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@@ -0,0 +1,151 @@ + +LZMA Utils +---------- + +Warning + + This is an early alpha version. Don't trust the files produced by + this version of the software - not even if the software can + uncompress the files properly! This is because the file format + isn't completely frozen yet. + + So please test a lot, but don't use for anything serious yet. + + +Overview + + LZMA is a general purporse compression algorithm designed by + Igor Pavlov as part of 7-Zip. It provides high compression ratio + while keeping the decompression speed fast. + + LZMA Utils are an attempt to make LZMA compression easy to use + on free (as in freedom) operating systems. This is achieved by + providing tools and libraries which are similar to use than the + equivalents of the most popular existing compression algorithms. + + LZMA Utils consist of a few relatively separate parts: + * liblzma is an encoder/decoder library with support for several + filters (algorithm implementations). The primary filter is LZMA. + * libzfile enables reading from and writing to gzip, bzip2 and + LZMA compressed and uncompressed files with an API similar to + the standard ANSI-C file I/O. + [ NOTE: libzfile is not implemented yet. ] + * lzma command line tool has almost identical syntax than gzip + and bzip2. It makes LZMA easy for average users, but also + provides advanced options to finetune the compression settings. + * A few shell scripts make diffing and grepping LZMA compressed + files easy. The scripts were adapted from gzip and bzip2. + + +Supported platforms + + LZMA Utils are developed on GNU+Linux, but they should work at + least on *BSDs and Solaris. They probably work on some other + POSIX-like operating systems too. + + If you use GCC to compile LZMA Utils, you need at least version + 3.x.x. GCC version 2.xx.x doesn't support some C99 features used + in LZMA Utils source code, thus GCC 2 won't compile LZMA Utils. + + If you have written patches to make LZMA Utils to work on previously + unsupported platform, please send the patches to me! I will consider + including them to the official version. It's nice to minimize the + need of third-party patching. + + One exception: Don't request or send patches to change the whole + source package to C89. I find C99 substantially nicer to write and + maintain. However, the public library headers must be in C89 to + avoid frustrating those who maintain programs, which are strictly + in C89 or C++. + + +configure options + + If you are not familiar with `configure' scripts, read the file + INSTALL first. + + In most cases, the default --enable/--disable/--with/--without options + are what you want. Don't touch them if you are unsure. + + --disable-encoder + Do not compile the encoder component of liblzma. This + implies --disable-match-finders. If you need only + the decoder, you can decrease the library size + dramatically with this option. + + The default is to build the encoder. + + --disable-decoder + Do not compile the decoder component of liblzma. + + The default is to build the decoder. + + --enable-filters= + liblzma supports several filters. See liblzma-intro.txt + for a little more information about these. + + The default is to build all the filters. + + --enable-match-finders= + liblzma includes two categories of match finders: + hash chains and binary trees. Hash chains (hc3 and hc4) + are quite fast but they don't provide the best compression + ratio. Binary trees (bt2, bt3 and bt4) give excellent + compression ratio, but they are slower and need more + memory than hash chains. + + You need to enable at least one match finder to build the + LZMA filter encoder. Usually hash chains are used only in + the fast mode, while binary trees are used to when the best + compression ratio is wanted. + + The default is to build all the match finders. + + --enable-checks= + liblzma support multiple integrity checks. CRC32 is + mandatory, and cannot be omitted. See liblzma-intro.txt + for more information about usage of the integrity checks. + + --disable-assembler + liblzma includes some assembler optimizations. Currently + there is only assembler code for CRC32 and CRC64 for + 32-bit x86. + + All the assembler code in liblzma is position-independent + code, which is suitable for use in shared libraries and + position-independent executables. + + --enable-small + Omits precomputed tables. This makes liblzma a few KiB + smaller. Startup time increases, because the tables need + to be computed first. + + --enable-debug + This enables the assert() macro and possibly some other + run-time consistency checks. It slows down things somewhat, + so you normally don't want to have this enabled. + + --enable-werror + Makes all compiler warnings an error, that abort the + compilation. This may help catching bugs, and should work + on most systems. This has no effect on the resulting + binaries. + + +Static vs. dynamic linking of the command line tools + + By default, the command line tools are linked statically against + liblzma. There a are a few reasons: + + - The executable(s) can be in /bin while the shared liblzma can still + be in /usr/lib (if the distro uses such file system hierachy). + + - It's easier to copy the executables to other systems, since they + depend only on libc. + + - It's slightly faster on some architectures like x86. + + If you don't like this, you can get the command line tools linked + against the shared liblzma by specifying --disable-static to configure. + This disables building static liblzma completely. + |