Class: LIS::Transfer::PacketizedProtocol

Inherits:
Base
  • Object
show all
Defined in:
lib/lis/packetized_protocol.rb

Overview

splits a stream into lis packets and only lets packets through that are inside a session delimited by ENQ .. EOT

check the checksum and do acknowledgement of messages

forwards the following events:

  • :message, String

    when a message is received

  • :idle

    when a transmission is finished (after EOT is received)

Constant Summary

ACK = 
"\006"
NAK = 
"\025"
ENQ = 
"\005"
EOT = 
"\004"
RX =

format of a message

/(?:
  \005 | # ENQ - start a transaction
  \004 | # EOT - ends a transaction
  \005 | # ACK
  \025 | # NAK
  (?:\002 (.) (.*?) \015 \003 (.+?) \015 \012) # a message with a checksum
        #  |   |               `-- checksum
        #  |   `------------------ message
        #  `---------------------- frame number
  )
/xm

Instance Method Summary (collapse)

Methods inherited from Base

#<<, #forward, #on_data

Constructor Details

- (PacketizedProtocol) initialize(*args)

A new instance of PacketizedProtocol



33
34
35
36
37
 
# File 'lib/lis/packetized_protocol.rb', line 33

def initialize(*args)
  super(*args)
  @memo = ""
  @inside_transmission = false
end

Instance Method Details

- (Object) receive(data) 



39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
 
# File 'lib/lis/packetized_protocol.rb', line 39

def receive(data)
  scanner = StringScanner.new(@memo + data)
  while scanner.scan_until(RX)
    match = scanner.matched
    case match
      when ENQ then transmission_start
      when EOT then transmission_end
      when ACK, NAK then nil
    else
      received_message(match)
      write :ack
    end
  end
  @memo = scanner.rest
  nil
end

- (Object) write(type, data = nil) 



56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
 
# File 'lib/lis/packetized_protocol.rb', line 56

def write(type, data = nil)
  str = case type
    when :ack then ACK
    when :nak then NAK
    when :begin then
      @frame_number = 0
      ENQ
    when :idle then EOT
    when :message then
      @frame_number = (@frame_number + 1) % 8
      self.class.wrap_message(data, @frame_number)
  else
    raise ArgumentError
  end
  super(str)
end