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CLK/Reflection/Struct.h

109 lines
2.9 KiB
C++

//
// Struct.h
// Clock Signal
//
// Created by Thomas Harte on 06/03/2020.
// Copyright © 2020 Thomas Harte. All rights reserved.
//
#ifndef Struct_h
#define Struct_h
#include <string>
#include <typeindex>
#include <typeinfo>
#include <unordered_map>
#include <vector>
namespace Reflection {
#define DeclareField(Name) declare(&Name, #Name)
template <typename Owner> class Struct {
public:
/*!
@returns the value of type @c Type that is loaded from the offset registered for the field @c name.
It is the caller's responsibility to provide an appropriate type of data.
*/
template <typename Type> const Type *get(const std::string &name) {
const auto iterator = contents_.find(name);
if(iterator == contents_.end()) return nullptr;
return reinterpret_cast<Type *>(reinterpret_cast<uint8_t *>(this) + iterator->second.offset);
}
/*!
Stores the @c value of type @c Type to the offset registered for the field @c name.
It is the caller's responsibility to provide an appropriate type of data.
*/
template <typename Type> void set(const std::string &name, const Type &value) {
const auto iterator = contents_.find(name);
if(iterator == contents_.end()) return;
*reinterpret_cast<Type *>(reinterpret_cast<uint8_t *>(this) + iterator->second.offset) = value;
}
/*!
@returns @c type_info for the field @c name.
*/
const std::type_info *type_of(const std::string &name) {
const auto iterator = contents_.find(name);
if(iterator == contents_.end()) return nullptr;
return iterator->second.type;
}
/*!
@returns A vector of all declared fields for this struct.
*/
std::vector<std::string> all_keys() {
std::vector<std::string> keys;
for(const auto &pair: contents_) {
keys.push_back(pair.first);
}
return keys;
}
protected:
/*
This interface requires reflective structs to declare all fields;
specifically they should call:
declare_field(&field1, "field1");
declare_field(&field2, "field2");
Fields are registered in class storage. So callers can use needs_declare()
to determine whether a class of this type has already established the
reflective fields.
*/
/*!
Exposes the field pointed to by @c t for reflection as @c name.
*/
template <typename Type> void declare(Type *t, const std::string &name) {
contents_.emplace(
std::make_pair(
name,
Field(typeid(Type), reinterpret_cast<uint8_t *>(t) - reinterpret_cast<uint8_t *>(this))
));
}
/*!
@returns @c true if this subclass of @c Struct has not yet declared any fields.
*/
bool needs_declare() {
return !contents_.size();
}
private:
struct Field {
const std::type_info *type;
ssize_t offset;
Field(const std::type_info &type, ssize_t offset) :
type(&type), offset(offset) {}
};
static inline std::unordered_map<std::string, Field> contents_;
};
}
#endif /* Struct_h */