Add base::UnguessableToken

base/nonce.cc

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/nonce.h"
+
+#include "base/format_macros.h"
+#include "base/rand_util.h"
+#include "base/strings/stringprintf.h"
+
+namespace base {
+
+Nonce::Nonce(uint64_t high, uint64_t low) : high_(high), low_(low) {}
+
+std::string Nonce::ToString() const {
+  return base::StringPrintf("(%" PRIu64 ":%" PRIu64 ")", high_, low_);
+}
+
+// Static
+Nonce Nonce::Generate() {
+  Nonce nonce;
+  // Use base::RandBytes instead of crypto::RandBytes, because crypto calls the
+  // base version directly, and to prevent the dependency from base/ to crypto/.
+  base::RandBytes(&nonce, sizeof(nonce));

[Avi (use Gerrit), 2016/09/13 20:28:38]

This potentially could scribble across padding. Along with the static_assert for
the POD-ness of Nonce, do you want to assert that sizeof(Nonce) ==
2*sizeof(uint64_t) or do you not mind the padding scribble?

[tguilbert, 2016/09/13 21:11:44]

Since I have removed the call to memcpy and send the nonce as 2 uint64_ts
instead, the PODness is no longer all that important. I am replacing the POD
assert with the sizeof assert, and updated the comment. TY for the suggestion!

+  return nonce;
+}
+
+// Static
+Nonce Nonce::Deserialize(uint64_t high, uint64_t low) {
+  return Nonce(high, low);
+}
+
+}  // namespace base