Adding upstream version 1.17~rc1.upstream/1.17_rc1

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

27 files changed, 625 insertions, 241 deletions

diff --git a/ChangeLog b/ChangeLog
index 98719e2..d6529ef 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,7 +1,14 @@
+2015-01-21  Antonio Diaz Diaz  <antonio@gnu.org>
+
+	* Version 1.17-rc1 released.
+	* repair.cc: Repair time has been reduced by 15%.
+	* Added new option '-y, --debug-delay'.
+	* Added new option '-z, --debug-repair'.
+
 2014-10-16  Antonio Diaz Diaz  <antonio@gnu.org>
 
 	* Version 1.17-pre1 released.
-	* merge.cc: New block selection algorithm makes merge much faster.
+	* New block selection algorithm makes merge up to 100 times faster.
 	* Makefile.in: Added new targets 'install*-compress'.
 	* testsuite/unzcrash.cc: Moved to top directory.
 	* Added chapter 'File names' to the manual.
@@ -9,7 +16,7 @@
 2014-08-29  Antonio Diaz Diaz  <antonio@gnu.org>
 
 	* Version 1.16 released.
-	* New class LZ_mtester makes repair much faster.
+	* New class LZ_mtester makes repair up to 10 times faster.
 	* main.cc (close_and_set_permissions): Behave like 'cp -p'.
 	* lziprecover.texinfo: Renamed to lziprecover.texi.
 	* License changed to GPL version 2 or later.
@@ -99,7 +106,7 @@
 	* testsuite/unzcrash.cc: Test all 1-byte errors.
 
 
-Copyright (C) 2009-2014 Antonio Diaz Diaz.
+Copyright (C) 2009-2015 Antonio Diaz Diaz.
 
 This file is a collection of facts, and thus it is not copyrightable,
 but just in case, you have unlimited permission to copy, distribute and
diff --git a/INSTALL b/INSTALL
index 4f27d5c..7ec0887 100644
--- a/INSTALL
+++ b/INSTALL
@@ -62,7 +62,7 @@ After running 'configure', you can run 'make' and 'make install' as
 explained above.
 
 
-Copyright (C) 2009-2014 Antonio Diaz Diaz.
+Copyright (C) 2009-2015 Antonio Diaz Diaz.
 
 This file is free documentation: you have unlimited permission to copy,
 distribute and modify it.
diff --git a/Makefile.in b/Makefile.in
index ae25dd6..d9c2033 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -6,8 +6,8 @@ INSTALL_DATA = $(INSTALL) -m 644
 INSTALL_DIR = $(INSTALL) -d -m 755
 SHELL = /bin/sh
 
-objs = arg_parser.o file_index.o merge.o mtester.o range_dec.o repair.o \
-       split.o decoder.o main.o
+objs = arg_parser.o block.o file_index.o merge.o mtester.o range_dec.o \
+       repair.o split.o decoder.o main.o
 unzobjs = arg_parser.o unzcrash.o
 
 
@@ -36,14 +36,15 @@ unzcrash.o : unzcrash.cc
 
 $(objs)      : Makefile
 arg_parser.o : arg_parser.h
+block.o      : block.h
 decoder.o    : lzip.h decoder.h
-file_index.o : lzip.h file_index.h
-main.o       : arg_parser.h lzip.h decoder.h
-merge.o      : lzip.h decoder.h file_index.h
+file_index.o : lzip.h block.h file_index.h
+main.o       : arg_parser.h lzip.h decoder.h block.h
+merge.o      : lzip.h decoder.h block.h file_index.h
 mtester.o    : lzip.h mtester.h
-range_dec.o  : lzip.h decoder.h file_index.h
-repair.o     : lzip.h file_index.h mtester.h
-split.o      : lzip.h
+range_dec.o  : lzip.h decoder.h block.h file_index.h
+repair.o     : lzip.h mtester.h block.h file_index.h
+split.o      : lzip.h block.h file_index.h
 unzcrash.o   : arg_parser.h Makefile
 
 
diff --git a/NEWS b/NEWS
index da32c67..70fd3fd 100644
--- a/NEWS
+++ b/NEWS
@@ -6,6 +6,14 @@ magnitude faster depending on number of files and number of errors.
 Please, report as a bug any files correctly merged by lziprecover 1.16
 that this version can't merge.
 
+Repair time has been reduced by 15%.
+
+The new option "-y, --debug-delay", which finds the max error detection
+delay in a given range of positions, has been added.
+
+The new option "-z, --debug-repair", which test repairs a one-byte error
+at a given position, has been added.
+
 The targets "install-compress", "install-strip-compress",
 "install-info-compress" and "install-man-compress" have been added to
 the Makefile.
diff --git a/README b/README
index c457365..d660810 100644
--- a/README
+++ b/README
@@ -75,7 +75,7 @@ unzcrash.c from Julian Seward's bzip2. Type 'make unzcrash' in the
 lziprecover source directory to build it. Then try 'unzcrash --help'.
 
 
-Copyright (C) 2009-2014 Antonio Diaz Diaz.
+Copyright (C) 2009-2015 Antonio Diaz Diaz.
 
 This file is free documentation: you have unlimited permission to copy,
 distribute and modify it.
diff --git a/arg_parser.cc b/arg_parser.cc
index 74f9298..55764bd 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) 2006-2014 Antonio Diaz Diaz.
+    Copyright (C) 2006-2015 Antonio Diaz Diaz.
 
     This library is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
diff --git a/arg_parser.h b/arg_parser.h
index d80c353..2e8731c 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) 2006-2014 Antonio Diaz Diaz.
+    Copyright (C) 2006-2015 Antonio Diaz Diaz.
 
     This library is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
diff --git a/block.cc b/block.cc
new file mode 100644
index 0000000..31e82c7
--- /dev/null
+++ b/block.cc
@@ -0,0 +1,33 @@
+/*  Lziprecover - Data recovery tool for the lzip format
+    Copyright (C) 2009-2015 Antonio Diaz Diaz.
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <string>
+#include <vector>
+
+#include "block.h"
+
+
+Block Block::split( const long long pos )
+  {
+  if( pos > pos_ && pos < end() )
+    {
+    const Block b( pos_, pos - pos_ );
+    pos_ = pos; size_ -= b.size_;
+    return b;
+    }
+  return Block( 0, 0 );
+  }
diff --git a/block.h b/block.h
new file mode 100644
index 0000000..4b2ab39
--- /dev/null
+++ b/block.h
@@ -0,0 +1,62 @@
+/*  Lziprecover - Data recovery tool for the lzip format
+    Copyright (C) 2009-2015 Antonio Diaz Diaz.
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef INT64_MAX
+#define INT64_MAX  0x7FFFFFFFFFFFFFFFLL
+#endif
+
+
+class Block
+  {
+  long long pos_, size_;		// pos + size <= INT64_MAX
+
+public:
+  Block( const long long p, const long long s ) : pos_( p ), size_( s ) {}
+
+  long long pos() const { return pos_; }
+  long long size() const { return size_; }
+  long long end() const { return pos_ + size_; }
+
+  void pos( const long long p ) { pos_ = p; }
+  void size( const long long s ) { size_ = s; }
+
+  bool operator==( const Block & b ) const
+    { return pos_ == b.pos_ && size_ == b.size_; }
+  bool operator!=( const Block & b ) const
+    { return pos_ != b.pos_ || size_ != b.size_; }
+
+  bool operator<( const Block & b ) const { return pos_ < b.pos_; }
+
+  bool includes( const long long pos ) const
+    { return ( pos_ <= pos && end() > pos ); }
+  bool overlaps( const Block & b ) const
+    { return ( pos_ < b.end() && b.pos_ < end() ); }
+
+  void shift( Block & b ) { ++size_; ++b.pos_; --b.size_; }
+  Block split( const long long pos );
+  };
+
+
+// defined in range_dec.cc
+int range_decompress( const std::string & input_filename,
+                      const std::string & output_filename,
+                      Block range, const int verbosity, const bool force,
+                      const bool ignore, const bool to_stdout );
+
+// defined in repair.cc
+int debug_delay( const std::string & input_filename, Block range,
+                 const int verbosity );
diff --git a/configure b/configure
index 5cba27a..747b3a9 100755
--- a/configure
+++ b/configure
@@ -1,12 +1,12 @@
 #! /bin/sh
 # configure script for Lziprecover - Data recovery tool for the lzip format
-# Copyright (C) 2009-2014 Antonio Diaz Diaz.
+# Copyright (C) 2009-2015 Antonio Diaz Diaz.
 #
 # This configure script is free software: you have unlimited permission
 # to copy, distribute and modify it.
 
