Re: return varchar from C function

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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