796 lines
30 KiB
C++
796 lines
30 KiB
C++
//
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// read_at.hpp
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// ~~~~~~~~~~~
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//
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// Copyright (c) 2003-2023 Christopher M. Kohlhoff (chris at kohlhoff dot com)
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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#ifndef ASIO_READ_AT_HPP
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#define ASIO_READ_AT_HPP
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#if defined(_MSC_VER) && (_MSC_VER >= 1200)
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# pragma once
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#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
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#include "asio/detail/config.hpp"
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#include <cstddef>
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#include "asio/async_result.hpp"
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#include "asio/completion_condition.hpp"
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#include "asio/detail/cstdint.hpp"
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#include "asio/error.hpp"
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#if !defined(ASIO_NO_EXTENSIONS)
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# include "asio/basic_streambuf_fwd.hpp"
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#endif // !defined(ASIO_NO_EXTENSIONS)
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#include "asio/detail/push_options.hpp"
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namespace asio {
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namespace detail {
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template <typename> class initiate_async_read_at;
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#if !defined(ASIO_NO_IOSTREAM)
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template <typename> class initiate_async_read_at_streambuf;
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#endif // !defined(ASIO_NO_IOSTREAM)
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} // namespace detail
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/**
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* @defgroup read_at asio::read_at
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*
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* @brief The @c read_at function is a composed operation that reads a certain
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* amount of data at the specified offset before returning.
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*/
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/*@{*/
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/// Attempt to read a certain amount of data at the specified offset before
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/// returning.
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/**
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* This function is used to read a certain number of bytes of data from a
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* random access device at the specified offset. The call will block until one
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* of the following conditions is true:
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*
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* @li The supplied buffers are full. That is, the bytes transferred is equal to
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* the sum of the buffer sizes.
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*
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* @li An error occurred.
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*
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* This operation is implemented in terms of zero or more calls to the device's
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* read_some_at function.
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*
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* @param d The device from which the data is to be read. The type must support
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* the SyncRandomAccessReadDevice concept.
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*
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* @param offset The offset at which the data will be read.
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*
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* @param buffers One or more buffers into which the data will be read. The sum
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* of the buffer sizes indicates the maximum number of bytes to read from the
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* device.
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*
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* @returns The number of bytes transferred.
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*
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* @throws asio::system_error Thrown on failure.
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*
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* @par Example
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* To read into a single data buffer use the @ref buffer function as follows:
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* @code asio::read_at(d, 42, asio::buffer(data, size)); @endcode
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* See the @ref buffer documentation for information on reading into multiple
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* buffers in one go, and how to use it with arrays, boost::array or
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* std::vector.
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*
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* @note This overload is equivalent to calling:
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* @code asio::read_at(
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* d, 42, buffers,
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* asio::transfer_all()); @endcode
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*/
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template <typename SyncRandomAccessReadDevice, typename MutableBufferSequence>
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std::size_t read_at(SyncRandomAccessReadDevice& d,
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uint64_t offset, const MutableBufferSequence& buffers);
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/// Attempt to read a certain amount of data at the specified offset before
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/// returning.
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/**
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* This function is used to read a certain number of bytes of data from a
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* random access device at the specified offset. The call will block until one
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* of the following conditions is true:
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*
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* @li The supplied buffers are full. That is, the bytes transferred is equal to
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* the sum of the buffer sizes.
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*
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* @li An error occurred.
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*
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* This operation is implemented in terms of zero or more calls to the device's
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* read_some_at function.
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*
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* @param d The device from which the data is to be read. The type must support
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* the SyncRandomAccessReadDevice concept.
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*
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* @param offset The offset at which the data will be read.
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*
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* @param buffers One or more buffers into which the data will be read. The sum
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* of the buffer sizes indicates the maximum number of bytes to read from the
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* device.
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*
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* @param ec Set to indicate what error occurred, if any.
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*
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* @returns The number of bytes transferred.
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*
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* @par Example
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* To read into a single data buffer use the @ref buffer function as follows:
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* @code asio::read_at(d, 42,
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* asio::buffer(data, size), ec); @endcode
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* See the @ref buffer documentation for information on reading into multiple
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* buffers in one go, and how to use it with arrays, boost::array or
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* std::vector.
