Exemple #1
0
func testFrac(c *C, v mysql.Decimal) {
	b := EncodeDecimal([]byte{}, v)
	_, d, err := DecodeDecimal(b)
	c.Assert(err, IsNil)
	c.Assert(v.Equals(d), IsTrue)
	c.Assert(v.FracDigits(), Equals, d.FracDigits())
	c.Assert(v.String(), Equals, d.String())
}
Exemple #2
0
// DecodeDecimal decodes bytes to decimal.
// DecodeFloat decodes a float from a byte slice
// Decimal decoding:
// Byte -> value sign
// DecodeInt -> exp value
// DecodeBytes -> abs value bytes
func DecodeDecimal(b []byte) ([]byte, mysql.Decimal, error) {
	var (
		r   = b
		d   mysql.Decimal
		err error
	)

	// Decode value sign.
	valSign := int64(r[0])
	r = r[1:]
	if valSign == zeroSign {
		d, err = mysql.ParseDecimal("0")
		return r, d, errors.Trace(err)
	}

	// Decode exp value.
	expVal := int64(0)
	r, expVal, err = DecodeInt(r)
	if err != nil {
		return r, d, errors.Trace(err)
	}

	// Decode abs value bytes.
	value := []byte{}
	if valSign == negativeSign {
		expVal = -expVal
		r, value, err = DecodeBytesDesc(r)
	} else {
		r, value, err = DecodeBytes(r)
	}
	if err != nil {
		return r, d, errors.Trace(err)
	}

	// Set decimal sign and point to value.
	if valSign == negativeSign {
		value = append([]byte("-0."), value...)
	} else {
		value = append([]byte("0."), value...)
	}

	numberDecimal, err := mysql.ParseDecimal(string(value))
	if err != nil {
		return r, d, errors.Trace(err)
	}

	expDecimal := mysql.NewDecimalFromInt(1, int32(expVal))
	d = numberDecimal.Mul(expDecimal)
	if expDecimal.Exponent() > 0 {
		// For int64(3), it will be converted to value=0.3 and exp=1 when doing encode.
		// Its frac will be changed after we run d = numberDecimal.Mul(expDecimal).
		// So we try to get frac to the original one.
		d.SetFracDigits(d.FracDigits() - expDecimal.Exponent())
	}
	return r, d, nil
}