7215d4bfe9
these unused includes were identifier by clang-include-cleaner. after auditing these source files, all of the reports have been confirmed. please note, because quite a few source files relied on `utils/to_string.hh` to pull in the specialization of `fmt::formatter<std::optional<T>>`, after removing `#include <fmt/std.h>` from `utils/to_string.hh`, we have to include `fmt/std.h` directly. Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
52 lines
1.4 KiB
C++
52 lines
1.4 KiB
C++
/*
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* Copyright (C) 2018-present ScyllaDB
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*/
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/*
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* SPDX-License-Identifier: LicenseRef-ScyllaDB-Source-Available-1.0
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*/
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#pragma once
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#include <seastar/core/loop.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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}
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