5128eecc9f 2011-02-23        kinaba: /* adler32.c -- compute the Adler-32 checksum of a data stream
5128eecc9f 2011-02-23        kinaba:  * Copyright (C) 1995-1998 Mark Adler
5128eecc9f 2011-02-23        kinaba:  * For conditions of distribution and use, see copyright notice in zlib.h
5128eecc9f 2011-02-23        kinaba:  */
5128eecc9f 2011-02-23        kinaba: 
5128eecc9f 2011-02-23        kinaba: /* @(#) $Id$ */
5128eecc9f 2011-02-23        kinaba: 
5128eecc9f 2011-02-23        kinaba: #include "zlib.h"
5128eecc9f 2011-02-23        kinaba: 
5128eecc9f 2011-02-23        kinaba: #define BASE 65521L /* largest prime smaller than 65536 */
5128eecc9f 2011-02-23        kinaba: #define NMAX 5552
5128eecc9f 2011-02-23        kinaba: /* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */
5128eecc9f 2011-02-23        kinaba: 
5128eecc9f 2011-02-23        kinaba: #define DO1(buf,i)  {s1 += buf[i]; s2 += s1;}
5128eecc9f 2011-02-23        kinaba: #define DO2(buf,i)  DO1(buf,i); DO1(buf,i+1);
5128eecc9f 2011-02-23        kinaba: #define DO4(buf,i)  DO2(buf,i); DO2(buf,i+2);
5128eecc9f 2011-02-23        kinaba: #define DO8(buf,i)  DO4(buf,i); DO4(buf,i+4);
5128eecc9f 2011-02-23        kinaba: #define DO16(buf)   DO8(buf,0); DO8(buf,8);
5128eecc9f 2011-02-23        kinaba: 
5128eecc9f 2011-02-23        kinaba: /* ========================================================================= */
5128eecc9f 2011-02-23        kinaba: uLong ZEXPORT adler32(adler, buf, len)
5128eecc9f 2011-02-23        kinaba:     uLong adler;
5128eecc9f 2011-02-23        kinaba:     const Bytef *buf;
5128eecc9f 2011-02-23        kinaba:     uInt len;
5128eecc9f 2011-02-23        kinaba: {
5128eecc9f 2011-02-23        kinaba:     unsigned long s1 = adler & 0xffff;
5128eecc9f 2011-02-23        kinaba:     unsigned long s2 = (adler >> 16) & 0xffff;
5128eecc9f 2011-02-23        kinaba:     int k;
5128eecc9f 2011-02-23        kinaba: 
5128eecc9f 2011-02-23        kinaba:     if (buf == Z_NULL) return 1L;
5128eecc9f 2011-02-23        kinaba: 
5128eecc9f 2011-02-23        kinaba:     while (len > 0) {
5128eecc9f 2011-02-23        kinaba:         k = len < NMAX ? len : NMAX;
5128eecc9f 2011-02-23        kinaba:         len -= k;
5128eecc9f 2011-02-23        kinaba:         while (k >= 16) {
5128eecc9f 2011-02-23        kinaba:             DO16(buf);
5128eecc9f 2011-02-23        kinaba: 	    buf += 16;
5128eecc9f 2011-02-23        kinaba:             k -= 16;
5128eecc9f 2011-02-23        kinaba:         }
5128eecc9f 2011-02-23        kinaba:         if (k != 0) do {
5128eecc9f 2011-02-23        kinaba:             s1 += *buf++;
5128eecc9f 2011-02-23        kinaba: 	    s2 += s1;
5128eecc9f 2011-02-23        kinaba:         } while (--k);
5128eecc9f 2011-02-23        kinaba:         s1 %= BASE;
5128eecc9f 2011-02-23        kinaba:         s2 %= BASE;
5128eecc9f 2011-02-23        kinaba:     }
5128eecc9f 2011-02-23        kinaba:     return (s2 << 16) | s1;
5128eecc9f 2011-02-23        kinaba: }