1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
|
/****************************************************************************
**
** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
** Contact: http://www.qt-project.org/legal
**
** This file is part of the QtDeclarative module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and Digia. For licensing terms and
** conditions see http://qt.digia.com/licensing. For further information
** use the contact form at http://qt.digia.com/contact-us.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 2.1 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL included in the
** packaging of this file. Please review the following information to
** ensure the GNU Lesser General Public License version 2.1 requirements
** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** In addition, as a special exception, Digia gives you certain additional
** rights. These rights are described in the Digia Qt LGPL Exception
** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3.0 as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL included in the
** packaging of this file. Please review the following information to
** ensure the GNU General Public License version 3.0 requirements will be
** met: http://www.gnu.org/copyleft/gpl.html.
**
**
** $QT_END_LICENSE$
**
****************************************************************************/
#include "private/qpacketprotocol_p.h"
#include <QBuffer>
#include <QElapsedTimer>
QT_BEGIN_NAMESPACE
#define MAX_PACKET_SIZE 0x7FFFFFFF
/*!
\class QPacketProtocol
\internal
\brief The QPacketProtocol class encapsulates communicating discrete packets
across fragmented IO channels, such as TCP sockets.
QPacketProtocol makes it simple to send arbitrary sized data "packets" across
fragmented transports such as TCP and UDP.
As transmission boundaries are not respected, sending packets over protocols
like TCP frequently involves "stitching" them back together at the receiver.
QPacketProtocol makes this easier by performing this task for you. Packet
data sent using QPacketProtocol is prepended with a 4-byte size header
allowing the receiving QPacketProtocol to buffer the packet internally until
it has all been received. QPacketProtocol does not perform any sanity
checking on the size or on the data, so this class should only be used in
prototyping or trusted situations where DOS attacks are unlikely.
QPacketProtocol does not perform any communications itself. Instead it can
operate on any QIODevice that supports the QIODevice::readyRead() signal. A
logical "packet" is encapsulated by the companion QPacket class. The
following example shows two ways to send data using QPacketProtocol. The
transmitted data is equivalent in both.
\code
QTcpSocket socket;
// ... connect socket ...
QPacketProtocol protocol(&socket);
// Send packet the quick way
protocol.send() << "Hello world" << 123;
// Send packet the longer way
QPacket packet;
packet << "Hello world" << 123;
protocol.send(packet);
\endcode
Likewise, the following shows how to read data from QPacketProtocol, assuming
that the QPacketProtocol::readyRead() signal has been emitted.
\code
// ... QPacketProtocol::readyRead() is emitted ...
int a;
QByteArray b;
// Receive packet the quick way
protocol.read() >> a >> b;
// Receive packet the longer way
QPacket packet = protocol.read();
p >> a >> b;
\endcode
\ingroup io
\sa QPacket
*/
class QPacketProtocolPrivate : public QObject
{
Q_OBJECT
public:
QPacketProtocolPrivate(QPacketProtocol * parent, QIODevice * _dev)
: QObject(parent), inProgressSize(-1), maxPacketSize(MAX_PACKET_SIZE),
waitingForPacket(false), dev(_dev)
{
Q_ASSERT(4 == sizeof(qint32));
QObject::connect(this, SIGNAL(readyRead()),
parent, SIGNAL(readyRead()));
QObject::connect(this, SIGNAL(packetWritten()),
parent, SIGNAL(packetWritten()));
QObject::connect(this, SIGNAL(invalidPacket()),
parent, SIGNAL(invalidPacket()));
QObject::connect(dev, SIGNAL(readyRead()),
this, SLOT(readyToRead()));
QObject::connect(dev, SIGNAL(aboutToClose()),
this, SLOT(aboutToClose()));
QObject::connect(dev, SIGNAL(bytesWritten(qint64)),
this, SLOT(bytesWritten(qint64)));
}
Q_SIGNALS:
void readyRead();
void packetWritten();
void invalidPacket();
public Q_SLOTS:
void aboutToClose()
{
inProgress.clear();
sendingPackets.clear();
inProgressSize = -1;
}
void bytesWritten(qint64 bytes)
{
Q_ASSERT(!sendingPackets.isEmpty());
while(bytes) {
if(sendingPackets.at(0) > bytes) {
sendingPackets[0] -= bytes;
bytes = 0;
} else {
bytes -= sendingPackets.at(0);
sendingPackets.removeFirst();
emit packetWritten();
}
}
}
void readyToRead()
{
bool gotPackets = false;
while (true) {
// Get size header (if not in progress)
if (-1 == inProgressSize) {
// We need a size header of sizeof(qint32)
if (sizeof(qint32) > (uint)dev->bytesAvailable()) {
if (gotPackets)
emit readyRead();
return; // no more data available
}
// Read size header
int read = dev->read((char *)&inProgressSize, sizeof(qint32));
Q_ASSERT(read == sizeof(qint32));
Q_UNUSED(read);
// Check sizing constraints
if (inProgressSize > maxPacketSize) {
QObject::disconnect(dev, SIGNAL(readyRead()),
this, SLOT(readyToRead()));
QObject::disconnect(dev, SIGNAL(aboutToClose()),
this, SLOT(aboutToClose()));
QObject::disconnect(dev, SIGNAL(bytesWritten(qint64)),
this, SLOT(bytesWritten(qint64)));
dev = 0;
emit invalidPacket();
return;
}
inProgressSize -= sizeof(qint32);
} else {
inProgress.append(dev->read(inProgressSize - inProgress.size()));
if (inProgressSize == inProgress.size()) {
// Packet has arrived!
