Golang tarball.Walk函数代码示例

func getParent(file *os.File, imgID string) (string, error) {
	var parent string

	_, err := file.Seek(0, 0)
	if err != nil {
		return "", fmt.Errorf("error seeking file: %v", err)
	}

	jsonPath := filepath.Join(imgID, "json")
	parentWalker := func(t *tarball.TarFile) error {
		if filepath.Clean(t.Name()) == jsonPath {
			jsonb, err := ioutil.ReadAll(t.TarStream)
			if err != nil {
				return fmt.Errorf("error reading layer json: %v", err)
			}

			var dockerData types.DockerImageData
			if err := json.Unmarshal(jsonb, &dockerData); err != nil {
				return fmt.Errorf("error unmarshaling layer data: %v", err)
			}

			parent = dockerData.Parent
		}

		return nil
	}

	tr := tar.NewReader(file)
	if err := tarball.Walk(*tr, parentWalker); err != nil {
		return "", err
	}

	log.Debug(fmt.Sprintf("Layer %q depends on layer %q", imgID, parent))
	return parent, nil
}

func getTarFileBytes(file *os.File, path string) ([]byte, error) {
	_, err := file.Seek(0, 0)
	if err != nil {
		return nil, fmt.Errorf("error seeking file: %v", err)
	}

	var fileBytes []byte
	fileWalker := func(t *tarball.TarFile) error {
		if filepath.Clean(t.Name()) == path {
			fileBytes, err = ioutil.ReadAll(t.TarStream)
			if err != nil {
				return err
			}
		}

		return nil
	}

	tr := tar.NewReader(file)
	if err := tarball.Walk(*tr, fileWalker); err != nil {
		return nil, err
	}

	if fileBytes == nil {
		return nil, fmt.Errorf("file %q not found", path)
	}

	return fileBytes, nil
}

func extractEmbeddedLayer(file *os.File, layerTarPath string, outputPath string) (*os.File, error) {
	log.Info("Extracting ", layerTarPath, "\n")
	_, err := file.Seek(0, 0)
	if err != nil {
		return nil, fmt.Errorf("error seeking file: %v", err)
	}

	var layerFile *os.File
	fileWalker := func(t *tarball.TarFile) error {
		if filepath.Clean(t.Name()) == layerTarPath {
			layerFile, err = os.Create(outputPath)
			if err != nil {
				return fmt.Errorf("error creating layer: %v", err)
			}

			_, err = io.Copy(layerFile, t.TarStream)
			if err != nil {
				return fmt.Errorf("error getting layer: %v", err)
			}
		}

		return nil
	}

	tr := tar.NewReader(file)
	if err := tarball.Walk(*tr, fileWalker); err != nil {
		return nil, err
	}

	if layerFile == nil {
		return nil, fmt.Errorf("file %q not found", layerTarPath)
	}

	return layerFile, nil
}

func getDataFromManifest(file *os.File, manifestID string) (string, []string, error) {
	_, err := file.Seek(0, 0)
	if err != nil {
		return "", nil, fmt.Errorf("error seeking file: %v", err)
	}

	parts := append([]string{"blobs"}, strings.Split(manifestID, ":")...)
	jsonPath := path.Join(parts...)

	var imageID string
	var ancestry []string
	reposWalker := func(t *tarball.TarFile) error {
		clean := filepath.Clean(t.Name())
		if clean == jsonPath {

			manb, err := ioutil.ReadAll(t.TarStream)
			if err != nil {
				return fmt.Errorf("error reading image manifest: %v", err)
			}

			var manifest typesV2.ImageManifest
			if err := json.Unmarshal(manb, &manifest); err != nil {
				return fmt.Errorf("error unmarshaling image manifest")
			}
			if manifest.Config == nil {
				return fmt.Errorf("manifest does not contain a config")
			}
			imageID = manifest.Config.Digest
			// put them in reverse order
			for i := len(manifest.Layers) - 1; i >= 0; i-- {
				ancestry = append(ancestry, manifest.Layers[i].Digest)
			}
		}
		return nil
	}

	tr := tar.NewReader(file)
	if err := tarball.Walk(*tr, reposWalker); err != nil {
		return "", nil, err
	}

	return imageID, ancestry, nil
}

func getImageID(file *os.File, dockerURL *types.ParsedDockerURL, name string) (string, []string, *types.ParsedDockerURL, error) {
	log.Debug("getting image id...")
	type tags map[string]string
	type apps map[string]tags

