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