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Description
Lzd is a simplified decompressor for the lzip format with an educational
purpose. Studying its source code is a good first step to understand how
lzip works. Lzd is written in C++.
The source code of lzd is used in the lzip manual as a reference
decompressor in the description of the lzip file format. Reading the lzip
manual will help you understand the source code. Lzd is compliant with the
lzip specification; it verifies the 3 integrity factors.
The source code of lzd is also used as a reference in the description of the
media type 'application/lzip'.
See http://datatracker.ietf.org/doc/draft-diaz-lzip
Lzd decompresses from standard input to standard output. It accepts (and
ignores) the option '-d' for compatibility with other lzip tools. In
particular, accepting the option '-d' allows lzd to be used as argument to
the option '--lz' of the tools from the zutils package.
Lzd will correctly decompress the concatenation of two or more compressed
files. The result is the concatenation of the corresponding decompressed
data. Integrity of such concatenated compressed input is also verified.
The lzip file format is designed for data sharing and long-term archiving,
taking into account both data integrity and decoder availability:
* The lzip format provides very safe integrity checking and some data
recovery means. The program lziprecover can repair bit flip errors
(one of the most common forms of data corruption) in lzip files, and
provides data recovery capabilities, including error-checked merging
of damaged copies of a file.
* The lzip format is as simple as possible (but not simpler). The lzip
manual provides the source code of a simple decompressor along with a
detailed explanation of how it works, so that with the only help of the
lzip manual it would be possible for a digital archaeologist to extract
the data from a lzip file long after quantum computers eventually
render LZMA obsolete.
* Additionally the lzip reference implementation is copylefted, which
guarantees that it will remain free forever.
A nice feature of the lzip format is that a corrupt byte is easier to repair
the nearer it is from the beginning of the file. Therefore, with the help of
lziprecover, losing an entire archive just because of a corrupt byte near
the beginning is a thing of the past.
The ideas embodied in lzd are due to (at least) the following people:
Abraham Lempel and Jacob Ziv (for the LZ algorithm), Andrei Markov (for the
definition of Markov chains), G.N.N. Martin (for the definition of range
encoding), and Igor Pavlov (for putting all the above together in LZMA).
Copyright (C) 2013-2022 Antonio Diaz Diaz.
This file is free documentation: you have unlimited permission to copy,
distribute, and modify it.
The file Makefile.in is a data file used by configure to produce the
Makefile. It has the same copyright owner and permissions that configure
itself.
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