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authorDaniel Baumann <mail@daniel-baumann.ch>2015-11-07 15:08:12 +0000
committerDaniel Baumann <mail@daniel-baumann.ch>2015-11-07 15:08:12 +0000
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+\input texinfo @c -*-texinfo-*-
+@c %**start of header
+@setfilename plzip.info
+@settitle Plzip Manual
+@finalout
+@c %**end of header
+
+@set UPDATED 5 December 2009
+@set VERSION 0.1
+
+@dircategory Data Compression
+@direntry
+* Plzip: (plzip). Parallel version of the lzip data compressor
+@end direntry
+
+
+@titlepage
+@title Plzip
+@subtitle A data compressor based on the LZMA algorithm
+@subtitle for Plzip version @value{VERSION}, @value{UPDATED}
+@author by Antonio Diaz Diaz
+
+@page
+@vskip 0pt plus 1filll
+@end titlepage
+
+@contents
+
+@node Top
+@top
+
+This manual is for Plzip (version @value{VERSION}, @value{UPDATED}).
+
+@menu
+* Introduction:: Purpose and features of plzip
+* Invoking Plzip:: Command line interface
+* File Format:: Detailed format of the compressed file
+* Problems:: Reporting bugs
+* Concept Index:: Index of concepts
+@end menu
+
+@sp 1
+Copyright @copyright{} 2008, 2009 Antonio Diaz Diaz.
+
+This manual is free documentation: you have unlimited permission
+to copy, distribute and modify it.
+
+
+@node Introduction
+@chapter Introduction
+@cindex introduction
+
+Plzip is a parallel version of the lzip data compressor. Currently only
+compression is performed in parallel. Parallel decompression is planned
+to be implemented soon.
+
+Lzip is a lossless data compressor based on the LZMA algorithm, with
+very safe integrity checking and a user interface similar to the one of
+gzip or bzip2. Lzip decompresses almost as fast as gzip and compresses
+better than bzip2, which makes it well suited for software distribution
+and data archiving.
+
+Plzip replaces every file given in the command line with a compressed
+version of itself, with the name "original_name.lz". Each compressed
+file has the same modification date, permissions, and, when possible,
+ownership as the corresponding original, so that these properties can be
+correctly restored at decompression time. Plzip is able to read from some
+types of non regular files if the @samp{--stdout} option is specified.
+
+If no file names are specified, plzip compresses (or decompresses) from
+standard input to standard output. In this case, plzip will decline to
+write compressed output to a terminal, as this would be entirely
+incomprehensible and therefore pointless.
+
+Plzip will correctly decompress a file which is the concatenation of two
+or more compressed files. The result is the concatenation of the
+corresponding uncompressed files. Integrity testing of concatenated
+compressed files is also supported.
+
+When decompressing, plzip attempts to guess the name for the decompressed
+file from that of the compressed file as follows:
+
+@multitable {anyothername} {becomes} {anyothername.out}
+@item filename.lz @tab becomes @tab filename
+@item filename.tlz @tab becomes @tab filename.tar
+@item anyothername @tab becomes @tab anyothername.out
+@end multitable
+
+As a self-check for your protection, plzip stores in the member trailer
+the 32-bit CRC of the original data and the size of the original data,
+to make sure that the decompressed version of the data is identical to
+the original. This guards against corruption of the compressed data, and
+against undetected bugs in plzip (hopefully very unlikely). The chances
+of data corruption going undetected are microscopic, less than one
+chance in 4000 million for each member processed. Be aware, though, that
+the check occurs upon decompression, so it can only tell you that
+something is wrong. It can't help you recover the original uncompressed
+data.
+
+Return values: 0 for a normal exit, 1 for environmental problems (file
+not found, invalid flags, I/O errors, etc), 2 to indicate a corrupt or
+invalid input file, 3 for an internal consistency error (eg, bug) which
+caused plzip to panic.
+
+
+@node Invoking Plzip
+@chapter Invoking Plzip
+@cindex invoking
+@cindex options
+@cindex usage
+@cindex version
+
+The format for running plzip is:
+
+@example
+plzip [@var{options}] [@var{files}]
+@end example
+
+Plzip supports the following options:
+
+@table @samp
+@item --help
+@itemx -h
+Print an informative help message describing the options and exit.
+
+@item --version
+@itemx -V
+Print the version number of plzip on the standard output and exit.
+
+@item --stdout
+@itemx -c
+Compress or decompress to standard output. Needed when reading from a
+named pipe (fifo) or from a device.
+
+@item --decompress
+@itemx -d
+Decompress.
+
+@item --force
+@itemx -f
+Force overwrite of output file.
+
+@item --keep
+@itemx -k
+Keep (don't delete) input files during compression or decompression.
+
+@item --match-length=@var{length}
+@itemx -m @var{length}
+Set the match length limit in bytes. Valid values range from 5 to 273.
+Larger values usually give better compression ratios but longer
+compression times.
+
+@item --output=@var{file}
+@itemx -o @var{file}
+When reading from standard input and @samp{--stdout} has not been
+specified, use @samp{@var{file}} as the virtual name of the uncompressed
+file. This produces a file named @samp{@var{file}} when decompressing,
+and a file named @samp{@var{file}.lz} when compressing.
+
+@item --quiet
+@itemx -q
+Quiet operation. Suppress all messages.
