summaryrefslogtreecommitdiffstats
path: root/generic/tclListObj.c
blob: 7505569f25624c4387b09cbe4bd06e0867c8bb91 (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
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
/*
 * tclListObj.c --
 *
 *	This file contains functions that implement the Tcl list object type.
 *
 * Copyright (c) 1995-1997 Sun Microsystems, Inc.
 * Copyright (c) 1998 by Scriptics Corporation.
 * Copyright (c) 2001 by Kevin B. Kenny.  All rights reserved.
 *
 * See the file "license.terms" for information on usage and redistribution of
 * this file, and for a DISCLAIMER OF ALL WARRANTIES.
 *
 * RCS: @(#) $Id: tclListObj.c,v 1.52 2008/08/23 10:54:24 dkf Exp $
 */

#include "tclInt.h"

/*
 * Prototypes for functions defined later in this file:
 */

static List *		NewListIntRep(int objc, Tcl_Obj *const objv[]);
static void		DupListInternalRep(Tcl_Obj *srcPtr, Tcl_Obj *copyPtr);
static void		FreeListInternalRep(Tcl_Obj *listPtr);
static int		SetListFromAny(Tcl_Interp *interp, Tcl_Obj *objPtr);
static void		UpdateStringOfList(Tcl_Obj *listPtr);

/*
 * The structure below defines the list Tcl object type by means of functions
 * that can be invoked by generic object code.
 *
 * The internal representation of a list object is a two-pointer
 * representation. The first pointer designates a List structure that contains
 * an array of pointers to the element objects, together with integers that
 * represent the current element count and the allocated size of the array.
 * The second pointer is normally NULL; during execution of functions in this
 * file that operate on nested sublists, it is occasionally used as working
 * storage to avoid an auxiliary stack.
 */

Tcl_ObjType tclListType = {
    "list",			/* name */
    FreeListInternalRep,	/* freeIntRepProc */
    DupListInternalRep,		/* dupIntRepProc */
    UpdateStringOfList,		/* updateStringProc */
    SetListFromAny		/* setFromAnyProc */
};

/*
 *----------------------------------------------------------------------
 *
 * NewListIntRep --
 *
 *	If objc>0 and objv!=NULL, this function creates a list internal rep
 *	with objc elements given in the array objv. If objc>0 and objv==NULL
 *	it creates the list internal rep of a list with 0 elements, where
 *	enough space has been preallocated to store objc elements. If objc<=0,
 *	it returns NULL.
 *
 * Results:
 *	A new List struct is returned. If objc<=0 or if the allocation fails
 *	for lack of memory, NULL is returned. The list returned has refCount
 *	0.
 *
 * Side effects:
 *	The ref counts of the elements in objv are incremented since the
 *	resulting list now refers to them.
 *
 *----------------------------------------------------------------------
 */

static List *
NewListIntRep(
    int objc,
    Tcl_Obj *const objv[])
{
    List *listRepPtr;

    if (objc <= 0) {
	return NULL;
    }

    /*
     * First check to see if we'd overflow and try to allocate an object
     * larger than our memory allocator allows. Note that this is actually a
     * fairly small value when you're on a serious 64-bit machine, but that
     * requires API changes to fix. See [Bug 219196] for a discussion.
     */

    if ((size_t)objc > INT_MAX/sizeof(Tcl_Obj *)) {
	return NULL;
    }

    listRepPtr = (List *)
	    attemptckalloc(sizeof(List) + ((objc-1) * sizeof(Tcl_Obj *)));
    if (listRepPtr == NULL) {
	return NULL;
    }

    listRepPtr->canonicalFlag = 0;
    listRepPtr->refCount = 0;
    listRepPtr->maxElemCount = objc;

    if (objv) {
	Tcl_Obj **elemPtrs;
	int i;

	listRepPtr->elemCount = objc;
	elemPtrs = &listRepPtr->elements;
	for (i = 0;  i < objc;  i++) {
	    elemPtrs[i] = objv[i];
	    Tcl_IncrRefCount(elemPtrs[i]);
	}
    } else {
	listRepPtr->elemCount = 0;
    }
    return listRepPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_NewListObj --
 *
 *	This function is normally called when not debugging: i.e., when
 *	TCL_MEM_DEBUG is not defined. It creates a new list object from an
 *	(objc,objv) array: that is, each of the objc elements of the array
 *	referenced by objv is inserted as an element into a new Tcl object.
 *
 *	When TCL_MEM_DEBUG is defined, this function just returns the result
 *	of calling the debugging version Tcl_DbNewListObj.
 *
 * Results:
 *	A new list object is returned that is initialized from the object
 *	pointers in objv. If objc is less than or equal to zero, an empty
 *	object is returned. The new object's string representation is left
 *	NULL. The resulting new list object has ref count 0.
 *
 * Side effects:
 *	The ref counts of the elements in objv are incremented since the
 *	resulting list now refers to them.
 *
 *----------------------------------------------------------------------
 */

#ifdef TCL_MEM_DEBUG
#undef Tcl_NewListObj

Tcl_Obj *
Tcl_NewListObj(
    int objc,			/* Count of objects referenced by objv. */
    Tcl_Obj *const objv[])	/* An array of pointers to Tcl objects. */
{
    return Tcl_DbNewListObj(objc, objv, "unknown", 0);
}

#else /* if not TCL_MEM_DEBUG */

Tcl_Obj *
Tcl_NewListObj(
    int objc,			/* Count of objects referenced by objv. */
    Tcl_Obj *const objv[])	/* An array of pointers to Tcl objects. */
{
    List *listRepPtr;
    Tcl_Obj *listPtr;

    TclNewObj(listPtr);

    if (objc <= 0) {
	return listPtr;
    }

    /*
     * Create the internal rep.
     */

    listRepPtr = NewListIntRep(objc, objv);
    if (!listRepPtr) {
	Tcl_Panic("Not enough memory to allocate list");
    }

    /*
     * Now create the object.
     */

    Tcl_InvalidateStringRep(listPtr);
    listPtr->internalRep.twoPtrValue.ptr1 = (void *) listRepPtr;
    listPtr->internalRep.twoPtrValue.ptr2 = NULL;
    listPtr->typePtr = &tclListType;
    listRepPtr->refCount++;

    return listPtr;
}
#endif /* if TCL_MEM_DEBUG */

/*
 *----------------------------------------------------------------------
 *
 * Tcl_DbNewListObj --
 *
 *	This function is normally called when debugging: i.e., when
 *	TCL_MEM_DEBUG is defined. It creates new list objects. It is the same
 *	as the Tcl_NewListObj function above except that it calls
 *	Tcl_DbCkalloc directly with the file name and line number from its
 *	caller. This simplifies debugging since then the [memory active]
 *	command will report the correct file name and line number when
 *	reporting objects that haven't been freed.
 *
 *	When TCL_MEM_DEBUG is not defined, this function just returns the
 *	result of calling Tcl_NewListObj.
 *
 * Results:
 *	A new list object is returned that is initialized from the object
 *	pointers in objv. If objc is less than or equal to zero, an empty
 *	object is returned. The new object's string representation is left
 *	NULL. The new list object has ref count 0.
 *
 * Side effects:
 *	The ref counts of the elements in objv are incremented since the
 *	resulting list now refers to them.
 *
 *----------------------------------------------------------------------
 */

