Encode decimals as floats without precision loss

Makefile

@@ -2,4 +2,4 @@ install:
 	dep ensure
 
 test:
-	go test -v ./tests
+	go test -v ./{mysql,tests}

mysql/decimal.go

@@ -2,13 +2,23 @@ package mysql
 
 import (
 	"bytes"
+	"database/sql/driver"
 	"encoding/binary"
+	"encoding/json"
 	"fmt"
+	"strconv"
+	"strings"
 )
 
+// Decimal represents a decimal type that retains precision until converted to
+// a float. It is designed to be marshaled into JSON without losing precision.
+type Decimal struct {
+	str string
+}
+
 // DecodeDecimal decodes a decimal value.
 // Implementation borrowed from https://github.com/siddontang/go-mysql/
-func DecodeDecimal(data []byte, precision int, decimals int) (string, int) {
+func DecodeDecimal(data []byte, precision int, decimals int) (Decimal, int) {
 	const digitsPerInteger int = 9
 	var compressedBytes = [...]int{0, 1, 1, 2, 2, 3, 3, 4, 4, 4}
 
@@ -21,6 +31,7 @@ func DecodeDecimal(data []byte, precision int, decimals int) (string, int) {
 		value = uint32(DecodeVarLen64BigEndian(databuff))
 		return
 	}
+
 	// See python mysql replication and https://github.com/jeremycole/mysql_binlog
 	integral := (precision - decimals)
 	uncompIntegral := int(integral / digitsPerInteger)
@@ -73,5 +84,49 @@ func DecodeDecimal(data []byte, precision int, decimals int) (string, int) {
 		pos += size
 	}
 
-	return res.String(), pos
+	return NewDecimal(res.String()), pos
+}
+
+// NewDecimal creates a new decimal with given value.
+func NewDecimal(str string) Decimal {
+	var sign string
+	if str[0] == '-' {
+		str = str[1:]
+		sign = "-"
+	}
+	str = strings.Trim(str, "0")
+	if str[0] == '.' {
+		str = "0" + str
+	}
+	if str[len(str)-1] == '.' {
+		str += "0"
+	}
+	return Decimal{sign + str}
+}
+
+// Float64 returns a float representation of the decimal. Precision could be
+// lost.
+func (d Decimal) Float64() float64 {
+	f, _ := strconv.ParseFloat(d.str, 64)
+	return f
+}
+
+var _ json.Marshaler = Decimal{}
+
+// MarshalJSON returns the JSON encoding of the decimal.
+func (d Decimal) MarshalJSON() ([]byte, error) {
+	return []byte(d.str), nil
+}
+
+var _ fmt.Stringer = Decimal{}
+
+func (d Decimal) String() string {
+	return d.str
+}
+
+var _ driver.Valuer = Decimal{}
+
+// Value returns a driver Value.
+func (d Decimal) Value() (driver.Value, error) {
+	return d.str, nil
 }

