Avoid calling ByteData.setUint64.

lib/src/hash_sink.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.
 
 import 'dart:typed_data';
 
 import 'package:typed_data/typed_data.dart';
 
 import 'digest.dart';
 import 'utils.dart';
@@ skipping 110 matching lines @@
     var lengthInBits = _lengthInBytes * bitsPerByte;
     if (lengthInBits > maxUint64) {
       throw new UnsupportedError(
           "Hashing is unsupported for messages with more than 2^64 bits.");
     }
 
     // Add the full length of the input data as a 64-bit value at the end of the
     // hash.
     var offset = _pendingData.length;
     _pendingData.addAll(new Uint8List(8));
-    _pendingData.buffer.asByteData().setUint64(offset, lengthInBits, _endian);
+    var byteData = _pendingData.buffer.asByteData();
+
+    // We're essentially doing byteData.setUint64(offset, lengthInBits, _endian)
+    // here, but that method isn't supported on dart2js so we implement it
+    // manually instead.
+    var highBits = lengthInBits >> 32;

[sra1, 2016/03/23 22:15:50]

This won't actually do what you want in dart2js.
dart2js bit operations assume the inputs are 32 bit unsigned values.
The result will always be zero.  It is probably always zero in practice.

You could use
 
   lengthInBits ~/ 4294967296

if you want it to work in JS for data of size 0.5GB.

[nweiz, 2016/03/23 22:21:26]

Presumably in dart2js, lengthInBits can't be higher than 2^32 anyway, right? 

+    var lowBits = lengthInBits & mask32;
+    if (_endian == Endianness.BIG_ENDIAN) {
+      byteData.setUint32(offset, highBits, _endian);
+      byteData.setUint32(offset + bytesPerWord, lowBits, _endian);
+    } else {
+      byteData.setUint32(offset, lowBits, _endian);
+      byteData.setUint32(offset + bytesPerWord, highBits, _endian);
+    }
   }
 
   /// Rounds [val] up to the next multiple of [n], as long as [n] is a power of
   /// two.
   int _roundUp(int val, int n) => (val + n - 1) & -n;
 }