	_, err := file.Seek(0, 0)
	if err != nil {
		return "", nil, nil, fmt.Errorf("error seeking file: %v", err)
	}

	tag := "latest"
	if dockerURL != nil {
		tag = dockerURL.Tag
	}

	var imageID string
	var ancestry []string
	var appName string
	reposWalker := func(t *tarball.TarFile) error {
		clean := filepath.Clean(t.Name())
		if clean == "repositories" {
			repob, err := ioutil.ReadAll(t.TarStream)
			if err != nil {
				return fmt.Errorf("error reading repositories file: %v", err)
			}

			var repositories apps
			if err := json.Unmarshal(repob, &repositories); err != nil {
				return fmt.Errorf("error unmarshaling repositories file")
			}

			if dockerURL == nil {
				n := len(repositories)
				switch {
				case n == 1:
					for key, _ := range repositories {
						appName = key
					}
				case n > 1:
					var appNames []string
					for key, _ := range repositories {
						appNames = append(appNames, key)
					}
					return &common.ErrSeveralImages{
						Msg:    "several images found",
						Images: appNames,
					}
				default:
					return fmt.Errorf("no images found")
				}
			} else {
				appName = dockerURL.ImageName
			}

			app, ok := repositories[appName]
			if !ok {
				return fmt.Errorf("app %q not found", appName)
			}

			_, ok = app[tag]
			if !ok {
				if len(app) == 1 {
					for key, _ := range app {
						tag = key
					}
				} else {
					return fmt.Errorf("tag %q not found", tag)
				}
			}

			if dockerURL == nil {
				dockerURL = &types.ParsedDockerURL{
					IndexURL:  "",
					Tag:       tag,
					ImageName: appName,
				}
			}

			imageID = string(app[tag])
		}

		if clean == "refs/"+tag {
			refb, err := ioutil.ReadAll(t.TarStream)
			if err != nil {
				return fmt.Errorf("error reading ref descriptor for tag %s: %v", tag, err)
			}

			if dockerURL == nil {
				dockerURL = &types.ParsedDockerURL{
					IndexURL:  "",
					Tag:       tag,
					ImageName: name,
				}
			}

			var ref spec.Descriptor
			if err := json.Unmarshal(refb, &ref); err != nil {
				return fmt.Errorf("error unmarshaling ref descriptor for tag %s", tag)
			}
			imageID, ancestry, err = getDataFromManifest(file, ref.Digest)
//.........这里部分代码省略.........

func writeSquashedImage(outputFile *os.File, renderedACI acirenderer.RenderedACI, aciProvider acirenderer.ACIProvider, manifests []schema.ImageManifest, compression common.Compression) error {
	var tarWriterTarget io.WriteCloser = outputFile

	switch compression {
	case common.NoCompression:
	case common.GzipCompression:
		tarWriterTarget = gzip.NewWriter(outputFile)
		defer tarWriterTarget.Close()
	default:
		return fmt.Errorf("unexpected compression enum value: %d", compression)
	}

	outputWriter := tar.NewWriter(tarWriterTarget)
	defer outputWriter.Close()

	finalManifest := mergeManifests(manifests)

	if err := internal.WriteManifest(outputWriter, finalManifest); err != nil {
		return err
	}

	if err := internal.WriteRootfsDir(outputWriter); err != nil {
		return err
	}

	type hardLinkEntry struct {
		firstLinkCleanName string
		firstLinkHeader    tar.Header
		keepOriginal       bool
		walked             bool
	}
	// map aciFileKey -> cleanTarget -> hardLinkEntry
	hardLinks := make(map[string]map[string]hardLinkEntry)

