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.