runtime/cpp/emboss_array_view.h - third_party/github.com/google/emboss - Git at Google

 // Copyright 2019 Google LLC
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //     https://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.

 // View classes for arrays and bit arrays.
 #ifndef EMBOSS_RUNTIME_CPP_EMBOSS_ARRAY_VIEW_H_
 #define EMBOSS_RUNTIME_CPP_EMBOSS_ARRAY_VIEW_H_

 #include <cstddef>
 #include <iterator>
 #include <tuple>
 #include <type_traits>

 #include "runtime/cpp/emboss_arithmetic.h"
 #include "runtime/cpp/emboss_array_view.h"
 #include "runtime/cpp/emboss_text_util.h"

 namespace emboss {

 // Forward declarations for use by WriteShorthandArrayCommentToTextStream.
 namespace prelude {
 template <class Parameters, class BitViewType>
 class UIntView;
 template <class Parameters, class BitViewType>
 class IntView;
 }  // namespace prelude

 namespace support {

 // Advance direction for ElementViewIterator.
 enum class ElementViewIteratorDirection { kForward, kReverse };

 // Iterator adapter for elements in a GenericArrayView.
 template <class GenericArrayView, ElementViewIteratorDirection kDirection>
 class ElementViewIterator {
  public:
   using iterator_category = ::std::random_access_iterator_tag;
   using value_type = typename GenericArrayView::ViewType;
   using difference_type = ::std::ptrdiff_t;
   using pointer = typename ::std::add_pointer<value_type>::type;
   using reference = typename ::std::add_lvalue_reference<value_type>::type;

   explicit ElementViewIterator(const GenericArrayView *array_view,
                                ::std::ptrdiff_t index)
       : array_view_(array_view), view_((*array_view)[index]), index_(index) {}

   ElementViewIterator() = default;

   reference operator*() { return view_; }

   pointer operator->() { return &view_; }

   ElementViewIterator &operator+=(difference_type d) {
     index_ += (kDirection == ElementViewIteratorDirection::kForward ? d : -d);
     view_ = (*array_view_)[index_];
     return *this;
   }

   ElementViewIterator &operator-=(difference_type d) { return *this += (-d); }

   ElementViewIterator &operator++() {
     *this += 1;
     return *this;
   }

   ElementViewIterator &operator--() {
     *this -= 1;
     return *this;
   }

   ElementViewIterator operator++(int) {
     auto copy = *this;
     ++(*this);
     return copy;
   }

   ElementViewIterator operator--(int) {
     auto copy = *this;
     --(*this);
     return copy;
   }

   ElementViewIterator operator+(difference_type d) const {
     auto copy = *this;
     copy += d;
     return copy;
   }

   ElementViewIterator operator-(difference_type d) const {
     return *this + (-d);
   }

   difference_type operator-(const ElementViewIterator &other) const {
     return kDirection == ElementViewIteratorDirection::kForward
                ? index_ - other.index_
                : other.index_ - index_;
   }

   bool operator==(const ElementViewIterator &other) const {
     return array_view_ == other.array_view_ && index_ == other.index_;
   }

   bool operator!=(const ElementViewIterator &other) const {
     return !(*this == other);
   }

   bool operator<(const ElementViewIterator &other) const {
     return kDirection == ElementViewIteratorDirection::kForward
                ? index_ < other.index_
                : other.index_ < index_;
   }

   bool operator<=(const ElementViewIterator &other) const {
     return kDirection == ElementViewIteratorDirection::kForward
                ? index_ <= other.index_
                : other.index_ <= index_;
   }

   bool operator>(const ElementViewIterator &other) const {
     return !(*this <= other);
   }

   bool operator>=(const ElementViewIterator &other) const {
     return !(*this < other);
   }

  private:
   const GenericArrayView *array_view_;
   typename GenericArrayView::ViewType view_;
   ::std::ptrdiff_t index_;
 };

