7 This is an early alpha version. Don't trust the files produced by
8 this version of the software - not even if the software can
9 uncompress the files properly! This is because the file format
10 isn't completely frozen yet.
12 So please test a lot, but don't use for anything serious yet.
17 LZMA is a general purporse compression algorithm designed by
18 Igor Pavlov as part of 7-Zip. It provides high compression ratio
19 while keeping the decompression speed fast.
21 LZMA Utils are an attempt to make LZMA compression easy to use
22 on free (as in freedom) operating systems. This is achieved by
23 providing tools and libraries which are similar to use than the
24 equivalents of the most popular existing compression algorithms.
26 LZMA Utils consist of a few relatively separate parts:
27 * liblzma is an encoder/decoder library with support for several
28 filters (algorithm implementations). The primary filter is LZMA.
29 * libzfile enables reading from and writing to gzip, bzip2 and
30 LZMA compressed and uncompressed files with an API similar to
31 the standard ANSI-C file I/O.
32 [ NOTE: libzfile is not implemented yet. ]
33 * lzma command line tool has almost identical syntax than gzip
34 and bzip2. It makes LZMA easy for average users, but also
35 provides advanced options to finetune the compression settings.
36 * A few shell scripts make diffing and grepping LZMA compressed
37 files easy. The scripts were adapted from gzip and bzip2.
42 LZMA Utils are developed on GNU+Linux, but they should work at
43 least on *BSDs and Solaris. They probably work on some other
44 POSIX-like operating systems too.
46 If you use GCC to compile LZMA Utils, you need at least version
47 3.x.x. GCC version 2.xx.x doesn't support some C99 features used
48 in LZMA Utils source code, thus GCC 2 won't compile LZMA Utils.
50 If you have written patches to make LZMA Utils to work on previously
51 unsupported platform, please send the patches to me! I will consider
52 including them to the official version. It's nice to minimize the
53 need of third-party patching.
55 One exception: Don't request or send patches to change the whole
56 source package to C89. I find C99 substantially nicer to write and
57 maintain. However, the public library headers must be in C89 to
58 avoid frustrating those who maintain programs, which are strictly
64 Starting from LZMA Utils 5, the version number of LZMA Utils has
65 absolutely nothing to do with the version number of LZMA SDK or
66 7-Zip. The new version number format of LZMA Utils is X.Y.ZS:
68 - X is the major version. When this is incremented, the library
71 - Y is the minor version. It is incremented when new features are
72 added without breaking existing API or ABI. Even Y indicates
73 stable release and odd Y indicates unstable (alpha or beta
76 - Z is the revision. This has different meaning for stable and
78 * Stable: Z is incremented when bugs get fixed without adding
80 * Unstable: Z is just a counter. API or ABI of features added
81 in earlier unstable releases having the same X.Y may break.
83 - S indicates stability of the release. It is missing from the
84 stable releases where Y is an even number. When Y is odd, S
85 is either "alpha" or "beta" to make it very clear that such
86 versions are not stable releases. The same X.Y.Z combination is
87 not used for more than one stability level i.e. after X.Y.Zalpha,
88 the next version can be X.Y.(Z+1)beta but not X.Y.Zbeta.
93 If you are not familiar with `configure' scripts, read the file
96 In most cases, the default --enable/--disable/--with/--without options
97 are what you want. Don't touch them if you are unsure.
100 Do not compile the encoder component of liblzma. This
101 implies --disable-match-finders. If you need only
102 the decoder, you can decrease the library size
103 dramatically with this option.
105 The default is to build the encoder.
108 Do not compile the decoder component of liblzma.
110 The default is to build the decoder.
113 liblzma supports several filters. See liblzma-intro.txt
114 for a little more information about these.
116 The default is to build all the filters.
118 --enable-match-finders=
119 liblzma includes two categories of match finders:
120 hash chains and binary trees. Hash chains (hc3 and hc4)
121 are quite fast but they don't provide the best compression
122 ratio. Binary trees (bt2, bt3 and bt4) give excellent
123 compression ratio, but they are slower and need more
124 memory than hash chains.
126 You need to enable at least one match finder to build the
127 LZMA filter encoder. Usually hash chains are used only in
128 the fast mode, while binary trees are used to when the best
129 compression ratio is wanted.
131 The default is to build all the match finders.
134 liblzma support multiple integrity checks. CRC32 is
135 mandatory, and cannot be omitted. See liblzma-intro.txt
136 for more information about usage of the integrity checks.
139 liblzma includes some assembler optimizations. Currently
140 there is only assembler code for CRC32 and CRC64 for
143 All the assembler code in liblzma is position-independent
144 code, which is suitable for use in shared libraries and
145 position-independent executables. So far only i386
146 instructions are used, but the code is optimized for i686
147 class CPUs. If you are compiling liblzma exclusively for
148 pre-i686 systems, you may want to disable the assembler
152 Omits precomputed tables. This makes liblzma a few KiB
153 smaller. Startup time increases, because the tables need
154 to be computed first.
157 This enables the assert() macro and possibly some other
158 run-time consistency checks. It slows down things somewhat,
159 so you normally don't want to have this enabled.
162 Makes all compiler warnings an error, that abort the
163 compilation. This may help catching bugs, and should work
164 on most systems. This has no effect on the resulting
168 Static vs. dynamic linking of the command line tools
170 By default, the command line tools are linked statically against
171 liblzma. There a are a few reasons:
173 - The executable(s) can be in /bin while the shared liblzma can still
174 be in /usr/lib (if the distro uses such file system hierachy).
176 - It's easier to copy the executables to other systems, since they
179 - It's slightly faster on some architectures like x86.
181 If you don't like this, you can get the command line tools linked
182 against the shared liblzma by specifying --disable-static to configure.
183 This disables building static liblzma completely.