a[0] = b
	for i, l := 1, len(a); i < l; i *= 2 {
		copy(a[i:], a[:i])
	}
}

func (r *rleBuffer) ReadAt(p []byte, off int64) (n int, err error) {
	if len(p) == 0 {
		return
	}
	skipParts := sort.Search(len(r.buf), func(i int) bool {
		part := &r.buf[i]
		return part.off+part.n > off
	})
	parts := r.buf[skipParts:]
	if len(parts) > 0 {
		skipBytes := off - parts[0].off
		for _, part := range parts {