bug#40407: [PATCH] slow ENCODE_FILE and DECODE_FILE

[Eli Zaretskii]

> From: Mattias Engdegård <mattiase@acm.org>
> Date: Sat, 4 Apr 2020 20:06:23 +0200
> Cc: 40407@debbugs.gnu.org
> 
> 4 apr. 2020 kl. 19.37 skrev Eli Zaretskii <eliz@gnu.org>:
> 
> > Btw, if we want this particular use case to be as fast as possible,
> > then Fcopy_sequence is not the best way, because it is not optimized
> > for the case of copying a single string.  We could do better by
> > calling make_uninit_multibyte/unibyte_string and memcpy directly.
> 
> Yes, if that would provide a benefit. The pattern should probably be 
> encapsulated in copy_string or similar, if it doesn't already exist.

I wouldn't make it a separate function for the benefit of just one
caller.  Every function call is a slowdown, albeit a small one.

> (Should it copy properties? Probably not.)

Definitely not.