[ViewVC] Diff of: cvs/libev/ev.3

Comparing libev/ev.3 (file contents):
Revision 1.23 by root, Tue Nov 27 08:20:42 2007 UTC vs.
Revision 1.62 by root, Sun Mar 16 16:38:23 2008 UTC

-.\" Automatically generated by Pod::Man v1.37, Pod::Parser v1.35
+.\" Automatically generated by Pod::Man 2.16 (Pod::Simple 3.05)
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-.IX Title ""<STANDARD INPUT>" 1"
+.IX Title "EV 1"
-.TH "<STANDARD INPUT>" 1 "2007-11-27" "perl v5.8.8" "User Contributed Perl Documentation"
+.TH EV 1 "2008-03-13" "perl v5.10.0" "User Contributed Perl Documentation"
+.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
+.\" way too many mistakes in technical documents.
+.if n .ad l
+.nh
 .SH "NAME"
 libev \- a high performance full\-featured event loop written in C
 .SH "SYNOPSIS"
 .IX Header "SYNOPSIS"
 .Vb 1
 \&  #include <ev.h>
 .Ve
+.Sh "\s-1EXAMPLE\s0 \s-1PROGRAM\s0"
+.IX Subsection "EXAMPLE PROGRAM"
+.Vb 2
+\&  // a single header file is required
+\&  #include <ev.h>
+\&
+\&  // every watcher type has its own typedef\*(Aqd struct
+\&  // with the name ev_<type>
+\&  ev_io stdin_watcher;
+\&  ev_timer timeout_watcher;
+\&
+\&  // all watcher callbacks have a similar signature
+\&  // this callback is called when data is readable on stdin
+\&  static void
+\&  stdin_cb (EV_P_ struct ev_io *w, int revents)
+\&  {
+\&    puts ("stdin ready");
+\&    // for one\-shot events, one must manually stop the watcher
+\&    // with its corresponding stop function.
+\&    ev_io_stop (EV_A_ w);
+\&
+\&    // this causes all nested ev_loop\*(Aqs to stop iterating
+\&    ev_unloop (EV_A_ EVUNLOOP_ALL);
+\&  }
+\&
+\&  // another callback, this time for a time\-out
+\&  static void
+\&  timeout_cb (EV_P_ struct ev_timer *w, int revents)
+\&  {
+\&    puts ("timeout");
+\&    // this causes the innermost ev_loop to stop iterating
+\&    ev_unloop (EV_A_ EVUNLOOP_ONE);
+\&  }
+\&
+\&  int
+\&  main (void)
+\&  {
+\&    // use the default event loop unless you have special needs
+\&    struct ev_loop *loop = ev_default_loop (0);
+\&
+\&    // initialise an io watcher, then start it
+\&    // this one will watch for stdin to become readable
+\&    ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
+\&    ev_io_start (loop, &stdin_watcher);
+\&
+\&    // initialise a timer watcher, then start it
+\&    // simple non\-repeating 5.5 second timeout
+\&    ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
+\&    ev_timer_start (loop, &timeout_watcher);
+\&
+\&    // now wait for events to arrive
+\&    ev_loop (loop, 0);
+\&
+\&    // unloop was called, so exit
+\&    return 0;
+\&  }
+.Ve
 .SH "DESCRIPTION"
 .IX Header "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: <http://cvs.schmorp.de/libev/ev.html>.
+.PP
 Libev is an event loop: you register interest in certain events (such as a
-file descriptor being readable or a timeout occuring), and it will manage
+file descriptor being readable or a timeout occurring), and it will manage
 these event sources and provide your program with events.
 .PP
 To do this, it must take more or less complete control over your process
 (or thread) by executing the \fIevent loop\fR handler, and will then
 communicate events via a callback mechanism.
 .PP
 You register interest in certain events by registering so-called \fIevent
 watchers\fR, which are relatively small C structures you initialise with the
 details of the event, and then hand it over to libev by \fIstarting\fR the
 watcher.
-.SH "FEATURES"
+.Sh "\s-1FEATURES\s0"
-.IX Header "FEATURES"
+.IX Subsection "FEATURES"
-Libev supports select, poll, the linux-specific epoll and the bsd-specific
+Libev supports \f(CW\*(C`select\*(C'\fR, \f(CW\*(C`poll\*(C'\fR, the Linux-specific \f(CW\*(C`epoll\*(C'\fR, the
-kqueue mechanisms for file descriptor events, relative timers, absolute
+BSD-specific \f(CW\*(C`kqueue\*(C'\fR and the Solaris-specific event port mechanisms
-timers with customised rescheduling, signal events, process status change
+for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), the Linux \f(CW\*(C`inotify\*(C'\fR interface
-events (related to \s-1SIGCHLD\s0), and event watchers dealing with the event
+(for \f(CW\*(C`ev_stat\*(C'\fR), relative timers (\f(CW\*(C`ev_timer\*(C'\fR), absolute timers
-loop mechanism itself (idle, prepare and check watchers). It also is quite
+with customised rescheduling (\f(CW\*(C`ev_periodic\*(C'\fR), synchronous signals
-fast (see this benchmark comparing
+(\f(CW\*(C`ev_signal\*(C'\fR), process status change events (\f(CW\*(C`ev_child\*(C'\fR), and event
-it to libevent for example).
+watchers dealing with the event loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR,
+\&\f(CW\*(C`ev_embed\*(C'\fR, \f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR watchers) as well as
+file watchers (\f(CW\*(C`ev_stat\*(C'\fR) and even limited support for fork events
+(\f(CW\*(C`ev_fork\*(C'\fR).
+.PP
+It also is quite fast (see this
+benchmark comparing it to libevent
+for example).
-.SH "CONVENTIONS"
+.Sh "\s-1CONVENTIONS\s0"
-.IX Header "CONVENTIONS"
+.IX Subsection "CONVENTIONS"
-Libev is very configurable. In this manual the default configuration
+Libev is very configurable. In this manual the default (and most common)
-will be described, which supports multiple event loops. For more info
+configuration will be described, which supports multiple event loops. For
-about various configuration options please have a look at the file
+more info about various configuration options please have a look at
-\&\fI\s-1README\s0.embed\fR in the libev distribution. If libev was configured without
+\&\fB\s-1EMBED\s0\fR section in this manual. If libev was configured without support
-support for multiple event loops, then all functions taking an initial
+for multiple event loops, then all functions taking an initial argument of
-argument of name \f(CW\*(C`loop\*(C'\fR (which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR)
+name \f(CW\*(C`loop\*(C'\fR (which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR) will not have
-will not have this argument.
+this argument.
-.SH "TIME REPRESENTATION"
+.Sh "\s-1TIME\s0 \s-1REPRESENTATION\s0"
-.IX Header "TIME REPRESENTATION"
+.IX Subsection "TIME REPRESENTATION"
 Libev represents time as a single floating point number, representing the
 (fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near
 the beginning of 1970, details are complicated, don't ask). This type is
 called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use too. It usually aliases
 to the \f(CW\*(C`double\*(C'\fR type in C, and when you need to do any calculations on
-it, you should treat it as such.
+it, you should treat it as some floatingpoint value. Unlike the name
+component \f(CW\*(C`stamp\*(C'\fR might indicate, it is also used for time differences
+throughout libev.
 .SH "GLOBAL FUNCTIONS"
 .IX Header "GLOBAL FUNCTIONS"
 These functions can be called anytime, even before initialising the
 library in any way.
 .IP "ev_tstamp ev_time ()" 4
 .IX Item "ev_tstamp ev_time ()"
 Returns the current time as libev would use it. Please note that the
 \&\f(CW\*(C`ev_now\*(C'\fR function is usually faster and also often returns the timestamp
 you actually want to know.
+.IP "ev_sleep (ev_tstamp interval)" 4
+.IX 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 \f(CW\*(C`sleep ()\*(C'\fR.
 .IP "int ev_version_major ()" 4
 .IX Item "int ev_version_major ()"
 .PD 0
 .IP "int ev_version_minor ()" 4
 .IX Item "int ev_version_minor ()"
 .PD
-You can find out the major and minor version numbers of the library
+You can find out the major and minor \s-1ABI\s0 version numbers of the library
 you linked against by calling the functions \f(CW\*(C`ev_version_major\*(C'\fR and
 \&\f(CW\*(C`ev_version_minor\*(C'\fR. If you want, you can compare against the global
 symbols \f(CW\*(C`EV_VERSION_MAJOR\*(C'\fR and \f(CW\*(C`EV_VERSION_MINOR\*(C'\fR, which specify the
 version of the library your program was compiled against.
 .Sp
+These version numbers refer to the \s-1ABI\s0 version of the library, not the
+release version.
+.Sp
 Usually, it's a good idea to terminate if the major versions mismatch,
-as this indicates an incompatible change.  Minor versions are usually
+as this indicates an incompatible change. Minor versions are usually
 compatible to older versions, so a larger minor version alone is usually
 not a problem.
 .Sp
-Example: make sure we haven't accidentally been linked against the wrong
+Example: Make sure we haven't accidentally been linked against the wrong
-version:
+version.
 .Sp
 .Vb 3
 \&  assert (("libev version mismatch",
 \&           ev_version_major () == EV_VERSION_MAJOR
 \&           && ev_version_minor () >= EV_VERSION_MINOR));
 (assuming you know what you are doing). This is the set of backends that
 libev will probe for if you specify no backends explicitly.
 .IP "unsigned int ev_embeddable_backends ()" 4
 .IX Item "unsigned int ev_embeddable_backends ()"
 Returns the set of backends that are embeddable in other event loops. This
-is the theoretical, all\-platform, value. To find which backends
+is the theoretical, all-platform, value. To find which backends
 might be supported on the current system, you would need to look at
 \&\f(CW\*(C`ev_embeddable_backends () & ev_supported_backends ()\*(C'\fR, likewise for
 recommended ones.
 .Sp
 See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info.
 .IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4
 .IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))"
-Sets the allocation function to use (the prototype is similar to the
+Sets the allocation function to use (the prototype is similar \- the
-realloc C function, the semantics are identical). It is used to allocate
+semantics is identical \- to the realloc C function). It is used to
-and free memory (no surprises here). If it returns zero when memory
+allocate and free memory (no surprises here). If it returns zero when
-needs to be allocated, the library might abort or take some potentially
+memory needs to be allocated, the library might abort or take some
-destructive action. The default is your system realloc function.
+potentially destructive action. The default is your system realloc
+function.
 .Sp
 You could override this function in high-availability programs to, say,
 free some memory if it cannot allocate memory, to use a special allocator,
 or even to sleep a while and retry until some memory is available.
 .Sp
-Example: replace the libev allocator with one that waits a bit and then
+Example: Replace the libev allocator with one that waits a bit and then
-retries: better than mine).
+retries).
 .Sp
 .Vb 6
 \&   static void *
-\&   persistent_realloc (void *ptr, long size)
+\&   persistent_realloc (void *ptr, size_t size)
 \&   {
 \&     for (;;)
 \&       {
 \&         void *newptr = realloc (ptr, size);
-.Ve
+\&
-.Sp
-.Vb 2
 \&         if (newptr)
 \&           return newptr;
-.Ve
+\&
-.Sp
-.Vb 3
 \&         sleep (60);
 \&       }
 \&   }
-.Ve
+\&
-.Sp
-.Vb 2
 \&   ...
 \&   ev_set_allocator (persistent_realloc);
 .Ve
 .IP "ev_set_syserr_cb (void (*cb)(const char *msg));" 4
 .IX Item "ev_set_syserr_cb (void (*cb)(const char *msg));"
 callback is set, then libev will expect it to remedy the sitution, 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).
 .Sp
-Example: do the same thing as libev does internally:
+Example: This is basically the same thing that libev does internally, too.
 .Sp
 .Vb 6
 \&   static void
 \&   fatal_error (const char *msg)
 \&   {
 \&     perror (msg);
 \&     abort ();
 \&   }
-.Ve
+\&
-.Sp
-.Vb 2
 \&   ...
 \&   ev_set_syserr_cb (fatal_error);
 .Ve
 .SH "FUNCTIONS CONTROLLING THE EVENT LOOP"
 .IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP"
 false. If it already was initialised it simply returns it (and ignores the
 flags. If that is troubling you, check \f(CW\*(C`ev_backend ()\*(C'\fR afterwards).
 .Sp
 If you don't know what event loop to use, use the one returned from this
 function.
+.Sp
+The default loop is the only loop that can handle \f(CW\*(C`ev_signal\*(C'\fR and
+\&\f(CW\*(C`ev_child\*(C'\fR watchers, and to do this, it always registers a handler
+for \f(CW\*(C`SIGCHLD\*(C'\fR. If this is a problem for your app you can either
+create a dynamic loop with \f(CW\*(C`ev_loop_new\*(C'\fR that doesn't do that, or you
+can simply overwrite the \f(CW\*(C`SIGCHLD\*(C'\fR signal handler \fIafter\fR calling
+\&\f(CW\*(C`ev_default_init\*(C'\fR.
 .Sp
 The flags argument can be used to specify special behaviour or specific
 backends to use, and is usually specified as \f(CW0\fR (or \f(CW\*(C`EVFLAG_AUTO\*(C'\fR).
 .Sp
 The following flags are supported:
 or setgid) then libev will \fInot\fR look at the environment variable
 \&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. 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.
+.ie n .IP """EVFLAG_FORKCHECK""" 4
+.el .IP "\f(CWEVFLAG_FORKCHECK\fR" 4
+.IX Item "EVFLAG_FORKCHECK"
+Instead of calling \f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR manually after
+a fork, you can also make libev check for a fork in each iteration by
+enabling this flag.
+.Sp
+This works by calling \f(CW\*(C`getpid ()\*(C'\fR 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, \f(CW\*(C`getpid\*(C'\fR is actually a simple 5\-insn sequence
+without a syscall and thus \fIvery\fR fast, but my GNU/Linux system also has
+\&\f(CW\*(C`pthread_atfork\*(C'\fR which is even faster).
+.Sp
+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.
+.Sp
+This flag setting cannot be overriden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR
+environment variable.
 .ie n .IP """EVBACKEND_SELECT""  (value 1, portable select backend)" 4
 .el .IP "\f(CWEVBACKEND_SELECT\fR  (value 1, portable select backend)" 4
 .IX Item "EVBACKEND_SELECT  (value 1, portable select backend)"
 This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as
 libev tries to roll its own fd_set with no limits on the number of fds,
 but if that fails, expect a fairly low limit on the number of fds when
-using this backend. It doesn't scale too well (O(highest_fd)), but its usually
+using this backend. It doesn't scale too well (O(highest_fd)), but its
-the fastest backend for a low number of fds.
+usually the fastest backend for a low number of (low-numbered :) fds.
+.Sp
+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
+writing a server, you should \f(CW\*(C`accept ()\*(C'\fR in a loop to accept as many
+connections as possible during one iteration. You might also want to have
+a look at \f(CW\*(C`ev_set_io_collect_interval ()\*(C'\fR to increase the amount of
+readyness notifications you get per iteration.
