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360 lines
11 KiB
C++
360 lines
11 KiB
C++
//
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// Struct.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 06/03/2020.
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// Copyright © 2020 Thomas Harte. All rights reserved.
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//
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#ifndef Struct_hpp
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#define Struct_hpp
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#include <cstdarg>
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#include <cstring>
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#include <string>
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#include <typeindex>
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#include <typeinfo>
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#include <type_traits>
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#include <unordered_map>
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#include <vector>
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#include "Enum.hpp"
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namespace Reflection {
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#define DeclareField(Name) declare(&Name, #Name)
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struct Struct {
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virtual std::vector<std::string> all_keys() const = 0;
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virtual const std::type_info *type_of(const std::string &name) const = 0;
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virtual size_t count_of(const std::string &name) const = 0;
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virtual void set(const std::string &name, const void *value) = 0;
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virtual void *get(const std::string &name) = 0;
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virtual const void *get(const std::string &name) const = 0;
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virtual std::vector<std::string> values_for(const std::string &name) const = 0;
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virtual ~Struct() {}
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/*!
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@returns A string describing this struct. This string has no guaranteed layout, may not be
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sufficiently formed for a formal language parser, etc.
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*/
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std::string description() const;
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/*!
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Serialises this struct in BSON format.
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Supported field types:
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* [u]int[8/16/32/64]_t;
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* float and double;
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* bool;
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* std::string;
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* plain C-style arrays of any of the above;
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* other reflective structs;
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* std::vector<uint8_t> as raw binary data.
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TODO: vector of string, possibly? Or more general vector support?
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@returns The BSON serialisation.
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*/
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std::vector<uint8_t> serialise() const;
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/*!
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Applies as many fields as possible from the incoming BSON. Supports the same types
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as @c serialise.
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*/
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bool deserialise(const std::vector<uint8_t> &bson);
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/*!
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Called to determine whether @c key should be included in the serialisation of this struct.
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*/
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virtual bool should_serialise(const std::string &key) const { return true; }
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private:
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void append(std::ostringstream &stream, const std::string &key, const std::type_info *type, size_t offset) const;
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bool deserialise(const uint8_t *bson, size_t size);
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};
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/*!
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Attempts to set the property @c name to @c value ; will perform limited type conversions.
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@returns @c true if the property was successfully set; @c false otherwise.
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*/
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template <typename Type> bool set(Struct &target, const std::string &name, Type value);
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/*!
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Setting an int:
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* to an int copies the int;
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* to a smaller type, truncates the int;
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* to an int64_t promotes the int; and
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* to a registered enum, copies the int.
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*/
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template <> bool set(Struct &target, const std::string &name, int64_t value);
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template <> bool set(Struct &target, const std::string &name, int value);
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/*!
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Setting a string:
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* to an enum, if the string names a member of the enum, sets the value.
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*/
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template <> bool set(Struct &target, const std::string &name, const std::string &value);
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template <> bool set(Struct &target, const std::string &name, const char *value);
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/*!
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Setting a bool:
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* to a bool, copies the value.
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*/
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template <> bool set(Struct &target, const std::string &name, bool value);
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template <> bool set(Struct &target, const std::string &name, float value);
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template <> bool set(Struct &target, const std::string &name, double value);
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/*!
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Fuzzy-set attempts to set any property based on a string value. This is intended to allow input provided by the user.
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Amongst other steps, it might:
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* if the target is a bool, map true, false, yes, no, y, n, etc;
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* if the target is an integer, parse like strtrol;
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* if the target is a float, parse like strtod; or
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* if the target is a reflective enum, attempt to match to enum members (possibly doing so in a case insensitive fashion).
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This method reserves the right to perform more or fewer attempted mappings, using any other logic it
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decides is appropriate.
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@returns @c true if the property was successfully set; @c false otherwise.
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*/
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bool fuzzy_set(Struct &target, const std::string &name, const std::string &value);
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/*!
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Attempts to get the property @c name to @c value ; will perform limited type conversions.
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@returns @c true if the property was successfully read; @c false otherwise.
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*/
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template <typename Type> bool get(const Struct &target, const std::string &name, Type &value, size_t offset = 0);
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/*!
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Attempts to get the property @c name to @c value ; will perform limited type conversions.
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@returns @c true if the property was successfully read; a default-constructed instance of Type otherwise.
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*/
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template <typename Type> Type get(const Struct &target, const std::string &name, size_t offset = 0);
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template <typename Owner> class StructImpl: public Struct {
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public:
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/*!
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@returns the value of type @c Type that is loaded from the offset registered for the field @c name.
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It is the caller's responsibility to provide an appropriate type of data.
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*/
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void *get(const std::string &name) final {
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const auto iterator = contents_.find(name);
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if(iterator == contents_.end()) return nullptr;
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return reinterpret_cast<uint8_t *>(this) + iterator->second.offset;
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}
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const void *get(const std::string &name) const final {
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const auto iterator = contents_.find(name);
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if(iterator == contents_.end()) return nullptr;
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return reinterpret_cast<const uint8_t *>(this) + iterator->second.offset;
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}
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/*!
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Stores the @c value of type @c Type to the offset registered for the field @c name.
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It is the caller's responsibility to provide an appropriate type of data.
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*/
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void set(const std::string &name, const void *value) final {
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const auto iterator = contents_.find(name);
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if(iterator == contents_.end()) return;
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memcpy(reinterpret_cast<uint8_t *>(this) + iterator->second.offset, value, iterator->second.size);
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}
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/*!
