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<td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>QDeepCopy Class Reference</h1>
<p>The QDeepCopy class is a template class which ensures that
implicitly shared and explicitly shared classes reference unique
data.
<a href="#details">More...</a>
<p>All the functions in this class are <a href="threads.html#reentrant">reentrant</a> when Qt is built with thread support.</p>
<p><tt>#include <<a href="qdeepcopy-h.html">qdeepcopy.h</a>></tt>
<p><a href="qdeepcopy-members.html">List of all member functions.</a>
<h2>Public Members</h2>
<ul>
<li><div class=fn><a href="#QDeepCopy"><b>QDeepCopy</b></a> ()</div></li>
<li><div class=fn><a href="#QDeepCopy-2"><b>QDeepCopy</b></a> ( const T & t )</div></li>
<li><div class=fn>QDeepCopy<T> & <a href="#operator-eq"><b>operator=</b></a> ( const T & t )</div></li>
<li><div class=fn><a href="#operator-T"><b>operator T</b></a> ()</div></li>
</ul>
<hr><a name="details"></a><h2>Detailed Description</h2>
The QDeepCopy class is a template class which ensures that
<a href="shclass.html#implicitly-shared">implicitly shared</a> and <a href="shclass.html#explicitly-shared">explicitly shared</a> classes reference unique
data.
<p>
<p>
<p> Normally, shared copies reference the same data to optimize memory
use and for maximum speed. In the example below, <tt>s1</tt>, <tt>s2</tt>, <tt>s3</tt>, <tt>s4</tt> and <tt>s5</tt> share data.
<p> <pre>
// all 5 strings share the same data
<a href="qstring.html">QString</a> s1 = "abcd";
<a href="qstring.html">QString</a> s2 = s1;
<a href="qstring.html">QString</a> s3 = s2;
<a href="qstring.html">QString</a> s4 = s3;
<a href="qstring.html">QString</a> s5 = s2;
</pre>
<p> QDeepCopy can be used several ways to ensure that an object
references unique, unshared data. In the example below, <tt>s1</tt>, <tt>s2</tt> and <tt>s5</tt> share data, while neither <tt>s3</tt> nor <tt>s4</tt> share data.
<pre>
// s1, s2 and s5 share the same data, neither s3 nor s4 are shared
<a href="qstring.html">QString</a> s1 = "abcd";
<a href="qstring.html">QString</a> s2 = s1;
QDeepCopy<QString> s3 = s2; // s3 is a <a href="shclass.html#deep-copy">deep copy</a> of s2
<a href="qstring.html">QString</a> s4 = s3; // s4 is a deep copy of s3
<a href="qstring.html">QString</a> s5 = s2;
</pre>
<p> In the example below, <tt>s1</tt>, <tt>s2</tt> and <tt>s5</tt> share data, and <tt>s3</tt>
and <tt>s4</tt> share data.
<pre>
// s1, s2 and s5 share the same data, s3 and s4 share the same data
<a href="qstring.html">QString</a> s1 = "abcd";
<a href="qstring.html">QString</a> s2 = s1;
<a href="qstring.html">QString</a> s3 = QDeepCopy<QString>( s2 ); // s3 is a deep copy of s2
<a href="qstring.html">QString</a> s4 = s3; // s4 is a <a href="shclass.html#shallow-copy">shallow copy</a> of s3
<a href="qstring.html">QString</a> s5 = s2;
</pre>
<p> QDeepCopy can also provide safety in multithreaded applications
that use shared classes. In the example below, the variable <tt>global_string</tt> is used safely since the data contained in <tt>global_string</tt> is always a deep copy. This ensures that all threads
get a unique copy of the data, and that any assignments to <tt>global_string</tt> will result in a deep copy.
<p> <pre>
QDeepCopy<QString> global_string; // global string data
<a href="qmutex.html">QMutex</a> global_mutex; // mutex to protext global_string
...
void setGlobalString( const <a href="qstring.html">QString</a> &str )
{
global_mutex.<a href="qmutex.html#lock">lock</a>();
global_string = str; // global_string is a deep copy of str
global_mutex.<a href="qmutex.html#unlock">unlock</a>();
}
...
void MyThread::run()
{
global_mutex.<a href="qmutex.html#lock">lock</a>();
<a href="qstring.html">QString</a> str = global_string; // str is a deep copy of global_string
global_mutex.<a href="qmutex.html#unlock">unlock</a>();
// process the string data
...
// update global_string
setGlobalString( str );
}
</pre>
<p> <b>Warning:</b> It is the application developer's responsibility to
protect the object shared across multiple threads.
<p> The examples above use <a href="qstring.html">QString</a>, which is an implicitly shared
class. The behavior of QDeepCopy is the same when using explicitly
shared classes like <a href="qbytearray.html">QByteArray</a>.
<p> Currently, QDeepCopy works with the following classes:
<ul>
<li> <a href="qmemarray.html">QMemArray</a> (including subclasses like QByteArray and <a href="qcstring.html">QCString</a>)
<li> <a href="qmap.html">QMap</a>
<li> QString
<li> <a href="qvaluelist.html">QValueList</a> (including subclasses like <a href="qstringlist.html">QStringList</a> and <a href="qvaluestack.html">QValueStack</a>)
<li> <a href="qvaluevector.html">QValueVector</a>
</ul>
<p> <p>See also <a href="threads.html">Thread Support in Qt</a>, <a href="shared.html">Implicitly and Explicitly Shared Classes</a>, and <a href="tools.html">Non-GUI Classes</a>.
<hr><h2>Member Function Documentation</h2>
<h3 class=fn><a name="QDeepCopy"></a>QDeepCopy::QDeepCopy ()
</h3>
<p> Constructs an empty instance of type <em>T</em>.
<h3 class=fn><a name="QDeepCopy-2"></a>QDeepCopy::QDeepCopy ( const T & t )
</h3>
<p> Constructs a <a href="shclass.html#deep-copy">deep copy</a> of <em>t</em>.
<h3 class=fn><a name="operator-T"></a>QDeepCopy::operator T ()
</h3>
<p> Returns a <a href="shclass.html#deep-copy">deep copy</a> of the encapsulated data.
<h3 class=fn><a href="qdeepcopy.html">QDeepCopy</a><T> & <a name="operator-eq"></a>QDeepCopy::operator= ( const T & t )
</h3>
<p> Assigns a <a href="shclass.html#deep-copy">deep copy</a> of <em>t</em>.
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