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

Comparing libev/ev.3 (file contents):
Revision 1.38 by root, Fri Dec 7 18:09:38 2007 UTC vs.
Revision 1.74 by root, Wed Nov 19 10:33:32 2008 UTC

-.\" Automatically generated by Pod::Man v1.37, Pod::Parser v1.35
+.\" Automatically generated by Pod::Man 2.16 (Pod::Simple 3.05)
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+.ie \nF \{\
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-.IX Title ""<STANDARD INPUT>" 1"
+.IX Title "LIBEV 3"
-.TH "<STANDARD INPUT>" 1 "2007-12-07" "perl v5.8.8" "User Contributed Perl Documentation"
+.TH LIBEV 3 "2008-11-17" "libev-3.49" "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 "EXAMPLE PROGRAM"
+.Sh "\s-1EXAMPLE\s0 \s-1PROGRAM\s0"
-.IX Header "EXAMPLE PROGRAM"
+.IX Subsection "EXAMPLE PROGRAM"
-.Vb 1
-\&  #include <ev.h>
-.Ve
-.PP
 .Vb 2
+\&   // a single header file is required
+\&   #include <ev.h>
+\&
+\&   #include <stdio.h> // for puts
+\&
+\&   // every watcher type has its own typedef\*(Aqd struct
+\&   // with the name ev_TYPE
-\&  ev_io stdin_watcher;
+\&   ev_io stdin_watcher;
-\&  ev_timer timeout_watcher;
+\&   ev_timer timeout_watcher;
-.Ve
+\&
-.PP
+\&   // all watcher callbacks have a similar signature
-.Vb 8
-\&  /* called when data 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");
-\&    ev_io_stop (EV_A_ w); /* just a syntax example */
+\&     // for one\-shot events, one must manually stop the watcher
-\&    ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
+\&     // with its corresponding stop function.
+\&     ev_io_stop (EV_A_ w);
+\&
+\&     // this causes all nested ev_loop\*(Aqs to stop iterating
+\&     ev_unloop (EV_A_ EVUNLOOP_ALL);
-\&  }
+\&   }
-.Ve
+\&
-.PP
+\&   // another callback, this time for a time\-out
-.Vb 6
-\&  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");
-\&    ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
+\&     // this causes the innermost ev_loop to stop iterating
+\&     ev_unloop (EV_A_ EVUNLOOP_ONE);
-\&  }
+\&   }
-.Ve
+\&
-.PP
-.Vb 4
-\&  int
+\&   int
-\&  main (void)
+\&   main (void)
-\&  {
+\&   {
+\&     // use the default event loop unless you have special needs
-\&    struct ev_loop *loop = ev_default_loop (0);
+\&     ev_loop *loop = ev_default_loop (0);
-.Ve
+\&
-.PP
-.Vb 3
-\&    /* initialise an io watcher, then start it */
+\&     // initialise an io watcher, then start it
+\&     // this one will watch for stdin to become readable
-\&    ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
+\&     ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
-\&    ev_io_start (loop, &stdin_watcher);
+\&     ev_io_start (loop, &stdin_watcher);
-.Ve
+\&
-.PP
+\&     // initialise a timer watcher, then start it
-.Vb 3
-\&    /* 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);
-.Ve
+\&
-.PP
+\&     // now wait for events to arrive
-.Vb 2
-\&    /* loop till timeout or data ready */
-\&    ev_loop (loop, 0);
+\&     ev_loop (loop, 0);
-.Ve
+\&
-.PP
+\&     // unloop was called, so exit
-.Vb 2
-\&    return 0;
+\&     return 0;
-\&  }
+\&   }
 .Ve
 .SH "DESCRIPTION"
 .IX Header "DESCRIPTION"
+The newest version of this document is also available as an html-formatted
+web page you might find easier to navigate when reading it for the first
+time: <http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
+.PP
 Libev is an event loop: you register interest in certain events (such as a
-file descriptor being readable or a timeout occuring), and it will manage
+file descriptor being readable or a timeout occurring), and it will manage
 these event sources and provide your program with events.
 .PP
 To do this, it must take more or less complete control over your process
 (or thread) by executing the \fIevent loop\fR handler, and will then
 communicate events via a callback mechanism.
 .PP
 You register interest in certain events by registering so-called \fIevent
 watchers\fR, which are relatively small C structures you initialise with the
 details of the event, and then hand it over to libev by \fIstarting\fR the
 watcher.
-.SH "FEATURES"
+.Sh "\s-1FEATURES\s0"
-.IX Header "FEATURES"
+.IX Subsection "FEATURES"
 Libev supports \f(CW\*(C`select\*(C'\fR, \f(CW\*(C`poll\*(C'\fR, the Linux-specific \f(CW\*(C`epoll\*(C'\fR, the
 BSD-specific \f(CW\*(C`kqueue\*(C'\fR and the Solaris-specific event port mechanisms
 for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), the Linux \f(CW\*(C`inotify\*(C'\fR interface
 (for \f(CW\*(C`ev_stat\*(C'\fR), relative timers (\f(CW\*(C`ev_timer\*(C'\fR), absolute timers
 with customised rescheduling (\f(CW\*(C`ev_periodic\*(C'\fR), synchronous signals
 (\f(CW\*(C`ev_fork\*(C'\fR).
 .PP
 It also is quite fast (see this
 benchmark comparing it to libevent
 for example).
-.SH "CONVENTIONS"
+.Sh "\s-1CONVENTIONS\s0"
-.IX Header "CONVENTIONS"
+.IX Subsection "CONVENTIONS"
-Libev is very configurable. In this manual the default configuration will
+Libev is very configurable. In this manual the default (and most common)
-be described, which supports multiple event loops. For more info about
+configuration will be described, which supports multiple event loops. For
-various configuration options please have a look at \fB\s-1EMBED\s0\fR section in
+more info about various configuration options please have a look at
-this manual. If libev was configured without support for multiple event
+\&\fB\s-1EMBED\s0\fR section in this manual. If libev was configured without support
-loops, then all functions taking an initial argument of name \f(CW\*(C`loop\*(C'\fR
+for multiple event loops, then all functions taking an initial argument of
-(which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR) will not have this argument.
+name \f(CW\*(C`loop\*(C'\fR (which is always of type \f(CW\*(C`ev_loop *\*(C'\fR) will not have
-.SH "TIME REPRESENTATION"
+this argument.
+.Sh "\s-1TIME\s0 \s-1REPRESENTATION\s0"
-.IX Header "TIME REPRESENTATION"
+.IX Subsection "TIME REPRESENTATION"
 Libev represents time as a single floating point number, representing the
 (fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near
 the beginning of 1970, details are complicated, don't ask). This type is
 called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use too. It usually aliases
 to the \f(CW\*(C`double\*(C'\fR type in C, and when you need to do any calculations on
-it, you should treat it as such.
+it, you should treat it as some floating point value. Unlike the name
+component \f(CW\*(C`stamp\*(C'\fR might indicate, it is also used for time differences
+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
+Libev also has a few internal error-checking \f(CW\*(C`assert\*(C'\fRions, and also has
+extensive consistency checking code. 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.
+.IP "ev_sleep (ev_tstamp interval)" 4
+.IX Item "ev_sleep (ev_tstamp interval)"
+Sleep for the given interval: The current thread will be blocked until
+either it is interrupted or the given time interval has passed. Basically
+this is a sub-second-resolution \f(CW\*(C`sleep ()\*(C'\fR.
 .IP "int ev_version_major ()" 4
 .IX Item "int ev_version_major ()"
 .PD 0
 .IP "int ev_version_minor ()" 4
 .IX Item "int ev_version_minor ()"
 .PD
-You can find out the major and minor version numbers of the library
+You can find out the major and minor \s-1ABI\s0 version numbers of the library
 you linked against by calling the functions \f(CW\*(C`ev_version_major\*(C'\fR and
 \&\f(CW\*(C`ev_version_minor\*(C'\fR. If you want, you can compare against the global
 symbols \f(CW\*(C`EV_VERSION_MAJOR\*(C'\fR and \f(CW\*(C`EV_VERSION_MINOR\*(C'\fR, which specify the
 version of the library your program was compiled against.
 .Sp
+These version numbers refer to the \s-1ABI\s0 version of the library, not the
+release version.
+.Sp
 Usually, it's a good idea to terminate if the major versions mismatch,
-as this indicates an incompatible change.  Minor versions are usually
+as this indicates an incompatible change. Minor versions are usually
 compatible to older versions, so a larger minor version alone is usually
 not a problem.
 .Sp
 Example: Make sure we haven't accidentally been linked against the wrong
 version.
 .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
 recommended for this platform. This set is often smaller than the one
 returned by \f(CW\*(C`ev_supported_backends\*(C'\fR, as for example kqueue is broken on
-most BSDs and will not be autodetected unless you explicitly request it
+most BSDs and will not be auto-detected unless you explicitly request it
 (assuming you know what you are doing). This is the set of backends that
 libev will probe for if you specify no backends explicitly.
 .IP "unsigned int ev_embeddable_backends ()" 4
 .IX Item "unsigned int ev_embeddable_backends ()"
 Returns the set of backends that are embeddable in other event loops. This
-is the theoretical, all\-platform, value. To find which backends
+is the theoretical, all-platform, value. To find which backends
 might be supported on the current system, you would need to look at
 \&\f(CW\*(C`ev_embeddable_backends () & ev_supported_backends ()\*(C'\fR, likewise for
 recommended ones.
 .Sp
 See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info.
-.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4
+.IP "ev_set_allocator (void *(*cb)(void *ptr, long size)) [\s-1NOT\s0 \s-1REENTRANT\s0]" 4
-.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))"
+.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]"
 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: Replace the libev allocator with one that waits a bit and then
-retries).
+retries (example requires a standards-compliant \f(CW\*(C`realloc\*(C'\fR).
 .Sp
 .Vb 6
 \&   static void *
 \&   persistent_realloc (void *ptr, size_t size)
 \&   {
 \&     for (;;)
 \&       {
 \&         void *newptr = realloc (ptr, size);
-.Ve
+\&
-.Sp
-.Vb 2
 \&         if (newptr)
 \&           return newptr;
-.Ve
+\&
-.Sp
-.Vb 3
 \&         sleep (60);
 \&       }
 \&   }
-.Ve
+\&
-.Sp
-.Vb 2
 \&   ...
 \&   ev_set_allocator (persistent_realloc);
 .Ve
-.IP "ev_set_syserr_cb (void (*cb)(const char *msg));" 4
+.IP "ev_set_syserr_cb (void (*cb)(const char *msg)); [\s-1NOT\s0 \s-1REENTRANT\s0]" 4
-.IX Item "ev_set_syserr_cb (void (*cb)(const char *msg));"
+.IX Item "ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]"
-Set the callback function to call on a retryable syscall error (such
+Set the callback function to call on a retryable system call error (such
 as failed select, poll, epoll_wait). The message is a printable string
 indicating the system call or subsystem causing the problem. If this
-callback is set, then libev will expect it to remedy the sitution, no
+callback is set, then libev will expect it to remedy the situation, no
 matter what, when it returns. That is, libev will generally retry the
 requested operation, or, if the condition doesn't go away, do bad stuff
 (such as abort).
 .Sp
 Example: This is basically the same thing that libev does internally, too.
 \&   fatal_error (const char *msg)
 \&   {
 \&     perror (msg);
 \&     abort ();
 \&   }
-.Ve
+\&
-.Sp
-.Vb 2
 \&   ...
 \&   ev_set_syserr_cb (fatal_error);
 .Ve
 .SH "FUNCTIONS CONTROLLING THE EVENT LOOP"
 .IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP"
-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
-types of such loops, the \fIdefault\fR loop, which supports signals and child
+is \fInot\fR optional in this case, as there is also an \f(CW\*(C`ev_loop\*(C'\fR
-events, and dynamically created loops which do not.
+\&\fIfunction\fR).
 .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 signals and child events, and dynamically created loops which do
-create, you also create another event loop. Libev itself does no locking
+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
 yet and return it. If the default loop could not be initialised, returns
 false. If it already was initialised it simply returns it (and ignores the
 flags. If that is troubling you, check \f(CW\*(C`ev_backend ()\*(C'\fR afterwards).
 .Sp
 If you don't know what event loop to use, use the one returned from this
 function.
+.Sp
+Note that this function is \fInot\fR thread-safe, so if you want to use it
+from multiple threads, you have to lock (note also that this is unlikely,
+as loops cannot 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
+\&\f(CW\*(C`ev_child\*(C'\fR watchers, and to do this, it always registers a handler
+for \f(CW\*(C`SIGCHLD\*(C'\fR. If this is a problem for your application you can either
+create a dynamic loop with \f(CW\*(C`ev_loop_new\*(C'\fR that doesn't do that, or you
+can simply overwrite the \f(CW\*(C`SIGCHLD\*(C'\fR signal handler \fIafter\fR calling
+\&\f(CW\*(C`ev_default_init\*(C'\fR.
 .Sp
 The flags argument can be used to specify special behaviour or specific
 backends to use, and is usually specified as \f(CW0\fR (or \f(CW\*(C`EVFLAG_AUTO\*(C'\fR).
 .Sp
 The following flags are supported:
 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
 around bugs.
 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
-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 sequence
-without a syscall and thus \fIvery\fR fast, but my Linux system also has
+without a system call and thus \fIvery\fR fast, but my GNU/Linux system also has
 \&\f(CW\*(C`pthread_atfork\*(C'\fR which is even faster).
 .Sp
 The big advantage of this flag is that you can forget about fork (and
 forget about forgetting to tell libev about forking) when you use this
 flag.
 .Sp
-This flag setting cannot be overriden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR
+This flag setting cannot be overridden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR
 environment variable.
 .ie n .IP """EVBACKEND_SELECT""  (value 1, portable select backend)" 4
 .el .IP "\f(CWEVBACKEND_SELECT\fR  (value 1, portable select backend)" 4
 .IX Item "EVBACKEND_SELECT  (value 1, portable select backend)"
 This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as
 libev tries to roll its own fd_set with no limits on the number of fds,
 but if that fails, expect a fairly low limit on the number of fds when
-using this backend. It doesn't scale too well (O(highest_fd)), but its usually
+using this backend. It doesn't scale too well (O(highest_fd)), but its
-the fastest backend for a low number of fds.
+usually the fastest backend for a low number of (low-numbered :) fds.
+.Sp
+To get good performance out of this backend you need a high amount of
+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
+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)"
-And this is your standard \fIpoll\fR\|(2) backend. It's more complicated than
+And this is your standard \fIpoll\fR\|(2) backend. It's more complicated
-select, but handles sparse fds better and has no artificial limit on the
+than select, but handles sparse fds better and has no artificial
-number of fds you can use (except it will slow down considerably with a
+limit on the number of fds you can use (except it will slow down
-lot of inactive fds). It scales similarly to select, i.e. O(total_fds).
+considerably with a lot of inactive fds). It scales similarly to select,
+i.e. O(total_fds). See the entry for \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR, above, for
+performance tips.
+.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)"
 For few fds, this backend is a bit little slower than poll and select,
-but it scales phenomenally better. While poll and select usually scale like
+but it scales phenomenally better. While poll and select usually scale
-O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
+like O(total_fds) where n is the total number of fds (or the highest fd),
-either O(1) or O(active_fds).
+epoll scales either O(1) or O(active_fds).
 .Sp
+The epoll mechanism deserves honorable mention as the most misdesigned
+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 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.
+.Sp
-While stopping and starting an I/O watcher in the same iteration will
+While stopping, setting and starting an I/O watcher in the same iteration
-result in some caching, there is still a syscall per such incident
+will result in some caching, there is still a 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, \fIdup()\fRed file descriptors might not work very
+\&\fIfile description\fR now), so its best to avoid that. Also, \f(CW\*(C`dup ()\*(C'\fR'ed
-well if you register events for both fds.
+file descriptors might not work very well if you register events for both
+file descriptors.
 .Sp
-Please note that epoll sometimes generates spurious notifications, so you
+Best performance from this backend is achieved by not unregistering all
-need to use non-blocking I/O or other means to avoid blocking when no data
+watchers for a file descriptor until it has been closed, if possible,
-(or space) is available.
