closeable.hh

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/*
 * This file is open source software, licensed to you under the terms
 * of the Apache License, Version 2.0 (the "License").  See the NOTICE file
 * distributed with this work for additional information regarding copyright
 * ownership.  You may not use this file except in compliance with the License.
 *
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
/*
 * Copyright (C) 2021 Cloudius Systems, Ltd.
 */
 
#pragma once
 
#include <functional>
#include <seastar/core/future.hh>
#include <seastar/util/concepts.hh>
#include <seastar/util/defer.hh>
 
 
 
namespace seastar {
 
SEASTAR_CONCEPT(
template <typename Object>
concept closeable = requires (Object o) {
    { o.close() } SEASTAR_DEFERRED_ACTION_NOEXCEPT -> std::same_as<future<>>;
};
)
 
template <typename Object>
SEASTAR_CONCEPT( requires closeable<Object> )
class [[nodiscard]] deferred_close {
    std::reference_wrapper<Object> _obj;
    bool _closed = false;
 
    void do_close() noexcept {
        if (!_closed) {
            _closed = true;
            _obj.get().close().get();
        }
    }
public:
    deferred_close(Object& obj) noexcept : _obj(obj) {}
    deferred_close(deferred_close&& x) noexcept : _obj(x._obj), _closed(std::exchange(x._closed, true)) {}
    deferred_close(const deferred_close&) = delete;
    deferred_close& operator=(deferred_close&& x) noexcept {
        do_close();
        _obj = x._obj;
        _closed = std::exchange(x._closed, true);
        return *this;
    }
    ~deferred_close() {
        do_close();
    }
    void close_now() noexcept {
        assert(!_closed);
        do_close();
    }
 
    void cancel() noexcept {
        _closed = true;
    }
};
 
template <typename Closeable, typename Func>
SEASTAR_CONCEPT(
requires closeable<Closeable> && std::invocable<Func, Closeable&> &&
        std::is_nothrow_move_constructible_v<Closeable> && std::is_nothrow_move_constructible_v<Func>
)
inline futurize_t<std::invoke_result_t<Func, Closeable&>>
with_closeable(Closeable&& obj, Func func) noexcept {
    return do_with(std::move(obj), [func = std::move(func)] (Closeable& obj) mutable {
        return futurize_invoke(func, obj).finally([&obj] {
            return obj.close();
        });
    });
}
 
SEASTAR_CONCEPT(
template <typename Object>
concept stoppable = requires (Object o) {
    { o.stop() } SEASTAR_DEFERRED_ACTION_NOEXCEPT -> std::same_as<future<>>;
};
)
 
template <typename Object>
SEASTAR_CONCEPT( requires stoppable<Object> )
class [[nodiscard]] deferred_stop {
    std::reference_wrapper<Object> _obj;
    bool _stopped = false;
 
    void do_stop() noexcept {
        if (!_stopped) {
            _stopped = true;
            _obj.get().stop().get();
        }
    }
public:
    deferred_stop(Object& obj) noexcept : _obj(obj) {}
    deferred_stop(deferred_stop&& x) noexcept : _obj(x._obj), _stopped(std::exchange(x._stopped, true)) {}
    deferred_stop(const deferred_stop&) = delete;
    deferred_stop& operator=(deferred_stop&& x) noexcept {
        do_stop();
        _obj = x._obj;
        _stopped = std::exchange(x._stopped, true);
        return *this;
    }
    ~deferred_stop() {
        do_stop();
    }
    void stop_now() noexcept {
        assert(!_stopped);
        do_stop();
    }
 
    void cancel() noexcept {
        _stopped = true;
    }
};
 
template <typename Stoppable, typename Func>
SEASTAR_CONCEPT(
requires stoppable<Stoppable> && std::invocable<Func, Stoppable&> &&
        std::is_nothrow_move_constructible_v<Stoppable> && std::is_nothrow_move_constructible_v<Func>
)
inline futurize_t<std::invoke_result_t<Func, Stoppable&>>
with_stoppable(Stoppable&& obj, Func func) noexcept {
    return do_with(std::move(obj), [func = std::move(func)] (Stoppable& obj) mutable {
        return futurize_invoke(func, obj).finally([&obj] {
            return obj.stop();
        });
    });
}
 
} // namespace seastar