CSE2410 Fall 2014 Bounce

// Copyright 2012 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

//       with the distribution.

//     * Neither the name of Google Inc. nor the names of its

//       contributors may be used to endorse or promote products derived

//       from this software without specific prior written permission.

//

// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT

// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#include "v8.h"

#include "accessors.h"

#include "api.h"

#include "arguments.h"

#include "bootstrapper.h"

#include "compiler.h"

#include "debug.h"

#include "execution.h"

#include "global-handles.h"

#include "natives.h"

#include "runtime.h"

#include "string-search.h"

#include "stub-cache.h"

#include "vm-state-inl.h"

namespace v8 {

namespace internal {

int HandleScope::NumberOfHandles(Isolate* isolate) {

  HandleScopeImplementer* impl = isolate->handle_scope_implementer();

  int n = impl->blocks()->length();

  if (n == 0) return 0;

  return ((n - 1) * kHandleBlockSize) + static_cast<int>(

      (isolate->handle_scope_data()->next - impl->blocks()->last()));

}

Object** HandleScope::Extend(Isolate* isolate) {

  v8::ImplementationUtilities::HandleScopeData* current =

      isolate->handle_scope_data();

  Object** result = current->next;

  ASSERT(result == current->limit);

  // Make sure there's at least one scope on the stack and that the

  // top of the scope stack isn't a barrier.

  if (current->level == 0) {

    Utils::ReportApiFailure("v8::HandleScope::CreateHandle()",

                            "Cannot create a handle without a HandleScope");

    return NULL;

  }

  HandleScopeImplementer* impl = isolate->handle_scope_implementer();

  // If there's more room in the last block, we use that. This is used

  // for fast creation of scopes after scope barriers.

  if (!impl->blocks()->is_empty()) {

    Object** limit = &impl->blocks()->last()[kHandleBlockSize];

    if (current->limit != limit) {

      current->limit = limit;

      ASSERT(limit - current->next < kHandleBlockSize);

    }

  }

  // If we still haven't found a slot for the handle, we extend the

  // current handle scope by allocating a new handle block.

  if (result == current->limit) {

    // If there's a spare block, use it for growing the current scope.

    result = impl->GetSpareOrNewBlock();

    // Add the extension to the global list of blocks, but count the

    // extension as part of the current scope.

    impl->blocks()->Add(result);

    current->limit = &result[kHandleBlockSize];

  }

  return result;

}

void HandleScope::DeleteExtensions(Isolate* isolate) {

  v8::ImplementationUtilities::HandleScopeData* current =

      isolate->handle_scope_data();

  isolate->handle_scope_implementer()->DeleteExtensions(current->limit);

}

#ifdef ENABLE_HANDLE_ZAPPING

void HandleScope::ZapRange(Object** start, Object** end) {

  ASSERT(end - start <= kHandleBlockSize);

  for (Object** p = start; p != end; p++) {

    *reinterpret_cast<Address*>(p) = v8::internal::kHandleZapValue;

  }

}

#endif

Address HandleScope::current_level_address(Isolate* isolate) {

  return reinterpret_cast<Address>(&isolate->handle_scope_data()->level);

}

Address HandleScope::current_next_address(Isolate* isolate) {

  return reinterpret_cast<Address>(&isolate->handle_scope_data()->next);

}

Address HandleScope::current_limit_address(Isolate* isolate) {

  return reinterpret_cast<Address>(&isolate->handle_scope_data()->limit);

}

Handle<FixedArray> AddKeysFromJSArray(Handle<FixedArray> content,

                                      Handle<JSArray> array) {

  CALL_HEAP_FUNCTION(content->GetIsolate(),

                     content->AddKeysFromJSArray(*array), FixedArray);

}

Handle<FixedArray> UnionOfKeys(Handle<FixedArray> first,

                               Handle<FixedArray> second) {

  CALL_HEAP_FUNCTION(first->GetIsolate(),

                     first->UnionOfKeys(*second), FixedArray);

}

Handle<JSGlobalProxy> ReinitializeJSGlobalProxy(

    Handle<JSFunction> constructor,

    Handle<JSGlobalProxy> global) {

  CALL_HEAP_FUNCTION(

      constructor->GetIsolate(),

      constructor->GetHeap()->ReinitializeJSGlobalProxy(*constructor, *global),

      JSGlobalProxy);

