code: public static void writeBytes(byte b[], int offset, byte[] value) {
      System.arraycopy(value, 0, b, offset, value.length);
    }
docs: Serializes a byte[] into a byte array at a specific offset
  
  @param b byte array in which to write a byte[] value.
  @param offset offset within byte array to start writing.
  @param value byte[] to write to byte array.