bug#20154: 25.0.50; json-encode-string is too slow for large strings

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sat, 21 Mar 2015 22:00:46 +0200
> From: Dmitry Gutov <dgutov@yandex.ru>
> CC: 20154@debbugs.gnu.org
> 
> On 03/21/2015 09:58 AM, Eli Zaretskii wrote:
> 
> > It depends on your requirements.  How fast would it need to run to
> > satisfy your needs?
> 
> In this case, the buffer contents are encoded to JSON at most once per 
> keypress. So 50ms or below should be fast enough, especially since most 
> files are smaller than that.

So each keypress you need to encode the whole buffer, including the
last keypress and all those before it?

I guess I don't really understand why each keypress should trigger
encoding of the whole buffer.

> > You don't really need regexp replacement functions with all its
> > features here, do you?  What you need is a way to skip characters that
> > are "okay", then replace the character that is "not okay" with its
> > encoded form, then repeat.
> 
> It doesn't seem like regexp searching is the slow part: save for the GC 
> pauses, looking for the non-matching regexp in the same string -
> 
> (replace-regexp-in-string "x" "z" s1 t t)
> 
> - only takes ~3ms.

Then a series of calls to replace-regexp-in-string, one each for every
one of the "special" characters, should get you close to your goal,
right?

> And likewise, after changing them to use `concat' instead of `format', 
> both alternative json-encode-string implementations that I have "encode" 
> a numbers-only (without newlines) string of the same length in a few 
> milliseconds. Again, save for the GC pauses, which can add 30-40ms.

So does this mean you have your solution?