 pkgname=lziprecover
-pkgversion=1.17-pre1
+pkgversion=1.17-rc1
 progname=lziprecover
 srctrigger=doc/${pkgname}.texi
 
@@ -165,7 +165,7 @@ echo "LDFLAGS = ${LDFLAGS}"
 rm -f Makefile
 cat > Makefile << EOF
 # Makefile for Lziprecover - Data recovery tool for the lzip format
-# Copyright (C) 2009-2014 Antonio Diaz Diaz.
+# Copyright (C) 2009-2015 Antonio Diaz Diaz.
 # This file was generated automatically by configure. Do not edit.
 #
 # This Makefile is free software: you have unlimited permission
diff --git a/decoder.cc b/decoder.cc
index f7e8f54..59587e0 100644
--- a/decoder.cc
+++ b/decoder.cc
@@ -1,5 +1,5 @@
 /*  Lziprecover - Data recovery tool for the lzip format
-    Copyright (C) 2009-2014 Antonio Diaz Diaz.
+    Copyright (C) 2009-2015 Antonio Diaz Diaz.
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
diff --git a/decoder.h b/decoder.h
index 740d7b2..6d8c919 100644
--- a/decoder.h
+++ b/decoder.h
@@ -1,5 +1,5 @@
 /*  Lziprecover - Data recovery tool for the lzip format
-    Copyright (C) 2009-2014 Antonio Diaz Diaz.
+    Copyright (C) 2009-2015 Antonio Diaz Diaz.
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
diff --git a/doc/lziprecover.1 b/doc/lziprecover.1
index 7eefb7a..c2f55d7 100644
--- a/doc/lziprecover.1
+++ b/doc/lziprecover.1
@@ -1,5 +1,5 @@
 .\" DO NOT MODIFY THIS FILE!  It was generated by help2man 1.46.1.
-.TH LZIPRECOVER "1" "October 2014" "lziprecover 1.17-pre1" "User Commands"
+.TH LZIPRECOVER "1" "January 2015" "lziprecover 1.17-rc1" "User Commands"
 .SH NAME
 lziprecover \- recovers data from damaged lzip files
 .SH SYNOPSIS
@@ -7,6 +7,7 @@ lziprecover \- recovers data from damaged lzip files
 [\fI\,options\/\fR] [\fI\,files\/\fR]
 .SH DESCRIPTION
 Lziprecover \- Data recovery tool and decompressor for the lzip format.
+.PP
 Lziprecover can repair perfectly most files with small errors (up to one
 single\-byte error per member), without the need of any extra redundance
 at all. Losing an entire archive just because of a corrupt byte near the
@@ -76,7 +77,7 @@ Report bugs to lzip\-bug@nongnu.org
 .br
 Lziprecover home page: http://www.nongnu.org/lzip/lziprecover.html
 .SH COPYRIGHT
-Copyright \(co 2014 Antonio Diaz Diaz.
+Copyright \(co 2015 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/lziprecover.info b/doc/lziprecover.info
index 6c636e8..05c1196 100644
--- a/doc/lziprecover.info
+++ b/doc/lziprecover.info
@@ -12,12 +12,13 @@ File: lziprecover.info,  Node: Top,  Next: Introduction,  Up: (dir)
 Lziprecover Manual
 ******************
 
-This manual is for Lziprecover (version 1.17-pre1, 16 October 2014).
+This manual is for Lziprecover (version 1.17-rc1, 21 January 2015).
 
 * Menu:
 
 * Introduction::           Purpose and features of lziprecover
 * Invoking lziprecover::   Command line interface
+* Data safety::            Protecting data from accidental loss
 * Repairing files::        Fixing bit-flip and similar errors
 * Merging files::          Fixing several damaged copies
 * File names::             Names of the files produced by lziprecover
@@ -28,7 +29,7 @@ This manual is for Lziprecover (version 1.17-pre1, 16 October 2014).
 * Concept index::          Index of concepts
 
 
-   Copyright (C) 2009-2014 Antonio Diaz Diaz.
+   Copyright (C) 2009-2015 Antonio Diaz Diaz.
 
    This manual is free documentation: you have unlimited permission to
 copy, distribute and modify it.
@@ -104,7 +105,7 @@ like lzip or lunzip.
 line of defense for the case where the backups are also damaged.
 
 
-File: lziprecover.info,  Node: Invoking lziprecover,  Next: Repairing files,  Prev: Introduction,  Up: Top
+File: lziprecover.info,  Node: Invoking lziprecover,  Next: Data safety,  Prev: Introduction,  Up: Top
 
 2 Invoking lziprecover
 **********************
@@ -252,20 +253,66 @@ invalid input file, 3 for an internal consistency error (eg, bug) which
 caused lziprecover to panic.
 
 
-File: lziprecover.info,  Node: Repairing files,  Next: Merging files,  Prev: Invoking lziprecover,  Up: Top
+File: lziprecover.info,  Node: Data safety,  Next: Repairing files,  Prev: Invoking lziprecover,  Up: Top
 
-3 Repairing files
+3 Protecting data from accidental loss
+**************************************
+
+There are 3 main types of data corruption that may cause data loss:
+single-byte errors, multi-byte errors (generally affecting a whole
+sector in a block device), and total device failure.
+
+   Lziprecover protects natively against single-byte errors (*note
+Repairing files::), as long as file integrity is checked frequently
+enough that a second single-byte error does not develop in the same
+member before the first one is repaired.
+
+   Lziprecover also protects against multi-byte errors (*note Merging
+files::), if at least one backup copy of the file is made.
+
+   The only remedy for total device failure is storing backup copies in
+separate media.
+
+   How does lzip compare with gzip and bzip2 with respect to data
+safety?  Lets suppose that you made a backup copy of your valuable
+scientific data, compressed it, and stored two copies on separate
+media. Years later you notice that both copies are corrupt.
+
+   If you compressed with gzip and both copies suffer any damage in the
+data stream, even if it is just one altered bit, the original data can't
+be recovered.
+
+   If you used bzip2, and if the file is large enough to contain more
+than one compressed data block (usually larger than 900 kB), and if no
+block is damaged in both files, then the data can be manually recovered
+by splitting the files with bzip2recover, verifying every block and then
+copying the right blocks in the right order in another file.
+
+   But if you used lzip, the data can be automatically recovered as
+long as no byte is damaged in both files.
+
+   Note that each error in a bzip2 file makes a whole block unusable,
+but each error in a lzip file only affects the damaged bytes, making it
+possible to recover a file with thousands of errors.
+
+
+File: lziprecover.info,  Node: Repairing files,  Next: Merging files,  Prev: Data safety,  Up: Top
+
+4 Repairing files
 *****************
 
 Lziprecover can repair perfectly most files with small errors (up to one
 single-byte error per member), without the need of any extra redundance
 at all. If the reparation is successful, the repaired file will be
-identical bit for bit to the original.
+identical bit for bit to the original. This makes lzip files resistant
+to bit-flip, one of the most common forms of data corruption.
 
