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/*
Copyright (C) 1990 Free Software Foundation
written by Doug Lea (dl@rocky.oswego.edu)
This file is part of the GNU C++ Library. This library 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 of the License, or (at your
option) any later version. This library 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 library; if not, write to the Free Software
Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#ifdef __GNUG__
#pragma implementation
#endif
#include <builtin.h>
/*
some useful hash functions
*/
unsigned int hashpjw(const char* x) // From Dragon book, p436
{
unsigned int h = 0;
unsigned int g;
while (*x != 0)
{
h = (h << 4) + *x++;
if ((g = h & 0xf0000000) != 0)
h = (h ^ (g >> 24)) ^ g;
}
return h;
}
unsigned int multiplicativehash(int x)
{
// uses a const close to golden ratio * pow(2,32)
return ((unsigned)x) * 2654435767;
}
unsigned int foldhash(double x)
{
union { unsigned int i[2]; double d; } u;
u.d = x;
unsigned int u0 = u.i[0];
unsigned int u1 = u.i[1];
return u0 ^ u1;
}
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