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1 | // |
2 | // read_at.hpp | |
3 | // ~~~~~~~~~~~ | |
4 | // | |
5 | // Copyright (c) 2003-2016 Christopher M. Kohlhoff (chris at kohlhoff dot com) | |
6 | // | |
7 | // Distributed under the Boost Software License, Version 1.0. (See accompanying | |
8 | // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) | |
9 | // | |
10 | ||
11 | #ifndef BOOST_ASIO_READ_AT_HPP | |
12 | #define BOOST_ASIO_READ_AT_HPP | |
13 | ||
14 | #if defined(_MSC_VER) && (_MSC_VER >= 1200) | |
15 | # pragma once | |
16 | #endif // defined(_MSC_VER) && (_MSC_VER >= 1200) | |
17 | ||
18 | #include <boost/asio/detail/config.hpp> | |
19 | #include <cstddef> | |
20 | #include <boost/asio/async_result.hpp> | |
21 | #include <boost/asio/basic_streambuf_fwd.hpp> | |
22 | #include <boost/asio/detail/cstdint.hpp> | |
23 | #include <boost/asio/error.hpp> | |
24 | ||
25 | #include <boost/asio/detail/push_options.hpp> | |
26 | ||
27 | namespace boost { | |
28 | namespace asio { | |
29 | ||
30 | /** | |
31 | * @defgroup read_at boost::asio::read_at | |
32 | * | |
33 | * @brief Attempt to read a certain amount of data at the specified offset | |
34 | * before returning. | |
35 | */ | |
36 | /*@{*/ | |
37 | ||
38 | /// Attempt to read a certain amount of data at the specified offset before | |
39 | /// returning. | |
40 | /** | |
41 | * This function is used to read a certain number of bytes of data from a | |
42 | * random access device at the specified offset. The call will block until one | |
43 | * of the following conditions is true: | |
44 | * | |
45 | * @li The supplied buffers are full. That is, the bytes transferred is equal to | |
46 | * the sum of the buffer sizes. | |
47 | * | |
48 | * @li An error occurred. | |
49 | * | |
50 | * This operation is implemented in terms of zero or more calls to the device's | |
51 | * read_some_at function. | |
52 | * | |
53 | * @param d The device from which the data is to be read. The type must support | |
54 | * the SyncRandomAccessReadDevice concept. | |
55 | * | |
56 | * @param offset The offset at which the data will be read. | |
57 | * | |
58 | * @param buffers One or more buffers into which the data will be read. The sum | |
59 | * of the buffer sizes indicates the maximum number of bytes to read from the | |
60 | * device. | |
61 | * | |
62 | * @returns The number of bytes transferred. | |
63 | * | |
64 | * @throws boost::system::system_error Thrown on failure. | |
65 | * | |
66 | * @par Example | |
67 | * To read into a single data buffer use the @ref buffer function as follows: | |
68 | * @code boost::asio::read_at(d, 42, boost::asio::buffer(data, size)); @endcode | |
69 | * See the @ref buffer documentation for information on reading into multiple | |
70 | * buffers in one go, and how to use it with arrays, boost::array or | |
71 | * std::vector. | |
72 | * | |
73 | * @note This overload is equivalent to calling: | |
74 | * @code boost::asio::read_at( | |
75 | * d, 42, buffers, | |
76 | * boost::asio::transfer_all()); @endcode | |
77 | */ | |
78 | template <typename SyncRandomAccessReadDevice, typename MutableBufferSequence> | |
79 | std::size_t read_at(SyncRandomAccessReadDevice& d, | |
80 | uint64_t offset, const MutableBufferSequence& buffers); | |
81 | ||
82 | /// Attempt to read a certain amount of data at the specified offset before | |
83 | /// returning. | |
84 | /** | |
85 | * This function is used to read a certain number of bytes of data from a | |
86 | * random access device at the specified offset. The call will block until one | |
87 | * of the following conditions is true: | |
88 | * | |
89 | * @li The supplied buffers are full. That is, the bytes transferred is equal to | |
90 | * the sum of the buffer sizes. | |
91 | * | |
92 | * @li An error occurred. | |
93 | * | |
94 | * This operation is implemented in terms of zero or more calls to the device's | |
95 | * read_some_at function. | |
96 | * | |
