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<a href="index.html" class="qtref"><span>Qt Reference Documentation</span></a>
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<li class="level1"><a href="#public-types">Public Types</a></li>
<li class="level1"><a href="#public-functions">Public Functions</a></li>
<li class="level1"><a href="#protected-functions">Protected Functions</a></li>
<li class="level1"><a href="#details">Detailed Description</a></li>
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<h1 class="title">QExplicitlySharedDataPointer Class Reference</h1>
<!-- $$$QExplicitlySharedDataPointer-brief -->
<p>The QExplicitlySharedDataPointer class represents a pointer to an explicitly shared object. <a href="#details">More...</a></p>
<!-- @@@QExplicitlySharedDataPointer -->
<pre class="cpp"> <span class="preprocessor">#include <QExplicitlySharedDataPointer></span></pre><p><b>Note:</b> All functions in this class are <a href="threads-reentrancy.html#reentrant">reentrant</a>.</p>
<p>This class was introduced in Qt 4.4.</p>
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<li><a href="qexplicitlyshareddatapointer-members.html">List of all members, including inherited members</a></li>
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<a name="public-types"></a>
<h2>Public Types</h2>
<table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> typedef </td><td class="memItemRight bottomAlign"><b><a href="qexplicitlyshareddatapointer.html#Type-typedef">Type</a></b></td></tr>
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<a name="public-functions"></a>
<h2>Public Functions</h2>
<table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qexplicitlyshareddatapointer.html#QExplicitlySharedDataPointer">QExplicitlySharedDataPointer</a></b> ()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qexplicitlyshareddatapointer.html#QExplicitlySharedDataPointer-2">QExplicitlySharedDataPointer</a></b> ( T * <i>sharedData</i> )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qexplicitlyshareddatapointer.html#QExplicitlySharedDataPointer-3">QExplicitlySharedDataPointer</a></b> ( const QExplicitlySharedDataPointer<T> & <i>other</i> )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qexplicitlyshareddatapointer.html#QExplicitlySharedDataPointer-4">QExplicitlySharedDataPointer</a></b> ( const QExplicitlySharedDataPointer<X> & <i>other</i> )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qexplicitlyshareddatapointer.html#dtor.QExplicitlySharedDataPointer">~QExplicitlySharedDataPointer</a></b> ()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> const T * </td><td class="memItemRight bottomAlign"><b><a href="qexplicitlyshareddatapointer.html#constData">constData</a></b> () const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> T * </td><td class="memItemRight bottomAlign"><b><a href="qexplicitlyshareddatapointer.html#data">data</a></b> () const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qexplicitlyshareddatapointer.html#detach">detach</a></b> ()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qexplicitlyshareddatapointer.html#reset">reset</a></b> ()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qexplicitlyshareddatapointer.html#swap">swap</a></b> ( QExplicitlySharedDataPointer & <i>other</i> )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qexplicitlyshareddatapointer.html#operator-bool">operator bool</a></b> () const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qexplicitlyshareddatapointer.html#operator-not">operator!</a></b> () const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qexplicitlyshareddatapointer.html#operator-not-eq">operator!=</a></b> ( const QExplicitlySharedDataPointer<T> & <i>other</i> ) const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qexplicitlyshareddatapointer.html#operator-not-eq-2">operator!=</a></b> ( const T * <i>ptr</i> ) const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> T & </td><td class="memItemRight bottomAlign"><b><a href="qexplicitlyshareddatapointer.html#operator-2a">operator*</a></b> () const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> T * </td><td class="memItemRight bottomAlign"><b><a href="qexplicitlyshareddatapointer.html#operator--gt">operator-></a></b> ()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> T * </td><td class="memItemRight bottomAlign"><b><a href="qexplicitlyshareddatapointer.html#operator--gt-2">operator-></a></b> () const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QExplicitlySharedDataPointer<T> & </td><td class="memItemRight bottomAlign"><b><a href="qexplicitlyshareddatapointer.html#operator-eq">operator=</a></b> ( const QExplicitlySharedDataPointer<T> & <i>other</i> )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QExplicitlySharedDataPointer & </td><td class="memItemRight bottomAlign"><b><a href="qexplicitlyshareddatapointer.html#operator-eq-2">operator=</a></b> ( T * <i>sharedData</i> )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qexplicitlyshareddatapointer.html#operator-eq-eq">operator==</a></b> ( const QExplicitlySharedDataPointer<T> & <i>other</i> ) const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qexplicitlyshareddatapointer.html#operator-eq-eq-2">operator==</a></b> ( const T * <i>ptr</i> ) const</td></tr>
