libcruft-util/hash.cpp

49 lines
1.3 KiB
C++

/*
* This file is part of libgim.
*
* Waif 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 3 of the License, or (at your option) any later
* version.
*
* Waif 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 General Public License
* along with libgim. If not, see <http://www.gnu.org/licenses/>.
*
* Copyright 2010 Danny Robson <danny@blubinc.net>
*/
#include "hash.hpp"
uint32_t
util::wang32 (uint32_t key) {
uint32_t c2 = 0x27d4eb2d; // a prime or an odd constant
key = (key ^ 61) ^ (key >> 16);
key = key + (key << 3);
key = key ^ (key >> 4);
key = key * c2;
key = key ^ (key >> 15);
return key;
}
uint64_t
util::wang64 (uint64_t key) {
key = (~key) + (key << 21); // key = (key << 21) - key - 1;
key = key ^ (key >> 24);
key = (key + (key << 3)) + (key << 8); // key * 265
key = key ^ (key >> 14);
key = (key + (key << 2)) + (key << 4); // key * 21
key = key ^ (key >> 28);
key = key + (key << 31);
return key;
}