. /include/boost/corosio /stream_file.hpp
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1   // 1   //
2   // Copyright (c) 2026 Michael Vandeberg 2   // Copyright (c) 2026 Michael Vandeberg
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_STREAM_FILE_HPP 10   #ifndef BOOST_COROSIO_STREAM_FILE_HPP
11   #define BOOST_COROSIO_STREAM_FILE_HPP 11   #define BOOST_COROSIO_STREAM_FILE_HPP
12   12  
13   #include <boost/corosio/detail/config.hpp> 13   #include <boost/corosio/detail/config.hpp>
14   #include <boost/corosio/detail/platform.hpp> 14   #include <boost/corosio/detail/platform.hpp>
15   #include <boost/corosio/detail/except.hpp> 15   #include <boost/corosio/detail/except.hpp>
16   #include <boost/corosio/detail/native_handle.hpp> 16   #include <boost/corosio/detail/native_handle.hpp>
17   #include <boost/corosio/file_base.hpp> 17   #include <boost/corosio/file_base.hpp>
18   #include <boost/corosio/io/io_stream.hpp> 18   #include <boost/corosio/io/io_stream.hpp>
19   #include <boost/capy/ex/execution_context.hpp> 19   #include <boost/capy/ex/execution_context.hpp>
20   #include <boost/capy/concept/executor.hpp> 20   #include <boost/capy/concept/executor.hpp>
21   #include <boost/capy/io_result.hpp> 21   #include <boost/capy/io_result.hpp>
22   22  
23   #include <concepts> 23   #include <concepts>
24   #include <cstdint> 24   #include <cstdint>
25   #include <filesystem> 25   #include <filesystem>
26   #include <system_error> 26   #include <system_error>
27   27  
28   namespace boost::corosio { 28   namespace boost::corosio {
29   29  
30 - /** Reads and writes a file sequentially, from a coroutine. 30 + /** An asynchronous sequential file for coroutine I/O.
31   31  
32   Provides asynchronous read and write operations on a regular 32   Provides asynchronous read and write operations on a regular
33   file with an implicit position that advances after each 33   file with an implicit position that advances after each
34   operation. 34   operation.
35   35  
36   Inherits from @ref io_stream, so `read_some` and `write_some` 36   Inherits from @ref io_stream, so `read_some` and `write_some`
37   are available and work with any algorithm that accepts an 37   are available and work with any algorithm that accepts an
38   `io_stream&`. 38   `io_stream&`.
39   39  
40   On POSIX platforms, file I/O is dispatched to a thread pool 40   On POSIX platforms, file I/O is dispatched to a thread pool
41   (blocking `preadv`/`pwritev`) with completion posted back to 41   (blocking `preadv`/`pwritev`) with completion posted back to
42   the scheduler. On Windows, true overlapped I/O is used via IOCP. 42   the scheduler. On Windows, true overlapped I/O is used via IOCP.
43   43  
44   @par Thread Safety 44   @par Thread Safety
45   Distinct objects: Safe.@n 45   Distinct objects: Safe.@n
46   Shared objects: Unsafe. Only one asynchronous operation 46   Shared objects: Unsafe. Only one asynchronous operation
47   may be in flight at a time. 47   may be in flight at a time.
48   48  
49   @par Example 49   @par Example
50   @par !example stream_file 50   @par !example stream_file
51   */ 51   */
52   class BOOST_COROSIO_DECL stream_file : public io_stream 52   class BOOST_COROSIO_DECL stream_file : public io_stream
53   { 53   {
54   public: 54   public:
55 - /** Defines the file operations a platform backend implements. 55 + /** Platform-specific file implementation interface.
56   56  
57   Backends derive from this to provide file I/O. 57   Backends derive from this to provide file I/O.
58   `read_some` and `write_some` are inherited from 58   `read_some` and `write_some` are inherited from
59   @ref io_stream::implementation. 59   @ref io_stream::implementation.
