From 5dbf4468f2fa0b36fa575354f87a8ea870177161 Mon Sep 17 00:00:00 2001
From: Klaus Basan <klaus.basan@klausbasan.de>
Date: Sun, 30 Sep 2018 22:28:37 +0200
Subject: [PATCH] COM frequency rounding + testcase

---
 src/blackmisc/aviation/comsystem.cpp          | 14 ++++++------
 .../aviation/testaviation/testaviation.cpp    | 22 +++++++++++++++++++
 2 files changed, 29 insertions(+), 7 deletions(-)

diff --git a/src/blackmisc/aviation/comsystem.cpp b/src/blackmisc/aviation/comsystem.cpp
index f6c17eb72..9622b35b1 100644
--- a/src/blackmisc/aviation/comsystem.cpp
+++ b/src/blackmisc/aviation/comsystem.cpp
@@ -125,14 +125,14 @@ namespace BlackMisc
         {
             if (frequency.isNull()) { return; }
             const double channelSpacingKHz = CComSystem::channelSpacingToFrequencyKHz(channelSpacing);
-            const double f = frequency.valueRounded(CFrequencyUnit::kHz(), 0);
-            const quint32 d = static_cast<quint32>(f / channelSpacingKHz);
+            const double fKHz = frequency.valueRounded(CFrequencyUnit::kHz(), 0);
+            const int dDown = static_cast<int>(fKHz / channelSpacingKHz);
+            const double fDownKHz = dDown * channelSpacingKHz;
+            const double fUpKHz = (dDown + 1) * channelSpacingKHz;
+            const bool down = qAbs(fKHz - fDownKHz) < qAbs(fUpKHz - fKHz); // which is the closest value
+            const double fMHz(CMathUtils::round((down ? fDownKHz : fUpKHz) / 1000.0, 3));
             frequency.switchUnit(CFrequencyUnit::MHz());
-            const double f0 = frequency.valueRounded(CFrequencyUnit::MHz(), 3);
-            const double f1 = CMathUtils::round(d * (channelSpacingKHz / 1000.0), 3);
-            const double f2 = CMathUtils::round((d + 1) * (channelSpacingKHz / 1000.0), 3);
-            const bool down = qAbs(f1 - f0) < qAbs(f2 - f0); // which is the closest value
-            frequency.setCurrentUnitValue(down ? f1 : f2);
+            frequency.setCurrentUnitValue(fMHz);
         }
 
         bool CComSystem::isWithinChannelSpacing(const CFrequency &setFrequency, const CFrequency &compareFrequency, CComSystem::ChannelSpacing channelSpacing)
diff --git a/tests/blackmisc/aviation/testaviation/testaviation.cpp b/tests/blackmisc/aviation/testaviation/testaviation.cpp
index 9bebe8a67..42f4aa6c7 100644
--- a/tests/blackmisc/aviation/testaviation/testaviation.cpp
+++ b/tests/blackmisc/aviation/testaviation/testaviation.cpp
@@ -59,6 +59,9 @@ namespace BlackMiscTest
         //! COM and NAV units
         void comAndNav();
 
+        //! COM frequency rounding
+        void comFrequencyRounding();
+
         //! Transponder
         void transponder();
 
@@ -108,6 +111,25 @@ namespace BlackMiscTest
         QVERIFY2(!CNavSystem::isValidCivilNavigationFrequency(CFrequency(200.0, CFrequencyUnit::MHz())), "Expect invalid nav frequency");
     }
 
+    void CTestAviation::comFrequencyRounding()
+    {
+        const CFrequency f1 = CFrequency(122.8, CFrequencyUnit::MHz());
+        const CFrequency f2 = CFrequency(122.795, CFrequencyUnit::MHz());
+        const CFrequency f3 = CFrequency(122.805, CFrequencyUnit::MHz());
+
+        QVERIFY2(f1 == f1, "Ups, how can this fail");
+        QVERIFY2(f1 != f2, "Ups, how can this fail");
+        QVERIFY2(f1 != f3, "Ups, how can this fail");
+
+        CFrequency up(f2);
+        CComSystem::roundToChannelSpacing(up, CComSystem::ChannelSpacing25KHz);
+        QVERIFY2(up == f1, "Expect rounding up");
+
+        CFrequency down(f3);
+        CComSystem::roundToChannelSpacing(down, CComSystem::ChannelSpacing25KHz);
+        QVERIFY2(down == f1, "Expect rounding up");
+    }
+
     void CTestAviation::transponder()
     {
         CTransponder t1 = CTransponder::getStandardTransponder(7000, CTransponder::StateStandby);