—# Filter::Reference partial copyright 1998 Artur Bergman
# <artur@vogon-solutions.com>. Partial copyright 1999 Philip Gwyn.
package
POE::Filter::Reference;
use
strict;
use
POE::Filter;
$VERSION
=
'1.311'
;
# NOTE - Should be #.### (three decimal places)
@ISA
=
qw(POE::Filter)
;
sub
BUFFER () { 0 }
sub
FREEZE () { 1 }
sub
THAW () { 2 }
sub
COMPRESS () { 3 }
#------------------------------------------------------------------------------
# Try to require one of the default freeze/thaw packages.
BEGIN {
local
$SIG
{
'__DIE__'
} =
'DEFAULT'
;
my
@packages
=
qw(Storable FreezeThaw YAML)
;
foreach
my
$package
(
@packages
) {
eval
{
require
"$package.pm"
;
import
$package
(); };
if
($@) {
warn
$@;
next
;
}
# Found a good freezer!
$DEF_FREEZER
=
$package
;
last
;
}
die
"Filter::Reference requires one of @packages"
unless
defined
$DEF_FREEZER
;
}
# Some processing here
(
$DEF_FREEZE
,
$DEF_THAW
) = _get_methods(
$DEF_FREEZER
);
#------------------------------------------------------------------------------
# Try to acquire Compress::Zlib at run time.
my
$zlib_status
=
undef
;
sub
_include_zlib {
local
$SIG
{
'__DIE__'
} =
'DEFAULT'
;
unless
(
defined
$zlib_status
) {
eval
"use Compress::Zlib qw(compress uncompress)"
;
if
($@) {
$zlib_status
= $@;
eval
(
"sub compress { @_ }\n"
.
"sub uncompress { @_ }"
);
}
else
{
$zlib_status
=
''
;
}
}
$zlib_status
;
}
#------------------------------------------------------------------------------
sub
_get_methods {
my
(
$freezer
)=
@_
;
my
$freeze
=
$freezer
->can(
'nfreeze'
) ||
$freezer
->can(
'freeze'
);
my
$thaw
=
$freezer
->can(
'thaw'
);
return
unless
$freeze
and
$thaw
;
return
(
$freeze
,
$thaw
);
}
#------------------------------------------------------------------------------
sub
new {
my
(
$type
,
$freezer
,
$compression
) =
@_
;
my
(
$freeze
,
$thaw
);
unless
(
defined
$freezer
) {
# Okay, load the default one!
$freezer
=
$DEF_FREEZER
;
$freeze
=
$DEF_FREEZE
;
$thaw
=
$DEF_THAW
;
}
else
{
# What did we get?
if
(
ref
$freezer
) {
# It's an object, create an closure
my
(
$freezetmp
,
$thawtmp
) = _get_methods(
$freezer
);
$freeze
=
sub
{
$freezetmp
->(
$freezer
,
@_
) };
$thaw
=
sub
{
$thawtmp
-> (
$freezer
,
@_
) };
}
else
{
# A package name?
# First, find out if the package has the necessary methods.
(
$freeze
,
$thaw
) = _get_methods(
$freezer
);
# If not, try to reload the module.
unless
(
$freeze
and
$thaw
) {
my
$path
=
$freezer
;
$path
=~ s{::}{/}g;
$path
.=
'.pm'
;
# Force a reload if necessary. This is naive and can leak
# memory, so we only do it until we get the desired methods.
delete
$INC
{
$path
};
eval
{
local
$^W = 0;
require
$path
;
$freezer
->
import
();
};
carp $@
if
$@;
(
$freeze
,
$thaw
) = _get_methods(
$freezer
);
}
}
}
# Now get the methods we want
carp
"$freezer doesn't have a freeze or nfreeze method"
unless
$freeze
;
carp
"$freezer doesn't have a thaw method"
unless
$thaw
;
