in reply to Creating (and using) a custom encoding.

I like Anonymous Monk's suggestion, as it facilitates "compiled" encodings. I'd still like to figure out the Encode::Encoding method though. Afterward I can probably post a tutorial on both methods.

Here's a self-contained snippet that should be a framework from which to work on getting the Encode::Encoding method going. Unfortunately, it doesn't work (ie, the rot13 encoding doesn't take place) because I'm still unclear on how Encode's define_encoding() fits into the mix. If anyone can fill in the blank, or possibly point to the documentation that I seem to have missed, I would certainly appreciate it.

package Encode::ROT13;

use strict;
use warnings;

use parent qw( Encode::Encoding );

__PACKAGE__->Define( 'rot13' );

sub encode($$;$){
  my( $obj, $str, $chk ) = @_;
  $str =~ tr/A-Za-z/N-ZA-Mn-za-m/;
  $_[1] = '' if $chk; # $_[1] is aliased through the call. Inplace edi
+t.
  return $str;
}

no warnings 'once';
*Encode::ROT13::decode = \&encode; # Because rot13( rot13() ) is a rou
+nd-trip.

1;


package main;

use strict;
use warnings;

use Encode 'define_encoding';

use File::Slurp;

# define_encoding( $object, 'rot13' ); # Um....?

my @words = read_file( \*DATA, chomp => 1, binmode => ':rot13' );


print "$_\n" for @words;


__DATA__
Apple
cat
dog
strawberry
watermelon

[download]

Dave

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Re^2: Creating (and using) a custom encoding.
by Khen1950fx (Canon) on May 30, 2013 at 20:29 UTC
    OK. Now that I'm thoroughly confused:-): 
    package Encode::ROT13;

use strict;
use warnings;
use Encode;

use parent qw( Encode::Encoding );

__PACKAGE__->Define( 'rot13' );

no warnings 'redefine';

sub encode($$;$){
  my( $obj, $str, $chk ) = @_;
  $str =~ tr/A-Za-z/N-ZA-Mn-za-m/;
  $_[1] = '' if $chk;
  return $str;
}

*decode = \&encode;

1;


package main;

use strict;
use warnings;

use Encode 'define_encoding';
use File::Slurp;

my $object = {};
bless($object, 'Encode::ROT13');

define_encoding( $object, 'rot13' ); 

my(@words) = read_file( \*DATA, chomp => 1, binmode => ':rot13' );
print "$_\n" for @words;

my(@list) = Encode->encodings();

print "Checking for rot13: \n";
foreach my $list(@list) {
    print "\t$list\n";;
}

__DATA__
Apple
cat
dog
strawberry
watermelon

    [download]
[reply]
[d/l]

      I'm guessing that doesn't work for you either.

      A few nits (even though neither of us have it working yet): Encode doesn't need to be 'used' in package Encode::ROT13 (and eliminating it eliminates the "redefined" warnings). Also, blessing the object into package Encode::ROT13 may as well be written as a constructor in Encode::ROT13, and then called with the traditional Encode::ROT13->new syntax from the calling package (main) .... not that it matters -- it still doesn't work.

      Also, even if you completely eliminate 'use Encode qw/ define_encoding /; from package main, and eliminate the object construction as well as the call to define_encoding, 'rot13' still shows up in the encodings list. However, placing a "warn" inside of Encode::ROT13::encode shows that the function never gets called.

      What are we missing? :) There really seems to be a disconnect between the POD and reality. But I'm sure it works for someone (who knows how to do it right). Otherwise, the whole Encode::Encoding module is pretty useless.


      Dave

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        Thanks for the clarification.
[reply]
Re^2: Creating (and using) a custom encoding. (fudge :encoding(rot13))
by Anonymous Monk on May 30, 2013 at 23:41 UTC

    Well , I guess it won't work. Substitute UTF-7 or encoding(UTF-7) for binmode and Encode::Unicode::UTF7 won't get loaded

    There is one test of Encode::Encoding in http://cpansearch.perl.org/src/DANKOGAI/Encode-2.51/t/Encoder.t and it doesn't use binmode/layers, its encode/decode functions

    Fudge always saves :) File::Slurp is hiding the critical warnings
    you should use :encoding(rot13)

    your start

    Read more... (813 Bytes)

    the fudge 

    use Data::Dump ; 
dd\%Encode::Encoding;
for my $enc ( qw/
 :rot13
 :ROT13
 :encoding(rot13)
 :encoding(ROT13)
 :UTF-7
 :encoding(UTF-7)
 :via(ROT13)
 :via(Encode::ROT13)
                / )
{
    fudge( $enc );
}
dd\%Encode::Encoding;

our $tell;
sub fudge {
    my( $layer ) = @_;
    $tell ||= tell DATA;
    seek DATA, $tell, 0;
    print "## binmode DATA, $layer \n";
    binmode DATA, $layer;
    dd [<DATA>];
}
__DATA__
Apple
cat
dog
strawberry
watermelon

    [download]

    output

    Read more... (5 kB)
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