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 #ifndef INCLUDED_SC_INC_SUBTOTAL_HXX
  21 #define INCLUDED_SC_INC_SUBTOTAL_HXX
  22
  23 #include "global.hxx"
  24
  25 class SubTotal
  26 {
  27 public:
  28     static bool SafePlus( double& fVal1, double fVal2);
  29     static bool SafeMult( double& fVal1, double fVal2);
  30     static bool SafeDiv( double& fVal1, double fVal2);
  31 };
  32
  33 class ScFunctionData;
  34
  35 /** Implements the Welford Online one-pass algorithm.
  36     See https://en.wikipedia.org/wiki/Algorithms_for_calculating_variance#Welford's_Online_algorithm
  37     and Donald E. Knuth, TAoCP vol.2, 3rd edn., p. 232
  38  */
  39 class WelfordRunner
  40 {
  41 public:
  42     WelfordRunner() : mfMean(0.0), mfM2(0.0), mnCount(0) {}
  43     void        update( double fVal );
  44     sal_uInt64  getCount() const                { return mnCount; }
  45     double      getVarianceSample() const       { return mnCount > 1 ? mfM2 / (mnCount-1) : 0.0; }
  46     double      getVariancePopulation() const   { return mnCount > 0 ? mfM2 / mnCount : 0.0; }
  47
  48     // The private variables can be abused by ScFunctionData as general
  49     // sum/min/max/ave/count/... variables to reduce memory footprint for that
  50     // ScFunctionData may be a mass object during consolidation.
  51     // ScFunctionData::update() and getResult() take care that purposes are not
  52     // mixed.
  53     friend class ScFunctionData;
  54 private:
  55     double      mfMean;
  56     double      mfM2;
  57     sal_uInt64  mnCount;
  58 };
  59
  60 /** To calculate a single subtotal function. */
  61 class ScFunctionData
  62 {
  63 public:
  64     ScFunctionData() : meFunc(SUBTOTAL_FUNC_NONE), mbError(false) {}
  65     ScFunctionData( ScSubTotalFunc eFn ) : meFunc(eFn), mbError(false) {}
  66
  67     void            update( double fNewVal );
  68     /// Check getError() after (!) obtaining the result.
  69     double          getResult();
  70     bool            getError() const    { return mbError; }
  71     ScSubTotalFunc  getFunc() const     { return meFunc; }
  72     void            setError()          { mbError = true; }
  73
  74 private:
  75     WelfordRunner   maWelford;
  76     ScSubTotalFunc  meFunc;
  77     bool            mbError;
  78
  79     double&         getValueRef()   { return maWelford.mfMean; }
  80     sal_uInt64&     getCountRef()   { return maWelford.mnCount; }
  81 };
  82
  83 #endif
  84
  85 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */