lsl_core

lsl_core holds the parts of Lab Streaming Layer that need no native library: channel formats and a codec for their values, samples and chunks, clock offsets, and the helpers for receiving and polling streams. It is pure Dart and runs on all platforms, including the web.

liblsl (the FFI bindings) re-exports its LSL* types and adds their native side, so code using liblsl sees no difference. lsl_tools, xdf and the coordinators build on it, so the same types and code are shared instead of copied.

API documentation

Installation

dart pub add lsl_core

What is in it

• Formats and values. LSLChannelFormat, and a little-endian codec for every format (readValues, writeValues, asFormat, typedListFor): values stay in their own format, so nothing is lost on the way. int64 is exact where ints are 64-bit; in a browser, ints are JavaScript numbers and hold integers exactly only up to ±2^53 (exactInt64 says which).
• Samples. LSLSample, LSLChunk, LSLChunkTyped, LSLTimedChunk, and LslChunk, the chunk the inlet facade hands out.
• Clocks. LSLTimeCorrection, and ClockModel, ClockHop and ClockChain: how a time stamp maps onto this computer's clock, hop by hop, with error bounds and latency.
• The inlet and outlet facade. LslBackend, LslInlet, LslOutlet and their options, which lsl_tools implements with liblsl, a WebSocket bridge, or nothing (on the web).
• Receiving and polling. receiveChunks (event-driven with a fallback to polling), drainInlet, pullCapacity, pollIntervalFor, ListenerRestartSchedule, TimeCorrectionSchedule and runPreciseInterval.
• Configuration and metadata. LSLApiConfig, LSLContentType, and stream info XML (buildInfoXml, infoField, channelsOf).

Example

import 'dart:typed_data';

import 'package:lsl_core/lsl_core.dart';

void main() {
  // Eight bytes per int64, little-endian, exactly.
  final d = ByteData(16);
  writeValues(d, 0, LSLChannelFormat.int64, [(1 << 60) + 1, -7], 2);
  final back = readValues(d, 0, LSLChannelFormat.int64, 2);
  print(back); // [1152921504606846977, -7]
}