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/**
* Copyright (C) 2016 Eistec AB
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License v2.1. See the file LICENSE in the top level
* directory for more details.
*
* @ingroup sys_util
* @{
* @file
* @brief Integer division function implementations
*
* @author Joakim Nohlgård <joakim.nohlgard@eistec.se>
*
* @}
*/
#include <stdint.h>
#include <stdio.h>
#include "div.h"
uint64_t _div_mulhi64(const uint64_t a, const uint64_t b)
{
/* Handle overflow explicit because we don't have 128 bit integers on
* our platforms. */
const uint32_t a_lo = (const uint32_t)a;
const uint32_t a_hi = (const uint32_t)(a >> 32);
const uint32_t b_lo = (const uint32_t)b;
const uint32_t b_hi = (const uint32_t)(b >> 32);
const uint64_t a_x_b_mid = (const uint64_t)a_hi * b_lo;
const uint64_t b_x_a_mid = (const uint64_t)b_hi * a_lo;
const uint64_t a_x_b_lo = (const uint64_t)a_lo * b_lo;
const uint64_t a_x_b_hi = (const uint64_t)a_hi * b_hi;
/* We may get up to 2 carry bits from the lower part of the multiplication */
const uint32_t carry_bits = ((uint64_t)(uint32_t)a_x_b_mid +
(uint64_t)(uint32_t)b_x_a_mid +
(a_x_b_lo >> 32) ) >> 32;
const uint64_t multhi = a_x_b_hi +
(a_x_b_mid >> 32) + (b_x_a_mid >> 32) +
carry_bits;
return multhi;
}