. /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   /** An asynchronous sequential file for coroutine I/O. 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   /** Platform-specific file implementation interface. 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   virtual std::uint64_t size() const = 0; 70   virtual std::uint64_t size() const = 0;
71   71  
72   /// Resize the file to @p new_size bytes. 72   /// Resize the file to @p new_size bytes.
73   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;
74   74  
75   /// Synchronize file data to stable storage. 75   /// Synchronize file data to stable storage.
76   virtual std::error_code sync_data() noexcept = 0; 76   virtual std::error_code sync_data() noexcept = 0;
77   77  
78   /// Synchronize file data and metadata to stable storage. 78   /// Synchronize file data and metadata to stable storage.
79   virtual std::error_code sync_all() noexcept = 0; 79   virtual std::error_code sync_all() noexcept = 0;
80   80  
81   /// Release ownership of the native handle. 81   /// Release ownership of the native handle.
82   virtual native_handle_type release() = 0; 82   virtual native_handle_type release() = 0;
83   83  
84   /// Adopt an existing native handle. 84   /// Adopt an existing native handle.
85   virtual std::error_code assign(native_handle_type handle) noexcept = 0; 85   virtual std::error_code assign(native_handle_type handle) noexcept = 0;
86   86  
87   /** Move the file position. 87   /** Move the file position.
88   88  
89   @param offset Signed offset from @p origin. 89   @param offset Signed offset from @p origin.
90   @param origin The reference point for the seek. 90   @param origin The reference point for the seek.
91   @return The error code and new absolute position. 91   @return The error code and new absolute position.
92   */ 92   */
93   virtual capy::io_result<std::uint64_t> 93   virtual capy::io_result<std::uint64_t>
94   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;
95   }; 95   };
96   96  
97   /** Destructor. 97   /** Destructor.
98   98  
99   Closes the file if open, cancelling any pending operations. 99   Closes the file if open, cancelling any pending operations.
100   */ 100   */
101   ~stream_file() override; 101   ~stream_file() override;
102   102  
103   /** Construct from an execution context. 103   /** Construct from an execution context.
104   104  
105   @param ctx The execution context that will own this file. 105   @param ctx The execution context that will own this file.
106   */ 106   */
107   explicit stream_file(capy::execution_context& ctx); 107   explicit stream_file(capy::execution_context& ctx);
108   108  
109   /** Construct from an executor. 109   /** Construct from an executor.
110   110  
111   @param ex The executor whose context will own this file. 111   @param ex The executor whose context will own this file.
112   */ 112   */
113   template<class Ex> 113   template<class Ex>
114   requires(!std::same_as<std::remove_cvref_t<Ex>, stream_file>) && 114   requires(!std::same_as<std::remove_cvref_t<Ex>, stream_file>) &&
115   capy::Executor<Ex> 115   capy::Executor<Ex>
HITCBC 116   2 explicit stream_file(Ex const& ex) : stream_file(ex.context()) 116   2 explicit stream_file(Ex const& ex) : stream_file(ex.context())
117   { 117   {
HITCBC 118   2 } 118   2 }
119   119  
120   /** Move constructor. 120   /** Move constructor.
121   121  
122   Transfers ownership of the file resources. 122   Transfers ownership of the file resources.
123   */ 123   */
HITCBC 124   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)) {}
125   125  
126   /** Move assignment operator. 126   /** Move assignment operator.
127   127  
128   Closes any existing file and transfers ownership. 128   Closes any existing file and transfers ownership.
129   */ 129   */
HITCBC 130   2 stream_file& operator=(stream_file&& other) noexcept 130   2 stream_file& operator=(stream_file&& other) noexcept
131   { 131   {
HITCBC 132   2 if (this != &other) 132   2 if (this != &other)
133   { 133   {
HITCBC 134   2 close(); 134   2 close();
HITCBC 135   2 h_ = std::move(other.h_); 135   2 h_ = std::move(other.h_);
136   } 136   }
HITCBC 137   2 return *this; 137   2 return *this;
138   } 138   }
139   139  
140   stream_file(stream_file const&) = delete; 140   stream_file(stream_file const&) = delete;
141   stream_file& operator=(stream_file const&) = delete; 141   stream_file& operator=(stream_file const&) = delete;
142   142  
143   // read_some() inherited from io_read_stream 143   // read_some() inherited from io_read_stream
144   // write_some() inherited from io_write_stream 144   // write_some() inherited from io_write_stream
145   145  
146   /** Open a file. 146   /** Open a file.
147   147  
148   Failures such as a missing file or insufficient permissions 148   Failures such as a missing file or insufficient permissions
149   are expected runtime conditions and are reported through the 149   are expected runtime conditions and are reported through the
150   returned error code. If the file is already open, it is 150   returned error code. If the file is already open, it is
151   closed first. 151   closed first.
152   152  
153   @param path The filesystem path to open. 153   @param path The filesystem path to open.
154   @param mode Bitmask of @ref file_base::flags specifying 154   @param mode Bitmask of @ref file_base::flags specifying
155   access mode and creation behavior. 155   access mode and creation behavior.
156   156  
157   @return The error code, empty on success. 157   @return The error code, empty on success.
158   */ 158   */
159   [[nodiscard]] std::error_code open( 159   [[nodiscard]] std::error_code open(
160   std::filesystem::path const& path, 160   std::filesystem::path const& path,
161   file_base::flags mode = file_base::read_only) noexcept; 161   file_base::flags mode = file_base::read_only) noexcept;
162   162  
163   /** Close the file. 163   /** Close the file.
164   164  
165   Releases file resources. Any pending operations complete 165   Releases file resources. Any pending operations complete
166   with `errc::operation_canceled`. 166   with `errc::operation_canceled`.
167   */ 167   */
168   void close() noexcept; 168   void close() noexcept;
169   169  
170   /** Check if the file is open. 170   /** Check if the file is open.
171   171  
172   @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.
173   */ 173   */
HITCBC 174   795 bool is_open() const noexcept 174   795 bool is_open() const noexcept
175   { 175   {
176   #if BOOST_COROSIO_HAS_IOCP && !defined(BOOST_COROSIO_MRDOCS) 176   #if BOOST_COROSIO_HAS_IOCP && !defined(BOOST_COROSIO_MRDOCS)
177   return h_ && get().native_handle() != ~native_handle_type(0); 177   return h_ && get().native_handle() != ~native_handle_type(0);
178   #else 178   #else
HITCBC 179   795 return h_ && get().native_handle() >= 0; 179   795 return h_ && get().native_handle() >= 0;
180   #endif 180   #endif
181   } 181   }
182   182  
183   /** Cancel pending asynchronous operations. 183   /** Cancel pending asynchronous operations.
184   184  
185   Operations still in flight complete with 185   Operations still in flight complete with
186   `errc::operation_canceled`; an operation whose result is 186   `errc::operation_canceled`; an operation whose result is
187   already decided reports that result. 187   already decided reports that result.
188   */ 188   */
189   void cancel() noexcept; 189   void cancel() noexcept;
190   190  
191   /** Get the native file descriptor or handle. 191   /** Get the native file descriptor or handle.
192   192  
193   @return The native handle, or -1/INVALID_HANDLE_VALUE 193   @return The native handle, or -1/INVALID_HANDLE_VALUE
194   if not open. 194   if not open.
195   */ 195   */
196   native_handle_type native_handle() const noexcept; 196   native_handle_type native_handle() const noexcept;
197   197  
198   /** Return the file size in bytes. 198   /** Return the file size in bytes.
199   199  
200   @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
201   underlying size query fails. 201   underlying size query fails.
202   */ 202   */
203   std::uint64_t size() const; 203   std::uint64_t size() const;
204   204  
205   /** Resize the file to @p new_size bytes. 205   /** Resize the file to @p new_size bytes.
206   206  
207   Failures such as insufficient disk space are reported 207   Failures such as insufficient disk space are reported
208   through the returned error code. A closed file reports 208   through the returned error code. A closed file reports
209   `errc::bad_file_descriptor`. 209   `errc::bad_file_descriptor`.
210   210  
211   @param new_size The new file size. 211   @param new_size The new file size.
212   212  
213   @return The error code, empty on success. 213   @return The error code, empty on success.
214   */ 214   */
215   [[nodiscard]] std::error_code resize(std::uint64_t new_size) noexcept; 215   [[nodiscard]] std::error_code resize(std::uint64_t new_size) noexcept;
216   216  
217   /** Synchronize file data to stable storage. 217   /** Synchronize file data to stable storage.
218   218  
219   Write-back failures such as device I/O errors surface here 219   Write-back failures such as device I/O errors surface here
220   and are reported through the returned error code. A closed 220   and are reported through the returned error code. A closed
221   file reports `errc::bad_file_descriptor`. 221   file reports `errc::bad_file_descriptor`.
222   222  
223   @return The error code, empty on success. 223   @return The error code, empty on success.
224   */ 224   */
225   [[nodiscard]] std::error_code sync_data() noexcept; 225   [[nodiscard]] std::error_code sync_data() noexcept;
226   226  
227   /** Synchronize file data and metadata to stable storage. 227   /** Synchronize file data and metadata to stable storage.
228   228  
229   Write-back failures such as device I/O errors surface here 229   Write-back failures such as device I/O errors surface here
230   and are reported through the returned error code. A closed 230   and are reported through the returned error code. A closed
231   file reports `errc::bad_file_descriptor`. 231   file reports `errc::bad_file_descriptor`.
232   232  
233   @return The error code, empty on success. 233   @return The error code, empty on success.
234   */ 234   */
235   [[nodiscard]] std::error_code sync_all() noexcept; 235   [[nodiscard]] std::error_code sync_all() noexcept;
236   236  
237   /** Release ownership of the native handle. 237   /** Release ownership of the native handle.
238   238  
239   The file object becomes not-open. The caller is 239   The file object becomes not-open. The caller is
240   responsible for closing the returned handle. 240   responsible for closing the returned handle.
241   241  
242   @return The native file descriptor or handle. 242   @return The native file descriptor or handle.
243   243  
244   @throws std::system_error `errc::bad_file_descriptor` if the 244   @throws std::system_error `errc::bad_file_descriptor` if the
245   file is not open. 245   file is not open.
246   */ 246   */
247   native_handle_type release(); 247   native_handle_type release();
248   248  
249   /** Adopt an existing native handle. 249   /** Adopt an existing native handle.
250   250  
251   Closes any currently open file before adopting. 251   Closes any currently open file before adopting.
252   The file object takes ownership of the handle. Handles 252   The file object takes ownership of the handle. Handles
253   created elsewhere may be unsuitable for asynchronous I/O; 253   created elsewhere may be unsuitable for asynchronous I/O;
254   such failures are reported through the returned error code. 254   such failures are reported through the returned error code.
255   255  
256   @param handle The native file descriptor or handle. 256   @param handle The native file descriptor or handle.
257   257  
258   @return The error code, empty on success. 258   @return The error code, empty on success.
259   */ 259   */
260   [[nodiscard]] std::error_code assign(native_handle_type handle) noexcept; 260   [[nodiscard]] std::error_code assign(native_handle_type handle) noexcept;
261   261  
262   /** Move the file position. 262   /** Move the file position.
263   263  
264   Positions beyond the end of the file are allowed. A 264   Positions beyond the end of the file are allowed. A
265   resulting negative position is reported through the error 265   resulting negative position is reported through the error
266   code, as offsets often originate from file contents. A 266   code, as offsets often originate from file contents. A
267   closed file reports `errc::bad_file_descriptor`. 267   closed file reports `errc::bad_file_descriptor`.
268   268  
269   @param offset Signed offset from @p origin. 269   @param offset Signed offset from @p origin.
270   @param origin The reference point for the seek. 270   @param origin The reference point for the seek.
271   271  
272   @return The error code and new absolute position. 272   @return The error code and new absolute position.
273   */ 273   */
274   [[nodiscard]] capy::io_result<std::uint64_t> seek( 274   [[nodiscard]] capy::io_result<std::uint64_t> seek(
275   std::int64_t offset, 275   std::int64_t offset,
276   file_base::seek_basis origin = file_base::seek_set) noexcept; 276   file_base::seek_basis origin = file_base::seek_set) noexcept;
277   277  
278   protected: 278   protected:
279   /// Default-construct (for derived types that initialize io_object directly). 279   /// Default-construct (for derived types that initialize io_object directly).
HITCBC 280   16 stream_file() noexcept = default; 280   16 stream_file() noexcept = default;
281   281  
282   /// Construct from a pre-built handle (for native_stream_file). 282   /// Construct from a pre-built handle (for native_stream_file).
283   explicit stream_file(handle h) noexcept : io_object(std::move(h)) {} 283   explicit stream_file(handle h) noexcept : io_object(std::move(h)) {}
284   284  
285   private: 285   private:
HITCBC 286   1131 inline implementation& get() const noexcept 286   1131 inline implementation& get() const noexcept
287   { 287   {
HITCBC 288   1131 return *static_cast<implementation*>(h_.get()); 288   1131 return *static_cast<implementation*>(h_.get());
289   } 289   }
290   }; 290   };
291   291  
292   } // namespace boost::corosio 292   } // namespace boost::corosio
293   293  
294   #endif // BOOST_COROSIO_STREAM_FILE_HPP 294   #endif // BOOST_COROSIO_STREAM_FILE_HPP