#ifdef TCL_MEM_DEBUG

Tcl_Obj *
Tcl_DbNewListObj(
    int objc,			/* Count of objects referenced by objv. */
    Tcl_Obj *const objv[],	/* An array of pointers to Tcl objects. */
    const char *file,		/* The name of the source file calling this
				 * function; used for debugging. */
    int line)			/* Line number in the source file; used for
				 * debugging. */
{
    Tcl_Obj *listPtr;
    List *listRepPtr;

    TclDbNewObj(listPtr, file, line);

    if (objc <= 0) {
	return listPtr;
    }

    /*
     * Create the internal rep.
     */

    listRepPtr = NewListIntRep(objc, objv);
    if (!listRepPtr) {
	Tcl_Panic("Not enough memory to allocate list");
    }

    /*
     * Now create the object.
     */

    Tcl_InvalidateStringRep(listPtr);
    listPtr->internalRep.twoPtrValue.ptr1 = (void *) listRepPtr;
    listPtr->internalRep.twoPtrValue.ptr2 = NULL;
    listPtr->typePtr = &tclListType;
    listRepPtr->refCount++;

    return listPtr;
}

#else /* if not TCL_MEM_DEBUG */

Tcl_Obj *
Tcl_DbNewListObj(
    int objc,			/* Count of objects referenced by objv. */
    Tcl_Obj *const objv[],	/* An array of pointers to Tcl objects. */
    const char *file,		/* The name of the source file calling this
				 * function; used for debugging. */
    int line)			/* Line number in the source file; used for
				 * debugging. */
{
    return Tcl_NewListObj(objc, objv);
}
#endif /* TCL_MEM_DEBUG */

/*
 *----------------------------------------------------------------------
 *
 * Tcl_SetListObj --
 *
 *	Modify an object to be a list containing each of the objc elements of
 *	the object array referenced by objv.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	The object is made a list object and is initialized from the object
 *	pointers in objv. If objc is less than or equal to zero, an empty
 *	object is returned. The new object's string representation is left
 *	NULL. The ref counts of the elements in objv are incremented since the
 *	list now refers to them. The object's old string and internal
 *	representations are freed and its type is set NULL.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_SetListObj(
    Tcl_Obj *objPtr,		/* Object whose internal rep to init. */
    int objc,			/* Count of objects referenced by objv. */
    Tcl_Obj *const objv[])	/* An array of pointers to Tcl objects. */
{
    List *listRepPtr;

    if (Tcl_IsShared(objPtr)) {
	Tcl_Panic("%s called with shared object", "Tcl_SetListObj");
    }

    /*
     * Free any old string rep and any internal rep for the old type.
     */

    TclFreeIntRep(objPtr);
    objPtr->typePtr = NULL;
    Tcl_InvalidateStringRep(objPtr);

    /*
     * Set the object's type to "list" and initialize the internal rep.
     * However, if there are no elements to put in the list, just give the
     * object an empty string rep and a NULL type.
     */

    if (objc > 0) {
	listRepPtr = NewListIntRep(objc, objv);
	if (!listRepPtr) {
	    Tcl_Panic("Cannot allocate enough memory for Tcl_SetListObj");
	}
	objPtr->internalRep.twoPtrValue.ptr1 = (void *) listRepPtr;
	objPtr->internalRep.twoPtrValue.ptr2 = NULL;
	objPtr->typePtr = &tclListType;
	listRepPtr->refCount++;
    } else {
	objPtr->bytes = tclEmptyStringRep;
	objPtr->length = 0;
    }
}

/*
 *----------------------------------------------------------------------
 *
 * TclListObjCopy --
 *
 *	Makes a "pure list" copy of a list value. This provides for the C
 *	level a counterpart of the [lrange $list 0 end] command, while using
 *	internals details to be as efficient as possible.
 *
 * Results:
 *	Normally returns a pointer to a new Tcl_Obj, that contains the same
 *	list value as *listPtr does. The returned Tcl_Obj has a refCount of
 *	zero. If *listPtr does not hold a list, NULL is returned, and if
 *	interp is non-NULL, an error message is recorded there.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

Tcl_Obj *
TclListObjCopy(
    Tcl_Interp *interp,		/* Used to report errors if not NULL. */
    Tcl_Obj *listPtr)		/* List object for which an element array is
				 * to be returned. */
{
    Tcl_Obj *copyPtr;

    if (listPtr->typePtr != &tclListType) {
	if (SetListFromAny(interp, listPtr) != TCL_OK) {
	    return NULL;
	}
    }

    TclNewObj(copyPtr);
    TclInvalidateStringRep(copyPtr);
    DupListInternalRep(listPtr, copyPtr);
    return copyPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_ListObjGetElements --
 *
 *	This function returns an (objc,objv) array of the elements in a list
 *	object.
 *
 * Results:
 *	The return value is normally TCL_OK; in this case *objcPtr is set to
 *	the count of list elements and *objvPtr is set to a pointer to an
 *	array of (*objcPtr) pointers to each list element. If listPtr does not
 *	refer to a list object and the object can not be converted to one,
 *	TCL_ERROR is returned and an error message will be left in the
 *	interpreter's result if interp is not NULL.
 *
 *	The objects referenced by the returned array should be treated as
 *	readonly and their ref counts are _not_ incremented; the caller must
 *	do that if it holds on to a reference. Furthermore, the pointer and
 *	length returned by this function may change as soon as any function is
 *	called on the list object; be careful about retaining the pointer in a
 *	local data structure.
 *
 * Side effects:
 *	The possible conversion of the object referenced by listPtr
 *	to a list object.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_ListObjGetElements(
    Tcl_Interp *interp,		/* Used to report errors if not NULL. */
    register Tcl_Obj *listPtr,	/* List object for which an element array is
				 * to be returned. */
    int *objcPtr,		/* Where to store the count of objects
				 * referenced by objv. */
    Tcl_Obj ***objvPtr)		/* Where to store the pointer to an array of
				 * pointers to the list's objects. */
{
    register List *listRepPtr;

    if (listPtr->typePtr != &tclListType) {
	int result, length;

	(void) TclGetStringFromObj(listPtr, &length);
	if (!length) {
	    *objcPtr = 0;
	    *objvPtr = NULL;
	    return TCL_OK;
	}

	result = SetListFromAny(interp, listPtr);
	if (result != TCL_OK) {
	    return result;
	}
    }
    listRepPtr = (List *) listPtr->internalRep.twoPtrValue.ptr1;
    *objcPtr = listRepPtr->elemCount;
    *objvPtr = &listRepPtr->elements;
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_ListObjAppendList --
 *
 *	This function appends the objects in the list referenced by
 *	elemListPtr to the list object referenced by listPtr. If listPtr is
 *	not already a list object, an attempt will be made to convert it to
 *	one.
 *
 * Results:
 *	The return value is normally TCL_OK. If listPtr or elemListPtr do not
 *	refer to list objects and they can not be converted to one, TCL_ERROR
 *	is returned and an error message is left in the interpreter's result
 *	if interp is not NULL.
 *
 * Side effects:
 *	The reference counts of the elements in elemListPtr are incremented
 *	since the list now refers to them. listPtr and elemListPtr are
 *	converted, if necessary, to list objects. Also, appending the new
 *	elements may cause listObj's array of element pointers to grow.
 *	listPtr's old string representation, if any, is invalidated.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_ListObjAppendList(
    Tcl_Interp *interp,		/* Used to report errors if not NULL. */
    register Tcl_Obj *listPtr,	/* List object to append elements to. */
    Tcl_Obj *elemListPtr)	/* List obj with elements to append. */
{
    int listLen, objc, result;
    Tcl_Obj **objv;

    if (Tcl_IsShared(listPtr)) {
	Tcl_Panic("%s called with shared object", "Tcl_ListObjAppendList");
    }

    result = TclListObjLength(interp, listPtr, &listLen);
    if (result != TCL_OK) {
	return result;
    }

    result = TclListObjGetElements(interp, elemListPtr, &objc, &objv);
    if (result != TCL_OK) {
	return result;
    }

