// // read.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_HPP #define ASIO_READ_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/buffer.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 asio::read * * @brief Attempt to read a certain amount of data from a stream before * returning. */ /*@{*/ /// Attempt to read a certain amount of data from a stream before returning. /** * This function is used to read a certain number of bytes of data from a * stream. 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 stream's * read_some function. * * @param s The stream from which the data is to be read. The type must support * the SyncReadStream concept. * * @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 * stream. * * @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(s, 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( * s, buffers, * asio::transfer_all()); @endcode */ template std::size_t read(SyncReadStream& s, const MutableBufferSequence& buffers, typename enable_if< is_mutable_buffer_sequence::value >::type* = 0); /// Attempt to read a certain amount of data from a stream before returning. /** * This function is used to read a certain number of bytes of data from a * stream. 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 stream's * read_some function. * * @param s The stream from which the data is to be read. The type must support * the SyncReadStream concept. * * @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 * stream. * * @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(s, 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( * s, buffers, * asio::transfer_all(), ec); @endcode */ template std::size_t read(SyncReadStream& s, const MutableBufferSequence& buffers, asio::error_code& ec, typename enable_if< is_mutable_buffer_sequence::value >::type* = 0); /// Attempt to read a certain amount of data from a stream before returning. /** * This function is used to read a certain number of bytes of data from a * stream. 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 stream's * read_some function. * * @param s The stream from which the data is to be read. The type must support * the SyncReadStream concept. * * @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 * stream. * * @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 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 stream's read_some 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(s, 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(SyncReadStream& s, const MutableBufferSequence& buffers, CompletionCondition completion_condition, typename enable_if< is_mutable_buffer_sequence::value >::type* = 0); /// Attempt to read a certain amount of data from a stream before returning. /** * This function is used to read a certain number of bytes of data from a * stream. 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 stream's * read_some function. * * @param s The stream from which the data is to be read. The type must support * the SyncReadStream concept. * * @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 * stream. * * @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 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 stream's read_some 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(SyncReadStream& s, const MutableBufferSequence& buffers, CompletionCondition completion_condition, asio::error_code& ec, typename enable_if< is_mutable_buffer_sequence::value >::type* = 0); /// Attempt to read a certain amount of data from a stream before returning. /** * This function is used to read a certain number of bytes of data from a * stream. The call will block until one of the following conditions is true: * * @li The specified dynamic buffer sequence is full (that is, it has reached * maximum size). * * @li An error occurred. * * This operation is implemented in terms of zero or more calls to the stream's * read_some function. * * @param s The stream from which the data is to be read. The type must support * the SyncReadStream concept. * * @param buffers The dynamic buffer sequence 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( * s, buffers, * asio::transfer_all()); @endcode */ template std::size_t read(SyncReadStream& s, ASIO_MOVE_ARG(DynamicBuffer) buffers, typename enable_if< is_dynamic_buffer::type>::value >::type* = 0); /// Attempt to read a certain amount of data from a stream before returning. /** * This function is used to read a certain number of bytes of data from a * stream. The call will block until one of the following conditions is true: * * @li The supplied buffer is full (that is, it has reached maximum size). * * @li An error occurred. * * This operation is implemented in terms of zero or more calls to the stream's * read_some function. * * @param s The stream from which the data is to be read. The type must support * the SyncReadStream concept. * * @param buffers The dynamic buffer sequence 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( * s, buffers, * asio::transfer_all(), ec); @endcode */ template std::size_t read(SyncReadStream& s, ASIO_MOVE_ARG(DynamicBuffer) buffers, asio::error_code& ec, typename enable_if< is_dynamic_buffer::type>::value >::type* = 0); /// Attempt to read a certain amount of data from a stream before returning. /** * This function is used to read a certain number of bytes of data from a * stream. The call will block until one of the following conditions is true: * * @li The specified dynamic buffer sequence is full (that is, it has reached * maximum size). * * @li The completion_condition function object returns 0. * * This operation is implemented in terms of zero or more calls to the stream's * read_some function. * * @param s The stream from which the data is to be read. The type must support * the SyncReadStream concept. * * @param buffers The dynamic buffer sequence 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 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 stream's read_some function. * * @returns The number of bytes transferred. * * @throws asio::system_error Thrown on failure. */ template std::size_t read(SyncReadStream& s, ASIO_MOVE_ARG(DynamicBuffer) buffers, CompletionCondition completion_condition, typename enable_if< is_dynamic_buffer::type>::value >::type* = 0); /// Attempt to read a certain amount of data from a stream before returning. /** * This function is used to read a certain number of bytes of data from a * stream. The call will block until one of the following conditions is true: * * @li The specified dynamic buffer sequence is full (that is, it has reached * maximum size). * * @li The completion_condition function object returns 0. * * This operation is