async_write (1 of 6 overloads)

Start an asynchronous operation to write all of the supplied data to a stream.

template<
    typename AsyncWriteStream,
    typename ConstBufferSequence,
    typename WriteHandler>
DEDUCED async_write(
    AsyncWriteStream & s,
    const ConstBufferSequence & buffers,
    WriteHandler && handler,
    typename enable_if< is_const_buffer_sequence< ConstBufferSequence >::value >::type *  = 0);

This function is used to asynchronously write a certain number of bytes of data to a stream. The function call always returns immediately. The asynchronous operation will continue until one of the following conditions is true:

All of the data in the supplied buffers has been written. That is, the bytes transferred is equal to the sum of the buffer sizes.
An error occurred.

This operation is implemented in terms of zero or more calls to the stream's async_write_some function, and is known as a composed operation. The program must ensure that the stream performs no other write operations (such as async_write, the stream's async_write_some function, or any other composed operations that perform writes) until this operation completes.

Parameters

s

The stream to which the data is to be written. The type must support the AsyncWriteStream concept.

buffers

One or more buffers containing the data to be written. 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 write 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& error, // Result of operation.

  std::size_t bytes_transferred           // Number of bytes written from the
                                          // buffers. If an error occurred,
                                          // this will be less than the sum
                                          // of the buffer sizes.
);

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_context::post().

Example

To write a single data buffer use the buffer function as follows:

boost::asio::async_write(s, boost::asio::buffer(data, size), handler);

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