#include <algorithm>
#include <iterator>
#include <memory>

namespace sg14 {

  template<typename T>
  class buffer : public std::iterator_traits<T*> {
  public:
    using size_type = typename buffer<T>::difference_type;

    buffer() noexcept = default;

    buffer(buffer const& rhs)
        :buffer(rhs.size())
    {
      std::copy(std::begin(rhs), std::end(rhs), std::begin(*this));
    }

    buffer(int size)
        :first(new T[size]), last(data() + size) { }

    buffer& operator=(buffer const& rhs)
    {
      using std::swap;

      auto copy = rhs;
      swap(*this, copy);

      return *this;
    }

    bool empty() const noexcept
    {
      return cbegin() == cend();
    }

    size_type size() const noexcept
    {
      return std::distance(cbegin(), cend());
    }

    T* begin() noexcept
    {
      return data();
    }

    T const* begin() const noexcept
    {
      return data();
    }

    T const* cbegin() const noexcept
    {
      return data();
    }

    T* end() noexcept
    {
      return last;
    }

    T const* end() const noexcept
    {
      return last;
    }

    T const* cend() const noexcept
    {
      return last;
    }

    T* data() noexcept
    {
      return first.get();
    }

    T const* data() const noexcept
    {
      return first.get();
    }

    friend void swap(buffer& lhs, buffer& rhs) noexcept
    {
      using std::swap;
      swap(lhs.first, rhs.first);
      swap(lhs.last, rhs.last);
    }

  private:
    std::unique_ptr<T[]> first;
    T* last = nullptr;
  };

  template<typename LT, typename RT>
  bool
  operator==(buffer<LT> const& lhs, buffer<RT> const& rhs) noexcept(noexcept(std::equal(std::begin(lhs), std::end(lhs),
      std::begin(rhs))))
  {
    return (lhs.size() == rhs.size()) && std::equal(std::begin(lhs), std::end(lhs), std::begin(rhs));
  }

  template<typename LT, typename RT>
  bool operator!=(buffer<LT> const& lhs, buffer<RT> const& rhs) noexcept(noexcept(lhs == rhs))
  {
    return !(lhs == rhs);
  }

}

#include <cassert>
#include <iostream>
#include <string>
#include <type_traits>

namespace {
  using byte = std::uint8_t;
  constexpr auto uninitialized = byte{0x1a};

  template<typename T>
  void test(T const& some_value)
  {
    using buffer = sg14::buffer<T>;
    static_assert(sizeof(buffer) == 2 * sizeof(T*), "");
    static_assert(std::is_same<typename buffer::iterator_category, std::random_access_iterator_tag>::value, "");
    static_assert(std::is_same<typename buffer::value_type, T>::value, "");
    static_assert(std::is_same<typename buffer::difference_type, std::ptrdiff_t>::value, "");
    static_assert(std::is_same<typename buffer::pointer, T*>::value, "");
    static_assert(std::is_same<typename buffer::reference, T&>::value, "");
    static_assert(std::is_same<typename buffer::size_type, std::ptrdiff_t>::value, "");

    buffer sequence(10);
    std::fill(std::begin(sequence), std::end(sequence), some_value);

    auto empty_sequence = buffer();
    assert(empty_sequence.size() == 0);

    {
      auto copied_sequence(sequence);
      assert(sequence == copied_sequence);
      assert(empty_sequence != copied_sequence);

      copied_sequence = empty_sequence;
      assert(sequence != copied_sequence);
      assert(empty_sequence == copied_sequence);
    }

    assert(sequence != empty_sequence);

    for (auto n : sequence) {
      assert(n == some_value);
    }
  }

  template<typename T>
  void test_pod(sg14::buffer<T> const& default_sequence, T const& some_value)
  {
    // for every byte in the buffer.
    auto data_begin = reinterpret_cast<std::uint8_t const*>(default_sequence.data());
    auto data_end = reinterpret_cast<std::uint8_t const*>(default_sequence.data() + default_sequence.size());

    std::for_each(data_begin, data_end, [](T b) {
      assert(b == uninitialized);
    });

    test(some_value);
  }

  template<typename T>
  void test_non_pod(sg14::buffer<T> const& default_sequence, T const& some_value)
  {
    std::for_each(std::begin(default_sequence), std::end(default_sequence), [](T e) {
      assert(e == T());
    });

    test(some_value);
  }

  void trash_heap()
  {
    constexpr auto bytes_of_heap_to_trash = 10000;

    auto buffer = (std::uint8_t*) (malloc(bytes_of_heap_to_trash));
    std::fill(buffer, buffer + bytes_of_heap_to_trash, uninitialized);
    delete buffer;
  }
}

int main()
{
  trash_heap();

  auto char_buffer = sg14::buffer<char>(10);
  auto int_buffer = sg14::buffer<int>(10);
  auto double_buffer = sg14::buffer<double>(10);
  auto string_buffer = sg14::buffer<std::string>(10);

  test_pod(char_buffer, char{0x7f});
  test_pod(int_buffer, 0x12345678);
  test_pod(double_buffer, 98765.4321);
  test_non_pod(string_buffer, std::string{"abc XYZ 987"});
}