fsfw/contrib/fsfw_contrib/etl-20.39.4/include/etl/private/bitset_new.h

///\file
/******************************************************************************
The MIT License(MIT)

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

Copyright(c) 2022 John Wellbelove

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files(the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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******************************************************************************/

#ifndef ETL_BITSET_NEW_INCLUDED
#define ETL_BITSET_NEW_INCLUDED

#include "../platform.h"
#include "../algorithm.h"
#include "../iterator.h"
#include "../integral_limits.h"
#include "../algorithm.h"
#include "../nullptr.h"
#include "../log.h"
#include "../exception.h"
#include "../integral_limits.h"
#include "../binary.h"
#include "../char_traits.h"
#include "../static_assert.h"
#include "../error_handler.h"
#include "../span.h"
#include "../string.h"
#include "../enum_type.h"
#include "../largest.h"
#include "../smallest.h"

#include <string.h>
#include <stddef.h>
#include <stdint.h>

#if ETL_USING_STL
#include <algorithm>
#endif

#include "minmax_push.h"

#if defined(ETL_COMPILER_KEIL)
#pragma diag_suppress 1300
#endif

#if ETL_USING_CPP11
  #define ETL_STR(x)  x
  #define ETL_STRL(x) L##x
  #define ETL_STRu(x) u##x
  #define ETL_STRU(x) U##x
#else
  #define ETL_STR(x)  x
  #define ETL_STRL(x) x
  #define ETL_STRu(x) x
  #define ETL_STRU(x) x
#endif

//*****************************************************************************
///\defgroup bitset bitset
/// Similar to std::bitset but without requiring std::string.
///\ingroup containers
//*****************************************************************************

namespace etl
{
  //***************************************************************************
  /// Flags to indicate whether the bitset is contained in a single element
  /// or spread over an array of elements.
  ///\ingroup bitset
  //***************************************************************************
  struct bitset_storage_model
  {
    enum enum_type
    {
      Undefined = 0,
      Single    = 1,
      Multi     = 2
    };

    ETL_DECLARE_ENUM_TYPE(bitset_storage_model, char)
    ETL_ENUM_TYPE(Undefined, "Undefined")
    ETL_ENUM_TYPE(Single,    "Single")
    ETL_ENUM_TYPE(Multi,     "Multi")
    ETL_END_ENUM_TYPE
  };

  //***************************************************************************
  /// Exception base for bitset
  ///\ingroup bitset
  //***************************************************************************
  class bitset_exception : public etl::exception
  {
  public:

    bitset_exception(string_type reason_, string_type file_name_, numeric_type line_number_)
      : exception(reason_, file_name_, line_number_)
    {
    }
  };

  //***************************************************************************
  /// Bitset type_too_small exception.
  ///\ingroup bitset
  //***************************************************************************
  class bitset_string_too_small : public bitset_exception
  {
  public:

    bitset_string_too_small(string_type file_name_, numeric_type line_number_)
      : bitset_exception(ETL_ERROR_TEXT("bitset:type_too_small", ETL_BITSET_FILE_ID"A"), file_name_, line_number_)
    {
    }
  };

  //***************************************************************************
  /// Bitset overflow exception.
  ///\ingroup bitset
  //***************************************************************************
  class bitset_overflow : public bitset_exception
  {
  public:

    bitset_overflow(string_type file_name_, numeric_type line_number_)
      : bitset_exception(ETL_ERROR_TEXT("bitset:overflow", ETL_BITSET_FILE_ID"C"), file_name_, line_number_)
    {
    }
  };

  //***************************************************************************
  /// Bitset nullptr buffer exception.
  ///\ingroup bitset
  //***************************************************************************
  class bitset_invalid_buffer : public bitset_exception
  {
  public:

    bitset_invalid_buffer(string_type file_name_, numeric_type line_number_)
      : bitset_exception(ETL_ERROR_TEXT("bitset:invalid buffer", ETL_BITSET_FILE_ID"D"), file_name_, line_number_)
    {
    }
  };

  //***************************************************************************
  namespace private_bitset
  {
    template <typename TElement>
    class bitset_impl_common
    {
    public:

      typedef TElement        element_type;
      typedef TElement*       pointer;
      typedef const TElement* const_pointer;

      static ETL_CONSTANT size_t   npos              = etl::integral_limits<size_t>::max;
      static ETL_CONSTANT size_t   Bits_Per_Element  = etl::integral_limits<TElement>::bits;
      static ETL_CONSTANT TElement All_Set_Element   = etl::integral_limits<TElement>::max;
      static ETL_CONSTANT TElement All_Clear_Element = element_type(0);
    };

    template <typename TElement>
    ETL_CONSTANT size_t bitset_impl_common<TElement>::npos;

    template <typename TElement>
    ETL_CONSTANT size_t bitset_impl_common<TElement>::Bits_Per_Element;

    template <typename TElement>
    ETL_CONSTANT TElement bitset_impl_common<TElement>::All_Set_Element;

    template <typename TElement>
    ETL_CONSTANT TElement bitset_impl_common<TElement>::All_Clear_Element;
  }

  //*************************************************************************
  /// Bitset implementation declaration.
  ///\ingroup bitset
  //*************************************************************************
  template <typename TElement, char Bitset_Layout>
  class bitset_impl;

  //*************************************************************************
  /// The implementation class for single element etl::bitset
  ///\ingroup bitset
  //*************************************************************************
  template <typename TElement>
  class bitset_impl<TElement, etl::bitset_storage_model::Single> : public etl::private_bitset::bitset_impl_common<TElement>
  {
  public:

    using typename etl::private_bitset::bitset_impl_common<TElement>::element_type;
    using typename etl::private_bitset::bitset_impl_common<TElement>::pointer;
    using typename etl::private_bitset::bitset_impl_common<TElement>::const_pointer;

    using etl::private_bitset::bitset_impl_common<TElement>::Bits_Per_Element;
    using etl::private_bitset::bitset_impl_common<TElement>::All_Set_Element;
    using etl::private_bitset::bitset_impl_common<TElement>::All_Clear_Element;

    using etl::private_bitset::bitset_impl_common<TElement>::npos;

    //*************************************************************************
    /// Set all of the bits.
    //*************************************************************************
    static
    ETL_CONSTEXPR14 
    void set_all(pointer      pbuffer,
                 size_t       /*number_of_elements*/,
                 element_type top_mask) ETL_NOEXCEPT
    {
      *pbuffer = All_Set_Element & top_mask;
    }

    //*************************************************************************
    /// Set the bit at the position.
    //*************************************************************************
    static
    ETL_CONSTEXPR14
    void set_position(pointer pbuffer, 
                      size_t  position, 
                      bool    value = true)
    {
      const element_type mask = element_type(element_type(1) << position);

      if (value == true)
      {
        *pbuffer |= mask;
      }
      else
      {
        *pbuffer &= ~mask;
      }
    }

    //*************************************************************************
    /// Set the bit at the position.
    //*************************************************************************
    template <size_t Position>
    static
    ETL_CONSTEXPR14
    void set_position(pointer pbuffer,
                      bool    value = true)
    {
      const element_type mask = element_type(element_type(1) << Position);

      if (value == true)
      {
        *pbuffer |= mask;
      }
      else
      {
        *pbuffer &= ~mask;
      }
    }

    //*************************************************************************
    /// Set the bit at the position.
    //*************************************************************************
    template <size_t Position, bool Value>
    static
    ETL_CONSTEXPR14
    void set_position(pointer pbuffer)
    {
      const element_type mask = element_type(element_type(1) << Position);

      if (Value == true)
      {
        *pbuffer |= mask;
      }
      else
      {
        *pbuffer &= ~mask;
      }
    }

    //*************************************************************************
    /// Reset all of the bits.
    //*************************************************************************
    static
    ETL_CONSTEXPR14
    void reset_all(pointer pbuffer, 
                   size_t  /*number_of_elements*/) ETL_NOEXCEPT
    {
      *pbuffer = All_Clear_Element;
    }

    //*************************************************************************
    /// Reset the bit at the position.
    //*************************************************************************
    static
    ETL_CONSTEXPR14

    void reset_position(pointer pbuffer, 
                        size_t  position)
    {
      const element_type mask = element_type(element_type(1) << position);
      *pbuffer &= ~mask;
    }

    //*************************************************************************
    /// Set from a string.
    //*************************************************************************
    static
    ETL_CONSTEXPR14
    void from_string(pointer     pbuffer, 
                     size_t      /*number_of_elements*/, 
                     size_t      active_bits, 
                     const char* text) ETL_NOEXCEPT
    {
      reset_all(pbuffer, 1U);

      if (text != ETL_NULLPTR)
      {
        size_t string_length = etl::strlen(text);

        // Build from the string.
        string_length = etl::min(active_bits, string_length);

        element_type mask = element_type(element_type(1) << (string_length - 1U));

        for (size_t i = 0U; i < string_length; ++i)
        {
          if (text[i] == ETL_STR('1'))
          {
            *pbuffer |= mask;
          }

          mask >>= 1U;
        }
      }
    }

    //*************************************************************************
    /// Set from a wide string.
    //*************************************************************************
    static
    ETL_CONSTEXPR14
    void from_string(pointer        pbuffer, 
                     size_t         /*number_of_elements*/, 
                     size_t         active_bits, 
                     const wchar_t* text) ETL_NOEXCEPT
    {
      reset_all(pbuffer, 1U);

      if (text != ETL_NULLPTR)
      {
        size_t string_length = etl::strlen(text);

        // Build from the string.
        string_length = etl::min(active_bits, string_length);

        element_type mask = element_type(element_type(1) << (string_length - 1U));

        for (size_t i = 0U; i < string_length; ++i)
        {
          if (text[i] == ETL_STRL('1'))
          {
            *pbuffer |= mask;
          }

          mask >>= 1U;
        }
      }
    }

    //*************************************************************************
    /// Set from a u16 string.
    //*************************************************************************
    static
    ETL_CONSTEXPR14 
    void from_string(pointer         pbuffer, 
                     size_t          /*number_of_elements*/, 
                     size_t          active_bits, 
                     const char16_t* text) ETL_NOEXCEPT
    {
      reset_all(pbuffer, 1U);

      if (text != ETL_NULLPTR)
      {
        size_t string_length = etl::strlen(text);

        // Build from the string.
        string_length = etl::min(active_bits, string_length);

        element_type mask = element_type(element_type(1) << (string_length - 1U));

        for (size_t i = 0U; i < string_length; ++i)
        {
          if (text[i] == ETL_STRu('1'))
          {
            *pbuffer |= mask;
          }

          mask >>= 1U;
        }
      }
    }

    //*************************************************************************
    /// Set from a u32 string.
    //*************************************************************************
    static
    ETL_CONSTEXPR14 
    void from_string(pointer         pbuffer, 
                     size_t          /*number_of_elements*/, 
                     size_t          active_bits, 
                     const char32_t* text) ETL_NOEXCEPT
    {
      reset_all(pbuffer, 1U);

      if (text != ETL_NULLPTR)
      {
        size_t string_length = etl::strlen(text);

        // Build from the string.
        string_length = etl::min(active_bits, string_length);

        element_type mask = element_type(element_type(1) << (string_length - 1U));

        for (size_t i = 0U; i < string_length; ++i)
        {
          if (text[i] == ETL_STRU('1'))
          {
            *pbuffer |= mask;
          }

          mask >>= 1U;
        }
      }
    }

    //*************************************************************************
    /// Get as an integral value.
    //*************************************************************************
    template <typename T>
    static
    ETL_CONSTEXPR14
    T value(const_pointer pbuffer, 
            size_t        /*number_of_elements*/) ETL_NOEXCEPT
    {
      return T(*pbuffer);
    }

    //*************************************************************************
    /// Extract an integral value from an arbitrary position and length.
    //*************************************************************************
    template <typename T>
    static
    ETL_CONSTEXPR14
    T extract(const_pointer pbuffer, 
              size_t        position, 
              size_t        length = etl::integral_limits<T>::bits)
    {
      typedef typename etl::make_unsigned<T>::type unsigned_t;

      const unsigned_t Mask  = etl::make_lsb_mask<unsigned_t>(length);
      const unsigned_t Shift = position % Bits_Per_Element;

      unsigned_t value = static_cast<unsigned_t>(*pbuffer >> Shift) & Mask;

      if ((length != etl::integral_limits<T>::bits) && etl::integral_limits<T>::is_signed)
      {
        value = etl::sign_extend<T>(value, length);
      }

      return static_cast<T>(value);
    }

    //*************************************************************************
    /// Extract an integral value from an arbitrary position and length.
    //*************************************************************************
#if ETL_USING_CPP11
    template <typename T, size_t Position, size_t Length = etl::integral_limits<T>::bits>
#else
		template <typename T, size_t Position, size_t Length>
#endif
    static
    ETL_CONSTEXPR14
    T extract(const_pointer pbuffer)
    {
      typedef typename etl::make_unsigned<T>::type unsigned_t;

      const unsigned_t Mask  = etl::make_lsb_mask<unsigned_t>(Length);
      const unsigned_t Shift = Position % Bits_Per_Element;

      unsigned_t value = static_cast<unsigned_t>(*pbuffer >> Shift) & Mask;

      if ((Length != etl::integral_limits<T>::bits) && etl::integral_limits<T>::is_signed)
      {
        value = etl::sign_extend<T>(value, Length);
      }

      return static_cast<T>(value);
    }

    //*************************************************************************
    /// Tests a bit at a position.
    /// Positions greater than the number of configured bits will return <b>false</b>.
    //*************************************************************************
    static
    ETL_CONSTEXPR14 
    bool test(const_pointer pbuffer, 
              size_t        position)
    {
      const element_type mask = element_type(element_type(1) << position);
      return (*pbuffer & mask) != 0U;
    }

    //*************************************************************************
    /// Count the number of bits set.
    //*************************************************************************
    static
    ETL_CONSTEXPR14
    size_t count(const_pointer pbuffer, 
                 size_t        /*number_of_elements*/) ETL_NOEXCEPT
    {
      return etl::count_bits(*pbuffer);
    }

    //*************************************************************************
    // Are all the bits sets?
    //*************************************************************************
    static
    ETL_CONSTEXPR14
    bool all(const_pointer pbuffer, 
             size_t        /*number_of_elements*/, 
             element_type  top_mask) ETL_NOEXCEPT
    {
      return (*pbuffer & top_mask) == top_mask;
    }

    //*************************************************************************
    // Are all the mask bits sets?
    //*************************************************************************
    static
    ETL_CONSTEXPR14 
    bool all(const_pointer pbuffer, 
             size_t        /*number_of_elements*/, 
             element_type  top_mask, 
             element_type  mask) ETL_NOEXCEPT
    {
      return (*pbuffer & top_mask & mask) == mask;
    }

    //*************************************************************************
    /// Are none of the bits set?
    //*************************************************************************
    static
    ETL_CONSTEXPR14 
    bool none(const_pointer pbuffer, 
              size_t        /*number_of_elements*/) ETL_NOEXCEPT
    {
      return *pbuffer == All_Clear_Element;
    }

    //*************************************************************************
    /// Are none of the mask bits set?
    //*************************************************************************
    static
    ETL_CONSTEXPR14 
    bool none(const_pointer pbuffer, 
              size_t        /*number_of_elements*/, 
              element_type  mask) ETL_NOEXCEPT
    {
      return (*pbuffer & mask) == All_Clear_Element;
    }

    //*************************************************************************
    /// Are any of the bits set?
    //*************************************************************************
    static
    ETL_CONSTEXPR14 
    bool any(const_pointer pbuffer, 
             size_t        /*number_of_elements*/) ETL_NOEXCEPT
    {
      return *pbuffer != All_Clear_Element;
    }

    //*************************************************************************
    /// Are any of the mask bits set?
    //*************************************************************************
    static
    ETL_CONSTEXPR14 
    bool any(const_pointer pbuffer, 
             size_t        /*number_of_elements*/, 
             element_type  mask) ETL_NOEXCEPT
    {
      return (*pbuffer & mask) != All_Clear_Element;
    }

