9fee0ec4ca
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@7101 a1c6a512-1295-4272-9138-f99709370657
70 lines
1.9 KiB
Java
70 lines
1.9 KiB
Java
/*
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* 11/19/04 : 1.0 moved to LGPL.
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*
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* 02/12/99 : Java Conversion by E.B , javalayer@javazoom.net
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*
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* @(#) crc.h 1.5, last edit: 6/15/94 16:55:32
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* @(#) Copyright (C) 1993, 1994 Tobias Bading (bading@cs.tu-berlin.de)
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* @(#) Berlin University of Technology
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*-----------------------------------------------------------------------
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU Library General Public License as published
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* by the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Library General Public License for more details.
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*
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* You should have received a copy of the GNU Library General Public
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* License along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*----------------------------------------------------------------------
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*/
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package javazoom.jl.decoder;
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/**
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* 16-Bit CRC checksum
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*/
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public final class Crc16
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{
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private static short polynomial=(short)0x8005;
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private short crc;
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/**
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* Dummy Constructor
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*/
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public Crc16()
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{
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crc = (short) 0xFFFF;
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}
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/**
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* Feed a bitstring to the crc calculation (0 < length <= 32).
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*/
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public void add_bits (int bitstring, int length)
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{
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int bitmask = 1 << (length - 1);
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do
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if (((crc & 0x8000) == 0) ^ ((bitstring & bitmask) == 0 ))
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{
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crc <<= 1;
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crc ^= polynomial;
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}
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else
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crc <<= 1;
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while ((bitmask >>>= 1) != 0);
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}
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/**
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* Return the calculated checksum.
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* Erase it for next calls to add_bits().
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*/
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public short checksum()
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{
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short sum = crc;
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crc = (short) 0xFFFF;
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return sum;
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}
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}
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