src/handles-inl.h

// Copyright 2006-2008 the V8 project authors. All rights reserved.
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// modification, are permitted provided that the following conditions are
// met:
//
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//       notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
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//       with the distribution.
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#ifndef V8_HANDLES_INL_H_
#define V8_HANDLES_INL_H_

#include "api.h"
#include "apiutils.h"
#include "handles.h"
#include "isolate.h"

namespace v8 {
namespace internal {

template<typename T>
Handle<T>::Handle(T* obj) {
  ASSERT(!obj->IsFailure());
  location_ = HandleScope::CreateHandle(obj->GetIsolate(), obj);
}


template<typename T>
Handle<T>::Handle(T* obj, Isolate* isolate) {
  ASSERT(!obj->IsFailure());
  location_ = HandleScope::CreateHandle(isolate, obj);
}


template <typename T>
inline bool Handle<T>::is_identical_to(const Handle<T> other) const {
  ASSERT(location_ == NULL || !(*location_)->IsFailure());
  if (location_ == other.location_) return true;
  if (location_ == NULL || other.location_ == NULL) return false;
  // Dereferencing deferred handles to check object equality is safe.
  SLOW_ASSERT(IsDereferenceAllowed(true) && other.IsDereferenceAllowed(true));
  return *location_ == *other.location_;
}


template <typename T>
inline T* Handle<T>::operator*() const {
  ASSERT(location_ != NULL && !(*location_)->IsFailure());
  SLOW_ASSERT(IsDereferenceAllowed(false));
  return *BitCast<T**>(location_);
}

template <typename T>
inline T** Handle<T>::location() const {
  ASSERT(location_ == NULL || !(*location_)->IsFailure());
  SLOW_ASSERT(location_ == NULL || IsDereferenceAllowed(false));
  return location_;
}

#ifdef DEBUG
template <typename T>
bool Handle<T>::IsDereferenceAllowed(bool allow_deferred) const {
  ASSERT(location_ != NULL);
  Object* object = *BitCast<T**>(location_);
  if (object->IsSmi()) return true;
  HeapObject* heap_object = HeapObject::cast(object);
  Isolate* isolate = heap_object->GetIsolate();
  Object** handle = reinterpret_cast<Object**>(location_);
  Object** roots_array_start = isolate->heap()->roots_array_start();
  if (roots_array_start <= handle &&
      handle < roots_array_start + Heap::kStrongRootListLength) {
    return true;
  }
  if (isolate->optimizing_compiler_thread()->IsOptimizerThread() &&
      !Heap::RelocationLock::IsLockedByOptimizerThread(isolate->heap())) {
    return false;
  }
  switch (isolate->HandleDereferenceGuardState()) {
    case HandleDereferenceGuard::ALLOW:
      return true;
    case HandleDereferenceGuard::DISALLOW:
      return false;
    case HandleDereferenceGuard::DISALLOW_DEFERRED:
      // Accessing maps and internalized strings is safe.
      if (heap_object->IsMap()) return true;
      if (heap_object->IsInternalizedString()) return true;
      return allow_deferred || !isolate->IsDeferredHandle(handle);
  }
  return false;
}
#endif



HandleScope::HandleScope(Isolate* isolate) {
  v8::ImplementationUtilities::HandleScopeData* current =
      isolate->handle_scope_data();
  isolate_ = isolate;
  prev_next_ = current->next;
  prev_limit_ = current->limit;
  current->level++;
}


HandleScope::~HandleScope() {
  CloseScope();
}

void HandleScope::CloseScope() {
  v8::ImplementationUtilities::HandleScopeData* current =
      isolate_->handle_scope_data();
  current->next = prev_next_;
  current->level--;
  if (current->limit != prev_limit_) {
    current->limit = prev_limit_;
    DeleteExtensions(isolate_);
  }
#ifdef ENABLE_EXTRA_CHECKS
  ZapRange(prev_next_, prev_limit_);
#endif
}


template <typename T>
Handle<T> HandleScope::CloseAndEscape(Handle<T> handle_value) {
  T* value = *handle_value;
  // Throw away all handles in the current scope.
  CloseScope();
  v8::ImplementationUtilities::HandleScopeData* current =
      isolate_->handle_scope_data();
  // Allocate one handle in the parent scope.
  ASSERT(current->level > 0);
  Handle<T> result(CreateHandle<T>(isolate_, value));
  // 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;
}


template <typename T>
T** HandleScope::CreateHandle(Isolate* isolate, T* value) {
  v8::ImplementationUtilities::HandleScopeData* current =
      isolate->handle_scope_data();

  internal::Object** cur = current->next;
  if (cur == current->limit) cur = Extend(isolate);
  // Update the current next field, set the value in the created
  // handle, and return the result.
  ASSERT(cur < current->limit);
  current->next = cur + 1;

  T** result = reinterpret_cast<T**>(cur);
  *result = value;
  return result;
}


#ifdef DEBUG
inline NoHandleAllocation::NoHandleAllocation(Isolate* isolate)
    : isolate_(isolate) {
  v8::ImplementationUtilities::HandleScopeData* current =
      isolate_->handle_scope_data();

  active_ = !isolate->optimizing_compiler_thread()->IsOptimizerThread();
  if (active_) {
    // Shrink the current handle scope to make it impossible to do
    // handle allocations without an explicit handle scope.
    current->limit = current->next;

    level_ = current->level;
    current->level = 0;
  }
}


inline NoHandleAllocation::~NoHandleAllocation() {
  if (active_) {
    // Restore state in current handle scope to re-enable handle
    // allocations.
    v8::ImplementationUtilities::HandleScopeData* data =
        isolate_->handle_scope_data();
    ASSERT_EQ(0, data->level);
    data->level = level_;
  }
}


HandleDereferenceGuard::HandleDereferenceGuard(Isolate* isolate, State state)
    : isolate_(isolate) {
  old_state_ = isolate_->HandleDereferenceGuardState();
  isolate_->SetHandleDereferenceGuardState(state);
}


HandleDereferenceGuard::~HandleDereferenceGuard() {
  isolate_->SetHandleDereferenceGuardState(old_state_);
}

#endif

} }  // namespace v8::internal

#endif  // V8_HANDLES_INL_H_