/* 
 * tclWinTime.c --
 *
 *	Contains Windows specific versions of Tcl functions that
 *	obtain time values from the operating system.
 *
 * Copyright 1995-1998 by Sun Microsystems, Inc.
 *
 * See the file "license.terms" for information on usage and redistribution
 * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
 *
 * RCS: @(#) $Id: tclWinTime.c,v 1.14 2003/02/14 22:16:27 kennykb Exp $
 * RCS: @(#) $Id: tclWinTime.c,v 1.15 2003/04/12 19:08:56 kennykb Exp $
 */

#include "tclWinInt.h"

#define SECSPERDAY (60L * 60L * 24L)
#define SECSPERYEAR (SECSPERDAY * 365L)
#define SECSPER4YEAR (SECSPERYEAR * 4L + SECSPERDAY)

/*
 * Number of samples over which to estimate the performance counter
 */
#define SAMPLES 64

/*
 * The following arrays contain the day of year for the last day of
 * each month, where index 1 is January.
 */

static int normalDays[] = {
    -1, 30, 58, 89, 119, 150, 180, 211, 242, 272, 303, 333, 364
};

static int leapDays[] = {
    -1, 30, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365
};

typedef struct ThreadSpecificData {
    char tzName[64];		/* Time zone name */
    struct tm tm;		/* time information */
} ThreadSpecificData;
static Tcl_ThreadDataKey dataKey;

/*
 * Calibration interval for the high-resolution timer, in msec
 */

static CONST unsigned long clockCalibrateWakeupInterval = 10000;
				/* FIXME: 10 s -- should be about 10 min! */

/*
 * Data for managing high-resolution timers.
 */

typedef struct TimeInfo {

    CRITICAL_SECTION cs;	/* Mutex guarding this structure */

    HANDLE calibrationThread;	/* Handle to the thread that keeps the
				 * virtual clock calibrated. */

    HANDLE readyEvent;		/* System event used to
				 * trigger the requesting thread
				 * when the clock calibration procedure
				 * is initialized for the first time */

    HANDLE exitEvent; 		/* Event to signal out of an exit handler
				 * to tell the calibration loop to
				 * terminate */

    LARGE_INTEGER nominalFreq;	/* Nominal frequency of the system
				 * performance counter, that is, the value
				 * returned from QueryPerformanceFrequency. */

    /*
     * The following values are used for calculating virtual time.
     * Virtual time is always equal to:
     *    lastFileTime + (current perf counter - lastCounter) 
     *				* 10000000 / curCounterFreq
     * and lastFileTime and lastCounter are updated any time that
     * virtual time is returned to a caller.
     */

    ULARGE_INTEGER lastFileTime;
    LARGE_INTEGER lastCounter;
    ULARGE_INTEGER fileTimeLastCall;
    LARGE_INTEGER perfCounterLastCall;
    LARGE_INTEGER curCounterFreq;

    /* 
     * The next two values are used only in the calibration thread, to track
     * the frequency of the performance counter.
    /*
     * Data used in developing the estimate of performance counter
     * frequency
     */

    ULONGLONG fileTimeSample[SAMPLES];
    LONGLONG lastPerfCounter;	/* Performance counter the last time
				 * that UpdateClockEachSecond was called */
    LONGLONG lastSysTime;	/* System clock at the last time
				/* Last 64 samples of system time */
				 * that UpdateClockEachSecond was called */
    LONGLONG estPerfCounterFreq;
				/* Current estimate of the counter frequency
				 * using the system clock as the standard */
    LONGLONG perfCounterSample[SAMPLES];
				/* Last 64 samples of performance counter */
    int sampleNo;		/* Current sample number */


} TimeInfo;

static TimeInfo timeInfo = {
    { NULL },
    0,
    0,

#else
    0,
    0,
    0,
#endif
    0,
    0,
    0,
    { 0 },
    { 0 },
    0,
    0
};

CONST static FILETIME posixEpoch = { 0xD53E8000, 0x019DB1DE };
    
/*
 * Declarations for functions defined later in this file.
 */

static struct tm *	ComputeGMT _ANSI_ARGS_((const time_t *tp));
static void		StopCalibration _ANSI_ARGS_(( ClientData ));
static DWORD WINAPI     CalibrationThread _ANSI_ARGS_(( LPVOID arg ));
static void 		UpdateTimeEachSecond _ANSI_ARGS_(( void ));
static void		ResetCounterSamples _ANSI_ARGS_((
			    ULONGLONG fileTime, 
                            LONGLONG perfCounter,
			    LONGLONG perfFreq
			));
static LONGLONG		AccumulateSample _ANSI_ARGS_((
			    LONGLONG perfCounter,
			    ULONGLONG fileTime
			));

/*
 *----------------------------------------------------------------------
 *
 * TclpGetSeconds --
 *
 *	This procedure returns the number of seconds from the epoch.

