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19
doc/clzip.1
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@ -1,12 +1,23 @@
.\" DO NOT MODIFY THIS FILE! It was generated by help2man 1.46.1.
.TH CLZIP "1" "February 2018" "clzip 1.10" "User Commands"
.TH CLZIP "1" "January 2019" "clzip 1.11" "User Commands"
.SH NAME
clzip \- reduces the size of files
.SH SYNOPSIS
.B clzip
[\fI\,options\/\fR] [\fI\,files\/\fR]
.SH DESCRIPTION
Clzip \- LZMA lossless data compressor.
Clzip is a C language version of lzip, fully compatible with lzip 1.4 or
newer. As clzip is written in C, it may be easier to integrate in
applications like package managers, embedded devices, or systems lacking
a C++ compiler.
.PP
Lzip is a lossless data compressor with a user interface similar to the
one of gzip or bzip2. Lzip can compress about as fast as gzip (lzip \fB\-0\fR)
or compress most files more than bzip2 (lzip \fB\-9\fR). 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.
.SH OPTIONS
.TP
\fB\-h\fR, \fB\-\-help\fR
@ -52,7 +63,7 @@ suppress all messages
set dictionary size limit in bytes [8 MiB]
.TP
\fB\-S\fR, \fB\-\-volume\-size=\fR<bytes>
set volume size limit in bytes, implies \fB\-k\fR
set volume size limit in bytes
.TP
\fB\-t\fR, \fB\-\-test\fR
test compressed file integrity
@ -93,7 +104,7 @@ Report bugs to lzip\-bug@nongnu.org
.br
Clzip home page: http://www.nongnu.org/lzip/clzip.html
.SH COPYRIGHT
Copyright \(co 2018 Antonio Diaz Diaz.
Copyright \(co 2019 Antonio Diaz Diaz.
License GPLv2+: GNU GPL version 2 or later <http://gnu.org/licenses/gpl.html>
.br
This is free software: you are free to change and redistribute it.

316
doc/clzip.info
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@ -11,7 +11,7 @@ File: clzip.info, Node: Top, Next: Introduction, Up: (dir)
Clzip Manual
************
This manual is for Clzip (version 1.10, 6 February 2018).
This manual is for Clzip (version 1.11, 3 January 2019).
* Menu:
@ -29,7 +29,7 @@ This manual is for Clzip (version 1.10, 6 February 2018).
* Concept index:: Index of concepts
Copyright (C) 2010-2018 Antonio Diaz Diaz.
Copyright (C) 2010-2019 Antonio Diaz Diaz.
This manual is free documentation: you have unlimited permission to
copy, distribute and modify it.
@ -40,14 +40,14 @@ File: clzip.info, Node: Introduction, Next: Output, Prev: Top, Up: Top
1 Introduction
**************
Clzip is a C language version of lzip, fully compatible with lzip-1.4 or
newer. As clzip is written in C, it may be easier to integrate in
applications like package managers, embedded devices, or systems lacking
a C++ compiler.
Clzip is a C language version of lzip, fully compatible with lzip 1.4
or newer. As clzip is written in C, it may be easier to integrate in
applications like package managers, embedded devices, or systems
lacking a C++ compiler.
Lzip is a lossless data compressor with a user interface similar to
the one of gzip or bzip2. Lzip can compress about as fast as gzip
(lzip -0), or compress most files more than bzip2 (lzip -9).
(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.
@ -88,15 +88,15 @@ 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 lzip and
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 uses the same well-defined exit status values used by lzip,
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 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.
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.
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
@ -116,7 +116,7 @@ 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
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).
@ -214,6 +214,7 @@ command line.
'-V'
'--version'
Print the version number of clzip on the standard output and exit.
This version number should be included in all bug reports.
'-a'
'--trailing-error'
@ -298,12 +299,14 @@ command line.
'-s BYTES'
'--dictionary-size=BYTES'
When compressing, set the dictionary size limit in bytes. Clzip
will use the smallest possible dictionary size for each file
without exceeding 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. Note that dictionary sizes are quantized. If
the specified size does not match one of the valid sizes, it will
be rounded upwards by adding up to (BYTES / 8) to it.
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 specified size does not match one of
the valid sizes, it will be 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
@ -342,27 +345,32 @@ command line.
Two or more '-v' options show the progress of (de)compression.
'-0 .. -9'
Set the compression parameters (dictionary size and match length
limit) as shown in the table below. The default compression level
is '-6'. Note that '-9' can be much slower than '-0'. These
options have no effect when decompressing, testing or listing.
Compression level. Set the compression parameters (dictionary size
and match length limit) as shown in the table below. The default
compression level is '-6', equivalent to '-s8MiB -m36'. Note that
'-9' can be much slower than '-0'. These options have no effect
when decompressing, testing or listing.
