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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::XMulYToZZ;
use crate::num::basic::integers::USIZE_IS_U32;
use crate::num::basic::unsigneds::PrimitiveUnsigned;
use crate::num::conversion::half::{wide_join_halves, wide_split_in_half, wide_upper_half};
use crate::num::conversion::traits::{HasHalf, SplitInHalf, WrappingFrom};
fn implicit_x_mul_y_to_zz<T, DT: From<T> + HasHalf<Half = T> + PrimitiveUnsigned + SplitInHalf>(
x: T,
y: T,
) -> (T, T) {
(DT::from(x) * DT::from(y)).split_in_half()
}
pub_test! {explicit_x_mul_y_to_zz<T: PrimitiveUnsigned>(x: T, y: T) -> (T, T) {
let (x_1, x_0) = wide_split_in_half(x);
let (y_1, y_0) = wide_split_in_half(y);
let x_0_y_0 = x_0 * y_0;
let mut x_0_y_1 = x_0 * y_1;
let x_1_y_0 = x_1 * y_0;
let mut x_1_y_1 = x_1 * y_1;
let (x_0_y_0_1, x_0_y_0_0) = wide_split_in_half(x_0_y_0);
x_0_y_1.wrapping_add_assign(x_0_y_0_1);
if x_0_y_1.overflowing_add_assign(x_1_y_0) {
x_1_y_1.wrapping_add_assign(T::power_of_2(T::WIDTH >> 1));
}
let z_1 = x_1_y_1.wrapping_add(wide_upper_half(x_0_y_1));
let z_0 = wide_join_halves(x_0_y_1, x_0_y_0_0);
(z_1, z_0)
}}
macro_rules! implicit_x_mul_y_to_zz {
($t:ident, $dt:ident) => {
impl XMulYToZZ for $t {
/// Multiplies two numbers, returning the product as a pair of `Self` values.
///
/// The more significant value always comes first.
///
/// $$
/// f(x, y) = (z_1, z_0),
/// $$
/// where $W$ is `Self::WIDTH`,
///
/// $x, y, z_1, z_0 < 2^W$, and
/// $$
/// xy = 2^Wz_1 + z_0.
/// $$
///
/// # Worst-case complexity
/// Constant time and additional memory.
///
/// # Examples
/// See [here](super::x_mul_y_to_zz#x_mul_y_to_zz).
///
/// This is equivalent to `umul_ppmm` from `longlong.h`, GMP 6.2.1, where `(w1, w0)` is
/// returned.
#[inline]
fn x_mul_y_to_zz(x: $t, y: $t) -> ($t, $t) {
implicit_x_mul_y_to_zz::<$t, $dt>(x, y)
}
}
};
}
implicit_x_mul_y_to_zz!(u8, u16);
implicit_x_mul_y_to_zz!(u16, u32);
implicit_x_mul_y_to_zz!(u32, u64);
implicit_x_mul_y_to_zz!(u64, u128);
impl XMulYToZZ for usize {
/// Multiplies two numbers, returning the product as a pair of [`usize`] values.
///
/// The more significant value always comes first.
///
/// $$
/// f(x, y) = (z_1, z_0),
/// $$
/// where $W$ is `Self::WIDTH`,
///
/// $x, y, z_1, z_0 < 2^W$, and
/// $$
/// xy = 2^Wz_1 + z_0.
/// $$
///
/// # Worst-case complexity
/// Constant time and additional memory.
///
/// # Examples
/// See [here](super::x_mul_y_to_zz#x_mul_y_to_zz).
///
/// This is equivalent to `umul_ppmm` from `longlong.h`, GMP 6.2.1, where `(w1, w0)` is
/// returned.
fn x_mul_y_to_zz(x: Self, y: Self) -> (Self, Self) {
if USIZE_IS_U32 {
let (z_1, z_0) = u32::x_mul_y_to_zz(u32::wrapping_from(x), u32::wrapping_from(y));
(Self::wrapping_from(z_1), Self::wrapping_from(z_0))
} else {
let (z_1, z_0) = u64::x_mul_y_to_zz(u64::wrapping_from(x), u64::wrapping_from(y));
(Self::wrapping_from(z_1), Self::wrapping_from(z_0))
}
}
}
impl XMulYToZZ for u128 {
/// Multiplies two numbers, returning the product as a pair of [`u128`] values.
///
/// The more significant value always comes first.
///
/// $$
/// f(x, y) = (z_1, z_0),
/// $$
/// where $W$ is `Self::WIDTH`,
///
/// $x, y, z_1, z_0 < 2^W$, and
/// $$
/// xy = 2^Wz_1 + z_0.
/// $$
///
/// # Worst-case complexity
/// Constant time and additional memory.
///
/// # Examples
/// See [here](super::x_mul_y_to_zz#x_mul_y_to_zz).
///
/// This is equivalent to `umul_ppmm` from `longlong.h`, GMP 6.2.1, where `(w1, w0)` is
/// returned.
#[inline]
fn x_mul_y_to_zz(x: Self, y: Self) -> (Self, Self) {
explicit_x_mul_y_to_zz(x, y)
}
}