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ton/tdutils/td/utils/optional.h

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2019-09-07 12:03:22 +02:00
/*
This file is part of TON Blockchain Library.
TON Blockchain Library is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation, either version 2 of the License, or
(at your option) any later version.
TON Blockchain Library 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 Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with TON Blockchain Library. If not, see <http://www.gnu.org/licenses/>.
Copyright 2017-2019 Telegram Systems LLP
*/
#pragma once
#include "td/utils/common.h"
#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>();
}
return *this;
}
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();
}
T unwrap() {
CHECK(*this);
auto res = std::move(value());
impl_ = {};
return res;
}
template <class... ArgsT>
void emplace(ArgsT &&... args) {
impl_.emplace(std::forward<ArgsT>(args)...);
}
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