97 | * @param d The device from which the data is to be read. The type must support | |
98 | * the SyncRandomAccessReadDevice concept. | |
99 | * | |
100 | * @param offset The offset at which the data will be read. | |
101 | * | |
102 | * @param buffers One or more buffers into which the data will be read. The sum | |
103 | * of the buffer sizes indicates the maximum number of bytes to read from the | |
104 | * device. | |
105 | * | |
106 | * @param ec Set to indicate what error occurred, if any. | |
107 | * | |
108 | * @returns The number of bytes transferred. | |
109 | * | |
110 | * @par Example | |
111 | * To read into a single data buffer use the @ref buffer function as follows: | |
112 | * @code boost::asio::read_at(d, 42, | |
113 | * boost::asio::buffer(data, size), ec); @endcode | |
114 | * See the @ref buffer documentation for information on reading into multiple | |
115 | * buffers in one go, and how to use it with arrays, boost::array or | |
116 | * std::vector. | |
117 | * | |
118 | * @note This overload is equivalent to calling: | |
119 | * @code boost::asio::read_at( | |
120 | * d, 42, buffers, | |
121 | * boost::asio::transfer_all(), ec); @endcode | |
122 | */ | |
123 | template <typename SyncRandomAccessReadDevice, typename MutableBufferSequence> | |
124 | std::size_t read_at(SyncRandomAccessReadDevice& d, | |
125 | uint64_t offset, const MutableBufferSequence& buffers, | |
126 | boost::system::error_code& ec); | |
127 | ||
128 | /// Attempt to read a certain amount of data at the specified offset before | |
129 | /// returning. | |
130 | /** | |
131 | * This function is used to read a certain number of bytes of data from a | |
132 | * random access device at the specified offset. The call will block until one | |
133 | * of the following conditions is true: | |
134 | * | |
135 | * @li The supplied buffers are full. That is, the bytes transferred is equal to | |
136 | * the sum of the buffer sizes. | |
137 | * | |
138 | * @li The completion_condition function object returns 0. | |
139 | * | |
140 | * This operation is implemented in terms of zero or more calls to the device's | |
141 | * read_some_at function. | |
142 | * | |
143 | * @param d The device from which the data is to be read. The type must support | |
144 | * the SyncRandomAccessReadDevice concept. | |
145 | * | |
146 | * @param offset The offset at which the data will be read. | |
147 | * | |
148 | * @param buffers One or more buffers into which the data will be read. The sum | |
149 | * of the buffer sizes indicates the maximum number of bytes to read from the | |
150 | * device. | |
151 | * | |
152 | * @param completion_condition The function object to be called to determine | |
153 | * whether the read operation is complete. The signature of the function object | |
154 | * must be: | |
155 | * @code std::size_t completion_condition( | |
156 | * // Result of latest read_some_at operation. | |
157 | * const boost::system::error_code& error, | |
158 | * | |
159 | * // Number of bytes transferred so far. | |
160 | * std::size_t bytes_transferred | |
161 | * ); @endcode | |
162 | * A return value of 0 indicates that the read operation is complete. A non-zero | |
163 | * return value indicates the maximum number of bytes to be read on the next | |
164 | * call to the device's read_some_at function. | |
165 | * | |
166 | * @returns The number of bytes transferred. | |
167 | * | |
168 | * @throws boost::system::system_error Thrown on failure. | |
169 | * | |
170 | * @par Example | |
171 | * To read into a single data buffer use the @ref buffer function as follows: | |
172 | * @code boost::asio::read_at(d, 42, boost::asio::buffer(data, size), | |
173 | * boost::asio::transfer_at_least(32)); @endcode | |
174 | * See the @ref buffer documentation for information on reading into multiple | |
175 | * buffers in one go, and how to use it with arrays, boost::array or | |
176 | * std::vector. | |
177 | */ | |
178 | template <typename SyncRandomAccessReadDevice, typename MutableBufferSequence, | |