    The error may be located anywhere in the file except in the header
 (first 6 bytes of each member) or in the 'Member size' field of the
-trailer (last 8 bytes of each member). This makes lzip files resistant
-to bit-flip, one of the most common forms of data corruption.
+trailer (last 8 bytes of each member). If the error is in the header it
+can be easily repaired with a text editor like GNU Moe (*note File
+format::). If the error is in the member size, it is enough to ignore
+the message about 'bad member size' when decompressing.
 
    Bit-flip happens when one bit in the file is changed from 0 to 1 or
 vice versa. It may be caused by bad RAM or even by natural radiation. I
@@ -289,7 +336,7 @@ lziprecover repairs more efficiently the worst errors.
 
 File: lziprecover.info,  Node: Merging files,  Next: File names,  Prev: Repairing files,  Up: Top
 
-4 Merging files
+5 Merging files
 ***************
 
 If you have several copies of a file but all of them are too damaged to
@@ -330,7 +377,7 @@ errors are randomly located inside each copy).
 
 File: lziprecover.info,  Node: File names,  Next: File format,  Prev: Merging files,  Up: Top
 
-5 Names of the files produced by lziprecover
+6 Names of the files produced by lziprecover
 ********************************************
 
 The name of the fixed file produced by '--merge' and '--repair' is made
@@ -341,7 +388,7 @@ original file name ends with one of the extensions '.tar.lz', '.lz' or
 
 File: lziprecover.info,  Node: File format,  Next: Examples,  Prev: File names,  Up: Top
 
-6 File format
+7 File format
 *************
 
 Perfection is reached, not when there is no longer anything to add, but
@@ -414,7 +461,7 @@ additional information before, between, or after them.
 
 File: lziprecover.info,  Node: Examples,  Next: Unzcrash,  Prev: File format,  Up: Top
 
-7 A small tutorial with examples
+8 A small tutorial with examples
 ********************************
 
 Example 1: Restore a regular file from its compressed version
@@ -485,7 +532,7 @@ correct file produced is saved in 'big_db_00001.lz'.
 
 File: lziprecover.info,  Node: Unzcrash,  Next: Problems,  Prev: Examples,  Up: Top
 
-8 Testing the robustness of decompressors
+9 Testing the robustness of decompressors
 *****************************************
 
 The lziprecover package also includes unzcrash, a program written to
@@ -562,8 +609,8 @@ caused unzcrash to panic.
 
 File: lziprecover.info,  Node: Problems,  Next: Concept index,  Prev: Unzcrash,  Up: Top
 
-9 Reporting bugs
-****************
+10 Reporting bugs
+*****************
 
 There are probably bugs in lziprecover. There are certainly errors and
 omissions in this manual. If you report them, they will get fixed. If
@@ -584,6 +631,7 @@ Concept index
 * Menu:
 
 * bugs:                                  Problems.              (line 6)
+* data safety:                           Data safety.           (line 6)
 * examples:                              Examples.              (line 6)
 * file format:                           File format.           (line 6)
 * file names:                            File names.            (line 6)
@@ -598,17 +646,18 @@ Concept index
 
 Tag Table:
 Node: Top231
-Node: Introduction1153
-Node: Invoking lziprecover4249
-Node: Repairing files9686
-Node: Merging files11371
-Node: File names13212
-Node: File format13676
-Node: Examples16183
-Ref: ddrescue-example17384
-Node: Unzcrash18493
-Node: Problems21047
-Node: Concept index21597
+Node: Introduction1216
+Node: Invoking lziprecover4312
+Node: Data safety9745
+Node: Repairing files11661
+Node: Merging files13563
+Node: File names15404
+Node: File format15868
+Node: Examples18375
+Ref: ddrescue-example19576
+Node: Unzcrash20685
+Node: Problems23239
+Node: Concept index23791
 
 End Tag Table
 
diff --git a/doc/lziprecover.texi b/doc/lziprecover.texi
index 08d4312..85f0385 100644
--- a/doc/lziprecover.texi
+++ b/doc/lziprecover.texi
@@ -6,8 +6,8 @@
 @finalout
 @c %**end of header
 
-@set UPDATED 16 October 2014
-@set VERSION 1.17-pre1
+@set UPDATED 21 January 2015
+@set VERSION 1.17-rc1
 
 @dircategory Data Compression
 @direntry
@@ -37,6 +37,7 @@ This manual is for Lziprecover (version @value{VERSION}, @value{UPDATED}).
 @menu
 * Introduction::           Purpose and features of lziprecover
 * Invoking lziprecover::   Command line interface
+* Data safety::            Protecting data from accidental loss
 * Repairing files::        Fixing bit-flip and similar errors
 * Merging files::          Fixing several damaged copies
 * File names::             Names of the files produced by lziprecover
@@ -48,7 +49,7 @@ This manual is for Lziprecover (version @value{VERSION}, @value{UPDATED}).
 @end menu
 
 @sp 1
-Copyright @copyright{} 2009-2014 Antonio Diaz Diaz.
+Copyright @copyright{} 2009-2015 Antonio Diaz Diaz.
 
 This manual is free documentation: you have unlimited permission
 to copy, distribute and modify it.
@@ -281,6 +282,48 @@ invalid input file, 3 for an internal consistency error (eg, bug) which
 caused lziprecover to panic.
 
