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-rw-r--r--ChangeLog15
-rw-r--r--README13
-rwxr-xr-xconfigure2
-rw-r--r--decoder.cc28
-rw-r--r--decoder.h16
-rw-r--r--doc/lzip.14
-rw-r--r--doc/lzip.info506
-rw-r--r--doc/lzip.texi475
-rw-r--r--encoder.cc42
-rw-r--r--encoder.h18
-rw-r--r--encoder_base.cc2
-rw-r--r--encoder_base.h40
-rw-r--r--fast_encoder.cc4
-rw-r--r--fast_encoder.h4
-rw-r--r--lzip.h20
-rw-r--r--main.cc67
-rwxr-xr-xtestsuite/check.sh3
17 files changed, 643 insertions, 616 deletions
diff --git a/ChangeLog b/ChangeLog
index aa3faae..e3ebebe 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,17 +1,8 @@
-2015-05-25 Antonio Diaz Diaz <antonio@gnu.org>
+2015-07-12 Antonio Diaz Diaz <antonio@gnu.org>
- * Version 1.17-rc2 released.
- * lzip.texi: Added chapter 'Quality assurance'.
-
-2015-04-17 Antonio Diaz Diaz <antonio@gnu.org>
-
- * Version 1.17-rc1 released.
- * main.cc (compress): Fixed spurious warning about uninitialized var.
-
-2015-03-26 Antonio Diaz Diaz <antonio@gnu.org>
-
- * Version 1.17-pre1 released.
+ * Version 1.17 released.
* Reorganization of the compression code.
+ * lzip.texi: Added chapter 'Quality assurance'.
* Makefile.in: Added new targets 'install*-compress'.
2014-08-26 Antonio Diaz Diaz <antonio@gnu.org>
diff --git a/README b/README
index 894b77a..8a31263 100644
--- a/README
+++ b/README
@@ -40,6 +40,13 @@ 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.
+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
+limit, else 2) plus 9 times the dictionary size really used. The option
+'-0' is special and only requires about 1.5 MiB at most. The amount of
+memory required for decompression is about 46 kB larger than the
+dictionary size really used.
+
When compressing, lzip replaces every file given in the command line
with a compressed version of itself, with the name "original_name.lz".
When decompressing, lzip attempts to guess the name for the decompressed
@@ -69,8 +76,8 @@ corresponding uncompressed files. Integrity testing of concatenated
compressed files is also supported.
Lzip can produce multi-member files and safely recover, with
-lziprecover, the undamaged members in case of file damage. Lzip can also
-split the compressed output in volumes of a given size, even when
+lziprecover, the undamaged members in case of file damage. Lzip can
+also split the compressed output in volumes of a given size, even when
reading from standard input. This allows the direct creation of
multivolume compressed tar archives.
@@ -88,7 +95,7 @@ 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).
+(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
diff --git a/configure b/configure
index 2a09e4f..9845c11 100755
--- a/configure
+++ b/configure
@@ -6,7 +6,7 @@
# to copy, distribute and modify it.
pkgname=lzip
-pkgversion=1.17-rc2
+pkgversion=1.17
progname=lzip
srctrigger=doc/${pkgname}.texi
diff --git a/decoder.cc b/decoder.cc
index 5eb9221..113479a 100644
--- a/decoder.cc
+++ b/decoder.cc
@@ -43,7 +43,7 @@ void Pretty_print::operator()( const char * const msg ) const
first_post = false;
std::fprintf( stderr, " %s: ", name_.c_str() );
for( unsigned i = 0; i < longest_name - name_.size(); ++i )
- std::fprintf( stderr, " " );
+ std::fputc( ' ', stderr );
if( !msg ) std::fflush( stderr );
}
if( msg ) std::fprintf( stderr, "%s\n", msg );
@@ -62,7 +62,7 @@ int readblock( const int fd, uint8_t * const buf, const int size )
{
const int n = read( fd, buf + sz, size - sz );
if( n > 0 ) sz += n;
- else if( n == 0 ) break; /* EOF */
+ else if( n == 0 ) break; // EOF
else if( errno != EINTR ) break;
errno = 0;
}
@@ -149,7 +149,7 @@ bool LZ_decoder::verify_trailer( const Pretty_print & pp ) const
if( verbosity >= 0 )
{
pp();
- std::fprintf( stderr, "CRC mismatch; trailer says %08X, data CRC is %08X.\n",
+ std::fprintf( stderr, "CRC mismatch; trailer says %08X, data CRC is %08X\n",
trailer.data_crc(), crc() );
}
}
@@ -159,7 +159,7 @@ bool LZ_decoder::verify_trailer( const Pretty_print & pp ) const
if( verbosity >= 0 )
{
pp();
- std::fprintf( stderr, "Data size mismatch; trailer says %llu, data size is %llu (0x%llX).\n",
+ std::fprintf( stderr, "Data size mismatch; trailer says %llu, data size is %llu (0x%llX)\n",
trailer.data_size(), data_position(), data_position() );
}
}
@@ -169,7 +169,7 @@ bool LZ_decoder::verify_trailer( const Pretty_print & pp ) const
if( verbosity >= 0 )
{
pp();
- std::fprintf( stderr, "Member size mismatch; trailer says %llu, member size is %llu (0x%llX).\n",
+ std::fprintf( stderr, "Member size mismatch; trailer says %llu, member size is %llu (0x%llX)\n",
trailer.member_size(), member_size, member_size );
}
}
@@ -201,9 +201,9 @@ int LZ_decoder::decode_member( const Pretty_print & pp )
Bit_model bm_align[dis_align_size];
Len_model match_len_model;
Len_model rep_len_model;
- unsigned rep0 = 0; /* rep[0-3] latest four distances */
- unsigned rep1 = 0; /* used for efficient coding of */
- unsigned rep2 = 0; /* repeated distances */
+ unsigned rep0 = 0; // rep[0-3] latest four distances
+ unsigned rep1 = 0; // used for efficient coding of
+ unsigned rep2 = 0; // repeated distances
unsigned rep3 = 0;
State state;
@@ -226,7 +226,7 @@ int LZ_decoder::decode_member( const Pretty_print & pp )
peek( rep0 ) ) );
}
}
- else
+ else // match or repeated match
{
int len;
if( rdec.decode_bit( bm_rep[state()] ) != 0 ) // 2nd bit
@@ -255,7 +255,7 @@ int LZ_decoder::decode_member( const Pretty_print & pp )
state.set_rep();
len = min_match_len + rdec.decode_len( rep_len_model, pos_state );
}
- else
+ else // match
{
const unsigned rep0_saved = rep0;
len = min_match_len + rdec.decode_len( match_len_model, pos_state );
@@ -272,23 +272,23 @@ int LZ_decoder::decode_member( const Pretty_print & pp )
{
rep0 += rdec.decode( direct_bits - dis_align_bits ) << dis_align_bits;
rep0 += rdec.decode_tree_reversed4( bm_align );
- if( rep0 == 0xFFFFFFFFU ) /* marker found */
+ if( rep0 == 0xFFFFFFFFU ) // marker found
{
rep0 = rep0_saved;
rdec.normalize();
flush_data();
- if( len == min_match_len ) /* End Of Stream marker */
+ if( len == min_match_len ) // End Of Stream marker
{
if( verify_trailer( pp ) ) return 0; else return 3;
}
- if( len == min_match_len + 1 ) /* Sync Flush marker */
+ if( len == min_match_len + 1 ) // Sync Flush marker
{
rdec.load(); continue;
}
if( verbosity >= 0 )
{
pp();
- std::fprintf( stderr, "Unsupported marker code '%d'.\n", len );
+ std::fprintf( stderr, "Unsupported marker code '%d'\n", len );
}
return 4;
}
diff --git a/decoder.h b/decoder.h
index 9419669..98d42ce 100644
--- a/decoder.h
+++ b/decoder.h
@@ -19,12 +19,12 @@ class Range_decoder
{
enum { buffer_size = 16384 };
unsigned long long partial_member_pos;
- uint8_t * const buffer; /* input buffer */
- int pos; /* current pos in buffer */
- int stream_pos; /* when reached, a new block must be read */
+ uint8_t * const buffer; // input buffer
+ int pos; // current pos in buffer
+ int stream_pos; // when reached, a new block must be read
uint32_t code;
uint32_t range;
- const int infd; /* input file descriptor */
+ const int infd; // input file descriptor
bool at_stream_end;
bool read_block();
@@ -213,11 +213,11 @@ class LZ_decoder
Range_decoder & rdec;
const unsigned dictionary_size;
const int buffer_size;
- uint8_t * const buffer; /* output buffer */
- int pos; /* current pos in buffer */
- int stream_pos; /* first byte not yet written to file */
+ uint8_t * const buffer; // output buffer
+ int pos; // current pos in buffer
+ int stream_pos; // first byte not yet written to file
uint32_t crc_;
- const int outfd; /* output file descriptor */
+ const int outfd; // output file descriptor
const int member_version;
void flush_data();
diff --git a/doc/lzip.1 b/doc/lzip.1
index 6b779f1..b6acca6 100644
--- a/doc/lzip.1
+++ b/doc/lzip.1
@@ -1,5 +1,5 @@
.\" DO NOT MODIFY THIS FILE! It was generated by help2man 1.46.1.
