1. Remove recursion during snapshot writing and reading

vm/dart_api_message.h

Index: vm/dart_api_message.h
===================================================================
--- vm/dart_api_message.h	(revision 8515)
+++ vm/dart_api_message.h	(working copy)
@@ -33,6 +33,22 @@
   Dart_CObject* ReadMessage();
 
  private:
+  class BackRefNode {
+   public:
+    BackRefNode(Dart_CObject* reference, DeserializeState state)
+        : reference_(reference), state_(state) {}
+    Dart_CObject* reference() const { return reference_; }
+    void set_reference(Dart_CObject* reference) { reference_ = reference; }
+    bool is_deserialized() const { return state_ == kIsDeserialized; }
+    void set_state(DeserializeState value) { state_ = value; }
+
+   private:
+    Dart_CObject* reference_;
+    DeserializeState state_;
+
+    DISALLOW_COPY_AND_ASSIGN(BackRefNode);
+  };
+
   // Allocates a Dart_CObject object.
   Dart_CObject* AllocateDartCObject();
   // Allocates a Dart_CObject object with the specified type.
@@ -58,18 +74,25 @@
   Dart_CObject* AllocateDartCObjectUint8Array(intptr_t length);
   // Allocates a C array of Dart_CObject objects.
   Dart_CObject* AllocateDartCObjectArray(intptr_t length);
+  // Allocates a backwards reference node.
+  BackRefNode* AllocateBackRefNode(Dart_CObject* ref, DeserializeState state);
 
   void Init();
 
   intptr_t LookupInternalClass(intptr_t class_header);
+  Dart_CObject* ReadInternalVMObject(intptr_t class_id, intptr_t object_id);
   Dart_CObject* ReadInlinedObject(intptr_t object_id);
-  Dart_CObject* ReadObjectImpl(intptr_t header);
+  Dart_CObject* ReadObjectImpl();
   Dart_CObject* ReadIndexedObject(intptr_t object_id);
+  Dart_CObject* ReadObjectRef();
   Dart_CObject* ReadObject();
 
   // Add object to backward references.
-  void AddBackwardReference(intptr_t id, Dart_CObject* obj);
+  void AddBackRef(intptr_t id, Dart_CObject* obj, DeserializeState state);
 
+  // Get an object from the backward references list.
+  Dart_CObject* GetBackRef(intptr_t id);
+
   Dart_CObject_Internal* AsInternal(Dart_CObject* object) {
     ASSERT(object->type >= Dart_CObject::kNumberOfTypes);
     return reinterpret_cast<Dart_CObject_Internal*>(object);
@@ -79,7 +102,7 @@
   // either in the supplied zone or using the supplied allocation
   // function.
   ReAlloc alloc_;
-  ApiGrowableArray<Dart_CObject*> backward_references_;
+  ApiGrowableArray<BackRefNode*> backward_references_;
 
   Dart_CObject type_arguments_marker;
   Dart_CObject dynamic_type_marker;
@@ -89,10 +112,13 @@
 class ApiMessageWriter : public BaseWriter {
  public:
   ApiMessageWriter(uint8_t** buffer, ReAlloc alloc)
-      : BaseWriter(buffer, alloc), object_id_(0) {
+      : BaseWriter(buffer, alloc), object_id_(0),
+        forward_list_(NULL), forward_list_length_(0), forward_id_(0) {
     ASSERT(kDartCObjectTypeMask >= Dart_CObject::kNumberOfTypes - 1);
   }
-  ~ApiMessageWriter() { }
+  ~ApiMessageWriter() {
+    delete forward_list_;
+  }
 
   // Writes a message of integers.
   void WriteMessage(intptr_t field_count, intptr_t *data);
@@ -114,6 +140,7 @@
   bool IsCObjectMarked(Dart_CObject* object);
   intptr_t GetMarkedCObjectMark(Dart_CObject* object);
   void UnmarkAllCObjects(Dart_CObject* object);
+  void AddToForwardList(Dart_CObject* object);
 
   void WriteSmi(int64_t value);
   void WriteMint(Dart_CObject* object, int64_t value);
@@ -121,8 +148,14 @@
   void WriteInt64(Dart_CObject* object);
   void WriteInlinedHeader(Dart_CObject* object);
   void WriteCObject(Dart_CObject* object);
+  void WriteCObjectRef(Dart_CObject* object);
+  void WriteForwardedCObject(Dart_CObject* object);
+  void WriteCObjectInlined(Dart_CObject* object, Dart_CObject::Type type);
 
   intptr_t object_id_;
+  Dart_CObject** forward_list_;
+  intptr_t forward_list_length_;
+  intptr_t forward_id_;
 
   DISALLOW_COPY_AND_ASSIGN(ApiMessageWriter);
 };