examples/Base/IPC/condvar/condvarglobal/src/subtractor.cpp

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Description: Implements the write operation on a shared memory block.  
*/



#include "sharedmem.h"
#include "subtractor.h"

CSubtractor* CSubtractor::NewL(CConsoleBase* aConsole)
        {
        CSubtractor* self = new (ELeave) CSubtractor;
        CleanupStack::PushL(self);
        self->ConstructL(aConsole);
        CleanupStack::Pop(self);
        return self;
        }

void CSubtractor::RunL()
        {
        // Get the key code.
        TUint8 option = iConsole->KeyCode();
        // Print the selected option.
        _LIT(KTextFormat,"%c\n");
        iConsole->Printf(KTextFormat,option);
        // Stop the timer and the active scheduler.
        StopTimer();
        CActiveScheduler::Stop();
        }

void CSubtractor::DoCancel()
        {
        if(IsActive())
                {
                // Cancel any outstanding read requests.
                iConsole->ReadCancel();
                }
        }

CSubtractor::~CSubtractor()
        {
        // Cancel all outstanding requests.
        DoCancel();
        // Delete the timer object.
        iPeriodic->Cancel();
        delete iPeriodic;
        }

CSubtractor::CSubtractor():CActive(EPriorityUserInput)
        {
        }

void CSubtractor::ConstructL(CConsoleBase* aConsole)
        {
        // Open the global condition variable.
        User::LeaveIfError(iCondVar.OpenGlobal(KCondVarName));
        // Open the global chunk variable.
        User::LeaveIfError(iChunk.OpenGlobal(KChunkName,EFalse));
        // Open the global mutex variable.
        User::LeaveIfError(iMutex.OpenGlobal(KMutexName));

        // Create the CPeriodic object.
        iPeriodic = CPeriodic::NewL(CActive::EPriorityUserInput);
        iConsole = aConsole;

        // Add the object to the active scheduler.
        CActiveScheduler::Add(this);
        }

void CSubtractor::ReadFunction()
        {
        _LIT(KTextMessage,"Press a key to exit...\n");
        iConsole->Printf(KTextMessage);
        // Wait for a key press event.
        iConsole->Read(iStatus);
        SetActive();
        }

void CSubtractor::StartTimer()
        {
        iPeriodic->Start(0,3000000,TCallBack(SubtractFunction,this));
        }

void CSubtractor::StopTimer()
        {
        // Cancel the  outstanding request.
        iPeriodic->Cancel();
        }

TInt CSubtractor::SubtractFunction(TAny* aPtr)
        {
        CSubtractor* ptr = static_cast<CSubtractor*> (aPtr);
        _LIT(KTxtPanic,"Unexpected datatype\n");
        __ASSERT_ALWAYS(ptr,User::Panic(KTxtPanic,-1));
        // Invoke the Subtract() function.
        ptr->Subtract();
        return KErrNone;
        }

void CSubtractor::Subtract()
        {
        // Acquire the mutex.
        iMutex.Wait();

        // Get a random number.
        TInt randVal = Math::Random() % 10;

        // Get the address of the chunk.
        TUint8 *ptr = iChunk.Base();

        // Print the value of the chunk before subtraction.
        iConsole->Printf(_L("Value read from the shared memory: %d\n"),*ptr);

        // Subtract the random value from the shared memory variable.
        *ptr -= randVal;

        while(*ptr < KLowerThreshold)
                {
                // Wait on the condition variable if the result is lesser than 0.
                _LIT(KBlockMessage,"Subtractor blocked by condVar until Adder signals that value has been increased.\nIntermediate value of the chunk = %d\n");
                iConsole->Printf(KBlockMessage,*ptr);
                iCondVar.Wait(iMutex);
                }
        // Print the updated value of the chunk.
        iConsole->Printf(_L("Value of the shared memory decreased to : %d\n"),*ptr);

        // Signal the mutex and the condition variable.
        if(*ptr < KUpperThreshold)
                {
                // Signal that the level is safe for addition to (re)start.
                iCondVar.Signal();
                }
        iMutex.Signal();
        }

LOCAL_D CConsoleBase* console;
LOCAL_C void DoExampleL();
LOCAL_C void callExampleL();

LOCAL_C void DoExampleL()
        {
        // Create and install the active scheduler.
        CActiveScheduler* scheduler = new (ELeave) CActiveScheduler();
        CleanupStack::PushL(scheduler);
        CActiveScheduler::Install(scheduler);

        // Create the CSubtractor object.
        CSubtractor* subtractor = CSubtractor::NewL(console);
        CleanupStack::PushL(subtractor);

        // Start the timer of the CSubtractor object.
        subtractor->StartTimer();
        // Issue an asynchronous read request.
        subtractor->ReadFunction();
        // Start the active scheduler.
        CActiveScheduler::Start();

        CleanupStack::PopAndDestroy(2,scheduler);
        }

GLDEF_C TInt E32Main() // main function called by E32
    {
        __UHEAP_MARK;
        CTrapCleanup* cleanup=CTrapCleanup::New(); // get clean-up stack
        TRAPD(error,callExampleL()); // more initializations, then do example
        delete cleanup; // destroy clean-up stack
        __ASSERT_ALWAYS(!error,User::Panic(KTxtEPOC32EX,error));
        __UHEAP_MARKEND;
        return 0; // and return
    }

LOCAL_C void callExampleL() // initialise and call example code under cleanup stack
    {
        console=Console::NewL(KTxtExampleCode,TSize(KConsFullScreen,KConsFullScreen));
        CleanupStack::PushL(console);
        TRAPD(error,DoExampleL()); // perform example function
        if (error)
                console->Printf(KFormatFailed, error);
        else
                console->Printf(KTxtOK);
        console->Printf(KTxtPressAnyKey);
        console->Getch(); // get and ignore character
        CleanupStack::PopAndDestroy(); // close console
    }

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