hash-string.h
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上传日期:2013-03-10
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Visual C++
- /* Description of GNU message catalog format: string hashing function.
- Copyright (C) 1995, 1997, 1998, 2000, 2001 Free Software Foundation, Inc.
- This program is free software; you can redistribute it and/or modify it
- under the terms of the GNU Library 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
- Library General Public License for more details.
- You should have received a copy of the GNU Library 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. */
- /* @@ end of prolog @@ */
- #ifndef PARAMS
- # if __STDC__ || defined __GNUC__ || defined __SUNPRO_C || defined __cplusplus || __PROTOTYPES
- # 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 int hash_string PARAMS ((const char *__str_param));
- static inline unsigned long int
- 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 != ' ')
- {
- hval <<= 4;
- hval += (unsigned long int) *str++;
- g = hval & ((unsigned long int) 0xf << (HASHWORDBITS - 4));
- if (g != 0)
- {
- hval ^= g >> (HASHWORDBITS - 8);
- hval ^= g;
- }
- }
- return hval;
- }