hash-pjw.c

来自「Linux下文件工具。」· C语言 代码 · 共 43 行

/* hash-pjw.c -- compute a hash value from a NUL-terminated string.
   Copyright 2001 Free Software Foundation, Inc.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU 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 General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software Foundation,
   Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */

#if HAVE_CONFIG_H
# include <config.h>
#endif

#include "hash-pjw.h"

/* A hash function for NUL-terminated char* strings using
   the method described in Aho, Sethi, & Ullman, p 436. */

unsigned int
hash_pjw (const void *x, unsigned int tablesize)
{
  const char *s = x;
  unsigned int h = 0;
  unsigned int g;

  while (*s != 0)
    {
      h = (h << 4) + *s++;
      if ((g = h & (unsigned int) 0xf0000000) != 0)
        h = (h ^ (g >> 24)) ^ g;
    }

  return (h % tablesize);
}