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 "src/api.h"
10#include "src/handles.h"
11#include "src/heap/heap.h"
12#include "src/isolate.h"
13
14namespace v8 {
15namespace internal {
16
17template<typename T>
18Handle<T>::Handle(T* obj) {
19  location_ = HandleScope::CreateHandle(obj->GetIsolate(), obj);
20}
21
22
23template<typename T>
24Handle<T>::Handle(T* obj, Isolate* isolate) {
25  location_ = HandleScope::CreateHandle(isolate, obj);
26}
27
28
29template <typename T>
30inline bool Handle<T>::is_identical_to(const Handle<T> o) const {
31  // Dereferencing deferred handles to check object equality is safe.
32  SLOW_DCHECK(
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
41template <typename T>
42inline T* Handle<T>::operator*() const {
43  SLOW_DCHECK(IsDereferenceAllowed(INCLUDE_DEFERRED_CHECK));
44  return *bit_cast<T**>(location_);
45}
46
47template <typename T>
48inline T** Handle<T>::location() const {
49  SLOW_DCHECK(location_ == NULL ||
50              IsDereferenceAllowed(INCLUDE_DEFERRED_CHECK));
51  return location_;
52}
53
54#ifdef DEBUG
55template <typename T>
56bool Handle<T>::IsDereferenceAllowed(DereferenceCheckMode mode) const {
57  DCHECK(location_ != NULL);
58  Object* object = *bit_cast<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
85HandleScope::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
94HandleScope::~HandleScope() {
95  CloseScope(isolate_, prev_next_, prev_limit_);
96}
97
98
99void 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
118template <typename T>
119Handle<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  DCHECK(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
137template <typename T>
138T** HandleScope::CreateHandle(Isolate* isolate, T* value) {
139  DCHECK(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  DCHECK(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
156inline 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
169inline SealHandleScope::~SealHandleScope() {
170  // Restore state in current handle scope to re-enable handle
171  // allocations.
172  HandleScopeData* current = isolate_->handle_scope_data();
173  DCHECK_EQ(0, current->level);
174  current->level = level_;
175  DCHECK_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_
184