xz
==============================================================
This package provides a data compression library and utilities
supporting the .xz and .lzma file formats, which use the LZMA
compression algorithm.  LZMA provides high compression ratios
and very fast decompression, with minimal memory requirements
for decompression. XZ Utils is the latest generation of this
software, supplanting the older LZMA Utils.

The cygwin xz package replaces and obsoletes the cygwin lzma package.

LZMA Utils (and its own antecedent, the LZMA SDK) provided
the 'lzma' tool, which supported the 'LZMA-Alone' file
format usually indicated by the extension '.lzma'.  Internally,
this file format used what is now called the LZMA1 compression
algorithm.

XZ Utils provides the xz tool, which supports the new .xz
file format usually indicated by the extension '.xz'. Internally,
it uses a variation of the original LZMA compression algorithm,
called LZMA2.  However, the new xz tool also seamlessly supports
the older .lzma files and LZMA1 compression.

==============================================================
Runtime requirements
  cygwin-1.7.0-60
  libintl8-0.17-11
  libiconv2-1.13-10

Build requirements
  cygport-0.9.9
  binutils-2.19.51-1
  gcc-core-3.4.4-999
  bash-3.2.49-23
  make-3.81-2
  autoconf2.5
  automake1.11
  libtool
  gettext-0.17-11
  gettext-devel-0.17-11
  cvs-1.12.13-10 (for autopoint)
  libiconv-1.13-10

Canonical homepage:
  http://tukaani.org/xz/

Canonical download:
  http://tukaani.org/xz/download

License:
  liblzma:               public domain
  xz, xzdec, lzmadec:    public domain (LGPLv2.1+ under certain circumstances)
  lzdiff, other scripts: GPLv2+
  build system:          varies: public domain, GPLv2+, GPLv3+

Language:
  C, shell

==============================================================

Build instructions:
  unpack xz-VER-REL-src.tar.bz2
    if you use setup to install this src package, it will be unpacked
    under /usr/src automatically
  cd /usr/src
  cygport xz-VER-REL.cygport all

This will create:
  /usr/src/xz-VER-REL.tar.bz2
  /usr/src/liblzma-devel-VER-REL.tar.bz2
  /usr/src/liblzma1-VER-REL.tar.bz2
  /usr/src/xz-VER-REL-src.tar.bz2

==============================================================

Files included in the packages:

Files in liblzma1:          /usr/bin/cyglzma-1.dll
Files in liblzma-devel:     see 'cygcheck -l liblzma-devel' output 
Files in xz:                see 'cygcheck -l xz' output


History:
==============================================================

1. LZMA SDK
First there was the LZMA SDK. Upstream, it shipped no libraries;
only a few executables such as 'lzma'. The source code was
provided for public use (under a variety of licenses), but it
was expected that developers would incorporate the source code
directly into their own projects.  This is not The Unix Way.

The LZMA SDK was tightly coupled with the 7zip compression
program, and both were developed on and solely for the Windows 
platform.  7zip -- but not the LZMA SDK -- was ported to
Unix under the auspices of the p7zip ("Portable 7zip") project.
(As an aside, p7zip was then ported to cygwin...to come full
circle). However, it should be clear that the file format used
by 7zip (and p7zip) was completely different from the one
supported by the LZMA SDK's 'lzma' tool.  The latter used what
was called the 'LZMA-Alone' format, which consisted of 13 bytes
of header information followed by a raw lzma-compressed byte-
stream.  7zip, on the other hand, used a much more complicated
file format capable of hosting multiple files, spanned archives,
and other features. The only similarity is that the core data 
compression algorithm used by both is LZMA.

2. LZMA Utils
Eventually, a unix port of the LZMA SDK appeared, in the form of
the LZMA Utils distribution, which reorganized the original
source code, and provided the decompression code in library form
(liblzmadec). It also provided a version of the 'lzma' program,
but with a completely different command-line interface. The
LZMA Utils version consciously mimicked the command-line options
of the familiar gzip and bzip2 tools, while the original LZMA
SDK version was...different. Very different. This is because the
LZMA SDK's tool was originally intended just as a test and
development utility, to help refine the algorithm. So, it has a
number of 'compression guru' options that no sane user cares to
use, and very few of the 'normal user' options that they would.

   LZMA Utils: (Lasse Collin)
      lzma -d foo.tar.lzma
         uncompress to (implied) foo.tar, and remove
         original compressed file.
      lzma foo.tar
         compress to (implied) foo.tar.lzma, and remove
         original uncompressed file.
      Supports familiar "tuning" options like -0 .. -9
      Sends output data to stdout using -c
      Could be invoked under alternate names (symlinks) 
      for different behavior:
          unlzma == lzma -d  (uncompress)
          lzcat  == lzma -dc (uncompress to stdout)

   LZMA SDK: (Igor Pavlov)
      lzma d foo.tar.lzma foo.tar
      lzma e foo.tar      foo.tar.lzma   
         mode d/e is the required first non-option argument
         both input and output files must be specified
      stdout? what's that?