 // View for an array in a structure.
 //
 // ElementView should be the view class for a single array element (e.g.,
 // UIntView<...> or ArrayView<...>).
 //
 // BufferType is the storage type that will be passed into the array.
 //
 // kElementSize is the fixed size of a single element, in addressable units.
 //
 // kAddressableUnitSize is the size of a single addressable unit.  It should be
 // either 1 (one bit) or 8 (one byte).
 //
 // ElementViewParameterTypes is a list of the types of parameters which must be
 // passed down to each element of the array.  ElementViewParameterTypes can be
 // empty.
 template <class ElementView, class BufferType, ::std::size_t kElementSize,
           ::std::size_t kAddressableUnitSize,
           typename... ElementViewParameterTypes>
 class GenericArrayView final {
  public:
   using ViewType = ElementView;
   using ForwardIterator =
       ElementViewIterator<GenericArrayView,
                           ElementViewIteratorDirection::kForward>;
   using ReverseIterator =
       ElementViewIterator<GenericArrayView,
                           ElementViewIteratorDirection::kReverse>;

   GenericArrayView() : buffer_() {}
   explicit GenericArrayView(const ElementViewParameterTypes &... parameters,
                             BufferType buffer)
       : parameters_{parameters...}, buffer_{buffer} {}

   ElementView operator[](::std::size_t index) const {
     return IndexOperatorHelper<sizeof...(ElementViewParameterTypes) ==
                                0>::ConstructElement(parameters_, buffer_,
                                                     index);
   }

   ForwardIterator begin() const { return ForwardIterator(this, 0); }
   ForwardIterator end() const { return ForwardIterator(this, ElementCount()); }
   ReverseIterator rbegin() const {
     return ReverseIterator(this, ElementCount() - 1);
   }
   ReverseIterator rend() const { return ReverseIterator(this, -1); }

   // In order to selectively enable SizeInBytes and SizeInBits, it is
   // necessary to make them into templates.  Further, it is necessary for
   // ::std::enable_if to have a dependency on the template parameter, otherwise
   // SFINAE won't kick in.  Thus, these are templated on an int, and that int
   // is (spuriously) used as the left argument to `,` in the enable_if
   // condition.  The explicit cast to void is needed to silence GCC's
   // -Wunused-value.
   template <int N = 0>
   typename ::std::enable_if<((void)N, kAddressableUnitSize == 8),
                             ::std::size_t>::type
   SizeInBytes() const {
     return buffer_.SizeInBytes();
   }
   template <int N = 0>
   typename ::std::enable_if<((void)N, kAddressableUnitSize == 1),
                             ::std::size_t>::type
   SizeInBits() const {
     return buffer_.SizeInBits();
   }

   ::std::size_t ElementCount() const { return SizeOfBuffer() / kElementSize; }
   bool Ok() const {
     if (!buffer_.Ok()) return false;
     if (SizeOfBuffer() % kElementSize != 0) return false;
     for (::std::size_t i = 0; i < ElementCount(); ++i) {
       if (!(*this)[i].Ok()) return false;
     }
     return true;
   }
   template <class OtherElementView, class OtherBufferType>
   bool Equals(
       const GenericArrayView<OtherElementView, OtherBufferType, kElementSize,
                              kAddressableUnitSize> &other) const {
     if (ElementCount() != other.ElementCount()) return false;
     for (::std::size_t i = 0; i < ElementCount(); ++i) {
       if (!(*this)[i].Equals(other[i])) return false;
     }
     return true;
   }
   template <class OtherElementView, class OtherBufferType>
   bool UncheckedEquals(
       const GenericArrayView<OtherElementView, OtherBufferType, kElementSize,
                              kAddressableUnitSize> &other) const {
     if (ElementCount() != other.ElementCount()) return false;
     for (::std::size_t i = 0; i < ElementCount(); ++i) {
       if (!(*this)[i].UncheckedEquals(other[i])) return false;
     }
     return true;
   }
   bool IsComplete() const { return buffer_.Ok(); }

   template <class Stream>
   bool UpdateFromTextStream(Stream *stream) const {
     return ReadArrayFromTextStream(this, stream);
   }

   template <class Stream>
   void WriteToTextStream(Stream *stream,
                          const TextOutputOptions &options) const {
     WriteArrayToTextStream(this, stream, options);
   }

   static constexpr bool IsAggregate() { return true; }

   BufferType BackingStorage() const { return buffer_; }

   // Forwards to BufferType's ToString(), if any, but only if ElementView is a
   // 1-byte type.
   template <typename String>
   typename ::std::enable_if<kAddressableUnitSize == 8 && kElementSize == 1,
                             String>::type
   ToString() const {
     EMBOSS_CHECK(Ok());
     return BackingStorage().template ToString<String>();
   }

  private:
   // This uses the same technique to select the correct definition of
   // SizeOfBuffer() as in the SizeInBits()/SizeInBytes() selection above.
   template <int N = 0>
   typename ::std::enable_if<((void)N, kAddressableUnitSize == 8),
                             ::std::size_t>::type
   SizeOfBuffer() const {
     return SizeInBytes();
   }
   template <int N = 0>
   typename ::std::enable_if<((void)N, kAddressableUnitSize == 1),
                             ::std::size_t>::type
   SizeOfBuffer() const {
     return SizeInBits();
   }

   // This mess is needed to expand the parameters_ tuple into individual
   // arguments to the ElementView constructor.  If parameters_ has M elements,
   // then:
   //
   // IndexOperatorHelper<false>::ConstructElement() calls
   // IndexOperatorHelper<false, 0>::ConstructElement(), which calls
   // IndexOperatorHelper<false, 0, 1>::ConstructElement(), and so on, up to
   // IndexOperatorHelper<false, 0, 1, ..., M-1>::ConstructElement(), which calls
   // IndexOperatorHelper<true, 0, 1, ..., M>::ConstructElement()
   //
   // That last call will resolve to the second, specialized version of
   // IndexOperatorHelper.  That version's ConstructElement() uses
   // `std::get<N>(parameters)...`, which will be expanded into
   // `std::get<0>(parameters), std::get<1>(parameters), std::get<2>(parameters),
   // ..., std::get<M>(parameters)`.
   //
   // If there are 0 parameters, then operator[]() will call
   // IndexOperatorHelper<true>::ConstructElement(), which still works --
   // `std::get<N>(parameters)...,` will be replaced by ``.
   //
   // In C++14, a lot of this can be replaced by std::index_sequence_of, and in
   // C++17 it can be replaced with std::apply and a lambda.
   //
   // An alternate solution would be to force each parameterized view to have a
   // constructor that accepts a tuple, instead of individual parameters, but
   // that (further) complicates the matrix of constructors for view types.
   template <bool, ::std::size_t... N>
   struct IndexOperatorHelper {
     static ElementView ConstructElement(
         const ::std::tuple<ElementViewParameterTypes...> &parameters,
         BufferType buffer, ::std::size_t index) {
       return IndexOperatorHelper<
           sizeof...(ElementViewParameterTypes) == 1 + sizeof...(N), N...,
           sizeof...(N)>::ConstructElement(parameters, buffer, index);
     }
   };

   template </**/ ::std::size_t... N>
   struct IndexOperatorHelper<true, N...> {
     static ElementView ConstructElement(
         const ::std::tuple<ElementViewParameterTypes...> &parameters,
         BufferType buffer, ::std::size_t index) {
       return ElementView(::std::get<N>(parameters)...,
                          buffer.template GetOffsetStorage<kElementSize, 0>(
                              kElementSize * index, kElementSize));
     }
   };

   ::std::tuple<ElementViewParameterTypes...> parameters_;
   BufferType buffer_;
 };

 // Optionally prints a shorthand representation of a BitArray in a comment.
 template <class ElementView, class BufferType, ::std::size_t kElementSize,
           ::std::size_t kAddressableUnitSize, class Stream>
 void WriteShorthandArrayCommentToTextStream(
     const GenericArrayView<ElementView, BufferType, kElementSize,
                            kAddressableUnitSize> *array,
     Stream *stream, const TextOutputOptions &options) {
   // Intentionally empty.  Overload for specific element types.
   // Avoid unused parameters error:
   static_cast<void>(array);
   static_cast<void>(stream);
   static_cast<void>(options);
 }

