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

   my $self = shift;
   return $self->{IO_Async_Notifier__notifier_name} || "";
}

=head2 adopt_future

   $f = $notifier->adopt_future( $f )

Stores a reference to the L<Future> instance within the notifier itself, so
the reference doesn't get lost. This reference will be dropped when the future
becomes ready (either by success or failure). Additionally, if the future
failed the notifier's C<invoke_error> method will be informed.

This means that if the notifier does not provide an C<on_error> handler, nor
is there one anywhere in the parent chain, this will be fatal to the caller of
C<< $f->fail >>. To avoid this being fatal if the failure is handled
elsewhere, use the C<else_done> method on the future to obtain a sequence one
that never fails.

 $notifier->adopt_future( $f->else_done() )

The future itself is returned.

=cut

sub adopt_future
{
   my $self = shift;
   my ( $f ) = @_;

   my $fkey = "$f"; # stable stringification

   $self->{IO_Async_Notifier__futures}{$fkey} = $f;

   $f->on_ready( $self->_capture_weakself( sub {
      my $self = shift;
      my ( $f ) = @_;

      delete $self->{IO_Async_Notifier__futures}{$fkey};

      $self->invoke_error( $f->failure ) if $f->is_failed;
   }));

   return $f;
}

=head1 CHILD NOTIFIERS

During the execution of a program, it may be the case that certain IO handles
cause other handles to be created; for example, new sockets that have been
C<accept()>ed from a listening socket. To facilitate these, a notifier may
contain child notifier objects, that are automatically added to or removed
from the L<IO::Async::Loop> that manages their parent.

=cut

=head2 parent

   $parent = $notifier->parent

Returns the parent of the notifier, or C<undef> if does not have one.

=cut

sub parent
{
   my $self = shift;
   return $self->{IO_Async_Notifier__parent};
}

=head2 children

   @children = $notifier->children

Returns a list of the child notifiers contained within this one.

=cut

sub children
{
   my $self = shift;
   return unless $self->{IO_Async_Notifier__children};
   return @{ $self->{IO_Async_Notifier__children} };
}

=head2 add_child

   $notifier->add_child( $child )

Adds a child notifier. This notifier will be added to the containing loop, if
the parent has one. Only a notifier that does not currently have a parent and
is not currently a member of any loop may be added as a child. If the child
itself has grandchildren, these will be recursively added to the containing
loop.

=cut

sub add_child
{
   my $self = shift;
   my ( $child ) = @_;

   croak "Cannot add a child that already has a parent" if defined $child->{IO_Async_Notifier__parent};

   croak "Cannot add a child that is already a member of a loop" if defined $child->loop;

   if( defined( my $loop = $self->loop ) ) {
      $loop->add( $child );
   }

   push @{ $self->{IO_Async_Notifier__children} }, $child;
   $child->{IO_Async_Notifier__parent} = $self;
   weaken( $child->{IO_Async_Notifier__parent} );

   return;
}

=head2 remove_child

   $notifier->remove_child( $child )

Removes a child notifier. The child will be removed from the containing loop,
if the parent has one. If the child itself has grandchildren, these will be
recurively removed from the loop.

=cut

sub remove_child
{
   my $self = shift;
   my ( $child ) = @_;

   LOOP: {
      my $childrenref = $self->{IO_Async_Notifier__children};
      for my $i ( 0 .. $#$childrenref ) {
         next unless $childrenref->[$i] == $child;
         splice @$childrenref, $i, 1, ();
         last LOOP;
      }

      croak "Cannot remove child from a parent that doesn't contain it";
   }

   undef $child->{IO_Async_Notifier__parent};

   if( defined( my $loop = $self->loop ) ) {
      $loop->remove( $child );
   }
}

=head2 remove_from_parent

   $notifier->remove_from_parent

Removes this notifier object from its parent (either another notifier object
or the containing loop) if it has one. If the notifier is not a child of
another notifier nor a member of a loop, this method does nothing.

=cut

sub remove_from_parent
{
   my $self = shift;

   if( my $parent = $self->parent ) {
      $parent->remove_child( $self );
   }
   elsif( my $loop = $self->loop ) {
      $loop->remove( $self );
   }
}

=head1 SUBCLASS METHODS

C<IO::Async::Notifier> is a base class provided so that specific subclasses of
it provide more specific behaviour. The base class provides a number of
methods that subclasses may wish to override.

If a subclass implements any of these, be sure to invoke the superclass method
at some point within the code.

=cut

=head2 _init

   $notifier->_init( $paramsref )

This method is called by the constructor just before calling C<configure>.
It is passed a reference to the HASH storing the constructor arguments.

This method may initialise internal details of the Notifier as required,
possibly by using parameters from the HASH. If any parameters are
construction-only they should be C<delete>d from the hash.

