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Giac_maj/giac-1.4.9/intl/hash-string.h 1.6 KB
6663b6c9   adorian   projet complet av...
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  /* Description of GNU message catalog format: string hashing function.
     Copyright (C) 1995, 1997-1998, 2000-2003 Free Software Foundation, Inc.
  
     This program is free software; you can redistribute it and/or modify it
     under the terms of the GNU Library General Public License as published
     by the Free Software Foundation; either version 2, or (at your option)
     any later version.
  
     This program is distributed in the hope that it will be useful,
     but WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     Library General Public License for more details.
  
     You should have received a copy of the GNU Library General Public
     License along with this program; if not, write to the Free Software
     Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
     USA.  */
  
  /* @@ end of prolog @@ */
  
  /* We assume to have `unsigned long int' value with at least 32 bits.  */
  #define HASHWORDBITS 32
  
  
  /* Defines the so called `hashpjw' function by P.J. Weinberger
     [see Aho/Sethi/Ullman, COMPILERS: Principles, Techniques and Tools,
     1986, 1987 Bell Telephone Laboratories, Inc.]  */
  static inline unsigned long int
  hash_string (const char *str_param)
  {
    unsigned long int hval, g;
    const char *str = str_param;
  
    /* Compute the hash value for the given string.  */
    hval = 0;
    while (*str != '\0')
      {
        hval <<= 4;
        hval += (unsigned char) *str++;
        g = hval & ((unsigned long int) 0xf << (HASHWORDBITS - 4));
        if (g != 0)
  	{
  	  hval ^= g >> (HASHWORDBITS - 8);
  	  hval ^= g;
  	}
      }
    return hval;
  }