     * since it avoids an extra mutex lock in the common case.
     */

    if ( !timeInfo.initialized ) { 
	TclpInitLock();
	if ( !timeInfo.initialized ) {
	    timeInfo.perfCounterAvailable
		= QueryPerformanceFrequency( &timeInfo.curCounterFreq );
		= QueryPerformanceFrequency( &timeInfo.nominalFreq );

	    /*
	     * Some hardware abstraction layers use the CPU clock
	     * in place of the real-time clock as a performance counter
	     * reference.  This results in:
	     *    - inconsistent results among the processors on
	     *      multi-processor systems.

	     * frequency (perhaps in an attempt to calibrate the clock?)
	     * we use the latter rule rather than an exact match.
	     */

	    if ( timeInfo.perfCounterAvailable
		 /* The following lines would do an exact match on
		  * crystal frequency:
		  * && timeInfo.curCounterFreq.QuadPart != (LONGLONG) 1193182
		  * && timeInfo.curCounterFreq.QuadPart != (LONGLONG) 3579545
		  * && timeInfo.nominalFreq.QuadPart != (LONGLONG) 1193182
		  * && timeInfo.nominalFreq.QuadPart != (LONGLONG) 3579545
		  */
		 && timeInfo.curCounterFreq.QuadPart > (LONGLONG) 15000000 ) {
		 && timeInfo.nominalFreq.QuadPart > (LONGLONG) 15000000 ) {
		timeInfo.perfCounterAvailable = FALSE;
	    }

	    /*
	     * If the performance counter is available, start a thread to
	     * calibrate it.
	     */

	posixEpoch.LowPart = 0xD53E8000;
	posixEpoch.HighPart = 0x019DB1DE;

	EnterCriticalSection( &timeInfo.cs );

	QueryPerformanceCounter( &curCounter );

	/* 
	 * If it appears to be more than 1.1 seconds since the last trip
	 * through the calibration loop, the performance counter may
	 * have jumped. Discard it. See MSDN Knowledge Base article
	 * have jumped forward. (See MSDN Knowledge Base article
	 * Q274323 for a description of the hardware problem that makes
	 * this test necessary.
	 * this test necessary.) If the counter jumps, we don't want
	 * to use it directly. Instead, we must return system time.
	 * Eventually, the calibration loop should recover.
	 */
	if ( curCounter.QuadPart - timeInfo.lastPerfCounter
	     < 11 * timeInfo.estPerfCounterFreq / 10 ) {
	if ( curCounter.QuadPart - timeInfo.perfCounterLastCall.QuadPart
	     < 11 * timeInfo.curCounterFreq.QuadPart / 10 ) {
	    
	    curFileTime = timeInfo.lastFileTime.QuadPart
		+ ( ( curCounter.QuadPart - timeInfo.lastCounter.QuadPart )
	    curFileTime = timeInfo.fileTimeLastCall.QuadPart
		+ ( ( curCounter.QuadPart - timeInfo.perfCounterLastCall.QuadPart )
		    * 10000000 / timeInfo.curCounterFreq.QuadPart );
	    timeInfo.lastFileTime.QuadPart = curFileTime;
	    timeInfo.lastCounter.QuadPart = curCounter.QuadPart;
	    timeInfo.fileTimeLastCall.QuadPart = curFileTime;
	    timeInfo.perfCounterLastCall.QuadPart = curCounter.QuadPart;
	    usecSincePosixEpoch = ( curFileTime - posixEpoch.QuadPart ) / 10;
	    timePtr->sec = (time_t) ( usecSincePosixEpoch / 1000000 );
	    timePtr->usec = (unsigned long ) ( usecSincePosixEpoch % 1000000 );
	    useFtime = 0;
	}	    
	}

	LeaveCriticalSection( &timeInfo.cs );
    }
	
    if ( useFtime ) {
	
	/* High resolution timer is not available.  Just use ftime */

 *	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.
 *	At an interval of 1 s, 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 );
    QueryPerformanceCounter( &timeInfo.perfCounterLastCall );
    QueryPerformanceFrequency( &timeInfo.curCounterFreq );
    timeInfo.lastFileTime.LowPart = curFileTime.dwLowDateTime;
    timeInfo.lastFileTime.HighPart = curFileTime.dwHighDateTime;
    timeInfo.fileTimeLastCall.LowPart = curFileTime.dwLowDateTime;
    timeInfo.fileTimeLastCall.HighPart = curFileTime.dwHighDateTime;