implemented in terms of zero or more calls to the stream's * read_some function. * * @param s The stream from which the data is to be read. The type must support * the SyncReadStream concept. * * @param buffers The dynamic buffer sequence 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 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 stream's read_some 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(SyncReadStream& s, ASIO_MOVE_ARG(DynamicBuffer) buffers, CompletionCondition completion_condition, asio::error_code& ec, typename enable_if< is_dynamic_buffer::type>::value >::type* = 0); #if !defined(ASIO_NO_EXTENSIONS) #if !defined(ASIO_NO_IOSTREAM) /// Attempt to read a certain amount of data from a stream before returning. /** * This function is used to read a certain number of bytes of data from a * stream. The call will block until one of the following conditions is true: * * @li The supplied buffer is full (that is, it has reached maximum size). * * @li An error occurred. * * This operation is implemented in terms of zero or more calls to the stream's * read_some function. * * @param s The stream from which the data is to be read. The type must support * the SyncReadStream concept. * * @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( * s, b, * asio::transfer_all()); @endcode */ template std::size_t read(SyncReadStream& s, basic_streambuf& b); /// Attempt to read a certain amount of data from a stream before returning. /** * This function is used to read a certain number of bytes of data from a * stream. The call will block until one of the following conditions is true: * * @li The supplied buffer is full (that is, it has reached maximum size). * * @li An error occurred. * * This operation is implemented in terms of zero or more calls to the stream's * read_some function. * * @param s The stream from which the data is to be read. The type must support * the SyncReadStream concept. * * @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( * s, b, * asio::transfer_all(), ec); @endcode */ template std::size_t read(SyncReadStream& s, basic_streambuf& b, asio::error_code& ec); /// Attempt to read a certain amount of data from a stream before returning. /** * This function is used to read a certain number of bytes of data from a * stream. The call will block until one of the following conditions is true: * * @li The supplied buffer is full (that is, it has reached maximum size). * * @li The completion_condition function object returns 0. * * This operation is implemented in terms of zero or more calls to the stream's * read_some function. * * @param s The stream from which the data is to be read. The type must support * the SyncReadStream concept. * * @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 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 stream's read_some function. * * @returns The number of bytes transferred. * * @throws asio::system_error Thrown on failure. */ template std::size_t read(SyncReadStream& s, basic_streambuf& b, CompletionCondition completion_condition); /// Attempt to read a certain amount of data from a stream before returning. /** * This function is used to read a certain number of bytes of data from a * stream. The call will block until one of the following conditions is true: * * @li The supplied buffer is full (that is, it has reached maximum size). * * @li The completion_condition function object returns 0. * * This operation is implemented in terms of zero or more calls to the stream's * read_some function. * * @param s The stream from which the data is to be read. The type must support * the SyncReadStream concept. * * @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 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 stream's read_some 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(SyncReadStream& s, basic_streambuf& b, CompletionCondition completion_condition, asio::error_code& ec); #endif // !defined(ASIO_NO_IOSTREAM) #endif // !defined(ASIO_NO_EXTENSIONS) /*@}*/ /** * @defgroup async_read asio::async_read * * @brief Start an asynchronous operation to read a certain amount of data from * a stream. */ /*@{*/ /// Start an asynchronous operation to read a certain amount of data from a /// stream. /** * This function is used to asynchronously read a certain number of bytes of * data from a stream. 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 stream's * async_read_some function, and is known as a composed operation. The * program must ensure that the stream performs no other read operations (such * as async_read, the stream's async_read_some function, or any other composed * operations that perform reads) until this operation completes. * * @param s The stream from which the data is to be read. The type must support * the AsyncReadStream concept. * * @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 * stream. 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( * const asio::error_code& error, // Result of operation. * * std::size_t bytes_transferred // Number of bytes copied into the * // buffers. If an error occurred, * // this will be the number of * // bytes successfully transferred * // prior to the error. * ); @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(s, 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( * s, buffers, * asio::transfer_all(), * handler); @endcode */ template ASIO_INITFN_RESULT_TYPE(ReadHandler, void (asio::error_code, std::size_t)) async_read(AsyncReadStream& s, const MutableBufferSequence& buffers, ASIO_MOVE_ARG(ReadHandler) handler, typename enable_if< is_mutable_buffer_sequence::value >::type* = 0); /// Start an asynchronous operation to read a certain amount of data from a /// stream. /** * This function is used to asynchronously read a certain number of bytes of * data from a stream. 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 s The stream from which the data is to be read. The type must support * the AsyncReadStream concept. * * @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 * stream. 