diff options
Diffstat (limited to 'include/value.h')
| -rw-r--r-- | include/value.h | 408 |
1 files changed, 218 insertions, 190 deletions
diff --git a/include/value.h b/include/value.h index 36b55ffa57..08a23ab111 100644 --- a/include/value.h +++ b/include/value.h @@ -33,195 +33,223 @@ namespace nbt { -/** - * @brief Contains an NBT value of fixed type - * - * This class is a convenience wrapper for @c std::unique_ptr<tag>. - * A value can contain any kind of tag or no tag (nullptr) and provides - * operations for handling tags of which the type is not known at compile time. - * Assignment or the set method on a value with no tag will fill in the value. - * - * The rationale for the existance of this class is to provide a type-erasured - * means of storing tags, especially when they are contained in tag_compound - * or tag_list. The alternative would be directly using @c std::unique_ptr<tag> - * and @c tag&, which is how it was done in libnbt++1. The main drawback is that - * it becomes very cumbersome to deal with tags of unknown type. - * - * For example, in this case it would not be possible to allow a syntax like - * <tt>compound["foo"] = 42</tt>. If the key "foo" does not exist beforehand, - * the left hand side could not have any sensible value if it was of type - * @c tag&. - * Firstly, the compound tag would have to create a new tag_int there, but it - * cannot know that the new tag is going to be assigned an integer. - * Also, if the type was @c tag& and it allowed assignment of integers, that - * would mean the tag base class has assignments and conversions like this. - * Which means that all other tag classes would inherit them from the base - * class, even though it does not make any sense to allow converting a - * tag_compound into an integer. Attempts like this should be caught at - * compile time. - * - * This is why all the syntactic sugar for tags is contained in the value class - * while the tag class only contains common operations for all tag types. - */ -class NBT_EXPORT value -{ -public: - //Constructors - value() noexcept {} - explicit value(std::unique_ptr<tag>&& t) noexcept: tag_(std::move(t)) {} - explicit value(tag&& t); - - //Moving - value(value&&) noexcept = default; - value& operator=(value&&) noexcept = default; - - //Copying - explicit value(const value& rhs); - value& operator=(const value& rhs); - - /** - * @brief Assigns the given value to the tag if the type matches - * @throw std::bad_cast if the type of @c t is not the same as the type - * of this value - */ - value& operator=(tag&& t); - void set(tag&& t); - - //Conversion to tag - /** - * @brief Returns the contained tag - * - * If the value is uninitialized, the behavior is undefined. - */ - operator tag&() { return get(); } - operator const tag&() const { return get(); } - tag& get() { return *tag_; } - const tag& get() const { return *tag_; } - - /** - * @brief Returns a reference to the contained tag as an instance of T - * @throw std::bad_cast if the tag is not of type T - */ - template<class T> - T& as(); - template<class T> - const T& as() const; - - //Assignment of primitives and string - /** - * @brief Assigns the given value to the tag if the type is compatible - * @throw std::bad_cast if the value is not convertible to the tag type - * via a widening conversion - */ - value& operator=(int8_t val); - value& operator=(int16_t val); - value& operator=(int32_t val); - value& operator=(int64_t val); - value& operator=(float val); - value& operator=(double val); - - /** - * @brief Assigns the given string to the tag if it is a tag_string - * @throw std::bad_cast if the contained tag is not a tag_string - */ - value& operator=(const std::string& str); - value& operator=(std::string&& str); - - //Conversions to primitives and string - /** - * @brief Returns the contained value if the type is compatible - * @throw std::bad_cast if the tag type is not convertible to the desired - * type via a widening conversion - */ - explicit operator int8_t() const; - explicit operator int16_t() const; - explicit operator int32_t() const; - explicit operator int64_t() const; - explicit operator float() const; - explicit operator double() const; - - /** - * @brief Returns the contained string if the type is tag_string - * - * If the value is uninitialized, the behavior is undefined. - * @throw std::bad_cast if the tag type is not tag_string - */ - explicit operator const