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

       POE::Filter::Reference deviates from the standard POE::Filter API in the following ways.

   new [SERIALIZER [, COMPRESSION [, NO_FATALS]]]
       new() creates and initializes a POE::Filter::Reference object.  It will use Storable as
       its default SERIALIZER if none other is specified.

       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.

       If NO_FATALS is true, messages will be thawed inside a block eval.  By default, however,
       thaw() is allowed to die normally.  If an error occurs while NO_FATALS is in effect,
       POE::Filter::Reference will return a string containing the contents of $@ at the time the
       eval failed.  So when using NO_FATALS, 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";
           }
         }

       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" version will be
       used.

       SERIALIZER may be a class name:

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

         # A choose-your-own-serializer adventure!
         # We'll still deal with compressed data, however.
         my $filter = POE::Filter::Reference->new(undef, 1);

       POE::Filter::Reference will try to compress frozen strings and uncompress them before
       thawing if COMPRESSION is true.  It uses Compress::Zlib for this.  POE::Filter::Reference
       doesn't need Compress::Zlib if COMPRESSION is false.

       new() will try to load any classes it needs.

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.