ladybird/AK/IntegralMath.h

89 lines
1.6 KiB
C
Raw Normal View History

/*
* Copyright (c) 2022, Leon Albrecht <leon2002.la@gmail.com>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <AK/BuiltinWrappers.h>
#include <AK/Concepts.h>
#include <AK/Types.h>
namespace AK {
template<Integral T>
constexpr T exp2(T exponent)
{
return static_cast<T>(1) << exponent;
}
template<Integral T>
constexpr T log2(T x)
{
return x ? (8 * sizeof(T) - 1) - count_leading_zeroes(static_cast<MakeUnsigned<T>>(x)) : 0;
}
template<Integral T>
constexpr T ceil_log2(T x)
{
if (x <= 1)
return 0;
return AK::log2(x - 1) + 1;
}
template<Integral I>
constexpr I pow(I base, I exponent)
{
// https://en.wikipedia.org/wiki/Exponentiation_by_squaring
if (exponent < 0)
return 0;
if (exponent == 0)
return 1;
I res = 1;
while (exponent > 0) {
if (exponent & 1)
res *= base;
base *= base;
exponent /= 2u;
}
return res;
}
template<auto base, Unsigned U = decltype(base)>
constexpr bool is_power_of(U x)
{
if constexpr (base == 1)
return x == 1;
else if constexpr (base == 2)
return is_power_of_two(x);
if (base == 0 && x == 0)
return true;
if (base == 0 || x == 0)
return false;
while (x != 1) {
if (x % base != 0)
return false;
x /= base;
}
return true;
}
template<Unsigned T>
constexpr T reinterpret_as_octal(T decimal)
{
T result = 0;
T n = 0;
while (decimal > 0) {
result += pow<T>(8, n++) * (decimal % 10);
decimal /= 10;
}
return result;
}
}