signalthread.h revision f74420b3285b9fe04a7e00aa3b8c0ab07ea344bc 
1/*
2 * libjingle
3 * Copyright 2004--2009, 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,
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26 */
27
28#ifndef TALK_BASE_SIGNALTHREAD_H_
29#define TALK_BASE_SIGNALTHREAD_H_
30
31#include "talk/base/thread.h"
32#include "talk/base/sigslot.h"
33
34namespace talk_base {
35
36///////////////////////////////////////////////////////////////////////////////
37// SignalThread - Base class for worker threads.  The main thread should call
38//  Start() to begin work, and then follow one of these models:
39//   Normal: Wait for SignalWorkDone, and then call Release to destroy.
40//   Cancellation: Call Release(true), to abort the worker thread.
41//   Fire-and-forget: Call Release(false), which allows the thread to run to
42//    completion, and then self-destruct without further notification.
43//   Periodic tasks: Wait for SignalWorkDone, then eventually call Start()
44//    again to repeat the task. When the instance isn't needed anymore,
45//    call Release. DoWork, OnWorkStart and OnWorkStop are called again,
46//    on a new thread.
47//  The subclass should override DoWork() to perform the background task.  By
48//   periodically calling ContinueWork(), it can check for cancellation.
49//   OnWorkStart and OnWorkDone can be overridden to do pre- or post-work
50//   tasks in the context of the main thread.
51///////////////////////////////////////////////////////////////////////////////
52
53class SignalThread : public sigslot::has_slots<>, protected MessageHandler {
54 public:
55  SignalThread();
56
57  // Context: Main Thread.  Call before Start to change the worker's priority.
58  void SetPriority(ThreadPriority priority);
59
60  // Context: Main Thread.  Call to begin the worker thread.
61  void Start();
62
63  // Context: Main Thread.  If the worker thread is not running, deletes the
64  // object immediately.  Otherwise, asks the worker thread to abort processing,
65  // and schedules the object to be deleted once the worker exits.
66  // SignalWorkDone will not be signalled.  If wait is true, does not return
67  // until the thread is deleted.
68  void Destroy(bool wait);
69
70  // Context: Main Thread.  If the worker thread is complete, deletes the
71  // object immediately.  Otherwise, schedules the object to be deleted once
72  // the worker thread completes.  SignalWorkDone will be signalled.
73  void Release();
74
75  // Context: Main Thread.  Signalled when work is complete.
76  sigslot::signal1<SignalThread *> SignalWorkDone;
77
78  enum { ST_MSG_WORKER_DONE, ST_MSG_FIRST_AVAILABLE };
79
80 protected:
81  virtual ~SignalThread();
82
83  Thread* worker() { return &worker_; }
84
85  // Context: Main Thread.  Subclass should override to do pre-work setup.
86  virtual void OnWorkStart() { }
87
88  // Context: Worker Thread.  Subclass should override to do work.
89  virtual void DoWork() = 0;
90
91  // Context: Worker Thread.  Subclass should call periodically to
92  // dispatch messages and determine if the thread should terminate.
93  bool ContinueWork();
94
95  // Context: Worker Thread.  Subclass should override when extra work is
96  // needed to abort the worker thread.
97  virtual void OnWorkStop() { }
98
99  // Context: Main Thread.  Subclass should override to do post-work cleanup.
100  virtual void OnWorkDone() { }
101
102  // Context: Any Thread.  If subclass overrides, be sure to call the base
103  // implementation.  Do not use (message_id < ST_MSG_FIRST_AVAILABLE)
104  virtual void OnMessage(Message *msg);
105
106 private:
107  enum State {
108    kInit,            // Initialized, but not started
109    kRunning,         // Started and doing work
110    kReleasing,       // Same as running, but to be deleted when work is done
111    kComplete,        // Work is done
112    kStopping,        // Work is being interrupted
113  };
114
115  friend class Worker;
116  class Worker : public Thread {
117   public:
118    SignalThread* parent_;
119    virtual void Run() { parent_->Run(); }
120  };
121
122  friend class EnterExit;
123  class EnterExit {
124   public:
125    explicit EnterExit(SignalThread* t) : t_(t) {
126      t_->cs_.Enter();
127      t_->refcount_ += 1;
128    }
129    ~EnterExit() {
130      bool d = (0 == (--(t_->refcount_)));
131      t_->cs_.Leave();
132      if (d)
133        delete t_;
134    }
135   private:
136    SignalThread* t_;
137  };
138
139  void Run();
140  void OnMainThreadDestroyed();
141
142  Thread* main_;
143  Worker worker_;
144  CriticalSection cs_;
145  State state_;
146  int refcount_;
147};
148
149///////////////////////////////////////////////////////////////////////////////
150
151}  // namespace talk_base
152
153#endif  // TALK_BASE_SIGNALTHREAD_H_
154