span.h

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/******************************************************************************
The MIT License(MIT)
 
Embedded Template Library.
https://github.com/ETLCPP/etl
https://www.etlcpp.com
 
Copyright(c) 2020 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
copies of the Software, and to permit persons to whom the Software is
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The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
 
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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******************************************************************************/
 
#ifndef ETL_SPAN_INCLUDED
#define ETL_SPAN_INCLUDED
 
#include "platform.h"
 
#include "error_handler.h"
#include "exception.h"
#include "alignment.h"
#include "iterator.h"
#include "algorithm.h"
#include "circular_iterator.h"
#include "nullptr.h"
#include "hash.h"
#include "type_traits.h"
#include "integral_limits.h"
#include "memory.h"
#include "array.h"
#include "byte.h"
#include "static_assert.h"
 
#include "private/dynamic_extent.h"
 
 
namespace etl
{
  //***************************************************************************
  // Tag to indicate a class is a span.
  //***************************************************************************
  class span_tag {};
 
  //***************************************************************************
  //***************************************************************************
  class span_exception : public exception
  {
  public:
 
    span_exception(string_type reason_, string_type file_name_, numeric_type line_number_)
      : exception(reason_, file_name_, line_number_)
    {
    }
  };
 
  //***************************************************************************
  //***************************************************************************
  class span_alignment_exception : public span_exception
  {
  public:
 
    span_alignment_exception(string_type file_name_, numeric_type line_number_)
      : span_exception(ETL_ERROR_TEXT("span:alignment", ETL_SPAN_FILE_ID"A"), file_name_, line_number_)
    {
    }
  };
 
  //***************************************************************************
  //***************************************************************************
  class span_size_mismatch : public span_exception
  {
  public:
 
    span_size_mismatch(string_type file_name_, numeric_type line_number_)
      : span_exception(ETL_ERROR_TEXT("span:size", ETL_SPAN_FILE_ID"B"), file_name_, line_number_)
    {
    }
  };
 
  //***************************************************************************
  //***************************************************************************
  template <typename T, size_t Extent = etl::dynamic_extent>
  class span : public span_tag
  {
  public:
 
    typedef T                                element_type;
    typedef typename etl::remove_cv<T>::type value_type;
    typedef size_t                           size_type;
    typedef T&                               reference;
    typedef const T&                         const_reference;
    typedef T*                               pointer;
    typedef const T*                         const_pointer;
 
    typedef T*                                           iterator;
    typedef const T*                                     const_iterator;
    typedef ETL_OR_STD::reverse_iterator<iterator>       reverse_iterator;
    typedef ETL_OR_STD::reverse_iterator<const_iterator> const_reverse_iterator;
 
    typedef etl::circular_iterator<pointer>                                circular_iterator;
    typedef etl::circular_iterator<ETL_OR_STD::reverse_iterator<pointer> > reverse_circular_iterator;
 
    static ETL_CONSTANT size_t extent = Extent;
 
    //*************************************************************************
    //*************************************************************************
    template <typename TIterator, typename TSize>
    ETL_CONSTEXPR explicit span(const TIterator begin_, const TSize /*size_*/) ETL_NOEXCEPT
      : pbegin(etl::to_address(begin_))
    {
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename TIterator>
    ETL_CONSTEXPR explicit span(const TIterator begin_, const TIterator /*end_*/)
      : pbegin(etl::to_address(begin_))
    {
    }
 
    //*************************************************************************
    //*************************************************************************
#if ETL_USING_CPP11
    template<size_t Array_Size, typename = typename etl::enable_if<(Array_Size == Extent), void>::type>
    ETL_CONSTEXPR span(element_type(&begin_)[Array_Size]) ETL_NOEXCEPT
      : pbegin(begin_)
    {
    }
#else
    //*************************************************************************
    //*************************************************************************
    template<size_t Array_Size>
    ETL_CONSTEXPR span(element_type(&begin_)[Array_Size], typename etl::enable_if<(Array_Size == Extent), void>::type* = 0) ETL_NOEXCEPT
      : pbegin(begin_)
    {
    }
#endif
 
