. /include/boost/corosio /random_access_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_RANDOM_ACCESS_FILE_HPP 10   #ifndef BOOST_COROSIO_RANDOM_ACCESS_FILE_HPP
11   #define BOOST_COROSIO_RANDOM_ACCESS_FILE_HPP 11   #define BOOST_COROSIO_RANDOM_ACCESS_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/detail/buffer_param.hpp> 17   #include <boost/corosio/detail/buffer_param.hpp>
18   #include <boost/corosio/file_base.hpp> 18   #include <boost/corosio/file_base.hpp>
19   #include <boost/corosio/io/io_object.hpp> 19   #include <boost/corosio/io/io_object.hpp>
20   #include <boost/capy/io_result.hpp> 20   #include <boost/capy/io_result.hpp>
21   #include <boost/capy/ex/executor_ref.hpp> 21   #include <boost/capy/ex/executor_ref.hpp>
22   #include <boost/capy/ex/execution_context.hpp> 22   #include <boost/capy/ex/execution_context.hpp>
23   #include <boost/capy/ex/io_env.hpp> 23   #include <boost/capy/ex/io_env.hpp>
24   #include <boost/capy/concept/executor.hpp> 24   #include <boost/capy/concept/executor.hpp>
25   #include <boost/capy/buffers.hpp> 25   #include <boost/capy/buffers.hpp>
26   26  
27   #include <concepts> 27   #include <concepts>
28   #include <coroutine> 28   #include <coroutine>
29   #include <cstddef> 29   #include <cstddef>
30   #include <cstdint> 30   #include <cstdint>
31   #include <type_traits> 31   #include <type_traits>
32   #include <filesystem> 32   #include <filesystem>
33   #include <stop_token> 33   #include <stop_token>
34   #include <system_error> 34   #include <system_error>
35   35  
36   namespace boost::corosio { 36   namespace boost::corosio {
37   37  
38   /** An asynchronous random-access file for coroutine I/O. 38   /** An asynchronous random-access file for coroutine I/O.
39   39  
40   Provides asynchronous read and write operations at explicit 40   Provides asynchronous read and write operations at explicit
41   byte offsets, without maintaining an implicit file position. 41   byte offsets, without maintaining an implicit file position.
42   42  
43   On POSIX platforms, file I/O is dispatched to a thread pool 43   On POSIX platforms, file I/O is dispatched to a thread pool
44   (blocking `preadv`/`pwritev`) with completion posted back to 44   (blocking `preadv`/`pwritev`) with completion posted back to
45   the scheduler. On Windows, true overlapped I/O is used via IOCP. 45   the scheduler. On Windows, true overlapped I/O is used via IOCP.
46   46  
47   @par Thread Safety 47   @par Thread Safety
48   Distinct objects: Safe.@n 48   Distinct objects: Safe.@n
49   Shared objects: Unsafe. Multiple concurrent reads and writes 49   Shared objects: Unsafe. Multiple concurrent reads and writes
50   are supported from coroutines sharing the same file object, 50   are supported from coroutines sharing the same file object,
51   but external synchronization is required for non-async 51   but external synchronization is required for non-async
52   operations (open, close, size, resize, etc.). 52   operations (open, close, size, resize, etc.).
53   53  
54   @par Example 54   @par Example
55   @par !example random_access_file 55   @par !example random_access_file
56   */ 56   */
57   class BOOST_COROSIO_DECL random_access_file : public io_object 57   class BOOST_COROSIO_DECL random_access_file : public io_object
58   { 58   {
59   public: 59   public:
60   /** Platform-specific random-access file implementation interface. 60   /** Platform-specific random-access file implementation interface.
61   61  
62   Backends derive from this to provide offset-based file I/O. 62   Backends derive from this to provide offset-based file I/O.
63   */ 63   */
64   struct implementation : io_object::implementation 64   struct implementation : io_object::implementation
65   { 65   {
66   /** Initiate a read at the given offset. 66   /** Initiate a read at the given offset.
67   67  
68   @param offset Byte offset into the file. 68   @param offset Byte offset into the file.
