1 /* $NetBSD: hash-string.h,v 1.1.1.1 2016/01/10 21:36:17 christos Exp $ */ 2 3 /* Description of GNU message catalog format: string hashing function. 4 Copyright (C) 1995, 1997, 1998, 2000, 2001 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 #ifndef PARAMS 24 # if __STDC__ || defined __GNUC__ || defined __SUNPRO_C || defined __cplusplus || __PROTOTYPES 25 # define PARAMS(Args) Args 26 # else 27 # define PARAMS(Args) () 28 # endif 29 #endif 30 31 /* We assume to have `unsigned long int' value with at least 32 bits. */ 32 #define HASHWORDBITS 32 33 34 35 /* Defines the so called `hashpjw' function by P.J. Weinberger 36 [see Aho/Sethi/Ullman, COMPILERS: Principles, Techniques and Tools, 37 1986, 1987 Bell Telephone Laboratories, Inc.] */ 38 static unsigned long int hash_string PARAMS ((const char *__str_param)); 39 40 static inline unsigned long int 41 hash_string (str_param) 42 const char *str_param; 43 { 44 unsigned long int hval, g; 45 const char *str = str_param; 46 47 /* Compute the hash value for the given string. */ 48 hval = 0; 49 while (*str != '\0') 50 { 51 hval <<= 4; 52 hval += (unsigned long int) *str++; 53 g = hval & ((unsigned long int) 0xf << (HASHWORDBITS - 4)); 54 if (g != 0) 55 { 56 hval ^= g >> (HASHWORDBITS - 8); 57 hval ^= g; 58 } 59 } 60 return hval; 61 } 62