xz-analysis-mirror/TODO

XZ Utils To-Do List
===================

Known bugs
----------

    The test suite is too incomplete.

    If the memor usage limit is less than about 13 MiB, xz is unable to
    automatically scale down the compression settings enough even though
    it would be  possible by switching from BT2/BT3/BT4 match finder to
    HC3/HC4.

    The code to detect number of CPU cores doesn't count hyperthreading
    as multiple cores. In context of xz, it probably should.
    Hyperthreading is good at least with p7zip.

    XZ Utils compress some files significantly worse than LZMA Utils.
    This is due to faster compression presets used by XZ Utils, and
    can be worked around by using "xz --extreme". However, the presets
    need some tweaking and maybe this issue can be minimized without
    making the typical case too much slower.

    xz doesn't quote unprintable characters when it displays file names
    given on the command line.


Missing features
----------------

    "xz --list"

    xz could create sparse files when decompressing. (Some prototyping
    has been done.)

    xz doesn't support copying extended attributes, access control
    lists etc. from source to target file.

    Multithreaded compression

    Multithreaded decompression

    Buffer-to-buffer coding could use less RAM (especially when
    decompressing LZMA1 or LZMA2).

    I/O library is not implemented. It will possibly be named libzzf.


Documentation
-------------

    Some tutorial is needed for liblzma. I have planned to write some
    extremely well commented example programs, which would work as
    a tutorial. I suppose the Doxygen tags are quite OK as a quick
    reference once one is familiar with the liblzma API.

    Document the LZMA1 and LZMA2 algorithms.