utils: parse using byteslice in parseDateTime (go-sql-driver#1113)

* fixed the way of parsing datetime when byte slice string

The benchmark results

$ go test -benchmem . -bench "^BenchmarkParseByte"
goos: darwin
goarch: amd64
pkg: github.com/go-sql-driver/mysql
BenchmarkParseByteDateTime-4                    12023173               104 ns/op               0 B/op          0 allocs/op
BenchmarkParseByteDateTimeStringCast-4           3394239               355 ns/op              32 B/op          1 allocs/op

* added line to AUTHORS file

* fixed error handling

* fixed nanosec digits

* added more tests for error

* renamed parseByteDateTime to parseDateTime

* reverted base null time

* Update utils.go

Co-authored-by: Inada Naoki <songofacandy@gmail.com>

* Update utils.go

Co-authored-by: Inada Naoki <songofacandy@gmail.com>

* Update utils.go

Co-authored-by: Inada Naoki <songofacandy@gmail.com>

* removed deprecatedParseDateTime from test

Co-authored-by: Inada Naoki <songofacandy@gmail.com>

AUTHORS

@@ -56,6 +56,7 @@ Julien Schmidt <go-sql-driver at julienschmidt.com>
 Justin Li <jli at j-li.net>
 Justin Nuß <nuss.justin at gmail.com>
 Kamil Dziedzic <kamil at klecza.pl>
+Kei Kamikawa <x00.x7f.x86 at gmail.com>
 Kevin Malachowski <kevin at chowski.com>
 Kieron Woodhouse <kieron.woodhouse at infosum.com>
 Lennart Rudolph <lrudolph at hmc.edu>

nulltime.go

@@ -28,11 +28,11 @@ func (nt *NullTime) Scan(value interface{}) (err error) {
 		nt.Time, nt.Valid = v, true
 		return
 	case []byte:
-		nt.Time, err = parseDateTime(string(v), time.UTC)
+		nt.Time, err = parseDateTime(v, time.UTC)
 		nt.Valid = (err == nil)
 		return
 	case string:
-		nt.Time, err = parseDateTime(v, time.UTC)
+		nt.Time, err = parseDateTime([]byte(v), time.UTC)
 		nt.Valid = (err == nil)
 		return
 	}

packets.go

@@ -778,7 +778,7 @@ func (rows *textRows) readRow(dest []driver.Value) error {
 					case fieldTypeTimestamp, fieldTypeDateTime,
 						fieldTypeDate, fieldTypeNewDate:
 						dest[i], err = parseDateTime(
-							string(dest[i].([]byte)),
+							dest[i].([]byte),
 							mc.cfg.Loc,
 						)
 						if err == nil {

utils.go

@@ -106,21 +106,136 @@ func readBool(input string) (value bool, valid bool) {
 *                           Time related utils                                *
 ******************************************************************************/
 
