Public Class clsTEST

    Private Sub Test

        Dim testIP As String
        Dim testCIDR As String
        Dim c As New clsCIDR

        ' Test parameters
        testIP = "192.168.1.2"
        testCIDR = "192.168.0.0/16"

        ' Test cases
        MsgBox("Is " & testIP & " an ip adress?" & vbCrLf & c.IsIPAddress(testIP))
        MsgBox("Is " & testCIDR & " an CIDR mask ?" & vbCrLf & c.IsCIDRMask(testCIDR))
        MsgBox("Max adress of " & testCIDR & " is: " & vbCrLf & c.CIDRMaxAddress(testCIDR))
        MsgBox("Is " & testIP & " valid within " & testCIDR & "?" & vbCrLf & c.IPValidateCIDR(testCIDR, testIP))

        c = Nothing
        End

    End Sub

End Class


Public Class clsCIDR


    ' CIDR class (C) 2005-2009 Glenn Larsson
    ' ------------------------------------------------
    ' Free for non-commercial use. Commercial use prohibited!


    ' --------------------------------------------------------------------------------
    ' IsIPAddress : Test if the provided variable an IP Adress
    ' --------------------------------------------------------------------------------
    Public Function IsIPAddress(ByVal IPAddress As String) As Boolean

        IsIPAddress = False

        Const VALIDCHARS = "0123456789."                        ' Set Valid chars for IP Address
        Dim t As String
        Dim n As Integer
        Dim x() As String

        For n = 1 To Len(IPAddress)                             ' Check for invalid characters
            t = Mid(IPAddress, n, 1)
            'If InStr(1, VALIDCHARS, t) = 0 Then Exit Function '(VB6 syntax)
            If Microsoft.VisualBasic.InStr(VALIDCHARS, t) = 0 Then Exit Function
        Next n

        If InStr(1, IPAddress, "..") > 0 Then Exit Function ' Skip ".."
        If InStr(1, IPAddress, ".00") > 0 Then Exit Function ' Skip ".00" and ".000"
        x = Split(IPAddress, ".")


        If UBound(x) <> 3 Then Exit Function ' IP V4 adresses only (4 digits exactly)

        For n = 0 To UBound(x)                                  ' Values between 0-255 and not ""
            If Trim(x(n)) = "" Then Exit Function
            If CLng(x(n)) < 0 Then Exit Function
            If CLng(x(n)) > 255 Then Exit Function
        Next n

        Return True

    End Function


    ' --------------------------------------------------------------------------------
    ' IsCIDRMask = Test if the provided variable a CIDR mask
    ' --------------------------------------------------------------------------------
    Public Function IsCIDRMask(ByVal CIDRMask As String) As Boolean

        IsCIDRMask = False
        Const VALIDCHARS = "0123456789./"                       ' Set valid chars for CIDR mask
        Dim n As Integer
        Dim T As String
        Dim X() As String

        For n = 1 To Len(CIDRMask)                              ' Check valid chars
            T = Mid(CIDRMask, n, 1)
            If InStr(1, VALIDCHARS, T) = 0 Then Exit Function
        Next n

        If InStr(1, CIDRMask, "/") = 0 Then Exit Function ' No "/" ?
        If InStr(1, CIDRMask, "//") > 0 Then Exit Function ' No "//" ?
        If Left(CIDRMask, 1) = "/" Then Exit Function ' no Left "/"
        If Right(CIDRMask, 1) = "/" Then Exit Function ' no Right "/"

        If InstrCnt(CIDRMask, "/") <> 1 Then Exit Function ' Only ONE slash ("/") please

        X = Split(CIDRMask, "/")

        If UBound(X) <> 1 Then Exit Function ' Must be 2 fields (0-1)

        If IsIPAddress(CStr(X(0))) = False Then Exit Function ' Left part must be IP Address format

        If Trim(X(1)) = "" Then Exit Function ' no ""

        If CLng(X(1)) < 1 Then Exit Function ' Valid range = 31-1 (no 0.0.0.0 or 255.255.255.255)
        If CLng(X(1)) > 31 Then Exit Function

        Return True

    End Function


    ' --------------------------------------------------------------------------------
    ' IPValidateCIDR = Validate if a given IP Adress is allowed within a CIDR mask
    ' --------------------------------------------------------------------------------
    Public Function IPValidateCIDR(ByVal CIDRMask As String, ByVal IPAddress As String) As Boolean

        IPValidateCIDR = False

        Dim n As Integer
        Dim T() As String
        Dim CIP() As String
        Dim z As String
        Dim BaseIP() As String
        Dim Mask As String

        ' Test the obvious first
        If IsCIDRMask(CIDRMask) = False Then Exit Function ' Make sure CIDRMask is a CIDR Mask
        If IsIPAddress(IPAddress) = False Then Exit Function 'Make sure IPAddress is an IP Address

        T = Split(CIDRMask, "/")
        BaseIP = Split(T(0), ".") ' Split into IP address
        Mask = T(1)

        ' Set up Max IP
        Dim MaxIP(3) As Long

        For n = 0 To 3
            MaxIP(n) = 255
        Next n

        Mask = Mask + 1 ' Bit 128 in Left Octet

        For n = 0 To 3 ' Build up CIDR Mask

            If Mask > 1 Then
                MaxIP(n) = MaxIP(n) - 128
                Mask = Mask - 1
            End If

