#! /usr/bin/python

# This program is released under the GPLv2, please see:
# http://www.gnu.org/copyleft/gpl.html

# The original author is David Timms <au.net.iinet@dtimms> ;)

# archive-teleconstructor.py
# version 2007-06-01 v0.04
from __future__ import division
import sys, getopt, string, signal, os

def signal_handler(signalRx, frame):
  if signalRx==signal.SIGINT:
    print "  user interrupt with ctrl-c. exiting..."
    sys.exit(0)
  elif signalRx==signal.SIGALRM:   # as 1 second timer
    global showStats   # otherwise assigning to a global variable name is
# actually creating a new local variable
    showStats = True
    signal.alarm(1) #seconds
    
def help_message():
  print '''  archive-teleconstructor.py
Copyright (c) 2007 David Timms
    -h  --help               display this help message
    -v  --version            display the version information
  Parameters to be used on a machine with the original iso image:
        --iso-source=        iso image file to decompose
        --dump-iso-info      create an iso-info structure dump
  Parameters to be used to locally reconstruct the iso image:
    -d  --file-iso-dest=     iso image file to construct
    -c  --createiso          {future} build an empty iso image at file-iso-dest
        --file-iso-info      structure dump of the iso-source using 
                                 dump-iso-info 
    -s  --directory-source=  locations of files known to be on the iso image
                                 can be specified multiple times
        --file-sha1sum       {future} sha1sum results to check files against
        --verify-files       check for files in iso-info structure in the list
                                 of directory-sources provided
        --insert-files       insert files from directory-sources into 
                                 the iso image file-iso-dest, as determined 
                                 from dump-iso-info
  Parameters for testing purposes:
         --correlate         compare the iso-source with file-iso-dest,
                                 providing stats during the process
         --debug             print progress messages to help with debugging
  '''
  sys.exit(0)

def debug_message(message):
  if debug:
    print message

def create_iso():
  print '\n  create_iso:'
  if os.path.isfile(fileIsoDest):
    print '  destfile [' + fileIsoDest + '] already exists. exiting...'
    sys.exit(0)
  else:
    print "creating iso..."
    block2k=''
    for char in range(1,2048):
      block2k = block2k + '\x00'
      
    try:
      try:
        fileDest = open(fileIsoDest, 'wb')
        # l8r need to infer fileBlocks from maybe .torrent or ftp listing
        # note that insert-files will extend an existing or grow a new file
        fileBlocks = 293000   
        debug_message('\n  Takes about 66second for 3GB, del in 8 secs.')
        for blockNo in range(1,fileBlocks):
          fileDest.write(block2k)
#later dude          print "."
        size = fileDest.tell()
        debug_message("  ;) empty iso: size=" + str(size))
          
      finally:
##        fileDest.close();
        pass
    except IOError:
      print '    something went wrong[' + fileIsoDest + ']'
##        fileDest.close;
      sys.exit(0)
    
def dump_iso():
  print '  dump_iso:'
  if len(fileIsoSource):
    isoInfoCommand="/usr/bin/iso-info -q -l -i " + fileIsoSource + ">" + fileIsoSource + ".iso-info.txt"
    debug_message("  isoInfoCommand=" + isoInfoCommand)
    stdin, stdout, stderr = os.popen3(isoInfoCommand)

    infoResult = stdout.read()
    infoErrors = stderr.read()
    stdin.close(); stdout.close(); stderr.close()
    debug_message(infoResult)
    debug_message(infoErrors)
    print "  dump_iso: file generated at: " + fileIsoSource + ".iso-info.txt"
  else:
    print '  error:dump_iso: you must also specify --iso-source=`/path/to/your_iso.iso`'
    sys.exit(0)

def extract_file_info():
  print '  extract_file_info:'
  try:
    try:
      fileIsoInfoContent = open(fileisoinfo, 'r')
      isoInfo = fileIsoInfoContent.readlines()
      splitline = []
      for line in isoInfo:
        splitline = line.split
#        print splitline()
        if len(splitline())==1:
          (foldersplit) = splitline()
          folderstr=foldersplit[0]
          if folderstr[0]=='/' and folderstr[len(folderstr)-1]==':':
            folder = folderstr[0:len(folderstr)-1]
            print folder
            
