summaryrefslogtreecommitdiffstats
path: root/generic/tclIORChan.c
blob: 9781a5a69c4dfd95c412f4f142c068f8a58ac002 (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
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572
2573
2574
2575
2576
2577
2578
2579
2580
2581
2582
2583
2584
2585
2586
2587
2588
2589
2590
2591
2592
2593
2594
2595
2596
2597
2598
2599
2600
2601
2602
2603
2604
2605
2606
2607
2608
2609
2610
2611
2612
2613
2614
2615
2616
2617
2618
2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633
2634
2635
2636
2637
2638
2639
2640
2641
2642
2643
2644
2645
2646
2647
2648
2649
2650
2651
2652
2653
2654
2655
2656
2657
2658
2659
2660
2661
2662
2663
2664
2665
2666
2667
2668
2669
2670
2671
2672
2673
2674
2675
2676
2677
2678
2679
2680
2681
2682
2683
2684
2685
2686
2687
2688
2689
2690
2691
2692
2693
2694
2695
2696
2697
2698
2699
2700
2701
2702
2703
2704
2705
2706
2707
2708
2709
2710
2711
2712
2713
2714
2715
2716
2717
2718
2719
2720
2721
2722
2723
2724
2725
2726
2727
2728
2729
2730
2731
2732
2733
2734
2735
2736
2737
2738
2739
2740
2741
2742
2743
2744
2745
2746
2747
2748
2749
2750
2751
2752
2753
2754
2755
2756
2757
2758
2759
2760
2761
2762
2763
2764
2765
2766
2767
2768
2769
2770
2771
2772
2773
2774
2775
2776
2777
2778
2779
2780
2781
2782
2783
2784
2785
2786
2787
2788
2789
2790
2791
2792
2793
2794
2795
2796
2797
2798
2799
2800
2801
2802
2803
2804
2805
2806
2807
2808
2809
2810
2811
2812
2813
2814
2815
2816
2817
2818
2819
2820
2821
2822
2823
2824
2825
2826
2827
2828
2829
2830
2831
2832
2833
2834
2835
2836
2837
2838
2839
2840
2841
2842
2843
2844
2845
2846
2847
2848
2849
2850
2851
2852
2853
2854
2855
2856
2857
2858
2859
2860
2861
2862
2863
2864
2865
2866
2867
2868
2869
2870
2871
2872
2873
2874
2875
2876
2877
2878
2879
2880
2881
2882
2883
2884
2885
2886
2887
2888
2889
2890
2891
2892
2893
2894
2895
2896
2897
2898
2899
2900
2901
2902
2903
2904
2905
2906
2907
2908
2909
2910
2911
2912
2913
2914
2915
2916
2917
2918
2919
2920
2921
2922
2923
2924
2925
2926
2927
2928
2929
2930
2931
2932
2933
2934
2935
2936
2937
2938
2939
2940
2941
2942
2943
2944
2945
2946
2947
2948
2949
2950
2951
2952
2953
2954
2955
2956
2957
2958
2959
2960
2961
2962
2963
2964
2965
2966
2967
2968
2969
2970
2971
2972
2973
2974
2975
2976
2977
2978
2979
2980
2981
2982
2983
2984
2985
2986
2987
2988
2989
2990
2991
2992
2993
2994
2995
2996
2997
2998
2999
3000
3001
3002
3003
3004
3005
3006
3007
3008
3009
/*
 * tclIORChan.c --
 *
 *	This file contains the implementation of Tcl's generic channel
 *	reflection code, which allows the implementation of Tcl channels in
 *	Tcl code.
 *
 *	Parts of this file are based on code contributed by Jean-Claude
 *	Wippler.
 *
 *	See TIP #219 for the specification of this functionality.
 *
 * Copyright (c) 2004-2005 ActiveState, a divison of Sophos
 *
 * See the file "license.terms" for information on usage and redistribution of
 * this file, and for a DISCLAIMER OF ALL WARRANTIES.
 *
 * RCS: @(#) $Id: tclIORChan.c,v 1.28.2.3 2008/04/24 18:50:42 andreas_kupries Exp $
 */

