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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 = [ |
53 | 'fileSize' => self::extractUInt32( $fileSize ), |
54 | 'fourCC' => $fourCC, |
55 | 'chunks' => [], |
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'][] = [ |
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 | return unpack( 'V', $string )[1]; |
98 | } |
99 | } |