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

Comparing libev/ev.3 (file contents):
Revision 1.60 by root, Mon Jan 28 12:23:02 2008 UTC vs.
Revision 1.63 by root, Wed Apr 2 15:23:11 2008 UTC

 .\}
 .rm #[ #] #H #V #F C
 .\" ========================================================================
 .\"
 .IX Title "EV 1"
-.TH EV 1 "2008-01-28" "perl v5.10.0" "User Contributed Perl Documentation"
+.TH EV 1 "2008-04-02" "perl v5.10.0" "User Contributed Perl Documentation"
 .\" For nroff, turn off justification.  Always turn off hyphenation; it makes
 .\" way too many mistakes in technical documents.
 .if n .ad l
 .nh
 .SH "NAME"
 .Vb 1
 \&  #include <ev.h>
 .Ve
 .Sh "\s-1EXAMPLE\s0 \s-1PROGRAM\s0"
 .IX Subsection "EXAMPLE PROGRAM"
-.Vb 1
+.Vb 2
+\&  // a single header file is required
 \&  #include <ev.h>
 \&
+\&  // every watcher type has its own typedef\*(Aqd struct
+\&  // with the name ev_<type>
 \&  ev_io stdin_watcher;
 \&  ev_timer timeout_watcher;
 \&
+\&  // all watcher callbacks have a similar signature
-\&  /* called when data readable on stdin */
+\&  // this callback is called when data is readable on stdin
 \&  static void
 \&  stdin_cb (EV_P_ struct ev_io *w, int revents)
 \&  {
-\&    /* puts ("stdin ready"); */
+\&    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);
 \&  }
 \&
+\&  // another callback, this time for a time\-out
 \&  static void
 \&  timeout_cb (EV_P_ struct 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);
 \&  }
 \&
 \&  int
 \&  main (void)
 \&  {
+\&    // use the default event loop unless you have special needs
 \&    struct ev_loop *loop = ev_default_loop (0);
 \&
-\&    /* initialise an io watcher, then start it */
+\&    // initialise an io watcher, then start it
+\&    // this one will watch for stdin to become readable
 \&    ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
 \&    ev_io_start (loop, &stdin_watcher);
 \&
+\&    // initialise a timer watcher, then start it
-\&    /* simple non\-repeating 5.5 second timeout */
+\&    // simple non\-repeating 5.5 second timeout
 \&    ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
 \&    ev_timer_start (loop, &timeout_watcher);
 \&
-\&    /* loop till timeout or data ready */
+\&    // now wait for events to arrive
 \&    ev_loop (loop, 0);
 \&
+\&    // unloop was called, so exit
 \&    return 0;
 \&  }
 .Ve
 .SH "DESCRIPTION"
 .IX Header "DESCRIPTION"
-The newest version of this document is also available as a html-formatted
+The newest version of this document is also available as an html-formatted
 web page you might find easier to navigate when reading it for the first
 time: <http://cvs.schmorp.de/libev/ev.html>.
 .PP
 Libev is an event loop: you register interest in certain events (such as a
 file descriptor being readable or a timeout occurring), and it will manage
 It also is quite fast (see this
 benchmark comparing it to libevent
 for example).
 .Sh "\s-1CONVENTIONS\s0"
 .IX Subsection "CONVENTIONS"
-Libev is very configurable. In this manual the default 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`struct ev_loop *\*(C'\fR) will not have
+this argument.
 .Sh "\s-1TIME\s0 \s-1REPRESENTATION\s0"
 .IX Subsection "TIME REPRESENTATION"
 Libev represents time as a single floating point number, representing the
 (fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near
 the beginning of 1970, details are complicated, don't ask). This type is
 flags. If that is troubling you, check \f(CW\*(C`ev_backend ()\*(C'\fR afterwards).
 .Sp
 If you don't know what event loop to use, use the one returned from this
 function.
 .Sp
+Note that this function is \fInot\fR thread-safe, so if you want to use it
+from multiple threads, you have to lock (note also that this is unlikely,
+as loops cannot bes hared easily between threads anyway).