}

void FlattenString(Handle<String> string) {

  CALL_HEAP_FUNCTION_VOID(string->GetIsolate(), string->TryFlatten());

}

Handle<String> FlattenGetString(Handle<String> string) {

  CALL_HEAP_FUNCTION(string->GetIsolate(), string->TryFlatten(), String);

}

Handle<Object> SetProperty(Isolate* isolate,

                           Handle<Object> object,

                           Handle<Object> key,

                           Handle<Object> value,

                           PropertyAttributes attributes,

                           StrictModeFlag strict_mode) {

  CALL_HEAP_FUNCTION(

      isolate,

      Runtime::SetObjectProperty(

          isolate, object, key, value, attributes, strict_mode),

      Object);

}

Handle<Object> ForceSetProperty(Handle<JSObject> object,

                                Handle<Object> key,

                                Handle<Object> value,

                                PropertyAttributes attributes) {

  Isolate* isolate = object->GetIsolate();

  CALL_HEAP_FUNCTION(

      isolate,

      Runtime::ForceSetObjectProperty(

          isolate, object, key, value, attributes),

      Object);

}

Handle<Object> DeleteProperty(Handle<JSObject> object, Handle<Object> key) {

  Isolate* isolate = object->GetIsolate();

  CALL_HEAP_FUNCTION(isolate,

                     Runtime::DeleteObjectProperty(

                         isolate, object, key, JSReceiver::NORMAL_DELETION),

                     Object);

}

Handle<Object> ForceDeleteProperty(Handle<JSObject> object,

                                   Handle<Object> key) {

  Isolate* isolate = object->GetIsolate();

  CALL_HEAP_FUNCTION(isolate,

                     Runtime::DeleteObjectProperty(

                         isolate, object, key, JSReceiver::FORCE_DELETION),

                     Object);

}

Handle<Object> HasProperty(Handle<JSReceiver> obj, Handle<Object> key) {

  Isolate* isolate = obj->GetIsolate();

  CALL_HEAP_FUNCTION(isolate,

                     Runtime::HasObjectProperty(isolate, obj, key), Object);

}

Handle<Object> GetProperty(Handle<JSReceiver> obj,

                           const char* name) {

  Isolate* isolate = obj->GetIsolate();

  Handle<String> str = isolate->factory()->InternalizeUtf8String(name);

  CALL_HEAP_FUNCTION(isolate, obj->GetProperty(*str), Object);

}

Handle<Object> GetProperty(Isolate* isolate,

                           Handle<Object> obj,

                           Handle<Object> key) {

  CALL_HEAP_FUNCTION(isolate,

                     Runtime::GetObjectProperty(isolate, obj, key), Object);

}

Handle<Object> LookupSingleCharacterStringFromCode(Isolate* isolate,

                                                   uint32_t index) {

  CALL_HEAP_FUNCTION(

      isolate,

      isolate->heap()->LookupSingleCharacterStringFromCode(index), Object);

}

// Wrappers for scripts are kept alive and cached in weak global

// handles referred from foreign objects held by the scripts as long as

// they are used. When they are not used anymore, the garbage

// collector will call the weak callback on the global handle

// associated with the wrapper and get rid of both the wrapper and the

// handle.

static void ClearWrapperCache(v8::Isolate* v8_isolate,

                              Persistent<v8::Value>* handle,

                              void*) {

  Handle<Object> cache = Utils::OpenPersistent(handle);

  JSValue* wrapper = JSValue::cast(*cache);

  Foreign* foreign = Script::cast(wrapper->value())->wrapper();

  ASSERT(foreign->foreign_address() ==

         reinterpret_cast<Address>(cache.location()));

  foreign->set_foreign_address(0);

  Isolate* isolate = reinterpret_cast<Isolate*>(v8_isolate);

  isolate->global_handles()->Destroy(cache.location());

  isolate->counters()->script_wrappers()->Decrement();

}

Handle<JSValue> GetScriptWrapper(Handle<Script> script) {

  if (script->wrapper()->foreign_address() != NULL) {

    // Return the script wrapper directly from the cache.

    return Handle<JSValue>(

        reinterpret_cast<JSValue**>(script->wrapper()->foreign_address()));

  }

  Isolate* isolate = script->GetIsolate();

  // Construct a new script wrapper.

  isolate->counters()->script_wrappers()->Increment();

  Handle<JSFunction> constructor = isolate->script_function();

  Handle<JSValue> result =

      Handle<JSValue>::cast(isolate->factory()->NewJSObject(constructor));

  // The allocation might have triggered a GC, which could have called this

  // function recursively, and a wrapper has already been created and cached.

