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package Encode::Base58;
use strict;
use 5.008_001;
our $VERSION = '0.01';
use base qw(Exporter);
our @EXPORT = qw( encode_base58 decode_base58 );
my @alpha = qw(
1 2 3 4 5 6 7 8 9
a b c d e f g h i
j k m n o p q r s
t u v w x y z A B
C D E F G H J K L
M N P Q R S T U V
W X Y Z
);
my $i = 0;
my %alpha = map { $_ => $i++ } @alpha;
sub encode_base58 {
my $num = shift;
return $alpha[0] if $num == 0;
my $res = '';
my $base = @alpha;
while ($num > 0) {
my $remain = $num % $base;
$num = int($num / $base);
$res = $alpha[$remain] . $res;
}
return $res;
}
sub decode_base58 {
my $str = shift;
my $decoded = 0;
my $multi = 1;
my $base = @alpha;
while (length $str > 0) {
my $digit = chop $str;
$decoded += $multi * $alpha{$digit};
$multi *= $base;
}
return $decoded;
}
1;
__END__
=encoding utf-8
=for stopwords
Flickr Flickr's
=for test_synopsis
my $number;
=head1 NAME
Encode::Base58 - Base58 encodings (for Flickr short URI)
=head1 SYNOPSIS
use Encode::Base58;
my $short = encode_base58($number);
my $number = decode_base58($short);
=head1 DESCRIPTION
Encode::Base58 is a base58 encoder/decoder implementation in
Perl. Base58 encoding is used in shortening ID numbers into a short
string for Flickr's short URL (C<flic.kr>).
=head1 AUTHOR
Tatsuhiko Miyagawa E<lt>miyagawa@bulknews.netE<gt>
=head1 LICENSE
This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.
=head1 SEE ALSO
L<http://www.flickr.com/groups/api/discuss/72157616713786392/>
L<http://gist.github.com/101753> (in Ruby)
L<http://gist.github.com/101674> (in Objective-C and unit tests)
=cut
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