[ViewVC] Diff of: cvs/AnyEvent/lib/AnyEvent.pm

Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.232 by root, Thu Jul 9 01:08:22 2009 UTC vs.
Revision 1.241 by root, Fri Jul 17 18:08:35 2009 UTC

 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 is different, it expects somebody else to run the event loop and
+AnyEvent is slightly different: it expects somebody else to run the event
-will only block when necessary (usually when told by the user).
+loop and will only block when necessary (usually when told by the user).
 The instrument to do that is called a "condition variable", so called
 because they represent a condition that must become true.
+Now is probably a good time to look at the examples further below.
 Condition variables can be created by calling the C<< AnyEvent->condvar
 >> method, usually without arguments. The only argument pair allowed is
 C<cb>, which specifies a callback to be called when the condition variable
 becomes true, with the condition variable as the first argument (but not
 the results).
 After creation, the condition variable is "false" until it becomes "true"
       after => 1,
       cb    => sub { $result_ready->send },
    );
    # this "blocks" (while handling events) till the callback
-   # calls send
+   # calls -<send
    $result_ready->recv;
-Example: wait for a timer, but take advantage of the fact that
+Example: wait for a timer, but take advantage of the fact that condition
-condition variables are also code references.
+variables are also callable directly.
    my $done = AnyEvent->condvar;
    my $delay = AnyEvent->timer (after => 5, cb => $done);
    $done->recv;
    ...
    my @info = $couchdb->info->recv;
-And this is how you would just ste a callback to be called whenever the
+And this is how you would just set a callback to be called whenever the
 results are available:
    $couchdb->info->cb (sub {
       my @info = $_[0]->recv;
    });
 immediately from within send.
 Any arguments passed to the C<send> call will be returned by all
 future C<< ->recv >> calls.
-Condition variables are overloaded so one can call them directly
+Condition variables are overloaded so one can call them directly (as if
-(as a code reference). Calling them directly is the same as calling
+they were a code reference). Calling them directly is the same as calling
-C<send>. Note, however, that many C-based event loops do not handle
+C<send>.
-overloading, so as tempting as it may be, passing a condition variable
-instead of a callback does not work. Both the pure perl and EV loops
-support overloading, however, as well as all functions that use perl to
-invoke a callback (as in L<AnyEvent::Socket> and L<AnyEvent::DNS> for
-example).
 =item $cv->croak ($error)
 Similar to send, but causes all call's to C<< ->recv >> to invoke
 C<Carp::croak> with the given error message/object/scalar.
 This can be used to signal any errors to the condition variable
-user/consumer.
+user/consumer. Doing it this way instead of calling C<croak> directly
+delays the error detetcion, but has the overwhelmign advantage that it
+diagnoses the error at the place where the result is expected, and not
+deep in some event clalback without connection to the actual code causing
+the problem.
 =item $cv->begin ([group callback])
 =item $cv->end
 function will call C<croak>.
 In list context, all parameters passed to C<send> will be returned,
 in scalar context only the first one will be returned.
+Note that doing a blocking wait in a callback is not supported by any
+event loop, that is, recursive invocation of a blocking C<< ->recv
+>> is not allowed, and the C<recv> call will C<croak> if such a
+condition is detected. This condition can be slightly loosened by using
+L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
+any thread that doesn't run the event loop itself.
 Not all event models support a blocking wait - some die in that case
 (programs might want to do that to stay interactive), so I<if you are
-using this from a module, never require a blocking wait>, but let the
+using this from a module, never require a blocking wait>. Instead, let the
 caller decide whether the call will block or not (for example, by coupling
 condition variables with some kind of request results and supporting
 callbacks so the caller knows that getting the result will not block,
 while still supporting blocking waits if the caller so desires).
-Another reason I<never> to C<< ->recv >> in a module is that you cannot
-sensibly have two C<< ->recv >>'s in parallel, as that would require
-multiple interpreters or coroutines/threads, none of which C<AnyEvent>
-can supply.
-The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
-fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
-versions and also integrates coroutines into AnyEvent, making blocking
-C<< ->recv >> calls perfectly safe as long as they are done from another
-coroutine (one that doesn't run the event loop).
 You can ensure that C<< -recv >> never blocks by setting a callback and
 only calling C<< ->recv >> from within that callback (or at a later
 time). This will work even when the event loop does not support blocking
 waits otherwise.
 =back
 =head1 GLOBAL VARIABLES AND FUNCTIONS
+These are not normally required to use AnyEvent, but can be useful to
+write AnyEvent extension modules.
 =over 4
 =item $AnyEvent::MODEL
-Contains C<undef> until the first watcher is being created. Then it
+Contains C<undef> until the first watcher is being created, before the
+backend has been autodetected.
-contains the event model that is being used, which is the name of the
+Afterwards it contains the event model that is being used, which is the
-Perl class implementing the model. This class is usually one of the
+name of the Perl class implementing the model. This class is usually one
-C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
+of the C<AnyEvent::Impl:xxx> modules, but can be any other class in the
-AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
+case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
