summaryrefslogtreecommitdiffstats
path: root/win/tclWinTime.c
blob: 18702e7da543968455809d5030e8932e93bde490 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
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
126
127
128
129
130
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
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
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
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
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
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
/*
 * 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.
 */

#include "tclInt.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.
 */

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

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

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

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

typedef struct {
    CRITICAL_SECTION cs;	/* Mutex guarding this structure. */
    int initialized;		/* Flag == 1 if this structure is
				 * initialized. */
    int perfCounterAvailable;	/* Flag == 1 if the hardware has a performance
				 * counter. */
    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 fileTimeLastCall;
    LARGE_INTEGER perfCounterLastCall;
    LARGE_INTEGER curCounterFreq;

    /*
     * Data used in developing the estimate of performance counter frequency
     */

    Tcl_WideUInt fileTimeSample[SAMPLES];
				/* Last 64 samples of system time. */
    Tcl_WideInt perfCounterSample[SAMPLES];
				/* Last 64 samples of performance counter. */
    int sampleNo;		/* Current sample number. */
} TimeInfo;

static TimeInfo timeInfo = {
    { NULL, 0, 0, NULL, NULL, 0 },
    0,
    0,
    (HANDLE) NULL,
    (HANDLE) NULL,
    (HANDLE) NULL,
#ifdef HAVE_CAST_TO_UNION
    (LARGE_INTEGER) (Tcl_WideInt) 0,
    (ULARGE_INTEGER) (DWORDLONG) 0,
    (LARGE_INTEGER) (Tcl_WideInt) 0,
    (LARGE_INTEGER) (Tcl_WideInt) 0,
#else
    0,
    0,
    0,
    0,
#endif
    { 0 },
    { 0 },
    0
};

/*
 * Declarations for functions defined later in this file.
 */

#ifndef TCL_NO_DEPRECATED
static struct tm *	ComputeGMT(const time_t *tp);
#endif /* TCL_NO_DEPRECATED */
static void		StopCalibration(ClientData clientData);
static DWORD WINAPI	CalibrationThread(LPVOID arg);
static void 		UpdateTimeEachSecond(void);
static void		ResetCounterSamples(Tcl_WideUInt fileTime,
			    Tcl_WideInt perfCounter, Tcl_WideInt perfFreq);
static Tcl_WideInt	AccumulateSample(Tcl_WideInt perfCounter,
			    Tcl_WideUInt fileTime);
static void		NativeScaleTime(Tcl_Time* timebuf,
			    ClientData clientData);
static void		NativeGetTime(Tcl_Time* timebuf,
			    ClientData clientData);

/*
 * TIP #233 (Virtualized Time): Data for the time hooks, if any.
 */

Tcl_GetTimeProc *tclGetTimeProcPtr = NativeGetTime;
Tcl_ScaleTimeProc *tclScaleTimeProcPtr = NativeScaleTime;
ClientData tclTimeClientData = NULL;

/*
 *----------------------------------------------------------------------
 *
 * TclpGetSeconds --
 *
 *	This procedure returns the number of seconds from the epoch. On most
 *	Unix systems the epoch is Midnight Jan 1, 1970 GMT.
 *
 * Results:
 *	Number of seconds from the epoch.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

unsigned long
TclpGetSeconds(void)
{
    Tcl_Time t;

    tclGetTimeProcPtr(&t, tclTimeClientData);	/* Tcl_GetTime inlined. */
    return t.sec;
}

/*
 *----------------------------------------------------------------------
 *
 * TclpGetClicks --
 *
 *	This procedure returns a value that represents the highest resolution
 *	clock available on the system. There are no guarantees on what the
 *	resolution will be. In Tcl we will call this value a "click". The
 *	start time is also system dependant.
 *
 * Results:
 *	Number of clicks from some start time.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

unsigned long
TclpGetClicks(void)
{
    /*
     * Use the Tcl_GetTime abstraction to get the time in microseconds, as
     * nearly as we can, and return it.
     */

    Tcl_Time now;		/* Current Tcl time */
    unsigned long retval;	/* Value to return */

    tclGetTimeProcPtr(&now, tclTimeClientData);	/* Tcl_GetTime inlined */

    retval = (now.sec * 1000000) + now.usec;
    return retval;

