boost/asio/impl/read_at.hpp

   1 //
   2 // impl/read_at.hpp
   3 // ~~~~~~~~~~~~~~~~
   4 //
   5 // Copyright (c) 2003-2019 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_IMPL_READ_AT_HPP
  12 #define BOOST_ASIO_IMPL_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 <algorithm>
  19 #include <boost/asio/associated_allocator.hpp>
  20 #include <boost/asio/associated_executor.hpp>
  21 #include <boost/asio/buffer.hpp>
  22 #include <boost/asio/completion_condition.hpp>
  23 #include <boost/asio/detail/array_fwd.hpp>
  24 #include <boost/asio/detail/base_from_completion_cond.hpp>
  25 #include <boost/asio/detail/bind_handler.hpp>
  26 #include <boost/asio/detail/consuming_buffers.hpp>
  27 #include <boost/asio/detail/dependent_type.hpp>
  28 #include <boost/asio/detail/handler_alloc_helpers.hpp>
  29 #include <boost/asio/detail/handler_cont_helpers.hpp>
  30 #include <boost/asio/detail/handler_invoke_helpers.hpp>
  31 #include <boost/asio/detail/handler_type_requirements.hpp>
  32 #include <boost/asio/detail/non_const_lvalue.hpp>
  33 #include <boost/asio/detail/throw_error.hpp>
  34 #include <boost/asio/error.hpp>
  35
  36 #include <boost/asio/detail/push_options.hpp>
  37
  38 namespace boost {
  39 namespace asio {
  40
  41 namespace detail
  42 {
  43   template <typename SyncRandomAccessReadDevice, typename MutableBufferSequence,
  44       typename MutableBufferIterator, typename CompletionCondition>
  45   std::size_t read_at_buffer_sequence(SyncRandomAccessReadDevice& d,
  46       uint64_t offset, const MutableBufferSequence& buffers,
  47       const MutableBufferIterator&, CompletionCondition completion_condition,
  48       boost::system::error_code& ec)
  49   {
  50     ec = boost::system::error_code();
  51     boost::asio::detail::consuming_buffers<mutable_buffer,
  52         MutableBufferSequence, MutableBufferIterator> tmp(buffers);
  53     while (!tmp.empty())
  54     {
  55       if (std::size_t max_size = detail::adapt_completion_condition_result(
  56             completion_condition(ec, tmp.total_consumed())))
  57       {
  58         tmp.consume(d.read_some_at(offset + tmp.total_consumed(),
  59               tmp.prepare(max_size), ec));
  60       }
  61       else
  62         break;
  63     }
  64     return tmp.total_consumed();;
  65   }
  66 } // namespace detail
  67
  68 template <typename SyncRandomAccessReadDevice, typename MutableBufferSequence,
  69     typename CompletionCondition>
  70 std::size_t read_at(SyncRandomAccessReadDevice& d,
  71     uint64_t offset, const MutableBufferSequence& buffers,
  72     CompletionCondition completion_condition, boost::system::error_code& ec)
  73 {
  74   return detail::read_at_buffer_sequence(d, offset, buffers,
  75       boost::asio::buffer_sequence_begin(buffers),
  76       BOOST_ASIO_MOVE_CAST(CompletionCondition)(completion_condition), ec);
  77 }
  78
  79 template <typename SyncRandomAccessReadDevice, typename MutableBufferSequence>
  80 inline std::size_t read_at(SyncRandomAccessReadDevice& d,
  81     uint64_t offset, const MutableBufferSequence& buffers)
  82 {
  83   boost::system::error_code ec;
  84   std::size_t bytes_transferred = read_at(
  85       d, offset, buffers, transfer_all(), ec);
  86   boost::asio::detail::throw_error(ec, "read_at");
  87   return bytes_transferred;
  88 }
  89
  90 template <typename SyncRandomAccessReadDevice, typename MutableBufferSequence>
  91 inline std::size_t read_at(SyncRandomAccessReadDevice& d,
  92     uint64_t offset, const MutableBufferSequence& buffers,
  93     boost::system::error_code& ec)
  94 {
