Linecount and sequence number

[amasanell-kineis]

Hello,
I'm currently doing consulting work for Kineis and your library is used there.
We have 2 requirements for the ais/nmea that this library does not cover:

• in the encoder we don't need the line count (https://github.com/BertoldVdb/go-ais/blob/master/aisnmea/tagblocks.go#L85)
• the tag sequence number usage differ slightly:
  • the sentence sequence number wraps at 9 (current behavior)
  • the tag sequence wraps at 9999 instead of 9

here is the modified code we currently use for the sequence number (original code: https://github.com/BertoldVdb/go-ais/blob/master/aisnmea/nmea.go#L181-L198):

			sentence := fmt.Sprintf("!%s%s,%d,%d,%d,%c,%s,%d", p.TalkerID, p.MessageType, msgNum, msgIndex, nc.seqNo%10, channel, sub, suffix)

			sentence = addChecksum(sentence)

			tagBlock := encodeTagBlock(&p.TagBlock, msgIndex, msgNum, nc.seqNo)
			if tagBlock != "" {
				sentence = fmt.Sprintf("%s%s", tagBlock, sentence)
			}

			output = append(output, sentence)

			msgIndex++
		}

		nc.seqNo++
		if nc.seqNo == 10000 {
			nc.seqNo = 0
		}

this modification is quick & dirty but does the job.

From what I understand of the code, those 2 modifications could be optional and integrated in the codec here: https://github.com/BertoldVdb/go-ais/blob/master/codec.go

Are you interested in a contribution with those 2 elements ?