pub fn seq_delta(a: u16, b: u16) -> i16Expand description
Wrap-aware signed difference of two 16-bit sequence numbers (a - b).
Every frame-id comparison must go through this. The prototype had a real
bug from unsigned arithmetic: one reordered chunk from an older frame made
the eviction sweep compute (old - current) & 0xFFFF ≈ 65500 for the frame
being assembled and delete it.