GH-1047 parse world files and integrate MCEdit with world page

depends/libnbtplusplus/include/value.h

@@ -0,0 +1,223 @@
+/*
+ * 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>
+
+#include "nbt++_export.h"
+
+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;
+
+    NBT___EXPORT friend bool operator==(const value& lhs, const value& rhs);
+    NBT___EXPORT friend 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>();
+}
+
+}
+
+#endif // TAG_REF_PROXY_H_INCLUDED