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/mordor/util.cpp

http://github.com/mozy/mordor
C++ | 59 lines | 26 code | 5 blank | 28 comment | 1 complexity | bb1c3c8ebb7ee9339a9aae9d45445bae MD5 | raw file
 1#include "util.h"
 2#include "endian.h"
 3
 4namespace Mordor
 5{
 6
 7// muldiv64() was adapted from
 8// http://www.virtualbox.org/browser/trunk/src/VBox/Devices/muldiv64.c?rev=1
 9//
10// the following copyright notice applies:
11/*
12 * QEMU System Emulator
13 *
14 * Copyright (c) 2003-2004 Fabrice Bellard
15 *
16 * Permission is hereby granted, free of charge, to any person obtaining a copy
17 * of this software and associated documentation files (the "Software"), to deal
18 * in the Software without restriction, including without limitation the rights
19 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
20 * copies of the Software, and to permit persons to whom the Software is
21 * furnished to do so, subject to the following conditions:
22 *
23 * The above copyright notice and this permission notice shall be included in
24 * all copies or substantial portions of the Software.
25 *
26 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
27 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
28 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
29 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
30 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
31 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
32 * THE SOFTWARE.
33 */
34
35/* compute with 96 bit intermediate result: (a*b)/c */
36uint64_t muldiv64(uint64_t a, uint32_t b, uint64_t c)
37{
38    union {
39        uint64_t ll;
40        struct {
41#if MORDOR_BYTE_ORDER == MORDOR_BIG_ENDIAN
42            uint32_t high, low;
43#else
44            uint32_t low, high;
45#endif
46        } l;
47    } u, res;
48    uint64_t rl, rh;
49
50    u.ll = a;
51    rl = (uint64_t)u.l.low * (uint64_t)b;
52    rh = (uint64_t)u.l.high * (uint64_t)b;
53    rh += (rl >> 32);
54    res.l.high = (uint32_t)(rh / c);
55    res.l.low = (uint32_t)((((rh % c) << 32) + (rl & 0xffffffff)) / c);
56    return res.ll;
57}
58
59};