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

Comparing libev/ev.3 (file contents):
Revision 1.61 by root, Thu Mar 13 13:06:15 2008 UTC vs.
Revision 1.125 by sf-exg, Sun May 14 19:02:31 2023 UTC

-.\" Automatically generated by Pod::Man 2.16 (Pod::Simple 3.05)
+.\" Automatically generated by Pod::Man 4.11 (Pod::Simple 3.35)
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+.\" titles (.TH), headers (.SH), subsections (.SS), items (.Ip), and index
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-.IX Title "EV 1"
+.IX Title "LIBEV 3"
-.TH EV 1 "2008-03-08" "perl v5.10.0" "User Contributed Perl Documentation"
+.TH LIBEV 3 "2021-01-11" "libev-4.33" "libev - high performance full featured event loop"
 .\" 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>
+\&   #include <ev.h>
 .Ve
-.Sh "\s-1EXAMPLE\s0 \s-1PROGRAM\s0"
+.SS "\s-1EXAMPLE PROGRAM\s0"
 .IX Subsection "EXAMPLE PROGRAM"
 .Vb 2
-\&  // a single header file is required
+\&   // a single header file is required
-\&  #include <ev.h>
+\&   #include <ev.h>
 \&
+\&   #include <stdio.h> // for puts
+\&
-\&  // every watcher type has its own typedef\*(Aqd struct
+\&   // every watcher type has its own typedef\*(Aqd struct
-\&  // with the name ev_<type>
+\&   // with the name ev_TYPE
-\&  ev_io stdin_watcher;
+\&   ev_io stdin_watcher;
-\&  ev_timer timeout_watcher;
+\&   ev_timer timeout_watcher;
 \&
-\&  // all watcher callbacks have a similar signature
+\&   // all watcher callbacks have a similar signature
-\&  // this callback is called when data is readable on stdin
+\&   // this callback is called when data is readable on stdin
-\&  static void
+\&   static void
-\&  stdin_cb (EV_P_ struct ev_io *w, int revents)
+\&   stdin_cb (EV_P_ ev_io *w, int revents)
-\&  {
+\&   {
-\&    puts ("stdin ready");
+\&     puts ("stdin ready");
-\&    // for one\-shot events, one must manually stop the watcher
+\&     // for one\-shot events, one must manually stop the watcher
-\&    // with its corresponding stop function.
+\&     // with its corresponding stop function.
-\&    ev_io_stop (EV_A_ w);
+\&     ev_io_stop (EV_A_ w);
 \&
-\&    // this causes all nested ev_loop\*(Aqs to stop iterating
+\&     // this causes all nested ev_run\*(Aqs to stop iterating
-\&    ev_unloop (EV_A_ EVUNLOOP_ALL);
+\&     ev_break (EV_A_ EVBREAK_ALL);
-\&  }
+\&   }
 \&
-\&  // another callback, this time for a time\-out
+\&   // another callback, this time for a time\-out
-\&  static void
+\&   static void
-\&  timeout_cb (EV_P_ struct ev_timer *w, int revents)
+\&   timeout_cb (EV_P_ ev_timer *w, int revents)
-\&  {
+\&   {
-\&    puts ("timeout");
+\&     puts ("timeout");
-\&    // this causes the innermost ev_loop to stop iterating
+\&     // this causes the innermost ev_run to stop iterating
-\&    ev_unloop (EV_A_ EVUNLOOP_ONE);
+\&     ev_break (EV_A_ EVBREAK_ONE);
-\&  }
+\&   }
 \&
-\&  int
+\&   int
-\&  main (void)
+\&   main (void)
-\&  {
+\&   {
-\&    // use the default event loop unless you have special needs
+\&     // use the default event loop unless you have special needs
-\&    struct ev_loop *loop = ev_default_loop (0);
+\&     struct ev_loop *loop = EV_DEFAULT;
 \&
-\&    // initialise an io watcher, then start it
+\&     // initialise an io watcher, then start it
-\&    // this one will watch for stdin to become readable
+\&     // this one will watch for stdin to become readable
-\&    ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
+\&     ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
-\&    ev_io_start (loop, &stdin_watcher);
+\&     ev_io_start (loop, &stdin_watcher);
 \&
-\&    // initialise a timer watcher, then start it
+\&     // initialise a timer watcher, then start it
-\&    // simple non\-repeating 5.5 second timeout
+\&     // simple non\-repeating 5.5 second timeout
-\&    ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
+\&     ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
-\&    ev_timer_start (loop, &timeout_watcher);
+\&     ev_timer_start (loop, &timeout_watcher);
 \&
-\&    // now wait for events to arrive
+\&     // now wait for events to arrive
-\&    ev_loop (loop, 0);
+\&     ev_run (loop, 0);
 \&
-\&    // unloop was called, so exit
+\&     // break was called, so exit
-\&    return 0;
+\&     return 0;
-\&  }
+\&   }
 .Ve
-.SH "DESCRIPTION"
+.SH "ABOUT THIS DOCUMENT"
-.IX Header "DESCRIPTION"
+.IX Header "ABOUT THIS DOCUMENT"
+This document documents the libev software package.
+.PP
 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>.
+time: <http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
 .PP
+While this document tries to be as complete as possible in documenting
+libev, its usage and the rationale behind its design, it is not a tutorial
+on event-based programming, nor will it introduce event-based programming
+with libev.
+.PP
+Familiarity with event based programming techniques in general is assumed
+throughout this document.
+.SH "WHAT TO READ WHEN IN A HURRY"
+.IX Header "WHAT TO READ WHEN IN A HURRY"
+This manual tries to be very detailed, but unfortunately, this also makes
+it very long. If you just want to know the basics of libev, I suggest
+reading \*(L"\s-1ANATOMY OF A WATCHER\*(R"\s0, then the \*(L"\s-1EXAMPLE PROGRAM\*(R"\s0 above and
+look up the missing functions in \*(L"\s-1GLOBAL FUNCTIONS\*(R"\s0 and the \f(CW\*(C`ev_io\*(C'\fR and
+\&\f(CW\*(C`ev_timer\*(C'\fR sections in \*(L"\s-1WATCHER TYPES\*(R"\s0.
+.SH "ABOUT LIBEV"
+.IX Header "ABOUT LIBEV"
 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
 .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"
+.SS "\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
+Libev supports \f(CW\*(C`select\*(C'\fR, \f(CW\*(C`poll\*(C'\fR, the Linux-specific aio and \f(CW\*(C`epoll\*(C'\fR
-BSD-specific \f(CW\*(C`kqueue\*(C'\fR and the Solaris-specific event port mechanisms
+interfaces, the BSD-specific \f(CW\*(C`kqueue\*(C'\fR and the Solaris-specific event port
-for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), the Linux \f(CW\*(C`inotify\*(C'\fR interface
+mechanisms for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), the Linux \f(CW\*(C`inotify\*(C'\fR
-(for \f(CW\*(C`ev_stat\*(C'\fR), relative timers (\f(CW\*(C`ev_timer\*(C'\fR), absolute timers
+interface (for \f(CW\*(C`ev_stat\*(C'\fR), Linux eventfd/signalfd (for faster and cleaner
-with customised rescheduling (\f(CW\*(C`ev_periodic\*(C'\fR), synchronous signals
+inter-thread wakeup (\f(CW\*(C`ev_async\*(C'\fR)/signal handling (\f(CW\*(C`ev_signal\*(C'\fR)) relative
-(\f(CW\*(C`ev_signal\*(C'\fR), process status change events (\f(CW\*(C`ev_child\*(C'\fR), and event
+timers (\f(CW\*(C`ev_timer\*(C'\fR), absolute timers with customised rescheduling
-watchers dealing with the event loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR,
+(\f(CW\*(C`ev_periodic\*(C'\fR), synchronous signals (\f(CW\*(C`ev_signal\*(C'\fR), process status
-\&\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
+change events (\f(CW\*(C`ev_child\*(C'\fR), and event watchers dealing with the event
-file watchers (\f(CW\*(C`ev_stat\*(C'\fR) and even limited support for fork events
+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_fork\*(C'\fR).
+\&\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
+benchmark <http://libev.schmorp.de/bench.html> comparing it to libevent
 for example).
-.Sh "\s-1CONVENTIONS\s0"
+.SS "\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"
+.SS "\s-1TIME REPRESENTATION\s0"
 .IX Subsection "TIME REPRESENTATION"
-Libev represents time as a single floating point number, representing the
+Libev represents time as a single floating point number, representing
-(fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near
+the (fractional) number of seconds since the (\s-1POSIX\s0) epoch (in practice
-the beginning of 1970, details are complicated, don't ask). This type is
+somewhere near the beginning of 1970, details are complicated, don't
-called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use too. It usually aliases
+ask). This type is called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use
-to the \f(CW\*(C`double\*(C'\fR type in C, and when you need to do any calculations on
+too. It usually aliases to the \f(CW\*(C`double\*(C'\fR type in C. When you need to do
-it, you should treat it as some floatingpoint value. Unlike the name
+any calculations on it, you should treat it as some floating point value.
+.PP
-component \f(CW\*(C`stamp\*(C'\fR might indicate, it is also used for time differences
+Unlike the name component \f(CW\*(C`stamp\*(C'\fR might indicate, it is also used for
-throughout libev.
+time differences (e.g. delays) throughout libev.
+.SH "ERROR HANDLING"
+.IX Header "ERROR HANDLING"
+Libev knows three classes of errors: operating system errors, usage errors
+and internal errors (bugs).
+.PP
+When libev catches an operating system error it cannot handle (for example
+a system call indicating a condition libev cannot fix), it calls the callback
+set via \f(CW\*(C`ev_set_syserr_cb\*(C'\fR, which is supposed to fix the problem or
+abort. The default is to print a diagnostic message and to call \f(CW\*(C`abort
+()\*(C'\fR.
+.PP
+When libev detects a usage error such as a negative timer interval, then
+it will print a diagnostic message and abort (via the \f(CW\*(C`assert\*(C'\fR mechanism,
+so \f(CW\*(C`NDEBUG\*(C'\fR will disable this checking): these are programming errors in
+the libev caller and need to be fixed there.
+.PP
+Via the \f(CW\*(C`EV_FREQUENT\*(C'\fR macro you can compile in and/or enable extensive
+consistency checking code inside libev that can be used to check for
+internal inconsistencies, suually caused by application bugs.
+.PP
+Libev also has a few internal error-checking \f(CW\*(C`assert\*(C'\fRions. These do not
+trigger under normal circumstances, as they indicate either a bug in libev
+or worse.
 .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.
+you actually want to know. Also interesting is the combination of
+\&\f(CW\*(C`ev_now_update\*(C'\fR and \f(CW\*(C`ev_now\*(C'\fR.
 .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
+Sleep for the given interval: The current thread will be blocked
-either it is interrupted or the given time interval has passed. Basically
+until either it is interrupted or the given time interval has
+passed (approximately \- it might return a bit earlier even if not
+interrupted). Returns immediately if \f(CW\*(C`interval <= 0\*(C'\fR.
+.Sp
-this is a subsecond-resolution \f(CW\*(C`sleep ()\*(C'\fR.
+Basically this is a sub-second-resolution \f(CW\*(C`sleep ()\*(C'\fR.
+.Sp
+The range of the \f(CW\*(C`interval\*(C'\fR is limited \- libev only guarantees to work
+with sleep times of up to one day (\f(CW\*(C`interval <= 86400\*(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 ()"
 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.
+version (note, however, that this will not detect other \s-1ABI\s0 mismatches,
+such as \s-1LFS\s0 or reentrancy).
 .Sp
 .Vb 3
-\&  assert (("libev version mismatch",
+\&   assert (("libev version mismatch",
-\&           ev_version_major () == EV_VERSION_MAJOR
+\&            ev_version_major () == EV_VERSION_MAJOR
-\&           && ev_version_minor () >= EV_VERSION_MINOR));
+\&            && ev_version_minor () >= EV_VERSION_MINOR));
 .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
 .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",
+\&   assert (("sorry, no epoll, no sex",
-\&           ev_supported_backends () & EVBACKEND_EPOLL));
+\&            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
+Return the set of all backends compiled into this binary of libev and
-recommended for this platform. This set is often smaller than the one
+also recommended for this platform, meaning it will work for most file
+descriptor types. This set is often smaller than the one returned by
-returned by \f(CW\*(C`ev_supported_backends\*(C'\fR, as for example kqueue is broken on
+\&\f(CW\*(C`ev_supported_backends\*(C'\fR, as for example kqueue is broken on most BSDs
-most BSDs and will not be autodetected unless you explicitly request it
+and will not be auto-detected unless you explicitly request it (assuming
-(assuming you know what you are doing). This is the set of backends that
+you know what you are doing). This is the set of backends that libev will
-libev will probe for if you specify no backends explicitly.
+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
+value is platform-specific but can include backends not available on the
-might be supported on the current system, you would need to look at
+current system. To find which embeddable backends might be supported on
-\&\f(CW\*(C`ev_embeddable_backends () & ev_supported_backends ()\*(C'\fR, likewise for
+the current system, you would need to look at \f(CW\*(C`ev_embeddable_backends ()
-recommended ones.
+& 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
+.IP "ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())" 4
-.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))"
+.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())"
 Sets the allocation function to use (the prototype is similar \- the
-semantics is identical \- to the realloc C function). It is used to
+semantics are identical to the \f(CW\*(C`realloc\*(C'\fR C89/SuS/POSIX function). It is
-allocate and free memory (no surprises here). If it returns zero when
+used to allocate and free memory (no surprises here). If it returns zero
-memory needs to be allocated, the library might abort or take some
+when memory needs to be allocated (\f(CW\*(C`size != 0\*(C'\fR), the library might abort
-potentially destructive action. The default is your system realloc
+or take some potentially destructive action.
-function.
+.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: The following is the \f(CW\*(C`realloc\*(C'\fR function that libev itself uses
+which should work with \f(CW\*(C`realloc\*(C'\fR and \f(CW\*(C`free\*(C'\fR functions of all kinds and
+is probably a good basis for your own implementation.
+.Sp
+.Vb 5
+\&   static void *
+\&   ev_realloc_emul (void *ptr, long size) EV_NOEXCEPT
+\&   {
+\&     if (size)
+\&       return realloc (ptr, size);
+\&
+\&     free (ptr);
+\&     return 0;
+\&   }
+.Ve
+.Sp
 Example: Replace the libev allocator with one that waits a bit and then
-retries).
+retries.
 .Sp
-.Vb 6
+.Vb 8
 \&   static void *
 \&   persistent_realloc (void *ptr, size_t size)
 \&   {
+\&     if (!size)
+\&       {
+\&         free (ptr);
+\&         return 0;
+\&       }
+\&
 \&     for (;;)
 \&       {
 \&         void *newptr = realloc (ptr, size);
 \&
 \&         if (newptr)
 \&   }
 \&
 \&   ...
 \&   ev_set_allocator (persistent_realloc);
 .Ve
-.IP "ev_set_syserr_cb (void (*cb)(const char *msg));" 4
+.IP "ev_set_syserr_cb (void (*cb)(const char *msg) throw ())" 4
-.IX Item "ev_set_syserr_cb (void (*cb)(const char *msg));"
+.IX Item "ev_set_syserr_cb (void (*cb)(const char *msg) throw ())"
-Set the callback function to call on a retryable syscall error (such
+Set the callback function to call on a retryable system call error (such
 as failed select, poll, epoll_wait). The message is a printable string
 indicating the system call or subsystem causing the problem. If this
-callback is set, then libev will expect it to remedy the sitution, no
+callback is set, then libev will expect it to remedy the situation, no
 matter what, when it returns. That is, libev will generally retry the
 requested operation, or, if the condition doesn't go away, do bad stuff
 (such as abort).
 .Sp
 Example: This is basically the same thing that libev does internally, too.
 \&   }
 \&
 \&   ...
 \&   ev_set_syserr_cb (fatal_error);
 .Ve
+.IP "ev_feed_signal (int signum)" 4
+.IX Item "ev_feed_signal (int signum)"
+This function can be used to \*(L"simulate\*(R" a signal receive. It is completely
+safe to call this function at any time, from any context, including signal
+handlers or random threads.
+.Sp
+Its main use is to customise signal handling in your process, especially
+in the presence of threads. For example, you could block signals
+by default in all threads (and specifying \f(CW\*(C`EVFLAG_NOSIGMASK\*(C'\fR when
+creating any loops), and in one thread, use \f(CW\*(C`sigwait\*(C'\fR or any other
+mechanism to wait for signals, then \*(L"deliver\*(R" them to libev by calling
+\&\f(CW\*(C`ev_feed_signal\*(C'\fR.
-.SH "FUNCTIONS CONTROLLING THE EVENT LOOP"
+.SH "FUNCTIONS CONTROLLING EVENT LOOPS"
-.IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP"
+.IX Header "FUNCTIONS CONTROLLING EVENT LOOPS"
-An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR. The library knows two
+An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR (the \f(CW\*(C`struct\*(C'\fR is
-types of such loops, the \fIdefault\fR loop, which supports signals and child
+\&\fInot\fR optional in this case unless libev 3 compatibility is disabled, as
-events, and dynamically created loops which do not.
+libev 3 had an \f(CW\*(C`ev_loop\*(C'\fR function colliding with the struct name).
 .PP
-If you use threads, a common model is to run the default event loop
+The library knows two types of such loops, the \fIdefault\fR loop, which
-in your main thread (or in a separate thread) and for each thread you
+supports child process events, and dynamically created event loops which
-create, you also create another event loop. Libev itself does no locking
+do not.
-whatsoever, so if you mix calls to the same event loop in different
-threads, make sure you lock (this is usually a bad idea, though, even if
-done correctly, because it's hideous and inefficient).
 .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
+This returns the \*(L"default\*(R" event loop object, which is what you should
-yet and return it. If the default loop could not be initialised, returns
+normally use when you just need \*(L"the event loop\*(R". Event loop objects and
-false. If it already was initialised it simply returns it (and ignores the
+the \f(CW\*(C`flags\*(C'\fR parameter are described in more detail in the entry for
-flags. If that is troubling you, check \f(CW\*(C`ev_backend ()\*(C'\fR afterwards).
+\&\f(CW\*(C`ev_loop_new\*(C'\fR.
+.Sp
+If the default loop is already initialised then this function simply
+returns it (and ignores the flags. If that is troubling you, check
+\&\f(CW\*(C`ev_backend ()\*(C'\fR afterwards). Otherwise it will create it with the given
+flags, which should almost always be \f(CW0\fR, unless the caller is also the
+one calling \f(CW\*(C`ev_run\*(C'\fR or otherwise qualifies as \*(L"the main program\*(R".
 .Sp
 If you don't know what event loop to use, use the one returned from this
-function.
+function (or via the \f(CW\*(C`EV_DEFAULT\*(C'\fR macro).
 .Sp
+Note that this function is \fInot\fR thread-safe, so if you want to use it
+from multiple threads, you have to employ some kind of mutex (note also
+that this case is unlikely, as loops cannot be shared easily between
+threads anyway).
+.Sp
-The default loop is the only loop that can handle \f(CW\*(C`ev_signal\*(C'\fR and
+The default loop is the only loop that can handle \f(CW\*(C`ev_child\*(C'\fR watchers,
-\&\f(CW\*(C`ev_child\*(C'\fR watchers, and to do this, it always registers a handler
+and to do this, it always registers a handler for \f(CW\*(C`SIGCHLD\*(C'\fR. If this is
-for \f(CW\*(C`SIGCHLD\*(C'\fR. If this is a problem for your app you can either
+a problem for your application you can either create a dynamic loop with
-create a dynamic loop with \f(CW\*(C`ev_loop_new\*(C'\fR that doesn't do that, or you
+\&\f(CW\*(C`ev_loop_new\*(C'\fR which doesn't do that, or you can simply overwrite the
-can simply overwrite the \f(CW\*(C`SIGCHLD\*(C'\fR signal handler \fIafter\fR calling
+\&\f(CW\*(C`SIGCHLD\*(C'\fR signal handler \fIafter\fR calling \f(CW\*(C`ev_default_init\*(C'\fR.
-\&\f(CW\*(C`ev_default_init\*(C'\fR.
+.Sp
+Example: This is the most typical usage.
+.Sp
+.Vb 2
+\&   if (!ev_default_loop (0))
+\&     fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
+.Ve
+.Sp
+Example: 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
+.IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4
+.IX Item "struct ev_loop *ev_loop_new (unsigned int flags)"
+This will create and initialise a new event loop object. If the loop
+could not be initialised, returns false.
+.Sp
+This function is thread-safe, and one common 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
 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:
 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
+If this flag bit is or'ed 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
+useful to try out specific backends to test their performance, to work
-around bugs.
+around bugs, or to make libev threadsafe (accessing environment variables
+cannot be done in a threadsafe way, but usually it works if no other
+thread modifies them).
 .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
+Instead of calling \f(CW\*(C`ev_loop_fork\*(C'\fR manually after a fork, you can also
-a fork, you can also make libev check for a fork in each iteration by
+make libev check for a fork in each iteration by enabling this flag.
-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
+GNU/Linux system for example, \f(CW\*(C`getpid\*(C'\fR is actually a simple 5\-insn
-without a syscall and thus \fIvery\fR fast, but my GNU/Linux system also has
+sequence without a system call and thus \fIvery\fR fast, but my GNU/Linux
-\&\f(CW\*(C`pthread_atfork\*(C'\fR which is even faster).
+system also has \f(CW\*(C`pthread_atfork\*(C'\fR which is even faster). (Update: glibc
+versions 2.25 apparently removed the \f(CW\*(C`getpid\*(C'\fR optimisation again).
 .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
+forget about forgetting to tell libev about forking, although you still
-flag.
+have to ignore \f(CW\*(C`SIGPIPE\*(C'\fR) when you use this flag.
 .Sp
-This flag setting cannot be overriden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR
+This flag setting cannot be overridden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR
 environment variable.
+.ie n .IP """EVFLAG_NOINOTIFY""" 4
+.el .IP "\f(CWEVFLAG_NOINOTIFY\fR" 4
+.IX Item "EVFLAG_NOINOTIFY"
+When this flag is specified, then libev will not attempt to use the
+\&\fIinotify\fR \s-1API\s0 for its \f(CW\*(C`ev_stat\*(C'\fR watchers. Apart from debugging and
+testing, this flag can be useful to conserve inotify file descriptors, as
+otherwise each loop using \f(CW\*(C`ev_stat\*(C'\fR watchers consumes one inotify handle.
+.ie n .IP """EVFLAG_SIGNALFD""" 4
+.el .IP "\f(CWEVFLAG_SIGNALFD\fR" 4
+.IX Item "EVFLAG_SIGNALFD"
+When this flag is specified, then libev will attempt to use the
+\&\fIsignalfd\fR \s-1API\s0 for its \f(CW\*(C`ev_signal\*(C'\fR (and \f(CW\*(C`ev_child\*(C'\fR) watchers. This \s-1API\s0
+delivers signals synchronously, which makes it both faster and might make
+it possible to get the queued signal data. It can also simplify signal
+handling with threads, as long as you properly block signals in your
+threads that are not interested in handling them.
+.Sp
+Signalfd will not be used by default as this changes your signal mask, and
+there are a lot of shoddy libraries and programs (glib's threadpool for
+example) that can't properly initialise their signal masks.
+.ie n .IP """EVFLAG_NOSIGMASK""" 4
+.el .IP "\f(CWEVFLAG_NOSIGMASK\fR" 4
+.IX Item "EVFLAG_NOSIGMASK"
+When this flag is specified, then libev will avoid to modify the signal
+mask. Specifically, this means you have to make sure signals are unblocked
+when you want to receive them.
+.Sp
+This behaviour is useful when you want to do your own signal handling, or
+want to handle signals only in specific threads and want to avoid libev
+unblocking the signals.
+.Sp
+It's also required by \s-1POSIX\s0 in a threaded program, as libev calls
+\&\f(CW\*(C`sigprocmask\*(C'\fR, whose behaviour is officially unspecified.
+.ie n .IP """EVFLAG_NOTIMERFD""" 4
+.el .IP "\f(CWEVFLAG_NOTIMERFD\fR" 4
+.IX Item "EVFLAG_NOTIMERFD"
+When this flag is specified, the libev will avoid using a \f(CW\*(C`timerfd\*(C'\fR to
+detect time jumps. It will still be able to detect time jumps, but takes
+longer and has a lower accuracy in doing so, but saves a file descriptor
+per loop.
+.Sp
+The current implementation only tries to use a \f(CW\*(C`timerfd\*(C'\fR when the first
+\&\f(CW\*(C`ev_periodic\*(C'\fR watcher is started and falls back on other methods if it
+cannot be created, but this behaviour might change in the future.
 .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)"
+.IX Item "EVBACKEND_SELECT (value 1, portable select backend)"
-This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as
+This is your standard \fBselect\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
+parallelism (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.
+readiness notifications you get per iteration.
+.Sp
+This backend maps \f(CW\*(C`EV_READ\*(C'\fR to the \f(CW\*(C`readfds\*(C'\fR set and \f(CW\*(C`EV_WRITE\*(C'\fR to the
+\&\f(CW\*(C`writefds\*(C'\fR set (and to work around Microsoft Windows bugs, also onto the
+\&\f(CW\*(C`exceptfds\*(C'\fR set on that platform).
 .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)"
+.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
+And this is your standard \fBpoll\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.
+.Sp
+This backend maps \f(CW\*(C`EV_READ\*(C'\fR to \f(CW\*(C`POLLIN | POLLERR | POLLHUP\*(C'\fR, and
+\&\f(CW\*(C`EV_WRITE\*(C'\fR to \f(CW\*(C`POLLOUT | POLLERR | POLLHUP\*(C'\fR.
 .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)"
+.IX Item "EVBACKEND_EPOLL (value 4, Linux)"
+Use the Linux-specific \fBepoll\fR\|(7) interface (for both pre\- and post\-2.6.9
+kernels).
+.Sp
-For few fds, this backend is a bit little slower than poll and select,
+For few fds, this backend is a bit little slower than poll and select, but
-but it scales phenomenally better. While poll and select usually scale
+it scales phenomenally better. While poll and select usually scale like
-like O(total_fds) where n is the total number of fds (or the highest fd),
+O(total_fds) where total_fds is the total number of fds (or the highest
-epoll scales either O(1) or O(active_fds). The epoll design has a number
+fd), epoll scales either O(1) or O(active_fds).
-of shortcomings, such as silently dropping events in some hard-to-detect
+.Sp
-cases and rewiring a syscall per fd change, no fork support and bad
+The epoll mechanism deserves honorable mention as the most misdesigned
-support for dup.
+of the more advanced event mechanisms: mere annoyances include silently
+dropping file descriptors, requiring a system call per change per file
+descriptor (and unnecessary guessing of parameters), problems with dup,
+returning before the timeout value, resulting in additional iterations
+(and only giving 5ms accuracy while select on the same platform gives
+0.1ms) and so on. The biggest issue is fork races, however \- if a program
+forks then \fIboth\fR parent and child process have to recreate the epoll
+set, which can take considerable time (one syscall per file descriptor)
+and is of course hard to detect.
+.Sp
+Epoll is also notoriously buggy \- embedding epoll fds \fIshould\fR work,
+but of course \fIdoesn't\fR, and epoll just loves to report events for
+totally \fIdifferent\fR file descriptors (even already closed ones, so
+one cannot even remove them from the set) than registered in the set
+(especially on \s-1SMP\s0 systems). Libev tries to counter these spurious
+notifications by employing an additional generation counter and comparing
+that against the events to filter out spurious ones, recreating the set
+when required. Epoll also erroneously rounds down timeouts, but gives you
+no way to know when and by how much, so sometimes you have to busy-wait
+because epoll returns immediately despite a nonzero timeout. And last
+not least, it also refuses to work with some file descriptors which work
+perfectly fine with \f(CW\*(C`select\*(C'\fR (files, many character devices...).
+.Sp
+Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
+cobbled together in a hurry, no thought to design or interaction with
+others. Oh, the pain, will it ever stop...
 .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
+will result in some caching, there is still a system call per such
-(because the fd could point to a different file description now), so its
+incident (because the same \fIfile descriptor\fR could point to a different
-best to avoid that. Also, \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors might not work
+\&\fIfile description\fR now), so its best to avoid that. Also, \f(CW\*(C`dup ()\*(C'\fR'ed
-very well if you register events for both fds.
+file descriptors might not work very well if you register events for both
-.Sp
+file descriptors.
-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.
+watchers for a file descriptor until it has been closed, if possible,
-keep at least one watcher active per fd at all times.
+i.e. keep at least one watcher active per fd at all times. Stopping and
+starting a watcher (without re-setting it) also usually doesn't cause
+extra overhead. A fork can both result in spurious notifications as well
+as in libev having to destroy and recreate the epoll object, which can
+take considerable time and thus should be avoided.
 .Sp
+All this means that, in practice, \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR can be as fast or
+faster than epoll for maybe up to a hundred file descriptors, depending on
+the usage. So sad.
+.Sp
-While nominally embeddeble in other event loops, this feature is broken in
+While nominally embeddable in other event loops, this feature is broken in
-all kernel versions tested so far.
+a lot of kernel revisions, but probably(!) works in current versions.
+.Sp
+This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as
+\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
+.ie n .IP """EVBACKEND_LINUXAIO""   (value 64, Linux)" 4
+.el .IP "\f(CWEVBACKEND_LINUXAIO\fR   (value 64, Linux)" 4
+.IX Item "EVBACKEND_LINUXAIO (value 64, Linux)"
+Use the Linux-specific Linux \s-1AIO\s0 (\fInot\fR \f(CWaio(7)\fR but \f(CWio_submit(2)\fR) event interface available in post\-4.18 kernels (but libev
+only tries to use it in 4.19+).
+.Sp
+This is another Linux train wreck of an event interface.
+.Sp
+If this backend works for you (as of this writing, it was very
+experimental), it is the best event interface available on Linux and might
+be well worth enabling it \- if it isn't available in your kernel this will
+be detected and this backend will be skipped.
+.Sp
+This backend can batch oneshot requests and supports a user-space ring
+buffer to receive events. It also doesn't suffer from most of the design
+problems of epoll (such as not being able to remove event sources from
+the epoll set), and generally sounds too good to be true. Because, this
+being the Linux kernel, of course it suffers from a whole new set of
+limitations, forcing you to fall back to epoll, inheriting all its design
+issues.
+.Sp
+For one, it is not easily embeddable (but probably could be done using
+an event fd at some extra overhead). It also is subject to a system wide
+limit that can be configured in \fI/proc/sys/fs/aio\-max\-nr\fR. If no \s-1AIO\s0
+requests are left, this backend will be skipped during initialisation, and
+will switch to epoll when the loop is active.
+.Sp
+Most problematic in practice, however, is that not all file descriptors
+work with it. For example, in Linux 5.1, \s-1TCP\s0 sockets, pipes, event fds,
+files, \fI/dev/null\fR and many others are supported, but ttys do not work
+properly (a known bug that the kernel developers don't care about, see
+<https://lore.kernel.org/patchwork/patch/1047453/>), so this is not
+(yet?) a generic event polling interface.
+.Sp
+Overall, it seems the Linux developers just don't want it to have a
+generic event handling mechanism other than \f(CW\*(C`select\*(C'\fR or \f(CW\*(C`poll\*(C'\fR.
+.Sp
+To work around all these problem, the current version of libev uses its
+epoll backend as a fallback for file descriptor types that do not work. Or
+falls back completely to epoll if the kernel acts up.
