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| -rw-r--r-- | doc/plzip.1 | 50 | ||||
| -rw-r--r-- | doc/plzip.info | 692 | ||||
| -rw-r--r-- | doc/plzip.texi | 325 |
3 files changed, 578 insertions, 489 deletions
diff --git a/doc/plzip.1 b/doc/plzip.1 index 694a99d..deb0ea5 100644 --- a/doc/plzip.1 +++ b/doc/plzip.1 @@ -1,5 +1,5 @@ -.\" DO NOT MODIFY THIS FILE! It was generated by help2man 1.46.1. -.TH PLZIP "1" "January 2019" "plzip 1.8" "User Commands" +.\" DO NOT MODIFY THIS FILE! It was generated by help2man 1.47.16. +.TH PLZIP "1" "January 2021" "plzip 1.9" "User Commands" .SH NAME plzip \- reduces the size of files .SH SYNOPSIS @@ -7,22 +7,24 @@ plzip \- reduces the size of files [\fI\,options\/\fR] [\fI\,files\/\fR] .SH DESCRIPTION Plzip is a massively parallel (multi\-threaded) implementation of lzip, fully -compatible with lzip 1.4 or newer. Plzip uses the lzlib compression library. +compatible with lzip 1.4 or newer. Plzip uses the compression library lzlib. .PP -Lzip is a lossless data compressor with a user interface similar to the -one of gzip or bzip2. Lzip can compress about as fast as gzip (lzip \fB\-0\fR) -or compress most files more than bzip2 (lzip \fB\-9\fR). 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. +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, chosen to maximize safety and +interoperability. Lzip can compress about as fast as gzip (lzip \fB\-0\fR) or +compress most files more than bzip2 (lzip \fB\-9\fR). 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. .PP -Plzip can compress/decompress large files on multiprocessor machines -much faster than lzip, at the cost of a slightly reduced compression -ratio (0.4 to 2 percent larger compressed files). Note that the number -of usable threads is limited by file size; on files larger than a few GB -plzip can use hundreds of processors, but on files of only a few MB -plzip is no faster than lzip. +Plzip can compress/decompress large files on multiprocessor machines much +faster than lzip, at the cost of a slightly reduced compression ratio (0.4 +to 2 percent larger compressed files). Note that the number of usable +threads is limited by file size; on files larger than a few GB plzip can use +hundreds of processors, but on files of only a few MB plzip is no faster +than lzip. .SH OPTIONS .TP \fB\-h\fR, \fB\-\-help\fR @@ -62,7 +64,7 @@ set match length limit in bytes [36] set number of (de)compression threads [2] .TP \fB\-o\fR, \fB\-\-output=\fR<file> -if reading standard input, write to <file> +write to <file>, keep input files .TP \fB\-q\fR, \fB\-\-quiet\fR suppress all messages @@ -93,6 +95,9 @@ number of 1 MiB input packets buffered [4] .TP \fB\-\-out\-slots=\fR<n> number of 1 MiB output packets buffered [64] +.TP +\fB\-\-check\-lib\fR +compare version of lzlib.h with liblz.{a,so} .PP If no file names are given, or if a file is '\-', plzip compresses or decompresses from standard input to standard output. @@ -103,8 +108,11 @@ to 2^29 bytes. .PP 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 \fB\-\-dictionary\-size\fR and \fB\-\-match\-length\fR -options directly to achieve optimal performance. +etc, you may need to use the options \fB\-\-dictionary\-size\fR and \fB\-\-match\-length\fR +directly to achieve optimal performance. +.PP +To extract all the files from archive 'foo.tar.lz', use the commands +\&'tar \fB\-xf\fR foo.tar.lz' or 'plzip \fB\-cd\fR foo.tar.lz | tar \fB\-xf\fR \-'. .PP 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 @@ -117,8 +125,8 @@ Plzip home page: http://www.nongnu.org/lzip/plzip.html .SH COPYRIGHT Copyright \(co 2009 Laszlo Ersek. .br -Copyright \(co 2019 Antonio Diaz Diaz. -Using lzlib 1.11 +Copyright \(co 2021 Antonio Diaz Diaz. +Using lzlib 1.12 License GPLv2+: GNU GPL version 2 or later <http://gnu.org/licenses/gpl.html> .br This is free software: you are free to change and redistribute it. diff --git a/doc/plzip.info b/doc/plzip.info index 2b7aa52..d70163e 100644 --- a/doc/plzip.info +++ b/doc/plzip.info @@ -11,7 +11,7 @@ File: plzip.info, Node: Top, Next: Introduction, Up: (dir) Plzip Manual ************ -This manual is for Plzip (version 1.8, 5 January 2019). +This manual is for Plzip (version 1.9, 3 January 2021). * Menu: @@ -28,10 +28,10 @@ This manual is for Plzip (version 1.8, 5 January 2019). * Concept index:: Index of concepts - Copyright (C) 2009-2019 Antonio Diaz Diaz. + Copyright (C) 2009-2021 Antonio Diaz Diaz. - This manual is free documentation: you have unlimited permission to -copy, distribute and modify it. + This manual is free documentation: you have unlimited permission to copy, +distribute, and modify it. File: plzip.info, Node: Introduction, Next: Output, Prev: Top, Up: Top @@ -39,88 +39,89 @@ File: plzip.info, Node: Introduction, Next: Output, Prev: Top, Up: Top 1 Introduction ************** -Plzip is a massively parallel (multi-threaded) implementation of lzip, -fully compatible with lzip 1.4 or newer. Plzip uses the lzlib -compression library. - - Lzip is a lossless data compressor with a user interface similar to -the one of gzip or bzip2. 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 to 2 percent larger compressed files). Note that the number -of usable threads is limited by file size; on files larger than a few GB -plzip can use hundreds of processors, but on files of only a few MB -plzip is no faster than lzip. *Note Minimum file sizes::. +Plzip is a massively parallel (multi-threaded) implementation of lzip, fully +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, chosen to maximize safety and +interoperability. 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 +to 2 percent larger compressed files). Note that the number of usable +threads is limited by file size; on files larger than a few GB plzip can use +hundreds of processors, but on files of only a few MB plzip is no faster +than lzip. *Note Minimum file sizes::. + + For creation and manipulation of compressed tar archives tarlz can be +more efficient than using tar and plzip because tarlz is able to keep the +alignment between tar members and lzip members. *Note tarlz manual: +(tarlz)Top. The lzip file format is designed for data sharing and long-term -archiving, taking into account both data integrity and decoder -availability: +archiving, taking into account both data integrity and decoder availability: * The lzip format provides very safe integrity checking and some data - recovery means. The lziprecover program can repair bit flip errors - (one of the most common forms of data corruption) in lzip files, - and provides data recovery capabilities, including error-checked - merging of damaged copies of a file. *Note Data safety: - (lziprecover)Data safety. - - * The lzip format is as simple as possible (but not simpler). The - lzip manual provides the source code of a simple decompressor - along with a detailed explanation of how it works, so that with - the only help of the lzip manual it would be possible for a - digital archaeologist to extract the data from a lzip file long - after quantum computers eventually render LZMA obsolete. + recovery means. The program lziprecover can repair bit flip errors + (one of the most common forms of data corruption) in lzip files, and + provides data recovery capabilities, including error-checked merging + of damaged copies of a file. *Note Data safety: (lziprecover)Data + safety. + + * The lzip format is as simple as possible (but not simpler). The lzip + manual provides the source code of a simple decompressor along with a + detailed explanation of how it works, so that with the only help of the + lzip manual it would be possible for a digital archaeologist to extract + the data from a lzip file long after quantum computers eventually + render LZMA obsolete. * Additionally the lzip reference implementation is copylefted, which guarantees that it will remain free forever. A nice feature of the lzip format is that a corrupt byte is easier to -repair the nearer it is from the beginning of the file. Therefore, with -the help of lziprecover, losing an entire archive just because of a -corrupt byte near the beginning is a thing of the past. +repair the nearer it is from the beginning of the file. Therefore, with the +help of lziprecover, losing an entire archive just because of a corrupt +byte near the beginning is a thing of the past. - 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 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 choice of dictionary size limit. *Note Memory -requirements::. + 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::. When compressing, plzip replaces every file given in the command line -with a compressed version of itself, with the name "original_name.lz". -When decompressing, plzip attempts to guess the name for the -decompressed file from that of the compressed file as follows: +with a compressed version of itself, with the name "original_name.lz". When +decompressing, plzip attempts to guess the name for the decompressed file +from that of the compressed file as follows: filename.lz becomes filename 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). + (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). - Plzip is able to read from some types of non regular files if the -'--stdout' option is specified. + Plzip is able to read from some types of non-regular files if either the +option '-c' or the option '-o' is specified. - If no file names are specified, plzip compresses (or decompresses) -from standard input to standard output. In this case, plzip will -decline to write compressed output to a terminal, as this would be -entirely incomprehensible and therefore pointless. + 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 will correctly decompress a file which is the concatenation of -two or more compressed files. The result is the concatenation of the + 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. @@ -135,41 +136,40 @@ The output of plzip looks like this: plzip -v foo foo: 6.676:1, 14.98% ratio, 85.02% saved, 450560 in, 67493 out. - plzip -tvv foo.lz - foo.lz: 6.676:1, 14.98% ratio, 85.02% saved. ok + plzip -tvvv foo.lz + foo.lz: 6.676:1, 14.98% ratio, 85.02% saved. 450560 out, 67493 in. ok The meaning of each field is as follows: 'N:1' - The compression ratio (uncompressed_size / compressed_size), shown - as N to 1. + The compression ratio (uncompressed_size / compressed_size), shown as + N to 1. 'ratio' - The inverse compression ratio - (compressed_size / uncompressed_size), shown as a percentage. A - decimal ratio is easily obtained by moving the decimal point two - places to the left; 14.98% = 0.1498. + The inverse compression ratio (compressed_size / uncompressed_size), + shown as a percentage. A decimal ratio is easily obtained by moving the + decimal point two places to the left; 14.98% = 0.1498. 'saved' The space saved by compression (1 - ratio), shown as a percentage. 'in' - The size of the uncompressed data. When decompressing or testing, - it is shown as 'decompressed'. Note that plzip always prints the - uncompressed size before the compressed size when compressing, - decompressing, testing or listing. + Size of the input data. This is the uncompressed size when + compressing, or the compressed size when decompressing or testing. + Note that plzip always prints the uncompressed size before the + compressed size when compressing, decompressing, testing, or listing. 'out' - The size of the compressed data. When decompressing or testing, it - is shown as 'compressed'. + Size of the output data. This is the compressed size when compressing, + or the decompressed size when decompressing or testing. When decompressing or testing at verbosity level 4 (-vvvv), the dictionary size used to compress the file is also shown. - LANGUAGE NOTE: Uncompressed = not compressed = plain data; it may -never have been compressed. Decompressed is used to refer to data which -have undergone the process of decompression. + LANGUAGE NOTE: Uncompressed = not compressed = plain data; it may never +have been compressed. Decompressed is used to refer to data which have +undergone the process of decompression. File: plzip.info, Node: Invoking plzip, Next: Program design, Prev: Output, Up: Top @@ -181,11 +181,13 @@ The format for running plzip is: plzip [OPTIONS] [FILES] -'-' 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. +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. - plzip supports the following options: + plzip supports the following options: *Note Argument syntax: +(arg_parser)Argument syntax. '-h' '--help' @@ -199,32 +201,33 @@ command line. '-a' '--trailing-error' Exit with error status 2 if any remaining input is detected after - decompressing the last member. Such remaining input is usually - trailing garbage that can be safely ignored. *Note - concat-example::. + decompressing the last member. Such remaining input is usually trailing + garbage that can be safely ignored. *Note concat-example::. '-B BYTES' '--data-size=BYTES' - When compressing, set the size of the input data blocks in bytes. - The input file will be 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 chosen data size. + When compressing, set the size of the input data blocks in bytes. The + input file will be 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::. '-c' '--stdout' - Compress or decompress to standard output; keep input files - unchanged. If compressing several files, each file is compressed - independently. This option is needed when reading from a named - pipe (fifo) or from a device. + 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. '-d' '--decompress' - Decompress the specified files. If a file does not exist or can't - be opened, plzip continues decompressing the rest of the files. If - a file fails to decompress, or is a terminal, plzip exits - immediately without decompressing the rest of the files. + Decompress the files specified. If a file does not exist or can't be + opened, plzip continues decompressing the rest of the files. If a file + fails to decompress, or is a terminal, plzip exits immediately without + decompressing the rest of the files. '-f' '--force' @@ -232,59 +235,69 @@ command line. '-F' '--recompress' - When compressing, force re-compression of files whose name already - has the '.lz' or '.tlz' suffix. + When compressing, force re-compression of files whose name already has + the '.lz' or '.tlz' suffix. '-k' '--keep' - Keep (don't delete) input files during compression or - decompression. + Keep (don't delete) input files during compression or decompression. '-l' '--list' - Print the uncompressed size, compressed size and percentage saved - of the specified files. 