Sortable CObList class

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// SortableObList.h
/////////////////////////////////////////////////////////////////////

class CSortableObList : public CObList
{
public:
CSortableObList(int nBlockSize = 10) : CObList(nBlockSize) { }

void Sort(int(*CompareFunc)(CObject* pFirstObj, CObject*pSecondObj));
void Sort(POSITION posStart, int iElements, int (*CompareFunc)(CObject* pFirstObj, CObject* pSecondObj));
};

template< class TYPE >
class CTypedSortableObList : public CSortableObList
{
public:
// Construction
CTypedSortableObList(int nBlockSize = 10) : CSortableObList(nBlockSize) { }

// peek at head or tail
TYPE& GetHead()
{ return (TYPE&)CSortableObList::GetHead(); }
TYPE GetHead() const
{ return (TYPE)CSortableObList::GetHead(); }
TYPE& GetTail()
{ return (TYPE&)CSortableObList::GetTail(); }
TYPE GetTail() const
{ return (TYPE)CSortableObList::GetTail(); }

// get head or tail (and remove it) – don’t call on empty list!
TYPE RemoveHead()
{ return (TYPE)CSortableObList::RemoveHead(); }
TYPE RemoveTail()
{ return (TYPE)CSortableObList::RemoveTail(); }

// add before head or after tail
POSITION AddHead(TYPE newElement)
{ return CSortableObList::AddHead(newElement); }
POSITION AddTail(TYPE newElement)
{ return CSortableObList::AddTail(newElement); }

// add another list of elements before head or after tail
void AddHead(CTypedSortableObList< TYPE >* pNewList)
{ CSortableObList::AddHead(pNewList); }
void AddTail(CTypedSortableObList< TYPE >* pNewList)
{ CSortableObList::AddTail(pNewList); }

// iteration
TYPE& GetNext(POSITION& rPosition)
{ return (TYPE&)CSortableObList::GetNext(rPosition); }
TYPE GetNext(POSITION& rPosition) const
{ return (TYPE)CSortableObList::GetNext(rPosition); }
TYPE& GetPrev(POSITION& rPosition)
{ return (TYPE&)CSortableObList::GetPrev(rPosition); }
TYPE GetPrev(POSITION& rPosition) const
{ return (TYPE)CSortableObList::GetPrev(rPosition); }

// getting/modifying an element at a given position
TYPE& GetAt(POSITION position)
{ return (TYPE&)CSortableObList::GetAt(position); }
TYPE GetAt(POSITION position) const
{ return (TYPE)CSortableObList::GetAt(position); }
void SetAt(POSITION pos, TYPE newElement)
{ CSortableObList::SetAt(pos, newElement); }

void Sort( int(*CompareFunc)(TYPE pFirstObj, TYPE pSecondObj) )
{ CSortableObList::Sort((int(*)(CObject*,CObject*))CompareFunc); }
void Sort( POSITION posStart, int iElements, int(*CompareFunc)(TYPE pFirstObj, TYPE pSecondObj) )
{ CSortableObList::Sort(posStart, iElements, (int(*)(CObject*,CObject*))CompareFunc); }
};

// SortableObList.cpp
///////////////////////////////////////////////////////////////////

void CSortableObList::Sort(int (*CompareFunc)(CObject* pFirstObj, CObject* pSecondObj))
{
// CompareFunc is expected to return a positive integer if pFirstObj
// should follow pSecondObj (is greater than)

// Uses Insertion Sort

// The Shell Sort is much faster than a straight insertion sort, however, it cannot
// be performed on a linked list (it COULD, but the resulting code would probably be
// much slower as a Shell Sort jumps all around the reletive positions of elements).

// An Insertion Sort works by evaluating an item, if that item should
// precede the item in front of it, than it shifts all the items that
// should follow that item up one place until it finds the correct position
// for the item, whereby it then ‘inserts’ that item.

ASSERT_VALID(this);

// If the list contains no items, the HEAD position will be NULL
if (m_pNodeHead == NULL)
return;

CObject *pOtemp;
CObList::CNode *pNi,*pNj;

// Walk the list
for (pNi = m_pNodeHead->pNext; pNi != NULL; pNi = pNi->pNext)
{
// Save data pointer
pOtemp = pNi->data;

// Walk the list backwards from pNi to the beginning of the list or until
// the CompareFunc() determines that this item is in it’s correct position
// shifting all items upwards as it goes
for (pNj = pNi; pNj->pPrev != NULL && CompareFunc(pNj->pPrev->data,pOtemp) > 0; pNj = pNj->pPrev)
pNj->data = pNj->pPrev->data;

// Insert data pointer into it’s proper position
pNj->data = pOtemp;
}

}

void CSortableObList::Sort(POSITION posStart, int iElements, int (*CompareFunc)(CObject* pFirstObj, CObject* pSecondObj))
{
// This variation allows you to sort only a portion of the list

// iElements can be larger than the number of remaining elements without harm
// iElements can be -1 which will always sort to the end of the list

ASSERT_VALID(this);
ASSERT( AfxIsValidAddress((CObList::CNode*)posStart, sizeof(CObList::CNode)) );

// Make certain posStart is a position value obtained by a GetHeadPosition or Find member function call
// as there is no way to test whether or not posStart is a valid CNode pointer from this list.
// Ok, there is one way, we could walk the entire list and verify that posStart is in the chain, but even
// for debug builds that’s a bit much.

// If the list contains no items, the HEAD position will be NULL
if (m_pNodeHead == NULL)
return;

CObject *pOtemp;
CObList::CNode *pNi,*pNj;

// Walk the list
for (pNi = (CObList::CNode*)posStart; pNi != NULL && iElements != 0; pNi = pNi->pNext, iElements–)
{
// Save data pointer
pOtemp = pNi->data;

// Walk the list backwards from pNi to the beginning of the sort or until
// the CompareFunc() determines that this item is in it’s correct position
// shifting all items upwards as it goes
for (pNj = pNi; pNj->pPrev != NULL && pNj->pPrev != ((CObList::CNode*)posStart)->pPrev && CompareFunc(pNj->pPrev->data,pOtemp) > 0; pNj = pNj->pPrev)
pNj->data = pNj->pPrev->data;

// Insert data pointer into it’s proper position
pNj->data = pOtemp;
}

}

// Usage
//////////////////////////////////////////////////////////

// Create a CObject based class
// Create a CObject based class
class CMyObject : public CObject
{
public:
CString name;
static int CompBackward(CMyObject* pFirstObj, CMyObject* pSecondObj)
{
return -lstrcmp((LPCTSTR)pFirstObj->name,(LPCTSTR)pSecondObj->name);
}
};

// Create a list object
CTypedSortableObList< CMyObject* > list;

// Fill the list with a bunch of objects
for (int i=0; i < 10; i++) { CMyObject * pObj = new CMyObject; pObj->name.Format(“Object #%d”,i);
list.AddTail(pObj);
}

// Sort the list
list.Sort(CMyObject::CompBackward);

// Display the contents of the now sorted list
for (POSITION pos = list.GetHeadPosition(); pos != NULL; )
{
CMyObject* pObj = list.GetNext(pos);
TRACE1(“%sn”,pObj->name);
}


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