1 /* $NetBSD: hash-string.h,v 1.1.1.1 2016/01/14 00:11:27 christos Exp $ */ 2 3 /* Description of GNU message catalog format: string hashing function. 4 Copyright (C) 1995, 1997-1998, 2000-2003 Free Software Foundation, Inc. 5 6 This program is free software; you can redistribute it and/or modify it 7 under the terms of the GNU Library General Public License as published 8 by the Free Software Foundation; either version 2, or (at your option) 9 any later version. 10 11 This program is distributed in the hope that it will be useful, 12 but WITHOUT ANY WARRANTY; without even the implied warranty of 13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14 Library General Public License for more details. 15 16 You should have received a copy of the GNU Library General Public 17 License along with this program; if not, write to the Free Software 18 Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, 19 USA. */ 20 21 /* @@ end of prolog @@ */ 22 23 /* We assume to have `unsigned long int' value with at least 32 bits. */ 24 #define HASHWORDBITS 32 25 26 27 /* Defines the so called `hashpjw' function by P.J. Weinberger 28 [see Aho/Sethi/Ullman, COMPILERS: Principles, Techniques and Tools, 29 1986, 1987 Bell Telephone Laboratories, Inc.] */ 30 static inline unsigned long int 31 hash_string (const char *str_param) 32 { 33 unsigned long int hval, g; 34 const char *str = str_param; 35 36 /* Compute the hash value for the given string. */ 37 hval = 0; 38 while (*str != '\0') 39 { 40 hval <<= 4; 41 hval += (unsigned char) *str++; 42 g = hval & ((unsigned long int) 0xf << (HASHWORDBITS - 4)); 43 if (g != 0) 44 { 45 hval ^= g >> (HASHWORDBITS - 8); 46 hval ^= g; 47 } 48 } 49 return hval; 50 } 51