1 /* 2 * Copyright 2003 Sun Microsystems, Inc. All rights reserved. 3 * Use is subject to license terms. 4 */ 5 6 #pragma ident "%Z%%M% %I% %E% SMI" 7 8 /* 9 * adler32.c -- compute the Adler-32 checksum of a data stream 10 * Copyright (C) 1995-1998 Mark Adler 11 * For conditions of distribution and use, see copyright notice in zlib.h 12 */ 13 14 #include "zlib.h" 15 16 #define BASE 65521L /* largest prime smaller than 65536 */ 17 #define NMAX 5552 18 /* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */ 19 20 #define DO1(buf,i) {s1 += buf[i]; s2 += s1;} 21 #define DO2(buf,i) DO1(buf,i); DO1(buf,i+1); 22 #define DO4(buf,i) DO2(buf,i); DO2(buf,i+2); 23 #define DO8(buf,i) DO4(buf,i); DO4(buf,i+4); 24 #define DO16(buf) DO8(buf,0); DO8(buf,8); 25 26 uLong ZEXPORT adler32(adler, buf, len) 27 uLong adler; 28 const Bytef *buf; 29 uInt len; 30 { 31 unsigned long s1 = adler & 0xffff; 32 unsigned long s2 = (adler >> 16) & 0xffff; 33 int k; 34 35 if (buf == Z_NULL) return 1L; 36 37 while (len > 0) { 38 k = len < NMAX ? len : NMAX; 39 len -= k; 40 while (k >= 16) { 41 DO16(buf); 42 buf += 16; 43 k -= 16; 44 } 45 if (k != 0) do { 46 s1 += *buf++; 47 s2 += s1; 48 } while (--k); 49 s1 %= BASE; 50 s2 %= BASE; 51 } 52 return (s2 << 16) | s1; 53 } 54