Flushed any outstanding buffers in the stream. Will block during
the operation. Closing the stream will implicitly cause a flush.
This function is optional for inherited classes.
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.
Flushed any outstanding buffers in the stream. Will block during the operation. Closing the stream will implicitly cause a flush. This function is optional for inherited classes. 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.