    /*
     * Insert objc new elements starting after the lists's last element.
     * Delete zero existing elements.
     */

    return Tcl_ListObjReplace(interp, listPtr, listLen, 0, objc, objv);
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_ListObjAppendElement --
 *
 *	This function is a special purpose version of Tcl_ListObjAppendList:
 *	it appends a single object referenced by objPtr to the list object
 *	referenced by listPtr. If listPtr is not already a list object, an
 *	attempt will be made to convert it to one.
 *
 * Results:
 *	The return value is normally TCL_OK; in this case objPtr is added to
 *	the end of listPtr's list. If listPtr does not refer to a list object
 *	and the object can not be converted to one, TCL_ERROR is returned and
 *	an error message will be left in the interpreter's result if interp is
 *	not NULL.
 *
 * Side effects:
 *	The ref count of objPtr is incremented since the list now refers to
 *	it. listPtr will be converted, if necessary, to a list object. Also,
 *	appending the new element may cause listObj's array of element
 *	pointers to grow. listPtr's old string representation, if any, is
 *	invalidated.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_ListObjAppendElement(
    Tcl_Interp *interp,		/* Used to report errors if not NULL. */
    Tcl_Obj *listPtr,		/* List object to append objPtr to. */
    Tcl_Obj *objPtr)		/* Object to append to listPtr's list. */
{
    register List *listRepPtr;
    register Tcl_Obj **elemPtrs;
    int numElems, numRequired, newMax, newSize, i;

    if (Tcl_IsShared(listPtr)) {
	Tcl_Panic("%s called with shared object", "Tcl_ListObjAppendElement");
    }
    if (listPtr->typePtr != &tclListType) {
	int result, length;

	(void) TclGetStringFromObj(listPtr, &length);
	if (!length) {
	    Tcl_SetListObj(listPtr, 1, &objPtr);
	    return TCL_OK;
	}

	result = SetListFromAny(interp, listPtr);
	if (result != TCL_OK) {
	    return result;
	}
    }

    listRepPtr = (List *) listPtr->internalRep.twoPtrValue.ptr1;
    numElems = listRepPtr->elemCount;
    numRequired = numElems + 1 ;

    /*
     * If there is no room in the current array of element pointers, allocate
     * a new, larger array and copy the pointers to it. If the List struct is
     * shared, allocate a new one.
     */

    if (numRequired > listRepPtr->maxElemCount){
	newMax = 2 * numRequired;
	newSize = sizeof(List) + ((newMax-1) * sizeof(Tcl_Obj *));
    } else {
	newMax = listRepPtr->maxElemCount;
	newSize = 0;
    }

    if (listRepPtr->refCount > 1) {
	List *oldListRepPtr = listRepPtr;
	Tcl_Obj **oldElems;

	listRepPtr = NewListIntRep(newMax, NULL);
	if (!listRepPtr) {
	    Tcl_Panic("Not enough memory to allocate list");
	}
	oldElems = &oldListRepPtr->elements;
	elemPtrs = &listRepPtr->elements;
	for (i=0; i<numElems; i++) {
	    elemPtrs[i] = oldElems[i];
	    Tcl_IncrRefCount(elemPtrs[i]);
	}
	listRepPtr->elemCount = numElems;
	listRepPtr->refCount++;
	oldListRepPtr->refCount--;
	listPtr->internalRep.twoPtrValue.ptr1 = (void *) listRepPtr;
    } else if (newSize) {
	listRepPtr = (List *) ckrealloc((char *)listRepPtr, (size_t)newSize);
	listRepPtr->maxElemCount = newMax;
	listPtr->internalRep.twoPtrValue.ptr1 = (void *) listRepPtr;
    }

    /*
     * Add objPtr to the end of listPtr's array of element pointers. Increment
     * the ref count for the (now shared) objPtr.
     */

    elemPtrs = &listRepPtr->elements;
    elemPtrs[numElems] = objPtr;
    Tcl_IncrRefCount(objPtr);
    listRepPtr->elemCount++;

    /*
     * Invalidate any old string representation since the list's internal
     * representation has changed.
     */

    Tcl_InvalidateStringRep(listPtr);
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_ListObjIndex --
 *
 *	This function returns a pointer to the index'th object from the list
 *	referenced by listPtr. The first element has index 0. If index is
 *	negative or greater than or equal to the number of elements in the
 *	list, a NULL is returned. If listPtr is not a list object, an attempt
 *	will be made to convert it to a list.
 *
 * Results:
 *	The return value is normally TCL_OK; in this case objPtrPtr is set to
 *	the Tcl_Obj pointer for the index'th list element or NULL if index is
 *	out of range. This object should be treated as readonly and its ref
 *	count is _not_ incremented; the caller must do that if it holds on to
 *	the reference. If listPtr does not refer to a list and can't be
 *	converted to one, TCL_ERROR is returned and an error message is left
 *	in the interpreter's result if interp is not NULL.
 *
 * Side effects:
 *	listPtr will be converted, if necessary, to a list object.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_ListObjIndex(
    Tcl_Interp *interp,		/* Used to report errors if not NULL. */
    register Tcl_Obj *listPtr,	/* List object to index into. */
    register int index,		/* Index of element to return. */
    Tcl_Obj **objPtrPtr)	/* The resulting Tcl_Obj* is stored here. */
{
    register List *listRepPtr;

    if (listPtr->typePtr != &tclListType) {
	int result, length;

	(void) TclGetStringFromObj(listPtr, &length);
	if (!length) {
	    *objPtrPtr = NULL;
	    return TCL_OK;
	}

	result = SetListFromAny(interp, listPtr);
	if (result != TCL_OK) {
	    return result;
	}
    }

    listRepPtr = (List *) listPtr->internalRep.twoPtrValue.ptr1;
    if ((index < 0) || (index >= listRepPtr->elemCount)) {
	*objPtrPtr = NULL;
    } else {
	*objPtrPtr = (&listRepPtr->elements)[index];
    }

    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_ListObjLength --
 *
 *	This function returns the number of elements in a list object. If the
 *	object is not already a list object, an attempt will be made to
 *	convert it to one.
 *
 * Results:
 *	The return value is normally TCL_OK; in this case *intPtr will be set
 *	to the integer count of list elements. If listPtr does not refer to a
 *	list object and the object can not be converted to one, TCL_ERROR is
 *	returned and an error message will be left in the interpreter's result
 *	if interp is not NULL.
 *
 * Side effects:
 *	The possible conversion of the argument object to a list object.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_ListObjLength(
    Tcl_Interp *interp,		/* Used to report errors if not NULL. */
    register Tcl_Obj *listPtr,	/* List object whose #elements to return. */
    register int *intPtr)	/* The resulting int is stored here. */
{
    register List *listRepPtr;

    if (listPtr->typePtr != &tclListType) {
	int result, length;