# Should ->new() return undef() it if fails to find the methods it
# wants?
return
unless
$freeze
and
$thaw
;
# Compression
$compression
||= 0;
if
(
$compression
) {
my
$zlib_status
= _include_zlib();
if
(
$zlib_status
ne
''
) {
warn
"Compress::Zlib load failed with error: $zlib_status\n"
;
carp
"Filter::Reference compression option ignored"
;
$compression
= 0;
}
}
my
$self
=
bless
[
''
,
# BUFFER
$freeze
,
# FREEZE
$thaw
,
# THAW
$compression
,
# COMPRESS
],
$type
;
$self
;
}
#------------------------------------------------------------------------------
sub
get {
my
(
$self
,
$stream
) =
@_
;
my
@return
;
$self
->get_one_start(
$stream
);
while
(1) {
my
$next
=
$self
->get_one();
last
unless
@$next
;
push
@return
,
@$next
;
}
return
\
@return
;
}
#------------------------------------------------------------------------------
# 2001-07-27 RCC: The get_one() variant of get() allows Wheel::Xyz to
# retrieve one filtered block at a time. This is necessary for filter
# changing and proper input flow control.
sub
get_one_start {
my
(
$self
,
$stream
) =
@_
;
$self
->[BUFFER] .=
join
(
''
,
@$stream
);
}
sub
get_one {
my
$self
=
shift
;
# Need to check lengths in octets, not characters.
if
(
$self
->[BUFFER] =~ /^(\d+)\0/ and
length
(
$self
->[BUFFER]) >= $1 +
length
($1) + 1
) {
substr
(
$self
->[BUFFER], 0,
length
($1) + 1) =
""
;
my
$return
=
substr
(
$self
->[BUFFER], 0, $1);
substr
(
$self
->[BUFFER], 0, $1) =
""
;
$return
= uncompress(
$return
)
if
$self
->[COMPRESS];
return
[
$self
->[THAW]->(
$return
) ];
}
return
[ ];
}
#------------------------------------------------------------------------------
# freeze one or more references, and return a string representing them
sub
put {
my
(
$self
,
$references
) =
@_
;
# Need to check lengths in octets, not characters.
my
@raw
=
map
{
my
$frozen
=
$self
->[FREEZE]->(
$_
);
$frozen
= compress(
$frozen
)
if
$self
->[COMPRESS];
length
(
$frozen
) .
"\0"
.
$frozen
;
}
@$references
;
\
@raw
;
}
#------------------------------------------------------------------------------
# Return everything we have outstanding. Do not destroy our framing
# buffer, though.
sub
get_pending {
my
$self
=
shift
;
return
undef
unless
length
$self
->[BUFFER];
return
[
$self
->[BUFFER] ];
}
1;
__END__
=head1 NAME
POE::Filter::Reference - freeze and thaw arbitrary Perl data
=head1 SYNOPSIS
#!perl
use YAML;
use POE qw(Wheel::ReadWrite Filter::Reference);
POE::Session->create(
inline_states => {
_start => sub {
pipe(my($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;
=head1 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.
=head1 PUBLIC FILTER METHODS
POE::Filter::Reference deviates from the standard POE::Filter API in
the following ways.
=head2 new [SERIALIZER [, COMPRESSION]]
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.
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.
=head1 SERIALIZER API
Here's what POE::Filter::Reference expects of its serializers.
=head2 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;
}
=head2 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;
}
=head2 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().
=head1 SEE ALSO
Please see L<POE::Filter> for documentation regarding the base
interface.
The SEE ALSO section in L<POE> contains a table of contents covering
the entire POE distribution.
=head1 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 their
blessings work.
=head1 AUTHORS & COPYRIGHTS
The Reference filter was contributed by Artur Bergman, with changes
by Philip Gwyn.
Please see L<POE> for more information about authors and contributors.
=cut
# rocco // vim: ts=2 sw=2 expandtab
# TODO - Edit.