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Use std::function for base::lambda implementation.
(cherry picked from commit 101d4f6)
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| Original file line number | Diff line number | Diff line change |
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| /* | ||
| This file is part of Telegram Desktop, | ||
| the official desktop version of Telegram messaging app, see https://telegram.org | ||
| Telegram Desktop is free software: you can redistribute it and/or modify | ||
| it under the terms of the GNU General Public License as published by | ||
| the Free Software Foundation, either version 3 of the License, or | ||
| (at your option) any later version. | ||
| It is distributed in the hope that it will be useful, | ||
| but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | ||
| GNU General Public License for more details. | ||
| In addition, as a special exception, the copyright holders give permission | ||
| to link the code of portions of this program with the OpenSSL library. | ||
| Full license: https://github.com/telegramdesktop/tdesktop/blob/master/LICENSE | ||
| Copyright (c) 2014-2017 John Preston, https://desktop.telegram.org | ||
| */ | ||
| #pragma once | ||
|
|
||
| #include <functional> | ||
|
|
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| #ifndef Unexpected | ||
| #define Unexpected(message) std::abort() | ||
| #define UniqueFunctionUnexpected | ||
| #endif // Unexpected | ||
|
|
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| namespace base { | ||
| namespace details { | ||
|
|
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| template <typename Callable> class moveable_callable_wrap { | ||
| public: | ||
| static_assert(std::is_move_constructible_v<Callable>, "Should be at least moveable."); | ||
|
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| moveable_callable_wrap(Callable &&other) | ||
| : _value(std::move(other)) {} | ||
| moveable_callable_wrap &operator=(Callable &&other) { | ||
| _value = std::move(other); | ||
| return *this; | ||
| } | ||
| moveable_callable_wrap(moveable_callable_wrap &&other) | ||
| : _value(std::move(other._value)) {} | ||
| moveable_callable_wrap(const moveable_callable_wrap &other) | ||
| : _value(fail_construct()) {} | ||
| moveable_callable_wrap &operator=(moveable_callable_wrap &&other) { | ||
| _value = std::move(other._value); | ||
| return *this; | ||
| } | ||
| moveable_callable_wrap &operator=(const moveable_callable_wrap &other) { | ||
| return fail_assign(); | ||
| } | ||
|
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| template <typename... Args> decltype(auto) operator()(Args &&... args) const { | ||
| return _value(std::forward<Args>(args)...); | ||
| } | ||
|
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| private: | ||
| [[noreturn]] Callable fail_construct() { | ||
| Unexpected("Attempt to copy-construct a move-only type."); | ||
| }[[noreturn]] moveable_callable_wrap &fail_assign() { | ||
| Unexpected("Attempt to copy-assign a move-only type."); | ||
| } | ||
|
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| mutable Callable _value; | ||
| }; | ||
|
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| } // namespace details | ||
|
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| template <typename Function> class unique_function; | ||
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| template <typename Return, typename... Args> class unique_function<Return(Args...)> final { | ||
| public: | ||
| unique_function(std::nullptr_t = nullptr) noexcept {} | ||
| unique_function(const unique_function &other) = delete; | ||
| unique_function &operator=(const unique_function &other) = delete; | ||
|
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| // Move construct / assign from the same type. | ||
| unique_function(unique_function &&other) | ||
| : _impl(std::move(other._impl)) {} | ||
| unique_function &operator=(unique_function &&other) { | ||
| _impl = std::move(other._impl); | ||
| return *this; | ||
| } | ||
|
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| template <typename Callable, typename = std::enable_if_t<std::is_convertible_v< | ||
| decltype(std::declval<Callable>()(std::declval<Args>()...)), Return>>> | ||
| unique_function(Callable &&other) | ||
| : unique_function(std::forward<Callable>(other), std::is_copy_constructible<std::decay_t<Callable>>{}) {} | ||
|
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| template <typename Callable, typename = std::enable_if_t<std::is_convertible_v< | ||
| decltype(std::declval<Callable>()(std::declval<Args>()...)), Return>>> | ||
| unique_function &operator=(Callable &&other) { | ||
| using Decayed = std::decay_t<Callable>; | ||
| if constexpr (std::is_copy_constructible_v<Decayed>) { | ||
| _impl = std::forward<Callable>(other); | ||
| } else if constexpr (std::is_move_constructible_v<Decayed>) { | ||
| _impl = details::moveable_callable_wrap<Decayed>(std::forward<Callable>(other)); | ||
| } else { | ||
| static_assert(false_t(other), "Should be moveable."); | ||
| } | ||
| return *this; | ||
| } | ||
|
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| void swap(unique_function &other) { | ||
| _impl.swap(other._impl); | ||
| } | ||
|
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| template <typename... OtherArgs> Return operator()(OtherArgs &&... args) { | ||
| return _impl(std::forward<OtherArgs>(args)...); | ||
| } | ||
|
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| explicit operator bool() const { | ||
| return _impl.operator bool(); | ||
| } | ||
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| friend inline bool operator==(const unique_function &value, std::nullptr_t) noexcept { | ||
| return value._impl == nullptr; | ||
| } | ||
| friend inline bool operator==(std::nullptr_t, const unique_function &value) noexcept { | ||
| return value._impl == nullptr; | ||
| } | ||
| friend inline bool operator!=(const unique_function &value, std::nullptr_t) noexcept { | ||
| return value._impl != nullptr; | ||
| } | ||
| friend inline bool operator!=(std::nullptr_t, const unique_function &value) noexcept { | ||
| return value._impl != nullptr; | ||
| } | ||
|
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| private: | ||
| template <typename Callable> | ||
| unique_function(Callable &&other, std::true_type) | ||
| : _impl(std::forward<Callable>(other)) {} | ||
|
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| template <typename Callable> | ||
| unique_function(Callable &&other, std::false_type) | ||
| : _impl(details::moveable_callable_wrap<std::decay_t<Callable>>(std::forward<Callable>(other))) {} | ||
|
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| std::function<Return(Args...)> _impl; | ||
| }; | ||
|
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| } // namespace base | ||
|
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| #ifdef UniqueFunctionUnexpected | ||
| #undef UniqueFunctionUnexpected | ||
| #undef Unexpected | ||
| #endif // UniqueFunctionUnexpectedb |
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