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74 lines
2.6 KiB
C++
74 lines
2.6 KiB
C++
// Copyright (c) 2012 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef BASE_IOS_SCOPED_CRITICAL_ACTION_H_
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#define BASE_IOS_SCOPED_CRITICAL_ACTION_H_
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#include "base/macros.h"
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#include "base/memory/ref_counted.h"
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#include "base/synchronization/lock.h"
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namespace base {
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namespace ios {
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// This class attempts to allow the application to continue to run for a period
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// of time after it transitions to the background. The construction of an
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// instance of this class marks the beginning of a task that needs background
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// running time when the application is moved to the background and the
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// destruction marks the end of such a task.
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//
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// Note there is no guarantee that the task will continue to finish when the
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// application is moved to the background.
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//
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// This class should be used at times where leaving a task unfinished might be
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// detrimental to user experience. For example, it should be used to ensure that
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// the application has enough time to save important data or at least attempt to
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// save such data.
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class ScopedCriticalAction {
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public:
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ScopedCriticalAction();
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~ScopedCriticalAction();
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private:
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// Core logic; ScopedCriticalAction should not be reference counted so
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// that it follows the normal pattern of stack-allocating ScopedFoo objects,
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// but the expiration handler needs to have a reference counted object to
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// refer to.
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class Core : public base::RefCountedThreadSafe<Core> {
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public:
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Core();
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// Informs the OS that the background task has started. This is a
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// static method to ensure that the instance has a non-zero refcount.
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static void StartBackgroundTask(scoped_refptr<Core> core);
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// Informs the OS that the background task has completed. This is a
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// static method to ensure that the instance has a non-zero refcount.
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static void EndBackgroundTask(scoped_refptr<Core> core);
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private:
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friend base::RefCountedThreadSafe<Core>;
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~Core();
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// |UIBackgroundTaskIdentifier| returned by
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// |beginBackgroundTaskWithExpirationHandler:| when marking the beginning of
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// a long-running background task. It is defined as an |unsigned int|
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// instead of a |UIBackgroundTaskIdentifier| so this class can be used in
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// .cc files.
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unsigned int background_task_id_;
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Lock background_task_id_lock_;
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DISALLOW_COPY_AND_ASSIGN(Core);
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};
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// The instance of the core that drives the background task.
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scoped_refptr<Core> core_;
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DISALLOW_COPY_AND_ASSIGN(ScopedCriticalAction);
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};
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} // namespace ios
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} // namespace base
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#endif // BASE_IOS_SCOPED_CRITICAL_ACTION_H_
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