Add benchmarks testing the constructors

Cargo.toml

@@ -11,3 +11,10 @@ keywords    = ["xdg", "basedir", "app_dirs", "path", "folder"]
 
 [dependencies]
 winapi = { version = "0.3", features = ["knownfolders", "objbase", "shlobj"] }
+
+[dev-dependencies]
+bencher = "0.1.5"
+
+[[bench]]
+name = "constructors"
+harness = false

benches/constructors.rs

@@ -0,0 +1,41 @@
+#[macro_use]
+extern crate bencher;
+extern crate directories;
+
+use bencher::Bencher;
+use bencher::black_box;
+use directories::BaseDirs;
+use directories::ProjectDirs;
+use directories::UserDirs;
+
+fn base_dirs(b: &mut Bencher) {
+    b.iter(|| {
+        let _ = black_box(BaseDirs::new());
+    });
+}
+
+fn user_dirs(b: &mut Bencher) {
+    b.iter(|| {
+        let _ = black_box(UserDirs::new());
+    });
+}
+
+fn project_dirs_from_path(b: &mut Bencher) {
+    b.iter(|| {
+        let _ = black_box(ProjectDirs::from_path(Default::default()));
+    });
+}
+
+fn project_dirs(b: &mut Bencher) {
+    b.iter(|| {
+        let _ = black_box(ProjectDirs::from("org", "foo", "Bar App"));
+    });
+}
+
+benchmark_group!(constructors,
+    base_dirs,
+    user_dirs,
+    project_dirs_from_path,
+    project_dirs,
+);
+benchmark_main!(constructors);