Golang image.NewImgJSON函数代码示例

func (s *TagStore) recursiveLoad(eng *engine.Engine, address, tmpImageDir string) error {
	if err := eng.Job("image_get", address).Run(); err != nil {
		log.Debugf("Loading %s", address)

		imageJson, err := ioutil.ReadFile(path.Join(tmpImageDir, "repo", address, "json"))
		if err != nil {
			log.Debugf("Error reading json", err)
			return err
		}

		layer, err := os.Open(path.Join(tmpImageDir, "repo", address, "layer.tar"))
		if err != nil {
			log.Debugf("Error reading embedded tar", err)
			return err
		}
		img, err := image.NewImgJSON(imageJson)
		if err != nil {
			log.Debugf("Error unmarshalling json", err)
			return err
		}
		if img.Parent != "" {
			if !s.graph.Exists(img.Parent) {
				if err := s.recursiveLoad(eng, img.Parent, tmpImageDir); err != nil {
					return err
				}
			}
		}
		if err := s.graph.Register(img, imageJson, layer); err != nil {
			return err
		}
	}
	log.Debugf("Completed processing %s", address)

	return nil
}

func newContentAddressableImage(v1Compatibility []byte, blobSum digest.Digest, parent digest.Digest) (contentAddressableDescriptor, error) {
	img := contentAddressableDescriptor{
		v1Compatibility: v1Compatibility,
	}

	var err error
	img.config, err = image.MakeImageConfig(v1Compatibility, blobSum, parent)
	if err != nil {
		return img, err
	}
	img.strongID, err = image.StrongID(img.config)
	if err != nil {
		return img, err
	}

	unmarshalledConfig, err := image.NewImgJSON(v1Compatibility)
	if err != nil {
		return img, err
	}

	img.compatibilityID = unmarshalledConfig.ID
	img.id = img.strongID.Hex()

	return img, nil
}

// storeImage stores file system layer data for the given image to the
// graph's storage driver. Image metadata is stored in a file
// at the specified root directory.
func (graph *Graph) storeImage(id, parent string, config []byte, layerData io.Reader, root string) (err error) {
	var size int64
	// Store the layer. If layerData is not nil, unpack it into the new layer
	if layerData != nil {
		if size, err = graph.disassembleAndApplyTarLayer(id, parent, layerData, root); err != nil {
			return err
		}
	}

	if err := graph.saveSize(root, size); err != nil {
		return err
	}

	if err := ioutil.WriteFile(jsonPath(root), config, 0600); err != nil {
		return err
	}

	// If image is pointing to a parent via CompatibilityID write the reference to disk
	img, err := image.NewImgJSON(config)
	if err != nil {
		return err
	}

	if img.ParentID.Validate() == nil && parent != img.ParentID.Hex() {
		if err := ioutil.WriteFile(filepath.Join(root, parentFileName), []byte(parent), 0600); err != nil {
			return err
		}
	}
	return nil
}

// storeImage stores file system layer data for the given image to the
// graph's storage driver. Image metadata is stored in a file
// at the specified root directory.
func (graph *Graph) storeImage(id, parent string, config []byte, layerData archive.ArchiveReader, root string) (err error) {
	var size int64
	if wd, ok := graph.driver.(*windows.WindowsGraphDriver); ok {
		// Store the layer. If layerData is not nil and this isn't a base image,
		// unpack it into the new layer
		if layerData != nil && parent != "" {
			var ids []string
			parentImg, err := graph.Get(parent)
			if err != nil {
				return err
			}

			ids, err = graph.ParentLayerIds(parentImg)
			if err != nil {
				return err
			}

			if size, err = wd.Import(id, layerData, wd.LayerIdsToPaths(ids)); err != nil {
				return err
			}
		}

	} else {
		// We keep this functionality here so that we can still work with the
		// VFS driver during development. This will not be used for actual running
		// of Windows containers. Without this code, it would not be possible to
		// docker pull using the VFS driver.