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 '-v', the dictionary size, the number of members in - the file, and the amount of trailing data (if any) are also - printed. With '-vv', the positions and sizes of each member in - multimember files are also printed. '-lq' can be used to verify - quickly (without decompressing) the structural integrity of the - specified files. (Use '--test' to verify the data integrity). - '-alq' additionally verifies that none of the specified files - contain trailing data. + 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 + '-v', the dictionary size, the number of members in the file, and the + amount of trailing data (if any) are also printed. With '-vv', the + positions and sizes of each member in multimember files are also + printed. + + '-lq' can be used to verify 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. '-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. + 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. '-n N' '--threads=N' - Set the number of worker threads, overriding the system's default. - Valid values range from 1 to "as many as your system can support". - If this option is not used, plzip tries to detect the number of - processors in the system and use it as default value. When - compressing on a 32 bit system, plzip tries to limit the memory - use to under 2.22 GiB (4 worker threads at level -9) by reducing - the number of threads below the system's default. 'plzip --help' - shows the system's default value. - - Note that the number of usable threads is limited to - ceil( file_size / data_size ) during compression (*note Minimum - file sizes::), and to the number of members in the input during - decompression. + Set the maximum number of worker threads, overriding the system's + default. Valid values range from 1 to "as many as your system can + support". If this option is not used, plzip tries to detect the number + of processors in the system and use it as default value. When + compressing on a 32 bit system, plzip tries to limit the memory use to + under 2.22 GiB (4 worker threads at level -9) by reducing the number + of threads below the system's default. 'plzip --help' shows the + system's default value. + + Plzip starts the number of threads required by each file without + exceeding the value specified. Note that the number of usable threads + is limited to ceil( file_size / data_size ) during compression (*note + Minimum file sizes::), and to the number of members in the input + during decompression. You can find the number of members in a lzip + file by running 'plzip -lv file.lz'. '-o FILE' '--output=FILE' - When reading from standard input and '--stdout' has not been - specified, use 'FILE' as the virtual name of the uncompressed - file. This produces a file named 'FILE' when decompressing, or a - file named 'FILE.lz' when compressing. A second '.lz' extension is - not added if 'FILE' already ends in '.lz' or '.tlz'. + 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 + equivalent to '-c'. '-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 '.lz' is appended to FILE unless it already ends + in '.lz' or '.tlz'. This feature will be removed in a future version + of plzip. Meanwhile, redirection may be used instead of '-o' to write + the compressed output to a file without the extension '.lz' in its + name: 'plzip < file > foo'. '-q' '--quiet' @@ -292,30 +305,28 @@ 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 specified size does not match one of - the valid sizes, it will be 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 is affected at compression time by the choice of - dictionary size limit. + 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. + + For maximum compression you should use a dictionary size limit as large + as possible, but keep in mind that the decompression memory requirement + is affected at compression time by the choice of dictionary size limit. '-t' '--test' - Check integrity of the specified files, but don't decompress them. - This really performs a trial decompression and throws away the - result. Use it together with '-v' to see information about the - files. If a file does not exist, can't be opened, or is a - terminal, plzip continues checking the rest of the files. If a - file fails the test, plzip may be unable to check the rest of the - files. + 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 '-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. '-v' '--verbose' @@ -323,26 +334,26 @@ command line. When compressing, show the compression ratio and size for each file 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 '-v' options show the progress of (de)compression, - except for single-member files. + verbosity level, showing status, compression ratio, dictionary size, + decompressed size, and compressed size. + Two or more '-v' options show the progress of (de)compression, except + for single-member files. '-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 '-6', equivalent to '-s8MiB -m36'. Note that - '-9' can be much slower than '-0'. These options have no effect - when decompressing, testing or listing. + Compression level. Set the compression parameters (dictionary size and + match length limit) as shown in the table below. The default + compression level is '-6', equivalent to '-s8MiB -m36'. Note that '-9' + can be much slower than '-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 '--dictionary-size' and - '--match-length' options 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 '--dictionary-size' and + '--match-length' directly to achieve optimal performance. - If several compression levels or '-s' or '-m' options are given, - the last setting is used. For example '-9 -s64MiB' is equivalent - to '-s64MiB -m273' + If several compression levels or '-s' or '-m' options are given, the + last setting is used. For example '-9 -s64MiB' is equivalent to + '-s64MiB -m273' Level Dictionary size (-s) Match length limit (-m) -0 64 KiB 16 bytes @@ -361,23 +372,33 @@ command line. Aliases for GNU gzip compatibility. '--loose-trailing' - When decompressing, testing or listing, allow trailing data whose - first bytes are so similar to the magic bytes of a lzip header - that they can be confused with a corrupt header. Use this option - if a file triggers a "corrupt header" error and the cause is not - indeed a corrupt header. + When decompressing, testing, or listing, allow trailing data whose + first bytes are so similar to the magic bytes of a lzip header that + they can be confused with a corrupt header. Use this option if a file + triggers a "corrupt header" error and the cause is not indeed a + corrupt header. '--in-slots=N' Number of 1 MiB input packets buffered per worker thread when - decompressing from non-seekable input. Increasing the number of - packets may increase decompression speed, but requires more - memory. Valid values range from 1 to 64. The default value is 4. + decompressing from non-seekable input. Increasing the number of packets + may increase decompression speed, but requires more memory. Valid + values range from 1 to 64. The default value is 4. '--out-slots=N' Number of 1 MiB output packets buffered per worker thread when - decompressing to non-seekable output. Increasing the number of - packets may increase decompression speed, but requires more - memory. Valid values