fcb8d040e8
Instead of lengthy blurbs, switch to single-line, machine-readable standardized (https://spdx.dev) license identifiers. The Linux kernel switched long ago, so there is strong precedent. Three cases are handled: AGPL-only, Apache-only, and dual licensed. For the latter case, I chose (AGPL-3.0-or-later and Apache-2.0), reasoning that our changes are extensive enough to apply our license. The changes we applied mechanically with a script, except to licenses/README.md. Closes #9937
52 lines
1.4 KiB
C++
52 lines
1.4 KiB
C++
/*
|
|
* Copyright (C) 2018-present ScyllaDB
|
|
*/
|
|
|
|
/*
|
|
* SPDX-License-Identifier: AGPL-3.0-or-later
|
|
*/
|
|
|
|
#pragma once
|
|
|
|
#include <functional>
|
|
#include <seastar/core/future-util.hh>
|
|
#include <seastar/util/noncopyable_function.hh>
|
|
|
|
#include "seastarx.hh"
|
|
|
|
namespace utils {
|
|
|
|
// 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.
|
|
// After that, run() should not be invoked any more.
|
|
//
|
|
// 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.
|
|
//
|
|
// One simple way to drive the operation to completion:
|
|
//
|
|
// coroutine c;
|
|
// while (c.run() == stop_iteartion::no) {}
|
|
//
|
|
class coroutine final {
|
|
public:
|
|
coroutine() = default;
|
|
coroutine(noncopyable_function<stop_iteration()> f) : _run(std::move(f)) {}
|
|
stop_iteration run() { return _run(); }
|
|
explicit operator bool() const { return bool(_run); }
|
|
private:
|
|
noncopyable_function<stop_iteration()> _run;
|
|
};
|
|
|
|
// Makes a coroutine which does nothing.
|
|
inline
|
|
coroutine make_empty_coroutine() {
|
|
return coroutine([] { return stop_iteration::yes; });
|
|
}
|
|
|
|
} |