Function fill_bytes 

pub fn fill_bytes(
    prng: &mut Pcg64Mcg,
    memory: impl MemoryAccess,
    remote_buf: AddrMut<'_, u8>,
    len: usize,
    dettid: DetTid,
    source: &str,
) -> Result<usize, Error>

Fill guest memory from the same stream/chunk/write algorithm used by the normal Detcore handler. No syscall/scheduler accounting is performed here.