 // Prints out the elements of an 8-bit Int or UInt array as characters.
 template <class Array, class Stream>
 void WriteShorthandAsciiArrayCommentToTextStream(
     const Array *array, Stream *stream, const TextOutputOptions &options) {
   if (!options.multiline()) return;
   if (!options.comments()) return;
   if (array->ElementCount() == 0) return;
   static constexpr int kCharsPerBlock = 64;
   static constexpr char kStandInForNonPrintableChar = '.';
   auto start_new_line = [&]() {
     stream->Write("\n");
     stream->Write(options.current_indent());
     stream->Write("# ");
   };
   for (int i = 0, n = array->ElementCount(); i < n; ++i) {
     const int c = (*array)[i].Read();
     const bool c_is_printable = (c >= 32 && c <= 126);
     const bool starting_new_block = ((i % kCharsPerBlock) == 0);
     if (starting_new_block) start_new_line();
     stream->Write(c_is_printable ? static_cast<char>(c)
                                  : kStandInForNonPrintableChar);
   }
 }

 // Overload for arrays of UInt.
 // Prints out the elements as ASCII characters for arrays of UInt:8.
 template <class BufferType, class BitViewType, class Stream,
           ::std::size_t kElementSize, class Parameters,
           class = typename ::std::enable_if<Parameters::kBits == 8>::type>
 void WriteShorthandArrayCommentToTextStream(
     const GenericArrayView<prelude::UIntView<Parameters, BitViewType>,
                            BufferType, kElementSize, 8> *array,
     Stream *stream, const TextOutputOptions &options) {
   WriteShorthandAsciiArrayCommentToTextStream(array, stream, options);
 }

 // Overload for arrays of UInt.
 // Prints out the elements as ASCII characters for arrays of Int:8.
 template <class BufferType, class BitViewType, class Stream,
           ::std::size_t kElementSize, class Parameters,
           class = typename ::std::enable_if<Parameters::kBits == 8>::type>
 void WriteShorthandArrayCommentToTextStream(
     const GenericArrayView<prelude::IntView<Parameters, BitViewType>,
                            BufferType, kElementSize, 8> *array,
     Stream *stream, const TextOutputOptions &options) {
   WriteShorthandAsciiArrayCommentToTextStream(array, stream, options);
 }

 }  // namespace support
 }  // namespace emboss

 #endif  // EMBOSS_RUNTIME_CPP_EMBOSS_ARRAY_VIEW_H_
	// Copyright 2019 Google LLC
	//
	// Licensed under the Apache License, Version 2.0 (the "License");
	// you may not use this file except in compliance with the License.
	// You may obtain a copy of the License at
	//
	// https://www.apache.org/licenses/LICENSE-2.0
	//
	// Unless required by applicable law or agreed to in writing, software
	// distributed under the License is distributed on an "AS IS" BASIS,
	// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	// See the License for the specific language governing permissions and
	// limitations under the License.

	// View classes for arrays and bit arrays.
	#ifndef EMBOSS_RUNTIME_CPP_EMBOSS_ARRAY_VIEW_H_
	#define EMBOSS_RUNTIME_CPP_EMBOSS_ARRAY_VIEW_H_

	#include <cstddef>
	#include <iterator>
	#include <tuple>
	#include <type_traits>

	#include "runtime/cpp/emboss_arithmetic.h"
	#include "runtime/cpp/emboss_array_view.h"
	#include "runtime/cpp/emboss_text_util.h"

	namespace emboss {

	// Forward declarations for use by WriteShorthandArrayCommentToTextStream.
	namespace prelude {
	template <class Parameters, class BitViewType>
	class UIntView;
	template <class Parameters, class BitViewType>
	class IntView;
	} // namespace prelude

	namespace support {

	// Advance direction for ElementViewIterator.
	enum class ElementViewIteratorDirection { kForward, kReverse };

	// Iterator adapter for elements in a GenericArrayView.
	template <class GenericArrayView, ElementViewIteratorDirection kDirection>
	class ElementViewIterator {
	public:
	using iterator_category = ::std::random_access_iterator_tag;
	using value_type = typename GenericArrayView::ViewType;
	using difference_type = ::std::ptrdiff_t;
	using pointer = typename ::std::add_pointer<value_type>::type;
	using reference = typename ::std::add_lvalue_reference<value_type>::type;

	explicit ElementViewIterator(const GenericArrayView *array_view,
	::std::ptrdiff_t index)
	: array_view_(array_view), view_((*array_view)[index]), index_(index) {}

