dart_wrappable.h

// Copyright 2015 The Fuchsia 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 LIB_TONIC_DART_WRAPPABLE_H_
#define LIB_TONIC_DART_WRAPPABLE_H_

#include "third_party/dart/runtime/include/dart_api.h"
#include "tonic/common/macros.h"
#include "tonic/converter/dart_converter.h"
#include "tonic/dart_state.h"
#include "tonic/dart_wrapper_info.h"
#include "tonic/logging/dart_error.h"

#include <type_traits>

namespace tonic {

// DartWrappable is a base class that you can inherit from in order to be
// exposed to Dart code as an interface.
class DartWrappable {
public:
  enum DartNativeFields {
    kPeerIndex, // Must be first to work with Dart_GetNativeReceiver.
    kWrapperInfoIndex,
    kNumberOfNativeFields,
  };

  DartWrappable() : dart_wrapper_(nullptr) {}

  // Subclasses that wish to expose a new interface must override this function
  // and provide information about their wrapper. There is no need to call your
  // base class's implementation of this function.
  // Implement using IMPLEMENT_WRAPPERTYPEINFO macro
  virtual const DartWrapperInfo &GetDartWrapperInfo() const = 0;

  // Override this to customize the object size reported to the Dart garbage
  // collector.
  // Implement using IMPLEMENT_WRAPPERTYPEINFO macro
  virtual size_t GetAllocationSize();

  virtual void RetainDartWrappableReference() const = 0;

  virtual void ReleaseDartWrappableReference() const = 0;

  Dart_Handle CreateDartWrapper(DartState *dart_state);
  void AssociateWithDartWrapper(Dart_NativeArguments args);
  void ClearDartWrapper(); // Warning: Might delete this.
  Dart_WeakPersistentHandle dart_wrapper() const { return dart_wrapper_; }

protected:
  virtual ~DartWrappable();

  static Dart_PersistentHandle
  GetTypeForWrapper(tonic::DartState *dart_state,
                    const tonic::DartWrapperInfo &wrapper_info);

private:
  static void FinalizeDartWrapper(void *isolate_callback_data,
                                  Dart_WeakPersistentHandle wrapper,
                                  void *peer);

  Dart_WeakPersistentHandle dart_wrapper_;

  TONIC_DISALLOW_COPY_AND_ASSIGN(DartWrappable);
};

#define DEFINE_WRAPPERTYPEINFO()                                               \
public:                                                                        \
  const tonic::DartWrapperInfo &GetDartWrapperInfo() const override {          \
    return dart_wrapper_info_;                                                 \
  }                                                                            \
  static Dart_PersistentHandle GetDartType(tonic::DartState *dart_state) {     \
    return GetTypeForWrapper(dart_state, dart_wrapper_info_);                  \
  }                                                                            \
                                                                               \
private:                                                                       \
  static const tonic::DartWrapperInfo &dart_wrapper_info_

#define IMPLEMENT_WRAPPERTYPEINFO(LibraryName, ClassName)                      \
  static const tonic::DartWrapperInfo                                          \
      kDartWrapperInfo_##LibraryName_##ClassName = {                           \
          #LibraryName,                                                        \
          #ClassName,                                                          \
          sizeof(ClassName),                                                   \
  };                                                                           \
  const tonic::DartWrapperInfo &ClassName::dart_wrapper_info_ =                \
      kDartWrapperInfo_##LibraryName_##ClassName;

struct DartConverterWrappable {
  static DartWrappable *FromDart(Dart_Handle handle);
  static DartWrappable *FromArguments(Dart_NativeArguments args, int index,
                                      Dart_Handle &exception);
};

template <typename T>
struct DartConverter<T *, typename std::enable_if<std::is_convertible<
                              T *, const DartWrappable *>::value>::type> {
  static Dart_Handle ToDart(DartWrappable *val) {
    if (!val)
      return Dart_Null();
    if (Dart_WeakPersistentHandle wrapper = val->dart_wrapper())
      return Dart_HandleFromWeakPersistent(wrapper);
    return val->CreateDartWrapper(DartState::Current());
  }

  static void SetReturnValue(Dart_NativeArguments args, DartWrappable *val,
                             bool auto_scope = true) {
    if (!val)
      Dart_SetReturnValue(args, Dart_Null());
    else if (Dart_WeakPersistentHandle wrapper = val->dart_wrapper())
      Dart_SetWeakHandleReturnValue(args, wrapper);
    else
      Dart_SetReturnValue(args, val->CreateDartWrapper(DartState::Current()));
  }

  static T *FromDart(Dart_Handle handle) {
    // TODO(abarth): We're missing a type check.
    return static_cast<T *>(DartConverterWrappable::FromDart(handle));
  }

  static T *FromArguments(Dart_NativeArguments args, int index,
                          Dart_Handle &exception, bool auto_scope = true) {
    // TODO(abarth): We're missing a type check.
    return static_cast<T *>(
        DartConverterWrappable::FromArguments(args, index, exception));
  }
};

template <typename T> inline T *GetReceiver(Dart_NativeArguments args) {
  intptr_t receiver;
  Dart_Handle result = Dart_GetNativeReceiver(args, &receiver);
  TONIC_DCHECK(!Dart_IsError(result));
  if (!receiver)
    Dart_ThrowException(ToDart("Object has been disposed."));
  return static_cast<T *>(reinterpret_cast<DartWrappable *>(receiver));
}

} // namespace tonic

#endif // LIB_TONIC_DART_WRAPPABLE_H_