code: func pad(input []byte, size int, left bool) []byte {
  	if len(input) >= size {
  		return input[:size]
  	}
  	padded := make([]byte, size)
  	if left {
  		copy(padded[size-len(input):], input)
  	} else {
  		copy(padded, input)
  	}
  	return padded
  }
docs: // quick helper padding