godoc/dl/dl.go - tools - Git at Google

 // Copyright 2015 The Go Authors. All rights reserved.
 // Use of this source code is governed by the Apache 2.0
 // license that can be found in the LICENSE file.

 // +build appengine

 // Package dl implements a simple downloads frontend server.
 //
 // It accepts HTTP POST requests to create a new download metadata entity, and
 // lists entities with sorting and filtering.
 // It is designed to run only on the instance of godoc that serves golang.org.
 package dl

 import (
 	"crypto/hmac"
 	"crypto/md5"
 	"encoding/json"
 	"fmt"
 	"html/template"
 	"io"
 	"net/http"
 	"regexp"
 	"sort"
 	"strconv"
 	"strings"
 	"sync"
 	"time"

 	"golang.org/x/net/context"

 	"google.golang.org/appengine"
 	"google.golang.org/appengine/datastore"
 	"google.golang.org/appengine/log"
 	"google.golang.org/appengine/memcache"
 )

 const (
 	downloadBaseURL = "https://dl.google.com/go/"
 	cacheKey        = "download_list_3" // increment if listTemplateData changes
 	cacheDuration   = time.Hour
 )

 func RegisterHandlers(mux *http.ServeMux) {
 	mux.Handle("/dl", http.RedirectHandler("/dl/", http.StatusFound))
 	mux.HandleFunc("/dl/", getHandler) // also serves listHandler
 	mux.HandleFunc("/dl/upload", uploadHandler)
 	mux.HandleFunc("/dl/init", initHandler)
 }

 type File struct {
 	Filename       string
 	OS             string
 	Arch           string
 	Version        string
 	Checksum       string `datastore:",noindex"` // SHA1; deprecated
 	ChecksumSHA256 string `datastore:",noindex"`
 	Size           int64  `datastore:",noindex"`
 	Kind           string // "archive", "installer", "source"
 	Uploaded       time.Time
 }

 func (f File) ChecksumType() string {
 	if f.ChecksumSHA256 != "" {
 		return "SHA256"
 	}
 	return "SHA1"
 }

 func (f File) PrettyChecksum() string {
 	if f.ChecksumSHA256 != "" {
 		return f.ChecksumSHA256
 	}
 	return f.Checksum
 }

 func (f File) PrettyOS() string {
 	if f.OS == "darwin" {
 		switch {
 		case strings.Contains(f.Filename, "osx10.8"):
 			return "OS X 10.8+"
 		case strings.Contains(f.Filename, "osx10.6"):
 			return "OS X 10.6+"
 		}
 	}
 	return pretty(f.OS)
 }

 func (f File) PrettySize() string {
 	const mb = 1 << 20
 	if f.Size == 0 {
 		return ""
 	}
 	if f.Size < mb {
 		// All Go releases are >1mb, but handle this case anyway.
 		return fmt.Sprintf("%v bytes", f.Size)
 	}
 	return fmt.Sprintf("%.0fMB", float64(f.Size)/mb)
 }

 var primaryPorts = map[string]bool{
 	"darwin/amd64":  true,
 	"linux/386":     true,
 	"linux/amd64":   true,
 	"linux/armv6l":  true,
 	"windows/386":   true,
 	"windows/amd64": true,
 }

 func (f File) PrimaryPort() bool {
 	if f.Kind == "source" {
 		return true
 	}
 	return primaryPorts[f.OS+"/"+f.Arch]
 }

 func (f File) Highlight() bool {
 	switch {
 	case f.Kind == "source":
 		return true
 	case f.Arch == "amd64" && f.OS == "linux":
 		return true
 	case f.Arch == "amd64" && f.Kind == "installer":
 		switch f.OS {
 		case "windows":
 			return true
 		case "darwin":
 			if !strings.Contains(f.Filename, "osx10.6") {
 				return true
 			}
 		}
 	}
 	return false
 }

 func (f File) URL() string {
 	return downloadBaseURL + f.Filename
 }

 type Release struct {
 	Version        string
 	Stable         bool
 	Files          []File
 	Visible        bool // show files on page load
 	SplitPortTable bool // whether files should be split by primary/other ports.
 }

 type Feature struct {
 	// The File field will be filled in by the first stable File
 	// whose name matches the given fileRE.
 	File
 	fileRE *regexp.Regexp

