| 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 | |