/* $Id: time-win.cpp 69111 2017-10-17 14:26:02Z vboxsync $ */
/** @file
 * IPRT - Time, Windows.
 */

/*
 * Copyright (C) 2006-2017 Oracle Corporation
 *
 * This file is part of VirtualBox Open Source Edition (OSE), as
 * available from http://www.virtualbox.org. This file is free software;
 * you can redistribute it and/or modify it under the terms of the GNU
 * General Public License (GPL) as published by the Free Software
 * Foundation, in version 2 as it comes in the "COPYING" file of the
 * VirtualBox OSE distribution. VirtualBox OSE is distributed in the
 * hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
 *
 * The contents of this file may alternatively be used under the terms
 * of the Common Development and Distribution License Version 1.0
 * (CDDL) only, as it comes in the "COPYING.CDDL" file of the
 * VirtualBox OSE distribution, in which case the provisions of the
 * CDDL are applicable instead of those of the GPL.
 *
 * You may elect to license modified versions of this file under the
 * terms and conditions of either the GPL or the CDDL or both.
 */


/*********************************************************************************************************************************
*   Header Files                                                                                                                 *
*********************************************************************************************************************************/
#define LOG_GROUP RTLOGGROUP_TIME
#include <iprt/win/windows.h>

#include <iprt/time.h>
#include "internal/iprt.h"

#include <iprt/asm.h>
#include <iprt/assert.h>
#include <iprt/err.h>
#include "internal/time.h"

/*
 * Note! The selected time source be the exact same one as we use in kernel land!
 */
//#define USE_TICK_COUNT
//#define USE_PERFORMANCE_COUNTER
//# define USE_FILE_TIME
//#if defined(RT_ARCH_X86) || defined(RT_ARCH_AMD64)
# define USE_INTERRUPT_TIME
//#else
//# define USE_TICK_COUNT
//#endif


#ifdef USE_INTERRUPT_TIME

typedef struct _MY_KSYSTEM_TIME
{
    ULONG LowPart;
    LONG High1Time;
    LONG High2Time;
} MY_KSYSTEM_TIME;

typedef struct _MY_KUSER_SHARED_DATA
{
    ULONG TickCountLowDeprecated;
    ULONG TickCountMultiplier;
    volatile MY_KSYSTEM_TIME InterruptTime;
    /* The rest is not relevant. */
} MY_KUSER_SHARED_DATA, *PMY_KUSER_SHARED_DATA;

#endif /* USE_INTERRUPT_TIME */


DECLINLINE(uint64_t) rtTimeGetSystemNanoTS(void)
{
#if defined USE_TICK_COUNT
    /*
     * This would work if it didn't flip over every 49 (or so) days.
     */
    return (uint64_t)GetTickCount() * RT_NS_1MS_64;

#elif defined USE_PERFORMANCE_COUNTER
    /*
     * Slow and not derived from InterruptTime.
     */
    static LARGE_INTEGER    llFreq;
    static unsigned         uMult;
    if (!llFreq.QuadPart)
    {
        if (!QueryPerformanceFrequency(&llFreq))
            return (uint64_t)GetTickCount() * RT_NS_1MS_64;
        llFreq.QuadPart /=    1000;
        uMult            = 1000000;     /* no math genius, but this seemed to help avoiding floating point. */
    }

    LARGE_INTEGER   ll;
    if (QueryPerformanceCounter(&ll))
        return (ll.QuadPart * uMult) / llFreq.QuadPart;
    return (uint64_t)GetTickCount() * RT_NS_1MS_64;

#elif defined USE_FILE_TIME
    /*
     * This is SystemTime not InterruptTime.
     */
    uint64_t u64; /* manual say larger integer, should be safe to assume it's the same. */
    GetSystemTimeAsFileTime((LPFILETIME)&u64);
    return u64 * 100;

#elif defined USE_INTERRUPT_TIME
# if 0 /* ASSUME 0x7ffe0000 is set in stone */
    /*
     * This is exactly what we want, but we have to obtain it by non-official
     * means.
     */
    static MY_KUSER_SHARED_DATA *s_pUserSharedData = NULL;
    if (!s_pUserSharedData)
    {
        /** @todo find official way of getting this or some more clever
         * detection algorithm if necessary. The com debugger class
         * exports this too, windbg knows it too... */
        s_pUserSharedData = (PMY_KUSER_SHARED_DATA)(uintptr_t)0x7ffe0000;
    }
# endif
    PMY_KUSER_SHARED_DATA pUserSharedData = (PMY_KUSER_SHARED_DATA)(uintptr_t)0x7ffe0000;

    /* use interrupt time */
    LARGE_INTEGER Time;
    do
    {
        Time.HighPart = pUserSharedData->InterruptTime.High1Time;
        Time.LowPart  = pUserSharedData->InterruptTime.LowPart;
    } while (pUserSharedData->InterruptTime.High2Time != Time.HighPart);

    return (uint64_t)Time.QuadPart * 100;

#else
# error "Must select a method bright guy!"
#endif
}


RTDECL(uint64_t) RTTimeSystemNanoTS(void)
{
    return rtTimeGetSystemNanoTS();
}


RTDECL(uint64_t) RTTimeSystemMilliTS(void)
{
    return rtTimeGetSystemNanoTS() / RT_NS_1MS;
}


RTDECL(PRTTIMESPEC) RTTimeNow(PRTTIMESPEC pTime)
{
    uint64_t u64;
    AssertCompile(sizeof(u64) == sizeof(FILETIME));
    GetSystemTimeAsFileTime((LPFILETIME)&u64);
    return RTTimeSpecSetNtTime(pTime, u64);
}


RTDECL(PRTTIMESPEC) RTTimeLocalNow(PRTTIMESPEC pTime)
{
    uint64_t u64;
    AssertCompile(sizeof(u64) == sizeof(FILETIME));
    GetSystemTimeAsFileTime((LPFILETIME)&u64);
    uint64_t u64Local;
    if (!FileTimeToLocalFileTime((FILETIME const *)&u64, (LPFILETIME)&u64Local))
        u64Local = u64;
    return RTTimeSpecSetNtTime(pTime, u64Local);
}


RTDECL(int64_t) RTTimeLocalDeltaNano(void)
{
    /*
     * UTC = local + Tzi.Bias;
     * The bias is given in minutes.
     */
    TIME_ZONE_INFORMATION Tzi;
    Tzi.Bias = 0;
    if (GetTimeZoneInformation(&Tzi) != TIME_ZONE_ID_INVALID)
        return -(int64_t)Tzi.Bias * 60 * RT_NS_1SEC_64;
    return 0;
}