Tcl Source Code

Check-in [feb76896c3]
Login
Bounty program for improvements to Tcl and certain Tcl packages.
Tcl 2019 Conference, Houston/TX, US, Nov 4-8
Send your abstracts to tclconference@googlegroups.com
or submit via the online form by Sep 9.

Many hyperlinks are disabled.
Use anonymous login to enable hyperlinks.

Overview
Comment:Merge 8.7
Downloads: Tarball | ZIP archive | SQL archive
Timelines: family | ancestors | descendants | both | trunk
Files: files | file ages | folders
SHA3-256:feb76896c378ad4406b82394fd43903d7f13ea9eb8f1a70be6dd11b2c0529570
User & Date: jan.nijtmans 2019-03-07 08:39:37
Context
2019-03-07
14:20
(core-8-branch merge) Fix automatic pkgIndex generation for multiplatform installs. check-in: fa308cbee6 user: apnadkarni tags: trunk
08:39
Merge 8.7 check-in: feb76896c3 user: jan.nijtmans tags: trunk
08:31
Merge 8.6. Remove unneeded code from init.tcl check-in: 3efa92355e user: jan.nijtmans tags: core-8-branch
2019-03-06
12:34
merge 8.7 check-in: 17eb5e790b user: sebres tags: trunk
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to generic/tclCmdMZ.c.

4082
4083
4084
4085
4086
4087
4088
4089
4090
4091
4092
4093
4094
4095
4096
4097
....
4105
4106
4107
4108
4109
4110
4111
4112
4113
4114
4115
4116
4117
4118
4119
4120
....
4194
4195
4196
4197
4198
4199
4200
4201
4202
4203
4204
4205
4206
4207
4208
4209
4210
4211
4212
4213
4214
....
4217
4218
4219
4220
4221
4222
4223
4224
4225
4226
4227
4228
4229
4230
4231
....
4318
4319
4320
4321
4322
4323
4324
4325
4326
4327
4328
4329
4330
4331
4332
....
4417
4418
4419
4420
4421
4422
4423
4424
4425
4426
4427
4428
4429
4430
4431
 
/*
 *----------------------------------------------------------------------
 *
 * Tcl_TimeRateObjCmd --
 *
 *	This object-based procedure is invoked to process the "timerate" Tcl
 *	command. 
 *	This is similar to command "time", except the execution limited by 
 *	given time (in milliseconds) instead of repetition count.
 *
 * Example:
 *	timerate {after 5} 1000 ; # equivalent for `time {after 5} [expr 1000/5]`
 *
 * Results:
 *	A standard Tcl object result.
................................................................................
int
Tcl_TimeRateObjCmd(
    ClientData dummy,		/* Not used. */
    Tcl_Interp *interp,		/* Current interpreter. */
    int objc,			/* Number of arguments. */
    Tcl_Obj *const objv[])	/* Argument objects. */
{
    static 
    double measureOverhead = 0; /* global measure-overhead */
    double overhead = -1;	/* given measure-overhead */
    register Tcl_Obj *objPtr;
    register int result, i;
    Tcl_Obj *calibrate = NULL, *direct = NULL;
    Tcl_WideUInt count = 0;	/* Holds repetition count */
    Tcl_WideInt  maxms  = WIDE_MIN;
				/* Maximal running time (in milliseconds) */
................................................................................
    if (calibrate) {

	/* if no time specified for the calibration */
	if (maxms == WIDE_MIN) {
	    Tcl_Obj *clobjv[6];
	    Tcl_WideInt maxCalTime = 5000;
	    double lastMeasureOverhead = measureOverhead;
	    
	    clobjv[0] = objv[0]; 
	    i = 1;
	    if (direct) {
	    	clobjv[i++] = direct;
	    }
	    clobjv[i++] = objPtr; 

	    /* reset last measurement overhead */
	    measureOverhead = (double)0;

	    /* self-call with 100 milliseconds to warm-up,
	     * before entering the calibration cycle */
	    TclNewIntObj(clobjv[i], 100);
................................................................................
	    Tcl_DecrRefCount(clobjv[i]);
	    if (result != TCL_OK) {
		return result;
	    }

	    i--;
	    clobjv[i++] = calibrate;
	    clobjv[i++] = objPtr; 

