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/*========================================================================= |
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Program: Insight Segmentation & Registration Toolkit |
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Module: $RCSfile: itkConditionVariable.h.html,v $ |
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Language: C++ |
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Date: $Date: 2006/01/17 19:15:34 $ |
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Version: $Revision: 1.4 $ |
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Copyright (c) Insight Software Consortium. All rights reserved. |
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See ITKCopyright.txt or http://www.itk.org/HTML/Copyright.htm for details. |
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This software is distributed WITHOUT ANY WARRANTY; without even |
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the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR |
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PURPOSE. See the above copyright notices for more information. |
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=========================================================================*/ |
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#ifndef _itkConditionVariable_h_ |
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#define _itkConditionVariable_h_ |
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#include "itkConfigure.h" |
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// This implementation uses a routine called SignalObjectAndWait() |
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// which is only defined on WinNT 4.0 or greater systems. We need to |
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// define this symbol in order to get the prototype for the |
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// routine. This needs to be done before we load any system headers. |
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#ifdef ITK_USE_WIN32_THREADS |
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#undef _WIN32_WINNT |
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#define _WIN32_WINNT 0x0400 |
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#endif |
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#include "itkMutexLock.h" |
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#include "itkLightObject.h" |
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namespace itk { |
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/** \class ConditionVariable |
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* \brief A thread synchronization object used to suspend execution until some |
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* condition on shared data is met. |
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* |
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* A thread calls Wait() to suspend its execution until the condition is |
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* met. Each call to Signal() from an executing thread will then cause a single |
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* waiting thread to be released. A call to Signal() means, "signal |
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* that the condition is true." Broadcast() releases all threads waiting on |
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* the condition variable. |
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* |
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* The ITK ConditionVariable implementation is consistent with the standard |
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* definition and use of condition variables in pthreads and other common |
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* thread libraries. |
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* |
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* IMPORTANT: A condition variable always requires an associated SimpleMutexLock |
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* object. The mutex object is used to avoid a dangerous race condition when |
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* Wait() and Signal() are called simultaneously from two different |
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* threads. |
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* |
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* On systems using pthreads, this implementation abstract the |
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* standard calls to the pthread condition variable. On Win32 |
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* systems, there is no system provided condition variable. This |
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* class implements a condition variable using a critical section, a |
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* semphore, an event and a number of counters. The implementation is |
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* almost an extract translation of the implementation presented by |
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* Douglas C Schmidt and Irfan Pyarali in "Strategies for Implementing |
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* POSIX Condition Variables on Win32". This article can be found at |
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* http://www.cs.wustl.edu/~schmidt/win32-cv-1.html |
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* |
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*/ |
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class ITKCommon_EXPORT ConditionVariable : public LightObject |
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{ |
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public: |
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/** Standard class typedefs. */ |
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typedef ConditionVariable Self; |
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typedef LightObject Superclass; |
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typedef SmartPointer<Self> Pointer; |
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typedef SmartPointer<const Self> ConstPointer; |
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/** Method for creation through the object factory. */ |
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itkNewMacro(Self); |
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/** Run-time type information (and related methods). */ |
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itkTypeMacro(ConditionVariable, LightObject); |
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/** Suspend execution of this thread until the condition is signaled. The |
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* argument is a SimpleMutex object that must be locked prior to calling |
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* this method. */ |
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void Wait(SimpleMutexLock * mutex); |
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/** Signal that the condition is true and release one waiting thread */ |
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void Signal(); |
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/** Signal that the condition is true and release all waiting threads */ |
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void Broadcast(); |
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protected: |
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ConditionVariable(); |
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~ConditionVariable(); |
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private: |
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ConditionVariable(const Self & other); |
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const Self & operator=( const Self & ); |
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#ifdef ITK_USE_PTHREADS |
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pthread_cond_t m_ConditionVariable; |
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MutexType m_Mutex; |
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#else |
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int m_NumberOfWaiters; // number of waiting threads |
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#ifdef WIN32 |
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CRITICAL_SECTION m_NumberOfWaitersLock; // Serialize access to m_NumberOfWaiters |
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HANDLE m_Semaphore; // Semaphore to queue threads |
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HANDLE m_WaitersAreDone; // Auto-reset event used by the |
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*******************************************// broadcast/signal thread to |
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*******************************************// wait for all the waiting |
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*******************************************// threads to wake up and |
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*******************************************// release the semaphore |
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size_t m_WasBroadcast; // Keeps track of whether we |
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*******************************************// were broadcasting or signaling |
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#endif |
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#endif |
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}; |
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}//end of itk namespace |
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#endif |
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