for i, cache, remain := n-1, src.Int63(), letterIdxMax; i >= 0; {
		if remain == 0 {
			cache, remain = src.Int63(), letterIdxMax
		}
		if idx := int(cache & letterIdxMask); idx < len(letterBytes) {
			b[i] = letterBytes[idx]
			i--
		}
		cache >>= letterIdxBits
		remain--
	}

	return *(*string)(unsafe.Pointer(&b))
}