Implement client interface for transfer service

Signed-off-by: Derek McGowan <derek@mcg.dev>

transfer.go

@@ -0,0 +1,74 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package containerd
+
+import (
+	"context"
+
+	transferapi "github.com/containerd/containerd/api/services/transfer/v1"
+	"github.com/containerd/containerd/pkg/streaming"
+	"github.com/containerd/containerd/pkg/transfer"
+	"github.com/containerd/typeurl"
+	"google.golang.org/protobuf/types/known/anypb"
+)
+
+func (c *Client) Transfer(ctx context.Context, src interface{}, dst interface{}, opts ...transfer.Opt) error {
+	// Conver Options
+	// Convert Source
+	// Convert Destinations
+	// Get Stream Manager
+
+	asrc, err := c.toAny(ctx, src)
+	if err != nil {
+		return err
+	}
+
+	adst, err := c.toAny(ctx, dst)
+	if err != nil {
+		return err
+	}
+
+	_, err = transferapi.NewTransferClient(c.conn).Transfer(ctx, &transferapi.TransferRequest{
+		Source: &anypb.Any{
+			TypeUrl: asrc.GetTypeUrl(),
+			Value:   asrc.GetValue(),
+		},
+		Destination: &anypb.Any{
+			TypeUrl: adst.GetTypeUrl(),
+			Value:   adst.GetValue(),
+		},
+	})
+	return err
+}
+
+func (c *Client) toAny(ctx context.Context, i interface{}) (a typeurl.Any, err error) {
+	switch v := i.(type) {
+	case toAny:
+		//Get stream manager
+		a, err = v.ToAny(ctx, nil)
+	case typeurl.Any:
+		a = v
+	default:
+		a, err = typeurl.MarshalAny(i)
+	}
+
+	return
+}
+
+type toAny interface {
+	ToAny(context.Context, streaming.StreamManager) (typeurl.Any, error)
+}