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       1                 :             : /*
       2                 :             :  * Copyright 2025 Jinwoo Sung
       3                 :             :  *
       4                 :             :  * Licensed under the Apache License, Version 2.0 (the "License");
       5                 :             :  * you may not use this file except in compliance with the License.
       6                 :             :  * You may obtain a copy of the License at
       7                 :             :  *
       8                 :             :  *     http://www.apache.org/licenses/LICENSE-2.0
       9                 :             :  *
      10                 :             :  * Unless required by applicable law or agreed to in writing, software
      11                 :             :  * distributed under the License is distributed on an "AS IS" BASIS,
      12                 :             :  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
      13                 :             :  * See the License for the specific language governing permissions and
      14                 :             :  * limitations under the License.
      15                 :             :  */
      16                 :             : 
      17                 :             : #pragma once
      18                 :             : 
      19                 :             : #include <boost/asio.hpp>
      20                 :             : #include <functional>
      21                 :             : #include <memory>
      22                 :             : #include <vector>
      23                 :             : 
      24                 :             : #include "wirestead/base/platform.hpp"
      25                 :             : #include "wirestead/base/visibility.hpp"
      26                 :             : 
      27                 :             : namespace wirestead {
      28                 :             : namespace interface {
      29                 :             : 
      30                 :             : namespace net = boost::asio;
      31                 :             : 
      32                 :             : /**
      33                 :             :  * @brief An interface abstracting Boost.Asio's local::stream_protocol::socket for testability.
      34                 :             :  * This is an internal interface used for dependency injection and mocking.
      35                 :             :  */
      36                 :             : class WIRESTEAD_API UdsSocketInterface {
      37                 :             :  public:
      38                 :          73 :   virtual ~UdsSocketInterface() = default;
      39                 :             : 
      40                 :             :   virtual void async_read_some(const net::mutable_buffer& buffer,
      41                 :             :                                std::function<void(const boost::system::error_code&, std::size_t)> handler) = 0;
      42                 :             :   virtual void async_write(const net::const_buffer& buffer,
      43                 :             :                            std::function<void(const boost::system::error_code&, std::size_t)> handler) = 0;
      44                 :             : 
      45                 :             :   // Scatter-gather write: sends every buffer in `buffers` as one operation,
      46                 :             :   // completing once with the total byte count or the first error. Draining
      47                 :             :   // several queued messages this way turns N send syscalls into one.
      48                 :             :   //
      49                 :             :   // The memory the buffers point at must stay valid until the handler runs.
      50                 :             :   //
      51                 :             :   // The default flattens into one buffer and delegates to the single-buffer
      52                 :             :   // overload above: correct, but it copies, so implementations backed by a real
      53                 :             :   // socket override it. Test doubles can rely on the default.
      54                 :             :   virtual void async_write(const std::vector<net::const_buffer>& buffers,
      55                 :             :                            std::function<void(const boost::system::error_code&, std::size_t)> handler);
      56                 :             :   virtual void async_connect(const net::local::stream_protocol::endpoint& endpoint,
      57                 :             :                              std::function<void(const boost::system::error_code&)> handler) = 0;
      58                 :             :   virtual void shutdown(net::local::stream_protocol::socket::shutdown_type what, boost::system::error_code& ec) = 0;
      59                 :             :   virtual void close(boost::system::error_code& ec) = 0;
      60                 :             :   virtual net::local::stream_protocol::endpoint remote_endpoint(boost::system::error_code& ec) const = 0;
      61                 :             : };
      62                 :             : 
      63                 :             : // Flattens into one contiguous buffer and delegates. Copies, which is why a
      64                 :             : // socket-backed implementation overrides this; kept here so test doubles and
      65                 :             : // any not-yet-converted implementation stay correct for free. `flat` is
      66                 :             : // owned by the completion lambda, so it outlives the delegated write.
      67                 :          14 : inline void UdsSocketInterface::async_write(
      68                 :             :     const std::vector<net::const_buffer>& buffers,
      69                 :             :     std::function<void(const boost::system::error_code&, std::size_t)> handler) {
      70         [ +  - ]:          14 :   auto flat = std::make_shared<std::vector<unsigned char>>();
      71                 :          14 :   std::size_t total = 0;
      72         [ +  + ]:          28 :   for (const auto& b : buffers) total += b.size();
      73                 :          14 :   flat->reserve(total);
      74         [ +  + ]:          28 :   for (const auto& b : buffers) {
      75                 :          14 :     const auto* p = static_cast<const unsigned char*>(b.data());
      76                 :          14 :     flat->insert(flat->end(), p, p + b.size());
      77                 :             :   }
      78                 :          14 :   async_write(net::const_buffer(flat->data(), flat->size()),
      79                 :          28 :               [flat, handler = std::move(handler)](const boost::system::error_code& ec, std::size_t n) {
      80         [ +  - ]:          12 :                 if (handler) handler(ec, n);
      81                 :          12 :               });
      82                 :          14 : }
      83                 :             : 
      84                 :             : }  // namespace interface
      85                 :             : }  // namespace wirestead