 	Platform     string // "Microsoft Windows", "Apple macOS", "Linux"
 	Requirements string // "Windows XP and above, 64-bit Intel Processor"
 }

 // featuredFiles lists the platforms and files to be featured
 // at the top of the downloads page.
 var featuredFiles = []Feature{
 	{
 		Platform:     "Microsoft Windows",
 		Requirements: "Windows XP SP2 or later, Intel 64-bit processor",
 		fileRE:       regexp.MustCompile(`\.windows-amd64\.msi$`),
 	},
 	{
 		Platform:     "Apple macOS",
 		Requirements: "macOS 10.8 or later, Intel 64-bit processor",
 		fileRE:       regexp.MustCompile(`\.darwin-amd64(-osx10\.8)?\.pkg$`),
 	},
 	{
 		Platform:     "Linux",
 		Requirements: "Linux 2.6.23 or later, Intel 64-bit processor",
 		fileRE:       regexp.MustCompile(`\.linux-amd64\.tar\.gz$`),
 	},
 	{
 		Platform: "Source",
 		fileRE:   regexp.MustCompile(`\.src\.tar\.gz$`),
 	},
 }

 // data to send to the template; increment cacheKey if you change this.
 type listTemplateData struct {
 	Featured                  []Feature
 	Stable, Unstable, Archive []Release
 }

 var (
 	listTemplate  = template.Must(template.New("").Funcs(templateFuncs).Parse(templateHTML))
 	templateFuncs = template.FuncMap{"pretty": pretty}
 )

 func listHandler(w http.ResponseWriter, r *http.Request) {
 	if r.Method != "GET" {
 		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
 		return
 	}
 	var (
 		c = appengine.NewContext(r)
 		d listTemplateData
 	)
 	if _, err := memcache.Gob.Get(c, cacheKey, &d); err != nil {
 		if err == memcache.ErrCacheMiss {
 			log.Debugf(c, "cache miss")
 		} else {
 			log.Errorf(c, "cache get error: %v", err)
 		}

 		var fs []File
 		_, err := datastore.NewQuery("File").Ancestor(rootKey(c)).GetAll(c, &fs)
 		if err != nil {
 			log.Errorf(c, "error listing: %v", err)
 			return
 		}
 		d.Stable, d.Unstable, d.Archive = filesToReleases(fs)
 		if len(d.Stable) > 0 {
 			d.Featured = filesToFeatured(d.Stable[0].Files)
 		}

 		item := &memcache.Item{Key: cacheKey, Object: &d, Expiration: cacheDuration}
 		if err := memcache.Gob.Set(c, item); err != nil {
 			log.Errorf(c, "cache set error: %v", err)
 		}
 	}
 	if err := listTemplate.ExecuteTemplate(w, "root", d); err != nil {
 		log.Errorf(c, "error executing template: %v", err)
 	}
 }

 func filesToFeatured(fs []File) (featured []Feature) {
 	for _, feature := range featuredFiles {
 		for _, file := range fs {
 			if feature.fileRE.MatchString(file.Filename) {
 				feature.File = file
 				featured = append(featured, feature)
 				break
 			}
 		}
 	}
 	return
 }

 func filesToReleases(fs []File) (stable, unstable, archive []Release) {
 	sort.Sort(fileOrder(fs))

 	var r *Release
 	var stableMaj, stableMin int
 	add := func() {
 		if r == nil {
 			return
 		}
 		if !r.Stable {
 			if len(unstable) != 0 {
 				// Only show one (latest) unstable version.
 				return
 			}
 			maj, min, _ := parseVersion(r.Version)
 			if maj < stableMaj || maj == stableMaj && min <= stableMin {
 				// Display unstable version only if newer than the
 				// latest stable release.
 				return
 			}
 			unstable = append(unstable, *r)
 		}

 		// Reports whether the release is the most recent minor version of the
 		// two most recent major versions.
 		shouldAddStable := func() bool {
 			if len(stable) >= 2 {
 				// Show up to two stable versions.
 				return false
 			}
 			if len(stable) == 0 {
 				// Most recent stable version.
 				stableMaj, stableMin, _ = parseVersion(r.Version)
 				return true
 			}
 			if maj, _, _ := parseVersion(r.Version); maj == stableMaj {
 				// Older minor version of most recent major version.
 				return false
 			}
 			// Second most recent stable version.
 			return true
 		}
 		if !shouldAddStable() {
 			archive = append(archive, *r)
 			return
 		}

 		// Split the file list into primary/other ports for the stable releases.
 		// NOTE(cbro): This is only done for stable releases because maintaining the historical
 		// nature of primary/other ports for older versions is infeasible.
 		// If freebsd is considered primary some time in the future, we'd not want to
 		// mark all of the older freebsd binaries as "primary".
 		// It might be better if we set that as a flag when uploading.
 		r.SplitPortTable = true
 		r.Visible = true // Toggle open all stable releases.
 		stable = append(stable, *r)
 	}
 	for _, f := range fs {
 		if r == nil || f.Version != r.Version {
 			add()
 			r = &Release{
 				Version: f.Version,
 				Stable:  isStable(f.Version),
 			}
 		}
 		r.Files = append(r.Files, f)
 	}
 	add()
 	return
 }

 // isStable reports whether the version string v is a stable version.
 func isStable(v string) bool {
 	return !strings.Contains(v, "beta") && !strings.Contains(v, "rc")
 }

 type fileOrder []File

 func (s fileOrder) Len() int      { return len(s) }
 func (s fileOrder) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
 func (s fileOrder) Less(i, j int) bool {
 	a, b := s[i], s[j]
 	if av, bv := a.Version, b.Version; av != bv {
 		return versionLess(av, bv)
 	}
 	if a.OS != b.OS {
 		return a.OS < b.OS
 	}
 	if a.Arch != b.Arch {
 		return a.Arch < b.Arch
 	}
 	if a.Kind != b.Kind {
 		return a.Kind < b.Kind
 	}
 	return a.Filename < b.Filename
 }

 func versionLess(a, b string) bool {
 	// Put stable releases first.
 	if isStable(a) != isStable(b) {
 		return isStable(a)
 	}
 	maja, mina, ta := parseVersion(a)
 	majb, minb, tb := parseVersion(b)
 	if maja == majb {
 		if mina == minb {
 			return ta >= tb
 		}
 		return mina >= minb
 	}
 	return maja >= majb
 }

 func parseVersion(v string) (maj, min int, tail string) {
 	if i := strings.Index(v, "beta"); i > 0 {
 		tail = v[i:]
 		v = v[:i]
 	}
 	if i := strings.Index(v, "rc"); i > 0 {
 		tail = v[i:]
 		v = v[:i]
 	}
 	p := strings.Split(strings.TrimPrefix(v, "go1."), ".")
 	maj, _ = strconv.Atoi(p[0])
 	if len(p) < 2 {
 		return
 	}
 	min, _ = strconv.Atoi(p[1])
 	return
 }

 func uploadHandler(w http.ResponseWriter, r *http.Request) {
 	if r.Method != "POST" {
 		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
 		return
 	}
 	c := appengine.NewContext(r)

 	// Authenticate using a user token (same as gomote).
 	user := r.FormValue("user")
 	if !validUser(user) {
 		http.Error(w, "bad user", http.StatusForbidden)
 		return
 	}
 	if r.FormValue("key") != userKey(c, user) {
 		http.Error(w, "bad key", http.StatusForbidden)
 		return
 	}

