Merge pull request #1 from wagoodman/list-layers

List layers in docker image

tar-read.go

@@ -2,9 +2,13 @@ package main
 
 import (
 	"archive/tar"
+	"bytes"
+	"crypto/md5"
+	"encoding/json"
 	"fmt"
 	"io"
 	"os"
+	"strings"
 )
 
 func main() {
@@ -22,7 +26,64 @@ func main() {
 	// }
 
 	tarReader := tar.NewReader(f)
+	targetName := "manifest.json"
+	var m Manifest
+	var trees []*Tree
+	for {
+		header, err := tarReader.Next()
 
+		if err == io.EOF {
+			break
+		}
+
+		if err != nil {
+			fmt.Println(err)
+			os.Exit(1)
+		}
+
+		name := header.Name
+		if name == targetName {
+			m = handleManifest(tarReader, header)
+		}
+
+		switch header.Typeflag {
+		case tar.TypeDir:
+			continue
+		case tar.TypeReg:
+			//fmt.Println("File: ", name)
+			if strings.HasSuffix(name, "layer.tar") {
+				fmt.Println("Containing:")
+				tree := NewTree()
+				tree.name = strings.TrimSuffix(name, "layer.tar")
+				fileInfos := getFileList(tarReader, header)
+				for _, element := range fileInfos {
+					tree.AddPath(element.path, element)
+				}
+				trees = append(trees, tree)
+			}
+		default:
+			fmt.Printf("%s : %c %s %s\n",
+				"hmmm?",
+				header.Typeflag,
+				"in file",
+				name,
+			)
+		}
+	}
+	fmt.Printf("%+v\n", m)
+	fmt.Printf("%+v\n", trees)
+}
+
+func getFileList(parentReader *tar.Reader, h *tar.Header) []FileChangeInfo {
+	var files []FileChangeInfo
+	size := h.Size
+	tarredBytes := make([]byte, size)
+	_, err := parentReader.Read(tarredBytes)
+	if err != nil {
+		panic(err)
+	}
+	r := bytes.NewReader(tarredBytes)
+	tarReader := tar.NewReader(r)
 	for {
 		header, err := tarReader.Next()
 
@@ -39,11 +100,12 @@ func main() {
 
 		switch header.Typeflag {
 		case tar.TypeDir:
-			continue
+			files = append(files, makeEntry(tarReader, header, name))
 		case tar.TypeReg:
-			fmt.Println("File: ", name)
+			files = append(files, makeEntry(tarReader, header, name))
-			// show the contents
+			continue
-			// io.Copy(os.Stdout, tarReader)
+		case tar.TypeSymlink:
+			files = append(files, makeEntry(tarReader, header, name))
 		default:
 			fmt.Printf("%s : %c %s %s\n",
 				"hmmm?",
@@ -53,4 +115,55 @@ func main() {
 			)
 		}
 	}
+	return files
+}
+
+func makeEntry(r *tar.Reader, h *tar.Header, path string) FileChangeInfo {
+	if h.Typeflag == tar.TypeDir {
+		return FileChangeInfo{
+			path:     path,
+			typeflag: h.Typeflag,
+			md5sum:   zeros,
+		}
+	}
+	fileBytes := make([]byte, h.Size)
+	_, err := r.Read(fileBytes)
+	if err != nil && err != io.EOF {
+		panic(err)
+	}
+	hash := md5.Sum(fileBytes)
+	return FileChangeInfo{
+		path:     path,
+		typeflag: h.Typeflag,
+		md5sum:   hash,
+	}
+}
+
+var zeros = [16]byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
+
+type FileChangeInfo struct {
+	path     string
+	typeflag byte
+	md5sum   [16]byte
+}
+
+type Manifest struct {
+	Config   string
+	RepoTags []string
+	Layers   []string
+}
+
+func handleManifest(r *tar.Reader, header *tar.Header) Manifest {
+	size := header.Size
+	manifestBytes := make([]byte, size)
+	_, err := r.Read(manifestBytes)
+	if err != nil {
+		panic(err)
+	}
+	var m [1]Manifest
+	err = json.Unmarshal(manifestBytes, &m)
+	if err != nil {
+		panic(err)
+	}
+	return m[0]
 }

tree.go

@@ -16,6 +16,7 @@ const (
 type Tree struct {
 	root Node
 	size int
+	name string
 }
 
 type Node struct {