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Source code changes of the file "README" between
lzlib-1.11.tar.lz and lzlib-1.12-rc1.tar.lz

About: Lzlib is a data compression library providing in-memory LZMA compression and decompression functions using the lzip format. Release candidate.

README  (lzlib-1.11.tar.lz):README  (lzlib-1.12-rc1.tar.lz)
Description Description
Lzlib is a data compression library providing in-memory LZMA compression Lzlib is a data compression library providing in-memory LZMA compression and
and decompression functions, including integrity checking of the decompression functions, including integrity checking of the decompressed
decompressed data. The compressed data format used by the library is the data. The compressed data format used by the library is the lzip format.
lzip format. Lzlib is written in C. Lzlib is written in C.
The lzip file format is designed for data sharing and long-term archiving, The lzip file format is designed for data sharing and long-term archiving,
taking into account both data integrity and decoder availability: taking into account both data integrity and decoder availability:
* The lzip format provides very safe integrity checking and some data * The lzip format provides very safe integrity checking and some data
recovery means. The lziprecover program can repair bit flip errors recovery means. The program lziprecover can repair bit flip errors
(one of the most common forms of data corruption) in lzip files, (one of the most common forms of data corruption) in lzip files, and
and provides data recovery capabilities, including error-checked provides data recovery capabilities, including error-checked merging
merging of damaged copies of a file. of damaged copies of a file.
* The lzip format is as simple as possible (but not simpler). The * The lzip format is as simple as possible (but not simpler). The lzip
lzip manual provides the source code of a simple decompressor manual provides the source code of a simple decompressor along with a
along with a detailed explanation of how it works, so that with detailed explanation of how it works, so that with the only help of the
the only help of the lzip manual it would be possible for a lzip manual it would be possible for a digital archaeologist to extract
digital archaeologist to extract the data from a lzip file long the data from a lzip file long after quantum computers eventually
after quantum computers eventually render LZMA obsolete. render LZMA obsolete.
* Additionally the lzip reference implementation is copylefted, which * Additionally the lzip reference implementation is copylefted, which
guarantees that it will remain free forever. guarantees that it will remain free forever.
A nice feature of the lzip format is that a corrupt byte is easier to A nice feature of the lzip format is that a corrupt byte is easier to repair
repair the nearer it is from the beginning of the file. Therefore, with the nearer it is from the beginning of the file. Therefore, with the help of
the help of lziprecover, losing an entire archive just because of a lziprecover, losing an entire archive just because of a corrupt byte near
corrupt byte near the beginning is a thing of the past. the beginning is a thing of the past.
The functions and variables forming the interface of the compression The functions and variables forming the interface of the compression library
library are declared in the file 'lzlib.h'. Usage examples of the are declared in the file 'lzlib.h'. Usage examples of the library are given
library are given in the files 'main.c' and 'bbexample.c' from the in the files 'bbexample.c', 'ffexample.c', and 'main.c' from the source
source distribution. distribution.
Compression/decompression is done by repeatedly calling a couple of Compression/decompression is done by repeatedly calling a couple of
read/write functions until all the data have been processed by the read/write functions until all the data have been processed by the library.
library. This interface is safer and less error prone than the This interface is safer and less error prone than the traditional zlib
traditional zlib interface. interface.
Compression/decompression is done when the read function is called. This Compression/decompression is done when the read function is called. This
means the value returned by the position functions will not be updated means the value returned by the position functions will not be updated until
until a read call, even if a lot of data are written. If you want the a read call, even if a lot of data are written. If you want the data to be
data to be compressed in advance, just call the read function with a compressed in advance, just call the read function with a size equal to 0.
size equal to 0.
If all the data to be compressed are written in advance, lzlib will If all the data to be compressed are written in advance, lzlib will
automatically adjust the header of the compressed data to use the automatically adjust the header of the compressed data to use the largest
largest dictionary size that does not exceed neither the data size nor dictionary size that does not exceed neither the data size nor the limit