 
+@node Data safety
+@chapter Protecting data from accidental loss
+@cindex data safety
+
+There are 3 main types of data corruption that may cause data loss:
+single-byte errors, multi-byte errors (generally affecting a whole
+sector in a block device), and total device failure.
+
+Lziprecover protects natively against single-byte errors
+(@pxref{Repairing files}), as long as file integrity is checked
+frequently enough that a second single-byte error does not develop in
+the same member before the first one is repaired.
+
+Lziprecover also protects against multi-byte errors (@pxref{Merging
+files}), if at least one backup copy of the file is made.
+
+The only remedy for total device failure is storing backup copies in
+separate media.
+
+How does lzip compare with gzip and bzip2 with respect to data safety?
+Lets suppose that you made a backup copy of your valuable scientific
+data, compressed it, and stored two copies on separate media. Years
+later you notice that both copies are corrupt.
+
+If you compressed with gzip and both copies suffer any damage in the
+data stream, even if it is just one altered bit, the original data can't
+be recovered.
+
+If you used bzip2, and if the file is large enough to contain more than
+one compressed data block (usually larger than 900 kB), and if no block
+is damaged in both files, then the data can be manually recovered by
+splitting the files with bzip2recover, verifying every block and then
+copying the right blocks in the right order in another file.
+
+But if you used lzip, the data can be automatically recovered as long as
+no byte is damaged in both files.
+
+Note that each error in a bzip2 file makes a whole block unusable, but
+each error in a lzip file only affects the damaged bytes, making it
+possible to recover a file with thousands of errors.
+
+
 @node Repairing files
 @chapter Repairing files
 @cindex repairing files
@@ -288,12 +331,15 @@ caused lziprecover to panic.
 Lziprecover can repair perfectly most files with small errors (up to one
 single-byte error per member), without the need of any extra redundance
 at all. If the reparation is successful, the repaired file will be
-identical bit for bit to the original.
+identical bit for bit to the original. This makes lzip files resistant
+to bit-flip, one of the most common forms of data corruption.
 
 The error may be located anywhere in the file except in the header
 (first 6 bytes of each member) or in the @samp{Member size} field of the
-trailer (last 8 bytes of each member). This makes lzip files resistant
-to bit-flip, one of the most common forms of data corruption.
+trailer (last 8 bytes of each member). If the error is in the header it
+can be easily repaired with a text editor like GNU Moe (@pxref{File
+format}). If the error is in the member size, it is enough to ignore the
+message about @samp{bad member size} when decompressing.
 
 Bit-flip happens when one bit in the file is changed from 0 to 1 or vice
 versa. It may be caused by bad RAM or even by natural radiation. I have
@@ -641,7 +687,7 @@ for all eternity, if not longer.
 
 If you find a bug in lziprecover, please send electronic mail to
 @email{lzip-bug@@nongnu.org}. Include the version number, which you can
-find by running @w{@samp{lziprecover --version}}.
+find by running @w{@code{lziprecover --version}}.
 
 
 @node Concept index
diff --git a/file_index.cc b/file_index.cc
index f7e1cd0..de685a3 100644
--- a/file_index.cc
+++ b/file_index.cc
@@ -1,5 +1,5 @@
 /*  Lziprecover - Data recovery tool for the lzip format
-    Copyright (C) 2009-2014 Antonio Diaz Diaz.
+    Copyright (C) 2009-2015 Antonio Diaz Diaz.
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -25,6 +25,7 @@
 #include <unistd.h>
 
 #include "lzip.h"
+#include "block.h"
 #include "file_index.h"
 
 
@@ -37,18 +38,6 @@ int seek_read( const int fd, uint8_t * const buf, const int size,
   }
 
 
-Block Block::split( const long long pos )
-  {
-  if( pos > pos_ && pos < end() )
-    {
-    const Block b( pos_, pos - pos_ );
-    pos_ = pos; size_ -= b.size_;
-    return b;
-    }
-  return Block( 0, 0 );
-  }
-
-
 void File_index::set_errno_error( const char * const msg )
   {
   error_ = msg; error_ += std::strerror( errno ); error_ += '.';
diff --git a/file_index.h b/file_index.h
index cf42d83..eff1157 100644
--- a/file_index.h
+++ b/file_index.h
@@ -1,5 +1,5 @@
 /*  Lziprecover - Data recovery tool for the lzip format
-    Copyright (C) 2009-2014 Antonio Diaz Diaz.
+    Copyright (C) 2009-2015 Antonio Diaz Diaz.
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -15,39 +15,6 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-#ifndef INT64_MAX
-#define INT64_MAX  0x7FFFFFFFFFFFFFFFLL
-#endif
-
-
-class Block
-  {
-  long long pos_, size_;		// pos + size <= INT64_MAX
-
-public:
-  Block( const long long p, const long long s ) : pos_( p ), size_( s ) {}
-
-  long long pos() const { return pos_; }
-  long long size() const { return size_; }
-  long long end() const { return pos_ + size_; }
-
-  void pos( const long long p ) { pos_ = p; }
-  void size( const long long s ) { size_ = s; }
-
-  bool operator==( const Block & b ) const
-    { return pos_ == b.pos_ && size_ == b.size_; }
-  bool operator!=( const Block & b ) const
-    { return pos_ != b.pos_ || size_ != b.size_; }
-
-  bool operator<( const Block & b ) const { return pos_ < b.pos_; }
-
-  bool overlaps( const Block & b ) const
-    { return ( pos_ < b.end() && b.pos_ < end() ); }
-  void shift( Block & b ) { ++size_; ++b.pos_; --b.size_; }
-  Block split( const long long pos );
-  };
-
-
 class File_index
   {
   struct Member
diff --git a/lzip.h b/lzip.h
index 61c0445..58de55f 100644
--- a/lzip.h
+++ b/lzip.h
@@ -1,5 +1,5 @@
 /*  Lziprecover - Data recovery tool for the lzip format
-    Copyright (C) 2009-2014 Antonio Diaz Diaz.
+    Copyright (C) 2009-2015 Antonio Diaz Diaz.
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -309,18 +309,19 @@ int merge_files( const std::vector< std::string > & filenames,
                  const bool force );
 
 // defined in range_dec.cc
+const char * format_num( unsigned long long num,
+                         unsigned long long limit = -1ULL,
+                         const int set_prefix = 0 );
 bool safe_seek( const int fd, const long long pos );
 int list_files( const std::vector< std::string > & filenames,
                 const int verbosity );
-int range_decompress( const std::string & input_filename,
-                      const std::string & default_output_filename,
-                      const std::string & range_string, const int verbosity,
-                      const bool force, const bool ignore, const bool to_stdout );
 
 // defined in repair.cc
 int repair_file( const std::string & input_filename,
                  const std::string & output_filename, const int verbosity,
                  const bool force );
+int debug_repair( const std::string & input_filename, const long long bad_pos,
+                  const int verbosity, const uint8_t bad_value );
 
 // defined in split.cc
 int split_file( const std::string & input_filename,
diff --git a/main.cc b/main.cc
index 167e8c6..192f32b 100644
--- a/main.cc
+++ b/main.cc
@@ -1,5 +1,5 @@
 /*  Lziprecover - Data recovery tool for the lzip format
-    Copyright (C) 2009-2014 Antonio Diaz Diaz.
+    Copyright (C) 2009-2015 Antonio Diaz Diaz.
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -55,6 +55,7 @@
 #include "arg_parser.h"
 #include "lzip.h"
 #include "decoder.h"
+#include "block.h"
 
 #ifndef O_BINARY
 #define O_BINARY 0
@@ -69,7 +70,7 @@ namespace {
 
 const char * const Program_name = "Lziprecover";
 const char * const program_name = "lziprecover";
-const char * const program_year = "2014";
+const char * const program_year = "2015";
 const char * invocation_name = 0;
 
 struct { const char * from; const char * to; } const known_extensions[] = {
@@ -77,8 +78,8 @@ struct { const char * from; const char * to; } const known_extensions[] = {
   { ".tlz", ".tar" },
   { 0,      0      } };
 
