Adding upstream version 1.15~pre1.upstream/1.15_pre1

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

15 files changed, 1443 insertions, 131 deletions

diff --git a/ChangeLog b/ChangeLog
index 296049a..62ceec2 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2013-03-21  Antonio Diaz Diaz  <ant_diaz@teleline.es>
+
+	* Version 1.15-pre1 released.
+	* Decompression time has been reduced by 1%.
+	* main.cc (show_header): Show header version if verbosity >= 4.
+	* Ignore option '-n, --threads' for compatibility with plzip.
+	* Added chapter 'Stream Format' and appendix 'Reference source code'
+	  to the manual.
+
 2013-02-17  Antonio Diaz Diaz  <ant_diaz@teleline.es>
 
 	* Version 1.14 released.
diff --git a/NEWS b/NEWS
index 0bf236a..b39fd81 100644
--- a/NEWS
+++ b/NEWS
@@ -1,11 +1,11 @@
-Changes in version 1.14:
+Changes in version 1.15:
 
-Multi-step trials have been implemented.
+Decompression time has been reduced by 1%.
 
-Compression ratio has been slightly increased.
+File version is now shown only if verbosity >= 4.
 
-Compression time has been reduced by 5%.
+Option "-n, --threads" is now accepted and ignored for compatibility
+with plzip.
 
-Decompression time has been reduced by 12%.
-
-The target "install-bin" has been added to the Makefile.
+The chapter "Stream Format" and the appendix "Reference source code"
+have been added to the manual.
diff --git a/arg_parser.cc b/arg_parser.cc
index 13bcbcb..a28d2ba 100644
--- a/arg_parser.cc
+++ b/arg_parser.cc
@@ -1,5 +1,5 @@
 /*  Arg_parser - POSIX/GNU command line argument parser. (C++ version)
-    Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012
+    Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013
     Antonio Diaz Diaz.
 
     This library is free software: you can redistribute it and/or modify
@@ -44,7 +44,7 @@ bool Arg_parser::parse_long_option( const char * const opt, const char * const a
 
   // Test all long options for either exact match or abbreviated matches.
   for( int i = 0; options[i].code != 0; ++i )
-    if( options[i].name && !std::strncmp( options[i].name, &opt[2], len ) )
+    if( options[i].name && std::strncmp( options[i].name, &opt[2], len ) == 0 )
       {
       if( std::strlen( options[i].name ) == len )	// Exact match found
         { index = i; exact = true; break; }
diff --git a/arg_parser.h b/arg_parser.h
index 4fbd1af..5248cb1 100644
--- a/arg_parser.h
+++ b/arg_parser.h
@@ -1,5 +1,5 @@
 /*  Arg_parser - POSIX/GNU command line argument parser. (C++ version)
-    Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012
+    Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013
     Antonio Diaz Diaz.
 
     This library is free software: you can redistribute it and/or modify
diff --git a/configure b/configure
index b30d534..91ff0e4 100755
--- a/configure
+++ b/configure
@@ -8,9 +8,9 @@
 args=
 no_create=
 pkgname=lzip
-pkgversion=1.14
+pkgversion=1.15-pre1
 progname=lzip
-srctrigger=lzip.h
+srctrigger=doc/lzip.texinfo
 
 # clear some things potentially inherited from environment.
 LC_ALL=C
diff --git a/decoder.cc b/decoder.cc
index 537143f..1d4774f 100644
--- a/decoder.cc
+++ b/decoder.cc
@@ -122,10 +122,10 @@ bool LZ_decoder::verify_trailer( const Pretty_print & pp ) const
   File_trailer trailer;
   const int trailer_size = File_trailer::size( member_version );
   const unsigned long long member_size =
-    range_decoder.member_position() + trailer_size;
+    rdec.member_position() + trailer_size;
   bool error = false;
 
-  int size = range_decoder.read_data( trailer.data, trailer_size );
+  int size = rdec.read_data( trailer.data, trailer_size );
   if( size < trailer_size )
     {
     error = true;
@@ -140,7 +140,7 @@ bool LZ_decoder::verify_trailer( const Pretty_print & pp ) const
 
   if( member_version == 0 ) trailer.member_size( member_size );
 
-  if( !range_decoder.code_is_zero() )
+  if( !rdec.code_is_zero() )
     {
     error = true;
     pp( "Range decoder final code is not zero" );
@@ -201,82 +201,79 @@ int LZ_decoder::decode_member( const Pretty_print & pp )
   Bit_model bm_dis_slot[max_dis_states][1<<dis_slot_bits];
   Bit_model bm_dis[modeled_distances-end_dis_model];
   Bit_model bm_align[dis_align_size];
-  Len_decoder len_decoder;
-  Len_decoder rep_match_len_decoder;
+  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 rep3 = 0;
-
   State state;
-  range_decoder.load();
 
-  while( !range_decoder.finished() )
+  rdec.load();
+  while( !rdec.finished() )
     {
     const int pos_state = data_position() & pos_state_mask;
-    if( range_decoder.decode_bit( bm_match[state()][pos_state] ) == 0 )
+    if( rdec.decode_bit( bm_match[state()][pos_state] ) == 0 )
       {
       const uint8_t prev_byte = get_prev_byte();
       if( state.is_char() )
-        put_byte( range_decoder.decode_tree( bm_literal[get_lit_state(prev_byte)], 8 ) );
+        put_byte( rdec.decode_tree( bm_literal[get_lit_state(prev_byte)], 8 ) );
       else
-        put_byte( range_decoder.decode_matched( bm_literal[get_lit_state(prev_byte)],
-                                                get_byte( rep0 ) ) );
+        put_byte( rdec.decode_matched( bm_literal[get_lit_state(prev_byte)],
+                                       get_byte( rep0 ) ) );
       state.set_char();
       }
     else
       {
       int len;
-      if( range_decoder.decode_bit( bm_rep[state()] ) == 1 )
+      if( rdec.decode_bit( bm_rep[state()] ) == 1 )
         {
-        len = 0;
-        if( range_decoder.decode_bit( bm_rep0[state()] ) == 1 )
+        if( rdec.decode_bit( bm_rep0[state()] ) == 0 )
+          {
+          if( rdec.decode_bit( bm_len[state()][pos_state] ) == 0 )
+            { state.set_short_rep(); put_byte( get_byte( rep0 ) ); continue; }
+          }
+        else
           {
           unsigned distance;
-          if( range_decoder.decode_bit( bm_rep1[state()] ) == 0 )
+          if( rdec.decode_bit( bm_rep1[state()] ) == 0 )
             distance = rep1;
           else
             {
-            if( range_decoder.decode_bit( bm_rep2[state()] ) == 0 )
+            if( rdec.decode_bit( bm_rep2[state()] ) == 0 )
               distance = rep2;
-            else { distance = rep3; rep3 = rep2; }
+            else
+              { distance = rep3; rep3 = rep2; }
             rep2 = rep1;
             }
           rep1 = rep0;
           rep0 = distance;
           }
-        else
-          {
-          if( range_decoder.decode_bit( bm_len[state()][pos_state] ) == 0 )
-            { state.set_short_rep(); len = 1; }
-          }
-        if( len == 0 )
-          {
-          state.set_rep();
-          len = min_match_len + rep_match_len_decoder.decode( range_decoder, pos_state );
-          }
+        len = min_match_len + rdec.decode_len( rep_len_model, pos_state );
+        state.set_rep();
         }
       else
         {
         const unsigned rep0_saved = rep0;
-        len = min_match_len + len_decoder.decode( range_decoder, pos_state );
-        const int dis_slot = range_decoder.decode_tree6( bm_dis_slot[get_dis_state(len)] );
+        len = min_match_len + rdec.decode_len( match_len_model, pos_state );
+        const int dis_slot = rdec.decode_tree6( bm_dis_slot[get_dis_state(len)] );
         if( dis_slot < start_dis_model ) rep0 = dis_slot;
         else
           {
           const int direct_bits = ( dis_slot >> 1 ) - 1;
           rep0 = ( 2 | ( dis_slot & 1 ) ) << direct_bits;
           if( dis_slot < end_dis_model )
-            rep0 += range_decoder.decode_tree_reversed( bm_dis + rep0 - dis_slot - 1, direct_bits );
+            rep0 += rdec.decode_tree_reversed( bm_dis + rep0 - dis_slot - 1,
+                                               direct_bits );
           else
             {
-            rep0 += range_decoder.decode( direct_bits - dis_align_bits ) << dis_align_bits;
-            rep0 += range_decoder.decode_tree_reversed4( bm_align );
+            rep0 += rdec.decode( direct_bits - dis_align_bits ) << dis_align_bits;
+            rep0 += rdec.decode_tree_reversed4( bm_align );
             if( rep0 == 0xFFFFFFFFU )		// Marker found
               {
               rep0 = rep0_saved;
-              range_decoder.normalize();
+              rdec.normalize();
               flush_data();
               if( len == min_match_len )	// End Of Stream marker
                 {
@@ -284,7 +281,7 @@ int LZ_decoder::decode_member( const Pretty_print & pp )
                 }
               if( len == min_match_len + 1 )	// Sync Flush marker
                 {
-                range_decoder.load(); continue;
+                rdec.load(); continue;
                 }
               if( pp.verbosity() >= 0 )
                 {
diff --git a/decoder.h b/decoder.h
index a3559ad..a25f0f1 100644
--- a/decoder.h
+++ b/decoder.h
@@ -122,22 +122,22 @@ public:
 
