Start an asynchronous operation to write all of the supplied data at the specified offset.
template< typename AsyncRandomAccessWriteDevice, typename Allocator, typename WriteToken = DEFAULT> DEDUCED async_write_at( AsyncRandomAccessWriteDevice & d, uint64_t offset, basic_streambuf< Allocator > & b, WriteToken && token = DEFAULT);
This function is used to asynchronously write a certain number of bytes of data to a random access device at a specified offset. 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:
basic_streambuf
has been written.
This operation is implemented in terms of zero or more calls to the device's async_write_some_at function, and is known as a composed operation. The program must ensure that the device performs no overlapping write operations (such as async_write_at, the device's async_write_some_at function, or any other composed operations that perform writes) until this operation completes. Operations are overlapping if the regions defined by their offsets, and the numbers of bytes to write, intersect.
The device to which the data is to be written. The type must support the AsyncRandomAccessWriteDevice concept.
The offset at which the data will be written.
A basic_streambuf
object from which data will be written. Ownership of the streambuf
is retained by the caller, which must guarantee that it remains valid
until the completion handler is called.
The completion
token that will be used to produce a completion handler, which
will be called when the write completes. Potential completion tokens
include use_future
,
use_awaitable
,
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 asio::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 post
.
void(asio::error_code, std::size_t)
This asynchronous operation supports cancellation for the following cancellation_type
values:
cancellation_type::terminal
cancellation_type::partial
if they are also supported by the AsyncRandomAccessWriteDevice
type's async_write_some_at operation.