1// Copyright 2012 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#include "src/v8.h"
6
7#include "src/handles.h"
8
9namespace v8 {
10namespace internal {
11
12
13int HandleScope::NumberOfHandles(Isolate* isolate) {
14  HandleScopeImplementer* impl = isolate->handle_scope_implementer();
15  int n = impl->blocks()->length();
16  if (n == 0) return 0;
17  return ((n - 1) * kHandleBlockSize) + static_cast<int>(
18      (isolate->handle_scope_data()->next - impl->blocks()->last()));
19}
20
21
22Object** HandleScope::Extend(Isolate* isolate) {
23  HandleScopeData* current = isolate->handle_scope_data();
24
25  Object** result = current->next;
26
27  DCHECK(result == current->limit);
28  // Make sure there's at least one scope on the stack and that the
29  // top of the scope stack isn't a barrier.
30  if (!Utils::ApiCheck(current->level != 0,
31                       "v8::HandleScope::CreateHandle()",
32                       "Cannot create a handle without a HandleScope")) {
33    return NULL;
34  }
35  HandleScopeImplementer* impl = isolate->handle_scope_implementer();
36  // If there's more room in the last block, we use that. This is used
37  // for fast creation of scopes after scope barriers.
38  if (!impl->blocks()->is_empty()) {
39    Object** limit = &impl->blocks()->last()[kHandleBlockSize];
40    if (current->limit != limit) {
41      current->limit = limit;
42      DCHECK(limit - current->next < kHandleBlockSize);
43    }
44  }
45
46  // If we still haven't found a slot for the handle, we extend the
47  // current handle scope by allocating a new handle block.
48  if (result == current->limit) {
49    // If there's a spare block, use it for growing the current scope.
50    result = impl->GetSpareOrNewBlock();
51    // Add the extension to the global list of blocks, but count the
52    // extension as part of the current scope.
53    impl->blocks()->Add(result);
54    current->limit = &result[kHandleBlockSize];
55  }
56
57  return result;
58}
59
60
61void HandleScope::DeleteExtensions(Isolate* isolate) {
62  HandleScopeData* current = isolate->handle_scope_data();
63  isolate->handle_scope_implementer()->DeleteExtensions(current->limit);
64}
65
66
67#ifdef ENABLE_HANDLE_ZAPPING
68void HandleScope::ZapRange(Object** start, Object** end) {
69  DCHECK(end - start <= kHandleBlockSize);
70  for (Object** p = start; p != end; p++) {
71    *reinterpret_cast<Address*>(p) = v8::internal::kHandleZapValue;
72  }
73}
74#endif
75
76
77Address HandleScope::current_level_address(Isolate* isolate) {
78  return reinterpret_cast<Address>(&isolate->handle_scope_data()->level);
79}
80
81
82Address HandleScope::current_next_address(Isolate* isolate) {
83  return reinterpret_cast<Address>(&isolate->handle_scope_data()->next);
84}
85
86
87Address HandleScope::current_limit_address(Isolate* isolate) {
88  return reinterpret_cast<Address>(&isolate->handle_scope_data()->limit);
89}
90
91
92DeferredHandleScope::DeferredHandleScope(Isolate* isolate)
93    : impl_(isolate->handle_scope_implementer()) {
94  impl_->BeginDeferredScope();
95  HandleScopeData* data = impl_->isolate()->handle_scope_data();
96  Object** new_next = impl_->GetSpareOrNewBlock();
97  Object** new_limit = &new_next[kHandleBlockSize];
98  DCHECK(data->limit == &impl_->blocks()->last()[kHandleBlockSize]);
99  impl_->blocks()->Add(new_next);
100
101#ifdef DEBUG
102  prev_level_ = data->level;
103#endif
104  data->level++;
105  prev_limit_ = data->limit;
106  prev_next_ = data->next;
107  data->next = new_next;
108  data->limit = new_limit;
109}
110
111
112DeferredHandleScope::~DeferredHandleScope() {
113  impl_->isolate()->handle_scope_data()->level--;
114  DCHECK(handles_detached_);
115  DCHECK(impl_->isolate()->handle_scope_data()->level == prev_level_);
116}
117
118
119DeferredHandles* DeferredHandleScope::Detach() {
120  DeferredHandles* deferred = impl_->Detach(prev_limit_);
121  HandleScopeData* data = impl_->isolate()->handle_scope_data();
122  data->next = prev_next_;
123  data->limit = prev_limit_;
124#ifdef DEBUG
125  handles_detached_ = true;
126#endif
127  return deferred;
128}
129
130} }  // namespace v8::internal
131