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*
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* @note This overload is equivalent to calling:
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* @code asio::read_at(
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* d, 42, buffers,
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* asio::transfer_all(), ec); @endcode
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*/
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template <typename SyncRandomAccessReadDevice, typename MutableBufferSequence>
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std::size_t read_at(SyncRandomAccessReadDevice& d,
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uint64_t offset, const MutableBufferSequence& buffers,
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asio::error_code& ec);
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/// Attempt to read a certain amount of data at the specified offset before
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/// returning.
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/**
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* This function is used to read a certain number of bytes of data from a
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* random access device at the specified offset. The call will block until one
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* of the following conditions is true:
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*
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* @li The supplied buffers are full. That is, the bytes transferred is equal to
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* the sum of the buffer sizes.
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*
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* @li The completion_condition function object returns 0.
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*
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* This operation is implemented in terms of zero or more calls to the device's
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* read_some_at function.
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*
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* @param d The device from which the data is to be read. The type must support
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* the SyncRandomAccessReadDevice concept.
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*
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* @param offset The offset at which the data will be read.
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*
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* @param buffers One or more buffers into which the data will be read. The sum
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* of the buffer sizes indicates the maximum number of bytes to read from the
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* device.
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*
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* @param completion_condition The function object to be called to determine
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* whether the read operation is complete. The signature of the function object
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* must be:
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* @code std::size_t completion_condition(
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* // Result of latest read_some_at operation.
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* const asio::error_code& error,
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*
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* // Number of bytes transferred so far.
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* std::size_t bytes_transferred
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* ); @endcode
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* A return value of 0 indicates that the read operation is complete. A non-zero
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* return value indicates the maximum number of bytes to be read on the next
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* call to the device's read_some_at function.
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*
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* @returns The number of bytes transferred.
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*
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* @throws asio::system_error Thrown on failure.
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*
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* @par Example
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* To read into a single data buffer use the @ref buffer function as follows:
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* @code asio::read_at(d, 42, asio::buffer(data, size),
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* asio::transfer_at_least(32)); @endcode
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* See the @ref buffer documentation for information on reading into multiple
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* buffers in one go, and how to use it with arrays, boost::array or
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* std::vector.
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*/
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template <typename SyncRandomAccessReadDevice, typename MutableBufferSequence,
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typename CompletionCondition>
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std::size_t read_at(SyncRandomAccessReadDevice& d,
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uint64_t offset, const MutableBufferSequence& buffers,
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CompletionCondition completion_condition);
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/// Attempt to read a certain amount of data at the specified offset before
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/// returning.
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/**
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* This function is used to read a certain number of bytes of data from a
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* random access device at the specified offset. The call will block until one
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* of the following conditions is true:
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*
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* @li The supplied buffers are full. That is, the bytes transferred is equal to
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* the sum of the buffer sizes.
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*
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* @li The completion_condition function object returns 0.
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*
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* This operation is implemented in terms of zero or more calls to the device's
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* read_some_at function.
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*
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* @param d The device from which the data is to be read. The type must support
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* the SyncRandomAccessReadDevice concept.
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*
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* @param offset The offset at which the data will be read.
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*
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* @param buffers One or more buffers into which the data will be read. The sum
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* of the buffer sizes indicates the maximum number of bytes to read from the
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* device.
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*
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* @param completion_condition The function object to be called to determine
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* whether the read operation is complete. The signature of the function object
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* must be:
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* @code std::size_t completion_condition(
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* // Result of latest read_some_at operation.
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* const asio::error_code& error,
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*
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* // Number of bytes transferred so far.
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* std::size_t bytes_transferred
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* ); @endcode
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* A return value of 0 indicates that the read operation is complete. A non-zero
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* return value indicates the maximum number of bytes to be read on the next
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* call to the device's read_some_at function.
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*
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* @param ec Set to indicate what error occurred, if any.
