Add 'libnbtplusplus/' from commit '1a0ffe372f4da8408c5d08a36013536a3396b9e6'

git-subtree-dir: libnbtplusplus
git-subtree-mainline: 7fb132859fda54aa96bc9dd46d302b343eeb5a02
git-subtree-split: 1a0ffe372f4da8408c5d08a36013536a3396b9e6

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