layout: implement unpacking and validation

.gitignore

@@ -1,4 +1,4 @@
 code-of-conduct.md
-oci-image-tool
-oci-validate-examples
+/oci-image-tool
+/oci-validate-examples
 output

cmd/oci-image-tool/autodetect.go

@@ -0,0 +1,103 @@
+// 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 main
+
+import (
+	"encoding/json"
+	"io"
+	"io/ioutil"
+	"net/http"
+	"os"
+
+	"github.com/opencontainers/image-spec/schema"
+	"github.com/pkg/errors"
+)
+
+// supported autodetection types
+const (
+	typeImageLayout  = "imageLayout"
+	typeImage        = "image"
+	typeManifest     = "manifest"
+	typeManifestList = "manifestList"
+	typeConfig       = "config"
+)
+
+// autodetect detects the validation type for the given path
+// or an error if the validation type could not be resolved.
+func autodetect(path string) (string, error) {
+	fi, err := os.Stat(path)
+	if err != nil {
+		return "", errors.Wrapf(err, "unable to access path") // err from os.Stat includes path name
+	}
+
+	if fi.IsDir() {
+		return typeImageLayout, nil
+	}
+
+	f, err := os.Open(path)
+	if err != nil {
+		return "", errors.Wrap(err, "unable to open file") // os.Open includes the filename
+	}
+	defer f.Close()
+
+	buf, err := ioutil.ReadAll(io.LimitReader(f, 512)) // read some initial bytes to detect content
+	if err != nil {
+		return "", errors.Wrap(err, "unable to read")
+	}
+
+	mimeType := http.DetectContentType(buf)
+
+	switch mimeType {
+	case "application/x-gzip":
+		return typeImage, nil
+
+	case "application/octet-stream":
+		return typeImage, nil
+
+	case "text/plain; charset=utf-8":
+		// might be a JSON file, will be handled below
+
+	default:
+		return "", errors.New("unknown file type")
+	}
+
+	if _, err := f.Seek(0, os.SEEK_SET); err != nil {
+		return "", errors.Wrap(err, "unable to seek")
+	}
+
+	header := struct {
+		SchemaVersion int         `json:"schemaVersion"`
+		MediaType     string      `json:"mediaType"`
+		Config        interface{} `json:"config"`
+	}{}
+
+	if err := json.NewDecoder(f).Decode(&header); err != nil {
+		return "", errors.Wrap(err, "unable to parse JSON")
+	}
+
+	switch {
+	case header.MediaType == string(schema.MediaTypeManifest):
+		return typeManifest, nil
+
+	case header.MediaType == string(schema.MediaTypeManifestList):
+		return typeManifestList, nil
+
+	case header.MediaType == "" && header.SchemaVersion == 0 && header.Config != nil:
+		// config files don't have mediaType/schemaVersion header
+		return typeConfig, nil
+	}
+
+	return "", errors.New("unknown media type")
+}

cmd/oci-image-tool/main.go

@@ -31,6 +31,8 @@ func main() {
 	stderr := log.New(os.Stderr, "", 0)
 
 	cmd.AddCommand(newValidateCmd(stdout, stderr))
+	cmd.AddCommand(newUnpackCmd(stdout, stderr))
+
 	if err := cmd.Execute(); err != nil {
 		stderr.Println(err)
 		os.Exit(1)

cmd/oci-image-tool/unpack.go

@@ -0,0 +1,102 @@
+// 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 main
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"strings"
+
+	"github.com/opencontainers/image-spec/image"
+	"github.com/spf13/cobra"
+)
+
+// supported unpack types
+var unpackTypes = []string{
+	typeImageLayout,
+	typeImage,
+}
+
+type unpackCmd struct {
+	stdout *log.Logger
+	stderr *log.Logger
+	typ    string // the type to validate, can be empty string
+	ref    string
+}
+
+func newUnpackCmd(stdout, stderr *log.Logger) *cobra.Command {
+	v := &unpackCmd{
+		stdout: stdout,
+		stderr: stderr,
+	}
+
+	cmd := &cobra.Command{
+		Use:   "unpack [src] [dest]",
+		Short: "Unpack an image or image source layout",
+		Long:  `Unpack the OCI image .tar file or OCI image layout directory present at [src] to the destination directory [dest].`,
+		Run:   v.Run,
+	}
+
+	cmd.Flags().StringVar(
+		&v.typ, "type", "",
+		fmt.Sprintf(
+			`Type of the file to unpack. If unset, oci-image-tool will try to auto-detect the type. One of "%s"`,
+			strings.Join(unpackTypes, ","),
+		),
+	)
+
+	cmd.Flags().StringVar(
+		&v.ref, "ref", "v1.0",
+		`The ref pointing to the manifest to be unpacked. This must be present in the "refs" subdirectory of the image.`,
+	)
+
+	return cmd
+}
+
+func (v *unpackCmd) Run(cmd *cobra.Command, args []string) {
+	if len(args) != 2 {
+		v.stderr.Print("both src and dest must be provided")
+		if err := cmd.Usage(); err != nil {
+			v.stderr.Println(err)
+		}
+		os.Exit(1)
+	}
+
+	if v.typ == "" {
+		typ, err := autodetect(args[0])
+		if err != nil {
+			v.stderr.Printf("%q: autodetection failed: %v", args[0], err)
+			os.Exit(1)
+		}
+		v.typ = typ
+	}
+
+	var err error
+	switch v.typ {
+	case typeImageLayout:
+		err = image.UnpackLayout(args[0], args[1], v.ref)
+
+	case typeImage:
+		err = image.Unpack(args[0], args[1], v.ref)
+	}
+
+	if err != nil {
+		v.stderr.Printf("unpacking failed: %v", err)
+		os.Exit(1)
+	}
+
+	os.Exit(0)
+}