  95   return read_at(d, offset, buffers, transfer_all(), ec);
  96 }
  97
  98 template <typename SyncRandomAccessReadDevice, typename MutableBufferSequence,
  99     typename CompletionCondition>
 100 inline std::size_t read_at(SyncRandomAccessReadDevice& d,
 101     uint64_t offset, const MutableBufferSequence& buffers,
 102     CompletionCondition completion_condition)
 103 {
 104   boost::system::error_code ec;
 105   std::size_t bytes_transferred = read_at(d, offset, buffers,
 106       BOOST_ASIO_MOVE_CAST(CompletionCondition)(completion_condition), ec);
 107   boost::asio::detail::throw_error(ec, "read_at");
 108   return bytes_transferred;
 109 }
 110
 111 #if !defined(BOOST_ASIO_NO_EXTENSIONS)
 112 #if !defined(BOOST_ASIO_NO_IOSTREAM)
 113
 114 template <typename SyncRandomAccessReadDevice, typename Allocator,
 115     typename CompletionCondition>
 116 std::size_t read_at(SyncRandomAccessReadDevice& d,
 117     uint64_t offset, boost::asio::basic_streambuf<Allocator>& b,
 118     CompletionCondition completion_condition, boost::system::error_code& ec)
 119 {
 120   ec = boost::system::error_code();
 121   std::size_t total_transferred = 0;
 122   std::size_t max_size = detail::adapt_completion_condition_result(
 123         completion_condition(ec, total_transferred));
 124   std::size_t bytes_available = read_size_helper(b, max_size);
 125   while (bytes_available > 0)
 126   {
 127     std::size_t bytes_transferred = d.read_some_at(
 128         offset + total_transferred, b.prepare(bytes_available), ec);
 129     b.commit(bytes_transferred);
 130     total_transferred += bytes_transferred;
 131     max_size = detail::adapt_completion_condition_result(
 132           completion_condition(ec, total_transferred));
 133     bytes_available = read_size_helper(b, max_size);
 134   }
 135   return total_transferred;
 136 }
 137
 138 template <typename SyncRandomAccessReadDevice, typename Allocator>
 139 inline std::size_t read_at(SyncRandomAccessReadDevice& d,
 140     uint64_t offset, boost::asio::basic_streambuf<Allocator>& b)
 141 {
 142   boost::system::error_code ec;
 143   std::size_t bytes_transferred = read_at(
 144       d, offset, b, transfer_all(), ec);
 145   boost::asio::detail::throw_error(ec, "read_at");
 146   return bytes_transferred;
 147 }
 148
 149 template <typename SyncRandomAccessReadDevice, typename Allocator>
 150 inline std::size_t read_at(SyncRandomAccessReadDevice& d,
 151     uint64_t offset, boost::asio::basic_streambuf<Allocator>& b,
 152     boost::system::error_code& ec)
 153 {
 154   return read_at(d, offset, b, transfer_all(), ec);
 155 }
 156
 157 template <typename SyncRandomAccessReadDevice, typename Allocator,
 158     typename CompletionCondition>
 159 inline std::size_t read_at(SyncRandomAccessReadDevice& d,
 160     uint64_t offset, boost::asio::basic_streambuf<Allocator>& b,
 161     CompletionCondition completion_condition)
 162 {
 163   boost::system::error_code ec;
 164   std::size_t bytes_transferred = read_at(d, offset, b,
 165       BOOST_ASIO_MOVE_CAST(CompletionCondition)(completion_condition), ec);
 166   boost::asio::detail::throw_error(ec, "read_at");
 167   return bytes_transferred;
 168 }
 169
 170 #endif // !defined(BOOST_ASIO_NO_IOSTREAM)
 171 #endif // !defined(BOOST_ASIO_NO_EXTENSIONS)
 172
 173 namespace detail
 174 {
 175   template <typename AsyncRandomAccessReadDevice,
 176       typename MutableBufferSequence, typename MutableBufferIterator,
 177       typename CompletionCondition, typename ReadHandler>
 178   class read_at_op
 179     : detail::base_from_completion_cond<CompletionCondition>
 180   {
 181   public:
