includes/libs/RiffExtractor.php

   1 <?php
   2 /**
   3  * Extractor for the Resource Interchange File Format
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  * @author Bryan Tong Minh
  22  * @ingroup Media
  23  */
  24
  25 class RiffExtractor {
  26         public static function findChunksFromFile( $filename, $maxChunks = -1 ) {
  27                 $file = fopen( $filename, 'rb' );
  28                 $info = self::findChunks( $file, $maxChunks );
  29                 fclose( $file );
  30                 return $info;
  31         }
  32
  33         public static function findChunks( $file, $maxChunks = -1 ) {
  34                 $riff = fread( $file, 4 );
  35                 if ( $riff !== 'RIFF' ) {
  36                         return false;
  37                 }
  38
  39                 // Next four bytes are fileSize
  40                 $fileSize = fread( $file, 4 );
  41                 if ( !$fileSize || strlen( $fileSize ) != 4 ) {
  42                         return false;
  43                 }
  44
  45                 // Next four bytes are the FourCC
  46                 $fourCC = fread( $file, 4 );
  47                 if ( !$fourCC || strlen( $fourCC ) != 4 ) {
  48                         return false;
  49                 }
  50
  51                 // Create basic info structure
  52                 $info = array(
  53                         'fileSize' => self::extractUInt32( $fileSize ),
  54                         'fourCC' => $fourCC,
  55                         'chunks' => array(),
  56                 );
  57                 $numberOfChunks = 0;
  58
  59                 // Find out the chunks
  60                 while ( !feof( $file ) && !( $numberOfChunks >= $maxChunks && $maxChunks >= 0 ) ) {
  61                         $chunkStart = ftell( $file );
  62
  63                         $chunkFourCC = fread( $file, 4 );
  64                         if ( !$chunkFourCC || strlen( $chunkFourCC ) != 4 ) {
  65                                 return $info;
  66                         }
  67
  68                         $chunkSize = fread( $file, 4 );
  69                         if ( !$chunkSize || strlen( $chunkSize ) != 4 ) {
  70                                 return $info;
  71                         }
  72                         $intChunkSize = self::extractUInt32( $chunkSize );
  73
  74                         // Add chunk info to the info structure
  75                         $info['chunks'][] = array(
  76                                 'fourCC' => $chunkFourCC,
  77                                 'start' => $chunkStart,
  78                                 'size' => $intChunkSize
  79                         );
  80
  81                         // Uneven chunks have padding bytes
  82                         $padding = $intChunkSize % 2;
  83                         // Seek to the next chunk
  84                         fseek( $file, $intChunkSize + $padding, SEEK_CUR );
  85
  86                 }
  87
  88                 return $info;
  89         }
  90
  91         /**
  92          * Extract a little-endian uint32 from a 4 byte string
  93          * @param string $string 4-byte string
  94          * @return int
  95          */
  96         public static function extractUInt32( $string ) {
  97                 $unpacked = unpack( 'V', $string );
  98                 return $unpacked[1];
  99         }
 100 };