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POE::Filter::Block.3pm

NAME

POE::Filter::Block - filter between streams and blocks

SYNOPSIS

   $filter = POE::Filter::Block->new( BlockSize => 1024 );
   $filter = POE::Filter::Block->new(
     LengthCodec => [ \&encoder, \&decoder ]
   );
   $arrayref_of_blocks =
     $filter->get($arrayref_of_raw_chunks_from_driver);
   $arrayref_of_streamable_chunks_for_driver =
     $filter->put($arrayref_of_blocks);
   $arrayref_of_leftovers =
     $filter->get_pending();
 
 

DESCRIPTION

The Block filter translates data between serial streams and blocks. It can handle two kinds of block: fixed-length and length-prepended.

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 to be soundly spanked.

In variable-length mode, a LengthCodec parameter is valid. The LengthCodec should be a list reference 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. The length is separated from the buffer by an ASCII NUL (``\0'') character.

   sub _default_encoder {
     my $stuff = shift;
     substr($$stuff, 0, 0) = length($$stuff) . "\0";
     return;
   }
 
 

Sensibly enough, the corresponding decoder removes the prepended length and separator, returning its numeric value. 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 METHODS

Please see POE::Filter.

SEE ALSO

POE::Filter.

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.