diff options
Diffstat (limited to '')
| -rw-r--r-- | doc/clzip.info | 168 |
1 files changed, 104 insertions, 64 deletions
diff --git a/doc/clzip.info b/doc/clzip.info index 2bab8b6..b7ad665 100644 --- a/doc/clzip.info +++ b/doc/clzip.info @@ -12,17 +12,17 @@ File: clzip.info, Node: Top, Next: Introduction, Up: (dir) Clzip Manual ************ -This manual is for Clzip (version 1.0, 5 April 2010). +This manual is for Clzip (version 1.1-rc2, 7 December 2010). * Menu: -* Introduction:: Purpose and features of clzip -* Algorithm:: How clzip compresses the data -* Invoking Clzip:: Command line interface -* File Format:: Detailed format of the compressed file -* Examples:: A small tutorial with examples -* Problems:: Reporting bugs -* Concept Index:: Index of concepts +* Introduction:: Purpose and features of clzip +* Algorithm:: How clzip compresses the data +* Invoking Clzip:: Command line interface +* File Format:: Detailed format of the compressed file +* Examples:: A small tutorial with examples +* Problems:: Reporting bugs +* Concept Index:: Index of concepts Copyright (C) 2010 Antonio Diaz Diaz. @@ -74,10 +74,12 @@ multivolume compressed tar archives. or 2 times the dictionary size limit (1 if input file size is less than dictionary size limit, else 2) plus 8 times the dictionary size really used. For decompression it is a little more than the dictionary size -really used. Clzip will automatically use the smallest possible -dictionary size without exceeding the given limit. It is important to -appreciate that the decompression memory requirement is affected at -compression time by the choice of dictionary size limit. +really used. + + Clzip will automatically use the smallest possible dictionary size +without exceeding the given limit. Keep in mind that the decompression +memory requirement is affected at compression time by the choice of +dictionary size limit. When decompressing, clzip attempts to guess the name for the decompressed file from that of the compressed file as follows: @@ -109,14 +111,12 @@ File: clzip.info, Node: Algorithm, Next: Invoking Clzip, Prev: Introduction, *********** Clzip implements a simplified version of the LZMA (Lempel-Ziv-Markov -chain-Algorithm) algorithm. The original LZMA algorithm was designed by -Igor Pavlov. - - The high compression of LZMA comes from combining two basic, -well-proven compression ideas: sliding dictionaries (LZ77/78) and -markov models (the thing used by every compression algorithm that uses -a range encoder or similar order-0 entropy coder as its last stage) -with segregation of contexts according to what the bits are used for. +chain-Algorithm) algorithm. The high compression of LZMA comes from +combining two basic, well-proven compression ideas: sliding dictionaries +(LZ77/78) and markov models (the thing used by every compression +algorithm that uses a range encoder or similar order-0 entropy coder as +its last stage) with segregation of contexts according to what the bits +are used for. Clzip is a two stage compressor. The first stage is a Lempel-Ziv coder, which reduces redundancy by translating chunks of data to their @@ -158,6 +158,13 @@ member or volume size limits are reached. 10) If there are more data to compress, go back to step 1. + +The ideas embodied in clzip are due to (at least) the following people: +Abraham Lempel and Jacob Ziv (for the LZ algorithm), Andrey Markov (for +the definition of Markov chains), G.N.N. Martin (for the definition of +range encoding), Igor Pavlov (for putting all the above together in +LZMA), and Julian Seward (for bzip2's CLI and the idea of unzcrash). + File: clzip.info, Node: Invoking Clzip, Next: File Format, Prev: Algorithm, Up: Top @@ -170,49 +177,50 @@ The format for running clzip is: Clzip supports the following options: -`--help' `-h' +`--help' Print an informative help message describing the options and exit. -`--version' `-V' +`--version' Print the version number of clzip on the standard output and exit. -`--member-size=SIZE' `-b SIZE' +`--member-size=SIZE' Produce a multimember file and set the member size limit to SIZE bytes. Minimum member size limit is 100kB. Small member size may degrade compression ratio, so use it only when needed. The default - is to produce single member files. + is to produce single-member files. -`--stdout' `-c' +`--stdout' Compress or decompress to standard output. Needed when reading from a named pipe (fifo) or from a device. Use it to recover as much of the uncompressed data as possible when decompressing a corrupt file. -`--decompress' `-d' +`--decompress' Decompress. -`--force' `-f' +`--force' Force overwrite of output file. -`--keep' `-k' +`--keep' Keep (don't delete) input files during compression or decompression. -`--match-length=LENGTH' `-m LENGTH' - Set the match length limit in bytes. Valid values range from 5 to - 273. Larger values usually give better compression ratios but - longer compression times. +`--match-length=LENGTH' + 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. -`--output=FILE' `-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, a file @@ -220,20 +228,25 @@ The format for running clzip is: `FILE00001.lz', `FILE00002.lz', etc, when compressing and splitting the output in volumes. -`--quiet' `-q' +`--quiet' Quiet operation. Suppress all messages. -`--dictionary-size=SIZE' `-s SIZE' +`--dictionary-size=SIZE' Set the dictionary size limit in bytes. Valid values range from 4KiB to 512MiB. Clzip will use the smallest possible dictionary size for each member without exceeding this limit. Note that dictionary sizes are quantized. If the specified size does not match one of the valid sizes, it will be rounded upwards. -`--volume-size=SIZE' + 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. + `-S SIZE' +`--volume-size=SIZE' Split the compressed output into several volume files with names `original_name00001.lz', `original_name00002.lz', etc, and set the volume size limit to SIZE bytes. Each volume is a complete, maybe @@ -241,15 +254,15 @@ The format for running clzip is: volume size may degrade compression ratio, so use it only when needed. -`--test' `-t' +`--test' Check integrity of the specified file(s), but don't decompress them. This really performs a trial decompression and throws away - the result. Use `-tvv' or `-tvvv' to see information about the - file. + the result. Use it together with `-v' to see information about + the file. -`--verbose' `-v' +`--verbose' Verbose mode. Show the compression ratio for each file processed. Further -v's increase the verbosity level. @@ -258,15 +271,21 @@ The format for running clzip is: limit) as shown in the table below. Note that `-9' can be much slower than `-1'. These options have no effect when decompressing. + 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 `--match-length' and + `--dictionary-size' options directly to achieve optimal + performance. + Level Dictionary size Match length limit - -1 1 MiB 10 bytes - -2 1.5 MiB 12 bytes - -3 2 MiB 17 bytes - -4 3 MiB 26 bytes - -5 4 MiB 44 bytes - -6 8 MiB 80 bytes - -7 16 MiB 108 bytes - -8 24 MiB 163 bytes + -1 1 MiB 5 bytes + -2 1.5 MiB 6 bytes + -3 2 MiB 8 bytes + -4 3 MiB 12 bytes + -5 4 MiB 20 bytes + -6 8 MiB 36 bytes + -7 16 MiB 68 bytes + -8 24 MiB 132 bytes -9 32 MiB 273 bytes `--fast' @@ -321,7 +340,7 @@ additional information before, between, or after them. All multibyte values are stored in little endian order. `ID string' - A four byte string, identifying the member type, with the value + A four byte string, identifying the lzip format, with the value "LZIP". `VN (version number, 1 byte)' @@ -358,9 +377,12 @@ File: clzip.info, Node: Examples, Next: Problems, Prev: File Format, Up: Top 5 A small tutorial with examples ******************************** -WARNING! If your data is important, give the `--keep' option to clzip -and do not remove the original file until you verify the compressed -file with a command like `clzip -cd file.lz | cmp file -'. +WARNING! Even if clzip is bug-free, other causes may result in a corrupt +compressed file (bugs in the system libraries, memory errors, etc). +Therefore, if the data you are going to compress is important give the +`--keep' option to clzip and do not remove the original file until you +verify the compressed file with a command like +`clzip -cd file.lz | cmp file -'. Example 1: Replace a regular file with its compressed version file.lz @@ -370,29 +392,47 @@ and show the compression ratio. Example 2: Like example 1 but the created file.lz is multimember with a -member size of 1MiB. +member size of 1MiB. The compression ratio is not shown. clzip -b 1MiB file -Example 3: Compress a whole floppy in /dev/fd0 and send the output to +Example 3: Restore a regular file from its compressed version file.lz. +If the operation is successful, file.lz is removed. + + clzip -d file.lz + + +Example 4: Verify the integrity of the compressed file file.lz and show +status. + + clzip -tv file.lz + + +Example 5: Compress a whole floppy in /dev/fd0 and send the output to file.lz. clzip -c /dev/fd0 > file.lz -Example 4: Create a multivolume compressed tar archive with a volume +Example 6: Decompress file.lz partially until 10KiB of decompressed data +are produced. + + clzip -cd file.lz | dd bs=1024 count=10 + + +Example 7: Create a multivolume compressed tar archive with a volume size of 1440KiB. tar -c some_directory | clzip -S 1440KiB -o volume_name -Example 5: Extract a multivolume compressed tar archive. +Example 8: Extract a multivolume compressed tar archive. clzip -cd volume_name*.lz | tar -xf - -Example 6: Create a multivolume compressed backup of a big database file +Example 9: Create a multivolume compressed backup of a big database file with a volume size of 650MB, where each volume is a multimember file with a member size of 32MiB. @@ -437,12 +477,12 @@ Concept Index Tag Table: Node: Top226 -Node: Introduction830 -Node: Algorithm4377 -Node: Invoking Clzip6608 -Node: File Format10964 -Node: Examples12920 -Node: Problems14097 -Node: Concept Index14623 +Node: Introduction905 +Node: Algorithm4439 +Node: Invoking Clzip6963 +Node: File Format11904 +Node: Examples13860 +Node: Problems15629 +Node: Concept Index16155 End Tag Table |