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/*
* This file has been modified for the cdrkit suite.
*
* The behaviour and appearence of the program code below can differ to a major
* extent from the version distributed by the original author(s).
*
* For details, see Changelog file distributed with the cdrkit package. If you
* received this file from another source then ask the distributing person for
* a log of modifications.
*
*/
/* @(#)crc16.c 1.6 04/03/02 Copyright 1998-2004 J. Schilling */
/*
* Q-subchannel CRC subroutines
*
* Polynom is: p(x) = x ** 16 + x ** 12 + x ** 5 + 1
* If computed over 12 bytes, the result must be zero.
* On the disk the CRC bits are inverted.
*
* Copyright (c) 1998-2003 J. Schilling
*/
/*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2
* as published by the Free Software Foundation.
*
* 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; see the file COPYING. If not, write to the Free Software
* Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/
#include <mconfig.h>
#include <standard.h>
#include <utypes.h>
#include "crc16.h"
static UInt16_t updcrc(Uint p_crc, UInt8_t *cp, Uint cnt);
UInt16_t calcCRC(Uchar *buf, Uint bsize);
UInt16_t fillcrc(Uchar *buf, Uint bsize);
UInt16_t flip_crc_error_corr(Uchar *b, Uint bsize, Uint p_crc);
/* number of bits in CRC: don't change it. */
#define BPW 16
/* this the number of bits per char: don't change it. */
#define BPB 8
static UInt16_t crctab[1<<BPB] = {
0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50a5, 0x60c6, 0x70e7,
0x8108, 0x9129, 0xa14a, 0xb16b, 0xc18c, 0xd1ad, 0xe1ce, 0xf1ef,
0x1231, 0x0210, 0x3273, 0x2252, 0x52b5, 0x4294, 0x72f7, 0x62d6,
0x9339, 0x8318, 0xb37b, 0xa35a, 0xd3bd, 0xc39c, 0xf3ff, 0xe3de,
0x2462, 0x3443, 0x0420, 0x1401, 0x64e6, 0x74c7, 0x44a4, 0x5485,
0xa56a, 0xb54b, 0x8528, 0x9509, 0xe5ee, 0xf5cf, 0xc5ac, 0xd58d,
0x3653, 0x2672, 0x1611, 0x0630, 0x76d7, 0x66f6, 0x5695, 0x46b4,
0xb75b, 0xa77a, 0x9719, 0x8738, 0xf7df, 0xe7fe, 0xd79d, 0xc7bc,
0x48c4, 0x58e5, 0x6886, 0x78a7, 0x0840, 0x1861, 0x2802, 0x3823,
0xc9cc, 0xd9ed, 0xe98e, 0xf9af, 0x8948, 0x9969, 0xa90a, 0xb92b,
0x5af5, 0x4ad4, 0x7ab7, 0x6a96, 0x1a71, 0x0a50, 0x3a33, 0x2a12,
0xdbfd, 0xcbdc, 0xfbbf, 0xeb9e, 0x9b79, 0x8b58, 0xbb3b, 0xab1a,
0x6ca6, 0x7c87, 0x4ce4, 0x5cc5, 0x2c22, 0x3c03, 0x0c60, 0x1c41,
0xedae, 0xfd8f, 0xcdec, 0xddcd, 0xad2a, 0xbd0b, 0x8d68, 0x9d49,
0x7e97, 0x6eb6, 0x5ed5, 0x4ef4, 0x3e13, 0x2e32, 0x1e51, 0x0e70,
0xff9f, 0xefbe, 0xdfdd, 0xcffc, 0xbf1b, 0xaf3a, 0x9f59, 0x8f78,
0x9188, 0x81a9, 0xb1ca, 0xa1eb, 0xd10c, 0xc12d, 0xf14e, 0xe16f,
0x1080, 0x00a1, 0x30c2, 0x20e3, 0x5004, 0x4025, 0x7046, 0x6067,
0x83b9, 0x9398, 0xa3fb, 0xb3da, 0xc33d, 0xd31c, 0xe37f, 0xf35e,
0x02b1, 0x1290, 0x22f3, 0x32d2, 0x4235, 0x5214, 0x6277, 0x7256,
0xb5ea, 0xa5cb, 0x95a8, 0x8589, 0xf56e, 0xe54f, 0xd52c, 0xc50d,
0x34e2, 0x24c3, 0x14a0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405,
0xa7db, 0xb7fa, 0x8799, 0x97b8, 0xe75f, 0xf77e, 0xc71d, 0xd73c,
0x26d3, 0x36f2, 0x0691, 0x16b0, 0x6657, 0x7676, 0x4615, 0x5634,
0xd94c, 0xc96d, 0xf90e, 0xe92f, 0x99c8, 0x89e9, 0xb98a, 0xa9ab,
0x5844, 0x4865, 0x7806, 0x6827, 0x18c0, 0x08e1, 0x3882, 0x28a3,
0xcb7d, 0xdb5c, 0xeb3f, 0xfb1e, 0x8bf9, 0x9bd8, 0xabbb, 0xbb9a,
0x4a75, 0x5a54, 0x6a37, 0x7a16, 0x0af1, 0x1ad0, 0x2ab3, 0x3a92,
0xfd2e, 0xed0f, 0xdd6c, 0xcd4d, 0xbdaa, 0xad8b, 0x9de8, 0x8dc9,
0x7c26, 0x6c07, 0x5c64, 0x4c45, 0x3ca2, 0x2c83, 0x1ce0, 0x0cc1,
0xef1f, 0xff3e, 0xcf5d, 0xdf7c, 0xaf9b, 0xbfba, 0x8fd9, 0x9ff8,
0x6e17, 0x7e36, 0x4e55, 0x5e74, 0x2e93, 0x3eb2, 0x0ed1, 0x1ef0,
};
#define SUBSIZE 96 /* 12 bytes with 8 bits */
static UInt16_t
updcrc(Uint p_crc, register UInt8_t *cp, register Uint cnt)
{
register UInt16_t crc = p_crc;
while (cnt-- > 0) {
crc = (crc<<BPB) ^ crctab[(crc>>(BPW-BPB)) ^ (*cp++)];
}
return (crc);
}
/*static UInt16_t*/
UInt16_t
calcCRC(Uchar *buf, Uint bsize)
{
return (updcrc(0x0000, (UInt8_t *)buf, bsize));
}
/*
* CRC für Q-Sub füllen
*/
UInt16_t
fillcrc(Uchar *buf, Uint bsize)
{
UInt16_t crc = calcCRC(buf, bsize-2);
/*
* Invert CRC bits for RED Book compliance.
*/
crc = crc ^ 0xFFFF;
buf[bsize-2] = (crc >> 8) & 0xFF;
buf[bsize-1] = crc & 0xFF;
return (crc);
}
static UInt8_t fliptab[BPB] = {
0x01,
0x02,
0x04,
0x08,
0x10,
0x20,
0x40,
0x80,
};
UInt16_t
flip_crc_error_corr(Uchar *b, Uint bsize, Uint p_crc)
{
register UInt16_t crc = p_crc;
register Uint btsize = bsize * BPB;
if (crc != 0) {
int i;
for (i = 0; i < btsize; i++) {
UInt8_t c;
c = fliptab[i % BPB];
b[i / BPB] ^= c;
if ((crc = calcCRC(b, bsize)) == 0) {
return (crc);
}
b[i / BPB] ^= c;
}
}
return (crc & 0xffff);
}
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