Struct regex_automata::dfa::remapper::IndexMapper

struct IndexMapper {
    stride2: usize,
}

A simple type for mapping between state indices and state IDs.

The reason why this exists is because state IDs are “premultiplied.” That is, in order to get to the transitions for a particular state, one need only use the state ID as-is, instead of having to multiple it by transition table’s stride.

The downside of this is that it’s inconvenient to map between state IDs using a dense map, e.g., Vec. That’s because state IDs look like 0, 0+stride, 0+2*stride, 0+3*stride, etc., instead of 0, 1, 2, 3, etc.

Since our state IDs are premultiplied, we can convert back-and-forth between IDs and indices by simply unmultiplying the IDs and multiplying the indices.

Fields

stride2: usize

The power of 2 corresponding to the stride of the corresponding transition table. ‘id >> stride2’ de-multiplies an ID while ‘index << stride2’ pre-multiplies an index to an ID.

Implementations

impl IndexMapper

fn to_index(&self, id: StateID) -> usize

Convert a state ID to a state index.

fn to_state_id(&self, index: usize) -> StateID

Convert a state index to a state ID.

Trait Implementations

impl Debug for IndexMapper

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.