-enum Mode { m_none, m_decompress, m_list, m_merge, m_range, m_repair,
-            m_split, m_test };
+enum Mode { m_none, m_debug_delay, m_debug_repair, m_decompress, m_list,
+            m_merge, m_range_dec, m_repair, m_split, m_test };
 
 std::string output_filename;
 int outfd = -1;
@@ -92,7 +93,7 @@ bool delete_output_on_interrupt = false;
 void show_help()
   {
   std::printf( "%s - Data recovery tool and decompressor for the lzip format.\n", Program_name );
-  std::printf( "Lziprecover can repair perfectly most files with small errors (up to one\n"
+  std::printf( "\nLziprecover can repair perfectly most files with small errors (up to one\n"
                "single-byte error per member), without the need of any extra redundance\n"
                "at all. Losing an entire archive just because of a corrupt byte near the\n"
                "beginning is a thing of the past.\n"
@@ -116,8 +117,13 @@ void show_help()
                "  -R, --repair                    try to repair a small error in file\n"
                "  -s, --split                     split multi-member file in single-member files\n"
                "  -t, --test                      test compressed file integrity\n"
-               "  -v, --verbose                   be verbose (a 2nd -v gives more)\n"
-               "Numbers may be followed by a multiplier: k = kB = 10^3 = 1000,\n"
+               "  -v, --verbose                   be verbose (a 2nd -v gives more)\n" );
+  if( verbosity >= 1 )
+    {
+    std::printf( "  -y, --debug-delay=<range>       find max error detection delay in <range>\n"
+                 "  -z, --debug-repair=<pos>,<val>  test repair one-byte error at <pos>\n" );
+    }
+  std::printf( "Numbers may be followed by a multiplier: k = kB = 10^3 = 1000,\n"
                "Ki = KiB = 2^10 = 1024, M = 10^6, Mi = 2^20, G = 10^9, Gi = 2^30, etc...\n"
                "\nExit status: 0 for a normal exit, 1 for environmental problems (file\n"
                "not found, invalid flags, I/O errors, etc), 2 to indicate a corrupt or\n"
@@ -141,22 +147,109 @@ void show_version()
 
 void show_header( const File_header & header )
   {
-  const char * const prefix[8] =
-    { "Ki", "Mi", "Gi", "Ti", "Pi", "Ei", "Zi", "Yi" };
-  enum { factor = 1024 };
-  const char * p = "";
-  const char * np = "  ";
-  unsigned num = header.dictionary_size();
-  bool exact = ( num % factor == 0 );
-
-  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, "dictionary size %s%4u %sB.  ", np, num, p );
+  if( verbosity >= 3 )
+    {
+    const char * const prefix[8] =
+      { "Ki", "Mi", "Gi", "Ti", "Pi", "Ei", "Zi", "Yi" };
+    enum { factor = 1024 };
+    const char * p = "";
+    const char * np = "  ";
+    unsigned num = header.dictionary_size();
+    bool exact = ( num % factor == 0 );
+
+    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, "dictionary size %s%4u %sB.  ", np, num, p );
+    }
   }
 
 namespace {
 
+// Returns the number of chars read, or 0 if error.
+//
+int parse_long_long( const char * const ptr, long long & value )
+  {
+  char * tail;
+  errno = 0;
+  value = strtoll( ptr, &tail, 0 );
+  if( tail == ptr || errno || value < 0 ) return 0;
+  int c = tail - ptr;
+
+  if( ptr[c] )
+    {
+    const int factor = ( ptr[c+1] == 'i' ) ? 1024 : 1000;
+    int exponent = 0;
+    switch( ptr[c] )
+      {
+      case 'Y': exponent = 8; break;
+      case 'Z': exponent = 7; break;
+      case 'E': exponent = 6; break;
+      case 'P': exponent = 5; break;
+      case 'T': exponent = 4; break;
+      case 'G': exponent = 3; break;
+      case 'M': exponent = 2; break;
+      case 'K': if( factor == 1024 ) exponent = 1; else return 0; break;
+      case 'k': if( factor == 1000 ) exponent = 1; else return 0; break;
+      }
+    if( exponent > 0 )
+      {
+      ++c;
+      if( ptr[c] == 'i' ) { ++c; if( value ) format_num( 0, 0, -1 ); }
+      if( ptr[c] == 'B' ) ++c;
+      for( int i = 0; i < exponent; ++i )
+        {
+        if( INT64_MAX / factor >= value ) value *= factor;
+        else return 0;
+        }
+      }
+    }
+  return c;
+  }
+
+
+// Recognized formats: <begin> <begin>-<end> <begin>,<size>
+//
+void parse_range( const char * const ptr, Block & range )
+  {
+  long long value = 0;
+  int c = parse_long_long( ptr, value );		// pos
+  if( c && value >= 0 && value < INT64_MAX &&
+      ( ptr[c] == 0 || ptr[c] == ',' || ptr[c] == '-' ) )
+    {
+    range.pos( value );
+    if( ptr[c] == 0 ) { range.size( INT64_MAX - value ); return; }
+    const bool issize = ( ptr[c] == ',' );
+    c = parse_long_long( ptr + c + 1, value );		// size
+    if( c && value > 0 && ( issize || value > range.pos() ) )
+      {
+      if( !issize ) value -= range.pos();
+      if( INT64_MAX - range.pos() >= value ) { range.size( value ); return; }
+      }
+    }
+  show_error( "Bad decompression range.", 0, true );
+  std::exit( 1 );
+  }
+
+
+// Recognized format: <pos>,<value>
+//
+void parse_pos_value( const char * const ptr, long long & pos, uint8_t & value )
+  {
+  long long val = 0;
+  int c = parse_long_long( ptr, val );			// pos
+  if( c && val >= 0 && val < INT64_MAX && ptr[c] == ',' )
+    {
+    pos = val;
+    c = parse_long_long( ptr + c + 1, val );		// value
+    if( c && val >= 0 && val < 256 )
+      { value = val; return; }
+    }
+  show_error( "Bad file position or byte value.", 0, true );
+  std::exit( 1 );
+  }
+
+
 void one_file( const int files )
   {
   if( files != 1 )
@@ -400,7 +493,7 @@ int decompress( const int infd, const Pretty_print & pp, const bool testing )
         { pp( "Invalid dictionary size in member header." ); retval = 2; break; }
 
       if( verbosity >= 2 || ( verbosity == 1 && first_member ) )
-        { pp(); if( verbosity >= 3 ) show_header( header ); }
+        { pp(); show_header( header ); }
 