 182     read_at_op(AsyncRandomAccessReadDevice& device,
 183         uint64_t offset, const MutableBufferSequence& buffers,
 184         CompletionCondition& completion_condition, ReadHandler& handler)
 185       : detail::base_from_completion_cond<
 186           CompletionCondition>(completion_condition),
 187         device_(device),
 188         offset_(offset),
 189         buffers_(buffers),
 190         start_(0),
 191         handler_(BOOST_ASIO_MOVE_CAST(ReadHandler)(handler))
 192     {
 193     }
 194
 195 #if defined(BOOST_ASIO_HAS_MOVE)
 196     read_at_op(const read_at_op& other)
 197       : detail::base_from_completion_cond<CompletionCondition>(other),
 198         device_(other.device_),
 199         offset_(other.offset_),
 200         buffers_(other.buffers_),
 201         start_(other.start_),
 202         handler_(other.handler_)
 203     {
 204     }
 205
 206     read_at_op(read_at_op&& other)
 207       : detail::base_from_completion_cond<CompletionCondition>(
 208           BOOST_ASIO_MOVE_CAST(detail::base_from_completion_cond<
 209             CompletionCondition>)(other)),
 210         device_(other.device_),
 211         offset_(other.offset_),
 212         buffers_(BOOST_ASIO_MOVE_CAST(buffers_type)(other.buffers_)),
 213         start_(other.start_),
 214         handler_(BOOST_ASIO_MOVE_CAST(ReadHandler)(other.handler_))
 215     {
 216     }
 217 #endif // defined(BOOST_ASIO_HAS_MOVE)
 218
 219     void operator()(const boost::system::error_code& ec,
 220         std::size_t bytes_transferred, int start = 0)
 221     {
 222       std::size_t max_size;
 223       switch (start_ = start)
 224       {
 225         case 1:
 226         max_size = this->check_for_completion(ec, buffers_.total_consumed());
 227         do
 228         {
 229           device_.async_read_some_at(
 230               offset_ + buffers_.total_consumed(), buffers_.prepare(max_size),
 231               BOOST_ASIO_MOVE_CAST(read_at_op)(*this));
 232           return; default:
 233           buffers_.consume(bytes_transferred);
 234           if ((!ec && bytes_transferred == 0) || buffers_.empty())
 235             break;
 236           max_size = this->check_for_completion(ec, buffers_.total_consumed());
 237         } while (max_size > 0);
 238
 239         handler_(ec, buffers_.total_consumed());
 240       }
 241     }
 242
 243   //private:
 244     typedef boost::asio::detail::consuming_buffers<mutable_buffer,
 245         MutableBufferSequence, MutableBufferIterator> buffers_type;
 246
 247     AsyncRandomAccessReadDevice& device_;
 248     uint64_t offset_;
 249     buffers_type buffers_;
 250     int start_;
 251     ReadHandler handler_;
 252   };
 253
 254   template <typename AsyncRandomAccessReadDevice,
 255       typename MutableBufferSequence, typename MutableBufferIterator,
 256       typename CompletionCondition, typename ReadHandler>
 257   inline void* asio_handler_allocate(std::size_t size,
 258       read_at_op<AsyncRandomAccessReadDevice, MutableBufferSequence,
 259         MutableBufferIterator, CompletionCondition, ReadHandler>* this_handler)
 260   {
 261     return boost_asio_handler_alloc_helpers::allocate(
 262         size, this_handler->handler_);
 263   }
 264
 265   template <typename AsyncRandomAccessReadDevice,
 266       typename MutableBufferSequence, typename MutableBufferIterator,
 267       typename CompletionCondition, typename ReadHandler>
 268   inline void asio_handler_deallocate(void* pointer, std::size_t size,
 269       read_at_op<AsyncRandomAccessReadDevice, MutableBufferSequence,
