bind method

@override Stream bind(Stream<List<int>> stream)

Transforms the provided stream.

Returns a new stream with events that are computed from events of the provided stream.

The StreamTransformer interface is completely generic, so it cannot say what subclasses do. Each StreamTransformer should document clearly how it transforms the stream (on the class or variable used to access the transformer), as well as any differences from the following typical behavior:

• When the returned stream is listened to, it starts listening to the input stream.
• Subscriptions of the returned stream forward (in a reasonable time) a StreamSubscription.pause call to the subscription of the input stream.
• Similarly, canceling a subscription of the returned stream eventually (in reasonable time) cancels the subscription of the input stream.

"Reasonable time" depends on the transformer and stream. Some transformers, like a "timeout" transformer, might make these operations depend on a duration. Others might not delay them at all, or just by a microtask.

Transformers are free to handle errors in any way. A transformer implementation may choose to propagate errors, or convert them to other events, or ignore them completely, but if errors are ignored, it should be documented explicitly.

Implementation

@override
Stream<dynamic> bind(Stream<List<int>> stream) async* {
  final reader = StreamBinaryReader();

  await for (final chunk in stream) {
    reader.addChunk(chunk);

    while (reader.availableBytes > 0) {
      reader.bookmark();
      final bytesBefore = reader.availableBytes;

      try {
        // Use the scanner to quickly validate and find the exact byte size
        // of the next message.
        MessagePackScanner.skip(reader);
        final consumed = bytesBefore - reader.availableBytes;

        // Rollback so we can read the exact full payload
        reader.rollback();

        // Read the exact payload and decode it optimally
        final payload = reader.readBytes(consumed);
        yield _mp.unpack<dynamic>(payload);
      } on NotEnoughDataException {
        // The message is incomplete. Rollback and wait for the next chunk.
        reader.rollback();
        break;
      } catch (e) {
        // In case of parsing errors, rollback to clean up state
        reader.rollback();
        rethrow;
      }
    }
  }
}