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

vendor/github.com/gogo/protobuf/test/empty-issue70/empty.pb.go

@@ -0,0 +1,208 @@
+// Code generated by protoc-gen-gogo.
+// source: empty.proto
+// DO NOT EDIT!
+
+/*
+Package empty is a generated protocol buffer package.
+
+It is generated from these files:
+	empty.proto
+
+It has these top-level messages:
+	TestRequest
+*/
+package empty
+
+import proto "github.com/gogo/protobuf/proto"
+import fmt "fmt"
+import math "math"
+import _ "github.com/gogo/protobuf/gogoproto"
+
+import io "io"
+
+// Reference imports to suppress errors if they are not otherwise used.
+var _ = proto.Marshal
+var _ = fmt.Errorf
+var _ = math.Inf
+
+// This is a compile-time assertion to ensure that this generated file
+// is compatible with the proto package it is being compiled against.
+const _ = proto.GoGoProtoPackageIsVersion1
+
+type TestRequest struct {
+	XXX_unrecognized []byte `json:"-"`
+}
+
+func (m *TestRequest) Reset()                    { *m = TestRequest{} }
+func (m *TestRequest) String() string            { return proto.CompactTextString(m) }
+func (*TestRequest) ProtoMessage()               {}
+func (*TestRequest) Descriptor() ([]byte, []int) { return fileDescriptorEmpty, []int{0} }
+
+func init() {
+	proto.RegisterType((*TestRequest)(nil), "empty.TestRequest")
+}
+func (m *TestRequest) Unmarshal(data []byte) error {
+	l := len(data)
+	iNdEx := 0
+	for iNdEx < l {
+		preIndex := iNdEx
+		var wire uint64
+		for shift := uint(0); ; shift += 7 {
+			if shift >= 64 {
+				return ErrIntOverflowEmpty
+			}
+			if iNdEx >= l {
+				return io.ErrUnexpectedEOF
+			}
+			b := data[iNdEx]
+			iNdEx++
+			wire |= (uint64(b) & 0x7F) << shift
+			if b < 0x80 {
+				break
+			}
+		}
+		fieldNum := int32(wire >> 3)
+		wireType := int(wire & 0x7)
+		if wireType == 4 {
+			return fmt.Errorf("proto: TestRequest: wiretype end group for non-group")
+		}
+		if fieldNum <= 0 {
+			return fmt.Errorf("proto: TestRequest: illegal tag %d (wire type %d)", fieldNum, wire)
+		}
+		switch fieldNum {
+		default:
+			iNdEx = preIndex
+			skippy, err := skipEmpty(data[iNdEx:])
+			if err != nil {
+				return err
+			}
+			if skippy < 0 {
+				return ErrInvalidLengthEmpty
+			}
+			if (iNdEx + skippy) > l {
+				return io.ErrUnexpectedEOF
+			}
+			m.XXX_unrecognized = append(m.XXX_unrecognized, data[iNdEx:iNdEx+skippy]...)
+			iNdEx += skippy
+		}
+	}
+
+	if iNdEx > l {
+		return io.ErrUnexpectedEOF
+	}
+	return nil
+}
+func skipEmpty(data []byte) (n int, err error) {
+	l := len(data)
+	iNdEx := 0
+	for iNdEx < l {
+		var wire uint64
+		for shift := uint(0); ; shift += 7 {
+			if shift >= 64 {
+				return 0, ErrIntOverflowEmpty
+			}
+			if iNdEx >= l {
+				return 0, io.ErrUnexpectedEOF
+			}
+			b := data[iNdEx]
+			iNdEx++
+			wire |= (uint64(b) & 0x7F) << shift
+			if b < 0x80 {
+				break
+			}
+		}
+		wireType := int(wire & 0x7)
+		switch wireType {
+		case 0:
+			for shift := uint(0); ; shift += 7 {
+				if shift >= 64 {
+					return 0, ErrIntOverflowEmpty
+				}
+				if iNdEx >= l {
+					return 0, io.ErrUnexpectedEOF
+				}
+				iNdEx++
+				if data[iNdEx-1] < 0x80 {
+					break
+				}
+			}
+			return iNdEx, nil
+		case 1:
+			iNdEx += 8
+			return iNdEx, nil
+		case 2:
+			var length int
+			for shift := uint(0); ; shift += 7 {
+				if shift >= 64 {
+					return 0, ErrIntOverflowEmpty
+				}
+				if iNdEx >= l {
+					return 0, io.ErrUnexpectedEOF
+				}
+				b := data[iNdEx]
+				iNdEx++
+				length |= (int(b) & 0x7F) << shift
+				if b < 0x80 {
+					break
+				}
+			}
+			iNdEx += length
+			if length < 0 {
+				return 0, ErrInvalidLengthEmpty
+			}
+			return iNdEx, nil
+		case 3:
+			for {
+				var innerWire uint64
+				var start int = iNdEx
+				for shift := uint(0); ; shift += 7 {
+					if shift >= 64 {
+						return 0, ErrIntOverflowEmpty
+					}
+					if iNdEx >= l {
+						return 0, io.ErrUnexpectedEOF
+					}
+					b := data[iNdEx]
+					iNdEx++
+					innerWire |= (uint64(b) & 0x7F) << shift
+					if b < 0x80 {
+						break
+					}
+				}
+				innerWireType := int(innerWire & 0x7)
+				if innerWireType == 4 {
+					break
+				}
+				next, err := skipEmpty(data[start:])
+				if err != nil {
+					return 0, err
+				}
+				iNdEx = start + next
+			}
+			return iNdEx, nil
+		case 4:
+			return iNdEx, nil
+		case 5:
+			iNdEx += 4
+			return iNdEx, nil
+		default:
+			return 0, fmt.Errorf("proto: illegal wireType %d", wireType)
+		}
+	}
+	panic("unreachable")
+}
+
+var (
+	ErrInvalidLengthEmpty = fmt.Errorf("proto: negative length found during unmarshaling")
+	ErrIntOverflowEmpty   = fmt.Errorf("proto: integer overflow")
+)
+
+var fileDescriptorEmpty = []byte{
+	// 91 bytes of a gzipped FileDescriptorProto
+	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x09, 0x6e, 0x88, 0x02, 0xff, 0xe2, 0xe2, 0x4e, 0xcd, 0x2d, 0x28,
+	0xa9, 0xd4, 0x2b, 0x28, 0xca, 0x2f, 0xc9, 0x17, 0x62, 0x05, 0x73, 0xa4, 0x74, 0xd3, 0x33, 0x4b,
+	0x32, 0x4a, 0x93, 0xf4, 0x92, 0xf3, 0x73, 0xf5, 0xd3, 0xf3, 0xd3, 0xf3, 0xf5, 0xc1, 0xb2, 0x49,
+	0xa5, 0x69, 0x60, 0x1e, 0x98, 0x03, 0x66, 0x41, 0x74, 0x29, 0xf1, 0x72, 0x71, 0x87, 0xa4, 0x16,
+	0x97, 0x04, 0xa5, 0x16, 0x96, 0x02, 0x29, 0x27, 0x96, 0x0b, 0x8f, 0xe4, 0x18, 0x01, 0x01, 0x00,
+	0x00, 0xff, 0xff, 0x0e, 0xe3, 0x23, 0x3d, 0x58, 0x00, 0x00, 0x00,
+}