forked from electricdusk/rushlink
Implement retrieval of redirects
This commit is contained in:
Daan Sprenkels
236
handlers.go
Normal file
236
handlers.go
Normal file
@@ -0,0 +1,236 @@
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package main
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//go:generate go get github.com/go-bindata/go-bindata
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//go:generate go get -u github.com/go-bindata/go-bindata/...
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//go:generate go-bindata -pkg $GOPACKAGE assets/
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import (
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"crypto/rand"
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"fmt"
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"io"
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"log"
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"net/http"
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"net/url"
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"time"
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gobmarsh "gitea.hashru.nl/dsprenkels/rushlink/gobmarsh"
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mux "github.com/gorilla/mux"
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errors "github.com/pkg/errors"
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bolt "go.etcd.io/bbolt"
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)
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type StoredURLState int
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type StoredURL struct {
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State StoredURLState
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RawURL string
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Key []byte
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TimeCreated time.Time
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}
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const (
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Present StoredURLState = iota
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Deleted
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)
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var base64Alphabet = []byte("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_")
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var indexContents = MustAsset("assets/index.txt")
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func indexGetHandler(w http.ResponseWriter, r *http.Request) {
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_, err := w.Write(indexContents)
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if err != nil {
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panic(err)
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}
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}
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func indexPostHandler(w http.ResponseWriter, r *http.Request) {
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if err := r.ParseMultipartForm(50 * 1000 * 1000); err != nil {
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w.WriteHeader(http.StatusInternalServerError)
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fmt.Fprintf(w, "Internal server error: %v", err)
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return
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}
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// Determine what kind of post this is, currently only `shorten=...`
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if len(r.PostForm) == 0 {
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w.WriteHeader(http.StatusBadRequest)
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var buf []byte
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r.Body.Read(buf)
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io.WriteString(w, "empty body in POST request")
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return
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}
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shorten_values, prs := r.PostForm["shorten"]
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if !prs {
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w.WriteHeader(http.StatusBadRequest)
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io.WriteString(w, "no 'shorten' param supplied")
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return
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}
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if len(shorten_values) != 1 {
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w.WriteHeader(http.StatusBadRequest)
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io.WriteString(w, "only one 'shorten' param is allowed per request")
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return
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}
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shortenPostHandler(w, r)
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}
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func redirectHandler(w http.ResponseWriter, r *http.Request) {
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vars := mux.Vars(r)
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key := vars["key"]
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var storedURL *StoredURL
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if err := db.View(func(tx *bolt.Tx) error {
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var err error
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storedURL, err = getURL(tx, []byte(key))
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return err
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}); err != nil {
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w.WriteHeader(http.StatusInternalServerError)
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log.Printf("error: %v\n", err)
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fmt.Fprintf(w, "internal server error: %v", err)
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return
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}
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if storedURL == nil {
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w.WriteHeader(http.StatusNotFound)
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fmt.Fprintf(w, "url key not found in the database")
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}
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switch storedURL.State {
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case Present:
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w.Header().Set("Location", storedURL.RawURL)
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w.WriteHeader(http.StatusTemporaryRedirect)
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case Deleted:
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w.WriteHeader(http.StatusGone)
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fmt.Fprintf(w, "key has been deleted")
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default:
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w.WriteHeader(http.StatusInternalServerError)
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log.Printf("error: invalid storedURL.State (%v) for key '%v'\n", storedURL.State, storedURL.Key)
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fmt.Fprintf(w, "internal server error: invalid storedURL.State (%v)", storedURL.State)
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}
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}
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func shortenPostHandler(w http.ResponseWriter, r *http.Request) {
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rawurl := r.PostForm.Get("shorten")
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userURL, err := url.ParseRequestURI(rawurl)
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if err != nil {
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w.WriteHeader(http.StatusBadRequest)
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fmt.Fprintf(w, "invalid url (%v): %v", err, rawurl)
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return
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}
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if userURL.Scheme == "" {
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w.WriteHeader(http.StatusBadRequest)
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fmt.Fprintf(w, "invalid url (unspecified scheme)", rawurl)
