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Semaphore.h

//
// Semaphore.h
//
// $Id: //poco/1.3/Foundation/include/Poco/Semaphore.h#2 $
//
// Library: Foundation
// Package: Threading
// Module:  Semaphore
//
// Definition of the Semaphore class.
//
// Copyright (c) 2004-2006, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// Permission is hereby granted, free of charge, to any person or organization
// obtaining a copy of the software and accompanying documentation covered by
// this license (the "Software") to use, reproduce, display, distribute,
// execute, and transmit the Software, and to prepare derivative works of the
// Software, and to permit third-parties to whom the Software is furnished to
// do so, all subject to the following:
// 
// The copyright notices in the Software and this entire statement, including
// the above license grant, this restriction and the following disclaimer,
// must be included in all copies of the Software, in whole or in part, and
// all derivative works of the Software, unless such copies or derivative
// works are solely in the form of machine-executable object code generated by
// a source language processor.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
//


#ifndef Foundation_Semaphore_INCLUDED
#define Foundation_Semaphore_INCLUDED


#include "Poco/Foundation.h"
#include "Poco/Exception.h"


#if defined(POCO_OS_FAMILY_WINDOWS)
#include "Poco/Semaphore_WIN32.h"
#else
#include "Poco/Semaphore_POSIX.h"
#endif


namespace Poco {


00057 class Foundation_API Semaphore: private SemaphoreImpl
      /// A Semaphore is a synchronization object with the following 
      /// characteristics:
      /// A semaphore has a value that is constrained to be a non-negative
      /// integer and two atomic operations. The allowable operations are V 
      /// (here called set()) and P (here called wait()). A V (set()) operation 
      /// increases the value of the semaphore by one. 
      /// A P (wait()) operation decreases the value of the semaphore by one, 
      /// provided that can be done without violating the constraint that the 
      /// value be non-negative. A P (wait()) operation that is initiated when 
      /// the value of the semaphore is 0 suspends the calling thread. 
      /// The calling thread may continue when the value becomes positive again.
{
public:
      Semaphore(int n);
      Semaphore(int n, int max);
            /// Creates the semaphore. The current value
            /// of the semaphore is given in n. The
            /// maximum value of the semaphore is given
            /// in max.
            /// If only n is given, it must be greater than
            /// zero.
            /// If both n and max are given, max must be
            /// greater than zero, n must be greater than
            /// or equal to zero and less than or equal
            /// to max.
            
      ~Semaphore();
            /// Destroys the semaphore.

      void set();
            /// Increments the semaphore's value by one and
            /// thus signals the semaphore. Another thread
            /// waiting for the semaphore will be able
            /// to continue.

      void wait();
            /// Waits for the semaphore to become signalled.
            /// To become signalled, a semaphore's value must
            /// be greater than zero. 
            /// Decrements the semaphore's value by one.

      void wait(long milliseconds);
            /// Waits for the semaphore to become signalled.
            /// To become signalled, a semaphore's value must
            /// be greater than zero.
            /// Throws a TimeoutException if the semaphore
            /// does not become signalled within the specified
            /// time interval.
            /// Decrements the semaphore's value by one
            /// if successful.

      bool tryWait(long milliseconds);
            /// Waits for the semaphore to become signalled.
            /// To become signalled, a semaphore's value must
            /// be greater than zero.
            /// Returns true if the semaphore
            /// became signalled within the specified
            /// time interval, false otherwise.
            /// Decrements the semaphore's value by one
            /// if successful.
      
private:
      Semaphore();
      Semaphore(const Semaphore&);
      Semaphore& operator = (const Semaphore&);
};


//
// inlines
//
00129 inline void Semaphore::set()
{
      setImpl();
}


00135 inline void Semaphore::wait()
{
      waitImpl();
}


00141 inline void Semaphore::wait(long milliseconds)
{
      if (!waitImpl(milliseconds))
            throw TimeoutException();
}


00148 inline bool Semaphore::tryWait(long milliseconds)
{
      return waitImpl(milliseconds);
}


} // namespace Poco


#endif // Foundation_Semaphore_INCLUDED

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