mysql/decimal_test.go

@@ -0,0 +1,231 @@
+package mysql
+
+import (
+	"encoding/json"
+	"testing"
+)
+
+func BenchmarkDecodeDecimal(b *testing.B) {
+	data := []byte{129, 134, 159, 59, 154, 201, 255, 59, 154, 201, 255, 0, 152, 150, 127, 10, 0}
+	precision := 30
+	decimals := 25
+
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		DecodeDecimal(data, precision, decimals)
+	}
+}
+
+func TestDecodeDecimalOrig(t *testing.T) {
+	testcases := []struct {
+		Data        []byte
+		Precision   int
+		Decimals    int
+		Expected    string
+		ExpectedPos int
+	}{
+		{[]byte{117, 200, 127, 255}, 4, 2, "-10.55", 2},
+		{[]byte{127, 255, 244, 127, 245}, 5, 0, "-11.0", 3},
+		{[]byte{127, 245, 253, 217, 127, 255}, 7, 3, "-10.55", 4},
+		{[]byte{127, 255, 255, 245, 200, 127, 255}, 10, 2, "-10.55", 5},
+		{[]byte{127, 255, 255, 245, 253, 217, 127, 255}, 10, 3, "-10.55", 6},
+		{[]byte{127, 255, 255, 255, 245, 200, 118, 196}, 13, 2, "-10.55", 6},
+		{[]byte{118, 196, 101, 54, 0, 254, 121, 96, 127, 255}, 15, 14, "-9.99999999999999", 8},
+		{[]byte{127, 255, 255, 255, 245, 223, 55, 170, 127, 255, 127, 255}, 20, 10, "-10.55", 10},
+		{[]byte{127, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 245, 255, 41, 39, 127, 255}, 30, 5, "-10.55", 15},
+		{[]byte{127, 255, 255, 255, 245, 223, 55, 170, 127, 255, 255, 255, 255, 255, 127, 255}, 30, 20, "-10.55", 14},
+		{[]byte{127, 255, 245, 223, 55, 170, 127, 255, 255, 255, 255, 255, 255, 255, 255, 4, 0}, 30, 25, "-10.55", 15},
+		{[]byte{128, 1, 128, 0}, 4, 2, "0.01", 2},
+		{[]byte{128, 0, 0, 128, 0}, 5, 0, "0.0", 3},
+		{[]byte{128, 0, 0, 12, 128, 0}, 7, 3, "0.012", 4},
+		{[]byte{128, 0, 0, 0, 1, 128, 0}, 10, 2, "0.01", 5},
+		{[]byte{128, 0, 0, 0, 0, 12, 128, 0}, 10, 3, "0.012", 6},
+		{[]byte{128, 0, 0, 0, 0, 1, 128, 0}, 13, 2, "0.01", 6},
+		{[]byte{128, 0, 188, 97, 78, 1, 96, 11, 128, 0}, 15, 14, "0.01234567890123", 8},
+		{[]byte{128, 0, 0, 0, 0, 0, 188, 97, 78, 9, 128, 0}, 20, 10, "0.0123456789", 10},
+		{[]byte{128, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 4, 211, 128, 0}, 30, 5, "0.01235", 15},
+		{[]byte{128, 0, 0, 0, 0, 0, 188, 97, 78, 53, 183, 191, 135, 89, 128, 0}, 30, 20, "0.01234567890123456789", 14},
+		{[]byte{128, 0, 0, 0, 188, 97, 78, 53, 183, 191, 135, 0, 135, 253, 217, 30, 0}, 30, 25, "0.0123456789012345678912345", 15},
+		{[]byte{227, 99, 128, 48}, 4, 2, "99.99", 2},
+		{[]byte{128, 48, 57, 167, 15}, 5, 0, "12345.0", 3},
+		{[]byte{167, 15, 3, 231, 128, 0}, 7, 3, "9999.999", 4},
+		{[]byte{128, 0, 48, 57, 0, 128, 0}, 10, 2, "12345.0", 5},
+		{[]byte{128, 0, 48, 57, 0, 0, 128, 0}, 10, 3, "12345.0", 6},
