[new lib]add reflection lib (#717)

NOTICE

@@ -28,5 +28,5 @@ Distributed under the Boost Software License, Version 1.0. (See accompanying
 file LICENSE_1_0.txt or copy at <http://www.boost.org/LICENSE_1_0.txt>)
 
 ===================================================================
-The reflection of a struct and data format borrow various ideas from zpp_bits and msgpack.
+The reflection of a struct and data format borrow various ideas from zpp_bits, reflect-cpp and msgpack.
 coro_rpc borrow various ideas from rest_rpc.

include/ylt/reflection/member_count.hpp

@@ -0,0 +1,141 @@
+
+#pragma once
+#include <optional>
+#include <tuple>
+#include <type_traits>
+#include <vector>
+
+namespace ylt::reflection {
+namespace internal {
+#if __cpp_concepts >= 201907L
+template <typename Type>
+concept tuple_size = requires(Type tuple) {
+  std::tuple_size<std::remove_cvref_t<Type>>::value;
+};
+#else
+template <typename T, typename = void>
+struct tuple_size_impl : std::false_type {};
+
+template <typename T>
+struct tuple_size_impl<
+    T, std::void_t<decltype(std::tuple_size<remove_cvref_t<T>>::value)>>
+    : std::true_type {};
+
+template <typename T>
+constexpr bool tuple_size = tuple_size_impl<T>::value;
+#endif
+
+#if __cpp_concepts >= 201907L
+template <typename Type>
+concept optional = requires(Type optional) {
+  optional.value();
+  optional.has_value();
+  optional.operator*();
+  typename std::remove_cvref_t<Type>::value_type;
+};
+#else
+template <typename T, typename = void>
+struct optional_impl : std::false_type {};
+
+template <typename T>
+struct optional_impl<T, std::void_t<decltype(std::declval<T>().value()),
+                                    decltype(std::declval<T>().has_value()),
+                                    decltype(std::declval<T>().operator*()),
+                                    typename remove_cvref_t<T>::value_type>>
+    : std::true_type {};
+
+template <typename T>
+constexpr bool optional = !expected<T> && optional_impl<T>::value;
+#endif
+
+template <typename T, uint64_t version = 0>
+struct compatible;
+
+template <typename Type>
+constexpr inline bool is_compatible_v = false;
+
+template <typename Type, uint64_t version>
+constexpr inline bool is_compatible_v<compatible<Type, version>> = true;
+
+struct UniversalVectorType {
+  template <typename T>
+  operator std::vector<T>();
+};
+
+struct UniversalType {
+  template <typename T>
+  operator T();
+};
+
+struct UniversalIntegralType {
+  template <typename T, typename = std::enable_if_t<std::is_integral_v<T>>>
+  operator T();
+};
+
+struct UniversalNullptrType {
+  operator std::nullptr_t();
+};
+
+struct UniversalOptionalType {
+  template <typename U, typename = std::enable_if_t<optional<U>>>
+  operator U();
+};
+
+struct UniversalCompatibleType {
+  template <typename U, typename = std::enable_if_t<is_compatible_v<U>>>
+  operator U();
+};
+
+template <typename T, typename construct_param_t, typename = void,
+          typename... Args>
+struct is_constructable_impl : std::false_type {};
+template <typename T, typename construct_param_t, typename... Args>
+struct is_constructable_impl<
+    T, construct_param_t,
+    std::void_t<decltype(T{{Args{}}..., {construct_param_t{}}})>, Args...>
+    : std::true_type {};
+
+template <typename T, typename construct_param_t, typename... Args>
+constexpr bool is_constructable =
+    is_constructable_impl<T, construct_param_t, void, Args...>::value;
+
+template <typename T, typename... Args>
+inline constexpr std::size_t members_count_impl() {
+  if constexpr (is_constructable<T, UniversalVectorType, Args...>) {
+    return members_count_impl<T, Args..., UniversalVectorType>();
+  }
+  else if constexpr (is_constructable<T, UniversalType, Args...>) {
+    return members_count_impl<T, Args..., UniversalType>();
+  }
+  else if constexpr (is_constructable<T, UniversalOptionalType, Args...>) {
+    return members_count_impl<T, Args..., UniversalOptionalType>();
+  }
+  else if constexpr (is_constructable<T, UniversalIntegralType, Args...>) {
+    return members_count_impl<T, Args..., UniversalIntegralType>();
+  }
+  else if constexpr (is_constructable<T, UniversalNullptrType, Args...>) {
+    return members_count_impl<T, Args..., UniversalNullptrType>();
+  }
+  else if constexpr (is_constructable<T, UniversalCompatibleType, Args...>) {
+    return members_count_impl<T, Args..., UniversalCompatibleType>();
+  }
+  else {
+    return sizeof...(Args);
+  }
+}
+}  // namespace internal
+
+template <typename T>
+inline constexpr std::size_t members_count() {
+  using type = std::remove_cvref_t<T>;
+  if constexpr (internal::tuple_size<type>) {
+    return std::tuple_size<type>::value;
+  }
+  else {
+    return internal::members_count_impl<type>();
+  }
+}
+
+template <typename T>
+constexpr std::size_t members_count_v = members_count<T>();
+}  // namespace ylt::reflection