</table>
<a name="protected-functions"></a>
<h2>Protected Functions</h2>
<table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> T * </td><td class="memItemRight bottomAlign"><b><a href="qexplicitlyshareddatapointer.html#clone">clone</a></b> ()</td></tr>
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<a name="details"></a>
<!-- $$$QExplicitlySharedDataPointer-description -->
<div class="descr">
<h2>Detailed Description</h2>
<p>The QExplicitlySharedDataPointer class represents a pointer to an explicitly shared object.</p>
<p>QExplicitlySharedDataPointer<T> makes writing your own explicitly shared classes easy. QExplicitlySharedDataPointer implements <a href="threads-reentrancy.html#thread-safe">thread-safe</a> reference counting, ensuring that adding QExplicitlySharedDataPointers to your <a href="threads-reentrancy.html#reentrant">reentrant</a> classes won't make them non-reentrant.</p>
<p>Except for one big difference, QExplicitlySharedDataPointer is just like <a href="qshareddatapointer.html">QSharedDataPointer</a>. The big difference is that member functions of QExplicitlySharedDataPointer <i>do not</i> do the automatic <i>copy on write</i> operation (<a href="qexplicitlyshareddatapointer.html#detach">detach</a>()) that non-const members of <a href="qshareddatapointer.html">QSharedDataPointer</a> do before allowing the shared data object to be modified. There is a <a href="qexplicitlyshareddatapointer.html#detach">detach</a>() function available, but if you really want to <a href="qexplicitlyshareddatapointer.html#detach">detach</a>(), you have to call it yourself. This means that QExplicitlySharedDataPointers behave like regular C++ pointers, except that by doing reference counting and not deleting the shared data object until the reference count is 0, they avoid the dangling pointer problem.</p>
<p>It is instructive to compare QExplicitlySharedDataPointer with <a href="qshareddatapointer.html">QSharedDataPointer</a> by way of an example. Consider the <a href="qshareddatapointer.html#employee-example">Employee example</a> in <a href="qshareddatapointer.html">QSharedDataPointer</a>, modified to use explicit sharing as explained in the discussion <a href="qshareddatapointer.html#implicit-vs-explicit-sharing">Implicit vs Explicit Sharing</a>.</p>
<p>Note that if you use this class but find you are calling <a href="qexplicitlyshareddatapointer.html#detach">detach</a>() a lot, you probably should be using <a href="qshareddatapointer.html">QSharedDataPointer</a> instead.</p>
<p>In the member function documentation, <i>d pointer</i> always refers to the internal pointer to the shared data object.</p>
</div>
<p><b>See also </b><a href="qshareddata.html">QSharedData</a> and <a href="qshareddatapointer.html">QSharedDataPointer</a>.</p>
<!-- @@@QExplicitlySharedDataPointer -->
<div class="types">
<h2>Member Type Documentation</h2>
<!-- $$$Type -->
<h3 class="fn"><a name="Type-typedef"></a>typedef QExplicitlySharedDataPointer::<span class="name">Type</span></h3>
<p>This is the type of the shared data object. The <i>d pointer</i> points to an object of this type.</p>
<!-- @@@Type -->
</div>
<div class="func">
<h2>Member Function Documentation</h2>
<!-- $$$QExplicitlySharedDataPointer[overload1]$$$QExplicitlySharedDataPointer -->
<h3 class="fn"><a name="QExplicitlySharedDataPointer"></a>QExplicitlySharedDataPointer::<span class="name">QExplicitlySharedDataPointer</span> ()</h3>
<p>Constructs a <a href="qexplicitlyshareddatapointer.html">QExplicitlySharedDataPointer</a> initialized with a null <i>d pointer</i>.</p>
<!-- @@@QExplicitlySharedDataPointer -->
<!-- $$$QExplicitlySharedDataPointer$$$QExplicitlySharedDataPointerT* -->
<h3 class="fn"><a name="QExplicitlySharedDataPointer-2"></a>QExplicitlySharedDataPointer::<span class="name">QExplicitlySharedDataPointer</span> ( <span class="type">T</span> * <i>sharedData</i> )</h3>
<p>Constructs a <a href="qexplicitlyshareddatapointer.html">QExplicitlySharedDataPointer</a> with <i>d pointer</i> set to <i>sharedData</i> and increments <i>sharedData</i>'s reference count.</p>
