Merging upstream version 1.8.

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

3 files changed, 259 insertions, 115 deletions

diff --git a/doc/clzip.1 b/doc/clzip.1
index 32b3bde..5dbb695 100644
--- a/doc/clzip.1
+++ b/doc/clzip.1
@@ -1,5 +1,5 @@
 .\" DO NOT MODIFY THIS FILE!  It was generated by help2man 1.46.1.
-.TH CLZIP "1" "July 2015" "clzip 1.7" "User Commands"
+.TH CLZIP "1" "May 2016" "clzip 1.8" "User Commands"
 .SH NAME
 clzip \- reduces the size of files
 .SH SYNOPSIS
@@ -15,11 +15,14 @@ display this help and exit
 \fB\-V\fR, \fB\-\-version\fR
 output version information and exit
 .TP
+\fB\-a\fR, \fB\-\-trailing\-error\fR
+exit with error status if trailing data
+.TP
 \fB\-b\fR, \fB\-\-member\-size=\fR<bytes>
 set member size limit in bytes
 .TP
 \fB\-c\fR, \fB\-\-stdout\fR
-send output to standard output
+write to standard output, keep input files
 .TP
 \fB\-d\fR, \fB\-\-decompress\fR
 decompress
@@ -37,7 +40,7 @@ keep (don't delete) input files
 set match length limit in bytes [36]
 .TP
 \fB\-o\fR, \fB\-\-output=\fR<file>
-if reading stdin, place the output into <file>
+if reading standard input, write to <file>
 .TP
 \fB\-q\fR, \fB\-\-quiet\fR
 suppress all messages
@@ -63,13 +66,16 @@ alias for \fB\-0\fR
 \fB\-\-best\fR
 alias for \fB\-9\fR
 .PP
-If no file names are given, clzip compresses or decompresses
-from standard input to standard output.
+If no file names are given, or if a file is '\-', clzip compresses or
+decompresses from standard input to standard output.
 Numbers may be followed by a multiplier: k = kB = 10^3 = 1000,
 Ki = KiB = 2^10 = 1024, M = 10^6, Mi = 2^20, G = 10^9, Gi = 2^30, etc...
+Dictionary sizes 12 to 29 are interpreted as powers of two, meaning 2^12
+to 2^29 bytes.
+.PP
 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 \fB\-\-match\-length\fR and \fB\-\-dictionary\-size\fR
+etc, you may need to use the \fB\-\-dictionary\-size\fR and \fB\-\-match\-length\fR
 options directly to achieve optimal performance.
 .PP
 Exit status: 0 for a normal exit, 1 for environmental problems (file
@@ -81,7 +87,7 @@ Report bugs to lzip\-bug@nongnu.org
 .br
 Clzip home page: http://www.nongnu.org/lzip/clzip.html
 .SH COPYRIGHT
-Copyright \(co 2015 Antonio Diaz Diaz.
+Copyright \(co 2016 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.
diff --git a/doc/clzip.info b/doc/clzip.info
index 786d8c1..c590473 100644
--- a/doc/clzip.info
+++ b/doc/clzip.info
@@ -11,7 +11,7 @@ File: clzip.info,  Node: Top,  Next: Introduction,  Up: (dir)
 Clzip Manual
 ************
 
-This manual is for Clzip (version 1.7, 7 July 2015).
+This manual is for Clzip (version 1.8, 13 May 2016).
 
 * Menu:
 
@@ -19,12 +19,13 @@ This manual is for Clzip (version 1.7, 7 July 2015).
 * Invoking clzip::         Command line interface
 * File format::            Detailed format of the compressed file
 * Algorithm::              How clzip compresses the data
+* Trailing data::          Extra data appended to the file
 * Examples::               A small tutorial with examples
 * Problems::               Reporting bugs
 * Concept index::          Index of concepts
 
 
-   Copyright (C) 2010-2015 Antonio Diaz Diaz.
+   Copyright (C) 2010-2016 Antonio Diaz Diaz.
 
    This manual is free documentation: you have unlimited permission to
 copy, distribute and modify it.
@@ -53,7 +54,7 @@ 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.  *note Data safety:
+     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
@@ -73,15 +74,14 @@ corrupt byte near the beginning is a thing of the past.
 
