Introduce pgproto3 package

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

function_call_response.go

@@ -0,0 +1,73 @@
+package pgproto3
+
+import (
+	"bytes"
+	"encoding/binary"
+	"encoding/hex"
+	"encoding/json"
+)
+
+type FunctionCallResponse struct {
+	Result []byte
+}
+
+func (*FunctionCallResponse) Backend() {}
+
+func (dst *FunctionCallResponse) UnmarshalBinary(src []byte) error {
+	buf := bytes.NewBuffer(src)
+
+	if buf.Len() < 4 {
+		return &invalidMessageFormatErr{messageType: "FunctionCallResponse"}
+	}
+	resultSize := int(binary.BigEndian.Uint32(buf.Next(4)))
+	if buf.Len() != resultSize {
+		return &invalidMessageFormatErr{messageType: "FunctionCallResponse"}
+	}
+
+	dst.Result = make([]byte, resultSize)
+	copy(dst.Result, buf.Bytes())
+
+	return nil
+}
+
+func (src *FunctionCallResponse) MarshalBinary() ([]byte, error) {
+	var bigEndian BigEndianBuf
+	buf := &bytes.Buffer{}
+
+	buf.WriteByte('V')
+	buf.Write(bigEndian.Uint32(uint32(4 + 4 + len(src.Result))))
+
+	if src.Result == nil {
+		buf.Write(bigEndian.Int32(-1))
+	} else {
+		buf.Write(bigEndian.Int32(int32(len(src.Result))))
+		buf.Write(src.Result)
+	}
+
+	return buf.Bytes(), nil
+}
+
+func (src *FunctionCallResponse) MarshalJSON() ([]byte, error) {
+	var formattedValue map[string]string
+	var hasNonPrintable bool
+	for _, b := range src.Result {
+		if b < 32 {
+			hasNonPrintable = true
+			break
+		}
+	}
+
+	if hasNonPrintable {
+		formattedValue = map[string]string{"binary": hex.EncodeToString(src.Result)}
+	} else {
+		formattedValue = map[string]string{"text": string(src.Result)}
+	}
+
+	return json.Marshal(struct {
+		Type   string
+		Result map[string]string
+	}{
+		Type:   "FunctionCallResponse",
+		Result: formattedValue,
+	})
+}