}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetTime --
 *
 *	Gets the current system time in seconds and microseconds since the
 *	beginning of the epoch: 00:00 UCT, January 1, 1970.
 *
 * Results:
 *	Returns the current time in timePtr.
 *
 * Side effects:
 *	On the first call, initializes a set of static variables to keep track
 *	of the base value of the performance counter, the corresponding wall
 *	clock (obtained through ftime) and the frequency of the performance
 *	counter. Also spins a thread whose function is to wake up periodically
 *	and monitor these values, adjusting them as necessary to correct for
 *	drift in the performance counter's oscillator.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_GetTime(
    Tcl_Time *timePtr)		/* Location to store time information. */
{
    tclGetTimeProcPtr(timePtr, tclTimeClientData);
}

/*
 *----------------------------------------------------------------------
 *
 * NativeScaleTime --
 *
 *	TIP #233: Scale from virtual time to the real-time. For native scaling
 *	the relationship is 1:1 and nothing has to be done.
 *
 * Results:
 *	Scales the time in timePtr.
 *
 * Side effects:
 *	See above.
 *
 *----------------------------------------------------------------------
 */

static void
NativeScaleTime(
    Tcl_Time *timePtr,
    ClientData clientData)
{
    /*
     * Native scale is 1:1. Nothing is done.
     */
}

/*
 *----------------------------------------------------------------------
 *
 * NativeGetTime --
 *
 *	TIP #233: Gets the current system time in seconds and microseconds
 *	since the beginning of the epoch: 00:00 UCT, January 1, 1970.
 *
 * Results:
 *	Returns the current time in timePtr.
 *
 * Side effects:
 *	On the first call, initializes a set of static variables to keep track
 *	of the base value of the performance counter, the corresponding wall
 *	clock (obtained through ftime) and the frequency of the performance
 *	counter. Also spins a thread whose function is to wake up periodically
 *	and monitor these values, adjusting them as necessary to correct for
 *	drift in the performance counter's oscillator.
 *
 *----------------------------------------------------------------------
 */

static void
NativeGetTime(
    Tcl_Time *timePtr,
    ClientData clientData)
{
    struct _timeb t;

    /*
     * Initialize static storage on the first trip through.
     *
     * Note: Outer check for 'initialized' is a performance win since it
     * avoids an extra mutex lock in the common case.
     */

    if (!timeInfo.initialized) {
	TclpInitLock();
	if (!timeInfo.initialized) {
	    timeInfo.perfCounterAvailable =
		    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.
	     *    - unpredictable changes in performance counter frequency on
	     *      "gearshift" processors such as Transmeta and SpeedStep.
	     *
	     * There seems to be no way to test whether the performance
	     * counter is reliable, but a useful heuristic is that if its
	     * frequency is 1.193182 MHz or 3.579545 MHz, it's derived from a
	     * colorburst crystal and is therefore the RTC rather than the
	     * TSC.
	     *
	     * A sloppier but serviceable heuristic is that the RTC crystal is
	     * normally less than 15 MHz while the TSC crystal is virtually
	     * assured to be greater than 100 MHz. Since Win98SE appears to
	     * fiddle with the definition of the perf counter frequency
	     * (perhaps in an attempt to calibrate the clock?), we use the
	     * latter rule rather than an exact match.
	     *
	     * We also assume (perhaps questionably) that the vendors have
	     * gotten their act together on Win64, so bypass all this rubbish
	     * on that platform.
	     */

#if !defined(_WIN64)
	    if (timeInfo.perfCounterAvailable
		    /*
		     * The following lines would do an exact match on crystal
		     * frequency:
		     * && timeInfo.nominalFreq.QuadPart != (Tcl_WideInt)1193182
		     * && timeInfo.nominalFreq.QuadPart != (Tcl_WideInt)3579545
		     */
		    && timeInfo.nominalFreq.QuadPart > (Tcl_WideInt) 15000000){
		/*
		 * As an exception, if every logical processor on the system
		 * is on the same chip, we use the performance counter anyway,
		 * presuming that everyone's TSC is locked to the same
		 * oscillator.
		 */

		SYSTEM_INFO systemInfo;
		int regs[4];

		GetSystemInfo(&systemInfo);
		if (TclWinCPUID(0, regs) == TCL_OK
			&& regs[1] == 0x756e6547	/* "Genu" */
			&& regs[3] == 0x49656e69	/* "ineI" */
			&& regs[2] == 0x6c65746e	/* "ntel" */
			&& TclWinCPUID(1, regs) == TCL_OK
			&& ((regs[0]&0x00000F00) == 0x00000F00 /* Pentium 4 */
			|| ((regs[0] & 0x00F00000)	/* Extended family */
			&& (regs[3] & 0x10000000)))	/* Hyperthread */
			&& (((regs[1]&0x00FF0000) >> 16)/* CPU count */
			    == (int)systemInfo.dwNumberOfProcessors)) {
		    timeInfo.perfCounterAvailable = TRUE;
		} else {
		    timeInfo.perfCounterAvailable = FALSE;
		}
	    }
#endif /* above code is Win32 only */

