[VB6] clsStrToIntArray.cls - Cast String To Integer Array

[Bonnie West]

This simple class makes it very easy to typecast a String into an Integer array. Treating a String as an array enables some kinds of String processing to be done much quicker than is possible with VB's intrinsic String functions.


clsStrToIntArray.cls

Option Explicit

Private Const FADF_AUTO      As Integer = &H1   'An array that is allocated on the stack.
Private Const FADF_FIXEDSIZE As Integer = &H10  'An array that may not be resized or reallocated.

Private Type SAFEARRAY1D    'Represents a safe array. (One Dimensional)
    cDims      As Integer   'The count of dimensions.
    fFeatures  As Integer   'Flags used by the SafeArray.
    cbElements As Long      'The size of an array element.
    cLocks     As Long      'The number of times the array has been locked without a corresponding unlock.
    pvData     As Long      'Pointer to the data.
    cElements  As Long      'The number of elements in the dimension.
    lLbound    As Long      'The lower bound of the dimension.
End Type                    'http://msdn.microsoft.com/en-us/library/ms221482(v=vs.85).aspx

Private Declare Function VarPtrArray Lib "msvbvm60.dll" Alias "VarPtr" (ByRef ArrayVar() As Any) As Long
Private Declare Sub PutMem4 Lib "msvbvm60.dll" (ByVal Addr As Long, ByVal NewVal As Long)

Private Ptr  As Long
Private SA1D As SAFEARRAY1D

Private Sub Class_Initialize()
    With SA1D
        .cDims = 1
        .fFeatures = FADF_AUTO Or FADF_FIXEDSIZE
        .cbElements = 2&
        .cLocks = 1&
        .lLbound = 1&
    End With
End Sub

'This should be the first method called right after instantiating
'the class and should be invoked only once per class instance.
'Pass the Integer array that will substitute for the String.

Public Sub InitArray(ByRef IntArray_OUT() As Integer)
    Erase IntArray_OUT
    Ptr = VarPtrArray(IntArray_OUT())
    PutMem4 Ptr, VarPtr(SA1D)
End Sub

'This function typecasts the passed String into an Integer array.
'That is, the characters of the String can be treated as elements
'of the Integer array. Any number of Strings can be typecast to
'the Integer array by calling this function repeatedly. However,
'the array should not be Erased when assigning another String.
'This function fails (returns False) if passed an empty string.

Public Function CastString(ByRef String_IN As String) As Boolean
    Dim StrLen As Long

    If Ptr Then
        StrLen = Len(String_IN)
        If StrLen Then
            With SA1D
               .pvData = StrPtr(String_IN)
               .cElements = StrLen
                CastString = .pvData <> 0&
            End With
        End If
    End If
End Function

Private Sub Class_Terminate()
    If Ptr Then PutMem4 Ptr, 0&
End Sub

modMain.bas

Option Explicit

Private Sub Main()
    Dim aintChars() As Integer, i As Long
    Dim sControlChars As String, sPrintableChars As String

    sControlChars = Space$(31&)
    sPrintableChars = String$(224&, 0)

    With New clsStrToIntArray
       .InitArray aintChars()

        If .CastString(sPrintableChars) Then
            For i = LBound(aintChars) To UBound(aintChars)
                aintChars(i) = i + 31&
            Next
            Debug.Print """" & sPrintableChars & """"
        End If

        If .CastString(sControlChars) Then
            For i = LBound(aintChars) To UBound(aintChars)
                aintChars(i) = i
            Next
            Debug.Print """" & sControlChars & """"
        End If
    End With
End Sub