etl/power.h

///\file

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

Embedded Template Library.
https://github.com/ETLCPP/etl

Copyright(c) 2014 jwellbelove

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files(the "Software"), to deal
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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******************************************************************************/

#ifndef __ETL_POW__
#define __ETL_POW__

#include <stddef.h>
#include "log.h"

///\defgroup power power
/// power<N, POWER> : Calculates N to the power POWER.
///\ingroup maths

namespace etl 
{
  //***************************************************************************
  ///\ingroup power
  /// Calculates powers.
  //***************************************************************************
  template <const size_t N, const size_t POWER>
  struct power
  {
    enum value_type
    {
      value = N * power<N, POWER - 1>::value
    };
  };

  //***************************************************************************
  /// Calculates powers.
  /// Specialisation for POWER == 0.
  //***************************************************************************
  template <const size_t N>
  struct power<N, 0>
  {
    enum value_type
    {
      value = 1
    };
  };

  //***************************************************************************
  ///\ingroup power
  /// Calculates the rounded up power of 2.
  //***************************************************************************
  template <const size_t N>
  struct power_of_2_round_up
  {
    enum value_type
    {
      value = 1 << (etl::log2<N - 1>::value + 1)
    };
  };

  //***************************************************************************
  ///\ingroup power
  /// Calculates the rounded up power of 2.
  /// Specialisation for 0.
  //***************************************************************************
  template <>
  struct power_of_2_round_up<0>
  {
    enum value_type
    {
      value = 2
    };
  };

  //***************************************************************************
  ///\ingroup power
  /// Calculates the rounded down power of 2.
  //***************************************************************************
  template <const size_t N>
  struct power_of_2_round_down
  {
    enum value_type
    {
      value = 1 << (etl::log2<N - 1>::value)
    };
  };

  //***************************************************************************
  ///\ingroup power
  /// Calculates the rounded down power of 2.
  /// Specialisation for 0.
  //***************************************************************************
  template <>
  struct power_of_2_round_down<0>
  {
    enum value_type
    {
      value = 2
    };
  };

  //***************************************************************************
  ///\ingroup power
  /// Calculates the rounded down power of 2.
  /// Specialisation for 1.
  //***************************************************************************
  template <>
  struct power_of_2_round_down<1>
  {
    enum value_type
    {
      value = 2
    };
  };

  //***************************************************************************
  ///\ingroup power
  /// Calculates the rounded down power of 2.
  /// Specialisation for 2.
  //***************************************************************************
  template <>
  struct power_of_2_round_down<2>
  {
    enum value_type
    {
      value = 2
    };
  };

  //***************************************************************************
  ///\ingroup power
  /// Checks if N is a power of 2.
  //***************************************************************************
  template <const size_t N>
  struct is_power_of_2
  {
    static const bool value = (N & (N - 1)) == 0;
  };

  //***************************************************************************
  ///\ingroup power
  /// Checks if N is a power of 2.
  /// Specialisation for 0.
  //***************************************************************************
  template <>
  struct is_power_of_2<0>
  {
    static const bool value = false;
  };

  //***************************************************************************
  ///\ingroup power
  /// Checks if N is a power of 2.
  /// Specialisation for 1.
  //***************************************************************************
  template <>
  struct is_power_of_2<1>
  {
    static const bool value = false;
  };
}

#endif