	(void) TclGetStringFromObj(listPtr, &length);
	if (!length) {
	    *intPtr = 0;
	    return TCL_OK;
	}

	result = SetListFromAny(interp, listPtr);
	if (result != TCL_OK) {
	    return result;
	}
    }

    listRepPtr = (List *) listPtr->internalRep.twoPtrValue.ptr1;
    *intPtr = listRepPtr->elemCount;
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_ListObjReplace --
 *
 *	This function replaces zero or more elements of the list referenced by
 *	listPtr with the objects from an (objc,objv) array. The objc elements
 *	of the array referenced by objv replace the count elements in listPtr
 *	starting at first.
 *
 *	If the argument first is zero or negative, it refers to the first
 *	element. If first is greater than or equal to the number of elements
 *	in the list, then no elements are deleted; the new elements are
 *	appended to the list. Count gives the number of elements to replace.
 *	If count is zero or negative then no elements are deleted; the new
 *	elements are simply inserted before first.
 *
 *	The argument objv refers to an array of objc pointers to the new
 *	elements to be added to listPtr in place of those that were deleted.
 *	If objv is NULL, no new elements are added. If listPtr is not a list
 *	object, an attempt will be made to convert it to one.
 *
 * Results:
 *	The return value is normally TCL_OK. If listPtr does not refer to a
 *	list object and can not be converted to one, TCL_ERROR is returned and
 *	an error message will be left in the interpreter's result if interp is
 *	not NULL.
 *
 * Side effects:
 *	The ref counts of the objc elements in objv are incremented since the
 *	resulting list now refers to them. Similarly, the ref counts for
 *	replaced objects are decremented. listPtr is converted, if necessary,
 *	to a list object. listPtr's old string representation, if any, is
 *	freed.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_ListObjReplace(
    Tcl_Interp *interp,		/* Used for error reporting if not NULL. */
    Tcl_Obj *listPtr,		/* List object whose elements to replace. */
    int first,			/* Index of first element to replace. */
    int count,			/* Number of elements to replace. */
    int objc,			/* Number of objects to insert. */
    Tcl_Obj *const objv[])	/* An array of objc pointers to Tcl objects to
				 * insert. */
{
    List *listRepPtr;
    register Tcl_Obj **elemPtrs;
    int numElems, numRequired, numAfterLast, start, i, j, isShared;

    if (Tcl_IsShared(listPtr)) {
	Tcl_Panic("%s called with shared object", "Tcl_ListObjReplace");
    }
    if (listPtr->typePtr != &tclListType) {
	int length;

	(void) TclGetStringFromObj(listPtr, &length);
	if (!length) {
	    if (objc) {
		Tcl_SetListObj(listPtr, objc, NULL);
	    } else {
		return TCL_OK;
	    }
	} else {
	    int result = SetListFromAny(interp, listPtr);

	    if (result != TCL_OK) {
		return result;
	    }
	}
    }

    /*
     * Note that when count == 0 and objc == 0, this routine is logically a
     * no-op, removing and adding no elements to the list. However, by flowing
     * through this routine anyway, we get the important side effect that the
     * resulting listPtr is a list in canoncial form. This is important.
     * Resist any temptation to optimize this case.
     */

    listRepPtr = (List *) listPtr->internalRep.twoPtrValue.ptr1;
    elemPtrs = &listRepPtr->elements;
    numElems = listRepPtr->elemCount;

    if (first < 0) {
	first = 0;
    }
    if (first >= numElems) {
	first = numElems;	/* So we'll insert after last element. */
    }
    if (count < 0) {
	count = 0;
    } else if (numElems < first+count) {
	count = numElems - first;
    }

    isShared = (listRepPtr->refCount > 1);
    numRequired = numElems - count + objc;

    if ((numRequired <= listRepPtr->maxElemCount) && !isShared) {
	int shift;

	/*
	 * Can use the current List struct. First "delete" count elements
	 * starting at first.
	 */

	for (j = first;  j < first + count;  j++) {
	    Tcl_Obj *victimPtr = elemPtrs[j];

	    TclDecrRefCount(victimPtr);
	}

	/*
	 * Shift the elements after the last one removed to their new
	 * locations.
	 */

	start = first + count;
	numAfterLast = numElems - start;
	shift = objc - count;	/* numNewElems - numDeleted */
	if ((numAfterLast > 0) && (shift != 0)) {
	    Tcl_Obj **src = elemPtrs + start;

	    memmove(src+shift, src, (size_t) numAfterLast * sizeof(Tcl_Obj*));
	}
    } else {
	/*
	 * Cannot use the current List struct; it is shared, too small, or
	 * both. Allocate a new struct and insert elements into it.
	 */

	List *oldListRepPtr = listRepPtr;
	Tcl_Obj **oldPtrs = elemPtrs;
	int newMax;

	if (numRequired > listRepPtr->maxElemCount){
	    newMax = 2 * numRequired;
	} else {
	    newMax = listRepPtr->maxElemCount;
	}

	listRepPtr = NewListIntRep(newMax, NULL);
	if (!listRepPtr) {
	    Tcl_Panic("Not enough memory to allocate list");
	}

	listPtr->internalRep.twoPtrValue.ptr1 = (void *) listRepPtr;
	listRepPtr->refCount++;

	elemPtrs = &listRepPtr->elements;

	if (isShared) {
	    /*
	     * The old struct will remain in place; need new refCounts for the
	     * new List struct references. Copy over only the surviving
	     * elements.
	     */

	    for (i=0; i < first; i++) {
		elemPtrs[i] = oldPtrs[i];
		Tcl_IncrRefCount(elemPtrs[i]);
	    }
	    for (i = first + count, j = first + objc;
		    j < numRequired; i++, j++) {
		elemPtrs[j] = oldPtrs[i];
		Tcl_IncrRefCount(elemPtrs[j]);
	    }

	    oldListRepPtr->refCount--;
	} else {
	    /*
	     * The old struct will be removed; use its inherited refCounts.
	     */

	    if (first > 0) {
		memcpy(elemPtrs, oldPtrs, (size_t) first * sizeof(Tcl_Obj *));
	    }

	    /*
	     * "Delete" count elements starting at first.
	     */

	    for (j = first;  j < first + count;  j++) {
		Tcl_Obj *victimPtr = oldPtrs[j];

		TclDecrRefCount(victimPtr);
	    }

	    /*
	     * Copy the elements after the last one removed, shifted to their
	     * new locations.
	     */

	    start = first + count;
	    numAfterLast = numElems - start;
	    if (numAfterLast > 0) {
		memcpy(elemPtrs + first + objc, oldPtrs + start,
			(size_t) numAfterLast * sizeof(Tcl_Obj *));
	    }

	    ckfree((char *) oldListRepPtr);
	}
    }

    /*
     * Insert the new elements into elemPtrs before "first". We don't do a
     * memcpy here because we must increment the reference counts for the
     * added elements, so we must explicitly loop anyway.
     */

    for (i=0,j=first ; i<objc ; i++,j++) {
	elemPtrs[j] = objv[i];
	Tcl_IncrRefCount(objv[i]);
    }

    /*
     * Update the count of elements.
     */

    listRepPtr->elemCount = numRequired;

    /*
     * Invalidate and free any old string representation since it no longer
     * reflects the list's internal representation.
     */

