PostgreSQL type extensions for IP and MAC addresses.
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$Id: README,v 1.2 1998/02/14 17:58:03 scrappy Exp $

I needed to record IP and MAC level ethernet addresses in a data
base, and I really didn't want to store them as plain strings, with
no enforced error checking, so I put together the accompanying code
as my first experiment with adding a data type to PostgreSQL.  I
then thought that this might be useful to others, both directly and
as a very simple example of how to do this sort of thing, so here
it is, in the hope that it will be useful.

IP addresses are implemented as a 6 byte struct (this may be 1 byte
more than is useful, but I figured that since it has to be at least 5,
it might as well be an even number of bytes) that contains the four
byte address and a mask width.  The external representation of an IP
address looks like '158.37.96.15/32' (or just '158.37.96.15', which is
understood to mean the same thing).  This address happens to be part
of a subnet where I work; '158.37.96.0/24', which itself is a part of
the larger subnet allocated to our site, which is '158.37.96.0/21',
which again, if you go by the old book, is part of the class "B" net
called '158.37.0.0/16'.

Input and output functions are supplied, along with the "normal" <,
<=, =, >=, > and <> operators, which all do what you expect.  In
addition, there is a function to check whether a given address is a
member of a given subnet: ipaddr_in_net(addr, net), and functions to
return the netmask and the broadcast address of a given network:
ipaddr_mask(net) and ipaddr_bcast(net).

MAC level ethernet addresses are implemented as a 6 byte struct that
contains the address as unsigned chars.  Several input forms are
accepted; the following are all the same address: '08002b:010203',
'08002b-010203', '0800.2b01.0203', '08-00-2b-01-02-03' and
'08:00:2b:01:02:03'.  Upper and lower case is accepted for the digits
'a' through 'f'.  Output is always in the latter of the given forms.

As with IP addresses, input and output functions are supplied as well
as the "normal" operators, which do what you expect.  As an extra
feature, a function macaddr_manuf() is defined, which returns the name
of the manufacturer as a string.  This is currently held in a
hard-coded struct internal to the C module -- it might be smarter to
put this information into an actual data base table, and look up the
manufacturer there.  (Another TODO, for both new data types, is to
interface them to indices.  If anyone can explain this to me in a way
that is easier to understand than the current documentation, I would
be most grateful!)

I don't know what changes are needed to the Makefile for other systems
than the one I'm running (NetBSD 1.3), but anyway: to install on a BSD
system: fix the path names in the SQL files and the Makefile if you
need to, then make, make install, slurp the SQL files into psql or
whatever, and you're off.  Enjoy!

Bergen, Norway, 1998-01-31, Tom Ivar Helbekkmo (tih@Hamartun.Priv.NO).
