From: Massimiliano Mirra <list@...>
Date: 2002-07-22T20:32:22+09:00
Subject: Re: SV: SV: [ANN] Archive 0.2

On Wed, Jul 10, 2002 at 07:10:28AM +0900, Thomas S�ndergaard wrote:
> > > the raw header data. Also, I don't see a reason for treating the header
> and
> > > data parts as if they are somewhat similar (ie. parts). It seems like
> > > "over-generalization"?
> It's not that I think it will cause problems other than it is unnecessarily
> complex for users of the API. 

Do you suggest adding a more abstracted interface to the archive
entry?  Sounds reasonable.

> > > With a general archive interface it is
> > > possible to do better, and write generic code for writing entries of one
> > > archive to another regardless of the archive type.
> >
> > I have troubles figuring this.  Could you please post a pseudo code
> > example?
> 
> I can try. This is what you wrote earlier:
> 
> quote = <<END_OF_QUOTE
> in = File.open("/var/mail/joe")
> out = File.open("/home/joe/mails.zip")
> 
> mbox = Archive::Reader::Mbox.new(in)
> zip = Archive::Writer::Zip.new(out)
> 
> mbox.scan do |entry|
> zip.add(entry)
> end
> 
> The `add' method from Archive::Writer will see that we're trying to
> write on a zip and that we have a Mbox::Entry#to_zip method, so will
> use that, and we'll have converted from Mbox to Zip on the fly.
> END_OF_QUOTE
> 
> I think this example is basically fine, except your comment about how
> zip.add(anEntry) will recognize that Mbox::Entry has a to_zip method. This
> should not be necessary because Entry is (or should be) an object that
> implements an interface that is common for all archive entries.

Sorry, I wasn't clear.  The pseudo code I was asking is the one for
the solution you are proposing.

> Ok. It seems to me that your design is heavily influenced by the structure
> of tar.gz files, where the archive is compressed, instead of the archive
> containing compressed entries

I'm not sure I follow you here.  The module I wrote is a .tar reader,
not a .tar.gz reader.

> (I think this is a short-coming in tar.gz
> files). Are there other archive types that are as expensive to scan? What
> other archives would benefit significantly from cached (to disk) maps of the
> archive? 

mbox does.  I know, I've been opening ruby-talk mboxes on a 486
lately. :-)

> Or from the iterative access, where you have to iterate over
> entries, even if you know the id or name of a particular entry that has your
> interest.

Every archive format that does not save a `table of contents', I
guess.


Massimiliano