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

	    if (timeInfo.perfCounterAvailable) {
		DWORD id;

		InitializeCriticalSection(&timeInfo.cs);
		timeInfo.readyEvent = CreateEvent(NULL, FALSE, FALSE, NULL);
		timeInfo.exitEvent = CreateEvent(NULL, FALSE, FALSE, NULL);
		timeInfo.calibrationThread = CreateThread(NULL, 256,
			CalibrationThread, (LPVOID) NULL, 0, &id);
		SetThreadPriority(timeInfo.calibrationThread,
			THREAD_PRIORITY_HIGHEST);

		/*
		 * Wait for the thread just launched to start running, and
		 * create an exit handler that kills it so that it doesn't
		 * outlive unloading tclXX.dll
		 */

		WaitForSingleObject(timeInfo.readyEvent, INFINITE);
		CloseHandle(timeInfo.readyEvent);
		Tcl_CreateExitHandler(StopCalibration, NULL);
	    }
	    timeInfo.initialized = TRUE;
	}
	TclpInitUnlock();
    }

    if (timeInfo.perfCounterAvailable && timeInfo.curCounterFreq.QuadPart!=0) {
	/*
	 * Query the performance counter and use it to calculate the current
	 * time.
	 */

	ULARGE_INTEGER fileTimeLastCall;
	LARGE_INTEGER perfCounterLastCall, curCounterFreq;
				/* Copy with current data of calibration cycle */

	LARGE_INTEGER curCounter;
				/* Current performance counter. */
	Tcl_WideInt curFileTime;/* Current estimated time, expressed as 100-ns
				 * ticks since the Windows epoch. */
	static LARGE_INTEGER posixEpoch;
				/* Posix epoch expressed as 100-ns ticks since
				 * the windows epoch. */
	Tcl_WideInt usecSincePosixEpoch;
				/* Current microseconds since Posix epoch. */

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

	QueryPerformanceCounter(&curCounter);

	/*
	 * Hold time section locked as short as possible
	 */
	EnterCriticalSection(&timeInfo.cs);

	fileTimeLastCall.QuadPart = timeInfo.fileTimeLastCall.QuadPart;
	perfCounterLastCall.QuadPart = timeInfo.perfCounterLastCall.QuadPart;
	curCounterFreq.QuadPart = timeInfo.curCounterFreq.QuadPart;

	LeaveCriticalSection(&timeInfo.cs);

	/*
	 * If calibration cycle occurred after we get curCounter
	 */
	if (curCounter.QuadPart <= perfCounterLastCall.QuadPart) {
	    usecSincePosixEpoch =
		(fileTimeLastCall.QuadPart - posixEpoch.QuadPart) / 10;
	    timePtr->sec = (long) (usecSincePosixEpoch / 1000000);
	    timePtr->usec = (unsigned long) (usecSincePosixEpoch % 1000000);
	    return;
	}

	/*
	 * If it appears to be more than 1.1 seconds since the last trip
	 * through the calibration loop, the performance counter may have
	 * jumped forward. (See MSDN Knowledge Base article Q274323 for a
	 * description of the hardware problem that makes 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 - perfCounterLastCall.QuadPart <
		11 * curCounterFreq.QuadPart / 10
	) {
	    curFileTime = fileTimeLastCall.QuadPart +
		 ((curCounter.QuadPart - perfCounterLastCall.QuadPart)
		    * 10000000 / curCounterFreq.QuadPart);

	    usecSincePosixEpoch = (curFileTime - posixEpoch.QuadPart) / 10;
	    timePtr->sec = (long) (usecSincePosixEpoch / 1000000);
	    timePtr->usec = (unsigned long) (usecSincePosixEpoch % 1000000);
	    return;
	}
    }

    /*
     * High resolution timer is not available. Just use ftime.
     */

    _ftime(&t);
    timePtr->sec = (long)t.time;
    timePtr->usec = t.millitm * 1000;
}

