chromium/base/task/sequence_manager/task_queue.h

// Copyright 2018 The Chromium Authors
// 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_TASK_QUEUE_H_
#define BASE_TASK_SEQUENCE_MANAGER_TASK_QUEUE_H_

#include <cstdint>
#include <memory>
#include <optional>
#include <type_traits>

#include "base/base_export.h"
#include "base/check.h"
#include "base/task/common/checked_lock.h"
#include "base/task/common/lazy_now.h"
#include "base/task/sequence_manager/tasks.h"
#include "base/task/single_thread_task_runner.h"
#include "base/task/task_observer.h"
#include "base/threading/platform_thread.h"
#include "base/time/time.h"
#include "base/trace_event/base_tracing.h"
#include "base/trace_event/base_tracing_forward.h"

namespace perfetto {
class EventContext;
}

namespace base {

class TaskObserver;

namespace sequence_manager {

QueueName;

namespace internal {
class SequenceManagerImpl;
class TaskQueueImpl;
}  // namespace internal

// A `TaskQueue` represents an ordered list of tasks sharing common properties,
// e.g. priority, throttling, etc. `TaskQueue`s are associated with a
// `SequenceManager` instance, which chooses the next task from its set of
// queues. `TaskQueue`s should typically be used on a single thread since most
// methods are not thread safe (enforeced via CHECKs), but cross-thread task
// posting is supported with thread-safe task runners.
//
// A `TaskQueue` is unregistered (stops accepting and running tasks) when either
// its associated `TaskQueue::Handle` or `SequenceManager` is destroyed. If the
// handle is destroyed while the `SequenceManager` is still alive, the
// `SequenceManager` takes ownership of the queue and schedules it for deletion
// after the current task finishes. Otherwise, if the handle outlives the
// sequence manager, the queue is destroyed when the handle is destroyed.
class BASE_EXPORT TaskQueue { … };

}  // namespace sequence_manager
}  // namespace base

#endif  // BASE_TASK_SEQUENCE_MANAGER_TASK_QUEUE_H_