// dbImageGet gets an ImageBaseInfo object from the database.
// The argument fingerprint will be queried with a LIKE query, means you can
// pass a shortform and will get the full fingerprint.
// There can never be more than one image with a given fingerprint, as it is
// enforced by a UNIQUE constraint in the schema.
func dbImageGet(db *sql.DB, fingerprint string, public bool, strictMatching bool) (int, *shared.ImageInfo, error) {
	var err error
	var create, expire, used, upload *time.Time // These hold the db-returned times

	// The object we'll actually return
	image := shared.ImageInfo{}
	id := -1
	arch := -1

	// These two humongous things will be filled by the call to DbQueryRowScan
	outfmt := []interface{}{&id, &image.Fingerprint, &image.Filename,
		&image.Size, &image.Cached, &image.Public, &image.AutoUpdate, &arch,
		&create, &expire, &used, &upload}

	var query string

	var inargs []interface{}
	if strictMatching {
		inargs = []interface{}{fingerprint}
		query = `
        SELECT
            id, fingerprint, filename, size, cached, public, auto_update, architecture,
            creation_date, expiry_date, last_use_date, upload_date
        FROM
            images
        WHERE fingerprint = ?`
	} else {
		inargs = []interface{}{fingerprint + "%"}
		query = `
        SELECT
            id, fingerprint, filename, size, cached, public, auto_update, architecture,
            creation_date, expiry_date, last_use_date, upload_date
        FROM
            images
        WHERE fingerprint LIKE ?`
	}

	if public {
		query = query + " AND public=1"
	}

	err = dbQueryRowScan(db, query, inargs, outfmt)

	if err != nil {
		return -1, nil, err // Likely: there are no rows for this fingerprint
	}

	// Some of the dates can be nil in the DB, let's process them.
	if create != nil {
		image.CreationDate = *create
	} else {
		image.CreationDate = time.Time{}
	}

	if expire != nil {
		image.ExpiryDate = *expire
	} else {
		image.ExpiryDate = time.Time{}
	}

	if used != nil {
		image.LastUsedDate = *used
	} else {
		image.LastUsedDate = time.Time{}
	}

	image.Architecture, _ = shared.ArchitectureName(arch)

	// The upload date is enforced by NOT NULL in the schema, so it can never be nil.
	image.UploadDate = *upload

	// Get the properties
	q := "SELECT key, value FROM images_properties where image_id=?"
	var key, value, name, desc string
	inargs = []interface{}{id}
	outfmt = []interface{}{key, value}
	results, err := dbQueryScan(db, q, inargs, outfmt)
	if err != nil {
		return -1, nil, err
	}

	properties := map[string]string{}
	for _, r := range results {
		key = r[0].(string)
		value = r[1].(string)
		properties[key] = value
	}

	image.Properties = properties

	// Get the aliases
	q = "SELECT name, description FROM images_aliases WHERE image_id=?"
	inargs = []interface{}{id}
	outfmt = []interface{}{name, desc}
	results, err = dbQueryScan(db, q, inargs, outfmt)
//.........这里部分代码省略.........

//.........这里部分代码省略.........
			"Previous download succeeded",
			log.Ctx{"image": fp})

		return fp, nil
	}

	d.imagesDownloadingLock.RUnlock()

	if op == nil {
		ctxMap = log.Ctx{"alias": alias, "server": server}
	} else {
		ctxMap = log.Ctx{"trigger": op.url, "image": fp, "operation": op.id, "alias": alias, "server": server}
	}

	shared.LogInfo("Downloading image", ctxMap)

	// Add the download to the queue
	d.imagesDownloadingLock.Lock()
	d.imagesDownloading[fp] = make(chan bool)
	d.imagesDownloadingLock.Unlock()

	// Unlock once this func ends.
	defer func() {
		d.imagesDownloadingLock.Lock()
		if waitChannel, ok := d.imagesDownloading[fp]; ok {
			close(waitChannel)
			delete(d.imagesDownloading, fp)
		}
		d.imagesDownloadingLock.Unlock()
	}()

	exporturl := server

	var info shared.ImageInfo
	info.Fingerprint = fp

	destDir := shared.VarPath("images")
	destName := filepath.Join(destDir, fp)
	if shared.PathExists(destName) {
		d.Storage.ImageDelete(fp)
	}

	progress := func(progressInt int64, speedInt int64) {
		if op == nil {
			return
		}

		meta := op.metadata
		if meta == nil {
			meta = make(map[string]interface{})
		}

		progress := fmt.Sprintf("%d%% (%s/s)", progressInt, shared.GetByteSizeString(speedInt))

		if meta["download_progress"] != progress {
			meta["download_progress"] = progress
			op.UpdateMetadata(meta)
		}
	}

	if protocol == "lxd" {
		/* grab the metadata from /1.0/images/%s */
		var url string
		if secret != "" {
			url = fmt.Sprintf(
				"%s/%s/images/%s?secret=%s",

