1e-3);
-    ev_timer_start (loop, &tw);
+     ev_timer_start (loop, &tw);
-    // create one ev_io per pollfd
+     // create one ev_io per pollfd
-    for (int i = 0; i < nfd; ++i)
+     for (int i = 0; i < nfd; ++i)
-      {
+       {
-        ev_io_init (iow + i, io_cb, fds [i].fd,
+         ev_io_init (iow + i, io_cb, fds [i].fd,
-          ((fds [i].events & POLLIN ? EV_READ : 0)
+           ((fds [i].events & POLLIN ? EV_READ : 0)
-           | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
+            | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
-        fds [i].revents = 0;
+         fds [i].revents = 0;
-        ev_io_start (loop, iow + i);
+         ev_io_start (loop, iow + i);
-      }
+       }
-  }
+   }
-  // stop all watchers after blocking
+   // stop all watchers after blocking
-  static void
+   static void
-  adns_check_cb (ev_loop *loop, ev_check *w, int revents)
+   adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
-  {
+   {
-    ev_timer_stop (loop, &tw);
+     ev_timer_stop (loop, &tw);
-    for (int i = 0; i < nfd; ++i)
+     for (int i = 0; i < nfd; ++i)
-      {
+       {
-        // set the relevant poll flags
+         // set the relevant poll flags
-        // could also call adns_processreadable etc. here
+         // could also call adns_processreadable etc. here
-        struct pollfd *fd = fds + i;
+         struct pollfd *fd = fds + i;
-        int revents = ev_clear_pending (iow + i);
+         int revents = ev_clear_pending (iow + i);
-        if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
+         if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
-        if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
+         if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
-        // now stop the watcher
+         // now stop the watcher
-        ev_io_stop (loop, iow + i);
+         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
+notification (libadns does), you can also make use of the actual watcher
 callbacks, and only destroy/create the watchers in the prepare watcher.
-  static void
+   static void
-  timer_cb (EV_P_ ev_timer *w, int revents)
+   timer_cb (EV_P_ ev_timer *w, int revents)
-  {
+   {
-    adns_state ads = (adns_state)w->data;
+     adns_state ads = (adns_state)w->data;
-    update_now (EV_A);
+     update_now (EV_A);
-    adns_processtimeouts (ads, &tv_now);
+     adns_processtimeouts (ads, &tv_now);
-  }
+   }
-  static void
+   static void
-  io_cb (EV_P_ ev_io *w, int revents)
+   io_cb (EV_P_ ev_io *w, int revents)
-  {
+   {
-    adns_state ads = (adns_state)w->data;
+     adns_state ads = (adns_state)w->data;
-    update_now (EV_A);
+     update_now (EV_A);
-    if (revents & EV_READ ) adns_processreadable  (ads, w->fd, &tv_now);
+     if (revents & EV_READ ) adns_processreadable  (ads, w->fd, &tv_now);
-    if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
+     if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
-  }
+   }
-  // do not ever call adns_afterpoll
+   // 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
+want to embed is not flexible enough to support it. Instead, you can
-their poll function.  The drawback with this solution is that the main
+override their poll function. The drawback with this solution is that the
-loop is now no longer controllable by EV. The C<Glib::EV> module does
+main loop is now no longer controllable by EV. The C<Glib::EV> module uses
-this.
+this approach, effectively embedding EV as a client into the horrible
+libglib event loop.
-  static gint
+   static gint
-  event_poll_func (GPollFD *fds, guint nfds, gint timeout)
+   event_poll_func (GPollFD *fds, guint nfds, gint timeout)
-  {
+   {
-    int got_events = 0;
+     int got_events = 0;
-    for (n = 0; n < nfds; ++n)
+     for (n = 0; n < nfds; ++n)
-      // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
+       // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
-    if (timeout >= 0)
+     if (timeout >= 0)
-      // create/start timer
+       // create/start timer
-    // poll
+     // poll
-    ev_loop (EV_A_ 0);
+     ev_loop (EV_A_ 0);
-    // stop timer again
+     // stop timer again
-    if (timeout >= 0)
+     if (timeout >= 0)
-      ev_timer_stop (EV_A_ &to);
+       ev_timer_stop (EV_A_ &to);
-    // stop io watchers again - their callbacks should have set
+     // stop io watchers again - their callbacks should have set
-    for (n = 0; n < nfds; ++n)
+     for (n = 0; n < nfds; ++n)
-      ev_io_stop (EV_A_ iow [n]);
+       ev_io_stop (EV_A_ iow [n]);
-    return got_events;
+     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
 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
+so nicely. In this case, you would create a kqueue-based loop and embed
-into your default loop (which might use e.g. poll). Overall operation will
+it into your default loop (which might use e.g. poll). Overall operation
-be a bit slower because first libev has to poll and then call kevent, but
+will be a bit slower because first libev has to call C<poll> and then
-at least you can use both at what they are best.
+C<kevent>, but at least you can use both mechanisms for what they are
+best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
-As for prioritising I/O: rarely you have the case where some fds have
+As for prioritising I/O: under rare circumstances you have the case where
-to be watched and handled very quickly (with low latency), and even
+some fds have to be watched and handled very quickly (with low latency),
-priorities and idle watchers might have too much overhead. In this case
+and even priorities and idle watchers might have too much overhead. In
-you would put all the high priority stuff in one loop and all the rest in
+this case you would put all the high priority stuff in one loop and all
-a second one, and embed the second one in the first.
