jcs.org
Serenity Operating System
1/*
2 * Copyright (c) 2022, Leon Albrecht <leon2002.la@gmail.com>
3 *
4 * SPDX-License-Identifier: BSD-2-Clause
5 */
6
7#pragma once
8
9#include <AK/BuiltinWrappers.h>
10#include <AK/Concepts.h>
11#include <AK/Types.h>
12
13namespace AK {
14
15template<Integral T>
16constexpr T exp2(T exponent)
17{
18 return 1u << exponent;
19}
20
21template<Integral T>
22constexpr T log2(T x)
23{
24 return x ? (8 * sizeof(T) - 1) - count_leading_zeroes(static_cast<MakeUnsigned<T>>(x)) : 0;
25}
26
27template<Integral T>
28constexpr T ceil_log2(T x)
29{
30 if (!x)
31 return 0;
32
33 T log = AK::log2(x);
34 log += (x & ((((T)1) << (log - 1)) - 1)) != 0;
35 return log;
36}
37
38template<Integral I>
39constexpr I pow(I base, I exponent)
40{
41 // https://en.wikipedia.org/wiki/Exponentiation_by_squaring
42 if (exponent < 0)
43 return 0;
44 if (exponent == 0)
45 return 1;
46
47 I res = 1;
48 while (exponent > 0) {
49 if (exponent & 1)
50 res *= base;
51 base *= base;
52 exponent /= 2u;
53 }
54 return res;
55}
56
57}