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return
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}
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if userURL.Host == "" {
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w.WriteHeader(http.StatusBadRequest)
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fmt.Fprintf(w, "invalid url (unspecified host)", rawurl)
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return
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}
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var storedURL *StoredURL
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if err := db.Update(func(tx *bolt.Tx) error {
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u, err := shortenURL(tx, userURL)
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storedURL = u
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return err
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}); err != nil {
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w.WriteHeader(http.StatusInternalServerError)
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log.Printf("error: %v\n", err)
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fmt.Fprintf(w, "internal server error: %v", err)
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return
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}
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w.WriteHeader(http.StatusOK)
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fmt.Fprintf(w, "URL saved at /%v", string(storedURL.Key))
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}
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// Retrieve a URL from the database
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func getURL(tx *bolt.Tx, key []byte) (*StoredURL, error) {
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shortenBucket := tx.Bucket([]byte(BUCKET_SHORTEN))
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if shortenBucket == nil {
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return nil, fmt.Errorf("bucket %v does not exist", BUCKET_SHORTEN)
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}
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storedBytes := shortenBucket.Get(key)
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if storedBytes == nil {
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return nil, nil
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}
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storedURL := &StoredURL{}
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err := gobmarsh.Unmarshal(storedBytes, storedURL)
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return storedURL, err
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}
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// Add a new URL to the database
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//
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// Returns the new ID if the url was successfully shortened
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func shortenURL(tx *bolt.Tx, userURL *url.URL) (*StoredURL, error) {
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shortenBucket := tx.Bucket([]byte(BUCKET_SHORTEN))
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if shortenBucket == nil {
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return nil, fmt.Errorf("bucket %v does not exist", BUCKET_SHORTEN)
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}
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// Generate a key until it is not in the database, this occurs in O(log N),
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// where N is the amount of keys stored in the url-shorten database.
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epoch := 0
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var urlKey []byte
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for {
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var err error
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urlKey, err = generateURLKey(epoch)
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if err != nil {
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return nil, errors.Wrap(err, "url-key generation failed")
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}
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found := shortenBucket.Get(urlKey)
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if found == nil {
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break
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}
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epoch++
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}
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// Store the new key
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storedURL := StoredURL{
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State: Present,
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RawURL: userURL.String(),
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Key: urlKey,
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TimeCreated: time.Now().UTC(),
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}
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storedBytes, err := gobmarsh.Marshal(storedURL)
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if err != nil {
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return nil, errors.Wrap(err, "encoding for database failed")
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}
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if err := shortenBucket.Put(urlKey, storedBytes); err != nil {
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return nil, errors.Wrap(err, "database transaction failed")
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}
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return &storedURL, nil
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}
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func generateURLKey(epoch int) ([]byte, error) {
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urlKey := make([]byte, 4+epoch)
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_, err := rand.Read(urlKey)
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if err != nil {
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return nil, err
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}
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// Put all the values in the range 0..64 for easier base64-encoding
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for i := 0; i < len(urlKey); i++ {
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urlKey[i] &= 0x3F
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}
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// Implement truncate-resistance by forcing the prefix to
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// 0b111110xxxxxxxxxx
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// ^----- {epoch} ones followed by a single 0
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//
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// Example when epoch is 1: prefix is 0b10.
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i := 0
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for i < epoch {
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// Set this bit to 1
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limb := i / 6
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bit := i % 6
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urlKey[limb] |= 1 << uint(5-bit)
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i++
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}
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// Finally set the next bit to 0
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limb := i / 6
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bit := i % 6
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urlKey[limb] &= ^(1 << uint(5-bit))
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// Convert this ID to a canonical base64 notation
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for i := range urlKey {
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urlKey[i] = base64Alphabet[urlKey[i]]
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}
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return urlKey, nil
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}
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