            If Mask > 1 Then
                MaxIP(n) = MaxIP(n) - 64
                Mask = Mask - 1
            End If

            If Mask > 1 Then
                MaxIP(n) = MaxIP(n) - 32
                Mask = Mask - 1
            End If

            If Mask > 1 Then
                MaxIP(n) = MaxIP(n) - 16
                Mask = Mask - 1
            End If

            If Mask > 1 Then
                MaxIP(n) = MaxIP(n) - 8
                Mask = Mask - 1
            End If

            If Mask > 1 Then
                MaxIP(n) = MaxIP(n) - 4
                Mask = Mask - 1
            End If

            If Mask > 1 Then
                MaxIP(n) = MaxIP(n) - 2
                Mask = Mask - 1
            End If

            If Mask > 1 Then
                MaxIP(n) = MaxIP(n) - 1
                Mask = Mask - 1
            End If

            If Mask < 1 Then Exit For

        Next n

        For n = 0 To 3 ' Calculate Max IP Address
            z = BaseIP(n) + MaxIP(n)
            If CInt(z) > 255 Then z = 255
            MaxIP(n) = z
        Next n

        CIP = Split(IPAddress, ".")

        Dim cmpBaseIp As Long
        Dim cmpMaxIp As Long
        Dim cmpCurrentIp As Long

        ' Build Current IP
        cmpCurrentIp = (CLng(CIP(0) * 16777216) + CLng(CIP(1) * 65536) + CLng(CIP(2) * 256) + CLng(CIP(3)))

        ' Build Base IP
        cmpBaseIp = (CLng(BaseIP(0) * 16777216) + CLng(BaseIP(1) * 65536) + CLng(BaseIP(2) * 256) + CLng(BaseIP(3)))

        ' Build Max IP
        cmpMaxIp = (CLng(MaxIP(0) * 16777216) + CLng(MaxIP(1) * 65536) + CLng(MaxIP(2) * 256) + CLng(MaxIP(3)))

        ' Compare if within range
        If cmpCurrentIp < cmpBaseIp Then Exit Function
        If cmpCurrentIp > cmpMaxIp Then Exit Function

        Return True ' If we got this far...

    End Function


    ' --------------------------------------------------------------------------------
    ' CIDRMaxAddress = Return the maximum (Top adress) for a CIDR mask)
    ' --------------------------------------------------------------------------------
    Public Function CIDRMaxAddress(ByVal CIDRMask As String) As String

        CIDRMaxAddress = "255.255.255.255" ' Default CIDRMaxAddress - if fail.

        Dim n As Integer
        Dim z As String
        Dim T() As String
        Dim BaseIP() As String
        Dim Mask As String

        If IsCIDRMask(CIDRMask) = False Then Exit Function ' Make sure CIDRMask is a CIDR mask

        T = Split(CIDRMask, "/")
        BaseIP = Split(T(0), ".")
        Mask = T(1)

        Dim MaxIP(3) As Long

        For n = 0 To 3 ' Get Max IP
            MaxIP(n) = 255
        Next n

        Mask = Mask + 1

        For n = 0 To 3

            If Mask > 1 Then
                MaxIP(n) = MaxIP(n) - 128
                Mask = Mask - 1
            End If

            If Mask > 1 Then
                MaxIP(n) = MaxIP(n) - 64
                Mask = Mask - 1
            End If

            If Mask > 1 Then
                MaxIP(n) = MaxIP(n) - 32
                Mask = Mask - 1
            End If

            If Mask > 1 Then
                MaxIP(n) = MaxIP(n) - 16
                Mask = Mask - 1
            End If

            If Mask > 1 Then
                MaxIP(n) = MaxIP(n) - 8
                Mask = Mask - 1
            End If

            If Mask > 1 Then
                MaxIP(n) = MaxIP(n) - 4
                Mask = Mask - 1
            End If

            If Mask > 1 Then
                MaxIP(n) = MaxIP(n) - 2
                Mask = Mask - 1
            End If

            If Mask > 1 Then
                MaxIP(n) = MaxIP(n) - 1
                Mask = Mask - 1
            End If

            If Mask < 1 Then Exit For

        Next n

        CIDRMaxAddress = ""

        For n = 0 To 3 ' reassemble into an IP Address
            z = BaseIP(n) + MaxIP(n)
            If CInt(z) > 255 Then z = 255
            CIDRMaxAddress = CIDRMaxAddress & z & "."
        Next n

        Return Left(CIDRMaxAddress, Len(CIDRMaxAddress) - 1)

    End Function


    ' --------------------------------------------------------------------------------
    ' InstrCnt = Calculate nr of matches within a string
    ' --------------------------------------------------------------------------------
    Private Function InstrCnt(ByVal Data As String, ByVal Match As String) As Long

        If Data = "" Or Match = "" Then Exit Function
        Dim N As Integer

        For N = 1 To (Data.Length - (Match.Length - 1))
            If Mid(Data, N, Match.Length) = Match Then
                InstrCnt = InstrCnt + 1
            End If
        Next N

        Return InstrCnt
    End Function

End Class