	    /* set last measurement overhead to max */
	    measureOverhead = (double)UWIDE_MAX;

	    /* calibration cycle until it'll be preciser */
	    maxms = -1000;
	    do {
................................................................................
		goto done;
	    }
	    /* force stop immediately */
	    threshold = 1;
	    maxcnt = 0;
	    result = TCL_OK;
	}
	
	/* don't check time up to threshold */
	if (--threshold > 0) continue;

	/* check stop time reached, estimate new threshold */
    #ifdef TCL_WIDE_CLICKS
	middle = TclpGetWideClicks();
    #else
................................................................................
	    if (val < 1000)  { fmt = "%.3f"; } else
	    if (val < 10000) { fmt = "%.2f"; } else
			     { fmt = "%.1f"; };
	    objs[0] = Tcl_ObjPrintf(fmt, ((double)middle)/count);
	}

	objs[2] = Tcl_NewWideIntObj(count); /* iterations */
	
	/* calculate speed as rate (count) per sec */
	if (!middle) middle++; /* +1 ms, just to avoid divide by zero */
	if (count < (WIDE_MAX / 1000000)) {
	    val = (count * 1000000) / middle;
	    if (val < 100000) {
		if (val < 100)	{ fmt = "%.3f"; } else
		if (val < 1000) { fmt = "%.2f"; } else







|
|







 







<
|







 







|
|




|







 







|







 







|







 







|







4082
4083
4084
4085
4086
4087
4088
4089
4090
4091
4092
4093
4094
4095
4096
4097
....
4105
4106
4107
4108
4109
4110
4111

4112
4113
4114
4115
4116
4117
4118
4119
....
4193
4194
4195
4196
4197
4198
4199
4200
4201
4202
4203
4204
4205
4206
4207
4208
4209
4210
4211
4212
4213
....
4216
4217
4218
4219
4220
4221
4222
4223
4224
4225
4226
4227
4228
4229
4230
....
4317
4318
4319
4320
4321
4322
4323
4324
4325
4326
4327
4328
4329
4330
4331
....
4416
4417
4418
4419
4420
4421
4422
4423
4424
4425
4426
4427
4428
4429
4430
 
/*
 *----------------------------------------------------------------------
 *
 * Tcl_TimeRateObjCmd --
 *
 *	This object-based procedure is invoked to process the "timerate" Tcl
 *	command.
 *	This is similar to command "time", except the execution limited by
 *	given time (in milliseconds) instead of repetition count.
 *
 * Example:
 *	timerate {after 5} 1000 ; # equivalent for `time {after 5} [expr 1000/5]`
 *
 * Results:
 *	A standard Tcl object result.
................................................................................
int
Tcl_TimeRateObjCmd(
    ClientData dummy,		/* Not used. */
    Tcl_Interp *interp,		/* Current interpreter. */
    int objc,			/* Number of arguments. */
    Tcl_Obj *const objv[])	/* Argument objects. */
{

    static double measureOverhead = 0; /* global measure-overhead */
    double overhead = -1;	/* given measure-overhead */
    register Tcl_Obj *objPtr;
    register int result, i;
    Tcl_Obj *calibrate = NULL, *direct = NULL;
    Tcl_WideUInt count = 0;	/* Holds repetition count */
    Tcl_WideInt  maxms  = WIDE_MIN;
				/* Maximal running time (in milliseconds) */
................................................................................
    if (calibrate) {

	/* if no time specified for the calibration */
	if (maxms == WIDE_MIN) {
	    Tcl_Obj *clobjv[6];
	    Tcl_WideInt maxCalTime = 5000;
	    double lastMeasureOverhead = measureOverhead;

	    clobjv[0] = objv[0];
	    i = 1;
	    if (direct) {
	    	clobjv[i++] = direct;
	    }
	    clobjv[i++] = objPtr;

	    /* reset last measurement overhead */
	    measureOverhead = (double)0;

