Read files in chunks, not relaying on size.

sdk/lib/io/buffer_list.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.
 
 part of dart.io;
 
 /**
  * Utility class that holds a number of byte buffers and can deliver
  * the bytes either one by one or in chunks.
  */
@@ skipping 51 matching lines @@
     return value;
   }
 
   /**
    * Read [count] bytes from the buffer list. If the number of bytes
    * requested is not available null will be returned.
    */
   List<int> readBytes([int count]) {
     if (count == null) count = length;
     List<int> result;
-    if (_length == 0 || _length < count) return null;
+    if (_length == 0) return new Uint8List(0);
+    if (_length < count) return null;
     if (_index == 0 && _buffers.first.length == count) {
       result = _buffers.first;
       _buffers.removeFirst();
       _index = 0;
       _length -= count;
       return result;
     } else {
       int firstRemaining = _buffers.first.length - _index;
       if (firstRemaining >= count) {
         result = _buffers.first.sublist(_index, _index + count);
@@ skipping 68 matching lines @@
   void clear() {
     _index = 0;
     _length = 0;
     _buffers = new Queue();
   }
 
   int _length;  // Total number of bytes remaining in the buffers.
   Queue<List<int>> _buffers;  // List of data buffers.
   int _index;  // Index of the next byte in the first buffer.
 }