packets.append(inProgress);
inProgressSize = -1;
inProgress.clear();
waitingForPacket = false;
gotPackets = true;
} else {
if (gotPackets)
emit readyRead();
return; // packet in progress is not yet complete
}
}
}
}
public:
QList<qint64> sendingPackets;
QList<QByteArray> packets;
QByteArray inProgress;
qint32 inProgressSize;
qint32 maxPacketSize;
bool waitingForPacket;
QIODevice * dev;
};
/*!
Construct a QPacketProtocol instance that works on \a dev with the
specified \a parent.
*/
QPacketProtocol::QPacketProtocol(QIODevice * dev, QObject * parent)
: QObject(parent), d(new QPacketProtocolPrivate(this, dev))
{
Q_ASSERT(dev);
}
/*!
Destroys the QPacketProtocol instance.
*/
QPacketProtocol::~QPacketProtocol()
{
}
/*!
Returns the maximum packet size allowed. By default this is
2,147,483,647 bytes.
If a packet claiming to be larger than the maximum packet size is received,
the QPacketProtocol::invalidPacket() signal is emitted.
\sa QPacketProtocol::setMaximumPacketSize()
*/
qint32 QPacketProtocol::maximumPacketSize() const
{
return d->maxPacketSize;
}
/*!
Sets the maximum allowable packet size to \a max.
\sa QPacketProtocol::maximumPacketSize()
*/
qint32 QPacketProtocol::setMaximumPacketSize(qint32 max)
{
if(max > (signed)sizeof(qint32))
d->maxPacketSize = max;
return d->maxPacketSize;
}
/*!
Returns a streamable object that is transmitted on destruction. For example
\code
protocol.send() << "Hello world" << 123;
\endcode
will send a packet containing "Hello world" and 123. To construct more
complex packets, explicitly construct a QPacket instance.
*/
QPacketAutoSend QPacketProtocol::send()
{
return QPacketAutoSend(this);
}
/*!
\fn void QPacketProtocol::send(const QPacket & packet)
Transmit the \a packet.
*/
void QPacketProtocol::send(const QPacket & p)
{
if(p.b.isEmpty())
return; // We don't send empty packets
qint64 sendSize = p.b.size() + sizeof(qint32);
d->sendingPackets.append(sendSize);
qint32 sendSize32 = sendSize;
qint64 writeBytes = d->dev->write((char *)&sendSize32, sizeof(qint32));
Q_ASSERT(writeBytes == sizeof(qint32));
writeBytes = d->dev->write(p.b);
Q_ASSERT(writeBytes == p.b.size());
}
/*!
Returns the number of received packets yet to be read.
*/
qint64 QPacketProtocol::packetsAvailable() const
{
return d->packets.count();
}
/*!
Discard any unread packets.
*/
void QPacketProtocol::clear()
{
d->packets.clear();
}
/*!
Return the next unread packet, or an invalid QPacket instance if no packets
are available. This method does NOT block.
*/
QPacket QPacketProtocol::read()
{
if(0 == d->packets.count())
return QPacket();
QPacket rv(d->packets.at(0));
d->packets.removeFirst();
return rv;
}
/*
Returns the difference between msecs and elapsed. If msecs is -1,
however, -1 is returned.
*/
static int qt_timeout_value(int msecs, int elapsed)
{
if (msecs == -1)
return -1;
int timeout = msecs - elapsed;
return timeout < 0 ? 0 : timeout;
}
/*!
This function locks until a new packet is available for reading and the
\l{QIODevice::}{readyRead()} signal has been emitted. The function
will timeout after \a msecs milliseconds; the default timeout is
30000 milliseconds.