  // In that case, simply return the cached wrapper.

  if (script->wrapper()->foreign_address() != NULL) {

    return Handle<JSValue>(

        reinterpret_cast<JSValue**>(script->wrapper()->foreign_address()));

  }

  result->set_value(*script);

  // Create a new weak global handle and use it to cache the wrapper

  // for future use. The cache will automatically be cleared by the

  // garbage collector when it is not used anymore.

  Handle<Object> handle = isolate->global_handles()->Create(*result);

  isolate->global_handles()->MakeWeak(handle.location(),

                                      NULL,

                                      &ClearWrapperCache);

  script->wrapper()->set_foreign_address(

      reinterpret_cast<Address>(handle.location()));

  return result;

}

// Init line_ends array with code positions of line ends inside script

// source.

void InitScriptLineEnds(Handle<Script> script) {

  if (!script->line_ends()->IsUndefined()) return;

  Isolate* isolate = script->GetIsolate();

  if (!script->source()->IsString()) {

    ASSERT(script->source()->IsUndefined());

    Handle<FixedArray> empty = isolate->factory()->NewFixedArray(0);

    script->set_line_ends(*empty);

    ASSERT(script->line_ends()->IsFixedArray());

    return;

  }

  Handle<String> src(String::cast(script->source()), isolate);

  Handle<FixedArray> array = CalculateLineEnds(src, true);

  if (*array != isolate->heap()->empty_fixed_array()) {

    array->set_map(isolate->heap()->fixed_cow_array_map());

  }

  script->set_line_ends(*array);

  ASSERT(script->line_ends()->IsFixedArray());

}

template <typename SourceChar>

static void CalculateLineEnds(Isolate* isolate,

                              List<int>* line_ends,

                              Vector<const SourceChar> src,

                              bool with_last_line) {

  const int src_len = src.length();

  StringSearch<uint8_t, SourceChar> search(isolate, STATIC_ASCII_VECTOR("\n"));

  // Find and record line ends.

  int position = 0;

  while (position != -1 && position < src_len) {

    position = search.Search(src, position);

    if (position != -1) {

      line_ends->Add(position);

      position++;

    } else if (with_last_line) {

      // Even if the last line misses a line end, it is counted.

      line_ends->Add(src_len);

      return;

    }

  }

}

Handle<FixedArray> CalculateLineEnds(Handle<String> src,

                                     bool with_last_line) {

  src = FlattenGetString(src);

  // Rough estimate of line count based on a roughly estimated average

  // length of (unpacked) code.

  int line_count_estimate = src->length() >> 4;

  List<int> line_ends(line_count_estimate);

  Isolate* isolate = src->GetIsolate();

  {

    DisallowHeapAllocation no_allocation;  // ensure vectors stay valid.

    // Dispatch on type of strings.

    String::FlatContent content = src->GetFlatContent();

    ASSERT(content.IsFlat());

    if (content.IsAscii()) {

      CalculateLineEnds(isolate,

                        &line_ends,

                        content.ToOneByteVector(),

                        with_last_line);

    } else {

      CalculateLineEnds(isolate,

                        &line_ends,

                        content.ToUC16Vector(),

                        with_last_line);

    }

  }

  int line_count = line_ends.length();

  Handle<FixedArray> array = isolate->factory()->NewFixedArray(line_count);

  for (int i = 0; i < line_count; i++) {

    array->set(i, Smi::FromInt(line_ends[i]));

  }

  return array;

}

// Convert code position into line number.

int GetScriptLineNumber(Handle<Script> script, int code_pos) {

  InitScriptLineEnds(script);

  DisallowHeapAllocation no_allocation;

  FixedArray* line_ends_array = FixedArray::cast(script->line_ends());

  const int line_ends_len = line_ends_array->length();

  if (!line_ends_len) return -1;

  if ((Smi::cast(line_ends_array->get(0)))->value() >= code_pos) {

    return script->line_offset()->value();

  }

  int left = 0;

  int right = line_ends_len;

  while (int half = (right - left) / 2) {

    if ((Smi::cast(line_ends_array->get(left + half)))->value() > code_pos) {

      right -= half;