+		{[]byte{128, 0, 0, 48, 57, 0, 137, 59}, 13, 2, "12345.0", 6},
+		{[]byte{137, 59, 154, 201, 255, 1, 134, 159, 128, 0}, 15, 14, "9.99999999999999", 8},
+		{[]byte{128, 0, 0, 48, 57, 0, 0, 0, 0, 0, 128, 0}, 20, 10, "12345.0", 10},
+		{[]byte{128, 0, 0, 0, 0, 0, 0, 0, 0, 0, 48, 57, 0, 0, 0, 128, 0}, 30, 5, "12345.0", 15},
+		{[]byte{128, 0, 0, 48, 57, 0, 0, 0, 0, 0, 0, 0, 0, 0, 128, 48}, 30, 20, "12345.0", 14},
+		{[]byte{128, 48, 57, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 5, 0}, 30, 25, "12345.0", 15},
+		{[]byte{227, 99, 128, 48}, 4, 2, "99.99", 2},
+		{[]byte{128, 48, 57, 167, 15}, 5, 0, "12345.0", 3},
+		{[]byte{167, 15, 3, 231, 128, 0}, 7, 3, "9999.999", 4},
+		{[]byte{128, 0, 48, 57, 0, 128, 0}, 10, 2, "12345.0", 5},
+		{[]byte{128, 0, 48, 57, 0, 0, 128, 0}, 10, 3, "12345.0", 6},
+		{[]byte{128, 0, 0, 48, 57, 0, 137, 59}, 13, 2, "12345.0", 6},
+		{[]byte{137, 59, 154, 201, 255, 1, 134, 159, 128, 0}, 15, 14, "9.99999999999999", 8},
+		{[]byte{128, 0, 0, 48, 57, 0, 0, 0, 0, 0, 128, 0}, 20, 10, "12345.0", 10},
+		{[]byte{128, 0, 0, 0, 0, 0, 0, 0, 0, 0, 48, 57, 0, 0, 0, 128, 0}, 30, 5, "12345.0", 15},
+		{[]byte{128, 0, 0, 48, 57, 0, 0, 0, 0, 0, 0, 0, 0, 0, 128, 48}, 30, 20, "12345.0", 14},
+		{[]byte{128, 48, 57, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 10, 0}, 30, 25, "12345.0", 15},
+		{[]byte{227, 99, 128, 0}, 4, 2, "99.99", 2},
+		{[]byte{128, 0, 123, 128, 123}, 5, 0, "123.0", 3},
+		{[]byte{128, 123, 1, 194, 128, 0}, 7, 3, "123.45", 4},
+		{[]byte{128, 0, 0, 123, 45, 128, 0}, 10, 2, "123.45", 5},
+		{[]byte{128, 0, 0, 123, 1, 194, 128, 0}, 10, 3, "123.45", 6},
+		{[]byte{128, 0, 0, 0, 123, 45, 137, 59}, 13, 2, "123.45", 6},
+		{[]byte{137, 59, 154, 201, 255, 1, 134, 159, 128, 0}, 15, 14, "9.99999999999999", 8},
+		{[]byte{128, 0, 0, 0, 123, 26, 210, 116, 128, 0, 128, 0}, 20, 10, "123.45", 10},
+		{[]byte{128, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 123, 0, 175, 200, 128, 0}, 30, 5, "123.45", 15},
+		{[]byte{128, 0, 0, 0, 123, 26, 210, 116, 128, 0, 0, 0, 0, 0, 128, 0}, 30, 20, "123.45", 14},
+		{[]byte{128, 0, 123, 26, 210, 116, 128, 0, 0, 0, 0, 0, 0, 0, 0, 10, 0}, 30, 25, "123.45", 15},
+		{[]byte{28, 156, 127, 255}, 4, 2, "-99.99", 2},
+		{[]byte{127, 255, 132, 127, 132}, 5, 0, "-123.0", 3},
+		{[]byte{127, 132, 254, 61, 127, 255}, 7, 3, "-123.45", 4},
+		{[]byte{127, 255, 255, 132, 210, 127, 255}, 10, 2, "-123.45", 5},
+		{[]byte{127, 255, 255, 132, 254, 61, 127, 255}, 10, 3, "-123.45", 6},
+		{[]byte{127, 255, 255, 255, 132, 210, 118, 196}, 13, 2, "-123.45", 6},
+		{[]byte{118, 196, 101, 54, 0, 254, 121, 96, 127, 255}, 15, 14, "-9.99999999999999", 8},
