Introduce pgproto3 package

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

data_row.go

@@ -0,0 +1,103 @@
+package pgproto3
+
+import (
+	"bytes"
+	"encoding/binary"
+	"encoding/hex"
+	"encoding/json"
+)
+
+type DataRow struct {
+	Values [][]byte
+}
+
+func (*DataRow) Backend() {}
+
+func (dst *DataRow) UnmarshalBinary(src []byte) error {
+	buf := bytes.NewBuffer(src)
+
+	if buf.Len() < 2 {
+		return &invalidMessageFormatErr{messageType: "DataRow"}
+	}
+	fieldCount := int(binary.BigEndian.Uint16(buf.Next(2)))
+
+	dst.Values = make([][]byte, fieldCount)
+
+	for i := 0; i < fieldCount; i++ {
+		if buf.Len() < 4 {
+			return &invalidMessageFormatErr{messageType: "DataRow"}
+		}
+
+		msgSize := int(int32(binary.BigEndian.Uint32(buf.Next(4))))
+
+		// null
+		if msgSize == -1 {
+			continue
+		}
+
+		value := make([]byte, msgSize)
+		_, err := buf.Read(value)
+		if err != nil {
+			return err
+		}
+
+		dst.Values[i] = value
+	}
+
+	return nil
+}
+
+func (src *DataRow) MarshalBinary() ([]byte, error) {
+	var bigEndian BigEndianBuf
+	buf := &bytes.Buffer{}
+
+	buf.WriteByte('D')
+	buf.Write(bigEndian.Uint32(0))
+
+	buf.Write(bigEndian.Uint16(uint16(len(src.Values))))
+
+	for _, v := range src.Values {
+		if v == nil {
+			buf.Write(bigEndian.Int32(-1))
+			continue
+		}
+
+		buf.Write(bigEndian.Int32(int32(len(v))))
+		buf.Write(v)
+	}
+
+	binary.BigEndian.PutUint32(buf.Bytes()[1:5], uint32(buf.Len()-1))
+
+	return buf.Bytes(), nil
+}
+
+func (src *DataRow) MarshalJSON() ([]byte, error) {
+	formattedValues := make([]map[string]string, len(src.Values))
+	for i, v := range src.Values {
+		if v == nil {
+			continue
+		}
+
+		var hasNonPrintable bool
+		for _, b := range v {
+			if b < 32 {
+				hasNonPrintable = true
+				break
+			}
+		}
+
+		if hasNonPrintable {
+			formattedValues[i] = map[string]string{"binary": hex.EncodeToString(v)}
+		} else {
+			formattedValues[i] = map[string]string{"text": string(v)}
+		}
+	}
+
+	return json.Marshal(struct {
+		Type   string
+		Values []map[string]string
+	}{
+		Type:   "DataRow",
+		Values: formattedValues,
+	})
+}