Message.hpp
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Message.hpp
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	//===-- rosa/core/Message.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/core/Message.hpp
	///
	/// \author David Juhasz (david.juhasz@tuwien.ac.at)
	///
	/// \date 2017-2019
	///
	/// \brief Declaration of \c rosa::Message base-class.
	///
	//===----------------------------------------------------------------------===//

	#ifndef ROSA_CORE_MESSAGE_HPP
	#define ROSA_CORE_MESSAGE_HPP

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

	#include "rosa/core/forward_declarations.h"

	namespace rosa {

	/// Message interface.
	///
	/// The interface provides means to check the type of the stored values, but
	/// actual data is to be managed by derived implementations.
	///
	/// A \c rosa::Message instance is an immutable data object that obtains its
	/// data upon creation and provides only constant references for the stored
	/// values.
	///
	/// \note Any reference obtained from a \c rosa::Message instance remains valid
	/// only as long as the owning \c rosa::Message object is not destroyed.
	///
	/// \todo Some member functions of \c rosa::Message duplicate member functions
	/// of \c rosa::TokenizedStorage, which cannot be easily factored out into a
	/// common base class due to eventual diamond inheritance issues in derived
	/// classes. Could this duplication be avoided?
	class Message {
	protected:
	/// Creates a new instance.
	///
	/// \note No implementation for empty list.
	///
	/// \tparam Type type of the mandatory first argument
	/// \tparam Types types of any further arguments
	///
	/// \note the actual arguments are ignored by the constructor it is only
	/// their type that matters. The actual values are supposed to be handled by
	/// any implementation derived from \c rosa::Message.
	///
	/// \pre \p Type and \p Types are all built-in types and the number of stored
	/// values does not exceed \c rosa::token::MaxTokenizableListSize.
	template <typename Type, typename... Types>
	Message(const Type &, const Types &...) noexcept;

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

	public:
	/// Creates a \c rosa::message_t object from constant lvalue references.
	///
	/// \tparam Type type of the mandatory first argument
	/// \tparam Types types of any further arguments
	///
	/// \param T the first value to include in the \c rosa::Message
	/// \param Ts optional further values to include in the \c rosa::Message
	///
	/// \return new \c rosa::message_t object created from the given arguments
	template <typename Type, typename... Types>
	static message_t create(const Type &T, const Types &... Ts) noexcept;

	/// Creates a \c rosa::message_t object from rvalue references.
	///
	/// \tparam Type type of the mandatory first argument
	/// \tparam Types types of any further arguments
	///
	/// \param T the first value to include in the \c rosa::Message
	/// \param Ts optional further values to include in the \c rosa::Message
	///
	/// \return new \c rosa::message_t object created from the given arguments
	template <typename Type, typename... Types>
	static message_t create(Type &&T, Types &&... Ts) noexcept;

	/// Represents the types of the values stored in \p this object.
	///
	/// A valid, non-empty \c rosa::Token representing the types of the values
	/// stored in \p this object.
	const Token T;

	/// The number of values stored in \p this object.
	///
	/// That is the number of types encoded in \c rosa::Message::T.
	const token_size_t Size;

	/// Destroys \p this object.
	virtual ~Message(void);

	/// 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 Type 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 Type
	///
	/// \pre \p Pos is a valid index:\code
	/// Pos < Size
	/// \endcode
	template <typename Type> bool isTypeAt(const token_size_t Pos) const noexcept;

	/// Gives a constant reference of a value of a given type stored at a given
	/// index.
	///
	/// \tparam Type type to give a reference of
	///
	/// \param Pos index to set the reference for
	///
	/// \return constant reference of \p Type 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 Type:
	/// \code
	/// Pos < Size && isTypeAt<Type>(Pos)
	/// \endcode
	template <typename Type>
	const Type &valueAt(const token_size_t Pos) const noexcept;

	protected:
	/// Provides an untyped pointer for the value at a given index.
	///
	/// \param Pos index to take a 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 const void *pointerTo(const token_size_t Pos) const noexcept = 0;
	};

