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1 | #ifndef BOOST_STATECHART_FIFO_WORKER_HPP_INCLUDED |
2 | #define BOOST_STATECHART_FIFO_WORKER_HPP_INCLUDED | |
3 | ////////////////////////////////////////////////////////////////////////////// | |
4 | // Copyright 2002-2008 Andreas Huber Doenni | |
5 | // Distributed under the Boost Software License, Version 1.0. (See accompany- | |
6 | // ing file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) | |
7 | ////////////////////////////////////////////////////////////////////////////// | |
8 | ||
9 | ||
10 | ||
11 | #include <boost/assert.hpp> | |
12 | #include <boost/noncopyable.hpp> | |
13 | #include <boost/function/function0.hpp> | |
14 | #include <boost/bind.hpp> | |
15 | // BOOST_HAS_THREADS, BOOST_MSVC | |
16 | #include <boost/config.hpp> | |
17 | ||
18 | #include <boost/detail/allocator_utilities.hpp> | |
19 | ||
20 | #ifdef BOOST_HAS_THREADS | |
21 | # ifdef BOOST_MSVC | |
22 | # pragma warning( push ) | |
23 | // "conditional expression is constant" in basic_timed_mutex.hpp | |
24 | # pragma warning( disable: 4127 ) | |
25 | // "conversion from 'int' to 'unsigned short'" in microsec_time_clock.hpp | |
26 | # pragma warning( disable: 4244 ) | |
27 | // "... needs to have dll-interface to be used by clients of class ..." | |
28 | # pragma warning( disable: 4251 ) | |
29 | // "... assignment operator could not be generated" | |
30 | # pragma warning( disable: 4512 ) | |
31 | // "Function call with parameters that may be unsafe" in | |
32 | // condition_variable.hpp | |
33 | # pragma warning( disable: 4996 ) | |
34 | # endif | |
35 | ||
36 | # include <boost/thread/mutex.hpp> | |
37 | # include <boost/thread/condition.hpp> | |
38 | ||
39 | # ifdef BOOST_MSVC | |
40 | # pragma warning( pop ) | |
41 | # endif | |
42 | #endif | |
43 | ||
44 | #include <list> | |
45 | #include <memory> // std::allocator | |
46 | ||
47 | ||
48 | namespace boost | |
49 | { | |
50 | namespace statechart | |
51 | { | |
52 | ||
53 | ||
54 | ||
55 | template< class Allocator = std::allocator< void > > | |
56 | class fifo_worker : noncopyable | |
57 | { | |
58 | public: | |
59 | ////////////////////////////////////////////////////////////////////////// | |
60 | #ifdef BOOST_HAS_THREADS | |
61 | fifo_worker( bool waitOnEmptyQueue = false ) : | |
62 | waitOnEmptyQueue_( waitOnEmptyQueue ), | |
63 | #else | |
64 | fifo_worker() : | |
65 | #endif | |
66 | terminated_( false ) | |
67 | { | |
68 | } | |
69 | ||
70 | typedef function0< void > work_item; | |
71 | ||
72 | // We take a non-const reference so that we can move (i.e. swap) the item | |
73 | // into the queue, what avoids copying the (possibly heap-allocated) | |
74 | // implementation object inside work_item. | |
75 | void queue_work_item( work_item & item ) | |
76 | { | |
77 | if ( item.empty() ) | |
78 | { | |
79 | return; | |
80 | } | |
81 | ||
82 | #ifdef BOOST_HAS_THREADS | |
83 | mutex::scoped_lock lock( mutex_ ); | |
84 | #endif | |
85 | ||
86 | workQueue_.push_back( work_item() ); | |
87 | workQueue_.back().swap( item ); | |
88 | ||
89 | #ifdef BOOST_HAS_THREADS | |
90 | queueNotEmpty_.notify_one(); | |
91 | #endif | |
92 | } | |
93 | ||
94 | // Convenience overload so that temporary objects can be passed directly | |
95 | // instead of having to create a work_item object first. Under most | |