	    /* self-call with 100 milliseconds to warm-up,
	     * before entering the calibration cycle */
	    TclNewIntObj(clobjv[i], 100);
................................................................................
	    Tcl_DecrRefCount(clobjv[i]);
	    if (result != TCL_OK) {
		return result;
	    }

	    i--;
	    clobjv[i++] = calibrate;
	    clobjv[i++] = objPtr;

	    /* set last measurement overhead to max */
	    measureOverhead = (double)UWIDE_MAX;

	    /* calibration cycle until it'll be preciser */
	    maxms = -1000;
	    do {
................................................................................
		goto done;
	    }
	    /* force stop immediately */
	    threshold = 1;
	    maxcnt = 0;
	    result = TCL_OK;
	}

	/* don't check time up to threshold */
	if (--threshold > 0) continue;

	/* check stop time reached, estimate new threshold */
    #ifdef TCL_WIDE_CLICKS
	middle = TclpGetWideClicks();
    #else
................................................................................
	    if (val < 1000)  { fmt = "%.3f"; } else
	    if (val < 10000) { fmt = "%.2f"; } else
			     { fmt = "%.1f"; };
	    objs[0] = Tcl_ObjPrintf(fmt, ((double)middle)/count);
	}

	objs[2] = Tcl_NewWideIntObj(count); /* iterations */

	/* calculate speed as rate (count) per sec */
	if (!middle) middle++; /* +1 ms, just to avoid divide by zero */
	if (count < (WIDE_MAX / 1000000)) {
	    val = (count * 1000000) / middle;
	    if (val < 100000) {
		if (val < 100)	{ fmt = "%.3f"; } else
		if (val < 1000) { fmt = "%.2f"; } else

Changes to generic/tclEnv.c.

131
132
133
134
135
136
137












138
139
140
141
142
143
144
		 */

		Tcl_DStringFree(&envString);
		continue;
	    }
	    p2++;
	    p2[-1] = '\0';












	    obj1 = Tcl_NewStringObj(p1, -1);
	    obj2 = Tcl_NewStringObj(p2, -1);
	    Tcl_DStringFree(&envString);

	    Tcl_IncrRefCount(obj1);
	    Tcl_IncrRefCount(obj2);
	    Tcl_ObjSetVar2(interp, varNamePtr, obj1, obj2, TCL_GLOBAL_ONLY);







>
>
>
>
>
>
>
>
>
>
>
>







131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
		 */

		Tcl_DStringFree(&envString);
		continue;
	    }
	    p2++;
	    p2[-1] = '\0';
#if defined(_WIN32)
	    /*
	     * Enforce PATH and COMSPEC to be all uppercase. This eliminates
	     * additional trace logic otherwise required in init.tcl.
	     */

	    if (strcasecmp(p1, "PATH") == 0) {
		p1 = "PATH";
	    } else if (strcasecmp(p1, "COMSPEC") == 0) {
		p1 = "COMSPEC";
	    }
#endif
	    obj1 = Tcl_NewStringObj(p1, -1);
	    obj2 = Tcl_NewStringObj(p2, -1);
	    Tcl_DStringFree(&envString);

	    Tcl_IncrRefCount(obj1);
	    Tcl_IncrRefCount(obj2);
	    Tcl_ObjSetVar2(interp, varNamePtr, obj1, obj2, TCL_GLOBAL_ONLY);

Changes to library/init.tcl.

76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
	    encoding dirs $Path
        }
    }
}

namespace eval tcl::Pkg {}

# Windows specific end of initialization

if {(![interp issafe]) && ($tcl_platform(platform) eq "windows")} {
    namespace eval tcl {
	proc EnvTraceProc {lo n1 n2 op} {
	    global env
	    set x $env($n2)
	    set env($lo) $x
	    set env([string toupper $lo]) $x
	}
	proc InitWinEnv {} {
	    global env tcl_platform
	    foreach p [array names env] {
		set u [string toupper $p]
		if {$u ne $p} {
		    switch -- $u {
			COMSPEC -
			PATH {
			    set temp $env($p)
			    unset env($p)
			    set env($u) $temp
			    trace add variable env($p) write \
				    [namespace code [list EnvTraceProc $p]]
			    trace add variable env($u) write \
				    [namespace code [list EnvTraceProc $p]]
			}
		    }
		}
	    }
	    if {![info exists env(COMSPEC)]} {
		set env(COMSPEC) cmd.exe
	    }
	}
	InitWinEnv
    }
}

