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@ -11,13 +11,13 @@ File: clzip.info, Node: Top, Next: Introduction, Up: (dir)
Clzip Manual
************
This manual is for Clzip (version 1.13, 24 January 2022).
This manual is for Clzip (version 1.14-rc1, 20 December 2023).
* Menu:
* Introduction:: Purpose and features of clzip
* Output:: Meaning of clzip's output
* Invoking clzip:: Command line interface
* Invoking clzip:: Command-line interface
* Quality assurance:: Design, development, and testing of lzip
* Algorithm:: How clzip compresses the data
* File format:: Detailed format of the compressed file
@ -29,7 +29,7 @@ This manual is for Clzip (version 1.13, 24 January 2022).
* Concept index:: Index of concepts
Copyright (C) 2010-2022 Antonio Diaz Diaz.
Copyright (C) 2010-2023 Antonio Diaz Diaz.
This manual is free documentation: you have unlimited permission to copy,
distribute, and modify it.
@ -47,14 +47,15 @@ C++ compiler.
Lzip is a lossless data compressor with a user interface similar to the
one of gzip or bzip2. Lzip uses a simplified form of the 'Lempel-Ziv-Markov
chain-Algorithm' (LZMA) stream format and provides a 3 factor integrity
checking to maximize interoperability and optimize safety. Lzip can compress
about as fast as gzip (lzip -0) or compress most files more than bzip2
(lzip -9). Decompression speed is intermediate between gzip and bzip2. Lzip
is better than gzip and bzip2 from a data recovery perspective. Lzip has
been designed, written, and tested with great care to replace gzip and
bzip2 as the standard general-purpose compressed format for unix-like
systems.
chain-Algorithm' (LZMA) stream format to maximize interoperability. The
maximum dictionary size is 512 MiB so that any lzip file can be decompressed
on 32-bit machines. Lzip provides accurate and robust 3-factor integrity
checking. Lzip can compress about as fast as gzip (lzip -0) or compress most
files more than bzip2 (lzip -9). Decompression speed is intermediate between
gzip and bzip2. Lzip is better than gzip and bzip2 from a data recovery
perspective. Lzip has been designed, written, and tested with great care to
replace gzip and bzip2 as the standard general-purpose compressed format for
Unix-like systems.
For compressing/decompressing large files on multiprocessor machines
plzip can be much faster than lzip at the cost of a slightly reduced
@ -92,22 +93,22 @@ byte near the beginning is a thing of the past.
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 "End Of Stream" marker, provide a 3 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.
with the "End Of Stream" marker, provide a 3-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.
Clzip uses the same well-defined exit status values used by bzip2, which
makes it safer than compressors returning ambiguous warning values (like
gzip) when it is used as a back end for other programs like tar or zutils.
Clzip will automatically use for each file the largest dictionary size
that does not exceed neither the file size nor the limit given. Keep in
mind that the decompression memory requirement is affected at compression
time by the choice of dictionary size limit.
Clzip automatically uses for each file the largest dictionary size that
does not exceed neither the file size nor the limit given. Keep in mind
that the decompression memory requirement is affected at compression time
by the choice of dictionary size limit.
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
@ -126,22 +127,22 @@ filename.tlz becomes filename.tar
anyothername becomes anyothername.out
(De)compressing a file is much like copying or moving it. Therefore clzip
preserves the access and modification dates, permissions, and, when
possible, ownership of the file just as 'cp -p' does. (If the user ID or
the group ID can't be duplicated, the file permission bits S_ISUID and
S_ISGID are cleared).
preserves the access and modification dates, permissions, and, if you have
appropriate privileges, ownership of the file just as 'cp -p' does. (If the
user ID or the group ID can't be duplicated, the file permission bits
S_ISUID and S_ISGID are cleared).
Clzip is able to read from some types of non-regular files if either the
option '-c' or the option '-o' is specified.
Clzip will refuse to read compressed data from a terminal or write
compressed data to a terminal, as this would be entirely incomprehensible
and might leave the terminal in an abnormal state.
Clzip refuses to read compressed data from a terminal or write compressed
data to a terminal, as this would be entirely incomprehensible and might
leave the terminal in an abnormal state.
Clzip will correctly decompress a file which is the concatenation of two
or more compressed files. The result is the concatenation of the
corresponding decompressed files. Integrity testing of concatenated
compressed files is also supported.
