VB Shell Programming

The PIDL Manager

Before we continue, we really need to discuss pidlMgr.cls. This class is a helper class that we will use to manage functions involving PIDLs. These helper functions include things like creating, copying, and deleting PIDLs, getting the last PIDL in a list of PIDLs, getting the next PIDL in a list of PIDLs, as well as additional functions that are more specific to our particular namespace extension.

So add a new class to the project called pidlMgr.cls, and let’s start implementing some of the functionality of this class.

Delete

We have used three functions from this class so far: Delete, Copy, and Create. Delete is by far the easiest of the functions to implement. It just wraps a call to IMalloc::Free. Delete looks like this:

'pidlMgr.cls

Private m_  pMalloc As IMalloc

Private Sub Class_Initialize(  )
    Set m_  pMalloc = GetMalloc
End Sub

Private Sub Class_Terminate(  )
    Set m_  pMalloc = Nothing
End Sub

Public Sub Delete(ByVal pidl As LPITEMIDLIST)
    m_  pMalloc.Free pidl
End Sub

Copy

Copy is used to make a copy of the PIDL:

Public Function Copy(ByVal pidlSource As LPITEMIDLIST) As LPITEMIDLIST
    Dim pidlTarget As LPITEMIDLIST
    Dim cbSource As UINT
    
    Copy = 0
    
    If (pidlSource = 0) Then
        Exit Function
    End If
    
    cbSource = GetSize(pidlSource)
    
    pidlTarget = m_pMalloc.Alloc(cbSource)
    If (pidlTarget > 0) Then
        CopyMemory ByVal pidlTarget, ByVal pidlSource, cbSource
        Copy = pidlTarget
    End If
    
End Function

Create

This method is a little more involved, but the reason for this requires some background ...