FFI and capturing external program input in Squeak/Pharo

I'm working on making a clean interface layer on top of FFI (and  
possibly Alien and NativeBoost).

It will look something like:

        FFIParse createFFI: #System category: 'My-Category' library: 'System'.
        System parseSystemHeader: 'sys/resource.h'.
        rusage := System struct: #rusage.
        System getrusage: 0 with: rusage.
        Transcript show: 'Used ';
                         show: rusage ru_utime tv_sec;
                         show: '.';
                         show: rusage ru_utime tv_usec;
                         show: ' seconds of user CPU time';
                         cr.
        System parseSystemHeaer: 'unistd.h';
                sleep: 5.
        pid := System getpid

I have a very compact, almost compete C header parser but I need to be  
able to get the output from
        popen("echo \"#include <unistd.h>\"|gcc -E -","r")
or equivalent.  The popen is easy enough to get at through FFI, but is  
there a way to connect either the FILE* or the file descriptor up to  
some ReadStream.  In the worst case, I could probably use FFI to call  
fread(3) but is there a better way?

I'd also appreciate any simple examples of using FFI, especially with  
ExternalStructure subclasses.

Finally is there a way to get external variables such as 'extern int  
errno;' ?

Thanks in advance!

../Dave

I'm working on making a clean interface layer on top of FFI (and  
possibly Alien and NativeBoost).

It will look something like:

        FFIParse createFFI: #System category: 'My-Category' library: 'System'.
        System parseSystemHeader: 'sys/resource.h'.
        rusage := System struct: #rusage.
        System getrusage: 0 with: rusage.
        Transcript show: 'Used ';
                         show: rusage ru_utime tv_sec;
                         show: '.';
                         show: rusage ru_utime tv_usec;
                         show: ' seconds of user CPU time';
                         cr.
        System parseSystemHeaer: 'unistd.h';
                sleep: 5.
        pid := System getpid

I have a very compact, almost compete C header parser but I need to be  
able to get the output from
        popen("echo \"#include <unistd.h>\"|gcc -E -","r")
or equivalent.  The popen is easy enough to get at through FFI, but is  
there a way to connect either the FILE* or the file descriptor up to  
some ReadStream.  In the worst case, I could probably use FFI to call  
fread(3) but is there a better way?

I'd also appreciate any simple examples of using FFI, especially with  
ExternalStructure subclasses.

Finally is there a way to get external variables such as 'extern int  
errno;' ?

Thanks in advance!

../Dave

--
Mariano
http://marianopeck.wordpress.com

Hi! It's nice to hear this. As Mariano said, I started to work in something like this some months ago, but I couldn't make something useful yet because I don't have much free time. I can give you a hand if you need. I don't know about OS Process, but I have some experience with FFI, so I'll look for some examples. I also have some questions,

Hi Javier,

On 2011-Jun-20, at 18:51 , Javier Pimás wrote:

> Hi! It's nice to hear this. As Mariano said, I started to work in  
> something like this some months ago, but I couldn't make something  
> useful yet because I don't have much free time. I can give you a  
> hand if you need. I don't know about OS Process, but I have some  
> experience with FFI, so I'll look for some examples.

That would be great.  FFI, Alien, and NativeBoost evidence an itch...  
but actual uses that depend on the code seem to be harder to find.  I  
get the impression that many potential users have devolved to writing  
their own purpose-built plugins.

> I also have some questions,
>
> - how did you implement the parser, by hand or with a framework?

By hand.  It doesn't handle all of C, but that part you will find in  
include files.

> - did you implement a preprocessor or used the output of something  
> like CPP?

I'm using CPP at the moment.  The only serious downside that I see is  
that lots of C headers pre-date the introduction of enums into C, so  
constants are often #defined rather than being part of an enum.  So I  
may end up adding a pre-processor to recover these constants.

> - what about the output of the parser, do you create an AST?

No, I directly build the data structures I need to generate the FFI  
interfaces.

> On Fri, Jun 17, 2011 at 1:34 PM, Dave Mason <[hidden email]>  
> wrote:
> I'm working on making a clean interface layer on top of FFI (and  
> possibly Alien and NativeBoost).