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

runtime/vm/snapshot.cc

Index: runtime/vm/snapshot.cc
diff --git a/runtime/vm/snapshot.cc b/runtime/vm/snapshot.cc
index d1d4055eda8cd5efa0b4548382cfce1ae64cec6b..2278e4c2fe5928ab88dcdd957633ec7f34eff35a 100644
--- a/runtime/vm/snapshot.cc
+++ b/runtime/vm/snapshot.cc
@@ -440,7 +440,9 @@ RawObject* SnapshotReader::ReadInlinedObject(intptr_t object_id) {
 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.
@@ -548,6 +550,7 @@ Dart_CObject* CMessageReader::ReadInlinedObject(intptr_t object_id) {
     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++) {
@@ -559,6 +562,8 @@ Dart_CObject* CMessageReader::ReadInlinedObject(intptr_t object_id) {
     }
     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).
@@ -567,7 +572,6 @@ Dart_CObject* CMessageReader::ReadInlinedObject(intptr_t object_id) {
           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();
       }
@@ -576,21 +580,24 @@ Dart_CObject* CMessageReader::ReadInlinedObject(intptr_t object_id) {
     }
     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:
@@ -624,7 +631,10 @@ Dart_CObject* CMessageReader::ReadIndexedObject(intptr_t object_id) {
     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;
@@ -654,6 +664,12 @@ Dart_CObject* CMessageReader::ReadObject() {
 }
 
 
+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);