writerfilter/source/resourcemodel/Fraction.cxx

   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 #include <resourcemodel/Fraction.hxx>
  21
  22 namespace writerfilter {
  23 namespace resourcemodel {
  24
  25 // Stein's binary GCD for non-negative integers
  26 // https://en.wikipedia.org/wiki/Binary_GCD_algorithm
  27 static sal_uInt32 gcd(sal_uInt32 a, sal_uInt32 b)
  28 {
  29     if (a == 0 || b == 0)
  30         return a | b;
  31
  32     sal_uInt32 nShift = 0;
  33     while (((a | b) & 1) == 0)
  34     {
  35         a >>= 1;
  36         b >>= 1;
  37         ++nShift;
  38     }
  39
  40     while ((a & 1) == 0)
  41         a >>= 1;
  42
  43     do
  44     {
  45         while ((b & 1) == 0)
  46             b >>= 1;
  47
  48         if (a < b)
  49         {
  50             b -= a;
  51         }
  52         else
  53         {
  54             sal_uInt32 nDiff = a - b;
  55             a = b;
  56             b = nDiff;
  57         }
  58
  59         b >>= 1;
  60     }
  61     while (b != 0);
  62
  63     return a << nShift;
  64 }
  65
  66 static sal_uInt32 lcm(sal_Int32 a, sal_Int32 b)
  67 {
  68     return abs(a * b) / gcd(abs(a), abs(b));
  69 }
  70
  71 Fraction::Fraction(sal_Int32 nNumerator, sal_Int32 nDenominator)
  72 {
  73     init(nNumerator, nDenominator);
  74 }
  75
  76 Fraction::~Fraction()
  77 {
  78 }
  79
  80 void Fraction::init(sal_Int32 nNumerator, sal_Int32 nDenominator)
  81 {
  82     // fdo#41068 pass non-negative numbers to gcd
  83     sal_Int32 const nGCD = gcd(abs(nNumerator), abs(nDenominator));
  84
  85     // fdo#76803 do signed division
  86     mnNumerator = nNumerator / nGCD;
  87     mnDenominator = nDenominator / nGCD;
  88 }
  89
  90 void Fraction::assign(const Fraction & rFraction)
  91 {
  92     init(rFraction.mnNumerator, rFraction.mnDenominator);
  93 }
  94
  95 Fraction Fraction::inverse() const
  96 {
  97     return Fraction(mnDenominator, mnNumerator);
  98 }
  99
 100 Fraction Fraction::operator + (const Fraction & rFraction) const
 101 {
 102     sal_uInt32 nLCM = lcm(mnDenominator, rFraction.mnDenominator);
 103
 104     return Fraction(mnNumerator * nLCM / mnDenominator + rFraction.mnNumerator * nLCM / rFraction.mnDenominator, nLCM);
 105 }
 106
 107 Fraction Fraction::operator - (const Fraction & rFraction) const
 108 {
 109     sal_uInt32 nLCM = lcm(mnDenominator, rFraction.mnDenominator);
 110
 111     return Fraction(mnNumerator * nLCM / mnDenominator - rFraction.mnNumerator * nLCM / rFraction.mnDenominator, nLCM);
 112 }
 113
 114 Fraction Fraction::operator * (const Fraction & rFraction) const
 115 {
 116     return Fraction(mnNumerator * rFraction.mnNumerator, mnDenominator * rFraction.mnDenominator);
 117 }
 118
 119 Fraction Fraction::operator / (const Fraction & rFraction) const
 120 {
 121     return *this * rFraction.inverse();
 122 }
 123
 124 Fraction Fraction::operator = (const Fraction & rFraction)
 125 {
 126     assign(rFraction);
 127
 128     return *this;
 129 }
 130
 131 Fraction::operator sal_Int32() const
 132 {
 133     return mnNumerator / mnDenominator;
 134 }
 135
 136 Fraction::operator float() const
 137 {
 138     return static_cast<float>(mnNumerator) / static_cast<float>(mnDenominator);
 139 }
 140
 141 }}
 142
 143 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */