Inherited from basic_file.
Cancel all asynchronous operations associated with the file.
void cancel( asio::error_code & ec);
This function causes all outstanding asynchronous read and write operations
to finish immediately, and the handlers for cancelled operations will
be passed the
Set to indicate what error occurred, if any.
will always fail with
when run on Windows XP, Windows Server 2003, and earlier versions of
Windows, unless ASIO_ENABLE_CANCELIO is defined. However, the CancelIo
function has two issues that should be considered before enabling its
For portable cancellation, consider using the
close() function to simultaneously cancel the
outstanding operations and close the file.
When running on Windows Vista, Windows Server 2008, and later, the CancelIoEx function is always used. This function does not have the problems described above.