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diff --git a/doc/lzip.texinfo b/doc/lzip.texinfo index 0ebc9ca..76ccfc9 100644 --- a/doc/lzip.texinfo +++ b/doc/lzip.texinfo @@ -6,8 +6,8 @@ @finalout @c %**end of header -@set UPDATED 24 February 2012 -@set VERSION 1.13 +@set UPDATED 17 February 2013 +@set VERSION 1.14 @dircategory Data Compression @direntry @@ -45,7 +45,8 @@ This manual is for Lzip (version @value{VERSION}, @value{UPDATED}). @end menu @sp 1 -Copyright @copyright{} 2008, 2009, 2010, 2011, 2012 Antonio Diaz Diaz. +Copyright @copyright{} 2008, 2009, 2010, 2011, 2012, 2013 +Antonio Diaz Diaz. This manual is free documentation: you have unlimited permission to copy, distribute and modify it. @@ -87,12 +88,16 @@ split the compressed output in volumes of a given size, even when reading from standard input. This allows the direct creation of multivolume compressed tar archives. -The amount of memory required for compression is about 5 MiB plus 1 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. The option @samp{-0} is special and only requires about 1.5 MiB at -most. The amount of memory required for decompression is only a few tens -of KiB larger than the dictionary size really used. +Lzip is able to compress and decompress streams of unlimited size by +automatically creating multi-member output. The members so created are +large (about 2^60 bytes 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 option +@samp{-0} is special and only requires about 1.5 MiB at most. The amount +of memory required for decompression is only a few tens of KiB larger +than the dictionary size really used. Lzip will automatically use the smallest possible dictionary size without exceeding the given limit. Keep in mind that the decompression @@ -348,6 +353,11 @@ Table of SI and binary prefixes (unit multipliers): @chapter File Format @cindex file format +Perfection is reached, not when there is no longer anything to add, but +when there is no longer anything to take away.@* +--- Antoine de Saint-Exupery + +@sp 1 In the diagram below, a box like this: @verbatim +---+ @@ -383,15 +393,16 @@ All multibyte values are stored in little endian order. A four byte string, identifying the lzip format, with the value "LZIP". @item VN (version number, 1 byte) -Just in case something needs to be modified in the future. Valid values -are 0 and 1. Version 0 files are deprecated. They can contain only one -member and lack the @samp{Member size} field. +Just in case something needs to be modified in the future. 1 for now. @item DS (coded dictionary size, 1 byte) -Bits 4-0 contain the base 2 logarithm of the base dictionary size.@* -Bits 7-5 contain the number of "wedges" to substract from the base -dictionary size to obtain the dictionary size. The size of a wedge is -(base dictionary size / 16).@* +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).@* +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.@* Valid values for dictionary size range from 4KiB to 512MiB. @item Lzma stream @@ -405,8 +416,9 @@ CRC of the uncompressed original data. Size of the uncompressed original data. @item Member size (8 bytes) -Total size of the member, including header and trailer. This facilitates -safe recovery of undamaged members from multi-member files. +Total size of the member, including header and trailer. This field acts +as a distributed index, and facilitates safe recovery of undamaged +members from multi-member files. @end table @@ -419,8 +431,8 @@ WARNING! Even if lzip 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 @samp{--keep} option to lzip and do not remove the original file until -you verify the compressed file with a command like @w{@samp{lzip -cd -file.lz | cmp file -}}. +you verify the compressed file with a command like +@w{@samp{lzip -cd file.lz | cmp file -}}. @sp 1 @noindent |