src/handles/handles-inl.h

// Copyright 2006-2008 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef V8_HANDLES_HANDLES_INL_H_
#define V8_HANDLES_HANDLES_INL_H_

#include "src/execution/isolate.h"
#include "src/execution/off-thread-isolate.h"
#include "src/handles/handles.h"
#include "src/handles/local-handles-inl.h"
#include "src/sanitizer/msan.h"

namespace v8 {
namespace internal {

class LocalHeap;

HandleBase::HandleBase(Address object, Isolate* isolate)
    : location_(HandleScope::GetHandle(isolate, object)) {}

HandleBase::HandleBase(Address object, OffThreadIsolate* isolate)
    : location_(isolate->NewHandle(object)) {}

HandleBase::HandleBase(Address object, LocalHeap* local_heap)
    : location_(LocalHandleScope::GetHandle(local_heap, object)) {}

// Allocate a new handle for the object, do not canonicalize.

template <typename T>
Handle<T> Handle<T>::New(T object, Isolate* isolate) {
  return Handle(HandleScope::CreateHandle(isolate, object.ptr()));
}

template <typename T>
template <typename S>
const Handle<T> Handle<T>::cast(Handle<S> that) {
  T::cast(*FullObjectSlot(that.location()));
  return Handle<T>(that.location_);
}

template <typename T>
Handle<T>::Handle(T object, Isolate* isolate)
    : HandleBase(object.ptr(), isolate) {}

template <typename T>
Handle<T>::Handle(T object, OffThreadIsolate* isolate)
    : HandleBase(object.ptr(), isolate) {}

template <typename T>
Handle<T>::Handle(T object, LocalHeap* local_heap)
    : HandleBase(object.ptr(), local_heap) {}

template <typename T>
V8_INLINE Handle<T> handle(T object, Isolate* isolate) {
  return Handle<T>(object, isolate);
}

template <typename T>
V8_INLINE Handle<T> handle(T object, OffThreadIsolate* isolate) {
  return Handle<T>(object, isolate);
}

template <typename T>
V8_INLINE Handle<T> handle(T object, LocalHeap* local_heap) {
  return Handle<T>(object, local_heap);
}

// Convenience overloads for when we already have a Handle, but want
// either a Handle or an Handle.
template <typename T>
V8_INLINE Handle<T> handle(Handle<T> handle, Isolate* isolate) {
  return handle;
}
template <typename T>
V8_INLINE Handle<T> handle(Handle<T> handle, OffThreadIsolate* isolate) {
  return Handle<T>(*handle);
}
template <typename T>
V8_INLINE Handle<T> handle(Handle<T> handle, LocalHeap* local_heap) {
  return Handle<T>(*handle, local_heap);
}

template <typename T>
inline std::ostream& operator<<(std::ostream& os, Handle<T> handle) {
  return os << Brief(*handle);
}

HandleScope::HandleScope(Isolate* isolate) {
  HandleScopeData* data = isolate->handle_scope_data();
  isolate_ = isolate;
  prev_next_ = data->next;
  prev_limit_ = data->limit;
  data->level++;
}

HandleScope::HandleScope(HandleScope&& other) V8_NOEXCEPT
    : isolate_(other.isolate_),
      prev_next_(other.prev_next_),
      prev_limit_(other.prev_limit_) {
  other.isolate_ = nullptr;
}

HandleScope::~HandleScope() {
  if (isolate_ == nullptr) return;
  CloseScope(isolate_, prev_next_, prev_limit_);
}

HandleScope& HandleScope::operator=(HandleScope&& other) V8_NOEXCEPT {
  if (isolate_ == nullptr) {
    isolate_ = other.isolate_;
  } else {
    DCHECK_EQ(isolate_, other.isolate_);
    CloseScope(isolate_, prev_next_, prev_limit_);
  }
  prev_next_ = other.prev_next_;
  prev_limit_ = other.prev_limit_;
  other.isolate_ = nullptr;
  return *this;
}

void HandleScope::CloseScope(Isolate* isolate, Address* prev_next,
                             Address* prev_limit) {
#ifdef DEBUG
  int before = FLAG_check_handle_count ? NumberOfHandles(isolate) : 0;
#endif
  DCHECK_NOT_NULL(isolate);
  HandleScopeData* current = isolate->handle_scope_data();

  std::swap(current->next, prev_next);
  current->level--;
  Address* limit = prev_next;
  if (current->limit != prev_limit) {
    current->limit = prev_limit;
    limit = prev_limit;
    DeleteExtensions(isolate);
  }
#ifdef ENABLE_HANDLE_ZAPPING
  ZapRange(current->next, limit);
#endif
  MSAN_ALLOCATED_UNINITIALIZED_MEMORY(
      current->next,
      static_cast<size_t>(reinterpret_cast<Address>(limit) -
                          reinterpret_cast<Address>(current->next)));
#ifdef DEBUG
  int after = FLAG_check_handle_count ? NumberOfHandles(isolate) : 0;
  DCHECK_LT(after - before, kCheckHandleThreshold);
  DCHECK_LT(before, kCheckHandleThreshold);
#endif
}

template <typename T>
Handle<T> HandleScope::CloseAndEscape(Handle<T> handle_value) {
  HandleScopeData* current = isolate_->handle_scope_data();
  T value = *handle_value;
  // Throw away all handles in the current scope.
  CloseScope(isolate_, prev_next_, prev_limit_);
  // Allocate one handle in the parent scope.
  DCHECK(current->level > current->sealed_level);
  Handle<T> result(value, isolate_);
  // Reinitialize the current scope (so that it's ready
  // to be used or closed again).
  prev_next_ = current->next;
  prev_limit_ = current->limit;
  current->level++;
  return result;
}

Address* HandleScope::CreateHandle(Isolate* isolate, Address value) {
  DCHECK(AllowHandleAllocation::IsAllowed());
  HandleScopeData* data = isolate->handle_scope_data();
  Address* result = data->next;
  if (result == data->limit) {
    result = Extend(isolate);
  }
  // Update the current next field, set the value in the created handle,
  // and return the result.
  DCHECK_LT(reinterpret_cast<Address>(result),
            reinterpret_cast<Address>(data->limit));
  data->next = reinterpret_cast<Address*>(reinterpret_cast<Address>(result) +
                                          sizeof(Address));
  *result = value;
  return result;
}

Address* HandleScope::GetHandle(Isolate* isolate, Address value) {
  DCHECK(AllowHandleAllocation::IsAllowed());
  HandleScopeData* data = isolate->handle_scope_data();
  CanonicalHandleScope* canonical = data->canonical_scope;
  return canonical ? canonical->Lookup(value) : CreateHandle(isolate, value);
}

#ifdef DEBUG
inline SealHandleScope::SealHandleScope(Isolate* isolate) : isolate_(isolate) {
  // Make sure the current thread is allowed to create handles to begin with.
  DCHECK(AllowHandleAllocation::IsAllowed());
  HandleScopeData* current = isolate_->handle_scope_data();
  // Shrink the current handle scope to make it impossible to do
  // handle allocations without an explicit handle scope.
  prev_limit_ = current->limit;
  current->limit = current->next;
  prev_sealed_level_ = current->sealed_level;
  current->sealed_level = current->level;
}

inline SealHandleScope::~SealHandleScope() {
  // Restore state in current handle scope to re-enable handle
  // allocations.
  HandleScopeData* current = isolate_->handle_scope_data();
  DCHECK_EQ(current->next, current->limit);
  current->limit = prev_limit_;
  DCHECK_EQ(current->level, current->sealed_level);
  current->sealed_level = prev_sealed_level_;
}

#endif

template <typename T>
Handle<T> OffThreadHandleScope::CloseAndEscape(Handle<T> handle_value) {
  // At the moment, off-thread handle scopes do nothing on close, so we can
  // safely return the same handle value.
  return handle_value;
}

}  // namespace internal
}  // namespace v8

#endif  // V8_HANDLES_HANDLES_INL_H_