If @cancellable is not %NULL, then the operation can be cancelled by
triggering the cancellable object from another thread. If the operation
was cancelled, the error %G_IO_ERROR_CANCELLED will be returned. If an
operation was partially finished when the operation was cancelled the
partial result will be returned, without an error.
Truncates a stream with a given #offset.
If @cancellable is not %NULL, then the operation can be cancelled by triggering the cancellable object from another thread. If the operation was cancelled, the error %G_IO_ERROR_CANCELLED will be returned. If an operation was partially finished when the operation was cancelled the partial result will be returned, without an error.