type_token.hpp
No OneTemporary
Actions

Size

11 KB

Referenced Files

None

Subscribers

None

type_token.hpp
View Options

	//===-- rosa/support/type_token.hpp ------------------------------ C++ --===//
	//
	// The RoSA Framework
	//
	//===----------------------------------------------------------------------===//
	///
	/// \file rosa/support/type_token.hpp
	///
	/// \author David Juhasz (david.juhasz@tuwien.ac.at)
	///
	/// \date 2017-2019
	///
	/// \brief Facilities for encoding TypeLists as unsigned integer values.
	///
	/// \note **On the compatibility between different versions of the type token
	/// implementation:**
	/// Different software versions produce compatible type tokens as long as
	/// backward compatibility of \c rosa::BuiltinTypes is maintained (denoted by
	/// \c rosa::TypeNumberVersion) and the type token implementation uses the same
	/// type as \c rosa::token_t (boiling down to the same \c rosa::token::TokenBits
	/// value) and the same \c rosa::token::RepresentationBits value. Thus,
	/// interacting software need to cross-validate the aforementioned values to
	/// check compatibility. Interoperation between compatible sofware is limited
	/// to backward compatiblity, that is builtin types defined in both software
	/// versions are handled correctly but a newer system may produce a type token
	/// which is invalid in an old one. Therefore, tokens obtained from a compatible
	/// remote system need to be validated.
	///
	//===----------------------------------------------------------------------===//

	#ifndef ROSA_SUPPORT_TYPE_TOKEN_HPP
	#define ROSA_SUPPORT_TYPE_TOKEN_HPP

	#include "rosa/support/type_numbers.hpp"

	namespace rosa {

	/// Integer type to store type tokens.
	///
	/// \note The trade-off between the binary overhead of type encoding and the
	/// maximal size of encodable lists can be tuned by using unsigned integer types
	/// of different widths as \c rosa::token_t.
	using token_t = uint64_t;

	/// Sanity check in case someone would change \c rosa::token_t.
	STATIC_ASSERT(std::is_unsigned<token_t>::value,
	"token_t is not an unsigned integer");

	/// Turn \c rosa::token_t into a strongly typed enumeration.
	///
	/// Values of \c rosa::token_t casted to \c rosa::Token can be used in a
	/// type-safe way.
	enum class Token : token_t {};

	/// A type to cast tokens into in order to output them to streams as
	/// numbers and not ASCII-codes.
	///
	/// \note Use it for safety, necessary for printing \c uint8_t values.
	using printable_token_t = printable_t<token_t>;

	/// Casts a \c rosa::Token into \c rosa::printable_token_t.
	///
	/// \param T \c rosa::Token to cast
	#define PRINTABLE_TOKEN(T) static_cast<printable_token_t>(T)

	/// Encloses constants related to the implementation of \c rosa::Token.
	namespace token {

	/// The number of bits in one \c rosa::Token.
	constexpr size_t TokenBits = sizeof(Token) * 8;

	/// The number of bits a builtin type can be uniquely encoded into, that is any
	/// valid \c rosa::TypeNumber can fit into.
	///
	/// \note There is one extra bit position added for encoding so that providing a
	/// better chance to maintain backward comaptibility when \c rosa::BuiltinTypes
	/// is extended.
	constexpr size_t RepresentationBits = log2(NumberOfBuiltinTypes) + 1;

	/// Maximal size of uniquely tokenizable \c rosa::TypeList.
	constexpr size_t MaxTokenizableListSize = TokenBits / RepresentationBits;

	} // End namespace token

	/// Integer type to store length of a \c rosa::Token.
	///
	/// \note The narrowest unsigned integer type that is wide enough to
	/// represent \c rosa::token::MaxTokenizableListSize different values.
	using token_size_t = typename TypeListFind<
	typename TypeListDrop<log2(token::MaxTokenizableListSize) / 8 + 1,
	IntegerTypesBySize>::Type,
	IsNotNoneType>::Type::Second;

	/// \defgroup TypeListTokenImpl Implementation of rosa::TypeListToken
	///
	/// \brief Generates a \c rosa::Token for a squashed \c rosa::TypeList.
	///
	/// \note Only to be used by the implementation of \c rosa::TypeListToken.
	///@{

	/// Declaration of the template.
	///
	/// \tparam List \c rosa::TypeList to generate \c rosa::Token for
	template <typename List> struct TypeListTokenImpl;

