Add Digest.hashCode.

lib/src/digest.dart

 // Copyright (c) 2015, 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 'package:collection/collection.dart';
 import 'package:convert/convert.dart';
 
 /// A message digest as computed by a [Hash] or [HMAC] function.
 class Digest {
   /// The message digest as an array of bytes.
   final List<int> bytes;
 
   Digest(this.bytes);
 
   /// Returns whether this is equal to another digest.
   ///
   /// This should be used instead of manual comparisons to avoid leaking
   /// information via timing.
   bool operator ==(Object other) {
     if (other is! Digest) return false;
 
     var digest = other as Digest;

[kevmoo, 2016/03/23 22:03:00]

might could use ListEquality.equals here?

[nweiz, 2016/03/23 22:05:22]

I'm guessing the bitwise stuff is more efficient, since it takes advantage of
the fact that the list contains only bytes.

[kevmoo, 2016/03/23 22:07:17]

Sure – then another thought: would it be good to short-circuit the comparison if
there is a diff before the end of the list?

[nweiz, 2016/03/23 22:11:29]

On second thought, I will just switch to ListEquality. There's no reason to
believe that microefficiency is crucial here.

     if (digest.bytes.length != bytes.length) return false;
 
     var result = 0;
     for (var i = 0; i < bytes.length; i++) {
       result |= bytes[i] ^ digest.bytes[i];
     }
     return result == 0;
   }
 
+  int get hashCode => const IterableEquality().hash(bytes);
+
   /// The message digest as a string of hexadecimal digits.
   String toString() => hex.encode(bytes);
 }