Overview ▾

The unmarshal plugin generates a Unmarshal method for each message. The `Unmarshal([]byte) error` method results in the fact that the message implements the Unmarshaler interface. The allows proto.Unmarshal to be faster by calling the generated Unmarshal method rather than using reflect.

If is enabled by the following extensions:

- unmarshaler
- unmarshaler_all

Or the following extensions:

- unsafe_unmarshaler
- unsafe_unmarshaler_all

That is if you want to use the unsafe package in your generated code. The speed up using the unsafe package is not very significant.

The generation of unmarshalling tests are enabled using one of the following extensions:

- testgen
- testgen_all

And benchmarks given it is enabled using one of the following extensions:

- benchgen
- benchgen_all

Let us look at:

github.com/gogo/protobuf/test/example/example.proto

Btw all the output can be seen at:

github.com/gogo/protobuf/test/example/*

The following message:

  option (gogoproto.unmarshaler_all) = true;

  message B {
	option (gogoproto.description) = true;
	optional A A = 1 [(gogoproto.nullable) = false, (gogoproto.embed) = true];
	repeated bytes G = 2 [(gogoproto.customtype) = "github.com/gogo/protobuf/test/custom.Uint128", (gogoproto.nullable) = false];
  }

given to the unmarshal plugin, will generate the following code:

  func (m *B) Unmarshal(dAtA []byte) error {
	l := len(dAtA)
	iNdEx := 0
	for iNdEx < l {
		var wire uint64
		for shift := uint(0); ; shift += 7 {
			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)
		switch fieldNum {
		case 1:
			if wireType != 2 {
				return proto.ErrWrongType
			}
			var msglen int
			for shift := uint(0); ; shift += 7 {
				if iNdEx >= l {
					return io.ErrUnexpectedEOF
				}
				b := dAtA[iNdEx]
				iNdEx++
				msglen |= (int(b) & 0x7F) << shift
				if b < 0x80 {
					break
				}
			}
			postIndex := iNdEx + msglen
			if postIndex > l {
				return io.ErrUnexpectedEOF
			}
			if err := m.A.Unmarshal(dAtA[iNdEx:postIndex]); err != nil {
				return err
			}
			iNdEx = postIndex
		case 2:
			if wireType != 2 {
				return proto.ErrWrongType
			}
			var byteLen int
			for shift := uint(0); ; shift += 7 {
				if iNdEx >= l {
					return io.ErrUnexpectedEOF
				}
				b := dAtA[iNdEx]
				iNdEx++
				byteLen |= (int(b) & 0x7F) << shift
				if b < 0x80 {
					break
				}
			}
			postIndex := iNdEx + byteLen
			if postIndex > l {
				return io.ErrUnexpectedEOF
			}
			m.G = append(m.G, github_com_gogo_protobuf_test_custom.Uint128{})
			if err := m.G[len(m.G)-1].Unmarshal(dAtA[iNdEx:postIndex]); err != nil {
				return err
			}
			iNdEx = postIndex
		default:
			var sizeOfWire int
			for {
				sizeOfWire++
				wire >>= 7
				if wire == 0 {
					break
				}
			}
			iNdEx -= sizeOfWire
			skippy, err := skip(dAtA[iNdEx:])
			if err != nil {
				return err
			}
			if (iNdEx + skippy) > l {
				return io.ErrUnexpectedEOF
			}
			m.XXX_unrecognized = append(m.XXX_unrecognized, dAtA[iNdEx:iNdEx+skippy]...)
			iNdEx += skippy
		}
	}
	return nil
  }

Remember when using this code to call proto.Unmarshal. This will call m.Reset and invoke the generated Unmarshal method for you. If you call m.Unmarshal without m.Reset you could be merging protocol buffers.

Index ▾

Package files

unmarshal.go