FreeTDS Development Group

[ZIGLIO Frediano <Frediano.Ziglio AT vodafoneomnitel.it>]

Current cvs tds_atoi have some problem.
Converting "-pippo" just return 0.
atoi return 0 on error (some implementation even on overflow, other return
strange number) so unrecognid string return 0 (there is no way to understand
reason for 0). 

I rewritten an implementation who care this problem (first idea was using
strtol but check overflow with errno can give threadsafe problem on some
platform).

TDS_INT
tds_atoi(const char *buf,TDS_INT* res)
{
enum { blank = ' ' };
const char *p;
int     sign;
unsigned int num,n; /* we use unsigned here for best overflow check */

        p = buf;

        /* ignore leading spaces */
        while( *p == blank )
                ++p;

        /* check for sign */
        sign = 0;
        switch ( *p ) {
        case '-':
                sign = 1;
                /* fall thru */
        case '+':
                /* skip spaces between sign and number */
                while( *++p == blank );
                break;
        }

        /* a digit must be present */
        if (!*p)
                return TDS_FAIL;

        num = 0;
        for(;*p;++p) {
                /* check for trailing spaces */
                if (*p == blank) {
                        while( *++p == blank);
                        if (*p) return TDS_FAIL;
                        break;
                }

                /* must be a digit */
                if (!isdigit(*p))
                        return TDS_FAIL;

                /* add a digit to number and check for overflow */
                n = num * 10 + (*p-'0');
                if (n < num)
                        return TDS_FAIL;
                num = n;
        }

        /* check for overflow and convert unsigned to signed */
        if (sign) {
                if (num > 2147483648u)
                        return TDS_FAIL;
                num = -num;
        } else {
                if (num >= 2147483648u)
                        return TDS_FAIL;
        }

        *res = num;
        return TDS_SUCCEED;
}

Some question. Are you sure that library ignore blanks between sign and
digits (select convert(int, ' - 13 ') is not a good test, this is the
behaviour of sql server, not libraries)?
What about conversion to TDS_INT8? Perhaps this function should be changed
to return a TDS_INT8 instead a TDS_INT?

freddy77

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