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+
+LZMA Utils history
+------------------
+
+Tukaani distribution
+
+    In 2005, there was a small group working on Tukaani distribution, which
+    was a Slackware fork. One of the project goals was to fit the distro on
+    a single 700 MiB ISO-9660 image. Using LZMA instead of gzip helped a
+    lot. Roughly speaking, one could fit data that took 1000 MiB in gzipped
+    form into 700 MiB with LZMA. Naturally compression ratio varied across
+    packages, but this was what we got on average.
+
+    Slackware packages have traditionally had .tgz as the filename suffix,
+    which is an abbreviation of .tar.gz. A logical naming for LZMA
+    compressed packages was .tlz, being an abbreviation of .tar.lzma.
+
+    At the end of the year 2007, there's no distribution under the Tukaani
+    project anymore. Development of LZMA Utils still continues. Still,
+    there are .tlz packages around, because at least Vector Linux (a
+    Slackware based distribution) uses LZMA for its packages.
+
+    First versions of the modified pkgtools used the LZMA_Alone tool from
+    Igor Pavlov's LZMA SDK as is. It was fine, because users wouldn't need
+    to interact with LZMA_Alone directly. But people soon wanted to use
+    LZMA for other files too, and the interface of LZMA_Alone wasn't
+    comfortable for those used to gzip and bzip2.
+
+
+First steps of LZMA Utils
+
+    The first version of LZMA Utils (4.22.0) included a shell script called
+    lzmash. It was wrapper that had gzip-like command line interface. It
+    used the LZMA_Alone tool from LZMA SDK to do all the real work. zgrep,
+    zdiff, and related scripts from gzip were adapted work with LZMA and
+    were part of the first LZMA Utils release too.
+
+    LZMA Utils 4.22.0 included also lzmadec, which was a small (less than
+    10 KiB) decoder-only command line tool. It was written on top of the
+    decoder-only C code found from the LZMA SDK. lzmadec was convenient in
+    situations where LZMA_Alone (a few hundred KiB) would be too big.
+
+    lzmash and lzmadec were written by Lasse Collin.
+
+
+Second generation
+
+    The lzmash script was an ugly and not very secure hack. The last
+    version of LZMA Utils to use lzmash was 4.27.1.
+
+    LZMA Utils 4.32.0beta1 introduced a new lzma command line tool written
+    by Ville Koskinen. It was written in C++, and used the encoder and
+    decoder from C++ LZMA SDK with little modifications. This tool replaced
+    both the lzmash script and the LZMA_Alone command line tool in LZMA
+    Utils.
+
+    Introducing this new tool caused some temporary incompatibilities,
+    because LZMA_Alone executable was simply named lzma like the new
+    command line tool, but they had completely different command line
+    interface. The file format was still the same.
+
+    Lasse wrote liblzmadec, which was a small decoder-only library based on
+    the C code found from LZMA SDK. liblzmadec had API similar to zlib,
+    although there were some significant differences, which made it
+    non-trivial to use it in some applications designed for zlib and
+    libbzip2.
+
+    The lzmadec command line tool was converted to use liblzmadec.
+
+    Alexandre Sauvé helped converting build system to use GNU Autotools.
+    This made is easier to test for certain less portable features needed
+    by the new command line tool.
+
+    Since the new command line tool never got completely finished (for
+    example, it didn't support LZMA_OPT environment variable), the intent
+    was to not call 4.32.x stable. Similarly, liblzmadec wasn't polished,
+    but appeared to work well enough, so some people started using it too.
+
+    Because the development of the third generation of LZMA Utils was
+    delayed considerably (roughly two years), the 4.32.x branch had to be
+    kept maintained. It got some bug fixes now and then, and finally it was
+    decided to call it stable, although most of the missing features were
+    never added.
+
+
+File format problems
+
+    The file format used by LZMA_Alone was primitive. It was designed for
+    embedded systems in mind, and thus provided only minimal set of
+    features. The two biggest problems for non-embedded use were lack of
+    magic bytes and integrity check.
+
+    Igor and Lasse started developing a new file format with some help from
+    Ville Koskinen, Mark Adler and Mikko Pouru. Designing the new format
+    took quite a long time. It was mostly because Lasse was quite slow at
+    getting things done due to personal reasons.
+
+    Near the end of the year 2007 the new format was practically finished.
+    Compared to LZMA_Alone format and the .gz format used by gzip, the new
+    .lzma format is quite complex as a whole. This means that tools having
+    *full* support for the new format would be larger and more complex than
+    the tools supporting only the old LZMA_Alone format.
+
+    For the situations where the full support for the .lzma format wouldn't
+    be required (embedded systems, operating system kernels), the new
+    format has a well-defined subset, which is easy to support with small
+    amount of code. It wouldn't be as small as an implementation using the
+    LZMA_Alone format, but the difference shouldn't be significant.
+
+    The new .lzma format allows dividing the data in multiple independent
+    blocks, which can be compressed and uncompressed independenly. This
+    makes multi-threading possible with algorithms that aren't inherently
+    parallel (such as LZMA). There's also a central index of the sizes of
+    the blocks, which makes it possible to do limited random-access reading
+    with granularity of the block size.
+
+    The new .lzma format uses the same filename suffix that was used for
+    LZMA_Alone files. The advantage is that users using the new tools won't
+    notice the change to the new format. The disadvantage is that the old
+    tools won't work with the new files.
+
+
+Third generation
+
+    LZMA Utils 4.42.0alphas drop the rest of the C++ LZMA SDK. The LZMA and
+    other included filters (algorithm implementations) are still directly
+    based on LZMA SDK, but ported to C.
+
+    liblzma is now the core of LZMA Utils. It has zlib-like API, which
+    doesn't suffer from the problems of the API of liblzmadec. liblzma
+    supports not only LZMA, but several other filters, which together
+    can improve compression ratio even further with certain file types.
+
+    The lzma and lzmadec command line tools have been rewritten. They uses
+    liblzma to do the actual compressing or uncompressing.
+
+    The development of LZMA Utils 4.42.x is still in alpha stage. Several
+    features are still missing or don't fully work yet. Documentation is
+    also very minimal.
+