156 lines
6.2 KiB
Plaintext
156 lines
6.2 KiB
Plaintext
|
|
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.
|
|
|
|
At the moment the assembler code is not compatible with
|
|
Darwin, so --disable-assembler must be specified when
|
|
building on Darwin.
|
|
|
|
--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.
|
|
|