Semaphore.h

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//==============================================================================================
//  FILENAME    :   Semaphore.h
//  AUTHOR      :   Douglas Meyer
//  CREATION    :   10/29/2001
//  Copyright (C) MicroStrategy Incorporated 2001
//==============================================================================================
#ifndef MSynch_Semaphore_h
#define MSynch_Semaphore_h

#include "Base/Defines/StrongPtr.h"
#include "Base/Defines/NoCopy.h"
#include "Base/Interfaces/BaseException.h"

#include "Synch.h"

namespace MSynch 
{

    class Semaphore 
    {
    public:

        typedef MBase::StrongPtr<Semaphore, MBase::DeleteOperatorGeneric<Semaphore> > Ptr;
        typedef MBase::ReturnPtr<Semaphore, MBase::DeleteOperatorGeneric<Semaphore> > ReturnPtr;

        enum WaitForResourceResult {TIMED_OUT = 0,RESOURCE_AVAILABLE};


        class DLL_SYNCH_EXIM SmartLock:
            public MBase::NoCopy
        {
        public:     
            //The constructor does NOT attempt to wait for a resource.
            SmartLock(Semaphore& irSemaphore);

            //If a resource is being held the destructor will automatically make the resource available
            //If Dismiss was called before destruction then the resource will NOT be made available
            ~SmartLock() throw();

            WaitForResourceResult WaitForResource(unsigned Int32 inMilliseconds);

            // Same as WaitForResource, but will not come back until the resource is available.
            WaitForResourceResult WaitForeverForResource();

            //Causes the destructor to NOT make the resource available
            void Dismiss() throw();

            //Release the resource back to the semaphore. It can only release the resource that 
            //it previously acquired. Dismiss has no effect on the operation of this method.
            void ReleaseResource() throw();

        private:
            Semaphore& mrSemaphore;
            bool mbHoldingResource;
        };

        //ResourceIsAvailable adds a resource to the pool.
        virtual void ResourceIsAvailable() = 0;

        virtual void Delete() throw() = 0;

    private:
        friend class SmartLock;

        virtual WaitForResourceResult WaitForResource(unsigned Int32 inMilliseconds) = 0;

        // Same as WaitForResource, but will not come back until the resource is available.
        virtual WaitForResourceResult WaitForeverForResource() = 0;
    };

    // this typedef is obsolete
    typedef Semaphore::Ptr SemaphorePtr;

    DLL_SYNCH_EXIM Semaphore* CreateSemaphore(
        unsigned Int32 inInitialAvailableResourceCount,
        unsigned Int32 inMaximumResourceCount);

}

#endif // MSynch_Semaphore_h