		// Store the layer. If layerData is not nil, unpack it into the new layer
		if layerData != nil {
			if size, err = graph.disassembleAndApplyTarLayer(id, parent, layerData, root); err != nil {
				return err
			}
		}

		if err := graph.saveSize(root, size); err != nil {
			return err
		}

		if err := ioutil.WriteFile(jsonPath(root), config, 0600); err != nil {
			return err
		}

		// If image is pointing to a parent via CompatibilityID write the reference to disk
		img, err := image.NewImgJSON(config)
		if err != nil {
			return err
		}

		if img.ParentID.Validate() == nil && parent != img.ParentID.Hex() {
			if err := ioutil.WriteFile(filepath.Join(root, parentFileName), []byte(parent), 0600); err != nil {
				return err
			}
		}

		return nil
	}
}

func (graph *FakeGraph) SetExists(imageID string, imgJSON []byte) {
	graph.mutex.Lock()
	defer graph.mutex.Unlock()
	img, err := image.NewImgJSON(imgJSON)
	if err != nil {
		panic("bad imgJSON for imageID: " + imageID)
	}
	graph.exists[imageID] = img
}

// getV1ID returns the compatibilityID for the ID in the graph. compatibilityID
// is read from from the v1Compatibility config file in the disk.
func (p *v1Pusher) getV1ID(id string) (string, error) {
	jsonData, err := p.getV1Config(id)
	if err != nil {
		return "", err
	}
	img, err := image.NewImgJSON(jsonData)
	if err != nil {
		return "", err
	}
	return img.ID, nil
}

func (s *TagStore) recursiveLoad(eng *engine.Engine, address, tmpImageDir string) error {
	if err := eng.Job("image_get", address).Run(); err != nil {
		logrus.Debugf("Loading %s", address)

		imageJson, err := ioutil.ReadFile(path.Join(tmpImageDir, "repo", address, "json"))
		if err != nil {
			logrus.Debugf("Error reading json", err)
			return err
		}

		layer, err := os.Open(path.Join(tmpImageDir, "repo", address, "layer.tar"))
		if err != nil {
			logrus.Debugf("Error reading embedded tar", err)
			return err
		}
		img, err := image.NewImgJSON(imageJson)
		if err != nil {
			logrus.Debugf("Error unmarshalling json", err)
			return err
		}
		if err := utils.ValidateID(img.ID); err != nil {
			logrus.Debugf("Error validating ID: %s", err)
			return err
		}

		// ensure no two downloads of the same layer happen at the same time
		if c, err := s.poolAdd("pull", "layer:"+img.ID); err != nil {
			if c != nil {
				logrus.Debugf("Image (id: %s) load is already running, waiting: %v", img.ID, err)
				<-c
				return nil
			}

			return err
		}

		defer s.poolRemove("pull", "layer:"+img.ID)

		if img.Parent != "" {
			if !s.graph.Exists(img.Parent) {
				if err := s.recursiveLoad(eng, img.Parent, tmpImageDir); err != nil {
					return err
				}
			}
		}
		if err := s.graph.Register(img, layer); err != nil {
			return err
		}
	}
	logrus.Debugf("Completed processing %s", address)

	return nil
}

func (s *TagStore) recursiveLoad(address, tmpImageDir string) error {
	if _, err := s.LookupImage(address); err != nil {
		logrus.Debugf("Loading %s", address)

		imageJSON, err := ioutil.ReadFile(filepath.Join(tmpImageDir, "repo", address, "json"))
		if err != nil {
			logrus.Debugf("Error reading json: %v", err)
			return err
		}

		layer, err := os.Open(filepath.Join(tmpImageDir, "repo", address, "layer.tar"))
		if err != nil {
			logrus.Debugf("Error reading embedded tar: %v", err)
			return err
		}
		img, err := image.NewImgJSON(imageJSON)
		if err != nil {
			logrus.Debugf("Error unmarshalling json: %v", err)
			return err
		}
		if err := image.ValidateID(img.ID); err != nil {
			logrus.Debugf("Error validating ID: %v", err)
			return err
		}

		// ensure no two downloads of the same layer happen at the same time
		poolKey := "layer:" + img.ID
		broadcaster, found := s.poolAdd("pull", poolKey)
		if found {
			logrus.Debugf("Image (id: %s) load is already running, waiting", img.ID)
			return broadcaster.Wait()
		}

		defer s.poolRemove("pull", poolKey)

		if img.Parent != "" {
			if !s.graph.Exists(img.Parent) {
				if err := s.recursiveLoad(img.Parent, tmpImageDir); err != nil {
					return err
				}
			}
		}
		if err := s.graph.Register(v1Descriptor{img}, layer); err != nil {
			return err
		}
		logrus.Debugf("Completed processing %s", address)
		return nil
	}
	logrus.Debugf("already loaded %s", address)

