1  /* Implements a string hashing function.
       2     Copyright (C) 1995-2016 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, see
      17     <https://www.gnu.org/licenses/>.  */
      18  
      19  #ifdef HAVE_CONFIG_H
      20  # include <config.h>
      21  #endif
      22  
      23  /* Specification.  */
      24  #include "hash-string.h"
      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  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  }