range from 1 to 1024. The default value is 64. + decompressing to non-seekable output. Increasing the number of packets + may increase decompression speed, but requires more memory. Valid + values range from 1 to 1024. The default value is 64. + +'--check-lib' + Compare the version of lzlib used to compile plzip with the version + actually being used at run time and exit. Report any differences + found. Exit with error status 1 if differences are found. A mismatch + may indicate that lzlib is not correctly installed or that a different + version of lzlib has been installed after compiling plzip. + 'plzip -v --check-lib' shows the version of lzlib being used and the + value of 'LZ_API_VERSION' (if defined). *Note Library version: + (lzlib)Library version. Numbers given as arguments to options may be followed by a multiplier @@ -396,36 +417,36 @@ Z zettabyte (10^21) | Zi zebibyte (2^70) Y yottabyte (10^24) | Yi yobibyte (2^80) - 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. + 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. File: plzip.info, Node: Program design, Next: File format, Prev: Invoking plzip, Up: Top -4 Program design -**************** +4 Internal structure of plzip +***************************** -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. +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. - 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 -'-b' option was used) because lzip usually produces single-member -files, which can't be decompressed in parallel. + 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 '-b' was used) +because lzip usually produces single-member files, which can't be +decompressed in parallel. For each input file, a splitter thread and several worker threads are created, acting the main thread as muxer (multiplexer) thread. A "packet -courier" takes care of data transfers among threads and limits the -maximum number of data blocks (packets) being processed simultaneously. +courier" takes care of data transfers among threads and limits the maximum +number of data blocks (packets) being processed simultaneously. - The splitter reads data blocks from the input file, and distributes -them to the workers. The workers (de)compress the blocks received from -the splitter. The muxer collects processed packets from the workers, and -writes them to the output file. + The splitter reads data blocks from the input file, and distributes them +to the workers. The workers (de)compress the blocks received from the +splitter. The muxer collects processed packets from the workers, and writes +them to the output file. ,------------, ,-->| worker 0 |--, @@ -438,13 +459,12 @@ writes them to the output file. `-->| worker N-1 |--' `------------' - When decompressing from a regular file, the splitter is removed and -the workers read directly from the input file. If the output file is -also a regular file, the muxer is also removed and the workers write -directly to the output file. With these optimizations, the use of RAM -is greatly reduced and the decompression speed of large files with many -members is only limited by the number of processors available and by -I/O speed. + When decompressing from a regular file, the splitter is removed and the +workers read directly from the input file. If the output file is also a +regular file, the muxer is also removed and the workers write directly to +the output file. With these optimizations, the use of RAM is greatly +reduced and the decompression 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: File format, Next: Memory requirements, Prev: Program design, Up: Top @@ -458,11 +478,13 @@ when there is no longer anything to take away. In the diagram below, a box like this: + +---+ | | <-- the vertical bars might be missing +---+ represents one byte; a box like this: + +==============+ | | +==============+ @@ -471,10 +493,11 @@ when there is no longer anything to take away. A lzip file consists of a series of "members" (compressed data sets). -The members simply appear one after another in the file, with no -additional information before, between, or after them. +The members simply appear one after another in the file, with no additional +information before, between, or after them. Each member has the following structure: + +--+--+--+--+----+----+=============+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ID string | VN | DS | LZMA stream | CRC32 | Data size | Member size | +--+--+--+--+----+----+=============+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ @@ -482,17 +505,16 @@ additional information before, between, or after them. All multibyte values are stored in little endian order. 'ID string (the "magic" bytes)' - A four byte string, identifying the lzip format, with the value - "LZIP" (0x4C, 0x5A, 0x49, 0x50). + A four byte string, identifying the lzip format, with the value "LZIP" + (0x4C, 0x5A, 0x49, 0x50). 'VN (version number, 1 byte)' - Just in case something needs to be modified in the future. 1 for - now. + Just in case something needs to be modified in the future. 1 for now. 'DS (coded dictionary size, 1 byte)' The dictionary size is calculated by taking a power of 2 (the base - size) and subtracting from it a fraction between 0/16 and 7/16 of - the base size. + size) and subtracting from it a fraction between 0/16 and 7/16 of the + base size. Bits 4-0 contain the base 2 logarithm of the base size (12 to 29). Bits 7-5 contain the numerator of the fraction (0 to 7) to subtract from the base size to obtain the dictionary size. @@ -501,20 +523,20 @@ additional information before, between, or after them. 'LZMA stream' The LZMA stream, finished by an end of stream marker. Uses default - values for encoder properties. *Note Stream format: (lzip)Stream + values for encoder properties. *Note Stream format: (lzip)Stream format, for a complete description. 'CRC32 (4 bytes)' - CRC of the uncompressed original data. + Cyclic Redundancy Check (CRC) of the uncompressed original data. 'Data size (8 bytes)' Size of the uncompressed original data. '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 safe recovery of undamaged members from - multimember files. + Total size of the member, including header and trailer. This field acts + as a distributed index, allows the verification of stream integrity, + and facilitates safe recovery of undamaged members from multimember + files. @@ -526,20 +548,20 @@ File: plzip.info, Node: Memory requirements, Next: Minimum file sizes, Prev: The amount of memory required *per worker thread* for decompression or testing is approximately the following: - * For decompression of a regular (seekable) file to another regular - file, or for testing of a regular file; the dictionary size. + * For decompression of a regular (seekable) file to another regular file, + or for testing of a regular file; the dictionary size. - * For testing of a non-seekable file or of standard input; the - dictionary size plus 1 MiB plus up to the number of 1 MiB input - packets buffered (4 by default). + * For testing of a non-seekable file or of standard input; the dictionary + size plus 1 MiB plus up to the number of 1 MiB input packets buffered + (4 by default). * For decompression of a regular file to a non-seekable file or to standard output; the dictionary size plus up to the number of 1 MiB output packets buffered (64 by