if _, ok := err.(BackendDown); ok {
			return err
		}
		return tierPermErr{
			Op:  tierDelete,
			Err: err,
		}
	}
	return err
}

type tierOp uint8

const (
	_ tierOp = iota
	tierGet
	tierPut
	tierDelete
)

func (op tierOp) String() string {
	switch op {
	case tierGet:
		return "GET"
	case tierPut:
		return "PUT"

// the buffer, so that UnreadRune and UnreadByte can check for
// invalid usage. opReadRuneX constants are chosen such that
// converted to int they correspond to the rune size that was read.
type readOp int8

// Don't use iota for these, as the values need to correspond with the
// names and comments, which is easier to see when being explicit.
const (
	opRead      readOp = -1 // Any other read operation.