tokenized_storages.hpp
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tokenized_storages.hpp
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	//===-- rosa/support/tokenized_storages.hpp ---------------------- C++ --===//
	//
	// The RoSA Framework
	//
	// Distributed under the terms and conditions of the Boost Software License 1.0.
	// See accompanying file LICENSE.
	//
	// If you did not receive a copy of the license file, see
	// http://www.boost.org/LICENSE_1_0.txt.
	//
	//===----------------------------------------------------------------------===//
	///
	/// \file rosa/support/tokenized_storages.hpp
	///
	/// \author David Juhasz (david.juhasz@tuwien.ac.at)
	///
	/// \date 2017-2020
	///
	/// \brief Definition of storage helper template for storing values in a
	/// type-safe way based on type tokens.
	///
	//===----------------------------------------------------------------------===//

	#ifndef ROSA_SUPPORT_TOKENIZED_STORAGES_HPP
	#define ROSA_SUPPORT_TOKENIZED_STORAGES_HPP

	#include "rosa/support/log.h"
	#include "rosa/support/type_token.hpp"

	#include <memory>
	#include <vector>

	namespace rosa {

	/// Defines a simple interface for storing and accessing values of different
	/// types.
	///
	/// While the interface provides features to access values and know their
	/// types, it is the users responsibility to use particular values according to
	/// their actual types. No facilities for type-safe access of values is
	/// provided by the class.
	///
	/// \see \c rosa::TokenizedStorage for a type-safe specialization of the
	/// interface.
	class AbstractTokenizedStorage {
	protected:
	/// Protected constructor restricts instantiation for derived classes.
	AbstractTokenizedStorage(void) noexcept = default;

	public:
	/// No copying and moving of \c rosa::AbstractTokenizedStorage instances.
	///@{
	AbstractTokenizedStorage(const AbstractTokenizedStorage &) = delete;
	AbstractTokenizedStorage &
	operator=(const AbstractTokenizedStorage &) = delete;
	AbstractTokenizedStorage(AbstractTokenizedStorage &&Other) = delete;
	AbstractTokenizedStorage &operator=(AbstractTokenizedStorage &&) = delete;
	///@}

	/// Destroys \p this object.
	virtual ~AbstractTokenizedStorage(void) noexcept = default;

	/// Tells how many values are stored in \p this object.
	///
	/// \return number of values stored in \p this object
	virtual size_t size(void) const noexcept = 0;

	/// Tells the type of the value stored at a position.
	///
	/// \param Pos the index of the value whose type is to returned
	///
	/// \return \c rosa::TypeNumber for the value stored at index \p Pos
	///
	/// \pre \p Pos is a valid index:\code
	/// Pos < size()
	/// \endcode
	virtual TypeNumber typeAt(const token_size_t Pos) const noexcept = 0;

	/// Provides an untyped pointer for the value stored at a position.
	///
	/// \param Pos the index of the value to return an untyped pointer for
	///
	/// \return untyped pointer for the value stored at index \p Pos
	///
	/// \pre \p Pos is a valid index:\code
	/// Pos < size()
	/// \endcode
	virtual void *pointerTo(const token_size_t Pos) noexcept = 0;

	/// Provides a constant untyped pointer for the value stored at a position.
	///
	/// \param Pos the index of the value to return an untyped pointer for
	///
	/// \return constant untyped pointer for the value stored at index \p Pos
	///
	/// \pre \p Pos is a valid index:\code
	/// Pos < size()
	/// \endcode
	virtual const void *pointerTo(const token_size_t Pos) const noexcept = 0;
	};

	/// Template class storing values and providing dynamic type-safe access to
	/// them in a lightweight way based on type tokens.
	///
	/// \see rosa/support/type_token.hpp
	///
	/// \tparam Types types whose values are to be stored
	template <typename... Types> class TokenizedStorage;

