e9d26dd7ed
The class name `coroutine` became problematic since seastar introduced it as a namespace for coroutine helpers. To avoid a clash, the class from scylla is wrapped in a separate namespace. Without this patch, Seastar submodule update fails to compile. Message-Id: <6cb91455a7ac3793bc78d161e2cb4174cf6a1606.1626949573.git.sarna@scylladb.com>
65 lines
2.0 KiB
C++
65 lines
2.0 KiB
C++
/*
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* Copyright (C) 2018-present 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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#include "seastarx.hh"
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namespace utils {
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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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} |