code: @Implementation
    protected ByteBuffer map(int prot, int offset, int length) throws ErrnoException {
      ReflectionHelpers.callInstanceMethod(realObject, "checkOpen");
      File file = filesByFd.get(getRealFileDescriptor());
      if (file == null) {
        throw new IllegalStateException("SharedMemory from a parcel isn't yet implemented!");
      }
  
      try (RandomAccessFile randomAccessFile = new RandomAccessFile(file, "rw")) {
        // It would be easy to support a MapMode.READ_ONLY type mapping as well except none of the
        // OsConstants fields are even initialized by robolectric and so "prot" is always zero!
        return randomAccessFile.getChannel().map(MapMode.READ_WRITE, offset, length);
      } catch (IOException e) {
        throw new ErrnoException(e.getMessage(), OsConstants.EIO, e);
      }
    }
docs: Only works on {@link SharedMemory} instances from {@link SharedMemory#create}.
  
  <p>"prot" is ignored -- all mappings are read/write.