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local/lib/perl5/IO/Async/Loop.pm  view on Meta::CPAN

module will be chosen afterwards as a last-case attempt. If this also fails,
then the magic constructor itself will throw an exception.

=back

If any of the explicitly-requested loop types (C<$ENV{IO_ASYNC_LOOP}> or
C<$IO::Async::Loop::LOOP>) fails to load then a warning is printed detailing
the error.

Implementors of new C<IO::Async::Loop> subclasses should see the notes about
C<API_VERSION> below.

=cut

sub __try_new
{
   my ( $class ) = @_;

   ( my $file = "$class.pm" ) =~ s{::}{/}g;

   eval {
      local $SIG{__WARN__} = sub {};
      require $file;
   } or return;

   my $self;
   $self = eval { $class->new } and return $self;

   # Oh dear. We've loaded the code OK but for some reason the constructor
   # wasn't happy. Being polite we ought really to unload the file again,
   # but perl doesn't actually provide us a way to do this.

   return undef;
}

sub new
{
   return our $ONE_TRUE_LOOP ||= shift->really_new;
}

# Ensure that the loop is DESTROYed recursively at exit time, before GD happens
END {
   undef our $ONE_TRUE_LOOP;
}

sub really_new
{
   shift;  # We're going to ignore the class name actually given
   my $self;

   my @candidates;

   push @candidates, split( m/,/, $ENV{IO_ASYNC_LOOP} ) if defined $ENV{IO_ASYNC_LOOP};

   push @candidates, split( m/,/, $LOOP ) if defined $LOOP;

   foreach my $class ( @candidates ) {
      $class =~ m/::/ or $class = "IO::Async::Loop::$class";
      $self = __try_new( $class ) and return $self;

      my ( $topline ) = split m/\n/, $@; # Ignore all the other lines; they'll be require's verbose output
      warn "Unable to use $class - $topline\n";
   }

   unless( $LOOP_NO_OS ) {
      foreach my $class ( IO::Async::OS->LOOP_PREFER_CLASSES, "IO::Async::Loop::$^O" ) {
         $class =~ m/::/ or $class = "IO::Async::Loop::$class";
         $self = __try_new( $class ) and return $self;

         # Don't complain about these ones
      }
   }

   return IO::Async::Loop->new_builtin;
}

sub new_builtin
{
   shift;
   my $self;

   foreach my $class ( IO::Async::OS->LOOP_BUILTIN_CLASSES ) {
      $self = __try_new( "IO::Async::Loop::$class" ) and return $self;
   }

   croak "Cannot find a suitable candidate class";
}

#######################
# Notifier management #
#######################

=head1 NOTIFIER MANAGEMENT

The following methods manage the collection of L<IO::Async::Notifier> objects.

=cut

=head2 add

   $loop->add( $notifier )

This method adds another notifier object to the stored collection. The object
may be a L<IO::Async::Notifier>, or any subclass of it.

When a notifier is added, any children it has are also added, recursively. In
this way, entire sections of a program may be written within a tree of
notifier objects, and added or removed on one piece.

=cut

sub add
{
   my $self = shift;
   my ( $notifier ) = @_;

   if( defined $notifier->parent ) {
      croak "Cannot add a child notifier directly - add its parent";
   }

   if( defined $notifier->loop ) {