    //*************************************************************************
    /// Flip all of the bits.
    //*************************************************************************
    static
    ETL_CONSTEXPR14 
    void flip_all(pointer pbuffer, 
                     size_t  /*number_of_elements*/) ETL_NOEXCEPT
    {
      *pbuffer = ~*pbuffer;
    }

    //*************************************************************************
    /// Flip some of the bits.
    //*************************************************************************
    static
    ETL_CONSTEXPR14 
    void flip_bits(pointer      pbuffer, 
                   element_type mask = etl::integral_limits<element_type>::max) ETL_NOEXCEPT
    {
      *pbuffer ^= mask;
    }

    //*************************************************************************
    /// Flip the bit at the position.
    //*************************************************************************
    static
    ETL_CONSTEXPR14 
    void flip_position(pointer pbuffer, 
                       size_t  position)
    {
      const element_type mask = element_type(element_type(1) << position);
      *pbuffer ^= mask;
    }

    //*************************************************************************
    /// Returns a string representing the bitset.
    //*************************************************************************
    template <typename TString>
    static
    ETL_CONSTEXPR14 
    TString to_string(const_pointer pbuffer,
                      size_t active_bits,
                      typename TString::value_type zero = typename TString::value_type('0'),
                      typename TString::value_type one  = typename TString::value_type('1'))
    {
      TString result;

      result.resize(active_bits, '\0');

      // Check that the string type can contain the digits.
      ETL_ASSERT_OR_RETURN_VALUE(result.size() == active_bits, ETL_ERROR(etl::bitset_string_too_small), result);

      for (size_t i = active_bits; i > 0; --i)
      {
        result[active_bits - i] = test(pbuffer, i - 1) ? one : zero;
      }

      return result;
    }

    //*************************************************************************
    /// Finds the next bit in the specified state.
    ///\param state    The state to search for.
    ///\param position The position to start from.
    ///\returns The position of the bit or npos if none were found.
    //*************************************************************************
    static
    ETL_CONSTEXPR14 
    size_t find_next(const_pointer pbuffer, 
                     size_t        /*number_of_elements*/, 
                     size_t        active_bits, 
                     bool          state, 
                     size_t        position) ETL_NOEXCEPT
    {
      if (position < active_bits)
      {
        // Where to start.
        size_t bit = position;

        element_type mask = 1U << position;

        // Needs checking?
        if ((state && (*pbuffer != All_Clear_Element)) || (!state && (*pbuffer != All_Set_Element)))
        {
          // For each bit in the element...
          while (bit < active_bits)
          {
            // Equal to the required state?
            if (((*pbuffer & mask) != 0) == state)
            {
              return bit;
            }

            // Move on to the next bit.
            mask <<= 1;
            ++bit;
          }
        }
      }

      return npos;
    }

    //*************************************************************************
    /// operator assignment
    /// Assigns rhs to lhs
    //*************************************************************************
    static
    ETL_CONSTEXPR14 
    void operator_assignment(pointer       lhs_pbuffer, 
                             const_pointer rhs_pbuffer, 
                             size_t        /*number_of_elements*/) ETL_NOEXCEPT
    {
      *lhs_pbuffer = *rhs_pbuffer;
    }

    //*************************************************************************
    /// operator and
    /// AND lhs and rhs and put the result in lhs
    //*************************************************************************
    static
    ETL_CONSTEXPR14 
    void operator_and(pointer       lhs_pbuffer, 
                      const_pointer rhs_pbuffer, 
                      size_t        /*number_of_elements*/) ETL_NOEXCEPT
    {
      *lhs_pbuffer &= *rhs_pbuffer;
    }

    //*************************************************************************
    /// operator or
    /// OR lhs and rhs and put the result in lhs
    //*************************************************************************
    static
    ETL_CONSTEXPR14 
    void operator_or(pointer       lhs_pbuffer, 
                     const_pointer rhs_pbuffer, 
                     size_t        /*number_of_elements*/) ETL_NOEXCEPT
    {
      *lhs_pbuffer |= *rhs_pbuffer;
    }

    //*************************************************************************
    /// operator xor
    /// XOR lhs and rhs and put the result in lhs
    //*************************************************************************
    static
    ETL_CONSTEXPR14 
    void operator_xor(pointer       lhs_pbuffer, 
                      const_pointer rhs_pbuffer, 
                      size_t        /*number_of_elements*/) ETL_NOEXCEPT
    {
      *lhs_pbuffer ^= *rhs_pbuffer;
    }

    //*************************************************************************
    /// operator ~
    /// NOT the value in the buffer
    //*************************************************************************
    static
    ETL_CONSTEXPR14 
    void operator_not(pointer pbuffer, 
                      size_t  /*number_of_elements*/) ETL_NOEXCEPT
    {
      *pbuffer = ~*pbuffer;
    }

    //*************************************************************************
    /// operator_shift_left
    //*************************************************************************
    static
    ETL_CONSTEXPR14 
    void operator_shift_left(pointer pbuffer, 
                             size_t  /*number_of_elements*/, 
                             size_t  active_bits, 
                             size_t  shift) ETL_NOEXCEPT
    {
      if (shift >= active_bits)
      {
        reset_all(pbuffer, 1U);
      }
      else
      {
        *pbuffer <<= shift;
      }
    }

    //*************************************************************************
    /// operator_shift_right
    //*************************************************************************
    static
    ETL_CONSTEXPR14 
    void operator_shift_right(pointer pbuffer, 
                              size_t  /*number_of_elements*/, 
                              size_t  active_bits, 
                              size_t  shift) ETL_NOEXCEPT
    {
      if (shift >= active_bits)
      {
        reset_all(pbuffer, 1U);
      }
      else
      {
        *pbuffer >>= shift;
      }
    }

    //*************************************************************************
    /// operator_equality
    //*************************************************************************
    static
    ETL_CONSTEXPR14 
    bool operator_equality(const_pointer lhs_pbuffer, 
                           const_pointer rhs_pbuffer, 
                           size_t        /*number_of_elements*/) ETL_NOEXCEPT
    {
      return (*lhs_pbuffer == *rhs_pbuffer);
    }

    //*************************************************************************
    /// Initialise from an unsigned long long.
    //*************************************************************************
    template <typename TElementType>
    static
    ETL_CONSTEXPR14 
    void initialise(pointer            pbuffer, 
                    size_t             /*number_of_elements*/,
                    unsigned long long value) ETL_NOEXCEPT
    {
      *pbuffer = static_cast<TElementType>(value);
    }

    //*************************************************************************
    /// swap
    //*************************************************************************
    static
    ETL_CONSTEXPR14 
    void swap(pointer lhs_pbuffer, 
              pointer rhs_pbuffer, 
              size_t  /*number_of_elements*/) ETL_NOEXCEPT
    {
      element_type temp = *lhs_pbuffer;
      *lhs_pbuffer = *rhs_pbuffer;
      *rhs_pbuffer = temp;
    }
  };

  //*************************************************************************
  /// The implementation class for multi element etl::bitset
  ///\ingroup bitset
  //*************************************************************************
  template <typename TElement>
  class bitset_impl<TElement, etl::bitset_storage_model::Multi> : public etl::private_bitset::bitset_impl_common<TElement>
  {
  private:

    typedef etl::private_bitset::bitset_impl_common<TElement> common;

  public:

    using typename etl::private_bitset::bitset_impl_common<TElement>::element_type;
    using typename etl::private_bitset::bitset_impl_common<TElement>::pointer;
    using typename etl::private_bitset::bitset_impl_common<TElement>::const_pointer;

    using etl::private_bitset::bitset_impl_common<TElement>::Bits_Per_Element;
    using etl::private_bitset::bitset_impl_common<TElement>::All_Set_Element;
    using etl::private_bitset::bitset_impl_common<TElement>::All_Clear_Element;

    using etl::private_bitset::bitset_impl_common<TElement>::npos;

    //*************************************************************************
    /// Check to see if the requested extract is contained within one element.
    //*************************************************************************
    template <size_t Position, size_t Length, size_t Bits_Per_Element>
    struct value_is_in_one_element
    {
      static ETL_CONSTANT bool value = ((Position + Length - 1) >> etl::log2<Bits_Per_Element>::value) == (Position >> etl::log2<Bits_Per_Element>::value);
    };

    //*************************************************************************
    /// Tests a bit at a position.
    /// Positions greater than the number of configured bits will return <b>false</b>.
    //*************************************************************************
    static
    ETL_CONSTEXPR14 
    bool test(const_pointer pbuffer,
              size_t        position) ETL_NOEXCEPT
    {
      size_t index      = position >> etl::log2<Bits_Per_Element>::value;
      element_type mask = element_type(1) << (position & (Bits_Per_Element - 1));

      return (pbuffer[index] & mask) != 0;
    }

    //*************************************************************************
    /// Count the number of bits set.
    //*************************************************************************
    static
    ETL_CONSTEXPR14
    size_t count(const_pointer pbuffer,
                 size_t        number_of_elements) ETL_NOEXCEPT
    {
      size_t count = 0;

      while (number_of_elements-- != 0)
      {
        count += etl::count_bits(*pbuffer++);
      }

      return count;
    }

    //*************************************************************************
    // Are all the bits sets?
    //*************************************************************************
    static
    ETL_CONSTEXPR14
    bool all(const_pointer pbuffer,
             size_t        number_of_elements,
             element_type  top_mask) ETL_NOEXCEPT
    {
      // All but the last.
      while (number_of_elements-- != 1U)
      {
        if (*pbuffer++ != All_Set_Element)
        {
          return false;
        }
      }

      // The last.
      if ((*pbuffer & top_mask) != top_mask)
      {
        return false;
      }

      return true;
    }

    //*************************************************************************
    /// Are none of the bits set?
    //*************************************************************************
    static
    ETL_CONSTEXPR14
    bool none(const_pointer pbuffer,
              size_t        number_of_elements) ETL_NOEXCEPT
    {
      while (number_of_elements-- != 0)
      {
        if (*pbuffer++ != 0)
        {
          return false;
        }
      }

      return true;
    }

    //*************************************************************************
    /// Are any of the bits set?
    //*************************************************************************
    static
    ETL_CONSTEXPR14
    bool any(const_pointer pbuffer,
             size_t        number_of_elements) ETL_NOEXCEPT
    {
      bool any_set = false;

      while (number_of_elements-- != 0)
      {
        if (*pbuffer++ != All_Clear_Element)
        {
          any_set = true;
          break;
        }
      }

      return any_set;
    }

    //*************************************************************************
    /// Set all bits
    //*************************************************************************
    static
    ETL_CONSTEXPR14
    void set_all(pointer      pbuffer,
                 size_t       number_of_elements,
                 element_type top_mask) ETL_NOEXCEPT
    {
      while (number_of_elements-- != 1U)
      {
        *pbuffer++ = All_Set_Element;
      }

      *pbuffer = (All_Set_Element & top_mask);
    }

    //*************************************************************************
    /// Set the bit at the position.
    //*************************************************************************
    static
    ETL_CONSTEXPR14
    void set_position(pointer pbuffer, 
                      size_t  position, 
                      bool    value = true) ETL_NOEXCEPT
    {
      size_t       index = position >> etl::log2<Bits_Per_Element>::value;
      element_type bit   = element_type(1) << (position & (Bits_Per_Element - 1));

      if (value == true)
      {
        pbuffer[index] |= bit;
      }
      else
      {
        pbuffer[index] &= ~bit;
      }
    }

    //*************************************************************************
    /// Set the bit at the position.
    //*************************************************************************
    template <size_t Position>
    static
    ETL_CONSTEXPR14
    void set_position(pointer pbuffer,
                      bool    value = true)
    {
      size_t       index = Position >> etl::log2<Bits_Per_Element>::value;
      element_type bit   = element_type(1) << (Position & (Bits_Per_Element - 1));

      if (value == true)
      {
        pbuffer[index] |= bit;
      }
      else
      {
        pbuffer[index] &= ~bit;
      }
    }

    //*************************************************************************
    /// Set the bit at the position.
    //*************************************************************************
    template <size_t Position, bool Value>
    static
    ETL_CONSTEXPR14
    void set_position(pointer pbuffer)
    {
      size_t       index = Position >> etl::log2<Bits_Per_Element>::value;
      element_type bit = element_type(1) << (Position & (Bits_Per_Element - 1));

      if (Value == true)
      {
        pbuffer[index] |= bit;
      }
      else
      {
        pbuffer[index] &= ~bit;
      }
    }

    //*************************************************************************
    /// Set from a string.
    //*************************************************************************
    static
    ETL_CONSTEXPR14 
    void from_string(pointer     pbuffer, 
                     size_t      number_of_elements, 
                     size_t      total_bits, 
                     const char* text) ETL_NOEXCEPT
    {
      if (text == ETL_NULLPTR)
      {
        etl::fill_n(pbuffer, number_of_elements, All_Clear_Element);
      }
      else
      {
        size_t string_length = etl::strlen(text);
        size_t index = etl::min(number_of_elements - 1U, (string_length / Bits_Per_Element));

        // Only reset elements we need to.
        while (index != number_of_elements)
        {
          pbuffer[index++] = All_Clear_Element;
        }

        // Build from the string.
        size_t i = etl::min(total_bits, string_length);

        while (i > 0)
        {
          set_position(pbuffer, --i, *text++ == ETL_STR('1'));
        }
      }
    }

    //*************************************************************************
    /// Set from a wide string.
    //*************************************************************************
    static
    ETL_CONSTEXPR14
    void from_string(pointer        pbuffer, 
                     size_t         number_of_elements, 
                     size_t         total_bits, 
                     const wchar_t* text) ETL_NOEXCEPT
    {
      if (text == ETL_NULLPTR)
      {
        etl::fill_n(pbuffer, number_of_elements, All_Clear_Element);
      }
      else
      {
        size_t string_length = etl::strlen(text);
        size_t index = etl::min(number_of_elements - 1U, (string_length / Bits_Per_Element));

        // Only reset elements we need to.
        while (index != number_of_elements)
        {
          pbuffer[index++] = All_Clear_Element;
        }

        // Build from the string.
        size_t i = etl::min(total_bits, string_length);

        while (i > 0)
        {
          set_position(pbuffer, --i, *text++ == ETL_STRL('1'));
        }
      }
    }

    //*************************************************************************
    /// Set from a u16 string.
    //*************************************************************************
    static
    ETL_CONSTEXPR14
    void from_string(pointer         pbuffer, 
                     size_t          number_of_elements, 
                     size_t          total_bits, 
                     const char16_t* text) ETL_NOEXCEPT
    {
      if (text == ETL_NULLPTR)
      {
        etl::fill_n(pbuffer, number_of_elements, All_Clear_Element);
      }
      else
      {
        size_t string_length = etl::strlen(text);
        size_t index = etl::min(number_of_elements - 1U, (string_length / Bits_Per_Element));

        // Only reset elements we need to.
        while (index != number_of_elements)
        {
          pbuffer[index++] = All_Clear_Element;
        }

        // Build from the string.
        size_t i = etl::min(total_bits, string_length);

        while (i > 0)
        {
          set_position(pbuffer, --i, *text++ == ETL_STRu('1'));
        }
      }
    }

    //*************************************************************************
    /// Set from a u32 string.
    //*************************************************************************
    static
    ETL_CONSTEXPR14
    void from_string(pointer         pbuffer, 
                     size_t          number_of_elements, 
                     size_t          total_bits, 
                     const char32_t* text) ETL_NOEXCEPT
    {
      if (text == ETL_NULLPTR)
      {
        etl::fill_n(pbuffer, number_of_elements, All_Clear_Element);
      }
      else
      {
        size_t string_length = etl::strlen(text);
        size_t index = etl::min(number_of_elements - 1U, (string_length / Bits_Per_Element));

        // Only reset elements we need to.
        while (index != number_of_elements)
        {
          pbuffer[index++] = All_Clear_Element;
        }

        // Build from the string.
        size_t i = etl::min(total_bits, string_length);

        while (i > 0)
        {
          set_position(pbuffer, --i, *text++ == ETL_STRU('1'));
        }
      }
    }