        elif len(splitline())==12:   # was 13
# lsn = logical sector number
          (permissionssplit, dummy, dummy, dummy, dummy, lsnsplit, \
              size, d, d, d, d, filename)  = splitline()
          permissionsstr = permissionssplit[0]
          if permissionsstr[0]=='-':   # entry is a file
#            print permissionssplit, ' ', lsnsplit, ' ', size, ' ', filename
            if lsnsplit[len(lsnsplit)-1]==']':   # remove right ]
              lsn = lsnsplit[0:len(lsnsplit)-1]
              debug_message(folder + ' * ' + filename + ' * ' + size + ' * ' + lsn)
              fileInfo.append((folder, filename, size, lsn))
# dont forget to shasum later!
        else:
          pass    

    finally:
      fileIsoInfoContent.close();
      debug_message("  extract_file_info:finally")
  except IOError:
    print '  error: extract_file_info: trouble with file [' + fileIsoInfo + ']'
    sys.exit(0)

def file_find_matching(item):
#  print '  file_find_matching'
  foundlocation = ''
#  item is (path, filename, size, lsn)  
  debug_message(item[0]+item[1]+' '+item[2])
  debug_message('++++++++++++++dirSources=')
  debug_message(dirSources)
  print '  searching for file [' + item[1] + ']'
  for location in dirSources:
#    print 'item=' + item[0]+ item[1]
    debug_message('---------location=')
    debug_message(location)
    testfilepaths=[]
    testfilepaths.append(location + item[1])
    testfilepaths.append(location + item[0] + item[1])
    debug_message(testfilepaths)
    for testfilepath in testfilepaths:
      debug_message(testfilepath)
      if os.path.isfile(testfilepath):
        if os.path.getsize(testfilepath)==long(item[2]):   #compare longs
          foundlocation = testfilepath
          return foundlocation
        else:
          print ' * file had different size: ' + testfilepath + ' size=' + str(os.path.getsize(testfilepath)) + 'refsize=' + item[2]
          pass
      else:
        debug_message(' & filepath not found: ' + testfilepath)
        pass
          
  debug_message("------" +foundlocation)
  return foundlocation

def insert_file(entry, filepath):
  print '    insert_file:'
  if os.path.isfile(fileIsoDest):
    fileInsertCommand="/bin/dd if=" + filepath + " of=" + fileIsoDest + " conv=notrunc ibs=" + entry[2] + " obs=2048 seek=" + entry[3]
    debug_message("    fileInsertCommand:" + fileInsertCommand)
    stdin, stdout, stderr = os.popen3(fileInsertCommand)

    infoResult = stdout.read()
    infoErrors = stderr.read()
    stdin.close(); stdout.close(); stderr.close()
    debug_message(infoResult)
    debug_message(infoErrors)
  else:
    print "  err:insert_file: --file-iso-dest must already exist"
    sys.exit(0)
  
def verify_files():
  print ''
  print '  verify_files:'
  debug_message('    file-iso-info=' + fileisoinfo)
  debug_message('      sha1sums=')
  debug_message(sha1sums)
  debug_message('      directory-sources=*******************')
  debug_message(dirSources)
  if fileisoinfo <> '':
    extract_file_info()
    debug_message(fileInfo)
    missingfilescount=0
    foundfilescount=0
    missingfiles=[]
    for entry in fileInfo:
#   do sha1sum later, but for now just check size ;-)
      fileExists=False
      debug_message(entry)
      filepath=file_find_matching(entry)
      if filepath != '':
        print "    found: " + filepath
        foundfilescount +=1
        if insertfiles:
          insert_file(entry, filepath)
      else:
        print "    missing. "
        missingfiles.append(entry)
        missingfilescount += 1
  
    if missingfilescount >= 1:
      print "  error: verify_files: could not find local files for: " + str(missingfilescount) + ' files'
      allstr = ""
    else:
      allstr = " all"
    print "  verify_files: found local files for" + allstr + ": " + str(foundfilescount) + ' files'
  else:
    print "  verify_files: you must specify the iso-info dump file with --file-iso-info="

def correlate_isos():   #find out if it worked !
  print '  correlate_isos... please wait'
  global showStats

