etl/ipriority_queue.h

///\file

/******************************************************************************
The MIT License(MIT)

Embedded Template Library.
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http://www.etlcpp.com

Copyright(c) 2015 jwellbelove, rlindeman

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#ifndef __ETL_IPRIORITY_QUEUE__
#define __ETL_IPRIORITY_QUEUE__
#define __ETL_IN_IPRIORITY_QUEUE_H__

#include <stddef.h>
#include <algorithm>

#include "private/priority_queue_base.h"
#include "type_traits.h"
#include "parameter_type.h"
#include "error_handler.h"

namespace etl
{
  //***************************************************************************
  ///\ingroup queue
  ///\brief This is the base for all priority queues that contain a particular type.
  ///\details Normally a reference to this type will be taken from a derived queue.
  /// The TContainer specified must provide the front, push_back, pop_back, and
  /// assign methods to work correctly with priority_queue.
  ///\code
  /// etl::priority_queue<int, 10> myPriorityQueue;
  /// etl::ipriority_queue<int>& iQueue = myPriorityQueue;
  ///\endcode
  /// \warning This priority queue cannot be used for concurrent access from
  /// multiple threads.
  /// \tparam T The type of value that the queue holds.
  /// \tparam TContainer to hold the T queue values
  /// \tparam TCompare to use in comparing T values
  //***************************************************************************
  template <typename T, typename TContainer, typename TCompare>
  class ipriority_queue : public priority_queue_base
  {
  public:

    typedef T                     value_type;         ///< The type stored in the queue.
    typedef TContainer            container_type;     ///< The container type used for priority queue.
    typedef T&                    reference;          ///< A reference to the type used in the queue.
    typedef const T&              const_reference;    ///< A const reference to the type used in the queue.
    typedef priority_queue_base::size_type size_type; ///< The type used for determining the size of the queue.
    typedef typename std::iterator_traits<typename TContainer::iterator>::difference_type difference_type;

  private:

    typedef typename parameter_type<T>::type parameter_t;

  public:

    //*************************************************************************
    /// Gets a reference to the highest priority value in the priority queue.<br>
    /// \return A reference to the highest priority value in the priority queue.
    //*************************************************************************
    reference top()
    {
      return container.front();
    }

    //*************************************************************************
    /// Gets a const reference to the highest priority value in the priority queue.<br>
    /// \return A const reference to the highest priority value in the priority queue.
    //*************************************************************************
    const_reference top() const
    {
      return container.front();
    }

    //*************************************************************************
    /// Adds a value to the queue.
    /// If ETL_THROW_EXCEPTIONS is defined, throws an etl::priority_queue_full
    /// is the priority queue is already full, otherwise does nothing if full.
    ///\param value The value to push to the queue.
    //*************************************************************************
    void push(parameter_t value)
    {
      if (ETL_ASSERT(!full(), ETL_ERROR(priority_queue_full)))
      {
        // Put element at end
        container.push_back(value);
        // Pre-increment size
        ++current_size;
        // Make elements in container into heap
        std::push_heap(container.begin(), container.end(), TCompare());
      }
    }

    //*************************************************************************
    /// Clears the queue to the empty state.
    //*************************************************************************
    void clear()
    {
      container.clear();
      current_size = 0;
    }

    //*********************************************************************
    /// Assigns values to the priority queue.
    /// If ETL_THROW_EXCEPTIONS is defined, emits priority_queue_full if
    /// priority queue does not have enough free space.
    /// If ETL_THROW_EXCEPTIONS is defined, emits priority_iterator if the
    /// iterators are reversed.
    ///\param first The iterator to the first element.
    ///\param last  The iterator to the last element + 1.
    //*********************************************************************
    template <typename TIterator>
    void assign(TIterator first, TIterator last)
    {
#ifdef _DEBUG
      difference_type count = std::distance(first, last);
      ETL_ASSERT(count >= 0, ETL_ERROR(priority_queue_iterator));
      ETL_ASSERT(static_cast<size_t>(count) <= MAX_SIZE, ETL_ERROR(priority_queue_full));
#endif

      clear();
      container.assign(first, last);
      std::make_heap(container.begin(), container.end(), TCompare());
      current_size = container.size();
    }

    //*************************************************************************
    /// Removes the oldest value from the back of the priority queue.
    /// Does nothing if the priority queue is already empty.
    //*************************************************************************
    void pop()
    {
      if (!empty())
      {
        // Move largest element to end
	      std::pop_heap(container.begin(), container.end(), TCompare());
        // Actually remove largest element at end
        container.pop_back();
        // Decrement size
        --current_size;
      }
    }

  protected:

    //*************************************************************************
    /// Make this a clone of the supplied priority queue
    //*************************************************************************
    void clone(const ipriority_queue& other)
    {
      assign(other.container.cbegin(), other.container.cend());
    }

    //*************************************************************************
    /// The constructor that is called from derived classes.
    //*************************************************************************
    ipriority_queue(size_type max_size)
      : priority_queue_base(max_size)
    {
    }

  private:

    /// The container specified at instantiation of the priority_queue
    TContainer container;
  };
}

#undef __ETL_IN_IPRIORITY_QUEUE_H__
#endif