Avoid parsing path and query string more than once

sdk/lib/core/uri.dart

Index: sdk/lib/core/uri.dart
diff --git a/sdk/lib/core/uri.dart b/sdk/lib/core/uri.dart
index c8277e7fc6b4b035ad7624e195049d0817a80740..4f371394ee3bc1bcdce517394dea1f911cb65301 100644
--- a/sdk/lib/core/uri.dart
+++ b/sdk/lib/core/uri.dart
@@ -81,6 +81,9 @@ class Uri {
    */
   final String fragment;
 
+  List<String> _pathSegments;

[Lasse Reichstein Nielsen, 2013/05/30 11:57:50]

Dartdoc saying that this caches the computed return value of [pathSegments].

[Søren Gjesse, 2013/05/30 13:38:25]

Done.

+  Map<String, String> _queryParameters;

[Lasse Reichstein Nielsen, 2013/05/30 11:57:50]

Similar.

[Søren Gjesse, 2013/05/30 13:38:25]

Done.

+
   /**
    * Creates a new URI object by parsing a URI string.
    */
@@ -167,10 +170,19 @@ class Uri {
    * Returns the URI path split into its segments. Each of the
    * segments in the returned list have been decoded. If the path is
    * empty the empty list will be returned.
+   *
+   * The returned list should not be modified as the same object will
+   * be returned for each call.

[Lasse Reichstein Nielsen, 2013/05/30 11:57:50]

"should not" isn't very safe. Could you make it unmodifiable?

[Søren Gjesse, 2013/05/30 13:38:25]

Created an immutable list wrapper.

    */
   List<String> get pathSegments {
-    if (path == "") return const<String>[];
-    return path.split("/").map(Uri.decodeComponent).toList(growable: false);
+    if (_pathSegments == null) {
+      _pathSegments =
+        path == "" ? const<String>[]
+                   : path.split("/")
+                         .map(Uri.decodeComponent)
+                         .toList(growable: false);
+    }
+    return _pathSegments;
   }
 
   /*
@@ -178,9 +190,13 @@ class Uri {
    * specified for FORM post in the HTML 4.01 specification. Each key
    * and value in the returned map have been decoded. If there is no
    * query the empty map will be returned.
+   *
+   * The returned map should not be modified as the same object will
+   * be returned for each call.
    */
   Map<String, String> get queryParameters {
-    return query.split("&").fold({}, (map, element) {
+    if (_queryParameters == null) {
+      _queryParameters = query.split("&").fold({}, (map, element) {
         int index = element.indexOf("=");
         if (index == -1) {
           if (!element.isEmpty) map[element] = "";
@@ -190,7 +206,9 @@ class Uri {
           map[Uri.decodeQueryComponent(key)] = decodeQueryComponent(value);
         }
         return map;
-    });
+      });
+    }
+    return _queryParameters;
   }
 
   static String _makeScheme(String scheme) {