/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */

/*

 * This file is part of the LibreOffice project.

 *

 * This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this

 * file, You can obtain one at http://mozilla.org/MPL/2.0/.

 *

 * This file incorporates work covered by the following license notice:

 *

 *   Licensed to the Apache Software Foundation (ASF) under one or more

 *   contributor license agreements. See the NOTICE file distributed

 *   with this work for additional information regarding copyright

 *   ownership. The ASF licenses this file to you under the Apache

 *   License, Version 2.0 (the "License"); you may not use this file

 *   except in compliance with the License. You may obtain a copy of

 *   the License at http://www.apache.org/licenses/LICENSE-2.0 .

 */

#pragma once

#include "global.hxx"

class SubTotal

{

public:

    static bool SafePlus( double& fVal1, double fVal2);

    static bool SafeMult( double& fVal1, double fVal2);

    static bool SafeDiv( double& fVal1, double fVal2);

};

/** Implements the Welford Online one-pass algorithm.

    See https://en.wikipedia.org/wiki/Algorithms_for_calculating_variance#Welford's_Online_algorithm

    and Donald E. Knuth, TAoCP vol.2, 3rd edn., p. 232

 */

class WelfordRunner

{

public:

    WelfordRunner() : mfMean(0.0), mfM2(0.0), mnCount(0) {}

    void        update( double fVal );

    sal_uInt64  getCount() const                { return mnCount; }

    double      getVarianceSample() const       { return mnCount > 1 ? mfM2 / (mnCount-1) : 0.0; }

    double      getVariancePopulation() const   { return mnCount > 0 ? mfM2 / mnCount : 0.0; }

    // The private variables can be abused by ScFunctionData as general

    // sum/min/max/ave/count/... variables to reduce memory footprint for that

    // ScFunctionData may be a mass object during consolidation.

    // ScFunctionData::update() and getResult() take care that purposes are not

    // mixed.

    friend class ScFunctionData;

private:

    double      mfMean;

    double      mfM2;

    sal_uInt64  mnCount;

};

/** To calculate a single subtotal function. */

class ScFunctionData

{

public:

    ScFunctionData() : meFunc(SUBTOTAL_FUNC_NONE), mbError(false) {}

    ScFunctionData( ScSubTotalFunc eFn ) : meFunc(eFn), mbError(false) {}

    void            update( double fNewVal );

    /// Check getError() after (!) obtaining the result.

    double          getResult();

    bool            getError() const    { return mbError; }

    ScSubTotalFunc  getFunc() const     { return meFunc; }

    void            setError()          { mbError = true; }

private:

    WelfordRunner   maWelford;

    ScSubTotalFunc  meFunc;

    bool            mbError;

    double&         getValueRef()   { return maWelford.mfMean; }

    sal_uInt64&     getCountRef()   { return maWelford.mnCount; }

};

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