Add method flush to output stream

runtime/bin/file_impl.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.
 
 class _FileInputStream extends _BaseDataInputStream implements InputStream {
   _FileInputStream(String name)
       : _data = [],
         _position = 0,
         _filePosition = 0 {
     var file = new File(name);
@@ skipping 111 matching lines @@
   static final int _bufferLength = 64 * 1024;
 
   RandomAccessFile _openedFile;
   List<int> _data;
   int _position;
   int _filePosition;
   int _fileLength;
 }
 
 
+class _PendingOperation {
+  const _PendingOperation(this._id);
+  static final _PendingOperation CLOSE = const _PendingOperation(0);
+  static final _PendingOperation FLUSH = const _PendingOperation(1);
+  final int _id;
+}
+
+
 class _FileOutputStream extends _BaseOutputStream implements OutputStream {
   _FileOutputStream(String name, FileMode mode) {
-    _pendingOperations = new List<List<int>>();
+    _pendingOperations = new List();
     var f = new File(name);
     var openFuture = f.open(mode);
     openFuture.then((openedFile) {
       _file = openedFile;
       _processPendingOperations();
     });
     openFuture.handleException((e) {
       _reportError(e);
       return true;
     });
@@ skipping 24 matching lines @@
     var length = buffer.length - offset;
     if (len != null) {
       if (len > length) throw new IndexOutOfRangeException(len);
       length = len;
     }
     var copy = new Uint8List(length);
     copy.setRange(0, length, buffer, offset);
     return write(copy);
   }
 
+
+  void flush() {
+    if (_file == null) {
+      _pendingOperations.add(_PendingOperation.FLUSH);
+    } else {
+      _file.flush().then((ignored) => null);
+    }
+  }
+
+
   void close() {
     if (_file == null) {
-      _pendingOperations.add(null);
+      _pendingOperations.add(_PendingOperation.CLOSE);
     } else if (!_streamMarkedClosed) {
       _file.close().then((ignore) {
         if (_onClosed != null) _onClosed();
       });
       _streamMarkedClosed = true;
     }
   }
 
   void set onNoPendingWrites(void callback()) {
     _onNoPendingWrites = callback;
     if (((_pendingOperations == null) || (_pendingOperations.length == 0)) &&
         (outstandingWrites == 0) &&
         !_streamMarkedClosed &&
         (_onNoPendingWrites != null)) {
       new Timer(0, (t) {
         if (_onNoPendingWrites != null) {
           _onNoPendingWrites();
         }
       });
     }
   }
 
   void set onClosed(void callback()) {
     _onClosed = callback;
   }
 
   void _processPendingOperations() {
     _pendingOperations.forEach((buffer) {
-      (buffer != null) ? write(buffer) : close();
+      if (buffer is _PendingOperation) {
+        if (buffer === _PendingOperation.CLOSE) {
+          close();
+        } else {
+          assert(buffer === _PendingOperation.FLUSH);
+          flush();
+        }
+      } else {
+        write(buffer);
+      }
     });
     _pendingOperations = null;
   }
 
   void _write(List<int> buffer, int offset, int len) {
     outstandingWrites++;
     var writeListFuture = _file.writeList(buffer, offset, len);
     writeListFuture.then((ignore) {
         outstandingWrites--;
         if ((outstandingWrites == 0) &&
@@ skipping 17 matching lines @@
 
   // When this is set to true the close callback has been called and
   // the stream is fully closed.
   bool _closeCallbackCalled = false;
 
   // Number of writes that have not yet completed.
   int outstandingWrites = 0;
 
   // List of pending writes that were issued before the underlying
   // file was successfully opened.
-  List<List<int>> _pendingOperations;
+  List _pendingOperations;
 
   Function _onNoPendingWrites;
   Function _onClosed;
 }
 
 
 // Helper class containing static file helper methods.
 class _FileUtils {
   static final EXISTS_REQUEST = 0;
   static final CREATE_REQUEST = 1;
@@ skipping 845 matching lines @@
           new FileIOException("File closed '$_name'"));
     });
     return completer.future;
   }
 
   final String _name;
   int _id;
 
   SendPort _fileService;
 }