+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 embeddable in other event loops, this feature is broken in
+all kernel versions tested so far.
+.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)"
 Kqueue deserves special mention, as at the time of this writing, it
-was broken on all BSDs except NetBSD (usually it doesn't work with
+was broken on all BSDs except NetBSD (usually it doesn't work reliably
-anything but sockets and pipes, except on Darwin, where of course its
+with anything but sockets and pipes, except on Darwin, where of course
-completely useless). For this reason its not being \*(L"autodetected\*(R"
+it's completely useless). Unlike epoll, however, whose brokenness
+is by design, these kqueue bugs can (and eventually will) be fixed
+without \s-1API\s0 changes to existing programs. For this reason it's not being
-unless you explicitly specify it explicitly in the flags (i.e. using
+\&\*(L"auto-detected\*(R" unless you explicitly specify it in the flags (i.e. using
-\&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR).
+\&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR) or libev was compiled on a known-to-be-good (\-enough)
+system like NetBSD.
+.Sp
+You still can embed kqueue into a normal poll or select backend and use it
+only for sockets (after having made sure that sockets work with kqueue on
+the target platform). See \f(CW\*(C`ev_embed\*(C'\fR watchers for more info.
 .Sp
 It scales in the same way as the epoll backend, but the interface to the
 kernel is more efficient (which says nothing about its actual speed, of
-course). While starting and stopping an I/O watcher does not cause an
+course). While stopping, setting and starting an I/O watcher does never
-extra syscall as with epoll, it still adds up to four event changes per
+cause an extra system call as with \f(CW\*(C`EVBACKEND_EPOLL\*(C'\fR, it still adds up to
-incident, so its best to avoid that.
+two event changes per incident. Support for \f(CW\*(C`fork ()\*(C'\fR is very bad (but
+sane, unlike 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, 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).
+This is not implemented yet (and might never be, unless you send me an
+implementation). According to reports, \f(CW\*(C`/dev/poll\*(C'\fR only supports sockets
+and is not embeddable, which would limit the usefulness of this backend
+immensely.
 .ie n .IP """EVBACKEND_PORT""    (value 32, Solaris 10)" 4
 .el .IP "\f(CWEVBACKEND_PORT\fR    (value 32, Solaris 10)" 4
 .IX Item "EVBACKEND_PORT    (value 32, Solaris 10)"
-This uses the Solaris 10 port mechanism. As with everything on Solaris,
+This uses the Solaris 10 event port mechanism. As with everything on Solaris,
 it's really slow, but it still scales very well (O(active_fds)).
 .Sp
-Please note that solaris ports can result in a lot of spurious
+Please note that Solaris event ports can deliver a lot of spurious
 notifications, so you need to use non-blocking I/O or other means to avoid
 blocking when no data (or space) is available.
+.Sp
+While this backend scales well, it requires one system call per active
+file descriptor per loop iteration. For small and medium numbers of file
+descriptors a \*(L"slow\*(R" \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR backend
+might perform better.
+.Sp
+On the positive side, with the exception of the spurious readiness
+notifications, this backend actually performed fully to specification
+in all tests and is fully embeddable, which is a rare feat among the
+OS-specific backends (I vastly prefer correctness over speed hacks).
+.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.
 .RE
 .RS 4
 .Sp
-If one or more of these are ored into the flags value, then only these
+If one or more of these are or'ed into the flags value, then only these
-backends will be tried (in the reverse order as given here). If none are
+backends will be tried (in the reverse order as listed here). If none are
-specified, most compiled-in backend will be tried, usually in reverse
+specified, all backends in \f(CW\*(C`ev_recommended_backends ()\*(C'\fR will be tried.
-order of their flag values :)
 .Sp
-The most typical usage is like this:
+Example: This is the most typical usage.
 .Sp
 .Vb 2
-\&  if (!ev_default_loop (0))
+\&   if (!ev_default_loop (0))
-\&    fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
+\&     fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
 .Ve
 .Sp
-Restrict libev to the select and poll backends, and do not allow
+Example: Restrict libev to the select and poll backends, and do not allow
 environment settings to be taken into account:
 .Sp
 .Vb 1
-\&  ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
+\&   ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
 .Ve
 .Sp
-Use whatever libev has to offer, but make sure that kqueue is used if
+Example: Use whatever libev has to offer, but make sure that kqueue is
-available (warning, breaks stuff, best use only with your own private
+used if available (warning, breaks stuff, best use only with your own
-event loop and only if you know the \s-1OS\s0 supports your types of fds):
+private event loop and only if you know the \s-1OS\s0 supports your types of
+fds):
 .Sp
 .Vb 1
-\&  ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
+\&   ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
 .Ve
 .RE
 .IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4
 .IX Item "struct ev_loop *ev_loop_new (unsigned int flags)"
 Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is
 always distinct from the default loop. Unlike the default loop, it cannot
 handle signal and child watchers, and attempts to do so will be greeted by
 undefined behaviour (or a failed assertion if assertions are enabled).
 .Sp
+Note that this function \fIis\fR thread-safe, and the recommended way to use
+libev with threads is indeed to create one loop per thread, and using the
+default loop in the \*(L"main\*(R" or \*(L"initial\*(R" thread.
+.Sp
 Example: Try to create a event loop that uses epoll and nothing else.
 .Sp
 .Vb 3
-\&  struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
+\&   struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
-\&  if (!epoller)
+\&   if (!epoller)
-\&    fatal ("no epoll found here, maybe it hides under your chair");
+\&     fatal ("no epoll found here, maybe it hides under your chair");
 .Ve
 .IP "ev_default_destroy ()" 4
 .IX Item "ev_default_destroy ()"
 Destroys the default loop again (frees all memory and kernel state
 etc.). None of the active event watchers will be stopped in the normal
 sense, so e.g. \f(CW\*(C`ev_is_active\*(C'\fR might still return true. It is your
-responsibility to either stop all watchers cleanly yoursef \fIbefore\fR
+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, youc na just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them
+the easiest thing, you can just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them
 for example).
+.Sp
+Note that certain global state, such as signal state (and installed signal
+handlers), will not be freed by this function, and related watchers (such
+as signal and child watchers) would need to be stopped manually.
+.Sp
+In general it is not advisable to call this function except in the
+rare occasion where you really need to free e.g. the signal handling
+pipe fds. If you need dynamically allocated loops it is better to use
+\&\f(CW\*(C`ev_loop_new\*(C'\fR and \f(CW\*(C`ev_loop_destroy\*(C'\fR).
 .IP "ev_loop_destroy (loop)" 4
 .IX Item "ev_loop_destroy (loop)"
 Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an
 earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR.
 .IP "ev_default_fork ()" 4
 .IX Item "ev_default_fork ()"
+This function sets a flag that causes subsequent \f(CW\*(C`ev_loop\*(C'\fR iterations
-This function reinitialises the kernel state for backends that have
+to reinitialise the kernel state for backends that have one. Despite the
-one. Despite the name, you can call it anytime, but it makes most sense
+name, you can call it anytime, but it makes most sense after forking, in
-after forking, in either the parent or child process (or both, but that
+the child process (or both child and parent, but that again makes little
-again makes little sense).
+sense). You \fImust\fR call it in the child before using any of the libev
+functions, and it will only take effect at the next \f(CW\*(C`ev_loop\*(C'\fR iteration.
 .Sp
-You \fImust\fR call this function in the child process after forking if and
+On the other hand, you only need to call this function in the child
-only if you want to use the event library in both processes. If you just
+process if and only if you want to use the event library in the child. If
-fork+exec, you don't have to call it.
+you just fork+exec, you don't have to call it at all.
 .Sp
 The function itself is quite fast and it's usually not a problem to call
 it just in case after a fork. To make this easy, the function will fit in
 quite nicely into a call to \f(CW\*(C`pthread_atfork\*(C'\fR:
 .Sp
 .Vb 1
 \&    pthread_atfork (0, 0, ev_default_fork);
 .Ve
-.Sp
-At the moment, \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and \f(CW\*(C`EVBACKEND_POLL\*(C'\fR are safe to use
-without calling this function, so if you force one of those backends you
-do not need to care.
 .IP "ev_loop_fork (loop)" 4
 .IX Item "ev_loop_fork (loop)"
 Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by
 \&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop
-after fork, and how you do this is entirely your own problem.
+after fork that you want to re-use in the child, and how you do this is
+entirely your own problem.
+.IP "int ev_is_default_loop (loop)" 4
+.IX Item "int ev_is_default_loop (loop)"
+Returns true when the given loop is, in fact, the default loop, and false
+otherwise.
 .IP "unsigned int ev_loop_count (loop)" 4
 .IX Item "unsigned int ev_loop_count (loop)"
 Returns the count of loop iterations for the loop, which is identical to
 the number of times libev did poll for new events. It starts at \f(CW0\fR and
 happily wraps around with enough iterations.
 .IX Item "ev_tstamp ev_now (loop)"
 Returns the current \*(L"event loop time\*(R", which is the time the event loop
 received events and started processing them. This timestamp does not
 change as long as callbacks are being processed, and this is also the base
 time used for relative timers. You can treat it as the timestamp of the
-event occuring (or more correctly, libev finding out about it).
+event occurring (or more correctly, libev finding out about it).
+.IP "ev_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_loop ()\*(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_loop (loop, int flags)" 4
 .IX Item "ev_loop (loop, int flags)"
 Finally, this is it, the event handler. This function usually is called
 after you initialised all your watchers and you want to start handling
 events.
 If the flags argument is specified as \f(CW0\fR, it will not return until
 either no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called.
 .Sp
 Please note that an explicit \f(CW\*(C`ev_unloop\*(C'\fR is usually better than
 relying on all watchers to be stopped when deciding when a program has
-finished (especially in interactive programs), but having a program that
+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
 A flags value of \f(CW\*(C`EVLOOP_NONBLOCK\*(C'\fR will look for new events, will handle
-those events and any outstanding ones, but will not block your process in
+those events and any already outstanding ones, but will not block your
-case there are no events and will return after one iteration of the loop.
+process in case there are no events and will return after one iteration of
+the loop.
 .Sp
 A flags value of \f(CW\*(C`EVLOOP_ONESHOT\*(C'\fR will look for new events (waiting if
-neccessary) and will handle those and any outstanding ones. It will block
+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_loop\*(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:
 .Sp
-.Vb 18
+.Vb 10
-\&   * If there are no active watchers (reference count is zero), return.
+\&   \- Before the first iteration, call any pending watchers.
-\&   - Queue prepare watchers and then call all outstanding watchers.
+\&   * If EVFLAG_FORKCHECK was used, check for a fork.
+\&   \- If a fork was detected (by any means), queue and call all fork watchers.
+\&   \- Queue and call all prepare watchers.
-\&   - If we have been forked, recreate the kernel state.
+\&   \- If we have been forked, detach and recreate the kernel state
+\&     as to not disturb the other process.
-\&   - Update the kernel state with all outstanding changes.
+\&   \- Update the kernel state with all outstanding changes.
-\&   - Update the "event loop time".
+\&   \- Update the "event loop time" (ev_now ()).
-\&   - Calculate for how long to block.
+\&   \- Calculate for how long to sleep or block, if at all
+\&     (active idle watchers, EVLOOP_NONBLOCK or not having
+\&     any active watchers at all will result in not sleeping).
+\&   \- Sleep if the I/O and timer collect interval say so.
-\&   - Block the process, waiting for any events.
+\&   \- Block the process, waiting for any events.
-\&   - Queue all outstanding I/O (fd) events.
+\&   \- Queue all outstanding I/O (fd) events.
-\&   - Update the "event loop time" and do time jump handling.
+\&   \- Update the "event loop time" (ev_now ()), and do time jump adjustments.
-\&   - Queue all outstanding timers.
+\&   \- Queue all expired timers.
-\&   - Queue all outstanding periodics.
+\&   \- Queue all expired periodics.
-\&   - If no events are pending now, queue all idle watchers.
+\&   \- Unless any events are pending now, queue all idle watchers.
-\&   - Queue all check watchers.
+\&   \- Queue all check watchers.
-\&   - Call all queued watchers in reverse order (i.e. check watchers first).
+\&   \- Call all queued watchers in reverse order (i.e. check watchers first).
 \&     Signals and child watchers are implemented as I/O watchers, and will
 \&     be handled here by queueing them when their watcher gets executed.
-\&   - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
+\&   \- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
-\&     were used, return, otherwise continue with step *.
+\&     were used, or there are no active watchers, return, otherwise
+\&     continue with step *.
 .Ve
 .Sp
-Example: Queue some jobs and then loop until no events are outsanding
+Example: Queue some jobs and then loop until no events are outstanding
 anymore.
 .Sp
 .Vb 4
 \&   ... queue jobs here, make sure they register event watchers as long
 \&   ... as they still have work to do (even an idle watcher will do..)
 \&   ev_loop (my_loop, 0);
-\&   ... jobs done. yeah!
+\&   ... jobs done or somebody called unloop. yeah!
 .Ve
 .IP "ev_unloop (loop, how)" 4
 .IX Item "ev_unloop (loop, how)"
 Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it
 has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either
 \&\f(CW\*(C`EVUNLOOP_ONE\*(C'\fR, which will make the innermost \f(CW\*(C`ev_loop\*(C'\fR call return, or
 \&\f(CW\*(C`EVUNLOOP_ALL\*(C'\fR, which will make all nested \f(CW\*(C`ev_loop\*(C'\fR calls return.
+.Sp
+This \*(L"unloop state\*(R" will be cleared when entering \f(CW\*(C`ev_loop\*(C'\fR again.
+.Sp
+It is safe to call \f(CW\*(C`ev_unloop\*(C'\fR from otuside any \f(CW\*(C`ev_loop\*(C'\fR calls.
 .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_loop\*(C'\fR will not return on its own.
+.Sp
-a watcher you never unregister that should not keep \f(CW\*(C`ev_loop\*(C'\fR from
+If you have a watcher you never unregister that should not keep \f(CW\*(C`ev_loop\*(C'\fR
-returning, \fIev_unref()\fR after starting, and \fIev_ref()\fR before stopping it. For
+from returning, call \fIev_unref()\fR after starting, and \fIev_ref()\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 is
-visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if
+not visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting
-no event watchers registered by it are active. It is also an excellent
+if no event watchers registered by it are active. It is also an excellent
 way to do this for generic recurring timers or from within third-party
-libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR.
+libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR
+(but only if the watcher wasn't active before, or was active before,
+respectively).
 .Sp
 Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR
 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);
+\&   evf_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 time intervals are by default \f(CW0\fR, meaning that libev
+will try to invoke timer/periodic callbacks and I/O callbacks with minimum
+latency.
+.Sp
+Setting these to a higher value (the \f(CW\*(C`interval\*(C'\fR \fImust\fR be >= \f(CW0\fR)
+allows libev to delay invocation of I/O and timer/periodic callbacks
+to increase efficiency of loop iterations (or to increase power-saving
+opportunities).
+.Sp
+The idea is that sometimes your program runs just fast enough to handle
+one (or very few) event(s) per loop iteration. While this makes the
+program responsive, it also wastes a lot of \s-1CPU\s0 time to poll for new
+events, especially with backends like \f(CW\*(C`select ()\*(C'\fR which have a high
+overhead for the actual polling but can deliver many events at once.
+.Sp
+By setting a higher \fIio collect interval\fR you allow libev to spend more
+time collecting I/O events, so you can handle more events per iteration,
+at the cost of increasing latency. Timeouts (both \f(CW\*(C`ev_periodic\*(C'\fR and
+\&\f(CW\*(C`ev_timer\*(C'\fR) will be not affected. Setting this to a non-null value will
+introduce an additional \f(CW\*(C`ev_sleep ()\*(C'\fR call into most loop iterations.
+.Sp
+Likewise, by setting a higher \fItimeout collect interval\fR you allow libev
+to spend more time collecting timeouts, at the expense of increased
+latency/jitter/inexactness (the watcher callback will be called
+later). \f(CW\*(C`ev_io\*(C'\fR watchers will not be affected. Setting this to a non-null
+value will not introduce any overhead in libev.