    } else {

      left += half;

    }

  }

  return right + script->line_offset()->value();

}

// Convert code position into column number.

int GetScriptColumnNumber(Handle<Script> script, int code_pos) {

  int line_number = GetScriptLineNumber(script, code_pos);

  if (line_number == -1) return -1;

  DisallowHeapAllocation no_allocation;

  FixedArray* line_ends_array = FixedArray::cast(script->line_ends());

  line_number = line_number - script->line_offset()->value();

  if (line_number == 0) return code_pos + script->column_offset()->value();

  int prev_line_end_pos =

      Smi::cast(line_ends_array->get(line_number - 1))->value();

  return code_pos - (prev_line_end_pos + 1);

}

int GetScriptLineNumberSafe(Handle<Script> script, int code_pos) {

  DisallowHeapAllocation no_allocation;

  if (!script->line_ends()->IsUndefined()) {

    return GetScriptLineNumber(script, code_pos);

  }

  // Slow mode: we do not have line_ends. We have to iterate through source.

  if (!script->source()->IsString()) {

    return -1;

  }

  String* source = String::cast(script->source());

  int line = 0;

  int len = source->length();

  for (int pos = 0; pos < len; pos++) {

    if (pos == code_pos) {

      break;

    }

    if (source->Get(pos) == '\n') {

      line++;

    }

  }

  return line;

}

// Compute the property keys from the interceptor.

// TODO(rossberg): support symbols in API, and filter here if needed.

v8::Handle<v8::Array> GetKeysForNamedInterceptor(Handle<JSReceiver> receiver,

                                                 Handle<JSObject> object) {

  Isolate* isolate = receiver->GetIsolate();

  Handle<InterceptorInfo> interceptor(object->GetNamedInterceptor());

  PropertyCallbackArguments

      args(isolate, interceptor->data(), *receiver, *object);

  v8::Handle<v8::Array> result;

  if (!interceptor->enumerator()->IsUndefined()) {

    v8::NamedPropertyEnumeratorCallback enum_fun =

        v8::ToCData<v8::NamedPropertyEnumeratorCallback>(

            interceptor->enumerator());

    LOG(isolate, ApiObjectAccess("interceptor-named-enum", *object));

    result = args.Call(enum_fun);

  }

#if ENABLE_EXTRA_CHECKS

  CHECK(result.IsEmpty() || v8::Utils::OpenHandle(*result)->IsJSObject());

#endif

  return v8::Local<v8::Array>::New(reinterpret_cast<v8::Isolate*>(isolate),

                                   result);

}

// Compute the element keys from the interceptor.

v8::Handle<v8::Array> GetKeysForIndexedInterceptor(Handle<JSReceiver> receiver,

                                                   Handle<JSObject> object) {

  Isolate* isolate = receiver->GetIsolate();

  Handle<InterceptorInfo> interceptor(object->GetIndexedInterceptor());

  PropertyCallbackArguments

      args(isolate, interceptor->data(), *receiver, *object);

  v8::Handle<v8::Array> result;

  if (!interceptor->enumerator()->IsUndefined()) {

    v8::IndexedPropertyEnumeratorCallback enum_fun =

        v8::ToCData<v8::IndexedPropertyEnumeratorCallback>(

            interceptor->enumerator());

    LOG(isolate, ApiObjectAccess("interceptor-indexed-enum", *object));

    result = args.Call(enum_fun);

#if ENABLE_EXTRA_CHECKS

    CHECK(result.IsEmpty() || v8::Utils::OpenHandle(*result)->IsJSObject());

#endif

  }

  return v8::Local<v8::Array>::New(reinterpret_cast<v8::Isolate*>(isolate),

                                   result);

}

Handle<Object> GetScriptNameOrSourceURL(Handle<Script> script) {

  Isolate* isolate = script->GetIsolate();

  Handle<String> name_or_source_url_key =

      isolate->factory()->InternalizeOneByteString(

          STATIC_ASCII_VECTOR("nameOrSourceURL"));

  Handle<JSValue> script_wrapper = GetScriptWrapper(script);

  Handle<Object> property = GetProperty(isolate,

                                        script_wrapper,

                                        name_or_source_url_key);

  ASSERT(property->IsJSFunction());

  Handle<JSFunction> method = Handle<JSFunction>::cast(property);

  bool caught_exception;

