[#198] sdk: Implement XHeader type

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

pkg/xheader.go

@@ -0,0 +1,47 @@
+package pkg
+
+import (
+	"github.com/nspcc-dev/neofs-api-go/v2/session"
+)
+
+// XHeader represents v2-compatible XHeader.
+type XHeader session.XHeader
+
+// NewXHeaderFromV2 wraps v2 XHeader message to XHeader.
+func NewXHeaderFromV2(v *session.XHeader) *XHeader {
+	return (*XHeader)(v)
+}
+
+// NewXHeader creates, initializes and returns blank XHeader instance.
+func NewXHeader() *XHeader {
+	return NewXHeaderFromV2(new(session.XHeader))
+}
+
+// ToV2 converts XHeader to v2 XHeader message.
+func (x *XHeader) ToV2() *session.XHeader {
+	return (*session.XHeader)(x)
+}
+
+// Key returns key to X-Header.
+func (x *XHeader) Key() string {
+	return (*session.XHeader)(x).
+		GetKey()
+}
+
+// SetKey sets key to X-Header.
+func (x *XHeader) SetKey(k string) {
+	(*session.XHeader)(x).
+		SetKey(k)
+}
+
+// Value returns value of X-Header.
+func (x *XHeader) Value() string {
+	return (*session.XHeader)(x).
+		GetValue()
+}
+
+// SetValue sets value of X-Header.
+func (x *XHeader) SetValue(k string) {
+	(*session.XHeader)(x).
+		SetValue(k)
+}

pkg/xheader_test.go

@@ -0,0 +1,25 @@
+package pkg
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestXHeader(t *testing.T) {
+	x := NewXHeader()
+
+	key := "some key"
+	val := "some value"
+
+	x.SetKey(key)
+	x.SetValue(val)
+
+	require.Equal(t, key, x.Key())
+	require.Equal(t, val, x.Value())
+
+	xV2 := x.ToV2()
+
+	require.Equal(t, key, xV2.GetKey())
+	require.Equal(t, val, xV2.GetValue())
+}