'
' Function to add two unsigned numbers together as in C.
' Overflows are ignored!
'
Private Function LongOverflowAdd(Val1 As Long, Val2 As Long) As Long
    Dim lngHighWord As Long
    Dim lngLowWord As Long
    Dim lngOverflow As Long

    lngLowWord = (Val1 And &HFFFF&) + (Val2 And &HFFFF&)
    lngOverflow = lngLowWord \ 65536
    lngHighWord = (((Val1 And &HFFFF0000) \ 65536) + ((Val2 And &HFFFF0000) \ 65536) + lngOverflow) And &HFFFF&
    LongOverflowAdd = UnsignedToLong((lngHighWord * 65536#) + (lngLowWord And &HFFFF&))
End Function

'
' Function to add two unsigned numbers together as in C.
' Overflows are ignored!
'
Private Function LongOverflowAdd4(Val1 As Long, Val2 As Long, val3 As Long, val4 As Long) As Long
    Dim lngHighWord As Long
    Dim lngLowWord As Long
    Dim lngOverflow As Long

    lngLowWord = (Val1 And &HFFFF&) + (Val2 And &HFFFF&) + (val3 And &HFFFF&) + (val4 And &HFFFF&)
    lngOverflow = lngLowWord \ 65536
    lngHighWord = (((Val1 And &HFFFF0000) \ 65536) + _
                   ((Val2 And &HFFFF0000) \ 65536) + _
                   ((val3 And &HFFFF0000) \ 65536) + _
                   ((val4 And &HFFFF0000) \ 65536) + _
                   lngOverflow) And &HFFFF&
    LongOverflowAdd4 = UnsignedToLong((lngHighWord * 65536#) + (lngLowWord And &HFFFF&))
End Function

'
' Convert an unsigned double into a long
'
Private Function UnsignedToLong(value As Double) As Long
        If value < 0 Or value >= OFFSET_4 Then Error 6 ' Overflow
        If value <= MAXINT_4 Then
          UnsignedToLong = value
        Else
          UnsignedToLong = value - OFFSET_4
        End If
      End Function

'
' Convert a long to an unsigned Double
'
Private Function LongToUnsigned(value As Long) As Double
        If value < 0 Then
          LongToUnsigned = value + OFFSET_4
        Else
          LongToUnsigned = value
        End If
End Function

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