/* adler32.c -- compute the Adler-32 checksum of a data stream * Copyright (C) 1995-2002 Mark Adler * For conditions of distribution and use, see copyright notice in zlib.h */ /* @(#) $Id: adler32.c,v 1.2 2002/11/06 22:32:54 davidT Exp $ */ #include "zlib.h" #define BASE 65521L /* largest prime smaller than 65536 */#define NMAX 5552/* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */ #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); /* ========================================================================= */ZEXTERNDEF uLong ZEXPORT adler32(adler, buf, len)    uLong adler;    const Bytef *buf;    uInt len;{    unsigned long s1 = adler & 0xffff;    unsigned long s2 = (adler >> 16) & 0xffff;    int k;     if (buf == Z_NULL) return 1L;     while (len > 0) {        k = len < NMAX ? len : NMAX;        len -= k;        while (k >= 16) {            DO16(buf);	    buf += 16;            k -= 16;        }        if (k != 0) do {            s1 += *buf++;	    s2 += s1;        } while (--k);        s1 %= BASE;        s2 %= BASE;    }    return (s2 << 16) | s1;}