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

I'd like to return a coderef (for an iterator) from an XS function. I haven't a clue how to go about it.

Is it even possible? Does anyone know of any existing examples?

The only notion that crosses my mind so far is using eval_pv() or eval_sv() to bring that iterator into existence.

Better thoughts?

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Re: (XS): returning an iterator.
by salva (Canon) on Sep 23, 2010 at 09:19 UTC
    I did something similar for Sort::Key, emulating a closure in XS. The trick I used was to return a new XSUB with the state attached in a magic table.

    The source code is here. The function returning the XSUB closure is _multikeysorter and there are two auxiliary functions _xclosure_make and _xclosure_defaults to set and retrieve the data attached to the XSUB.

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      You make it look simple enough. But... :) where does cv come from in the following line from XS_Sort__Key__multikeysort? 

          AV *defaults = _xclosure_defaults(aTHX_ cv);

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      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.
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        It gets introduced by the XS macro.
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Re: (XS): returning an iterator.
by ikegami (Patriarch) on Sep 23, 2010 at 03:19 UTC

    Instead of compiling code repeatedly, you could call a PP closure generator from XS.

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Re: (XS): returning an iterator.
by Anonymous Monk on Sep 23, 2010 at 02:45 UTC
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