Re: Efficient output for integer types

On Sat, Sep 21, 2019 at 03:36:21AM +0100, Andrew Gierth wrote:
> >>>>> "David" == David Fetter <david(at)fetter(dot)org> writes:
>
> David> + /* Compute the result string. */
> David> + if (value >= 100000000)
> David> + {
> David> + const uint32 value2 = value % 100000000;
> David> +
> David> + const uint32 c = value2 % 10000;
> David> + const uint32 d = value2 / 10000;
> David> + const uint32 c0 = (c % 100) << 1;
> David> + const uint32 c1 = (c / 100) << 1;
> David> + const uint32 d0 = (d % 100) << 1;
> David> + const uint32 d1 = (d / 100) << 1;
> David> +
> David> + char *pos = a + olength - i;
> David> +
> David> + value /= 100000000;
> David> +
> David> + memcpy(pos - 2, DIGIT_TABLE + c0, 2);
> David> + memcpy(pos - 4, DIGIT_TABLE + c1, 2);
> David> + memcpy(pos - 6, DIGIT_TABLE + d0, 2);
> David> + memcpy(pos - 8, DIGIT_TABLE + d1, 2);
> David> + i += 8;
> David> + }
>
> For the 32-bit case, there's no point in doing an 8-digit divide
> specially, it doesn't save any time. It's sufficient to just change
>
> David> + if (value >= 10000)
>
> to while(value >= 10000)

Done.

> in order to process 4 digits at a time.
>
> David> + for(int i = 0; i < minwidth - len; i++)
> David> + {
> David> + memcpy(str + i, DIGIT_TABLE, 1);
> David> + }
>
> Should be:
> memset(str, '0', minwidth-len);

Done.

Best,
David.
--
David Fetter <david(at)fetter(dot)org> http://fetter.org/
Phone: +1 415 235 3778

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