The bidimensional parameter space of LZMA can't be mapped to a
linear scale optimal for all files. If your files are large, very
repetitive, etc, you may need to use the '--dictionary-size' and
'--match-length' options directly to achieve optimal performance.
Level Dictionary size Match length limit
-0 64 KiB 16 bytes
-1 1 MiB 5 bytes
-2 1.5 MiB 6 bytes
-3 2 MiB 8 bytes
-4 3 MiB 12 bytes
-5 4 MiB 20 bytes
-6 8 MiB 36 bytes
-7 16 MiB 68 bytes
-8 24 MiB 132 bytes
-9 32 MiB 273 bytes
If several compression levels or '-s' or '-m' options are given,
the last setting is used. For example '-9 -s64MiB' is equivalent
to '-s64MiB -m273'
Level Dictionary size (-s) Match length limit (-m)
-0 64 KiB 16 bytes
-1 1 MiB 5 bytes
-2 1.5 MiB 6 bytes
-3 2 MiB 8 bytes
-4 3 MiB 12 bytes
-5 4 MiB 20 bytes
-6 8 MiB 36 bytes
-7 16 MiB 68 bytes
-8 24 MiB 132 bytes
-9 32 MiB 273 bytes
'--fast'
'--best'
@ -409,10 +417,10 @@ is to 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 be the
standard general-purpose compressor for unix-like systems. This chapter
describes the lessons learned from previous compressors (gzip and
bzip2), and their application to the design of lzip.
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
@ -455,17 +463,20 @@ error detection. Any distance larger than the dictionary size acts as a
forbidden symbol, allowing the decompressor to detect the approximate
position of errors, and leaving very little work for the check sequence
(CRC and data sizes) in the detection of errors. Lzip is usually able
to detect all posible bit flips in the compressed data without
to detect all possible bit flips in the compressed data without
resorting to the check sequence. It would be difficult to write an
automatic recovery tool like lziprecover for the gzip format. And, as
far as I know, it has never been written.
Lzip, like gzip and bzip2, uses a CRC32 to check the integrity of the
decompressed data because it provides more accurate error detection than
CRC64 up to a compressed size of about 16 GiB, a size larger than that
of most files. In the case of lzip, the additional detection capability
of the decompressor reduces the probability of undetected errors more
than a million times beyond what the CRC32 alone provides.
decompressed data because it provides optimal accuracy in the detection
of errors up to a compressed size of about 16 GiB, a size larger than
that of most files. In the case of lzip, the additional detection
capability of the decompressor reduces the probability of undetected
errors about four million times more, resulting in a combined integrity
checking optimally accurate for any member size produced by lzip.
Preliminary results suggest that the lzip format is safe enough to be
used in critical safety avionics systems.
The lzip format is designed for long-term archiving. Therefore it
excludes any unneeded features that may interfere with the future
@ -520,7 +531,7 @@ extraction of the decompressed data.
Bzip2 does not store the uncompressed size of the file.
The lzip format provides a 64-bit field for the uncompressed size.
Additionaly, lzip produces multimember output automatically when
Additionally, lzip produces multimember output automatically when
the size is too large for a single member, allowing for an
unlimited uncompressed size.
@ -568,9 +579,9 @@ extraction of the decompressed data.
(lziprecover)Unzcrash.
'Dictionary size'
Lzip automatically uses the smallest possible dictionary size for
each file. In addition to reducing the amount of memory required
for decompression, this feature also minimizes the probability of
Lzip automatically adapts the dictionary size to the size of each
file. In addition to reducing the amount of memory required for
decompression, this feature also minimizes the probability of
being affected by RAM errors during compression.
'Exit status'
@ -624,11 +635,11 @@ additional information before, between, or after them.
'DS (coded dictionary size, 1 byte)'
The dictionary size is calculated by taking a power of 2 (the base
size) and substracting from it a fraction between 0/16 and 7/16 of
size) and subtracting from it a fraction between 0/16 and 7/16 of
the base size.
Bits 4-0 contain the base 2 logarithm of the base size (12 to 29).
Bits 7-5 contain the numerator of the fraction (0 to 7) to
substract from the base size to obtain the dictionary size.
Bits 7-5 contain the numerator of the fraction (0 to 7) to subtract
from the base size to obtain the dictionary size.
Example: 0xD3 = 2^19 - 6 * 2^15 = 512 KiB - 6 * 32 KiB = 320 KiB
Valid values for dictionary size range from 4 KiB to 512 MiB.
@ -767,7 +778,7 @@ reusing a recently used distance). There are 7 different coding
sequences:
Bit sequence Name Description
---------------------------------------------------------------------------
------------------------------------------------------------------------
0 + byte literal literal byte
1 + 0 + len + dis match distance-length pair
1 + 1 + 0 + 0 shortrep 1 byte match at latest used distance
@ -787,7 +798,7 @@ order, from MSB to LSB, except where noted otherwise.