   int decode_tree( Bit_model bm[], const int num_bits )
     {
-    int model = 1;
+    int symbol = 1;
     for( int i = num_bits; i > 0; --i )
-      model = ( model << 1 ) | decode_bit( bm[model] );
-    return model - (1 << num_bits);
+      symbol = ( symbol << 1 ) | decode_bit( bm[symbol] );
+    return symbol - (1 << num_bits);
     }
 
   int decode_tree6( Bit_model bm[] )
     {
-    int model = 1;
-    model = ( model << 1 ) | decode_bit( bm[model] );
-    model = ( model << 1 ) | decode_bit( bm[model] );
-    model = ( model << 1 ) | decode_bit( bm[model] );
-    model = ( model << 1 ) | decode_bit( bm[model] );
-    model = ( model << 1 ) | decode_bit( bm[model] );
-    model = ( model << 1 ) | decode_bit( bm[model] );
-    return model - (1 << 6);
+    int symbol = 1;
+    symbol = ( symbol << 1 ) | decode_bit( bm[symbol] );
+    symbol = ( symbol << 1 ) | decode_bit( bm[symbol] );
+    symbol = ( symbol << 1 ) | decode_bit( bm[symbol] );
+    symbol = ( symbol << 1 ) | decode_bit( bm[symbol] );
+    symbol = ( symbol << 1 ) | decode_bit( bm[symbol] );
+    symbol = ( symbol << 1 ) | decode_bit( bm[symbol] );
+    return symbol - (1 << 6);
     }
 
   int decode_tree_reversed( Bit_model bm[], const int num_bits )
@@ -186,27 +186,16 @@ public:
       }
     return symbol - 0x100;
     }
-  };
 
-
-class Len_decoder
-  {
-  Bit_model choice1;
-  Bit_model choice2;
-  Bit_model bm_low[pos_states][len_low_symbols];
-  Bit_model bm_mid[pos_states][len_mid_symbols];
-  Bit_model bm_high[len_high_symbols];
-
-public:
-  int decode( Range_decoder & range_decoder, const int pos_state )
+  int decode_len( Len_model & lm, const int pos_state )
     {
-    if( range_decoder.decode_bit( choice1 ) == 0 )
-      return range_decoder.decode_tree( bm_low[pos_state], len_low_bits );
-    if( range_decoder.decode_bit( choice2 ) == 0 )
+    if( decode_bit( lm.choice1 ) == 0 )
+      return decode_tree( lm.bm_low[pos_state], len_low_bits );
+    if( decode_bit( lm.choice2 ) == 0 )
       return len_low_symbols +
-             range_decoder.decode_tree( bm_mid[pos_state], len_mid_bits );
+             decode_tree( lm.bm_mid[pos_state], len_mid_bits );
     return len_low_symbols + len_mid_symbols +
-           range_decoder.decode_tree( bm_high, len_high_bits );
+           decode_tree( lm.bm_high, len_high_bits );
     }
   };
 
@@ -214,7 +203,7 @@ public:
 class LZ_decoder
   {
   unsigned long long partial_data_pos;
-  Range_decoder & range_decoder;
+  Range_decoder & rdec;
   const int dictionary_size;
   const int buffer_size;
   uint8_t * const buffer;	// output buffer
@@ -267,10 +256,10 @@ class LZ_decoder
   void operator=( const LZ_decoder & );		// declared as private
 
 public:
-  LZ_decoder( const File_header & header, Range_decoder & rdec, const int ofd )
+  LZ_decoder( const File_header & header, Range_decoder & rde, const int ofd )
     :
     partial_data_pos( 0 ),
-    range_decoder( rdec ),
+    rdec( rde ),
     dictionary_size( header.dictionary_size() ),
     buffer_size( std::max( 65536, dictionary_size ) ),
     buffer( new uint8_t[buffer_size] ),
diff --git a/doc/lzip.1 b/doc/lzip.1
index e0b9ad0..0c6f516 100644
--- a/doc/lzip.1
+++ b/doc/lzip.1
@@ -1,5 +1,5 @@
 .\" DO NOT MODIFY THIS FILE!  It was generated by help2man 1.37.1.
-.TH LZIP "1" "February 2013" "Lzip 1.14" "User Commands"
+.TH LZIP "1" "March 2013" "Lzip 1.15-pre1" "User Commands"
 .SH NAME
 Lzip \- reduces the size of files
 .SH SYNOPSIS
diff --git a/doc/lzip.info b/doc/lzip.info
index e61550e..5c4cf81 100644
--- a/doc/lzip.info
+++ b/doc/lzip.info
@@ -11,17 +11,19 @@ File: lzip.info,  Node: Top,  Next: Introduction,  Up: (dir)
 Lzip Manual
 ***********
 
-This manual is for Lzip (version 1.14, 17 February 2013).
+This manual is for Lzip (version 1.15-pre1, 21 March 2013).
 
 * Menu:
 
-* Introduction::          Purpose and features of lzip
-* Algorithm::             How lzip compresses the data
-* Invoking Lzip::         Command line interface
-* File Format::           Detailed format of the compressed file
-* Examples::              A small tutorial with examples
-* Problems::              Reporting bugs
-* Concept Index::         Index of concepts
+* Introduction::           Purpose and features of lzip
+* Algorithm::              How lzip compresses the data
+* Invoking Lzip::          Command line interface
+* File Format::            Detailed format of the compressed file
+* Stream Format::          Format of the LZMA stream in lzip files
+* Examples::               A small tutorial with examples
+* Problems::               Reporting bugs
+* Reference source code::  Source code illustrating stream format
+* Concept Index::          Index of concepts
 
 
    Copyright (C) 2008, 2009, 2010, 2011, 2012, 2013 Antonio Diaz Diaz.
@@ -324,7 +326,7 @@ Z        zettabyte (10^21)         |   Zi       zebibyte (2^70)
 Y        yottabyte (10^24)         |   Yi       yobibyte (2^80)
 
 
-File: lzip.info,  Node: File Format,  Next: Examples,  Prev: Invoking Lzip,  Up: Top
+File: lzip.info,  Node: File Format,  Next: Stream Format,  Prev: Invoking Lzip,  Up: Top
 
 4 File Format
 *************
@@ -375,6 +377,7 @@ additional information before, between, or after them.
      Bits 4-0 contain the base 2 logarithm of the base size (12 to 29).
      Bits 7-5 contain the number of wedges (0 to 7) to substract from
      the base size to obtain the dictionary size.
+     Example: 0xD3 = (2^19 - 6 * 2^15) = (512KiB - 6 * 32KiB) = 320KiB
      Valid values for dictionary size range from 4KiB to 512MiB.
 
 `Lzma stream'
@@ -394,9 +397,201 @@ additional information before, between, or after them.
 
 
 