 .ie n .IP """EVBACKEND_POLL""    (value 2, poll backend, available everywhere except on windows)" 4
 .el .IP "\f(CWEVBACKEND_POLL\fR    (value 2, poll backend, available everywhere except on windows)" 4
 .IX Item "EVBACKEND_POLL    (value 2, poll backend, available everywhere except on windows)"
-And this is your standard \fIpoll\fR\|(2) backend. It's more complicated than
+And this is your standard \fIpoll\fR\|(2) backend. It's more complicated
-select, but handles sparse fds better and has no artificial limit on the
+than select, but handles sparse fds better and has no artificial
-number of fds you can use (except it will slow down considerably with a
+limit on the number of fds you can use (except it will slow down
-lot of inactive fds). It scales similarly to select, i.e. O(total_fds).
+considerably with a lot of inactive fds). It scales similarly to select,
+i.e. O(total_fds). See the entry for \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR, above, for
+performance tips.
 .ie n .IP """EVBACKEND_EPOLL""   (value 4, Linux)" 4
 .el .IP "\f(CWEVBACKEND_EPOLL\fR   (value 4, Linux)" 4
 .IX Item "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
+but it scales phenomenally better. While poll and select usually scale
-O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
+like O(total_fds) where n is the total number of fds (or the highest fd),
-either O(1) or O(active_fds).
+epoll scales either O(1) or O(active_fds). The epoll design has a number
+of shortcomings, such as silently dropping events in some hard-to-detect
+cases and rewiring a syscall per fd change, no fork support and bad
+support for dup.
 .Sp
-While stopping and starting an I/O watcher in the same iteration will
+While stopping, setting and starting an I/O watcher in the same iteration
-result in some caching, there is still a syscall per such incident
+will result in some caching, there is still a syscall per such incident
 (because the fd could point to a different file description now), so its
-best to avoid that. Also, \fIdup()\fRed file descriptors might not work very
+best to avoid that. Also, \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors might not work
-well if you register events for both fds.
+very well if you register events for both fds.
 .Sp
 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.
+.Sp
+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.
+keep at least one watcher active per fd at all times.
+.Sp
+While nominally embeddeble in other event loops, this feature is broken in
+all kernel versions tested so far.
 .ie n .IP """EVBACKEND_KQUEUE""  (value 8, most \s-1BSD\s0 clones)" 4
 .el .IP "\f(CWEVBACKEND_KQUEUE\fR  (value 8, most \s-1BSD\s0 clones)" 4
 .IX Item "EVBACKEND_KQUEUE  (value 8, most BSD clones)"
 Kqueue deserves special mention, as at the time of this writing, it
-was broken on all BSDs except NetBSD (usually it doesn't work with
+was broken on all BSDs except NetBSD (usually it doesn't work reliably
-anything but sockets and pipes, except on Darwin, where of course its
+with anything but sockets and pipes, except on Darwin, where of course
-completely useless). For this reason its not being \*(L"autodetected\*(R"
+it's completely useless). For this reason it's not being \*(L"autodetected\*(R"
 unless you explicitly specify it explicitly in the flags (i.e. using
-\&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR).
+\&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR) or libev was compiled on a known-to-be-good (\-enough)
+system like NetBSD.
+.Sp
+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 \f(CW\*(C`ev_embed\*(C'\fR watchers for more info.
 .Sp
 It scales in the same way as the epoll backend, but the interface to the
 kernel is more efficient (which says nothing about its actual speed, of
-course). While starting and stopping an I/O watcher does not cause an
+course). While stopping, setting and starting an I/O watcher does never
-extra syscall as with epoll, it still adds up to four event changes per
+cause an extra syscall as with \f(CW\*(C`EVBACKEND_EPOLL\*(C'\fR, it still adds up to
-incident, so its best to avoid that.
+two event changes per incident, support for \f(CW\*(C`fork ()\*(C'\fR is very bad and it
+drops fds silently in similarly hard-to-detect cases.
+.Sp
+This backend usually performs well under most conditions.
+.Sp
+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. \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR) and using it only for
+sockets.
 .ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4
 .el .IP "\f(CWEVBACKEND_DEVPOLL\fR (value 16, Solaris 8)" 4
 .IX Item "EVBACKEND_DEVPOLL (value 16, Solaris 8)"
-This is not implemented yet (and might never be).
+This is not implemented yet (and might never be, unless you send me an
+implementation). According to reports, \f(CW\*(C`/dev/poll\*(C'\fR only supports sockets
+and is not embeddable, which would limit the usefulness of this backend
+immensely.
 .ie n .IP """EVBACKEND_PORT""    (value 32, Solaris 10)" 4
 .el .IP "\f(CWEVBACKEND_PORT\fR    (value 32, Solaris 10)" 4
 .IX Item "EVBACKEND_PORT    (value 32, Solaris 10)"
-This uses the Solaris 10 port mechanism. As with everything on Solaris,
+This uses the Solaris 10 event port mechanism. As with everything on Solaris,
 it's really slow, but it still scales very well (O(active_fds)).
 .Sp
-Please note that solaris ports can result in a lot of spurious
+Please note that solaris event ports can deliver a lot of spurious
 notifications, so you need to use non-blocking I/O or other means to avoid
 blocking when no data (or space) is available.
+.Sp
+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 \*(L"slow\*(R" \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR backend
+might perform better.
+.Sp
+On the positive side, ignoring the spurious readyness notifications, this
+backend actually performed to specification in all tests and is fully
+embeddable, which is a rare feat among the OS-specific backends.
 .ie n .IP """EVBACKEND_ALL""" 4
 .el .IP "\f(CWEVBACKEND_ALL\fR" 4
 .IX Item "EVBACKEND_ALL"
 Try all backends (even potentially broken ones that wouldn't be tried
 with \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). Since this is a mask, you can do stuff such as
 \&\f(CW\*(C`EVBACKEND_ALL & ~EVBACKEND_KQUEUE\*(C'\fR.
+.Sp
+It is definitely not recommended to use this flag.
 .RE
 .RS 4
 .Sp
 If one or more of these are ored into the flags value, then only these
-backends will be tried (in the reverse order as given here). If none are
+backends will be tried (in the reverse order as listed here). If none are
-specified, most compiled-in backend will be tried, usually in reverse
+specified, all backends in \f(CW\*(C`ev_recommended_backends ()\*(C'\fR will be tried.
-order of their flag values :)
 .Sp
 The most typical usage is like this:
 .Sp
 .Vb 2
 \&  if (!ev_default_loop (0))
 Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is
 always distinct from the default loop. Unlike the default loop, it cannot
 handle signal and child watchers, and attempts to do so will be greeted by
 undefined behaviour (or a failed assertion if assertions are enabled).
 .Sp
-Example: try to create a event loop that uses epoll and nothing else.
+Example: Try to create a event loop that uses epoll and nothing else.
 .Sp
 .Vb 3
 \&  struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
 \&  if (!epoller)
 \&    fatal ("no epoll found here, maybe it hides under your chair");
 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. \f(CW\*(C`ev_is_active\*(C'\fR might still return true. It is your
 responsibility to either stop all watchers cleanly yoursef \fIbefore\fR
 calling this function, or cope with the fact afterwards (which is usually
-the easiest thing, youc na just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them
+the easiest thing, you can just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them
 for example).
+.Sp
+Note that certain global state, such as signal state, will not be freed by
+this function, and related watchers (such as signal and child watchers)
+would need to be stopped manually.
+.Sp
+In general it is not advisable to call this function except in the
+rare occasion where you really need to free e.g. the signal handling
+pipe fds. If you need dynamically allocated loops it is better to use
+\&\f(CW\*(C`ev_loop_new\*(C'\fR and \f(CW\*(C`ev_loop_destroy\*(C'\fR).
 .IP "ev_loop_destroy (loop)" 4
 .IX Item "ev_loop_destroy (loop)"
 Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an
 earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR.
 .IP "ev_default_fork ()" 4
 .IX Item "ev_default_fork ()"
+This function sets a flag that causes subsequent \f(CW\*(C`ev_loop\*(C'\fR iterations
-This function reinitialises the kernel state for backends that have
+to reinitialise the kernel state for backends that have one. Despite the
-one. Despite the name, you can call it anytime, but it makes most sense
+name, you can call it anytime, but it makes most sense after forking, in
-after forking, in either the parent or child process (or both, but that
+the child process (or both child and parent, but that again makes little
-again makes little sense).
+sense). You \fImust\fR call it in the child before using any of the libev
+functions, and it will only take effect at the next \f(CW\*(C`ev_loop\*(C'\fR iteration.
 .Sp
-You \fImust\fR call this function in the child process after forking if and
+On the other hand, you only need to call this function in the child
-only if you want to use the event library in both processes. If you just
+process if and only if you want to use the event library in the child. If
-fork+exec, you don't have to call it.
+you just fork+exec, you don't have to call it at all.
 .Sp
 The function itself is quite fast and it's usually not a problem to call
 it just in case after a fork. To make this easy, the function will fit in
 quite nicely into a call to \f(CW\*(C`pthread_atfork\*(C'\fR:
 .Sp
 .Vb 1
 \&    pthread_atfork (0, 0, ev_default_fork);
 .Ve
-.Sp
-At the moment, \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and \f(CW\*(C`EVBACKEND_POLL\*(C'\fR are safe to use
-without calling this function, so if you force one of those backends you
-do not need to care.
 .IP "ev_loop_fork (loop)" 4
 .IX Item "ev_loop_fork (loop)"
 Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by
 \&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop
 after fork, and how you do this is entirely your own problem.
+.IP "int ev_is_default_loop (loop)" 4
+.IX Item "int ev_is_default_loop (loop)"
+Returns true when the given loop actually is the default loop, false otherwise.
+.IP "unsigned int ev_loop_count (loop)" 4
+.IX 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 \f(CW0\fR and
+happily wraps around with enough iterations.
+.Sp
+This value can sometimes be useful as a generation counter of sorts (it
+\&\*(L"ticks\*(R" the number of loop iterations), as it roughly corresponds with
+\&\f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR calls.
 .IP "unsigned int ev_backend (loop)" 4
 .IX Item "unsigned int ev_backend (loop)"
 Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in
 use.
 .IP "ev_tstamp ev_now (loop)" 4
 .IX Item "ev_tstamp ev_now (loop)"
 Returns the current \*(L"event loop time\*(R", which is the time the event loop
 received events and started processing them. This timestamp does not
 change as long as callbacks are being processed, and this is also the base
 time used for relative timers. You can treat it as the timestamp of the
-event occuring (or more correctly, libev finding out about it).
+event occurring (or more correctly, libev finding out about it).
 .IP "ev_loop (loop, int flags)" 4
 .IX 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.
 libev watchers. However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is
 usually a better approach for this kind of thing.
 .Sp
 Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does:
 .Sp
-.Vb 18
+.Vb 10
-\&   * If there are no active watchers (reference count is zero), return.
+\&   \- Before the first iteration, call any pending watchers.
-\&   - Queue prepare watchers and then call all outstanding watchers.
+\&   * If EVFLAG_FORKCHECK was used, check for a fork.
+\&   \- If a fork was detected, 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, recreate the kernel state.
-\&   - Update the kernel state with all outstanding changes.
+\&   \- Update the kernel state with all outstanding changes.
-\&   - Update the "event loop time".
+\&   \- Update the "event loop time".
-\&   - Calculate for how long to block.
+\&   \- 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.
+\&   \- Block the process, waiting for any events.
-\&   - Queue all outstanding I/O (fd) events.
+\&   \- Queue all outstanding I/O (fd) events.
-\&   - Update the "event loop time" and do time jump handling.
+\&   \- Update the "event loop time" and do time jump handling.
-\&   - Queue all outstanding timers.
+\&   \- Queue all outstanding timers.
-\&   - Queue all outstanding periodics.
+\&   \- Queue all outstanding periodics.
-\&   - If no events are pending now, queue all idle watchers.
+\&   \- If no events are pending now, queue all idle watchers.
-\&   - Queue all check watchers.
+\&   \- Queue all check watchers.
-\&   - Call all queued watchers in reverse order (i.e. check watchers first).
+\&   \- 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
+\&   \- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
-\&     were used, return, otherwise continue with step *.
+\&     were used, or there are no active watchers, return, otherwise
+\&     continue with step *.
 .Ve
 .Sp
-Example: queue some jobs and then loop until no events are outsanding
+Example: Queue some jobs and then loop until no events are outstanding
 anymore.
 .Sp
 .Vb 4
 \&   ... queue jobs here, make sure they register event watchers as long
 \&   ... as they still have work to do (even an idle watcher will do..)
 .IX Item "ev_unloop (loop, how)"
 Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it
 has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either
 \&\f(CW\*(C`EVUNLOOP_ONE\*(C'\fR, which will make the innermost \f(CW\*(C`ev_loop\*(C'\fR call return, or
 \&\f(CW\*(C`EVUNLOOP_ALL\*(C'\fR, which will make all nested \f(CW\*(C`ev_loop\*(C'\fR calls return.
+.Sp
+This \*(L"unloop state\*(R" will be cleared when entering \f(CW\*(C`ev_loop\*(C'\fR again.
 .IP "ev_ref (loop)" 4
 .IX Item "ev_ref (loop)"
 .PD 0
 .IP "ev_unref (loop)" 4
 .IX Item "ev_unref (loop)"
 returning, \fIev_unref()\fR after starting, and \fIev_ref()\fR before stopping it. For
 example, libev itself uses this for its internal signal pipe: It is not
 visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting 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 \fIunref after start\fR and \fIref before stop\fR.
+libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR
+(but only if the watcher wasn't active before, or was active before,
+respectively).
 .Sp
-Example: create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR
+Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR
 running when nothing else is active.
 .Sp
 .Vb 4
-\&  struct dv_signal exitsig;
+\&  struct ev_signal exitsig;
 \&  ev_signal_init (&exitsig, sig_cb, SIGINT);
-\&  ev_signal_start (myloop, &exitsig);
+\&  ev_signal_start (loop, &exitsig);
-\&  evf_unref (myloop);
+\&  evf_unref (loop);
 .Ve
 .Sp
-Example: for some weird reason, unregister the above signal handler again.
+Example: For some weird reason, unregister the above signal handler again.
 .Sp
 .Vb 2
-\&  ev_ref (myloop);
+\&  ev_ref (loop);
-\&  ev_signal_stop (myloop, &exitsig);
+\&  ev_signal_stop (loop, &exitsig);
 .Ve
+.IP "ev_set_io_collect_interval (loop, ev_tstamp interval)" 4
+.IX Item "ev_set_io_collect_interval (loop, ev_tstamp interval)"
+.PD 0
+.IP "ev_set_timeout_collect_interval (loop, ev_tstamp interval)" 4
+.IX Item "ev_set_timeout_collect_interval (loop, ev_tstamp interval)"
+.PD
+These advanced functions influence the time that libev will spend waiting
+for events. Both are by default \f(CW0\fR, meaning that libev will try to
+invoke timer/periodic callbacks and I/O callbacks with minimum latency.
+.Sp
+Setting these to a higher value (the \f(CW\*(C`interval\*(C'\fR \fImust\fR be >= \f(CW0\fR)
+allows libev to delay invocation of I/O and timer/periodic callbacks to
+increase efficiency of loop iterations.
