bulkBarrierPreWriteSrcOnly(uintptr(p), uintptr(oldPtr), lenmem-et.Size_+et.PtrBytes, et)
		}
	}
	memmove(p, oldPtr, lenmem)

	return slice{p, newLen, newcap}
}

// nextslicecap computes the next appropriate slice length.
func nextslicecap(newLen, oldCap int) int {
	newcap := oldCap
	doublecap := newcap + newcap
	if newLen > doublecap {
		return newLen
	}

	const threshold = 256
	if oldCap < threshold {

			"bucketMask",
			"bucketShift",
			"chanbuf",
			"evacuated",
			"fastlog2",
			"float64bits",
			"funcspdelta",
			"getm",
			"getMCache",
			"isDirectIface",
			"itabHashFunc",
			"nextslicecap",
			"noescape",
			"pcvalueCacheKey",
			"rand32",
			"readUnaligned32",
			"readUnaligned64",
			"releasem",
			"roundupsize",
			"stackmapdata",
			"stringStructOf",
			"subtract1",

		got, err := ReadDataAt(sr, 0, 0)
		if err != nil {
			t.Fatal(err)
		}
		if len(got) > 0 {
			t.Errorf("got %d bytes, expected 0", len(got))
		}
	})
}

func TestSliceCap(t *testing.T) {
	t.Run("small", func(t *testing.T) {
		c := SliceCap[int](10)
		if c != 10 {
			t.Errorf("got capacity %d, want %d", c, 10)
		}
	})

	t.Run("large", func(t *testing.T) {