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+.rm #[ #] #H #V #F C
+.\" ========================================================================
+.\"
+.IX Title "LIBEIO 3"
+.TH LIBEIO 3 "2008-05-11" "libeio-1.0" "libeio - truly asynchronous POSIX I/O"
+.\" 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 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 "\s-1FEATURES\s0"
+.IX Subsection "FEATURES"
+Libev supports \f(CW\*(C`select\*(C'\fR, \f(CW\*(C`poll\*(C'\fR, the Linux-specific \f(CW\*(C`epoll\*(C'\fR, the
+BSD-specific \f(CW\*(C`kqueue\*(C'\fR and the Solaris-specific event port mechanisms
+for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), the Linux \f(CW\*(C`inotify\*(C'\fR interface
+(for \f(CW\*(C`ev_stat\*(C'\fR), relative timers (\f(CW\*(C`ev_timer\*(C'\fR), absolute timers
+with customised rescheduling (\f(CW\*(C`ev_periodic\*(C'\fR), synchronous signals
+(\f(CW\*(C`ev_signal\*(C'\fR), process status change events (\f(CW\*(C`ev_child\*(C'\fR), and event
+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 "\s-1CONVENTIONS\s0"
+.IX Subsection "CONVENTIONS"
+Libev is very configurable. In this manual the default (and most common)
+configuration will be described, which supports multiple event loops. For
+more info about various configuration options please have a look at
+\&\fB\s-1EMBED\s0\fR section in this manual. If libev was configured without support
+for multiple event loops, then all functions taking an initial argument of
+name \f(CW\*(C`loop\*(C'\fR (which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR) will not have
+this argument.
+.Sh "\s-1TIME\s0 \s-1REPRESENTATION\s0"
+.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 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 \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
+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
+version.
+.Sp
+.Vb 3
+\&  assert (("libev version mismatch",
+\&           ev_version_major () == EV_VERSION_MAJOR
+\&           && ev_version_minor () >= EV_VERSION_MINOR));
+.Ve
+.IP "unsigned int ev_supported_backends ()" 4
+.IX Item "unsigned int ev_supported_backends ()"
+Return the set of all backends (i.e. their corresponding \f(CW\*(C`EV_BACKEND_*\*(C'\fR
+value) compiled into this binary of libev (independent of their
+availability on the system you are running on). See \f(CW\*(C`ev_default_loop\*(C'\fR for
+a description of the set values.
+.Sp
+Example: make sure we have the epoll method, because yeah this is cool and
+a must have and can we have a torrent of it please!!!11
+.Sp
+.Vb 2
+\&  assert (("sorry, no epoll, no sex",
+\&           ev_supported_backends () & EVBACKEND_EPOLL));
+.Ve
+.IP "unsigned int ev_recommended_backends ()" 4
+.IX Item "unsigned int ev_recommended_backends ()"
+Return the set of all backends compiled into this binary of libev and also
+recommended for this platform. This set is often smaller than the one
+returned by \f(CW\*(C`ev_supported_backends\*(C'\fR, as for example kqueue is broken on
+most BSDs and will not be autodetected unless you explicitly request it
+(assuming you know what you are doing). This is the set of backends that
+libev will probe for if you specify no backends explicitly.
+.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
+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 \- the
+semantics are identical to the \f(CW\*(C`realloc\*(C'\fR C89/SuS/POSIX function). It is
+used to allocate and free memory (no surprises here). If it returns zero
+when memory needs to be allocated (\f(CW\*(C`size != 0\*(C'\fR), the library might abort
+or take some potentially destructive action.
+.Sp
+Since some systems (at least OpenBSD and Darwin) fail to implement
+correct \f(CW\*(C`realloc\*(C'\fR semantics, libev will use a wrapper around the system
+\&\f(CW\*(C`realloc\*(C'\fR and \f(CW\*(C`free\*(C'\fR functions by default.
+.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
+retries (example requires a standards-compliant \f(CW\*(C`realloc\*(C'\fR).
+.Sp
+.Vb 6
+\&   static void *
+\&   persistent_realloc (void *ptr, size_t size)
+\&   {
+\&     for (;;)
+\&       {
+\&         void *newptr = realloc (ptr, size);
+\&
+\&         if (newptr)
+\&           return newptr;
+\&
+\&         sleep (60);
+\&       }
+\&   }
+\&
+\&   ...
+\&   ev_set_allocator (persistent_realloc);
+.Ve
+.IP "ev_set_syserr_cb (void (*cb)(const char *msg));" 4
+.IX Item "ev_set_syserr_cb (void (*cb)(const char *msg));"
+Set the callback function to call on a retryable syscall error (such
+as failed select, poll, epoll_wait). The message is a printable string
+indicating the system call or subsystem causing the problem. If this
+callback is set, then libev will expect it to remedy the sitution, no
+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: This is basically the same thing that libev does internally, too.
+.Sp
+.Vb 6
+\&   static void
+\&   fatal_error (const char *msg)
+\&   {
+\&     perror (msg);
+\&     abort ();
+\&   }
+\&
+\&   ...
+\&   ev_set_syserr_cb (fatal_error);
+.Ve
+.SH "FUNCTIONS CONTROLLING THE EVENT LOOP"
+.IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP"
+An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR. The library knows two
+types of such loops, the \fIdefault\fR loop, which supports signals and child
+events, and dynamically created loops which do not.
+.IP "struct ev_loop *ev_default_loop (unsigned int flags)" 4
+.IX Item "struct ev_loop *ev_default_loop (unsigned int flags)"
+This will initialise the default event loop if it hasn't been initialised
+yet and return it. If the default loop could not be initialised, returns
+false. If it already was initialised it simply returns it (and ignores the
+flags. 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
+Note that this function is \fInot\fR thread-safe, so if you want to use it
+from multiple threads, you have to lock (note also that this is unlikely,
+as loops cannot bes hared easily between threads anyway).
+.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:
+.RS 4
+.ie n .IP """EVFLAG_AUTO""" 4
+.el .IP "\f(CWEVFLAG_AUTO\fR" 4
+.IX Item "EVFLAG_AUTO"
+The default flags value. Use this if you have no clue (it's the right
+thing, believe me).
+.ie n .IP """EVFLAG_NOENV""" 4
+.el .IP "\f(CWEVFLAG_NOENV\fR" 4
+.IX Item "EVFLAG_NOENV"
+If this flag bit is ored into the flag value (or the program runs setuid
+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 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 select, but handles sparse fds better and has no artificial
+limit on the number of fds you can use (except it will slow down
+considerably with a lot of inactive fds). It scales similarly to select,
+i.e. O(total_fds). See the entry for \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 O(total_fds) where n is the total number of fds (or the highest fd),
+epoll scales either O(1) or O(active_fds). The epoll design has a number
+of shortcomings, such as silently dropping events in some hard-to-detect
+cases and requiring a syscall per fd change, no fork support and bad
+support for dup.
+.Sp
+While stopping, setting and starting an I/O watcher in the same iteration
+will result in some caching, there is still a syscall per such incident
+(because the fd could point to a different file description now), so its
+best to avoid that. Also, \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors might not work
+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 reliably
+with anything but sockets and pipes, except on Darwin, where of course
+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) 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 stopping, setting and starting an I/O watcher does never
+cause an extra syscall as with \f(CW\*(C`EVBACKEND_EPOLL\*(C'\fR, it still adds up to
+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, 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 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 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 listed here). If none are
+specified, all backends in \f(CW\*(C`ev_recommended_backends ()\*(C'\fR will be tried.
+.Sp
+The most typical usage is like this:
+.Sp
+.Vb 2
+\&  if (!ev_default_loop (0))
+\&    fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
+.Ve
+.Sp
+Restrict libev to the select and poll backends, and do not allow
+environment settings to be taken into account:
+.Sp
+.Vb 1
+\&  ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
+.Ve
+.Sp
+Use whatever libev has to offer, but make sure that kqueue is used if
+available (warning, breaks stuff, best use only with your own private
+event loop and only if you know the \s-1OS\s0 supports your types of fds):
+.Sp
+.Vb 1
+\&  ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
+.Ve
+.RE
+.IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4
+.IX Item "struct ev_loop *ev_loop_new (unsigned int flags)"
+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
+Note that this function \fIis\fR thread-safe, and the recommended way to use
+libev with threads is indeed to create one loop per thread, and using the
+default loop in the \*(L"main\*(R" or \*(L"initial\*(R" thread.
