Calling a C++ subroutine from Perl

ibm1620 has asked for the wisdom of the Perl Monks concerning the following question:

Dear Monks,

Our company obtained a C++ source code license for Metaphone3 and I want to test it using Perl as a driver. I'm wondering what my options are. In the past, when I needed to call a complex C subroutine from Perl, I've written a standalone C++ program that accepted command-line parameters, called the subroutine, and wrote the output to STDOUT, and then "called" it using qx//. That's certainly still a possibility, but on the offchance that the forking and IPC would pose a performance hit (I'm going to test 100M's of strings), I wondered if XS was a practical possibility.

I have never written an XS module, and it looks daunting, but I thought there might be some XS stub code out there that I could easily tweak so that a Perl program could call one subroutine, passing in one string and getting two strings back; end of story.

Any thoughts on the subject? Other approaches?

(Metaphone3 is also available in Perl, but unfortunately that's a separate license.)

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Re: Calling a C++ subroutine from Perl by tobyink (Canon) on Mar 19, 2019 at 01:02 UTC
Inline::CPP should be pretty easy to get started with. Internally, I believe it translates stuff to XS (Inline::C does anyway), so once you have a working solution, you can grab that code and use that as the basis for an XS version. toby döt ink	[reply]
Re^2: Calling a C++ subroutine from Perl by syphilis (Archbishop) on Mar 19, 2019 at 11:44 UTC
Internally, I believe it translates stuff to XS Yep - it writes the XS file, compiles it and then executes the script. Cheers, Rob	[reply]
Re^3: Calling a C++ subroutine from Perl by ibm1620 (Hermit) on Mar 19, 2019 at 15:10 UTC
And caches the compilation so you don't have to recompile on every invocation of the script, as I read the doc. Pretty cool!	[reply]
Re: Calling a C++ subroutine from Perl by swl (Parson) on Mar 19, 2019 at 02:29 UTC
Have a look at FFI::Platypus. No XS is required, and the documentation is pretty comprehensive.	[reply]
Re^2: Calling a C++ subroutine from Perl by ibm1620 (Hermit) on Mar 19, 2019 at 15:19 UTC
Thank you. I will look into both of these suggestions. My admiration and gratitude for both Perl and the Perlmonks website are unbounded.	[reply]
Re: Calling a C++ subroutine from Perl by markong (Pilgrim) on Mar 19, 2019 at 16:59 UTC
And to complete the list, there is also the always mighty SWIG, with excellent C++ support and documentation!	[reply]
Re: Calling a C++ subroutine from Perl by bliako (Monsignor) on Mar 19, 2019 at 18:26 UTC
I will mention the possibility to embed a perl interpreter inside a C program. See perlembed. It has benefits if your main logic is in C/C++ and you just want a quick regex engine or accessing a database). For example: in perl embeded engine access database, retrieve data, filter data, use regex and other easy-peasy perl string mamipulations, then pass result back to C for metaphone. That gives you additional freedom depending where your main program logic is. There is a bigger prize though: parallelism. Theoretically you can have many perl interpreters in same C program. And you may find the C++ threads model, option of shared memory etc., is better suited for your needs than Perl's. I have not tried compiling a C++ program with perl embeded, only with C. The reason I am mentioning it is that it gives you one more way to experiment. I can give more details if you want to proceed. I must say that you may encounter a few hiccups in compiling and linking with perl's headers and library. But the major difficulty will be that the same compiler used in compiling your perl must also be used in compiling the perl-embedded C/C++ program. That means C++. Which theoretically should be OK but in practice it may complain about c++XYZ standard of the month forbidding this or that. bw, bliako	[reply]
Re: Calling a C++ subroutine from Perl by misc (Friar) on Mar 20, 2019 at 08:54 UTC
There's also this tutorial: perlxstut It's been quite a while ago, so I'm not so sure about my solution with XS. But I still remember, first this XS stuff really confused me. But after getting an idea about the mechanisms, with the help of (I believe) the linked tutorial, it showed up quite straightforward and useful. Just don't give up too quick, it pays out. Best wishes, Michael	[reply]
Re^2: Calling a C++ subroutine from Perl by ibm1620 (Hermit) on Mar 20, 2019 at 17:12 UTC
Thanks Michael - it would be a great tool to be able to use. I'll give it a look.	[reply]


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