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Fix a few typos and add some missing articles in some documents.
Also hyphenate several compound adjectives. Signed-off-by: Benno Schulenberg <bensberg@justemail.net>
This commit is contained in:
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4 changed files with 65 additions and 65 deletions
6
AUTHORS
6
AUTHORS
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@ -16,11 +16,11 @@ Authors of XZ Utils
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Some scripts have been adapted from gzip. The original versions
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were written by Jean-loup Gailly, Charles Levert, and Paul Eggert.
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Andrew Dudman helped adapting the script and their man pages for
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Andrew Dudman helped adapting the scripts and their man pages for
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XZ Utils.
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The GNU Autotools based build system contains files from many authors,
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which I'm not trying list here.
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The GNU Autotools-based build system contains files from many authors,
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which I'm not trying to list here.
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Several people have contributed fixes or reported bugs. Most of them
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are mentioned in the file THANKS.
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42
README
42
README
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@ -5,7 +5,7 @@ XZ Utils
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0. Overview
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1. Documentation
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1.1. Overall documentation
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1.2. Documentation for command line tools
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1.2. Documentation for command-line tools
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1.3. Documentation for liblzma
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2. Version numbering
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3. Reporting bugs
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@ -17,21 +17,21 @@ XZ Utils
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0. Overview
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-----------
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XZ Utils provide a general-purpose data compression library and
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command line tools. The native file format is the .xz format, but
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XZ Utils provide a general-purpose data-compression library plus
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command-line tools. The native file format is the .xz format, but
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also the legacy .lzma format is supported. The .xz format supports
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multiple compression algorithms, which are called "filters" in
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multiple compression algorithms, which are called "filters" in the
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context of XZ Utils. The primary filter is currently LZMA2. With
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typical files, XZ Utils create about 30 % smaller files than gzip.
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To ease adapting support for the .xz format into existing applications
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and scripts, the API of liblzma is somewhat similar to the API of the
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popular zlib library. For the same reason, the command line tool xz
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has similar command line syntax than that of gzip.
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popular zlib library. For the same reason, the command-line tool xz
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has a command-line syntax similar to that of gzip.
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When aiming for the highest compression ratio, LZMA2 encoder uses
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When aiming for the highest compression ratio, the LZMA2 encoder uses
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a lot of CPU time and may use, depending on the settings, even
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hundreds of megabytes of RAM. However, in fast modes, LZMA2 encoder
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hundreds of megabytes of RAM. However, in fast modes, the LZMA2 encoder
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competes with bzip2 in compression speed, RAM usage, and compression
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ratio.
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@ -44,8 +44,8 @@ XZ Utils
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since that needs to be done only once to benefit many people.
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With some file types, combining (or "chaining") LZMA2 with an
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additional filter can improve compression ratio. A filter chain may
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contain up to four filters, although usually only one two is used.
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additional filter can improve the compression ratio. A filter chain may
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contain up to four filters, although usually only one or two are used.
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For example, putting a BCJ (Branch/Call/Jump) filter before LZMA2
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in the filter chain can improve compression ratio of executable files.
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@ -88,9 +88,9 @@ XZ Utils
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packages.
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1.2. Documentation for command line tools
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1.2. Documentation for command-line tools
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The command line tools are documented as man pages. In source code
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The command-line tools are documented as man pages. In source code
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releases (and possibly also in some binary packages), the man pages
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are also provided in plain text (ASCII only) and PDF formats in the
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directory "doc/man" to make the man pages more accessible to those
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@ -109,7 +109,7 @@ XZ Utils
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written yet.
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For now, if you have never used liblzma, libbzip2, or zlib, I
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recommend learning *basics* of zlib API. Once you know that, it
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recommend learning the *basics* of the zlib API. Once you know that, it
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should be easier to learn liblzma.
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http://zlib.net/manual.html
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@ -125,11 +125,11 @@ XZ Utils
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API and ABI break.
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- Y is the minor version. It is incremented when new features are
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added without breaking existing API or ABI. Even Y indicates
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stable release and odd Y indicates unstable (alpha or beta
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added without breaking the existing API or ABI. An even Y indicates
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a stable release and an odd Y indicates unstable (alpha or beta
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version).