+.Sp
+The background is that sometimes your program runs just fast enough to
+handle one (or very few) event(s) per loop iteration. While this makes
+the program responsive, it also wastes a lot of \s-1CPU\s0 time to poll for new
+events, especially with backends like \f(CW\*(C`select ()\*(C'\fR which have a high
+overhead for the actual polling but can deliver many events at once.
+.Sp
+By setting a higher \fIio collect interval\fR you allow libev to spend more
+time collecting I/O events, so you can handle more events per iteration,
+at the cost of increasing latency. Timeouts (both \f(CW\*(C`ev_periodic\*(C'\fR and
+\&\f(CW\*(C`ev_timer\*(C'\fR) will be not affected. Setting this to a non-null value will
+introduce an additional \f(CW\*(C`ev_sleep ()\*(C'\fR call into most loop iterations.
+.Sp
+Likewise, by setting a higher \fItimeout collect interval\fR you allow libev
+to spend more time collecting timeouts, at the expense of increased
+latency (the watcher callback will be called later). \f(CW\*(C`ev_io\*(C'\fR watchers
+will not be affected. Setting this to a non-null value will not introduce
+any overhead in libev.
+.Sp
+Many (busy) programs can usually benefit by setting the io collect
+interval to a value near \f(CW0.1\fR 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 \f(CW0.01\fR,
+as this approsaches the timing granularity of most systems.
 .SH "ANATOMY OF A WATCHER"
 .IX Header "ANATOMY OF A WATCHER"
 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 \s-1STDIN\s0 to
 become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that:
 \&  static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
 \&  {
 \&    ev_io_stop (w);
 \&    ev_unloop (loop, EVUNLOOP_ALL);
 \&  }
-.Ve
+\&
-.PP
-.Vb 6
 \&  struct ev_loop *loop = ev_default_loop (0);
 \&  struct ev_io stdin_watcher;
 \&  ev_init (&stdin_watcher, my_cb);
 \&  ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
 \&  ev_io_start (loop, &stdin_watcher);
 \&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any
 received events. Callbacks of both watcher types can start and stop as
 many watchers as they want, and all of them will be taken into account
 (for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep
 \&\f(CW\*(C`ev_loop\*(C'\fR from blocking).
+.ie n .IP """EV_EMBED""" 4
+.el .IP "\f(CWEV_EMBED\fR" 4
+.IX Item "EV_EMBED"
+The embedded event loop specified in the \f(CW\*(C`ev_embed\*(C'\fR watcher needs attention.
+.ie n .IP """EV_FORK""" 4
+.el .IP "\f(CWEV_FORK\fR" 4
+.IX Item "EV_FORK"
+The event loop has been resumed in the child process after fork (see
+\&\f(CW\*(C`ev_fork\*(C'\fR).
+.ie n .IP """EV_ASYNC""" 4
+.el .IP "\f(CWEV_ASYNC\fR" 4
+.IX Item "EV_ASYNC"
+The given async watcher has been asynchronously notified (see \f(CW\*(C`ev_async\*(C'\fR).
 .ie n .IP """EV_ERROR""" 4
 .el .IP "\f(CWEV_ERROR\fR" 4
 .IX Item "EV_ERROR"
 An unspecified error has occured, the watcher has been stopped. This might
 happen because the watcher could not be properly started because libev
 .IP "bool ev_is_pending (ev_TYPE *watcher)" 4
 .IX Item "bool ev_is_pending (ev_TYPE *watcher)"
 Returns a true value iff the watcher is pending, (i.e. it has outstanding
 events but its callback has not yet been invoked). As long as a watcher
 is pending (but not active) you must not call an init function on it (but
-\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe) and you must make sure the watcher is available to
+\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe), you must not change its priority, and you must
-libev (e.g. you cnanot \f(CW\*(C`free ()\*(C'\fR it).
+make sure the watcher is available to libev (e.g. you cannot \f(CW\*(C`free ()\*(C'\fR
+it).
-.IP "callback = ev_cb (ev_TYPE *watcher)" 4
+.IP "callback ev_cb (ev_TYPE *watcher)" 4
-.IX Item "callback = ev_cb (ev_TYPE *watcher)"
+.IX Item "callback ev_cb (ev_TYPE *watcher)"
 Returns the callback currently set on the watcher.
 .IP "ev_cb_set (ev_TYPE *watcher, callback)" 4
 .IX Item "ev_cb_set (ev_TYPE *watcher, callback)"
 Change the callback. You can change the callback at virtually any time
 (modulo threads).
+.IP "ev_set_priority (ev_TYPE *watcher, priority)" 4
+.IX Item "ev_set_priority (ev_TYPE *watcher, priority)"
+.PD 0
+.IP "int ev_priority (ev_TYPE *watcher)" 4
+.IX Item "int ev_priority (ev_TYPE *watcher)"
+.PD
+Set and query the priority of the watcher. The priority is a small
+integer between \f(CW\*(C`EV_MAXPRI\*(C'\fR (default: \f(CW2\fR) and \f(CW\*(C`EV_MINPRI\*(C'\fR
+(default: \f(CW\*(C`\-2\*(C'\fR). Pending watchers with higher priority will be invoked
+before watchers with lower priority, but priority will not keep watchers
+from being executed (except for \f(CW\*(C`ev_idle\*(C'\fR watchers).
+.Sp
+This means that priorities are \fIonly\fR used for ordering callback
+invocation after new events have been received. This is useful, for
+example, to reduce latency after idling, or more often, to bind two
+watchers on the same event and make sure one is called first.
+.Sp
+If you need to suppress invocation when higher priority events are pending
+you need to look at \f(CW\*(C`ev_idle\*(C'\fR watchers, which provide this functionality.
+.Sp
+You \fImust not\fR change the priority of a watcher as long as it is active or
+pending.
+.Sp
+The default priority used by watchers when no priority has been set is
+always \f(CW0\fR, which is supposed to not be too high and not be too low :).
+.Sp
+Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR 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.
+.IP "ev_invoke (loop, ev_TYPE *watcher, int revents)" 4
+.IX Item "ev_invoke (loop, ev_TYPE *watcher, int revents)"
+Invoke the \f(CW\*(C`watcher\*(C'\fR with the given \f(CW\*(C`loop\*(C'\fR and \f(CW\*(C`revents\*(C'\fR. Neither
+\&\f(CW\*(C`loop\*(C'\fR nor \f(CW\*(C`revents\*(C'\fR need to be valid as long as the watcher callback
+can deal with that fact.
+.IP "int ev_clear_pending (loop, ev_TYPE *watcher)" 4
+.IX Item "int ev_clear_pending (loop, ev_TYPE *watcher)"
+If the watcher is pending, this function returns clears its pending status
+and returns its \f(CW\*(C`revents\*(C'\fR bitset (as if its callback was invoked). If the
+watcher isn't pending it does nothing and returns \f(CW0\fR.
 .Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0"
 .IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER"
 Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change
 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
 \&    struct my_io *w = (struct my_io *)w_;
 \&    ...
 \&  }
 .Ve
 .PP
-More interesting and less C\-conformant ways of catsing your callback type
+More interesting and less C\-conformant ways of casting your callback type
-have been omitted....
+instead have been omitted.
+.PP
+Another common scenario is having some data structure with multiple
+watchers:
+.PP
+.Vb 6
+\&  struct my_biggy
+\&  {
+\&    int some_data;
+\&    ev_timer t1;
+\&    ev_timer t2;
+\&  }
+.Ve
+.PP
+In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more complicated,
+you need to use \f(CW\*(C`offsetof\*(C'\fR:
+.PP
+.Vb 1
+\&  #include <stddef.h>
+\&
+\&  static void
+\&  t1_cb (EV_P_ struct ev_timer *w, int revents)
+\&  {
+\&    struct my_biggy big = (struct my_biggy *
+\&      (((char *)w) \- offsetof (struct my_biggy, t1));
+\&  }
+\&
+\&  static void
+\&  t2_cb (EV_P_ struct ev_timer *w, int revents)
+\&  {
+\&    struct my_biggy big = (struct my_biggy *
+\&      (((char *)w) \- offsetof (struct my_biggy, t2));
+\&  }
+.Ve
 .SH "WATCHER TYPES"
 .IX Header "WATCHER TYPES"
 This section describes each watcher in detail, but will not repeat
 information given in the last section. Any initialisation/set macros,
 functions and members specific to the watcher type are explained.
 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).
 .PP
-You have to be careful with dup'ed file descriptors, though. Some backends
-(the linux epoll backend is a notable example) cannot handle dup'ed file
-descriptors correctly if you register interest in two or more fds pointing
-to the same underlying file/socket/etc. description (that is, they share
-the same underlying \*(L"file open\*(R").
-.PP
 If you must do this, then force the use of a known-to-be-good backend
 (at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and
 \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR).
 .PP
 Another thing you have to watch out for is that it is quite easy to
 it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning
 \&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives.
 .PP
 If you cannot run the fd in non-blocking mode (for example you should not
 play around with an Xlib connection), then you have to seperately re-test
-wether a file descriptor is really ready with a known-to-be good interface
+whether a file descriptor is really ready with a known-to-be good interface
 such as poll (fortunately in our Xlib example, Xlib already does this on
 its own, so its quite safe to use).
+.PP
+\fIThe special problem of disappearing file descriptors\fR
+.IX Subsection "The special problem of disappearing file descriptors"
+.PP
+Some backends (e.g. kqueue, epoll) need to be told about closing a file
+descriptor (either by calling \f(CW\*(C`close\*(C'\fR explicitly or by any other means,
+such as \f(CW\*(C`dup\*(C'\fR). 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.
+.PP
+To avoid having to explicitly tell libev about such cases, libev follows
+the following policy:  Each time \f(CW\*(C`ev_io_set\*(C'\fR is being called, libev
+will assume that this is potentially a new file descriptor, otherwise
+it is assumed that the file descriptor stays the same. That means that
+you \fIhave\fR to call \f(CW\*(C`ev_io_set\*(C'\fR (or \f(CW\*(C`ev_io_init\*(C'\fR) when you change the
+descriptor even if the file descriptor number itself did not change.
+.PP
+This is how one would do it normally anyway, the important point is that
+the libev application should not optimise around libev but should leave
+optimisations to libev.
+.PP
+\fIThe special problem of dup'ed file descriptors\fR
+.IX Subsection "The special problem of dup'ed file descriptors"
+.PP
+Some backends (e.g. epoll), cannot register events for file descriptors,
+but only events for the underlying file descriptions. That means when you
+have \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors or weirder constellations, and register
+events for them, only one file descriptor might actually receive events.
+.PP
+There is no workaround possible except not registering events
+for potentially \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors, or to resort to
+\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
+.PP
+\fIThe special problem of fork\fR
+.IX Subsection "The special problem of fork"
+.PP
+Some backends (epoll, kqueue) do not support \f(CW\*(C`fork ()\*(C'\fR at all or exhibit
+useless behaviour. Libev fully supports fork, but needs to be told about
+it in the child.
+.PP
+To support fork in your programs, you either have to call
+\&\f(CW\*(C`ev_default_fork ()\*(C'\fR or \f(CW\*(C`ev_loop_fork ()\*(C'\fR after a fork in the child,
+enable \f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR, or resort to \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or
+\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
+.PP
+\fIWatcher-Specific Functions\fR
+.IX Subsection "Watcher-Specific Functions"
 .IP "ev_io_init (ev_io *, callback, int fd, int events)" 4
 .IX Item "ev_io_init (ev_io *, callback, int fd, int events)"
 .PD 0
 .IP "ev_io_set (ev_io *, int fd, int events)" 4
 .IX Item "ev_io_set (ev_io *, int fd, int events)"
 The file descriptor being watched.
 .IP "int events [read\-only]" 4
 .IX Item "int events [read-only]"
 The events being watched.
 .PP
+\fIExamples\fR
+.IX Subsection "Examples"
+.PP
-Example: call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well
+Example: Call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well
-readable, but only once. Since it is likely line\-buffered, you could
+readable, but only once. Since it is likely line-buffered, you could
-attempt to read a whole line in the callback:
+attempt to read a whole line in the callback.
 .PP
 .Vb 6
 \&  static void
 \&  stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
 \&  {
 \&     ev_io_stop (loop, w);
-\&    .. read from stdin here (or from w->fd) and haqndle any I/O errors
+\&    .. read from stdin here (or from w\->fd) and haqndle any I/O errors
 \&  }
-.Ve
+\&
-.PP
-.Vb 6
 \&  ...
 \&  struct ev_loop *loop = ev_default_init (0);
 \&  struct ev_io stdin_readable;
 \&  ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
 \&  ev_io_start (loop, &stdin_readable);
 of the event triggering whatever timeout you are modifying/starting. If
 you suspect event processing to be delayed and you \fIneed\fR to base the timeout
 on the current time, use something like this to adjust for this:
 .PP
 .Vb 1
-\&   ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
+\&   ev_timer_set (&timer, after + ev_now () \- ev_time (), 0.);
 .Ve
 .PP
 The callback is guarenteed to be invoked only when its timeout has passed,
 but if multiple timers become ready during the same loop iteration then
 order of execution is undefined.
+.PP
+\fIWatcher-Specific Functions and Data Members\fR
+.IX Subsection "Watcher-Specific Functions and Data Members"
 .IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4
 .IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)"
 .PD 0
 .IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4
 .IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)"
 The timer itself will do a best-effort at avoiding drift, that is, if you
 configure a timer to trigger every 10 seconds, then it will trigger at
 exactly 10 second intervals. If, however, your program cannot keep up with
 the timer (because it takes longer than those 10 seconds to do stuff) the
 timer will not fire more than once per event loop iteration.
-.IP "ev_timer_again (loop)" 4
+.IP "ev_timer_again (loop, ev_timer *)" 4
-.IX Item "ev_timer_again (loop)"
+.IX 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:
 .Sp
+If the timer is pending, its pending status is cleared.
+.Sp
-If the timer is started but nonrepeating, stop it.
+If the timer is started but nonrepeating, stop it (as if it timed out).
 .Sp
-If the timer is repeating, either start it if necessary (with the repeat
+If the timer is repeating, either start it if necessary (with the
-value), or reset the running timer to the repeat value.
+\&\f(CW\*(C`repeat\*(C'\fR value), or reset the running timer to the \f(CW\*(C`repeat\*(C'\fR value.
 .Sp
 This sounds a bit complicated, but here is a useful and typical
-example: Imagine you have a tcp connection and you want a so-called
+example: Imagine you have a tcp connection and you want a so-called idle
-idle timeout, that is, you want to be called when there have been,
+timeout, that is, you want to be called when there have been, say, 60
-say, 60 seconds of inactivity on the socket. The easiest way to do
+seconds of inactivity on the socket. The easiest way to do this is to
-this is to configure an \f(CW\*(C`ev_timer\*(C'\fR with \f(CW\*(C`after\*(C'\fR=\f(CW\*(C`repeat\*(C'\fR=\f(CW60\fR and calling
+configure an \f(CW\*(C`ev_timer\*(C'\fR with a \f(CW\*(C`repeat\*(C'\fR value of \f(CW60\fR and then call
 \&\f(CW\*(C`ev_timer_again\*(C'\fR each time you successfully read or write some data. If
 you go into an idle state where you do not expect data to travel on the
-socket, you can stop the timer, and again will automatically restart it if
+socket, you can \f(CW\*(C`ev_timer_stop\*(C'\fR the timer, and \f(CW\*(C`ev_timer_again\*(C'\fR will
-need be.
