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/****************************************************************************
**
** Implementation of QDeepCopy class
**
** Created : 20020613
**
** Copyright (C) 1992-2008 Trolltech ASA. All rights reserved.
**
** This file is part of the kernel module of the Qt GUI Toolkit.
**
** This file may be used under the terms of the GNU General
** Public License versions 2.0 or 3.0 as published by the Free
** Software Foundation and appearing in the files LICENSE.GPL2
** and LICENSE.GPL3 included in the packaging of this file.
** Alternatively you may (at your option) use any later version
** of the GNU General Public License if such license has been
** publicly approved by Trolltech ASA (or its successors, if any)
** and the KDE Free Qt Foundation.
**
** Please review the following information to ensure GNU General
** Public Licensing requirements will be met:
** http://trolltech.com/products/qt/licenses/licensing/opensource/.
** If you are unsure which license is appropriate for your use, please
** review the following information:
** http://trolltech.com/products/qt/licenses/licensing/licensingoverview
** or contact the sales department at sales@trolltech.com.
**
** This file may be used under the terms of the Q Public License as
** defined by Trolltech ASA and appearing in the file LICENSE.QPL
** included in the packaging of this file. Licensees holding valid Qt
** Commercial licenses may use this file in accordance with the Qt
** Commercial License Agreement provided with the Software.
**
** This file is provided "AS IS" with NO WARRANTY OF ANY KIND,
** INCLUDING THE WARRANTIES OF DESIGN, MERCHANTABILITY AND FITNESS FOR
** A PARTICULAR PURPOSE. Trolltech reserves all rights not granted
** herein.
**
**********************************************************************/
#include "qdeepcopy.h"
/*!
\class QDeepCopy qdeepcopy.h
\brief The QDeepCopy class is a template class which ensures that
implicitly shared and explicitly shared classes reference unique
data.
\reentrant
\ingroup tools
\ingroup shared
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.
\code
// all 5 strings share the same data
QString s1 = "abcd";
QString s2 = s1;
QString s3 = s2;
QString s4 = s3;
QString s5 = s2;
\endcode
QDeepCopy 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.
\code
// s1, s2 and s5 share the same data, neither s3 nor s4 are shared
QString s1 = "abcd";
QString s2 = s1;
QDeepCopy<QString> s3 = s2; // s3 is a deep copy of s2
QString s4 = s3; // s4 is a deep copy of s3
QString s5 = s2;
\endcode
In the example below, \c s1, \c s2 and \c s5 share data, and \c s3
and \c s4 share data.
\code
// s1, s2 and s5 share the same data, s3 and s4 share the same data
QString s1 = "abcd";
QString s2 = s1;
QString s3 = QDeepCopy<QString>( s2 ); // s3 is a deep copy of s2
QString s4 = s3; // s4 is a shallow copy of s3
QString s5 = s2;
\endcode
QDeepCopy 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.
\code
QDeepCopy<QString> global_string; // global string data
QMutex global_mutex; // mutex to protext global_string
...
void setGlobalString( const QString &str )
{
global_mutex.lock();
global_string = str; // global_string is a deep copy of str
global_mutex.unlock();
}
...
void MyThread::run()
{
global_mutex.lock();
QString str = global_string; // str is a deep copy of global_string
global_mutex.unlock();
// process the string data
...
// update global_string
setGlobalString( str );
}
\endcode
\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 QDeepCopy is the same when using explicitly
shared classes like QByteArray.
Currently, QDeepCopy 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 QDeepCopy::QDeepCopy()
Constructs an empty instance of type \e T.
*/
/*!
\fn QDeepCopy::QDeepCopy( const T &t )
Constructs a deep copy of \a t.
*/
/*!
\fn QDeepCopy<T>& QDeepCopy::operator=( const T &t )
Assigns a deep copy of \a t.
*/
/*!
\fn QDeepCopy::operator T ()
Returns a deep copy of the encapsulated data.
*/
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