libcruft-util/hash.cpp

/*
 * 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;
}