69   @param h Coroutine handle to resume on completion. 69   @param h Coroutine handle to resume on completion.
70   @param ex Executor for dispatching the completion. 70   @param ex Executor for dispatching the completion.
71   @param buf The buffer to read into. 71   @param buf The buffer to read into.
72   @param token Stop token for cancellation. 72   @param token Stop token for cancellation.
73   @param ec Output error code. 73   @param ec Output error code.
74   @param bytes_out Output bytes transferred. 74   @param bytes_out Output bytes transferred.
75   @return Coroutine handle to resume immediately. 75   @return Coroutine handle to resume immediately.
76   */ 76   */
77   virtual std::coroutine_handle<> read_some_at( 77   virtual std::coroutine_handle<> read_some_at(
78   std::uint64_t offset, 78   std::uint64_t offset,
79   std::coroutine_handle<> h, 79   std::coroutine_handle<> h,
80   capy::executor_ref ex, 80   capy::executor_ref ex,
81   buffer_param buf, 81   buffer_param buf,
82   std::stop_token token, 82   std::stop_token token,
83   std::error_code* ec, 83   std::error_code* ec,
84   std::size_t* bytes_out) = 0; 84   std::size_t* bytes_out) = 0;
85   85  
86   /** Initiate a write at the given offset. 86   /** Initiate a write at the given offset.
87   87  
88   @param offset Byte offset into the file. 88   @param offset Byte offset into the file.
89   @param h Coroutine handle to resume on completion. 89   @param h Coroutine handle to resume on completion.
90   @param ex Executor for dispatching the completion. 90   @param ex Executor for dispatching the completion.
91   @param buf The buffer to write from. 91   @param buf The buffer to write from.
92   @param token Stop token for cancellation. 92   @param token Stop token for cancellation.
93   @param ec Output error code. 93   @param ec Output error code.
94   @param bytes_out Output bytes transferred. 94   @param bytes_out Output bytes transferred.
95   @return Coroutine handle to resume immediately. 95   @return Coroutine handle to resume immediately.
96   */ 96   */
97   virtual std::coroutine_handle<> write_some_at( 97   virtual std::coroutine_handle<> write_some_at(
98   std::uint64_t offset, 98   std::uint64_t offset,
99   std::coroutine_handle<> h, 99   std::coroutine_handle<> h,
100   capy::executor_ref ex, 100   capy::executor_ref ex,
101   buffer_param buf, 101   buffer_param buf,
102   std::stop_token token, 102   std::stop_token token,
103   std::error_code* ec, 103   std::error_code* ec,
104   std::size_t* bytes_out) = 0; 104   std::size_t* bytes_out) = 0;
105   105  
106   /// Return the platform file descriptor or handle. 106   /// Return the platform file descriptor or handle.
107   virtual native_handle_type native_handle() const noexcept = 0; 107   virtual native_handle_type native_handle() const noexcept = 0;
108   108  
109   /// Cancel pending asynchronous operations. 109   /// Cancel pending asynchronous operations.
110   virtual void cancel() noexcept = 0; 110   virtual void cancel() noexcept = 0;
111   111  
112   /// Return the file size in bytes. 112   /// Return the file size in bytes.
113   virtual std::uint64_t size() const = 0; 113   virtual std::uint64_t size() const = 0;
114   114  
115   /// Resize the file to @p new_size bytes. 115   /// Resize the file to @p new_size bytes.
116   virtual std::error_code resize(std::uint64_t new_size) noexcept = 0; 116   virtual std::error_code resize(std::uint64_t new_size) noexcept = 0;
117   117  
118   /// Synchronize file data to stable storage. 118   /// Synchronize file data to stable storage.
119   virtual std::error_code sync_data() noexcept = 0; 119   virtual std::error_code sync_data() noexcept = 0;
120   120  
121   /// Synchronize file data and metadata to stable storage. 121   /// Synchronize file data and metadata to stable storage.
122   virtual std::error_code sync_all() noexcept = 0; 122   virtual std::error_code sync_all() noexcept = 0;
123   123  
124   /// Release ownership of the native handle. 124   /// Release ownership of the native handle.