-.TH LZIP "1" "May 2015" "lzip 1.17-rc2" "User Commands"
+.TH LZIP "1" "July 2015" "lzip 1.17" "User Commands"
.SH NAME
lzip \- reduces the size of files
.SH SYNOPSIS
@@ -28,7 +28,7 @@ decompress
overwrite existing output files
.TP
\fB\-F\fR, \fB\-\-recompress\fR
-force recompression of compressed files
+force re\-compression of compressed files
.TP
\fB\-k\fR, \fB\-\-keep\fR
keep (don't delete) input files
diff --git a/doc/lzip.info b/doc/lzip.info
index 6854503..f0aa011 100644
--- a/doc/lzip.info
+++ b/doc/lzip.info
@@ -11,16 +11,16 @@ File: lzip.info, Node: Top, Next: Introduction, Up: (dir)
Lzip Manual
***********
-This manual is for Lzip (version 1.17-rc2, 25 May 2015).
+This manual is for Lzip (version 1.17, 12 July 2015).
* Menu:
* Introduction:: Purpose and features of lzip
-* Algorithm:: How lzip compresses the data
* Invoking lzip:: Command line interface
+* Quality assurance:: Design, development and testing of lzip
* File format:: Detailed format of the compressed file
+* Algorithm:: How lzip compresses the data
* Stream format:: Format of the LZMA stream in lzip files
-* Quality assurance:: Design, development and testing of lzip
* Examples:: A small tutorial with examples
* Problems:: Reporting bugs
* Reference source code:: Source code illustrating stream format
@@ -33,7 +33,7 @@ This manual is for Lzip (version 1.17-rc2, 25 May 2015).
copy, distribute and modify it.

-File: lzip.info, Node: Introduction, Next: Algorithm, Prev: Top, Up: Top
+File: lzip.info, Node: Introduction, Next: Invoking lzip, Prev: Top, Up: Top
1 Introduction
**************
@@ -51,7 +51,8 @@ availability:
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.
+ merging of damaged copies of a file. *note Data safety:
+ (lziprecover)Data safety.
* The lzip format is as simple as possible (but not simpler). The
lzip manual provides the code of a simple decompressor along with
@@ -85,6 +86,11 @@ 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.
+ Lzip 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.
+
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 limit, else 2) plus 9 times the dictionary size really used. The
@@ -92,11 +98,6 @@ option '-0' is special and only requires about 1.5 MiB at most. The
amount of memory required for decompression is about 46 kB larger than
the dictionary size really used.
- Lzip 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, lzip replaces every file given in the command line
with a compressed version of itself, with the name "original_name.lz".
When decompressing, lzip attempts to guess the name for the decompressed
@@ -126,8 +127,8 @@ corresponding uncompressed files. Integrity testing of concatenated
compressed files is also supported.
Lzip can produce multi-member files and safely recover, with
-lziprecover, the undamaged members in case of file damage. Lzip can also
-split the compressed output in volumes of a given size, even when
+lziprecover, the undamaged members in case of file damage. Lzip can
+also split the compressed output in volumes of a given size, even when
reading from standard input. This allows the direct creation of
multivolume compressed tar archives.
@@ -136,75 +137,9 @@ automatically creating multi-member output. The members so created are
large, about 2 PiB each.

-File: lzip.info, Node: Algorithm, Next: Invoking lzip, Prev: Introduction, Up: Top
-
-2 Algorithm
-***********
-
-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
-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 size 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).
-
- 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.
-
- Lzip is a two stage compressor. The first stage is a Lempel-Ziv
-coder, which reduces redundancy by translating chunks of data to their
-corresponding distance-length pairs. The second stage is a range encoder
-that uses a different probability model for each type of data;
-distances, lengths, literal bytes, etc.
-
- Here is how it works, step by step:
-
- 1) The member header is written to the output stream.
-
- 2) The first byte is coded literally, because there are no previous
-bytes to which the match finder can refer to.
-
- 3) The main encoder advances to the next byte in the input data and
-calls the match finder.
-
- 4) The match finder fills an array with the minimum distances before
-the current byte where a match of a given length can be found.
-
- 5) Go back to step 3 until a sequence (formed of pairs, repeated
-distances and literal bytes) of minimum price has been formed. Where the
-price represents the number of output bits produced.
-
- 6) The range encoder encodes the sequence produced by the main
-encoder and sends the produced bytes to the output stream.
-
- 7) Go back to step 3 until the input data are finished or until the
-member or volume size limits are reached.
-
- 8) The range encoder is flushed.
-
- 9) The member trailer is written to the output stream.
-
- 10) If there are more data to compress, go back to step 1.
-
-
-The ideas embodied in lzip are due to (at least) the following people:
-Abraham Lempel and Jacob Ziv (for the LZ algorithm), Andrey 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).
-
-
-File: lzip.info, Node: Invoking lzip, Next: File format, Prev: Algorithm, Up: Top
+File: lzip.info, Node: Invoking lzip, Next: Quality assurance, Prev: Introduction, Up: Top
-3 Invoking lzip
+2 Invoking lzip
***************
The format for running lzip is:
@@ -244,7 +179,7 @@ The format for running lzip is:
'-F'
'--recompress'
- Force recompression of files whose name already has the '.lz' or
+ Force re-compression of files whose name already has the '.lz' or
'.tlz' suffix.
'-k'
@@ -362,7 +297,155 @@ invalid input file, 3 for an internal consistency error (eg, bug) which
caused lzip to panic.

-File: lzip.info, Node: File format, Next: Stream format, Prev: Invoking lzip, Up: Top
+File: lzip.info, Node: Quality assurance, Next: File format, Prev: Invoking lzip, Up: Top
+
+3 Design, development and testing of lzip
+*****************************************
+
+There are two ways of constructing a software design. One way is to make
+it so simple that there are obviously no deficiencies and the other is
+to make it so complicated that there are no obvious deficiencies.
+-- 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.
+
+
+3.1 Format design
+=================
+
+When gzip was designed in 1992, computers and operating systems were
+much less capable than they are today. Gzip tried to work around some of
+those limitations, like 8.3 file names, with additional fields in its
+file format.
+
+ Today those limitations have mostly disappeared, and the format of
+gzip has proved to be unnecessarily complicated. It includes fields
+that were never used, others that have lost its usefulness, and finally
+others that have become too limited.
+
+ Bzip2 was designed 5 years later, and its format is simpler than the
+one of gzip.
+
+ Probably the worst defect of the gzip format from the point of view
+of data safety is the variable size of its header. If the byte at
+offset 3 (flags) of a gzip member gets corrupted, it mat become very
+difficult to recover the data, even if the compressed blocks are
+intact, because it can't be known with certainty where the compressed
+blocks begin.
+
+ By contrast, the header of a lzip member has a fixed length of 6. The
+lzma stream in a lzip member always starts at offset 6, making it
+trivial to recover the data even if the whole header becomes corrupt.
+
+ Bzip2 also provides a header of fixed length and marks the begin and
+end of each compressed block with six magic bytes, making it possible to
+find the compressed blocks even in case of file damage. But bzip2 does
+not store the size of each compressed block, as lzip does.
+
+ Lzip provides better data recovery capabilities than any other
+gzip-like compressor because its format has been designed from the
+beginning to be simple and safe. It would be very difficult to write an
+automatic recovery tool like lziprecover for the gzip format. And, as
+far as I know, it has never been writen.
+
+ The lzip format is designed for long-term archiving. Therefore it
+excludes any unneeded features that may interfere with the future
+extraction of the uncompressed data.
+
+
+3.1.1 Gzip format (mis)features not present in lzip
+---------------------------------------------------
+
+'Multiple algorithms'
+ Gzip provides a CM (Compression Method) field that has never been
+ used because it is a bad idea to begin with. New compression
+ methods may require additional fields, making it impossible to
+ implement new methods and, at the same time, keep the same format.
+ This field does not solve the problem of format proliferation; it
+ just makes the problem less obvious.
+
+'Optional fields in header'
+ Unless special precautions are taken, optional fields are
+ generally a bad idea because they produce a header of variable
+ size. The gzip header has 2 fields that, in addition to being
+ optional, are zero-terminated. This means that if any byte inside
+ the field gets zeroed, or if the terminating zero gets altered,
+ gzip won't be able to find neither the header CRC nor the
+ compressed blocks.
+
+'Optional CRC for the header'
+ Using an optional checksum for the header is not only a bad idea,
+ it is an error; it may prevent the extraction of perfectly good
+ data. For example, if the checksum 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.
+
+
+3.1.2 Lzip format improvements over gzip and bzip2
+--------------------------------------------------
+
+'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.
+
+ 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 multi-member output automatically when
+ the size is too large for a single member, allowing for an
+ unlimited uncompressed size.
+
+'Distributed index'
+ The lzip format provides a distributed index that, among other
+ things, helps plzip to decompress several times faster than pigz
+ and helps lziprecover do its job. Neither the gzip format nor the
+ bzip2 format do provide an index.
+
+ A distributed index is safer and more scalable than a monolithic
+ index. The monolithic index introduces a single point of failure
+ in the compressed file and may limit the number of members or the
+ total uncompressed size.
+
+
+3.2 Quality of implementation
+=============================
+
+'Multiple implementations'
+ Just like the lzip format provides 4 factor protection against
+ undetected data corruption, the development methodology of the lzip
+ 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 subjected to a hundred hours of
+ intensive testing to verify 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.
+
+'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.
+
+'Exit status'
+ Returning a warning status of 2 is a design flaw of compress that
+ leaked into the design of gzip. Both bzip2 and lzip are free from
+ this flaw.
+
+
+
+File: lzip.info, Node: File format, Next: Algorithm, Prev: Quality assurance, Up: Top
4 File format
*************
@@ -433,9 +516,75 @@ additional information before, between, or after them.