 270         MutableBufferIterator, CompletionCondition, ReadHandler>* this_handler)
 271   {
 272     boost_asio_handler_alloc_helpers::deallocate(
 273         pointer, size, this_handler->handler_);
 274   }
 275
 276   template <typename AsyncRandomAccessReadDevice,
 277       typename MutableBufferSequence, typename MutableBufferIterator,
 278       typename CompletionCondition, typename ReadHandler>
 279   inline bool asio_handler_is_continuation(
 280       read_at_op<AsyncRandomAccessReadDevice, MutableBufferSequence,
 281         MutableBufferIterator, CompletionCondition, ReadHandler>* this_handler)
 282   {
 283     return this_handler->start_ == 0 ? true
 284       : boost_asio_handler_cont_helpers::is_continuation(
 285           this_handler->handler_);
 286   }
 287
 288   template <typename Function, typename AsyncRandomAccessReadDevice,
 289       typename MutableBufferSequence, typename MutableBufferIterator,
 290       typename CompletionCondition, typename ReadHandler>
 291   inline void asio_handler_invoke(Function& function,
 292       read_at_op<AsyncRandomAccessReadDevice, MutableBufferSequence,
 293         MutableBufferIterator, CompletionCondition, ReadHandler>* this_handler)
 294   {
 295     boost_asio_handler_invoke_helpers::invoke(
 296         function, this_handler->handler_);
 297   }
 298
 299   template <typename Function, typename AsyncRandomAccessReadDevice,
 300       typename MutableBufferSequence, typename MutableBufferIterator,
 301       typename CompletionCondition, typename ReadHandler>
 302   inline void asio_handler_invoke(const Function& function,
 303       read_at_op<AsyncRandomAccessReadDevice, MutableBufferSequence,
 304         MutableBufferIterator, CompletionCondition, ReadHandler>* this_handler)
 305   {
 306     boost_asio_handler_invoke_helpers::invoke(
 307         function, this_handler->handler_);
 308   }
 309
 310   template <typename AsyncRandomAccessReadDevice,
 311       typename MutableBufferSequence, typename MutableBufferIterator,
 312       typename CompletionCondition, typename ReadHandler>
 313   inline void start_read_at_buffer_sequence_op(AsyncRandomAccessReadDevice& d,
 314       uint64_t offset, const MutableBufferSequence& buffers,
 315       const MutableBufferIterator&, CompletionCondition& completion_condition,
 316       ReadHandler& handler)
 317   {
 318     detail::read_at_op<AsyncRandomAccessReadDevice, MutableBufferSequence,
 319       MutableBufferIterator, CompletionCondition, ReadHandler>(
 320         d, offset, buffers, completion_condition, handler)(
 321           boost::system::error_code(), 0, 1);
 322   }
 323
 324   template <typename AsyncRandomAccessReadDevice>
 325   class initiate_async_read_at_buffer_sequence
 326   {
 327   public:
 328     typedef typename AsyncRandomAccessReadDevice::executor_type executor_type;
 329
 330     explicit initiate_async_read_at_buffer_sequence(
 331         AsyncRandomAccessReadDevice& device)
 332       : device_(device)
 333     {
 334     }
 335
 336     executor_type get_executor() const BOOST_ASIO_NOEXCEPT
 337     {
 338       return device_.get_executor();
 339     }
 340
 341     template <typename ReadHandler, typename MutableBufferSequence,
 342         typename CompletionCondition>
 343     void operator()(BOOST_ASIO_MOVE_ARG(ReadHandler) handler,
 344         uint64_t offset, const MutableBufferSequence& buffers,
 345         BOOST_ASIO_MOVE_ARG(CompletionCondition) completion_cond) const
 346     {
 347       // If you get an error on the following line it means that your handler
 348       // does not meet the documented type requirements for a ReadHandler.