#include <tclInt.h>
#include <tclIO.h>
#include <assert.h>

#ifndef EINVAL
#define EINVAL	9
#endif
#ifndef EOK
#define EOK	0
#endif

/*
 * Signatures of all functions used in the C layer of the reflection.
 */

static int		ReflectClose(ClientData clientData,
			    Tcl_Interp *interp);
static int		ReflectInput(ClientData clientData, char *buf,
			    int toRead, int *errorCodePtr);
static int		ReflectOutput(ClientData clientData, const char *buf,
			    int toWrite, int *errorCodePtr);
static void		ReflectWatch(ClientData clientData, int mask);
static int		ReflectBlock(ClientData clientData, int mode);
static Tcl_WideInt	ReflectSeekWide(ClientData clientData,
			    Tcl_WideInt offset, int mode, int *errorCodePtr);
static int		ReflectSeek(ClientData clientData, long offset,
			    int mode, int *errorCodePtr);
static int		ReflectGetOption(ClientData clientData,
			    Tcl_Interp *interp, const char *optionName,
			    Tcl_DString *dsPtr);
static int		ReflectSetOption(ClientData clientData,
			    Tcl_Interp *interp, const char *optionName,
			    const char *newValue);

/*
 * The C layer channel type/driver definition used by the reflection. This is
 * a version 3 structure.
 */

static Tcl_ChannelType tclRChannelType = {
    "tclrchannel",         /* Type name.                                  */
    TCL_CHANNEL_VERSION_5, /* v5 channel */
    ReflectClose,          /* Close channel, clean instance data          */
    ReflectInput,          /* Handle read request                         */
    ReflectOutput,         /* Handle write request                        */
    ReflectSeek,           /* Move location of access point.   NULL'able  */
    ReflectSetOption,      /* Set options.                     NULL'able  */
    ReflectGetOption,      /* Get options.                     NULL'able  */
    ReflectWatch,          /* Initialize notifier                         */
    NULL,                  /* Get OS handle from the channel.  NULL'able  */
    NULL,                  /* No close2 support.               NULL'able  */
    ReflectBlock,          /* Set blocking/nonblocking.        NULL'able  */
    NULL,                  /* Flush channel. Not used by core. NULL'able  */
    NULL,                  /* Handle events.                   NULL'able  */
    ReflectSeekWide,       /* Move access point (64 bit).      NULL'able  */
    NULL,                  /* thread action */
    NULL,                  /* truncate */
};

/*
 * Instance data for a reflected channel. ===========================
 */

typedef struct {
    Tcl_Channel chan;		/* Back reference to generic channel
				 * structure. */
    Tcl_Interp *interp;		/* Reference to the interpreter containing the
				 * Tcl level part of the channel. NULL here
				 * signals the channel is dead because the
				 * interpreter/thread containing its Tcl
				 * command is gone.
				 */
#ifdef TCL_THREADS
    Tcl_ThreadId thread;	/* Thread the 'interp' belongs to. */
#endif

    /* See [==] as well.
     * Storage for the command prefix and the additional words required for
     * the invocation of methods in the command handler.
     *
     * argv [0] ... [.] | [argc-2] [argc-1] | [argc]  [argc+2]
     *      cmd ... pfx | method   chan     | detail1 detail2
     *      ~~~~ CT ~~~            ~~ CT ~~
     *
     * CT = Belongs to the 'Command handler Thread'.
     */

    int argc;			/* Number of preallocated words - 2 */
    Tcl_Obj **argv;		/* Preallocated array for calling the handler.
				 * args[0] is placeholder for cmd word.
				 * Followed by the arguments in the prefix,
				 * plus 4 placeholders for method, channel,
				 * and at most two varying (method specific)
				 * words. */
    int methods;		/* Bitmask of supported methods */

    /*
     * NOTE (9): Should we have predefined shared literals for the method
     * names?
     */

    int mode;			/* Mask of R/W mode */
    int interest;		/* Mask of events the channel is interested
				 * in. */

    /*
     * Note regarding the usage of timers.
     *
     * Most channel implementations need a timer in the C level to ensure that
     * data in buffers is flushed out through the generation of fake file
     * events.
     *
     * See 'rechan', 'memchan', etc.
     *
     * Here this is _not_ required. Interest in events is posted to the Tcl
     * level via 'watch'. And posting of events is possible from the Tcl level
     * as well, via 'chan postevent'. This means that the generation of all
     * events, fake or not, timer based or not, is completely in the hands of
     * the Tcl level. Therefore no timer here.
     */
} ReflectedChannel;

