hammer_crc_t
hammer_crc_t entry_crc;
hammer_crc_t layer2_crc; /* xor'd crc's of HAMMER_BLOCKSIZE */
hammer_crc_t layer1_crc; /* MUST BE LAST FIELD OF STRUCTURE*/
hammer_crc_t entry_crc;
hammer_crc_t hdr_crc; /* XOR crc up to field w/ crc after field */
hammer_crc_t vol_crc; /* header crc */
sizeof(hammer_crc_t))