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 | /* ========================================================================= */ |
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 | /* ========================================================================= */ |
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 | |