-File: lzip.info,  Node: Examples,  Next: Problems,  Prev: File Format,  Up: Top
+File: lzip.info,  Node: Stream Format,  Next: Examples,  Prev: File Format,  Up: Top
+
+5 Format of the LZMA stream in lzip files
+*****************************************
+
+The LZMA algorithm has three parameters, called "special LZMA
+properties", to adjust it for some kinds of binary data. These
+parameters are; `literal_context_bits' (with a default value of 3),
+`literal_pos_state_bits' (with a default value of 0), and
+`pos_state_bits' (with a default value of 2). As a general purpose
+compressor, lzip only uses the default values for these parameters.
+
+   Lzip also finishes the LZMA stream with an "End Of Stream" marker
+(the distance-length pair 0xFFFFFFFFU, 2), which in conjunction with the
+"member size" field in the member trailer allows the verification of
+stream integrity. The LZMA stream in lzip files always has these two
+features (default properties and EOS marker) and is referred to in this
+document as LZMA-302eos or LZMA-lzip.
+
+   The second stage of LZMA is a range encoder that uses a different
+probability model for each type of symbol; distances, lengths, literal
+bytes, etc. Range encoding conceptually encodes all the symbols of the
+message into one number. Unlike Huffman coding, which assigns to each
+symbol a bit-pattern and concatenates all the bit-patterns together,
+range encoding can compress one symbol to less than one bit. Therefore
+the compressed data produced by a range encoder can't be split in pieces
+that could be individually described.
+
+   It seems that the only way of describing the LZMA-302eos stream is
+describing the algorithm that decodes it. And given the many details
+about the range decoder that need to be described accurately, the source
+code of a real decoder seems the only appropiate reference to use.
+
+   What follows is a description of the decoding algorithm for
+LZMA-302eos streams using as reference the source code of "lzd", an
+educational decompressor for lzip files which can be downloaded from
+the lzip download directory. The source code of lzd is included in
+appendix A.  *note Reference source code::
+
+
+5.1 What is coded
+=================
+
+The LZMA stream includes literals, matches and repeated matches (matches
+reusing a recently used distance). There are 7 different coding
+sequences:
+
+Bit sequence              Name       Description
+--------------------------------------------------------------------------- 
+0 + byte                  literal    literal byte
+1 + 0 + len + dis         match      distance-length pair
+1 + 1 + 0 + 0             shortrep   1 byte match at latest used distance
+1 + 1 + 0 + 1 + len       rep0       len bytes match at latest used
+                                     distance
+1 + 1 + 1 + 0 + len       rep1       len bytes match at second latest
+                                     used distance
+1 + 1 + 1 + 1 + 0 + len   rep2       len bytes match at third latest used
+                                     distance
+1 + 1 + 1 + 1 + 1 + len   rep3       len bytes match at fourth latest
+                                     used distance
+
+
+   In the following tables, multi-bit sequences are coded in normal
+order, from MSB to LSB, except where noted otherwise.
+
+   Lengths (the `len' in the table above) are coded as follows:
+
+Bit sequence                         Description
+-------------------------------------------------------------------------- 
+0 + 3 bits                           lengths from 2 to 9
+1 + 0 + 3 bits                       lengths from 10 to 17
+1 + 1 + 8 bits                       lengths from 18 to 273
+
+
+   The coding of distances is a little more complicated. LZMA divides
+the interval between any two powers of 2 into 2 halves, named slots. As
+possible distances range from 0 to (2^32 - 1), there are 64 slots (0 to
+63). The slot number is context-coded in 6 bits. `direct_bits' are the
+remaining bits (from 0 to 30) needed to form a complete distance, and
+are calculated as (slot >> 1) - 1. If a distance needs 6 or more
+direct_bits, the last 4 bits are coded separately. The last piece
+(direct_bits for distances 4 to 127 or the last 4 bits for distances >=
+128) is context-coded in reverse order (from LSB to MSB). For distances
+>= 128, the `direct_bits - 4' part is coded with fixed 0.5 probability.
+
+Bit sequence                         Description
+-------------------------------------------------------------------------- 
+slot                                 distances from 0 to 3
+slot + direct_bits                   distances from 4 to 127
+slot + (direct_bits - 4) + 4 bits    distances from 128 to 2^32 - 1
+
+
+5.2 The coding contexts
+=======================
+
+These contexts (`Bit_model' in the source), are integers or arrays of
+integers representing the probability of the corresponding bit being 0.
+
+   The indices used in these arrays are:
+
+`state'
+     A state machine (`State' in the source) coding the latest 2 to 4
+     types of sequences processed. The initial state is 0.
+
+`pos_state'
+     Value of the 2 least significant bits of the current position in
+     the decoded data.
+
+`literal_state'
+     Value of the 3 most significant bits of the latest byte decoded.
+
+`dis_state'
+     Coded value of length (real length - 2), with a maximum of 3. The
+     resulting value is in the range 0 to 3.
+
+
+   The contexts for decoding the type of coding sequence are:
+
+Name           Indices                       Used when
+--------------------------------------------------------------------------- 
+bm_match       state, pos_state              sequence start
+bm_rep         state                         after sequence 1
+bm_rep0        state                         after sequence 11
+bm_rep1        state                         after sequence 111
+bm_rep2        state                         after sequence 1111
+bm_len         state, pos_state              after sequence 110
 
-5 A small tutorial with examples
+
+   The contexts for decoding distances are:
+
+Name           Indices                       Used when
+--------------------------------------------------------------------------- 
+bm_dis_slot    dis_state, bit tree           distance start
+bm_dis         reverse bit tree              after slots 4 to 13
+bm_align       reverse bit tree              for distances >= 128, after
+                                             fixed probability bits
+
+
+   There are two separated sets of length contexts (`Len_model' in the
+source). One for normal matches, the other for repeated matches. The
+contexts in each Len_model are (see `decode_len' in the source):
+
+Name           Indices                       Used when
+--------------------------------------------------------------------------- 
+choice1        none                          length start
+choice2        none                          after sequence 1
+bm_low         pos_state, bit tree           after sequence 0
+bm_mid         pos_state, bit tree           after sequence 10
+bm_high        bit tree                      after sequence 11
+
+
+   The context array `bm_literal' is special. In principle it acts as a
+normal bit tree context, the one selected by `literal_state'. But if
+the previous decoded byte was not a literal, two other bit tree
+contexts are used depending on the value of each bit in `match_byte'
+(the byte at the latest used distance), until a bit is decoded that is
+different from its corresponding bit in `match_byte'. After the first
+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
+=====================
+
+The LZMA stream is consumed one byte at a time by the range decoder.
+(See `normalize' in the source). Every byte consumed produces a
+variable number of decoded bits, depending on how well these bits agree
+with their context. (See `decode_bit' in the source).
+
+   The range decoder state consists of two unsigned 32-bit variables,
+`range' (representing the most significant part of the range size not
+yet decoded), and `code' (representing the current point within
+`range'). `range' is initialized to (2^32 - 1), and `code' is
+initialized to 0.
+
+   The range encoder produces a first 0 byte that must be ignored by the
+range decoder. This is done by shifting 5 bytes in the initialization of
+`code' instead of 4. (See the `Range_decoder' constructor in the
+source).
+
+
+5.4 Decoding the LZMA stream
+============================
+
+After decoding the member header and obtaining the dictionary size, the
+range decoder is initialized and then the LZMA decoder enters a loop
+(See `decode_member' in the source) where it invokes the range decoder
+with the appropiate contexts to decode the different coding sequences
+(matches, repeated matches, and literal bytes), until the "End Of
+Stream" marker is decoded.
+
+
+File: lzip.info,  Node: Examples,  Next: Problems,  Prev: Stream Format,  Up: Top
+
+6 A small tutorial with examples
 ********************************
 
 WARNING! Even if lzip is bug-free, other causes may result in a corrupt
@@ -467,9 +662,9 @@ file with a member size of 32MiB.
      lzip -b 32MiB -S 650MB big_db
 
 
-File: lzip.info,  Node: Problems,  Next: Concept Index,  Prev: Examples,  Up: Top
+File: lzip.info,  Node: Problems,  Next: Reference source code,  Prev: Examples,  Up: Top
 
-6 Reporting Bugs
+7 Reporting Bugs
 ****************
 
 There are probably bugs in lzip. There are certainly errors and
@@ -482,7 +677,461 @@ for all eternity, if not longer.
 by running `lzip --version'.
 