	/// \defgroup TokenizedStorageForTypeList Implementation of
	/// rosa::TokenizedStorageForTypeList
	///
	/// \brief Transforms a \c rosa::TypeList instance to the corresponding
	/// \c rosa::TokenizedStorage instance.
	///
	/// A \c rosa::TypeList \c List instance can be turned into a corresponding \c
	/// rosa::TokenizedStorage instance as \code
	/// typename TokenizedStorageForTypeList<List>::Type
	/// \endcode
	///
	/// For example, the following expression evaluates to `true`: \code
	/// std::is_same<typename TokenizedStorageForTypeList<TypeList<T1, T2>>::Type,
	/// TokenizedStorage<T1, T2>>::value
	/// \endcode
	///@{

	/// Declaration of the template.
	///
	/// \tparam List \c rosa::TypeList to transform
	template <typename List> struct TokenizedStorageForTypeList;

	/// Implementation of the template for \c rosa::TypeList instances.
	template <typename... Ts> struct TokenizedStorageForTypeList<TypeList<Ts...>> {
	using Type = TokenizedStorage<Ts...>;
	};

	///@}

	/// Nested namespace with implementation for \c rosa::TokenizedStorage, consider
	/// it private.
	namespace {

	/// Initializes a pre-allocated memory area with values from constant lvalue
	/// references.
	///
	/// \tparam Types types whose values are to be stored
	///
	/// \param Arena pre-allocated memory area to store values to
	/// \param Ts the values to store in \p Arena
	///
	/// \note \p Arena needs to be a valid pointer to a memory area big enough for
	/// values of \p Types.
	template <typename... Types>
	inline void createArenaElements(void *const Arena,
	const Types &... Ts) noexcept;

	/// \defgroup createLvalueArenaElement Implementation of creating lvalue arena
	/// elements
	///
	/// Stores values from constant lvalue references into a pre-allocated memory
	/// area.
	///
	/// \note To be used by the implementation of \c createArenaElements.
	///
	/// \todo Document these functions.
	///@{

	/// \note This terminal case is used for both constant lvalue references and
	/// value references.
	template <size_t Pos>
	inline void createArenaElement(void *const,
	const std::vector<size_t> &Offsets) {
	ASSERT(Pos == Offsets.size());
	}

	template <size_t Pos, typename Type, typename... Types>
	inline void createArenaElement(void *const Arena,
	const std::vector<size_t> &Offsets,
	const Type &T, const Types &... Ts) noexcept {
	ASSERT(Arena != nullptr && Pos < Offsets.size());
	new (static_cast<Type >(static_cast<void >(static_cast<uint8_t *>(Arena) +
	Offsets[Pos]))) Type(T);
	createArenaElement<Pos + 1>(Arena, Offsets, Ts...);
	}

	template <size_t Pos, AtomValue V, typename... Types>
	inline void
	createArenaElement(void *const Arena, const std::vector<size_t> &Offsets,
	const AtomConstant<V> &, const Types &... Ts) noexcept {
	ASSERT(Arena != nullptr && Pos < Offsets.size());
	static_cast<AtomValue >(
	static_cast<void >(static_cast<uint8_t >(Arena) + Offsets[Pos])) = V;
	createArenaElement<Pos + 1>(Arena, Offsets, Ts...);
	}

	///@}

	/// Implementation of the template.
	///
	/// \tparam Types types of values to store
	///
	/// \param Arena pre-allocated memory area to store values to
	/// \param Ts values to store in \p Arena
	///
	/// \pre \p Arena is not \p nullptr.
	template <typename... Types>
	inline void createArenaElements(void *const Arena,
	const Types &... Ts) noexcept {
	ASSERT(Arena != nullptr);
	createArenaElement<0>(Arena, TokenizedStorage<Types...>::offsets(), Ts...);
	}