	// first pass: read all the entries and build the hardLinks map in memory
	// but don't write on disk
	for _, aciFile := range renderedACI {
		rs, err := aciProvider.ReadStream(aciFile.Key)
		if err != nil {
			return err
		}
		defer rs.Close()

		hardLinks[aciFile.Key] = map[string]hardLinkEntry{}

		squashWalker := func(t *tarball.TarFile) error {
			cleanName := filepath.Clean(t.Name())
			// the rootfs and the squashed manifest are added separately
			if cleanName == "manifest" || cleanName == "rootfs" {
				return nil
			}
			_, keep := aciFile.FileMap[cleanName]
			if keep && t.Header.Typeflag == tar.TypeLink {
				cleanTarget := filepath.Clean(t.Linkname())
				if _, ok := hardLinks[aciFile.Key][cleanTarget]; !ok {
					_, keepOriginal := aciFile.FileMap[cleanTarget]
					hardLinks[aciFile.Key][cleanTarget] = hardLinkEntry{cleanName, *t.Header, keepOriginal, false}
				}
			}
			return nil
		}

		tr := tar.NewReader(rs)
		if err := tarball.Walk(*tr, squashWalker); err != nil {
			return err
		}
	}

	// second pass: write on disk
	for _, aciFile := range renderedACI {
		rs, err := aciProvider.ReadStream(aciFile.Key)
		if err != nil {
			return err
		}
		defer rs.Close()

		squashWalker := func(t *tarball.TarFile) error {
			cleanName := filepath.Clean(t.Name())
			// the rootfs and the squashed manifest are added separately
			if cleanName == "manifest" || cleanName == "rootfs" {
				return nil
			}
			_, keep := aciFile.FileMap[cleanName]

			if link, ok := hardLinks[aciFile.Key][cleanName]; ok {
				if keep != link.keepOriginal {
					return fmt.Errorf("logic error: should we keep file %q?", cleanName)
				}
				if keep {
					if err := outputWriter.WriteHeader(t.Header); err != nil {
						return fmt.Errorf("error writing header: %v", err)
					}
					if _, err := io.Copy(outputWriter, t.TarStream); err != nil {
						return fmt.Errorf("error copying file into the tar out: %v", err)
					}
				} else {
					// The current file does not remain but there is a hard link pointing to
					// it. Write the current file but with the filename of the first hard link
					// pointing to it. That first hard link will not be written later, see
					// variable "alreadyWritten".
//.........这里部分代码省略.........

func writeACI(layer io.ReadSeeker, manifest schema.ImageManifest, curPwl []string, output string, compression common.Compression) (*schema.ImageManifest, error) {
	aciFile, err := os.Create(output)
	if err != nil {
		return nil, fmt.Errorf("error creating ACI file: %v", err)
	}
	defer aciFile.Close()

	var w io.WriteCloser = aciFile
	if compression == common.GzipCompression {
		w = gzip.NewWriter(aciFile)
		defer w.Close()
	}
	trw := tar.NewWriter(w)
	defer trw.Close()

	if err := WriteRootfsDir(trw); err != nil {
		return nil, fmt.Errorf("error writing rootfs entry: %v", err)
	}

	fileMap := make(map[string]struct{})
	var whiteouts []string
	convWalker := func(t *tarball.TarFile) error {
		name := t.Name()
		if name == "./" {
			return nil
		}
		t.Header.Name = path.Join("rootfs", name)
		absolutePath := strings.TrimPrefix(t.Header.Name, "rootfs")

		if filepath.Clean(absolutePath) == "/dev" && t.Header.Typeflag != tar.TypeDir {
			return fmt.Errorf(`invalid layer: "/dev" is not a directory`)
		}