96 | // circumstances, this will lead to one unnecessary copy of the | |
97 | // function implementation object. | |
98 | void queue_work_item( const work_item & item ) | |
99 | { | |
100 | work_item copy = item; | |
101 | queue_work_item( copy ); | |
102 | } | |
103 | ||
104 | void terminate() | |
105 | { | |
106 | work_item item = boost::bind( &fifo_worker::terminate_impl, this ); | |
107 | queue_work_item( item ); | |
108 | } | |
109 | ||
110 | // Is not mutex-protected! Must only be called from the thread that also | |
111 | // calls operator(). | |
112 | bool terminated() const | |
113 | { | |
114 | return terminated_; | |
115 | } | |
116 | ||
117 | unsigned long operator()( unsigned long maxItemCount = 0 ) | |
118 | { | |
119 | unsigned long itemCount = 0; | |
120 | ||
121 | while ( !terminated() && | |
122 | ( ( maxItemCount == 0 ) || ( itemCount < maxItemCount ) ) ) | |
123 | { | |
124 | work_item item = dequeue_item(); | |
125 | ||
126 | if ( item.empty() ) | |
127 | { | |
128 | // item can only be empty when the queue is empty, which only | |
129 | // happens in ST builds or when users pass false to the fifo_worker | |
130 | // constructor | |
131 | return itemCount; | |
132 | } | |
133 | ||
134 | item(); | |
135 | ++itemCount; | |
136 | } | |
137 | ||
138 | return itemCount; | |
139 | } | |
140 | ||
141 | private: | |
142 | ////////////////////////////////////////////////////////////////////////// | |
143 | work_item dequeue_item() | |
144 | { | |
145 | #ifdef BOOST_HAS_THREADS | |
146 | mutex::scoped_lock lock( mutex_ ); | |
147 | ||
148 | if ( !waitOnEmptyQueue_ && workQueue_.empty() ) | |
149 | { | |
150 | return work_item(); | |
151 | } | |
152 | ||
153 | while ( workQueue_.empty() ) | |
154 | { | |
155 | queueNotEmpty_.wait( lock ); | |
156 | } | |
157 | #else | |
158 | // If the queue happens to run empty in a single-threaded system, | |
159 | // waiting for new work items (which means to loop indefinitely!) is | |
160 | // pointless as there is no way that new work items could find their way | |
161 | // into the queue. The only sensible thing is to exit the loop and | |
162 | // return to the caller in this case. | |
163 | // Users can then queue new work items before calling operator() again. | |
164 | if ( workQueue_.empty() ) | |
165 | { | |
166 | return work_item(); | |
167 | } | |
168 | #endif | |
169 | ||
170 | // Optimization: Swap rather than assign to avoid the copy of the | |
171 | // implementation object inside function | |
172 | work_item result; | |
173 | result.swap( workQueue_.front() ); | |
174 | workQueue_.pop_front(); | |
175 | return result; | |
176 | } | |
177 | ||
178 | void terminate_impl() | |
179 | { | |
180 | terminated_ = true; | |
181 | } | |
182 | ||
183 | ||
184 | typedef std::list< | |
185 | work_item, | |
186 | typename boost::detail::allocator::rebind_to< | |
187 | Allocator, work_item >::type | |
188 | > work_queue_type; | |
189 | ||
190 | work_queue_type workQueue_; | |
191 | ||
192 | #ifdef BOOST_HAS_THREADS | |
193 | mutex mutex_; | |
194 | condition queueNotEmpty_; | |
195 | const bool waitOnEmptyQueue_; | |
196 | #endif | |
197 | ||
198 | bool terminated_; | |
199 | }; | |
200 | ||
201 | ||
202 | ||
203 | } // namespace statechart | |
204 | } // namespace boost | |
205 | ||
206 | ||
207 | ||
208 | #endif |