    //*************************************************************************
    /// Reset all of the bits.
    //*************************************************************************
    static
    ETL_CONSTEXPR14
    void reset_all(pointer pbuffer,
                   size_t  number_of_elements) ETL_NOEXCEPT
    {
      while (number_of_elements-- != 0U)
      {
        *pbuffer++ = All_Clear_Element;
      }
    }

    //*************************************************************************
    /// Reset the bit at the position.
    //*************************************************************************
    static
    ETL_CONSTEXPR14
    void reset_position(pointer pbuffer, 
                        size_t  position) ETL_NOEXCEPT
    {
      const size_t       index = position >> etl::log2<Bits_Per_Element>::value;;
      const element_type bit = element_type(1) << (position & (Bits_Per_Element - 1));

      pbuffer[index] &= ~bit;
    }

    //*************************************************************************
    /// Get as a value.
    //*************************************************************************
    template <typename T>
    static
    ETL_CONSTEXPR14
    T value(const_pointer pbuffer, 
            size_t        number_of_elements) ETL_NOEXCEPT
    {
      T v = T(0);

      const bool OK = (sizeof(T) * CHAR_BIT) >= (number_of_elements * Bits_Per_Element);

      if (OK)
      {
        uint_least8_t shift = 0U;

        for (size_t i = 0UL; i < number_of_elements; ++i)
        {
          v |= T(typename etl::make_unsigned<T>::type(pbuffer[i]) << shift);
          shift += uint_least8_t(Bits_Per_Element);
        }
      }

      return v;
    }

    //*************************************************************************
    /// Extract an value from multiple elements.
    //*************************************************************************
    template <typename T>
    static
    ETL_CONSTEXPR14
    typename etl::make_unsigned<T>::type extract_from_multiple_elements(const element_type* pbuffer,
                                                                        int                 element_index,
                                                                        size_t              active_bits_in_msb,
                                                                        size_t              length) ETL_NOEXCEPT
    {
      typedef typename etl::make_unsigned<T>::type unsigned_t;

      unsigned_t value(0);

      // Extract the first element, if partially filled.
      if (active_bits_in_msb < Bits_Per_Element)
      {
        element_type mask = etl::make_lsb_mask< element_type>(active_bits_in_msb);
        value = pbuffer[element_index] & mask;
        length -= active_bits_in_msb;
        if (length >= Bits_Per_Element)
        {
          value = value << Bits_Per_Element;
        }
        --element_index;
      }

      // Loop through the fully filled elements
      while (length >= Bits_Per_Element)
      {
        value |= pbuffer[element_index];
        length -= Bits_Per_Element;
        if (length >= Bits_Per_Element)
        {
          value = value << Bits_Per_Element;
        }
        --element_index;
      }

      // Extract the last element, if partially filled.
      if (length != 0)
      {
        value = value << length;
        element_type mask = etl::make_lsb_mask< element_type>(length);
        value |= (pbuffer[element_index] >> (Bits_Per_Element - length)) & mask;
      }

      return value;
    }

    //*************************************************************************
    /// Extract an integral value from an arbitrary position and length.
    /// Run time position and length.
    //*************************************************************************
    template <typename T>
    static
    ETL_CONSTEXPR14
    typename etl::make_unsigned<T>::type extract_from_buffer(const_pointer pbuffer, 
                                                             size_t        position, 
                                                             size_t        length) ETL_NOEXCEPT
    {
      typedef typename etl::make_unsigned<T>::type unsigned_t;

      unsigned_t value(0);

      const int Msb_Element_Index = (position + length - 1) >> etl::log2<Bits_Per_Element>::value;
      const int Lsb_Element_Index = position >> etl::log2<Bits_Per_Element>::value;

      // Is the value contained within one element?
      if (Msb_Element_Index == Lsb_Element_Index)
      {
        const unsigned_t Mask  = etl::make_lsb_mask< unsigned_t>(length);
        const unsigned_t Shift = position % Bits_Per_Element;

        value = static_cast<unsigned_t>(pbuffer[Msb_Element_Index] >> Shift) & Mask;
      }
      else
      {
        // Get the number of active bits in the msb element 
        size_t active_bits_in_msb = (position + length) - (Msb_Element_Index * Bits_Per_Element);

        // Start with index of the element containing the msb.
        int element_index = Msb_Element_Index;

        value = extract_from_multiple_elements<T>(pbuffer, element_index, active_bits_in_msb, length);
      }

      return value;
    }

    //*************************************************************************
    /// Extract an integral value when the value fits in one element.
    /// Compile time position and length.
    //*************************************************************************
    template <typename T, size_t Position, size_t Length>
    static
    ETL_CONSTEXPR14
    typename etl::enable_if<value_is_in_one_element<Position, Length, Bits_Per_Element>::value, typename etl::make_unsigned<T>::type>::type
      extract_from_buffer(const_pointer pbuffer)
    {
      typedef typename etl::make_unsigned<T>::type unsigned_t;

      const int        Element_Index = (Position + Length - 1) >> etl::log2<Bits_Per_Element>::value;
      const unsigned_t Mask          = etl::lsb_mask<unsigned_t, Length>::value;
      const unsigned_t Shift         = Position % Bits_Per_Element;
      
      return  static_cast<unsigned_t>(pbuffer[Element_Index] >> Shift) & Mask;
    }

    //*************************************************************************
    /// Extract an integral value when the value spans more than one element.
    /// Compile time position and length.
    //*************************************************************************
    template <typename T, size_t Position, size_t Length>
    static
    ETL_CONSTEXPR14
    typename etl::enable_if<!value_is_in_one_element<Position, Length, Bits_Per_Element>::value, typename etl::make_unsigned<T>::type>::type
      extract_from_buffer(const_pointer pbuffer)
    {      
      // Start with index of the element containing the msb.
      const int Msb_Element_Index = (Position + Length - 1) >> etl::log2<Bits_Per_Element>::value;

      // Get the number of active bits in the first element 
      const size_t Active_Bits_In_Msb = ((Position + Length - 1) % Bits_Per_Element) + 1;

      return extract_from_multiple_elements<T>(pbuffer, Msb_Element_Index, Active_Bits_In_Msb, Length);
    }

    //*************************************************************************
    /// Extract an integral value from an arbitrary position and length.
    //*************************************************************************
    template <typename T>
    static
    ETL_CONSTEXPR14
    T extract(const_pointer pbuffer,
              size_t        position,
              size_t        length = etl::integral_limits<T>::bits)
    {
      typedef typename etl::make_unsigned<T>::type unsigned_t;

      unsigned_t value = extract_from_buffer<unsigned_t>(pbuffer, position, length);

      if ((length != etl::integral_limits<T>::bits) && etl::integral_limits<T>::is_signed)
      {
        value = etl::sign_extend<T>(value, length);
      }

      return static_cast<T>(value);
    }

    //*************************************************************************
    /// Extract an integral value from an arbitrary position and length.
    //*************************************************************************
    template <typename T, size_t Position, size_t Length>
    static
    ETL_CONSTEXPR14
    T extract(const_pointer pbuffer)
    {
      typedef typename etl::make_unsigned<T>::type unsigned_t;

      unsigned_t value = extract_from_buffer<unsigned_t, Position, Length>(pbuffer);

      if ((Length != etl::integral_limits<T>::bits) && etl::integral_limits<T>::is_signed)
      {
        value = etl::sign_extend<T>(value, Length);
      }

      return static_cast<T>(value);
    }

    //*************************************************************************
    /// Flip all of the bits.
    //*************************************************************************
    static
    ETL_CONSTEXPR14
    void flip_all(pointer pbuffer, 
                     size_t  number_of_elements) ETL_NOEXCEPT
    {
      operator_not(pbuffer, number_of_elements);
    }

    //*************************************************************************
    /// Flip the bit at the position.
    //*************************************************************************
    static
    ETL_CONSTEXPR14
    void flip_position(pointer pbuffer, 
                       size_t  position) ETL_NOEXCEPT
    {
      const size_t       index = position >> etl::log2<Bits_Per_Element>::value;;
      const element_type bit   = element_type(1) << (position & (Bits_Per_Element - 1));

      pbuffer[index] ^= bit;
    }

    //*************************************************************************
    /// Finds the next bit in the specified state.
    ///\param state    The state to search for.
    ///\param position The position to start from.
    ///\returns The position of the bit or npos if none were found.
    //*************************************************************************
    static
    ETL_CONSTEXPR14
    size_t find_next(const_pointer pbuffer, 
                     size_t        number_of_elements, 
                     size_t        total_bits, 
                     bool          state, 
                     size_t        position) ETL_NOEXCEPT
    {
      // Where to start.
      size_t index = position >> log2<Bits_Per_Element>::value;
      size_t bit   = position & (Bits_Per_Element - 1);

      element_type mask = 1 << bit;

      // For each element in the bitset...
      while (index < number_of_elements)
      {
        element_type value = pbuffer[index];

        // Needs checking?
        if ((state && (value != All_Clear_Element)) ||
            (!state && (value != All_Set_Element)))
        {
          // For each bit in the element...
          while ((bit < Bits_Per_Element) && (position < total_bits))
          {
            // Equal to the required state?
            if (((value & mask) != 0) == state)
            {
              return position;
            }

            // Move on to the next bit.
            mask <<= 1;
            ++position;
            ++bit;
          }
        }
        else
        {
          position += (Bits_Per_Element - bit);
        }

        // Start at the beginning for all other elements.
        bit = 0;
        mask = 1;

        ++index;
      }

      return npos;
    }

    //*************************************************************************
    /// Returns a string representing the bitset.
    //*************************************************************************
    template <typename TString>
    static
    ETL_CONSTEXPR14
    TString to_string(const_pointer                pbuffer,
                      size_t                       active_bits, 
                      typename TString::value_type zero, 
                      typename TString::value_type one)
    {
      TString result;

      result.resize(active_bits, '\0');

      // Check that the string type can contain the digits.
      ETL_ASSERT_OR_RETURN_VALUE(result.size() == active_bits, ETL_ERROR(etl::bitset_string_too_small), result);      

      for (size_t i = active_bits; i > 0; --i)
      {
        result[active_bits - i] = test(pbuffer, i - 1) ? one : zero;
      }

      return result;
    }

    //*************************************************************************
    /// operator assignment
    //*************************************************************************
    static
    ETL_CONSTEXPR14
    void operator_assignment(pointer       lhs_pbuffer, 
                             const_pointer rhs_pbuffer, 
                             size_t        number_of_elements) ETL_NOEXCEPT
    {
      while (number_of_elements-- != 0)
      {
        *lhs_pbuffer = *rhs_pbuffer;
        ++lhs_pbuffer;
        ++rhs_pbuffer;
      }
    }

    //*************************************************************************
    /// operator and
    //*************************************************************************
    static
    ETL_CONSTEXPR14
    void operator_and(pointer       lhs_pbuffer, 
                      const_pointer rhs_pbuffer, 
                      size_t        number_of_elements) ETL_NOEXCEPT
    {
      while (number_of_elements-- != 0)
      {
        *lhs_pbuffer &= *rhs_pbuffer;
        ++lhs_pbuffer;
        ++rhs_pbuffer;
      }
    }

    //*************************************************************************
    /// operator or
    //*************************************************************************
    static
    ETL_CONSTEXPR14
    void operator_or(pointer       lhs_pbuffer, 
                     const_pointer rhs_pbuffer, 
                     size_t        number_of_elements) ETL_NOEXCEPT
    {
      while (number_of_elements-- != 0)
      {
        *lhs_pbuffer |= *rhs_pbuffer;
        ++lhs_pbuffer;
        ++rhs_pbuffer;
      }
    }

    //*************************************************************************
    /// operator xor
    //*************************************************************************
    static
    ETL_CONSTEXPR14
    void operator_xor(pointer       lhs_pbuffer, 
                      const_pointer rhs_pbuffer, 
                      size_t        number_of_elements) ETL_NOEXCEPT
    {
      while (number_of_elements-- != 0)
      {
        *lhs_pbuffer ^= *rhs_pbuffer;
        ++lhs_pbuffer;
        ++rhs_pbuffer;
      }
    }

    //*************************************************************************
    /// operator not
    //*************************************************************************
    static
    ETL_CONSTEXPR14
    void operator_not(pointer pbuffer, 
                      size_t  number_of_elements) ETL_NOEXCEPT
    {
      while (number_of_elements-- != 0)
      {
        *pbuffer = ~*pbuffer;
        ++pbuffer;
      }
    }

    //*************************************************************************
    /// operator_shift_left
    //*************************************************************************
    static
    ETL_CONSTEXPR14
    void operator_shift_left(pointer pbuffer, 
                             size_t  number_of_elements, 
                             size_t  active_bits, 
                             size_t  shift) ETL_NOEXCEPT
    {
      if (shift >= active_bits)
      {
        reset_all(pbuffer, number_of_elements);
      }
      else
      {
        // The place where the elements are split when shifting.
        const size_t split_position = Bits_Per_Element - (shift % Bits_Per_Element);

        // Where we are shifting from.
        int src_index = int(number_of_elements - (shift / Bits_Per_Element) - 1U);

        // Where we are shifting to.
        int dst_index = int(number_of_elements - 1U);

        // Shift control constants.
        const size_t lsb_shift = Bits_Per_Element - split_position;
        const size_t msb_shift = split_position;

        const element_type lsb_mask = element_type(etl::integral_limits<element_type>::max >> (Bits_Per_Element - split_position));
        const element_type msb_mask = etl::integral_limits<element_type>::max - lsb_mask;
        const element_type lsb_shifted_mask = element_type(lsb_mask << lsb_shift);

        // First lsb.
        element_type lsb = element_type((pbuffer[src_index] & lsb_mask) << lsb_shift);
        pbuffer[dst_index] = lsb;
        --src_index;

        // Now do the shifting.
        while (src_index >= 0)
        {
          // Shift msb.
          element_type msb = element_type((pbuffer[src_index] & msb_mask) >> msb_shift);
          pbuffer[dst_index] = pbuffer[dst_index] | msb;
          --dst_index;

          // Shift lsb.
          lsb = element_type((pbuffer[src_index] & lsb_mask) << lsb_shift);
          pbuffer[dst_index] = lsb;
          --src_index;
        }

        // Clear the remaining bits.
        // First lsb.
        pbuffer[dst_index] &= lsb_shifted_mask;

        // The other remaining bytes on the right.
        for (int i = 0; i < dst_index; ++i)
        {
          pbuffer[i] = 0;
        }
      }
    }

    //*************************************************************************
    /// operator_shift_right
    //*************************************************************************
    static
    ETL_CONSTEXPR14
    void operator_shift_right(pointer pbuffer, 
                              size_t  number_of_elements, 
                              size_t  active_bits, 
                              size_t  shift) ETL_NOEXCEPT
    {
      if (shift >= active_bits)
      {
        reset_all(pbuffer, number_of_elements);
      }
      else
      {
        // The place where the elements are split when shifting.
        const size_t split_position = shift % Bits_Per_Element;

        // Where we are shifting from.
        int src_index = int(shift / Bits_Per_Element);

        // Where we are shifting to.
        int dst_index = 0;

        // Shift control constants.
        const size_t lsb_shift = Bits_Per_Element - split_position;
        const size_t msb_shift = split_position;

        const element_type lsb_mask = element_type(etl::integral_limits<element_type>::max >> (Bits_Per_Element - split_position));
        const element_type msb_mask = etl::integral_limits<element_type>::max - lsb_mask;
        const element_type msb_shifted_mask = element_type(msb_mask >> msb_shift);

        // Now do the shifting.
        while (src_index < int(number_of_elements - 1))
        {
          // Shift msb.
          element_type msb = element_type((pbuffer[src_index] & msb_mask) >> msb_shift);
          ++src_index;

          // Shift lsb.
          element_type lsb = element_type((pbuffer[src_index] & lsb_mask) << lsb_shift);

          // Combine them.
          pbuffer[dst_index] = lsb | msb;
          ++dst_index;
        }

