Using vec() from XS

BrowserUk has asked for the wisdom of the Perl Monks concerning the following question:

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Re: Using vec() from XS by salva (Canon) on Sep 23, 2008 at 13:48 UTC
Some ways to do it: Write a wrapper function in Perl and call it. There should be a way to create a sequence of OPs (containing the required pp_vec) and run it. Copy & paste the source code for pp_vec and its helpers into your code changing the interface to suit your needs.	[reply]
Re^2: Using vec() from XS by BrowserUk (Patriarch) on Sep 23, 2008 at 15:18 UTC
There should be a way to create a sequence of OPs (containing the required pp_vec) and run it. Could you expand on this a little please? Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice. "Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."	[reply]
Re^3: Using vec() from XS by salva (Canon) on Sep 23, 2008 at 16:13 UTC
I don't know the details, but it should be something like this: synthesize an OP `o` for `vec` set up the runtime environment: push the arguments on the stack, save PL_op and make it point to the synthesized OP `o`, set any other interpreter globals, stacks, etc. call `CALLRUNOPS` retrieve the result from `o->op_targ` clean up For and example, look at `Perl_fold_constants` from op.c from the perl source. Try running it inside a C debugger with a simple fold-able expression as `print(1+2)`. The C function `Perl_op_dump` can be used to dump an OP tree once it has been properly build (otherwise it will crash).	[reply] [d/l] [select]
Re^4: Using vec() from XS by BrowserUk (Patriarch) on Sep 24, 2008 at 01:12 UTC
Re^5: Using vec() from XS by salva (Canon) on Sep 24, 2008 at 07:48 UTC
Re^3: Using vec() from XS by tsee (Curate) on Sep 24, 2008 at 07:38 UTC
Most likely, you already know that Perl is compiled to a tree of ops. pp_vec is one such op type -- corresponding to the Perl vec() function. Now, you could create op structures from XS and inject them into the running program. B::Generate does stuff like that. The one example I'm aware of where this actually works well is List::Util::shuffle. Instead of repeating what's happening there, check for yourself: List::Util XS code. I tried to do something similar in order to get caller() in XS, but that experiment mostly failed. I would not suggest going down that route. Cheers, Steffen	[reply]
Re: Using vec() from XS by ysth (Canon) on Sep 23, 2008 at 15:37 UTC
Just use sv_insert instead? -- Online Fortune Cookie Search Office Space merchandise	[reply]
Re^2: Using vec() from XS by BrowserUk (Patriarch) on Sep 23, 2008 at 15:56 UTC
I'm not sure how that helps? vec doesn't do any inserts, just update in-place or grow if the offest calculates beyond the current end of string. It isn't too hard to re-code the math and bit-twiddling, the main problem is getting the memory management right. As vec does everything I need (and more), it would have been nice to find a way to re-use that code without having to either c&p or callback to perl in order to do it. Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice. "Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."	[reply]
Re^3: Using vec() from XS by ysth (Canon) on Sep 23, 2008 at 16:17 UTC
sv_insert doesn't just insert, it's the guts behind substr and s///. But I see your point. Non-lvalue use of vec boils down to: `sv_setuv(TARG, do_vecget(src, offset, size));` [download] which should give you what you want. -- Online Fortune Cookie Search Office Space merchandise	[reply] [d/l]
Re^4: Using vec() from XS by salva (Canon) on Sep 23, 2008 at 16:33 UTC