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- Z is the revision. This has different meaning for stable and
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- Z is the revision. This has a different meaning for stable and
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unstable releases:
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* Stable: Z is incremented when bugs get fixed without adding
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@ -141,10 +141,10 @@ XZ Utils
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in earlier unstable releases having the same X.Y may break.
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- S indicates stability of the release. It is missing from the
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stable releases where Y is an even number. When Y is odd, S
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stable releases, where Y is an even number. When Y is odd, S
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is either "alpha" or "beta" to make it very clear that such
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versions are not stable releases. The same X.Y.Z combination is
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not used for more than one stability level i.e. after X.Y.Zalpha,
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not used for more than one stability level, i.e. after X.Y.Zalpha,
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the next version can be X.Y.(Z+1)beta but not X.Y.Zbeta.
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@ -180,7 +180,7 @@ XZ Utils
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Don't send core dump files or any executables. If you have a small
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example file(s) (total size less than 256 KiB), please include
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it/them as an attachment. If you have bigger test files, put them
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online somewhere and include an URL to the file(s) in the bug report.
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online somewhere and include a URL to the file(s) in the bug report.
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Always include the exact version number of XZ Utils in the bug report.
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If you are using a snapshot from the git repository, use "git describe"
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@ -197,7 +197,7 @@ XZ Utils
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The messages from the xz tool have been translated into a few
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languages. Before starting to translate into a new language, ask
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the author that someone else hasn't already started working on it.
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the author whether someone else hasn't already started working on it.
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Test your translation. Testing includes comparing the translated
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output to the original English version by running the same commands
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@ -218,7 +218,7 @@ XZ Utils
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Note especially the following:
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- The output of --help and --long-help must look nice on
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a 80-column terminal. It's OK to add extra lines if needed.
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an 80-column terminal. It's OK to add extra lines if needed.
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- In contrast, don't add extra lines to error messages and such.
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They are often preceded with e.g. a filename on the same line,
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24
doc/faq.txt
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doc/faq.txt
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@ -26,7 +26,7 @@ Q: There are many LZMA related projects. How does XZ Utils relate to them?
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A: 7-Zip and LZMA SDK are the original projects. LZMA SDK is roughly
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a subset of the 7-Zip source tree.
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p7zip is 7-Zip's command line tools ported to POSIX-like systems.
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p7zip is 7-Zip's command-line tools ported to POSIX-like systems.
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LZMA Utils provide a gzip-like lzma tool for POSIX-like systems.
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LZMA Utils are based on LZMA SDK. XZ Utils are the successor to
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A: When the designing of the .xz format began, the idea was to replace
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the .lzma format and use the same .lzma suffix. It would have been
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quite OK to reuse the suffix when there were very few .lzma files
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around. However, the old .lzma format become popular before the
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around. However, the old .lzma format became popular before the
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new format was finished. The new format was renamed to .xz but the
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name of liblzma wasn't changed.
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Technically, there is a way to make the conversion relatively fast
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(roughly twice the time that normal decompression takes). Writing
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such a tool would take quite a bit time though, and would probably
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such a tool would take quite a bit of time though, and would probably
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be useful to only a few people. If you really want such a conversion
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tool, contact Lasse Collin and offer some money.
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A: xz -dc foo.tar.xz | tar xf -
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Q: Can I recover parts of a broken .xz file (e.g. corrupted CD-R)?
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Q: Can I recover parts of a broken .xz file (e.g. a corrupted CD-R)?
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A: It may be possible if the file consists of multiple blocks, which
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typically is not the case if the file was created in single-threaded
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Q: Is (some part of) XZ Utils patented?
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A: Lasse Collin is not aware of any patents that could affect XZ Utils.
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However, due to nature of software patents, it's not possible to
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However, due to the nature of software patents, it's not possible to
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guarantee that XZ Utils isn't affected by any third party patent(s).
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filters.
