71 lines
1.9 KiB
Java
71 lines
1.9 KiB
Java
|
/*
|
||
|
|
* 11/19/04 : 1.0 moved to LGPL.
|
||
|
|
*
|
||
|
|
* 02/12/99 : Java Conversion by E.B , javalayer@javazoom.net
|
||
|
|
*
|
||
|
|
* @(#) crc.h 1.5, last edit: 6/15/94 16:55:32
|
||
|
|
* @(#) Copyright (C) 1993, 1994 Tobias Bading (bading@cs.tu-berlin.de)
|
||
|
|
* @(#) Berlin University of Technology
|
||
|
|
*-----------------------------------------------------------------------
|
||
|
|
* This program is free software; you can redistribute it and/or modify
|
||
|
|
* it under the terms of the GNU Library 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 Library General Public License for more details.
|
||
|
|
*
|
||
|
|
* You should have received a copy of the GNU Library General Public
|
||
|
|
* License along with this program; if not, write to the Free Software
|
||
|
|
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
|
||
|
|
*----------------------------------------------------------------------
|
||
|
|
*/
|
||
|
|
package javazoom.jl.decoder;
|
||
|
|
|
||
|
|
/**
|
||
|
|
* 16-Bit CRC checksum
|
||
|
|
*/
|
||
|
|
public final class Crc16
|
||
|
|
{
|
||
|
|
private static short polynomial=(short)0x8005;
|
||
|
|
private short crc;
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Dummy Constructor
|
||
|
|
*/
|
||
|
|
public Crc16()
|
||
|
|
{
|
||
|
|
crc = (short) 0xFFFF;
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Feed a bitstring to the crc calculation (0 < length <= 32).
|
||
|
|
*/
|
||
|
|
public void add_bits (int bitstring, int length)
|
||
|
|
{
|
||
|
|
int bitmask = 1 << (length - 1);
|
||
|
|
do
|
||
|
|
if (((crc & 0x8000) == 0) ^ ((bitstring & bitmask) == 0 ))
|
||
|
|
{
|
||
|
|
crc <<= 1;
|
||
|
|
crc ^= polynomial;
|
||
|
|
}
|
||
|
|
else
|
||
|
|
crc <<= 1;
|
||
|
|
while ((bitmask >>>= 1) != 0);
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Return the calculated checksum.
|
||
|
|
* Erase it for next calls to add_bits().
|
||
|
|
*/
|
||
|
|
public short checksum()
|
||
|
|
{
|
||
|
|
short sum = crc;
|
||
|
|
crc = (short) 0xFFFF;
|
||
|
|
return sum;
|
||
|
|
}
|
||
|
|
}
|