    The member trailer stores the 32-bit CRC of the original data, the
 size of the original data and the size of the member. These values,
-together with the value remaining in the range decoder and the
-end-of-stream marker, provide a 4 factor integrity checking which
-guarantees that the decompressed version of the data is identical to
-the original. This guards against corruption of the compressed data,
-and against undetected bugs in clzip (hopefully very unlikely). The
-chances of data corruption going undetected are microscopic. Be aware,
-though, that the check occurs upon decompression, so it can only tell
-you that something is wrong. It can't help you recover the original
-uncompressed data.
+together with the end-of-stream marker, provide a 3 factor integrity
+checking which guarantees that the decompressed version of the data is
+identical to the original. This guards against corruption of the
+compressed data, and against undetected bugs in clzip (hopefully very
+unlikely). The chances of data corruption going undetected are
+microscopic. Be aware, though, that the check occurs upon
+decompression, so it can only tell you that something is wrong. It
+can't help you recover the original uncompressed data.
 
    Clzip uses the same well-defined exit status values used by lzip and
 bzip2, which makes it safer than compressors returning ambiguous warning
@@ -128,14 +128,14 @@ two or more compressed files. The result is the concatenation of the
 corresponding uncompressed files. Integrity testing of concatenated
 compressed files is also supported.
 
-   Clzip can produce multi-member files and safely recover, with
+   Clzip can produce multimember files and safely recover, with
 lziprecover, the undamaged members in case of file damage. Clzip 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.
 
    Clzip is able to compress and decompress streams of unlimited size by
-automatically creating multi-member output. The members so created are
+automatically creating multimember output. The members so created are
 large, about 2 PiB each.
 
 
@@ -148,6 +148,10 @@ The format for running clzip is:
 
      clzip [OPTIONS] [FILES]
 
+'-' used as a FILE argument means standard input. It can be mixed with
+other FILES and is read just once, the first time it appears in the
+command line.
+
    Clzip supports the following options:
 
 '-h'
@@ -158,6 +162,13 @@ The format for running clzip is:
 '--version'
      Print the version number of clzip on the standard output and exit.
 
+'-a'
+'--trailing-error'
+     Exit with error status 2 if any remaining input is detected after
+     decompressing the last member. Such remaining input is usually
+     trailing garbage that can be safely ignored. *Note
+     concat-example::.
+
 '-b BYTES'
 '--member-size=BYTES'
      Set the member size limit to BYTES. A small member size may
@@ -166,14 +177,19 @@ The format for running clzip is:
 
 '-c'
 '--stdout'
-     Compress or decompress to standard output. Needed when reading
-     from a named pipe (fifo) or from a device. Use it to recover as
-     much of the uncompressed data as possible when decompressing a
-     corrupt file.
+     Compress or decompress to standard output; keep input files
+     unchanged.  If compressing several files, each file is compressed
+     independently.  This option is needed when reading from a named
+     pipe (fifo) or from a device. Use it also to recover as much of
+     the uncompressed data as possible when decompressing a corrupt
+     file.
 
 '-d'
 '--decompress'
-     Decompress.
+     Decompress the specified file(s). If a file does not exist or
+     can't be opened, clzip continues decompressing the rest of the
+     files. If a file fails to decompress, clzip exits immediately
+     without decompressing the rest of the files.
 
 '-f'
 '--force'
@@ -211,12 +227,13 @@ The format for running clzip is:
 
 '-s BYTES'
 '--dictionary-size=BYTES'
-     Set the dictionary size limit in bytes. Valid values range from 4
-     KiB to 512 MiB. Clzip will use the smallest possible dictionary
-     size for each file without exceeding this limit. 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 / 16) to it.
+     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.
 
      For maximum compression you should use a dictionary size limit as
      large as possible, but keep in mind that the decompression memory
@@ -228,16 +245,17 @@ The format for running clzip is:
      Split the compressed output into several volume files with names
      'original_name00001.lz', 'original_name00002.lz', etc, and set the
      volume size limit to BYTES. Each volume is a complete, maybe
-     multi-member, lzip file. A small volume size may degrade
-     compression ratio, so use it only when needed. Valid values range
-     from 100 kB to 4 EiB.
+     multimember, lzip file. A small volume size may degrade compression
+     ratio, so use it only when needed. Valid values range from 100 kB
+     to 4 EiB.
 
