From bcf78a20978d76f64b7cd46d1a4d7a79a578c77b Mon Sep 17 00:00:00 2001 From: Mark Adler Date: Fri, 9 Sep 2011 22:36:31 -0700 Subject: zlib 0.71 --- adler32.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 46 insertions(+) create mode 100644 adler32.c (limited to 'adler32.c') diff --git a/adler32.c b/adler32.c new file mode 100644 index 0000000..0b2b820 --- /dev/null +++ b/adler32.c @@ -0,0 +1,46 @@ +/* adler32.c -- compute the Adler-32 checksum of a data stream + * Copyright (C) 1995 Mark Adler + * For conditions of distribution and use, see copyright notice in zlib.h + */ + +/* $Id: adler32.c,v 1.5 1995/04/14 14:49:51 jloup Exp $ */ + +#include "zutil.h" + +#define BASE 65521 /* 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) {s1 += *buf++; s2 += s1;} +#define DO2(buf) DO1(buf); DO1(buf); +#define DO4(buf) DO2(buf); DO2(buf); +#define DO8(buf) DO4(buf); DO4(buf); +#define DO16(buf) DO8(buf); DO8(buf); + +/* ========================================================================= */ +uLong adler32(adler, buf, len) + uLong adler; + Byte *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); + k -= 16; + } + if (k != 0) do { + DO1(buf); + } while (--k); + s1 %= BASE; + s2 %= BASE; + } + return (s2 << 16) | s1; +} -- cgit v1.2.3-55-g6feb