       LZ_decoder decoder( header, rdec, outfd );
       const int result = decoder.decode_member( pp );
@@ -504,12 +597,14 @@ void internal_error( const char * const msg )
 
 int main( const int argc, const char * const argv[] )
   {
+  Block range( 0, 0 );
+  long long bad_pos = 0;
   std::string input_filename;
   std::string default_output_filename;
-  std::string range_string;
   std::vector< std::string > filenames;
   int infd = -1;
   Mode program_mode = m_none;
+  uint8_t bad_value = 0;
   bool force = false;
   bool ignore = false;
   bool keep_input_files = false;
@@ -535,6 +630,8 @@ int main( const int argc, const char * const argv[] )
     { 't', "test",             Arg_parser::no  },
     { 'v', "verbose",          Arg_parser::no  },
     { 'V', "version",          Arg_parser::no  },
+    { 'y', "debug-delay",      Arg_parser::yes },
+    { 'z', "debug-repair",     Arg_parser::yes },
     {  0 ,  0,                 Arg_parser::no  } };
 
   const Arg_parser parser( argc, argv, options );
@@ -551,8 +648,8 @@ int main( const int argc, const char * const argv[] )
       {
       case 'c': to_stdout = true; break;
       case 'd': set_mode( program_mode, m_decompress ); break;
-      case 'D': set_mode( program_mode, m_range );
-                range_string = arg; break;
+      case 'D': set_mode( program_mode, m_range_dec );
+                parse_range( arg.c_str(), range ); break;
       case 'f': force = true; break;
       case 'h': show_help(); return 0;
       case 'i': ignore = true; break;
@@ -567,6 +664,10 @@ int main( const int argc, const char * const argv[] )
       case 't': set_mode( program_mode, m_test ); break;
       case 'v': if( verbosity < 4 ) ++verbosity; break;
       case 'V': show_version(); return 0;
+      case 'y': set_mode( program_mode, m_debug_delay );
+                parse_range( arg.c_str(), range ); break;
+      case 'z': set_mode( program_mode, m_debug_repair );
+                parse_pos_value( arg.c_str(), bad_pos, bad_value ); break;
       default : internal_error( "uncaught option." );
       }
     } // end process options
@@ -593,6 +694,12 @@ int main( const int argc, const char * const argv[] )
   switch( program_mode )
     {
     case m_none: internal_error( "invalid operation." ); break;
+    case m_debug_delay:
+      one_file( filenames.size() );
+      return debug_delay( filenames[0], range, verbosity );
+    case m_debug_repair:
+      one_file( filenames.size() );
+      return debug_repair( filenames[0], bad_pos, verbosity, bad_value );
     case m_decompress: break;
     case m_list:
       if( filenames.size() < 1 )
@@ -604,10 +711,10 @@ int main( const int argc, const char * const argv[] )
       if( default_output_filename.empty() )
         default_output_filename = insert_fixed( filenames[0] );
       return merge_files( filenames, default_output_filename, verbosity, force );
-    case m_range:
+    case m_range_dec:
       one_file( filenames.size() );
       return range_decompress( filenames[0], default_output_filename,
-                               range_string, verbosity, force, ignore, to_stdout );
+                               range, verbosity, force, ignore, to_stdout );
     case m_repair:
       one_file( filenames.size() );
       if( default_output_filename.empty() )
diff --git a/merge.cc b/merge.cc
index 5f034eb..36c2faf 100644
--- a/merge.cc
+++ b/merge.cc
@@ -1,5 +1,5 @@
 /*  Lziprecover - Data recovery tool for the lzip format
-    Copyright (C) 2009-2014 Antonio Diaz Diaz.
+    Copyright (C) 2009-2015 Antonio Diaz Diaz.
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -30,6 +30,7 @@
 
 #include "lzip.h"
 #include "decoder.h"
+#include "block.h"
 #include "file_index.h"
 
 
@@ -255,6 +256,7 @@ int open_input_files( const std::vector< std::string > & filenames,
   }
 
 
+     // merge block by block
 bool try_merge_member( const long long mpos, const long long msize,
                        const std::vector< Block > & block_vector,
                        const std::vector< int > & color_vector,
@@ -318,6 +320,7 @@ bool try_merge_member( const long long mpos, const long long msize,
   }
 
 
+     // merge a single block split at every possible position
 bool try_merge_member1( const long long mpos, const long long msize,
                         const std::vector< Block > & block_vector,
                         const std::vector< int > & color_vector,
diff --git a/mtester.cc b/mtester.cc
index 58a56ed..c23d51b 100644
--- a/mtester.cc
+++ b/mtester.cc
@@ -1,5 +1,5 @@
 /*  Lziprecover - Data recovery tool for the lzip format
-    Copyright (C) 2009-2014 Antonio Diaz Diaz.
+    Copyright (C) 2009-2015 Antonio Diaz Diaz.
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
diff --git a/mtester.h b/mtester.h
index 2896a44..f4da88f 100644
--- a/mtester.h
+++ b/mtester.h
@@ -1,5 +1,5 @@
 /*  Lziprecover - Data recovery tool for the lzip format
-    Copyright (C) 2009-2014 Antonio Diaz Diaz.
+    Copyright (C) 2009-2015 Antonio Diaz Diaz.
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
diff --git a/range_dec.cc b/range_dec.cc
index 0fa9708..8b4d6e0 100644
--- a/range_dec.cc
+++ b/range_dec.cc
@@ -1,5 +1,5 @@
 /*  Lziprecover - Data recovery tool for the lzip format
-    Copyright (C) 2009-2014 Antonio Diaz Diaz.
+    Copyright (C) 2009-2015 Antonio Diaz Diaz.
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -30,101 +30,12 @@
 
 #include "lzip.h"
 #include "decoder.h"
+#include "block.h"
 #include "file_index.h"
 
 
 namespace {
 
-const char * format_num( unsigned long long num,
-                         unsigned long long limit = -1ULL,
-                         const int set_prefix = 0 )
-  {
-  const char * const si_prefix[8] =
-    { "k", "M", "G", "T", "P", "E", "Z", "Y" };
-  const char * const binary_prefix[8] =
-    { "Ki", "Mi", "Gi", "Ti", "Pi", "Ei", "Zi", "Yi" };
-  static bool si = true;
-  static char buf[32];
-
-  if( set_prefix ) si = ( set_prefix > 0 );
-  const unsigned factor = ( si ? 1000 : 1024 );
-  const char * const * prefix = ( si ? si_prefix : binary_prefix );
-  const char * p = "";
-  bool exact = ( num % factor == 0 );
-
-  for( int i = 0; i < 8 && ( num > limit || ( exact && num >= factor ) ); ++i )
-    { num /= factor; if( num % factor != 0 ) exact = false; p = prefix[i]; }
-  snprintf( buf, sizeof buf, "%llu %s", num, p );
-  return buf;
-  }
-
-
-// Returns the number of chars read, or 0 if error.
-//
-int parse_long_long( const char * const ptr, long long & value )
-  {
-  char * tail;
-  errno = 0;
-  value = strtoll( ptr, &tail, 0 );
-  if( tail == ptr || errno || value < 0 ) return 0;
-  int c = tail - ptr;
-
-  if( ptr[c] )
-    {
-    const int factor = ( ptr[c+1] == 'i' ) ? 1024 : 1000;
-    int exponent = 0;
-    switch( ptr[c] )
-      {
-      case 'Y': exponent = 8; break;
-      case 'Z': exponent = 7; break;
-      case 'E': exponent = 6; break;
-      case 'P': exponent = 5; break;
-      case 'T': exponent = 4; break;
-      case 'G': exponent = 3; break;
-      case 'M': exponent = 2; break;
-      case 'K': if( factor == 1024 ) exponent = 1; else return 0; break;
-      case 'k': if( factor == 1000 ) exponent = 1; else return 0; break;
-      }
-    if( exponent > 0 )
-      {
-      ++c;
-      if( ptr[c] == 'i' ) { ++c; if( value ) format_num( 0, 0, -1 ); }
-      if( ptr[c] == 'B' ) ++c;
-      for( int i = 0; i < exponent; ++i )
-        {
-        if( INT64_MAX / factor >= value ) value *= factor;
-        else return 0;
-        }
-      }
-    }
-  return c;
-  }
-
-
-// Recognized formats: <begin> <begin>-<end> <begin>,<size>
-//
-void parse_range( const char * const ptr, Block & range )
-  {
-  long long value = 0;
-  int c = parse_long_long( ptr, value );		// pos
-  if( c && value >= 0 && value < INT64_MAX &&
-      ( ptr[c] == 0 || ptr[c] == ',' || ptr[c] == '-' ) )
-    {
-    range.pos( value );
-    if( ptr[c] == 0 ) { range.size( INT64_MAX - value ); return; }
-    const bool issize = ( ptr[c] == ',' );
-    c = parse_long_long( ptr + c + 1, value );		// size
-    if( c && value > 0 && ( issize || value > range.pos() ) )
-      {
-      if( !issize ) value -= range.pos();
-      if( INT64_MAX - range.pos() >= value ) { range.size( value ); return; }
-      }
-    }
-  show_error( "Bad decompression range.", 0, true );
-  std::exit( 1 );
-  }
-
-
 int decompress_member( const int infd, const int outfd,
                        const Pretty_print & pp,
                        const unsigned long long mpos,
@@ -221,6 +132,30 @@ int list_file( const char * const input_filename, const Pretty_print & pp )
 } // end namespace
 
