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//! Module containing logical right shift intrinsic.

use crate::U256;
use core::mem::MaybeUninit;

#[inline]
pub fn shr2(r: &mut U256, a: u32) {
    debug_assert!(a < 256, "shr intrinsic called with overflowing shift");

    let (hi, lo) = if a == 0 {
        return;
    } else if a < 128 {
        ((r.high() >> a) | (r.low() << (128 - a)), r.low() >> a)
    } else {
        (r.low() >> (a & 0x7f), 0)
    };

    *r = U256::from_words(hi, lo);
}

#[inline]
pub fn shr3(r: &mut MaybeUninit<U256>, a: &U256, b: u32) {
    debug_assert!(b < 256, "shr intrinsic called with overflowing shift");

    let (hi, lo) = if b == 0 {
        (*a.high(), *a.low())
    } else if b < 128 {
        (a.high() >> b, a.low() >> b | (a.high() << (128 - b)))
    } else {
        (0, a.high() >> (b & 0x7f))
    };

    unsafe {
        r.as_mut_ptr().write(U256::from_words(hi, lo));
    }
}