00001 /* Description of GNU message catalog format: string hashing function. 00002 Copyright (C) 1995, 1997, 1998, 2000, 2001 Free Software Foundation, Inc. 00003 00004 This program is free software; you can redistribute it and/or modify 00005 it under the terms of the GNU General Public License as published by 00006 the Free Software Foundation; either version 2, or (at your option) 00007 any later version. 00008 00009 This program is distributed in the hope that it will be useful, 00010 but WITHOUT ANY WARRANTY; without even the implied warranty of 00011 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 00012 GNU General Public License for more details. 00013 00014 You should have received a copy of the GNU General Public License 00015 along with this program; if not, write to the Free Software Foundation, 00016 Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ 00017 00018 /* @@ end of prolog @@ */ 00019 00020 #ifndef PARAMS 00021 # if __STDC__ 00022 # define PARAMS(Args) Args 00023 # else 00024 # define PARAMS(Args) () 00025 # endif 00026 #endif 00027 00028 /* We assume to have `unsigned long int' value with at least 32 bits. */ 00029 #define HASHWORDBITS 32 00030 00031 00032 /* Defines the so called `hashpjw' function by P.J. Weinberger 00033 [see Aho/Sethi/Ullman, COMPILERS: Principles, Techniques and Tools, 00034 1986, 1987 Bell Telephone Laboratories, Inc.] */ 00035 static unsigned long int hash_string PARAMS ((const char *__str_param)); 00036 00037 static inline unsigned long int 00038 hash_string (str_param) 00039 const char *str_param; 00040 { 00041 unsigned long int hval, g; 00042 const char *str = str_param; 00043 00044 /* Compute the hash value for the given string. */ 00045 hval = 0; 00046 while (*str != '\0') 00047 { 00048 hval <<= 4; 00049 hval += (unsigned long int) *str++; 00050 g = hval & ((unsigned long int) 0xf << (HASHWORDBITS - 4)); 00051 if (g != 0) 00052 { 00053 hval ^= g >> (HASHWORDBITS - 8); 00054 hval ^= g; 00055 } 00056 } 00057 return hval; 00058 }