#if ETL_USING_CPP11
    //*************************************************************************
    //*************************************************************************
    template <typename TContainer, typename = typename etl::enable_if<!etl::is_base_of<span_tag, etl::remove_reference_t<TContainer>>::value &&
                                                                      !etl::is_pointer<etl::remove_reference_t<TContainer>>::value &&
                                                                      !etl::is_array<etl::remove_reference_t<TContainer>>::value&&
                                                                      etl::is_same<etl::remove_cv_t<T>, etl::remove_cv_t<typename etl::remove_reference_t<TContainer>::value_type>>::value, void>::type>
    ETL_CONSTEXPR span(TContainer&& a) ETL_NOEXCEPT
      : pbegin(a.data())
    {
    }
#else
    //*************************************************************************
    //*************************************************************************
    template <typename TContainer>
    span(TContainer& a, typename etl::enable_if<!etl::is_base_of<span_tag, typename etl::remove_reference<TContainer>::type>::value &&
                                                !etl::is_pointer<typename etl::remove_reference<TContainer>::type>::value &&
                                                !etl::is_array<TContainer>::value &&
                                                etl::is_same<typename etl::remove_cv<T>::type, typename etl::remove_cv<typename etl::remove_reference<TContainer>::type::value_type>::type>::value, void>::type* = 0) ETL_NOEXCEPT
      : pbegin(a.data())
    {
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename TContainer>
    span(const TContainer& a, typename etl::enable_if<!etl::is_base_of<span_tag, typename etl::remove_reference<TContainer>::type>::value &&
                                                      !etl::is_pointer<typename etl::remove_reference<TContainer>::type>::value &&
                                                      !etl::is_array<TContainer>::value&&
                                                      etl::is_same<typename etl::remove_cv<T>::type, typename etl::remove_cv<typename etl::remove_reference<TContainer>::type::value_type>::type>::value, void>::type* = 0) ETL_NOEXCEPT
      : pbegin(a.data())
    {
    }
#endif
 
    //*************************************************************************
    //*************************************************************************
    ETL_CONSTEXPR span(const span& other) ETL_NOEXCEPT
      : pbegin(other.pbegin)
    {
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename U, size_t N>
    ETL_CONSTEXPR span(const etl::span<U, N>& other, typename etl::enable_if<N == Extent, void>::type* = 0) ETL_NOEXCEPT
      : pbegin(other.data())
    {
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename U, size_t N>
    ETL_CONSTEXPR14 span(const etl::span<U, N>& other, typename etl::enable_if<N == etl::dynamic_extent, void>::type* = 0)
      : pbegin(other.data())
    {
      ETL_ASSERT(other.size() == Extent, ETL_ERROR(span_size_mismatch));
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR reference front() const ETL_NOEXCEPT
    {
      return *pbegin;
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR reference back() const ETL_NOEXCEPT
    {
      return *((pbegin + Extent) - 1);
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR pointer data() const ETL_NOEXCEPT
    {
      return pbegin;
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR const_iterator cbegin() const ETL_NOEXCEPT
    {
      return pbegin;
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR iterator begin() const ETL_NOEXCEPT
    {
      return pbegin;
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR circular_iterator begin_circular() const ETL_NOEXCEPT
    {
      return circular_iterator(begin(), end());
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR const_iterator cend() const ETL_NOEXCEPT
    {
      return (pbegin + Extent);
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR iterator end() const ETL_NOEXCEPT
    {
      return (pbegin + Extent);
    }
 
    //*************************************************************************
    // Returns a const reverse iterator to the reverse beginning of the span.
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR const_reverse_iterator crbegin() const ETL_NOEXCEPT
    {
      return const_reverse_iterator((pbegin + Extent));
    }
 
