[#79] Implement type for subnet information

Create `subnet` package. Define `Info` type of the subnet info. Support
encoding and transport over the NeoFS API V2 protocol. Add methods to
work with identifier and owner.

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

subnet/subnet.go

@@ -0,0 +1,92 @@
+package subnet
+
+import (
+	"github.com/nspcc-dev/neofs-api-go/v2/refs"
+	"github.com/nspcc-dev/neofs-api-go/v2/subnet"
+	"github.com/nspcc-dev/neofs-sdk-go/owner"
+	subnetid "github.com/nspcc-dev/neofs-sdk-go/subnet/id"
+)
+
+// Info represents information about NeoFS subnet.
+//
+// The type is compatible with the corresponding message from NeoFS API V2 protocol.
+//
+// Zero value and nil pointer to it represents zero subnet w/o an owner.
+type Info subnet.Info
+
+// FromV2 initializes Info from subnet.Info message structure. Must not be called on nil.
+func (x *Info) FromV2(msg subnet.Info) {
+	*x = Info(msg)
+}
+
+// WriteToV2 writes Info to subnet.Info message structure. The message must not be nil.
+func (x Info) WriteToV2(msg *subnet.Info) {
+	*msg = subnet.Info(x)
+}
+
+// Marshal encodes Info into a binary format of NeoFS API V2 protocol (Protocol Buffers with direct field order).
+func (x *Info) Marshal() ([]byte, error) {
+	return (*subnet.Info)(x).StableMarshal(nil)
+}
+
+// Unmarshal decodes Info from NeoFS API V2 binary format (see Marshal). Must not be called on nil.
+//
+// Note: empty data corresponds to zero Info value or nil pointer to it.
+func (x *Info) Unmarshal(data []byte) error {
+	return (*subnet.Info)(x).Unmarshal(data)
+}
+
+// SetID sets the identifier of the subnet that Info describes.
+func (x *Info) SetID(id subnetid.ID) {
+	infov2 := (*subnet.Info)(x)
+
+	idv2 := infov2.ID()
+	if idv2 == nil {
+		idv2 = new(refs.SubnetID)
+		infov2.SetID(idv2)
+	}
+
+	id.WriteToV2(idv2)
+}
+
+// ReadID reads the identifier of the subnet that Info describes. Arg must not be nil.
+func (x Info) ReadID(id *subnetid.ID) {
+	infov2 := (subnet.Info)(x)
+
+	idv2 := infov2.ID()
+	if idv2 == nil {
+		subnetid.MakeZero(id)
+		return
+	}
+
+	id.FromV2(*idv2)
+}
+
+// SetOwner sets subnet owner ID.
+func (x *Info) SetOwner(id owner.ID) {
+	infov2 := (*subnet.Info)(x)
+
+	idv2 := infov2.Owner()
+	if idv2 == nil {
+		idv2 = new(refs.OwnerID)
+		infov2.SetOwner(idv2)
+	}
+
+	// FIXME: we need to implement and use owner.ID.WriteToV2() method
+	*idv2 = *id.ToV2()
+}
+
+// HasOwner checks if subnet owner is set.
+func (x Info) HasOwner() bool {
+	return (*subnet.Info)(&x).Owner() != nil
+}
+
+// ReadOwner reads the identifier of the subnet that Info describes.
+// Must be called only if owner is set (see HasOwner). Arg must not be nil.
+func (x Info) ReadOwner(id *owner.ID) {
+	infov2 := (subnet.Info)(x)
+
+	// FIXME: we need to implement and use owner.ID.FromV2 method
+	id2 := owner.NewIDFromV2(infov2.Owner())
+	*id = *id2
+}

subnet/subnet_test.go

@@ -0,0 +1,79 @@
+package subnet_test
+
+import (
+	"testing"
+
+	subnetv2 "github.com/nspcc-dev/neofs-api-go/v2/subnet"
+	subnettest "github.com/nspcc-dev/neofs-api-go/v2/subnet/test"
+	"github.com/nspcc-dev/neofs-sdk-go/owner"
+	ownertest "github.com/nspcc-dev/neofs-sdk-go/owner/test"
+	"github.com/nspcc-dev/neofs-sdk-go/subnet"
+	subnetid "github.com/nspcc-dev/neofs-sdk-go/subnet/id"
+	"github.com/stretchr/testify/require"
+)
+
+func TestInfoZero(t *testing.T) {
+	var info subnet.Info
+
+	var id subnetid.ID
+	info.ReadID(&id)
+
+	require.True(t, subnetid.IsZero(id))
+
+	require.False(t, info.HasOwner())
+}
+
+func TestInfo_SetID(t *testing.T) {
+	var (
+		idFrom, idTo subnetid.ID
+
+		info subnet.Info
+	)
+
+	idFrom.SetNumber(222)
+
+	info.SetID(idFrom)
+
+	info.ReadID(&idTo)
+
+	require.True(t, idTo.Equals(&idFrom))
+}
+
+func TestInfo_SetOwner(t *testing.T) {
+	var (
+		idFrom, idTo owner.ID
+
+		info subnet.Info
+	)
+
+	idFrom = *ownertest.GenerateID()
+
+	require.False(t, info.HasOwner())
+
+	info.SetOwner(idFrom)
+
+	require.True(t, info.HasOwner())
+
+	info.ReadOwner(&idTo)
+
+	require.True(t, idTo.Equal(&idFrom))
+}
+
+func TestInfo_WriteToV2(t *testing.T) {
+	var (
+		infoTo, infoFrom subnet.Info
+
+		infoV2From, infoV2To subnetv2.Info
+	)
+
+	infoV2From = *subnettest.GenerateSubnetInfo(false)
+
+	infoFrom.FromV2(infoV2From)
+
+	infoFrom.WriteToV2(&infoV2To)
+
+	infoTo.FromV2(infoV2To)
+
+	require.Equal(t, infoV2From, infoV2To)
+	require.Equal(t, infoFrom, infoTo)
+}