ktime.c.svn-base

来自「wipfw 是windows下的网络控制工具」· SVN-BASE 代码 · 共 104 行

/*
 * Copyright (c) 2003 Vladislav Goncharov
 *
 * Redistribution and use in source forms, with and without modification,
 * are permitted provided that this entire comment appears intact.
 *
 * Redistribution in binary form may occur without any restrictions.
 * Obviously, it would be nice if you gave credit where credit is due
 * but requiring it would be too onerous.
 *
 * This software is provided ``AS IS'' without any warranties of any kind.
 */

#include <ntddk.h>
#include "ktime.h"

#define TICKSPERMIN        600000000
#define TICKSPERSEC        10000000
#define TICKSPERMSEC       10000
#define SECSPERDAY         86400
#define SECSPERHOUR        3600
#define SECSPERMIN         60
#define MINSPERHOUR        60
#define HOURSPERDAY        24
#define EPOCHWEEKDAY       0
#define DAYSPERWEEK        7
#define EPOCHYEAR          1601
#define DAYSPERNORMALYEAR  365
#define DAYSPERLEAPYEAR    366
#define MONSPERYEAR        12

static const int YearLengths[2] = {DAYSPERNORMALYEAR, DAYSPERLEAPYEAR};
static const int MonthLengths[2][MONSPERYEAR] = {
    { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 },
    { 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }
};

static int  IsLeapYear(int Year);

void
KernelTimeToSystemTime(PLARGE_INTEGER KernelTime, SYSTEMTIME *lpSystemTime)
{
    const int *Months;
    int LeapSecondCorrections, SecondsInDay, CurYear;
    int LeapYear, CurMonth;
    long Days;
    __int64 Time = KernelTime->QuadPart;
    
    /* Extract millisecond from time and convert time into seconds */
    lpSystemTime->wMilliseconds = (USHORT)((Time % TICKSPERSEC) / TICKSPERMSEC);
    Time = Time / TICKSPERSEC;
    
    LeapSecondCorrections = 0;
    
    /* Split the time into days and seconds within the day */
    Days = (long)(Time / SECSPERDAY);
    SecondsInDay = (long)(Time % SECSPERDAY);
    
    /* Adjust the values for GMT and leap seconds */
    SecondsInDay += LeapSecondCorrections;
    while (SecondsInDay < 0) {
        SecondsInDay += SECSPERDAY;
        Days--;
    }
    while (SecondsInDay >= SECSPERDAY) {
        SecondsInDay -= SECSPERDAY;
        Days++;
    }
    
    /* compute time of day */
    lpSystemTime->wHour = (USHORT)(SecondsInDay / SECSPERHOUR);
    SecondsInDay = SecondsInDay % SECSPERHOUR;
    lpSystemTime->wMinute = (USHORT)(SecondsInDay / SECSPERMIN);
    lpSystemTime->wSecond = (USHORT)(SecondsInDay % SECSPERMIN);
    
    /* compute day of week */
    lpSystemTime->wDayOfWeek = (USHORT)((EPOCHWEEKDAY + Days) % DAYSPERWEEK);
    
    /* compute year */
    CurYear = EPOCHYEAR;

    for (;;) {
        LeapYear = IsLeapYear(CurYear);
        if (Days < (long)YearLengths[LeapYear])
            break;
        CurYear++;
        Days = Days - (long)YearLengths[LeapYear];
    }
    lpSystemTime->wYear = (USHORT)CurYear;
    
    /* Compute month of year */
    Months = MonthLengths[LeapYear];
    for (CurMonth = 0; Days >= (long)Months[CurMonth]; CurMonth++)
        Days = Days - (long)Months[CurMonth];
    lpSystemTime->wMonth = (USHORT)(CurMonth + 1);
    lpSystemTime->wDay = (USHORT)(Days + 1);
}

int
IsLeapYear(int Year)
{
    return Year % 4 == 0 && (Year % 100 != 0 || Year % 400 == 0) ? 1 : 0;
}