add error handling to QXmlStreamWriter

introduce QXmlStreamWriter::hasError(). set the error flag when any
write error occurs. ignore subsequent writes after the first error.

Reviewed-by: denis

3 files changed, 116 insertions, 5 deletions

diff --git a/src/corelib/xml/qxmlstream.cpp b/src/corelib/xml/qxmlstream.cpp
index 3d8af9b..64a9857 100644
--- a/src/corelib/xml/qxmlstream.cpp
+++ b/src/corelib/xml/qxmlstream.cpp
@@ -2941,6 +2941,9 @@ QStringRef QXmlStreamReader::documentEncoding() const
   By default, QXmlStreamWriter encodes XML in UTF-8. Different
   encodings can be enforced using setCodec().
 
+  If an error occurs while writing to the underlying device, hasError()
+  starts returning true and subsequent writes are ignored.
+
   The \l{QXmlStream Bookmarks Example} illustrates how to use a
   stream writer to write an XML bookmark file (XBEL) that
   was previously read in by a QXmlStreamReader.
@@ -2976,6 +2979,7 @@ public:
     uint inEmptyElement :1;
     uint lastWasStartElement :1;
     uint wroteSomething :1;
+    uint hasError :1;
     uint autoFormatting :1;
     QByteArray autoFormattingIndent;
     NamespaceDeclaration emptyNamespace;
@@ -3008,6 +3012,7 @@ QXmlStreamWriterPrivate::QXmlStreamWriterPrivate(QXmlStreamWriter *q)
 #endif
     inStartElement = inEmptyElement = false;
     wroteSomething = false;
+    hasError = false;
     lastWasStartElement = false;
     lastNamespaceDeclaration = 1;
     autoFormatting = false;
@@ -3017,11 +3022,15 @@ QXmlStreamWriterPrivate::QXmlStreamWriterPrivate(QXmlStreamWriter *q)
 void QXmlStreamWriterPrivate::write(const QStringRef &s)
 {
     if (device) {
+        if (hasError)
+            return;
 #ifdef QT_NO_TEXTCODEC
-        device->write(s.toString().toLatin1(), s.size());
+        QByteArray bytes = s.toLatin1();
 #else
-        device->write(encoder->fromUnicode(s.constData(), s.size()));
+        QByteArray bytes = encoder->fromUnicode(s.constData(), s.size());
 #endif
+        if (device->write(bytes) != bytes.size())
+            hasError = true;
     }
     else if (stringDevice)
         s.appendTo(stringDevice);
@@ -3032,11 +3041,15 @@ void QXmlStreamWriterPrivate::write(const QStringRef &s)
 void QXmlStreamWriterPrivate::write(const QString &s)
 {
     if (device) {
+        if (hasError)
+            return;
 #ifdef QT_NO_TEXTCODEC
-        device->write(s.toLatin1(), s.size());
+        QByteArray bytes = s.toLatin1();
 #else
-        device->write(encoder->fromUnicode(s));
+        QByteArray bytes = encoder->fromUnicode(s);
 #endif
+        if (device->write(bytes) != bytes.size())
+            hasError = true;
     }
     else if (stringDevice)
         stringDevice->append(s);
@@ -3078,7 +3091,10 @@ void QXmlStreamWriterPrivate::writeEscaped(const QString &s, bool escapeWhitespa
 void QXmlStreamWriterPrivate::write(const char *s, int len)
 {
     if (device) {
-        device->write(s, len);
+        if (hasError)
+            return;
+        if (device->write(s, len) != len)
+            hasError = true;
     } else if (stringDevice) {
         stringDevice->append(QString::fromLatin1(s, len));
     } else
@@ -3359,6 +3375,17 @@ int QXmlStreamWriter::autoFormattingIndent() const
     return d->autoFormattingIndent.count(' ') - d->autoFormattingIndent.count('\t');
 }
 
+/*!
+    Returns \c true if the stream failed to write to the underlying device.
+
+    The error status is never reset. Writes happening after the error
+    occurred are ignored, even if the error condition is cleared.
+ */
+bool QXmlStreamWriter::hasError() const
+{
+    Q_D(const QXmlStreamWriter);
+    return d->hasError;
+}
 
 /*!
   \overload
diff --git a/src/corelib/xml/qxmlstream.h b/src/corelib/xml/qxmlstream.h
index d7143bd..244d3d4 100644
--- a/src/corelib/xml/qxmlstream.h
+++ b/src/corelib/xml/qxmlstream.h
@@ -474,6 +474,8 @@ public:
     void writeCurrentToken(const QXmlStreamReader &reader);
 #endif
 