+automatically restart it if need be.
 .Sp
-You can also ignore the \f(CW\*(C`after\*(C'\fR value and \f(CW\*(C`ev_timer_start\*(C'\fR altogether
+That means you can ignore the \f(CW\*(C`after\*(C'\fR value and \f(CW\*(C`ev_timer_start\*(C'\fR
-and only ever use the \f(CW\*(C`repeat\*(C'\fR value:
+altogether and only ever use the \f(CW\*(C`repeat\*(C'\fR value and \f(CW\*(C`ev_timer_again\*(C'\fR:
 .Sp
 .Vb 8
 \&   ev_timer_init (timer, callback, 0., 5.);
 \&   ev_timer_again (loop, timer);
 \&   ...
-\&   timer->again = 17.;
+\&   timer\->again = 17.;
 \&   ev_timer_again (loop, timer);
 \&   ...
-\&   timer->again = 10.;
+\&   timer\->again = 10.;
 \&   ev_timer_again (loop, timer);
 .Ve
 .Sp
-This is more efficient then stopping/starting the timer eahc time you want
+This is more slightly efficient then stopping/starting the timer each time
-to modify its timeout value.
+you want to modify its timeout value.
 .IP "ev_tstamp repeat [read\-write]" 4
 .IX Item "ev_tstamp repeat [read-write]"
 The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out
 or \f(CW\*(C`ev_timer_again\*(C'\fR is called and determines the next timeout (if any),
 which is also when any modifications are taken into account.
 .PP
+\fIExamples\fR
+.IX Subsection "Examples"
+.PP
-Example: create a timer that fires after 60 seconds.
+Example: Create a timer that fires after 60 seconds.
 .PP
 .Vb 5
 \&  static void
 \&  one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
 \&  {
 \&    .. one minute over, w is actually stopped right here
 \&  }
-.Ve
+\&
-.PP
-.Vb 3
 \&  struct ev_timer mytimer;
 \&  ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
 \&  ev_timer_start (loop, &mytimer);
 .Ve
 .PP
-Example: create a timeout timer that times out after 10 seconds of
+Example: Create a timeout timer that times out after 10 seconds of
 inactivity.
 .PP
 .Vb 5
 \&  static void
 \&  timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
 \&  {
 \&    .. ten seconds without any activity
 \&  }
-.Ve
+\&
-.PP
-.Vb 4
 \&  struct ev_timer mytimer;
 \&  ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
 \&  ev_timer_again (&mytimer); /* start timer */
 \&  ev_loop (loop, 0);
-.Ve
+\&
-.PP
-.Vb 3
 \&  // and in some piece of code that gets executed on any "activity":
 \&  // reset the timeout to start ticking again at 10 seconds
 \&  ev_timer_again (&mytimer);
 .Ve
 .ie n .Sh """ev_periodic"" \- to cron or not to cron?"
 but on wallclock time (absolute time). You can tell a periodic watcher
 to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a
 periodic watcher to trigger in 10 seconds (by specifiying e.g. \f(CW\*(C`ev_now ()
 + 10.\*(C'\fR) and then reset your system clock to the last year, then it will
 take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger
-roughly 10 seconds later and of course not if you reset your system time
+roughly 10 seconds later).
-again).
 .PP
 They can also be used to implement vastly more complex timers, such as
-triggering an event on eahc midnight, local time.
+triggering an event on each midnight, local time or other, complicated,
+rules.
 .PP
 As with timers, the callback is guarenteed to be invoked only when the
 time (\f(CW\*(C`at\*(C'\fR) has been passed, but if multiple periodic timers become ready
 during the same loop iteration then order of execution is undefined.
+.PP
+\fIWatcher-Specific Functions and Data Members\fR
+.IX Subsection "Watcher-Specific Functions and Data Members"
 .IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4
 .IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)"
 .PD 0
 .IP "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 4
 .IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)"
 .PD
 Lots of arguments, lets sort it out... There are basically three modes of
 operation, and we will explain them from simplest to complex:
 .RS 4
+.IP "\(bu" 4
-.IP "* absolute timer (interval = reschedule_cb = 0)" 4
+absolute timer (at = time, interval = reschedule_cb = 0)
-.IX Item "absolute timer (interval = reschedule_cb = 0)"
+.Sp
 In this configuration the watcher triggers an event at the wallclock time
 \&\f(CW\*(C`at\*(C'\fR and doesn't repeat. It will not adjust when a time jump occurs,
 that is, if it is to be run at January 1st 2011 then it will run when the
 system time reaches or surpasses this time.
+.IP "\(bu" 4
-.IP "* non-repeating interval timer (interval > 0, reschedule_cb = 0)" 4
+repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
-.IX Item "non-repeating interval timer (interval > 0, reschedule_cb = 0)"
+.Sp
 In this mode the watcher will always be scheduled to time out at the next
-\&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N) and then repeat, regardless
+\&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N, which can also be negative)
-of any time jumps.
+and then repeat, regardless of any time jumps.
 .Sp
 This can be used to create timers that do not drift with respect to system
 time:
 .Sp
 .Vb 1
 by 3600.
 .Sp
 Another way to think about it (for the mathematically inclined) is that
 \&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible
 time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps.
-.IP "* manual reschedule mode (reschedule_cb = callback)" 4
+.Sp
-.IX Item "manual reschedule mode (reschedule_cb = callback)"
+For numerical stability it is preferable that the \f(CW\*(C`at\*(C'\fR value is near
+\&\f(CW\*(C`ev_now ()\*(C'\fR (the current time), but there is no range requirement for
+this value.
+.IP "\(bu" 4
+manual reschedule mode (at and interval ignored, reschedule_cb = callback)
+.Sp
 In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR 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.
 .Sp
 \&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher,
 ever, or make any event loop modifications\fR. If you need to stop it,
 return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop it afterwards (e.g. by
-starting a prepare watcher).
+starting an \f(CW\*(C`ev_prepare\*(C'\fR watcher, which is legal).
 .Sp
 Its prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
 ev_tstamp now)\*(C'\fR, e.g.:
 .Sp
 .Vb 4
 .IX Item "ev_periodic_again (loop, ev_periodic *)"
 Simply stops and restarts the periodic watcher again. This is only useful
 when you changed some parameters or the reschedule callback would return
 a different time than the last time it was called (e.g. in a crond like
 program when the crontabs have changed).
+.IP "ev_tstamp offset [read\-write]" 4
+.IX Item "ev_tstamp offset [read-write]"
+When repeating, this contains the offset value, otherwise this is the
+absolute point in time (the \f(CW\*(C`at\*(C'\fR value passed to \f(CW\*(C`ev_periodic_set\*(C'\fR).
+.Sp
+Can be modified any time, but changes only take effect when the periodic
+timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
 .IP "ev_tstamp interval [read\-write]" 4
 .IX Item "ev_tstamp interval [read-write]"
 The current interval value. Can be modified any time, but changes only
 take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being
 called.
 .IP "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read\-write]" 4
 .IX Item "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]"
 The current reschedule callback, or \f(CW0\fR, if this functionality is
 switched off. Can be changed any time, but changes only take effect when
 the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
+.IP "ev_tstamp at [read\-only]" 4
+.IX Item "ev_tstamp at [read-only]"
+When active, contains the absolute time that the watcher is supposed to
+trigger next.
 .PP
+\fIExamples\fR
+.IX Subsection "Examples"
+.PP
-Example: call a callback every hour, or, more precisely, whenever the
+Example: Call a callback every hour, or, more precisely, whenever the
 system clock is divisible by 3600. The callback invocation times have
 potentially a lot of jittering, but good long-term stability.
 .PP
 .Vb 5
 \&  static void
 \&  clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
 \&  {
 \&    ... its now a full hour (UTC, or TAI or whatever your clock follows)
 \&  }
-.Ve
+\&
-.PP
-.Vb 3
 \&  struct ev_periodic hourly_tick;
 \&  ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
 \&  ev_periodic_start (loop, &hourly_tick);
 .Ve
 .PP
-Example: the same as above, but use a reschedule callback to do it:
+Example: The same as above, but use a reschedule callback to do it:
 .PP
 .Vb 1
 \&  #include <math.h>
-.Ve
+\&
-.PP
-.Vb 5
 \&  static ev_tstamp
 \&  my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
 \&  {
 \&    return fmod (now, 3600.) + 3600.;
 \&  }
-.Ve
+\&
-.PP
-.Vb 1
 \&  ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
 .Ve
 .PP
-Example: call a callback every hour, starting now:
+Example: Call a callback every hour, starting now:
 .PP
 .Vb 4
 \&  struct ev_periodic hourly_tick;
 \&  ev_periodic_init (&hourly_tick, clock_cb,
 \&                    fmod (ev_now (loop), 3600.), 3600., 0);
 first watcher gets started will libev actually register a signal watcher
 with the kernel (thus it coexists with your own signal handlers as long
 as you don't register any with libev). Similarly, when the last signal
 watcher for a signal is stopped libev will reset the signal handler to
 \&\s-1SIG_DFL\s0 (regardless of what it was set to before).
+.PP
+If possible and supported, libev will install its handlers with
+\&\f(CW\*(C`SA_RESTART\*(C'\fR behaviour enabled, so syscalls should not be unduly
+interrupted. If you have a problem with syscalls getting interrupted by
+signals you can block all signals in an \f(CW\*(C`ev_check\*(C'\fR watcher and unblock
+them in an \f(CW\*(C`ev_prepare\*(C'\fR watcher.
+.PP
+\fIWatcher-Specific Functions and Data Members\fR
+.IX Subsection "Watcher-Specific Functions and Data Members"
 .IP "ev_signal_init (ev_signal *, callback, int signum)" 4
 .IX Item "ev_signal_init (ev_signal *, callback, int signum)"
 .PD 0
 .IP "ev_signal_set (ev_signal *, int signum)" 4
 .IX Item "ev_signal_set (ev_signal *, int signum)"
 Configures the watcher to trigger on the given signal number (usually one
 of the \f(CW\*(C`SIGxxx\*(C'\fR constants).
 .IP "int signum [read\-only]" 4
 .IX Item "int signum [read-only]"
 The signal the watcher watches out for.
+.PP
+\fIExamples\fR
+.IX Subsection "Examples"
+.PP
+Example: Try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0.
+.PP
+.Vb 5
+\&  static void
+\&  sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
+\&  {
+\&    ev_unloop (loop, EVUNLOOP_ALL);
+\&  }
+\&
+\&  struct ev_signal signal_watcher;
+\&  ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
+\&  ev_signal_start (loop, &sigint_cb);
+.Ve
 .ie n .Sh """ev_child"" \- watch out for process status changes"
 .el .Sh "\f(CWev_child\fP \- watch out for process status changes"
 .IX Subsection "ev_child - watch out for process status changes"
 Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to
-some child status changes (most typically when a child of yours dies).
+some child status changes (most typically when a child of yours dies). It
+is permissible to install a child watcher \fIafter\fR the child has been
+forked (which implies it might have already exited), as long as the event
+loop isn't entered (or is continued from a watcher).
+.PP
+Only the default event loop is capable of handling signals, and therefore
+you can only rgeister child watchers in the default event loop.
+.PP
+\fIProcess Interaction\fR
+.IX Subsection "Process Interaction"
+.PP
+Libev grabs \f(CW\*(C`SIGCHLD\*(C'\fR 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
+of \f(CW\*(C`SIGCHLD\*(C'\fR 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.
+.PP
+\fIOverriding the Built-In Processing\fR
+.IX Subsection "Overriding the Built-In Processing"
+.PP
+Libev offers no special support for overriding the built-in child
+processing, but if your application collides with libev's default child
+handler, you can override it easily by installing your own handler for
+\&\f(CW\*(C`SIGCHLD\*(C'\fR 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 \f(CW\*(C`ev_child\*(C'\fR watchers freely.
+.PP
+\fIWatcher-Specific Functions and Data Members\fR
+.IX Subsection "Watcher-Specific Functions and Data Members"
-.IP "ev_child_init (ev_child *, callback, int pid)" 4
+.IP "ev_child_init (ev_child *, callback, int pid, int trace)" 4
-.IX Item "ev_child_init (ev_child *, callback, int pid)"
+.IX Item "ev_child_init (ev_child *, callback, int pid, int trace)"
 .PD 0
-.IP "ev_child_set (ev_child *, int pid)" 4
+.IP "ev_child_set (ev_child *, int pid, int trace)" 4
-.IX Item "ev_child_set (ev_child *, int pid)"
+.IX Item "ev_child_set (ev_child *, int pid, int trace)"
 .PD
 Configures the watcher to wait for status changes of process \f(CW\*(C`pid\*(C'\fR (or
 \&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look
 at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see
 the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems
 \&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the
-process causing the status change.
+process causing the status change. \f(CW\*(C`trace\*(C'\fR must be either \f(CW0\fR (only
+activate the watcher when the process terminates) or \f(CW1\fR (additionally
+activate the watcher when the process is stopped or continued).
 .IP "int pid [read\-only]" 4
 .IX Item "int pid [read-only]"
 The process id this watcher watches out for, or \f(CW0\fR, meaning any process id.
 .IP "int rpid [read\-write]" 4
 .IX Item "int rpid [read-write]"
 .IP "int rstatus [read\-write]" 4
 .IX Item "int rstatus [read-write]"
 The process exit/trace status caused by \f(CW\*(C`rpid\*(C'\fR (see your systems
 \&\f(CW\*(C`waitpid\*(C'\fR and \f(CW\*(C`sys/wait.h\*(C'\fR documentation for details).
 .PP
-Example: try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0.
+\fIExamples\fR
+.IX Subsection "Examples"
 .PP
+Example: \f(CW\*(C`fork()\*(C'\fR a new process and install a child handler to wait for
+its completion.
+.PP
-.Vb 5
+.Vb 1
+\&  ev_child cw;
+\&
 \&  static void
-\&  sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
+\&  child_cb (EV_P_ struct ev_child *w, int revents)
 \&  {
-\&    ev_unloop (loop, EVUNLOOP_ALL);
+\&    ev_child_stop (EV_A_ w);
+\&    printf ("process %d exited with status %x\en", w\->rpid, w\->rstatus);
 \&  }
-.Ve
+\&
-.PP
+\&  pid_t pid = fork ();
-.Vb 3
+\&
-\&  struct ev_signal signal_watcher;
+\&  if (pid < 0)
-\&  ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
+\&    // error
-\&  ev_signal_start (loop, &sigint_cb);
+\&  else if (pid == 0)
+\&    {
+\&      // the forked child executes here
+\&      exit (1);
+\&    }
+\&  else
+\&    {
+\&      ev_child_init (&cw, child_cb, pid, 0);
+\&      ev_child_start (EV_DEFAULT_ &cw);
+\&    }
 .Ve
 .ie n .Sh """ev_stat"" \- did the file attributes just change?"
