1<?php
2declare(strict_types=1);
3namespace ParagonIE\ConstantTime;
4
5/**
6 *  Copyright (c) 2016 - 2018 Paragon Initiative Enterprises.
7 *  Copyright (c) 2014 Steve "Sc00bz" Thomas (steve at tobtu dot com)
8 *
9 *  Permission is hereby granted, free of charge, to any person obtaining a copy
10 *  of this software and associated documentation files (the "Software"), to deal
11 *  in the Software without restriction, including without limitation the rights
12 *  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
13 *  copies of the Software, and to permit persons to whom the Software is
14 *  furnished to do so, subject to the following conditions:
15 *
16 *  The above copyright notice and this permission notice shall be included in all
17 *  copies or substantial portions of the Software.
18 *
19 *  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
20 *  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
21 *  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
22 *  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
23 *  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
24 *  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
25 *  SOFTWARE.
26 */
27
28/**
29 * Class Base64UrlSafe
30 * [A-Z][a-z][0-9]\-_
31 *
32 * @package ParagonIE\ConstantTime
33 */
34abstract class Base64UrlSafe extends Base64
35{
36
37    /**
38     * Uses bitwise operators instead of table-lookups to turn 6-bit integers
39     * into 8-bit integers.
40     *
41     * Base64 character set:
42     * [A-Z]      [a-z]      [0-9]      -     _
43     * 0x41-0x5a, 0x61-0x7a, 0x30-0x39, 0x2d, 0x5f
44     *
45     * @param int $src
46     * @return int
47     */
48    protected static function decode6Bits(int $src): int
49    {
50        $ret = -1;
51
52        // if ($src > 0x40 && $src < 0x5b) $ret += $src - 0x41 + 1; // -64
53        $ret += (((0x40 - $src) & ($src - 0x5b)) >> 8) & ($src - 64);
54
55        // if ($src > 0x60 && $src < 0x7b) $ret += $src - 0x61 + 26 + 1; // -70
56        $ret += (((0x60 - $src) & ($src - 0x7b)) >> 8) & ($src - 70);
57
58        // if ($src > 0x2f && $src < 0x3a) $ret += $src - 0x30 + 52 + 1; // 5
59        $ret += (((0x2f - $src) & ($src - 0x3a)) >> 8) & ($src + 5);
60
61        // if ($src == 0x2c) $ret += 62 + 1;
62        $ret += (((0x2c - $src) & ($src - 0x2e)) >> 8) & 63;
63
64        // if ($src == 0x5f) ret += 63 + 1;
65        $ret += (((0x5e - $src) & ($src - 0x60)) >> 8) & 64;
66
67        return $ret;
68    }
69
70    /**
71     * Uses bitwise operators instead of table-lookups to turn 8-bit integers
72     * into 6-bit integers.
73     *
74     * @param int $src
75     * @return string
76     */
77    protected static function encode6Bits(int $src): string
78    {
79        $diff = 0x41;
80
81        // if ($src > 25) $diff += 0x61 - 0x41 - 26; // 6
82        $diff += ((25 - $src) >> 8) & 6;
83
84        // if ($src > 51) $diff += 0x30 - 0x61 - 26; // -75
85        $diff -= ((51 - $src) >> 8) & 75;
86
87        // if ($src > 61) $diff += 0x2d - 0x30 - 10; // -13
88        $diff -= ((61 - $src) >> 8) & 13;
89
90        // if ($src > 62) $diff += 0x5f - 0x2b - 1; // 3
91        $diff += ((62 - $src) >> 8) & 49;
92
93        return \pack('C', $src + $diff);
94    }
95}
96