+.Sp
+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");
+.Ve
+.IP "ev_default_destroy ()" 4
+.IX Item "ev_default_destroy ()"
+Destroys the default loop again (frees all memory and kernel state
+etc.). None of the active event watchers will be stopped in the normal
+sense, so e.g. \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, 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
+to reinitialise the kernel state for backends that have one. Despite the
+name, you can call it anytime, but it makes most sense after forking, in
+the child process (or both child and parent, but that again makes little
+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
+On the other hand, you only need to call this function in the child
+process if and only if you want to use the event library in the child. If
+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
+.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 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.
+.Sp
+If the flags argument is specified as \f(CW0\fR, it will not return until
+either no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called.
+.Sp
+Please note that an explicit \f(CW\*(C`ev_unloop\*(C'\fR is usually better than
+relying on all watchers to be stopped when deciding when a program has
+finished (especially in interactive programs), but having a program that
+automatically loops as long as it has to and no longer by virtue of
+relying on its watchers stopping correctly is a thing of beauty.
+.Sp
+A flags value of \f(CW\*(C`EVLOOP_NONBLOCK\*(C'\fR will look for new events, will handle
+those events and any outstanding ones, but will not block your process in
+case there are no events and will return after one iteration of the loop.
+.Sp
+A flags value of \f(CW\*(C`EVLOOP_ONESHOT\*(C'\fR will look for new events (waiting if
+neccessary) and will handle those and any outstanding ones. It will block
+your process until at least one new event arrives, and will return after
+one iteration of the loop. This is useful if you are waiting for some
+external event in conjunction with something not expressible using other
+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 10
+\&   \- Before the first iteration, call any pending watchers.
+\&   * If EVFLAG_FORKCHECK was used, check for a fork.
+\&   \- If a fork was detected, queue and call all fork watchers.
+\&   \- Queue and call all prepare watchers.
+\&   \- If we have been forked, recreate the kernel state.
+\&   \- Update the kernel state with all outstanding changes.
+\&   \- Update the "event loop time".
+\&   \- Calculate for how long to sleep or block, if at all
+\&     (active idle watchers, EVLOOP_NONBLOCK or not having
+\&     any active watchers at all will result in not sleeping).
+\&   \- Sleep if the I/O and timer collect interval say so.
+\&   \- Block the process, waiting for any events.
+\&   \- Queue all outstanding I/O (fd) events.
+\&   \- Update the "event loop time" and do time jump handling.
+\&   \- Queue all outstanding timers.
+\&   \- Queue all outstanding periodics.
+\&   \- If no events are pending now, queue all idle watchers.
+\&   \- Queue all check watchers.
+\&   \- Call all queued watchers in reverse order (i.e. check watchers first).
+\&     Signals and child watchers are implemented as I/O watchers, and will
+\&     be handled here by queueing them when their watcher gets executed.
+\&   \- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
+\&     were used, or there are no active watchers, return, otherwise
+\&     continue with step *.
+.Ve
+.Sp
+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..)
+\&   ev_loop (my_loop, 0);
+\&   ... jobs done. yeah!
+.Ve
+.IP "ev_unloop (loop, how)" 4
+.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)"
+.PD
+Ref/unref can be used to add or remove a reference count on the event
+loop: Every watcher keeps one reference, and as long as the reference
+count is nonzero, \f(CW\*(C`ev_loop\*(C'\fR will not return on its own. If you have
+a watcher you never unregister that should not keep \f(CW\*(C`ev_loop\*(C'\fR from
+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
+(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
+running when nothing else is active.
+.Sp
+.Vb 4
+\&  struct ev_signal exitsig;
+\&  ev_signal_init (&exitsig, sig_cb, SIGINT);
+\&  ev_signal_start (loop, &exitsig);
+\&  evf_unref (loop);
+.Ve
+.Sp
+Example: For some weird reason, unregister the above signal handler again.
+.Sp
+.Vb 2
+\&  ev_ref (loop);
+\&  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:
+.PP
+.Vb 5
+\&  static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
+\&  {
+\&    ev_io_stop (w);
+\&    ev_unloop (loop, EVUNLOOP_ALL);
+\&  }
+\&
+\&  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);
+\&  ev_loop (loop, 0);
+.Ve
+.PP
+As you can see, you are responsible for allocating the memory for your
+watcher structures (and it is usually a bad idea to do this on the stack,
+although this can sometimes be quite valid).
+.PP
+Each watcher structure must be initialised by a call to \f(CW\*(C`ev_init
+(watcher *, callback)\*(C'\fR, which expects a callback to be provided. This
+callback gets invoked each time the event occurs (or, in the case of io
+watchers, each time the event loop detects that the file descriptor given
+is readable and/or writable).
+.PP
+Each watcher type has its own \f(CW\*(C`ev_<type>_set (watcher *, ...)\*(C'\fR macro
+with arguments specific to this watcher type. There is also a macro
+to combine initialisation and setting in one call: \f(CW\*(C`ev_<type>_init
+(watcher *, callback, ...)\*(C'\fR.
+.PP
+To make the watcher actually watch out for events, you have to start it
+with a watcher-specific start function (\f(CW\*(C`ev_<type>_start (loop, watcher
+*)\*(C'\fR), and you can stop watching for events at any time by calling the
+corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR.
+.PP
+As long as your watcher is active (has been started but not stopped) you
+must not touch the values stored in it. Most specifically you must never
+reinitialise it or call its \f(CW\*(C`set\*(C'\fR macro.
+.PP
+Each and every callback receives the event loop pointer as first, the
+registered watcher structure as second, and a bitset of received events as
+third argument.
+.PP
+The received events usually include a single bit per event type received
+(you can receive multiple events at the same time). The possible bit masks
+are:
+.ie n .IP """EV_READ""" 4
+.el .IP "\f(CWEV_READ\fR" 4
+.IX Item "EV_READ"
+.PD 0
+.ie n .IP """EV_WRITE""" 4
+.el .IP "\f(CWEV_WRITE\fR" 4
+.IX Item "EV_WRITE"
+.PD
+The file descriptor in the \f(CW\*(C`ev_io\*(C'\fR watcher has become readable and/or
+writable.
+.ie n .IP """EV_TIMEOUT""" 4
+.el .IP "\f(CWEV_TIMEOUT\fR" 4
+.IX Item "EV_TIMEOUT"
+The \f(CW\*(C`ev_timer\*(C'\fR watcher has timed out.
+.ie n .IP """EV_PERIODIC""" 4
+.el .IP "\f(CWEV_PERIODIC\fR" 4
+.IX Item "EV_PERIODIC"
+The \f(CW\*(C`ev_periodic\*(C'\fR watcher has timed out.
+.ie n .IP """EV_SIGNAL""" 4
+.el .IP "\f(CWEV_SIGNAL\fR" 4
+.IX Item "EV_SIGNAL"
+The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread.
+.ie n .IP """EV_CHILD""" 4
+.el .IP "\f(CWEV_CHILD\fR" 4
+.IX Item "EV_CHILD"
+The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change.
+.ie n .IP """EV_STAT""" 4
+.el .IP "\f(CWEV_STAT\fR" 4
+.IX Item "EV_STAT"
+The path specified in the \f(CW\*(C`ev_stat\*(C'\fR watcher changed its attributes somehow.
+.ie n .IP """EV_IDLE""" 4
+.el .IP "\f(CWEV_IDLE\fR" 4
+.IX Item "EV_IDLE"
+The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do.
+.ie n .IP """EV_PREPARE""" 4
+.el .IP "\f(CWEV_PREPARE\fR" 4
+.IX Item "EV_PREPARE"
+.PD 0
+.ie n .IP """EV_CHECK""" 4
+.el .IP "\f(CWEV_CHECK\fR" 4
+.IX Item "EV_CHECK"
+.PD
+All \f(CW\*(C`ev_prepare\*(C'\fR watchers are invoked just \fIbefore\fR \f(CW\*(C`ev_loop\*(C'\fR starts
+to gather new events, and all \f(CW\*(C`ev_check\*(C'\fR watchers are invoked just after
+\&\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
+ran out of memory, a file descriptor was found to be closed or any other
+problem. You best act on it by reporting the problem and somehow coping
+with the watcher being stopped.
