Re: Reliable after-change-functions (via: Using incremental parsing in Emacs)

[Eli Zaretskii]

> From: Stephen Leake <address@hidden>
> Date: Fri, 03 Apr 2020 16:04:04 -0800
> 
> >> Since are are calling the parser from C (if it is linked into Emacs, or
> >> in a module), I still don't understand. Does C code have to cons to
> >> create a string?
> >
> > If course.  How else do you get a UTF-8 encoded string to pass to the
> > parser as a copy of buffer text?
> 
> malloc and memcpy.

How do you know how much memory to allocate?  And memcpy doesn't cut
it, because you forgot the encoding step.

You could, of course, take the low-level encoding code from coding.c
and make your own high-level functions that don't work with Lisp
objects.  But (a) why bother doing that? and (b) I think you will
quickly find out that this is a non-trivial job, since coding.c
"knows", to the lowest level, that it's dealing with Lisp objects
(buffers or strings), so you'd need pretty much to rewrite everything.

It's no accident that the Cygwin port uses the Lisp string machinery
even when it needs to convert strings from UTF-16 (see from_unicode),
even though it basically needs to convert C strings.

> I guess that's what you mean by "cons"; I was assuming you meant the
> actual elisp function.

No, I meant "consing" as in "make a Lisp string", then encode it
(which makes another Lisp string).