+		{[]byte{127, 255, 255, 255, 132, 229, 45, 139, 127, 255, 127, 255}, 20, 10, "-123.45", 10},
+		{[]byte{127, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 132, 255, 80, 55, 127, 255}, 30, 5, "-123.45", 15},
+		{[]byte{127, 255, 255, 255, 132, 229, 45, 139, 127, 255, 255, 255, 255, 255, 127, 255}, 30, 20, "-123.45", 14},
+		{[]byte{127, 255, 132, 229, 45, 139, 127, 255, 255, 255, 255, 255, 255, 255, 255, 20, 0}, 30, 25, "-123.45", 15},
+		{[]byte{128, 0, 128, 0}, 4, 2, "0.0", 2},
+		{[]byte{128, 0, 0, 128, 0}, 5, 0, "0.0", 3},
+		{[]byte{128, 0, 0, 0, 128, 0}, 7, 3, "0.0", 4},
+		{[]byte{128, 0, 0, 0, 0, 128, 0}, 10, 2, "0.0", 5},
+		{[]byte{128, 0, 0, 0, 0, 0, 128, 0}, 10, 3, "0.0", 6},
+		{[]byte{128, 0, 0, 0, 0, 0, 128, 0}, 13, 2, "0.0", 6},
+		{[]byte{128, 0, 1, 226, 58, 0, 0, 99, 128, 0}, 15, 14, "0.00012345000099", 8},
+		{[]byte{128, 0, 0, 0, 0, 0, 1, 226, 58, 0, 128, 0}, 20, 10, "0.00012345", 10},
+		{[]byte{128, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 12, 128, 0}, 30, 5, "0.00012", 15},
+		{[]byte{128, 0, 0, 0, 0, 0, 1, 226, 58, 0, 15, 18, 2, 0, 128, 0}, 30, 20, "0.00012345000098765", 14},
+		{[]byte{128, 0, 0, 0, 1, 226, 58, 0, 15, 18, 2, 0, 0, 0, 0, 15, 0}, 30, 25, "0.00012345000098765", 15},
+		{[]byte{128, 0, 128, 0}, 4, 2, "0.0", 2},
+		{[]byte{128, 0, 0, 128, 0}, 5, 0, "0.0", 3},
+		{[]byte{128, 0, 0, 0, 128, 0}, 7, 3, "0.0", 4},
+		{[]byte{128, 0, 0, 0, 0, 128, 0}, 10, 2, "0.0", 5},
+		{[]byte{128, 0, 0, 0, 0, 0, 128, 0}, 10, 3, "0.0", 6},
+		{[]byte{128, 0, 0, 0, 0, 0, 128, 0}, 13, 2, "0.0", 6},
+		{[]byte{128, 0, 1, 226, 58, 0, 0, 99, 128, 0}, 15, 14, "0.00012345000099", 8},
+		{[]byte{128, 0, 0, 0, 0, 0, 1, 226, 58, 0, 128, 0}, 20, 10, "0.00012345", 10},
+		{[]byte{128, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 12, 128, 0}, 30, 5, "0.00012", 15},
+		{[]byte{128, 0, 0, 0, 0, 0, 1, 226, 58, 0, 15, 18, 2, 0, 128, 0}, 30, 20, "0.00012345000098765", 14},
+		{[]byte{128, 0, 0, 0, 1, 226, 58, 0, 15, 18, 2, 0, 0, 0, 0, 22, 0}, 30, 25, "0.00012345000098765", 15},
+		{[]byte{128, 12, 128, 0}, 4, 2, "0.12", 2},
+		{[]byte{128, 0, 0, 128, 0}, 5, 0, "0.0", 3},
+		{[]byte{128, 0, 0, 123, 128, 0}, 7, 3, "0.123", 4},
+		{[]byte{128, 0, 0, 0, 12, 128, 0}, 10, 2, "0.12", 5},
+		{[]byte{128, 0, 0, 0, 0, 123, 128, 0}, 10, 3, "0.123", 6},
+		{[]byte{128, 0, 0, 0, 0, 12, 128, 7}, 13, 2, "0.12", 6},
+		{[]byte{128, 7, 91, 178, 144, 1, 129, 205, 128, 0}, 15, 14, "0.12345000098765", 8},
+		{[]byte{128, 0, 0, 0, 0, 7, 91, 178, 145, 0, 128, 0}, 20, 10, "0.123450001", 10},