+.Sp
+Many (busy) programs can usually benefit by setting the 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 approaches the timing granularity of most systems.
+.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.
+.IP "ev_loop_verify (loop)" 4
+.IX Item "ev_loop_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
 interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to
 become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that:
 .PP
 .Vb 5
-\&  static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
+\&   static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
-\&  {
+\&   {
-\&    ev_io_stop (w);
+\&     ev_io_stop (w);
-\&    ev_unloop (loop, EVUNLOOP_ALL);
+\&     ev_unloop (loop, EVUNLOOP_ALL);
-\&  }
+\&   }
-.Ve
+\&
-.PP
-.Vb 6
-\&  struct ev_loop *loop = ev_default_loop (0);
+\&   struct ev_loop *loop = ev_default_loop (0);
+\&
-\&  struct ev_io stdin_watcher;
+\&   ev_io stdin_watcher;
+\&
-\&  ev_init (&stdin_watcher, my_cb);
+\&   ev_init (&stdin_watcher, my_cb);
-\&  ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
+\&   ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
-\&  ev_io_start (loop, &stdin_watcher);
+\&   ev_io_start (loop, &stdin_watcher);
+\&
-\&  ev_loop (loop, 0);
+\&   ev_loop (loop, 0);
 .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
 (watcher *, callback)\*(C'\fR, which expects a callback to be provided. This
-callback gets invoked each time the event occurs (or, in the case of io
+callback gets invoked each time the event occurs (or, in the case of I/O
 watchers, each time the event loop detects that the file descriptor given
 is readable and/or writable).
 .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
-reinitialise it or call its \f(CW\*(C`set\*(C'\fR macro.
+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
 .ie n .IP """EV_FORK""" 4
 .el .IP "\f(CWEV_FORK\fR" 4
 .IX Item "EV_FORK"
 The event loop has been resumed in the child process after fork (see
 \&\f(CW\*(C`ev_fork\*(C'\fR).
+.ie n .IP """EV_ASYNC""" 4
+.el .IP "\f(CWEV_ASYNC\fR" 4
+.IX Item "EV_ASYNC"
+The given async watcher has been asynchronously notified (see \f(CW\*(C`ev_async\*(C'\fR).
 .ie n .IP """EV_ERROR""" 4
 .el .IP "\f(CWEV_ERROR\fR" 4
 .IX Item "EV_ERROR"
-An unspecified error has occured, the watcher has been stopped. This might
+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 \fIread()\fR or \fIwrite()\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"
 .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
 .el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4
 .IX Item "ev_TYPE_set (ev_TYPE *, [args])"
 This macro initialises the type-specific parts of a watcher. You need to
 call \f(CW\*(C`ev_init\*(C'\fR at least once before you call this macro, but you can
 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
 .el .IP "\f(CWev_TYPE_start\fR (loop *, ev_TYPE *watcher)" 4
 .IX Item "ev_TYPE_start (loop *, ev_TYPE *watcher)"
 Starts (activates) the given watcher. Only active watchers will receive
 events. If the watcher is already active nothing will happen.
+.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
 .el .IP "\f(CWev_TYPE_stop\fR (loop *, ev_TYPE *watcher)" 4
 .IX Item "ev_TYPE_stop (loop *, ev_TYPE *watcher)"
-Stops the given watcher again (if active) and clears the pending
+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.
 .IP "bool ev_is_pending (ev_TYPE *watcher)" 4
 .IX Item "bool ev_is_pending (ev_TYPE *watcher)"
 Returns a true value iff the watcher is pending, (i.e. it has outstanding
 events but its callback has not yet been invoked). As long as a watcher
 is pending (but not active) you must not call an init function on it (but
-\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe) and you must make sure the watcher is available to
+\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe), you must not change its priority, and you must
-libev (e.g. you cnanot \f(CW\*(C`free ()\*(C'\fR it).
+make sure the watcher is available to libev (e.g. you cannot \f(CW\*(C`free ()\*(C'\fR
+it).
 .IP "callback ev_cb (ev_TYPE *watcher)" 4
 .IX Item "callback ev_cb (ev_TYPE *watcher)"
 Returns the callback currently set on the watcher.
 .IP "ev_cb_set (ev_TYPE *watcher, callback)" 4
 .IX Item "ev_cb_set (ev_TYPE *watcher, callback)"
 watchers on the same event and make sure one is called first.
 .Sp
 If you need to suppress invocation when higher priority events are pending
 you need to look at \f(CW\*(C`ev_idle\*(C'\fR watchers, which provide this functionality.
 .Sp
+You \fImust not\fR change the priority of a watcher as long as it is active or
+pending.
+.Sp
 The default priority used by watchers when no priority has been set is
 always \f(CW0\fR, which is supposed to not be too high and not be too low :).
 .Sp
 Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR is
 fine, as long as you do not mind that the priority value you query might
-or might not have been adjusted to be within valid range.
+or might not have been clamped to the 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, 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 clears its pending status and
+returns its \f(CW\*(C`revents\*(C'\fR bitset (as if its callback was invoked). If the
+watcher isn't pending it does nothing and returns \f(CW0\fR.
+.Sp
+Sometimes it can be useful to \*(L"poll\*(R" a watcher instead of waiting for its
+callback to be invoked, which can be accomplished with this function.
 .Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0"
 .IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER"
 Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change
-and read at any time, libev will completely ignore it. This can be used
+and read at any time: libev will completely ignore it. This can be used
 to associate arbitrary data with your watcher. If you need more data and
 don't want to allocate memory and store a pointer to it in that data
 member, you can also \*(L"subclass\*(R" the watcher type and provide your own
 data:
 .PP
 .Vb 7
-\&  struct my_io
+\&   struct my_io
-\&  {
+\&   {
-\&    struct ev_io io;
+\&     ev_io io;
-\&    int otherfd;
+\&     int otherfd;
-\&    void *somedata;
+\&     void *somedata;
-\&    struct whatever *mostinteresting;
+\&     struct whatever *mostinteresting;
-\&  }
+\&   };
+\&
+\&   ...
+\&   struct my_io w;
+\&   ev_io_init (&w.io, my_cb, fd, EV_READ);
 .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)
+\&   static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
-\&  {
+\&   {
-\&    struct my_io *w = (struct my_io *)w_;
+\&     struct my_io *w = (struct my_io *)w_;
-\&    ...
+\&     ...
-\&  }
+\&   }
 .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
+Another common scenario is to use some data structure with multiple
-watchers:
+embedded watchers:
 .PP
 .Vb 6
-\&  struct my_biggy
+\&   struct my_biggy
-\&  {
+\&   {
-\&    int some_data;
+\&     int some_data;
-\&    ev_timer t1;
+\&     ev_timer t1;
-\&    ev_timer t2;
+\&     ev_timer t2;
-\&  }
+\&   }
 .Ve
 .PP
-In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more complicated,
+In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more
-you need to use \f(CW\*(C`offsetof\*(C'\fR:
+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 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>
+\&   #include <stddef.h>
-.Ve
+\&
-.PP
-.Vb 6
-\&  static void
+\&   static void
-\&  t1_cb (EV_P_ struct ev_timer *w, int revents)
+\&   t1_cb (EV_P_ ev_timer *w, int revents)
-\&  {
+\&   {
-\&    struct my_biggy big = (struct my_biggy *
+\&     struct my_biggy big = (struct my_biggy *
-\&      (((char *)w) - offsetof (struct my_biggy, t1));
+\&       (((char *)w) \- offsetof (struct my_biggy, t1));
-\&  }
+\&   }
-.Ve
+\&
-.PP
-.Vb 6
-\&  static void
+\&   static void
-\&  t2_cb (EV_P_ struct ev_timer *w, int revents)
+\&   t2_cb (EV_P_ ev_timer *w, int revents)
-\&  {
+\&   {
-\&    struct my_biggy big = (struct my_biggy *
+\&     struct my_biggy big = (struct my_biggy *
-\&      (((char *)w) - offsetof (struct my_biggy, t2));
+\&       (((char *)w) \- offsetof (struct my_biggy, t2));
-\&  }
+\&   }
 .Ve
 .SH "WATCHER TYPES"
 .IX Header "WATCHER TYPES"
 This section describes each watcher in detail, but will not repeat
 information given in the last section. Any initialisation/set macros,
 In general you can register as many read and/or write event watchers per
 fd as you want (as long as you don't confuse yourself). Setting all file
 descriptors to non-blocking mode is also usually a good idea (but not
 required if you know what you are doing).
 .PP
-You have to be careful with dup'ed file descriptors, though. Some backends
+If you cannot use non-blocking mode, then force the use of a
-(the linux epoll backend is a notable example) cannot handle dup'ed file
+known-to-be-good backend (at the time of this writing, this includes only
-descriptors correctly if you register interest in two or more fds pointing
+\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and \f(CW\*(C`EVBACKEND_POLL\*(C'\fR).
-to the same underlying file/socket/etc. description (that is, they share
-the same underlying \*(L"file open\*(R").
-.PP
-If you must do this, then force the use of a known-to-be-good backend
-(at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and
-\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR).
 .PP
 Another thing you have to watch out for is that it is quite easy to
-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
-lot of those (for example solaris ports), it is very easy to get into
+lot of those (for example Solaris ports), it is very easy to get into
 this situation even with a relatively standard program structure. Thus
 it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning
 \&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives.
 .PP
-If you cannot run the fd in non-blocking mode (for example you should not
+If you cannot run the fd in non-blocking mode (for example you should
-play around with an Xlib connection), then you have to seperately re-test
+not play around with an Xlib connection), then you have to separately
-whether a file descriptor is really ready with a known-to-be good interface
+re-test whether a file descriptor is really ready with a known-to-be good
-such as poll (fortunately in our Xlib example, Xlib already does this on
+interface such as poll (fortunately in our Xlib example, Xlib already
-its own, so its quite safe to use).
+does this on its own, so its quite safe to use). Some people additionally
+use \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
+descriptor (either due to calling \f(CW\*(C`close\*(C'\fR explicitly or any other means,
+such as \f(CW\*(C`dup2\*(C'\fR). The reason is that you register interest in some file
+descriptor, but when it goes away, the operating system will silently drop
+this interest. If another file descriptor with the same number then is
+registered with libev, there is no efficient way to see that this is, in
+fact, a different file descriptor.
+.PP
+To avoid having to explicitly tell libev about such cases, libev follows
+the following policy:  Each time \f(CW\*(C`ev_io_set\*(C'\fR is being called, libev
+will assume that this is potentially a new file descriptor, otherwise
+it is assumed that the file descriptor stays the same. That means that
+you \fIhave\fR to call \f(CW\*(C`ev_io_set\*(C'\fR (or \f(CW\*(C`ev_io_init\*(C'\fR) when you change the
+descriptor even if the file descriptor number itself did not change.
+.PP
+This is how one would do it normally anyway, the important point is that
+the libev application should not optimise around libev but should leave
+optimisations to libev.
+.PP
+\fIThe special problem of dup'ed file descriptors\fR
+.IX Subsection "The special problem of dup'ed file descriptors"
+.PP
+Some backends (e.g. epoll), cannot register events for file descriptors,
+but only events for the underlying file descriptions. That means when you
+have \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors or weirder constellations, and register
+events for them, only one file descriptor might actually receive events.
+.PP
+There is no workaround possible except not registering events
+for potentially \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors, or to resort to
+\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
+.PP
+\fIThe special problem of fork\fR
+.IX Subsection "The special problem of fork"
+.PP
+Some backends (epoll, kqueue) do not support \f(CW\*(C`fork ()\*(C'\fR at all or exhibit
+useless behaviour. Libev fully supports fork, but needs to be told about
+it in the child.
+.PP
+To support fork in your programs, you either have to call
+\&\f(CW\*(C`ev_default_fork ()\*(C'\fR or \f(CW\*(C`ev_loop_fork ()\*(C'\fR after a fork in the child,
+enable \f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR, or resort to \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or
+\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
+.PP
+\fIThe special problem of \s-1SIGPIPE\s0\fR
+.IX Subsection "The special problem of SIGPIPE"
+.PP
+While not really specific to libev, it is easy to forget about \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
+\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 or
-\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR to receive the given events.
+\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR, to express the desire to receive the given events.
 .IP "int fd [read\-only]" 4
 .IX Item "int fd [read-only]"
 The file descriptor being watched.
 .IP "int events [read\-only]" 4
 .IX Item "int events [read-only]"
 The events being watched.
 .PP
+\fIExamples\fR
+.IX Subsection "Examples"
+.PP
 Example: Call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well
-readable, but only once. Since it is likely line\-buffered, you could
+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
-\&  }
+\&   }
-.Ve
+\&
-.PP
-.Vb 6
-\&  ...
+\&   ...
-\&  struct ev_loop *loop = ev_default_init (0);
+\&   struct ev_loop *loop = ev_default_init (0);
-\&  struct ev_io stdin_readable;
+\&   ev_io stdin_readable;
-\&  ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
+\&   ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
-\&  ev_io_start (loop, &stdin_readable);
+\&   ev_io_start (loop, &stdin_readable);
-\&  ev_loop (loop, 0);
+\&   ev_loop (loop, 0);
 .Ve
 .ie n .Sh """ev_timer"" \- relative and optionally repeating timeouts"
 .el .Sh "\f(CWev_timer\fP \- relative and optionally repeating timeouts"
 .IX Subsection "ev_timer - relative and optionally repeating timeouts"
 Timer watchers are simple relative timers that generate an event after a
 given time, and optionally repeating in regular intervals after that.
 .PP
 The timers are based on real time, that is, if you register an event that
-times out after an hour and you reset your system clock to last years
+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, but if multiple timers become ready during the same loop iteration
+then order of execution is undefined.
+.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_timer_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 1
+\&   ev_tstamp last_activity; // time of last activity
+\&
+\&   static void
+\&   callback (EV_P_ ev_timer *w, int revents)
+\&   {
+\&     ev_tstamp now     = ev_now (EV_A);
+\&     ev_tstamp timeout = last_activity + 60.;
+\&
+\&     // if last_activity + 60. is older than now, we did time out
+\&     if (timeout < now)
+\&       {
+\&         // timeout occured, take action
+\&       }
+\&     else
+\&       {
+\&         // callback was invoked, but there was some activity, re\-arm
+\&         // the watcher to fire in last_activity + 60, which is
+\&         // guaranteed to be in the future, so "again" is positive:
+\&         w\->repeat = timeout \- now;
+\&         ev_timer_again (EV_A_ w);
+\&       }
+\&   }
+.Ve
+.Sp
+To summarise the callback: first calculate the real timeout (defined
+as \*(L"60 seconds after the last activity\*(R"), then check if that time has
+been reached, which means something \fIdid\fR, in fact, time out. Otherwise
+the callback was invoked too early (\f(CW\*(C`timeout\*(C'\fR is in the future), so
+re-schedule the timer to fire at that future time, to see if maybe we have
+a timeout then.
+.Sp
+Note how \f(CW\*(C`ev_timer_again\*(C'\fR is used, taking advantage of the
+\&\f(CW\*(C`ev_timer_again\*(C'\fR optimisation when the timer is already running.
+.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 timer, simply initialise the watcher and set \f(CW\*(C`last_activity\*(C'\fR
+to the current time (meaning we just have some activity :), then call the
+callback, which will \*(L"do the right thing\*(R" and start the timer:
+.Sp
+.Vb 3
+\&   ev_timer_init (timer, callback);
+\&   last_activity = ev_now (loop);
+\&   callback (loop, timer, EV_TIMEOUT);
+.Ve
+.Sp
+And 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 1
+\&   last_actiivty = ev_now (loop);
+.Ve
+.Sp
+This technique is slightly more complex, but in most cases where the
+time-out is unlikely to be triggered, much more efficient.
+.Sp
+Changing the timeout is trivial as well (if it isn't hard-coded in the
+callback :) \- just change the timeout and invoke the callback, which will
+fix things for you.
+.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 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 two system calls): \s-1EV\s0 therefore updates its idea of the current
+time only before and after \f(CW\*(C`ev_loop\*(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 this to adjust for this:
 .PP
 .Vb 1
-\&   ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
+\&   ev_timer_set (&timer, after + ev_now () \- ev_time (), 0.);
 .Ve
 .PP
-The callback is guarenteed to be invoked only when its timeout has passed,
+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.
