lib/protocol, lib/discover, lib/db: Use protocol buffer serialization (fixes #3080)

This changes the BEP protocol to use protocol buffer serialization
instead of XDR, and therefore also the database format. The local
discovery protocol is also updated to be protocol buffer format.

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/3276
LGTM: AudriusButkevicius

lib/db/structs.go

@@ -0,0 +1,57 @@
+// Copyright (C) 2014 The Syncthing Authors.
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this file,
+// You can obtain one at http://mozilla.org/MPL/2.0/.
+
+//go:generate go run ../../script/protofmt.go structs.proto
+//go:generate protoc --proto_path=../../../../../:../../../../gogo/protobuf/protobuf:. --gogofast_out=. structs.proto
+
+package db
+
+import (
+	"fmt"
+
+	"github.com/syncthing/syncthing/lib/protocol"
+)
+
+func (f FileInfoTruncated) String() string {
+	return fmt.Sprintf("File{Name:%q, Permissions:0%o, Modified:%d, Version:%v, Length:%d, Deleted:%v, Invalid:%v, NoPermissions:%v}",
+		f.Name, f.Permissions, f.Modified, f.Version, f.Size, f.Deleted, f.Invalid, f.NoPermissions)
+}
+
+func (f FileInfoTruncated) IsDeleted() bool {
+	return f.Deleted
+}
+
+func (f FileInfoTruncated) IsInvalid() bool {
+	return f.Invalid
+}
+
+func (f FileInfoTruncated) IsDirectory() bool {
+	return f.Type == protocol.FileInfoTypeDirectory
+}
+
+func (f FileInfoTruncated) IsSymlink() bool {
+	switch f.Type {
+	case protocol.FileInfoTypeSymlinkDirectory, protocol.FileInfoTypeSymlinkFile, protocol.FileInfoTypeSymlinkUnknown:
+		return true
+	default:
+		return false
+	}
+}
+
+func (f FileInfoTruncated) HasPermissionBits() bool {
+	return !f.NoPermissions
+}
+
+func (f FileInfoTruncated) FileSize() int64 {
+	if f.IsDirectory() || f.IsDeleted() {
+		return 128
+	}
+	return f.Size
+}
+
+func (f FileInfoTruncated) FileName() string {
+	return f.Name
+}