Description

Pdlzip is a permissively licensed implementation of the lzip data
compressor, intended for those who can't distribute (or even use) GPL
licensed Free Software. The name of pdlzip comes from 'public domain lzip'.
Pdlzip is written in C and is (hope)fully compatible with lzip 1.4 or newer.

Lzip is a lossless data compressor with a user interface similar to the one
of gzip or bzip2. Lzip uses a simplified form of the 'Lempel-Ziv-Markov
chain-Algorithm' (LZMA) stream format to maximize interoperability. The
maximum dictionary size is 512 MiB so that any lzip file can be decompressed
on 32-bit machines. Lzip provides accurate and robust 3-factor integrity
checking. Lzip can compress about as fast as gzip (lzip -0) or compress most
files more than bzip2 (lzip -9). Decompression speed is intermediate between
gzip and bzip2. Lzip is better than gzip and bzip2 from a data recovery
perspective. Lzip has been designed, written, and tested with great care to
replace gzip and bzip2 as the standard general-purpose compressed format for
Unix-like systems.

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.

Pdlzip is also able to decompress legacy lzma-alone (.lzma) files.
Lzma-alone is a very bad format; it is essentially a raw LZMA stream.
If you keep any lzma-alone files, it is advisable to recompress them to
lzip format. Lziprecover can convert some lzma-alone files to lzip format
without recompressing.

Pdlzip includes public domain compression/decompression code from the LZMA
SDK (Software Development Kit) written by Igor Pavlov.

I would not write non-copylefted software unless it is too simple to be
worth copylefting it, but one of the uses of the lzip format is the
interchange of information, and it is therefore desirable that even the
users of the most non-free platforms can share lzip files with everybody
else.


Copyright (C) 2010-2023 Antonio Diaz Diaz.

This file is free documentation: you have unlimited permission to copy,
distribute, and modify it.

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