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Diffstat (limited to 'songdbj/javazoom/jl/decoder/Crc16.java')
-rw-r--r-- | songdbj/javazoom/jl/decoder/Crc16.java | 70 |
1 files changed, 70 insertions, 0 deletions
diff --git a/songdbj/javazoom/jl/decoder/Crc16.java b/songdbj/javazoom/jl/decoder/Crc16.java new file mode 100644 index 0000000000..c35cc19341 --- /dev/null +++ b/songdbj/javazoom/jl/decoder/Crc16.java | |||
@@ -0,0 +1,70 @@ | |||
1 | /* | ||
2 | * 11/19/04 : 1.0 moved to LGPL. | ||
3 | * | ||
4 | * 02/12/99 : Java Conversion by E.B , javalayer@javazoom.net | ||
5 | * | ||
6 | * @(#) crc.h 1.5, last edit: 6/15/94 16:55:32 | ||
7 | * @(#) Copyright (C) 1993, 1994 Tobias Bading (bading@cs.tu-berlin.de) | ||
8 | * @(#) Berlin University of Technology | ||
9 | *----------------------------------------------------------------------- | ||
10 | * This program is free software; you can redistribute it and/or modify | ||
11 | * it under the terms of the GNU Library General Public License as published | ||
12 | * by the Free Software Foundation; either version 2 of the License, or | ||
13 | * (at your option) any later version. | ||
14 | * | ||
15 | * This program is distributed in the hope that it will be useful, | ||
16 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
17 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | ||
18 | * GNU Library General Public License for more details. | ||
19 | * | ||
20 | * You should have received a copy of the GNU Library General Public | ||
21 | * License along with this program; if not, write to the Free Software | ||
22 | * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. | ||
23 | *---------------------------------------------------------------------- | ||
24 | */ | ||
25 | package javazoom.jl.decoder; | ||
26 | |||
27 | /** | ||
28 | * 16-Bit CRC checksum | ||
29 | */ | ||
30 | public final class Crc16 | ||
31 | { | ||
32 | private static short polynomial=(short)0x8005; | ||
33 | private short crc; | ||
34 | |||
35 | /** | ||
36 | * Dummy Constructor | ||
37 | */ | ||
38 | public Crc16() | ||
39 | { | ||
40 | crc = (short) 0xFFFF; | ||
41 | } | ||
42 | |||
43 | /** | ||
44 | * Feed a bitstring to the crc calculation (0 < length <= 32). | ||
45 | */ | ||
46 | public void add_bits (int bitstring, int length) | ||
47 | { | ||
48 | int bitmask = 1 << (length - 1); | ||
49 | do | ||
50 | if (((crc & 0x8000) == 0) ^ ((bitstring & bitmask) == 0 )) | ||
51 | { | ||
52 | crc <<= 1; | ||
53 | crc ^= polynomial; | ||
54 | } | ||
55 | else | ||
56 | crc <<= 1; | ||
57 | while ((bitmask >>>= 1) != 0); | ||
58 | } | ||
59 | |||
60 | /** | ||
61 | * Return the calculated checksum. | ||
62 | * Erase it for next calls to add_bits(). | ||
63 | */ | ||
64 | public short checksum() | ||
65 | { | ||
66 | short sum = crc; | ||
67 | crc = (short) 0xFFFF; | ||
68 | return sum; | ||
69 | } | ||
70 | } | ||