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Try to get rid of std::variant in json_container.hpp

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This commit is contained in:
Siarhei Fedartsou 2024-09-28 21:34:24 +02:00
parent 4f1c62a768
commit dbc52728c3
1 changed files with 124 additions and 11 deletions
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135
include/util/json_container.hpp
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@ -90,33 +90,146 @@ struct Null
{
};
/**
* Typed Value sum-type implemented as a variant able to represent tree-like JSON structures.
*
* Dispatch on its type by either by using apply_visitor or its get function.
*/
using Value = std::variant<String, Number, Object, Array, True, False, Null>;
/**
* Typed Object.
*
* Unwrap the key-value pairs holding type via its values member attribute.
*/
struct Object
{
std::unordered_map<std::string, Value> values;
};
struct Object;
/**
* Typed Array.
*
* Unwrap the Value holding type via its values member attribute.
*/
struct Array;
struct Value;
// Definitions of Object and Array (must come after Value is defined)
struct Object
{
std::unordered_map<std::string, Value> values;
};
struct Array
{
std::vector<Value> values;
};
struct Value {
enum class Type {
Invalid,
String,
Number,
Object,
Array,
True,
False,
Null
};
String string;
Number number;
Object object;
Array array;
Type type;
Value() noexcept : type(Type::Invalid) {}
Value(const Null&) noexcept : type(Type::Null) {}
Value(const True&) noexcept : type(Type::True) {}
Value(const False&) noexcept : type(Type::False) {}
Value(String &&string_) noexcept : string(std::move(string_)), type(Type::String) {}
Value(const Number &number_) noexcept : number(number_), type(Type::Number) {}
Value(const Object &object_) noexcept : object(object_), type(Type::Object) {}
Value(const Array &array_) noexcept : array(array_), type(Type::Array) {}
Value(double number) noexcept : number(number), type(Type::Number) {}
Value(std::string string) noexcept : string(std::move(string)), type(Type::String) {}
Value(const char* string) noexcept : string(string), type(Type::String) {}
};
} // namespace osrm::util::json
namespace std {
template <typename T>
inline T& get(osrm::util::json::Value& value) noexcept;
template<>
inline osrm::util::json::String& get<osrm::util::json::String>(osrm::util::json::Value& value) noexcept
{
return value.string;
}
template<>
inline osrm::util::json::Number& get<osrm::util::json::Number>(osrm::util::json::Value& value) noexcept
{
return value.number;
}
template<>
inline osrm::util::json::Object& get<osrm::util::json::Object>(osrm::util::json::Value& value) noexcept
{
return value.object;
}
template<>
inline osrm::util::json::Array& get<osrm::util::json::Array>(osrm::util::json::Value& value) noexcept
{
return value.array;
}
template <typename T>
inline const T& get(const osrm::util::json::Value& value) noexcept;
template<>
inline const osrm::util::json::String& get<osrm::util::json::String>(const osrm::util::json::Value& value) noexcept
{
return value.string;
}
template<>
inline const osrm::util::json::Number& get<osrm::util::json::Number>(const osrm::util::json::Value& value) noexcept
{
return value.number;
}
template<>
inline const osrm::util::json::Object& get<osrm::util::json::Object>(const osrm::util::json::Value& value) noexcept
{
return value.object;
}
template<typename Visitor>
inline void visit(Visitor&& visitor, const osrm::util::json::Value& value)
{
switch (value.type)
{
case osrm::util::json::Value::Type::String:
visitor(value.string);
break;
case osrm::util::json::Value::Type::Number:
visitor(value.number);
break;
case osrm::util::json::Value::Type::Object:
visitor(value.object);
break;
case osrm::util::json::Value::Type::Array:
visitor(value.array);
break;
case osrm::util::json::Value::Type::True:
visitor(osrm::util::json::True{});
break;
case osrm::util::json::Value::Type::False:
visitor(osrm::util::json::False{});
break;
case osrm::util::json::Value::Type::Null:
visitor(osrm::util::json::Null{});
break;
case osrm::util::json::Value::Type::Invalid:
break;
}
}
}// namespace std
#endif // JSON_CONTAINER_HPP