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@returns @c type_info for the field @c name.
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*/
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const std::type_info *type_of(const std::string &name) const final {
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const auto iterator = contents_.find(name);
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if(iterator == contents_.end()) return nullptr;
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return iterator->second.type;
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}
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/*!
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@returns The number of instances of objects of the same type as @c name that sit consecutively in memory.
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*/
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size_t count_of(const std::string &name) const final {
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const auto iterator = contents_.find(name);
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if(iterator == contents_.end()) return 0;
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return iterator->second.count;
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}
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/*!
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@returns a list of the valid enum value names for field @c name if it is a declared enum field of this struct;
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the empty list otherwise.
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*/
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std::vector<std::string> values_for(const std::string &name) const final {
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std::vector<std::string> result;
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// Return an empty vector if this field isn't declared.
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const auto type = type_of(name);
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if(!type) return result;
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// Also return an empty vector if this field isn't a registered enum.
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const auto all_values = Enum::all_values(*type);
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if(all_values.empty()) return result;
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// If no restriction is stored, return all values.
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const auto permitted_values = permitted_enum_values_.find(name);
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if(permitted_values == permitted_enum_values_.end()) return all_values;
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// Compile a vector of only those values the stored set indicates.
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auto value = all_values.begin();
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auto flag = permitted_values->second.begin();
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while(value != all_values.end() && flag != permitted_values->second.end()) {
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if(*flag) {
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result.push_back(*value);
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}
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++flag;
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++value;
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}
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return result;
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}
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/*!
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@returns A vector of all declared fields for this struct.
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*/
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std::vector<std::string> all_keys() const final {
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std::vector<std::string> keys;
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for(const auto &pair: contents_) {
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keys.push_back(pair.first);
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}
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return keys;
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}
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protected:
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/*
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This interface requires reflective structs to declare all fields;
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specifically they should call:
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declare_field(&field1, "field1");
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declare_field(&field2, "field2");
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Fields are registered in class storage. So callers can use needs_declare()
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to determine whether a class of this type has already established the
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reflective fields.
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*/
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/*!
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Exposes the field pointed to by @c t for reflection as @c name. If @c t is itself a Reflection::Struct,
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it'll be the struct that's exposed.
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*/
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template <typename Type> void declare(Type *t, const std::string &name) {
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// If the declared item is a class, see whether it can be dynamically cast
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// to a reflectable for emplacement. If so, exit early.
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if constexpr (std::is_class<Type>()) {
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if(declare_reflectable(t, name)) return;
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}
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// If the declared item is an array, record it as a pointer to the
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// first element plus a size.
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if constexpr (std::is_array<Type>()) {
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declare_emplace(&(*t)[0], name, sizeof(*t) / sizeof(*t[0]));
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return;
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}
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declare_emplace(t, name);
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}
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/*!
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If @c t is a previously-declared field that links to a declared enum then the variable
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arguments provide a list of the acceptable values for that field. The list should be terminated
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with a value of -1.
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*/
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template <typename Type> void limit_enum(Type *t, ...) {
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const auto name = name_of(t);
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if(name.empty()) return;
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// The default vector size of '8' isn't especially scientific,
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// but I feel like it's a good choice.
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std::vector<bool> permitted_values(8);
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va_list list;
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va_start(list, t);
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while(true) {
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const int next = va_arg(list, int);
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if(next < 0) break;
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if(permitted_values.size() <= size_t(next)) {
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permitted_values.resize(permitted_values.size() << 1);
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}
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permitted_values[size_t(next)] = true;
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}
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va_end(list);
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permitted_enum_values_.emplace(std::make_pair(name, permitted_values));
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}
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/*!
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@returns @c true if this subclass of @c Struct has not yet declared any fields.
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*/
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bool needs_declare() {
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return contents_.empty();
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}
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/*!
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Performs a reverse lookup from field to name.
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*/
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std::string name_of(void *field) {
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const ssize_t offset = reinterpret_cast<uint8_t *>(field) - reinterpret_cast<uint8_t *>(this);
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auto iterator = contents_.begin();
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while(iterator != contents_.end()) {
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if(iterator->second.offset == offset) break;
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++iterator;
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}
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if(iterator != contents_.end()) {
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return iterator->first;
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} else {
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return "";
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}
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}
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private:
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template <typename Type> bool declare_reflectable(Type *t, const std::string &name) {
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if constexpr (std::is_base_of<Reflection::Struct, Type>::value) {
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Reflection::Struct *const str = static_cast<Reflection::Struct *>(t);
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declare_emplace(str, name);
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return true;
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}
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return false;
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}
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template <typename Type> void declare_emplace(Type *t, const std::string &name, size_t count = 1) {
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contents_.emplace(
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std::make_pair(
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name,
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Field(typeid(Type), reinterpret_cast<uint8_t *>(t) - reinterpret_cast<uint8_t *>(this), sizeof(Type), count)
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));
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}
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struct Field {
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const std::type_info *type;
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ssize_t offset;
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size_t size;
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size_t count;
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Field(const std::type_info &type, ssize_t offset, size_t size, size_t count) :
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type(&type), offset(offset), size(size), count(count) {}
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};
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static inline std::unordered_map<std::string, Field> contents_;
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static inline std::unordered_map<std::string, std::vector<bool>> permitted_enum_values_;
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};
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}
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#endif /* Struct_hpp */
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