    //*************************************************************************
    // Returns an reverse iterator to the reverse beginning of the span.
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR reverse_iterator rbegin() const ETL_NOEXCEPT
    {
      return reverse_iterator((pbegin + Extent));
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR reverse_circular_iterator rbegin_circular() const ETL_NOEXCEPT
    {
      return reverse_circular_iterator(rbegin(), rend());
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR const_reverse_iterator crend() const ETL_NOEXCEPT
    {
      return const_reverse_iterator(pbegin);
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR reverse_iterator rend() const ETL_NOEXCEPT
    {
      return reverse_iterator(pbegin);
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR bool empty() const ETL_NOEXCEPT
    {
      return Extent == 0;
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR size_t size() const ETL_NOEXCEPT
    {
      return Extent;
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR size_t size_bytes() const ETL_NOEXCEPT
    {
      return sizeof(element_type) * Extent;
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR size_t max_size() const ETL_NOEXCEPT
    {
      return size();
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_CONSTEXPR14 span& operator =(const span& other) ETL_NOEXCEPT
    {
      pbegin = other.pbegin;
      return *this;
    } 
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR14 reference at(size_t i)
    {
      ETL_ASSERT(i < size(), ETL_ERROR(array_out_of_range));
 
      return pbegin[i];
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR14 const_reference at(size_t i) const
    {
      ETL_ASSERT(i < size(), ETL_ERROR(array_out_of_range));
 
      return pbegin[i];
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_CONSTEXPR reference operator[](const size_t i) const
    {
      return pbegin[i];
    }
 
    //*************************************************************************
    //*************************************************************************
    template <size_t COUNT>
    ETL_NODISCARD ETL_CONSTEXPR etl::span<element_type, COUNT> first() const ETL_NOEXCEPT
    {
      // If Extent is static, check that original span contains at least COUNT elements
      ETL_STATIC_ASSERT((Extent != etl::dynamic_extent) ? COUNT <= Extent : true, "Original span does not contain COUNT elements");
 
      return etl::span<element_type, COUNT>(pbegin, pbegin + COUNT);
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR etl::span<element_type, etl::dynamic_extent> first(size_t count) const ETL_NOEXCEPT
    {
      return etl::span<element_type, etl::dynamic_extent>(pbegin, pbegin + count);
    }
 
    //*************************************************************************
    //*************************************************************************
    template <size_t COUNT>
    ETL_NODISCARD ETL_CONSTEXPR etl::span<element_type, COUNT> last() const ETL_NOEXCEPT
    {
      // If Extent is static, check that original span contains at least COUNT elements
      ETL_STATIC_ASSERT((Extent != etl::dynamic_extent) ? COUNT <= Extent : true, "Original span does not contain COUNT elements");
 
      return etl::span<element_type, COUNT>(pbegin + Extent - COUNT, (pbegin + Extent));
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR etl::span<element_type, etl::dynamic_extent> last(size_t count) const ETL_NOEXCEPT
    {
      return etl::span<element_type, etl::dynamic_extent>((pbegin + Extent) - count, (pbegin + Extent));
    }
 
#if ETL_USING_CPP11
    //*************************************************************************
    //*************************************************************************
    template <size_t OFFSET, size_t COUNT = etl::dynamic_extent>
    ETL_NODISCARD ETL_CONSTEXPR
      etl::span<element_type, COUNT != etl::dynamic_extent ? COUNT : Extent - OFFSET> subspan() const ETL_NOEXCEPT
    {
      // If Extent is static, check that OFFSET is within the original span
      ETL_STATIC_ASSERT((Extent != etl::dynamic_extent) ? OFFSET <= Extent : true, "OFFSET is not within the original span");
 
      // If count is also static, check that OFFSET + COUNT is within the original span
      ETL_STATIC_ASSERT((Extent != etl::dynamic_extent) && (COUNT != etl::dynamic_extent) ? COUNT <= (Extent - OFFSET) : true, "OFFSET + COUNT is not within the original span");
 
      return (COUNT == etl::dynamic_extent) ? etl::span<element_type, COUNT != etl::dynamic_extent ? COUNT : Extent - OFFSET>(pbegin + OFFSET, (pbegin + Extent))
                                            : etl::span<element_type, COUNT != etl::dynamic_extent ? COUNT : Extent - OFFSET>(pbegin + OFFSET, pbegin + OFFSET + COUNT);
    }
#else
    //*************************************************************************
    //*************************************************************************
    template <size_t OFFSET, size_t COUNT>
    etl::span<element_type, COUNT != etl::dynamic_extent ? COUNT : Extent - OFFSET> subspan() const
    {
      // If Extent is static, check that OFFSET is within the original span
      ETL_STATIC_ASSERT((Extent != etl::dynamic_extent) ? OFFSET <= Extent : true, "OFFSET is not within the original span");
 
