size

Overview ¶

The size plugin generates a Size or ProtoSize method for each message. This is useful with the MarshalTo method generated by the marshalto plugin and the gogoproto.marshaler and gogoproto.marshaler_all extensions.

It is enabled by the following extensions:

• sizer
• sizer_all
• protosizer
• protosizer_all

The size plugin also generates a test given it is enabled using one of the following extensions:

• testgen
• testgen_all

And a benchmark 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.sizer_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 size plugin, will generate the following code:

  func (m *B) Size() (n int) {
	var l int
	_ = l
	l = m.A.Size()
	n += 1 + l + sovExample(uint64(l))
	if len(m.G) > 0 {
		for _, e := range m.G {
			l = e.Size()
			n += 1 + l + sovExample(uint64(l))
		}
	}
	if m.XXX_unrecognized != nil {
		n += len(m.XXX_unrecognized)
	}
	return n
  }

and the following test code:

func TestBSize(t *testing5.T) {
	popr := math_rand5.New(math_rand5.NewSource(time5.Now().UnixNano()))
	p := NewPopulatedB(popr, true)
	dAtA, err := github_com_gogo_protobuf_proto2.Marshal(p)
	if err != nil {
		panic(err)
	}
	size := p.Size()
	if len(dAtA) != size {
		t.Fatalf("size %v != marshalled size %v", size, len(dAtA))
	}
}

func BenchmarkBSize(b *testing5.B) {
	popr := math_rand5.New(math_rand5.NewSource(616))
	total := 0
	pops := make([]*B, 1000)
	for i := 0; i < 1000; i++ {
		pops[i] = NewPopulatedB(popr, false)
	}
	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		total += pops[i%1000].Size()
	}
	b.SetBytes(int64(total / b.N))
}

The sovExample function is a size of varint function for the example.pb.go file.