server: write tarball in 4 MiB chunks

server/server.go

@@ -166,17 +166,19 @@ func handleArtistAlbumPage(w http.ResponseWriter, req *http.Request) {
 		if musicindex.ArtistExists(artist) {
 			album, ok := musicindex.FindArtist(artist).Albums[albumName]
 			if ok {
-				contents, err := os.ReadFile(album.Tarball)
-
+				f, err := os.Open(album.Tarball)
 				if err != nil {
-					http.Error(w, err.Error(), http.StatusNotFound)
+					http.Error(w, "internal server error: " + err.Error(),
+						http.StatusInternalServerError)
 					return
 				}
+				defer f.Close()
+
 				w.Header().Set("Content-Disposition", `attachment; filename="` +
 					strings.ReplaceAll(album.Name, `"`, `'`) + `.tar.gz"`)
 				w.Header().Set("Content-Length",
 					fmt.Sprintf("%d", album.TarballSize))
-				w.Write(contents)
+				util.DoChunks(f, 4 * 1024, func (buf []byte) { w.Write(buf) })
 				return
 			}
 		}