Introduce pgproto3 package

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

parameter_description.go

@@ -0,0 +1,60 @@
+package pgproto3
+
+import (
+	"bytes"
+	"encoding/binary"
+	"encoding/json"
+)
+
+type ParameterDescription struct {
+	ParameterOIDs []uint32
+}
+
+func (*ParameterDescription) Backend() {}
+
+func (dst *ParameterDescription) UnmarshalBinary(src []byte) error {
+	buf := bytes.NewBuffer(src)
+
+	if buf.Len() < 2 {
+		return &invalidMessageFormatErr{messageType: "ParameterDescription"}
+	}
+
+	// Reported parameter count will be incorrect when number of args is greater than uint16
+	buf.Next(2)
+	// Instead infer parameter count by remaining size of message
+	parameterCount := buf.Len() / 4
+
+	*dst = ParameterDescription{ParameterOIDs: make([]uint32, parameterCount)}
+
+	for i := 0; i < parameterCount; i++ {
+		dst.ParameterOIDs[i] = binary.BigEndian.Uint32(buf.Next(4))
+	}
+
+	return nil
+}
+
+func (src *ParameterDescription) MarshalBinary() ([]byte, error) {
+	var bigEndian BigEndianBuf
+	buf := &bytes.Buffer{}
+
+	buf.WriteByte('t')
+	buf.Write(bigEndian.Uint32(uint32(4 + 2 + 4*len(src.ParameterOIDs))))
+
+	buf.Write(bigEndian.Uint16(uint16(len(src.ParameterOIDs))))
+
+	for _, oid := range src.ParameterOIDs {
+		buf.Write(bigEndian.Uint32(oid))
+	}
+
+	return buf.Bytes(), nil
+}
+
+func (src *ParameterDescription) MarshalJSON() ([]byte, error) {
+	return json.Marshal(struct {
+		Type          string
+		ParameterOIDs []uint32
+	}{
+		Type:          "ParameterDescription",
+		ParameterOIDs: src.ParameterOIDs,
+	})
+}