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1 ///////////////////////////////////////////////////////////////////////////////
2 // Name: wx/thread.h
3 // Purpose: Message queues for inter-thread communication
4 // Author: Evgeniy Tarassov
5 // Created: 2007-10-31
6 // RCS-ID: $Id$
7 // Copyright: (C) 2007 TT-Solutions SARL
8 // Licence: wxWindows licence
9 ///////////////////////////////////////////////////////////////////////////////
10
11 #ifndef _WX_MSGQUEUE_H_
12 #define _WX_MSGQUEUE_H_
13
14 // ----------------------------------------------------------------------------
15 // headers
16 // ----------------------------------------------------------------------------
17
18 #include "wx/thread.h"
19
20 #if wxUSE_THREADS
21
22 #include "wx/stopwatch.h"
23
24 #include "wx/beforestd.h"
25 #include <queue>
26 #include "wx/afterstd.h"
27
28 enum wxMessageQueueError
29 {
30 wxMSGQUEUE_NO_ERROR = 0, // operation completed successfully
31 wxMSGQUEUE_TIMEOUT, // no messages received before timeout expired
32 wxMSGQUEUE_MISC_ERROR // some unexpected (and fatal) error has occurred
33 };
34
35 // ---------------------------------------------------------------------------
36 // Message queue allows passing message between threads.
37 //
38 // This class is typically used for communicating between the main and worker
39 // threads. The main thread calls Post() and the worker thread calls Receive().
40 //
41 // For this class a message is an object of arbitrary type T. Notice that
42 // typically there must be some special message indicating that the thread
43 // should terminate as there is no other way to gracefully shutdown a thread
44 // waiting on the message queue.
45 // ---------------------------------------------------------------------------
46 template <typename T>
47 class wxMessageQueue
48 {
49 public:
50 // The type of the messages transported by this queue
51 typedef T Message;
52
53 // Default ctor creates an initially empty queue
54 wxMessageQueue()
55 : m_conditionNotEmpty(m_mutex)
56 {
57 }
58
59 // Add a message to this queue and signal the threads waiting for messages.
60 //
61 // This method is safe to call from multiple threads in parallel.
62 wxMessageQueueError Post(const Message& msg)
63 {
64 wxMutexLocker locker(m_mutex);
65
66 wxCHECK( locker.IsOk(), wxMSGQUEUE_MISC_ERROR );
67
68 m_messages.push(msg);
69
70 m_conditionNotEmpty.Signal();
71
72 return wxMSGQUEUE_NO_ERROR;
73 }
74
75 // Wait no more than timeout milliseconds until a message becomes available.
76 //
77 // Setting timeout to 0 is equivalent to an infinite timeout. See Receive().
78 wxMessageQueueError ReceiveTimeout(long timeout, T& msg)
79 {
80 wxCHECK( IsOk(), wxMSGQUEUE_MISC_ERROR );
81
82 wxMutexLocker locker(m_mutex);
83
84 wxCHECK( locker.IsOk(), wxMSGQUEUE_MISC_ERROR );
85
86 const wxMilliClock_t waitUntil = wxGetLocalTimeMillis() + timeout;
87 while ( m_messages.empty() )
88 {
89 wxCondError result = m_conditionNotEmpty.WaitTimeout(timeout);
90
91 if ( result == wxCOND_NO_ERROR )
92 continue;
93
94 wxCHECK( result == wxCOND_TIMEOUT, wxMSGQUEUE_MISC_ERROR );
95
96 const wxMilliClock_t now = wxGetLocalTimeMillis();
97
98 if ( now >= waitUntil )
99 return wxMSGQUEUE_TIMEOUT;
100
101 timeout = (waitUntil - now).ToLong();
102 wxASSERT(timeout > 0);
103 }
104
105 msg = m_messages.front();
106 m_messages.pop();
107
108 return wxMSGQUEUE_NO_ERROR;
109 }
110
111 // Same as ReceiveTimeout() but waits for as long as it takes for a message
112 // to become available (so it can't return wxMSGQUEUE_TIMEOUT)
113 wxMessageQueueError Receive(T& msg)
114 {
115 wxCHECK( IsOk(), wxMSGQUEUE_MISC_ERROR );
116
117 wxMutexLocker locker(m_mutex);
118
119 wxCHECK( locker.IsOk(), wxMSGQUEUE_MISC_ERROR );
120
121 while ( m_messages.empty() )
122 {
123 wxCondError result = m_conditionNotEmpty.Wait();
124
125 wxCHECK( result == wxCOND_NO_ERROR, wxMSGQUEUE_MISC_ERROR );
126 }
127
128 msg = m_messages.front();
129 m_messages.pop();
130
131 return wxMSGQUEUE_NO_ERROR;
132 }
133
134 // Return false only if there was a fatal error in ctor
135 bool IsOk() const
136 {
137 return m_conditionNotEmpty.IsOk();
138 }
139
140 private:
141 // Disable copy ctor and assignment operator
142 wxMessageQueue(const wxMessageQueue<T>& rhs);
143 wxMessageQueue<T>& operator=(const wxMessageQueue<T>& rhs);
144
145 mutable wxMutex m_mutex;
146 wxCondition m_conditionNotEmpty;
147
148 std::queue<T> m_messages;
149 };
150
151 #endif // wxUSE_THREADS
152
153 #endif // _WX_MSGQUEUE_H_