henrike@webrtc.org | f7795df | 2014-05-13 18:00:26 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 2004 The WebRTC Project Authors. All rights reserved. |
| 3 | * |
| 4 | * Use of this source code is governed by a BSD-style license |
| 5 | * that can be found in the LICENSE file in the root of the source |
| 6 | * tree. An additional intellectual property rights grant can be found |
| 7 | * in the file PATENTS. All contributing project authors may |
| 8 | * be found in the AUTHORS file in the root of the source tree. |
| 9 | */ |
| 10 | |
| 11 | #ifndef WEBRTC_BASE_WORKER_H_ |
| 12 | #define WEBRTC_BASE_WORKER_H_ |
| 13 | |
| 14 | #include "webrtc/base/constructormagic.h" |
| 15 | #include "webrtc/base/messagehandler.h" |
| 16 | |
| 17 | namespace rtc { |
| 18 | |
| 19 | class Thread; |
| 20 | |
| 21 | // A worker is an object that performs some specific long-lived task in an |
| 22 | // event-driven manner. |
| 23 | // The only method that should be considered thread-safe is HaveWork(), which |
| 24 | // allows you to signal the availability of work from any thread. All other |
| 25 | // methods are thread-hostile. Specifically: |
| 26 | // StartWork()/StopWork() should not be called concurrently with themselves or |
| 27 | // each other, and it is an error to call them while the worker is running on |
| 28 | // a different thread. |
| 29 | // The destructor may not be called if the worker is currently running |
| 30 | // (regardless of the thread), but you can call StopWork() in a subclass's |
| 31 | // destructor. |
| 32 | class Worker : private MessageHandler { |
| 33 | public: |
| 34 | Worker(); |
| 35 | |
| 36 | // Destroys this Worker, but it must have already been stopped via StopWork(). |
| 37 | virtual ~Worker(); |
| 38 | |
| 39 | // Attaches the worker to the current thread and begins processing work if not |
| 40 | // already doing so. |
| 41 | bool StartWork(); |
| 42 | // Stops processing work if currently doing so and detaches from the current |
| 43 | // thread. |
| 44 | bool StopWork(); |
| 45 | |
| 46 | protected: |
| 47 | // Signal that work is available to be done. May only be called within the |
| 48 | // lifetime of a OnStart()/OnStop() pair. |
| 49 | void HaveWork(); |
| 50 | |
| 51 | // These must be implemented by a subclass. |
| 52 | // Called on the worker thread to start working. |
| 53 | virtual void OnStart() = 0; |
| 54 | // Called on the worker thread when work has been signalled via HaveWork(). |
| 55 | virtual void OnHaveWork() = 0; |
| 56 | // Called on the worker thread to stop working. Upon return, any pending |
| 57 | // OnHaveWork() calls are cancelled. |
| 58 | virtual void OnStop() = 0; |
| 59 | |
| 60 | private: |
| 61 | // Inherited from MessageHandler. |
| 62 | virtual void OnMessage(Message *msg); |
| 63 | |
| 64 | // The thread that is currently doing the work. |
| 65 | Thread *worker_thread_; |
| 66 | |
| 67 | DISALLOW_COPY_AND_ASSIGN(Worker); |
| 68 | }; |
| 69 | |
| 70 | } // namespace rtc |
| 71 | |
| 72 | #endif // WEBRTC_BASE_WORKER_H_ |