	ElementViewIterator() = default;

	reference operator*() { return view_; }

	pointer operator->() { return &view_; }

	ElementViewIterator &operator+=(difference_type d) {
	index_ += (kDirection == ElementViewIteratorDirection::kForward ? d : -d);
	view_ = (*array_view_)[index_];
	return *this;
	}

	ElementViewIterator &operator-=(difference_type d) { return *this += (-d); }

	ElementViewIterator &operator++() {
	*this += 1;
	return *this;
	}

	ElementViewIterator &operator--() {
	*this -= 1;
	return *this;
	}

	ElementViewIterator operator++(int) {
	auto copy = *this;
	++(*this);
	return copy;
	}

	ElementViewIterator operator--(int) {
	auto copy = *this;
	--(*this);
	return copy;
	}

	ElementViewIterator operator+(difference_type d) const {
	auto copy = *this;
	copy += d;
	return copy;
	}

	ElementViewIterator operator-(difference_type d) const {
	return *this + (-d);
	}

	difference_type operator-(const ElementViewIterator &other) const {
	return kDirection == ElementViewIteratorDirection::kForward
	? index_ - other.index_
	: other.index_ - index_;
	}

	bool operator==(const ElementViewIterator &other) const {
	return array_view_ == other.array_view_ && index_ == other.index_;
	}

	bool operator!=(const ElementViewIterator &other) const {
	return !(*this == other);
	}

	bool operator<(const ElementViewIterator &other) const {
	return kDirection == ElementViewIteratorDirection::kForward
	? index_ < other.index_
	: other.index_ < index_;
	}

	bool operator<=(const ElementViewIterator &other) const {
	return kDirection == ElementViewIteratorDirection::kForward
	? index_ <= other.index_
	: other.index_ <= index_;
	}

	bool operator>(const ElementViewIterator &other) const {
	return !(*this <= other);
	}

	bool operator>=(const ElementViewIterator &other) const {
	return !(*this < other);
	}

	private:
	const GenericArrayView *array_view_;
	typename GenericArrayView::ViewType view_;
	::std::ptrdiff_t index_;
	};

	// View for an array in a structure.
	//
	// ElementView should be the view class for a single array element (e.g.,
	// UIntView<...> or ArrayView<...>).
	//
	// BufferType is the storage type that will be passed into the array.
	//
	// kElementSize is the fixed size of a single element, in addressable units.
	//
	// kAddressableUnitSize is the size of a single addressable unit. It should be
	// either 1 (one bit) or 8 (one byte).
	//
	// ElementViewParameterTypes is a list of the types of parameters which must be
	// passed down to each element of the array. ElementViewParameterTypes can be
	// empty.
	template <class ElementView, class BufferType, ::std::size_t kElementSize,
	::std::size_t kAddressableUnitSize,
	typename... ElementViewParameterTypes>
	class GenericArrayView final {
	public:
	using ViewType = ElementView;
	using ForwardIterator =
	ElementViewIterator<GenericArrayView,
	ElementViewIteratorDirection::kForward>;
	using ReverseIterator =
	ElementViewIterator<GenericArrayView,
	ElementViewIteratorDirection::kReverse>;

	GenericArrayView() : buffer_() {}
	explicit GenericArrayView(const ElementViewParameterTypes &... parameters,
	BufferType buffer)
	: parameters_{parameters...}, buffer_{buffer} {}

	ElementView operator[](::std::size_t index) const {
	return IndexOperatorHelper<sizeof...(ElementViewParameterTypes) ==
	0>::ConstructElement(parameters_, buffer_,
	index);
	}

	ForwardIterator begin() const { return ForwardIterator(this, 0); }
	ForwardIterator end() const { return ForwardIterator(this, ElementCount()); }
	ReverseIterator rbegin() const {
	return ReverseIterator(this, ElementCount() - 1);
	}
	ReverseIterator rend() const { return ReverseIterator(this, -1); }

	// In order to selectively enable SizeInBytes and SizeInBits, it is
	// necessary to make them into templates. Further, it is necessary for
	// ::std::enable_if to have a dependency on the template parameter, otherwise
	// SFINAE won't kick in. Thus, these are templated on an int, and that int
	// is (spuriously) used as the left argument to `,` in the enable_if
	// condition. The explicit cast to void is needed to silence GCC's
	// -Wunused-value.
	template <int N = 0>
	typename ::std::enable_if<((void)N, kAddressableUnitSize == 8),
	::std::size_t>::type
	SizeInBytes() const {
	return buffer_.SizeInBytes();
	}
	template <int N = 0>
	typename ::std::enable_if<((void)N, kAddressableUnitSize == 1),
	::std::size_t>::type
	SizeInBits() const {
	return buffer_.SizeInBits();
	}

