diff options
Diffstat (limited to 'doc/lzlib.texi')
| -rw-r--r-- | doc/lzlib.texi | 30 |
1 files changed, 15 insertions, 15 deletions
diff --git a/doc/lzlib.texi b/doc/lzlib.texi index 417cc7b..228d747 100644 --- a/doc/lzlib.texi +++ b/doc/lzlib.texi @@ -6,8 +6,8 @@ @finalout @c %**end of header -@set UPDATED 24 February 2015 -@set VERSION 1.7-pre1 +@set UPDATED 23 May 2015 +@set VERSION 1.7-rc1 @dircategory Data Compression @direntry @@ -126,13 +126,14 @@ All the library functions are thread safe. The library does not install any signal handler. The decoder checks the consistency of the compressed data, so the library should never crash even in case of corrupted input. -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. Lzlib currently implements two variants of the LZMA algorithm; fast (used by option -0 of minilzip) and normal (used by all other @@ -667,13 +668,12 @@ 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. |