# Setup the unknown package handler


if {[interp issafe]} {
    package unknown {::tcl::tm::UnknownHandler ::tclPkgUnknown}
} else {







<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<







76
77
78
79
80
81
82




































83
84
85
86
87
88
89
	    encoding dirs $Path
        }
    }
}

namespace eval tcl::Pkg {}






































# Setup the unknown package handler


if {[interp issafe]} {
    package unknown {::tcl::tm::UnknownHandler ::tclPkgUnknown}
} else {

Changes to unix/tclUnixTime.c.

219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
}
 
/*
 *----------------------------------------------------------------------
 *
 * TclpWideClickInMicrosec --
 *
 *	This procedure return scale to convert click values from the 
 *	TclpGetWideClicks native resolution to microsecond resolution
 *	and back.
 *
 * Results:
 * 	1 click in microseconds as double.
 *
 * Side effects:







|







219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
}
 
/*
 *----------------------------------------------------------------------
 *
 * TclpWideClickInMicrosec --
 *
 *	This procedure return scale to convert click values from the
 *	TclpGetWideClicks native resolution to microsecond resolution
 *	and back.
 *
 * Results:
 * 	1 click in microseconds as double.
 *
 * Side effects:

Changes to win/nmakehlp.c.

789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
 *      If found, the command prints
 *         name_DIRPATH=<full path of located directory>
 *      and returns 0. If not found, does not print anything and returns 1.
 */
static int LocateDependency(const char *keypath)
{
    int i, ret;
    static char *paths[] = {"..", "..\\..", "..\\..\\.."};

    for (i = 0; i < (sizeof(paths)/sizeof(paths[0])); ++i) {
	ret = LocateDependencyHelper(paths[i], keypath);
	if (ret == 0)
	    return ret;
    }
    return ret;







|







789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
 *      If found, the command prints
 *         name_DIRPATH=<full path of located directory>
 *      and returns 0. If not found, does not print anything and returns 1.
 */
static int LocateDependency(const char *keypath)
{
    int i, ret;
    static const char *paths[] = {"..", "..\\..", "..\\..\\.."};

    for (i = 0; i < (sizeof(paths)/sizeof(paths[0])); ++i) {
	ret = LocateDependencyHelper(paths[i], keypath);
	if (ret == 0)
	    return ret;
    }
    return ret;

Changes to win/tclWinTime.c.

229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
...
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
...
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
...
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
...
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
...
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
    LARGE_INTEGER curCounter;

    if (!wideClick.initialized) {
	LARGE_INTEGER perfCounterFreq;

	/*
	 * The frequency of the performance counter is fixed at system boot and
	 * is consistent across all processors. Therefore, the frequency need 
	 * only be queried upon application initialization.
	 */
	if (QueryPerformanceFrequency(&perfCounterFreq)) {
	    wideClick.perfCounter = 1;
	    wideClick.microsecsScale = 1000000.0 / perfCounterFreq.QuadPart;
	} else {
	    /* fallback using microseconds */
	    wideClick.perfCounter = 0;
	    wideClick.microsecsScale = 1;
	}
	
	wideClick.initialized = 1;
    }
    if (wideClick.perfCounter) {
	if (QueryPerformanceCounter(&curCounter)) {
	    return (Tcl_WideInt)curCounter.QuadPart;
	}
	/* fallback using microseconds */
................................................................................
}
 
/*
 *----------------------------------------------------------------------
 *
 * TclpWideClickInMicrosec --
 *
 *	This procedure return scale to convert wide click values from the 
 *	TclpGetWideClicks native resolution to microsecond resolution
 *	and back.
 *
 * Results:
 * 	1 click in microseconds as double.
 *
 * Side effects:
................................................................................
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