+.Sp
+Libev will usually signal a few \*(L"dummy\*(R" events together with an error,
+for example it might indicate that a fd is readable or writable, and if
+your callbacks is well-written it can just attempt the operation and cope
+with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded
+programs, though, so beware.
+.Sh "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0"
+.IX Subsection "GENERIC WATCHER FUNCTIONS"
+In the following description, \f(CW\*(C`TYPE\*(C'\fR stands for the watcher type,
+e.g. \f(CW\*(C`timer\*(C'\fR for \f(CW\*(C`ev_timer\*(C'\fR watchers and \f(CW\*(C`io\*(C'\fR for \f(CW\*(C`ev_io\*(C'\fR watchers.
+.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4
+.el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4
+.IX Item "ev_init (ev_TYPE *watcher, callback)"
+This macro initialises the generic portion of a watcher. The contents
+of the watcher object can be arbitrary (so \f(CW\*(C`malloc\*(C'\fR will do). Only
+the generic parts of the watcher are initialised, you \fIneed\fR to call
+the type-specific \f(CW\*(C`ev_TYPE_set\*(C'\fR macro afterwards to initialise the
+type-specific parts. For each type there is also a \f(CW\*(C`ev_TYPE_init\*(C'\fR macro
+which rolls both calls into one.
+.Sp
+You can reinitialise a watcher at any time as long as it has been stopped
+(or never started) and there are no pending events outstanding.
+.Sp
+The callback is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher,
+int revents)\*(C'\fR.
+.ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4
+.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4
+.IX Item "ev_TYPE_set (ev_TYPE *, [args])"
+This macro initialises the type-specific parts of a watcher. You need to
+call \f(CW\*(C`ev_init\*(C'\fR at least once before you call this macro, but you can
+call \f(CW\*(C`ev_TYPE_set\*(C'\fR any number of times. You must not, however, call this
+macro on a watcher that is active (it can be pending, however, which is a
+difference to the \f(CW\*(C`ev_init\*(C'\fR macro).
+.Sp
+Although some watcher types do not have type-specific arguments
+(e.g. \f(CW\*(C`ev_prepare\*(C'\fR) you still need to call its \f(CW\*(C`set\*(C'\fR macro.
+.ie n .IP """ev_TYPE_init"" (ev_TYPE *watcher, callback, [args])" 4
+.el .IP "\f(CWev_TYPE_init\fR (ev_TYPE *watcher, callback, [args])" 4
+.IX Item "ev_TYPE_init (ev_TYPE *watcher, callback, [args])"
+This convinience macro rolls both \f(CW\*(C`ev_init\*(C'\fR and \f(CW\*(C`ev_TYPE_set\*(C'\fR macro
+calls into a single call. This is the most convinient method to initialise
+a watcher. The same limitations apply, of course.
+.ie n .IP """ev_TYPE_start"" (loop *, ev_TYPE *watcher)" 4
+.el .IP "\f(CWev_TYPE_start\fR (loop *, ev_TYPE *watcher)" 4
+.IX Item "ev_TYPE_start (loop *, ev_TYPE *watcher)"
+Starts (activates) the given watcher. Only active watchers will receive
+events. If the watcher is already active nothing will happen.
+.ie n .IP """ev_TYPE_stop"" (loop *, ev_TYPE *watcher)" 4
+.el .IP "\f(CWev_TYPE_stop\fR (loop *, ev_TYPE *watcher)" 4
+.IX Item "ev_TYPE_stop (loop *, ev_TYPE *watcher)"
+Stops the given watcher again (if active) and clears the pending
+status. It is possible that stopped watchers are pending (for example,
+non-repeating timers are being stopped when they become pending), but
+\&\f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor pending. If
+you want to free or reuse the memory used by the watcher it is therefore a
+good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function.
+.IP "bool ev_is_active (ev_TYPE *watcher)" 4
+.IX Item "bool ev_is_active (ev_TYPE *watcher)"
+Returns a true value iff the watcher is active (i.e. it has been started
+and not yet been stopped). As long as a watcher is active you must not modify
+it.
+.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), you must not change its priority, and you must
+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
+.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
+don't want to allocate memory and store a pointer to it in that data
+member, you can also \*(L"subclass\*(R" the watcher type and provide your own
+data:
+.PP
+.Vb 7
+\&  struct my_io
+\&  {
+\&    struct ev_io io;
+\&    int otherfd;
+\&    void *somedata;
+\&    struct whatever *mostinteresting;
+\&  }
+.Ve
+.PP
+And since your callback will be called with a pointer to the watcher, you
+can cast it back to your own type:
+.PP
+.Vb 5
+\&  static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
+\&  {
+\&    struct my_io *w = (struct my_io *)w_;
+\&    ...
+\&  }
+.Ve
+.PP
+More interesting and less C\-conformant ways of casting your callback type
+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.
+.PP
+Members are additionally marked with either \fI[read\-only]\fR, meaning that,
+while the watcher is active, you can look at the member and expect some
+sensible content, but you must not modify it (you can modify it while the
+watcher is stopped to your hearts content), or \fI[read\-write]\fR, which
+means you can expect it to have some sensible content while the watcher
+is active, but you can also modify it. Modifying it may not do something
+sensible or take immediate effect (or do anything at all), but libev will
+not crash or malfunction in any way.
+.ie n .Sh """ev_io"" \- is this file descriptor readable or writable?"
+.el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable?"
+.IX Subsection "ev_io - is this file descriptor readable or writable?"
+I/O watchers check whether a file descriptor is readable or writable
+in each iteration of the event loop, or, more precisely, when reading
+would not block the process and writing would at least be able to write
+some data. This behaviour is called level-triggering because you keep
+receiving events as long as the condition persists. Remember you can stop
+the watcher if you don't want to act on the event and neither want to
+receive future events.
+.PP
+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
+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
+receive \*(L"spurious\*(R" readyness notifications, that is your callback might
+be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block
+because there is no data. Not only are some backends known to create a
+lot of those (for example solaris ports), it is very easy to get into
+this situation even with a relatively standard program structure. Thus
+it is best to always use non-blocking I/O: An extra \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
+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
+\fIThe special problem of \s-1SIGPIPE\s0\fR
+.IX Subsection "The special problem of SIGPIPE"
+.PP
+While not really specific to libev, it is easy to forget about \s-1SIGPIPE:\s0
+when reading from a pipe whose other end has been closed, your program
+gets send a \s-1SIGPIPE\s0, which, by default, aborts your program. For most
+programs this is sensible behaviour, for daemons, this is usually
+undesirable.
+.PP
+So when you encounter spurious, unexplained daemon exits, make sure you
+ignore \s-1SIGPIPE\s0 (and maybe make sure you log the exit status of your daemon
+somewhere, as that would have given you a big clue).
+.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)"
+.PD
+Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to
+rceeive events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or
+\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR to receive the given events.
+.IP "int fd [read\-only]" 4
+.IX Item "int fd [read-only]"
+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
+readable, but only once. Since it is likely line-buffered, you could
+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
+\&  }
+\&
+\&  ...
+\&  struct ev_loop *loop = ev_default_init (0);
+\&  struct ev_io stdin_readable;
+\&  ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
+\&  ev_io_start (loop, &stdin_readable);
+\&  ev_loop (loop, 0);
+.Ve
+.ie n .Sh """ev_timer"" \- relative and optionally repeating timeouts"
+.el .Sh "\f(CWev_timer\fP \- relative and optionally repeating timeouts"
+.IX Subsection "ev_timer - relative and optionally repeating timeouts"
+Timer watchers are simple relative timers that generate an event after a
+given time, and optionally repeating in regular intervals after that.
+.PP
+The timers are based on real time, that is, if you register an event that
+times out after an hour and you reset your system clock to last years
+time, it will still time out after (roughly) and hour. \*(L"Roughly\*(R" because
+detecting time jumps is hard, and some inaccuracies are unavoidable (the
+monotonic clock option helps a lot here).
