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