FreeTDS Development Group

["James K. Lowden" <jklowden AT freetds.org>]

On Mon, 22 Aug 2011 10:53:02 -0400
Brian Bruns <brian AT bruns.com> wrote:

> If I'm understanding you correctly, you want a structure with an enum
> and essentially an array of void * to all the elements and then to use
> it you need to cast the void * back depending on the value of the
> attached datatype?  

Yes, it's an array of aliases to the members of the struct.  And,
because void*, they'd have to be cast.  

> struct {
>    uint16 flags;
>    uint16 unknown;
>    uint32 rowcount;
> } tds_done_inproc;
> 
> tds_member_t done_in_proc_reader[] = {
> {
> offsetof(tds_done_inproc, flags),
> tds_read_uint16
> },
> {
> offsetof(tds_done_inproc, unknown),
> tds_read_uint16
> },
> {
> offsetof(tds_done_inproc, rowcount),
> tds_read_uint32
> },
> };
> 
> The nice part is this is easily generated from a table of grammars,
> and you get a nice usable structure on the other end (as opposed to a
> nameless array of elements if I'm understanding you correctly), no
> casting from void * necessary.  Do the same in reverse for
> writing..things like XOR key password could be a function and you just
> pass the plain text and the function pointer handles the ugly bits.

Thank you.  Yes, that's the kind of thing I hope to get from the
formal grammar.  Not having ever actually used a parser-generator, I
had in mind a more brute-force method.  I agree the above is more
attractive.  

The key is to be able to iterate over the struct elements, for both
input and output.  

Regards, 

--jkl