fix interface, implement appender, add benchmarks

Author: mlange-42

ecs/entity.go

@@ -85,11 +85,19 @@ func (e *Entity) UnmarshalJSON(data []byte) error {
 }
 
 // MarshalBinary returns a binary representation of the entity, for serialization and networking purposes.
-func (e *Entity) MarshalBinary() []byte {
+func (e *Entity) MarshalBinary() (data []byte, err error) {
 	buf := make([]byte, 8)
 	binary.BigEndian.PutUint32(buf[0:4], uint32(e.id))
 	binary.BigEndian.PutUint32(buf[4:8], e.gen)
-	return buf
+	return buf, nil
+}
+
+// AppendBinary appends the binary representation of the entity to the given slice,
+// for serialization and networking purposes.
+func (e *Entity) AppendBinary(buf []byte) ([]byte, error) {
+	buf = binary.BigEndian.AppendUint32(buf, uint32(e.id))
+	buf = binary.BigEndian.AppendUint32(buf, e.gen)
+	return buf, nil
 }
 
 // UnmarshalBinary into an entity.

ecs/entity_test.go

@@ -1,7 +1,9 @@
 package ecs
 
 import (
+	"encoding"
 	"encoding/json"
+	"runtime"
 	"testing"
 )
 
@@ -34,16 +36,15 @@ func TestReservedEntities(t *testing.T) {
 func TestEntityMarshal(t *testing.T) {
 	e := Entity{2, 3}
 
+	var _ json.Marshaler = &e
+	var _ json.Unmarshaler = &e
+
 	jsonData, err := json.Marshal(&e)
-	if err != nil {
-		t.Fatal(err)
-	}
+	expectNil(t, err)
 
 	e2 := Entity{}
 	err = json.Unmarshal(jsonData, &e2)
-	if err != nil {
-		t.Fatal(err)
-	}
+	expectNil(t, err)
 
 	expectEqual(t, e2, e)
 
@@ -54,19 +55,98 @@ func TestEntityMarshal(t *testing.T) {
 func TestEntityMarshalBinary(t *testing.T) {
 	e := Entity{2, 3}
 
-	binData, err := json.Marshal(&e)
-	if err != nil {
-		t.Fatal(err)
-	}
+	var _ encoding.BinaryMarshaler = &e
+	var _ encoding.BinaryUnmarshaler = &e
+	var _ encoding.BinaryAppender = &e
+
+	binData, err := e.MarshalBinary()
+	expectNil(t, err)
 
 	e2 := Entity{}
-	err = json.Unmarshal(binData, &e2)
-	if err != nil {
-		t.Fatal(err)
-	}
+	err = e2.UnmarshalBinary(binData)
+	expectNil(t, err)
+	expectEqual(t, 8, len(binData))
 
 	expectEqual(t, e2, e)
 
-	err = e2.UnmarshalJSON(make([]byte, 9))
+	err = e2.UnmarshalBinary(make([]byte, 9))
 	expectNotNil(t, err)
+
+	e = Entity{4, 5}
+	binData, err = e.AppendBinary(binData)
+	expectNil(t, err)
+	expectEqual(t, 16, len(binData))
+
+	err = e2.UnmarshalBinary(binData[8:])
+	expectNil(t, err)
+	expectEqual(t, e2, e)
+
+	err = e2.UnmarshalBinary(binData[:8])
+	expectNil(t, err)
+	expectEqual(t, e2, Entity{2, 3})
+}
+
+func BenchmarkEntityMarshalBinary_1000(b *testing.B) {
+	w := NewWorld()
+
+	entities := make([]Entity, 0, 1000)
+	w.NewEntities(1000, func(e Entity) {
+		entities = append(entities, e)
+	})
+
+	var binData []byte
+	loop := func() {
+		for _, e := range entities {
+			binData, _ = e.MarshalBinary()
+		}
+	}
+	for b.Loop() {
+		loop()
+	}
+
+	runtime.KeepAlive(binData)
+}
+
+func BenchmarkEntityAppendBinary_1000(b *testing.B) {
+	w := NewWorld()
+
+	entities := make([]Entity, 0, 1000)
+	w.NewEntities(1000, func(e Entity) {
+		entities = append(entities, e)
+	})
+
+	binData := make([]byte, 0, 8000)
+	loop := func() {
+		binData = binData[:0]
+		for _, e := range entities {
+			binData, _ = e.AppendBinary(binData)
+		}
+	}
+	for b.Loop() {
+		loop()
+	}
+
+	runtime.KeepAlive(binData)
+}
+
+func BenchmarkEntityUnmarshalBinary_1000(b *testing.B) {
+	w := NewWorld()
+
+	entities := make([][]byte, 0, 1000)
+	w.NewEntities(1000, func(e Entity) {
+		binData, _ := e.MarshalBinary()
+		entities = append(entities, binData)
+	})
+
+	var entity Entity
+	loop := func() {
+		for _, e := range entities {
+			_ = entity.UnmarshalBinary(e)
+		}
+	}
+	for b.Loop() {
+		loop()
+	}
+
+	runtime.KeepAlive(entity)
 }