179 | typename CompletionCondition> | |
180 | std::size_t read_at(SyncRandomAccessReadDevice& d, | |
181 | uint64_t offset, const MutableBufferSequence& buffers, | |
182 | CompletionCondition completion_condition); | |
183 | ||
184 | /// Attempt to read a certain amount of data at the specified offset before | |
185 | /// returning. | |
186 | /** | |
187 | * This function is used to read a certain number of bytes of data from a | |
188 | * random access device at the specified offset. The call will block until one | |
189 | * of the following conditions is true: | |
190 | * | |
191 | * @li The supplied buffers are full. That is, the bytes transferred is equal to | |
192 | * the sum of the buffer sizes. | |
193 | * | |
194 | * @li The completion_condition function object returns 0. | |
195 | * | |
196 | * This operation is implemented in terms of zero or more calls to the device's | |
197 | * read_some_at function. | |
198 | * | |
199 | * @param d The device from which the data is to be read. The type must support | |
200 | * the SyncRandomAccessReadDevice concept. | |
201 | * | |
202 | * @param offset The offset at which the data will be read. | |
203 | * | |
204 | * @param buffers One or more buffers into which the data will be read. The sum | |
205 | * of the buffer sizes indicates the maximum number of bytes to read from the | |
206 | * device. | |
207 | * | |
208 | * @param completion_condition The function object to be called to determine | |
209 | * whether the read operation is complete. The signature of the function object | |
210 | * must be: | |
211 | * @code std::size_t completion_condition( | |
212 | * // Result of latest read_some_at operation. | |
213 | * const boost::system::error_code& error, | |
214 | * | |
215 | * // Number of bytes transferred so far. | |
216 | * std::size_t bytes_transferred | |
217 | * ); @endcode | |
218 | * A return value of 0 indicates that the read operation is complete. A non-zero | |
219 | * return value indicates the maximum number of bytes to be read on the next | |
220 | * call to the device's read_some_at function. | |
221 | * | |
222 | * @param ec Set to indicate what error occurred, if any. | |
223 | * | |
224 | * @returns The number of bytes read. If an error occurs, returns the total | |
225 | * number of bytes successfully transferred prior to the error. | |
226 | */ | |
227 | template <typename SyncRandomAccessReadDevice, typename MutableBufferSequence, | |
228 | typename CompletionCondition> | |
229 | std::size_t read_at(SyncRandomAccessReadDevice& d, | |
230 | uint64_t offset, const MutableBufferSequence& buffers, | |
231 | CompletionCondition completion_condition, boost::system::error_code& ec); | |
232 | ||
233 | #if !defined(BOOST_ASIO_NO_IOSTREAM) | |
234 | ||
235 | /// Attempt to read a certain amount of data at the specified offset before | |
236 | /// returning. | |
237 | /** | |
238 | * This function is used to read a certain number of bytes of data from a | |
239 | * random access device at the specified offset. The call will block until one | |
240 | * of the following conditions is true: | |
241 | * | |
242 | * @li An error occurred. | |
243 | * | |
244 | * This operation is implemented in terms of zero or more calls to the device's | |
245 | * read_some_at function. | |
246 | * | |
247 | * @param d The device from which the data is to be read. The type must support | |
248 | * the SyncRandomAccessReadDevice concept. | |
249 | * | |
250 | * @param offset The offset at which the data will be read. | |
251 | * | |
252 | * @param b The basic_streambuf object into which the data will be read. | |
253 | * | |
254 | * @returns The number of bytes transferred. | |
255 | * | |
256 | * @throws boost::system::system_error Thrown on failure. | |
257 | * | |
258 | * @note This overload is equivalent to calling: | |
259 | * @code boost::asio::read_at( | |
260 | * d, 42, b, | |
261 | * boost::asio::transfer_all()); @endcode | |
262 | */ | |
