lua-editor.lua

Editor = {
   "1. First Line",
   "2. Second Line",
   "3. Third Line",
   "4. Fourth Line",
   "5. Fifth Line",
}

function timeit(fun,info)
   info = info or ""
   local t = os.clock()
   fun()
   print( info .. " took " .. tostring(os.clock() - t) .. " seconds" )
end

function Editor.LoadFile(self, name)
   name = name or "/Users/malkia/pp/lua-editor/1"
   local f = io.input(name)
   assert(f, "Editor:LoadFile - Can't open " .. name)
   while #self > 0 do
      self[#self] = nil
   end
   for line in f:lines() do
      self[#self + 1] = line
   end
end

function Editor.SaveFile(self, name)
   name = name or "/Users/malkia/pp/lua-editor/2"
   local f = io.output(name)
   assert(f, "Editor:SaveFile - Can't create " .. name)
   for i=1,#self do
      f:write(self[i], "\n")
   end
   f:close()
end


function Editor.DeleteLines(self, firstLine, lineCount)
   assert( firstLine >= 1 )
   assert( firstLine <= #self )
   assert( lineCount >= 1 )
   assert( lineCount <= #self - firstLine + 1 )

   -- Save the lines to be deleted for the undo operation
   local deletedLines = {}
   for i=0, lineCount - 1 do
      deletedLines[#deletedLines + 1] = self[firstLine + i]
   end

   -- Move the lines from the next-to-be line to the end of the file
   -- To the firstLine
   local nextLine = firstLine + lineCount
   for i=0, #self - nextLine do
      self[firstLine + i] = self[nextLine + i]
   end

   -- Delete the lines at the end, after the movement
   for i=1, lineCount do
      self[#self] = nil
   end

   -- Return an undo operation
   return function()
	     Editor:InsertLines(firstLine, deletedLines)
	  end
end

function Editor.InsertLines(self, firstLine, linesToInsert)
   if type(linesToInsert)=="string" then
      linesToInsert = { linesToInsert }
   else 
      if type(linesToInsert)=="number" then
	 local cnt = linesToInsert
	 linesToInsert = {}
	 for i=1,cnt do
	    linesToInsert[#linesToInsert + 1] = ""
	 end
      end
   end

   assert( firstLine >= 1, "firstLine >= 1" )
   assert( firstLine <= #self + 1, "firstLine <= #self + 1" )

   local linesToInsertCount = #linesToInsert
   assert( linesToInsertCount >= 1, "linesToInsertCount >= 1" )

   if firstLine == #self + 1 then
      -- Append
      for i=1, linesToInsertCount do
	 self[#self + 1] = linesToInsert[i]
      end
   else
      -- Expand the number of lines
      for i=1, linesToInsertCount do
	 self[#self + 1] = ""
      end

      -- Move the lines at the end to 
      -- Make space for the new lines
      local nextLine = firstLine + linesToInsertCount
      for i=#self, nextLine, -1 do
	 self[i] = self[i - linesToInsertCount]
      end

      -- Put the new lines
      for i=0, linesToInsertCount - 1 do
	 self[firstLine + i] = linesToInsert[i + 1]
      end
   end
   return function()
	     Editor:DeleteLines(firstLine, linesToInsertCount)
	  end
end

function Editor.DeleteCharacters(self, line, column, charactersCount)
   if line < 1 or line > #self then
      error( "Editor:DeleteCharacters - invalid line"..tostring(line) )
   end
end

print("")
timeit(function() Editor:LoadFile() end, "LoadFile")
for i=1,10 do
   local undo
   timeit(function() undo = Editor:DeleteLines(2, 200000) end, "DeleteLines")
   timeit(undo, "Undo (InsertLines)")
end
timeit(function() Editor:SaveFile() end, "aveFile")