Struct aho_corasick::util::prefilter::RareByteOffset

struct RareByteOffset {
    max: u8,
}

Offsets associated with an occurrence of a “rare” byte in any of the patterns used to construct a single Aho-Corasick automaton.

Fields

max: u8

The maximum offset at which a particular byte occurs from the start of any pattern. This is used as a shift amount. That is, when an occurrence of this byte is found, the candidate position reported by the prefilter is position_of_byte - max, such that the automaton will begin its search at a position that is guaranteed to observe a match.

To avoid accidentally quadratic behavior, a prefilter is considered ineffective when it is asked to start scanning from a position that it has already scanned past.

Using a u8 here means that if we ever see a pattern that’s longer than 255 bytes, then the entire rare byte prefilter is disabled.

Implementations

impl RareByteOffset

fn new(max: usize) -> Option<RareByteOffset>

Create a new rare byte offset. If the given offset is too big, then None is returned. In that case, callers should render the rare bytes prefilter inert.

Trait Implementations

impl Clone for RareByteOffset

fn clone(&self) -> RareByteOffset

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for RareByteOffset

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

Formats the value using the given formatter.

impl Default for RareByteOffset

fn default() -> RareByteOffset

Returns the “default value” for a type.

impl Copy for RareByteOffset