pub fn tail_pair(input: &[u8], width: usize, index: usize) -> Result<(u64, u64)>Expand description
Two neighbouring values of a run, read from one load where the pair fits inside it.
index is the later of the two and the answer is the pair at index - 1 and index. A text
column asks for exactly this once per string it hands out, because a value starts where the one
before it ended. Two calls to tail_at read the same eight bytes twice and do the bounds
arithmetic twice, where a pair of seventeen bit offsets, which is what a block of text carries,
both lie inside one load.
ยงErrors
If index is zero, if width exceeds 64, or if the pair would run past the end of input.