. /include/boost/corosio /io /io_write_stream.hpp
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1   // 1   //
2   // Copyright (c) 2026 Steve Gerbino 2   // Copyright (c) 2026 Steve Gerbino
3   // 3   //
4   // Distributed under the Boost Software License, Version 1.0. (See accompanying 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) 5   // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
6   // 6   //
7   // Official repository: https://github.com/cppalliance/corosio 7   // Official repository: https://github.com/cppalliance/corosio
8   // 8   //
9   9  
10   #ifndef BOOST_COROSIO_IO_IO_WRITE_STREAM_HPP 10   #ifndef BOOST_COROSIO_IO_IO_WRITE_STREAM_HPP
11   #define BOOST_COROSIO_IO_IO_WRITE_STREAM_HPP 11   #define BOOST_COROSIO_IO_IO_WRITE_STREAM_HPP
12   12  
13   #include <boost/corosio/detail/config.hpp> 13   #include <boost/corosio/detail/config.hpp>
14   #include <boost/corosio/detail/op_base.hpp> 14   #include <boost/corosio/detail/op_base.hpp>
15   #include <boost/corosio/io/io_object.hpp> 15   #include <boost/corosio/io/io_object.hpp>
16   #include <boost/corosio/detail/buffer_param.hpp> 16   #include <boost/corosio/detail/buffer_param.hpp>
17   #include <boost/capy/io_result.hpp> 17   #include <boost/capy/io_result.hpp>
18   #include <boost/capy/ex/executor_ref.hpp> 18   #include <boost/capy/ex/executor_ref.hpp>
19   #include <boost/capy/ex/io_env.hpp> 19   #include <boost/capy/ex/io_env.hpp>
20   20  
21   #include <coroutine> 21   #include <coroutine>
22   #include <cstddef> 22   #include <cstddef>
23   #include <stop_token> 23   #include <stop_token>
24   #include <system_error> 24   #include <system_error>
25   25  
26   namespace boost::corosio { 26   namespace boost::corosio {
27   27  
28 - /** Abstract base for streams that support async writes. 28 + /** Writes bytes to a stream asynchronously.
29   29  
30   Provides the `write_some` operation via a pure virtual 30   Provides the `write_some` operation via a pure virtual
31   `do_write_some` dispatch point. Concrete classes override 31   `do_write_some` dispatch point. Concrete classes override
32   `do_write_some` to route through their implementation. 32   `do_write_some` to route through their implementation.
33   33  
34   Uses virtual inheritance from @ref io_object so that 34   Uses virtual inheritance from @ref io_object so that
35   @ref io_stream can combine this with @ref io_read_stream 35   @ref io_stream can combine this with @ref io_read_stream
36   without duplicating the `io_object` base. 36   without duplicating the `io_object` base.
37   37  
38   @par Thread Safety 38   @par Thread Safety
39   Distinct objects: Safe. 39   Distinct objects: Safe.
40   Shared objects: Unsafe. 40   Shared objects: Unsafe.
41   41  
42   @see io_read_stream, io_stream, io_object 42   @see io_read_stream, io_stream, io_object
43   */ 43   */
44   class BOOST_COROSIO_DECL io_write_stream : virtual public io_object 44   class BOOST_COROSIO_DECL io_write_stream : virtual public io_object
45   { 45   {
46   protected: 46   protected:
47   /// Awaitable for async write operations. 47   /// Awaitable for async write operations.
48   template<class ConstBufferSequence> 48   template<class ConstBufferSequence>
49   struct write_some_awaitable 49   struct write_some_awaitable
50   : detail::bytes_op_base<write_some_awaitable<ConstBufferSequence>> 50   : detail::bytes_op_base<write_some_awaitable<ConstBufferSequence>>
51   { 51   {
52 - io_write_stream& ios_; 52 + private:
53 - ConstBufferSequence buffers_; 53 + friend io_write_stream;
54   54  
HITCBC 55   201196 write_some_awaitable( 55   197521 write_some_awaitable(
56   io_write_stream& ios, ConstBufferSequence buffers) noexcept 56   io_write_stream& ios, ConstBufferSequence buffers) noexcept
HITCBC 57   201196 : ios_(ios) 57   197521 : ios_(ios)
HITCBC 58   201196 , buffers_(std::move(buffers)) 58   197521 , buffers_(std::move(buffers))
59   { 59   {
HITCBC 60   201196 } 60   197521 }
61   61  
  62 + friend detail::bytes_op_base<write_some_awaitable<ConstBufferSequence>>;
  63 + io_write_stream& ios_;
  64 + ConstBufferSequence buffers_;
  65 +
62   std::coroutine_handle<> 66   std::coroutine_handle<>
HITCBC 63   201190 dispatch(std::coroutine_handle<> h, capy::executor_ref ex) const 67   197515 dispatch(std::coroutine_handle<> h, capy::executor_ref ex) const
64   { 68   {
HITCBC 65   402380 return ios_.do_write_some( 69   395030 return ios_.do_write_some(
HITCBC 66   603570 h, ex, buffers_, this->token_, &this->ec_, &this->bytes_); 70   592545 h, ex, buffers_, this->token_, &this->ec_, &this->bytes_);
67   } 71   }
68   }; 72   };
69   73  
70   /** Dispatch a write through the concrete implementation. 74   /** Dispatch a write through the concrete implementation.
