Method: OpenC3::CcsdsParser#unsegment_packet

Defined in:
lib/openc3/ccsds/ccsds_parser.rb

#unsegment_packet(packet) ⇒ String|nil

Given a segment of a larger CCSDS packet, stores the data until a complete unsegmented packet can be created. Returns the unsegmented packet data once it is complete, or nil if still in progress. Raises CcsdsParser::CcsdsSegmentationError if a problem is encountered while unsegmenting.

Parameters:

  • packet (Packet) —

    A CCSDS packet

Returns:

  • (String|nil) —

    The reconstituted CCSDS packet buffer or nil if the packet has not yet been fully assembled



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# File 'lib/openc3/ccsds/ccsds_parser.rb', line 67

def unsegment_packet(packet)
  @ccsds_packet.buffer = packet.buffer

  previous_sequence_count = @sequence_count
  @sequence_count = @ccsds_packet.read('CcsdsSeqcnt')

  # Handle each segment
  case @ccsds_packet.read('CcsdsSeqflags')
  when CcsdsPacket::CONTINUATION
    #####################################################
    # Continuation packet - only process if in progress
    #####################################################

    if @state == :IN_PROGRESS
      if @sequence_count == ((previous_sequence_count + 1) % 16384)
        @in_progress_data << @ccsds_packet.read('CcsdsData')
        return nil
      else
        reset()
        raise CcsdsSegmentationError, "Missing packet(s) before continuation packet detected. Current Sequence Count #{@sequence_count}, Previous Sequence Count #{previous_sequence_count}"
      end
    else
      reset()
      raise CcsdsSegmentationError, "Unexpected continuation packet"
    end

  when CcsdsPacket::FIRST
    #######################################################
    # First packet - always process
    #######################################################

    if @state == :IN_PROGRESS
      reset()
      @state = :IN_PROGRESS
      @in_progress_data << @ccsds_packet.buffer
      raise CcsdsSegmentationError, "Unexpected first packet"
    else
      @state = :IN_PROGRESS
      @in_progress_data << @ccsds_packet.buffer
      return nil
    end

  when CcsdsPacket::LAST
    ######################################################################
    # Last packet - only process if in progress
    ######################################################################

    if @state == :IN_PROGRESS
      if @sequence_count == ((previous_sequence_count + 1) % 16384)
        @in_progress_data << @ccsds_packet.read('CcsdsData')
        @unsegmented_data = @in_progress_data
        reset()
        return @unsegmented_data
      else
        reset()
        raise CcsdsSegmentationError, "Missing packet(s) before last packet detected. Current Sequence Count #{@sequence_count}, Previous Sequence Count #{previous_sequence_count}"
      end
    else
      reset()
      raise CcsdsSegmentationError, "Unexpected last packet"
    end

  when CcsdsPacket::STANDALONE
    ############################################################
    # Standalone packet - save and return its data
    ############################################################

    # Update most recent unsegmented data
    @unsegmented_data = @ccsds_packet.buffer

    if @state == :IN_PROGRESS
      reset()
      raise CcsdsSegmentationError, "Unexpected standalone packet"
    else
      reset()
      return @unsegmented_data
    end

  end # case raw_sequence_flags
end