code: func New(cmp comparer.BasicComparer, capacity int) *DB {
  	p := &DB{
  		cmp:       cmp,
  		rnd:       rand.New(rand.NewSource(0xdeadbeef)),
  		maxHeight: 1,
  		kvData:    make([]byte, 0, capacity),
  		nodeData:  make([]int, 4+tMaxHeight),
  	}
  	p.nodeData[nHeight] = tMaxHeight
  	return p
  }
docs: // New creates a new initialized in-memory key/value DB. The capacity
  // is the initial key/value buffer capacity. The capacity is advisory,
  // not enforced.
  //
  // This DB is append-only, deleting an entry would remove entry node but not
  // reclaim KV buffer.
  //
  // The returned DB instance is safe for concurrent use.