// // read_at.hpp // ~~~~~~~~~~~ // // Copyright (c) 2003-2018 Christopher M. Kohlhoff (chris at kohlhoff dot com) // // Distributed under the Boost Software License, Version 1.0. (See accompanying // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) // #ifndef ASIO_READ_AT_HPP #define ASIO_READ_AT_HPP #if defined(_MSC_VER) && (_MSC_VER >= 1200) # pragma once #endif // defined(_MSC_VER) && (_MSC_VER >= 1200) #include "asio/detail/config.hpp" #include #include "asio/async_result.hpp" #include "asio/detail/cstdint.hpp" #include "asio/error.hpp" #if !defined(ASIO_NO_EXTENSIONS) # include "asio/basic_streambuf_fwd.hpp" #endif // !defined(ASIO_NO_EXTENSIONS) #include "asio/detail/push_options.hpp" namespace asio { /** * @defgroup read_at asio::read_at * * @brief Attempt to read a certain amount of data at the specified offset * before returning. */ /*@{*/ /// Attempt to read a certain amount of data at the specified offset before /// returning. /** * This function is used to read a certain number of bytes of data from a * random access device at the specified offset. The call will block 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 An error occurred. * * This operation is implemented in terms of zero or more calls to the device's * read_some_at function. * * @param d The device from which the data is to be read. The type must support * the SyncRandomAccessReadDevice 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. * * @returns The number of bytes transferred. * * @throws asio::system_error Thrown on failure. * * @par Example * To read into a single data buffer use the @ref buffer function as follows: * @code asio::read_at(d, 42, asio::buffer(data, size)); @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. * * @note This overload is equivalent to calling: * @code asio::read_at( * d, 42, buffers, * asio::transfer_all()); @endcode */ template std::size_t read_at(SyncRandomAccessReadDevice& d, uint64_t offset, const MutableBufferSequence& buffers); /// Attempt to read a certain amount of data at the specified offset before /// returning. /** * This function is used to read a certain number of bytes of data from a * random access device at the specified offset. The call will block 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 An error occurred. * * This operation is implemented in terms of zero or more calls to the device's * read_some_at function. * * @param d The device from which the data is to be read. The type must support * the SyncRandomAccessReadDevice 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. * * @param ec Set to indicate what error occurred, if any. * * @returns The number of bytes transferred. * * @par Example * To read into a single data buffer use the @ref buffer function as follows: * @code asio::read_at(d, 42, * asio::buffer(data, size), ec); @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. * * @note This overload is equivalent to calling: * @code asio::read_at( * d, 42, buffers, * asio::transfer_all(), ec); @endcode */ template std::size_t read_at(SyncRandomAccessReadDevice& d, uint64_t offset, const MutableBufferSequence& buffers, asio::error_code& ec); /// Attempt to read a certain amount of data at the specified offset before /// returning. /** * This function is used to read a certain number of bytes of data from a * random access device at the specified offset. The call will block 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. * * This operation is implemented in terms of zero or more calls to the device's * read_some_at function. * * @param d The device from which the data is to be read. The type must support * the SyncRandomAccessReadDevice 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. * * @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 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 read_some_at function. * * @returns The number of bytes transferred. * * @throws asio::system_error Thrown on failure. * * @par Example * To read into a single data buffer use the @ref buffer function as follows: * @code asio::read_at(d, 42, asio::buffer(data, size), * asio::transfer_at_least(32)); @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. */ template std::size_t read_at(SyncRandomAccessReadDevice& d, uint64_t offset, const MutableBufferSequence& buffers, CompletionCondition completion_condition); /// Attempt to read a certain amount of data at the specified offset before /// returning. /** * This function is used to read a certain number of bytes of data from a * random access device at the specified offset. The call will block 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. * * This operation is implemented in terms of zero or more calls to the device's * read_some_at function. * * @param d The device from which the data is to be read. The type must support * the SyncRandomAccessReadDevice 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. * * @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 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 read_some_at function. * * @param ec Set to indicate what error occurred, if any. * * @returns The number of bytes read. If an error occurs, returns the total * number of bytes successfully transferred prior to the error. */ template std::size_t read_at(SyncRandomAccessReadDevice& d, uint64_t offset, const MutableBufferSequence& buffers, CompletionCondition completion_condition, asio::error_code& ec); #if !defined(ASIO_NO_EXTENSIONS) #if !defined(ASIO_NO_IOSTREAM) /// Attempt to read a certain amount of data at the specified offset before /// returning. /** * This function is used to read a certain number of bytes of data from a * random access device at the specified offset. The call will block 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 * read_some_at function. * * @param d The device from which the data is to be read. The type must support * the SyncRandomAccessReadDevice concept. * * @param offset The offset at which the data will be read. * * @param b The basic_streambuf object into which the data will be read. * * @returns The number of bytes transferred. * * @throws asio::system_error Thrown on failure. * * @note This overload is equivalent to calling: * @code asio::read_at( * d, 42, b, * asio::transfer_all()); @endcode */ template std::size_t read_at(SyncRandomAccessReadDevice& d, uint64_t offset, basic_streambuf& b); /// Attempt to read a certain amount of data at the specified offset before /// returning. /** * This function is used to read a certain number of bytes of data from a * random access device at the specified offset. The call will block 