	/// Specialization for \c rosa::EmptyTypeList.
	template <> struct TypeListTokenImpl<EmptyTypeList> {
	static constexpr Token Value = static_cast<Token>(0);
	};

	/// Specialization for a non-empty \c rosa::TypeList.
	template <typename T, typename... Ts>
	struct TypeListTokenImpl<TypeList<T, Ts...>> {
	static constexpr TypeNumber TN = TypeNumberOf<T>::Value;
	// Check if the generated type number is valid.
	STATIC_ASSERT(validTypeNumber(TN), "non-builtin type");
	static constexpr Token Value = static_cast<Token>(
	(static_cast<token_t>(TypeListTokenImpl<TypeList<Ts...>>::Value)
	<< token::RepresentationBits) \|
	static_cast<type_nr_t>(TN));
	};

	///@}

	/// \name TypeListToken
	///
	/// \brief Generates a \c rosa::Token for a \c rosa::TypeList.
	///
	/// \c rosa::Token for a \c rosa::TypeList \c List can be obtained as \code
	/// TypeListToken<List>::Value
	/// \endcode
	///
	/// \note The \c rosa::TypeList cannot have more than
	/// \c rosa::token::MaxTokenizableListSize elements and must be a subset of
	/// \c rosa::BuiltinTypes with respect to squashed integers.
	///
	/// \note A generated \c rosa::Token uniquely represents a list of types, except
	/// for \c rosa::AtomConstant types. Observe that any \c rosa::AtomConstant is
	/// encoded as the type \c rosa::AtomValue. The type information on all separate
	/// \c rosa::AtomConstant types are lost and replaced by the \c rosa::AtomValue
	/// type whose actual value needs to be used in order to obtain the original
	/// \c rosa::AtomConstant type and so the full type information on the encoded
	/// \c rosa::TypeList.
	///
	///@{

	/// Declaration of the template.
	///
	/// \tparam List \c rosa::TypeList to generate \c rosa::Token for
	template <typename List> struct TypeListToken;

	/// Implementation using \c rosa::TypeListTokenImpl.
	template <typename... Ts> struct TypeListToken<TypeList<Ts...>> {
	/// \note \c rosa::TypeNumber is computed against \c rosa::squased_t, so let's
	/// do the same here.
	using List = typename SquashedTypeList<TypeList<Ts...>>::Type;
	/// Check the length of the list here.
	/// \note Type validation is done one-by-one in \c rosa::TypeListTokenImpl.
	STATIC_ASSERT((TypeListSize<List>::Value <= token::MaxTokenizableListSize),
	"too long list of types");
	/// The \c rosa::Token for \p List.
	static constexpr Token Value = TypeListTokenImpl<List>::Value;
	};

	///@}

	/// Convenience template to generate \c rosa::Token for a list of types.
	template <typename... Ts> using TypeToken = TypeListToken<TypeList<Ts...>>;

	/// Tells if a given \c rosa::Token is valid.
	///
	/// A \c rosa::Token is considered valid if it can be decoded by the current
	/// software.
	///
	/// \note Validation gives a correct result only when \p T was generated by a
	/// compatible software.
	///
	/// \sa Note for type_token.hpp on compatibility.
	///
	/// \param T \c rosa::Token to validate
	///
	/// \return if \p T is valid
	bool validToken(const Token T);

	/// Tells if a \c rosa::Token does encode an empty list of types.
	///
	/// \param T \c rosa::Token to check
	///
	/// \return if \p T encodes an empty list of types
	bool emptyToken(const Token T);

	/// Tells how many types are encoded in a \c rosa::Token.
	///
	/// \param T \c rosa::Token to check
	///
	/// \return how many types are encoded in \p T
	token_size_t lengthOfToken(const Token T);

	/// Tells the full memory size of the types encoded in a \c rosa::Token.
	///
	/// The full memory size of the types encoded in a \c rosa::Token is the sum of
	/// the separate memory sizes of all the types encoded in the \c rosa::Token.
	///
	/// \param T \c rosa::Token to check
	///
	/// \return full memory size of the types encoded in \p T
	///
	/// \pre \p T is valid:\code
	/// validToken(T)
	/// \endcode
	size_t sizeOfValuesOfToken(const Token T);