      // If count is also static, check that OFFSET + COUNT is within the original span
      ETL_STATIC_ASSERT((Extent != etl::dynamic_extent) && (COUNT != etl::dynamic_extent) ? COUNT <= (Extent - OFFSET) : true, "OFFSET + COUNT is not within the original span");
 
      if (COUNT == etl::dynamic_extent)
      {
        return etl::span<element_type, (COUNT != etl::dynamic_extent ? COUNT : Extent - OFFSET)>(pbegin + OFFSET, (pbegin + Extent));
      }
      else
      {
        return etl::span<element_type, COUNT != etl::dynamic_extent ? COUNT : Extent - OFFSET>(pbegin + OFFSET, pbegin + OFFSET + COUNT);
      }
    }
#endif
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR etl::span<element_type, etl::dynamic_extent> subspan(size_t offset, size_t count = etl::dynamic_extent) const ETL_NOEXCEPT
    {
      return (count == etl::dynamic_extent) ? etl::span<element_type, etl::dynamic_extent>(pbegin + offset, (pbegin + Extent))
                                            : etl::span<element_type, etl::dynamic_extent>(pbegin + offset, pbegin + offset + count);
    }
 
    //*************************************************************************
    //*************************************************************************
    void advance(size_t elements) ETL_NOEXCEPT
    {
      elements = etl::min(elements, size());
      pbegin += elements;
    }
 
    //*************************************************************************
    //*************************************************************************
    template<typename TNew>
    ETL_NODISCARD ETL_CONSTEXPR14 etl::span<TNew, etl::dynamic_extent> reinterpret_as() const
    {
      ETL_ASSERT(etl::is_aligned<etl::alignment_of<TNew>::value>(pbegin), ETL_ERROR(span_alignment_exception));
 
      return etl::span<TNew, etl::dynamic_extent>(reinterpret_cast<TNew*>(pbegin),
                       Extent * sizeof(element_type) / sizeof(TNew));
    }
 
  private:
 
    pointer pbegin;
  };
 
  //*************************************************************************
  //*************************************************************************
  template <typename T, size_t Extent>
  ETL_CONSTEXPR span<T, Extent> make_span(T (&data)[Extent])
  {
    return span<T, Extent>(data);
  }
 
  //***************************************************************************
  //***************************************************************************
  template <typename T>
  class  span<T, etl::dynamic_extent> : public span_tag
  {
  public:
 
    typedef T        element_type;
    typedef typename etl::remove_cv<T>::type value_type;
    typedef size_t   size_type;
    typedef T&       reference;
    typedef const T& const_reference;
    typedef T*       pointer;
    typedef const T* const_pointer;
 
    typedef T*                                           iterator;
    typedef const T*                                     const_iterator;
    typedef ETL_OR_STD::reverse_iterator<iterator>       reverse_iterator;
    typedef ETL_OR_STD::reverse_iterator<const_iterator> const_reverse_iterator;
 
    typedef etl::circular_iterator<pointer>                                circular_iterator;
    typedef etl::circular_iterator<ETL_OR_STD::reverse_iterator<pointer> > reverse_circular_iterator;
 
    static ETL_CONSTANT size_t extent = etl::dynamic_extent;
 
    //*************************************************************************
    //*************************************************************************
    ETL_CONSTEXPR span() ETL_NOEXCEPT
      : pbegin(ETL_NULLPTR)
      , pend(ETL_NULLPTR)
    {
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename TIterator, typename TSize>
    ETL_CONSTEXPR span(const TIterator begin_, const TSize size_) ETL_NOEXCEPT
      : pbegin(etl::to_address(begin_))
      , pend(etl::to_address(begin_) + size_)
    {
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename TIterator>
    ETL_CONSTEXPR span(const TIterator begin_, const TIterator end_)
      : pbegin(etl::to_address(begin_))
      , pend(etl::to_address(begin_) + etl::distance(begin_, end_))
    {
    }
 
