time.Time is not follow the msgpack spec. about msgp

[klauspost]

The extension code used by msgp is 5, not -1, so it doesn't have to follow the predefined time type.

According to the docs you can annotate with msg:"name,extension" and register your new type.

This package predates the time extension proposal so that is probably why it is like this.

[sonirico]

I've bumped into this and I would like to understand. The current implementation does not provide interoperability between other libraries such as https://www.npmjs.com/package/msgpack5, for instance. In this case, msgpack5 for node yields Error: unable to find ext type 5 when trying to deserialize time.Time types serialized by msgp. I am very surprised that this is happening... and not so people are complaining. Other libs like github.com/vmihailenco/msgpack/v5 do not incur in this error.

I understand that the implementation chosen here might be different in order to strongly adhere to specs, but how is the global situation and the motivation to do this?

[klauspost]

//msgp:ignore Time

// Time is a time.Time that serializes to/from Msgpack Extension -1.
type Time struct {
	time.Time
}

func (t Time) ExtensionType() int8 {
	return -1
}

func (t Time) Len() int {
	// Time round towards zero time.
	secPrec := t.Round(time.Second)
	remain := t.Sub(secPrec)
	asSecs := secPrec.Unix()
	if remain == 0 && asSecs > 0 && asSecs <= math.MaxUint32 {
		return 4
	}
	if asSecs < 0 || asSecs >= (1<<34) {
		return 12
	}
	return 8
}

func (t Time) MarshalBinaryTo(bytes []byte) error {
	// Time rounded towards zero.
	secPrec := t.Truncate(time.Second)
	remain := t.Sub(secPrec).Nanoseconds()
	asSecs := secPrec.Unix()
	if remain == 0 && asSecs > 0 && asSecs <= math.MaxUint32 {
		if len(bytes) != 4 {
			return fmt.Errorf("expected length 4, got %d", len(bytes))
		}
		binary.BigEndian.PutUint32(bytes, uint32(asSecs))
		return nil
	}
	if asSecs < 0 || asSecs >= (1<<34) {
		if len(bytes) != 12 {
			return fmt.Errorf("expected length 12, got %d", len(bytes))
		}
		binary.BigEndian.PutUint32(bytes[:4], uint32(remain))
		binary.BigEndian.PutUint64(bytes[4:], uint64(asSecs))
		return nil
	}
	if len(bytes) != 8 {
		return fmt.Errorf("expected length 8, got %d", len(bytes))
	}
	binary.BigEndian.PutUint64(bytes, uint64(asSecs)|(uint64(remain)<<34))
	return nil
}

func (t *Time) UnmarshalBinary(bytes []byte) error {
	switch len(bytes) {
	case 4:
		secs := binary.BigEndian.Uint32(bytes)
		t.Time = time.Unix(int64(secs), 0)
		return nil
	case 8:
		data64 := binary.BigEndian.Uint64(bytes)
		nsecs := int64(data64 >> 34)
		if nsecs > 999999999 {
			// In timestamp 64 and timestamp 96 formats, nanoseconds must not be larger than 999999999.
			return fmt.Errorf("nsecs overflow")
		}
		secs := int64(data64 & 0x3ffffffff)
		t.Time = time.Unix(secs, nsecs)
		return nil
	case 12:
		nsecs := int64(binary.BigEndian.Uint32(bytes[:4]))
		if nsecs > 999999999 {
			// In timestamp 64 and timestamp 96 formats, nanoseconds must not be larger than 999999999.
			return fmt.Errorf("nsecs overflow")
		}
		secs := int64(binary.BigEndian.Uint64(bytes[4:]))
		t.Time = time.Unix(secs, nsecs)
		return nil
	}
	return fmt.Errorf("unknown time format length: %v", len(bytes))
}

The spec doesn't specify explicitly that numbers are big endian, but since the other msgpack are, I assume they are.

Annotate with ",extension", eg:

	Modtime Time   `msg:"Modtime,extension"`.

Roundtrip Test

func TestTime_MarshalBinaryTo(t *testing.T) {
	rng := rand.New(rand.NewSource(0))
	for i := 0; i < 10000; i++ {
		in := Time{
			Time: time.Unix(rng.Int63()-1<<62, rng.Int63n(999999999+1)),
		}
		dst := make([]byte, in.Len())
		err := in.MarshalBinaryTo(dst)
		if err != nil {
			t.Fatal(err)
		}
		var got Time
		err = got.UnmarshalBinary(dst)
		if err != nil {
			t.Fatal(err)
		}
		if !in.Equal(got.Time) {
			t.Errorf("%v != %v", in.Time, got.Time)
		}
	}
	for i := 0; i < 10000; i++ {
		in := Time{
			Time: time.Unix(rng.Int63n(1<<32), 0),
		}
		dst := make([]byte, in.Len())
		if len(dst) != 4 {
			t.Errorf("unexpected length: %v", len(dst))
		}
		err := in.MarshalBinaryTo(dst)
		if err != nil {
			t.Fatal(err)
		}
		var got Time
		err = got.UnmarshalBinary(dst)
		if err != nil {
			t.Fatal(err)
		}
		if !in.Equal(got.Time) {
			t.Errorf("%v != %v", in.Time, got.Time)
		}
	}
	for i := 0; i < 10000; i++ {
		in := Time{
			Time: time.Unix(rng.Int63n(1<<34), rng.Int63n(999999999+1)),
		}
		dst := make([]byte, in.Len())
		if len(dst) > 8 {
			t.Errorf("unexpected length: %v", len(dst))
		}
		err := in.MarshalBinaryTo(dst)
		if err != nil {
			t.Fatal(err)
		}
		var got Time
		err = got.UnmarshalBinary(dst)
		if err != nil {
			t.Fatal(err)
		}
		if !in.Equal(got.Time) {
			t.Errorf("%v != %v", in.Time, got.Time)
		}
	}
}

[sonirico]

@klauspost you certainly were quick in answering and providing this solution! Is there any repo with extensions like this?

