1 /* $NetBSD: crc32.c,v 1.4 2009/03/26 22:18:14 he Exp $ */
2
3 /* crc32.c -- compute the CRC-32 of a data stream
4 *
5 * Adapted from zlib's crc code.
6 *
7 * Copyright (C) 1995-2005 Mark Adler
8 * For conditions of distribution and use, see copyright notice in zlib.h
9 *
10 * Thanks to Rodney Brown <rbrown64@csc.com.au> for his contribution of faster
11 * CRC methods: exclusive-oring 32 bits of data at a time, and pre-computing
12 * tables for updating the shift register in one step with three exclusive-ors
13 * instead of four steps with four exclusive-ors. This results in about a
14 * factor of two increase in speed on a Power PC G4 (PPC7455) using gcc -O3.
15 */
16
17 /* @(#) Id */
18
19 #include <sys/param.h>
20 #include <machine/endian.h>
21
22 typedef uint32_t u4;
23
24 /* Definitions for doing the crc four data bytes at a time. */
25 #define REV(w) (((w)>>24)+(((w)>>8)&0xff00)+ \
26 (((w)&0xff00)<<8)+(((w)&0xff)<<24))
27
28 /* ========================================================================
29 * Tables of CRC-32s of all single-byte values, made by make_crc_table().
30 */
31 #include <lib/libkern/libkern.h>
32 #include "crc32.h"
33
34 #if BYTE_ORDER == LITTLE_ENDIAN
35 /* ========================================================================= */
36 #define DOLIT4 c ^= *buf4++; \
37 c = crc_table[3][c & 0xff] ^ crc_table[2][(c >> 8) & 0xff] ^ \
38 crc_table[1][(c >> 16) & 0xff] ^ crc_table[0][c >> 24]
39 #define DOLIT32 DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4
40
41 /* ========================================================================= */
crc32(uint32_t crc,const uint8_t * buf,size_t len)42 uint32_t crc32(uint32_t crc, const uint8_t *buf, size_t len)
43 {
44 register u4 c;
45 register const u4 *buf4;
46
47 if (buf == NULL) return 0UL;
48
49 c = (u4)crc;
50 c = ~c;
51 while (len && ((uintptr_t)buf & 3)) {
52 c = crc_table[0][(c ^ *buf++) & 0xff] ^ (c >> 8);
53 len--;
54 }
55
56 buf4 = (const u4 *)(const void *)buf;
57 while (len >= 32) {
58 DOLIT32;
59 len -= 32;
60 }
61 while (len >= 4) {
62 DOLIT4;
63 len -= 4;
64 }
65 buf = (const unsigned char *)buf4;
66
67 if (len) do {
68 c = crc_table[0][(c ^ *buf++) & 0xff] ^ (c >> 8);
69 } while (--len);
70 c = ~c;
71 return (uint32_t)c;
72 }
73
74 #else /* BIG_ENDIAN */
75
76 /* ========================================================================= */
77 #define DOBIG4 c ^= *++buf4; \
78 c = crc_table[4][c & 0xff] ^ crc_table[5][(c >> 8) & 0xff] ^ \
79 crc_table[6][(c >> 16) & 0xff] ^ crc_table[7][c >> 24]
80 #define DOBIG32 DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4
81
82 /* ========================================================================= */
crc32(uint32_t crc,const uint8_t * buf,size_t len)83 uint32_t crc32(uint32_t crc, const uint8_t *buf, size_t len)
84 {
85 register u4 c;
86 register const u4 *buf4;
87
88 if (buf == NULL) return 0UL;
89
90 c = REV((u4)crc);
91 c = ~c;
92 while (len && ((uintptr_t)buf & 3)) {
93 c = crc_table[4][(c >> 24) ^ *buf++] ^ (c << 8);
94 len--;
95 }
96
97 buf4 = (const u4 *)(const void *)buf;
98 buf4--;
99 while (len >= 32) {
100 DOBIG32;
101 len -= 32;
102 }
103 while (len >= 4) {
104 DOBIG4;
105 len -= 4;
106 }
107 buf4++;
108 buf = (const unsigned char *)buf4;
109
110 if (len) do {
111 c = crc_table[4][(c >> 24) ^ *buf++] ^ (c << 8);
112 } while (--len);
113 c = ~c;
114 return (uint32_t)(REV(c));
115 }
116 #endif
117