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Signed-off-by: Daniel Baumann <daniel@debian.org>
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doc/clzip.info
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@ -1,5 +1,4 @@
This is clzip.info, produced by makeinfo version 4.13 from
clzip.texinfo.
This is clzip.info, produced by makeinfo version 4.13+ from clzip.texi.
INFO-DIR-SECTION Data Compression
START-INFO-DIR-ENTRY
@ -12,7 +11,7 @@ File: clzip.info, Node: Top, Next: Introduction, Up: (dir)
Clzip Manual
************
This manual is for Clzip (version 1.5, 17 September 2013).
This manual is for Clzip (version 1.6-pre1, 30 January 2014).
* Menu:
@ -25,7 +24,7 @@ This manual is for Clzip (version 1.5, 17 September 2013).
* Concept index:: Index of concepts
Copyright (C) 2010, 2011, 2012, 2013 Antonio Diaz Diaz.
Copyright (C) 2010, 2011, 2012, 2013, 2014 Antonio Diaz Diaz.
This manual is free documentation: you have unlimited permission to
copy, distribute and modify it.
@ -37,10 +36,10 @@ File: clzip.info, Node: Introduction, Next: Algorithm, Prev: Top, Up: Top
**************
Clzip is a lossless data compressor with a user interface similar to the
one of gzip or bzip2. Clzip decompresses almost as fast as gzip and
compresses more than bzip2, which makes it well suited for software
distribution and data archiving. Clzip is a clean implementation of the
LZMA algorithm.
one of gzip or bzip2. Clzip decompresses almost as fast as gzip,
compresses most files more than bzip2, and is better than both from a
data recovery perspective. Clzip is a clean implementation of the LZMA
algorithm.
Clzip uses the lzip file format; the files produced by clzip are
fully compatible with lzip-1.4 or newer, and can be rescued with
@ -48,17 +47,24 @@ lziprecover. Clzip is in fact a C language version of lzip, intended
for embedded devices or systems lacking a C++ compiler.
The lzip file format is designed for long-term data archiving and
provides very safe integrity checking. The member trailer stores the
32-bit CRC of the original data, the size of the original data and the
size of the member. These values, together with the value remaining in
the range decoder and the end-of-stream marker, provide a 4 factor
integrity checking which guarantees that the decompressed version of the
data is identical to the original. This guards against corruption of the
compressed data, and against undetected bugs in clzip (hopefully very
unlikely). The chances of data corruption going undetected are
microscopic. Be aware, though, that the check occurs upon decompression,
so it can only tell you that something is wrong. It can't help you
recover the original uncompressed data.
provides very safe integrity checking. It is as simple as possible (but
not simpler), 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 lzip is copylefted, which guarantees that it will remain
free forever.
The member trailer stores the 32-bit CRC of the original data, the
size of the original data and the size of the member. These values,
together with the value remaining in the range decoder and the
end-of-stream marker, provide a 4 factor integrity checking which
guarantees that the decompressed version of the data is identical to
the original. This guards against corruption of the compressed data,
and against undetected bugs in clzip (hopefully very unlikely). The
chances of data corruption going undetected are microscopic. Be aware,
though, that the check occurs upon decompression, so it can only tell
you that something is wrong. It can't help you recover the original
uncompressed data.
If you ever need to recover data from a damaged lzip file, try the
lziprecover program. Lziprecover makes lzip files resistant to bit-flip
@ -67,15 +73,26 @@ recovery capabilities, including error-checked merging of damaged copies
of a file.
Clzip uses the same well-defined exit status values used by lzip and
bzip2, which makes it safer when used in pipes or scripts than
compressors returning ambiguous warning values, like gzip.
bzip2, which makes it safer than compressors returning ambiguous warning
values (like gzip) when it is used as a back end for tar or zutils.
Clzip replaces every file given in the command line with a compressed
version of itself, with the name "original_name.lz". Each compressed
file has the same modification date, permissions, and, when possible,
ownership as the corresponding original, so that these properties can be
correctly restored at decompression time. Clzip is able to read from
some types of non regular files if the `--stdout' option is specified.
When compressing, clzip replaces every file given in the command line
with a compressed version of itself, with the name "original_name.lz".
