[ViewVC] Diff of: cvs/cvsroot/Coro/Coro.pm

Comparing cvsroot/Coro/Coro.pm (file contents):
Revision 1.181 by root, Fri May 9 22:04:37 2008 UTC vs.
Revision 1.224 by root, Wed Nov 19 05:52:42 2008 UTC

   cede; # yield to coroutine
   print "3\n";
   cede; # and again
   # use locking
+  use Coro::Semaphore;
   my $lock = new Coro::Semaphore;
   my $locked;
   $lock->down;
   $locked = 1;
 parallel access are rarely an issue, making coroutine programming much
 safer and easier than threads programming.
 Unlike a normal perl program, however, coroutines allow you to have
 multiple running interpreters that share data, which is especially useful
-to code pseudo-parallel processes, such as multiple HTTP-GET requests
+to code pseudo-parallel processes and for event-based programming, such as
-running concurrently.
+multiple HTTP-GET requests running concurrently. See L<Coro::AnyEvent> to
+learn more.
 Coroutines are also useful because Perl has no support for threads (the so
 called "threads" that perl offers are nothing more than the (bad) process
 emulation coming from the Windows platform: On standard operating systems
 they serve no purpose whatsoever, except by making your programs slow and
 =cut
 package Coro;
-use strict;
+use strict qw(vars subs);
 no warnings "uninitialized";
 use Coro::State;
 use base qw(Coro::State Exporter);
 our $idle;    # idle handler
 our $main;    # main coroutine
 our $current; # current coroutine
-our $VERSION = 4.6;
+our $VERSION = 5.0;
 our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
 our %EXPORT_TAGS = (
       prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
 );
 =item $Coro::main
 This variable stores the coroutine object that represents the main
 program. While you cna C<ready> it and do most other things you can do to
 coroutines, it is mainly useful to compare again C<$Coro::current>, to see
-wether you are running in the main program or not.
+whether you are running in the main program or not.
 =cut
-$main = new Coro;
+# $main is now being initialised by Coro::State
 =item $Coro::current
 The coroutine object representing the current coroutine (the last
 coroutine that the Coro scheduler switched to). The initial value is
-C<$main> (of course).
+C<$Coro::main> (of course).
 This variable is B<strictly> I<read-only>. You can take copies of the
 value stored in it and use it as any other coroutine object, but you must
 not otherwise modify the variable itself.
 =cut
-$main->{desc} = "[main::]";
-# maybe some other module used Coro::Specific before...
-$main->{_specific} = $current->{_specific}
-   if $current;
-_set_current $main;
 sub current() { $current } # [DEPRECATED]
 =item $Coro::idle
    $self->_destroy
       or return;
    # call all destruction callbacks
    $_->(@{$self->{_status}})
-      for @{(delete $self->{_on_destroy}) || []};
+      for @{ delete $self->{_on_destroy} || [] };
 }
 # this coroutine is necessary because a coroutine
 # cannot destroy itself.
 my @destroy;
          while @destroy;
       &schedule;
    }
 };
-$manager->desc ("[coro manager]");
+$manager->{desc} = "[coro manager]";
 $manager->prio (PRIO_MAX);
 =back
 =head2 SIMPLE COROUTINE CREATION
 terminate or join on it (although you are allowed to), and you get a
 coroutine that might have executed other code already (which can be good
 or bad :).
 On the plus side, this function is faster than creating (and destroying)
-a completely new coroutine, so if you need a lot of generic coroutines in
+a completly new coroutine, so if you need a lot of generic coroutines in
 quick successsion, use C<async_pool>, not C<async>.
 The code block is executed in an C<eval> context and a warning will be
 issued in case of an exception instead of terminating the program, as
 C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
 The priority will be reset to C<0> after each run, tracing will be
 disabled, the description will be reset and the default output filehandle
 gets restored, so you can change all these. Otherwise the coroutine will
 be re-used "as-is": most notably if you change other per-coroutine global
-stuff such as C<$/> you I<must needs> to revert that change, which is most
+stuff such as C<$/> you I<must needs> revert that change, which is most
-simply done by using local as in: C< local $/ >.
+simply done by using local as in: C<< local $/ >>.
-The pool size is limited to C<8> idle coroutines (this can be adjusted by
+The idle pool size is limited to C<8> idle coroutines (this can be
-changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
+adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
-required.
+coros as required.
 If you are concerned about pooled coroutines growing a lot because a
 single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
 { terminate }> once per second or so to slowly replenish the pool. In
 addition to that, when the stacks used by a handler grows larger than 16kb
             _pool_2 $cb;
             &schedule;
          }
       };
+      if ($@) {
-      last if $@ eq "\3async_pool terminate\2\n";
+         last if $@ eq "\3async_pool terminate\2\n";
-      warn $@ if $@;
+         warn $@;
+      }
    }
 }
 sub async_pool(&@) {
-   # this is also inlined into the unlock_scheduler