60   */ 60   */
61   struct implementation : io_stream::implementation 61   struct implementation : io_stream::implementation
62   { 62   {
63   /// Return the platform file descriptor or handle. 63   /// Return the platform file descriptor or handle.
64   virtual native_handle_type native_handle() const noexcept = 0; 64   virtual native_handle_type native_handle() const noexcept = 0;
65   65  
66   /// Cancel pending asynchronous operations. 66   /// Cancel pending asynchronous operations.
67   virtual void cancel() noexcept = 0; 67   virtual void cancel() noexcept = 0;
68   68  
69 - /** Return the file size in bytes. 69 + /// Return the file size in bytes.
70 -  
71 - @return The current size of the file, in bytes.  
72 -  
73 - @throws std::system_error if the underlying size query fails.  
74 - */  
75   virtual std::uint64_t size() const = 0; 70   virtual std::uint64_t size() const = 0;
76   71  
77 - /** Resize the file to @p new_size bytes. 72 + /// Resize the file to @p new_size bytes.
78 -  
79 - @param new_size The requested size in bytes.  
80 -  
81 - @return The error code, empty on success.  
82 - */  
83   virtual std::error_code resize(std::uint64_t new_size) noexcept = 0; 73   virtual std::error_code resize(std::uint64_t new_size) noexcept = 0;
84   74  
85 - /** Synchronize file data to stable storage. 75 + /// Synchronize file data to stable storage.
86 -  
87 - @return The error code, empty on success.  
88 - */  
89   virtual std::error_code sync_data() noexcept = 0; 76   virtual std::error_code sync_data() noexcept = 0;
90   77  
91 - /** Synchronize file data and metadata to stable storage. 78 + /// Synchronize file data and metadata to stable storage.
92 -  
93 - @return The error code, empty on success.  
94 - */  
95   virtual std::error_code sync_all() noexcept = 0; 79   virtual std::error_code sync_all() noexcept = 0;
96   80  
97 - /** Release ownership of the native handle. 81 + /// Release ownership of the native handle.
98 -  
99 - @return The native handle, which the caller now owns.  
100 -  
101 - @throws std::system_error if the file is not open.  
102 - */  
103   virtual native_handle_type release() = 0; 82   virtual native_handle_type release() = 0;
104   83  
105 - /** Adopt an existing native handle. 84 + /// Adopt an existing native handle.
106 -  
107 - @param handle The native handle to adopt. The implementation takes  
108 - ownership and closes it.  
109 -  
110 - @return The error code, empty on success.  
111 - */  
112   virtual std::error_code assign(native_handle_type handle) noexcept = 0; 85   virtual std::error_code assign(native_handle_type handle) noexcept = 0;
113   86  
114   /** Move the file position. 87   /** Move the file position.
115   88  
116   @param offset Signed offset from @p origin. 89   @param offset Signed offset from @p origin.
117   @param origin The reference point for the seek. 90   @param origin The reference point for the seek.
118   @return The error code and new absolute position. 91   @return The error code and new absolute position.
119   */ 92   */
120   virtual capy::io_result<std::uint64_t> 93   virtual capy::io_result<std::uint64_t>
121   seek(std::int64_t offset, file_base::seek_basis origin) noexcept = 0; 94   seek(std::int64_t offset, file_base::seek_basis origin) noexcept = 0;
122   }; 95   };
123   96  
124 - /** Closes the file if open, cancelling any pending operations. 97 + /** Destructor.
  98 +
  99 + Closes the file if open, cancelling any pending operations.
125   */ 100   */
126   ~stream_file() override; 101   ~stream_file() override;
127   102  
128   /** Construct from an execution context. 103   /** Construct from an execution context.
129   104  
130 - @param ctx The execution context that owns this file. 105 + @param ctx The execution context that will own this file.
131   */ 106   */
132   explicit stream_file(capy::execution_context& ctx); 107   explicit stream_file(capy::execution_context& ctx);
133   108  
134   /** Construct from an executor. 109   /** Construct from an executor.
135   110  
136 - @param ex The executor whose context owns this file. 111 + @param ex The executor whose context will own this file.