 
-File: lzip.info,  Node: Concept Index,  Prev: Problems,  Up: Top
+File: lzip.info,  Node: Reference source code,  Next: Concept Index,  Prev: Problems,  Up: Top
+
+Appendix A Reference source code
+********************************
+
+#include <algorithm>
+#include <cerrno>
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+#include <stdint.h>
+#include <unistd.h>
+
+
+class State
+  {
+  int st;
+
+public:
+  enum { states = 12 };
+  State() : st( 0 ) {}
+  int operator()() const { return st; }
+  bool is_char() const { return st < 7; }
+
+  void set_char()
+    {
+    static const int next[states] = { 0, 0, 0, 0, 1, 2, 3, 4, 5, 6, 4, 5 };
+    st = next[st];
+    }
+
+  void set_match()     { st = ( ( st < 7 ) ? 7 : 10 ); }
+  void set_rep()       { st = ( ( st < 7 ) ? 8 : 11 ); }
+  void set_short_rep() { st = ( ( st < 7 ) ? 9 : 11 ); }
+  };
+
+
+enum {
+  literal_context_bits = 3,
+  pos_state_bits = 2,
+  pos_states = 1 << pos_state_bits,
+  pos_state_mask = pos_states - 1,
+
+  max_dis_states = 4,
+  dis_slot_bits = 6,
+  start_dis_model = 4,
+  end_dis_model = 14,
+  modeled_distances = 1 << (end_dis_model / 2),		// 128
+  dis_align_bits = 4,
+  dis_align_size = 1 << dis_align_bits,
+
+  len_low_bits = 3,
+  len_mid_bits = 3,
+  len_high_bits = 8,
+  len_low_symbols = 1 << len_low_bits,
+  len_mid_symbols = 1 << len_mid_bits,
+  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
+
+  bit_model_move_bits = 5,
+  bit_model_total_bits = 11,
+  bit_model_total = 1 << bit_model_total_bits };
+
+
+struct Bit_model
+  {
+  int probability;
+  Bit_model() : probability( bit_model_total / 2 ) {}
+  };
+
+
+struct Len_model
+  {
+  Bit_model choice1;
+  Bit_model choice2;
+  Bit_model bm_low[pos_states][len_low_symbols];
+  Bit_model bm_mid[pos_states][len_mid_symbols];
+  Bit_model bm_high[len_high_symbols];
+  };
+
+
+class Range_decoder
+  {
+  uint32_t code;
+  uint32_t range;
+
+public:
+  Range_decoder() : code( 0 ), range( 0xFFFFFFFFU )
+    {
+    for( int i = 0; i < 5; ++i ) code = (code << 8) | std::getc( stdin );
+    }
+
+  int decode( const int num_bits )
+    {
+    int symbol = 0;
+    for( int i = 0; i < num_bits; ++i )
+      {
+      range >>= 1;
+      symbol <<= 1;
+      if( code >= range ) { code -= range; symbol |= 1; }
+      if( range <= 0x00FFFFFFU )			// normalize
+        { range <<= 8; code = (code << 8) | std::getc( stdin ); }
+      }
+    return symbol;
+    }
+
+  int decode_bit( Bit_model & bm )
+    {
+    int symbol;
+    const uint32_t bound = ( range >> bit_model_total_bits ) * bm.probability;
+    if( code < bound )
+      {
+      range = bound;
+      bm.probability += (bit_model_total - bm.probability) >> bit_model_move_bits;
+      symbol = 0;
+      }
+    else
+      {
+      range -= bound;
+      code -= bound;
+      bm.probability -= bm.probability >> bit_model_move_bits;
+      symbol = 1;
+      }
+    if( range <= 0x00FFFFFFU )				// normalize
+      { range <<= 8; code = (code << 8) | std::getc( stdin ); }
+    return symbol;
+    }
+
+  int decode_tree( Bit_model bm[], const int num_bits )
+    {
+    int symbol = 1;
+    for( int i = 0; i < num_bits; ++i )
+      symbol = ( symbol << 1 ) | decode_bit( bm[symbol] );
+    return symbol - (1 << num_bits);
+    }
+
+  int decode_tree_reversed( Bit_model bm[], const int num_bits )
+    {
+    int symbol = decode_tree( bm, num_bits );
+    int reversed_symbol = 0;
+    for( int i = 0; i < num_bits; ++i )
+      {
+      reversed_symbol = ( reversed_symbol << 1 ) | ( symbol & 1 );
+      symbol >>= 1;
+      }
+    return reversed_symbol;
+    }
+
+  int decode_matched( Bit_model bm[], const int match_byte )
+    {
+    Bit_model * const bm1 = bm + 0x100;
+    int symbol = 1;
+    for( int i = 7; i >= 0; --i )
+      {
+      const int match_bit = ( match_byte >> i ) & 1;
+      const int bit = decode_bit( bm1[(match_bit<<8)+symbol] );
+      symbol = ( symbol << 1 ) | bit;
+      if( match_bit != bit )
+        {
+        while( symbol < 0x100 )
+          symbol = ( symbol << 1 ) | decode_bit( bm[symbol] );
+        break;
+        }
+      }
+    return symbol - 0x100;
+    }
+
+  int decode_len( Len_model & lm, const int pos_state )
+    {
+    if( decode_bit( lm.choice1 ) == 0 )
+      return min_match_len +
+             decode_tree( lm.bm_low[pos_state], len_low_bits );
+    if( decode_bit( lm.choice2 ) == 0 )
+      return min_match_len + len_low_symbols +
+             decode_tree( lm.bm_mid[pos_state], len_mid_bits );
+    return min_match_len + len_low_symbols + len_mid_symbols +
+           decode_tree( lm.bm_high, len_high_bits );
+    }
+  };
+
+
+class LZ_decoder
+  {
+  unsigned long long partial_data_pos;
+  Range_decoder rdec;
+  const unsigned dictionary_size;
+  uint8_t * const buffer;	// output buffer
+  unsigned pos;			// current pos in buffer
+  unsigned stream_pos;		// first byte not yet written to stdout
+  uint32_t crc_;
+
+  void flush_data();
+
+  uint8_t get_byte( const unsigned distance ) const
+    {
+    int i = pos - distance - 1;
+    if( i < 0 ) i += dictionary_size;
+    return buffer[i];
+    }
+
+  void put_byte( const uint8_t b )
+    {
+    buffer[pos] = b;
+    if( ++pos >= dictionary_size ) flush_data();
+    }
+
+public:
+  LZ_decoder( const unsigned dict_size )
+    :
+    partial_data_pos( 0 ),
+    dictionary_size( dict_size ),
+    buffer( new uint8_t[dictionary_size] ),
+    pos( 0 ),
+    stream_pos( 0 ),
+    crc_( 0xFFFFFFFFU )
+    { buffer[dictionary_size-1] = 0; }		// prev_byte of first_byte
+
+  ~LZ_decoder() { delete[] buffer; }
+
+  unsigned crc() const { return crc_ ^ 0xFFFFFFFFU; }
+  unsigned long long data_position() const { return partial_data_pos + pos; }
+
+  bool decode_member();
+  };
+
+
+class CRC32
+  {
+  uint32_t data[256];		// Table of CRCs of all 8-bit messages.
+
+public:
+  CRC32()
+    {
+    for( unsigned n = 0; n < 256; ++n )
+      {
+      unsigned c = n;
+      for( int k = 0; k < 8; ++k )
+        { if( c & 1 ) c = 0xEDB88320U ^ ( c >> 1 ); else c >>= 1; }
+      data[n] = c;
+      }
+    }
+
+  void update( uint32_t & crc, const uint8_t * buffer, const int size ) const
+    {
+    for( int i = 0; i < size; ++i )
+      crc = data[(crc^buffer[i])&0xFF] ^ ( crc >> 8 );
+    }
+  };
+
+const CRC32 crc32;
+
+
+void LZ_decoder::flush_data()
+  {
+  if( pos > stream_pos )
+    {
+    const unsigned size = pos - stream_pos;
+    crc32.update( 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::exit( 1 ); }
+    if( pos >= dictionary_size ) { partial_data_pos += pos; pos = 0; }
+    stream_pos = pos;
+    }
+  }
+
+
+bool LZ_decoder::decode_member()		// Returns false if error
+  {
+  Bit_model bm_literal[1<<literal_context_bits][0x300];
+  Bit_model bm_match[State::states][pos_states];
+  Bit_model bm_rep[State::states];
+  Bit_model bm_rep0[State::states];
+  Bit_model bm_rep1[State::states];
+  Bit_model bm_rep2[State::states];
+  Bit_model bm_len[State::states][pos_states];
+  Bit_model bm_dis_slot[max_dis_states][1<<dis_slot_bits];
+  Bit_model bm_dis[modeled_distances-end_dis_model];
+  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 rep3 = 0;
+  State state;
+
+  while( !std::feof( stdin ) && !std::ferror( stdin ) )
+    {
+    const int pos_state = data_position() & pos_state_mask;
+    if( rdec.decode_bit( bm_match[state()][pos_state] ) == 0 )	// 1st bit
+      {
+      const uint8_t prev_byte = get_byte( 0 );
+      const int literal_state = prev_byte >> ( 8 - literal_context_bits );
+      Bit_model * const bm = bm_literal[literal_state];
+      if( state.is_char() )
+        put_byte( rdec.decode_tree( bm, 8 ) );
+      else
+        put_byte( rdec.decode_matched( bm, get_byte( rep0 ) ) );
+      state.set_char();
+      }
+    else
+      {
+      int len;
+      if( rdec.decode_bit( bm_rep[state()] ) == 1 )		// 2nd bit
+        {
+        if( rdec.decode_bit( bm_rep0[state()] ) == 0 )		// 3rd bit
+          {
+          if( rdec.decode_bit( bm_len[state()][pos_state] ) == 0 ) // 4th bit
+            { state.set_short_rep(); put_byte( get_byte( rep0 ) ); continue; }
+          }
+        else
+          {
+          unsigned distance;
+          if( rdec.decode_bit( bm_rep1[state()] ) == 0 )	// 4th bit
+            distance = rep1;
+          else
+            {
+            if( rdec.decode_bit( bm_rep2[state()] ) == 0 )	// 5th bit
+              distance = rep2;
+            else
+              { distance = rep3; rep3 = rep2; }
+            rep2 = rep1;
+            }
+          rep1 = rep0;
+          rep0 = distance;
+          }
+        len = rdec.decode_len( rep_len_model, pos_state );
+        state.set_rep();
+        }
+      else
+        {
+        rep3 = rep2; rep2 = rep1; rep1 = rep0;
+        len = rdec.decode_len( match_len_model, pos_state );
+        const int dis_state = std::min( len - min_match_len, max_dis_states - 1 );
+        const int dis_slot =
+          rdec.decode_tree( bm_dis_slot[dis_state], dis_slot_bits );
+        if( dis_slot < start_dis_model ) rep0 = dis_slot;
+        else
+          {
+          const int direct_bits = ( dis_slot >> 1 ) - 1;
+          rep0 = ( 2 | ( dis_slot & 1 ) ) << direct_bits;
+          if( dis_slot < end_dis_model )
+            rep0 += rdec.decode_tree_reversed( bm_dis + rep0 - dis_slot - 1,
+                                               direct_bits );
+          else
+            {
+            rep0 += rdec.decode( direct_bits - dis_align_bits ) << dis_align_bits;
+            rep0 += rdec.decode_tree_reversed( bm_align, dis_align_bits );
+            if( rep0 == 0xFFFFFFFFU )		// Marker found
+              {
+              flush_data();
+              return ( len == min_match_len );	// End Of Stream marker
+              }
+            }
+          }
+        state.set_match();
+        if( rep0 >= dictionary_size || ( rep0 >= pos && !partial_data_pos ) )
+          return false;
+        }
+      for( int i = 0; i < len; ++i )
+        put_byte( get_byte( rep0 ) );
+      }
+    }
+  return false;
+  }
+
+
+enum { min_dictionary_size = 1 << 12,
+       max_dictionary_size = 1 << 29 };
+
+typedef uint8_t File_header[6];	// 0-3 magic, 4 version, 5 coded_dict_size
+
+typedef uint8_t File_trailer[20];
+			//  0-3  CRC32 of the uncompressed data
+			//  4-11 size of the uncompressed data
+			// 12-19 member size including header and trailer
+
+
+/*  Return values: 0 for a normal exit, 1 for environmental problems
+    (file not found, invalid flags, I/O errors, etc), 2 to indicate a
+    corrupt or invalid input file. */
+
+int main( const int argc, const char * const argv[] )
+  {
+  if( argc > 1 )
+    {
+    std::printf( "Lzd %s - Educational decompressor for lzip files.\n",
+                 PROGVERSION );
+    std::printf( "Study the source to learn how a simple lzip decompressor works.\n"
+                 "It is not safe to use it for any real work.\n"
+                 "\nUsage: %s < file.lz > file\n", argv[0] );
+    std::printf( "Lzd decompresses from standard input to standard output.\n"
+                 "\nCopyright (C) 2013 Antonio Diaz Diaz.\n"
+                 "This is free software: you are free to change and redistribute it.\n"
+                 "There is NO WARRANTY, to the extent permitted by law.\n"
+                 "Report bugs to lzip-bug@nongnu.org\n"
+                 "Lzip home page: http://www.nongnu.org/lzip/lzip.html\n" );
+    return 0;
+    }
+
+  if( isatty( STDIN_FILENO ) )
+    {
+    std::fprintf( stderr, "I won't read compressed data from a terminal.\n"
+                          "Try '%s --help' for more information.\n", argv[0] );
+    return 1;
+    }
+
+  for( bool first_member = true; ; first_member = false )
+    {
+    File_header header;
+    for( int i = 0; i < 6; ++i )
+      header[i] = std::getc( stdin );
+    if( std::feof( stdin ) || std::memcmp( header, "LZIP", 4 ) != 0 )
+      {
+      if( first_member )
+        { std::fprintf( stderr, "Bad magic number (file not in lzip format)\n" );
+          return 2; }
+      break;
+      }
+    if( header[4] != 1 )
+      {
+      std::fprintf( stderr, "Version %d member format not supported.\n",
+                    header[4] );
+      return 2;
+      }
+    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" );
+        return 2; }
+
+    LZ_decoder decoder( dict_size );
+    if( !decoder.decode_member() )
+      { std::fprintf( stderr, "Data error\n" ); return 2; }
+
+    File_trailer trailer;
+    for( int i = 0; i < 20; ++i ) trailer[i] = std::getc( stdin );
+    unsigned crc = 0;
+    for( int i = 3; i >= 0; --i ) { crc <<= 8; crc += trailer[i]; }
+    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; }
+    }
+
+  if( std::fclose( stdout ) != 0 )
+    { std::fprintf( stderr, "Can't close stdout: %s\n", std::strerror( errno ) );
+      return 1; }
+  return 0;
+  }
+
+
+File: lzip.info,  Node: Concept Index,  Prev: Reference source code,  Up: Top
 