125   virtual native_handle_type release() = 0; 125   virtual native_handle_type release() = 0;
126   126  
127   /// Adopt an existing native handle. 127   /// Adopt an existing native handle.
128   virtual std::error_code assign(native_handle_type handle) noexcept = 0; 128   virtual std::error_code assign(native_handle_type handle) noexcept = 0;
129   }; 129   };
130   130  
131   /** Awaitable for async read-at operations. */ 131   /** Awaitable for async read-at operations. */
132   template<class MutableBufferSequence> 132   template<class MutableBufferSequence>
133   struct read_some_at_awaitable 133   struct read_some_at_awaitable
134   { 134   {
135   random_access_file& f_; 135   random_access_file& f_;
136   std::uint64_t offset_; 136   std::uint64_t offset_;
137   MutableBufferSequence buffers_; 137   MutableBufferSequence buffers_;
138   std::stop_token token_; 138   std::stop_token token_;
139   mutable std::error_code ec_; 139   mutable std::error_code ec_;
140   mutable std::size_t bytes_ = 0; 140   mutable std::size_t bytes_ = 0;
141   141  
HITCBC 142   293 read_some_at_awaitable( 142   293 read_some_at_awaitable(
143   random_access_file& f, 143   random_access_file& f,
144   std::uint64_t offset, 144   std::uint64_t offset,
145   MutableBufferSequence 145   MutableBufferSequence
146   buffers) noexcept(std:: 146   buffers) noexcept(std::
147   is_nothrow_move_constructible_v< 147   is_nothrow_move_constructible_v<
148   MutableBufferSequence>) 148   MutableBufferSequence>)
HITCBC 149   293 : f_(f) 149   293 : f_(f)
HITCBC 150   293 , offset_(offset) 150   293 , offset_(offset)
HITCBC 151   293 , buffers_(std::move(buffers)) 151   293 , buffers_(std::move(buffers))
152   { 152   {
HITCBC 153   293 } 153   293 }
154   154  
HITCBC 155   293 bool await_ready() const noexcept 155   293 bool await_ready() const noexcept
156   { 156   {
157   // A pre-set ec_ means the initiator failed before 157   // A pre-set ec_ means the initiator failed before
158   // dispatch (e.g. a closed object). 158   // dispatch (e.g. a closed object).
HITCBC 159   293 return static_cast<bool>(ec_) || token_.stop_requested(); 159   293 return static_cast<bool>(ec_) || token_.stop_requested();
160   } 160   }
161   161  
HITCBC 162   291 [[nodiscard]] capy::io_result<std::size_t> await_resume() const noexcept 162   291 [[nodiscard]] capy::io_result<std::size_t> await_resume() const noexcept
163   { 163   {
HITCBC 164   291 if (token_.stop_requested()) 164   291 if (token_.stop_requested())
HITCBC 165   4 return {make_error_code(std::errc::operation_canceled), 0}; 165   4 return {make_error_code(std::errc::operation_canceled), 0};
HITCBC 166   287 return {ec_, bytes_}; 166   287 return {ec_, bytes_};
167   } 167   }
168   168  
HITCBC 169   291 auto await_suspend(std::coroutine_handle<> h, capy::io_env const* env) 169   291 auto await_suspend(std::coroutine_handle<> h, capy::io_env const* env)
170   -> std::coroutine_handle<> 170   -> std::coroutine_handle<>
171   { 171   {
HITCBC 172   291 token_ = env->stop_token; 172   291 token_ = env->stop_token;
HITCBC 173   873 return f_.get().read_some_at( 173   873 return f_.get().read_some_at(
HITCBC 174   873 offset_, h, env->executor, buffers_, token_, &ec_, &bytes_); 174   873 offset_, h, env->executor, buffers_, token_, &ec_, &bytes_);
175   } 175   }
176   }; 176   };
177   177  
178   /** Awaitable for async write-at operations. */ 178   /** Awaitable for async write-at operations. */
179   template<class ConstBufferSequence> 179   template<class ConstBufferSequence>
