[EasyUnlock] Port PermitMessage class to native code.

components/proximity_auth/wire_message.cc

 // Copyright 2014 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 "components/proximity_auth/wire_message.h"
 
+#include "base/base64.h"
+#include "base/json/json_reader.h"
+#include "base/logging.h"
+#include "base/macros.h"
+#include "base/values.h"
+
+// The wire messages have a simple format:
+// [ message version ] [ body length ] [ JSON body ]
+//       1 byte            2 bytes      body length
+// The JSON body contains two fields: an optional permit_id field and a required
+// data field.
+
 namespace proximity_auth {
+namespace {
+
+// The length of the message header, in bytes.
+const size_t kHeaderLength = 3;
+
+// The protocol version of the message format.
+const int kExpectedMessageFormatVersion = 3;
+
+const char kPayloadKey[] = "payload";
+const char kPermitIdKey[] = "permit_id";
+
+// Parses the |serialized_message|'s header. Returns |true| iff the message has
+// a valid header, is complete, and is well-formed according to the header. Sets
+// |is_incomplete_message| to true iff the message does not have enough data to
+// parse the header, or if the message length encoded in the message header
+// exceeds the size of the |serialized_message|.
+bool ParseHeader(const std::string& serialized_message,
+                 bool* is_incomplete_message) {
+  *is_incomplete_message = false;
+  if (serialized_message.size() < kHeaderLength) {
+    *is_incomplete_message = true;
+    return false;
+  }
+
+  COMPILE_ASSERT(kHeaderLength > 2, header_length_too_small);
+  size_t version = serialized_message[0];
+  if (version != kExpectedMessageFormatVersion) {
+    VLOG(1) << "Error: Invalid message version. Got " << version
+            << ", expected " << kExpectedMessageFormatVersion;
+    return false;
+  }
+
+  size_t expected_body_length =
+      (static_cast<size_t>(serialized_message[1]) << 8) |
+      (static_cast<size_t>(serialized_message[2]) << 0);
+  size_t expected_message_length = kHeaderLength + expected_body_length;
+  if (serialized_message.size() < expected_message_length) {
+    *is_incomplete_message = true;
+    return false;
+  }
+  if (serialized_message.size() != expected_message_length) {
+    VLOG(1) << "Error: Invalid message length. Got "
+            << serialized_message.size() << ", expected "
+            << expected_message_length;
+    return false;
+  }
+
+  return true;
+}
+
+}  // namespace
 
 WireMessage::~WireMessage() {
 }
 
 // static
-bool WireMessage::IsCompleteMessage(const std::string& serialized_message) {
-  // TODO(isherman): Implement.
-  return false;
+scoped_ptr<WireMessage> WireMessage::Deserialize(
+    const std::string& serialized_message,
+    bool* is_incomplete_message) {
+  if (!ParseHeader(serialized_message, is_incomplete_message))
+    return scoped_ptr<WireMessage>();
+
+  scoped_ptr<base::Value> body_value(
+      base::JSONReader::Read(serialized_message.substr(kHeaderLength)));
+  if (!body_value || !body_value->IsType(base::Value::TYPE_DICTIONARY)) {
+    VLOG(1) << "Error: Unable to parse message as JSON.";
+    return scoped_ptr<WireMessage>();
+  }
+
+  base::DictionaryValue* body;
+  bool success = body_value->GetAsDictionary(&body);
+  DCHECK(success);
+
+  // The permit ID is optional. In the Easy Unlock protocol, only the first
+  // message includes this field.
+  std::string permit_id;
+  body->GetString(kPermitIdKey, &permit_id);
+
+  std::string payload_base64;
+  if (!body->GetString(kPayloadKey, &payload_base64) ||
+      payload_base64.empty()) {
+    VLOG(1) << "Error: Missing payload.";
+    return scoped_ptr<WireMessage>();
+  }
+
+  std::string payload;
+  if (!base::Base64Decode(payload_base64, &payload)) {
+    VLOG(1) << "Error: Invalid base64 encoding for payload.";
+    return scoped_ptr<WireMessage>();
+  }
+
+  return scoped_ptr<WireMessage>(new WireMessage(permit_id, payload));
 }
 
-// static
-scoped_ptr<WireMessage> WireMessage::Deserialize(
-    const std::string& serialized_message) {
-  // TODO(isherman): Implement.
-  return scoped_ptr<WireMessage>();
-}
-
-WireMessage::WireMessage() {
-  // TODO(isherman): Implement.
+WireMessage::WireMessage(const std::string& permit_id,
+                         const std::string& payload)
+    : permit_id_(permit_id),
+      payload_(payload) {
 }
 
 }  // namespace proximity_auth