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      1 /* Implements a string hashing function.
      2    Copyright (C) 1995, 1997, 1998, 2000, 2003 Free Software Foundation, Inc.
      3    This file is part of the GNU C Library.
      4 
      5    The GNU C Library is free software; you can redistribute it and/or
      6    modify it under the terms of the GNU Lesser General Public
      7    License as published by the Free Software Foundation; either
      8    version 2.1 of the License, or (at your option) any later version.
      9 
     10    The GNU C Library is distributed in the hope that it will be useful,
     11    but WITHOUT ANY WARRANTY; without even the implied warranty of
     12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     13    Lesser General Public License for more details.
     14 
     15    You should have received a copy of the GNU Lesser General Public
     16    License along with the GNU C Library; if not, write to the Free
     17    Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
     18    Boston, MA 02110-1301, USA.  */
     19 
     20 #ifdef HAVE_CONFIG_H
     21 # include <config.h>
     22 #endif
     23 
     24 /* Specification.  */
     25 #include "hash-string.h"
     26 
     27 
     28 /* Defines the so called `hashpjw' function by P.J. Weinberger
     29    [see Aho/Sethi/Ullman, COMPILERS: Principles, Techniques and Tools,
     30    1986, 1987 Bell Telephone Laboratories, Inc.]  */
     31 unsigned long int
     32 __hash_string (const char *str_param)
     33 {
     34   unsigned long int hval, g;
     35   const char *str = str_param;
     36 
     37   /* Compute the hash value for the given string.  */
     38   hval = 0;
     39   while (*str != '\0')
     40     {
     41       hval <<= 4;
     42       hval += (unsigned char) *str++;
     43       g = hval & ((unsigned long int) 0xf << (HASHWORDBITS - 4));
     44       if (g != 0)
     45 	{
     46 	  hval ^= g >> (HASHWORDBITS - 8);
     47 	  hval ^= g;
     48 	}
     49     }
     50   return hval;
     51 }
     52