FreeTDS Development Group

["Lowden, James K" <LowdenJK AT bernstein.com>]

> From: Frediano Ziglio [mailto:freddyz77 AT tin.it]
> Sent: January 26, 2004 3:49 PM
> 
> >From read_and_convert
> 
> suppress->einval = *wire_size > 0; /* EINVAL matters only on the last
> chunk. */
> if (-1 == tds_iconv(tds, iconv_info, to_client, &bufp, 
> &bufleft, outbuf,
> outbytesleft)) {
>       tdsdump_log(TDS_DBG_NETWORK, "%L Error: 
> read_and_convert: tds_iconv
> returned errno %d\n", errno);
>       if (errno != EILSEQ) {
>               tdsdump_log(TDS_DBG_NETWORK, "%L Error: 
> read_and_convert: "
>                                            "Gave up 
> converting %d bytes due to error %d.\n", bufleft,
> errno);
...
> note errno != EILSEQ

Noted.  I think it's a mistake, too.  We should test for EINVAL, because 
we're looking for an incomplete (not illegal) sequence.  That's why 
tds_put_string()'s test is different.  

I looked at read_and_convert() when I patched tds_put_string() (as you might 
be able to tell).  I didn't change it, because I was trying to fix just that 
one bug.  

> Another problem is wire state. If we start sending a string (in this
> case a query) and we stop in the middle what should we do?

I think it's OK, more or less.  tds_put_string() only stuffs text into a 
packet; it doesn't set up the packet or flush it.  If it writes less text 
than it was asked to, the text arriving at the server will be shorter than 
was intended.  The state will be fine, although it would be better not to 
send the string at all.  

More worrisome:  Suppose tds_put_string() gets a really big input, say 10,000 
bytes, that overlaps several packets.  Suppose the first packet is sent OK 
(last packet indicator 0x00), and we hit an EILSEQ partway through Packet 2.  
What now?  How to tell the server to ignore Packet 1?  

I don't know of any way to retract packets after they've been sent.  

--jkl
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