library: Add a very simple microbenchmark for splitn

Author: workingjubilee

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;
+                }
+            })
+        }
+    })
+}

library/std/benches/string.rs

@@ -0,0 +1,38 @@
+    let response = String::from("HTTP/1.1 418 I'm a teapot\r\n");
+    let mut res: (&str, &str, &str) = ("", "", "");
+    let start = Instant::now();
+    for _ in 0..100_000_000 {
+        res = match parse_http(&response) {
+            Ok(data) => data,
+            Err(_) => {
+                continue;
+            }
+        };
+    }
+    let duration = start.elapsed();
+
+    println!("version:{}\ncode:{}\ndescription:{}\n", res.0, res.1, res.2);
+    println!("Time elapsed in parse_response() is: {:?}", duration);
+    
+    let start2 = Instant::now();
+    for _ in 0..100_000_000 {
+        res = match parse_http2(&response) {
+            Ok(data) => data,
+            Err(_) => {
+                continue;
+            }
+        };
+    }
+    let duration2 = start2.elapsed();
+
+    println!("version:{}\ncode:{}\ndescription:{}\n", res.0, res.1, res.2);
+    println!("Time elapsed in parse_response() is: {:?}", duration2);
+}
+
+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))
+}