Struct regex_automata::dfa::onepass::Cache

pub struct Cache { /* private fields */ }

Available on (crate features dfa-search or dfa-onepass) and crate feature dfa-onepass only.

A cache represents mutable state that a one-pass DFA requires during a search.

For a given one-pass DFA, its corresponding cache may be created either via DFA::create_cache, or via Cache::new. They are equivalent in every way, except the former does not require explicitly importing Cache.

A particular Cache is coupled with the one-pass DFA from which it was created. It may only be used with that one-pass DFA. A cache and its allocations may be re-purposed via Cache::reset, in which case, it can only be used with the new one-pass DFA (and not the old one).

Implementations

impl Cache

pub fn new(re: &DFA) -> Cache

Create a new onepass::DFA cache.

A potentially more convenient routine to create a cache is DFA::create_cache, as it does not require also importing the Cache type.

If you want to reuse the returned Cache with some other one-pass DFA, then you must call Cache::reset with the desired one-pass DFA.

pub fn reset(&mut self, re: &DFA)

Reset this cache such that it can be used for searching with a different onepass::DFA.

A cache reset permits reusing memory already allocated in this cache with a different one-pass DFA.

Example

This shows how to re-purpose a cache for use with a different one-pass DFA.

use regex_automata::{dfa::onepass::DFA, Match};

let re1 = DFA::new(r"\w")?;
let re2 = DFA::new(r"\W")?;
let mut caps1 = re1.create_captures();
let mut caps2 = re2.create_captures();

let mut cache = re1.create_cache();
assert_eq!(
    Some(Match::must(0, 0..2)),
    { re1.captures(&mut cache, "Δ", &mut caps1); caps1.get_match() },
);

// Using 'cache' with re2 is not allowed. It may result in panics or
// incorrect results. In order to re-purpose the cache, we must reset
// it with the one-pass DFA we'd like to use it with.
//
// Similarly, after this reset, using the cache with 're1' is also not
// allowed.
re2.reset_cache(&mut cache);
assert_eq!(
    Some(Match::must(0, 0..3)),
    { re2.captures(&mut cache, "☃", &mut caps2); caps2.get_match() },
);

pub fn memory_usage(&self) -> usize

Returns the heap memory usage, in bytes, of this cache.

This does not include the stack size used up by this cache. To compute that, use std::mem::size_of::<Cache>().

Trait Implementations

impl Clone for Cache

fn clone(&self) -> Cache

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for Cache

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

Formats the value using the given formatter.