		fileMap[absolutePath] = struct{}{}
		if strings.Contains(t.Header.Name, "/.wh.") {
			whiteouts = append(whiteouts, strings.Replace(absolutePath, ".wh.", "", 1))
			return nil
		}
		if t.Header.Typeflag == tar.TypeLink {
			t.Header.Linkname = path.Join("rootfs", t.Linkname())
		}

		if err := trw.WriteHeader(t.Header); err != nil {
			return err
		}
		if _, err := io.Copy(trw, t.TarStream); err != nil {
			return err
		}

		if !util.In(curPwl, absolutePath) {
			curPwl = append(curPwl, absolutePath)
		}

		return nil
	}
	tr, err := aci.NewCompressedTarReader(layer)
	if err == nil {
		defer tr.Close()
		// write files in rootfs/
		if err := tarball.Walk(*tr.Reader, convWalker); err != nil {
			return nil, err
		}
	} else {
		// ignore errors: empty layers in tars generated by docker save are not
		// valid tar files so we ignore errors trying to open them. Converted
		// ACIs will have the manifest and an empty rootfs directory in any
		// case.
	}
	newPwl := subtractWhiteouts(curPwl, whiteouts)

	newPwl, err = writeStdioSymlinks(trw, fileMap, newPwl)
	if err != nil {
		return nil, err
	}
	// Let's copy the newly generated PathWhitelist to avoid unintended
	// side-effects
	manifest.PathWhitelist = make([]string, len(newPwl))
	copy(manifest.PathWhitelist, newPwl)

	if err := WriteManifest(trw, manifest); err != nil {
		return nil, fmt.Errorf("error writing manifest: %v", err)
	}

	return &manifest, nil
}

func getImageID(file *os.File, dockerURL *types.ParsedDockerURL) (string, *types.ParsedDockerURL, error) {
	type tags map[string]string
	type apps map[string]tags

	_, err := file.Seek(0, 0)
	if err != nil {
		return "", nil, fmt.Errorf("error seeking file: %v", err)
	}

	var imageID string
	var appName string
	reposWalker := func(t *tarball.TarFile) error {
		if filepath.Clean(t.Name()) == "repositories" {
			repob, err := ioutil.ReadAll(t.TarStream)
			if err != nil {
				return fmt.Errorf("error reading repositories file: %v", err)
			}

			var repositories apps
			if err := json.Unmarshal(repob, &repositories); err != nil {
				return fmt.Errorf("error unmarshaling repositories file")
			}

			if dockerURL == nil {
				n := len(repositories)
				switch {
				case n == 1:
					for key, _ := range repositories {
						appName = key
					}
				case n > 1:
					var appNames []string
					for key, _ := range repositories {
						appNames = append(appNames, key)
					}
					return &common.ErrSeveralImages{
						Msg:    "several images found",
						Images: appNames,
					}
				default:
					return fmt.Errorf("no images found")
				}
			} else {
				appName = dockerURL.ImageName
			}

			tag := "latest"
			if dockerURL != nil {
				tag = dockerURL.Tag
			}

			app, ok := repositories[appName]
			if !ok {
				return fmt.Errorf("app %q not found", appName)
			}

			_, ok = app[tag]
			if !ok {
				if len(app) == 1 {
					for key, _ := range app {
						tag = key
					}
				} else {
					return fmt.Errorf("tag %q not found", tag)
				}
			}

			if dockerURL == nil {
				dockerURL = &types.ParsedDockerURL{
					IndexURL:  "",
					Tag:       tag,
					ImageName: appName,
				}
			}

			imageID = string(app[tag])
		}

		return nil
	}

	tr := tar.NewReader(file)
	if err := tarball.Walk(*tr, reposWalker); err != nil {
		return "", nil, err
	}

	if imageID == "" {
		return "", nil, fmt.Errorf("repositories file not found")
	}

	return imageID, dockerURL, nil
}