Re: Efficient output for integer types

>>>>> "David" == David Fetter <david(at)fetter(dot)org> writes:

David> + return pg_ltostr_zeropad(str, (uint32)0 - (uint32)value, minwidth - 1);

No, this is just reintroducing the undefined behavior again. Once the
value has been converted to unsigned you can't cast it back to signed or
pass it to a function expecting a signed value, since it will overflow
in the INT_MIN case. (and in this example would probably output '-'
signs until it ran off the end of memory).

Here's how I would do it:

char *
pg_ltostr_zeropad(char *str, int32 value, int32 minwidth)
{
int32 len;
uint32 uvalue = value;

Assert(minwidth > 0);

if (value >= 0)
{
if (value < 100 && minwidth == 2) /* Short cut for common case */
{
memcpy(str, DIGIT_TABLE + value*2, 2);
return str + 2;
}
}
else
{
*str++ = '-';
minwidth -= 1;
uvalue = (uint32)0 - uvalue;
}

len = pg_ultoa_n(uvalue, str);
if (len >= minwidth)
return str + len;

memmove(str + minwidth - len, str, len);
memset(str, '0', minwidth - len);
return str + minwidth;
}

David> pg_ltostr(char *str, int32 value)
David> + int32 len = pg_ultoa_n(value, str);
David> + return str + len;

This seems to have lost its handling of negative numbers entirely (which
doesn't say much for the regression test coverage)

--
Andrew (irc:RhodiumToad)