json.el speed-ups

json.el speed-ups

[T. V. Raman]

I've been using the following mods to json.el with good results,
am attaching diff output.

Change Summary:

Use forward-char in json-advance 
Use skip-syntax-forward to implement skipping whitespace

diff json.el  ~/sourceforge/emacs/lisp/json.el
126,127c126,130
<   (forward-char n))
< 
---
>   (unless n (setq n 1))
>   (let ((goal (+ (point) n)))
>     (goto-char goal)
>     (when (< (point) goal)
>       (signal 'end-of-file nil))))
142c145
< (defsubst json-skip-whitespace ()
---
> (defun json-skip-whitespace ()
144c147,148
<   (skip-syntax-forward " "))
---
>   (while (looking-at "[\t\r\n\f\b ]")
>     (goto-char (match-end 0))))
06:28:10 labrador g-client $ 

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Re: json.el speed-ups

[Stefan Monnier]

> I've been using the following mods to json.el with good results,
> am attaching diff output.

Please use unified diffs (or context diffs).

> <   (forward-char n))
> ---
>> (unless n (setq n 1))
>> (let ((goal (+ (point) n)))
>> (goto-char goal)
>> (when (< (point) goal)
>> (signal 'end-of-file nil))))

That looks OK, as long as the code doesn't catch `end-of-file' or
`end-of-buffer' explicitly elsewhere.

> 144c147,148
> <   (skip-syntax-forward " "))
> ---
>> (while (looking-at "[\t\r\n\f\b ]")
>> (goto-char (match-end 0))))

Using (skip-chars-forward "\t\r\n\f\b ") would make the diff more
obviously correct.  Have you checked that all those chars have the
"whitespace" syntax in the syntax-table?


        Stefan

Re: json.el speed-ups

[T. V. Raman]

Yes, the \b should be added as you suggest to be equivalent.



Eventually I think json.el should be sped up by creating a json
specific syntax table. This would help enormously in things like
parsing numbers etc; for now, json-read-number loops through each
char making up the number. As does json-read-keyword, and many
other functions.

>>>>> "Stefan" == Stefan Monnier <monnier@IRO.UMontreal.CA> writes:
    >> I've been using the following mods to json.el with good
    >> results, am attaching diff output.
    Stefan> 
    Stefan> Please use unified diffs (or context diffs).
    Stefan> 
    >> < (forward-char n))
    >> ---
    >>> (unless n (setq n 1)) (let ((goal (+ (point) n)))
    >>> (goto-char goal) (when (< (point) goal) (signal
    >>> 'end-of-file nil))))
    Stefan> 
    Stefan> That looks OK, as long as the code doesn't catch
    Stefan> `end-of-file' or `end-of-buffer' explicitly
    Stefan> elsewhere.
    Stefan> 
    >> 144c147,148 < (skip-syntax-forward " "))
    >> ---
    >>> (while (looking-at "[\t\r\n\f\b ]") (goto-char (match-end
    >>> 0))))
    Stefan> 
    Stefan> Using (skip-chars-forward "\t\r\n\f\b ") would make
    Stefan> the diff more obviously correct.  Have you checked
    Stefan> that all those chars have the "whitespace" syntax in
    Stefan> the syntax-table?
    Stefan> 
    Stefan> 
    Stefan>         Stefan

-- 
Best Regards,
--raman

      
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