tclwintime.c

这是leon3处理器的交叉编译链

	     * Skip the offset string and get the DST string.
	     */

	    p = zone + len;
	    p += strspn(p, "+-:0123456789");
	    if (*p != '\0') {
		zone = p;
		len = strlen(zone);
		if (len > 3) {
		    len = 3;
		}
	    }
	}
	Tcl_ExternalToUtf(NULL, NULL, zone, len, 0, NULL, name,
		sizeof(tsdPtr->tzName), NULL, NULL, NULL);
    }
    if (name[0] == '\0') {
	if (GetTimeZoneInformation(&tz) == TIME_ZONE_ID_UNKNOWN) {
	    /*
	     * MSDN: On NT this is returned if DST is not used in
	     * the current TZ
	     */
	    dst = 0;
	}
	encoding = Tcl_GetEncoding(NULL, "unicode");
	Tcl_ExternalToUtf(NULL, encoding, 
		(char *) ((dst) ? tz.DaylightName : tz.StandardName), -1, 
		0, NULL, name, sizeof(tsdPtr->tzName), NULL, NULL, NULL);
	Tcl_FreeEncoding(encoding);
    } 
    return name;
}

/*
 *----------------------------------------------------------------------
 *
 * TclpGetDate --
 *
 *	This function converts between seconds and struct tm.  If
 *	useGMT is true, then the returned date will be in Greenwich
 *	Mean Time (GMT).  Otherwise, it will be in the local time zone.
 *
 * Results:
 *	Returns a static tm structure.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

struct tm *
TclpGetDate(t, useGMT)
    TclpTime_t t;
    int useGMT;
{
    const time_t *tp = (const time_t *) t;
    struct tm *tmPtr;
    long time;

    if (!useGMT) {
	tzset();

	/*
	 * If we are in the valid range, let the C run-time library
	 * handle it.  Otherwise we need to fake it.  Note that this
	 * algorithm ignores daylight savings time before the epoch.
	 */

	if (*tp >= 0) {
	    return localtime(tp);
	}

	time = *tp - _timezone;
	
	/*
	 * If we aren't near to overflowing the long, just add the bias and
	 * use the normal calculation.  Otherwise we will need to adjust
	 * the result at the end.
	 */

	if (*tp < (LONG_MAX - 2 * SECSPERDAY)
		&& *tp > (LONG_MIN + 2 * SECSPERDAY)) {
	    tmPtr = ComputeGMT(&time);
	} else {
	    tmPtr = ComputeGMT(tp);

	    tzset();

	    /*
	     * Add the bias directly to the tm structure to avoid overflow.
	     * Propagate seconds overflow into minutes, hours and days.
	     */

	    time = tmPtr->tm_sec - _timezone;
	    tmPtr->tm_sec = (int)(time % 60);
	    if (tmPtr->tm_sec < 0) {
		tmPtr->tm_sec += 60;
		time -= 60;
	    }
    
	    time = tmPtr->tm_min + time/60;
	    tmPtr->tm_min = (int)(time % 60);
	    if (tmPtr->tm_min < 0) {
		tmPtr->tm_min += 60;
		time -= 60;
	    }

	    time = tmPtr->tm_hour + time/60;
	    tmPtr->tm_hour = (int)(time % 24);
	    if (tmPtr->tm_hour < 0) {
		tmPtr->tm_hour += 24;
		time -= 24;
	    }

	    time /= 24;
	    tmPtr->tm_mday += time;
	    tmPtr->tm_yday += time;
	    tmPtr->tm_wday = (tmPtr->tm_wday + time) % 7;
	}
    } else {
	tmPtr = ComputeGMT(tp);
    }
    return tmPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * ComputeGMT --
 *
 *	This function computes GMT given the number of seconds since
 *	the epoch (midnight Jan 1 1970).
 *
 * Results:
 *	Returns a (per thread) statically allocated struct tm.
 *
 * Side effects:
 *	Updates the values of the static struct tm.
 *
 *----------------------------------------------------------------------
 */

static struct tm *
ComputeGMT(tp)
    const time_t *tp;
{
    struct tm *tmPtr;
    long tmp, rem;
    int isLeap;
    int *days;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    tmPtr = &tsdPtr->tm;

    /*
     * Compute the 4 year span containing the specified time.
     */

    tmp = *tp / SECSPER4YEAR;
    rem = *tp % SECSPER4YEAR;