+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
 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.
+yourself - but you can use a fork watcher to handle this automatically,
+and future versions of libev might do just that.
-Unfortunately, not all backends are embeddable, only the ones returned by
+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.
+=head3 C<ev_embed> and fork
+While the C<ev_embed> watcher is running, forks in the embedding loop will
+automatically be applied to the embedded loop as well, so no special
+fork handling is required in that case. When the watcher is not running,
+however, it is still the task of the libev user to call C<ev_loop_fork ()>
+as applicable.
 =head3 Watcher-Specific Functions and Data Members
 =over 4
 =item ev_embed_init (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).
+if you do not want that, 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.
+appropriate way for embedded loops.
 =item struct ev_loop *other [read-only]
 The embedded event loop.
 =head3 Examples
 Example: Try to get an embeddable event loop and embed it into the default
 event loop. If that is not possible, use the default loop. The default
-loop is stored in C<loop_hi>, while the mebeddable loop is stored in
+loop is stored in C<loop_hi>, while the embeddable loop is stored in
-C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
+C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
 used).
-  struct ev_loop *loop_hi = ev_default_init (0);
+   struct ev_loop *loop_hi = ev_default_init (0);
-  struct ev_loop *loop_lo = 0;
+   struct ev_loop *loop_lo = 0;
-  struct ev_embed embed;
+   ev_embed embed;
-  // see if there is a chance of getting one that works
+   // see if there is a chance of getting one that works
-  // (remember that a flags value of 0 means autodetection)
+   // (remember that a flags value of 0 means autodetection)
-  loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
+   loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
-    ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
+     ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
-    : 0;
+     : 0;
-  // if we got one, then embed it, otherwise default to loop_hi
+   // if we got one, then embed it, otherwise default to loop_hi
-  if (loop_lo)
+   if (loop_lo)
-    {
+     {
-      ev_embed_init (&embed, 0, loop_lo);
+       ev_embed_init (&embed, 0, loop_lo);
-      ev_embed_start (loop_hi, &embed);
+       ev_embed_start (loop_hi, &embed);
-    }
+     }
-  else
+   else
-    loop_lo = loop_hi;
+     loop_lo = loop_hi;
 Example: Check if kqueue is available but not recommended and create
 a kqueue backend for use with sockets (which usually work with any
 kqueue implementation). Store the kqueue/socket-only event loop in
 C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
-  struct ev_loop *loop = ev_default_init (0);
+   struct ev_loop *loop = ev_default_init (0);
-  struct ev_loop *loop_socket = 0;
+   struct ev_loop *loop_socket = 0;
-  struct ev_embed embed;
+   ev_embed embed;
-  if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
+   if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
-    if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
+     if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
-      {
+       {
-        ev_embed_init (&embed, 0, loop_socket);
+         ev_embed_init (&embed, 0, loop_socket);
-        ev_embed_start (loop, &embed);
+         ev_embed_start (loop, &embed);
-      }
+       }
-  if (!loop_socket)
+   if (!loop_socket)
-    loop_socket = loop;
+     loop_socket = loop;
-  // now use loop_socket for all sockets, and loop for everything else
+   // now use loop_socket for all sockets, and loop for everything else
 =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
 is that the author does not know of a simple (or any) algorithm for a
 multiple-writer-single-reader queue that works in all cases and doesn't
 need elaborate support such as pthreads.
 That means that if you want to queue data, you have to provide your own
-queue. But at least I can tell you would implement locking around your
+queue. But at least I can tell you how to implement locking around your
 queue:
 =over 4
 =item queueing from a signal handler context
 To implement race-free queueing, you simply add to the queue in the signal
-handler but you block the signal handler in the watcher callback. Here is an example that does that for
+handler but you block the signal handler in the watcher callback. Here is
-some fictitiuous SIGUSR1 handler:
+an example that does that for some fictitious SIGUSR1 handler:
    static ev_async mysig;
    static void
    sigusr1_handler (void)
 =item ev_async_init (ev_async *, callback)
 Initialises and configures the async watcher - it has no parameters of any
 kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
-believe me.
+trust me.
 =item ev_async_send (loop, ev_async *)
 Sends/signals/activates the given C<ev_async> watcher, that is, feeds
 an C<EV_ASYNC> event on the watcher into the event loop. Unlike
-C<ev_feed_event>, this call is safe to do in other threads, signal or
+C<ev_feed_event>, this call is safe to do from other threads, signal or
-similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
+similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
 section below on what exactly this means).
-This call incurs the overhead of a syscall only once per loop iteration,
+This call incurs the overhead of a system call only once per loop iteration,
-so while the overhead might be noticable, it doesn't apply to repeated
+so while the overhead might be noticeable, it doesn't apply to repeated
 calls to C<ev_async_send>.
 =item bool = ev_async_pending (ev_async *)
 Returns a non-zero value when C<ev_async_send> has been called on the
 event loop.
 C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
 the loop iterates next and checks for the watcher to have become active,
 it will reset the flag again. C<ev_async_pending> can be used to very
-quickly check wether invoking the loop might be a good idea.
+quickly check whether invoking the loop might be a good idea.
