67 lines
2.0 KiB
C
67 lines
2.0 KiB
C
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// Copyright 2021 The Chromium Authors
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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_TASK_SEQUENCE_MANAGER_FENCE_H_
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#define BASE_TASK_SEQUENCE_MANAGER_FENCE_H_
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#include "base/base_export.h"
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#include "base/task/sequence_manager/enqueue_order.h"
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#include "base/task/sequence_manager/task_order.h"
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namespace base {
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class TimeTicks;
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namespace sequence_manager {
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namespace internal {
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class TaskQueueImpl;
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// `Fence`s are used to prevent the execution of tasks starting with a
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// particular `TaskOrder`, such that for a `Task` and a `Fence`, if
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// task.task_order() >= fence.task_order(), then the task is blocked from
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// running. Blocking fences are a special kind of fence that have a `TaskOrder`
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// less than that of any `Task`.
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class BASE_EXPORT Fence {
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public:
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// Creates a `Fence` with the same `TaskOrder` as `task_order`, which is
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// useful for creating a fence relative to a particular `Task`.
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// `task_order.enqueue_order()` must be "set", i.e. it cannot be
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// `EnqueueOrder::none()`.
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explicit Fence(const TaskOrder& task_order);
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Fence(const Fence& other);
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Fence& operator=(const Fence& other);
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~Fence();
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// Creates a blocking fence which has a `TaskOrder` that is less than that of
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// all tasks.
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static Fence BlockingFence();
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const TaskOrder& task_order() const { return task_order_; }
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// Returns true iff this is a blocking fence.
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bool IsBlockingFence() const {
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return task_order_.enqueue_order() == EnqueueOrder::blocking_fence();
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}
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private:
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friend class TaskQueueImpl; // For `CreateWithEnqueueOrder()`.
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Fence(EnqueueOrder enqueue_order,
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TimeTicks delayed_run_time,
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int sequence_num);
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// Creates a `Fence` with `enqueue_order` and a null delayed run time.
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// `enqueue_order` cannot be EnqueueOrder::none().
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static Fence CreateWithEnqueueOrder(EnqueueOrder enqueue_order);
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TaskOrder task_order_;
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};
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} // namespace internal
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} // namespace sequence_manager
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} // namespace base
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#endif // BASE_TASK_SEQUENCE_MANAGER_FENCE_H_
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