+.PP
+The relative timeouts are calculated relative to the \f(CW\*(C`ev_now ()\*(C'\fR
+time. This is usually the right thing as this timestamp refers to the time
+of the event triggering whatever timeout you are modifying/starting. If
+you suspect event processing to be delayed and you \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.);
+.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)"
+.PD
+Configure the timer to trigger after \f(CW\*(C`after\*(C'\fR seconds. If \f(CW\*(C`repeat\*(C'\fR is
+\&\f(CW0.\fR, then it will automatically be stopped. If it is positive, then the
+timer will automatically be configured to trigger again \f(CW\*(C`repeat\*(C'\fR seconds
+later, again, and again, until stopped manually.
+.Sp
+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, ev_timer *)" 4
+.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 (as if it timed out).
+.Sp
+If the timer is repeating, either start it if necessary (with the
+\&\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 idle
+timeout, that is, you want to be called when there have been, say, 60
+seconds of inactivity on the socket. The easiest way to do this is to
+configure an \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 \f(CW\*(C`ev_timer_stop\*(C'\fR the timer, and \f(CW\*(C`ev_timer_again\*(C'\fR will
+automatically restart it if need be.
+.Sp
+That means you can ignore the \f(CW\*(C`after\*(C'\fR value and \f(CW\*(C`ev_timer_start\*(C'\fR
+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.;
+\&   ev_timer_again (loop, timer);
+\&   ...
+\&   timer\->again = 10.;
+\&   ev_timer_again (loop, timer);
+.Ve
+.Sp
+This is more slightly efficient then stopping/starting the timer each time
+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.
+.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
+\&  }
+\&
+\&  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
+inactivity.
+.PP
+.Vb 5
+\&  static void
+\&  timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
+\&  {
+\&    .. ten seconds without any activity
+\&  }
+\&
+\&  struct ev_timer mytimer;
+\&  ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
+\&  ev_timer_again (&mytimer); /* start timer */
+\&  ev_loop (loop, 0);
+\&
+\&  // and in some piece of code that gets executed on any "activity":
+\&  // reset the timeout to start ticking again at 10 seconds
+\&  ev_timer_again (&mytimer);
+.Ve
+.ie n .Sh """ev_periodic"" \- to cron or not to cron?"
+.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron?"
+.IX Subsection "ev_periodic - to cron or not to cron?"
+Periodic watchers are also timers of a kind, but they are very versatile
+(and unfortunately a bit complex).
+.PP
+Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time)
+but on wallclock time (absolute time). You can tell a periodic watcher
+to trigger \*(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).
+.PP
+They can also be used to implement vastly more complex timers, such as
+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
+absolute timer (at = time, 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
+repeating interval timer (at = offset, 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, which can also be negative)
+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
+\&   ev_periodic_set (&periodic, 0., 3600., 0);
+.Ve
+.Sp
+This doesn't mean there will always be 3600 seconds in between triggers,
+but only that the the callback will be called when the system time shows a
+full hour (\s-1UTC\s0), or more correctly, when the system time is evenly divisible
+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.
+.Sp
+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 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
+\&   static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
+\&   {
+\&     return now + 60.;
+\&   }
+.Ve
+.Sp
+It must return the next time to trigger, based on the passed time value
+(that is, the lowest time value larger than to the second argument). It
+will usually be called just before the callback will be triggered, but
+might be called at other times, too.
+.Sp
+\&\s-1NOTE:\s0 \fIThis callback must always return a time that is later than the
+passed \f(CI\*(C`now\*(C'\fI value\fR. Not even \f(CW\*(C`now\*(C'\fR itself will do, it \fImust\fR be larger.
+.Sp
+This can be used to create very complex timers, such as a timer that
+triggers on each midnight, local time. To do this, you would calculate the
+next midnight after \f(CW\*(C`now\*(C'\fR and return the timestamp value for this. How
+you do this is, again, up to you (but it is not trivial, which is the main
+reason I omitted it as an example).
+.RE
+.RS 4
+.RE
+.IP "ev_periodic_again (loop, ev_periodic *)" 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 ev_periodic_at (ev_periodic *)" 4
+.IX Item "ev_tstamp ev_periodic_at (ev_periodic *)"
+When active, returns the absolute time that the watcher is supposed to
+trigger next.
+.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.
+.PP
+\fIExamples\fR
+.IX Subsection "Examples"
+.PP
+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)
+\&  }
+\&
+\&  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:
+.PP
+.Vb 1
+\&  #include <math.h>
+\&
+\&  static ev_tstamp
+\&  my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
+\&  {
+\&    return fmod (now, 3600.) + 3600.;
+\&  }
+\&
+\&  ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
+.Ve
+.PP
+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);
+\&  ev_periodic_start (loop, &hourly_tick);
+.Ve
+.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled!"
+.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled!"
+.IX Subsection "ev_signal - signal me when a signal gets signalled!"
+Signal watchers will trigger an event when the process receives a specific
+signal one or more times. Even though signals are very asynchronous, libev
+will try it's best to deliver signals synchronously, i.e. as part of the
+normal event processing, like any other event.
+.PP
+You can configure as many watchers as you like per signal. Only when the
+first watcher gets started will libev actually register a signal watcher
+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)"
+.PD
+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). 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, int trace)" 4
+.IX Item "ev_child_init (ev_child *, callback, int pid, int trace)"
+.PD 0
+.IP "ev_child_set (ev_child *, int pid, int trace)" 4
+.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. \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]"
+The process id that detected a status change.
+.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
+\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 1
+\&  ev_child cw;
+\&
+\&  static void
+\&  child_cb (EV_P_ struct ev_child *w, int revents)
+\&  {
+\&    ev_child_stop (EV_A_ w);
+\&    printf ("process %d exited with status %x\en", w\->rpid, w\->rstatus);
+\&  }
+\&
+\&  pid_t pid = fork ();
+\&
+\&  if (pid < 0)
+\&    // error
+\&  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
+\&\f(CW\*(C`stat\*(C'\fR regularly (or when the \s-1OS\s0 says it changed) and sees if it changed
+compared to the last time, invoking the callback if it did.
+.PP
+The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does
+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 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.
+.PP
+At the time of this writing, only the Linux inotify interface is
+implemented (implementing kqueue support is left as an exercise for the
+reader, note, however, that the author sees no way of implementing ev_stat
+semantics with kqueue). 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
+\fI\s-1ABI\s0 Issues (Largefile Support)\fR
+.IX Subsection "ABI Issues (Largefile Support)"
+.PP
+Libev by default (unless the user overrides this) uses the default
+compilation environment, which means that on systems with optionally
+disabled large file support, you get the 32 bit version of the stat
+structure. When using the library from programs that change the \s-1ABI\s0 to
+use 64 bit file offsets the programs will fail. In that case you have to
+compile libev with the same flags to get binary compatibility. This is
+obviously the case with any flags that change the \s-1ABI\s0, but the problem is
+most noticably with ev_stat and largefile support.
+.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 presence 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 presence 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 can
+easily 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 as the stat
+data does not change.
+.PP
+The solution to this is to delay acting on a change for slightly more
+than second (or till slightly after the next full second boundary), using
+a roughly one-second-delay \f(CW\*(C`ev_timer\*(C'\fR (e.g. \f(CW\*(C`ev_timer_set (w, 0., 1.02);
+ev_timer_again (loop, w)\*(C'\fR).
+.PP
+The \f(CW.02\fR offset is added to work around small timing inconsistencies
+of some operating systems (where the second counter of the current time
+might be be delayed. One such system is the Linux kernel, where a call to
+\&\f(CW\*(C`gettimeofday\*(C'\fR might return a timestamp with a full second later than
+a subsequent \f(CW\*(C`time\*(C'\fR call \- if the equivalent of \f(CW\*(C`time ()\*(C'\fR is used to
+update file times then there will be a small window where the kernel uses
+the previous second to update file times but libev might already execute
+the timer callback).
+.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)"
+.PD
+Configures the watcher to wait for status changes of the given
+\&\f(CW\*(C`path\*(C'\fR. The \f(CW\*(C`interval\*(C'\fR is a hint on how quickly a change is expected to
+be detected and should normally be specified as \f(CW0\fR to let libev choose
+a suitable value. The memory pointed to by \f(CW\*(C`path\*(C'\fR must point to the same
+path for as long as the watcher is active.
