Fix FILETIME <-> wxDateTime conversions while DST is in effect in wxMSW.

The result was (consistently, so the tests still passed) off by an hour when
the program was ran while DST was in effect. Fix this by avoiding the use of
FileTimeToLocalFileTime() and LocalFileTimeToFileTime() and just directly
converting FILETIME values to wxDateTime. Not only this is more correct but
it's also simpler and more efficient as well.

Also add a unit test for wxFileName::SetTimes() too.

Closes #13098.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74423 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/changes.txt

@@ -711,6 +711,7 @@ wxMSW:
 - Fix filter checks in wxDir::FindFirst/Next() (Catalin Raceanu).
 - Add support for wxICON_AUTH_NEEDED to wxMessageDialog (Chris Spencer).
 - Fix printing too many copies of the document in some cases (John Roberts).
+- Fix DST confusion in wxFileName::{Set,Get}Times().
 
 wxOSX/Cocoa:
 

src/common/filename.cpp

@@ -93,6 +93,7 @@
 #include "wx/config.h"          // for wxExpandEnvVars
 #include "wx/dynlib.h"
 #include "wx/dir.h"
+#include "wx/longlong.h"
 
 #if defined(__WIN32__) && defined(__MINGW32__)
     #include "wx/msw/gccpriv.h"
@@ -231,49 +232,30 @@ private:
 
 #if wxUSE_DATETIME && defined(__WIN32__) && !defined(__WXMICROWIN__)
 
-// convert between wxDateTime and FILETIME which is a 64-bit value representing
-// the number of 100-nanosecond intervals since January 1, 1601.
+// Convert between wxDateTime and FILETIME which is a 64-bit value representing
+// the number of 100-nanosecond intervals since January 1, 1601 UTC.
+//
+// This is the offset between FILETIME epoch and the Unix/wxDateTime Epoch.
+static wxInt64 EPOCH_OFFSET_IN_MSEC = wxLL(11644473600000);
 
 static void ConvertFileTimeToWx(wxDateTime *dt, const FILETIME &ft)
 {
-    FILETIME ftcopy = ft;
-    FILETIME ftLocal;
-    if ( !::FileTimeToLocalFileTime(&ftcopy, &ftLocal) )
-    {
-        wxLogLastError(wxT("FileTimeToLocalFileTime"));
-    }
+    wxLongLong t(ft.dwHighDateTime, ft.dwLowDateTime);
+    t /= 10000; // Convert hundreds of nanoseconds to milliseconds.
+    t -= EPOCH_OFFSET_IN_MSEC;
 
-    SYSTEMTIME st;
-    if ( !::FileTimeToSystemTime(&ftLocal, &st) )
-    {
-        wxLogLastError(wxT("FileTimeToSystemTime"));
-    }
-
-    dt->Set(st.wDay, wxDateTime::Month(st.wMonth - 1), st.wYear,
-            st.wHour, st.wMinute, st.wSecond, st.wMilliseconds);
+    *dt = wxDateTime(t);
 }
 
 static void ConvertWxToFileTime(FILETIME *ft, const wxDateTime& dt)
 {
-    SYSTEMTIME st;
-    st.wDay = dt.GetDay();
-    st.wMonth = (WORD)(dt.GetMonth() + 1);
-    st.wYear = (WORD)dt.GetYear();
-    st.wHour = dt.GetHour();
-    st.wMinute = dt.GetMinute();
-    st.wSecond = dt.GetSecond();
-    st.wMilliseconds = dt.GetMillisecond();
+    // Undo the conversions above.
+    wxLongLong t(dt.GetValue());
+    t += EPOCH_OFFSET_IN_MSEC;
+    t *= 10000;
 
-    FILETIME ftLocal;
-    if ( !::SystemTimeToFileTime(&st, &ftLocal) )
-    {
-        wxLogLastError(wxT("SystemTimeToFileTime"));
-    }
-
-    if ( !::LocalFileTimeToFileTime(&ftLocal, ft) )
-    {
-        wxLogLastError(wxT("LocalFileTimeToFileTime"));
-    }
+    ft->dwHighDateTime = t.GetHi();
+    ft->dwLowDateTime = t.GetLo();
 }
 
 #endif // wxUSE_DATETIME && __WIN32__

tests/filename/filenametest.cpp

@@ -35,6 +35,7 @@
 #endif // __UNIX__
 
 #include "testfile.h"
+#include "testdate.h"
 
 // ----------------------------------------------------------------------------
 // test data
@@ -139,6 +140,7 @@ private:
         CPPUNIT_TEST( TestVolumeUniqueName );
         CPPUNIT_TEST( TestCreateTempFileName );
         CPPUNIT_TEST( TestGetTimes );
+        CPPUNIT_TEST( TestSetTimes );
         CPPUNIT_TEST( TestExists );
         CPPUNIT_TEST( TestIsSame );
 #if defined(__UNIX__)
@@ -161,6 +163,7 @@ private:
     void TestVolumeUniqueName();
     void TestCreateTempFileName();
     void TestGetTimes();
+    void TestSetTimes();
     void TestExists();
     void TestIsSame();
 #if defined(__UNIX__)
@@ -664,6 +667,27 @@ void FileNameTestCase::TestGetTimes()
     CPPUNIT_ASSERT(dtAccess.IsEqualUpTo(wxDateTime::Now(), wxTimeSpan(0,1)));
 }
 
+void FileNameTestCase::TestSetTimes()
+{
+    wxFileName fn(wxFileName::CreateTempFileName("filenametest"));
+    CPPUNIT_ASSERT( fn.IsOk() );
+    wxON_BLOCK_EXIT1( wxRemoveFile, fn.GetFullPath() );
+
+    const wxDateTime dtAccess(1, wxDateTime::Jan, 2013);
+    const wxDateTime dtModify(1, wxDateTime::Feb, 2013);
+    const wxDateTime dtCreate(1, wxDateTime::Mar, 2013);
+
+    CPPUNIT_ASSERT( fn.SetTimes(&dtAccess, &dtModify, &dtCreate) );
+
+    wxDateTime dtAccess2,
+               dtModify2,
+               dtCreate2;
+    CPPUNIT_ASSERT( fn.GetTimes(&dtAccess2, &dtModify2, &dtCreate2) );
+    CPPUNIT_ASSERT_EQUAL( dtAccess, dtAccess2 );
+    CPPUNIT_ASSERT_EQUAL( dtModify, dtModify2 );
+    CPPUNIT_ASSERT_EQUAL( dtCreate, dtCreate2 );
+}
+
 void FileNameTestCase::TestExists()
 {
     wxFileName fn(wxFileName::CreateTempFileName("filenametest"));