 '-t'
 '--test'
      Check integrity of the specified file(s), but don't decompress
      them.  This really performs a trial decompression and throws away
      the result.  Use it together with '-v' to see information about
-     the file.
+     the file(s). If a file fails the test, clzip continues checking
+     the rest of the files.
 
 '-v'
 '--verbose'
@@ -246,18 +264,19 @@ The format for running clzip is:
      processed. A second '-v' shows the progress of compression.
      When decompressing or testing, further -v's (up to 4) increase the
      verbosity level, showing status, compression ratio, dictionary
-     size, and trailer contents (CRC, data size, member size).
+     size, trailer contents (CRC, data size, member size), and up to 6
+     bytes of trailing data (if any).
 
 '-0 .. -9'
      Set the compression parameters (dictionary size and match length
-     limit) as shown in the table below. Note that '-9' can be much
-     slower than '-0'. These options have no effect when decompressing.
+     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.
 
      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 '--match-length' and
-     '--dictionary-size' options directly to achieve optimal
-     performance.
+     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
@@ -327,12 +346,12 @@ additional information before, between, or after them.
 
    Each member has the following structure:
 +--+--+--+--+----+----+=============+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| ID string | VN | DS | Lzma stream | CRC32 |   Data size   |  Member size  |
+| ID string | VN | DS | LZMA stream | CRC32 |   Data size   |  Member size  |
 +--+--+--+--+----+----+=============+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 
    All multibyte values are stored in little endian order.
 
-'ID string'
+'ID string (the "magic" bytes)'
      A four byte string, identifying the lzip format, with the value
      "LZIP" (0x4C, 0x5A, 0x49, 0x50).
 
@@ -350,8 +369,8 @@ additional information before, between, or after them.
      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.
 
-'Lzma stream'
-     The lzma stream, finished by an end of stream marker. Uses default
+'LZMA stream'
+     The LZMA stream, finished by an end of stream marker. Uses default
      values for encoder properties.  *Note Stream format: (lzip)Stream
      format, for a complete description.
 
@@ -365,11 +384,11 @@ additional information before, between, or after them.
      Total size of the member, including header and trailer. This field
      acts as a distributed index, allows the verification of stream
      integrity, and facilitates safe recovery of undamaged members from
-     multi-member files.
+     multimember files.
 
 
 
-File: clzip.info,  Node: Algorithm,  Next: Examples,  Prev: File format,  Up: Top
+File: clzip.info,  Node: Algorithm,  Next: Trailing data,  Prev: File format,  Up: Top
 
 4 Algorithm
 ***********
@@ -435,15 +454,48 @@ range encoding), Igor Pavlov (for putting all the above together in
 LZMA), and Julian Seward (for bzip2's CLI).
 
 
-File: clzip.info,  Node: Examples,  Next: Problems,  Prev: Algorithm,  Up: Top
+File: clzip.info,  Node: Trailing data,  Next: Examples,  Prev: Algorithm,  Up: Top
+
+5 Extra data appended to the file
+*********************************
+
+Sometimes extra data is found appended to a lzip file after the last
+member. Such trailing data may be:
+
+   * Padding added to make the file size a multiple of some block size,
+     for example when writing to a tape.
+
+   * Garbage added by some not totally successful copy operation.
+
+   * Useful data added by the user; a cryptographically secure hash, a
+     description of file contents, etc.
+
+   * Malicious data added to the file in order to make its total size
+     and hash value (for a chosen hash) coincide with those of another
+     file.
 
-5 A small tutorial with examples
+   * In very rare cases, trailing data could be the corrupt header of
+     another member. In multimember or concatenated files the
+     probability of corruption happening in the magic bytes is 5 times
+     smaller than the probability of getting a false positive caused by
+     the corruption of the integrity information itself. Therefore it
+     can be considered to be below the noise level.
+
+   Trailing data can be safely ignored in most cases. In some cases,
+like that of user-added data, it is expected to be ignored. In those
+cases where a file containing trailing data must be rejected, the option
+'--trailing-error' can be used. *Note --trailing-error::.
+
+
+File: clzip.info,  Node: Examples,  Next: Problems,  Prev: Trailing data,  Up: Top
+
+6 A small tutorial with examples
 ********************************
 
 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
-'--keep' option to clzip and do not remove the original file until you
+'--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 -'.
 