 349       BOOST_ASIO_READ_HANDLER_CHECK(ReadHandler, handler) type_check;
 350
 351       non_const_lvalue<ReadHandler> handler2(handler);
 352       non_const_lvalue<CompletionCondition> completion_cond2(completion_cond);
 353       start_read_at_buffer_sequence_op(device_, offset, buffers,
 354           boost::asio::buffer_sequence_begin(buffers),
 355           completion_cond2.value, handler2.value);
 356     }
 357
 358   private:
 359     AsyncRandomAccessReadDevice& device_;
 360   };
 361 } // namespace detail
 362
 363 #if !defined(GENERATING_DOCUMENTATION)
 364
 365 template <typename AsyncRandomAccessReadDevice,
 366     typename MutableBufferSequence, typename MutableBufferIterator,
 367     typename CompletionCondition, typename ReadHandler, typename Allocator>
 368 struct associated_allocator<
 369     detail::read_at_op<AsyncRandomAccessReadDevice, MutableBufferSequence,
 370     MutableBufferIterator, CompletionCondition, ReadHandler>,
 371     Allocator>
 372 {
 373   typedef typename associated_allocator<ReadHandler, Allocator>::type type;
 374
 375   static type get(
 376       const detail::read_at_op<AsyncRandomAccessReadDevice,
 377       MutableBufferSequence, MutableBufferIterator,
 378       CompletionCondition, ReadHandler>& h,
 379       const Allocator& a = Allocator()) BOOST_ASIO_NOEXCEPT
 380   {
 381     return associated_allocator<ReadHandler, Allocator>::get(h.handler_, a);
 382   }
 383 };
 384
 385 template <typename AsyncRandomAccessReadDevice,
 386     typename MutableBufferSequence, typename MutableBufferIterator,
 387     typename CompletionCondition, typename ReadHandler, typename Executor>
 388 struct associated_executor<
 389     detail::read_at_op<AsyncRandomAccessReadDevice, MutableBufferSequence,
 390     MutableBufferIterator, CompletionCondition, ReadHandler>,
 391     Executor>
 392 {
 393   typedef typename associated_executor<ReadHandler, Executor>::type type;
 394
 395   static type get(
 396       const detail::read_at_op<AsyncRandomAccessReadDevice,
 397       MutableBufferSequence, MutableBufferIterator,
 398       CompletionCondition, ReadHandler>& h,
 399       const Executor& ex = Executor()) BOOST_ASIO_NOEXCEPT
 400   {
 401     return associated_executor<ReadHandler, Executor>::get(h.handler_, ex);
 402   }
 403 };
 404
 405 #endif // !defined(GENERATING_DOCUMENTATION)
 406
 407 template <typename AsyncRandomAccessReadDevice,
 408     typename MutableBufferSequence, typename CompletionCondition,
 409     BOOST_ASIO_COMPLETION_TOKEN_FOR(void (boost::system::error_code,
 410       std::size_t)) ReadHandler>
 411 inline BOOST_ASIO_INITFN_AUTO_RESULT_TYPE(ReadHandler,
 412     void (boost::system::error_code, std::size_t))
 413 async_read_at(AsyncRandomAccessReadDevice& d,
 414     uint64_t offset, const MutableBufferSequence& buffers,
 415     CompletionCondition completion_condition,
 416     BOOST_ASIO_MOVE_ARG(ReadHandler) handler)
 417 {
 418   return async_initiate<ReadHandler,
 419     void (boost::system::error_code, std::size_t)>(
 420       detail::initiate_async_read_at_buffer_sequence<
 421         AsyncRandomAccessReadDevice>(d),
 422       handler, offset, buffers,
 423       BOOST_ASIO_MOVE_CAST(CompletionCondition)(completion_condition));
 424 }
 425
 426 template <typename AsyncRandomAccessReadDevice, typename MutableBufferSequence,
 427     BOOST_ASIO_COMPLETION_TOKEN_FOR(void (boost::system::error_code,
 428       std::size_t)) ReadHandler>
 429 inline BOOST_ASIO_INITFN_AUTO_RESULT_TYPE(ReadHandler,
 430     void (boost::system::error_code, std::size_t))
