src/v8/src/handles-inl.h

   1 // Copyright 2006-2008 the V8 project authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4 //
   5
   6 #ifndef V8_HANDLES_INL_H_
   7 #define V8_HANDLES_INL_H_
   8
   9 #include "api.h"
  10 #include "handles.h"
  11 #include "heap.h"
  12 #include "isolate.h"
  13
  14 namespace v8 {
  15 namespace internal {
  16
  17 template<typename T>
  18 Handle<T>::Handle(T* obj) {
  19   location_ = HandleScope::CreateHandle(obj->GetIsolate(), obj);
  20 }
  21
  22
  23 template<typename T>
  24 Handle<T>::Handle(T* obj, Isolate* isolate) {
  25   location_ = HandleScope::CreateHandle(isolate, obj);
  26 }
  27
  28
  29 template <typename T>
  30 inline bool Handle<T>::is_identical_to(const Handle<T> o) const {
  31   // Dereferencing deferred handles to check object equality is safe.
  32   SLOW_ASSERT(
  33       (location_ == NULL || IsDereferenceAllowed(NO_DEFERRED_CHECK)) &&
  34       (o.location_ == NULL || o.IsDereferenceAllowed(NO_DEFERRED_CHECK)));
  35   if (location_ == o.location_) return true;
  36   if (location_ == NULL || o.location_ == NULL) return false;
  37   return *location_ == *o.location_;
  38 }
  39
  40
  41 template <typename T>
  42 inline T* Handle<T>::operator*() const {
  43   SLOW_ASSERT(IsDereferenceAllowed(INCLUDE_DEFERRED_CHECK));
  44   return *BitCast<T**>(location_);
  45 }
  46
  47 template <typename T>
  48 inline T** Handle<T>::location() const {
  49   SLOW_ASSERT(location_ == NULL ||
  50               IsDereferenceAllowed(INCLUDE_DEFERRED_CHECK));
  51   return location_;
  52 }
  53
  54 #ifdef DEBUG
  55 template <typename T>
  56 bool Handle<T>::IsDereferenceAllowed(DereferenceCheckMode mode) const {
  57   ASSERT(location_ != NULL);
  58   Object* object = *BitCast<T**>(location_);
  59   if (object->IsSmi()) return true;
  60   HeapObject* heap_object = HeapObject::cast(object);
  61   Heap* heap = heap_object->GetHeap();
  62   Object** handle = reinterpret_cast<Object**>(location_);
  63   Object** roots_array_start = heap->roots_array_start();
  64   if (roots_array_start <= handle &&
  65       handle < roots_array_start + Heap::kStrongRootListLength &&
  66       heap->RootCanBeTreatedAsConstant(
  67         static_cast<Heap::RootListIndex>(handle - roots_array_start))) {
  68     return true;
  69   }
  70   if (!AllowHandleDereference::IsAllowed()) return false;
  71   if (mode == INCLUDE_DEFERRED_CHECK &&
  72       !AllowDeferredHandleDereference::IsAllowed()) {
  73     // Accessing cells, maps and internalized strings is safe.
  74     if (heap_object->IsCell()) return true;
  75     if (heap_object->IsMap()) return true;
  76     if (heap_object->IsInternalizedString()) return true;
  77     return !heap->isolate()->IsDeferredHandle(handle);
  78   }
  79   return true;
  80 }
  81 #endif
  82
  83
  84
  85 HandleScope::HandleScope(Isolate* isolate) {
  86   HandleScopeData* current = isolate->handle_scope_data();
  87   isolate_ = isolate;
  88   prev_next_ = current->next;
  89   prev_limit_ = current->limit;
  90   current->level++;
  91 }
  92
  93
  94 HandleScope::~HandleScope() {
  95   CloseScope(isolate_, prev_next_, prev_limit_);
  96 }
  97
  98
  99 void HandleScope::CloseScope(Isolate* isolate,
 100                              Object** prev_next,
 101                              Object** prev_limit) {
 102   HandleScopeData* current = isolate->handle_scope_data();
 103
 104   std::swap(current->next, prev_next);
 105   current->level--;
 106   if (current->limit != prev_limit) {
 107     current->limit = prev_limit;
 108     DeleteExtensions(isolate);
 109 #ifdef ENABLE_HANDLE_ZAPPING
 110     ZapRange(current->next, prev_limit);
 111   } else {
 112     ZapRange(current->next, prev_next);
 113 #endif
 114   }
 115 }
 116
 117
 118 template <typename T>
 119 Handle<T> HandleScope::CloseAndEscape(Handle<T> handle_value) {
 120   HandleScopeData* current = isolate_->handle_scope_data();
 121
 122   T* value = *handle_value;
 123   // Throw away all handles in the current scope.
 124   CloseScope(isolate_, prev_next_, prev_limit_);
 125   // Allocate one handle in the parent scope.
 126   ASSERT(current->level > 0);
 127   Handle<T> result(CreateHandle<T>(isolate_, value));
 128   // Reinitialize the current scope (so that it's ready
 129   // to be used or closed again).
 130   prev_next_ = current->next;
 131   prev_limit_ = current->limit;
 132   current->level++;
 133   return result;
 134 }
 135
 136
 137 template <typename T>
 138 T** HandleScope::CreateHandle(Isolate* isolate, T* value) {
 139   ASSERT(AllowHandleAllocation::IsAllowed());
 140   HandleScopeData* current = isolate->handle_scope_data();
 141
 142   internal::Object** cur = current->next;
 143   if (cur == current->limit) cur = Extend(isolate);
 144   // Update the current next field, set the value in the created
 145   // handle, and return the result.
 146   ASSERT(cur < current->limit);
 147   current->next = cur + 1;
 148
 149   T** result = reinterpret_cast<T**>(cur);
 150   *result = value;
 151   return result;
 152 }
 153
 154
 155 #ifdef DEBUG
 156 inline SealHandleScope::SealHandleScope(Isolate* isolate) : isolate_(isolate) {
 157   // Make sure the current thread is allowed to create handles to begin with.
 158   CHECK(AllowHandleAllocation::IsAllowed());
 159   HandleScopeData* current = isolate_->handle_scope_data();
 160   // Shrink the current handle scope to make it impossible to do
 161   // handle allocations without an explicit handle scope.
 162   limit_ = current->limit;
 163   current->limit = current->next;
 164   level_ = current->level;
 165   current->level = 0;
 166 }
 167
 168
 169 inline SealHandleScope::~SealHandleScope() {
 170   // Restore state in current handle scope to re-enable handle
 171   // allocations.
 172   HandleScopeData* current = isolate_->handle_scope_data();
 173   ASSERT_EQ(0, current->level);
 174   current->level = level_;
 175   ASSERT_EQ(current->next, current->limit);
 176   current->limit = limit_;
 177 }
 178
 179 #endif
 180
 181 } }  // namespace v8::internal
 182
 183 #endif  // V8_HANDLES_INL_H_