[rac] Use stale libaddressinput data if download fails

third_party/libaddressinput/chromium/cpp/src/wrapper.cc

+// Copyright (C) 2014 Google Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Wrapper prepends timestamp and checksum to data. Format:
+//
+//    timestamp=<timestamp>
+//    checksum=<checksum>
+//    <data>
+//
+// The timestamp is the time_t that was returned from time(NULL) function. The
+// timestamp does not need to be portable because it is written and read only by
+// Wrapper. The value is somewhat human-readable: it is the number of seconds
+// since the epoch.
+//
+// The checksum is the 32-character hexadecimal MD5 checksum of <data>. It is
+// meant to protect from random file changes on disk.
+
+#include "wrapper.h"
+
+#include <cassert>
+#include <cstddef>
+#include <cstdlib>
+#include <ctime>
+#include <string>
+
+#include "time_to_string.h"
+#include "util/md5.h"
+
+namespace i18n {
+namespace addressinput {
+
+namespace {
+
+const char kTimestampPrefix[] = "timestamp=";
+const size_t kTimestampPrefixLength = sizeof kTimestampPrefix - 1;
+
+const char kChecksumPrefix[] = "checksum=";
+const size_t kChecksumPrefixLength = sizeof kChecksumPrefix - 1;
+
+const char kSeparator = '\n';
+
+// Places the header value into |header_value| parameter and erases the header
+// from |data|. Returns |true| if the header format is valid.
+bool UnwrapHeader(const char* header_prefix,
+                  size_t header_prefix_length,
+                  std::string* data,
+                  std::string* header_value) {
+  assert(header_prefix != NULL);
+  assert(data != NULL);
+  assert(header_value != NULL);
+
+  if (data->compare(
+          0, header_prefix_length, header_prefix, header_prefix_length) != 0) {
+    return false;
+  }
+
+  std::string::size_type separator_position =
+      data->find(kSeparator, header_prefix_length);
+  if (separator_position == std::string::npos) {
+    return false;
+  }
+
+  header_value->assign(
+      *data, header_prefix_length, separator_position - header_prefix_length);
+  data->erase(0, separator_position + 1);
+
+  return true;
+}
+
+}  // namespace
+
+// static
+std::string Wrapper::Wrap(const std::string& data) {
+  std::string wrapped;
+  wrapped.append(kTimestampPrefix, kTimestampPrefixLength);
+  wrapped.append(TimeToString(time(NULL)));
+  wrapped.push_back(kSeparator);
+
+  wrapped.append(kChecksumPrefix, kChecksumPrefixLength);
+  wrapped.append(MD5String(data));
+  wrapped.push_back(kSeparator);
+  wrapped.append(data);
+
+  return wrapped;
+}
+
+// static
+bool Wrapper::Unwrap(std::string* data, double* age_in_seconds) {
+  assert(data != NULL);
+  assert(age_in_seconds != NULL);
+
+  std::string timestamp_string;
+  if (!UnwrapHeader(
+           kTimestampPrefix, kTimestampPrefixLength, data, &timestamp_string)) {
+    return false;
+  }
+
+  time_t timestamp = atol(timestamp_string.c_str());
+  if (timestamp < 0) {
+    return false;
+  }
+
+  *age_in_seconds = difftime(time(NULL), timestamp);
+  if (*age_in_seconds < 0.0) {
+    return false;
+  }
+
+  std::string checksum;
+  if (!UnwrapHeader(kChecksumPrefix, kChecksumPrefixLength, data, &checksum)) {
+    return false;
+  }
+
+  return checksum == MD5String(*data);
+}
+
+}  // namespace addressinput
+}  // namespace i18n