Re: [Bug-tar] Lzip support in GNU tar 1.23

[Antonio Diaz Diaz]

Tim Kientzle wrote:
> > A lzip file consists of a series of "members" (compressed data sets).
> > Each member has the following structure:
> >
> > +--+--+--+--+----+----+=============+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> > | ID string | VN | DS | Lzma stream | CRC32 |   Data size   |  Member size  |
> > +--+--+--+--+----+----+=============+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>
> Out of curiosity, can the LZMA stream data here be
> decompressed/compressed with liblzma from XZ utils?

I suppose it can. Certainly it can be decompressed/compressed with the 
lzma_alone tool from Pavlov's LZMA SDK if you change the header. Lzip's 
LZMA algorithm is identical to the original from Pavlov except lzip only 
uses default values for LZMA "properties".


> The biggest problem I have with LZMA right now is that there seem to
> be a lot of incompatible compression algorithms and file formats all
> using the same name.  It's very confusing.

AFAIK there are only two "LZMA algorithms", the original LZMA from 
Pavlov, used by lzma_alone, lzma-utils, lzip, easylzma and lzmatools, 
and LZMA2, used by xz-utils.

There seem to exist three LZMA file formats, the original lzma_alone 
from Pavlov, lzip and xz. Both lzip and xz claim to be the successor of 
lzma_alone, but given that xz supports several compression algorithms 
and filters, and after reading this from the lzma-utils README file:
  "The current LZMA_Alone file format will be replaced with a new .lzma
   format. The new format fixes various problems the LZMA_Alone format
   such as lack of magic bytes and integrity check."
I think lzip is the only possible successor to the "title" of "LZMA file 
format".


Regards,
Antonio.