	return nil
}

func (fetcher *RemoteV1Fetcher) fetchLayer(request *FetchRequest, endpointURL string, layerID string, remaining int64, logger lager.Logger) (*dockerLayer, error) {
	fetcher.GraphLock.Acquire(layerID)
	defer fetcher.GraphLock.Release(layerID)

	if img, err := fetcher.Cake.Get(layercake.DockerImageID(layerID)); err == nil {
		request.Logger.Info("using-cached", lager.Data{
			"layer": layerID,
			"size":  img.Size,
		})

		return &dockerLayer{imgEnv(img, request.Logger), imgVolumes(img), img.Size}, nil
	}

	imgJSON, imgSize, err := request.Session.GetRemoteImageJSON(layerID, endpointURL)
	if err != nil {
		return nil, fmt.Errorf("get remote image JSON: %v", err)
	}

	img, err := image.NewImgJSON(imgJSON)
	if err != nil {
		return nil, fmt.Errorf("new image JSON: %v", err)
	}

	layer, err := request.Session.GetRemoteImageLayer(img.ID, endpointURL, int64(imgSize))
	if err != nil {
		return nil, fmt.Errorf("get remote image layer: %v", err)
	}

	defer layer.Close()

	started := time.Now()

	request.Logger.Info("downloading", lager.Data{
		"layer": layerID,
	})

	err = fetcher.Cake.Register(img, &QuotaedReader{R: layer, N: remaining})
	if err != nil {
		return nil, fmt.Errorf("register: %s", err)
	}

	request.Logger.Info("downloaded", lager.Data{
		"layer": layerID,
		"took":  time.Since(started),
		"vols":  imgVolumes(img),
		"size":  img.Size,
	})

	return &dockerLayer{imgEnv(img, request.Logger), imgVolumes(img), img.Size}, nil
}

// fixManifestLayers removes repeated layers from the manifest and checks the
// correctness of the parent chain.
func fixManifestLayers(m *schema1.Manifest) error {
	images := make([]*image.Image, len(m.FSLayers))
	for i := range m.FSLayers {
		img, err := image.NewImgJSON([]byte(m.History[i].V1Compatibility))
		if err != nil {
			return err
		}
		images[i] = img
		if err := image.ValidateID(img.ID); err != nil {
			return err
		}
	}

	if images[len(images)-1].Parent != "" && !allowBaseParentImage {
		// Windows base layer can point to a base layer parent that is not in manifest.
		return errors.New("Invalid parent ID in the base layer of the image.")
	}

	// check general duplicates to error instead of a deadlock
	idmap := make(map[string]struct{})

	var lastID string
	for _, img := range images {
		// skip IDs that appear after each other, we handle those later
		if _, exists := idmap[img.ID]; img.ID != lastID && exists {
			return fmt.Errorf("ID %+v appears multiple times in manifest", img.ID)
		}
		lastID = img.ID
		idmap[lastID] = struct{}{}
	}

	// backwards loop so that we keep the remaining indexes after removing items
	for i := len(images) - 2; i >= 0; i-- {
		if images[i].ID == images[i+1].ID { // repeated ID. remove and continue
			m.FSLayers = append(m.FSLayers[:i], m.FSLayers[i+1:]...)
			m.History = append(m.History[:i], m.History[i+1:]...)
		} else if images[i].Parent != images[i+1].ID {
			return fmt.Errorf("Invalid parent ID. Expected %v, got %v.", images[i+1].ID, images[i].Parent)
		}
	}

	return nil
}

func (fetcher *RemoteV2Fetcher) fetchImagesMetadata(request *FetchRequest) ([]*image.Image, *registry.RequestAuthorization, []digest.Digest, error) {
	request.Logger.Debug("docker-v2-fetch", lager.Data{
		"request": request,
	})

	auth, err := request.Session.GetV2Authorization(request.Endpoint, request.RemotePath, true)
	if err != nil {
		return nil, nil, nil, FetchError("GetV2Authorization", request.Endpoint.URL.Host, request.Path, err)
	}

