Restructure chromoting_jni_instance handling of Java strings

remoting/client/jni/chromoting_jni_instance.h

 // Copyright 2013 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_CLIENT_CHROMOTING_JNI_INSTANCE_H_
 #define REMOTING_CLIENT_CHROMOTING_JNI_INSTANCE_H_
 
 #include <jni.h>
 #include <string>
 
@@ skipping 19 matching lines @@
 // Class and package name of the Java class supporting the methods we call.
 const char* const JAVA_CLASS = "org/chromium/chromoting/jni/JNIInterface";
 
 // TODO(solb) Move into location shared with client plugin.
 const char* const CHAT_SERVER = "talk.google.com";
 const int CHAT_PORT = 5222;
 const bool CHAT_USE_TLS = true;
 const char* const CHAT_AUTH_METHOD = "oauth2";
 
 // ClientUserInterface that makes and (indirectly) receives JNI calls.
+// It also keeps the references to various Chromium components (e.g. message
+// loops and task runners) that must outlive any use of the rest of Chromoting.

[Wez, 2013/07/12 00:24:48]

This still doesn't explain why; IIUC this object simply contains global
resources such as the TaskRunners on which Chromoting components run, right?

[solb, 2013/07/12 01:14:22]

Right.

 class ChromotingJNIInstance : public ClientUserInterface {
  public:
+  // This class is instantiated at process initialization and persists until
+  // we close. It reuses many of its components between connections (i.e. when
+  // a DisconnectFromHost() call is followed by a ConnectToHost() one.
   static ChromotingJNIInstance* GetInstance();
 
-  // Call from UI thread.
+  // Should only be called while disconnected.
   void ConnectToHost(
-      jstring username,
-      jstring auth_token,
-      jstring host_jid,
-      jstring host_id,
-      jstring host_pubkey);
+      const char* username,
+      const char* auth_token,
+      const char* host_jid,
+      const char* host_id,
+      const char* host_pubkey);
 
-  // Call from UI thread.
+  // Must only be called during a successful or failed connection.

[Wez, 2013/07/12 00:24:48]

See above.

[solb, 2013/07/12 01:14:22]

As covered in another comment, it's not racy because it's invoked on the same
thread as ConnectToHost().

   void DisconnectFromHost();
 
-  // Call from UI thread.
-  void AuthenticateWithPin(jstring pin);
+  void AuthenticateWithPin(const char* pin);

[Wez, 2013/07/12 00:24:48]

Comment to explain this, please!

[solb, 2013/07/12 01:14:22]

Done.

 
-  // Called by client authenticator.
-  // Gets notified if the user needs to enter a PIN, and notifies Java in turn.
+  // Called by client authenticator. Calls to Java to prompt for the ser's PIN.
   void FetchSecret(bool pairable,
-                   const protocol::SecretFetchedCallback& callback_encore);
+                   const protocol::SecretFetchedCallback& callback);
 
-  // ClientUserInterface implementation:
+  // ClientUserInterface implementation.
   virtual void OnConnectionState(
       protocol::ConnectionToHost::State state,
       protocol::ErrorCode error) OVERRIDE;
   virtual void OnConnectionReady(bool ready) OVERRIDE;
   virtual void SetCapabilities(const std::string& capabilities) OVERRIDE;
   virtual void SetPairingResponse(
       const protocol::PairingResponse& response) OVERRIDE;
   virtual protocol::ClipboardStub* GetClipboardStub() OVERRIDE;
   virtual protocol::CursorShapeStub* GetCursorShapeStub() OVERRIDE;
   virtual scoped_ptr<protocol::ThirdPartyClientAuthenticator::TokenFetcher>
       GetTokenFetcher(const std::string& host_public_key) OVERRIDE;
 
  private:
   ChromotingJNIInstance();
+
+  // Any existing or attempted connection must have been terminated using
+  // DisconnectFromHost() before this singleton is destroyed.
   virtual ~ChromotingJNIInstance();
 
   void ConnectToHostOnDisplayThread();
   void ConnectToHostOnNetworkThread();
 
   void DisconnectFromHostOnNetworkThread();
 
