1QDeepCopy(3qt)                                                  QDeepCopy(3qt)
2
3
4

NAME

6       QDeepCopy - Template class which ensures that
7

SYNOPSIS

9       All the functions in this class are reentrant when Qt is built with
10       thread support.</p>
11
12       #include <qdeepcopy.h>
13
14   Public Members
15       QDeepCopy ()
16       QDeepCopy ( const T & t )
17       QDeepCopy<T> & operator= ( const T & t )
18       operator T ()
19

DESCRIPTION

21       The QDeepCopy class is a template class which ensures that implicitly
22       shared and explicitly shared classes reference unique data.
23
24       Normally, shared copies reference the same data to optimize memory use
25       and for maximum speed. In the example below, s1, s2, s3, s4 and s5
26       share data.
27
28           // all 5 strings share the same data
29           QString s1 = "abcd";
30           QString s2 = s1;
31           QString s3 = s2;
32           QString s4 = s3;
33           QString s5 = s2;
34
35       QDeepCopy can be used several ways to ensure that an object references
36       unique, unshared data. In the example below, s1, s2 and s5 share data,
37       while neither s3 nor s4 share data.
38
39           // s1, s2 and s5 share the same data, neither s3 nor s4 are shared
40           QString s1 = "abcd";
41           QString s2 = s1;
42           QDeepCopy<QString> s3 = s2;  // s3 is a deep copy of s2
43           QString s4 = s3;             // s4 is a deep copy of s3
44           QString s5 = s2;
45
46       In the example below, s1, s2 and s5 share data, and s3 and s4 share
47       data.
48
49           // s1, s2 and s5 share the same data, s3 and s4 share the same data
50           QString s1 = "abcd";
51           QString s2 = s1;
52           QString s3 = QDeepCopy<QString>( s2 );  // s3 is a deep copy of s2
53           QString s4 = s3;                        // s4 is a shallow copy of s3
54           QString s5 = s2;
55
56       QDeepCopy can also provide safety in multithreaded applications that
57       use shared classes. In the example below, the variable global_string is
58       used safely since the data contained in global_string is always a deep
59       copy. This ensures that all threads get a unique copy of the data, and
60       that any assignments to global_string will result in a deep copy.
61
62           QDeepCopy<QString> global_string;  // global string data
63           QMutex global_mutex;               // mutex to protext global_string
64           ...
65           void setGlobalString( const QString &str )
66           {
67               global_mutex.lock();
68               global_string = str;           // global_string is a deep copy of str
69               global_mutex.unlock();
70           }
71           ...
72           void MyThread::run()
73           {
74               global_mutex.lock();
75               QString str = global_string;          // str is a deep copy of global_string
76               global_mutex.unlock();
77               // process the string data
78               ...
79               // update global_string
80               setGlobalString( str );
81           }
82
83       Warning: It is the application developer's responsibility to protect
84       the object shared across multiple threads.
85
86       The examples above use QString, which is an implicitly shared class.
87       The behavior of QDeepCopy is the same when using explicitly shared
88       classes like QByteArray.
89
90       Currently, QDeepCopy works with the following classes:
91
92       QMemArray (including subclasses like QByteArray and QCString)
93
94       QMap
95
96       QString
97
98       QValueList (including subclasses like QStringList and QValueStack)
99
100       QValueVector
101
102       See also Thread Support in Qt, Implicitly and Explicitly Shared
103       Classes, and Non-GUI Classes.
104

MEMBER FUNCTION DOCUMENTATION

QDeepCopy::QDeepCopy ()
107       Constructs an empty instance of type T.
108

QDeepCopy::QDeepCopy ( const T & t )
110       Constructs a deep copy of t.
111

QDeepCopy::operator T ()
113       Returns a deep copy of the encapsulated data.
114

QDeepCopy<T> & QDeepCopy::operator= ( const T & t )
116       Assigns a deep copy of t.
117
118

SEE ALSO
120       http://doc.trolltech.com/qdeepcopy.html
121       http://www.trolltech.com/faq/tech.html
122

124       Copyright 1992-2007 Trolltech ASA, http://www.trolltech.com.  See the
125       license file included in the distribution for a complete license
126       statement.
127

AUTHOR
129       Generated automatically from the source code.
130

BUGS
132       If you find a bug in Qt, please report it as described in
133       http://doc.trolltech.com/bughowto.html.  Good bug reports help us to
134       help you. Thank you.
135
136       The definitive Qt documentation is provided in HTML format; it is
137       located at $QTDIR/doc/html and can be read using Qt Assistant or with a
138       web browser. This man page is provided as a convenience for those users
139       who prefer man pages, although this format is not officially supported
140       by Trolltech.
141
142       If you find errors in this manual page, please report them to qt-
143       bugs@trolltech.com.  Please include the name of the manual page
144       (qdeepcopy.3qt) and the Qt version (3.3.8).
145
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148Trolltech AS                    2 February 2007                 QDeepCopy(3qt)



        

    


            
        

        

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