[#159] sdk: Define object range in object pkg

Define Range type in object package. Replace Range in client package with
the new one.

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

pkg/object/range.go

@@ -0,0 +1,47 @@
+package object
+
+import (
+	"github.com/nspcc-dev/neofs-api-go/v2/object"
+)
+
+// Range represents v2-compatible object payload range.
+type Range object.Range
+
+// NewRangeFromV2 wraps v2 Range message to Range.
+func NewRangeFromV2(rV2 *object.Range) *Range {
+	return (*Range)(rV2)
+}
+
+// NewRange creates and initializes blank Range.
+func NewRange() *Range {
+	return NewRangeFromV2(new(object.Range))
+}
+
+// ToV2 converts Range to v2 Range message.
+func (r *Range) ToV2() *object.Range {
+	return (*object.Range)(r)
+}
+
+// GetLength returns payload range size.
+func (r *Range) GetLength() uint64 {
+	return (*object.Range)(r).
+		GetLength()
+}
+
+// SetLength sets payload range size.
+func (r *Range) SetLength(v uint64) {
+	(*object.Range)(r).
+		SetLength(v)
+}
+
+// GetOffset sets payload range offset from start.
+func (r *Range) GetOffset() uint64 {
+	return (*object.Range)(r).
+		GetOffset()
+}
+
+// SetOffset gets payload range offset from start.
+func (r *Range) SetOffset(v uint64) {
+	(*object.Range)(r).
+		SetOffset(v)
+}

pkg/object/range_test.go

@@ -0,0 +1,25 @@
+package object
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestRange_SetOffset(t *testing.T) {
+	r := NewRange()
+
+	off := uint64(13)
+	r.SetOffset(off)
+
+	require.Equal(t, off, r.GetOffset())
+}
+
+func TestRange_SetLength(t *testing.T) {
+	r := NewRange()
+
+	ln := uint64(7)
+	r.SetLength(ln)
+
+	require.Equal(t, ln, r.GetLength())
+}