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| 1 | <?php |
| 2 | /** |
| 3 | * This program is free software; you can redistribute it and/or modify |
| 4 | * it under the terms of the GNU General Public License as published by |
| 5 | * the Free Software Foundation; either version 2 of the License, or |
| 6 | * (at your option) any later version. |
| 7 | * |
| 8 | * This program is distributed in the hope that it will be useful, |
| 9 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 10 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 11 | * GNU General Public License for more details. |
| 12 | * |
| 13 | * You should have received a copy of the GNU General Public License along |
| 14 | * with this program; if not, write to the Free Software Foundation, Inc., |
| 15 | * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. |
| 16 | * http://www.gnu.org/copyleft/gpl.html |
| 17 | * |
| 18 | * @file |
| 19 | * @ingroup FileBackend |
| 20 | */ |
| 21 | |
| 22 | /** |
| 23 | * Helper class for tracking counterfactual file states when pre-checking file operation batches |
| 24 | * |
| 25 | * The file states are represented with (existence,size,sha1) triples. When combined with the |
| 26 | * current state of files in the backend, this can be used to simulate how a batch of operations |
| 27 | * would play out as a "dry run". This is used in FileBackend::doOperations() to bail out if any |
| 28 | * failure can be predicted before modifying any data. This includes file operation batches where |
| 29 | * the same file gets modified by different operations within the batch. |
| 30 | * |
| 31 | * @internal Only for use within FileBackend |
| 32 | */ |
| 33 | class FileStatePredicates { |
| 34 | protected const EXISTS = 'exists'; |
| 35 | protected const SIZE = 'size'; |
| 36 | protected const SHA1 = 'sha1'; |
| 37 | |
| 38 | /** @var array<string,array> Map of (storage path => file state map) */ |
| 39 | private $fileStateByPath; |
| 40 | |
| 41 | public function __construct() { |
| 42 | $this->fileStateByPath = []; |
| 43 | } |
| 44 | |
| 45 | /** |
| 46 | * Predicate that a file exists at the path |
| 47 | * |
| 48 | * @param string $path Storage path |
| 49 | * @param int|false|Closure $size File size or idempotent function yielding the size |
| 50 | * @param string|Closure $sha1Base36 File hash, or, idempotent function yielding the hash |
| 51 | */ |
| 52 | public function assumeFileExists( string $path, $size, $sha1Base36 ) { |
| 53 | $this->fileStateByPath[$path] = [ |
| 54 | self::EXISTS => true, |
| 55 | self::SIZE => $size, |
| 56 | self::SHA1 => $sha1Base36 |
| 57 | ]; |
| 58 | } |
| 59 | |
| 60 | /** |
| 61 | * Predicate that no file exists at the path |
| 62 | * |
| 63 | * @param string $path Storage path |
| 64 | */ |
| 65 | public function assumeFileDoesNotExist( string $path ) { |
| 66 | $this->fileStateByPath[$path] = [ |
| 67 | self::EXISTS => false, |
| 68 | self::SIZE => false, |
| 69 | self::SHA1 => false |
| 70 | ]; |
| 71 | } |
| 72 | |
| 73 | /** |
| 74 | * Get the hypothetical existance a file given predicated and current state of files |
| 75 | * |
| 76 | * @param string $path Storage path |
| 77 | * @param Closure $curExistenceFunc Function to compute the current existence for a given path |
| 78 | * @return bool|null Whether the file exists; null on error |
| 79 | */ |
| 80 | public function resolveFileExistence( string $path, $curExistenceFunc ) { |
| 81 | return self::resolveFileProperty( $path, self::EXISTS, $curExistenceFunc ); |
| 82 | } |
| 83 | |
| 84 | /** |
| 85 | * Get the hypothetical size of a file given predicated and current state of files |
| 86 | * |
| 87 | * @param string $path Storage path |
| 88 | * @param Closure $curSizeFunc Function to compute the current size for a given path |
| 89 | * @return int|false Bytes; false on error |
| 90 | */ |
| 91 | public function resolveFileSize( string $path, $curSizeFunc ) { |
| 92 | return self::resolveFileProperty( $path, self::SIZE, $curSizeFunc ); |
| 93 | } |
| 94 | |
| 95 | /** |
| 96 | * Get the hypothetical SHA-1 hash of a file given predicated and current state of files |
| 97 | * |
| 98 | * @param string $path Storage path |
| 99 | * @param Closure $curSha1Func Function to compute the current SHA-1 hash for a given path |
| 100 | * @return string|false Base 36 SHA-1 hash; false on error |
| 101 | */ |
| 102 | public function resolveFileSha1Base36( string $path, $curSha1Func ) { |
| 103 | return self::resolveFileProperty( $path, self::SHA1, $curSha1Func ); |
| 104 | } |
| 105 | |
| 106 | /** |
| 107 | * @param string $path Storage path |
| 108 | * @param string $property One of (self::EXISTS, self::SIZE, self::SHA1) |
| 109 | * @param Closure $curValueFunc Function to compute the current value for a given path |
| 110 | * @return mixed |
| 111 | */ |
| 112 | private function resolveFileProperty( $path, $property, $curValueFunc ) { |
| 113 | if ( isset( $this->fileStateByPath[$path] ) ) { |
| 114 | // File is predicated to have a counterfactual state |
| 115 | $value = $this->fileStateByPath[$path][$property]; |
| 116 | if ( $value instanceof Closure ) { |
| 117 | $value = $value(); |
| 118 | $this->fileStateByPath[$path][$property] = $value; |
| 119 | } |
| 120 | } else { |
| 121 | // File is not predicated to have a counterfactual state; use the current state |
| 122 | $value = $curValueFunc( $path ); |
| 123 | } |
| 124 | |
| 125 | return $value; |
| 126 | } |
| 127 | |
| 128 | /** |
| 129 | * @param string[] $paths List of storage paths |
| 130 | * @return self Clone predicates limited to the given paths |
| 131 | */ |
| 132 | public function snapshot( array $paths ) { |
| 133 | $snapshot = new self(); |
| 134 | foreach ( $paths as $path ) { |
| 135 | if ( isset( $this->fileStateByPath[$path] ) ) { |
| 136 | $snapshot->fileStateByPath[$path] = $this->fileStateByPath[$path]; |
| 137 | } |
| 138 | } |
| 139 | |
| 140 | return $snapshot; |
| 141 | } |
| 142 | } |