    Tcl_InvalidateStringRep(listPtr);
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * TclLindexList --
 *
 *	This procedure handles the 'lindex' command when objc==3.
 *
 * Results:
 *	Returns a pointer to the object extracted, or NULL if an error
 *	occurred. The returned object already includes one reference count for
 *	the pointer returned.
 *
 * Side effects:
 *	None.
 *
 * Notes:
 *	This procedure is implemented entirely as a wrapper around
 *	TclLindexFlat. All it does is reconfigure the argument format into the
 *	form required by TclLindexFlat, while taking care to manage shimmering
 *	in such a way that we tend to keep the most useful intreps and/or
 *	avoid the most expensive conversions.
 *
 *----------------------------------------------------------------------
 */

Tcl_Obj *
TclLindexList(
    Tcl_Interp *interp,		/* Tcl interpreter. */
    Tcl_Obj *listPtr,		/* List being unpacked. */
    Tcl_Obj *argPtr)		/* Index or index list. */
{

    int index;			/* Index into the list. */
    Tcl_Obj **indices;		/* Array of list indices. */
    int indexCount;		/* Size of the array of list indices. */
    Tcl_Obj *indexListCopy;

    /*
     * Determine whether argPtr designates a list or a single index. We have
     * to be careful about the order of the checks to avoid repeated
     * shimmering; see TIP#22 and TIP#33 for the details.
     */

    if (argPtr->typePtr != &tclListType
	    && TclGetIntForIndexM(NULL , argPtr, 0, &index) == TCL_OK) {
	/*
	 * argPtr designates a single index.
	 */

	return TclLindexFlat(interp, listPtr, 1, &argPtr);
    }

    /*
     * Here we make a private copy of the index list argument to avoid any
     * shimmering issues that might invalidate the indices array below while
     * we are still using it. This is probably unnecessary. It does not appear
     * that any damaging shimmering is possible, and no test has been devised
     * to show any error when this private copy is not made. But it's cheap,
     * and it offers some future-proofing insurance in case the TclLindexFlat
     * implementation changes in some unexpected way, or some new form of
     * trace or callback permits things to happen that the current
     * implementation does not.
     */

    indexListCopy = TclListObjCopy(NULL, argPtr);
    if (indexListCopy == NULL) {
	/*
	 * argPtr designates something that is neither an index nor a
	 * well-formed list. Report the error via TclLindexFlat.
	 */

	return TclLindexFlat(interp, listPtr, 1, &argPtr);
    }

    TclListObjGetElements(NULL, indexListCopy, &indexCount, &indices);
    listPtr = TclLindexFlat(interp, listPtr, indexCount, indices);
    Tcl_DecrRefCount(indexListCopy);
    return listPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * TclLindexFlat --
 *
 *	This procedure is the core of the 'lindex' command, with all index
 *	arguments presented as a flat list.
 *
 * Results:
 *	Returns a pointer to the object extracted, or NULL if an error
 *	occurred. The returned object already includes one reference count for
 *	the pointer returned.
 *
 * Side effects:
 *	None.
 *
 * Notes:
 *	The reference count of the returned object includes one reference
 *	corresponding to the pointer returned. Thus, the calling code will
 *	usually do something like:
 *		Tcl_SetObjResult(interp, result);
 *		Tcl_DecrRefCount(result);
 *
 *----------------------------------------------------------------------
 */

Tcl_Obj *
TclLindexFlat(
    Tcl_Interp *interp,		/* Tcl interpreter. */
    Tcl_Obj *listPtr,		/* Tcl object representing the list. */
    int indexCount,		/* Count of indices. */
    Tcl_Obj *const indexArray[])/* Array of pointers to Tcl objects that
				 * represent the indices in the list. */
{
    int i;

    Tcl_IncrRefCount(listPtr);

    for (i=0 ; i<indexCount && listPtr ; i++) {
	int index, listLen = 0;
	Tcl_Obj **elemPtrs = NULL, *sublistCopy;

	/*
	 * Here we make a private copy of the current sublist, so we avoid any
	 * shimmering issues that might invalidate the elemPtr array below
	 * while we are still using it. See test lindex-8.4.
	 */

	sublistCopy = TclListObjCopy(interp, listPtr);
	Tcl_DecrRefCount(listPtr);
	listPtr = NULL;

	if (sublistCopy == NULL) {
	    /*
	     * The sublist is not a list at all => error.
	     */

	    break;
	}
	TclListObjGetElements(NULL, sublistCopy, &listLen, &elemPtrs);

	if (TclGetIntForIndexM(interp, indexArray[i], /*endValue*/ listLen-1,
		&index) == TCL_OK) {
	    if (index<0 || index>=listLen) {
		/*
		 * Index is out of range. Break out of loop with empty result.
		 * First check remaining indices for validity
		 */

		while (++i < indexCount) {
		    if (TclGetIntForIndexM(interp, indexArray[i], -1, &index)
			!= TCL_OK) {
			Tcl_DecrRefCount(sublistCopy);
			return NULL;
		    }
		}
		listPtr = Tcl_NewObj();
	    } else {
		/*
		 * Extract the pointer to the appropriate element.
		 */

		listPtr = elemPtrs[index];
	    }
	    Tcl_IncrRefCount(listPtr);
	}
	Tcl_DecrRefCount(sublistCopy);
    }

    return listPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * TclLsetList --
 *
 *	Core of the 'lset' command when objc == 4. Objv[2] may be either a
 *	scalar index or a list of indices.
 *
 * Results:
 *	Returns the new value of the list variable, or NULL if there was an
 *	error. The returned object includes one reference count for the
 *	pointer returned.
 *
 * Side effects:
 *	None.
 *
 * Notes:
 *	This procedure is implemented entirely as a wrapper around
 *	TclLsetFlat. All it does is reconfigure the argument format into the
 *	form required by TclLsetFlat, while taking care to manage shimmering
 *	in such a way that we tend to keep the most useful intreps and/or
 *	avoid the most expensive conversions.
 *
 *----------------------------------------------------------------------
 */

Tcl_Obj *
TclLsetList(
    Tcl_Interp *interp,		/* Tcl interpreter. */
    Tcl_Obj *listPtr,		/* Pointer to the list being modified. */
    Tcl_Obj *indexArgPtr,	/* Index or index-list arg to 'lset'. */
    Tcl_Obj *valuePtr)		/* Value arg to 'lset'. */
{
    int indexCount = 0;		/* Number of indices in the index list. */
    Tcl_Obj **indices = NULL;	/* Vector of indices in the index list. */
    Tcl_Obj *retValuePtr;	/* Pointer to the list to be returned. */
    int index;			/* Current index in the list - discarded. */
    Tcl_Obj *indexListCopy;

    /*
     * Determine whether the index arg designates a list or a single index.
     * We have to be careful about the order of the checks to avoid repeated
     * shimmering; see TIP #22 and #23 for details.
     */

    if (indexArgPtr->typePtr != &tclListType
	    && TclGetIntForIndexM(NULL, indexArgPtr, 0, &index) == TCL_OK) {
	/*
	 * indexArgPtr designates a single index.
	 */

	return TclLsetFlat(interp, listPtr, 1, &indexArgPtr, valuePtr);

    }

    indexListCopy = TclListObjCopy(NULL, indexArgPtr);
    if (indexListCopy == NULL) {
	/*
	 * indexArgPtr designates something that is neither an index nor a
	 * well formed list. Report the error via TclLsetFlat.
	 */

	return TclLsetFlat(interp, listPtr, 1, &indexArgPtr, valuePtr);
    }
    TclListObjGetElements(NULL, indexArgPtr, &indexCount, &indices);

    /*
     * Let TclLsetFlat handle the actual lset'ting.
     */

    retValuePtr = TclLsetFlat(interp, listPtr, indexCount, indices, valuePtr);