 Concept Index
 *************
@@ -494,10 +1143,12 @@ Concept Index
 * bugs:                                  Problems.              (line 6)
 * examples:                              Examples.              (line 6)
 * file format:                           File Format.           (line 6)
+* format of the LZMA stream:             Stream Format.         (line 6)
 * getting help:                          Problems.              (line 6)
 * introduction:                          Introduction.          (line 6)
 * invoking:                              Invoking Lzip.         (line 6)
 * options:                               Invoking Lzip.         (line 6)
+* reference source code:                 Reference source code. (line 6)
 * usage:                                 Invoking Lzip.         (line 6)
 * version:                               Invoking Lzip.         (line 6)
 
@@ -505,13 +1156,15 @@ Concept Index
 
 Tag Table:
 Node: Top224
-Node: Introduction925
-Node: Algorithm4590
-Node: Invoking Lzip7108
-Node: File Format12460
-Node: Examples14767
-Node: Problems16714
-Node: Concept Index17236
+Node: Introduction1067
+Node: Algorithm4732
+Node: Invoking Lzip7250
+Node: File Format12602
+Node: Stream Format14985
+Node: Examples23695
+Node: Problems25644
+Node: Reference source code26174
+Node: Concept Index39424
 
 End Tag Table
 
diff --git a/doc/lzip.texinfo b/doc/lzip.texinfo
index 76ccfc9..632abc5 100644
--- a/doc/lzip.texinfo
+++ b/doc/lzip.texinfo
@@ -6,8 +6,8 @@
 @finalout
 @c %**end of header
 
-@set UPDATED 17 February 2013
-@set VERSION 1.14
+@set UPDATED 21 March 2013
+@set VERSION 1.15-pre1
 
 @dircategory Data Compression
 @direntry
@@ -35,13 +35,15 @@
 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
-* File Format::           Detailed format of the compressed file
-* Examples::              A small tutorial with examples
-* Problems::              Reporting bugs
-* Concept Index::         Index of concepts
+* Introduction::           Purpose and features of lzip
+* Algorithm::              How lzip compresses the data
+* Invoking Lzip::          Command line interface
+* File Format::            Detailed format of the compressed file
+* Stream Format::          Format of the LZMA stream in lzip files
+* Examples::               A small tutorial with examples
+* Problems::               Reporting bugs
+* Reference source code::  Source code illustrating stream format
+* Concept Index::          Index of concepts
 @end menu
 
 @sp 1
@@ -403,6 +405,7 @@ wedges between 0 and 7. The size of a wedge is (base_size / 16).@*
 Bits 4-0 contain the base 2 logarithm of the base size (12 to 29).@*
 Bits 7-5 contain the number of wedges (0 to 7) to substract from the
 base size to obtain the dictionary size.@*
+Example: 0xD3 = (2^19 - 6 * 2^15) = (512KiB - 6 * 32KiB) = 320KiB@*
 Valid values for dictionary size range from 4KiB to 512MiB.
 
 @item Lzma stream
@@ -423,6 +426,206 @@ members from multi-member files.
 @end table
 
