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authorDaniel Baumann <mail@daniel-baumann.ch>2015-11-06 12:52:24 +0000
committerDaniel Baumann <mail@daniel-baumann.ch>2015-11-06 12:52:24 +0000
commitf3418da4287ccac0e1139dacde5669aa091fadb1 (patch)
tree0a24633209a77b4bbe7ceb1f2c582f69aaaca102 /doc/clzip.texi
parentAdding upstream version 1.7~pre1. (diff)
downloadclzip-f3418da4287ccac0e1139dacde5669aa091fadb1.tar.xz
clzip-f3418da4287ccac0e1139dacde5669aa091fadb1.zip
Adding upstream version 1.7~rc1.upstream/1.7_rc1
Signed-off-by: Daniel Baumann <mail@daniel-baumann.ch>
Diffstat (limited to 'doc/clzip.texi')
-rw-r--r--doc/clzip.texi43
1 files changed, 21 insertions, 22 deletions
diff --git a/doc/clzip.texi b/doc/clzip.texi
index 01f5f39..a74ec6f 100644
--- a/doc/clzip.texi
+++ b/doc/clzip.texi
@@ -6,8 +6,8 @@
@finalout
@c %**end of header
-@set UPDATED 26 February 2015
-@set VERSION 1.7-pre1
+@set UPDATED 23 May 2015
+@set VERSION 1.7-rc1
@dircategory Data Compression
@direntry
@@ -58,8 +58,7 @@ to copy, distribute and modify it.
Clzip is a lossless data compressor with a user interface similar to the
one of gzip or bzip2. Clzip is about 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
-(Lempel-Ziv-Markov chain-Algorithm) "algorithm".
+perspective.
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 lziprecover.
@@ -162,23 +161,24 @@ multivolume compressed tar archives.
Clzip is able to compress and decompress streams of unlimited size by
automatically creating multi-member output. The members so created are
-large, about 64 PiB each.
+large, about 2 PiB each.
@node Algorithm
@chapter Algorithm
@cindex algorithm
-There is no such thing as a "LZMA algorithm"; it is more like a "LZMA
-coding scheme". For example, the option '-0' of lzip uses the scheme in
-almost the simplest way possible; issuing the longest match it can find,
-or a literal byte if it can't find a match. Inversely, a much more
-elaborated way of finding coding sequences of minimum price than the one
-currently used by lzip could be developed, and the resulting sequence
-could also be coded using the LZMA coding scheme.
+In spite of its name (Lempel-Ziv-Markov chain-Algorithm), LZMA is not a
+concrete algorithm; it is more like "any algorithm using the LZMA coding
+scheme". For example, the option '-0' of lzip uses the scheme in almost
+the simplest way possible; issuing the longest match it can find, or a
+literal byte if it can't find a match. Inversely, a much more elaborated
+way of finding coding sequences of minimum size than the one currently
+used by lzip could be developed, and the resulting sequence could also
+be coded using the LZMA coding scheme.
-Clzip currently implements two variants of the LZMA algorithm; fast (used
-by option -0) and normal (used by all other compression levels).
+Clzip currently implements two variants of the LZMA algorithm; fast
+(used by option -0) and normal (used by all other compression levels).
The high compression of LZMA comes from combining two basic, well-proven
compression ideas: sliding dictionaries (LZ77/78) and markov models (the
@@ -245,7 +245,7 @@ clzip [@var{options}] [@var{files}]
Clzip supports the following options:
-@table @samp
+@table @code
@item -h
@itemx --help
Print an informative help message describing the options and exit.
@@ -258,7 +258,7 @@ Print the version number of clzip on the standard output and exit.
@itemx --member-size=@var{bytes}
Set the member size limit to @var{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.
+range from 100 kB to 2 PiB. Defaults to 2 PiB.
@item -c
@itemx --stdout
@@ -441,13 +441,12 @@ A four byte string, identifying the lzip format, with the value "LZIP"
Just in case something needs to be modified in the future. 1 for now.
@item 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 from it a number of
-wedges between 0 and 7. The size of a wedge is (base_size / 16).@*
+The dictionary size is calculated by taking a power of 2 (the base size)
+and substracting 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 number of wedges (0 to 7) to substract from the
-base size to obtain the dictionary size.@*
+Bits 7-5 contain the numerator of the fraction (0 to 7) to substract
+from the base size to obtain the dictionary size.@*
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.