serialization_traits.h

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//
//
// Copyright 2015 gRPC authors.
//
// 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.
//
//
 
#ifndef GRPCPP_IMPL_SERIALIZATION_TRAITS_H
#define GRPCPP_IMPL_SERIALIZATION_TRAITS_H
 
#include <grpc/event_engine/memory_allocator.h>
 
#include <type_traits>
#include <utility>
 
namespace grpc {
 
template <class Message,
          class UnusedButHereForPartialTemplateSpecialization = void>
class SerializationTraits;
 
namespace impl {
 
// Helper trait to robustly check if the allocator-aware Serialize exists.
template <typename Message, typename BufferPtr, typename = void>
struct has_allocator_serialize : std::false_type {};
 
template <typename Message, typename BufferPtr>
struct has_allocator_serialize<
    Message, BufferPtr,
    std::void_t<decltype(SerializationTraits<Message>::Serialize(
        std::declval<grpc_event_engine::experimental::MemoryAllocator*>(),
        std::declval<const Message&>(), std::declval<BufferPtr>(),
        std::declval<bool*>()))>> : std::true_type {};
 
template <typename Message, typename BufferPtr>
inline constexpr bool has_allocator_serialize_v =
    has_allocator_serialize<Message, BufferPtr>::value;
 
// Primary template for SerializeDispatch, now switched by a bool.
template <typename Message, typename BufferPtr,
          bool = has_allocator_serialize_v<Message, BufferPtr>>
struct SerializeDispatch;
 
// Specialization for when the allocator-aware Serialize *exists*.
template <typename Message, typename BufferPtr>
struct SerializeDispatch<Message, BufferPtr, true> {
  static auto Serialize(
      grpc_event_engine::experimental::MemoryAllocator* allocator,
      const Message& msg, BufferPtr buffer, bool* own_buffer) {
    return SerializationTraits<Message>::Serialize(allocator, msg, buffer,
                                                   own_buffer);
  }
};
 
// Specialization for when the allocator-aware Serialize *does not* exist.
template <typename Message, typename BufferPtr>
struct SerializeDispatch<Message, BufferPtr, false> {
  static auto Serialize(
      grpc_event_engine::experimental::MemoryAllocator* /*allocator*/,
      const Message& msg, BufferPtr buffer, bool* own_buffer) {
    // Fallback to the old Serialize, ignoring the allocator.
    return SerializationTraits<Message>::Serialize(msg, buffer, own_buffer);
  }
};
 
}  // namespace impl
 
template <typename Message, typename BufferPtr>
auto Serialize(grpc_event_engine::experimental::MemoryAllocator* allocator,
               const Message& msg, BufferPtr buffer, bool* own_buffer) {
  return impl::SerializeDispatch<Message, BufferPtr>::Serialize(
      allocator, msg, buffer, own_buffer);
}
 
template <typename BufferPtr, typename Message>
auto Deserialize(BufferPtr buffer, Message* msg) {
  return SerializationTraits<Message>::Deserialize(buffer, msg);
}
 
}  // namespace grpc
 
#endif  // GRPCPP_IMPL_SERIALIZATION_TRAITS_H