pub fn preamble_bytes(kind: FrameKind, header_len: u64) -> ([u8; 10], usize)Expand description
A preamble for header_len bytes of header, and how many of the returned
bytes are it.
Returned in a fixed array rather than pushed into a Vec, so a send path
that already owns a buffer allocates nothing to write one: the frame’s
length field precedes the header it measures, so the header has to be
encoded first, and a caller that encodes it at MAX_PREAMBLE_LEN can then
right-align this preamble against it and write one contiguous slice
(B-250).