std::string&() const; - - ///Returns true if the value is not uninitialized - explicit operator bool() const { return tag_ != nullptr; } - - /** - * @brief In case of a tag_compound, accesses a tag by key with bounds checking - * - * If the value is uninitialized, the behavior is undefined. - * @throw std::bad_cast if the tag type is not tag_compound - * @throw std::out_of_range if given key does not exist - * @sa tag_compound::at - */ - value& at(const std::string& key); - const value& at(const std::string& key) const; - - /** - * @brief In case of a tag_compound, accesses a tag by key - * - * If the value is uninitialized, the behavior is undefined. - * @throw std::bad_cast if the tag type is not tag_compound - * @sa tag_compound::operator[] - */ - value& operator[](const std::string& key); - value& operator[](const char* key); //need this overload because of conflict with built-in operator[] - - /** - * @brief In case of a tag_list, accesses a tag by index with bounds checking - * - * If the value is uninitialized, the behavior is undefined. - * @throw std::bad_cast if the tag type is not tag_list - * @throw std::out_of_range if the index is out of range - * @sa tag_list::at - */ - value& at(size_t i); - const value& at(size_t i) const; - - /** - * @brief In case of a tag_list, accesses a tag by index - * - * No bounds checking is performed. If the value is uninitialized, the - * behavior is undefined. - * @throw std::bad_cast if the tag type is not tag_list - * @sa tag_list::operator[] - */ - value& operator[](size_t i); - const value& operator[](size_t i) const; - - ///Returns a reference to the underlying std::unique_ptr<tag> - std::unique_ptr<tag>& get_ptr() { return tag_; } - const std::unique_ptr<tag>& get_ptr() const { return tag_; } - ///Resets the underlying std::unique_ptr<tag> to a different value - void set_ptr(std::unique_ptr<tag>&& t) { tag_ = std::move(t); } - - ///@sa tag::get_type - tag_type get_type() const; - - friend NBT_EXPORT bool operator==(const value& lhs, const value& rhs); - friend NBT_EXPORT bool operator!=(const value& lhs, const value& rhs); - -private: - std::unique_ptr<tag> tag_; -}; - -template<class T> -T& value::as() -{ - return tag_->as<T>(); -} - -template<class T> -const T& value::as() const -{ - return tag_->as<T>(); -} - -} + /** + * @brief Contains an NBT value of fixed type + * + * This class is a convenience wrapper for @c std::unique_ptr<tag>. + * A value can contain any kind of tag or no tag (nullptr) and provides + * operations for handling tags of which the type is not known at compile + * time. Assignment or the set method on a value with no tag will fill in + * the value. + * + * The rationale for the existance of this class is to provide a + * type-erasured means of storing tags, especially when they are contained + * in tag_compound or tag_list. The alternative would be directly using @c + * std::unique_ptr<tag> and @c tag&, which is how it was done in libnbt++1. + * The main drawback is that it becomes very cumbersome to deal with tags of + * unknown type. + * + * For example, in this case it would not be possible to allow a syntax like + * <tt>compound["foo"] = 42</tt>. If the key "foo" does not exist + * beforehand, the left hand side could not have any sensible value if it + * was of type + * @c tag&. + * Firstly, the compound tag would have to create a new tag_int there, but + * it cannot know that the new tag is going to be assigned an integer. Also, + * if the type was @c tag& and it allowed assignment of integers, that would + * mean the tag base class has assignments and conversions like this. Which + * means that all other tag classes would inherit them from the base class, + * even though it does not make any sense to allow converting a tag_compound + * into an integer. Attempts like this should be caught at compile time. + * + * This is why all the syntactic sugar for tags is contained in the value + * class while the tag class only contains common operations for all tag + * types. + */ + class NBT_EXPORT value + { + public: + // Constructors + value() noexcept {} + explicit value(std::unique_ptr<tag>&& t) noexcept : tag_(std::move(t)) + { + } + explicit value(tag&& t); + + // Moving + value(value&&) noexcept = default; + value& operator=(value&&) noexcept = default; + + // Copying + explicit value(const value& rhs); + value& operator=(const value& rhs); + + /** + * @brief Assigns the given value to the