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Documenting LZMA and LZMA2 is planned, but for now, there is no other
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documentation that the source code. Before you begin, you should know
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the basics of LZ77 and range coding algorithms. LZMA is based on LZ77,
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documentation than the source code. Before you begin, you should know
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the basics of LZ77 and range-coding algorithms. LZMA is based on LZ77,
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but LZMA is a lot more complex. Range coding is used to compress
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the final bitstream like Huffman coding is used in Deflate.
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@ -148,7 +148,7 @@ A: See the documentation in XZ Embedded. In short, something like
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xz --check=crc32 --powerpc --lzma2=preset=6e,dict=64KiB
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Adjust dictionary size to get a good compromise between
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Adjust the dictionary size to get a good compromise between
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compression ratio and decompressor memory usage. Note that
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in single-call decompression mode of XZ Embedded, a big
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dictionary doesn't increase memory usage.
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The third method is pigz-style threading (I use that name, because
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pigz <http://www.zlib.net/pigz/> uses that method). It doesn't
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affect compression ratio significantly and scales to many cores.
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The memory usage scales linearly when threads are added. It isn't
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significant with pigz, because Deflate uses only 32 KiB dictionary,
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The memory usage scales linearly when threads are added. This isn't
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significant with pigz, because Deflate uses only a 32 KiB dictionary,
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but with LZMA2 the memory usage will increase dramatically just like
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with the independent blocks method. There is also a constant
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with the independent-blocks method. There is also a constant
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computational overhead, which may make pigz-method a bit dull on
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dual-core compared to the parallel match finder method, but with more
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cores the overhead is not a big deal anymore.
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can cut the memory usage by 50 %.
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It is possible that the single-threaded method will be modified to
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create files indentical to the pigz-style method. We'll see once
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create files identical to the pigz-style method. We'll see once
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pigz-style threading has been implemented in liblzma.
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@ -4,11 +4,11 @@ History of LZMA Utils and XZ Utils
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Tukaani distribution
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In 2005, there was a small group working on Tukaani distribution, which
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was a Slackware fork. One of the project goals was to fit the distro on
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In 2005, there was a small group working on the Tukaani distribution, which
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was a Slackware fork. One of the project's goals was to fit the distro on
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a single 700 MiB ISO-9660 image. Using LZMA instead of gzip helped a
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lot. Roughly speaking, one could fit data that took 1000 MiB in gzipped
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form into 700 MiB with LZMA. Naturally compression ratio varied across
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form into 700 MiB with LZMA. Naturally, the compression ratio varied across
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packages, but this was what we got on average.
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Slackware packages have traditionally had .tgz as the filename suffix,
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First steps of LZMA Utils
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The first version of LZMA Utils (4.22.0) included a shell script called
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lzmash. It was wrapper that had gzip-like command line interface. It
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lzmash. It was a wrapper that had a gzip-like command-line interface. It
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used the LZMA_Alone tool from LZMA SDK to do all the real work. zgrep,
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zdiff, and related scripts from gzip were adapted work with LZMA and
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zdiff, and related scripts from gzip were adapted to work with LZMA and
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were part of the first LZMA Utils release too.
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LZMA Utils 4.22.0 included also lzmadec, which was a small (less than
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10 KiB) decoder-only command line tool. It was written on top of the
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10 KiB) decoder-only command-line tool. It was written on top of the
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decoder-only C code found from the LZMA SDK. lzmadec was convenient in
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situations where LZMA_Alone (a few hundred KiB) would be too big.
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The lzmash script was an ugly and not very secure hack. The last
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version of LZMA Utils to use lzmash was 4.27.1.
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LZMA Utils 4.32.0beta1 introduced a new lzma command line tool written
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LZMA Utils 4.32.0beta1 introduced a new lzma command-line tool written
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by Ville Koskinen. It was written in C++, and used the encoder and
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decoder from C++ LZMA SDK with little modifications. This tool replaced
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both the lzmash script and the LZMA_Alone command line tool in LZMA
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decoder from C++ LZMA SDK with some little modifications. This tool replaced
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both the lzmash script and the LZMA_Alone command-line tool in LZMA
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Utils.