 
+const char * format_num( unsigned long long num,
+                         unsigned long long limit,
+                         const int set_prefix )
+  {
+  const char * const si_prefix[8] =
+    { "k", "M", "G", "T", "P", "E", "Z", "Y" };
+  const char * const binary_prefix[8] =
+    { "Ki", "Mi", "Gi", "Ti", "Pi", "Ei", "Zi", "Yi" };
+  static bool si = true;
+  static char buf[32];
+
+  if( set_prefix ) si = ( set_prefix > 0 );
+  const unsigned factor = ( si ? 1000 : 1024 );
+  const char * const * prefix = ( si ? si_prefix : binary_prefix );
+  const char * p = "";
+  bool exact = ( num % factor == 0 );
+
+  for( int i = 0; i < 8 && ( num > limit || ( exact && num >= factor ) ); ++i )
+    { num /= factor; if( num % factor != 0 ) exact = false; p = prefix[i]; }
+  snprintf( buf, sizeof buf, "%llu %s", num, p );
+  return buf;
+  }
+
+
 bool safe_seek( const int fd, const long long pos )
   {
   if( lseek( fd, pos, SEEK_SET ) == pos ) return true;
@@ -245,11 +180,9 @@ int list_files( const std::vector< std::string > & filenames,
 
 int range_decompress( const std::string & input_filename,
                       const std::string & output_filename,
-                      const std::string & range_string, const int verbosity,
-                      const bool force, const bool ignore, const bool to_stdout )
+                      Block range, const int verbosity, const bool force,
+                      const bool ignore, const bool to_stdout )
   {
-  Block range( 0, 0 );
-  parse_range( range_string.c_str(), range );
   struct stat in_stats;
   const int infd = open_instream( input_filename.c_str(), &in_stats, true, true );
   if( infd < 0 ) return 1;
@@ -262,7 +195,7 @@ int range_decompress( const std::string & input_filename,
   if( range.end() > file_index.data_end() )
     range.size( std::max( 0LL, file_index.data_end() - range.pos() ) );
   if( range.size() <= 0 )
-    { if( verbosity >= 1 ) pp( "Nothing to do." ); return 0; }
+    { if( verbosity >= 0 ) pp( "Nothing to do." ); return 0; }
 
   if( verbosity >= 1 )
     {
diff --git a/repair.cc b/repair.cc
index 54a4d89..066b5bd 100644
--- a/repair.cc
+++ b/repair.cc
@@ -1,5 +1,5 @@
 /*  Lziprecover - Data recovery tool for the lzip format
-    Copyright (C) 2009-2014 Antonio Diaz Diaz.
+    Copyright (C) 2009-2015 Antonio Diaz Diaz.
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -29,9 +29,12 @@
 #include <sys/stat.h>
 
 #include "lzip.h"
-#include "file_index.h"
 #include "mtester.h"
+#include "block.h"
+#include "file_index.h"
+
 
+namespace {
 
 int seek_write( const int fd, const uint8_t * const buf, const int size,
                 const long long pos )
@@ -41,6 +44,8 @@ int seek_write( const int fd, const uint8_t * const buf, const int size,
   return 0;
   }
 
