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// Copyright 2018 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef BASE_TASK_SEQUENCE_MANAGER_TASKS_H_
#define BASE_TASK_SEQUENCE_MANAGER_TASKS_H_
#include "base/pending_task.h"
#include "base/sequenced_task_runner.h"
#include "base/task/sequence_manager/enqueue_order.h"
namespace base {
namespace sequence_manager {
using TaskType = uint8_t;
constexpr TaskType kTaskTypeNone = 0;
namespace internal {
enum class WakeUpResolution { kLow, kHigh };
// Wrapper around PostTask method arguments and the assigned task type.
// Eventually it becomes a PendingTask once accepted by a TaskQueueImpl.
struct BASE_EXPORT PostedTask {
explicit PostedTask(scoped_refptr<SequencedTaskRunner> task_runner,
OnceClosure callback = OnceClosure(),
Location location = Location(),
TimeDelta delay = TimeDelta(),
Nestable nestable = Nestable::kNestable,
TaskType task_type = kTaskTypeNone);
PostedTask(PostedTask&& move_from) noexcept;
~PostedTask();
OnceClosure callback;
Location location;
TimeDelta delay;
Nestable nestable;
TaskType task_type;
// The task runner this task is running on. Can be used by task runners that
// support posting back to the "current sequence".
scoped_refptr<SequencedTaskRunner> task_runner;
// The time at which the task was queued.
TimeTicks queue_time;
DISALLOW_COPY_AND_ASSIGN(PostedTask);
};
// Represents a time at which a task wants to run. Tasks scheduled for the
// same point in time will be ordered by their sequence numbers.
struct DelayedWakeUp {
TimeTicks time;
int sequence_num;
bool operator!=(const DelayedWakeUp& other) const {
return time != other.time || other.sequence_num != sequence_num;
}
bool operator==(const DelayedWakeUp& other) const {
return !(*this != other);
}
bool operator<=(const DelayedWakeUp& other) const {
if (time == other.time) {
// Debug gcc builds can compare an element against itself.
DCHECK(sequence_num != other.sequence_num || this == &other);
// |sequence_num| is int and might wrap around to a negative number when
// casted from EnqueueOrder. This way of comparison handles that properly.
return (sequence_num - other.sequence_num) <= 0;
}
return time < other.time;
}
};
} // namespace internal
// PendingTask with extra metadata for SequenceManager.
struct BASE_EXPORT Task : public PendingTask {
Task(internal::PostedTask posted_task,
TimeTicks delayed_run_time,
EnqueueOrder sequence_order,
EnqueueOrder enqueue_order = EnqueueOrder(),
internal::WakeUpResolution wake_up_resolution =
internal::WakeUpResolution::kLow);
Task(Task&& move_from);
~Task();
Task& operator=(Task&& other);
internal::DelayedWakeUp delayed_wake_up() const {
return internal::DelayedWakeUp{delayed_run_time, sequence_num};
}
// SequenceManager is particularly sensitive to enqueue order,
// so we have accessors for safety.
EnqueueOrder enqueue_order() const {
DCHECK(enqueue_order_);
return enqueue_order_;
}
void set_enqueue_order(EnqueueOrder enqueue_order) {
DCHECK(!enqueue_order_);
enqueue_order_ = enqueue_order;
}
bool enqueue_order_set() const { return enqueue_order_; }
TaskType task_type;
// The task runner this task is running on. Can be used by task runners that
// support posting back to the "current sequence".
scoped_refptr<SequencedTaskRunner> task_runner;
#if DCHECK_IS_ON()
bool cross_thread_;
#endif
private:
// Similar to |sequence_num|, but ultimately the |enqueue_order| is what
// the scheduler uses for task ordering. For immediate tasks |enqueue_order|
// is set when posted, but for delayed tasks it's not defined until they are
// enqueued. This is because otherwise delayed tasks could run before
// an immediate task posted after the delayed task.
EnqueueOrder enqueue_order_;
};
} // namespace sequence_manager
} // namespace base
#endif // BASE_TASK_SEQUENCE_MANAGER_TASKS_H_
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