tag if the type matches + * @throw std::bad_cast if the type of @c t is not the same as the type + * of this value + */ + value& operator=(tag&& t); + void set(tag&& t); + + // Conversion to tag + /** + * @brief Returns the contained tag + * + * If the value is uninitialized, the behavior is undefined. + */ + operator tag&() + { + return get(); + } + operator const tag&() const + { + return get(); + } + tag& get() + { + return *tag_; + } + const tag& get() const + { + return *tag_; + } + + /** + * @brief Returns a reference to the contained tag as an instance of T + * @throw std::bad_cast if the tag is not of type T + */ + template <class T> T& as(); + template <class T> const T& as() const; + + // Assignment of primitives and string + /** + * @brief Assigns the given value to the tag if the type is compatible + * @throw std::bad_cast if the value is not convertible to the tag type + * via a widening conversion + */ + value& operator=(int8_t val); + value& operator=(int16_t val); + value& operator=(int32_t val); + value& operator=(int64_t val); + value& operator=(float val); + value& operator=(double val); + + /** + * @brief Assigns the given string to the tag if it is a tag_string + * @throw std::bad_cast if the contained tag is not a tag_string + */ + value& operator=(const std::string& str); + value& operator=(std::string&& str); + + // Conversions to primitives and string + /** + * @brief Returns the contained value if the type is compatible + * @throw std::bad_cast if the tag type is not convertible to the + * desired type via a widening conversion + */ + explicit operator int8_t() const; + explicit operator int16_t() const; + explicit operator int32_t() const; + explicit operator int64_t() const; + explicit operator float() const; + explicit operator double() const; + + /** + * @brief Returns the contained string if the type is tag_string + * + * If the value is uninitialized, the behavior is undefined. + * @throw std::bad_cast if the tag type is not tag_string + */ + explicit operator const std::string&() const; + + /// Returns true if the value is not uninitialized + explicit operator bool() const + { + return tag_ != nullptr; + } + + /** + * @brief In case of a tag_compound, accesses a tag by key with bounds + * checking + * + * If the value is uninitialized, the behavior is undefined. + * @throw std::bad_cast if the tag type is not tag_compound + * @throw std::out_of_range if given key does not exist + * @sa tag_compound::at + */ + value& at(const std::string& key); + const value& at(const std::string& key) const; + + /** + * @brief In case of a tag_compound, accesses a tag by key + * + * If the value is uninitialized, the behavior is undefined. + * @throw std::bad_cast if the tag type is not tag_compound + * @sa tag_compound::operator[] + */ + value& operator[](const std::string& key); + value& operator[](const char* key); // need this overload because of + // conflict with built-in operator[] + + /** + * @brief In case of a tag_list, accesses a tag by index with bounds + * checking + * + * If the value is uninitialized, the behavior is undefined. + * @throw std::bad_cast if the tag type is not tag_list + * @throw std::out_of_range if the index is out of range + * @sa tag_list::at + */ + value& at(size_t i); + const value& at(size_t i) const; + + /** + * @brief In case of a tag_list, accesses a tag by index + * + * No bounds checking is performed. If the value is uninitialized, the + * behavior is undefined. + * @throw std::bad_cast if the tag type is not tag_list + * @sa tag_list::operator[] + */ + value& operator[](size_t i); + const value& operator[](size_t i) const; + + /// Returns a reference to the underlying std::unique_ptr<tag> + std::unique_ptr<tag>& get_ptr() + { + return tag_; + } + const std::unique_ptr<tag>& get_ptr() const + { + return tag_; + } + /// Resets the underlying std::unique_ptr<tag> to a different value + void set_ptr(std::unique_ptr<tag>&& t) + { + tag_ = std::move(t); + } + + ///@sa tag::get_type + tag_type get_type() const; + + friend NBT_EXPORT bool operator==(const value& lhs, const value& rhs); + friend NBT_EXPORT bool operator!=(const value& lhs, const value& rhs); + + private: + std::unique_ptr<tag> tag_; + }; + + template <class T> T& value::as() + { + return tag_->as<T>(); + } + + template <class T> const T& value::as() const + { + return tag_->as<T>(); + } + +} // namespace nbt #endif // TAG_REF_PROXY_H_INCLUDED |