+.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. If \f(CW\*(C`repeat\*(C'\fR
-\&\f(CW0.\fR, then it will automatically be stopped. If it is positive, then the
+is \f(CW0.\fR, then it will automatically be stopped once the timeout is
-timer will automatically be configured to trigger again \f(CW\*(C`repeat\*(C'\fR seconds
+reached. If it is positive, then the timer will automatically be
-later, again, and again, until stopped manually.
+configured to trigger again \f(CW\*(C`repeat\*(C'\fR seconds later, again, and again,
+until stopped manually.
 .Sp
-The timer itself will do a best-effort at avoiding drift, that is, if you
+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)" 4
+.IP "ev_timer_again (loop, ev_timer *)" 4
-.IX Item "ev_timer_again (loop)"
+.IX Item "ev_timer_again (loop, ev_timer *)"
 This will act as if the timer timed out and restart it again if it is
 repeating. The exact semantics are:
 .Sp
 If the timer is pending, its pending status is cleared.
 .Sp
-If the timer is started but nonrepeating, stop it (as if it timed out).
+If the timer is started but non-repeating, stop it (as if it timed out).
 .Sp
 If the timer is repeating, either start it if necessary (with the
 \&\f(CW\*(C`repeat\*(C'\fR value), or reset the running timer to the \f(CW\*(C`repeat\*(C'\fR value.
 .Sp
-This sounds a bit complicated, but here is a useful and typical
+This sounds a bit complicated, see \*(L"Be smart about timeouts\*(R", above, for a
-example: Imagine you have a tcp connection and you want a so-called idle
+usage example.
-timeout, that is, you want to be called when there have been, say, 60
-seconds of inactivity on the socket. The easiest way to do this is to
-configure an \f(CW\*(C`ev_timer\*(C'\fR with a \f(CW\*(C`repeat\*(C'\fR value of \f(CW60\fR and then call
-\&\f(CW\*(C`ev_timer_again\*(C'\fR each time you successfully read or write some data. If
-you go into an idle state where you do not expect data to travel on the
-socket, you can \f(CW\*(C`ev_timer_stop\*(C'\fR the timer, and \f(CW\*(C`ev_timer_again\*(C'\fR will
-automatically restart it if need be.
-.Sp
-That means you can ignore the \f(CW\*(C`after\*(C'\fR value and \f(CW\*(C`ev_timer_start\*(C'\fR
-altogether and only ever use the \f(CW\*(C`repeat\*(C'\fR value and \f(CW\*(C`ev_timer_again\*(C'\fR:
-.Sp
-.Vb 8
-\&   ev_timer_init (timer, callback, 0., 5.);
-\&   ev_timer_again (loop, timer);
-\&   ...
-\&   timer->again = 17.;
-\&   ev_timer_again (loop, timer);
-\&   ...
-\&   timer->again = 10.;
-\&   ev_timer_again (loop, timer);
-.Ve
-.Sp
-This is more slightly efficient then stopping/starting the timer each time
-you want to modify its timeout value.
 .IP "ev_tstamp repeat [read\-write]" 4
 .IX Item "ev_tstamp repeat [read-write]"
 The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out
-or \f(CW\*(C`ev_timer_again\*(C'\fR is called and determines the next timeout (if any),
+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
-\&  }
+\&   }
-.Ve
+\&
-.PP
-.Vb 3
-\&  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
-\&  }
+\&   }
-.Ve
+\&
-.PP
-.Vb 4
-\&  struct ev_timer mytimer;
+\&   ev_timer mytimer;
-\&  ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
+\&   ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
-\&  ev_timer_again (&mytimer); /* start timer */
+\&   ev_timer_again (&mytimer); /* start timer */
-\&  ev_loop (loop, 0);
+\&   ev_loop (loop, 0);
-.Ve
+\&
-.PP
-.Vb 3
-\&  // 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?"
 .el .Sh "\f(CWev_periodic\fP \- to cron or not to cron?"
 .IX Subsection "ev_periodic - to cron or not to cron?"
 Periodic watchers are also timers of a kind, but they are very versatile
 (and unfortunately a bit complex).
 .PP
 Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time)
-but on wallclock time (absolute time). You can tell a periodic watcher
+but on wall clock time (absolute time). You can tell a periodic watcher
-to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a
+to trigger after some specific point in time. For example, if you tell a
-periodic watcher to trigger in 10 seconds (by specifiying e.g. \f(CW\*(C`ev_now ()
+periodic watcher to trigger in 10 seconds (by specifying e.g. \f(CW\*(C`ev_now ()
-+ 10.\*(C'\fR) and then reset your system clock to the last year, then it will
++ 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 more than year
-take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger
+to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would still trigger
-roughly 10 seconds later and of course not if you reset your system time
+roughly 10 seconds later as it uses a relative timeout).
-again).
 .PP
-They can also be used to implement vastly more complex timers, such as
+\&\f(CW\*(C`ev_periodic\*(C'\fRs can also be used to implement vastly more complex timers,
-triggering an event on eahc midnight, local time.
+such as triggering an event on each \*(L"midnight, local time\*(R", or other
+complicated rules.
 .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
+time (\f(CW\*(C`at\*(C'\fR) has passed, but if multiple periodic timers become ready
-during the same loop iteration then order of execution is undefined.
+during the same loop iteration, then order of execution is undefined.
+.PP
+\fIWatcher-Specific Functions and Data Members\fR
+.IX Subsection "Watcher-Specific Functions and Data Members"
 .IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4
 .IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)"
 .PD 0
 .IP "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 4
 .IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)"
 .PD
 Lots of arguments, lets sort it out... There are basically three modes of
-operation, and we will explain them from simplest to complex:
+operation, and we will explain them from simplest to most complex:
 .RS 4
+.IP "\(bu" 4
-.IP "* absolute timer (interval = reschedule_cb = 0)" 4
+absolute timer (at = time, interval = reschedule_cb = 0)
-.IX Item "absolute timer (interval = reschedule_cb = 0)"
+.Sp
-In this configuration the watcher triggers an event at the wallclock time
+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`at\*(C'\fR has passed. It will not repeat and will not adjust when a time
-that is, if it is to be run at January 1st 2011 then it will run when the
+jump occurs, that is, if it is to be run at January 1st 2011 then it will
-system time reaches or surpasses this time.
+only run when the system clock reaches or surpasses this time.
+.IP "\(bu" 4
-.IP "* non-repeating interval timer (interval > 0, reschedule_cb = 0)" 4
+repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
-.IX Item "non-repeating interval timer (interval > 0, reschedule_cb = 0)"
+.Sp
 In this mode the watcher will always be scheduled to time out at the next
-\&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N) and then repeat, regardless
+\&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N, which can also be negative)
-of any time jumps.
+and then repeat, regardless of any time jumps.
 .Sp
-This can be used to create timers that do not drift with respect to system
+This can be used to create timers that do not drift with respect to the
-time:
+system clock, for example, here is a \f(CW\*(C`ev_periodic\*(C'\fR that triggers each
+hour, on the hour:
 .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.
-.IP "* manual reschedule mode (reschedule_cb = callback)" 4
+.Sp
-.IX Item "manual reschedule mode (reschedule_cb = callback)"
+For numerical stability it is preferable that the \f(CW\*(C`at\*(C'\fR value is near
+\&\f(CW\*(C`ev_now ()\*(C'\fR (the current time), but there is no range requirement for
+this value, and in fact is often specified as zero.
+.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)
+.Sp
 In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR are both being
 ignored. Instead, each time the periodic watcher gets scheduled, the
 reschedule callback will be called with the watcher as first, and the
 current time as second argument.
 .Sp
 \&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher,
-ever, or make any event loop modifications\fR. If you need to stop it,
+ever, or make \s-1ANY\s0 event loop modifications whatsoever\fR.
-return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop it afterwards (e.g. by
-starting a prepare watcher).
 .Sp
+If you need to stop it, return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop
+it afterwards (e.g. by starting an \f(CW\*(C`ev_prepare\*(C'\fR watcher, which is 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 the
 next midnight after \f(CW\*(C`now\*(C'\fR and return the timestamp value for this. How
 you do this is, again, up to you (but it is not trivial, which is the main
 reason I omitted it as an example).
 .RE
 .RS 4
 .IX Item "ev_periodic_again (loop, ev_periodic *)"
 Simply stops and restarts the periodic watcher again. This is only useful
 when you changed some parameters or the reschedule callback would return
 a different time than the last time it was called (e.g. in a crond like
 program when the crontabs have changed).
+.IP "ev_tstamp ev_periodic_at (ev_periodic *)" 4
+.IX Item "ev_tstamp ev_periodic_at (ev_periodic *)"
+When active, returns the absolute time that the watcher is supposed to
+trigger next.
+.IP "ev_tstamp offset [read\-write]" 4
+.IX Item "ev_tstamp offset [read-write]"
+When repeating, this contains the offset value, otherwise this is the
+absolute point in time (the \f(CW\*(C`at\*(C'\fR value passed to \f(CW\*(C`ev_periodic_set\*(C'\fR).
+.Sp
+Can be modified any time, but changes only take effect when the periodic
+timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
 .IP "ev_tstamp interval [read\-write]" 4
 .IX Item "ev_tstamp interval [read-write]"
 The current interval value. Can be modified any time, but changes only
 take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being
 called.
-.IP "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read\-write]" 4
+.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.
 .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_io *w, int revents)
-\&  {
+\&   {
-\&    ... its now a full hour (UTC, or TAI or whatever your clock follows)
+\&     ... its now a full hour (UTC, or TAI or whatever your clock follows)
-\&  }
+\&   }
-.Ve
+\&
-.PP
-.Vb 3
-\&  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>
-.Ve
+\&
-.PP
-.Vb 5
-\&  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.));
-\&  }
+\&   }
-.Ve
+\&
-.PP
-.Vb 1
-\&  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!"
 .el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled!"
 .IX Subsection "ev_signal - signal me when a signal gets signalled!"
 Signal watchers will trigger an event when the process receives a specific
 signal one or more times. Even though signals are very asynchronous, libev
 will try it's best to deliver signals synchronously, i.e. as part of the
 normal event processing, like any other event.
 .PP
+If you want signals 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
-first watcher gets started will libev actually register a signal watcher
+first watcher gets started will libev actually register a signal handler
-with the kernel (thus it coexists with your own signal handlers as long
+with the kernel (thus it coexists with your own signal handlers as long as
-as you don't register any with libev). Similarly, when the last signal
+you don't register any with libev for the same signal). Similarly, when
-watcher for a signal is stopped libev will reset the signal handler to
+the last signal watcher for a signal is stopped, libev will reset the
-\&\s-1SIG_DFL\s0 (regardless of what it was set to before).
+signal handler to \s-1SIG_DFL\s0 (regardless of what it was set to before).
+.PP
+If possible and supported, libev will install its handlers with
+\&\f(CW\*(C`SA_RESTART\*(C'\fR behaviour enabled, so system calls should not be unduly
+interrupted. If you have a problem with system calls getting interrupted by
+signals you can block all signals in an \f(CW\*(C`ev_check\*(C'\fR watcher and unblock
+them in an \f(CW\*(C`ev_prepare\*(C'\fR watcher.
+.PP
+\fIWatcher-Specific Functions and Data Members\fR
+.IX Subsection "Watcher-Specific Functions and Data Members"
 .IP "ev_signal_init (ev_signal *, callback, int signum)" 4
 .IX Item "ev_signal_init (ev_signal *, callback, int signum)"
 .PD 0
 .IP "ev_signal_set (ev_signal *, int signum)" 4
 .IX Item "ev_signal_set (ev_signal *, int signum)"
 Configures the watcher to trigger on the given signal number (usually one
 of the \f(CW\*(C`SIGxxx\*(C'\fR constants).
 .IP "int signum [read\-only]" 4
 .IX Item "int signum [read-only]"
 The signal the watcher watches out for.
+.PP
+\fIExamples\fR
+.IX Subsection "Examples"
+.PP
+Example: Try to exit cleanly on \s-1SIGINT\s0.
+.PP
+.Vb 5
+\&   static void
+\&   sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
+\&   {
+\&     ev_unloop (loop, EVUNLOOP_ALL);
+\&   }
+\&
+\&   ev_signal signal_watcher;
+\&   ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
+\&   ev_signal_start (loop, &signal_watcher);
+.Ve
 .ie n .Sh """ev_child"" \- watch out for process status changes"
 .el .Sh "\f(CWev_child\fP \- watch out for process status changes"
 .IX Subsection "ev_child - watch out for process status changes"
 Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to
-some child status changes (most typically when a child of yours dies).
+some child status changes (most typically when a child of yours dies or
+exits). It is permissible to install a child watcher \fIafter\fR the child
+has been forked (which implies it might have already exited), as long
+as the event loop isn't entered (or is continued from a watcher), i.e.,
+forking and then immediately registering a watcher for the child is fine,
+but forking and registering a watcher a few event loop iterations later is
+not.
+.PP
+Only the default event loop is capable of handling signals, and therefore
+you can only register child watchers in the default event loop.
+.PP
+\fIProcess Interaction\fR
+.IX Subsection "Process Interaction"
+.PP
+Libev grabs \f(CW\*(C`SIGCHLD\*(C'\fR as soon as the default event loop is
+initialised. This is necessary to guarantee proper behaviour even if
+the first child watcher is started after the child exits. The 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
+.IX Subsection "Overriding the Built-In Processing"
+.PP
+Libev offers no special support for overriding the built-in child
+processing, but if your application collides with libev's default child
+handler, you can override it easily by installing your own handler for
+\&\f(CW\*(C`SIGCHLD\*(C'\fR after initialising the default loop, and making sure the
+default loop never gets destroyed. You are encouraged, however, to use an
+event-based approach to child reaping and thus use libev's support for
+that, so other libev users can use \f(CW\*(C`ev_child\*(C'\fR watchers freely.
+.PP
+\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.
+.PP
+\fIWatcher-Specific Functions and Data Members\fR
+.IX Subsection "Watcher-Specific Functions and Data Members"
-.IP "ev_child_init (ev_child *, callback, int pid)" 4
+.IP "ev_child_init (ev_child *, callback, int pid, int trace)" 4
-.IX Item "ev_child_init (ev_child *, callback, int pid)"
+.IX Item "ev_child_init (ev_child *, callback, int pid, int trace)"
 .PD 0
-.IP "ev_child_set (ev_child *, int pid)" 4
+.IP "ev_child_set (ev_child *, int pid, int trace)" 4
-.IX Item "ev_child_set (ev_child *, int pid)"
+.IX Item "ev_child_set (ev_child *, int pid, int trace)"
 .PD
 Configures the watcher to wait for status changes of process \f(CW\*(C`pid\*(C'\fR (or
 \&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look
 at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see
 the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems
 \&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the
-process causing the status change.
+process causing the status change. \f(CW\*(C`trace\*(C'\fR must be either \f(CW0\fR (only
+activate the watcher when the process terminates) or \f(CW1\fR (additionally
+activate the watcher when the process is stopped or continued).
 .IP "int pid [read\-only]" 4
 .IX Item "int pid [read-only]"
 The process id this watcher watches out for, or \f(CW0\fR, meaning any process id.
 .IP "int rpid [read\-write]" 4
 .IX Item "int rpid [read-write]"
 .IP "int rstatus [read\-write]" 4
 .IX Item "int rstatus [read-write]"
 The process exit/trace status caused by \f(CW\*(C`rpid\*(C'\fR (see your systems
 \&\f(CW\*(C`waitpid\*(C'\fR and \f(CW\*(C`sys/wait.h\*(C'\fR documentation for details).
 .PP
-Example: Try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0.
+\fIExamples\fR
+.IX Subsection "Examples"
 .PP
+Example: \f(CW\*(C`fork()\*(C'\fR a new process and install a child handler to wait for
+its completion.
