Ascii null in varchars

We try to migrate some projects from commercial Ingres to postgres.

One problem we found:

varchars can hold any byte from \000 to \377. In Ingres we could
specify all these characters as a hex-string, e.g. X'4163006341',
meaning a string "Ac\000cA".

Construction of varchars in postgres do obviously not know of
any comparable method, this means, saying:

select char_length(varchar 'ab\000defghi');

will result in 2 and not in 9 as expected. I can somehow understand,
why it works this way, so I came to the thought of saying instead:

select char_length(translate(varchar 'abcdefghi','c','\000'));

which returns '9' as expected.

But this is really not nice...

The documentation does not tell anything about constructions of
varchars (or char / text) beyond this '||', the mentioned functions
do also not give any hint - does it mean, there is no such facility
(in 6.4.2)?

We would like to hear some comments,

Thank you anyway,

Thomas Mack
TU Braunschweig, Abt. Informationssysteme