Clzip correctly decompresses a file which is the concatenation of two or
more compressed files. The result is the concatenation of the corresponding
decompressed files. Integrity testing of concatenated compressed files is
also supported.
Clzip can produce multimember files, and lziprecover can safely recover
the undamaged members in case of file damage. Clzip can also split the
@ -213,7 +214,8 @@ The format for running clzip is:
If no file names are specified, clzip compresses (or decompresses) from
standard input to standard output. A hyphen '-' used as a FILE argument
means standard input. It can be mixed with other FILES and is read just
once, the first time it appears in the command line.
once, the first time it appears in the command line. Remember to prepend
'./' to any file name beginning with a hyphen, or use '--'.
clzip supports the following options: *Note Argument syntax:
(arg_parser)Argument syntax.
@ -253,13 +255,14 @@ once, the first time it appears in the command line.
'-d'
'--decompress'
Decompress the files specified. If a file does not exist, can't be
opened, or the destination file already exists and '--force' has not
been specified, clzip continues decompressing the rest of the files
and exits with error status 1. If a file fails to decompress, or is a
terminal, clzip exits immediately with error status 2 without
decompressing the rest of the files. A terminal is considered an
uncompressed file, and therefore invalid.
Decompress the files specified. The integrity of the files specified is
checked. If a file does not exist, can't be opened, or the destination
file already exists and '--force' has not been specified, clzip
continues decompressing the rest of the files and exits with error
status 1. If a file fails to decompress, or is a terminal, clzip exits
immediately with error status 2 without decompressing the rest of the
files. A terminal is considered an uncompressed file, and therefore
invalid.
'-f'
'--force'
@ -286,26 +289,27 @@ once, the first time it appears in the command line.
printed.
If any file is damaged, does not exist, can't be opened, or is not
regular, the final exit status will be > 0. '-lq' can be used to verify
regular, the final exit status is > 0. '-lq' can be used to check
quickly (without decompressing) the structural integrity of the files
specified. (Use '--test' to verify the data integrity). '-alq'
additionally verifies that none of the files specified contain
trailing data.
specified. (Use '--test' to check the data integrity). '-alq'
additionally checks that none of the files specified contain trailing
data.
'-m BYTES'
'--match-length=BYTES'
When compressing, set the match length limit in bytes. After a match
this long is found, the search is finished. Valid values range from 5
to 273. Larger values usually give better compression ratios but longer
compression times.
to 273. Larger values usually give better compression ratios but
longer compression times.
'-o FILE'
'--output=FILE'
If '-c' has not been also specified, write the (de)compressed output to
FILE; keep input files unchanged. If compressing several files, each
file is compressed independently. (The output consists of a sequence of
independently compressed members). This option (or '-c') is needed when
reading from a named pipe (fifo) or from a device. '-o -' is
If '-c' has not been also specified, write the (de)compressed output
to FILE, automatically creating any missing parent directories; keep
input files unchanged. If compressing several files, each file is
compressed independently. (The output consists of a sequence of
independently compressed members). This option (or '-c') is needed
when reading from a named pipe (fifo) or from a device. '-o -' is
equivalent to '-c'. '-o' has no effect when testing or listing.
In order to keep backward compatibility with clzip versions prior to
@ -326,14 +330,14 @@ once, the first time it appears in the command line.
'-s BYTES'
'--dictionary-size=BYTES'
When compressing, set the dictionary size limit in bytes. Clzip will
use for each file the largest dictionary size that does not exceed
neither the file size nor this limit. Valid values range from 4 KiB to
512 MiB. Values 12 to 29 are interpreted as powers of two, meaning
2^12 to 2^29 bytes. Dictionary sizes are quantized so that they can be
coded in just one byte (*note coded-dict-size::). If the size specified
does not match one of the valid sizes, it will be rounded upwards by
adding up to (BYTES / 8) to it.
When compressing, set the dictionary size limit in bytes. Clzip uses
for each file the largest dictionary size that does not exceed neither
the file size nor this limit. Valid values range from 4 KiB to 512 MiB.
Values 12 to 29 are interpreted as powers of two, meaning 2^12 to 2^29
bytes. Dictionary sizes are quantized so that they can be coded in
just one byte (*note coded-dict-size::). If the size specified does
not match one of the valid sizes, it is rounded upwards by adding up
to (BYTES / 8) to it.