+.Sp
+This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as
+\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
 .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)"
+.IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)"
-Kqueue deserves special mention, as at the time of this writing, it
+Kqueue deserves special mention, as at the time this backend was
-was broken on all BSDs except NetBSD (usually it doesn't work reliably
+implemented, it was broken on all BSDs except NetBSD (usually it doesn't
-with anything but sockets and pipes, except on Darwin, where of course
+work reliably with anything but sockets and pipes, except on Darwin,
-it's completely useless). For this reason it's not being \*(L"autodetected\*(R"
+where of course it's completely useless). Unlike epoll, however, whose
-unless you explicitly specify it explicitly in the flags (i.e. using
+brokenness is by design, these kqueue bugs can be (and mostly have been)
-\&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR) or libev was compiled on a known-to-be-good (\-enough)
+fixed without \s-1API\s0 changes to existing programs. For this reason it's not
-system like NetBSD.
+being \*(L"auto-detected\*(R" on all platforms unless you explicitly specify it
+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
+cause an extra system call 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
+two event changes per incident. Support for \f(CW\*(C`fork ()\*(C'\fR is very bad (you
+might have to leak fds on fork, but it's more sane than epoll) 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
+(e.g. \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR (but \f(CW\*(C`poll\*(C'\fR is of course
-sockets.
+also broken on \s-1OS X\s0)) and, did I mention it, using it only for sockets.
+.Sp
+This backend maps \f(CW\*(C`EV_READ\*(C'\fR into an \f(CW\*(C`EVFILT_READ\*(C'\fR kevent with
+\&\f(CW\*(C`NOTE_EOF\*(C'\fR, and \f(CW\*(C`EV_WRITE\*(C'\fR into an \f(CW\*(C`EVFILT_WRITE\*(C'\fR kevent with
+\&\f(CW\*(C`NOTE_EOF\*(C'\fR.
 .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)"
+.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
+On the positive side, this backend actually performed fully to
-backend actually performed to specification in all tests and is fully
+specification in all tests and is fully embeddable, which is a rare feat
-embeddable, which is a rare feat among the OS-specific backends.
+among the OS-specific backends (I vastly prefer correctness over speed
+hacks).
+.Sp
+On the negative side, the interface is \fIbizarre\fR \- so bizarre that
+even sun itself gets it wrong in their code examples: The event polling
+function sometimes returns events to the caller even though an error
+occurred, but with no indication whether it has done so or not (yes, it's
+even documented that way) \- deadly for edge-triggered interfaces where you
+absolutely have to know whether an event occurred or not because you have
+to re-arm the watcher.
+.Sp
+Fortunately libev seems to be able to work around these idiocies.
+.Sp
+This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as
+\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
 .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.
+It is definitely not recommended to use this flag, use whatever
+\&\f(CW\*(C`ev_recommended_backends ()\*(C'\fR returns, or simply do not specify a backend
+at all.
+.ie n .IP """EVBACKEND_MASK""" 4
+.el .IP "\f(CWEVBACKEND_MASK\fR" 4
+.IX Item "EVBACKEND_MASK"
+Not a backend at all, but a mask to select all backend bits from a
+\&\f(CW\*(C`flags\*(C'\fR value, in case you want to mask out any backends from a flags
+value (e.g. when modifying the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR environment variable).
 .RE
 .RS 4
 .Sp
-If one or more of these are ored into the flags value, then only these
+If one or more of the backend flags are or'ed into the flags value,
-backends will be tried (in the reverse order as listed here). If none are
+then only these backends will be tried (in the reverse order as listed
-specified, all backends in \f(CW\*(C`ev_recommended_backends ()\*(C'\fR will be tried.
+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:
+Example: Try to create a event loop that uses epoll and nothing else.
 .Sp
-.Vb 2
+.Vb 3
-\&  if (!ev_default_loop (0))
+\&   struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
-\&    fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
+\&   if (!epoller)
+\&     fatal ("no epoll found here, maybe it hides under your chair");
 .Ve
 .Sp
-Restrict libev to the select and poll backends, and do not allow
+Example: Use whatever libev has to offer, but make sure that kqueue is
-environment settings to be taken into account:
+used if available.
 .Sp
 .Vb 1
-\&  ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
+\&   struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
 .Ve
 .Sp
-Use whatever libev has to offer, but make sure that kqueue is used if
+Example: Similarly, on linux, you mgiht want to take advantage of the
-available (warning, breaks stuff, best use only with your own private
+linux aio backend if possible, but fall back to something else if that
-event loop and only if you know the \s-1OS\s0 supports your types of fds):
+isn't available.
 .Sp
 .Vb 1
-\&  ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
+\&   struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_LINUXAIO);
 .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
-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
+.IP "ev_loop_destroy (loop)" 4
-.IX Item "ev_default_destroy ()"
+.IX Item "ev_loop_destroy (loop)"
-Destroys the default loop again (frees all memory and kernel state
+Destroys an event loop object (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
+responsibility to either stop all watchers cleanly yourself \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
+Note that certain global state, such as signal state (and installed signal
-this function, and related watchers (such as signal and child watchers)
+handlers), will not be freed by this function, and related watchers (such
-would need to be stopped manually.
+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
+This function is normally used on loop objects allocated by
-rare occasion where you really need to free e.g. the signal handling
+\&\f(CW\*(C`ev_loop_new\*(C'\fR, but it can also be used on the default loop returned by
-pipe fds. If you need dynamically allocated loops it is better to use
+\&\f(CW\*(C`ev_default_loop\*(C'\fR, in which case it is not thread-safe.
-\&\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
+Note that it is not advisable to call this function on the default loop
-process if and only if you want to use the event library in the child. If
+except in the rare occasion where you really need to free its resources.
-you just fork+exec, you don't have to call it at all.
+If you need dynamically allocated loops it is better to use \f(CW\*(C`ev_loop_new\*(C'\fR
-.Sp
+and \f(CW\*(C`ev_loop_destroy\*(C'\fR.
-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
+This function sets a flag that causes subsequent \f(CW\*(C`ev_run\*(C'\fR iterations
-\&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop
+to reinitialise the kernel state for backends that have one. Despite
-after fork, and how you do this is entirely your own problem.
+the name, you can call it anytime you are allowed to start or stop
+watchers (except inside an \f(CW\*(C`ev_prepare\*(C'\fR callback), but it makes most
+sense after forking, in the child process. You \fImust\fR call it (or use
+\&\f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR) in the child before resuming or calling \f(CW\*(C`ev_run\*(C'\fR.
+.Sp
+In addition, if you want to reuse a loop (via this function or
+\&\f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR), you \fIalso\fR have to ignore \f(CW\*(C`SIGPIPE\*(C'\fR.
+.Sp
+Again, you \fIhave\fR to call it on \fIany\fR loop that you want to re-use after
+a fork, \fIeven if you do not plan to use the loop in the parent\fR. This is
+because some kernel interfaces *cough* \fIkqueue\fR *cough* do funny things
+during fork.
+.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 loop in the child. If
+you just fork+exec or create a new loop in the child, you don't have to
+call it at all (in fact, \f(CW\*(C`epoll\*(C'\fR is so badly broken that it makes a
+difference, but libev will usually detect this case on its own and do a
+costly reset of the backend).
+.Sp
+The function itself is quite fast and it's usually not a problem to call
+it just in case after a fork.
+.Sp
+Example: Automate calling \f(CW\*(C`ev_loop_fork\*(C'\fR on the default loop when
+using pthreads.
+.Sp
+.Vb 5
+\&   static void
+\&   post_fork_child (void)
+\&   {
+\&     ev_loop_fork (EV_DEFAULT);
+\&   }
+\&
+\&   ...
+\&   pthread_atfork (0, 0, post_fork_child);
+.Ve
 .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.
+Returns true when the given loop is, in fact, the default loop, and false
+otherwise.
-.IP "unsigned int ev_loop_count (loop)" 4
+.IP "unsigned int ev_iteration (loop)" 4
-.IX Item "unsigned int ev_loop_count (loop)"
+.IX Item "unsigned int ev_iteration (loop)"
-Returns the count of loop iterations for the loop, which is identical to
+Returns the current iteration count for the event loop, which is identical
-the number of times libev did poll for new events. It starts at \f(CW0\fR and
+to the number of times libev did poll for new events. It starts at \f(CW0\fR
-happily wraps around with enough iterations.
+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.
+\&\f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR calls \- and is incremented between the
+prepare and check phases.
+.IP "unsigned int ev_depth (loop)" 4
+.IX Item "unsigned int ev_depth (loop)"
+Returns the number of times \f(CW\*(C`ev_run\*(C'\fR was entered minus the number of
+times \f(CW\*(C`ev_run\*(C'\fR was exited normally, in other words, the recursion depth.
+.Sp
+Outside \f(CW\*(C`ev_run\*(C'\fR, this number is zero. In a callback, this number is
+\&\f(CW1\fR, unless \f(CW\*(C`ev_run\*(C'\fR was invoked recursively (or from another thread),
+in which case it is higher.
+.Sp
+Leaving \f(CW\*(C`ev_run\*(C'\fR abnormally (setjmp/longjmp, cancelling the thread,
+throwing an exception etc.), doesn't count as \*(L"exit\*(R" \- consider this
+as a hint to avoid such ungentleman-like behaviour unless it's really
+convenient, in which case it is fully supported.
 .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
 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_now_update (loop)" 4
+.IX Item "ev_now_update (loop)"
+Establishes the current time by querying the kernel, updating the time
+returned by \f(CW\*(C`ev_now ()\*(C'\fR in the progress. This is a costly operation and
+is usually done automatically within \f(CW\*(C`ev_run ()\*(C'\fR.
+.Sp
+This function is rarely useful, but when some event callback runs for a
+very long time without entering the event loop, updating libev's idea of
+the current time is a good idea.
+.Sp
+See also \*(L"The special problem of time updates\*(R" in the \f(CW\*(C`ev_timer\*(C'\fR section.
+.IP "ev_suspend (loop)" 4
+.IX Item "ev_suspend (loop)"
+.PD 0
+.IP "ev_resume (loop)" 4
+.IX Item "ev_resume (loop)"
+.PD
+These two functions suspend and resume an event loop, for use when the
+loop is not used for a while and timeouts should not be processed.
+.Sp
+A typical use case would be an interactive program such as a game:  When
+the user presses \f(CW\*(C`^Z\*(C'\fR to suspend the game and resumes it an hour later it
+would be best to handle timeouts as if no time had actually passed while
+the program was suspended. This can be achieved by calling \f(CW\*(C`ev_suspend\*(C'\fR
+in your \f(CW\*(C`SIGTSTP\*(C'\fR handler, sending yourself a \f(CW\*(C`SIGSTOP\*(C'\fR and calling
+\&\f(CW\*(C`ev_resume\*(C'\fR directly afterwards to resume timer processing.
+.Sp
+Effectively, all \f(CW\*(C`ev_timer\*(C'\fR watchers will be delayed by the time spend
+between \f(CW\*(C`ev_suspend\*(C'\fR and \f(CW\*(C`ev_resume\*(C'\fR, and all \f(CW\*(C`ev_periodic\*(C'\fR watchers
+will be rescheduled (that is, they will lose any events that would have
+occurred while suspended).
+.Sp
+After calling \f(CW\*(C`ev_suspend\*(C'\fR you \fBmust not\fR call \fIany\fR function on the
+given loop other than \f(CW\*(C`ev_resume\*(C'\fR, and you \fBmust not\fR call \f(CW\*(C`ev_resume\*(C'\fR
+without a previous call to \f(CW\*(C`ev_suspend\*(C'\fR.
+.Sp
+Calling \f(CW\*(C`ev_suspend\*(C'\fR/\f(CW\*(C`ev_resume\*(C'\fR has the side effect of updating the
+event loop time (see \f(CW\*(C`ev_now_update\*(C'\fR).
-.IP "ev_loop (loop, int flags)" 4
+.IP "bool ev_run (loop, int flags)" 4
-.IX Item "ev_loop (loop, int flags)"
+.IX Item "bool ev_run (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
+after you have initialised all your watchers and you want to start
-events.
+handling events. It will ask the operating system for any new events, call
+the watcher callbacks, and then repeat the whole process indefinitely: This
+is why event loops are called \fIloops\fR.
 .Sp
-If the flags argument is specified as \f(CW0\fR, it will not return until
+If the flags argument is specified as \f(CW0\fR, it will keep handling events
-either no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called.
+until either no event watchers are active anymore or \f(CW\*(C`ev_break\*(C'\fR was
+called.
 .Sp
+The return value is false if there are no more active watchers (which
+usually means \*(L"all jobs done\*(R" or \*(L"deadlock\*(R"), and true in all other cases
+(which usually means " you should call \f(CW\*(C`ev_run\*(C'\fR again").
+.Sp
-Please note that an explicit \f(CW\*(C`ev_unloop\*(C'\fR is usually better than
+Please note that an explicit \f(CW\*(C`ev_break\*(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
+finished (especially in interactive programs), but having a program
-automatically loops as long as it has to and no longer by virtue of
+that automatically loops as long as it has to and no longer by virtue
-relying on its watchers stopping correctly is a thing of beauty.
+of relying on its watchers stopping correctly, that is truly a thing of
+beauty.
 .Sp
+This function is \fImostly\fR exception-safe \- you can break out of a
+\&\f(CW\*(C`ev_run\*(C'\fR call by calling \f(CW\*(C`longjmp\*(C'\fR in a callback, throwing a \*(C+
+exception and so on. This does not decrement the \f(CW\*(C`ev_depth\*(C'\fR value, nor
+will it clear any outstanding \f(CW\*(C`EVBREAK_ONE\*(C'\fR breaks.
+.Sp
-A flags value of \f(CW\*(C`EVLOOP_NONBLOCK\*(C'\fR will look for new events, will handle
+A flags value of \f(CW\*(C`EVRUN_NOWAIT\*(C'\fR will look for new events, will handle
-those events and any outstanding ones, but will not block your process in
+those events and any already outstanding ones, but will not wait and
-case there are no events and will return after one iteration of the loop.
+block your process in case there are no events and will return after one
+iteration of the loop. This is sometimes useful to poll and handle new
+events while doing lengthy calculations, to keep the program responsive.
 .Sp
-A flags value of \f(CW\*(C`EVLOOP_ONESHOT\*(C'\fR will look for new events (waiting if
+A flags value of \f(CW\*(C`EVRUN_ONCE\*(C'\fR will look for new events (waiting if
-neccessary) and will handle those and any outstanding ones. It will block
+necessary) and will handle those and any already outstanding ones. It
-your process until at least one new event arrives, and will return after
+will block your process until at least one new event arrives (which could
-one iteration of the loop. This is useful if you are waiting for some
+be an event internal to libev itself, so there is no guarantee that a
-external event in conjunction with something not expressible using other
+user-registered callback will be called), and will return after one
+iteration of the loop.
+.Sp
+This is useful if you are waiting for some external event in conjunction
+with something not expressible using other libev watchers (i.e. "roll your
-libev watchers. However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is
+own \f(CW\*(C`ev_run\*(C'\fR"). 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:
+Here are the gory details of what \f(CW\*(C`ev_run\*(C'\fR does (this is for your
+understanding, not a guarantee that things will work exactly like this in
+future versions):
 .Sp
 .Vb 10
+\&   \- Increment loop depth.
+\&   \- Reset the ev_break status.
 \&   \- Before the first iteration, call any pending watchers.
+\&   LOOP:
-\&   * If EVFLAG_FORKCHECK was used, check for a fork.
+\&   \- If EVFLAG_FORKCHECK was used, check for a fork.
-\&   \- If a fork was detected, queue and call all fork watchers.
+\&   \- If a fork was detected (by any means), queue and call all fork watchers.
 \&   \- Queue and call all prepare watchers.
+\&   \- If ev_break was called, goto FINISH.
-\&   \- If we have been forked, recreate the kernel state.
+\&   \- If we have been forked, detach and recreate the kernel state
+\&     as to not disturb the other process.
 \&   \- Update the kernel state with all outstanding changes.
-\&   \- Update the "event loop time".
+\&   \- Update the "event loop time" (ev_now ()).
 \&   \- Calculate for how long to sleep or block, if at all
-\&     (active idle watchers, EVLOOP_NONBLOCK or not having
+\&     (active idle watchers, EVRUN_NOWAIT or not having
 \&     any active watchers at all will result in not sleeping).
 \&   \- Sleep if the I/O and timer collect interval say so.
+\&   \- Increment loop iteration counter.
 \&   \- Block the process, waiting for any events.
 \&   \- Queue all outstanding I/O (fd) events.
-\&   \- Update the "event loop time" and do time jump handling.
+\&   \- Update the "event loop time" (ev_now ()), and do time jump adjustments.
-\&   \- Queue all outstanding timers.
+\&   \- Queue all expired timers.
-\&   \- Queue all outstanding periodics.
+\&   \- Queue all expired periodics.
-\&   \- If no events are pending now, queue all idle watchers.
+\&   \- Queue all idle watchers with priority higher than that of pending events.
 \&   \- 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
+\&     Signals, async and child watchers are implemented as I/O watchers, and
-\&     be handled here by queueing them when their watcher gets executed.
+\&     will be handled here by queueing them when their watcher gets executed.
-\&   \- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
+\&   \- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
-\&     were used, or there are no active watchers, return, otherwise
+\&     were used, or there are no active watchers, goto FINISH, otherwise
-\&     continue with step *.
+\&     continue with step LOOP.
+\&   FINISH:
+\&   \- Reset the ev_break status iff it was EVBREAK_ONE.
+\&   \- Decrement the loop depth.
+\&   \- Return.
 .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);
+\&   ev_run (my_loop, 0);
-\&   ... jobs done. yeah!
+\&   ... jobs done or somebody called break. yeah!
 .Ve
-.IP "ev_unloop (loop, how)" 4
+.IP "ev_break (loop, how)" 4
-.IX Item "ev_unloop (loop, how)"
+.IX Item "ev_break (loop, how)"
-Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it
+Can be used to make a call to \f(CW\*(C`ev_run\*(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`EVBREAK_ONE\*(C'\fR, which will make the innermost \f(CW\*(C`ev_run\*(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.
+\&\f(CW\*(C`EVBREAK_ALL\*(C'\fR, which will make all nested \f(CW\*(C`ev_run\*(C'\fR calls return.
 .Sp
-This \*(L"unloop state\*(R" will be cleared when entering \f(CW\*(C`ev_loop\*(C'\fR again.
+This \*(L"break state\*(R" will be cleared on the next call to \f(CW\*(C`ev_run\*(C'\fR.
+.Sp
+It is safe to call \f(CW\*(C`ev_break\*(C'\fR from outside any \f(CW\*(C`ev_run\*(C'\fR calls, too, in
+which case it will have no effect.
 .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
+count is nonzero, \f(CW\*(C`ev_run\*(C'\fR will not return on its own.
-a watcher you never unregister that should not keep \f(CW\*(C`ev_loop\*(C'\fR from
+.Sp
-returning, \fIev_unref()\fR after starting, and \fIev_ref()\fR before stopping it. For
+This is useful when you have a watcher that you never intend to
+unregister, but that nevertheless should not keep \f(CW\*(C`ev_run\*(C'\fR from
+returning. In such a case, call \f(CW\*(C`ev_unref\*(C'\fR after starting, and \f(CW\*(C`ev_ref\*(C'\fR
+before stopping it.
+.Sp
-example, libev itself uses this for its internal signal pipe: It is not
+As an example, libev itself uses this for its internal signal pipe: It
-visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if
+is not visible to the libev user and should not keep \f(CW\*(C`ev_run\*(C'\fR from
-no event watchers registered by it are active. It is also an excellent
+exiting if no event watchers registered by it are active. It is also an
-way to do this for generic recurring timers or from within third-party
+excellent way to do this for generic recurring timers or from within
-libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR
+third-party libraries. Just remember to \fIunref after start\fR and \fIref
-(but only if the watcher wasn't active before, or was active before,
+before stop\fR (but only if the watcher wasn't active before, or was active
-respectively).
+before, respectively. Note also that libev might stop watchers itself
+(e.g. non-repeating timers) in which case you have to \f(CW\*(C`ev_ref\*(C'\fR
+in the callback).
 .Sp
-Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR
+Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_run\*(C'\fR
 running when nothing else is active.
 .Sp
 .Vb 4
-\&  struct ev_signal exitsig;
+\&   ev_signal exitsig;
-\&  ev_signal_init (&exitsig, sig_cb, SIGINT);
+\&   ev_signal_init (&exitsig, sig_cb, SIGINT);
-\&  ev_signal_start (loop, &exitsig);
+\&   ev_signal_start (loop, &exitsig);
-\&  evf_unref (loop);
+\&   ev_unref (loop);
 .Ve
 .Sp
 Example: For some weird reason, unregister the above signal handler again.
 .Sp
 .Vb 2
-\&  ev_ref (loop);
+\&   ev_ref (loop);
-\&  ev_signal_stop (loop, &exitsig);
+\&   ev_signal_stop (loop, &exitsig);
 .Ve
 .IP "ev_set_io_collect_interval (loop, ev_tstamp interval)" 4
 .IX Item "ev_set_io_collect_interval (loop, ev_tstamp interval)"
 .PD 0
 .IP "ev_set_timeout_collect_interval (loop, ev_tstamp interval)" 4
 .IX Item "ev_set_timeout_collect_interval (loop, ev_tstamp interval)"
 .PD
 These advanced functions influence the time that libev will spend waiting
-for events. Both are by default \f(CW0\fR, meaning that libev will try to
+for events. Both time intervals are by default \f(CW0\fR, meaning that libev
-invoke timer/periodic callbacks and I/O callbacks with minimum latency.
+will try to invoke timer/periodic callbacks and I/O callbacks with minimum
+latency.
 .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
+allows libev to delay invocation of I/O and timer/periodic callbacks
-increase efficiency of loop iterations.
+to increase efficiency of loop iterations (or to increase power-saving
+opportunities).
 .Sp
-The background is that sometimes your program runs just fast enough to
+The idea is that sometimes your program runs just fast enough to handle
-handle one (or very few) event(s) per loop iteration. While this makes
+one (or very few) event(s) per loop iteration. While this makes the
-the program responsive, it also wastes a lot of \s-1CPU\s0 time to poll for new
+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
+\&\f(CW\*(C`ev_timer\*(C'\fR) will not be affected. Setting this to a non-null value will
-introduce an additional \f(CW\*(C`ev_sleep ()\*(C'\fR call into most loop iterations.
+introduce an additional \f(CW\*(C`ev_sleep ()\*(C'\fR call into most loop iterations. The
+sleep time ensures that libev will not poll for I/O events more often then
+once per this interval, on average (as long as the host time resolution is
+good enough).
 .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
+latency/jitter/inexactness (the watcher callback will be called
-will not be affected. Setting this to a non-null value will not introduce
+later). \f(CW\*(C`ev_io\*(C'\fR watchers will not be affected. Setting this to a non-null
-any overhead in libev.
+value will not introduce any overhead in libev.
 .Sp
-Many (busy) programs can usually benefit by setting the io collect
+Many (busy) programs can usually benefit by setting the I/O collect
 interval to a value near \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.
+as this approaches the timing granularity of most systems. Note that if
+you do transactions with the outside world and you can't increase the
+parallelity, then this setting will limit your transaction rate (if you
+need to poll once per transaction and the I/O collect interval is 0.01,
+then you can't do more than 100 transactions per second).
+.Sp
+Setting the \fItimeout collect interval\fR can improve the opportunity for
+saving power, as the program will \*(L"bundle\*(R" timer callback invocations that
+are \*(L"near\*(R" in time together, by delaying some, thus reducing the number of
+times the process sleeps and wakes up again. Another useful technique to
+reduce iterations/wake\-ups is to use \f(CW\*(C`ev_periodic\*(C'\fR watchers and make sure
+they fire on, say, one-second boundaries only.
+.Sp
+Example: we only need 0.1s timeout granularity, and we wish not to poll
+more often than 100 times per second:
+.Sp
+.Vb 2
+\&   ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
+\&   ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
+.Ve
+.IP "ev_invoke_pending (loop)" 4
+.IX Item "ev_invoke_pending (loop)"
+This call will simply invoke all pending watchers while resetting their
+pending state. Normally, \f(CW\*(C`ev_run\*(C'\fR does this automatically when required,
+but when overriding the invoke callback this call comes handy. This
+function can be invoked from a watcher \- this can be useful for example
+when you want to do some lengthy calculation and want to pass further
+event handling to another thread (you still have to make sure only one
+thread executes within \f(CW\*(C`ev_invoke_pending\*(C'\fR or \f(CW\*(C`ev_run\*(C'\fR of course).
+.IP "int ev_pending_count (loop)" 4
+.IX Item "int ev_pending_count (loop)"
+Returns the number of pending watchers \- zero indicates that no watchers
+are pending.
+.IP "ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(\s-1EV_P\s0))" 4
+.IX Item "ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))"
+This overrides the invoke pending functionality of the loop: Instead of
+invoking all pending watchers when there are any, \f(CW\*(C`ev_run\*(C'\fR will call
+this callback instead. This is useful, for example, when you want to
+invoke the actual watchers inside another context (another thread etc.).
+.Sp
+If you want to reset the callback, use \f(CW\*(C`ev_invoke_pending\*(C'\fR as new
+callback.
+.IP "ev_set_loop_release_cb (loop, void (*release)(\s-1EV_P\s0) throw (), void (*acquire)(\s-1EV_P\s0) throw ())" 4
+.IX Item "ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())"
+Sometimes you want to share the same loop between multiple threads. This
+can be done relatively simply by putting mutex_lock/unlock calls around
+each call to a libev function.
+.Sp
+However, \f(CW\*(C`ev_run\*(C'\fR can run an indefinite time, so it is not feasible
+to wait for it to return. One way around this is to wake up the event
+loop via \f(CW\*(C`ev_break\*(C'\fR and \f(CW\*(C`ev_async_send\*(C'\fR, another way is to set these
+\&\fIrelease\fR and \fIacquire\fR callbacks on the loop.
+.Sp
+When set, then \f(CW\*(C`release\*(C'\fR will be called just before the thread is
+suspended waiting for new events, and \f(CW\*(C`acquire\*(C'\fR is called just
+afterwards.
+.Sp
+Ideally, \f(CW\*(C`release\*(C'\fR will just call your mutex_unlock function, and
+\&\f(CW\*(C`acquire\*(C'\fR will just call the mutex_lock function again.
+.Sp
+While event loop modifications are allowed between invocations of
+\&\f(CW\*(C`release\*(C'\fR and \f(CW\*(C`acquire\*(C'\fR (that's their only purpose after all), no
+modifications done will affect the event loop, i.e. adding watchers will
+have no effect on the set of file descriptors being watched, or the time
+waited. Use an \f(CW\*(C`ev_async\*(C'\fR watcher to wake up \f(CW\*(C`ev_run\*(C'\fR when you want it
+to take note of any changes you made.
+.Sp
+In theory, threads executing \f(CW\*(C`ev_run\*(C'\fR will be async-cancel safe between
+invocations of \f(CW\*(C`release\*(C'\fR and \f(CW\*(C`acquire\*(C'\fR.
+.Sp
+See also the locking example in the \f(CW\*(C`THREADS\*(C'\fR section later in this
+document.
+.IP "ev_set_userdata (loop, void *data)" 4
+.IX Item "ev_set_userdata (loop, void *data)"
+.PD 0
+.IP "void *ev_userdata (loop)" 4
+.IX Item "void *ev_userdata (loop)"
+.PD
+Set and retrieve a single \f(CW\*(C`void *\*(C'\fR associated with a loop. When
+\&\f(CW\*(C`ev_set_userdata\*(C'\fR has never been called, then \f(CW\*(C`ev_userdata\*(C'\fR returns
+\&\f(CW0\fR.
+.Sp
+These two functions can be used to associate arbitrary data with a loop,
+and are intended solely for the \f(CW\*(C`invoke_pending_cb\*(C'\fR, \f(CW\*(C`release\*(C'\fR and
+\&\f(CW\*(C`acquire\*(C'\fR callbacks described above, but of course can be (ab\-)used for
+any other purpose as well.
+.IP "ev_verify (loop)" 4
+.IX Item "ev_verify (loop)"
+This function only does something when \f(CW\*(C`EV_VERIFY\*(C'\fR support has been
+compiled in, which is the default for non-minimal builds. It tries to go
+through all internal structures and checks them for validity. If anything
+is found to be inconsistent, it will print an error message to standard
+error and call \f(CW\*(C`abort ()\*(C'\fR.
+.Sp
+This can be used to catch bugs inside libev itself: under normal
+circumstances, this function will never abort as of course libev keeps its
+data structures consistent.
 .SH "ANATOMY OF A WATCHER"
 .IX Header "ANATOMY OF A WATCHER"
+In the following description, uppercase \f(CW\*(C`TYPE\*(C'\fR in names stands for the
+watcher type, e.g. \f(CW\*(C`ev_TYPE_start\*(C'\fR can mean \f(CW\*(C`ev_timer_start\*(C'\fR for timer
+watchers and \f(CW\*(C`ev_io_start\*(C'\fR for I/O watchers.
+.PP
-A watcher is a structure that you create and register to record your
+A watcher is an opaque structure that you allocate and register to record
-interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to
+your interest in some event. To make a concrete example, imagine you want
-become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that:
+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)
+\&   static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
-\&  {
+\&   {
-\&    ev_io_stop (w);
+\&     ev_io_stop (w);
-\&    ev_unloop (loop, EVUNLOOP_ALL);
+\&     ev_break (loop, EVBREAK_ALL);
-\&  }
+\&   }
 \&
-\&  struct ev_loop *loop = ev_default_loop (0);
+\&   struct ev_loop *loop = ev_default_loop (0);
+\&
-\&  struct ev_io stdin_watcher;
+\&   ev_io stdin_watcher;
+\&
-\&  ev_init (&stdin_watcher, my_cb);
+\&   ev_init (&stdin_watcher, my_cb);
-\&  ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
+\&   ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
-\&  ev_io_start (loop, &stdin_watcher);
+\&   ev_io_start (loop, &stdin_watcher);
+\&
-\&  ev_loop (loop, 0);
+\&   ev_run (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,
+watcher structures (and it is \fIusually\fR a bad idea to do this on the
-although this can sometimes be quite valid).
+stack).
 .PP
+Each watcher has an associated watcher structure (called \f(CW\*(C`struct ev_TYPE\*(C'\fR
+or simply \f(CW\*(C`ev_TYPE\*(C'\fR, as typedefs are provided for all watcher structs).
+.PP
-Each watcher structure must be initialised by a call to \f(CW\*(C`ev_init
+Each watcher structure must be initialised by a call to \f(CW\*(C`ev_init (watcher
-(watcher *, callback)\*(C'\fR, which expects a callback to be provided. This
+*, callback)\*(C'\fR, which expects a callback to be provided. This callback is
-callback gets invoked each time the event occurs (or, in the case of io
+invoked each time the event occurs (or, in the case of I/O watchers, each
-watchers, each time the event loop detects that the file descriptor given
+time the event loop detects that the file descriptor given is readable
-is readable and/or writable).
+and/or writable).
 .PP
-Each watcher type has its own \f(CW\*(C`ev_<type>_set (watcher *, ...)\*(C'\fR macro
+Each watcher type further has its own \f(CW\*(C`ev_TYPE_set (watcher *, ...)\*(C'\fR
-with arguments specific to this watcher type. There is also a macro
+macro to configure it, with arguments specific to the watcher type. There
-to combine initialisation and setting in one call: \f(CW\*(C`ev_<type>_init
+is also a macro to combine initialisation and setting in one call: \f(CW\*(C`ev_TYPE_init (watcher *, callback, ...)\*(C'\fR.
