Copy-on-write arrays.

src/objects.cc

 // Copyright 2006-2009 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2308 matching lines @@
   RETURN_IF_SCHEDULED_EXCEPTION();
   return raw_result;
 }
 
 
 Object* JSObject::DeleteElementPostInterceptor(uint32_t index,
                                                DeleteMode mode) {
   ASSERT(!HasPixelElements() && !HasExternalArrayElements());
   switch (GetElementsKind()) {
     case FAST_ELEMENTS: {
+      Object* obj = EnsureWritableFastElements();
+      if (obj->IsFailure()) return obj;
       uint32_t length = IsJSArray() ?
       static_cast<uint32_t>(Smi::cast(JSArray::cast(this)->length())->value()) :
       static_cast<uint32_t>(FixedArray::cast(elements())->length());
       if (index < length) {
         FixedArray::cast(elements())->set_the_hole(index);
       }
       break;
     }
     case DICTIONARY_ELEMENTS: {
       NumberDictionary* dictionary = element_dictionary();
@@ skipping 60 matching lines @@
   if (HasIndexedInterceptor()) {
     // Skip interceptor if forcing deletion.
     if (mode == FORCE_DELETION) {
       return DeleteElementPostInterceptor(index, mode);
     }
     return DeleteElementWithInterceptor(index);
   }
 
   switch (GetElementsKind()) {
     case FAST_ELEMENTS: {
+      Object* obj = EnsureWritableFastElements();
+      if (obj->IsFailure()) return obj;
       uint32_t length = IsJSArray() ?
       static_cast<uint32_t>(Smi::cast(JSArray::cast(this)->length())->value()) :
       static_cast<uint32_t>(FixedArray::cast(elements())->length());
       if (index < length) {
         FixedArray::cast(elements())->set_the_hole(index);
       }
       break;
     }
     case PIXEL_ELEMENTS:
     case EXTERNAL_BYTE_ELEMENTS:
@@ skipping 2571 matching lines @@
     // Also drop the back pointer for that map transition, so that this
     // map is not reached again by following a back pointer from a
     // non-live object.
     PropertyDetails details(Smi::cast(contents->get(i + 1)));
     if (details.type() == MAP_TRANSITION ||
         details.type() == CONSTANT_TRANSITION) {
       Map* target = reinterpret_cast<Map*>(contents->get(i));
       ASSERT(target->IsHeapObject());
       if (!target->IsMarked()) {
         ASSERT(target->IsMap());
-        contents->set(i + 1, NullDescriptorDetails);
-        contents->set_null(i);
+        contents->set_unchecked(i + 1, NullDescriptorDetails);
+        contents->set_null_unchecked(i);
         ASSERT(target->prototype() == this ||
                target->prototype() == real_prototype);
         // Getter prototype() is read-only, set_prototype() has side effects.
         *RawField(target, Map::kPrototypeOffset) = real_prototype;
       }
     }
   }
 }
 
 
@@ skipping 560 matching lines @@
 
   Object* smi_length = len->ToSmi();
   if (smi_length->IsSmi()) {
     const int value = Smi::cast(smi_length)->value();
     if (value < 0) return ArrayLengthRangeError();
     switch (GetElementsKind()) {
       case FAST_ELEMENTS: {
         int old_capacity = FixedArray::cast(elements())->length();
         if (value <= old_capacity) {
           if (IsJSArray()) {
+            Object* obj = EnsureWritableFastElements();
+            if (obj->IsFailure()) return obj;
             int old_length = FastD2I(JSArray::cast(this)->length()->Number());
             // NOTE: We may be able to optimize this by removing the
             // last part of the elements backing storage array and
             // setting the capacity to the new size.
             for (int i = value; i < old_length; i++) {
               FixedArray::cast(elements())->set_the_hole(i);
             }
             JSArray::cast(this)->set_length(Smi::cast(smi_length));
           }
           return this;
@@ skipping 445 matching lines @@
   return NULL;
 }
 
 
 // Adding n elements in fast case is O(n*n).
 // Note: revisit design to have dual undefined values to capture absent
 // elements.
 Object* JSObject::SetFastElement(uint32_t index, Object* value) {
   ASSERT(HasFastElements());
 
-  FixedArray* elms = FixedArray::cast(elements());
+  Object* elms_obj = EnsureWritableFastElements();
+  if (elms_obj->IsFailure()) return elms_obj;
+  FixedArray* elms = FixedArray::cast(elms_obj);
   uint32_t elms_length = static_cast<uint32_t>(elms->length());
 
   if (!IsJSArray() && (index >= elms_length || elms->get(index)->IsTheHole())) {
     if (SetElementWithCallbackSetterInPrototypes(index, value)) {
       return value;
     }
   }
 
   // Check whether there is extra space in fixed array..
   if (index < elms_length) {
@@ skipping 23 matching lines @@
     }
   }
 
   // Otherwise default to slow case.
   Object* obj = NormalizeElements();
   if (obj->IsFailure()) return obj;
   ASSERT(HasDictionaryElements());
   return SetElement(index, value);
 }
 
+
 Object* JSObject::SetElement(uint32_t index, Object* value) {
   // Check access rights if needed.
   if (IsAccessCheckNeeded() &&
       !Top::MayIndexedAccess(this, index, v8::ACCESS_SET)) {
     HandleScope scope;
     Handle<Object> value_handle(value);
     Top::ReportFailedAccessCheck(this, v8::ACCESS_SET);
     return *value_handle;
   }
 
@@ skipping 1458 matching lines @@
 
     PretenureFlag tenure = Heap::InNewSpace(this) ? NOT_TENURED: TENURED;
     Object* new_array =
         Heap::AllocateFixedArray(dict->NumberOfElements(), tenure);
     if (new_array->IsFailure()) return new_array;
     FixedArray* fast_elements = FixedArray::cast(new_array);
     dict->CopyValuesTo(fast_elements);
 
     set_map(new_map);
     set_elements(fast_elements);
+  } else {
+    Object* obj = EnsureWritableFastElements();
+    if (obj->IsFailure()) return obj;
   }
   ASSERT(HasFastElements());
 
   // Collect holes at the end, undefined before that and the rest at the
   // start, and return the number of non-hole, non-undefined values.
 
   FixedArray* elements = FixedArray::cast(this->elements());
   uint32_t elements_length = static_cast<uint32_t>(elements->length());
   if (limit > elements_length) {
     limit = elements_length ;
@@ skipping 1175 matching lines @@
   if (break_point_objects()->IsUndefined()) return 0;
   // Single beak point.
   if (!break_point_objects()->IsFixedArray()) return 1;
   // Multiple break points.
   return FixedArray::cast(break_point_objects())->length();
 }
 #endif
 
 
 } }  // namespace v8::internal