From 844f338a1102f3d0614b2a9d4ab80be68a408e50 Mon Sep 17 00:00:00 2001
From: Marc Mutz <marc.mutz@qt.io>
Date: Mon, 12 Dec 2022 15:17:54 +0100
Subject: [PATCH] tst_qmlstream: re-use QBuffer instance in readBack()

This improves the runtime of this particular test function by
almost 17% on my machine.

Change-Id: Icd77cdda92374b92121988c99e56787d405fa2d9
Reviewed-by: Mate Barany <mate.barany@qt.io>
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
(cherry picked from commit 7fa6670fa4ff5a916477f14d5754f9337ec9f1a8)
---
 .../corelib/serialization/qxmlstream/tst_qxmlstream.cpp    | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/tests/auto/corelib/serialization/qxmlstream/tst_qxmlstream.cpp b/tests/auto/corelib/serialization/qxmlstream/tst_qxmlstream.cpp
index 7f81d79672f..cd9dbda9f03 100644
--- a/tests/auto/corelib/serialization/qxmlstream/tst_qxmlstream.cpp
+++ b/tests/auto/corelib/serialization/qxmlstream/tst_qxmlstream.cpp
@@ -1681,10 +1681,11 @@ static bool isValidSingleTextChar(const ushort c)
 
 void tst_QXmlStream::readBack() const
 {
-    for (ushort c = 0; c < std::numeric_limits<ushort>::max(); ++c) {
-        QBuffer buffer;
+    QBuffer buffer;
 
-        QVERIFY(buffer.open(QIODevice::WriteOnly));
+    for (ushort c = 0; c < std::numeric_limits<ushort>::max(); ++c) {
+
+        QVERIFY(buffer.open(QIODevice::WriteOnly|QIODevice::Truncate));
         QXmlStreamWriter writer(&buffer);
         writer.writeStartDocument();
         writer.writeTextElement("a", QString(QChar(c)));