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
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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 "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 "private/dynamic_extent.h"
 
#if ETL_USING_STL && ETL_USING_CPP11
  #include <array>
#endif
 
 
namespace etl
{
  //***************************************************************************
  //***************************************************************************
  template <typename T, size_t Extent = etl::dynamic_extent>
  class span
  {
  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 ETL_OR_STD::reverse_iterator<iterator> 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;
 
    //*************************************************************************
    //*************************************************************************
    ETL_CONSTEXPR span() ETL_NOEXCEPT
      : pbegin(ETL_NULLPTR)
    {
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename TIterator, typename TSize>
    ETL_CONSTEXPR explicit span(const TIterator begin_, const TSize /*size_*/) ETL_NOEXCEPT
      : pbegin(etl::addressof(*begin_))
    {
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename TIterator>
    ETL_CONSTEXPR explicit span(const TIterator begin_, const TIterator /*end_*/)
      : pbegin(etl::addressof(*begin_))
    {
    }
 
    //*************************************************************************
    //*************************************************************************
    template<size_t Array_Size>
    ETL_CONSTEXPR span(element_type(&begin_)[Array_Size]) ETL_NOEXCEPT
      : pbegin(begin_)
    {
    }
 
#if ETL_USING_CPP11
    //*************************************************************************
    //*************************************************************************
    template <typename U, size_t N, typename = typename etl::enable_if<(N == Extent) && etl::is_same<etl::remove_cv_t<T>, etl::remove_cv_t<U>>::value, void>::type>
    ETL_CONSTEXPR span(etl::array<U, N>& a) ETL_NOEXCEPT
      : pbegin(a.data())
    {
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename U, size_t N, typename = typename etl::enable_if<(N == Extent) && etl::is_same<etl::remove_cv_t<T>, etl::remove_cv_t<U>>::value, void>::type>
    ETL_CONSTEXPR span(const etl::array<U, N>& a) ETL_NOEXCEPT
      : pbegin(a.data())
    {
    }
#else
    //*************************************************************************
    //*************************************************************************
    template <typename U, size_t N>
    ETL_CONSTEXPR span(etl::array<U, N>& a, typename etl::enable_if<(N == Extent) && etl::is_same<typename etl::remove_cv<T>::type, typename etl::remove_cv<U>::type>::value, void>::type* = 0) ETL_NOEXCEPT
      : pbegin(a.data())
    {
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename U, size_t N>
    ETL_CONSTEXPR span(const etl::array<U, N>& a, typename etl::enable_if<(N == Extent) && etl::is_same<typename etl::remove_cv<T>::type, typename etl::remove_cv<U>::type>::value, void>::type* = 0) ETL_NOEXCEPT
      : pbegin(a.data())
    {
    }
#endif
 
#if ETL_USING_STL && ETL_USING_CPP11
    //*************************************************************************
    //*************************************************************************
    template <typename U, size_t N, typename = typename etl::enable_if<(N == Extent) && etl::is_same<etl::remove_cv_t<T>, etl::remove_cv_t<U>>::value, void>::type>
    ETL_CONSTEXPR span(std::array<U, N>& a) ETL_NOEXCEPT
      : pbegin(a.data())
    {
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename U, size_t N, typename = typename etl::enable_if<(N == Extent) && etl::is_same<etl::remove_cv_t<T>, etl::remove_cv_t<U>>::value, void>::type>
    ETL_CONSTEXPR span(const std::array<U, N>& a) ETL_NOEXCEPT
      : pbegin(a.data())
    {
    }
#endif
 
#if ETL_USING_CPP11
    //*************************************************************************
    //*************************************************************************
    template <typename TContainer, typename = typename etl::enable_if<!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_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>
    ETL_CONSTEXPR span(const TContainer& a, typename etl::enable_if<!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<(Extent == etl::dynamic_extent) || (N == etl::dynamic_extent) || (N == Extent), void>::type) ETL_NOEXCEPT
      : pbegin(other.data())
    {
    }
 
    //*************************************************************************
    //*************************************************************************
    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 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 iterator end() const ETL_NOEXCEPT
    {
      return (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 reverse_iterator rend() const ETL_NOEXCEPT
    {
      return reverse_iterator(pbegin);
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR bool empty() const ETL_NOEXCEPT
    {
      return false;
    }
 
    //*************************************************************************
    //*************************************************************************
    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_CONSTEXPR reference operator[](const size_t i) const
    {
      return pbegin[i];
    }
 
    //template <typename Type2, size_t N2, typename etl::enable_if<etl::is_same<typename etl::remove_cv<Type2>::type, value_type>::value, bool>::type = true>
    //ETL_NODISCARD ETL_CONSTEXPR bool operator==(const etl::span<Type2, N2>& other) const ETL_NOEXCEPT
    //{
    //  return ((begin() == other.begin()) && (Extent == other.size())) ||
    //         etl::equal(begin(), end(), other.begin(), other.end());
    //}
 
