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Updated the totally outdated TODO file.
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Lasse Collin
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117
TODO
117
TODO
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@ -1,109 +1,46 @@
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LZMA Utils TODO List
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--------------------
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XZ Utils To-Do List
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===================
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Major missing features
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Known bugs
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----------
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Memory limits in the command line tool apply only to compression.
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The test suite is too incomplete.
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Threading support in the lzma command line tool is still primitive.
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It cannot split a file in pieces yet.
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The --list mode isn't implemented in the command line tool.
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Handling of Multi-Block Stream information should be separated
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from Stream encoder and decoder. Those would be useful to implement
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multi-threaded coding in applications.
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Buffer to buffer coding is not implemented in liblzma. Probably
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a naive version should be written first, which would simply wrap
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things around lzma_stream. Later, there should be separate buffer
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coding functions, that are slightly faster (less memcpy()) and
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have smaller memory usage than the functions using lzma_stream.
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libzfile is not implemented.
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LZMA filter doesn't support predefined history buffer.
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If the memor usage limit is less than about 13 MiB, xz is unable to
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automatically scale down the compression settings enough even though
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it would be possible by switching from BT2/BT3/BT4 match finder to
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HC3/HC4.
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Security
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Missing features
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----------------
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Search for bugs, especially security related issues. Security is
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important in every piece of code in LZMA Utils, but it is extremely
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important in the decoder part of liblzma.
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"xz --list"
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Subblock: If there is LZMA as a Subfilter but without EOPM, can it
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trigger infinite loop when Subblock's "Unset Subfilter" flag is hit?
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xz could create sparse files when decompressing. (Some prototyping
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has been done.)
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Similarly, can LZ decoder get stuck in infinite loop if the next
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filter in the chain returns LZMA_STREAM_END but the decoded data
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doesn't allow finishing the LZ decoding?
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xz doesn't support copying extended attributes, access control
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lists etc. from source to target file.
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Multithreaded compression
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Reliability
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Multithreaded decompression
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Create a test suite to be run with "make check".
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Buffer-to-buffer coding could use less RAM (especially when
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decompressing LZMA1 or LZMA2).
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Should we use strlimit() and getrlimit() for memory usage limitting?
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Performance
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Benchmark the CRC code on non-x86 CPUs. Won't have huge effect on
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overall speed, but it would still be nice to know what algorithm
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variant is the best on different CPUs.
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Third party support
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Add support for LZMA to various applications. This naturally requires
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cooperating with the authors of the specific applications.
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* GNU grep and GNU diffutils: BSD grep already uses zlib directly
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instead of ugly shell scripts. It would be nice to get similar
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feature into relevant GNU tools. With libzfile, multiple
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compression formats would be easy to support.
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* kioslave for KDE
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* Magic for the `file' command
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* GNU Midnight Commander
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* GNU Texinfo
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* The `man' command
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* Package managers
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Test the patches already written. The patches should be sent to
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upstream developers _once_ LZMA Utils APIs are stable enough (so
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people don't need to fix those patches all the time).
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Mandriva has quite a few patches. Some of them are OK, some need
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adapting for new LZMA Utils.
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I/O library is not implemented. It will possibly be named libzzf.
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Documentation
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-------------
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Revise the man page of lzma command line tool.
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Some tutorial is needed for liblzma. I have planned to write some
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extremely well commented example programs, which would work as
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a tutorial. I suppose the Doxygen tags are quite OK as a quick
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reference once one is familiar with the liblzma API.
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If the Doxygen docs aren't enough, write good Texinfo manual for
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liblzma. It's been a long time I've even tried to build the Doxygen
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docs, so they may look quite bad at the moment.
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Document LZMA as an algorithm. It would be great to have detailed
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description of the algorithm in English. Many people think, that
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reading the source code is not the optimal way to learn how LZMA
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works.
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Other
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Some things return LZMA_PROG_ERROR with invalid options, some
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LZMA_HEADER_ERROR. These must be checked carefully and made so
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that LZMA_HEADER_ERROR is used only when the given option could
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make sense in future version of libzma.
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lzma_restrict vs. restrict
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Usage of LZMA_RUN vs. LZMA_FINISH with Metadata coders.
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Port the Deflate implementation from 7-Zip into liblzma. 7-Zip's
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Deflate compresses better than zlib, gzip or Info-ZIP. I don't
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know if Deflate will be included in .lzma format (probably not),
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but it's still useful once we also add support for .gz file format.
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Document the LZMA1 and LZMA2 algorithms.
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