fix small Read() big rate for slow.Reader

src/asses/one.go

@@ -11,9 +11,23 @@ import (
 	"os"
 	"path"
 	"show-rss/src/slow"
+   "strconv"
+   "golang.org/x/time/rate"
 	"time"
 )
 
+var EnvCksumBPS = func() int {
+   s := os.Getenv("CKSUM_BPS")
+   if s == "" {
+      return 50_000_000
+   }
+   n, err := strconv.Atoi(s)
+   if err != nil || n < 1 {
+      panic(err)
+   }
+   return n
+}()
+
 func One(ctx context.Context, p string) error {
 	shortp := path.Join("...", path.Base(path.Dir(p)), path.Base(p))
 
@@ -86,6 +100,6 @@ func Cksum(ctx context.Context, p string) (string, error) {
 	defer f.Close()
 
 	hasher := md5.New()
-	_, err = io.Copy(hasher, slow.NewReader(ctx, 50_000_000, f))
+	_, err = io.Copy(hasher, slow.NewReader(ctx, rate.Limit(EnvCksumBPS), f))
 	return base64.StdEncoding.EncodeToString(hasher.Sum(nil)), err
 }

src/asses/one_test.go

@@ -17,20 +17,24 @@ func TestOne(t *testing.T) {
 	p := path.Join(d, "f.mkv")
 	os.WriteFile(p, b, os.ModePerm)
 
+	t.Logf("initial cksum...")
 	cksum, _ := asses.Cksum(context.Background(), p)
 
+	t.Logf("one && one...")
 	if err := asses.One(ctx, p); err != nil {
 		t.Fatal(err)
 	} else if err := asses.One(ctx, p); err != nil {
 		t.Fatal(err)
 	}
 
+	t.Logf("test -f...")
 	if _, err := os.Stat(p); err != nil {
 		t.Fatalf("lost original mkv: %v", err)
 	} else if _, err := os.Stat(path.Join(d, "f.srt")); err != nil {
 		t.Fatalf("no new srt: %v", err)
 	}
 
+	t.Logf("final cksum...")
 	newCksum, _ := asses.Cksum(context.Background(), p)
 	if cksum == newCksum {
 		t.Fatalf("cksum unchanged")

src/slow/reader.go

@@ -9,30 +9,36 @@ import (
 
 type Reader struct {
 	ctx     context.Context
-	limiter *rate.Limiter
+	limiter rate.Limiter
 	r       io.Reader
 }
 
-var _ io.Reader = Reader{}
+var _ io.Reader = &Reader{}
 
-func NewReader(ctx context.Context, bps rate.Limit, r io.Reader) Reader {
-	return Reader{
+func NewReader(ctx context.Context, bps rate.Limit, r io.Reader) *Reader {
+	return &Reader{
 		ctx:     ctx,
-		limiter: rate.NewLimiter(bps, int(bps)),
+		limiter: *rate.NewLimiter(bps, int(bps)),
 		r:       r,
 	}
 }
 
-func (r Reader) Read(b []byte) (int, error) {
+func (r *Reader) Read(b []byte) (int, error) {
 	n, err := r.r.Read(b)
 
 	m := 0
 	burst := r.limiter.Burst()
 	for m < n {
-		if err := r.limiter.WaitN(r.ctx, burst); err != nil {
+		page := burst
+		if left := n - m; page > left {
+			page = left
+		}
+
+		if err := r.limiter.WaitN(r.ctx, page); err != nil {
 			return n, err
 		}
-		m += burst
+
+		m += page
 	}
 
 	return n, err