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 ~Worker() override; 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 void OnMessage(Message* msg) override; 63 64 // The thread that is currently doing the work. 65 Thread *worker_thread_; 66 67 RTC_DISALLOW_COPY_AND_ASSIGN(Worker); 68 }; 69 70 } // namespace rtc 71 72 #endif // WEBRTC_BASE_WORKER_H_ 73