  if os.path.isfile(fileIsoSource):
    if os.path.isfile(fileIsoDest):
      sumByteIdentical=0
      sumByteDifferent=0
      sumCorrelation=0
      try: 
        try: 
          signal.alarm(1) #seconds
          blockSize=2048
          fileSource = open(fileIsoSource, 'rb')
          fileDest   = open(fileIsoDest, 'rb')
# // is integer result          
          blocks = os.path.getsize(min(fileIsoSource,fileIsoDest)) // blockSize
          debug_message('    blockSize: '+ str(blockSize))
          showStats = True
          for block in range(1, blocks):
            sourceBlock = fileSource.read(blockSize)
            destBlock   = fileDest.read(blockSize)
            smallerBlock = min(len(sourceBlock), len(destBlock))
            byteIdentical=0
            byteDifferent=0
            for byte in range(0,smallerBlock):   #who invented 0 based strings/arrays anyway ?
              if sourceBlock[byte] == destBlock[byte]:
                byteIdentical = byteIdentical + 1
              else:
                byteDifferent = byteDifferent + 1
            sumByteIdentical = sumByteIdentical + byteIdentical
            sumByteDifferent = sumByteDifferent + byteDifferent
            if showStats == True:
              if byteIdentical + byteDifferent >= 1:
                blockCorrelation = 100 * byteIdentical / (byteIdentical + byteDifferent)
                sumCorrelation = 100 * sumByteIdentical / (sumByteIdentical + sumByteDifferent)
              else:
	              blockCorrelation = 0  
	              sumCorrelation = 0
              print '    stats: block %7d of %7d: %6.3f%% {%6d:%6d} running=%6.3f%% {%6d:%6d}'\
                  %(block, blocks, blockCorrelation, byteIdentical\
                  , byteDifferent, sumCorrelation, sumByteIdentical\
                  , sumByteDifferent)
              showStats=False
              signal.alarm(1) #seconds
        except:
          print "  error:correlate_isos: `an earth shattering kaboom` - looney tunes"
          print "Unhandled error: how'd ya do dat ?", sys.exc_info()[0]
          raise
          sys.exit(0)
      finally:
        fileSource.close()
        fileDest.close()
        print '    overall statistics: identical:different %10d:%10d {%7.4f%%}'\
            %(sumByteIdentical, sumByteDifferent, sumCorrelation)
    else:
      print "  error:correlate_isos: you must also specify --file-iso-dest= for the comparison."
      sys.exit(0)
  else:
    print "  error:correlate_isos: you must also specify --iso-source= for the comparison."
    sys.exit(0)
    
# main...
signal.signal(signal.SIGINT, signal_handler)
signal.signal(signal.SIGALRM, signal_handler)
try:
  options, xarguments = getopt.getopt(sys.argv[1:], 'hvdcsi'
      , ['help', 'version', 'iso-source=','dump-iso-info'\
      , 'file-iso-dest=', 'createiso', 'file-iso-info=', 'directory-source='\
      , 'file-sha1sum=', 'verify-files', 'insert-files'\
      , 'correlate', 'debug'])
except getopt.error:
  print '''  error: you provided an unknown option, or an argument\'s option\n
    was missing. Run:
    `archive-teleconstructor.py --help` for more information.'''
  sys.exit(0)

 
fileIsoDest=''
fileIsoSource=''
dumpiso=False
createiso=False
verifyfiles=False
insertfiles=False
fileisoinfo=''
dirSources=[]
sha1sums=[]
fileInfo=[]
correlate=False
showStats=False
debug=False

for arg in options[:]:
  debug_message('[' + arg[0] +']=['+arg[1]+']')

  if arg[0] == '-h' or arg[0] == '--help':
    help_message()

  elif arg[0]=='-v' or arg[0]=='--version':
    print '  version: 2007-06-01 v0.04'
    sys.exit(0)

  elif arg[0]=='--iso-source':
    if arg[1] != '':
      fileIsoSource=arg[1]
      print '    --iso-source=[' +fileIsoSource+ ']'
      if os.path.isfile(fileIsoSource):
        pass
      else:  
        print '  error:--iso-source: the specified file must already exist'
        sys.exit(0)
    else:
      print '  error:--iso-source: you must specify a source iso9660 image'
      sys.exit(0)

  elif arg[0]=='--dump-iso-info':
    if arg[1] == '':
      dumpiso=True
    else:
      print '  error:--dump-iso-info: does not accept parameters'
      sys.exit(0)

  elif arg[0]=='-d' or arg[0]=='--file-iso-dest':
    fileIsoDest=arg[1]
    if fileIsoDest <> '':
      print '  --file-iso-dest=' + fileIsoDest
    else:
      print '  error:--file-iso-dest file location must be specified.'
      sys.exit(0)

