/mordor/util.cpp

#include "util.h"
#include "endian.h"

namespace Mordor
{

// muldiv64() was adapted from
// http://www.virtualbox.org/browser/trunk/src/VBox/Devices/muldiv64.c?rev=1
//
// the following copyright notice applies:
/*
 * QEMU System Emulator
 *
 * Copyright (c) 2003-2004 Fabrice Bellard
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

/* compute with 96 bit intermediate result: (a*b)/c */
uint64_t muldiv64(uint64_t a, uint32_t b, uint64_t c)
{
    union {
        uint64_t ll;
        struct {
#if MORDOR_BYTE_ORDER == MORDOR_BIG_ENDIAN
            uint32_t high, low;
#else
            uint32_t low, high;
#endif
        } l;
    } u, res;
    uint64_t rl, rh;

    u.ll = a;
    rl = (uint64_t)u.l.low * (uint64_t)b;
    rh = (uint64_t)u.l.high * (uint64_t)b;
    rh += (rl >> 32);
    res.l.high = (uint32_t)(rh / c);
    res.l.low = (uint32_t)((((rh % c) << 32) + (rl & 0xffffffff)) / c);
    return res.ll;
}

};