-  // Reusable between sessions:
-  jclass class_;  // Reference to the Java class into which we make JNI calls.
+  // The below variables are reused across consecutive sessions.
+
+  // Reference to the Java class into which we make JNI calls.
+  jclass class_;
+
+  // Used by the Chromium libraries to clean up the base and net libraries' JNI
+  // bindings. It must persist for the lifetime of the singleton.
   scoped_ptr<base::AtExitManager> collector_;
+
+  // Chromium code's connection to the Java message loop.
   scoped_ptr<base::MessageLoopForUI> ui_loop_;
-  scoped_refptr<AutoThreadTaskRunner> ui_runner_;
-  scoped_refptr<AutoThreadTaskRunner> net_runner_;
-  scoped_refptr<AutoThreadTaskRunner> disp_runner_;
+
+  // Runners that allow posting tasks to the various native threads.
+  scoped_refptr<AutoThreadTaskRunner> ui_task_runner_;
+  scoped_refptr<AutoThreadTaskRunner> network_task_runner_;
+  scoped_refptr<AutoThreadTaskRunner> display_task_runner_;
+
   scoped_refptr<net::URLRequestContextGetter> url_requester_;
-  scoped_refptr<FrameConsumerProxy> frames_;
+  scoped_refptr<FrameConsumerProxy> frame_consumer_;
 
-  // Specific to each session:
+  // The below variables are specific to each connection.
+
+  // Whether we're in the connected state, meaning we're attempting to connect,
+  // we're currently connected, or the connection has failed somehow.

[Wez, 2013/07/12 00:24:48]

Chromium comment style would be something like:
"True if ConnectToHost() has been called without a subsequent
DisconnectFromHost(). i.e. |connected_| is true while connecting, or after the
connection has failed, until explicitly cleared via DisconnectFromHost()."

[solb, 2013/07/12 01:14:22]

Done.

+  bool connected_;
+
   scoped_ptr<ClientConfig> client_config_;
   scoped_ptr<ClientContext> client_context_;
   scoped_ptr<protocol::ConnectionToHost> connection_;
   scoped_ptr<ChromotingClient> client_;
-  scoped_ptr<XmppSignalStrategy::XmppServerConfig> chat_config_;
-  scoped_ptr<XmppSignalStrategy> chat_;  // must outlive client_
-  scoped_ptr<NetworkSettings> netset_;
-  protocol::SecretFetchedCallback announce_secret_;
+  scoped_ptr<XmppSignalStrategy::XmppServerConfig> signaling_config_;
+  scoped_ptr<XmppSignalStrategy> signaling_;  // must outlive client_
+  scoped_ptr<NetworkSettings> network_settings_;
+  protocol::SecretFetchedCallback pin_callback_;
 
-  // Java string handles:
-  jstring username_jstr_;
-  jstring auth_token_jstr_;
-  jstring host_jid_jstr_;
-  jstring host_id_jstr_;
-  jstring host_pubkey_jstr_;
-  jstring pin_jstr_;
-
-  // C string pointers:
-  const char* username_cstr_;
-  const char* auth_token_cstr_;
-  const char* host_jid_cstr_;
-  const char* host_id_cstr_;
-  const char* host_pubkey_cstr_;
-  const char* pin_cstr_;
+  // These strings describe the current connection, and are not reused.
+  std::string username_;
+  std::string auth_token_;
+  std::string host_jid_;
+  std::string host_id_;
+  std::string host_pubkey_;
+  std::string pin_;
 
   friend struct DefaultSingletonTraits<ChromotingJNIInstance>;
 
   DISALLOW_COPY_AND_ASSIGN(ChromotingJNIInstance);
 };
 
 }  // namespace remoting
 
 #endif