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 * read_some_at function. * * @param d The device from which the data is to be read. The type must support * the SyncRandomAccessReadDevice concept. * * @param offset The offset at which the data will be read. * * @param b The basic_streambuf object into which the data will be read. * * @param ec Set to indicate what error occurred, if any. * * @returns The number of bytes transferred. * * @note This overload is equivalent to calling: * @code asio::read_at( * d, 42, b, * asio::transfer_all(), ec); @endcode */ template std::size_t read_at(SyncRandomAccessReadDevice& d, uint64_t offset, basic_streambuf& b, asio::error_code& ec); /// Attempt to read a certain amount of data at the specified offset before /// returning. /** * This function is used to read a certain number of bytes of data from a * random access device at the specified offset. The call will block 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 * read_some_at function. * * @param d The device from which the data is to be read. The type must support * the SyncRandomAccessReadDevice concept. * * @param offset The offset at which the data will be read. * * @param b The basic_streambuf object into which the data will be read. * * @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 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 read_some_at function. * * @returns The number of bytes transferred. * * @throws asio::system_error Thrown on failure. */ template std::size_t read_at(SyncRandomAccessReadDevice& d, uint64_t offset, basic_streambuf& b, CompletionCondition completion_condition); /// Attempt to read a certain amount of data at the specified offset before /// returning. /** * This function is used to read a certain number of bytes of data from a * random access device at the specified offset. The call will block 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 * read_some_at function. * * @param d The device from which the data is to be read. The type must support * the SyncRandomAccessReadDevice concept. * * @param offset The offset at which the data will be read. * * @param b The basic_streambuf object into which the data will be read. * * @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 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 read_some_at function. * * @param ec Set to indicate what error occurred, if any. * * @returns The number of bytes read. If an error occurs, returns the total * number of bytes successfully transferred prior to the error. */ template std::size_t read_at(SyncRandomAccessReadDevice& d, uint64_t offset, basic_streambuf& b, CompletionCondition completion_condition, asio::error_code& ec); #endif // !defined(ASIO_NO_IOSTREAM) #endif // !defined(ASIO_NO_EXTENSIONS) /*@}*/ /** * @defgroup async_read_at asio::async_read_at * * @brief Start an asynchronous operation to read a certain amount of data at * the specified offset. */ /*@{*/ /// 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. The function call * 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 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 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 handler is called. * * @param handler The handler to be called when the read operation completes. * Copies will be made of the handler as required. The function signature of the * 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 handler will not be invoked from within this function. Invocation of * the handler will be performed in a manner equivalent to using * asio::io_context::post(). * * @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), 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. * * @note This overload is equivalent to calling: * @code asio::async_read_at( * d, 42, buffers, * asio::transfer_all(), * handler); @endcode */ template ASIO_INITFN_RESULT_TYPE(ReadHandler, void (asio::error_code, std::size_t)) async_read_at(AsyncRandomAccessReadDevice& d, uint64_t offset, const MutableBufferSequence& buffers, ASIO_MOVE_ARG(ReadHandler) handler); /// 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. The function call * 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 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 handler The handler to be called when the read operation completes. * Copies will be made of the handler as required. The function signature of the * 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 handler will not be invoked from within this function. Invocation of * the handler will be performed in a manner equivalent to using * asio::io_context::post(). * * @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. */ template ASIO_INITFN_RESULT_TYPE(ReadHandler, void (asio::error_code, std::size_t)) async_read_at(AsyncRandomAccessReadDevice& d, uint64_t offset, const MutableBufferSequence& buffers, CompletionCondition completion_condition, ASIO_MOVE_ARG(ReadHandler) handler); #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. The function call * 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 handler is called. * * @param handler The handler to be called when the read operation completes. * Copies will be made of the handler as required. The function signature of the * 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 handler will not be invoked from within this function. Invocation of * the handler will be performed in a manner equivalent to using * asio::io_context::post(). * * @note This overload is equivalent to calling: * @code asio::async_read_at( * d, 42, b, * asio::transfer_all(), * handler); @endcode */ template ASIO_INITFN_RESULT_TYPE(ReadHandler, void (asio::error_code, std::size_t)) async_read_at(AsyncRandomAccessReadDevice& d, uint64_t offset, basic_streambuf& b, ASIO_MOVE_ARG(ReadHandler) handler); /// 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. The function call * 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 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 handler The handler to be called when the read operation completes. * Copies will be made of the handler as required. The function signature of the * 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 handler will not be invoked from within this function. Invocation of * the handler will be performed in a manner equivalent to using * asio::io_context::post(). */ template ASIO_INITFN_RESULT_TYPE(ReadHandler, void (asio::error_code, std::size_t)) async_read_at(AsyncRandomAccessReadDevice& d, uint64_t offset, basic_streambuf& b, CompletionCondition completion_condition, ASIO_MOVE_ARG(ReadHandler) handler); #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