How to achieve buffer of nodejs similar functionality in dart

Question

I am stuck in writing a similar code of nodejs in dart.

_createUInt32LEBuffer(value, bufferSize = 4) {
    const buffer = Buffer.alloc(bufferSize);
    buffer.writeUInt32LE(value, 0);
    if (i === 300) {
     console.log(Buffer.from(buffer).toString('base64').toString());
    }
    return buffer;
}

I have searched the web and got this solution but it's not working correctly:

Uint8List int32bytes(int value, {int size: 4}) {
    final re = Uint8List(size)..buffer.asUint8List();
    re[0] = value;
    if (value == 300) {
       print(base64Encode(re));
    }
return re;

}

Solution

This is because bytes are in reversed order in comparison to Buffer. So rewriting this to:

List<int> _createUInt32LE(int value, {int size: 4}) {
    final re = Uint8List(size)..buffer.asByteData().setUint32(0, value);
    return re.reversed.toList();
}

should work

EDIT: Solution above is not most performant. This should be better one:

List<int> _createUInt32LE(int value, {int size: 4}) {
  final result = Uint8List(size);
  for(int i = 0; i < size; i++, value >>= 8) {
    result[i] = value & 0xFF;
  }
  return result;
}

Comments

[julemand101]

Can you give an example of input and expected output values for us without any experience with nodejs? :)

[Kawaljeet Singh]

when the value is given as 300 then the output in base64 in nodejs is LAEAAA== but with dart the output after base64 is LAAAAA== and so on as it reches to higher values the output difference increases. for lower values like 0 to 200 the output is same