Add a flush operations to IOSink

sdk/lib/io/io_sink.dart

Index: sdk/lib/io/io_sink.dart
diff --git a/sdk/lib/io/io_sink.dart b/sdk/lib/io/io_sink.dart
index ac4ce0a1daabeeece9aa0e78da3e55533a5750cf..de4122db95b4f1cf60e98587b8cf09b3bd0ab8a7 100644
--- a/sdk/lib/io/io_sink.dart
+++ b/sdk/lib/io/io_sink.dart
@@ -46,6 +46,18 @@ abstract class IOSink implements StreamSink<List<int>>, StringSink {
   Future addStream(Stream<List<int>> stream);
 
   /**
+   * Flushes the data currently buffered in the stream through the
+   * synchronous Sink methods, to the underlying storage, if possible.
+   *
+   * Returns a future which completes when the flush operation is
+   * complete. If the target of the [IOSink] is a file then a file
+   * system flush will be performed as well.
+   *
+   * If [addStream] is currently active this method will fail.
+   */
+  Future flush();

[Anders Johnsen, 2013/10/28 15:13:22]

I still disagree that this should be part of the IOSink. It's far to few
interfaces which supports this, and the user can create IOSinks for any
StreamConsumer.

+
+  /**
    * Close the target.
    */
   Future close();
@@ -231,4 +243,15 @@ class _IOSinkImpl extends _StreamSinkImpl<List<int>> implements IOSink {
   void writeCharCode(int charCode) {
     write(new String.fromCharCode(charCode));
   }
+
+  Future flush() {
+    return addStream((new StreamController()..close()).stream)
+        .then((_) {
+          if (_target is _FileStreamConsumer) {
+            return _target.flush();
+          } else {
+            return new Future.value(null);
+          }
+        });
+  }
 }