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// -*- C++ -*-

// Copyright (C) 2005 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 2, 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.

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

// with this library; see the file COPYING.  If not, write to the Free

// Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,

// USA.

// As a special exception, you may use this file as part of a free software

// library without restriction.  Specifically, if other files instantiate

// templates or use macros or inline functions from this file, or you compile

// this file and link it with other files to produce an executable, this

// file does not by itself cause the resulting executable to be covered by

// the GNU General Public License.  This exception does not however

// invalidate any other reasons why the executable file might be covered by

// the GNU General Public License.

// 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 hash_shift_mask_example.cpp

 * An example showing how to write a range-hasing functor.

 */

// For cc_hash_assoc_cntnr.

#include <ext/pb_assoc/assoc_cntnr.hpp>

// For hash-related policies.

#include <ext/pb_assoc/hash_policy.hpp>

// For unary_function and binary_function

#include <functional>

/*

 * A simple hash functor.

 *      std::hash could serve instead of this functor,

 *      but it is not yet standard everywhere.

 */

struct simple_int_hash : public std::unary_function<

  int,

             size_t>

{

  inline size_t

  operator()(int i) const

  {

    return (i);

  }

};

// A range-hashing function which shifts 2 bits right and then masks.

class shift_two_mask_range_hashing : private pb_assoc::direct_mask_range_hashing<>

{

public:

  typedef size_t size_type;

public:

  /*

   * Swaps with a different instant.

   */

  void

  swap(shift_two_mask_range_hashing& r_other)

  {

    pb_assoc::direct_mask_range_hashing<>::swap(r_other);

  }

  /*

   * Called by the container when internally resized.

   */

  void

  notify_resized(size_type size)

  {

    pb_assoc::direct_mask_range_hashing<>::notify_resized(size);

  }

  /*

   * Given a hash value, returns a number in the range of the

   *    internal size of the container.

   */

  inline size_type

  operator()(size_type hash) const

  {

    return (pb_assoc::direct_mask_range_hashing<>::operator()(

                                                              hash >> 2));

  }

};

int

main()

{

  /*

   * A collision-chaining hash table mapping ints to chars.

   */

  typedef

    pb_assoc::cc_hash_assoc_cntnr<

    int,

    char,

    // Hash function.

    simple_int_hash,

    std::equal_to<int>,

    // Range hashing function.

    shift_two_mask_range_hashing>

    map_t;

  map_t h;

  // Use normally.

  h[16] = 'a';

  h[256] = 'e';

  h[4] = 'z';

}