sc/inc/subtotal.hxx

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
   2 /*
   3  * This file is part of the LibreOffice project.
   4  *
   5  * This Source Code Form is subject to the terms of the Mozilla Public
   6  * License, v. 2.0. If a copy of the MPL was not distributed with this
   7  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
   8  *
   9  * This file incorporates work covered by the following license notice:
  10  *
  11  *   Licensed to the Apache Software Foundation (ASF) under one or more
  12  *   contributor license agreements. See the NOTICE file distributed
  13  *   with this work for additional information regarding copyright
  14  *   ownership. The ASF licenses this file to you under the Apache
  15  *   License, Version 2.0 (the "License"); you may not use this file
  16  *   except in compliance with the License. You may obtain a copy of
  17  *   the License at http://www.apache.org/licenses/LICENSE-2.0 .
  18  */
  19
  20 #pragma once
  21
  22 #include "global.hxx"
  23
  24 class SubTotal
  25 {
  26 public:
  27     static bool SafePlus( double& fVal1, double fVal2);
  28     static bool SafeMult( double& fVal1, double fVal2);
  29     static bool SafeDiv( double& fVal1, double fVal2);
  30 };
  31
  32 class ScFunctionData;
  33
  34 /** Implements the Welford Online one-pass algorithm.
  35     See https://en.wikipedia.org/wiki/Algorithms_for_calculating_variance#Welford's_Online_algorithm
  36     and Donald E. Knuth, TAoCP vol.2, 3rd edn., p. 232
  37  */
  38 class WelfordRunner
  39 {
  40 public:
  41     WelfordRunner() : mfMean(0.0), mfM2(0.0), mnCount(0) {}
  42     void        update( double fVal );
  43     sal_uInt64  getCount() const                { return mnCount; }
  44     double      getVarianceSample() const       { return mnCount > 1 ? mfM2 / (mnCount-1) : 0.0; }
  45     double      getVariancePopulation() const   { return mnCount > 0 ? mfM2 / mnCount : 0.0; }
  46
  47     // The private variables can be abused by ScFunctionData as general
  48     // sum/min/max/ave/count/... variables to reduce memory footprint for that
  49     // ScFunctionData may be a mass object during consolidation.
  50     // ScFunctionData::update() and getResult() take care that purposes are not
  51     // mixed.
  52     friend class ScFunctionData;
  53 private:
  54     double      mfMean;
  55     double      mfM2;
  56     sal_uInt64  mnCount;
  57 };
  58
  59 /** To calculate a single subtotal function. */
  60 class ScFunctionData
  61 {
  62 public:
  63     ScFunctionData() : meFunc(SUBTOTAL_FUNC_NONE), mbError(false) {}
  64     ScFunctionData( ScSubTotalFunc eFn ) : meFunc(eFn), mbError(false) {}
  65
  66     void            update( double fNewVal );
  67     /// Check getError() after (!) obtaining the result.
  68     double          getResult();
  69     bool            getError() const    { return mbError; }
  70     ScSubTotalFunc  getFunc() const     { return meFunc; }
  71     void            setError()          { mbError = true; }
  72
  73 private:
  74     WelfordRunner   maWelford;
  75     ScSubTotalFunc  meFunc;
  76     bool            mbError;
  77
  78     double&         getValueRef()   { return maWelford.mfMean; }
  79     sal_uInt64&     getCountRef()   { return maWelford.mnCount; }
  80 };
  81
  82 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */