etl/iqueue.h

///\file

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

Embedded Template Library.

Copyright(c) 2014 jwellbelove

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******************************************************************************/

#ifndef __etl_iqueue__
#define __etl_iqueue__

#include <cstddef>

#include "queue_base.h"

namespace etl
{
  //***************************************************************************
  ///\ingroup queue
  ///\brief This is the base for all queues that contain a particular type.
  ///\details Normally a reference to this type will be taken from a derived queue.
  ///\code
  /// etl::queue<int, 10> myQueue;
  /// etl::iqueue<int>& iQueue = myQueue;
  ///\endcode
  /// \warning This queue cannot be used for concurrent access from multiple threads.
  /// \tparam T The type of item that the queue holds.
  //***************************************************************************
  template <typename T>
  class iqueue : public queue_base
  {
  public:

    typedef queue_base::size_type size_type;       ///< The type used for determining the size of queue.
    typedef T                     value_type;      ///< The type stored in the 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 T*                    pointer;         ///< A pointer to the type used in the queue.
    typedef const T*              const_pointer;   ///< A const pointer to the type used in the queue.

    //*************************************************************************
    /// Adds an item to the queue.
    /// If ETL_USE_EXCEPTIONS is defined, throws an etl::queue_full_exception is the queue is already full,
    /// otherwise does nothing if full.
    ///\param item The item to push to the queue.
    //*************************************************************************
    void push(const_reference item)
    {
      if (!full())
      {
        buffer[in++] = item;
        in = (in == (MAX_SIZE - 1)) ? 0 : ++in;
        ++size;
      }
#ifdef ETL_USE_EXCEPTIONS
      else
      {
        throw queue_full_exception();
      }
#endif
    }

    //*************************************************************************
    /// Allows a possibly more efficient 'push' by moving to the next input item
    /// and returning a reference to it.
    /// This may eliminate a copy by allowing direct construction in-place.<br>
    /// If ETL_USE_EXCEPTIONS is defined, throws an etl::queue_full_exception is the queue is already full,
    /// otherwise does nothing if full.
    /// \return A reference to the position to 'push' to.
    //*************************************************************************
    reference push()
    {
      const size_type next = in;

      if (!full())
      {
        in = (in == (MAX_SIZE - 1)) ? 0 : ++in;
        ++size;
      }
#ifdef ETL_USE_EXCEPTIONS
      else
      {
        throw queue_full_exception();
      }
#endif

      return buffer[next];
    }

    //*************************************************************************
    /// Gets a reference to the item at the front of the queue.<br>
    /// If ETL_USE_EXCEPTIONS is defined, throws an etl::queue_empty_exception if the queue is empty.<br>
    /// If ETL_USE_EXCEPTIONS is not defined and the queue is empty, the return value is undefined.
    /// \return A reference to the item at the front of the queue.
    //*************************************************************************
    reference front()
    {
#ifdef ETL_USE_EXCEPTIONS
      if (empty())
      {
        throw queue_empty_exception();
      }
#endif

      return buffer[out];
    }

    //*************************************************************************
    /// Gets a const reference to the item at the front of the queue.<br>
    /// If ETL_USE_EXCEPTIONS is defined, throws an etl::queue_empty_exception if the queue is empty.<br>
    /// If ETL_USE_EXCEPTIONS is not defined and the queue is empty, the return value is undefined.
    /// \return A const reference to the item at the front of the queue.
    //*************************************************************************
    const_reference front() const
    {
#ifdef ETL_USE_EXCEPTIONS
      if (empty())
      {
        throw queue_empty_exception();
      }
#endif

      return buffer[out];
    }

  protected:

    //*************************************************************************
    /// The constructor that is called from derived classes.
    //*************************************************************************
    queue(T* buffer, size_type max_size)
      : queue_base(max_size),
        buffer(buffer)
    {
    }

  private:

    T* buffer; ///< The internal buffer.
  };
}