+		{[]byte{128, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 48, 57, 128, 0}, 30, 5, "0.12345", 15},
+		{[]byte{128, 0, 0, 0, 0, 7, 91, 178, 144, 58, 222, 87, 208, 0, 128, 0}, 30, 20, "0.12345000098765", 14},
+		{[]byte{128, 0, 0, 7, 91, 178, 144, 58, 222, 87, 208, 0, 0, 0, 0, 30, 0}, 30, 25, "0.12345000098765", 15},
+		{[]byte{128, 0, 128, 0}, 4, 2, "0.0", 2},
+		{[]byte{128, 0, 0, 128, 0}, 5, 0, "0.0", 3},
+		{[]byte{128, 0, 0, 0, 128, 0}, 7, 3, "0.0", 4},
+		{[]byte{128, 0, 0, 0, 0, 128, 0}, 10, 2, "0.0", 5},
+		{[]byte{128, 0, 0, 0, 0, 0, 128, 0}, 10, 3, "0.0", 6},
+		{[]byte{128, 0, 0, 0, 0, 0, 127, 255}, 13, 2, "0.0", 6},
+		{[]byte{127, 255, 255, 255, 243, 255, 121, 59, 127, 255}, 15, 14, "-0.000000012345", 8},
+		{[]byte{127, 255, 255, 255, 255, 255, 255, 255, 243, 252, 128, 0}, 20, 10, "-0.0000000123", 10},
+		{[]byte{128, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 127, 255}, 30, 5, "0.0", 15},
+		{[]byte{127, 255, 255, 255, 255, 255, 255, 255, 243, 235, 111, 183, 93, 178, 127, 255}, 30, 20, "-0.00000001234500009877", 14},
+		{[]byte{127, 255, 255, 255, 255, 255, 243, 235, 111, 183, 93, 255, 139, 69, 47, 30, 0}, 30, 25, "-0.000000012345000098765", 15},
+		{[]byte{227, 99, 129, 134}, 4, 2, "99.99", 2},
+		{[]byte{129, 134, 159, 167, 15}, 5, 0, "99999.0", 3},
+		{[]byte{167, 15, 3, 231, 133, 245}, 7, 3, "9999.999", 4},
+		{[]byte{133, 245, 224, 255, 99, 128, 152}, 10, 2, "99999999.99", 5},
+		{[]byte{128, 152, 150, 127, 3, 231, 227, 59}, 10, 3, "9999999.999", 6},
+		{[]byte{227, 59, 154, 201, 255, 99, 137, 59}, 13, 2, "99999999999.99", 6},
+		{[]byte{137, 59, 154, 201, 255, 1, 134, 159, 137, 59}, 15, 14, "9.99999999999999", 8},
+		{[]byte{137, 59, 154, 201, 255, 59, 154, 201, 255, 9, 128, 0}, 20, 10, "9999999999.9999999999", 10},
+		{[]byte{128, 0, 0, 0, 0, 0, 4, 210, 29, 205, 139, 148, 0, 195, 80, 137, 59}, 30, 5, "1234500009876.5", 15},
+		{[]byte{137, 59, 154, 201, 255, 59, 154, 201, 255, 59, 154, 201, 255, 99, 129, 134}, 30, 20, "9999999999.99999999999999999999", 14},
+		{[]byte{129, 134, 159, 59, 154, 201, 255, 59, 154, 201, 255, 0, 152, 150, 127, 30, 0}, 30, 25, "99999.9999999999999999999999999", 15},
+		{[]byte{227, 99, 129, 134}, 4, 2, "99.99", 2},
+		{[]byte{129, 134, 159, 167, 15}, 5, 0, "99999.0", 3},
+		{[]byte{167, 15, 3, 231, 133, 245}, 7, 3, "9999.999", 4},
+		{[]byte{133, 245, 224, 255, 99, 128, 152}, 10, 2, "99999999.99", 5},
+		{[]byte{128, 152, 150, 127, 3, 231, 128, 6}, 10, 3, "9999999.999", 6},
+		{[]byte{128, 6, 159, 107, 199, 11, 137, 59}, 13, 2, "111111111.11", 6},
+		{[]byte{137, 59, 154, 201, 255, 1, 134, 159, 128, 6}, 15, 14, "9.99999999999999", 8},
