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package Math::Base36;
use strict;
use warnings;
use base qw( Exporter );
use Carp 'croak';
use Math::BigInt ();
our %EXPORT_TAGS = ( 'all' => [ qw(encode_base36 decode_base36) ] );
our @EXPORT_OK = ( @{ $EXPORT_TAGS{ 'all' } } );
our $VERSION = '0.14';
sub decode_base36 {
    my $base36 = uc( shift );
    croak "Invalid base36 number ($base36)" if $base36 =~ m{[^0-9A-Z]};
    my ( $result, $digit ) = ( 0, 0 );
    for my $char ( split( //, reverse $base36 ) ) {
        my $value = $char =~ m{\d} ? $char : ord( $char ) - 55;
        $result += $value * Math::BigInt->new( 36 )->bpow( $digit++ );
    }
    return $result;
}
sub encode_base36 {
    my ( $number, $padlength ) = @_;
    $padlength ||= 1;
    croak "Invalid base10 number ($number)"  if $number    =~ m{\D};
    croak "Invalid padding length ($padlength)" if $padlength =~ m{\D};
    $number = Math::BigInt->new( $number );
    my $result = '';
    while ( $number ) {
        my $remainder = $number % 36;
        $result .= $remainder <= 9 ? $remainder : chr( 55 + $remainder );
        $number = int $number / 36;
    }
    my $padding = $padlength - length $result;
    my $return = reverse( $result );
    $return = '0' x $padding . $return if $padding > 0;
    return $return;
}
1;
__END__
HideShow 48 lines of Pod
=head1 NAME
Math::Base36 - Encoding and decoding of base36 strings
=head1 SYNOPSIS
  use Math::Base36 ':all';
  $b36 = encode_base36( $number, $padlength );
  $number = decode_base36( $b36 );
=head1 DESCRIPTION
This module converts to and from Base36 numbers (0..9 - A..Z)
It was created because of an article/challenge in "The Perl Review"
=head1 METHODS
=head2 encode_base36( $number, [$padlength] )
Accepts a unsigned int and returns a Base36 string representation of the
number. optionally zero-padded to C<$padlength>.
=head2 decode_base36( $b36 )
Accepts a base36 string and returns a Base10 string representation of the
number.
=head1 AUTHOR
Rune Henssel E<lt>perl@henssel.dkE<gt>
=head1 MAINTAINER 
Brian Cassidy E<lt>bricas@cpan.orgE<gt>
=head1 COPYRIGHT AND LICENSE
Copyright 2002 by Rune Henssel
Copyright 2007-2015 by Brian Cassidy
This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself. 
=cut