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/*
* 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
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