 	var f File
 	defer r.Body.Close()
 	if err := json.NewDecoder(r.Body).Decode(&f); err != nil {
 		log.Errorf(c, "error decoding upload JSON: %v", err)
 		http.Error(w, "Something broke", http.StatusInternalServerError)
 		return
 	}
 	if f.Filename == "" {
 		http.Error(w, "Must provide Filename", http.StatusBadRequest)
 		return
 	}
 	if f.Uploaded.IsZero() {
 		f.Uploaded = time.Now()
 	}
 	k := datastore.NewKey(c, "File", f.Filename, 0, rootKey(c))
 	if _, err := datastore.Put(c, k, &f); err != nil {
 		log.Errorf(c, "putting File entity: %v", err)
 		http.Error(w, "could not put File entity", http.StatusInternalServerError)
 		return
 	}
 	if err := memcache.Delete(c, cacheKey); err != nil {
 		log.Errorf(c, "cache delete error: %v", err)
 	}
 	io.WriteString(w, "OK")
 }

 func getHandler(w http.ResponseWriter, r *http.Request) {
 	name := strings.TrimPrefix(r.URL.Path, "/dl/")
 	if name == "" {
 		listHandler(w, r)
 		return
 	}
 	if !fileRe.MatchString(name) {
 		http.NotFound(w, r)
 		return
 	}
 	http.Redirect(w, r, downloadBaseURL+name, http.StatusFound)
 }

 func validUser(user string) bool {
 	switch user {
 	case "adg", "bradfitz", "cbro", "andybons":
 		return true
 	}
 	return false
 }

 func userKey(c context.Context, user string) string {
 	h := hmac.New(md5.New, []byte(secret(c)))
 	h.Write([]byte("user-" + user))
 	return fmt.Sprintf("%x", h.Sum(nil))
 }

 var fileRe = regexp.MustCompile(`^go[0-9a-z.]+\.[0-9a-z.-]+\.(tar\.gz|pkg|msi|zip)$`)

 func initHandler(w http.ResponseWriter, r *http.Request) {
 	var fileRoot struct {
 		Root string
 	}
 	c := appengine.NewContext(r)
 	k := rootKey(c)
 	err := datastore.RunInTransaction(c, func(c context.Context) error {
 		err := datastore.Get(c, k, &fileRoot)
 		if err != nil && err != datastore.ErrNoSuchEntity {
 			return err
 		}
 		_, err = datastore.Put(c, k, &fileRoot)
 		return err
 	}, nil)
 	if err != nil {
 		http.Error(w, err.Error(), 500)
 		return
 	}
 	io.WriteString(w, "OK")
 }

 // rootKey is the ancestor of all File entities.
 func rootKey(c context.Context) *datastore.Key {
 	return datastore.NewKey(c, "FileRoot", "root", 0, nil)
 }

 // pretty returns a human-readable version of the given OS, Arch, or Kind.
 func pretty(s string) string {
 	t, ok := prettyStrings[s]
 	if !ok {
 		return s
 	}
 	return t
 }

 var prettyStrings = map[string]string{
 	"darwin":  "macOS",
 	"freebsd": "FreeBSD",
 	"linux":   "Linux",
 	"windows": "Windows",

 	"386":    "x86",
 	"amd64":  "x86-64",
 	"armv6l": "ARMv6",
 	"arm64":  "ARMv8",

 	"archive":   "Archive",
 	"installer": "Installer",
 	"source":    "Source",
 }

 // Code below copied from x/build/app/key

 var theKey struct {
 	sync.RWMutex
 	builderKey
 }

 type builderKey struct {
 	Secret string
 }

 func (k *builderKey) Key(c context.Context) *datastore.Key {
 	return datastore.NewKey(c, "BuilderKey", "root", 0, nil)
 }

 func secret(c context.Context) string {
 	// check with rlock
 	theKey.RLock()
 	k := theKey.Secret
 	theKey.RUnlock()
 	if k != "" {
 		return k
 	}

 	// prepare to fill; check with lock and keep lock
 	theKey.Lock()
 	defer theKey.Unlock()
 	if theKey.Secret != "" {
 		return theKey.Secret
 	}

 	// fill
 	if err := datastore.Get(c, theKey.Key(c), &theKey.builderKey); err != nil {
 		if err == datastore.ErrNoSuchEntity {
 			// If the key is not stored in datastore, write it.
 			// This only happens at the beginning of a new deployment.
 			// The code is left here for SDK use and in case a fresh
 			// deployment is ever needed.  "gophers rule" is not the
 			// real key.
 			if !appengine.IsDevAppServer() {
 				panic("lost key from datastore")
 			}
 			theKey.Secret = "gophers rule"
 			datastore.Put(c, theKey.Key(c), &theKey.builderKey)
 			return theKey.Secret
 		}
 		panic("cannot load builder key: " + err.Error())
 	}

 	return theKey.Secret
 }
	// Copyright 2015 The Go Authors. All rights reserved.
	// Use of this source code is governed by the Apache 2.0
	// license that can be found in the LICENSE file.

	// +build appengine

	// Package dl implements a simple downloads frontend server.
	//
	// It accepts HTTP POST requests to create a new download metadata entity, and
	// lists entities with sorting and filtering.
	// It is designed to run only on the instance of godoc that serves golang.org.
	package dl

	import (
	"crypto/hmac"
	"crypto/md5"
	"encoding/json"
	"fmt"
	"html/template"
	"io"
	"net/http"
	"regexp"
	"sort"
	"strconv"
	"strings"
	"sync"
	"time"

	"golang.org/x/net/context"

	"google.golang.org/appengine"
	"google.golang.org/appengine/datastore"
	"google.golang.org/appengine/log"
	"google.golang.org/appengine/memcache"
	)

	const (
	downloadBaseURL = "https://dl.google.com/go/"
	cacheKey = "download_list_3" // increment if listTemplateData changes
	cacheDuration = time.Hour
	)

	func RegisterHandlers(mux *http.ServeMux) {
	mux.Handle("/dl", http.RedirectHandler("/dl/", http.StatusFound))
	mux.HandleFunc("/dl/", getHandler) // also serves listHandler
	mux.HandleFunc("/dl/upload", uploadHandler)
	mux.HandleFunc("/dl/init", initHandler)
	}

	type File struct {
	Filename string
	OS string
	Arch string
	Version string
	Checksum string `datastore:",noindex"` // SHA1; deprecated
	ChecksumSHA256 string `datastore:",noindex"`
	Size int64 `datastore:",noindex"`
	Kind string // "archive", "installer", "source"
	Uploaded time.Time
	}

	func (f File) ChecksumType() string {
	if f.ChecksumSHA256 != "" {
	return "SHA256"
	}
	return "SHA1"
	}

	func (f File) PrettyChecksum() string {
	if f.ChecksumSHA256 != "" {
	return f.ChecksumSHA256
	}
	return f.Checksum
	}

	func (f File) PrettyOS() string {
	if f.OS == "darwin" {
	switch {
	case strings.Contains(f.Filename, "osx10.8"):
	return "OS X 10.8+"
	case strings.Contains(f.Filename, "osx10.6"):
	return "OS X 10.6+"
	}
	}
	return pretty(f.OS)
	}

	func (f File) PrettySize() string {
	const mb = 1 << 20
	if f.Size == 0 {
	return ""
	}
	if f.Size < mb {
	// All Go releases are >1mb, but handle this case anyway.
	return fmt.Sprintf("%v bytes", f.Size)
	}
	return fmt.Sprintf("%.0fMB", float64(f.Size)/mb)
	}

	var primaryPorts = map[string]bool{
	"darwin/amd64": true,
	"linux/386": true,
	"linux/amd64": true,
	"linux/armv6l": true,
	"windows/386": true,
	"windows/amd64": true,
	}

	func (f File) PrimaryPort() bool {
	if f.Kind == "source" {
	return true
	}
	return primaryPorts[f.OS+"/"+f.Arch]
	}

	func (f File) Highlight() bool {
	switch {
	case f.Kind == "source":
	return true
	case f.Arch == "amd64" && f.OS == "linux":
	return true
	case f.Arch == "amd64" && f.Kind == "installer":
	switch f.OS {
	case "windows":
	return true
	case "darwin":
	if !strings.Contains(f.Filename, "osx10.6") {
	return true
	}
	}
	}
	return false
	}

	func (f File) URL() string {
	return downloadBaseURL + f.Filename
	}

	type Release struct {
	Version string
	Stable bool
	Files []File
	Visible bool // show files on page load
	SplitPortTable bool // whether files should be split by primary/other ports.
	}

	type Feature struct {
	// The File field will be filled in by the first stable File
	// whose name matches the given fileRE.
	File
	fileRE *regexp.Regexp