-(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
+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.
+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
+must not touch the values stored in it except when explicitly documented
-reinitialise it or call its \f(CW\*(C`set\*(C'\fR macro.
+otherwise. Most specifically you must never reinitialise it or call its
+\&\f(CW\*(C`ev_TYPE_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
 .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
+.ie n .IP """EV_TIMER""" 4
-.el .IP "\f(CWEV_TIMEOUT\fR" 4
+.el .IP "\f(CWEV_TIMER\fR" 4
-.IX Item "EV_TIMEOUT"
+.IX Item "EV_TIMER"
 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.
 .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
+All \f(CW\*(C`ev_prepare\*(C'\fR watchers are invoked just \fIbefore\fR \f(CW\*(C`ev_run\*(C'\fR starts to
-to gather new events, and all \f(CW\*(C`ev_check\*(C'\fR watchers are invoked just after
+gather new events, and all \f(CW\*(C`ev_check\*(C'\fR watchers are queued (not invoked)
-\&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any
+just after \f(CW\*(C`ev_run\*(C'\fR has gathered them, but before it queues any callbacks
+for any received events. That means \f(CW\*(C`ev_prepare\*(C'\fR watchers are the last
+watchers invoked before the event loop sleeps or polls for new events, and
+\&\f(CW\*(C`ev_check\*(C'\fR watchers will be invoked before any other watchers of the same
+or lower priority within an event loop iteration.
+.Sp
-received events. Callbacks of both watcher types can start and stop as
+Callbacks of both watcher types can start and stop as many watchers as
-many watchers as they want, and all of them will be taken into account
+they want, and all of them will be taken into account (for example, a
-(for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep
+\&\f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep \f(CW\*(C`ev_run\*(C'\fR from
-\&\f(CW\*(C`ev_loop\*(C'\fR from blocking).
+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_CLEANUP""" 4
+.el .IP "\f(CWEV_CLEANUP\fR" 4
+.IX Item "EV_CLEANUP"
+The event loop is about to be destroyed (see \f(CW\*(C`ev_cleanup\*(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_CUSTOM""" 4
+.el .IP "\f(CWEV_CUSTOM\fR" 4
+.IX Item "EV_CUSTOM"
+Not ever sent (or otherwise used) by libev itself, but can be freely used
+by libev users to signal watchers (e.g. via \f(CW\*(C`ev_feed_event\*(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
+An unspecified error has occurred, the watcher has been stopped. This might
 happen because the watcher could not be properly started because libev
 ran out of memory, a file descriptor was found to be closed or any other
+problem. Libev considers these application bugs.
+.Sp
-problem. You best act on it by reporting the problem and somehow coping
+You best act on it by reporting the problem and somehow coping with the
-with the watcher being stopped.
+watcher being stopped. Note that well-written programs should not receive
+an error ever, so when your watcher receives it, this usually indicates a
+bug in your program.
 .Sp
-Libev will usually signal a few \*(L"dummy\*(R" events together with an error,
+Libev will usually signal a few \*(L"dummy\*(R" events together with an error, for
-for example it might indicate that a fd is readable or writable, and if
+example it might indicate that a fd is readable or writable, and if your
-your callbacks is well-written it can just attempt the operation and cope
+callbacks is well-written it can just attempt the operation and cope with
-with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded
+the error from \fBread()\fR or \fBwrite()\fR. This will not work in multi-threaded
-programs, though, so beware.
+programs, though, as the fd could already be closed and reused for another
+thing, so beware.
-.Sh "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0"
+.SS "\s-1GENERIC WATCHER FUNCTIONS\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
 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,
+The callback is always of type \f(CW\*(C`void (*)(struct ev_loop *loop, ev_TYPE *watcher,
 int revents)\*(C'\fR.
+.Sp
+Example: Initialise an \f(CW\*(C`ev_io\*(C'\fR watcher in two steps.
+.Sp
+.Vb 3
+\&   ev_io w;
+\&   ev_init (&w, my_cb);
+\&   ev_io_set (&w, STDIN_FILENO, EV_READ);
+.Ve
-.ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4
+.ie n .IP """ev_TYPE_set"" (ev_TYPE *watcher, [args])" 4
-.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4
+.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *watcher, [args])" 4
-.IX Item "ev_TYPE_set (ev_TYPE *, [args])"
+.IX Item "ev_TYPE_set (ev_TYPE *watcher, [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.
+.Sp
+See \f(CW\*(C`ev_init\*(C'\fR, above, for an example.
 .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
+This convenience 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
+calls into a single call. This is the most convenient method to initialise
 a watcher. The same limitations apply, of course.
+.Sp
+Example: Initialise and set an \f(CW\*(C`ev_io\*(C'\fR watcher in one step.
+.Sp
+.Vb 1
+\&   ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
+.Ve
-.ie n .IP """ev_TYPE_start"" (loop *, ev_TYPE *watcher)" 4
+.ie n .IP """ev_TYPE_start"" (loop, ev_TYPE *watcher)" 4
-.el .IP "\f(CWev_TYPE_start\fR (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)"
+.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.
+.Sp
+Example: Start the \f(CW\*(C`ev_io\*(C'\fR watcher that is being abused as example in this
+whole section.
+.Sp
+.Vb 1
+\&   ev_io_start (EV_DEFAULT_UC, &w);
+.Ve
-.ie n .IP """ev_TYPE_stop"" (loop *, ev_TYPE *watcher)" 4
+.ie n .IP """ev_TYPE_stop"" (loop, ev_TYPE *watcher)" 4
-.el .IP "\f(CWev_TYPE_stop\fR (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)"
+.IX Item "ev_TYPE_stop (loop, ev_TYPE *watcher)"
-Stops the given watcher again (if active) and clears the pending
+Stops the given watcher if active, and clears the pending status (whether
+the watcher was active or not).
+.Sp
-status. It is possible that stopped watchers are pending (for example,
+It is possible that stopped watchers are pending \- for example,
-non-repeating timers are being stopped when they become pending), but
+non-repeating timers are being stopped when they become pending \- but
-\&\f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor pending. If
+calling \f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor
-you want to free or reuse the memory used by the watcher it is therefore a
+pending. If you want to free or reuse the memory used by the watcher it is
-good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function.
+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.
+it unless documented otherwise.
 .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
 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
+.IP "ev_set_cb (ev_TYPE *watcher, callback)" 4
-.IX Item "ev_cb_set (ev_TYPE *watcher, callback)"
+.IX Item "ev_set_cb (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
+.IP "ev_set_priority (ev_TYPE *watcher, int priority)" 4
-.IX Item "ev_set_priority (ev_TYPE *watcher, priority)"
+.IX Item "ev_set_priority (ev_TYPE *watcher, int 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
+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 clamped to the valid range.
+.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
+See \*(L"\s-1WATCHER PRIORITY MODELS\*(R"\s0, below, for a more thorough treatment of
-fine, as long as you do not mind that the priority value you query might
+priorities.
-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.
+can deal with that fact, as both are simply passed through to the
+callback.
 .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
+If the watcher is pending, this function clears its pending status and
-and returns its \f(CW\*(C`revents\*(C'\fR bitset (as if its callback was invoked). If the
+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"
+.Sp
-.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER"
+Sometimes it can be useful to \*(L"poll\*(R" a watcher instead of waiting for its
-Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change
+callback to be invoked, which can be accomplished with this function.
-and read at any time, libev will completely ignore it. This can be used
+.IP "ev_feed_event (loop, ev_TYPE *watcher, int revents)" 4
-to associate arbitrary data with your watcher. If you need more data and
+.IX Item "ev_feed_event (loop, ev_TYPE *watcher, int revents)"
-don't want to allocate memory and store a pointer to it in that data
+Feeds the given event set into the event loop, as if the specified event
-member, you can also \*(L"subclass\*(R" the watcher type and provide your own
+had happened for the specified watcher (which must be a pointer to an
-data:
+initialised but not necessarily started event watcher). Obviously you must
+not free the watcher as long as it has pending events.
+.Sp
+Stopping the watcher, letting libev invoke it, or calling
+\&\f(CW\*(C`ev_clear_pending\*(C'\fR will clear the pending event, even if the watcher was
+not started in the first place.
+.Sp
+See also \f(CW\*(C`ev_feed_fd_event\*(C'\fR and \f(CW\*(C`ev_feed_signal_event\*(C'\fR for related
+functions that do not need a watcher.
 .PP
+See also the \*(L"\s-1ASSOCIATING CUSTOM DATA WITH A WATCHER\*(R"\s0 and \*(L"\s-1BUILDING YOUR
+OWN COMPOSITE WATCHERS\*(R"\s0 idioms.
+.SS "\s-1WATCHER STATES\s0"
+.IX Subsection "WATCHER STATES"
+There are various watcher states mentioned throughout this manual \-
+active, pending and so on. In this section these states and the rules to
+transition between them will be described in more detail \- and while these
+rules might look complicated, they usually do \*(L"the right thing\*(R".
+.IP "initialised" 4
+.IX Item "initialised"
+Before a watcher can be registered with the event loop it has to be
+initialised. This can be done with a call to \f(CW\*(C`ev_TYPE_init\*(C'\fR, or calls to
+\&\f(CW\*(C`ev_init\*(C'\fR followed by the watcher-specific \f(CW\*(C`ev_TYPE_set\*(C'\fR function.
+.Sp
+In this state it is simply some block of memory that is suitable for
+use in an event loop. It can be moved around, freed, reused etc. at
+will \- as long as you either keep the memory contents intact, or call
+\&\f(CW\*(C`ev_TYPE_init\*(C'\fR again.
+.IP "started/running/active" 4
+.IX Item "started/running/active"
+Once a watcher has been started with a call to \f(CW\*(C`ev_TYPE_start\*(C'\fR it becomes
+property of the event loop, and is actively waiting for events. While in
+this state it cannot be accessed (except in a few documented ways), moved,
+freed or anything else \- the only legal thing is to keep a pointer to it,
+and call libev functions on it that are documented to work on active watchers.
+.IP "pending" 4
+.IX Item "pending"
+If a watcher is active and libev determines that an event it is interested
+in has occurred (such as a timer expiring), it will become pending. It will
+stay in this pending state until either it is stopped or its callback is
+about to be invoked, so it is not normally pending inside the watcher
+callback.
+.Sp
+The watcher might or might not be active while it is pending (for example,
+an expired non-repeating timer can be pending but no longer active). If it
+is stopped, it can be freely accessed (e.g. by calling \f(CW\*(C`ev_TYPE_set\*(C'\fR),
+but it is still property of the event loop at this time, so cannot be
+moved, freed or reused. And if it is active the rules described in the
+previous item still apply.
+.Sp
+It is also possible to feed an event on a watcher that is not active (e.g.
+via \f(CW\*(C`ev_feed_event\*(C'\fR), in which case it becomes pending without being
+active.
+.IP "stopped" 4
+.IX Item "stopped"
+A watcher can be stopped implicitly by libev (in which case it might still
+be pending), or explicitly by calling its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function. The
+latter will clear any pending state the watcher might be in, regardless
+of whether it was active or not, so stopping a watcher explicitly before
+freeing it is often a good idea.
+.Sp
+While stopped (and not pending) the watcher is essentially in the
+initialised state, that is, it can be reused, moved, modified in any way
+you wish (but when you trash the memory block, you need to \f(CW\*(C`ev_TYPE_init\*(C'\fR
+it again).
+.SS "\s-1WATCHER PRIORITY MODELS\s0"
+.IX Subsection "WATCHER PRIORITY MODELS"
+Many event loops support \fIwatcher priorities\fR, which are usually small
+integers that influence the ordering of event callback invocation
+between watchers in some way, all else being equal.
+.PP
+In libev, watcher priorities can be set using \f(CW\*(C`ev_set_priority\*(C'\fR. See its
+description for the more technical details such as the actual priority
+range.
+.PP
+There are two common ways how these these priorities are being interpreted
+by event loops:
+.PP
+In the more common lock-out model, higher priorities \*(L"lock out\*(R" invocation
+of lower priority watchers, which means as long as higher priority
+watchers receive events, lower priority watchers are not being invoked.
+.PP
+The less common only-for-ordering model uses priorities solely to order
+callback invocation within a single event loop iteration: Higher priority
+watchers are invoked before lower priority ones, but they all get invoked
+before polling for new events.
+.PP
+Libev uses the second (only-for-ordering) model for all its watchers
+except for idle watchers (which use the lock-out model).
+.PP
+The rationale behind this is that implementing the lock-out model for
+watchers is not well supported by most kernel interfaces, and most event
+libraries will just poll for the same events again and again as long as
+their callbacks have not been executed, which is very inefficient in the
+common case of one high-priority watcher locking out a mass of lower
+priority ones.
+.PP
+Static (ordering) priorities are most useful when you have two or more
+watchers handling the same resource: a typical usage example is having an
+\&\f(CW\*(C`ev_io\*(C'\fR watcher to receive data, and an associated \f(CW\*(C`ev_timer\*(C'\fR to handle
+timeouts. Under load, data might be received while the program handles
+other jobs, but since timers normally get invoked first, the timeout
+handler will be executed before checking for data. In that case, giving
+the timer a lower priority than the I/O watcher ensures that I/O will be
+handled first even under adverse conditions (which is usually, but not
+always, what you want).
+.PP
+Since idle watchers use the \*(L"lock-out\*(R" model, meaning that idle watchers
+will only be executed when no same or higher priority watchers have
+received events, they can be used to implement the \*(L"lock-out\*(R" model when
+required.
+.PP
+For example, to emulate how many other event libraries handle priorities,
+you can associate an \f(CW\*(C`ev_idle\*(C'\fR watcher to each such watcher, and in
+the normal watcher callback, you just start the idle watcher. The real
+processing is done in the idle watcher callback. This causes libev to
+continuously poll and process kernel event data for the watcher, but when
+the lock-out case is known to be rare (which in turn is rare :), this is
+workable.
+.PP
+Usually, however, the lock-out model implemented that way will perform
+miserably under the type of load it was designed to handle. In that case,
+it might be preferable to stop the real watcher before starting the
+idle watcher, so the kernel will not have to process the event in case
+the actual processing will be delayed for considerable time.
+.PP
+Here is an example of an I/O watcher that should run at a strictly lower
+priority than the default, and which should only process data when no
+other events are pending:
+.PP
-.Vb 7
+.Vb 2
-\&  struct my_io
+\&   ev_idle idle; // actual processing watcher
-\&  {
+\&   ev_io io;     // actual event watcher
-\&    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
+\&   static void
-\&  t1_cb (EV_P_ struct ev_timer *w, int revents)
+\&   io_cb (EV_P_ ev_io *w, int revents)
-\&  {
+\&   {
-\&    struct my_biggy big = (struct my_biggy *
+\&     // stop the I/O watcher, we received the event, but
-\&      (((char *)w) \- offsetof (struct my_biggy, t1));
+\&     // are not yet ready to handle it.
+\&     ev_io_stop (EV_A_ w);
+\&
+\&     // start the idle watcher to handle the actual event.
+\&     // it will not be executed as long as other watchers
+\&     // with the default priority are receiving events.
+\&     ev_idle_start (EV_A_ &idle);
-\&  }
+\&   }
 \&
-\&  static void
+\&   static void
-\&  t2_cb (EV_P_ struct ev_timer *w, int revents)
+\&   idle_cb (EV_P_ ev_idle *w, int revents)
-\&  {
+\&   {
-\&    struct my_biggy big = (struct my_biggy *
+\&     // actual processing
-\&      (((char *)w) \- offsetof (struct my_biggy, t2));
+\&     read (STDIN_FILENO, ...);
+\&
+\&     // have to start the I/O watcher again, as
+\&     // we have handled the event
+\&     ev_io_start (EV_P_ &io);
-\&  }
+\&   }
+\&
+\&   // initialisation
+\&   ev_idle_init (&idle, idle_cb);
+\&   ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
+\&   ev_io_start (EV_DEFAULT_ &io);
 .Ve
+.PP
+In the \*(L"real\*(R" world, it might also be beneficial to start a timer, so that
+low-priority connections can not be locked out forever under load. This
+enables your program to keep a lower latency for important connections
+during short periods of high load, while not completely locking out less
+important ones.
 .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,
+Most members are additionally marked with either \fI[read\-only]\fR, meaning
-while the watcher is active, you can look at the member and expect some
+that, while the watcher is active, you can look at the member and expect
-sensible content, but you must not modify it (you can modify it while the
+some sensible content, but you must not modify it (you can modify it while
-watcher is stopped to your hearts content), or \fI[read\-write]\fR, which
+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
+means you can expect it to have some sensible content while the watcher is
-is active, but you can also modify it. Modifying it may not do something
+active, but you can also modify it (within the same thread as the event
+loop, i.e. without creating data races). 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.
+.PP
+In any case, the documentation for each member will explain what the
+effects are, and if there are any additional access restrictions.
-.ie n .Sh """ev_io"" \- is this file descriptor readable or writable?"
+.ie n .SS """ev_io"" \- is this file descriptor readable or writable?"
-.el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable?"
+.el .SS "\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
 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
+receive \*(L"spurious\*(R" readiness 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
+because there is no data. It is very easy to get into this situation even
-lot of those (for example solaris ports), it is very easy to get into
+with a relatively standard program structure. Thus it is best to always
-this situation even with a relatively standard program structure. Thus
+use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning \f(CW\*(C`EAGAIN\*(C'\fR is far
-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.
+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
+If you cannot run the fd in non-blocking mode (for example you should
-play around with an Xlib connection), then you have to seperately re-test
+not play around with an Xlib connection), then you have to separately
-whether a file descriptor is really ready with a known-to-be good interface
+re-test whether a file descriptor is really ready with a known-to-be good
-such as poll (fortunately in our Xlib example, Xlib already does this on
+interface such as poll (fortunately in the case of Xlib, it already does
-its own, so its quite safe to use).
+this on its own, so its quite safe to use). Some people additionally
+use \f(CW\*(C`SIGALRM\*(C'\fR and an interval timer, just to be sure you won't block
+indefinitely.
+.PP
+But really, best use non-blocking mode.
 .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
+Some backends (e.g. kqueue, epoll, linuxaio) need to be told about closing
-descriptor (either by calling \f(CW\*(C`close\*(C'\fR explicitly or by any other means,
+a file descriptor (either due to calling \f(CW\*(C`close\*(C'\fR explicitly or any other
-such as \f(CW\*(C`dup\*(C'\fR). The reason is that you register interest in some file
+means, such as \f(CW\*(C`dup2\*(C'\fR). The reason is that you register interest in some
-descriptor, but when it goes away, the operating system will silently drop
+file descriptor, but when it goes away, the operating system will silently
-this interest. If another file descriptor with the same number then is
+drop this interest. If another file descriptor with the same number then
-registered with libev, there is no efficient way to see that this is, in
+is registered with libev, there is no efficient way to see that this is,
-fact, a different file descriptor.
+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
 .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 files\fR
+.IX Subsection "The special problem of files"
+.PP
+Many people try to use \f(CW\*(C`select\*(C'\fR (or libev) on file descriptors
+representing files, and expect it to become ready when their program
+doesn't block on disk accesses (which can take a long time on their own).
+.PP
+However, this cannot ever work in the \*(L"expected\*(R" way \- you get a readiness
+notification as soon as the kernel knows whether and how much data is
+there, and in the case of open files, that's always the case, so you
+always get a readiness notification instantly, and your read (or possibly
+write) will still block on the disk I/O.
+.PP
+Another way to view it is that in the case of sockets, pipes, character
+devices and so on, there is another party (the sender) that delivers data
+on its own, but in the case of files, there is no such thing: the disk
+will not send data on its own, simply because it doesn't know what you
+wish to read \- you would first have to request some data.
+.PP
+Since files are typically not-so-well supported by advanced notification
+mechanism, libev tries hard to emulate \s-1POSIX\s0 behaviour with respect
+to files, even though you should not use it. The reason for this is
+convenience: sometimes you want to watch \s-1STDIN\s0 or \s-1STDOUT,\s0 which is
+usually a tty, often a pipe, but also sometimes files or special devices
+(for example, \f(CW\*(C`epoll\*(C'\fR on Linux works with \fI/dev/random\fR but not with
+\&\fI/dev/urandom\fR), and even though the file might better be served with
+asynchronous I/O instead of with non-blocking I/O, it is still useful when
+it \*(L"just works\*(R" instead of freezing.
+.PP
+So avoid file descriptors pointing to files when you know it (e.g. use
+libeio), but use them when it is convenient, e.g. for \s-1STDIN/STDOUT,\s0 or
+when you rarely read from a file instead of from a socket, and want to
+reuse the same code path.
+.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
+Some backends (epoll, kqueue, linuxaio, iouring) do not support \f(CW\*(C`fork ()\*(C'\fR
-useless behaviour. Libev fully supports fork, but needs to be told about
+at all or exhibit useless behaviour. Libev fully supports fork, but needs
-it in the child.
+to be told about it in the child if you want to continue to use it in the
+child.
 .PP
-To support fork in your programs, you either have to call
+To support fork in your child processes, you have to call \f(CW\*(C`ev_loop_fork
-\&\f(CW\*(C`ev_default_fork ()\*(C'\fR or \f(CW\*(C`ev_loop_fork ()\*(C'\fR after a fork in the child,
+()\*(C'\fR after a fork in the child, enable \f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR, or resort to
-enable \f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR, or resort to \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or
+\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
-\&\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 \f(CW\*(C`SIGPIPE\*(C'\fR:
+when writing to a pipe whose other end has been closed, your program gets
+sent 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
+\fIThe special problem of \f(BIaccept()\fIing when you can't\fR
+.IX Subsection "The special problem of accept()ing when you can't"
+.PP
+Many implementations of the \s-1POSIX\s0 \f(CW\*(C`accept\*(C'\fR function (for example,
+found in post\-2004 Linux) have the peculiar behaviour of not removing a
+connection from the pending queue in all error cases.
+.PP
+For example, larger servers often run out of file descriptors (because
+of resource limits), causing \f(CW\*(C`accept\*(C'\fR to fail with \f(CW\*(C`ENFILE\*(C'\fR but not
+rejecting the connection, leading to libev signalling readiness on
+the next iteration again (the connection still exists after all), and
+typically causing the program to loop at 100% \s-1CPU\s0 usage.
+.PP
+Unfortunately, the set of errors that cause this issue differs between
+operating systems, there is usually little the app can do to remedy the
+situation, and no known thread-safe method of removing the connection to
+cope with overload is known (to me).
+.PP
+One of the easiest ways to handle this situation is to just ignore it
+\&\- when the program encounters an overload, it will just loop until the
+situation is over. While this is a form of busy waiting, no \s-1OS\s0 offers an
+event-based way to handle this situation, so it's the best one can do.
+.PP
+A better way to handle the situation is to log any errors other than
+\&\f(CW\*(C`EAGAIN\*(C'\fR and \f(CW\*(C`EWOULDBLOCK\*(C'\fR, making sure not to flood the log with such
+messages, and continue as usual, which at least gives the user an idea of
+what could be wrong (\*(L"raise the ulimit!\*(R"). For extra points one could stop
+the \f(CW\*(C`ev_io\*(C'\fR watcher on the listening fd \*(L"for a while\*(R", which reduces \s-1CPU\s0
+usage.
+.PP
+If your program is single-threaded, then you could also keep a dummy file
+descriptor for overload situations (e.g. by opening \fI/dev/null\fR), and
+when you run into \f(CW\*(C`ENFILE\*(C'\fR or \f(CW\*(C`EMFILE\*(C'\fR, close it, run \f(CW\*(C`accept\*(C'\fR,
+close that fd, and create a new dummy fd. This will gracefully refuse
+clients under typical overload conditions.
+.PP
+The last way to handle it is to simply log the error and \f(CW\*(C`exit\*(C'\fR, as
+is often done with \f(CW\*(C`malloc\*(C'\fR failures, but this results in an easy
+opportunity for a DoS attack.
 .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
+receive events for and \f(CW\*(C`events\*(C'\fR is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR, both
-\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR to receive the given events.
+\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR or \f(CW0\fR, to express the desire to receive the given
+events.
+.Sp
+Note that setting the \f(CW\*(C`events\*(C'\fR to \f(CW0\fR and starting the watcher is
+supported, but not specially optimized \- if your program sometimes happens
+to generate this combination this is fine, but if it is easy to avoid
+starting an io watcher watching for no events you should do so.
+.IP "ev_io_modify (ev_io *, int events)" 4
+.IX Item "ev_io_modify (ev_io *, int events)"
+Similar to \f(CW\*(C`ev_io_set\*(C'\fR, but only changes the requested events. Using this
+might be faster with some backends, as libev can assume that the \f(CW\*(C`fd\*(C'\fR
+still refers to the same underlying file description, something it cannot
+do when using \f(CW\*(C`ev_io_set\*(C'\fR.
-.IP "int fd [read\-only]" 4
+.IP "int fd [no\-modify]" 4
-.IX Item "int fd [read-only]"
+.IX Item "int fd [no-modify]"
-The file descriptor being watched.
+The file descriptor being watched. While it can be read at any time, you
+must not modify this member even when the watcher is stopped \- always use
+\&\f(CW\*(C`ev_io_set\*(C'\fR for that.
-.IP "int events [read\-only]" 4
+.IP "int events [no\-modify]" 4
-.IX Item "int events [read-only]"
+.IX Item "int events [no-modify]"
-The events being watched.
+The set of events the fd is being watched for, among other flags. Remember
+that this is a bit set \- to test for \f(CW\*(C`EV_READ\*(C'\fR, use \f(CW\*(C`w\->events &
+EV_READ\*(C'\fR, and similarly for \f(CW\*(C`EV_WRITE\*(C'\fR.
+.Sp
+As with \f(CW\*(C`fd\*(C'\fR, you must not modify this member even when the watcher is
+stopped, always use \f(CW\*(C`ev_io_set\*(C'\fR or \f(CW\*(C`ev_io_modify\*(C'\fR for that.
 .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
+\&   static void
-\&  stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
+\&   stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
-\&  {
+\&   {
-\&     ev_io_stop (loop, w);
+\&      ev_io_stop (loop, w);
-\&    .. read from stdin here (or from w\->fd) and haqndle any I/O errors
+\&     .. read from stdin here (or from w\->fd) and handle any I/O errors
-\&  }
+\&   }
 \&
-\&  ...
+\&   ...
-\&  struct ev_loop *loop = ev_default_init (0);
+\&   struct ev_loop *loop = ev_default_init (0);
-\&  struct ev_io stdin_readable;
+\&   ev_io stdin_readable;
-\&  ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
+\&   ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
-\&  ev_io_start (loop, &stdin_readable);
+\&   ev_io_start (loop, &stdin_readable);
-\&  ev_loop (loop, 0);
+\&   ev_run (loop, 0);
 .Ve
-.ie n .Sh """ev_timer"" \- relative and optionally repeating timeouts"
+.ie n .SS """ev_timer"" \- relative and optionally repeating timeouts"
-.el .Sh "\f(CWev_timer\fP \- relative and optionally repeating timeouts"
+.el .SS "\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
+times out after an hour and you reset your system clock to January last
-time, it will still time out after (roughly) and hour. \*(L"Roughly\*(R" because
+year, it will still time out after (roughly) one 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 callback is guaranteed to be invoked only \fIafter\fR its timeout has
+passed (not \fIat\fR, so on systems with very low-resolution clocks this
+might introduce a small delay, see \*(L"the special problem of being too
+early\*(R", below). If multiple timers become ready during the same loop
+iteration then the ones with earlier time-out values are invoked before
+ones of the same priority with later time-out values (but this is no
+longer true when a callback calls \f(CW\*(C`ev_run\*(C'\fR recursively).
+.PP
+\fIBe smart about timeouts\fR
+.IX Subsection "Be smart about timeouts"
+.PP
+Many real-world problems involve some kind of timeout, usually for error
+recovery. A typical example is an \s-1HTTP\s0 request \- if the other side hangs,
+you want to raise some error after a while.
+.PP
+What follows are some ways to handle this problem, from obvious and
+inefficient to smart and efficient.
+.PP
+In the following, a 60 second activity timeout is assumed \- a timeout that
+gets reset to 60 seconds each time there is activity (e.g. each time some
+data or other life sign was received).
+.IP "1. Use a timer and stop, reinitialise and start it on activity." 4
+.IX Item "1. Use a timer and stop, reinitialise and start it on activity."
+This is the most obvious, but not the most simple way: In the beginning,
+start the watcher:
+.Sp
+.Vb 2
+\&   ev_timer_init (timer, callback, 60., 0.);
+\&   ev_timer_start (loop, timer);
+.Ve
+.Sp
+Then, each time there is some activity, \f(CW\*(C`ev_timer_stop\*(C'\fR it, initialise it
+and start it again:
+.Sp
+.Vb 3
+\&   ev_timer_stop (loop, timer);
+\&   ev_timer_set (timer, 60., 0.);
+\&   ev_timer_start (loop, timer);
+.Ve
+.Sp
+This is relatively simple to implement, but means that each time there is
+some activity, libev will first have to remove the timer from its internal
+data structure and then add it again. Libev tries to be fast, but it's
+still not a constant-time operation.
+.ie n .IP "2. Use a timer and re-start it with ""ev_timer_again"" inactivity." 4
+.el .IP "2. Use a timer and re-start it with \f(CWev_timer_again\fR inactivity." 4
+.IX Item "2. Use a timer and re-start it with ev_timer_again inactivity."
+This is the easiest way, and involves using \f(CW\*(C`ev_timer_again\*(C'\fR instead of
+\&\f(CW\*(C`ev_timer_start\*(C'\fR.
+.Sp
+To implement this, 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 at start and each time you
+successfully read or write some data. If you go into an idle state where
+you do not expect data to travel on the socket, you can \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 both the \f(CW\*(C`ev_timer_start\*(C'\fR function and the
+\&\f(CW\*(C`after\*(C'\fR argument to \f(CW\*(C`ev_timer_set\*(C'\fR, and only ever use the \f(CW\*(C`repeat\*(C'\fR
+member and \f(CW\*(C`ev_timer_again\*(C'\fR.
+.Sp
+At start:
+.Sp
+.Vb 3
+\&   ev_init (timer, callback);
+\&   timer\->repeat = 60.;
+\&   ev_timer_again (loop, timer);
+.Ve
+.Sp
+Each time there is some activity:
+.Sp
+.Vb 1
+\&   ev_timer_again (loop, timer);
+.Ve
+.Sp
+It is even possible to change the time-out on the fly, regardless of
+whether the watcher is active or not:
+.Sp
+.Vb 2
+\&   timer\->repeat = 30.;
+\&   ev_timer_again (loop, timer);
+.Ve
+.Sp
+This is slightly more efficient then stopping/starting the timer each time
+you want to modify its timeout value, as libev does not have to completely
+remove and re-insert the timer from/into its internal data structure.
+.Sp
+It is, however, even simpler than the \*(L"obvious\*(R" way to do it.
+.IP "3. Let the timer time out, but then re-arm it as required." 4
+.IX Item "3. Let the timer time out, but then re-arm it as required."
+This method is more tricky, but usually most efficient: Most timeouts are
+relatively long compared to the intervals between other activity \- in
+our example, within 60 seconds, there are usually many I/O events with
+associated activity resets.