263 | template <typename SyncRandomAccessReadDevice, typename Allocator> | |
264 | std::size_t read_at(SyncRandomAccessReadDevice& d, | |
265 | uint64_t offset, basic_streambuf<Allocator>& b); | |
266 | ||
267 | /// Attempt to read a certain amount of data at the specified offset before | |
268 | /// returning. | |
269 | /** | |
270 | * This function is used to read a certain number of bytes of data from a | |
271 | * random access device at the specified offset. The call will block until one | |
272 | * of the following conditions is true: | |
273 | * | |
274 | * @li An error occurred. | |
275 | * | |
276 | * This operation is implemented in terms of zero or more calls to the device's | |
277 | * read_some_at function. | |
278 | * | |
279 | * @param d The device from which the data is to be read. The type must support | |
280 | * the SyncRandomAccessReadDevice concept. | |
281 | * | |
282 | * @param offset The offset at which the data will be read. | |
283 | * | |
284 | * @param b The basic_streambuf object into which the data will be read. | |
285 | * | |
286 | * @param ec Set to indicate what error occurred, if any. | |
287 | * | |
288 | * @returns The number of bytes transferred. | |
289 | * | |
290 | * @note This overload is equivalent to calling: | |
291 | * @code boost::asio::read_at( | |
292 | * d, 42, b, | |
293 | * boost::asio::transfer_all(), ec); @endcode | |
294 | */ | |
295 | template <typename SyncRandomAccessReadDevice, typename Allocator> | |
296 | std::size_t read_at(SyncRandomAccessReadDevice& d, | |
297 | uint64_t offset, basic_streambuf<Allocator>& b, | |
298 | boost::system::error_code& ec); | |
299 | ||
300 | /// Attempt to read a certain amount of data at the specified offset before | |
301 | /// returning. | |
302 | /** | |
303 | * This function is used to read a certain number of bytes of data from a | |
304 | * random access device at the specified offset. The call will block until one | |
305 | * of the following conditions is true: | |
306 | * | |
307 | * @li The completion_condition function object returns 0. | |
308 | * | |
309 | * This operation is implemented in terms of zero or more calls to the device's | |
310 | * read_some_at function. | |
311 | * | |
312 | * @param d The device from which the data is to be read. The type must support | |
313 | * the SyncRandomAccessReadDevice concept. | |
314 | * | |
315 | * @param offset The offset at which the data will be read. | |
316 | * | |
317 | * @param b The basic_streambuf object into which the data will be read. | |
318 | * | |
319 | * @param completion_condition The function object to be called to determine | |
320 | * whether the read operation is complete. The signature of the function object | |
321 | * must be: | |
322 | * @code std::size_t completion_condition( | |
323 | * // Result of latest read_some_at operation. | |
324 | * const boost::system::error_code& error, | |
325 | * | |
326 | * // Number of bytes transferred so far. | |
327 | * std::size_t bytes_transferred | |
328 | * ); @endcode | |
329 | * A return value of 0 indicates that the read operation is complete. A non-zero | |
330 | * return value indicates the maximum number of bytes to be read on the next | |
331 | * call to the device's read_some_at function. | |
332 | * | |
333 | * @returns The number of bytes transferred. | |
334 | * | |
335 | * @throws boost::system::system_error Thrown on failure. | |
336 | */ | |
337 | template <typename SyncRandomAccessReadDevice, typename Allocator, | |
338 | typename CompletionCondition> | |
339 | std::size_t read_at(SyncRandomAccessReadDevice& d, | |
340 | uint64_t offset, basic_streambuf<Allocator>& b, | |
341 | CompletionCondition completion_condition); | |
342 | ||
343 | /// Attempt to read a certain amount of data at the specified offset before | |
344 | /// returning. | |
345 | /** | |
346 | * This function is used to read a certain number of bytes of data from a | |
347 | * random access device at the specified offset. The call will block until one | |
