--- Coro/Coro.pm	2001/07/13 13:05:38	1.7
+++ Coro/Coro.pm	2006/12/01 03:47:55	1.92
@@ -1,139 +1,449 @@
 =head1 NAME
 
-Coro - create and manage simple coroutines
+Coro - coroutine process abstraction
 
 =head1 SYNOPSIS
 
  use Coro;
 
- $new = new Coro sub {
-    print "in coroutine, switching back\n";
-    $new->transfer($main);
-    print "in coroutine again, switching back\n";
-    $new->transfer($main);
+ async {
+    # some asynchronous thread of execution
  };
 
- $main = new Coro;
+ # alternatively create an async coroutine like this:
 
- print "in main, switching to coroutine\n";
- $main->transfer($new);
- print "back in main, switch to coroutine again\n";
- $main->transfer($new);
- print "back in main\n";
+ sub some_func : Coro {
+    # some more async code
+ }
+
+ cede;
 
 =head1 DESCRIPTION
 
-This module implements coroutines. Coroutines, similar to continuations,
-allow you to run more than one "thread of execution" in parallel. Unlike
-threads this, only voluntary switching is used so locking problems are
-greatly reduced.
-
-Although this is the "main" module of the Coro family it provides only
-low-level functionality. See L<Coro::Process> and related modules for a
-more useful process abstraction including scheduling.
+This module collection manages coroutines. Coroutines are similar to
+threads but don't run in parallel.
 
-=over 4
+In this module, coroutines are defined as "callchain + lexical variables
++ @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own
+callchain, it's own set of lexicals and it's own set of perl's most
+important global variables.
 
 =cut
 
 package Coro;
 
-BEGIN {
-   $VERSION = 0.03;
+use strict;
+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 $VERSION = '3.0';
+
+our @EXPORT = qw(async cede schedule terminate current unblock_sub);
+our %EXPORT_TAGS = (
+      prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
+);
+our @EXPORT_OK = @{$EXPORT_TAGS{prio}};
+
+{
+   my @async;
+   my $init;
+
+   # this way of handling attributes simply is NOT scalable ;()
+   sub import {
+      no strict 'refs';
+
+      Coro->export_to_level(1, @_);
+
+      my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
+      *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
+         my ($package, $ref) = (shift, shift);
+         my @attrs;
+         for (@_) {
+            if ($_ eq "Coro") {
+               push @async, $ref;
+               unless ($init++) {
+                  eval q{
+                     sub INIT {
+                        &async(pop @async) while @async;
+                     }
+                  };
+               }
+            } else {
+               push @attrs, $_;
+            }
+         }
+         return $old ? $old->($package, $ref, @attrs) : @attrs;
+      };
+   }
+
+}
+
+=over 4
+
+=item $main
+
+This coroutine represents the main program.
+
+=cut
+
+$main = new Coro;
+
+=item $current (or as function: current)
+
+The current coroutine (the last coroutine switched to). The initial value
+is C<$main> (of course).
+
+This variable is B<strictly> I<read-only>. It is provided for performance
+reasons. If performance is not essentiel you are encouraged to use the
+C<Coro::current> function instead.
+
+=cut
+
+# maybe some other module used Coro::Specific before...
+if ($current) {
+   $main->{specific} = $current->{specific};
+}
+
+$current = $main;
+
+sub current() { $current }
+
+=item $idle
+
+A callback that is called whenever the scheduler finds no ready coroutines
+to run. The default implementation prints "FATAL: deadlock detected" and
+exits, because the program has no other way to continue.
+
+This hook is overwritten by modules such as C<Coro::Timer> and
+C<Coro::Event> to wait on an external event that hopefully wake up a
+coroutine so the scheduler can run it.
+
+Please note that if your callback recursively invokes perl (e.g. for event
+handlers), then it must be prepared to be called recursively.
 
