QDataStream: handle incomplete reads from QIODevice

This adds a way to resume reading from a stream after a ReadPastEnd error.
This is done by introducing a stream read transaction mechanism that keeps
read data in an internal buffer and rolls it back on failure.

[ChangeLog][QtCore] Added QDataStream startTransaction(),
commitTransaction(), rollbackTransaction(), abortTransaction()
functions to support read transactions.

Task-number: QTBUG-44418
Change-Id: Ibf946e1939a5573c4182fea7e26608947218c2d9
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/src/corelib/io/qdatastream.h b/src/corelib/io/qdatastream.h
index 744829c659..a72842671a 100644
--- a/src/corelib/io/qdatastream.h
+++ b/src/corelib/io/qdatastream.h
@@ -168,6 +168,11 @@ public:
 
     int skipRawData(int len);
 
+    void startTransaction();
+    bool commitTransaction();
+    void rollbackTransaction();
+    void abortTransaction();
+
 private:
     Q_DISABLE_COPY(QDataStream)
 
@@ -179,6 +184,8 @@ private:
     ByteOrder byteorder;
     int ver;
     Status q_status;
+
+    int readBlock(char *data, int len);
 };