1 files changed, 114 insertions, 0 deletions
diff --git a/www/wiki/includes/utils/FileContentsHasher.php b/www/wiki/includes/utils/FileContentsHasher.php
new file mode 100644
index 00000000..e390f217
--- /dev/null
+++ b/www/wiki/includes/utils/FileContentsHasher.php
@@ -0,0 +1,114 @@
+<?php
+/**
+ * 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 {
+
+	/** @var BagOStuff */
+	protected $cache;
+
+	/** @var FileContentsHasher */
+	private static $instance;
+
+	public function __construct() {
+		$this->cache = ObjectCache::getLocalServerInstance( 'hash' );
+	}
+
+	/**
+	 * Get the singleton instance of this class.
+	 *
+	 * @return FileContentsHasher
+	 */
+	public static function singleton() {
+		if ( !self::$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.
+	 *
+	 * @private
+	 * @param string $filePath Full path to the file.
+	 * @param string $algo Name of selected hashing algorithm.
+	 * @return string|bool Hash of file contents, or false if the file could not be read.
+	 */
+	public 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;
+	}
+
+	/**
+	 * 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.
+	 * @param string $algo Name of selected hashing algorithm.
+	 * @return string|bool Hash of files' contents, or false if no file could not be read.
+	 */
+	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 = array_map( function ( $filePath ) use ( $instance, $algo ) {
+			return $instance->getFileContentsHashInternal( $filePath, $algo ) ?: '';
+		}, $filePaths );
+
+		Wikimedia\restoreWarnings();
+
+		$hashes = implode( '', $hashes );
+		return $hashes ? hash( $algo, $hashes ) : false;
+	}
+}