Add a flush operations to IOSink

sdk/lib/io/io_sink.dart

 // Copyright (c) 2013, 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.
 
 part of dart.io;
 
 /**
  * Helper class to wrap a [StreamConsumer<List<int>>] and provide
  * utility functions for writing to the StreamConsumer directly. The
  * [IOSink] buffers the input given by all [StringSink] methods and will delay
@@ skipping 28 matching lines @@
    * Writes an error to the consumer.
    */
   void addError(error);
 
   /**
    * Adds all elements of the given [stream] to `this`.
    */
   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();
 
   /**
    * Get a future that will complete when all synchronous have completed, or an
    * error happened. This future is identical to the future returned from close.
    */
   Future get done;
 }
@@ skipping 165 matching lines @@
   }
 
   void writeln([Object obj = ""]) {
     write(obj);
     write("\n");
   }
 
   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);
+          }
+        });
+  }
 }