+		{[]byte{128, 6, 159, 107, 199, 6, 142, 119, 128, 0, 128, 0}, 20, 10, "111111111.11", 10},
+		{[]byte{128, 0, 0, 0, 0, 0, 0, 0, 6, 159, 107, 199, 0, 42, 248, 128, 6}, 30, 5, "111111111.11", 15},
+		{[]byte{128, 6, 159, 107, 199, 6, 142, 119, 128, 0, 0, 0, 0, 0, 129, 134}, 30, 20, "111111111.11", 14},
+		{[]byte{129, 134, 159, 59, 154, 201, 255, 59, 154, 201, 255, 0, 152, 150, 127, 10, 0}, 30, 25, "99999.9999999999999999999999999", 15},
+		{[]byte{128, 1, 128, 0}, 4, 2, "0.01", 2},
+		{[]byte{128, 0, 0, 128, 0}, 5, 0, "0.0", 3},
+		{[]byte{128, 0, 0, 10, 128, 0}, 7, 3, "0.01", 4},
+		{[]byte{128, 0, 0, 0, 1, 128, 0}, 10, 2, "0.01", 5},
+		{[]byte{128, 0, 0, 0, 0, 10, 128, 0}, 10, 3, "0.01", 6},
+		{[]byte{128, 0, 0, 0, 0, 1, 128, 0}, 13, 2, "0.01", 6},
+		{[]byte{128, 0, 152, 150, 128, 0, 0, 0, 128, 0}, 15, 14, "0.01", 8},
+		{[]byte{128, 0, 0, 0, 0, 0, 152, 150, 128, 0, 128, 0}, 20, 10, "0.01", 10},
+		{[]byte{128, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 232, 128, 0}, 30, 5, "0.01", 15},
+		{[]byte{128, 0, 0, 0, 0, 0, 152, 150, 128, 0, 0, 0, 0, 0, 128, 0}, 30, 20, "0.01", 14},
+		{[]byte{128, 0, 0, 0, 152, 150, 128, 0, 0, 0, 0, 0, 0, 0, 0, 7, 0}, 30, 25, "0.01", 15},
+		{[]byte{227, 99, 128, 0}, 4, 2, "99.99", 2},
+		{[]byte{128, 0, 123, 128, 123}, 5, 0, "123.0", 3},
+		{[]byte{128, 123, 1, 144, 128, 0}, 7, 3, "123.4", 4},
+		{[]byte{128, 0, 0, 123, 40, 128, 0}, 10, 2, "123.4", 5},
+		{[]byte{128, 0, 0, 123, 1, 144, 128, 0}, 10, 3, "123.4", 6},
+		{[]byte{128, 0, 0, 0, 123, 40, 137, 59}, 13, 2, "123.4", 6},
+		{[]byte{137, 59, 154, 201, 255, 1, 134, 159, 128, 0}, 15, 14, "9.99999999999999", 8},
+		{[]byte{128, 0, 0, 0, 123, 23, 215, 132, 0, 0, 128, 0}, 20, 10, "123.4", 10},
+		{[]byte{128, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 123, 0, 156, 64, 128, 0}, 30, 5, "123.4", 15},
+		{[]byte{128, 0, 0, 0, 123, 23, 215, 132, 0, 0, 0, 0, 0, 0, 128, 0}, 30, 20, "123.4", 14},
+		{[]byte{128, 0, 123, 23, 215, 132, 0, 0, 0, 0, 0, 0, 0, 0, 0, 10, 0}, 30, 25, "123.4", 15},
+		{[]byte{28, 156, 127, 253}, 4, 2, "-99.99", 2},
+		{[]byte{127, 253, 204, 125, 205}, 5, 0, "-563.0", 3},
+		{[]byte{125, 205, 253, 187, 127, 255}, 7, 3, "-562.58", 4},
+		{[]byte{127, 255, 253, 205, 197, 127, 255}, 10, 2, "-562.58", 5},
+		{[]byte{127, 255, 253, 205, 253, 187, 127, 255}, 10, 3, "-562.58", 6},
+		{[]byte{127, 255, 255, 253, 205, 197, 118, 196}, 13, 2, "-562.58", 6},
+		{[]byte{118, 196, 101, 54, 0, 254, 121, 96, 127, 255}, 15, 14, "-9.99999999999999", 8},
+		{[]byte{127, 255, 255, 253, 205, 221, 109, 230, 255, 255, 127, 255}, 20, 10, "-562.58", 10},
