bug#34873: 27.0.50; Creating unibyte string in emacs modules

[Eli Zaretskii]

> From: Evgeny Zajcev <lg.zevlg@gmail.com>
> Date: Fri, 15 Mar 2019 23:52:17 +0300
> 
> There is no possibility to create unibyte strings from emacs modules in order 
> to create some binary data
> representation
> 
> The only solution for now is to call `make_string` method and then apply 
> `encode-coding-string' with utf-8
> encoding to the result.  But on large data this became very slow
> 
> I used this patch to bypass the conversion steps and it works pretty nice
> 
> Ideally I would like to use user-ptr objects as `:data' in image 
> specification, but solution with `make_data'
> module method will be suitable enough

Please explain why you need to create a unibyte string for that.  I
guess what's missing is more details regarding what you are trying to
do (the single sentence above about :data wasn't enough for me), and
how is your module involved in that, in particular why do you need a
module to display an image in Emacs.