Deserialize same symbol as same Dart_CObject

runtime/vm/dart_api_message.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/dart_api_message.h"
 #include "vm/object.h"
 #include "vm/snapshot_ids.h"
 #include "vm/symbols.h"
 #include "vm/unicode.h"
 
 namespace dart {
 
 static const int kNumInitialReferences = 4;
 
 ApiMessageReader::ApiMessageReader(const uint8_t* buffer,
                                    intptr_t length,
                                    ReAlloc alloc)
     : BaseReader(buffer, length),
       alloc_(alloc),
-      backward_references_(kNumInitialReferences) {
+      backward_references_(kNumInitialReferences),
+      vm_symbol_references_(NULL) {
   Init();
 }
 
 
 void ApiMessageReader::Init() {
   // 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));
@@ skipping 177 matching lines @@
     }
     return value;
   }
 
   return ReadInternalVMObject(class_id, 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.
   return AllocateDartCObjectNull();
 }
 
 
 Dart_CObject* ApiMessageReader::ReadObjectRef() {
   int64_t value = Read<int64_t>();
   if ((value & kSmiTagMask) == 0) {
@@ skipping 630 matching lines @@
     if (!success) {
       UnmarkAllCObjects(object);
       return false;
     }
   }
   UnmarkAllCObjects(object);
   return true;
 }
 
 }  // namespace dart