I was writing a program to unpack Uint8 and Uint32 integers from a stream, and encountered this issue where I couldn’t pass a non-multiple-of-4 value as start argument of Uint32List.sublistView() function. I understand that end - start should be a multiple of 4, but why should the value of start be multiple of 4?

Example:

Assume that I have a byte stream which represents an array of Uint32s. The first byte of the stream is a Uint8 value representing the count of Uint32 values. Below is a simplified version of the code I am trying to accomplish.

import 'dart:typed_data';

void main() {
    // First byte (2) represents the number of Uint32 values. The 2 Uint32 values are 7 and 5
    // represented in Endian.little. Please note this is just a simplified representation, 
    // I do have other data elements in my original byte stream.
    var bytes = Uint8List.fromList([2, 7, 0, 0, 0, 5, 0, 0, 0]);

    // I would just like pull the Uint32 values list without performing any copy.
    // as in the below line.
    var uint32List = Uint32List.sublistView(bytes, 1, 1 + bytes[0]*4);

    // However, the above line throws
    // RangeError: Offset (1) must be a multiple of BYTES_PER_ELEMENT (4) error.
    // Instead I have to copy the bytes to a different buffer
    // or use some kind of iteration over ByteData. like:
    var elements = Uint8List.fromList(Uint8List.sublistView(bytes, 1)); // copy bytes
    print(Uint32List.sublistView(elements)); // prints [7, 5]
}

Dart documentation: https://api.dart.dev/stable/3.4.4/dart-typed_data/Uint32List/Uint32List.sublistView.html