For maximum compression you should use a dictionary size limit as large
as possible, but keep in mind that the decompression memory requirement
@ -355,7 +359,7 @@ once, the first time it appears in the command line.
really performs a trial decompression and throws away the result. Use
it together with '-v' to see information about the files. If a file
fails the test, does not exist, can't be opened, or is a terminal,
clzip continues checking the rest of the files. A final diagnostic is
clzip continues testing the rest of the files. A final diagnostic is
shown at verbosity level 1 or higher if any file fails the test when
testing multiple files.
@ -403,6 +407,16 @@ once, the first time it appears in the command line.
'--best'
Aliases for GNU gzip compatibility.
'--empty-error'
Exit with error status 2 if any empty member is found in the input
files.
'--marking-error'
Exit with error status 2 if the first LZMA byte is non-zero in any
member of the input files. This may be caused by data corruption or by
deliberate insertion of tracking information in the file. Use
'lziprecover --clear-marking' to clear any such non-zero bytes.
'--loose-trailing'
When decompressing, testing, or listing, allow trailing data whose
first bytes are so similar to the magic bytes of a lzip header that
@ -411,26 +425,29 @@ once, the first time it appears in the command line.
corrupt header.
Numbers given as arguments to options may be followed by a multiplier
and an optional 'B' for "byte".
Numbers given as arguments to options may be expressed in decimal,
hexadecimal, or octal (using the same syntax as integer constants in C++),
and may be followed by a multiplier and an optional 'B' for "byte".
Table of SI and binary prefixes (unit multipliers):
Prefix Value | Prefix Value
k kilobyte (10^3 = 1000) | Ki kibibyte (2^10 = 1024)
M megabyte (10^6) | Mi mebibyte (2^20)
G gigabyte (10^9) | Gi gibibyte (2^30)
T terabyte (10^12) | Ti tebibyte (2^40)
P petabyte (10^15) | Pi pebibyte (2^50)
E exabyte (10^18) | Ei exbibyte (2^60)
Z zettabyte (10^21) | Zi zebibyte (2^70)
Y yottabyte (10^24) | Yi yobibyte (2^80)
Prefix Value | Prefix Value
k kilobyte (10^3 = 1000) | Ki kibibyte (2^10 = 1024)
M megabyte (10^6) | Mi mebibyte (2^20)
G gigabyte (10^9) | Gi gibibyte (2^30)
T terabyte (10^12) | Ti tebibyte (2^40)
P petabyte (10^15) | Pi pebibyte (2^50)
E exabyte (10^18) | Ei exbibyte (2^60)
Z zettabyte (10^21) | Zi zebibyte (2^70)
Y yottabyte (10^24) | Yi yobibyte (2^80)
R ronnabyte (10^27) | Ri robibyte (2^90)
Q quettabyte (10^30) | Qi quebibyte (2^100)
Exit status: 0 for a normal exit, 1 for environmental problems (file not
found, invalid flags, I/O errors, etc), 2 to indicate a corrupt or invalid
input file, 3 for an internal consistency error (e.g., bug) which caused
clzip to panic.
found, invalid command-line options, I/O errors, etc), 2 to indicate a
corrupt or invalid input file, 3 for an internal consistency error (e.g.,
bug) which caused clzip to panic.

File: clzip.info, Node: Quality assurance, Next: Algorithm, Prev: Invoking clzip, Up: Top
@ -444,6 +461,11 @@ make it so complicated that there are no obvious deficiencies. The first
method is far more difficult.
-- C.A.R. Hoare
Lzip has been designed, written, and tested with great care to replace
gzip and bzip2 as the standard general-purpose compressed format for
Unix-like systems. This chapter describes the lessons learned from these
previous formats, and their application to the design of lzip.
Lzip is developed by volunteers who lack the resources required for
extensive testing in all circumstances. It is up to you to test lzip before
using it in mission-critical applications. However, a compressor like lzip
@ -451,11 +473,6 @@ is not a toy, and maintaining it is not a hobby. Many people's data depend
on it. Therefore the lzip file format has been reviewed carefully and is
believed to be free from negligent design errors.