+.PP
-.Vb 5
+.Vb 1
+\&   ev_child cw;
+\&
-\&  static void
+\&   static void
-\&  sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
+\&   child_cb (EV_P_ ev_child *w, int revents)
-\&  {
+\&   {
-\&    ev_unloop (loop, EVUNLOOP_ALL);
+\&     ev_child_stop (EV_A_ w);
+\&     printf ("process %d exited with status %x\en", w\->rpid, w\->rstatus);
-\&  }
+\&   }
-.Ve
+\&
-.PP
+\&   pid_t pid = fork ();
-.Vb 3
+\&
-\&  struct ev_signal signal_watcher;
+\&   if (pid < 0)
-\&  ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
+\&     // error
-\&  ev_signal_start (loop, &sigint_cb);
+\&   else if (pid == 0)
+\&     {
+\&       // the forked child executes here
+\&       exit (1);
+\&     }
+\&   else
+\&     {
+\&       ev_child_init (&cw, child_cb, pid, 0);
+\&       ev_child_start (EV_DEFAULT_ &cw);
+\&     }
 .Ve
 .ie n .Sh """ev_stat"" \- did the file attributes just change?"
 .el .Sh "\f(CWev_stat\fP \- did the file attributes just change?"
 .IX Subsection "ev_stat - did the file attributes just change?"
-This watches a filesystem path for attribute changes. That is, it calls
+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.
 .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.
+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
+.PP
-usually detected immediately, and if the file exists there will be no
+\fI\s-1ABI\s0 Issues (Largefile Support)\fR
-polling.
+.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 and Kqueue"
+.PP
+When \f(CW\*(C`inotify (7)\*(C'\fR support has been compiled into libev and present at
+runtime, it will be used to speed up change detection where possible. The
+inotify descriptor will be created lazily when the first \f(CW\*(C`ev_stat\*(C'\fR
+watcher is being started.
+.PP
+Inotify presence does not change the semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers
+except that changes might be detected earlier, and in some cases, to avoid
+making regular \f(CW\*(C`stat\*(C'\fR calls. Even in the presence of inotify support
+there are many cases where libev has to resort to regular \f(CW\*(C`stat\*(C'\fR polling,
+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
+implement this functionality, due to the requirement of having a file
+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 suually 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 system call only supports full-second resolution portably,
+and even on systems where the resolution is higher, most file systems
+still only support whole seconds.
+.PP
+That means that, if the time is the only thing that changes, you can
+easily miss updates: on the first update, \f(CW\*(C`ev_stat\*(C'\fR detects a change and
+calls your callback, which does something. When there is another update
+within the same second, \f(CW\*(C`ev_stat\*(C'\fR will be unable to detect 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 slightly more
+than a second (or till slightly after the next full second boundary), using
+a roughly one-second-delay \f(CW\*(C`ev_timer\*(C'\fR (e.g. \f(CW\*(C`ev_timer_set (w, 0., 1.02);
+ev_timer_again (loop, w)\*(C'\fR).
+.PP
+The \f(CW.02\fR offset is added to work around small timing inconsistencies
+of some operating systems (where the second counter of the current time
+might be be delayed. One such system is the Linux kernel, where a call to
+\&\f(CW\*(C`gettimeofday\*(C'\fR might return a timestamp with a full second later than
+a subsequent \f(CW\*(C`time\*(C'\fR call \- if the equivalent of \f(CW\*(C`time ()\*(C'\fR is used to
+update file times then there will be a small window where the kernel uses
+the previous second to update file times but libev might already execute
+the timer callback).
+.PP
+\fIWatcher-Specific Functions and Data Members\fR
+.IX Subsection "Watcher-Specific Functions and Data Members"
 .IP "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 4
 .IX Item "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)"
 .PD 0
 .IP "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" 4
 .IX Item "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)"
 \&\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 (ev_stat *)" 4
+.IP "ev_stat_stat (loop, ev_stat *)" 4
-.IX Item "ev_stat_stat (ev_stat *)"
+.IX Item "ev_stat_stat (loop, ev_stat *)"
 Updates the stat buffer immediately with new values. If you change the
-watched path in your callback, you could call this fucntion to avoid
+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 15
+.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_init (&passwd, passwd_cb, "/etc/passwd", 0.);
+\&   ev_stat_start (loop, &passwd);
 .Ve
+.PP
+Example: Like above, but additionally use a one-second delay so we do not
+miss updates (however, frequent updates will delay processing, too, so
+one might do the work both on \f(CW\*(C`ev_stat\*(C'\fR callback invocation \fIand\fR on
+\&\f(CW\*(C`ev_timer\*(C'\fR callback invocation).
 .PP
 .Vb 2
+\&   static ev_stat passwd;
+\&   static ev_timer timer;
+\&
+\&   static void
+\&   timer_cb (EV_P_ ev_timer *w, int revents)
+\&   {
+\&     ev_timer_stop (EV_A_ w);
+\&
+\&     /* now it\*(Aqs one second after the most recent passwd change */
+\&   }
+\&
+\&   static void
+\&   stat_cb (EV_P_ ev_stat *w, int revents)
+\&   {
+\&     /* reset the one\-second timer */
+\&     ev_timer_again (EV_A_ &timer);
+\&   }
+\&
-\&  ...
+\&   ...
-\&  ev_stat passwd;
-.Ve
-.PP
-.Vb 2
-\&  ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
+\&   ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
-\&  ev_stat_start (loop, &passwd);
+\&   ev_stat_start (loop, &passwd);
+\&   ev_timer_init (&timer, timer_cb, 0., 1.02);
 .Ve
 .ie n .Sh """ev_idle"" \- when you've got nothing better to do..."
 .el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do..."
 .IX Subsection "ev_idle - when you've got nothing better to do..."
 Idle watchers trigger events when no other events of the same or higher
-priority are pending (prepare, check and other idle watchers do not
+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
 The most noteworthy effect is that as long as any idle watchers are
 active, the process will not block when waiting for new events.
 .PP
 Apart from keeping your process non-blocking (which is a useful
 effect on its own sometimes), idle watchers are a good place to do
-\&\*(L"pseudo\-background processing\*(R", or delay processing stuff to after the
+\&\*(L"pseudo-background processing\*(R", or delay processing stuff to after the
 event loop has handled all outstanding events.
+.PP
+\fIWatcher-Specific Functions and Data Members\fR
+.IX Subsection "Watcher-Specific Functions and Data Members"
 .IP "ev_idle_init (ev_signal *, callback)" 4
 .IX Item "ev_idle_init (ev_signal *, callback)"
 Initialises and configures the idle watcher \- it has no parameters of any
 kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless,
 believe me.
 .PP
+\fIExamples\fR
+.IX Subsection "Examples"
+.PP
 Example: Dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR watcher, start it, and in the
 callback, free it. Also, use no error checking, as usual.
 .PP
 .Vb 7
-\&  static void
+\&   static void
-\&  idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
+\&   idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
-\&  {
+\&   {
-\&    free (w);
+\&     free (w);
-\&    // now do something you wanted to do when the program has
+\&     // now do something you wanted to do when the program has
-\&    // no longer asnything immediate to do.
+\&     // no longer anything immediate to do.
-\&  }
+\&   }
-.Ve
+\&
-.PP
-.Vb 3
-\&  struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
+\&   ev_idle *idle_watcher = malloc (sizeof (ev_idle));
-\&  ev_idle_init (idle_watcher, idle_cb);
+\&   ev_idle_init (idle_watcher, idle_cb);
-\&  ev_idle_start (loop, idle_cb);
+\&   ev_idle_start (loop, idle_cb);
 .Ve
 .ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop!"
 .el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!"
 .IX Subsection "ev_prepare and ev_check - customise your event loop!"
-Prepare and check watchers are usually (but not always) used in tandem:
+Prepare and check watchers are usually (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
 the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR
 those watchers, i.e. the sequence will always be \f(CW\*(C`ev_prepare\*(C'\fR, blocking,
 \&\f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each kind they will always be
 called in pairs bracketing the blocking call.
 .PP
 Their main purpose is to integrate other event mechanisms into libev and
-their use is somewhat advanced. This could be used, for example, to track
+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)
+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
+Also, \f(CW\*(C`ev_check\*(C'\fR watchers (and \f(CW\*(C`ev_prepare\*(C'\fR watchers, too) should not
+activate (\*(L"feed\*(R") events into libev. While libev fully supports this, they
+might get executed before other \f(CW\*(C`ev_check\*(C'\fR watchers did their job. As
+\&\f(CW\*(C`ev_check\*(C'\fR watchers are often used to embed other (non-libev) event
+loops those other event loops might be in an unusable state until their
+\&\f(CW\*(C`ev_check\*(C'\fR watcher ran (always remind yourself to coexist peacefully with
+others).
+.PP
+\fIWatcher-Specific Functions and Data Members\fR
+.IX Subsection "Watcher-Specific Functions and Data Members"
 .IP "ev_prepare_init (ev_prepare *, callback)" 4
 .IX Item "ev_prepare_init (ev_prepare *, callback)"
 .PD 0
 .IP "ev_check_init (ev_check *, callback)" 4
 .IX Item "ev_check_init (ev_check *, callback)"
 .PD
 Initialises and configures the prepare or check watcher \- they have no
 parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR
-macros, but using them is utterly, utterly and completely pointless.
+macros, but using them is utterly, utterly, utterly and completely
+pointless.
 .PP
-Example: To include a library such as adns, you would add \s-1IO\s0 watchers
+\fIExamples\fR
-and a timeout watcher in a prepare handler, as required by libadns, and
+.IX Subsection "Examples"
+.PP
+There are a number of principal ways to embed other event loops or modules
+into libev. Here are some ideas on how to include libadns into libev
+(there is a Perl module named \f(CW\*(C`EV::ADNS\*(C'\fR that does this, which you could
+use as a working example. Another Perl module named \f(CW\*(C`EV::Glib\*(C'\fR embeds a
+Glib main context into libev, and finally, \f(CW\*(C`Glib::EV\*(C'\fR embeds \s-1EV\s0 into the
+Glib event loop).
+.PP
+Method 1: Add \s-1IO\s0 watchers and a timeout watcher in a prepare handler,
-in a check watcher, destroy them and call into libadns. What follows is
+and in a check watcher, destroy them and call into libadns. What follows
-pseudo-code only of course:
+is pseudo-code only of course. This requires you to either use a low
+priority for the check watcher or use \f(CW\*(C`ev_clear_pending\*(C'\fR explicitly, as
+the callbacks for the IO/timeout watchers might not have been called yet.
 .PP
 .Vb 2
-\&  static ev_io iow [nfd];
+\&   static ev_io iow [nfd];
-\&  static ev_timer tw;
+\&   static ev_timer tw;
-.Ve
+\&
-.PP
-.Vb 9
-\&  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)
-\&  {
+\&   {
-\&    // set the relevant poll flags
-\&    // could also call adns_processreadable etc. here
-\&    struct pollfd *fd = (struct pollfd *)w->data;
-\&    if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
-\&    if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
-\&  }
+\&   }
-.Ve
+\&
-.PP
-.Vb 8
-\&  // 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 ()));
-.Ve
+\&
-.PP
-.Vb 3
-\&    /* the callback is illegal, but won't be called as we stop during check */
+\&     /* the callback is illegal, but won\*(Aqt be called as we stop during check */
-\&    ev_timer_init (&tw, 0, timeout * 1e-3);
+\&     ev_timer_init (&tw, 0, timeout * 1e\-3);
-\&    ev_timer_start (loop, &tw);
+\&     ev_timer_start (loop, &tw);
-.Ve
+\&
-.PP
-.Vb 6
-\&    // create on ev_io per pollfd
+\&     // create one ev_io per pollfd
-\&    for (int i = 0; i < nfd; ++i)
+\&     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;
+\&         ev_io_start (loop, iow + i);
+\&       }
+\&   }
+\&
+\&   // stop all watchers after blocking
+\&   static void
+\&   adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
+\&   {
+\&     ev_timer_stop (loop, &tw);
+\&
+\&     for (int i = 0; i < nfd; ++i)
+\&       {
+\&         // set the relevant poll flags
+\&         // could also call adns_processreadable etc. here
+\&         struct pollfd *fd = fds + i;
+\&         int revents = ev_clear_pending (iow + i);
+\&         if (revents & EV_READ ) fd\->revents |= fd\->events & POLLIN;
+\&         if (revents & EV_WRITE) fd\->revents |= fd\->events & POLLOUT;
+\&
+\&         // now stop the watcher
+\&         ev_io_stop (loop, iow + i);
+\&       }
+\&
+\&     adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
+\&   }
 .Ve
+.PP
+Method 2: This would be just like method 1, but you run \f(CW\*(C`adns_afterpoll\*(C'\fR
+in the prepare watcher and would dispose of the check watcher.
+.PP
+Method 3: If the module to be embedded supports explicit event
+notification (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
-\&        fds [i].revents = 0;
-\&        iow [i].data = fds + i;
-\&        ev_io_start (loop, iow + i);
-\&      }
-\&  }
-.Ve
-.PP
-.Vb 5
-\&  // stop all watchers after blocking
-\&  static void
+\&   static void
-\&  adns_check_cb (ev_loop *loop, ev_check *w, int revents)
+\&   timer_cb (EV_P_ ev_timer *w, int revents)
-\&  {
+\&   {
-\&    ev_timer_stop (loop, &tw);
+\&     adns_state ads = (adns_state)w\->data;
-.Ve
+\&     update_now (EV_A);
-.PP
+\&
-.Vb 2
+\&     adns_processtimeouts (ads, &tv_now);
-\&    for (int i = 0; i < nfd; ++i)
-\&      ev_io_stop (loop, iow + i);
-.Ve
-.PP
-.Vb 2
-\&    adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
-\&  }
+\&   }
+\&
+\&   static void
+\&   io_cb (EV_P_ ev_io *w, int revents)
+\&   {
+\&     adns_state ads = (adns_state)w\->data;
+\&     update_now (EV_A);
+\&
+\&     if (revents & EV_READ ) adns_processreadable  (ads, w\->fd, &tv_now);
+\&     if (revents & EV_WRITE) adns_processwriteable (ads, w\->fd, &tv_now);
+\&   }
+\&
+\&   // do not ever call adns_afterpoll
+.Ve
+.PP
+Method 4: Do not use a prepare or check watcher because the module you
+want to embed is not flexible enough to support it. Instead, you can
+override their poll function. The drawback with this solution is that the
+main loop is now no longer controllable by \s-1EV\s0. The \f(CW\*(C`Glib::EV\*(C'\fR module uses
+this approach, effectively embedding \s-1EV\s0 as a client into the horrible
+libglib event loop.
+.PP
+.Vb 4
+\&   static gint
+\&   event_poll_func (GPollFD *fds, guint nfds, gint timeout)
+\&   {
+\&     int got_events = 0;
+\&
+\&     for (n = 0; n < nfds; ++n)
+\&       // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
+\&
+\&     if (timeout >= 0)
+\&       // create/start timer
+\&
+\&     // poll
+\&     ev_loop (EV_A_ 0);
+\&
+\&     // stop timer again
+\&     if (timeout >= 0)
+\&       ev_timer_stop (EV_A_ &to);
+\&
+\&     // stop io watchers again \- their callbacks should have set
+\&     for (n = 0; n < nfds; ++n)
+\&       ev_io_stop (EV_A_ iow [n]);
+\&
+\&     return got_events;
+\&   }
 .Ve
 .ie n .Sh """ev_embed"" \- when one backend isn't enough..."
 .el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..."
 .IX Subsection "ev_embed - when one backend isn't enough..."
 This is a rather advanced watcher type that lets you embed one event loop
 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
 there might be events pending in the embedded loop. The callback must then
 call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single sweep and invoke
 their callbacks (you could also start an idle watcher to give the embedded
 interested in that.
 .PP
 Also, there have not currently been made special provisions for forking:
 when you fork, you not only have to call \f(CW\*(C`ev_loop_fork\*(C'\fR on both loops,
 but you will also have to stop and restart any \f(CW\*(C`ev_embed\*(C'\fR watchers
-yourself.
+yourself \- but you can use a fork watcher to handle this automatically,
+and future versions of libev might do just that.
 .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:
+create it, and if that fails, use the normal loop for everything.
