[#34] services/object: Replace local placement to util

Replace local placement tool in order to reuse it in different object
services.

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

pkg/services/object/util/local.go

@@ -0,0 +1,45 @@
+package util
+
+import (
+	"github.com/nspcc-dev/neofs-api-go/pkg/netmap"
+	"github.com/nspcc-dev/neofs-api-go/pkg/object"
+	"github.com/nspcc-dev/neofs-node/pkg/network"
+	"github.com/nspcc-dev/neofs-node/pkg/services/object_manager/placement"
+	"github.com/pkg/errors"
+)
+
+type localPlacement struct {
+	builder placement.Builder
+
+	localAddrSrc network.LocalAddressSource
+}
+
+func NewLocalPlacement(b placement.Builder, s network.LocalAddressSource) placement.Builder {
+	return &localPlacement{
+		builder:      b,
+		localAddrSrc: s,
+	}
+}
+
+func (p *localPlacement) BuildPlacement(addr *object.Address, policy *netmap.PlacementPolicy) ([]netmap.Nodes, error) {
+	vs, err := p.builder.BuildPlacement(addr, policy)
+	if err != nil {
+		return nil, errors.Wrapf(err, "(%T) could not build object placement", p)
+	}
+
+	for i := range vs {
+		for j := range vs[i] {
+			addr, err := network.AddressFromString(vs[i][j].NetworkAddress())
+			if err != nil {
+				// TODO: log error
+				continue
+			}
+
+			if network.IsLocalAddress(p.localAddrSrc, addr) {
+				return []netmap.Nodes{{vs[i][j]}}, nil
+			}
+		}
+	}
+
+	return nil, errors.Errorf("(%T) local node is outside of object placement", p)
+}