1/*
2 * COPYRIGHT (C) 1986 Gary S. Brown. You may use this program, or
3 * code or tables extracted from it, as desired without restriction.
4 *
5 * First, the polynomial itself and its table of feedback terms. The
6 * polynomial is
7 * 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
8 *

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26 * The feedback terms table consists of 256, 32-bit entries. Notes
27 *
28 * The table can be generated at runtime if desired; code to do so
29 * is shown later. It might not be obvious, but the feedback
30 * terms simply represent the results of eight shift/xor opera
31 * tions for all combinations of data and CRC register values
32 *
33 * The values must be right-shifted by eight bits by the "updcrc
34 * logic; the shift must be unsigned (bring in zeroes). On some
35 * hardware you could probably optimize the shift in assembler by
36 * using byte-swap instructions
37 * polynomial $edb88320
38 */
39
40
41#include "includes.h"
42RCSID("$OpenBSD: crc32.c,v 1.7 2000/09/07 20:27:51 deraadt Exp $");
43
44#include "crc32.h"
45
46static unsigned int crc32_tab[] = {
47 0x00000000L, 0x77073096L, 0xee0e612cL, 0x990951baL, 0x076dc419L,
48 0x706af48fL, 0xe963a535L, 0x9e6495a3L, 0x0edb8832L, 0x79dcb8a4L,
49 0xe0d5e91eL, 0x97d2d988L, 0x09b64c2bL, 0x7eb17cbdL, 0xe7b82d07L,
50 0x90bf1d91L, 0x1db71064L, 0x6ab020f2L, 0xf3b97148L, 0x84be41deL,
51 0x1adad47dL, 0x6ddde4ebL, 0xf4d4b551L, 0x83d385c7L, 0x136c9856L,
52 0x646ba8c0L, 0xfd62f97aL, 0x8a65c9ecL, 0x14015c4fL, 0x63066cd9L,
53 0xfa0f3d63L, 0x8d080df5L, 0x3b6e20c8L, 0x4c69105eL, 0xd56041e4L,
54 0xa2677172L, 0x3c03e4d1L, 0x4b04d447L, 0xd20d85fdL, 0xa50ab56bL,

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95 0xbdbdf21cL, 0xcabac28aL, 0x53b39330L, 0x24b4a3a6L, 0xbad03605L,
96 0xcdd70693L, 0x54de5729L, 0x23d967bfL, 0xb3667a2eL, 0xc4614ab8L,
97 0x5d681b02L, 0x2a6f2b94L, 0xb40bbe37L, 0xc30c8ea1L, 0x5a05df1bL,
98 0x2d02ef8dL
99};
100
101/* Return a 32-bit CRC of the contents of the buffer. */
102
103unsigned int
104ssh_crc32(const unsigned char *s, unsigned int len)
105{
106 unsigned int i;
107 unsigned int crc32val;
108
109 crc32val = 0;
110 for (i = 0; i < len; i ++) {
111 crc32val = crc32_tab[(crc32val ^ s[i]) & 0xff] ^ (crc32val >> 8);
112 }
113 return crc32val;
114}