-File: lzip.info, Node: Stream format, Next: Quality assurance, Prev: File format, Up: Top
+File: lzip.info, Node: Algorithm, Next: Stream format, Prev: File format, Up: Top
+
+5 Algorithm
+***********
+
+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
+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 size 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).
+
+ 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.
+
+ Lzip is a two stage compressor. The first stage is a Lempel-Ziv
+coder, which reduces redundancy by translating chunks of data to their
+corresponding distance-length pairs. The second stage is a range encoder
+that uses a different probability model for each type of data;
+distances, lengths, literal bytes, etc.
+
+ Here is how it works, step by step:
+
+ 1) The member header is written to the output stream.
+
+ 2) The first byte is coded literally, because there are no previous
+bytes to which the match finder can refer to.
+
+ 3) The main encoder advances to the next byte in the input data and
+calls the match finder.
+
+ 4) The match finder fills an array with the minimum distances before
+the current byte where a match of a given length can be found.
+
+ 5) Go back to step 3 until a sequence (formed of pairs, repeated
+distances and literal bytes) of minimum price has been formed. Where the
+price represents the number of output bits produced.
+
+ 6) The range encoder encodes the sequence produced by the main
+encoder and sends the produced bytes to the output stream.
+
+ 7) Go back to step 3 until the input data are finished or until the
+member or volume size limits are reached.
+
+ 8) The range encoder is flushed.
+
+ 9) The member trailer is written to the output stream.
+
+ 10) If there are more data to compress, go back to step 1.
+
+
+The ideas embodied in lzip are due to (at least) the following people:
+Abraham Lempel and Jacob Ziv (for the LZ algorithm), Andrey 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).
+
+
+File: lzip.info, Node: Stream format, Next: Examples, Prev: Algorithm, Up: Top
-5 Format of the LZMA stream in lzip files
+6 Format of the LZMA stream in lzip files
*****************************************
The LZMA algorithm has three parameters, called "special LZMA
@@ -473,7 +622,7 @@ the lzip download directory. The source code of lzd is included in
appendix A. *note Reference source code::
-5.1 What is coded
+6.1 What is coded
=================
The LZMA stream includes literals, matches and repeated matches (matches
@@ -525,7 +674,7 @@ slot + direct_bits distances from 4 to 127
slot + (direct_bits - 4) + 4 bits distances from 128 to 2^32 - 1
-5.2 The coding contexts
+6.2 The coding contexts
=======================
These contexts ('Bit_model' in the source), are integers or arrays of
@@ -615,7 +764,7 @@ difference is found, the rest of the byte is decoded using the normal
bit tree context. (See 'decode_matched' in the source).
-5.3 The range decoder
+6.3 The range decoder
=====================
The LZMA stream is consumed one byte at a time by the range decoder.
@@ -635,7 +784,7 @@ range decoder. This is done by shifting 5 bytes in the initialization of
source).
-5.4 Decoding the LZMA stream
+6.4 Decoding the LZMA stream
============================
After decoding the member header and obtaining the dictionary size, the
@@ -646,144 +795,7 @@ with the appropriate contexts to decode the different coding sequences
Stream" marker is decoded.

-File: lzip.info, Node: Quality assurance, Next: Examples, Prev: Stream format, Up: Top
-
-6 Design, development and testing of lzip
-*****************************************
-
-There are two ways of constructing a software design. One way is to make
-it so simple that there are obviously no deficiencies and the other is
-to make it so complicated that there are no obvious deficiencies.
--- 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.
-
-
-6.1 Format design
-=================
-
-When gzip was designed in 1992, computers and operating systems were
-much less capable than they are today. Gzip tried to work around some of
-those limitations, like 8.3 file names, with additional fields in its
-file format.
-
- Today those limitations have mostly disappeared, and the format of
-gzip has proved to be unnecessarily complicated. It includes fields
-that were never used, others that have lost its usefulness, and finally
-others that have become too limited.
-
- Bzip2 was designed 5 years later, and its format is in some aspects
-simpler than the one of gzip. But bzip2 also shows complexities in its
-file format which slow down decompression and, in retrospect, are
-unnecessary.
-
- Probably the worst defect of the gzip format from the point of view
-of data safety is the variable size of its header. If the byte at
-offset 3 (flags) of a gzip member gets corrupted, it mat become very
-difficult to recover the data, even if the compressed blocks are
-intact, because it can't be known with certainty where the compressed
-blocks begin.
-
- By contrast, the lzma stream in a lzip member always starts at
-offset 6, making it trivial to recover the data even if the whole
-header becomes corrupt.
-
- Lzip provides better data recovery capabilities than any other
-gzip-like compressor because its format has been designed from the
-beginning to be simple and safe. It would be very difficult to write an
-automatic recovery tool like lziprecover for the gzip format. And, as
-far as I know, it has never been writen.
-
- The lzip format is designed for long-term archiving. Therefore it
-excludes any unneeded features that may interfere with the future
-extraction of the uncompressed data.
-
-
-6.1.1 Gzip format (mis)features not present in lzip
----------------------------------------------------
-
-'Multiple algorithms'
- Gzip provides a CM (Compression Method) field that has never been
- used because it is a bad idea to begin with. New compression
- methods may require additional fields, making it impossible to
- implement new methods and, at the same time, keep the same format.
- This field does not solve the problem of format proliferation; it
- just makes the problem less obvious.
-
-'Optional fields in header'
- Unless special precautions are taken, optional fields are
- generally a bad idea because they produce a header of variable
- size. The gzip header has 2 fields that, in addition to being
- optional, are zero-terminated. This means that if any byte inside
- the field gets zeroed, or if the terminating zero gets altered,
- gzip won't be able to find neither the header CRC nor the
- compressed blocks.
-
- Using an optional checksum for the header is not only a bad idea,
- it is an error; it may prevent the extraction of perfectly good
- data. For example, if the checksum 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.
-
-
-6.1.2 Lzip format improvements over gzip
-----------------------------------------
-
-'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.
-
- The lzip format provides a 64-bit field for the uncompressed size.
- Additionaly, lzip produces multi-member output automatically when
- the size is too large for a single member, allowing an unlimited
- uncompressed size.
-
-'Distributed index'
- The lzip format provides a distributed index that, among other
- things, helps plzip to decompress several times faster than pigz
- and helps lziprecover do its job. The gzip format does not provide
- an index.
-
- A distributed index is safer and more scalable than a monolithic
- index. The monolithic index introduces a single point of failure
- in the compressed file and may limit the number of members or the
- total uncompressed size.
-
-
-6.2 Quality of implementation
-=============================
-
-Three related but independent compressor implementations, lzip, clzip
-and minilzip/lzlib, are developed concurrently. Every stable release of
-any of them is subjected to a hundred hours of intensive testing to
-verify 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.
-
- Just like the lzip format provides 4 factor protection against
-undetected data corruption, the development methodology described above
-provides 3 factor protection against undetected programming errors in
-lzip.
-
- 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.
-
- Returning a warning status of 2 is a design flaw of compress that
-leaked into the design of gzip. Both bzip2 and lzip are free form this
-flaw.
-
-
-File: lzip.info, Node: Examples, Next: Problems, Prev: Quality assurance, Up: Top
+File: lzip.info, Node: Examples, Next: Problems, Prev: Stream format, Up: Top
7 A small tutorial with examples
********************************
@@ -876,7 +888,7 @@ File: lzip.info, Node: Reference source code, Next: Concept index, Prev: Prob
Appendix A Reference source code
********************************
-/* Lzd - Educational decompressor for lzip files
+/* Lzd - Educational decompressor for the lzip format
Copyright (C) 2013-2015 Antonio Diaz Diaz.
