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CLK/Reflection/Struct.hpp

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//
// Struct.hpp
// Clock Signal
//
// Created by Thomas Harte on 06/03/2020.
// Copyright © 2020 Thomas Harte. All rights reserved.
//
#pragma once
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#include <cassert>
#include <cstdarg>
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#include <cstring>
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#include <cstddef>
#include <cstdint>
#include <string>
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#include <typeindex>
#include <typeinfo>
#include <type_traits>
#include <unordered_map>
#include <vector>
#include "Enum.hpp"
#include "TypeInfo.hpp"
namespace Reflection {
#define DeclareField(Name) declare(&Name, #Name)
#define BEGIN_DECLARATIONS void declare_fields() {
#define END_DECLARATIONS } \
struct Declarer { Declarer() { Target t; t.declare_fields(); } }; \
static Declarer declarer;
struct Struct {
virtual std::vector<std::string> 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<Struct *>(this)->get(name);
}
virtual std::vector<std::string> values_for(const std::string &name) const = 0;
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virtual ~Struct() = default;
/*!
@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<uint8_t> as raw binary data.
TODO: vector of string, possibly? Or more general vector support?
@returns The BSON serialisation.
*/
std::vector<uint8_t> serialise() const;
/*!
Applies as many fields as possible from the incoming BSON. Supports the same types
as @c serialise.
*/
bool deserialise(const std::vector<uint8_t> &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 <typename Type> 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);
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/*!
Setting a bool:
* to a bool, copies the value.
*/
template <> bool set(Struct &target, const std::string &name, bool value, size_t offset);
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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 <typename Type> 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 <typename Type> Type get(const Struct &target, const std::string &name, size_t offset = 0);
template <typename Owner> 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<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.
*/
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<uint8_t *>(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<std::string> values_for(const std::string &name) const final {
std::vector<std::string> 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<std::string> all_keys() const final {
std::vector<std::string> keys;
for(const auto &pair: contents_) {
keys.push_back(pair.first);
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}
return keys;
}
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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 <typename Type> 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<Type>()) {
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<Type>()) {
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 <typename Type> 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<bool> 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(name, permitted_values);
}
/*!
@returns @c true if this subclass of @c Struct has not yet declared any fields.
*/
bool needs_declare() const {
return contents_.empty();
}
/*!
Performs a reverse lookup from field to name.
*/
std::string name_of(void *field) {
const ssize_t offset = reinterpret_cast<uint8_t *>(field) - reinterpret_cast<uint8_t *>(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 std::string();
}
}
private:
template <typename Type> bool declare_reflectable([[maybe_unused]] Type *t, const std::string &name) {
if constexpr (std::is_base_of<Reflection::Struct, Type>::value) {
Reflection::Struct *const str = static_cast<Reflection::Struct *>(t);
declare_emplace(str, name);
return true;
}
return false;
}
template <typename Type> void declare_emplace(Type *t, const std::string &name, size_t count = 1) {
contents_.emplace(
std::make_pair(
name,
Field(typeid(Type), reinterpret_cast<uint8_t *>(t) - reinterpret_cast<uint8_t *>(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<std::string, Field> contents_;
static inline std::unordered_map<std::string, std::vector<bool>> permitted_enum_values_;
};
// MARK: - IMPLEMENTATION DETAILS BELOW
// DO NOT RELY ON THE IMPLEMENTATIONS BELOW.
// Please use the documentation above.
// MARK: - Getters
template <typename Type> 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<const uint8_t *>(target.get(name)) + offset * sizeof(Type);
value = *reinterpret_cast<const Type *>(address);
return true;
}
// If the type is a registered enum and the value type is int, copy.
if constexpr (std::is_integral<Type>::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<Type>::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<Type>::value)) {
const auto address = reinterpret_cast<const uint8_t *>(target.get(name)) + offset * target_size;
#define Map(x) if(*target_type == typeid(x)) { value = static_cast<Type>(*reinterpret_cast<const x *>(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<Type>::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<const uint8_t *>(target.get(name)) + offset * target_size;
#define Map(x) if(*target_type == typeid(x)) { value = static_cast<Type>(*reinterpret_cast<const x *>(address)); }
ForAllFloats(Map);
#undef Map
return true;
}
}
return false;
}
template <typename Type> Type get(const Struct &target, const std::string &name, size_t offset) {
Type value{};
get(target, name, value, offset);
return value;
}
}