CSE2410 Fall 2014 Bounce

// Copyright 2006-2008 the V8 project authors. All rights reserved.

// Redistribution and use in source and binary forms, with or without

// modification, are permitted provided that the following conditions are

// met:

//

//     * Redistributions of source code must retain the above copyright

//       notice, this list of conditions and the following disclaimer.

//     * Redistributions in binary form must reproduce the above

//       copyright notice, this list of conditions and the following

//       disclaimer in the documentation and/or other materials provided

//       with the distribution.

//     * Neither the name of Google Inc. nor the names of its

//       contributors may be used to endorse or promote products derived

//       from this software without specific prior written permission.

//

// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT

// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

//

#ifndef V8_HANDLES_INL_H_

#define V8_HANDLES_INL_H_

#include "api.h"

#include "apiutils.h"

#include "handles.h"

#include "heap.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(NO_DEFERRED_CHECK) &&

              other.IsDereferenceAllowed(NO_DEFERRED_CHECK));

  return *location_ == *other.location_;

}

template <typename T>

inline T* Handle<T>::operator*() const {

  ASSERT(location_ != NULL && !(*location_)->IsFailure());

  SLOW_ASSERT(IsDereferenceAllowed(INCLUDE_DEFERRED_CHECK));

  return *BitCast<T**>(location_);

}

template <typename T>

inline T** Handle<T>::location() const {

  ASSERT(location_ == NULL || !(*location_)->IsFailure());

  SLOW_ASSERT(location_ == NULL ||

              IsDereferenceAllowed(INCLUDE_DEFERRED_CHECK));

  return location_;

}

#ifdef DEBUG

template <typename T>

bool Handle<T>::IsDereferenceAllowed(DereferenceCheckMode mode) const {

  ASSERT(location_ != NULL);

  Object* object = *BitCast<T**>(location_);

  if (object->IsSmi()) return true;

  HeapObject* heap_object = HeapObject::cast(object);

  Heap* heap = heap_object->GetHeap();

  Object** handle = reinterpret_cast<Object**>(location_);

  Object** roots_array_start = heap->roots_array_start();

  if (roots_array_start <= handle &&

      handle < roots_array_start + Heap::kStrongRootListLength &&

      heap->RootCanBeTreatedAsConstant(

        static_cast<Heap::RootListIndex>(handle - roots_array_start))) {

    return true;

  }

  if (!AllowHandleDereference::IsAllowed()) return false;

  if (mode == INCLUDE_DEFERRED_CHECK &&

      !AllowDeferredHandleDereference::IsAllowed()) {

    // Accessing maps and internalized strings is safe.

    if (heap_object->IsMap()) return true;

    if (heap_object->IsInternalizedString()) return true;

    return !heap->isolate()->IsDeferredHandle(handle);

  }

  return true;

}

#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(isolate_, prev_next_, prev_limit_);

}

void HandleScope::CloseScope(Isolate* isolate,

                             Object** prev_next,

                             Object** prev_limit) {

  v8::ImplementationUtilities::HandleScopeData* current =

      isolate->handle_scope_data();

  std::swap(current->next, prev_next);

  current->level--;

  if (current->limit != prev_limit) {

    current->limit = prev_limit;

    DeleteExtensions(isolate);

#ifdef ENABLE_HANDLE_ZAPPING

    ZapRange(current->next, prev_limit);

  } else {

    ZapRange(current->next, prev_next);

#endif

  }

}

template <typename T>

Handle<T> HandleScope::CloseAndEscape(Handle<T> handle_value) {

  v8::ImplementationUtilities::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.

  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) {

  ASSERT(AllowHandleAllocation::IsAllowed());

  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 SealHandleScope::SealHandleScope(Isolate* isolate) : isolate_(isolate) {

  // Make sure the current thread is allowed to create handles to begin with.

  CHECK(AllowHandleAllocation::IsAllowed());

  v8::ImplementationUtilities::HandleScopeData* current =

      isolate_->handle_scope_data();

  // Shrink the current handle scope to make it impossible to do

  // handle allocations without an explicit handle scope.

  limit_ = current->limit;

  current->limit = current->next;

  level_ = current->level;

  current->level = 0;

}

inline SealHandleScope::~SealHandleScope() {

  // Restore state in current handle scope to re-enable handle

  // allocations.

  v8::ImplementationUtilities::HandleScopeData* current =

      isolate_->handle_scope_data();

  ASSERT_EQ(0, current->level);

  current->level = level_;

  ASSERT_EQ(current->next, current->limit);

  current->limit = limit_;

}

#endif

} }  // namespace v8::internal

#endif  // V8_HANDLES_INL_H_