Sort list (numeric/text) using callback

This is a small class which permits to sort list controls. It works “substituting” every original item data with a small class (preserving the value), sort it using the standard (fast!) list control way, and then putting the things right back.

Step 1: implementing the class

The class will contain two subclasses to manage numeric and text column data. The numeric is provided to avoid the sorting of 11 before 2 as it would occur with string comparison; there are also 4 comparing routines (for ascending and descending text and integer columns).

The header file of the class should be like this:

class CSortClass
{
public:
	CSortClass(CListCtrl * _pWnd, const int _iCol, const bool _bIsNumeric);
	virtual ~CSortClass();

	int iCol;
	CListCtrl * pWnd;
	bool bIsNumeric;
	void Sort(const bool bAsc);

	static int CALLBACK CompareAsc(LPARAM lParam1, LPARAM lParam2, LPARAM lParamSort);
	static int CALLBACK CompareDes(LPARAM lParam1, LPARAM lParam2, LPARAM lParamSort);

	static int CALLBACK CompareAscI(LPARAM lParam1, LPARAM lParam2, LPARAM lParamSort);
	static int CALLBACK CompareDesI(LPARAM lParam1, LPARAM lParam2, LPARAM lParamSort);

public:
	class CSortItem
	{
	public:
		virtual  ~CSortItem();
		CSortItem(const DWORD _dw, const CString &_txt);
		CString txt;
		DWORD dw;
	};
	class CSortItemInt
	{
	public:
		CSortItemInt(const DWORD _dw, const CString &_txt);
		int iInt ;
		DWORD dw;
	};
};

The CPP file will implement all the above:

/////////////////////////////////////////////////////////////////////////////
// CSortClass

CSortClass::CSortClass(CListCtrl * _pWnd, const int _iCol, const bool _bIsNumeric)
{
	iCol = _iCol;
	pWnd = _pWnd;
	bIsNumeric = _bIsNumeric;

	ASSERT(pWnd);
	int max = pWnd->GetItemCount();
	DWORD dw;
	CString txt;
	if (bIsNumeric)
	{
		for (int t = 0; t < max; t++)
		{
			dw = pWnd->GetItemData(t);
			txt = pWnd->GetItemText(t, iCol);
			pWnd->SetItemData(t, (DWORD) new CSortItemInt(dw, txt));
		}
	}
	else
	{
		for (int t = 0; t < max; t++)
		{
			dw = pWnd->GetItemData(t);
			txt = pWnd->GetItemText(t, iCol);
			pWnd->SetItemData(t, (DWORD) new CSortItem(dw, txt));
		}
	}
}

CSortClass::~CSortClass()
{
	ASSERT(pWnd);
	int max = pWnd->GetItemCount();
	if (bIsNumeric)
	{
		CSortItemInt * pItem;
		for (int t = 0; t < max; t++)
		{
			pItem = (CSortItemInt *) pWnd->GetItemData(t);
			ASSERT(pItem);
			pWnd->SetItemData(t, pItem->dw);
			delete pItem;
		}
	}
	else
	{
		CSortItem * pItem;
		for (int t = 0; t < max; t++)
		{
			pItem = (CSortItem *) pWnd->GetItemData(t);
			ASSERT(pItem);
			pWnd->SetItemData(t, pItem->dw);
			delete pItem;
		}
	}
}

void
CSortClass::Sort(const bool bAsc)
{
	if (bIsNumeric)
	{
		if (bAsc)
			pWnd->SortItems(CompareAscI, 0L);
		else
			pWnd->SortItems(CompareDesI, 0L);
	}
	else
	{
		if (bAsc)
			pWnd->SortItems(CompareAsc, 0L);
		else
			pWnd->SortItems(CompareDes, 0L);
	}
}

int CALLBACK CSortClass::CompareAsc(LPARAM lParam1, LPARAM lParam2, LPARAM lParamSort)
{
	CSortItem * i1 = (CSortItem *) lParam1;
	CSortItem * i2 = (CSortItem *) lParam2;
	ASSERT(i1 && i2);
	return i1->txt.CompareNoCase(i2->txt);
}

int CALLBACK CSortClass::CompareDes(LPARAM lParam1, LPARAM lParam2, LPARAM lParamSort)
{
	CSortItem * i1 = (CSortItem *) lParam1;
	CSortItem * i2 = (CSortItem *) lParam2;
	ASSERT(i1 && i2);
	return i2->txt.CompareNoCase(i1->txt);
}

int CALLBACK CSortClass::CompareAscI(LPARAM lParam1, LPARAM lParam2, LPARAM lParamSort)
{
	CSortItemInt * i1 = (CSortItemInt *) lParam1;
	CSortItemInt * i2 = (CSortItemInt *) lParam2;
	ASSERT(i1 && i2);
	if (i1->iInt == i2->iInt) return 0;
	return i1->iInt > i2->iInt ? 1 : -1;
}

int CALLBACK CSortClass::CompareDesI(LPARAM lParam1, LPARAM lParam2, LPARAM lParamSort)
{
	CSortItemInt * i1 = (CSortItemInt *) lParam1;
	CSortItemInt * i2 = (CSortItemInt *) lParam2;
	ASSERT(i1 && i2);
	if (i1->iInt == i2->iInt) return 0;
	return i1->iInt < i2->iInt ? 1 : -1;
}

CSortClass::CSortItem::CSortItem(const DWORD _dw, const CString & _txt)
{
	dw = _dw;
	txt = _txt;
}

CSortClass::CSortItem::~CSortItem()
{
}

CSortClass::CSortItemInt::CSortItemInt(const DWORD _dw, const CString & _txt)
{
	iInt = atoi(_txt);
	dw = _dw;
}

Step 2: using it

The class is designed to be easy usable. In answer to a column click message in a list control, we can write something like this:

void CMyListCtrl::OnColumnclick(NMHDR* pNMHDR, LRESULT* pResult)
{
	NM_LISTVIEW* pNMListView = (NM_LISTVIEW*)pNMHDR;

	// bAscending will be use to order from lower to higher or higher to lower
	bool bAscending = true;

	CSortClass csc(this, pNMListView->iSubItem, bAscending);
	csc.Sort(bAsc);

	*pResult = 0;
}