POE::Filter::Block(3) User Contributed Perl DocumentationPOE::Filter::Block(3)NAMEPOE::Filter::Block - translate data between streams and blocks
SYNOPSIS
#!perl
use warnings;
use strict;
use POE::Filter::Block;
my $filter = POE::Filter::Block->new( BlockSize => 8 );
# Prints three lines: abcdefgh, ijklmnop, qrstuvwx.
# Bytes "y" and "z" remain in the buffer and await completion of the
# next 8-byte block.
$filter->get_one_start([ "abcdefghijklmnopqrstuvwxyz" ]);
while (1) {
my $block = $filter->get_one();
last unless @$block;
print $block->[0], "\n";
}
# Print one line: yz123456
$filter->get_one_start([ "123456" ]);
while (1) {
my $block = $filter->get_one();
last unless @$block;
print $block->[0], "\n";
}
DESCRIPTIONPOE::Filter::Block translates data between serial streams and blocks.
It can handle fixed-length and length-prepended blocks, and it may be
extended to handle other block types.
Fixed-length blocks are used when Block's constructor is called with a
BlockSize value. Otherwise the Block filter uses length-prepended
blocks.
Users who specify block sizes less than one deserve what they get.
In variable-length mode, a LengthCodec parameter may be specified. The
LengthCodec value should be a reference to a list of two functions: the
length encoder, and the length decoder:
LengthCodec => [ \&encoder, \&decoder ]
The encoder takes a reference to a buffer and prepends the buffer's
length to it. The default encoder prepends the ASCII representation of
the buffer's length and a chr(0) byte to separate the length from the
actual data:
sub _default_encoder {
my $stuff = shift;
substr($$stuff, 0, 0) = length($$stuff) . "\0";
return;
}
The corresponding decoder returns the block length after removing it
and the separator from the buffer. It returns nothing if no length can
be determined.
sub _default_decoder {
my $stuff = shift;
unless ($$stuff =~ s/^(\d+)\0//s) {
warn length($1), " strange bytes removed from stream"
if $$stuff =~ s/^(\D+)//s;
return;
}
return $1;
}
This filter holds onto incomplete blocks until they are completed.
PUBLIC FILTER METHODSPOE::Filter::Block has no additional public methods.
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
The put() method doesn't verify block sizes.
AUTHORS & COPYRIGHTS
The Block filter was contributed by Dieter Pearcey, with changes by
Rocco Caputo.
Please see POE for more information about authors and contributors.
perl v5.14.2 2011-12-15 POE::Filter::Block(3)