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*
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* @returns The number of bytes read. If an error occurs, returns the total
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* number of bytes successfully transferred prior to the error.
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*/
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template <typename SyncRandomAccessReadDevice, typename MutableBufferSequence,
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typename CompletionCondition>
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std::size_t read_at(SyncRandomAccessReadDevice& d,
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uint64_t offset, const MutableBufferSequence& buffers,
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CompletionCondition completion_condition, asio::error_code& ec);
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#if !defined(ASIO_NO_EXTENSIONS)
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#if !defined(ASIO_NO_IOSTREAM)
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/// Attempt to read a certain amount of data at the specified offset before
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/// returning.
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/**
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* This function is used to read a certain number of bytes of data from a
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* random access device at the specified offset. The call will block until one
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* of the following conditions is true:
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*
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* @li An error occurred.
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*
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* This operation is implemented in terms of zero or more calls to the device's
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* read_some_at function.
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*
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* @param d The device from which the data is to be read. The type must support
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* the SyncRandomAccessReadDevice concept.
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*
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* @param offset The offset at which the data will be read.
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*
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* @param b The basic_streambuf object into which the data will be read.
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*
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* @returns The number of bytes transferred.
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*
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* @throws asio::system_error Thrown on failure.
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*
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* @note This overload is equivalent to calling:
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* @code asio::read_at(
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* d, 42, b,
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* asio::transfer_all()); @endcode
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*/
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template <typename SyncRandomAccessReadDevice, typename Allocator>
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std::size_t read_at(SyncRandomAccessReadDevice& d,
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uint64_t offset, basic_streambuf<Allocator>& b);
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/// Attempt to read a certain amount of data at the specified offset before
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/// returning.
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/**
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* This function is used to read a certain number of bytes of data from a
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* random access device at the specified offset. The call will block until one
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* of the following conditions is true:
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*
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* @li An error occurred.
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*
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* This operation is implemented in terms of zero or more calls to the device's
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* read_some_at function.
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*
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* @param d The device from which the data is to be read. The type must support
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* the SyncRandomAccessReadDevice concept.
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*
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* @param offset The offset at which the data will be read.
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*
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* @param b The basic_streambuf object into which the data will be read.
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*
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* @param ec Set to indicate what error occurred, if any.
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*
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* @returns The number of bytes transferred.
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*
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* @note This overload is equivalent to calling:
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* @code asio::read_at(
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* d, 42, b,
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* asio::transfer_all(), ec); @endcode
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*/
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template <typename SyncRandomAccessReadDevice, typename Allocator>
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std::size_t read_at(SyncRandomAccessReadDevice& d,
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uint64_t offset, basic_streambuf<Allocator>& b,
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asio::error_code& ec);
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/// Attempt to read a certain amount of data at the specified offset before
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/// returning.
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/**
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* This function is used to read a certain number of bytes of data from a
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* random access device at the specified offset. The call will block until one
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* of the following conditions is true:
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*
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* @li The completion_condition function object returns 0.
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*
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* This operation is implemented in terms of zero or more calls to the device's
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* read_some_at function.
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*
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* @param d The device from which the data is to be read. The type must support
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* the SyncRandomAccessReadDevice concept.
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*
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* @param offset The offset at which the data will be read.
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*
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* @param b The basic_streambuf object into which the data will be read.
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*
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* @param completion_condition The function object to be called to determine
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* whether the read operation is complete. The signature of the function object
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* must be:
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* @code std::size_t completion_condition(
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* // Result of latest read_some_at operation.
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* const asio::error_code& error,
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*
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* // Number of bytes transferred so far.
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* std::size_t bytes_transferred
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* ); @endcode
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* A return value of 0 indicates that the read operation is complete. A non-zero
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* return value indicates the maximum number of bytes to be read on the next
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* call to the device's read_some_at function.
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*
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* @returns The number of bytes transferred.
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*
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* @throws asio::system_error Thrown on failure.
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*/
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template <typename SyncRandomAccessReadDevice, typename Allocator,
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typename CompletionCondition>
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std::size_t read_at(SyncRandomAccessReadDevice& d,
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uint64_t offset, basic_streambuf<Allocator>& b,
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CompletionCondition completion_condition);
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/// Attempt to read a certain amount of data at the specified offset before
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/// returning.