  elif arg[0]=='-c' or arg[0]=='--createiso':
    createiso=True

  elif arg[0]=='--file-iso-info':
    try:
      fileisoinfo=arg[1]
      if os.path.isfile(fileisoinfo):
        print '  --file-iso-info: [' + fileisoinfo + '] found.'
      else:
        print '  error:--file-iso-info: the specified file must ' \
            + 'already exist.'
        sys.exit(0)
    except:
      print "  error:--file-iso-info: except"

  elif arg[0]=='-s' or arg[0]=='--directory-source':
    try:
      dirSourceName=arg[1]
      if os.path.isdir(dirSourceName):
        dirSources.append(dirSourceName)
        print '  --directory-source: added [' + dirSourceName + ']'
        debug_message('=========dirSources=')
        debug_message(dirSources)
      else:
        print '  error:--directory-source: the specified directory must ' \
            + 'already exist and preferably contain files that may be present on the iso.'
        sys.exit(0)
    except:
      print "  error:--directory-source: except"

  elif arg[0]=='--file-sha1sum':
    try:
      fileSha1sum=arg[1]
      if os.path.isfile(fileSha1sum):
        sha1sums.append(fileSha1sum)
        print '  --file-sha1sum: added [' + fileSha1sum + ']'
      else:
        print '  error:--file-sha1sum: the specified file must ' \
            + 'already exist.'
        sys.exit(0)
    except:
      print "  error:--file-sha1sum: except"

  elif arg[0]=='--verify-files':
    if arg[1] == '':
      verifyfiles=True
    else:
      print '  error:--verify-files: does not accept parameters'
      sys.exit(0)

  elif arg[0]=='--insert-files':
    if arg[1] == '':
      insertfiles=True
    else:
      print '  error:--insert-files: does not accept parameters'
      sys.exit(0)

  elif arg[0]=='--correlate':
    if arg[1] == '':
      correlate=True
    else:
      print '  error:--correlate: does not accept parameters'
      sys.exit(0)

  elif arg[0]=='--debug':
    if arg[1] == '':
      debug=True
    else:
      print '  error:--debug: does not accept parameters'
      sys.exit(0)

  else:
    print '  [' + arg[0] + ']=[' + arg[1] +'] is not a legit option !'
    sys.exit(0)

# remove each argument as it is handled - so it wont be read again {?}
  options.remove(arg)


if dumpiso:
  dump_iso()
elif createiso:
  create_iso()
elif verifyfiles:
  verify_files()
elif insertfiles:
  verify_files()
elif correlate:
  correlate_isos()
debug_message('  ===== it\'s the end. =====')

# the following is all comments, and some things to do.
# naming
# construct
# warp  transporter  teleport  beem beam   teleconstructor
#   archive-teleconstructor.py
# with a iso library, you could read the iso toc stuff directly from a remote 
#   server over http or ftp ?
# this would be good cause then you can use this without getting the remote party
#   hosting the iso to run iso-info and make it available
# fuse driver for ftp /http ?
#   request byte range needed on the servers necessary