 
+@node Stream Format
+@chapter Format of the LZMA stream in lzip files
+@cindex format of the LZMA stream
+
+The LZMA algorithm has three parameters, called "special LZMA
+properties", to adjust it for some kinds of binary data. These
+parameters are; @samp{literal_context_bits} (with a default value of 3),
+@samp{literal_pos_state_bits} (with a default value of 0), and
+@samp{pos_state_bits} (with a default value of 2). As a general purpose
+compressor, lzip only uses the default values for these parameters.
+
+Lzip also finishes the LZMA stream with an "End Of Stream" marker (the
+distance-length pair 0xFFFFFFFFU, 2), which in conjunction with the
+"member size" field in the member trailer allows the verification of
+stream integrity. The LZMA stream in lzip files always has these two
+features (default properties and EOS marker) and is referred to in this
+document as LZMA-302eos or LZMA-lzip.
+
+The second stage of LZMA is a range encoder that uses a different
+probability model for each type of symbol; distances, lengths, literal
+bytes, etc. Range encoding conceptually encodes all the symbols of the
+message into one number. Unlike Huffman coding, which assigns to each
+symbol a bit-pattern and concatenates all the bit-patterns together,
+range encoding can compress one symbol to less than one bit. Therefore
+the compressed data produced by a range encoder can't be split in pieces
+that could be individually described.
+
+It seems that the only way of describing the LZMA-302eos stream is
+describing the algorithm that decodes it. And given the many details
+about the range decoder that need to be described accurately, the source
+code of a real decoder seems the only appropiate reference to use.
+
+What follows is a description of the decoding algorithm for LZMA-302eos
+streams using as reference the source code of "lzd", an educational
+decompressor for lzip files which can be downloaded from the lzip
+download directory. The source code of lzd is included in appendix A.
+@ref{Reference source code}
+
+@sp 1
+@section What is coded
+
+The LZMA stream includes literals, matches and repeated matches (matches
+reusing a recently used distance). There are 7 different coding sequences:
+
+@multitable @columnfractions .35 .14 .51
+@headitem Bit sequence @tab Name @tab Description
+@item 0 + byte @tab literal @tab literal byte
+@item 1 + 0 + len + dis @tab match @tab distance-length pair
+@item 1 + 1 + 0 + 0 @tab shortrep @tab 1 byte match at latest used
+distance
+@item 1 + 1 + 0 + 1 + len @tab rep0 @tab len bytes match at latest used
+distance
+@item 1 + 1 + 1 + 0 + len @tab rep1 @tab len bytes match at second
+latest used distance
+@item 1 + 1 + 1 + 1 + 0 + len @tab rep2 @tab len bytes match at third
+latest used distance
+@item 1 + 1 + 1 + 1 + 1 + len @tab rep3 @tab len bytes match at fourth
+latest used distance
+@end multitable
+
+@sp 1
+In the following tables, multi-bit sequences are coded in normal order,
+from MSB to LSB, except where noted otherwise.
+
+Lengths (the @samp{len} in the table above) are coded as follows:
+
+@multitable @columnfractions .5 .5
+@headitem Bit sequence @tab Description
+@item 0 + 3 bits @tab lengths from 2 to 9
+@item 1 + 0 + 3 bits @tab lengths from 10 to 17
+@item 1 + 1 + 8 bits @tab lengths from 18 to 273
+@end multitable
+
+@sp 1
+The coding of distances is a little more complicated. LZMA divides the
+interval between any two powers of 2 into 2 halves, named slots. As
+possible distances range from 0 to (2^32 - 1), there are 64 slots (0 to
+63). The slot number is context-coded in 6 bits. @samp{direct_bits} are
+the remaining bits (from 0 to 30) needed to form a complete distance,
+and are calculated as (slot >> 1) - 1. If a distance needs 6 or more
+direct_bits, the last 4 bits are coded separately. The last piece
+(direct_bits for distances 4 to 127 or the last 4 bits for distances >=
+128) is context-coded in reverse order (from LSB to MSB). For distances
+>= 128, the @samp{direct_bits - 4} part is coded with fixed 0.5
+probability.
+
+@multitable @columnfractions .5 .5
+@headitem Bit sequence @tab Description
+@item slot @tab distances from 0 to 3
+@item slot + direct_bits @tab distances from 4 to 127
+@item slot + (direct_bits - 4) + 4 bits @tab distances from 128 to
+2^32 - 1
+@end multitable
+
+@sp 1
+@section The coding contexts
+
+These contexts (@samp{Bit_model} in the source), are integers or arrays
+of integers representing the probability of the corresponding bit being 0.
+
+The indices used in these arrays are:
+
+@table @samp
+@item state
+
+A state machine (@samp{State} in the source) coding the latest 2 to 4
+types of sequences processed. The initial state is 0.
+
+@item pos_state
+Value of the 2 least significant bits of the current position in the
+decoded data.
+
+@item literal_state
+Value of the 3 most significant bits of the latest byte decoded.
+
+@item dis_state
+Coded value of length (real length - 2), with a maximum of 3. The
+resulting value is in the range 0 to 3.
+
+@end table
+
+
+The contexts for decoding the type of coding sequence are:
+
+@multitable @columnfractions .2 .4 .4
+@headitem Name @tab Indices @tab Used when
+@item bm_match @tab state, pos_state @tab sequence start
+@item bm_rep @tab state @tab after sequence 1
+@item bm_rep0 @tab state @tab after sequence 11
+@item bm_rep1 @tab state @tab after sequence 111
+@item bm_rep2 @tab state @tab after sequence 1111
+@item bm_len @tab state, pos_state @tab after sequence 110
+@end multitable
+
+@sp 1
+The contexts for decoding distances are:
+
+@multitable @columnfractions .2 .4 .4
+@headitem Name @tab Indices @tab Used when
+@item bm_dis_slot @tab dis_state, bit tree @tab distance start
+@item bm_dis @tab reverse bit tree @tab after slots 4 to 13
+@item bm_align @tab reverse bit tree @tab for distances >= 128, after
+fixed probability bits
+@end multitable
+
+@sp 1
+There are two separated sets of length contexts (@samp{Len_model} in the
+source). One for normal matches, the other for repeated matches. The
+contexts in each Len_model are (see @samp{decode_len} in the source):
+
+@multitable @columnfractions .2 .4 .4
+@headitem Name @tab Indices @tab Used when
+@item choice1 @tab none @tab length start
+@item choice2 @tab none @tab after sequence 1
+@item bm_low @tab pos_state, bit tree @tab after sequence 0
+@item bm_mid @tab pos_state, bit tree @tab after sequence 10
+@item bm_high @tab bit tree @tab after sequence 11
+@end multitable
+
+@sp 1
+The context array @samp{bm_literal} is special. In principle it acts as
+a normal bit tree context, the one selected by @samp{literal_state}. But
+if the previous decoded byte was not a literal, two other bit tree
+contexts are used depending on the value of each bit in
+@samp{match_byte} (the byte at the latest used distance), until a bit is
+decoded that is different from its corresponding bit in
+@samp{match_byte}. After the first difference is found, the rest of the
+byte is decoded using the normal bit tree context. (See
+@samp{decode_matched} in the source).
+
+@sp 1
+@section The range decoder
+
+The LZMA stream is consumed one byte at a time by the range decoder.
+(See @samp{normalize} in the source). Every byte consumed produces a
+variable number of decoded bits, depending on how well these bits agree
+with their context. (See @samp{decode_bit} in the source).
+
+The range decoder state consists of two unsigned 32-bit variables,
+@code{range} (representing the most significant part of the range size
+not yet decoded), and @code{code} (representing the current point within
+@code{range}). @code{range} is initialized to (2^32 - 1), and
+@code{code} is initialized to 0.
+
+The range encoder produces a first 0 byte that must be ignored by the
+range decoder. This is done by shifting 5 bytes in the initialization of
+@code{code} instead of 4. (See the @samp{Range_decoder} constructor in
+the source).
+
+@sp 1
+@section Decoding the LZMA stream
+
+After decoding the member header and obtaining the dictionary size, the
+range decoder is initialized and then the LZMA decoder enters a loop
+(See @samp{decode_member} in the source) where it invokes the range
+decoder with the appropiate contexts to decode the different coding
+sequences (matches, repeated matches, and literal bytes), until the "End
+Of Stream" marker is decoded.
+
+
 @node Examples
 @chapter A small tutorial with examples
 @cindex examples
@@ -541,6 +744,461 @@ If you find a bug in lzip, please send electronic mail to
 find by running @w{@samp{lzip --version}}.
 
