Hello
cstring is clasic c (zero terminated) string and is used only in some
PostgreSQL functions. This type isn't compatible with text and you have to
explicit cast trick with textin function.
root=# select textin(('abc'::cstring));
textin
--------
abc
(1 row)
Standard is using VARLENA types like text, varchar, ... You can find info in
PostgreSQL FAQ. These types are similar Pascal string -> first four bytes
cary length and next bytes are data without spec. ending symbol.
http://www.varlena.com/GeneralBits/68.php
using text type in C function is simple:
Datum *const_fce(PG_FUNCTION_ARGS)
{
text *txt = palloc(5 + VARHDRSZ);
memcpy(VARDATA(txt), "pavel", 5);
VARATT_SIZE(txt) = 5 + VARHDRSZ;
PG_RETURN_TEXT_P(txt);
}
please look to source code my orafce contrib module (you can find it on
pgfoundry).
Regards
Pavel Stehule
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