=cut

sub _init
{
   # empty default
}

=head2 configure

   $notifier->configure( %params )

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

sub _add_to_loop
{
   # empty default
}

=head2 _remove_from_loop

   $notifier->_remove_from_loop( $loop )

This method is called when the Notifier has been removed from a Loop; either
directly, or indirectly through being a child of a Notifier removed from the
loop.

This method may be used to undo the effects of any setup that the
C<_add_to_loop> method had originally done.

=cut

sub _remove_from_loop
{
   # empty default
}

=head1 UTILITY METHODS

=cut

=head2 _capture_weakself

   $mref = $notifier->_capture_weakself( $code )

Returns a new CODE ref which, when invoked, will invoke the originally-passed
ref, with additionally a reference to the Notifier as its first argument. The
Notifier reference is stored weakly in C<$mref>, so this CODE ref may be
stored in the Notifier itself without creating a cycle.

For example,

 my $mref = $notifier->_capture_weakself( sub {
    my ( $notifier, $arg ) = @_;
    print "Notifier $notifier got argument $arg\n";
 } );

 $mref->( 123 );

This is provided as a utility for Notifier subclasses to use to build a
callback CODEref to pass to a Loop method, but which may also want to store
the CODE ref internally for efficiency.

The C<$code> argument may also be a plain string, which will be used as a
method name; the returned CODE ref will then invoke that method on the object.
In this case the method name is stored symbolically in the returned CODE
reference, and dynamically dispatched each time the reference is invoked. This
allows it to follow code reloading, dynamic replacement of class methods, or
other similar techniques.

If the C<$mref> CODE reference is being stored in some object other than the
one it refers to, remember that since the Notifier is only weakly captured, it
is possible that it has been destroyed by the time the code runs, and so the
reference will be passed as C<undef>. This should be protected against by the
code body.

 $other_object->{on_event} = $notifier->_capture_weakself( sub {
    my $notifier = shift or return;
    my ( @event_args ) = @_;
    ...
 } );

For stand-alone generic implementation of this behaviour, see also L<curry>
and C<curry::weak>.

=cut

sub _capture_weakself
{
   my $self = shift;
   my ( $code ) = @_;   # actually bare method names work too

   if( !ref $code ) {
      my $class = ref $self;
      # Don't save this coderef, or it will break dynamic method dispatch,
      # which means code reloading, dynamic replacement, or other funky
      # techniques stop working
      $self->can( $code ) or
         croak qq(Can't locate object method "$code" via package "$class");
   }

   weaken $self;

   return sub {
      my $cv = ref( $code ) ? $code : $self->can( $code );

      if( HAS_BROKEN_TRAMPOLINES ) {
         return $cv->( $self, @_ );
      }
      else {
         unshift @_, $self;
         goto &$cv;
      }
   };
}

=head2 _replace_weakself

   $mref = $notifier->_replace_weakself( $code )

Returns a new CODE ref which, when invoked, will invoke the originally-passed
ref, with a reference to the Notifier replacing its first argument. The
Notifier reference is stored weakly in C<$mref>, so this CODE ref may be
stored in the Notifier itself without creating a cycle.

For example,

 my $mref = $notifier->_replace_weakself( sub {
    my ( $notifier, $arg ) = @_;
    print "Notifier $notifier got argument $arg\n";
 } );

 $mref->( $object, 123 );

This is provided as a utility for Notifier subclasses to use for event
callbacks on other objects, where the delegated object is passed in the
function's arguments.

The C<$code> argument may also be a plain string, which will be used as a
method name; the returned CODE ref will then invoke that method on the object.
As with C<_capture_weakself> this is stored symbolically.

As with C<_capture_weakself>, care should be taken against Notifier
destruction if the C<$mref> CODE reference is stored in some other object.

=cut

sub _replace_weakself
{
   my $self = shift;
   my ( $code ) = @_;   # actually bare method names work too

   if( !ref $code ) {
      # Don't save this coderef, see _capture_weakself for why
      my $class = ref $self;
      $self->can( $code ) or
         croak qq(Can't locate object method "$code" via package "$class");
   }

   weaken $self;

   return sub {
      my $cv = ref( $code ) ? $code : $self->can( $code );

      if( HAS_BROKEN_TRAMPOLINES ) {
         return $cv->( $self, @_[1..$#_] );
      }
      else {
         # Don't assign to $_[0] directly or we will change caller's first argument
         shift @_;
         unshift @_, $self;
         goto &$cv;
      }
   };
}

=head2 can_event

   $code = $notifier->can_event( $event_name )

Returns a C<CODE> reference if the object can perform the given event name,
either by a configured C<CODE> reference parameter, or by implementing a
method. If the object is unable to handle this event, C<undef> is returned.