default). * For decompression of a non-seekable file or of standard input; the - dictionary size plus 1 MiB plus up to the number of 1 MiB input - and output packets buffered (68 by default). + dictionary size plus 1 MiB plus up to the number of 1 MiB input and + output packets buffered (68 by default). The amount of memory required *per worker thread* for compression is approximately the following: @@ -550,9 +572,8 @@ approximately the following: * For compression at other levels; 11 times the dictionary size plus 3.375 times the data size. Default is 142 MiB. -The following table shows the memory required *per thread* for -compression at a given level, using the default data size for each -level: +The following table shows the memory required *per thread* for compression +at a given level, using the default data size for each level: Level Memory required -0 4.875 MiB @@ -572,22 +593,22 @@ File: plzip.info, Node: Minimum file sizes, Next: Trailing data, Prev: Memory 7 Minimum file sizes required for full compression speed ******************************************************** -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. +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 (*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 8 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 (*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 +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 data size for each level: + The following table shows the minimum uncompressed file size needed for +full use of N processors at a given compression level, using the default +data size for each level: Processors 2 4 8 16 64 256 ------------------------------------------------------------------ @@ -612,43 +633,40 @@ File: plzip.info, Node: Trailing data, Next: Examples, Prev: Minimum file siz Sometimes extra data are found appended to a lzip file after the last member. Such trailing data may be: - * Padding added to make the file size a multiple of some block size, - for example when writing to a tape. It is safe to append any - amount of padding zero bytes to a lzip file. + * Padding added to make the file size a multiple of some block size, for + 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 - 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. + 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. * Garbage added by some not totally successful copy operation. - * Malicious data added to the file in order to make its total size - and hash value (for a chosen hash) coincide with those of another - file. + * Malicious data added to the file in order to make its total size and + hash value (for a chosen hash) coincide with those of another file. * In rare cases, trailing data could be the corrupt header of another member. In multimember or concatenated files the probability of corruption happening in the magic bytes is 5 times smaller than the - probability of getting a false positive caused by the corruption - of the 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 '--trailing-error' guarantees that any corrupt header will - be detected. + probability of getting a false positive caused by the corruption of the + 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 '--trailing-error' + guarantees that any corrupt header will be 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 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 + 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 '--trailing-error' can be used. *Note --trailing-error::. @@ -660,62 +678,70 @@ 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 -'--keep' option to plzip and don't remove the original file until you +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. +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'. + + tar -xf foo.tar.lz + or + plzip -cd foo.tar.lz | tar -xf - -Example 1: Replace a regular file with its compressed version 'file.lz' -and show the compression ratio. +Example 2: Replace a regular file with its compressed version 'file.lz' and +show the compression ratio. plzip -v file -Example 2: Like example 1 but the created 'file.lz' has a block size of +Example 3: Like example 1 but the created 'file.lz' has a block size of 1 MiB. The compression ratio is not shown. plzip -B 1MiB file -Example 3: Restore a regular file from its compressed version -'file.lz'. If the operation is successful, 'file.lz' is removed. +Example 4: Restore a regular file from its compressed version 'file.lz'. If +the operation is successful, 'file.lz' is removed. plzip -d file.lz -Example 4: Verify the integrity of the compressed file 'file.lz' and -show status. +Example 5: Verify the integrity of the compressed file 'file.lz' and show +status. plzip -tv file.lz -Example 5: Compress a whole device in /dev/sdc and send the output to +Example 6: Compress a whole device in /dev/sdc and send the output to 'file.lz'. - plzip -c /dev/sdc > file.lz + plzip -c /dev/sdc > file.lz + or + plzip /dev/sdc -o file.lz -Example 6: The right way of concatenating the decompressed output of two -or more compressed files. *Note Trailing data::. +Example 7: The right way of concatenating the decompressed output of two or +more compressed files. *Note Trailing data::. Don't do this - cat file1.lz file2.lz file3.lz | plzip -d + cat file1.lz file2.lz file3.lz | plzip -d - Do this instead plzip -cd file1.lz file2.lz file3.lz -Example 7: Decompress 'file.lz' partially until 10 KiB of decompressed -data are produced. +Example 8: Decompress 'file.lz' partially until 10 KiB of decompressed data +are produced. plzip -cd file.lz | dd bs=1024 count=10 -Example 8: Decompress 'file.lz' partially from decompressed byte 10000 -to decompressed byte 15000 (5000 bytes are produced). +Example 9: Decompress 'file.lz' partially from decompressed byte at offset +10000 to decompressed byte at offset 14999 (5000 bytes are produced). plzip -cd file.lz | dd bs=1000 skip=10 count=5 @@ -725,14 +751,14 @@ File: plzip.info, Node: Problems, Next: Concept index, Prev: Examples, Up: T 10 Reporting bugs ***************** -There are probably bugs in plzip. There are certainly errors and -omissions in this manual. If you report them, they will get fixed. If -you don't, no one will ever know about them and they will remain unfixed -for all eternity, if not longer. +There are probably bugs in plzip. There are certainly errors and omissions +in this manual. If you report them, they will get fixed. If you don't, no +one will ever know about them and they will remain unfixed for all +eternity, if not longer. If you find a bug in plzip, please send electronic mail to -<lzip-bug@nongnu.org>. Include the version number, which you can find -by running 'plzip --version'. +<lzip-bug@nongnu.org>. Include the version number, which you can find by +running 'plzip --version'. File: plzip.info, Node: Concept index, Prev: Problems, Up: Top @@ -743,40 +769,40 @@ Concept index * Menu: -* bugs: Problems. (line 6) -* examples: Examples. (line 6) -* file format: File format. (line 6) -* getting help: Problems. (line 6) -* introduction: Introduction. (line 6) -* invoking: Invoking plzip. (line 6) -* memory requirements: Memory requirements. (line 6) -* minimum file sizes: Minimum file sizes. (line 6) -* options: Invoking plzip. (line 6) -* output: Output. (line 6) -* program design: Program design. (line 6) -* trailing