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	my $digits = shift;
	my $ndigits = length($digits);
	my $npadbytes = 3 - ($ndigits + 3) % 4;
	$digits .= '.' x $npadbytes;
	my $bytes = '';
	for(my $i = 0; $i < $ndigits; $i += 4) {
		my $v = index($base64_digits, substr $digits, $i, 1) |
			(index($base64_digits, substr $digits, $i + 1, 1) << 6) |
			(index($base64_digits, substr $digits, $i + 2, 1) << 12) |
			(index($base64_digits, substr $digits, $i + 3, 1) << 18);
		$bytes .= chr($v & 0xff) . chr(($v >> 8) & 0xff) . chr(($v >> 16) & 0xff);
	}
	substr $bytes, -$npadbytes, $npadbytes, '';
	return $bytes;
}

sub encode_crypt64_number {
	my ($input, $length) = @_;
	my $output = '';
	for (1 .. $length) {
		my $remainder = $input % 64;
		$output .= substr $base64_digits, $remainder, 1;
		$input = int($input / 64);
	}
	croak "Number doesn't fit in $length characters" if $input != 0;
	return $output;
}

sub decode_crypt64_number {
	my $input = shift;
	my $result = 0;
	for (0 .. length($input) - 1) {
		$result += index($base64_digits, substr $input, $_, 1) * (1 << (6 * $_));
	}
	return $result;
}

1;

# ABSTRACT: An implementation of the crypt64 encoding

__END__

=pod

=encoding UTF-8

=head1 NAME

Crypt::Passphrase::Util::Crypt64 - An implementation of the crypt64 encoding

=head1 VERSION

version 0.022

=head1 SYNOPSIS

 use Crypt::Passphrase::Crypt64 ':all';

 my $encoded = encode_crypt64('abcd');
 my $decoded = decode_crypt64($encoded);

=head1 DESCRIPTION

This module provides functions to encode and decode strings into and from the crypt64 encoding. This is similar to base64, but incompatible because it uses a slightl different alphabet and because it's little-endian. This encoding is traditionally us...

=head1 FUNCTIONS

=head2 encode_crypt64

This takes a bytestring and encodes it in crypt64.

=head2 decode_crypt64

This takes a crypt64 encoded string and decodes it to a bytestring.

=head2 endcode_crypt64_number

This takes a number to encode, and optionally a desired length.

=head2 decode_crypt64_number

This takes a crypt64 encoded number, and decodes it to a number.

=head1 AUTHOR

Leon Timmermans <fawaka@gmail.com>

=head1 COPYRIGHT AND LICENSE

This software is copyright (c) 2021 by Leon Timmermans.

This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.

=cut