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 8411)
+++ vm/dart_api_message.h	(working copy)
@@ -33,6 +33,22 @@
   Dart_CObject* ReadMessage();
 
  private:
+  class BackwardReferenceNode {
+   public:
+    BackwardReferenceNode(Dart_CObject* reference, bool is_deserialized)
+        : reference_(reference), is_deserialized_(is_deserialized) {}
+    Dart_CObject* reference() const { return reference_; }
+    void set_reference(Dart_CObject* reference) { reference_ = reference; }
+    bool is_deserialized() const { return is_deserialized_; }
+    void set_is_deserialized(bool value) { is_deserialized_ = value; }
+
+   private:
+    Dart_CObject* reference_;
+    bool is_deserialized_;
+
+    DISALLOW_COPY_AND_ASSIGN(BackwardReferenceNode);
+  };
+
   // Allocates a Dart_CObject object.
   Dart_CObject* AllocateDartCObject();
   // Allocates a Dart_CObject object with the specified type.
@@ -58,18 +74,28 @@
   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.
+  BackwardReferenceNode* AllocateBackwardReferenceNode(Dart_CObject* reference,

[cshapiro, 2012/06/08 22:04:39]

Just a suggestion: we already shorten "Reference" to "Ref" in this context. 
Seeing as how the indentation is getting crazy here and elsewhere to accommodate
the long name, you couldwant shorten "BackwardReference" to "BackwardRef" or
even "BackRef" to keep things more naturally within the margin.

[siva, 2012/06/11 20:49:06]

Done.

+                                                       bool is_deserialized);
 
   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 AddBackwardReference(intptr_t id,
+                            Dart_CObject* obj,
+                            bool is_deserialized);
 
+  // Get an object from the backward references list.
+  Dart_CObject* GetBackwardReference(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 +105,7 @@
   // either in the supplied zone or using the supplied allocation
   // function.
   ReAlloc alloc_;
-  ApiGrowableArray<Dart_CObject*> backward_references_;
+  ApiGrowableArray<BackwardReferenceNode*> backward_references_;
 
   Dart_CObject type_arguments_marker;
   Dart_CObject dynamic_type_marker;
@@ -89,10 +115,13 @@
 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 +143,7 @@
   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 +151,14 @@
   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);
 };