CMathUtils::roundToMultipleOf

refs #556

src/blackmisc/math/mathutils.cpp

@@ -93,5 +93,21 @@ namespace BlackMisc
             return r % ((high + 1) - low) + low;
         }
 
+        int CMathUtils::roundToMultipleOf(int value, int divisor)
+        {
+            Q_ASSERT(divisor != 0);
+            Q_ASSERT(divisor >= - std::numeric_limits<int>::max());
+            divisor = std::abs(divisor);
+            Q_ASSERT(std::abs(value) < std::numeric_limits<int>::max() - divisor / 2);
+
+            int multiplier = value / divisor;
+            int remainder = std::abs(value % divisor);
+            int shortfall = divisor - remainder;
+
+            if (shortfall < remainder) { multiplier += value < 0 ? -1 : 1; }
+
+            return multiplier * divisor;
+        }
+
     } // namespace
 } // namespace

src/blackmisc/math/mathutils.h

@@ -101,6 +101,9 @@ namespace BlackMisc
 
             //! Random number between low and high
             static int randomInteger(int low, int high);
+
+            //! Round numToRound to the nearest multiple of multiple
+            static int roundToMultipleOf(int value, int divisor);
         };
 
     } // namespace

tests/blackmisc/testblackmiscmain.cpp

@@ -17,6 +17,7 @@
 #include "testvaluecache.h"
 #include "testblackmiscmain.h"
 #include "testweather.h"
+#include "testmath.h"
 
 namespace BlackMiscTest
 {
@@ -36,6 +37,7 @@ namespace BlackMiscTest
             CTestIdentifier identifierTests;
             CTestValueCache valueCacheTests;
             CTestWeather weatherTests;
+            CTestMath mathTests;
             status |= QTest::qExec(&pqBaseTests, argc, argv);
             status |= QTest::qExec(&avBaseTests, argc, argv);
             status |= QTest::qExec(&geoTests, argc, argv);
@@ -45,6 +47,7 @@ namespace BlackMiscTest
             status |= QTest::qExec(&inputTests, argc, argv);
             status |= QTest::qExec(&valueCacheTests, argc, argv);
             status |= QTest::qExec(&weatherTests, argc, argv);
+            status |= QTest::qExec(&mathTests, argc, argv);
         }
         return status;
     }

tests/blackmisc/testmath.cpp

@@ -0,0 +1,38 @@
+/* Copyright (C) 2016
+ * swift Project Community / Contributors
+ *
+ * This file is part of swift project. It is subject to the license terms in the LICENSE file found in the top-level
+ * directory of this distribution and at http://www.swift-project.org/license.html. No part of swift project,
+ * including this file, may be copied, modified, propagated, or distributed except according to the terms
+ * contained in the LICENSE file.
+ */
+
+#include "testmath.h"
+#include "blackmisc/math/mathutils.h"
+
+using namespace BlackMisc::Math;
+
+namespace BlackMiscTest
+{
+    void CTestMath::testRoundToMultipleOf()
+    {
+        QVERIFY2(CMathUtils::roundToMultipleOf(0, 3) == 0, "Nearest multiple of 3 from 0 should be 0");
+        QVERIFY2(CMathUtils::roundToMultipleOf(1, 3) == 0, "Nearest multiple of 3 from 1 should be 0");
+        QVERIFY2(CMathUtils::roundToMultipleOf(2, 3) == 3, "Nearest multiple of 3 from 2 should be 3");
+        QVERIFY2(CMathUtils::roundToMultipleOf(3, 3) == 3, "Nearest multiple of 3 from 3 should be 3");
+
+        QVERIFY2(CMathUtils::roundToMultipleOf(0, -3) == 0, "Nearest multiple of -3 from 0 should be 0");
+        QVERIFY2(CMathUtils::roundToMultipleOf(1, -3) == 0, "Nearest multiple of -3 from 1 should be 0");
+        QVERIFY2(CMathUtils::roundToMultipleOf(2, -3) == 3, "Nearest multiple of -3 from 2 should be 3");
+        QVERIFY2(CMathUtils::roundToMultipleOf(3, -3) == 3, "Nearest multiple of -3 from 3 should be 3");
+
+        QVERIFY2(CMathUtils::roundToMultipleOf(-1, 3) == 0, "Nearest multiple of 3 from -1 should be 0");
+        QVERIFY2(CMathUtils::roundToMultipleOf(-2, 3) == -3, "Nearest multiple of 3 from -2 should be -3");
+        QVERIFY2(CMathUtils::roundToMultipleOf(-3, 3) == -3, "Nearest multiple of 3 from -3 should be -3");
+
+        QVERIFY2(CMathUtils::roundToMultipleOf(-1, -3) == 0, "Nearest multiple of -3 from -1 should be 0");
+        QVERIFY2(CMathUtils::roundToMultipleOf(-2, -3) == -3, "Nearest multiple of -3 from -2 should be -3");
+        QVERIFY2(CMathUtils::roundToMultipleOf(-3, -3) == -3, "Nearest multiple of -3 from -3 should be -3");
+    }
+
+} // namespace

tests/blackmisc/testmath.h

@@ -0,0 +1,36 @@
+/* Copyright (C) 2016
+ * swift project community / contributors
+ *
+ * This file is part of swift project. It is subject to the license terms in the LICENSE file found in the top-level
+ * directory of this distribution and at http://www.swift-project.org/license.html. No part of swift project,
+ * including this file, may be copied, modified, propagated, or distributed except according to the terms
+ * contained in the LICENSE file.
+ */
+
+//! \file
+
+#ifndef BLACKMISCTEST_TESTMATH_H
+#define BLACKMISCTEST_TESTMATH_H
+
+#include <QtTest/QtTest>
+
+namespace BlackMiscTest
+{
+
+    //! Math classes tests
+    class CTestMath : public QObject
+    {
+        Q_OBJECT
+
+    public:
+        //! Standard test case constructor
+        explicit CTestMath(QObject *parent = nullptr) : QObject(parent) {}
+
+    private slots:
+        //! Unit test for round to multiple of
+        void testRoundToMultipleOf();
+    };
+
+} // namespace
+
+#endif // guard