[#140] sdk: Refactor reference types

Refactor v2-compatible reference types to be wrappers over corresponding
types from v2.

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

pkg/container/id.go

@@ -4,44 +4,29 @@ import (
 	"crypto/sha256"
 
 	"github.com/nspcc-dev/neofs-api-go/v2/refs"
-	"github.com/pkg/errors"
 )
 
-// ID represents container identifier
-// that supports different type of values.
-type ID struct {
-	val []byte
+// ID represents v2-compatible container identifier.
+type ID refs.ContainerID
+
+// NewIDFromV2 wraps v2 ContainerID message to ID.
+func NewIDFromV2(idV2 *refs.ContainerID) *ID {
+	return (*ID)(idV2)
+}
+
+// NewID creates and initializes blank ID.
+//
+// Works similar to NewIDFromV2(new(ContainerID)).
+func NewID() *ID {
+	return NewIDFromV2(new(refs.ContainerID))
 }
 
 // SetSHA256 sets container identifier value to SHA256 checksum.
 func (id *ID) SetSHA256(v [sha256.Size]byte) {
-	if id != nil {
-		id.val = v[:]
-	}
+	(*refs.ContainerID)(id).SetValue(v[:])
 }
 
 // ToV2 returns the v2 container ID message.
 func (id *ID) ToV2() *refs.ContainerID {
-	if id != nil {
-		idV2 := new(refs.ContainerID)
-		idV2.SetValue(id.val)
-
-		return idV2
-	}
-
-	return nil
-}
-
-func IDFromV2(idV2 *refs.ContainerID) (*ID, error) {
-	val := idV2.GetValue()
-	if ln := len(val); ln != sha256.Size {
-		return nil, errors.Errorf(
-			"could not convert %T to %T: expected length %d, received %d",
-			idV2, (*ID)(nil), sha256.Size, ln,
-		)
-	}
-
-	return &ID{
-		val: val,
-	}, nil
+	return (*refs.ContainerID)(id)
 }

pkg/container/id_test.go

@@ -9,7 +9,7 @@ import (
 )
 
 func TestIDV2_0(t *testing.T) {
-	cid := new(ID)
+	cid := NewID()
 
 	checksum := [sha256.Size]byte{}
 
@@ -20,8 +20,5 @@ func TestIDV2_0(t *testing.T) {
 
 	cidV2 := cid.ToV2()
 
-	cid2, err := IDFromV2(cidV2)
-	require.NoError(t, err)
-
-	require.Equal(t, cid, cid2)
+	require.Equal(t, checksum[:], cidV2.GetValue())
 }