FreeTDS Development Group

[Frediano Ziglio <freddyz77 AT tin.it>]

Il ven, 2004-06-04 alle 23:16, Lowden, James K ha scritto:
> > 
> > > 
> > > typedef struct tds_column
> > > {
> > > ...
> > >   TDS_SMALLINT *column_nullbind;
> > > ...
> > > } TDSCOLUMN;
> > > 
> > > blk_bind(CS_BLKDESC * blkdesc, CS_INT item, CS_DATAFMT * 
> > > datafmt, CS_VOID
> > > * buffer, CS_INT * datalen, CS_SMALLINT * indicator)
> > > 
> > > dbnullbind(DBPROCESS * dbproc, int column, DBINT * indicator)
> > >                                            ^^^^^
> > 
> > Last Bill patch change the pointer from TDS_CHAR* to TDS_INT *.
> > 
> > >From include/tds.h
> > 
> ...
> > These fields are only used by client libraries (not libTDS) so every
> > library should use as they like. Perhaps an union like
> > 
> >     union {
> >             struct {
> >                     ...
> >             } db;
> >             struct {
> >                     ...
> >             } ct;
> >     } lib;
> > would be better ??
> 
> I don't think it's necessary.  AFAIK:
> 
> 1.  db-lib expects the caller to provide a DBINT buffer.  
> 2.  ct-lib expects the caller to provide a CS_SMALLINT buffer.  
> 
> I think what Bill did is basically right.  ct-lib and libtds use a 16-bit 
> buffer, provided by the caller.  The db-lib API requires the user to 
> provide a 32-bit buffer that libtds will treat as a 16-bit int.  
> 

libtds to not use these fields.

> The db-lib caller, however, will examine his 32-bit buffer as a 32-bit int. 
>  In buffer_transfer_bound_data(), I think we all we have to do is treat the 
> nullbind indicator thus:  
> 
>       if (curcol->column_nullbind) {
>               if (tds_get_null(resinfo->current_row, i)) {
>                       *(DBINT*)(curcol->column_nullbind) = -1;
>               } else {
>                       *(DBINT*)(curcol->column_nullbind) = 0;
>               }
>       }
> 
> (N.B.  There's missing logic here.  Per the docs, the nullbind indicator 
> should hold a positive value representing  "The full length of column's 
> data, in bytes, if column was bound to a program variable through dbbind, 
> the binding did not specify any data conversions, and the bound data was 
> truncated because the program variable was too small to hold data for 
> column."  Whew.  I wonder what exactly "did not specify any data 
> conversions" means?  srctype==desttype?)
> 
> Tell me if that looks good to you, and what happens on the ODBC side.  
> 

Using grep like


grep -rw
'\(column_bindtype\|column_bindfmt\|column_bindlen\|column_nullbind\|column_varaddr\|column_lenbind\|column_textpos\|column_text_sqlgetdatapos\)'
 * 

you will found that ODBC use only column_text_sqlgetdatapos (not used by 
dblib or ctlib)

freddy77