    /*
     * Correct for weird mod semantics so the remainder is always positive.
     */

    if (rem < 0) {
	tmp--;
	rem += SECSPER4YEAR;
    }

    /*
     * Compute the year after 1900 by taking the 4 year span and adjusting
     * for the remainder.  This works because 2000 is a leap year, and
     * 1900/2100 are out of the range.
     */

    tmp = (tmp * 4) + 70;
    isLeap = 0;
    if (rem >= SECSPERYEAR) {			  /* 1971, etc. */
	tmp++;
	rem -= SECSPERYEAR;
	if (rem >= SECSPERYEAR) {		  /* 1972, etc. */
	    tmp++;
	    rem -= SECSPERYEAR;
	    if (rem >= SECSPERYEAR + SECSPERDAY) { /* 1973, etc. */
		tmp++;
		rem -= SECSPERYEAR + SECSPERDAY;
	    } else {
		isLeap = 1;
	    }
	}
    }
    tmPtr->tm_year = tmp;

    /*
     * Compute the day of year and leave the seconds in the current day in
     * the remainder.
     */

    tmPtr->tm_yday = rem / SECSPERDAY;
    rem %= SECSPERDAY;
    
    /*
     * Compute the time of day.
     */

    tmPtr->tm_hour = rem / 3600;
    rem %= 3600;
    tmPtr->tm_min = rem / 60;
    tmPtr->tm_sec = rem % 60;

    /*
     * Compute the month and day of month.
     */

    days = (isLeap) ? leapDays : normalDays;
    for (tmp = 1; days[tmp] < tmPtr->tm_yday; tmp++) {
    }
    tmPtr->tm_mon = --tmp;
    tmPtr->tm_mday = tmPtr->tm_yday - days[tmp];

    /*
     * Compute day of week.  Epoch started on a Thursday.
     */

    tmPtr->tm_wday = (*tp / SECSPERDAY) + 4;
    if ((*tp % SECSPERDAY) < 0) {
	tmPtr->tm_wday--;
    }
    tmPtr->tm_wday %= 7;
    if (tmPtr->tm_wday < 0) {
	tmPtr->tm_wday += 7;
    }

    return tmPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * CalibrationThread --
 *
 *	Thread that manages calibration of the hi-resolution time
 *	derived from the performance counter, to keep it synchronized
 *	with the system clock.
 *
 * Parameters:
 *	arg -- Client data from the CreateThread call.  This parameter
 *             points to the static TimeInfo structure.
 *
 * Return value:
 *	None.  This thread embeds an infinite loop.
 *
 * Side effects:
 *	At an interval of clockCalibrateWakeupInterval ms, this thread
 *	performs virtual time discipline.
 *
 * Note: When this thread is entered, TclpInitLock has been called
 * to safeguard the static storage.  There is therefore no synchronization
 * in the body of this procedure.
 *
 *----------------------------------------------------------------------
 */

static DWORD WINAPI
CalibrationThread( LPVOID arg )
{
    FILETIME curFileTime;
    DWORD waitResult;

    /* Get initial system time and performance counter */

    GetSystemTimeAsFileTime( &curFileTime );
    QueryPerformanceCounter( &timeInfo.lastCounter );
    QueryPerformanceFrequency( &timeInfo.curCounterFreq );
    timeInfo.lastFileTime.LowPart = curFileTime.dwLowDateTime;
    timeInfo.lastFileTime.HighPart = curFileTime.dwHighDateTime;

    /* Initialize the working storage for the calibration callback */

    timeInfo.lastPerfCounter = timeInfo.lastCounter.QuadPart;
    timeInfo.estPerfCounterFreq = timeInfo.curCounterFreq.QuadPart;

    /*
     * Wake up the calling thread.  When it wakes up, it will release the
     * initialization lock.
     */

    SetEvent( timeInfo.readyEvent );

    /* Run the calibration once a second */

    for ( ; ; ) {

	/* If the exitEvent is set, break out of the loop. */

	waitResult = WaitForSingleObjectEx(timeInfo.exitEvent, 1000, FALSE);
	if ( waitResult == WAIT_OBJECT_0 ) {
	    break;
	}
	UpdateTimeEachSecond();
    }

    /* lint */
    return (DWORD) 0;
}

/*
 *----------------------------------------------------------------------
 *
 * UpdateTimeEachSecond --
 *
 *	Callback from the waitable timer in the clock calibration thread
 *	that updates system time.
 *
 * Parameters:
 *	info -- Pointer to the static TimeInfo structure
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Performs virtual time calibration discipline.
 *
 *----------------------------------------------------------------------
 */

static void
UpdateTimeEachSecond()
{

    LARGE_INTEGER curPerfCounter;
				/* Current value returned from
				 * QueryPerformanceCounter */

