xref: /illumos-gate/usr/src/contrib/ast/src/lib/libast/hash/memsum.c (revision b30d193948be5a7794d7ae3ba0ed9c2f72c88e0f)
1 /***********************************************************************
2 *                                                                      *
3 *               This software is part of the ast package               *
4 *          Copyright (c) 1985-2011 AT&T Intellectual Property          *
5 *                      and is licensed under the                       *
6 *                 Eclipse Public License, Version 1.0                  *
7 *                    by AT&T Intellectual Property                     *
8 *                                                                      *
9 *                A copy of the License is available at                 *
10 *          http://www.eclipse.org/org/documents/epl-v10.html           *
11 *         (with md5 checksum b35adb5213ca9657e911e9befb180842)         *
12 *                                                                      *
13 *              Information and Software Systems Research               *
14 *                            AT&T Research                             *
15 *                           Florham Park NJ                            *
16 *                                                                      *
17 *                 Glenn Fowler <gsf@research.att.com>                  *
18 *                  David Korn <dgk@research.att.com>                   *
19 *                   Phong Vo <kpv@research.att.com>                    *
20 *                                                                      *
21 ***********************************************************************/
22 #pragma prototyped
23 /*
24  * Glenn Fowler
25  * AT&T Bell Laboratories
26  *
27  * hash table library
28  */
29 
30 #include "hashlib.h"
31 
32 /*
33  * return a running 32 bit checksum of buffer b of length n
34  *
35  * c is the return value from a previous
36  * memsum() or strsum() call, 0 on the first call
37  *
38  * the result is the same on all implementations
39  */
40 
41 unsigned long
memsum(const void * ap,int n,register unsigned long c)42 memsum(const void* ap, int n, register unsigned long c)
43 {
44 	register const unsigned char*	p = (const unsigned char*)ap;
45 	register const unsigned char*	e = p + n;
46 
47 	while (p < e) HASHPART(c, *p++);
48 #if LONG_MAX > 2147483647
49 	return(c & 0xffffffff);
50 #else
51 	return(c);
52 #endif
53 }
54