1# Copyright 2021 Google LLC 2# 3# Licensed under the Apache License, Version 2.0 (the "License"); 4# you may not use this file except in compliance with the License. 5# You may obtain a copy of the License at 6# 7# http://www.apache.org/licenses/LICENSE-2.0 8# 9# Unless required by applicable law or agreed to in writing, software 10# distributed under the License is distributed on an "AS IS" BASIS, 11# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12# See the License for the specific language governing permissions and 13# limitations under the License. 14"""This module contains some utility functions for big integers.""" 15 16 17def num_to_bytes(n: int) -> bytes: 18 """Converts a non-negative n into an unsigned big integer in big-endian.""" 19 if n < 0: 20 raise OverflowError("number can't be negative") 21 if n == 0: 22 return b'\x00' 23 return n.to_bytes((n.bit_length() + 7) // 8, byteorder='big') 24