QIODevice: implement a "zero-copy" strategy for buffered writes

It works as follows:

  - user calls write(const QByteArray &);
  - this function keeps a pointer to the chunk and calls a regular
    write(data, len);
  - write(data, len) calls a virtual writeData();
  - subclass calls a new QIODevicePrivate::write();
  - QIODevicePrivate::write() makes a shallow copy of
    the byte array.

Proposed solution is fully compatible with existing subclasses.
By replacing a call to d->writeBuffer.append() with d->write(),
subclasses can improve their performance.

Bump the TypeInformationVersion field in qtHookData, to notify the
Qt Creator developers that the offset of QFilePrivate::fileName was
changed and dumpers should be adapted.

Change-Id: I24713386cc74a9f37e5223c617e4b1ba97f968dc
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>

1 files changed, 1 insertions, 1 deletions

diff --git a/src/network/socket/qlocalsocket_win.cpp b/src/network/socket/qlocalsocket_win.cpp
index b585bea625..e174952b96 100644
--- a/src/network/socket/qlocalsocket_win.cpp
+++ b/src/network/socket/qlocalsocket_win.cpp
@@ -214,7 +214,7 @@ qint64 QLocalSocket::writeData(const char *data, qint64 len)
     Q_D(QLocalSocket);
     if (len == 0)
         return 0;
-    d->writeBuffer.append(data, len);
+    d->write(data, len);
     if (!d->pipeWriter) {
         d->pipeWriter = new QWindowsPipeWriter(d->handle, this);
         connect(d->pipeWriter, &QWindowsPipeWriter::bytesWritten,