@@ -454,8 +506,8 @@ and show the compression ratio.
      clzip -v file
 
 
-Example 2: Like example 1 but the created 'file.lz' is multi-member
-with a member size of 1 MiB. The compression ratio is not shown.
+Example 2: Like example 1 but the created 'file.lz' is multimember with
+a member size of 1 MiB. The compression ratio is not shown.
 
      clzip -b 1MiB file
 
@@ -472,37 +524,46 @@ show status.
      clzip -tv file.lz
 
 
-Example 5: Compress a whole floppy in /dev/fd0 and send the output to
+Example 5: Compress a whole device in /dev/sdc and send the output to
 'file.lz'.
 
-     clzip -c /dev/fd0 > file.lz
+     clzip -c /dev/sdc > file.lz
+
+
+Example 6: The right way of concatenating compressed files.  *Note
+Trailing data::.
+
+     Don't do this
+       cat file1.lz file2.lz file3.lz | clzip -d
+     Do this instead
+       clzip -cd file1.lz file2.lz file3.lz
 
 
-Example 6: Decompress 'file.lz' partially until 10 KiB of decompressed
+Example 7: Decompress 'file.lz' partially until 10 KiB of decompressed
 data are produced.
 
      clzip -cd file.lz | dd bs=1024 count=10
 
 
-Example 7: Decompress 'file.lz' partially from decompressed byte 10000
+Example 8: Decompress 'file.lz' partially from decompressed byte 10000
 to decompressed byte 15000 (5000 bytes are produced).
 
      clzip -cd file.lz | dd bs=1000 skip=10 count=5
 
 
-Example 8: Create a multivolume compressed tar archive with a volume
+Example 9: Create a multivolume compressed tar archive with a volume
 size of 1440 KiB.
 
      tar -c some_directory | clzip -S 1440KiB -o volume_name
 
 
-Example 9: Extract a multivolume compressed tar archive.
+Example 10: Extract a multivolume compressed tar archive.
 
      clzip -cd volume_name*.lz | tar -xf -
 
 
-Example 10: Create a multivolume compressed backup of a large database
-file with a volume size of 650 MB, where each volume is a multi-member
+Example 11: Create a multivolume compressed backup of a large database
+file with a volume size of 650 MB, where each volume is a multimember
 file with a member size of 32 MiB.
 
      clzip -b 32MiB -S 650MB big_db
@@ -510,7 +571,7 @@ file with a member size of 32 MiB.
 
 File: clzip.info,  Node: Problems,  Next: Concept index,  Prev: Examples,  Up: Top
 
-6 Reporting bugs
+7 Reporting bugs
 ****************
 
 There are probably bugs in clzip. There are certainly errors and
@@ -539,6 +600,7 @@ Concept index
 * introduction:                          Introduction.          (line 6)
 * invoking:                              Invoking clzip.        (line 6)
 * options:                               Invoking clzip.        (line 6)
+* trailing data:                         Trailing data.         (line 6)
 * usage:                                 Invoking clzip.        (line 6)
 * version:                               Invoking clzip.        (line 6)
 
@@ -546,13 +608,16 @@ Concept index
 
 Tag Table:
 Node: Top210
-Node: Introduction893
-Node: Invoking clzip6152
-Node: File format11705
-Node: Algorithm14108
-Node: Examples16933
-Node: Problems18900
-Node: Concept index19426
+Node: Introduction952
+Node: Invoking clzip6164
+Ref: --trailing-error6730
+Node: File format12728
+Node: Algorithm15150
+Node: Trailing data17980
+Node: Examples19355
+Ref: concat-example20537
+Node: Problems21544
+Node: Concept index22070
 
