Refactor of Authenticator to allow it to ProcessMessage asynchronously and then call a callback

remoting/protocol/authenticator.h

 // Copyright (c) 2012 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.
 
 #ifndef REMOTING_PROTOCOL_AUTHENTICATOR_H_
 #define REMOTING_PROTOCOL_AUTHENTICATOR_H_
 
 #include <string>
 
+#include "base/callback.h"
 #include "base/memory/scoped_ptr.h"
 
 namespace buzz {
 class XmlElement;
 }  // namespace buzz
 
 namespace remoting {
 namespace protocol {
 
 class ChannelAuthenticator;
@@ skipping 11 matching lines @@
 // and session-accept messages or in a session-info
 // message. Session-info messages are used only if authenticators need
 // to exchange more than one message.
 class Authenticator {
  public:
   // Allowed state transitions:
   // When ProcessMessage() is called:
   //    WAITING_MESSAGE -> MESSAGE_READY
   //    WAITING_MESSAGE -> ACCEPTED
   //    WAITING_MESSAGE -> REJECTED
+  //    WAITING_MESSAGE -> PROCESSING_MESSAGE -> MESSAGE_READY

[Sergey Ulanov, 2013/03/01 01:28:30]

Move the second transition to a separate line and add a comment that it happens
asynchronously later (not in ProcessMessage())

[rmsousa, 2013/03/01 02:22:11]

Done.

   // When GetNextMessage() is called:
   //    MESSAGE_READY -> WAITING_MESSAGE
   //    MESSAGE_READY -> ACCEPTED
   enum State {
     // Waiting for the next message from the peer.
     WAITING_MESSAGE,
 
     // Next message is ready to be sent to the peer.
     MESSAGE_READY,
 
     // Session is authenticated successufully.
     ACCEPTED,
 
     // Session is rejected.
     REJECTED,
+
+    // Asynchronously processing the last message from the peer.
+    PROCESSING_MESSAGE,
   };
 
   enum RejectionReason {
     INVALID_CREDENTIALS,
     PROTOCOL_ERROR,
   };
 
   // Returns true if |message| is an Authenticator message.
   static bool IsAuthenticatorMessage(const buzz::XmlElement* message);
 
   // Creates an empty Authenticator message, owned by the caller.
   static scoped_ptr<buzz::XmlElement> CreateEmptyAuthenticatorMessage();
 
   // Finds Authenticator message among child elements of |message|, or
   // returns NULL otherwise.
   static const buzz::XmlElement* FindAuthenticatorMessage(
       const buzz::XmlElement* message);
 
   Authenticator() {}
   virtual ~Authenticator() {}
 
   // Returns current state of the authenticator.
   virtual State state() const = 0;
 
   // Returns rejection reason. Can be called only when in REJECTED state.
   virtual RejectionReason rejection_reason() const = 0;
 
   // Called in response to incoming message received from the peer.
-  // Should only be called when in WAITING_MESSAGE state. Caller
-  // retains ownership of |message|.
-  virtual void ProcessMessage(const buzz::XmlElement* message) = 0;
+  // Should only be called when in WAITING_MESSAGE state. Caller retains
+  // ownership of |message|. |resume_callback| will be called when processing is
+  // finished. The implementation must guarantee that |resume_callback| is not
+  // called after the Authenticator is destroyed.
+  virtual void ProcessMessage(const base::Closure& resume_callback,

[Sergey Ulanov, 2013/03/01 01:28:30]

It would be more natural to have message argument first and the callback second
- usually completion callback goes last in list of arguments.

[rmsousa, 2013/03/01 02:22:11]

Done.

+                              const buzz::XmlElement* message) = 0;
 
   // Must be called when in MESSAGE_READY state. Returns next
   // authentication message that needs to be sent to the peer.
   virtual scoped_ptr<buzz::XmlElement> GetNextMessage() = 0;
 
   // Creates new authenticator for a channel. Can be called only in
   // the ACCEPTED state.
   virtual scoped_ptr<ChannelAuthenticator>
       CreateChannelAuthenticator() const = 0;
 };
@@ skipping 15 matching lines @@
   virtual scoped_ptr<Authenticator> CreateAuthenticator(
       const std::string& local_jid,
       const std::string& remote_jid,
       const buzz::XmlElement* first_message) = 0;
 };
 
 }  // namespace protocol
 }  // namespace remoting
 
 #endif  // REMOTING_PROTOCOL_AUTHENTICATOR_H_