This program is free software: you have unlimited permission
@@ -1133,7 +1145,7 @@ class LZ_decoder
}
public:
- LZ_decoder( const unsigned dict_size )
+ explicit LZ_decoder( const unsigned dict_size )
:
partial_data_pos( 0 ),
dictionary_size( dict_size ),
@@ -1160,7 +1172,7 @@ void LZ_decoder::flush_data()
crc32.update_buf( crc_, buffer + stream_pos, size );
errno = 0;
if( std::fwrite( buffer + stream_pos, 1, size, stdout ) != size )
- { std::fprintf( stderr, "Write error: %s.\n", std::strerror( errno ) );
+ { std::fprintf( stderr, "Write error: %s\n", std::strerror( errno ) );
std::exit( 1 ); }
if( pos >= dictionary_size ) { partial_data_pos += pos; pos = 0; }
stream_pos = pos;
@@ -1202,7 +1214,7 @@ bool LZ_decoder::decode_member() // Returns false if error
put_byte( rdec.decode_matched( bm, peek( rep0 ) ) );
state.set_char();
}
- else
+ else // match or repeated match
{
int len;
if( rdec.decode_bit( bm_rep[state()] ) != 0 ) // 2nd bit
@@ -1231,7 +1243,7 @@ bool LZ_decoder::decode_member() // Returns false if error
state.set_rep();
len = min_match_len + rdec.decode_len( rep_len_model, pos_state );
}
- else
+ else // match
{
rep3 = rep2; rep2 = rep1; rep1 = rep0;
len = min_match_len + rdec.decode_len( match_len_model, pos_state );
@@ -1273,7 +1285,7 @@ int main( const int argc, const char * const argv[] )
{
if( argc > 1 )
{
- std::printf( "Lzd %s - Educational decompressor for lzip files.\n",
+ std::printf( "Lzd %s - Educational decompressor for the lzip format.\n",
PROGVERSION );
std::printf( "Study the source to learn how a lzip decompressor works.\n"
"See the lzip manual for an explanation of the code.\n"
@@ -1300,19 +1312,19 @@ int main( const int argc, const char * const argv[] )
if( std::feof( stdin ) || std::memcmp( header, "LZIP\x01", 5 ) != 0 )
{
if( first_member )
- { std::fprintf( stderr, "Bad magic number (file not in lzip format)\n" );
+ { std::fputs( "Bad magic number (file not in lzip format).\n", stderr );
return 2; }
break;
}
unsigned dict_size = 1 << ( header[5] & 0x1F );
dict_size -= ( dict_size / 16 ) * ( ( header[5] >> 5 ) & 7 );
if( dict_size < min_dictionary_size || dict_size > max_dictionary_size )
- { std::fprintf( stderr, "Invalid dictionary size in member header\n" );
+ { std::fputs( "Invalid dictionary size in member header.\n", stderr );
return 2; }
LZ_decoder decoder( dict_size );
if( !decoder.decode_member() )
- { std::fprintf( stderr, "Data error\n" ); return 2; }
+ { std::fputs( "Data error\n", stderr ); return 2; }
File_trailer trailer;
for( int i = 0; i < 20; ++i ) trailer[i] = std::getc( stdin );
@@ -1321,11 +1333,11 @@ int main( const int argc, const char * const argv[] )
unsigned long long data_size = 0;
for( int i = 11; i >= 4; --i ) { data_size <<= 8; data_size += trailer[i]; }
if( crc != decoder.crc() || data_size != decoder.data_position() )
- { std::fprintf( stderr, "CRC error\n" ); return 2; }
+ { std::fputs( "CRC error\n", stderr ); return 2; }
}
if( std::fclose( stdout ) != 0 )
- { std::fprintf( stderr, "Can't close stdout: %s.\n", std::strerror( errno ) );
+ { std::fprintf( stderr, "Can't close stdout: %s\n", std::strerror( errno ) );
return 1; }
return 0;
}
@@ -1357,16 +1369,16 @@ Concept index

Tag Table:
Node: Top208
-Node: Introduction1090
-Node: Algorithm6008
-Node: Invoking lzip8833
-Node: File format14421
-Node: Stream format16806
-Node: Quality assurance26247
-Node: Examples32269
-Node: Problems34230
-Node: Reference source code34760
-Node: Concept index48358
+Node: Introduction1087
+Node: Invoking lzip6060
+Node: Quality assurance11658
+Node: File format18171
+Node: Algorithm20556
+Node: Stream format23382
+Node: Examples32812
+Node: Problems34769
+Node: Reference source code35299
+Node: Concept index48952

End Tag Table
diff --git a/doc/lzip.texi b/doc/lzip.texi
index ac44ee9..69f44ae 100644
--- a/doc/lzip.texi
+++ b/doc/lzip.texi
@@ -6,8 +6,8 @@
@finalout
@c %**end of header
-@set UPDATED 25 May 2015
-@set VERSION 1.17-rc2
+@set UPDATED 12 July 2015
+@set VERSION 1.17
@dircategory Data Compression
@direntry
@@ -36,11 +36,11 @@ This manual is for Lzip (version @value{VERSION}, @value{UPDATED}).
@menu
* Introduction:: Purpose and features of lzip
-* Algorithm:: How lzip compresses the data
* Invoking lzip:: Command line interface
+* Quality assurance:: Design, development and testing of lzip
* File format:: Detailed format of the compressed file
+* Algorithm:: How lzip compresses the data
* Stream format:: Format of the LZMA stream in lzip files
-* Quality assurance:: Design, development and testing of lzip
* Examples:: A small tutorial with examples
* Problems:: Reporting bugs
* Reference source code:: Source code illustrating stream format
@@ -70,10 +70,14 @@ availability:
@itemize @bullet
@item
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.
+recovery means. The
+@uref{http://www.nongnu.org/lzip/manual/lziprecover_manual.html#Data-safety,,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.
+@ifnothtml
+@ref{Data safety,,,lziprecover}.
+@end ifnothtml
@item
The lzip format is as simple as possible (but not simpler). The lzip
@@ -109,6 +113,11 @@ 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.
+Lzip 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.
+
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
limit, else 2) plus 9 times the dictionary size really used. The option
@@ -116,11 +125,6 @@ limit, else 2) plus 9 times the dictionary size really used. The option
of memory required for decompression is about 46 kB larger than the
dictionary size really used.
-Lzip 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, lzip replaces every file given in the command line
with a compressed version of itself, with the name "original_name.lz".
When decompressing, lzip attempts to guess the name for the decompressed
@@ -152,8 +156,8 @@ corresponding uncompressed files. Integrity testing of concatenated
compressed files is also supported.
Lzip can produce multi-member files and safely recover, with
-lziprecover, the undamaged members in case of file damage. Lzip can also
-split the compressed output in volumes of a given size, even when
+lziprecover, the undamaged members in case of file damage. Lzip can
+also split the compressed output in volumes of a given size, even when
reading from standard input. This allows the direct creation of
multivolume compressed tar archives.
@@ -162,72 +166,6 @@ automatically creating multi-member output. The members so created are
large, about 2 PiB each.
-@node Algorithm
-@chapter Algorithm
-@cindex algorithm
-
-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
-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 size 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).
-
-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.
-
-Lzip is a two stage compressor. The first stage is a Lempel-Ziv coder,
-which reduces redundancy by translating chunks of data to their
-corresponding distance-length pairs. The second stage is a range encoder
-that uses a different probability model for each type of data;
-distances, lengths, literal bytes, etc.
-
-Here is how it works, step by step:
-
-1) The member header is written to the output stream.
-
-2) The first byte is coded literally, because there are no previous
-bytes to which the match finder can refer to.
-
-3) The main encoder advances to the next byte in the input data and
-calls the match finder.
-
-4) The match finder fills an array with the minimum distances before the
-current byte where a match of a given length can be found.
-
-5) Go back to step 3 until a sequence (formed of pairs, repeated
-distances and literal bytes) of minimum price has been formed. Where the
-price represents the number of output bits produced.
-
-6) The range encoder encodes the sequence produced by the main encoder
-and sends the produced bytes to the output stream.
-
-7) Go back to step 3 until the input data are finished or until the
-member or volume size limits are reached.
-
-8) The range encoder is flushed.
-
-9) The member trailer is written to the output stream.
-
-10) If there are more data to compress, go back to step 1.
-
-@sp 1
-@noindent
-The ideas embodied in lzip are due to (at least) the following people:
-Abraham Lempel and Jacob Ziv (for the LZ algorithm), Andrey 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).
-
-
@node Invoking lzip
@chapter Invoking lzip
@cindex invoking
@@ -274,7 +212,7 @@ Force overwrite of output files.
@item -F
@itemx --recompress
-Force recompression of files whose name already has the @samp{.lz} or
+Force re-compression of files whose name already has the @samp{.lz} or
@samp{.tlz} suffix.
@item -k
@@ -392,6 +330,157 @@ invalid input file, 3 for an internal consistency error (eg, bug) which
caused lzip to panic.
+@node Quality assurance
+@chapter Design, development and testing of lzip
+@cindex quality assurance
+
+There are two ways of constructing a software design. One way is to make
+it so simple that there are obviously no deficiencies and the other is
+to make it so complicated that there are no obvious deficiencies.@*
+--- 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.
+
+@sp 1
+@section Format design
+
+When gzip was designed in 1992, computers and operating systems were
+much less capable than they are today. Gzip tried to work around some of
+those limitations, like 8.3 file names, with additional fields in its
+file format.
+
+Today those limitations have mostly disappeared, and the format of gzip
+has proved to be unnecessarily complicated. It includes fields that were
+never used, others that have lost its usefulness, and finally others
+that have become too limited.
+
+Bzip2 was designed 5 years later, and its format is simpler than the one
+of gzip.
+
+Probably the worst defect of the gzip format from the point of view of
+data safety is the variable size of its header. If the byte at offset 3
+(flags) of a gzip member gets corrupted, it mat become very difficult to
+recover the data, even if the compressed blocks are intact, because it
+can't be known with certainty where the compressed blocks begin.
+
+By contrast, the header of a lzip member has a fixed length of 6. The
+lzma stream in a lzip member always starts at offset 6, making it
+trivial to recover the data even if the whole header becomes corrupt.
+
+Bzip2 also provides a header of fixed length and marks the begin and end
+of each compressed block with six magic bytes, making it possible to
+find the compressed blocks even in case of file damage. But bzip2 does
+not store the size of each compressed block, as lzip does.
+
+Lzip provides better data recovery capabilities than any other gzip-like
+compressor because its format has been designed from the beginning to be
+simple and safe. It would be very difficult to write an automatic
+recovery tool like lziprecover for the gzip format. And, as far as I
+know, it has never been writen.
+
+The lzip format is designed for long-term archiving. Therefore it
+excludes any unneeded features that may interfere with the future
+extraction of the uncompressed data.
+
+@sp 1
+@subsection Gzip format (mis)features not present in lzip
+
+@table @samp
+@item Multiple algorithms
+
+Gzip provides a CM (Compression Method) field that has never been used
+because it is a bad idea to begin with. New compression methods may
+require additional fields, making it impossible to implement new methods
+and, at the same time, keep the same format. This field does not solve
+the problem of format proliferation; it just makes the problem less
+obvious.
+
+@item Optional fields in header
+
+Unless special precautions are taken, optional fields are generally a
+bad idea because they produce a header of variable size. The gzip header
+has 2 fields that, in addition to being optional, are zero-terminated.
+This means that if any byte inside the field gets zeroed, or if the
+terminating zero gets altered, gzip won't be able to find neither the
+header CRC nor the compressed blocks.
