DateTime::CreateFromWin32FileDateTime: FILETIME is uint64

Called with a (stray value read from file?) sometimes absurdly high value
treated as an int64 negative value which the algorithm couldn't cope with,
resulting in weird DateTime ctor arguments that now assert.

Changed to uint64 and replaced calculation with Date::operator+=(long)

Change-Id: Ia8dbc10c4c633208730fce583e43afd828e7546f

1 files changed, 21 insertions, 30 deletions

diff --git a/tools/source/datetime/datetime.cxx b/tools/source/datetime/datetime.cxx
index d24f6f818184..eedbdea51abb 100644
--- a/tools/source/datetime/datetime.cxx
+++ b/tools/source/datetime/datetime.cxx
@@ -244,42 +244,33 @@ void DateTime::GetWin32FileDateTime( sal_uInt32 & rLower, sal_uInt32 & rUpper )
 
 DateTime DateTime::CreateFromWin32FileDateTime( sal_uInt32 rLower, sal_uInt32 rUpper )
 {
-    const sal_Int64 a100nPerSecond = SAL_CONST_INT64( 10000000 );
-    const sal_Int64 a100nPerDay = a100nPerSecond * sal_Int64( 60 * 60 * 24 );
+    // (rUpper|rLower) = 100-nanosecond intervals since 1601-01-01 00:00
+    const sal_uInt64 a100nPerSecond = SAL_CONST_UINT64( 10000000 );
+    const sal_uInt64 a100nPerDay = a100nPerSecond * sal_uInt64( 60 * 60 * 24 );
 
-    sal_Int64 aTime = sal_Int64(
+    sal_uInt64 aTime =
             sal_uInt64( rUpper ) * SAL_CONST_UINT64( 0x100000000 ) +
-            sal_uInt64( rLower ) );
+            sal_uInt64( rLower );
 
-    sal_Int64 nDays = aTime / a100nPerDay;
-    sal_Int64 nYears =
-        ( nDays -
-          ( nDays / ( 4 * 365 ) ) +
-          ( nDays / ( 100 * 365 ) ) -
-          ( nDays / ( 400 * 365 ) ) ) / 365;
-    nDays -= nYears * 365 + nYears / 4 - nYears / 100 + nYears / 400;
+    SAL_WARN_IF( static_cast<sal_Int64>(aTime) < 0, "tools.datetime",
+            "DateTime::CreateFromWin32FileDateTime - absurdly high value expected?");
 
-    sal_uInt16 nMonths = 0;
-    for( sal_Int64 nDaysCount = nDays; nDaysCount >= 0; )
-    {
-        nDays = nDaysCount;
-        nMonths ++;
-        nDaysCount -= Date(
-            1, nMonths, sal::static_int_cast< sal_uInt16 >(1601 + nYears) ).
-            GetDaysInMonth();
-    }
+    sal_uInt64 nDays = aTime / a100nPerDay;
+
+    Date aDate(1,1,1601);
+    // (0xffffffffffffffff / a100nPerDay = 21350398) fits into long
+    // (0x7fffffff = 2147483647)
+    aDate += static_cast<long>(nDays);
 
-    Date _aDate(
-        (sal_uInt16)( nDays + 1 ), nMonths,
-        sal::static_int_cast< sal_uInt16 >(nYears + 1601) );
-    tools::Time _aTime(
-        static_cast<sal_uInt32>( ( aTime / ( a100nPerSecond * 60 * 60 ) ) % sal_Int64( 24 ) ),
-        static_cast<sal_uInt32>( ( aTime / ( a100nPerSecond * 60 ) )      % sal_Int64( 60 ) ),
-        static_cast<sal_uInt32>( ( aTime / ( a100nPerSecond ) )           % sal_Int64( 60 ) ),
-        static_cast<sal_uInt64>(aTime % a100nPerSecond) * 100
-    );
+    SAL_WARN_IF( aDate - Date(1,1,1601) != static_cast<long>(nDays), "tools.datetime",
+            "DateTime::CreateFromWin32FileDateTime - date truncated to max");
 
-    return DateTime( _aDate, _aTime );
+    sal_uInt64 nNanos = (aTime - (nDays * a100nPerDay)) * 100;
+    return DateTime( aDate, tools::Time(
+                static_cast<sal_uInt32>((nNanos / tools::Time::nanoSecPerHour)   % sal_uInt64( 24 )),
+                static_cast<sal_uInt32>((nNanos / tools::Time::nanoSecPerMinute) % sal_uInt64( 60 )),
+                static_cast<sal_uInt32>((nNanos / tools::Time::nanoSecPerSec)    % sal_uInt64( 60 )),
+                static_cast<sal_uInt64>( nNanos % tools::Time::nanoSecPerSec)));
 }
 
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