	::std::size_t ElementCount() const { return SizeOfBuffer() / kElementSize; }
	bool Ok() const {
	if (!buffer_.Ok()) return false;
	if (SizeOfBuffer() % kElementSize != 0) return false;
	for (::std::size_t i = 0; i < ElementCount(); ++i) {
	if (!(*this)[i].Ok()) return false;
	}
	return true;
	}
	template <class OtherElementView, class OtherBufferType>
	bool Equals(
	const GenericArrayView<OtherElementView, OtherBufferType, kElementSize,
	kAddressableUnitSize> &other) const {
	if (ElementCount() != other.ElementCount()) return false;
	for (::std::size_t i = 0; i < ElementCount(); ++i) {
	if (!(*this)[i].Equals(other[i])) return false;
	}
	return true;
	}
	template <class OtherElementView, class OtherBufferType>
	bool UncheckedEquals(
	const GenericArrayView<OtherElementView, OtherBufferType, kElementSize,
	kAddressableUnitSize> &other) const {
	if (ElementCount() != other.ElementCount()) return false;
	for (::std::size_t i = 0; i < ElementCount(); ++i) {
	if (!(*this)[i].UncheckedEquals(other[i])) return false;
	}
	return true;
	}
	bool IsComplete() const { return buffer_.Ok(); }

	template <class Stream>
	bool UpdateFromTextStream(Stream *stream) const {
	return ReadArrayFromTextStream(this, stream);
	}

	template <class Stream>
	void WriteToTextStream(Stream *stream,
	const TextOutputOptions &options) const {
	WriteArrayToTextStream(this, stream, options);
	}

	static constexpr bool IsAggregate() { return true; }

	BufferType BackingStorage() const { return buffer_; }

	// Forwards to BufferType's ToString(), if any, but only if ElementView is a
	// 1-byte type.
	template <typename String>
	typename ::std::enable_if<kAddressableUnitSize == 8 && kElementSize == 1,
	String>::type
	ToString() const {
	EMBOSS_CHECK(Ok());
	return BackingStorage().template ToString<String>();
	}

	private:
	// This uses the same technique to select the correct definition of
	// SizeOfBuffer() as in the SizeInBits()/SizeInBytes() selection above.
	template <int N = 0>
	typename ::std::enable_if<((void)N, kAddressableUnitSize == 8),
	::std::size_t>::type
	SizeOfBuffer() const {
	return SizeInBytes();
	}
	template <int N = 0>
	typename ::std::enable_if<((void)N, kAddressableUnitSize == 1),
	::std::size_t>::type
	SizeOfBuffer() const {
	return SizeInBits();
	}

	// This mess is needed to expand the parameters_ tuple into individual
	// arguments to the ElementView constructor. If parameters_ has M elements,
	// then:
	//
	// IndexOperatorHelper<false>::ConstructElement() calls
	// IndexOperatorHelper<false, 0>::ConstructElement(), which calls
	// IndexOperatorHelper<false, 0, 1>::ConstructElement(), and so on, up to
	// IndexOperatorHelper<false, 0, 1, ..., M-1>::ConstructElement(), which calls
	// IndexOperatorHelper<true, 0, 1, ..., M>::ConstructElement()
	//
	// That last call will resolve to the second, specialized version of
	// IndexOperatorHelper. That version's ConstructElement() uses
	// `std::get<N>(parameters)...`, which will be expanded into
	// `std::get<0>(parameters), std::get<1>(parameters), std::get<2>(parameters),
	// ..., std::get<M>(parameters)`.
	//
	// If there are 0 parameters, then operator[]() will call
	// IndexOperatorHelper<true>::ConstructElement(), which still works --
	// `std::get<N>(parameters)...,` will be replaced by ``.
	//
	// In C++14, a lot of this can be replaced by std::index_sequence_of, and in
	// C++17 it can be replaced with std::apply and a lambda.
	//
	// An alternate solution would be to force each parameterized view to have a
	// constructor that accepts a tuple, instead of individual parameters, but
	// that (further) complicates the matrix of constructors for view types.
	template <bool, ::std::size_t... N>
	struct IndexOperatorHelper {
	static ElementView ConstructElement(
	const ::std::tuple<ElementViewParameterTypes...> &parameters,
	BufferType buffer, ::std::size_t index) {
	return IndexOperatorHelper<
	sizeof...(ElementViewParameterTypes) == 1 + sizeof...(N), N...,
	sizeof...(N)>::ConstructElement(parameters, buffer, index);
	}
	};