Lengths (the 'len' in the table above) are coded as follows:
Bit sequence Description
--------------------------------------------------------------------------
------------------------------------------------------------------------
0 + 3 bits lengths from 2 to 9
1 + 0 + 3 bits lengths from 10 to 17
1 + 1 + 8 bits lengths from 18 to 273
@ -828,7 +839,7 @@ order (from LSB to MSB). For distances >= 128, the 'direct_bits - 4'
part is coded with fixed 0.5 probability.
Bit sequence Description
--------------------------------------------------------------------------
------------------------------------------------------------------------
slot distances from 0 to 3
slot + direct_bits distances from 4 to 127
slot + (direct_bits - 4) + 4 bits distances from 128 to 2^32 - 1
@ -864,7 +875,7 @@ byte. 'rep' is any one of 'rep0', 'rep1', 'rep2' or 'rep3'. The types
of previous sequences corresponding to each state are:
State Types of previous sequences
--------------------------------------------------------
------------------------------------------------------
0 literal, literal, literal
1 match, literal, literal
2 rep or (!literal, shortrep), literal, literal
@ -881,24 +892,24 @@ State Types of previous sequences
The contexts for decoding the type of coding sequence are:
Name Indices Used when
---------------------------------------------------------------------------
bm_match state, pos_state sequence start
bm_rep state after sequence 1
bm_rep0 state after sequence 11
bm_rep1 state after sequence 111
bm_rep2 state after sequence 1111
bm_len state, pos_state after sequence 110
Name Indices Used when
-----------------------------------------------------------------------
bm_match state, pos_state sequence start
bm_rep state after sequence 1
bm_rep0 state after sequence 11
bm_rep1 state after sequence 111
bm_rep2 state after sequence 1111
bm_len state, pos_state after sequence 110
The contexts for decoding distances are:
Name Indices Used when
---------------------------------------------------------------------------
bm_dis_slot len_state, bit tree distance start
bm_dis reverse bit tree after slots 4 to 13
bm_align reverse bit tree for distances >= 128, after
fixed probability bits
Name Indices Used when
------------------------------------------------------------------------
bm_dis_slot len_state, bit tree distance start
bm_dis reverse bit tree after slots 4 to 13
bm_align reverse bit tree for distances >= 128, after fixed
probability bits
There are two separate sets of contexts for lengths ('Len_model' in
@ -906,7 +917,7 @@ the source). One for normal matches, the other for repeated matches. The
contexts in each Len_model are (see 'decode_len' in the source):
Name Indices Used when
---------------------------------------------------------------------------
------------------------------------------------------------------------
choice1 none length start
choice2 none after sequence 1
bm_low pos_state, bit tree after sequence 0
@ -1013,7 +1024,11 @@ compressed file (bugs in the system libraries, memory errors, etc).
Therefore, if the data you are going to compress are important, give the
'--keep' option 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 -'.
'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: Replace a regular file with its compressed version 'file.lz'
@ -1106,7 +1121,7 @@ Appendix A Reference source code
********************************
/* Lzd - Educational decompressor for the lzip format
Copyright (C) 2013-2018 Antonio Diaz Diaz.
Copyright (C) 2013-2019 Antonio Diaz Diaz.
This program is free software. Redistribution and use in source and
binary forms, with or without modification, are permitted provided
@ -1136,7 +1151,7 @@ Appendix A Reference source code
#include <cstring>
#include <stdint.h>
#include <unistd.h>
#if defined(__MSVCRT__) || defined(__OS2__) || defined(_MSC_VER)
#if defined(__MSVCRT__) || defined(__OS2__) || defined(__DJGPP__)
#include <fcntl.h>
#include <io.h>
#endif
@ -1237,9 +1252,9 @@ public:
const CRC32 crc32;
typedef uint8_t File_header[6]; // 0-3 magic, 4 version, 5 coded_dict_size
typedef uint8_t Lzip_header[6]; // 0-3 magic, 4 version, 5 coded_dict_size
typedef uint8_t File_trailer[20];
typedef uint8_t Lzip_trailer[20];
// 0-3 CRC32 of the uncompressed data
// 4-11 size of the uncompressed data
// 12-19 member size including header and trailer