/*
 * Structure of the table maping from channel handles to reflected
 * channels. Each interpreter which has the handler command for one or more
 * reflected channels records them in such a table, so that 'chan postevent'
 * is able to find them even if the actual channel was moved to a different
 * interpreter and/or thread.
 *
 * The table is reachable via the standard interpreter AssocData, the key is
 * defined below.
 */

typedef struct {
    Tcl_HashTable map;
} ReflectedChannelMap;

#define RCMKEY "ReflectedChannelMap"

/*
 * Event literals. ==================================================
 */

static const char *eventOptions[] = {
    "read", "write", NULL
};
typedef enum {
    EVENT_READ, EVENT_WRITE
} EventOption;

/*
 * Method literals. ==================================================
 */

static const char *methodNames[] = {
    "blocking",		/* OPT */
    "cget",		/* OPT \/ Together or none */
    "cgetall",		/* OPT /\ of these two     */
    "configure",	/* OPT */
    "finalize",		/*     */
    "initialize",	/*     */
    "read",		/* OPT */
    "seek",		/* OPT */
    "watch",		/*     */
    "write",		/* OPT */
    NULL
};
typedef enum {
    METH_BLOCKING,
    METH_CGET,
    METH_CGETALL,
    METH_CONFIGURE,
    METH_FINAL,
    METH_INIT,
    METH_READ,
    METH_SEEK,
    METH_WATCH,
    METH_WRITE
} MethodName;

#define FLAG(m) (1 << (m))
#define REQUIRED_METHODS \
	(FLAG(METH_INIT) | FLAG(METH_FINAL) | FLAG(METH_WATCH))
#define NULLABLE_METHODS \
	(FLAG(METH_BLOCKING) | FLAG(METH_SEEK) | \
	FLAG(METH_CONFIGURE) | FLAG(METH_CGET) | FLAG(METH_CGETALL))

#define RANDW \
	(TCL_READABLE | TCL_WRITABLE)

#define IMPLIES(a,b)	((!(a)) || (b))
#define NEGIMPL(a,b)
#define HAS(x,f)	(x & FLAG(f))

#ifdef TCL_THREADS
/*
 * Thread specific types and structures.
 *
 * We are here essentially creating a very specific implementation of 'thread
 * send'.
 */

/*
 * Enumeration of all operations which can be forwarded.
 */

typedef enum {
    ForwardedClose,
    ForwardedInput,
    ForwardedOutput,
    ForwardedSeek,
    ForwardedWatch,
    ForwardedBlock,
    ForwardedSetOpt,
    ForwardedGetOpt,
    ForwardedGetOptAll
} ForwardedOperation;

/*
 * Event used to forward driver invocations to the thread actually managing
 * the channel. We cannot construct the command to execute and forward that.
 * Because then it will contain a mixture of Tcl_Obj's belonging to both the
 * command handler thread (CT), and the thread managing the channel (MT),
 * executed in CT. Tcl_Obj's are not allowed to cross thread boundaries. So we
 * forward an operation code, the argument details, and reference to results.
 * The command is assembled in the CT and belongs fully to that thread. No
 * sharing problems.
 */

typedef struct ForwardParamBase {
    int code;			/* O: Ok/Fail of the cmd handler */
    char *msgStr;		/* O: Error message for handler failure */
    int mustFree;		/* O: True if msgStr is allocated, false if
				 * otherwise (static). */
} ForwardParamBase;

/*
 * Operation specific parameter/result structures. (These are "subtypes" of
 * ForwardParamBase. Where an operation does not need any special types, it
 * has no "subtype" and just uses ForwardParamBase, as listed above.)
 */