Lzip has been designed, written, and tested with great care to replace
gzip and bzip2 as the standard general-purpose compressed format for
unix-like systems. This chapter describes the lessons learned from these
previous formats, and their application to the design of lzip.
4.1 Format design
=================
@ -537,10 +554,10 @@ extraction of the decompressed data.
Using an optional CRC for the header is not only a bad idea, it is an
error; it circumvents the Hamming distance (HD) of the CRC and may
prevent the extraction of perfectly good data. For example, if the CRC
is used and the bit enabling it is reset by a bit flip, the header
will appear to be intact (in spite of being corrupt) while the
compressed blocks will appear to be totally unrecoverable (in spite of
being intact). Very misleading indeed.
is used and the bit enabling it is reset by a bit flip, then the
header seems to be intact (in spite of being corrupt) while the
compressed blocks seem to be totally unrecoverable (in spite of being
intact). Very misleading indeed.
'Metadata'
The gzip format stores some metadata, like the modification time of the
@ -555,8 +572,8 @@ extraction of the decompressed data.
'64-bit size field'
Probably the most frequently reported shortcoming of the gzip format
is that it only stores the least significant 32 bits of the
uncompressed size. The size of any file larger than 4 GiB gets
truncated.
uncompressed size. The size of any file larger or equal than 4 GiB
gets truncated.
Bzip2 does not store the uncompressed size of the file.
@ -580,8 +597,12 @@ extraction of the decompressed data.
4.2 Quality of implementation
=============================
Our civilization depends critically on software; it had better be quality
software.
-- Bjarne Stroustrup
'Accurate and robust error detection'
The lzip format provides 3 factor integrity checking, and the
The lzip format provides 3-factor integrity checking, and the
decompressors report mismatches in each factor separately. This method
detects most false positives for corruption. If just one byte in one
factor fails but the other two factors match the data, it probably
@ -590,15 +611,15 @@ extraction of the decompressed data.
trailer.
'Multiple implementations'
Just like the lzip format provides 3 factor protection against
Just like the lzip format provides 3-factor protection against
undetected data corruption, the development methodology of the lzip
family of compressors provides 3 factor protection against undetected
family of compressors provides 3-factor protection against undetected
programming errors.
Three related but independent compressor implementations, lzip, clzip,
and minilzip/lzlib, are developed concurrently. Every stable release
of any of them is tested to verify that it produces identical output
to the other two. This guarantees that all three implement the same
of any of them is tested to check that it produces identical output to
the other two. This guarantees that all three implement the same
algorithm, and makes it unlikely that any of them may contain serious
undiscovered errors. In fact, no errors have been discovered in lzip
since 2009.
@ -642,10 +663,10 @@ using the LZMA coding scheme.
(used by option '-0') and normal (used by all other compression levels).
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.
compression ideas: sliding dictionaries (LZ77) 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.
Clzip is a two stage compressor. The first stage is a Lempel-Ziv coder,
which reduces redundancy by translating chunks of data to their
@ -690,7 +711,7 @@ intervals get longer with higher compression levels because dictionary size
increases (and compression speed decreases) with compression level.
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 the
Abraham Lempel and Jacob Ziv (for the LZ algorithm), Andrei Markov (for the
definition of Markov chains), G.N.N. Martin (for the definition of range
encoding), Igor Pavlov (for putting all the above together in LZMA), and
Julian Seward (for bzip2's CLI).
@ -721,7 +742,7 @@ when there is no longer anything to take away.
represents a variable number of bytes.
A lzip file consists of a series of independent "members" (compressed
A lzip file consists of one or more independent "members" (compressed
data sets). The members simply appear one after another in the file, with no
additional information before, between, or after them. Each member can
encode in compressed form up to 16 EiB - 1 byte of uncompressed data. The
@ -765,10 +786,10 @@ size of a multimember file is unlimited.
'Member size (8 bytes)'
Total size of the member, including header and trailer. This field acts
as a distributed index, allows the verification of stream integrity,
and facilitates the safe recovery of undamaged members from
multimember files. Member size should be limited to 2 PiB to prevent
the data size field from overflowing.
as a distributed index, improves the checking of stream integrity, and
facilitates the safe recovery of undamaged members from multimember
files. Lzip limits the member size to 2 PiB to prevent the data size
field from overflowing.

@ -788,12 +809,12 @@ in the code.
