code: func Len(v int32) int {
  	u := uint32(v)
  	switch {
  	case u < 0x80:
  		return 1
  	case u < 0x4000:
  		return 2
  	case u < 0x200000:
  		return 3
  	case u < 0x10000000:
  		return 4
  	default:
  		return 5
  	}
  }
docs: // Len returns the number of bytes required to encode u.