[#140] sdk: Define Signature type

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

pkg/signature.go

@@ -0,0 +1,44 @@
+package pkg
+
+import (
+	"github.com/nspcc-dev/neofs-api-go/v2/refs"
+)
+
+// Signature represents v2-compatible signature.
+type Signature refs.Signature
+
+// NewSignatureFromV2 wraps v2 Signature message to Signature.
+func NewSignatureFromV2(sV2 *refs.Signature) *Signature {
+	return (*Signature)(sV2)
+}
+
+// NewSignature creates and initializes blank Signature.
+//
+// Works similar as NewSignatureFromV2(new(Signature)).
+func NewSignature() *Signature {
+	return NewSignatureFromV2(new(refs.Signature))
+}
+
+// GetKey sets binary public key.
+func (s *Signature) GetKey() []byte {
+	return (*refs.Signature)(s).GetKey()
+}
+
+// SetKey returns binary public key.
+func (s *Signature) SetKey(v []byte) {
+	(*refs.Signature)(s).SetKey(v)
+}
+
+// GetSign return signature value.
+func (s *Signature) GetSign() []byte {
+	return (*refs.Signature)(s).GetSign()
+}
+
+// SetSign sets signature value.
+func (s *Signature) SetSign(v []byte) {
+	(*refs.Signature)(s).SetSign(v)
+}
+
+func (s *Signature) ToV2() *refs.Signature {
+	return (*refs.Signature)(s)
+}