        // Final msb.
        element_type msb = element_type((pbuffer[src_index] & msb_mask) >> msb_shift);
        pbuffer[dst_index] = msb;

        // Clear the remaining bits.
        // First msb.
        pbuffer[dst_index] &= msb_shifted_mask;
        ++dst_index;

        // The other remaining bytes.
        while (dst_index < int(number_of_elements))
        {
          pbuffer[dst_index] = 0;
          ++dst_index;
        }
      }
    }

    //*************************************************************************
    /// operator_equality
    //*************************************************************************
    static
    ETL_CONSTEXPR14
    bool operator_equality(const_pointer lhs_pbuffer, 
                           const_pointer rhs_pbuffer, 
                           size_t        number_of_elements) ETL_NOEXCEPT
    {
      return etl::equal(lhs_pbuffer, lhs_pbuffer + number_of_elements, rhs_pbuffer);
    }

    //*************************************************************************
    /// Initialise from an unsigned long long.
    /// Enabled if the number of bits in the element equals the number of bits in an unsigned long long.
    //*************************************************************************
    template <typename TElementType>
    static
    ETL_CONSTEXPR14
    typename etl::enable_if<etl::integral_limits<TElementType>::bits == etl::integral_limits<unsigned long long>::bits, void>::type
      initialise(pointer            pbuffer, 
                 size_t             number_of_elements, 
                 unsigned long long value) ETL_NOEXCEPT
    {
      size_t i = 0UL;
      
      // Set the non-zero elements.
      pbuffer[i++] = value;

      // Clear the remaining elements.
      while (i != number_of_elements)
      {
        pbuffer[i++] = All_Clear_Element;
      }
    }

    //*************************************************************************
    /// Initialise from an unsigned long long.
    /// Enabled if the number of bits in the element doesn't equal the number of bits in an unsigned long long.
    //*************************************************************************
    template <typename TElementType>
    static
    ETL_CONSTEXPR14
    typename etl::enable_if<etl::integral_limits<TElementType>::bits != etl::integral_limits<unsigned long long>::bits, void>::type
      initialise(pointer            pbuffer,
                 size_t             number_of_elements,
                 unsigned long long value) ETL_NOEXCEPT
    {
      size_t i = 0UL;

      // Set the non-zero elements.
      const unsigned long long Shift = etl::integral_limits<element_type>::bits;

      while ((value != 0) && (i != number_of_elements))
      {
        pbuffer[i++] = value & All_Set_Element;
        value = value >> Shift;
      }

      // Clear the remaining elements.
      while (i != number_of_elements)
      {
        pbuffer[i++] = All_Clear_Element;
      }
    }

    //*************************************************************************
    /// Swap bitset buffers.
    //*************************************************************************
    static
    ETL_CONSTEXPR14
    void swap(pointer pbuffer1, 
              pointer pbuffer2, 
              size_t  number_of_elements)
    {
      etl::swap_ranges(pbuffer1, pbuffer1 + number_of_elements, pbuffer2);
    }
  };

  namespace private_bitset
  {
    //***************************************************************************
    template <size_t Active_Bits, typename TElement>
    class bitset_common : public etl::private_bitset::bitset_impl_common<TElement>
    {
    public:

      typedef typename etl::private_bitset::bitset_impl_common<TElement>::element_type element_type;
      
      using etl::private_bitset::bitset_impl_common<TElement>::Bits_Per_Element;
      using etl::private_bitset::bitset_impl_common<TElement>::All_Set_Element;
      using etl::private_bitset::bitset_impl_common<TElement>::All_Clear_Element;

      static ETL_CONSTANT size_t Number_Of_Elements = (Active_Bits % Bits_Per_Element == 0) ? Active_Bits / Bits_Per_Element : Active_Bits / Bits_Per_Element + 1;
      static ETL_CONSTANT size_t Size               = Active_Bits;
      static ETL_CONSTANT size_t Allocated_Bits     = Number_Of_Elements * Bits_Per_Element;

#if ETL_USING_CPP11
      static ETL_CONSTANT etl::bitset_storage_model Storage_Model = (bitset_common<Active_Bits, TElement>::Number_Of_Elements == 1U) ? etl::bitset_storage_model::Single : etl::bitset_storage_model::Multi;
#else
      static ETL_CONSTANT etl::bitset_storage_model Storage_Model;
#endif

      typedef etl::span<element_type,       Number_Of_Elements> span_type;
      typedef etl::span<const element_type, Number_Of_Elements> const_span_type;

    private:

      static ETL_CONSTANT size_t Top_Mask_Shift = ((Bits_Per_Element - ((Number_Of_Elements * Bits_Per_Element) - Active_Bits)) % Bits_Per_Element);

    public:

      static ETL_CONSTANT TElement Top_Mask = element_type(Top_Mask_Shift == 0 ? All_Set_Element : ~(All_Set_Element << Top_Mask_Shift));
    };


    template <size_t Active_Bits, typename TElement>
    ETL_CONSTANT size_t bitset_common<Active_Bits, TElement>::Number_Of_Elements;

    template <size_t Active_Bits, typename TElement>
    ETL_CONSTANT size_t bitset_common<Active_Bits, TElement>::Size;

#if ETL_USING_CPP11
    template <size_t Active_Bits, typename TElement>
    ETL_CONSTANT etl::bitset_storage_model bitset_common<Active_Bits, TElement>::Storage_Model;
#else
    template <size_t Active_Bits, typename TElement>
    ETL_CONSTANT etl::bitset_storage_model bitset_common<Active_Bits, TElement>::Storage_Model = (bitset_common<Active_Bits, TElement>::Number_Of_Elements == 1U) ? etl::bitset_storage_model::Single : etl::bitset_storage_model::Multi;
#endif

    template <size_t Active_Bits, typename TElement>
    ETL_CONSTANT size_t bitset_common<Active_Bits, TElement>::Top_Mask_Shift;

    template <size_t Active_Bits, typename TElement>
    ETL_CONSTANT TElement bitset_common<Active_Bits, TElement>::Top_Mask;  
  }

  //***************************************************************************
  /// Bitset forward declaration
  //***************************************************************************
  template <size_t   Active_Bits = 0U,
            typename TElement    = unsigned char>
  class bitset;

  //***************************************************************************
  /// Specialisation for zero bits.
  //***************************************************************************
  template <>
  class bitset<0U, unsigned char> : public etl::private_bitset::bitset_common<0U, unsigned char>
  {
  public:

    typedef etl::private_bitset::bitset_common<0U, unsigned char>::element_type    element_type;
    typedef etl::private_bitset::bitset_common<0U, unsigned char>::span_type       span_type;
    typedef etl::private_bitset::bitset_common<0U, unsigned char>::const_span_type const_span_type;

    using etl::private_bitset::bitset_common<0U, unsigned char>::Bits_Per_Element;
    using etl::private_bitset::bitset_common<0U, unsigned char>::All_Set_Element;
    using etl::private_bitset::bitset_common<0U, unsigned char>::All_Clear_Element;
    using etl::private_bitset::bitset_common<0U, unsigned char>::Number_Of_Elements;
    using etl::private_bitset::bitset_common<0U, unsigned char>::Size;
    using etl::private_bitset::bitset_common<0U, unsigned char>::Storage_Model;
    using etl::private_bitset::bitset_common<0U, unsigned char>::Top_Mask;
    using etl::private_bitset::bitset_common<0U, unsigned char>::Allocated_Bits;
  };

  //*************************************************************************
  /// The bitset top level template.
  //*************************************************************************
  template <size_t Active_Bits, typename TElement>
  class bitset : public etl::private_bitset::bitset_common<Active_Bits, TElement>
  {
  public:

    ETL_STATIC_ASSERT(etl::is_unsigned<TElement>::value, "The element type must be unsigned");

    typedef typename etl::private_bitset::bitset_common<Active_Bits, TElement>::element_type    element_type;
    typedef typename etl::private_bitset::bitset_common<Active_Bits, TElement>::span_type       span_type;
    typedef typename etl::private_bitset::bitset_common<Active_Bits, TElement>::const_span_type const_span_type;

    using etl::private_bitset::bitset_common<Active_Bits, TElement>::Bits_Per_Element;
    using etl::private_bitset::bitset_common<Active_Bits, TElement>::All_Set_Element;
    using etl::private_bitset::bitset_common<Active_Bits, TElement>::All_Clear_Element;
    using etl::private_bitset::bitset_common<Active_Bits, TElement>::Number_Of_Elements;
    using etl::private_bitset::bitset_common<Active_Bits, TElement>::Size;
    using etl::private_bitset::bitset_common<Active_Bits, TElement>::Storage_Model;
    using etl::private_bitset::bitset_common<Active_Bits, TElement>::Top_Mask;
    using etl::private_bitset::bitset_common<Active_Bits, TElement>::Allocated_Bits;

    //*************************************************************************
    /// The reference type returned.
    //*************************************************************************
    class bit_reference
    {
    public:

      friend class bitset;

      //*******************************
      /// Copy constructor.
      //*******************************
      ETL_CONSTEXPR14 bit_reference(const bit_reference& other) ETL_NOEXCEPT
        : p_bitset(other.p_bitset)
        , position(other.position)
      {
      }

      //*******************************
      /// Conversion operator.
      //*******************************
      ETL_CONSTEXPR14 operator bool() const ETL_NOEXCEPT
      {
        return p_bitset->test(position);
      }

      //*******************************
      /// Assignment operator.
      //*******************************
      ETL_CONSTEXPR14 bit_reference& operator = (bool b) ETL_NOEXCEPT
      {
        p_bitset->set(position, b);
        return *this;
      }

      //*******************************
      /// Assignment operator.
      //*******************************
      ETL_CONSTEXPR14 bit_reference& operator = (const bit_reference& r) ETL_NOEXCEPT
      {
        p_bitset->set(position, bool(r));
        return *this;
      }

      //*******************************
      /// Flip the bit.
      //*******************************
      ETL_CONSTEXPR14 bit_reference& flip() ETL_NOEXCEPT
      {
        p_bitset->flip(position);
        return *this;
      }

      //*******************************
      /// Return the logical inverse of the bit.
      //*******************************
      ETL_CONSTEXPR14 bool operator~() const ETL_NOEXCEPT
      {
        return !p_bitset->test(position);
      }

    private:

      //*******************************
      /// Default constructor.
      //*******************************
      ETL_CONSTEXPR14 bit_reference() ETL_NOEXCEPT
        : p_bitset(ETL_NULLPTR)
        , position(0)
      {
      }

      //*******************************
      /// Constructor.
      //*******************************
      ETL_CONSTEXPR14 bit_reference(bitset<Active_Bits, TElement>& r_bitset, size_t position_) ETL_NOEXCEPT
        : p_bitset(&r_bitset)
        , position(position_)
      {
      }

      bitset<Active_Bits, TElement>* p_bitset; ///< The bitset.
      size_t position; ///< The position in the bitset.
    };

    //*************************************************************************
    /// Default constructor.
    //*************************************************************************
    ETL_CONSTEXPR14 bitset() ETL_NOEXCEPT
      : buffer()
    {
      implementation::reset_all(buffer, Number_Of_Elements);
    }

    //*************************************************************************
    /// Copy constructor.
    //*************************************************************************
    ETL_CONSTEXPR14 bitset(const bitset<Active_Bits, TElement>& other) ETL_NOEXCEPT
      : buffer()
    {
      implementation::operator_assignment(buffer, other.buffer, Number_Of_Elements);
    }

    //*************************************************************************
    /// Construct from a value.
    //*************************************************************************
    template <typename TValue>
    ETL_CONSTEXPR14 bitset(TValue value, typename etl::enable_if<is_integral<TValue>::value>::type* = 0) ETL_NOEXCEPT
      : buffer()
    {
      implementation::template initialise<element_type>(buffer, Number_Of_Elements, value);
    }

    //*************************************************************************
    /// Construct from a string.
    //*************************************************************************
    template <typename TPString>
    ETL_CONSTEXPR14 bitset(TPString text, typename etl::enable_if<is_same<TPString, const char*>::value>::type* = 0) ETL_NOEXCEPT
      : buffer()
    {
      implementation::from_string(buffer, Number_Of_Elements, Active_Bits, text);
    }

    //*************************************************************************
    /// Construct from a string.
    //*************************************************************************
    template <typename TPString>
    ETL_CONSTEXPR14 bitset(TPString text, typename etl::enable_if<is_same<TPString, const wchar_t*>::value>::type* = 0) ETL_NOEXCEPT
      : buffer()
    {
      implementation::from_string(buffer, Number_Of_Elements, Active_Bits, text);
    }

    //*************************************************************************
    /// Construct from a string.
    //*************************************************************************
    template <typename TPString>
    ETL_CONSTEXPR14 bitset(TPString text, typename etl::enable_if<is_same<TPString, const char16_t*>::value>::type* = 0) ETL_NOEXCEPT
      : buffer()
    {
      implementation::from_string(buffer, Number_Of_Elements, Active_Bits, text);
    }

    //*************************************************************************
    /// Construct from a string.
    //*************************************************************************
    template <typename TPString>
    ETL_CONSTEXPR14 bitset(TPString text, typename etl::enable_if<is_same<TPString, const char32_t*>::value>::type* = 0) ETL_NOEXCEPT
      : buffer()
    {
      implementation::from_string(buffer, Number_Of_Elements, Active_Bits, text);
    }

    //*************************************************************************
    /// Assignment operator.
    //*************************************************************************
    ETL_CONSTEXPR14 bitset& operator =(const bitset<Active_Bits, TElement>& other) ETL_NOEXCEPT
    {
      implementation::operator_assignment(buffer, other.buffer, Number_Of_Elements);

      return *this;
    }

    //*************************************************************************
    /// Set all of the bits.
    //*************************************************************************
    ETL_CONSTEXPR14 bitset<Active_Bits, TElement>& set() ETL_NOEXCEPT
    {
      implementation::set_all(buffer, Number_Of_Elements, Top_Mask);

      return *this;
    }

    //*************************************************************************
    /// Set the bit at the position.
    //*************************************************************************
    ETL_CONSTEXPR14
    bitset<Active_Bits, TElement>& set(size_t position, bool value = true)
    {
      ETL_ASSERT_OR_RETURN_VALUE(position < Active_Bits, ETL_ERROR(bitset_overflow), *this);

      implementation::set_position(buffer, position, value);
      
      return *this;
    }

    //*************************************************************************
    /// Set the bit at the position.
    //*************************************************************************
    template <size_t Position>
    ETL_CONSTEXPR14 bitset<Active_Bits, TElement>& set(bool value = true)
    {
      ETL_STATIC_ASSERT(Position < Active_Bits, "Position out of bounds");

      implementation::template set_position<Position>(buffer, value);

      return *this;
    }

    //*************************************************************************
    /// Set the bit at the position.
    //*************************************************************************
    template <size_t Position, bool Value>
    ETL_CONSTEXPR14 bitset<Active_Bits, TElement>& set()
    {
      ETL_STATIC_ASSERT(Position < Active_Bits, "Position out of bounds");

      implementation::template set_position<Position, Value>(buffer);

      return *this;
    }

    //*************************************************************************
    /// Set from a string.
    //*************************************************************************
    template <typename TPString>
    ETL_CONSTEXPR14
    typename etl::enable_if<etl::is_same<TPString, const char*>::value, bitset<Active_Bits, TElement>&>::type
      set(TPString text) ETL_NOEXCEPT
    {
      implementation::from_string(buffer, Number_Of_Elements, Active_Bits, text);

      return *this;
    }

    //*************************************************************************
    /// Set from a wide string.
    //*************************************************************************
    template <typename TPString>
    ETL_CONSTEXPR14
    typename etl::enable_if<etl::is_same<TPString, const wchar_t*>::value, bitset<Active_Bits, TElement>&>::type
      set(TPString text) ETL_NOEXCEPT
    {
      implementation::from_string(buffer, Number_Of_Elements, Active_Bits, text);

