zcrc32.c

来自「umon bootloader source code, support mip」· C语言 代码 · 共 34 行

/* crc32.c -- compute the CRC-32 of a data stream
 * Copyright (C) 1995-1998 Mark Adler
 * For conditions of distribution and use, see copyright notice in zlib.h 
 */

#include "zlib.h"

#define local static
extern unsigned long crc32tab[];

#define DO1(buf) crc = crc32tab[((int)crc ^ (*buf++)) & 0xff] ^ (crc >> 8);
#define DO2(buf)  DO1(buf); DO1(buf);
#define DO4(buf)  DO2(buf); DO2(buf);
#define DO8(buf)  DO4(buf); DO4(buf);

/* ========================================================================= */
uLong ZEXPORT zcrc32(crc, buf, len)
uLong crc;
const Bytef *buf;
uInt len;
{
	if (buf == Z_NULL)
		return 0L;
	crc = crc ^ 0xffffffffL;
	while (len >= 8) {
		DO8(buf);
		len -= 8;
	}
	if (len) do {
		DO1(buf);
	} while (--len);
	return crc ^ 0xffffffffL;
}