# tools: result
#$ iso-info -q -l -i /home/old/6/FC4-i386-DVD.iso 
#iso-info version 0.77 i686-redhat-linux-gnu
#Copyright (c) 2003, 2004, 2005 R. Bernstein
#This is free software; see the source for copying conditions.
#There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
#PARTICULAR PURPOSE.
#__________________________________
#ISO-9660 Information
#/:
#  drwxr-xr-x   5 0 0 [LSN     29]      4096 Jun 07 2005 02:45:14  .
#  drwxr-xr-x   6 0 0 [LSN     29]      4096 Jun 07 2005 02:45:14  ..
#  -rwxr-xr-x   2 0 0 [LSN    277]       248 Jun 07 2005 02:25:47  autorun
#  -rw-r--r--  10 0 0 [LSN    278]      5616 Jun 07 2005 02:25:47  eula.txt
#  drwxr-xr-x   4 0 0 [LSN     32]      2048 Jun 07 2005 02:25:23  Fedora
#  -rw-r--r--  10 0 0 [LSN    281]     18385 Jun 07 2005 02:25:47  GPL
#  drwxr-xr-x   3 0 0 [LSN    174]      2048 Jun 07 2005 02:52:37  images
#  drwxr-xr-x   2 0 0 [LSN     31]      2048 Jun 07 2005 02:39:44  isolinux
#  -rw-r--r--  10 0 0 [LSN    290]      5232 Jun 07 2005 02:25:47  README
#  -rw-r--r--   2 0 0 [LSN    293]     12667 Jun 07 2005 02:25:47  README-Accessibility
#  -rw-r--r--   2 0 0 [LSN    300]     51265 Jun 07 2005 02:25:47  RELEASE-NOTES
#  -rw-r--r--  10 0 0 [LSN    326]      1232 Jun 07 2005 02:25:47  RPM-GPG-KEY-rawhide
#  -rw-r--r--  10 0 0 [LSN    327]      1076 Jun 07 2005 02:25:47  RPM-GPG-KEY-fedora-test
#  -rw-r--r--  10 0 0 [LSN    328]      1105 Jun 07 2005 02:25:47  RPM-GPG-KEY-fedora-rawhide
#  -rw-r--r--  10 0 0 [LSN    329]      1519 Jun 07 2005 02:25:47  RPM-GPG-KEY-fedora
#  -rw-r--r--  10 0 0 [LSN    330]      1706 Jun 07 2005 02:25:47  RPM-GPG-KEY-beta
#  -rw-r--r--  10 0 0 [LSN    331]      1910 Jun 07 2005 02:25:47  RPM-GPG-KEY
#  -r--r--r--   1 0 0 [LSN    332]      3591 Jun 07 2005 03:01:49  TRANS.TBL
#  -rw-r--r--   1 0 0 [LSN    334]        86 Jun 07 2005 02:45:12  .discinfo
#
#/Fedora/:
#  drwxr-xr-x   4 0 0 [LSN     32]      2048 Jun 07 2005 02:25:23  .
#  drwxr-xr-x   5 0 0 [LSN     29]      4096 Jun 07 2005 02:45:14  ..
#  drwxr-xr-x   2 0 0 [LSN    173]      2048 Jun 07 2005 02:54:01  base
#  drwxr-xr-x   2 0 0 [LSN     33]    286720 Jun 07 2005 02:54:01  RPMS
#  -r--r--r--   1 0 0 [LSN   3420]       432 Jun 07 2005 03:01:49  TRANS.TBL
#
#/Fedora/base/:
#  drwxr-xr-x   2 0 0 [LSN    173]      2048 Jun 07 2005 02:54:01  .
#  drwxr-xr-x   4 0 0 [LSN     32]      2048 Jun 07 2005 02:25:23  ..
#  -rw-r--r--   4 0 0 [LSN 114659]  10481002 Jun 07 2005 02:54:01  comps.rpm
#  -rw-r--r--   2 0 0 [LSN 1203484]    709886 Jun 07 2005 02:25:48  comps.xml
#  -rw-r--r--   2 0 0 [LSN 1203831]   9840328 Jun 07 2005 02:52:31  hdlist
#  -rw-r--r--   2 0 0 [LSN 1208636]  25029836 Jun 07 2005 02:52:31  hdlist2
#...
#  -r--r--r--   1 0 0 [LSN 1342905]      1105 Jun 07 2005 03:01:49  TRANS.TBL
#
#/images/pxeboot/:
#  drwxr-xr-x   2 0 0 [LSN    175]      2048 Jun 07 2005 02:39:47  .
#  drwxr-xr-x   3 0 0 [LSN    174]      2048 Jun 07 2005 02:52:37  ..
#  -rw-r--r--   4 0 0 [LSN    337]   4492627 Jun 07 2005 02:39:35  initrd.img
#  -rw-r--r--   2 0 0 [LSN 1342906]       275 Jun 07 2005 02:39:47  README
#  -r--r--r--   1 0 0 [LSN 1342907]       659 Jun 07 2005 03:01:49  TRANS.TBL
#  -rw-r--r--   4 0 0 [LSN   2588]   1702587 Jun 07 2005 02:39:36  vmlinuz
#
#/isolinux/:
#  drwxr-xr-x   2 0 0 [LSN     31]      2048 Jun 07 2005 02:39:44  .
#  drwxr-xr-x   5 0 0 [LSN     29]      4096 Jun 07 2005 02:45:14  ..
#  -r--r--r--   1 0 0 [LSN    270]      2048 Jun 07 2005 03:01:49  boot.cat
#  -rw-r--r--   2 0 0 [LSN    335]       292 Jun 07 2005 02:39:44  boot.msg
#  -rw-r--r--   2 0 0 [LSN    336]      1034 Jun 07 2005 02:39:44  general.msg
#  -rw-r--r--   4 0 0 [LSN    337]   4492627 Jun 07 2005 02:39:35  initrd.img
#  -r--r--r--   2 0 0 [LSN    271]     10424 Jun 07 2005 02:54:01  isolinux.bin
#  -r-xr-xr-x   2 0 0 [LSN   2531]       595 Jun 07 2005 02:39:44  isolinux.cfg
#  -r--r--r--   2 0 0 [LSN   2532]     94600 Jun 07 2005 02:39:44  memtest
#  -rw-r--r--   2 0 0 [LSN   2579]       788 Jun 07 2005 02:39:44  options.msg
#  -rw-r--r--   2 0 0 [LSN   2580]       872 Jun 07 2005 02:39:44  param.msg
#  -rw-r--r--   2 0 0 [LSN   2581]       490 Jun 07 2005 02:39:44  rescue.msg
#  -rw-r--r--   2 0 0 [LSN   2582]       549 Jun 07 2005 02:39:44  snake.msg
#  -rw-r--r--   2 0 0 [LSN   2583]      5692 Jun 07 2005 02:39:44  splash.lss
#  -r--r--r--   1 0 0 [LSN   2586]      2880 Jun 07 2005 03:01:49  TRANS.TBL
#  -rw-r--r--   4 0 0 [LSN   2588]   1702587 Jun 07 2005 02:39:36  vmlinuz
#