	template </**/ ::std::size_t... N>
	struct IndexOperatorHelper<true, N...> {
	static ElementView ConstructElement(
	const ::std::tuple<ElementViewParameterTypes...> &parameters,
	BufferType buffer, ::std::size_t index) {
	return ElementView(::std::get<N>(parameters)...,
	buffer.template GetOffsetStorage<kElementSize, 0>(
	kElementSize * index, kElementSize));
	}
	};

	::std::tuple<ElementViewParameterTypes...> parameters_;
	BufferType buffer_;
	};

	// Optionally prints a shorthand representation of a BitArray in a comment.
	template <class ElementView, class BufferType, ::std::size_t kElementSize,
	::std::size_t kAddressableUnitSize, class Stream>
	void WriteShorthandArrayCommentToTextStream(
	const GenericArrayView<ElementView, BufferType, kElementSize,
	kAddressableUnitSize> *array,
	Stream *stream, const TextOutputOptions &options) {
	// Intentionally empty. Overload for specific element types.
	// Avoid unused parameters error:
	static_cast<void>(array);
	static_cast<void>(stream);
	static_cast<void>(options);
	}

	// Prints out the elements of an 8-bit Int or UInt array as characters.
	template <class Array, class Stream>
	void WriteShorthandAsciiArrayCommentToTextStream(
	const Array array, Stream stream, const TextOutputOptions &options) {
	if (!options.multiline()) return;
	if (!options.comments()) return;
	if (array->ElementCount() == 0) return;
	static constexpr int kCharsPerBlock = 64;
	static constexpr char kStandInForNonPrintableChar = '.';
	auto start_new_line = [&]() {
	stream->Write("\n");
	stream->Write(options.current_indent());
	stream->Write("# ");
	};
	for (int i = 0, n = array->ElementCount(); i < n; ++i) {
	const int c = (*array)[i].Read();
	const bool c_is_printable = (c >= 32 && c <= 126);
	const bool starting_new_block = ((i % kCharsPerBlock) == 0);
	if (starting_new_block) start_new_line();
	stream->Write(c_is_printable ? static_cast<char>(c)
	: kStandInForNonPrintableChar);
	}
	}

	// Overload for arrays of UInt.
	// Prints out the elements as ASCII characters for arrays of UInt:8.
	template <class BufferType, class BitViewType, class Stream,
	::std::size_t kElementSize, class Parameters,
	class = typename ::std::enable_if<Parameters::kBits == 8>::type>
	void WriteShorthandArrayCommentToTextStream(
	const GenericArrayView<prelude::UIntView<Parameters, BitViewType>,
	BufferType, kElementSize, 8> *array,
	Stream *stream, const TextOutputOptions &options) {
	WriteShorthandAsciiArrayCommentToTextStream(array, stream, options);
	}

	// Overload for arrays of UInt.
	// Prints out the elements as ASCII characters for arrays of Int:8.
	template <class BufferType, class BitViewType, class Stream,
	::std::size_t kElementSize, class Parameters,
	class = typename ::std::enable_if<Parameters::kBits == 8>::type>
	void WriteShorthandArrayCommentToTextStream(
	const GenericArrayView<prelude::IntView<Parameters, BitViewType>,
	BufferType, kElementSize, 8> *array,
	Stream *stream, const TextOutputOptions &options) {
	WriteShorthandAsciiArrayCommentToTextStream(array, stream, options);
	}

	} // namespace support
	} // namespace emboss

	#endif // EMBOSS_RUNTIME_CPP_EMBOSS_ARRAY_VIEW_H_