+    bool hasError() const;
+
 private:
     Q_DISABLE_COPY(QXmlStreamWriter)
     Q_DECLARE_PRIVATE(QXmlStreamWriter)
diff --git a/tests/auto/qxmlstream/tst_qxmlstream.cpp b/tests/auto/qxmlstream/tst_qxmlstream.cpp
index 19e4b90..9e4f3ec 100644
--- a/tests/auto/qxmlstream/tst_qxmlstream.cpp
+++ b/tests/auto/qxmlstream/tst_qxmlstream.cpp
@@ -574,6 +574,7 @@ private slots:
     void checkCommentIndentation() const;
     void checkCommentIndentation_data() const;
     void qtbug9196_crash() const;
+    void hasError() const;
 
 private:
     static QByteArray readFile(const QString &filename);
@@ -1560,5 +1561,86 @@ void tst_QXmlStream::qtbug9196_crash() const
     }
 }
 
+class FakeBuffer : public QBuffer
+{
+protected:
+    qint64 writeData(const char *c, qint64 i)
+    {
+        qint64 ai = qMin(m_capacity, i);
+        m_capacity -= ai;
+        return ai ? QBuffer::writeData(c, ai) : 0;
+    }
+public:
+    void setCapacity(int capacity) { m_capacity = capacity; }
+private:
+    qint64 m_capacity;
+};
+
+void tst_QXmlStream::hasError() const
+{
+    {
+        FakeBuffer fb;
+        QVERIFY(fb.open(QBuffer::ReadWrite));
+        fb.setCapacity(1000);
+        QXmlStreamWriter writer(&fb);
+        writer.writeStartDocument();
+        writer.writeEndDocument();
+        QVERIFY(!writer.hasError());
+        QCOMPARE(fb.data(), QByteArray("<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n"));
+    }
+
+    {
+        // Failure caused by write(QString)
+        FakeBuffer fb;
+        QVERIFY(fb.open(QBuffer::ReadWrite));
+        fb.setCapacity(strlen("<?xml version=\""));
+        QXmlStreamWriter writer(&fb);
+        writer.writeStartDocument();
+        QVERIFY(writer.hasError());
+        QCOMPARE(fb.data(), QByteArray("<?xml version=\""));
+    }
+
+    {
+        // Failure caused by write(char *)
+        FakeBuffer fb;
+        QVERIFY(fb.open(QBuffer::ReadWrite));
+        fb.setCapacity(strlen("<?xml version=\"1.0"));
+        QXmlStreamWriter writer(&fb);
+        writer.writeStartDocument();
+        QVERIFY(writer.hasError());
+        QCOMPARE(fb.data(), QByteArray("<?xml version=\"1.0"));
+    }
+
+    {
+        // Failure caused by write(QStringRef)
+        FakeBuffer fb;
+        QVERIFY(fb.open(QBuffer::ReadWrite));
+        fb.setCapacity(strlen("<?xml version=\"1.0\" encoding=\"UTF-8\"?><test xmlns:"));
+        QXmlStreamWriter writer(&fb);
+        writer.writeStartDocument();
+        writer.writeStartElement("test");
+        writer.writeNamespace("http://foo.bar", "foo");
+        QVERIFY(writer.hasError());
+        QCOMPARE(fb.data(), QByteArray("<?xml version=\"1.0\" encoding=\"UTF-8\"?><test xmlns:"));
+    }
+
+    {
+        // Refusal to write after 1st failure
+        FakeBuffer fb;
+        QVERIFY(fb.open(QBuffer::ReadWrite));
+        fb.setCapacity(10);
+        QXmlStreamWriter writer(&fb);
+        writer.writeStartDocument();
+        QVERIFY(writer.hasError());
+        QCOMPARE(fb.data(), QByteArray("<?xml vers"));
+        fb.setCapacity(1000);
+        writer.writeStartElement("test"); // literal & qstring
+        writer.writeNamespace("http://foo.bar", "foo"); // literal & qstringref
+        QVERIFY(writer.hasError());
+        QCOMPARE(fb.data(), QByteArray("<?xml vers"));
+    }
+
+}
+
 #include "tst_qxmlstream.moc"
 // vim: et:ts=4:sw=4:sts=4