+.Sp
+In this case, it would be more efficient to leave the \f(CW\*(C`ev_timer\*(C'\fR alone,
+but remember the time of last activity, and check for a real timeout only
+within the callback:
+.Sp
+.Vb 3
+\&   ev_tstamp timeout = 60.;
+\&   ev_tstamp last_activity; // time of last activity
+\&   ev_timer timer;
+\&
+\&   static void
+\&   callback (EV_P_ ev_timer *w, int revents)
+\&   {
+\&     // calculate when the timeout would happen
+\&     ev_tstamp after = last_activity \- ev_now (EV_A) + timeout;
+\&
+\&     // if negative, it means we the timeout already occurred
+\&     if (after < 0.)
+\&       {
+\&         // timeout occurred, take action
+\&       }
+\&     else
+\&       {
+\&         // callback was invoked, but there was some recent
+\&         // activity. simply restart the timer to time out
+\&         // after "after" seconds, which is the earliest time
+\&         // the timeout can occur.
+\&         ev_timer_set (w, after, 0.);
+\&         ev_timer_start (EV_A_ w);
+\&       }
+\&   }
+.Ve
+.Sp
+To summarise the callback: first calculate in how many seconds the
+timeout will occur (by calculating the absolute time when it would occur,
+\&\f(CW\*(C`last_activity + timeout\*(C'\fR, and subtracting the current time, \f(CW\*(C`ev_now
+(EV_A)\*(C'\fR from that).
+.Sp
+If this value is negative, then we are already past the timeout, i.e. we
+timed out, and need to do whatever is needed in this case.
+.Sp
+Otherwise, we now the earliest time at which the timeout would trigger,
+and simply start the timer with this timeout value.
+.Sp
+In other words, each time the callback is invoked it will check whether
+the timeout occurred. If not, it will simply reschedule itself to check
+again at the earliest time it could time out. Rinse. Repeat.
+.Sp
+This scheme causes more callback invocations (about one every 60 seconds
+minus half the average time between activity), but virtually no calls to
+libev to change the timeout.
+.Sp
+To start the machinery, simply initialise the watcher and set
+\&\f(CW\*(C`last_activity\*(C'\fR to the current time (meaning there was some activity just
+now), then call the callback, which will \*(L"do the right thing\*(R" and start
+the timer:
+.Sp
+.Vb 3
+\&   last_activity = ev_now (EV_A);
+\&   ev_init (&timer, callback);
+\&   callback (EV_A_ &timer, 0);
+.Ve
+.Sp
+When there is some activity, simply store the current time in
+\&\f(CW\*(C`last_activity\*(C'\fR, no libev calls at all:
+.Sp
+.Vb 2
+\&   if (activity detected)
+\&     last_activity = ev_now (EV_A);
+.Ve
+.Sp
+When your timeout value changes, then the timeout can be changed by simply
+providing a new value, stopping the timer and calling the callback, which
+will again do the right thing (for example, time out immediately :).
+.Sp
+.Vb 3
+\&   timeout = new_value;
+\&   ev_timer_stop (EV_A_ &timer);
+\&   callback (EV_A_ &timer, 0);
+.Ve
+.Sp
+This technique is slightly more complex, but in most cases where the
+time-out is unlikely to be triggered, much more efficient.
+.IP "4. Wee, just use a double-linked list for your timeouts." 4
+.IX Item "4. Wee, just use a double-linked list for your timeouts."
+If there is not one request, but many thousands (millions...), all
+employing some kind of timeout with the same timeout value, then one can
+do even better:
+.Sp
+When starting the timeout, calculate the timeout value and put the timeout
+at the \fIend\fR of the list.
+.Sp
+Then use an \f(CW\*(C`ev_timer\*(C'\fR to fire when the timeout at the \fIbeginning\fR of
+the list is expected to fire (for example, using the technique #3).
+.Sp
+When there is some activity, remove the timer from the list, recalculate
+the timeout, append it to the end of the list again, and make sure to
+update the \f(CW\*(C`ev_timer\*(C'\fR if it was taken from the beginning of the list.
+.Sp
+This way, one can manage an unlimited number of timeouts in O(1) time for
+starting, stopping and updating the timers, at the expense of a major
+complication, and having to use a constant timeout. The constant timeout
+ensures that the list stays sorted.
+.PP
+So which method the best?
+.PP
+Method #2 is a simple no-brain-required solution that is adequate in most
+situations. Method #3 requires a bit more thinking, but handles many cases
+better, and isn't very complicated either. In most case, choosing either
+one is fine, with #3 being better in typical situations.
+.PP
+Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
+rather complicated, but extremely efficient, something that really pays
+off after the first million or so of active timers, i.e. it's usually
+overkill :)
+.PP
+\fIThe special problem of being too early\fR
+.IX Subsection "The special problem of being too early"
+.PP
+If you ask a timer to call your callback after three seconds, then
+you expect it to be invoked after three seconds \- but of course, this
+cannot be guaranteed to infinite precision. Less obviously, it cannot be
+guaranteed to any precision by libev \- imagine somebody suspending the
+process with a \s-1STOP\s0 signal for a few hours for example.
+.PP
+So, libev tries to invoke your callback as soon as possible \fIafter\fR the
+delay has occurred, but cannot guarantee this.
+.PP
+A less obvious failure mode is calling your callback too early: many event
+loops compare timestamps with a \*(L"elapsed delay >= requested delay\*(R", but
+this can cause your callback to be invoked much earlier than you would
+expect.
+.PP
+To see why, imagine a system with a clock that only offers full second
+resolution (think windows if you can't come up with a broken enough \s-1OS\s0
+yourself). If you schedule a one-second timer at the time 500.9, then the
+event loop will schedule your timeout to elapse at a system time of 500
+(500.9 truncated to the resolution) + 1, or 501.
+.PP
+If an event library looks at the timeout 0.1s later, it will see \*(L"501 >=
+501\*(R" and invoke the callback 0.1s after it was started, even though a
+one-second delay was requested \- this is being \*(L"too early\*(R", despite best
+intentions.
+.PP
+This is the reason why libev will never invoke the callback if the elapsed
+delay equals the requested delay, but only when the elapsed delay is
+larger than the requested delay. In the example above, libev would only invoke
+the callback at system time 502, or 1.1s after the timer was started.
+.PP
+So, while libev cannot guarantee that your callback will be invoked
+exactly when requested, it \fIcan\fR and \fIdoes\fR guarantee that the requested
+delay has actually elapsed, or in other words, it always errs on the \*(L"too
+late\*(R" side of things.
+.PP
+\fIThe special problem of time updates\fR
+.IX Subsection "The special problem of time updates"
+.PP
+Establishing the current time is a costly operation (it usually takes
+at least one system call): \s-1EV\s0 therefore updates its idea of the current
+time only before and after \f(CW\*(C`ev_run\*(C'\fR collects new events, which causes a
+growing difference between \f(CW\*(C`ev_now ()\*(C'\fR and \f(CW\*(C`ev_time ()\*(C'\fR when handling
+lots of events in one iteration.
 .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
+you suspect event processing to be delayed and you \fIneed\fR to base the
-on the current time, use something like this to adjust for this:
+timeout on the current time, use something like the following to adjust
+for it:
 .PP
 .Vb 1
-\&   ev_timer_set (&timer, after + ev_now () \- ev_time (), 0.);
+\&   ev_timer_set (&timer, after + (ev_time () \- ev_now ()), 0.);
 .Ve
 .PP
-The callback is guarenteed to be invoked only when its timeout has passed,
+If the event loop is suspended for a long time, you can also force an
-but if multiple timers become ready during the same loop iteration then
+update of the time returned by \f(CW\*(C`ev_now ()\*(C'\fR by calling \f(CW\*(C`ev_now_update
-order of execution is undefined.
+()\*(C'\fR, although that will push the event time of all outstanding events
+further into the future.
+.PP
+\fIThe special problem of unsynchronised clocks\fR
+.IX Subsection "The special problem of unsynchronised clocks"
+.PP
+Modern systems have a variety of clocks \- libev itself uses the normal
+\&\*(L"wall clock\*(R" clock and, if available, the monotonic clock (to avoid time
+jumps).
+.PP
+Neither of these clocks is synchronised with each other or any other clock
+on the system, so \f(CW\*(C`ev_time ()\*(C'\fR might return a considerably different time
+than \f(CW\*(C`gettimeofday ()\*(C'\fR or \f(CW\*(C`time ()\*(C'\fR. On a GNU/Linux system, for example,
+a call to \f(CW\*(C`gettimeofday\*(C'\fR might return a second count that is one higher
+than a directly following call to \f(CW\*(C`time\*(C'\fR.
+.PP
+The moral of this is to only compare libev-related timestamps with
+\&\f(CW\*(C`ev_time ()\*(C'\fR and \f(CW\*(C`ev_now ()\*(C'\fR, at least if you want better precision than
+a second or so.
+.PP
+One more problem arises due to this lack of synchronisation: if libev uses
+the system monotonic clock and you compare timestamps from \f(CW\*(C`ev_time\*(C'\fR
+or \f(CW\*(C`ev_now\*(C'\fR from when you started your timer and when your callback is
+invoked, you will find that sometimes the callback is a bit \*(L"early\*(R".
+.PP
+This is because \f(CW\*(C`ev_timer\*(C'\fRs work in real time, not wall clock time, so
+libev makes sure your callback is not invoked before the delay happened,
+\&\fImeasured according to the real time\fR, not the system clock.
+.PP
+If your timeouts are based on a physical timescale (e.g. \*(L"time out this
+connection after 100 seconds\*(R") then this shouldn't bother you as it is
+exactly the right behaviour.
+.PP
+If you want to compare wall clock/system timestamps to your timers, then
+you need to use \f(CW\*(C`ev_periodic\*(C'\fRs, as these are based on the wall clock
+time, where your comparisons will always generate correct results.
+.PP
+\fIThe special problems of suspended animation\fR
+.IX Subsection "The special problems of suspended animation"
+.PP
+When you leave the server world it is quite customary to hit machines that
+can suspend/hibernate \- what happens to the clocks during such a suspend?
+.PP
+Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
+all processes, while the clocks (\f(CW\*(C`times\*(C'\fR, \f(CW\*(C`CLOCK_MONOTONIC\*(C'\fR) continue
+to run until the system is suspended, but they will not advance while the
+system is suspended. That means, on resume, it will be as if the program
+was frozen for a few seconds, but the suspend time will not be counted
+towards \f(CW\*(C`ev_timer\*(C'\fR when a monotonic clock source is used. The real time
+clock advanced as expected, but if it is used as sole clocksource, then a
+long suspend would be detected as a time jump by libev, and timers would
+be adjusted accordingly.
+.PP
+I would not be surprised to see different behaviour in different between
+operating systems, \s-1OS\s0 versions or even different hardware.
+.PP
+The other form of suspend (job control, or sending a \s-1SIGSTOP\s0) will see a
+time jump in the monotonic clocks and the realtime clock. If the program
+is suspended for a very long time, and monotonic clock sources are in use,
+then you can expect \f(CW\*(C`ev_timer\*(C'\fRs to expire as the full suspension time
+will be counted towards the timers. When no monotonic clock source is in
+use, then libev will again assume a timejump and adjust accordingly.
+.PP
+It might be beneficial for this latter case to call \f(CW\*(C`ev_suspend\*(C'\fR
+and \f(CW\*(C`ev_resume\*(C'\fR in code that handles \f(CW\*(C`SIGTSTP\*(C'\fR, to at least get
+deterministic behaviour in this case (you can do nothing against
+\&\f(CW\*(C`SIGSTOP\*(C'\fR).
 .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
+Configure the timer to trigger after \f(CW\*(C`after\*(C'\fR seconds (fractional and
-\&\f(CW0.\fR, then it will automatically be stopped. If it is positive, then the
+negative values are supported). If \f(CW\*(C`repeat\*(C'\fR is \f(CW0.\fR, then it will
+automatically be stopped once the timeout is reached. If it is positive,
-timer will automatically be configured to trigger again \f(CW\*(C`repeat\*(C'\fR seconds
+then the timer will automatically be configured to trigger again \f(CW\*(C`repeat\*(C'\fR
-later, again, and again, until stopped manually.
+seconds later, again, and again, until stopped manually.
 .Sp
-The timer itself will do a best-effort at avoiding drift, that is, if you
+The timer itself will do a best-effort at avoiding drift, that is, if
-configure a timer to trigger every 10 seconds, then it will trigger at
+you configure a timer to trigger every 10 seconds, then it will normally
-exactly 10 second intervals. If, however, your program cannot keep up with
+trigger at exactly 10 second intervals. If, however, your program cannot
-the timer (because it takes longer than those 10 seconds to do stuff) the
+keep up with the timer (because it takes longer than those 10 seconds to
-timer will not fire more than once per event loop iteration.
+do stuff) the timer will not fire more than once per event loop iteration.
 .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
+This will act as if the timer timed out, and restarts it again if it is
-repeating. The exact semantics are:
+repeating. It basically works like calling \f(CW\*(C`ev_timer_stop\*(C'\fR, updating the
+timeout to the \f(CW\*(C`repeat\*(C'\fR value and calling \f(CW\*(C`ev_timer_start\*(C'\fR.
 .Sp
+The exact semantics are as in the following rules, all of which will be
+applied to the watcher:
+.RS 4
-If the timer is pending, its pending status is cleared.
+.IP "If the timer is pending, the pending status is always cleared." 4
-.Sp
+.IX Item "If the timer is pending, the pending status is always cleared."
+.PD 0
-If the timer is started but nonrepeating, stop it (as if it timed out).
+.IP "If the timer is started but non-repeating, stop it (as if it timed out, without invoking it)." 4
+.IX Item "If the timer is started but non-repeating, stop it (as if it timed out, without invoking it)."
+.ie n .IP "If the timer is repeating, make the ""repeat"" value the new timeout and start the timer, if necessary." 4
+.el .IP "If the timer is repeating, make the \f(CWrepeat\fR value the new timeout and start the timer, if necessary." 4
+.IX Item "If the timer is repeating, make the repeat value the new timeout and start the timer, if necessary."
+.RE
+.RS 4
+.PD
 .Sp
-If the timer is repeating, either start it if necessary (with the
+This sounds a bit complicated, see \*(L"Be smart about timeouts\*(R", above, for a
-\&\f(CW\*(C`repeat\*(C'\fR value), or reset the running timer to the \f(CW\*(C`repeat\*(C'\fR value.
+usage example.
+.RE
+.IP "ev_tstamp ev_timer_remaining (loop, ev_timer *)" 4
+.IX Item "ev_tstamp ev_timer_remaining (loop, ev_timer *)"
+Returns the remaining time until a timer fires. If the timer is active,
+then this time is relative to the current event loop time, otherwise it's
+the timeout value currently configured.
 .Sp
-This sounds a bit complicated, but here is a useful and typical
+That is, after an \f(CW\*(C`ev_timer_set (w, 5, 7)\*(C'\fR, \f(CW\*(C`ev_timer_remaining\*(C'\fR returns
-example: Imagine you have a tcp connection and you want a so-called idle
+\&\f(CW5\fR. When the timer is started and one second passes, \f(CW\*(C`ev_timer_remaining\*(C'\fR
-timeout, that is, you want to be called when there have been, say, 60
+will return \f(CW4\fR. When the timer expires and is restarted, it will return
-seconds of inactivity on the socket. The easiest way to do this is to
+roughly \f(CW7\fR (likely slightly less as callback invocation takes some time,
-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
+too), and so on.
-\&\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),
+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
+\&   static void
-\&  one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
+\&   one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
-\&  {
+\&   {
-\&    .. one minute over, w is actually stopped right here
+\&     .. one minute over, w is actually stopped right here
-\&  }
+\&   }
 \&
-\&  struct ev_timer mytimer;
+\&   ev_timer mytimer;
-\&  ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
+\&   ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
-\&  ev_timer_start (loop, &mytimer);
+\&   ev_timer_start (loop, &mytimer);
 .Ve
 .PP
 Example: Create a timeout timer that times out after 10 seconds of
 inactivity.
 .PP
 .Vb 5
-\&  static void
+\&   static void
-\&  timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
+\&   timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
-\&  {
+\&   {
-\&    .. ten seconds without any activity
+\&     .. ten seconds without any activity
-\&  }
+\&   }
 \&
-\&  struct ev_timer mytimer;
+\&   ev_timer mytimer;
-\&  ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
+\&   ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
-\&  ev_timer_again (&mytimer); /* start timer */
+\&   ev_timer_again (&mytimer); /* start timer */
-\&  ev_loop (loop, 0);
+\&   ev_run (loop, 0);
 \&
-\&  // and in some piece of code that gets executed on any "activity":
+\&   // and in some piece of code that gets executed on any "activity":
-\&  // reset the timeout to start ticking again at 10 seconds
+\&   // reset the timeout to start ticking again at 10 seconds
-\&  ev_timer_again (&mytimer);
+\&   ev_timer_again (&mytimer);
 .Ve
-.ie n .Sh """ev_periodic"" \- to cron or not to cron?"
+.ie n .SS """ev_periodic"" \- to cron or not to cron?"
-.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron?"
+.el .SS "\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)
+Unlike \f(CW\*(C`ev_timer\*(C'\fR, periodic watchers are not based on real time (or
-but on wallclock time (absolute time). You can tell a periodic watcher
+relative time, the physical time that passes) but on wall clock time
-to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a
+(absolute time, the thing you can read on your calendar or clock). The
-periodic watcher to trigger in 10 seconds (by specifiying e.g. \f(CW\*(C`ev_now ()
+difference is that wall clock time can run faster or slower than real
-+ 10.\*(C'\fR) and then reset your system clock to the last year, then it will
+time, and time jumps are not uncommon (e.g. when you adjust your
-take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger
+wrist-watch).
-roughly 10 seconds later).
 .PP
-They can also be used to implement vastly more complex timers, such as
+You can tell a periodic watcher to trigger after some specific point
-triggering an event on each midnight, local time or other, complicated,
+in time: for example, if you tell a periodic watcher to trigger \*(L"in 10
-rules.
+seconds\*(R" (by specifying e.g. \f(CW\*(C`ev_now () + 10.\*(C'\fR, that is, an absolute time
+not a delay) and then reset your system clock to January of the previous
+year, then it will take a year or more to trigger the event (unlike an
+\&\f(CW\*(C`ev_timer\*(C'\fR, which would still trigger roughly 10 seconds after starting
+it, as it uses a relative timeout).
 .PP
+\&\f(CW\*(C`ev_periodic\*(C'\fR watchers can also be used to implement vastly more complex
+timers, such as triggering an event on each \*(L"midnight, local time\*(R", or
+other complicated rules. This cannot easily be done with \f(CW\*(C`ev_timer\*(C'\fR
+watchers, as those cannot react to time jumps.
+.PP
-As with timers, the callback is guarenteed to be invoked only when the
+As with timers, the callback is guaranteed to be invoked only when the
-time (\f(CW\*(C`at\*(C'\fR) has been passed, but if multiple periodic timers become ready
+point in time where it is supposed to trigger has passed. If multiple
-during the same loop iteration then order of execution is undefined.
+timers become ready during the same loop iteration then the ones with
+earlier time-out values are invoked before ones with later time-out values
+(but this is no longer true when a callback calls \f(CW\*(C`ev_run\*(C'\fR recursively).
 .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
+.IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)" 4
-.IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)"
+.IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)"
 .PD 0
-.IP "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 4
+.IP "ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)" 4
-.IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)"
+.IX Item "ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)"
 .PD
-Lots of arguments, lets sort it out... There are basically three modes of
+Lots of arguments, let's sort it out... There are basically three modes of
-operation, and we will explain them from simplest to complex:
+operation, and we will explain them from simplest to most complex:
 .RS 4
 .IP "\(bu" 4
-absolute timer (at = time, interval = reschedule_cb = 0)
+absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
 .Sp
-In this configuration the watcher triggers an event at the wallclock time
+In this configuration the watcher triggers an event after the wall clock
-\&\f(CW\*(C`at\*(C'\fR and doesn't repeat. It will not adjust when a time jump occurs,
+time \f(CW\*(C`offset\*(C'\fR has passed. It will not repeat and will not adjust when a
-that is, if it is to be run at January 1st 2011 then it will run when the
+time jump occurs, that is, if it is to be run at January 1st 2011 then it
-system time reaches or surpasses this time.
+will be stopped and invoked when the system clock reaches or surpasses
+this point in time.
 .IP "\(bu" 4
-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
+repeating interval timer (offset = offset within interval, 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)
+\&\f(CW\*(C`offset + N * interval\*(C'\fR time (for some integer N, which can also be
-and then repeat, regardless of any time jumps.
+negative) and then repeat, regardless of any time jumps. The \f(CW\*(C`offset\*(C'\fR
+argument is merely an offset into the \f(CW\*(C`interval\*(C'\fR periods.
 .Sp
-This can be used to create timers that do not drift with respect to system
+This can be used to create timers that do not drift with respect to the
-time:
+system clock, for example, here is an \f(CW\*(C`ev_periodic\*(C'\fR that triggers each
+hour, on the hour (with respect to \s-1UTC\s0):
 .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
+but only that 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.
+time where \f(CW\*(C`time = offset (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
+The \f(CW\*(C`interval\*(C'\fR \fI\s-1MUST\s0\fR be positive, and for numerical stability, the
-\&\f(CW\*(C`ev_now ()\*(C'\fR (the current time), but there is no range requirement for
+interval value should be higher than \f(CW\*(C`1/8192\*(C'\fR (which is around 100
-this value.
+microseconds) and \f(CW\*(C`offset\*(C'\fR should be higher than \f(CW0\fR and should have
+at most a similar magnitude as the current time (say, within a factor of
+ten). Typical values for offset are, in fact, \f(CW0\fR or something between
+\&\f(CW0\fR and \f(CW\*(C`interval\*(C'\fR, which is also the recommended range.
+.Sp
+Note also that there is an upper limit to how often a timer can fire (\s-1CPU\s0
+speed for example), so if \f(CW\*(C`interval\*(C'\fR is very small then timing stability
+will of course deteriorate. Libev itself tries to be exact to be about one
+millisecond (if the \s-1OS\s0 supports it and the machine is fast enough).
 .IP "\(bu" 4
-manual reschedule mode (at and interval ignored, reschedule_cb = callback)
+manual reschedule mode (offset ignored, 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
+In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`offset\*(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,
+\&\s-1NOTE:\s0 \fIThis callback \s-1MUST NOT\s0 stop or destroy any periodic watcher, ever,
-ever, or make any event loop modifications\fR. If you need to stop it,
+or make \s-1ANY\s0 other event loop modifications whatsoever, unless explicitly
-return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop it afterwards (e.g. by
+allowed by documentation here\fR.
+.Sp
+If you need to stop it, return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop
-starting an \f(CW\*(C`ev_prepare\*(C'\fR watcher, which is legal).
+it afterwards (e.g. by starting an \f(CW\*(C`ev_prepare\*(C'\fR watcher, which is the
+only event loop modification you are allowed to do).
 .Sp
-Its prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
+The callback prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(ev_periodic
-ev_tstamp now)\*(C'\fR, e.g.:
+*w, ev_tstamp now)\*(C'\fR, e.g.:
 .Sp
-.Vb 4
+.Vb 5
+\&   static ev_tstamp
-\&   static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
+\&   my_rescheduler (ev_periodic *w, ev_tstamp now)
 \&   {
 \&     return now + 60.;
 \&   }
 .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
+\&\s-1NOTE:\s0 \fIThis callback must always return a time that is higher than or
-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.
+equal to the passed \f(CI\*(C`now\*(C'\fI value\fR.
 .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
+triggers on \*(L"next midnight, local time\*(R". To do this, you would calculate
-next midnight after \f(CW\*(C`now\*(C'\fR and return the timestamp value for this. How
+the next midnight after \f(CW\*(C`now\*(C'\fR and return the timestamp value for
-you do this is, again, up to you (but it is not trivial, which is the main
+this. Here is a (completely untested, no error checking) example on how to
-reason I omitted it as an example).
+do this:
+.Sp
+.Vb 1
+\&   #include <time.h>
+\&
+\&   static ev_tstamp
+\&   my_rescheduler (ev_periodic *w, ev_tstamp now)
+\&   {
+\&     time_t tnow = (time_t)now;
+\&     struct tm tm;
+\&     localtime_r (&tnow, &tm);
+\&
+\&     tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day
+\&     ++tm.tm_mday; // midnight next day
+\&
+\&     return mktime (&tm);
+\&   }
+.Ve
+.Sp
+Note: this code might run into trouble on days that have more then two
+midnights (beginning and end).
 .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. This is not the same as the \f(CW\*(C`offset\*(C'\fR argument to
+\&\f(CW\*(C`ev_periodic_set\*(C'\fR, but indeed works even in interval and manual
+rescheduling modes.
 .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).
+absolute point in time (the \f(CW\*(C`offset\*(C'\fR value passed to \f(CW\*(C`ev_periodic_set\*(C'\fR,
+although libev might modify this value for better numerical stability).
 .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
+.IP "ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read\-write]" 4
-.IX Item "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]"
+.IX Item "ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]"
 The current reschedule callback, or \f(CW0\fR, if this functionality is
 switched off. Can be changed any time, but changes only take effect when
 the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
-.IP "ev_tstamp at [read\-only]" 4
-.IX Item "ev_tstamp at [read-only]"
-When active, contains the absolute time that the watcher is supposed to
-trigger next.
 .PP
 \fIExamples\fR
 .IX Subsection "Examples"
 .PP
 Example: Call a callback every hour, or, more precisely, whenever the
-system clock is divisible by 3600. The callback invocation times have
+system time is divisible by 3600. The callback invocation times have
-potentially a lot of jittering, but good long-term stability.
+potentially a lot of jitter, but good long-term stability.
 .PP
 .Vb 5
-\&  static void
+\&   static void
-\&  clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
+\&   clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
-\&  {
+\&   {
-\&    ... its now a full hour (UTC, or TAI or whatever your clock follows)
+\&     ... its now a full hour (UTC, or TAI or whatever your clock follows)
-\&  }
+\&   }
 \&
-\&  struct ev_periodic hourly_tick;
+\&   ev_periodic hourly_tick;
-\&  ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
+\&   ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
-\&  ev_periodic_start (loop, &hourly_tick);
+\&   ev_periodic_start (loop, &hourly_tick);
 .Ve
 .PP
 Example: The same as above, but use a reschedule callback to do it:
 .PP
 .Vb 1
-\&  #include <math.h>
+\&   #include <math.h>
 \&
-\&  static ev_tstamp
+\&   static ev_tstamp
-\&  my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
+\&   my_scheduler_cb (ev_periodic *w, ev_tstamp now)
-\&  {
+\&   {
-\&    return fmod (now, 3600.) + 3600.;
+\&     return now + (3600. \- fmod (now, 3600.));
-\&  }
+\&   }
 \&
-\&  ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
+\&   ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
 .Ve
 .PP
 Example: Call a callback every hour, starting now:
 .PP
 .Vb 4
-\&  struct ev_periodic hourly_tick;
+\&   ev_periodic hourly_tick;
-\&  ev_periodic_init (&hourly_tick, clock_cb,
+\&   ev_periodic_init (&hourly_tick, clock_cb,
-\&                    fmod (ev_now (loop), 3600.), 3600., 0);
+\&                     fmod (ev_now (loop), 3600.), 3600., 0);
-\&  ev_periodic_start (loop, &hourly_tick);
+\&   ev_periodic_start (loop, &hourly_tick);
 .Ve
-.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled!"
+.ie n .SS """ev_signal"" \- signal me when a signal gets signalled!"
-.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled!"
+.el .SS "\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
+will try its best to deliver signals synchronously, i.e. as part of the
 normal event processing, like any other event.
 .PP
+If you want signals to be delivered truly asynchronously, just use
+\&\f(CW\*(C`sigaction\*(C'\fR as you would do without libev and forget about sharing
+the signal. You can even use \f(CW\*(C`ev_async\*(C'\fR from a signal handler to
+synchronously wake up an event loop.
+.PP
-You can configure as many watchers as you like per signal. Only when the
+You can configure as many watchers as you like for the same signal, but
-first watcher gets started will libev actually register a signal watcher
+only within the same loop, i.e. you can watch for \f(CW\*(C`SIGINT\*(C'\fR in your
-with the kernel (thus it coexists with your own signal handlers as long
+default loop and for \f(CW\*(C`SIGIO\*(C'\fR in another loop, but you cannot watch for
-as you don't register any with libev). Similarly, when the last signal
+\&\f(CW\*(C`SIGINT\*(C'\fR in both the default loop and another loop at the same time. At
-watcher for a signal is stopped libev will reset the signal handler to
+the moment, \f(CW\*(C`SIGCHLD\*(C'\fR is permanently tied to the default loop.
-\&\s-1SIG_DFL\s0 (regardless of what it was set to before).
+.PP
+Only after the first watcher for a signal is started will libev actually
+register something with the kernel. It thus coexists with your own signal
+handlers as long as you don't register any with libev for the same signal.
 .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
+\&\f(CW\*(C`SA_RESTART\*(C'\fR (or equivalent) behaviour enabled, so system calls should
-interrupted. If you have a problem with syscalls getting interrupted by
+not be unduly interrupted. If you have a problem with system calls getting
-signals you can block all signals in an \f(CW\*(C`ev_check\*(C'\fR watcher and unblock
+interrupted by signals you can block all signals in an \f(CW\*(C`ev_check\*(C'\fR watcher
-them in an \f(CW\*(C`ev_prepare\*(C'\fR watcher.
+and unblock them in an \f(CW\*(C`ev_prepare\*(C'\fR watcher.
+.PP
+\fIThe special problem of inheritance over fork/execve/pthread_create\fR
+.IX Subsection "The special problem of inheritance over fork/execve/pthread_create"
+.PP
+Both the signal mask (\f(CW\*(C`sigprocmask\*(C'\fR) and the signal disposition
+(\f(CW\*(C`sigaction\*(C'\fR) are unspecified after starting a signal watcher (and after
+stopping it again), that is, libev might or might not block the signal,
+and might or might not set or restore the installed signal handler (but
+see \f(CW\*(C`EVFLAG_NOSIGMASK\*(C'\fR).
+.PP
+While this does not matter for the signal disposition (libev never
+sets signals to \f(CW\*(C`SIG_IGN\*(C'\fR, so handlers will be reset to \f(CW\*(C`SIG_DFL\*(C'\fR on
+\&\f(CW\*(C`execve\*(C'\fR), this matters for the signal mask: many programs do not expect
+certain signals to be blocked.
+.PP
+This means that before calling \f(CW\*(C`exec\*(C'\fR (from the child) you should reset
+the signal mask to whatever \*(L"default\*(R" you expect (all clear is a good
+choice usually).
+.PP
+The simplest way to ensure that the signal mask is reset in the child is
+to install a fork handler with \f(CW\*(C`pthread_atfork\*(C'\fR that resets it. That will
+catch fork calls done by libraries (such as the libc) as well.
+.PP
+In current versions of libev, the signal will not be blocked indefinitely
+unless you use the \f(CW\*(C`signalfd\*(C'\fR \s-1API\s0 (\f(CW\*(C`EV_SIGNALFD\*(C'\fR). While this reduces
+the window of opportunity for problems, it will not go away, as libev
+\&\fIhas\fR to modify the signal mask, at least temporarily.
+.PP
+So I can't stress this enough: \fIIf you do not reset your signal mask when
+you expect it to be empty, you have a race condition in your code\fR. This
+is not a libev-specific thing, this is true for most event libraries.
