Make a bunch of API changes.

lib/src/utils.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.
 
 library oauth2.utils;
 
+import 'dart:convert';
+
+import 'package:crypto/crypto.dart';
+
 /// Adds additional query parameters to [url], overwriting the original
 /// parameters if a name conflict occurs.
 Uri addQueryParameters(Uri url, Map<String, String> parameters) => url.replace(
     queryParameters: new Map.from(url.queryParameters)..addAll(parameters));
 
+String basicAuthHeader(String identifier, String secret) {
+  var userPass = Uri.encodeFull(identifier) + ":" + Uri.encodeFull(secret);
+  return "Basic " + CryptoUtils.bytesToBase64(ASCII.encode(userPass));
+}
+
 /// Like [String.split], but only splits on the first occurrence of the pattern.
 ///
 /// This will always return a list of two elements or fewer.
 List<String> split1(String toSplit, String pattern) {
   if (toSplit.isEmpty) return [];
 
   var index = toSplit.indexOf(pattern);
   if (index == -1) return [toSplit];
   return [toSplit.substring(0, index),
       toSplit.substring(index + pattern.length)];
@@ skipping 37 matching lines @@
       parameters[match.group(1).toLowerCase()] = match.group(2);
     } while (match.group(3) != null);
 
     if (!paramString.trim().isEmpty) {
       throw new FormatException('Invalid WWW-Authenticate header: "$header"');
     }
 
     return new AuthenticateHeader(scheme, parameters);
   }
 }