data: Trailing data. (line 6) -* usage: Invoking plzip. (line 6) -* version: Invoking plzip. (line 6) +* bugs: Problems. (line 6) +* examples: Examples. (line 6) +* file format: File format. (line 6) +* getting help: Problems. (line 6) +* introduction: Introduction. (line 6) +* invoking: Invoking plzip. (line 6) +* memory requirements: Memory requirements. (line 6) +* minimum file sizes: Minimum file sizes. (line 6) +* options: Invoking plzip. (line 6) +* output: Output. (line 6) +* program design: Program design. (line 6) +* trailing data: Trailing data. (line 6) +* usage: Invoking plzip. (line 6) +* version: Invoking plzip. (line 6) Tag Table: Node: Top222 -Node: Introduction1158 -Node: Output5456 -Node: Invoking plzip6936 -Ref: --trailing-error7563 -Ref: --data-size7806 -Node: Program design16267 -Node: File format18419 -Ref: coded-dict-size19719 -Node: Memory requirements20849 -Node: Minimum file sizes22531 -Node: Trailing data24540 -Node: Examples26823 -Ref: concat-example28238 -Node: Problems28813 -Node: Concept index29341 +Node: Introduction1159 +Node: Output5788 +Node: Invoking plzip7351 +Ref: --trailing-error8146 +Ref: --data-size8384 +Node: Program design18364 +Node: File format20542 +Ref: coded-dict-size21840 +Node: Memory requirements22995 +Node: Minimum file sizes24677 +Node: Trailing data26693 +Node: Examples28961 +Ref: concat-example30556 +Node: Problems31153 +Node: Concept index31681 End Tag Table diff --git a/doc/plzip.texi b/doc/plzip.texi index b5469b9..26c0820 100644 --- a/doc/plzip.texi +++ b/doc/plzip.texi @@ -6,8 +6,8 @@ @finalout @c %**end of header -@set UPDATED 5 January 2019 -@set VERSION 1.8 +@set UPDATED 3 January 2021 +@set VERSION 1.9 @dircategory Data Compression @direntry @@ -29,6 +29,7 @@ @contents @end ifnothtml +@ifnottex @node Top @top @@ -49,35 +50,47 @@ This manual is for Plzip (version @value{VERSION}, @value{UPDATED}). @end menu @sp 1 -Copyright @copyright{} 2009-2019 Antonio Diaz Diaz. +Copyright @copyright{} 2009-2021 Antonio Diaz Diaz. -This manual is free documentation: you have unlimited permission -to copy, distribute and modify it. +This manual is free documentation: you have unlimited permission to copy, +distribute, and modify it. +@end ifnottex @node Introduction @chapter Introduction @cindex introduction -@uref{http://www.nongnu.org/lzip/plzip.html,,Plzip} is a massively parallel -(multi-threaded) implementation of lzip, fully compatible with lzip 1.4 or -newer. Plzip uses the lzlib compression library. - -@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 -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 to 2 percent larger compressed files). Note that the number -of usable threads is limited by file size; on files larger than a few GB -plzip can use hundreds of processors, but on files of only a few MB -plzip is no faster than lzip. @xref{Minimum file sizes}. +@uref{http://www.nongnu.org/lzip/plzip.html,,Plzip} +is a massively parallel (multi-threaded) implementation of lzip, fully +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, chosen to maximize safety and +interoperability. 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 +to 2 percent larger compressed files). Note that the number of usable +threads is limited by file size; on files larger than a few GB plzip can use +hundreds of processors, but on files of only a few MB plzip is no faster +than lzip. @xref{Minimum file sizes}. + +For creation and manipulation of compressed tar archives +@uref{http://www.nongnu.org/lzip/manual/tarlz_manual.html,,tarlz} can be +more efficient than using tar and plzip because tarlz is able to keep the +alignment between tar members and lzip members. +@ifnothtml +@xref{Top,tarlz manual,,tarlz}. +@end ifnothtml The lzip file format is designed for data sharing and long-term archiving, taking into account both data integrity and decoder availability: @@ -85,11 +98,11 @@ taking into account both data integrity and decoder availability: @itemize @bullet @item The lzip format provides very safe integrity checking and some data -recovery means. The +recovery means. The program @uref{http://www.nongnu.org/lzip/manual/lziprecover_manual.html#Data-safety,,lziprecover} -program can repair bit flip errors (one of the most common forms of data -corruption) in lzip files, and provides data recovery capabilities, -including error-checked merging of damaged copies of a file. +can repair bit flip errors (one of the most common forms of data corruption) +in lzip files, and provides data recovery capabilities, including +error-checked merging of damaged copies of a file. @ifnothtml @xref{Data safety,,,lziprecover}. @end ifnothtml @@ -107,10 +120,10 @@ Additionally the lzip reference implementation is copylefted, which guarantees that it will remain free forever. @end itemize -A nice feature of the lzip format is that a corrupt byte is easier to -repair the nearer it is from the beginning of the file. Therefore, with -the help of lziprecover, losing an entire archive just because of a -corrupt byte near the beginning is a thing of the past. +A nice feature of the lzip format is that a corrupt byte is easier to repair +the nearer it is from the beginning of the file. Therefore, with the help of +lziprecover, losing an entire archive just because of a corrupt byte near +the beginning is a thing of the past. Plzip uses the same well-defined exit status values used by lzip, which makes it safer than compressors returning ambiguous warning values (like @@ -138,13 +151,12 @@ possible, ownership of the file just as @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 the -@samp{--stdout} option is specified. +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. -If no file names are specified, plzip compresses (or decompresses) from -standard input to standard output. In this case, plzip will decline to -write compressed output to a terminal, as this would be entirely -incomprehensible and therefore pointless. +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 will correctly decompress a file which is the concatenation of two or more compressed files. The result is the concatenation of the corresponding @@ -162,16 +174,16 @@ The output of plzip looks like this: plzip -v foo foo: 6.676:1, 14.98% ratio, 85.02% saved, 450560 in, 67493 out. -plzip -tvv foo.lz - foo.lz: 6.676:1, 14.98% ratio, 85.02% saved. ok +plzip -tvvv foo.lz + foo.lz: 6.676:1, 14.98% ratio, 85.02% saved. 