    Tcl_DecrRefCount(indexListCopy);
    return retValuePtr;
}

/*
 *----------------------------------------------------------------------
 *
 * TclLsetFlat --
 *
 *	Core engine of the 'lset' command.
 *
 * Results:
 *	Returns the new value of the list variable, or NULL if an error
 *	occurred. The returned object includes one reference count for
 *	the pointer returned.
 *
 * Side effects:
 *	On entry, the reference count of the variable value does not reflect
 *	any references held on the stack. The first action of this function is
 *	to determine whether the object is shared, and to duplicate it if it
 *	is. The reference count of the duplicate is incremented. At this
 *	point, the reference count will be 1 for either case, so that the
 *	object will appear to be unshared.
 *
 *	If an error occurs, and the object has been duplicated, the reference
 *	count on the duplicate is decremented so that it is now 0: this
 *	dismisses any memory that was allocated by this function.
 *
 *	If no error occurs, the reference count of the original object is
 *	incremented if the object has not been duplicated, and nothing is done
 *	to a reference count of the duplicate. Now the reference count of an
 *	unduplicated object is 2 (the returned pointer, plus the one stored in
 *	the variable). The reference count of a duplicate object is 1,
 *	reflecting that the returned pointer is the only active reference. The
 *	caller is expected to store the returned value back in the variable
 *	and decrement its reference count. (INST_STORE_* does exactly this.)
 *
 *	Surgery is performed on the unshared list value to produce the result.
 *	TclLsetFlat maintains a linked list of Tcl_Obj's whose string
 *	representations must be spoilt by threading via 'ptr2' of the
 *	two-pointer internal representation. On entry to TclLsetFlat, the
 *	values of 'ptr2' are immaterial; on exit, the 'ptr2' field of any
 *	Tcl_Obj that has been modified is set to NULL.
 *
 *----------------------------------------------------------------------
 */

Tcl_Obj *
TclLsetFlat(
    Tcl_Interp *interp,		/* Tcl interpreter. */
    Tcl_Obj *listPtr,		/* Pointer to the list being modified. */
    int indexCount,		/* Number of index args. */
    Tcl_Obj *const indexArray[],
				/* Index args. */
    Tcl_Obj *valuePtr)		/* Value arg to 'lset'. */
{
    int index, result;
    Tcl_Obj *subListPtr, *retValuePtr, *chainPtr;

    /*
     * If there are no indices, simply return the new value.
     * (Without indices, [lset] is a synonym for [set].
     */

    if (indexCount == 0) {
	Tcl_IncrRefCount(valuePtr);
	return valuePtr;
    }

    /*
     * If the list is shared, make a copy we can modify (copy-on-write).
     * We use Tcl_DuplicateObj() instead of TclListObjCopy() for a few
     * reasons: 1) we have not yet confirmed listPtr is actually a list;
     * 2) We make a verbatim copy of any existing string rep, and when
     * we combine that with the delayed invalidation of string reps of
     * modified Tcl_Obj's implemented below, the outcome is that any
     * error condition that causes this routine to return NULL, will
     * leave the string rep of listPtr and all elements to be unchanged.
     */

    subListPtr = Tcl_IsShared(listPtr) ? Tcl_DuplicateObj(listPtr) : listPtr;

    /*
     * Anchor the linked list of Tcl_Obj's whose string reps must be
     * invalidated if the operation succeeds.
     */

    retValuePtr = subListPtr;
    chainPtr = NULL;

    /*
     * Loop through all the index arguments, and for each one dive
     * into the appropriate sublist.
     */

    do {
	int elemCount;
	Tcl_Obj *parentList, **elemPtrs;

	/* Check for the possible error conditions... */
	result = TCL_ERROR;
	if (TclListObjGetElements(interp, subListPtr, &elemCount, &elemPtrs)
		!= TCL_OK) {
	    /* ...the sublist we're indexing into isn't a list at all. */
	    break;
	}

	/*
	 * WARNING: the macro TclGetIntForIndexM is not safe for
	 * post-increments, avoid '*indexArray++' here.
	 */
	
	if (TclGetIntForIndexM(interp, *indexArray, elemCount - 1, &index)
		!= TCL_OK)  {
	    /* ...the index we're trying to use isn't an index at all. */
	    indexArray++;
	    break;
	}
	indexArray++;

	if (index < 0 || index >= elemCount) {
	    /* ...the index points outside the sublist. */
	    Tcl_SetObjResult(interp,
		    Tcl_NewStringObj("list index out of range", -1));
	    break;
	}

	/*
	 * No error conditions.  As long as we're not yet on the last
	 * index, determine the next sublist for the next pass through
	 * the loop, and take steps to make sure it is an unshared copy,
	 * as we intend to modify it.
	 */

	result = TCL_OK;
	if (--indexCount) {
	    parentList = subListPtr;
	    subListPtr = elemPtrs[index];
	    if (Tcl_IsShared(subListPtr)) {
		subListPtr = Tcl_DuplicateObj(subListPtr);
	    }

	    /*
	     * Replace the original elemPtr[index] in parentList with a copy
	     * we know to be unshared.  This call will also deal with the
	     * situation where parentList shares its intrep with other
	     * Tcl_Obj's.  Dealing with the shared intrep case can cause
	     * subListPtr to become shared again, so detect that case and
	     * make and store another copy.
	     */

	    TclListObjSetElement(NULL, parentList, index, subListPtr);
	    if (Tcl_IsShared(subListPtr)) {
		subListPtr = Tcl_DuplicateObj(subListPtr);
		TclListObjSetElement(NULL, parentList, index, subListPtr);
	    }

	    /*
	     * The TclListObjSetElement() calls do not spoil the string
	     * rep of parentList, and that's fine for now, since all we've
	     * done so far is replace a list element with an unshared copy.
	     * The list value remains the same, so the string rep. is still
	     * valid, and unchanged, which is good because if this whole
	     * routine returns NULL, we'd like to leave no change to the
	     * value of the lset variable.  Later on, when we set valuePtr
	     * in its proper place, then all containing lists will have
	     * their values changed, and will need their string reps spoiled.
	     * We maintain a list of all those Tcl_Obj's (via a little intrep
	     * surgery) so we can spoil them at that time.
	     */

	    parentList->internalRep.twoPtrValue.ptr2 = (void *) chainPtr;
	    chainPtr = parentList;
	}
    } while (indexCount > 0);

    /*
     * Either we've detected and error condition, and exited the loop
     * with result == TCL_ERROR, or we've successfully reached the last
     * index, and we're ready to store valuePtr.  In either case, we
     * need to clean up our string spoiling list of Tcl_Obj's.
     */

    while (chainPtr) {
	Tcl_Obj *objPtr = chainPtr;

	if (result == TCL_OK) {

	    /*
	     * We're going to store valuePtr, so spoil string reps
	     * of all containing lists.
	     */

	    Tcl_InvalidateStringRep(objPtr);
	}

	/* Clear away our intrep surgery mess */
	chainPtr = (Tcl_Obj *) objPtr->internalRep.twoPtrValue.ptr2;
	objPtr->internalRep.twoPtrValue.ptr2 = NULL;
    }

    if (result != TCL_OK) {
	/* 
	 * Error return; message is already in interp. Clean up
	 * any excess memory. 
	 */
	if (retValuePtr != listPtr) {
	    Tcl_DecrRefCount(retValuePtr);
	}
	return NULL;
    }