 .PP
-.Vb 3
+\fI\f(CI\*(C`ev_embed\*(C'\fI and fork\fR
-\&  struct ev_loop *loop_hi = ev_default_init (0);
+.IX Subsection "ev_embed and fork"
-\&  struct ev_loop *loop_lo = 0;
-\&  struct ev_embed embed;
-.Ve
 .PP
-.Vb 5
+While the \f(CW\*(C`ev_embed\*(C'\fR watcher is running, forks in the embedding loop will
-\&  // see if there is a chance of getting one that works
+automatically be applied to the embedded loop as well, so no special
-\&  // (remember that a flags value of 0 means autodetection)
+fork handling is required in that case. When the watcher is not running,
-\&  loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
+however, it is still the task of the libev user to call \f(CW\*(C`ev_loop_fork ()\*(C'\fR
-\&    ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
+as applicable.
-\&    : 0;
-.Ve
 .PP
-.Vb 8
+\fIWatcher-Specific Functions and Data Members\fR
-\&  // if we got one, then embed it, otherwise default to loop_hi
+.IX Subsection "Watcher-Specific Functions and Data Members"
-\&  if (loop_lo)
-\&    {
-\&      ev_embed_init (&embed, 0, loop_lo);
-\&      ev_embed_start (loop_hi, &embed);
-\&    }
-\&  else
-\&    loop_lo = loop_hi;
-.Ve
 .IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
 .IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)"
 .PD 0
 .IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
 .IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)"
 .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
-apropriate way for embedded loops.
+appropriate way for embedded loops.
-.IP "struct ev_loop *loop [read\-only]" 4
+.IP "struct ev_loop *other [read\-only]" 4
-.IX Item "struct ev_loop *loop [read-only]"
+.IX Item "struct ev_loop *other [read-only]"
 The embedded event loop.
+.PP
+\fIExamples\fR
+.IX Subsection "Examples"
+.PP
+Example: Try to get an embeddable event loop and embed it into the default
+event loop. If that is not possible, use the default loop. The default
+loop is stored in \f(CW\*(C`loop_hi\*(C'\fR, while the embeddable loop is stored in
+\&\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_lo = 0;
+\&   ev_embed embed;
+\&
+\&   // see if there is a chance of getting one that works
+\&   // (remember that a flags value of 0 means autodetection)
+\&   loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
+\&     ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
+\&     : 0;
+\&
+\&   // if we got one, then embed it, otherwise default to loop_hi
+\&   if (loop_lo)
+\&     {
+\&       ev_embed_init (&embed, 0, loop_lo);
+\&       ev_embed_start (loop_hi, &embed);
+\&     }
+\&   else
+\&     loop_lo = loop_hi;
+.Ve
+.PP
+Example: Check if kqueue is available but not recommended and create
+a kqueue backend for use with sockets (which usually work with any
+kqueue implementation). Store the kqueue/socket\-only event loop in
+\&\f(CW\*(C`loop_socket\*(C'\fR. (One might optionally use \f(CW\*(C`EVFLAG_NOENV\*(C'\fR, too).
+.PP
+.Vb 3
+\&   struct ev_loop *loop = ev_default_init (0);
+\&   struct ev_loop *loop_socket = 0;
+\&   ev_embed embed;
+\&
+\&   if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
+\&     if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
+\&       {
+\&         ev_embed_init (&embed, 0, loop_socket);
+\&         ev_embed_start (loop, &embed);
+\&       }
+\&
+\&   if (!loop_socket)
+\&     loop_socket = loop;
+\&
+\&   // now use loop_socket for all sockets, and loop for everything else
+.Ve
 .ie n .Sh """ev_fork"" \- the audacity to resume the event loop after a fork"
 .el .Sh "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork"
 .IX Subsection "ev_fork - the audacity to resume the event loop after a fork"
 Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because
 whoever is a good citizen cared to tell libev about it by calling
 \&\f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the
 event loop blocks next and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called,
 and only in the child after the fork. If whoever good citizen calling
 \&\f(CW\*(C`ev_default_fork\*(C'\fR cheats and calls it in the wrong process, the fork
 handlers will be invoked, too, of course.
+.PP
+\fIWatcher-Specific Functions and Data Members\fR
+.IX Subsection "Watcher-Specific Functions and Data Members"
 .IP "ev_fork_init (ev_signal *, callback)" 4
 .IX Item "ev_fork_init (ev_signal *, callback)"
 Initialises and configures the fork watcher \- it has no parameters of any
 kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless,
 believe me.
+.ie n .Sh """ev_async"" \- how to wake up another event loop"
+.el .Sh "\f(CWev_async\fP \- how to wake up another event loop"
+.IX Subsection "ev_async - how to wake up another event loop"
+In general, you cannot use an \f(CW\*(C`ev_loop\*(C'\fR from multiple threads or other
+asynchronous sources such as signal handlers (as opposed to multiple event
+loops \- those are of course safe to use in different threads).
+.PP
+Sometimes, however, you need to wake up another event loop you do not
+control, for example because it belongs to another thread. This is what
+\&\f(CW\*(C`ev_async\*(C'\fR watchers do: as long as the \f(CW\*(C`ev_async\*(C'\fR watcher is active, you
+can signal it by calling \f(CW\*(C`ev_async_send\*(C'\fR, which is thread\- and signal
+safe.
+.PP
+This functionality is very similar to \f(CW\*(C`ev_signal\*(C'\fR watchers, as signals,
+too, are asynchronous in nature, and signals, too, will be compressed
+(i.e. the number of callback invocations may be less than the number of
+\&\f(CW\*(C`ev_async_sent\*(C'\fR calls).
+.PP
+Unlike \f(CW\*(C`ev_signal\*(C'\fR watchers, \f(CW\*(C`ev_async\*(C'\fR works with any event loop, not
+just the default loop.
+.PP
+\fIQueueing\fR
+.IX Subsection "Queueing"
+.PP
+\&\f(CW\*(C`ev_async\*(C'\fR does not support queueing of data in any way. The reason
+is that the author does not know of a simple (or any) algorithm for a
+multiple-writer-single-reader queue that works in all cases and doesn't
+need elaborate support such as pthreads.
+.PP
+That means that if you want to queue data, you have to provide your own
+queue. But at least I can tell you 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 some fictitious \s-1SIGUSR1\s0 handler:
+.Sp
+.Vb 1
+\&   static ev_async mysig;
+\&
+\&   static void
+\&   sigusr1_handler (void)
+\&   {
+\&     sometype data;
+\&
+\&     // no locking etc.
+\&     queue_put (data);
+\&     ev_async_send (EV_DEFAULT_ &mysig);
+\&   }
+\&
+\&   static void
+\&   mysig_cb (EV_P_ ev_async *w, int revents)
+\&   {
+\&     sometype data;
+\&     sigset_t block, prev;
+\&
+\&     sigemptyset (&block);
+\&     sigaddset (&block, SIGUSR1);
+\&     sigprocmask (SIG_BLOCK, &block, &prev);
+\&
+\&     while (queue_get (&data))
+\&       process (data);
+\&
+\&     if (sigismember (&prev, SIGUSR1)
+\&       sigprocmask (SIG_UNBLOCK, &block, 0);
+\&   }
+.Ve
+.Sp
+(Note: pthreads in theory requires you to use \f(CW\*(C`pthread_setmask\*(C'\fR
+instead of \f(CW\*(C`sigprocmask\*(C'\fR when you use threads, but libev doesn't do it
+either...).
+.IP "queueing from a thread context" 4
+.IX Item "queueing from a thread context"
+The strategy for threads is different, as you cannot (easily) block
+threads but you can easily preempt them, so to queue safely you need to
+employ a traditional mutex lock, such as in this pthread example:
+.Sp
+.Vb 2
+\&   static ev_async mysig;
+\&   static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
+\&
+\&   static void
+\&   otherthread (void)
+\&   {
+\&     // only need to lock the actual queueing operation
+\&     pthread_mutex_lock (&mymutex);
+\&     queue_put (data);
+\&     pthread_mutex_unlock (&mymutex);
+\&
+\&     ev_async_send (EV_DEFAULT_ &mysig);
+\&   }
+\&
+\&   static void
+\&   mysig_cb (EV_P_ ev_async *w, int revents)
+\&   {
+\&     pthread_mutex_lock (&mymutex);
+\&
+\&     while (queue_get (&data))
+\&       process (data);
+\&
+\&     pthread_mutex_unlock (&mymutex);
+\&   }
+.Ve
+.PP
+\fIWatcher-Specific Functions and Data Members\fR
+.IX Subsection "Watcher-Specific Functions and Data Members"
+.IP "ev_async_init (ev_async *, callback)" 4
+.IX Item "ev_async_init (ev_async *, callback)"
+Initialises and configures the async watcher \- it has no parameters of any
+kind. There is a \f(CW\*(C`ev_async_set\*(C'\fR macro, but using it is utterly pointless,
+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
+\&\f(CW\*(C`ev_feed_event\*(C'\fR, this call is safe to do from other threads, signal or
+similar contexts (see the discussion of \f(CW\*(C`EV_ATOMIC_T\*(C'\fR in the embedding
+section below on what exactly this means).
+.Sp
+This call incurs the overhead of a system call only once per loop iteration,
+so while the overhead might be noticeable, it doesn't apply to repeated
+calls to \f(CW\*(C`ev_async_send\*(C'\fR.
+.IP "bool = ev_async_pending (ev_async *)" 4
+.IX Item "bool = ev_async_pending (ev_async *)"
+Returns a non-zero value when \f(CW\*(C`ev_async_send\*(C'\fR has been called on the
+watcher but the event has not yet been processed (or even noted) by the
+event loop.
+.Sp
+\&\f(CW\*(C`ev_async_send\*(C'\fR sets a flag in the watcher and wakes up the loop. When
+the loop iterates next and checks for the watcher to have become active,
+it will reset the flag again. \f(CW\*(C`ev_async_pending\*(C'\fR can be used to very
+quickly check 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.
 .SH "OTHER FUNCTIONS"
 .IX Header "OTHER FUNCTIONS"
 There are some other functions of possible interest. Described. Here. Now.
 .IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4
 .IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)"
 This function combines a simple timer and an I/O watcher, calls your
-callback on whichever event happens first and automatically stop both
+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
 passed an \f(CW\*(C`revents\*(C'\fR set like normal event callbacks (a combination of
 \&\f(CW\*(C`EV_ERROR\*(C'\fR, \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or \f(CW\*(C`EV_TIMEOUT\*(C'\fR) and the \f(CW\*(C`arg\*(C'\fR
-value passed to \f(CW\*(C`ev_once\*(C'\fR:
+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_TIMEOUT)
-\&      /* doh, nothing entered */;
-\&    else if (revents & EV_READ)
+\&     if (revents & EV_READ)
-\&      /* stdin might have data for us, joy! */;
+\&       /* stdin might have data for us, joy! */;
+\&     else if (revents & EV_TIMEOUT)
+\&       /* doh, nothing entered */;
-\&  }
+\&   }
-.Ve
+\&
-.Sp
-.Vb 1
-\&  ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
+\&   ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
 .Ve
-.IP "ev_feed_event (ev_loop *, watcher *, int revents)" 4
+.IP "ev_feed_event (struct ev_loop *, watcher *, int revents)" 4
-.IX Item "ev_feed_event (ev_loop *, watcher *, int revents)"
+.IX Item "ev_feed_event (struct ev_loop *, watcher *, int revents)"
 Feeds the given event set into the event loop, as if the specified event
 had happened for the specified watcher (which must be a pointer to an
 initialised but not necessarily started event watcher).
-.IP "ev_feed_fd_event (ev_loop *, int fd, int revents)" 4
+.IP "ev_feed_fd_event (struct ev_loop *, int fd, int revents)" 4
-.IX Item "ev_feed_fd_event (ev_loop *, int fd, int revents)"
+.IX Item "ev_feed_fd_event (struct ev_loop *, int fd, int revents)"
 Feed an event on the given fd, as if a file descriptor backend detected
 the given events it.
-.IP "ev_feed_signal_event (ev_loop *loop, int signum)" 4
+.IP "ev_feed_signal_event (struct ev_loop *loop, int signum)" 4
-.IX Item "ev_feed_signal_event (ev_loop *loop, int signum)"
+.IX Item "ev_feed_signal_event (struct ev_loop *loop, int signum)"
-Feed an event as if the given signal occured (\f(CW\*(C`loop\*(C'\fR must be the default
+Feed an event as if the given signal occurred (\f(CW\*(C`loop\*(C'\fR must be the default
 loop!).
 .SH "LIBEVENT EMULATION"
 .IX Header "LIBEVENT EMULATION"
 Libev offers a compatibility emulation layer for libevent. It cannot
 emulate the internals of libevent, so here are some usage hints:
+.IP "\(bu" 4
-.IP "* Use it by including <event.h>, as usual." 4
+Use it by including <event.h>, as usual.
-.IX Item "Use it by including <event.h>, as usual."
+.IP "\(bu" 4
-.PD 0
+The following members are fully supported: ev_base, ev_callback,
-.IP "* The following members are fully supported: ev_base, ev_callback, ev_arg, ev_fd, ev_res, ev_events." 4
+ev_arg, ev_fd, ev_res, ev_events.
-.IX Item "The following members are fully supported: ev_base, ev_callback, ev_arg, ev_fd, ev_res, ev_events."
+.IP "\(bu" 4
-.IP "* Avoid using ev_flags and the EVLIST_*\-macros, while it is maintained by libev, it does not work exactly the same way as in libevent (consider it a private \s-1API\s0)." 4
+Avoid using ev_flags and the EVLIST_*\-macros, while it is
-.IX Item "Avoid using ev_flags and the EVLIST_*-macros, while it is maintained by libev, it does not work exactly the same way as in libevent (consider it a private API)."
+maintained by libev, it does not work exactly the same way as in libevent (consider
-.IP "* Priorities are not currently supported. Initialising priorities will fail and all watchers will have the same priority, even though there is an ev_pri field." 4
+it a private \s-1API\s0).
-.IX Item "Priorities are not currently supported. Initialising priorities will fail and all watchers will have the same priority, even though there is an ev_pri field."
+.IP "\(bu" 4
+Priorities are not currently supported. Initialising priorities
+will fail and all watchers will have the same priority, even though there
+is an ev_pri field.
+.IP "\(bu" 4
+In libevent, the last base created gets the signals, in libev, the
+first base created (== the default loop) gets the signals.
+.IP "\(bu" 4
-.IP "* Other members are not supported." 4
+Other members are not supported.
-.IX Item "Other members are not supported."
+.IP "\(bu" 4
-.IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4
+The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need
-.IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library."
+to use the libev header file and library.
-.PD
 .SH "\*(C+ SUPPORT"
 .IX Header " SUPPORT"
 Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow
-you to use some convinience methods to start/stop watchers and also change
+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
-(it is not installed by default). This automatically includes \fIev.h\fR
+This automatically includes \fIev.h\fR and puts all of its definitions (many
-and puts all of its definitions (many of them macros) into the global
+of them macros) into the global namespace. All \*(C+ specific things are
-namespace. All \*(C+ specific things are put into the \f(CW\*(C`ev\*(C'\fR namespace.
+put into the \f(CW\*(C`ev\*(C'\fR namespace. It should support all the same embedding
+options as \fIev.h\fR, most notably \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR.
 .PP
-It should support all the same embedding options as \fIev.h\fR, most notably
+Care has been taken to keep the overhead low. The only data member the \*(C+
-\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR.
+classes add (compared to plain C\-style watchers) is the event loop pointer
+that the watcher is associated with (or no additional members at all if
+you disable \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR when embedding libev).
+.PP
+Currently, functions, and static and non-static member functions can be
+used as callbacks. Other types should be easy to add as long as they only
+need one additional pointer for context. If you need support for other
+types of functors please contact the author (preferably after implementing
+it).
 .PP
 Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace:
 .ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4
 .el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4
 .IX Item "ev::READ, ev::WRITE etc."
 which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro
 defines by many implementations.