180   struct write_some_at_awaitable 180   struct write_some_at_awaitable
181   { 181   {
182   random_access_file& f_; 182   random_access_file& f_;
183   std::uint64_t offset_; 183   std::uint64_t offset_;
184   ConstBufferSequence buffers_; 184   ConstBufferSequence buffers_;
185   std::stop_token token_; 185   std::stop_token token_;
186   mutable std::error_code ec_; 186   mutable std::error_code ec_;
187   mutable std::size_t bytes_ = 0; 187   mutable std::size_t bytes_ = 0;
188   188  
HITCBC 189   43 write_some_at_awaitable( 189   43 write_some_at_awaitable(
190   random_access_file& f, 190   random_access_file& f,
191   std::uint64_t offset, 191   std::uint64_t offset,
192   ConstBufferSequence 192   ConstBufferSequence
193   buffers) noexcept(std:: 193   buffers) noexcept(std::
194   is_nothrow_move_constructible_v< 194   is_nothrow_move_constructible_v<
195   ConstBufferSequence>) 195   ConstBufferSequence>)
HITCBC 196   43 : f_(f) 196   43 : f_(f)
HITCBC 197   43 , offset_(offset) 197   43 , offset_(offset)
HITCBC 198   43 , buffers_(std::move(buffers)) 198   43 , buffers_(std::move(buffers))
199   { 199   {
HITCBC 200   43 } 200   43 }
201   201  
HITCBC 202   43 bool await_ready() const noexcept 202   43 bool await_ready() const noexcept
203   { 203   {
204   // A pre-set ec_ means the initiator failed before 204   // A pre-set ec_ means the initiator failed before
205   // dispatch (e.g. a closed object). 205   // dispatch (e.g. a closed object).
HITCBC 206   43 return static_cast<bool>(ec_) || token_.stop_requested(); 206   43 return static_cast<bool>(ec_) || token_.stop_requested();
207   } 207   }
208   208  
HITCBC 209   43 [[nodiscard]] capy::io_result<std::size_t> await_resume() const noexcept 209   43 [[nodiscard]] capy::io_result<std::size_t> await_resume() const noexcept
210   { 210   {
HITCBC 211   43 if (token_.stop_requested()) 211   43 if (token_.stop_requested())
HITCBC 212   2 return {make_error_code(std::errc::operation_canceled), 0}; 212   2 return {make_error_code(std::errc::operation_canceled), 0};
HITCBC 213   41 return {ec_, bytes_}; 213   41 return {ec_, bytes_};
214   } 214   }
215   215  
HITCBC 216   41 auto await_suspend(std::coroutine_handle<> h, capy::io_env const* env) 216   41 auto await_suspend(std::coroutine_handle<> h, capy::io_env const* env)
217   -> std::coroutine_handle<> 217   -> std::coroutine_handle<>
218   { 218   {
HITCBC 219   41 token_ = env->stop_token; 219   41 token_ = env->stop_token;
HITCBC 220   123 return f_.get().write_some_at( 220   123 return f_.get().write_some_at(
HITCBC 221   123 offset_, h, env->executor, buffers_, token_, &ec_, &bytes_); 221   123 offset_, h, env->executor, buffers_, token_, &ec_, &bytes_);
222   } 222   }
223   }; 223   };
224   224  
225   public: 225   public:
226   /** Destructor. 226   /** Destructor.
227   227  
228   Closes the file if open, cancelling any pending operations. 228   Closes the file if open, cancelling any pending operations.
229   */ 229   */
230   ~random_access_file() override; 230   ~random_access_file() override;
231   231  
232   /** Construct from an execution context. 232   /** Construct from an execution context.
233   233  
234   @param ctx The execution context that will own this file. 234   @param ctx The execution context that will own this file.
235   */ 235   */
236   explicit random_access_file(capy::execution_context& ctx); 236   explicit random_access_file(capy::execution_context& ctx);
237   237  
238   /** Construct from an executor. 238   /** Construct from an executor.