450560 out, 67493 in. ok @end example The meaning of each field is as follows: @table @code @item N:1 -The compression ratio @w{(uncompressed_size / compressed_size)}, shown -as N to 1. +The compression ratio @w{(uncompressed_size / compressed_size)}, shown as +@w{N to 1}. @item ratio The inverse compression ratio @w{(compressed_size / uncompressed_size)}, @@ -182,23 +194,23 @@ decimal point two places to the left; @w{14.98% = 0.1498}. The space saved by compression @w{(1 - ratio)}, shown as a percentage. @item in -The size of the uncompressed data. When decompressing or testing, it is -shown as @code{decompressed}. Note that plzip always prints the -uncompressed size before the compressed size when compressing, -decompressing, testing or listing. +Size of the input data. This is the uncompressed size when compressing, or +the compressed size when decompressing or testing. Note that plzip always +prints the uncompressed size before the compressed size when compressing, +decompressing, testing, or listing. @item out -The size of the compressed data. When decompressing or testing, it is -shown as @code{compressed}. +Size of the output data. This is the compressed size when compressing, or +the decompressed size when decompressing or testing. @end table -When decompressing or testing at verbosity level 4 (-vvvv), the -dictionary size used to compress the file is also shown. +When decompressing or testing at verbosity level 4 (-vvvv), the dictionary +size used to compress the file is also shown. -LANGUAGE NOTE: Uncompressed = not compressed = plain data; it may never -have been compressed. Decompressed is used to refer to data which have -undergone the process of decompression. +LANGUAGE NOTE: Uncompressed = not compressed = plain data; it may never have +been compressed. Decompressed is used to refer to data which have undergone +the process of decompression. @node Invoking plzip @@ -215,11 +227,16 @@ plzip [@var{options}] [@var{files}] @end example @noindent -@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. +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. -plzip supports the following options: +plzip supports the following +@uref{http://www.nongnu.org/arg-parser/manual/arg_parser_manual.html#Argument-syntax,,options}: +@ifnothtml +@xref{Argument syntax,,,arg_parser}. +@end ifnothtml @table @code @item -h @@ -246,18 +263,20 @@ 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 chosen data size. +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 is needed when reading from a named pipe (fifo) or from a -device. +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 +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. @item -d @itemx --decompress -Decompress the specified files. If a file does not exist or can't be +Decompress the files specified. If a file does not exist or can't be opened, plzip continues decompressing the rest of the files. If a file fails to decompress, or is a terminal, plzip exits immediately without decompressing the rest of the files. @@ -277,17 +296,18 @@ Keep (don't delete) input files during compression or decompression. @item -l @itemx --list -Print the uncompressed size, compressed size and percentage saved of the -specified files. 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 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 member in multimember files are also -printed. @samp{-lq} can be used to verify quickly (without -decompressing) the structural integrity of the specified files. (Use -@samp{--test} to verify the data integrity). @samp{-alq} additionally -verifies that none of the specified files contain trailing data. +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 +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 +member in multimember files are also printed. + +@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. @item -m @var{bytes} @itemx --match-length=@var{bytes} @@ -298,27 +318,36 @@ compression times. @item -n @var{n} @itemx --threads=@var{n} -Set the number of worker threads, overriding the system's default. Valid -values range from 1 to "as many as your system can support". If this -option is not used, plzip tries to detect the number of processors in -the system and use it as default value. When compressing on a @w{32 bit} -system, plzip tries to limit the memory use to under @w{2.22 GiB} (4 -worker threads at level -9) by reducing the number of threads below the -system's default. @w{@samp{plzip --help}} shows the system's default -value. - -Note that the number of usable threads is limited to @w{ceil( file_size -/ data_size )} during compression (@pxref{Minimum file sizes}), and to -the number of members in the input during decompression. +Set the maximum number of worker threads, overriding the system's default. +Valid values range from 1 to "as many as your system can support". If this +option is not used, plzip tries to detect the number of processors in the +system and use it as default value. When compressing on a @w{32 bit} system, +plzip tries to limit the memory use to under @w{2.22 GiB} (4 worker threads +at level -9) by reducing the number of threads below the system's default. +@w{@samp{plzip --help}} shows the system's default value. + +Plzip starts the number of threads required by each file without exceeding +the value specified. Note that the number of usable threads is limited to +@w{ceil( file_size / data_size )} during compression (@pxref{Minimum file +sizes}), and to the number of members in the input during decompression. You +can find the number of members in a lzip file by running +@w{@samp{plzip -lv file.lz}}. @item -o @var{file} @itemx --output=@var{file} -When reading from standard input and @samp{--stdout} has not been -specified, use @samp{@var{file}} as the virtual name of the uncompressed -file. This produces a file named @samp{@var{file}} when decompressing, -or a file named @samp{@var{file}.lz} when compressing. A second -@samp{.lz} extension is not added if @samp{@var{file}} already ends in -@samp{.lz} or @samp{.tlz}. +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. + +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 +the compressed output to a file without the extension @samp{.lz} in its +name: @w{@samp{plzip < file > foo}}. @item -q @itemx --quiet @@ -331,7 +360,7 @@ 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 specified size +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. @@ -341,12 +370,13 @@ is affected at compression time by the choice of dictionary size limit. @item -t @itemx --test -Check integrity of the specified files, but don't decompress them. This +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 -does not exist, can't be opened, or is a terminal, plzip continues -checking the rest of the files. If a file fails the test, plzip may be -unable to check the rest of the files. +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. @item -v @itemx --verbose @@ -364,12 +394,12 @@ 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 -effect when decompressing, testing or listing. +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 @samp{--dictionary-size} and -@samp{--match-length} options directly to achieve optimal performance. +etc, you may need to use the options @samp{--dictionary-size} and +@samp{--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 @@ -394,7 +424,7 @@ equivalent to @w{@samp{-s64MiB -m273}} Aliases for GNU gzip compatibility. @item --loose-trailing -When decompressing, testing or listing, allow trailing data whose first +When decompressing, testing, or listing, allow trailing data whose first bytes are so similar to the magic bytes of a lzip header that they can be confused with a corrupt header. Use this option if a file triggers a "corrupt header" error and the cause is not indeed a corrupt header. @@ -411,6 +441,19 @@ decompressing to non-seekable output. Increasing the number of packets may increase decompression speed, but requires more memory. Valid values range from 1 to 1024. The default value is 64. +@item --check-lib +Compare the +@uref{http://www.nongnu.org/lzip/manual/lzlib_manual.html#Library-version,,version of lzlib} +used to compile plzip with the version actually being used at run time and +exit. Report any differences found. Exit with error status 1 if differences +are found. A mismatch may indicate that lzlib is not correctly installed or +that a different version of lzlib has been installed after compiling plzip. +@w{@samp{plzip -v --check-lib}} shows the version of lzlib being used and +the value of @samp{LZ_API_VERSION} (if defined). +@ifnothtml +@xref{Library version,,,lzlib}. +@end ifnothtml + @end table Numbers given as arguments to options may be followed by a multiplier @@ -438,16 +481,16 @@ caused plzip to panic. @node Program design -@chapter Program design +@chapter Internal structure of plzip @cindex program design -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. +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. 