Display isolate message queue in Observatory debugger

runtime/vm/message.cc

Index: runtime/vm/message.cc
diff --git a/runtime/vm/message.cc b/runtime/vm/message.cc
index ea9b9861425510f59e1b38ca9e79ab209aad79b7..90335d101203ed6262c6349097728a6832ccaa31 100644
--- a/runtime/vm/message.cc
+++ b/runtime/vm/message.cc
@@ -4,6 +4,9 @@
 
 #include "vm/message.h"
 
+#include "vm/dart_entry.h"
+#include "vm/json_stream.h"
+#include "vm/object.h"
 #include "vm/port.h"
 
 namespace dart {
@@ -18,6 +21,26 @@ bool Message::RedirectToDeliveryFailurePort() {
 }
 
 
+intptr_t Message::Id() const {
+  // Messages are allocated on the C heap. Use the raw address as the id.
+  return reinterpret_cast<intptr_t>(this);
+}
+
+const char* Message::PriorityAsString(Priority priority) {
+  switch (priority) {
+    case kNormalPriority:
+      return "Normal";
+    break;
+    case kOOBPriority:
+      return "OOB";
+    break;
+    default:
+      UNIMPLEMENTED();
+      return NULL;
+  }
+}
+
+
 MessageQueue::MessageQueue() {
   head_ = NULL;
   tail_ = NULL;
@@ -106,4 +129,98 @@ void MessageQueue::Clear() {
 }
 
 
+MessageQueue::Iterator::Iterator(const MessageQueue* queue)
+    : current_(NULL),
+      queue_(queue) {
+  Reset(queue);
+}
+
+
+MessageQueue::Iterator::~Iterator() {
+}
+
+void MessageQueue::Iterator::Reset(const MessageQueue* queue) {
+  queue_ = queue;
+  if (queue_ == NULL) {
+    current_ = NULL;
+    return;
+  }
+  current_ = queue_->head_;
+}
+
+// returns false when iterator has reached end of message queue.
+bool MessageQueue::Iterator::HasNext() {
+  return current() != NULL;
+}
+
+// Moves forward and then returns current().
+Message* MessageQueue::Iterator::Next() {
+  if (!HasNext()) {
+    return current();

[turnidge, 2015/05/04 17:47:13]

Your Next() and HasNext() are a bit different than those found, e.g., in Java. 
Do we use this pattern elsewhere in the VM already?  It is odd to me that I can
call Next() as many times as I like and it just sticks to the end of the queue
when HasNext is false, seems like it could hide errors.

I would be more used to seeing a Next() function that unconditionally returns
the next element and kills the VM if it goes out of bounds.  Loops would look
like this:

while (it.HasNext()) {
  Message* current = it.Next();
  ... do work here...
}

[Cutch, 2015/05/04 19:56:51]

Done.

+  }
+  current_ = current_->next_;
+  return current();
+}
+
+
+intptr_t MessageQueue::Length() const {
+  MessageQueue::Iterator it(this);
+  intptr_t length = 0;
+  for (; it.HasNext(); it.Next()) {
+    length++;
+  }
+  return length;
+}
+
+
+Message* MessageQueue::FindMessageById(intptr_t id) {
+  MessageQueue::Iterator it(this);
+  for (; it.HasNext(); it.Next()) {
+    Message* message = it.current();
+    ASSERT(message != NULL);
+    if (message->Id() == id) {
+      return message;
+    }
+  }
+  return NULL;
+}
+
+
+void MessageQueue::PrintJSON(JSONStream* stream) {
+  Isolate* isolate = Isolate::Current();
+  JSONArray messages(stream);
+
+  MessageQueue::Iterator it(this);
+  intptr_t depth = 0;
+
+  Object& msg_handler = Object::Handle(isolate);
+  for (; it.HasNext(); it.Next()) {
+    Message* current = it.current();
+    JSONObject message(&messages);
+    message.AddProperty("type", "IsolateMessage");

[turnidge, 2015/05/04 17:47:13]

IsolateMessage?  I don't like the "Isolate".  Maybe just Message?

[Cutch, 2015/05/04 19:56:51]

Done.

+    message.AddPropertyF("name", "Isolate Message (%" Px ")", current->Id());
+    message.AddPropertyF("messageObjectId", "messages/0x%" Px "",
+                         current->Id());
+    message.AddProperty("size", current->len());
+    message.AddProperty("depth", depth++);
+    message.AddProperty("destinationPort",

[turnidge, 2015/05/04 17:47:13]

Make this _destinationPort.

[Cutch, 2015/05/04 19:56:51]

Done.

+        static_cast<intptr_t>(current->dest_port()));
+    message.AddProperty("priority",
+        Message::PriorityAsString(current->priority()));
+    msg_handler = DartLibraryCalls::LookupHandler(current->dest_port());

[turnidge, 2015/05/04 17:47:13]

Add a TODO to move this map into the VM so we can avoid this call into Dart...
(as discussed offline w/ iposva).

[Cutch, 2015/05/04 19:56:51]

Done.

+    if (msg_handler.IsInstance() && Instance::Cast(msg_handler).IsClosure()) {
+      // Grab function from closure.
+      msg_handler = Closure::function(Instance::Cast(msg_handler));
+    }
+    if (!msg_handler.IsFunction()) {
+      // No handler function.
+      continue;
+    }
+    const Function& function = Function::Cast(msg_handler);
+    const Script& script = Script::Handle(isolate, function.script());
+    message.AddProperty("handlerFunction", function);
+    message.AddProperty("handlerScript", script);

[turnidge, 2015/05/04 17:47:13]

Consider dropping handlerScript.  Up to you.

[Cutch, 2015/05/04 19:56:51]

Done.

+  }
+}
+
 }  // namespace dart