Struct regex_automata::dense::Premultiplied

pub struct Premultiplied<T: AsRef<[S]>, S: StateID>(_);

A dense DFA that premultiplies all of its state identifiers in its transition table.

This saves an instruction per byte at match time which improves search performance.

The only downside of premultiplication is that it may prevent one from using a smaller state identifier representation than you otherwise could.

Generally, it isn’t necessary to use this type directly, since a DenseDFA can be used for searching directly. One possible reason why one might want to use this type directly is if you are implementing your own search routines by walking a DFA’s transitions directly. In that case, you’ll want to use this type (or any of the other DFA variant types) directly, since they implement next_state more efficiently.

Trait Implementations

impl<T: Clone + AsRef<[S]>, S: Clone + StateID> Clone for Premultiplied<T, S>

fn clone(&self) -> Premultiplied<T, S>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T: AsRef<[S]>, S: StateID> DFA for Premultiplied<T, S>

type ID = S

The representation used for state identifiers in this DFA.

fn start_state(&self) -> S

Return the identifier of this DFA’s start state.

fn is_match_state(&self, id: S) -> bool

Returns true if and only if the given identifier corresponds to a match state.

fn is_dead_state(&self, id: S) -> bool

Returns true if and only if the given identifier corresponds to a dead state. When a DFA enters a dead state, it is impossible to leave and thus can never lead to a match.

fn is_match_or_dead_state(&self, id: S) -> bool

Returns true if and only if the given identifier corresponds to either a dead state or a match state, such that one of is_match_state(id) or is_dead_state(id) must return true.

fn is_anchored(&self) -> bool

Returns true if and only if this DFA is anchored.

fn next_state(&self, current: S, input: u8) -> S

Given the current state that this DFA is in and the next input byte, this method returns the identifier of the next state. The identifier returned is always valid, but it may correspond to a dead state.

unsafe fn next_state_unchecked(&self, current: S, input: u8) -> S

Like next_state, but its implementation may look up the next state without memory safety checks such as bounds checks. As such, callers must ensure that the given identifier corresponds to a valid DFA state. Implementors must, in turn, ensure that this routine is safe for all valid state identifiers and for all possible u8 values.

fn is_match(&self, bytes: &[u8]) -> bool

Returns true if and only if the given bytes match this DFA.

fn shortest_match(&self, bytes: &[u8]) -> Option<usize>

Returns the first position at which a match is found.

fn find(&self, bytes: &[u8]) -> Option<usize>

Returns the end offset of the longest match. If no match exists, then None is returned.

fn rfind(&self, bytes: &[u8]) -> Option<usize>

Returns the start offset of the longest match in reverse, by searching from the end of the input towards the start of the input. If no match exists, then None is returned. In other words, this has the same match semantics as find, but in reverse.

fn is_match_at(&self, bytes: &[u8], start: usize) -> bool

Returns the same as is_match, but starts the search at the given offset.

fn shortest_match_at(&self, bytes: &[u8], start: usize) -> Option<usize>

Returns the same as shortest_match, but starts the search at the given offset.

fn find_at(&self, bytes: &[u8], start: usize) -> Option<usize>

Returns the same as find, but starts the search at the given offset.

fn rfind_at(&self, bytes: &[u8], start: usize) -> Option<usize>

Returns the same as rfind, but starts the search at the given offset.

impl<T: Debug + AsRef<[S]>, S: Debug + StateID> Debug for Premultiplied<T, S>

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

Formats the value using the given formatter.