Fix few issues with copy command

pgproto3/copy_fail.go

@@ -0,0 +1,48 @@
+package pgproto3
+
+import (
+	"bytes"
+	"encoding/json"
+
+	"github.com/jackc/pgx/pgio"
+)
+
+type CopyFail struct {
+	Message string
+}
+
+func (*CopyFail) Backend() {}
+
+func (dst *CopyFail) Decode(src []byte) error {
+	idx := bytes.IndexByte(src, 0)
+	if idx != len(src)-1 {
+		return &invalidMessageFormatErr{messageType: "CopyFail"}
+	}
+
+	dst.Message = string(src[:idx])
+
+	return nil
+}
+
+func (src *CopyFail) Encode(dst []byte) []byte {
+	dst = append(dst, 'f')
+	sp := len(dst)
+	dst = pgio.AppendInt32(dst, -1)
+
+	dst = append(dst, src.Message...)
+	dst = append(dst, 0)
+
+	pgio.SetInt32(dst[sp:], int32(len(dst[sp:])))
+
+	return dst
+}
+
+func (src *CopyFail) MarshalJSON() ([]byte, error) {
+	return json.Marshal(struct {
+		Type       string
+		Message string
+	}{
+		Type:       "CopyFail",
+		Message: src.Message,
+	})
+}

pgproto3/copy_out_response.go

@@ -44,6 +44,8 @@ func (src *CopyOutResponse) Encode(dst []byte) []byte {
 	sp := len(dst)
 	dst = pgio.AppendInt32(dst, -1)
 
+	dst = append(dst, src.OverallFormat)
+
 	dst = pgio.AppendUint16(dst, uint16(len(src.ColumnFormatCodes)))
 	for _, fc := range src.ColumnFormatCodes {
 		dst = pgio.AppendUint16(dst, fc)

pgproto3/frontend.go

@@ -23,6 +23,7 @@ type Frontend struct {
 	copyInResponse       CopyInResponse
 	copyOutResponse      CopyOutResponse
 	copyDone             CopyDone
+        copyFail             CopyFail
 	dataRow              DataRow
 	emptyQueryResponse   EmptyQueryResponse
 	errorResponse        ErrorResponse
@@ -75,6 +76,8 @@ func (b *Frontend) Receive() (BackendMessage, error) {
 		msg = &b.notificationResponse
 	case 'c':
 		msg = &b.copyDone
+        case 'f':
+                msg = &b.copyFail
 	case 'C':
 		msg = &b.commandComplete
 	case 'd':