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authortromey <tromey@138bc75d-0d04-0410-961f-82ee72b054a4>1999-05-04 19:30:25 +0000
committertromey <tromey@138bc75d-0d04-0410-961f-82ee72b054a4>1999-05-04 19:30:25 +0000
commitd8b6dda417667abf7f0dfc976a60ecfe9bbb2aaf (patch)
treee97105783ac15ce06e3efe366d641f3693aa8974 /zlib/adler32.c
parent64511c32eb0c3d7cb2346f34c6f1c20346b48751 (diff)
downloadgcc-d8b6dda417667abf7f0dfc976a60ecfe9bbb2aaf.tar.gz
Initial revision
git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@26770 138bc75d-0d04-0410-961f-82ee72b054a4
Diffstat (limited to 'zlib/adler32.c')
-rw-r--r--zlib/adler32.c48
1 files changed, 48 insertions, 0 deletions
diff --git a/zlib/adler32.c b/zlib/adler32.c
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+/* adler32.c -- compute the Adler-32 checksum of a data stream
+ * Copyright (C) 1995-1998 Mark Adler
+ * For conditions of distribution and use, see copyright notice in zlib.h
+ */
+
+/* @(#) $Id$ */
+
+#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 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 ? 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;
+}