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/**
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* This function is used to read a certain number of bytes of data from a
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* random access device at the specified offset. The call will block until one
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* of the following conditions is true:
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*
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* @li The completion_condition function object returns 0.
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*
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* This operation is implemented in terms of zero or more calls to the device's
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* read_some_at function.
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*
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* @param d The device from which the data is to be read. The type must support
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* the SyncRandomAccessReadDevice concept.
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*
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* @param offset The offset at which the data will be read.
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*
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* @param b The basic_streambuf object into which the data will be read.
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*
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* @param completion_condition The function object to be called to determine
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* whether the read operation is complete. The signature of the function object
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* must be:
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* @code std::size_t completion_condition(
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* // Result of latest read_some_at operation.
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* const asio::error_code& error,
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*
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* // Number of bytes transferred so far.
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* std::size_t bytes_transferred
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* ); @endcode
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* A return value of 0 indicates that the read operation is complete. A non-zero
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* return value indicates the maximum number of bytes to be read on the next
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* call to the device's read_some_at function.
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*
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* @param ec Set to indicate what error occurred, if any.
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*
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* @returns The number of bytes read. If an error occurs, returns the total
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* number of bytes successfully transferred prior to the error.
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*/
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template <typename SyncRandomAccessReadDevice, typename Allocator,
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typename CompletionCondition>
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std::size_t read_at(SyncRandomAccessReadDevice& d,
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uint64_t offset, basic_streambuf<Allocator>& b,
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CompletionCondition completion_condition, asio::error_code& ec);
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#endif // !defined(ASIO_NO_IOSTREAM)
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#endif // !defined(ASIO_NO_EXTENSIONS)
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/*@}*/
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/**
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* @defgroup async_read_at asio::async_read_at
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*
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* @brief The @c async_read_at function is a composed asynchronous operation
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* that reads a certain amount of data at the specified offset.
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*/
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/*@{*/
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/// Start an asynchronous operation to read a certain amount of data at the
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/// specified offset.
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/**
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* This function is used to asynchronously read a certain number of bytes of
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* data from a random access device at the specified offset. It is an
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* initiating function for an @ref asynchronous_operation, and always returns
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* immediately. The asynchronous operation will continue until one of the
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* following conditions is true:
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*
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* @li The supplied buffers are full. That is, the bytes transferred is equal to
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* the sum of the buffer sizes.
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*
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* @li An error occurred.
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*
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* This operation is implemented in terms of zero or more calls to the device's
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* async_read_some_at function.
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*
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* @param d The device from which the data is to be read. The type must support
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* the AsyncRandomAccessReadDevice concept.
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*
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* @param offset The offset at which the data will be read.
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*
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* @param buffers One or more buffers into which the data will be read. The sum
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* of the buffer sizes indicates the maximum number of bytes to read from the
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* device. Although the buffers object may be copied as necessary, ownership of
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* the underlying memory blocks is retained by the caller, which must guarantee
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* that they remain valid until the completion handler is called.
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*
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* @param token The @ref completion_token that will be used to produce a
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* completion handler, which will be called when the read completes.
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* Potential completion tokens include @ref use_future, @ref use_awaitable,
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* @ref yield_context, or a function object with the correct completion
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* signature. The function signature of the completion handler must be:
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* @code void handler(
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* // Result of operation.
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* const asio::error_code& error,
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*
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* // Number of bytes copied into the buffers. If an error
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* // occurred, this will be the number of bytes successfully
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* // transferred prior to the error.
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* std::size_t bytes_transferred
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* ); @endcode
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* Regardless of whether the asynchronous operation completes immediately or
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* not, the completion handler will not be invoked from within this function.
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* On immediate completion, invocation of the handler will be performed in a
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* manner equivalent to using asio::post().