  Handle<Object> result = Execution::TryCall(method, script_wrapper, 0,

                                             NULL, &caught_exception);

  if (caught_exception) {

    result = isolate->factory()->undefined_value();

  }

  return result;

}

static bool ContainsOnlyValidKeys(Handle<FixedArray> array) {

  int len = array->length();

  for (int i = 0; i < len; i++) {

    Object* e = array->get(i);

    if (!(e->IsString() || e->IsNumber())) return false;

  }

  return true;

}

Handle<FixedArray> GetKeysInFixedArrayFor(Handle<JSReceiver> object,

                                          KeyCollectionType type,

                                          bool* threw) {

  USE(ContainsOnlyValidKeys);

  Isolate* isolate = object->GetIsolate();

  Handle<FixedArray> content = isolate->factory()->empty_fixed_array();

  Handle<JSObject> arguments_boilerplate = Handle<JSObject>(

      isolate->context()->native_context()->arguments_boilerplate(),

      isolate);

  Handle<JSFunction> arguments_function = Handle<JSFunction>(

      JSFunction::cast(arguments_boilerplate->map()->constructor()),

      isolate);

  // Only collect keys if access is permitted.

  for (Handle<Object> p = object;

       *p != isolate->heap()->null_value();

       p = Handle<Object>(p->GetPrototype(isolate), isolate)) {

    if (p->IsJSProxy()) {

      Handle<JSProxy> proxy(JSProxy::cast(*p), isolate);

      Handle<Object> args[] = { proxy };

      Handle<Object> names = Execution::Call(isolate,

                                             isolate->proxy_enumerate(),

                                             object,

                                             ARRAY_SIZE(args),

                                             args,

                                             threw);

      if (*threw) return content;

      content = AddKeysFromJSArray(content, Handle<JSArray>::cast(names));

      break;

    }

    Handle<JSObject> current(JSObject::cast(*p), isolate);

    // Check access rights if required.

    if (current->IsAccessCheckNeeded() &&

        !isolate->MayNamedAccess(*current,

                                 isolate->heap()->undefined_value(),

                                 v8::ACCESS_KEYS)) {

      isolate->ReportFailedAccessCheck(*current, v8::ACCESS_KEYS);

      if (isolate->has_scheduled_exception()) {

        isolate->PromoteScheduledException();

        *threw = true;

      }

      break;

    }

    // Compute the element keys.

    Handle<FixedArray> element_keys =

        isolate->factory()->NewFixedArray(current->NumberOfEnumElements());

    current->GetEnumElementKeys(*element_keys);

    content = UnionOfKeys(content, element_keys);

    ASSERT(ContainsOnlyValidKeys(content));

    // Add the element keys from the interceptor.

    if (current->HasIndexedInterceptor()) {

      v8::Handle<v8::Array> result =

          GetKeysForIndexedInterceptor(object, current);

      if (!result.IsEmpty())

        content = AddKeysFromJSArray(content, v8::Utils::OpenHandle(*result));

      ASSERT(ContainsOnlyValidKeys(content));

    }

    // We can cache the computed property keys if access checks are

    // not needed and no interceptors are involved.

    //

    // We do not use the cache if the object has elements and

    // therefore it does not make sense to cache the property names

    // for arguments objects.  Arguments objects will always have

    // elements.

    // Wrapped strings have elements, but don't have an elements

    // array or dictionary.  So the fast inline test for whether to

    // use the cache says yes, so we should not create a cache.

    bool cache_enum_keys =

        ((current->map()->constructor() != *arguments_function) &&

         !current->IsJSValue() &&

         !current->IsAccessCheckNeeded() &&

         !current->HasNamedInterceptor() &&

         !current->HasIndexedInterceptor());

    // Compute the property keys and cache them if possible.

    content =

        UnionOfKeys(content, GetEnumPropertyKeys(current, cache_enum_keys));

    ASSERT(ContainsOnlyValidKeys(content));

    // Add the property keys from the interceptor.

    if (current->HasNamedInterceptor()) {

      v8::Handle<v8::Array> result =

          GetKeysForNamedInterceptor(object, current);

      if (!result.IsEmpty())

        content = AddKeysFromJSArray(content, v8::Utils::OpenHandle(*result));

      ASSERT(ContainsOnlyValidKeys(content));

    }

    // If we only want local properties we bail out after the first

    // iteration.

    if (type == LOCAL_ONLY)

      break;

