1// Copyright (C) 2016 The Qt Company Ltd.
2// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
3
4#include "qpacket_p.h"
5
6QT_BEGIN_NAMESPACE
7
8/*!
9 \class QPacket
10 \internal
11
12 \brief The QPacket class encapsulates an unfragmentable packet of data to be
13 transmitted by QPacketProtocol.
14
15 The QPacket class works together with QPacketProtocol to make it simple to
16 send arbitrary sized data "packets" across fragmented transports such as TCP
17 and UDP.
18
19 QPacket provides a QDataStream interface to an unfragmentable packet.
20 Applications should construct a QPacket, propagate it with data and then
21 transmit it over a QPacketProtocol instance. For example:
22 \code
23 int version = QDataStream::Qt_DefaultCompiledVersion;
24 QPacketProtocol protocol(...);
25
26 QPacket myPacket(version);
27 myPacket << "Hello world!" << 123;
28 protocol.send(myPacket.data());
29 \endcode
30
31 As long as both ends of the connection are using the QPacketProtocol class
32 and the same data stream version, the data within this packet will be
33 delivered unfragmented at the other end, ready for extraction.
34
35 \code
36 QByteArray greeting;
37 int count;
38
39 QPacket myPacket(version, protocol.read());
40
41 myPacket >> greeting >> count;
42 \endcode
43
44 Only packets constructed from raw byte arrays may be read from. Empty QPacket
45 instances are for transmission only and are considered "write only". Attempting
46 to read data from them will result in undefined behavior.
47
48 \ingroup io
49 \sa QPacketProtocol
50 */
51
52
53/*!
54 Constructs an empty write-only packet.
55 */
56QPacket::QPacket(int version)
57{
58 buf.open(openMode: QIODevice::WriteOnly);
59 setDevice(&buf);
60 setVersion(version);
61}
62
63/*!
64 Constructs a read-only packet.
65 */
66QPacket::QPacket(int version, const QByteArray &data)
67{
68 buf.setData(data);
69 buf.open(openMode: QIODevice::ReadOnly);
70 setDevice(&buf);
71 setVersion(version);
72}
73
74/*!
75 Returns a reference to the raw packet data.
76 */
77const QByteArray &QPacket::data() const
78{
79 return buf.data();
80}
81
82/*!
83 Returns a copy of the raw packet data, with extra reserved space removed.
84 Mind that this triggers a deep copy. Use it if you anticipate the data to be detached soon anyway.
85 */
86QByteArray QPacket::squeezedData() const
87{
88 QByteArray ret = buf.data();
89 ret.squeeze();
90 return ret;
91}
92
93/*!
94 Clears the packet, discarding any data.
95 */
96void QPacket::clear()
97{
98 buf.reset();
99 QByteArray &buffer = buf.buffer();
100 // Keep the old size to prevent unnecessary allocations
101 buffer.reserve(asize: buffer.capacity());
102 buffer.truncate(pos: 0);
103}
104
105QT_END_NAMESPACE
106

source code of qtdeclarative/src/plugins/qmltooling/packetprotocol/qpacket.cpp