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diff --git a/doc/plzip.texi b/doc/plzip.texi index 818ecf5..323fad1 100644 --- a/doc/plzip.texi +++ b/doc/plzip.texi @@ -6,8 +6,8 @@ @finalout @c %**end of header -@set UPDATED 24 January 2022 -@set VERSION 1.10 +@set UPDATED 21 January 2024 +@set VERSION 1.11 @dircategory Compression @direntry @@ -38,7 +38,7 @@ This manual is for Plzip (version @value{VERSION}, @value{UPDATED}). @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 @@ -50,7 +50,7 @@ This manual is for Plzip (version @value{VERSION}, @value{UPDATED}). @end menu @sp 1 -Copyright @copyright{} 2009-2022 Antonio Diaz Diaz. +Copyright @copyright{} 2009-2024 Antonio Diaz Diaz. This manual is free documentation: you have unlimited permission to copy, distribute, and modify it. @@ -62,21 +62,22 @@ distribute, and modify it. @cindex introduction @uref{http://www.nongnu.org/lzip/plzip.html,,Plzip} -is a massively parallel (multi-threaded) implementation of lzip, fully +is a massively parallel (multi-threaded) implementation of lzip, compatible with lzip 1.4 or newer. Plzip uses the compression library @uref{http://www.nongnu.org/lzip/lzlib.html,,lzlib}. @uref{http://www.nongnu.org/lzip/lzip.html,,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 @w{(lzip -0)} or compress most files more than bzip2 -@w{(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 @w{(lzip -0)} or compress most +files more than bzip2 @w{(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 @@ -130,9 +131,9 @@ Plzip uses the same well-defined exit status values used by lzip, which 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 +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. @xref{Memory requirements}. When compressing, plzip replaces every file given in the command line @@ -147,19 +148,19 @@ file from that of the compressed file as follows: @end multitable (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 @w{@samp{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 @w{@samp{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 @samp{-c} or the option @samp{-o} is specified. +option @option{-c} or the option @option{-o} is specified. -Plzip will refuse to read compressed data from a terminal or write compressed +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 +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. @@ -231,7 +232,8 @@ plzip [@var{options}] [@var{files}] If no file names are specified, plzip compresses (or decompresses) from standard input to standard output. A hyphen @samp{-} used as a @var{file} argument means standard input. It can be mixed with other @var{files} and is -read just once, the first time it appears in the command line. +read just once, the first time it appears in the command line. Remember to +prepend @file{./} to any file name beginning with a hyphen, or use @samp{--}. plzip supports the following @uref{http://www.nongnu.org/arg-parser/manual/arg_parser_manual.html#Argument-syntax,,options}: @@ -259,30 +261,32 @@ garbage that can be safely ignored. @xref{concat-example}. @anchor{--data-size} @item -B @var{bytes} @itemx --data-size=@var{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 -performed. Valid values range from @w{8 KiB} to @w{1 GiB}. Default value -is two times the dictionary size, except for option @samp{-0} where it -defaults to @w{1 MiB}. Plzip will reduce the dictionary size if it is -larger than the data size specified. @xref{Minimum file sizes}. +When compressing, set the size in bytes of the input data blocks. The input +file is divided in chunks of this size before compression is performed. +Valid values range from @w{8 KiB} to @w{1 GiB}. Default value is two times +the dictionary size, except for option @option{-0} where it defaults to +@w{1 MiB}. Plzip reduces the dictionary size if it is larger than the data +size specified. @xref{Minimum file sizes}. @item -c @itemx --stdout Compress or decompress to standard output; keep input files unchanged. If -compressing several files, each file is compressed independently. This -option (or @samp{-o}) is needed when reading from a named pipe (fifo) or +compressing several files, each file is compressed independently. (The +output consists of a sequence of independently compressed members). This +option (or @option{-o}) is needed when reading from a named pipe (fifo) or from a device. Use @w{@samp{lziprecover -cd -i}} to recover as much of the -decompressed data as possible when decompressing a corrupt file. @samp{-c} -overrides @samp{-o}. @samp{-c} has no effect when testing or listing. +decompressed data as possible when decompressing a corrupt file. @option{-c} +overrides @option{-o}. @option{-c} has no effect when testing or listing. @item -d @itemx --decompress -Decompress the files specified. If a file does not exist, can't be opened, -or the destination file already exists and @samp{--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 @option{--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. @item -f @itemx --force @@ -302,23 +306,23 @@ Keep (don't delete) input files during compression or decompression. Print the uncompressed size, compressed size, and percentage saved of the files specified. Trailing data are ignored. The values produced are correct even for