/*
 *----------------------------------------------------------------------
 *
 * StopCalibration --
 *
 *	Turns off the calibration thread in preparation for exiting the
 *	process.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Sets the 'exitEvent' event in the 'timeInfo' structure to ask the
 *	thread in question to exit, and waits for it to do so.
 *
 *----------------------------------------------------------------------
 */

static void
StopCalibration(
    ClientData unused)		/* Client data is unused */
{
    SetEvent(timeInfo.exitEvent);

    /*
     * If Tcl_Finalize was called from DllMain, the calibration thread is in a
     * paused state so we need to timeout and continue.
     */

    WaitForSingleObject(timeInfo.calibrationThread, 100);
    CloseHandle(timeInfo.exitEvent);
    CloseHandle(timeInfo.calibrationThread);
}

/*
 *----------------------------------------------------------------------
 *
 * 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.
 *
 *----------------------------------------------------------------------
 */

#ifndef TCL_NO_DEPRECATED
struct tm *
TclpGetDate(
    const time_t *t,
    int useGMT)
{
    struct tm *tmPtr;
    time_t 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.
	 */

	/*
	 * Hm, Borland's localtime manages to return NULL under certain
	 * circumstances (e.g. wintime.test, test 1.2). Nobody tests for this,
	 * since 'localtime' isn't supposed to do this, possibly leading to
	 * crashes.
	 *
	 * Patch: We only call this function if we are at least one day into
	 * the epoch, else we handle it ourselves (like we do for times < 0).
	 * H. Giese, June 2003
	 */

#ifdef __BORLANDC__
#define LOCALTIME_VALIDITY_BOUNDARY	SECSPERDAY
#else
#define LOCALTIME_VALIDITY_BOUNDARY	0
#endif

	if (*t >= LOCALTIME_VALIDITY_BOUNDARY) {
	    return TclpLocaltime(t);
	}

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

	    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 += (int)time;
	    tmPtr->tm_yday += (int)time;
	    tmPtr->tm_wday = (tmPtr->tm_wday + (int)time) % 7;
	}
    } else {
	tmPtr = ComputeGMT(t);
    }
    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(
    const time_t *tp)
{
    struct tm *tmPtr;
    long tmp, rem;
    int isLeap;
    const int *days;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    tmPtr = &tsdPtr->tm;

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

    tmp = (long)(*tp / SECSPER4YEAR);
    rem = (long)(*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++) {
	/* empty body */
    }
    tmPtr->tm_mon = --tmp;
    tmPtr->tm_mday = tmPtr->tm_yday - days[tmp];

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

    tmPtr->tm_wday = (long)(*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;
}
#endif /* TCL_NO_DEPRECATED */

/*
 *----------------------------------------------------------------------
 *
 * 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 1s, 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.perfCounterLastCall);
    QueryPerformanceFrequency(&timeInfo.curCounterFreq);
    timeInfo.fileTimeLastCall.LowPart = curFileTime.dwLowDateTime;
    timeInfo.fileTimeLastCall.HighPart = curFileTime.dwHighDateTime;

    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);

    /*
     * Run the calibration once a second.
     */

    while (timeInfo.perfCounterAvailable) {
	/*
	 * 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(void)
{
    LARGE_INTEGER curPerfCounter;
				/* Current value returned from
				 * QueryPerformanceCounter. */
    FILETIME curSysTime;	/* Current system time. */
    LARGE_INTEGER curFileTime;	/* File time at the time this callback was
				 * scheduled. */
    Tcl_WideInt estFreq;	/* Estimated perf counter frequency. */
    Tcl_WideInt vt0;		/* Tcl time right now. */
    Tcl_WideInt vt1;		/* Tcl time one second from now. */
    Tcl_WideInt tdiff;		/* Difference between system clock and Tcl
				 * time. */
    Tcl_WideInt driftFreq;	/* Frequency needed to drift virtual time into
				 * step over 1 second. */

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

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

    EnterCriticalSection(&timeInfo.cs);

    /*
     * 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
     * timeInfo.perfCounterAvailable in order to cause the calibration thread
     * to shut itself down, then return without additional processing.
     */

    if (timeInfo.curCounterFreq.QuadPart == 0){
	LeaveCriticalSection(&timeInfo.cs);
	timeInfo.perfCounterAvailable = 0;
	return;
    }

    /*
     * 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 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.
     */

    estFreq = AccumulateSample(curPerfCounter.QuadPart,
	    (Tcl_WideUInt) curFileTime.QuadPart);