#dd if=FC4-i386-DVD.iso of=eula.txt.extracted bs=1 count=5616 skip=569344
# skip is the 2048*LSN from above listing


# weird bug: in iso-info
#  dump_iso:
#  isoInfoCommand=/usr/bin/iso-info -q -l -i /home/davidt/#borland.delphi.7.enterprise.iso>/home/davidt/#borland.delphi.7.enterprise.iso.iso-info.txt
#*** stack smashing detected ***: /usr/bin/iso-info terminated
#
#/bin/sh: line 1:  4419 Aborted                 /usr/bin/iso-info -q -l -i /#home/davidt/borland.delphi.7.enterprise.iso >/home/davidt/#borland.delphi.7.enterprise.iso.iso-info.txt

# note: use azureus to create the iso {disable internal code}

# operation:

# If you have the source iso that you want to distribute:
#   1. $ ./archive-teleconstructor.py --iso-source=my-source-iso.iso
#          --dump-iso-info
#   2. make the iso and the my-source-iso.iso.iso-info.txt file available.
#   3. make the above available as a torrent

# If you want to accelerate your iso download:
#   1. in your web browser, download the providers torrent file.
#   2. open the .torrent in azureus
#   3. if necessary tell azureus not to download files you aren't interested in
#   4. check the disk to determine when azureus has finished building the
#      empty donwload iso file
#   5. in azureus stop the download.
#   6. quit azureus
#   7. $ ./archive-teleconstructor.py --file-iso-dest=my-source-iso.iso
#          --file-iso-info=my-source-iso.iso.iso-info.txt
#          --directory-source=/home/install/fedora/development/i386/os
#          --directory-source=/home/install/fedora/7t4/i386/disc
#          --verify-files
#     This will give you some spew regarding files found of correct name
#     and size, along with a summary.
#  8. repeat command 7. but append --insert-files
#     This takes around 10 minutes for F7t4 to F7 release DVD.
#  9. let the standard tools continue the download:
#    a. rsync is preferable if available
#     rsync --progress --stats --inplace -a 
#         rsync.server.com::fedora/etc/my-source-iso.iso
#         /home/mystuff/
#       the progress gives a hint as to what is happening: it takes a while ;)
#       the status can be read at the end, provides the speedup efficiency
#    b. azureus: restart it
#       right-click on the stopped download, select force recheck !! 
#       wait
#       once the recheck is finished notice how the complete % has jumped
#         from the value it was {hopefully}
#       restart the download: it's going to still take a while.


# bugs: / future
# - tidy up whether inputs and extracted paths include /
# - speed could be faster for correlation - experiment with block size|try diff -ub ?
# - need to use the SHA1SUM to confirm success.
# - the discrepancy in block size between an iso image {2048 B}, and bittorrent {eg 256kB},
#     means that eg azureus will throw away blocks that have lots of correct inserted data
#     because it only works on the whole 256k block.
#     Whenever a contained file is less than 2x 256k, there is a high chance that azureus
#     will re-fetch the whole block, wasting the work done by this program 
#
# 
# ./ the correlation function does not work correctly. the percent and numbers seems random.
# ./ compare if file sizes are different, dont read past the end of the array !
# ./ document the parameters
# ./ add debug function and parameter
# ./ change commented prints into debug_messages