fix an incorrect OpenMode flags handling in QBuffer::open()

which leads to absurd statement (QBuffer::open() == !QBuffer::isOpen()) to be true.
also treat Truncate as (Truncate | WriteOnly) to satisfy lazy ones

Reviewed-by: Joao
Merge-request: 2612
(cherry picked from commit 6b91affb9a355e668bc9d06dee580d95230ac63a)

Change-Id: I657d4d0a33f7993313fe2a1a8ba408371991717f
Reviewed-on: http://codereview.qt.nokia.com/447
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Peter Hartmann <peter.hartmann@nokia.com>

2 files changed, 56 insertions, 11 deletions

diff --git a/src/corelib/io/qbuffer.cpp b/src/corelib/io/qbuffer.cpp
index 38e406b1a4..35e7b6809c 100644
--- a/src/corelib/io/qbuffer.cpp
+++ b/src/corelib/io/qbuffer.cpp
@@ -333,23 +333,18 @@ bool QBuffer::open(OpenMode flags)
 {
     Q_D(QBuffer);
 
-    if ((flags & Append) == Append)
+    if ((flags & (Append | Truncate)) != 0)
         flags |= WriteOnly;
-    setOpenMode(flags);
-    if (!(isReadable() || isWritable())) {
-        qWarning("QFile::open: File access not specified");
+    if ((flags & (ReadOnly | WriteOnly)) == 0) {
+        qWarning("QBuffer::open: Buffer access not specified");
         return false;
     }
 
-    if ((flags & QIODevice::Truncate) == QIODevice::Truncate) {
+    if ((flags & Truncate) == Truncate)
         d->buf->resize(0);
-    }
-    if ((flags & QIODevice::Append) == QIODevice::Append) // append to end of buffer
-        seek(d->buf->size());
-    else
-        seek(0);
+    d->ioIndex = (flags & Append) == Append ? d->buf->size() : 0;
 
-    return true;
+    return QIODevice::open(flags);
 }
 
 /*!
diff --git a/tests/auto/qbuffer/tst_qbuffer.cpp b/tests/auto/qbuffer/tst_qbuffer.cpp
index 776935d6e0..bf4842ff94 100644
--- a/tests/auto/qbuffer/tst_qbuffer.cpp
+++ b/tests/auto/qbuffer/tst_qbuffer.cpp
@@ -56,6 +56,7 @@ public:
     tst_QBuffer();
 
 private slots:
+    void open();
     void getSetCheck();
     void readBlock();
     void readBlockPastEnd();
@@ -104,6 +105,55 @@ tst_QBuffer::tst_QBuffer()
 {
 }
 
+void tst_QBuffer::open()
+{
+    QByteArray data(10, 'f');
+
+    QBuffer b;
+
+    QTest::ignoreMessage(QtWarningMsg, "QBuffer::open: Buffer access not specified");
+    QVERIFY(!b.open(QIODevice::NotOpen));
+    QVERIFY(!b.isOpen());
+    b.close();
+
+    QTest::ignoreMessage(QtWarningMsg, "QBuffer::open: Buffer access not specified");
+    QVERIFY(!b.open(QIODevice::Text));
+    QVERIFY(!b.isOpen());
+    b.close();
+
+    QTest::ignoreMessage(QtWarningMsg, "QBuffer::open: Buffer access not specified");
+    QVERIFY(!b.open(QIODevice::Unbuffered));
+    QVERIFY(!b.isOpen());
+    b.close();
+
+    QVERIFY(b.open(QIODevice::ReadOnly));
+    QVERIFY(b.isReadable());
+    b.close();
+
+    QVERIFY(b.open(QIODevice::WriteOnly));
+    QVERIFY(b.isWritable());
+    b.close();
+
+    b.setData(data);
+    QVERIFY(b.open(QIODevice::Append));
+    QVERIFY(b.isWritable());
+    QCOMPARE(b.size(), qint64(10));
+    QCOMPARE(b.pos(), b.size());
+    b.close();
+
+    b.setData(data);
+    QVERIFY(b.open(QIODevice::Truncate));
+    QVERIFY(b.isWritable());
+    QCOMPARE(b.size(), qint64(0));
+    QCOMPARE(b.pos(), qint64(0));
+    b.close();
+
+    QVERIFY(b.open(QIODevice::ReadWrite));
+    QVERIFY(b.isReadable());
+    QVERIFY(b.isWritable());
+    b.close();
+}
+
 // some status() tests, too
 void tst_QBuffer::readBlock()
 {