wikimedia / mediawiki

includes/libs/RiffExtractor.php

<?php

For compatibility and reusability of your code, PSR1 recommends that a file should introduce either new symbols (like classes, functions, etc.) or have side-effects (like outputting something, or including other files), but not both at the same time. The first symbol is defined on line 25 and the first side effect is on line 99.

/**
 * Extractor for the Resource Interchange File Format
 *
 * 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
 * @author Bryan Tong Minh
 * @ingroup Media
 */

class RiffExtractor {
	public static function findChunksFromFile( $filename, $maxChunks = -1 ) {
		$file = fopen( $filename, 'rb' );
		$info = self::findChunks( $file, $maxChunks );
		fclose( $file );
		return $info;
	}

	public static function findChunks( $file, $maxChunks = -1 ) {
		$riff = fread( $file, 4 );
		if ( $riff !== 'RIFF' ) {
			return false;
		}

		// Next four bytes are fileSize
		$fileSize = fread( $file, 4 );
		if ( !$fileSize || strlen( $fileSize ) != 4 ) {
			return false;
		}

		// Next four bytes are the FourCC
		$fourCC = fread( $file, 4 );
		if ( !$fourCC || strlen( $fourCC ) != 4 ) {
			return false;
		}

		// Create basic info structure
		$info = [
			'fileSize' => self::extractUInt32( $fileSize ),
			'fourCC' => $fourCC,
			'chunks' => [],
		];
		$numberOfChunks = 0;

		// Find out the chunks
		while ( !feof( $file ) && !( $numberOfChunks >= $maxChunks && $maxChunks >= 0 ) ) {
			$chunkStart = ftell( $file );

			$chunkFourCC = fread( $file, 4 );
			if ( !$chunkFourCC || strlen( $chunkFourCC ) != 4 ) {
				return $info;
			}

			$chunkSize = fread( $file, 4 );
			if ( !$chunkSize || strlen( $chunkSize ) != 4 ) {
				return $info;
			}
			$intChunkSize = self::extractUInt32( $chunkSize );

			// Add chunk info to the info structure
			$info['chunks'][] = [
				'fourCC' => $chunkFourCC,
				'start' => $chunkStart,
				'size' => $intChunkSize
			];

			// Uneven chunks have padding bytes
			$padding = $intChunkSize % 2;
			// Seek to the next chunk
			fseek( $file, $intChunkSize + $padding, SEEK_CUR );

		}

		return $info;
	}

	/**
	 * Extract a little-endian uint32 from a 4 byte string
	 * @param string $string 4-byte string
	 * @return int
	 */
	public static function extractUInt32( $string ) {
		return unpack( 'V', $string )[1];
	}
};