  }

  return content;

}

Handle<JSArray> GetKeysFor(Handle<JSReceiver> object, bool* threw) {

  Isolate* isolate = object->GetIsolate();

  isolate->counters()->for_in()->Increment();

  Handle<FixedArray> elements =

      GetKeysInFixedArrayFor(object, INCLUDE_PROTOS, threw);

  return isolate->factory()->NewJSArrayWithElements(elements);

}

Handle<FixedArray> ReduceFixedArrayTo(Handle<FixedArray> array, int length) {

  ASSERT(array->length() >= length);

  if (array->length() == length) return array;

  Handle<FixedArray> new_array =

      array->GetIsolate()->factory()->NewFixedArray(length);

  for (int i = 0; i < length; ++i) new_array->set(i, array->get(i));

  return new_array;

}

Handle<FixedArray> GetEnumPropertyKeys(Handle<JSObject> object,

                                       bool cache_result) {

  Isolate* isolate = object->GetIsolate();

  if (object->HasFastProperties()) {

    if (object->map()->instance_descriptors()->HasEnumCache()) {

      int own_property_count = object->map()->EnumLength();

      // If we have an enum cache, but the enum length of the given map is set

      // to kInvalidEnumCache, this means that the map itself has never used the

      // present enum cache. The first step to using the cache is to set the

      // enum length of the map by counting the number of own descriptors that

      // are not DONT_ENUM or SYMBOLIC.

      if (own_property_count == Map::kInvalidEnumCache) {

        own_property_count = object->map()->NumberOfDescribedProperties(

            OWN_DESCRIPTORS, DONT_SHOW);

        if (cache_result) object->map()->SetEnumLength(own_property_count);

      }

      DescriptorArray* desc = object->map()->instance_descriptors();

      Handle<FixedArray> keys(desc->GetEnumCache(), isolate);

      // In case the number of properties required in the enum are actually

      // present, we can reuse the enum cache. Otherwise, this means that the

      // enum cache was generated for a previous (smaller) version of the

      // Descriptor Array. In that case we regenerate the enum cache.

      if (own_property_count <= keys->length()) {

        isolate->counters()->enum_cache_hits()->Increment();

        return ReduceFixedArrayTo(keys, own_property_count);

      }

    }

    Handle<Map> map(object->map());

    if (map->instance_descriptors()->IsEmpty()) {

      isolate->counters()->enum_cache_hits()->Increment();

      if (cache_result) map->SetEnumLength(0);

      return isolate->factory()->empty_fixed_array();

    }

    isolate->counters()->enum_cache_misses()->Increment();

    int num_enum = map->NumberOfDescribedProperties(ALL_DESCRIPTORS, DONT_SHOW);

    Handle<FixedArray> storage = isolate->factory()->NewFixedArray(num_enum);

    Handle<FixedArray> indices = isolate->factory()->NewFixedArray(num_enum);

    Handle<DescriptorArray> descs =

        Handle<DescriptorArray>(object->map()->instance_descriptors(), isolate);

    int real_size = map->NumberOfOwnDescriptors();

    int enum_size = 0;

    int index = 0;

    for (int i = 0; i < descs->number_of_descriptors(); i++) {

      PropertyDetails details = descs->GetDetails(i);

      Object* key = descs->GetKey(i);

      if (!(details.IsDontEnum() || key->IsSymbol())) {

        if (i < real_size) ++enum_size;

        storage->set(index, key);

        if (!indices.is_null()) {

          if (details.type() != FIELD) {

            indices = Handle<FixedArray>();

          } else {

            int field_index = descs->GetFieldIndex(i);

            if (field_index >= map->inobject_properties()) {

              field_index = -(field_index - map->inobject_properties() + 1);

            }

            indices->set(index, Smi::FromInt(field_index));

          }

        }

        index++;

      }

    }

    ASSERT(index == storage->length());

    Handle<FixedArray> bridge_storage =

        isolate->factory()->NewFixedArray(

            DescriptorArray::kEnumCacheBridgeLength);

    DescriptorArray* desc = object->map()->instance_descriptors();

    desc->SetEnumCache(*bridge_storage,

                       *storage,

                       indices.is_null() ? Object::cast(Smi::FromInt(0))

                                         : Object::cast(*indices));

    if (cache_result) {

      object->map()->SetEnumLength(enum_size);

    }

    return ReduceFixedArrayTo(storage, enum_size);

  } else {

    Handle<NameDictionary> dictionary(object->property_dictionary());

    int length = dictionary->NumberOfElements();

    if (length == 0) {

      return Handle<FixedArray>(isolate->heap()->empty_fixed_array());

    }

    // The enumeration array is generated by allocating an array big enough to

    // hold all properties that have been seen, whether they are are deleted or

    // not. Subsequently all visible properties are added to the array. If some

    // properties were not visible, the array is trimmed so it only contains

    // visible properties. This improves over adding elements and sorting by

    // index by having linear complexity rather than n*log(n).