	/// Initializes a pre-allocated memory area with values from rvalue references.
	///
	/// \tparam Types types whose values are to be stored
	///
	/// \param Arena pre-allocated memory area to store values to
	/// \param Ts the values to store in \p Arena
	///
	/// \note \p Arena needs to be a valid pointer to a memory area big enough for
	/// values of \p Types.
	template <typename... Types>
	inline void createArenaElements(void *const Arena, Types &&... Ts) noexcept;

	/// \defgroup createRvalueArenaElement Implementation of creating rvalue arena
	/// elements
	///
	/// Stores values from rvalue references into a pre-allocated memory area.
	///
	/// \note To be used by the implementation of \c createArenaElements.
	///
	/// \todo Document these functions.
	///@{

	template <size_t Pos, typename Type, typename... Types>
	inline void createArenaElement(void *const Arena,
	const std::vector<size_t> &Offsets, Type &&T,
	Types &&... Ts) noexcept {
	ASSERT(Arena != nullptr && Pos < Offsets.size());
	new (static_cast<Type >(static_cast<void >(
	static_cast<uint8_t *>(Arena) + Offsets[Pos]))) Type(std::move(T));
	createArenaElement<Pos + 1>(Arena, Offsets, std::move(Ts)...);
	}

	template <size_t Pos, AtomValue V, typename... Types>
	inline void createArenaElement(void *const Arena,
	const std::vector<size_t> &Offsets,
	AtomConstant<V> &&, Types &&... Ts) noexcept {
	ASSERT(Arena != nullptr && Pos < Offsets.size());
	static_cast<AtomValue >(
	static_cast<void >(static_cast<uint8_t >(Arena) + Offsets[Pos])) = V;
	createArenaElement<Pos + 1>(Arena, Offsets, std::move(Ts)...);
	}

	///@}

	/// Implementation of the template.
	///
	/// \tparam Types types of values to store
	///
	/// \param Arena pre-allocated memory area to store values to
	/// \param Ts values to store in \p Arena
	///
	/// \pre \p Arena is not \c nullptr.
	template <typename... Types>
	inline void createArenaElements(void *const Arena, Types &&... Ts) noexcept {
	ASSERT(Arena != nullptr);
	createArenaElement<0>(Arena, TokenizedStorage<Types...>::offsets(),
	std::move(Ts)...);
	}

	/// Destroys values allocated by \c createArenaElements.
	///
	/// \tparam Types types whose values are stored in \p Arena
	///
	/// \param Arena the memory area to destroy values from
	///
	/// \note \p Arena needs to be a valid pointer to a memory area where values of
	/// \p Types are stored.
	template <typename... Types>
	inline void destroyArenaElements(void *const Arena) noexcept;

	/// \defgroup destroyArenaElement Implementation of destroying arena elements
	///
	/// Destroys values from a memory area.
	///
	/// \note To be used by the implementation of \c destroyArenaElements.
	///
	/// \todo Document these functions.
	///@{

	template <size_t Pos>
	inline void destroyArenaElement(void *const,
	const std::vector<size_t> &Offsets) noexcept {
	ASSERT(Pos == Offsets.size());
	}

	template <size_t Pos, typename Type, typename... Types>
	inline void destroyArenaElement(void *const Arena,
	const std::vector<size_t> &Offsets) noexcept {
	ASSERT(Arena != nullptr && Pos < Offsets.size());
	static_cast<Type *>(
	static_cast<void >(static_cast<uint8_t >(Arena) + Offsets[Pos]))
	->~Type();
	destroyArenaElement<Pos + 1, Types...>(Arena, Offsets);
	}

	///@}

	/// Implementation of the template.
	///
	/// \tparam Types types of values to destroy
	///
	/// \param Arena the memory area to destroy values from
	///
	/// \pre \p Arena is not \c nullptr.
	template <typename... Types>
	inline void destroyArenaElements(void *const Arena) noexcept {
	ASSERT(Arena != nullptr);
	destroyArenaElement<0, Types...>(Arena,
	TokenizedStorage<Types...>::offsets());
	}

