- unsigned_sum = 0;
- signed_sum = 0;
- p = header->buffer;
- for (i = sizeof *header; i-- != 0;)
- {
- unsigned_sum += (unsigned char) *p;
- signed_sum += (signed char) (*p++);
- }
-
- if (unsigned_sum == 0)
- return HEADER_ZERO_BLOCK;
-
- /* Adjust checksum to count the "chksum" field as blanks. */
-
- for (i = sizeof header->header.chksum; i-- != 0;)
- {
- unsigned_sum -= (unsigned char) header->header.chksum[i];
- signed_sum -= (signed char) (header->header.chksum[i]);
- }
- unsigned_sum += ' ' * sizeof header->header.chksum;
- signed_sum += ' ' * sizeof header->header.chksum;
-
- parsed_sum = from_header (header->header.chksum,
- sizeof header->header.chksum, 0,
- (uintmax_t) 0,
- (uintmax_t) TYPE_MAXIMUM (int));
- if (parsed_sum == (uintmax_t) -1)
- return HEADER_FAILURE;
-
- recorded_sum = parsed_sum;
-
- if (unsigned_sum != recorded_sum && signed_sum != recorded_sum)
- return HEADER_FAILURE;