-Not that this does I<not> check wether the watcher itself is pending, only
+Not that this does I<not> check whether the watcher itself is pending, only
-wether it has been requested to make this watcher pending.
+whether it has been requested to make this watcher pending.
 =back
 =head1 OTHER FUNCTIONS
 =over 4
 =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
 This function combines a simple timer and an I/O watcher, calls your
-callback on whichever event happens first and automatically stop both
+callback on whichever event happens first and automatically stops both
 watchers. This is useful if you want to wait for a single event on an fd
 or timeout without having to allocate/configure/start/stop/free one or
 more watchers yourself.
-If C<fd> is less than 0, then no I/O watcher will be started and events
+If C<fd> is less than 0, then no I/O watcher will be started and the
-is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
+C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
-C<events> set will be craeted and started.
+the given C<fd> and C<events> set will be created and started.
 If C<timeout> is less than 0, then no timeout watcher will be
 started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
-repeat = 0) will be started. While C<0> is a valid timeout, it is of
+repeat = 0) will be started. C<0> is a valid timeout.
-dubious value.
 The callback has the type C<void (*cb)(int revents, void *arg)> and gets
 passed an C<revents> set like normal event callbacks (a combination of
 C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
-value passed to C<ev_once>:
+value passed to C<ev_once>. Note that it is possible to receive I<both>
+a timeout and an io event at the same time - you probably should give io
+events precedence.
+Example: wait up to ten seconds for data to appear on STDIN_FILENO.
-  static void stdin_ready (int revents, void *arg)
+   static void stdin_ready (int revents, void *arg)
-  {
+   {
-    if (revents & EV_TIMEOUT)
-      /* doh, nothing entered */;
-    else if (revents & EV_READ)
+     if (revents & EV_READ)
-      /* stdin might have data for us, joy! */;
+       /* stdin might have data for us, joy! */;
+     else if (revents & EV_TIMEOUT)
+       /* doh, nothing entered */;
-  }
+   }
-  ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
+   ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
-=item ev_feed_event (ev_loop *, watcher *, int revents)
+=item ev_feed_event (struct ev_loop *, watcher *, int revents)
 Feeds the given event set into the event loop, as if the specified event
 had happened for the specified watcher (which must be a pointer to an
 initialised but not necessarily started event watcher).
-=item ev_feed_fd_event (ev_loop *, int fd, int revents)
+=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
 Feed an event on the given fd, as if a file descriptor backend detected
 the given events it.
-=item ev_feed_signal_event (ev_loop *loop, int signum)
+=item ev_feed_signal_event (struct ev_loop *loop, int signum)
-Feed an event as if the given signal occured (C<loop> must be the default
+Feed an event as if the given signal occurred (C<loop> must be the default
 loop!).
 =back
 =back
 =head1 C++ SUPPORT
 Libev comes with some simplistic wrapper classes for C++ that mainly allow
-you to use some convinience methods to start/stop watchers and also change
+you to use some convenience 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>
+   #include <ev++.h>
 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>.
 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
+   struct myclass
-  {
+   {
-    void io_cb (ev::io &w, int revents) { }
+     void io_cb (ev::io &w, int revents) { }
-  }
+   }
-  myclass obj;
+   myclass obj;
-  ev::io iow;
+   ev::io iow;
-  iow.set <myclass, &myclass::io_cb> (&obj);
+   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
 The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
 See the method-C<set> above for more details.
-Example:
+Example: Use a plain function as callback.
-  static void io_cb (ev::io &w, int revents) { }
+   static void io_cb (ev::io &w, int revents) { }
-  iow.set <io_cb> ();
+   iow.set <io_cb> ();
 =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])
+=item w->set ([arguments])
-Basically the same as C<ev_TYPE_set>, with the same args. Must be
+Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
 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 ()
 =back
 Example: Define a class with an IO and idle watcher, start one of them in
 the constructor.
-  class myclass
+   class myclass
-  {
+   {
-    ev::io   io;  void io_cb   (ev::io   &w, int revents);
+     ev::io   io  ; void io_cb   (ev::io   &w, int revents);
-    ev:idle idle  void idle_cb (ev::idle &w, int revents);
+     ev::idle idle; void idle_cb (ev::idle &w, int revents);
-    myclass (int fd)
+     myclass (int fd)
-    {
+     {
-      io  .set <myclass, &myclass::io_cb  > (this);
+       io  .set <myclass, &myclass::io_cb  > (this);
-      idle.set <myclass, &myclass::idle_cb> (this);
+       idle.set <myclass, &myclass::idle_cb> (this);
-      io.start (fd, ev::READ);
+       io.start (fd, ev::READ);
-    }
+     }
-  };
+   };
 =head1 OTHER LANGUAGE BINDINGS
 Libev does not offer other language bindings itself, but bindings for a
-numbe rof languages exist in the form of third-party packages. If you know
+number of languages exist in the form of third-party packages. If you know
 any interesting language binding in addition to the ones listed here, drop
 me a note.
 =over 4
 =item Perl
 The EV module implements the full libev API and is actually used to test
 libev. EV is developed together with libev. Apart from the EV core module,
 there are additional modules that implement libev-compatible interfaces
-to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
+to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
-C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
+C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
+and C<EV::Glib>).
-It can be found and installed via CPAN, its homepage is found at
+It can be found and installed via CPAN, its homepage is at
 L<http://software.schmorp.de/pkg/EV>.
+=item Python
+Python bindings can be found at L<http://code.google.com/p/pyev/>. It
+seems to be quite complete and well-documented. Note, however, that the
+patch they require for libev is outright dangerous as it breaks the ABI
+for everybody else, and therefore, should never be applied in an installed
+libev (if python requires an incompatible ABI then it needs to embed
+libev).
 =item Ruby
 Tony Arcieri has written a ruby extension that offers access to a subset
-of the libev API and adds filehandle abstractions, asynchronous DNS and
+of the libev API and adds file handle abstractions, asynchronous DNS and
 more on top of it. It can be found via gem servers. Its homepage is at
 L<http://rev.rubyforge.org/>.
 =item D
 Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
-be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.
+be found at L<http://proj.llucax.com.ar/wiki/evd>.
+=item Ocaml
+Erkki Seppala has written Ocaml bindings for libev, to be found at
+L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
 =back
 =head1 MACRO MAGIC
-Libev can be compiled with a variety of options, the most fundamantal
+Libev can be compiled with a variety of options, the most fundamental
 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:
 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_unref (EV_A);
-  ev_timer_add (EV_A_ watcher);
+   ev_timer_add (EV_A_ watcher);
-  ev_loop (EV_A_ 0);
+   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
+   // this is how ev_unref is being declared
-  static void ev_unref (EV_P);
+   static void ev_unref (EV_P);
-  // this is how you can declare your typical callback
+   // this is how you can declare your typical callback
-  static void cb (EV_P_ ev_timer *w, int revents)
+   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_>
 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
+   static void
-  check_cb (EV_P_ ev_timer *w, int revents)
+   check_cb (EV_P_ ev_timer *w, int revents)
-  {
+   {
-    ev_check_stop (EV_A_ w);
+     ev_check_stop (EV_A_ w);
-  }
+   }
-  ev_check check;
+   ev_check check;
-  ev_check_init (&check, check_cb);
+   ev_check_init (&check, check_cb);
-  ev_check_start (EV_DEFAULT_ &check);
+   ev_check_start (EV_DEFAULT_ &check);
-  ev_loop (EV_DEFAULT_ 0);
+   ev_loop (EV_DEFAULT_ 0);
 =head1 EMBEDDING
 Libev can (and often is) directly embedded into host
 applications. Examples of applications that embed it include the Deliantra
 libev somewhere in your source tree).
 =head2 FILESETS
 Depending on what features you need you need to include one or more sets of files
-in your app.
+in your application.
 =head3 CORE EVENT LOOP
 To include only the libev core (all the C<ev_*> functions), with manual
 configuration (no autoconf):
-  #define EV_STANDALONE 1
+   #define EV_STANDALONE 1
-  #include "ev.c"
+   #include "ev.c"
 This will automatically include F<ev.h>, too, and should be done in a
 single C source file only to provide the function implementations. To use
 it, do the same for F<ev.h> in all files wishing to use this API (best
 done by writing a wrapper around F<ev.h> that you can include instead and
 where you can put other configuration options):
-  #define EV_STANDALONE 1
+   #define EV_STANDALONE 1
-  #include "ev.h"
+   #include "ev.h"
 Both header files and implementation files can be compiled with a C++
 compiler (at least, thats a stated goal, and breakage will be treated
 as a bug).
 You need the following files in your source tree, or in a directory
 in your include path (e.g. in libev/ when using -Ilibev):
-  ev.h
+   ev.h
-  ev.c
+   ev.c
-  ev_vars.h
+   ev_vars.h
-  ev_wrap.h
+   ev_wrap.h
-  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 enabled 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_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_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_kqueue.c     only when the kqueue backend is enabled (disabled by default)
-  ev_port.c       only when the solaris port backend is enabled (disabled by default)
+   ev_port.c       only when the solaris port backend is enabled (disabled by default)
 F<ev.c> includes the backend files directly when enabled, so you only need
 to compile this single file.
 =head3 LIBEVENT COMPATIBILITY API
 To include the libevent compatibility API, also include:
-  #include "event.c"
+   #include "event.c"
 in the file including F<ev.c>, and:
-  #include "event.h"
+   #include "event.h"
 in the files that want to use the libevent API. This also includes F<ev.h>.
 You need the following additional files for this:
-  event.h
+   event.h
-  event.c
+   event.c
 =head3 AUTOCONF SUPPORT
-Instead of using C<EV_STANDALONE=1> and providing your config in
+Instead of using C<EV_STANDALONE=1> and providing your configuration in
 whatever way you want, you can also C<m4_include([libev.m4])> in your
 F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
 include F<config.h> and configure itself accordingly.
 For this of course you need the m4 file:
-  libev.m4
+   libev.m4
 =head2 PREPROCESSOR SYMBOLS/MACROS
 Libev can be configured via a variety of preprocessor symbols you have to
-define before including any of its files. The default in the absense of
+define before including any of its files. The default in the absence of
-autoconf is noted for every option.
+autoconf is documented for every option.
 =over 4
 =item EV_STANDALONE
 F<event.h> that are not directly supported by the libev core alone.
 =item EV_USE_MONOTONIC
 If defined to be C<1>, libev will try to detect the availability of the
-monotonic clock option at both compiletime and runtime. Otherwise no use
+monotonic clock option at both compile time 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, although you have
 to make sure you link against any libraries where the C<clock_gettime>
 function is hiding in (often F<-lrt>).
