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
|
/****************************************************************************
**
** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
** Contact: Nokia Corporation (qt-info@nokia.com)
**
** This file is part of the Qt3Support module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** No Commercial Usage
** This file contains pre-release code and may not be distributed.
** You may use this file in accordance with the terms and conditions
** contained in the either Technology Preview License Agreement or the
** Beta Release License Agreement.
**
** 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, Nokia gives you certain
** additional rights. These rights are described in the Nokia Qt LGPL
** Exception version 1.0, 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.
**
** If you are unsure which license is appropriate for your use, please
** contact the sales department at http://qt.nokia.com/contact.
** $QT_END_LICENSE$
**
****************************************************************************/
#include "q3deepcopy.h"
QT_BEGIN_NAMESPACE
/*!
\class Q3DeepCopy
\brief The Q3DeepCopy class is a template class which ensures that
implicitly shared and explicitly shared classes reference unique
data.
\reentrant
\compat
Normally, shared copies reference the same data to optimize memory
use and for maximum speed. In the example below, \c s1, \c s2, \c
s3, \c s4 and \c s5 share data.
\snippet doc/src/snippets/code/src_qt3support_tools_q3deepcopy.cpp 0
Q3DeepCopy can be used several ways to ensure that an object
references unique, unshared data. In the example below, \c s1, \c
s2 and \c s5 share data, while neither \c s3 nor \c s4 share data.
\snippet doc/src/snippets/code/src_qt3support_tools_q3deepcopy.cpp 1
In the example below, \c s1, \c s2 and \c s5 share data, and \c s3
and \c s4 share data.
\snippet doc/src/snippets/code/src_qt3support_tools_q3deepcopy.cpp 2
Q3DeepCopy can also provide safety in multithreaded applications
that use shared classes. In the example below, the variable \c
global_string is used safely since the data contained in \c
global_string is always a deep copy. This ensures that all threads
get a unique copy of the data, and that any assignments to \c
global_string will result in a deep copy.
\snippet doc/src/snippets/code/src_qt3support_tools_q3deepcopy.cpp 3
\warning It is the application developer's responsibility to
protect the object shared across multiple threads.
The examples above use QString, which is an implicitly shared
class. The behavior of Q3DeepCopy is the same when using explicitly
shared classes like QByteArray.
Currently, Q3DeepCopy works with the following classes:
\list
\i QMemArray (including subclasses like QByteArray and QCString)
\i QMap
\i QString
\i QValueList (including subclasses like QStringList and QValueStack)
\i QValueVector
\endlist
\sa \link threads.html Thread Support in Qt \endlink
*/
/*!
\fn Q3DeepCopy::Q3DeepCopy()
Constructs an empty instance of type \e T.
*/
/*!
\fn Q3DeepCopy::Q3DeepCopy( const T &t )
Constructs a deep copy of \a t.
*/
/*!
\fn Q3DeepCopy<T>& Q3DeepCopy::operator=( const T &t )
Assigns a deep copy of \a t.
*/
/*!
\fn Q3DeepCopy::operator T ()
Returns a deep copy of the encapsulated data.
*/
QT_END_NAMESPACE
|
