Class: OpenC3::CcsdsParser

Inherits:
Object show all
Defined in:
lib/openc3/ccsds/ccsds_parser.rb

Overview

Unsegments CCSDS packets and perform other CCSDS processing tasks.

Defined Under Namespace

Classes: CcsdsSegmentationError

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ CcsdsParser

Create a new OpenC3::CcsdsPacket and set the state to :READY



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# File 'lib/openc3/ccsds/ccsds_parser.rb', line 48

def initialize
  @ccsds_packet = CcsdsPacket.new
  @unsegmented_data = nil
  @sequence_count = nil
  reset()
end

Instance Attribute Details

#in_progress_data ⇒ String (readonly) 



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# File 'lib/openc3/ccsds/ccsds_parser.rb', line 39

def in_progress_data
  @in_progress_data
end

#sequence_count ⇒ Integer (readonly) 



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# File 'lib/openc3/ccsds/ccsds_parser.rb', line 45

def sequence_count
  @sequence_count
end

#state ⇒ Symbol (readonly) 



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# File 'lib/openc3/ccsds/ccsds_parser.rb', line 34

def state
  @state
end

#unsegmented_data ⇒ String (readonly) 



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# File 'lib/openc3/ccsds/ccsds_parser.rb', line 42

def unsegmented_data
  @unsegmented_data
end

Instance Method Details

#reset ⇒ Object

Resets internal state to :READY and clears the in_progress_data



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# File 'lib/openc3/ccsds/ccsds_parser.rb', line 56

def reset
  @state = :READY
  @in_progress_data = ''
end

#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.



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# File 'lib/openc3/ccsds/ccsds_parser.rb', line 70

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

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

  # Handle each segment
  seq_flags = @ccsds_packet.read('CcsdsSeqflags')
  case seq_flags
  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

  else
    reset()
    raise CcsdsSegmentationError, "Unknown sequence flags #{seq_flags}"
  end
end