code: func (dec *Decoder) Postings(b []byte) (int, Postings, error) {
  	d := encoding.Decbuf{B: b}
  	n := d.Be32int()
  	l := d.Get()
  	return n, newBigEndianPostings(l), d.Err()
  }
docs: // Postings returns a postings list for b and its number of elements.