 .el .Sh "\f(CWev_stat\fP \- did the file attributes just change?"
 .IX Subsection "ev_stat - did the file attributes just change?"
 This watches a filesystem path for attribute changes. That is, it calls
 not exist\*(R" is a status change like any other. The condition \*(L"path does
 not exist\*(R" is signified by the \f(CW\*(C`st_nlink\*(C'\fR field being zero (which is
 otherwise always forced to be at least one) and all the other fields of
 the stat buffer having unspecified contents.
 .PP
+The path \fIshould\fR be absolute and \fImust not\fR end in a slash. If it is
+relative and your working directory changes, the behaviour is undefined.
+.PP
 Since there is no standard to do this, the portable implementation simply
-calls \f(CW\*(C`stat (2)\*(C'\fR regulalry on the path to see if it changed somehow. You
+calls \f(CW\*(C`stat (2)\*(C'\fR regularly on the path to see if it changed somehow. You
 can specify a recommended polling interval for this case. If you specify
 a polling interval of \f(CW0\fR (highly recommended!) then a \fIsuitable,
 unspecified default\fR value will be used (which you can expect to be around
 five seconds, although this might change dynamically). Libev will also
 impose a minimum interval which is currently around \f(CW0.1\fR, but thats
 usually overkill.
 .PP
 This watcher type is not meant for massive numbers of stat watchers,
 as even with OS-supported change notifications, this can be
-resource\-intensive.
+resource-intensive.
 .PP
-At the time of this writing, no specific \s-1OS\s0 backends are implemented, but
+At the time of this writing, only the Linux inotify interface is
-if demand increases, at least a kqueue and inotify backend will be added.
+implemented (implementing kqueue support is left as an exercise for the
+reader). Inotify will be used to give hints only and should not change the
+semantics of \f(CW\*(C`ev_stat\*(C'\fR 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.
+.PP
+\fIInotify\fR
+.IX Subsection "Inotify"
+.PP
+When \f(CW\*(C`inotify (7)\*(C'\fR support has been compiled into libev (generally only
+available on Linux) and present at runtime, it will be used to speed up
+change detection where possible. The inotify descriptor will be created lazily
+when the first \f(CW\*(C`ev_stat\*(C'\fR watcher is being started.
+.PP
+Inotify presense does not change the semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers
+except that changes might be detected earlier, and in some cases, to avoid
+making regular \f(CW\*(C`stat\*(C'\fR calls. Even in the presense of inotify support
+there are many cases where libev has to resort to regular \f(CW\*(C`stat\*(C'\fR polling.
+.PP
+(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).
+.PP
+\fIThe special problem of stat time resolution\fR
+.IX Subsection "The special problem of stat time resolution"
+.PP
+The \f(CW\*(C`stat ()\*(C'\fR syscall only supports full-second resolution portably, and
+even on systems where the resolution is higher, many filesystems still
+only support whole seconds.
+.PP
+That means that, if the time is the only thing that changes, you might
+miss updates: on the first update, \f(CW\*(C`ev_stat\*(C'\fR detects a change and calls
+your callback, which does something. When there is another update within
+the same second, \f(CW\*(C`ev_stat\*(C'\fR will be unable to detect it.
+.PP
+The solution to this is to delay acting on a change for a second (or till
+the next second boundary), using a roughly one-second delay \f(CW\*(C`ev_timer\*(C'\fR
+(\f(CW\*(C`ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)\*(C'\fR). The \f(CW.01\fR
+is added to work around small timing inconsistencies of some operating
+systems.
+.PP
+\fIWatcher-Specific Functions and Data Members\fR
+.IX Subsection "Watcher-Specific Functions and Data Members"
 .IP "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 4
 .IX Item "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)"
 .PD 0
 .IP "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" 4
 .IX Item "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)"
 path for as long as the watcher is active.
 .Sp
 The callback will be receive \f(CW\*(C`EV_STAT\*(C'\fR when a change was detected,
 relative to the attributes at the time the watcher was started (or the
 last change was detected).
-.IP "ev_stat_stat (ev_stat *)" 4
+.IP "ev_stat_stat (loop, ev_stat *)" 4
-.IX Item "ev_stat_stat (ev_stat *)"
+.IX 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 fucntion to avoid
 detecting this change (while introducing a race condition). Can also be
 useful simply to find out the new values.
 .IP "ev_statdata attr [read\-only]" 4
 The specified interval.
 .IP "const char *path [read\-only]" 4
 .IX Item "const char *path [read-only]"
 The filesystem path that is being watched.
 .PP
+\fIExamples\fR
+.IX Subsection "Examples"
+.PP
 Example: Watch \f(CW\*(C`/etc/passwd\*(C'\fR for attribute changes.
 .PP
-.Vb 15
+.Vb 10
 \&  static void
 \&  passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
 \&  {
 \&    /* /etc/passwd changed in some way */
-\&    if (w->attr.st_nlink)
+\&    if (w\->attr.st_nlink)
 \&      {
-\&        printf ("passwd current size  %ld\en", (long)w->attr.st_size);
+\&        printf ("passwd current size  %ld\en", (long)w\->attr.st_size);
-\&        printf ("passwd current atime %ld\en", (long)w->attr.st_mtime);
+\&        printf ("passwd current atime %ld\en", (long)w\->attr.st_mtime);
-\&        printf ("passwd current mtime %ld\en", (long)w->attr.st_mtime);
+\&        printf ("passwd current mtime %ld\en", (long)w\->attr.st_mtime);
 \&      }
 \&    else
 \&      /* you shalt not abuse printf for puts */
 \&      puts ("wow, /etc/passwd is not there, expect problems. "
 \&            "if this is windows, they already arrived\en");
 \&  }
-.Ve
+\&
-.PP
-.Vb 2
 \&  ...
 \&  ev_stat passwd;
+\&
+\&  ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
+\&  ev_stat_start (loop, &passwd);
 .Ve
+.PP
+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 \f(CW\*(C`ev_stat\*(C'\fR callback invocation \fIand\fR on
+\&\f(CW\*(C`ev_timer\*(C'\fR callback invocation).
 .PP
 .Vb 2
+\&  static ev_stat passwd;
+\&  static ev_timer timer;
+\&
+\&  static void
+\&  timer_cb (EV_P_ ev_timer *w, int revents)
+\&  {
+\&    ev_timer_stop (EV_A_ w);
+\&
+\&    /* now it\*(Aqs one second after the most recent passwd change */
+\&  }
+\&
+\&  static void
+\&  stat_cb (EV_P_ ev_stat *w, int revents)
+\&  {
+\&    /* reset the one\-second timer */
+\&    ev_timer_again (EV_A_ &timer);
+\&  }
+\&
+\&  ...
-\&  ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
+\&  ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
 \&  ev_stat_start (loop, &passwd);
+\&  ev_timer_init (&timer, timer_cb, 0., 1.01);
 .Ve
 .ie n .Sh """ev_idle"" \- when you've got nothing better to do..."
 .el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do..."
 .IX Subsection "ev_idle - when you've got nothing better to do..."
-Idle watchers trigger events when there are no other events are pending
+Idle watchers trigger events when no other events of the same or higher
-(prepare, check and other idle watchers do not count). That is, as long
+priority are pending (prepare, check and other idle watchers do not
-as your process is busy handling sockets or timeouts (or even signals,
+count).
-imagine) it will not be triggered. But when your process is idle all idle
+.PP
-watchers are being called again and again, once per event loop iteration \-
+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
-until stopped, that is, or your process receives more events and becomes
+iteration \- until stopped, that is, or your process receives more events
-busy.
+and becomes busy again with higher priority stuff.
 .PP
 The most noteworthy effect is that as long as any idle watchers are
 active, the process will not block when waiting for new events.
 .PP
 Apart from keeping your process non-blocking (which is a useful
 effect on its own sometimes), idle watchers are a good place to do
-\&\*(L"pseudo\-background processing\*(R", or delay processing stuff to after the
+\&\*(L"pseudo-background processing\*(R", or delay processing stuff to after the
 event loop has handled all outstanding events.
+.PP
+\fIWatcher-Specific Functions and Data Members\fR
+.IX Subsection "Watcher-Specific Functions and Data Members"
 .IP "ev_idle_init (ev_signal *, callback)" 4
 .IX Item "ev_idle_init (ev_signal *, callback)"
 Initialises and configures the idle watcher \- it has no parameters of any
 kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless,
 believe me.
 .PP
+\fIExamples\fR
+.IX Subsection "Examples"
+.PP
-Example: dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR, start it, and in the
+Example: Dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR watcher, start it, and in the
-callback, free it. Alos, use no error checking, as usual.
+callback, free it. Also, use no error checking, as usual.
 .PP
 .Vb 7
 \&  static void
 \&  idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
 \&  {
 \&    free (w);
 \&    // now do something you wanted to do when the program has
-\&    // no longer asnything immediate to do.
+\&    // no longer anything immediate to do.
 \&  }
-.Ve
+\&
-.PP
-.Vb 3
 \&  struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
 \&  ev_idle_init (idle_watcher, idle_cb);
 \&  ev_idle_start (loop, idle_cb);
 .Ve
 .ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop!"
 are ready to run (it's actually more complicated: it only runs coroutines
 with priority higher than or equal to the event loop and one coroutine
 of lower priority, but only once, using idle watchers to keep the event
 loop from blocking if lower-priority coroutines are active, thus mapping
 low-priority coroutines to idle/background tasks).
+.PP
+It is recommended to give \f(CW\*(C`ev_check\*(C'\fR watchers highest (\f(CW\*(C`EV_MAXPRI\*(C'\fR)
+priority, to ensure that they are being run before any other watchers
+after the poll. Also, \f(CW\*(C`ev_check\*(C'\fR watchers (and \f(CW\*(C`ev_prepare\*(C'\fR watchers,
+too) should not activate (\*(L"feed\*(R") events into libev. While libev fully
+supports this, they will be called before other \f(CW\*(C`ev_check\*(C'\fR watchers
+did their job. As \f(CW\*(C`ev_check\*(C'\fR watchers are often used to embed other
+(non-libev) event loops those other event loops might be in an unusable
+state until their \f(CW\*(C`ev_check\*(C'\fR watcher ran (always remind yourself to
+coexist peacefully with others).
+.PP
+\fIWatcher-Specific Functions and Data Members\fR
+.IX Subsection "Watcher-Specific Functions and Data Members"
 .IP "ev_prepare_init (ev_prepare *, callback)" 4
 .IX Item "ev_prepare_init (ev_prepare *, callback)"
 .PD 0
 .IP "ev_check_init (ev_check *, callback)" 4
 .IX Item "ev_check_init (ev_check *, callback)"
 .PD
 Initialises and configures the prepare or check watcher \- they have no
 parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR
 macros, but using them is utterly, utterly and completely pointless.
 .PP
-Example: To include a library such as adns, you would add \s-1IO\s0 watchers
+\fIExamples\fR
-and a timeout watcher in a prepare handler, as required by libadns, and
+.IX Subsection "Examples"
+.PP
+There are a number of principal ways to embed other event loops or modules
+into libev. Here are some ideas on how to include libadns into libev
+(there is a Perl module named \f(CW\*(C`EV::ADNS\*(C'\fR that does this, which you could
+use for an actually working example. Another Perl module named \f(CW\*(C`EV::Glib\*(C'\fR
+embeds a Glib main context into libev, and finally, \f(CW\*(C`Glib::EV\*(C'\fR embeds \s-1EV\s0
+into the Glib event loop).
+.PP
+Method 1: Add \s-1IO\s0 watchers and a timeout watcher in a prepare handler,
-in a check watcher, destroy them and call into libadns. What follows is
+and in a check watcher, destroy them and call into libadns. What follows
-pseudo-code only of course:
+is pseudo-code only of course. This requires you to either use a low
+priority for the check watcher or use \f(CW\*(C`ev_clear_pending\*(C'\fR explicitly, as
+the callbacks for the IO/timeout watchers might not have been called yet.
 .PP
 .Vb 2
 \&  static ev_io iow [nfd];
 \&  static ev_timer tw;
-.Ve
+\&
-.PP
-.Vb 9
 \&  static void
 \&  io_cb (ev_loop *loop, ev_io *w, int revents)
 \&  {
-\&    // set the relevant poll flags
-\&    // could also call adns_processreadable etc. here
-\&    struct pollfd *fd = (struct pollfd *)w->data;
-\&    if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
-\&    if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
 \&  }
-.Ve
+\&
-.PP
-.Vb 7
 \&  // create io watchers for each fd and a timer before blocking
 \&  static void
 \&  adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
 \&  {
-\&    int timeout = 3600000;truct pollfd fds [nfd];
+\&    int timeout = 3600000;
+\&    struct pollfd fds [nfd];
 \&    // actual code will need to loop here and realloc etc.
 \&    adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
-.Ve
+\&
-.PP
-.Vb 3
-\&    /* the callback is illegal, but won't be called as we stop during check */
+\&    /* the callback is illegal, but won\*(Aqt 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);
-.Ve
+\&
-.PP
-.Vb 6
-\&    // create on ev_io per pollfd
+\&    // create one ev_io per pollfd
 \&    for (int i = 0; i < nfd; ++i)
 \&      {
 \&        ev_io_init (iow + i, io_cb, fds [i].fd,
 \&          ((fds [i].events & POLLIN ? EV_READ : 0)
 \&           | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
-.Ve
+\&
-.PP
-.Vb 5
 \&        fds [i].revents = 0;
-\&        iow [i].data = fds + i;
 \&        ev_io_start (loop, iow + i);
 \&      }
 \&  }
-.Ve
+\&
-.PP
-.Vb 5
 \&  // stop all watchers after blocking
 \&  static void
 \&  adns_check_cb (ev_loop *loop, ev_check *w, int revents)
 \&  {
 \&    ev_timer_stop (loop, &tw);
-.Ve
+\&
-.PP
-.Vb 2
 \&    for (int i = 0; i < nfd; ++i)
+\&      {
+\&        // set the relevant poll flags
+\&        // could also call adns_processreadable etc. here
+\&        struct pollfd *fd = fds + i;
+\&        int revents = ev_clear_pending (iow + i);
+\&        if (revents & EV_READ ) fd\->revents |= fd\->events & POLLIN;
+\&        if (revents & EV_WRITE) fd\->revents |= fd\->events & POLLOUT;
+\&
+\&        // now stop the watcher
-\&      ev_io_stop (loop, iow + i);
+\&        ev_io_stop (loop, iow + i);
-.Ve
+\&      }
-.PP
+\&
-.Vb 2
 \&    adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
+\&  }
+.Ve
+.PP
+Method 2: This would be just like method 1, but you run \f(CW\*(C`adns_afterpoll\*(C'\fR
+in the prepare watcher and would dispose of the check watcher.
+.PP
+Method 3: If the module to be embedded supports explicit event
+notification (adns does), you can also make use of the actual watcher
+callbacks, and only destroy/create the watchers in the prepare watcher.
