Re: [PATCHES] Text <-> C string

On 26/03/2008, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> There are no textout/textin calls left, but I may have missed some
> places that were doing it the hard way with direct palloc/memcpy
> manipulations. It might be worth trolling all the VARDATA() references
> to see if any more are easily replaceable.
>

I think there are perhaps a dozen such sites, and I hope to submit a
cleanup patch that gets rid of these soon.

I did come across one site I'm not sure about in utils/adt/xml.c:291

/*
* We need a null-terminated string to pass to parse_xml_decl(). Rather
* than make a separate copy, make the temporary result one byte bigger
* than it needs to be.
*/
result = palloc(nbytes + 1 + VARHDRSZ);
SET_VARSIZE(result, nbytes + VARHDRSZ);
memcpy(VARDATA(result), str, nbytes);
str = VARDATA(result);
str[nbytes] = '\0';

The author seemed pretty sure he didn't want to make a separate copy
of the string, so I'm thinking there's not a whole lot I can do to
improve this site.

> I notice in particular that xfunc.sgml contains sample C functions to
> copy and concatenate text. While these aren't directly replaceable
> with the new functions, I wonder whether we ought to change the examples
> to make them less certain to break if we ever change text's
> representation.
>

Yes, these sample C functions are shown in tutorial/funcs.c and
funcs_new.c as well. I agree that the examples could do with
changing, but don't have any keen insight on what to change them to.