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Introducing this new tool caused some temporary incompatibilities,
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because LZMA_Alone executable was simply named lzma like the new
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command line tool, but they had completely different command line
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because the LZMA_Alone executable was simply named lzma like the new
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command-line tool, but they had a completely different command-line
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interface. The file format was still the same.
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Lasse wrote liblzmadec, which was a small decoder-only library based
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on the C code found from LZMA SDK. liblzmadec had API similar to zlib,
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on the C code found from LZMA SDK. liblzmadec had an API similar to zlib,
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although there were some significant differences, which made it
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non-trivial to use it in some applications designed for zlib and
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libbzip2.
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The lzmadec command line tool was converted to use liblzmadec.
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The lzmadec command-line tool was converted to use liblzmadec.
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Alexandre Sauvé helped converting build system to use GNU Autotools.
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This made is easier to test for certain less portable features needed
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by the new command line tool.
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Alexandre Sauvé helped converting the build system to use GNU Autotools.
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This made it easier to test for certain less portable features needed
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by the new command-line tool.
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Since the new command line tool never got completely finished (for
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example, it didn't support LZMA_OPT environment variable), the intent
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Since the new command-line tool never got completely finished (for
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example, it didn't support the LZMA_OPT environment variable), the intent
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was to not call 4.32.x stable. Similarly, liblzmadec wasn't polished,
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but appeared to work well enough, so some people started using it too.
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File format problems
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The file format used by LZMA_Alone was primitive. It was designed for
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embedded systems in mind, and thus provided only minimal set of
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features. The two biggest problems for non-embedded use were lack of
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magic bytes and integrity check.
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The file format used by LZMA_Alone was primitive. It was designed with
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embedded systems in mind, and thus provided only a minimal set of
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features. The two biggest problems for non-embedded use were the lack of
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magic bytes and an integrity check.
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Igor and Lasse started developing a new file format with some help
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from Ville Koskinen. Also Mark Adler, Mikko Pouru, H. Peter Anvin,
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and Lars Wirzenius helped with some minor things at some point of the
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development. Designing the new format took quite a long time (actually,
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too long time would be more appropriate expression). It was mostly
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too long a time would be a more appropriate expression). It was mostly
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because Lasse was quite slow at getting things done due to personal
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reasons.
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that was already used by the old file format. Switching to the new
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format wouldn't have caused much trouble when the old format wasn't
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used by many people. But since the development of the new format took
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so long time, the old format got quite popular, and it was decided
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such a long time, the old format got quite popular, and it was decided
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that the new file format must use a different suffix.
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It was decided to use .xz as the suffix of the new file format. The
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The early versions of XZ Utils were called LZMA Utils. The first
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releases were 4.42.0alphas. They dropped the rest of the C++ LZMA SDK.
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The code was still directly based on LZMA SDK but ported to C and
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converted from callback API to stateful API. Later, Igor Pavlov made
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C version of the LZMA encoder too; these ports from C++ to C were
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converted from a callback API to a stateful API. Later, Igor Pavlov made
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a C version of the LZMA encoder too; these ports from C++ to C were
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independent in LZMA SDK and LZMA Utils.
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The core of the new LZMA Utils was liblzma, a compression library with
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zlib-like API. liblzma supported both the old and new file format. The
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gzip-like lzma command line tool was rewritten to use liblzma.
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a zlib-like API. liblzma supported both the old and new file format. The
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gzip-like lzma command-line tool was rewritten to use liblzma.
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The new LZMA Utils code base was renamed to XZ Utils when the name
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of the new file format had been decided. The liblzma compression
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@ -139,7 +139,7 @@ Transition to XZ Utils
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caused unnecessary breakage in applications already using the early
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liblzma snapshots.
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The xz command line tool can emulate the gzip-like lzma tool by
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The xz command-line tool can emulate the gzip-like lzma tool by
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creating appropriate symlinks (e.g. lzma -> xz). Thus, practically
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all scripts using the lzma tool from LZMA Utils will work as is with
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XZ Utils (and will keep using the old .lzma format). Still, the .lzma
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