+
+@item --dictionary-size=@var{size}
+@itemx -s @var{size}
+Set the dictionary size limit in bytes. Valid values range from 4KiB to
+512MiB. Note that dictionary sizes are quantized. If the specified size
+does not match one of the valid sizes, it will be rounded upwards.
+
+@item --test
+@itemx -t
+Check integrity of the specified file(s), but don't decompress them.
+This really performs a trial decompression and throws away the result.
+Use @samp{-tvv} or @samp{-tvvv} to see information about the file.
+
+@item --verbose
+@itemx -v
+Verbose mode. Show the compression ratio for each file processed.
+Further -v's increase the verbosity level.
+
+@item -1 .. -9
+Set the compression parameters (dictionary size and match length limit)
+as shown in the table below. Note that @samp{-9} can be much slower than
+@samp{-1}. These options have no effect when decompressing.
+
+@multitable {Level} {Dictionary size} {Match length limit}
+@item Level @tab Dictionary size @tab Match length limit
+@item -1 @tab 1MiB @tab 10 bytes
+@item -2 @tab 1MiB @tab 12 bytes
+@item -3 @tab 1MiB @tab 17 bytes
+@item -4 @tab 2MiB @tab 26 bytes
+@item -5 @tab 4MiB @tab 44 bytes
+@item -6 @tab 8MiB @tab 80 bytes
+@item -7 @tab 16MiB @tab 108 bytes
+@item -8 @tab 16MiB @tab 163 bytes
+@item -9 @tab 32MiB @tab 273 bytes
+@end multitable
+
+@item --fast
+@itemx --best
+Aliases for GNU gzip compatibility.
+
+@end table
+
+@sp 1
+Numbers given as arguments to options may be followed by a multiplier
+and an optional @samp{B} for "byte".
+
+Table of SI and binary prefixes (unit multipliers):
+
+@multitable {Prefix} {kilobyte (10^3 = 1000)} {|} {Prefix} {kibibyte (2^10 = 1024)}
+@item Prefix @tab Value @tab | @tab Prefix @tab Value
+@item k @tab kilobyte (10^3 = 1000) @tab | @tab Ki @tab kibibyte (2^10 = 1024)
+@item M @tab megabyte (10^6) @tab | @tab Mi @tab mebibyte (2^20)
+@item G @tab gigabyte (10^9) @tab | @tab Gi @tab gibibyte (2^30)
+@item T @tab terabyte (10^12) @tab | @tab Ti @tab tebibyte (2^40)
+@item P @tab petabyte (10^15) @tab | @tab Pi @tab pebibyte (2^50)
+@item E @tab exabyte (10^18) @tab | @tab Ei @tab exbibyte (2^60)
+@item Z @tab zettabyte (10^21) @tab | @tab Zi @tab zebibyte (2^70)
+@item Y @tab yottabyte (10^24) @tab | @tab Yi @tab yobibyte (2^80)
+@end multitable
+
+
+@node File Format
+@chapter File Format
+@cindex file format
+
+In the diagram below, a box like this:
+@verbatim
++---+
+| | <-- the vertical bars might be missing
++---+
+@end verbatim
+
+represents one byte; a box like this:
+@verbatim
++==============+
+| |
++==============+
+@end verbatim
+
+represents a variable number of bytes.
+
+@sp 1
+A lzip file consists of a series of "members" (compressed data sets).
+The members simply appear one after another in the file, with no
+additional information before, between, or after them.
+
+Each member has the following structure:
+@verbatim
++--+--+--+--+----+----+=============+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| ID string | VN | DS | Lzma stream | CRC32 | Data size | Member size |
++--+--+--+--+----+----+=============+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+@end verbatim
+
+All multibyte values are stored in little endian order.
+
+@table @samp
+@item ID string
+A four byte string, identifying the member type, with the value "LZIP".
+
+@item VN (version number, 1 byte)
+Just in case something needs to be modified in the future. Valid values
+are 0 and 1. Version 0 files have only one member and lack @samp{Member
+size}.
+
+@item DS (coded dictionary size, 1 byte)
+Bits 4-0 contain the base 2 logarithm of the base dictionary size.@*
+Bits 7-5 contain the number of "wedges" to substract from the base
+dictionary size to obtain the dictionary size. The size of a wedge is
+(base dictionary size / 16).@*
+Valid values for dictionary size range from 4KiB to 512MiB.
+
+@item Lzma stream
+The lzma stream, finished by an end of stream marker. Uses default values
+for encoder properties.
+
+@item CRC32 (4 bytes)
+CRC of the uncompressed original data.
+
+@item Data size (8 bytes)
+Size of the uncompressed original data.
+
+@item Member size (8 bytes)
+Total size of the member, including header and trailer. This facilitates
+safe recovery of undamaged members from multimember files.
+
+@end table
+
+
+@node Problems
+@chapter Reporting Bugs
+@cindex bugs
+@cindex getting help
+
+There are probably bugs in plzip. There are certainly errors and
+omissions in this manual. If you report them, they will get fixed. If
+you don't, no one will ever know about them and they will remain unfixed
+for all eternity, if not longer.
+
+If you find a bug in plzip, please send electronic mail to
+@email{lzip-bug@@nongnu.org}. Include the version number, which you can
+find by running @w{@samp{plzip --version}}.
+
+
+@node Concept Index
+@unnumbered Concept Index
+
+@printindex cp
+
+@bye