 =item EV_USE_REALTIME
 If defined to be C<1>, libev will try to detect the availability of the
-realtime clock option at compiletime (and assume its availability at
+real-time clock option at compile time (and assume its availability at
-runtime if successful). Otherwise no use of the realtime clock option will
+runtime if successful). Otherwise no use of the real-time clock option will
 be attempted. This effectively replaces C<gettimeofday> by C<clock_get
 (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
 2.7 or newer, otherwise disabled.
 =item EV_USE_SELECT
 If undefined or defined to be C<1>, libev will compile in support for the
-C<select>(2) backend. No attempt at autodetection will be done: if no
+C<select>(2) backend. No attempt at auto-detection will be done: if no
 other method takes over, select will be it. Otherwise the select backend
 will not be compiled in.
 =item EV_SELECT_USE_FD_SET
 If defined to C<1>, then the select backend will use the system C<fd_set>
 structure. This is useful if libev doesn't compile due to a missing
-C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on
+C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
 exotic systems. This usually limits the range of file descriptors to some
 low limit such as 1024 or might have other limitations (winsocket only
 allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
 influence the size of the C<fd_set> used.
 otherwise another method will be used as fallback. This is the preferred
 backend for Solaris 10 systems.
 =item EV_USE_DEVPOLL
-reserved for future expansion, works like the USE symbols above.
+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
 access is atomic with respect to other threads or signal contexts. No such
 type is easily found in the C language, so you can provide your own type
 that you know is safe for your purposes. It is used both for signal handler "locking"
 as well as for signal and thread safety in C<ev_async> watchers.
-In the absense of this define, libev will use C<sig_atomic_t volatile>
+In the absence of this define, libev will use C<sig_atomic_t volatile>
 (from F<signal.h>), which is usually good enough on most platforms.
 =item EV_H
 The name of the F<ev.h> header file used to include it. The default if
 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
+If your embedding application does not need any priorities, defining these
-C<0> will save some memory and cpu.
+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_EMBED_ENABLE
 If undefined or defined to be C<1>, then embed watchers are supported. If
-defined to be C<0>, then they are not.
+defined to be C<0>, then they are not. Embed watchers rely on most other
+watcher types, which therefore must not be disabled.
 =item EV_STAT_ENABLE
 If undefined or defined to be C<1>, then stat watchers are supported. If
 defined to be C<0>, then they are not.
 =item EV_MINIMAL
 If you need to shave off some kilobytes of code at the expense of some
 speed, define this symbol to C<1>. Currently this is used to override some
-inlining decisions, saves roughly 30% codesize of amd64. It also selects a
+inlining decisions, saves roughly 30% code size on amd64. It also selects a
 much smaller 2-heap for timer management over the default 4-heap.
 =item EV_PID_HASHSIZE
 C<ev_child> 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_USE_4HEAP
+Heaps are not very cache-efficient. To improve the cache-efficiency of the
+timer and periodics heaps, libev uses a 4-heap when this symbol is defined
+to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
+faster performance with many (thousands) of watchers.
+The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
+(disabled).
+=item EV_HEAP_CACHE_AT
+Heaps are not very cache-efficient. To improve the cache-efficiency of the
+timer and periodics heaps, libev can cache the timestamp (I<at>) within
+the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
+which uses 8-12 bytes more per watcher and a few hundred bytes more code,
+but avoids random read accesses on heap changes. This improves performance
+noticeably with many (hundreds) of watchers.
+The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
+(disabled).
+=item EV_VERIFY
+Controls how much internal verification (see C<ev_loop_verify ()>) will
+be done: If set to C<0>, no internal verification code will be compiled
+in. If set to C<1>, then verification code will be compiled in, but not
+called. If set to C<2>, then the internal verification code will be
+called once per loop, which can slow down libev. If set to C<3>, then the
+verification code will be called very frequently, which will slow down
+libev considerably.
+The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
+C<0>.
 =item EV_COMMON
 By default, all watchers have a C<void *data> member. By redefining
 this macro to a something else you can include more and other types of
 members. You have to define it each time you include one of the files,
 though, and it must be identical each time.
 For example, the perl EV module uses something like this:
-  #define EV_COMMON                       \
+   #define EV_COMMON                       \
-    SV *self; /* contains this struct */  \
+     SV *self; /* contains this struct */  \
-    SV *cb_sv, *fh /* note no trailing ";" */
+     SV *cb_sv, *fh /* note no trailing ";" */
 =item EV_CB_DECLARE (type)
 =item EV_CB_INVOKE (watcher, revents)
 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++.
+=back
 =head2 EXPORTED API SYMBOLS
-If you need to re-export the API (e.g. via a dll) and you need a list of
+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.ev      for libev proper
-  Symbols.event   for the libevent emulation
+   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).
+itself, but sometimes it is inconvenient 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
 file.