+.PP
+\fIThe special problem of threads signal handling\fR
+.IX Subsection "The special problem of threads signal handling"
+.PP
+\&\s-1POSIX\s0 threads has problematic signal handling semantics, specifically,
+a lot of functionality (sigfd, sigwait etc.) only really works if all
+threads in a process block signals, which is hard to achieve.
+.PP
+When you want to use sigwait (or mix libev signal handling with your own
+for the same signals), you can tackle this problem by globally blocking
+all signals before creating any threads (or creating them with a fully set
+sigprocmask) and also specifying the \f(CW\*(C`EVFLAG_NOSIGMASK\*(C'\fR when creating
+loops. Then designate one thread as \*(L"signal receiver thread\*(R" which handles
+these signals. You can pass on any signals that libev might be interested
+in by calling \f(CW\*(C`ev_feed_signal\*(C'\fR.
 .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)"
 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.
+Example: Try to exit cleanly on \s-1SIGINT.\s0
 .PP
 .Vb 5
-\&  static void
+\&   static void
-\&  sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
+\&   sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
-\&  {
+\&   {
-\&    ev_unloop (loop, EVUNLOOP_ALL);
+\&     ev_break (loop, EVBREAK_ALL);
-\&  }
+\&   }
 \&
-\&  struct ev_signal signal_watcher;
+\&   ev_signal signal_watcher;
-\&  ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
+\&   ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
-\&  ev_signal_start (loop, &sigint_cb);
+\&   ev_signal_start (loop, &signal_watcher);
 .Ve
-.ie n .Sh """ev_child"" \- watch out for process status changes"
+.ie n .SS """ev_child"" \- watch out for process status changes"
-.el .Sh "\f(CWev_child\fP \- watch out for process status changes"
+.el .SS "\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
+some child status changes (most typically when a child of yours dies or
-is permissible to install a child watcher \fIafter\fR the child has been
+exits). It is permissible to install a child watcher \fIafter\fR the child
-forked (which implies it might have already exited), as long as the event
+has been forked (which implies it might have already exited), as long
-loop isn't entered (or is continued from a watcher).
+as the event loop isn't entered (or is continued from a watcher), i.e.,
+forking and then immediately registering a watcher for the child is fine,
+but forking and registering a watcher a few event loop iterations later or
+in the next callback invocation is not.
 .PP
 Only the default event loop is capable of handling signals, and therefore
-you can only rgeister child watchers in the default event loop.
+you can only register child watchers in the default event loop.
+.PP
+Due to some design glitches inside libev, child watchers will always be
+handled at maximum priority (their priority is set to \f(CW\*(C`EV_MAXPRI\*(C'\fR by
+libev)
 .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
+initialised. This is necessary to guarantee proper behaviour even if the
-the first child watcher is started after the child exits. The occurance
+first child watcher is started after the child exits. The occurrence
 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
 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
+\fIStopping the Child Watcher\fR
+.IX Subsection "Stopping the Child Watcher"
+.PP
+Currently, the child watcher never gets stopped, even when the
+child terminates, so normally one needs to stop the watcher in the
+callback. Future versions of libev might stop the watcher automatically
+when a child exit is detected (calling \f(CW\*(C`ev_child_stop\*(C'\fR twice is not a
+problem).
 .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)"
 .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;
+\&   ev_child cw;
 \&
-\&  static void
+\&   static void
-\&  child_cb (EV_P_ struct ev_child *w, int revents)
+\&   child_cb (EV_P_ ev_child *w, int revents)
-\&  {
+\&   {
-\&    ev_child_stop (EV_A_ w);
+\&     ev_child_stop (EV_A_ w);
-\&    printf ("process %d exited with status %x\en", w\->rpid, w\->rstatus);
+\&     printf ("process %d exited with status %x\en", w\->rpid, w\->rstatus);
-\&  }
+\&   }
 \&
-\&  pid_t pid = fork ();
+\&   pid_t pid = fork ();
 \&
-\&  if (pid < 0)
+\&   if (pid < 0)
-\&    // error
+\&     // error
-\&  else if (pid == 0)
+\&   else if (pid == 0)
-\&    {
+\&     {
-\&      // the forked child executes here
+\&       // the forked child executes here
-\&      exit (1);
+\&       exit (1);
-\&    }
+\&     }
-\&  else
+\&   else
-\&    {
+\&     {
-\&      ev_child_init (&cw, child_cb, pid, 0);
+\&       ev_child_init (&cw, child_cb, pid, 0);
-\&      ev_child_start (EV_DEFAULT_ &cw);
+\&       ev_child_start (EV_DEFAULT_ &cw);
-\&    }
+\&     }
 .Ve
-.ie n .Sh """ev_stat"" \- did the file attributes just change?"
+.ie n .SS """ev_stat"" \- did the file attributes just change?"
-.el .Sh "\f(CWev_stat\fP \- did the file attributes just change?"
+.el .SS "\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
+This watches a file system 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
+\&\f(CW\*(C`stat\*(C'\fR on that path in regular intervals (or when the \s-1OS\s0 says it changed)
-compared to the last time, invoking the callback if it did.
+and sees if it changed compared to the last time, invoking the callback
+if it did. Starting the watcher \f(CW\*(C`stat\*(C'\fR's the file, so only changes that
+happen after the watcher has been started will be reported.
 .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 a status change like any other. The condition \*(L"path does not
-not exist\*(R" is signified by the \f(CW\*(C`st_nlink\*(C'\fR field being zero (which is
+exist\*(R" (or more correctly \*(L"path cannot be stat'ed\*(R") is signified by the
-otherwise always forced to be at least one) and all the other fields of
+\&\f(CW\*(C`st_nlink\*(C'\fR field being zero (which is otherwise always forced to be at
-the stat buffer having unspecified contents.
+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
+The path \fImust not\fR end in a slash or contain special components such as
+\&\f(CW\*(C`.\*(C'\fR or \f(CW\*(C`..\*(C'\fR. The path \fIshould\fR be absolute: If it is relative and
-relative and your working directory changes, the behaviour is undefined.
+your working directory changes, then the behaviour is undefined.
 .PP
-Since there is no standard to do this, the portable implementation simply
+Since there is no portable change notification interface available, the
-calls \f(CW\*(C`stat (2)\*(C'\fR regularly on the path to see if it changed somehow. You
+portable implementation simply calls \f(CWstat(2)\fR regularly on the path
-can specify a recommended polling interval for this case. If you specify
+to see if it changed somehow. You can specify a recommended polling
-a polling interval of \f(CW0\fR (highly recommended!) then a \fIsuitable,
+interval for this case. If you specify a polling interval of \f(CW0\fR (highly
-unspecified default\fR value will be used (which you can expect to be around
+recommended!) then a \fIsuitable, unspecified default\fR value will be used
-five seconds, although this might change dynamically). Libev will also
+(which you can expect to be around five seconds, although this might
-impose a minimum interval which is currently around \f(CW0.1\fR, but thats
+change dynamically). Libev will also impose a minimum interval which is
-usually overkill.
+currently around \f(CW0.1\fR, but that's 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
+At the time of this writing, the only OS-specific interface implemented
-implemented (implementing kqueue support is left as an exercise for the
+is the Linux inotify interface (implementing kqueue support is left as an
-reader). Inotify will be used to give hints only and should not change the
+exercise for the reader. Note, however, that the author sees no way of
-semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers, which means that libev sometimes needs
+implementing \f(CW\*(C`ev_stat\*(C'\fR semantics with kqueue, except as a hint).
-to fall back to regular polling again even with inotify, but changes are
-usually detected immediately, and if the file exists there will be no
-polling.
 .PP
-\fIInotify\fR
+\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 large file
+support disabled by default, 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 noticeably displayed with ev_stat and large file support.
+.PP
+The solution for this is to lobby your distribution maker to make large
+file interfaces available by default (as e.g. FreeBSD does) and not
+optional. Libev cannot simply switch on large file support because it has
+to exchange stat structures with application programs compiled using the
+default compilation environment.
+.PP
+\fIInotify and Kqueue\fR
-.IX Subsection "Inotify"
+.IX Subsection "Inotify and Kqueue"
 .PP
-When \f(CW\*(C`inotify (7)\*(C'\fR support has been compiled into libev (generally only
+When \f(CW\*(C`inotify (7)\*(C'\fR support has been compiled into libev and present at
-available on Linux) and present at runtime, it will be used to speed up
+runtime, it will be used to speed up change detection where possible. The
-change detection where possible. The inotify descriptor will be created lazily
+inotify descriptor will be created lazily when the first \f(CW\*(C`ev_stat\*(C'\fR
-when the first \f(CW\*(C`ev_stat\*(C'\fR watcher is being started.
+watcher is being started.
 .PP
-Inotify presense does not change the semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers
+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 presense of inotify support
+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.
+there are many cases where libev has to resort to regular \f(CW\*(C`stat\*(C'\fR polling,
+but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
+many bugs), the path exists (i.e. stat succeeds), and the path resides on
+a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
+xfs are fully working) libev usually gets away without polling.
 .PP
-(There is no support for kqueue, as apparently it cannot be used to
+There is no support for kqueue, as apparently it cannot be used to
 implement this functionality, due to the requirement of having a file
-descriptor open on the object at all times).
+descriptor open on the object at all times, and detecting renames, unlinks
+etc. is difficult.
+.PP
+\fI\f(CI\*(C`stat ()\*(C'\fI is a synchronous operation\fR
+.IX Subsection "stat () is a synchronous operation"
+.PP
+Libev doesn't normally do any kind of I/O itself, and so is not blocking
+the process. The exception are \f(CW\*(C`ev_stat\*(C'\fR watchers \- those call \f(CW\*(C`stat
+()\*(C'\fR, which is a synchronous operation.
+.PP
+For local paths, this usually doesn't matter: unless the system is very
+busy or the intervals between stat's are large, a stat call will be fast,
+as the path data is usually in memory already (except when starting the
+watcher).
+.PP
+For networked file systems, calling \f(CW\*(C`stat ()\*(C'\fR can block an indefinite
+time due to network issues, and even under good conditions, a stat call
+often takes multiple milliseconds.
+.PP
+Therefore, it is best to avoid using \f(CW\*(C`ev_stat\*(C'\fR watchers on networked
+paths, although this is fully supported by libev.
 .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
+The \f(CW\*(C`stat ()\*(C'\fR system call only supports full-second resolution portably,
-even on systems where the resolution is higher, many filesystems still
+and even on systems where the resolution is higher, most file systems
-only support whole seconds.
+still only support whole seconds.
 .PP
-That means that, if the time is the only thing that changes, you might
+That means that, if the time is the only thing that changes, you can
-miss updates: on the first update, \f(CW\*(C`ev_stat\*(C'\fR detects a change and calls
+easily miss updates: on the first update, \f(CW\*(C`ev_stat\*(C'\fR detects a change and
-your callback, which does something. When there is another update within
+calls your callback, which does something. When there is another update
-the same second, \f(CW\*(C`ev_stat\*(C'\fR will be unable to detect it.
+within the same second, \f(CW\*(C`ev_stat\*(C'\fR will be unable to detect unless the
+stat data does change in other ways (e.g. file size).
 .PP
-The solution to this is to delay acting on a change for a second (or till
+The solution to this is to delay acting on a change for slightly more
-the next second boundary), using a roughly one-second delay \f(CW\*(C`ev_timer\*(C'\fR
+than a second (or till slightly after the next full second boundary), using
-(\f(CW\*(C`ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)\*(C'\fR). The \f(CW.01\fR
+a roughly one-second-delay \f(CW\*(C`ev_timer\*(C'\fR (e.g. \f(CW\*(C`ev_timer_set (w, 0., 1.02);
-is added to work around small timing inconsistencies of some operating
+ev_timer_again (loop, w)\*(C'\fR).
-systems.
+.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)"
 \&\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 be receive \f(CW\*(C`EV_STAT\*(C'\fR when a change was detected,
+The callback will receive an \f(CW\*(C`EV_STAT\*(C'\fR event 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 fucntion to avoid
+watched path in your callback, you could call this function to avoid
-detecting this change (while introducing a race condition). Can also be
+detecting this change (while introducing a race condition if you are not
-useful simply to find out the new values.
+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 of
+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
-suitable for your system. If the \f(CW\*(C`st_nlink\*(C'\fR member is \f(CW0\fR, then there
+members to be present. If the \f(CW\*(C`st_nlink\*(C'\fR member is \f(CW0\fR, then there was
-was some error while \f(CW\*(C`stat\*(C'\fRing the file.
+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.
+\&\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.
+The file system 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
+\&   static void
-\&  passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
+\&   passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
-\&  {
+\&   {
-\&    /* /etc/passwd changed in some way */
+\&     /* /etc/passwd changed in some way */
-\&    if (w\->attr.st_nlink)
+\&     if (w\->attr.st_nlink)
-\&      {
+\&       {
-\&        printf ("passwd current size  %ld\en", (long)w\->attr.st_size);
+\&         printf ("passwd current size  %ld\en", (long)w\->attr.st_size);
-\&        printf ("passwd current atime %ld\en", (long)w\->attr.st_mtime);
+\&         printf ("passwd current atime %ld\en", (long)w\->attr.st_mtime);
-\&        printf ("passwd current mtime %ld\en", (long)w\->attr.st_mtime);
+\&         printf ("passwd current mtime %ld\en", (long)w\->attr.st_mtime);
-\&      }
+\&       }
-\&    else
+\&     else
-\&      /* you shalt not abuse printf for puts */
+\&       /* you shalt not abuse printf for puts */
-\&      puts ("wow, /etc/passwd is not there, expect problems. "
+\&       puts ("wow, /etc/passwd is not there, expect problems. "
-\&            "if this is windows, they already arrived\en");
+\&             "if this is windows, they already arrived\en");
-\&  }
+\&   }
 \&
-\&  ...
+\&   ...
-\&  ev_stat passwd;
+\&   ev_stat passwd;
 \&
-\&  ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
+\&   ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
-\&  ev_stat_start (loop, &passwd);
+\&   ev_stat_start (loop, &passwd);
 .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_stat passwd;
-\&  static ev_timer timer;
+\&   static ev_timer timer;
 \&
-\&  static void
+\&   static void
-\&  timer_cb (EV_P_ ev_timer *w, int revents)
+\&   timer_cb (EV_P_ ev_timer *w, int revents)
-\&  {
+\&   {
-\&    ev_timer_stop (EV_A_ w);
+\&     ev_timer_stop (EV_A_ w);
 \&
-\&    /* now it\*(Aqs one second after the most recent passwd change */
+\&     /* now it\*(Aqs one second after the most recent passwd change */
-\&  }
+\&   }
 \&
-\&  static void
+\&   static void
-\&  stat_cb (EV_P_ ev_stat *w, int revents)
+\&   stat_cb (EV_P_ ev_stat *w, int revents)
-\&  {
+\&   {
-\&    /* reset the one\-second timer */
+\&     /* reset the one\-second timer */
-\&    ev_timer_again (EV_A_ &timer);
+\&     ev_timer_again (EV_A_ &timer);
-\&  }
+\&   }
 \&
-\&  ...
+\&   ...
-\&  ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
+\&   ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
-\&  ev_stat_start (loop, &passwd);
+\&   ev_stat_start (loop, &passwd);
-\&  ev_timer_init (&timer, timer_cb, 0., 1.01);
+\&   ev_timer_init (&timer, timer_cb, 0., 1.02);
 .Ve
-.ie n .Sh """ev_idle"" \- when you've got nothing better to do..."
+.ie n .SS """ev_idle"" \- when you've got nothing better to do..."
-.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do..."
+.el .SS "\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
+priority are pending (prepare, check and other idle watchers do not count
-count).
+as receiving \*(L"events\*(R").
 .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
 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
+\fIAbusing an \f(CI\*(C`ev_idle\*(C'\fI watcher for its side-effect\fR
+.IX Subsection "Abusing an ev_idle watcher for its side-effect"
+.PP
+As long as there is at least one active idle watcher, libev will never
+sleep unnecessarily. Or in other words, it will loop as fast as possible.
+For this to work, the idle watcher doesn't need to be invoked at all \- the
+lowest priority will do.
+.PP
+This mode of operation can be useful together with an \f(CW\*(C`ev_check\*(C'\fR watcher,
+to do something on each event loop iteration \- for example to balance load
+between different connections.
+.PP
+See \*(L"Abusing an ev_check watcher for its side-effect\*(R" for a longer
+example.
+.PP
 \fIWatcher-Specific Functions and Data Members\fR
 .IX Subsection "Watcher-Specific Functions and Data Members"
-.IP "ev_idle_init (ev_signal *, callback)" 4
+.IP "ev_idle_init (ev_idle *, callback)" 4
-.IX Item "ev_idle_init (ev_signal *, callback)"
+.IX Item "ev_idle_init (ev_idle *, 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
+.Vb 5
-\&  static void
+\&   static void
-\&  idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
+\&   idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
-\&  {
+\&   {
+\&     // stop the watcher
+\&     ev_idle_stop (loop, w);
+\&
+\&     // now we can free it
-\&    free (w);
+\&     free (w);
+\&
-\&    // now do something you wanted to do when the program has
+\&     // now do something you wanted to do when the program has
-\&    // no longer anything immediate to do.
+\&     // no longer anything immediate to do.
-\&  }
+\&   }
 \&
-\&  struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
+\&   ev_idle *idle_watcher = malloc (sizeof (ev_idle));
-\&  ev_idle_init (idle_watcher, idle_cb);
+\&   ev_idle_init (idle_watcher, idle_cb);
-\&  ev_idle_start (loop, idle_cb);
+\&   ev_idle_start (loop, idle_watcher);
 .Ve
-.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop!"
+.ie n .SS """ev_prepare"" and ""ev_check"" \- customise your event loop!"
-.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!"
+.el .SS "\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 and check watchers are often (but not always) used in pairs:
 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
+You \fImust not\fR call \f(CW\*(C`ev_run\*(C'\fR (or similar functions that enter the
-the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR
+current event loop) or \f(CW\*(C`ev_loop_fork\*(C'\fR from either \f(CW\*(C`ev_prepare\*(C'\fR or
-watchers. Other loops than the current one are fine, however. The
+\&\f(CW\*(C`ev_check\*(C'\fR watchers. Other loops than the current one are fine,
-rationale behind this is that you do not need to check for recursion in
+however. The rationale behind this is that you do not need to check
-those watchers, i.e. the sequence will always be \f(CW\*(C`ev_prepare\*(C'\fR, blocking,
+for recursion in those watchers, i.e. the sequence will always be
-\&\f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each kind they 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
-called in pairs bracketing the blocking call.
+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
+their use is somewhat advanced. They could be used, for example, to track
 variable changes, implement your own watchers, integrate net-snmp or a
 coroutine library and lots more. They are also occasionally useful if
 you cache some data and want to flush it before blocking (for example,
 in X programs you might want to do an \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
+This is done by examining in each prepare call which file descriptors
-to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for
+need to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers
-them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries
+for them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many
-provide just this functionality). Then, in the check watcher you check for
+libraries provide exactly this functionality). Then, in the check watcher,
-any events that occured (by checking the pending status of all watchers
+you check for any events that occurred (by checking the pending status
-and stopping them) and call back into the library. The I/O and timer
+of all watchers and stopping them) and call back into the library. The
-callbacks will never actually be called (but must be valid nevertheless,
+I/O and timer callbacks will never actually be called (but must be valid
-because you never know, you know?).
+nevertheless, because you never know, you know?).
 .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)
+When used for this purpose, it is recommended to give \f(CW\*(C`ev_check\*(C'\fR watchers
-priority, to ensure that they are being run before any other watchers
+highest (\f(CW\*(C`EV_MAXPRI\*(C'\fR) priority, to ensure that they are being run before
+any other watchers after the poll (this doesn't matter for \f(CW\*(C`ev_prepare\*(C'\fR
+watchers).
+.PP
-after the poll. Also, \f(CW\*(C`ev_check\*(C'\fR watchers (and \f(CW\*(C`ev_prepare\*(C'\fR watchers,
+Also, \f(CW\*(C`ev_check\*(C'\fR watchers (and \f(CW\*(C`ev_prepare\*(C'\fR watchers, too) should not
-too) should not activate (\*(L"feed\*(R") events into libev. While libev fully
+activate (\*(L"feed\*(R") events into libev. While libev fully supports this, they
-supports this, they will be called before other \f(CW\*(C`ev_check\*(C'\fR watchers
+might get executed before other \f(CW\*(C`ev_check\*(C'\fR watchers did their job. As
-did their job. As \f(CW\*(C`ev_check\*(C'\fR watchers are often used to embed other
+\&\f(CW\*(C`ev_check\*(C'\fR watchers are often used to embed other (non-libev) event
-(non-libev) event loops those other event loops might be in an unusable
+loops those other event loops might be in an unusable state until their
-state until their \f(CW\*(C`ev_check\*(C'\fR watcher ran (always remind yourself to
+\&\f(CW\*(C`ev_check\*(C'\fR watcher ran (always remind yourself to coexist peacefully with
-coexist peacefully with others).
+others).
+.PP
+\fIAbusing an \f(CI\*(C`ev_check\*(C'\fI watcher for its side-effect\fR
+.IX Subsection "Abusing an ev_check watcher for its side-effect"
+.PP
+\&\f(CW\*(C`ev_check\*(C'\fR (and less often also \f(CW\*(C`ev_prepare\*(C'\fR) watchers can also be
+useful because they are called once per event loop iteration. For
+example, if you want to handle a large number of connections fairly, you
+normally only do a bit of work for each active connection, and if there
+is more work to do, you wait for the next event loop iteration, so other
+connections have a chance of making progress.
+.PP
+Using an \f(CW\*(C`ev_check\*(C'\fR watcher is almost enough: it will be called on the
+next event loop iteration. However, that isn't as soon as possible \-
+without external events, your \f(CW\*(C`ev_check\*(C'\fR watcher will not be invoked.
+.PP
+This is where \f(CW\*(C`ev_idle\*(C'\fR watchers come in handy \- all you need is a
+single global idle watcher that is active as long as you have one active
+\&\f(CW\*(C`ev_check\*(C'\fR watcher. The \f(CW\*(C`ev_idle\*(C'\fR watcher makes sure the event loop
+will not sleep, and the \f(CW\*(C`ev_check\*(C'\fR watcher makes sure a callback gets
+invoked. Neither watcher alone can do that.
 .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)"
 .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.
+macros, but using them is utterly, 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 for an actually working example. Another Perl module named \f(CW\*(C`EV::Glib\*(C'\fR
+use as a working example. Another Perl module named \f(CW\*(C`EV::Glib\*(C'\fR embeds a
-embeds a Glib main context into libev, and finally, \f(CW\*(C`Glib::EV\*(C'\fR embeds \s-1EV\s0
+Glib main context into libev, and finally, \f(CW\*(C`Glib::EV\*(C'\fR embeds \s-1EV\s0 into the
-into the Glib event loop).
+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_io iow [nfd];
-\&  static ev_timer tw;
+\&   static ev_timer tw;
 \&
-\&  static void
+\&   static void
-\&  io_cb (ev_loop *loop, ev_io *w, int revents)
+\&   io_cb (struct ev_loop *loop, ev_io *w, int revents)
-\&  {
+\&   {
-\&  }
+\&   }
 \&
-\&  // create io watchers for each fd and a timer before blocking
+\&   // create io watchers for each fd and a timer before blocking
-\&  static void
+\&   static void
-\&  adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
+\&   adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
-\&  {
+\&   {
-\&    int timeout = 3600000;
+\&     int timeout = 3600000;
-\&    struct pollfd fds [nfd];
+\&     struct pollfd fds [nfd];
-\&    // actual code will need to loop here and realloc etc.
+\&     // actual code will need to loop here and realloc etc.
-\&    adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
+\&     adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
 \&
-\&    /* the callback is illegal, but won\*(Aqt be called as we stop during check */
+\&     /* the callback is illegal, but won\*(Aqt be called as we stop during check */
-\&    ev_timer_init (&tw, 0, timeout * 1e\-3);
+\&     ev_timer_init (&tw, 0, timeout * 1e\-3, 0.);
-\&    ev_timer_start (loop, &tw);
+\&     ev_timer_start (loop, &tw);
 \&
-\&    // create one ev_io per pollfd
+\&     // create one ev_io per pollfd
-\&    for (int i = 0; i < nfd; ++i)
+\&     for (int i = 0; i < nfd; ++i)
-\&      {
+\&       {
-\&        ev_io_init (iow + i, io_cb, fds [i].fd,
+\&         ev_io_init (iow + i, io_cb, fds [i].fd,
-\&          ((fds [i].events & POLLIN ? EV_READ : 0)
+\&           ((fds [i].events & POLLIN ? EV_READ : 0)
-\&           | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
+\&            | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
 \&
-\&        fds [i].revents = 0;
+\&         fds [i].revents = 0;
-\&        ev_io_start (loop, iow + i);
+\&         ev_io_start (loop, iow + i);
-\&      }
+\&       }
-\&  }
+\&   }
 \&
-\&  // stop all watchers after blocking
+\&   // stop all watchers after blocking
-\&  static void
+\&   static void
-\&  adns_check_cb (ev_loop *loop, ev_check *w, int revents)
+\&   adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
-\&  {
+\&   {
-\&    ev_timer_stop (loop, &tw);
+\&     ev_timer_stop (loop, &tw);
 \&
-\&    for (int i = 0; i < nfd; ++i)
+\&     for (int i = 0; i < nfd; ++i)
-\&      {
+\&       {
-\&        // set the relevant poll flags
+\&         // set the relevant poll flags
-\&        // could also call adns_processreadable etc. here
+\&         // could also call adns_processreadable etc. here
-\&        struct pollfd *fd = fds + i;
+\&         struct pollfd *fd = fds + i;
-\&        int revents = ev_clear_pending (iow + i);
+\&         int revents = ev_clear_pending (iow + i);
-\&        if (revents & EV_READ ) fd\->revents |= fd\->events & POLLIN;
+\&         if (revents & EV_READ ) fd\->revents |= fd\->events & POLLIN;
-\&        if (revents & EV_WRITE) fd\->revents |= fd\->events & POLLOUT;
+\&         if (revents & EV_WRITE) fd\->revents |= fd\->events & POLLOUT;
 \&
-\&        // now stop the watcher
+\&         // now stop the watcher
-\&        ev_io_stop (loop, iow + i);
+\&         ev_io_stop (loop, iow + i);
-\&      }
+\&       }
 \&
-\&    adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
+\&     adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
-\&  }
+\&   }
 .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
+notification (libadns 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
+\&   static void
-\&  timer_cb (EV_P_ ev_timer *w, int revents)
+\&   timer_cb (EV_P_ ev_timer *w, int revents)
-\&  {
+\&   {
-\&    adns_state ads = (adns_state)w\->data;
+\&     adns_state ads = (adns_state)w\->data;
-\&    update_now (EV_A);
+\&     update_now (EV_A);
 \&
-\&    adns_processtimeouts (ads, &tv_now);
+\&     adns_processtimeouts (ads, &tv_now);
-\&  }
+\&   }
 \&
-\&  static void
+\&   static void
-\&  io_cb (EV_P_ ev_io *w, int revents)
+\&   io_cb (EV_P_ ev_io *w, int revents)
-\&  {
+\&   {
-\&    adns_state ads = (adns_state)w\->data;
+\&     adns_state ads = (adns_state)w\->data;
-\&    update_now (EV_A);
+\&     update_now (EV_A);
 \&
-\&    if (revents & EV_READ ) adns_processreadable  (ads, w\->fd, &tv_now);
+\&     if (revents & EV_READ ) adns_processreadable  (ads, w\->fd, &tv_now);
-\&    if (revents & EV_WRITE) adns_processwriteable (ads, w\->fd, &tv_now);
+\&     if (revents & EV_WRITE) adns_processwriteable (ads, w\->fd, &tv_now);
-\&  }
+\&   }
 \&
-\&  // do not ever call adns_afterpoll
+\&   // do not ever call adns_afterpoll
 .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
+want to embed is not flexible enough to support it. Instead, you can
-their poll function.  The drawback with this solution is that the main
+override their poll function. The drawback with this solution is that the
-loop is now no longer controllable by \s-1EV\s0. The \f(CW\*(C`Glib::EV\*(C'\fR module does
+main loop is now no longer controllable by \s-1EV.\s0 The \f(CW\*(C`Glib::EV\*(C'\fR module uses
-this.
+this approach, effectively embedding \s-1EV\s0 as a client into the horrible
+libglib event loop.
 .PP
 .Vb 4
-\&  static gint
+\&   static gint
-\&  event_poll_func (GPollFD *fds, guint nfds, gint timeout)
+\&   event_poll_func (GPollFD *fds, guint nfds, gint timeout)
-\&  {
+\&   {
-\&    int got_events = 0;
+\&     int got_events = 0;
 \&
-\&    for (n = 0; n < nfds; ++n)
+\&     for (n = 0; n < nfds; ++n)
-\&      // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
+\&       // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
 \&
-\&    if (timeout >= 0)
+\&     if (timeout >= 0)
-\&      // create/start timer
+\&       // create/start timer
 \&
-\&    // poll
+\&     // poll
-\&    ev_loop (EV_A_ 0);
+\&     ev_run (EV_A_ 0);
 \&
-\&    // stop timer again
+\&     // stop timer again
-\&    if (timeout >= 0)
+\&     if (timeout >= 0)
-\&      ev_timer_stop (EV_A_ &to);
+\&       ev_timer_stop (EV_A_ &to);
 \&
-\&    // stop io watchers again \- their callbacks should have set
+\&     // stop io watchers again \- their callbacks should have set
-\&    for (n = 0; n < nfds; ++n)
+\&     for (n = 0; n < nfds; ++n)
-\&      ev_io_stop (EV_A_ iow [n]);
+\&       ev_io_stop (EV_A_ iow [n]);
 \&
-\&    return got_events;
+\&     return got_events;
-\&  }
+\&   }
 .Ve
-.ie n .Sh """ev_embed"" \- when one backend isn't enough..."
+.ie n .SS """ev_embed"" \- when one backend isn't enough..."
-.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..."
+.el .SS "\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).
 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
+so nicely. In this case, you would create a kqueue-based loop and embed
-into your default loop (which might use e.g. poll). Overall operation will
+it into your default loop (which might use e.g. poll). Overall operation
-be a bit slower because first libev has to poll and then call kevent, but
+will be a bit slower because first libev has to call \f(CW\*(C`poll\*(C'\fR and then
-at least you can use both at what they are best.
+\&\f(CW\*(C`kevent\*(C'\fR, but at least you can use both mechanisms for what they are
+best: \f(CW\*(C`kqueue\*(C'\fR for scalable sockets and \f(CW\*(C`poll\*(C'\fR if you want it to work :)
 .PP
-As for prioritising I/O: rarely you have the case where some fds have
+As for prioritising I/O: under rare circumstances you have the case where
-to be watched and handled very quickly (with low latency), and even
+some fds have to be watched and handled very quickly (with low latency),
-priorities and idle watchers might have too much overhead. In this case
+and even priorities and idle watchers might have too much overhead. In
-you would put all the high priority stuff in one loop and all the rest in
+this case you would put all the high priority stuff in one loop and all
-a second one, and embed the second one in the first.
+the rest in a second one, and embed the second one in the first.
