Round fraction if possible, else truncate; tools::Time::GetClock()

With this also some test cases can be narrowed.

Change-Id: Ic754baf135dbd362b80fac1cf080758f46017e01
Reviewed-on: https://gerrit.libreoffice.org/59753Reviewed-by: Eike Rathke <erack@redhat.com>
Tested-by: Jenkins

tools/qa/cppunit/test_time.cxx

@@ -96,24 +96,42 @@ void TimeTest::testClockValues()
     CPPUNIT_ASSERT_EQUAL_MESSAGE("Hour value.", sal_uInt16(0), nHour);
     CPPUNIT_ASSERT_EQUAL_MESSAGE("Minute value.", sal_uInt16(0), nMinute);
     CPPUNIT_ASSERT_EQUAL_MESSAGE("Second value.", sal_uInt16(0), nSecond);
-    // Last digit may differ.
-    CPPUNIT_ASSERT_DOUBLES_EQUAL_MESSAGE("Fraction value.", 0.999, fFractionOfSecond, 1.1e-3);
+    // Expect this to be a truncated 0.999999
+    CPPUNIT_ASSERT_DOUBLES_EQUAL_MESSAGE("Fraction value.", 0.999, fFractionOfSecond, 0.0);
 
     fTime = 0.524268391203704;
     Time::GetClock(fTime, nHour, nMinute, nSecond, fFractionOfSecond, 3);
     CPPUNIT_ASSERT_EQUAL_MESSAGE("Hour value.", sal_uInt16(12), nHour);
     CPPUNIT_ASSERT_EQUAL_MESSAGE("Minute value.", sal_uInt16(34), nMinute);
     CPPUNIT_ASSERT_EQUAL_MESSAGE("Second value.", sal_uInt16(56), nSecond);
-    // Last digit may differ.
-    CPPUNIT_ASSERT_DOUBLES_EQUAL_MESSAGE("Fraction value.", 0.789, fFractionOfSecond, 1.1e-3);
+    CPPUNIT_ASSERT_DOUBLES_EQUAL_MESSAGE("Fraction value.", 0.789, fFractionOfSecond, 0.0);
 
     fTime = -0.000001;
-    Time::GetClock(fTime, nHour, nMinute, nSecond, fFractionOfSecond, 9);
+    Time::GetClock(fTime, nHour, nMinute, nSecond, fFractionOfSecond, 13);
     CPPUNIT_ASSERT_EQUAL_MESSAGE("Hour value.", sal_uInt16(23), nHour);
     CPPUNIT_ASSERT_EQUAL_MESSAGE("Minute value.", sal_uInt16(59), nMinute);
     CPPUNIT_ASSERT_EQUAL_MESSAGE("Second value.", sal_uInt16(59), nSecond);
     // Expect this to be exact within floating point accuracy.
-    CPPUNIT_ASSERT_DOUBLES_EQUAL_MESSAGE("Fraction value.", 0.913599999, fFractionOfSecond, 1e-15);
+    // This is a hairy rounding condition, if it yields problems on any
+    // platform feel free to disable the test for that platform.
+    CPPUNIT_ASSERT_DOUBLES_EQUAL_MESSAGE("Fraction value.", 0.9135999999999, fFractionOfSecond,
+                                         1e-14);
+
+    fTime = -0.000001;
+    Time::GetClock(fTime, nHour, nMinute, nSecond, fFractionOfSecond, 4);
+    CPPUNIT_ASSERT_EQUAL_MESSAGE("Hour value.", sal_uInt16(23), nHour);
+    CPPUNIT_ASSERT_EQUAL_MESSAGE("Minute value.", sal_uInt16(59), nMinute);
+    CPPUNIT_ASSERT_EQUAL_MESSAGE("Second value.", sal_uInt16(59), nSecond);
+    // Expect this to be rounded.
+    CPPUNIT_ASSERT_DOUBLES_EQUAL_MESSAGE("Fraction value.", 0.9136, fFractionOfSecond, 0.0);
+
+    fTime = -0.00000000001;
+    Time::GetClock(fTime, nHour, nMinute, nSecond, fFractionOfSecond, 4);
+    CPPUNIT_ASSERT_EQUAL_MESSAGE("Hour value.", sal_uInt16(23), nHour);
+    CPPUNIT_ASSERT_EQUAL_MESSAGE("Minute value.", sal_uInt16(59), nMinute);
+    CPPUNIT_ASSERT_EQUAL_MESSAGE("Second value.", sal_uInt16(59), nSecond);
+    // Expect this to be a truncated 0.999999
+    CPPUNIT_ASSERT_DOUBLES_EQUAL_MESSAGE("Fraction value.", 0.9999, fFractionOfSecond, 0.0);
 
     fTime = -1e-24; // value insignificant for time
     Time::GetClock(fTime, nHour, nMinute, nSecond, fFractionOfSecond, 0);

tools/source/datetime/ttime.cxx

@@ -313,10 +313,18 @@ void tools::Time::GetClock( double fTimeInDays,
     nSecond = fSeconds;
     fSeconds -= nSecond;
 
-    // Do not round the fraction, otherwise .999 would end up as .00 again.
+    assert(fSeconds < 1.0);     // or back to the drawing board..
+
     if (nFractionDecimals > 0)
-        fFractionOfSecond = rtl::math::pow10Exp( std::trunc(
-                    rtl::math::pow10Exp( fSeconds, nFractionDecimals)), -nFractionDecimals);
+    {
+        // Do not simply round the fraction, otherwise .999 would end up as .00
+        // again. Truncate instead if rounding would round up into an integer
+        // value.
+        fFractionOfSecond = rtl::math::round( fSeconds, nFractionDecimals);
+        if (fFractionOfSecond >= 1.0)
+            fFractionOfSecond = rtl::math::pow10Exp( std::trunc(
+                        rtl::math::pow10Exp( fSeconds, nFractionDecimals)), -nFractionDecimals);
+    }
     else
         fFractionOfSecond = fSeconds;
 }