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+<?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];
+ }
+};