      return *this;
    }

    //*************************************************************************
    /// Set from a char16 string.
    //*************************************************************************
    template <typename TPString>
    ETL_CONSTEXPR14
    typename etl::enable_if<etl::is_same<TPString, const char16_t*>::value, bitset<Active_Bits, TElement>&>::type
      set(TPString text) ETL_NOEXCEPT
    {
      implementation::from_string(buffer, Number_Of_Elements, Active_Bits, text);

      return *this;
    }

    //*************************************************************************
    /// Set from a char32 string.
    //*************************************************************************
    template <typename TPString>
    ETL_CONSTEXPR14 
    typename etl::enable_if<etl::is_same<TPString, const char32_t*>::value, bitset<Active_Bits, TElement>&>::type
      set(TPString text) ETL_NOEXCEPT
    {
      implementation::from_string(buffer, Number_Of_Elements, Active_Bits, text);

      return *this;
    }

    //*************************************************************************
    /// Set from a string.
    //*************************************************************************
    ETL_CONSTEXPR14 bitset<Active_Bits, TElement>& from_string(const char* text) ETL_NOEXCEPT
    {
      implementation::from_string(buffer, Number_Of_Elements, Active_Bits, text);

      return *this;
    }

    //*************************************************************************
    /// Set from a wide string.
    //*************************************************************************
    ETL_CONSTEXPR14 bitset<Active_Bits, TElement>& from_string(const wchar_t* text) ETL_NOEXCEPT
    {
      implementation::from_string(buffer, Number_Of_Elements, Active_Bits, text);

      return *this;
    }

    //*************************************************************************
    /// Set from a u16 string.
    //*************************************************************************
    ETL_CONSTEXPR14 bitset<Active_Bits, TElement>& from_string(const char16_t* text) ETL_NOEXCEPT
    {
      implementation::from_string(buffer, Number_Of_Elements, Active_Bits, text);

      return *this;
    }

    //*************************************************************************
    /// Set from a u32 string.
    //*************************************************************************
    ETL_CONSTEXPR14 bitset<Active_Bits, TElement>& from_string(const char32_t* text) ETL_NOEXCEPT
    {
      implementation::from_string(buffer, Number_Of_Elements, Active_Bits, text);

      return *this;
    }

    //*************************************************************************
    /// Get as an integral value.
    //*************************************************************************
    template <typename T>
    ETL_CONSTEXPR14
    typename etl::enable_if<etl::is_integral<T>::value, T>::type
      value() const ETL_NOEXCEPT
    {
      ETL_STATIC_ASSERT(etl::is_integral<T>::value, "Only integral types are supported");
      ETL_STATIC_ASSERT(etl::integral_limits<T>::bits >= (Number_Of_Elements * Bits_Per_Element), "Type too small");

      return implementation::template value<T>(buffer, Number_Of_Elements);
    }

    //*************************************************************************
    /// Extract an integral value from an arbitrary position and length.
    /// Run time position and length.
    //*************************************************************************
    template <typename T>
    ETL_CONSTEXPR14
    T extract(size_t position, size_t length = etl::integral_limits<T>::bits) const
    {
      ETL_STATIC_ASSERT(etl::is_integral<T>::value, "Only integral types are supported");

      ETL_ASSERT_OR_RETURN_VALUE(length <= etl::integral_limits<T>::bits, ETL_ERROR(bitset_overflow), 0);
      ETL_ASSERT_OR_RETURN_VALUE((position + length) <= Active_Bits,      ETL_ERROR(bitset_overflow), 0);

      return implementation::template extract<T>(buffer, position, length);
    }

    //*************************************************************************
    /// Extract an integral value from an arbitrary position and length.
    /// Compile time position and length.
    //*************************************************************************
#if ETL_USING_CPP11    
		template <typename T, size_t Position, size_t Length = etl::integral_limits<T>::bits>
#else
	  template <typename T, size_t Position, size_t Length>
#endif
    ETL_CONSTEXPR14
    T extract() const
    {
      ETL_STATIC_ASSERT(etl::is_integral<T>::value,              "Only integral types are supported");
      ETL_STATIC_ASSERT(Length <= etl::integral_limits<T>::bits, "Length is larger that the required type");
      ETL_STATIC_ASSERT((Position + Length) <= Active_Bits,      "Position/Length overflows bitset");

      return implementation::template extract<T, Position, Length>(buffer);
    }

    //*************************************************************************
    /// Get as an unsigned long.
    //*************************************************************************
    unsigned long to_ulong() const
    {
      ETL_ASSERT(etl::integral_limits<unsigned long>::bits >= Active_Bits, ETL_ERROR(etl::bitset_overflow));

      return implementation::template value<unsigned long>(buffer, Number_Of_Elements);
    }

    //*************************************************************************
    /// Get as an unsigned long long.
    //*************************************************************************
    unsigned long long to_ullong() const
    {
      ETL_ASSERT(etl::integral_limits<unsigned long long>::bits >= Active_Bits, ETL_ERROR(etl::bitset_overflow));

      return implementation::template value<unsigned long long>(buffer, Number_Of_Elements);
    }

    //*************************************************************************
    /// Reset all of the bits.
    //*************************************************************************
    ETL_CONSTEXPR14 bitset<Active_Bits, TElement>& reset() ETL_NOEXCEPT
    {
      implementation::reset_all(buffer, Number_Of_Elements);

      return *this;
    }

    //*************************************************************************
    /// Reset the bit at the position.
    //*************************************************************************
    ETL_CONSTEXPR14 bitset<Active_Bits, TElement>& reset(size_t position)
    {
      ETL_ASSERT_OR_RETURN_VALUE(position < Active_Bits, ETL_ERROR(bitset_overflow), *this);

      implementation::reset_position(buffer, position);

      return *this;
    }

    //*************************************************************************
    /// Tests a bit at a position.
    /// Positions greater than the number of configured bits will return <b>false</b>.
    //*************************************************************************
    ETL_CONSTEXPR14 bool test(size_t position) const
    {
      ETL_ASSERT_OR_RETURN_VALUE(position < Active_Bits, ETL_ERROR(bitset_overflow), false);

      return implementation::test(buffer, position);
    }
 
    //*************************************************************************
    /// Tests a bit at a position.
    /// Positions greater than the number of configured bits will not compile.
    //*************************************************************************
    template <size_t Position>
    ETL_CONSTEXPR14 bool test() const
    {
      ETL_STATIC_ASSERT(Position < Active_Bits, "Position out of bounds");

      return implementation::test(buffer, Position);
    }

    //*************************************************************************
    /// The number of bits in the bitset.
    //*************************************************************************
    static ETL_CONSTEXPR size_t size() ETL_NOEXCEPT
    {
      return Active_Bits;
    }

    //*************************************************************************
    /// The number of storage elements in the bitset.
    //*************************************************************************
    static ETL_CONSTEXPR size_t number_of_elements() ETL_NOEXCEPT
    {
      return Number_Of_Elements;
    }

    //*************************************************************************
    /// The value of a set element.
    //*************************************************************************
    static ETL_CONSTEXPR element_type all_set_element() ETL_NOEXCEPT
    {
      return All_Set_Element;
    }

    //*************************************************************************
    /// The value of a clear element.
    //*************************************************************************
    static ETL_CONSTEXPR element_type all_clear_element() ETL_NOEXCEPT
    {
      return All_Clear_Element;
    }

    //*************************************************************************
    /// The number of bits in an element.
    //*************************************************************************
    static ETL_CONSTEXPR size_t bits_per_element() ETL_NOEXCEPT
    {
      return Bits_Per_Element;
    }

    //*************************************************************************
    /// The mask for the msb element.
    //*************************************************************************
    static ETL_CONSTEXPR element_type top_mask() ETL_NOEXCEPT
    {
      return Top_Mask;
    }

    //*************************************************************************
    /// The total number of bits of storage, including unused.
    //*************************************************************************
    static ETL_CONSTEXPR size_t allocated_bits() ETL_NOEXCEPT
    {
      return Number_Of_Elements * Bits_Per_Element;
    }

    //*************************************************************************
    /// The storage model for the bitset.
    /// etl::bitset_storage_model::Single
    /// etl::bitset_storage_model::Multi
    //*************************************************************************
    static ETL_CONSTEXPR etl::bitset_storage_model storage_model() ETL_NOEXCEPT
    {
      return Storage_Model;
    }

    //*************************************************************************
    /// Count the number of bits set.
    //*************************************************************************
    ETL_CONSTEXPR14 size_t count() const ETL_NOEXCEPT
    {
      return implementation::count(buffer, Number_Of_Elements);
    }

    //*************************************************************************
    // Are all the bits sets?
    //*************************************************************************
    ETL_CONSTEXPR14 bool all() const ETL_NOEXCEPT
    {
      return implementation::all(buffer, Number_Of_Elements, Top_Mask);
    }

    //*************************************************************************
    // Are all the mask bits sets?
    //*************************************************************************
    ETL_CONSTEXPR14 bool all(element_type mask) const ETL_NOEXCEPT
    {
      ETL_STATIC_ASSERT(Storage_Model == etl::bitset_storage_model::Single, "Not supported for 'Multi' bitset storage model");

      return implementation::all(buffer, Number_Of_Elements, Top_Mask, mask);
    }

    //*************************************************************************
    /// Are none of the bits set?
    //*************************************************************************
    ETL_CONSTEXPR14 bool none() const ETL_NOEXCEPT
    {
      return implementation::none(buffer, Number_Of_Elements);
    }

    //*************************************************************************
    /// Are none of the mask bits set?
    //*************************************************************************
    ETL_CONSTEXPR14 bool none(element_type mask) const ETL_NOEXCEPT
    {
      ETL_STATIC_ASSERT(Storage_Model == etl::bitset_storage_model::Single, "Not supported for 'Multi' bitset storage model");

      return implementation::none(buffer, Number_Of_Elements, mask);
    }

    //*************************************************************************
    /// Are any of the bits set?
    //*************************************************************************
    ETL_CONSTEXPR14 bool any() const ETL_NOEXCEPT
    {
      return implementation::any(buffer, Number_Of_Elements);
    }
 
    //*************************************************************************
    /// Are any of the mask bits set?
    //*************************************************************************
    ETL_CONSTEXPR14 bool any(element_type mask) const ETL_NOEXCEPT
    {
      ETL_STATIC_ASSERT(Storage_Model == etl::bitset_storage_model::Single, "Not supported for 'Multi' bitset storage model");

      return implementation::any(buffer, Number_Of_Elements, mask);
    }

    //*************************************************************************
    /// Flip all of the bits.
    //*************************************************************************
    ETL_CONSTEXPR14 bitset<Active_Bits, TElement>& flip() ETL_NOEXCEPT
    {
      implementation::flip_all(buffer, Number_Of_Elements);

      return *this;
    }

    //*************************************************************************
    /// Flip the bit at the position.
    //*************************************************************************
    ETL_CONSTEXPR14 bitset<Active_Bits, TElement>& flip(size_t position)
    {
      ETL_ASSERT_OR_RETURN_VALUE(position < Active_Bits, ETL_ERROR(bitset_overflow), *this);

      implementation::flip_position(buffer, position);

      return *this;
    }

    //*************************************************************************
    /// Read [] operator.
    //*************************************************************************
    ETL_CONSTEXPR14 bool operator[] (size_t position) const ETL_NOEXCEPT
    {
      return implementation::test(buffer, position);
    }

    //*************************************************************************
    /// Write [] operator.
    //*************************************************************************
    ETL_CONSTEXPR14 bit_reference operator [] (size_t position) ETL_NOEXCEPT
    {
      return bit_reference(*this, position);
    }

    //*************************************************************************
    /// Returns a string representing the bitset.
    //*************************************************************************
#if ETL_USING_CPP11
    template <typename TString = etl::string<Active_Bits>>
#else
    template <typename TString>
#endif
    ETL_CONSTEXPR14 TString to_string(typename TString::value_type zero = typename TString::value_type('0'),
                                      typename TString::value_type one  = typename TString::value_type('1')) const
    {
      return implementation::template to_string<TString>(buffer, Active_Bits, zero, one);
    }

    //*************************************************************************
    /// Finds the first bit in the specified state.
    ///\param state The state to search for.
    ///\returns The position of the bit or npos if none were found.
    //*************************************************************************
    ETL_CONSTEXPR14 size_t find_first(bool state) const ETL_NOEXCEPT
    {
      return implementation::find_next(buffer, Number_Of_Elements, Active_Bits, state, 0);
    }

    //*************************************************************************
    /// Finds the next bit in the specified state.
    ///\param state    The state to search for.
    ///\param position The position to start from.
    ///\returns The position of the bit or npos if none were found.
    //*************************************************************************
    ETL_CONSTEXPR14 size_t find_next(bool state, size_t position) const ETL_NOEXCEPT
    {
      return implementation::find_next(buffer, Number_Of_Elements, Active_Bits, state, position);
    }

    //*************************************************************************
    /// operator &
    //*************************************************************************
    ETL_CONSTEXPR14 bitset<Active_Bits, TElement> operator &(const bitset<Active_Bits, TElement>& other) const ETL_NOEXCEPT
    {
      etl::bitset<Active_Bits, TElement> temp(*this);

      implementation::operator_and(temp.buffer, other.buffer, Number_Of_Elements);

      return temp;
    }

    //*************************************************************************
    /// operator &=
    //*************************************************************************
    ETL_CONSTEXPR14 bitset<Active_Bits, TElement>& operator &=(const bitset<Active_Bits, TElement>& other) ETL_NOEXCEPT
    {
      implementation::operator_and(buffer, other.buffer, Number_Of_Elements);

      return *this;
    }

    //*************************************************************************
    /// operator |
    //*************************************************************************
    ETL_CONSTEXPR14 bitset<Active_Bits, TElement> operator |(const bitset<Active_Bits, TElement>& other) const ETL_NOEXCEPT
    {
      etl::bitset<Active_Bits, TElement> temp(*this);

      implementation::operator_or(temp.buffer, other.buffer, Number_Of_Elements);

      return temp;
    }

    //*************************************************************************
    /// operator |=
    //*************************************************************************
    ETL_CONSTEXPR14 bitset<Active_Bits, TElement>& operator |=(const bitset<Active_Bits, TElement>& other) ETL_NOEXCEPT
    {
      implementation::operator_or(&buffer[0], &other.buffer[0], Number_Of_Elements);

      return *this;
    }

    //*************************************************************************
    /// operator ^
    //*************************************************************************
    ETL_CONSTEXPR14 bitset<Active_Bits, TElement> operator ^(const bitset<Active_Bits, TElement>& other) const ETL_NOEXCEPT
    {
      etl::bitset<Active_Bits, TElement> temp(*this);

      implementation::operator_xor(temp.buffer, other.buffer, Number_Of_Elements);

      return temp;
    }

    //*************************************************************************
    /// operator ^=
    //*************************************************************************
    ETL_CONSTEXPR14 bitset<Active_Bits, TElement>& operator ^=(const bitset<Active_Bits, TElement>& other) ETL_NOEXCEPT
    {
      implementation::operator_xor(buffer, other.buffer, Number_Of_Elements);

      return *this;
    }

    //*************************************************************************
    /// operator ~
    //*************************************************************************
    ETL_CONSTEXPR14 bitset<Active_Bits, TElement> operator ~() const ETL_NOEXCEPT
    {
      etl::bitset<Active_Bits, TElement> temp(*this);

      implementation::flip_all(temp.buffer, Number_Of_Elements);

      return temp;
    }

    //*************************************************************************
    /// operator <<
    //*************************************************************************
    ETL_CONSTEXPR14 bitset<Active_Bits, TElement> operator <<(size_t shift) const ETL_NOEXCEPT
    {
      etl::bitset<Active_Bits, TElement> temp(*this);

      implementation::operator_shift_left(temp.buffer, Number_Of_Elements, Active_Bits, shift);

      return temp;
    }

    //*************************************************************************
    /// operator <<=
    //*************************************************************************
    ETL_CONSTEXPR14 bitset<Active_Bits, TElement>& operator <<=(size_t shift) ETL_NOEXCEPT
    {
      if (shift >= Active_Bits)
      {
        implementation::reset_all(buffer, Number_Of_Elements);
      }
      else
      {
        implementation::operator_shift_left(buffer, Number_Of_Elements, Active_Bits, shift);
      }
      
      return *this;
    }

    //*************************************************************************
    /// operator >>
    //*************************************************************************
    ETL_CONSTEXPR14 bitset<Active_Bits, TElement> operator >>(size_t shift) const ETL_NOEXCEPT
    {
      bitset<Active_Bits, TElement> temp(*this);

      implementation::operator_shift_right(temp.buffer, Number_Of_Elements, Active_Bits, shift);

      return temp;
    }

    //*************************************************************************
    /// operator >>=
    //*************************************************************************
    ETL_CONSTEXPR14 bitset<Active_Bits, TElement>& operator >>=(size_t shift) ETL_NOEXCEPT
    {
      if (shift >= Active_Bits)
      {
        implementation::reset_all(buffer, Number_Of_Elements);
      }
      else
      {
        implementation::operator_shift_right(buffer, Number_Of_Elements, Active_Bits, shift);
      }

      return *this;
    }

    //*************************************************************************
    /// operator ==
    //*************************************************************************
    friend ETL_CONSTEXPR14 bool operator ==(const bitset<Active_Bits, TElement>& lhs, const bitset<Active_Bits, TElement>& rhs) ETL_NOEXCEPT
    {
      return implementation::operator_equality(lhs.buffer, rhs.buffer, lhs.Number_Of_Elements);
    }

    //*************************************************************************
    /// operator !=
    //*************************************************************************
    friend ETL_CONSTEXPR14 bool operator !=(const bitset<Active_Bits, TElement>& lhs, const bitset<Active_Bits, TElement>& rhs) ETL_NOEXCEPT
    {
      return !(lhs == rhs);
    }

    //*************************************************************************
    /// swap
    //*************************************************************************
    ETL_CONSTEXPR14 void swap(etl::bitset<Active_Bits, TElement>& other) ETL_NOEXCEPT
    {
      implementation::swap(buffer, other.buffer, Number_Of_Elements);
    }

    //*************************************************************************
    /// span
    /// Returns a span of the underlying buffer.
    //*************************************************************************
    ETL_CONSTEXPR14 span_type span() ETL_NOEXCEPT
    {
      return span_type(buffer, Number_Of_Elements);
    }

    //*************************************************************************
    /// span
    /// Returns a const span of the underlying buffer.
    //*************************************************************************
    ETL_CONSTEXPR14 const_span_type span() const ETL_NOEXCEPT
    {
      return const_span_type(buffer, Number_Of_Elements);
    }

  private:

    // The implementation of the bitset functionality.
    typedef etl::bitset_impl<element_type, (Number_Of_Elements == 1U) ? etl::bitset_storage_model::Single : etl::bitset_storage_model::Multi> implementation;

    // The storage for the bitset.
    element_type buffer[Number_Of_Elements];
  };

  //***************************************************************************
  /// operator &
  ///\ingroup bitset
  //***************************************************************************
  template <size_t Active_Bits, typename TElement>
  ETL_CONSTEXPR14 bitset<Active_Bits> operator & (const bitset<Active_Bits, TElement>& lhs, const bitset<Active_Bits, TElement>& rhs) ETL_NOEXCEPT
  {
    bitset<Active_Bits> temp(lhs);
    temp &= rhs;
    return temp;
  }

  //***************************************************************************
  /// operator |
  ///\ingroup bitset
  //***************************************************************************
  template<size_t Active_Bits, typename TElement>
  ETL_CONSTEXPR14 bitset<Active_Bits> operator | (const bitset<Active_Bits, TElement>& lhs, const bitset<Active_Bits, TElement>& rhs) ETL_NOEXCEPT
  {
    bitset<Active_Bits> temp(lhs);
    temp |= rhs;
    return temp;
  }

  //***************************************************************************
  /// operator ^
  ///\ingroup bitset
  //***************************************************************************
  template<size_t Active_Bits, typename TElement>
  ETL_CONSTEXPR14 bitset<Active_Bits> operator ^ (const bitset<Active_Bits, TElement>& lhs, const bitset<Active_Bits, TElement>& rhs) ETL_NOEXCEPT
  {
    bitset<Active_Bits> temp(lhs);
    temp ^= rhs;
    return temp;
  }
}

//***************************************************************************
/// operator !=
///\ingroup bitset
//***************************************************************************
template<size_t Active_Bits, typename TElement>
ETL_CONSTEXPR14 bool operator != (const etl::bitset<Active_Bits, TElement>& lhs, const etl::bitset<Active_Bits, TElement>& rhs) ETL_NOEXCEPT
{
  return !(lhs == rhs);
}

//*************************************************************************
/// swap
//*************************************************************************
template <size_t Active_Bits, typename TElement>
ETL_CONSTEXPR14 void swap(etl::bitset<Active_Bits, TElement>& lhs, etl::bitset<Active_Bits, TElement>& rhs) ETL_NOEXCEPT
{
  lhs.swap(rhs);
}

//***************************************************************************
/// bitset_ext
//***************************************************************************
namespace etl
{
  //***************************************************************************
  template <size_t Active_Bits = 0U,
            typename TElement = unsigned char>
  class bitset_ext;

  //***************************************************************************
  /// Specialisation for zero bits.
  //***************************************************************************
  template <>
  class bitset_ext<0U, unsigned char> : public etl::private_bitset::bitset_common<0U, unsigned char>
  {
  public:

    typedef etl::private_bitset::bitset_common<0U, unsigned char>::element_type    element_type;
    typedef etl::private_bitset::bitset_common<0U, unsigned char>::span_type       span_type;
    typedef etl::private_bitset::bitset_common<0U, unsigned char>::const_span_type const_span_type;

    using etl::private_bitset::bitset_common<0U, unsigned char>::Bits_Per_Element;
    using etl::private_bitset::bitset_common<0U, unsigned char>::All_Set_Element;
    using etl::private_bitset::bitset_common<0U, unsigned char>::All_Clear_Element;
    using etl::private_bitset::bitset_common<0U, unsigned char>::Number_Of_Elements;
    using etl::private_bitset::bitset_common<0U, unsigned char>::Size;
    using etl::private_bitset::bitset_common<0U, unsigned char>::Storage_Model;
    using etl::private_bitset::bitset_common<0U, unsigned char>::Top_Mask;
    using etl::private_bitset::bitset_common<0U, unsigned char>::Allocated_Bits;
  };

  //*************************************************************************
  /// A bitset that uses externally declared storage.
  //*************************************************************************
  template <size_t Active_Bits, typename TElement>
  class bitset_ext : public etl::private_bitset::bitset_common<Active_Bits, TElement>
  {
  public:

    ETL_STATIC_ASSERT(etl::is_unsigned<TElement>::value, "The element type must be unsigned");

    typedef typename etl::private_bitset::bitset_common<Active_Bits, TElement>::element_type    element_type;
    typedef typename etl::private_bitset::bitset_common<Active_Bits, TElement>::span_type       span_type;
    typedef typename etl::private_bitset::bitset_common<Active_Bits, TElement>::const_span_type const_span_type;
    
    using etl::private_bitset::bitset_common<Active_Bits, TElement>::Bits_Per_Element;
    using etl::private_bitset::bitset_common<Active_Bits, TElement>::All_Set_Element;
    using etl::private_bitset::bitset_common<Active_Bits, TElement>::All_Clear_Element;
    using etl::private_bitset::bitset_common<Active_Bits, TElement>::Number_Of_Elements;
    using etl::private_bitset::bitset_common<Active_Bits, TElement>::Size;
    using etl::private_bitset::bitset_common<Active_Bits, TElement>::Storage_Model;
    using etl::private_bitset::bitset_common<Active_Bits, TElement>::Top_Mask;
    using etl::private_bitset::bitset_common<Active_Bits, TElement>::Allocated_Bits;

    typedef etl::array<TElement, Number_Of_Elements> buffer_type;

    //*************************************************************************
    /// The reference type returned.
    //*************************************************************************
    class bit_reference
    {
    public:

      friend class bitset_ext;

      //*******************************
      /// Copy constructor
      //*******************************
      ETL_CONSTEXPR14 bit_reference(const bit_reference& other) ETL_NOEXCEPT
        : p_bitset(other.p_bitset)
        , position(other.position)
      {
      }

      //*******************************
      /// Conversion operator.
      //*******************************
      ETL_CONSTEXPR14 operator bool() const ETL_NOEXCEPT
      {
        return p_bitset->test(position);
      }

      //*******************************
      /// Assignment operator.
      //*******************************
      ETL_CONSTEXPR14 bit_reference& operator = (bool b) ETL_NOEXCEPT
      {
        p_bitset->set(position, b);
        return *this;
      }

      //*******************************
      /// Assignment operator.
      //*******************************
      ETL_CONSTEXPR14 bit_reference& operator = (const bit_reference& r) ETL_NOEXCEPT
      {
        p_bitset->set(position, bool(r));
        return *this;
      }

      //*******************************
      /// Flip the bit.
      //*******************************
      ETL_CONSTEXPR14 bit_reference& flip() ETL_NOEXCEPT
      {
        p_bitset->flip(position);
        return *this;
      }

      //*******************************
      /// Return the logical inverse of the bit.
      //*******************************
      ETL_CONSTEXPR14 bool operator~() const ETL_NOEXCEPT
      {
        return !p_bitset->test(position);
      }

    private:

      //*******************************
      /// Default constructor.
      //*******************************
      ETL_CONSTEXPR14 bit_reference() ETL_NOEXCEPT
        : p_bitset(ETL_NULLPTR)
        , position(0)
      {
      }

      //*******************************
      /// Constructor.
      //*******************************
      ETL_CONSTEXPR14 bit_reference(bitset_ext<Active_Bits, TElement>& r_bitset, size_t position_) ETL_NOEXCEPT
        : p_bitset(&r_bitset)
        , position(position_)
      {
      }

      bitset_ext<Active_Bits, TElement>* p_bitset; ///< The bitset.
      size_t position; ///< The position in the bitset.
    };

    //*************************************************************************
    /// Default constructor.
    //*************************************************************************
    ETL_CONSTEXPR14 explicit bitset_ext(element_type* pbuffer_)
      : pbuffer(pbuffer_)
    {
      ETL_ASSERT(pbuffer != ETL_NULLPTR, ETL_ERROR(etl::bitset_invalid_buffer));
      implementation::reset_all(pbuffer, Number_Of_Elements);
    }

    //*************************************************************************
    /// Default constructor.
    //*************************************************************************
    ETL_CONSTEXPR14 explicit bitset_ext(buffer_type& buffer)
      : pbuffer(buffer.data())
    {
      ETL_ASSERT(pbuffer != ETL_NULLPTR, ETL_ERROR(etl::bitset_invalid_buffer));
      implementation::reset_all(pbuffer, Number_Of_Elements);
    }

    //*************************************************************************
    /// Construct copy.
    //*************************************************************************
    ETL_CONSTEXPR14 bitset_ext(const bitset_ext<Active_Bits, TElement>& other, element_type* pbuffer_)
      : pbuffer(pbuffer_)
    {
      ETL_ASSERT(pbuffer != ETL_NULLPTR, ETL_ERROR(etl::bitset_invalid_buffer));
      implementation::operator_assignment(pbuffer, other.pbuffer, Number_Of_Elements);
    }

    //*************************************************************************
    /// Construct copy.
    //*************************************************************************
    ETL_CONSTEXPR14 bitset_ext(const bitset_ext<Active_Bits, TElement>& other, buffer_type& buffer) ETL_NOEXCEPT
      : pbuffer(buffer.data())
    {
      implementation::operator_assignment(pbuffer, other.pbuffer, Number_Of_Elements);
    }

    //*************************************************************************
    /// Copy Constructor (Deleted).
    //*************************************************************************
    ETL_CONSTEXPR14 bitset_ext(const bitset_ext<Active_Bits, TElement>& other) ETL_NOEXCEPT ETL_DELETE;

    //*************************************************************************
    /// Construct from a value.
    //*************************************************************************
    ETL_CONSTEXPR14 bitset_ext(unsigned long long value, element_type* pbuffer_)
      : pbuffer(pbuffer_)
    {
      ETL_ASSERT(pbuffer != ETL_NULLPTR, ETL_ERROR(etl::bitset_invalid_buffer));
      implementation::template initialise<element_type>(pbuffer, Number_Of_Elements, value);
    }

    //*************************************************************************
    /// Construct from a value.
    //*************************************************************************
    template <typename TValue>
    ETL_CONSTEXPR14 bitset_ext(TValue value, buffer_type& buffer, typename etl::enable_if<is_integral<TValue>::value>::type* = 0) ETL_NOEXCEPT
      : pbuffer(buffer.data())
    {
      implementation::template initialise<element_type>(pbuffer, Number_Of_Elements, value);
    }

    //*************************************************************************
    /// Construct from a string.
    //*************************************************************************
    template <typename TPString>
    ETL_CONSTEXPR14 bitset_ext(TPString text, element_type* pbuffer_, typename etl::enable_if<is_same<TPString, const char*>::value>::type* = 0)
      : pbuffer(pbuffer_)
    {
      ETL_ASSERT(pbuffer != ETL_NULLPTR, ETL_ERROR(etl::bitset_invalid_buffer));
      implementation::from_string(pbuffer, Number_Of_Elements, Active_Bits, text);
    }

    //*************************************************************************
    /// Construct from a string.
    //*************************************************************************
    template <typename TPString>
    ETL_CONSTEXPR14 bitset_ext(TPString text, buffer_type& buffer, typename etl::enable_if<is_same<TPString, const char*>::value>::type* = 0) ETL_NOEXCEPT
      : pbuffer(buffer.data())
    {
      implementation::from_string(pbuffer, Number_Of_Elements, Active_Bits, text);
    }

    //*************************************************************************
    /// Construct from a string.
    //*************************************************************************
    template <typename TPString>
    ETL_CONSTEXPR14 bitset_ext(TPString text, element_type* pbuffer_, typename etl::enable_if<is_same<TPString, const wchar_t*>::value>::type* = 0)
      : pbuffer(pbuffer_)
    {
      ETL_ASSERT(pbuffer != ETL_NULLPTR, ETL_ERROR(etl::bitset_invalid_buffer));
      implementation::from_string(pbuffer, Number_Of_Elements, Active_Bits, text);
    }

    //*************************************************************************
    /// Construct from a string.
    //*************************************************************************
    template <typename TPString>
    ETL_CONSTEXPR14 bitset_ext(TPString text, buffer_type& buffer, typename etl::enable_if<is_same<TPString, const wchar_t*>::value>::type* = 0) ETL_NOEXCEPT
      : pbuffer(buffer.data())
    {
      implementation::from_string(pbuffer, Number_Of_Elements, Active_Bits, text);
    }

    //*************************************************************************
    /// Construct from a string.
    //*************************************************************************
    template <typename TPString>
    ETL_CONSTEXPR14 bitset_ext(TPString text, element_type* pbuffer_, typename etl::enable_if<is_same<TPString, const char16_t*>::value>::type* = 0)
      : pbuffer(pbuffer_)
    {
      ETL_ASSERT(pbuffer != ETL_NULLPTR, ETL_ERROR(etl::bitset_invalid_buffer));
      implementation::from_string(pbuffer, Number_Of_Elements, Active_Bits, text);
    }

    //*************************************************************************
    /// Construct from a string.
    //*************************************************************************
    template <typename TPString>
    ETL_CONSTEXPR14 bitset_ext(TPString text, buffer_type& buffer, typename etl::enable_if<is_same<TPString, const char16_t*>::value>::type* = 0) ETL_NOEXCEPT
      : pbuffer(buffer.data())
    {
      implementation::from_string(pbuffer, Number_Of_Elements, Active_Bits, text);
    }

