Move lcl_getHourMinuteSecond() to tools::Time::GetClock()

Also add fFractionOfSecond and nFractionDecimals to obtain the
remaining fraction of second.

In preparation to use this in the number formatter and other
places that obtain the wall clock time particles, which likely so
far use bad rounding as well.

Change-Id: I4fbea4165c560646438b06c340756c97dafa7c78
Reviewed-on: https://gerrit.libreoffice.org/59700
Reviewed-by: Eike Rathke <erack@redhat.com>
Tested-by: Jenkins

1 files changed, 51 insertions, 0 deletions

diff --git a/tools/source/datetime/ttime.cxx b/tools/source/datetime/ttime.cxx
index a8b3a5d52b58..d9bfc40dfc02 100644
--- a/tools/source/datetime/ttime.cxx
+++ b/tools/source/datetime/ttime.cxx
@@ -39,6 +39,7 @@
 #endif
 
 #include <sal/log.hxx>
+#include <rtl/math.hxx>
 #include <tools/time.hxx>
 #include <osl/diagnose.h>
 
@@ -269,6 +270,56 @@ double tools::Time::GetTimeInDays() const
     return (nHour + (nMin / 60) + (nSec / (minInHour * secInMin)) + (nNanoSec / (minInHour * secInMin * nanoSecInSec))) / 24 * nSign;
 }
 
+// static
+void tools::Time::GetClock( double fTimeInDays,
+                            sal_uInt16& nHour, sal_uInt16& nMinute, sal_uInt16& nSecond,
+                            double& fFractionOfSecond, int nFractionDecimals )
+{
+    const double fTime = fTimeInDays - rtl::math::approxFloor(fTimeInDays); // date part absent
+
+    // If 0 then full day (or no day), shortcut.
+    // If < 0 then approxFloor() effectively returned the ceiling (note this
+    // also holds for negative fTimeInDays values) because of a near identical
+    // value, shortcut this to a full day as well.
+    // If >= 1.0 (actually == 1.0) then fTimeInDays is a negative small value
+    // not significant for a representable time and approxFloor() returned -1,
+    // shortcut to 0:0:0, otherwise it would become 24:0:0.
+    if (fTime <= 0.0 || fTime >= 1.0)
+    {
+        nHour = nMinute = nSecond = 0;
+        return;
+    }
+
+    // In seconds, including milli and nano.
+    const double fRawSeconds = fTime * tools::Time::secondPerDay;
+
+    // Round to nanoseconds, which is the highest resolution this could be
+    // influenced by.
+    double fSeconds = rtl::math::round( fRawSeconds, 9);
+
+    // If this ended up as a full day the original value was very very close
+    // but not quite. Take that.
+    if (fSeconds >= tools::Time::secondPerDay)
+        fSeconds = fRawSeconds;
+
+    // Now do not round values (specifically not up), but truncate to the next
+    // magnitude, so 23:59:59.99 is still 23:59:59 and not 24:00:00 (or even
+    // 00:00:00 which Excel does).
+    nHour = fSeconds / tools::Time::secondPerHour;
+    fSeconds -= nHour * tools::Time::secondPerHour;
+    nMinute = fSeconds / tools::Time::secondPerMinute;
+    fSeconds -= nMinute * tools::Time::secondPerMinute;
+    nSecond = fSeconds;
+    fSeconds -= nSecond;
+
+    // Do not round the fraction, otherwise .999 would end up as .00 again.
+    if (nFractionDecimals > 0)
+        fFractionOfSecond = rtl::math::pow10Exp( std::trunc(
+                    rtl::math::pow10Exp( fSeconds, nFractionDecimals)), -nFractionDecimals);
+    else
+        fFractionOfSecond = fSeconds;
+}
+
 Time& tools::Time::operator =( const tools::Time& rTime )
 {
     nTime = rTime.nTime;