	_, manifestBytes, err := request.Session.GetV2ImageManifest(request.Endpoint, request.RemotePath, request.Tag, auth)
	if err != nil {
		return nil, nil, nil, FetchError("GetV2ImageManifest", request.Endpoint.URL.Host, request.Path, err)
	}

	var manifest registry.ManifestData
	if err := json.Unmarshal(manifestBytes, &manifest); err != nil {
		return nil, nil, nil, FetchError("UnmarshalManifest", request.Endpoint.URL.Host, request.Path, err)
	}

	var hashes []digest.Digest
	var images []*image.Image

	for index, layer := range manifest.FSLayers {
		hash, err := digest.ParseDigest(layer.BlobSum)
		if err != nil {
			return nil, nil, nil, FetchError("ParseDigest", request.Endpoint.URL.Host, request.Path, err)
		}

		img, err := image.NewImgJSON([]byte(manifest.History[index].V1Compatibility))
		if err != nil {
			return nil, nil, nil, FetchError("NewImgJSON", request.Endpoint.URL.Host, request.Path, err)
		}

		images = append(images, img)
		hashes = append(hashes, hash)
	}

	return images, auth, hashes, nil
}

// CmdSet stores a new image in the graph.
// Images are stored in the graph using 4 elements:
//	- A user-defined ID
//	- A collection of metadata describing the image
//	- A directory tree stored as a tar archive (also called the "layer")
//	- A reference to a "parent" ID on top of which the layer should be applied
//
// NOTE: even though the parent ID is only useful in relation to the layer and how
// to apply it (ie you could represent the full directory tree as 'parent_layer + layer',
// it is treated as a top-level property of the image. This is an artifact of early
// design and should probably be cleaned up in the future to simplify the design.
//
// Syntax: image_set ID
// Input:
//	- Layer content must be streamed in tar format on stdin. An empty input is
//	valid and represents a nil layer.
//
//	- Image metadata must be passed in the command environment.
//		'json': a json-encoded object with all image metadata.
//			It will be stored as-is, without any encoding/decoding artifacts.
//			That is a requirement of the current registry client implementation,
//			because a re-encoded json might invalidate the image checksum at
//			the next upload, even with functionaly identical content.
func (s *TagStore) CmdSet(job *engine.Job) error {
	if len(job.Args) != 1 {
		return fmt.Errorf("usage: %s NAME", job.Name)
	}
	var (
		imgJSON = []byte(job.Getenv("json"))
		layer   = job.Stdin
	)
	if len(imgJSON) == 0 {
		return fmt.Errorf("mandatory key 'json' is not set")
	}
	// We have to pass an *image.Image object, even though it will be completely
	// ignored in favor of the redundant json data.
	// FIXME: the current prototype of Graph.Register is redundant.
	img, err := image.NewImgJSON(imgJSON)
	if err != nil {
		return err
	}
	if err := s.graph.Register(img, layer); err != nil {
		return err
	}
	return nil
}

func (s *TagStore) pushV2Repository(r *registry.Session, eng *engine.Engine, out io.Writer, repoInfo *registry.RepositoryInfo, tag string, sf *utils.StreamFormatter) error {
	if repoInfo.Official {
		j := eng.Job("trust_update_base")
		if err := j.Run(); err != nil {
			log.Errorf("error updating trust base graph: %s", err)
		}
	}

	endpoint, err := r.V2RegistryEndpoint(repoInfo.Index)
	if err != nil {
		if repoInfo.Index.Official {
			log.Debugf("Unable to push to V2 registry, falling back to v1: %s", err)
			return ErrV2RegistryUnavailable
		}
		return fmt.Errorf("error getting registry endpoint: %s", err)
	}

	tags, err := s.getImageTags(repoInfo.LocalName, tag)
	if err != nil {
		return err
	}
	if len(tags) == 0 {
		return fmt.Errorf("No tags to push for %s", repoInfo.LocalName)
	}

	auth, err := r.GetV2Authorization(endpoint, repoInfo.RemoteName, false)
	if err != nil {
		return fmt.Errorf("error getting authorization: %s", err)
	}

	for _, tag := range tags {
		log.Debugf("Pushing %s:%s to v2 repository", repoInfo.LocalName, tag)
		mBytes, err := s.newManifest(repoInfo.LocalName, repoInfo.RemoteName, tag)
		if err != nil {
			return err
		}
		js, err := libtrust.NewJSONSignature(mBytes)
		if err != nil {
			return err
		}

		if err = js.Sign(s.trustKey); err != nil {
			return err
		}

		signedBody, err := js.PrettySignature("signatures")
		if err != nil {
			return err
		}
		log.Infof("Signed manifest for %s:%s using daemon's key: %s", repoInfo.LocalName, tag, s.trustKey.KeyID())

