From: Daniel Berger <Daniel.Berger@...>
Date: 2006-04-07T06:19:19+09:00
Subject: Re: Archive::Tar uncompress question

Dimitri Aivaliotis wrote:
> Hi Dan,
> 
> On 4/6/06, Berger, Daniel <Daniel.Berger@qwest.com> wrote:
>> It basically boils down to a case of unexpected usage.  The assumption
>> is that you're creating (or going to create) an archive when you use
>> Archive::Tar.new.
>>
> 
> I actually chose Archive::Tar over Archive::Tar::Minitar because I
> needed something quick-and-dirty that could handle all the kinds of
> archives in my original post.  My application only deals with the
> un-packing of these archives - the originals stay where they are, and
> my app doesn't create them.
> 
>> You are, of course, free to redefine uncompress_archive, but rather than
>> patching the lib itself, I recommend taking advantage of Ruby's open
>> classes:
>>
>> # Somewhere in your code:
> 
> <snip>
> 
> This is actually what I have done.  I just presented it in
> pseudo-patch form for conciseness, and perhaps to convince you that it
> really isn't an error, but could be handled differently. :)
> 
>> I suppose I could add class methods that would do the sort of thing
>> you're trying to do.  Or, you could add your own class method.
> 
> A la
> 
> module Archive
>   class Tar
>     attr_accessor :compressed_archive_name
>   end
> end
> 
> ?
> 
> That still involves redefinition.  I try to avoid that with
> non-standard-lib libraries.  You never know when the name is going to
> change. :)

I thought about that, too.  I don't see the harm, really.  If you want to 
uncompress an existing archive then it would just be a matter of assigning to 
that attribute first, then uncompressing.

What makes more sense and/or which would you prefer?

t = Tar::External.new
t.compressed_archive_name = 'somefile.tar.gz'
t.uncompress

# or

Tar::External.uncompress('somefile.tar.gz')

The advantage to the latter is that it's simpler.  The drawback is that it 
wouldn't return an object.

Come to think of it, I should probably manually define compressed_archive_name= 
like so in order to ensure other instance variables are set properly:

How about this patch:

# Assign a compressed archive name.  This autogenerates the archive_name
# based on the extension of the name provided, unless you provide the
# extension yourself.  If the extension is '.tgz', then the base of the
# name + '.tar' will be the new archive name.
#
# This should only be used if you have a pre-existing, compressed archive
# that you want to uncompress.
def compressed_archive_name=(name, ext=File.extname(name))
    if ext == ".tgz" || ext == '.TGZ'
       @archive_name = File.basename(name, ext) + '.tar'
    else
       @archive_name = File.basename(name, ext)
    end
    @compressed_archive_name = name
end

Thoughts?

Dan

PS - Perhaps we should continue this over on the Shards project page under 
"Open Discussion".  See http://www.rubyforge.org/projects/shards.