@ -1433,6 +1448,7 @@ bool LZ_decoder::decode_member() // Returns false if error
const int pos_state = data_position() & pos_state_mask;
if( rdec.decode_bit( bm_match[state()][pos_state] ) == 0 ) // 1st bit
{
// literal byte
const uint8_t prev_byte = peek( 0 );
const int literal_state = prev_byte >> ( 8 - literal_context_bits );
Bit_model * const bm = bm_literal[literal_state];
@ -1441,67 +1457,66 @@ bool LZ_decoder::decode_member() // Returns false if error
else
put_byte( rdec.decode_matched( bm, peek( rep0 ) ) );
state.set_char();
continue;
}
else // match or repeated match
// match or repeated match
int len;
if( rdec.decode_bit( bm_rep[state()] ) != 0 ) // 2nd bit
{
int len;
if( rdec.decode_bit( bm_rep[state()] ) != 0 ) // 2nd bit
if( rdec.decode_bit( bm_rep0[state()] ) == 0 ) // 3rd bit
{
if( rdec.decode_bit( bm_rep0[state()] ) == 0 ) // 3rd bit
{
if( rdec.decode_bit( bm_len[state()][pos_state] ) == 0 ) // 4th bit
{ state.set_short_rep(); put_byte( peek( rep0 ) ); continue; }
}
if( rdec.decode_bit( bm_len[state()][pos_state] ) == 0 ) // 4th bit
{ state.set_short_rep(); put_byte( peek( rep0 ) ); continue; }
}
else
{
unsigned distance;
if( rdec.decode_bit( bm_rep1[state()] ) == 0 ) // 4th bit
distance = rep1;
else
{
unsigned distance;
if( rdec.decode_bit( bm_rep1[state()] ) == 0 ) // 4th bit
distance = rep1;
if( rdec.decode_bit( bm_rep2[state()] ) == 0 ) // 5th bit
distance = rep2;
else
{
if( rdec.decode_bit( bm_rep2[state()] ) == 0 ) // 5th bit
distance = rep2;
else
{ distance = rep3; rep3 = rep2; }
rep2 = rep1;
}
rep1 = rep0;
rep0 = distance;
{ distance = rep3; rep3 = rep2; }
rep2 = rep1;
}
state.set_rep();
len = min_match_len + rdec.decode_len( rep_len_model, pos_state );
rep1 = rep0;
rep0 = distance;
}
else // match
{
rep3 = rep2; rep2 = rep1; rep1 = rep0;
len = min_match_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 )
{
const unsigned dis_slot = rep0;
const int direct_bits = ( dis_slot >> 1 ) - 1;
rep0 = ( 2 | ( dis_slot & 1 ) ) << direct_bits;
if( dis_slot < end_dis_model )
rep0 += rdec.decode_tree_reversed( bm_dis + ( rep0 - dis_slot ),
direct_bits );
else
{
rep0 += rdec.decode( direct_bits - dis_align_bits ) << dis_align_bits;
rep0 += rdec.decode_tree_reversed( bm_align, dis_align_bits );
if( rep0 == 0xFFFFFFFFU ) // marker found
{
flush_data();
return ( len == min_match_len ); // End Of Stream marker
}
}
}
state.set_match();
if( rep0 >= dictionary_size || ( rep0 >= pos && !pos_wrapped ) )
{ flush_data(); return false; }
}
for( int i = 0; i < len; ++i ) put_byte( peek( rep0 ) );
state.set_rep();
len = min_match_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 );
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 )
{
const unsigned dis_slot = rep0;
const int direct_bits = ( dis_slot >> 1 ) - 1;
rep0 = ( 2 | ( dis_slot & 1 ) ) << direct_bits;
if( dis_slot < end_dis_model )
rep0 += rdec.decode_tree_reversed( bm_dis + ( rep0 - dis_slot ),
direct_bits );
else
{
rep0 += rdec.decode( direct_bits - dis_align_bits ) << dis_align_bits;
rep0 += rdec.decode_tree_reversed( bm_align, dis_align_bits );
if( rep0 == 0xFFFFFFFFU ) // marker found
{
flush_data();
return ( len == min_match_len ); // End Of Stream marker
}
}
}
state.set_match();
if( rep0 >= dictionary_size || ( rep0 >= pos && !pos_wrapped ) )
{ flush_data(); return false; }
}
for( int i = 0; i < len; ++i ) put_byte( peek( rep0 ) );
}
flush_data();
return false;
@ -1519,7 +1534,7 @@ int main( const int argc, const char * const argv[] )
"It is not safe to use lzd for any real work.\n"
"\nUsage: %s < file.lz > file\n", argv[0] );
std::printf( "Lzd decompresses from standard input to standard output.\n"
"\nCopyright (C) 2018 Antonio Diaz Diaz.\n"
"\nCopyright (C) 2019 Antonio Diaz Diaz.\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"
"Report bugs to lzip-bug@nongnu.org\n"
@ -1527,14 +1542,14 @@ int main( const int argc, const char * const argv[] )
return 0;
}
#if defined(__MSVCRT__) || defined(__OS2__) || defined(_MSC_VER)
setmode( fileno( stdin ), O_BINARY );
setmode( fileno( stdout ), O_BINARY );
#if defined(__MSVCRT__) || defined(__OS2__) || defined(__DJGPP__)
setmode( STDIN_FILENO, O_BINARY );
setmode( STDOUT_FILENO, O_BINARY );
#endif
for( bool first_member = true; ; first_member = false )
{
File_header header; // verify header
Lzip_header header; // verify header
for( int i = 0; i < 6; ++i ) header[i] = std::getc( stdin );