	Platform string // "Microsoft Windows", "Apple macOS", "Linux"
	Requirements string // "Windows XP and above, 64-bit Intel Processor"
	}

	// featuredFiles lists the platforms and files to be featured
	// at the top of the downloads page.
	var featuredFiles = []Feature{
	{
	Platform: "Microsoft Windows",
	Requirements: "Windows XP SP2 or later, Intel 64-bit processor",
	fileRE: regexp.MustCompile(`\.windows-amd64\.msi$`),
	},
	{
	Platform: "Apple macOS",
	Requirements: "macOS 10.8 or later, Intel 64-bit processor",
	fileRE: regexp.MustCompile(`\.darwin-amd64(-osx10\.8)?\.pkg$`),
	},
	{
	Platform: "Linux",
	Requirements: "Linux 2.6.23 or later, Intel 64-bit processor",
	fileRE: regexp.MustCompile(`\.linux-amd64\.tar\.gz$`),
	},
	{
	Platform: "Source",
	fileRE: regexp.MustCompile(`\.src\.tar\.gz$`),
	},
	}

	// data to send to the template; increment cacheKey if you change this.
	type listTemplateData struct {
	Featured []Feature
	Stable, Unstable, Archive []Release
	}

	var (
	listTemplate = template.Must(template.New("").Funcs(templateFuncs).Parse(templateHTML))
	templateFuncs = template.FuncMap{"pretty": pretty}
	)

	func listHandler(w http.ResponseWriter, r *http.Request) {
	if r.Method != "GET" {
	http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
	return
	}
	var (
	c = appengine.NewContext(r)
	d listTemplateData
	)
	if _, err := memcache.Gob.Get(c, cacheKey, &d); err != nil {
	if err == memcache.ErrCacheMiss {
	log.Debugf(c, "cache miss")
	} else {
	log.Errorf(c, "cache get error: %v", err)
	}

	var fs []File
	_, err := datastore.NewQuery("File").Ancestor(rootKey(c)).GetAll(c, &fs)
	if err != nil {
	log.Errorf(c, "error listing: %v", err)
	return
	}
	d.Stable, d.Unstable, d.Archive = filesToReleases(fs)
	if len(d.Stable) > 0 {
	d.Featured = filesToFeatured(d.Stable[0].Files)
	}

	item := &memcache.Item{Key: cacheKey, Object: &d, Expiration: cacheDuration}
	if err := memcache.Gob.Set(c, item); err != nil {
	log.Errorf(c, "cache set error: %v", err)
	}
	}
	if err := listTemplate.ExecuteTemplate(w, "root", d); err != nil {
	log.Errorf(c, "error executing template: %v", err)
	}
	}

	func filesToFeatured(fs []File) (featured []Feature) {
	for _, feature := range featuredFiles {
	for _, file := range fs {
	if feature.fileRE.MatchString(file.Filename) {
	feature.File = file
	featured = append(featured, feature)
	break
	}
	}
	}
	return
	}

	func filesToReleases(fs []File) (stable, unstable, archive []Release) {
	sort.Sort(fileOrder(fs))

	var r *Release
	var stableMaj, stableMin int
	add := func() {
	if r == nil {
	return
	}
	if !r.Stable {
	if len(unstable) != 0 {
	// Only show one (latest) unstable version.
	return
	}
	maj, min, _ := parseVersion(r.Version)
	if maj < stableMaj \|\| maj == stableMaj && min <= stableMin {
	// Display unstable version only if newer than the
	// latest stable release.
	return
	}
	unstable = append(unstable, *r)
	}

