<?php /** * 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 = array( 'fileSize' => self::extractUInt32( $fileSize ), 'fourCC' => $fourCC, 'chunks' => array(), ); $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'][] = array( '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 ) { $unpacked = unpack( 'V', $string ); return $unpacked[1]; } };