if( std::feof( stdin ) || std::memcmp( header, "LZIP\x01", 5 ) != 0 )
{
@ -1553,7 +1568,7 @@ int main( const int argc, const char * const argv[] )
if( !decoder.decode_member() )
{ std::fputs( "Data error\n", stderr ); return 2; }
File_trailer trailer; // verify trailer
Lzip_trailer trailer; // verify trailer
for( int i = 0; i < 20; ++i ) trailer[i] = std::getc( stdin );
unsigned crc = 0;
for( int i = 3; i >= 0; --i ) { crc <<= 8; crc += trailer[i]; }
@ -1598,20 +1613,21 @@ Concept index

Tag Table:
Node: Top210
Node: Introduction1210
Node: Output6491
Node: Invoking clzip8011
Ref: --trailing-error8577
Node: Quality assurance16230
Node: File format24640
Node: Algorithm27045
Node: Stream format29875
Node: Trailing data40616
Node: Examples42894
Ref: concat-example44076
Node: Problems45121
Node: Reference source code45657
Node: Concept index59974
Node: Introduction1209
Node: Output6498
Node: Invoking clzip8018
Ref: --trailing-error8648
Node: Quality assurance16666
Node: File format25271
Ref: coded-dict-size26564
Node: Algorithm27674
Node: Stream format30504
Node: Trailing data41156
Node: Examples43434
Ref: concat-example44866
Node: Problems45911
Node: Reference source code46447
Node: Concept index60660

End Tag Table

251
doc/clzip.texi
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@ -6,8 +6,8 @@
@finalout
@c %**end of header
@set UPDATED 6 February 2018
@set VERSION 1.10
@set UPDATED 3 January 2019
@set VERSION 1.11
@dircategory Data Compression
@direntry
@ -50,7 +50,7 @@ This manual is for Clzip (version @value{VERSION}, @value{UPDATED}).
@end menu
@sp 1
Copyright @copyright{} 2010-2018 Antonio Diaz Diaz.
Copyright @copyright{} 2010-2019 Antonio Diaz Diaz.
This manual is free documentation: you have unlimited permission
to copy, distribute and modify it.
@ -60,20 +60,20 @@ to copy, distribute and modify it.
@chapter Introduction
@cindex introduction
Clzip is a C language version of lzip, fully compatible with lzip-1.4 or
newer. As clzip is written in C, it may be easier to integrate in
applications like package managers, embedded devices, or systems lacking
a C++ compiler.
@uref{http://www.nongnu.org/lzip/clzip.html,,Clzip} is a C language version
of lzip, fully compatible with @w{lzip 1.4} or newer. As clzip is written in
C, it may be easier to integrate in applications like package managers,
embedded devices, or systems lacking a C++ compiler.
Lzip is a lossless data compressor with a user interface similar to the
one of gzip or bzip2. Lzip can compress about as fast as gzip
@w{(lzip -0)}, or compress most files more than bzip2 @w{(lzip -9)}.
Decompression speed is intermediate between gzip and bzip2. Lzip is
better than gzip and bzip2 from a data recovery perspective.
@uref{http://www.nongnu.org/lzip/lzip.html,,Lzip} is a lossless data
compressor with a user interface similar to the one of gzip or bzip2. Lzip
can compress about as fast as gzip @w{(lzip -0)} or compress most files more
than bzip2 @w{(lzip -9)}. Decompression speed is intermediate between gzip
and bzip2. Lzip is better than gzip and bzip2 from a data recovery
perspective.
The lzip file format is designed for data sharing and long-term
archiving, taking into account both data integrity and decoder
availability:
The lzip file format is designed for data sharing and long-term archiving,
taking into account both data integrity and decoder availability:
@itemize @bullet
@item
@ -116,15 +116,14 @@ 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 lzip and
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 uses the same well-defined exit status values used by lzip, 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 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.
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.
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
@ -146,7 +145,7 @@ file from that of the compressed file as follows:
(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
possible, ownership of the file just as @samp{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).
@ -252,6 +251,7 @@ Print an informative help message describing the options and exit.
@item -V
@itemx --version
Print the version number of clzip on the standard output and exit.
This version number should be included in all bug reports.
@anchor{--trailing-error}
@item -a
@ -333,12 +333,13 @@ Quiet operation. Suppress all messages.