Thanks so much!

[sonirico]

@klauspost I made as you pointed, but now I get this error when running tests (and thus running msgp autogenerated tests): EOF. Debugging reached me to this function of the fwd package.

// ReadMapHeader reads the next object
// as a map header and returns the size
// of the map and the number of bytes written.
// It will return a TypeError{} if the next
// object is not a map.
func (m *Reader) ReadMapHeader() (sz uint32, err error) {
}

My time struct is defined as follows:

//msgp:ignore Time

// Time is a time.Time that serializes to/from Msgpack Extension -1.
type Time struct {
	time.Time
}

func (t Time) Equal(other Time) bool {
	return t.Time.Equal(other.Time)
}

func (t Time) FromTime(native time.Time) Time {
	t.Time = native
	return t
}

func (t Time) Truncate(d time.Duration) Time {
	return Time{Time: t.Time.Truncate(d)}
}

func (t Time) Add(d time.Duration) Time {
	return Time{Time: t.Time.Add(d)}
}

func (t Time) ExtensionType() int8 {
	return -1
}

func (t Time) Len() int {
	// Time round towards zero time.
	secPrec := t.Round(time.Second)
	remain := t.Sub(secPrec)
	asSecs := secPrec.Unix()
	if remain == 0 && asSecs > 0 && asSecs <= math.MaxUint32 {
		return 4
	}
	if asSecs < 0 || asSecs >= (1<<34) {
		return 12
	}
	return 8
}

func (t Time) MarshalBinaryTo(bytes []byte) error {
	// Time rounded towards zero.
	secPrec := t.Time.Truncate(time.Second)
	remain := t.Sub(secPrec).Nanoseconds()
	asSecs := secPrec.Unix()
	if remain == 0 && asSecs > 0 && asSecs <= math.MaxUint32 {
		if len(bytes) != 4 {
			return fmt.Errorf("expected length 4, got %d", len(bytes))
		}
		binary.BigEndian.PutUint32(bytes, uint32(asSecs))
		return nil
	}
	if asSecs < 0 || asSecs >= (1<<34) {
		if len(bytes) != 12 {
			return fmt.Errorf("expected length 12, got %d", len(bytes))
		}
		binary.BigEndian.PutUint32(bytes[:4], uint32(remain))
		binary.BigEndian.PutUint64(bytes[4:], uint64(asSecs))
		return nil
	}
	if len(bytes) != 8 {
		return fmt.Errorf("expected length 8, got %d", len(bytes))
	}
	binary.BigEndian.PutUint64(bytes, uint64(asSecs)|(uint64(remain)<<34))
	return nil
}

func (t *Time) UnmarshalBinary(bytes []byte) error {
	switch len(bytes) {
	case 4:
		secs := binary.BigEndian.Uint32(bytes)
		t.Time = time.Unix(int64(secs), 0)
		return nil
	case 8:
		data64 := binary.BigEndian.Uint64(bytes)
		nsecs := int64(data64 >> 34)
		if nsecs > 999999999 {
			// In timestamp 64 and timestamp 96 formats, nanoseconds must not be larger than 999999999.
			return fmt.Errorf("nsecs overflow")
		}
		secs := int64(data64 & 0x3ffffffff)
		t.Time = time.Unix(secs, nsecs)
		return nil
	case 12:
		nsecs := int64(binary.BigEndian.Uint32(bytes[:4]))
		if nsecs > 999999999 {
			// In timestamp 64 and timestamp 96 formats, nanoseconds must not be larger than 999999999.
			return fmt.Errorf("nsecs overflow")
		}
		secs := int64(binary.BigEndian.Uint64(bytes[4:]))
		t.Time = time.Unix(secs, nsecs)
		return nil
	}
	return fmt.Errorf("unknown time format length: %v", len(bytes))
}

func init() {
	// Registering an extension is as simple as matching the
	// appropriate type number with a function that initializes
	// a freshly-allocated object of that type
	msgp.RegisterExtension(-1, func() msgp.Extension { return new(Time) })
}

and the model is

	Model struct {
		Time   Time    `json:"time"         msg:"time,extension"`
		//... some other fields
	}

[klauspost]

Seems like MarshalBinaryTo cannot expect to be given the exact output size. Fixed:

func (t Time) MarshalBinaryTo(bytes []byte) error {
	// Time rounded towards zero.
	secPrec := t.Time.Truncate(time.Second)
	remain := t.Sub(secPrec).Nanoseconds()
	asSecs := secPrec.Unix()
	if remain == 0 && asSecs > 0 && asSecs <= math.MaxUint32 {
		if len(bytes) < 4 {
			return fmt.Errorf("need length 4, got %d", len(bytes))
		}
		binary.BigEndian.PutUint32(bytes, uint32(asSecs))
		return nil
	}
	if asSecs < 0 || asSecs >= (1<<34) {
		if len(bytes) < 12 {
			return fmt.Errorf("need length 12, got %d", len(bytes))
		}
		binary.BigEndian.PutUint32(bytes[:4], uint32(remain))
		binary.BigEndian.PutUint64(bytes[4:], uint64(asSecs))
		return nil
	}
	if len(bytes) < 8 {
		return fmt.Errorf("need length 8, got %d", len(bytes))
	}
	binary.BigEndian.PutUint64(bytes, uint64(asSecs)|(uint64(remain)<<34))
	return nil
}