README.md

 
' Used for unsigned arithmetic
Private Const DW_MSB = &H80000000 ' DWord Most Significant Bit
 
 ' + Sum Unsigned Long ++++++++++++++++++++++
 
 ' Enables valid addition and subtraction of unsigned long integers.
 ' Treats lPtr as an unsigned long and returns an unsigned long.
 ' Allows safe arithmetic operations on memory address pointers.
 ' Assumes valid pointer and pointer offset.
 
Private Function SumUnsignedLong(ByVal lPtr As Long, ByVal lOffset As Long) As Long
 
  If lOffset > 0& Then
     If lPtr And DW_MSB Then             ' if ptr < 0
        SumUnsignedLong = lPtr + lOffset ' ignors > unsigned max (see assumption)
 
     ElseIf (lPtr Or DW_MSB) < -lOffset Then
        SumUnsignedLong = lPtr + lOffset ' result is below signed int max
 
     Else                                ' result wraps to min signed int
        SumUnsignedLong = (lPtr + DW_MSB) + (lOffset + DW_MSB)
     End If
 
  ElseIf lOffset = 0& Then
     SumUnsignedLong = lPtr
 
  Else 'If lOffset < 0 Then
     If (lPtr And DW_MSB) = 0& Then      ' if ptr > 0
        SumUnsignedLong = lPtr + lOffset ' ignors unsigned < zero (see assumption)
 
     ElseIf (lPtr - DW_MSB) >= -lOffset Then
        SumUnsignedLong = lPtr + lOffset ' result is above signed int min
 
     Else                                ' result wraps to max signed int
        SumUnsignedLong = (lOffset - DW_MSB) + (lPtr - DW_MSB)
     End If
  End If
End Function
 
 ' ++++++++++++++++++++++++++++++++++++++++++
 
 ' Extract from the classic ShellSort algorithm
 
Dim s1 As String, lpStr1 As Long
Dim s2 As String, lpStr2 As Long
 
lpStr1 = VarPtr(s1)
lpStr2 = VarPtr(s2)
 
lpArr = VarPtr(sArr(lb))
 
 'lpLast = lpArr + ((ub - lb) * 4&)
 lpLast = SumUnsignedLong(lpArr, (ub - lb) * 4&)
 '...
 
  CopyMemByV lpStr1, lpLast, 4&
 
  'CopyMemByV lpStr2, lpLast - lRange, 4&
  CopyMemByV lpStr2, SumUnsignedLong(lpLast, -lRange), 4&
 
  If StrComp(s2, s1, eMethod) = eComp Then
  '...