Convert CIDR formatted string to its IPAddress Range representation

''' <summary>
''' Converts a CIDR formatted string to the IPAddress-range it represents. (Function handles IPv4 only).
''' </summary>
''' <param name="zCIDR">CIDR formatted string, example: "209.85.134.0/23"</param>
''' <returns>A List(Of IPAddress): (0)=StartIP, (1)=EndIP</returns>
''' <remarks>the machine's endianness is not considered by this function! Little Endian is assumed here.</remarks>
Private Function CIDR_to_IPRange(ByVal zCIDR As String) As List(Of IPAddress)

    '   zReturn will contain:  zReturn(0) = StartIP, zReturn(1) = EndIP
    Dim zReturn As New List(Of IPAddress)

    '   Split out the StartIP and /suffix from zCIDR = "255.255.255.255/32"
    '   zSAP(0) should then contain the IP prefix = "255.255.255.255"
    '   zSAP(1) will contain the suffix = "32"
    Dim zSAP As New List(Of String) _
            (zCIDR.Trim.Split("/".ToCharArray, 2, StringSplitOptions.RemoveEmptyEntries))


    '   Add the StartIP
    Try
        zReturn.Add(IPAddress.Parse(zSAP(0)))

    Catch ex As Exception
        '   No StartIP found, so return Nothing
        Return Nothing

    End Try


    '   Calculate and add the EndIP
    Try
        '   NOTE :: the wildcard bits calculation =  2^(32-zSuffix) - 1
        '   zPrefix must be in the 0-32 range (a suffix of 32 means the StartIP is the same as EndIP)
        Dim zSuffix As Long = Math.Min(32, Math.Max(0, CLng(zSAP(1))))
        zReturn.Add(New IPAddress( _
                        IP_to_Long(zReturn(0).GetAddressBytes, True) _
                        + IP_to_Long(New IPAddress(2 ^ (32 - zSuffix) - 1).GetAddressBytes, False)))

    Catch ex As Exception
        '   Either the /suffix wasn't given, or the IPAddress is out of range (maximum: 4294967295)
        '   I'm choosing to set the EndIP = StartIP if an error happens
        zReturn.Add(zReturn(0))

    End Try


    Return zReturn

End Function

''' <summary>
''' Converts an IPv4 IPAddress, which is just a 32bit Unsigned Integer, to a Long
''' </summary>
''' <param name="zAddressBytes">IPAddress in Byte array form.</param>
''' <param name="zReverse">This allows you to consider the order of the given Byte array.</param>
''' <returns>A Long representing an IPAddress</returns>
''' <remarks></remarks>
Public Function IP_to_Long(ByVal zAddressBytes() As Byte, _
                           Optional ByRef zReverse As Boolean = False) As Long

    If zReverse Then
        Return CLng( _
                CUInt(zAddressBytes(3)) << 24) _
                + (CUInt(zAddressBytes(2)) << 16) _
                + (CUInt(zAddressBytes(1)) << 8) _
                + (CUInt(zAddressBytes(0)))

    Else
        Return CLng( _
                CUInt(zAddressBytes(0)) << 24) _
                + (CUInt(zAddressBytes(1)) << 16) _
                + (CUInt(zAddressBytes(2)) << 8) _
                + (CUInt(zAddressBytes(3)))

    End If

End Function