<!-- @@@QExplicitlySharedDataPointer -->
<!-- $$$QExplicitlySharedDataPointer$$$QExplicitlySharedDataPointerconstQExplicitlySharedDataPointer<T>& -->
<h3 class="fn"><a name="QExplicitlySharedDataPointer-3"></a>QExplicitlySharedDataPointer::<span class="name">QExplicitlySharedDataPointer</span> ( const <span class="type">QExplicitlySharedDataPointer</span><<span class="type">T</span>> & <i>other</i> )</h3>
<p>This standard copy constructor sets the <i>d pointer</i> of <i>this</i> to the <i>d pointer</i> in <i>other</i> and increments the reference count of the shared data object.</p>
<!-- @@@QExplicitlySharedDataPointer -->
<!-- $$$QExplicitlySharedDataPointer$$$QExplicitlySharedDataPointerconstQExplicitlySharedDataPointer<X>& -->
<h3 class="fn"><a name="QExplicitlySharedDataPointer-4"></a>QExplicitlySharedDataPointer::<span class="name">QExplicitlySharedDataPointer</span> ( const <span class="type">QExplicitlySharedDataPointer</span><<span class="type">X</span>> & <i>other</i> )</h3>
<p>This copy constructor is different in that it allows <i>other</i> to be a different type of explicitly shared data pointer but one that has a compatible shared data object. It performs a static cast of the <i>d pointer</i> in <i>other</i> and sets the <i>d pointer</i> of <i>this</i> to the converted <i>d pointer</i>. It increments the reference count of the shared data object.</p>
<!-- @@@QExplicitlySharedDataPointer -->
<!-- $$$~QExplicitlySharedDataPointer[overload1]$$$~QExplicitlySharedDataPointer -->
<h3 class="fn"><a name="dtor.QExplicitlySharedDataPointer"></a>QExplicitlySharedDataPointer::<span class="name">~QExplicitlySharedDataPointer</span> ()</h3>
<p>Decrements the reference count of the shared data object. If the reference count becomes 0, the shared data object is deleted. <i>This</i> is then destroyed.</p>
<!-- @@@~QExplicitlySharedDataPointer -->
<!-- $$$clone[overload1]$$$clone -->
<h3 class="fn"><a name="clone"></a><span class="type">T</span> * QExplicitlySharedDataPointer::<span class="name">clone</span> ()<tt> [protected]</tt></h3>
<p>Creates and returns a deep copy of the current data. This function is called by <a href="qexplicitlyshareddatapointer.html#detach">detach</a>() when the reference count is greater than 1 in order to create the new copy. This function uses the <i>operator new</i> and calls the copy constructor of the type T.</p>
<p>See <a href="qshareddatapointer.html#clone">QSharedDataPointer::clone</a>() for an explanation of how to use it.</p>
<p>This function was introduced in Qt 4.5.</p>
<!-- @@@clone -->
<!-- $$$constData[overload1]$$$constData -->
<h3 class="fn"><a name="constData"></a>const <span class="type">T</span> * QExplicitlySharedDataPointer::<span class="name">constData</span> () const</h3>
<p>Returns a const pointer to the shared data object.</p>
<p><b>See also </b><a href="qexplicitlyshareddatapointer.html#data">data</a>().</p>
<!-- @@@constData -->
<!-- $$$data[overload1]$$$data -->
<h3 class="fn"><a name="data"></a><span class="type">T</span> * QExplicitlySharedDataPointer::<span class="name">data</span> () const</h3>
<p>Returns a pointer to the shared data object.</p>
<!-- @@@data -->
<!-- $$$detach[overload1]$$$detach -->
<h3 class="fn"><a name="detach"></a><span class="type">void</span> QExplicitlySharedDataPointer::<span class="name">detach</span> ()</h3>
<p>If the shared data object's reference count is greater than 1, this function creates a deep copy of the shared data object and sets the <i>d pointer</i> of <i>this</i> to the copy.</p>
<p>Because <a href="qexplicitlyshareddatapointer.html">QExplicitlySharedDataPointer</a> does not do the automatic <i>copy on write</i> operations that members of <a href="qshareddatapointer.html">QSharedDataPointer</a> do, detach() is <i>not</i> called automatically anywhere in the member functions of this class. If you find that you are calling detach() everywhere in your code, consider using <a href="qshareddatapointer.html">QSharedDataPointer</a> instead.</p>
<!-- @@@detach -->
<!-- $$$reset[overload1]$$$reset -->
<h3 class="fn"><a name="reset"></a><span class="type">void</span> QExplicitlySharedDataPointer::<span class="name">reset</span> ()</h3>
<p>Resets <i>this</i> to be null. i.e., this function sets the <i>d pointer</i> of <i>this</i> to 0, but first it decrements the reference count of the shared data object and deletes the shared data object if the reference count became 0.</p>
<!-- @@@reset -->
<!-- $$$swap[overload1]$$$swapQExplicitlySharedDataPointer& -->