239   239  
240   @param ex The executor whose context will own this file. 240   @param ex The executor whose context will own this file.
241   */ 241   */
242   template<class Ex> 242   template<class Ex>
243   requires(!std::same_as<std::remove_cvref_t<Ex>, random_access_file>) && 243   requires(!std::same_as<std::remove_cvref_t<Ex>, random_access_file>) &&
244   capy::Executor<Ex> 244   capy::Executor<Ex>
HITCBC 245   2 explicit random_access_file(Ex const& ex) : random_access_file(ex.context()) 245   2 explicit random_access_file(Ex const& ex) : random_access_file(ex.context())
246   { 246   {
HITCBC 247   2 } 247   2 }
248   248  
249   /** Move constructor. */ 249   /** Move constructor. */
HITCBC 250   2 random_access_file(random_access_file&& other) noexcept 250   2 random_access_file(random_access_file&& other) noexcept
HITCBC 251   2 : io_object(std::move(other)) 251   2 : io_object(std::move(other))
252   { 252   {
HITCBC 253   2 } 253   2 }
254   254  
255   /** Move assignment operator. */ 255   /** Move assignment operator. */
256   random_access_file& operator=(random_access_file&& other) noexcept 256   random_access_file& operator=(random_access_file&& other) noexcept
257   { 257   {
258   if (this != &other) 258   if (this != &other)
259   { 259   {
260   close(); 260   close();
261   h_ = std::move(other.h_); 261   h_ = std::move(other.h_);
262   } 262   }
263   return *this; 263   return *this;
264   } 264   }
265   265  
266   random_access_file(random_access_file const&) = delete; 266   random_access_file(random_access_file const&) = delete;
267   random_access_file& operator=(random_access_file const&) = delete; 267   random_access_file& operator=(random_access_file const&) = delete;
268   268  
269   /** Open a file. 269   /** Open a file.
270   270  
271   Failures such as a missing file or insufficient permissions 271   Failures such as a missing file or insufficient permissions
272   are expected runtime conditions and are reported through the 272   are expected runtime conditions and are reported through the
273   returned error code. If the file is already open, it is 273   returned error code. If the file is already open, it is
274   closed first. 274   closed first.
275   275  
276   @param path The filesystem path to open. 276   @param path The filesystem path to open.
277   @param mode Bitmask of @ref file_base::flags specifying 277   @param mode Bitmask of @ref file_base::flags specifying
278   access mode and creation behavior. 278   access mode and creation behavior.
279   279  
280   @return The error code, empty on success. 280   @return The error code, empty on success.
281   */ 281   */
282   [[nodiscard]] std::error_code open( 282   [[nodiscard]] std::error_code open(
283   std::filesystem::path const& path, 283   std::filesystem::path const& path,
284   file_base::flags mode = file_base::read_only) noexcept; 284   file_base::flags mode = file_base::read_only) noexcept;
285   285  
286   /** Close the file. 286   /** Close the file.
287   287  
288   Releases file resources. Any pending operations complete 288   Releases file resources. Any pending operations complete
289   with `errc::operation_canceled`. 289   with `errc::operation_canceled`.
290   */ 290   */
291   void close() noexcept; 291   void close() noexcept;
292   292  
293   /** Check if the file is open. */ 293   /** Check if the file is open. */
HITCBC 294   682 bool is_open() const noexcept 294   682 bool is_open() const noexcept
295   { 295   {
296   #if BOOST_COROSIO_HAS_IOCP && !defined(BOOST_COROSIO_MRDOCS) 296   #if BOOST_COROSIO_HAS_IOCP && !defined(BOOST_COROSIO_MRDOCS)
297   return h_ && get().native_handle() != ~native_handle_type(0); 297   return h_ && get().native_handle() != ~native_handle_type(0);
298   #else 298   #else
HITCBC 299   682 return h_ && get().native_handle() >= 0; 299   682 return h_ && get().native_handle() >= 0;
300   #endif 300   #endif
301   } 301   }
302   302  
303   /** Read data at the given offset. 303   /** Read data at the given offset.