    // By comparing the monotonous NextEnumerationIndex to the NumberOfElements,

    // we can predict the number of holes in the final array. If there will be

    // more than 50% holes, regenerate the enumeration indices to reduce the

    // number of holes to a minimum. This avoids allocating a large array if

    // many properties were added but subsequently deleted.

    int next_enumeration = dictionary->NextEnumerationIndex();

    if (!object->IsGlobalObject() && next_enumeration > (length * 3) / 2) {

      NameDictionary::DoGenerateNewEnumerationIndices(dictionary);

      next_enumeration = dictionary->NextEnumerationIndex();

    }

    Handle<FixedArray> storage =

        isolate->factory()->NewFixedArray(next_enumeration);

    storage = Handle<FixedArray>(dictionary->CopyEnumKeysTo(*storage));

    ASSERT(storage->length() == object->NumberOfLocalProperties(DONT_SHOW));

    return storage;

  }

}

Handle<ObjectHashSet> ObjectHashSetAdd(Handle<ObjectHashSet> table,

                                       Handle<Object> key) {

  CALL_HEAP_FUNCTION(table->GetIsolate(),

                     table->Add(*key),

                     ObjectHashSet);

}

Handle<ObjectHashSet> ObjectHashSetRemove(Handle<ObjectHashSet> table,

                                          Handle<Object> key) {

  CALL_HEAP_FUNCTION(table->GetIsolate(),

                     table->Remove(*key),

                     ObjectHashSet);

}

Handle<ObjectHashTable> PutIntoObjectHashTable(Handle<ObjectHashTable> table,

                                               Handle<Object> key,

                                               Handle<Object> value) {

  CALL_HEAP_FUNCTION(table->GetIsolate(),

                     table->Put(*key, *value),

                     ObjectHashTable);

}

DeferredHandleScope::DeferredHandleScope(Isolate* isolate)

    : impl_(isolate->handle_scope_implementer()) {

  impl_->BeginDeferredScope();

  v8::ImplementationUtilities::HandleScopeData* data =

      impl_->isolate()->handle_scope_data();

  Object** new_next = impl_->GetSpareOrNewBlock();

  Object** new_limit = &new_next[kHandleBlockSize];

  ASSERT(data->limit == &impl_->blocks()->last()[kHandleBlockSize]);

  impl_->blocks()->Add(new_next);

#ifdef DEBUG

  prev_level_ = data->level;

#endif

  data->level++;

  prev_limit_ = data->limit;

  prev_next_ = data->next;

  data->next = new_next;

  data->limit = new_limit;

}

DeferredHandleScope::~DeferredHandleScope() {

  impl_->isolate()->handle_scope_data()->level--;

  ASSERT(handles_detached_);

  ASSERT(impl_->isolate()->handle_scope_data()->level == prev_level_);

}

DeferredHandles* DeferredHandleScope::Detach() {

  DeferredHandles* deferred = impl_->Detach(prev_limit_);

  v8::ImplementationUtilities::HandleScopeData* data =

      impl_->isolate()->handle_scope_data();

  data->next = prev_next_;

  data->limit = prev_limit_;

#ifdef DEBUG

  handles_detached_ = true;

#endif

  return deferred;

}

void AddWeakObjectToCodeDependency(Heap* heap,

                                   Handle<Object> object,

                                   Handle<Code> code) {

  heap->EnsureWeakObjectToCodeTable();

  Handle<DependentCode> dep(heap->LookupWeakObjectToCodeDependency(*object));

  dep = DependentCode::Insert(dep, DependentCode::kWeaklyEmbeddedGroup, code);

  CALL_HEAP_FUNCTION_VOID(heap->isolate(),

                          heap->AddWeakObjectToCodeDependency(*object, *dep));

}

} }  // namespace v8::internal