-func parseDateTime(str string, loc *time.Location) (t time.Time, err error) {
-	base := "0000-00-00 00:00:00.0000000"
-	switch len(str) {
+func parseDateTime(b []byte, loc *time.Location) (time.Time, error) {
+	const base = "0000-00-00 00:00:00.000000"
+	switch len(b) {
 	case 10, 19, 21, 22, 23, 24, 25, 26: // up to "YYYY-MM-DD HH:MM:SS.MMMMMM"
-		if str == base[:len(str)] {
-			return
+		if string(b) == base[:len(b)] {
+			return time.Time{}, nil
 		}
-		if loc == time.UTC {
-			return time.Parse(timeFormat[:len(str)], str)
+
+		year, err := parseByteYear(b)
+		if err != nil {
+			return time.Time{}, err
+		}
+		if year <= 0 {
+			year = 1
+		}
+
+		if b[4] != '-' {
+			return time.Time{}, fmt.Errorf("bad value for field: `%c`", b[4])
+		}
+
+		m, err := parseByte2Digits(b[5], b[6])
+		if err != nil {
+			return time.Time{}, err
+		}
+		if m <= 0 {
+			m = 1
+		}
+		month := time.Month(m)
+
+		if b[7] != '-' {
+			return time.Time{}, fmt.Errorf("bad value for field: `%c`", b[7])
+		}
+
+		day, err := parseByte2Digits(b[8], b[9])
+		if err != nil {
+			return time.Time{}, err
+		}
+		if day <= 0 {
+			day = 1
+		}
+		if len(b) == 10 {
+			return time.Date(year, month, day, 0, 0, 0, 0, loc), nil
+		}
+
+		if b[10] != ' ' {
+			return time.Time{}, fmt.Errorf("bad value for field: `%c`", b[10])
+		}
+
+		hour, err := parseByte2Digits(b[11], b[12])
+		if err != nil {
+			return time.Time{}, err
+		}
+		if b[13] != ':' {
+			return time.Time{}, fmt.Errorf("bad value for field: `%c`", b[13])
+		}
+
+		min, err := parseByte2Digits(b[14], b[15])
+		if err != nil {
+			return time.Time{}, err
+		}
+		if b[16] != ':' {
+			return time.Time{}, fmt.Errorf("bad value for field: `%c`", b[16])
 		}
-		return time.ParseInLocation(timeFormat[:len(str)], str, loc)
+
+		sec, err := parseByte2Digits(b[17], b[18])
+		if err != nil {
+			return time.Time{}, err
+		}
+		if len(b) == 19 {
+			return time.Date(year, month, day, hour, min, sec, 0, loc), nil
+		}
+
+		if b[19] != '.' {
+			return time.Time{}, fmt.Errorf("bad value for field: `%c`", b[19])
+		}
+		nsec, err := parseByteNanoSec(b[20:])
+		if err != nil {
+			return time.Time{}, err
+		}
+		return time.Date(year, month, day, hour, min, sec, nsec, loc), nil
 	default:
-		err = fmt.Errorf("invalid time string: %s", str)
-		return
+		return time.Time{}, fmt.Errorf("invalid time bytes: %s", b)
+	}
+}
+
+func parseByteYear(b []byte) (int, error) {
+	year, n := 0, 1000
+	for i := 0; i < 4; i++ {
+		v, err := bToi(b[i])
+		if err != nil {
+			return 0, err
+		}
+		year += v * n
+		n = n / 10
+	}
+	return year, nil
+}
+
+func parseByte2Digits(b1, b2 byte) (int, error) {
+	d1, err := bToi(b1)
+	if err != nil {
+		return 0, err
+	}
+	d2, err := bToi(b2)
+	if err != nil {
+		return 0, err
+	}
+	return d1*10 + d2, nil
+}
+
+func parseByteNanoSec(b []byte) (int, error) {
+	ns, digit := 0, 100000 // max is 6-digits
+	for i := 0; i < len(b); i++ {
+		v, err := bToi(b[i])
+		if err != nil {
+			return 0, err
+		}
+		ns += v * digit
+		digit /= 10
+	}
+	// nanoseconds has 10-digits. (needs to scale digits)
+	// 10 - 6 = 4, so we have to multiple 1000.
+	return ns * 1000, nil
+}
+
+func bToi(b byte) (int, error) {
+	if b < '0' || b > '9' {
+		return 0, errors.New("not [0-9]")
 	}
+	return int(b - '0'), nil
 }
 
 func parseBinaryDateTime(num uint64, data []byte, loc *time.Location) (driver.Value, error) {

