Fix regression in QXmlStreamWriter with codec set to UTF-16

Actually, this broke using QXmlStreamWriter with any codec
where characters in the ASCII range have a different encoding
than the ASCII standard.

This was a regression from 558fe9383ba0aecbec09cc411c0ebab132aac137

Task-number: QTBUG-23310

Change-Id: I75bd013e9d5de53da564a76c2f06e95ff35303a8
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>

1 files changed, 25 insertions, 7 deletions

diff --git a/src/corelib/xml/qxmlstream.cpp b/src/corelib/xml/qxmlstream.cpp
index 46c0e5d297..2345cb1881 100644
--- a/src/corelib/xml/qxmlstream.cpp
+++ b/src/corelib/xml/qxmlstream.cpp
@@ -2980,6 +2980,7 @@ public:
     uint wroteSomething :1;
     uint hasError :1;
     uint autoFormatting :1;
+    uint isCodecASCIICompatible :1;
     QByteArray autoFormattingIndent;
     NamespaceDeclaration emptyNamespace;
     int lastNamespaceDeclaration;
@@ -2988,6 +2989,7 @@ public:
     QTextCodec *codec;
     QTextEncoder *encoder;
 #endif
+    void checkIfASCIICompatibleCodec();
 
     NamespaceDeclaration &findNamespace(const QString &namespaceUri, bool writeDeclaration = false, bool noDefault = false);
     void writeNamespaceDeclaration(const NamespaceDeclaration &namespaceDeclaration);
@@ -3009,6 +3011,7 @@ QXmlStreamWriterPrivate::QXmlStreamWriterPrivate(QXmlStreamWriter *q)
     codec = QTextCodec::codecForMib(106); // utf8
     encoder = codec->makeEncoder(QTextCodec::IgnoreHeader); // no byte order mark for utf8
 #endif
+    checkIfASCIICompatibleCodec();
     inStartElement = inEmptyElement = false;
     wroteSomething = false;
     hasError = false;
@@ -3018,6 +3021,18 @@ QXmlStreamWriterPrivate::QXmlStreamWriterPrivate(QXmlStreamWriter *q)
     namespacePrefixCount = 0;
 }
 
+void QXmlStreamWriterPrivate::checkIfASCIICompatibleCodec()
+{
+#ifndef QT_NO_TEXTCODEC
+    Q_ASSERT(encoder);
+    // assumes ASCII-compatibility for all 8-bit encodings
+    const QByteArray bytes = encoder->fromUnicode(QStringLiteral(" "));
+    isCodecASCIICompatible = (bytes.count() == 1);
+#else
+    isCodecASCIICompatible = true;
+#endif
+}
+
 void QXmlStreamWriterPrivate::write(const QStringRef &s)
 {
     if (device) {
@@ -3086,18 +3101,20 @@ void QXmlStreamWriterPrivate::writeEscaped(const QString &s, bool escapeWhitespa
     write(escaped);
 }
 
-// ASCII only!
+// Converts from ASCII to output encoding
 void QXmlStreamWriterPrivate::write(const char *s, int len)
 {
     if (device) {
         if (hasError)
             return;
-        if (device->write(s, len) != len)
-            hasError = true;
-    } else if (stringDevice) {
-        stringDevice->append(QString::fromLatin1(s, len));
-    } else
-        qWarning("QXmlStreamWriter: No device");
+        if (isCodecASCIICompatible) {
+            if (device->write(s, len) != len)
+                hasError = true;
+            return;
+        }
+    }
+
+    write(QString::fromLatin1(s, len));
 }
 
 void QXmlStreamWriterPrivate::writeNamespaceDeclaration(const NamespaceDeclaration &namespaceDeclaration) {
@@ -3279,6 +3296,7 @@ void QXmlStreamWriter::setCodec(QTextCodec *codec)
         d->codec = codec;
         delete d->encoder;
         d->encoder = codec->makeEncoder(QTextCodec::IgnoreHeader); // no byte order mark for utf8
+        d->checkIfASCIICompatibleCodec();
     }
 }