Re: Developing new syntaxes and ordering rules

[Hallvard B Furuseth <h.b.furuseth@usit.uio.no>]

John Borwick writes:
> How does one go about creating a new syntax?  Does it still require 
> changing to the openldap source code?

Yes, schema_*.c.  I don't know of any documentation, or even how
the indexing and filtering stuff works.

> I have the same question for ordering and substring.  Is it possible to 
> create an ordering or substring for a new syntax with openldap?  Is 
> there any documentation about how to implement these filters?

Check e.g. integerMatch() in schema_init.c, which also is used for
the integerOrderingMatch definition in mrule_defs[] further down.

> The idea is that it would be nice to store IP (v4) addresses using 
> octets, and allow filters like
> 
> (myIpHostNumber=1.2.3*)   ( as an example: just 1.2.3.* domains )

If you use the syntax 1.2.3.* and do not allow '*' next to a number,
you can use quite normal substring matching rules.  Unless you
want 001.2.3.* to match 1.2.3.4, but then I think you can add a
normalization step which removes unnecessary zeroes.

> (&(myIpHostNumber>1.2.99.0)(myIpHostNumber<1.2.99.100)
> 
> With the IDEAL being something like
> 
> (myIpHostNumber ~= 1.2.3.0/22 )

I think an approx matching rule must have the same assertion value
syntax as the equality matching rule, so you'd have to allow
(myIpHostNumber = 1.2.3.0/22) as well.  Though I suppose you could
define the equality rule to return Undefined for that match.

BTW, if you only need to allow '*' at the end of the substring match,
maybe you'd want to use (myIpHostNumber ~= 1.2.3*) instead, and
represent that and (myIpHostNumber ~= 1.2.3.0/24) the same way
in an approx index.

Another note: I would either call these IPv4 syntaxes and matching rules
or make them support both IPv4 and IPv6 addresses.  IPv6 will become
common Real Soon Now, you know:-)

-- 
Hallvard