When decompressing, clzip 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
clzip 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).
Clzip is able to read from some types of non regular files if the
'--stdout' option is specified.
If no file names are specified, clzip compresses (or decompresses)
from standard input to standard output. In this case, clzip will
@ -100,21 +117,14 @@ large, about 64 PiB each.
The amount of memory required for compression is about 1 or 2 times
the dictionary size limit (1 if input file size is less than dictionary
size limit, else 2) plus 9 times the dictionary size really used. The
amount of memory required for decompression is only a few tens of KiB
larger than the dictionary size really used.
amount of memory required for decompression is about 46 kB larger than
the dictionary size 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:
filename.lz becomes filename
filename.tlz becomes filename.tar
anyothername becomes anyothername.out

File: clzip.info, Node: Algorithm, Next: Invoking clzip, Prev: Introduction, Up: Top
@ -160,7 +170,7 @@ price represents the number of output bits produced.
6) The range encoder encodes the sequence produced by the main
encoder and sends the produced bytes to the output stream.
7) Go back to step 3 until the input data is finished or until the
7) Go back to step 3 until the input data are finished or until the
member or volume size limits are reached.
8) The range encoder is flushed.
@ -188,67 +198,67 @@ The format for running clzip is:
Clzip supports the following options:
`-h'
`--help'
'-h'
'--help'
Print an informative help message describing the options and exit.
`-V'
`--version'
'-V'
'--version'
Print the version number of clzip on the standard output and exit.
`-b BYTES'
`--member-size=BYTES'
'-b BYTES'
'--member-size=BYTES'
Set the member size limit to BYTES. A small member size may
degrade compression ratio, so use it only when needed. Valid values
range from 100 kB to 64 PiB. Defaults to 64 PiB.
`-c'
`--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.
`-d'
`--decompress'
'-d'
'--decompress'
Decompress.
`-f'
`--force'
'-f'
'--force'
Force overwrite of output files.
`-F'
`--recompress'
Force recompression of files whose name already has the `.lz' or
`.tlz' suffix.
'-F'
'--recompress'
Force recompression of files whose name already has the '.lz' or
'.tlz' suffix.
`-k'
`--keep'
'-k'
'--keep'
Keep (don't delete) input files during compression or
decompression.
`-m BYTES'
`--match-length=BYTES'
'-m BYTES'
'--match-length=BYTES'
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.
`-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
named `FILE.lz' when compressing, and several files named
`FILE00001.lz', `FILE00002.lz', etc, when compressing and
'-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
named 'FILE.lz' when compressing, and several files named
'FILE00001.lz', 'FILE00002.lz', etc, when compressing and
splitting the output in volumes.
`-q'
`--quiet'
'-q'
'--quiet'
Quiet operation. Suppress all messages.
`-s BYTES'
`--dictionary-size=BYTES'
'-s BYTES'
'--dictionary-size=BYTES'
Set the dictionary size limit in bytes. Valid values range from 4
KiB to 512 MiB. Clzip will use the smallest possible dictionary
size for each member without exceeding this limit. Note that
@ -261,42 +271,42 @@ The format for running clzip is:
requirement is affected at compression time by the choice of
dictionary size limit.
`-S BYTES'
`--volume-size=BYTES'
'-S BYTES'
'--volume-size=BYTES'
Split the compressed output into several volume files with names
`original_name00001.lz', `original_name00002.lz', etc, and set the
'original_name00001.lz', 'original_name00002.lz', etc, and set the
volume size limit to BYTES. Each volume is a complete, maybe
multi-member, lzip file. A small volume size may degrade
compression ratio, so use it only when needed. Valid values range
from 100 kB to 4 EiB.
`-t'
`--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 it together with `-v' to see information about
the result. Use it together with '-v' to see information about
the file.
`-v'
`--verbose'
'-v'
'--verbose'
Verbose mode.
When compressing, show the compression ratio for each file
processed. A second `-v' shows the progress of compression.
processed. A second '-v' shows the progress of compression.
When decompressing or testing, further -v's (up to 4) increase the
verbosity level, showing status, compression ratio, dictionary
size, and trailer contents (CRC, data size, member size).
