不錯的主要用於加密的vbs(asp)位移運算類

<script language="vbscript">
' Aother: 奔騰的心
' QQ: 7180001
' Date: 2008-01-17

Class mShift

Private m_lPower2(31)

Public Function RShift(ByVal lThis, ByVal lBits)
On Error Resume Next
Init
If (lBits <= 0) Then
RShift = lThis
ElseIf (lBits > 63) Then
' .. error ...
ElseIf (lBits > 31) Then
RShift = 0
Else
If (lThis And m_lPower2(31 - lBits)) = m_lPower2(31 - lBits) Then
RShift = (lThis And (m_lPower2(31 - lBits) - 1)) * m_lPower2(lBits) Or
m_lPower2(31)
Else
RShift = (lThis And (m_lPower2(31 - lBits) - 1)) * m_lPower2(lBits)
End If
End If
End Function

Public Function LShift(ByVal lThis, ByVal lBits)
On Error Resume Next
Init
If (lBits <= 0) Then
LShift = lThis
ElseIf (lBits > 63) Then
' ... error ...
ElseIf (lBits > 31) Then
LShift = 0
Else
If (lThis And m_lPower2(31)) = m_lPower2(31) Then
LShift = (lThis And &H7FFFFFFF) \ m_lPower2(lBits) Or m_lPower2(31 - lBits)
Else
LShift = lThis \ m_lPower2(lBits)
End If
End If
End Function

Private Sub Init()
On Error Resume Next
m_lPower2(0) = &H1&
m_lPower2(1) = &H2&
m_lPower2(2) = &H4&
m_lPower2(3) = &H8&
m_lPower2(4) = &H10&
m_lPower2(5) = &H20&
m_lPower2(6) = &H40&
m_lPower2(7) = &H80&
m_lPower2(8) = &H100&
m_lPower2(9) = &H200&
m_lPower2(10) = &H400&
m_lPower2(11) = &H800&
m_lPower2(12) = &H1000&
m_lPower2(13) = &H2000&
m_lPower2(14) = &H4000&
m_lPower2(15) = &H8000&
m_lPower2(16) = &H10000
m_lPower2(17) = &H20000
m_lPower2(18) = &H40000
m_lPower2(19) = &H80000
m_lPower2(20) = &H100000
m_lPower2(21) = &H200000
m_lPower2(22) = &H400000
m_lPower2(23) = &H800000
m_lPower2(24) = &H1000000
m_lPower2(25) = &H2000000
m_lPower2(26) = &H4000000
m_lPower2(27) = &H8000000
m_lPower2(28) = &H10000000
m_lPower2(29) = &H20000000
m_lPower2(30) = &H40000000
m_lPower2(31) = &H80000000
End Sub

End Class

Dim sft
Set sft = New mShift
MsgBox sft.RShift(200, 4)
MsgBox sft.LShift(200, 4)
Set sft = Nothing
</script>

<script language="javascript">
alert(200<<4);
alert(200>>4);
</script>