/* 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 *//* @(#) $Id$ */#define ZLIB_INTERNAL#include "zlib.h"#define BASE 65521UL    /* 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);#ifdef NO_DIVIDE#  define MOD(a) \    do { \        if (a >= (BASE << 16)) a -= (BASE << 16); \        if (a >= (BASE << 15)) a -= (BASE << 15); \        if (a >= (BASE << 14)) a -= (BASE << 14); \        if (a >= (BASE << 13)) a -= (BASE << 13); \        if (a >= (BASE << 12)) a -= (BASE << 12); \        if (a >= (BASE << 11)) a -= (BASE << 11); \        if (a >= (BASE << 10)) a -= (BASE << 10); \        if (a >= (BASE << 9)) a -= (BASE << 9); \        if (a >= (BASE << 8)) a -= (BASE << 8); \        if (a >= (BASE << 7)) a -= (BASE << 7); \        if (a >= (BASE << 6)) a -= (BASE << 6); \        if (a >= (BASE << 5)) a -= (BASE << 5); \        if (a >= (BASE << 4)) a -= (BASE << 4); \        if (a >= (BASE << 3)) a -= (BASE << 3); \        if (a >= (BASE << 2)) a -= (BASE << 2); \        if (a >= (BASE << 1)) a -= (BASE << 1); \        if (a >= BASE) a -= BASE; \    } while (0)#else#  define MOD(a) a %= BASE#endif/* ========================================================================= */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 ? (int)len : NMAX;        len -= k;        while (k >= 16) {            DO16(buf);            buf += 16;            k -= 16;        }        if (k != 0) do {            s1 += *buf++;            s2 += s1;        } while (--k);        MOD(s1);        MOD(s2);    }    return (s2 << 16) | s1;}