 End Tag Table
 
diff --git a/doc/clzip.texi b/doc/clzip.texi
index e2ca889..331d4eb 100644
--- a/doc/clzip.texi
+++ b/doc/clzip.texi
@@ -6,8 +6,8 @@
 @finalout
 @c %**end of header
 
-@set UPDATED 7 July 2015
-@set VERSION 1.7
+@set UPDATED 13 May 2016
+@set VERSION 1.8
 
 @dircategory Data Compression
 @direntry
@@ -39,13 +39,14 @@ This manual is for Clzip (version @value{VERSION}, @value{UPDATED}).
 * Invoking clzip::         Command line interface
 * File format::            Detailed format of the compressed file
 * Algorithm::              How clzip compresses the data
+* Trailing data::          Extra data appended to the file
 * Examples::               A small tutorial with examples
 * Problems::               Reporting bugs
 * Concept index::          Index of concepts
 @end menu
 
 @sp 1
-Copyright @copyright{} 2010-2015 Antonio Diaz Diaz.
+Copyright @copyright{} 2010-2016 Antonio Diaz Diaz.
 
 This manual is free documentation: you have unlimited permission
 to copy, distribute and modify it.
@@ -78,7 +79,7 @@ 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}.
+@xref{Data safety,,,lziprecover}.
 @end ifnothtml
 
 @item
@@ -101,14 +102,14 @@ corrupt byte near the beginning is a thing of the past.
 
 The member trailer stores the 32-bit CRC of the original data, the size
 of the original data and the size of the member. These values, together
-with the value remaining in the range decoder and the end-of-stream
-marker, provide a 4 factor integrity checking which guarantees that the
-decompressed version of the data is identical to the original. This
-guards against corruption of the compressed data, and against undetected
-bugs in clzip (hopefully very unlikely). The chances of data corruption
-going undetected are microscopic. Be aware, though, that the check
-occurs upon decompression, so it can only tell you that something is
-wrong. It can't help you recover the original uncompressed data.
+with the end-of-stream marker, provide a 3 factor integrity checking
+which guarantees that the decompressed version of the data is identical
+to the original. This guards against corruption of the compressed data,
+and against undetected bugs in clzip (hopefully very unlikely). The
+chances of data corruption going undetected are microscopic. Be aware,
+though, that the check occurs upon decompression, so it can only tell
+you that something is wrong. It can't help you recover the original
+uncompressed data.
 
 Clzip uses the same well-defined exit status values used by lzip and
 bzip2, which makes it safer than compressors returning ambiguous warning
@@ -157,14 +158,14 @@ or more compressed files. The result is the concatenation of the
 corresponding uncompressed files. Integrity testing of concatenated
 compressed files is also supported.
 
-Clzip can produce multi-member files and safely recover, with
+Clzip can produce multimember files and safely recover, with
 lziprecover, the undamaged members in case of file damage. Clzip 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.
 
 Clzip is able to compress and decompress streams of unlimited size by
-automatically creating multi-member output. The members so created are
+automatically creating multimember output. The members so created are
 large, about 2 PiB each.
 
 
@@ -181,6 +182,11 @@ The format for running clzip is:
 clzip [@var{options}] [@var{files}]
 @end example
 
+@noindent
+@samp{-} used as a @var{file} argument means standard input. It can be
+mixed with other @var{files} and is read just once, the first time it
+appears in the command line.
+
 Clzip supports the following options:
 
 @table @code
@@ -192,6 +198,13 @@ Print an informative help message describing the options and exit.
 @itemx --version
 Print the version number of clzip on the standard output and exit.
 
+@anchor{--trailing-error}
+@item -a
+@itemx --trailing-error
+Exit with error status 2 if any remaining input is detected after
+decompressing the last member. Such remaining input is usually trailing
+garbage that can be safely ignored. @xref{concat-example}.
+
 @item -b @var{bytes}
 @itemx --member-size=@var{bytes}
 Set the member size limit to @var{bytes}. A small member size may
@@ -200,13 +213,18 @@ range from 100 kB to 2 PiB. Defaults to 2 PiB.
 