+.Sp
 The default loop is the only loop that can handle \f(CW\*(C`ev_signal\*(C'\fR and
 \&\f(CW\*(C`ev_child\*(C'\fR watchers, and to do this, it always registers a handler
 for \f(CW\*(C`SIGCHLD\*(C'\fR. If this is a problem for your app you can either
 create a dynamic loop with \f(CW\*(C`ev_loop_new\*(C'\fR that doesn't do that, or you
 can simply overwrite the \f(CW\*(C`SIGCHLD\*(C'\fR signal handler \fIafter\fR calling
 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 syscall and thus \fIvery\fR fast, but my GNU/Linux system also has
 \&\f(CW\*(C`pthread_atfork\*(C'\fR which is even faster).
 .Sp
 The big advantage of this flag is that you can forget about fork (and
 forget about forgetting to tell libev about forking) when you use this
 flag.
 Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is
 always distinct from the default loop. Unlike the default loop, it cannot
 handle signal and child watchers, and attempts to do so will be greeted by
 undefined behaviour (or a failed assertion if assertions are enabled).
 .Sp
+Note that this function \fIis\fR thread-safe, and the recommended way to use
+libev with threads is indeed to create one loop per thread, and using the
+default loop in the \*(L"main\*(R" or \*(L"initial\*(R" thread.
+.Sp
 Example: Try to create a event loop that uses epoll and nothing else.
 .Sp
 .Vb 3
 \&  struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
 \&  if (!epoller)
 .IP "ev_loop_fork (loop)" 4
 .IX Item "ev_loop_fork (loop)"
 Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by
 \&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop
 after fork, and how you do this is entirely your own problem.
+.IP "int ev_is_default_loop (loop)" 4
+.IX Item "int ev_is_default_loop (loop)"
+Returns true when the given loop actually is the default loop, false otherwise.
 .IP "unsigned int ev_loop_count (loop)" 4
 .IX Item "unsigned int ev_loop_count (loop)"
 Returns the count of loop iterations for the loop, which is identical to
 the number of times libev did poll for new events. It starts at \f(CW0\fR and
 happily wraps around with enough iterations.
 .ie n .IP """EV_FORK""" 4
 .el .IP "\f(CWEV_FORK\fR" 4
 .IX Item "EV_FORK"
 The event loop has been resumed in the child process after fork (see
 \&\f(CW\*(C`ev_fork\*(C'\fR).
+.ie n .IP """EV_ASYNC""" 4
+.el .IP "\f(CWEV_ASYNC\fR" 4
+.IX Item "EV_ASYNC"
+The given async watcher has been asynchronously notified (see \f(CW\*(C`ev_async\*(C'\fR).
 .ie n .IP """EV_ERROR""" 4
 .el .IP "\f(CWEV_ERROR\fR" 4
 .IX Item "EV_ERROR"
 An unspecified error has occured, the watcher has been stopped. This might
 happen because the watcher could not be properly started because libev
 To support fork in your programs, you either have to call
 \&\f(CW\*(C`ev_default_fork ()\*(C'\fR or \f(CW\*(C`ev_loop_fork ()\*(C'\fR after a fork in the child,
 enable \f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR, or resort to \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or
 \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
 .PP
+\fIThe special problem of \s-1SIGPIPE\s0\fR
+.IX Subsection "The special problem of SIGPIPE"
+.PP
+While not really specific to libev, it is easy to forget about \s-1SIGPIPE:\s0
+when reading from a pipe whose other end has been closed, your program
+gets send a \s-1SIGPIPE\s0, which, by default, aborts your program. For most
+programs this is sensible behaviour, for daemons, this is usually
+undesirable.
+.PP
+So when you encounter spurious, unexplained daemon exits, make sure you
+ignore \s-1SIGPIPE\s0 (and maybe make sure you log the exit status of your daemon
+somewhere, as that would have given you a big clue).
+.PP
 \fIWatcher-Specific Functions\fR
 .IX Subsection "Watcher-Specific Functions"
 .IP "ev_io_init (ev_io *, callback, int fd, int events)" 4
 .IX Item "ev_io_init (ev_io *, callback, int fd, int events)"
 .PD 0
 The timer itself will do a best-effort at avoiding drift, that is, if you
 configure a timer to trigger every 10 seconds, then it will trigger at
 exactly 10 second intervals. If, however, your program cannot keep up with
 the timer (because it takes longer than those 10 seconds to do stuff) the
 timer will not fire more than once per event loop iteration.
