The Checksummed Blob

Implement blob write/read with integrity checking. The boilerplate declares: ``c /* format: 4-byte magic "CJB1" | uint32 len LE | len payload bytes | 4-byte FNV-1a checksum of the payload, LE */ int blob_write(const char *path, const unsigned char *data, size_t len); /* reads and verifies: 0 ok (fills *out = malloc'd payload, *len), -1 on any error: missing file, bad magic, checksum mismatch, allocation failure. Caller frees *out. */ int blob_read(const char *path, unsigned char **out, size_t *len); `` FNV-1a: h = 2166136261u; per byte: h ^= b; h *= 16777619u.

Difficulty: intermediate