+.Sp
+The callback will 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 (loop, ev_stat *)" 4
+.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 function to avoid
+detecting this change (while introducing a race condition if you are not
+the only one changing the path). Can also be useful simply to find out the
+new values.
+.IP "ev_statdata attr [read\-only]" 4
+.IX Item "ev_statdata attr [read-only]"
+The most-recently detected attributes of the file. Although the type is
+\&\f(CW\*(C`ev_statdata\*(C'\fR, this is usually the (or one of the) \f(CW\*(C`struct stat\*(C'\fR types
+suitable for your system, but you can only rely on the POSIX-standardised
+members to be present. If the \f(CW\*(C`st_nlink\*(C'\fR member is \f(CW0\fR, then there was
+some error while \f(CW\*(C`stat\*(C'\fRing the file.
+.IP "ev_statdata prev [read\-only]" 4
+.IX Item "ev_statdata prev [read-only]"
+The previous attributes of the file. The callback gets invoked whenever
+\&\f(CW\*(C`prev\*(C'\fR != \f(CW\*(C`attr\*(C'\fR, or, more precisely, one or more of these members
+differ: \f(CW\*(C`st_dev\*(C'\fR, \f(CW\*(C`st_ino\*(C'\fR, \f(CW\*(C`st_mode\*(C'\fR, \f(CW\*(C`st_nlink\*(C'\fR, \f(CW\*(C`st_uid\*(C'\fR,
+\&\f(CW\*(C`st_gid\*(C'\fR, \f(CW\*(C`st_rdev\*(C'\fR, \f(CW\*(C`st_size\*(C'\fR, \f(CW\*(C`st_atime\*(C'\fR, \f(CW\*(C`st_mtime\*(C'\fR, \f(CW\*(C`st_ctime\*(C'\fR.
+.IP "ev_tstamp interval [read\-only]" 4
+.IX Item "ev_tstamp interval [read-only]"
+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 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)
+\&      {
+\&        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 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");
+\&  }
+\&
+\&  ...
+\&  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, stat_cb, "/etc/passwd", 0.);
+\&  ev_stat_start (loop, &passwd);
+\&  ev_timer_init (&timer, timer_cb, 0., 1.02);
+.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 no other events of the same or higher
+priority are pending (prepare, check and other idle watchers do not
+count).
+.PP
+That is, as long as your process is busy handling sockets or timeouts
+(or even signals, imagine) of the same or higher priority it will not be
+triggered. But when your process is idle (or only lower-priority watchers
+are pending), the idle watchers are being called once per event loop
+iteration \- until stopped, that is, or your process receives more events
+and becomes busy again with higher priority stuff.
+.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
+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 watcher, start it, and in the
+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 anything immediate to do.
+\&  }
+\&
+\&  struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
+\&  ev_idle_init (idle_watcher, idle_cb);
+\&  ev_idle_start (loop, idle_cb);
+.Ve
+.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop!"
+.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!"
+.IX Subsection "ev_prepare and ev_check - customise your event loop!"
+Prepare and check watchers are usually (but not always) used in tandem:
+prepare watchers get invoked before the process blocks and check watchers
+afterwards.
+.PP
+You \fImust not\fR call \f(CW\*(C`ev_loop\*(C'\fR or similar functions that enter
+the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR
+watchers. Other loops than the current one are fine, however. The
+rationale behind this is that you do not need to check for recursion in
+those watchers, i.e. the sequence will always be \f(CW\*(C`ev_prepare\*(C'\fR, blocking,
+\&\f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each kind they will always be
+called in pairs bracketing the blocking call.
+.PP
+Their main purpose is to integrate other event mechanisms into libev and
+their use is somewhat advanced. This could be used, for example, to track
+variable changes, implement your own watchers, integrate net-snmp or a
+coroutine library and lots more. They are also occasionally useful if
+you cache some data and want to flush it before blocking (for example,
+in X programs you might want to do an \f(CW\*(C`XFlush ()\*(C'\fR in an \f(CW\*(C`ev_prepare\*(C'\fR
+watcher).
+.PP
+This is done by examining in each prepare call which file descriptors need
+to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for
+them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries
+provide just this functionality). Then, in the check watcher you check for
+any events that occured (by checking the pending status of all watchers
+and stopping them) and call back into the library. The I/O and timer
+callbacks will never actually be called (but must be valid nevertheless,
+because you never know, you know?).
+.PP
+As another example, the Perl Coro module uses these hooks to integrate
+coroutines into libev programs, by yielding to other active coroutines
+during each prepare and only letting the process block if no coroutines
+are ready to run (it's actually more complicated: it only runs coroutines
+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 might get executed 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
+\fIExamples\fR
+.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 as a 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,
+and in a check watcher, destroy them and call into libadns. What follows
+is pseudo-code only of course. This requires you to either use a low
+priority for the check watcher or use \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;
+\&
+\&  static void
+\&  io_cb (ev_loop *loop, ev_io *w, int revents)
+\&  {
+\&  }
+\&
+\&  // create io watchers for each fd and a timer before blocking
+\&  static void
+\&  adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
+\&  {
+\&    int timeout = 3600000;
+\&    struct pollfd fds [nfd];
+\&    // actual code will need to loop here and realloc etc.
+\&    adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
+\&
+\&    /* the callback is illegal, but won\*(Aqt be called as we stop during check */
+\&    ev_timer_init (&tw, 0, timeout * 1e\-3);
+\&    ev_timer_start (loop, &tw);
+\&
+\&    // 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)));
+\&
+\&        fds [i].revents = 0;
+\&        ev_io_start (loop, iow + i);
+\&      }
+\&  }
+\&
+\&  // stop all watchers after blocking
+\&  static void
+\&  adns_check_cb (ev_loop *loop, ev_check *w, int revents)
+\&  {
+\&    ev_timer_stop (loop, &tw);
+\&
+\&    for (int i = 0; i < nfd; ++i)
+\&      {
+\&        // set the relevant poll flags
+\&        // could also call adns_processreadable etc. here
+\&        struct pollfd *fd = fds + i;
+\&        int revents = ev_clear_pending (iow + i);
+\&        if (revents & EV_READ ) fd\->revents |= fd\->events & POLLIN;
+\&        if (revents & EV_WRITE) fd\->revents |= fd\->events & POLLOUT;
+\&
+\&        // now stop the watcher
+\&        ev_io_stop (loop, iow + i);
+\&      }
+\&
+\&    adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
+\&  }
+.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..."
+This is a rather advanced watcher type that lets you embed one event loop
+into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded
+loop, other types of watchers might be handled in a delayed or incorrect
+fashion and must not be used).
+.PP
+There are primarily two reasons you would want that: work around bugs and
+prioritise I/O.
+.PP
+As an example for a bug workaround, the kqueue backend might only support
+sockets on some platform, so it is unusable as generic backend, but you
+still want to make use of it because you have many sockets and it scales
+so nicely. In this case, you would create a kqueue-based loop and embed it
+into your default loop (which might use e.g. poll). Overall operation will
+be a bit slower because first libev has to poll and then call kevent, but
+at least you can use both at what they are best.
+.PP
+As for prioritising I/O: rarely you have the case where some fds have
+to be watched and handled very quickly (with low latency), and even
+priorities and idle watchers might have too much overhead. In this case
+you would put all the high priority stuff in one loop and all the rest in
+a second one, and embed the second one in the first.
+.PP
+As long as the watcher is active, the callback will be invoked every time
+there might be events pending in the embedded loop. The callback must then
+call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single sweep and invoke
+their callbacks (you could also start an idle watcher to give the embedded
+loop strictly lower priority for example). You can also set the callback
+to \f(CW0\fR, in which case the embed watcher will automatically execute the
+embedded loop sweep.
+.PP
+As long as the watcher is started it will automatically handle events. The
+callback will be invoked whenever some events have been handled. You can
+set the callback to \f(CW0\fR to avoid having to specify one if you are not
+interested in that.
