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

    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.

For the reason why this trait is marked unsafe, see the parent trait Searcher.

Required Methods

🔬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

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 laying 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

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

Finds the next Match result. See next_back().

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

Finds the next Reject result. See next_back().