function copy_array_buffer_to_uint8array(array_buffer) {
    const source = new Uint8Array(array_buffer);
    return new Uint8Array(source.subarray(0, source.length));
}
Copies an ArrayBuffer to a Uint8Array.
Note! This method is supposed to be extremely performant as it is used by the Body parser.
@param {ArrayBuffer} array_buffer