FileContentsHasher.php

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<?php
class FileContentsHasher {
 
    protected $cache;
 
    private static $instance;
 
    public function __construct() {
        $this->cache = ObjectCache::getLocalServerInstance( 'hash' );
    }
 
    public static function singleton() {
        if ( !self::$instance ) {
            self::$instance = new self;
        }
 
        return self::$instance;
    }
 
    private function getFileContentsHashInternal( $filePath, $algo = 'md4' ) {
        $mtime = filemtime( $filePath );
        if ( $mtime === false ) {
            return false;
        }
 
        $cacheKey = $this->cache->makeGlobalKey( __CLASS__, $filePath, $mtime, $algo );
        $hash = $this->cache->get( $cacheKey );
 
        if ( $hash ) {
            return $hash;
        }
 
        $contents = file_get_contents( $filePath );
        if ( $contents === false ) {
            return false;
        }
 
        $hash = hash( $algo, $contents );
        $this->cache->set( $cacheKey, $hash, 60 * 60 * 24 );  // 24h
 
        return $hash;
    }
 
    public static function getFileContentsHash( $filePaths, $algo = 'md4' ) {
        $instance = self::singleton();
 
        if ( !is_array( $filePaths ) ) {
            $filePaths = (array)$filePaths;
        }
 
        Wikimedia\suppressWarnings();
 
        if ( count( $filePaths ) === 1 ) {
            $hash = $instance->getFileContentsHashInternal( $filePaths[0], $algo );
            Wikimedia\restoreWarnings();
            return $hash;
        }
 
        sort( $filePaths );
        $hashes = [];
        foreach ( $filePaths as $filePath ) {
            $hashes[] = $instance->getFileContentsHashInternal( $filePath, $algo ) ?: '';
        }
 
        Wikimedia\restoreWarnings();
 
        $hashes = implode( '', $hashes );
        return $hashes ? hash( $algo, $hashes ) : false;
    }
}