348 | * of the following conditions is true: | |
349 | * | |
350 | * @li The completion_condition function object returns 0. | |
351 | * | |
352 | * This operation is implemented in terms of zero or more calls to the device's | |
353 | * read_some_at function. | |
354 | * | |
355 | * @param d The device from which the data is to be read. The type must support | |
356 | * the SyncRandomAccessReadDevice concept. | |
357 | * | |
358 | * @param offset The offset at which the data will be read. | |
359 | * | |
360 | * @param b The basic_streambuf object into which the data will be read. | |
361 | * | |
362 | * @param completion_condition The function object to be called to determine | |
363 | * whether the read operation is complete. The signature of the function object | |
364 | * must be: | |
365 | * @code std::size_t completion_condition( | |
366 | * // Result of latest read_some_at operation. | |
367 | * const boost::system::error_code& error, | |
368 | * | |
369 | * // Number of bytes transferred so far. | |
370 | * std::size_t bytes_transferred | |
371 | * ); @endcode | |
372 | * A return value of 0 indicates that the read operation is complete. A non-zero | |
373 | * return value indicates the maximum number of bytes to be read on the next | |
374 | * call to the device's read_some_at function. | |
375 | * | |
376 | * @param ec Set to indicate what error occurred, if any. | |
377 | * | |
378 | * @returns The number of bytes read. If an error occurs, returns the total | |
379 | * number of bytes successfully transferred prior to the error. | |
380 | */ | |
381 | template <typename SyncRandomAccessReadDevice, typename Allocator, | |
382 | typename CompletionCondition> | |
383 | std::size_t read_at(SyncRandomAccessReadDevice& d, | |
384 | uint64_t offset, basic_streambuf<Allocator>& b, | |
385 | CompletionCondition completion_condition, boost::system::error_code& ec); | |
386 | ||
387 | #endif // !defined(BOOST_ASIO_NO_IOSTREAM) | |
388 | ||
389 | /*@}*/ | |
390 | /** | |
391 | * @defgroup async_read_at boost::asio::async_read_at | |
392 | * | |
393 | * @brief Start an asynchronous operation to read a certain amount of data at | |
394 | * the specified offset. | |
395 | */ | |
396 | /*@{*/ | |
397 | ||
398 | /// Start an asynchronous operation to read a certain amount of data at the | |
399 | /// specified offset. | |
400 | /** | |
401 | * This function is used to asynchronously read a certain number of bytes of | |
402 | * data from a random access device at the specified offset. The function call | |
403 | * always returns immediately. The asynchronous operation will continue until | |
404 | * one of the following conditions is true: | |
405 | * | |
406 | * @li The supplied buffers are full. That is, the bytes transferred is equal to | |
407 | * the sum of the buffer sizes. | |
408 | * | |
409 | * @li An error occurred. | |
410 | * | |
411 | * This operation is implemented in terms of zero or more calls to the device's | |
412 | * async_read_some_at function. | |
413 | * | |
414 | * @param d The device from which the data is to be read. The type must support | |
415 | * the AsyncRandomAccessReadDevice concept. | |
416 | * | |
417 | * @param offset The offset at which the data will be read. | |
418 | * | |
419 | * @param buffers One or more buffers into which the data will be read. The sum | |
420 | * of the buffer sizes indicates the maximum number of bytes to read from the | |
421 | * device. Although the buffers object may be copied as necessary, ownership of | |
422 | * the underlying memory blocks is retained by the caller, which must guarantee | |
423 | * that they remain valid until the handler is called. | |
424 | * | |
425 | * @param handler The handler to be called when the read operation completes. | |
426 | * Copies will be made of the handler as required. The function signature of the | |
427 | * handler must be: | |
428 | * @code void handler( | |
