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// -*- C++ -*-

// Copyright (C) 2005, 2006, 2009 Free Software Foundation, Inc.

//

// This file is part of the GNU ISO C++ Library.  This library 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, or (at your option) any later

// version.

// This library 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.

// Under Section 7 of GPL version 3, you are granted additional

// permissions described in the GCC Runtime Library Exception, version

// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and

// a copy of the GCC Runtime Library Exception along with this program;

// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see

// <http://www.gnu.org/licenses/>.

// Copyright (C) 2004 Ami Tavory and Vladimir Dreizin, IBM-HRL.

// Permission to use, copy, modify, sell, and distribute this software

// is hereby granted without fee, provided that the above copyright

// notice appears in all copies, and that both that copyright notice

// and this permission notice appear in supporting documentation. None

// of the above authors, nor IBM Haifa Research Laboratories, make any

// representation about the suitability of this software for any

// purpose. It is provided "as is" without express or implied

// warranty.

/**

 * @file mask_based_range_hashing.hpp

 * Contains a range hashing policy base.

 */

#ifndef PB_DS_MASK_BASED_RANGE_HASHING_HPP

#define PB_DS_MASK_BASED_RANGE_HASHING_HPP

namespace __gnu_pbds

{

  namespace detail

  {

    /// Range hashing policy.

    template<typename Size_Type>

    class mask_based_range_hashing

    {

    protected:

      typedef Size_Type         size_type;

      void

      swap(mask_based_range_hashing& other)

      { std::swap(m_mask, other.m_mask); }

      void

      notify_resized(size_type size);

      inline size_type

      range_hash(size_type hash) const

      { return size_type(hash & m_mask); }

    private:

      size_type                 m_mask;

      const static size_type    s_num_bits_in_size_type;

      const static size_type    s_highest_bit_1;

    };

    template<typename Size_Type>

    const typename mask_based_range_hashing<Size_Type>::size_type

    mask_based_range_hashing<Size_Type>::s_num_bits_in_size_type =

      sizeof(typename mask_based_range_hashing<Size_Type>::size_type) << 3;

    template<typename Size_Type>

    const typename mask_based_range_hashing<Size_Type>::size_type mask_based_range_hashing<Size_Type>::s_highest_bit_1 = static_cast<typename mask_based_range_hashing<Size_Type>::size_type>(1) << (s_num_bits_in_size_type - 1);

    template<typename Size_Type>

    void

    mask_based_range_hashing<Size_Type>::

    notify_resized(size_type size)

    {

      size_type i = 0;

      while (size ^ s_highest_bit_1)

        {

          size <<= 1;

          ++i;

        }

      m_mask = 1;

      i += 2;

      while (i++ < s_num_bits_in_size_type)

        m_mask = (m_mask << 1) ^ 1;

    }

  } // namespace detail

} // namespace __gnu_pbds

#endif