IPv6

[DigiRev]

I'm writing a class module to represent an IP address and it works fine for IPv4 addresses. But I'm wanting to support IPv6 addresses also. IPv6 addresses are 128 bits in size, and VB doesn't have a data type that can store a number that large.

Is it possible to use 2 64-bit values (high and low)? If so, how?

My IP class has a property to get the IP in decimal form (not dotted notation like "123.123.123.123") but just a plain integer.

Would I need to make another class to store the 128-bit value and use that class as a return type for the property? Example:

Public Property Get IPAddressDecimal() As Large128BitIntegerClass
'?
End Property

[David.Poundall]

Why not store the IPV6 number as an array of bytes? The problem goes away then.

[LaVolpe]

If an array of bytes or an array of 4 longs doesn't do the trick? You may consider using a function/sub vs a property.... rough example using longs, currency datatype may be a posibility too.

Public Function IPv6(Part1 As Long, Part2 As Long, Part3 As Long, Part4 As Long)

End Function

Another option... You can always have the property pass a pointer to a 128bit structure. The receiving end can use copymemory to transfer the data....

 ' class
Private Type IPv6Structure
    Part1 As Long
    Part2 As Long
    Part3 As Long
    Part4 As Long
End Type
Private m_Address As IPV6Structure

Public Property Get IPV6Address() As Long
    IPV6Address = VarPtr(m_Address)
End Type

[DigiRev]

Sorry for taking so long to reply...

I have the IP address stored in an array of bytes. It's working good for IPv4 addresses.

I want to store the IP numerically because it's faster to compare it to other IP addresses (like checking a ban list).

I think I'll do a struct instead like LaVolpe's example, though. But can a Currency variable hold an IPv6 address? I was assuming it couldn't (64-bit).

[LaVolpe]

Currency is 64 bits; so you'd need 2 currency variables.

Regarding comparing byte arrays. You can use this API on NT based systems. Note that since memory pointers are used in the parameters, it can point to a byte array, long array, and other possible storage structures like UDTs for example.

Private Declare Function CompMemory Lib "ntdll.dll" Alias "RtlCompareMemory" _
(ByRef Destination As Any, ByRef Source As Any, ByVal Length As Long) As Long

' example
1   If CompareMemory(myIP6(0), banIP(0), 16&)=16& Then ' equal data
2   If CompareMemory(myUDT, banUDT, 16&)=16& Then ' equal data
' assuming UDT is 4 longs, 2 currency, 8 Integers, or something else tallying 16 bytes