+.PP
+.Vb 5
+\&  static void
+\&  timer_cb (EV_P_ ev_timer *w, int revents)
+\&  {
+\&    adns_state ads = (adns_state)w\->data;
+\&    update_now (EV_A);
+\&
+\&    adns_processtimeouts (ads, &tv_now);
+\&  }
+\&
+\&  static void
+\&  io_cb (EV_P_ ev_io *w, int revents)
+\&  {
+\&    adns_state ads = (adns_state)w\->data;
+\&    update_now (EV_A);
+\&
+\&    if (revents & EV_READ ) adns_processreadable  (ads, w\->fd, &tv_now);
+\&    if (revents & EV_WRITE) adns_processwriteable (ads, w\->fd, &tv_now);
+\&  }
+\&
+\&  // do not ever call adns_afterpoll
+.Ve
+.PP
+Method 4: Do not use a prepare or check watcher because the module you
+want to embed is too inflexible to support it. Instead, youc na override
+their poll function.  The drawback with this solution is that the main
+loop is now no longer controllable by \s-1EV\s0. The \f(CW\*(C`Glib::EV\*(C'\fR module does
+this.
+.PP
+.Vb 4
+\&  static gint
+\&  event_poll_func (GPollFD *fds, guint nfds, gint timeout)
+\&  {
+\&    int got_events = 0;
+\&
+\&    for (n = 0; n < nfds; ++n)
+\&      // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
+\&
+\&    if (timeout >= 0)
+\&      // create/start timer
+\&
+\&    // poll
+\&    ev_loop (EV_A_ 0);
+\&
+\&    // stop timer again
+\&    if (timeout >= 0)
+\&      ev_timer_stop (EV_A_ &to);
+\&
+\&    // stop io watchers again \- their callbacks should have set
+\&    for (n = 0; n < nfds; ++n)
+\&      ev_io_stop (EV_A_ iow [n]);
+\&
+\&    return got_events;
 \&  }
 .Ve
 .ie n .Sh """ev_embed"" \- when one backend isn't enough..."
 .el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..."
 .IX Subsection "ev_embed - when one backend isn't enough..."
 portable one.
 .PP
 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:
+create it, and if that fails, use the normal loop for everything.
 .PP
-.Vb 3
+\fIWatcher-Specific Functions and Data Members\fR
-\&  struct ev_loop *loop_hi = ev_default_init (0);
+.IX Subsection "Watcher-Specific Functions and Data Members"
-\&  struct ev_loop *loop_lo = 0;
-\&  struct ev_embed embed;
-.Ve
-.PP
-.Vb 5
-\&  // see if there is a chance of getting one that works
-\&  // (remember that a flags value of 0 means autodetection)
-\&  loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
-\&    ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
-\&    : 0;
-.Ve
-.PP
-.Vb 8
-\&  // if we got one, then embed it, otherwise default to loop_hi
-\&  if (loop_lo)
-\&    {
-\&      ev_embed_init (&embed, 0, loop_lo);
-\&      ev_embed_start (loop_hi, &embed);
-\&    }
-\&  else
-\&    loop_lo = loop_hi;
-.Ve
 .IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
 .IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)"
 .PD 0
 .IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
 .IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)"
 .IP "ev_embed_sweep (loop, ev_embed *)" 4
 .IX Item "ev_embed_sweep (loop, ev_embed *)"
 Make a single, non-blocking sweep over the embedded loop. This works
 similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most
 apropriate way for embedded loops.
-.IP "struct ev_loop *loop [read\-only]" 4
+.IP "struct ev_loop *other [read\-only]" 4
-.IX Item "struct ev_loop *loop [read-only]"
+.IX Item "struct ev_loop *other [read-only]"
 The embedded event loop.
+.PP
+\fIExamples\fR
+.IX Subsection "Examples"
+.PP
+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 \f(CW\*(C`loop_hi\*(C'\fR, while the mebeddable loop is stored in
+\&\f(CW\*(C`loop_lo\*(C'\fR (which is \f(CW\*(C`loop_hi\*(C'\fR in the acse no embeddable loop can be
+used).
+.PP
+.Vb 3
+\&  struct ev_loop *loop_hi = ev_default_init (0);
+\&  struct ev_loop *loop_lo = 0;
+\&  struct ev_embed embed;
+\&
+\&  // see if there is a chance of getting one that works
+\&  // (remember that a flags value of 0 means autodetection)
+\&  loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
+\&    ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
+\&    : 0;
+\&
+\&  // if we got one, then embed it, otherwise default to loop_hi
+\&  if (loop_lo)
+\&    {
+\&      ev_embed_init (&embed, 0, loop_lo);
+\&      ev_embed_start (loop_hi, &embed);
+\&    }
+\&  else
+\&    loop_lo = loop_hi;
+.Ve
+.PP
+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
+\&\f(CW\*(C`loop_socket\*(C'\fR. (One might optionally use \f(CW\*(C`EVFLAG_NOENV\*(C'\fR, too).
+.PP
+.Vb 3
+\&  struct ev_loop *loop = ev_default_init (0);
+\&  struct ev_loop *loop_socket = 0;
+\&  struct ev_embed embed;
+\&
+\&  if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
+\&    if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
+\&      {
+\&        ev_embed_init (&embed, 0, loop_socket);
+\&        ev_embed_start (loop, &embed);
+\&      }
+\&
+\&  if (!loop_socket)
+\&    loop_socket = loop;
+\&
+\&  // now use loop_socket for all sockets, and loop for everything else
+.Ve
+.ie n .Sh """ev_fork"" \- the audacity to resume the event loop after a fork"
+.el .Sh "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork"
+.IX Subsection "ev_fork - the audacity to resume the event loop after a fork"
+Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because
+whoever is a good citizen cared to tell libev about it by calling
+\&\f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the
+event loop blocks next and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called,
+and only in the child after the fork. If whoever good citizen calling
+\&\f(CW\*(C`ev_default_fork\*(C'\fR cheats and calls it in the wrong process, the fork
+handlers will be invoked, too, of course.
+.PP
+\fIWatcher-Specific Functions and Data Members\fR
+.IX Subsection "Watcher-Specific Functions and Data Members"
+.IP "ev_fork_init (ev_signal *, callback)" 4
+.IX Item "ev_fork_init (ev_signal *, callback)"
+Initialises and configures the fork watcher \- it has no parameters of any
+kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless,
+believe me.
+.ie n .Sh """ev_async"" \- how to wake up another event loop"
+.el .Sh "\f(CWev_async\fP \- how to wake up another event loop"
+.IX Subsection "ev_async - how to wake up another event loop"
+In general, you cannot use an \f(CW\*(C`ev_loop\*(C'\fR from multiple threads or other
+asynchronous sources such as signal handlers (as opposed to multiple event
+loops \- those are of course safe to use in different threads).
+.PP
+Sometimes, however, you need to wake up another event loop you do not
+control, for example because it belongs to another thread. This is what
+\&\f(CW\*(C`ev_async\*(C'\fR watchers do: as long as the \f(CW\*(C`ev_async\*(C'\fR watcher is active, you
+can signal it by calling \f(CW\*(C`ev_async_send\*(C'\fR, which is thread\- and signal
+safe.
+.PP
+This functionality is very similar to \f(CW\*(C`ev_signal\*(C'\fR watchers, as signals,
+too, are asynchronous in nature, and signals, too, will be compressed
+(i.e. the number of callback invocations may be less than the number of
+\&\f(CW\*(C`ev_async_sent\*(C'\fR calls).
+.PP
+Unlike \f(CW\*(C`ev_signal\*(C'\fR watchers, \f(CW\*(C`ev_async\*(C'\fR works with any event loop, not
+just the default loop.
+.PP
+\fIQueueing\fR
+.IX Subsection "Queueing"
+.PP
+\&\f(CW\*(C`ev_async\*(C'\fR does not support queueing of data in any way. The reason
+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.
+.PP
+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:
+.IP "queueing from a signal handler context" 4
+.IX 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
+some fictitiuous \s-1SIGUSR1\s0 handler:
+.Sp
+.Vb 1
+\&   static ev_async mysig;
+\&
+\&   static void
+\&   sigusr1_handler (void)
+\&   {
+\&     sometype data;
+\&
+\&     // no locking etc.
+\&     queue_put (data);
+\&     ev_async_send (EV_DEFAULT_ &mysig);
+\&   }
+\&
+\&   static void
+\&   mysig_cb (EV_P_ ev_async *w, int revents)
+\&   {
+\&     sometype data;
+\&     sigset_t block, prev;
+\&
+\&     sigemptyset (&block);
+\&     sigaddset (&block, SIGUSR1);
+\&     sigprocmask (SIG_BLOCK, &block, &prev);
+\&
+\&     while (queue_get (&data))
+\&       process (data);
+\&
+\&     if (sigismember (&prev, SIGUSR1)
+\&       sigprocmask (SIG_UNBLOCK, &block, 0);
+\&   }
+.Ve
+.Sp
+(Note: pthreads in theory requires you to use \f(CW\*(C`pthread_setmask\*(C'\fR
+instead of \f(CW\*(C`sigprocmask\*(C'\fR when you use threads, but libev doesn't do it
+either...).
+.IP "queueing from a thread context" 4
+.IX Item "queueing from a thread context"
+The strategy for threads is different, as you cannot (easily) block
+threads but you can easily preempt them, so to queue safely you need to
+employ a traditional mutex lock, such as in this pthread example:
+.Sp
+.Vb 2
+\&   static ev_async mysig;
+\&   static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
+\&
+\&   static void
+\&   otherthread (void)
+\&   {
+\&     // only need to lock the actual queueing operation
+\&     pthread_mutex_lock (&mymutex);
+\&     queue_put (data);
+\&     pthread_mutex_unlock (&mymutex);
+\&
+\&     ev_async_send (EV_DEFAULT_ &mysig);
+\&   }
+\&
+\&   static void
+\&   mysig_cb (EV_P_ ev_async *w, int revents)
+\&   {
+\&     pthread_mutex_lock (&mymutex);
+\&
+\&     while (queue_get (&data))
+\&       process (data);
+\&
+\&     pthread_mutex_unlock (&mymutex);
+\&   }
+.Ve
+.PP
+\fIWatcher-Specific Functions and Data Members\fR
+.IX Subsection "Watcher-Specific Functions and Data Members"
+.IP "ev_async_init (ev_async *, callback)" 4
+.IX Item "ev_async_init (ev_async *, callback)"
+Initialises and configures the async watcher \- it has no parameters of any
+kind. There is a \f(CW\*(C`ev_asynd_set\*(C'\fR macro, but using it is utterly pointless,
+believe me.
+.IP "ev_async_send (loop, ev_async *)" 4
+.IX Item "ev_async_send (loop, ev_async *)"
+Sends/signals/activates the given \f(CW\*(C`ev_async\*(C'\fR watcher, that is, feeds
+an \f(CW\*(C`EV_ASYNC\*(C'\fR event on the watcher into the event loop. Unlike
+\&\f(CW\*(C`ev_feed_event\*(C'\fR, this call is safe to do in other threads, signal or
+similar contexts (see the dicusssion of \f(CW\*(C`EV_ATOMIC_T\*(C'\fR in the embedding
+section below on what exactly this means).
+.Sp
+This call incurs the overhead of a syscall only once per loop iteration,
+so while the overhead might be noticable, it doesn't apply to repeated
+calls to \f(CW\*(C`ev_async_send\*(C'\fR.
 .SH "OTHER FUNCTIONS"
 .IX Header "OTHER FUNCTIONS"
 There are some other functions of possible interest. Described. Here. Now.
 .IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4
 .IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)"
 \&    if (revents & EV_TIMEOUT)
 \&      /* doh, nothing entered */;
 \&    else if (revents & EV_READ)
 \&      /* stdin might have data for us, joy! */;
 \&  }
-.Ve
+\&
-.Sp
-.Vb 1
 \&  ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
 .Ve
 .IP "ev_feed_event (ev_loop *, watcher *, int revents)" 4
 .IX Item "ev_feed_event (ev_loop *, watcher *, int revents)"
 Feeds the given event set into the event loop, as if the specified event
 loop!).
 .SH "LIBEVENT EMULATION"
 .IX Header "LIBEVENT EMULATION"
 Libev offers a compatibility emulation layer for libevent. It cannot
 emulate the internals of libevent, so here are some usage hints:
+.IP "\(bu" 4
-.IP "* Use it by including <event.h>, as usual." 4
+Use it by including <event.h>, as usual.
-.IX Item "Use it by including <event.h>, as usual."
+.IP "\(bu" 4
-.PD 0
+The following members are fully supported: ev_base, ev_callback,
-.IP "* The following members are fully supported: ev_base, ev_callback, ev_arg, ev_fd, ev_res, ev_events." 4
+ev_arg, ev_fd, ev_res, ev_events.
-.IX Item "The following members are fully supported: ev_base, ev_callback, ev_arg, ev_fd, ev_res, ev_events."
+.IP "\(bu" 4
-.IP "* Avoid using ev_flags and the EVLIST_*\-macros, while it is maintained by libev, it does not work exactly the same way as in libevent (consider it a private \s-1API\s0)." 4
+Avoid using ev_flags and the EVLIST_*\-macros, while it is
-.IX Item "Avoid using ev_flags and the EVLIST_*-macros, while it is maintained by libev, it does not work exactly the same way as in libevent (consider it a private API)."
+maintained by libev, it does not work exactly the same way as in libevent (consider
-.IP "* Priorities are not currently supported. Initialising priorities will fail and all watchers will have the same priority, even though there is an ev_pri field." 4
+it a private \s-1API\s0).
-.IX Item "Priorities are not currently supported. Initialising priorities will fail and all watchers will have the same priority, even though there is an ev_pri field."
+.IP "\(bu" 4
+Priorities are not currently supported. Initialising priorities
+will fail and all watchers will have the same priority, even though there
+is an ev_pri field.
+.IP "\(bu" 4
-.IP "* Other members are not supported." 4
+Other members are not supported.
-.IX Item "Other members are not supported."
+.IP "\(bu" 4
-.IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4
+The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need
-.IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library."
+to use the libev header file and library.
-.PD
 .SH "\*(C+ SUPPORT"
 .IX Header " SUPPORT"
 Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow
 you to use some convinience methods to start/stop watchers and also change
 the callback model to a model using method callbacks on objects.
 .PP
 .Vb 1
 \&  #include <ev++.h>
 .Ve
 .PP
-(it is not installed by default). This automatically includes \fIev.h\fR
+This automatically includes \fIev.h\fR and puts all of its definitions (many
-and puts all of its definitions (many of them macros) into the global
+of them macros) into the global namespace. All \*(C+ specific things are
-namespace. All \*(C+ specific things are put into the \f(CW\*(C`ev\*(C'\fR namespace.
+put into the \f(CW\*(C`ev\*(C'\fR namespace. It should support all the same embedding
+options as \fIev.h\fR, most notably \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR.
 .PP
-It should support all the same embedding options as \fIev.h\fR, most notably
+Care has been taken to keep the overhead low. The only data member the \*(C+
-\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR.
+classes add (compared to plain C\-style watchers) is the event loop pointer
+that the watcher is associated with (or no additional members at all if
+you disable \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR when embedding libev).
+.PP
+Currently, functions, and static and non-static member functions can be
+used as callbacks. Other types should be easy to add as long as they only
+need one additional pointer for context. If you need support for other
+types of functors please contact the author (preferably after implementing
+it).