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

	/// Template class for an implementation of \c rosa::Message.
	///
	/// \tparam Types types whose values are to be stored
	template <typename... Types> class LocalMessage;

	/// Implementation of the template \c rosa::LocalMessage providing facilities
	/// for storing values as a \c rosa::Message object.
	///
	/// \tparam Type type of the first mandatory value of the \c rosa::Message
	/// \tparam Types of any further values
	template <typename Type, typename... Types>
	class LocalMessage<Type, Types...> final
	: public Message,
	private TokenizedStorage<Type, Types...> {
	public:
	/// Creates an instance from constant lvalue references.
	///
	/// \param T the mandatory first value to store in the \c rosa::Message object
	/// \param Ts optional further values to store in the \c rosa::Message object
	LocalMessage(const Type &T, const Types &... Ts) noexcept
	: Message(T, Ts...),
	TokenizedStorage<Type, Types...>(T, Ts...) {
	ASSERT(this->T == this->ST && Size == this->size()); // Sanity check.
	}

	/// Creates an instance from rvalue references.
	///
	/// \param T the mandatory first value to store in the \c rosa::Message object
	/// \param Ts optional further values to store in the \c rosa::Message object
	LocalMessage(Type &&T, Types &&... Ts) noexcept
	: Message(T, Ts...),
	TokenizedStorage<Type, Types...>(std::move(T), std::move(Ts)...) {
	ASSERT(this->T == this->ST && Size == this->size()); // Sanity check.
	}

	/// Provides an untyped pointer for the constant value stored at a position.
	///
	/// \param Pos the index of the value to return an untyped pointer for
	///
	/// \return untyped pointer for the constant 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 TokenizedStorage<Type, Types...>::pointerTo(Pos);
	}

	/// Aborts the program!
	///
	/// Since \c rosa::Message instances are supposed to be immutable, the
	/// non-const inherited function is overridden so that it aborts execution.
	void *pointerTo(const token_size_t) noexcept override {
	ROSA_CRITICAL("Unallowed operation of rosa::LocalMessage");
	}
	};

	} // End namespace

	template <typename Type, typename... Types>
	Message::Message(const Type &, const Types &...) noexcept
	: T(TypeToken<typename std::decay<Type>::type,
	typename std::decay<Types>::type...>::Value),
	Size(lengthOfToken(T)) {
	ASSERT(validToken(T) &&
	lengthOfToken(T) == (1 + sizeof...(Types))); // Sanity check.
	LOG_TRACE("Creating Message with Token(" + std::to_string(T) + ")");
	}

	/// \note The implementation instantiates a private local template class
	/// \c LocalMessage.
	template <typename Type, typename... Types>
	message_t Message::create(const Type &T, const Types &... Ts) noexcept {
	return message_t(new LocalMessage<Type, Types...>(T, Ts...));
	}

	/// \note The implementation instantiates a private local template class
	/// \c LocalMessage.
	template <typename Type, typename... Types>
	message_t Message::create(Type &&T, Types &&... Ts) noexcept {
	return message_t(
	new LocalMessage<Type, Types...>(std::move(T), std::move(Ts)...));
	}

	template <typename Type>
	bool Message::isTypeAt(const token_size_t Pos) const noexcept {
	ASSERT(Pos < Size);
	Token TT = T;
	dropNOfToken(TT, Pos);
	return isHeadOfTokenTheSameType<Type>(TT);
	}

	template <typename Type>
	const Type &Message::valueAt(const token_size_t Pos) const noexcept {
	ASSERT(Pos < Size && isTypeAt<Type>(Pos));
	return static_cast<const Type >(pointerTo(Pos));
	}

	} // End namespace rosa

	#endif // ROSA_CORE_MESSAGE_HPP

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