QTime: restore Qt3 compatibility in the QDataStream operators

A Qt5 program writing a null QTime() using setVersion(QDataStream::Qt_3_3), and then a Qt3 program reading that, would lead to a weird QTime, with isNull=false, isValid=false, hour=1193, minute=2, second=47, ms=295. This commit restores interoperability, by writing out the expected value (0) for a null QTime rather than the -1 value used by Qt4 and Qt5. Change-Id: Icde468a8f6fc9434ef7018296725819b44d672af Reviewed-by: Thiago Macieira <[email protected]>
RawnHelly · Jul 2, 2016 · 1af4916 · 1af4916
1 parent 9964b85
commit 1af4916
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Showing 2 changed files with 38 additions and 3 deletions.
diff --git a/src/corelib/tools/qdatetime.cpp b/src/corelib/tools/qdatetime.cpp
@@ -4759,7 +4759,12 @@ QDataStream &operator>>(QDataStream &in, QDate &date)
 
 QDataStream &operator<<(QDataStream &out, const QTime &time)
 {
-    return out << quint32(time.mds);
+    if (out.version() >= QDataStream::Qt_4_0) {
+        return out << quint32(time.mds);
+    } else {
+        // Qt3 had no support for reading -1, QTime() was valid and serialized as 0
+        return out << quint32(time.isNull() ? 0 : time.mds);
+    }
 }
 
 /*!
@@ -4774,7 +4779,12 @@ QDataStream &operator>>(QDataStream &in, QTime &time)
 {
     quint32 ds;
     in >> ds;
-    time.mds = int(ds);
+    if (in.version() >= QDataStream::Qt_4_0) {
+        time.mds = int(ds);
+    } else {
+        // Qt3 would write 0 for a null time
+        time.mds = (ds == 0) ? QTime::NullTime : int(ds);
+    }
     return in;
 }
 

diff --git a/tests/auto/corelib/io/qdatastream/tst_qdatastream.cpp b/tests/auto/corelib/io/qdatastream/tst_qdatastream.cpp
@@ -1203,10 +1203,11 @@ static QTime qTimeData(int index)
     case 57: return QTime(23, 59, 59, 99);
     case 58: return QTime(23, 59, 59, 100);
     case 59: return QTime(23, 59, 59, 999);
+    case 60: return QTime();
     }
     return QTime(0, 0, 0);
 }
-#define MAX_QTIME_DATA 60
+#define MAX_QTIME_DATA 61
 
 void tst_QDataStream::stream_QTime_data()
 {
@@ -3081,6 +3082,30 @@ void tst_QDataStream::compatibility_Qt3()
         QVERIFY(in_palette.brush(QPalette::Button).style() == Qt::NoBrush);
         QVERIFY(in_palette.color(QPalette::Light) == Qt::green);
     }
+    // QTime() was serialized to (0, 0, 0, 0) in Qt3, not (0xFF, 0xFF, 0xFF, 0xFF)
+    // This is because in Qt3 a null time was valid, and there was no support for deserializing a value of -1.
+    {
+        QByteArray stream;
+        {
+            QDataStream out(&stream, QIODevice::WriteOnly);
+            out.setVersion(QDataStream::Qt_3_3);
+            out << QTime();
+        }
+        QTime in_time;
+        {
+            QDataStream in(stream);
+            in.setVersion(QDataStream::Qt_3_3);
+            in >> in_time;
+        }
+        QVERIFY(in_time.isNull());
+
+        quint32 rawValue;
+        QDataStream in(stream);
+        in.setVersion(QDataStream::Qt_3_3);
+        in >> rawValue;
+        QCOMPARE(rawValue, quint32(0));
+    }
+
 }
 
 void tst_QDataStream::compatibility_Qt2()