- Implement Isolate.ping.

runtime/vm/message.cc

Index: runtime/vm/message.cc
===================================================================
--- runtime/vm/message.cc	(revision 41942)
+++ runtime/vm/message.cc	(working copy)
@@ -31,19 +31,49 @@
 }
 
 
-void MessageQueue::Enqueue(Message* msg) {
+void MessageQueue::Enqueue(Message* msg, bool before_events) {
   // Make sure messages are not reused.
   ASSERT(msg->next_ == NULL);
-  if (head_ == NULL) {
-    // Only element in the queue.
-    ASSERT(tail_ == NULL);
-    head_ = msg;
-    tail_ = msg;
+  if (!before_events) {
+    if (head_ == NULL) {
+      // Only element in the queue.
+      ASSERT(tail_ == NULL);
+      head_ = msg;
+      tail_ = msg;
+    } else {
+      ASSERT(tail_ != NULL);
+      // Append at the tail.
+      tail_->next_ = msg;
+      tail_ = msg;
+    }
   } else {
-    ASSERT(tail_ != NULL);
-    // Append at the tail.
-    tail_->next_ = msg;
-    tail_ = msg;
+    ASSERT(msg->dest_port() == Message::kIllegalPort);
+    if (tail_ == NULL) {
+      ASSERT(head_ == NULL);
+      head_ = msg;
+      tail_ = msg;

[siva, 2014/12/01 19:48:05]

The "only element in queue" case is common always why not hoist that out to make
the code simpler to read:

if (head_ == NULL) {
  // Only element in the queue.
  ASSERT(tail_ == NULL);
  head_= msg;
  tail_ = msg;
} else {
  if (!before_events) {
    ASSERT(tail_ != NULL);
    // Append at the tail.
    ...
    ...
  } else {
    ASSERT(head_ != NULL);
    if (head->dest_port() != Message::kIllegalPort) {
      ...
      ...
    } else {
      Message* cur = head_;
      ...
      ...
    }
  }
}

[Ivan Posva, 2014/12/12 20:21:46]

Done.

+    } else if (head_->dest_port() != Message::kIllegalPort) {
+      msg->next_ = head_;
+      head_ = msg;
+    } else {
+      ASSERT(head_ != NULL);  // Is guaranteed by "if (tail_ == NULL)" above.
+      Message* cur = head_;
+      while (cur->next_ != NULL) {
+        if (cur->next_->dest_port() != Message::kIllegalPort) {
+          // Splice in the new message at the break.
+          msg->next_ = cur->next_;
+          cur->next_ = msg;
+          return;
+        }
+        cur = cur->next_;
+      }
+      // All pending messages are isolate library control messages. Append at
+      // the tail.
+      ASSERT(tail_ == cur);
+      ASSERT(tail_->dest_port() == Message::kIllegalPort);
+      tail_->next_ = msg;
+      tail_ = msg;
+    }
   }
 }