+   # this is also inlined into the unblock_scheduler
    my $coro = (pop @async_pool) || new Coro \&pool_handler;
    $coro->{_invoke} = [@_];
    $coro->ready;
 This makes C<schedule> I<the> generic method to use to block the current
 coroutine and wait for events: first you remember the current coroutine in
 a variable, then arrange for some callback of yours to call C<< ->ready
 >> on that once some event happens, and last you call C<schedule> to put
 yourself to sleep. Note that a lot of things can wake your coroutine up,
-so you need to check wether the event indeed happened, e.g. by storing the
+so you need to check whether the event indeed happened, e.g. by storing the
 status in a variable.
-The canonical way to wait on external events is this:
+See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
-   {
-      # remember current coroutine
-      my $current = $Coro::current;
-      # register a hypothetical event handler
-      on_event_invoke sub {
-         # wake up sleeping coroutine
-         $current->ready;
-         undef $current;
-      };
-      # call schedule until event occurred.
-      # in case we are woken up for other reasons
-      # (current still defined), loop.
-      Coro::schedule while $current;
-   }
 =item cede
 "Cede" to other coroutines. This function puts the current coroutine into
 the ready queue and calls C<schedule>, which has the effect of giving
 Kills/terminates/cancels all coroutines except the currently running
 one. This is useful after a fork, either in the child or the parent, as
 usually only one of them should inherit the running coroutines.
 Note that while this will try to free some of the main programs resources,
-you cnanot free all of them, so if a coroutine that is not the main
+you cannot free all of them, so if a coroutine that is not the main
 program calls this function, there will be some one-time resource leak.
 =cut
 sub terminate {
 once all the coroutines of higher priority and all coroutines of the same
 priority that were put into the ready queue earlier have been resumed.
 =item $is_ready = $coroutine->is_ready
-Return wether the coroutine is currently the ready queue or not,
+Return whether the coroutine is currently the ready queue or not,
 =item $coroutine->cancel (arg...)
 Terminates the given coroutine and makes it return the given arguments as
 status (default: the empty list). Never returns if the coroutine is the
    } else {
       $self->_cancel;
    }
 }
+=item $coroutine->throw ([$scalar])
+If C<$throw> is specified and defined, it will be thrown as an exception
+inside the coroutine at the next convenient point in time. Otherwise
+clears the exception object.
+Coro will check for the exception each time a schedule-like-function
+returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
+>>, C<< Coro::Handle->readable >> and so on. Most of these functions
+detect this case and return early in case an exception is pending.
+The exception object will be thrown "as is" with the specified scalar in
+C<$@>, i.e. if it is a string, no line number or newline will be appended
+(unlike with C<die>).
+This can be used as a softer means than C<cancel> to ask a coroutine to
+end itself, although there is no guarantee that the exception will lead to
+termination, and if the exception isn't caught it might well end the whole
+program.
+You might also think of C<throw> as being the moral equivalent of
+C<kill>ing a coroutine with a signal (in this case, a scalar).
 =item $coroutine->join
 Wait until the coroutine terminates and return any values given to the
 C<terminate> or C<cancel> functions. C<join> can be called concurrently
 from multiple coroutines, and all will be resumed and given the status
 higher values mean lower priority, just as in unix).
 =item $olddesc = $coroutine->desc ($newdesc)
 Sets (or gets in case the argument is missing) the description for this
-coroutine. This is just a free-form string you can associate with a coroutine.
+coroutine. This is just a free-form string you can associate with a
+coroutine.
-This method simply sets the C<< $coroutine->{desc} >> member to the given string. You
+This method simply sets the C<< $coroutine->{desc} >> member to the given
-can modify this member directly if you wish.
+string. You can modify this member directly if you wish.
-=item $coroutine->throw ([$scalar])
-If C<$throw> is specified and defined, it will be thrown as an exception
-inside the coroutine at the next convinient point in time (usually after
-it gains control at the next schedule/transfer/cede). Otherwise clears the
-exception object.
-The exception object will be thrown "as is" with the specified scalar in
-C<$@>, i.e. if it is a string, no line number or newline will be appended
-(unlike with C<die>).
-This can be used as a softer means than C<cancel> to ask a coroutine to
-end itself, although there is no guarentee that the exception will lead to
-termination, and if the exception isn't caught it might well end the whole
-program.
 =cut
 sub desc {
    my $old = $_[0]{desc};
 creating event callbacks that want to block.
 If your handler does not plan to block (e.g. simply sends a message to
