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.
Virtual: truncate_fn
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. Virtual: truncate_fn