Lzip finishes the LZMA stream with an "End Of Stream" (EOS) marker (the
distance-length pair 0xFFFFFFFFU, 2), which in conjunction with the 'member
size' field in the member trailer allows the verification of stream
integrity. The EOS marker is the only marker allowed in lzip files. The
LZMA stream in lzip files always has these two features (default properties
and EOS marker) and is referred to in this document as LZMA-302eos. This
simplified form of the LZMA stream format has been chosen to maximize
interoperability and safety.
size' field in the member trailer allows the checking of stream integrity.
The EOS marker is the only LZMA marker allowed in lzip files. The LZMA
stream in lzip files always has these two features (default properties and
EOS marker) and is referred to in this document as LZMA-302eos. This
simplified and marker-terminated form of the LZMA stream format has been
chosen to maximize interoperability and safety.
The second stage of LZMA is a range encoder that uses a different
probability model for each type of symbol: distances, lengths, literal
@ -811,9 +832,9 @@ a real decompressor seems the only appropriate reference to use.
What follows is a description of the decoding algorithm for LZMA-302eos
streams using as reference the source code of "lzd", an educational
decompressor for lzip files which can be downloaded from the lzip download
directory. Lzd is written in C++11 and its source code is included in
appendix A. *Note Reference source code::.
decompressor for lzip files, included in appendix A. *Note Reference source
code::. Lzd is written in C++11 and can be downloaded from the lzip download
directory.
7.1 What is coded
@ -878,10 +899,10 @@ the distance is >= 4, the remaining bits are encoded as follows.
'direct_bits' is the amount of remaining bits (from 1 to 30) needed to form
a complete distance, and is calculated as (slot >> 1) - 1. If a distance
needs 6 or more direct_bits, the last 4 bits are encoded separately. The
last piece (all the direct_bits for distances 4 to 127, or the last 4 bits
for distances >= 128) is context-coded in reverse order (from LSB to MSB).
For distances >= 128, the 'direct_bits - 4' part is encoded with fixed 0.5
probability.
last piece (all the direct_bits for distances 4 to 127 (slots 4 to 13), or
the last 4 bits for distances >= 128 (slot >= 14)) is context-coded in
reverse order (from LSB to MSB). For distances >= 128, the
'direct_bits - 4' part is encoded with fixed 0.5 probability.
Bit sequence Description
----------------------------------------------------------------------------
@ -999,8 +1020,8 @@ range decoder. This is done by shifting 5 bytes in the initialization of
'code' instead of 4. (See the 'Range_decoder' constructor in the source).
7.4 Decoding and verifying the LZMA stream
==========================================
7.4 Decoding and checking the LZMA stream
=========================================
After decoding the member header and obtaining the dictionary size, the
range decoder is initialized and then the LZMA decoder enters a loop (see
@ -1010,9 +1031,9 @@ repeated matches, and literal bytes), until the "End Of Stream" marker is
decoded.
Once the "End Of Stream" marker has been decoded, the decompressor reads
and decodes the member trailer, and verifies that the three integrity
factors stored there (CRC, data size, and member size) match those computed
from the data.
and decodes the member trailer, and checks that the three integrity factors
stored there (CRC, data size, and member size) match those computed from the
data.

File: clzip.info, Node: Trailing data, Next: Examples, Prev: Stream format, Up: Top
@ -1027,12 +1048,13 @@ member. Such trailing data may be:
example when writing to a tape. It is safe to append any amount of
padding zero bytes to a lzip file.
* Useful data added by the user; a cryptographically secure hash, a
* Useful data added by the user; an "End Of File" string (to check that
the file has not been truncated), a cryptographically secure hash, a
description of file contents, etc. It is safe to append any amount of
text to a lzip file as long as none of the first four bytes of the text
match the corresponding byte in the string "LZIP", and the text does
not contain any zero bytes (null characters). Nonzero bytes and zero
bytes can't be safely mixed in trailing data.
text to a lzip file as long as none of the first four bytes of the
text matches the corresponding byte in the string "LZIP", and the text
does not contain any zero bytes (null characters). Nonzero bytes and
zero bytes can't be safely mixed in trailing data.
* Garbage added by some not totally successful copy operation.
