phpMan > man > POE::Filter::Reference(3pm)

NAME
    POE::Filter::Reference - freeze and thaw arbitrary Perl data

SYNOPSIS
      #!perl

      use YAML;
      use POE qw(Wheel::ReadWrite Filter::Reference);

      POE::Session->create(
        inline_states => {
          _start => sub {
            pipe(my($read, $write)) or die $!;
            $_[HEAP]{io} = POE::Wheel::ReadWrite->new(
              InputHandle => $read,
              OutputHandle => $write,
              Filter => POE::Filter::Reference->new(),
              InputEvent => "got_perl_data",
            );

            $_[HEAP]{io}->put(
              { key_1 => 111, key_2 => 222 }
            );
          },
          got_perl_data => sub {
            print "Got data:\n", YAML::Dump($_[ARG0]);
            print "Bye!\n";
            delete $_[HEAP]{io};
          }
        }
      );

      POE::Kernel->run();
      exit;

DESCRIPTION
    POE::Filter::Reference allows programs to send and receive arbitrary Perl data structures
    without worrying about a line protocol. Its put() method serializes Perl data into a byte stream
    suitable for transmission. get_one() parses the data structures back out of such a stream.

    By default, POE::Filter::Reference uses Storable to do its magic. A different serializer may be
    specified at construction time.

PUBLIC FILTER METHODS
  new
    new() creates and initializes a POE::Filter::Reference object. It accepts a list of named
    parameters.

   Serializer
    Any class that supports nfreeze() (or freeze()) and thaw() may be used as a Serializer. If a
    Serializer implements both nfreeze() and freeze(), then the "network" (nfreeze) version will be
    used.

    Serializer may be a class name:

      # Use Storable explicitly, specified by package name.
      my $filter = POE::Filter::Reference->newer( Serializer=>"Storable" );

      # Use YAML instead.  Compress its output, as it may be verbose.
      my $filter = POE::Filter::Reference->new("YAML", 1);

    Serializer may also be an object:

      # Use an object.
      my $serializer = Data::Serializer::Something->new();
      my $filter = POE::Filter::Reference->newer( Serializer => $serializer );

    If Serializer is omitted or undef, the Reference filter will try to use Storable, FreezeThaw,
    and YAML in that order. POE::Filter::Reference will die if it cannot find one of these
    serializers, but this rarely happens now that Storable and YAML are bundled with Perl.

   Compression
    If Compression is true, Compress::Zlib will be called upon to reduce the size of serialized
    data. It will also decompress the incoming stream data.

   MaxBuffer
    "MaxBuffer" sets the maximum amount of data that the filter will hold onto while trying to build
    a new reference. Defaults to 512 MB.

   NoFatals
    If NoFatals is true, messages will be thawed inside a block eval. By default, however, thaw() is
    allowed to die normally. If an error occurs while NoFatals is in effect, POE::Filter::Reference
    will return a string containing the contents of $@ at the time the eval failed. So when using
    NoFatals, it's important to check whether input is really a reference:

      sub got_reference {
        my $message = $_[ARG0];
        if (ref $message) {
          print "Got data:\n", YAML::Dump($message);
        }
        else {
          warn "Input decode error: $message\n";
        }
      }

    new() will try to load any classes it needs for "Compression" or "Serializer".

  new [SERIALIZER [, COMPRESSION [, NO_FATALS]]]
    This is the old constructor synatx. It does not conform to the normal POE::Filter constructor
    parameter syntax. Please use the new syntax instead.

    Calling "new" like this is equivalent to

        POE::Filter::Reference->new( Serializer => SERIALIZER,
                                     Compression => COMPRESSION,
                                     NoFatals  => NO_FATALS );

    Please note that if you have a custom serializer class called "Serializer" you will have to
    update your code to the new syntax.

SERIALIZER API
    Here's what POE::Filter::Reference expects of its serializers.

  thaw SERIALIZED
    thaw() is required. It accepts two parameters: $self and a scalar containing a SERIALIZED byte
    stream representing a single Perl data structure. It returns a reconstituted Perl data
    structure.

      sub thaw {
        my ($self, $stream) = @_;
        my $reference = $self->_deserialization_magic($stream);
        return $reference;
      }

  nfreeze REFERENCE
    Either nfreeze() or freeze() is required. They behave identically, except that nfreeze() is
    guaranteed to be portable across networks and between machine architectures.

    These freezers accept two parameters: $self and a REFERENCE to Perl data. They return a
    serialized version of the REFERENCEd data.

      sub nfreeze {
        my ($self, $reference) = @_;
        my $stream = $self->_serialization_magic($reference);
        return $stream;
      }

  freeze REFERENCE
    freeze() is an alternative form of nfreeze(). It has the same call signature as nfreeze(), but
    it doesn't guarantee that serialized data will be portable across machine architectures.

    If you must choose between implementing freeze() and nfreeze() for use with
    POE::Filter::Reference, go with nfreeze().

SEE ALSO
    Please see POE::Filter for documentation regarding the base interface.

    The SEE ALSO section in POE contains a table of contents covering the entire POE distribution.

BUGS
    Not so much bugs as caveats:

    It's important to use identical serializers on each end of a connection. Even different versions
    of the same serializer can break data in transit.

    Most (if not all) serializers will re-bless data at the destination, but many of them will not
    load the necessary classes to make those blessings work. Make sure the same classes and versions
    are available on either end of the wire.

AUTHORS & COPYRIGHTS
    The Reference filter was contributed by Artur Bergman, with changes by Philip Gwyn.

    Please see POE for more information about authors and contributors.