-   require XSLoader;
-   XSLoader::load Coro, $VERSION;
+=cut
+
+$idle = sub {
+   print STDERR "FATAL: deadlock detected\n";
+   exit (51);
+};
+
+# this coroutine is necessary because a coroutine
+# cannot destroy itself.
+my @destroy;
+my $manager; $manager = new Coro sub {
+   while () {
+      # by overwriting the state object with the manager we destroy it
+      # while still being able to schedule this coroutine (in case it has
+      # been readied multiple times. this is harmless since the manager
+      # can be called as many times as neccessary and will always
+      # remove itself from the runqueue
+      while (@destroy) {
+         my $coro = pop @destroy;
+         $coro->{status} ||= [];
+         $_->ready for @{delete $coro->{join} || []};
+
+         # the next line destroys the coro state, but keeps the
+         # coroutine itself intact (we basically make it a zombie
+         # coroutine that always runs the manager thread, so it's possible
+         # to transfer() to this coroutine).
+         $coro->_clone_state_from ($manager);
+      }
+      &schedule;
+   }
+};
+
+# static methods. not really.
+
+=back
+
+=head2 STATIC METHODS
+
+Static methods are actually functions that operate on the current coroutine only.
+
+=over 4
+
+=item async { ... } [@args...]
+
+Create a new asynchronous coroutine and return it's coroutine object
+(usually unused). When the sub returns the new coroutine is automatically
+terminated.
+
+Calling C<exit> in a coroutine will not work correctly, so do not do that.
+
+When the coroutine dies, the program will exit, just as in the main
+program.
+
+   # create a new coroutine that just prints its arguments
+   async {
+      print "@_\n";
+   } 1,2,3,4;
+
+=cut
+
+sub async(&@) {
+   my $pid = new Coro @_;
+   $pid->ready;
+   $pid
 }
 
-=item $coro = new [$coderef [, @args]]
+=item schedule
+
+Calls the scheduler. Please note that the current coroutine will not be put
+into the ready queue, so calling this function usually means you will
+never be called again unless something else (e.g. an event handler) calls
+ready.
 
-Create a new coroutine and return it. The first C<transfer> call to this
-coroutine will start execution at the given coderef. If, the subroutine
-returns it will be executed again.
+The canonical way to wait on external events is this:
 
-If the coderef is omitted this function will create a new "empty"
-coroutine, i.e. a coroutine that cannot be transfered to but can be used
-to save the current coroutine in.
+   {
+      # 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 occured.
+      # 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 up the
+current "timeslice" to other coroutines of the same or higher priority.
+
+=item terminate [arg...]
+
+Terminates the current coroutine with the given status values (see L<cancel>).
 
 =cut
 
+sub terminate {
+   $current->cancel (@_);
+}
+
+=back
+
+# dynamic methods
+
+=head2 COROUTINE METHODS
+
+These are the methods you can call on coroutine objects.
+
+=over 4
+
+=item new Coro \&sub [, @args...]
+
+Create a new coroutine and return it. When the sub returns the coroutine
+automatically terminates as if C<terminate> with the returned values were
+called. To make the coroutine run you must first put it into the ready queue
+by calling the ready method.
+
+Calling C<exit> in a coroutine will not work correctly, so do not do that.
+
+=cut
+
+sub _new_coro {
+   terminate &{+shift};
+}
+
 sub new {
-   my $class = $_[0];
-   my $proc = $_[1] || sub { die "tried to transfer to an empty coroutine" };
-   bless _newprocess {
-      do {
-         eval { &$proc };
-         if ($@) {
-            $error_msg  = $@;
-            $error_coro = _newprocess { };
-            &transfer($error_coro, $error);
-         }
-      } while (1);
-   }, $class;
+   my $class = shift;
+
+   $class->SUPER::new (\&_new_coro, @_)
 }
 
-=item $prev->transfer($next)
+=item $success = $coroutine->ready
+
+Put the given coroutine into the ready queue (according to it's priority)
+and return true. If the coroutine is already in the ready queue, do nothing
+and return false.
 
-Save the state of the current subroutine in C<$prev> and switch to the
-coroutine saved in C<$next>.
+=item $is_ready = $coroutine->is_ready
 
-The "state" of a subroutine only ever includes scope, i.e. lexical
-variables and the current execution state. It does not save/restore any
-global variables such as C<$_> or C<$@> or any other special or non
-special variables. So remember that every function call that might call
-C<transfer> (such as C<Coro::Channel::put>) might clobber any global
-and/or special variables. Yes, this is by design ;) You cna always create
-your own process abstraction model that saves these variables.
+Return wether the coroutine is currently the ready queue or not,
 
-The easiest way to do this is to create your own scheduling primitive like this:
+=item $coroutine->cancel (arg...)
 
-  sub schedule {
-     local ($_, $@, ...);
-     $old->transfer($new);
-  }
+Terminates the given coroutine and makes it return the given arguments as
+status (default: the empty list).
 
 =cut
 
-# I call the _transfer function from a perl function
-# because that way perl saves all important things on
-# the stack. Actually, I'd do it from within XS, but
-# I couldn't get it to work.
-sub transfer {
-   _transfer($_[0], $_[1]);
+sub cancel {
+   my $self = shift;
+   $self->{status} = [@_];
+   push @destroy, $self;
+   $manager->ready;
+   &schedule if $current == $self;
 }
 
-=item $error, $error_msg, $error_coro
+=item $coroutine->join
 
-This coroutine will be called on fatal errors. C<$error_msg> and
-C<$error_coro> return the error message and the error-causing coroutine
-(NOT an object) respectively. This API might change.
+Wait until the coroutine terminates and return any values given to the
+C<terminate> or C<cancel> functions. C<join> can be called multiple times
+from multiple coroutine.
 