304   304  
305   @param offset Byte offset into the file. 305   @param offset Byte offset into the file.
306   @param buffers The buffer sequence to read into. 306   @param buffers The buffer sequence to read into.
307   307  
308   @return An awaitable yielding `(error_code, std::size_t)`. 308   @return An awaitable yielding `(error_code, std::size_t)`.
309   309  
310   A closed file reports `errc::bad_file_descriptor`. 310   A closed file reports `errc::bad_file_descriptor`.
311   */ 311   */
312   template<capy::MutableBufferSequence MB> 312   template<capy::MutableBufferSequence MB>
HITCBC 313   293 [[nodiscard]] auto read_some_at(std::uint64_t offset, MB const& buffers) 313   293 [[nodiscard]] auto read_some_at(std::uint64_t offset, MB const& buffers)
314   { 314   {
HITCBC 315   293 read_some_at_awaitable<MB> aw(*this, offset, buffers); 315   293 read_some_at_awaitable<MB> aw(*this, offset, buffers);
HITCBC 316   293 if (!is_open()) 316   293 if (!is_open())
HITCBC 317   2 aw.ec_ = make_error_code(std::errc::bad_file_descriptor); 317   2 aw.ec_ = make_error_code(std::errc::bad_file_descriptor);
HITCBC 318   293 return aw; 318   293 return aw;
319   } 319   }
320   320  
321   /** Write data at the given offset. 321   /** Write data at the given offset.
322   322  
323   @param offset Byte offset into the file. 323   @param offset Byte offset into the file.
324   @param buffers The buffer sequence to write from. 324   @param buffers The buffer sequence to write from.
325   325  
326   @return An awaitable yielding `(error_code, std::size_t)`. 326   @return An awaitable yielding `(error_code, std::size_t)`.
327   327  
328   A closed file reports `errc::bad_file_descriptor`. 328   A closed file reports `errc::bad_file_descriptor`.
329   */ 329   */
330   template<capy::ConstBufferSequence CB> 330   template<capy::ConstBufferSequence CB>
HITCBC 331   43 [[nodiscard]] auto write_some_at(std::uint64_t offset, CB const& buffers) 331   43 [[nodiscard]] auto write_some_at(std::uint64_t offset, CB const& buffers)
332   { 332   {
HITCBC 333   43 write_some_at_awaitable<CB> aw(*this, offset, buffers); 333   43 write_some_at_awaitable<CB> aw(*this, offset, buffers);
HITCBC 334   43 if (!is_open()) 334   43 if (!is_open())
HITCBC 335   2 aw.ec_ = make_error_code(std::errc::bad_file_descriptor); 335   2 aw.ec_ = make_error_code(std::errc::bad_file_descriptor);
HITCBC 336   43 return aw; 336   43 return aw;
337   } 337   }
338   338  
339   /** Cancel pending asynchronous operations. */ 339   /** Cancel pending asynchronous operations. */
340   void cancel() noexcept; 340   void cancel() noexcept;
341   341  
342   /** Get the native file descriptor or handle. */ 342   /** Get the native file descriptor or handle. */
343   native_handle_type native_handle() const noexcept; 343   native_handle_type native_handle() const noexcept;
344   344  
345   /** Return the file size in bytes. 345   /** Return the file size in bytes.
346   346  
347   @throws std::system_error If the file is not open, or if the 347   @throws std::system_error If the file is not open, or if the
348   underlying size query fails. 348   underlying size query fails.
349   */ 349   */
350   std::uint64_t size() const; 350   std::uint64_t size() const;
351   351  
352   /** Resize the file to @p new_size bytes. 352   /** Resize the file to @p new_size bytes.
353   353  
354   Failures such as insufficient disk space are reported 354   Failures such as insufficient disk space are reported
355   through the returned error code. A closed file reports 355   through the returned error code. A closed file reports
356   `errc::bad_file_descriptor`. 356   `errc::bad_file_descriptor`.
357   357  
358   @param new_size The new file size. 358   @param new_size The new file size.
359   359  
360   @return The error code, empty on success. 360   @return The error code, empty on success.
