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Classes and Traits |
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| LZW | |
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| compress | |
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| decompress | |
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| 1 | <?php |
| 2 | /** |
| 3 | * Jingga |
| 4 | * |
| 5 | * PHP Version 8.1 |
| 6 | * |
| 7 | * @package phpOMS\Utils\Compression |
| 8 | * @copyright Dennis Eichhorn |
| 9 | * @license OMS License 2.0 |
| 10 | * @version 1.0.0 |
| 11 | * @link https://jingga.app |
| 12 | */ |
| 13 | declare(strict_types=1); |
| 14 | |
| 15 | namespace phpOMS\Utils\Compression; |
| 16 | |
| 17 | /** |
| 18 | * LZW compression class |
| 19 | * |
| 20 | * @package phpOMS\Utils\Compression |
| 21 | * @license OMS License 2.0 |
| 22 | * @link https://jingga.app |
| 23 | * @since 1.0.0 |
| 24 | */ |
| 25 | class LZW implements CompressionInterface |
| 26 | { |
| 27 | /** |
| 28 | * {@inheritdoc} |
| 29 | */ |
| 30 | public function compress(string $source) : string |
| 31 | { |
| 32 | $w = ''; |
| 33 | $dictionary = []; |
| 34 | $result = []; |
| 35 | $dictSize = 256; |
| 36 | |
| 37 | for ($i = 0; $i < 256; ++$i) { |
| 38 | $dictionary[\chr($i)] = $i; |
| 39 | } |
| 40 | |
| 41 | $length = \strlen($source); |
| 42 | for ($i = 0; $i < $length; ++$i) { |
| 43 | $c = $source[$i]; |
| 44 | $wc = $w . $c; |
| 45 | |
| 46 | if (\array_key_exists($w . $c, $dictionary)) { |
| 47 | $w .= $c; |
| 48 | } else { |
| 49 | $result[] = $dictionary[$w]; |
| 50 | $dictionary[$wc] = $dictSize++; |
| 51 | $w = $c; |
| 52 | } |
| 53 | } |
| 54 | |
| 55 | if ($w !== '') { |
| 56 | $result[] = $dictionary[$w]; |
| 57 | } |
| 58 | |
| 59 | return \implode(',', $result); |
| 60 | } |
| 61 | |
| 62 | /** |
| 63 | * {@inheritdoc} |
| 64 | * |
| 65 | * @throws \Exception |
| 66 | */ |
| 67 | public function decompress(string $compressed) : string |
| 68 | { |
| 69 | $compressed = \explode(',', $compressed); |
| 70 | $dictionary = []; |
| 71 | $entry = ''; |
| 72 | $dictSize = 256; |
| 73 | |
| 74 | if (empty($compressed) || $compressed === ['']) { |
| 75 | return ''; |
| 76 | } |
| 77 | |
| 78 | for ($i = 0; $i < 256; ++$i) { |
| 79 | $dictionary[$i] = \chr($i); |
| 80 | } |
| 81 | |
| 82 | $w = \chr((int) $compressed[0]); |
| 83 | $result = $dictionary[(int) ($compressed[0])] ?? ''; |
| 84 | $count = \count($compressed); |
| 85 | |
| 86 | for ($i = 1; $i < $count; ++$i) { |
| 87 | $k = (int) $compressed[$i]; |
| 88 | |
| 89 | if (isset($dictionary[$k]) && !empty($dictionary[$k])) { |
| 90 | $entry = $dictionary[$k]; |
| 91 | } elseif ($k === $dictSize) { |
| 92 | $entry = $w . $w[0]; |
| 93 | } else { |
| 94 | throw new \Exception('Wrong dictionary size!' . $k . '.' . $dictSize); // @codeCoverageIgnore |
| 95 | } |
| 96 | |
| 97 | $result .= $entry; |
| 98 | $dictionary[$dictSize++] = $w . $entry[0]; |
| 99 | $w = $entry; |
| 100 | } |
| 101 | |
| 102 | /** @var string $result */ |
| 103 | return $result; |
| 104 | } |
| 105 | } |