expression: add parsing benchmark

Author: apoelstra

src/expression.rs

@@ -260,7 +260,6 @@ where
 
 #[cfg(test)]
 mod tests {
-
     use super::parse_num;
 
     #[test]
@@ -282,3 +281,30 @@ mod tests {
         assert_eq!(valid_chars, super::VALID_CHARS);
     }
 }
+
+#[cfg(bench)]
+mod benches {
+    use test::{black_box, Bencher};
+
+    use super::*;
+
+    #[bench]
+    pub fn parse_tree(bh: &mut Bencher) {
+        bh.iter(|| {
+            let tree = Tree::from_str(
+                "and(thresh(2,and(sha256(H),or(sha256(H),pk(A))),pk(B),pk(C),pk(D),sha256(H)),pk(E))",
+            ).unwrap();
+            black_box(tree);
+        });
+    }
+
+    #[bench]
+    pub fn parse_tree_deep(bh: &mut Bencher) {
+        bh.iter(|| {
+            let tree = Tree::from_str(
+                "and(and(and(and(and(and(and(and(and(and(and(and(and(and(and(and(and(and(and(and(1,2),3),4),5),6),7),8),9),10),11),12),13),14),15),16),17),18),19),20),21)"
+            ).unwrap();
+            black_box(tree);
+        });
+    }
+}