137   */ 112   */
138   template<class Ex> 113   template<class Ex>
139   requires(!std::same_as<std::remove_cvref_t<Ex>, stream_file>) && 114   requires(!std::same_as<std::remove_cvref_t<Ex>, stream_file>) &&
140   capy::Executor<Ex> 115   capy::Executor<Ex>
HITCBC 141   2 explicit stream_file(Ex const& ex) : stream_file(ex.context()) 116   2 explicit stream_file(Ex const& ex) : stream_file(ex.context())
142   { 117   {
HITCBC 143   2 } 118   2 }
144   119  
145 - /** Transfers ownership of the file resources. 120 + /** Move constructor.
  121 +
  122 + Transfers ownership of the file resources.
146   */ 123   */
HITCBC 147   2 stream_file(stream_file&& other) noexcept : io_object(std::move(other)) {} 124   2 stream_file(stream_file&& other) noexcept : io_object(std::move(other)) {}
148   125  
149 - /** Closes any existing file and transfers ownership. 126 + /** Move assignment operator.
150   127  
151 - @return Reference to this object. 128 + Closes any existing file and transfers ownership.
152   */ 129   */
HITCBC 153   2 stream_file& operator=(stream_file&& other) noexcept 130   2 stream_file& operator=(stream_file&& other) noexcept
154   { 131   {
HITCBC 155   2 if (this != &other) 132   2 if (this != &other)
156   { 133   {
HITCBC 157   2 close(); 134   2 close();
HITCBC 158   2 h_ = std::move(other.h_); 135   2 h_ = std::move(other.h_);
159   } 136   }
HITCBC 160   2 return *this; 137   2 return *this;
161   } 138   }
162   139  
163 - /// Copy construction is disabled; the handle is uniquely owned. 140 + stream_file(stream_file const&) = delete;
164 - stream_file(stream_file const&) = delete;  
165 - /// Copy assignment is disabled; the handle is uniquely owned.  
166   stream_file& operator=(stream_file const&) = delete; 141   stream_file& operator=(stream_file const&) = delete;
167   142  
168   // read_some() inherited from io_read_stream 143   // read_some() inherited from io_read_stream
169   // write_some() inherited from io_write_stream 144   // write_some() inherited from io_write_stream
170   145  
171   /** Open a file. 146   /** Open a file.
172   147  
173   Failures such as a missing file or insufficient permissions 148   Failures such as a missing file or insufficient permissions
174   are expected runtime conditions and are reported through the 149   are expected runtime conditions and are reported through the
175   returned error code. If the file is already open, it is 150   returned error code. If the file is already open, it is
176   closed first. 151   closed first.
177   152  
178   @param path The filesystem path to open. 153   @param path The filesystem path to open.
179   @param mode Bitmask of @ref file_base::flags specifying 154   @param mode Bitmask of @ref file_base::flags specifying
180   access mode and creation behavior. 155   access mode and creation behavior.
181   156  
182   @return The error code, empty on success. 157   @return The error code, empty on success.
183   */ 158   */
184   [[nodiscard]] std::error_code open( 159   [[nodiscard]] std::error_code open(
185   std::filesystem::path const& path, 160   std::filesystem::path const& path,
186   file_base::flags mode = file_base::read_only) noexcept; 161   file_base::flags mode = file_base::read_only) noexcept;
187   162  
188   /** Close the file. 163   /** Close the file.
189   164  
190 - Releases file resources. Pending operations complete through the 165 + Releases file resources. Any pending operations complete
191 - same path as @ref cancel: one still in flight completes with 166 + with `errc::operation_canceled`.
192 - `errc::operation_canceled`. An operation whose result is already  
193 - decided reports that result.  
194   */ 167   */
195   void close() noexcept; 168   void close() noexcept;
196   169  
197   /** Check if the file is open. 170   /** Check if the file is open.
198   171  
199   @return `true` if the file is open and ready for I/O. 172   @return `true` if the file is open and ready for I/O.
