template< typename ConstBufferSequence, typename WriteToken = DEFAULT> DEDUCED async_write_some_at( uint64_t offset, const ConstBufferSequence & buffers, WriteToken && token = DEFAULT);
This function is used to asynchronously write data to the random-access handle. It is an initiating function for an asynchronous operation, and always returns immediately.
The offset at which the data will be written.
One or more data buffers to be written to the handle. 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.
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( const boost::system::error_code& error, // Result of operation. std::size_t bytes_transferred // Number of bytes written. );
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
The write operation may not write all of the data to the file. Consider
async_write_at function if you
need to ensure that all data is written before the asynchronous operation
To write a single data buffer use the
buffer function as follows:
handle.async_write_some_at(42, boost::asio::buffer(data, size), 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