On Tue, Mar 22, 2011 at 11:57 AM, Adrian Schreyer <ams214@xxxxxxxxx> wrote: > On Tue, Mar 22, 2011 at 16:07, Merlin Moncure <mmoncure@xxxxxxxxx> wrote: >> On Tue, Mar 22, 2011 at 8:22 AM, Adrian Schreyer <ams214@xxxxxxxxx> wrote: >>> Hi, >>> >>> I have a weird problem with my custom functions (written in C,C++) >>> that use bytea as input type (cstring works fine). The functions will >>> work as expected if they are the only function that uses the bytea >>> column in a query; as soon as there is a second function using the >>> same column, the C function will return one of the following: an empty >>> cstring, a substring of the bytea or the correct cstring. Based on >>> these symptoms I assume there is something fundamental that I do wrong >>> (or that is missing) with handling the bytea pointer. >>> >>> In one specific example, the bytea contains a binary file format that >>> the function converts into a string format. I convert the bytea to a >>> C++ string with string(VARDATA(b), VARSIZE(b)-VARHDRSZ). >>> >>> bytea *b = PG_GETARG_BYTEA_P(0); >>> char *ism; >>> >>> ism = function(b); >>> >>> PG_RETURN_CSTRING(ism); >> >> your problem is probably inside 'function' -- are you properly copying >> the data out of the bytea struct?. also, are you really sure you want >> to be returning cstring type, not text? >> >> merlin >> > > yes, the function in the C++ toolkit I use takes a std::string as > input. So far I have used string(VARDATA(oeb), VARSIZE(oeb)-VARHDRSZ) > to convert it. I want to change both input and output to text later on > once this is working. I suspect I will get similar problems with > pg_getarg_text_p() or any other struct. I think you are right, I am > not coping the data out of the struct correctly; all my functions that > use VARDATA() have these problems. What would be the proper way? Well, C++ string constructor is proper in the sense it makes copy of the source data. however, it's a little weird that you are passing bytea like this...bytea can contain null and c++ string initialization stops at any 0 byte. Maybe you should be encoding the data to text (say, to hex) first? merlin -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
