variant.h

/* Copyright (c) 2018 PaddlePaddle Authors. All Rights Reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License. */

#include "common/enforce.h"
#include "common/log.h"

#pragma once

namespace paddle_mobile {
template <int ID, typename Type>
struct IDToType {
  typedef Type type_t;
};

template <typename F, typename... Ts>
struct VariantHelper {
  static const size_t size = sizeof(F) > VariantHelper<Ts...>::size
                                 ? sizeof(F)
                                 : VariantHelper<Ts...>::size;

  inline static void Destroy(size_t id, void *data) {
    if (id == typeid(F).hash_code()) {
      reinterpret_cast<F *>(data)->~F();
    } else {
      VariantHelper<Ts...>::Destroy(id, data);
    }
  }
};

template <typename F>
struct VariantHelper<F> {
  static const size_t size = sizeof(F);
  inline static void Destroy(size_t id, void *data) {
    if (id == typeid(F).hash_code()) {
      //              reinterpret_cast<F*>(data)->~F();
    } else {
      //              std::cout << "未匹配到 " << std::endl;
    }
  }
};

template <size_t size>
class RawData {
 public:
  char data[size];
  RawData() {}
  RawData(const RawData &raw_data) { strcpy(data, raw_data.data); }
};

template <typename... Ts>
struct Variant {
  Variant(const Variant &variant) {
    type_id = variant.type_id;
    data = variant.data;
  }

  Variant() : type_id(invalid_type()) {}
  ~Variant() {
    //        helper::Destroy(type_id, &data);
  }

  template <typename T, typename... Args>
  void Set(Args &&... args) {
    helper::Destroy(type_id, &data);
    new (&data) T(std::forward<Args>(args)...);
    type_id = typeid(T).hash_code();
  }

  template <typename T>
  T &Get() const {
    if (type_id == typeid(T).hash_code()) {
      return *const_cast<T *>(reinterpret_cast<const T *>(&data));
    } else {
      PADDLE_MOBILE_THROW_EXCEPTION(" bad cast in variant ");
      exit(0);
    }
  }

  size_t TypeId() const { return type_id; }

 private:
  static inline size_t invalid_type() { return typeid(void).hash_code(); }
  typedef VariantHelper<Ts...> helper;
  size_t type_id;
  RawData<helper::size> data;
};

template <typename T>
struct Vistor {
  typedef T type_t;
};

}  // namespace paddle_mobile