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*
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* @par Completion Signature
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* @code void(asio::error_code, std::size_t) @endcode
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*
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* @par Example
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* To read into a single data buffer use the @ref buffer function as follows:
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* @code
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* asio::async_read_at(d, 42, asio::buffer(data, size), handler);
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* @endcode
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* See the @ref buffer documentation for information on reading into multiple
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* buffers in one go, and how to use it with arrays, boost::array or
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* std::vector.
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*
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* @note This overload is equivalent to calling:
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* @code asio::async_read_at(
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* d, 42, buffers,
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* asio::transfer_all(),
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* handler); @endcode
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*
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* @par Per-Operation Cancellation
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* This asynchronous operation supports cancellation for the following
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* asio::cancellation_type values:
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*
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* @li @c cancellation_type::terminal
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*
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* @li @c cancellation_type::partial
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*
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* if they are also supported by the @c AsyncRandomAccessReadDevice type's
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* async_read_some_at operation.
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*/
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|
template <typename AsyncRandomAccessReadDevice, typename MutableBufferSequence,
|
|
ASIO_COMPLETION_TOKEN_FOR(void (asio::error_code,
|
|
std::size_t)) ReadToken
|
|
ASIO_DEFAULT_COMPLETION_TOKEN_TYPE(
|
|
typename AsyncRandomAccessReadDevice::executor_type)>
|
|
ASIO_INITFN_AUTO_RESULT_TYPE_PREFIX(ReadToken,
|
|
void (asio::error_code, std::size_t))
|
|
async_read_at(AsyncRandomAccessReadDevice& d, uint64_t offset,
|
|
const MutableBufferSequence& buffers,
|
|
ASIO_MOVE_ARG(ReadToken) token
|
|
ASIO_DEFAULT_COMPLETION_TOKEN(
|
|
typename AsyncRandomAccessReadDevice::executor_type))
|
|
ASIO_INITFN_AUTO_RESULT_TYPE_SUFFIX((
|
|
async_initiate<ReadToken,
|
|
void (asio::error_code, std::size_t)>(
|
|
declval<detail::initiate_async_read_at<AsyncRandomAccessReadDevice> >(),
|
|
token, offset, buffers, transfer_all())));
|
|
|
|
/// Start an asynchronous operation to read a certain amount of data at the
|
|
/// specified offset.
|
|
/**
|
|
* This function is used to asynchronously read a certain number of bytes of
|
|
* data from a random access device at the specified offset. It is an
|
|
* initiating function for an @ref asynchronous_operation, and always returns
|
|
* immediately. The asynchronous operation will continue until one of the
|
|
* following conditions is true:
|
|
*
|
|
* @li The supplied buffers are full. That is, the bytes transferred is equal to
|
|
* the sum of the buffer sizes.
|
|
*
|
|
* @li The completion_condition function object returns 0.
|
|
*
|
|
* @param d The device from which the data is to be read. The type must support
|
|
* the AsyncRandomAccessReadDevice concept.
|
|
*
|
|
* @param offset The offset at which the data will be read.
|
|
*
|
|
* @param buffers One or more buffers into which the data will be read. The sum
|
|
* of the buffer sizes indicates the maximum number of bytes to read from the
|
|
* device. Although the buffers object may be copied as necessary, ownership of
|
|
* the underlying memory blocks is retained by the caller, which must guarantee
|
|
* that they remain valid until the completion handler is called.
|
|
*
|
|
* @param completion_condition The function object to be called to determine
|
|
* whether the read operation is complete. The signature of the function object
|
|
* must be:
|
|
* @code std::size_t completion_condition(
|
|
* // Result of latest async_read_some_at operation.
|
|
* const asio::error_code& error,
|
|
*
|
|
* // Number of bytes transferred so far.
|
|
* std::size_t bytes_transferred
|
|
* ); @endcode
|
|
* A return value of 0 indicates that the read operation is complete. A non-zero
|
|
* return value indicates the maximum number of bytes to be read on the next
|
|
* call to the device's async_read_some_at function.
|
|
*
|
|
* @param token The @ref completion_token that will be used to produce a
|
|
* completion handler, which will be called when the read completes.