		manifestBytes := string(signedBody)

		manifest, verified, err := s.loadManifest(eng, signedBody)
		if err != nil {
			return fmt.Errorf("error verifying manifest: %s", err)
		}

		if err := checkValidManifest(manifest); err != nil {
			return fmt.Errorf("invalid manifest: %s", err)
		}

		if verified {
			log.Infof("Pushing verified image, key %s is registered for %q", s.trustKey.KeyID(), repoInfo.RemoteName)
		}

		for i := len(manifest.FSLayers) - 1; i >= 0; i-- {
			var (
				sumStr  = manifest.FSLayers[i].BlobSum
				imgJSON = []byte(manifest.History[i].V1Compatibility)
			)

			sumParts := strings.SplitN(sumStr, ":", 2)
			if len(sumParts) < 2 {
				return fmt.Errorf("Invalid checksum: %s", sumStr)
			}
			manifestSum := sumParts[1]

			img, err := image.NewImgJSON(imgJSON)
			if err != nil {
				return fmt.Errorf("Failed to parse json: %s", err)
			}

			// Call mount blob
			exists, err := r.HeadV2ImageBlob(endpoint, repoInfo.RemoteName, sumParts[0], manifestSum, auth)
			if err != nil {
				out.Write(sf.FormatProgress(common.TruncateID(img.ID), "Image push failed", nil))
				return err
			}

			if !exists {
				if err := s.pushV2Image(r, img, endpoint, repoInfo.RemoteName, sumParts[0], manifestSum, sf, out, auth); err != nil {
					return err
				}
			} else {
				out.Write(sf.FormatProgress(common.TruncateID(img.ID), "Image already exists", nil))
			}
		}

		// push the manifest
//.........这里部分代码省略.........

func (p *v1Puller) pullImage(out io.Writer, imgID, endpoint string) (layersDownloaded bool, err error) {
	var history []string
	history, err = p.session.GetRemoteHistory(imgID, endpoint)
	if err != nil {
		return false, err
	}
	out.Write(p.sf.FormatProgress(stringid.TruncateID(imgID), "Pulling dependent layers", nil))
	// FIXME: Try to stream the images?
	// FIXME: Launch the getRemoteImage() in goroutines

	sessionID := p.session.ID()
	// As imgID has been retained in pullRepository, no need to retain again
	p.graph.Retain(sessionID, history[1:]...)
	defer p.graph.Release(sessionID, history[1:]...)

	layersDownloaded = false
	for i := len(history) - 1; i >= 0; i-- {
		id := history[i]

		// ensure no two downloads of the same layer happen at the same time
		poolKey := "layer:" + id
		broadcaster, found := p.poolAdd("pull", poolKey)
		broadcaster.Add(out)
		if found {
			logrus.Debugf("Image (id: %s) pull is already running, skipping", id)
			err = broadcaster.Wait()
			if err != nil {
				return layersDownloaded, err
			}
			continue
		}

		// This must use a closure so it captures the value of err when
		// the function returns, not when the 'defer' is evaluated.
		defer func() {
			p.poolRemoveWithError("pull", poolKey, err)
		}()

		if !p.graph.Exists(id) {
			broadcaster.Write(p.sf.FormatProgress(stringid.TruncateID(id), "Pulling metadata", nil))
			var (
				imgJSON []byte
				imgSize int64
				err     error
				img     *image.Image
			)
			retries := 5
			for j := 1; j <= retries; j++ {
				imgJSON, imgSize, err = p.session.GetRemoteImageJSON(id, endpoint)
				if err != nil && j == retries {
					broadcaster.Write(p.sf.FormatProgress(stringid.TruncateID(id), "Error pulling dependent layers", nil))
					return layersDownloaded, err
				} else if err != nil {
					time.Sleep(time.Duration(j) * 500 * time.Millisecond)
					continue
				}
				img, err = image.NewImgJSON(imgJSON)
				layersDownloaded = true
				if err != nil && j == retries {
					broadcaster.Write(p.sf.FormatProgress(stringid.TruncateID(id), "Error pulling dependent layers", nil))
					return layersDownloaded, fmt.Errorf("Failed to parse json: %s", err)
				} else if err != nil {
					time.Sleep(time.Duration(j) * 500 * time.Millisecond)
					continue
				} else {
					break
				}
			}

			for j := 1; j <= retries; j++ {
				// Get the layer
				status := "Pulling fs layer"
				if j > 1 {
					status = fmt.Sprintf("Pulling fs layer [retries: %d]", j)
				}
				broadcaster.Write(p.sf.FormatProgress(stringid.TruncateID(id), status, nil))
				layer, err := p.session.GetRemoteImageLayer(img.ID, endpoint, imgSize)
				if uerr, ok := err.(*url.Error); ok {
					err = uerr.Err
				}
				if terr, ok := err.(net.Error); ok && terr.Timeout() && j < retries {
					time.Sleep(time.Duration(j) * 500 * time.Millisecond)
					continue
				} else if err != nil {
					broadcaster.Write(p.sf.FormatProgress(stringid.TruncateID(id), "Error pulling dependent layers", nil))
					return layersDownloaded, err
				}
				layersDownloaded = true
				defer layer.Close()

				err = p.graph.Register(img,
					progressreader.New(progressreader.Config{
						In:        layer,
						Out:       broadcaster,
						Formatter: p.sf,
						Size:      imgSize,
						NewLines:  false,
						ID:        stringid.TruncateID(id),
						Action:    "Downloading",
					}))
//.........这里部分代码省略.........

func (p *v2Puller) pullV2Tag(out io.Writer, tag, taggedName string) (verified bool, err error) {
	logrus.Debugf("Pulling tag from V2 registry: %q", tag)

	manSvc, err := p.repo.Manifests(context.Background())
	if err != nil {
		return false, err
	}

	manifest, err := manSvc.GetByTag(tag)
	if err != nil {
		return false, err
	}
	verified, err = p.validateManifest(manifest, tag)
	if err != nil {
		return false, err
	}
	if verified {
		logrus.Printf("Image manifest for %s has been verified", taggedName)
	}

	out.Write(p.sf.FormatStatus(tag, "Pulling from %s", p.repo.Name()))

	var downloads []*downloadInfo

	var layerIDs []string
	defer func() {
		p.graph.Release(p.sessionID, layerIDs...)

		for _, d := range downloads {
			p.poolRemoveWithError("pull", d.poolKey, err)
			if d.tmpFile != nil {
				d.tmpFile.Close()
				if err := os.RemoveAll(d.tmpFile.Name()); err != nil {
					logrus.Errorf("Failed to remove temp file: %s", d.tmpFile.Name())
				}
			}
		}
	}()

	for i := len(manifest.FSLayers) - 1; i >= 0; i-- {
		img, err := image.NewImgJSON([]byte(manifest.History[i].V1Compatibility))
		if err != nil {
			logrus.Debugf("error getting image v1 json: %v", err)
			return false, err
		}
		p.graph.Retain(p.sessionID, img.ID)
		layerIDs = append(layerIDs, img.ID)

		// Check if exists
		if p.graph.Exists(img.ID) {
			logrus.Debugf("Image already exists: %s", img.ID)
			out.Write(p.sf.FormatProgress(stringid.TruncateID(img.ID), "Already exists", nil))
			continue
		}
		out.Write(p.sf.FormatProgress(stringid.TruncateID(img.ID), "Pulling fs layer", nil))

		d := &downloadInfo{
			img:     img,
			poolKey: "layer:" + img.ID,
			digest:  manifest.FSLayers[i].BlobSum,
			// TODO: seems like this chan buffer solved hanging problem in go1.5,
			// this can indicate some deeper problem that somehow we never take
			// error from channel in loop below
			err: make(chan error, 1),
		}

		tmpFile, err := ioutil.TempFile("", "GetImageBlob")
		if err != nil {
			return false, err
		}
		d.tmpFile = tmpFile

		downloads = append(downloads, d)

		broadcaster, found := p.poolAdd("pull", d.poolKey)
		broadcaster.Add(out)
		d.broadcaster = broadcaster
		if found {
			d.err <- nil
		} else {
			go p.download(d)
		}
	}

	var tagUpdated bool
	for _, d := range downloads {
		if err := <-d.err; err != nil {
			return false, err
		}

		if d.layer == nil {
			// Wait for a different pull to download and extract
			// this layer.
			err = d.broadcaster.Wait()
			if err != nil {
				return false, err
			}
			continue
		}

//.........这里部分代码省略.........