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<?php
use Wikimedia\ObjectCache\APCUBagOStuff;
use Wikimedia\ObjectCache\BagOStuff;
use Wikimedia\ObjectCache\EmptyBagOStuff;
/**
* Generate hash digests of file contents to help with cache invalidation.
*
* 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 2 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, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
* http://www.gnu.org/copyleft/gpl.html
*
* @file
*/
class FileContentsHasher {
private const ALGO = 'md4';
/** @var BagOStuff */
protected $cache;
/** @var FileContentsHasher */
private static $instance;
public function __construct() {
$this->cache = function_exists( 'apcu_fetch' ) ? new APCUBagOStuff() : new EmptyBagOStuff();
}
/**
* Get the singleton instance of this class.
*
* @return FileContentsHasher
*/
public static function singleton() {
if ( !self::$instance ) {
self::$instance = new self;
}
return self::$instance;
}
/**
* Get a hash of a file's contents, either by retrieving a previously-
* computed hash from the cache, or by computing a hash from the file.
*
* @param string $filePath Full path to the file.
* @return string|bool Hash of file contents, or false if the file could not be read.
*/
private function getFileContentsHashInternal( $filePath ) {
// phpcs:ignore Generic.PHP.NoSilencedErrors.Discouraged
$mtime = @filemtime( $filePath );
if ( $mtime === false ) {
return false;
}
$cacheKey = $this->cache->makeGlobalKey( __CLASS__, $filePath, $mtime, self::ALGO );
return $this->cache->getWithSetCallback(
$cacheKey,
$this->cache::TTL_DAY,
static function () use ( $filePath ) {
// phpcs:ignore Generic.PHP.NoSilencedErrors.Discouraged
$contents = @file_get_contents( $filePath );
if ( $contents === false ) {
// Don't cache false
return false;
}
return hash( self::ALGO, $contents );
}
);
}
/**
* Get a hash of the combined contents of one or more files, either by
* retrieving a previously-computed hash from the cache, or by computing
* a hash from the files.
*
* @param string|string[] $filePaths One or more file paths.
* @return string|bool Hash of files' contents, or false if no file could not be read.
*/
public static function getFileContentsHash( $filePaths ) {
$instance = self::singleton();
if ( !is_array( $filePaths ) ) {
$filePaths = (array)$filePaths;
}
if ( count( $filePaths ) === 1 ) {
$hash = $instance->getFileContentsHashInternal( $filePaths[0] );
return $hash;
}
sort( $filePaths );
$hashes = [];
foreach ( $filePaths as $filePath ) {
$hashes[] = $instance->getFileContentsHashInternal( $filePath ) ?: '';
}
$hashes = implode( '', $hashes );
return $hashes ? hash( self::ALGO, $hashes ) : false;
}
}
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