|
|
* Potential completion tokens include @ref use_future, @ref use_awaitable,
|
|
* @ref yield_context, or a function object with the correct completion
|
|
* signature. The function signature of the completion handler must be:
|
|
* @code void handler(
|
|
* // Result of operation.
|
|
* const asio::error_code& error,
|
|
*
|
|
* // Number of bytes copied into the buffers. If an error
|
|
* // occurred, this will be the number of bytes successfully
|
|
* // transferred prior to the error.
|
|
* std::size_t bytes_transferred
|
|
* ); @endcode
|
|
* Regardless of whether the asynchronous operation completes immediately or
|
|
* not, the completion handler will not be invoked from within this function.
|
|
* On immediate completion, invocation of the handler will be performed in a
|
|
* manner equivalent to using asio::post().
|
|
*
|
|
* @par Completion Signature
|
|
* @code void(asio::error_code, std::size_t) @endcode
|
|
*
|
|
* @par Example
|
|
* To read into a single data buffer use the @ref buffer function as follows:
|
|
* @code asio::async_read_at(d, 42,
|
|
* asio::buffer(data, size),
|
|
* asio::transfer_at_least(32),
|
|
* handler); @endcode
|
|
* See the @ref buffer documentation for information on reading into multiple
|
|
* buffers in one go, and how to use it with arrays, boost::array or
|
|
* std::vector.
|
|
*
|
|
* @par Per-Operation Cancellation
|
|
* This asynchronous operation supports cancellation for the following
|
|
* asio::cancellation_type values:
|
|
*
|
|
* @li @c cancellation_type::terminal
|
|
*
|
|
* @li @c cancellation_type::partial
|
|
*
|
|
* if they are also supported by the @c AsyncRandomAccessReadDevice type's
|
|
* async_read_some_at operation.
|
|
*/
|
|
template <typename AsyncRandomAccessReadDevice,
|
|
typename MutableBufferSequence, typename CompletionCondition,
|
|
ASIO_COMPLETION_TOKEN_FOR(void (asio::error_code,
|
|
std::size_t)) ReadToken
|
|
ASIO_DEFAULT_COMPLETION_TOKEN_TYPE(
|
|
typename AsyncRandomAccessReadDevice::executor_type)>
|
|
ASIO_INITFN_AUTO_RESULT_TYPE_PREFIX(ReadToken,
|
|
void (asio::error_code, std::size_t))
|
|
async_read_at(AsyncRandomAccessReadDevice& d,
|
|
uint64_t offset, const MutableBufferSequence& buffers,
|
|
CompletionCondition completion_condition,
|
|
ASIO_MOVE_ARG(ReadToken) token
|
|
ASIO_DEFAULT_COMPLETION_TOKEN(
|
|
typename AsyncRandomAccessReadDevice::executor_type))
|
|
ASIO_INITFN_AUTO_RESULT_TYPE_SUFFIX((
|
|
async_initiate<ReadToken,
|
|
void (asio::error_code, std::size_t)>(
|
|
declval<detail::initiate_async_read_at<AsyncRandomAccessReadDevice> >(),
|
|
token, offset, buffers,
|
|
ASIO_MOVE_CAST(CompletionCondition)(completion_condition))));
|
|
|
|
#if !defined(ASIO_NO_EXTENSIONS)
|
|
#if !defined(ASIO_NO_IOSTREAM)
|
|
|
|
/// Start an asynchronous operation to read a certain amount of data at the
|
|
/// specified offset.
|
|
/**
|
|
* This function is used to asynchronously read a certain number of bytes of
|
|
* data from a random access device at the specified offset. It is an
|
|
* initiating function for an @ref asynchronous_operation, and always returns
|
|
* immediately. The asynchronous operation will continue until one of the
|
|
* following conditions is true:
|
|
*
|
|
* @li An error occurred.
|
|
*
|
|
* This operation is implemented in terms of zero or more calls to the device's
|
|
* async_read_some_at function.
|
|
*
|
|
* @param d The device from which the data is to be read. The type must support
|
|
* the AsyncRandomAccessReadDevice concept.
|
|
*
|
|
* @param offset The offset at which the data will be read.