 The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
 that everybody includes and which overrides some configure choices:
-  #define EV_MINIMAL 1
+   #define EV_MINIMAL 1
-  #define EV_USE_POLL 0
+   #define EV_USE_POLL 0
-  #define EV_MULTIPLICITY 0
+   #define EV_MULTIPLICITY 0
-  #define EV_PERIODIC_ENABLE 0
+   #define EV_PERIODIC_ENABLE 0
-  #define EV_STAT_ENABLE 0
+   #define EV_STAT_ENABLE 0
-  #define EV_FORK_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_MINPRI 0
-  #define EV_MAXPRI 0
+   #define EV_MAXPRI 0
-  #include "ev++.h"
+   #include "ev++.h"
 And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
-  #include "ev_cpp.h"
+   #include "ev_cpp.h"
-  #include "ev.c"
+   #include "ev.c"
+=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
-=head1 THREADS AND COROUTINES
+=head2 THREADS AND COROUTINES
-=head2 THREADS
+=head3 THREADS
-Libev itself is completely threadsafe, but it uses no locking. This
+All libev functions are reentrant and thread-safe unless explicitly
+documented otherwise, but libev implements no locking itself. This means
-means that you can use as many loops as you want in parallel, as long as
+that you can use as many loops as you want in parallel, as long as there
-only one thread ever calls into one libev function with the same loop
+are no concurrent calls into any libev function with the same loop
-parameter.
+parameter (C<ev_default_*> calls have an implicit default loop parameter,
+of course): libev guarantees that different event loops share no data
+structures that need any locking.
-Or put differently: calls with different loop parameters can be done in
+Or to put it differently: calls with different loop parameters can be done
-parallel from multiple threads, calls with the same loop parameter must be
+concurrently from multiple threads, calls with the same loop parameter
-done serially (but can be done from different threads, as long as only one
+must be done serially (but can be done from different threads, as long as
-thread ever is inside a call at any point in time, e.g. by using a mutex
+only one thread ever is inside a call at any point in time, e.g. by using
-per loop).
+a mutex per loop).
-If you want to know which design is best for your problem, then I cannot
+Specifically to support threads (and signal handlers), libev implements
+so-called C<ev_async> watchers, which allow some limited form of
+concurrency on the same event loop, namely waking it up "from the
+outside".
+If you want to know which design (one loop, locking, or multiple loops
+without or something else still) is best for your problem, then I cannot
-help you but by giving some generic advice:
+help you, but here is some generic advice:
 =over 4
 =item * most applications have a main thread: use the default libev loop
-in that thread, or create a seperate thread running only the default loop.
+in that thread, or create a separate thread running only the default loop.
 This helps integrating other libraries or software modules that use libev
 themselves and don't care/know about threading.
 =item * one loop per thread is usually a good model.
 Doing this is almost never wrong, sometimes a better-performance model
 exists, but it is always a good start.
 =item * other models exist, such as the leader/follower pattern, where one
-loop is handed through multiple threads in a kind of round-robbin fashion.
+loop is handed through multiple threads in a kind of round-robin fashion.
-Chosing a model is hard - look around, learn, know that usually you cna do
+Choosing a model is hard - look around, learn, know that usually you can do
 better than you currently do :-)
 =item * often you need to talk to some other thread which blocks in the
+event loop.
-event loop - C<ev_async> watchers can be used to wake them up from other
+C<ev_async> watchers can be used to wake them up from other threads safely
-threads safely (or from signal contexts...).
+(or from signal contexts...).
+An example use would be to communicate signals or other events that only
+work in the default loop by registering the signal watcher with the
+default loop and triggering an C<ev_async> watcher from the default loop
+watcher callback into the event loop interested in the signal.
 =back
-=head2 COROUTINES
+=head3 COROUTINES
-Libev is much more accomodating to coroutines ("cooperative threads"):
+Libev is very accommodating to coroutines ("cooperative threads"):
-libev fully supports nesting calls to it's functions from different
+libev fully supports nesting calls to its functions from different
 coroutines (e.g. you can call C<ev_loop> on the same loop from two
-different coroutines and switch freely between both coroutines running the
+different coroutines, and switch freely between both coroutines running the
 loop, as long as you don't confuse yourself). The only exception is that
 you must not do this from C<ev_periodic> reschedule callbacks.
-Care has been invested into making sure that libev does not keep local
+Care has been taken to ensure that libev does not keep local state inside
-state inside C<ev_loop>, and other calls do not usually allow coroutine
+C<ev_loop>, and other calls do not usually allow for coroutine switches as
-switches.
+they do not clal any callbacks.
+=head2 COMPILER WARNINGS
-=head1 COMPLEXITIES
+Depending on your compiler and compiler settings, you might get no or a
+lot of warnings when compiling libev code. Some people are apparently
+scared by this.
-In this section the complexities of (many of) the algorithms used inside
+However, these are unavoidable for many reasons. For one, each compiler
-libev will be explained. For complexity discussions about backends see the
+has different warnings, and each user has different tastes regarding
-documentation for C<ev_default_init>.
+warning options. "Warn-free" code therefore cannot be a goal except when
+targeting a specific compiler and compiler-version.
-All of the following are about amortised time: If an array needs to be
+Another reason is that some compiler warnings require elaborate
-extended, libev needs to realloc and move the whole array, but this
+workarounds, or other changes to the code that make it less clear and less
-happens asymptotically never with higher number of elements, so O(1) might
+maintainable.
-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
+And of course, some compiler warnings are just plain stupid, or simply
+wrong (because they don't actually warn about the condition their message
+seems to warn about). For example, certain older gcc versions had some
+warnings that resulted an extreme number of false positives. These have
+been fixed, but some people still insist on making code warn-free with
+such buggy versions.
