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Description
Plzip is a massively parallel (multi-threaded), lossless data compressor
-based on the lzlib compression library, with very safe integrity
-checking and a user interface similar to the one of bzip2, gzip or lzip.
+based on the lzlib compression library, with a user interface similar to
+the one of lzip, bzip2 or gzip.
-Plzip is intended for faster compression/decompression of big files on
-multiprocessor machines, which makes it specially well suited for
-distribution of big software files and large scale data archiving. On
-files big enough (several GB), plzip can use hundreds of processors.
-
-Plzip uses the lzip file format; the files produced by plzip are fully
-compatible with lzip-1.4 or newer, and can be rescued with lziprecover.
+Plzip can compress/decompress large files on multiprocessor machines
+much faster than lzip, at the cost of a slightly reduced compression
+ratio. On files large enough (several GB), plzip can use hundreds of
+processors. On files of only a few MB it is better to use lzip.
Plzip uses the same well-defined exit status values used by lzip and
bzip2, which makes it safer when used in pipes or scripts than
compressors returning ambiguous warning values, like gzip.
+Plzip uses the lzip file format; the files produced by plzip are fully
+compatible with lzip-1.4 or newer, and can be rescued with lziprecover.
+
+The lzip file format is designed for long-term data archiving and
+provides very safe integrity checking. 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 plzip (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.
+
Plzip replaces every file given in the command line with a compressed
version of itself, with the name "original_name.lz". Each compressed
file has the same modification date, permissions, and, when possible,
@@ -33,18 +52,6 @@ or more compressed files. The result is the concatenation of the
corresponding uncompressed files. Integrity testing of concatenated
compressed files is also supported.
-As a self-check for your protection, plzip stores in the member trailer
-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 very safe 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 plzip (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.
-
Copyright (C) 2009, 2010, 2011, 2012, 2013 Antonio Diaz Diaz.