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tdlib-fork/tdutils/td/utils/optional.h

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//
// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2019
//
// 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)
//
#pragma once
#include "td/utils/Status.h"
#include <type_traits>
#include <utility>
namespace td {
template <class T, bool = std::is_copy_constructible<T>::value>
class optional {
public:
optional() = default;
template <class T1,
std::enable_if_t<!std::is_same<std::decay_t<T1>, optional>::value && std::is_constructible<T, T1>::value,
int> = 0>
optional(T1 &&t) : impl_(std::forward<T1>(t)) {
}
optional(const optional &other) {
if (other) {
impl_ = Result<T>(other.value());
}
}
optional &operator=(const optional &other) {
if (other) {
impl_ = Result<T>(other.value());
} else {
impl_ = Result<T>();
}
}
optional(optional &&other) = default;
optional &operator=(optional &&other) = default;
~optional() = default;
explicit operator bool() const {
return impl_.is_ok();
}
T &value() {
return impl_.ok_ref();
}
const T &value() const {
return impl_.ok_ref();
}
T &operator*() {
return value();
}
private:
Result<T> impl_;
};
template <typename T>
struct optional<T, false> : optional<T, true> {
optional() = default;
using optional<T, true>::optional;
optional(const optional &other) = delete;
optional &operator=(const optional &other) = delete;
optional(optional &&) = default;
optional &operator=(optional &&) = default;
~optional() = default;
};
} // namespace td