Re: RPM C API (and other fun acronyms)

[Jeff Johnson <n3npq jbj gmail com>]

On Sep 28, 2006, at 5:49 PM, R. Tyler Ballance wrote:

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> On Sep 27, 2006, at 5:17 PM, Jeff Johnson wrote:
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> > On Sep 27, 2006, at 3:15 PM, R. Tyler Ballance wrote:
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> > > Sorry for prolonging this thread, but I wanted to tack on one  
> > > more question ;)
> > >
> > > Is there a sort of wildcard for the rpm db functions to where I  
> > > can essentially query similar to an `rpm -qa` and list all the  
> > > installed packages.
> > >
> > > Am I naive in thinking that "*" would work? :)
> >
> > Well, its a database, and so has records and record boundaries  
> > which need to be taken into account.
> >
> > Meanwhile, there's some logic to filter on tag values. Try the  
> > following
> > 	rpm -qa a\*
> > 	rpm -qa 'arch=noarch'
> > 	rpm -qa '!arch=i*'
> > etc, etc ("arch" is a tag name, substitute any tag name displayed  
> > by rpm --querytags, multiple items
> > are implicitly &&)
> >
> > Note that the search is sequential through all headers and so dirt  
> > slow. Adding --nodigest and --nosignature
> > will recover some of the speed back.
> >
> > Note also that there are "optional" tags as well, that may or may  
> > not exist, and so matching a value
> > that is not present is undefined and may not be to your expectations.
> >
> > The matching "works" within the above caveats.
> >
> > See <rpm/rpmdb.h> for the method to set from C after  
> > rpmdbInitIterator() call, look for MIRE as in
> > Match Iterator Regular Expression.
>
> I apologize for being dense, but after staring at the rpmdb.h  
> header, as well as the header documentation (via doxygen) and I'm  
> still not seeing a solution
>
> I'm assuming you're referring to
> int rpmdbSetIteratorRE (rpmdbMatchIterator mi, rpmTag tag,  
> rpmMireMode mode, const char *pattern);

Yep.

> So I'm wondering, do I just not use rpmdbInitIterator() (since I've  
> got to set the key string there) and will rpmdbSetIteratorRE()  
> create the proper iterator for dumping all the packages on the  
> machine?

The programming paradigm for irpmdb iteratotrs is
    1) initialize using rpmdbInitIterator
    2) (optional) qualify the iteration using, say, rpmdbSetIterorRE()
    3) iterate
    4) (optional) save headers of interest by referencing using  
headerLink().
    5) destroy the iterator.
> Again, I apologize if I'm coming across dense, I've been working on  
> code marshalling between C and C#, I'm just trying to find  
> something to dump the contents of the rpm db (i.e. the installed  
> packages) in such a manner that I can basically fill out an array  
> of Header structures.

Hint: Call headerSprintf() on headers that match your criteria to  
extract strings that can be passed into C#.

73 de Jeff