429 | * // Result of operation. | |
430 | * const boost::system::error_code& error, | |
431 | * | |
432 | * // Number of bytes copied into the buffers. If an error | |
433 | * // occurred, this will be the number of bytes successfully | |
434 | * // transferred prior to the error. | |
435 | * std::size_t bytes_transferred | |
436 | * ); @endcode | |
437 | * Regardless of whether the asynchronous operation completes immediately or | |
438 | * not, the handler will not be invoked from within this function. Invocation of | |
439 | * the handler will be performed in a manner equivalent to using | |
440 | * boost::asio::io_service::post(). | |
441 | * | |
442 | * @par Example | |
443 | * To read into a single data buffer use the @ref buffer function as follows: | |
444 | * @code | |
445 | * boost::asio::async_read_at(d, 42, boost::asio::buffer(data, size), handler); | |
446 | * @endcode | |
447 | * See the @ref buffer documentation for information on reading into multiple | |
448 | * buffers in one go, and how to use it with arrays, boost::array or | |
449 | * std::vector. | |
450 | * | |
451 | * @note This overload is equivalent to calling: | |
452 | * @code boost::asio::async_read_at( | |
453 | * d, 42, buffers, | |
454 | * boost::asio::transfer_all(), | |
455 | * handler); @endcode | |
456 | */ | |
457 | template <typename AsyncRandomAccessReadDevice, typename MutableBufferSequence, | |
458 | typename ReadHandler> | |
459 | BOOST_ASIO_INITFN_RESULT_TYPE(ReadHandler, | |
460 | void (boost::system::error_code, std::size_t)) | |
461 | async_read_at(AsyncRandomAccessReadDevice& d, uint64_t offset, | |
462 | const MutableBufferSequence& buffers, | |
463 | BOOST_ASIO_MOVE_ARG(ReadHandler) handler); | |
464 | ||
465 | /// Start an asynchronous operation to read a certain amount of data at the | |
466 | /// specified offset. | |
467 | /** | |
468 | * This function is used to asynchronously read a certain number of bytes of | |
469 | * data from a random access device at the specified offset. The function call | |
470 | * always returns immediately. The asynchronous operation will continue until | |
471 | * one of the following conditions is true: | |
472 | * | |
473 | * @li The supplied buffers are full. That is, the bytes transferred is equal to | |
474 | * the sum of the buffer sizes. | |
475 | * | |
476 | * @li The completion_condition function object returns 0. | |
477 | * | |
478 | * @param d The device from which the data is to be read. The type must support | |
479 | * the AsyncRandomAccessReadDevice concept. | |
480 | * | |
481 | * @param offset The offset at which the data will be read. | |
482 | * | |
483 | * @param buffers One or more buffers into which the data will be read. The sum | |
484 | * of the buffer sizes indicates the maximum number of bytes to read from the | |
485 | * device. Although the buffers object may be copied as necessary, ownership of | |
486 | * the underlying memory blocks is retained by the caller, which must guarantee | |
487 | * that they remain valid until the handler is called. | |
488 | * | |
489 | * @param completion_condition The function object to be called to determine | |
490 | * whether the read operation is complete. The signature of the function object | |
491 | * must be: | |
492 | * @code std::size_t completion_condition( | |
493 | * // Result of latest async_read_some_at operation. | |
494 | * const boost::system::error_code& error, | |
495 | * | |
496 | * // Number of bytes transferred so far. | |
497 | * std::size_t bytes_transferred | |
498 | * ); @endcode | |
499 | * A return value of 0 indicates that the read operation is complete. A non-zero | |
500 | * return value indicates the maximum number of bytes to be read on the next | |
501 | * call to the device's async_read_some_at function. | |
502 | * | |
503 | * @param handler The handler to be called when the read operation completes. | |
504 | * Copies will be made of the handler as required. The function signature of the | |
