From: "Thomas Søndergaard" <thomass@...>
Date: 2002-07-10T01:07:04+09:00
Subject: Re: SV: SV: [ANN] Archive 0.2


> Basically, you need an Archive::Entry::Zip < Archive::Entry::Generic
> that, given a io stream passed to initialize, reads and parses an
> archive entry, and leaves the io cursor at the beginning of the next
> one.  If it can also output itself in Zip format again, you will be
> able to pass entries to Archive::Writer for writing.
>
> Each Entry::XYZ has `parts': a Zip entry will most likely have a
> `data' and a `header' part.  Each part, in turn, has a `raw' and a
> `parsed' attribute: `raw' points to the raw stuff as read from the
> stream, `parsed' to a structure modifiable from code.  You will
> probably create an Archive::Entry::Zip::Header object that takes care
> of receiving the Zip raw header, parse it, and initialize itself.  The
> data part will usually remain unparsed.

Isn't this unnecessarily low level access - I don't see a need for exposing
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"?

>
> One nice thing of this design is that a mbox Entry can, for example,
> implement a to_zip method. [...]

I don't see any reason that mbox Entry should now about zip archives (to_zip
method implies some knowledge). 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.


> If you have any questions, just ask.

I don't understand the interface completely. When you iterate over the items
in the archive, will you generate Entry objects that contain the full
uncompressed contents of the archive entry? That *might* be reasonable for
mbox files but for zip and tar archives it seems unreasonable, especially
for large archives. In rubyzip I have a ZipInputStream, which allows you to
iterate over the contents of a zip archive, without having to read more than
the header of the entries, that you do not care for. Like this:

require 'zip'

Zip::ZipInputStream.open("test/rubycode.zip") {
  |zipStream|
  while (entry = zipStream.getNextEntry)
    # entry contains the header information. If you want the
    # data read it from the zipStream as if it is an IO object
    puts "entry is #{entry.name}"
    puts "first 5 characters: '#{zipStream.read(5)}'"
  end
}

Don't you think this is better? The interface for iterating over the entries
in the archive is a little raw, but that is only because ZipInputStream is
not the preferred way of iterating over the contents of a zip file - instead
ZipFile will read the central directory, so you can do this:

Zip::ZipFile.foreach("test/rubycode.zip") {
  |entry|
  puts "entry is #{entry.name}"
  puts "first 5 characters: '#{entry.getInputStream { |is| is.read(5) }}'"
}

In either case, the data is only uncompressed and read on demand.

> p.s.: Sorry to ask, isn't there some way to have your mail client set
> correct References: or at least not modify the subject?

I have been using Outlook Web Access from home to read mail, and there are
no configuration options for the sending format. This one is send with
Outlook Express - I hope the format is more agreeable to you.

Thomas