 @item -c
 @itemx --stdout
-Compress or decompress to standard output. Needed when reading from a
-named pipe (fifo) or from a device. Use it to recover as much of the
-uncompressed data as possible when decompressing a corrupt file.
+Compress or decompress to standard output; keep input files unchanged.
+If compressing several files, each file is compressed independently.
+This option is needed when reading from a named pipe (fifo) or from a
+device. Use it also to recover as much of the uncompressed data as
+possible when decompressing a corrupt file.
 
 @item -d
 @itemx --decompress
-Decompress.
+Decompress the specified file(s). If a file does not exist or can't be
+opened, clzip continues decompressing the rest of the files. If a file
+fails to decompress, clzip exits immediately without decompressing the
+rest of the files.
 
 @item -f
 @itemx --force
@@ -242,11 +260,13 @@ Quiet operation. Suppress all messages.
 
 @item -s @var{bytes}
 @itemx --dictionary-size=@var{bytes}
-Set the dictionary size limit in bytes. Valid values range from 4 KiB to
-512 MiB. Clzip will use the smallest possible dictionary size for each
-file without exceeding this limit. 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 (@var{bytes} / 16) to it.
+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
+@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
@@ -257,7 +277,7 @@ is affected at compression time by the choice of dictionary size limit.
 Split the compressed output into several volume files with names
 @samp{original_name00001.lz}, @samp{original_name00002.lz}, etc, and set
 the volume size limit to @var{bytes}. Each volume is a complete, maybe
-multi-member, lzip file. A small volume size may degrade compression
+multimember, lzip file. A small volume size may degrade compression
 ratio, so use it only when needed. Valid values range from 100 kB to 4
 EiB.
 
@@ -265,7 +285,8 @@ EiB.
 @itemx --test
 Check integrity of the specified file(s), but don't decompress them.
 This really performs a trial decompression and throws away the result.
-Use it together with @samp{-v} to see information about the file.
+Use it together with @samp{-v} to see information about the file(s). If
+a file fails the test, clzip continues checking the rest of the files.
 
 @item -v
 @itemx --verbose
@@ -274,18 +295,19 @@ When compressing, show the compression ratio for each file processed. A
 second @samp{-v} shows the progress of compression.@*
 When decompressing or testing, further -v's (up to 4) increase the
 verbosity level, showing status, compression ratio, dictionary size,
-and trailer contents (CRC, data size, member size).
+trailer contents (CRC, data size, member size), and up to 6 bytes of
+trailing data (if any).
 
 @item -0 .. -9
 Set the compression parameters (dictionary size and match length limit)
-as shown in the table below. Note that @samp{-9} can be much slower than
-@samp{-0}. These options have no effect when decompressing.
+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.
 
 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{--match-length} and
-@samp{--dictionary-size} options directly to achieve optimal
-performance.
+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
@@ -364,14 +386,14 @@ additional information before, between, or after them.
 Each member has the following structure:
 @verbatim
 +--+--+--+--+----+----+=============+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| ID string | VN | DS | Lzma stream | CRC32 |   Data size   |  Member size  |
+| ID string | VN | DS | LZMA stream | CRC32 |   Data size   |  Member size  |
 +--+--+--+--+----+----+=============+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 @end verbatim
 
 All multibyte values are stored in little endian order.
 
 @table @samp
-@item ID string
+@item ID string (the "magic" bytes)
 A four byte string, identifying the lzip format, with the value "LZIP"
 (0x4C, 0x5A, 0x49, 0x50).
 
@@ -388,8 +410,8 @@ 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.
 
-@item Lzma stream
-The lzma stream, finished by an end of stream marker. Uses default
+@item LZMA stream
+The LZMA stream, finished by an end of stream marker. Uses default
 values for encoder properties.
 @ifnothtml
 @xref{Stream format,,,lzip},
@@ -409,7 +431,7 @@ Size of the uncompressed original data.
 @item Member size (8 bytes)
 Total size of the member, including header and trailer. This field acts
 as a distributed index, allows the verification of stream integrity, and
-facilitates safe recovery of undamaged members from multi-member files.
+facilitates safe recovery of undamaged members from multimember files.
 
 @end table
 
@@ -480,6 +502,44 @@ range encoding), Igor Pavlov (for putting all the above together in
 LZMA), and Julian Seward (for bzip2's CLI).
 
