faster charsearcher

library/core/src/str/pattern.rs

@@ -429,8 +429,18 @@ unsafe impl<'a> Searcher<'a> for CharSearcher<'a> {
             SearchStep::Done
         }
     }
-    #[inline]
+    #[inline(always)]
     fn next_match(&mut self) -> Option<(usize, usize)> {
+        if self.utf8_size == 1 {
+            let find = |haystack: &[u8]| memchr::memchr(self.utf8_encoded[0], haystack);
+            return match find(self.haystack.as_bytes().get(self.finger..self.finger_back)?) {
+                Some(x) => {
+                    self.finger += x + 1;
+                    Some((self.finger - 1, self.finger))
+                }
+                None => None,
+            };
+        }
         loop {
             // get the haystack after the last character found
             let bytes = self.haystack.as_bytes().get(self.finger..self.finger_back)?;
@@ -498,6 +508,16 @@ unsafe impl<'a> ReverseSearcher<'a> for CharSearcher<'a> {
     }
     #[inline]
     fn next_match_back(&mut self) -> Option<(usize, usize)> {
+        if self.utf8_size == 1 {
+            let find = |haystack: &[u8]| memchr::memrchr(self.utf8_encoded[0], haystack);
+            return match find(self.haystack.as_bytes().get(self.finger..self.finger_back)?) {
+                Some(x) => {
+                    self.finger_back = self.finger + x;
+                    Some((self.finger_back, self.finger_back + 1))
+                }
+                None => None,
+            };
+        }
         let haystack = self.haystack.as_bytes();
         loop {
             // get the haystack up to but not including the last character searched

library/coretests/benches/pattern.rs

@@ -39,3 +39,27 @@ fn ends_with_str(b: &mut Bencher) {
         }
     })
 }
+
+#[bench]
+fn splitn_on_http_response(b: &mut Bencher) {
+    fn parse_http(s: &str) -> Result<(&str, &str, &str), &str> {
+        let mut parts = s.splitn(3, ' ');
+        let version = parts.next().ok_or("No version")?;
+        let code = parts.next().ok_or("No status code")?;
+        let description = parts.next().ok_or("No description")?;
+        Ok((version, code, description))
+    }
+
+    let response = String::from("HTTP/1.1 418 I'm a teapot\r\n");
+    let mut res: (&str, &str, &str) = ("", "", "");
+    b.iter(|| {
+        for _ in 0..1024 {
+            res = black_box(match parse_http(black_box(&response)) {
+                Ok(data) => data,
+                Err(_) => {
+                    continue;
+                }
+            })
+        }
+    })
+}