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

    timeInfo.lastPerfCounter = timeInfo.lastCounter.QuadPart;
    timeInfo.estPerfCounterFreq = timeInfo.curCounterFreq.QuadPart;
    ResetCounterSamples( timeInfo.fileTimeLastCall.QuadPart,
			 timeInfo.perfCounterLastCall.QuadPart,
			 timeInfo.curCounterFreq.QuadPart );

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

    SetEvent( timeInfo.readyEvent );

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 estFreq;		/* Estimated perf counter frequency */

    LONGLONG delta;		/* Increment to add to the estimated
    LONGLONG vt0;		/* Tcl time right now */
				 * performance counter frequency in the
				 * loop filter */

    LONGLONG vt1;		/* Tcl time one second from now */
    LONGLONG fuzz;		/* Tolerance for the perf counter frequency */

    LONGLONG lowBound;		/* Lower bound for the frequency assuming
				 * 1000 ppm tolerance */
    LONGLONG tdiff;		/* Difference between system clock and
				 * Tcl time. */

    LONGLONG hiBound;		/* Upper bound for the frequency */
    LONGLONG driftFreq;		/* Frequency needed to drift virtual time
				 * into step over 1 second */

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

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

    EnterCriticalSection( &timeInfo.cs );

    /*
     * Several things may have gone wrong here that have to
     * be checked for.
     * 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.
     * (1) The performance counter may have jumped.
     * (2) The system clock may have been reset.
     *
     * In either case, we'll need to reinitialize the circular buffer
     * with samples relative to the current system time and the NOMINAL
     * performance frequency (not the actual, because the actual has
     * probably run slow in the first case). Our estimated frequency
     * will be the nominal frequency.
     */

    /*
     * Store the current sample into the circular buffer of samples,
     * and estimate the performance counter frequency.
     */
    perfCounterDiff = curPerfCounter.QuadPart - timeInfo.lastPerfCounter;
    timeInfo.lastPerfCounter = curPerfCounter.QuadPart;

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

    /*
     * We want to adjust things so that time appears to be continuous.
     * Virtual file time, right now, is 
     *
     * vt0 = 10000000 * ( curPerfCounter - perfCounterLastCall )
     *       / curCounterFreq
     *       + fileTimeLastCall
     *
     * Ideally, we would like to drift the clock into place over a
     * period of 2 sec, so that virtual time 2 sec from now will be
     *
     * vt1 = 20000000 + curFileTime
     * 
     * Consider this a timing glitch if instant frequency varies
     * The frequency that we need to use to drift the counter back into
     * significantly from the current estimate.
     * place is estFreq * 20000000 / ( vt1 - vt0 )
     */

    fuzz = timeInfo.estPerfCounterFreq >> 10;
    lowBound = timeInfo.estPerfCounterFreq - fuzz;
    hiBound = timeInfo.estPerfCounterFreq + fuzz;
    
    vt0 = 10000000 * ( curPerfCounter.QuadPart
		       - timeInfo.perfCounterLastCall.QuadPart )
	/ timeInfo.curCounterFreq.QuadPart
    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.fileTimeLastCall.QuadPart;
    vt1 = 20000000 + curFileTime.QuadPart;

    /*
     * If we've gotten more than a second away from system time,
     * then drifting the clock is going to be pretty hopeless.
     * Just let it jump. Otherwise, compute the drift frequency and
     * fill in everything.
     */

    tdiff = vt0 - curFileTime.QuadPart;
    if ( tdiff > 10000000 || tdiff < -10000000 ) {
	timeInfo.fileTimeLastCall.QuadPart = curFileTime.QuadPart;
	timeInfo.curCounterFreq.QuadPart = estFreq;
    } else {
	driftFreq = estFreq * 20000000 / ( vt1 - vt0 );
	if ( driftFreq > 1003 * estFreq / 1000 ) {
	    driftFreq = 1003 * estFreq / 1000;
	}
	if ( driftFreq < 997 * estFreq / 1000 ) {
	    driftFreq = 997 * estFreq / 1000;
	}
	timeInfo.fileTimeLastCall.QuadPart = vt0;
	timeInfo.curCounterFreq.QuadPart = driftFreq;
    }

    timeInfo.perfCounterLastCall.QuadPart = curPerfCounter.QuadPart;

    LeaveCriticalSection( &timeInfo.cs );

