code: private static int compressionLevel(int blockSize) {
          if (blockSize < MIN_BLOCK_SIZE || blockSize > MAX_BLOCK_SIZE) {
              throw new IllegalArgumentException(String.format(
                      "blockSize: %d (expected: %d-%d)", blockSize, MIN_BLOCK_SIZE, MAX_BLOCK_SIZE));
          }
          int compressionLevel = 32 - Integer.numberOfLeadingZeros(blockSize - 1); // ceil of log2
          compressionLevel = Math.max(0, compressionLevel - COMPRESSION_LEVEL_BASE);
          return compressionLevel;
      }
docs: Calculates compression level on the basis of block size.