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

From: Dmitry Gutov <[email-masked]>
Date: Sun, 22 Mar 2015 20:13:30 +0200

On 03/22/2015 07:31 PM, Eli Zaretskii wrote:

> I understand why you _send_ everything, but not why you need to
> _encode_ everything.  Why not encode only the new stuff?

That's the protocol. You're welcome to bring the question up with the 
author, but for now, as already described, there has been no need to 
complicate it, because Vim compiled with Python support can encode even 
a large buffer quickly enough.

>>> 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?

Actually, that wouldn't work anyway: aside from the special characters, 
JSON \\u1234 needs to encode any non-ASCII characters. Look at the 
"Fallback: UCS code point" comment.

> I meant something like
>
>    (replace-regexp-in-string "\n" "\\n" s1 t t)
>    (replace-regexp-in-string "\f" "\\f" s1 t t)
>
> etc.  After all, the list of characters to be encoded is not very
> long, is it?

One (replace-regexp-in-string "\n" "\\n" s1 t t) call already takes 
~100ms, which is more than the latest proposed json-encode-string 
implementation takes.

> But when you've encoded them once, you only need to encode the
> additions, no?  If you can do this incrementally, the amount of work
> for each keystroke will be much smaller, I think.

Sure, that's optimizable, with a sufficiently smart server (which ycmd 
currently isn't), and at the cost of some buffer state tracking and 
diffing logic.