	/// Extracts the \c rosa::TypeNumber of the first encoded type of a
	/// \c rosa::Token.
	///
	/// \note The returned type number is not validated.
	///
	/// \param T \c rosa::Token to take the first \c rosa::TypeNumber from
	///
	/// \return the first \c rosa::TypeNumber encoded in \p T
	inline TypeNumber headOfToken(const Token T) {
	return static_cast<TypeNumber>(static_cast<token_t>(T) &
	((1 << token::RepresentationBits) - 1));
	}

	/// Tells the memory size of the first type encoded in a \c rosa::Token.
	///
	/// \param T \c rosa::Token to check the first encoded type of
	///
	/// \return memory size of the first type encoded in \p T
	///
	/// \pre \p T is not empty and valid:\code
	/// !empty(T) && validToken(T)
	/// \endcode
	size_t sizeOfHeadOfToken(const Token T);

	/// Gives the textual representation of the first type encoded in a
	/// \c rosa::Token.
	///
	/// \param T \c rosa::Token to take the name of its first encoded type
	///
	/// \return textual representation of the first type encoded in \p T
	///
	/// \pre \p T is not empty and valid:\code
	/// !empty(T) && validToken(T)
	/// \endcode
	const char *nameOfHeadOfToken(const Token T);

	/// Updates a \c rosa::Token by dropping its first encoded type.
	///
	/// \param [in,out] T \c rosa::Token to drop the first encoded type of
	void dropHeadOfToken(Token &T);

	/// Updates a \c rosa::Token by dropping a number of its first encoded types
	///
	/// \param [in,out] T \c rosa::Token to drop the first \p N encoded types of
	/// \param N the number of types to drop from \p T
	void dropNOfToken(Token &T, const size_t N);

	/// Tells what type is encoded at Position \p Pos in the \c rosa::Token \p T
	///
	/// \param T \c rosa::Token to check
	/// \param Pos the position to check
	///
	/// \return \c rosa::TypeNumber of the type encodeded at position \p Pos of \c
	/// rosa::Token \p T
	///
	/// \pre \p T is valid and it encodes \p Pos types: \code
	/// validToken(T) && Pos < static_cast<size_t>(lengthOfToken(T))
	/// \endcode
	inline TypeNumber typeAtPositionOfToken(const Token T, const size_t Pos) {
	ASSERT(validToken(T) && Pos < static_cast<size_t>(lengthOfToken(T)));
	Token TT = T;
	dropNOfToken(TT, Pos);
	return headOfToken(TT);
	}

	/// Tells if the first encoded type of a \c rosa::Token is a given type.
	///
	/// \tparam Type type to match the first encoded type of \p T against
	///
	/// \param T \c rosa::Token whose first encoded type is to be matched against
	/// \p Type
	///
	/// \return if the first encoded type of \p T is \p Type
	///
	/// \pre \p T is not empty and valid:\code
	/// !empty(T) && validToken(T)
	/// \endcode
	template <typename Type> bool isHeadOfTokenTheSameType(const Token T) {
	ASSERT(!emptyToken(T) && validToken(T));
	return TypeNumberOf<Type>::Value == headOfToken(T);
	}

	} // End namespace rosa

	namespace std {

	/// Converts a \c rosa::Token into \c std::string.
	///
	/// \param T \c rosa::Token to convert
	///
	/// \return \c std::string representing \p T
	inline string to_string(const rosa::Token T) {
	return to_string(static_cast<rosa::token_t>(T));
	}

	/// Dumps a \c rosa::Token to a given \c std::ostream.
	///
	/// \param [in,out] OS output stream to dump to
	/// \param T \c rosa::Token to dump
	///
	/// \return \p OS after dumping \p N to it
	inline ostream &operator<<(ostream &OS, const rosa::Token &T) {
	OS << to_string(T);
	return OS;
	}

	} // End namespace std

	#endif // ROSA_SUPPORT_TYPE_TOKEN_HPP

File Metadata

Mime Type: text/x-c++
Expires: Sun, Jun 8, 8:19 PM (1 d, 7 h)
Storage Engine: blob
Storage Format: Raw Data
Storage Handle: 150477
Default Alt Text: type_token.hpp (11 KB)

type_token.hppNo OneTemporaryActions

type_token.hppView Options

File Metadata

Event Timeline

type_token.hpp
No OneTemporary
Actions

type_token.hpp
View Options