Deserialize same symbol as same Dart_CObject

runtime/vm/dart_api_message.cc

Index: runtime/vm/dart_api_message.cc
diff --git a/runtime/vm/dart_api_message.cc b/runtime/vm/dart_api_message.cc
index 64eea311b36bbefba79d1888f3a34d9b83c4fc4d..b661136f5dbbda611ce071d400ef005ac19db8ce 100644
--- a/runtime/vm/dart_api_message.cc
+++ b/runtime/vm/dart_api_message.cc
@@ -17,7 +17,8 @@ ApiMessageReader::ApiMessageReader(const uint8_t* buffer,
                                    ReAlloc alloc)
     : BaseReader(buffer, length),
       alloc_(alloc),
-      backward_references_(kNumInitialReferences) {
+      backward_references_(kNumInitialReferences),
+      vm_symbol_references_(NULL) {
   Init();
 }
 
@@ -215,13 +216,31 @@ Dart_CObject* ApiMessageReader::ReadInlinedObject(intptr_t object_id) {
 
 Dart_CObject* ApiMessageReader::ReadVMSymbol(intptr_t object_id) {
   if (Symbols::IsVMSymbolId(object_id)) {
+    intptr_t symbol_id = object_id - kMaxPredefinedObjectIds;
+    Dart_CObject* object;
+    if (vm_symbol_references_ != NULL &&
+        (object = vm_symbol_references_[symbol_id]) != NULL) {
+      return object;
+    }
+
+    if (vm_symbol_references_ == NULL) {
+      intptr_t size = sizeof(*vm_symbol_references_) * Symbols::kMaxId;
+      vm_symbol_references_ =
+          reinterpret_cast<Dart_CObject**>(alloc_(NULL, 0, size));
+#ifdef DEBUG

[Florian Schneider, 2012/11/19 14:30:08]

I think you need to zero-initialize this array in any case.

[Søren Gjesse, 2012/11/19 14:54:47]

Absolutely, thanks for spotting.

+      memset(vm_symbol_references_, 0, size);
+#endif
+    }
+
     RawOneByteString* str =
         reinterpret_cast<RawOneByteString*>(Symbols::GetVMSymbol(object_id));
     intptr_t len = Smi::Value(str->ptr()->length_);
-    Dart_CObject* object = AllocateDartCObjectString(len);
+    object = AllocateDartCObjectString(len);
     char* p = object->value.as_string;
     memmove(p, str->ptr()->data_, len);
     p[len] = '\0';
+    ASSERT(vm_symbol_references_[symbol_id] == NULL);
+    vm_symbol_references_[symbol_id] = object;
     return object;
   }
   // No other VM isolate objects are supported.