+.PP
+Also, there have not currently been made special provisions for forking:
+when you fork, you not only have to call \f(CW\*(C`ev_loop_fork\*(C'\fR on both loops,
+but you will also have to stop and restart any \f(CW\*(C`ev_embed\*(C'\fR watchers
+yourself.
+.PP
+Unfortunately, not all backends are embeddable, only the ones returned by
+\&\f(CW\*(C`ev_embeddable_backends\*(C'\fR are, which, unfortunately, does not include any
+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.
+.PP
+\fIWatcher-Specific Functions and Data Members\fR
+.IX Subsection "Watcher-Specific Functions and Data Members"
+.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)"
+.PD
+Configures the watcher to embed the given loop, which must be
+embeddable. If the callback is \f(CW0\fR, then \f(CW\*(C`ev_embed_sweep\*(C'\fR will be
+invoked automatically, otherwise it is the responsibility of the callback
+to invoke it (it will continue to be called until the sweep has been done,
+if you do not want thta, you need to temporarily stop the embed watcher).
+.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 *other [read\-only]" 4
+.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.
+.IP "bool = ev_async_pending (ev_async *)" 4
+.IX Item "bool = ev_async_pending (ev_async *)"
+Returns a non-zero value when \f(CW\*(C`ev_async_send\*(C'\fR has been called on the
+watcher but the event has not yet been processed (or even noted) by the
+event loop.
+.Sp
+\&\f(CW\*(C`ev_async_send\*(C'\fR sets a flag in the watcher and wakes up the loop. When
+the loop iterates next and checks for the watcher to have become active,
+it will reset the flag again. \f(CW\*(C`ev_async_pending\*(C'\fR can be used to very
+quickly check wether invoking the loop might be a good idea.
+.Sp
+Not that this does \fInot\fR check wether the watcher itself is pending, only
+wether it has been requested to make this watcher pending.
+.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)"
+This function combines a simple timer and an I/O watcher, calls your
+callback on whichever event happens first and automatically stop both
+watchers. This is useful if you want to wait for a single event on an fd
+or timeout without having to allocate/configure/start/stop/free one or
+more watchers yourself.
+.Sp
+If \f(CW\*(C`fd\*(C'\fR is less than 0, then no I/O watcher will be started and events
+is being ignored. Otherwise, an \f(CW\*(C`ev_io\*(C'\fR watcher for the given \f(CW\*(C`fd\*(C'\fR and
+\&\f(CW\*(C`events\*(C'\fR set will be craeted and started.
+.Sp
+If \f(CW\*(C`timeout\*(C'\fR is less than 0, then no timeout watcher will be
+started. Otherwise an \f(CW\*(C`ev_timer\*(C'\fR watcher with after = \f(CW\*(C`timeout\*(C'\fR (and
+repeat = 0) will be started. While \f(CW0\fR is a valid timeout, it is of
+dubious value.
+.Sp
+The callback has the type \f(CW\*(C`void (*cb)(int revents, void *arg)\*(C'\fR and gets
+passed an \f(CW\*(C`revents\*(C'\fR set like normal event callbacks (a combination of
+\&\f(CW\*(C`EV_ERROR\*(C'\fR, \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or \f(CW\*(C`EV_TIMEOUT\*(C'\fR) and the \f(CW\*(C`arg\*(C'\fR
+value passed to \f(CW\*(C`ev_once\*(C'\fR:
+.Sp
+.Vb 7
+\&  static void stdin_ready (int revents, void *arg)
+\&  {
+\&    if (revents & EV_TIMEOUT)
+\&      /* doh, nothing entered */;
+\&    else if (revents & EV_READ)
+\&      /* stdin might have data for us, joy! */;
+\&  }
+\&
+\&  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
+had happened for the specified watcher (which must be a pointer to an
+initialised but not necessarily started event watcher).
+.IP "ev_feed_fd_event (ev_loop *, int fd, int revents)" 4
+.IX Item "ev_feed_fd_event (ev_loop *, int fd, int revents)"
+Feed an event on the given fd, as if a file descriptor backend detected
+the given events it.
+.IP "ev_feed_signal_event (ev_loop *loop, int signum)" 4
+.IX Item "ev_feed_signal_event (ev_loop *loop, int signum)"
+Feed an event as if the given signal occured (\f(CW\*(C`loop\*(C'\fR must be the default
+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
+Use it by including <event.h>, as usual.
+.IP "\(bu" 4
+The following members are fully supported: ev_base, ev_callback,
+ev_arg, ev_fd, ev_res, ev_events.
+.IP "\(bu" 4
+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).
+.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
+In libevent, the last base created gets the signals, in libev, the
+first base created (== the default loop) gets the signals.
+.IP "\(bu" 4
+Other members are not supported.
+.IP "\(bu" 4
+The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need
+to use the libev header file and library.
+.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
+To use it,
+.PP
+.Vb 1
+\&  #include <ev++.h>
+.Ve
+.PP
+This automatically includes \fIev.h\fR and puts all of its definitions (many
+of them macros) into the global namespace. All \*(C+ specific things are
+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
+Care has been taken to keep the overhead low. The only data member the \*(C+
+classes add (compared to plain C\-style watchers) is the event loop pointer
+that the watcher is associated with (or no additional members at all if
+you disable \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."
+These are just enum values with the same values as the \f(CW\*(C`EV_READ\*(C'\fR etc.
+macros from \fIev.h\fR.
+.ie n .IP """ev::tstamp""\fR, \f(CW""ev::now""" 4
+.el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4
+.IX Item "ev::tstamp, ev::now"
+Aliases to the same types/functions as with the \f(CW\*(C`ev_\*(C'\fR prefix.
+.ie n .IP """ev::io""\fR, \f(CW""ev::timer""\fR, \f(CW""ev::periodic""\fR, \f(CW""ev::idle""\fR, \f(CW""ev::sig"" etc." 4
+.el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4
+.IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc."
+For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of
+the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR
+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 ()" 4
+.IX Item "ev::TYPE::TYPE ()"
+.PD 0
+.IP "ev::TYPE::TYPE (struct ev_loop *)" 4
+.IX Item "ev::TYPE::TYPE (struct ev_loop *)"
+.IP "ev::TYPE::~TYPE" 4
+.IX Item "ev::TYPE::~TYPE"
+.PD
+The constructor (optionally) takes an event loop to associate the watcher
+with. If it is omitted, it will use \f(CW\*(C`EV_DEFAULT\*(C'\fR.
+.Sp
+The constructor calls \f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the
+\&\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
+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
+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
+.el .IP "w\->again () (\f(CWev::timer\fR, \f(CWev::periodic\fR only)" 4
+.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
+.el .IP "w\->sweep () (\f(CWev::embed\fR only)" 4
+.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
+.el .IP "w\->update () (\f(CWev::stat\fR only)" 4
+.IX Item "w->update () (ev::stat only)"
+Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR.
+.RE
+.RS 4
+.RE
+.PP
+Example: Define a class with an \s-1IO\s0 and idle watcher, start one of them in
+the constructor.
+.PP
+.Vb 4
+\&  class myclass
+\&  {
+\&    ev::io   io;  void io_cb   (ev::io   &w, int revents);
+\&    ev:idle idle  void idle_cb (ev::idle &w, int revents);
+\&
+\&    myclass (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
+\&  // 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").
+.ie n .IP """EV_DEFAULT_UC""\fR, \f(CW""EV_DEFAULT_UC_""" 4
+.el .IP "\f(CWEV_DEFAULT_UC\fR, \f(CWEV_DEFAULT_UC_\fR" 4
+.IX Item "EV_DEFAULT_UC, EV_DEFAULT_UC_"
+Usage identical to \f(CW\*(C`EV_DEFAULT\*(C'\fR and \f(CW\*(C`EV_DEFAULT_\*(C'\fR, but requires that the
+default loop has been initialised (\f(CW\*(C`UC\*(C'\fR == unchecked). Their behaviour
+is undefined when the default loop has not been initialised by a previous
+execution of \f(CW\*(C`EV_DEFAULT\*(C'\fR, \f(CW\*(C`EV_DEFAULT_\*(C'\fR or \f(CW\*(C`ev_default_init (...)\*(C'\fR.
