src/hashtable.cpp

   1 /* Copyright (C) 2007-2011 Vincent Ollivier
   2  *
   3  * Purple Haze is free software: you can redistribute it and/or modify
   4  * it under the terms of the GNU General Public License as published by
   5  * the Free Software Foundation, either version 3 of the License, or
   6  * (at your option) any later version.
   7  *
   8  * Purple Haze is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  11  * GNU General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public License
  14  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  15  */
  16
  17 #include "hashtable.h"
  18 #include "tt.h"
  19
  20 template <class T>
  21 T HashTable<T>::lookup(Hash h, bool* is_empty)
  22 {
  23     Entry entry = entries[h & (SIZE - 1)];
  24     if (entry.hash == h) {
  25         // FIXME 'entry.hash' is initialized to '0'
  26         // Problem when 'h == 0' and 'entry.value' is empty.
  27         *is_empty = false;
  28 #ifndef NDEBUG
  29         ++hits;
  30 #endif
  31         return entry.value;
  32 #ifndef NDEBUG
  33     } else if (entry.hash != 0) {
  34         ++collisions;
  35 #endif
  36     }
  37     *is_empty = true;
  38 #ifndef NDEBUG
  39     ++misses;
  40 #endif
  41     return T();
  42 }
  43
  44 template <class T>
  45 void HashTable<T>::clear()
  46 {
  47     for (int i = 0; i < SIZE; ++i) {
  48         entries[i].hash = 0;
  49         entries[i].value = T();
  50     }
  51     hits = 0;
  52     misses = 0;
  53 }
  54
  55 template <class T>
  56 int HashTable<T>::get_usage() const
  57 {
  58     int res = 0;
  59     for (int i = 0; i < SIZE; ++i) if (entries[i].hash) ++res;
  60     return res;
  61 }
  62
  63 template class HashTable<int>; // To avoid linker errors
  64 template class HashTable<Transposition>; // To avoid linker errors