read_stream::async_read

read_stream::async_read_some

Asynchronously reads some data from the stream.

template<
    typename MutableBufferSequence,
    typename Handler>
void async_read_some(
    const MutableBufferSequence & buffers,
    Handler handler);

Parameters

buffers

One or more buffers into which the data will be read. The type must meet the requirements for MutableBufferSequence, as defined in the Boost.Asio documentation. 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.

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:

void handler(
  const boost::system::error_code& ec, // Result of operation.
  std::size_t bytes_transferred        // Number of bytes read.
);

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 boost::asio::io_service::post().

Remarks

The asynchronous operation will continue until one or more bytes of data has been read successfully, or until an error occurs.

The async_read_some operation may not read all of the requested number of bytes. Consider using the boost::asio::async_read function if you need to ensure that the requested amount of data is read before the asynchronous operation completes.

Example

To read into a single data buffer use the boost::asio::buffer function as follows:

read_stream.async_read_some(boost::asio::buffer(data, size), handler);

See the documentation for the boost::asio::buffer function for information on reading into multiple buffers in one go, and how to use it with arrays, boost::array or std::vector.