adler32.c
上传用户:maxiaolivb
上传日期:2022-06-07
资源大小:915k
文件大小:1k
- /* adler32.c -- compute the Adler-32 checksum of a data stream
- * Copyright (C) 1995-2003 Mark Adler
- * For conditions of distribution and use, see copyright notice in zlib.h
- */
- /* @(#) $Id: adler32.c,v 1.1 2005/11/23 14:29:59 stingerx Exp $ */
- #define ZLIB_INTERNAL
- #include "zlib.h"
- #define DO1(buf,i) { s1 += buf[i]; s2 += s1; }
- #define DO2(buf,i) DO1(buf,i); DO1(buf,i+1);
- #define DO4(buf,i) DO2(buf,i); DO2(buf,i+2);
- #define DO8(buf,i) DO4(buf,i); DO4(buf,i+4);
- #define DO16(buf) DO8(buf,0); DO8(buf,8);
- /* ========================================================================= */
- DWORD ZEXPORT adler32(DWORD adler, const BYTE *buf, DWORD len)
- {
- DWORD s1 = adler &0xFFFF;
- DWORD s2 = (adler >> 16) &0xFFFF;
- DWORD k;
- if (buf == Z_NULL)
- {
- return 1;
- }
- while (len)
- {
- k = len < 5552 ? len : 5552;
- len -= k;
- while (k >= 16)
- {
- DO16(buf);
- buf += 16;
- k -= 16;
- }
- while (k)
- {
- s1 += *buf++;
- s2 += s1;
- k--;
- }
- s1 = s1 % 65521;
- s2 = s2 % 65521;
- }
- return (s2 << 16) | s1;
- }