/* $NetBSD: crc32.c,v 1.4 2009/03/26 22:18:14 he Exp $ */
/* crc32.c -- compute the CRC-32 of a data stream
*
* Adapted from zlib's crc code.
*
* Copyright (C) 1995-2005 Mark Adler
* For conditions of distribution and use, see copyright notice in zlib.h
*
* Thanks to Rodney Brown <
[email protected]> for his contribution of faster
* CRC methods: exclusive-oring 32 bits of data at a time, and pre-computing
* tables for updating the shift register in one step with three exclusive-ors
* instead of four steps with four exclusive-ors. This results in about a
* factor of two increase in speed on a Power PC G4 (PPC7455) using gcc -O3.
*/
/* @(#) Id */
#include <sys/param.h>
#include <machine/endian.h>
typedef uint32_t u4;
/* Definitions for doing the crc four data bytes at a time. */
#define REV(w) (((w)>>24)+(((w)>>8)&0xff00)+ \
(((w)&0xff00)<<8)+(((w)&0xff)<<24))
/* ========================================================================
* Tables of CRC-32s of all single-byte values, made by make_crc_table().
*/
#include <lib/libkern/libkern.h>
#include "crc32.h"
#if BYTE_ORDER == LITTLE_ENDIAN
/* ========================================================================= */
#define DOLIT4 c ^= *buf4++; \
c = crc_table[3][c & 0xff] ^ crc_table[2][(c >> 8) & 0xff] ^ \
crc_table[1][(c >> 16) & 0xff] ^ crc_table[0][c >> 24]
#define DOLIT32 DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4
/* ========================================================================= */
uint32_t crc32(uint32_t crc, const uint8_t *buf, size_t len)
{
register u4 c;
register const u4 *buf4;
if (buf == NULL) return 0UL;
c = (u4)crc;
c = ~c;
while (len && ((uintptr_t)buf & 3)) {
c = crc_table[0][(c ^ *buf++) & 0xff] ^ (c >> 8);
len--;
}
buf4 = (const u4 *)(const void *)buf;
while (len >= 32) {
DOLIT32;
len -= 32;
}
while (len >= 4) {
DOLIT4;
len -= 4;
}
buf = (const unsigned char *)buf4;
if (len) do {
c = crc_table[0][(c ^ *buf++) & 0xff] ^ (c >> 8);
} while (--len);
c = ~c;
return (uint32_t)c;
}
#else /* BIG_ENDIAN */
/* ========================================================================= */
#define DOBIG4 c ^= *++buf4; \
c = crc_table[4][c & 0xff] ^ crc_table[5][(c >> 8) & 0xff] ^ \
crc_table[6][(c >> 16) & 0xff] ^ crc_table[7][c >> 24]
#define DOBIG32 DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4
/* ========================================================================= */
uint32_t crc32(uint32_t crc, const uint8_t *buf, size_t len)
{
register u4 c;
register const u4 *buf4;
if (buf == NULL) return 0UL;
c = REV((u4)crc);
c = ~c;
while (len && ((uintptr_t)buf & 3)) {
c = crc_table[4][(c >> 24) ^ *buf++] ^ (c << 8);
len--;
}
buf4 = (const u4 *)(const void *)buf;
buf4--;
while (len >= 32) {
DOBIG32;
len -= 32;
}
while (len >= 4) {
DOBIG4;
len -= 4;
}
buf4++;
buf = (const unsigned char *)buf4;
if (len) do {
c = crc_table[4][(c >> 24) ^ *buf++] ^ (c << 8);
} while (--len);
c = ~c;
return (uint32_t)(REV(c));
}
#endif