	// Reports whether the release is the most recent minor version of the
	// two most recent major versions.
	shouldAddStable := func() bool {
	if len(stable) >= 2 {
	// Show up to two stable versions.
	return false
	}
	if len(stable) == 0 {
	// Most recent stable version.
	stableMaj, stableMin, _ = parseVersion(r.Version)
	return true
	}
	if maj, _, _ := parseVersion(r.Version); maj == stableMaj {
	// Older minor version of most recent major version.
	return false
	}
	// Second most recent stable version.
	return true
	}
	if !shouldAddStable() {
	archive = append(archive, *r)
	return
	}

	// Split the file list into primary/other ports for the stable releases.
	// NOTE(cbro): This is only done for stable releases because maintaining the historical
	// nature of primary/other ports for older versions is infeasible.
	// If freebsd is considered primary some time in the future, we'd not want to
	// mark all of the older freebsd binaries as "primary".
	// It might be better if we set that as a flag when uploading.
	r.SplitPortTable = true
	r.Visible = true // Toggle open all stable releases.
	stable = append(stable, *r)
	}
	for _, f := range fs {
	if r == nil \|\| f.Version != r.Version {
	add()
	r = &Release{
	Version: f.Version,
	Stable: isStable(f.Version),
	}
	}
	r.Files = append(r.Files, f)
	}
	add()
	return
	}

	// isStable reports whether the version string v is a stable version.
	func isStable(v string) bool {
	return !strings.Contains(v, "beta") && !strings.Contains(v, "rc")
	}

	type fileOrder []File

	func (s fileOrder) Len() int { return len(s) }
	func (s fileOrder) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
	func (s fileOrder) Less(i, j int) bool {
	a, b := s[i], s[j]
	if av, bv := a.Version, b.Version; av != bv {
	return versionLess(av, bv)
	}
	if a.OS != b.OS {
	return a.OS < b.OS
	}
	if a.Arch != b.Arch {
	return a.Arch < b.Arch
	}
	if a.Kind != b.Kind {
	return a.Kind < b.Kind
	}
	return a.Filename < b.Filename
	}

	func versionLess(a, b string) bool {
	// Put stable releases first.
	if isStable(a) != isStable(b) {
	return isStable(a)
	}
	maja, mina, ta := parseVersion(a)
	majb, minb, tb := parseVersion(b)
	if maja == majb {
	if mina == minb {
	return ta >= tb
	}
	return mina >= minb
	}
	return maja >= majb
	}

	func parseVersion(v string) (maj, min int, tail string) {
	if i := strings.Index(v, "beta"); i > 0 {
	tail = v[i:]
	v = v[:i]
	}
	if i := strings.Index(v, "rc"); i > 0 {
	tail = v[i:]
	v = v[:i]
	}
	p := strings.Split(strings.TrimPrefix(v, "go1."), ".")
	maj, _ = strconv.Atoi(p[0])
	if len(p) < 2 {
	return
	}
	min, _ = strconv.Atoi(p[1])
	return
	}

	func uploadHandler(w http.ResponseWriter, r *http.Request) {
	if r.Method != "POST" {
	http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
	return
	}
	c := appengine.NewContext(r)

	// Authenticate using a user token (same as gomote).
	user := r.FormValue("user")
	if !validUser(user) {
	http.Error(w, "bad user", http.StatusForbidden)
	return
	}
	if r.FormValue("key") != userKey(c, user) {
	http.Error(w, "bad key", http.StatusForbidden)
	return
	}

	var f File
	defer r.Body.Close()
	if err := json.NewDecoder(r.Body).Decode(&f); err != nil {
	log.Errorf(c, "error decoding upload JSON: %v", err)
	http.Error(w, "Something broke", http.StatusInternalServerError)
	return
	}
	if f.Filename == "" {
	http.Error(w, "Must provide Filename", http.StatusBadRequest)
	return
	}
	if f.Uploaded.IsZero() {
	f.Uploaded = time.Now()
	}
	k := datastore.NewKey(c, "File", f.Filename, 0, rootKey(c))
	if _, err := datastore.Put(c, k, &f); err != nil {
	log.Errorf(c, "putting File entity: %v", err)
	http.Error(w, "could not put File entity", http.StatusInternalServerError)
	return
	}
	if err := memcache.Delete(c, cacheKey); err != nil {
	log.Errorf(c, "cache delete error: %v", err)
	}
	io.WriteString(w, "OK")
	}

