serial printer by ruby

sp_printer.rb

#!/usr/local/rvm/rubies/ruby-1.9.2-p180/bin/ruby
#encoding: utf-8
require "yaml"
require File.expand_path(File.join(File.dirname(__FILE__), "serialport.rb"))
require File.expand_path(File.join(File.dirname(__FILE__), "memq.rb"))



class String
  def to_bin
    [self].pack("H*")
  end

  def add_zero
    self.length == 1 ? "0" + self : self
  end

  def to_hex
    str=""
    self.each_byte{|b| str << b.to_s(16).add_zero }
    str
  end

  def reverse_printing length = 40
    if self.length <= length
    else
      return chunk_intel(length).map{|l| l.center(length)}.reverse * ""
    end
    self
  end

  def chunk_string length = 40
    strs = []
    newstr = self
    while newstr.length > length
      strs << newstr[0..length-1]
      newstr = newstr[length..-1]
    end
    strs << newstr
  end

  def chunk_intel length = 40
    newstr=self
    strs = []
    elems = self.split(" ")
    str_index=0
    strs[str_index]=""
    elems.each do |elem|
      expected_len = (strs[str_index] +" "+ elem).length
      if strs[str_index].length == 0 # empty line
        if elem.length > length
          elem_lines = elem.chunk_string
          strs += elem_lines
          str_index += elem_lines.length
        else
          strs[str_index] = elem
        end
      elsif expected_len > length # new line needed
        str_index += 1
        if elem.length > length
          elem_lines = elem.chunk_string
          strs += elem_lines
          str_index += elem_lines.length
        else
          strs[str_index] = elem
        end
      elsif expected_len < length # within line
        strs[str_index] += (" " + elem)
      elsif expected_len == length # within line, no new space needed
        strs[str_index] += (" " + elem)
      end

    end
    strs
  end
end

sp = SerialPort.new "/dev/ttyUSB0", 9600, 8, 1, SerialPort::NONE
str= ARGV[0].reverse_printing
sp.write("1b3800"+str.to_hex+"0d".to_bin)