How to read part of a chunked stream - dart

Question

In Dart, stdin is a Stream<List<int>>. Bytes come in in chunks. What I want is a function that reads from stdin until I get some character (say '\0'), and then returns, so that future readers of stdin get the data after the '\0'.
Unfortunately because of the chunking, the '\0' byte might be in the middle of a chunk, so I kind of want to read a chunk, remove part of it, and then push it back to the start of the stream. But there isn't any way to do this.
Another option would be readByteSync() but reading bytes one at a time is going to be slow and this is in a GUI program so I can't use sync methods.

Answer 1

I think actually because a Stream<> can only ever be listened to once - even if a previous listener cancels its subscription - the only way is to have something permanently filtering the stream's events until the end of time. So you may as well just split the stream into two streams:
import 'dart:async';
class StdioPreambleSplitter {
StdioPreambleSplitter(this._input) {
var preambleFinished = false;
_input.listen((chunk) {
if (preambleFinished) {
_dataStream.add(chunk);
} else {
final nullByte = chunk.indexOf(0);
if (nullByte == -1) {
_dataStream.add(chunk);
} else {
preambleFinished = true;
_preambleStream.add(chunk.sublist(0, nullByte));
_dataStream.add(chunk.sublist(nullByte));
}
}
});
}
Stream<List<int>> preambleStream() {
return _preambleStream.stream;
}
Stream<List<int>> dataStream() {
return _dataStream.stream;
}
final Stream<List<int>> _input;
final StreamController<List<int>> _preambleStream = new StreamController();
final StreamController<List<int>> _dataStream = new StreamController();
}
Hopefully it doesn't add too much overhead.