the limit given to LZ_compress_open. This feature reduces the amount of given to LZ_compress_open. This feature reduces the amount of memory needed
memory needed for decompression and allows minilzip to produce identical for decompression and allows minilzip to produce identical compressed output
compressed output as lzip. as lzip.
Lzlib will correctly decompress a data stream which is the concatenation Lzlib will correctly decompress a data stream which is the concatenation of
of two or more compressed data streams. The result is the concatenation two or more compressed data streams. The result is the concatenation of the
of the corresponding decompressed data streams. Integrity testing of corresponding decompressed data streams. Integrity testing of concatenated
concatenated compressed data streams is also supported. compressed data streams is also supported.
Lzlib is able to compress and decompress streams of unlimited size by Lzlib is able to compress and decompress streams of unlimited size by
automatically creating multimember output. The members so created are automatically creating multimember output. The members so created are large,
large, about 2 PiB each. about 2 PiB each.
All the library functions are thread safe. The library does not install All the library functions are thread safe. The library does not install
any signal handler. The decoder checks the consistency of the compressed any signal handler. The decoder checks the consistency of the compressed
data, so the library should never crash even in case of corrupted input. data, so the library should never crash even in case of corrupted input.
In spite of its name (Lempel-Ziv-Markov chain-Algorithm), LZMA is not a 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 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 scheme". For example, the option '-0' of lzip uses the scheme in almost the
the simplest way possible; issuing the longest match it can find, or a simplest way possible; issuing the longest match it can find, or a literal
literal byte if it can't find a match. Inversely, a much more elaborated byte if it can't find a match. Inversely, a much more elaborated way of
way of finding coding sequences of minimum size than the one currently finding coding sequences of minimum size than the one currently used by lzip
used by lzip could be developed, and the resulting sequence could also could be developed, and the resulting sequence could also be coded using the
be coded using the LZMA coding scheme. LZMA coding scheme.
Lzlib currently implements two variants of the LZMA algorithm; fast Lzlib currently implements two variants of the LZMA algorithm; fast (used by
(used by option '-0' of minilzip) and normal (used by all other option '-0' of minilzip) and normal (used by all other compression levels).
compression levels).
The high compression of LZMA comes from combining two basic, well-proven The high compression of LZMA comes from combining two basic, well-proven
compression ideas: sliding dictionaries (LZ77/78) and markov models (the compression ideas: sliding dictionaries (LZ77/78) and markov models (the
thing used by every compression algorithm that uses a range encoder or thing used by every compression algorithm that uses a range encoder or
similar order-0 entropy coder as its last stage) with segregation of similar order-0 entropy coder as its last stage) with segregation of
contexts according to what the bits are used for. contexts according to what the bits are used for.
The ideas embodied in lzlib are due to (at least) the following people: The ideas embodied in lzlib are due to (at least) the following people:
Abraham Lempel and Jacob Ziv (for the LZ algorithm), Andrey Markov (for Abraham Lempel and Jacob Ziv (for the LZ algorithm), Andrey Markov (for the
the definition of Markov chains), G.N.N. Martin (for the definition of definition of Markov chains), G.N.N. Martin (for the definition of range
range encoding), Igor Pavlov (for putting all the above together in encoding), Igor Pavlov (for putting all the above together in LZMA), and
LZMA), and Julian Seward (for bzip2's CLI). Julian Seward (for bzip2's CLI).
LANGUAGE NOTE: Uncompressed = not compressed = plain data; it may never LANGUAGE NOTE: Uncompressed = not compressed = plain data; it may never have
have been compressed. Decompressed is used to refer to data which have been compressed. Decompressed is used to refer to data which have undergone
undergone the process of decompression. the process of decompression.
Copyright (C) 2009-2019 Antonio Diaz Diaz. Copyright (C) 2009-2020 Antonio Diaz Diaz.
This file is free documentation: you have unlimited permission to copy, This file is free documentation: you have unlimited permission to copy,
distribute and modify it. distribute, and modify it.
The file Makefile.in is a data file used by configure to produce the The file Makefile.in is a data file used by configure to produce the
Makefile. It has the same copyright owner and permissions that configure Makefile. It has the same copyright owner and permissions that configure
itself. itself.
 End of changes. 11 change blocks. 
63 lines changed or deleted 61 lines changed or added

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