|
|
*
|
|
* @param b A basic_streambuf object into which the data will be read. Ownership
|
|
* of the streambuf is retained by the caller, which must guarantee that it
|
|
* remains valid until the completion handler is called.
|
|
*
|
|
* @param token The @ref completion_token that will be used to produce a
|
|
* completion handler, which will be called when the read completes.
|
|
* Potential completion tokens include @ref use_future, @ref use_awaitable,
|
|
* @ref yield_context, or a function object with the correct completion
|
|
* signature. The function signature of the completion handler must be:
|
|
* @code void handler(
|
|
* // Result of operation.
|
|
* const asio::error_code& error,
|
|
*
|
|
* // Number of bytes copied into the buffers. If an error
|
|
* // occurred, this will be the number of bytes successfully
|
|
* // transferred prior to the error.
|
|
* std::size_t bytes_transferred
|
|
* ); @endcode
|
|
* Regardless of whether the asynchronous operation completes immediately or
|
|
* not, the completion handler will not be invoked from within this function.
|
|
* On immediate completion, invocation of the handler will be performed in a
|
|
* manner equivalent to using asio::post().
|
|
*
|
|
* @par Completion Signature
|
|
* @code void(asio::error_code, std::size_t) @endcode
|
|
*
|
|
* @note This overload is equivalent to calling:
|
|
* @code asio::async_read_at(
|
|
* d, 42, b,
|
|
* asio::transfer_all(),
|
|
* handler); @endcode
|
|
*
|
|
* @par Per-Operation Cancellation
|
|
* This asynchronous operation supports cancellation for the following
|
|
* asio::cancellation_type values:
|
|
*
|
|
* @li @c cancellation_type::terminal
|
|
*
|
|
* @li @c cancellation_type::partial
|
|
*
|
|
* if they are also supported by the @c AsyncRandomAccessReadDevice type's
|
|
* async_read_some_at operation.
|
|
*/
|
|
template <typename AsyncRandomAccessReadDevice, typename Allocator,
|
|
ASIO_COMPLETION_TOKEN_FOR(void (asio::error_code,
|
|
std::size_t)) ReadToken
|
|
ASIO_DEFAULT_COMPLETION_TOKEN_TYPE(
|
|
typename AsyncRandomAccessReadDevice::executor_type)>
|
|
ASIO_INITFN_AUTO_RESULT_TYPE_PREFIX(ReadToken,
|
|
void (asio::error_code, std::size_t))
|
|
async_read_at(AsyncRandomAccessReadDevice& d,
|
|
uint64_t offset, basic_streambuf<Allocator>& b,
|
|
ASIO_MOVE_ARG(ReadToken) token
|
|
ASIO_DEFAULT_COMPLETION_TOKEN(
|
|
typename AsyncRandomAccessReadDevice::executor_type))
|
|
ASIO_INITFN_AUTO_RESULT_TYPE_SUFFIX((
|
|
async_initiate<ReadToken,
|
|
void (asio::error_code, std::size_t)>(
|
|
declval<detail::initiate_async_read_at_streambuf<
|
|
AsyncRandomAccessReadDevice> >(),
|
|
token, offset, &b, transfer_all())));
|
|
|
|
/// Start an asynchronous operation to read a certain amount of data at the
|
|
/// specified offset.
|
|
/**
|
|
* This function is used to asynchronously read a certain number of bytes of
|
|
* data from a random access device at the specified offset. It is an
|
|
* initiating function for an @ref asynchronous_operation, and always returns
|
|
* immediately. The asynchronous operation will continue until one of the
|
|
* following conditions is true:
|
|
*
|
|
* @li The completion_condition function object returns 0.
|
|
*
|
|
* This operation is implemented in terms of zero or more calls to the device's
|
|
* async_read_some_at function.
|
|
*
|
|
* @param d The device from which the data is to be read. The type must support
|
|
* the AsyncRandomAccessReadDevice concept.
|
|
*
|
|
* @param offset The offset at which the data will be read.