-.IP "ev_timer_again (loop)" 4
+.IP "ev_timer_again (loop, ev_timer *)" 4
-.IX Item "ev_timer_again (loop)"
+.IX Item "ev_timer_again (loop, ev_timer *)"
 This will act as if the timer timed out and restart it again if it is
 repeating. The exact semantics are:
 .Sp
 If the timer is pending, its pending status is cleared.
 .Sp
 In this configuration the watcher triggers an event at the wallclock time
 \&\f(CW\*(C`at\*(C'\fR and doesn't repeat. It will not adjust when a time jump occurs,
 that is, if it is to be run at January 1st 2011 then it will run when the
 system time reaches or surpasses this time.
 .IP "\(bu" 4
-non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
+repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
 .Sp
 In this mode the watcher will always be scheduled to time out at the next
 \&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N, which can also be negative)
 and then repeat, regardless of any time jumps.
 .Sp
 with the kernel (thus it coexists with your own signal handlers as long
 as you don't register any with libev). Similarly, when the last signal
 watcher for a signal is stopped libev will reset the signal handler to
 \&\s-1SIG_DFL\s0 (regardless of what it was set to before).
 .PP
+If possible and supported, libev will install its handlers with
+\&\f(CW\*(C`SA_RESTART\*(C'\fR behaviour enabled, so syscalls should not be unduly
+interrupted. If you have a problem with syscalls getting interrupted by
+signals you can block all signals in an \f(CW\*(C`ev_check\*(C'\fR watcher and unblock
+them in an \f(CW\*(C`ev_prepare\*(C'\fR watcher.
+.PP
 \fIWatcher-Specific Functions and Data Members\fR
 .IX Subsection "Watcher-Specific Functions and Data Members"
 .IP "ev_signal_init (ev_signal *, callback, int signum)" 4
 .IX Item "ev_signal_init (ev_signal *, callback, int signum)"
 .PD 0
 Configures the watcher to trigger on the given signal number (usually one
 of the \f(CW\*(C`SIGxxx\*(C'\fR constants).
 .IP "int signum [read\-only]" 4
 .IX Item "int signum [read-only]"
 The signal the watcher watches out for.
+.PP
+\fIExamples\fR
+.IX Subsection "Examples"
+.PP
+Example: Try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0.
+.PP
+.Vb 5
+\&  static void
+\&  sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
+\&  {
+\&    ev_unloop (loop, EVUNLOOP_ALL);
+\&  }
+\&
+\&  struct ev_signal signal_watcher;
+\&  ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
+\&  ev_signal_start (loop, &sigint_cb);
+.Ve
 .ie n .Sh """ev_child"" \- watch out for process status changes"
 .el .Sh "\f(CWev_child\fP \- watch out for process status changes"
 .IX Subsection "ev_child - watch out for process status changes"
 Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to
-some child status changes (most typically when a child of yours dies).
+some child status changes (most typically when a child of yours dies). It
+is permissible to install a child watcher \fIafter\fR the child has been
+forked (which implies it might have already exited), as long as the event
+loop isn't entered (or is continued from a watcher).
+.PP
+Only the default event loop is capable of handling signals, and therefore
+you can only rgeister child watchers in the default event loop.
+.PP
+\fIProcess Interaction\fR
+.IX Subsection "Process Interaction"
+.PP
+Libev grabs \f(CW\*(C`SIGCHLD\*(C'\fR as soon as the default event loop is
+initialised. This is necessary to guarantee proper behaviour even if
+the first child watcher is started after the child exits. The occurance
+of \f(CW\*(C`SIGCHLD\*(C'\fR is recorded asynchronously, but child reaping is done
+synchronously as part of the event loop processing. Libev always reaps all
+children, even ones not watched.
+.PP
+\fIOverriding the Built-In Processing\fR
+.IX Subsection "Overriding the Built-In Processing"
+.PP
+Libev offers no special support for overriding the built-in child
+processing, but if your application collides with libev's default child
+handler, you can override it easily by installing your own handler for
+\&\f(CW\*(C`SIGCHLD\*(C'\fR after initialising the default loop, and making sure the
+default loop never gets destroyed. You are encouraged, however, to use an
+event-based approach to child reaping and thus use libev's support for
+that, so other libev users can use \f(CW\*(C`ev_child\*(C'\fR watchers freely.
