etl/cyclic_value.h

///\file

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#ifndef __ETL_CYCLIC_VALUE__
#define __ETL_CYCLIC_VALUE__

#include <cstddef>

///\defgroup cyclic_value cyclic_value
/// Provides a value that cycles between two limits.
/// \ingroup utilities

#include <algorithm>

#include "static_assert.h"
#include "exception.h"

namespace etl
{
#ifdef ETL_USE_EXCEPTIONS
  //***************************************************************************
  ///\ingroup cyclic_value
  /// The base class for cyclic_value exceptions.
  //***************************************************************************
  class cyclic_value_exception : public exception
  {
  public:

    cyclic_value_exception(const char* what)
      : exception(what)
    {
    }
  };

  //***************************************************************************
  ///\ingroup cyclic_value
  /// The illegal range exception.
  //***************************************************************************
  class cyclic_value_illegal_range : public cyclic_value_exception
  {
  public:

    cyclic_value_illegal_range()
      : cyclic_value_exception("cyclic_value illegal range")
    {
    }
  };
#endif

	//***************************************************************************
	/// Provides a value that cycles between two limits.
  /// Supports incrementing and decrementing.
	///\tparam T     The type of the variable.
	///\tparam FIRST The first value of the range.
	///\tparam LAST  The last value of the range.
  ///\tparam STEP  The amount to increment or decrement. Default = 1.
  ///\note LAST - FIRST + 1 must be a multiple of STEP.
  ///\ingroup cyclic_value
	//***************************************************************************
	template <typename T, const T FIRST = 0, const T LAST = 0, const T STEP = 1>
	class cyclic_value
	{
	public:

		//*************************************************************************
		/// Constructor.
		/// Sets 'first' and 'last' to the template parameter values.
    /// The initial value is set to the first value.
		//*************************************************************************
		cyclic_value()
			: value(FIRST),
        first_value(FIRST),
			  last_value(LAST),
        step_value(STEP)
		{
      STATIC_ASSERT(((LAST - FIRST + 1) % STEP) == 0, "LAST - FIRST + 1 is not a multiple of STEP");
		}

		//*************************************************************************
		/// Constructor.
    /// Sets the value to the first of the range.
    ///\param first The first value in the range.
		///\param last  The last value in the range.
		//*************************************************************************
		cyclic_value(const T& first_, const T& last_)
			: value(first_),
        first_value(first_),
			  last_value(last_),
        step_value(STEP)
		{
		}

    //*************************************************************************
    /// Constructor.
    /// Sets the value to the first of the range.
    ///\param first The first value in the range.
    ///\param last  The last value in the range.
    //*************************************************************************
    cyclic_value(const T& first_, const T& last_, const T& step_)
      : value(first_),
        first_value(first_),
        last_value(last_),
        step_value(step_)
    {
    }

		//*************************************************************************
		/// Sets the range.
		/// Sets the value to the first of the range.
    ///\param first The first value in the range.
		///\param last  The last value in the range.
    ///\param step  The step value. Default = 1.
		//*************************************************************************
		void set(const T& first_, const T& last_, const T& step_ = 1)
		{
			first_value = first_;
			last_value  = last_;
      step_value  = step_;
			value       = first_;

#if ETL_USE_EXCEPTIONS
      if (((last_value - first_value + 1) % step_value) != 0)
      {
        throw cyclic_value_illegal_range();
      }
#endif
		}

    //*************************************************************************
    /// Resets the value to the first in the range.
    //*************************************************************************
    void to_first()
    {
      value = first_value;
    }

    //*************************************************************************
    /// Resets the value to the last in the range.
    //*************************************************************************
    void to_last()
    {
      value = last_value;
    }

    //*************************************************************************
    /// Advances to value by a number of steps.
    ///\param n The number of steps to advance.
    //*************************************************************************
    void advance(int n)
    {
      if (n > 0)
      {
        for (int i = 0; i < n; ++i)
        {
          operator ++();
        }
      }
      else
      {
        for (int i = 0; i < -n; ++i)
        {
          operator --();
        }
      }
    }

		//*************************************************************************
		/// Conversion operator.
    /// \return The value of the underlying type.
		//*************************************************************************
		operator T()
		{
			return value;
		}

		//*************************************************************************
		/// Const conversion operator.
		/// \return The value of the underlying type.
		//*************************************************************************
		operator const T() const
		{
			return value;
		}

		//*************************************************************************
		/// ++ operator.
		//*************************************************************************
		cyclic_value& operator ++()
		{
			if (value == last_value)
			{
				value = first_value;
			}
			else
			{
				value += step_value;
			}

			return *this;
		}

		//*************************************************************************
		/// ++ operator.
		//*************************************************************************
		cyclic_value operator ++(int)
		{
			cyclic_value temp(*this);

			operator++();

			return temp;
		}

		//*************************************************************************
		/// -- operator.
		//*************************************************************************
		cyclic_value& operator --()
		{
			if (value == first_value)
			{
				value = last_value;
			}
			else
			{
				value -= step_value;
			}

			return *this;
		}

		//*************************************************************************
		/// -- operator.
		//*************************************************************************
		cyclic_value operator --(int)
		{
			cyclic_value temp(*this);

			operator--();

			return temp;
		}

    //*************************************************************************
		/// Gets the first value.
		//*************************************************************************
    const T& first() const
    {
      return first_value;
    }

  	//*************************************************************************
		/// Gets the last value.
		//*************************************************************************
    const T& last() const
    {
      return last_value;
    }

    //*************************************************************************
		/// Gets the last value.
		//*************************************************************************
    const T& step() const
    {
      return step_value;
    }

    //*************************************************************************
    /// Gets the number of steps in a cycle.
    //*************************************************************************
    size_t number_of_steps() const
    {
      return (last_value - first_value + 1) / step_value;
    }

	private:

    T value;       ///< The current value.
    T first_value; ///< The first value in the range.
		T last_value;  ///< The last value in the range.
    T step_value;  ///< The value to step.
	};
}

#endif