    LONGLONG perfCounterDiff;	/* Difference between the current value
				 * and the value of 1 second ago */

    FILETIME curSysTime;	/* Current system time */

    LARGE_INTEGER curFileTime;	/* File time at the time this callback
				 * was scheduled. */

    LONGLONG fileTimeDiff;	/* Elapsed time on the system clock
				 * since the last time this procedure
				 * was called */

    LONGLONG instantFreq;	/* Instantaneous estimate of the
				 * performance counter frequency */

    LONGLONG delta;		/* Increment to add to the estimated
				 * performance counter frequency in the
				 * loop filter */

    LONGLONG fuzz;		/* Tolerance for the perf counter frequency */

    LONGLONG lowBound;		/* Lower bound for the frequency assuming
				 * 1000 ppm tolerance */

    LONGLONG hiBound;		/* Upper bound for the frequency */

    /*
     * Get current performance counter and system time.
     */

    QueryPerformanceCounter( &curPerfCounter );
    GetSystemTimeAsFileTime( &curSysTime );
    curFileTime.LowPart = curSysTime.dwLowDateTime;
    curFileTime.HighPart = curSysTime.dwHighDateTime;

    EnterCriticalSection( &timeInfo.cs );

    /*
     * Find out how many ticks of the performance counter and the
     * system clock have elapsed since we got into this procedure.
     * Estimate the current frequency.
     */

    perfCounterDiff = curPerfCounter.QuadPart - timeInfo.lastPerfCounter;
    timeInfo.lastPerfCounter = curPerfCounter.QuadPart;
    fileTimeDiff = curFileTime.QuadPart - timeInfo.lastSysTime;
    timeInfo.lastSysTime = curFileTime.QuadPart;
    instantFreq = ( 10000000 * perfCounterDiff / fileTimeDiff );

    /*
     * Consider this a timing glitch if instant frequency varies
     * significantly from the current estimate.
     */

    fuzz = timeInfo.estPerfCounterFreq >> 10;
    lowBound = timeInfo.estPerfCounterFreq - fuzz;
    hiBound = timeInfo.estPerfCounterFreq + fuzz;
    if ( instantFreq < lowBound || instantFreq > hiBound ) {
	LeaveCriticalSection( &timeInfo.cs );
	return;
    }

    /*
     * Update the current estimate of performance counter frequency.
     * This code is equivalent to the loop filter of a phase locked
     * loop.
     */

    delta = ( instantFreq - timeInfo.estPerfCounterFreq ) >> 6;
    timeInfo.estPerfCounterFreq += delta;

    /*
     * Update the current virtual time.
     */

    timeInfo.lastFileTime.QuadPart
	+= ( ( curPerfCounter.QuadPart - timeInfo.lastCounter.QuadPart )
	     * 10000000 / timeInfo.curCounterFreq.QuadPart );
    timeInfo.lastCounter.QuadPart = curPerfCounter.QuadPart;

    delta = curFileTime.QuadPart - timeInfo.lastFileTime.QuadPart;
    if ( delta > 10000000 || delta < -10000000 ) {

	/*
	 * If the virtual time slip exceeds one second, then adjusting
	 * the counter frequency is hopeless (it'll take over fifteen
	 * minutes to line up with the system clock).  The most likely
	 * cause of this large a slip is a sudden change to the system
	 * clock, perhaps because it was being corrected by wristwatch
	 * and eyeball.  Accept the system time, and set the performance
	 * counter frequency to the current estimate.
	 */

	timeInfo.lastFileTime.QuadPart = curFileTime.QuadPart;
	timeInfo.curCounterFreq.QuadPart = timeInfo.estPerfCounterFreq;

    } else {

	/*
	 * Compute a counter frequency that will cause virtual time to line
	 * up with system time one second from now, assuming that the
	 * performance counter continues to tick at timeInfo.estPerfCounterFreq.
	 */
	
	timeInfo.curCounterFreq.QuadPart
	    = 10000000 * timeInfo.estPerfCounterFreq / ( delta + 10000000 );

	/*
	 * Limit frequency excursions to 1000 ppm from estimate
	 */
	
	if ( timeInfo.curCounterFreq.QuadPart < lowBound ) {
	    timeInfo.curCounterFreq.QuadPart = lowBound;
	} else if ( timeInfo.curCounterFreq.QuadPart > hiBound ) {
	    timeInfo.curCounterFreq.QuadPart = hiBound;
	}
    }

    LeaveCriticalSection( &timeInfo.cs );

}