code: public UnsafeMappedBuffer map(long size, FileChannel.MapMode mode) {
      return map(position(), size, mode);
    }
docs: Maps a portion of the underlying file into memory starting at the current position up to the given {@code count}.
  
  @param size The count of the bytes to map into memory.
  @param mode The mode in which to map the bytes into memory.
  @return The mapped buffer.
  @throws IllegalArgumentException If {@code count} is greater than the maximum allowed
  {@link java.nio.MappedByteBuffer} count: {@link Integer#MAX_VALUE}