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// Copyright 2024 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef COMPONENTS_UPDATE_CLIENT_CANCELLATION_H_
#define COMPONENTS_UPDATE_CLIENT_CANCELLATION_H_
#include "base/functional/callback.h"
#include "base/functional/callback_helpers.h"
#include "base/memory/ref_counted.h"
#include "base/sequence_checker.h"
namespace update_client {
// Some update_client operations may be cancelled by the user while underway.
// When this happens, update_client conducts an orderly tear-down by
// interrupting ongoing work, and returning via the normal control flow (but
// most likely with error results instead of useful results).
//
// Depending on how much progress the operation has made, different steps may
// be required to interrupt and cancel ongoing work. A `Cancellation` is a
// container for these steps. When a function starts interruptible work, it
// should add a closure to interrupt the work to a `Cancellation` using
// `OnCancel`. When the work is completed or can no longer be interrupted, it
// should `Clear` the `Cancellation`. All functions of `Cancellation` must be
// called on the sequence on which the `Cancellation` was created.
class Cancellation : public base::RefCountedThreadSafe<Cancellation> {
public:
Cancellation();
Cancellation(const Cancellation&) = delete;
Cancellation& operator=(const Cancellation&) = delete;
// Trigger cancellation: sets the state to cancelled, and calls any closure
// registered via `OnCancel`.
void Cancel();
// Returns whether `Cancel` was previously called.
[[nodiscard]] bool IsCancelled();
// Registers a closure to be called when Cancel is called. If `Cancel` has
// already been called, a task will be posted to run the callback. Only one
// task may be registered at once.
void OnCancel(base::OnceClosure callback);
// Unregisters the cancellation callback.
void Clear();
private:
friend class base::RefCountedThreadSafe<Cancellation>;
~Cancellation();
SEQUENCE_CHECKER(sequence_checker_);
bool cancelled_ = false;
base::OnceClosure task_ = base::DoNothing();
};
} // namespace update_client
#endif // COMPONENTS_UPDATE_CLIENT_CANCELLATION_H_
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