@ -1048,7 +1070,7 @@ member. Such trailing data may be:
discriminate trailing data from a corrupt header has a Hamming
distance (HD) of 3, and the 3 bit flips must happen in different magic
bytes for the test to fail. In any case, the option '--trailing-error'
guarantees that any corrupt header will be detected.
guarantees that any corrupt header is detected.
Trailing data are in no way part of the lzip file format, but tools
reading lzip files are expected to behave as correctly and usefully as
@ -1068,12 +1090,12 @@ File: clzip.info, Node: Examples, Next: Problems, Prev: Trailing data, Up: T
WARNING! Even if clzip 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 are important, give the
option '--keep' to clzip and don't remove the original file until you
verify the compressed file with a command like
'clzip -cd file.lz | cmp file -'. Most RAM errors happening during
compression can only be detected by comparing the compressed file with the
original because the corruption happens before clzip compresses the RAM
contents, resulting in a valid compressed file containing wrong data.
option '--keep' to clzip and don't remove the original file until you check
the compressed file with a command like 'clzip -cd file.lz | cmp file -'.
Most RAM errors happening during compression can only be detected by
comparing the compressed file with the original because the corruption
happens before clzip compresses the RAM contents, resulting in a valid
compressed file containing wrong data.
Example 1: Extract all the files from archive 'foo.tar.lz'.
@ -1101,7 +1123,7 @@ the operation is successful, 'file.lz' is removed.
clzip -d file.lz
Example 5: Verify the integrity of the compressed file 'file.lz' and show
Example 5: Check the integrity of the compressed file 'file.lz' and show
status.
clzip -tv file.lz
@ -1175,7 +1197,7 @@ Appendix A Reference source code
********************************
/* Lzd - Educational decompressor for the lzip format
Copyright (C) 2013-2022 Antonio Diaz Diaz.
Copyright (C) 2013-2023 Antonio Diaz Diaz.
This program is free software. Redistribution and use in source and
binary forms, with or without modification, are permitted provided
@ -1194,8 +1216,8 @@ Appendix A Reference source code
*/
/*
Exit status: 0 for a normal exit, 1 for environmental problems
(file not found, invalid flags, I/O errors, etc), 2 to indicate a
corrupt or invalid input file.
(file not found, invalid command-line options, I/O errors, etc), 2 to
indicate a corrupt or invalid input file.
*/
#include <algorithm>
@ -1306,10 +1328,11 @@ public:
const CRC32 crc32;
typedef uint8_t Lzip_header[6]; // 0-3 magic bytes
// 4 version
// 5 coded dictionary size
typedef uint8_t Lzip_trailer[20];
enum { header_size = 6, trailer_size = 20 };
typedef uint8_t Lzip_header[header_size]; // 0-3 magic bytes
// 4 version
// 5 coded dictionary size
typedef uint8_t Lzip_trailer[trailer_size];
// 0-3 CRC32 of the uncompressed data
// 4-11 size of the uncompressed data
// 12-19 member size including header and trailer
@ -1321,9 +1344,11 @@ class Range_decoder
uint32_t range;
public:
Range_decoder() : member_pos( 6 ), code( 0 ), range( 0xFFFFFFFFU )
Range_decoder()
: member_pos( header_size ), code( 0 ), range( 0xFFFFFFFFU )
{
for( int i = 0; i < 5; ++i ) code = ( code << 8 ) | get_byte();
get_byte(); // discard first byte of the LZMA stream
for( int i = 0; i < 4; ++i ) code = ( code << 8 ) | get_byte();
}
uint8_t get_byte() { ++member_pos; return std::getc( stdin ); }
@ -1356,8 +1381,8 @@ public:
}
else
{
range -= bound;
code -= bound;
range -= bound;
bm.probability -= bm.probability >> bit_model_move_bits;
symbol = 1;
}
@ -1407,11 +1432,12 @@ public:
unsigned decode_len( Len_model & lm, const int pos_state )
{
if( decode_bit( lm.choice1 ) == 0 )
return decode_tree( lm.bm_low[pos_state], len_low_bits );
return min_match_len +