+will be C<urxvt::anyevent>).
 =item AnyEvent::detect
 Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
 if necessary. You should only call this function right before you would
 have created an AnyEvent watcher anyway, that is, as late as possible at
-runtime.
+runtime, and not e.g. while initialising of your module.
+If you need to do some initialisation before AnyEvent watchers are
+created, use C<post_detect>.
 =item $guard = AnyEvent::post_detect { BLOCK }
 Arranges for the code block to be executed as soon as the event model is
 autodetected (or immediately if this has already happened).
+The block will be executed I<after> the actual backend has been detected
+(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
+created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
+other initialisations - see the sources of L<AnyEvent::Strict> or
+L<AnyEvent::AIO> to see how this is used.
+The most common usage is to create some global watchers, without forcing
+event module detection too early, for example, L<AnyEvent::AIO> creates
+and installs the global L<IO::AIO> watcher in a C<post_detect> block to
+avoid autodetecting the event module at load time.
 If called in scalar or list context, then it creates and returns an object
 that automatically removes the callback again when it is destroyed. See
 L<Coro::BDB> for a case where this is useful.
 If there are any code references in this array (you can C<push> to it
 before or after loading AnyEvent), then they will called directly after
 the event loop has been chosen.
 You should check C<$AnyEvent::MODEL> before adding to this array, though:
-if it contains a true value then the event loop has already been detected,
+if it is defined then the event loop has already been detected, and the
-and the array will be ignored.
+array will be ignored.
-Best use C<AnyEvent::post_detect { BLOCK }> instead.
+Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
+it,as it takes care of these details.
+This variable is mainly useful for modules that can do something useful
+when AnyEvent is used and thus want to know when it is initialised, but do
+not need to even load it by default. This array provides the means to hook
+into AnyEvent passively, without loading it.
 =back
 =head1 WHAT TO DO IN A MODULE
 package AnyEvent;
 no warnings;
 use strict qw(vars subs);
-use Carp;
+use Carp ();
-our $VERSION = 4.801;
+our $VERSION = 4.83;
 our $MODEL;
 our $AUTOLOAD;
 our @ISA;
    # as the pureperl backend should work everywhere
    # and is usually faster
    [Glib::                 => AnyEvent::Impl::Glib::],     # becomes extremely slow with many watchers
    [Event::Lib::           => AnyEvent::Impl::EventLib::], # too buggy
    [Tk::                   => AnyEvent::Impl::Tk::],       # crashes with many handles
+   [Qt::                   => AnyEvent::Impl::Qt::],       # requires special main program
    [POE::Kernel::          => AnyEvent::Impl::POE::],      # lasciate ogni speranza
-   [Qt::                   => AnyEvent::Impl::Qt::],       # requires special main program
    [Wx::                   => AnyEvent::Impl::POE::],
    [Prima::                => AnyEvent::Impl::POE::],
    # IO::Async is just too broken - we would need workarounds for its
    # byzantine signal and broken child handling, among others.
    # IO::Async is rather hard to detect, as it doesn't have any
       if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
          my $model = "AnyEvent::Impl::$1";
          if (eval "require $model") {
             $MODEL = $model;
-            warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;
+            warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $verbose > 1;
          } else {
-            warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;
+            warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $verbose;
          }
       }
       # check for already loaded models
       unless ($MODEL) {
 sub AUTOLOAD {
    (my $func = $AUTOLOAD) =~ s/.*://;
    $method{$func}
-      or croak "$func: not a valid method for AnyEvent objects";
+      or Carp::croak "$func: not a valid method for AnyEvent objects";
    detect unless $MODEL;
    my $class = shift;
    $class->$func (@_);
 # allow only one watcher per fd, so we dup it to get a different one).
 sub _dupfh($$;$$) {
    my ($poll, $fh, $r, $w) = @_;
    # cygwin requires the fh mode to be matching, unix doesn't
-   my ($rw, $mode) = $poll eq "r" ? ($r, "<") : ($w, ">");
+   my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
-   open my $fh2, "$mode&", $fh
+   open my $fh2, $mode, $fh
       or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
    # we assume CLOEXEC is already set by perl in all important cases
    ($fh2, $rw)
 use overload
    '&{}'    => sub { my $self = shift; sub { $self->send (@_) } },
    fallback => 1;
+our $WAITING;
 sub _send {
    # nop
 }
 sub send {
 sub ready {
    $_[0]{_ae_sent}
 }
 sub _wait {
+   $WAITING
+      and !$_[0]{_ae_sent}
+      and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
+   local $WAITING = 1;
    AnyEvent->one_event while !$_[0]{_ae_sent};
 }
 sub recv {
    $_[0]->_wait;
 A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
 emulation for event loops that do not support them natively. Also, some
 event loops install a similar handler.
-If, when AnyEvent is loaded, SIGCHLD is set to IGNORE, then AnyEvent will
+Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
-reset it to default, to avoid losing child exit statuses.
+AnyEvent will reset it to default, to avoid losing child exit statuses.
 =item SIGPIPE
 A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
 when AnyEvent gets loaded.

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing AnyEvent/lib/AnyEvent.pm (file contents): Revision 1.232 by root, Thu Jul 9 01:08:22 2009 UTC vs. Revision 1.241 by root, Fri Jul 17 18:08:35 2009 UTC

Diff Legend

Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.232 by root, Thu Jul 9 01:08:22 2009 UTC vs.
Revision 1.241 by root, Fri Jul 17 18:08:35 2009 UTC