Add CryptoUtils class.

tests/lib/crypto/sha1_test.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 tag to allow dartium to run the test.
 #library('sha1_test');
 
 // TODO(ager): Replace with "dart:crypto" when ready.
 #import("../../../lib/crypto/crypto.dart");
 
 #source('sha1_long_test_vectors.dart');
 #source('sha1_short_test_vectors.dart');
 
 List<int> createTestArr(int len) {
   var arr = new List<int>(len);
   for (var i = 0; i < len; i++) {
     arr[i] = i;
   }
   return arr;
 }
 
-String digestToString(List<int> digest) {
-  var buf = new StringBuffer();
-  for (var part in digest) {
-    buf.add("${(part < 16) ? "0" : ""}${part.toRadixString(16).toLowerCase()}");
-  }
-  return buf.toString();
-}
-
 void test() {
   final expected_values = const [
     "da39a3ee5e6b4b0d3255bfef95601890afd80709",
     "5ba93c9db0cff93f52b521d7420e43f6eda2784f",
     "3f29546453678b855931c174a97d6c0894b8f546",
     "0c7a623fd2bbc05b06423be359e4021d36e721ad",
     "a02a05b025b928c039cf1ae7e8ee04e7c190c0db",
     "1cf251472d59f8fadeb3ab258e90999d8491be19",
     "868460d98d09d8bbb93d7b6cdd15cc7fbec676b9",
     "6dc86f11b8cdbe879bf8ba3832499c2f93c729ba",
@@ skipping 496 matching lines @@
     "d64a178d4759b796ec0e77626cf19257c28292fc",
     "6ae457f71b1cd60b1810fd4379c90bb38154568f",
     "063623280f208df296895ccd867dab8a73cf174d",
     "7a8b8c9aa0591603cf08e94ec2ae6a6350cbb8a2",
     "20c4232d3066c41e211eefe2834db78a8c083ea4",
     "82fdf2cccc77ab556aa35557d0923b162d1b98cf",
     "3dce8306f3c1810d5d81ed5ebb0ccea947277a61",
     "11bca5b61fc1f6d59078ec5354bc6d9adecc0c5d",
   ];
   for (var i = 0; i < expected_values.length; i++) {
-    Expect.equals(expected_values[i],
-                  digestToString(new SHA1().update(createTestArr(i)).digest()));
+    var digest = new SHA1().update(createTestArr(i)).digest();
+    Expect.equals(expected_values[i], CryptoUtils.bytesToHex(digest));
   }
 }
 
 void testInvalidUse() {
   var sha = new SHA1();
   sha.digest();
   Expect.throws(() => sha.update([0]), (e) => e is HashException);
 }
 
 void testRepeatedDigest() {
   var sha = new SHA1();
   var digest = sha.digest();
   Expect.listEquals(digest, sha.digest());
 }
 
 void testStandardVectors(inputs, mds) {
   for (var i = 0; i < inputs.length; i++) {
     var d = new SHA1().update(inputs[i]).digest();
-    Expect.equals(mds[i], digestToString(d), '$i');
+    Expect.equals(mds[i], CryptoUtils.bytesToHex(d), '$i');
   }
 }
 
 void main() {
   test();
   testInvalidUse();
   testRepeatedDigest();
   testStandardVectors(sha1_long_inputs, sha1_long_mds);
   testStandardVectors(sha1_short_inputs, sha1_short_mds);
 }