[egenix-users] Null termination differences in drivers - comment in mxODBC.c

[M.-A. Lemburg]

Martin J. Evans wrote:
> Could anyone explain the origin of the following comment in mxODBC.c
> (specifically the reference to the Easysoft Oracle driver)?

We had to add that work-around to make mxODBC work with the
EasySoft Oracle driver 1.0.0.6. Things may be different with
more recent versions. The work-around adapts accordingly.

> How do you reproduce this?

Simple: query a BLOB of say 1MB data from the database.

> Thanks.
> 
>             if (null_terminated) {
>                 /* Remove null termination; various ODBC drivers have bugs
>                    in the way the handle null-termination:
> 
>                    * EasySoft ODBC for Oracle does not null-terminate character
>                      columns, even though it should
> 
>                    * MS SQL Server ODBC always null-terminates Unicode columns
>                      with two nulls, even when fetching the data as SQL_C_CHAR
>                      where it should only append one null-termination character
> 
>                    The ODBC standard is unclear about what to do, but
>                    using sizeof(SQLWCHAR) seems to work in most
>                    cases. We have to careful here, since some database
>                    drivers allow passing binary data back through
>                    character columns, so embedded nulls are well
>                    possible.
> 
>                    Thanks to Tommi Auvinen for helping to track down
>                    the MS SQL Server problem.
> 
>                 */
>                 char *data = (char *)newdata;
>                 int endofdata = offset + received - 1;
>                 if (data[endofdata] == '\0') {
>                     received--;
> #ifdef SQL_WCHAR
>                     if (data[endofdata - 1] == '\0') {
>                         if (var->ctype == SQL_C_WCHAR ||
>                             var->sqltype == SQL_WCHAR ||
>                             var->sqltype == SQL_WVARCHAR ||
>                             var->sqltype == SQL_WLONGVARCHAR)
>                             received -= sizeof(SQLWCHAR) - 1;
>                     }
> #endif
>                 }
>             }
> 
> 
> --
> Martin J. Evans
> Easysoft Ltd, UK
> Development
> 
> 
> _______________________________________________________________________
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-- 
Marc-Andre Lemburg
eGenix.com

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