[#66] transformer: Accept constructor in NextTarget

The code of frostfs-node is not yet ready to reuse egress target for
multiple objects, let's postpone until #64.

Signed-off-by: Evgenii Stratonikov <e.stratonikov@yadro.com>

object/transformer/channel_test.go

@@ -16,9 +16,10 @@ func TestChannelTarget(t *testing.T) {
 
 	ch := make(chan *objectSDK.Object, 10)
 	tt := new(testTarget)
+	ct := NewChannelTarget(ch)
 
-	chTarget, _ := newPayloadSizeLimiter(maxSize, NewChannelTarget(ch))
-	testTarget, _ := newPayloadSizeLimiter(maxSize, tt)
+	chTarget, _ := newPayloadSizeLimiter(maxSize, func() ObjectTarget { return ct })
+	testTarget, _ := newPayloadSizeLimiter(maxSize, func() ObjectTarget { return tt })
 
 	ver := version.Current()
 	cnr := cidtest.ID()

object/transformer/transformer.go

@@ -28,11 +28,13 @@ type payloadSizeLimiter struct {
 	splitID *object.SplitID
 
 	parAttrs []object.Attribute
+
+	nextTarget ObjectTarget
 }
 
 type Params struct {
 	Key                    *ecdsa.PrivateKey
-	NextTarget             ObjectTarget
+	NextTargetInit         func() ObjectTarget
 	SessionToken           *session.Object
 	NetworkState           EpochSource
 	MaxSize                uint64
@@ -113,7 +115,7 @@ func fromObject(obj *object.Object) *object.Object {
 }
 
 func (s *payloadSizeLimiter) initializeCurrent() {
-	// create payload hashers
+	s.nextTarget = s.NextTargetInit()
 	s.writtenCurrent = 0
 	s.initPayloadHashers()
 }
@@ -156,11 +158,11 @@ func (s *payloadSizeLimiter) release(ctx context.Context, finalize bool) (*Acces
 		return nil, fmt.Errorf("fillHeader: %w", err)
 	}
 
-	if err := s.NextTarget.WriteHeader(ctx, s.current); err != nil {
+	if err := s.nextTarget.WriteHeader(ctx, s.current); err != nil {
 		return nil, fmt.Errorf("could not write header to next target: %w", err)
 	}
 
-	if _, err := s.NextTarget.Close(ctx); err != nil {
+	if _, err := s.nextTarget.Close(ctx); err != nil {
 		return nil, fmt.Errorf("could not close next target: %w", err)
 	}
 
@@ -275,7 +277,7 @@ func (s *payloadSizeLimiter) writeChunk(ctx context.Context, chunk []byte) error
 }
 
 func (s *payloadSizeLimiter) writeHashes(ctx context.Context, chunk []byte) error {
-	_, err := s.NextTarget.Write(ctx, chunk)
+	_, err := s.nextTarget.Write(ctx, chunk)
 	if err != nil {
 		return err
 	}

object/transformer/transformer_test.go

@@ -20,7 +20,7 @@ func TestTransformer(t *testing.T) {
 
 	tt := new(testTarget)
 
-	target, pk := newPayloadSizeLimiter(maxSize, tt)
+	target, pk := newPayloadSizeLimiter(maxSize, func() ObjectTarget { return tt })
 
 	cnr := cidtest.ID()
 	hdr := newObject(cnr)
@@ -131,7 +131,7 @@ func benchmarkTransformer(b *testing.B, header *objectSDK.Object, payloadSize in
 	b.ReportAllocs()
 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
-		f, _ := newPayloadSizeLimiter(maxSize, benchTarget{})
+		f, _ := newPayloadSizeLimiter(maxSize, func() ObjectTarget { return benchTarget{} })
 		if err := f.WriteHeader(ctx, header); err != nil {
 			b.Fatalf("write header: %v", err)
 		}
@@ -144,7 +144,7 @@ func benchmarkTransformer(b *testing.B, header *objectSDK.Object, payloadSize in
 	}
 }
 
-func newPayloadSizeLimiter(maxSize uint64, nextTarget ObjectTarget) (ObjectTarget, *keys.PrivateKey) {
+func newPayloadSizeLimiter(maxSize uint64, nextTarget func() ObjectTarget) (ObjectTarget, *keys.PrivateKey) {
 	p, err := keys.NewPrivateKey()
 	if err != nil {
 		panic(err)
@@ -152,7 +152,7 @@ func newPayloadSizeLimiter(maxSize uint64, nextTarget ObjectTarget) (ObjectTarge
 
 	return NewPayloadSizeLimiter(Params{
 		Key:                    &p.PrivateKey,
-		NextTarget:             nextTarget,
+		NextTargetInit:         nextTarget,
 		NetworkState:           dummyEpochSource(123),
 		MaxSize:                maxSize,
 		WithoutHomomorphicHash: true,