src_corelib_io_qdatastream.cpp

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// Copyright (C) 2016 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
 
void wrapInFunction()
{
 
QFile file("file.dat");
file.open(QIODevice::WriteOnly);
QDataStream out(&file);   // we will serialize the data into the file
out << QString("the answer is");   // serialize a string
out << (qint32)42;        // serialize an integer
 
 
QFile file("file.dat");
file.open(QIODevice::ReadOnly);
QDataStream in(&file);    // read the data serialized from the file
QString str;
qint32 a;
in >> str >> a;           // extract "the answer is" and 42
 
 
stream.setVersion(QDataStream::Qt_4_0);
 
 
QFile file("file.xxx");
file.open(QIODevice::WriteOnly);
QDataStream out(&file);
 
// Write a header with a "magic number" and a version
out << (quint32)0xA0B0C0D0;
out << (qint32)123;
 
out.setVersion(QDataStream::Qt_4_0);
 
// Write the data
out << lots_of_interesting_data;
 
 
QFile file("file.xxx");
file.open(QIODevice::ReadOnly);
QDataStream in(&file);
 
// Read and check the header
quint32 magic;
in >> magic;
if (magic != 0xA0B0C0D0)
    return XXX_BAD_FILE_FORMAT;
 
// Read the version
qint32 version;
in >> version;
if (version < 100)
    return XXX_BAD_FILE_TOO_OLD;
if (version > 123)
    return XXX_BAD_FILE_TOO_NEW;
 
if (version <= 110)
    in.setVersion(QDataStream::Qt_3_2);
else
    in.setVersion(QDataStream::Qt_4_0);
 
// Read the data
in >> lots_of_interesting_data;
if (version >= 120)
    in >> data_new_in_XXX_version_1_2;
in >> other_interesting_data;
 
 
QDataStream out(file);
out.setVersion(QDataStream::Qt_4_0);
 
in.startTransaction();
QString str;
qint32 a;
in >> str >> a; // try to read packet atomically
 
if (!in.commitTransaction())
    return;     // wait for more data
 
}