root/maint/gnulib/lib/hash-pjw.c

/* */

DEFINITIONS

1. hash_pjw

   1 /* hash-pjw.c -- compute a hash value from a NUL-terminated string.
   2 
   3    Copyright (C) 2001, 2003, 2006, 2009-2021 Free Software Foundation, Inc.
   4 
   5    This file is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU Lesser General Public License as
   7    published by the Free Software Foundation; either version 2.1 of the
   8    License, or (at your option) any later version.
   9 
  10    This file 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
  13    GNU Lesser General Public License for more details.
  14 
  15    You should have received a copy of the GNU Lesser General Public License
  16    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  17 
  18 #include <config.h>
  19 
  20 #include "hash-pjw.h"
  21 
  22 #include <limits.h>
  23 
  24 #define SIZE_BITS (sizeof (size_t) * CHAR_BIT)
  25 
  26 /* A hash function for NUL-terminated char* strings using
  27    the method described by Bruno Haible.
  28    See https://www.haible.de/bruno/hashfunc.html.  */
  29 
  30 size_t
  31 hash_pjw (const void *x, size_t tablesize)
     /*  */
  32 {
  33   const char *s;
  34   size_t h = 0;
  35 
  36   for (s = x; *s; s++)
  37     h = *s + ((h << 9) | (h >> (SIZE_BITS - 9)));
  38 
  39   return h % tablesize;
  40 }

/* */