@item -s @var{bytes}
@itemx --dictionary-size=@var{bytes}
When compressing, set the dictionary size limit in bytes. Clzip will use
the smallest possible dictionary size for each file without exceeding
this limit. Valid values range from @w{4 KiB} to @w{512 MiB}. Values 12
to 29 are interpreted as powers of two, meaning 2^12 to 2^29 bytes. Note
that dictionary sizes are quantized. If the specified size does not
match one of the valid sizes, it will be rounded upwards by adding up to
@w{(@var{bytes} / 8)} to it.
for each file the largest dictionary size that does not exceed neither
the file size nor this limit. Valid values range from @w{4 KiB} to
@w{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 (@pxref{coded-dict-size}). If the specified size
does not match one of the valid sizes, it will be rounded upwards by
adding up to @w{(@var{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
@ -376,18 +377,23 @@ ASCII characters.@*
Two or more @samp{-v} options show the progress of (de)compression.
@item -0 .. -9
Set the compression parameters (dictionary size and match length limit)
as shown in the table below. The default compression level is @samp{-6}.
Note that @samp{-9} can be much slower than @samp{-0}. These options
have no effect when decompressing, testing or listing.
Compression level. Set the compression parameters (dictionary size and
match length limit) as shown in the table below. The default compression
level is @samp{-6}, equivalent to @w{@samp{-s8MiB -m36}}. Note that
@samp{-9} can be much slower than @samp{-0}. These options have no
effect when decompressing, testing or listing.
The bidimensional parameter space of LZMA can't be mapped to a linear
scale optimal for all files. If your files are large, very repetitive,
etc, you may need to use the @samp{--dictionary-size} and
@samp{--match-length} options directly to achieve optimal performance.
@multitable {Level} {Dictionary size} {Match length limit}
@item Level @tab Dictionary size @tab Match length limit
If several compression levels or @samp{-s} or @samp{-m} options are
given, the last setting is used. For example @w{@samp{-9 -s64MiB}} is
equivalent to @w{@samp{-s64MiB -m273}}
@multitable {Level} {Dictionary size (-s)} {Match length limit (-m)}
@item Level @tab Dictionary size (-s) @tab Match length limit (-m)
@item -0 @tab 64 KiB @tab 16 bytes
@item -1 @tab 1 MiB @tab 5 bytes
@item -2 @tab 1.5 MiB @tab 6 bytes
@ -446,10 +452,10 @@ is to 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 be the
standard general-purpose compressor for unix-like systems. This chapter
describes the lessons learned from previous compressors (gzip and
bzip2), and their application to the design of lzip.
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.
@sp 1
@section Format design
@ -489,18 +495,21 @@ is extraordinarily safe. It provides embedded error detection. Any
distance larger than the dictionary size acts as a forbidden symbol,
allowing the decompressor to detect the approximate position of errors,
and leaving very little work for the check sequence (CRC and data sizes)
in the detection of errors. Lzip is usually able to detect all posible
in the detection of errors. Lzip is usually able to detect all possible
bit flips in the compressed data without resorting to the check
sequence. It would be difficult to write an automatic recovery tool like
lziprecover for the gzip format. And, as far as I know, it has never
been written.
Lzip, like gzip and bzip2, uses a CRC32 to check the integrity of the
decompressed data because it provides more accurate error detection than
CRC64 up to a compressed size of about @w{16 GiB}, a size larger than
that of most files. In the case of lzip, the additional detection
decompressed data because it provides optimal accuracy in the detection
of errors up to a compressed size of about @w{16 GiB}, a size larger
than that of most files. In the case of lzip, the additional detection
capability of the decompressor reduces the probability of undetected
errors more than a million times beyond what the CRC32 alone provides.
errors about four million times more, resulting in a combined integrity
checking optimally accurate for any member size produced by lzip.
Preliminary results suggest that the lzip format is safe enough to be
used in critical safety avionics systems.
The lzip format is designed for long-term archiving. Therefore it
excludes any unneeded features that may interfere with the future
@ -559,7 +568,7 @@ size. The size of any file larger than @w{4 GiB} gets truncated.
Bzip2 does not store the uncompressed size of the file.
The lzip format provides a 64-bit field for the uncompressed size.
Additionaly, lzip produces multimember output automatically when the
Additionally, lzip produces multimember output automatically when the
size is too large for a single member, allowing for an unlimited
uncompressed size.
@ -614,10 +623,10 @@ vulnerability or false negative.
@item Dictionary size
Lzip automatically uses the smallest possible dictionary size for each
file. In addition to reducing the amount of memory required for
decompression, this feature also minimizes the probability of being
affected by RAM errors during compression.
Lzip automatically adapts the dictionary size to the size of each file.
In addition to reducing the amount of memory required for decompression,
this feature also minimizes the probability of being affected by RAM
errors during compression. @c key4_mask
@item Exit status
@ -674,12 +683,13 @@ 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. 1 for now.