 .PP
 \fIWatcher-Specific Functions and Data Members\fR
 .IX Subsection "Watcher-Specific Functions and Data Members"
 .IP "ev_child_init (ev_child *, callback, int pid, int trace)" 4
 .IX Item "ev_child_init (ev_child *, callback, int pid, int trace)"
 \&\f(CW\*(C`waitpid\*(C'\fR and \f(CW\*(C`sys/wait.h\*(C'\fR documentation for details).
 .PP
 \fIExamples\fR
 .IX Subsection "Examples"
 .PP
-Example: Try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0.
+Example: \f(CW\*(C`fork()\*(C'\fR a new process and install a child handler to wait for
+its completion.
 .PP
-.Vb 5
+.Vb 1
+\&  ev_child cw;
+\&
 \&  static void
-\&  sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
+\&  child_cb (EV_P_ struct ev_child *w, int revents)
 \&  {
-\&    ev_unloop (loop, EVUNLOOP_ALL);
+\&    ev_child_stop (EV_A_ w);
+\&    printf ("process %d exited with status %x\en", w\->rpid, w\->rstatus);
 \&  }
 \&
-\&  struct ev_signal signal_watcher;
+\&  pid_t pid = fork ();
-\&  ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
+\&
-\&  ev_signal_start (loop, &sigint_cb);
+\&  if (pid < 0)
+\&    // error
+\&  else if (pid == 0)
+\&    {
+\&      // the forked child executes here
+\&      exit (1);
+\&    }
+\&  else
+\&    {
+\&      ev_child_init (&cw, child_cb, pid, 0);
+\&      ev_child_start (EV_DEFAULT_ &cw);
+\&    }
 .Ve
 .ie n .Sh """ev_stat"" \- did the file attributes just change?"
 .el .Sh "\f(CWev_stat\fP \- did the file attributes just change?"
 .IX Subsection "ev_stat - did the file attributes just change?"
 This watches a filesystem path for attribute changes. That is, it calls
 reader). Inotify will be used to give hints only and should not change the
 semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers, which means that libev sometimes needs
 to fall back to regular polling again even with inotify, but changes are
 usually detected immediately, and if the file exists there will be no
 polling.
+.PP
+\fI\s-1ABI\s0 Issues (Largefile Support)\fR
+.IX Subsection "ABI Issues (Largefile Support)"
+.PP
+Libev by default (unless the user overrides this) uses the default
+compilation environment, which means that on systems with optionally
+disabled large file support, you get the 32 bit version of the stat
+structure. When using the library from programs that change the \s-1ABI\s0 to
+use 64 bit file offsets the programs will fail. In that case you have to
+compile libev with the same flags to get binary compatibility. This is
+obviously the case with any flags that change the \s-1ABI\s0, but the problem is
+most noticably with ev_stat and largefile support.
 .PP
 \fIInotify\fR
 .IX Subsection "Inotify"
 .PP
 When \f(CW\*(C`inotify (7)\*(C'\fR support has been compiled into libev (generally only
 path for as long as the watcher is active.
 .Sp
 The callback will be receive \f(CW\*(C`EV_STAT\*(C'\fR when a change was detected,
 relative to the attributes at the time the watcher was started (or the
 last change was detected).
-.IP "ev_stat_stat (ev_stat *)" 4
+.IP "ev_stat_stat (loop, ev_stat *)" 4
-.IX Item "ev_stat_stat (ev_stat *)"
+.IX Item "ev_stat_stat (loop, ev_stat *)"
 Updates the stat buffer immediately with new values. If you change the
 watched path in your callback, you could call this fucntion to avoid
 detecting this change (while introducing a race condition). Can also be
 useful simply to find out the new values.
 .IP "ev_statdata attr [read\-only]" 4
 .IP "ev_fork_init (ev_signal *, callback)" 4
 .IX Item "ev_fork_init (ev_signal *, callback)"
 Initialises and configures the fork watcher \- it has no parameters of any
 kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless,
 believe me.
+.ie n .Sh """ev_async"" \- how to wake up another event loop"
+.el .Sh "\f(CWev_async\fP \- how to wake up another event loop"
+.IX Subsection "ev_async - how to wake up another event loop"
+In general, you cannot use an \f(CW\*(C`ev_loop\*(C'\fR from multiple threads or other
+asynchronous sources such as signal handlers (as opposed to multiple event
+loops \- those are of course safe to use in different threads).
