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authorTimothy Pearson <kb9vqf@pearsoncomputing.net>2011-07-10 15:17:53 -0500
committerTimothy Pearson <kb9vqf@pearsoncomputing.net>2011-07-10 15:17:53 -0500
commitdda8474928bd7276e1fad8fb7a601e7c83ff2bc2 (patch)
tree7f83910598b33b12730035f086df20b5a53ab99c /tqtinterface/qt4/src/kernel/tqguardedptr.cpp
parent6260b6178868c03aab1644bf93b0ef043654bdb0 (diff)
downloadexperimental-dda8474928bd7276e1fad8fb7a601e7c83ff2bc2.tar.gz
experimental-dda8474928bd7276e1fad8fb7a601e7c83ff2bc2.zip
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+/****************************************************************************
+**
+** Implementation of TQGuardedPtr class
+**
+** Created : 990929
+**
+** Copyright (C) 2010 Timothy Pearson and (C) 1992-2008 Trolltech ASA.
+**
+** This file is part of the kernel module of the TQt 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 TQt 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.TQPL
+** included in the packaging of this file. Licensees holding valid TQt
+** Commercial licenses may use this file in accordance with the TQt
+** 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 "tqguardedptr.h"
+
+/*!
+ \class TQGuardedPtr tqguardedptr.h
+ \brief The TQGuardedPtr class is a template class that provides guarded pointers to TQObjects.
+
+ \ingroup objectmodel
+ \mainclass
+
+ A guarded pointer, \c{TQGuardedPtr<X>}, behaves like a normal C++
+ pointer \c{X*}, except that it is automatically set to 0 when
+ the referenced object is destroyed (unlike normal C++ pointers,
+ which become "dangling pointers" in such cases). \c X must be a
+ subclass of TQObject.
+
+ Guarded pointers are useful whenever you need to store a pointer
+ to a TQObject that is owned by someone else and therefore might be
+ destroyed while you still hold a reference to it. You can safely
+ test the pointer for validity.
+
+ Example:
+ \code
+ TQGuardedPtr<TQLabel> label = new TQLabel( 0, "label" );
+ label->setText( "I like guarded pointers" );
+
+ delete (TQLabel*) label; // simulate somebody destroying the label
+
+ if ( label)
+ label->show();
+ else
+ qDebug("The label has been destroyed");
+ \endcode
+
+ The program will output \c{The label has been destroyed} rather
+ than dereferencing an invalid address in \c label->show().
+
+ The functions and operators available with a TQGuardedPtr are the
+ same as those available with a normal unguarded pointer, except
+ the pointer arithmetic operators (++, --, -, and +), which are
+ normally used only with arrays of objects. Use them like normal
+ pointers and you will not need to read this class documentation.
+
+ For creating guarded pointers, you can construct or assign to them
+ from an X* or from another guarded pointer of the same type. You
+ can compare them with each other using operator==() and
+ operator!=(), or test for 0 with isNull(). And you can dereference
+ them using either the \c *x or the \c x->member notation.
+
+ A guarded pointer will automatically cast to an X*, so you can
+ freely mix guarded and unguarded pointers. This means that if you
+ have a TQGuardedPtr<TQWidget>, you can pass it to a function that
+ requires a TQWidget*. For this reason, it is of little value to
+ declare functions to take a TQGuardedPtr as a parameter; just use
+ normal pointers. Use a TQGuardedPtr when you are storing a pointer
+ over time.
+
+ Note again that class \e X must inherit TQObject, or a compilation
+ or link error will result.
+*/
+
+/*!
+ \fn TQGuardedPtr::TQGuardedPtr()
+
+ Constructs a 0 guarded pointer.
+
+ \sa isNull()
+*/
+
+/*!
+ \fn TQGuardedPtr::TQGuardedPtr( T* p )
+
+ Constructs a guarded pointer that points to same object as \a p
+ points to.
+*/
+
+/*!
+ \fn TQGuardedPtr::TQGuardedPtr(const TQGuardedPtr<T> &p)
+
+ Copy one guarded pointer from another. The constructed guarded
+ pointer points to the same object that \a p points to (which may
+ be 0).
+*/
+
+/*!
+ \fn TQGuardedPtr::~TQGuardedPtr()
+
+ Destroys the guarded pointer. Just like a normal pointer,
+ destroying a guarded pointer does \e not destroy the object being
+ pointed to.
+*/
+
+/*!
+ \fn TQGuardedPtr<T>& TQGuardedPtr::operator=(const TQGuardedPtr<T> &p)
+
+ Assignment operator. This guarded pointer then points to the same
+ object as \a p points to.
+*/
+
+/*!
+ \overload TQGuardedPtr<T> & TQGuardedPtr::operator=(T* p)
+
+ Assignment operator. This guarded pointer then points to the same
+ object as \a p points to.
+*/
+
+/*!
+ \fn bool TQGuardedPtr::operator==( const TQGuardedPtr<T> &p ) const
+
+ Equality operator; implements traditional pointer semantics.
+ Returns TRUE if both \a p and this guarded pointer are 0, or if
+ both \a p and this pointer point to the same object; otherwise
+ returns FALSE.
+
+ \sa operator!=()
+*/
+
+/*!
+ \fn bool TQGuardedPtr::operator!= ( const TQGuardedPtr<T>& p ) const
+
+ Inequality operator; implements pointer semantics, the negation of
+ operator==(). Returns TRUE if \a p and this guarded pointer are
+ not pointing to the same object; otherwise returns FALSE.
+*/
+
+/*!
+ \fn bool TQGuardedPtr::isNull() const
+
+ Returns \c TRUE if the referenced object has been destroyed or if
+ there is no referenced object; otherwise returns FALSE.
+*/
+
+/*!
+ \fn T* TQGuardedPtr::operator->() const
+
+ Overloaded arrow operator; implements pointer semantics. Just use
+ this operator as you would with a normal C++ pointer.
+*/
+
+/*!
+ \fn T& TQGuardedPtr::operator*() const
+
+ Dereference operator; implements pointer semantics. Just use this
+ operator as you would with a normal C++ pointer.
+*/
+
+/*!
+ \fn TQGuardedPtr::operator T*() const
+
+ Cast operator; implements pointer semantics. Because of this
+ function you can pass a TQGuardedPtr\<X\> to a function where an X*
+ is required.
+*/
+
+
+/* Internal classes */
+
+
+TQGuardedPtrPrivate::TQGuardedPtrPrivate( TQObject* o)
+ : TQObject(0, "_ptrpriv" ), obj( o )
+{
+ if ( obj )
+ connect( obj, TQT_SIGNAL( destroyed() ), this, TQT_SLOT( objectDestroyed() ) );
+}
+
+
+TQGuardedPtrPrivate::~TQGuardedPtrPrivate()
+{
+}
+
+void TQGuardedPtrPrivate::reconnect( TQObject *o )
+{
+ if ( obj == o )
+ return;
+ if ( obj )
+ disconnect( obj, TQT_SIGNAL( destroyed() ),
+ this, TQT_SLOT( objectDestroyed() ) );
+ obj = o;
+ if ( obj )
+ connect( obj, TQT_SIGNAL( destroyed() ),
+ this, TQT_SLOT( objectDestroyed() ) );
+}
+
+void TQGuardedPtrPrivate::objectDestroyed()
+{
+ obj = 0;
+}