Finally, LZMA Utils also shipped a number of helpful
scripts similar to the familiar ones from gzip and bzip2:
  lzdiff/lzcmp, lzgrep/lzegrep/lzfgrep, lzless/lzmore

So, the LZMA SDK version was hardly suitable for replacing
or augmenting the existing bzip2 and gzip compression programs
on unix systems, expecially as the most common use was in
conjuction with tar.  But tar expects compression programs
to satisfy a common command-line argument format, and to be
able to manipulate data on standard streams. Most linux
distributions have standardized on LZMA Utils.

The lzma tool from both LZMA SDK and LZMA Utils each 
support the LZMA-Alone (.lzma) file format, as does the
liblzmadec library from LZMA Utils.

However, the .lzma file format (e.g. LZMA-Alone) is not
sufficient for modern needs, as it (1) had no 'signature
bytes' so compressed files were difficult to automatically
detect and verify, (2) it had no provision for internal
integrity checks, and (3) it could not support multi-file
archives.

3. XZ Utils
Approaching final non-beta release is the newest member of
this family, the XZ Utils. Addressing the shortcomings of the
LZMA-Alone file format, the xz file format and the (slightly
modified) LZMA2 compression algorithm were jointly developed
by Lasse Collin (LZMA Utils) and Igor Pavlov (LZMA SDK). The
xz tool has all of the benefits of the LZMA Utils' version of
the lzma tool, and ships with all of the same helpful scripts.
In addition, it can be invoked as either 'xz' (or xzcat, unxz)
or 'lzma' (or lzcat, unlzma) so you don't even need to retrain
your fingers.

You probably should, though, because .lzma files are already
being replaced by .xz files on by many software distribution
sites, including GNU ones.

Finally, the XZ Utils also provides the liblzma decompression
AND compression library, which supports both LZMA-Alone (that
is, the old .lzma) format, and the new .xz format.

The new .xz file format has an easily identifiable initial
signature for automated format detection and verification. It
supports integrity checks of several types including crypto-
graphic hashes. Finally, the format also supports multiple
compressed streams within the same file (that is, multi-file
archives).  However, the xz tool does NOT, at present, support
multi-file archives; only archives with a single compressed
stream.

As an aside, eventually the 7zip (and pz7ip) utilities will
support a "new" .7z format -- which will be simply a compatible
variant of the .xz file format, but with custom filters (codecs)
specified in the (highly extensible) header defined by the .xz
standard. This was the primary reason for the new .xz format
to support multi-file archives; because the xz tool has no
present need for them, and doesn't even support them (although
the liblzma library does).

Single File Compression
==============================================================
Although the xz file format supports multiple streams, the
xz tool itself is concerned only with single files that have
been compressed as a single complete stream using LZMA compression.
This is similar to the behavior of the older lzma tool and its
LZMA-Alone file format, or the archetypal gzip and bzip2
compression programs.

Just as with bzip2 and gzip (and the old lzma tool), to create
multi-file archives you should use tar and THEN compress with
xz.exe.  For an integrated compressed archive file format that
uses LZMA compression, see p7zip and the 7zip programs, and
their associated .7z file format.

==============================================================

Port Notes:

----------  xz-4.999.9beta-10 -- 2009 Aug 30 -----------
* Update to latest upstream release
* Use (new) upstream xz.1 in preference to cygwin-custom
  attempt at a man page.
* Upstream:
  - Lots of documentation updates
  - Fixes data corruption error
  - C++ compatiblity fixes
  - New lzmainfo utility
  - Fixes to helper scripts (xzdiff, xzless, etc)
  - Other miscellaneous bug fixes and build improvements
  - Distribute a changelog derived from git log.

----------  xz-4.999.8beta_20090714-10 -- 2009 Jul 18 -----------
* Update to latest git master 2009-07-14 21:10:36 +0300
  a35755c5de808df027675688855d1b621a4fb428
* Most cygwin/mingw patches have now been merged upstream.
  Remaining ones are:
  - Add support for automake-1.11 silent rules
  - use libtool-2.2.x macros instead of 1.5.x ones.

---------- xz-4.999.8betaCYG4-10 -- 2009 Jun 27 -----------
* Update to latest git master
* Includes additional patches currently pending upstream
  but the "pristine" source package already includes them.

---------- xz-4.999.8beta_20090605-10 -- 2009 Jun 19 -----------
* Update to latest git master (author says current top-of-tree
  is "much better" than 4.999beta8, but is not going to release
  a new beta anytime soon. Go figure.)
* However, there has been an ABI change so the DLL number needs
  to be bumped.
* Remove cygwin from requires: in hint files, as sourceware
  will take care of that.

---------- xz-4.999.8beta-10 -- 2009 Mar 14 -----------
* Fork for cygwin-1.7 development

---------- xz-4.999.8beta-1 -- 2009 Mar 14 -----------
* Initial cygwin port

==============================================================
Cygwin port maintained by: Chuck Wilson <cygwin@cygwin.com>