+		{[]byte{127, 255, 255, 255, 255, 255, 255, 255, 255, 255, 253, 205, 255, 29, 111, 127, 255}, 30, 5, "-562.58", 15},
+		{[]byte{127, 255, 255, 253, 205, 221, 109, 230, 255, 255, 255, 255, 255, 255, 127, 253}, 30, 20, "-562.58", 14},
+		{[]byte{127, 253, 205, 221, 109, 230, 255, 255, 255, 255, 255, 255, 255, 255, 255, 13, 0}, 30, 25, "-562.58", 15},
+		{[]byte{28, 156, 127, 241}, 4, 2, "-99.99", 2},
+		{[]byte{127, 241, 140, 113, 140}, 5, 0, "-3699.0", 3},
+		{[]byte{113, 140, 255, 245, 127, 255}, 7, 3, "-3699.01", 4},
+		{[]byte{127, 255, 241, 140, 254, 127, 255}, 10, 2, "-3699.01", 5},
+		{[]byte{127, 255, 241, 140, 255, 245, 127, 255}, 10, 3, "-3699.01", 6},
+		{[]byte{127, 255, 255, 241, 140, 254, 118, 196}, 13, 2, "-3699.01", 6},
+		{[]byte{118, 196, 101, 54, 0, 254, 121, 96, 127, 255}, 15, 14, "-9.99999999999999", 8},
+		{[]byte{127, 255, 255, 241, 140, 255, 103, 105, 127, 255, 127, 255}, 20, 10, "-3699.01", 10},
+		{[]byte{127, 255, 255, 255, 255, 255, 255, 255, 255, 255, 241, 140, 255, 252, 23, 127, 255}, 30, 5, "-3699.01", 15},
+		{[]byte{127, 255, 255, 241, 140, 255, 103, 105, 127, 255, 255, 255, 255, 255, 127, 241}, 30, 20, "-3699.01", 14},
+		{[]byte{127, 241, 140, 255, 103, 105, 127, 255, 255, 255, 255, 255, 255, 255, 255, 13, 0}, 30, 25, "-3699.01", 15},
+		{[]byte{28, 156, 127, 248}, 4, 2, "-99.99", 2},
+		{[]byte{127, 248, 99, 120, 99}, 5, 0, "-1948.0", 3},
+		{[]byte{120, 99, 255, 115, 127, 255}, 7, 3, "-1948.14", 4},
+		{[]byte{127, 255, 248, 99, 241, 127, 255}, 10, 2, "-1948.14", 5},
+		{[]byte{127, 255, 248, 99, 255, 115, 127, 255}, 10, 3, "-1948.14", 6},
+		{[]byte{127, 255, 255, 248, 99, 241, 118, 196}, 13, 2, "-1948.14", 6},
+		{[]byte{118, 196, 101, 54, 0, 254, 121, 96, 127, 255}, 15, 14, "-9.99999999999999", 8},
+		{[]byte{127, 255, 255, 248, 99, 247, 167, 196, 255, 255, 127, 255}, 20, 10, "-1948.14", 10},
+		{[]byte{127, 255, 255, 255, 255, 255, 255, 255, 255, 255, 248, 99, 255, 201, 79, 127, 255}, 30, 5, "-1948.14", 15},
+		{[]byte{127, 255, 255, 248, 99, 247, 167, 196, 255, 255, 255, 255, 255, 255, 127, 248}, 30, 20, "-1948.14", 14},
+		{[]byte{127, 248, 99, 247, 167, 196, 255, 255, 255, 255, 255, 255, 255, 255, 255, 13, 0}, 30, 25, "-1948.14", 15},
+	}
+
+	for _, tc := range testcases {
+		d, size := DecodeDecimal(tc.Data, tc.Precision, tc.Decimals)
+		b, err := json.Marshal(d)
+		if err != nil {
+			t.Fatalf("Unexpected error (exp: %q): %v", tc.Expected, err)
+		}
+		out := string(b)
+		if tc.Expected != out {
+			t.Errorf("Expected %s, got %s", tc.Expected, out)
+		}
+
+		if tc.ExpectedPos != size {
+			t.Errorf("Expected %d bytes, got %d", tc.ExpectedPos, size)
+		}
+	}
+}

