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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];
}
};
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