diff options
Diffstat (limited to 'doc/plzip.texinfo')
| -rw-r--r-- | doc/plzip.texinfo | 63 |
1 files changed, 35 insertions, 28 deletions
diff --git a/doc/plzip.texinfo b/doc/plzip.texinfo index 5e62234..b832884 100644 --- a/doc/plzip.texinfo +++ b/doc/plzip.texinfo @@ -6,8 +6,8 @@ @finalout @c %**end of header -@set UPDATED 8 March 2013 -@set VERSION 1.0-rc1 +@set UPDATED 29 May 2013 +@set VERSION 1.0 @dircategory Data Compression @direntry @@ -35,12 +35,12 @@ 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 -* Problems:: Reporting bugs -* Concept Index:: Index of concepts +* 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 +* Problems:: Reporting bugs +* Concept Index:: Index of concepts @end menu @sp 1 @@ -57,13 +57,18 @@ to copy, distribute and modify it. 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. -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 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, plzip can use hundreds of processors. +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 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 replaces every file given in the command line with a compressed version of itself, with the name "original_name.lz". Each compressed @@ -92,15 +97,16 @@ file from that of the compressed file as follows: @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. +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). @@ -109,11 +115,6 @@ Therefore, if the data you are going to compress is important, give the you verify the compressed file with a command like @w{@samp{plzip -cd file.lz | cmp file -}}. -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 Program Design @chapter Program Design @@ -289,6 +290,12 @@ Table of SI and binary prefixes (unit multipliers): @item Y @tab yottabyte (10^24) @tab | @tab Yi @tab yobibyte (2^80) @end multitable +@sp 1 +Exit status: 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 File Format @chapter File Format @@ -349,7 +356,7 @@ 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. +for encoder properties. See the lzip manual for a full description. @item CRC32 (4 bytes) CRC of the uncompressed original data. @@ -359,8 +366,8 @@ Size of the uncompressed original data. @item Member size (8 bytes) Total size of the member, including header and trailer. This field acts -as a distributed index, and facilitates safe recovery of undamaged -members from multi-member files. +as a distributed index, allows the verification of stream integrity, and +facilitates safe recovery of undamaged members from multi-member files. @end table |