autodetect.go:Increase the judgment criteria for the ImageLayout file type

Signed-off-by: zhouhao <zhouhao@cn.fujitsu.com>

Author: zhouhao

image/image.go

@@ -49,6 +49,10 @@ var validRefMediaTypes = []string{
 }
 
 func validate(w walker, refs []string, out *log.Logger) error {
+	if err := layoutValidate(w); err != nil {
+		return err
+	}
+
 	ds, err := listReferences(w)
 	if err != nil {
 		return err

image/layout.go

@@ -0,0 +1,68 @@
+// Copyright 2016 The Linux Foundation
+//
+// 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 image
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"strings"
+)
+
+var blobsFile, indexFile, layoutFile int
+
+func layoutValidate(w walker) error {
+	var err error
+	err = w.walk(func(path string, info os.FileInfo, r io.Reader) error {
+		if strings.EqualFold(path, "blobs") {
+			blobsFile++
+			return nil
+		}
+
+		if strings.EqualFold(path, "index.json") {
+			indexFile++
+			return nil
+		}
+
+		if strings.EqualFold(path, "oci-layout") {
+			layoutFile++
+			return nil
+		}
+
+		return nil
+	})
+
+	if err != nil {
+		return err
+	}
+
+	if err == nil {
+		if blobsFile != 1 {
+			return fmt.Errorf("image layout must contain blobs directory")
+		}
+
+		if indexFile != 1 {
+			return fmt.Errorf("image layout must contain index.json file")
+		}
+
+		if layoutFile != 1 {
+			return fmt.Errorf("image layout must contain an oci-layout file")
+		}
+
+		return nil
+	}
+
+	return nil
+}