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CSemaphore.h
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1 /* +---------------------------------------------------------------------------+
2  | The Mobile Robot Programming Toolkit (MRPT) C++ library |
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8  | This software was written by the Machine Perception and Intelligent |
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10  | Contact: Jose-Luis Blanco <jlblanco@ctima.uma.es> |
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27  +---------------------------------------------------------------------------+ */
28 #ifndef mrpt_synch_semaphore_H
29 #define mrpt_synch_semaphore_H
30 
31 #include <mrpt/utils/utils_defs.h>
32 #include <mrpt/utils/CStream.h>
33 #include <mrpt/utils/CReferencedMemBlock.h>
34 
35 /*---------------------------------------------------------------
36  Class
37  ---------------------------------------------------------------*/
38 namespace mrpt
39 {
40  namespace synch
41  {
42  /** A semaphore for inter-thread synchronization.
43  * The state of a semaphore object is signaled when its count is greater than zero,
44  * and nonsignaled when its count is equal to zero. The initialCount parameter specifies
45  * the initial count. Each time a waiting thread is released because of the semaphore's
46  * signaled state, the count of the semaphore is decreased by one. Use the release function
47  * to increment a semaphore's count by a specified amount. The count can never be less
48  * than zero or greater than the value specified in the maxCount parameter.
49  * \ingroup synch_grp
50  */
51  class BASE_IMPEXP CSemaphore
52  {
53  protected:
54  utils::CReferencedMemBlock m_data;
55  std::string m_name; //!< The name of the named semaphore, or empty if unnamed.
56 
57  public:
58  /** Creates a semaphore.
59  * If \a name is not an empty string, a named semaphore is created. In that case
60  * if the semaphore didn't exist it's created. Otherwise, the existing semaphore
61  * is linked to this object and then \a initialCount and \a maxCount are ignored.
62  */
63  CSemaphore(
64  unsigned int initialCount,
65  unsigned int maxCount,
66  const std::string &name=std::string("") );
67 
68  /** Destructor
69  */
70  virtual ~CSemaphore();
71 
72  /** Blocks until the count of the semaphore to be non-zero.
73  * \param timeout_ms The timeout in milliseconds, or set to zero to wait indefinidely.
74  * \return true if the semaphore has been signaled, false on timeout or any other error.
75  */
76  bool waitForSignal( unsigned int timeout_ms = 0 );
77 
78  /** Increments the count of the semaphore by a given amount.
79  */
80  void release(unsigned int increaseCount = 1);
81 
82 
83  /** Get the name of the named semaphore or an empty string if it's unnamed */
84  inline std::string getName() const { return m_name; }
85 
86  /** Return true if this is a named semaphore */
87  inline bool isNamed() const { return !m_name.empty(); }
88 
89 
90  };
91 
92  } // End of namespace
93 
94 } // End of namespace
95 
96 #endif


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