Revert of New task queueing primitive for async tasks: TaskQueue.

webrtc/base/task_queue.h

-/*
- *  Copyright 2016 The WebRTC Project Authors. All rights reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree. An additional intellectual property rights grant can be found
- *  in the file PATENTS.  All contributing project authors may
- *  be found in the AUTHORS file in the root of the source tree.
- */
-
-#ifndef WEBRTC_BASE_TASK_QUEUE_H_
-#define WEBRTC_BASE_TASK_QUEUE_H_
-
-#if defined(WEBRTC_POSIX) && !defined(WEBRTC_MAC)
-#define LIBEVENT_TASK_QUEUE
-#endif
-
-#include <list>
-#include <memory>
-
-#if defined(WEBRTC_MAC)
-#include <dispatch/dispatch.h>
-#endif
-
-#include "webrtc/base/constructormagic.h"
-#include "webrtc/base/criticalsection.h"
-
-#if !defined(WEBRTC_MAC)
-#include "webrtc/base/platform_thread.h"
-#endif
-
-#if defined(LIBEVENT_TASK_QUEUE)
-struct event_base;
-struct event;
-#endif
-
-namespace rtc {
-
-// Base interface for asynchronously executed tasks.
-// The interface basically consists of a single function, Run(), that executes
-// on the target queue.  For more details see the Run() method and TaskQueue.
-class QueuedTask {
- public:
-  QueuedTask() {}
-  virtual ~QueuedTask() {}
-
-  // Main routine that will run when the task is executed on the desired queue.
-  // The task should return |true| to indicate that it should be deleted or
-  // |false| to indicate that the queue should consider ownership of the task
-  // having been transferred.  Returning |false| can be useful if a task has
-  // re-posted itself to a different queue or is otherwise being re-used.
-  virtual bool Run() = 0;
-
- private:
-  RTC_DISALLOW_COPY_AND_ASSIGN(QueuedTask);
-};
-
-// Simple implementation of QueuedTask for use with rtc::Bind and lambdas.
-template <class Closure>
-class ClosureTask : public QueuedTask {
- public:
-  explicit ClosureTask(const Closure& closure) : closure_(closure) {}
-
- private:
-  bool Run() override {
-    closure_();
-    return true;
-  }
-
-  Closure closure_;
-};
-
-// Extends ClosureTask to also allow specifying cleanup code.
-// This is useful when using lambdas if guaranteeing cleanup, even if a task
-// was dropped (queue is too full), is required.
-template <class Closure, class Cleanup>
-class ClosureTaskWithCleanup : public ClosureTask<Closure> {
- public:
-  ClosureTaskWithCleanup(const Closure& closure, Cleanup cleanup)
-      : ClosureTask<Closure>(closure), cleanup_(cleanup) {}
-  ~ClosureTaskWithCleanup() { cleanup_(); }
-
- private:
-  Cleanup cleanup_;
-};
-
-// Convenience function to construct closures that can be passed directly
-// to methods that support std::unique_ptr<QueuedTask> but not template
-// based parameters.
-template <class Closure>
-static std::unique_ptr<QueuedTask> NewClosure(const Closure& closure) {
-  return std::unique_ptr<QueuedTask>(new ClosureTask<Closure>(closure));
-}
-
-template <class Closure, class Cleanup>
-static std::unique_ptr<QueuedTask> NewClosure(const Closure& closure,
-                                              const Cleanup& cleanup) {
-  return std::unique_ptr<QueuedTask>(
-      new ClosureTaskWithCleanup<Closure, Cleanup>(closure, cleanup));
-}
-
-// Implements a task queue that asynchronously executes tasks in a way that
-// guarantees that they're executed in FIFO order and that tasks never overlap.
-// Tasks may always execute on the same worker thread and they may not.
-// To DCHECK that tasks are executing on a known task queue, use IsCurrent().
-//
-// Here are some usage examples:
-//
-//   1) Asynchronously running a lambda:
-//
-//     class MyClass {
-//       ...
-//       TaskQueue queue_("MyQueue");
-//     };
-//
-//     void MyClass::StartWork() {
-//       queue_.PostTask([]() { Work(); });
-//     ...
-//
-//   2) Doing work asynchronously on a worker queue and providing a notification
-//      callback on the current queue, when the work has been done:
-//
-//     void MyClass::StartWorkAndLetMeKnowWhenDone(
-//         std::unique_ptr<QueuedTask> callback) {
-//       DCHECK(TaskQueue::Current()) << "Need to be running on a queue";
-//       queue_.PostTaskAndReply([]() { Work(); }, std::move(callback));
-//     }
-//     ...
-//     my_class->StartWorkAndLetMeKnowWhenDone(
-//         NewClosure([]() { LOG(INFO) << "The work is done!";}));
-//
-//   3) Posting a custom task on a timer.  The task posts itself again after
-//      every running:
-//
-//     class TimerTask : public QueuedTask {
-//      public:
-//       TimerTask() {}
-//      private:
-//       bool Run() override {
-//         ++count_;
-//         TaskQueue::Current()->PostDelayedTask(
-//             std::unique_ptr<QueuedTask>(this), 1000);
-//         // Ownership has been transferred to the next occurance,
-//         // so return false to prevent from being deleted now.
-//         return false;
-//       }
-//       int count_ = 0;
-//     };
-//     ...