+
+@item Optional CRC for the header
+
+Using an optional checksum for the header is not only a bad idea, it is
+an error; it may prevent the extraction of perfectly good data. For
+example, if the checksum 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.
+
+@end table
+
+@subsection Lzip format improvements over gzip and bzip2
+
+@table @samp
+@item 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.
+
+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 multi-member output automatically when the
+size is too large for a single member, allowing for an unlimited
+uncompressed size.
+
+@item Distributed index
+
+The lzip format provides a distributed index that, among other things,
+helps plzip to decompress several times faster than pigz and helps
+lziprecover do its job. Neither the gzip format nor the bzip2 format do
+provide an index.
+
+A distributed index is safer and more scalable than a monolithic index.
+The monolithic index introduces a single point of failure in the
+compressed file and may limit the number of members or the total
+uncompressed size.
+
+@end table
+
+@section Quality of implementation
+
+@table @samp
+@item Multiple implementations
+
+Just like the lzip format provides 4 factor protection against
+undetected data corruption, the development methodology of the lzip
+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 subjected to a hundred hours of intensive testing to
+verify 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.
+
+@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.
+
+@item Exit status
+
+Returning a warning status of 2 is a design flaw of compress that leaked
+into the design of gzip. Both bzip2 and lzip are free from this flaw.
+
+@end table
+
+
@node File format
@chapter File format
@cindex file format
@@ -468,6 +557,72 @@ facilitates safe recovery of undamaged members from multi-member files.
@end table
+@node Algorithm
+@chapter Algorithm
+@cindex algorithm
+
+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
+scheme". For example, the option @samp{-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 size 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 @samp{-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.
+
+Lzip is a two stage compressor. The first stage is a Lempel-Ziv coder,
+which reduces redundancy by translating chunks of data to their
+corresponding distance-length pairs. The second stage is a range encoder
+that uses a different probability model for each type of data;
+distances, lengths, literal bytes, etc.
+
+Here is how it works, step by step:
+
+1) The member header is written to the output stream.
+
+2) The first byte is coded literally, because there are no previous
+bytes to which the match finder can refer to.
+
+3) The main encoder advances to the next byte in the input data and
+calls the match finder.
+
+4) The match finder fills an array with the minimum distances before the
+current byte where a match of a given length can be found.
+
+5) Go back to step 3 until a sequence (formed of pairs, repeated
+distances and literal bytes) of minimum price has been formed. Where the
+price represents the number of output bits produced.
+
+6) The range encoder encodes the sequence produced by the main encoder
+and sends the produced bytes to the output stream.
+
+7) Go back to step 3 until the input data are finished or until the
+member or volume size limits are reached.
+
+8) The range encoder is flushed.
+
+9) The member trailer is written to the output stream.
+
+10) If there are more data to compress, go back to step 1.
+
+@sp 1
+@noindent
+The ideas embodied in lzip are due to (at least) the following people:
+Abraham Lempel and Jacob Ziv (for the LZ algorithm), Andrey 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).
+
+
@node Stream format
@chapter Format of the LZMA stream in lzip files
@cindex format of the LZMA stream
@@ -690,140 +845,6 @@ sequences (matches, repeated matches, and literal bytes), until the "End
Of Stream" marker is decoded.
-@node Quality assurance
-@chapter Design, development and testing of lzip
-@cindex quality assurance
-
-There are two ways of constructing a software design. One way is to make
-it so simple that there are obviously no deficiencies and the other is
-to make it so complicated that there are no obvious deficiencies.@*
---- 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.
-
-@sp 1
-@section Format design
-
-When gzip was designed in 1992, computers and operating systems were
-much less capable than they are today. Gzip tried to work around some of
-those limitations, like 8.3 file names, with additional fields in its
-file format.
-
-Today those limitations have mostly disappeared, and the format of gzip
-has proved to be unnecessarily complicated. It includes fields that were
-never used, others that have lost its usefulness, and finally others
-that have become too limited.
-
-Bzip2 was designed 5 years later, and its format is in some aspects
-simpler than the one of gzip. But bzip2 also shows complexities in its
-file format which slow down decompression and, in retrospect, are
-unnecessary.
-
-Probably the worst defect of the gzip format from the point of view of
-data safety is the variable size of its header. If the byte at offset 3
-(flags) of a gzip member gets corrupted, it mat become very difficult to
-recover the data, even if the compressed blocks are intact, because it
-can't be known with certainty where the compressed blocks begin.
-
-By contrast, the lzma stream in a lzip member always starts at offset 6,
-making it trivial to recover the data even if the whole header becomes
-corrupt.
-
-Lzip provides better data recovery capabilities than any other gzip-like
-compressor because its format has been designed from the beginning to be
-simple and safe. It would be very difficult to write an automatic
-recovery tool like lziprecover for the gzip format. And, as far as I
-know, it has never been writen.
-
-The lzip format is designed for long-term archiving. Therefore it
-excludes any unneeded features that may interfere with the future
-extraction of the uncompressed data.
-
-@sp 1
-@subsection Gzip format (mis)features not present in lzip
-
-@table @samp
-@item Multiple algorithms
-
-Gzip provides a CM (Compression Method) field that has never been used
-because it is a bad idea to begin with. New compression methods may
-require additional fields, making it impossible to implement new methods
-and, at the same time, keep the same format. This field does not solve
-the problem of format proliferation; it just makes the problem less
-obvious.
-
-@item Optional fields in header
-
-Unless special precautions are taken, optional fields are generally a
-bad idea because they produce a header of variable size. The gzip header
-has 2 fields that, in addition to being optional, are zero-terminated.
-This means that if any byte inside the field gets zeroed, or if the
-terminating zero gets altered, gzip won't be able to find neither the
-header CRC nor the compressed blocks.
-
-Using an optional checksum for the header is not only a bad idea, it is
-an error; it may prevent the extraction of perfectly good data. For
-example, if the checksum 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.
-
-@end table
-
-@subsection Lzip format improvements over gzip
-
-@table @samp
-@item 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.
-
-The lzip format provides a 64-bit field for the uncompressed size.
-Additionaly, lzip produces multi-member output automatically when the
-size is too large for a single member, allowing an unlimited
-uncompressed size.
-
-@item Distributed index
-
-The lzip format provides a distributed index that, among other things,
-helps plzip to decompress several times faster than pigz and helps
-lziprecover do its job. The gzip format does not provide an index.
-
-A distributed index is safer and more scalable than a monolithic index.
-The monolithic index introduces a single point of failure in the
-compressed file and may limit the number of members or the total
-uncompressed size.
-
-@end table
-
-@section Quality of implementation
-
-Three related but independent compressor implementations, lzip, clzip
-and minilzip/lzlib, are developed concurrently. Every stable release of
-any of them is subjected to a hundred hours of intensive testing to
-verify 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.
-
-Just like the lzip format provides 4 factor protection against
-undetected data corruption, the development methodology described above
-provides 3 factor protection against undetected programming errors in
-lzip.
-
-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.
-
-Returning a warning status of 2 is a design flaw of compress that leaked
-into the design of gzip. Both bzip2 and lzip are free form this flaw.
-
-
@node Examples
@chapter A small tutorial with examples
@cindex examples
@@ -947,7 +968,7 @@ find by running @w{@code{lzip --version}}.
@cindex reference source code
@verbatim
-/* Lzd - Educational decompressor for lzip files
+/* Lzd - Educational decompressor for the lzip format
Copyright (C) 2013-2015 Antonio Diaz Diaz.
