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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-14 12:57:09 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-14 12:57:09 +0000
commitae36dc179f7f9c26dd9e1463b9eb90fbc804d4d3 (patch)
tree3346607a82ffe01ef0a4a19bed6c8b8b6f96864e /README
parentInitial commit. (diff)
downloadplzip-upstream/1.11.tar.xz
plzip-upstream/1.11.zip
Adding upstream version 1.11.upstream/1.11upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+Description
+
+Plzip is a massively parallel (multi-threaded) implementation of lzip,
+compatible with lzip 1.4 or newer. Plzip uses the compression library lzlib.
+
+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.
+
+Plzip can compress/decompress large files on multiprocessor machines much
+faster than lzip, at the cost of a slightly reduced compression ratio (0.4
+to 2 percent larger compressed files). Note that the number of usable
+threads is limited by file size; on files larger than a few GB plzip can use
+hundreds of processors, but on files of only a few MB plzip is no faster
+than lzip.
+
+For creation and manipulation of compressed tar archives tarlz can be more
+efficient than using tar and plzip because tarlz is able to keep the
+alignment between tar members and lzip members.
+
+When compressing, plzip divides the input file into chunks and compresses as
+many chunks simultaneously as worker threads are chosen, creating a
+multimember compressed file. Each chunk is compressed in-place (using the
+same buffer for input and output), reducing the amount of RAM required.
+
+When decompressing, plzip decompresses as many members simultaneously as
+worker threads are chosen. Files that were compressed with lzip are not
+decompressed faster than using lzip (unless the option '-b' was used)
+because lzip usually produces single-member files, which can't be
+decompressed in parallel.
+
+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.
+
+Plzip uses the same well-defined exit status values used by lzip, which
+makes it safer than compressors returning ambiguous warning values (like
+gzip) when it is used as a back end for other programs like tar or zutils.
+
+Plzip automatically uses for each file the largest dictionary size that does
+not exceed neither the file size nor the limit given. Keep in mind that the
+decompression memory requirement is affected at compression time by the
+choice of dictionary size limit.
+
+When compressing, plzip replaces every file given in the command line
+with a compressed version of itself, with the name "original_name.lz".
+When decompressing, plzip attempts to guess the name for the decompressed
+file from that of the compressed file as follows:
+
+filename.lz becomes filename
+filename.tlz becomes filename.tar
+anyothername becomes anyothername.out
+
+(De)compressing a file is much like copying or moving it. Therefore plzip
+preserves the access and modification dates, permissions, and, if you have
+appropriate privileges, ownership of the file just as 'cp -p' does. (If the
+user ID or the group ID can't be duplicated, the file permission bits
+S_ISUID and S_ISGID are cleared).
+
+Plzip is able to read from some types of non-regular files if either the
+option '-c' or the option '-o' is specified.
+
+If no file names are specified, plzip compresses (or decompresses) from
+standard input to standard output. Plzip refuses to read compressed data
+from a terminal or write compressed data to a terminal, as this would be
+entirely incomprehensible and might leave the terminal in an abnormal state.
+
+Plzip correctly decompresses a file which is the concatenation of two or
+more compressed files. The result is the concatenation of the corresponding
+decompressed files. Integrity testing of concatenated compressed files is
+also supported.
+
+LANGUAGE NOTE: Uncompressed = not compressed = plain data; it may never have
+been compressed. Decompressed is used to refer to data which have undergone
+the process of decompression.
+
+
+Copyright (C) 2009-2024 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.