Unsigned Arithmetic in Visual Basic

Category:

Dates and Math

Type:

Snippets

Difficulty:

Advanced

Author:

Sergey Merzlikin

Version Compatibility: Visual Basic 6, Visual Basic 5

More information:

These functions allow to add and subtract two unsigned long values (DWord), for example, for memory address calculations.

Instructions: Copy the declarations and code below and paste directly into your VB project.

Declarations:
' (None)

Code:

Private Function UnsignedAdd(ByVal L1 As Long, ByVal L2 As Long) As Long
    Dim L11 As Long, L12 As Byte, L21 As Long, L22 As Byte, L31 As Long, L32 As Byte
    L11 = L1 And &HFFFFFF
    L12 = (L1 And &H7F000000) \ &H1000000
    If L1 < 0& Then L12 = L12 Or &H80
    L21 = L2 And &HFFFFFF
    L22 = (L2 And &H7F000000) \ &H1000000
    If L2 < 0& Then L22 = L22 Or &H80
    L32 = L12 + L22
    L31 = L11 + L21
    If (L31 And &H1000000) Then L32 = L32 + 1
    UnsignedAdd = (L31 And &HFFFFFF) + (L32 And &H7F) * &H1000000
    If L32 And &H80 Then UnsignedAdd = UnsignedAdd Or &H80000000
End Function

Private Function UnsignedSubtract(ByVal L1 As Long, ByVal L2 As Long) As Long
    Dim L11 As Long, L12 As Byte, L21 As Long, L22 As Byte, L31 As Long, L32 As Byte
    L11 = L1 And &HFFFFFF
    L12 = (L1 And &H7F000000) \ &H1000000
    If L1 < 0& Then L12 = L12 Or &H80
    L21 = L2 And &HFFFFFF
    L22 = (L2 And &H7F000000) \ &H1000000
    If L2 < 0& Then L22 = L22 Or &H80
    L32 = L12 - L22
    L31 = L11 - L21
    If L31 < 0 Then
        L32 = L32 - 1
        L31 = L31 + &H1000000
    End If
    UnsignedSubtract = L31 + (L32 And &H7F) * &H1000000
    If L32 And &H80 Then UnsignedSubtract = UnsignedSubtract Or &H80000000
End Function