    //*************************************************************************
    //*************************************************************************
    template<size_t Array_Size>
    ETL_CONSTEXPR span(element_type(&begin_)[Array_Size]) ETL_NOEXCEPT
      : pbegin(begin_)
      , pend(begin_ + Array_Size)
    {
    }
 
#if ETL_USING_CPP11
    //*************************************************************************
    //*************************************************************************
    template <typename TContainer, typename = typename etl::enable_if<!etl::is_base_of<span_tag, etl::remove_reference_t<TContainer>>::value &&
                                                                      !etl::is_pointer<etl::remove_reference_t<TContainer>>::value &&
                                                                      !etl::is_array<etl::remove_reference_t<TContainer>>::value &&
                                                                      etl::is_same<etl::remove_cv_t<T>, etl::remove_cv_t<typename etl::remove_reference_t<TContainer>::value_type>>::value, void>::type>
    ETL_CONSTEXPR span(TContainer&& a) ETL_NOEXCEPT
      : pbegin(a.data())
      , pend(a.data() + a.size())
    {
    }
#else
    //*************************************************************************
    //*************************************************************************
    template <typename TContainer>
    ETL_CONSTEXPR span(TContainer& a, typename etl::enable_if<!etl::is_base_of<span_tag, typename etl::remove_reference<TContainer>::type>::value &&
                                                              !etl::is_pointer<typename etl::remove_reference<TContainer>::type>::value &&
                                                              !etl::is_array<TContainer>::value &&
                                                              etl::is_same<typename etl::remove_cv<T>::type, typename etl::remove_cv<typename etl::remove_reference<TContainer>::type::value_type>::type>::value, void>::type* = 0) ETL_NOEXCEPT
      : pbegin(a.data())
      , pend(a.data() + a.size())
    {
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename TContainer>
    ETL_CONSTEXPR span(const TContainer& a, typename etl::enable_if<!etl::is_base_of<span_tag, typename etl::remove_reference<TContainer>::type>::value &&
                                                                    !etl::is_pointer<typename etl::remove_reference<TContainer>::type>::value &&
                                                                    !etl::is_array<TContainer>::value &&
                                                                    etl::is_same<typename etl::remove_cv<T>::type, typename etl::remove_cv<typename etl::remove_reference<TContainer>::type::value_type>::type>::value, void>::type* = 0) ETL_NOEXCEPT
      : pbegin(a.data())
      , pend(a.data() + a.size())
    {
    }
#endif
 
    //*************************************************************************
    //*************************************************************************
    ETL_CONSTEXPR span(const span& other) ETL_NOEXCEPT
      : pbegin(other.pbegin)
      , pend(other.pend)
    {
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename U, size_t N>
    ETL_CONSTEXPR span(const etl::span<U, N>& other) ETL_NOEXCEPT
      : pbegin(other.data())
      , pend(other.data() + other.size())
    {
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR reference front() const ETL_NOEXCEPT
    {
      return *pbegin;
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR reference back() const ETL_NOEXCEPT
    {
      return *(pend - 1);
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR pointer data() const ETL_NOEXCEPT
    {
      return pbegin;
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR const_iterator cbegin() const ETL_NOEXCEPT
    {
      return pbegin;
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR iterator begin() const ETL_NOEXCEPT
    {
      return pbegin;
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR circular_iterator begin_circular() const ETL_NOEXCEPT
    {
      return circular_iterator(begin(), end());
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR const_iterator cend() const ETL_NOEXCEPT
    {
      return pend;
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR iterator end() const ETL_NOEXCEPT
    {
      return pend;
    }
 
    //*************************************************************************
    // Returns an reverse iterator to the reverse beginning of the span.
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR reverse_iterator rbegin() const ETL_NOEXCEPT
    {
      return reverse_iterator(pend);
    }
 