This program is free software: you have unlimited permission
@@ -1204,7 +1225,7 @@ class LZ_decoder
}
public:
- LZ_decoder( const unsigned dict_size )
+ explicit LZ_decoder( const unsigned dict_size )
:
partial_data_pos( 0 ),
dictionary_size( dict_size ),
@@ -1231,7 +1252,7 @@ void LZ_decoder::flush_data()
crc32.update_buf( crc_, buffer + stream_pos, size );
errno = 0;
if( std::fwrite( buffer + stream_pos, 1, size, stdout ) != size )
- { std::fprintf( stderr, "Write error: %s.\n", std::strerror( errno ) );
+ { std::fprintf( stderr, "Write error: %s\n", std::strerror( errno ) );
std::exit( 1 ); }
if( pos >= dictionary_size ) { partial_data_pos += pos; pos = 0; }
stream_pos = pos;
@@ -1273,7 +1294,7 @@ bool LZ_decoder::decode_member() // Returns false if error
put_byte( rdec.decode_matched( bm, peek( rep0 ) ) );
state.set_char();
}
- else
+ else // match or repeated match
{
int len;
if( rdec.decode_bit( bm_rep[state()] ) != 0 ) // 2nd bit
@@ -1302,7 +1323,7 @@ bool LZ_decoder::decode_member() // Returns false if error
state.set_rep();
len = min_match_len + rdec.decode_len( rep_len_model, pos_state );
}
- else
+ else // match
{
rep3 = rep2; rep2 = rep1; rep1 = rep0;
len = min_match_len + rdec.decode_len( match_len_model, pos_state );
@@ -1344,7 +1365,7 @@ int main( const int argc, const char * const argv[] )
{
if( argc > 1 )
{
- std::printf( "Lzd %s - Educational decompressor for lzip files.\n",
+ std::printf( "Lzd %s - Educational decompressor for the lzip format.\n",
PROGVERSION );
std::printf( "Study the source to learn how a lzip decompressor works.\n"
"See the lzip manual for an explanation of the code.\n"
@@ -1371,19 +1392,19 @@ int main( const int argc, const char * const argv[] )
if( std::feof( stdin ) || std::memcmp( header, "LZIP\x01", 5 ) != 0 )
{
if( first_member )
- { std::fprintf( stderr, "Bad magic number (file not in lzip format)\n" );
+ { std::fputs( "Bad magic number (file not in lzip format).\n", stderr );
return 2; }
break;
}
unsigned dict_size = 1 << ( header[5] & 0x1F );
dict_size -= ( dict_size / 16 ) * ( ( header[5] >> 5 ) & 7 );
if( dict_size < min_dictionary_size || dict_size > max_dictionary_size )
- { std::fprintf( stderr, "Invalid dictionary size in member header\n" );
+ { std::fputs( "Invalid dictionary size in member header.\n", stderr );
return 2; }
LZ_decoder decoder( dict_size );
if( !decoder.decode_member() )
- { std::fprintf( stderr, "Data error\n" ); return 2; }
+ { std::fputs( "Data error\n", stderr ); return 2; }
File_trailer trailer;
for( int i = 0; i < 20; ++i ) trailer[i] = std::getc( stdin );
@@ -1392,11 +1413,11 @@ int main( const int argc, const char * const argv[] )
unsigned long long data_size = 0;
for( int i = 11; i >= 4; --i ) { data_size <<= 8; data_size += trailer[i]; }
if( crc != decoder.crc() || data_size != decoder.data_position() )
- { std::fprintf( stderr, "CRC error\n" ); return 2; }
+ { std::fputs( "CRC error\n", stderr ); return 2; }
}
if( std::fclose( stdout ) != 0 )
- { std::fprintf( stderr, "Can't close stdout: %s.\n", std::strerror( errno ) );
+ { std::fprintf( stderr, "Can't close stdout: %s\n", std::strerror( errno ) );
return 1; }
return 0;
}
diff --git a/encoder.cc b/encoder.cc
index 3e707f3..51c0069 100644
--- a/encoder.cc
+++ b/encoder.cc
@@ -75,7 +75,7 @@ int LZ_encoder::get_match_pairs( Pair * pairs )
while( maxlen < len_limit && data[maxlen-delta] == data[maxlen] )
++maxlen;
pairs[num_pairs-1].len = maxlen;
- if( maxlen >= len_limit ) pairs = 0; /* done. now just skip */
+ if( maxlen >= len_limit ) pairs = 0; // done. now just skip
}
if( maxlen < 3 ) maxlen = 3;
}
@@ -269,10 +269,10 @@ int LZ_encoder::sequence_optimizer( const int reps[num_rep_distances],
}
int cur = 0;
- while( true ) /* price optimization loop */
+ while( true ) // price optimization loop
{
move_pos();
- if( ++cur >= num_trials ) /* no more initialized trials */
+ if( ++cur >= num_trials ) // no more initialized trials
{
backward( cur );
return cur;
@@ -287,7 +287,7 @@ int LZ_encoder::sequence_optimizer( const int reps[num_rep_distances],
return cur;
}
- /* give final values to current trial */
+ // give final values to current trial
Trial & cur_trial = trials[cur];
State cur_state;
{
@@ -298,7 +298,7 @@ int LZ_encoder::sequence_optimizer( const int reps[num_rep_distances],
if( prev_index2 == single_step_trial )
{
cur_state = trials[prev_index].state;
- if( prev_index + 1 == cur ) /* len == 1 */
+ if( prev_index + 1 == cur ) // len == 1
{
if( dis == 0 ) cur_state.set_short_rep();
else cur_state.set_char(); // literal
@@ -306,14 +306,14 @@ int LZ_encoder::sequence_optimizer( const int reps[num_rep_distances],
else if( dis < num_rep_distances ) cur_state.set_rep();
else cur_state.set_match();
}
- else if( prev_index2 == dual_step_trial ) /* dis == 0 */
+ else if( prev_index2 == dual_step_trial ) // dis == 0
{
--prev_index;
cur_state = trials[prev_index].state;
cur_state.set_char();
cur_state.set_rep();
}
- else /* if( prev_index2 >= 0 ) */
+ else // if( prev_index2 >= 0 )
{
prev_index = prev_index2;
cur_state = trials[prev_index].state;
@@ -340,7 +340,7 @@ int LZ_encoder::sequence_optimizer( const int reps[num_rep_distances],
else
next_price += price_matched( prev_byte, cur_byte, match_byte );
- /* try last updates to next trial */
+ // try last updates to next trial
Trial & next_trial = trials[cur+1];
next_trial.update( next_price, -1, cur ); // literal
@@ -366,7 +366,7 @@ int LZ_encoder::sequence_optimizer( const int reps[num_rep_distances],
const int len_limit = std::min( match_len_limit, triable_bytes );
- /* try literal + rep0 */
+ // try literal + rep0
if( match_byte != cur_byte && next_trial.prev_index != cur )
{
const uint8_t * const data = ptr_to_current_pos();
@@ -390,7 +390,7 @@ int LZ_encoder::sequence_optimizer( const int reps[num_rep_distances],
int start_len = min_match_len;
- /* try rep distances */
+ // try rep distances
for( int rep = 0; rep < num_rep_distances; ++rep )
{
const uint8_t * const data = ptr_to_current_pos();
@@ -407,9 +407,9 @@ int LZ_encoder::sequence_optimizer( const int reps[num_rep_distances],
trials[cur+i].update( price + rep_len_prices.price( i, pos_state ),
rep, cur );
- if( rep == 0 ) start_len = len + 1; /* discard shorter matches */
+ if( rep == 0 ) start_len = len + 1; // discard shorter matches
- /* try rep + literal + rep0 */
+ // try rep + literal + rep0
int len2 = len + 1;
const int limit = std::min( match_len_limit + len2, triable_bytes );
while( len2 < limit && data[len2-dis] == data[len2] ) ++len2;
@@ -431,7 +431,7 @@ int LZ_encoder::sequence_optimizer( const int reps[num_rep_distances],
trials[cur+len+1+len2].update3( price, rep, cur + len + 1, cur );
}
- /* try matches */
+ // try matches
if( newlen >= start_len && newlen <= len_limit )
{
const int normal_match_price = match_price +
@@ -449,7 +449,7 @@ int LZ_encoder::sequence_optimizer( const int reps[num_rep_distances],
trials[cur+len].update( price, dis + num_rep_distances, cur );
- /* try match + literal + rep0 */
+ // try match + literal + rep0
if( len == pairs[i].len )
{
const uint8_t * const data = ptr_to_current_pos();
@@ -500,7 +500,7 @@ bool LZ_encoder::encode_member( const unsigned long long member_size )
for( int i = 0; i < num_rep_distances; ++i ) reps[i] = 0;
if( data_position() != 0 || renc.member_position() != File_header::size )
- return false; /* can be called only once */
+ return false; // can be called only once
if( !data_finished() ) // encode first byte
{
@@ -517,7 +517,7 @@ bool LZ_encoder::encode_member( const unsigned long long member_size )
{
if( price_counter <= 0 && pending_num_pairs == 0 )
{
- price_counter = price_count; /* recalculate prices every these bytes */
+ price_counter = price_count; // recalculate prices every these bytes
if( dis_price_counter <= 0 )
{ dis_price_counter = dis_price_count; update_distance_prices(); }
if( align_price_counter <= 0 )
@@ -531,7 +531,7 @@ bool LZ_encoder::encode_member( const unsigned long long member_size )
}
int ahead = sequence_optimizer( reps, state );
- if( ahead <= 0 ) return false; /* can't happen */
+ if( ahead <= 0 ) return false; // can't happen
price_counter -= ahead;
for( int i = 0; ahead > 0; )
@@ -542,7 +542,7 @@ bool LZ_encoder::encode_member( const unsigned long long member_size )
bool bit = ( dis < 0 );
renc.encode_bit( bm_match[state()][pos_state], !bit );
- if( bit ) /* literal byte */
+ if( bit ) // literal byte
{
const uint8_t prev_byte = peek( ahead + 1 );
const uint8_t cur_byte = peek( ahead );
@@ -556,13 +556,13 @@ bool LZ_encoder::encode_member( const unsigned long long member_size )
}
state.set_char();
}
- else /* match or repeated match */
+ else // match or repeated match
{
crc32.update_buf( crc_, ptr_to_current_pos() - ahead, len );
mtf_reps( dis, reps );
bit = ( dis < num_rep_distances );
renc.encode_bit( bm_rep[state()], bit );
- if( bit ) /* repeated match */
+ if( bit ) // repeated match
{
bit = ( dis == 0 );
renc.encode_bit( bm_rep0[state()], !bit );
@@ -582,7 +582,7 @@ bool LZ_encoder::encode_member( const unsigned long long member_size )
state.set_rep();
}
}
- else /* match */
+ else // match
{
encode_pair( dis - num_rep_distances, len, pos_state );
if( get_slot( dis - num_rep_distances ) >= end_dis_model )
diff --git a/encoder.h b/encoder.h
index 81cc1e0..9579a85 100644
--- a/encoder.h
+++ b/encoder.h
@@ -76,7 +76,7 @@ public:
class LZ_encoder : public LZ_encoder_base
{
- struct Pair /* distance-length pair */
+ struct Pair // distance-length pair
{
int dis;
int len;
@@ -90,12 +90,12 @@ class LZ_encoder : public LZ_encoder_base
struct Trial
{
State state;
- int price; /* dual use var; cumulative price, match length */
- int dis; /* rep index or match distance. (-1 for literal) */