200   */ 173   */
HITCBC 201   795 bool is_open() const noexcept 174   795 bool is_open() const noexcept
202   { 175   {
203   #if BOOST_COROSIO_HAS_IOCP && !defined(BOOST_COROSIO_MRDOCS) 176   #if BOOST_COROSIO_HAS_IOCP && !defined(BOOST_COROSIO_MRDOCS)
204   return h_ && get().native_handle() != ~native_handle_type(0); 177   return h_ && get().native_handle() != ~native_handle_type(0);
205   #else 178   #else
HITCBC 206   795 return h_ && get().native_handle() >= 0; 179   795 return h_ && get().native_handle() >= 0;
207   #endif 180   #endif
208   } 181   }
209   182  
210   /** Cancel pending asynchronous operations. 183   /** Cancel pending asynchronous operations.
211   184  
212   Operations still in flight complete with 185   Operations still in flight complete with
213   `errc::operation_canceled`; an operation whose result is 186   `errc::operation_canceled`; an operation whose result is
214   already decided reports that result. 187   already decided reports that result.
215   */ 188   */
216   void cancel() noexcept; 189   void cancel() noexcept;
217   190  
218   /** Get the native file descriptor or handle. 191   /** Get the native file descriptor or handle.
219   192  
220   @return The native handle, or -1/INVALID_HANDLE_VALUE 193   @return The native handle, or -1/INVALID_HANDLE_VALUE
221   if not open. 194   if not open.
222   */ 195   */
223   native_handle_type native_handle() const noexcept; 196   native_handle_type native_handle() const noexcept;
224   197  
225   /** Return the file size in bytes. 198   /** Return the file size in bytes.
226 - @return The file size in bytes.  
227 -  
228   199  
229   @throws std::system_error If the file is not open, or if the 200   @throws std::system_error If the file is not open, or if the
230   underlying size query fails. 201   underlying size query fails.
231   */ 202   */
232   std::uint64_t size() const; 203   std::uint64_t size() const;
233   204  
234   /** Resize the file to @p new_size bytes. 205   /** Resize the file to @p new_size bytes.
235   206  
236   Failures such as insufficient disk space are reported 207   Failures such as insufficient disk space are reported
237   through the returned error code. A closed file reports 208   through the returned error code. A closed file reports
238   `errc::bad_file_descriptor`. 209   `errc::bad_file_descriptor`.
239   210  
240   @param new_size The new file size. 211   @param new_size The new file size.
241   212  
242   @return The error code, empty on success. 213   @return The error code, empty on success.
243   */ 214   */
244   [[nodiscard]] std::error_code resize(std::uint64_t new_size) noexcept; 215   [[nodiscard]] std::error_code resize(std::uint64_t new_size) noexcept;
245   216  
246   /** Synchronize file data to stable storage. 217   /** Synchronize file data to stable storage.
247   218  
248   Write-back failures such as device I/O errors surface here 219   Write-back failures such as device I/O errors surface here
249   and are reported through the returned error code. A closed 220   and are reported through the returned error code. A closed
250   file reports `errc::bad_file_descriptor`. 221   file reports `errc::bad_file_descriptor`.
251   222  
252   @return The error code, empty on success. 223   @return The error code, empty on success.
253   */ 224   */
254   [[nodiscard]] std::error_code sync_data() noexcept; 225   [[nodiscard]] std::error_code sync_data() noexcept;
255   226  
256   /** Synchronize file data and metadata to stable storage. 227   /** Synchronize file data and metadata to stable storage.
257   228  
258   Write-back failures such as device I/O errors surface here 229   Write-back failures such as device I/O errors surface here
259   and are reported through the returned error code. A closed 230   and are reported through the returned error code. A closed
260   file reports `errc::bad_file_descriptor`. 231   file reports `errc::bad_file_descriptor`.
261   232  
262   @return The error code, empty on success. 233   @return The error code, empty on success.