	} // End namespace

	/// Implementation of the template \c rosa::TokenizedStorage as a
	/// specialization of \c rosa::AbstractTokenizedStorage.
	///
	/// The class provides facilities for storing values and providing type-safe
	/// access to them.
	///
	/// \tparam Types types of values to store
	template <typename... Types>
	class TokenizedStorage : public AbstractTokenizedStorage {
	public:
	/// \c rosa::Token for the stored values.
	static constexpr Token ST = TypeToken<std::decay_t<Types>...>::Value;

	/// Generates byte offsets for accessing values stored in
	/// \c rosa::TokenizedStorage::Arena.
	///
	/// \note Alignment requirement of each value is taken into account.
	///
	/// \return \c std::vector containing byte offsets for accessing values stored
	/// in \c rosa::TokenizedStorage::Arena
	static const std::vector<size_t> &offsets(void) noexcept {
	static std::vector<size_t> Offsets;

	// Initialize Offsets during the first invocation.
	if (Offsets.empty()) {
	Token T = ST; // Need a mutable copy.
	const token_size_t N =
	lengthOfToken(T); // Number of types encoded in \c T.
	Offsets.resize(N); // Allocate proper size right away.

	ASSERT(N > 0); // Sanity check, 0 element case has a specialization.

	token_size_t I = 0; // Start indexing from position \c 0.
	Offsets[0] = 0; // First offset is always \c 0; correctly aligned.
	while (I < N - 1) {
	ASSERT((size_t)I + 1 < Offsets.size() && lengthOfToken(T) == N - I);
	// Calculate next offset based on the previous one.
	// \note The offset of the last value is stored at `O[N - 1]`, which
	// is set when `I == N - 2`. Hence the limit of the loop.

	const auto LastOffset = Offsets[I];
	auto &Offset = Offsets[++I];

	const auto LastSize = sizeOfHeadOfToken(T);
	dropHeadOfToken(T);
	const auto CurrentAlign = alignmentOfHeadOfToken(T);

	Offset = LastOffset + LastSize;
	Offset += CurrentAlign - 1;
	Offset &= -std::make_signed_t<decltype(CurrentAlign)>(CurrentAlign);
	}
	ASSERT((size_t)I + 1 == Offsets.size() && lengthOfToken(T) == 1);
	}
	return Offsets;
	}

	/// Tells the size of \c rosa::TokenizedStorage::Arena.
	///
	/// \note Alignment requirement of each value is taken into account.
	///
	/// \return size of \c rosa::TokenizedStorage::Arena to store values
	static size_t arenaSize(void) noexcept {
	static size_t ArenaSize = 0;
	// Initialize ArenaSize during first invocation.
	if (!ArenaSize) {
	const auto &Offsets = offsets();
	Token T = ST;
	const auto N = lengthOfToken(T);
	dropNOfToken(T, N - 1); // Get to the last type
	// Full size is the offset for plus the size of the last value.
	ArenaSize = Offsets[N - 1] + sizeOfHeadOfToken(T);
	}
	return ArenaSize;
	}

	private:
	/// A BLOB storing all the values one after the other with necessary padding
	/// for correct alignment.
	void *const Arena;

	public:
	/// Creates an instance with default values.
	///
	/// \note This constructor requires that all actual template arguments \p
	/// Types... are default constructible.
	TokenizedStorage(void) noexcept
	: Arena(::operator new(arenaSize())) {
	ASSERT(Arena != nullptr); // Sanity check.
	createArenaElements(Arena, Types()...);
	}

	/// Creates an instance from constant lvalue references.
	///
	/// \param Ts values to store
	TokenizedStorage(const std::decay_t<Types> &... Ts) noexcept
	: Arena(::operator new(arenaSize())) {
	ASSERT(Arena != nullptr); // Sanity check.
	createArenaElements(Arena, Ts...);
	}