 =cut
 
-$error_msg =
-$error_coro = undef;
+sub join {
+   my $self = shift;
+   unless ($self->{status}) {
+      push @{$self->{join}}, $current;
+      &schedule;
+   }
+   wantarray ? @{$self->{status}} : $self->{status}[0];
+}
+
+=item $oldprio = $coroutine->prio ($newprio)
+
+Sets (or gets, if the argument is missing) the priority of the
+coroutine. Higher priority coroutines get run before lower priority
+coroutines. Priorities are small signed integers (currently -4 .. +3),
+that you can refer to using PRIO_xxx constants (use the import tag :prio
+to get then):
+
+   PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
+       3    >     1     >      0      >    -1    >    -3     >    -4
+
+   # set priority to HIGH
+   current->prio(PRIO_HIGH);
+
+The idle coroutine ($Coro::idle) always has a lower priority than any
+existing coroutine.
+
+Changing the priority of the current coroutine will take effect immediately,
+but changing the priority of coroutines in the ready queue (but not
+running) will only take effect after the next schedule (of that
+coroutine). This is a bug that will be fixed in some future version.
+
+=item $newprio = $coroutine->nice ($change)
+
+Similar to C<prio>, but subtract the given value from the priority (i.e.
+higher values mean lower priority, just as in unix).
+
+=item $olddesc = $coroutine->desc ($newdesc)
 
-$error = _newprocess {
-   print STDERR "FATAL: $error_msg\nprogram aborted\n";
-   exit 50;
+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.
+
+=cut
+
+sub desc {
+   my $old = $_[0]{desc};
+   $_[0]{desc} = $_[1] if @_ > 1;
+   $old;
+}
+
+=back
+
+=head2 UTILITY FUNCTIONS
+
+=over 4
+
+=item unblock_sub { ... }
+
+This utility function takes a BLOCK or code reference and "unblocks" it,
+returning the new coderef. This means that the new coderef will return
+immediately without blocking, returning nothing, while the original code
+ref will be called (with parameters) from within its own coroutine.
+
+The reason this fucntion exists is that many event libraries (such as the
+venerable L<Event|Event> module) are not coroutine-safe (a weaker form
+of thread-safety). This means you must not block within event callbacks,
+otherwise you might suffer from crashes or worse.
+
+This function allows your callbacks to block by executing them in another
+coroutine where it is safe to block. One example where blocking is handy
+is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
+disk.
+
+In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
+creating event callbacks that want to block.
+
+=cut
+
+our @unblock_pool;
+our @unblock_queue;
+our $UNBLOCK_POOL_SIZE = 2;
+
+sub unblock_handler_ {
+   while () {
+      my ($cb, @arg) = @{ delete $Coro::current->{arg} };
+      $cb->(@arg);
+
+      last if @unblock_pool >= $UNBLOCK_POOL_SIZE;
+      push @unblock_pool, $Coro::current;
+      schedule;
+   }        
+}           
+
+our $unblock_scheduler = async {
+   while () {
+      while (my $cb = pop @unblock_queue) {
+         my $handler = (pop @unblock_pool or new Coro \&unblock_handler_);
+         $handler->{arg} = $cb;
+         $handler->ready;
+         cede;
+      }
+
+      schedule;
+   }
 };
 
-1;
+sub unblock_sub(&) {
+   my $cb = shift;
+
+   sub {
+      push @unblock_queue, [$cb, @_];
+      $unblock_scheduler->ready;
+   }
+}
 
 =back
 
-=head1 BUGS
+=cut
 
-This module has not yet been extensively tested.
+1;
+
+=head1 BUGS/LIMITATIONS
+
+ - you must make very sure that no coro is still active on global
+   destruction. very bad things might happen otherwise (usually segfaults).
+
+ - this module is not thread-safe. You should only ever use this module
+   from the same thread (this requirement might be losened in the future
+   to allow per-thread schedulers, but Coro::State does not yet allow
+   this).
 
 =head1 SEE ALSO
 
-L<Coro::Process>, L<Coro::Signal>.
+Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
+
+Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
+
+Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
+
+Embedding: L<Coro:MakeMaker>
 
 =head1 AUTHOR
 
- Marc Lehmann <pcg@goof.com>
- http://www.goof.com/pcg/marc/
+ Marc Lehmann <schmorp@schmorp.de>
+ http://home.schmorp.de/
 
 =cut