263   */ 234   */
264   [[nodiscard]] std::error_code sync_all() noexcept; 235   [[nodiscard]] std::error_code sync_all() noexcept;
265   236  
266   /** Release ownership of the native handle. 237   /** Release ownership of the native handle.
267   238  
268   The file object becomes not-open. The caller is 239   The file object becomes not-open. The caller is
269   responsible for closing the returned handle. 240   responsible for closing the returned handle.
270   241  
271   @return The native file descriptor or handle. 242   @return The native file descriptor or handle.
272   243  
273   @throws std::system_error `errc::bad_file_descriptor` if the 244   @throws std::system_error `errc::bad_file_descriptor` if the
274   file is not open. 245   file is not open.
275   */ 246   */
276   native_handle_type release(); 247   native_handle_type release();
277   248  
278   /** Adopt an existing native handle. 249   /** Adopt an existing native handle.
279   250  
280   Closes any currently open file before adopting. 251   Closes any currently open file before adopting.
281   The file object takes ownership of the handle. Handles 252   The file object takes ownership of the handle. Handles
282 - created elsewhere may be unsuitable for asynchronous I/O. 253 + created elsewhere may be unsuitable for asynchronous I/O;
283 - Such failures are reported through the returned error code. 254 + such failures are reported through the returned error code.
284   255  
285   @param handle The native file descriptor or handle. 256   @param handle The native file descriptor or handle.
286   257  
287   @return The error code, empty on success. 258   @return The error code, empty on success.
288   */ 259   */
289   [[nodiscard]] std::error_code assign(native_handle_type handle) noexcept; 260   [[nodiscard]] std::error_code assign(native_handle_type handle) noexcept;
290   261  
291   /** Move the file position. 262   /** Move the file position.
292   263  
293   Positions beyond the end of the file are allowed. A 264   Positions beyond the end of the file are allowed. A
294   resulting negative position is reported through the error 265   resulting negative position is reported through the error
295   code, as offsets often originate from file contents. A 266   code, as offsets often originate from file contents. A
296   closed file reports `errc::bad_file_descriptor`. 267   closed file reports `errc::bad_file_descriptor`.
297   268  
298   @param offset Signed offset from @p origin. 269   @param offset Signed offset from @p origin.
299   @param origin The reference point for the seek. 270   @param origin The reference point for the seek.
300   271  
301   @return The error code and new absolute position. 272   @return The error code and new absolute position.
302   */ 273   */
303   [[nodiscard]] capy::io_result<std::uint64_t> seek( 274   [[nodiscard]] capy::io_result<std::uint64_t> seek(
304   std::int64_t offset, 275   std::int64_t offset,
305   file_base::seek_basis origin = file_base::seek_set) noexcept; 276   file_base::seek_basis origin = file_base::seek_set) noexcept;
306   277  
307   protected: 278   protected:
308   /// Default-construct (for derived types that initialize io_object directly). 279   /// Default-construct (for derived types that initialize io_object directly).
HITCBC 309   16 stream_file() noexcept = default; 280   16 stream_file() noexcept = default;
310   281  
311 - /** Construct from a pre-built handle (for native_stream_file). 282 + /// Construct from a pre-built handle (for native_stream_file).
312 -  
313 - @param h The pre-built handle to adopt.  
314 - */  
315   explicit stream_file(handle h) noexcept : io_object(std::move(h)) {} 283   explicit stream_file(handle h) noexcept : io_object(std::move(h)) {}
316   284  
317   private: 285   private:
HITCBC 318   1131 inline implementation& get() const noexcept 286   1131 inline implementation& get() const noexcept
319   { 287   {
HITCBC 320   1131 return *static_cast<implementation*>(h_.get()); 288   1131 return *static_cast<implementation*>(h_.get());
321   } 289   }
322   }; 290   };
323   291  
324   } // namespace boost::corosio 292   } // namespace boost::corosio
325   293  
326   #endif // BOOST_COROSIO_STREAM_FILE_HPP 294   #endif // BOOST_COROSIO_STREAM_FILE_HPP