/*

* Copyright (c) 2005 Nokia Corporation and/or its subsidiary(-ies). 

* All rights reserved.

* This component and the accompanying materials are made available

* under the terms of "Eclipse Public License v1.0"

* which accompanies this distribution, and is available

* at the URL "http://www.eclipse.org/legal/epl-v10.html".

*

* Initial Contributors:

* Nokia Corporation - initial contribution.

*

* Contributors:

*

* Description: 

*    This is a helper class for calculating progress during a search operation.

*

*/

// INCLUDE FILES

#include <e32math.h>

#include "EPos_TPosLmProgressHelper.h"

// CONSTANTS

const TInt KGuessNumOfEvaluatedRows = 16;

const TInt KGuessNumOfEvaluatedRowsNoSearchCondition = 257;

const TReal32 KTarget = 0.5;

const TReal32 KPosNumOfEvalsMinLimit = 1.0;

// ============================ MEMBER FUNCTIONS ===============================

// -----------------------------------------------------------------------------

// TPosLmProgressHelper::TPosLmProgressHelper

// C++ default constructor can NOT contain any code, that

// might leave.

// -----------------------------------------------------------------------------

//

TPosLmProgressHelper::TPosLmProgressHelper()

:   iEvalCounter(0),

    iGuessNumOfEvalsDivByTwo(0),

    iPreviousEvaluationProgress(0),

    iEvaluationProgress(0),

    iNumOfRowsInPreviousEvaluations(0),

    iNumOfRowsInEvaluation(0),

    iRowCounter(0)

    {

    }

// -----------------------------------------------------------------------------

// TPosLmProgressHelper::PrepareCalculateProgress

//

// (other items were commented in a header).

// -----------------------------------------------------------------------------

//

void TPosLmProgressHelper::PrepareCalculateProgress(

    TInt aNoOfRowsToEvaluate,

    TBool aSqlQueryIncludesSearchCondition)

    {

    iEvalCounter = 0;

    TInt guessNumOfEvaluatedRows = KGuessNumOfEvaluatedRows;

    if (!aSqlQueryIncludesSearchCondition)

        {

        guessNumOfEvaluatedRows = KGuessNumOfEvaluatedRowsNoSearchCondition;

        }

    TReal32 guessNumOfEvals =

        TReal32(aNoOfRowsToEvaluate) / TReal32(guessNumOfEvaluatedRows);

    if (guessNumOfEvals < KPosNumOfEvalsMinLimit)

        {

        // We always need to evaluate the view at least one time.

        guessNumOfEvals = KPosNumOfEvalsMinLimit;

        }

    iGuessNumOfEvalsDivByTwo = guessNumOfEvals * KTarget;

    }

// -----------------------------------------------------------------------------

// TPosLmProgressHelper::HandleViewPrepared

//

// (other items were commented in a header).

// -----------------------------------------------------------------------------

//

void TPosLmProgressHelper::HandleViewPrepared()

    {

    iNumOfRowsInPreviousEvaluations = 0;

    iNumOfRowsInEvaluation = 0;

    iRowCounter = 0;

    }

// -----------------------------------------------------------------------------

// TPosLmProgressHelper::HandleViewEvaluatedL

//

// (other items were commented in a header).

// -----------------------------------------------------------------------------

//

void TPosLmProgressHelper::HandleViewEvaluatedL(TInt aNumOfRowsInView)

    {

    iEvalCounter++;

    iPreviousEvaluationProgress = iEvaluationProgress;

    iEvaluationProgress = CalculateEvaluationProgressL();

    iNumOfRowsInEvaluation = aNumOfRowsInView - iNumOfRowsInPreviousEvaluations;

    iNumOfRowsInPreviousEvaluations = aNumOfRowsInView;

    iRowCounter = 0;

    }

// -----------------------------------------------------------------------------

// TPosLmProgressHelper::HandleViewGetRow

//

// (other items were commented in a header).

// -----------------------------------------------------------------------------

//

void TPosLmProgressHelper::HandleViewGetRow()

    {

    iRowCounter++;

    }

// -----------------------------------------------------------------------------

// TPosLmProgressHelper::CalculateProgressL

//

// (other items were commented in a header).

// -----------------------------------------------------------------------------

//

TReal32 TPosLmProgressHelper::CalculateProgressL()

    {

    TReal32 progress = iEvaluationProgress;

    if (iRowCounter != iNumOfRowsInEvaluation)

        {

        __ASSERT_DEBUG(iNumOfRowsInEvaluation != 0,

            User::Leave(KErrDivideByZero));

        progress = iPreviousEvaluationProgress +

                   (iEvaluationProgress - iPreviousEvaluationProgress) *

                   iRowCounter / iNumOfRowsInEvaluation;

        }

    return progress;

    }

// -----------------------------------------------------------------------------

// TPosLmProgressHelper::CalculateEvaluationProgressL

//

// (other items were commented in a header).

// -----------------------------------------------------------------------------

//

TReal32 TPosLmProgressHelper::CalculateEvaluationProgressL()

    {

    // The formula 1-2^(-steps/(guessed number of steps/2)) has the following

    // characteristics:

    // * After 0 steps, the progress is 0%

    // * Progress increases for each step

    // * After half the guessed number of steps, the progress is 50%

    // * Progress will increase towards 100% but will never get there even if

    //   the number of steps passes the guessed number of steps.

    TReal target;

    User::LeaveIfError(

        Math::Pow(target,

                  TReal(2),

                  TReal(-(iEvalCounter / iGuessNumOfEvalsDivByTwo))));

    return TReal32(1 - target);

    }

// End of File