mirror of
https://github.com/fadden/nulib2.git
synced 2024-11-01 18:05:42 +00:00
111 lines
4.9 KiB
C
111 lines
4.9 KiB
C
/*
|
|
* NuFX archive manipulation library
|
|
* Copyright (C) 2000-2003 by Andy McFadden, All Rights Reserved.
|
|
* This is free software; you can redistribute it and/or modify it under the
|
|
* terms of the GNU Library General Public License, see the file COPYING-LIB.
|
|
*
|
|
* Compute 16-bit CRCs. Depending on the hardware, the table version
|
|
* might be slower than the loop computation.
|
|
*/
|
|
#define __Crc16_c__ 1
|
|
#include "NufxLibPriv.h"
|
|
|
|
#define CRC_TAB
|
|
#ifdef CRC_TAB
|
|
/*
|
|
* updcrc macro derived from article Copyright (C) 1986 Stephen Satchell.
|
|
* NOTE: First srgument must be in range 0 to 255.
|
|
* Second argument is referenced twice.
|
|
*
|
|
* Programmers may incorporate any or all code into their programs,
|
|
* giving proper credit within the source. Publication of the
|
|
* source routines is permitted so long as proper credit is given
|
|
* to Stephen Satchell, Satchell Evaluations and Chuck Forsberg,
|
|
* Omen Technology.
|
|
*/
|
|
|
|
|
|
/*#define updcrc(cp, crc) ( crctab[((crc >> 8) & 255)] ^ (crc << 8) ^ cp)*/
|
|
#define updcrc(cp, crc) ( (crctab[((crc >> 8) & 0xFF) ^ cp] ^ (crc << 8)) & 0xFFFF)
|
|
|
|
|
|
/* crctab calculated by Mark G. Mendel, Network Systems Corporation */
|
|
const ushort gNuCrc16Table[256] = {
|
|
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
|
|
};
|
|
#endif
|
|
|
|
|
|
/*
|
|
* Calculate CRC on a region
|
|
*
|
|
* A CRC is the result of a mathematical operation based on the
|
|
* coefficients of a polynomial when multiplied by X^16 then divided by
|
|
* the generator polynomial (X^16 + X^12 + X^5 + 1) using modulo two
|
|
* arithmetic.
|
|
*
|
|
* This routine is a slightly modified verison of one found in:
|
|
* _Advanced Programming Techniques for the Apple //gs Toolbox_
|
|
* By Morgan Davis and Dan Gookin (Compute! Publications, Inc.)
|
|
* It can either calculate the CRC bit-by-bit or use a table.
|
|
*
|
|
* Depending on CPU architecture, one may be dramatically faster than
|
|
* the other.
|
|
*/
|
|
ushort
|
|
Nu_CalcCRC16(ushort seed, const uchar* ptr, int count)
|
|
{
|
|
ushort CRC = seed;
|
|
#ifndef CRC_TAB
|
|
int x;
|
|
Assert(sizeof(ushort) == 2); /* I think this is assumed */
|
|
#endif
|
|
|
|
do {
|
|
#ifndef CRC_TAB
|
|
CRC ^= *ptr++ << 8; /* XOR hi-byte of CRC w/dat */
|
|
for (x = 8; x; --x) /* Then, for 8 bit shifts... */
|
|
if (CRC & 0x8000) /* Test hi order bit of CRC */
|
|
CRC = CRC << 1 ^ 0x1021; /* if set, shift & XOR w/$1021 */
|
|
else
|
|
CRC <<= 1; /* Else, just shift left once. */
|
|
#else
|
|
CRC = Nu_UpdateCRC16(*ptr++, CRC); /* look up new value in table */
|
|
#endif
|
|
} while (--count);
|
|
|
|
return (CRC);
|
|
}
|
|
|