FreeTDS Development Group

["Thompson, William" <bill.d.thompson AT baml.com>]

Hi,

I've sorted why the code passes this if statement:

       if (!data_is_null && bindcol->column_bindlen >= 0) {

even when bindcol->column_bindlen = -1

it's because...

tds.h:  TDS_UINT column_bindlen;

I'm not mad after all...

I just need to decide what to do.
I think that if you can validly pass -1 to bcp_bind (in the varlen 
parameter), then column_bindlen shouldn't be unsigned...

Now I understand what's happened, I'll see waht's the best thing to do.
The code works at the moment, but is it more by luck than judgement?

Bill

-----Original Message-----
From: freetds-bounces AT lists.ibiblio.org 
[mailto:freetds-bounces AT lists.ibiblio.org] On Behalf Of Thompson, William
Sent: 23 May 2011 09:54
To: 'FreeTDS Development Group'
Subject: Re: [freetds] A couple of bugs in 0.91 with dblib bcp library


Hi Guys,

Thanks for your input on this. Of course you're right on the bcp_done() front.
I'll try and eliminate the extra call to bcp_done() from my application.
It was of course lazy programming in the first place, not mine I'll add.

Another small issue which kind of follows on from the _bcp_get_term_var() 
issue though:
I've fixed the problem, but I'm not sure if it's the *right* fix, and I'm 
puzzled by what's happening.
perhaps someone can shed some light...

So we have the following code (with some debug additions of mine) in 
_bcp_get_col_data():

        dataptr = (BYTE *) bindcol->column_varaddr;

        data_is_null = 0;
        collen = 0;

        /* If a prefix length specified, read the correct  amount of data. */

        if (bindcol->bcp_prefix_len > 0) {
            ...
        }
        printf("BILL after bcp_prefix_len (%d) column_bindlen = %d, collen = 
%d\n",
               bindcol->bcp_prefix_len, bindcol->column_bindlen, collen);

        /* if (Max) column length specified take that into consideration. */
        if (!data_is_null && bindcol->column_bindlen >= 0) {
                if (bindcol->column_bindlen == 0)
                        data_is_null = 1;
                else {
                        if (collen)
                                collen = (int) ((bindcol->column_bindlen < 
(TDS_UINT)collen) ? bindcol->column_bindlen : (TDS_UINT)collen);
                        else
                                collen = (int) bindcol->column_bindlen;
                }
        }
        printf("BILL 2 bcp_prefix_len (%d) column_bindlen = %d, collen = 
%d\n",
               bindcol->bcp_prefix_len, bindcol->column_bindlen, collen);

        desttype = tds_get_conversion_type(bindcol->column_type, 
bindcol->column_size);

        /* Fixed Length data - this overrides anything else specified */
        coltype = bindcol->column_bindtype == 0 ? desttype : 
bindcol->column_bindtype;
        if (is_fixed_type(coltype)) {
                collen = tds_get_size_by_type(coltype);
        }
        printf("BILL 3 bcp_prefix_len (%d) column_bindlen = %d, collen = 
%d\n",
                bindcol->bcp_prefix_len, bindcol->column_bindlen, collen);

        /* read the data, finally */
        if (bindcol->bcp_term_len > 0) {        /* terminated field */
                bytes_read = _bcp_get_term_var(dataptr, (BYTE 
*)bindcol->bcp_terminator, bindcol->bcp_term_len);
                printf("BILL bytes read = %d\n", bytes_read);

 /* CHANGED */  if (collen > 0)  /* FROM if (collen) */
                        collen = (bytes_read < collen) ? bytes_read : collen;
                else
                        collen = bytes_read;

                if (collen == 0)
                        data_is_null = 1;
        }

        if (data_is_null) {
                bindcol->bcp_column_data->datalen = 0;
                bindcol->bcp_column_data->is_null = 1;
        } else {
                if ((converted_data_size =
                     dbconvert(dbproc, coltype,
                               (BYTE *) dataptr, collen,
                               desttype, bindcol->bcp_column_data->data, 
bindcol->column_size)) == FAIL) {
                        printf("here %d\n", collen);
                        return TDS_FAIL;
                }

                bindcol->bcp_column_data->datalen = converted_data_size;
                bindcol->bcp_column_data->is_null = 0;
                assert(converted_data_size > 0);
        }

With the prior fix in place in _bcp_get_term_var, I get the following debug 
output, in a case where a character field was being processed, and it 
consisted entirely of '\0's...

BILL after bcp_prefix_len (0) column_bindlen = -1, collen = 0
BILL 2 bcp_prefix_len (0) column_bindlen = -1, collen = -1
BILL 3 bcp_prefix_len (0) column_bindlen = -1, collen = -1
BILL bytes read = 0

My original problem was that dbconvert() (at the end of this snippet) was 
getting called with collen = -1 and was failing.
I fixed that by changing the line marked "CHANGED" above. So far so good.
It now works, and the field gets rightly treated as NULL and dbconvert is not 
called.
I'm pretty sure this fix is correct, as the intent of that block of code is 
reasonably clear, namely:

"if I've been given a collen for the data, but the length of the data I've 
read is less than that collen, then I'll set collen to reflect the actual 
length of the data I'm going to process"

However, I'm now puzzled about my debug output "BILL 2"...
How on earth did collen get set to -1, when the only possible place it could 
get set is within the code following this if statment:

       if (!data_is_null && bindcol->column_bindlen >= 0) {

when just before this statement, column_bindlen is demonstrably -1 ???

Has anyone got any ideas ? have I missed something blindingly obvious ?

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in litigation and as required by law. 
The laws of the country of each sender/recipient may impact the handling of 
EC, and EC may be archived, supervised and produced in countries other than 
the country in which you are located. This message cannot be guaranteed to be 
secure or free of errors or viruses. 

References to "Sender" are references to any subsidiary of Bank of America 
Corporation. Securities and Insurance Products: * Are Not FDIC Insured * Are 
Not Bank Guaranteed * May Lose Value * Are Not a Bank Deposit * Are Not a 
Condition to Any Banking Service or Activity * Are Not Insured by Any Federal 
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