Function is_encrypted_log_record 

pub fn is_encrypted_log_record(payload: &[u8]) -> bool

Reports whether a log-record payload carries the encrypted-record header.

The plaintext record encoding starts with its transaction number as a big-endian u64, so LOG_MAGIC is only ambiguous with a t above 4.8 quintillion. A log that reached that many transactions would have exhausted every other counter in the system first.