@anchor{coded-dict-size}
@item DS (coded dictionary size, 1 byte)
The dictionary size is calculated by taking a power of 2 (the base size)
and substracting from it a fraction between 0/16 and 7/16 of the base
and subtracting from it a fraction between 0/16 and 7/16 of the base
size.@*
Bits 4-0 contain the base 2 logarithm of the base size (12 to 29).@*
Bits 7-5 contain the numerator of the fraction (0 to 7) to substract
Bits 7-5 contain the numerator of the fraction (0 to 7) to subtract
from the base size to obtain the dictionary size.@*
Example: 0xD3 = 2^19 - 6 * 2^15 = 512 KiB - 6 * 32 KiB = 320 KiB@*
Valid values for dictionary size range from 4 KiB to 512 MiB.
@ -939,7 +949,7 @@ are:
@sp 1
The contexts for decoding the type of coding sequence are:
@multitable @columnfractions .2 .4 .4
@multitable @columnfractions .2 .35 .45
@headitem Name @tab Indices @tab Used when
@item bm_match @tab state, pos_state @tab sequence start
@item bm_rep @tab state @tab after sequence 1
@ -952,7 +962,7 @@ The contexts for decoding the type of coding sequence are:
@sp 1
The contexts for decoding distances are:
@multitable @columnfractions .2 .4 .4
@multitable @columnfractions .2 .3 .5
@headitem Name @tab Indices @tab Used when
@item bm_dis_slot @tab len_state, bit tree @tab distance start
@item bm_dis @tab reverse bit tree @tab after slots 4 to 13
@ -1073,9 +1083,12 @@ where a file containing trailing data must be rejected, the option
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
@samp{--keep} option to clzip and don't remove the original file until
you verify the compressed file with a command like
@w{@samp{clzip -cd file.lz | cmp file -}}.
@samp{--keep} option to clzip and don't remove the original file until you
verify the compressed file with a command like
@w{@samp{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.
@sp 1
@noindent
@ -1203,7 +1216,7 @@ find by running @w{@code{clzip --version}}.
@verbatim
/* Lzd - Educational decompressor for the lzip format
Copyright (C) 2013-2018 Antonio Diaz Diaz.
Copyright (C) 2013-2019 Antonio Diaz Diaz.
This program is free software. Redistribution and use in source and
binary forms, with or without modification, are permitted provided
@ -1233,7 +1246,7 @@ find by running @w{@code{clzip --version}}.
#include <cstring>
#include <stdint.h>
#include <unistd.h>
#if defined(__MSVCRT__) || defined(__OS2__) || defined(_MSC_VER)
#if defined(__MSVCRT__) || defined(__OS2__) || defined(__DJGPP__)
#include <fcntl.h>
#include <io.h>
#endif
@ -1334,9 +1347,9 @@ public:
const CRC32 crc32;
typedef uint8_t File_header[6]; // 0-3 magic, 4 version, 5 coded_dict_size
typedef uint8_t Lzip_header[6]; // 0-3 magic, 4 version, 5 coded_dict_size
typedef uint8_t File_trailer[20];
typedef uint8_t Lzip_trailer[20];
// 0-3 CRC32 of the uncompressed data
// 4-11 size of the uncompressed data
// 12-19 member size including header and trailer
@ -1530,6 +1543,7 @@ bool LZ_decoder::decode_member() // Returns false if error
const int pos_state = data_position() & pos_state_mask;
if( rdec.decode_bit( bm_match[state()][pos_state] ) == 0 ) // 1st bit
{
// literal byte
const uint8_t prev_byte = peek( 0 );
const int literal_state = prev_byte >> ( 8 - literal_context_bits );
Bit_model * const bm = bm_literal[literal_state];
@ -1538,67 +1552,66 @@ bool LZ_decoder::decode_member() // Returns false if error
else
put_byte( rdec.decode_matched( bm, peek( rep0 ) ) );
state.set_char();
continue;
}
else // match or repeated match
// match or repeated match
int len;
if( rdec.decode_bit( bm_rep[state()] ) != 0 ) // 2nd bit
{
int len;
if( rdec.decode_bit( bm_rep[state()] ) != 0 ) // 2nd bit
if( rdec.decode_bit( bm_rep0[state()] ) == 0 ) // 3rd bit
{
if( rdec.decode_bit( bm_rep0[state()] ) == 0 ) // 3rd bit
{
if( rdec.decode_bit( bm_len[state()][pos_state] ) == 0 ) // 4th bit
{ state.set_short_rep(); put_byte( peek( rep0 ) ); continue; }
