Fix QTextStream::pos() causes buffer offset issues on large text files.

 When reading large files that are greater in size than the
TEXTSTREAM_BUFFERSIZE buffer, calling pos() caused erroneous buffer
positioning. The cause of this was QTextStreamPrivate::readBufferOffset
value being updated, but QTextStreamPrivate::readConverterSavedStateOffset
was not.  Usually, if pos() is called, it is called multiple times. Since
QTextStreamPrivate::readConverterSavedStateOffset was never reset,
QTextStreamPrivate::readBufferOffset would accumulate the wrong position
and QTextStreamPrivate::consume() will 'discard' the wrong number of
bytes from the buffer.

Task-number: QTBUG-9814
Merge-request: 2569
Reviewed-by: Olivier Goffart <olivier.goffart@nokia.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/src/corelib/io/qtextstream.cpp b/src/corelib/io/qtextstream.cpp
index b630502..a5837cb 100644
--- a/src/corelib/io/qtextstream.cpp
+++ b/src/corelib/io/qtextstream.cpp
@@ -1264,6 +1264,7 @@ qint64 QTextStream::pos() const
                 return qint64(-1);
         }
         thatd->readBufferOffset = oldReadBufferOffset;
+        thatd->readConverterSavedStateOffset = 0;
 
         // Return the device position.
         return d->device->pos();