decode_tree( lm.bm_low[pos_state], len_low_bits );
if( decode_bit( lm.choice2 ) == 0 )
return len_low_symbols +
return min_match_len + len_low_symbols +
decode_tree( lm.bm_mid[pos_state], len_mid_bits );
return len_low_symbols + len_mid_symbols +
return min_match_len + len_low_symbols + len_mid_symbols +
decode_tree( lm.bm_high, len_high_bits );
}
};
@ -1484,7 +1510,7 @@ void LZ_decoder::flush_data()
}
bool LZ_decoder::decode_member() // Returns false if error
bool LZ_decoder::decode_member() // Return false if error
{
Bit_model bm_literal[1<<literal_context_bits][0x300];
Bit_model bm_match[State::states][pos_states];
@ -1546,12 +1572,12 @@ bool LZ_decoder::decode_member() // Returns false if error
rep0 = distance;
}
state.set_rep();
len = min_match_len + rdec.decode_len( rep_len_model, pos_state );
len = rdec.decode_len( rep_len_model, pos_state );
}
else // match
{
rep3 = rep2; rep2 = rep1; rep1 = rep0;
len = min_match_len + rdec.decode_len( match_len_model, pos_state );
len = rdec.decode_len( match_len_model, pos_state );
const int len_state = std::min( len - min_match_len, len_states - 1 );
rep0 = rdec.decode_tree( bm_dis_slot[len_state], dis_slot_bits );
if( rep0 >= start_dis_model )
@ -1570,7 +1596,7 @@ bool LZ_decoder::decode_member() // Returns false if error
if( rep0 == 0xFFFFFFFFU ) // marker found
{
flush_data();
return ( len == min_match_len ); // End Of Stream marker
return len == min_match_len; // End Of Stream marker
}
}
}
@ -1591,11 +1617,11 @@ int main( const int argc, const char * const argv[] )
{
std::printf(
"Lzd %s - Educational decompressor for the lzip format.\n"
"Study the source to learn how a lzip decompressor works.\n"
"Study the source code to learn how a lzip decompressor works.\n"
"See the lzip manual for an explanation of the code.\n"
"\nUsage: %s [-d] < file.lz > file\n"
"Lzd decompresses from standard input to standard output.\n"
"\nCopyright (C) 2022 Antonio Diaz Diaz.\n"
"\nCopyright (C) 2023 Antonio Diaz Diaz.\n"
"License 2-clause BSD.\n"
"This is free software: you are free to change and redistribute it.\n"
"There is NO WARRANTY, to the extent permitted by law.\n"
@ -1612,8 +1638,8 @@ int main( const int argc, const char * const argv[] )
for( bool first_member = true; ; first_member = false )
{
Lzip_header header; // verify header
for( int i = 0; i < 6; ++i ) header[i] = std::getc( stdin );
Lzip_header header; // check header
for( int i = 0; i < header_size; ++i ) header[i] = std::getc( stdin );
if( std::feof( stdin ) || std::memcmp( header, "LZIP\x01", 5 ) != 0 )
{
if( first_member )
@ -1631,8 +1657,8 @@ int main( const int argc, const char * const argv[] )
if( !decoder.decode_member() )
{ std::fputs( "Data error\n", stderr ); return 2; }
Lzip_trailer trailer; // verify trailer
for( int i = 0; i < 20; ++i ) trailer[i] = decoder.get_byte();
Lzip_trailer trailer; // check trailer
for( int i = 0; i < trailer_size; ++i ) trailer[i] = decoder.get_byte();
int retval = 0;
unsigned crc = 0;
for( int i = 3; i >= 0; --i ) crc = ( crc << 8 ) + trailer[i];
@ -1688,22 +1714,22 @@ Concept index

Tag Table:
Node: Top205
Node: Introduction1207
Node: Output7226
Node: Invoking clzip8829
Ref: --trailing-error9627
Node: Quality assurance18961
Node: Algorithm27986
Node: File format31397
Ref: coded-dict-size32827
Node: Stream format34062
Ref: what-is-coded36459
Node: Trailing data45387
Node: Examples47650
Ref: concat-example49102
Node: Problems50332
Node: Reference source code50868
Node: Concept index65727
Node: Introduction1212
Node: Output7342
Node: Invoking clzip8945
Ref: --trailing-error9823
Node: Quality assurance19929
Node: Algorithm29060
Node: File format32468
Ref: coded-dict-size33898
Node: Stream format35129
Ref: what-is-coded37525
Node: Trailing data46478
Node: Examples48816
Ref: concat-example50266
Node: Problems51496
Node: Reference source code52032
Node: Concept index67094

End Tag Table