 
+@node Reference source code
+@appendix Reference source code
+@cindex reference source code
+
+@verbatim
+#include <algorithm>
+#include <cerrno>
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+#include <stdint.h>
+#include <unistd.h>
+
+
+class State
+  {
+  int st;
+
+public:
+  enum { states = 12 };
+  State() : st( 0 ) {}
+  int operator()() const { return st; }
+  bool is_char() const { return st < 7; }
+
+  void set_char()
+    {
+    static const int next[states] = { 0, 0, 0, 0, 1, 2, 3, 4, 5, 6, 4, 5 };
+    st = next[st];
+    }
+
+  void set_match()     { st = ( ( st < 7 ) ? 7 : 10 ); }
+  void set_rep()       { st = ( ( st < 7 ) ? 8 : 11 ); }
+  void set_short_rep() { st = ( ( st < 7 ) ? 9 : 11 ); }
+  };
+
+
+enum {
+  literal_context_bits = 3,
+  pos_state_bits = 2,
+  pos_states = 1 << pos_state_bits,
+  pos_state_mask = pos_states - 1,
+
+  max_dis_states = 4,
+  dis_slot_bits = 6,
+  start_dis_model = 4,
+  end_dis_model = 14,
+  modeled_distances = 1 << (end_dis_model / 2),		// 128
+  dis_align_bits = 4,
+  dis_align_size = 1 << dis_align_bits,
+
+  len_low_bits = 3,
+  len_mid_bits = 3,
+  len_high_bits = 8,
+  len_low_symbols = 1 << len_low_bits,
+  len_mid_symbols = 1 << len_mid_bits,
+  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
+
+  bit_model_move_bits = 5,
+  bit_model_total_bits = 11,
+  bit_model_total = 1 << bit_model_total_bits };
+
+
+struct Bit_model
+  {
+  int probability;
+  Bit_model() : probability( bit_model_total / 2 ) {}
+  };
+
+
+struct Len_model
+  {
+  Bit_model choice1;
+  Bit_model choice2;
+  Bit_model bm_low[pos_states][len_low_symbols];
+  Bit_model bm_mid[pos_states][len_mid_symbols];
+  Bit_model bm_high[len_high_symbols];
+  };
+
+
+class Range_decoder
+  {
+  uint32_t code;
+  uint32_t range;
+
+public:
+  Range_decoder() : code( 0 ), range( 0xFFFFFFFFU )
+    {
+    for( int i = 0; i < 5; ++i ) code = (code << 8) | std::getc( stdin );
+    }
+
+  int decode( const int num_bits )
+    {
+    int symbol = 0;
+    for( int i = 0; i < num_bits; ++i )
+      {
+      range >>= 1;
+      symbol <<= 1;
+      if( code >= range ) { code -= range; symbol |= 1; }
+      if( range <= 0x00FFFFFFU )			// normalize
+        { range <<= 8; code = (code << 8) | std::getc( stdin ); }
+      }
+    return symbol;
+    }
+
+  int decode_bit( Bit_model & bm )
+    {
+    int symbol;
+    const uint32_t bound = ( range >> bit_model_total_bits ) * bm.probability;
+    if( code < bound )
+      {
+      range = bound;
+      bm.probability += (bit_model_total - bm.probability) >> bit_model_move_bits;
+      symbol = 0;
+      }
+    else
+      {
+      range -= bound;
+      code -= bound;
+      bm.probability -= bm.probability >> bit_model_move_bits;
+      symbol = 1;
+      }
+    if( range <= 0x00FFFFFFU )				// normalize
+      { range <<= 8; code = (code << 8) | std::getc( stdin ); }
+    return symbol;
+    }
+
+  int decode_tree( Bit_model bm[], const int num_bits )
+    {
+    int symbol = 1;
+    for( int i = 0; i < num_bits; ++i )
+      symbol = ( symbol << 1 ) | decode_bit( bm[symbol] );
+    return symbol - (1 << num_bits);
+    }
+
+  int decode_tree_reversed( Bit_model bm[], const int num_bits )
+    {
+    int symbol = decode_tree( bm, num_bits );
+    int reversed_symbol = 0;
+    for( int i = 0; i < num_bits; ++i )
+      {
+      reversed_symbol = ( reversed_symbol << 1 ) | ( symbol & 1 );
+      symbol >>= 1;
+      }
+    return reversed_symbol;
+    }
+
+  int decode_matched( Bit_model bm[], const int match_byte )
+    {
+    Bit_model * const bm1 = bm + 0x100;
+    int symbol = 1;
+    for( int i = 7; i >= 0; --i )
+      {
+      const int match_bit = ( match_byte >> i ) & 1;
+      const int bit = decode_bit( bm1[(match_bit<<8)+symbol] );
+      symbol = ( symbol << 1 ) | bit;
+      if( match_bit != bit )
+        {
+        while( symbol < 0x100 )
+          symbol = ( symbol << 1 ) | decode_bit( bm[symbol] );
+        break;
+        }
+      }
+    return symbol - 0x100;
+    }
+
+  int decode_len( Len_model & lm, const int pos_state )
+    {
+    if( decode_bit( lm.choice1 ) == 0 )
+      return min_match_len +
+             decode_tree( lm.bm_low[pos_state], len_low_bits );
+    if( decode_bit( lm.choice2 ) == 0 )
+      return min_match_len + len_low_symbols +
+             decode_tree( lm.bm_mid[pos_state], len_mid_bits );
+    return min_match_len + len_low_symbols + len_mid_symbols +
+           decode_tree( lm.bm_high, len_high_bits );
+    }
+  };
+
+
+class LZ_decoder
+  {
+  unsigned long long partial_data_pos;
+  Range_decoder rdec;
+  const unsigned dictionary_size;
+  uint8_t * const buffer;	// output buffer
+  unsigned pos;			// current pos in buffer
+  unsigned stream_pos;		// first byte not yet written to stdout
+  uint32_t crc_;
+
+  void flush_data();
+
+  uint8_t get_byte( const unsigned distance ) const
+    {
+    int i = pos - distance - 1;
+    if( i < 0 ) i += dictionary_size;
+    return buffer[i];
+    }
+
+  void put_byte( const uint8_t b )
+    {
+    buffer[pos] = b;
+    if( ++pos >= dictionary_size ) flush_data();
+    }
+
+public:
+  LZ_decoder( const unsigned dict_size )
+    :
+    partial_data_pos( 0 ),
+    dictionary_size( dict_size ),
+    buffer( new uint8_t[dictionary_size] ),
+    pos( 0 ),
+    stream_pos( 0 ),
+    crc_( 0xFFFFFFFFU )
+    { buffer[dictionary_size-1] = 0; }		// prev_byte of first_byte
+
+  ~LZ_decoder() { delete[] buffer; }
+
+  unsigned crc() const { return crc_ ^ 0xFFFFFFFFU; }
+  unsigned long long data_position() const { return partial_data_pos + pos; }
+
+  bool decode_member();
+  };
+
+
+class CRC32
+  {
+  uint32_t data[256];		// Table of CRCs of all 8-bit messages.
+
+public:
+  CRC32()
+    {
+    for( unsigned n = 0; n < 256; ++n )
+      {
+      unsigned c = n;
+      for( int k = 0; k < 8; ++k )
+        { if( c & 1 ) c = 0xEDB88320U ^ ( c >> 1 ); else c >>= 1; }
+      data[n] = c;
+      }
+    }
+
+  void update( uint32_t & crc, const uint8_t * buffer, const int size ) const
+    {
+    for( int i = 0; i < size; ++i )
+      crc = data[(crc^buffer[i])&0xFF] ^ ( crc >> 8 );
+    }
+  };
+
+const CRC32 crc32;
+
+
+void LZ_decoder::flush_data()
+  {
+  if( pos > stream_pos )
+    {
+    const unsigned size = pos - stream_pos;
+    crc32.update( 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::exit( 1 ); }
+    if( pos >= dictionary_size ) { partial_data_pos += pos; pos = 0; }
+    stream_pos = pos;
+    }
+  }
+
+
+bool LZ_decoder::decode_member()		// Returns false if error
+  {
+  Bit_model bm_literal[1<<literal_context_bits][0x300];
+  Bit_model bm_match[State::states][pos_states];
+  Bit_model bm_rep[State::states];
+  Bit_model bm_rep0[State::states];
+  Bit_model bm_rep1[State::states];
+  Bit_model bm_rep2[State::states];
+  Bit_model bm_len[State::states][pos_states];
+  Bit_model bm_dis_slot[max_dis_states][1<<dis_slot_bits];
+  Bit_model bm_dis[modeled_distances-end_dis_model];
+  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 rep3 = 0;
+  State state;
+
+  while( !std::feof( stdin ) && !std::ferror( stdin ) )
+    {
+    const int pos_state = data_position() & pos_state_mask;
+    if( rdec.decode_bit( bm_match[state()][pos_state] ) == 0 )	// 1st bit
+      {
+      const uint8_t prev_byte = get_byte( 0 );
+      const int literal_state = prev_byte >> ( 8 - literal_context_bits );
+      Bit_model * const bm = bm_literal[literal_state];
+      if( state.is_char() )
+        put_byte( rdec.decode_tree( bm, 8 ) );
+      else
+        put_byte( rdec.decode_matched( bm, get_byte( rep0 ) ) );
+      state.set_char();
+      }
+    else
+      {
+      int len;
+      if( rdec.decode_bit( bm_rep[state()] ) == 1 )		// 2nd bit
+        {
+        if( rdec.decode_bit( bm_rep0[state()] ) == 0 )		// 3rd bit
+          {
+          if( rdec.decode_bit( bm_len[state()][pos_state] ) == 0 ) // 4th bit
+            { state.set_short_rep(); put_byte( get_byte( rep0 ) ); continue; }
+          }
+        else
+          {
+          unsigned distance;
+          if( rdec.decode_bit( bm_rep1[state()] ) == 0 )	// 4th bit
+            distance = rep1;
+          else
+            {
+            if( rdec.decode_bit( bm_rep2[state()] ) == 0 )	// 5th bit
+              distance = rep2;
+            else
+              { distance = rep3; rep3 = rep2; }
+            rep2 = rep1;
+            }
+          rep1 = rep0;
+          rep0 = distance;
+          }
+        len = rdec.decode_len( rep_len_model, pos_state );
+        state.set_rep();
+        }
+      else
+        {
+        rep3 = rep2; rep2 = rep1; rep1 = rep0;
+        len = rdec.decode_len( match_len_model, pos_state );
+        const int dis_state = std::min( len - min_match_len, max_dis_states - 1 );
+        const int dis_slot =
+          rdec.decode_tree( bm_dis_slot[dis_state], dis_slot_bits );
+        if( dis_slot < start_dis_model ) rep0 = dis_slot;
+        else
+          {
+          const int direct_bits = ( dis_slot >> 1 ) - 1;
+          rep0 = ( 2 | ( dis_slot & 1 ) ) << direct_bits;
+          if( dis_slot < end_dis_model )
+            rep0 += rdec.decode_tree_reversed( bm_dis + rep0 - dis_slot - 1,
+                                               direct_bits );
+          else
+            {
+            rep0 += rdec.decode( direct_bits - dis_align_bits ) << dis_align_bits;
+            rep0 += rdec.decode_tree_reversed( bm_align, dis_align_bits );
+            if( rep0 == 0xFFFFFFFFU )		// Marker found
+              {
+              flush_data();
+              return ( len == min_match_len );	// End Of Stream marker
+              }
+            }
+          }
+        state.set_match();
+        if( rep0 >= dictionary_size || ( rep0 >= pos && !partial_data_pos ) )
+          return false;
+        }
+      for( int i = 0; i < len; ++i )
+        put_byte( get_byte( rep0 ) );
+      }
+    }
+  return false;
+  }
+
+
+enum { min_dictionary_size = 1 << 12,
+       max_dictionary_size = 1 << 29 };
+
+typedef uint8_t File_header[6];	// 0-3 magic, 4 version, 5 coded_dict_size
+
+typedef uint8_t File_trailer[20];
+			//  0-3  CRC32 of the uncompressed data
+			//  4-11 size of the uncompressed data
+			// 12-19 member size including header and trailer
+
+
+/*  Return values: 0 for a normal exit, 1 for environmental problems
+    (file not found, invalid flags, I/O errors, etc), 2 to indicate a
+    corrupt or invalid input file. */
+
+int main( const int argc, const char * const argv[] )
+  {
+  if( argc > 1 )
+    {
+    std::printf( "Lzd %s - Educational decompressor for lzip files.\n",
+                 PROGVERSION );
+    std::printf( "Study the source to learn how a simple lzip decompressor works.\n"
+                 "It is not safe to use it for any real work.\n"
+                 "\nUsage: %s < file.lz > file\n", argv[0] );
+    std::printf( "Lzd decompresses from standard input to standard output.\n"
+                 "\nCopyright (C) 2013 Antonio Diaz Diaz.\n"
+                 "This is free software: you are free to change and redistribute it.\n"
+                 "There is NO WARRANTY, to the extent permitted by law.\n"
+                 "Report bugs to lzip-bug@nongnu.org\n"
+                 "Lzip home page: http://www.nongnu.org/lzip/lzip.html\n" );
+    return 0;
+    }
+
+  if( isatty( STDIN_FILENO ) )
+    {
+    std::fprintf( stderr, "I won't read compressed data from a terminal.\n"
+                          "Try '%s --help' for more information.\n", argv[0] );
+    return 1;
+    }
+
+  for( bool first_member = true; ; first_member = false )
+    {
+    File_header header;
+    for( int i = 0; i < 6; ++i )
+      header[i] = std::getc( stdin );
+    if( std::feof( stdin ) || std::memcmp( header, "LZIP", 4 ) != 0 )
+      {
+      if( first_member )
+        { std::fprintf( stderr, "Bad magic number (file not in lzip format)\n" );
+          return 2; }
+      break;
+      }
+    if( header[4] != 1 )
+      {
+      std::fprintf( stderr, "Version %d member format not supported.\n",
+                    header[4] );
+      return 2;
+      }
+    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" );
+        return 2; }
+
+    LZ_decoder decoder( dict_size );
+    if( !decoder.decode_member() )
+      { std::fprintf( stderr, "Data error\n" ); return 2; }
+
+    File_trailer trailer;
+    for( int i = 0; i < 20; ++i ) trailer[i] = std::getc( stdin );
+    unsigned crc = 0;
+    for( int i = 3; i >= 0; --i ) { crc <<= 8; crc += trailer[i]; }
+    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; }
+    }
+
+  if( std::fclose( stdout ) != 0 )
+    { std::fprintf( stderr, "Can't close stdout: %s\n", std::strerror( errno ) );
+      return 1; }
+  return 0;
+  }
+@end verbatim
+
+
 @node Concept Index
 @unnumbered Concept Index
 
