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Diffstat (limited to 'libnbtplusplus/include/value.h')
| -rw-r--r-- | libnbtplusplus/include/value.h | 255 |
1 files changed, 255 insertions, 0 deletions
diff --git a/libnbtplusplus/include/value.h b/libnbtplusplus/include/value.h new file mode 100644 index 0000000000..08a23ab111 --- /dev/null +++ b/libnbtplusplus/include/value.h @@ -0,0 +1,255 @@ +/* + * SPDX-FileCopyrightText: 2013, 2015 ljfa-ag <ljfa-ag@web.de> + * + * SPDX-License-Identifier: LGPL-3.0-or-later + */ + +/* + * libnbt++ - A library for the Minecraft Named Binary Tag format. + * Copyright (C) 2013, 2015 ljfa-ag + * + * This file is part of libnbt++. + * + * libnbt++ is free software: you can redistribute it and/or modify + * it under the terms of the GNU Lesser General Public License as published by + * the Free Software Foundation, either version 3 of the License, or + * (at your option) any later version. + * + * libnbt++ is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public License + * along with libnbt++. If not, see <http://www.gnu.org/licenses/>. + */ +#ifndef TAG_REF_PROXY_H_INCLUDED +#define TAG_REF_PROXY_H_INCLUDED + +#include "tag.h" +#include <string> +#include <type_traits> + +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>(); + } + +} // namespace nbt + +#endif // TAG_REF_PROXY_H_INCLUDED |