 another coroutine, or puts some other coroutine into the ready queue),
 there is no reason to use C<unblock_sub>.
+Note that you also need to use C<unblock_sub> for any other callbacks that
+are indirectly executed by any C-based event loop. For example, when you
+use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
+provides callbacks that are the result of some event callback, then you
+must not block either, or use C<unblock_sub>.
 =cut
 our @unblock_queue;
          cede; # for short-lived callbacks, this reduces pressure on the coro pool
       }
       schedule; # sleep well
    }
 };
-$unblock_scheduler->desc ("[unblock_sub scheduler]");
+$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
 sub unblock_sub(&) {
    my $cb = shift;
    sub {
       unshift @unblock_queue, [$cb, @_];
       $unblock_scheduler->ready;
    }
 }
+=item $cb = Coro::rouse_cb
+Create and return a "rouse callback". That's a code reference that, when
+called, will save its arguments and notify the owner coroutine of the
+callback.
+See the next function.
+=item @args = Coro::rouse_wait [$cb]
+Wait for the specified rouse callback (or the last one tht was created in
+this coroutine).
+As soon as the callback is invoked (or when the calback was invoked before
+C<rouse_wait>), it will return a copy of the arguments originally passed
+to the rouse callback.
+See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
 =back
 =cut
 1;
+=head1 HOW TO WAIT FOR A CALLBACK
+It is very common for a coroutine to wait for some callback to be
+called. This occurs naturally when you use coroutines in an otherwise
+event-based program, or when you use event-based libraries.
+These typically register a callback for some event, and call that callback
+when the event occured.  In a coroutine, however, you typically want to
+just wait for the event, simplyifying things.
+For example C<< AnyEvent->child >> registers a callback to be called when
+a specific child has exited:
+   my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
+But from withina coroutine, you often just want to write this:
+   my $status = wait_for_child $pid;
+Coro offers two functions specifically designed to make this easy,
+C<Coro::rouse_cb> and C<Coro::rouse_wait>.
+The first function, C<rouse_cb>, generates and returns a callback that,
+when invoked, will save it's arguments and notify the coroutine that
+created the callback.
+The second function, C<rouse_wait>, waits for the callback to be called
+(by calling C<schedule> to go to sleep) and returns the arguments
+originally passed to the callback.
+Using these functions, it becomes easy to write the C<wait_for_child>
+function mentioned above:
+   sub wait_for_child($) {
+      my ($pid) = @_;
+      my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
+      my ($rpid, $rstatus) = Coro::rouse_wait;
+      $rstatus
+   }
+In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
+you can roll your own, using C<schedule>:
+   sub wait_for_child($) {
+      my ($pid) = @_;
+      # store the current coroutine in $current,
+      # and provide result variables for the closure passed to ->child
+      my $current = $Coro::current;
+      my ($done, $rstatus);
+      # pass a closure to ->child
+      my $watcher = AnyEvent->child (pid => $pid, cb => sub {
+         $rstatus = $_[1]; # remember rstatus
+         $done = 1; # mark $rstatus as valud
+      });
+      # wait until the closure has been called
+      schedule while !$done;
+      $rstatus
+   }
 =head1 BUGS/LIMITATIONS
+=over 4
+=item fork with pthread backend
+When Coro is compiled using the pthread backend (which isn't recommended
+but required on many BSDs as their libcs are completely broken), then
+coroutines will not survive a fork. There is no known workaround except to
+fix your libc and use a saner backend.
+=item perl process emulation ("threads")
 This module is not perl-pseudo-thread-safe. You should only ever use this
 module from the same thread (this requirement might be removed in the
 future to allow per-thread schedulers, but Coro::State does not yet allow
-this). I recommend disabling thread support and using processes, as this
+this). I recommend disabling thread support and using processes, as having
-is much faster and uses less memory.
+the windows process emulation enabled under unix roughly halves perl
+performance, even when not used.
+=item coroutine switching not signal safe
+You must not switch to another coroutine from within a signal handler
+(only relevant with %SIG - most event libraries provide safe signals).
+That means you I<MUST NOT> call any function that might "block" the
+current coroutine - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
+anything that calls those. Everything else, including calling C<ready>,
+works.
+=back
 =head1 SEE ALSO
 Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.

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Comparing cvsroot/Coro/Coro.pm (file contents): Revision 1.181 by root, Fri May 9 22:04:37 2008 UTC vs. Revision 1.224 by root, Wed Nov 19 05:52:42 2008 UTC

Diff Legend

Comparing cvsroot/Coro/Coro.pm (file contents):
Revision 1.181 by root, Fri May 9 22:04:37 2008 UTC vs.
Revision 1.224 by root, Wed Nov 19 05:52:42 2008 UTC