expr: add a benchmark (#12578)

.github/workflows/benchmarks.yml

@@ -38,6 +38,7 @@ jobs:
           uu_du,
           uu_echo,
           uu_expand,
+          uu_expr,
           uu_fold,
           uu_hostname,
           uu_join,

Cargo.lock

@@ -3521,6 +3521,7 @@ name = "uu_expr"
 version = "0.9.0"
 dependencies = [
  "clap",
+ "codspeed-divan-compat",
  "fluent",
  "num-bigint",
  "num-traits",

src/uu/expr/Cargo.toml

@@ -27,6 +27,14 @@ uucore = { workspace = true, features = ["i18n-collator"] }
 thiserror = { workspace = true }
 fluent = { workspace = true }
 
+[dev-dependencies]
+divan = { workspace = true }
+uucore = { workspace = true, features = ["benchmark"] }
+
 [[bin]]
 name = "expr"
 path = "src/main.rs"
+
+[[bench]]
+name = "expr_bench"
+harness = false

src/uu/expr/benches/expr_bench.rs

@@ -0,0 +1,37 @@
+// This file is part of the uutils coreutils package.
+//
+// For the full copyright and license information, please view the LICENSE
+// file that was distributed with this source code.
+
+use divan::{Bencher, black_box};
+use uu_expr::uumain;
+use uucore::benchmark::run_util_function;
+
+/// Benchmark `expr index` worst case: the needle char set never matches, so the
+/// whole string is scanned. This is the input that exercised the old O(N * M)
+/// behavior.
+#[divan::bench]
+fn index_no_match(bencher: Bencher) {
+    let left = "A".repeat(100_000);
+    let right = "B".repeat(100_000);
+
+    bencher.bench(|| {
+        black_box(run_util_function(uumain, &["index", &left, &right]));
+    });
+}
+
+/// Benchmark `expr index` with a match near the end of the string.
+#[divan::bench]
+fn index_match_at_end(bencher: Bencher) {
+    let mut left = "A".repeat(100_000);
+    left.push('Z');
+    let right = "Z".repeat(100_000);
+
+    bencher.bench(|| {
+        black_box(run_util_function(uumain, &["index", &left, &right]));
+    });
+}
+
+fn main() {
+    divan::main();
+}