hashFunc_inl.h

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/***************************************************************************
 *   Copyright (C) 2005 by Christophe GONZALES and Pierre-Henri WUILLEMIN  *
 *   {prenom.nom}_at_lip6.fr                                               *
 *                                                                         *
 *   This program 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 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program 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 this program; if not, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
 ***************************************************************************/
#include <string>
#include <utility>

#include <agrum/agrum.h>

// to ease parsing in IDE
#include <agrum/core/hashFunc.h>

#ifndef DOXYGEN_SHOULD_SKIP_THIS

namespace gum {

  /* in aGrUM, the sizes of hash tables (number of slots) are powers of 2. This
   * is
   * not actually compulsory for the hash function we use. However, as it
   * speeds up the computations of hashed values, we chose to impose
   * this restriction. Function __hashTableLog2 thus returns the size in
   * bits - 1 necessary to store the smallest power of 2 greater than or
   * equal nb. */
  INLINE unsigned int __hashTableLog2(const Size nb) {
    unsigned int i = 0;

    for (Size nbb = nb; nbb > Size(1); ++i, nbb >>= 1) {};

    return ((Size(1) << i) < nb ? i + Size(1) : i);
  }

  // ===========================================================================

  INLINE Size HashFunc< std::string >::castToSize(const std::string& key) {
    Size        h = 0;
    Size        size = Size(key.size());
    const char* char_ptr = key.c_str();
    const Size* int_ptr = (const Size*)char_ptr;

    for (; size >= sizeof(Size); size -= sizeof(Size), ++int_ptr) {
      h = h * HashFuncConst::gold + *int_ptr;
    }

    for (char_ptr = (const char*)int_ptr; size != Size(0); --size, ++char_ptr) {
      h = Size(19) * h + Size(*char_ptr);
    }

    return h;
  }

  // Returns the hashed value of a key.
  INLINE Size HashFunc< std::string >::operator()(const std::string& key) const {
    return castToSize(key) & this->_hash_mask;
  }

  // ===========================================================================

  INLINE Size
         HashFunc< std::vector< Idx > >::castToSize(const std::vector< Idx >& key) {
    Size h = Size(0);
    Size size = Size(key.size());
    for (Size i = Size(0); i < size; ++i)
      h += i * Size(key[i]);

    return h;
  }

  // Returns the hashed value of a key.
  INLINE Size HashFunc< std::vector< Idx > >::
              operator()(const std::vector< Idx >& key) const {
    return (castToSize(key) * HashFuncConst::gold) & this->_hash_mask;
  }

  // ===========================================================================

  INLINE Size HashFunc< Debug >::castToSize(const Debug& key) {
    Size h = Size(0);

    for (Size i = Size(0), j = Size(key.size()); i < j; ++i)
      h = Size(19) * h + Size(key[i]);

    return h;
  }

  // Returns the hashed value of a key.
  INLINE Size HashFunc< Debug >::operator()(const Debug& key) const {
    return (castToSize(key) * HashFuncConst::gold) & this->_hash_mask;
  }


} /* namespace gum */

#endif /* DOXYGEN_SHOULD_SKIP_THIS */