Introduce pgproto3 package

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

row_description.go

@@ -0,0 +1,101 @@
+package pgproto3
+
+import (
+	"bytes"
+	"encoding/binary"
+	"encoding/json"
+)
+
+const (
+	TextFormat   = 0
+	BinaryFormat = 1
+)
+
+type FieldDescription struct {
+	Name                 string
+	TableOID             uint32
+	TableAttributeNumber uint16
+	DataTypeOID          uint32
+	DataTypeSize         int16
+	TypeModifier         uint32
+	Format               int16
+}
+
+type RowDescription struct {
+	Fields []FieldDescription
+}
+
+func (*RowDescription) Backend() {}
+
+func (dst *RowDescription) UnmarshalBinary(src []byte) error {
+	buf := bytes.NewBuffer(src)
+
+	if buf.Len() < 2 {
+		return &invalidMessageFormatErr{messageType: "RowDescription"}
+	}
+	fieldCount := int(binary.BigEndian.Uint16(buf.Next(2)))
+
+	*dst = RowDescription{Fields: make([]FieldDescription, fieldCount)}
+
+	for i := 0; i < fieldCount; i++ {
+		var fd FieldDescription
+		bName, err := buf.ReadBytes(0)
+		if err != nil {
+			return err
+		}
+		fd.Name = string(bName[:len(bName)-1])
+
+		// Since buf.Next() doesn't return an error if we hit the end of the buffer
+		// check Len ahead of time
+		if buf.Len() < 18 {
+			return &invalidMessageFormatErr{messageType: "RowDescription"}
+		}
+
+		fd.TableOID = binary.BigEndian.Uint32(buf.Next(4))
+		fd.TableAttributeNumber = binary.BigEndian.Uint16(buf.Next(2))
+		fd.DataTypeOID = binary.BigEndian.Uint32(buf.Next(4))
+		fd.DataTypeSize = int16(binary.BigEndian.Uint16(buf.Next(2)))
+		fd.TypeModifier = binary.BigEndian.Uint32(buf.Next(4))
+		fd.Format = int16(binary.BigEndian.Uint16(buf.Next(2)))
+
+		dst.Fields[i] = fd
+	}
+
+	return nil
+}
+
+func (src *RowDescription) MarshalBinary() ([]byte, error) {
+	var bigEndian BigEndianBuf
+	buf := &bytes.Buffer{}
+
+	buf.WriteByte('T')
+	buf.Write(bigEndian.Uint32(0))
+
+	buf.Write(bigEndian.Uint16(uint16(len(src.Fields))))
+
+	for _, fd := range src.Fields {
+		buf.WriteString(fd.Name)
+		buf.WriteByte(0)
+
+		buf.Write(bigEndian.Uint32(fd.TableOID))
+		buf.Write(bigEndian.Uint16(fd.TableAttributeNumber))
+		buf.Write(bigEndian.Uint32(fd.DataTypeOID))
+		buf.Write(bigEndian.Uint16(uint16(fd.DataTypeSize)))
+		buf.Write(bigEndian.Uint32(fd.TypeModifier))
+		buf.Write(bigEndian.Uint16(uint16(fd.Format)))
+	}
+
+	binary.BigEndian.PutUint32(buf.Bytes()[1:5], uint32(buf.Len()-1))
+
+	return buf.Bytes(), nil
+}
+
+func (src *RowDescription) MarshalJSON() ([]byte, error) {
+	return json.Marshal(struct {
+		Type   string
+		Fields []FieldDescription
+	}{
+		Type:   "RowDescription",
+		Fields: src.Fields,
+	})
+}