 .PP
 Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace:
 .ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4
 .el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4
 .IX Item "ev::READ, ev::WRITE etc."
 which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro
 defines by many implementations.
 .Sp
 All of those classes have these methods:
 .RS 4
-.IP "ev::TYPE::TYPE (object *, object::method *)" 4
+.IP "ev::TYPE::TYPE ()" 4
-.IX Item "ev::TYPE::TYPE (object *, object::method *)"
+.IX Item "ev::TYPE::TYPE ()"
 .PD 0
-.IP "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)" 4
+.IP "ev::TYPE::TYPE (struct ev_loop *)" 4
-.IX Item "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)"
+.IX Item "ev::TYPE::TYPE (struct ev_loop *)"
 .IP "ev::TYPE::~TYPE" 4
 .IX Item "ev::TYPE::~TYPE"
 .PD
-The constructor takes a pointer to an object and a method pointer to
+The constructor (optionally) takes an event loop to associate the watcher
-the event handler callback to call in this class. The constructor calls
+with. If it is omitted, it will use \f(CW\*(C`EV_DEFAULT\*(C'\fR.
-\&\f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the \f(CW\*(C`set\*(C'\fR method
+.Sp
-before starting it. If you do not specify a loop then the constructor
+The constructor calls \f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the
-automatically associates the default loop with this watcher.
+\&\f(CW\*(C`set\*(C'\fR method before starting it.
+.Sp
+It will not set a callback, however: You have to call the templated \f(CW\*(C`set\*(C'\fR
+method to set a callback before you can start the watcher.
+.Sp
+(The reason why you have to use a method is a limitation in \*(C+ which does
+not allow explicit template arguments for constructors).
 .Sp
 The destructor automatically stops the watcher if it is active.
+.IP "w\->set<class, &class::method> (object *)" 4
+.IX Item "w->set<class, &class::method> (object *)"
+This method sets the callback method to call. The method has to have a
+signature of \f(CW\*(C`void (*)(ev_TYPE &, int)\*(C'\fR, it receives the watcher as
+first argument and the \f(CW\*(C`revents\*(C'\fR as second. The object must be given as
+parameter and is stored in the \f(CW\*(C`data\*(C'\fR member of the watcher.
+.Sp
+This method synthesizes efficient thunking code to call your method from
+the C callback that libev requires. If your compiler can inline your
+callback (i.e. it is visible to it at the place of the \f(CW\*(C`set\*(C'\fR call and
+your compiler is good :), then the method will be fully inlined into the
+thunking function, making it as fast as a direct C callback.
+.Sp
+Example: simple class declaration and watcher initialisation
+.Sp
+.Vb 4
+\&  struct myclass
+\&  {
+\&    void io_cb (ev::io &w, int revents) { }
+\&  }
+\&
+\&  myclass obj;
+\&  ev::io iow;
+\&  iow.set <myclass, &myclass::io_cb> (&obj);
+.Ve
+.IP "w\->set<function> (void *data = 0)" 4
+.IX Item "w->set<function> (void *data = 0)"
+Also sets a callback, but uses a static method or plain function as
+callback. The optional \f(CW\*(C`data\*(C'\fR argument will be stored in the watcher's
+\&\f(CW\*(C`data\*(C'\fR member and is free for you to use.
+.Sp
+The prototype of the \f(CW\*(C`function\*(C'\fR must be \f(CW\*(C`void (*)(ev::TYPE &w, int)\*(C'\fR.
+.Sp
+See the method\-\f(CW\*(C`set\*(C'\fR above for more details.
+.Sp
+Example:
+.Sp
+.Vb 2
+\&  static void io_cb (ev::io &w, int revents) { }
+\&  iow.set <io_cb> ();
+.Ve
 .IP "w\->set (struct ev_loop *)" 4
 .IX Item "w->set (struct ev_loop *)"
 Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only
 do this when the watcher is inactive (and not pending either).
 .IP "w\->set ([args])" 4
 .IX Item "w->set ([args])"
 Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same args. Must be
-called at least once.  Unlike the C counterpart, an active watcher gets
+called at least once. Unlike the C counterpart, an active watcher gets
-automatically stopped and restarted.
+automatically stopped and restarted when reconfiguring it with this
+method.
 .IP "w\->start ()" 4
 .IX Item "w->start ()"
-Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument as the
+Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the
-constructor already takes the loop.
+constructor already stores the event loop.
 .IP "w\->stop ()" 4
 .IX Item "w->stop ()"
 Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument.
-.ie n .IP "w\->again ()       ""ev::timer""\fR, \f(CW""ev::periodic"" only" 4
+.ie n .IP "w\->again () (""ev::timer""\fR, \f(CW""ev::periodic"" only)" 4
-.el .IP "w\->again ()       \f(CWev::timer\fR, \f(CWev::periodic\fR only" 4
+.el .IP "w\->again () (\f(CWev::timer\fR, \f(CWev::periodic\fR only)" 4
-.IX Item "w->again ()       ev::timer, ev::periodic only"
+.IX Item "w->again () (ev::timer, ev::periodic only)"
 For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding
 \&\f(CW\*(C`ev_TYPE_again\*(C'\fR function.
-.ie n .IP "w\->sweep ()       ""ev::embed"" only" 4
+.ie n .IP "w\->sweep () (""ev::embed"" only)" 4
-.el .IP "w\->sweep ()       \f(CWev::embed\fR only" 4
+.el .IP "w\->sweep () (\f(CWev::embed\fR only)" 4
-.IX Item "w->sweep ()       ev::embed only"
+.IX Item "w->sweep () (ev::embed only)"
 Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR.
-.ie n .IP "w\->update ()      ""ev::stat"" only" 4
+.ie n .IP "w\->update () (""ev::stat"" only)" 4
-.el .IP "w\->update ()      \f(CWev::stat\fR only" 4
+.el .IP "w\->update () (\f(CWev::stat\fR only)" 4
-.IX Item "w->update ()      ev::stat only"
+.IX Item "w->update () (ev::stat only)"
 Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR.
 .RE
 .RS 4
 .RE
 .PP
 the constructor.
 .PP
 .Vb 4
 \&  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)
+\&    {
+\&      io  .set <myclass, &myclass::io_cb  > (this);
+\&      idle.set <myclass, &myclass::idle_cb> (this);
+\&
+\&      io.start (fd, ev::READ);
+\&    }
+\&  };
 .Ve
+.SH "OTHER LANGUAGE BINDINGS"
+.IX Header "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
+any interesting language binding in addition to the ones listed here, drop
+me a note.
+.IP "Perl" 4
+.IX Item "Perl"
+The \s-1EV\s0 module implements the full libev \s-1API\s0 and is actually used to test
+libev. \s-1EV\s0 is developed together with libev. Apart from the \s-1EV\s0 core module,
+there are additional modules that implement libev-compatible interfaces
+to \f(CW\*(C`libadns\*(C'\fR (\f(CW\*(C`EV::ADNS\*(C'\fR), \f(CW\*(C`Net::SNMP\*(C'\fR (\f(CW\*(C`Net::SNMP::EV\*(C'\fR) and the
+\&\f(CW\*(C`libglib\*(C'\fR event core (\f(CW\*(C`Glib::EV\*(C'\fR and \f(CW\*(C`EV::Glib\*(C'\fR).
+.Sp
+It can be found and installed via \s-1CPAN\s0, its homepage is found at
+<http://software.schmorp.de/pkg/EV>.
+.IP "Ruby" 4
+.IX Item "Ruby"
+Tony Arcieri has written a ruby extension that offers access to a subset
+of the libev \s-1API\s0 and adds filehandle abstractions, asynchronous \s-1DNS\s0 and
+more on top of it. It can be found via gem servers. Its homepage is at
+<http://rev.rubyforge.org/>.
+.IP "D" 4
+.IX Item "D"
+Leandro Lucarella has written a D language binding (\fIev.d\fR) for libev, to
+be found at <http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.
+.SH "MACRO MAGIC"
+.IX Header "MACRO MAGIC"
+Libev can be compiled with a variety of options, the most fundamantal
+of which is \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most)
+functions and callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument.
 .PP
+To make it easier to write programs that cope with either variant, the
+following macros are defined:
+.ie n .IP """EV_A""\fR, \f(CW""EV_A_""" 4
+.el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4
+.IX Item "EV_A, EV_A_"
+This provides the loop \fIargument\fR for functions, if one is required (\*(L"ev
+loop argument\*(R"). The \f(CW\*(C`EV_A\*(C'\fR form is used when this is the sole argument,
+\&\f(CW\*(C`EV_A_\*(C'\fR is used when other arguments are following. Example:
+.Sp
+.Vb 3
+\&  ev_unref (EV_A);
+\&  ev_timer_add (EV_A_ watcher);
+\&  ev_loop (EV_A_ 0);
+.Ve
+.Sp
+It assumes the variable \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR is in scope,
+which is often provided by the following macro.
+.ie n .IP """EV_P""\fR, \f(CW""EV_P_""" 4
+.el .IP "\f(CWEV_P\fR, \f(CWEV_P_\fR" 4
+.IX Item "EV_P, EV_P_"
+This provides the loop \fIparameter\fR for functions, if one is required (\*(L"ev
+loop parameter\*(R"). The \f(CW\*(C`EV_P\*(C'\fR form is used when this is the sole parameter,
+\&\f(CW\*(C`EV_P_\*(C'\fR is used when other parameters are following. Example:
+.Sp
 .Vb 2
-\&    myclass ();
+\&  // this is how ev_unref is being declared
+\&  static void ev_unref (EV_P);
+\&
+\&  // this is how you can declare your typical callback
+\&  static void cb (EV_P_ ev_timer *w, int revents)
+.Ve
+.Sp
+It declares a parameter \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR, quite
+suitable for use with \f(CW\*(C`EV_A\*(C'\fR.
+.ie n .IP """EV_DEFAULT""\fR, \f(CW""EV_DEFAULT_""" 4
+.el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4
+.IX Item "EV_DEFAULT, EV_DEFAULT_"
+Similar to the other two macros, this gives you the value of the default
+loop, if multiple loops are supported (\*(L"ev loop default\*(R").
+.PP
+Example: Declare and initialise a check watcher, utilising the above
+macros so it will work regardless of whether multiple loops are supported
+or not.
+.PP
+.Vb 5
+\&  static void
+\&  check_cb (EV_P_ ev_timer *w, int revents)
+\&  {
+\&    ev_check_stop (EV_A_ w);
 \&  }
-.Ve
+\&
-.PP
+\&  ev_check check;
-.Vb 6
+\&  ev_check_init (&check, check_cb);
-\&  myclass::myclass (int fd)
+\&  ev_check_start (EV_DEFAULT_ &check);
-\&  : io   (this, &myclass::io_cb),
+\&  ev_loop (EV_DEFAULT_ 0);
-\&    idle (this, &myclass::idle_cb)
-\&  {
-\&    io.start (fd, ev::READ);
-\&  }
 .Ve
 .SH "EMBEDDING"
 .IX Header "EMBEDDING"
 Libev can (and often is) directly embedded into host
 applications. Examples of applications that embed it include the Deliantra
 Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe)
-and rxvt\-unicode.
+and rxvt-unicode.
 .PP
-The goal is to enable you to just copy the neecssary files into your
+The goal is to enable you to just copy the necessary files into your
 source directory without having to change even a single line in them, so
 you can easily upgrade by simply copying (or having a checked-out copy of
 libev somewhere in your source tree).
 .Sh "\s-1FILESETS\s0"
 .IX Subsection "FILESETS"
 .Vb 4
 \&  ev.h
 \&  ev.c
 \&  ev_vars.h
 \&  ev_wrap.h
-.Ve
+\&
-.PP
-.Vb 1
 \&  ev_win32.c      required on win32 platforms only
-.Ve
+\&
-.PP
-.Vb 5
-\&  ev_select.c     only when select backend is enabled (which is by default)
+\&  ev_select.c     only when select backend is enabled (which is enabled by default)
 \&  ev_poll.c       only when poll backend is enabled (disabled by default)
 \&  ev_epoll.c      only when the epoll backend is enabled (disabled by default)
 \&  ev_kqueue.c     only when the kqueue backend is enabled (disabled by default)
 \&  ev_port.c       only when the solaris port backend is enabled (disabled by default)
 .Ve
 .IX Item "EV_USE_MONOTONIC"
 If defined to be \f(CW1\fR, libev will try to detect the availability of the
 monotonic clock option at both compiletime and runtime. Otherwise no use
 of the monotonic clock option will be attempted. If you enable this, you
 usually have to link against librt or something similar. Enabling it when
-the functionality isn't available is safe, though, althoguh you have
+the functionality isn't available is safe, though, although you have
 to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR
 function is hiding in (often \fI\-lrt\fR).
 .IP "\s-1EV_USE_REALTIME\s0" 4
 .IX Item "EV_USE_REALTIME"
 If defined to be \f(CW1\fR, libev will try to detect the availability of the
 realtime clock option at compiletime (and assume its availability at
 runtime if successful). Otherwise no use of the realtime clock option will
 be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get
-(CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See tzhe note about libraries
+(CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See the
-in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though.
+note about libraries in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though.
+.IP "\s-1EV_USE_NANOSLEEP\s0" 4
+.IX Item "EV_USE_NANOSLEEP"
+If defined to be \f(CW1\fR, libev will assume that \f(CW\*(C`nanosleep ()\*(C'\fR is available
+and will use it for delays. Otherwise it will use \f(CW\*(C`select ()\*(C'\fR.
 .IP "\s-1EV_USE_SELECT\s0" 4
 .IX Item "EV_USE_SELECT"
 If undefined or defined to be \f(CW1\fR, libev will compile in support for the
 \&\f(CW\*(C`select\*(C'\fR(2) backend. No attempt at autodetection will be done: if no
 other method takes over, select will be it. Otherwise the select backend
 wants osf handles on win32 (this is the case when the select to
 be used is the winsock select). This means that it will call
 \&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise,
 it is assumed that all these functions actually work on fds, even
 on win32. Should not be defined on non\-win32 platforms.
+.IP "\s-1EV_FD_TO_WIN32_HANDLE\s0" 4
+.IX Item "EV_FD_TO_WIN32_HANDLE"
+If \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR is enabled, then libev needs a way to map
+file descriptors to socket handles. When not defining this symbol (the
+default), then libev will call \f(CW\*(C`_get_osfhandle\*(C'\fR, which is usually
+correct. In some cases, programs use their own file descriptor management,
+in which case they can provide this function to map fds to socket handles.
 .IP "\s-1EV_USE_POLL\s0" 4
 .IX Item "EV_USE_POLL"
 If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2)
 backend. Otherwise it will be enabled on non\-win32 platforms. It
 takes precedence over select.
 otherwise another method will be used as fallback. This is the preferred
 backend for Solaris 10 systems.
 .IP "\s-1EV_USE_DEVPOLL\s0" 4
 .IX Item "EV_USE_DEVPOLL"
 reserved for future expansion, works like the \s-1USE\s0 symbols above.