+.PP
+Sometimes, however, you need to wake up another event loop you do not
+control, for example because it belongs to another thread. This is what
+\&\f(CW\*(C`ev_async\*(C'\fR watchers do: as long as the \f(CW\*(C`ev_async\*(C'\fR watcher is active, you
+can signal it by calling \f(CW\*(C`ev_async_send\*(C'\fR, which is thread\- and signal
+safe.
+.PP
+This functionality is very similar to \f(CW\*(C`ev_signal\*(C'\fR watchers, as signals,
+too, are asynchronous in nature, and signals, too, will be compressed
+(i.e. the number of callback invocations may be less than the number of
+\&\f(CW\*(C`ev_async_sent\*(C'\fR calls).
+.PP
+Unlike \f(CW\*(C`ev_signal\*(C'\fR watchers, \f(CW\*(C`ev_async\*(C'\fR works with any event loop, not
+just the default loop.
+.PP
+\fIQueueing\fR
+.IX Subsection "Queueing"
+.PP
+\&\f(CW\*(C`ev_async\*(C'\fR does not support queueing of data in any way. The reason
+is that the author does not know of a simple (or any) algorithm for a
+multiple-writer-single-reader queue that works in all cases and doesn't
+need elaborate support such as pthreads.
+.PP
+That means that if you want to queue data, you have to provide your own
+queue. But at least I can tell you would implement locking around your
+queue:
+.IP "queueing from a signal handler context" 4
+.IX Item "queueing from a signal handler context"
+To implement race-free queueing, you simply add to the queue in the signal
+handler but you block the signal handler in the watcher callback. Here is an example that does that for
+some fictitiuous \s-1SIGUSR1\s0 handler:
+.Sp
+.Vb 1
+\&   static ev_async mysig;
+\&
+\&   static void
+\&   sigusr1_handler (void)
+\&   {
+\&     sometype data;
+\&
+\&     // no locking etc.
+\&     queue_put (data);
+\&     ev_async_send (EV_DEFAULT_ &mysig);
+\&   }
+\&
+\&   static void
+\&   mysig_cb (EV_P_ ev_async *w, int revents)
+\&   {
+\&     sometype data;
+\&     sigset_t block, prev;
+\&
+\&     sigemptyset (&block);
+\&     sigaddset (&block, SIGUSR1);
+\&     sigprocmask (SIG_BLOCK, &block, &prev);
+\&
+\&     while (queue_get (&data))
+\&       process (data);
+\&
+\&     if (sigismember (&prev, SIGUSR1)
+\&       sigprocmask (SIG_UNBLOCK, &block, 0);
+\&   }
+.Ve
+.Sp
+(Note: pthreads in theory requires you to use \f(CW\*(C`pthread_setmask\*(C'\fR
+instead of \f(CW\*(C`sigprocmask\*(C'\fR when you use threads, but libev doesn't do it
+either...).
+.IP "queueing from a thread context" 4
+.IX Item "queueing from a thread context"
+The strategy for threads is different, as you cannot (easily) block
+threads but you can easily preempt them, so to queue safely you need to
+employ a traditional mutex lock, such as in this pthread example:
+.Sp
+.Vb 2
+\&   static ev_async mysig;
+\&   static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
+\&
+\&   static void
+\&   otherthread (void)
+\&   {
+\&     // only need to lock the actual queueing operation
+\&     pthread_mutex_lock (&mymutex);
+\&     queue_put (data);
+\&     pthread_mutex_unlock (&mymutex);
+\&
+\&     ev_async_send (EV_DEFAULT_ &mysig);
+\&   }
+\&
+\&   static void
+\&   mysig_cb (EV_P_ ev_async *w, int revents)
+\&   {
+\&     pthread_mutex_lock (&mymutex);
+\&
+\&     while (queue_get (&data))
+\&       process (data);
+\&
+\&     pthread_mutex_unlock (&mymutex);
+\&   }
+.Ve
+.PP
+\fIWatcher-Specific Functions and Data Members\fR
+.IX Subsection "Watcher-Specific Functions and Data Members"
+.IP "ev_async_init (ev_async *, callback)" 4
+.IX Item "ev_async_init (ev_async *, callback)"
+Initialises and configures the async watcher \- it has no parameters of any
+kind. There is a \f(CW\*(C`ev_asynd_set\*(C'\fR macro, but using it is utterly pointless,
+believe me.
