Make IPC::SyncChannel not duplicate the underlying MessageLoop implementation...

chrome/common/ipc_sync_channel.h

 // Copyright (c) 2006-2008 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 CHROME_COMMON_IPC_SYNC_SENDER_H__
 #define CHROME_COMMON_IPC_SYNC_SENDER_H__
 
 #include <windows.h>
 #include <string>
-#include <stack>
-#include <queue>
+#include <deque>
 #include "base/basictypes.h"
 #include "base/lock.h"
+#include "base/object_watcher.h"
 #include "base/ref_counted.h"
+#include "base/scoped_handle.h"
 #include "chrome/common/ipc_channel_proxy.h"
 
 namespace IPC {
 
 class SyncMessage;
 
 // This is similar to IPC::ChannelProxy, with the added feature of supporting
 // sending synchronous messages.
 // Note that care must be taken that the lifetime of the ipc_thread argument
 // is more than this object.  If the message loop goes away while this object
 // is running and it's used to send a message, then it will use the invalid
 // message loop pointer to proxy it to the ipc thread.
-class SyncChannel : public ChannelProxy {
+class SyncChannel : public ChannelProxy,
+                    public base::ObjectWatcher::Delegate {
  public:
   SyncChannel(const std::wstring& channel_id, Channel::Mode mode,
               Channel::Listener* listener, MessageFilter* filter,
               MessageLoop* ipc_message_loop, bool create_pipe_now,
-              HANDLE shutdown_handle);
+              HANDLE shutdown_event);
   ~SyncChannel();
 
   virtual bool Send(Message* message);
   virtual bool SendWithTimeout(Message* message, int timeout_ms);
-  bool UnblockListener(Message* message);
 
   // Whether we allow sending messages with no time-out.
   void set_sync_messages_with_no_timeout_allowed(bool value) {
     sync_messages_with_no_timeout_allowed_ = value;
   }
 
  protected:
   class ReceivedSyncMsgQueue;
   friend class ReceivedSyncMsgQueue;
 
   // SyncContext holds the per object data for SyncChannel, so that SyncChannel
   // can be deleted while it's being used in a different thread.  See
   // ChannelProxy::Context for more information.
-  class SyncContext : public Context {
+  class SyncContext : public Context,
+                      public base::ObjectWatcher::Delegate {
    public:
     SyncContext(Channel::Listener* listener,
                 MessageFilter* filter,
-                MessageLoop* ipc_thread);
+                MessageLoop* ipc_thread,
+                HANDLE shutdown_event);
 
     ~SyncContext();
 
     // Adds information about an outgoing sync message to the context so that
-    // we know how to deserialize the reply.  Returns a handle that's set when
-    // the reply has arrived.
-    HANDLE Push(IPC::SyncMessage* sync_msg);
+    // we know how to deserialize the reply.
+    void Push(IPC::SyncMessage* sync_msg);
 
-    // Returns true if the reply message was deserialized without any errors,
-    // or false otherwise.
-    bool reply_deserialize_result() { return reply_deserialize_result_; }
+    // Cleanly remove the top deserializer (and throw it away).  Returns the
+    // result of the Send call for that message.
+    bool Pop();
+
+    // Returns an event that's set when the send is complete, timed out or the
+    // process shut down.
+    HANDLE GetSendDoneEvent();
 
     // Returns an event that's set when an incoming message that's not the reply
     // needs to get dispatched (by calling SyncContext::DispatchMessages).
-    HANDLE blocking_event();
+    HANDLE GetDispatchEvent();
 
     void DispatchMessages();
-    void RemoveListener(Channel::Listener* listener);
 
     // Checks if the given message is blocking the listener thread because of a
     // synchronous send.  If it is, the thread is unblocked and true is returned.
     // Otherwise the function returns false.
-    bool UnblockListener(const Message* msg);
+    bool TryToUnblockListener(const Message* msg);
 
-    // Cleanly remove the top deserializer (and throw it away).
-    void PopDeserializer(bool close_reply_event);
+    // Called on the IPC thread when a sync send that runs a nested message loop
+    // times out.
+    void OnSendTimeout(int message_id);
+
+    HANDLE shutdown_event() { return shutdown_event_; }
 
    private:
-    void OnMessageReceived(const Message& msg);
-    void OnChannelError();
+    // IPC::ChannelProxy methods that we override.
+
+    // Called on the listener thread.
+   virtual void Clear();
+
+    // Called on the IPC thread.
+    virtual void OnMessageReceived(const Message& msg);
+    virtual void OnChannelError();
+    virtual void OnChannelOpened();
+    virtual void OnChannelClosed();
+
+    // Cancels all pending Send calls.
+    void CancelPendingSends();
+
+    // ObjectWatcher::Delegate implementation.
+    virtual void OnObjectSignaled(HANDLE object);
 
     // When sending a synchronous message, this structure contains an object that
     // knows how to deserialize the response.
     struct PendingSyncMsg {
       PendingSyncMsg(int id, IPC::MessageReplyDeserializer* d, HANDLE e) :
-          id(id), deserializer(d), reply_event(e) { }
+          id(id), deserializer(d), done_event(e), send_result(false) { }
       int id;
       IPC::MessageReplyDeserializer* deserializer;
-      HANDLE reply_event;
+      HANDLE done_event;
+      bool send_result;
     };
 
-    typedef std::stack<PendingSyncMsg> PendingSyncMessageQueue;
+    typedef std::deque<PendingSyncMsg> PendingSyncMessageQueue;
     PendingSyncMessageQueue deserializers_;
     Lock deserializers_lock_;
 
-    // This can't be a scoped_refptr because it needs to be released on the
-    // listener thread.
-    ReceivedSyncMsgQueue* received_sync_msgs_;
+    scoped_refptr<ReceivedSyncMsgQueue> received_sync_msgs_;
 
-    bool channel_closed_;
-    bool reply_deserialize_result_;
+    HANDLE shutdown_event_;
+    base::ObjectWatcher shutdown_watcher_;
   };
 
  private:
+  // ObjectWatcher::Delegate implementation.
+  virtual void OnObjectSignaled(HANDLE object);
+
   SyncContext* sync_context() { return reinterpret_cast<SyncContext*>(context()); }
 
-  // Copy of shutdown event that we get in constructor.
-  HANDLE shutdown_event_;
+  // Both these functions wait for a reply, timeout or process shutdown.  The
+  // latter one also runs a nested message loop in the meantime.
+  void WaitForReply(HANDLE pump_messages_event);
 
-  std::stack<HANDLE> pump_messages_events_;
+  // Runs a nested message loop until a reply arrives, times out, or the process
+  // shuts down.
+  void WaitForReplyWithNestedMessageLoop();
 
   bool sync_messages_with_no_timeout_allowed_;
 
+  // Used to signal events between the IPC and listener threads.
+  base::ObjectWatcher send_done_watcher_;
+  base::ObjectWatcher dispatch_watcher_;
+
   DISALLOW_EVIL_CONSTRUCTORS(SyncChannel);
 };
 
 }  // namespace IPC
 
 #endif  // CHROME_COMMON_IPC_SYNC_SENDER_H__