1: /* Implements hashing function for string with known length.
    2:    Copyright (C) 1996, 1997 Free Software Foundation, Inc.
    3:    This file is part of the GNU C Library.
    4:    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.
    5: 
    6:    The GNU C Library is free software; you can redistribute it and/or
    7:    modify it under the terms of the GNU Lesser General Public
    8:    License as published by the Free Software Foundation; either
    9:    version 2.1 of the License, or (at your option) any later version.
   10: 
   11:    The GNU C Library 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:    Lesser General Public License for more details.
   15: 
   16:    You should have received a copy of the GNU Lesser General Public
   17:    License along with the GNU C Library; if not, write to the Free
   18:    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   19:    02111-1307 USA.  */
   20: 
   21: #include <sys/types.h>
   22: 
   23: /* We assume to have `size_t' value with at least 32 bits.  */
   24: #define HASHWORDBITS 32
   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: static size_t hash_string (const char *__str_param, size_t __len);
   31: 
   32: static inline size_t
   33: hash_string (const char *str_param, size_t len)
   34: {
   35:   size_t hval, g;
   36:   const char *end_str = str_param + len;
   37: 
   38:   /* Compute the hash value for the given string.  */
   39:   hval = len;
   40:   while (str_param != end_str)
   41:     {
   42:       hval <<= 4;
   43:       hval += (size_t) *str_param++;
   44:       g = hval & ((size_t) 0xf << (HASHWORDBITS - 4));
   45:       if (g != 0)
   46:         {
   47:           hval ^= g >> (HASHWORDBITS - 8);
   48:           hval ^= g;
   49:         }
   50:     }
   51:   return hval;
   52: }