    //*************************************************************************
    /// Construct from a string.
    //*************************************************************************
    template <typename TPString>
    ETL_CONSTEXPR14 bitset_ext(TPString text, element_type* pbuffer_, typename etl::enable_if<is_same<TPString, const char32_t*>::value>::type* = 0)
      : pbuffer(pbuffer_)
    {
      ETL_ASSERT(pbuffer != ETL_NULLPTR, ETL_ERROR(etl::bitset_invalid_buffer));
      implementation::from_string(pbuffer, Number_Of_Elements, Active_Bits, text);
    }

    //*************************************************************************
    /// Construct from a string.
    //*************************************************************************
    template <typename TPString>
    ETL_CONSTEXPR14 bitset_ext(TPString text, buffer_type& buffer, typename etl::enable_if<is_same<TPString, const char32_t*>::value>::type* = 0) ETL_NOEXCEPT
      : pbuffer(buffer.data())
    {
      implementation::from_string(pbuffer, Number_Of_Elements, Active_Bits, text);
    }

    //*************************************************************************
    /// Assignment operator.
    //*************************************************************************
    ETL_CONSTEXPR14 bitset_ext& operator =(const bitset_ext<Active_Bits, TElement>& other) ETL_NOEXCEPT
    {
      implementation::operator_assignment(pbuffer, other.pbuffer, Number_Of_Elements);

      return *this;
    }

    //*************************************************************************
    /// Set all of the bits.
    //*************************************************************************
    ETL_CONSTEXPR14 bitset_ext<Active_Bits, TElement>& set() ETL_NOEXCEPT
    {
      implementation::set_all(pbuffer, Number_Of_Elements, Top_Mask);

      return *this;
    }

    //*************************************************************************
    /// Set the bit at the position.
    //*************************************************************************
    ETL_CONSTEXPR14
      bitset_ext<Active_Bits, TElement>& set(size_t position, bool value = true)
    {
      ETL_ASSERT_OR_RETURN_VALUE(position < Active_Bits, ETL_ERROR(bitset_overflow), *this);

      implementation::set_position(pbuffer, position, value);

      return *this;
    }

    //*************************************************************************
    /// Set the bit at the position.
    //*************************************************************************
    template <size_t Position>
    ETL_CONSTEXPR14 bitset_ext<Active_Bits, TElement>& set(bool value = true)
    {
      ETL_STATIC_ASSERT(Position < Active_Bits, "Position out of bounds");

      implementation::template set_position<Position>(pbuffer, value);

      return *this;
    }

    //*************************************************************************
    /// Set the bit at the position.
    //*************************************************************************
    template <size_t Position, bool Value>
    ETL_CONSTEXPR14 bitset_ext<Active_Bits, TElement>& set()
    {
      ETL_STATIC_ASSERT(Position < Active_Bits, "Position out of bounds");

      implementation::template set_position<Position, Value>(pbuffer);

      return *this;
    }

    //*************************************************************************
    /// Set from a string.
    //*************************************************************************
    template <typename TPString>
    ETL_CONSTEXPR14
    typename etl::enable_if<etl::is_same<TPString, const char*>::value, bitset_ext<Active_Bits, TElement>&>::type
      set(TPString text) ETL_NOEXCEPT
    {
      implementation::from_string(pbuffer, Number_Of_Elements, Active_Bits, text);

      return *this;
    }

    //*************************************************************************
    /// Set from a wide string.
    //*************************************************************************
    template <typename TPString>
    ETL_CONSTEXPR14
    typename etl::enable_if<etl::is_same<TPString, const wchar_t*>::value, bitset_ext<Active_Bits, TElement>&>::type
      set(TPString text) ETL_NOEXCEPT
    {
      implementation::from_string(pbuffer, Number_Of_Elements, Active_Bits, text);

      return *this;
    }

    //*************************************************************************
    /// Set from a char16 string.
    //*************************************************************************
    template <typename TPString>
    ETL_CONSTEXPR14
    typename etl::enable_if<etl::is_same<TPString, const char16_t*>::value, bitset_ext<Active_Bits, TElement>&>::type
      set(TPString text) ETL_NOEXCEPT
    {
      implementation::from_string(pbuffer, Number_Of_Elements, Active_Bits, text);

      return *this;
    }

    //*************************************************************************
    /// Set from a char32 string.
    //*************************************************************************
    template <typename TPString>
    ETL_CONSTEXPR14
    typename etl::enable_if<etl::is_same<TPString, const char32_t*>::value, bitset_ext<Active_Bits, TElement>&>::type
      set(TPString text) ETL_NOEXCEPT
    {
      implementation::from_string(pbuffer, Number_Of_Elements, Active_Bits, text);

      return *this;
    }

    //*************************************************************************
    /// Set from a string.
    //*************************************************************************
    ETL_CONSTEXPR14 bitset_ext<Active_Bits, TElement>& from_string(const char* text) ETL_NOEXCEPT
    {
      implementation::from_string(pbuffer, Number_Of_Elements, Active_Bits, text);

      return *this;
    }

    //*************************************************************************
    /// Set from a wide string.
    //*************************************************************************
    ETL_CONSTEXPR14 bitset_ext<Active_Bits, TElement>& from_string(const wchar_t* text) ETL_NOEXCEPT
    {
      implementation::from_string(pbuffer, Number_Of_Elements, Active_Bits, text);

      return *this;
    }

    //*************************************************************************
    /// Set from a u16 string.
    //*************************************************************************
    ETL_CONSTEXPR14 bitset_ext<Active_Bits, TElement>& from_string(const char16_t* text) ETL_NOEXCEPT
    {
      implementation::from_string(pbuffer, Number_Of_Elements, Active_Bits, text);

      return *this;
    }

    //*************************************************************************
    /// Set from a u32 string.
    //*************************************************************************
    ETL_CONSTEXPR14 bitset_ext<Active_Bits, TElement>& from_string(const char32_t* text) ETL_NOEXCEPT
    {
      implementation::from_string(pbuffer, Number_Of_Elements, Active_Bits, text);

      return *this;
    }

    //*************************************************************************
    /// Get as an integral value.
    //*************************************************************************
    template <typename T>
    ETL_CONSTEXPR14
    T value() const ETL_NOEXCEPT
    {
      ETL_STATIC_ASSERT(etl::is_integral<T>::value, "Only integral types are supported");
      ETL_STATIC_ASSERT(etl::integral_limits<T>::bits >= (Number_Of_Elements * Bits_Per_Element), "Type too small");

      return implementation::template value<T>(pbuffer, Number_Of_Elements);
    }

    //*************************************************************************
    /// Extract an integral value from an arbitrary position and length.
    /// Run time position and length.
    //*************************************************************************
    template <typename T>
    ETL_CONSTEXPR14
      T extract(size_t position, size_t length = etl::integral_limits<T>::bits)
    {
      ETL_STATIC_ASSERT(etl::is_integral<T>::value, "Only integral types are supported");

      ETL_ASSERT_OR_RETURN_VALUE(length <= etl::integral_limits<T>::bits, ETL_ERROR(bitset_overflow), 0);
      ETL_ASSERT_OR_RETURN_VALUE((position + length) <= Active_Bits,      ETL_ERROR(bitset_overflow), 0);

      return implementation::template extract<T>(pbuffer, position, length);
    }

    //*************************************************************************
    /// Extract an integral value from an arbitrary position and length.
    /// Compile time position and length.
    //*************************************************************************
#if ETL_USING_CPP11
    template <typename T, size_t Position, size_t Length = etl::integral_limits<T>::bits>
#else
    template <typename T, size_t Position, size_t Length>
#endif
    ETL_CONSTEXPR14
    T extract() const
    {
      ETL_STATIC_ASSERT(etl::is_integral<T>::value,              "Only integral types are supported");
      ETL_STATIC_ASSERT(Length <= etl::integral_limits<T>::bits, "Length is larger that the required type");
      ETL_STATIC_ASSERT((Position + Length) <= Active_Bits,      "Position/Length overflows bitset");

      return implementation::template extract<T, Position, Length>(pbuffer);
    }

    //*************************************************************************
    /// Get as an unsigned long.
    //*************************************************************************
    unsigned long to_ulong() const
    {
      ETL_ASSERT(etl::integral_limits<unsigned long>::bits >= Active_Bits, ETL_ERROR(etl::bitset_overflow));

      return implementation::template value<unsigned long>(pbuffer, Number_Of_Elements);
    }

    //*************************************************************************
    /// Get as an unsigned long long.
    //*************************************************************************
    unsigned long long to_ullong() const
    {
      ETL_ASSERT(etl::integral_limits<unsigned long long>::bits >= Active_Bits, ETL_ERROR(etl::bitset_overflow));

      return implementation::template value<unsigned long long>(pbuffer, Number_Of_Elements);
    }

    //*************************************************************************
    /// Reset all of the bits.
    //*************************************************************************
    ETL_CONSTEXPR14 bitset_ext<Active_Bits, TElement>& reset() ETL_NOEXCEPT
    {
      implementation::reset_all(pbuffer, Number_Of_Elements);

      return *this;
    }

    //*************************************************************************
    /// Reset the bit at the position.
    //*************************************************************************
    ETL_CONSTEXPR14 bitset_ext<Active_Bits, TElement>& reset(size_t position)
    {
      ETL_ASSERT_OR_RETURN_VALUE(position < Active_Bits, ETL_ERROR(bitset_overflow), *this);

      implementation::reset_position(pbuffer, position);

      return *this;
    }

    //*************************************************************************
    /// Tests a bit at a position.
    /// Positions greater than the number of configured bits will return <b>false</b>.
    //*************************************************************************
    ETL_CONSTEXPR14 bool test(size_t position) const
    {
      ETL_ASSERT_OR_RETURN_VALUE(position < Active_Bits, ETL_ERROR(bitset_overflow), false);
      
      return implementation::test(pbuffer, position);
    }

    //*************************************************************************
    /// Tests a bit at a position.
    /// Positions greater than the number of configured bits will not compile.
    //*************************************************************************
    template <size_t Position>
    ETL_CONSTEXPR14 bool test() const
    {
      ETL_STATIC_ASSERT(Position < Active_Bits, "Position out of bounds");

      return implementation::test(pbuffer, Position);
    }

    //*************************************************************************
    /// The number of bits in the bitset.
    //*************************************************************************
    static ETL_CONSTEXPR size_t size() ETL_NOEXCEPT
    {
      return Active_Bits;
    }

    //*************************************************************************
    /// The number of storage elements in the bitset.
    //*************************************************************************
    static ETL_CONSTEXPR size_t number_of_elements() ETL_NOEXCEPT
    {
      return Number_Of_Elements;
    }

    //*************************************************************************
    /// The value of a set element.
    //*************************************************************************
    static ETL_CONSTEXPR element_type all_set_element() ETL_NOEXCEPT
    {
      return All_Set_Element;
    }

    //*************************************************************************
    /// The value of a clear element.
    //*************************************************************************
    static ETL_CONSTEXPR element_type all_clear_element() ETL_NOEXCEPT
    {
      return All_Clear_Element;
    }

    //*************************************************************************
    /// The mask for the msb element.
    //*************************************************************************
    static ETL_CONSTEXPR element_type top_mask() ETL_NOEXCEPT
    {
      return Top_Mask;
    }

    //*************************************************************************
    /// The number of bits in an element.
    //*************************************************************************
    static ETL_CONSTEXPR size_t bits_per_element() ETL_NOEXCEPT
    {
      return Bits_Per_Element;
    }

    //*************************************************************************
    /// The total number of bits of storage, including unused.
    //*************************************************************************
    static ETL_CONSTEXPR size_t allocated_bits() ETL_NOEXCEPT
    {
      return Number_Of_Elements * Bits_Per_Element;
    }

    //*************************************************************************
    /// The storage model for the bitset.
    /// etl::bitset_storage_model::Single
    /// etl::bitset_storage_model::Multi
    //*************************************************************************
    static ETL_CONSTEXPR etl::bitset_storage_model storage_model() ETL_NOEXCEPT
    {
      return Storage_Model;
    }

    //*************************************************************************
    /// Count the number of bits set.
    //*************************************************************************
    ETL_CONSTEXPR14 size_t count() const ETL_NOEXCEPT
    {
      return implementation::count(pbuffer, Number_Of_Elements);
    }

    //*************************************************************************
    // Are all the bits sets?
    //*************************************************************************
    ETL_CONSTEXPR14 bool all() const ETL_NOEXCEPT
    {
      return implementation::all(pbuffer, Number_Of_Elements, Top_Mask);
    }

    //*************************************************************************
    // Are all the mask bits sets?
    //*************************************************************************
    ETL_CONSTEXPR14 bool all(element_type mask) const ETL_NOEXCEPT
    {
      ETL_STATIC_ASSERT(Storage_Model == etl::bitset_storage_model::Single, "Not supported for 'Multi' bitset storage model");

      return implementation::all(pbuffer, Number_Of_Elements, Top_Mask, mask);
    }

    //*************************************************************************
    /// Are none of the bits set?
    //*************************************************************************
    ETL_CONSTEXPR14 bool none() const ETL_NOEXCEPT
    {
      return implementation::none(pbuffer, Number_Of_Elements);
    }

    //*************************************************************************
    /// Are none of the mask bits set?
    //*************************************************************************
    ETL_CONSTEXPR14 bool none(element_type mask) const ETL_NOEXCEPT
    {
      ETL_STATIC_ASSERT(Storage_Model == etl::bitset_storage_model::Single, "Not supported for 'Multi' bitset storage model");

      return implementation::none(pbuffer, Number_Of_Elements, mask);
    }

    //*************************************************************************
    /// Are any of the bits set?
    //*************************************************************************
    ETL_CONSTEXPR14 bool any() const ETL_NOEXCEPT
    {
      return implementation::any(pbuffer, Number_Of_Elements);
    }

    //*************************************************************************
    /// Are any of the mask bits set?
    //*************************************************************************
    ETL_CONSTEXPR14 bool any(element_type mask) const ETL_NOEXCEPT
    {
      ETL_STATIC_ASSERT(Storage_Model == etl::bitset_storage_model::Single, "Not supported for 'Multi' bitset storage model");

      return implementation::any(pbuffer, Number_Of_Elements, mask);
    }

    //*************************************************************************
    /// Flip all of the bits.
    //*************************************************************************
    ETL_CONSTEXPR14 bitset_ext<Active_Bits, TElement>& flip() ETL_NOEXCEPT
    {
      implementation::flip_all(pbuffer, Number_Of_Elements);

      return *this;
    }

    //*************************************************************************
    /// Flip the bit at the position.
    //*************************************************************************
    ETL_CONSTEXPR14 bitset_ext<Active_Bits, TElement>& flip(size_t position)
    {
      ETL_ASSERT_OR_RETURN_VALUE(position < Active_Bits, ETL_ERROR(bitset_overflow), *this);
      
      implementation::flip_position(pbuffer, position);

      return *this;
    }

    //*************************************************************************
    /// Read [] operator.
    //*************************************************************************
    ETL_CONSTEXPR14 bool operator[] (size_t position) const ETL_NOEXCEPT
    {
      return implementation::test(pbuffer, position);
    }

    //*************************************************************************
    /// Write [] operator.
    //*************************************************************************
    ETL_CONSTEXPR14 bit_reference operator [] (size_t position) ETL_NOEXCEPT
    {
      return bit_reference(*this, position);
    }

    //*************************************************************************
    /// Returns a string representing the bitset.
    //*************************************************************************
#if ETL_USING_CPP11
    template <typename TString = etl::string<Active_Bits>>
#else
    template <typename TString>
#endif
    ETL_CONSTEXPR14 TString to_string(typename TString::value_type zero = typename TString::value_type('0'),
                                      typename TString::value_type one  = typename TString::value_type('1')) const
    {
      return implementation::template to_string<TString>(pbuffer, Active_Bits, zero, one);
    }

    //*************************************************************************
    /// Finds the first bit in the specified state.
    ///\param state The state to search for.
    ///\returns The position of the bit or npos if none were found.
    //*************************************************************************
    ETL_CONSTEXPR14 size_t find_first(bool state) const ETL_NOEXCEPT
    {
      return implementation::find_next(pbuffer, Number_Of_Elements, Active_Bits, state, 0);
    }

