Function update_short 

pub(crate) fn update_short(prev: u32, buf: &[u8]) -> u32

Like update_fast_16, but without the 16-byte loops, for buffers shorter than 16 bytes.

Up to 3 bytes go straight to the byte loop. Longer buffers are folded out of line, so a caller that inlines this doesn’t need the extra registers the slicing code uses.