83786ddeaf
Also rename .visit() with .match() in MTP types. Also add base::match_method() and base::match() for base::variant. Also add base::match() and .match() for base::optional_variant.
106 lines
2.8 KiB
C++
106 lines
2.8 KiB
C++
/*
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This file is part of Telegram Desktop,
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the official desktop application for the Telegram messaging service.
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For license and copyright information please follow this link:
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https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
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*/
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#pragma once
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#include <mapbox/variant.hpp>
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#include <rpl/details/type_list.h>
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#include "base/match_method.h"
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#include "base/assertion.h"
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// We use base::variant<> alias and base::get_if() helper while we don't have std::variant<>.
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namespace base {
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template <typename... Types>
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using variant = mapbox::util::variant<Types...>;
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template <typename T, typename... Types>
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inline T *get_if(variant<Types...> *v) {
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return (v && v->template is<T>()) ? &v->template get_unchecked<T>() : nullptr;
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}
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template <typename T, typename... Types>
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inline const T *get_if(const variant<Types...> *v) {
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return (v && v->template is<T>()) ? &v->template get_unchecked<T>() : nullptr;
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}
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namespace type_list = rpl::details::type_list;
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template <typename ...Types>
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struct normalized_variant {
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using list = type_list::list<Types...>;
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using distinct = type_list::distinct_t<list>;
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using type = std::conditional_t<
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type_list::size_v<distinct> == 1,
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type_list::get_t<0, distinct>,
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type_list::extract_to_t<distinct, base::variant>>;
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};
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template <typename ...Types>
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using normalized_variant_t
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= typename normalized_variant<Types...>::type;
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template <typename TypeList, typename Variant, typename ...Methods>
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struct match_helper;
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template <
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typename Type,
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typename ...Types,
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typename Variant,
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typename ...Methods>
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struct match_helper<type_list::list<Type, Types...>, Variant, Methods...> {
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static decltype(auto) call(Variant &value, Methods &&...methods) {
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if (const auto v = get_if<Type>(&value)) {
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return match_method(
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*v,
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std::forward<Methods>(methods)...);
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}
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return match_helper<
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type_list::list<Types...>,
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Variant,
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Methods...>::call(
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value,
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std::forward<Methods>(methods)...);
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}
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};
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template <
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typename Type,
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typename Variant,
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typename ...Methods>
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struct match_helper<type_list::list<Type>, Variant, Methods...> {
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static decltype(auto) call(Variant &value, Methods &&...methods) {
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if (const auto v = get_if<Type>(&value)) {
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return match_method(
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*v,
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std::forward<Methods>(methods)...);
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}
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Unexpected("Valueless variant in base::match().");
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}
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};
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template <typename ...Types, typename ...Methods>
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inline decltype(auto) match(
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variant<Types...> &value,
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Methods &&...methods) {
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return match_helper<
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type_list::list<Types...>,
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variant<Types...>,
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Methods...>::call(value, std::forward<Methods>(methods)...);
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}
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template <typename ...Types, typename ...Methods>
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inline decltype(auto) match(
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const variant<Types...> &value,
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Methods &&...methods) {
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return match_helper<
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type_list::list<Types...>,
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const variant<Types...>,
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Methods...>::call(value, std::forward<Methods>(methods)...);
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}
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} // namespace base
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