multimember files. If more than one file is given, a final line -containing the cumulative sizes is printed. With @samp{-v}, the dictionary +containing the cumulative sizes is printed. With @option{-v}, the dictionary size, the number of members in the file, and the amount of trailing data (if -any) are also printed. With @samp{-vv}, the positions and sizes of each +any) are also printed. With @option{-vv}, the positions and sizes of each member in multimember files are also printed. If any file is damaged, does not exist, can't be opened, or is not regular, -the final exit status will be @w{> 0}. @samp{-lq} can be used to verify -quickly (without decompressing) the structural integrity of the files -specified. (Use @samp{--test} to verify the data integrity). @samp{-alq} -additionally verifies that none of the files specified contain trailing data. +the final exit status is @w{> 0}. @option{-lq} can be used to check quickly +(without decompressing) the structural integrity of the files specified. +(Use @option{--test} to check the data integrity). @option{-alq} +additionally checks that none of the files specified contain trailing data. @item -m @var{bytes} @itemx --match-length=@var{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. +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. @item -n @var{n} @itemx --threads=@var{n} @@ -339,17 +343,19 @@ can find the number of members in a lzip file by running @item -o @var{file} @itemx --output=@var{file} -If @samp{-c} has not been also specified, write the (de)compressed output to -@var{file}; keep input files unchanged. If compressing several files, each -file is compressed independently. This option (or @samp{-c}) is needed when -reading from a named pipe (fifo) or from a device. @w{@samp{-o -}} is -equivalent to @samp{-c}. @samp{-o} has no effect when testing or listing. +If @option{-c} has not been also specified, write the (de)compressed output +to @var{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 @option{-c}) is needed when reading +from a named pipe (fifo) or from a device. @w{@option{-o -}} is equivalent +to @option{-c}. @option{-o} has no effect when testing or listing. In order to keep backward compatibility with plzip versions prior to 1.9, when compressing from standard input and no other file names are given, the extension @samp{.lz} is appended to @var{file} unless it already ends in @samp{.lz} or @samp{.tlz}. This feature will be removed in a future version -of plzip. Meanwhile, redirection may be used instead of @samp{-o} to write +of plzip. Meanwhile, redirection may be used instead of @option{-o} to write the compressed output to a file without the extension @samp{.lz} in its name: @w{@samp{plzip < file > foo}}. @@ -359,14 +365,14 @@ Quiet operation. Suppress all messages. @item -s @var{bytes} @itemx --dictionary-size=@var{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 @w{4 KiB} to -@w{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 (@pxref{coded-dict-size}). If the size specified -does not match one of the valid sizes, it will be rounded upwards by -adding up to @w{(@var{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 @w{4 KiB} to @w{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 (@pxref{coded-dict-size}). If the size specified does not match one of +the valid sizes, it is rounded upwards by adding up to @w{(@var{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 @@ -376,11 +382,11 @@ is affected at compression time by the choice of dictionary size limit. @itemx --test Check integrity of the files specified, but don't decompress them. This really performs a trial decompression and throws away the result. Use it -together with @samp{-v} to see information about the files. If a file +together with @option{-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 shown at -verbosity level 1 or higher if any file fails the test when testing -multiple files. +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. @item -v @itemx --verbose @@ -390,24 +396,24 @@ processed.@* When decompressing or testing, further -v's (up to 4) increase the verbosity level, showing status, compression ratio, dictionary size, decompressed size, and compressed size.@* -Two or more @samp{-v} options show the progress of (de)compression, +Two or more @option{-v} options show the progress of (de)compression, except for single-member files. @item -0 .. -9 Compression level. Set the compression parameters (dictionary size and match length limit) as shown in the table below. The default compression -level is @samp{-6}, equivalent to @w{@samp{-s8MiB -m36}}. Note that -@samp{-9} can be much slower than @samp{-0}. These options have no +level is @option{-6}, equivalent to @w{@option{-s8MiB -m36}}. Note that +@option{-9} can be much slower than @option{-0}. These options have no effect when decompressing, testing, or listing. -The bidimensional parameter space of LZMA can't be mapped to a linear -scale optimal for all files. If your files are large, very repetitive, -etc, you may need to use the options @samp{--dictionary-size} and -@samp{--match-length} directly to achieve optimal performance. +The bidimensional parameter space of LZMA can't be mapped to a linear scale +optimal for all files. If your files are large, very