alloc::str::pattern

Trait ReverseSearcher

pub unsafe trait ReverseSearcher<'a>: Searcher<'a> {
    // Required method
    fn next_back(&mut self) -> SearchStep;

    // Provided methods
    fn next_match_back(&mut self) -> Option<(usize, usize)> { ... }
    fn next_reject_back(&mut self) -> Option<(usize, usize)> { ... }
}

🔬This is a nightly-only experimental API. (pattern #27721)

Expand description

A reverse searcher for a string pattern.

This trait provides methods for searching for non-overlapping matches of a pattern starting from the back (right) of a string.

It will be implemented by associated Searcher types of the Pattern trait if the pattern supports searching for it from the back.

The index ranges returned by this trait are not required to exactly match those of the forward search in reverse.

§Safety

Implementers must ensure that all trait functions abide by the guarantees documented in the # Guarantees sections. The provided methods automatically satisfy their guarantees.

Required Methods§

Source

fn next_back(&mut self) -> SearchStep

🔬This is a nightly-only experimental API. (pattern #27721)

Performs the next search step starting from the back.

Returns Match(a, b) if haystack[a..b] matches the pattern.
Returns Reject(a, b) if haystack[a..b] can not match the pattern, even partially.
Returns Done if every byte of the haystack has been visited

§Guarantees

The stream of Match and Reject values up to a Done will contain index ranges that are adjacent, non-overlapping, covering the whole haystack, and lying on utf8 boundaries.

A Match result needs to contain the whole matched pattern, however Reject results may be split up into arbitrary many adjacent fragments. Both ranges may have zero length.

As an example, the pattern "aaa" and the haystack "cbaaaaab" might produce the stream [Reject(7, 8), Match(4, 7), Reject(1, 4), Reject(0, 1)].

Provided Methods§

Source

fn next_match_back(&mut self) -> Option<(usize, usize)>

🔬This is a nightly-only experimental API. (pattern #27721)

Finds the next Match result. See next_back().

§Guarantees

Every returned Some((a, b)) must satisfy a <= b <= self.haystack().len(), and both endpoints must lie on UTF-8 character boundaries.
Matched ranges must be returned in forward order, without revisiting previously consumed portions of the haystack.

Source

fn next_reject_back(&mut self) -> Option<(usize, usize)>

🔬This is a nightly-only experimental API. (pattern #27721)

Finds the next Reject result. See next_back().

§Guarantees

Every returned Some((a, b)) must satisfy a <= b <= self.haystack().len(), and both endpoints must lie on UTF-8 character boundaries.
Matched ranges must be returned in forward order, without revisiting previously consumed portions of the haystack.