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4e21cedc0f
Add a convenient function do_with(rvalue, func) which ensures that a (moved copy of) rvalue will live until the future returned by func concludes, and that func is passed this object. Needing to do this is a recurring idiom in Seastar applications. Signed-off-by: Nadav Har'El <nyh@cloudius-systems.com> [avi: mark inline]
49 lines
1.8 KiB
C++
49 lines
1.8 KiB
C++
/*
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* This file is open source software, licensed to you under the terms
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* of the Apache License, Version 2.0 (the "License"). See the NOTICE file
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* distributed with this work for additional information regarding copyright
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* ownership. You may not use this file except in compliance with the License.
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*
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing,
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* software distributed under the License is distributed on an
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* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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* KIND, either express or implied. See the License for the
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* specific language governing permissions and limitations
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* under the License.
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*/
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/*
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* Copyright (C) 2015 Cloudius Systems, Ltd.
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*/
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#pragma once
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#include <utility>
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#include <memory>
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// do_with() holds an object alive for the duration until a future
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// completes, and allow the code involved in making the future
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// complete to have easy access to this object.
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//
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// do_with() takes two arguments: The first is an temporary object (rvalue),
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// the second is a function returning a future (a so-called "promise").
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// The function is given (a moved copy of) this temporary object, by
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// reference, and it is ensured that the object will not be destructed until
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// the completion of the future returned by the function.
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//
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// do_with() returns a future which resolves to whatever value the given future
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// (returned by the given function) resolves to. This returned value must not
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// contain references to the temporary object, as at that point the temporary
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// is destructed.
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template<typename T, typename F>
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inline
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auto do_with(T&& rvalue, F&& f) {
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auto obj = std::make_unique<T>(std::forward<T>(rvalue));
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auto fut = f(*obj);
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return fut.finally([obj = std::move(obj)] () {});
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}
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