repetitive, etc, you +may need to use the options @option{--dictionary-size} and +@option{--match-length} directly to achieve optimal performance. -If several compression levels or @samp{-s} or @samp{-m} options are -given, the last setting is used. For example @w{@samp{-9 -s64MiB}} is -equivalent to @w{@samp{-s64MiB -m273}} +If several compression levels or @option{-s} or @option{-m} options are +given, the last setting is used. For example @w{@option{-9 -s64MiB}} is +equivalent to @w{@option{-s64MiB -m273}} @multitable {Level} {Dictionary size (-s)} {Match length limit (-m)} @item Level @tab Dictionary size (-s) @tab Match length limit (-m) @@ -461,28 +467,31 @@ and the value of LZ_API_VERSION (if defined). @end table -Numbers given as arguments to options may be followed by a multiplier -and an optional @samp{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 @samp{B} for "byte". Table of SI and binary prefixes (unit multipliers): -@multitable {Prefix} {kilobyte (10^3 = 1000)} {|} {Prefix} {kibibyte (2^10 = 1024)} +@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) +@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) +@item R @tab ronnabyte (10^27) @tab | @tab Ri @tab robibyte (2^90) +@item Q @tab quettabyte (10^30) @tab | @tab Qi @tab quebibyte (2^100) @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 (e.g., bug) which caused -plzip to panic. +Exit status: 0 for a normal exit, 1 for environmental problems +(file not 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. @node Program design @@ -495,8 +504,8 @@ 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 decompressed faster than using lzip (unless the option @samp{-b} was used) +worker threads are chosen. Files that were compressed with lzip are not +decompressed faster than using lzip (unless the option @option{-b} was used) because lzip usually produces single-member files, which can't be decompressed in parallel. @@ -600,14 +609,14 @@ When compressing, plzip divides the input file into chunks and compresses as many chunks simultaneously as worker threads are chosen, creating a 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 -(@pxref{--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 -@w{(file_size / data_size)}. For example, a tarball the size of gcc or -linux will scale up to 10 or 14 processors at level -9. +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 +(@pxref{--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 +@w{(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 full use of N processors at a given compression level, using the default @@ -657,7 +666,7 @@ represents one byte; a box like this: represents a variable number of bytes. @sp 1 -A lzip file consists of a series of independent "members" (compressed data +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 @w{16 EiB - 1 byte} of uncompressed data. @@ -711,10 +720,10 @@ Size of the original uncompressed data. @item 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 +as a distributed index, improves the checking of stream integrity, and facilitates the safe recovery of undamaged members from multimember files. -Member size should be limited to @w{2 PiB} to prevent the data size field -from overflowing. +Lzip limits the member size to @w{2 PiB} to prevent the data size field from +overflowing. @end table @@ -733,12 +742,13 @@ example when writing to a tape. It is safe to append any amount of padding zero bytes to a lzip file. @item -Useful data added by the user; 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. +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 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. @item Garbage added by some not totally successful copy operation. @@ -756,8 +766,8 @@ integrity information itself. Therefore it can be considered to be below the noise level. Additionally, the test used by plzip to 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 @samp{--trailing-error} guarantees that -any corrupt header will be detected. +fail. In any case, the option @option{--trailing-error} guarantees that +any corrupt header is detected. @end itemize Trailing data are in no way part of the lzip file format, but tools @@ -767,7 +777,7 @@ possible in the presence of trailing data. Trailing data can be safely ignored in most cases. In some cases, like that of user-added data, they are expected to be ignored. In those cases where a file containing trailing data must be rejected, the option -@samp{--trailing-error} can be used. @xref{--trailing-error}. +@option{--trailing-error} can be used. @xref{--trailing-error}. @node Examples @@ -777,8 +787,8 @@ where a file containing trailing data must be rejected, the option 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 @samp{--keep} to plzip and don't remove the original file until you -verify the compressed file with a command like +option @option{--keep} to plzip and don't remove the original file until you +check the compressed file with a command like @w{@samp{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 @@ -823,7 +833,7 @@ plzip -d file.lz @sp 1 @noindent -Example 5: Verify the integrity of the compressed file @samp{file.lz} and +Example 5: Check the integrity of the compressed file @samp{file.lz} and show status. @example |