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 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 stream's async_read_some 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( * const asio::error_code& error, // Result of operation. * * std::size_t bytes_transferred // Number of bytes copied into the * // buffers. If an error occurred, * // this will be the number of * // bytes successfully transferred * // prior to the error. * ); @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(s, * 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(AsyncReadStream& s, const MutableBufferSequence& buffers, CompletionCondition completion_condition, ASIO_MOVE_ARG(ReadHandler) handler, typename enable_if< is_mutable_buffer_sequence::value >::type* = 0); /// Start an asynchronous operation to read a certain amount of data from a /// stream. /** * This function is used to asynchronously read a certain number of bytes of * data from a stream. The function call always returns immediately. The * asynchronous operation will continue until one of the following conditions is * true: * * @li The specified dynamic buffer sequence is full (that is, it has reached * maximum size). * * @li An error occurred. * * This operation is implemented in terms of zero or more calls to the stream's * async_read_some function, and is known as a composed operation. The * program must ensure that the stream performs no other read operations (such * as async_read, the stream's async_read_some function, or any other composed * operations that perform reads) until this operation completes. * * @param s The stream from which the data is to be read. The type must support * the AsyncReadStream concept. * * @param buffers The dynamic buffer sequence into which the data will be read. * 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( * const asio::error_code& error, // Result of operation. * * std::size_t bytes_transferred // Number of bytes copied into the * // buffers. If an error occurred, * // this will be the number of * // bytes successfully transferred * // prior to the error. * ); @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( * s, buffers, * asio::transfer_all(), * handler); @endcode */ template ASIO_INITFN_RESULT_TYPE(ReadHandler, void (asio::error_code, std::size_t)) async_read(AsyncReadStream& s, ASIO_MOVE_ARG(DynamicBuffer) buffers, ASIO_MOVE_ARG(ReadHandler) handler, typename enable_if< is_dynamic_buffer::type>::value >::type* = 0); /// Start an asynchronous operation to read a certain amount of data from a /// stream. /** * This function is used to asynchronously read a certain number of bytes of * data from a stream. The function call always returns immediately. The * asynchronous operation will continue until one of the following conditions is * true: * * @li The specified dynamic buffer sequence is full (that is, it has reached * maximum size). * * @li The completion_condition function object returns 0. * * This operation is implemented in terms of zero or more calls to the stream's * async_read_some function, and is known as a composed operation. The * program must ensure that the stream performs no other read operations (such * as async_read, the stream's async_read_some function, or any other composed * operations that perform reads) until this operation completes. * * @param s The stream from which the data is to be read. The type must support * the AsyncReadStream concept. * * @param buffers The dynamic buffer sequence into which the data will be read. * 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 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 stream's async_read_some 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( * const asio::error_code& error, // Result of operation. * * std::size_t bytes_transferred // Number of bytes copied into the * // buffers. If an error occurred, * // this will be the number of * // bytes successfully transferred * // prior to the error. * ); @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(AsyncReadStream& s, ASIO_MOVE_ARG(DynamicBuffer) buffers, CompletionCondition completion_condition, ASIO_MOVE_ARG(ReadHandler) handler, typename enable_if< is_dynamic_buffer::type>::value >::type* = 0); #if !defined(ASIO_NO_EXTENSIONS) #if !defined(ASIO_NO_IOSTREAM) /// Start an asynchronous operation to read a certain amount of data from a /// stream. /** * This function is used to asynchronously read a certain number of bytes of * data from a stream. The function call always returns immediately. The * asynchronous operation will continue until one of the following conditions is * true: * * @li The supplied buffer is full (that is, it has reached maximum size). * * @li An error occurred. * * This operation is implemented in terms of zero or more calls to the stream's * async_read_some function, and is known as a composed operation. The * program must ensure that the stream performs no other read operations (such * as async_read, the stream's async_read_some function, or any other composed * operations that perform reads) until this operation completes. * * @param s The stream from which the data is to be read. The type must support * the AsyncReadStream concept. * * @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( * const asio::error_code& error, // Result of operation. * * std::size_t bytes_transferred // Number of bytes copied into the * // buffers. If an error occurred, * // this will be the number of * // bytes successfully transferred * // prior to the error. * ); @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( * s, b, * asio::transfer_all(), * handler); @endcode */ template ASIO_INITFN_RESULT_TYPE(ReadHandler, void (asio::error_code, std::size_t)) async_read(AsyncReadStream& s, basic_streambuf& b, ASIO_MOVE_ARG(ReadHandler) handler); /// Start an asynchronous operation to read a certain amount of data from a /// stream. /** * This function is used to asynchronously read a certain number of bytes of * data from a stream. The function call always returns immediately. The * asynchronous operation will continue until one of the following conditions is * true: * * @li The supplied buffer is full (that is, it has reached maximum size). * * @li The completion_condition function object returns 0. * * This operation is implemented in terms of zero or more calls to the stream's * async_read_some function, and is known as a composed operation. The * program must ensure that the stream performs no other read operations (such * as async_read, the stream's async_read_some function, or any other composed * operations that perform reads) until this operation completes. * * @param s The stream from which the data is to be read. The type must support * the AsyncReadStream concept. * * @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 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 stream's async_read_some 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( * const asio::error_code& error, // Result of operation. * * std::size_t bytes_transferred // Number of bytes copied into the * // buffers. If an error occurred, * // this will be the number of * // bytes successfully transferred * // prior to the error. * ); @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(AsyncReadStream& s, 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.hpp" #endif // ASIO_READ_HPP