Struct aho_corasick::util::prefilter::StartBytesBuilder

struct StartBytesBuilder {
    ascii_case_insensitive: bool,
    byteset: Vec<bool>,
    count: usize,
    rank_sum: u16,
}

A builder for constructing a starting byte prefilter.

A starting byte prefilter is a simplistic prefilter that looks for possible matches by reporting all positions corresponding to a particular byte. This generally only takes affect when there are at most 3 distinct possible starting bytes. e.g., the patterns foo, bar, and baz have two distinct starting bytes (f and b), and this prefilter returns all occurrences of either f or b.

In some cases, a heuristic frequency analysis may determine that it would be better not to use this prefilter even when there are 3 or fewer distinct starting bytes.

Fields

ascii_case_insensitive: bool

Whether this prefilter should account for ASCII case insensitivity or not.

byteset: Vec<bool>

The set of starting bytes observed.

count: usize

The number of bytes set to true in byteset.

rank_sum: u16

The sum of frequency ranks for the rare bytes detected. This is intended to give a heuristic notion of how rare the bytes are.

Implementations

impl StartBytesBuilder

fn new() -> StartBytesBuilder

Create a new builder for constructing a start byte prefilter.

fn ascii_case_insensitive(self, yes: bool) -> StartBytesBuilder

Enable ASCII case insensitivity. When set, byte strings added to this builder will be interpreted without respect to ASCII case.

fn build(&self) -> Option<Prefilter>

Build the starting bytes prefilter.

If there are more than 3 distinct starting bytes, or if heuristics otherwise determine that this prefilter should not be used, then None is returned.

fn add(&mut self, bytes: &[u8])

Add a byte string to this builder.

All patterns added to an Aho-Corasick automaton should be added to this builder before attempting to construct the prefilter.

fn add_one_byte(&mut self, byte: u8)

Trait Implementations

impl Clone for StartBytesBuilder

fn clone(&self) -> StartBytesBuilder

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for StartBytesBuilder

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

Formats the value using the given formatter.