505 | * handler must be: | |
506 | * @code void handler( | |
507 | * // Result of operation. | |
508 | * const boost::system::error_code& error, | |
509 | * | |
510 | * // Number of bytes copied into the buffers. If an error | |
511 | * // occurred, this will be the number of bytes successfully | |
512 | * // transferred prior to the error. | |
513 | * std::size_t bytes_transferred | |
514 | * ); @endcode | |
515 | * Regardless of whether the asynchronous operation completes immediately or | |
516 | * not, the handler will not be invoked from within this function. Invocation of | |
517 | * the handler will be performed in a manner equivalent to using | |
518 | * boost::asio::io_service::post(). | |
519 | * | |
520 | * @par Example | |
521 | * To read into a single data buffer use the @ref buffer function as follows: | |
522 | * @code boost::asio::async_read_at(d, 42, | |
523 | * boost::asio::buffer(data, size), | |
524 | * boost::asio::transfer_at_least(32), | |
525 | * handler); @endcode | |
526 | * See the @ref buffer documentation for information on reading into multiple | |
527 | * buffers in one go, and how to use it with arrays, boost::array or | |
528 | * std::vector. | |
529 | */ | |
530 | template <typename AsyncRandomAccessReadDevice, typename MutableBufferSequence, | |
531 | typename CompletionCondition, typename ReadHandler> | |
532 | BOOST_ASIO_INITFN_RESULT_TYPE(ReadHandler, | |
533 | void (boost::system::error_code, std::size_t)) | |
534 | async_read_at(AsyncRandomAccessReadDevice& d, | |
535 | uint64_t offset, const MutableBufferSequence& buffers, | |
536 | CompletionCondition completion_condition, | |
537 | BOOST_ASIO_MOVE_ARG(ReadHandler) handler); | |
538 | ||
539 | #if !defined(BOOST_ASIO_NO_IOSTREAM) | |
540 | ||
541 | /// Start an asynchronous operation to read a certain amount of data at the | |
542 | /// specified offset. | |
543 | /** | |
544 | * This function is used to asynchronously read a certain number of bytes of | |
545 | * data from a random access device at the specified offset. The function call | |
546 | * always returns immediately. The asynchronous operation will continue until | |
547 | * one of the following conditions is true: | |
548 | * | |
549 | * @li An error occurred. | |
550 | * | |
551 | * This operation is implemented in terms of zero or more calls to the device's | |
552 | * async_read_some_at function. | |
553 | * | |
554 | * @param d The device from which the data is to be read. The type must support | |
555 | * the AsyncRandomAccessReadDevice concept. | |
556 | * | |
557 | * @param offset The offset at which the data will be read. | |
558 | * | |
559 | * @param b A basic_streambuf object into which the data will be read. Ownership | |
560 | * of the streambuf is retained by the caller, which must guarantee that it | |
561 | * remains valid until the handler is called. | |
562 | * | |
563 | * @param handler The handler to be called when the read operation completes. | |
564 | * Copies will be made of the handler as required. The function signature of the | |
565 | * handler must be: | |
566 | * @code void handler( | |
567 | * // Result of operation. | |
568 | * const boost::system::error_code& error, | |
569 | * | |
570 | * // Number of bytes copied into the buffers. If an error | |
571 | * // occurred, this will be the number of bytes successfully | |
572 | * // transferred prior to the error. | |
573 | * std::size_t bytes_transferred | |
574 | * ); @endcode | |
575 | * Regardless of whether the asynchronous operation completes immediately or | |
576 | * not, the handler will not be invoked from within this function. Invocation of | |
577 | * the handler will be performed in a manner equivalent to using | |
578 | * boost::asio::io_service::post(). | |
579 | * | |
580 | * @note This overload is equivalent to calling: | |
581 | * @code boost::asio::async_read_at( | |
582 | * d, 42, b, | |
583 | * boost::asio::transfer_all(), | |
584 | * handler); @endcode | |
585 | */ | |
