Re: Maybe optimize adapt function in punycode.c (libind & libidn2)

[Simon Josefsson]

Igor V Belousov <address@hidden> writes:

> Hi,
> I'm modify code in punycode.c for faster run.

Hi.  Thanks for looking at the code.  Can you explain a bit more about:

1) How much faster is the code, in what kind of benchmark?

2) How the change is guaranteed to not change semantics?  Where do the
magic values 455 and 35 come from?

/Simon

> --- punycode_old.c      2013-10-29 11:13:31.000000000 +0400
> +++ punycode.c  2013-10-29 11:13:43.000000000 +0400
> @@ -146,12 +146,12 @@
>    /* delta >> 1 is a faster way of doing delta / 2 */
>    delta += delta / numpoints;
>
> -  for (k = 0; delta > ((base - tmin) * tmax) / 2; k += base)
> +  for (k = 0; delta > 455; k += base) //faster way
>      {
> -      delta /= base - tmin;
> +      delta /= 35;//faster way
>      }
>
> -  return k + (base - tmin + 1) * delta / (delta + skew);
> +  return k + base  * delta / (delta + skew);// base - tmin + 1 = base - 1 + 1
>  }
>
>  /*** Main encode function ***/
>
> Sorry bad English.
> Igor V Belousov.
>
>
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