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 @samp{-b} option was used) +be decompressed faster than using lzip (unless the option @samp{-b} was used) because lzip usually produces single-member files, which can't be decompressed in parallel. @@ -492,6 +535,7 @@ when there is no longer anything to take away.@* @sp 1 In the diagram below, a box like this: + @verbatim +---+ | | <-- the vertical bars might be missing @@ -499,6 +543,7 @@ In the diagram below, a box like this: @end verbatim represents one byte; a box like this: + @verbatim +==============+ | | @@ -513,6 +558,7 @@ The members simply appear one after another in the file, with no additional information before, between, or after them. Each member has the following structure: + @verbatim +--+--+--+--+----+----+=============+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ID string | VN | DS | LZMA stream | CRC32 | Data size | Member size | @@ -532,8 +578,7 @@ Just in case something needs to be modified in the future. 1 for now. @anchor{coded-dict-size} @item DS (coded dictionary size, 1 byte) The dictionary size is calculated by taking a power of 2 (the base size) -and subtracting from it a fraction between 0/16 and 7/16 of the base -size.@* +and subtracting from it a fraction between 0/16 and 7/16 of the base size.@* Bits 4-0 contain the base 2 logarithm of the base size (12 to 29).@* Bits 7-5 contain the numerator of the fraction (0 to 7) to subtract from the base size to obtain the dictionary size.@* @@ -541,8 +586,8 @@ Example: 0xD3 = 2^19 - 6 * 2^15 = 512 KiB - 6 * 32 KiB = 320 KiB@* Valid values for dictionary size range from 4 KiB to 512 MiB. @item LZMA stream -The LZMA stream, finished by an end of stream marker. Uses default -values for encoder properties. +The LZMA stream, finished by an end of stream marker. Uses default values +for encoder properties. @ifnothtml @xref{Stream format,,,lzip}, @end ifnothtml @@ -553,7 +598,7 @@ See for a complete description. @item CRC32 (4 bytes) -CRC of the uncompressed original data. +Cyclic Redundancy Check (CRC) of the uncompressed original data. @item Data size (8 bytes) Size of the uncompressed original data. @@ -570,8 +615,8 @@ facilitates safe recovery of undamaged members from multimember files. @chapter Memory required to compress and decompress @cindex memory requirements -The amount of memory required @strong{per worker thread} for -decompression or testing is approximately the following: +The amount of memory required @strong{per worker thread} for decompression +or testing is approximately the following: @itemize @bullet @item @@ -610,8 +655,7 @@ times the data size. Default is @w{142 MiB}. @noindent The following table shows the memory required @strong{per thread} for -compression at a given level, using the default data size for each -level: +compression at a given level, using the default data size for each level: @multitable {Level} {Memory required} @item Level @tab Memory required @@ -643,7 +687,7 @@ least as large as the number of worker threads times the chunk size 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 8 processors at level -9. +linux will scale 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 @@ -723,7 +767,7 @@ 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 -@samp{--keep} option to plzip and don't remove the original file until you +option @samp{--keep} to plzip and don't remove the original file until you verify 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 @@ -732,8 +776,18 @@ contents, resulting in a valid compressed file containing wrong data. @sp 1 @noindent -Example 1: Replace a regular file with its compressed version -@samp{file.lz} and show the compression ratio. +Example 1: Extract all the files from archive @samp{foo.tar.lz}. + +@example + tar -xf foo.tar.lz +or + plzip -cd foo.tar.lz | tar -xf - +@end example + +@sp 1 +@noindent +Example 2: Replace a regular file with its compressed version @samp{file.lz} +and show the compression ratio. @example plzip -v file @@ -741,8 +795,8 @@ plzip -v file @sp 1 @noindent -Example 2: Like example 1 but the created @samp{file.lz} has a block -size of @w{1 MiB}. The compression ratio is not shown. +Example 3: Like example 1 but the created @samp{file.lz} has a block size of +@w{1 MiB}. The compression ratio is not shown. @example plzip -B 1MiB file @@ -750,9 +804,8 @@ plzip -B 1MiB file @sp 1 @noindent -Example 3: Restore a regular file from its compressed version -@samp{file.lz}. If the operation is successful, @samp{file.lz} is -removed. +Example 4: Restore a regular file from its compressed version +@samp{file.lz}. If the operation is successful, @samp{file.lz} is removed. @example plzip -d file.lz @@ -760,8 +813,8 @@ plzip -d file.lz @sp 1 @noindent -Example 4: Verify the integrity of the compressed file @samp{file.lz} -and show status. +Example 5: Verify the integrity of the compressed file @samp{file.lz} and +show status. @example plzip -tv file.lz @@ -769,29 +822,31 @@ plzip -tv file.lz @sp 1 @noindent -Example 5: Compress a whole device in /dev/sdc and send the output to +Example 6: Compress a whole device in /dev/sdc and send the output to @samp{file.lz}. @example -plzip -c /dev/sdc > file.lz + plzip -c /dev/sdc > file.lz +or + plzip /dev/sdc -o file.lz @end example @sp 1 @anchor{concat-example} @noindent -Example 6: The right way of concatenating the decompressed output of two -or more compressed files. @xref{Trailing data}. +Example 7: The right way of concatenating the decompressed output of two or +more compressed files. @xref{Trailing data}. @example Don't do this - cat file1.lz file2.lz file3.lz | plzip -d + cat file1.lz file2.lz file3.lz | plzip -d - Do this instead plzip -cd file1.lz file2.lz file3.lz @end example @sp 1 @noindent -Example 7: Decompress @samp{file.lz} partially until @w{10 KiB} of +Example 8: Decompress @samp{file.lz} partially until @w{10 KiB} of decompressed data are produced. @example @@ -800,8 +855,8 @@ plzip -cd file.lz | dd bs=1024 count=10 @sp 1 @noindent -Example 8: Decompress @samp{file.lz} partially from decompressed byte -10000 to decompressed byte 15000 (5000 bytes are produced). +Example 9: Decompress @samp{file.lz} partially from decompressed byte at +offset 10000 to decompressed byte at offset 14999 (5000 bytes are produced). @example plzip -cd file.lz | dd bs=1000 skip=10 count=5 @@ -820,7 +875,7 @@ for all eternity, if not longer. If you find a bug in plzip, please send electronic mail to @email{lzip-bug@@nongnu.org}. Include the version number, which you can -find by running @w{@code{plzip --version}}. +find by running @w{@samp{plzip --version}}. @node Concept index |