src/api-arguments.h

// Copyright 2016 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_API_ARGUMENTS_H_
#define V8_API_ARGUMENTS_H_

#include "src/api.h"
#include "src/isolate.h"

namespace v8 {
namespace internal {

// Custom arguments replicate a small segment of stack that can be
// accessed through an Arguments object the same way the actual stack
// can.
template <int kArrayLength>
class CustomArgumentsBase : public Relocatable {
 public:
  virtual inline void IterateInstance(ObjectVisitor* v) {
    v->VisitPointers(values_, values_ + kArrayLength);
  }

 protected:
  inline Object** begin() { return values_; }
  explicit inline CustomArgumentsBase(Isolate* isolate)
      : Relocatable(isolate) {}
  Object* values_[kArrayLength];
};

template <typename T>
class CustomArguments : public CustomArgumentsBase<T::kArgsLength> {
 public:
  static const int kReturnValueOffset = T::kReturnValueIndex;

  typedef CustomArgumentsBase<T::kArgsLength> Super;
  ~CustomArguments() {
    this->begin()[kReturnValueOffset] =
        reinterpret_cast<Object*>(kHandleZapValue);
  }

 protected:
  explicit inline CustomArguments(Isolate* isolate) : Super(isolate) {}

  template <typename V>
  Handle<V> GetReturnValue(Isolate* isolate);

  inline Isolate* isolate() {
    return reinterpret_cast<Isolate*>(this->begin()[T::kIsolateIndex]);
  }
};

template <typename T>
template <typename V>
Handle<V> CustomArguments<T>::GetReturnValue(Isolate* isolate) {
  // Check the ReturnValue.
  Object** handle = &this->begin()[kReturnValueOffset];
  // Nothing was set, return empty handle as per previous behaviour.
  if ((*handle)->IsTheHole(isolate)) return Handle<V>();
  Handle<V> result = Handle<V>::cast(Handle<Object>(handle));
  result->VerifyApiCallResultType();
  return result;
}

class PropertyCallbackArguments
    : public CustomArguments<PropertyCallbackInfo<Value> > {
 public:
  typedef PropertyCallbackInfo<Value> T;
  typedef CustomArguments<T> Super;
  static const int kArgsLength = T::kArgsLength;
  static const int kThisIndex = T::kThisIndex;
  static const int kHolderIndex = T::kHolderIndex;
  static const int kDataIndex = T::kDataIndex;
  static const int kReturnValueDefaultValueIndex =
      T::kReturnValueDefaultValueIndex;
  static const int kIsolateIndex = T::kIsolateIndex;
  static const int kShouldThrowOnErrorIndex = T::kShouldThrowOnErrorIndex;

  PropertyCallbackArguments(Isolate* isolate, Object* data, Object* self,
                            JSObject* holder, Object::ShouldThrow should_throw)
      : Super(isolate) {
    Object** values = this->begin();
    values[T::kThisIndex] = self;
    values[T::kHolderIndex] = holder;
    values[T::kDataIndex] = data;
    values[T::kIsolateIndex] = reinterpret_cast<Object*>(isolate);
    values[T::kShouldThrowOnErrorIndex] =
        Smi::FromInt(should_throw == Object::THROW_ON_ERROR ? 1 : 0);

    // Here the hole is set as default value.
    // It cannot escape into js as it's remove in Call below.
    values[T::kReturnValueDefaultValueIndex] =
        isolate->heap()->the_hole_value();
    values[T::kReturnValueIndex] = isolate->heap()->the_hole_value();
    DCHECK(values[T::kHolderIndex]->IsHeapObject());
    DCHECK(values[T::kIsolateIndex]->IsSmi());
  }

/*
 * The following Call functions wrap the calling of all callbacks to handle
 * calling either the old or the new style callbacks depending on which one
 * has been registered.
 * For old callbacks which return an empty handle, the ReturnValue is checked
 * and used if it's been set to anything inside the callback.
 * New style callbacks always use the return value.
 */
  Handle<JSObject> Call(IndexedPropertyEnumeratorCallback f);

  inline Handle<Object> Call(AccessorNameGetterCallback f, Handle<Name> name);
  inline Handle<Object> Call(GenericNamedPropertyQueryCallback f,
                             Handle<Name> name);
  inline Handle<Object> Call(GenericNamedPropertyDeleterCallback f,
                             Handle<Name> name);

  inline Handle<Object> Call(IndexedPropertyGetterCallback f, uint32_t index);
  inline Handle<Object> Call(IndexedPropertyQueryCallback f, uint32_t index);
  inline Handle<Object> Call(IndexedPropertyDeleterCallback f, uint32_t index);

  inline Handle<Object> Call(GenericNamedPropertySetterCallback f,
                             Handle<Name> name, Handle<Object> value);

  inline Handle<Object> Call(IndexedPropertySetterCallback f, uint32_t index,
                             Handle<Object> value);

  inline void Call(AccessorNameSetterCallback f, Handle<Name> name,
                   Handle<Object> value);

 private:
  inline JSObject* holder() {
    return JSObject::cast(this->begin()[T::kHolderIndex]);
  }
};

class FunctionCallbackArguments
    : public CustomArguments<FunctionCallbackInfo<Value> > {
 public:
  typedef FunctionCallbackInfo<Value> T;
  typedef CustomArguments<T> Super;
  static const int kArgsLength = T::kArgsLength;
  static const int kHolderIndex = T::kHolderIndex;
  static const int kDataIndex = T::kDataIndex;
  static const int kReturnValueDefaultValueIndex =
      T::kReturnValueDefaultValueIndex;
  static const int kIsolateIndex = T::kIsolateIndex;
  static const int kCalleeIndex = T::kCalleeIndex;
  static const int kContextSaveIndex = T::kContextSaveIndex;
  static const int kNewTargetIndex = T::kNewTargetIndex;

  FunctionCallbackArguments(internal::Isolate* isolate, internal::Object* data,
                            internal::HeapObject* callee,
                            internal::Object* holder,
                            internal::HeapObject* new_target,
                            internal::Object** argv, int argc)
      : Super(isolate), argv_(argv), argc_(argc) {
    Object** values = begin();
    values[T::kDataIndex] = data;
    values[T::kCalleeIndex] = callee;
    values[T::kHolderIndex] = holder;
    values[T::kNewTargetIndex] = new_target;
    values[T::kContextSaveIndex] = isolate->heap()->the_hole_value();
    values[T::kIsolateIndex] = reinterpret_cast<internal::Object*>(isolate);
    // Here the hole is set as default value.
    // It cannot escape into js as it's remove in Call below.
    values[T::kReturnValueDefaultValueIndex] =
        isolate->heap()->the_hole_value();
    values[T::kReturnValueIndex] = isolate->heap()->the_hole_value();
    DCHECK(values[T::kCalleeIndex]->IsJSFunction() ||
           values[T::kCalleeIndex]->IsFunctionTemplateInfo());
    DCHECK(values[T::kHolderIndex]->IsHeapObject());
    DCHECK(values[T::kIsolateIndex]->IsSmi());
  }

  /*
   * The following Call function wraps the calling of all callbacks to handle
   * calling either the old or the new style callbacks depending on which one
   * has been registered.
   * For old callbacks which return an empty handle, the ReturnValue is checked
   * and used if it's been set to anything inside the callback.
   * New style callbacks always use the return value.
   */
  Handle<Object> Call(FunctionCallback f);

 private:
  internal::Object** argv_;
  int argc_;
};

}  // namespace internal
}  // namespace v8

#endif  // V8_API_ARGUMENTS_H_