Function AtomicMultiply

src/cryptlib/integer.cpp:232–273

}

static void AtomicMultiply(word *C, word A0, word A1, word B0, word B1)
{
    word s;
    dword_union d;

    if (A1 >= A0)
        if (B0 >= B1)
        {
            s = 0;
            d.dw = (dword)(A1-A0)*(B0-B1);
        }
        else
        {
            s = (A1-A0);
            d.dw = (dword)s*(word)(B0-B1);
        }
    else
        if (B0 > B1)
        {
            s = (B0-B1);
            d.dw = (word)(A1-A0)*(dword)s;
        }
        else
        {
            s = 0;
            d.dw = (dword)(A0-A1)*(B1-B0);
        }

    dword_union A0B0;
    A0B0.dw = (dword)A0*B0;
    C[0] = A0B0.low;

    dword_union A1B1;
    A1B1.dw = (dword)A1*B1;
    dword_union t;
    t.dw = (dword)A0B0.high + A0B0.low + d.low + A1B1.low;
    C[1] = t.low;

    t.dw = A1B1.dw + t.high + A0B0.high + d.high + A1B1.high - s;
    C[2] = t.low;
    C[3] = t.high;
}

static word AtomicMultiplyAdd(word *C, word A0, word A1, word B0, word B1)
{