    //*************************************************************************
    // Returns a const reverse iterator to the reverse beginning of the span.
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR const_reverse_iterator crbegin() const ETL_NOEXCEPT
    {
      return const_reverse_iterator(pend);
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR reverse_circular_iterator rbegin_circular() const ETL_NOEXCEPT
    {
      return reverse_circular_iterator(rbegin(), rend());
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR const_reverse_iterator crend() const ETL_NOEXCEPT
    {
      return const_reverse_iterator(pbegin);
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR reverse_iterator rend() const ETL_NOEXCEPT
    {
      return reverse_iterator(pbegin);
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR bool empty() const ETL_NOEXCEPT
    {
      return (pbegin == pend);
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR size_t size() const ETL_NOEXCEPT
    {
      return (pend - pbegin);
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR size_t size_bytes() const ETL_NOEXCEPT
    {
      return sizeof(element_type) * (pend - pbegin);
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR size_t max_size() const ETL_NOEXCEPT
    {
      return size();
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_CONSTEXPR14 span& operator =(const span& other) ETL_NOEXCEPT
    {
      pbegin = other.pbegin;
      pend = other.pend;
      return *this;
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR14 reference at(size_t i)
    {
      ETL_ASSERT(i < size(), ETL_ERROR(array_out_of_range));
 
      return pbegin[i];
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR14 const_reference at(size_t i) const
    {
      ETL_ASSERT(i < size(), ETL_ERROR(array_out_of_range));
 
      return pbegin[i];
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_CONSTEXPR reference operator[](const size_t i) const
    {
      return pbegin[i];
    }
 
    //*************************************************************************
    //*************************************************************************
    template <size_t COUNT>
    ETL_NODISCARD ETL_CONSTEXPR etl::span<element_type, COUNT> first() const ETL_NOEXCEPT
    {
      return etl::span<element_type, COUNT>(pbegin, pbegin + COUNT);
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR etl::span<element_type, etl::dynamic_extent> first(size_t count) const ETL_NOEXCEPT
    {
      return etl::span<element_type, etl::dynamic_extent>(pbegin, pbegin + count);
    }
 
    //*************************************************************************
    //*************************************************************************
    template <size_t COUNT>
    ETL_NODISCARD ETL_CONSTEXPR etl::span<element_type, COUNT> last() const ETL_NOEXCEPT
    {
      return etl::span<element_type, COUNT>(pend - COUNT, pend);
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR etl::span<element_type, etl::dynamic_extent> last(size_t count) const ETL_NOEXCEPT
    {
      return etl::span<element_type, etl::dynamic_extent>(pend - count, pend);
    }
 
#if ETL_USING_CPP11
    //*************************************************************************
    //*************************************************************************
    template <size_t OFFSET, size_t COUNT = etl::dynamic_extent>
    ETL_NODISCARD ETL_CONSTEXPR
      etl::span<element_type, COUNT != etl::dynamic_extent ? COUNT : etl::dynamic_extent> subspan() const ETL_NOEXCEPT
    {
      return (COUNT == etl::dynamic_extent) ? etl::span<element_type, COUNT != etl::dynamic_extent ? COUNT : etl::dynamic_extent>(pbegin + OFFSET, pend)
                                            : etl::span<element_type, COUNT != etl::dynamic_extent ? COUNT : etl::dynamic_extent>(pbegin + OFFSET, pbegin + OFFSET + COUNT);
    }
#else
    //*************************************************************************
    //*************************************************************************
    template <size_t OFFSET, size_t COUNT>
    etl::span<element_type, COUNT != etl::dynamic_extent ? COUNT : etl::dynamic_extent> subspan() const
    {
      if (COUNT == etl::dynamic_extent)
      {
        return etl::span<element_type, COUNT != etl::dynamic_extent ? COUNT : etl::dynamic_extent>(pbegin + OFFSET, pend);
      }
      else
      {
        return etl::span<element_type, COUNT != etl::dynamic_extent ? COUNT : etl::dynamic_extent>(pbegin + OFFSET, pbegin + OFFSET + COUNT);
      }
    }
#endif
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR14 etl::span<element_type, etl::dynamic_extent> subspan(size_t offset, size_t count = etl::dynamic_extent) const ETL_NOEXCEPT
    {
      return (count == etl::dynamic_extent) ? etl::span<element_type, etl::dynamic_extent>(pbegin + offset, pend)
                                            : etl::span<element_type, etl::dynamic_extent>(pbegin + offset, pbegin + offset + count);
    }
 
