ricardoboss/dart_nmea

An extensible NMEA0183 parser written 100% in dart.

nmea

An extensible NMEA0183 parser.

Take a look at the example to see how to use it.

Usage

// 1. declare your sentences (use TalkerSentence and ProprietarySentence)
class AbcSentence extends TalkerSentence {
  AbcSentence({required super.raw});
  
  String get data => fields[1];
  
  @override
  bool get valid => super.valid && fields.length == 2;
}

// 2. register your sentences
final decoder = NmeaDecoder()
  ..registerTalkerSentence("ABC", (line) => AbcSentence(raw: line));

// 3. decode a line
final sentence = decoder.decode("\$--ABC,123456789*5D");

// 4. consume your sentences
print(sentence.valid); // true
print(sentence.checksum); // 5D
print(sentence.source); // --
if (sentence is AbcSentence) {
  print(sentence.data); // 123456789
}

You can also use it as a StreamTransformer for a stream of Strings:

final stream = Stream.fromIterable(["\$--ABC,123456789*5D", "\$--DEF,987654321*5D"]);
final transformed = stream.transform(decoder);
transformed.listen((sentence) {
  print(sentence.valid); // true
  print(sentence.checksum); // 5D
  print(sentence.source); // --
  if (sentence is AbcSentence) {
    print(sentence.data); // 123456789
  }
});

dart_nmea's Issues

Support for custom sentences (non-standard)

From my discussion with @Wackymax at: 91a5d73#commitcomment-81132865

Data sent from some devices deviate from the NMEA0183 standard and provide sentences in a different format than what is expected (i.e. talker sentences without talker ID, sentences without $ in the beginning?).

While this is not great, it would be nice to at least add basic support for handling these cases.

Add support for split messages

Some sentences like GSV are split up into multiple messages.

The decoder could buffer those until all messages are received and then forward them as a single sentence.

I think a special MultipartNmeaSentence class is needed, which can access fields from multiple NmeaSentence instances. It should at least be able to aggregate multiple data fields.

Extensibility is also important. For example if the user wants to implement a custom message, it should be easy to re-use this MultipartNmeaSentence.

Limit size of `_incompleteSentences` in `NmeaDecoder`

Currently, the number of incomplete MultipartSentences held in NmeaDecoder and filled in bind, is unlimited.

This, however, could lead to a possible memory leak if the input stream produces only incomplete sentences (e.g., sent by a defective NMEA0183 device).

A solution would be to convert the _incompleteSentences field from a List<MultipartSentence<dynamic>> to a data structure which has a limited backlog and acts as a FIFO buffer (circular buffer).