|
|
*
|
|
* @param b A basic_streambuf object into which the data will be read. Ownership
|
|
* of the streambuf is retained by the caller, which must guarantee that it
|
|
* remains valid until the completion handler is called.
|
|
*
|
|
* @param completion_condition The function object to be called to determine
|
|
* whether the read operation is complete. The signature of the function object
|
|
* must be:
|
|
* @code std::size_t completion_condition(
|
|
* // Result of latest async_read_some_at operation.
|
|
* const asio::error_code& error,
|
|
*
|
|
* // Number of bytes transferred so far.
|
|
* std::size_t bytes_transferred
|
|
* ); @endcode
|
|
* A return value of 0 indicates that the read operation is complete. A non-zero
|
|
* return value indicates the maximum number of bytes to be read on the next
|
|
* call to the device's async_read_some_at function.
|
|
*
|
|
* @param token The @ref completion_token that will be used to produce a
|
|
* completion handler, which will be called when the read completes.
|
|
* Potential completion tokens include @ref use_future, @ref use_awaitable,
|
|
* @ref yield_context, or a function object with the correct completion
|
|
* signature. The function signature of the completion handler must be:
|
|
* @code void handler(
|
|
* // Result of operation.
|
|
* const asio::error_code& error,
|
|
*
|
|
* // Number of bytes copied into the buffers. If an error
|
|
* // occurred, this will be the number of bytes successfully
|
|
* // transferred prior to the error.
|
|
* std::size_t bytes_transferred
|
|
* ); @endcode
|
|
* Regardless of whether the asynchronous operation completes immediately or
|
|
* not, the completion handler will not be invoked from within this function.
|
|
* On immediate completion, invocation of the handler will be performed in a
|
|
* manner equivalent to using asio::post().
|
|
*
|
|
* @par Completion Signature
|
|
* @code void(asio::error_code, std::size_t) @endcode
|
|
*
|
|
* @par Per-Operation Cancellation
|
|
* This asynchronous operation supports cancellation for the following
|
|
* asio::cancellation_type values:
|
|
*
|
|
* @li @c cancellation_type::terminal
|
|
*
|
|
* @li @c cancellation_type::partial
|
|
*
|
|
* if they are also supported by the @c AsyncRandomAccessReadDevice type's
|
|
* async_read_some_at operation.
|
|
*/
|
|
template <typename AsyncRandomAccessReadDevice,
|
|
typename Allocator, typename CompletionCondition,
|
|
ASIO_COMPLETION_TOKEN_FOR(void (asio::error_code,
|
|
std::size_t)) ReadToken
|
|
ASIO_DEFAULT_COMPLETION_TOKEN_TYPE(
|
|
typename AsyncRandomAccessReadDevice::executor_type)>
|
|
ASIO_INITFN_AUTO_RESULT_TYPE_PREFIX(ReadToken,
|
|
void (asio::error_code, std::size_t))
|
|
async_read_at(AsyncRandomAccessReadDevice& d,
|
|
uint64_t offset, basic_streambuf<Allocator>& b,
|
|
CompletionCondition completion_condition,
|
|
ASIO_MOVE_ARG(ReadToken) token
|
|
ASIO_DEFAULT_COMPLETION_TOKEN(
|
|
typename AsyncRandomAccessReadDevice::executor_type))
|
|
ASIO_INITFN_AUTO_RESULT_TYPE_SUFFIX((
|
|
async_initiate<ReadToken,
|
|
void (asio::error_code, std::size_t)>(
|
|
declval<detail::initiate_async_read_at_streambuf<
|
|
AsyncRandomAccessReadDevice> >(),
|
|
token, offset, &b,
|
|
ASIO_MOVE_CAST(CompletionCondition)(completion_condition))));
|
|
|
|
#endif // !defined(ASIO_NO_IOSTREAM)
|
|
#endif // !defined(ASIO_NO_EXTENSIONS)
|
|
|
|
/*@}*/
|
|
|
|
} // namespace asio
|
|
|
|
#include "asio/detail/pop_options.hpp"
|
|
|
|
#include "asio/impl/read_at.hpp"
|
|
|
|
#endif // ASIO_READ_AT_HPP
|