Start an asynchronous operation to write a certain amount of data to a stream.
template< typename AsyncWriteStream, typename ConstBufferSequence, typename CompletionCondition, typename WriteToken> DEDUCED async_write( AsyncWriteStream & s, const ConstBufferSequence & buffers, CompletionCondition completion_condition, WriteToken && token, typename constraint< 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. It is an initiating function for an asynchronous operation, and always returns immediately. The asynchronous operation will continue until one of the following conditions is true:
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.
The stream to which the data is to be written. The type must support the AsyncWriteStream concept.
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 completion handler is called.
The function object to be called to determine whether the write operation is complete. The signature of the function object must be:
std::size_t completion_condition( // Result of latest async_write_some operation. const boost::system::error_code& error, // Number of bytes transferred so far. std::size_t bytes_transferred );
A return value of 0 indicates that the write operation is complete. A non-zero return value indicates the maximum number of bytes to be written on the next call to the stream's async_write_some function.
token that will be used to produce a completion handler, which
will be called when the write completes. Potential completion tokens
yield_context, or a function
object with the correct completion signature. The function signature
of the completion handler must be:
void handler( // Result of operation. const boost::system::error_code& error, // Number of bytes written from the buffers. If an error // occurred, this will be less than the sum of the buffer sizes. std::size_t bytes_transferred );
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
To write a single data buffer use the
buffer function as follows:
boost::asio::async_write(s, boost::asio::buffer(data, size), boost::asio::transfer_at_least(32), handler);
documentation for information on writing multiple buffers in one go, and
how to use it with arrays, boost::array or std::vector.
This asynchronous operation supports cancellation for the following
if they are also supported by the