-=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
+While libev is written to generate as few warnings as possible,
+"warn-free" code is not a goal, and it is recommended not to build libev
+with any compiler warnings enabled unless you are prepared to cope with
+them (e.g. by ignoring them). Remember that warnings are just that:
+warnings, not errors, or proof of bugs.
-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 roughly seven (C<ld 100>) of these watchers.
-=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
+=head2 VALGRIND
-That means that changing a timer costs less than removing/adding them
+Valgrind has a special section here because it is a popular tool that is
-as only the relative motion in the event queue has to be paid for.
+highly useful. Unfortunately, valgrind reports are very hard to interpret.
-=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
+If you think you found a bug (memory leak, uninitialised data access etc.)
+in libev, then check twice: If valgrind reports something like:
-These just add the watcher into an array or at the head of a list.
+   ==2274==    definitely lost: 0 bytes in 0 blocks.
+   ==2274==      possibly lost: 0 bytes in 0 blocks.
+   ==2274==    still reachable: 256 bytes in 1 blocks.
-=item Stopping check/prepare/idle/fork/async watchers: O(1)
+Then there is no memory leak, just as memory accounted to global variables
+is not a memleak - the memory is still being refernced, and didn't leak.
-=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
+Similarly, under some circumstances, valgrind might report kernel bugs
+as if it were a bug in libev (e.g. in realloc or in the poll backend,
+although an acceptable workaround has been found here), or it might be
+confused.
-These watchers are stored in lists then need to be walked to find the
+Keep in mind that valgrind is a very good tool, but only a tool. Don't
-correct watcher to remove. The lists are usually short (you don't usually
+make it into some kind of religion.
-have many watchers waiting for the same fd or signal).
-=item Finding the next timer in each loop iteration: O(1)
+If you are unsure about something, feel free to contact the mailing list
+with the full valgrind report and an explanation on why you think this
+is a bug in libev (best check the archives, too :). However, don't be
+annoyed when you get a brisk "this is no bug" answer and take the chance
+of learning how to interpret valgrind properly.
-By virtue of using a binary or 4-heap, the next timer is always found at a
+If you need, for some reason, empty reports from valgrind for your project
-fixed position in the storage array.
+I suggest using suppression lists.
-=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
+=head1 PORTABILITY NOTES
-libev to recalculate its status (and possibly tell the kernel, depending
-on backend and wether C<ev_io_set> was used).
-=item Activating one watcher (putting it into the pending state): O(1)
+=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
-=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, but starting/stopping and activating
-watchers becomes O(1) w.r.t. priority handling.
-=item Sending an ev_async: O(1)
-=item Processing ev_async_send: O(number_of_async_watchers)
-=item Processing signals: O(max_signal_number)
-Sending involves a syscall I<iff> there were no other C<ev_async_send>
-calls in the current loop iteration. Checking for async and signal events
-involves iterating over all running async watchers or all signal numbers.
-=back
-=head1 Win32 platform limitations and workarounds
 Win32 doesn't support any of the standards (e.g. POSIX) that libev
 requires, and its I/O model is fundamentally incompatible with the POSIX
 model. Libev still offers limited functionality on this platform in
 the form of the C<EVBACKEND_SELECT> backend, and only supports socket
 way (note also that glib is the slowest event library known to man).
 There is no supported compilation method available on windows except
 embedding it into other applications.
+Not a libev limitation but worth mentioning: windows apparently doesn't
+accept large writes: instead of resulting in a partial write, windows will
+either accept everything or return C<ENOBUFS> if the buffer is too large,
+so make sure you only write small amounts into your sockets (less than a
+megabyte seems safe, but this apparently depends on the amount of memory
+available).
 Due to the many, low, and arbitrary limits on the win32 platform and
 the abysmal performance of winsockets, using a large number of sockets
 is not recommended (and not reasonable). If your program needs to use
 more than a hundred or so sockets, then likely it needs to use a totally
-different implementation for windows, as libev offers the POSIX readyness
+different implementation for windows, as libev offers the POSIX readiness
 notification model, which cannot be implemented efficiently on windows
-(microsoft monopoly games).
+(Microsoft monopoly games).
+A typical way to use libev under windows is to embed it (see the embedding
+section for details) and use the following F<evwrap.h> header file instead
+of F<ev.h>:
+   #define EV_STANDALONE              /* keeps ev from requiring config.h */
+   #define EV_SELECT_IS_WINSOCKET 1   /* configure libev for windows select */
+   #include "ev.h"
+And compile the following F<evwrap.c> file into your project (make sure
+you do I<not> compile the F<ev.c> or any other embedded source files!):
+   #include "evwrap.h"
+   #include "ev.c"
 =over 4
 =item The winsocket select function
-The winsocket C<select> function doesn't follow POSIX in that it requires
+The winsocket C<select> function doesn't follow POSIX in that it
-socket I<handles> and not socket I<file descriptors>. This makes select
+requires socket I<handles> and not socket I<file descriptors> (it is
-very inefficient, and also requires a mapping from file descriptors
+also extremely buggy). This makes select very inefficient, and also
-to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
+requires a mapping from file descriptors to socket handles (the Microsoft
-C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
+C runtime provides the function C<_open_osfhandle> for this). See the
-symbols for more info.
+discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
+C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
-The configuration for a "naked" win32 using the microsoft runtime
+The configuration for a "naked" win32 using the Microsoft runtime
 libraries and raw winsocket select is:
-  #define EV_USE_SELECT 1
+   #define EV_USE_SELECT 1
-  #define EV_SELECT_IS_WINSOCKET 1   /* forces EV_SELECT_USE_FD_SET, too */
+   #define EV_SELECT_IS_WINSOCKET 1   /* forces EV_SELECT_USE_FD_SET, too */
 Note that winsockets handling of fd sets is O(n), so you can easily get a
 complexity in the O(n²) range when using win32.
 =item Limited number of file descriptors
 Windows has numerous arbitrary (and low) limits on things.
 Early versions of winsocket's select only supported waiting for a maximum
 of C<64> handles (probably owning to the fact that all windows kernels
-can only wait for C<64> things at the same time internally; microsoft
+can only wait for C<64> things at the same time internally; Microsoft
 recommends spawning a chain of threads and wait for 63 handles and the
 previous thread in each. Great).
 Newer versions support more handles, but you need to define C<FD_SETSIZE>
 to some high number (e.g. C<2048>) before compiling the winsocket select
 call (which might be in libev or elsewhere, for example, perl does its own
 select emulation on windows).
-Another limit is the number of file descriptors in the microsoft runtime
+Another limit is the number of file descriptors in the Microsoft runtime
 libraries, which by default is C<64> (there must be a hidden I<64> fetish
-or something like this inside microsoft). You can increase this by calling
+or something like this inside Microsoft). You can increase this by calling
 C<_setmaxstdio>, which can increase this limit to C<2048> (another
-arbitrary limit), but is broken in many versions of the microsoft runtime
+arbitrary limit), but is broken in many versions of the Microsoft runtime
 libraries.
 This might get you to about C<512> or C<2048> sockets (depending on
 windows version and/or the phase of the moon). To get more, you need to
 wrap all I/O functions and provide your own fd management, but the cost of
 calling select (O(n²)) will likely make this unworkable.
 =back
-=head1 PORTABILITY REQUIREMENTS
+=head2 PORTABILITY REQUIREMENTS
-In addition to a working ISO-C implementation, libev relies on a few
+In addition to a working ISO-C implementation and of course the
-additional extensions:
+backend-specific APIs, libev relies on a few additional extensions:
 =over 4
+=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
+calling conventions regardless of C<ev_watcher_type *>.
+Libev assumes not only that all watcher pointers have the same internal
+structure (guaranteed by POSIX but not by ISO C for example), but it also
+assumes that the same (machine) code can be used to call any watcher
+callback: The watcher callbacks have different type signatures, but libev
+calls them using an C<ev_watcher *> internally.
 =item C<sig_atomic_t volatile> must be thread-atomic as well
 The type C<sig_atomic_t volatile> (or whatever is defined as
-C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
+C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
 threads. This is not part of the specification for C<sig_atomic_t>, but is
 believed to be sufficiently portable.
 =item C<sigprocmask> must work in a threaded environment
 except the initial one, and run the default loop in the initial thread as
 well.
 =item C<long> must be large enough for common memory allocation sizes
-To improve portability and simplify using libev, libev uses C<long>
+To improve portability and simplify its API, libev uses C<long> internally
-internally instead of C<size_t> when allocating its data structures. On
+instead of C<size_t> when allocating its data structures. On non-POSIX
-non-POSIX systems (Microsoft...) this might be unexpectedly low, but
+systems (Microsoft...) this might be unexpectedly low, but is still at
-is still at least 31 bits everywhere, which is enough for hundreds of
+least 31 bits everywhere, which is enough for hundreds of millions of
-millions of watchers.
+watchers.
 =item C<double> must hold a time value in seconds with enough accuracy
 The type C<double> is used to represent timestamps. It is required to
 have at least 51 bits of mantissa (and 9 bits of exponent), which is good
 =back
 If you know of other additional requirements drop me a note.
+=head1 ALGORITHMIC COMPLEXITIES
+In this section the complexities of (many of) the algorithms used inside
+libev will be documented. 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 rarer with higher number of elements, so O(1) might
+mean that libev does 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)
+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 roughly seven (C<ld 100>) of these watchers.
+=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
+That means that 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/fork/async watchers: O(1)
+These just add the watcher into an array or at the head of a list.
+=item Stopping check/prepare/idle/fork/async watchers: O(1)
+=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, so they 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: one is typical, two
+is rare).
+=item Finding the next timer in each loop iteration: O(1)
+By virtue of using a binary or 4-heap, the next timer is always found at a
+fixed position in the storage array.
+=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, depending
+on backend and whether C<ev_io_set> was used).
+=item Activating one watcher (putting it into the pending state): 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, but starting/stopping and activating
+watchers becomes O(1) with respect to priority handling.
+=item Sending an ev_async: O(1)
+=item Processing ev_async_send: O(number_of_async_watchers)
+=item Processing signals: O(max_signal_number)
+Sending involves a system call I<iff> there were no other C<ev_async_send>
+calls in the current loop iteration. Checking for async and signal events
+involves iterating over all running async watchers or all signal numbers.
+=back
 =head1 AUTHOR
 Marc Lehmann <libev@schmorp.de>.

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Revision 1.202 by root, Fri Oct 24 08:30:01 2008 UTC