Rust extensions: the next step

[Georges Racinet]

Hi all,

first, many thanks for the Stockholm sprint, it was my first interaction
with the Mercurial community, and it's been very welcoming to me.

I've been pursuing some experiments I started then to convert the Rust
bindings I've done in the patch series about ancestry iteration (now
landed) to a proper Python extension, using the cpython crate and Python
capsules. In short, it works.

Early benchmarking shows that it's a few percent slower than the direct
bindings through C code, which I think is acceptable compared to the
other benefits (clearer integration, easier to generalise, no C code at
all).

The end result is a unique shared library importable as
'mercurial.rustext', which is itself made of several submodules, ie, one
can do:

   from mercurial.rustext.ancestor import AncestorsIterator

It will take me some more time, though, to get that experiment into a
reviewable state (have to switch soon to other, unrelated, works) and
we're too close to the freeze anyway, but if someone wants to see it, I
can share it right away.

Also, I could summarize some of these thoughts on the Oxidation wiki
page. Greg, are you okay with that ?

Regards,

-- 
Georges Racinet
Anybox SAS, http://anybox.fr
Téléphone: +33 6 51 32 07 27
GPG: B59E 22AB B842 CAED 77F7 7A7F C34F A519 33AB 0A35, sur serveurs publics