Change blobref.SeekerFromStreamingFetcher signature to not return an error.

Change-Id: I77f693e3b3d0d116e08bca3d3f4cb45ef2a00b27

cmd/camget/camget.go

@@ -106,7 +106,7 @@ func main() {
 			var rc io.ReadCloser
 			var err error
 			if *flagContents {
-				seekFetcher, _ := blobref.SeekerFromStreamingFetcher(cl)
+				seekFetcher := blobref.SeekerFromStreamingFetcher(cl)
 				rc, err = schema.NewFileReader(seekFetcher, br)
 			} else {
 				rc, err = fetch(cl, br)
@@ -213,7 +213,7 @@ func smartFetch(cl *client.Client, targ string, br *blobref.BlobRef) error {
 			return fmt.Errorf("file type: %v", err)
 		}
 		defer f.Close()
-		seekFetcher, _ := blobref.SeekerFromStreamingFetcher(cl)
+		seekFetcher := blobref.SeekerFromStreamingFetcher(cl)
 		fr, err := schema.NewFileReader(seekFetcher, br)
 		if err != nil {
 			return fmt.Errorf("NewFileReader: %v", err)

pkg/blobref/fetcher.go

@@ -187,19 +187,14 @@ func (s *MemoryStore) FetchStreaming(b *BlobRef) (file io.ReadCloser, size int64
 
 // SeekerFromStreamingFetcher returns the most efficient implementation of a seeking fetcher
 // from a provided streaming fetcher.
-func SeekerFromStreamingFetcher(f StreamingFetcher) (SeekFetcher, error) {
-	// TODO(bradfitz): this never returns errors now, so update signature and fix callers.
-	seeker, ok := f.(SeekFetcher)
-	if ok {
-		return seeker, nil
+func SeekerFromStreamingFetcher(f StreamingFetcher) SeekFetcher {
+	if sk, ok := f.(SeekFetcher); ok {
+		return sk
 	}
-	tester, ok := f.(SeekTester)
-	if ok {
-		if tester.IsFetcherASeeker() {
-			return &fetcherToSeekerWrapper{f}, nil
-		}
+	if tester, ok := f.(SeekTester); ok && tester.IsFetcherASeeker() {
+		return &fetcherToSeekerWrapper{f}
 	}
-	return bufferingSeekFetcherWrapper{f}, nil
+	return bufferingSeekFetcherWrapper{f}
 }
 
 // bufferingSeekFetcherWrapper is a SeekFetcher that implements

pkg/index/receive.go

@@ -110,12 +110,7 @@ func (ix *Index) populateMutation(br *blobref.BlobRef, sniffer *BlobSniffer, bm
 //      ss: the parsed file schema blob
 //      bm: keys to populate
 func (ix *Index) populateFile(blobRef *blobref.BlobRef, ss *schema.Superset, bm BatchMutation) error {
-	seekFetcher, err := blobref.SeekerFromStreamingFetcher(ix.BlobSource)
-	if err != nil {
-		return err
-	}
-
-	sha1 := sha1.New()
+	seekFetcher := blobref.SeekerFromStreamingFetcher(ix.BlobSource)
 	fr, err := ss.NewFileReader(seekFetcher)
 	if err != nil {
 		// TODO(bradfitz): propagate up a transient failure
@@ -127,6 +122,7 @@ func (ix *Index) populateFile(blobRef *blobref.BlobRef, ss *schema.Superset, bm
 	}
 	mime, reader := magic.MimeTypeFromReader(fr)
 
+	sha1 := sha1.New()
 	var copyDest io.Writer = sha1
 	var withCopyErr func(error) // or nil
 	if strings.HasPrefix(mime, "image/") {

pkg/server/download.go

@@ -34,7 +34,7 @@ type DownloadHandler struct {
 	ForceMime string // optional
 }
 