71   75  
72   @param h Coroutine handle to resume on completion. 76   @param h Coroutine handle to resume on completion.
73   @param ex Executor for dispatching the completion. 77   @param ex Executor for dispatching the completion.
74   @param buffers Source buffer sequence. 78   @param buffers Source buffer sequence.
75   @param token Stop token for cancellation. 79   @param token Stop token for cancellation.
76   @param ec Output error code. 80   @param ec Output error code.
77   @param bytes Output bytes transferred. 81   @param bytes Output bytes transferred.
78   82  
79   @return Coroutine handle to resume immediately. 83   @return Coroutine handle to resume immediately.
80   */ 84   */
81   virtual std::coroutine_handle<> do_write_some( 85   virtual std::coroutine_handle<> do_write_some(
82 - std::coroutine_handle<>, 86 + std::coroutine_handle<> h,
83 - capy::executor_ref, 87 + capy::executor_ref ex,
84 - buffer_param, 88 + buffer_param buffers,
85 - std::stop_token, 89 + std::stop_token token,
86 - std::error_code*, 90 + std::error_code* ec,
87 - std::size_t*) = 0; 91 + std::size_t* bytes) = 0;
88   92  
  93 + /// Default construct; the handle is supplied through @ref io_object.
HITCBC 89   10088 io_write_stream() noexcept = default; 94   7142 io_write_stream() noexcept = default;
90   95  
91 - io_write_stream(io_write_stream&&) noexcept = default; 96 + /// Move construct; the handle moves with @ref io_object.
  97 + io_write_stream(io_write_stream&&) noexcept = default;
  98 + /// Move assignment is disabled; reseating a live stream is not supported.
92   io_write_stream& operator=(io_write_stream&&) noexcept = delete; 99   io_write_stream& operator=(io_write_stream&&) noexcept = delete;
93 - io_write_stream(io_write_stream const&) = delete; 100 + /// Copy construction is disabled; the handle is uniquely owned.
94 - io_write_stream& operator=(io_write_stream const&) = delete; 101 + io_write_stream(io_write_stream const&) = delete;
  102 + /// Copy assignment is disabled; the handle is uniquely owned.
  103 + io_write_stream& operator=(io_write_stream const&) = delete;
95   104  
96   public: 105   public:
97   /** Asynchronously write data to the stream. 106   /** Asynchronously write data to the stream.
98   107  
99   Suspends the calling coroutine and initiates a kernel-level 108   Suspends the calling coroutine and initiates a kernel-level
100   write. The coroutine resumes when at least one byte is written, 109   write. The coroutine resumes when at least one byte is written,
101   an error occurs, or the operation is cancelled. 110   an error occurs, or the operation is cancelled.
102   111  
103   This stream must outlive the returned awaitable. The memory 112   This stream must outlive the returned awaitable. The memory
104   referenced by @p buffers must remain valid until the operation 113   referenced by @p buffers must remain valid until the operation
105   completes. 114   completes.
106   115  
107   A closed stream completes with `errc::bad_file_descriptor`. 116   A closed stream completes with `errc::bad_file_descriptor`.
108   117  
109   @param buffers The buffer sequence containing data to write. 118   @param buffers The buffer sequence containing data to write.
110   119  
111   @return An awaitable yielding `(error_code, std::size_t)`. 120   @return An awaitable yielding `(error_code, std::size_t)`.
112   121  
113   @see io_stream::read_some 122   @see io_stream::read_some
114   */ 123   */
115   template<capy::ConstBufferSequence CB> 124   template<capy::ConstBufferSequence CB>
HITCBC 116   201196 [[nodiscard]] auto write_some(CB const& buffers) 125   197521 [[nodiscard]] auto write_some(CB const& buffers)
117   { 126   {
HITCBC 118   201196 return write_some_awaitable<CB>(*this, buffers); 127   197521 return write_some_awaitable<CB>(*this, buffers);
119   } 128   }
120   }; 129   };
121   130  
122   } // namespace boost::corosio 131   } // namespace boost::corosio
123   132  
124   #endif 133   #endif