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  • From: "Thompson, William" <bill.d.thompson AT baml.com>
  • To: FreeTDS Development Group <freetds AT lists.ibiblio.org>
  • Subject: [freetds] Problem with src/tds/write.c
  • Date: Tue, 02 Feb 2016 14:20:10 +0000

Hi All,

I'm investigating an issue which is affecting some of my processes which use
the db-library bcp API.
I'm getting an error back from SQL Server: "The incoming tabular data stream
(TDS) protocol stream is incorrect. The stream ended unexpectedly."
After debugging it, It turns out we have an edge case involving some of the
functions in src/tds/write.c

The functions tds_put_int8, tds_put_int and tds_put_smallint do not check
that there is sufficient space in the packet buffer for their respective data
types.
As a consequence, data gets dropped if it happens that one of these data
types is being added to the packet buffer when the packet size is reached.

Having looked at the functions, I think I'm going to change these lines
(which occur in all the functions):

if (tds->out_pos >= tds->out_buf_max)
tds_write_packet(tds, 0x0);

to be:

if (tds->out_pos + sizeof(TDS_INT) >= tds->out_buf_max) /* or
TDS_INT8 or TDS_SMALLINT */
tds_write_packet(tds, 0x0);

If I do this there will be cases where the packet (although not a final
packet) is smaller than the maximum size,
but I REALLY don't want to go anywhere near those TDS_PUT_UA* macros. :)
Incidentally, what is the idea behind this TDS_ADDITIONAL_SPACE macro and all
those TDS_PUT macros? Life used to be much simpler (sigh), e.g.

<old code>
Int tds_put_smallint(TDSSOCKET * tds, TDS_SMALLINT si)
{
#if WORDS_BIGENDIAN
if (tds->emul_little_endian) {
tds_put_byte(tds, si & 0x000000FF);
tds_put_byte(tds, (si & 0x0000FF00) >> 8);
return 0;
}
#endif
return tds_put_n(tds, (const unsigned char *) &si, sizeof(TDS_SMALLINT));
}
<\old code>

Bill







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  • [freetds] Problem with src/tds/write.c, Thompson, William, 02/02/2016

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