[#137] sdk: Implement netmap filtering and selection

Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>

pkg/netmap/netmap.go

@@ -0,0 +1,73 @@
+package netmap
+
+import (
+	"fmt"
+
+	"github.com/nspcc-dev/hrw"
+	"github.com/nspcc-dev/neofs-api-go/v2/netmap"
+)
+
+// Netmap represents netmap which contains preprocessed nodes.
+type Netmap struct {
+	Nodes Nodes
+}
+
+// NewNetmap constructs netmap from the list of raw nodes.
+func NewNetmap(nodes Nodes) (*Netmap, error) {
+	return &Netmap{
+		Nodes: nodes,
+	}, nil
+}
+
+func flattenNodes(ns []Nodes) Nodes {
+	result := make(Nodes, 0, len(ns))
+	for i := range ns {
+		result = append(result, ns[i]...)
+	}
+	return result
+}
+
+// GetPlacementVectors returns placement vectors for an object given containerNodes cnt.
+func (m *Netmap) GetPlacementVectors(cnt ContainerNodes, pivot []byte) ([]Nodes, error) {
+	h := hrw.Hash(pivot)
+	wf := GetDefaultWeightFunc(m.Nodes)
+	result := make([]Nodes, len(cnt.Replicas()))
+	for i, rep := range cnt.Replicas() {
+		result[i] = make(Nodes, len(rep))
+		copy(result[i], rep)
+		hrw.SortSliceByWeightValue(result[i], result[i].Weights(wf), h)
+	}
+	return result, nil
+}
+
+// GetContainerNodes returns nodes corresponding to each replica.
+// Order of returned nodes corresponds to order of replicas in p.
+// pivot is a seed for HRW sorting.
+func (m *Netmap) GetContainerNodes(p *netmap.PlacementPolicy, pivot []byte) (ContainerNodes, error) {
+	c := NewContext(m)
+	c.setPivot(pivot)
+	if err := c.processFilters(p); err != nil {
+		return nil, err
+	}
+	if err := c.processSelectors(p); err != nil {
+		return nil, err
+	}
+	result := make([]Nodes, len(p.GetReplicas()))
+	for i, r := range p.GetReplicas() {
+		if r == nil {
+			return nil, fmt.Errorf("%w: REPLICA", ErrMissingField)
+		}
+		if r.GetSelector() == "" {
+			for _, s := range p.GetSelectors() {
+				result[i] = append(result[i], flattenNodes(c.Selections[s.GetName()])...)
+			}
+		}
+		nodes, ok := c.Selections[r.GetSelector()]
+		if !ok {
+			return nil, fmt.Errorf("%w: REPLICA '%s'", ErrSelectorNotFound, r.GetSelector())
+		}
+		result[i] = append(result[i], flattenNodes(nodes)...)
+
+	}
+	return containerNodes(result), nil
+}