Function BigInt_Multiply_int

numpy/core/src/multiarray/dragon4.c:449–473

result = lhs * rhs */

/* result = lhs * rhs */
static void
BigInt_Multiply_int(BigInt *result, const BigInt *lhs, npy_uint32 rhs)
{
    /* perform long multiplication */
    npy_uint32 carry = 0;
    npy_uint32 *resultCur = result->blocks;
    const npy_uint32 *pLhsCur = lhs->blocks;
    const npy_uint32 *pLhsEnd = lhs->blocks + lhs->length;
    for ( ; pLhsCur != pLhsEnd; ++pLhsCur, ++resultCur) {
        npy_uint64 product = (npy_uint64)(*pLhsCur) * rhs + carry;
        *resultCur = (npy_uint32)(product & bitmask_u64(32));
        carry = product >> 32;
    }

    /* if there is a remaining carry, grow the array */
    if (carry != 0) {
        /* grow the array */
        DEBUG_ASSERT(lhs->length + 1 <= c_BigInt_MaxBlocks);
        *resultCur = (npy_uint32)carry;
        result->length = lhs->length + 1;
    }
    else {
        result->length = lhs->length;
    }
}

/* result = in * 2 */
static void