'
' Visualize the difference between plaintext and encrypted values
' as a function of position and character.
'
' Requires: String.AsEncrypted, a script to encrypt arbitrary ASCII strings.
' Requires: LineFile.makeTemp, a script to create a temporary linefile (and its name).
'
strTitle = "Visualize encryption"
nLength = 100     ' Length of plaintext strings to encrypt (= number of columns in visualization)
nStart = 32       ' Start ASCII value (= bottom row in visualization)
nStop = 127       ' Ending ASCII value (= top row in visualization)
strNoData = "-999"' Used in ASCII grid representation for missing values
'
' Create output files for the plaintext and encrypted text.
'
lstPlain = av.Run("LineFile.MakeTemp", NIL)
lstCrypt = av.Run("LineFile.MakeTemp", NIL)
LFPlain = lstPlain.Get(1)
LFCrypt = lstCrypt.Get(1)
if ((LFPlain = NIL) or (LFCrypt = NIL)) then return NIL end
FNPlain = lstPlain.Get(0)
FNCrypt = lstCrypt.Get(0)
'
' (Grid construction technique: create an ASCII export file, then import it later.)
' Write the header records for the ASCII grid representation.
' These formulas will CENTER the cells at integral coordinates.
'
sHeader = 
          "ncols " + nLength.SetFormatPrecision(0).AsString + NL +
          "nrows " + (nStop-nStart+1).SetFormatPrecision(0).AsString + NL +
          "xllcorner -0.5"  + NL +
          "yllcorner " + (nStart-0.5).SetFormatPrecision(1).AsString + NL +
          "cellsize 1" + NL +
          "nodata_value " + strNoData
          
LFPlain.WriteElt(sHeader)
LFCrypt.WriteElt(sHeader)
'
' Loop over all ASCII characters from nStart through nStop.
' Go backwards, since ArcView reads grids from top row to bottom row.
'
av.ShowStopButton
av.SetStatus(0)
strErr = ""
for each i in (nStop max nStart)..(nStop min nStart) by -1
  doMore = av.SetStatus((nStop max nStart-i+0.5) * 100 / ((nStop-nStart).Abs + 1))
  if (not doMore) then return NIL end
  '
  ' Create a string of ASCII value i, length nLength,
  ' and encrypt it.
  '
  c = i.AsChar
  s = String.MakeBuffer(nLength).Substitute(" ", c)
  e = av.Run("String.AsEncrypted", s)
  '
  ' Test the expected one-for-one transliteration.
  '
  if (e.Count <> s.Count) then
    strErr = strErr + "Plaintext for" ++ c ++ " (" + i.AsString + ") has" ++ s.Count.AsString ++ 
      "characters while encrypted text has" ++ e.Count.AsString + NL
  end
  '
  ' Output the plaintext (s) and the encrypted text (e) as
  ' a series of ASCII values of their characters.
  '
  n = nLength
  strA = ""
  strB = ""
  while (s.IsNull.Not and e.IsNull.Not)
    a = (s.Left(1).AsASCII + 256) mod 256 ' On Windows machines at least, AsASCII can be negative!
    b = (e.Left(1).AsASCII + 256) mod 256
    s = s.Right(s.Count-1)
    e = e.Right(e.Count-1)
    n = n-1
    
    strA = strA ++ a.SetFormatPrecision(0).AsString
    strB = strB ++ b.SetFormatPrecision(0).AsString
  end
  
  if (n > 0) then ' Truncated lengths occur when \0x00 occurs in the encrypted string
    strOut = String.MakeBuffer(nLength).Substitute(" ", strNoData + " ")
  end
  
  LFPlain.WriteElt(strA)
  LFCrypt.WriteElt(strB)
end
if (strErr.IsNull.Not) then MsgBox.Report(strErr, strTitle) end

LFPlain.Close
LFCrypt.Close
'
' (One could delete the temporary files, but we leave them around for
' further processing if desired.)
'
'
' Create the grids.
'
useFloat = false
lstFN = {FNPlain, FNCrypt}
lstGrids = {}
for each theFN in lstFN
  lstGrids.Add(Grid.MakeFromASCII(theFN, useFloat))
end
lstGrids.Add( ( lstGrids.Get(1) - lstGrids.Get(0) ) + 128 % 256 - 128 )
'
' Obtain a view to show the results.
'
theView = av.GetActiveDoc
if (theView.Is(View).Not) then
  theView = av.FindDoc("View1")
end
if (theView = NIL) then
  theView = View.Make
end
'
' Visualize the grids.
'
lstNames = {"Plaintext", "Encrypted text", "Residual"}
for each i in 0..2
  G = lstGrids.Get(i)
  if (G.HasError) then
    MsgBox.Error("Cannot create the " + lstNames.Get(i) + " theme.", strTitle)
  else
    theTheme = GTheme.Make(G)
    theTheme.SetName(lstNames.Get(i))
    theView.AddTheme(theTheme)
  end
end
' end of script