-//     queue_.PostDelayedTask(
-//         std::unique_ptr<QueuedTask>(new TimerTask()), 1000);
-//
-// For more examples, see task_queue_unittests.cc.
-//
-// A note on destruction:
-//
-// When a TaskQueue is deleted, pending tasks will not be executed but they will
-// be deleted.  The deletion of tasks may happen asynchronously after the
-// TaskQueue itself has been deleted or it may happen synchronously while the
-// TaskQueue instance is being deleted.  This may vary from one OS to the next
-// so assumptions about lifetimes of pending tasks should not be made.
-class TaskQueue {
- public:
-  explicit TaskQueue(const char* queue_name);
-  // TODO(tommi): Implement move semantics?
-  ~TaskQueue();
-
-  static TaskQueue* Current();
-
-  // Used for DCHECKing the current queue.
-  static bool IsCurrent(const char* queue_name);
-  bool IsCurrent() const;
-
-  // TODO(tommi): For better debuggability, implement FROM_HERE.
-
-  // Ownership of the task is passed to PostTask.
-  void PostTask(std::unique_ptr<QueuedTask> task);
-  void PostTaskAndReply(std::unique_ptr<QueuedTask> task,
-                        std::unique_ptr<QueuedTask> reply,
-                        TaskQueue* reply_queue);
-  void PostTaskAndReply(std::unique_ptr<QueuedTask> task,
-                        std::unique_ptr<QueuedTask> reply);
-
-  void PostDelayedTask(std::unique_ptr<QueuedTask> task, uint32_t milliseconds);
-
-  template <class Closure>
-  void PostTask(const Closure& closure) {
-    PostTask(std::unique_ptr<QueuedTask>(new ClosureTask<Closure>(closure)));
-  }
-
-  template <class Closure>
-  void PostDelayedTask(const Closure& closure, uint32_t milliseconds) {
-    PostDelayedTask(
-        std::unique_ptr<QueuedTask>(new ClosureTask<Closure>(closure)),
-        milliseconds);
-  }
-
-  template <class Closure1, class Closure2>
-  void PostTaskAndReply(const Closure1& task,
-                        const Closure2& reply,
-                        TaskQueue* reply_queue) {
-    PostTaskAndReply(
-        std::unique_ptr<QueuedTask>(new ClosureTask<Closure1>(task)),
-        std::unique_ptr<QueuedTask>(new ClosureTask<Closure2>(reply)),
-        reply_queue);
-  }
-
-  template <class Closure>
-  void PostTaskAndReply(std::unique_ptr<QueuedTask> task,
-                        const Closure& reply) {
-    PostTaskAndReply(std::move(task), std::unique_ptr<QueuedTask>(
-                                          new ClosureTask<Closure>(reply)));
-  }
-
-  template <class Closure>
-  void PostTaskAndReply(const Closure& task,
-                        std::unique_ptr<QueuedTask> reply) {
-    PostTaskAndReply(
-        std::unique_ptr<QueuedTask>(new ClosureTask<Closure>(task)),
-        std::move(reply));
-  }
-
-  template <class Closure1, class Closure2>
-  void PostTaskAndReply(const Closure1& task, const Closure2& reply) {
-    PostTaskAndReply(
-        std::unique_ptr<QueuedTask>(new ClosureTask<Closure1>(task)),
-        std::unique_ptr<QueuedTask>(new ClosureTask<Closure2>(reply)));
-  }
-
- private:
-#if defined(LIBEVENT_TASK_QUEUE)
-  static bool ThreadMain(void* context);
-  static void OnWakeup(int socket, short flags, void* context);  // NOLINT
-  static void RunTask(int fd, short flags, void* context);       // NOLINT
-  static void RunTimer(int fd, short flags, void* context);      // NOLINT
-
-  class PostAndReplyTask;
-  class SetTimerTask;
-
-  void PrepareReplyTask(PostAndReplyTask* reply_task);
-  void ReplyTaskDone(PostAndReplyTask* reply_task);
-
-  struct QueueContext;
-
-  int wakeup_pipe_in_ = -1;
-  int wakeup_pipe_out_ = -1;
-  event_base* event_base_;
-  std::unique_ptr<event> wakeup_event_;
-  PlatformThread thread_;
-  rtc::CriticalSection pending_lock_;
-  std::list<std::unique_ptr<QueuedTask>> pending_ GUARDED_BY(pending_lock_);
-  std::list<PostAndReplyTask*> pending_replies_ GUARDED_BY(pending_lock_);
-#elif defined(WEBRTC_MAC)
-  struct QueueContext;
-  struct TaskContext;
-  struct PostTaskAndReplyContext;
-  dispatch_queue_t queue_;
-  QueueContext* const context_;
-#elif defined(WEBRTC_WIN)
-  static bool ThreadMain(void* context);
-
-  class WorkerThread : public PlatformThread {
-   public:
-    WorkerThread(ThreadRunFunction func, void* obj, const char* thread_name)
-        : PlatformThread(func, obj, thread_name) {}
-
-    bool QueueAPC(PAPCFUNC apc_function, ULONG_PTR data) {
-      return PlatformThread::QueueAPC(apc_function, data);
-    }
-  };
-  WorkerThread thread_;
-#else
-#error not supported.
-#endif
-
-  RTC_DISALLOW_COPY_AND_ASSIGN(TaskQueue);
-};
-
-}  // namespace rtc
-
-#endif  // WEBRTC_BASE_TASK_QUEUE_H_