+.IP "\s-1EV_USE_INOTIFY\s0" 4
+.IX Item "EV_USE_INOTIFY"
+If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify
+interface to speed up \f(CW\*(C`ev_stat\*(C'\fR watchers. Its actual availability will
+be detected at runtime.
+.IP "\s-1EV_ATOMIC_T\s0" 4
+.IX Item "EV_ATOMIC_T"
+Libev requires an integer type (suitable for storing \f(CW0\fR or \f(CW1\fR) whose
+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 \*(L"locking\*(R"
+as well as for signal and thread safety in \f(CW\*(C`ev_async\*(C'\fR watchers.
+.Sp
+In the absense of this define, libev will use \f(CW\*(C`sig_atomic_t volatile\*(C'\fR
+(from \fIsignal.h\fR), which is usually good enough on most platforms.
 .IP "\s-1EV_H\s0" 4
 .IX Item "EV_H"
 The name of the \fIev.h\fR header file used to include it. The default if
-undefined is \f(CW\*(C`<ev.h>\*(C'\fR in \fIevent.h\fR and \f(CW"ev.h"\fR in \fIev.c\fR. This
+undefined is \f(CW"ev.h"\fR in \fIevent.h\fR, \fIev.c\fR and \fIev++.h\fR. This can be
-can be used to virtually rename the \fIev.h\fR header file in case of conflicts.
+used to virtually rename the \fIev.h\fR header file in case of conflicts.
 .IP "\s-1EV_CONFIG_H\s0" 4
 .IX Item "EV_CONFIG_H"
 If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override
 \&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to
 \&\f(CW\*(C`EV_H\*(C'\fR, above.
 .IP "\s-1EV_EVENT_H\s0" 4
 .IX Item "EV_EVENT_H"
 Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea
-of how the \fIevent.h\fR header can be found.
+of how the \fIevent.h\fR header can be found, the default is \f(CW"event.h"\fR.
 .IP "\s-1EV_PROTOTYPES\s0" 4
 .IX Item "EV_PROTOTYPES"
 If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function
 prototypes, but still define all the structs and other symbols. This is
 occasionally useful if you want to provide your own wrapper functions
 If undefined or defined to \f(CW1\fR, then all event-loop-specific functions
 will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create
 additional independent event loops. Otherwise there will be no support
 for multiple event loops and there is no first event loop pointer
 argument. Instead, all functions act on the single default loop.
+.IP "\s-1EV_MINPRI\s0" 4
+.IX Item "EV_MINPRI"
+.PD 0
+.IP "\s-1EV_MAXPRI\s0" 4
+.IX Item "EV_MAXPRI"
+.PD
+The range of allowed priorities. \f(CW\*(C`EV_MINPRI\*(C'\fR must be smaller or equal to
+\&\f(CW\*(C`EV_MAXPRI\*(C'\fR, but otherwise there are no non-obvious limitations. You can
+provide for more priorities by overriding those symbols (usually defined
+to be \f(CW\*(C`\-2\*(C'\fR and \f(CW2\fR, respectively).
+.Sp
+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.
+.Sp
+If your embedding app does not need any priorities, defining these both to
+\&\f(CW0\fR will save some memory and cpu.
 .IP "\s-1EV_PERIODIC_ENABLE\s0" 4
 .IX Item "EV_PERIODIC_ENABLE"
 If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If
+defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
+code.
+.IP "\s-1EV_IDLE_ENABLE\s0" 4
+.IX Item "EV_IDLE_ENABLE"
+If undefined or defined to be \f(CW1\fR, then idle watchers are supported. If
 defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
 code.
 .IP "\s-1EV_EMBED_ENABLE\s0" 4
 .IX Item "EV_EMBED_ENABLE"
 If undefined or defined to be \f(CW1\fR, then embed watchers are supported. If
 defined to be \f(CW0\fR, then they are not.
 .IP "\s-1EV_STAT_ENABLE\s0" 4
 .IX Item "EV_STAT_ENABLE"
 If undefined or defined to be \f(CW1\fR, then stat watchers are supported. If
 defined to be \f(CW0\fR, then they are not.
+.IP "\s-1EV_FORK_ENABLE\s0" 4
+.IX Item "EV_FORK_ENABLE"
+If undefined or defined to be \f(CW1\fR, then fork watchers are supported. If
+defined to be \f(CW0\fR, then they are not.
+.IP "\s-1EV_ASYNC_ENABLE\s0" 4
+.IX Item "EV_ASYNC_ENABLE"
+If undefined or defined to be \f(CW1\fR, then async watchers are supported. If
+defined to be \f(CW0\fR, then they are not.
 .IP "\s-1EV_MINIMAL\s0" 4
 .IX Item "EV_MINIMAL"
 If you need to shave off some kilobytes of code at the expense of some
 speed, define this symbol to \f(CW1\fR. Currently only used for gcc to override
 some inlining decisions, saves roughly 30% codesize of amd64.
+.IP "\s-1EV_PID_HASHSIZE\s0" 4
+.IX Item "EV_PID_HASHSIZE"
+\&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by
+pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), usually more
+than enough. If you need to manage thousands of children you might want to
+increase this value (\fImust\fR be a power of two).
+.IP "\s-1EV_INOTIFY_HASHSIZE\s0" 4
+.IX Item "EV_INOTIFY_HASHSIZE"
+\&\f(CW\*(C`ev_stat\*(C'\fR watchers use a small hash table to distribute workload by
+inotify watch id. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR),
+usually more than enough. If you need to manage thousands of \f(CW\*(C`ev_stat\*(C'\fR
+watchers you might want to increase this value (\fImust\fR be a power of
+two).
 .IP "\s-1EV_COMMON\s0" 4
 .IX Item "EV_COMMON"
 By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR 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,
 .IP "ev_set_cb (ev, cb)" 4
 .IX Item "ev_set_cb (ev, cb)"
 .PD
 Can be used to change the callback member declaration in each watcher,
 and the way callbacks are invoked and set. Must expand to a struct member
-definition and a statement, respectively. See the \fIev.v\fR header file for
+definition and a statement, respectively. See the \fIev.h\fR header file for
 their default definitions. One possible use for overriding these is to
 avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use
 method calls instead of plain function calls in \*(C+.
+.Sh "\s-1EXPORTED\s0 \s-1API\s0 \s-1SYMBOLS\s0"
+.IX Subsection "EXPORTED API SYMBOLS"
+If you need to re-export the \s-1API\s0 (e.g. via a dll) and you need a list of
+exported symbols, you can use the provided \fISymbol.*\fR files which list
+all public symbols, one per line:
+.PP
+.Vb 2
+\&  Symbols.ev      for libev proper
+\&  Symbols.event   for the libevent emulation
+.Ve
+.PP
+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).
+.PP
+A sed command like this will create wrapper \f(CW\*(C`#define\*(C'\fR's that you need to
+include before including \fIev.h\fR:
+.PP
+.Vb 1
+\&   <Symbols.ev sed \-e "s/.*/#define & myprefix_&/" >wrap.h
+.Ve
+.PP
+This would create a file \fIwrap.h\fR which essentially looks like this:
+.PP
+.Vb 4
+\&   #define ev_backend     myprefix_ev_backend
+\&   #define ev_check_start myprefix_ev_check_start
+\&   #define ev_check_stop  myprefix_ev_check_stop
+\&   ...
+.Ve
 .Sh "\s-1EXAMPLES\s0"
 .IX Subsection "EXAMPLES"
 For a real-world example of a program the includes libev
 verbatim, you can have a look at the \s-1EV\s0 perl module
 (<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
 the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public
 interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file
 will be compiled. It is pretty complex because it provides its own header
 file.
-.Sp
+.PP
 The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file
-that everybody includes and which overrides some autoconf choices:
+that everybody includes and which overrides some configure choices:
-.Sp
+.PP
-.Vb 4
+.Vb 9
+\&  #define EV_MINIMAL 1
 \&  #define EV_USE_POLL 0
 \&  #define EV_MULTIPLICITY 0
-\&  #define EV_PERIODICS 0
+\&  #define EV_PERIODIC_ENABLE 0
+\&  #define EV_STAT_ENABLE 0
+\&  #define EV_FORK_ENABLE 0
 \&  #define EV_CONFIG_H <config.h>
-.Ve
+\&  #define EV_MINPRI 0
-.Sp
+\&  #define EV_MAXPRI 0
-.Vb 1
+\&
 \&  #include "ev++.h"
 .Ve
-.Sp
+.PP
 And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled:
-.Sp
+.PP
 .Vb 2
 \&  #include "ev_cpp.h"
 \&  #include "ev.c"
 .Ve
 .SH "COMPLEXITIES"
 .IX Header "COMPLEXITIES"
 In this section the complexities of (many of) the algorithms used inside
 libev will be explained. For complexity discussions about backends see the
 documentation for \f(CW\*(C`ev_default_init\*(C'\fR.
-.RS 4
+.PP
+All of the following are about amortised time: If an array needs to be
+extended, libev needs to realloc and move the whole array, but this
+happens asymptotically never with higher number of elements, so O(1) might
+mean it might do a lengthy realloc operation in rare cases, but on average
+it is much faster and asymptotically approaches constant time.
 .IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4
 .IX 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 (\f(CW\*(C`ld 100\*(C'\fR) of these watchers.
+.IP "Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)" 4
+.IX 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.
+.IP "Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)" 4
+.IX 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.
+.IP "Stopping check/prepare/idle/fork/async watchers: O(1)" 4
+.IX Item "Stopping check/prepare/idle/fork/async watchers: O(1)"
 .PD 0
-.IP "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)" 4
-.IX Item "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)"
-.IP "Starting io/check/prepare/idle/signal/child watchers: O(1)" 4
-.IX Item "Starting io/check/prepare/idle/signal/child watchers: O(1)"
-.IP "Stopping check/prepare/idle watchers: O(1)" 4
-.IX Item "Stopping check/prepare/idle watchers: O(1)"
-.IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))" 4
+.IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4
-.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))"
+.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))"
+.PD
+These watchers are stored in lists then need to be walked to find the
+correct watcher to remove. The lists are usually short (you don't usually
+have many watchers waiting for the same fd or signal).
-.IP "Finding the next timer per loop iteration: O(1)" 4
+.IP "Finding the next timer in each loop iteration: O(1)" 4
-.IX Item "Finding the next timer per loop iteration: O(1)"
+.IX Item "Finding the next timer in each loop iteration: O(1)"
+By virtue of using a binary heap, the next timer is always found at the
+beginning of the storage array.
 .IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4
 .IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)"
-.IP "Activating one watcher: O(1)" 4
+A change means an I/O watcher gets started or stopped, which requires
-.IX Item "Activating one watcher: O(1)"
+libev to recalculate its status (and possibly tell the kernel, depending
-.RE
+on backend and wether \f(CW\*(C`ev_io_set\*(C'\fR was used).
-.RS 4
+.IP "Activating one watcher (putting it into the pending state): O(1)" 4
+.IX Item "Activating one watcher (putting it into the pending state): O(1)"
+.PD 0
+.IP "Priority handling: O(number_of_priorities)" 4
+.IX Item "Priority handling: O(number_of_priorities)"
 .PD
+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.
+.IP "Sending an ev_async: O(1)" 4
+.IX Item "Sending an ev_async: O(1)"
+.PD 0
+.IP "Processing ev_async_send: O(number_of_async_watchers)" 4
+.IX Item "Processing ev_async_send: O(number_of_async_watchers)"
+.IP "Processing signals: O(max_signal_number)" 4
+.IX Item "Processing signals: O(max_signal_number)"
+.PD
+Sending involves a syscall \fIiff\fR there were no other \f(CW\*(C`ev_async_send\*(C'\fR
+calls in the current loop iteration. Checking for async and signal events
+involves iterating over all running async watchers or all signal numbers.
+.SH "Win32 platform limitations and workarounds"
+.IX Header "Win32 platform limitations and workarounds"
+Win32 doesn't support any of the standards (e.g. \s-1POSIX\s0) that libev
+requires, and its I/O model is fundamentally incompatible with the \s-1POSIX\s0
+model. Libev still offers limited functionality on this platform in
+the form of the \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR backend, and only supports socket
+descriptors. This only applies when using Win32 natively, not when using
+e.g. cygwin.
+.PP
+There is no supported compilation method available on windows except
+embedding it into other applications.
+.PP
+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 \s-1POSIX\s0 model, which cannot
+be implemented efficiently on windows (microsoft monopoly games).
+.IP "The winsocket select function" 4
+.IX Item "The winsocket select function"
+The winsocket \f(CW\*(C`select\*(C'\fR function doesn't follow \s-1POSIX\s0 in that it requires
+socket \fIhandles\fR and not socket \fIfile descriptors\fR. This makes select
+very inefficient, and also requires a mapping from file descriptors
+to socket handles. See the discussion of the \f(CW\*(C`EV_SELECT_USE_FD_SET\*(C'\fR,
+\&\f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR and \f(CW\*(C`EV_FD_TO_WIN32_HANDLE\*(C'\fR preprocessor
+symbols for more info.
+.Sp
+The configuration for a \*(L"naked\*(R" win32 using the microsoft runtime
+libraries and raw winsocket select is:
+.Sp
+.Vb 2
+\&  #define EV_USE_SELECT 1
+\&  #define EV_SELECT_IS_WINSOCKET 1   /* forces EV_SELECT_USE_FD_SET, too */
+.Ve
+.Sp
+Note that winsockets handling of fd sets is O(n), so you can easily get a
+complexity in the O(nA\*^X) range when using win32.
+.IP "Limited number of file descriptors" 4
+.IX 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 max. of \f(CW64\fR handles
+(probably owning to the fact that all windows kernels can only wait for
+\&\f(CW64\fR things at the same time internally; microsoft recommends spawning a
+chain of threads and wait for 63 handles and the previous thread in each).
+.Sp
+Newer versions support more handles, but you need to define \f(CW\*(C`FD_SETSIZE\*(C'\fR
+to some high number (e.g. \f(CW2048\fR) before compiling the winsocket select
+call (which might be in libev or elsewhere, for example, perl does its own
+select emulation on windows).
+.Sp
+Another limit is the number of file descriptors in the microsoft runtime
+libraries, which by default is \f(CW64\fR (there must be a hidden \fI64\fR fetish
+or something like this inside microsoft). You can increase this by calling
+\&\f(CW\*(C`_setmaxstdio\*(C'\fR, which can increase this limit to \f(CW2048\fR (another
+arbitrary limit), but is broken in many versions of the microsoft runtime
+libraries.
+.Sp
+This might get you to about \f(CW512\fR or \f(CW2048\fR 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(nA\*^X)) will likely make this unworkable.
 .SH "AUTHOR"
 .IX Header "AUTHOR"
 Marc Lehmann <libev@schmorp.de>.
+.SH "POD ERRORS"
+.IX Header "POD ERRORS"
+Hey! \fBThe above document had some coding errors, which are explained below:\fR
+.IP "Around line 2951:" 4
+.IX Item "Around line 2951:"
+You forgot a '=back' before '=head2'

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Comparing libev/ev.3 (file contents):
Revision 1.23 by root, Tue Nov 27 08:20:42 2007 UTC vs.
Revision 1.62 by root, Sun Mar 16 16:38:23 2008 UTC