<?php
/**
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 * PHP Google two-factor authentication module.
 *
 * See http://www.idontplaydarts.com/2011/07/google-totp-two-factor-authentication-for-php/
 * for more details
 *
 * @author Phil
 **/

class Base32 {

        private static $lut = array(
                "A" => 0,       "B" => 1,
                "C" => 2,       "D" => 3,
                "E" => 4,       "F" => 5,
                "G" => 6,       "H" => 7,
                "I" => 8,       "J" => 9,
                "K" => 10,      "L" => 11,
                "M" => 12,      "N" => 13,
                "O" => 14,      "P" => 15,
                "Q" => 16,      "R" => 17,
                "S" => 18,      "T" => 19,
                "U" => 20,      "V" => 21,
                "W" => 22,      "X" => 23,
                "Y" => 24,      "Z" => 25,
                "2" => 26,      "3" => 27,
                "4" => 28,      "5" => 29,
                "6" => 30,      "7" => 31
        );

        /**
         * Decodes a base32 string into a binary string according to RFC 4648.
         **/
        public static function decode($b32) {

                $b32    = strtoupper($b32);

                if (!preg_match('/^[ABCDEFGHIJKLMNOPQRSTUVWXYZ234567]+$/', $b32, $match))
                        throw new Exception('Invalid characters in the base32 string.');

                $l      = strlen($b32);
                $n      = 0;
                $j      = 0;
                $binary = "";

                for ($i = 0; $i < $l; $i++) {

                        $n = $n << 5;                           // Move buffer left by 5 to make room
                        $n = $n + self::$lut[$b32[$i]];         // Add value into buffer
                        $j = $j + 5;                            // Keep track of number of bits in buffer

                        if ($j >= 8) {
                                $j = $j - 8;
                                $binary .= chr(($n & (0xFF << $j)) >> $j);
                        }
                }

                return $binary;
        }

        /**
         * Encodes a binary string into a base32 string according to RFC 4648 (no padding).
         **/
        public static function encode($string) {

                if (empty($string))
                        throw new Exception('Empty string.');

                $b32      = "";
                $binary   = "";

                $bytes    = str_split($string);
                for ($i = 0; $i < count($bytes); $i++) {
                        $bits = base_convert(ord($bytes[$i]), 10, 2);
                        $binary .= str_pad($bits, 8, '0', STR_PAD_LEFT);
                }

                $map      = array_keys(self::$lut);
                $fivebits = str_split($binary, 5);
                for ($i = 0; $i < count($fivebits); $i++) {
                        $dec = base_convert(str_pad($fivebits[$i],  5, '0'), 2, 10);
                        $b32 .= $map[$dec];
                }

                return $b32;
        }
}
?>