hsms_message.rb

class SType
  BYTE_OFFSET = 9
  DATA_MESSAGE = 0
  SELECT_REQ = 1
  SELECT_RSP = 2
  DESELECT_REQ = 3
  DESELECT_RSP = 4
  SEPARATE_REQ = 9
end

class HSMSMessage
  MAX_BUFFER_SIZE = 0xFFFFFFFF
  LENGTH_BYTES = 4
  HEADER_BYTES = 10
  
  attr_reader :buffer
  
  def initialize
    @buffer = ""
    @length = 0
  end
  
  def feed(data)
    return if remain_buffer_size == 0
    @buffer << data
  end
  
  # TODO?
  # Request resend command if received length < header bytes.
  def length
    return @length unless @length == 0
    return 0 if buffer.length < LENGTH_BYTES
    LENGTH_BYTES.times { |i|
      @length <<= 8
      @length += @buffer[i]
    }
    return @length
  end
  
  def remain_buffer_size
    return MAX_BUFFER_SIZE if length == 0
    return LENGTH_BYTES + @length - @buffer.length
  end
  
  def s_type
    return buffer[SType::BYTE_OFFSET]
  end
  
  def self.empty_data(s_type)
    data = "\x00\x00\x00\x0A" + "\x00" * 10
    data[SType::BYTE_OFFSET] = s_type
    return data
  end
end