    //template <typename Type2, size_t N2, typename etl::enable_if<etl::is_same<typename etl::remove_cv<Type2>::type, value_type>::value, bool>::type = true>
    //ETL_NODISCARD ETL_CONSTEXPR bool operator!=(const etl::span<Type2, N2>& other) const ETL_NOEXCEPT
    //{
    //  return !(*this == other);
    //}
 
    //*************************************************************************
    //*************************************************************************
    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>(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
    {
      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 (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);
    }
 
  private:
 
    pointer pbegin;
  };
 
  //***************************************************************************
  //***************************************************************************
  template <typename T>
  class span<T, etl::dynamic_extent>
  {
  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 ETL_OR_STD::reverse_iterator<iterator> 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::addressof(*begin_))
      , pend(etl::addressof(*begin_) + size_)
    {
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename TIterator>
    ETL_CONSTEXPR span(const TIterator begin_, const TIterator end_)
      : pbegin(etl::addressof(*begin_))
      , pend(etl::addressof(*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 U, size_t N, typename = typename etl::enable_if<etl::is_same<etl::remove_cv_t<T>, etl::remove_cv_t<U>>::value, void>::type>
    ETL_CONSTEXPR span(etl::array<U, N>& a) ETL_NOEXCEPT
      : pbegin(a.data())
      , pend(a.data() + a.size())
    {
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename U, size_t N, typename = typename etl::enable_if<etl::is_same<etl::remove_cv_t<T>, etl::remove_cv_t<U>>::value, void>::type>
    ETL_CONSTEXPR span(const etl::array<U, N>& a) ETL_NOEXCEPT
      : pbegin(a.data())
      , pend(a.data() + a.size())
    {
    }
#else
    //*************************************************************************
    //*************************************************************************
    template <typename U, size_t N>
    ETL_CONSTEXPR span(etl::array<U, N>& a, typename etl::enable_if<etl::is_same<typename etl::remove_cv<T>::type, typename etl::remove_cv<U>::type>::value, void>::type* = 0) ETL_NOEXCEPT
      : pbegin(a.data())
      , pend(a.data() + a.size())
    {
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename U, size_t N>
    ETL_CONSTEXPR span(const etl::array<U, N>& a, typename etl::enable_if<etl::is_same<typename etl::remove_cv<T>::type, typename etl::remove_cv<U>::type>::value, void>::type* = 0) ETL_NOEXCEPT
      : pbegin(a.data())
      , pend(a.data() + a.size())
    {
    }
#endif
 
#if ETL_USING_STL && ETL_USING_CPP11
    //*************************************************************************
    //*************************************************************************
    template <typename U, size_t N, typename = typename etl::enable_if<etl::is_same<etl::remove_cv_t<T>, etl::remove_cv_t<U>>::value, void>::type>
    ETL_CONSTEXPR span(std::array<U, N>& a) ETL_NOEXCEPT
      : pbegin(a.data())
      , pend(a.data() + a.size())
    {
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename U, size_t N, typename = typename etl::enable_if<etl::is_same<etl::remove_cv_t<T>, etl::remove_cv_t<U>>::value, void>::type>
    ETL_CONSTEXPR span(const std::array<U, N>& a) ETL_NOEXCEPT
      : pbegin(a.data())
      , pend(a.data() + a.size())
    {
    }
#endif
 
#if ETL_USING_CPP11
    //*************************************************************************
    //*************************************************************************
    template <typename TContainer, typename = typename etl::enable_if<!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_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_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 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 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);
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD ETL_CONSTEXPR reverse_circular_iterator rbegin_circular() const ETL_NOEXCEPT
    {
      return reverse_circular_iterator(rbegin(), rend());
    }
 
    //*************************************************************************
    //*************************************************************************
    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_CONSTEXPR reference operator[](const size_t i) const
    {
      return pbegin[i];
    }
 
    //template <typename Type2, typename etl::enable_if<etl::is_same<typename etl::remove_cv<Type2>::type, value_type>::value, bool>::type = true>
    //ETL_NODISCARD ETL_CONSTEXPR bool operator==(const etl::span<Type2>& other) const ETL_NOEXCEPT
    //{
    //  return (empty() && other.empty()) ||
    //         ((begin() == other.begin()) && (end() == other.end())) ||
    //         etl::equal(begin(), end(), other.begin(), other.end());
    //}
 
    //template <typename Type2, typename etl::enable_if<etl::is_same<typename etl::remove_cv<Type2>::type, value_type>::value, bool>::type = true>
    //ETL_NODISCARD ETL_CONSTEXPR bool operator!=(const etl::span<Type2>& other) const ETL_NOEXCEPT
    //{
    //  return !(*this == other);
    //}
 
    //*************************************************************************
    //*************************************************************************
    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);
    }
 
  private:
 
    pointer pbegin;
    pointer pend;
  };
 
  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());
  }
 
  //*************************************************************************
  //*************************************************************************
#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