75 lines
1.7 KiB
C++
75 lines
1.7 KiB
C++
//
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// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2019
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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#pragma once
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#include "td/utils/Status.h"
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#include <type_traits>
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#include <utility>
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namespace td {
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template <class T, bool = std::is_copy_constructible<T>::value>
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class optional {
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public:
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optional() = default;
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template <class T1,
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std::enable_if_t<!std::is_same<std::decay_t<T1>, optional>::value && std::is_constructible<T, T1>::value,
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int> = 0>
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optional(T1 &&t) : impl_(std::forward<T1>(t)) {
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}
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optional(const optional &other) {
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if (other) {
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impl_ = Result<T>(other.value());
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}
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}
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optional &operator=(const optional &other) {
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if (other) {
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impl_ = Result<T>(other.value());
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} else {
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impl_ = Result<T>();
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}
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}
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optional(optional &&other) = default;
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optional &operator=(optional &&other) = default;
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~optional() = default;
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explicit operator bool() const {
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return impl_.is_ok();
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}
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T &value() {
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return impl_.ok_ref();
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}
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const T &value() const {
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return impl_.ok_ref();
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}
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T &operator*() {
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return value();
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}
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private:
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Result<T> impl_;
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};
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template <typename T>
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struct optional<T, false> : optional<T, true> {
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optional() = default;
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using optional<T, true>::optional;
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optional(const optional &other) = delete;
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optional &operator=(const optional &other) = delete;
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optional(optional &&) = default;
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optional &operator=(optional &&) = default;
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~optional() = default;
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};
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} // namespace td
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