Getting max. value size (libpq++)

Okay, maybe I'm just not finding it in the documentation, but is
there a way to find out the max size of a field? Specifically VARCHAR
fields. For instance if I have a table created with the SQL code:

CREATE TABLE temp_table
( name VARCHAR(30),
id VARCHAR(10),
address VARCHAR(60));

Now the program I'm writing will add whatever the user wants to
this table, of what ever size. I'm trying to avoid locking the size of
the HTML input fields. So is there anyway to get those numbers back from
Postgres? Right now they're hard-coded in, which really sucks. Thanks.

--Philippe Chaintreuil
peep(at)thefront(dot)com