	func getHandler(w http.ResponseWriter, r *http.Request) {
	name := strings.TrimPrefix(r.URL.Path, "/dl/")
	if name == "" {
	listHandler(w, r)
	return
	}
	if !fileRe.MatchString(name) {
	http.NotFound(w, r)
	return
	}
	http.Redirect(w, r, downloadBaseURL+name, http.StatusFound)
	}

	func validUser(user string) bool {
	switch user {
	case "adg", "bradfitz", "cbro", "andybons":
	return true
	}
	return false
	}

	func userKey(c context.Context, user string) string {
	h := hmac.New(md5.New, []byte(secret(c)))
	h.Write([]byte("user-" + user))
	return fmt.Sprintf("%x", h.Sum(nil))
	}

	var fileRe = regexp.MustCompile(`^go[0-9a-z.]+\.[0-9a-z.-]+\.(tar\.gz\|pkg\|msi\|zip)$`)

	func initHandler(w http.ResponseWriter, r *http.Request) {
	var fileRoot struct {
	Root string
	}
	c := appengine.NewContext(r)
	k := rootKey(c)
	err := datastore.RunInTransaction(c, func(c context.Context) error {
	err := datastore.Get(c, k, &fileRoot)
	if err != nil && err != datastore.ErrNoSuchEntity {
	return err
	}
	_, err = datastore.Put(c, k, &fileRoot)
	return err
	}, nil)
	if err != nil {
	http.Error(w, err.Error(), 500)
	return
	}
	io.WriteString(w, "OK")
	}

	// rootKey is the ancestor of all File entities.
	func rootKey(c context.Context) *datastore.Key {
	return datastore.NewKey(c, "FileRoot", "root", 0, nil)
	}

	// pretty returns a human-readable version of the given OS, Arch, or Kind.
	func pretty(s string) string {
	t, ok := prettyStrings[s]
	if !ok {
	return s
	}
	return t
	}

	var prettyStrings = map[string]string{
	"darwin": "macOS",
	"freebsd": "FreeBSD",
	"linux": "Linux",
	"windows": "Windows",

	"386": "x86",
	"amd64": "x86-64",
	"armv6l": "ARMv6",
	"arm64": "ARMv8",

	"archive": "Archive",
	"installer": "Installer",
	"source": "Source",
	}

	// Code below copied from x/build/app/key

	var theKey struct {
	sync.RWMutex
	builderKey
	}

	type builderKey struct {
	Secret string
	}

	func (k builderKey) Key(c context.Context) datastore.Key {
	return datastore.NewKey(c, "BuilderKey", "root", 0, nil)
	}

	func secret(c context.Context) string {
	// check with rlock
	theKey.RLock()
	k := theKey.Secret
	theKey.RUnlock()
	if k != "" {
	return k
	}

	// prepare to fill; check with lock and keep lock
	theKey.Lock()
	defer theKey.Unlock()
	if theKey.Secret != "" {
	return theKey.Secret
	}

	// fill
	if err := datastore.Get(c, theKey.Key(c), &theKey.builderKey); err != nil {
	if err == datastore.ErrNoSuchEntity {
	// If the key is not stored in datastore, write it.
	// This only happens at the beginning of a new deployment.
	// The code is left here for SDK use and in case a fresh
	// deployment is ever needed. "gophers rule" is not the
	// real key.
	if !appengine.IsDevAppServer() {
	panic("lost key from datastore")
	}
	theKey.Secret = "gophers rule"
	datastore.Put(c, theKey.Key(c), &theKey.builderKey)
	return theKey.Secret
	}
	panic("cannot load builder key: " + err.Error())
	}

	return theKey.Secret
	}