1. Remove recursion during snapshot writing and reading

vm/dart_api_message.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_DART_API_MESSAGE_H_
 #define VM_DART_API_MESSAGE_H_
 
 #include "vm/dart_api_state.h"
 #include "vm/snapshot.h"
 
@@ skipping 15 matching lines @@
 
 // Reads a message snapshot into a C structure.
 class ApiMessageReader : public BaseReader {
  public:
   ApiMessageReader(const uint8_t* buffer, intptr_t length, ReAlloc alloc);
   ~ApiMessageReader() { }
 
   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.
   Dart_CObject* AllocateDartCObject(Dart_CObject::Type type);
   // Allocates a Dart_CObject object representing an unsupported
   // object in the API message.
   Dart_CObject* AllocateDartCObjectUnsupported();
   // Allocates a Dart_CObject object for the null object.
   Dart_CObject* AllocateDartCObjectNull();
   // Allocates a Dart_CObject object for a boolean object.
   Dart_CObject* AllocateDartCObjectBool(bool value);
   // Allocates a Dart_CObject object for for a 32-bit integer.
   Dart_CObject* AllocateDartCObjectInt32(int32_t value);
   // Allocates a Dart_CObject object for for a 64-bit integer.
   Dart_CObject* AllocateDartCObjectInt64(int64_t value);
   // Allocates a Dart_CObject object for bigint data.
   Dart_CObject* AllocateDartCObjectBigint(intptr_t length);
   // Allocates a Dart_CObject object for a double.
   Dart_CObject* AllocateDartCObjectDouble(double value);
   // Allocates a Dart_CObject object for string data.
   Dart_CObject* AllocateDartCObjectString(intptr_t length);
   // Allocates a C Dart_CObject object for byte data.
   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);
   }
 
   // Allocation of the structures for the decoded message happens
   // 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;
 };
 
 
 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);
 
   void WriteCMessage(Dart_CObject* object);
 
   void FinalizeBuffer() {
     BaseWriter::FinalizeBuffer(Snapshot::kMessage);
   }
 
  private:
   static const intptr_t kDartCObjectTypeBits = 4;
   static const intptr_t kDartCObjectTypeMask = (1 << kDartCObjectTypeBits) - 1;
   static const intptr_t kDartCObjectMarkMask = ~kDartCObjectTypeMask;
   static const intptr_t kDartCObjectMarkOffset = 1;
 
   void MarkCObject(Dart_CObject* object, intptr_t object_id);
   void UnmarkCObject(Dart_CObject* object);
   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);
   void WriteInt32(Dart_CObject* object);
   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);
 };
 
 }  // namespace dart
 
 #endif  // VM_DART_API_MESSAGE_H_