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diff --git a/doc/plzip.texinfo b/doc/plzip.texinfo index b832884..c3b0613 100644 --- a/doc/plzip.texinfo +++ b/doc/plzip.texinfo @@ -6,8 +6,8 @@ @finalout @c %**end of header -@set UPDATED 29 May 2013 -@set VERSION 1.0 +@set UPDATED 20 July 2013 +@set VERSION 1.1-pre1 @dircategory Data Compression @direntry @@ -36,11 +36,11 @@ This manual is for Plzip (version @value{VERSION}, @value{UPDATED}). @menu * Introduction:: Purpose and features of plzip -* Program Design:: Internal structure of plzip -* Invoking Plzip:: Command line interface -* File Format:: Detailed format of the compressed file +* Program design:: Internal structure of plzip +* Invoking plzip:: Command line interface +* File format:: Detailed format of the compressed file * Problems:: Reporting bugs -* Concept Index:: Index of concepts +* Concept index:: Index of concepts @end menu @sp 1 @@ -55,21 +55,40 @@ to copy, distribute and modify it. @cindex introduction Plzip is a massively parallel (multi-threaded), lossless data compressor -based on the lzlib compression library, with very safe integrity -checking and a user interface similar to the one of bzip2, gzip or lzip. +based on the lzlib compression library, with a user interface similar to +the one of lzip, bzip2 or gzip. -Plzip is intended for faster compression/decompression of big files on -multiprocessor machines, which makes it specially well suited for -distribution of big software files and large scale data archiving. On -files big enough (several GB), plzip can use hundreds of processors. - -Plzip uses the lzip file format; the files produced by plzip are fully -compatible with lzip-1.4 or newer, and can be rescued with lziprecover. +Plzip can compress/decompress large files on multiprocessor machines +much faster than lzip, at the cost of a slightly reduced compression +ratio. On files large enough (several GB), plzip can use hundreds of +processors. On files of only a few MB it is better to use lzip. Plzip uses the same well-defined exit status values used by lzip and bzip2, which makes it safer when used in pipes or scripts than compressors returning ambiguous warning values, like gzip. +Plzip uses the lzip file format; the files produced by plzip are fully +compatible with lzip-1.4 or newer, and can be rescued with lziprecover. + +The lzip file format is designed for long-term data archiving and +provides very safe integrity checking. The member trailer stores the +32-bit CRC of the original data, the size of the original data and the +size of the member. These values, together with the value remaining in +the range decoder and the end-of-stream marker, provide a 4 factor +integrity checking which guarantees 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. 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. + +If you ever need to recover data from a damaged lzip file, try the +lziprecover program. Lziprecover makes lzip files resistant to bit-flip +(one of the most common forms of data corruption), and provides data +recovery capabilities, including error-checked merging of damaged copies +of a file. + 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, @@ -96,18 +115,6 @@ file from that of the compressed file as follows: @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, the size of the original data and -the size of the member. These values, together with the value remaining -in the range decoder and the end-of-stream marker, provide a very safe 4 -factor integrity checking which guarantees 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. 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. - WARNING! Even if plzip is bug-free, other causes may result in a corrupt compressed file (bugs in the system libraries, memory errors, etc). Therefore, if the data you are going to compress is important, give the @@ -116,8 +123,8 @@ you verify the compressed file with a command like @w{@samp{plzip -cd file.lz | cmp file -}}. -@node Program Design -@chapter Program Design +@node Program design +@chapter Program design @cindex program design For each input file, a splitter thread and several worker threads are @@ -138,8 +145,8 @@ large files with many members is only limited by the number of processors available and by I/O speed. -@node Invoking Plzip -@chapter Invoking Plzip +@node Invoking plzip +@chapter Invoking plzip @cindex invoking @cindex options @cindex usage @@ -237,7 +244,8 @@ Use it together with @samp{-v} to see information about the file. @item -v @itemx --verbose Verbose mode.@* -When compressing, show the compression ratio for each file processed.@* +When compressing, show the compression ratio for each file processed. A +second -v shows the progress of compression.@* When decompressing or testing, further -v's (up to 4) increase the verbosity level, showing status, compression ratio, decompressed size, and compressed size. @@ -297,8 +305,8 @@ invalid input file, 3 for an internal consistency error (eg, bug) which caused plzip to panic. -@node File Format -@chapter File Format +@node File format +@chapter File format @cindex file format Perfection is reached, not when there is no longer anything to add, but @@ -387,8 +395,8 @@ If you find a bug in plzip, please send electronic mail to find by running @w{@samp{plzip --version}}. -@node Concept Index -@unnumbered Concept Index +@node Concept index +@unnumbered Concept index @printindex cp |