Adding upstream version 1.6~pre2.upstream/1.6_pre2

Signed-off-by: Daniel Baumann <mail@daniel-baumann.ch>

1 files changed, 40 insertions, 36 deletions

diff --git a/README b/README
index 7fb35e2..765c73a 100644
--- a/README
+++ b/README
@@ -11,35 +11,34 @@ compatible with lzip-1.4 or newer, and can be rescued with 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. 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
-(one of the most common forms of data corruption), and provides data
-recovery capabilities, including error-checked merging of damaged copies
-of a file.
+The lzip file format is designed for long-term data archiving, taking
+into account both data integrity and decoder availability:
+
+   * The lzip format provides very safe integrity checking and some data
+     recovery means. The lziprecover program can repair bit-flip errors
+     (one of the most common forms of data corruption) in lzip files,
+     and provides data recovery capabilities, including error-checked
+     merging of damaged copies of a file.
+
+   * The lzip format is as simple as possible (but not simpler). The
+     lzip manual provides the code of a simple decompressor along with a
+     detailed explanation of how it works, 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.
 
 Clzip uses the same well-defined exit status values used by lzip and
 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 will automatically use the smallest possible dictionary size for
+each file 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 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
@@ -78,18 +77,23 @@ 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.
 
-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.
-
-Clzip implements a simplified version of the LZMA (Lempel-Ziv-Markov
-chain-Algorithm) algorithm. The high compression of LZMA comes from
-combining two basic, well-proven compression ideas: sliding dictionaries
-(LZ77/78) and markov models (the thing used by every compression
-algorithm that uses a range encoder or similar order-0 entropy coder as
-its last stage) with segregation of contexts according to what the bits
-are used for.
+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.
+
+Lzip currently implements two variants of the LZMA algorithm; fast (used
+by option -0) and normal (used by all other compression levels). Clzip
+just implements the "normal" variant.
+
+The high compression of LZMA comes from combining two basic, well-proven
+compression ideas: sliding dictionaries (LZ77/78) and markov models (the
+thing used by every compression algorithm that uses a range encoder or
+similar order-0 entropy coder as its last stage) with segregation of
+contexts according to what the bits are used for.
 
 The ideas embodied in clzip are due to (at least) the following people:
 Abraham Lempel and Jacob Ziv (for the LZ algorithm), Andrey Markov (for