How to encode to UTF16 Little Endian in Dart?

Question

I am attempting to manipulate some system variables used by a program using Dart. I have encountered the problem of dart's utf package being discontinued, and I have not found any way to encode to UTF 16 Little Endian for a File.write. Is there a library that can do a byte to UTF 16 LE conversion in Dart? I would use UTF anyway, but it is not null safe. I may end up trying to use the utf package source code, but I am checking here to see if there is a native (or pub) implementation I have missed, as I am new to the world of UTF and byte conversions.

My goal:

encodeAsUtf16le(String s);

I do not need to write a BOM.

Answer 1

Dart Strings internally use UTF-16. You can use String.codeUnits to get the UTF-16 code units and then write them in little-endian form:

  var s = '\u{1F4A9}';
  var codeUnits = s.codeUnits;
  var byteData = ByteData(codeUnits.length * 2);
  for (var i = 0; i < codeUnits.length; i += 1) {
    byteData.setUint16(i * 2, codeUnits[i], Endian.little);
  }
  
  var bytes = byteData.buffer.asUint8List();
  await File('output').writeAsBytes(bytes);

or assume that you're running on a little-endian system:

  var s = '\u{1F4A9}';
  var codeUnits = s.codeUnits;
  var bytes = Uint16List.fromList(codeUnits).buffer.asUint8List();
  await File('output').writeAsBytes(bytes);

Also see https://stackoverflow.com/a/67802971/, which is about encoding UTF-16LE to Strings.

I also feel compelled to advise against writing UTF-16 to disk unless you're forced to by external requirements.