<h3 class="fn"><a name="swap"></a><span class="type">void</span> QExplicitlySharedDataPointer::<span class="name">swap</span> ( <span class="type">QExplicitlySharedDataPointer</span> & <i>other</i> )</h3>
<p>Swap this instance's explicitly shared data pointer with the explicitly shared data pointer in <i>other</i>.</p>
<!-- @@@swap -->
<!-- $$$operator bool[overload1]$$$operator bool -->
<h3 class="fn"><a name="operator-bool"></a>QExplicitlySharedDataPointer::<span class="name">operator bool</span> () const</h3>
<p>Returns true if the <i>d pointer</i> of <i>this</i> is <i>not</i> null.</p>
<!-- @@@operator bool -->
<!-- $$$operator![overload1]$$$operator! -->
<h3 class="fn"><a name="operator-not"></a><span class="type">bool</span> QExplicitlySharedDataPointer::<span class="name">operator!</span> () const</h3>
<p>Returns true if the <i>d pointer</i> of <i>this</i> is null.</p>
<!-- @@@operator! -->
<!-- $$$operator!=[overload1]$$$operator!=constQExplicitlySharedDataPointer<T>& -->
<h3 class="fn"><a name="operator-not-eq"></a><span class="type">bool</span> QExplicitlySharedDataPointer::<span class="name">operator!=</span> ( const <span class="type">QExplicitlySharedDataPointer</span><<span class="type">T</span>> & <i>other</i> ) const</h3>
<p>Returns true if <i>other</i> and <i>this</i> do <i>not</i> have the same <i>d pointer</i>.</p>
<!-- @@@operator!= -->
<!-- $$$operator!=$$$operator!=constT* -->
<h3 class="fn"><a name="operator-not-eq-2"></a><span class="type">bool</span> QExplicitlySharedDataPointer::<span class="name">operator!=</span> ( const <span class="type">T</span> * <i>ptr</i> ) const</h3>
<p>Returns true if the <i>d pointer</i> of <i>this</i> is <i>not</i> <i>ptr</i>.</p>
<!-- @@@operator!= -->
<!-- $$$operator*[overload1]$$$operator* -->
<h3 class="fn"><a name="operator-2a"></a><span class="type">T</span> & QExplicitlySharedDataPointer::<span class="name">operator*</span> () const</h3>
<p>Provides access to the shared data object's members.</p>
<!-- @@@operator* -->
<!-- $$$operator->[overload1]$$$operator-> -->
<h3 class="fn"><a name="operator--gt"></a><span class="type">T</span> * QExplicitlySharedDataPointer::<span class="name">operator-></span> ()</h3>
<p>Provides access to the shared data object's members.</p>
<!-- @@@operator-> -->
<!-- $$$operator->$$$operator-> -->
<h3 class="fn"><a name="operator--gt-2"></a><span class="type">T</span> * QExplicitlySharedDataPointer::<span class="name">operator-></span> () const</h3>
<p>Provides const access to the shared data object's members.</p>
<!-- @@@operator-> -->
<!-- $$$operator=[overload1]$$$operator=constQExplicitlySharedDataPointer<T>& -->
<h3 class="fn"><a name="operator-eq"></a><span class="type">QExplicitlySharedDataPointer</span><<span class="type">T</span>> & QExplicitlySharedDataPointer::<span class="name">operator=</span> ( const <span class="type">QExplicitlySharedDataPointer</span><<span class="type">T</span>> & <i>other</i> )</h3>
<p>Sets the <i>d pointer</i> of <i>this</i> to the <i>d pointer</i> of <i>other</i> and increments the reference count of the shared data object. The reference count of the old shared data object of <i>this</i> is decremented. If the reference count of the old shared data object becomes 0, the old shared data object is deleted.</p>
<!-- @@@operator= -->
<!-- $$$operator=$$$operator=T* -->
<h3 class="fn"><a name="operator-eq-2"></a><span class="type">QExplicitlySharedDataPointer</span> & QExplicitlySharedDataPointer::<span class="name">operator=</span> ( <span class="type">T</span> * <i>sharedData</i> )</h3>
<p>Sets the <i>d pointer</i> of <i>this</i> to <i>sharedData</i> and increments <i>sharedData</i>'s reference count. The reference count of the old shared data object of <i>this</i> is decremented. If the reference count of the old shared data object becomes 0, the old shared data object is deleted.</p>
<!-- @@@operator= -->
<!-- $$$operator==[overload1]$$$operator==constQExplicitlySharedDataPointer<T>& -->
<h3 class="fn"><a name="operator-eq-eq"></a><span class="type">bool</span> QExplicitlySharedDataPointer::<span class="name">operator==</span> ( const <span class="type">QExplicitlySharedDataPointer</span><<span class="type">T</span>> & <i>other</i> ) const</h3>
<p>Returns true if <i>other</i> and <i>this</i> have the same <i>d pointer</i>.</p>
<!-- @@@operator== -->
<!-- $$$operator==$$$operator==constT* -->
<h3 class="fn"><a name="operator-eq-eq-2"></a><span class="type">bool</span> QExplicitlySharedDataPointer::<span class="name">operator==</span> ( const <span class="type">T</span> * <i>ptr</i> ) const</h3>
<p>Returns true if the <i>d pointer</i> of <i>this</i> is <i>ptr</i>.</p>
<!-- @@@operator== -->
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