=cut

sub can_event
{
   my $self = shift;
   my ( $event_name ) = @_;

   return $self->{$event_name} || $self->can( $event_name );
}

=head2 make_event_cb

   $callback = $notifier->make_event_cb( $event_name )

Returns a C<CODE> reference which, when invoked, will execute the given event
handler. Event handlers may either be subclass methods, or parameters given to
the C<new> or C<configure> method.

The event handler can be passed extra arguments by giving them to the C<CODE>
reference; the first parameter received will be a reference to the notifier
itself. This is stored weakly in the closure, so it is safe to store the
resulting C<CODE> reference in the object itself without causing a reference
cycle.

=cut

sub make_event_cb
{
   my $self = shift;
   my ( $event_name ) = @_;

   my $code = $self->can_event( $event_name )
      or croak "$self cannot handle $event_name event";

   my $caller = caller;

   return $self->_capture_weakself( 
      !$IO::Async::Debug::DEBUG ? $code : sub {
         my $self = $_[0];
         $self->_debug_printf_event( $caller, $event_name );
         goto &$code;
      }
   );
}

=head2 maybe_make_event_cb

   $callback = $notifier->maybe_make_event_cb( $event_name )

Similar to C<make_event_cb> but will return C<undef> if the object cannot
handle the named event, rather than throwing an exception.

=cut

sub maybe_make_event_cb
{
   my $self = shift;
   my ( $event_name ) = @_;

   my $code = $self->can_event( $event_name )
      or return undef;

   my $caller = caller;

   return $self->_capture_weakself(
      !$IO::Async::Debug::DEBUG ? $code : sub {
         my $self = $_[0];
         $self->_debug_printf_event( $caller, $event_name );
         goto &$code;
      }
   );
}

=head2 invoke_event

   @ret = $notifier->invoke_event( $event_name, @args )

Invokes the given event handler, passing in the given arguments. Event
handlers may either be subclass methods, or parameters given to the C<new> or
C<configure> method. Returns whatever the underlying method or CODE reference
returned.

=cut

sub invoke_event
{
   my $self = shift;
   my ( $event_name, @args ) = @_;

   my $code = $self->can_event( $event_name )
      or croak "$self cannot handle $event_name event";

   $self->_debug_printf_event( scalar caller, $event_name ) if $IO::Async::Debug::DEBUG;
   return $code->( $self, @args );
}

=head2 maybe_invoke_event

   $retref = $notifier->maybe_invoke_event( $event_name, @args )

Similar to C<invoke_event> but will return C<undef> if the object cannot
handle the name event, rather than throwing an exception. In order to
distinguish this from an event-handling function that simply returned
C<undef>, if the object does handle the event, the list that it returns will
be returned in an ARRAY reference.

=cut

sub maybe_invoke_event
{
   my $self = shift;
   my ( $event_name, @args ) = @_;

   my $code = $self->can_event( $event_name )
      or return undef;

   $self->_debug_printf_event( scalar caller, $event_name ) if $IO::Async::Debug::DEBUG;
   return [ $code->( $self, @args ) ];
}

=head1 DEBUGGING SUPPORT

=cut

=head2 debug_printf

   $notifier->debug_printf( $format, @args )

Conditionally print a debugging message to C<STDERR> if debugging is enabled.
If such a message is printed, it will be printed using C<printf> using the
given format and arguments. The message will be prefixed with an string, in
square brackets, to help identify the C<$notifier> instance. This string will
be the class name of the notifier, and any parent notifiers it is contained
by, joined by an arrow C<< <- >>. To ensure this string does not grow too
long, certain prefixes are abbreviated:

 IO::Async::Protocol::  =>  IaP:
 IO::Async::            =>  Ia:
 Net::Async::           =>  Na:

Finally, each notifier that has a name defined using the C<notifier_name>
parameter has that name appended in braces.

For example, invoking

 $stream->debug_printf( "EVENT on_read" )

On an L<IO::Async::Stream> instance reading and writing a file descriptor
whose C<fileno> is 4, which is a child of an L<IO::Async::Protocol::Stream>,
will produce a line of output:

 [Ia:Stream{rw=4}<-IaP:Stream] EVENT on_read

=cut

sub debug_printf
{
   $IO::Async::Debug::DEBUG or return;

   my $self = shift;
   my ( $format, @args ) = @_;

   my @id;
   while( $self ) {
      push @id, ref $self;

      my $name = $self->notifier_name;
      $id[-1] .= "{$name}" if defined $name and length $name;

      $self = $self->parent;
   }

   s/^IO::Async::Protocol::/IaP:/,
   s/^IO::Async::/Ia:/,
   s/^Net::Async::/Na:/ for @id;