[ViewVC] Diff of: cvs/AnyEvent/README

Comparing AnyEvent/README (file contents):
Revision 1.30 by root, Mon Sep 29 02:08:57 2008 UTC vs.
Revision 1.39 by root, Sun Jun 7 16:48:38 2009 UTC

 NAME
     AnyEvent - provide framework for multiple event loops
-    EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event
+    EV, Event, Glib, Tk, Perl, Event::Lib, Qt and POE are various supported
-    loops
+    event loops.
 SYNOPSIS
        use AnyEvent;
+       # file descriptor readable
-       my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub { ...  });
+       my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ...  });
+       # one-shot or repeating timers
        my $w = AnyEvent->timer (after => $seconds, cb => sub { ...  });
        my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
        print AnyEvent->now;  # prints current event loop time
        print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
+       # POSIX signal
        my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
+       # child process exit
        my $w = AnyEvent->child (pid => $pid, cb => sub {
           my ($pid, $status) = @_;
           ...
        });
+       # called when event loop idle (if applicable)
+       my $w = AnyEvent->idle (cb => sub { ... });
        my $w = AnyEvent->condvar; # stores whether a condition was flagged
        $w->send; # wake up current and all future recv's
        $w->recv; # enters "main loop" till $condvar gets ->send
        # use a condvar in callback mode:
     These watchers are normal Perl objects with normal Perl lifetime. After
     creating a watcher it will immediately "watch" for events and invoke the
     callback when the event occurs (of course, only when the event model is
     in control).
+    Note that callbacks must not permanently change global variables
+    potentially in use by the event loop (such as $_ or $[) and that
+    callbacks must not "die". The former is good programming practise in
+    Perl and the latter stems from the fact that exception handling differs
+    widely between event loops.
     To disable the watcher you have to destroy it (e.g. by setting the
     variable you store it in to "undef" or otherwise deleting all references
     to it).
     All watchers are created by calling a method on the "AnyEvent" class.
   I/O WATCHERS
     You can create an I/O watcher by calling the "AnyEvent->io" method with
     the following mandatory key-value pairs as arguments:
-    "fh" the Perl *file handle* (*not* file descriptor) to watch for events
+    "fh" is the Perl *file handle* (*not* file descriptor) to watch for
-    (AnyEvent might or might not keep a reference to this file handle).
+    events (AnyEvent might or might not keep a reference to this file
+    handle). Note that only file handles pointing to things for which
+    non-blocking operation makes sense are allowed. This includes sockets,
+    most character devices, pipes, fifos and so on, but not for example
+    files or block devices.
     "poll" must be a string that is either "r" or "w", which creates a
-    watcher waiting for "r"eadable or "w"ritable events, respectively. "cb"
+    watcher waiting for "r"eadable or "w"ritable events, respectively.
-    is the callback to invoke each time the file handle becomes ready.
+    "cb" is the callback to invoke each time the file handle becomes ready.
     Although the callback might get passed parameters, their value and
     presence is undefined and you cannot rely on them. Portable AnyEvent
     callbacks cannot use arguments passed to I/O watcher callbacks.
         In either case, if you care (and in most cases, you don't), then you
         can get whatever behaviour you want with any event loop, by taking
         the difference between "AnyEvent->time" and "AnyEvent->now" into
         account.
+    AnyEvent->now_update
+        Some event loops (such as EV or AnyEvent::Impl::Perl) cache the
+        current time for each loop iteration (see the discussion of
+        AnyEvent->now, above).
+        When a callback runs for a long time (or when the process sleeps),
+        then this "current" time will differ substantially from the real
+        time, which might affect timers and time-outs.
+        When this is the case, you can call this method, which will update
+        the event loop's idea of "current time".
+        Note that updating the time *might* cause some events to be handled.
   SIGNAL WATCHERS
     You can watch for signals using a signal watcher, "signal" is the signal
     *name* in uppercase and without any "SIG" prefix, "cb" is the Perl
     callback to be invoked whenever a signal occurs.
        );
    # do something else, then wait for process exit
        $done->recv;
+  IDLE WATCHERS
+    Sometimes there is a need to do something, but it is not so important to
+    do it instantly, but only when there is nothing better to do. This
+    "nothing better to do" is usually defined to be "no other events need
+    attention by the event loop".
+    Idle watchers ideally get invoked when the event loop has nothing better
+    to do, just before it would block the process to wait for new events.
+    Instead of blocking, the idle watcher is invoked.
+    Most event loops unfortunately do not really support idle watchers (only
+    EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
+    will simply call the callback "from time to time".
+    Example: read lines from STDIN, but only process them when the program
+    is otherwise idle:
+       my @lines; # read data
+       my $idle_w;
+       my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
+          push @lines, scalar <STDIN>;
+          # start an idle watcher, if not already done
+          $idle_w ||= AnyEvent->idle (cb => sub {
