QDnsLookup: merge some of the domain label expansion code

Use qt_ACE_do directly from QtCore, to avoid going through Latin1
(US-ASCII) multiple times.

Drive-by reduce the size of the buffers from PACKETSZ (512) to the
maximum name a label can be (255 plus 1 for the null, just in case).

Drive-by replace the last QString::fromWCharArray with QStringView,
saving an unnecessary memory allocation before calling
QtPrivate::convertToLatin1().

Change-Id: I3e3bfef633af4130a03afffd175d8be1feb5d74b
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>

1 files changed, 13 insertions, 1 deletions

diff --git a/src/network/kernel/qdnslookup_p.h b/src/network/kernel/qdnslookup_p.h
index 03767fd831..da4721411b 100644
--- a/src/network/kernel/qdnslookup_p.h
+++ b/src/network/kernel/qdnslookup_p.h
@@ -25,6 +25,7 @@
 #include "QtNetwork/qdnslookup.h"
 #include "QtNetwork/qhostaddress.h"
 #include "private/qobject_p.h"
+#include "private/qurl_p.h"
 
 QT_REQUIRE_CONFIG(dnslookup);
 
@@ -174,6 +175,12 @@ class QDnsLookupRunnable : public QObject, public QRunnable
     Q_OBJECT
 
 public:
+#ifdef Q_OS_WIN
+    using EncodedLabel = QString;
+#else
+    using EncodedLabel = QByteArray;
+#endif
+
     QDnsLookupRunnable(const QDnsLookupPrivate *d);
     void run() override;
 
@@ -181,8 +188,13 @@ signals:
     void finished(const QDnsLookupReply &reply);
 
 private:
+    template <typename T> static QString decodeLabel(T encodedLabel)
+    {
+        return qt_ACE_do(encodedLabel.toString(), NormalizeAce, ForbidLeadingDot);
+    }
     void query(QDnsLookupReply *reply);
-    QByteArray requestName;
+
+    EncodedLabel requestName;
     QHostAddress nameserver;
     QDnsLookup::Type requestType;
     quint16 port;