examples/SFExamples/Example_RArray/ArrayCreationExamples.cpp

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Description:  
*/

#include "ArrayCreationExamples.h"
#include "SharedCode.h"
#include <e32test.h>

extern CConsoleBase* console;

// ---------------------------------------------------------
// void TakeOwnershipL()
// This example shows how to take ownership of a dynamically
// allocated block of memory and assign it to an RArray
// ---------------------------------------------------------
//
LOCAL_C void TakeOwnershipL()
        {
        TExampleStruct* values = GenerateValuesLC();

        // This array does not own the the memory pointer to values
        // rather it just creates a very quick RArray that offers
        // all the functionality but onto a block of User::Alloc'd
        // memory.
        // A call to User::Leave will correctly leave
        // as GenerateRandomumbersLC put the memory on the
        // cleanup stack, so at this point the RArray does not own
        // the memory, the "values" pointer does.
        RExampleArray array(sizeof(TExampleStruct), values, KMaxElements);
        
        // now we want to transfer ownership of that memory block
        // to array, so we pop the "values" blob from the stack
        // and its implicitly transferred to the array
        // but now the array needs to put back on the cleanup stack
        // to prevent a memory leak as its taken ownership of the blob
        //
        // Note it might appear that PushL could leave but values would
        // not be on the stack. This is not the case, reading the documenation
        // for the cleanup stack, you will see PushL will always ensure there is
        // at least one element reserved at the top of the cleanup stack. It will
        // leave if it cannot preallocate the next element at the top of the stack
        
        CleanupStack::Pop(values);
        CleanupClosePushL(array);
        
        // you put your element manipulation code here
        
        // we are finished with the array
        CleanupStack::PopAndDestroy(&array);
        }

// ---------------------------------------------------------
// void ReserveAndAppendL()
// Another way to create an array is to reserve the space
// then add the items one by one
// obviously inefficient but we can optimize it by
// reserving the data before adding it to prevent
// thrashing (using Reserve)
// ---------------------------------------------------------
//
LOCAL_C void ReserveAndAppendL()
        {
        TExampleStruct* values = GenerateValuesLC();

        RExampleArray array;
        CleanupClosePushL(array);
        // Preallocate a lot of memory for all the elements
        User::LeaveIfError(array.Reserve(KMaxElements));
        // Now copy the elements over
        for (TInt i=0 ;i < KMaxElements; i++)
                User::LeaveIfError(array.Append(values[i]));
        
        CleanupStack::PopAndDestroy(2, values);
        }

// ---------------------------------------------------------
// void NonAllocatingArrayL()
// Example of creating an array that does not allocate memory
// ---------------------------------------------------------
//
LOCAL_C void NonAllocatingArrayL()
        {
        static const TInt32 KInts[] = { 1, 2, 3, 4, 5};
        const RArray<TInt32> array(sizeof(TInt32), (TInt32*)KInts, sizeof(KInts) / sizeof(KInts[0]));
        
        // no need to put it on the cleanup stack as does not own any memory
        // even a leave is safe were
        // remember indices are zero based
        if (array[2] != 3)
                {
                User::Leave(KErrNotFound);
                }
        
        
        }
// ---------------------------------------------------------
// void ArrayCreationExamplesL()
// Example code on creating an array
// ---------------------------------------------------------
//
void ArrayCreationExamplesL()
        {
        console->Printf(_L("RArray usage without allocating memory\n"));
        NonAllocatingArrayL();
        User::After(0);
        
        console->Printf(_L("Taking ownership of memory and transfering it an RArray\n"));       
        TakeOwnershipL();
        User::After(0);
        
        console->Printf(_L("Reserving space in the array before appending the elements\n"));
        ReserveAndAppendL();
        User::After(0); 
        }

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