include/ylt/reflection/member_names.hpp

@@ -0,0 +1,174 @@
+#pragma once
+#include <string_view>
+#include <variant>
+
+#include "template_string.hpp"
+#if __has_include(<concepts>) || defined(__clang__) || defined(_MSC_VER) || \
+    (defined(__GNUC__) && __GNUC__ > 10)
+#include "member_ptr.hpp"
+
+namespace ylt::reflection {
+
+namespace internal {
+
+template <class T>
+struct Wrapper {
+  using Type = T;
+  T v;
+};
+
+template <class T>
+Wrapper(T) -> Wrapper<T>;
+
+// This workaround is necessary for clang.
+template <class T>
+inline constexpr auto wrap(const T& arg) noexcept {
+  return Wrapper{arg};
+}
+
+template <auto ptr>
+inline constexpr std::string_view get_member_name() {
+#if defined(_MSC_VER)
+  constexpr std::string_view func_name = __FUNCSIG__;
+#else
+  constexpr std::string_view func_name = __PRETTY_FUNCTION__;
+#endif
+
+#if defined(__clang__)
+  auto split = func_name.substr(0, func_name.size() - 2);
+  return split.substr(split.find_last_of(":.") + 1);
+#elif defined(__GNUC__)
+  auto split = func_name.substr(0, func_name.rfind(")}"));
+  return split.substr(split.find_last_of(":") + 1);
+#elif defined(_MSC_VER)
+  auto split = func_name.substr(0, func_name.rfind("}>"));
+  return split.substr(split.rfind("->") + 2);
+#else
+  static_assert(false,
+                "You are using an unsupported compiler. Please use GCC, Clang "
+                "or MSVC or switch to the rfl::Field-syntax.");
+#endif
+}
+}  // namespace internal
+
+template <typename T>
+inline constexpr std::array<std::string_view, members_count_v<T>>
+get_member_names() {
+  constexpr size_t Count = members_count_v<T>;
+  constexpr auto tp = struct_to_tuple<T>();
+
+  std::array<std::string_view, Count> arr;
+  [&]<size_t... Is>(std::index_sequence<Is...>) mutable {
+    ((arr[Is] = internal::get_member_name<internal::wrap(std::get<Is>(tp))>()),
+     ...);
+  }
+  (std::make_index_sequence<Count>{});
+  return arr;
+}
+
+template <typename... Args>
+inline constexpr auto tuple_to_variant(std::tuple<Args...>) {
+  return std::variant<std::add_pointer_t<Args>...>{};
+}
+
+template <typename T>
+using struct_variant_t = decltype(tuple_to_variant(
+    std::declval<decltype(struct_to_tuple<std::remove_cvref_t<T>>())>));
+
+template <typename T>
+inline const auto& get_member_offset_arr() {
+  constexpr size_t Count = members_count_v<T>;
+  constexpr auto tp = struct_to_tuple<T>();
+
+  [[maybe_unused]] static std::array<size_t, Count> arr = {[&]<size_t... Is>(
+      std::index_sequence<Is...>) mutable {std::array<size_t, Count> arr;
+  ((arr[Is] = size_t((const char*)std::get<Is>(tp) -
+                     (char*)(&internal::wrapper<T>::value))),
+   ...);
+  return arr;
+}
+(std::make_index_sequence<Count>{})
+};  // namespace ylt::reflection
+
+return arr;
+}
+
+template <typename T>
+inline constexpr auto get_member_names_map() {
+  constexpr auto name_arr = get_member_names<T>();
+  return [&]<size_t... Is>(std::index_sequence<Is...>) mutable {
+    return frozen::unordered_map<frozen::string, size_t, name_arr.size()>{
+        {name_arr[Is], Is}...};
+  }
+  (std::make_index_sequence<name_arr.size()>{});
+}
+
+template <std::size_t N>
+struct FixedString {
+  char data[N];
+  template <std::size_t... I>
+  constexpr FixedString(const char (&s)[N], std::index_sequence<I...>)
+      : data{s[I]...} {}
+  constexpr FixedString(const char (&s)[N])
+      : FixedString(s, std::make_index_sequence<N>()) {}
+  constexpr std::string_view str() const {
+    return std::string_view{data, N - 1};
+  }
+};
+
+template <typename T>
+inline constexpr size_t index_of(std::string_view name) {
+  constexpr auto arr = get_member_names<T>();
+  for (size_t i = 0; i < arr.size(); i++) {
+    if (arr[i] == name) {
+      return i;
+    }
+  }
+
+  return arr.size();
+}
+
+template <typename T, FixedString name>
+inline constexpr size_t index_of() {
+  return index_of<T>(name.str());
+}
+
+template <typename T, size_t index>
+inline constexpr std::string_view name_of() {
+  static_assert(index < members_count_v<T>, "index out of range");
+  constexpr auto arr = get_member_names<T>();
+  return arr[index];
+}
+
+template <typename T>
+inline constexpr std::string_view name_of(size_t index) {
+  constexpr auto arr = get_member_names<T>();
+  if (index >= arr.size()) {
+    return "";
+  }
+
+  return arr[index];
+}
+
+template <typename T, typename Visit>
+inline constexpr void for_each(Visit func) {
+  constexpr auto arr = get_member_names<T>();
+  [&]<size_t... Is>(std::index_sequence<Is...>) mutable {
+    if constexpr (std::is_invocable_v<Visit, std::string_view, size_t>) {
+      (func(arr[Is], Is), ...);
+    }
+    else if constexpr (std::is_invocable_v<Visit, std::string_view>) {
+      (func(arr[Is]), ...);
+    }
+    else {
+      static_assert(sizeof(Visit) < 0,
+                    "invalid arguments, full arguments: [std::string_view, "
+                    "size_t], at least has std::string_view and make sure keep "
+                    "the order of arguments");
+    }
+  }
+  (std::make_index_sequence<arr.size()>{});
+}
+
+}  // namespace ylt::reflection
+#endif