a19c5cbc16
Represents a deferring operation which defers cooperatively with the caller.
The operation is started and resumed by calling run(), which returns
with stop_iteration::no whenever the operation defers and is not
completed yet. When the operation is finally complete, run() returns
with stop_iteration::yes.
This allows the caller to:
1) execute some post-defer and pre-resume actions atomically
2) have control over when the operation is resumed and in which context,
in particular the caller can cancel the operation at deferring points.
It will be used to implement deferring partition_version::apply_to_incomplete().
60 lines
2.0 KiB
C++
60 lines
2.0 KiB
C++
/*
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* Copyright (C) 2018 ScyllaDB
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*/
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/*
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* This file is part of Scylla.
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*
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* Scylla is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* Scylla is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with Scylla. If not, see <http://www.gnu.org/licenses/>.
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*/
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#pragma once
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#include <functional>
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#include <seastar/core/future-util.hh>
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#include <seastar/util/noncopyable_function.hh>
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// Represents a deferring operation which defers cooperatively with the caller.
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//
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// The operation is started and resumed by calling run(), which returns
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// with stop_iteration::no whenever the operation defers and is not completed yet.
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// When the operation is finally complete, run() returns with stop_iteration::yes.
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// After that, run() should not be invoked any more.
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//
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// This allows the caller to:
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// 1) execute some post-defer and pre-resume actions atomically
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// 2) have control over when the operation is resumed and in which context,
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// in particular the caller can cancel the operation at deferring points.
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//
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// One simple way to drive the operation to completion:
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//
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// coroutine c;
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// while (c.run() == stop_iteartion::no) {}
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//
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class coroutine final {
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public:
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coroutine() = default;
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coroutine(noncopyable_function<stop_iteration()> f) : _run(std::move(f)) {}
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stop_iteration run() { return _run(); }
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explicit operator bool() const { return bool(_run); }
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private:
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noncopyable_function<stop_iteration()> _run;
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};
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// Makes a coroutine which does nothing.
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inline
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coroutine make_empty_coroutine() {
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return coroutine([] { return stop_iteration::yes; });
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}
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