struct ForwardParamInput {
    ForwardParamBase base;	/* "Supertype". MUST COME FIRST. */
    char *buf;			/* O: Where to store the read bytes */
    int toRead;			/* I: #bytes to read,
				 * O: #bytes actually read */
};
struct ForwardParamOutput {
    ForwardParamBase base;	/* "Supertype". MUST COME FIRST. */
    const char *buf;		/* I: Where the bytes to write come from */
    int toWrite;		/* I: #bytes to write,
				 * O: #bytes actually written */
};
struct ForwardParamSeek {
    ForwardParamBase base;	/* "Supertype". MUST COME FIRST. */
    int seekMode;		/* I: How to seek */
    Tcl_WideInt offset;		/* I: Where to seek,
				 * O: New location */
};
struct ForwardParamWatch {
    ForwardParamBase base;	/* "Supertype". MUST COME FIRST. */
    int mask;			/* I: What events to watch for */
};
struct ForwardParamBlock {
    ForwardParamBase base;	/* "Supertype". MUST COME FIRST. */
    int nonblocking;		/* I: What mode to activate */
};
struct ForwardParamSetOpt {
    ForwardParamBase base;	/* "Supertype". MUST COME FIRST. */
    const char *name;		/* Name of option to set */
    const char *value;		/* Value to set */
};
struct ForwardParamGetOpt {
    ForwardParamBase base;	/* "Supertype". MUST COME FIRST. */
    const char *name;		/* Name of option to get, maybe NULL */
    Tcl_DString *value;		/* Result */
};

/*
 * Now join all these together in a single union for convenience.
 */

typedef union ForwardParam {
    ForwardParamBase base;
    struct ForwardParamInput input;
    struct ForwardParamOutput output;
    struct ForwardParamSeek seek;
    struct ForwardParamWatch watch;
    struct ForwardParamBlock block;
    struct ForwardParamSetOpt setOpt;
    struct ForwardParamGetOpt getOpt;
} ForwardParam;

/*
 * Forward declaration.
 */

typedef struct ForwardingResult ForwardingResult;

/*
 * General event structure, with reference to operation specific data.
 */

typedef struct ForwardingEvent {
    Tcl_Event event;		/* Basic event data, has to be first item */
    ForwardingResult *resultPtr;
    ForwardedOperation op;	/* Forwarded driver operation */
    ReflectedChannel *rcPtr;	/* Channel instance */
    ForwardParam *param;	/* Packaged arguments and return values, a
				 * ForwardParam pointer. */
} ForwardingEvent;

/*
 * Structure to manage the result of the forwarding. This is not the result of
 * the operation itself, but about the success of the forward event itself.
 * The event can be successful, even if the operation which was forwarded
 * failed. It is also there to manage the synchronization between the involved
 * threads.
 */

struct ForwardingResult {
    Tcl_ThreadId src;		/* Originating thread. */
    Tcl_ThreadId dst;		/* Thread the op was forwarded to. */
    Tcl_Interp*  dsti;          /* Interpreter in the thread the op was forwarded to. */
    /*
     * Note regarding 'dsti' above: Its information is also available via the
     * chain evPtr->rcPtr->interp, however, as can be seen, two more
     * indirections are needed to retrieve it. And the evPtr may be gone,
     * breaking the chain.
     */
    Tcl_Condition done;		/* Condition variable the forwarder blocks
				 * on. */
    int result;			/* TCL_OK or TCL_ERROR */
    ForwardingEvent *evPtr;	/* Event the result belongs to. */
    ForwardingResult *prevPtr, *nextPtr;
				/* Links into the list of pending forwarded
				 * results. */
};

typedef struct ThreadSpecificData {
    /*
     * Table of all reflected channels owned by this thread. This is the
     * per-thread version of the per-interpreter map.
     */

    ReflectedChannelMap* rcmPtr;
} ThreadSpecificData;

static Tcl_ThreadDataKey dataKey;

/*
 * List of forwarded operations which have not completed yet, plus the mutex
 * to protect the access to this process global list.
 */

static ForwardingResult *forwardList = NULL;
TCL_DECLARE_MUTEX(rcForwardMutex)

/*
 * Function containing the generic code executing a forward, and wrapper
 * macros for the actual operations we wish to forward. Uses ForwardProc as
 * the event function executed by the thread receiving a forwarding event
 * (which executes the appropriate function and collects the result, if any).
 *
 * The ExitProc ensures that things do not deadlock when the sending thread
 * involved in the forwarding exits. It also clean things up so that we don't
 * leak resources when threads go away.
 */

static void		ForwardOpToOwnerThread(ReflectedChannel *rcPtr,
			    ForwardedOperation op, const VOID *param);
static int		ForwardProc(Tcl_Event *evPtr, int mask);
static void		SrcExitProc(ClientData clientData);

