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examples/Base/ArraysAndLists/FixedArrays/RangeChecking.cpp

// Copyright (c) 2000-2009 Nokia Corporation and/or its subsidiary(-ies).
// All rights reserved.
// This component and the accompanying materials are made available
// under the terms of "Eclipse Public License v1.0"
// which accompanies this distribution, and is available
// at the URL "http://www.eclipse.org/legal/epl-v10.html".
//
// Initial Contributors:
// Nokia Corporation - initial contribution.
//
// Contributors:
//
// Description:
// Code to demonstrate the range checking wrapper class
// for C++ arrays; i.e. the TFixedArray<class T,TInt S>.
//

#include "CommonFramework.h"

//
// Definition of the TTest class
//
class TTest
        {       
public:
        TTest();
        TTest(TInt aValue);
        void SetValue(TInt aValue);
        TInt GetValue() const;
private :
        TInt     iX;
        TBuf<8>  iPadding; // never used in this example
        };

TTest::TTest()
        : iX(1)
        {}

TTest::TTest(TInt aValue)
        : iX(aValue)
        {}

TInt TTest::GetValue() const
        {
        return iX;
        }

void TTest::SetValue(TInt aValue)
        {
        iX = aValue;
        }

//
// Definition of the CTest class
//
class CTest : public CBase 
        {       
public:
        static CTest* NewL(const TDesC& aText);
        ~CTest();
        void ConstructL(const TDesC& aText);
private :
        HBufC*   iSomeText;
        };      

CTest* CTest::NewL(const TDesC& aText)
        {
        CTest* self=new (ELeave) CTest;
        CleanupStack::PushL(self);
        self->ConstructL(aText);
        CleanupStack::Pop();
        return self;
        }

void CTest::ConstructL(const TDesC& aText)
        {
        iSomeText = aText.AllocL();
        }

CTest::~CTest()
        {
        delete iSomeText;
        }



// Some source data
const TTest data[] = {TTest(1),TTest(2),TTest(3),TTest(4)};

//
// main body of the example
//
static void doExampleL()
    {

        // A C++ array of 4 elements of type class TTest.
        //
        // Effectively the same as if we had explicitly
        // declared: TTest array[4];
        //
        TFixedArray<TTest,4> array;
        
                        
        //
        // Copy 4 elements into the array.
        //
        // We could have constructed the array by:
        // TFixedArray<TTest,4> array(&data[0],4);
        array.Copy(&data[0],4);

        //
        // Trying to execute the following call would result
        // in a USER 133 panic in a debug build. The range checking
        // stops us from trying to write to a 5th element which 
        // does not (legitimately) exist.
        //
        //array.Copy(&array[0],5);

        //
        // Count() should return the number of array elements, i.e. 4
        //
        _LIT(KTxtFormat1,"Array size is %d\n");
        console->Printf(KTxtFormat1,array.Count());
        
        //
        // Length() should return the size of an array element; here
        // that should be the size of a TTest object.
        //
        _LIT(KTxtFormat2,"Length of an array element is %d\n\n");
        console->Printf(KTxtFormat2,array.Length());
        
        //
        // Pointers to the beginning and end of the array
        //
        _LIT(KTxtFormat3,"Array ends   at ---> 0x%x\n      starts at ---> 0x%x\n");
        _LIT(KTxtFormat4,"Difference is decimal %d bytes (hopefully 4 times the size of TTest)\n\n");
        console->Printf(KTxtFormat3,array.End(),array.Begin());
        console->Printf(KTxtFormat4,((TUint8*)array.End() - (TUint8*)array.Begin()));
        
        //
        // Access the second element of the array and change it
        // using At().
        //
        array.At(1).SetValue(100);

        //
        // Access the second element of the array and change it
        // using the [] operator.
        //
        array[1].SetValue(99);
        
        // The following call using At() will panic in both a
        // release and a debug build.
        //array.At(4).SetValue(100);

        // The following call using the [] operator will only panic
        // in a debug build. In a release build, this  code
        // will go undetected and cause damage.
        //array[4].SetValue(99);
        
        // In this example we can also replace an entire element;
        // here we replace the third element.
        // In more complex cases, the TTest class could have 
        // a suitable operator= defined 
        _LIT(KTxtFormat5,"The new 3rd element has value %d\n\n");
        TTest x(256);
        array.At(2) = x; 
        console->Printf(KTxtFormat5,array.At(2).GetValue());

        //
        // Construct a generic array.
        //
        // Once done, we can use the standard TArray functions
        // Count() and operator[]
        // Remember that a TArray cannot be used to change data in the
        // original array.
        //
        TArray<TTest> generic = array.Array();

        _LIT(KTxtFormat6,"Array size as reported by TArray's Count() is %d\n\n");
        console->Printf(KTxtFormat6,generic.Count());

        // The value contained in the 2nd TTest element of the array
        // using the generic array's operator[]
        _LIT(KTxtFormat7,"Value contained in the 2nd TTest element of\nthe array using TArray's operator[] is %d\n\n");
        console->Printf(KTxtFormat7,generic[1].GetValue());

        // the following line will NOT compile
        //generic[1].SetValue(101);

        
        // This is A C++ array of 4 elements to contain
        // pointers to CTest type objects.
        // This is equivalent to
        // the naked declaration:
        // CTest* ptrarray[4];
        // 
        //
        TFixedArray<CTest*,4> ptrarray;

        
        // Allocate 4 CTest objects and put their pointers
        // into the array.
        //
        // We ignore cleanup issues arising from possible
        // failure of 'new'; this would need to be
        // considered in a real application.

        _LIT(KTxtDefault,"Default text");
        _LIT(KTxtState1,"The 4 elements are:     ");
        _LIT(KTxtState2,"After Reset() they are: ");
        _LIT(KTxtNewLine,"\n");
        _LIT(KTxtFormat8,"0x%08x ");
                        
        CTest* ptr;
        TInt   ix;
        for (ix = 0; ix<4; ix++)
                {
                ptr = CTest::NewL(KTxtDefault);
                ptrarray.At(ix) = ptr;
                }

        console->Printf(KTxtState1);
        for (ix = 0; ix<4; ix++)
                {
                console->Printf(KTxtFormat8,ptrarray[ix]);
                }
        console->Printf(KTxtNewLine);

        // Now delete all the CTest objects
        ptrarray.DeleteAll();

        // Set the array's data members to NULL 
        ptrarray.Reset();

        console->Printf(KTxtState2);
        for (ix = 0; ix<4; ix++)
                {
                console->Printf(KTxtFormat8,ptrarray[ix]);
                }
        console->Printf(KTxtNewLine);

        }

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Copyright ©2010 Nokia Corporation and/or its subsidiary(-ies).
All rights reserved. Unless otherwise stated, these materials are provided under the terms of the Eclipse Public License v1.0.