Skip to content
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.

Sign up for GitHub

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

Improve code generated for starts_with(<literal char>) #67249

Merged
merged 4 commits into from
Dec 16, 2019
Merged

Improve code generated for starts_with(<literal char>) #67249

Changes from 3 commits
Commits
Show all changes
4 commits
Select commit Hold shift + click to select a range
cc863f0
Improve `str` prefix/suffix comparison
ranma42 Dec 11, 2019
1f6d023
Prefer encoding the char when checking for string prefix/suffix
ranma42 Dec 11, 2019
de7fefa
Minor cleanup in `Pattern::{is_prefix_of,is_suffix_of}` for `char`
ranma42 Dec 12, 2019
3de1923
Add benchmarks for `start_with` and `ends_with`
ranma42 Dec 16, 2019
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
19 changes: 4 additions & 15 deletions src/libcore/str/pattern.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -450,21 +450,13 @@ impl<'a> Pattern<'a> for char {

#[inline]
fn is_prefix_of(self, haystack: &'a str) -> bool {
if let Some(ch) = haystack.chars().next() {
self == ch
} else {
false
}
self.encode_utf8(&mut [0u8; 4]).is_prefix_of(haystack)
}

#[inline]
fn is_suffix_of(self, haystack: &'a str) -> bool where Self::Searcher: ReverseSearcher<'a>
{
if let Some(ch) = haystack.chars().next_back() {
self == ch
} else {
false
}
self.encode_utf8(&mut [0u8; 4]).is_suffix_of(haystack)
}
}

Expand Down Expand Up @@ -715,16 +707,13 @@ impl<'a, 'b> Pattern<'a> for &'b str {
/// Checks whether the pattern matches at the front of the haystack
#[inline]
fn is_prefix_of(self, haystack: &'a str) -> bool {
haystack.is_char_boundary(self.len()) &&
Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

This is interesting. According to git blame, @bluss added this in 2015. But yeah, this looks unnecessary to me and I agree with the change.

self == &haystack[..self.len()]
haystack.as_bytes().starts_with(self.as_bytes())
}

/// Checks whether the pattern matches at the back of the haystack
#[inline]
fn is_suffix_of(self, haystack: &'a str) -> bool {
self.len() <= haystack.len() &&
haystack.is_char_boundary(haystack.len() - self.len()) &&
self == &haystack[haystack.len() - self.len()..]
haystack.as_bytes().ends_with(self.as_bytes())
}
}

Expand Down