mirror of
https://github.com/matrix-construct/construct
synced 2024-06-28 14:58:20 +02:00
39 lines
872 B
C++
39 lines
872 B
C++
// Matrix Construct
|
|
//
|
|
// Copyright (C) Matrix Construct Developers, Authors & Contributors
|
|
// Copyright (C) 2016-2021 Jason Volk <jason@zemos.net>
|
|
//
|
|
// Permission to use, copy, modify, and/or distribute this software for any
|
|
// purpose with or without fee is hereby granted, provided that the above
|
|
// copyright notice and this permission notice is present in all copies. The
|
|
// full license for this software is available in the LICENSE file.
|
|
|
|
#pragma once
|
|
#define HAVE_IRCD_MATH_INV_H
|
|
|
|
namespace ircd::math
|
|
{
|
|
template<class Z> constexpr Z inv(Z a, const Z m);
|
|
}
|
|
|
|
/// Modular Inverse
|
|
template<class Z>
|
|
inline constexpr Z
|
|
ircd::math::inv(Z a,
|
|
const Z m)
|
|
{
|
|
auto b{m}, x0{0}, x1{1};
|
|
if(likely(m != 1)) while(a > 1)
|
|
{
|
|
auto t{b}, q{a / b};
|
|
b = a % b;
|
|
a = t;
|
|
t = x0;
|
|
x0 = x1 - q * x0;
|
|
x1 = t;
|
|
}
|
|
|
|
x1 += boolmask<Z>(x1 < 0) & m;
|
|
return x1;
|
|
}
|