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