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author | peter <peter@FreeBSD.org> | 1996-08-18 17:54:27 +0000 |
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committer | peter <peter@FreeBSD.org> | 1996-08-18 17:54:27 +0000 |
commit | 70c83c0586d07013fa8b7756f44d5ec3839b1db0 (patch) | |
tree | ce8fa1b80a1478f3869ad9324fb5d62892f66e07 /lib/libz/adler32.c | |
download | FreeBSD-src-70c83c0586d07013fa8b7756f44d5ec3839b1db0.zip FreeBSD-src-70c83c0586d07013fa8b7756f44d5ec3839b1db0.tar.gz |
Initial import of zlib-1.0.4
Diffstat (limited to 'lib/libz/adler32.c')
-rw-r--r-- | lib/libz/adler32.c | 48 |
1 files changed, 48 insertions, 0 deletions
diff --git a/lib/libz/adler32.c b/lib/libz/adler32.c new file mode 100644 index 0000000..c9dcf93 --- /dev/null +++ b/lib/libz/adler32.c @@ -0,0 +1,48 @@ +/* adler32.c -- compute the Adler-32 checksum of a data stream + * Copyright (C) 1995-1996 Mark Adler + * For conditions of distribution and use, see copyright notice in zlib.h + */ + +/* $Id: adler32.c,v 1.10 1996/05/22 11:52:18 me 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); + +/* ========================================================================= */ +uLong 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; +} |