func printStats(out io.Writer, bs *metrics.Stats) {
	fmt.Fprintln(out, "Bandwidth")
	fmt.Fprintf(out, "TotalIn: %s\n", humanize.Bytes(uint64(bs.TotalIn)))
	fmt.Fprintf(out, "TotalOut: %s\n", humanize.Bytes(uint64(bs.TotalOut)))
	fmt.Fprintf(out, "RateIn: %s/s\n", humanize.Bytes(uint64(bs.RateIn)))
	fmt.Fprintf(out, "RateOut: %s/s\n", humanize.Bytes(uint64(bs.RateOut)))
}

func (gc *GC) maybeGC(ctx context.Context, offset uint64) error {
	storage, err := gc.Repo.GetStorageUsage()
	if err != nil {
		return err
	}

	if storage+offset > gc.StorageMax {
		err := ErrMaxStorageExceeded
		log.Error(err)
		return err
	}

	if storage+offset > gc.StorageGC {
		// Do GC here
		log.Info("Starting repo GC...")
		defer log.EventBegin(ctx, "repoGC").Done()
		// 1 minute is sufficient for ~1GB unlink() blocks each of 100kb in SSD
		_ctx, cancel := context.WithTimeout(ctx, time.Duration(gc.SlackGB)*time.Minute)
		defer cancel()

		if err := GarbageCollect(gc.Node, _ctx); err != nil {
			return err
		}
		newStorage, err := gc.Repo.GetStorageUsage()
		if err != nil {
			return err
		}
		log.Infof("Repo GC done. Released %s\n", humanize.Bytes(uint64(storage-newStorage)))
		return nil
	}
	return nil
}

//.........这里部分代码省略.........
		w.Header().Set("Cache-Control", "public, max-age=29030400")

		// set modtime to a really long time ago, since files are immutable and should stay cached
		modtime = time.Unix(1, 0)
	}

	if err == nil {
		defer dr.Close()
		name := gopath.Base(urlPath)
		http.ServeContent(w, r, name, modtime, dr)
		return
	}

	// storage for directory listing
	var dirListing []directoryItem
	// loop through files
	foundIndex := false
	for _, link := range nd.Links {
		if link.Name == "index.html" {
			log.Debugf("found index.html link for %s", urlPath)
			foundIndex = true

			if urlPath[len(urlPath)-1] != '/' {
				// See comment above where originalUrlPath is declared.
				http.Redirect(w, r, originalUrlPath+"/", 302)
				log.Debugf("redirect to %s", originalUrlPath+"/")
				return
			}

			// return index page instead.
			nd, err := core.Resolve(ctx, i.node, path.Path(urlPath+"/index.html"))
			if err != nil {
				internalWebError(w, err)
				return
			}
			dr, err := uio.NewDagReader(ctx, nd, i.node.DAG)
			if err != nil {
				internalWebError(w, err)
				return
			}
			defer dr.Close()

			// write to request
			http.ServeContent(w, r, "index.html", modtime, dr)
			break
		}

		// See comment above where originalUrlPath is declared.
		di := directoryItem{humanize.Bytes(link.Size), link.Name, gopath.Join(originalUrlPath, link.Name)}
		dirListing = append(dirListing, di)
	}

	if !foundIndex {
		if r.Method != "HEAD" {
			// construct the correct back link
			// https://github.com/ipfs/go-ipfs/issues/1365
			var backLink string = prefix + urlPath

			// don't go further up than /ipfs/$hash/
			pathSplit := path.SplitList(backLink)
			switch {
			// keep backlink
			case len(pathSplit) == 3: // url: /ipfs/$hash

			// keep backlink
			case len(pathSplit) == 4 && pathSplit[3] == "": // url: /ipfs/$hash/

			// add the correct link depending on wether the path ends with a slash
			default:
				if strings.HasSuffix(backLink, "/") {
					backLink += "./.."
				} else {
					backLink += "/.."
				}
			}

			// strip /ipfs/$hash from backlink if IPNSHostnameOption touched the path.
			if ipnsHostname {
				backLink = prefix + "/"
				if len(pathSplit) > 5 {
					// also strip the trailing segment, because it's a backlink
					backLinkParts := pathSplit[3 : len(pathSplit)-2]
					backLink += path.Join(backLinkParts) + "/"
				}
			}

			// See comment above where originalUrlPath is declared.
			tplData := listingTemplateData{
				Listing:  dirListing,
				Path:     originalUrlPath,
				BackLink: backLink,
			}
			err := listingTemplate.Execute(w, tplData)
			if err != nil {
				internalWebError(w, err)
				return
			}
		}
	}
}

			first := true
			marshal := func(v interface{}) (io.Reader, error) {
				bs, ok := v.(*metrics.Stats)
				if !ok {
					return nil, u.ErrCast()
				}
				out := new(bytes.Buffer)
				if !polling {
					printStats(out, bs)
				} else {
					if first {
						fmt.Fprintln(out, "Total Up\t Total Down\t Rate Up\t Rate Down")
						first = false
					}
					fmt.Fprint(out, "\r")
					fmt.Fprintf(out, "%s \t\t", humanize.Bytes(uint64(bs.TotalOut)))
					fmt.Fprintf(out, " %s \t\t", humanize.Bytes(uint64(bs.TotalIn)))
					fmt.Fprintf(out, " %s/s   \t", humanize.Bytes(uint64(bs.RateOut)))
					fmt.Fprintf(out, " %s/s     ", humanize.Bytes(uint64(bs.RateIn)))
				}
				return out, nil

			}

			return &cmds.ChannelMarshaler{
				Channel:   outCh,
				Marshaler: marshal,
				Res:       res,
			}, nil
		},
	},