new: improved segment scanner performance

Cargo.toml

@@ -4,7 +4,7 @@ categories = ["command-line-utilities"]
 description = "Utility for viewing json-formatted log files."
 keywords = ["cli", "human", "log"]
 name = "hl"
-version = "0.25.1-beta.1"
+version = "0.25.1-beta.2"
 edition = "2021"
 build = "build.rs"
 

src/scanning.rs

@@ -241,22 +241,40 @@ impl<'a, 'b> ScannerIter<'a, 'b> {
             return None;
         }
 
-        for i in (0..self.next.size - k + 1).rev() {
-            if self.next.data[i..].starts_with(self.scanner.delimiter.as_bytes()) {
-                let n = self.next.size - i - k;
-                let mut result = self.scanner.sf.new_segment();
-                if result.data.len() < n {
-                    result.data.resize(n, 0);
-                }
-                if n > 0 {
-                    result.data[..n].copy_from_slice(&self.next.data[i + k..i + k + n]);
-                    result.size = n;
-                    self.next.size -= n;
+        if k == 1 {
+            let delimiter = self.scanner.delimiter.as_bytes()[0];
+            self.next.data[..self.next.size]
+                .rsplit(|x| *x == delimiter)
+                .next()
+                .map(|data| data.len())
+                .and_then(|n| self.split_n(n))
+        } else {
+            for i in (0..self.next.size - k + 1).rev() {
+                if self.next.data[i..self.next.size].starts_with(self.scanner.delimiter.as_bytes()) {
+                    return self.split_n(self.next.size - i - k);
                 }
-                return Some(result);
             }
+            None
+        }
+    }
+
+    #[inline(always)]
+    fn split_n(&mut self, n: usize) -> Option<SegmentBuf> {
+        let s = self.next.size;
+        if n == 0 || n == s {
+            return None;
+        }
+
+        let mut result = self.scanner.sf.new_segment();
+        if result.data.len() < n {
+            result.data.resize(n, 0);
         }
-        None
+
+        result.data[..n].copy_from_slice(&self.next.data[s - n..s]);
+        result.size = n;
+        self.next.size -= n;
+
+        Some(result)
     }
 }