www.pudn.com > gedit-2.8.3.rar > hash-string.h

/* Implements a string hashing function. 
   Copyright (C) 1995, 1997 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 Library General Public 
   License along with the GNU C Library; see the file COPYING.LIB.  If not, 
   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, 
   Boston, MA 02111-1307, USA.  */ 
 
/* @@ end of prolog @@ */ 
 
#ifndef PARAMS 
# if __STDC__ 
#  define PARAMS(Args) Args 
# else 
#  define PARAMS(Args) () 
# endif 
#endif 
 
/* 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 unsigned long hash_string PARAMS ((const char *__str_param)); 
 
static inline unsigned long 
hash_string (str_param) 
     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 long) *str++; 
      g = hval & ((unsigned long) 0xf << (HASHWORDBITS - 4)); 
      if (g != 0) 
	{ 
	  hval ^= g >> (HASHWORDBITS - 8); 
	  hval ^= g; 
	} 
    } 
  return hval; 
}