`-1 .. -9'
'-1 .. -9'
Set the compression parameters (dictionary size and match length
limit) as shown in the table below. Note that `-9' can be much
slower than `-1'. These options have no effect when decompressing.
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. For example, `-9m64' usually compresses executables
more (and faster) than `-9'.
repetitive, etc, you may need to use the '--match-length' and
'--dictionary-size' options directly to achieve optimal
performance. For example, '-9m64' usually compresses executables
more (and faster) than '-9'.
Level Dictionary size Match length limit
-1 1 MiB 5 bytes
@ -309,13 +319,13 @@ The format for running clzip is:
-8 24 MiB 132 bytes
-9 32 MiB 273 bytes
`--fast'
`--best'
'--fast'
'--best'
Aliases for GNU gzip compatibility.
Numbers given as arguments to options may be followed by a multiplier
and an optional `B' for "byte".
and an optional 'B' for "byte".
Table of SI and binary prefixes (unit multipliers):
@ -370,15 +380,15 @@ additional information before, between, or after them.
All multibyte values are stored in little endian order.
`ID string'
'ID string'
A four byte string, identifying the lzip format, with the value
"LZIP" (0x4C, 0x5A, 0x49, 0x50).
`VN (version number, 1 byte)'
'VN (version number, 1 byte)'
Just in case something needs to be modified in the future. 1 for
now.
`DS (coded dictionary size, 1 byte)'
'DS (coded dictionary size, 1 byte)'
Lzip divides the distance between any two powers of 2 into 8
equally spaced intervals, named "wedges". The dictionary size is
calculated by taking a power of 2 (the base size) and substracting
@ -390,18 +400,18 @@ additional information before, between, or after them.
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.
`Lzma stream'
'Lzma stream'
The lzma stream, finished by an end of stream marker. Uses default
values for encoder properties. See the lzip manual for a full
description.
`CRC32 (4 bytes)'
'CRC32 (4 bytes)'
CRC of the uncompressed original data.
`Data size (8 bytes)'
'Data size (8 bytes)'
Size of the uncompressed original data.
`Member size (8 bytes)'
'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
@ -416,49 +426,49 @@ File: clzip.info, Node: Examples, Next: Problems, Prev: File format, Up: Top
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
Therefore, if the data you are going to compress are 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 -'.
'clzip -cd file.lz | cmp file -'.
Example 1: Replace a regular file with its compressed version `file.lz'
Example 1: Replace a regular file with its compressed version 'file.lz'
and show the compression ratio.
clzip -v file
Example 2: Like example 1 but the created `file.lz' is multi-member
Example 2: Like example 1 but the created 'file.lz' is multi-member
with a member size of 1 MiB. The compression ratio is not shown.
clzip -b 1MiB file
Example 3: Restore a regular file from its compressed version
`file.lz'. If the operation is successful, `file.lz' is removed.
'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
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'.
'file.lz'.
clzip -c /dev/fd0 > file.lz
Example 6: Decompress `file.lz' partially until 10 KiB of decompressed
Example 6: Decompress 'file.lz' partially until 10 KiB of decompressed
data are produced.
clzip -cd file.lz | dd bs=1024 count=10
Example 7: Decompress `file.lz' partially from decompressed byte 10000
Example 7: Decompress 'file.lz' partially from decompressed byte 10000
to decompressed byte 15000 (5000 bytes are produced).
clzip -cd file.lz | dd bs=1000 skip=10 count=5
@ -494,7 +504,7 @@ for all eternity, if not longer.
If you find a bug in clzip, please send electronic mail to
<lzip-bug@nongnu.org>. Include the version number, which you can find
by running `clzip --version'.
by running 'clzip --version'.

File: clzip.info, Node: Concept index, Prev: Problems, Up: Top
@ -519,14 +529,14 @@ Concept index

Tag Table:
Node: Top212
Node: Introduction914
Node: Algorithm5091
Node: Invoking clzip7590
Node: File format13189
Node: Examples15694
Node: Problems17662
Node: Concept index18188
Node: Top210
Node: Introduction921
Node: Algorithm5557
Node: Invoking clzip8057
Node: File format13656
Node: Examples16161
Node: Problems18130
Node: Concept index18656

End Tag Table