server: write tarball in 4 MiB chunks

server/server.go

@@ -1,6 +1,7 @@
 package server
 
 import (
+	"fmt"
 	"log"
 	"os"
 	"regexp"
@@ -102,12 +103,14 @@ func serveMediaDirectory(w http.ResponseWriter, req *http.Request) {
 		http.Error(w, "is a directory; maybe you are looking for " + path, http.StatusForbidden)
 		return
 	}
+
 	f, err := os.Open(filePath)
 	if err != nil {
 		http.Error(w, "not found", http.StatusNotFound)
 		return
 	}
-	util.DoChunks(f, func (buf []byte) { w.Write(buf) })
+	defer f.Close()
+	util.DoChunks(f, 4, func (buf []byte) { w.Write(buf) })
 }
 
 func handleArtistAlbumPage(w http.ResponseWriter, req *http.Request) {
@@ -163,15 +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.Write(contents)
+				w.Header().Set("Content-Length",
+					fmt.Sprintf("%d", album.TarballSize))
+				util.DoChunks(f, 4 * 1024, func (buf []byte) { w.Write(buf) })
 				return
 			}
 		}

util/util.go

@@ -26,6 +26,7 @@ func Dirents(dir string) (entries []string, err error) {
 	if err != nil {
 		return nil, errors.New(err.Error())
 	}
+	defer d.Close()
 
 	names, err := d.Readdirnames(0)
 	if err != nil {
@@ -39,11 +40,11 @@ func Dirents(dir string) (entries []string, err error) {
 	return
 }
 
-func DoChunks(f io.Reader, fun func (buf []byte)) (err error) {
+func DoChunks(f io.Reader, kib uint, fun func (buf []byte)) (err error) {
 	err = nil
 	bytes, chunks := int64(0), int64(0)
 	r := bufio.NewReader(f)
-	buf := make([]byte, 0, 4*1024)
+	buf := make([]byte, 0, kib * 1024)
 
 	for {
 		var n int