    //*************************************************************************
    //*************************************************************************
    void advance(size_t elements) ETL_NOEXCEPT
    {
      elements = etl::min(elements, size());
      pbegin += elements;
    }
 
    //*************************************************************************
    //*************************************************************************
    template<typename TNew>
    ETL_NODISCARD ETL_CONSTEXPR14 etl::span<TNew, etl::dynamic_extent> reinterpret_as() const
    {
      ETL_ASSERT(etl::is_aligned<etl::alignment_of<TNew>::value>(pbegin), ETL_ERROR(span_alignment_exception));
 
      return etl::span<TNew, etl::dynamic_extent>(reinterpret_cast<TNew*>(pbegin),
                                                  (pend - pbegin) * sizeof(element_type) / sizeof(TNew));
    }
 
    //*************************************************************************
    //*************************************************************************
    template<typename TRet>
    ETL_NODISCARD etl::span<TRet> take(size_t const n)
    {
      ETL_STATIC_ASSERT(sizeof(TRet) % sizeof(element_type) == 0, "sizeof(TRet) must be divisible by sizeof(T)");
 
      ETL_ASSERT(etl::is_aligned<etl::alignment_of<TRet>::value>(pbegin), ETL_ERROR(span_alignment_exception));
      ETL_ASSERT(sizeof(TRet) * n <= sizeof(element_type) * size(), ETL_ERROR(span_size_mismatch));
 
      etl::span<TRet> result = reinterpret_as<TRet>().first(n);
      advance(sizeof(TRet) / sizeof(element_type) * n);
 
      return result;
    }
 
    //*************************************************************************
    //*************************************************************************
    template<typename TRet>
    ETL_NODISCARD TRet& take()
    {
      ETL_STATIC_ASSERT(sizeof(TRet) % sizeof(element_type) == 0, "sizeof(TRet) must be divisible by sizeof(T)");
 
      ETL_ASSERT(etl::is_aligned<etl::alignment_of<TRet>::value>(pbegin), ETL_ERROR(span_alignment_exception));
      ETL_ASSERT(sizeof(TRet) <= sizeof(element_type) * size(), ETL_ERROR(span_size_mismatch));
 
      TRet& result = *reinterpret_cast<TRet*>(data());
      advance(sizeof(TRet) / sizeof(element_type));
 
      return result;
    }
 
  private:
 
    pointer pbegin;
    pointer pend;
  };
 
  //*************************************************************************
  //*************************************************************************
  template <typename T>
  ETL_CONSTEXPR span<typename T::value_type, etl::dynamic_extent> make_span(T& data)
  {
    return span<typename T::value_type, etl::dynamic_extent>(data);
  }
 
  //*************************************************************************
  //*************************************************************************
  template <typename T>
  ETL_CONSTEXPR span<typename T::value_type const, etl::dynamic_extent> make_span(const T& data)
  {
    return span<typename T::value_type const, etl::dynamic_extent>(data);
  }
 
  template <typename T, size_t Extent>
  ETL_CONSTANT size_t span<T, Extent>::extent;
 
  template <typename T>
  ETL_CONSTANT size_t span<T, etl::dynamic_extent>::extent;
 
  //*************************************************************************
  //*************************************************************************
  template <typename T1, size_t N1, typename T2, size_t N2>
  ETL_NODISCARD 
  ETL_CONSTEXPR
  typename etl::enable_if<etl::is_same<typename etl::remove_cv<T1>::type, typename etl::remove_cv<T2>::type>::value, bool>::type
    operator ==(const etl::span<T1, N1>& lhs, const etl::span<T2, N2>& rhs) ETL_NOEXCEPT
  {
    return (lhs.begin() == rhs.begin()) && (lhs.size() == rhs.size());
  }
 