}

/*
 *----------------------------------------------------------------------
 *
 * ResetCounterSamples --
 *
 *	Fills the sample arrays in 'timeInfo' with dummy values that will
 *	yield the current performance counter and frequency.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	The array of samples is filled in so that it appears that there
 *	are SAMPLES samples at one-second intervals, separated by precisely
 *	the given frequency.
 *
 *----------------------------------------------------------------------
 */

static void
    timeInfo.lastFileTime.QuadPart
	+= ( ( curPerfCounter.QuadPart - timeInfo.lastCounter.QuadPart )
	     * 10000000 / timeInfo.curCounterFreq.QuadPart );
ResetCounterSamples( ULONGLONG fileTime,
				/* Current file time */
		     LONGLONG perfCounter,
				/* Current performance counter */
		     LONGLONG perfFreq )
    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
				/* Target performance frequency */
{
    int i;
    for ( i = SAMPLES-1; i >= 0; --i ) {
	timeInfo.perfCounterSample[i] = perfCounter;
	timeInfo.fileTimeSample[i] = fileTime;
	perfCounter -= perfFreq;
	fileTime -= 10000000;
    }
    timeInfo.sampleNo = 0;
}

/*
 *----------------------------------------------------------------------
 *
 * AccumulateSample --
 *
 *	Updates the circular buffer of performance counter and system
 *	time samples with a new data point.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	The new data point replaces the oldest point in the circular
 *	buffer, and the descriptive statistics are updated to accumulate
 *	the new point.
 *
 * Several things may have gone wrong here that have to
 * be checked for.
 * (1) The performance counter may have jumped.
 * (2) The system clock may have been reset.
 *
 * In either case, we'll need to reinitialize the circular buffer
 * with samples relative to the current system time and the NOMINAL
	 * 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.
	 */
 * performance frequency (not the actual, because the actual has
 * probably run slow in the first case).
 */

static LONGLONG
AccumulateSample( LONGLONG perfCounter,
	timeInfo.lastFileTime.QuadPart = curFileTime.QuadPart;
		  ULONGLONG fileTime )
	timeInfo.curCounterFreq.QuadPart = timeInfo.estPerfCounterFreq;

    } else {
{
    ULONGLONG workFTSample;	/* File time sample being removed
				 * from or added to the circular buffer */

    LONGLONG workPCSample;	/* Performance counter sample being
				 * removed from or added to the circular 
				 * buffer */

    ULONGLONG lastFTSample;	/* Last file time sample recorded */

    LONGLONG lastPCSample;	/* Last performance counter sample recorded */
	/*
	 * 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 );

    LONGLONG FTdiff;		/* Difference between last FT and current */

    LONGLONG PCdiff;		/* Difference between last PC and current */

    LONGLONG estFreq;		/* Estimated performance counter frequency */

    /* Test for jumps and reset the samples if we have one. */

    if ( timeInfo.sampleNo == 0 ) {
	lastPCSample = timeInfo.perfCounterSample[ timeInfo.sampleNo
						   + SAMPLES - 1 ];
	lastFTSample = timeInfo.fileTimeSample[ timeInfo.sampleNo
						+ SAMPLES - 1 ];
    } else {
	lastPCSample = timeInfo.perfCounterSample[ timeInfo.sampleNo - 1 ];
	lastFTSample = timeInfo.fileTimeSample[ timeInfo.sampleNo - 1 ];
    }
    PCdiff = perfCounter - lastPCSample;
    FTdiff = fileTime - lastFTSample;
    if ( PCdiff < timeInfo.nominalFreq.QuadPart * 9 / 10
	 || PCdiff > timeInfo.nominalFreq.QuadPart * 11 / 10
	 || FTdiff < 9000000
	 || FTdiff > 11000000 ) {
	ResetCounterSamples( fileTime, perfCounter,
			     timeInfo.nominalFreq.QuadPart );
	return timeInfo.nominalFreq.QuadPart;

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

    LeaveCriticalSection( &timeInfo.cs );

	workPCSample = timeInfo.perfCounterSample[ timeInfo.sampleNo ];
	workFTSample = timeInfo.fileTimeSample[ timeInfo.sampleNo ];
	estFreq = 10000000 * ( perfCounter - workPCSample )
	    / ( fileTime - workFTSample );
	timeInfo.perfCounterSample[ timeInfo.sampleNo ] = perfCounter;
	timeInfo.fileTimeSample[ timeInfo.sampleNo ] = (LONGLONG) fileTime;
	
	/* Advance the sample number */
	
	if ( ++timeInfo.sampleNo >= SAMPLES ) {
	    timeInfo.sampleNo = 0;
	} 
	
	return estFreq;
    }
}