This function adds two long numbers together as if they were unsigned, and does not cause an overflow error. You may need this when implementing the SHA-1 Hashing function.

' Add two numbers together, without overflow or signed bitsFunction FullAdd(ByVal x As Long, ByVal y As Long) As Long    Dim z As Long    Dim z1 As Boolean, z2 As Boolean, c2 As Boolean       ' First, add the two numbers without their top two bits (prevents overflow)    z = (x And &H3FFFFFFF) + (y And &H3FFFFFFF)        ' Perform a full addition on the 31st bit (carry is in z31)    z1 = CBool(z And &H40000000) Xor (CBool(y And &H40000000) Xor _   CBool(x And &H40000000))    c2 = (CBool(y And &H40000000) And CBool(x And &H40000000)) Or _   (CBool(z And &H40000000) _   And CBool(x And &H40000000)) _   Or (CBool(y And &H40000000) And CBool(z And &H40000000))    ' Now perform a full addition for the 32nd bit (but we don't care about the _   carry bit)    z2 = c2 Xor (CBool(y And &H80000000) Xor CBool(x And &H80000000))    ' If you wanted to test for an overflow you could test the carry bit here and _   raise the appropriate error    'If (CBool(y And &H80000000) And CBool(x And &H80000000)) Or _   (c2 And CBool(x And   &H80000000)) _    '        Or (CBool(y And &H80000000) And c2) Then Err.Raise6 , , _   "Overflow in FullAdd"    ' Now we can chuck it all together    FullAdd = (z And &H3FFFFFFF) Or (z1 And &H40000000) Or (z2 And &H80000000)        ' nb. an alternative would have been to add the first and second 16-bit groups    ' separately. Although neater, this would have need a 16-leftshift and 16-rightshift    ' As shifts are not natively supported, this method is quickerEnd Function