 .PP
-As long as the watcher is active, the callback will be invoked every time
+As long as the watcher is active, the callback will be invoked every
-there might be events pending in the embedded loop. The callback must then
+time there might be events pending in the embedded loop. The callback
-call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single sweep and invoke
+must then call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single
-their callbacks (you could also start an idle watcher to give the embedded
+sweep and invoke their callbacks (the callback doesn't need to invoke the
-loop strictly lower priority for example). You can also set the callback
+\&\f(CW\*(C`ev_embed_sweep\*(C'\fR function directly, it could also start an idle watcher
-to \f(CW0\fR, in which case the embed watcher will automatically execute the
+to give the embedded loop strictly lower priority for example).
-embedded loop sweep.
 .PP
-As long as the watcher is started it will automatically handle events. The
+You can also set the callback to \f(CW0\fR, in which case the embed watcher
-callback will be invoked whenever some events have been handled. You can
+will automatically execute the embedded loop sweep whenever necessary.
-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:
+Fork detection will be handled transparently while the \f(CW\*(C`ev_embed\*(C'\fR watcher
-when you fork, you not only have to call \f(CW\*(C`ev_loop_fork\*(C'\fR on both loops,
+is active, i.e., the embedded loop will automatically be forked when the
-but you will also have to stop and restart any \f(CW\*(C`ev_embed\*(C'\fR watchers
+embedding loop forks. In other cases, the user is responsible for calling
-yourself.
+\&\f(CW\*(C`ev_loop_fork\*(C'\fR on the embedded loop.
 .PP
-Unfortunately, not all backends are embeddable, only the ones returned by
+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
+\fI\f(CI\*(C`ev_embed\*(C'\fI and fork\fR
+.IX Subsection "ev_embed and fork"
+.PP
+While the \f(CW\*(C`ev_embed\*(C'\fR watcher is running, forks in the embedding loop will
+automatically be applied to the embedded loop as well, so no special
+fork handling is required in that case. When the watcher is not running,
+however, it is still the task of the libev user to call \f(CW\*(C`ev_loop_fork ()\*(C'\fR
+as applicable.
 .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
+.IP "ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)" 4
-.IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)"
+.IX Item "ev_embed_set (ev_embed *, 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).
+if you do not want that, 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
+similarly to \f(CW\*(C`ev_run (embedded_loop, EVRUN_NOWAIT)\*(C'\fR, but in the most
-apropriate way for embedded loops.
+appropriate 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
+loop is stored in \f(CW\*(C`loop_hi\*(C'\fR, while the embeddable 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
+\&\f(CW\*(C`loop_lo\*(C'\fR (which is \f(CW\*(C`loop_hi\*(C'\fR in the case no embeddable loop can be
 used).
 .PP
 .Vb 3
-\&  struct ev_loop *loop_hi = ev_default_init (0);
+\&   struct ev_loop *loop_hi = ev_default_init (0);
-\&  struct ev_loop *loop_lo = 0;
+\&   struct ev_loop *loop_lo = 0;
-\&  struct ev_embed embed;
+\&   ev_embed embed;
 \&
-\&  // see if there is a chance of getting one that works
+\&   // see if there is a chance of getting one that works
-\&  // (remember that a flags value of 0 means autodetection)
+\&   // (remember that a flags value of 0 means autodetection)
-\&  loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
+\&   loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
-\&    ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
+\&     ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
-\&    : 0;
+\&     : 0;
 \&
-\&  // if we got one, then embed it, otherwise default to loop_hi
+\&   // if we got one, then embed it, otherwise default to loop_hi
-\&  if (loop_lo)
+\&   if (loop_lo)
-\&    {
+\&     {
-\&      ev_embed_init (&embed, 0, loop_lo);
+\&       ev_embed_init (&embed, 0, loop_lo);
-\&      ev_embed_start (loop_hi, &embed);
+\&       ev_embed_start (loop_hi, &embed);
-\&    }
+\&     }
-\&  else
+\&   else
-\&    loop_lo = loop_hi;
+\&     loop_lo = loop_hi;
 .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 = ev_default_init (0);
-\&  struct ev_loop *loop_socket = 0;
+\&   struct ev_loop *loop_socket = 0;
-\&  struct ev_embed embed;
+\&   ev_embed embed;
 \&
-\&  if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
+\&   if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
-\&    if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
+\&     if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
-\&      {
+\&       {
-\&        ev_embed_init (&embed, 0, loop_socket);
+\&         ev_embed_init (&embed, 0, loop_socket);
-\&        ev_embed_start (loop, &embed);
+\&         ev_embed_start (loop, &embed);
-\&      }
+\&       }
 \&
-\&  if (!loop_socket)
+\&   if (!loop_socket)
-\&    loop_socket = loop;
+\&     loop_socket = loop;
 \&
-\&  // now use loop_socket for all sockets, and loop for everything else
+\&   // now use loop_socket for all sockets, and loop for everything else
 .Ve
-.ie n .Sh """ev_fork"" \- the audacity to resume the event loop after a fork"
+.ie n .SS """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"
+.el .SS "\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
+\&\f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the event loop blocks next
-event loop blocks next and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called,
+and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called, and only in the child
-and only in the child after the fork. If whoever good citizen calling
+after the fork. If whoever good citizen calling \f(CW\*(C`ev_default_fork\*(C'\fR cheats
-\&\f(CW\*(C`ev_default_fork\*(C'\fR cheats and calls it in the wrong process, the fork
+and calls it in the wrong process, the fork handlers will be invoked, too,
-handlers will be invoked, too, of course.
+of course.
+.PP
+\fIThe special problem of life after fork \- how is it possible?\fR
+.IX Subsection "The special problem of life after fork - how is it possible?"
+.PP
+Most uses of \f(CW\*(C`fork ()\*(C'\fR consist of forking, then some simple calls to set
+up/change the process environment, followed by a call to \f(CW\*(C`exec()\*(C'\fR. This
+sequence should be handled by libev without any problems.
+.PP
+This changes when the application actually wants to do event handling
+in the child, or both parent in child, in effect \*(L"continuing\*(R" after the
+fork.
+.PP
+The default mode of operation (for libev, with application help to detect
+forks) is to duplicate all the state in the child, as would be expected
+when \fIeither\fR the parent \fIor\fR the child process continues.
+.PP
+When both processes want to continue using libev, then this is usually the
+wrong result. In that case, usually one process (typically the parent) is
+supposed to continue with all watchers in place as before, while the other
+process typically wants to start fresh, i.e. without any active watchers.
+.PP
+The cleanest and most efficient way to achieve that with libev is to
+simply create a new event loop, which of course will be \*(L"empty\*(R", and
+use that for new watchers. This has the advantage of not touching more
+memory than necessary, and thus avoiding the copy-on-write, and the
+disadvantage of having to use multiple event loops (which do not support
+signal watchers).
+.PP
+When this is not possible, or you want to use the default loop for
+other reasons, then in the process that wants to start \*(L"fresh\*(R", call
+\&\f(CW\*(C`ev_loop_destroy (EV_DEFAULT)\*(C'\fR followed by \f(CW\*(C`ev_default_loop (...)\*(C'\fR.
+Destroying the default loop will \*(L"orphan\*(R" (not stop) all registered
+watchers, so you have to be careful not to execute code that modifies
+those watchers. Note also that in that case, you have to re-register any
+signal watchers.
 .PP
 \fIWatcher-Specific Functions and Data Members\fR
 .IX Subsection "Watcher-Specific Functions and Data Members"
-.IP "ev_fork_init (ev_signal *, callback)" 4
+.IP "ev_fork_init (ev_fork *, callback)" 4
-.IX Item "ev_fork_init (ev_signal *, callback)"
+.IX Item "ev_fork_init (ev_fork *, 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.
+really.
+.ie n .SS """ev_cleanup"" \- even the best things end"
+.el .SS "\f(CWev_cleanup\fP \- even the best things end"
+.IX Subsection "ev_cleanup - even the best things end"
+Cleanup watchers are called just before the event loop is being destroyed
+by a call to \f(CW\*(C`ev_loop_destroy\*(C'\fR.
+.PP
+While there is no guarantee that the event loop gets destroyed, cleanup
+watchers provide a convenient method to install cleanup hooks for your
+program, worker threads and so on \- you just to make sure to destroy the
+loop when you want them to be invoked.
+.PP
+Cleanup watchers are invoked in the same way as any other watcher. Unlike
+all other watchers, they do not keep a reference to the event loop (which
+makes a lot of sense if you think about it). Like all other watchers, you
+can call libev functions in the callback, except \f(CW\*(C`ev_cleanup_start\*(C'\fR.
+.PP
+\fIWatcher-Specific Functions and Data Members\fR
+.IX Subsection "Watcher-Specific Functions and Data Members"
+.IP "ev_cleanup_init (ev_cleanup *, callback)" 4
+.IX Item "ev_cleanup_init (ev_cleanup *, callback)"
+Initialises and configures the cleanup watcher \- it has no parameters of
+any kind. There is a \f(CW\*(C`ev_cleanup_set\*(C'\fR macro, but using it is utterly
+pointless, I assure you.
+.PP
+Example: Register an atexit handler to destroy the default loop, so any
+cleanup functions are called.
+.PP
+.Vb 5
+\&   static void
+\&   program_exits (void)
+\&   {
+\&     ev_loop_destroy (EV_DEFAULT_UC);
+\&   }
+\&
+\&   ...
+\&   atexit (program_exits);
+.Ve
-.ie n .Sh """ev_async"" \- how to wake up another event loop"
+.ie n .SS """ev_async"" \- how to wake up an event loop"
-.el .Sh "\f(CWev_async\fP \- how to wake up another event loop"
+.el .SS "\f(CWev_async\fP \- how to wake up an event loop"
-.IX Subsection "ev_async - how to wake up another event loop"
+.IX Subsection "ev_async - how to wake up an 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
+Sometimes, however, you need to wake up an event loop you do not control,
-control, for example because it belongs to another thread. This is what
+for example because it belongs to another thread. This is what \f(CW\*(C`ev_async\*(C'\fR
-\&\f(CW\*(C`ev_async\*(C'\fR watchers do: as long as the \f(CW\*(C`ev_async\*(C'\fR watcher is active, you
+watchers do: as long as the \f(CW\*(C`ev_async\*(C'\fR watcher is active, you can signal
-can signal it by calling \f(CW\*(C`ev_async_send\*(C'\fR, which is thread\- and signal
+it by calling \f(CW\*(C`ev_async_send\*(C'\fR, which is thread\- and signal safe.
-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).
+\&\f(CW\*(C`ev_async_send\*(C'\fR calls). In fact, you could use signal watchers as a kind
-.PP
+of \*(L"global async watchers\*(R" by using a watcher on an otherwise unused
-Unlike \f(CW\*(C`ev_signal\*(C'\fR watchers, \f(CW\*(C`ev_async\*(C'\fR works with any event loop, not
+signal, and \f(CW\*(C`ev_feed_signal\*(C'\fR to signal this watcher from another thread,
-just the default loop.
+even without knowing which loop owns the signal.
 .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.
+need elaborate support such as pthreads or unportable memory access
+semantics.
 .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. But at least I can tell you how to 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
+handler but you block the signal handler in the watcher callback. Here is
-some fictitiuous \s-1SIGUSR1\s0 handler:
+an example that does that for some fictitious \s-1SIGUSR1\s0 handler:
 .Sp
 .Vb 1
 \&   static ev_async mysig;
 \&
 \&   static void
 \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,
+kind. There is a \f(CW\*(C`ev_async_set\*(C'\fR macro, but using it is utterly pointless,
-believe me.
+trust 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
+an \f(CW\*(C`EV_ASYNC\*(C'\fR event on the watcher into the event loop, and instantly
+returns.
+.Sp
-\&\f(CW\*(C`ev_feed_event\*(C'\fR, this call is safe to do in other threads, signal or
+Unlike \f(CW\*(C`ev_feed_event\*(C'\fR, this call is safe to do from other threads,
-similar contexts (see the dicusssion of \f(CW\*(C`EV_ATOMIC_T\*(C'\fR in the embedding
+signal or similar contexts (see the discussion of \f(CW\*(C`EV_ATOMIC_T\*(C'\fR in the
-section below on what exactly this means).
+embedding section below on what exactly this means).
 .Sp
-This call incurs the overhead of a syscall only once per loop iteration,
+Note that, as with other watchers in libev, multiple events might get
-so while the overhead might be noticable, it doesn't apply to repeated
+compressed into a single callback invocation (another way to look at
-calls to \f(CW\*(C`ev_async_send\*(C'\fR.
+this is that \f(CW\*(C`ev_async\*(C'\fR watchers are level-triggered: they are set on
+\&\f(CW\*(C`ev_async_send\*(C'\fR, reset when the event loop detects that).
+.Sp
+This call incurs the overhead of at most one extra system call per event
+loop iteration, if the event loop is blocked, and no syscall at all if
+the event loop (or your program) is processing events. That means that
+repeated calls are basically free (there is no need to avoid calls for
+performance reasons) and that the overhead becomes smaller (typically
+zero) under load.
+.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 whether invoking the loop might be a good idea.
+.Sp
+Not that this does \fInot\fR check whether the watcher itself is pending,
+only whether it has been requested to make this watcher pending: there
+is a time window between the event loop checking and resetting the async
+notification, and the callback being invoked.
 .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
+.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)" 4
-.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)"
+.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)"
 This function combines a simple timer and an I/O watcher, calls your
-callback on whichever event happens first and automatically stop both
+callback on whichever event happens first and automatically stops both
 watchers. This is useful if you want to wait for a single event on an fd
 or timeout without having to allocate/configure/start/stop/free one or
 more watchers yourself.
 .Sp
-If \f(CW\*(C`fd\*(C'\fR is less than 0, then no I/O watcher will be started and events
+If \f(CW\*(C`fd\*(C'\fR is less than 0, then no I/O watcher will be started and the
-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 argument is being ignored. Otherwise, an \f(CW\*(C`ev_io\*(C'\fR watcher for
-\&\f(CW\*(C`events\*(C'\fR set will be craeted and started.
+the given \f(CW\*(C`fd\*(C'\fR and \f(CW\*(C`events\*(C'\fR set will be created 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
+repeat = 0) will be started. \f(CW0\fR is a valid timeout.
-dubious value.
 .Sp
-The callback has the type \f(CW\*(C`void (*cb)(int revents, void *arg)\*(C'\fR and gets
+The callback has the type \f(CW\*(C`void (*cb)(int revents, void *arg)\*(C'\fR and is
 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
+\&\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_TIMER\*(C'\fR) and the \f(CW\*(C`arg\*(C'\fR
-value passed to \f(CW\*(C`ev_once\*(C'\fR:
+value passed to \f(CW\*(C`ev_once\*(C'\fR. Note that it is possible to receive \fIboth\fR
+a timeout and an io event at the same time \- you probably should give io
+events precedence.
+.Sp
+Example: wait up to ten seconds for data to appear on \s-1STDIN_FILENO.\s0
 .Sp
 .Vb 7
-\&  static void stdin_ready (int revents, void *arg)
+\&   static void stdin_ready (int revents, void *arg)
+\&   {
+\&     if (revents & EV_READ)
+\&       /* stdin might have data for us, joy! */;
+\&     else if (revents & EV_TIMER)
+\&       /* doh, nothing entered */;
+\&   }
+\&
+\&   ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
+.Ve
+.IP "ev_feed_fd_event (loop, int fd, int revents)" 4
+.IX Item "ev_feed_fd_event (loop, int fd, int revents)"
+Feed an event on the given fd, as if a file descriptor backend detected
+the given events.
+.IP "ev_feed_signal_event (loop, int signum)" 4
+.IX Item "ev_feed_signal_event (loop, int signum)"
+Feed an event as if the given signal occurred. See also \f(CW\*(C`ev_feed_signal\*(C'\fR,
+which is async-safe.
+.SH "COMMON OR USEFUL IDIOMS (OR BOTH)"
+.IX Header "COMMON OR USEFUL IDIOMS (OR BOTH)"
+This section explains some common idioms that are not immediately
+obvious. Note that examples are sprinkled over the whole manual, and this
+section only contains stuff that wouldn't fit anywhere else.
+.SS "\s-1ASSOCIATING CUSTOM DATA WITH A WATCHER\s0"
+.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER"
+Each watcher has, by default, a \f(CW\*(C`void *data\*(C'\fR member that you can read
+or modify 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 separately 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
+\&   {
+\&     ev_io io;
+\&     int otherfd;
+\&     void *somedata;
+\&     struct whatever *mostinteresting;
+\&   };
+\&
+\&   ...
+\&   struct my_io w;
+\&   ev_io_init (&w.io, my_cb, fd, EV_READ);
+.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, 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
+function type instead have been omitted.
+.SS "\s-1BUILDING YOUR OWN COMPOSITE WATCHERS\s0"
+.IX Subsection "BUILDING YOUR OWN COMPOSITE WATCHERS"
+Another common scenario is to use some data structure with multiple
+embedded watchers, in effect creating your own watcher that combines
+multiple libev event sources into one \*(L"super-watcher\*(R":
+.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: Either you store the address of your \f(CW\*(C`my_biggy\*(C'\fR struct in
+the \f(CW\*(C`data\*(C'\fR member of the watcher (for woozies or \*(C+ coders), or you need
+to use some pointer arithmetic using \f(CW\*(C`offsetof\*(C'\fR inside your watchers (for
+real programmers):
+.PP
+.Vb 1
+\&   #include <stddef.h>
+\&
+\&   static void
+\&   t1_cb (EV_P_ 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_ ev_timer *w, int revents)
+\&   {
+\&     struct my_biggy big = (struct my_biggy *)
+\&       (((char *)w) \- offsetof (struct my_biggy, t2));
+\&   }
+.Ve
+.SS "\s-1AVOIDING FINISHING BEFORE RETURNING\s0"
+.IX Subsection "AVOIDING FINISHING BEFORE RETURNING"
+Often you have structures like this in event-based programs:
+.PP
+.Vb 4
+\&  callback ()
 \&  {
-\&    if (revents & EV_TIMEOUT)
+\&    free (request);
-\&      /* 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);
+\&  request = start_new_request (..., callback);
 .Ve
-.IP "ev_feed_event (ev_loop *, watcher *, int revents)" 4
+.PP
-.IX Item "ev_feed_event (ev_loop *, watcher *, int revents)"
+The intent is to start some \*(L"lengthy\*(R" operation. The \f(CW\*(C`request\*(C'\fR could be
-Feeds the given event set into the event loop, as if the specified event
+used to cancel the operation, or do other things with it.
-had happened for the specified watcher (which must be a pointer to an
+.PP
-initialised but not necessarily started event watcher).
+It's not uncommon to have code paths in \f(CW\*(C`start_new_request\*(C'\fR that
-.IP "ev_feed_fd_event (ev_loop *, int fd, int revents)" 4
+immediately invoke the callback, for example, to report errors. Or you add
-.IX Item "ev_feed_fd_event (ev_loop *, int fd, int revents)"
+some caching layer that finds that it can skip the lengthy aspects of the
-Feed an event on the given fd, as if a file descriptor backend detected
+operation and simply invoke the callback with the result.
-the given events it.
+.PP
-.IP "ev_feed_signal_event (ev_loop *loop, int signum)" 4
+The problem here is that this will happen \fIbefore\fR \f(CW\*(C`start_new_request\*(C'\fR
-.IX Item "ev_feed_signal_event (ev_loop *loop, int signum)"
+has returned, so \f(CW\*(C`request\*(C'\fR is not set.
-Feed an event as if the given signal occured (\f(CW\*(C`loop\*(C'\fR must be the default
+.PP
-loop!).
+Even if you pass the request by some safer means to the callback, you
+might want to do something to the request after starting it, such as
+canceling it, which probably isn't working so well when the callback has
+already been invoked.
+.PP
+A common way around all these issues is to make sure that
+\&\f(CW\*(C`start_new_request\*(C'\fR \fIalways\fR returns before the callback is invoked. If
+\&\f(CW\*(C`start_new_request\*(C'\fR immediately knows the result, it can artificially
+delay invoking the callback by using a \f(CW\*(C`prepare\*(C'\fR or \f(CW\*(C`idle\*(C'\fR watcher for
+example, or more sneakily, by reusing an existing (stopped) watcher and
+pushing it into the pending queue:
+.PP
+.Vb 2
+\&   ev_set_cb (watcher, callback);
+\&   ev_feed_event (EV_A_ watcher, 0);
+.Ve
+.PP
+This way, \f(CW\*(C`start_new_request\*(C'\fR can safely return before the callback is
+invoked, while not delaying callback invocation too much.
+.SS "\s-1MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS\s0"
+.IX Subsection "MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS"
+Often (especially in \s-1GUI\s0 toolkits) there are places where you have
+\&\fImodal\fR interaction, which is most easily implemented by recursively
+invoking \f(CW\*(C`ev_run\*(C'\fR.
+.PP
+This brings the problem of exiting \- a callback might want to finish the
+main \f(CW\*(C`ev_run\*(C'\fR call, but not the nested one (e.g. user clicked \*(L"Quit\*(R", but
+a modal \*(L"Are you sure?\*(R" dialog is still waiting), or just the nested one
+and not the main one (e.g. user clocked \*(L"Ok\*(R" in a modal dialog), or some
+other combination: In these cases, a simple \f(CW\*(C`ev_break\*(C'\fR will not work.
+.PP
+The solution is to maintain \*(L"break this loop\*(R" variable for each \f(CW\*(C`ev_run\*(C'\fR
+invocation, and use a loop around \f(CW\*(C`ev_run\*(C'\fR until the condition is
+triggered, using \f(CW\*(C`EVRUN_ONCE\*(C'\fR:
+.PP
+.Vb 2
+\&   // main loop
+\&   int exit_main_loop = 0;
+\&
+\&   while (!exit_main_loop)
+\&     ev_run (EV_DEFAULT_ EVRUN_ONCE);
+\&
+\&   // in a modal watcher
+\&   int exit_nested_loop = 0;
+\&
+\&   while (!exit_nested_loop)
+\&     ev_run (EV_A_ EVRUN_ONCE);
+.Ve
+.PP
+To exit from any of these loops, just set the corresponding exit variable:
+.PP
+.Vb 2
+\&   // exit modal loop
+\&   exit_nested_loop = 1;
+\&
+\&   // exit main program, after modal loop is finished
+\&   exit_main_loop = 1;
+\&
+\&   // exit both
+\&   exit_main_loop = exit_nested_loop = 1;
+.Ve
+.SS "\s-1THREAD LOCKING EXAMPLE\s0"
+.IX Subsection "THREAD LOCKING EXAMPLE"
+Here is a fictitious example of how to run an event loop in a different
+thread from where callbacks are being invoked and watchers are
+created/added/removed.
+.PP
+For a real-world example, see the \f(CW\*(C`EV::Loop::Async\*(C'\fR perl module,
+which uses exactly this technique (which is suited for many high-level
+languages).
+.PP
+The example uses a pthread mutex to protect the loop data, a condition
+variable to wait for callback invocations, an async watcher to notify the
+event loop thread and an unspecified mechanism to wake up the main thread.
+.PP
+First, you need to associate some data with the event loop:
+.PP
+.Vb 6
+\&   typedef struct {
+\&     pthread_mutex_t lock; /* global loop lock */
+\&     pthread_t tid;
+\&     pthread_cond_t invoke_cv;
+\&     ev_async async_w;
+\&   } userdata;
+\&
+\&   void prepare_loop (EV_P)
+\&   {
+\&      // for simplicity, we use a static userdata struct.
+\&      static userdata u;
+\&
+\&      ev_async_init (&u.async_w, async_cb);
+\&      ev_async_start (EV_A_ &u.async_w);
+\&
+\&      pthread_mutex_init (&u.lock, 0);
+\&      pthread_cond_init (&u.invoke_cv, 0);
+\&
+\&      // now associate this with the loop
+\&      ev_set_userdata (EV_A_ &u);
+\&      ev_set_invoke_pending_cb (EV_A_ l_invoke);
+\&      ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
+\&
+\&      // then create the thread running ev_run
+\&      pthread_create (&u.tid, 0, l_run, EV_A);
+\&   }
+.Ve
+.PP
+The callback for the \f(CW\*(C`ev_async\*(C'\fR watcher does nothing: the watcher is used
+solely to wake up the event loop so it takes notice of any new watchers
+that might have been added:
+.PP
+.Vb 5
+\&   static void
+\&   async_cb (EV_P_ ev_async *w, int revents)
+\&   {
+\&      // just used for the side effects
+\&   }
+.Ve
+.PP
+The \f(CW\*(C`l_release\*(C'\fR and \f(CW\*(C`l_acquire\*(C'\fR callbacks simply unlock/lock the mutex
+protecting the loop data, respectively.
+.PP
+.Vb 6
+\&   static void
+\&   l_release (EV_P)
+\&   {
+\&     userdata *u = ev_userdata (EV_A);
+\&     pthread_mutex_unlock (&u\->lock);
+\&   }
+\&
+\&   static void
+\&   l_acquire (EV_P)
+\&   {
+\&     userdata *u = ev_userdata (EV_A);
+\&     pthread_mutex_lock (&u\->lock);
+\&   }
+.Ve
+.PP
+The event loop thread first acquires the mutex, and then jumps straight
+into \f(CW\*(C`ev_run\*(C'\fR:
+.PP
+.Vb 4
+\&   void *
+\&   l_run (void *thr_arg)
+\&   {
+\&     struct ev_loop *loop = (struct ev_loop *)thr_arg;
+\&
+\&     l_acquire (EV_A);
+\&     pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
+\&     ev_run (EV_A_ 0);
+\&     l_release (EV_A);
+\&
+\&     return 0;
+\&   }
+.Ve
+.PP
+Instead of invoking all pending watchers, the \f(CW\*(C`l_invoke\*(C'\fR callback will
+signal the main thread via some unspecified mechanism (signals? pipe
+writes? \f(CW\*(C`Async::Interrupt\*(C'\fR?) and then waits until all pending watchers
+have been called (in a while loop because a) spurious wakeups are possible
+and b) skipping inter-thread-communication when there are no pending
+watchers is very beneficial):
+.PP
+.Vb 4
+\&   static void
+\&   l_invoke (EV_P)
+\&   {
+\&     userdata *u = ev_userdata (EV_A);
+\&
+\&     while (ev_pending_count (EV_A))
+\&       {
+\&         wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
+\&         pthread_cond_wait (&u\->invoke_cv, &u\->lock);
+\&       }
+\&   }
+.Ve
+.PP
+Now, whenever the main thread gets told to invoke pending watchers, it
+will grab the lock, call \f(CW\*(C`ev_invoke_pending\*(C'\fR and then signal the loop
+thread to continue:
+.PP
+.Vb 4
+\&   static void
+\&   real_invoke_pending (EV_P)
+\&   {
+\&     userdata *u = ev_userdata (EV_A);
+\&
+\&     pthread_mutex_lock (&u\->lock);
+\&     ev_invoke_pending (EV_A);
+\&     pthread_cond_signal (&u\->invoke_cv);
+\&     pthread_mutex_unlock (&u\->lock);
+\&   }
+.Ve
+.PP
+Whenever you want to start/stop a watcher or do other modifications to an
+event loop, you will now have to lock:
+.PP
+.Vb 2
+\&   ev_timer timeout_watcher;
+\&   userdata *u = ev_userdata (EV_A);
+\&
+\&   ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
+\&
+\&   pthread_mutex_lock (&u\->lock);
+\&   ev_timer_start (EV_A_ &timeout_watcher);
+\&   ev_async_send (EV_A_ &u\->async_w);
+\&   pthread_mutex_unlock (&u\->lock);
+.Ve
+.PP
+Note that sending the \f(CW\*(C`ev_async\*(C'\fR watcher is required because otherwise
+an event loop currently blocking in the kernel will have no knowledge
+about the newly added timer. By waking up the loop it will pick up any new
+watchers in the next event loop iteration.
+.SS "\s-1THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS\s0"
+.IX Subsection "THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS"
+While the overhead of a callback that e.g. schedules a thread is small, it
+is still an overhead. If you embed libev, and your main usage is with some
+kind of threads or coroutines, you might want to customise libev so that
+doesn't need callbacks anymore.
+.PP
+Imagine you have coroutines that you can switch to using a function
+\&\f(CW\*(C`switch_to (coro)\*(C'\fR, that libev runs in a coroutine called \f(CW\*(C`libev_coro\*(C'\fR
+and that due to some magic, the currently active coroutine is stored in a
+global called \f(CW\*(C`current_coro\*(C'\fR. Then you can build your own \*(L"wait for libev
+event\*(R" primitive by changing \f(CW\*(C`EV_CB_DECLARE\*(C'\fR and \f(CW\*(C`EV_CB_INVOKE\*(C'\fR (note
+the differing \f(CW\*(C`;\*(C'\fR conventions):
+.PP
+.Vb 2
+\&   #define EV_CB_DECLARE(type)   struct my_coro *cb;
+\&   #define EV_CB_INVOKE(watcher) switch_to ((watcher)\->cb)
+.Ve
+.PP
+That means instead of having a C callback function, you store the
+coroutine to switch to in each watcher, and instead of having libev call
+your callback, you instead have it switch to that coroutine.
+.PP
+A coroutine might now wait for an event with a function called
+\&\f(CW\*(C`wait_for_event\*(C'\fR. (the watcher needs to be started, as always, but it doesn't
+matter when, or whether the watcher is active or not when this function is
+called):
+.PP
+.Vb 6
+\&   void
+\&   wait_for_event (ev_watcher *w)
+\&   {
+\&     ev_set_cb (w, current_coro);
+\&     switch_to (libev_coro);
+\&   }
+.Ve
+.PP
+That basically suspends the coroutine inside \f(CW\*(C`wait_for_event\*(C'\fR and
+continues the libev coroutine, which, when appropriate, switches back to
+this or any other coroutine.
+.PP
+You can do similar tricks if you have, say, threads with an event queue \-
+instead of storing a coroutine, you store the queue object and instead of
+switching to a coroutine, you push the watcher onto the queue and notify
+any waiters.
+.PP
+To embed libev, see \*(L"\s-1EMBEDDING\*(R"\s0, but in short, it's easiest to create two
+files, \fImy_ev.h\fR and \fImy_ev.c\fR that include the respective libev files:
+.PP
+.Vb 4
+\&   // my_ev.h
+\&   #define EV_CB_DECLARE(type)   struct my_coro *cb;
+\&   #define EV_CB_INVOKE(watcher) switch_to ((watcher)\->cb)
+\&   #include "../libev/ev.h"
+\&
+\&   // my_ev.c
+\&   #define EV_H "my_ev.h"
+\&   #include "../libev/ev.c"
+.Ve
+.PP
+And then use \fImy_ev.h\fR when you would normally use \fIev.h\fR, and compile
+\&\fImy_ev.c\fR into your project. When properly specifying include paths, you
+can even use \fIev.h\fR as header file name directly.
 .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
+Only the libevent\-1.4.1\-beta \s-1API\s0 is being emulated.
+.Sp
+This was the newest libevent version available when libev was implemented,
+and is still mostly unchanged in 2010.
 .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
 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
+base that registered the signal 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"
+.SS "C \s-1API\s0"
+.IX Subsection "C API"
+The normal C \s-1API\s0 should work fine when used from \*(C+: both ev.h and the
+libev sources can be compiled as \*(C+. Therefore, code that uses the C \s-1API\s0
+will work fine.
+.PP
+Proper exception specifications might have to be added to callbacks passed
+to libev: exceptions may be thrown only from watcher callbacks, all other
+callbacks (allocator, syserr, loop acquire/release and periodic reschedule
+callbacks) must not throw exceptions, and might need a \f(CW\*(C`noexcept\*(C'\fR
+specification. If you have code that needs to be compiled as both C and
+\&\*(C+ you can use the \f(CW\*(C`EV_NOEXCEPT\*(C'\fR macro for this:
+.PP
+.Vb 6
+\&   static void
+\&   fatal_error (const char *msg) EV_NOEXCEPT
+\&   {
+\&     perror (msg);
+\&     abort ();
+\&   }
+\&
+\&   ...
+\&   ev_set_syserr_cb (fatal_error);
+.Ve
+.PP
+The only \s-1API\s0 functions that can currently throw exceptions are \f(CW\*(C`ev_run\*(C'\fR,
+\&\f(CW\*(C`ev_invoke\*(C'\fR, \f(CW\*(C`ev_invoke_pending\*(C'\fR and \f(CW\*(C`ev_loop_destroy\*(C'\fR (the latter
+because it runs cleanup watchers).
+.PP
+Throwing exceptions in watcher callbacks is only supported if libev itself
+is compiled with a \*(C+ compiler or your C and \*(C+ environments allow
+throwing exceptions through C libraries (most do).
+.SS "\*(C+ \s-1API\s0"
+.IX Subsection " API"
 Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow
-you to use some convinience methods to start/stop watchers and also change
+you to use some convenience methods to start/stop watchers and also change
 the callback model to a model using method callbacks on objects.
 .PP
 To use it,
 .PP
 .Vb 1
-\&  #include <ev++.h>
+\&   #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
 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
+Currently, functions, static and non-static member functions and classes
-used as callbacks. Other types should be easy to add as long as they only
+with \f(CW\*(C`operator ()\*(C'\fR can be used as callbacks. Other types should be easy
-need one additional pointer for context. If you need support for other
+to add as long as they only need one additional pointer for context. If
-types of functors please contact the author (preferably after implementing
+you need support for other types of functors please contact the author
-it).
+(preferably after implementing it).
+.PP
+For all this to work, your \*(C+ compiler either has to use the same calling
+conventions as your C compiler (for static member functions), or you have
+to embed libev and compile libev itself as \*(C+.
 .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
+.ie n .IP """ev::READ"", ""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
+.ie n .IP """ev::tstamp"", ""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
+.ie n .IP """ev::io"", ""ev::timer"", ""ev::periodic"", ""ev::idle"", ""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.
+defined 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
+.IP "ev::TYPE::TYPE (loop)" 4
-.IX Item "ev::TYPE::TYPE (struct ev_loop *)"
+.IX Item "ev::TYPE::TYPE (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.
 thunking function, making it as fast as a direct C callback.
 .Sp
 Example: simple class declaration and watcher initialisation
 .Sp
 .Vb 4
-\&  struct myclass
+\&   struct myclass
-\&  {
+\&   {
-\&    void io_cb (ev::io &w, int revents) { }
+\&     void io_cb (ev::io &w, int revents) { }
-\&  }
+\&   }
 \&
-\&  myclass obj;
+\&   myclass obj;
-\&  ev::io iow;
+\&   ev::io iow;
-\&  iow.set <myclass, &myclass::io_cb> (&obj);
+\&   iow.set <myclass, &myclass::io_cb> (&obj);
+.Ve
+.IP "w\->set (object *)" 4
+.IX Item "w->set (object *)"
+This is a variation of a method callback \- leaving out the method to call
+will default the method to \f(CW\*(C`operator ()\*(C'\fR, which makes it possible to use
+functor objects without having to manually specify the \f(CW\*(C`operator ()\*(C'\fR all
+the time. Incidentally, you can then also leave out the template argument
+list.
+.Sp
+The \f(CW\*(C`operator ()\*(C'\fR method prototype must be \f(CW\*(C`void operator ()(watcher &w,
+int revents)\*(C'\fR.
+.Sp
+See the method\-\f(CW\*(C`set\*(C'\fR above for more details.
+.Sp
+Example: use a functor object as callback.
+.Sp
+.Vb 7
+\&   struct myfunctor
+\&   {
+\&     void operator() (ev::io &w, int revents)
+\&     {
+\&       ...
+\&     }
+\&   }
+\&
+\&   myfunctor f;
+\&
+\&   ev::io w;
+\&   w.set (&f);
 .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
 .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:
+Example: Use a plain function as callback.
 .Sp
 .Vb 2
-\&  static void io_cb (ev::io &w, int revents) { }
+\&   static void io_cb (ev::io &w, int revents) { }
-\&  iow.set <io_cb> ();
+\&   iow.set <io_cb> ();
 .Ve
-.IP "w\->set (struct ev_loop *)" 4
+.IP "w\->set (loop)" 4
-.IX Item "w->set (struct ev_loop *)"
+.IX Item "w->set (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
+.IP "w\->set ([arguments])" 4
-.IX Item "w->set ([args])"
+.IX Item "w->set ([arguments])"
-Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same args. Must be
+Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR (except for \f(CW\*(C`ev::embed\*(C'\fR watchers>),
+with the same arguments. Either this method or a suitable start method
-called at least once. Unlike the C counterpart, an active watcher gets
+must be called at least once. Unlike the C counterpart, an active watcher
-automatically stopped and restarted when reconfiguring it with this
+gets automatically stopped and restarted when reconfiguring it with this
 method.
+.Sp
+For \f(CW\*(C`ev::embed\*(C'\fR watchers this method is called \f(CW\*(C`set_embed\*(C'\fR, to avoid
+clashing with the \f(CW\*(C`set (loop)\*(C'\fR method.
+.Sp
+For \f(CW\*(C`ev::io\*(C'\fR watchers there is an additional \f(CW\*(C`set\*(C'\fR method that acepts a
+new event mask only, and internally calls \f(CW\*(C`ev_io_modify\*(C'\fR.
 .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\->start ([arguments])" 4
+.IX Item "w->start ([arguments])"
+Instead of calling \f(CW\*(C`set\*(C'\fR and \f(CW\*(C`start\*(C'\fR methods separately, it is often
+convenient to wrap them in one call. Uses the same type of arguments as
+the configure \f(CW\*(C`set\*(C'\fR method of the watcher.
 .IP "w\->stop ()" 4
 .IX Item "w->stop ()"
 Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument.
-.ie n .IP "w\->again () (""ev::timer""\fR, \f(CW""ev::periodic"" only)" 4
+.ie n .IP "w\->again () (""ev::timer"", ""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
 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
+Example: Define a class with two I/O and idle watchers, start the I/O
-the constructor.
+watchers in the constructor.
 .PP
-.Vb 4
+.Vb 5
-\&  class myclass
+\&   class myclass
-\&  {
+\&   {
-\&    ev::io   io;  void io_cb   (ev::io   &w, int revents);
+\&     ev::io   io  ; void io_cb   (ev::io   &w, int revents);
+\&     ev::io   io2 ; void io2_cb  (ev::io   &w, int revents);
-\&    ev:idle idle  void idle_cb (ev::idle &w, int revents);
+\&     ev::idle idle; void idle_cb (ev::idle &w, int revents);
 \&
-\&    myclass (int fd)
+\&     myclass (int fd)
-\&    {
+\&     {
-\&      io  .set <myclass, &myclass::io_cb  > (this);
+\&       io  .set <myclass, &myclass::io_cb  > (this);
+\&       io2 .set <myclass, &myclass::io2_cb > (this);
-\&      idle.set <myclass, &myclass::idle_cb> (this);
+\&       idle.set <myclass, &myclass::idle_cb> (this);
 \&
-\&      io.start (fd, ev::READ);
+\&       io.set (fd, ev::WRITE); // configure the watcher
+\&       io.start ();            // start it whenever convenient
+\&
+\&       io2.start (fd, ev::READ); // set + start in one call
-\&    }
+\&     }
-\&  };
+\&   };
 .Ve
+.SH "OTHER LANGUAGE BINDINGS"
+.IX Header "OTHER LANGUAGE BINDINGS"
+Libev does not offer other language bindings itself, but bindings for a
+number of languages exist in the form of third-party packages. If you know
+any interesting language binding in addition to the ones listed here, drop
+me a note.
+.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, but \f(CW\*(C`AnyEvent::DNS\*(C'\fR is preferred nowadays),
+\&\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 at
+<http://software.schmorp.de/pkg/EV>.
+.IP "Python" 4
+.IX Item "Python"
+Python bindings can be found at <http://code.google.com/p/pyev/>. It
+seems to be quite complete and well-documented.
+.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 file handle 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/>.
+.Sp
+Roger Pack reports that using the link order \f(CW\*(C`\-lws2_32 \-lmsvcrt\-ruby\-190\*(C'\fR
+makes rev work even on mingw.
+.IP "Haskell" 4
+.IX Item "Haskell"
+A haskell binding to libev is available at
+<http://hackage.haskell.org/cgi\-bin/hackage\-scripts/package/hlibev>.
+.IP "D" 4
+.IX Item "D"
+Leandro Lucarella has written a D language binding (\fIev.d\fR) for libev, to
+be found at <http://www.llucax.com.ar/proj/ev.d/index.html>.
+.IP "Ocaml" 4
+.IX Item "Ocaml"
+Erkki Seppala has written Ocaml bindings for libev, to be found at
+<http://modeemi.cs.tut.fi/~flux/software/ocaml\-ev/>.
+.IP "Lua" 4
+.IX Item "Lua"
+Brian Maher has written a partial interface to libev for lua (at the
+time of this writing, only \f(CW\*(C`ev_io\*(C'\fR and \f(CW\*(C`ev_timer\*(C'\fR), to be found at
+<http://github.com/brimworks/lua\-ev>.
+.IP "Javascript" 4
+.IX Item "Javascript"
+Node.js (<http://nodejs.org>) uses libev as the underlying event library.
+.IP "Others" 4
+.IX Item "Others"
+There are others, and I stopped counting.
 .SH "MACRO MAGIC"
 .IX Header "MACRO MAGIC"
-Libev can be compiled with a variety of options, the most fundamantal
+Libev can be compiled with a variety of options, the most fundamental
 of which is \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
+.ie n .IP """EV_A"", ""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_unref (EV_A);
-\&  ev_timer_add (EV_A_ watcher);
+\&   ev_timer_add (EV_A_ watcher);
-\&  ev_loop (EV_A_ 0);
+\&   ev_run (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
+.ie n .IP """EV_P"", ""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
+\&   // this is how ev_unref is being declared
-\&  static void ev_unref (EV_P);
+\&   static void ev_unref (EV_P);
 \&
-\&  // this is how you can declare your typical callback
+\&   // this is how you can declare your typical callback
-\&  static void cb (EV_P_ ev_timer *w, int revents)
+\&   static void cb (EV_P_ ev_timer *w, int revents)
 .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
+.ie n .IP """EV_DEFAULT"", ""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").
+loop, if multiple loops are supported (\*(L"ev loop default\*(R"). The default loop
+will be initialised if it isn't already initialised.
+.Sp
+For non-multiplicity builds, these macros do nothing, so you always have
+to initialise the loop somewhere.
+.ie n .IP """EV_DEFAULT_UC"", ""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
+\&   static void
-\&  check_cb (EV_P_ ev_timer *w, int revents)
+\&   check_cb (EV_P_ ev_timer *w, int revents)
-\&  {
+\&   {
-\&    ev_check_stop (EV_A_ w);
+\&     ev_check_stop (EV_A_ w);
-\&  }
+\&   }
 \&
-\&  ev_check check;
+\&   ev_check check;
-\&  ev_check_init (&check, check_cb);
+\&   ev_check_init (&check, check_cb);
-\&  ev_check_start (EV_DEFAULT_ &check);
+\&   ev_check_start (EV_DEFAULT_ &check);
-\&  ev_loop (EV_DEFAULT_ 0);
+\&   ev_run (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
 .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"
+.SS "\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.
+in your application.
 .PP
-\fI\s-1CORE\s0 \s-1EVENT\s0 \s-1LOOP\s0\fR
+\fI\s-1CORE EVENT LOOP\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
+\&   #define EV_STANDALONE 1
-\&  #include "ev.c"
+\&   #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
+\&   #define EV_STANDALONE 1
-\&  #include "ev.h"
+\&   #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
+compiler (at least, that's 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.h
-\&  ev.c
+\&   ev.c
-\&  ev_vars.h
+\&   ev_vars.h
-\&  ev_wrap.h
+\&   ev_wrap.h
 \&
-\&  ev_win32.c      required on win32 platforms only
+\&   ev_win32.c      required on win32 platforms only
 \&
-\&  ev_select.c     only when select backend is enabled (which is enabled by default)
+\&   ev_select.c     only when select backend is enabled
-\&  ev_poll.c       only when poll backend is enabled (disabled by default)
+\&   ev_poll.c       only when poll backend is enabled
-\&  ev_epoll.c      only when the epoll backend is enabled (disabled by default)
+\&   ev_epoll.c      only when the epoll backend is enabled
+\&   ev_linuxaio.c   only when the linux aio backend is enabled
+\&   ev_iouring.c    only when the linux io_uring backend is enabled
-\&  ev_kqueue.c     only when the kqueue backend is enabled (disabled by default)
+\&   ev_kqueue.c     only when the kqueue backend is enabled
-\&  ev_port.c       only when the solaris port backend is enabled (disabled by default)
+\&   ev_port.c       only when the solaris port backend is enabled
 .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
+\fI\s-1LIBEVENT COMPATIBILITY API\s0\fR
 .IX Subsection "LIBEVENT COMPATIBILITY API"
 .PP
-To include the libevent compatibility \s-1API\s0, also include:
+To include the libevent compatibility \s-1API,\s0 also include:
 .PP
 .Vb 1
-\&  #include "event.c"
+\&   #include "event.c"
 .Ve
 .PP
 in the file including \fIev.c\fR, and:
 .PP
 .Vb 1
-\&  #include "event.h"
+\&   #include "event.h"
 .Ve
 .PP
-in the files that want to use the libevent \s-1API\s0. This also includes \fIev.h\fR.
+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.h
-\&  event.c
+\&   event.c
 .Ve
 .PP
-\fI\s-1AUTOCONF\s0 \s-1SUPPORT\s0\fR
+\fI\s-1AUTOCONF SUPPORT\s0\fR
 .IX Subsection "AUTOCONF SUPPORT"
 .PP
-Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your config in
+Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your configuration 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
+\&   libev.m4
 .Ve
-.Sh "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0"
+.SS "\s-1PREPROCESSOR SYMBOLS/MACROS\s0"
 .IX Subsection "PREPROCESSOR SYMBOLS/MACROS"
-Libev can be configured via a variety of preprocessor symbols you have to define
+Libev can be configured via a variety of preprocessor symbols you have to
-before including any of its files. The default is not to build for multiplicity
+define before including (or compiling) any of its files. The default in
-and only include the select backend.
+the absence of autoconf is documented for every option.
+.PP
+Symbols marked with \*(L"(h)\*(R" do not change the \s-1ABI,\s0 and can have different
+values when compiling libev vs. including \fIev.h\fR, so it is permissible
+to redefine them before including \fIev.h\fR without breaking compatibility
+to a compiled library. All other symbols change the \s-1ABI,\s0 which means all
+users of libev and the libev code itself must be compiled with compatible
+settings.
+.IP "\s-1EV_COMPAT3\s0 (h)" 4
+.IX Item "EV_COMPAT3 (h)"
+Backwards compatibility is a major concern for libev. This is why this
+release of libev comes with wrappers for the functions and symbols that
+have been renamed between libev version 3 and 4.
+.Sp
+You can disable these wrappers (to test compatibility with future
+versions) by defining \f(CW\*(C`EV_COMPAT3\*(C'\fR to \f(CW0\fR when compiling your
+sources. This has the additional advantage that you can drop the \f(CW\*(C`struct\*(C'\fR
+from \f(CW\*(C`struct ev_loop\*(C'\fR declarations, as libev will provide an \f(CW\*(C`ev_loop\*(C'\fR
+typedef in that case.
+.Sp
+In some future version, the default for \f(CW\*(C`EV_COMPAT3\*(C'\fR will become \f(CW0\fR,
+and in some even more future version the compatibility code will be
+removed completely.
-.IP "\s-1EV_STANDALONE\s0" 4
+.IP "\s-1EV_STANDALONE\s0 (h)" 4
-.IX Item "EV_STANDALONE"
+.IX Item "EV_STANDALONE (h)"
 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.
+.Sp
+In standalone mode, libev will still try to automatically deduce the
+configuration, but has to be more conservative.
+.IP "\s-1EV_USE_FLOOR\s0" 4
+.IX Item "EV_USE_FLOOR"
+If defined to be \f(CW1\fR, libev will use the \f(CW\*(C`floor ()\*(C'\fR function for its
+periodic reschedule calculations, otherwise libev will fall back on a
+portable (slower) implementation. If you enable this, you usually have to
+link against libm or something equivalent. Enabling this when the \f(CW\*(C`floor\*(C'\fR
+function is not available will fail, so the safe default is to not enable
+this.
 .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
+monotonic clock option at both compile time and runtime. Otherwise no
-of the monotonic clock option will be attempted. If you enable this, you
+use of the monotonic clock option will be attempted. If you enable this,
-usually have to link against librt or something similar. Enabling it when
+you usually have to link against librt or something similar. Enabling it
-the functionality isn't available is safe, though, although you have
+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).
+function is hiding in (often \fI\-lrt\fR). See also \f(CW\*(C`EV_USE_CLOCK_SYSCALL\*(C'\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
+real-time clock option at compile time (and assume its availability
-runtime if successful). Otherwise no use of the realtime clock option will
+at runtime if successful). Otherwise no use of the real-time clock
-be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get
+option will be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR
-(CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See the
+by \f(CW\*(C`clock_get (CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect
-note about libraries in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though.
+correctness. See the note about libraries in the description of
+\&\f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though. Defaults to the opposite value of
+\&\f(CW\*(C`EV_USE_CLOCK_SYSCALL\*(C'\fR.
+.IP "\s-1EV_USE_CLOCK_SYSCALL\s0" 4
+.IX Item "EV_USE_CLOCK_SYSCALL"
+If defined to be \f(CW1\fR, libev will try to use a direct syscall instead
+of calling the system-provided \f(CW\*(C`clock_gettime\*(C'\fR function. This option
+exists because on GNU/Linux, \f(CW\*(C`clock_gettime\*(C'\fR is in \f(CW\*(C`librt\*(C'\fR, but \f(CW\*(C`librt\*(C'\fR
+unconditionally pulls in \f(CW\*(C`libpthread\*(C'\fR, slowing down single-threaded
+programs needlessly. Using a direct syscall is slightly slower (in
+theory), because no optimised vdso implementation can be used, but avoids
+the pthread dependency. Defaults to \f(CW1\fR on GNU/Linux with glibc 2.x or
+higher, as it simplifies linking (no need for \f(CW\*(C`\-lrt\*(C'\fR).
 .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_SIGNALFD\s0" 4
+.IX Item "EV_USE_SIGNALFD"
+If defined to be \f(CW1\fR, then libev will assume that \f(CW\*(C`signalfd ()\*(C'\fR is
+available and will probe for kernel support at runtime. This enables
+the use of \s-1EVFLAG_SIGNALFD\s0 for faster and simpler signal handling. If
+undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
+2.7 or newer, otherwise disabled.
+.IP "\s-1EV_USE_TIMERFD\s0" 4
+.IX Item "EV_USE_TIMERFD"
+If defined to be \f(CW1\fR, then libev will assume that \f(CW\*(C`timerfd ()\*(C'\fR is
+available and will probe for kernel support at runtime. This allows
+libev to detect time jumps accurately. If undefined, it will be enabled
+if the headers indicate GNU/Linux + Glibc 2.8 or newer and define
+\&\f(CW\*(C`TFD_TIMER_CANCEL_ON_SET\*(C'\fR, otherwise disabled.
+.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
+\&\f(CW\*(C`select\*(C'\fR(2) backend. No attempt at auto-detection will be done: if no
 other method takes over, select will be it. Otherwise the select backend
 will not be compiled in.
 .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
+\&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it mis-guesses the bitset layout
-exotic systems. This usually limits the range of file descriptors to some
+on exotic systems. This usually limits the range of file descriptors to
-low limit such as 1024 or might have other limitations (winsocket only
+some low limit such as 1024 or might have other limitations (winsocket
-allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation, might
+only allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation,
-influence the size of the \f(CW\*(C`fd_set\*(C'\fR used.
+configures the maximum size of the \f(CW\*(C`fd_set\*(C'\fR.
 .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
+.IP "\s-1EV_FD_TO_WIN32_HANDLE\s0(fd)" 4
-.IX Item "EV_FD_TO_WIN32_HANDLE"
+.IX Item "EV_FD_TO_WIN32_HANDLE(fd)"
 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_WIN32_HANDLE_TO_FD\s0(handle)" 4
+.IX Item "EV_WIN32_HANDLE_TO_FD(handle)"
+If \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR then libev maps handles to file descriptors
+using the standard \f(CW\*(C`_open_osfhandle\*(C'\fR function. For programs implementing
+their own fd to handle mapping, overwriting this function makes it easier
+to do so. This can be done by defining this macro to an appropriate value.
+.IP "\s-1EV_WIN32_CLOSE_FD\s0(fd)" 4
+.IX Item "EV_WIN32_CLOSE_FD(fd)"
+If programs implement their own fd to handle mapping on win32, then this
+macro can be used to override the \f(CW\*(C`close\*(C'\fR function, useful to unregister
+file descriptors again. Note that the replacement function has to close
+the underlying \s-1OS\s0 handle.
+.IP "\s-1EV_USE_WSASOCKET\s0" 4
+.IX Item "EV_USE_WSASOCKET"
+If defined to be \f(CW1\fR, libev will use \f(CW\*(C`WSASocket\*(C'\fR to create its internal
+communication socket, which works better in some environments. Otherwise,
+the normal \f(CW\*(C`socket\*(C'\fR function will be used, which works better in other
+environments.
 .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
+otherwise another method will be used as fallback. This is the preferred
-preferred backend for GNU/Linux systems.
+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_LINUXAIO\s0" 4
+.IX Item "EV_USE_LINUXAIO"
+If defined to be \f(CW1\fR, libev will compile in support for the Linux aio
+backend (\f(CW\*(C`EV_USE_EPOLL\*(C'\fR must also be enabled). If undefined, it will be
+enabled on linux, otherwise disabled.
+.IP "\s-1EV_USE_IOURING\s0" 4
+.IX Item "EV_USE_IOURING"
+If defined to be \f(CW1\fR, libev will compile in support for the Linux
+io_uring backend (\f(CW\*(C`EV_USE_EPOLL\*(C'\fR must also be enabled). Due to it's
+current limitations it has to be requested explicitly. If undefined, it
+will be enabled on linux, 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
 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.
+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.
+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_NO_SMP\s0" 4
+.IX Item "EV_NO_SMP"
+If defined to be \f(CW1\fR, libev will assume that memory is always coherent
+between threads, that is, threads can be used, but threads never run on
+different cpus (or different cpu cores). This reduces dependencies
+and makes libev faster.
+.IP "\s-1EV_NO_THREADS\s0" 4
+.IX Item "EV_NO_THREADS"
+If defined to be \f(CW1\fR, libev will assume that it will never be called from
+different threads (that includes signal handlers), which is a stronger
+assumption than \f(CW\*(C`EV_NO_SMP\*(C'\fR, above. This reduces dependencies and makes
+libev faster.
 .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
+access is atomic with respect to other threads or signal contexts. No
-type is easily found in the C language, so you can provide your own type
+such type is easily found in the C language, so you can provide your own
-that you know is safe for your purposes. It is used both for signal handler \*(L"locking\*(R"
+type that you know is safe for your purposes. It is used both for signal
-as well as for signal and thread safety in \f(CW\*(C`ev_async\*(C'\fR watchers.
+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
+In the absence 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
+.IP "\s-1EV_H\s0 (h)" 4
-.IX Item "EV_H"
+.IX Item "EV_H (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
+.IP "\s-1EV_CONFIG_H\s0 (h)" 4
-.IX Item "EV_CONFIG_H"
+.IX Item "EV_CONFIG_H (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
+.IP "\s-1EV_EVENT_H\s0 (h)" 4
-.IX Item "EV_EVENT_H"
+.IX Item "EV_EVENT_H (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
+.IP "\s-1EV_PROTOTYPES\s0 (h)" 4
-.IX Item "EV_PROTOTYPES"
+.IX Item "EV_PROTOTYPES (h)"
 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
 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.
+.Sp
+Note that \f(CW\*(C`EV_DEFAULT\*(C'\fR and \f(CW\*(C`EV_DEFAULT_\*(C'\fR will no longer provide a
+default loop when multiplicity is switched off \- you always have to
+initialise the loop manually in this case.
 .IP "\s-1EV_MINPRI\s0" 4
 .IX Item "EV_MINPRI"
 .PD 0
 .IP "\s-1EV_MAXPRI\s0" 4
 .IX Item "EV_MAXPRI"
 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
+If your embedding application does not need any priorities, defining these
-\&\f(CW0\fR will save some memory and cpu.
+both to \f(CW0\fR will save some memory and \s-1CPU.\s0
-.IP "\s-1EV_PERIODIC_ENABLE\s0" 4
+.IP "\s-1EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE, EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE, EV_ASYNC_ENABLE, EV_CHILD_ENABLE.\s0" 4
-.IX Item "EV_PERIODIC_ENABLE"
+.IX Item "EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE, EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE, EV_ASYNC_ENABLE, EV_CHILD_ENABLE."
-If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If
+If undefined or defined to be \f(CW1\fR (and the platform supports it), then
-defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
+the respective watcher type is supported. If defined to be \f(CW0\fR, then it
-code.
+is not. Disabling watcher types mainly saves code size.
-.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
+.IP "\s-1EV_FEATURES\s0" 4
-.IX Item "EV_STAT_ENABLE"
+.IX Item "EV_FEATURES"
-If undefined or defined to be \f(CW1\fR, then stat watchers are supported. If
-defined to be \f(CW0\fR, then they are not.
-.IP "\s-1EV_FORK_ENABLE\s0" 4
-.IX Item "EV_FORK_ENABLE"
-If undefined or defined to be \f(CW1\fR, then fork watchers are supported. If
-defined to be \f(CW0\fR, then they are not.
-.IP "\s-1EV_ASYNC_ENABLE\s0" 4
-.IX Item "EV_ASYNC_ENABLE"
-If undefined or defined to be \f(CW1\fR, then async watchers are supported. If
-defined to be \f(CW0\fR, then they are not.
-.IP "\s-1EV_MINIMAL\s0" 4
-.IX Item "EV_MINIMAL"
 If you need to shave off some kilobytes of code at the expense of some
-speed, define this symbol to \f(CW1\fR. Currently only used for gcc to override
+speed (but with the full \s-1API\s0), you can define this symbol to request
-some inlining decisions, saves roughly 30% codesize of amd64.
+certain subsets of functionality. The default is to enable all features
+that can be enabled on the platform.
+.Sp
+A typical way to use this symbol is to define it to \f(CW0\fR (or to a bitset
+with some broad features you want) and then selectively re-enable
+additional parts you want, for example if you want everything minimal,
+but multiple event loop support, async and child watchers and the poll
+backend, use this:
+.Sp
+.Vb 5
+\&   #define EV_FEATURES 0
+\&   #define EV_MULTIPLICITY 1
+\&   #define EV_USE_POLL 1
+\&   #define EV_CHILD_ENABLE 1
+\&   #define EV_ASYNC_ENABLE 1
+.Ve
+.Sp
+The actual value is a bitset, it can be a combination of the following
+values (by default, all of these are enabled):
+.RS 4
+.ie n .IP "1 \- faster/larger code" 4
+.el .IP "\f(CW1\fR \- faster/larger code" 4
+.IX Item "1 - faster/larger code"
+Use larger code to speed up some operations.
+.Sp
+Currently this is used to override some inlining decisions (enlarging the
+code size by roughly 30% on amd64).
+.Sp
+When optimising for size, use of compiler flags such as \f(CW\*(C`\-Os\*(C'\fR with
+gcc is recommended, as well as \f(CW\*(C`\-DNDEBUG\*(C'\fR, as libev contains a number of
+assertions.
+.Sp
+The default is off when \f(CW\*(C`_\|_OPTIMIZE_SIZE_\|_\*(C'\fR is defined by your compiler
+(e.g. gcc with \f(CW\*(C`\-Os\*(C'\fR).
+.ie n .IP "2 \- faster/larger data structures" 4
+.el .IP "\f(CW2\fR \- faster/larger data structures" 4
+.IX Item "2 - faster/larger data structures"
+Replaces the small 2\-heap for timer management by a faster 4\-heap, larger
+hash table sizes and so on. This will usually further increase code size
+and can additionally have an effect on the size of data structures at
+runtime.
+.Sp
+The default is off when \f(CW\*(C`_\|_OPTIMIZE_SIZE_\|_\*(C'\fR is defined by your compiler
+(e.g. gcc with \f(CW\*(C`\-Os\*(C'\fR).
+.ie n .IP "4 \- full \s-1API\s0 configuration" 4
+.el .IP "\f(CW4\fR \- full \s-1API\s0 configuration" 4
+.IX Item "4 - full API configuration"
+This enables priorities (sets \f(CW\*(C`EV_MAXPRI\*(C'\fR=2 and \f(CW\*(C`EV_MINPRI\*(C'\fR=\-2), and
+enables multiplicity (\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR=1).
+.ie n .IP "8 \- full \s-1API\s0" 4
+.el .IP "\f(CW8\fR \- full \s-1API\s0" 4
+.IX Item "8 - full API"
+This enables a lot of the \*(L"lesser used\*(R" \s-1API\s0 functions. See \f(CW\*(C`ev.h\*(C'\fR for
+details on which parts of the \s-1API\s0 are still available without this
+feature, and do not complain if this subset changes over time.
+.ie n .IP "16 \- enable all optional watcher types" 4
+.el .IP "\f(CW16\fR \- enable all optional watcher types" 4
+.IX Item "16 - enable all optional watcher types"
+Enables all optional watcher types.  If you want to selectively enable
+only some watcher types other than I/O and timers (e.g. prepare,
+embed, async, child...) you can enable them manually by defining
+\&\f(CW\*(C`EV_watchertype_ENABLE\*(C'\fR to \f(CW1\fR instead.
+.ie n .IP "32 \- enable all backends" 4
+.el .IP "\f(CW32\fR \- enable all backends" 4
+.IX Item "32 - enable all backends"
+This enables all backends \- without this feature, you need to enable at
+least one backend manually (\f(CW\*(C`EV_USE_SELECT\*(C'\fR is a good choice).
+.ie n .IP "64 \- enable OS-specific ""helper"" APIs" 4
+.el .IP "\f(CW64\fR \- enable OS-specific ``helper'' APIs" 4
+.IX Item "64 - enable OS-specific helper APIs"
+Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
+default.
+.RE
+.RS 4
+.Sp
+Compiling with \f(CW\*(C`gcc \-Os \-DEV_STANDALONE \-DEV_USE_EPOLL=1 \-DEV_FEATURES=0\*(C'\fR
+reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
+code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
+watchers, timers and monotonic clock support.
+.Sp
+With an intelligent-enough linker (gcc+binutils are intelligent enough
+when you use \f(CW\*(C`\-Wl,\-\-gc\-sections \-ffunction\-sections\*(C'\fR) functions unused by
+your program might be left out as well \- a binary starting a timer and an
+I/O watcher then might come out at only 5Kb.