#define FreeReceivedError(p) \
	if ((p)->base.mustFree) { \
	    ckfree((p)->base.msgStr); \
	}
#define PassReceivedErrorInterp(i,p) \
	if ((i) != NULL) { \
	    Tcl_SetChannelErrorInterp((i), \
		    Tcl_NewStringObj((p)->base.msgStr, -1)); \
	} \
	FreeReceivedError(p)
#define PassReceivedError(c,p) \
	Tcl_SetChannelError((c), Tcl_NewStringObj((p)->base.msgStr, -1)); \
	FreeReceivedError(p)
#define ForwardSetStaticError(p,emsg) \
	(p)->base.code = TCL_ERROR; \
	(p)->base.mustFree = 0; \
	(p)->base.msgStr = (char *) (emsg)
#define ForwardSetDynamicError(p,emsg) \
	(p)->base.code = TCL_ERROR; \
	(p)->base.mustFree = 1; \
	(p)->base.msgStr = (char *) (emsg)

static void		ForwardSetObjError(ForwardParam *p, Tcl_Obj *objPtr);

static ReflectedChannelMap *	GetThreadReflectedChannelMap(void);
static void		DeleteThreadReflectedChannelMap(ClientData clientData);

#endif /* TCL_THREADS */

#define SetChannelErrorStr(c,msgStr) \
	Tcl_SetChannelError((c), Tcl_NewStringObj((msgStr), -1))

static Tcl_Obj *	MarshallError(Tcl_Interp *interp);
static void		UnmarshallErrorResult(Tcl_Interp *interp,
			    Tcl_Obj *msgObj);

/*
 * Static functions for this file:
 */

static int		EncodeEventMask(Tcl_Interp *interp,
			    const char *objName, Tcl_Obj *obj, int *mask);
static Tcl_Obj *	DecodeEventMask(int mask);
static ReflectedChannel * NewReflectedChannel(Tcl_Interp *interp,
			    Tcl_Obj *cmdpfxObj, int mode, Tcl_Obj *handleObj);
static Tcl_Obj *	NextHandle(void);
static void		FreeReflectedChannel(ReflectedChannel *rcPtr);
static int		InvokeTclMethod(ReflectedChannel *rcPtr,
			    const char *method, Tcl_Obj *argOneObj,
			    Tcl_Obj *argTwoObj, Tcl_Obj **resultObjPtr);

static ReflectedChannelMap *	GetReflectedChannelMap(Tcl_Interp *interp);
static void		DeleteReflectedChannelMap(ClientData clientData,
			    Tcl_Interp *interp);

/*
 * Global constant strings (messages). ==================
 * These string are used directly as bypass errors, thus they have to be valid
 * Tcl lists where the last element is the message itself. Hence the
 * list-quoting to keep the words of the message together. See also [x].
 */

static const char *msg_read_unsup = "{read not supported by Tcl driver}";
static const char *msg_read_toomuch = "{read delivered more than requested}";
static const char *msg_write_unsup = "{write not supported by Tcl driver}";
static const char *msg_write_toomuch = "{write wrote more than requested}";
static const char *msg_write_nothing = "{write wrote nothing}";
static const char *msg_seek_beforestart = "{Tried to seek before origin}";
#ifdef TCL_THREADS
static const char *msg_send_originlost = "{Channel thread lost}";
static const char *msg_send_dstlost    = "{Owner lost}";
#endif /* TCL_THREADS */
static const char *msg_dstlost    = "-code 1 -level 0 -errorcode NONE -errorinfo {} -errorline 1 {Owner lost}";