  //*************************************************************************
  //*************************************************************************
  template <typename T1, size_t N1, typename T2, size_t N2>
  ETL_NODISCARD
  ETL_CONSTEXPR
  bool operator !=(const etl::span<T1, N1>& lhs, const etl::span<T2, N2>& rhs) ETL_NOEXCEPT
  {
    return !(lhs == rhs);
  }
 
  //*************************************************************************
  //*************************************************************************
  template <typename T1, size_t N1, typename T2, size_t N2>
  typename etl::enable_if<etl::is_same<typename etl::remove_cv<T1>::type, typename etl::remove_cv<T2>::type>::value, bool>::type
    equal(const etl::span<T1, N1>& lhs, const etl::span<T2, N2>& rhs)
  {
    return (lhs.empty() && rhs.empty()) ||
           ((lhs.begin() == rhs.begin()) && (lhs.size() == rhs.size())) ||
           etl::equal(lhs.begin(), lhs.end(), rhs.begin(), rhs.end());
  }
 
  //*************************************************************************
  //*************************************************************************
  template <typename T1, size_t N1, typename T2, size_t N2>
  typename etl::enable_if<etl::is_same<typename etl::remove_cv<T1>::type, typename etl::remove_cv<T2>::type>::value &&
                          !etl::is_const<T2>::value, bool>::type
    copy(const etl::span<T1, N1>& src, const etl::span<T2, N2>& dst)
  {
    if (src.empty() || (src.begin() == dst.begin()))
    {
      return true;
    }
    if (src.size() > dst.size())
    {
      return false;
    }
    (void) etl::copy(src.begin(), src.end(), dst.begin());
    return true;
  }
 
  //*************************************************************************
  //*************************************************************************
#if ETL_USING_CPP17
  template <typename TIterator>
  span(const TIterator begin_, const TIterator end_)
    ->span<etl::remove_pointer_t<TIterator>, etl::dynamic_extent>;
 
  template <typename TIterator, typename TSize>
  span(const TIterator begin_, const TSize size_)
    ->span<etl::remove_pointer_t<TIterator>, etl::dynamic_extent>;
 
  template <typename T, size_t N>
  span(T(&)[N])
    -> span<T, N>;
 
  template <typename T, size_t N>
  span(etl::array<T, N>&)
    -> span<T, N>;
 
  template <typename T, size_t N>
  span(const etl::array<T, N>&)
    -> span<const T, N>;
 
#if ETL_USING_STL && ETL_USING_CPP11
  template <typename T, size_t N>
  span(std::array<T, N>&)
    ->span<T, N>;
 
  template <typename T, size_t N>
  span(const std::array<T, N>&)
    ->span<const T, N>;
#endif
#endif 
 
  //*************************************************************************
  //*************************************************************************
#if ETL_USING_8BIT_TYPES
  template <typename T, size_t Extent>
  struct hash<etl::span<T, Extent> >
  {
    size_t operator()(const etl::span<T>& view) const
    {
      return etl::private_hash::generic_hash<size_t>(reinterpret_cast<const uint8_t*>(view.data()),
                                                     reinterpret_cast<const uint8_t*>(view.data() + view.size()));
    }
  };
#endif
 
  //*************************************************************************
  //*************************************************************************
  template <class T, size_t N>
  span<const byte, (N == etl::dynamic_extent) ? (etl::dynamic_extent) : (N * sizeof(T))> 
    as_bytes(span<T, N> s) ETL_NOEXCEPT
  {
    return span<const byte, (N == etl::dynamic_extent) ? (etl::dynamic_extent) : (N * sizeof(T))>(reinterpret_cast<byte*>(s.data()), s.size_bytes());
  }
 
  //*************************************************************************
  //*************************************************************************
  template <class T, size_t N>
  span<byte, (N == etl::dynamic_extent) ? (etl::dynamic_extent) : (N * sizeof(T))> 
    as_writable_bytes(span<T, N> s) ETL_NOEXCEPT
  {
    ETL_STATIC_ASSERT(!etl::is_const<T>::value, "span<T> must be of non-const type");
    return span<byte, (N == etl::dynamic_extent) ? (etl::dynamic_extent) : (N * sizeof(T))>(reinterpret_cast<byte*>(s.data()), s.size_bytes());
  }
}
 
#endif