TLA  Line data    Source code

       1                 : //
       2                 : // Copyright (c) 2026 Steve Gerbino
       3                 : //
       4                 : // Distributed under the Boost Software License, Version 1.0. (See accompanying
       5                 : // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
       6                 : //
       7                 : // Official repository: https://github.com/cppalliance/corosio
       8                 : //
       9                 : 
      10                 : #ifndef BOOST_COROSIO_IO_IO_READ_STREAM_HPP
      11                 : #define BOOST_COROSIO_IO_IO_READ_STREAM_HPP
      12                 : 
      13                 : #include <boost/corosio/detail/config.hpp>
      14                 : #include <boost/corosio/io/io_object.hpp>
      15                 : #include <boost/corosio/io_buffer_param.hpp>
      16                 : #include <boost/capy/io_result.hpp>
      17                 : #include <boost/capy/ex/executor_ref.hpp>
      18                 : #include <boost/capy/ex/io_env.hpp>
      19                 : 
      20                 : #include <coroutine>
      21                 : #include <cstddef>
      22                 : #include <stop_token>
      23                 : #include <system_error>
      24                 : 
      25                 : namespace boost::corosio {
      26                 : 
      27                 : /** Abstract base for streams that support async reads.
      28                 : 
      29                 :     Provides the `read_some` operation via a pure virtual
      30                 :     `do_read_some` dispatch point. Concrete classes override
      31                 :     `do_read_some` to route through their implementation.
      32                 : 
      33                 :     Uses virtual inheritance from @ref io_object so that
      34                 :     @ref io_stream can combine this with @ref io_write_stream
      35                 :     without duplicating the `io_object` base.
      36                 : 
      37                 :     @par Thread Safety
      38                 :     Distinct objects: Safe.
      39                 :     Shared objects: Unsafe.
      40                 : 
      41                 :     @see io_write_stream, io_stream, io_object
      42                 : */
      43                 : class BOOST_COROSIO_DECL io_read_stream : virtual public io_object
      44                 : {
      45                 : protected:
      46                 :     /// Awaitable for async read operations.
      47                 :     template<class MutableBufferSequence>
      48                 :     struct read_some_awaitable
      49                 :     {
      50                 :         io_read_stream& ios_;
      51                 :         MutableBufferSequence buffers_;
      52                 :         std::stop_token token_;
      53                 :         mutable std::error_code ec_;
      54                 :         mutable std::size_t bytes_transferred_ = 0;
      55                 : 
      56 HIT      283291 :         read_some_awaitable(
      57                 :             io_read_stream& ios, MutableBufferSequence buffers) noexcept
      58          283291 :             : ios_(ios)
      59          283291 :             , buffers_(std::move(buffers))
      60                 :         {
      61          283291 :         }
      62                 : 
      63          283291 :         bool await_ready() const noexcept
      64                 :         {
      65          283291 :             return token_.stop_requested();
      66                 :         }
      67                 : 
      68          283291 :         capy::io_result<std::size_t> await_resume() const noexcept
      69                 :         {
      70          283291 :             if (token_.stop_requested())
      71             198 :                 return {make_error_code(std::errc::operation_canceled), 0};
      72          283093 :             return {ec_, bytes_transferred_};
      73                 :         }
      74                 : 
      75          283291 :         auto await_suspend(std::coroutine_handle<> h, capy::io_env const* env)
      76                 :             -> std::coroutine_handle<>
      77                 :         {
      78          283291 :             token_ = env->stop_token;
      79          566582 :             return ios_.do_read_some(
      80          849873 :                 h, env->executor, buffers_, token_, &ec_, &bytes_transferred_);
      81                 :         }
      82                 :     };
      83                 : 
      84                 :     /** Dispatch a read through the concrete implementation.
      85                 : 
      86                 :         @param h Coroutine handle to resume on completion.
      87                 :         @param ex Executor for dispatching the completion.
      88                 :         @param buffers Target buffer sequence.
      89                 :         @param token Stop token for cancellation.
      90                 :         @param ec Output error code.
      91                 :         @param bytes Output bytes transferred.
      92                 : 
      93                 :         @return Coroutine handle to resume immediately.
      94                 :     */
      95                 :     virtual std::coroutine_handle<> do_read_some(
      96                 :         std::coroutine_handle<>,
      97                 :         capy::executor_ref,
      98                 :         io_buffer_param,
      99                 :         std::stop_token,
     100                 :         std::error_code*,
     101                 :         std::size_t*) = 0;
     102                 : 
     103           15731 :     io_read_stream() noexcept = default;
     104                 : 
     105                 :     /// Construct from a handle.
     106                 :     explicit io_read_stream(handle h) noexcept : io_object(std::move(h)) {}
     107                 : 
     108                 : public:
     109                 :     /** Asynchronously read data from the stream.
     110                 : 
     111                 :         Suspends the calling coroutine and initiates a kernel-level
     112                 :         read. The coroutine resumes when at least one byte is read,
     113                 :         an error occurs, or the operation is cancelled.
     114                 : 
     115                 :         @param buffers The buffer sequence to read data into.
     116                 : 
     117                 :         @return An awaitable yielding `(error_code, std::size_t)`.
     118                 : 
     119                 :         @see io_stream::write_some
     120                 :     */
     121                 :     template<capy::MutableBufferSequence MB>
     122          283291 :     auto read_some(MB const& buffers)
     123                 :     {
     124          283291 :         return read_some_awaitable<MB>(*this, buffers);
     125                 :     }
     126                 : };
     127                 : 
     128                 : } // namespace boost::corosio
     129                 : 
     130                 : #endif