	/// Creates an instance from rvalue references.
	///
	/// \param Ts values to store
	TokenizedStorage(std::decay_t<Types> &&... Ts) noexcept
	: Arena(::operator new(arenaSize())) {
	ASSERT(Arena != nullptr); // Sanity check.
	createArenaElements(Arena, std::move(Ts)...);
	}

	/// No copying and moving of \c rosa::TokenizedStorage instances.
	///
	/// \note This restriction may be relaxed as moving should be easy to
	/// implement, only requires the possiblity to validate Arena pointer.
	///@{
	TokenizedStorage(const TokenizedStorage &) = delete;
	TokenizedStorage &operator=(const TokenizedStorage &) = delete;
	TokenizedStorage(TokenizedStorage &&Other) = delete;
	TokenizedStorage &operator=(TokenizedStorage &&) = delete;
	///@}

	// Destroys \p this object.
	~TokenizedStorage(void) {
	destroyArenaElements<std::decay_t<Types>...>(Arena);
	::operator delete(Arena);
	}

	/// Tells how many values are stored in \p this object.
	///
	/// \return number of values stored in \p this object
	size_t size(void) const noexcept override { return offsets().size(); }

	/// Tells the type of the value stored at a position.
	///
	/// \param Pos the index of the value whose type is to returned
	///
	/// \return \c rosa::TypeNumber for the value stored at index \p Pos
	///
	/// \pre \p Pos is a valid index:\code
	/// Pos < size()
	/// \endcode
	TypeNumber typeAt(const token_size_t Pos) const noexcept override {
	ASSERT(Pos < size());
	Token TT = ST;
	dropNOfToken(TT, Pos);
	return headOfToken(TT);
	}

	/// Provides an untyped pointer for the value stored at a position.
	///
	/// \param Pos the index of the value to return an untyped pointer for
	///
	/// \return untyped pointer for the value stored at index \p Pos
	///
	/// \pre \p Pos is a valid index:\code
	/// Pos < size()
	/// \endcode
	void *pointerTo(const token_size_t Pos) noexcept override {
	ASSERT(Pos < size());
	return static_cast<uint8_t *>(Arena) + offsets()[Pos];
	}

	/// Provides a constant untyped pointer for the value stored at a position.
	///
	/// \param Pos the index of the value to return an untyped pointer for
	///
	/// \return constant untyped pointer for the value stored at index \p Pos
	///
	/// \pre \p Pos is a valid index:\code
	/// Pos < size()
	/// \endcode
	const void *pointerTo(const token_size_t Pos) const noexcept override {
	ASSERT(Pos < size());
	return static_cast<const uint8_t *>(Arena) + offsets()[Pos];
	}

	/// Tells if the value stored at a given index is of a given type.
	///
	/// \note Any \c rosa::AtomConstant is encoded in \c rosa::Token as
	/// the \c rosa::AtomValue wrapped into it.
	///
	/// \tparam T type to match against
	///
	/// \param Pos index the type of the value at is to be matched against \p Type
	///
	/// \return if the value at index \p Pos of type \p T
	///
	/// \pre \p Pos is a valid index:\code
	/// Pos < size()
	/// \endcode
	template <typename T> bool isTypeAt(const size_t Pos) const noexcept {
	ASSERT(Pos < size());
	Token TT = ST;
	dropNOfToken(TT, Pos);
	return isHeadOfTokenTheSameType<T>(TT);
	}

	/// Gives a reference of a value of a given type stored at a given index.
	///
	/// \note The constant variant of the function relies on this implementation,
	/// the function may not modify \p this object!
	///
	/// \tparam T type to give a reference of
	///
	/// \param Pos index to set the reference for
	///
	/// \return reference of \p T for the value stored at index \p Pos
	///
	/// \pre \p Pos is a valid index and the value at index \p Pos is of type
	/// \p T:
	/// \code
	/// Pos < Size && isTypeAt<T>(Pos)
	/// \endcode
	template <typename T> T &valueAt(const token_size_t Pos) noexcept {
	ASSERT(Pos < size() && isTypeAt<T>(Pos));
	return static_cast<T >(pointerTo(Pos));
	}

