code: final int calcLevels(long length) {
          // The calculation is essentially a math log operation, but the table
          // lookup is faster.
          int index = Arrays.binarySearch(mLevelMaxSizes, length);
          return (index < 0) ? ~index : index;
      }
docs: Calculates the level of indirection needed to access a block in a file
  of the given length. If the level is zero, the file table points
  directly to a data block. If the level is one, the file table points to
  file table block. A file table block contains block ids which map to
  data blocks or more file table blocks.