dart2js: fetch http Resources

sdk/lib/_internal/js_runtime/lib/core_patch.dart

Index: sdk/lib/_internal/js_runtime/lib/core_patch.dart
diff --git a/sdk/lib/_internal/js_runtime/lib/core_patch.dart b/sdk/lib/_internal/js_runtime/lib/core_patch.dart
index 971b37f96e36270c2b6726a7f0ba5f2b83033563..799721c9f6b3c310b55174bb9b08ace2c0fde80e 100644
--- a/sdk/lib/_internal/js_runtime/lib/core_patch.dart
+++ b/sdk/lib/_internal/js_runtime/lib/core_patch.dart
@@ -17,7 +17,8 @@ import 'dart:_js_helper' show patch,
                               ConstantMap,
                               stringJoinUnchecked,
                               objectHashCode,
-                              Closure;
+                              Closure,
+                              readHttp;
 
 import 'dart:_native_typed_data' show NativeUint8List;
 
@@ -576,14 +577,35 @@ class _Resource implements Resource {
   }
 
   Stream<List<int>> _readAsStream(Uri uri) {
-    throw new UnimplementedError("Streaming bytes via HTTP");
+    var controller = new StreamController();

[Siggi Cherem (dart-lang), 2015/08/22 02:21:16]

couple comments:
- do we need to add an import to dart:async above?
- use a broadcast controller?

[Harry Terkelsen, 2015/08/25 00:03:57]

No, dart:core imports dart:async now
Done

+    // We only need to implement the listener as there is no way to provide
+    // back pressure into the channel.
+    controller.onListen = () {
+      // Once there is a listener, we kick off the loading of the resource.
+      readAsBytes().then((value) {
+        // The resource loading implementation sends all of the data in a
+        // single message. So the stream will only get a single value posted.

[Siggi Cherem (dart-lang), 2015/08/22 02:21:15]

seems like a good simplification for us. I guess we could potentially support
streaming if we use a streaming xhr under the hood, but it doesn't seem worth it
at this time. Not sure if we should add a TODO though. Up to you.

[Harry Terkelsen, 2015/08/25 00:03:57]

Done.

+        controller.add(value);
+        controller.close();
+      },
+      onError: (e, s) {
+        // In case the future terminates with an error we propagate it to the
+        // stream.
+        controller.addError(e, s);
+        controller.close();
+      });
+    };
+
+    return controller.stream;
   }
 
   Future<List<int>> _readAsBytes(Uri uri) {

[Siggi Cherem (dart-lang), 2015/08/22 02:21:15]

consider using `=>`:
    Future<List<int>> _readAsBytes(Uri uri) =>
      _readAsString(uri).then((s) => s.codeUnits);

[Harry Terkelsen, 2015/08/25 00:03:57]

Done.

-    throw new UnimplementedError("Reading bytes via HTTP");
+    return _readAsString(uri).then((data) {
+      return data.codeUnits;

[Siggi Cherem (dart-lang), 2015/08/22 02:21:15]

do we need to also handle results when the xhr.responseType is arraybuffer or
blob? (I expect responseText might be empty in those cases)

+    });
   }
 
   Future<String> _readAsString(Uri uri) {

[Siggi Cherem (dart-lang), 2015/08/22 02:21:16]

nit: use '=>' here too

[Harry Terkelsen, 2015/08/25 00:03:57]

Done.

-    throw new UnimplementedError("Reading string via HTTP");
+    return readHttp(uri.toString());

[Siggi Cherem (dart-lang), 2015/08/22 02:21:16]

nit: consider using '$uri' instead of uri.toString (it's equivalent, but shorter
:))

[Harry Terkelsen, 2015/08/25 00:03:57]

Done.

   }
 }