Tcl_WideInt 
TclpGetMicroseconds(void)
{
    Tcl_WideInt usecSincePosixEpoch;

    /* Try to use high resolution timer */
    if ( tclGetTimeProcPtr == NativeGetTime
      && (usecSincePosixEpoch = NativeGetMicroseconds())
................................................................................
static inline Tcl_WideInt
NativeCalc100NsTicks(
    ULONGLONG fileTimeLastCall,
    LONGLONG perfCounterLastCall,
    LONGLONG curCounterFreq,
    LONGLONG curCounter
) {
    return fileTimeLastCall + 
	((curCounter - perfCounterLastCall) * 10000000 / curCounterFreq);
}

static Tcl_WideInt
NativeGetMicroseconds(void)
{
    /*
................................................................................
      && curFileTime.QuadPart < lastFileTime.QuadPart +
      				    (timeInfo.calibrationInterv * 10000000)
    ) {
    	/* again in next one second */
	return;
    }
    QueryPerformanceCounter(&curPerfCounter);
    
    lastFileTime.QuadPart = curFileTime.QuadPart;

    /*
     * We devide by timeInfo.curCounterFreq.QuadPart in several places. That
     * value should always be positive on a correctly functioning system. But
     * it is good to be defensive about such matters. So if something goes
     * wrong and the value does goes to zero, we clear the
................................................................................
    if (tdiff > 10000000 || tdiff < -10000000) {
    	/* jump to current system time, use curent estimated frequency */
    	vt0 = curFileTime.QuadPart;
    } else {
    	/* calculate new frequency and estimate drift to the next second */
	vt1 = 20000000 + curFileTime.QuadPart;
	driftFreq = (estFreq * 20000000 / (vt1 - vt0));
	/* 
	 * Avoid too large drifts (only half of the current difference),
	 * that allows also be more accurate (aspire to the smallest tdiff),
	 * so then we can prolong calibration interval by tdiff < 100000
	 */
	driftFreq = timeInfo.curCounterFreq.QuadPart +
		(driftFreq - timeInfo.curCounterFreq.QuadPart) / 2;

	/* 
	 * Average between estimated, 2 current and 5 drifted frequencies,
	 * (do the soft drifting as possible)
	 */
	estFreq = (estFreq + 2 * timeInfo.curCounterFreq.QuadPart + 5 * driftFreq) / 8;
    }
    
    /* Avoid too large discrepancy from nominal frequency */
    if (estFreq > 1003*timeInfo.nominalFreq.QuadPart/1000) {
	estFreq = 1003*timeInfo.nominalFreq.QuadPart/1000;
	vt0 = curFileTime.QuadPart;
    } else if (estFreq < 997*timeInfo.nominalFreq.QuadPart/1000) {
	estFreq = 997*timeInfo.nominalFreq.QuadPart/1000;
	vt0 = curFileTime.QuadPart;
    } else if (vt0 != curFileTime.QuadPart) {
	/* 
	 * Be sure the clock ticks never backwards (avoid it by negative drifting)
	 * just compare native time (in 100-ns) before and hereafter using 
	 * new calibrated values) and do a small adjustment (short time freeze)
	 */
	LARGE_INTEGER newPerfCounter;
	Tcl_WideInt nt0, nt1;

	QueryPerformanceCounter(&newPerfCounter);
	nt0 = NativeCalc100NsTicks(timeInfo.fileTimeLastCall.QuadPart,







|










|







 







|







 







|







 







|







 







|







 







|







|





|








|

|







229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
...
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
...
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
...
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
...
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
...
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
    LARGE_INTEGER curCounter;

    if (!wideClick.initialized) {
	LARGE_INTEGER perfCounterFreq;

	/*
	 * The frequency of the performance counter is fixed at system boot and
	 * is consistent across all processors. Therefore, the frequency need
	 * only be queried upon application initialization.
	 */
	if (QueryPerformanceFrequency(&perfCounterFreq)) {
	    wideClick.perfCounter = 1;
	    wideClick.microsecsScale = 1000000.0 / perfCounterFreq.QuadPart;
	} else {
	    /* fallback using microseconds */
	    wideClick.perfCounter = 0;
	    wideClick.microsecsScale = 1;
	}

	wideClick.initialized = 1;
    }
    if (wideClick.perfCounter) {
	if (QueryPerformanceCounter(&curCounter)) {
	    return (Tcl_WideInt)curCounter.QuadPart;
	}
	/* fallback using microseconds */
................................................................................
}
 