+.IP "ev_async_send (loop, ev_async *)" 4
+.IX Item "ev_async_send (loop, ev_async *)"
+Sends/signals/activates the given \f(CW\*(C`ev_async\*(C'\fR watcher, that is, feeds
+an \f(CW\*(C`EV_ASYNC\*(C'\fR event on the watcher into the event loop. Unlike
+\&\f(CW\*(C`ev_feed_event\*(C'\fR, this call is safe to do in other threads, signal or
+similar contexts (see the dicusssion of \f(CW\*(C`EV_ATOMIC_T\*(C'\fR in the embedding
+section below on what exactly this means).
+.Sp
+This call incurs the overhead of a syscall only once per loop iteration,
+so while the overhead might be noticable, it doesn't apply to repeated
+calls to \f(CW\*(C`ev_async_send\*(C'\fR.
+.IP "bool = ev_async_pending (ev_async *)" 4
+.IX Item "bool = ev_async_pending (ev_async *)"
+Returns a non-zero value when \f(CW\*(C`ev_async_send\*(C'\fR has been called on the
+watcher but the event has not yet been processed (or even noted) by the
+event loop.
+.Sp
+\&\f(CW\*(C`ev_async_send\*(C'\fR sets a flag in the watcher and wakes up the loop. When
+the loop iterates next and checks for the watcher to have become active,
+it will reset the flag again. \f(CW\*(C`ev_async_pending\*(C'\fR can be used to very
+quickly check wether invoking the loop might be a good idea.
+.Sp
+Not that this does \fInot\fR check wether the watcher itself is pending, only
+wether it has been requested to make this watcher pending.
 .SH "OTHER FUNCTIONS"
 .IX Header "OTHER FUNCTIONS"
 There are some other functions of possible interest. Described. Here. Now.
 .IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4
 .IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)"
 \&
 \&      io.start (fd, ev::READ);
 \&    }
 \&  };
 .Ve
+.SH "OTHER LANGUAGE BINDINGS"
+.IX Header "OTHER LANGUAGE BINDINGS"
+Libev does not offer other language bindings itself, but bindings for a
+numbe rof languages exist in the form of third-party packages. If you know
+any interesting language binding in addition to the ones listed here, drop
+me a note.
+.IP "Perl" 4
+.IX Item "Perl"
+The \s-1EV\s0 module implements the full libev \s-1API\s0 and is actually used to test
+libev. \s-1EV\s0 is developed together with libev. Apart from the \s-1EV\s0 core module,
+there are additional modules that implement libev-compatible interfaces
+to \f(CW\*(C`libadns\*(C'\fR (\f(CW\*(C`EV::ADNS\*(C'\fR), \f(CW\*(C`Net::SNMP\*(C'\fR (\f(CW\*(C`Net::SNMP::EV\*(C'\fR) and the
+\&\f(CW\*(C`libglib\*(C'\fR event core (\f(CW\*(C`Glib::EV\*(C'\fR and \f(CW\*(C`EV::Glib\*(C'\fR).
+.Sp
+It can be found and installed via \s-1CPAN\s0, its homepage is found at
+<http://software.schmorp.de/pkg/EV>.
+.IP "Ruby" 4
+.IX Item "Ruby"
+Tony Arcieri has written a ruby extension that offers access to a subset
+of the libev \s-1API\s0 and adds filehandle abstractions, asynchronous \s-1DNS\s0 and
+more on top of it. It can be found via gem servers. Its homepage is at
+<http://rev.rubyforge.org/>.
+.IP "D" 4
+.IX Item "D"
+Leandro Lucarella has written a D language binding (\fIev.d\fR) for libev, to
+be found at <http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.
 .SH "MACRO MAGIC"
 .IX Header "MACRO MAGIC"
 Libev can be compiled with a variety of options, the most fundamantal
 of which is \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most)
 functions and callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument.
 .IP "\s-1EV_USE_INOTIFY\s0" 4
 .IX Item "EV_USE_INOTIFY"
 If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify
 interface to speed up \f(CW\*(C`ev_stat\*(C'\fR watchers. Its actual availability will
 be detected at runtime.
+.IP "\s-1EV_ATOMIC_T\s0" 4
+.IX Item "EV_ATOMIC_T"
+Libev requires an integer type (suitable for storing \f(CW0\fR or \f(CW1\fR) whose
+access is atomic with respect to other threads or signal contexts. No such
+type is easily found in the C language, so you can provide your own type
+that you know is safe for your purposes. It is used both for signal handler \*(L"locking\*(R"
+as well as for signal and thread safety in \f(CW\*(C`ev_async\*(C'\fR watchers.