// ImageDownload checks if we have that Image Fingerprint else
// downloads the image from a remote server.
func (d *Daemon) ImageDownload(op *operation, server string, protocol string, certificate string, secret string, alias string, forContainer bool, autoUpdate bool) (string, error) {
	var err error
	var ss *shared.SimpleStreams

	if protocol == "" {
		protocol = "lxd"
	}

	fp := alias

	// Expand aliases
	if protocol == "simplestreams" {
		ss, err = shared.SimpleStreamsClient(server, d.proxy)
		if err != nil {
			return "", err
		}

		target := ss.GetAlias(fp)
		if target != "" {
			fp = target
		}

		image, err := ss.GetImageInfo(fp)
		if err != nil {
			return "", err
		}

		if fp == alias {
			alias = image.Fingerprint
		}
		fp = image.Fingerprint
	} else if protocol == "lxd" {
		target, err := remoteGetImageFingerprint(d, server, certificate, fp)
		if err == nil && target != "" {
			fp = target
		}
	}

	if _, _, err := dbImageGet(d.db, fp, false, false); err == nil {
		shared.Log.Debug("Image already exists in the db", log.Ctx{"image": fp})
		// already have it
		return fp, nil
	}

	shared.Log.Info(
		"Image not in the db, downloading it",
		log.Ctx{"image": fp, "server": server})

	// Now check if we already downloading the image
	d.imagesDownloadingLock.RLock()
	if waitChannel, ok := d.imagesDownloading[fp]; ok {
		// We already download the image
		d.imagesDownloadingLock.RUnlock()

		shared.Log.Info(
			"Already downloading the image, waiting for it to succeed",
			log.Ctx{"image": fp})

		// Wait until the download finishes (channel closes)
		if _, ok := <-waitChannel; ok {
			shared.Log.Warn("Value transmitted over image lock semaphore?")
		}

		if _, _, err := dbImageGet(d.db, fp, false, true); err != nil {
			shared.Log.Error(
				"Previous download didn't succeed",
				log.Ctx{"image": fp})

			return "", fmt.Errorf("Previous download didn't succeed")
		}

		shared.Log.Info(
			"Previous download succeeded",
			log.Ctx{"image": fp})

		return fp, nil
	}

	d.imagesDownloadingLock.RUnlock()

	shared.Log.Info(
		"Downloading the image",
		log.Ctx{"image": fp})

	// Add the download to the queue
	d.imagesDownloadingLock.Lock()
	d.imagesDownloading[fp] = make(chan bool)
	d.imagesDownloadingLock.Unlock()

	// Unlock once this func ends.
	defer func() {
		d.imagesDownloadingLock.Lock()
		if waitChannel, ok := d.imagesDownloading[fp]; ok {
			close(waitChannel)
			delete(d.imagesDownloading, fp)
		}
		d.imagesDownloadingLock.Unlock()
	}()
//.........这里部分代码省略.........

// ImageDownload checks if we have that Image Fingerprint else
// downloads the image from a remote server.
func (d *Daemon) ImageDownload(op *operation,
	server, fp string, secret string, forContainer bool, directDownload bool) error {

	if _, err := dbImageGet(d.db, fp, false, false); err == nil {
		shared.Log.Debug("Image already exists in the db", log.Ctx{"image": fp})
		// already have it
		return nil
	}

	shared.Log.Info(
		"Image not in the db, downloading it",
		log.Ctx{"image": fp, "server": server})

	// Now check if we already downloading the image
	d.imagesDownloadingLock.RLock()
	if waitChannel, ok := d.imagesDownloading[fp]; ok {
		// We already download the image
		d.imagesDownloadingLock.RUnlock()

		shared.Log.Info(
			"Already downloading the image, waiting for it to succeed",
			log.Ctx{"image": fp})

		// Wait until the download finishes (channel closes)
		if _, ok := <-waitChannel; ok {
			shared.Log.Warn("Value transmitted over image lock semaphore?")
		}

		if _, err := dbImageGet(d.db, fp, false, true); err != nil {
			shared.Log.Error(
				"Previous download didn't succeed",
				log.Ctx{"image": fp})

			return fmt.Errorf("Previous download didn't succeed")
		}

		shared.Log.Info(
			"Previous download succeeded",
			log.Ctx{"image": fp})

		return nil
	}

	d.imagesDownloadingLock.RUnlock()

	shared.Log.Info(
		"Downloading the image",
		log.Ctx{"image": fp})

	// Add the download to the queue
	d.imagesDownloadingLock.Lock()
	d.imagesDownloading[fp] = make(chan bool)
	d.imagesDownloadingLock.Unlock()

	// Unlock once this func ends.
	defer func() {
		d.imagesDownloadingLock.Lock()
		if waitChannel, ok := d.imagesDownloading[fp]; ok {
			close(waitChannel)
			delete(d.imagesDownloading, fp)
		}
		d.imagesDownloadingLock.Unlock()
	}()

	exporturl := server

	var info shared.ImageInfo
	info.Fingerprint = fp

	if !directDownload {
		/* grab the metadata from /1.0/images/%s */
		var url string
		if secret != "" {
			url = fmt.Sprintf(
				"%s/%s/images/%s?secret=%s",
				server, shared.APIVersion, fp, secret)
		} else {
			url = fmt.Sprintf("%s/%s/images/%s", server, shared.APIVersion, fp)
		}

		resp, err := d.httpGetSync(url)
		if err != nil {
			shared.Log.Error(
				"Failed to download image metadata",
				log.Ctx{"image": fp, "err": err})

			return err
		}

		if err := json.Unmarshal(resp.Metadata, &info); err != nil {
			return err
		}

		/* now grab the actual file from /1.0/images/%s/export */
		if secret != "" {
			exporturl = fmt.Sprintf(
				"%s/%s/images/%s/export?secret=%s",
				server, shared.APIVersion, fp, secret)
//.........这里部分代码省略.........