refactor split Marks

Author: qingshi163

Cargo.toml

@@ -12,3 +12,4 @@ include = ["LICENSE", "src/**/*.rs"]
 [dependencies]
 num_enum = "0.5"
 bitflags = "1.2"
+optional = "0.5"

benches/benches.rs

@@ -23,7 +23,7 @@ impl Pattern {
         range: std::ops::Range<usize>,
     ) -> (engine::Request<'a, S>, engine::State<S>) {
         let req = engine::Request::new(string, range.start, range.end, self.code, false);
-        let state = engine::State::new();
+        let state = engine::State::default();
         (req, state)
     }
 }