 431 async_read_at(AsyncRandomAccessReadDevice& d,
 432     uint64_t offset, const MutableBufferSequence& buffers,
 433     BOOST_ASIO_MOVE_ARG(ReadHandler) handler)
 434 {
 435   return async_initiate<ReadHandler,
 436     void (boost::system::error_code, std::size_t)>(
 437       detail::initiate_async_read_at_buffer_sequence<
 438         AsyncRandomAccessReadDevice>(d),
 439       handler, offset, buffers, transfer_all());
 440 }
 441
 442 #if !defined(BOOST_ASIO_NO_EXTENSIONS)
 443 #if !defined(BOOST_ASIO_NO_IOSTREAM)
 444
 445 namespace detail
 446 {
 447   template <typename AsyncRandomAccessReadDevice, typename Allocator,
 448       typename CompletionCondition, typename ReadHandler>
 449   class read_at_streambuf_op
 450     : detail::base_from_completion_cond<CompletionCondition>
 451   {
 452   public:
 453     read_at_streambuf_op(AsyncRandomAccessReadDevice& device,
 454         uint64_t offset, basic_streambuf<Allocator>& streambuf,
 455         CompletionCondition& completion_condition, ReadHandler& handler)
 456       : detail::base_from_completion_cond<
 457           CompletionCondition>(completion_condition),
 458         device_(device),
 459         offset_(offset),
 460         streambuf_(streambuf),
 461         start_(0),
 462         total_transferred_(0),
 463         handler_(BOOST_ASIO_MOVE_CAST(ReadHandler)(handler))
 464     {
 465     }
 466
 467 #if defined(BOOST_ASIO_HAS_MOVE)
 468     read_at_streambuf_op(const read_at_streambuf_op& other)
 469       : detail::base_from_completion_cond<CompletionCondition>(other),
 470         device_(other.device_),
 471         offset_(other.offset_),
 472         streambuf_(other.streambuf_),
 473         start_(other.start_),
 474         total_transferred_(other.total_transferred_),
 475         handler_(other.handler_)
 476     {
 477     }
 478
 479     read_at_streambuf_op(read_at_streambuf_op&& other)
 480       : detail::base_from_completion_cond<CompletionCondition>(
 481           BOOST_ASIO_MOVE_CAST(detail::base_from_completion_cond<
 482             CompletionCondition>)(other)),
 483         device_(other.device_),
 484         offset_(other.offset_),
 485         streambuf_(other.streambuf_),
 486         start_(other.start_),
 487         total_transferred_(other.total_transferred_),
 488         handler_(BOOST_ASIO_MOVE_CAST(ReadHandler)(other.handler_))
 489     {
 490     }
 491 #endif // defined(BOOST_ASIO_HAS_MOVE)
 492
 493     void operator()(const boost::system::error_code& ec,
 494         std::size_t bytes_transferred, int start = 0)
 495     {
 496       std::size_t max_size, bytes_available;
 497       switch (start_ = start)
 498       {
 499         case 1:
 500         max_size = this->check_for_completion(ec, total_transferred_);
 501         bytes_available = read_size_helper(streambuf_, max_size);
 502         for (;;)
 503         {
 504           device_.async_read_some_at(offset_ + total_transferred_,
 505               streambuf_.prepare(bytes_available),
 506               BOOST_ASIO_MOVE_CAST(read_at_streambuf_op)(*this));
 507           return; default:
 508           total_transferred_ += bytes_transferred;
 509           streambuf_.commit(bytes_transferred);
 510           max_size = this->check_for_completion(ec, total_transferred_);
 511           bytes_available = read_size_helper(streambuf_, max_size);
 512           if ((!ec && bytes_transferred == 0) || bytes_available == 0)
 513             break;
 514         }
 515
 516         handler_(ec, static_cast<const std::size_t&>(total_transferred_));
 517       }
 518     }
 519
 520   //private:
