time: gob marshaler for Time

Addresses issue 2526

R=rsc, r
CC=golang-dev
https://golang.org/cl/5448114

src/pkg/time/time.go

@@ -736,6 +736,86 @@ func (t Time) UnixNano() int64 {
 	return (t.sec+internalToUnix)*1e9 + int64(t.nsec)
 }
 
+type gobError string
+
+func (g gobError) Error() string { return string(g) }
+
+const timeGobVersion byte = 1
+
+// GobEncode implements the gob.GobEncoder interface.
+func (t Time) GobEncode() ([]byte, error) {
+	var offsetMin int16 // minutes east of UTC. -1 is UTC.
+
+	if t.Location() == &utcLoc {
+		offsetMin = -1
+	} else {
+		_, offset := t.Zone()
+		if offset%60 != 0 {
+			return nil, gobError("Time.GobEncode: zone offset has fractional minute")
+		}
+		offset /= 60
+		if offset < -32768 || offset == -1 || offset > 32767 {
+			return nil, gobError("Time.GobEncode: unexpected zone offset")
+		}
+		offsetMin = int16(offset)
+	}
+
+	enc := []byte{
+		timeGobVersion,    // byte 0 : version
+		byte(t.sec >> 56), // bytes 1-8: seconds
+		byte(t.sec >> 48),
+		byte(t.sec >> 40),
+		byte(t.sec >> 32),
+		byte(t.sec >> 24),
+		byte(t.sec >> 16),
+		byte(t.sec >> 8),
+		byte(t.sec),
+		byte(t.nsec >> 24), // bytes 9-12: nanoseconds
+		byte(t.nsec >> 16),
+		byte(t.nsec >> 8),
+		byte(t.nsec),
+		byte(offsetMin >> 8), // bytes 13-14: zone offset in minutes
+		byte(offsetMin),
+	}
+
+	return enc, nil
+}
+
+// GobDecode implements the gob.GobDecoder interface.
+func (t *Time) GobDecode(buf []byte) error {
+	if len(buf) == 0 {
+		return gobError("Time.GobDecode: no data")
+	}
+
+	if buf[0] != timeGobVersion {
+		return gobError("Time.GobDecode: unsupported version")
+	}
+
+	if len(buf) != /*version*/ 1+ /*sec*/ 8+ /*nsec*/ 4+ /*zone offset*/ 2 {
+		return gobError("Time.GobDecode: invalid length")
+	}
+
+	buf = buf[1:]
+	t.sec = int64(buf[7]) | int64(buf[6])<<8 | int64(buf[5])<<16 | int64(buf[4])<<24 |
+		int64(buf[3])<<32 | int64(buf[2])<<40 | int64(buf[1])<<48 | int64(buf[0])<<56
+
+	buf = buf[8:]
+	t.nsec = int32(buf[3]) | int32(buf[2])<<8 | int32(buf[1])<<16 | int32(buf[0])<<24
+
+	buf = buf[4:]
+	offset := int(int16(buf[1])|int16(buf[0])<<8) * 60
+
+	if offset == -1*60 {
+		t.loc = &utcLoc
+	} else if _, localoff, _, _, _ := Local.lookup(t.sec + internalToUnix); offset == localoff {
+		t.loc = Local
+	} else {
+		t.loc = FixedZone("", offset)
+	}
+
+	return nil
+}
+
 // Unix returns the local Time corresponding to the given Unix time,
 // sec seconds and nsec nanoseconds since January 1, 1970 UTC.
 // It is valid to pass nsec outside the range [0, 999999999].

src/pkg/time/time_test.go

@@ -5,6 +5,8 @@
 package time_test
 
 import (
+	"bytes"
+	"encoding/gob"
 	"strconv"
 	"strings"
 	"testing"
@@ -666,6 +668,74 @@ func TestAddToExactSecond(t *testing.T) {
 	}
 }
 
+var gobTests = []Time{
+	Date(0, 1, 2, 3, 4, 5, 6, UTC),
+	Date(7, 8, 9, 10, 11, 12, 13, FixedZone("", 0)),
+	Unix(81985467080890095, 0x76543210), // Time.sec: 0x0123456789ABCDEF
+	Time{},                              // nil location
+	Date(1, 2, 3, 4, 5, 6, 7, FixedZone("", 32767*60)),
+	Date(1, 2, 3, 4, 5, 6, 7, FixedZone("", -32768*60)),
+}
+
+func TestTimeGob(t *testing.T) {
+	var b bytes.Buffer
+	enc := gob.NewEncoder(&b)
+	dec := gob.NewDecoder(&b)
+	for _, tt := range gobTests {
+		var gobtt Time
+		if err := enc.Encode(&tt); err != nil {
+			t.Errorf("%v gob Encode error = %q, want nil", tt, err)
+		} else if err := dec.Decode(&gobtt); err != nil {
+			t.Errorf("%v gob Decode error = %q, want nil", tt, err)
+		} else {
+			gobname, goboffset := gobtt.Zone()
+			name, offset := tt.Zone()
+			if !gobtt.Equal(tt) || goboffset != offset || gobname != name {
+				t.Errorf("Decoded time = %v, want %v", gobtt, tt)
+			}
+		}
+		b.Reset()
+	}
+}
+
+var invalidEncodingTests = []struct {
+	bytes []byte
+	want  string
+}{
+	{[]byte{}, "Time.GobDecode: no data"},
+	{[]byte{0, 2, 3}, "Time.GobDecode: unsupported version"},
+	{[]byte{1, 2, 3}, "Time.GobDecode: invalid length"},
+}
+
+func TestInvalidTimeGob(t *testing.T) {
+	for _, tt := range invalidEncodingTests {
+		var ignored Time
+		err := ignored.GobDecode(tt.bytes)
+		if err == nil || err.Error() != tt.want {
+			t.Errorf("time.GobDecode(%#v) error = %v, want %v", tt.bytes, err, tt.want)
+		}
+	}
+}
+
+var notEncodableTimes = []struct {
+	time Time
+	want string
+}{
+	{Date(0, 1, 2, 3, 4, 5, 6, FixedZone("", 1)), "Time.GobEncode: zone offset has fractional minute"},
+	{Date(0, 1, 2, 3, 4, 5, 6, FixedZone("", -1*60)), "Time.GobEncode: unexpected zone offset"},
+	{Date(0, 1, 2, 3, 4, 5, 6, FixedZone("", -32769*60)), "Time.GobEncode: unexpected zone offset"},
+	{Date(0, 1, 2, 3, 4, 5, 6, FixedZone("", 32768*60)), "Time.GobEncode: unexpected zone offset"},
+}
+
+func TestNotGobEncodableTime(t *testing.T) {
+	for _, tt := range notEncodableTimes {
+		_, err := tt.time.GobEncode()
+		if err == nil || err.Error() != tt.want {
+			t.Errorf("%v GobEncode error = %v, want %v", tt.time, err, tt.want)
+		}
+	}
+}
+
 func BenchmarkNow(b *testing.B) {
 	for i := 0; i < b.N; i++ {
 		Now()