Skip to content

Make StrSearcher behave correctly on empty needle #87062

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 2 commits into from
Jul 27, 2021
Merged
Show file tree
Hide file tree
Changes from all commits
Commits
File filter

Filter by extension

Filter by extension

Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
41 changes: 41 additions & 0 deletions library/alloc/tests/str.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1873,6 +1873,47 @@ mod pattern {
"* \t",
[Reject(0, 1), Reject(1, 2), Reject(2, 3),]
);

// See #85462
#[test]
fn str_searcher_empty_needle_after_done() {
// Empty needle and haystack
{
let mut searcher = "".into_searcher("");

assert_eq!(searcher.next(), SearchStep::Match(0, 0));
assert_eq!(searcher.next(), SearchStep::Done);
assert_eq!(searcher.next(), SearchStep::Done);
assert_eq!(searcher.next(), SearchStep::Done);

let mut searcher = "".into_searcher("");

assert_eq!(searcher.next_back(), SearchStep::Match(0, 0));
assert_eq!(searcher.next_back(), SearchStep::Done);
assert_eq!(searcher.next_back(), SearchStep::Done);
assert_eq!(searcher.next_back(), SearchStep::Done);
}
// Empty needle and non-empty haystack
{
let mut searcher = "".into_searcher("a");

assert_eq!(searcher.next(), SearchStep::Match(0, 0));
assert_eq!(searcher.next(), SearchStep::Reject(0, 1));
assert_eq!(searcher.next(), SearchStep::Match(1, 1));
assert_eq!(searcher.next(), SearchStep::Done);
assert_eq!(searcher.next(), SearchStep::Done);
assert_eq!(searcher.next(), SearchStep::Done);

let mut searcher = "".into_searcher("a");

assert_eq!(searcher.next_back(), SearchStep::Match(1, 1));
assert_eq!(searcher.next_back(), SearchStep::Reject(0, 1));
assert_eq!(searcher.next_back(), SearchStep::Match(0, 0));
assert_eq!(searcher.next_back(), SearchStep::Done);
assert_eq!(searcher.next_back(), SearchStep::Done);
assert_eq!(searcher.next_back(), SearchStep::Done);
}
}
}

macro_rules! generate_iterator_test {
Expand Down
19 changes: 17 additions & 2 deletions library/core/src/str/pattern.rs
Original file line number Diff line number Diff line change
Expand Up @@ -928,6 +928,8 @@ struct EmptyNeedle {
end: usize,
is_match_fw: bool,
is_match_bw: bool,
// Needed in case of an empty haystack, see #85462
is_finished: bool,
}

impl<'a, 'b> StrSearcher<'a, 'b> {
Expand All @@ -941,6 +943,7 @@ impl<'a, 'b> StrSearcher<'a, 'b> {
end: haystack.len(),
is_match_fw: true,
is_match_bw: true,
is_finished: false,
}),
}
} else {
Expand All @@ -966,13 +969,19 @@ unsafe impl<'a, 'b> Searcher<'a> for StrSearcher<'a, 'b> {
fn next(&mut self) -> SearchStep {
match self.searcher {
StrSearcherImpl::Empty(ref mut searcher) => {
if searcher.is_finished {
return SearchStep::Done;
}
// empty needle rejects every char and matches every empty string between them
let is_match = searcher.is_match_fw;
searcher.is_match_fw = !searcher.is_match_fw;
let pos = searcher.position;
match self.haystack[pos..].chars().next() {
_ if is_match => SearchStep::Match(pos, pos),
None => SearchStep::Done,
None => {
searcher.is_finished = true;
SearchStep::Done
}
Some(ch) => {
searcher.position += ch.len_utf8();
SearchStep::Reject(pos, searcher.position)
Expand Down Expand Up @@ -1045,12 +1054,18 @@ unsafe impl<'a, 'b> ReverseSearcher<'a> for StrSearcher<'a, 'b> {
fn next_back(&mut self) -> SearchStep {
match self.searcher {
StrSearcherImpl::Empty(ref mut searcher) => {
if searcher.is_finished {
return SearchStep::Done;
}
let is_match = searcher.is_match_bw;
searcher.is_match_bw = !searcher.is_match_bw;
let end = searcher.end;
match self.haystack[..end].chars().next_back() {
_ if is_match => SearchStep::Match(end, end),
None => SearchStep::Done,
None => {
searcher.is_finished = true;
SearchStep::Done
}
Some(ch) => {
searcher.end -= ch.len_utf8();
SearchStep::Reject(searcher.end, end)
Expand Down