-func (dh *DownloadHandler) storageSeekFetcher() (blobref.SeekFetcher, error) {
+func (dh *DownloadHandler) storageSeekFetcher() blobref.SeekFetcher {
 	return blobref.SeekerFromStreamingFetcher(dh.Fetcher) // TODO: pass dh.Cache?
 }
 
@@ -44,13 +44,7 @@ func (dh *DownloadHandler) ServeHTTP(rw http.ResponseWriter, req *http.Request,
 		return
 	}
 
-	fetchSeeker, err := dh.storageSeekFetcher()
-	if err != nil {
-		http.Error(rw, err.Error(), 500)
-		return
-	}
-
-	fr, err := schema.NewFileReader(fetchSeeker, file)
+	fr, err := schema.NewFileReader(dh.storageSeekFetcher(), file)
 	if err != nil {
 		http.Error(rw, "Can't serve file: "+err.Error(), 500)
 		return

pkg/server/filetree.go

@@ -30,7 +30,7 @@ type FileTreeHandler struct {
 	file    *blobref.BlobRef
 }
 
-func (fth *FileTreeHandler) storageSeekFetcher() (blobref.SeekFetcher, error) {
+func (fth *FileTreeHandler) storageSeekFetcher() blobref.SeekFetcher {
 	return blobref.SeekerFromStreamingFetcher(fth.Fetcher) // TODO: pass ih.Cache?
 }
 
@@ -42,14 +42,7 @@ func (fth *FileTreeHandler) ServeHTTP(rw http.ResponseWriter, req *http.Request)
 	ret := make(map[string]interface{})
 	defer httputil.ReturnJSON(rw, ret)
 
-	fetchSeeker, err := fth.storageSeekFetcher()
-	if err != nil {
-		http.Error(rw, "No storageSeekFetcher", 500)
-		log.Printf("getting fetcher: %v\n", err)
-		return
-	}
-
-	de, err := schema.NewDirectoryEntryFromBlobRef(fetchSeeker, fth.file)
+	de, err := schema.NewDirectoryEntryFromBlobRef(fth.storageSeekFetcher(), fth.file)
 	dir, err := de.Directory()
 	if err != nil {
 		http.Error(rw, "Error reading directory", 500)

pkg/server/image.go

@@ -46,7 +46,7 @@ type ImageHandler struct {
 	sc                  ScaledImage // optional cache for scaled images
 }
 
-func (ih *ImageHandler) storageSeekFetcher() (blobref.SeekFetcher, error) {
+func (ih *ImageHandler) storageSeekFetcher() blobref.SeekFetcher {
 	return blobref.SeekerFromStreamingFetcher(ih.Fetcher) // TODO: pass ih.Cache?
 }
 
@@ -97,11 +97,7 @@ func (ih *ImageHandler) cacheScaled(tr io.Reader, name string) error {
 }
 
 func (ih *ImageHandler) cached(br *blobref.BlobRef) (fr *schema.FileReader, err error) {
-	fetchSeeker, err := blobref.SeekerFromStreamingFetcher(ih.Cache)
-	if err != nil {
-		return nil, err
-	}
-
+	fetchSeeker := blobref.SeekerFromStreamingFetcher(ih.Cache)
 	fr, err = schema.NewFileReader(fetchSeeker, br)
 	if err != nil {
 		return nil, err
@@ -151,12 +147,7 @@ func (ih *ImageHandler) scaledCached(buf *bytes.Buffer, file *blobref.BlobRef) (
 func (ih *ImageHandler) scaleImage(buf *bytes.Buffer, file *blobref.BlobRef) (format string, err error) {
 	mw, mh := ih.MaxWidth, ih.MaxHeight
 
-	fetchSeeker, err := ih.storageSeekFetcher()
-	if err != nil {
-		return format, err
-	}
-
-	fr, err := schema.NewFileReader(fetchSeeker, file)
+	fr, err := schema.NewFileReader(ih.storageSeekFetcher(), file)
 	if err != nil {
 		return format, err
 	}