Add support for lists and backward references when decoding a message to a Dart_CObject object

runtime/vm/snapshot.cc

 // 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.
 
 #include "vm/snapshot.h"
 
 #include "platform/assert.h"
 #include "vm/bootstrap.h"
 #include "vm/exceptions.h"
 #include "vm/heap.h"
@@ skipping 422 matching lines @@
   if (kind_ == Snapshot::kFull) {
     obj_.SetCreatedFromSnapshot();
   }
   return obj_.raw();
 }
 
 
 CMessageReader::CMessageReader(const uint8_t* buffer,
                                intptr_t length,
                                ReAlloc alloc)
-    : BaseReader(buffer, length), alloc_(alloc) {
+    : BaseReader(buffer, length),
+      alloc_(alloc),
+      backward_references_(kNumInitialReferences) {
   // Initialize marker objects used to handle Lists.
   // TODO(sjesse): Remove this when message serialization format is
   // updated.
   memset(&type_arguments_marker, 0, sizeof(type_arguments_marker));
   memset(&dynamic_type_marker, 0, sizeof(dynamic_type_marker));
   type_arguments_marker.type =
       static_cast<Dart_CObject::Type>(Dart_CObject_Internal::kTypeArguments);
   dynamic_type_marker.type =
       static_cast<Dart_CObject::Type>(Dart_CObject_Internal::kDynamicType);
 }
@@ skipping 87 matching lines @@
 
   ASSERT((class_header & kSmiTagMask) != 0);
   class_id = LookupInternalClass(class_header);
   switch (class_id) {
     case Object::kClassClass: {
       return NULL;
     }
     case Object::kTypeArgumentsClass: {
       // TODO(sjesse): Remove this when message serialization format is
       // updated (currently length is leaked).
+      AddBackwardReference(object_id, NULL);
       Dart_CObject* length = ReadObject();
       ASSERT(length->type == Dart_CObject::kInt32);
       for (int i = 0; i < length->value.as_int32; i++) {
         Dart_CObject* type = ReadObject();
         if (type != &dynamic_type_marker) return NULL;
       }
       return &type_arguments_marker;
       break;
     }
     case ObjectStore::kArrayClass: {
       intptr_t len = ReadSmiValue();
+      Dart_CObject* value = AllocateDartCObjectArray(len);
+      AddBackwardReference(object_id, value);
       // Skip type arguments.
       // TODO(sjesse): Remove this when message serialization format is
       // updated (currently type_arguments is leaked).
       Dart_CObject* type_arguments = ReadObject();
       if (type_arguments != &type_arguments_marker &&
           type_arguments->type != Dart_CObject::kNull) {
         return NULL;
       }
-      Dart_CObject* value = AllocateDartCObjectArray(len);
       for (int i = 0; i < len; i++) {
         value->value.as_array.values[i] = ReadObject();
       }
       return value;
       break;
     }
     case ObjectStore::kDoubleClass: {
       // Read the double value for the object.
-      return AllocateDartCObjectDouble(Read<double>());
+      Dart_CObject* object = AllocateDartCObjectDouble(Read<double>());
+      AddBackwardReference(object_id, object);
+      return object;
       break;
     }
     case ObjectStore::kOneByteStringClass: {
       intptr_t len = ReadSmiValue();
       intptr_t hash = ReadSmiValue();
       USE(hash);
-      Dart_CObject* value = AllocateDartCObjectString(len);
-      char* p = value->value.as_string;
+      Dart_CObject* object = AllocateDartCObjectString(len);
+      AddBackwardReference(object_id, object);
+      char* p = object->value.as_string;
       for (intptr_t i = 0; i < len; i++) {
         *p = Read<uint8_t>();
         p++;
       }
       *p = '\0';
-      return value;
+      return object;
       break;
     }
     case ObjectStore::kTwoByteStringClass:
       // Two byte strings not supported.
       return NULL;
       break;
     case ObjectStore::kFourByteStringClass:
       // Four byte strings not supported.
       return NULL;
       break;
@@ skipping 12 matching lines @@
   } else if (object_id == ObjectStore::kFalseValue) {
     return AllocateDartCObjectBool(false);
   } else if (object_id == ObjectStore::kDynamicType ||
              object_id == ObjectStore::kDoubleInterface ||
              object_id == ObjectStore::kIntInterface ||
              object_id == ObjectStore::kBoolInterface ||
              object_id == ObjectStore::kStringInterface) {
     // Always return dynamic type (this is only a marker).
     return &dynamic_type_marker;
   } else {
     // TODO(sgjesse): Handle back-references.

[siva, 2012/02/02 04:01:57]

You are handling backward references now, the TODO can go.

[Søren Gjesse, 2012/02/02 09:59:49]

Done.

-    printf("Indexed object %d\n", object_id);
+    intptr_t index = object_id - kMaxPredefinedObjectIds;
+    ASSERT(index < backward_references_.length());
+    ASSERT(backward_references_[index] != NULL);
+    return backward_references_[index];
     UNREACHABLE();

[siva, 2012/02/02 04:01:57]

Is the UNREACHABLE needed?

[Søren Gjesse, 2012/02/02 09:59:49]

No, removed.

   }
   return NULL;
 }
 
 
 Dart_CObject* CMessageReader::ReadObjectImpl(intptr_t header) {
   SerializedHeaderType header_type = SerializedHeaderTag::decode(header);
   intptr_t header_value = SerializedHeaderData::decode(header);
 
   if (header_type == kObjectId) {
     return ReadIndexedObject(header_value);
   }
   ASSERT(header_type == kInlined);
   return ReadInlinedObject(header_value);
 }
 
 
 Dart_CObject* CMessageReader::ReadObject() {
   int64_t value = Read<int64_t>();
   if ((value & kSmiTagMask) == 0) {
     Dart_CObject* dart_value = AllocateDartCObjectInt32(value >> kSmiTagShift);
     return dart_value;
   }
   ASSERT((value <= kIntptrMax) && (value >= kIntptrMin));
   return ReadObjectImpl(value);
 }
 
 
+void CMessageReader::AddBackwardReference(intptr_t id, Dart_CObject* obj) {
+  ASSERT((id - kMaxPredefinedObjectIds) == backward_references_.length());
+  backward_references_.Add(obj);
+}
+
+
 void MessageWriter::WriteMessage(intptr_t field_count, intptr_t *data) {
   // Write out the serialization header value for this object.
   WriteSerializationMarker(kInlined, kMaxPredefinedObjectIds);
 
   // Write out the class and tags information.
   WriteObjectHeader(ObjectStore::kArrayClass, 0);
 
   // Write out the length field.
   Write<RawObject*>(Smi::New(field_count));
 
@@ skipping 212 matching lines @@
 
 
 void SnapshotWriterVisitor::VisitPointers(RawObject** first, RawObject** last) {
   for (RawObject** current = first; current <= last; current++) {
     RawObject* raw_obj = *current;
     writer_->WriteObject(raw_obj);
   }
 }
 
 }  // namespace dart