586 | template <typename AsyncRandomAccessReadDevice, typename Allocator, | |
587 | typename ReadHandler> | |
588 | BOOST_ASIO_INITFN_RESULT_TYPE(ReadHandler, | |
589 | void (boost::system::error_code, std::size_t)) | |
590 | async_read_at(AsyncRandomAccessReadDevice& d, uint64_t offset, | |
591 | basic_streambuf<Allocator>& b, BOOST_ASIO_MOVE_ARG(ReadHandler) handler); | |
592 | ||
593 | /// Start an asynchronous operation to read a certain amount of data at the | |
594 | /// specified offset. | |
595 | /** | |
596 | * This function is used to asynchronously read a certain number of bytes of | |
597 | * data from a random access device at the specified offset. The function call | |
598 | * always returns immediately. The asynchronous operation will continue until | |
599 | * one of the following conditions is true: | |
600 | * | |
601 | * @li The completion_condition function object returns 0. | |
602 | * | |
603 | * This operation is implemented in terms of zero or more calls to the device's | |
604 | * async_read_some_at function. | |
605 | * | |
606 | * @param d The device from which the data is to be read. The type must support | |
607 | * the AsyncRandomAccessReadDevice concept. | |
608 | * | |
609 | * @param offset The offset at which the data will be read. | |
610 | * | |
611 | * @param b A basic_streambuf object into which the data will be read. Ownership | |
612 | * of the streambuf is retained by the caller, which must guarantee that it | |
613 | * remains valid until the handler is called. | |
614 | * | |
615 | * @param completion_condition The function object to be called to determine | |
616 | * whether the read operation is complete. The signature of the function object | |
617 | * must be: | |
618 | * @code std::size_t completion_condition( | |
619 | * // Result of latest async_read_some_at operation. | |
620 | * const boost::system::error_code& error, | |
621 | * | |
622 | * // Number of bytes transferred so far. | |
623 | * std::size_t bytes_transferred | |
624 | * ); @endcode | |
625 | * A return value of 0 indicates that the read operation is complete. A non-zero | |
626 | * return value indicates the maximum number of bytes to be read on the next | |
627 | * call to the device's async_read_some_at function. | |
628 | * | |
629 | * @param handler The handler to be called when the read operation completes. | |
630 | * Copies will be made of the handler as required. The function signature of the | |
631 | * handler must be: | |
632 | * @code void handler( | |
633 | * // Result of operation. | |
634 | * const boost::system::error_code& error, | |
635 | * | |
636 | * // Number of bytes copied into the buffers. If an error | |
637 | * // occurred, this will be the number of bytes successfully | |
638 | * // transferred prior to the error. | |
639 | * std::size_t bytes_transferred | |
640 | * ); @endcode | |
641 | * Regardless of whether the asynchronous operation completes immediately or | |
642 | * not, the handler will not be invoked from within this function. Invocation of | |
643 | * the handler will be performed in a manner equivalent to using | |
644 | * boost::asio::io_service::post(). | |
645 | */ | |
646 | template <typename AsyncRandomAccessReadDevice, typename Allocator, | |
647 | typename CompletionCondition, typename ReadHandler> | |
648 | BOOST_ASIO_INITFN_RESULT_TYPE(ReadHandler, | |
649 | void (boost::system::error_code, std::size_t)) | |
650 | async_read_at(AsyncRandomAccessReadDevice& d, | |
651 | uint64_t offset, basic_streambuf<Allocator>& b, | |
652 | CompletionCondition completion_condition, | |
653 | BOOST_ASIO_MOVE_ARG(ReadHandler) handler); | |
654 | ||
655 | #endif // !defined(BOOST_ASIO_NO_IOSTREAM) | |
656 | ||
657 | /*@}*/ | |
658 | ||
659 | } // namespace asio | |
660 | } // namespace boost | |
661 | ||
662 | #include <boost/asio/detail/pop_options.hpp> | |
663 | ||
664 | #include <boost/asio/impl/read_at.hpp> | |
665 | ||
666 | #endif // BOOST_ASIO_READ_AT_HPP |