/*% cc -O -K -dos % -o crc.exe
*/

/*
 *  Crc - 32 BIT ANSI X3.66 CRC checksum files
 */
#include <stdio.h>
#define OK 0
#define ERROR (-1)
#define LINT_ARGS

/**********************************************************************\
|*                                                                    *|
|* Demonstration program to compute the 32-bit CRC used as the frame  *|
|* check sequence in ADCCP (ANSI X3.66, also known as FIPS PUB 71     *|
|* and FED-STD-1003, the U.S. versions of CCITT's X.25 link-level     *|
|* protocol).  The 32-bit FCS was added via the Federal Register,     *|
|* 1 June 1982, p.23798.  I presume but don't know for certain that   *|
|* this polynomial is or will be included in CCITT V.41, which        *|
|* defines the 16-bit CRC (often called CRC-CCITT) polynomial.  FIPS  *|
|* PUB 78 says that the 32-bit FCS reduces otherwise undetected       *|
|* errors by a factor of 10^-5 over 16-bit FCS.                       *|
|*                                                                    *|
\**********************************************************************/

/* Need an unsigned type capable of holding 32 bits; */
typedef unsigned long int UNS_32_BITS;

/*
 * Copyright (C) 1986 Gary S. Brown.  You may use this program, or
 * code or tables extracted from it, as desired without restriction.
 */
/* First, the polynomial itself and its table of feedback terms.  The  */
/* polynomial is                                                       */
/* X^32+X^26+X^23+X^22+X^16+X^12+X^11+X^10+X^8+X^7+X^5+X^4+X^2+X^1+X^0 */
/* Note that we take it "backwards" and put the highest-order term in  */
/* the lowest-order bit.  The X^32 term is "implied"; the LSB is the   */
/* X^31 term, etc.  The X^0 term (usually shown as "+1") results in    */
/* the MSB being 1.                                                    */

/* Note that the usual hardware shift register implementation, which   */
/* is what we're using (we're merely optimizing it by doing eight-bit  */
/* chunks at a time) shifts bits into the lowest-order term.  In our   */
/* implementation, that means shifting towards the right.  Why do we   */
/* do it this way?  Because the calculated CRC must be transmitted in  */
/* order from highest-order term to lowest-order term.  UARTs transmit */
/* characters in order from LSB to MSB.  By storing the CRC this way,  */
/* we hand it to the UART in the order low-byte to high-byte; the UART */
/* sends each low-bit to hight-bit; and the result is transmission bit */
/* by bit from highest- to lowest-order term without requiring any bit */
/* shuffling on our part.  Reception works similarly.                  */

/* The feedback terms table consists of 256, 32-bit entries.  Notes:   */
/*                                                                     */
/*  1. The table can be generated at runtime if desired; code to do so */
/*     is shown later.  It might not be obvious, but the feedback      */
/*     terms simply represent the results of eight shift/xor opera-    */
/*     tions for all combinations of data and CRC register values.     */
/*                                                                     */
/*  2. The CRC accumulation logic is the same for all CRC polynomials, */
/*     be they sixteen or thirty-two bits wide.  You simply choose the */
/*     appropriate table.  Alternatively, because the table can be     */
/*     generated at runtime, you can start by generating the table for */
/*     the polynomial in question and use exactly the same "updcrc",   */
/*     if your application needn't simultaneously handle two CRC       */
/*     polynomials.  (Note, however, that XMODEM is strange.)          */
/*                                                                     */
/*  3. For 16-bit CRCs, the table entries need be only 16 bits wide;   */
/*     of course, 32-bit entries work OK if the high 16 bits are zero. */
/*                                                                     */
/*  4. The values must be right-shifted by eight bits by the "updcrc"  */
/*     logic; the shift must be unsigned (bring in zeroes).  On some   */
/*     hardware you could probably optimize the shift in assembler by  */
/*     using byte-swap instructions.                                   */

static UNS_32_BITS crc_32_tab[] = { /* CRC polynomial 0xedb88320 */
0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f, 0xe963a535, 0x9e6495a3,
0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91,
0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de, 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9, 0xfa0f3d63, 0x8d080df5,
0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599, 0xb8bda50f,
0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924, 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d,
0x76dc4190, 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433,
0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457,
0x65b0d9c6, 0x12b7e950, 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb,
0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9,
0x5005713c, 0x270241aa, 0xbe0b1010, 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad,
0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683,
0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8, 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1,
0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb, 0x196c3671, 0x6e6b06e7,
0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef, 0x4669be79,
0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236, 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f,
0xc5ba3bbe, 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,
0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21,
0x86d3d2d4, 0xf1d4e242, 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45,
0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db,
0xaed16a4a, 0xd9d65adc, 0x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, 0xcdd70693, 0x54de5729, 0x23d967bf,
0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d
};

#define UPDC32(octet, crc) (crc_32_tab[((crc) ^ (octet)) & 0xff] ^ ((crc) >> 8))

int Block = 0;		/* Pad file with 032's to multiple of Block */

main(argc, argv)
char **argv;
{
	register errors = 0;

	if (! strcmp(argv[1], "-x")) {
		Block = 128; --argc; ++argv;
	}
	if (! strcmp(argv[1], "-k")) {
		Block = 1024; --argc; ++argv;
	}
	while( --argc > 0)
		errors |= crc32file( *++argv);
	exit(errors != 0);
}

crc32file(name)
char *name;
{
	register FILE *fin;
	register unsigned long oldcrc32;
	register unsigned long crc32;
	register unsigned long oldcrc;
	register c;
	register long charcnt;
	register long l;

	oldcrc32 = 0xFFFFFFFF; charcnt = 0;
#ifdef M_I86SM
	if ((fin=fopen(name, "rb"))==NULL)
#else
	if ((fin=fopen(name, "r"))==NULL)
#endif
	{
		perror(name);
		return ERROR;
	}
	while ((c=getc(fin))!=EOF) {
		++charcnt;
		oldcrc32 = UPDC32(c, oldcrc32);
	}

	if (ferror(fin)) {
		perror(name);
		fclose(fin); return ERROR;
	}
	else {
		if (Block) {
			for (l = charcnt; l % Block; ++l)
				oldcrc32 = UPDC32(032, oldcrc32);
		}
		crc32 = oldcrc32;  oldcrc = oldcrc32 = ~oldcrc32;

		printf("%08lX %7ld ", oldcrc, charcnt);
		if (Block == 128)
			printf("%5ld+%3ld ", charcnt/Block, charcnt%Block);
		if (Block == 1024)
			printf("%5ld+%4ld ", charcnt/Block, charcnt%Block);
		printf(" %s\n", name);
	}

	fclose(fin); return OK;
}

