1 /* 2 * libjingle 3 * Copyright 2004--2010, Google Inc. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions are met: 7 * 8 * 1. Redistributions of source code must retain the above copyright notice, 9 * this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright notice, 11 * this list of conditions and the following disclaimer in the documentation 12 * and/or other materials provided with the distribution. 13 * 3. The name of the author may not be used to endorse or promote products 14 * derived from this software without specific prior written permission. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED 17 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 18 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO 19 * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 20 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 21 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; 22 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 23 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR 24 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF 25 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 26 */ 27 28 #ifndef TALK_BASE_WORKER_H_ 29 #define TALK_BASE_WORKER_H_ 30 31 #include "talk/base/constructormagic.h" 32 #include "talk/base/messagehandler.h" 33 34 namespace talk_base { 35 36 class Thread; 37 38 // A worker is an object that performs some specific long-lived task in an 39 // event-driven manner. 40 // The only method that should be considered thread-safe is HaveWork(), which 41 // allows you to signal the availability of work from any thread. All other 42 // methods are thread-hostile. Specifically: 43 // StartWork()/StopWork() should not be called concurrently with themselves or 44 // each other, and it is an error to call them while the worker is running on 45 // a different thread. 46 // The destructor may not be called if the worker is currently running 47 // (regardless of the thread), but you can call StopWork() in a subclass's 48 // destructor. 49 class Worker : private MessageHandler { 50 public: 51 Worker(); 52 53 // Destroys this Worker, but it must have already been stopped via StopWork(). 54 virtual ~Worker(); 55 56 // Attaches the worker to the current thread and begins processing work if not 57 // already doing so. 58 bool StartWork(); 59 // Stops processing work if currently doing so and detaches from the current 60 // thread. 61 bool StopWork(); 62 63 protected: 64 // Signal that work is available to be done. May only be called within the 65 // lifetime of a OnStart()/OnStop() pair. 66 void HaveWork(); 67 68 // These must be implemented by a subclass. 69 // Called on the worker thread to start working. 70 virtual void OnStart() = 0; 71 // Called on the worker thread when work has been signalled via HaveWork(). 72 virtual void OnHaveWork() = 0; 73 // Called on the worker thread to stop working. Upon return, any pending 74 // OnHaveWork() calls are cancelled. 75 virtual void OnStop() = 0; 76 77 private: 78 // Inherited from MessageHandler. 79 virtual void OnMessage(Message *msg); 80 81 // The thread that is currently doing the work. 82 Thread *worker_thread_; 83 84 DISALLOW_COPY_AND_ASSIGN(Worker); 85 }; 86 87 } // namespace talk_base 88 89 #endif // TALK_BASE_WORKER_H_ 90