 521     AsyncRandomAccessReadDevice& device_;
 522     uint64_t offset_;
 523     boost::asio::basic_streambuf<Allocator>& streambuf_;
 524     int start_;
 525     std::size_t total_transferred_;
 526     ReadHandler handler_;
 527   };
 528
 529   template <typename AsyncRandomAccessReadDevice, typename Allocator,
 530       typename CompletionCondition, typename ReadHandler>
 531   inline void* asio_handler_allocate(std::size_t size,
 532       read_at_streambuf_op<AsyncRandomAccessReadDevice, Allocator,
 533         CompletionCondition, ReadHandler>* this_handler)
 534   {
 535     return boost_asio_handler_alloc_helpers::allocate(
 536         size, this_handler->handler_);
 537   }
 538
 539   template <typename AsyncRandomAccessReadDevice, typename Allocator,
 540       typename CompletionCondition, typename ReadHandler>
 541   inline void asio_handler_deallocate(void* pointer, std::size_t size,
 542       read_at_streambuf_op<AsyncRandomAccessReadDevice, Allocator,
 543         CompletionCondition, ReadHandler>* this_handler)
 544   {
 545     boost_asio_handler_alloc_helpers::deallocate(
 546         pointer, size, this_handler->handler_);
 547   }
 548
 549   template <typename AsyncRandomAccessReadDevice, typename Allocator,
 550       typename CompletionCondition, typename ReadHandler>
 551   inline bool asio_handler_is_continuation(
 552       read_at_streambuf_op<AsyncRandomAccessReadDevice, Allocator,
 553         CompletionCondition, ReadHandler>* this_handler)
 554   {
 555     return this_handler->start_ == 0 ? true
 556       : boost_asio_handler_cont_helpers::is_continuation(
 557           this_handler->handler_);
 558   }
 559
 560   template <typename Function, typename AsyncRandomAccessReadDevice,
 561       typename Allocator, typename CompletionCondition, typename ReadHandler>
 562   inline void asio_handler_invoke(Function& function,
 563       read_at_streambuf_op<AsyncRandomAccessReadDevice, Allocator,
 564         CompletionCondition, ReadHandler>* this_handler)
 565   {
 566     boost_asio_handler_invoke_helpers::invoke(
 567         function, this_handler->handler_);
 568   }
 569
 570   template <typename Function, typename AsyncRandomAccessReadDevice,
 571       typename Allocator, typename CompletionCondition, typename ReadHandler>
 572   inline void asio_handler_invoke(const Function& function,
 573       read_at_streambuf_op<AsyncRandomAccessReadDevice, Allocator,
 574         CompletionCondition, ReadHandler>* this_handler)
 575   {
 576     boost_asio_handler_invoke_helpers::invoke(
 577         function, this_handler->handler_);
 578   }
 579
 580   template <typename AsyncRandomAccessReadDevice>
 581   class initiate_async_read_at_streambuf
 582   {
 583   public:
 584     typedef typename AsyncRandomAccessReadDevice::executor_type executor_type;
 585
 586     explicit initiate_async_read_at_streambuf(
 587         AsyncRandomAccessReadDevice& device)
 588       : device_(device)
 589     {
 590     }
 591
 592     executor_type get_executor() const BOOST_ASIO_NOEXCEPT
 593     {
 594       return device_.get_executor();
 595     }
 596
 597     template <typename ReadHandler,
 598         typename Allocator, typename CompletionCondition>
 599     void operator()(BOOST_ASIO_MOVE_ARG(ReadHandler) handler,
 600         uint64_t offset, basic_streambuf<Allocator>* b,
 601         BOOST_ASIO_MOVE_ARG(CompletionCondition) completion_cond) const
 602     {
 603       // If you get an error on the following line it means that your handler
 604       // does not meet the documented type requirements for a ReadHandler.
