text: #ifndef cksum_h
  #define cksum_h
  
  /*
   * The CheckSum type holds a table of CRC byte checksums to facilitate up
   * the process of calculating the checksum of an array of bytes.
   */
  typedef struct CheckSum CheckSum;
  
  CheckSum *new_CheckSum(void);
  CheckSum *del_CheckSum(CheckSum *cs);
  
  /*
   * Compute a 32-bit cyclic redundancy checksum of an object of given
   * size, using the ethernet key.
   */
  unsigned long checksum_of_object(CheckSum *cs, void *obj, size_t nbyte);
  
  #endif
  