## modules/up/src/Core/gnu/hash.cc

/* [<][>][^][v][top][bottom][index][help] */

## FUNCTIONS

This source file includes following functions.

1. hashpjw
2. multiplicativehash
3. foldhash

       1 /*
       2 Copyright (C) 1990 Free Software Foundation
       3     written by Doug Lea (dl@rocky.oswego.edu)
       4
       5 This file is part of the GNU C++ Library.  This library is free
       6 software; you can redistribute it and/or modify it under the terms of
       7 the GNU Library General Public License as published by the Free
       8 Software Foundation; either version 2 of the License, or (at your
       9 option) any later version.  This library is distributed in the hope
      10 that it will be useful, but WITHOUT ANY WARRANTY; without even the
      11 implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
      12 PURPOSE.  See the GNU Library General Public License for more details.
      13 You should have received a copy of the GNU Library General Public
      14 License along with this library; if not, write to the Free Software
      15 Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
      16 */
      17
      18 #ifdef __GNUG__
      19 #pragma implementation
      20 #endif
      21
      22 /*
      23  some useful hash functions
      24 */
      25
      26 unsigned int hashpjw(const char* x) // From Dragon book, p436
         /* [<][>][^][v][top][bottom][index][help] */
      27 {
      28   unsigned int h = 0;
      29   unsigned int g;
      30
      31   while (*x != 0)
      32   {
      33     h = (h << 4) + *x++;
      34     if ((g = h & 0xf0000000) != 0)
      35       h = (h ^ (g >> 24)) ^ g;
      36   }
      37   return h;
      38 }
      39
      40 unsigned int multiplicativehash(int x)
         /* [<][>][^][v][top][bottom][index][help] */
      41 {
      42   // uses a const close to golden ratio * pow(2,32)
      43   return ((unsigned)x) * 2654435767u;
      44 }
      45
      46
      47 unsigned int foldhash(double x)
         /* [<][>][^][v][top][bottom][index][help] */
      48 {
      49   union { unsigned int i[2]; double d; } u;
      50   u.d = x;
      51   unsigned int u0 = u.i[0];
      52   unsigned int u1 = u.i[1];
      53   return u0 ^ u1;
      54 }
      55

/* [<][>][^][v][top][bottom][index][help] */