The function returns true if the readyRead() signal is emitted and
there is new data available for reading; otherwise it returns false
(if an error occurred or the operation timed out).
*/
bool QPacketProtocol::waitForReadyRead(int msecs)
{
if (!d->packets.isEmpty())
return true;
QElapsedTimer stopWatch;
stopWatch.start();
d->waitingForPacket = true;
do {
if (!d->dev->waitForReadyRead(msecs))
return false;
if (!d->waitingForPacket)
return true;
msecs = qt_timeout_value(msecs, stopWatch.elapsed());
} while (true);
}
/*!
Return the QIODevice passed to the QPacketProtocol constructor.
*/
QIODevice * QPacketProtocol::device()
{
return d->dev;
}
/*!
\fn void QPacketProtocol::readyRead()
Emitted whenever a new packet is received. Applications may use
QPacketProtocol::read() to retrieve this packet.
*/
/*!
\fn void QPacketProtocol::invalidPacket()
A packet larger than the maximum allowable packet size was received. The
packet will be discarded and, as it indicates corruption in the protocol, no
further packets will be received.
*/
/*!
\fn void QPacketProtocol::packetWritten()
Emitted each time a packet is completing written to the device. This signal
may be used for communications flow control.
*/
/*!
\class QPacket
\internal
\brief The QPacket class encapsulates an unfragmentable packet of data to be
transmitted by QPacketProtocol.
The QPacket class works together with QPacketProtocol to make it simple to
send arbitrary sized data "packets" across fragmented transports such as TCP
and UDP.
QPacket provides a QDataStream interface to an unfragmentable packet.
Applications should construct a QPacket, propagate it with data and then
transmit it over a QPacketProtocol instance. For example:
\code
QPacketProtocol protocol(...);
QPacket myPacket;
myPacket << "Hello world!" << 123;
protocol.send(myPacket);
\endcode
As long as both ends of the connection are using the QPacketProtocol class,
the data within this packet will be delivered unfragmented at the other end,
ready for extraction.
\code
QByteArray greeting;
int count;
QPacket myPacket = protocol.read();
myPacket >> greeting >> count;
\endcode
Only packets returned from QPacketProtocol::read() may be read from. QPacket
instances constructed by directly by applications are for transmission only
and are considered "write only". Attempting to read data from them will
result in undefined behavior.
\ingroup io
\sa QPacketProtocol
*/
/*!
Constructs an empty write-only packet.
*/
QPacket::QPacket()
: QDataStream(), buf(0)
{
buf = new QBuffer(&b);
buf->open(QIODevice::WriteOnly);
setDevice(buf);
setVersion(QDataStream::Qt_4_7);
}
/*!
Destroys the QPacket instance.
*/
QPacket::~QPacket()
{
if(buf) {
delete buf;
buf = 0;
}
}
/*!
Creates a copy of \a other. The initial stream positions are shared, but the
two packets are otherwise independent.
*/
QPacket::QPacket(const QPacket & other)
: QDataStream(), b(other.b), buf(0)
{
buf = new QBuffer(&b);
buf->open(other.buf->openMode());
setDevice(buf);
}
/*!
\internal
*/
QPacket::QPacket(const QByteArray & ba)
: QDataStream(), b(ba), buf(0)
{
buf = new QBuffer(&b);
buf->open(QIODevice::ReadOnly);
setDevice(buf);
}
/*!
Returns true if this packet is empty - that is, contains no data.
*/
bool QPacket::isEmpty() const
{
return b.isEmpty();
}
/*!
Returns raw packet data.
*/
QByteArray QPacket::data() const
{
return b;
}
/*!
Clears data in the packet. This is useful for reusing one writable packet.
For example
\code
QPacketProtocol protocol(...);
QPacket packet;
packet << "Hello world!" << 123;
protocol.send(packet);
packet.clear();
packet << "Goodbyte world!" << 789;
protocol.send(packet);
\endcode
*/
void QPacket::clear()
{
QBuffer::OpenMode oldMode = buf->openMode();
buf->close();
b.clear();
buf->setBuffer(&b); // reset QBuffer internals with new size of b.
buf->open(oldMode);
}
/*!
\class QPacketAutoSend
\internal
\internal
*/
QPacketAutoSend::QPacketAutoSend(QPacketProtocol * _p)
: QPacket(), p(_p)
{
}
QPacketAutoSend::~QPacketAutoSend()
{
if(!b.isEmpty())
p->send(*this);
}
QT_END_NAMESPACE
#include <qpacketprotocol.moc>
|