156 lines
3.8 KiB
C++
156 lines
3.8 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 <rpl/producer.h>
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#include <rpl/event_stream.h>
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namespace mapbox {
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namespace util {
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template <typename ...Types>
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class variant;
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} // namespace util
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} // namespace mapbox
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namespace rpl {
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namespace details {
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template <typename A, typename B>
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struct supports_equality_compare {
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template <typename U, typename V>
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static auto test(const U *u, const V *v)
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-> decltype(*u == *v, true_t());
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static false_t test(...);
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static constexpr bool value
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= (sizeof(test((const A*)nullptr, (const B*)nullptr))
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== sizeof(true_t));
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};
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// Fix for MSVC expression SFINAE.
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// It still doesn't work! :(
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//
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//template <typename Type1, typename ...Types1>
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//struct supports_equality_compare<
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// mapbox::util::variant<Type1, Types1...>,
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// mapbox::util::variant<Type1, Types1...>> {
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// static constexpr bool value
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// = (supports_equality_compare<Type1, Type1>::value
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// && supports_equality_compare<
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// mapbox::util::variant<Types1...>,
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// mapbox::util::variant<Types1...>>::value);
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//
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//};
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//template <typename Type>
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//struct supports_equality_compare<
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// mapbox::util::variant<Type>,
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// mapbox::util::variant<Type>> {
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// static constexpr bool value = supports_equality_compare<Type, Type>::value;
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//
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//};
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template <typename A, typename B>
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constexpr bool supports_equality_compare_v
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= supports_equality_compare<std::decay_t<A>, std::decay_t<B>>::value;
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} // namespace details
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template <typename Type>
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class variable final {
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public:
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variable() : _data{} {
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}
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variable(variable &&other) : _data(std::move(other._data)) {
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}
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variable &operator=(variable &&other) {
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return (*this = std::move(other._data));
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}
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template <
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typename OtherType,
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typename = std::enable_if_t<
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std::is_constructible_v<Type, OtherType&&>>>
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variable(OtherType &&data) : _data(std::forward<OtherType>(data)) {
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}
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template <
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typename OtherType,
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typename = std::enable_if_t<
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std::is_assignable_v<Type&, OtherType&&>>>
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variable &operator=(OtherType &&data) {
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_lifetime.destroy();
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return assign(std::forward<OtherType>(data));
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}
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template <
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typename OtherType,
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typename Error,
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typename Generator,
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typename = std::enable_if_t<
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std::is_assignable_v<Type&, OtherType>>>
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variable(producer<OtherType, Error, Generator> &&stream) {
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std::move(stream)
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| start_with_next([this](auto &&data) {
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assign(std::forward<decltype(data)>(data));
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}, _lifetime);
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}
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template <
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typename OtherType,
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typename Error,
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typename Generator,
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typename = std::enable_if_t<
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std::is_assignable_v<Type&, OtherType>>>
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variable &operator=(
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producer<OtherType, Error, Generator> &&stream) {
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_lifetime.destroy();
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std::move(stream)
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| start_with_next([this](auto &&data) {
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assign(std::forward<decltype(data)>(data));
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}, _lifetime);
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}
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Type current() const {
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return _data;
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}
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auto value() const {
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return _changes.events_starting_with_copy(_data);
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}
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auto changes() const {
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return _changes.events();
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}
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private:
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template <typename OtherType>
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variable &assign(OtherType &&data) {
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if constexpr (details::supports_equality_compare_v<Type, OtherType>) {
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if (!(_data == data)) {
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_data = std::forward<OtherType>(data);
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_changes.fire_copy(_data);
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}
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} else if constexpr (details::supports_equality_compare_v<Type, Type>) {
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auto old = std::move(_data);
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_data = std::forward<OtherType>(data);
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if (!(_data == old)) {
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_changes.fire_copy(_data);
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}
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} else {
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_data = std::forward<OtherType>(data);
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_changes.fire_copy(_data);
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}
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return *this;
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}
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Type _data;
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event_stream<Type> _changes;
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lifetime _lifetime;
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};
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} // namespace rpl
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