	/// Gives a constant reference of a value of a given type stored at a given
	/// index.
	///
	/// \tparam T type to give a reference of
	///
	/// \param Pos index to set the reference for
	///
	/// \return constant reference of \p T for the value stored at index \p Pos
	///
	/// \pre \p Pos is a valid index and the value at index \p Pos is of type
	/// \p T:
	/// \code
	/// Pos < Size && isTypeAt<T>(Pos)
	/// \endcode
	template <typename T>
	const T &valueAt(const token_size_t Pos) const noexcept {
	// \note Just use the non-const implementation as that does not modify
	// \p this object.
	return const_cast<TokenizedStorage *>(this)->valueAt<T>(Pos);
	}
	};

	/// Specialization of the template \c rosa::TokenizedStorage for storing
	/// nothing.
	///
	/// \note The specialization implements the interface defined by \c
	/// rosa::AbstractTokenizedStorage but most of the functions cannot be called
	/// because nothing is stored in instances of the class.
	template <> class TokenizedStorage<> : public AbstractTokenizedStorage {
	public:
	/// \c rosa::Token for the stored values.
	static constexpr Token ST = TypeToken<>::Value;

	/// Creates an instance.
	TokenizedStorage(void) noexcept = default;

	/// No copying and moving of \c rosa::TokenizedStorage instances.
	///
	/// \note This restriction may be relaxed as moving should be easy to
	/// implement, only requires the possiblity to validate Arena pointer.
	///@{
	TokenizedStorage(const TokenizedStorage &) = delete;
	TokenizedStorage &operator=(const TokenizedStorage &) = delete;
	TokenizedStorage(TokenizedStorage &&Other) = delete;
	TokenizedStorage &operator=(TokenizedStorage &&) = delete;
	///@}

	// Destroys \p this object.
	~TokenizedStorage(void) override {}

	/// Tells how many values are stored in \p this object.
	///
	/// \return `0`
	size_t size(void) const noexcept override { return 0; }

	/// Tells the type of the value stored at a position.
	///
	/// \pre Do not call.
	TypeNumber typeAt(const token_size_t) const noexcept override {
	LOG_ERROR("Called unsupported function");
	return TypeNumber(0);
	}

	/// Provides an untyped pointer for the value stored at a position.
	///
	/// \pre Do not call.
	void *pointerTo(const token_size_t) noexcept override {
	LOG_ERROR("Called unsupported function");
	return nullptr;
	}

	/// Provides a constant untyped pointer for the value stored at a position.
	///
	/// \pre Do not call.
	const void *pointerTo(const token_size_t) const noexcept override {
	LOG_ERROR("Called unsupported function");
	return nullptr;
	}

	/// Tells if the value stored at a given index is of a given type.
	///
	/// \pre Do not call.
	template <typename> bool isTypeAt(const size_t) const noexcept {
	LOG_ERROR("Called unsupported function");
	return false;
	}

	/// Gives a reference of a value of a given type stored at a given index.
	///
	/// \tparam T type to give a reference of
	/// \pre Do not call.
	template <typename T> T &valueAt(const token_size_t) noexcept {
	LOG_ERROR("Called unsupported function");
	return static_cast<T >(nullptr);
	}

	/// Gives a constant reference of a value of a given type stored at a given
	/// index.
	///
	/// \tparam T type to give a reference of
	///
	/// \pre Do not call.
	template <typename T> const T &valueAt(const token_size_t) const noexcept {
	LOG_ERROR("Called unsupported function");
	// \note Just use the non-const implementation as that does not modify
	// \p this object.
	return static_cast<T >(nullptr);
	}
	};

	} // End namespace rosa

	#endif // ROSA_SUPPORT_TOKENIZED_STORAGES_HPP

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