etl/alignment.h

///\file

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

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

Copyright(c) 2014 jwellbelove

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

#ifndef __ETL_ALIGNEMENT__
#define __ETL_ALIGNEMENT__

#include <stdint.h>

#include "type_traits.h"
#include "static_assert.h"

///\defgroup alignment alignment
/// Creates a variable of the specified type at the specified alignment.
/// \ingroup utilities

namespace etl
{
  namespace __private_alignment__
  {
    //***************************************************************************
    // Matcher.
    //***************************************************************************
    template <const bool IS_MATCH, const size_t ALIGNMENT, typename T1 = void, typename T2 = void, typename T3 = void, typename T4 = void, typename T5 = void, typename T6 = void, typename T7 = void, typename T8 = void>
    class type_with_alignment_matcher;

    // Matching alignment.
    template <const size_t ALIGNMENT, typename T1, typename T2, typename T3, typename T4, typename T5, typename T6, typename T7, typename T8>
    class type_with_alignment_matcher <true, ALIGNMENT, T1, T2, T3, T4, T5, T6, T7, T8>
    {
    public:

      typedef T1 type;
    };

    // Non-matching alignment.
    template <const size_t ALIGNMENT, typename T1, typename T2, typename T3, typename T4, typename T5, typename T6, typename T7, typename T8>
    class type_with_alignment_matcher <false, ALIGNMENT, T1, T2, T3, T4, T5, T6, T7, T8>
    {
    public:

      typedef typename type_with_alignment_matcher<ALIGNMENT == etl::alignment_of<T2>::value, ALIGNMENT, T2, T3, T4, T5, T6, T7, T8, void>::type type;
    };

    // Non-matching alignment, non left.
    template <const size_t ALIGNMENT>
    class type_with_alignment_matcher <false, ALIGNMENT, void, void, void, void, void, void, void, void>
    {
    public:
    };

    //***************************************************************************
    // Helper.
    //***************************************************************************
    template <const size_t ALIGNMENT, typename T1, typename T2 = void, typename T3 = void, typename T4 = void, typename T5 = void, typename T6 = void, typename T7 = void, typename T8 = void>
    class type_with_alignment_helper
    {
    public:

      typedef typename type_with_alignment_matcher<ALIGNMENT == etl::alignment_of<T1>::value, ALIGNMENT, T1, T2, T3, T4, T5, T6, T7, T8>::type type;
    };
  }

  //***************************************************************************
  /// Gets a type that has the same as the specified alignment.
  ///\ingroup alignment
  //***************************************************************************
  template <const size_t ALIGNMENT>
  class type_with_alignment
  {
  public:

    typedef typename __private_alignment__::type_with_alignment_helper<ALIGNMENT, int8_t, int16_t, int32_t, int64_t, float, double, void*>::type type;
  };

  //***************************************************************************
  /// Aligned storage
  ///\ingroup alignment
  //***************************************************************************
  template <const size_t LENGTH, const size_t ALIGNMENT>
  struct aligned_storage
  {
    struct type
    {
      /// Convert to T reference.
      template <typename T>
      operator T& ()
      {
        STATIC_ASSERT(ALIGNMENT % etl::alignment_of<T>::value == 0, "Incompatible alignment");
        return reinterpret_cast<T&>(*data);
      }

      /// Convert to const T reference.
      template <typename T>
      operator const T& () const
      {
        STATIC_ASSERT(ALIGNMENT % etl::alignment_of<T>::value == 0, "Incompatible alignment");
        return reinterpret_cast<const T&>(*data);
      }

      /// Convert to T pointer.
      template <typename T>
      operator T* ()
      {
        STATIC_ASSERT(ALIGNMENT % etl::alignment_of<T>::value == 0, "Incompatible alignment");
        return reinterpret_cast<T*>(data);
      }

      /// Convert to const T pointer.
      template <typename T>
      operator const T* () const
      {
        STATIC_ASSERT(ALIGNMENT % etl::alignment_of<T>::value == 0, "Incompatible alignment");
        return reinterpret_cast<const T*>(data);
      }

      /// Get address as T reference.
      template <typename T>
      T* get_reference()
      {
        STATIC_ASSERT(ALIGNMENT % etl::alignment_of<T>::value == 0, "Incompatible alignment");
        return reinterpret_cast<T&>(*data);
      }

      /// Get address as const T reference.
      template <typename T>
      const T* get_reference() const
      {
        STATIC_ASSERT(ALIGNMENT % etl::alignment_of<T>::value == 0, "Incompatible alignment");
        return reinterpret_cast<const T&>(*data);
      }

      /// Get address as T pointer.
      template <typename T>
      T* get_address()
      {
        STATIC_ASSERT(ALIGNMENT % etl::alignment_of<T>::value == 0, "Incompatible alignment");
        return reinterpret_cast<T*>(data);
      }

      /// Get address as const T pointer.
      template <typename T>
      const T* get_address() const
      {
        STATIC_ASSERT(ALIGNMENT % etl::alignment_of<T>::value == 0, "Incompatible alignment");
        return reinterpret_cast<const T*>(data);
      }

      union
      {
        uint8_t data[LENGTH];
        typename etl::type_with_alignment<ALIGNMENT>::type __etl_alignment_type__; // A POD type has has the same alignment as ALIGNMENT.
      };
    };
  };

  //***************************************************************************
  /// Aligned storage as
  ///\ingroup alignment
  //***************************************************************************
  template <const size_t LENGTH, typename T>
  struct aligned_storage_as : public etl::aligned_storage<LENGTH, etl::alignment_of<T>::value>
  {
  };
}

#endif