    //*************************************************************************
    /// Finds the next bit in the specified state.
    ///\param state    The state to search for.
    ///\param position The position to start from.
    ///\returns The position of the bit or npos if none were found.
    //*************************************************************************
    ETL_CONSTEXPR14 size_t find_next(bool state, size_t position) const ETL_NOEXCEPT
    {
      return implementation::find_next(pbuffer, Number_Of_Elements, Active_Bits, state, position);
    }

    //*************************************************************************
    /// operator &=
    //*************************************************************************
    ETL_CONSTEXPR14 bitset_ext<Active_Bits, TElement>& operator &=(const bitset_ext<Active_Bits, TElement>& other) ETL_NOEXCEPT
    {
      implementation::operator_and(&pbuffer[0], &other.pbuffer[0], Number_Of_Elements);

      return *this;
    }

    //*************************************************************************
    /// operator |=
    //*************************************************************************
    ETL_CONSTEXPR14 bitset_ext<Active_Bits, TElement>& operator |=(const bitset_ext<Active_Bits, TElement>& other) ETL_NOEXCEPT
    {
      implementation::operator_or(&pbuffer[0], &other.pbuffer[0], Number_Of_Elements);

      return *this;
    }

    //*************************************************************************
    /// operator ^=
    //*************************************************************************
    ETL_CONSTEXPR14 bitset_ext<Active_Bits, TElement>& operator ^=(const bitset_ext<Active_Bits, TElement>& other) ETL_NOEXCEPT
    {
      implementation::operator_xor(&pbuffer[0], &other.pbuffer[0], Number_Of_Elements);

      return *this;
    }

    //*************************************************************************
    /// operator <<=
    //*************************************************************************
    ETL_CONSTEXPR14 bitset_ext<Active_Bits, TElement>& operator <<=(size_t shift) ETL_NOEXCEPT
    {
      implementation::operator_shift_left(pbuffer, Number_Of_Elements, Active_Bits, shift);

      return *this;
    }

    //*************************************************************************
    /// operator >>=
    //*************************************************************************
    ETL_CONSTEXPR14 bitset_ext<Active_Bits, TElement>& operator >>=(size_t shift) ETL_NOEXCEPT
    {
      implementation::operator_shift_right(pbuffer, Number_Of_Elements, Active_Bits, shift);

      return *this;
    }

    //*************************************************************************
    /// operator ==
    //*************************************************************************
    friend ETL_CONSTEXPR14 bool operator ==(const bitset_ext<Active_Bits, TElement>& lhs, const bitset_ext<Active_Bits, TElement>& rhs) ETL_NOEXCEPT
    {
      return implementation::operator_equality(lhs.pbuffer, rhs.pbuffer, lhs.Number_Of_Elements);
    }

    //*************************************************************************
    /// operator !=
    //*************************************************************************
    friend ETL_CONSTEXPR14 bool operator !=(const bitset_ext<Active_Bits, TElement>& lhs, const bitset_ext<Active_Bits, TElement>& rhs) ETL_NOEXCEPT
    {
      return !(lhs == rhs);
    }

    //*************************************************************************
    /// swap
    //*************************************************************************
    ETL_CONSTEXPR14 void swap(etl::bitset_ext<Active_Bits, TElement>& other) ETL_NOEXCEPT
    {
      implementation::swap(pbuffer, other.pbuffer, Number_Of_Elements);
    }

    //*************************************************************************
    /// span
    /// Returns a span of the underlying pbuffer.
    //*************************************************************************
    ETL_CONSTEXPR14 span_type span() ETL_NOEXCEPT
    {
      return span_type(pbuffer, Number_Of_Elements);
    }

    //*************************************************************************
    /// span
    /// Returns a const span of the underlying pbuffer.
    //*************************************************************************
    ETL_CONSTEXPR14 const_span_type span() const ETL_NOEXCEPT
    {
      return const_span_type(pbuffer, Number_Of_Elements);
    }

  private:

    // The implementation of the bitset functionality.
    typedef etl::bitset_impl<element_type, (Number_Of_Elements == 1U) ? etl::bitset_storage_model::Single : etl::bitset_storage_model::Multi> implementation;

    // Pointer to the storage for the bitset.
    element_type* pbuffer;
  };
}

//***************************************************************************
/// operator !=
///\ingroup bitset
//***************************************************************************
template<size_t Active_Bits, typename TElement>
ETL_CONSTEXPR14 bool operator != (const etl::bitset_ext<Active_Bits, TElement>& lhs, const etl::bitset_ext<Active_Bits, TElement>& rhs) ETL_NOEXCEPT
{
  return !(lhs == rhs);
}

//*************************************************************************
/// swap
//*************************************************************************
template <size_t Active_Bits, typename TElement>
ETL_CONSTEXPR14 void swap(etl::bitset_ext<Active_Bits, TElement>& lhs, etl::bitset_ext<Active_Bits, TElement>& rhs) ETL_NOEXCEPT
{
  lhs.swap(rhs);
}

namespace etl
{
  namespace private_bitset
  {
    //*************************************************************************
    /// Compare bitset spans.
    /// Assumes that the lhs span's element type is larger than rhs's.
    //*************************************************************************
    template <typename TLhsSpan, typename TRhsSpan>
    bool compare_bitset_spans(const TLhsSpan& lhs_span, const TRhsSpan& rhs_span)
    {
      typedef typename TLhsSpan::value_type lhs_element_t;
      typedef typename TRhsSpan::value_type rhs_element_t;

      const int steps = static_cast<int>(sizeof(lhs_element_t) / sizeof(rhs_element_t));

      typename TLhsSpan::iterator lhs_itr = lhs_span.begin();
      typename TRhsSpan::iterator rhs_itr = rhs_span.begin();

      while (lhs_itr != lhs_span.end())
      {
        const lhs_element_t& lhs_value = *lhs_itr;

        // Build the rhs element in terms of the lhs element type.
        lhs_element_t rhs_value = 0;

        const int shift_step = etl::integral_limits<rhs_element_t>::bits;
        int shift = 0;

        for (int i = 0; i < steps; ++i)
        {
          rhs_value |= (static_cast<lhs_element_t>(*rhs_itr) << shift);
          ++rhs_itr;
          shift += shift_step;
        }

        if (lhs_value != rhs_value)
        {
          return false;
        }

        ++lhs_itr;
      }

      return true;
    }
  }
}

//***************************************************************************
/// operator ==
/// bitset 
/// Different element types
///\ingroup bitset
//***************************************************************************
template<size_t Active_Bits, typename TLhsElement, typename TRhsElement>
ETL_CONSTEXPR14
typename etl::enable_if<!etl::is_same<TLhsElement, TRhsElement>::value, bool>::type
  operator == (const etl::bitset<Active_Bits, TLhsElement>& lhs, const etl::bitset<Active_Bits, TRhsElement>& rhs) ETL_NOEXCEPT
{
  // Get a span of each type.
  typename etl::bitset<Active_Bits, TLhsElement>::const_span_type lhs_span = lhs.span();
  typename etl::bitset<Active_Bits, TRhsElement>::const_span_type rhs_span = rhs.span();

  // Put the bitset with the largest element type as the first argument.
  if ETL_IF_CONSTEXPR(sizeof(TLhsElement) > sizeof(TRhsElement))
  {
    return etl::private_bitset::compare_bitset_spans(lhs_span, rhs_span);
  }
  else
  {
    return etl::private_bitset::compare_bitset_spans(rhs_span, lhs_span);
  }
}

//***************************************************************************
/// operator !=
/// bitset 
/// Different element types
///\ingroup bitset
//***************************************************************************
template<size_t Active_Bits, typename TLhsElement, typename TRhsElement>
ETL_CONSTEXPR14
typename etl::enable_if<!etl::is_same<TLhsElement, TRhsElement>::value, bool>::type
  operator != (const etl::bitset<Active_Bits, TLhsElement>& lhs, const etl::bitset<Active_Bits, TRhsElement>& rhs) ETL_NOEXCEPT
{
  return !(lhs == rhs);
}

//***************************************************************************
/// operator ==
/// bitset_ext
/// Different element types
///\ingroup bitset
//***************************************************************************
template<size_t Active_Bits, typename TLhsElement, typename TRhsElement>
ETL_CONSTEXPR14
typename etl::enable_if<!etl::is_same<TLhsElement, TRhsElement>::value, bool>::type
  operator == (const etl::bitset_ext<Active_Bits, TLhsElement>& lhs, const etl::bitset_ext<Active_Bits, TRhsElement>& rhs) ETL_NOEXCEPT
{
  // Get a span of each type.
  typename etl::bitset_ext<Active_Bits, TLhsElement>::const_span_type lhs_span = lhs.span();
  typename etl::bitset_ext<Active_Bits, TRhsElement>::const_span_type rhs_span = rhs.span();

  // Put the bitset with the largest element type as the first argument.
  if ETL_IF_CONSTEXPR(sizeof(TLhsElement) > sizeof(TRhsElement))
  {
    return etl::private_bitset::compare_bitset_spans(lhs_span, rhs_span);
  }
  else
  {
    return etl::private_bitset::compare_bitset_spans(rhs_span, lhs_span);
  }
}

//***************************************************************************
/// operator !=
/// bitset_ext
/// Different element types
///\ingroup bitset
//***************************************************************************
template<size_t Active_Bits, typename TLhsElement, typename TRhsElement>
ETL_CONSTEXPR14
typename etl::enable_if<!etl::is_same<TLhsElement, TRhsElement>::value, bool>::type
  operator != (const etl::bitset_ext<Active_Bits, TLhsElement>& lhs, const etl::bitset_ext<Active_Bits, TRhsElement>& rhs) ETL_NOEXCEPT
{
  return !(lhs == rhs);
}

//***************************************************************************
/// operator ==
/// bitset compared with bitset_ext, same element types.
///\ingroup bitset
//***************************************************************************
template<size_t Active_Bits, typename TElement>
ETL_CONSTEXPR14
bool operator == (const etl::bitset<Active_Bits, TElement>& lhs, const etl::bitset_ext<Active_Bits, TElement>& rhs) ETL_NOEXCEPT
{
  const char   Storage_Model      = etl::bitset<Active_Bits, TElement>::Storage_Model;
  const size_t Number_Of_Elements = etl::bitset<Active_Bits, TElement>::Number_Of_Elements;

  typename etl::bitset<Active_Bits, TElement>::const_span_type     lhs_span = lhs.span();
  typename etl::bitset_ext<Active_Bits, TElement>::const_span_type rhs_span = rhs.span();

  typedef etl::bitset_impl<TElement, Storage_Model> implementation;

  return implementation::operator_equality(lhs_span.begin(), rhs_span.begin(), Number_Of_Elements);
}

//***************************************************************************
/// operator !=
/// bitset compared with bitset_ext, same element types.
///\ingroup bitset
//***************************************************************************
template<size_t Active_Bits, typename TElement>
ETL_CONSTEXPR14
bool operator != (const etl::bitset<Active_Bits, TElement>& lhs, const etl::bitset_ext<Active_Bits, TElement>& rhs) ETL_NOEXCEPT
{
  return !(lhs == rhs);
}

//***************************************************************************
/// operator ==
/// bitset_ext compared with bitset, same element types.
///\ingroup bitset
//***************************************************************************
template<size_t Active_Bits, typename TElement>
ETL_CONSTEXPR14
bool operator == (const etl::bitset_ext<Active_Bits, TElement>& lhs, const etl::bitset<Active_Bits, TElement>& rhs) ETL_NOEXCEPT
{
  const char   Storage_Model      = etl::bitset<Active_Bits, TElement>::Storage_Model;
  const size_t Number_Of_Elements = etl::bitset<Active_Bits, TElement>::Number_Of_Elements;

  typename etl::bitset_ext<Active_Bits, TElement>::const_span_type lhs_span = lhs.span();
  typename etl::bitset<Active_Bits, TElement>::const_span_type     rhs_span = rhs.span();

  typedef etl::bitset_impl<TElement, Storage_Model> implementation;

  return implementation::operator_equality(lhs_span.begin(), rhs_span.begin(), Number_Of_Elements);
}

//***************************************************************************
/// operator !=
/// bitset_ext compared with bitset, same element types.
///\ingroup bitset
//***************************************************************************
template<size_t Active_Bits, typename TElement>
ETL_CONSTEXPR14
bool operator != (const etl::bitset_ext<Active_Bits, TElement>& lhs, const etl::bitset<Active_Bits, TElement>& rhs) ETL_NOEXCEPT
{
  return !(lhs == rhs);
}

//***************************************************************************
/// operator ==
/// bitset compared with bitset_ext, different element types. 
///\ingroup bitset
//***************************************************************************
template<size_t Active_Bits, typename TLhsElement, typename TRhsElement>
ETL_CONSTEXPR14
typename etl::enable_if<!etl::is_same<TLhsElement, TRhsElement>::value, bool>::type
operator == (const etl::bitset<Active_Bits, TLhsElement>& lhs, const etl::bitset_ext<Active_Bits, TRhsElement>& rhs) ETL_NOEXCEPT
{
  // Get a span of each type.
  typename etl::bitset<Active_Bits, TLhsElement>::const_span_type     lhs_span = lhs.span();
  typename etl::bitset_ext<Active_Bits, TRhsElement>::const_span_type rhs_span = rhs.span();

  // Put the bitset with the largest element type as the first argument.
  if ETL_IF_CONSTEXPR(sizeof(TLhsElement) > sizeof(TRhsElement))
  {
    return etl::private_bitset::compare_bitset_spans(lhs_span, rhs_span);
  }
  else
  {
    return etl::private_bitset::compare_bitset_spans(rhs_span, lhs_span);
  }
}

//***************************************************************************
/// operator !=
/// bitset compared with bitset_ext, different element types. 
///\ingroup bitset
//***************************************************************************
template<size_t Active_Bits, typename TLhsElement, typename TRhsElement>
ETL_CONSTEXPR14
typename etl::enable_if<!etl::is_same<TLhsElement, TRhsElement>::value, bool>::type
  operator != (const etl::bitset<Active_Bits, TLhsElement>& lhs, const etl::bitset_ext<Active_Bits, TRhsElement>& rhs) ETL_NOEXCEPT
{
  return !(lhs == rhs);
}

//***************************************************************************
/// operator ==
/// bitset_ext compared with bitset, different element types. 
///\ingroup bitset
//***************************************************************************
template<size_t Active_Bits, typename TLhsElement, typename TRhsElement>
ETL_CONSTEXPR14
typename etl::enable_if<!etl::is_same<TLhsElement, TRhsElement>::value, bool>::type
  operator == (const etl::bitset_ext<Active_Bits, TLhsElement>& lhs, const etl::bitset<Active_Bits, TRhsElement>& rhs) ETL_NOEXCEPT
{
  // Get a span of each type.
  typename etl::bitset_ext<Active_Bits, TLhsElement>::const_span_type lhs_span = lhs.span();
  typename etl::bitset<Active_Bits, TRhsElement>::const_span_type     rhs_span = rhs.span();

  // Put the bitset with the largest element type as the first argument.
  if ETL_IF_CONSTEXPR(sizeof(TLhsElement) > sizeof(TRhsElement))
  {
    return etl::private_bitset::compare_bitset_spans(lhs_span, rhs_span);
  }
  else
  {
    return etl::private_bitset::compare_bitset_spans(rhs_span, lhs_span);
  }
}

//***************************************************************************
/// operator !=
/// bitset_ext compared with bitset, different element types. 
///\ingroup bitset
//***************************************************************************
template<size_t Active_Bits, typename TLhsElement, typename TRhsElement>
ETL_CONSTEXPR14
typename etl::enable_if<!etl::is_same<TLhsElement, TRhsElement>::value, bool>::type
  operator != (const etl::bitset_ext<Active_Bits, TLhsElement>& lhs, const etl::bitset<Active_Bits, TRhsElement>& rhs) ETL_NOEXCEPT
{
  return !(lhs == rhs);
}

#include "minmax_pop.h"

#endif