98 lines
3.2 KiB
C
98 lines
3.2 KiB
C
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// Copyright (c) 2013 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_DEFERRED_SEQUENCED_TASK_RUNNER_H_
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#define BASE_DEFERRED_SEQUENCED_TASK_RUNNER_H_
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#include <vector>
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#include "base/base_export.h"
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#include "base/callback.h"
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#include "base/compiler_specific.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/sequenced_task_runner.h"
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#include "base/synchronization/lock.h"
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#include "base/threading/platform_thread.h"
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#include "base/time/time.h"
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namespace base {
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// A DeferredSequencedTaskRunner is a subclass of SequencedTaskRunner that
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// queues up all requests until the first call to Start() is issued.
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// DeferredSequencedTaskRunner may be created in two ways:
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// . with an explicit SequencedTaskRunner that the events are flushed to
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// . without a SequencedTaskRunner. In this configuration the
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// SequencedTaskRunner is supplied in StartWithTaskRunner().
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class BASE_EXPORT DeferredSequencedTaskRunner : public SequencedTaskRunner {
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public:
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explicit DeferredSequencedTaskRunner(
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scoped_refptr<SequencedTaskRunner> target_runner);
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// Use this constructor when you don't have the target SequencedTaskRunner.
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// When using this call StartWithTaskRunner().
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DeferredSequencedTaskRunner();
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// TaskRunner implementation
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bool PostDelayedTask(const Location& from_here,
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OnceClosure task,
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TimeDelta delay) override;
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bool RunsTasksInCurrentSequence() const override;
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// SequencedTaskRunner implementation
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bool PostNonNestableDelayedTask(const Location& from_here,
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OnceClosure task,
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TimeDelta delay) override;
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// Start the execution - posts all queued tasks to the target executor. The
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// deferred tasks are posted with their initial delay, meaning that the task
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// execution delay is actually measured from Start.
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// Fails when called a second time.
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void Start();
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// Same as Start(), but must be used with the no-arg constructor.
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void StartWithTaskRunner(
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scoped_refptr<SequencedTaskRunner> target_task_runner);
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private:
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struct DeferredTask {
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DeferredTask();
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DeferredTask(DeferredTask&& other);
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~DeferredTask();
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DeferredTask& operator=(DeferredTask&& other);
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Location posted_from;
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OnceClosure task;
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// The delay this task was initially posted with.
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TimeDelta delay;
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bool is_non_nestable;
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};
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~DeferredSequencedTaskRunner() override;
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// Both variants of Start() call into this.
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void StartImpl();
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// Creates a |Task| object and adds it to |deferred_tasks_queue_|.
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void QueueDeferredTask(const Location& from_here,
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OnceClosure task,
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TimeDelta delay,
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bool is_non_nestable);
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// // Protects |started_| and |deferred_tasks_queue_|.
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mutable Lock lock_;
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const PlatformThreadId created_thread_id_;
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bool started_ = false;
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scoped_refptr<SequencedTaskRunner> target_task_runner_;
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std::vector<DeferredTask> deferred_tasks_queue_;
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DISALLOW_COPY_AND_ASSIGN(DeferredSequencedTaskRunner);
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};
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} // namespace base
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#endif // BASE_DEFERRED_SEQUENCED_TASK_RUNNER_H_
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