utils_test.go

@@ -294,43 +294,144 @@ func TestIsolationLevelMapping(t *testing.T) {
 }
 
 func TestParseDateTime(t *testing.T) {
-	// UTC loc
-	{
-		str := "2020-05-13 21:30:45"
-		t1, err := parseDateTime(str, time.UTC)
-		if err != nil {
-			t.Error(err)
-			return
-		}
-		t2 := time.Date(2020, 5, 13,
-			21, 30, 45, 0, time.UTC)
-		if !t1.Equal(t2) {
-			t.Errorf("want equal, have: %v, want: %v", t1, t2)
-			return
-		}
+	cases := []struct {
+		name string
+		str  string
+	}{
+		{
+			name: "parse date",
+			str:  "2020-05-13",
+		},
+		{
+			name: "parse null date",
+			str:  sDate0,
+		},
+		{
+			name: "parse datetime",
+			str:  "2020-05-13 21:30:45",
+		},
+		{
+			name: "parse null datetime",
+			str:  sDateTime0,
+		},
+		{
+			name: "parse datetime nanosec 1-digit",
+			str:  "2020-05-25 23:22:01.1",
+		},
+		{
+			name: "parse datetime nanosec 2-digits",
+			str:  "2020-05-25 23:22:01.15",
+		},
+		{
+			name: "parse datetime nanosec 3-digits",
+			str:  "2020-05-25 23:22:01.159",
+		},
+		{
+			name: "parse datetime nanosec 4-digits",
+			str:  "2020-05-25 23:22:01.1594",
+		},
+		{
+			name: "parse datetime nanosec 5-digits",
+			str:  "2020-05-25 23:22:01.15949",
+		},
+		{
+			name: "parse datetime nanosec 6-digits",
+			str:  "2020-05-25 23:22:01.159491",
+		},
 	}
-	// non-UTC loc
-	{
-		str := "2020-05-13 21:30:45"
-		loc := time.FixedZone("test", 8*60*60)
-		t1, err := parseDateTime(str, loc)
-		if err != nil {
-			t.Error(err)
-			return
-		}
-		t2 := time.Date(2020, 5, 13,
-			21, 30, 45, 0, loc)
-		if !t1.Equal(t2) {
-			t.Errorf("want equal, have: %v, want: %v", t1, t2)
-			return
+
+	for _, loc := range []*time.Location{
+		time.UTC,
+		time.FixedZone("test", 8*60*60),
+	} {
+		for _, cc := range cases {
+			t.Run(cc.name+"-"+loc.String(), func(t *testing.T) {
+				var want time.Time
+				if cc.str != sDate0 && cc.str != sDateTime0 {
+					var err error
+					want, err = time.ParseInLocation(timeFormat[:len(cc.str)], cc.str, loc)
+					if err != nil {
+						t.Fatal(err)
+					}
+				}
+				got, err := parseDateTime([]byte(cc.str), loc)
+				if err != nil {
+					t.Fatal(err)
+				}
+
+				if !want.Equal(got) {
+					t.Fatalf("want: %v, but got %v", want, got)
+				}
+			})
 		}
 	}
 }
 
-func BenchmarkParseDateTime(b *testing.B) {
-	str := "2020-05-13 21:30:45"
-	loc := time.FixedZone("test", 8*60*60)
-	for i := 0; i < b.N; i++ {
-		_, _ = parseDateTime(str, loc)
+func TestParseDateTimeFail(t *testing.T) {
+	cases := []struct {
+		name    string
+		str     string
+		wantErr string
+	}{
+		{
+			name:    "parse invalid time",
+			str:     "hello",
+			wantErr: "invalid time bytes: hello",
+		},
+		{
+			name:    "parse year",
+			str:     "000!-00-00 00:00:00.000000",
+			wantErr: "not [0-9]",
+		},
+		{
+			name:    "parse month",
+			str:     "0000-!0-00 00:00:00.000000",
+			wantErr: "not [0-9]",
+		},
+		{
+			name:    `parse "-" after parsed year`,
+			str:     "0000:00-00 00:00:00.000000",
+			wantErr: "bad value for field: `:`",
+		},
+		{
+			name:    `parse "-" after parsed month`,
+			str:     "0000-00:00 00:00:00.000000",
+			wantErr: "bad value for field: `:`",
+		},
+		{
+			name:    `parse " " after parsed date`,
+			str:     "0000-00-00+00:00:00.000000",
+			wantErr: "bad value for field: `+`",
+		},
+		{
+			name:    `parse ":" after parsed date`,
+			str:     "0000-00-00 00-00:00.000000",
+			wantErr: "bad value for field: `-`",
+		},
+		{
+			name:    `parse ":" after parsed hour`,
+			str:     "0000-00-00 00:00-00.000000",
+			wantErr: "bad value for field: `-`",
+		},
+		{
+			name:    `parse "." after parsed sec`,
+			str:     "0000-00-00 00:00:00?000000",
+			wantErr: "bad value for field: `?`",
+		},
+	}
+
+	for _, cc := range cases {
+		t.Run(cc.name, func(t *testing.T) {
+			got, err := parseDateTime([]byte(cc.str), time.UTC)
+			if err == nil {
+				t.Fatal("want error")
+			}
+			if cc.wantErr != err.Error() {
+				t.Fatalf("want `%s`, but got `%s`", cc.wantErr, err)
+			}
+			if !got.IsZero() {
+				t.Fatal("want zero time")
+			}
+		})
 	}
 }