}
if( rdec.decode_bit( bm_len[state()][pos_state] ) == 0 ) // 4th bit
{ state.set_short_rep(); put_byte( peek( rep0 ) ); continue; }
}
else
{
unsigned distance;
if( rdec.decode_bit( bm_rep1[state()] ) == 0 ) // 4th bit
distance = rep1;
else
{
unsigned distance;
if( rdec.decode_bit( bm_rep1[state()] ) == 0 ) // 4th bit
distance = rep1;
if( rdec.decode_bit( bm_rep2[state()] ) == 0 ) // 5th bit
distance = rep2;
else
{
if( rdec.decode_bit( bm_rep2[state()] ) == 0 ) // 5th bit
distance = rep2;
else
{ distance = rep3; rep3 = rep2; }
rep2 = rep1;
}
rep1 = rep0;
rep0 = distance;
{ distance = rep3; rep3 = rep2; }
rep2 = rep1;
}
state.set_rep();
len = min_match_len + rdec.decode_len( rep_len_model, pos_state );
rep1 = rep0;
rep0 = distance;
}
else // match
{
rep3 = rep2; rep2 = rep1; rep1 = rep0;
len = min_match_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 )
{
const unsigned dis_slot = rep0;
const int direct_bits = ( dis_slot >> 1 ) - 1;
rep0 = ( 2 | ( dis_slot & 1 ) ) << direct_bits;
if( dis_slot < end_dis_model )
rep0 += rdec.decode_tree_reversed( bm_dis + ( rep0 - dis_slot ),
direct_bits );
else
{
rep0 += rdec.decode( direct_bits - dis_align_bits ) << dis_align_bits;
rep0 += rdec.decode_tree_reversed( bm_align, dis_align_bits );
if( rep0 == 0xFFFFFFFFU ) // marker found
{
flush_data();
return ( len == min_match_len ); // End Of Stream marker
}
}
}
state.set_match();
if( rep0 >= dictionary_size || ( rep0 >= pos && !pos_wrapped ) )
{ flush_data(); return false; }
}
for( int i = 0; i < len; ++i ) put_byte( peek( rep0 ) );
state.set_rep();
len = min_match_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 );
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 )
{
const unsigned dis_slot = rep0;
const int direct_bits = ( dis_slot >> 1 ) - 1;
rep0 = ( 2 | ( dis_slot & 1 ) ) << direct_bits;
if( dis_slot < end_dis_model )
rep0 += rdec.decode_tree_reversed( bm_dis + ( rep0 - dis_slot ),
direct_bits );
else
{
rep0 += rdec.decode( direct_bits - dis_align_bits ) << dis_align_bits;
rep0 += rdec.decode_tree_reversed( bm_align, dis_align_bits );
if( rep0 == 0xFFFFFFFFU ) // marker found
{
flush_data();
return ( len == min_match_len ); // End Of Stream marker
}
}
}
state.set_match();
if( rep0 >= dictionary_size || ( rep0 >= pos && !pos_wrapped ) )
{ flush_data(); return false; }
}
for( int i = 0; i < len; ++i ) put_byte( peek( rep0 ) );
}
flush_data();
return false;
@ -1616,7 +1629,7 @@ int main( const int argc, const char * const argv[] )
"It is not safe to use lzd for any real work.\n"
"\nUsage: %s < file.lz > file\n", argv[0] );
std::printf( "Lzd decompresses from standard input to standard output.\n"
"\nCopyright (C) 2018 Antonio Diaz Diaz.\n"
"\nCopyright (C) 2019 Antonio Diaz Diaz.\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"
"Report bugs to lzip-bug@nongnu.org\n"
@ -1624,14 +1637,14 @@ int main( const int argc, const char * const argv[] )
return 0;
}
#if defined(__MSVCRT__) || defined(__OS2__) || defined(_MSC_VER)
setmode( fileno( stdin ), O_BINARY );
setmode( fileno( stdout ), O_BINARY );
#if defined(__MSVCRT__) || defined(__OS2__) || defined(__DJGPP__)
setmode( STDIN_FILENO, O_BINARY );
setmode( STDOUT_FILENO, O_BINARY );
#endif
for( bool first_member = true; ; first_member = false )
{
File_header header; // verify header
Lzip_header header; // verify header
for( int i = 0; i < 6; ++i ) header[i] = std::getc( stdin );
if( std::feof( stdin ) || std::memcmp( header, "LZIP\x01", 5 ) != 0 )
{
@ -1650,7 +1663,7 @@ int main( const int argc, const char * const argv[] )
if( !decoder.decode_member() )
{ std::fputs( "Data error\n", stderr ); return 2; }
File_trailer trailer; // verify trailer
Lzip_trailer trailer; // verify trailer
for( int i = 0; i < 20; ++i ) trailer[i] = std::getc( stdin );
unsigned crc = 0;
for( int i = 3; i >= 0; --i ) { crc <<= 8; crc += trailer[i]; }