/*
 *----------------------------------------------------------------------
 *
 * TclpWideClickInMicrosec --
 *
 *	This procedure return scale to convert wide click values from the
 *	TclpGetWideClicks native resolution to microsecond resolution
 *	and back.
 *
 * Results:
 * 	1 click in microseconds as double.
 *
 * Side effects:
................................................................................
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

Tcl_WideInt
TclpGetMicroseconds(void)
{
    Tcl_WideInt usecSincePosixEpoch;

    /* Try to use high resolution timer */
    if ( tclGetTimeProcPtr == NativeGetTime
      && (usecSincePosixEpoch = NativeGetMicroseconds())
................................................................................
static inline Tcl_WideInt
NativeCalc100NsTicks(
    ULONGLONG fileTimeLastCall,
    LONGLONG perfCounterLastCall,
    LONGLONG curCounterFreq,
    LONGLONG curCounter
) {
    return fileTimeLastCall +
	((curCounter - perfCounterLastCall) * 10000000 / curCounterFreq);
}

static Tcl_WideInt
NativeGetMicroseconds(void)
{
    /*
................................................................................
      && curFileTime.QuadPart < lastFileTime.QuadPart +
      				    (timeInfo.calibrationInterv * 10000000)
    ) {
    	/* again in next one second */
	return;
    }
    QueryPerformanceCounter(&curPerfCounter);

    lastFileTime.QuadPart = curFileTime.QuadPart;

    /*
     * We devide by timeInfo.curCounterFreq.QuadPart in several places. That
     * value should always be positive on a correctly functioning system. But
     * it is good to be defensive about such matters. So if something goes
     * wrong and the value does goes to zero, we clear the
................................................................................
    if (tdiff > 10000000 || tdiff < -10000000) {
    	/* jump to current system time, use curent estimated frequency */
    	vt0 = curFileTime.QuadPart;
    } else {
    	/* calculate new frequency and estimate drift to the next second */
	vt1 = 20000000 + curFileTime.QuadPart;
	driftFreq = (estFreq * 20000000 / (vt1 - vt0));
	/*
	 * Avoid too large drifts (only half of the current difference),
	 * that allows also be more accurate (aspire to the smallest tdiff),
	 * so then we can prolong calibration interval by tdiff < 100000
	 */
	driftFreq = timeInfo.curCounterFreq.QuadPart +
		(driftFreq - timeInfo.curCounterFreq.QuadPart) / 2;

	/*
	 * Average between estimated, 2 current and 5 drifted frequencies,
	 * (do the soft drifting as possible)
	 */
	estFreq = (estFreq + 2 * timeInfo.curCounterFreq.QuadPart + 5 * driftFreq) / 8;
    }

    /* Avoid too large discrepancy from nominal frequency */
    if (estFreq > 1003*timeInfo.nominalFreq.QuadPart/1000) {
	estFreq = 1003*timeInfo.nominalFreq.QuadPart/1000;
	vt0 = curFileTime.QuadPart;
    } else if (estFreq < 997*timeInfo.nominalFreq.QuadPart/1000) {
	estFreq = 997*timeInfo.nominalFreq.QuadPart/1000;
	vt0 = curFileTime.QuadPart;
    } else if (vt0 != curFileTime.QuadPart) {
	/*
	 * Be sure the clock ticks never backwards (avoid it by negative drifting)
	 * just compare native time (in 100-ns) before and hereafter using
	 * new calibrated values) and do a small adjustment (short time freeze)
	 */
	LARGE_INTEGER newPerfCounter;
	Tcl_WideInt nt0, nt1;

	QueryPerformanceCounter(&newPerfCounter);
	nt0 = NativeCalc100NsTicks(timeInfo.fileTimeLastCall.QuadPart,