    /* Store valuePtr in proper sublist and return */
    TclListObjSetElement(NULL, subListPtr, index, valuePtr);
    Tcl_InvalidateStringRep(subListPtr);
    Tcl_IncrRefCount(retValuePtr);
    return retValuePtr;
}

/*
 *----------------------------------------------------------------------
 *
 * TclListObjSetElement --
 *
 *	Set a single element of a list to a specified value
 *
 * Results:
 *	The return value is normally TCL_OK. If listPtr does not refer to a
 *	list object and cannot be converted to one, TCL_ERROR is returned and
 *	an error message will be left in the interpreter result if interp is
 *	not NULL. Similarly, if index designates an element outside the range
 *	[0..listLength-1], where listLength is the count of elements in the
 *	list object designated by listPtr, TCL_ERROR is returned and an error
 *	message is left in the interpreter result.
 *
 * Side effects:
 *	Tcl_Panic if listPtr designates a shared object. Otherwise, attempts
 *	to convert it to a list with a non-shared internal rep. Decrements the
 *	ref count of the object at the specified index within the list,
 *	replaces with the object designated by valuePtr, and increments the
 *	ref count of the replacement object.
 *
 *	It is the caller's responsibility to invalidate the string
 *	representation of the object.
 *
 *----------------------------------------------------------------------
 */

int
TclListObjSetElement(
    Tcl_Interp *interp,		/* Tcl interpreter; used for error reporting
				 * if not NULL. */
    Tcl_Obj *listPtr,		/* List object in which element should be
				 * stored. */
    int index,			/* Index of element to store. */
    Tcl_Obj *valuePtr)		/* Tcl object to store in the designated list
				 * element. */
{
    List *listRepPtr;		/* Internal representation of the list being
				 * modified. */
    Tcl_Obj **elemPtrs;		/* Pointers to elements of the list. */
    int elemCount;		/* Number of elements in the list. */

    /*
     * Ensure that the listPtr parameter designates an unshared list.
     */

    if (Tcl_IsShared(listPtr)) {
	Tcl_Panic("%s called with shared object", "TclListObjSetElement");
    }
    if (listPtr->typePtr != &tclListType) {
	int length, result;

	(void) TclGetStringFromObj(listPtr, &length);
	if (!length) {
	    Tcl_SetObjResult(interp,
		    Tcl_NewStringObj("list index out of range", -1));
	    return TCL_ERROR;
	}
	result = SetListFromAny(interp, listPtr);
	if (result != TCL_OK) {
	    return result;
	}
    }

    listRepPtr = (List *) listPtr->internalRep.twoPtrValue.ptr1;
    elemCount = listRepPtr->elemCount;
    elemPtrs = &listRepPtr->elements;

    /*
     * Ensure that the index is in bounds.
     */

    if (index<0 || index>=elemCount) {
	if (interp != NULL) {
	    Tcl_SetObjResult(interp,
		    Tcl_NewStringObj("list index out of range", -1));
	}
	return TCL_ERROR;
    }

    /*
     * If the internal rep is shared, replace it with an unshared copy.
     */

    if (listRepPtr->refCount > 1) {
	List *oldListRepPtr = listRepPtr;
	Tcl_Obj **oldElemPtrs = elemPtrs;
	int i;

	listRepPtr = NewListIntRep(listRepPtr->maxElemCount, NULL);
	if (listRepPtr == NULL) {
	    Tcl_Panic("Not enough memory to allocate list");
	}
	listRepPtr->canonicalFlag = oldListRepPtr->canonicalFlag;
	elemPtrs = &listRepPtr->elements;
	for (i=0; i < elemCount; i++) {
	    elemPtrs[i] = oldElemPtrs[i];
	    Tcl_IncrRefCount(elemPtrs[i]);
	}
	listRepPtr->refCount++;
	listRepPtr->elemCount = elemCount;
	listPtr->internalRep.twoPtrValue.ptr1 = (void *) listRepPtr;
	oldListRepPtr->refCount--;
    }

    /*
     * Add a reference to the new list element.
     */

    Tcl_IncrRefCount(valuePtr);

    /*
     * Remove a reference from the old list element.
     */

    Tcl_DecrRefCount(elemPtrs[index]);

    /*
     * Stash the new object in the list.
     */

    elemPtrs[index] = valuePtr;

    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * FreeListInternalRep --
 *
 *	Deallocate the storage associated with a list object's internal
 *	representation.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Frees listPtr's List* internal representation and sets listPtr's
 *	internalRep.twoPtrValue.ptr1 to NULL. Decrements the ref counts of all
 *	element objects, which may free them.
 *
 *----------------------------------------------------------------------
 */

static void
FreeListInternalRep(
    Tcl_Obj *listPtr)		/* List object with internal rep to free. */
{
    register List *listRepPtr = (List *) listPtr->internalRep.twoPtrValue.ptr1;
    register Tcl_Obj **elemPtrs = &listRepPtr->elements;
    register Tcl_Obj *objPtr;
    int numElems = listRepPtr->elemCount;
    int i;

    if (--listRepPtr->refCount <= 0) {
	for (i = 0;  i < numElems;  i++) {
	    objPtr = elemPtrs[i];
	    Tcl_DecrRefCount(objPtr);
	}
	ckfree((char *) listRepPtr);
    }

    listPtr->internalRep.twoPtrValue.ptr1 = NULL;
    listPtr->internalRep.twoPtrValue.ptr2 = NULL;
}

/*
 *----------------------------------------------------------------------
 *
 * DupListInternalRep --
 *
 *	Initialize the internal representation of a list Tcl_Obj to share the
 *	internal representation of an existing list object.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	The reference count of the List internal rep is incremented.
 *
 *----------------------------------------------------------------------
 */

static void
DupListInternalRep(
    Tcl_Obj *srcPtr,		/* Object with internal rep to copy. */
    Tcl_Obj *copyPtr)		/* Object with internal rep to set. */
{
    List *listRepPtr = (List *) srcPtr->internalRep.twoPtrValue.ptr1;

    listRepPtr->refCount++;
    copyPtr->internalRep.twoPtrValue.ptr1 = (void *) listRepPtr;
    copyPtr->internalRep.twoPtrValue.ptr2 = NULL;
    copyPtr->typePtr = &tclListType;
}

/*
 *----------------------------------------------------------------------
 *
 * SetListFromAny --
 *
 *	Attempt to generate a list internal form for the Tcl object "objPtr".
 *
 * Results:
 *	The return value is TCL_OK or TCL_ERROR. If an error occurs during
 *	conversion, an error message is left in the interpreter's result
 *	unless "interp" is NULL.
 *
 * Side effects:
 *	If no error occurs, a list is stored as "objPtr"s internal
 *	representation.
 *
 *----------------------------------------------------------------------
 */

static int
SetListFromAny(
    Tcl_Interp *interp,		/* Used for error reporting if not NULL. */
    Tcl_Obj *objPtr)		/* The object to convert. */
{
    char *string, *s;
    const char *elemStart, *nextElem;
    int lenRemain, length, estCount, elemSize, hasBrace, i, j, result;
    const char *limit;		/* Points just after string's last byte. */
    register const char *p;
    register Tcl_Obj **elemPtrs;
    register Tcl_Obj *elemPtr;
    List *listRepPtr;

