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diff --git a/Build/source/extra/xz-4.999.9beta-124-gb637/README b/Build/source/extra/xz-4.999.9beta-124-gb637/README new file mode 100644 index 00000000000..6b695d5ccdb --- /dev/null +++ b/Build/source/extra/xz-4.999.9beta-124-gb637/README @@ -0,0 +1,218 @@ + +XZ Utils +======== + + 0. Overview + 1. Documentation + 1.1. Overall documentation + 1.2. Documentation for command line tools + 1.3. Documentation for liblzma + 2. Version numbering + 3. Reporting bugs + 4. Other implementations of the .xz format + 5. Contact information + + +0. Overview +----------- + + XZ Utils provide a general-purpose data compression library and + command line tools. The native file format is the .xz format, but + also the legacy .lzma format is supported. The .xz format supports + multiple compression algorithms, which are called "filters" in + context of XZ Utils. The primary filter is currently LZMA2. With + typical files, XZ Utils create about 30 % smaller files than gzip. + + To ease adapting support for the .xz format into existing applications + and scripts, the API of liblzma is somewhat similar to the API of the + popular zlib library. For the same reason, the command line tool xz + has similar command line syntax than that of gzip. + + When aiming for the highest compression ratio, LZMA2 encoder uses + a lot of CPU time and may use, depending on the settings, even + hundreds of megabytes of RAM. However, in fast modes, LZMA2 encoder + competes with bzip2 in compression speed, RAM usage, and compression + ratio. + + LZMA2 is reasonably fast to decompress. It is a little slower than + gzip, but a lot faster than bzip2. Being fast to decompress means + that the .xz format is especially nice when the same file will be + decompressed very many times (usually on different computers), which + is the case e.g. when distributing software packages. In such + situations, it's not too bad if the compression takes some time, + since that needs to be done only once to benefit many people. + + With some file types, combining (or "chaining") LZMA2 with an + additional filter can improve compression ratio. A filter chain may + contain up to four filters, although usually only one two is used. + For example, putting a BCJ (Branch/Call/Jump) filter before LZMA2 + in the filter chain can improve compression ratio of executable files. + + Since the .xz format allows adding new filter IDs, it is possible that + some day there will be a filter that is, for example, much faster to + compress than LZMA2 (but probably with worse compression ratio). + Similarly, it is possible that some day there is a filter that will + compress better than LZMA2. + + XZ Utils doesn't support multithreaded compression or decompression + yet. It has been planned though and taken into account when designing + the .xz file format. + + +1. Documentation +---------------- + +1.1. Overall documentation + + README This file + + INSTALL.generic Generic install instructions for those not familiar + with packages using GNU Autotools + INSTALL Installation instructions specific to XZ Utils + PACKAGERS Information to packagers of XZ Utils + + COPYING XZ Utils copyright and license information + COPYING.GPLv2 GNU General Public License version 2 + COPYING.GPLv3 GNU General Public License version 3 + COPYING.LGPLv2.1 GNU Lesser General Public License version 2.1 + + AUTHORS The main authors of XZ Utils + THANKS Incomplete list of people who have helped making + this software + NEWS User-visible changes between XZ Utils releases + ChangeLog Detailed list of changes (commit log) + TODO Known bugs and some sort of to-do list + + Note that only some of the above files are included in binary + packages. + + +1.2. Documentation for command line tools + + The command line tools are documented as man pages. In source code + releases (and possibly also in some binary packages), the man pages + are also provided in plain text (ASCII only) and PDF formats in the + directory "doc/man" to make the man pages more accessible to those + whose operating system doesn't provide an easy way to view man pages. + + +1.3. Documentation for liblzma + + The liblzma API headers include short docs about each function + and data type as Doxygen tags. These docs should be quite OK as + a quick reference. + + I have planned to write a bunch of very well documented example + programs, which (due to comments) should work as a tutorial to + various features of liblzma. No such example programs have been + written yet. + + For now, if you have never used liblzma, libbzip2, or zlib, I + recommend learning *basics* of zlib API. Once you know that, it + should be easier to learn liblzma. + + http://zlib.net/manual.html + http://zlib.net/zlib_how.html + + +2. Version numbering +-------------------- + + The version number format of XZ Utils is X.Y.ZS: + + - X is the major version. When this is incremented, the library + API and ABI break. + + - Y is the minor version. It is incremented when new features are + added without breaking existing API or ABI. Even Y indicates + stable release and odd Y indicates unstable (alpha or beta + version). + + - Z is the revision. This has different meaning for stable and + unstable releases: + * Stable: Z is incremented when bugs get fixed without adding + any new features. + * Unstable: Z is just a counter. API or ABI of features added + in earlier unstable releases having the same X.Y may break. + + - S indicates stability of the release. It is missing from the + stable releases where Y is an even number. When Y is odd, S + is either "alpha" or "beta" to make it very clear that such + versions are not stable releases. The same X.Y.Z combination is + not used for more than one stability level i.e. after X.Y.Zalpha, + the next version can be X.Y.(Z+1)beta but not X.Y.Zbeta. + + +3. Reporting bugs +----------------- + + Naturally it is easiest for me if you already know what causes the + unexpected behavior. Even better if you have a patch to propose. + However, quite often the reason for unexpected behavior is unknown, + so here are a few things to do before sending a bug report: + + 1. Try to create a small example how to reproduce the issue. + + 2. Compile XZ Utils with debugging code using configure switches + --enable-debug and, if possible, --disable-shared. If you are + using GCC, use CFLAGS='-O0 -ggdb3'. Don't strip the resulting + binaries. + + 3. Turn on core dumps. The exact command depends on your shell; + for example in GNU bash it is done with "ulimit -c unlimited", + and in tcsh with "limit coredumpsize unlimited". + + 4. Try to reproduce the suspected bug. If you get "assertion failed" + message, be sure to include the complete message in your bug + report. If the application leaves a coredump, get a backtrace + using gdb: + $ gdb /path/to/app-binary # Load the app to the debugger. + (gdb) core core # Open the coredump. + (gdb) bt # Print the backtrace. Copy & paste to bug report. + (gdb) quit # Quit gdb. + + Report your bug via email or IRC (see Contact information below). + Don't send core dump files or any executables. If you have a small + example file(s) (total size less than 256 KiB), please include + it/them as an attachment. If you have bigger test files, put them + online somewhere and include an URL to the file(s) in the bug report. + + Always include the exact version number of XZ Utils in the bug report. + If you are using a snapshot from the git repository, use "git describe" + to get the exact snapshot version. If you are using XZ Utils shipped + in an operating system distribution, mention the distribution name, + distribution version, and exact xz package version; if you cannot + repeat the bug with the code compiled from unpatched source code, + you probably need to report a bug to your distribution's bug tracking + system. + + +4. Other implementations of the .xz format +------------------------------------------ + + 7-Zip and the p7zip port of 7-Zip support the .xz format starting + from the version 9.00alpha. + + http://7-zip.org/ + http://p7zip.sourceforge.net/ + + XZ Embedded is a limited implementation written for use in the Linux + kernel, but it is also suitable for other embedded use. + + http://tukaani.org/xz/embedded.html + + +5. Contact information +---------------------- + + If you have questions, bug reports, patches etc. related to XZ Utils, + contact Lasse Collin <lasse.collin@tukaani.org> (in Finnish or English). + tukaani.org uses greylisting to reduce spam, thus when you send your + first email, it may get delayed by a few hours. In addition to that, + I'm sometimes slow at replying. If you haven't got a reply within two + weeks, assume that your email has got lost and resend it or use IRC. + + You can find me also from #tukaani on Freenode; my nick is Larhzu. + The channel tends to be pretty quiet, so just ask your question and + someone may wake up. + |