+.Sp
+It is often prudent to use \f(CW\*(C`EV_DEFAULT\*(C'\fR when initialising the first
+watcher in a function but use \f(CW\*(C`EV_DEFAULT_UC\*(C'\fR afterwards.
+.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);
+\&  }
+\&
+\&  ev_check check;
+\&  ev_check_init (&check, check_cb);
+\&  ev_check_start (EV_DEFAULT_ &check);
+\&  ev_loop (EV_DEFAULT_ 0);
+.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.
+.PP
+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"
+Depending on what features you need you need to include one or more sets of files
+in your app.
+.PP
+\fI\s-1CORE\s0 \s-1EVENT\s0 \s-1LOOP\s0\fR
+.IX Subsection "CORE EVENT LOOP"
+.PP
+To include only the libev core (all the \f(CW\*(C`ev_*\*(C'\fR functions), with manual
+configuration (no autoconf):
+.PP
+.Vb 2
+\&  #define EV_STANDALONE 1
+\&  #include "ev.c"
+.Ve
+.PP
+This will automatically include \fIev.h\fR, too, and should be done in a
+single C source file only to provide the function implementations. To use
+it, do the same for \fIev.h\fR in all files wishing to use this \s-1API\s0 (best
+done by writing a wrapper around \fIev.h\fR that you can include instead and
+where you can put other configuration options):
+.PP
+.Vb 2
+\&  #define EV_STANDALONE 1
+\&  #include "ev.h"
+.Ve
+.PP
+Both header files and implementation files can be compiled with a \*(C+
+compiler (at least, thats a stated goal, and breakage will be treated
+as a bug).
+.PP
+You need the following files in your source tree, or in a directory
+in your include path (e.g. in libev/ when using \-Ilibev):
+.PP
+.Vb 4
+\&  ev.h
+\&  ev.c
+\&  ev_vars.h
+\&  ev_wrap.h
+\&
+\&  ev_win32.c      required on win32 platforms only
+\&
+\&  ev_select.c     only when select backend is enabled (which is enabled by default)
+\&  ev_poll.c       only when poll backend is enabled (disabled by default)
+\&  ev_epoll.c      only when the epoll backend is enabled (disabled by default)
+\&  ev_kqueue.c     only when the kqueue backend is enabled (disabled by default)
+\&  ev_port.c       only when the solaris port backend is enabled (disabled by default)
+.Ve
+.PP
+\&\fIev.c\fR includes the backend files directly when enabled, so you only need
+to compile this single file.
+.PP
+\fI\s-1LIBEVENT\s0 \s-1COMPATIBILITY\s0 \s-1API\s0\fR
+.IX Subsection "LIBEVENT COMPATIBILITY API"
+.PP
+To include the libevent compatibility \s-1API\s0, also include:
+.PP
+.Vb 1
+\&  #include "event.c"
+.Ve
+.PP
+in the file including \fIev.c\fR, and:
+.PP
+.Vb 1
+\&  #include "event.h"
+.Ve
+.PP
+in the files that want to use the libevent \s-1API\s0. This also includes \fIev.h\fR.
+.PP
+You need the following additional files for this:
+.PP
+.Vb 2
+\&  event.h
+\&  event.c
+.Ve
+.PP
+\fI\s-1AUTOCONF\s0 \s-1SUPPORT\s0\fR
+.IX Subsection "AUTOCONF SUPPORT"
+.PP
+Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your config in
+whatever way you want, you can also \f(CW\*(C`m4_include([libev.m4])\*(C'\fR in your
+\&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR undefined. \fIev.c\fR will then
+include \fIconfig.h\fR and configure itself accordingly.
+.PP
+For this of course you need the m4 file:
+.PP
+.Vb 1
+\&  libev.m4
+.Ve
+.Sh "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0"
+.IX Subsection "PREPROCESSOR SYMBOLS/MACROS"
+Libev can be configured via a variety of preprocessor symbols you have to
+define before including any of its files. The default in the absense of
+autoconf is noted for every option.
+.IP "\s-1EV_STANDALONE\s0" 4
+.IX Item "EV_STANDALONE"
+Must always be \f(CW1\fR if you do not use autoconf configuration, which
+keeps libev from including \fIconfig.h\fR, and it also defines dummy
+implementations for some libevent functions (such as logging, which is not
+supported). It will also not define any of the structs usually found in
+\&\fIevent.h\fR that are not directly supported by the libev core alone.
+.IP "\s-1EV_USE_MONOTONIC\s0" 4
+.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, 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 the
+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_EVENTFD\s0" 4
+.IX Item "EV_USE_EVENTFD"
+If defined to be \f(CW1\fR, then libev will assume that \f(CW\*(C`eventfd ()\*(C'\fR is
+available and will probe for kernel support at runtime. This will improve
+\&\f(CW\*(C`ev_signal\*(C'\fR and \f(CW\*(C`ev_async\*(C'\fR performance and reduce resource consumption.
+If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
+2.7 or newer, otherwise disabled.
+.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
+will not be compiled in.
+.IP "\s-1EV_SELECT_USE_FD_SET\s0" 4
+.IX Item "EV_SELECT_USE_FD_SET"
+If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR
+structure. This is useful if libev doesn't compile due to a missing
+\&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it misguesses the bitset layout on
+exotic systems. This usually limits the range of file descriptors to some
+low limit such as 1024 or might have other limitations (winsocket only
+allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation, might
+influence the size of the \f(CW\*(C`fd_set\*(C'\fR used.
+.IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4
+.IX Item "EV_SELECT_IS_WINSOCKET"
+When defined to \f(CW1\fR, the select backend will assume that
+select/socket/connect etc. don't understand file descriptors but
+wants osf handles on win32 (this is the case when the select to
+be used is the winsock select). This means that it will call
+\&\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.
+.IP "\s-1EV_USE_EPOLL\s0" 4
+.IX Item "EV_USE_EPOLL"
+If defined to be \f(CW1\fR, libev will compile in support for the Linux
+\&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime,
+otherwise another method will be used as fallback. This is the preferred
+backend for GNU/Linux systems. If undefined, it will be enabled if the
+headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
+.IP "\s-1EV_USE_KQUEUE\s0" 4
+.IX Item "EV_USE_KQUEUE"
+If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style
+\&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime,
+otherwise another method will be used as fallback. This is the preferred
+backend for \s-1BSD\s0 and BSD-like systems, although on most BSDs kqueue only
+supports some types of fds correctly (the only platform we found that
+supports ptys for example was NetBSD), so kqueue might be compiled in, but
+not be used unless explicitly requested. The best way to use it is to find
+out whether kqueue supports your type of fd properly and use an embedded
+kqueue loop.
+.IP "\s-1EV_USE_PORT\s0" 4
+.IX Item "EV_USE_PORT"
+If defined to be \f(CW1\fR, libev will compile in support for the Solaris
+10 port style backend. Its availability will be detected at runtime,
+otherwise another method will be used as fallback. This is the preferred
+backend for Solaris 10 systems.
+.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. If undefined, it will be enabled if the headers
+indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
+.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"ev.h"\fR in \fIevent.h\fR, \fIev.c\fR and \fIev++.h\fR. This can be
+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, 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
+around libev functions.
+.IP "\s-1EV_MULTIPLICITY\s0" 4
+.IX Item "EV_MULTIPLICITY"
+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 this is used to override some
+inlining decisions, saves roughly 30% codesize of amd64. It also selects a
+much smaller 2\-heap for timer management over the default 4\-heap.
+.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_USE_4HEAP\s0" 4
+.IX Item "EV_USE_4HEAP"
+Heaps are not very cache-efficient. To improve the cache-efficiency of the
+timer and periodics heap, libev uses a 4\-heap when this symbol is defined
+to \f(CW1\fR. The 4\-heap uses more complicated (longer) code but has a
+noticable after performance with many (thousands) of watchers.
+.Sp
+The default is \f(CW1\fR unless \f(CW\*(C`EV_MINIMAL\*(C'\fR is set in which case it is \f(CW0\fR
+(disabled).