- int prev_index; /* index of prev trial in trials[] */
- int prev_index2; /* -2 trial is single step */
- /* -1 literal + rep0 */
- /* >= 0 ( rep or match ) + literal + rep0 */
+ int price; // dual use var; cumulative price, match length
+ int dis; // rep index or match distance. (-1 for literal)
+ int prev_index; // index of prev trial in trials[]
+ int prev_index2; // -2 trial is single step
+ // -1 literal + rep0
+ // >= 0 ( rep or match ) + literal + rep0
int reps[num_rep_distances];
void update( const int pr, const int distance, const int p_i )
@@ -145,7 +145,7 @@ class LZ_encoder : public LZ_encoder_base
int get_match_pairs( Pair * pairs = 0 );
void update_distance_prices();
- /* move-to-front dis in/into reps if( dis > 0 ) */
+ // move-to-front dis in/into reps if( dis > 0 )
static void mtf_reps( const int dis, int reps[num_rep_distances] )
{
if( dis >= num_rep_distances )
@@ -255,7 +255,7 @@ class LZ_encoder : public LZ_encoder_base
const State state );
enum { before = max_num_trials + 1,
- /* bytes to keep in buffer after pos */
+ // bytes to keep in buffer after pos
after_size = ( 2 * max_match_len ) + 1,
dict_factor = 2,
num_prev_positions3 = 1 << 16,
diff --git a/encoder_base.cc b/encoder_base.cc
index 982f12c..a8bbbd7 100644
--- a/encoder_base.cc
+++ b/encoder_base.cc
@@ -142,7 +142,7 @@ void Range_encoder::flush_data()
}
- /* End Of Stream mark => (dis == 0xFFFFFFFFU, len == min_match_len) */
+ // End Of Stream mark => (dis == 0xFFFFFFFFU, len == min_match_len)
void LZ_encoder_base::full_flush( const State state )
{
const int pos_state = data_position() & pos_state_mask;
diff --git a/encoder_base.h b/encoder_base.h
index 27c7a90..b032fae 100644
--- a/encoder_base.h
+++ b/encoder_base.h
@@ -60,14 +60,14 @@ public:
for( int i = 0; i < bit_model_total >> price_step_bits; ++i )
{
unsigned val = ( i * price_step ) + ( price_step / 2 );
- int bits = 0; /* base 2 logarithm of val */
+ int bits = 0; // base 2 logarithm of val
for( int j = 0; j < price_shift_bits; ++j )
{
val = val * val;
bits <<= 1;
while( val >= 1 << 16 ) { val >>= 1; ++bits; }
}
- bits += 15; /* remaining bits in val */
+ bits += 15; // remaining bits in val
data[i] = ( bit_model_total_bits << price_shift_bits ) - bits;
}
}
@@ -155,7 +155,7 @@ inline int price_matched( const Bit_model bm[], int symbol, int match_byte )
symbol <<= 1;
const int bit = symbol & 0x100;
price += price_bit( bm[match_bit+(symbol>>9)+mask], bit );
- mask &= ~(match_byte ^ symbol); /* if( match_bit != bit ) mask = 0; */
+ mask &= ~(match_byte ^ symbol); // if( match_bit != bit ) mask = 0;
}
while( symbol < 0x10000 );
return price;
@@ -172,21 +172,21 @@ class Matchfinder_base
protected:
unsigned long long partial_data_pos;
- uint8_t * buffer; /* input buffer */
- int32_t * prev_positions; /* 1 + last seen position of key. else 0 */
- int32_t * pos_array; /* may be tree or chain */
- const int before_size; /* bytes to keep in buffer before dictionary */
+ uint8_t * buffer; // input buffer
+ int32_t * prev_positions; // 1 + last seen position of key. else 0
+ int32_t * pos_array; // may be tree or chain
+ const int before_size; // bytes to keep in buffer before dictionary
int buffer_size;
- int dictionary_size; /* bytes to keep in buffer before pos */
- int pos; /* current pos in buffer */
- int cyclic_pos; /* cycles through [0, dictionary_size] */
- int stream_pos; /* first byte not yet read from file */
- int pos_limit; /* when reached, a new block must be read */
+ int dictionary_size; // bytes to keep in buffer before pos
+ int pos; // current pos in buffer
+ int cyclic_pos; // cycles through [0, dictionary_size]
+ int stream_pos; // first byte not yet read from file
+ int pos_limit; // when reached, a new block must be read
int key4_mask;
- int num_prev_positions; /* size of prev_positions */
+ int num_prev_positions; // size of prev_positions
int pos_array_size;
- const int infd; /* input file descriptor */
- bool at_stream_end; /* stream_pos shows real end of file */
+ const int infd; // input file descriptor
+ bool at_stream_end; // stream_pos shows real end of file
Matchfinder_base( const int before, const int dict_size,
const int after_size, const int dict_factor,
@@ -228,11 +228,11 @@ class Range_encoder
enum { buffer_size = 65536 };
uint64_t low;
unsigned long long partial_member_pos;
- uint8_t * const buffer; /* output buffer */
- int pos; /* current pos in buffer */
+ uint8_t * const buffer; // output buffer
+ int pos; // current pos in buffer
uint32_t range;
unsigned ff_count;
- const int outfd; /* output file descriptor */
+ const int outfd; // output file descriptor
uint8_t cache;
File_header header;
@@ -377,7 +377,7 @@ public:
symbol <<= 1;
const int bit = symbol & 0x100;
encode_bit( bm[match_bit+(symbol>>9)+mask], bit );
- mask &= ~(match_byte ^ symbol); /* if( match_bit != bit ) mask = 0; */
+ mask &= ~(match_byte ^ symbol); // if( match_bit != bit ) mask = 0;
}
while( symbol < 0x10000 );
}
@@ -406,7 +406,7 @@ class LZ_encoder_base : public Matchfinder_base
{
protected:
enum { max_marker_size = 16,
- num_rep_distances = 4 }; /* must be 4 */
+ num_rep_distances = 4 }; // must be 4
uint32_t crc_;
diff --git a/fast_encoder.cc b/fast_encoder.cc
index 1ecd169..90361e9 100644
--- a/fast_encoder.cc
+++ b/fast_encoder.cc
@@ -88,7 +88,7 @@ bool FLZ_encoder::encode_member( const unsigned long long member_size )
for( int i = 0; i < num_rep_distances; ++i ) reps[i] = 0;
if( data_position() != 0 || renc.member_position() != File_header::size )
- return false; /* can be called only once */
+ return false; // can be called only once
if( !data_finished() ) // encode first byte
{
@@ -179,7 +179,7 @@ bool FLZ_encoder::encode_member( const unsigned long long member_size )
}
}
- /* literal byte */
+ // literal byte
renc.encode_bit( bm_match[state()][pos_state], 0 );
if( state.is_char() )
encode_literal( prev_byte, cur_byte );
diff --git a/fast_encoder.h b/fast_encoder.h
index b26e388..36177df 100644
--- a/fast_encoder.h
+++ b/fast_encoder.h
@@ -17,7 +17,7 @@
class FLZ_encoder : public LZ_encoder_base
{
- int key4; /* key made from latest 4 bytes */
+ int key4; // key made from latest 4 bytes
void reset_key4()
{
@@ -45,7 +45,7 @@ class FLZ_encoder : public LZ_encoder_base
enum { before = 0,
dict_size = 65536,
- /* bytes to keep in buffer after pos */
+ // bytes to keep in buffer after pos
after_size = max_match_len,
dict_factor = 16,
num_prev_positions23 = 0,
diff --git a/lzip.h b/lzip.h
index 4a8bc98..9c16ef2 100644
--- a/lzip.h
+++ b/lzip.h
@@ -40,7 +40,7 @@ public:
enum {
min_dictionary_bits = 12,
- min_dictionary_size = 1 << min_dictionary_bits, /* >= modeled_distances */
+ min_dictionary_size = 1 << min_dictionary_bits, // >= modeled_distances
max_dictionary_bits = 29,
max_dictionary_size = 1 << max_dictionary_bits,
literal_context_bits = 3,
@@ -52,7 +52,7 @@ enum {
dis_slot_bits = 6,
start_dis_model = 4,
end_dis_model = 14,
- modeled_distances = 1 << (end_dis_model / 2), /* 128 */
+ modeled_distances = 1 << (end_dis_model / 2), // 128
dis_align_bits = 4,
dis_align_size = 1 << dis_align_bits,
@@ -64,8 +64,8 @@ enum {
len_high_symbols = 1 << len_high_bits,
max_len_symbols = len_low_symbols + len_mid_symbols + len_high_symbols,
- min_match_len = 2, /* must be 2 */
- max_match_len = min_match_len + max_len_symbols - 1, /* 273 */
+ min_match_len = 2, // must be 2
+ max_match_len = min_match_len + max_len_symbols - 1, // 273
min_match_len_limit = 5 };
inline int get_len_state( const int len )
@@ -185,9 +185,9 @@ const uint8_t magic_string[4] = { 0x4C, 0x5A, 0x49, 0x50 }; // "LZIP"
struct File_header
{
- uint8_t data[6]; /* 0-3 magic bytes */
- /* 4 version */
- /* 5 coded_dict_size */
+ uint8_t data[6]; // 0-3 magic bytes
+ // 4 version
+ // 5 coded_dict_size
enum { size = 6 };
void set_magic() { std::memcpy( data, magic_string, 4 ); data[4] = 1; }
@@ -227,9 +227,9 @@ struct File_header
struct File_trailer
{
- uint8_t data[20]; /* 0-3 CRC32 of the uncompressed data */
- /* 4-11 size of the uncompressed data */
- /* 12-19 member size including header and trailer */
+ uint8_t data[20]; // 0-3 CRC32 of the uncompressed data
+ // 4-11 size of the uncompressed data
+ // 12-19 member size including header and trailer
static int size( const int version = 1 )
{ return ( ( version >= 1 ) ? 20 : 12 ); }
diff --git a/main.cc b/main.cc
index 27cc156..ac07852 100644
--- a/main.cc
+++ b/main.cc
@@ -83,8 +83,8 @@ struct { const char * from; const char * to; } const known_extensions[] = {
struct Lzma_options
{
- int dictionary_size; /* 4 KiB .. 512 MiB */
- int match_len_limit; /* 5 .. 273 */
+ int dictionary_size; // 4 KiB .. 512 MiB
+ int match_len_limit; // 5 .. 273
};
enum Mode { m_compress, m_decompress, m_test };
@@ -108,7 +108,7 @@ void show_help()
" -c, --stdout send output to standard output\n"
" -d, --decompress decompress\n"
" -f, --force overwrite existing output files\n"
- " -F, --recompress force recompression of compressed files\n"
+ " -F, --recompress force re-compression of compressed files\n"
" -k, --keep keep (don't delete) input files\n"
" -m, --match-length=<bytes> set match length limit in bytes [36]\n"
" -o, --output=<file> if reading stdin, place the output into <file>\n"
@@ -265,7 +265,7 @@ int open_instream( const char * const name, struct stat * const in_statsp,
if( infd < 0 )
{
if( verbosity >= 0 )
- std::fprintf( stderr, "%s: Can't open input file '%s': %s.\n",
+ std::fprintf( stderr, "%s: Can't open input file '%s': %s\n",
program_name, name, std::strerror( errno ) );
}
else
@@ -282,7 +282,7 @@ int open_instream( const char * const name, struct stat * const in_statsp,
std::fprintf( stderr, "%s: Input file '%s' is not a regular file%s.\n",
program_name, name,
( can_read && !no_ofile ) ?
