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diff --git a/doc/plzip.info b/doc/plzip.info index 2070f4f..72e9511 100644 --- a/doc/plzip.info +++ b/doc/plzip.info @@ -12,16 +12,16 @@ File: plzip.info, Node: Top, Next: Introduction, Up: (dir) Plzip Manual ************ -This manual is for Plzip (version 1.0, 29 May 2013). +This manual is for Plzip (version 1.1-pre1, 20 July 2013). * 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 Copyright (C) 2009, 2010, 2011, 2012, 2013 Antonio Diaz Diaz. @@ -30,27 +30,46 @@ This manual is for Plzip (version 1.0, 29 May 2013). copy, distribute and modify it. -File: plzip.info, Node: Introduction, Next: Program Design, Prev: Top, Up: Top +File: plzip.info, Node: Introduction, Next: Program design, Prev: Top, Up: Top 1 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 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. - 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. + 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 @@ -76,18 +95,6 @@ filename.lz becomes filename filename.tlz becomes filename.tar anyothername becomes anyothername.out - 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, @@ -96,9 +103,9 @@ until you verify the compressed file with a command like `plzip -cd file.lz | cmp file -'. -File: plzip.info, Node: Program Design, Next: Invoking Plzip, Prev: Introduction, Up: Top +File: plzip.info, Node: Program design, Next: Invoking plzip, Prev: Introduction, Up: Top -2 Program Design +2 Program design **************** For each input file, a splitter thread and several worker threads are @@ -119,9 +126,9 @@ speed of large files with many members is only limited by the number of processors available and by I/O speed. -File: plzip.info, Node: Invoking Plzip, Next: File Format, Prev: Program Design, Up: Top +File: plzip.info, Node: Invoking plzip, Next: File format, Prev: Program design, Up: Top -3 Invoking Plzip +3 Invoking plzip **************** The format for running plzip is: @@ -220,7 +227,7 @@ The format for running plzip is: `--verbose' Verbose mode. When compressing, show the compression ratio for each file - processed. + 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. @@ -275,9 +282,9 @@ invalid input file, 3 for an internal consistency error (eg, bug) which caused plzip to panic. -File: plzip.info, Node: File Format, Next: Problems, Prev: Invoking Plzip, Up: Top +File: plzip.info, Node: File format, Next: Problems, Prev: Invoking plzip, Up: Top -4 File Format +4 File format ************* Perfection is reached, not when there is no longer anything to add, but @@ -348,7 +355,7 @@ additional information before, between, or after them. -File: plzip.info, Node: Problems, Next: Concept Index, Prev: File Format, Up: Top +File: plzip.info, Node: Problems, Next: Concept index, Prev: File format, Up: Top 5 Reporting Bugs **************** @@ -363,34 +370,34 @@ for all eternity, if not longer. by running `plzip --version'. -File: plzip.info, Node: Concept Index, Prev: Problems, Up: Top +File: plzip.info, Node: Concept index, Prev: Problems, Up: Top -Concept Index +Concept index ************* * Menu: * bugs: Problems. (line 6) -* file format: File Format. (line 6) +* file format: File format. (line 6) * getting help: Problems. (line 6) * introduction: Introduction. (line 6) -* invoking: Invoking Plzip. (line 6) -* options: Invoking Plzip. (line 6) -* program design: Program Design. (line 6) -* usage: Invoking Plzip. (line 6) -* version: Invoking Plzip. (line 6) +* invoking: Invoking plzip. (line 6) +* options: Invoking plzip. (line 6) +* program design: Program design. (line 6) +* usage: Invoking plzip. (line 6) +* version: Invoking plzip. (line 6) Tag Table: Node: Top223 -Node: Introduction865 -Node: Program Design4113 -Node: Invoking Plzip5167 -Node: File Format10416 -Node: Problems12895 -Node: Concept Index13424 +Node: Introduction871 +Node: Program design4426 +Node: Invoking plzip5480 +Node: File format10776 +Node: Problems13255 +Node: Concept index13784 End Tag Table |