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| Commit | Line | Data |
|---|---|---|
| 15637ed4 RG |
1 | /* |
| 2 | Copyright (C) 1990 Free Software Foundation | |
| 3 | written by Doug Lea (dl@rocky.oswego.edu) | |
| 4 | ||
| 78ed81a3 | 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, 675 Mass Ave, Cambridge, MA 02139, USA. | |
| 15637ed4 RG |
16 | */ |
| 17 | ||
| 18 | #ifdef __GNUG__ | |
| 19 | #pragma implementation | |
| 20 | #endif | |
| 21 | #include <builtin.h> | |
| 22 | ||
| 23 | /* | |
| 24 | some useful hash functions | |
| 25 | */ | |
| 26 | ||
| 27 | unsigned int hashpjw(const char* x) // From Dragon book, p436 | |
| 28 | { | |
| 29 | unsigned int h = 0; | |
| 30 | unsigned int g; | |
| 31 | ||
| 32 | while (*x != 0) | |
| 33 | { | |
| 34 | h = (h << 4) + *x++; | |
| 35 | if ((g = h & 0xf0000000) != 0) | |
| 36 | h = (h ^ (g >> 24)) ^ g; | |
| 37 | } | |
| 38 | return h; | |
| 39 | } | |
| 40 | ||
| 41 | unsigned int multiplicativehash(int x) | |
| 42 | { | |
| 43 | // uses a const close to golden ratio * pow(2,32) | |
| 44 | return ((unsigned)x) * 2654435767; | |
| 45 | } | |
| 46 | ||
| 47 | ||
| 48 | unsigned int foldhash(double x) | |
| 49 | { | |
| 50 | union { unsigned int i[2]; double d; } u; | |
| 51 | u.d = x; | |
| 52 | unsigned int u0 = u.i[0]; | |
| 53 | unsigned int u1 = u.i[1]; | |
| 54 | return u0 ^ u1; | |
| 55 | } | |
| 56 |