Mojo: More plumbing required to transfer handles over MessagePipes.

mojo/system/proxy_message_pipe_endpoint.cc

 // 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.
 
 #include "mojo/system/proxy_message_pipe_endpoint.h"
 
 #include <string.h>
 
 #include "base/logging.h"
 #include "base/stl_util.h"
@@ skipping 33 matching lines @@
     (*it)->Destroy();
   }
   paused_message_queue_.clear();
 }
 
 bool ProxyMessagePipeEndpoint::OnPeerClose() {
   DCHECK(is_open_);
   DCHECK(is_peer_open_);
 
   is_peer_open_ = false;
-  if (EnqueueMessage(MessageInTransit::Create(
-          MessageInTransit::kTypeMessagePipe,
-          MessageInTransit::kSubtypeMessagePipePeerClosed,
-          NULL, 0), NULL) != MOJO_RESULT_OK) {
+  MessageInTransit* message =
+      MessageInTransit::Create(MessageInTransit::kTypeMessagePipe,
+                               MessageInTransit::kSubtypeMessagePipePeerClosed,
+                               NULL, 0);
+  if (CanEnqueueMessage(message, NULL) == MOJO_RESULT_OK) {
+    EnqueueMessage(message, NULL);
+  } else {
+    message->Destroy();
     // TODO(vtl): Do something more sensible on error here?
     LOG(WARNING) << "Failed to send peer closed control message";
   }
 
   // Return false -- to indicate that we should be destroyed -- if no messages
   // are still enqueued. (Messages may still be enqueued if we're not running
   // yet, but our peer was closed.)
   return !paused_message_queue_.empty();
 }
 
-MojoResult ProxyMessagePipeEndpoint::EnqueueMessage(
+MojoResult ProxyMessagePipeEndpoint::CanEnqueueMessage(
+    const MessageInTransit* /*message*/,
+    const std::vector<Dispatcher*>* dispatchers) {
+  // TODO(vtl): Support sending handles over OS pipes.
+  if (dispatchers) {
+    NOTIMPLEMENTED();
+    return MOJO_RESULT_UNIMPLEMENTED;
+  }
+  return MOJO_RESULT_OK;
+}
+
+void ProxyMessagePipeEndpoint::EnqueueMessage(
     MessageInTransit* message,
-    const std::vector<Dispatcher*>* dispatchers) {
+    std::vector<scoped_refptr<Dispatcher> >* dispatchers) {
   DCHECK(is_open_);
   // If our (local) peer isn't open, we should only be enqueueing our own
   // control messages.
   DCHECK(is_peer_open_ ||
          (message->type() == MessageInTransit::kTypeMessagePipe));
 
-  // TODO(vtl): Support sending handles over OS pipes.
-  if (dispatchers) {
-    message->Destroy();
-    NOTIMPLEMENTED();
-    return MOJO_RESULT_UNIMPLEMENTED;
-  }
-
-  MojoResult rv = MOJO_RESULT_OK;
+  // TODO(vtl)
+  DCHECK(!dispatchers || dispatchers->empty());
 
   if (is_running()) {
     message->set_source_id(local_id_);
     message->set_destination_id(remote_id_);
+    // TODO(vtl): Figure out error handling here (where it's rather late) --
+    // maybe move whatever checks we can into |CanEnqueueMessage()|.
     if (!channel_->WriteMessage(message))
-      rv = MOJO_RESULT_FAILED_PRECONDITION;
+      LOG(WARNING) << "Failed to write message to channel";
   } else {
     paused_message_queue_.push_back(message);
   }
-
-  return rv;
 }
 
 void ProxyMessagePipeEndpoint::Attach(scoped_refptr<Channel> channel,
                                       MessageInTransit::EndpointId local_id) {
   DCHECK(channel.get());
   DCHECK_NE(local_id, MessageInTransit::kInvalidEndpointId);
 
   DCHECK(!is_attached());
 
   AssertConsistentState();
   channel_ = channel;
   local_id_ = local_id;
   AssertConsistentState();
 }
 
 bool ProxyMessagePipeEndpoint::Run(MessageInTransit::EndpointId remote_id) {
   // Assertions about arguments:
   DCHECK_NE(remote_id, MessageInTransit::kInvalidEndpointId);
 
   // Assertions about current state:
   DCHECK(is_attached());
   DCHECK(!is_running());
 
   AssertConsistentState();
   remote_id_ = remote_id;
   AssertConsistentState();
 
-  MojoResult result = MOJO_RESULT_OK;
   for (std::deque<MessageInTransit*>::iterator it =
            paused_message_queue_.begin();
        it != paused_message_queue_.end();
        ++it) {
-    result = EnqueueMessage(*it, NULL);
-    if (result != MOJO_RESULT_OK) {
+    if (CanEnqueueMessage(*it, NULL) == MOJO_RESULT_OK) {
+      EnqueueMessage(*it, NULL);
+    } else {
+      (*it)->Destroy();
       // TODO(vtl): Do something more sensible on error here?
       LOG(WARNING) << "Failed to send message";
+      // TODO(vtl): Abort?
     }
   }
   paused_message_queue_.clear();
 
   // If the peer is not open, we should return false since we should be
   // destroyed.
   return is_peer_open_;
 }
 
 #ifndef NDEBUG
 void ProxyMessagePipeEndpoint::AssertConsistentState() const {
   if (is_attached()) {
     DCHECK_NE(local_id_, MessageInTransit::kInvalidEndpointId);
   } else {  // Not attached.
     DCHECK_EQ(local_id_, MessageInTransit::kInvalidEndpointId);
     DCHECK_EQ(remote_id_, MessageInTransit::kInvalidEndpointId);
   }
 }
 #endif
 
 }  // namespace system
 }  // namespace mojo