    /*
     * Dictionaries are a special case; they have a string representation such
     * that *all* valid dictionaries are valid lists. Hence we can convert
     * more directly.
     */

    if (objPtr->typePtr == &tclDictType) {
	Tcl_Obj *keyPtr, *valuePtr;
	Tcl_DictSearch search;
	int done, size;

	/*
	 * Create the new list representation. Note that we do not need to do
	 * anything with the string representation as the transformation (and
	 * the reverse back to a dictionary) are both order-preserving. Also
	 * note that since we know we've got a valid dictionary (by
	 * representation) we also know that fetching the size of the
	 * dictionary or iterating over it will not fail.
	 */

	Tcl_DictObjSize(NULL, objPtr, &size);
	listRepPtr = NewListIntRep(size > 0 ? 2*size : 1, NULL);
	if (!listRepPtr) {
	    Tcl_SetResult(interp,
		    "insufficient memory to allocate list working space",
		    TCL_STATIC);
	    return TCL_ERROR;
	}
	listRepPtr->elemCount = 2 * size;

	/*
	 * Populate the list representation.
	 */

	elemPtrs = &listRepPtr->elements;
	Tcl_DictObjFirst(NULL, objPtr, &search, &keyPtr, &valuePtr, &done);
	i = 0;
	while (!done) {
	    elemPtrs[i++] = keyPtr;
	    elemPtrs[i++] = valuePtr;
	    Tcl_IncrRefCount(keyPtr);
	    Tcl_IncrRefCount(valuePtr);
	    Tcl_DictObjNext(&search, &keyPtr, &valuePtr, &done);
	}

	/*
	 * Swap the representations.
	 */

	goto commitRepresentation;
    }

    /*
     * Get the string representation. Make it up-to-date if necessary.
     */

    string = TclGetStringFromObj(objPtr, &length);

    /*
     * Parse the string into separate string objects, and create a List
     * structure that points to the element string objects. We use a modified
     * version of Tcl_SplitList's implementation to avoid one malloc and a
     * string copy for each list element. First, estimate the number of
     * elements by counting the number of space characters in the list.
     */

    limit = string + length;
    estCount = 1;
    for (p = string;  p < limit;  p++) {
	if (isspace(UCHAR(*p))) { /* INTL: ISO space. */
	    estCount++;
	}
    }

    /*
     * Allocate a new List structure with enough room for "estCount" elements.
     * Each element is a pointer to a Tcl_Obj with the appropriate string rep.
     * The initial "estCount" elements are set using the corresponding "argv"
     * strings.
     */

    listRepPtr = NewListIntRep(estCount, NULL);
    if (!listRepPtr) {
	Tcl_SetObjResult(interp, Tcl_NewStringObj(
		"Not enough memory to allocate the list internal rep", -1));
	return TCL_ERROR;
    }
    elemPtrs = &listRepPtr->elements;

    for (p=string, lenRemain=length, i=0;
	    lenRemain > 0;
	    p=nextElem, lenRemain=limit-nextElem, i++) {
	result = TclFindElement(interp, p, lenRemain, &elemStart, &nextElem,
		&elemSize, &hasBrace);
	if (result != TCL_OK) {
	    for (j = 0;  j < i;  j++) {
		elemPtr = elemPtrs[j];
		Tcl_DecrRefCount(elemPtr);
	    }
	    ckfree((char *) listRepPtr);
	    return result;
	}
	if (elemStart >= limit) {
	    break;
	}
	if (i > estCount) {
	    Tcl_Panic("SetListFromAny: bad size estimate for list");
	}

	/*
	 * Allocate a Tcl object for the element and initialize it from the
	 * "elemSize" bytes starting at "elemStart".
	 */

	s = ckalloc((unsigned) elemSize + 1);
	if (hasBrace) {
	    memcpy(s, elemStart, (size_t) elemSize);
	    s[elemSize] = 0;
	} else {
	    elemSize = TclCopyAndCollapse(elemSize, elemStart, s);
	}

	TclNewObj(elemPtr);
	elemPtr->bytes = s;
	elemPtr->length = elemSize;
	elemPtrs[i] = elemPtr;
	Tcl_IncrRefCount(elemPtr);	/* Since list now holds ref to it. */
    }

    listRepPtr->elemCount = i;

    /*
     * Free the old internalRep before setting the new one. We do this as late
     * as possible to allow the conversion code, in particular
     * Tcl_GetStringFromObj, to use that old internalRep.
     */

  commitRepresentation:
    listRepPtr->refCount++;
    TclFreeIntRep(objPtr);
    objPtr->internalRep.twoPtrValue.ptr1 = listRepPtr;
    objPtr->internalRep.twoPtrValue.ptr2 = NULL;
    objPtr->typePtr = &tclListType;
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * UpdateStringOfList --
 *
 *	Update the string representation for a list object. Note: This
 *	function does not invalidate an existing old string rep so storage
 *	will be lost if this has not already been done.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	The object's string is set to a valid string that results from the
 *	list-to-string conversion. This string will be empty if the list has
 *	no elements. The list internal representation should not be NULL and
 *	we assume it is not NULL.
 *
 *----------------------------------------------------------------------
 */

static void
UpdateStringOfList(
    Tcl_Obj *listPtr)		/* List object with string rep to update. */
{
#   define LOCAL_SIZE 20
    int localFlags[LOCAL_SIZE], *flagPtr;
    List *listRepPtr = (List *) listPtr->internalRep.twoPtrValue.ptr1;
    int numElems = listRepPtr->elemCount;
    register int i;
    char *elem, *dst;
    int length;
    Tcl_Obj **elemPtrs;

    /*
     * Convert each element of the list to string form and then convert it to
     * proper list element form, adding it to the result buffer.
     */

    /*
     * Pass 1: estimate space, gather flags.
     */

    if (numElems <= LOCAL_SIZE) {
	flagPtr = localFlags;
    } else {
	flagPtr = (int *) ckalloc((unsigned) numElems * sizeof(int));
    }
    listPtr->length = 1;
    elemPtrs = &listRepPtr->elements;
    for (i = 0; i < numElems; i++) {
	elem = TclGetStringFromObj(elemPtrs[i], &length);
	listPtr->length += Tcl_ScanCountedElement(elem, length, flagPtr+i)+1;

	/*
	 * Check for continued sanity. [Bug 1267380]
	 */

	if (listPtr->length < 1) {
	    Tcl_Panic("string representation size exceeds sane bounds");
	}
    }

    /*
     * Pass 2: copy into string rep buffer.
     */

    listPtr->bytes = ckalloc((unsigned) listPtr->length);
    dst = listPtr->bytes;
    for (i = 0; i < numElems; i++) {
	elem = TclGetStringFromObj(elemPtrs[i], &length);
	dst += Tcl_ConvertCountedElement(elem, length, dst,
		flagPtr[i] | (i==0 ? 0 : TCL_DONT_QUOTE_HASH));
	*dst = ' ';
	dst++;
    }
    if (flagPtr != localFlags) {
	ckfree((char *) flagPtr);
    }
    if (dst == listPtr->bytes) {
	*dst = 0;
    } else {
	dst--;
	*dst = 0;
    }
    listPtr->length = dst - listPtr->bytes;

    /*
     * Mark the list as being canonical; although it has a string rep, it is
     * one we derived through proper "canonical" quoting and so it's known to
     * be free from nasties relating to [concat] and [eval].
     */

    listRepPtr->canonicalFlag = 1;
}

/*
 * Local Variables:
 * mode: c
 * c-basic-offset: 4
 * fill-column: 78
 * End:
 */