Re: Regex from XS

[hv]

I haven't tried to do this, but I'd start by unravelling the code in pp_hot.c:pp_match(), and see if you can extract from that the infrastructure you need.

The guts is incorporated in the CALLREGEXEC() macro, which (via a pluggable hook, used by the re module) makes its way to regexec.c:Perl_regexec_flags() where the actual match happens - the regexp compile already happens before this - and setting things up correctly before that call is the critical bit.

It would certainly help if you can find prior art - if you have a greppable CPAN mirror handy, a search for CALLREGEXEC and/or regexec_flags should tell you if there is any to be found there.

Time permitting, I'd be happy to help debug any problems you run into, feel free to give me a shout.

Hugo

[creamygoodness]

Hugo,

Thanks for the kind offer. I understand a bit more about the Perl executable now, and I understand why, in the only previous info I could find on the subject (a Nick Ing-Simmons p5p post), it's stated that you can't do this without "faking an op".

There doesn't appear to be prior art for this. While I don't happen to have a greppable mirror, Google indexes .pm, .xs, .c, and .h files, and a Google search for those terms limited to search.cpan.org doesn't turn up anything useful.

I banged my head against pp_hot.c for a while, but there's just too many things I don't understand yet. It will be a happy day when I figure out what a "shrieking SV" is. :) An awful lot happens in pp_match, so the right route is presumably "fake an op" and call pp_match directly, rather than duplicate its innards.

However, manipulation of the op tree is beyond me right now. It doesn't look like this is as simple as calling a couple macros that aren't listed in perlapi, and while I'm very interested in continuing to study the subject, I haven't got time right now to dig this deep in one go. Thanks a bunch for helping me to frame the problem.