    /*
     * 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
     *
     * The frequency that we need to use to drift the counter back into place
     * is estFreq * 20000000 / (vt1 - vt0)
     */

    vt0 = 10000000 * (curPerfCounter.QuadPart
		- timeInfo.perfCounterLastCall.QuadPart)
	    / timeInfo.curCounterFreq.QuadPart
	    + 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;
	} else 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
ResetCounterSamples(
    Tcl_WideUInt fileTime,	/* Current file time */
    Tcl_WideInt perfCounter,	/* Current performance counter */
    Tcl_WideInt perfFreq)	/* 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 performance frequency
 * (not the actual, because the actual has probably run slow in the first
 * case).
 */

static Tcl_WideInt
AccumulateSample(
    Tcl_WideInt perfCounter,
    Tcl_WideUInt fileTime)
{
    Tcl_WideUInt workFTSample;	/* File time sample being removed from or
				 * added to the circular buffer. */
    Tcl_WideInt workPCSample;	/* Performance counter sample being removed
				 * from or added to the circular buffer. */
    Tcl_WideUInt lastFTSample;	/* Last file time sample recorded */
    Tcl_WideInt lastPCSample;	/* Last performance counter sample recorded */
    Tcl_WideInt FTdiff;		/* Difference between last FT and current */
    Tcl_WideInt PCdiff;		/* Difference between last PC and current */
    Tcl_WideInt 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 {
	/*
	 * Estimate the frequency.
	 */

	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] = (Tcl_WideInt) fileTime;

	/*
	 * Advance the sample number.
	 */

	if (++timeInfo.sampleNo >= SAMPLES) {
	    timeInfo.sampleNo = 0;
	}

	return estFreq;
    }
}

/*
 *----------------------------------------------------------------------
 *
 * TclpGmtime --
 *
 *	Wrapper around the 'gmtime' library function to make it thread safe.
 *
 * Results:
 *	Returns a pointer to a 'struct tm' in thread-specific data.
 *
 * Side effects:
 *	Invokes gmtime or gmtime_r as appropriate.
 *
 *----------------------------------------------------------------------
 */

#ifndef TCL_NO_DEPRECATED
struct tm *
TclpGmtime(
    const time_t *timePtr)	/* Pointer to the number of seconds since the
				 * local system's epoch */
{
    /*
     * The MS implementation of gmtime is thread safe because it returns the
     * time in a block of thread-local storage, and Windows does not provide a
     * Posix gmtime_r function.
     */

    return gmtime(timePtr);
}

/*
 *----------------------------------------------------------------------
 *
 * TclpLocaltime --
 *
 *	Wrapper around the 'localtime' library function to make it thread
 *	safe.
 *
 * Results:
 *	Returns a pointer to a 'struct tm' in thread-specific data.
 *
 * Side effects:
 *	Invokes localtime or localtime_r as appropriate.
 *
 *----------------------------------------------------------------------
 */

struct tm *
TclpLocaltime(
    const time_t *timePtr)	/* Pointer to the number of seconds since the
				 * local system's epoch */
{
    /*
     * The MS implementation of localtime is thread safe because it returns
     * the time in a block of thread-local storage, and Windows does not
     * provide a Posix localtime_r function.
     */

    return localtime(timePtr);
}
#endif /* TCL_NO_DEPRECATED */

/*
 *----------------------------------------------------------------------
 *
 * Tcl_SetTimeProc --
 *
 *	TIP #233 (Virtualized Time): Registers two handlers for the
 *	virtualization of Tcl's access to time information.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Remembers the handlers, alters core behaviour.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_SetTimeProc(
    Tcl_GetTimeProc *getProc,
    Tcl_ScaleTimeProc *scaleProc,
    ClientData clientData)
{
    tclGetTimeProcPtr = getProc;
    tclScaleTimeProcPtr = scaleProc;
    tclTimeClientData = clientData;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_QueryTimeProc --
 *
 *	TIP #233 (Virtualized Time): Query which time handlers are registered.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_QueryTimeProc(
    Tcl_GetTimeProc **getProc,
    Tcl_ScaleTimeProc **scaleProc,
    ClientData *clientData)
{
    if (getProc) {
	*getProc = tclGetTimeProcPtr;
    }
    if (scaleProc) {
	*scaleProc = tclScaleTimeProcPtr;
    }
    if (clientData) {
	*clientData = tclTimeClientData;
    }
}

/*
 * Local Variables:
 * mode: c
 * c-basic-offset: 4
 * fill-column: 78
 * End:
 */