Introduce pgproto3 package

pgproto3 will wrap the message encoding and decoding for the PostgreSQL
frontend/backend protocol version 3.

notification_response.go

@@ -0,0 +1,65 @@
+package pgproto3
+
+import (
+	"bytes"
+	"encoding/binary"
+	"encoding/json"
+)
+
+type NotificationResponse struct {
+	PID     uint32
+	Channel string
+	Payload string
+}
+
+func (*NotificationResponse) Backend() {}
+
+func (dst *NotificationResponse) UnmarshalBinary(src []byte) error {
+	buf := bytes.NewBuffer(src)
+
+	pid := binary.BigEndian.Uint32(buf.Next(4))
+
+	b, err := buf.ReadBytes(0)
+	if err != nil {
+		return err
+	}
+	channel := string(b[:len(b)-1])
+
+	b, err = buf.ReadBytes(0)
+	if err != nil {
+		return err
+	}
+	payload := string(b[:len(b)-1])
+
+	*dst = NotificationResponse{PID: pid, Channel: channel, Payload: payload}
+	return nil
+}
+
+func (src *NotificationResponse) MarshalBinary() ([]byte, error) {
+	var bigEndian BigEndianBuf
+	buf := &bytes.Buffer{}
+
+	buf.WriteByte('A')
+	buf.Write(bigEndian.Uint32(uint32(4 + 4 + len(src.Channel) + len(src.Payload))))
+
+	buf.WriteString(src.Channel)
+	buf.WriteByte(0)
+	buf.WriteString(src.Payload)
+	buf.WriteByte(0)
+
+	return buf.Bytes(), nil
+}
+
+func (src *NotificationResponse) MarshalJSON() ([]byte, error) {
+	return json.Marshal(struct {
+		Type    string
+		PID     uint32
+		Channel string
+		Payload string
+	}{
+		Type:    "NotificationResponse",
+		PID:     src.PID,
+		Channel: src.Channel,
+		Payload: src.Payload,
+	})
+}