 605       BOOST_ASIO_READ_HANDLER_CHECK(ReadHandler, handler) type_check;
 606
 607       non_const_lvalue<ReadHandler> handler2(handler);
 608       non_const_lvalue<CompletionCondition> completion_cond2(completion_cond);
 609       read_at_streambuf_op<AsyncRandomAccessReadDevice, Allocator,
 610         CompletionCondition, typename decay<ReadHandler>::type>(
 611           device_, offset, *b, completion_cond2.value, handler2.value)(
 612             boost::system::error_code(), 0, 1);
 613     }
 614
 615   private:
 616     AsyncRandomAccessReadDevice& device_;
 617   };
 618 } // namespace detail
 619
 620 #if !defined(GENERATING_DOCUMENTATION)
 621
 622 template <typename AsyncRandomAccessReadDevice, typename Allocator,
 623     typename CompletionCondition, typename ReadHandler, typename Allocator1>
 624 struct associated_allocator<
 625     detail::read_at_streambuf_op<AsyncRandomAccessReadDevice,
 626       Allocator, CompletionCondition, ReadHandler>,
 627     Allocator1>
 628 {
 629   typedef typename associated_allocator<ReadHandler, Allocator1>::type type;
 630
 631   static type get(
 632       const detail::read_at_streambuf_op<AsyncRandomAccessReadDevice,
 633         Allocator, CompletionCondition, ReadHandler>& h,
 634       const Allocator1& a = Allocator1()) BOOST_ASIO_NOEXCEPT
 635   {
 636     return associated_allocator<ReadHandler, Allocator1>::get(h.handler_, a);
 637   }
 638 };
 639
 640 template <typename AsyncRandomAccessReadDevice, typename Executor,
 641     typename CompletionCondition, typename ReadHandler, typename Executor1>
 642 struct associated_executor<
 643     detail::read_at_streambuf_op<AsyncRandomAccessReadDevice,
 644       Executor, CompletionCondition, ReadHandler>,
 645     Executor1>
 646 {
 647   typedef typename associated_executor<ReadHandler, Executor1>::type type;
 648
 649   static type get(
 650       const detail::read_at_streambuf_op<AsyncRandomAccessReadDevice,
 651         Executor, CompletionCondition, ReadHandler>& h,
 652       const Executor1& ex = Executor1()) BOOST_ASIO_NOEXCEPT
 653   {
 654     return associated_executor<ReadHandler, Executor1>::get(h.handler_, ex);
 655   }
 656 };
 657
 658 #endif // !defined(GENERATING_DOCUMENTATION)
 659
 660 template <typename AsyncRandomAccessReadDevice,
 661     typename Allocator, typename CompletionCondition,
 662     BOOST_ASIO_COMPLETION_TOKEN_FOR(void (boost::system::error_code,
 663       std::size_t)) ReadHandler>
 664 inline BOOST_ASIO_INITFN_AUTO_RESULT_TYPE(ReadHandler,
 665     void (boost::system::error_code, std::size_t))
 666 async_read_at(AsyncRandomAccessReadDevice& d,
 667     uint64_t offset, boost::asio::basic_streambuf<Allocator>& b,
 668     CompletionCondition completion_condition,
 669     BOOST_ASIO_MOVE_ARG(ReadHandler) handler)
 670 {
 671   return async_initiate<ReadHandler,
 672     void (boost::system::error_code, std::size_t)>(
 673       detail::initiate_async_read_at_streambuf<AsyncRandomAccessReadDevice>(d),
 674       handler, offset, &b,
 675       BOOST_ASIO_MOVE_CAST(CompletionCondition)(completion_condition));
 676 }
 677
 678 template <typename AsyncRandomAccessReadDevice, typename Allocator,
 679     BOOST_ASIO_COMPLETION_TOKEN_FOR(void (boost::system::error_code,
 680       std::size_t)) ReadHandler>
 681 inline BOOST_ASIO_INITFN_AUTO_RESULT_TYPE(ReadHandler,
 682     void (boost::system::error_code, std::size_t))
 683 async_read_at(AsyncRandomAccessReadDevice& d,
 684     uint64_t offset, boost::asio::basic_streambuf<Allocator>& b,
 685     BOOST_ASIO_MOVE_ARG(ReadHandler) handler)
 686 {
 687   return async_initiate<ReadHandler,
 688     void (boost::system::error_code, std::size_t)>(
 689       detail::initiate_async_read_at_streambuf<AsyncRandomAccessReadDevice>(d),
 690       handler, offset, &b, transfer_all());
 691 }
 692
 693 #endif // !defined(BOOST_ASIO_NO_IOSTREAM)
 694 #endif // !defined(BOOST_ASIO_NO_EXTENSIONS)
 695
 696 } // namespace asio
 697 } // namespace boost
 698
 699 #include <boost/asio/detail/pop_options.hpp>
 700
 701 #endif // BOOST_ASIO_IMPL_READ_AT_HPP