bounded_queue_std.h

/* Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.

   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; version 2 of the License.

   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., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA */


#ifndef BOUNDED_HEAP_STD_INCLUDED
#define BOUNDED_HEAP_STD_INCLUDED

#include "my_global.h"
#include "my_base.h"
#include <vector>
#include <queue>

template<typename Element_type,
         typename Key_type,
         typename Key_generator,
         typename Key_compare = std::less<Key_type>
         >
class Bounded_queue_std
{
public:
  Bounded_queue_std()
    : m_cmp(),
      m_sort_keys(NULL),
      m_compare_length(0),
      m_sort_param(NULL),
      m_max_elements(0),
      m_num_elements(0)
  {}

  int init(ha_rows max_elements,
           Key_generator *sort_param,
           Key_type *sort_keys)
  {
    m_sort_keys= sort_keys;
    m_compare_length= sort_param->compare_length();
    m_sort_param= sort_param;
    m_max_elements= max_elements + 1;
    return 0;
  }

  void push(Element_type element)
  {
    if (m_num_elements == m_max_elements)
    {
      m_queue.pop();
      --m_num_elements;
    }
    {
      m_sort_param->make_sortkey(m_sort_keys[m_queue.size()], element);
      m_queue.push(m_sort_keys[m_queue.size()]);
      ++m_num_elements;
    }
  }

  size_t num_elements() const { return m_num_elements; }

  typedef std::priority_queue<Key_type,
                              std::vector<Key_type>,
                              Key_compare> Queue_type;

private:
  Queue_type         m_queue;
  Key_compare        m_cmp;
  Key_type          *m_sort_keys;
  size_t             m_compare_length;
  Key_generator     *m_sort_param;
  size_t             m_max_elements;
  size_t             m_num_elements;
};




#endif  // BOUNDED_HEAP_STD_INCLUDED