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// Copyright © 2026 Mikhail Hogrefe
//
// Uses code adopted from the GNU MP Library.
//
// Copyright © 1991-1994, 1996, 1997, 1999-2005, 2007-2009, 2011-2020 Free Software
// Foundation, Inc.
//
// This file is part of Malachite.
//
// Malachite is free software: you can redistribute it and/or modify it under the terms of the GNU
// Lesser General Public License (LGPL) as published by the Free Software Foundation; either version
// 3 of the License, or (at your option) any later version. See <https://www.gnu.org/licenses/>.
use crate::num::arithmetic::traits::XXAddYYToZZ;
use crate::num::basic::integers::USIZE_IS_U32;
use crate::num::basic::unsigneds::PrimitiveUnsigned;
use crate::num::conversion::traits::{JoinHalves, SplitInHalf, WrappingFrom};
fn implicit_xx_add_yy_to_zz<DT: JoinHalves + PrimitiveUnsigned + SplitInHalf>(
x_1: DT::Half,
x_0: DT::Half,
y_1: DT::Half,
y_0: DT::Half,
) -> (DT::Half, DT::Half) {
DT::join_halves(x_1, x_0)
.wrapping_add(DT::join_halves(y_1, y_0))
.split_in_half()
}
pub_test! {
explicit_xx_add_yy_to_zz<T: PrimitiveUnsigned>(x_1: T, x_0: T, y_1: T, y_0: T) -> (T, T) {
let (z_0, carry) = x_0.overflowing_add(y_0);
let mut z_1 = x_1.wrapping_add(y_1);
if carry {
z_1.wrapping_add_assign(T::ONE);
}
(z_1, z_0)
}}
macro_rules! implicit_xx_add_yy_to_zz {
($t:ident, $dt:ident) => {
impl XXAddYYToZZ for $t {
/// Adds two numbers, each composed of two `Self` values, returning the sum as a pair of
/// `Self` values.
///
/// The more significant value always comes first. Addition is wrapping, and overflow is
/// not indicated.
///
/// $$
/// f(x_1, x_0, y_1, y_0) = (z_1, z_0),
/// $$
/// where $W$ is `Self::WIDTH`,
///
/// $x_1, x_0, y_1, y_0, z_1, z_0 < 2^W$, and
/// $$
/// (2^Wx_1 + x_0) + (2^Wy_1 + y_0) \equiv 2^Wz_1 + z_0 \mod 2^{2W}.
/// $$
///
/// # Worst-case complexity
/// Constant time and additional memory.
///
/// # Examples
/// See [here](super::xx_add_yy_to_zz#xx_add_yy_to_zz).
///
/// This is equivalent to `add_ssaaaa` from `longlong.h`, GMP 6.2.1, where `(sh, sl)` is
/// returned.
#[inline]
fn xx_add_yy_to_zz(x_1: $t, x_0: $t, y_1: $t, y_0: $t) -> ($t, $t) {
implicit_xx_add_yy_to_zz::<$dt>(x_1, x_0, y_1, y_0)
}
}
};
}
implicit_xx_add_yy_to_zz!(u8, u16);
implicit_xx_add_yy_to_zz!(u16, u32);
implicit_xx_add_yy_to_zz!(u32, u64);
implicit_xx_add_yy_to_zz!(u64, u128);
impl XXAddYYToZZ for usize {
/// Adds two numbers, each composed of two [`usize`] values, returning the sum as a pair of
/// `usize` values.
///
/// The more significant value always comes first. Addition is wrapping, and overflow is not
/// indicated.
///
/// $$
/// f(x_1, x_0, y_1, y_0) = (z_1, z_0),
/// $$
/// where $W$ is `Self::WIDTH`,
///
/// $x_1, x_0, y_1, y_0, z_1, z_0 < 2^W$, and
/// $$
/// (2^Wx_1 + x_0) + (2^Wy_1 + y_0) \equiv 2^Wz_1 + z_0 \mod 2^{2W}.
/// $$
///
/// # Worst-case complexity
/// Constant time and additional memory.
///
/// # Examples
/// See [here](super::xx_add_yy_to_zz#xx_add_yy_to_zz).
///
/// This is equivalent to `add_ssaaaa` from `longlong.h`, GMP 6.2.1, where `(sh, sl)` is
/// returned.
fn xx_add_yy_to_zz(x_1: Self, x_0: Self, y_1: Self, y_0: Self) -> (Self, Self) {
if USIZE_IS_U32 {
let (z_1, z_0) = u32::xx_add_yy_to_zz(
u32::wrapping_from(x_1),
u32::wrapping_from(x_0),
u32::wrapping_from(y_1),
u32::wrapping_from(y_0),
);
(Self::wrapping_from(z_1), Self::wrapping_from(z_0))
} else {
let (z_1, z_0) = u64::xx_add_yy_to_zz(
u64::wrapping_from(x_1),
u64::wrapping_from(x_0),
u64::wrapping_from(y_1),
u64::wrapping_from(y_0),
);
(Self::wrapping_from(z_1), Self::wrapping_from(z_0))
}
}
}
impl XXAddYYToZZ for u128 {
/// Adds two numbers, each composed of two [`u128`] values, returning the sum as a pair of
/// [`u128`] values.
///
/// The more significant value always comes first. Addition is wrapping, and overflow is not
/// indicated.
///
/// $$
/// f(x_1, x_0, y_1, y_0) = (z_1, z_0),
/// $$
/// where $W$ is `Self::WIDTH`,
///
/// $x_1, x_0, y_1, y_0, z_1, z_0 < 2^W$, and
/// $$
/// (2^Wx_1 + x_0) + (2^Wy_1 + y_0) \equiv 2^Wz_1 + z_0 \mod 2^{2W}.
/// $$
///
/// # Worst-case complexity
/// Constant time and additional memory.
///
/// # Examples
/// See [here](super::xx_add_yy_to_zz#xx_add_yy_to_zz).
///
/// This is equivalent to `add_ssaaaa` from `longlong.h`, GMP 6.2.1, where `(sh, sl)` is
/// returned.
#[inline]
fn xx_add_yy_to_zz(x_1: Self, x_0: Self, y_1: Self, y_0: Self) -> (Self, Self) {
explicit_xx_add_yy_to_zz(x_1, x_0, y_1, y_0)
}
}