Re: [gentoo-dev] Parsing emerge

[Chris White <chriswhite@gentoo.org>]

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2005-03-04 (金) の 17:29 +0900 に Chris White さんは書きました:
I've updated the script now, it has a better more functional layout than
before (A large page script :).

Re-cap of the install is here:

> 
> http://dev.gentoo.org/~chriswhite/emerge_parse.pl
> 
> In order to install this, you'll need to `g-cpan.pl Expect` in order to
> get the Expect module (which interestingly enough also installs the dep
> of IO::Tty).

the main update was the parsing of category, package, and versions from
ebuilds.  The code of interest comes from these lines of code:

sub package_nvsplit {
        $i=0;
        while($_[$i] !~ /^\d/) {
                $i++;
        }
        $package_end=$i-1;
        $pn=join("-",@_[0..$package_end]);
        $pv=@_[$i..$#package_array];
        return $pn, $pv;
}

So for those interested in parsing out package versions and what not,
this is basically how to go about it.  First, you splitup the category
and the package name+version (or $P).  So...

media-video/xine-lib-1.0 gets splitup into:
media-video (category) and xine-lib-1.0 ($P).  Now then, to get package
and version seperation, one simply splits up $P with the - seperator.
This gives us:

xine lib 1.0

Which, a simple loop checks to see if we've hit a section that starts
with a digit (the version number), and re-combines the values before it
with -'s, giving us:

$pv = 1.0
$pn = xine-lib

So there you have it, the basis on seperation of package category, name,
and version.  Hopefully this will help those who wish to hack around a
little get an idea of what's involved in the minute areas of portage.
Note that while the code is perl, the concept is very language
non-specific (I could do one in C.. but I'd rather save some of my
sanity ;).

Next stop will be getting USE flag descriptions in a more speedy manner
than simple grep-ing.  Please note that suggestions for
improvement/comments/etc. are welcome, and I hope this turns into a nice
informative developer's discussion.  

_big note_
I'd also like to thank Nick (carpaski) for his insight on the above
code :).
_big note_

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