+             # handle only one line, when there are lines left
+             if (my $line = shift @lines) {
+                print "handled when idle: $line";
+             } else {
+                # otherwise disable the idle watcher again
+                undef $idle_w;
+             }
+          });
+       });
   CONDITION VARIABLES
     If you are familiar with some event loops you will know that all of them
     require you to run some blocking "loop", "run" or similar function that
     will actively watch for new events and call your callbacks.
     AnyEvent::IGS
         A non-blocking interface to the Internet Go Server protocol (used by
         App::IGS).
+    AnyEvent::IRC
+        AnyEvent based IRC client module family (replacing the older
-    Net::IRC3
+        Net::IRC3).
-        AnyEvent based IRC client module family.
     Net::XMPP2
         AnyEvent based XMPP (Jabber protocol) module family.
     Net::FCP
         mentioned will be used, and preference will be given to protocols
         mentioned earlier in the list.
         This variable can effectively be used for denial-of-service attacks
         against local programs (e.g. when setuid), although the impact is
-        likely small, as the program has to handle connection errors
+        likely small, as the program has to handle conenction and other
-        already-
+        failures anyways.
         Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over
         IPv6, but support both and try to use both.
         "PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to
         resolve or contact IPv6 addresses.
     *destroy* is the time, in microseconds, that it takes to destroy a
     single watcher.
    Results
               name watchers bytes create invoke destroy comment
-             EV/EV   400000   244   0.56   0.46    0.31 EV native interface
+             EV/EV   400000   224   0.47   0.35    0.27 EV native interface
-            EV/Any   100000   244   2.50   0.46    0.29 EV + AnyEvent watchers
+            EV/Any   100000   224   2.88   0.34    0.27 EV + AnyEvent watchers
-        CoroEV/Any   100000   244   2.49   0.44    0.29 coroutines + Coro::Signal
+        CoroEV/Any   100000   224   2.85   0.35    0.28 coroutines + Coro::Signal
-          Perl/Any   100000   513   4.92   0.87    1.12 pure perl implementation
+          Perl/Any   100000   452   4.13   0.73    0.95 pure perl implementation
-       Event/Event    16000   516  31.88  31.30    0.85 Event native interface
+       Event/Event    16000   517  32.20  31.80    0.81 Event native interface
-         Event/Any    16000   590  35.75  31.42    1.08 Event + AnyEvent watchers
+         Event/Any    16000   590  35.85  31.55    1.06 Event + AnyEvent watchers
-          Glib/Any    16000  1357  98.22  12.41   54.00 quadratic behaviour
+          Glib/Any    16000  1357 102.33  12.31   51.00 quadratic behaviour
-            Tk/Any     2000  1860  26.97  67.98   14.00 SEGV with >> 2000 watchers
+            Tk/Any     2000  1860  27.20  66.31   14.00 SEGV with >> 2000 watchers
-         POE/Event     2000  6644 108.64 736.02   14.73 via POE::Loop::Event
+         POE/Event     2000  6328 109.99 751.67   14.02 via POE::Loop::Event
-        POE/Select     2000  6343  94.13 809.12  565.96 via POE::Loop::Select
+        POE/Select     2000  6027  94.54 809.13  579.80 via POE::Loop::Select
    Discussion
     The benchmark does *not* measure scalability of the event loop very
     well. For example, a select-based event loop (such as the pure perl one)
     can never compete with an event loop that uses epoll when the number of
    Summary
     *   C-based event loops perform very well with small number of watchers,
         as the management overhead dominates.
+SIGNALS
+    AnyEvent currently installs handlers for these signals:
+    SIGCHLD
+        A handler for "SIGCHLD" is installed by AnyEvent's child watcher
+        emulation for event loops that do not support them natively. Also,
+        some event loops install a similar handler.
+    SIGPIPE
+        A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is
+        "undef" when AnyEvent gets loaded.
+        The rationale for this is that AnyEvent users usually do not really
+        depend on SIGPIPE delivery (which is purely an optimisation for
+        shell use, or badly-written programs), but "SIGPIPE" can cause
+        spurious and rare program exits as a lot of people do not expect
+        "SIGPIPE" when writing to some random socket.
+        The rationale for installing a no-op handler as opposed to ignoring
+        it is that this way, the handler will be restored to defaults on
+        exec.
+        Feel free to install your own handler, or reset it to defaults.
 FORK
     Most event libraries are not fork-safe. The ones who are usually are
     because they rely on inefficient but fork-safe "select" or "poll" calls.
     Only EV is fully fork-aware.
 BUGS
     Perl 5.8 has numerous memleaks that sometimes hit this module and are
     hard to work around. If you suffer from memleaks, first upgrade to Perl
     5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
-    annoying mamleaks, such as leaking on "map" and "grep" but it is usually
+    annoying memleaks, such as leaking on "map" and "grep" but it is usually
     not as pronounced).
 SEE ALSO
     Utility functions: AnyEvent::Util.

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Comparing AnyEvent/README (file contents): Revision 1.30 by root, Mon Sep 29 02:08:57 2008 UTC vs. Revision 1.39 by root, Sun Jun 7 16:48:38 2009 UTC

Diff Legend

Comparing AnyEvent/README (file contents):
Revision 1.30 by root, Mon Sep 29 02:08:57 2008 UTC vs.
Revision 1.39 by root, Sun Jun 7 16:48:38 2009 UTC