 .Sp
 All of those classes have these methods:
 .RS 4
-.IP "ev::TYPE::TYPE (object *, object::method *)" 4
+.IP "ev::TYPE::TYPE ()" 4
-.IX Item "ev::TYPE::TYPE (object *, object::method *)"
+.IX Item "ev::TYPE::TYPE ()"
 .PD 0
-.IP "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)" 4
+.IP "ev::TYPE::TYPE (struct ev_loop *)" 4
-.IX Item "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)"
+.IX Item "ev::TYPE::TYPE (struct ev_loop *)"
 .IP "ev::TYPE::~TYPE" 4
 .IX Item "ev::TYPE::~TYPE"
 .PD
-The constructor takes a pointer to an object and a method pointer to
+The constructor (optionally) takes an event loop to associate the watcher
-the event handler callback to call in this class. The constructor calls
+with. If it is omitted, it will use \f(CW\*(C`EV_DEFAULT\*(C'\fR.
-\&\f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the \f(CW\*(C`set\*(C'\fR method
+.Sp
-before starting it. If you do not specify a loop then the constructor
+The constructor calls \f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the
-automatically associates the default loop with this watcher.
+\&\f(CW\*(C`set\*(C'\fR method before starting it.
+.Sp
+It will not set a callback, however: You have to call the templated \f(CW\*(C`set\*(C'\fR
+method to set a callback before you can start the watcher.
+.Sp
+(The reason why you have to use a method is a limitation in \*(C+ which does
+not allow explicit template arguments for constructors).
 .Sp
 The destructor automatically stops the watcher if it is active.
+.IP "w\->set<class, &class::method> (object *)" 4
+.IX Item "w->set<class, &class::method> (object *)"
+This method sets the callback method to call. The method has to have a
+signature of \f(CW\*(C`void (*)(ev_TYPE &, int)\*(C'\fR, it receives the watcher as
+first argument and the \f(CW\*(C`revents\*(C'\fR as second. The object must be given as
+parameter and is stored in the \f(CW\*(C`data\*(C'\fR member of the watcher.
+.Sp
+This method synthesizes efficient thunking code to call your method from
+the C callback that libev requires. If your compiler can inline your
+callback (i.e. it is visible to it at the place of the \f(CW\*(C`set\*(C'\fR call and
+your compiler is good :), then the method will be fully inlined into the
+thunking function, making it as fast as a direct C callback.
+.Sp
+Example: simple class declaration and watcher initialisation
+.Sp
+.Vb 4
+\&   struct myclass
+\&   {
+\&     void io_cb (ev::io &w, int revents) { }
+\&   }
+\&
+\&   myclass obj;
+\&   ev::io iow;
+\&   iow.set <myclass, &myclass::io_cb> (&obj);
+.Ve
+.IP "w\->set<function> (void *data = 0)" 4
+.IX Item "w->set<function> (void *data = 0)"
+Also sets a callback, but uses a static method or plain function as
+callback. The optional \f(CW\*(C`data\*(C'\fR argument will be stored in the watcher's
+\&\f(CW\*(C`data\*(C'\fR member and is free for you to use.
+.Sp
+The prototype of the \f(CW\*(C`function\*(C'\fR must be \f(CW\*(C`void (*)(ev::TYPE &w, int)\*(C'\fR.
+.Sp
+See the method\-\f(CW\*(C`set\*(C'\fR above for more details.
+.Sp
+Example: Use a plain function as callback.
+.Sp
+.Vb 2
+\&   static void io_cb (ev::io &w, int revents) { }
+\&   iow.set <io_cb> ();
+.Ve
 .IP "w\->set (struct ev_loop *)" 4
 .IX Item "w->set (struct ev_loop *)"
 Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only
 do this when the watcher is inactive (and not pending either).
-.IP "w\->set ([args])" 4
+.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, with the same arguments. Must be
-called at least once.  Unlike the C counterpart, an active watcher gets
+called at least once. Unlike the C counterpart, an active watcher gets
-automatically stopped and restarted.
+automatically stopped and restarted when reconfiguring it with this
+method.
 .IP "w\->start ()" 4
 .IX Item "w->start ()"
-Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument as the
+Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the
-constructor already takes the loop.
+constructor already stores the event loop.
 .IP "w\->stop ()" 4
 .IX Item "w->stop ()"
 Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument.
-.ie n .IP "w\->again ()       ""ev::timer""\fR, \f(CW""ev::periodic"" only" 4
+.ie n .IP "w\->again () (""ev::timer""\fR, \f(CW""ev::periodic"" only)" 4
-.el .IP "w\->again ()       \f(CWev::timer\fR, \f(CWev::periodic\fR only" 4
+.el .IP "w\->again () (\f(CWev::timer\fR, \f(CWev::periodic\fR only)" 4
-.IX Item "w->again ()       ev::timer, ev::periodic only"
+.IX Item "w->again () (ev::timer, ev::periodic only)"
 For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding
 \&\f(CW\*(C`ev_TYPE_again\*(C'\fR function.
-.ie n .IP "w\->sweep ()       ""ev::embed"" only" 4
+.ie n .IP "w\->sweep () (""ev::embed"" only)" 4
-.el .IP "w\->sweep ()       \f(CWev::embed\fR only" 4
+.el .IP "w\->sweep () (\f(CWev::embed\fR only)" 4
-.IX Item "w->sweep ()       ev::embed only"
+.IX Item "w->sweep () (ev::embed only)"
 Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR.
-.ie n .IP "w\->update ()      ""ev::stat"" only" 4
+.ie n .IP "w\->update () (""ev::stat"" only)" 4
-.el .IP "w\->update ()      \f(CWev::stat\fR only" 4
+.el .IP "w\->update () (\f(CWev::stat\fR only)" 4
-.IX Item "w->update ()      ev::stat only"
+.IX Item "w->update () (ev::stat only)"
 Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR.
 .RE
 .RS 4
 .RE
 .PP
 Example: Define a class with an \s-1IO\s0 and idle watcher, start one of them in
 the constructor.
 .PP
 .Vb 4
-\&  class myclass
+\&   class myclass
-\&  {
+\&   {
-\&    ev_io   io;   void io_cb   (ev::io   &w, int revents);
+\&     ev::io   io  ; void io_cb   (ev::io   &w, int revents);
-\&    ev_idle idle  void idle_cb (ev::idle &w, int revents);
+\&     ev::idle idle; void idle_cb (ev::idle &w, int revents);
-.Ve
+\&
-.PP
-.Vb 2
-\&    myclass ();
+\&     myclass (int fd)
-\&  }
-.Ve
-.PP
-.Vb 6
-\&  myclass::myclass (int fd)
-\&  : io   (this, &myclass::io_cb),
-\&    idle (this, &myclass::idle_cb)
-\&  {
+\&     {
+\&       io  .set <myclass, &myclass::io_cb  > (this);
+\&       idle.set <myclass, &myclass::idle_cb> (this);
+\&
-\&    io.start (fd, ev::READ);
+\&       io.start (fd, ev::READ);
+\&     }
-\&  }
+\&   };
 .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. Note, however, that the
+patch they require for libev is outright dangerous as it breaks the \s-1ABI\s0
+for everybody else, and therefore, should never be applied in an installed
+libev (if python requires an incompatible \s-1ABI\s0 then it needs to embed
+libev).
+.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/>.
+.IP "D" 4
+.IX Item "D"
+Leandro Lucarella has written a D language binding (\fIev.d\fR) for libev, to
+be found at <http://proj.llucax.com.ar/wiki/evd>.
+.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/>.
 .SH "MACRO MAGIC"
 .IX Header "MACRO MAGIC"
-Libev can be compiled with a variety of options, the most fundemantal is
+Libev can be compiled with a variety of options, the most fundamental
-\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most) functions and
+of which is \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most)
-callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument.
+functions and callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument.
 .PP
 To make it easier to write programs that cope with either variant, the
 following macros are defined:
 .ie n .IP """EV_A""\fR, \f(CW""EV_A_""" 4
 .el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4
 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_loop (EV_A_ 0);
 .Ve
 .Sp
 It assumes the variable \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR is in scope,
 which is often provided by the following macro.
 .ie n .IP """EV_P""\fR, \f(CW""EV_P_""" 4
 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);
-.Ve
+\&
-.Sp
-.Vb 2
-\&  // 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
 .el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4
 .IX Item "EV_DEFAULT, EV_DEFAULT_"
 Similar to the other two macros, this gives you the value of the default
 loop, if multiple loops are supported (\*(L"ev loop default\*(R").
+.ie n .IP """EV_DEFAULT_UC""\fR, \f(CW""EV_DEFAULT_UC_""" 4
+.el .IP "\f(CWEV_DEFAULT_UC\fR, \f(CWEV_DEFAULT_UC_\fR" 4
+.IX Item "EV_DEFAULT_UC, EV_DEFAULT_UC_"
+Usage identical to \f(CW\*(C`EV_DEFAULT\*(C'\fR and \f(CW\*(C`EV_DEFAULT_\*(C'\fR, but requires that the
+default loop has been initialised (\f(CW\*(C`UC\*(C'\fR == unchecked). Their behaviour
+is undefined when the default loop has not been initialised by a previous
+execution of \f(CW\*(C`EV_DEFAULT\*(C'\fR, \f(CW\*(C`EV_DEFAULT_\*(C'\fR or \f(CW\*(C`ev_default_init (...)\*(C'\fR.
+.Sp
+It is often prudent to use \f(CW\*(C`EV_DEFAULT\*(C'\fR when initialising the first
+watcher in a function but use \f(CW\*(C`EV_DEFAULT_UC\*(C'\fR afterwards.
 .PP
 Example: Declare and initialise a check watcher, utilising the above
 macros so it will work regardless of whether multiple loops are supported
 or not.
 .PP
 .Vb 5
-\&  static void
+\&   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);
-\&  }
+\&   }
-.Ve
+\&
-.PP
-.Vb 4
-\&  ev_check check;
+\&   ev_check check;
-\&  ev_check_init (&check, check_cb);
+\&   ev_check_init (&check, check_cb);
-\&  ev_check_start (EV_DEFAULT_ &check);
+\&   ev_check_start (EV_DEFAULT_ &check);
-\&  ev_loop (EV_DEFAULT_ 0);
+\&   ev_loop (EV_DEFAULT_ 0);
 .Ve
 .SH "EMBEDDING"
 .IX Header "EMBEDDING"
 Libev can (and often is) directly embedded into host
 applications. Examples of applications that embed it include the Deliantra
 Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe)
-and rxvt\-unicode.
+and rxvt-unicode.
 .PP
-The goal is to enable you to just copy the neecssary files into your
+The goal is to enable you to just copy the necessary files into your
 source directory without having to change even a single line in them, so
 you can easily upgrade by simply copying (or having a checked-out copy of
 libev somewhere in your source tree).
 .Sh "\s-1FILESETS\s0"
 .IX Subsection "FILESETS"
 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
 .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
-.Ve
+\&
-.PP
-.Vb 1
-\&  ev_win32.c      required on win32 platforms only
+\&   ev_win32.c      required on win32 platforms only
-.Ve
+\&
-.PP
-.Vb 5
-\&  ev_select.c     only when select backend is enabled (which is enabled by default)
+\&   ev_select.c     only when select backend is enabled (which is enabled by default)
-\&  ev_poll.c       only when poll backend is enabled (disabled by default)
+\&   ev_poll.c       only when poll backend is enabled (disabled by default)
-\&  ev_epoll.c      only when the epoll backend is enabled (disabled by default)
+\&   ev_epoll.c      only when the epoll backend is enabled (disabled by default)
-\&  ev_kqueue.c     only when the kqueue backend is enabled (disabled by default)
+\&   ev_kqueue.c     only when the kqueue backend is enabled (disabled by default)
-\&  ev_port.c       only when the solaris port backend is enabled (disabled by default)
+\&   ev_port.c       only when the solaris port backend is enabled (disabled by default)
 .Ve
 .PP
 \&\fIev.c\fR includes the backend files directly when enabled, so you only need
 to compile this single file.
 .PP
 .IX Subsection "LIBEVENT COMPATIBILITY API"
 .PP
 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.
 .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
 .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"
 .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 any of its files. The default in the absence of
-and only include the select backend.
+autoconf is documented for every option.
 .IP "\s-1EV_STANDALONE\s0" 4
 .IX Item "EV_STANDALONE"
 Must always be \f(CW1\fR if you do not use autoconf configuration, which
 keeps libev from including \fIconfig.h\fR, and it also defines dummy
 implementations for some libevent functions (such as logging, which is not
 supported). It will also not define any of the structs usually found in
 \&\fIevent.h\fR that are not directly supported by the libev core alone.
 .IP "\s-1EV_USE_MONOTONIC\s0" 4
 .IX Item "EV_USE_MONOTONIC"
 If defined to be \f(CW1\fR, libev will try to detect the availability of the
-monotonic clock option at both compiletime and runtime. Otherwise no use
+monotonic clock option at both compile time and runtime. Otherwise no use
 of the monotonic clock option will be attempted. If you enable this, you
 usually have to link against librt or something similar. Enabling it when
-the functionality isn't available is safe, though, althoguh you have
+the functionality isn't available is safe, though, although you have
 to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR
 function is hiding in (often \fI\-lrt\fR).
 .IP "\s-1EV_USE_REALTIME\s0" 4
 .IX Item "EV_USE_REALTIME"
 If defined to be \f(CW1\fR, libev will try to detect the availability of the
-realtime clock option at compiletime (and assume its availability at
+real-time clock option at compile time (and assume its availability at
-runtime if successful). Otherwise no use of the realtime clock option will
+runtime if successful). Otherwise no use of the real-time clock option will
 be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get
-(CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See tzhe note about libraries
+(CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See the
-in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though.
+note about libraries in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though.
+.IP "\s-1EV_USE_NANOSLEEP\s0" 4
+.IX Item "EV_USE_NANOSLEEP"
+If defined to be \f(CW1\fR, libev will assume that \f(CW\*(C`nanosleep ()\*(C'\fR is available
+and will use it for delays. Otherwise it will use \f(CW\*(C`select ()\*(C'\fR.
+.IP "\s-1EV_USE_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 on
 exotic systems. This usually limits the range of file descriptors to some
 low limit such as 1024 or might have other limitations (winsocket only
 allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation, might
 influence the size of the \f(CW\*(C`fd_set\*(C'\fR used.
 .IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4
 wants osf handles on win32 (this is the case when the select to
 be used is the winsock select). This means that it will call
 \&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise,
 it is assumed that all these functions actually work on fds, even
 on win32. Should not be defined on non\-win32 platforms.
+.IP "\s-1EV_FD_TO_WIN32_HANDLE\s0" 4
+.IX Item "EV_FD_TO_WIN32_HANDLE"
+If \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR is enabled, then libev needs a way to map
+file descriptors to socket handles. When not defining this symbol (the
+default), then libev will call \f(CW\*(C`_get_osfhandle\*(C'\fR, which is usually
+correct. In some cases, programs use their own file descriptor management,
+in which case they can provide this function to map fds to socket handles.
 .IP "\s-1EV_USE_POLL\s0" 4
 .IX Item "EV_USE_POLL"
 If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2)
 backend. Otherwise it will be enabled on non\-win32 platforms. It
 takes precedence over select.
 .IP "\s-1EV_USE_EPOLL\s0" 4
 .IX Item "EV_USE_EPOLL"
 If defined to be \f(CW1\fR, libev will compile in support for the Linux
 \&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime,
-otherwise another method will be used as fallback. This is the
+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_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_ATOMIC_T\s0" 4
+.IX Item "EV_ATOMIC_T"
+Libev requires an integer type (suitable for storing \f(CW0\fR or \f(CW1\fR) whose
+access is atomic with respect to other threads or signal contexts. No such
+type is easily found in the C language, so you can provide your own type
+that you know is safe for your purposes. It is used both for signal handler \*(L"locking\*(R"
+as well as for signal and thread safety in \f(CW\*(C`ev_async\*(C'\fR watchers.
+.Sp
+In the 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
 .IX Item "EV_H"
 The name of the \fIev.h\fR header file used to include it. The default if
-undefined is \f(CW\*(C`<ev.h>\*(C'\fR in \fIevent.h\fR and \f(CW"ev.h"\fR in \fIev.c\fR. This
+undefined is \f(CW"ev.h"\fR in \fIevent.h\fR, \fIev.c\fR and \fIev++.h\fR. This can be
-can be used to virtually rename the \fIev.h\fR header file in case of conflicts.
