Struct regex_automata::sparse::ByteClass

pub struct ByteClass<T: AsRef<[u8]>, S: StateID = usize>(_);

A sparse DFA that shrinks its alphabet.

Alphabet shrinking is achieved by using a set of equivalence classes instead of using all possible byte values. Any two bytes belong to the same equivalence class if and only if they can be used interchangeably anywhere in the DFA while never discriminating between a match and a non-match.

Unlike dense DFAs, sparse DFAs do not tend to benefit nearly as much from using byte classes. In some cases, using byte classes can even marginally increase the size of a sparse DFA's transition table. The reason for this is that a sparse DFA already compacts each state's transitions separate from whether byte classes are used.

Generally, it isn't necessary to use this type directly, since a SparseDFA 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: AsRef<[u8]>, S: StateID> DFA for ByteClass<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: Clone + AsRef<[u8]>, S: Clone + StateID> Clone for ByteClass<T, S>

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

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<T: Debug + AsRef<[u8]>, S: Debug + StateID> Debug for ByteClass<T, S>

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

Formats the value using the given formatter.