FSHandler optimization: added WriteTo to fsFileReader. This should speed up io.Copy() from fsFileReader

fshandler.go

@@ -140,20 +140,40 @@ func (r *fsFileReader) Close() error {
 }
 
 func (r *fsFileReader) Read(p []byte) (int, error) {
-	if r.ff.f != nil {
-		n, err := r.ff.f.ReadAt(p, r.offset)
+	ff := r.ff
+
+	if ff.f != nil {
+		n, err := ff.f.ReadAt(p, r.offset)
 		r.offset += int64(n)
 		return n, err
 	}
 
-	if r.offset == int64(len(r.ff.dirIndex)) {
+	if r.offset == int64(len(ff.dirIndex)) {
 		return 0, io.EOF
 	}
-	n := copy(p, r.ff.dirIndex[r.offset:])
+	n := copy(p, ff.dirIndex[r.offset:])
 	r.offset += int64(n)
 	return n, nil
 }
 
+func (r *fsFileReader) WriteTo(w io.Writer) (int64, error) {
+	if r.offset != 0 {
+		panic("BUG: WriteTo must not be called after Read")
+	}
+
+	ff := r.ff
+
+	var err error
+	if ff.f != nil {
+		r.offset, err = copyZeroAlloc(w, ff.f)
+	} else {
+		var n int
+		n, err = w.Write(ff.dirIndex)
+		r.offset = int64(n)
+	}
+	return r.offset, err
+}
+
 func (h *fsHandler) cleanCache() {
 	t := time.Now()
 	h.cacheLock.Lock()

fshandler_test.go

@@ -91,6 +91,7 @@ func fsHandlerTest(t *testing.T, requestHandler RequestHandler, filenames []stri
 		}
 
 		ctx.URI().Update(name)
+		ctx.Response.Reset()
 		requestHandler(&ctx)
 		if ctx.Response.bodyStream == nil {
 			t.Fatalf("response body stream must be non-empty")
@@ -107,7 +108,23 @@ func fsHandlerTest(t *testing.T, requestHandler RequestHandler, filenames []stri
 			break
 		}
 	}
+
+	// verify index
+	ctx.URI().Update("/")
+	ctx.Response.Reset()
+	requestHandler(&ctx)
+	if ctx.Response.bodyStream == nil {
+		t.Fatalf("response body stream must be non-empty")
+	}
+	body, err := ioutil.ReadAll(ctx.Response.bodyStream)
+	if err != nil {
+		t.Fatalf("error when reading response body stream: %s", err)
+	}
+	if len(body) == 0 {
+		t.Fatalf("empty index file")
+	}
 }
+
 func TestStripPathSlashes(t *testing.T) {
 	testStripPathSlashes(t, "", 0, "")
 	testStripPathSlashes(t, "", 10, "")

http.go

@@ -543,28 +543,8 @@ func writeBodyChunked(w *bufio.Writer, r io.Reader) error {
 	return err
 }
 
-var limitReaderPool sync.Pool
-
 func writeBodyFixedSize(w *bufio.Writer, r io.Reader, size int) error {
-	vbuf := copyBufPool.Get()
-	if vbuf == nil {
-		vbuf = make([]byte, 4096)
-	}
-	buf := vbuf.([]byte)
-
-	vlr := limitReaderPool.Get()
-	if vlr == nil {
-		vlr = &io.LimitedReader{}
-	}
-	lr := vlr.(*io.LimitedReader)
-	lr.R = r
-	lr.N = int64(size)
-
-	n, err := io.CopyBuffer(w, lr, buf)
-
-	limitReaderPool.Put(vlr)
-	copyBufPool.Put(vbuf)
-
+	n, err := copyZeroAlloc(w, r)
 	if n != int64(size) && err == nil {
 		err = fmt.Errorf("read %d bytes from BodyStream instead of %d bytes", n, size)
 	}
@@ -580,6 +560,17 @@ func writeChunk(w *bufio.Writer, b []byte) error {
 	return err
 }
 
+func copyZeroAlloc(dst io.Writer, src io.Reader) (int64, error) {
+	vbuf := copyBufPool.Get()
+	if vbuf == nil {
+		vbuf = make([]byte, 4096)
+	}
+	buf := vbuf.([]byte)
+	n, err := io.CopyBuffer(dst, src, buf)
+	copyBufPool.Put(vbuf)
+	return n, err
+}
+
 var copyBufPool sync.Pool
 
 // ErrBodyTooLarge is returned if either request or response body exceeds