- " and '--stdout' was not specified" : "" );
+ ",\n and '--stdout' was not specified" : "" );
close( infd );
infd = -1;
}
@@ -314,7 +314,7 @@ void set_d_outname( const std::string & name, const int i )
}
output_filename = name; output_filename += ".out";
if( verbosity >= 1 )
- std::fprintf( stderr, "%s: Can't guess original name for '%s' -- using '%s'.\n",
+ std::fprintf( stderr, "%s: Can't guess original name for '%s' -- using '%s'\n",
program_name, name.c_str(), output_filename.c_str() );
}
@@ -331,7 +331,7 @@ bool open_outstream( const bool force )
std::fprintf( stderr, "%s: Output file '%s' already exists, skipping.\n",
program_name, output_filename.c_str() );
else
- std::fprintf( stderr, "%s: Can't create output file '%s': %s.\n",
+ std::fprintf( stderr, "%s: Can't create output file '%s': %s\n",
program_name, output_filename.c_str(), std::strerror( errno ) );
}
return ( outfd >= 0 );
@@ -371,14 +371,14 @@ void cleanup_and_fail( const int retval )
}
- /* Set permissions, owner and times. */
+ // Set permissions, owner and times.
void close_and_set_permissions( const struct stat * const in_statsp )
{
bool warning = false;
if( in_statsp )
{
const mode_t mode = in_statsp->st_mode;
- /* fchown will in many cases return with EPERM, which can be safely ignored. */
+ // fchown will in many cases return with EPERM, which can be safely ignored.
if( fchown( outfd, in_statsp->st_uid, in_statsp->st_gid ) == 0 )
{ if( fchmod( outfd, mode ) != 0 ) warning = true; }
else
@@ -440,7 +440,7 @@ int compress( const unsigned long long member_size,
}
unsigned long long in_size = 0, out_size = 0, partial_volume_size = 0;
- while( true ) /* encode one member per iteration */
+ while( true ) // encode one member per iteration
{
const unsigned long long size = ( volume_size > 0 ) ?
std::min( member_size, volume_size - partial_volume_size ) : member_size;
@@ -472,7 +472,7 @@ int compress( const unsigned long long member_size,
if( retval == 0 && verbosity >= 1 )
{
if( in_size == 0 || out_size == 0 )
- std::fprintf( stderr, " no data compressed.\n" );
+ std::fputs( " no data compressed.\n", stderr );
else
std::fprintf( stderr, "%6.3f:1, %6.3f bits/byte, "
"%5.2f%% saved, %llu in, %llu out.\n",
@@ -582,23 +582,20 @@ int decompress( const int infd, const Pretty_print & pp, const bool testing )
if( verbosity >= 0 && result <= 2 )
{
pp();
- if( result == 2 )
- std::fprintf( stderr, "File ends unexpectedly at pos %llu.\n",
- partial_file_pos );
- else
- std::fprintf( stderr, "Decoder error at pos %llu.\n",
- partial_file_pos );
+ std::fprintf( stderr, "%s at pos %llu\n", ( result == 2 ) ?
+ "File ends unexpectedly" : "Decoder error",
+ partial_file_pos );
}
retval = 2; break;
}
if( verbosity >= 2 )
- { std::fprintf( stderr, testing ? "ok\n" : "done\n" ); pp.reset(); }
+ { std::fputs( testing ? "ok\n" : "done\n", stderr ); pp.reset(); }
}
}
catch( std::bad_alloc ) { pp( "Not enough memory." ); retval = 1; }
catch( Error e ) { pp(); show_error( e.msg, errno ); retval = 1; }
if( verbosity == 1 && retval == 0 )
- std::fprintf( stderr, testing ? "ok\n" : "done\n" );
+ std::fputs( testing ? "ok\n" : "done\n", stderr );
return retval;
}
@@ -631,8 +628,8 @@ void show_error( const char * const msg, const int errcode, const bool help )
{
std::fprintf( stderr, "%s: %s", program_name, msg );
if( errcode > 0 )
- std::fprintf( stderr, ": %s.", std::strerror( errcode ) );
- std::fprintf( stderr, "\n" );
+ std::fprintf( stderr, ": %s", std::strerror( errcode ) );
+ std::fputc( '\n', stderr );
}
if( help )
std::fprintf( stderr, "Try '%s --help' for more information.\n",
@@ -654,14 +651,14 @@ void show_progress( const unsigned long long partial_size,
const Pretty_print * const p,
const unsigned long long cfile_size )
{
- static unsigned long long csize = 0; /* file_size / 100 */
+ static unsigned long long csize = 0; // file_size / 100
static unsigned long long psize = 0;
static const Matchfinder_base * mb = 0;
static const Pretty_print * pp = 0;
if( verbosity >= 2 )
{
- if( m ) /* initialize static vars */
+ if( m ) // initialize static vars
{ csize = cfile_size; psize = partial_size; mb = m; pp = p; }
if( mb && pp )
{
@@ -681,16 +678,16 @@ int main( const int argc, const char * const argv[] )
to the corresponding LZMA compression modes. */
const Lzma_options option_mapping[] =
{
- { 1 << 16, 16 }, /* -0 entry values not used */
- { 1 << 20, 5 }, /* -1 */
- { 3 << 19, 6 }, /* -2 */
- { 1 << 21, 8 }, /* -3 */
- { 3 << 20, 12 }, /* -4 */
- { 1 << 22, 20 }, /* -5 */
- { 1 << 23, 36 }, /* -6 */
- { 1 << 24, 68 }, /* -7 */
- { 3 << 23, 132 }, /* -8 */
- { 1 << 25, 273 } }; /* -9 */
+ { 1 << 16, 16 }, // -0 entry values not used
+ { 1 << 20, 5 }, // -1
+ { 3 << 19, 6 }, // -2
+ { 1 << 21, 8 }, // -3
+ { 3 << 20, 12 }, // -4
+ { 1 << 22, 20 }, // -5
+ { 1 << 23, 36 }, // -6
+ { 1 << 24, 68 }, // -7
+ { 3 << 23, 132 }, // -8
+ { 1 << 25, 273 } }; // -9
Lzma_options encoder_options = option_mapping[6]; // default = "-6"
const unsigned long long max_member_size = 0x0008000000000000ULL;
const unsigned long long max_volume_size = 0x4000000000000000ULL;
@@ -746,7 +743,7 @@ int main( const int argc, const char * const argv[] )
for( ; argind < parser.arguments(); ++argind )
{
const int code = parser.code( argind );
- if( !code ) break; /* no more options */
+ if( !code ) break; // no more options
const std::string & arg = parser.argument( argind );
switch( code )
{
@@ -777,7 +774,7 @@ int main( const int argc, const char * const argv[] )
case 'V': show_version(); return 0;
default : internal_error( "uncaught option." );
}
- } /* end process options */
+ } // end process options
#if defined(__MSVCRT__) || defined(__OS2__)
setmode( STDIN_FILENO, O_BINARY );
diff --git a/testsuite/check.sh b/testsuite/check.sh
index 1f9b9e4..ba77d0a 100755
--- a/testsuite/check.sh
+++ b/testsuite/check.sh
@@ -1,6 +1,6 @@
#! /bin/sh
# check script for Lzip - LZMA lossless data compressor
-# Copyright (C) 2008-2014 Antonio Diaz Diaz.
+# Copyright (C) 2008-2015 Antonio Diaz Diaz.
#
# This script is free software: you have unlimited permission
# to copy, distribute and modify it.
@@ -79,7 +79,6 @@ printf .
cat in in > in2 || framework_failure
"${LZIP}" -o copy2 < in2 || fail=1
"${LZIP}" -t copy2.lz || fail=1
-printf .
"${LZIP}" -cd copy2.lz > copy2 || fail=1
cmp in2 copy2 || fail=1
printf .