Provided by: libpoe-perl_1.3670-2_all bug


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



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

           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",

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



       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

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


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


       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


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


       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

         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".

       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.


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

       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

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


       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


       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.


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

       Please see POE for more information about authors and contributors.