361   */ 361   */
362   [[nodiscard]] std::error_code resize(std::uint64_t new_size) noexcept; 362   [[nodiscard]] std::error_code resize(std::uint64_t new_size) noexcept;
363   363  
364   /** Synchronize file data to stable storage. 364   /** Synchronize file data to stable storage.
365   365  
366   Write-back failures such as device I/O errors surface here 366   Write-back failures such as device I/O errors surface here
367   and are reported through the returned error code. A closed 367   and are reported through the returned error code. A closed
368   file reports `errc::bad_file_descriptor`. 368   file reports `errc::bad_file_descriptor`.
369   369  
370   @return The error code, empty on success. 370   @return The error code, empty on success.
371   */ 371   */
372   [[nodiscard]] std::error_code sync_data() noexcept; 372   [[nodiscard]] std::error_code sync_data() noexcept;
373   373  
374   /** Synchronize file data and metadata to stable storage. 374   /** Synchronize file data and metadata to stable storage.
375   375  
376   Write-back failures such as device I/O errors surface here 376   Write-back failures such as device I/O errors surface here
377   and are reported through the returned error code. A closed 377   and are reported through the returned error code. A closed
378   file reports `errc::bad_file_descriptor`. 378   file reports `errc::bad_file_descriptor`.
379   379  
380   @return The error code, empty on success. 380   @return The error code, empty on success.
381   */ 381   */
382   [[nodiscard]] std::error_code sync_all() noexcept; 382   [[nodiscard]] std::error_code sync_all() noexcept;
383   383  
384   /** Release ownership of the native handle. 384   /** Release ownership of the native handle.
385   385  
386   The file object becomes not-open. The caller is 386   The file object becomes not-open. The caller is
387   responsible for closing the returned handle. 387   responsible for closing the returned handle.
388   388  
389   @return The native file descriptor or handle. 389   @return The native file descriptor or handle.
390   390  
391   @throws std::system_error `errc::bad_file_descriptor` if the 391   @throws std::system_error `errc::bad_file_descriptor` if the
392   file is not open. 392   file is not open.
393   */ 393   */
394   native_handle_type release(); 394   native_handle_type release();
395   395  
396   /** Adopt an existing native handle. 396   /** Adopt an existing native handle.
397   397  
398   Closes any currently open file before adopting. 398   Closes any currently open file before adopting.
399   The file object takes ownership of the handle. Handles 399   The file object takes ownership of the handle. Handles
400   created elsewhere may be unsuitable for asynchronous I/O; 400   created elsewhere may be unsuitable for asynchronous I/O;
401   such failures are reported through the returned error code. 401   such failures are reported through the returned error code.
402   402  
403   @param handle The native file descriptor or handle. 403   @param handle The native file descriptor or handle.
404   404  
405   @return The error code, empty on success. 405   @return The error code, empty on success.
406   */ 406   */
407   [[nodiscard]] std::error_code assign(native_handle_type handle) noexcept; 407   [[nodiscard]] std::error_code assign(native_handle_type handle) noexcept;
408   408  
409   protected: 409   protected:
410   /// Construct from a pre-built handle (for native_random_access_file). 410   /// Construct from a pre-built handle (for native_random_access_file).
HITCBC 411   16 explicit random_access_file(handle h) noexcept : io_object(std::move(h)) {} 411   16 explicit random_access_file(handle h) noexcept : io_object(std::move(h)) {}
412   412  
413   private: 413   private:
HITCBC 414   1171 inline implementation& get() const noexcept 414   1171 inline implementation& get() const noexcept
415   { 415   {
HITCBC 416   1171 return *static_cast<implementation*>(h_.get()); 416   1171 return *static_cast<implementation*>(h_.get());
417   } 417   }
418   }; 418   };
419   419  
420   } // namespace boost::corosio 420   } // namespace boost::corosio
421   421  
422   #endif // BOOST_COROSIO_RANDOM_ACCESS_FILE_HPP 422   #endif // BOOST_COROSIO_RANDOM_ACCESS_FILE_HPP