+.Sp
+In the absense of this define, libev will use \f(CW\*(C`sig_atomic_t volatile\*(C'\fR
+(from \fIsignal.h\fR), which is usually good enough on most platforms.
 .IP "\s-1EV_H\s0" 4
 .IX Item "EV_H"
 The name of the \fIev.h\fR header file used to include it. The default if
 undefined is \f(CW"ev.h"\fR in \fIevent.h\fR, \fIev.c\fR and \fIev++.h\fR. This can be
 used to virtually rename the \fIev.h\fR header file in case of conflicts.
 defined to be \f(CW0\fR, then they are not.
 .IP "\s-1EV_FORK_ENABLE\s0" 4
 .IX Item "EV_FORK_ENABLE"
 If undefined or defined to be \f(CW1\fR, then fork watchers are supported. If
 defined to be \f(CW0\fR, then they are not.
+.IP "\s-1EV_ASYNC_ENABLE\s0" 4
+.IX Item "EV_ASYNC_ENABLE"
+If undefined or defined to be \f(CW1\fR, then async watchers are supported. If
+defined to be \f(CW0\fR, then they are not.
 .IP "\s-1EV_MINIMAL\s0" 4
 .IX Item "EV_MINIMAL"
 If you need to shave off some kilobytes of code at the expense of some
 speed, define this symbol to \f(CW1\fR. Currently only used for gcc to override
 some inlining decisions, saves roughly 30% codesize of amd64.
 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 watchers: O(1)" 4
+.IP "Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)" 4
-.IX Item "Starting io/check/prepare/idle/signal/child watchers: O(1)"
+.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 watchers: O(1)" 4
+.IP "Stopping check/prepare/idle/fork/async watchers: O(1)" 4
-.IX Item "Stopping check/prepare/idle watchers: O(1)"
+.IX Item "Stopping check/prepare/idle/fork/async watchers: O(1)"
 .PD 0
 .IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4
 .IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))"
 .PD
 These watchers are stored in lists then need to be walked to find the
 .IX Item "Priority handling: O(number_of_priorities)"
 .PD
 Priorities are implemented by allocating some space for each
 priority. When doing priority-based operations, libev usually has to
 linearly search all the priorities, but starting/stopping and activating
-watchers becomes O(1) w.r.t. prioritiy handling.
+watchers becomes O(1) w.r.t. priority handling.
+.IP "Sending an ev_async: O(1)" 4
+.IX Item "Sending an ev_async: O(1)"
+.PD 0
+.IP "Processing ev_async_send: O(number_of_async_watchers)" 4
+.IX Item "Processing ev_async_send: O(number_of_async_watchers)"
+.IP "Processing signals: O(max_signal_number)" 4
+.IX Item "Processing signals: O(max_signal_number)"
+.PD
+Sending involves a syscall \fIiff\fR there were no other \f(CW\*(C`ev_async_send\*(C'\fR
+calls in the current loop iteration. Checking for async and signal events
+involves iterating over all running async watchers or all signal numbers.
 .SH "Win32 platform limitations and workarounds"
 .IX Header "Win32 platform limitations and workarounds"
 Win32 doesn't support any of the standards (e.g. \s-1POSIX\s0) that libev
 requires, and its I/O model is fundamentally incompatible with the \s-1POSIX\s0
 model. Libev still offers limited functionality on this platform in
 .IX Header "AUTHOR"
 Marc Lehmann <libev@schmorp.de>.
 .SH "POD ERRORS"
 .IX Header "POD ERRORS"
 Hey! \fBThe above document had some coding errors, which are explained below:\fR
-.IP "Around line 2686:" 4
+.IP "Around line 2996:" 4
-.IX Item "Around line 2686:"
+.IX Item "Around line 2996:"
 You forgot a '=back' before '=head2'

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Comparing libev/ev.3 (file contents): Revision 1.60 by root, Mon Jan 28 12:23:02 2008 UTC vs. Revision 1.63 by root, Wed Apr 2 15:23:11 2008 UTC

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Comparing libev/ev.3 (file contents):
Revision 1.60 by root, Mon Jan 28 12:23:02 2008 UTC vs.
Revision 1.63 by root, Wed Apr 2 15:23:11 2008 UTC