diff --git a/encoder.cc b/encoder.cc
index 2e00c3d..3387bbf 100644
--- a/encoder.cc
+++ b/encoder.cc
@@ -416,7 +416,7 @@ int LZ_encoder::sequence_optimizer( const int reps[num_rep_distances],
     if( replens[rep] < min_match_len ) continue;
     const int price = rep_match_price + price_rep( rep, state, pos_state );
     for( int len = min_match_len; len <= replens[rep]; ++len )
-      trials[len].update( price + rep_match_len_encoder.price( len, pos_state ),
+      trials[len].update( price + rep_len_encoder.price( len, pos_state ),
                           rep, 0 );
     }
 
@@ -586,8 +586,7 @@ int LZ_encoder::sequence_optimizer( const int reps[num_rep_distances],
         trials[++num_trials].price = infinite_price;
       int price = rep_match_price + price_rep( rep, cur_state, pos_state );
       for( int i = min_match_len; i <= len; ++i )
-        trials[cur+i].update( price +
-                              rep_match_len_encoder.price( i, pos_state ),
+        trials[cur+i].update( price + rep_len_encoder.price( i, pos_state ),
                               rep, cur );
 
       if( rep == 0 ) start_len = len + 1;	// discard shorter matches
@@ -602,7 +601,7 @@ int LZ_encoder::sequence_optimizer( const int reps[num_rep_distances],
 
       int pos_state2 = ( pos_state + len ) & pos_state_mask;
       State state2 = cur_state; state2.set_rep();
-      price += rep_match_len_encoder.price( len, pos_state ) +
+      price += rep_len_encoder.price( len, pos_state ) +
                price0( bm_match[state2()][pos_state2] ) +
                price_matched( data[len-1], data[len], data[len-dis] );
       pos_state2 = ( pos_state2 + 1 ) & pos_state_mask;
@@ -750,7 +749,7 @@ bool LZ_encoder::encode_member( const unsigned long long member_size )
           if( len == 1 ) state.set_short_rep();
           else
             {
-            rep_match_len_encoder.encode( range_encoder, len, pos_state );
+            rep_len_encoder.encode( range_encoder, len, pos_state );
             state.set_rep();
             }
           }
diff --git a/encoder.h b/encoder.h
index da83a3c..d3f3e77 100644
--- a/encoder.h
+++ b/encoder.h
@@ -113,9 +113,9 @@ inline int price_symbol_reversed( const Bit_model bm[], int symbol,
   for( int i = num_bits; i > 0; --i )
     {
     const int bit = symbol & 1;
-    symbol >>= 1;
     price += price_bit( bm[model], bit );
     model = ( model << 1 ) | bit;
+    symbol >>= 1;
     }
   return price;
   }
@@ -372,13 +372,8 @@ public:
   };
 
 
-class Len_encoder
+class Len_encoder : public Len_model
   {
-  Bit_model choice1;
-  Bit_model choice2;
-  Bit_model bm_low[pos_states][len_low_symbols];
-  Bit_model bm_mid[pos_states][len_mid_symbols];
-  Bit_model bm_high[len_high_symbols];
   int prices[pos_states][max_len_symbols];
   const int len_symbols;
   int counters[pos_states];
@@ -438,8 +433,8 @@ protected:
   Bit_model bm_align[dis_align_size];
 
   Range_encoder range_encoder;
-  Len_encoder len_encoder;
-  Len_encoder rep_match_len_encoder;
+  Len_encoder match_len_encoder;
+  Len_encoder rep_len_encoder;
 
   const int num_dis_slots;
 
@@ -450,8 +445,8 @@ protected:
     :
     crc_( 0xFFFFFFFFU ),
     range_encoder( outfd ),
-    len_encoder( match_len_limit ),
-    rep_match_len_encoder( match_len_limit ),
+    match_len_encoder( match_len_limit ),
+    rep_len_encoder( match_len_limit ),
     num_dis_slots( 2 * real_bits( dictionary_size - 1 ) )
     {
     for( int i = 0; i < File_header::size; ++i )
@@ -492,7 +487,7 @@ protected:
 
   void encode_pair( const uint32_t dis, const int len, const int pos_state )
     {
-    len_encoder.encode( range_encoder, len, pos_state );
+    match_len_encoder.encode( range_encoder, len, pos_state );
     const int dis_slot = get_slot( dis );
     range_encoder.encode_tree( bm_dis_slot[get_dis_state(len)], dis_slot, dis_slot_bits );
 
@@ -598,7 +593,7 @@ class LZ_encoder : public LZ_encoder_base
   int price_rep0_len( const int len, const State state, const int pos_state ) const
     {
     return price_rep( 0, state, pos_state ) +
-           rep_match_len_encoder.price( len, pos_state );
+           rep_len_encoder.price( len, pos_state );
     }
 
   int price_dis( const int dis, const int dis_state ) const
@@ -612,7 +607,7 @@ class LZ_encoder : public LZ_encoder_base
 
   int price_pair( const int dis, const int len, const int pos_state ) const
     {
-    return len_encoder.price( len, pos_state ) +
+    return match_len_encoder.price( len, pos_state ) +
            price_dis( dis, get_dis_state( len ) );
     }
 
diff --git a/fast_encoder.cc b/fast_encoder.cc
index 954e671..fc5f891 100644
--- a/fast_encoder.cc
+++ b/fast_encoder.cc
@@ -169,7 +169,7 @@ bool FLZ_encoder::encode_member( const unsigned long long member_size )
         if( dis > 1 )
           range_encoder.encode_bit( bm_rep2[state()], dis > 2 );
         }
-      rep_match_len_encoder.encode( range_encoder, len, pos_state );
+      rep_len_encoder.encode( range_encoder, len, pos_state );
       state.set_rep();
       move_pos( len );
       continue;
diff --git a/lzip.h b/lzip.h
index 77aa73e..ffa2fb3 100644
--- a/lzip.h
+++ b/lzip.h
@@ -85,6 +85,15 @@ struct Bit_model
   Bit_model() : probability( bit_model_total / 2 ) {}
   };
 
+struct Len_model
+  {
+  Bit_model choice1;
+  Bit_model choice2;
+  Bit_model bm_low[pos_states][len_low_symbols];
+  Bit_model bm_mid[pos_states][len_mid_symbols];
+  Bit_model bm_high[len_high_symbols];
+  };
+
 
 class Pretty_print
   {
diff --git a/main.cc b/main.cc
index 068ca62..bd9bda0 100644
--- a/main.cc
+++ b/main.cc
@@ -160,8 +160,9 @@ void show_header( const File_header & header )
   for( int i = 0; i < 8 && ( num > 9999 || ( exact && num >= factor ) ); ++i )
     { num /= factor; if( num % factor != 0 ) exact = false;
       p = prefix[i]; np = ""; }
-  std::fprintf( stderr, "version %d, dictionary size %s%4u %sB.  ",
-                header.version(), np, num, p );
+  if( verbosity >= 4 )
+    std::fprintf( stderr, "version %d, ", header.version() );
+  std::fprintf( stderr, "dictionary size %s%4u %sB.  ", np, num, p );
   }
 
 
@@ -754,6 +755,7 @@ int main( const int argc, const char * const argv[] )
     { 'h', "help",            Arg_parser::no  },
     { 'k', "keep",            Arg_parser::no  },
     { 'm', "match-length",    Arg_parser::yes },
+    { 'n', "threads",         Arg_parser::yes },
     { 'o', "output",          Arg_parser::yes },
     { 'q', "quiet",           Arg_parser::no  },
     { 's', "dictionary-size", Arg_parser::yes },
@@ -790,6 +792,7 @@ int main( const int argc, const char * const argv[] )
       case 'm': encoder_options.match_len_limit =
                   getnum( arg, min_match_len_limit, max_match_len );
                 zero = false; break;
+      case 'n': break;
       case 'o': default_output_filename = arg; break;
       case 'q': verbosity = -1; break;
       case 's': encoder_options.dictionary_size = get_dict_size( arg );