A Safer STL Container Class

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class CElement
{
unsigned int m_magic_number;
…
CElement::CElement(const int index)
: m_magic_number(0xfeedface), m_index(index)
{
}

There are probably some other ways of doing it. For example, delete operator uses _BLOCK_TYPE_IS_VALID macro in debug mode. Either way, it is much safer to use for a little speed decrease.
Note: In case your class is derived from some base class, you would have to use 4 bytes offset when dereferencing a pointer inside IsBlockValid function:

return (*((unsigned int*)((int)pBlock + 4)) == 0xfeedface);

I also added some functions to make it MFC like: GetFirst(), GetNext(), RemoveLastRead(), etc.
In the sample code I added 10 elements into the map. Then I deleted elements 5 and 7 outside the map. Then I looped through displaying the content. Notice that after going through all the elements CTidyMap reports 8 to be the actual size.

Example Usage

CTidyMap<CElement, int&gt	mymap;

CElement* pElement[10];

for(int i = 0; i < 10; i++) {

 pElement[i] = new CElement(i);

 mymap.Add(pElement[i], i);

}
cout << “Number of elements in the map: ”

     << mymap.GetCount() << endl;
delete pElement[5];
cout << “Deleted Element number 5” << endl;

delete pElement[7];
cout << “Deleted Element number 7” << endl;
cout << “Still does not know about elements being deleted, size: ”

     << mymap.GetCount() << endl;
CElement* pExElem = mymap.GetFirst();

while(pExElem) {

 cout << “Found Element number: ”

      << pExElem->GetIndex()

      << endl;
 pExElem = mymap.GetNext();

}
cout << “Now the number of elements in the map: ”

     << mymap.GetCount()

     << endl;

Output

Number of elements in the map: 10

Deleted Element number 5

Deleted Element number 7

Still does not know about elements being deleted, size: 10

Found Element number: 0

Found Element number: 1

Found Element number: 2

Found Element number: 3

Found Element number: 4

Found Element number: 6

Found Element number: 8

Found Element number: 9

Now the number of elements in the map: 8

Bonus

I also made the feedface optional so if you initialize it like this:

CTidyMap<CElement, int&gt	mymap = false;

Downloads

Download demo project – 5 Kb