slowCh <- obj
					continue
				}

				batch = append(batch, obj.Item)

				if len(batch) < *r.Source.Snowball.Batch {
					continue
				}
				writeFn(batch)
				batch = batch[:0]
			}
			writeFn(batch)
			xioutil.SafeClose(slowCh)
		}()
	} else {
		slowCh = walkCh
	}

	if cap(buf) < len(buf)+20 {
		b := make([]byte, len(buf), 20+cap(buf)*2)
		copy(b, buf)
		buf = b
	}
	writeAt := len(buf)
	buf = buf[0 : len(buf)+ctxt.Arch.PtrSize]
	writePtr(ctxt, buf[writeAt:], word)
	return buf
}

// Write a pointer-sized uint to the beginning of buf.
func writePtr(ctxt *obj.Link, buf []byte, word uint64) {
	switch ctxt.Arch.PtrSize {
	case 4: