code: func DecodeDecimal(b []byte) ([]byte, *types.MyDecimal, int, int, error) {
  	failpoint.Inject("errorInDecodeDecimal", func(val failpoint.Value) {
  		if val.(bool) {
  			failpoint.Return(b, nil, 0, 0, errors.New("gofail error"))
  		}
  	})
  
  	if len(b) < 3 {
  		return b, nil, 0, 0, errors.New("insufficient bytes to decode value")
  	}
  	precision := int(b[0])
  	frac := int(b[1])
  	b = b[2:]
  	dec := new(types.MyDecimal)
  	binSize, err := dec.FromBin(b, precision, frac)
  	b = b[binSize:]
  	if err != nil {
  		return b, nil, precision, frac, errors.Trace(err)
  	}
  	return b, dec, precision, frac, nil
  }
docs: // DecodeDecimal decodes bytes to decimal.