+used to virtually rename the \fIev.h\fR header file in case of conflicts.
 .IP "\s-1EV_CONFIG_H\s0" 4
 .IX Item "EV_CONFIG_H"
 If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override
 \&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to
 \&\f(CW\*(C`EV_H\*(C'\fR, above.
 .IP "\s-1EV_EVENT_H\s0" 4
 .IX Item "EV_EVENT_H"
 Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea
-of how the \fIevent.h\fR header can be found.
+of how the \fIevent.h\fR header can be found, the default is \f(CW"event.h"\fR.
 .IP "\s-1EV_PROTOTYPES\s0" 4
 .IX Item "EV_PROTOTYPES"
 If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function
 prototypes, but still define all the structs and other symbols. This is
 occasionally useful if you want to provide your own wrapper functions
 If undefined or defined to \f(CW1\fR, then all event-loop-specific functions
 will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create
 additional independent event loops. Otherwise there will be no support
 for multiple event loops and there is no first event loop pointer
 argument. Instead, all functions act on the single default loop.
+.IP "\s-1EV_MINPRI\s0" 4
+.IX Item "EV_MINPRI"
+.PD 0
+.IP "\s-1EV_MAXPRI\s0" 4
+.IX Item "EV_MAXPRI"
+.PD
+The range of allowed priorities. \f(CW\*(C`EV_MINPRI\*(C'\fR must be smaller or equal to
+\&\f(CW\*(C`EV_MAXPRI\*(C'\fR, but otherwise there are no non-obvious limitations. You can
+provide for more priorities by overriding those symbols (usually defined
+to be \f(CW\*(C`\-2\*(C'\fR and \f(CW2\fR, respectively).
+.Sp
+When doing priority-based operations, libev usually has to linearly search
+all the priorities, so having many of them (hundreds) uses a lot of space
+and time, so using the defaults of five priorities (\-2 .. +2) is usually
+fine.
+.Sp
+If your embedding application does not need any priorities, defining these
+both to \f(CW0\fR will save some memory and \s-1CPU\s0.
 .IP "\s-1EV_PERIODIC_ENABLE\s0" 4
 .IX Item "EV_PERIODIC_ENABLE"
 If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If
 defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
 code.
 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.
+defined to be \f(CW0\fR, then they are not. Embed watchers rely on most other
+watcher types, which therefore must not be disabled.
 .IP "\s-1EV_STAT_ENABLE\s0" 4
 .IX Item "EV_STAT_ENABLE"
 If undefined or defined to be \f(CW1\fR, then stat watchers are supported. If
 defined to be \f(CW0\fR, then they are not.
 .IP "\s-1EV_FORK_ENABLE\s0" 4
 .IX Item "EV_FORK_ENABLE"
 If undefined or defined to be \f(CW1\fR, then fork watchers are supported. If
 defined to be \f(CW0\fR, then they are not.
+.IP "\s-1EV_ASYNC_ENABLE\s0" 4
+.IX Item "EV_ASYNC_ENABLE"
+If undefined or defined to be \f(CW1\fR, then async watchers are supported. If
+defined to be \f(CW0\fR, then they are not.
 .IP "\s-1EV_MINIMAL\s0" 4
 .IX Item "EV_MINIMAL"
 If you need to shave off some kilobytes of code at the expense of some
-speed, define this symbol to \f(CW1\fR. Currently only used for gcc to override
+speed, define this symbol to \f(CW1\fR. Currently this is used to override some
-some inlining decisions, saves roughly 30% codesize of amd64.
+inlining decisions, saves roughly 30% code size on amd64. It also selects a
+much smaller 2\-heap for timer management over the default 4\-heap.
 .IP "\s-1EV_PID_HASHSIZE\s0" 4
 .IX Item "EV_PID_HASHSIZE"
 \&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by
 pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), usually more
 than enough. If you need to manage thousands of children you might want to
 increase this value (\fImust\fR be a power of two).
 .IP "\s-1EV_INOTIFY_HASHSIZE\s0" 4
 .IX Item "EV_INOTIFY_HASHSIZE"
-\&\f(CW\*(C`ev_staz\*(C'\fR watchers use a small hash table to distribute workload by
+\&\f(CW\*(C`ev_stat\*(C'\fR watchers use a small hash table to distribute workload by
 inotify watch id. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR),
 usually more than enough. If you need to manage thousands of \f(CW\*(C`ev_stat\*(C'\fR
 watchers you might want to increase this value (\fImust\fR be a power of
 two).
+.IP "\s-1EV_USE_4HEAP\s0" 4
+.IX Item "EV_USE_4HEAP"
+Heaps are not very cache-efficient. To improve the cache-efficiency of the
+timer and periodics 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_MINIMAL\*(C'\fR is set in which case it is \f(CW0\fR
+(disabled).
+.IP "\s-1EV_HEAP_CACHE_AT\s0" 4
+.IX Item "EV_HEAP_CACHE_AT"
+Heaps are not very cache-efficient. To improve the cache-efficiency of the
+timer and periodics 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_MINIMAL\*(C'\fR is set in which case it is \f(CW0\fR
+(disabled).
+.IP "\s-1EV_VERIFY\s0" 4
+.IX Item "EV_VERIFY"
+Controls how much internal verification (see \f(CW\*(C`ev_loop_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
+The default is \f(CW1\fR, unless \f(CW\*(C`EV_MINIMAL\*(C'\fR is set, 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
 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
 .IP "ev_set_cb (ev, cb)" 4
 .IX Item "ev_set_cb (ev, cb)"
 .PD
 Can be used to change the callback member declaration in each watcher,
 and the way callbacks are invoked and set. Must expand to a struct member
-definition and a statement, respectively. See the \fIev.v\fR header file for
+definition and a statement, respectively. See the \fIev.h\fR header file for
 their default definitions. One possible use for overriding these is to
 avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use
 method calls instead of plain function calls in \*(C+.
+.Sh "\s-1EXPORTED\s0 \s-1API\s0 \s-1SYMBOLS\s0"
+.IX Subsection "EXPORTED API SYMBOLS"
+If you need to re-export the \s-1API\s0 (e.g. via a \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.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 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
+\&   <Symbols.ev sed \-e "s/.*/#define & myprefix_&/" >wrap.h
+.Ve
+.PP
+This would create a file \fIwrap.h\fR which essentially looks like this:
+.PP
+.Vb 4
+\&   #define ev_backend     myprefix_ev_backend
+\&   #define ev_check_start myprefix_ev_check_start
+\&   #define ev_check_stop  myprefix_ev_check_stop
+\&   ...
+.Ve
 .Sh "\s-1EXAMPLES\s0"
 .IX Subsection "EXAMPLES"
 For a real-world example of a program the includes libev
 verbatim, you can have a look at the \s-1EV\s0 perl module
 (<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
 the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public
 interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file
 will be compiled. It is pretty complex because it provides its own header
 file.
-.Sp
+.PP
 The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file
 that everybody includes and which overrides some configure choices:
-.Sp
+.PP
 .Vb 9
-\&  #define EV_MINIMAL 1
+\&   #define EV_MINIMAL 1
-\&  #define EV_USE_POLL 0
+\&   #define EV_USE_POLL 0
-\&  #define EV_MULTIPLICITY 0
+\&   #define EV_MULTIPLICITY 0
-\&  #define EV_PERIODIC_ENABLE 0
+\&   #define EV_PERIODIC_ENABLE 0
-\&  #define EV_STAT_ENABLE 0
+\&   #define EV_STAT_ENABLE 0
-\&  #define EV_FORK_ENABLE 0
+\&   #define EV_FORK_ENABLE 0
-\&  #define EV_CONFIG_H <config.h>
+\&   #define EV_CONFIG_H <config.h>
-\&  #define EV_MINPRI 0
+\&   #define EV_MINPRI 0
-\&  #define EV_MAXPRI 0
+\&   #define EV_MAXPRI 0
-.Ve
+\&
-.Sp
-.Vb 1
-\&  #include "ev++.h"
+\&   #include "ev++.h"
 .Ve
-.Sp
+.PP
 And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled:
-.Sp
+.PP
 .Vb 2
-\&  #include "ev_cpp.h"
+\&   #include "ev_cpp.h"
-\&  #include "ev.c"
+\&   #include "ev.c"
 .Ve
+.SH "INTERACTION WITH OTHER PROGRAMS OR LIBRARIES"
+.IX Header "INTERACTION WITH OTHER PROGRAMS OR LIBRARIES"
+.Sh "\s-1THREADS\s0 \s-1AND\s0 \s-1COROUTINES\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
+\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_loop\*(C'\fR on the same loop from two
+different coroutines, and switch freely between both coroutines running the
+loop, as long as you don't confuse yourself). The only exception is that
+you must not do this from \f(CW\*(C`ev_periodic\*(C'\fR reschedule callbacks.
+.PP
+Care has been taken to ensure that libev does not keep local state inside
+\&\f(CW\*(C`ev_loop\*(C'\fR, and other calls do not usually allow for coroutine switches as
+they do not call any callbacks.
+.Sh "\s-1COMPILER\s0 \s-1WARNINGS\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 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.
+.Sh "\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"
+.Sh "\s-1WIN32\s0 \s-1PLATFORM\s0 \s-1LIMITATIONS\s0 \s-1AND\s0 \s-1WORKAROUNDS\s0"
+.IX Subsection "WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS"
+Win32 doesn't support any of the standards (e.g. \s-1POSIX\s0) that libev
+requires, and its I/O model is fundamentally incompatible with the \s-1POSIX\s0
+model. Libev still offers limited functionality on this platform in
+the form of the \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR backend, and only supports socket
+descriptors. This only applies when using Win32 natively, not when using
+e.g. cygwin.
+.PP
+Lifting these limitations would basically require the full
+re-implementation of the I/O system. If you are into these kinds of
+things, then note that glib does exactly that for you in a very portable
+way (note also that glib is the slowest event library known to man).
+.PP
+There is no supported compilation method available on windows except
+embedding it into other applications.
+.PP
+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
+(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
+.IP "The winsocket select function" 4
+.IX Item "The winsocket select function"
+The winsocket \f(CW\*(C`select\*(C'\fR function doesn't follow \s-1POSIX\s0 in that it
+requires socket \fIhandles\fR and not socket \fIfile descriptors\fR (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.
+.Sp
+The configuration for a \*(L"naked\*(R" win32 using the Microsoft runtime
+libraries and raw winsocket select is:
+.Sp
+.Vb 2
+\&   #define EV_USE_SELECT 1
+\&   #define EV_SELECT_IS_WINSOCKET 1   /* forces EV_SELECT_USE_FD_SET, too */
+.Ve
+.Sp
+Note that winsockets handling of fd sets is O(n), so you can easily get a
+complexity in the O(nA\*^X) range when using win32.
+.IP "Limited number of file descriptors" 4
+.IX Item "Limited number of file descriptors"
+Windows has numerous arbitrary (and low) limits on things.
+.Sp
+Early versions of winsocket's select only supported waiting for a maximum
+of \f(CW64\fR handles (probably owning to the fact that all windows kernels
+can only wait for \f(CW64\fR things at the same time internally; Microsoft
+recommends spawning a chain of threads and wait for 63 handles and the
+previous thread in each. Great).
+.Sp
+Newer versions support more handles, but you need to define \f(CW\*(C`FD_SETSIZE\*(C'\fR
+to some high number (e.g. \f(CW2048\fR) before compiling the winsocket select
+call (which might be in libev or elsewhere, for example, perl does its own
+select emulation on windows).
+.Sp
+Another limit is the number of file descriptors in the Microsoft runtime
+libraries, which by default is \f(CW64\fR (there must be a hidden \fI64\fR fetish
+or something like this inside Microsoft). You can increase this by calling
+\&\f(CW\*(C`_setmaxstdio\*(C'\fR, which can increase this limit to \f(CW2048\fR (another
+arbitrary limit), but is broken in many versions of the Microsoft runtime
+libraries.
+.Sp
+This might get you to about \f(CW512\fR or \f(CW2048\fR sockets (depending on
+windows version and/or the phase of the moon). To get more, you need to
+wrap all I/O functions and provide your own fd management, but the cost of
+calling select (O(nA\*^X)) will likely make this unworkable.
+.Sh "\s-1PORTABILITY\s0 \s-1REQUIREMENTS\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)""\fR must have compatible calling conventions regardless of \f(CW""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\s0 C for example), but it also
+assumes that the same (machine) code can be used to call any watcher
+callback: The watcher callbacks have different type signatures, but libev
+calls them using an \f(CW\*(C`ev_watcher *\*(C'\fR internally.
+.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 default loop in the initial thread as
+well.
+.ie n .IP """long"" must be large enough for common memory allocation sizes" 4
+.el .IP "\f(CWlong\fR must be large enough for common memory allocation sizes" 4
+.IX Item "long must be large enough for common memory allocation sizes"
+To improve portability and simplify 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. This requirement is fulfilled by
+implementations implementing \s-1IEEE\s0 754 (basically all existing ones).
+.PP
+If you know of other additional requirements drop me a note.
-.SH "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.
-.RS 4
+.PP
+All of the following are about amortised time: If an array needs to be
+extended, libev needs to realloc and move the whole array, but this
+happens asymptotically rarer with higher number of elements, so O(1) might
+mean that libev does a lengthy realloc operation in rare cases, but on
+average it is much faster and asymptotically approaches constant time.
 .IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4
 .IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)"
+This means that, when you have a watcher that triggers in one hour and
+there are 100 watchers that would trigger before that, then inserting will
+have to skip roughly seven (\f(CW\*(C`ld 100\*(C'\fR) of these watchers.
+.IP "Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)" 4
+.IX Item "Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)"
+That means that changing a timer costs less than removing/adding them,
+as only the relative motion in the event queue has to be paid for.
+.IP "Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)" 4
+.IX Item "Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)"
+These just add the watcher into an array or at the head of a list.
+.IP "Stopping check/prepare/idle/fork/async watchers: O(1)" 4
+.IX Item "Stopping check/prepare/idle/fork/async watchers: O(1)"
 .PD 0
-.IP "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)" 4
-.IX Item "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)"
-.IP "Starting io/check/prepare/idle/signal/child watchers: O(1)" 4
-.IX Item "Starting io/check/prepare/idle/signal/child watchers: O(1)"
-.IP "Stopping check/prepare/idle watchers: O(1)" 4
-.IX Item "Stopping check/prepare/idle watchers: O(1)"
 .IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \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, so they need to be walked to find the
+correct watcher to remove. The lists are usually short (you don't usually
+have many watchers waiting for the same fd or signal: one is typical, two
+is rare).
-.IP "Finding the next timer per loop iteration: O(1)" 4
+.IP "Finding the next timer in each loop iteration: O(1)" 4
-.IX Item "Finding the next timer per loop iteration: O(1)"
+.IX Item "Finding the next timer in each loop iteration: O(1)"
+By virtue of using a binary or 4\-heap, the next timer is always found at a
+fixed position in the storage array.
 .IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4
 .IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)"
-.IP "Activating one watcher: O(1)" 4
+A change means an I/O watcher gets started or stopped, which requires
-.IX Item "Activating one watcher: O(1)"
+libev to recalculate its status (and possibly tell the kernel, depending
-.RE
+on backend and whether \f(CW\*(C`ev_io_set\*(C'\fR was used).
-.RS 4
+.IP "Activating one watcher (putting it into the pending state): O(1)" 4
+.IX Item "Activating one watcher (putting it into the pending state): O(1)"
+.PD 0
+.IP "Priority handling: O(number_of_priorities)" 4
+.IX Item "Priority handling: O(number_of_priorities)"
 .PD
+Priorities are implemented by allocating some space for each
+priority. When doing priority-based operations, libev usually has to
+linearly search all the priorities, but starting/stopping and activating
+watchers becomes O(1) 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 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
+involves iterating over all running async watchers or all signal numbers.
 .SH "AUTHOR"
 .IX Header "AUTHOR"
-Marc Lehmann <libev@schmorp.de>.
+Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.

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Revision 1.74 by root, Wed Nov 19 10:33:32 2008 UTC