Add benchmark to 'path' package, of the most common methods.

pkg/path/test/benchmark.dart

+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:unittest/unittest.dart';
+import 'package:path/path.dart' as path;
+
+void benchmark(String name, Function func) {
+  // Warmup.
+  for (int i = 0; i < 10000; i++) {
+    for (var p in PATHS) {
+      func(p);
+    }
+  }
+  var count = 100000;
+  var sw = new Stopwatch()..start();
+  for (int i = 0; i < count; i++) {
+    for (var p in PATHS) {
+      func(p);
+    }
+  }
+  print("$name: ${count / sw.elapsedMicroseconds} iter/us (${sw.elapsed})");
+}
+
+main() {
+  for (var style in [path.Style.posix, path.Style.url, path.Style.windows]) {
+    group(style.name, () {

[Bob Nystrom, 2014/08/05 15:41:58]

I'd consider not using unittest here since it doesn't add much value. Instead,
just add the style name to the string you interpolate in benchmark() and be done
with it?

[Anders Johnsen, 2014/08/06 07:42:27]

Done.

+      var context = new path.Context(style: style);
+      test('basename', () {
+        benchmark('${style.name}-basename', context.basename);
+      });
+      test('basenameWithoutExtension', () {
+        benchmark('${style.name}-basenameWithoutExtension',
+                  context.basenameWithoutExtension);
+      });
+      test('dirname', () {
+        benchmark('${style.name}-dirname', context.dirname);
+      });
+      test('extension', () {
+        benchmark('${style.name}-extension', context.extension);
+      });
+      test('rootPrefix', () {
+        benchmark('${style.name}-rootPrefix', context.rootPrefix);
+      });
+      test('isAbsolute', () {
+        benchmark('${style.name}-isAbsolute', context.isAbsolute);
+      });
+      test('isRelative', () {
+        benchmark('${style.name}-isRelative', context.isRelative);
+      });
+      test('isRootRelative', () {
+        benchmark('${style.name}-isRootRelative', context.isRootRelative);
+      });
+      test('normalize', () {
+        benchmark('${style.name}-normalize', context.normalize);
+      });
+      test('relative', () {
+        benchmark('${style.name}-relative', context.relative);
+      });
+      test('toUri', () {
+        benchmark('${style.name}-toUri', context.toUri);
+      });
+      test('prettyUri', () {
+        benchmark('${style.name}-prettyUri', context.prettyUri);
+      });
+    });
+  }
+}
+
+const PATHS = const [
+  '.',
+  '..',
+  'out/ReleaseIA32/packages',
+  '/home/user/dart/sdk/lib/indexed_db/dart2js/indexed_db_dart2js.dart',
+  'C:\\User\\me\\',

[Bob Nystrom, 2014/08/05 15:41:58]

Nit: use a raw string here and below?

[Anders Johnsen, 2014/08/06 07:42:27]

Done.

I think we should continue to add to this list over time, as having a nice large
set of paths will make this benchmark a lot more valuable.

If you have other paths that you want to have in, initially, please let me know.

+  '\\server\\share\\my\\folders\\some\\file.data',

[nweiz, 2014/08/05 19:40:33]

It doesn't seem like we should be running Windows paths against posix and URL
styles. It also seems like we should be testing URL-specific paths as well.

[Anders Johnsen, 2014/08/06 07:42:27]

Adding some url paths as well.

I'd actually prefer to use the same paths for all methods. That makes it
possible to see the extra overhead between platforms. E.g., if windows is 3x
slower than posix, it can indicate that it may be less optimized than posix.
Interestingly enough, it may also indicate that the differences (root, path
separators) may cause an extra overhead.

Overall, I think the value of using the same paths outweighs the concerns.

[nweiz, 2014/08/06 21:08:28]

I don't think you should take out the platform-specific paths, just that you
should only run them on contexts that support them. I don't think running
path.posix.dirname('C:\\User\\me\\') tells us anything particularly useful.

[Anders Johnsen, 2014/08/07 08:56:10]

Done.

+];