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diff --git a/doc/plzip.info b/doc/plzip.info index c38ea5c..becd133 100644 --- a/doc/plzip.info +++ b/doc/plzip.info @@ -11,13 +11,13 @@ File: plzip.info, Node: Top, Next: Introduction, Up: (dir) Plzip Manual ************ -This manual is for Plzip (version 1.10, 24 January 2022). +This manual is for Plzip (version 1.11, 21 January 2024). * Menu: * Introduction:: Purpose and features of plzip * Output:: Meaning of plzip's output -* Invoking plzip:: Command line interface +* Invoking plzip:: Command-line interface * Program design:: Internal structure of plzip * Memory requirements:: Memory required to compress and decompress * Minimum file sizes:: Minimum file sizes required for full speed @@ -28,7 +28,7 @@ This manual is for Plzip (version 1.10, 24 January 2022). * Concept index:: Index of concepts - Copyright (C) 2009-2022 Antonio Diaz Diaz. + Copyright (C) 2009-2024 Antonio Diaz Diaz. This manual is free documentation: you have unlimited permission to copy, distribute, and modify it. @@ -39,19 +39,20 @@ File: plzip.info, Node: Introduction, Next: Output, Prev: Top, Up: Top 1 Introduction ************** -Plzip is a massively parallel (multi-threaded) implementation of lzip, fully +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 and provides a 3 factor integrity -checking to maximize interoperability and optimize safety. 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. +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 @@ -94,10 +95,10 @@ byte near the beginning is a thing of the past. 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 will automatically use 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. *Note Memory requirements::. + 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. *Note Memory requirements::. When compressing, plzip replaces every file given in the command line with a compressed version of itself, with the name "original_name.lz". When @@ -109,22 +110,22 @@ 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, when -possible, 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). +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. - Plzip will refuse 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 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 will correctly decompress 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. + 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. File: plzip.info, Node: Output, Next: Invoking plzip, Prev: Introduction, Up: Top @@ -185,7 +186,8 @@ The format for running plzip is: If no file names are specified, plzip compresses (or decompresses) from standard input to standard output. A hyphen '-' used as a FILE argument means standard input. It can be mixed with other FILES and is read just -once, the first time it appears in the command line. +once, the first time it appears in the command line. Remember to prepend +'./' to any file name beginning with a hyphen, or use '--'. plzip supports the following options: *Note Argument syntax: (arg_parser)Argument syntax. @@ -208,30 +210,32 @@ once, the first time it appears in the command line. '-B BYTES' '--data-size=BYTES' When compressing, set the size in bytes of the input data blocks. The - input file will be divided in chunks of this size before compression is + input file is divided in chunks of this size before compression is performed. Valid values range from 8 KiB to 1 GiB. Default value is two times the dictionary size, except for option '-0' where it - defaults to 1 MiB. Plzip will reduce the dictionary size if it is - larger than the data size specified. *Note Minimum file sizes::. + defaults to 1 MiB. Plzip reduces the dictionary size if it is larger + than the data size specified. *Note Minimum file sizes::. '-c' '--stdout' Compress or decompress to standard output; keep input files unchanged. If compressing several files, each file is compressed independently. - This option (or '-o') is needed when reading from a named pipe (fifo) - or from a device. Use 'lziprecover -cd -i' to recover as much of the - decompressed data as possible when decompressing a corrupt file. '-c' - overrides '-o'. '-c' has no effect when testing or listing. + (The output consists of a sequence of independently compressed + members). This option (or '-o') is needed when reading from a named + pipe (fifo) or from a device. Use 'lziprecover -cd -i' to recover as + much of the decompressed data as possible when decompressing a corrupt + file. '-c' overrides '-o'. '-c' has no effect when testing or listing. '-d' '--decompress' - Decompress the files specified. If a file does not exist, can't be - opened, or the destination file already exists and '--force' has not - been specified, plzip continues decompressing the rest of the files - and exits with error status 1. If a file fails to decompress, or is a - terminal, plzip exits immediately with error status 2 without - decompressing the rest of the files. A terminal is considered an - uncompressed file, and therefore invalid. + Decompress the files specified. The integrity of the files specified is + checked. If a file does not exist, can't be opened, or the destination + file already exists and '--force' has not been specified, plzip + continues decompressing the rest of the files and exits with error + status 1. If a file fails to decompress, or is a terminal, plzip exits + immediately with error status 2 without decompressing the rest of the + files. A terminal is considered an uncompressed file, and therefore + invalid. '-f' '--force' @@ -258,18 +262,18 @@ once, the first time it appears in the command line. printed. If any file is damaged, does not exist, can't be opened, or is not - regular, the final exit status will be > 0. '-lq' can be used to verify + regular, the final exit status is > 0. '-lq' can be used to check quickly (without decompressing) the structural integrity of the files - specified. (Use '--test' to verify the data integrity). '-alq' - additionally verifies that none of the files specified contain - trailing data. + specified. (Use '--test' to check the data integrity). '-alq' + additionally checks that none of the files specified contain trailing + data. '-m BYTES' '--match-length=BYTES' When compressing, set the match length limit in bytes. After a match this long is found, the search is finished. Valid values range from 5 - to 273. Larger values usually give better compression ratios but longer - compression times. + to 273. Larger values usually give better compression ratios but + longer compression times. '-n N' '--threads=N' @@ -291,10 +295,12 @@ once, the first time it appears in the command line. '-o FILE' '--output=FILE' - If '-c' has not been also specified, write the (de)compressed output to - FILE; keep input files unchanged. If compressing several files, each - file is compressed independently. This option (or '-c') is needed when - reading from a named pipe (fifo) or from a device. '-o -' is + If '-c' has not been also specified, write the (de)compressed output + to FILE, automatically creating any missing parent directories; keep + input files unchanged. If compressing several files, each file is + compressed independently. (The output consists of a sequence of + independently compressed members). This option (or '-c') is needed + when reading from a named pipe (fifo) or from a device. '-o -' is equivalent to '-c'. '-o' has no effect when testing or listing. In order to keep backward compatibility with plzip versions prior to @@ -311,14 +317,14 @@ once, the first time it appears in the command line. '-s BYTES' '--dictionary-size=BYTES' - When compressing, set the dictionary size limit in bytes. Plzip will - use for each file the largest dictionary size that does not exceed - neither the file size nor this limit. Valid values range from 4 KiB to - 512 MiB. Values 12 to 29 are interpreted as powers of two, meaning - 2^12 to 2^29 bytes. Dictionary sizes are quantized so that they can be - coded in just one byte (*note coded-dict-size::). If the size specified - does not match one of the valid sizes, it will be rounded upwards by - adding up to (BYTES / 8) to it. + When compressing, set the dictionary size limit in bytes. Plzip uses + for each file the largest dictionary size that does not exceed neither + the file size nor this limit. Valid values range from 4 KiB to 512 MiB. + Values 12 to 29 are interpreted as powers of two, meaning 2^12 to 2^29 + bytes. Dictionary sizes are quantized so that they can be coded in + just one byte (*note coded-dict-size::). If the size specified does + not match one of the valid sizes, it is rounded upwards by adding up + to (BYTES / 8) to it. For maximum compression you should use a dictionary size limit as large as possible, but keep in mind that the decompression memory requirement @@ -330,7 +336,7 @@ once, the first time it appears in the command line. really performs a trial decompression and throws away the result. Use it together with '-v' to see information about the files. If a file fails the test, does not exist, can't be opened, or is a terminal, - plzip continues checking the rest of the files. A final diagnostic is + plzip continues testing the rest of the files. A final diagnostic is shown at verbosity level 1 or higher if any file fails the test when testing multiple files. @@ -408,26 +414,29 @@ once, the first time it appears in the command line. (lzlib)Library version. - Numbers given as arguments to options may be followed by a multiplier -and an optional 'B' for "byte". + Numbers given as arguments to options may be expressed in decimal, +hexadecimal, or octal (using the same syntax as integer constants in C++), +and may be followed by a multiplier and an optional 'B' for "byte". Table of SI and binary prefixes (unit multipliers): -Prefix Value | Prefix Value -k kilobyte (10^3 = 1000) | Ki kibibyte (2^10 = 1024) -M megabyte (10^6) | Mi mebibyte (2^20) -G gigabyte (10^9) | Gi gibibyte (2^30) -T terabyte (10^12) | Ti tebibyte (2^40) -P petabyte (10^15) | Pi pebibyte (2^50) -E exabyte (10^18) | Ei exbibyte (2^60) -Z zettabyte (10^21) | Zi zebibyte (2^70) -Y yottabyte (10^24) | Yi yobibyte (2^80) +Prefix Value | Prefix Value +k kilobyte (10^3 = 1000) | Ki kibibyte (2^10 = 1024) +M megabyte (10^6) | Mi mebibyte (2^20) +G gigabyte (10^9) | Gi gibibyte (2^30) +T terabyte (10^12) | Ti tebibyte (2^40) +P petabyte (10^15) | Pi pebibyte (2^50) +E exabyte (10^18) | Ei exbibyte (2^60) +Z zettabyte (10^21) | Zi zebibyte (2^70) +Y yottabyte (10^24) | Yi yobibyte (2^80) +R ronnabyte (10^27) | Ri robibyte (2^90) +Q quettabyte (10^30) | Qi quebibyte (2^100) 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 (e.g., bug) which caused -plzip to panic. +found, invalid command-line options, I/O errors, etc), 2 to indicate a +corrupt or invalid input file, 3 for an internal consistency error (e.g., +bug) which caused plzip to panic. File: plzip.info, Node: Program design, Next: Memory requirements, Prev: Invoking plzip, Up: Top @@ -441,7 +450,7 @@ 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 will not be +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. @@ -535,10 +544,10 @@ multimember compressed file. For this to work as expected (and roughly multiply the compression speed by the number of available processors), the uncompressed file must be at least as large as the number of worker threads times the chunk size (*note ---data-size::). Else some processors will not get any data to compress, and -compression will be proportionally slower. The maximum speed increase -achievable on a given file is limited by the ratio (file_size / data_size). -For example, a tarball the size of gcc or linux will scale up to 10 or 14 +--data-size::). Else some processors do not get any data to compress, and +compression is proportionally slower. The maximum speed increase achievable +on a given file is limited by the ratio (file_size / data_size). For +example, a tarball the size of gcc or linux scales up to 10 or 14 processors at level -9. The following table shows the minimum uncompressed file size needed for @@ -585,7 +594,7 @@ when there is no longer anything to take away. represents a variable number of bytes. - A lzip file consists of a series of independent "members" (compressed + A lzip file consists of one or more independent "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 can encode in compressed form up to 16 EiB - 1 byte of uncompressed data. The @@ -629,10 +638,10 @@ size of a multimember file is unlimited. 'Member size (8 bytes)' Total size of the member, including header and trailer. This field acts - as a distributed index, allows the verification of stream integrity, - and facilitates the safe recovery of undamaged members from - multimember files. Member size should be limited to 2 PiB to prevent - the data size field from overflowing. + as a distributed index, improves the checking of stream integrity, and + facilitates the safe recovery of undamaged members from multimember + files. Lzip limits the member size to 2 PiB to prevent the data size + field from overflowing. @@ -648,12 +657,13 @@ member. Such trailing data may be: example when writing to a tape. It is safe to append any amount of padding zero bytes to a lzip file. - * Useful data added by the user; a cryptographically secure hash, a + * Useful data added by the user; an "End Of File" string (to check that + the file has not been truncated), a cryptographically secure hash, a description of file contents, etc. It is safe to append any amount of - text to a lzip file as long as none of the first four bytes of the text - match the corresponding byte in the string "LZIP", and the text does - not contain any zero bytes (null characters). Nonzero bytes and zero - bytes can't be safely mixed in trailing data. + text to a lzip file as long as none of the first four bytes of the + text matches the corresponding byte in the string "LZIP", and the text + does not contain any zero bytes (null characters). Nonzero bytes and + zero bytes can't be safely mixed in trailing data. * Garbage added by some not totally successful copy operation. @@ -669,7 +679,7 @@ member. Such trailing data may be: discriminate trailing data from a corrupt header has a Hamming distance (HD) of 3, and the 3 bit flips must happen in different magic bytes for the test to fail. In any case, the option '--trailing-error' - guarantees that any corrupt header will be detected. + guarantees that any corrupt header is detected. Trailing data are in no way part of the lzip file format, but tools reading lzip files are expected to behave as correctly and usefully as @@ -689,12 +699,12 @@ File: plzip.info, Node: Examples, Next: Problems, Prev: Trailing data, Up: T 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 are important, give the -option '--keep' to plzip and don't remove the original file until you -verify the compressed file with a command like -'plzip -cd file.lz | cmp file -'. Most RAM errors happening during -compression can only be detected by comparing the compressed file with the -original because the corruption happens before plzip compresses the RAM -contents, resulting in a valid compressed file containing wrong data. +option '--keep' to plzip and don't remove the original file until you check +the compressed file with a command like 'plzip -cd file.lz | cmp file -'. +Most RAM errors happening during compression can only be detected by +comparing the compressed file with the original because the corruption +happens before plzip compresses the RAM contents, resulting in a valid +compressed file containing wrong data. Example 1: Extract all the files from archive 'foo.tar.lz'. @@ -722,7 +732,7 @@ the operation is successful, 'file.lz' is removed. plzip -d file.lz -Example 5: Verify the integrity of the compressed file 'file.lz' and show +Example 5: Check the integrity of the compressed file 'file.lz' and show status. plzip -tv file.lz @@ -800,20 +810,20 @@ Concept index Tag Table: Node: Top217 Node: Introduction1156 -Node: Output5829 -Node: Invoking plzip7392 -Ref: --trailing-error8187 -Ref: --data-size8425 -Node: Program design18819 -Node: Memory requirements21122 -Node: Minimum file sizes22807 -Node: File format24821 -Ref: coded-dict-size26260 -Node: Trailing data27514 -Node: Examples29775 -Ref: concat-example31210 -Node: Problems31967 -Node: Concept index32522 +Node: Output5934 +Node: Invoking plzip7497 +Ref: --trailing-error8372 +Ref: --data-size8610 +Node: Program design19519 +Node: Memory requirements21818 +Node: Minimum file sizes23503 +Node: File format25506 +Ref: coded-dict-size26945 +Node: Trailing data28195 +Node: Examples30531 +Ref: concat-example31964 +Node: Problems32721 +Node: Concept index33276 End Tag Table |