+.RE
+.IP "\s-1EV_API_STATIC\s0" 4
+.IX Item "EV_API_STATIC"
+If this symbol is defined (by default it is not), then all identifiers
+will have static linkage. This means that libev will not export any
+identifiers, and you cannot link against libev anymore. This can be useful
+when you embed libev, only want to use libev functions in a single file,
+and do not want its identifiers to be visible.
+.Sp
+To use this, define \f(CW\*(C`EV_API_STATIC\*(C'\fR and include \fIev.c\fR in the file that
+wants to use libev.
+.Sp
+This option only works when libev is compiled with a C compiler, as \*(C+
+doesn't support the required declaration syntax.
+.IP "\s-1EV_AVOID_STDIO\s0" 4
+.IX Item "EV_AVOID_STDIO"
+If this is set to \f(CW1\fR at compiletime, then libev will avoid using stdio
+functions (printf, scanf, perror etc.). This will increase the code size
+somewhat, but if your program doesn't otherwise depend on stdio and your
+libc allows it, this avoids linking in the stdio library which is quite
+big.
+.Sp
+Note that error messages might become less precise when this option is
+enabled.
+.IP "\s-1EV_NSIG\s0" 4
+.IX Item "EV_NSIG"
+The highest supported signal number, +1 (or, the number of
+signals): Normally, libev tries to deduce the maximum number of signals
+automatically, but sometimes this fails, in which case it can be
+specified. Also, using a lower number than detected (\f(CW32\fR should be
+good for about any system in existence) can save some memory, as libev
+statically allocates some 12\-24 bytes per signal number.
 .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
+pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_FEATURES\*(C'\fR disabled),
-than enough. If you need to manage thousands of children you might want to
+usually more than enough. If you need to manage thousands of children you
-increase this value (\fImust\fR be a power of two).
+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),
+inotify watch id. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_FEATURES\*(C'\fR
-usually more than enough. If you need to manage thousands of \f(CW\*(C`ev_stat\*(C'\fR
+disabled), usually more than enough. If you need to manage thousands of
-watchers you might want to increase this value (\fImust\fR be a power of
+\&\f(CW\*(C`ev_stat\*(C'\fR watchers you might want to increase this value (\fImust\fR be a
-two).
+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 heaps, libev uses a 4\-heap when this symbol is defined
+to \f(CW1\fR. The 4\-heap uses more complicated (longer) code but has noticeably
+faster performance with many (thousands) of watchers.
+.Sp
+The default is \f(CW1\fR, unless \f(CW\*(C`EV_FEATURES\*(C'\fR overrides it, in which case it
+will be \f(CW0\fR.
+.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 heaps, 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 improves performance
+noticeably with many (hundreds) of watchers.
+.Sp
+The default is \f(CW1\fR, unless \f(CW\*(C`EV_FEATURES\*(C'\fR overrides it, in which case it
+will be \f(CW0\fR.
+.IP "\s-1EV_VERIFY\s0" 4
+.IX Item "EV_VERIFY"
+Controls how much internal verification (see \f(CW\*(C`ev_verify ()\*(C'\fR) will
+be done: If set to \f(CW0\fR, no internal verification code will be compiled
+in. If set to \f(CW1\fR, then verification code will be compiled in, but not
+called. If set to \f(CW2\fR, then the internal verification code will be
+called once per loop, which can slow down libev. If set to \f(CW3\fR, then the
+verification code will be called very frequently, which will slow down
+libev considerably.
+.Sp
+Verification errors are reported via C's \f(CW\*(C`assert\*(C'\fR mechanism, so if you
+disable that (e.g. by defining \f(CW\*(C`NDEBUG\*(C'\fR) then no errors will be reported.
+.Sp
+The default is \f(CW1\fR, unless \f(CW\*(C`EV_FEATURES\*(C'\fR overrides it, in which case it
+will be \f(CW0\fR.
 .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
+this macro to 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
+\&   #define EV_COMMON                       \e
-\&    SV *self; /* contains this struct */  \e
+\&     SV *self; /* contains this struct */  \e
-\&    SV *cb_sv, *fh /* note no trailing ";" */
+\&     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
 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"
+.SS "\s-1EXPORTED API SYMBOLS\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
+If you need to re-export the \s-1API\s0 (e.g. via a \s-1DLL\s0) 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.ev      for libev proper
-\&  Symbols.event   for the libevent emulation
+\&   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).
+itself, but sometimes it is inconvenient 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
 \&   #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"
+.SS "\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
 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
+.Vb 8
-\&  #define EV_MINIMAL 1
+\&   #define EV_FEATURES 8
-\&  #define EV_USE_POLL 0
+\&   #define EV_USE_SELECT 1
-\&  #define EV_MULTIPLICITY 0
-\&  #define EV_PERIODIC_ENABLE 0
+\&   #define EV_PREPARE_ENABLE 1
+\&   #define EV_IDLE_ENABLE 1
-\&  #define EV_STAT_ENABLE 0
+\&   #define EV_SIGNAL_ENABLE 1
-\&  #define EV_FORK_ENABLE 0
+\&   #define EV_CHILD_ENABLE 1
+\&   #define EV_USE_STDEXCEPT 0
-\&  #define EV_CONFIG_H <config.h>
+\&   #define EV_CONFIG_H <config.h>
-\&  #define EV_MINPRI 0
-\&  #define EV_MAXPRI 0
 \&
-\&  #include "ev++.h"
+\&   #include "ev++.h"
 .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_cpp.h"
-\&  #include "ev.c"
+\&   #include "ev.c"
 .Ve
+.SH "INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT"
+.IX Header "INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT"
+.SS "\s-1THREADS AND COROUTINES\s0"
+.IX Subsection "THREADS AND COROUTINES"
+\fI\s-1THREADS\s0\fR
+.IX Subsection "THREADS"
+.PP
+All libev functions are reentrant and thread-safe unless explicitly
+documented otherwise, but libev implements no locking itself. This means
+that you can use as many loops as you want in parallel, as long as there
+are no concurrent calls into any libev function with the same loop
+parameter (\f(CW\*(C`ev_default_*\*(C'\fR calls have an implicit default loop parameter,
+of course): libev guarantees that different event loops share no data
+structures that need any locking.
+.PP
+Or to put it differently: calls with different loop parameters can be done
+concurrently 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
+Specifically to support threads (and signal handlers), libev implements
+so-called \f(CW\*(C`ev_async\*(C'\fR watchers, which allow some limited form of
+concurrency on the same event loop, namely waking it up \*(L"from the
+outside\*(R".
+.PP
+If you want to know which design (one loop, locking, or multiple loops
+without or something else still) is best for your problem, then I cannot
+help you, but here is some generic advice:
+.IP "\(bu" 4
+most applications have a main thread: use the default libev loop
+in that thread, or create a separate 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-robin fashion.
+.Sp
+Choosing a model is hard \- look around, learn, know that usually you can do
+better than you currently do :\-)
+.IP "\(bu" 4
+often you need to talk to some other thread which blocks in the
+event loop.
+.Sp
+\&\f(CW\*(C`ev_async\*(C'\fR watchers can be used to wake them up from other threads safely
+(or from signal contexts...).
+.Sp
+An example use would be to communicate signals or other events that only
+work in the default loop by registering the signal watcher with the
+default loop and triggering an \f(CW\*(C`ev_async\*(C'\fR watcher from the default loop
+watcher callback into the event loop interested in the signal.
+.PP
+See also \*(L"\s-1THREAD LOCKING EXAMPLE\*(R"\s0.
+.PP
+\fI\s-1COROUTINES\s0\fR
+.IX Subsection "COROUTINES"
+.PP
+Libev is very accommodating to coroutines (\*(L"cooperative threads\*(R"):
+libev fully supports nesting calls to its functions from different
+coroutines (e.g. you can call \f(CW\*(C`ev_run\*(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 taken to ensure that libev does not keep local state inside
+\&\f(CW\*(C`ev_run\*(C'\fR, and other calls do not usually allow for coroutine switches as
+they do not call any callbacks.
+.SS "\s-1COMPILER WARNINGS\s0"
+.IX Subsection "COMPILER WARNINGS"
+Depending on your compiler and compiler settings, you might get no or a
+lot of warnings when compiling libev code. Some people are apparently
+scared by this.
+.PP
+However, these are unavoidable for many reasons. For one, each compiler
+has different warnings, and each user has different tastes regarding
+warning options. \*(L"Warn-free\*(R" code therefore cannot be a goal except when
+targeting a specific compiler and compiler-version.
+.PP
+Another reason is that some compiler warnings require elaborate
+workarounds, or other changes to the code that make it less clear and less
+maintainable.
+.PP
+And of course, some compiler warnings are just plain stupid, or simply
+wrong (because they don't actually warn about the condition their message
+seems to warn about). For example, certain older gcc versions had some
+warnings that resulted in an extreme number of false positives. These have
+been fixed, but some people still insist on making code warn-free with
+such buggy versions.
+.PP
+While libev is written to generate as few warnings as possible,
+\&\*(L"warn-free\*(R" code is not a goal, and it is recommended not to build libev
+with any compiler warnings enabled unless you are prepared to cope with
+them (e.g. by ignoring them). Remember that warnings are just that:
+warnings, not errors, or proof of bugs.
+.SS "\s-1VALGRIND\s0"
+.IX Subsection "VALGRIND"
+Valgrind has a special section here because it is a popular tool that is
+highly useful. Unfortunately, valgrind reports are very hard to interpret.
+.PP
+If you think you found a bug (memory leak, uninitialised data access etc.)
+in libev, then check twice: If valgrind reports something like:
+.PP
+.Vb 3
+\&   ==2274==    definitely lost: 0 bytes in 0 blocks.
+\&   ==2274==      possibly lost: 0 bytes in 0 blocks.
+\&   ==2274==    still reachable: 256 bytes in 1 blocks.
+.Ve
+.PP
+Then there is no memory leak, just as memory accounted to global variables
+is not a memleak \- the memory is still being referenced, and didn't leak.
+.PP
+Similarly, under some circumstances, valgrind might report kernel bugs
+as if it were a bug in libev (e.g. in realloc or in the poll backend,
+although an acceptable workaround has been found here), or it might be
+confused.
+.PP
+Keep in mind that valgrind is a very good tool, but only a tool. Don't
+make it into some kind of religion.
+.PP
+If you are unsure about something, feel free to contact the mailing list
+with the full valgrind report and an explanation on why you think this
+is a bug in libev (best check the archives, too :). However, don't be
+annoyed when you get a brisk \*(L"this is no bug\*(R" answer and take the chance
+of learning how to interpret valgrind properly.
+.PP
+If you need, for some reason, empty reports from valgrind for your project
+I suggest using suppression lists.
+.SH "PORTABILITY NOTES"
+.IX Header "PORTABILITY NOTES"
+.SS "\s-1GNU/LINUX 32 BIT LIMITATIONS\s0"
+.IX Subsection "GNU/LINUX 32 BIT LIMITATIONS"
+GNU/Linux is the only common platform that supports 64 bit file/large file
+interfaces but \fIdisables\fR them by default.
+.PP
+That means that libev compiled in the default environment doesn't support
+files larger than 2GiB or so, which mainly affects \f(CW\*(C`ev_stat\*(C'\fR watchers.
+.PP
+Unfortunately, many programs try to work around this GNU/Linux issue
+by enabling the large file \s-1API,\s0 which makes them incompatible with the
+standard libev compiled for their system.
+.PP
+Likewise, libev cannot enable the large file \s-1API\s0 itself as this would
+suddenly make it incompatible to the default compile time environment,
+i.e. all programs not using special compile switches.
+.SS "\s-1OS/X AND DARWIN BUGS\s0"
+.IX Subsection "OS/X AND DARWIN BUGS"
+The whole thing is a bug if you ask me \- basically any system interface
+you touch is broken, whether it is locales, poll, kqueue or even the
+OpenGL drivers.
+.PP
+\fI\f(CI\*(C`kqueue\*(C'\fI is buggy\fR
+.IX Subsection "kqueue is buggy"
+.PP
+The kqueue syscall is broken in all known versions \- most versions support
+only sockets, many support pipes.
+.PP
+Libev tries to work around this by not using \f(CW\*(C`kqueue\*(C'\fR by default on this
+rotten platform, but of course you can still ask for it when creating a
+loop \- embedding a socket-only kqueue loop into a select-based one is
+probably going to work well.
+.PP
+\fI\f(CI\*(C`poll\*(C'\fI is buggy\fR
+.IX Subsection "poll is buggy"
+.PP
+Instead of fixing \f(CW\*(C`kqueue\*(C'\fR, Apple replaced their (working) \f(CW\*(C`poll\*(C'\fR
+implementation by something calling \f(CW\*(C`kqueue\*(C'\fR internally around the 10.5.6
+release, so now \f(CW\*(C`kqueue\*(C'\fR \fIand\fR \f(CW\*(C`poll\*(C'\fR are broken.
+.PP
+Libev tries to work around this by not using \f(CW\*(C`poll\*(C'\fR by default on
+this rotten platform, but of course you can still ask for it when creating
+a loop.
+.PP
+\fI\f(CI\*(C`select\*(C'\fI is buggy\fR
+.IX Subsection "select is buggy"
+.PP
+All that's left is \f(CW\*(C`select\*(C'\fR, and of course Apple found a way to fuck this
+one up as well: On \s-1OS/X,\s0 \f(CW\*(C`select\*(C'\fR actively limits the number of file
+descriptors you can pass in to 1024 \- your program suddenly crashes when
+you use more.
+.PP
+There is an undocumented \*(L"workaround\*(R" for this \- defining
+\&\f(CW\*(C`_DARWIN_UNLIMITED_SELECT\*(C'\fR, which libev tries to use, so select \fIshould\fR
+work on \s-1OS/X.\s0
+.SS "\s-1SOLARIS PROBLEMS AND WORKAROUNDS\s0"
+.IX Subsection "SOLARIS PROBLEMS AND WORKAROUNDS"
+\fI\f(CI\*(C`errno\*(C'\fI reentrancy\fR
+.IX Subsection "errno reentrancy"
+.PP
+The default compile environment on Solaris is unfortunately so
+thread-unsafe that you can't even use components/libraries compiled
+without \f(CW\*(C`\-D_REENTRANT\*(C'\fR in a threaded program, which, of course, isn't
+defined by default. A valid, if stupid, implementation choice.
+.PP
+If you want to use libev in threaded environments you have to make sure
+it's compiled with \f(CW\*(C`_REENTRANT\*(C'\fR defined.
+.PP
+\fIEvent port backend\fR
+.IX Subsection "Event port backend"
+.PP
+The scalable event interface for Solaris is called \*(L"event
+ports\*(R". Unfortunately, this mechanism is very buggy in all major
+releases. If you run into high \s-1CPU\s0 usage, your program freezes or you get
+a large number of spurious wakeups, make sure you have all the relevant
+and latest kernel patches applied. No, I don't know which ones, but there
+are multiple ones to apply, and afterwards, event ports actually work
+great.
+.PP
+If you can't get it to work, you can try running the program by setting
+the environment variable \f(CW\*(C`LIBEV_FLAGS=3\*(C'\fR to only allow \f(CW\*(C`poll\*(C'\fR and
+\&\f(CW\*(C`select\*(C'\fR backends.
+.SS "\s-1AIX POLL BUG\s0"
+.IX Subsection "AIX POLL BUG"
+\&\s-1AIX\s0 unfortunately has a broken \f(CW\*(C`poll.h\*(C'\fR header. Libev works around
+this by trying to avoid the poll backend altogether (i.e. it's not even
+compiled in), which normally isn't a big problem as \f(CW\*(C`select\*(C'\fR works fine
+with large bitsets on \s-1AIX,\s0 and \s-1AIX\s0 is dead anyway.
+.SS "\s-1WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS\s0"
+.IX Subsection "WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS"
+\fIGeneral issues\fR
+.IX Subsection "General issues"
+.PP
+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. Actually, it only applies to the microsofts own compilers,
+as every compiler comes with a slightly differently broken/incompatible
+environment.
+.PP
+Lifting these limitations would basically require the full
+re-implementation of the I/O system. If you are into this kind of thing,
+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
+Sensible signal handling is officially unsupported by Microsoft \- libev
+tries its best, but under most conditions, signals will simply not work.
+.PP
+Not a libev limitation but worth mentioning: windows apparently doesn't
+accept large writes: instead of resulting in a partial write, windows will
+either accept everything or return \f(CW\*(C`ENOBUFS\*(C'\fR if the buffer is too large,
+so make sure you only write small amounts into your sockets (less than a
+megabyte seems safe, but this apparently depends on the amount of memory
+available).
+.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 readiness
+notification model, which cannot be implemented efficiently on windows
+(due to Microsoft monopoly games).
+.PP
+A typical way to use libev under windows is to embed it (see the embedding
+section for details) and use the following \fIevwrap.h\fR header file instead
+of \fIev.h\fR:
+.PP
+.Vb 2
+\&   #define EV_STANDALONE              /* keeps ev from requiring config.h */
+\&   #define EV_SELECT_IS_WINSOCKET 1   /* configure libev for windows select */
+\&
+\&   #include "ev.h"
+.Ve
+.PP
+And compile the following \fIevwrap.c\fR file into your project (make sure
+you do \fInot\fR compile the \fIev.c\fR or any other embedded source files!):
+.PP
+.Vb 2
+\&   #include "evwrap.h"
+\&   #include "ev.c"
+.Ve
+.PP
+\fIThe winsocket \f(CI\*(C`select\*(C'\fI function\fR
+.IX Subsection "The winsocket select function"
+.PP
+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 (it is
+also extremely buggy). This makes select very inefficient, and also
+requires a mapping from file descriptors to socket handles (the Microsoft
+C runtime provides the function \f(CW\*(C`_open_osfhandle\*(C'\fR for this). 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.
+.PP
+The configuration for a \*(L"naked\*(R" win32 using the Microsoft runtime
+libraries and raw winsocket select is:
+.PP
+.Vb 2
+\&   #define EV_USE_SELECT 1
+\&   #define EV_SELECT_IS_WINSOCKET 1   /* forces EV_SELECT_USE_FD_SET, too */
+.Ve
+.PP
+Note that winsockets handling of fd sets is O(n), so you can easily get a
+complexity in the O(nX) range when using win32.
+.PP
+\fILimited number of file descriptors\fR
+.IX Subsection "Limited number of file descriptors"
+.PP
+Windows has numerous arbitrary (and low) limits on things.
+.PP
+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. Sounds great!).
+.PP
+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 and many
+other interpreters do their own select emulation on windows).
+.PP
+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. 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(nX)) will likely make this unworkable.
+.SS "\s-1PORTABILITY REQUIREMENTS\s0"
+.IX Subsection "PORTABILITY REQUIREMENTS"
+In addition to a working ISO-C implementation and of course the
+backend-specific APIs, libev relies on a few additional extensions:
+.ie n .IP """void (*)(ev_watcher_type *, int revents)"" must have compatible calling conventions regardless of ""ev_watcher_type *""." 4
+.el .IP "\f(CWvoid (*)(ev_watcher_type *, int revents)\fR must have compatible calling conventions regardless of \f(CWev_watcher_type *\fR." 4
+.IX Item "void (*)(ev_watcher_type *, int revents) must have compatible calling conventions regardless of ev_watcher_type *."
+Libev assumes not only that all watcher pointers have the same internal
+structure (guaranteed by \s-1POSIX\s0 but not by \s-1ISO C\s0 for example), but it also
+assumes that the same (machine) code can be used to call any watcher
+callback: The watcher callbacks have different type signatures, but libev
+calls them using an \f(CW\*(C`ev_watcher *\*(C'\fR internally.
+.IP "null pointers and integer zero are represented by 0 bytes" 4
+.IX Item "null pointers and integer zero are represented by 0 bytes"
+Libev uses \f(CW\*(C`memset\*(C'\fR to initialise structs and arrays to \f(CW0\fR bytes, and
+relies on this setting pointers and integers to null.
+.IP "pointer accesses must be thread-atomic" 4
+.IX Item "pointer accesses must be thread-atomic"
+Accessing a pointer value must be atomic, it must both be readable and
+writable in one piece \- this is the case on all current architectures.
+.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 with respect to 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 signal handling 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 its \s-1API,\s0 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 with millisecond accuracy
+(the design goal for libev). This requirement is overfulfilled by
+implementations using \s-1IEEE 754,\s0 which is basically all existing ones.
+.Sp
+With \s-1IEEE 754\s0 doubles, you get microsecond accuracy until at least the
+year 2255 (and millisecond accuracy till the year 287396 \- by then, libev
+is either obsolete or somebody patched it to use \f(CW\*(C`long double\*(C'\fR or
+something like that, just kidding).
+.PP
+If you know of other additional requirements drop me a note.
-.SH "COMPLEXITIES"
+.SH "ALGORITHMIC COMPLEXITIES"
-.IX Header "COMPLEXITIES"
+.IX Header "ALGORITHMIC COMPLEXITIES"
 In this section the complexities of (many of) the algorithms used inside
-libev will be explained. For complexity discussions about backends see the
+libev will be documented. For complexity discussions about backends see
-documentation for \f(CW\*(C`ev_default_init\*(C'\fR.
+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
+happens asymptotically rarer with higher number of elements, so O(1) might
-mean it might do a lengthy realloc operation in rare cases, but on average
+mean that libev does a lengthy realloc operation in rare cases, but on
-it is much faster and asymptotically approaches constant time.
+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
+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
+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
+These watchers are stored in lists, so they need to be walked to find the
 correct watcher to remove. The lists are usually short (you don't usually
-have many watchers waiting for the same fd or signal).
+have many watchers waiting for the same fd or signal: one is typical, two
+is rare).
 .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 heap, the next timer is always found at the
+By virtue of using a binary or 4\-heap, the next timer is always found at a
-beginning of the storage array.
+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).
+on backend and whether \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.
+watchers becomes O(1) with respect to 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
+Sending involves a system call \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
+calls in the current loop iteration and the loop is currently
+blocked. Checking for async and signal events involves iterating over all
-involves iterating over all running async watchers or all signal numbers.
+running async watchers or all signal numbers.
-.SH "Win32 platform limitations and workarounds"
+.SH "PORTING FROM LIBEV 3.X TO 4.X"
-.IX Header "Win32 platform limitations and workarounds"
+.IX Header "PORTING FROM LIBEV 3.X TO 4.X"
-Win32 doesn't support any of the standards (e.g. \s-1POSIX\s0) that libev
+The major version 4 introduced some incompatible changes to the \s-1API.\s0
-requires, and its I/O model is fundamentally incompatible with the \s-1POSIX\s0
-model. Libev still offers limited functionality on this platform in
-the form of the \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR backend, and only supports socket
-descriptors. This only applies when using Win32 natively, not when using
-e.g. cygwin.
 .PP
-There is no supported compilation method available on windows except
+At the moment, the \f(CW\*(C`ev.h\*(C'\fR header file provides compatibility definitions
-embedding it into other applications.
+for all changes, so most programs should still compile. The compatibility
-.PP
+layer might be removed in later versions of libev, so better update to the
-Due to the many, low, and arbitrary limits on the win32 platform and the
+new \s-1API\s0 early than late.
-abysmal performance of winsockets, using a large number of sockets is not
+.ie n .IP """EV_COMPAT3"" backwards compatibility mechanism" 4
-recommended (and not reasonable). If your program needs to use more than
+.el .IP "\f(CWEV_COMPAT3\fR backwards compatibility mechanism" 4
-a hundred or so sockets, then likely it needs to use a totally different
+.IX Item "EV_COMPAT3 backwards compatibility mechanism"
-implementation for windows, as libev offers the \s-1POSIX\s0 model, which cannot
+The backward compatibility mechanism can be controlled by
-be implemented efficiently on windows (microsoft monopoly games).
+\&\f(CW\*(C`EV_COMPAT3\*(C'\fR. See \*(L"\s-1PREPROCESSOR SYMBOLS/MACROS\*(R"\s0 in the \*(L"\s-1EMBEDDING\*(R"\s0
-.IP "The winsocket select function" 4
+section.
-.IX Item "The winsocket select function"
+.ie n .IP """ev_default_destroy"" and ""ev_default_fork"" have been removed" 4
-The winsocket \f(CW\*(C`select\*(C'\fR function doesn't follow \s-1POSIX\s0 in that it requires
+.el .IP "\f(CWev_default_destroy\fR and \f(CWev_default_fork\fR have been removed" 4
-socket \fIhandles\fR and not socket \fIfile descriptors\fR. This makes select
+.IX Item "ev_default_destroy and ev_default_fork have been removed"
-very inefficient, and also requires a mapping from file descriptors
+These calls can be replaced easily by their \f(CW\*(C`ev_loop_xxx\*(C'\fR counterparts:
-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
+\&   ev_loop_destroy (EV_DEFAULT_UC);
-\&  #define EV_SELECT_IS_WINSOCKET 1   /* forces EV_SELECT_USE_FD_SET, too */
+\&   ev_loop_fork (EV_DEFAULT);
 .Ve
+.IP "function/symbol renames" 4
+.IX Item "function/symbol renames"
+A number of functions and symbols have been renamed:
 .Sp
-Note that winsockets handling of fd sets is O(n), so you can easily get a
+.Vb 3
-complexity in the O(nA\*^X) range when using win32.
+\&  ev_loop         => ev_run
-.IP "Limited number of file descriptors" 4
+\&  EVLOOP_NONBLOCK => EVRUN_NOWAIT
-.IX Item "Limited number of file descriptors"
+\&  EVLOOP_ONESHOT  => EVRUN_ONCE
-Windows has numerous arbitrary (and low) limits on things. Early versions
+\&
-of winsocket's select only supported waiting for a max. of \f(CW64\fR handles
+\&  ev_unloop       => ev_break
-(probably owning to the fact that all windows kernels can only wait for
+\&  EVUNLOOP_CANCEL => EVBREAK_CANCEL
-\&\f(CW64\fR things at the same time internally; microsoft recommends spawning a
+\&  EVUNLOOP_ONE    => EVBREAK_ONE
-chain of threads and wait for 63 handles and the previous thread in each).
+\&  EVUNLOOP_ALL    => EVBREAK_ALL
+\&
+\&  EV_TIMEOUT      => EV_TIMER
+\&
+\&  ev_loop_count   => ev_iteration
+\&  ev_loop_depth   => ev_depth
+\&  ev_loop_verify  => ev_verify
+.Ve
 .Sp
-Newer versions support more handles, but you need to define \f(CW\*(C`FD_SETSIZE\*(C'\fR
+Most functions working on \f(CW\*(C`struct ev_loop\*(C'\fR objects don't have an
-to some high number (e.g. \f(CW2048\fR) before compiling the winsocket select
+\&\f(CW\*(C`ev_loop_\*(C'\fR prefix, so it was removed; \f(CW\*(C`ev_loop\*(C'\fR, \f(CW\*(C`ev_unloop\*(C'\fR and
-call (which might be in libev or elsewhere, for example, perl does its own
+associated constants have been renamed to not collide with the \f(CW\*(C`struct
-select emulation on windows).
+ev_loop\*(C'\fR anymore and \f(CW\*(C`EV_TIMER\*(C'\fR now follows the same naming scheme
+as all other watcher types. Note that \f(CW\*(C`ev_loop_fork\*(C'\fR is still called
+\&\f(CW\*(C`ev_loop_fork\*(C'\fR because it would otherwise clash with the \f(CW\*(C`ev_fork\*(C'\fR
+typedef.
+.ie n .IP """EV_MINIMAL"" mechanism replaced by ""EV_FEATURES""" 4
+.el .IP "\f(CWEV_MINIMAL\fR mechanism replaced by \f(CWEV_FEATURES\fR" 4
+.IX Item "EV_MINIMAL mechanism replaced by EV_FEATURES"
+The preprocessor symbol \f(CW\*(C`EV_MINIMAL\*(C'\fR has been replaced by a different
+mechanism, \f(CW\*(C`EV_FEATURES\*(C'\fR. Programs using \f(CW\*(C`EV_MINIMAL\*(C'\fR usually compile
+and work, but the library code will of course be larger.
+.SH "GLOSSARY"
+.IX Header "GLOSSARY"
+.IP "active" 4
+.IX Item "active"
+A watcher is active as long as it has been started and not yet stopped.
+See \*(L"\s-1WATCHER STATES\*(R"\s0 for details.
+.IP "application" 4
+.IX Item "application"
+In this document, an application is whatever is using libev.
+.IP "backend" 4
+.IX Item "backend"
+The part of the code dealing with the operating system interfaces.
+.IP "callback" 4
+.IX Item "callback"
+The address of a function that is called when some event has been
+detected. Callbacks are being passed the event loop, the watcher that
+received the event, and the actual event bitset.
+.IP "callback/watcher invocation" 4
+.IX Item "callback/watcher invocation"
+The act of calling the callback associated with a watcher.
+.IP "event" 4
+.IX Item "event"
+A change of state of some external event, such as data now being available
+for reading on a file descriptor, time having passed or simply not having
+any other events happening anymore.
 .Sp
-Another limit is the number of file descriptors in the microsoft runtime
+In libev, events are represented as single bits (such as \f(CW\*(C`EV_READ\*(C'\fR or
-libraries, which by default is \f(CW64\fR (there must be a hidden \fI64\fR fetish
+\&\f(CW\*(C`EV_TIMER\*(C'\fR).
-or something like this inside microsoft). You can increase this by calling
+.IP "event library" 4
-\&\f(CW\*(C`_setmaxstdio\*(C'\fR, which can increase this limit to \f(CW2048\fR (another
+.IX Item "event library"
-arbitrary limit), but is broken in many versions of the microsoft runtime
+A software package implementing an event model and loop.
-libraries.
+.IP "event loop" 4
-.Sp
+.IX Item "event loop"
-This might get you to about \f(CW512\fR or \f(CW2048\fR sockets (depending on
+An entity that handles and processes external events and converts them
-windows version and/or the phase of the moon). To get more, you need to
+into callback invocations.
-wrap all I/O functions and provide your own fd management, but the cost of
+.IP "event model" 4
-calling select (O(nA\*^X)) will likely make this unworkable.
+.IX Item "event model"
+The model used to describe how an event loop handles and processes
+watchers and events.
+.IP "pending" 4
+.IX Item "pending"
+A watcher is pending as soon as the corresponding event has been
+detected. See \*(L"\s-1WATCHER STATES\*(R"\s0 for details.
+.IP "real time" 4
+.IX Item "real time"
+The physical time that is observed. It is apparently strictly monotonic :)
+.IP "wall-clock time" 4
+.IX Item "wall-clock time"
+The time and date as shown on clocks. Unlike real time, it can actually
+be wrong and jump forwards and backwards, e.g. when you adjust your
+clock.
+.IP "watcher" 4
+.IX Item "watcher"
+A data structure that describes interest in certain events. Watchers need
+to be started (attached to an event loop) before they can receive events.
 .SH "AUTHOR"
 .IX Header "AUTHOR"
-Marc Lehmann <libev@schmorp.de>.
+Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
-.SH "POD ERRORS"
+Magnusson and Emanuele Giaquinta, and minor corrections by many others.
-.IX Header "POD ERRORS"
-Hey! \fBThe above document had some coding errors, which are explained below:\fR
-.IP "Around line 2916:" 4
-.IX Item "Around line 2916:"
-You forgot a '=back' before '=head2'

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Comparing libev/ev.3 (file contents):
Revision 1.61 by root, Thu Mar 13 13:06:15 2008 UTC vs.
Revision 1.125 by sf-exg, Sun May 14 19:02:31 2023 UTC