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// Copyright 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_MESSAGE_LOOP_INCOMING_TASK_QUEUE_H_
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#define BASE_MESSAGE_LOOP_INCOMING_TASK_QUEUE_H_
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#include "base/base_export.h"
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#include "base/memory/ref_counted.h"
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#include "base/pending_task.h"
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#include "base/synchronization/lock.h"
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#include "base/time/time.h"
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// Implements a queue of tasks posted to the message loop running on the current
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// thread. This class takes care of synchronizing posting tasks from different
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// threads and together with MessageLoop ensures clean shutdown.
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class BASE_EXPORT IncomingTaskQueue
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: public RefCountedThreadSafe<IncomingTaskQueue> {
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explicit IncomingTaskQueue(MessageLoop* message_loop);
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// Appends a task to the incoming queue. Posting of all tasks is routed though
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// AddToIncomingQueue() or TryAddToIncomingQueue() to make sure that posting
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// task is properly synchronized between different threads.
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// Returns true if the task was successfully added to the queue, otherwise
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// returns false. In all cases, the ownership of |task| is transferred to the
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bool AddToIncomingQueue(const tracked_objects::Location& from_here,
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// Returns true if the message loop has high resolution timers enabled.
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// Provided for testing.
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bool IsHighResolutionTimerEnabledForTesting();
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// Returns true if the message loop is "idle". Provided for testing.
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bool IsIdleForTesting();
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// Loads tasks from the |incoming_queue_| into |*work_queue|. Must be called
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// from the thread that is running the loop.
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void ReloadWorkQueue(TaskQueue* work_queue);
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// Disconnects |this| from the parent message loop.
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void WillDestroyCurrentMessageLoop();
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friend class RefCountedThreadSafe<IncomingTaskQueue>;
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virtual ~IncomingTaskQueue();
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// Calculates the time at which a PendingTask should run.
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TimeTicks CalculateDelayedRuntime(TimeDelta delay);
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// Adds a task to |incoming_queue_|. The caller retains ownership of
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// |pending_task|, but this function will reset the value of
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// |pending_task->task|. This is needed to ensure that the posting call stack
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// does not retain |pending_task->task| beyond this function call.
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bool PostPendingTask(PendingTask* pending_task);
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TimeTicks high_resolution_timer_expiration_;
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// The lock that protects access to |incoming_queue_|, |message_loop_| and
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// |next_sequence_num_|.
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base::Lock incoming_queue_lock_;
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// An incoming queue of tasks that are acquired under a mutex for processing
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// on this instance's thread. These tasks have not yet been been pushed to
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TaskQueue incoming_queue_;
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// Points to the message loop that owns |this|.
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MessageLoop* message_loop_;
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// The next sequence number to use for delayed tasks.
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int next_sequence_num_;
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DISALLOW_COPY_AND_ASSIGN(IncomingTaskQueue);
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} // namespace internal
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#endif // BASE_MESSAGE_LOOP_INCOMING_TASK_QUEUE_H_