+.IP "\s-1EV_HEAP_CACHE_AT\s0" 4
+.IX Item "EV_HEAP_CACHE_AT"
+Heaps are not very cache-efficient. To improve the cache-efficiency of the
+timer and periodics heap, libev can cache the timestamp (\fIat\fR) within
+the heap structure (selected by defining \f(CW\*(C`EV_HEAP_CACHE_AT\*(C'\fR to \f(CW1\fR),
+which uses 8\-12 bytes more per watcher and a few hundred bytes more code,
+but avoids random read accesses on heap changes. This noticably improves
+performance noticably with with many (hundreds) of watchers.
+.Sp
+The default is \f(CW1\fR unless \f(CW\*(C`EV_MINIMAL\*(C'\fR is set in which case it is \f(CW0\fR
+(disabled).
+.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,
+though, and it must be identical each time.
+.Sp
+For example, the perl \s-1EV\s0 module uses something like this:
+.Sp
+.Vb 3
+\&  #define EV_COMMON                       \e
+\&    SV *self; /* contains this struct */  \e
+\&    SV *cb_sv, *fh /* note no trailing ";" */
+.Ve
+.IP "\s-1EV_CB_DECLARE\s0 (type)" 4
+.IX Item "EV_CB_DECLARE (type)"
+.PD 0
+.IP "\s-1EV_CB_INVOKE\s0 (watcher, revents)" 4
+.IX Item "EV_CB_INVOKE (watcher, revents)"
+.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.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.
+.PP
+The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file
+that everybody includes and which overrides some configure choices:
+.PP
+.Vb 9
+\&  #define EV_MINIMAL 1
+\&  #define EV_USE_POLL 0
+\&  #define EV_MULTIPLICITY 0
+\&  #define EV_PERIODIC_ENABLE 0
+\&  #define EV_STAT_ENABLE 0
+\&  #define EV_FORK_ENABLE 0
+\&  #define EV_CONFIG_H <config.h>
+\&  #define EV_MINPRI 0
+\&  #define EV_MAXPRI 0
+\&
+\&  #include "ev++.h"
+.Ve
+.PP
+And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled:
+.PP
+.Vb 2
+\&  #include "ev_cpp.h"
+\&  #include "ev.c"
+.Ve
+.SH "THREADS AND COROUTINES"
+.IX Header "THREADS AND COROUTINES"
+.Sh "\s-1THREADS\s0"
+.IX Subsection "THREADS"
+Libev itself is completely threadsafe, but it uses no locking. This
+means that you can use as many loops as you want in parallel, as long as
+only one thread ever calls into one libev function with the same loop
+parameter.
+.PP
+Or put differently: calls with different loop parameters can be done in
+parallel from multiple threads, calls with the same loop parameter must be
+done serially (but can be done from different threads, as long as only one
+thread ever is inside a call at any point in time, e.g. by using a mutex
+per loop).
+.PP
+If you want to know which design is best for your problem, then I cannot
+help you but by giving some generic advice:
+.IP "\(bu" 4
+most applications have a main thread: use the default libev loop
+in that thread, or create a seperate thread running only the default loop.
+.Sp
+This helps integrating other libraries or software modules that use libev
+themselves and don't care/know about threading.
+.IP "\(bu" 4
+one loop per thread is usually a good model.
+.Sp
+Doing this is almost never wrong, sometimes a better-performance model
+exists, but it is always a good start.
+.IP "\(bu" 4
+other models exist, such as the leader/follower pattern, where one
+loop is handed through multiple threads in a kind of round-robbin fashion.
+.Sp
+Chosing a model is hard \- look around, learn, know that usually you cna do
+better than you currently do :\-)
+.IP "\(bu" 4
+often you need to talk to some other thread which blocks in the
+event loop \- \f(CW\*(C`ev_async\*(C'\fR watchers can be used to wake them up from other
+threads safely (or from signal contexts...).
+.Sh "\s-1COROUTINES\s0"
+.IX Subsection "COROUTINES"
+Libev is much more accomodating to coroutines (\*(L"cooperative threads\*(R"):
+libev fully supports nesting calls to it's functions from different
+coroutines (e.g. you can call \f(CW\*(C`ev_loop\*(C'\fR on the same loop from two
+different coroutines and switch freely between both coroutines running the
+loop, as long as you don't confuse yourself). The only exception is that
+you must not do this from \f(CW\*(C`ev_periodic\*(C'\fR reschedule callbacks.
+.PP
+Care has been invested into making sure that libev does not keep local
+state inside \f(CW\*(C`ev_loop\*(C'\fR, and other calls do not usually allow coroutine
+switches.
+.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.
+.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 "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 % 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 in each loop iteration: O(1)" 4
+.IX Item "Finding the next timer in each loop iteration: O(1)"
+By virtue of using a binary or 4\-heap, the next timer is always found at a
+fixed position in the storage array.
+.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)"
+A change means an I/O watcher gets started or stopped, which requires
+libev to recalculate its status (and possibly tell the kernel, depending
+on backend and wether \f(CW\*(C`ev_io_set\*(C'\fR was used).
+.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
+Lifting these limitations would basically require the full
+re-implementation of the I/O system. If you are into these kinds of
+things, then note that glib does exactly that for you in a very portable
+way (note also that glib is the slowest event library known to man).
+.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 readyness
+notification 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.
+.Sp
+Early versions of winsocket's select only supported waiting for a maximum
+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. Great).
+.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 "PORTABILITY REQUIREMENTS"
+.IX Header "PORTABILITY REQUIREMENTS"
+In addition to a working ISO-C implementation, libev relies on a few
+additional extensions:
+.ie n .IP """sig_atomic_t volatile"" must be thread-atomic as well" 4
+.el .IP "\f(CWsig_atomic_t volatile\fR must be thread-atomic as well" 4
+.IX Item "sig_atomic_t volatile must be thread-atomic as well"
+The type \f(CW\*(C`sig_atomic_t volatile\*(C'\fR (or whatever is defined as
+\&\f(CW\*(C`EV_ATOMIC_T\*(C'\fR) must be atomic w.r.t. accesses from different
+threads. This is not part of the specification for \f(CW\*(C`sig_atomic_t\*(C'\fR, but is
+believed to be sufficiently portable.
+.ie n .IP """sigprocmask"" must work in a threaded environment" 4
+.el .IP "\f(CWsigprocmask\fR must work in a threaded environment" 4
+.IX Item "sigprocmask must work in a threaded environment"
+Libev uses \f(CW\*(C`sigprocmask\*(C'\fR to temporarily block signals. This is not
+allowed in a threaded program (\f(CW\*(C`pthread_sigmask\*(C'\fR has to be used). Typical
+pthread implementations will either allow \f(CW\*(C`sigprocmask\*(C'\fR in the \*(L"main
+thread\*(R" or will block signals process-wide, both behaviours would
+be compatible with libev. Interaction between \f(CW\*(C`sigprocmask\*(C'\fR and
+\&\f(CW\*(C`pthread_sigmask\*(C'\fR could complicate things, however.
+.Sp
+The most portable way to handle signals is to block signals in all threads
+except the initial one, and run the default loop in the initial thread as
+well.
+.ie n .IP """long"" must be large enough for common memory allocation sizes" 4
+.el .IP "\f(CWlong\fR must be large enough for common memory allocation sizes" 4
+.IX Item "long must be large enough for common memory allocation sizes"
+To improve portability and simplify using libev, libev uses \f(CW\*(C`long\*(C'\fR
+internally instead of \f(CW\*(C`size_t\*(C'\fR when allocating its data structures. On
+non-POSIX systems (Microsoft...) this might be unexpectedly low, but
+is still at least 31 bits everywhere, which is enough for hundreds of
+millions of watchers.
+.ie n .IP """double"" must hold a time value in seconds with enough accuracy" 4
+.el .IP "\f(CWdouble\fR must hold a time value in seconds with enough accuracy" 4
+.IX Item "double must hold a time value in seconds with enough accuracy"
+The type \f(CW\*(C`double\*(C'\fR is used to represent timestamps. It is required to
+have at least 51 bits of mantissa (and 9 bits of exponent), which is good
+enough for at least into the year 4000. This requirement is fulfilled by
+implementations implementing \s-1IEEE\s0 754 (basically all existing ones).
+.PP
+If you know of other additional requirements drop me a note.
+.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 3052:" 4
+.IX Item "Around line 3052:"
+You forgot a '=back' before '=head2'