tests/decimal_test.go

@@ -19,8 +19,8 @@ func TestDecimal(t *testing.T) {
 			"99.9",
 		},
 		"6,2": {
-			"0.00",
+			"0.0",
-			"1.00",
+			"1.0",
 			"1.33",
 			"10.16",
 			"620.99",
@@ -28,18 +28,17 @@ func TestDecimal(t *testing.T) {
 			"9999.99",
 		},
 		"10,4": {
-			"0.0000",
+			"0.0",
 			"1.0001",
 			"1.3301",
-			"10.1600",
+			"10.16",
 			"620.9999",
 			"500000.0001",
 			"999999.9999",
 		},
 		"30,10": {
-			// NOTE: At certain length there's undesired zero fill :/
+			"0.0",
-			"0000000000000000000.0000000000",
+			"1.0000000001",
-			"0000000000000000001.0000000001",
 			"99999999999999999999.9999999999",
 		},
 	}
@@ -51,11 +50,11 @@ func TestDecimal(t *testing.T) {
 
 			for _, v := range vals {
 				t.Run(v, func(t *testing.T) {
-					suite.insertAndCompare(t, tbl, v)
+					suite.insertAndCompare(t, tbl, mysql.NewDecimal(v))
 				})
 				if !strings.HasPrefix(v, "0") {
 					t.Run("-"+v, func(t *testing.T) {
-						suite.insertAndCompare(t, tbl, "-"+v)
+						suite.insertAndCompare(t, tbl, mysql.NewDecimal("-"+v))
 					})
 				}
 			}

tests/suite_test.go

@@ -2,6 +2,7 @@ package tests
 
 import (
 	"bytes"
+	"context"
 	"database/sql"
 	"encoding/json"
 	"fmt"
@@ -201,9 +202,10 @@ func (s *testSuite) insertAndCompareExp(t *testing.T, tbl *table, vals, exps []i
 func (s *testSuite) expectValue(t *testing.T, tbl *table, exp []interface{}) {
 	t.Helper()
 	out := make(chan []interface{})
+	ctx := context.Background()
 	go func() {
 		for {
-			evt, err := suite.reader.ReadEvent()
+			evt, err := suite.reader.ReadEvent(ctx)
 			if err != nil {
 				t.Errorf("Failed to read event: %v", err)
 				return