Function peek_stamp_us 

pub fn peek_stamp_us(raw: &[u8], offset: usize) -> Option<u64>

Peek Time { i32 sec; u32 nanosec } little-endian at offset in a raw CDR receive buffer (encapsulation header included) and return µs since the UNIX epoch. None when the buffer is too short or the stamp is pre-epoch/zero (unstamped messages never fire age monitors).