 
+@node Trailing data
+@chapter Extra data appended to the file
+@cindex trailing data
+
+Sometimes extra data is found appended to a lzip file after the last
+member. Such trailing data may be:
+
+@itemize @bullet
+@item
+Padding added to make the file size a multiple of some block size, for
+example when writing to a tape.
+
+@item
+Garbage added by some not totally successful copy operation.
+
+@item
+Useful data added by the user; a cryptographically secure hash, a
+description of file contents, etc.
+
+@item
+Malicious data added to the file in order to make its total size and
+hash value (for a chosen hash) coincide with those of another file.
+
+@item
+In very rare cases, trailing data could be the corrupt header of another
+member. In multimember or concatenated files the probability of
+corruption happening in the magic bytes is 5 times smaller than the
+probability of getting a false positive caused by the corruption of the
+integrity information itself. Therefore it can be considered to be below
+the noise level.
+@end itemize
+
+Trailing data can be safely ignored in most cases. In some cases, like
+that of user-added data, it is expected to be ignored. In those cases
+where a file containing trailing data must be rejected, the option
+@samp{--trailing-error} can be used. @xref{--trailing-error}.
+
+
 @node Examples
 @chapter A small tutorial with examples
 @cindex examples
@@ -487,7 +547,7 @@ LZMA), and Julian Seward (for bzip2's CLI).
 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 do not remove the original file until
+@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 -}}.
 
@@ -502,7 +562,7 @@ clzip -v file
 
 @sp 1
 @noindent
-Example 2: Like example 1 but the created @samp{file.lz} is multi-member
+Example 2: Like example 1 but the created @samp{file.lz} is multimember
 with a member size of 1 MiB. The compression ratio is not shown.
 
 @example
@@ -530,16 +590,29 @@ clzip -tv file.lz
 
 @sp 1
 @noindent
-Example 5: Compress a whole floppy in /dev/fd0 and send the output to
+Example 5: Compress a whole device in /dev/sdc and send the output to
 @samp{file.lz}.
 
 @example
-clzip -c /dev/fd0 > file.lz
+clzip -c /dev/sdc > file.lz
+@end example
+
+@sp 1
+@anchor{concat-example}
+@noindent
+Example 6: The right way of concatenating compressed files.
+@xref{Trailing data}.
+
+@example
+Don't do this
+  cat file1.lz file2.lz file3.lz | clzip -d
+Do this instead
+  clzip -cd file1.lz file2.lz file3.lz
 @end example
 
 @sp 1
 @noindent
-Example 6: Decompress @samp{file.lz} partially until 10 KiB of
+Example 7: Decompress @samp{file.lz} partially until 10 KiB of
 decompressed data are produced.
 
 @example
@@ -548,7 +621,7 @@ clzip -cd file.lz | dd bs=1024 count=10
 
 @sp 1
 @noindent
-Example 7: Decompress @samp{file.lz} partially from decompressed byte
+Example 8: Decompress @samp{file.lz} partially from decompressed byte
 10000 to decompressed byte 15000 (5000 bytes are produced).
 
 @example
@@ -557,7 +630,7 @@ clzip -cd file.lz | dd bs=1000 skip=10 count=5
 
 @sp 1
 @noindent
-Example 8: Create a multivolume compressed tar archive with a volume
+Example 9: Create a multivolume compressed tar archive with a volume
 size of 1440 KiB.
 
 @example
@@ -566,7 +639,7 @@ tar -c some_directory | clzip -S 1440KiB -o volume_name
 
 @sp 1
 @noindent
-Example 9: Extract a multivolume compressed tar archive.
+Example 10: Extract a multivolume compressed tar archive.
 
 @example
 clzip -cd volume_name*.lz | tar -xf -
@@ -574,8 +647,8 @@ clzip -cd volume_name*.lz | tar -xf -
 
 @sp 1
 @noindent
-Example 10: Create a multivolume compressed backup of a large database
-file with a volume size of 650 MB, where each volume is a multi-member
+Example 11: Create a multivolume compressed backup of a large database
+file with a volume size of 650 MB, where each volume is a multimember
 file with a member size of 32 MiB.
 
 @example