+} // end namespace
+
 
 int repair_file( const std::string & input_filename,
                  const std::string & output_filename, const int verbosity,
@@ -80,13 +85,13 @@ int repair_file( const std::string & input_filename,
       cleanup_and_fail( output_filename, outfd, 1 );
     long pos = failure_pos;
     bool done = false;
-    while( pos >= File_header::size && pos > failure_pos - 40000 && !done )
+    while( pos >= File_header::size && pos > failure_pos - 50000 && !done )
       {
-      const long min_pos = std::max( (long)File_header::size, pos - 1000 );
+      const long min_pos = std::max( (long)File_header::size, pos - 100 );
       const LZ_mtester * master = prepare_master( mbuffer, msize, min_pos - 16 );
       if( !master )
         cleanup_and_fail( output_filename, outfd, 1 );
-      for( ; pos >= min_pos && !done ; --pos )
+      for( ; pos >= min_pos && !done; --pos )
         {
         if( verbosity >= 1 )
           {
@@ -141,3 +146,174 @@ int repair_file( const std::string & input_filename,
     std::fputs( "Copy of input file repaired successfully.\n", stdout );
   return 0;
   }
+
+
+int debug_delay( const std::string & input_filename, Block range,
+                 const int verbosity )
+  {
+  struct stat in_stats;
+  const int infd = open_instream( input_filename.c_str(), &in_stats, true, true );
+  if( infd < 0 ) return 1;
+
+  Pretty_print pp( input_filename, verbosity );
+  const File_index file_index( infd );
+  if( file_index.retval() != 0 )
+    { pp( file_index.error().c_str() ); return file_index.retval(); }
+
+  if( range.end() > file_index.file_end() )
+    range.size( std::max( 0LL, file_index.file_end() - range.pos() ) );
+  if( range.size() <= 0 )
+    { if( verbosity >= 0 ) pp( "Nothing to do." ); return 0; }
+
+  for( long i = 0; i < file_index.members(); ++i )
+    {
+    const Block & mb = file_index.mblock( i );
+    if( !range.overlaps( mb ) ) continue;
+    const long long mpos = file_index.mblock( i ).pos();
+    const long long msize = file_index.mblock( i ).size();
+    if( verbosity >= 1 )		// damaged member found
+      {
+      std::printf( "Finding max delay in member %ld of %ld  (member pos = %llu)\n",
+                   i + 1, (long)file_index.members(), mpos );
+      std::fflush( stdout );
+      }
+    uint8_t * const mbuffer = read_member( infd, mpos, msize );
+    if( !mbuffer )
+      { show_error( "Can't read member." ); return 1; }
+    long pos = std::max( range.pos() - mpos, File_header::size + 1LL );
+    const long end = std::min( range.end() - mpos, msize );
+    long max_delay = 0;
+    while( pos < end )
+      {
+      const LZ_mtester * master = prepare_master( mbuffer, msize, pos - 16 );
+      if( !master )
+        { show_error( "Can't prepare master." ); return 1; }
+      const long partial_end = std::min( pos + 100, end );
+      for( ; pos < partial_end; ++pos )
+        {
+        if( verbosity >= 1 )
+          {
+          std::printf( "Delays in position %llu \r", mpos + pos );
+          std::fflush( stdout );
+          }
+        int value = -1;
+        for( int j = 0; j < 256; ++j )
+          {
+          ++mbuffer[pos];
+          if( j == 255 ) break;
+          long failure_pos;
+          if( test_member_rest( *master, &failure_pos ) ) continue;
+          const long delay = failure_pos - pos;
+          if( delay > max_delay ) { max_delay = delay; value = mbuffer[pos]; }
+          }
+        if( value >= 0 && verbosity >= 0 )
+          {
+          std::printf( "New max delay %lu at position %llu (0x%02X)\n",
+                       max_delay, mpos + pos, value );
+          std::fflush( stdout );
+          }
+        if( pos + max_delay >= msize ) { pos = end; break; }
+        }
+      delete master;
+      }
+    delete[] mbuffer;
+    if( verbosity >= 1 ) std::fputs( "\n", stdout );
+    }
+
+  if( verbosity >= 1 ) std::fputs( "Done.\n", stdout );
+  return 0;
+  }
+
+
+int debug_repair( const std::string & input_filename, const long long bad_pos,
+                  const int verbosity, const uint8_t bad_value )
+  {
+  struct stat in_stats;
+  const int infd = open_instream( input_filename.c_str(), &in_stats, true, true );
+  if( infd < 0 ) return 1;
+
+  Pretty_print pp( input_filename, verbosity );
+  const File_index file_index( infd );
+  if( file_index.retval() != 0 )
+    { pp( file_index.error().c_str() ); return file_index.retval(); }
+
+  long idx = 0;
+  for( ; idx < file_index.members(); ++idx )
+    if( file_index.mblock( idx ).includes( bad_pos ) ) break;
+  if( idx >= file_index.members() )
+    { if( verbosity >= 0 ) pp( "Nothing to do." ); return 0; }
+
+  const long long mpos = file_index.mblock( idx ).pos();
+  const long long msize = file_index.mblock( idx ).size();
+  {
+  long long failure_pos = 0;
+  if( !safe_seek( infd, mpos ) )
+    { show_error( "Can't seek to member." ); return 1; }
+  if( !try_decompress_member( infd, msize, &failure_pos ) )
+    {
+    if( verbosity >= 0 )
+      std::printf( "Member %ld of %ld already damaged  (failure pos = %llu)\n",
+                   idx + 1, (long)file_index.members(), mpos + failure_pos );
+    return 1;
+    }
+  }
+  uint8_t * const mbuffer = read_member( infd, mpos, msize );
+  if( !mbuffer )
+    { show_error( "Can't read member." ); return 1; }
+  const uint8_t good_value = mbuffer[bad_pos];
+  mbuffer[bad_pos] = bad_value;
+  long failure_pos = 0;
+  {
+  const LZ_mtester * master = prepare_master( mbuffer, msize, 0 );
+  if( !master )
+    { show_error( "Can't prepare master." ); return 1; }
+  if( test_member_rest( *master, &failure_pos ) )
+    {
+    if( verbosity >= 1 )
+      std::fputs( "Member decompressed with no errors.\n", stdout );
+    return 0;
+    }
+  if( verbosity >= 1 )
+    {
+    std::printf( "Test repairing member %ld of %ld\n"
+                 "  (damage pos = %llu (0x%02X->0x%02X), failure pos = %llu)\n",
+                 idx + 1, (long)file_index.members(), mpos + bad_pos,
+                 good_value, bad_value, mpos + failure_pos );
+    std::fflush( stdout );
+    }
+  }
+  long pos = failure_pos;
+  bool done = false;
+  while( pos >= File_header::size && pos > failure_pos - 50000 && !done )
+    {
+    const long min_pos = std::max( (long)File_header::size, pos - 100 );
+    const LZ_mtester * master = prepare_master( mbuffer, msize, min_pos - 16 );
+    if( !master )
+      { show_error( "Can't prepare master." ); return 1; }
+    for( ; pos >= min_pos && !done; --pos )
+      {
+      if( verbosity >= 1 )
+        {
+        std::printf( "Trying position %llu \r", mpos + pos );
+        std::fflush( stdout );
+        }
+      for( int j = 0; j < 256; ++j )
+        {
+        ++mbuffer[pos];
+        if( j == 255 ) break;
+        if( test_member_rest( *master ) ) { done = true; break; }
+        }
+      }
+    delete master;
+    }
+  delete[] mbuffer;
+  if( verbosity >= 1 ) std::fputs( "\n", stdout );
+  if( !done )
+    {
+    show_error( "Can't repair input file. There is a bug somewhere." );
+    return 3;
+    }
+  if( verbosity >= 1 )
+    std::fputs( "Member repaired successfully.\n", stdout );
+  return 0;
+  }
diff --git a/split.cc b/split.cc
index 7b3f9fd..2ffb359 100644
--- a/split.cc
+++ b/split.cc
@@ -1,5 +1,5 @@
 /*  Lziprecover - Data recovery tool for the lzip format
-    Copyright (C) 2009-2014 Antonio Diaz Diaz.
+    Copyright (C) 2009-2015 Antonio Diaz Diaz.
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -28,6 +28,7 @@
 #include <sys/stat.h>
 
 #include "lzip.h"
+#include "block.h"
 #include "file_index.h"
 
 
@@ -81,7 +82,7 @@ bool verify_header( const File_header & header, const Pretty_print & pp )
 
 
 // Search forward from 'pos' for "LZIP" (Boyer-Moore algorithm)
-// Return pos of found string or 'pos+size' if not found.
+// Returns pos of found string or 'pos+size' if not found.
 //
 int find_magic( const uint8_t * const buffer, const int pos, const int size )
   {
diff --git a/testsuite/check.sh b/testsuite/check.sh
index ef60713..1df77a3 100755
--- a/testsuite/check.sh
+++ b/testsuite/check.sh
@@ -1,6 +1,6 @@
 #! /bin/sh
 # check script for Lziprecover - Data recovery tool for the lzip format
-# Copyright (C) 2009-2014 Antonio Diaz Diaz.
+# Copyright (C) 2009-2015 Antonio Diaz Diaz.
 #
 # This script is free software: you have unlimited permission
 # to copy, distribute and modify it.
diff --git a/unzcrash.cc b/unzcrash.cc
index 0b44997..fd1c816 100644
--- a/unzcrash.cc
+++ b/unzcrash.cc
@@ -1,6 +1,6 @@
 /*  Unzcrash - Tests robustness of decompressors to corrupted data.
     Inspired by unzcrash.c from Julian Seward's bzip2.
-    Copyright (C) 2008-2014 Antonio Diaz Diaz.
+    Copyright (C) 2008-2015 Antonio Diaz Diaz.
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -44,7 +44,7 @@ namespace {
 
 const char * const Program_name = "Unzcrash";
 const char * const program_name = "unzcrash";
-const char * const program_year = "2014";
+const char * const program_year = "2015";
 const char * invocation_name = 0;
 
 int verbosity = 0;