[#80] storageroup: Implement function to collect structure from container

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>

pkg/services/object_manager/storagegroup/collect.go

@@ -0,0 +1,56 @@
+package storagegroup
+
+import (
+	"github.com/nspcc-dev/neofs-api-go/pkg"
+	"github.com/nspcc-dev/neofs-api-go/pkg/client"
+	"github.com/nspcc-dev/neofs-api-go/pkg/container"
+	objectSDK "github.com/nspcc-dev/neofs-api-go/pkg/object"
+	"github.com/nspcc-dev/neofs-api-go/pkg/storagegroup"
+	"github.com/nspcc-dev/neofs-node/pkg/core/object"
+	objutil "github.com/nspcc-dev/neofs-node/pkg/services/object/util"
+	"github.com/nspcc-dev/tzhash/tz"
+)
+
+// CollectMembers creates new storage group structure and fills it
+// with information about members collected via HeadReceiver.
+//
+// Resulting storage group consists of physically stored objects only.
+func CollectMembers(r objutil.HeadReceiver, cid *container.ID, members []*objectSDK.ID) (*storagegroup.StorageGroup, error) {
+	var (
+		sumPhySize uint64
+		phyMembers []*objectSDK.ID
+		phyHashes  [][]byte
+		addr       = objectSDK.NewAddress()
+		sg         = storagegroup.New()
+	)
+
+	addr.SetContainerID(cid)
+
+	for i := range members {
+		addr.SetObjectID(members[i])
+
+		if err := objutil.IterateAllSplitLeaves(r, addr, func(leaf *object.Object) {
+			phyMembers = append(phyMembers, leaf.ID())
+			sumPhySize += leaf.PayloadSize()
+			phyHashes = append(phyHashes, leaf.PayloadHomomorphicHash().Sum())
+		}); err != nil {
+			return nil, err
+		}
+	}
+
+	sumHash, err := tz.Concat(phyHashes)
+	if err != nil {
+		return nil, err
+	}
+
+	cs := pkg.NewChecksum()
+	tzHash := [client.TZSize]byte{}
+	copy(tzHash[:], sumHash)
+	cs.SetTillichZemor(tzHash)
+
+	sg.SetMembers(phyMembers)
+	sg.SetValidationDataSize(sumPhySize)
+	sg.SetValidationDataHash(cs)
+
+	return sg, nil
+}