static long numChunks(long datasize, int bytesPerChecksum) {
    long numChunks = datasize / bytesPerChecksum;
    if (datasize % bytesPerChecksum != 0) {
      numChunks++;
    }
    return numChunks;
  }
Returns the number of checksum chunks needed to store the checksums for a specified data size
@param datasize         number of bytes of data
@param bytesPerChecksum number of bytes in a checksum chunk
@return The number of checksum chunks
hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/ChecksumUtil.java