/*
 * Main methods to plug into the 'chan' ensemble'. ==================
 */

/*
 *----------------------------------------------------------------------
 *
 * TclChanCreateObjCmd --
 *
 *	This function is invoked to process the "chan create" Tcl command.
 *	See the user documentation for details on what it does.
 *
 * Results:
 *	A standard Tcl result. The handle of the new channel is placed in the
 *	interp result.
 *
 * Side effects:
 *	Creates a new channel.
 *
 *----------------------------------------------------------------------
 */

int
TclChanCreateObjCmd(
    ClientData clientData,
    Tcl_Interp *interp,
    int objc,
    Tcl_Obj *const *objv)
{
    ReflectedChannel *rcPtr;	/* Instance data of the new channel */
    Tcl_Obj *rcId;		/* Handle of the new channel */
    int mode;			/* R/W mode of new channel. Has to match
				 * abilities of handler commands */
    Tcl_Obj *cmdObj;		/* Command prefix, list of words */
    Tcl_Obj *cmdNameObj;	/* Command name */
    Tcl_Channel chan;		/* Token for the new channel */
    Tcl_Obj *modeObj;		/* mode in obj form for method call */
    int listc;			/* Result of 'initialize', and of */
    Tcl_Obj **listv;		/* its sublist in the 2nd element */
    int methIndex;		/* Encoded method name */
    int result;			/* Result code for 'initialize' */
    Tcl_Obj *resObj;		/* Result data for 'initialize' */
    int methods;		/* Bitmask for supported methods. */
    Channel *chanPtr;		/* 'chan' resolved to internal struct. */
    Tcl_Obj *err;		/* Error message */
    ReflectedChannelMap* rcmPtr; /* Map of reflected channels with handlers in this interp */
    Tcl_HashEntry* hPtr;         /* Entry in the above map */
    int isNew;                   /* Placeholder. */

    /*
     * Syntax:   chan create MODE CMDPREFIX
     *           [0]  [1]    [2]  [3]
     *
     * Actually: rCreate MODE CMDPREFIX
     *           [0]     [1]  [2]
     */

#define MODE	(1)
#define CMD	(2)

    /*
     * Number of arguments...
     */

    if (objc != 3) {
	Tcl_WrongNumArgs(interp, 1, objv, "mode cmdprefix");
	return TCL_ERROR;
    }

    /*
     * First argument is a list of modes. Allowed entries are "read", "write".
     * Expect at least one list element. Abbreviations are ok.
     */

    modeObj = objv[MODE];
    if (EncodeEventMask(interp, "mode", objv[MODE], &mode) != TCL_OK) {
	return TCL_ERROR;
    }

    /*
     * Second argument is command prefix, i.e. list of words, first word is
     * name of handler command, other words are fixed arguments. Run the
     * 'initialize' method to get the list of supported methods. Validate
     * this.
     */

    cmdObj = objv[CMD];

    /*
     * Basic check that the command prefix truly is a list.
     */

    if (Tcl_ListObjIndex(interp, cmdObj, 0, &cmdNameObj) != TCL_OK) {
	return TCL_ERROR;
    }

    /*
     * Now create the channel.
     */

    rcId = NextHandle();
    rcPtr = NewReflectedChannel(interp, cmdObj, mode, rcId);
    chan = Tcl_CreateChannel(&tclRChannelType, TclGetString(rcId), rcPtr,
	    mode);
    rcPtr->chan = chan;
    chanPtr = (Channel *) chan;

    /*
     * Invoke 'initialize' and validate that the handler is present and ok.
     * Squash the channel if not.
     *
     * Note: The conversion of 'mode' back into a Tcl_Obj ensures that
     * 'initialize' is invoked with canonical mode names, and no
     * abbreviations. Using modeObj directly could feed abbreviations into the
     * handler, and the handler is not specified to handle such.
     */

    modeObj = DecodeEventMask(mode);
    result = InvokeTclMethod(rcPtr, "initialize", modeObj, NULL, &resObj);
    Tcl_DecrRefCount(modeObj);
    if (result != TCL_OK) {
	UnmarshallErrorResult(interp, resObj);
	Tcl_DecrRefCount(resObj);	/* Remove reference held from invoke */
	goto error;
    }

    /*
     * Verify the result.
     * - List, of method names. Convert to mask.
     *   Check for non-optionals through the mask.
     *   Compare open mode against optional r/w.
     */

    if (Tcl_ListObjGetElements(NULL, resObj, &listc, &listv) != TCL_OK) {
	TclNewLiteralStringObj(err, "chan handler \"");
	Tcl_AppendObjToObj(err, cmdObj);
	Tcl_AppendToObj(err, " initialize\" returned non-list: ", -1);
	Tcl_AppendObjToObj(err, resObj);
	Tcl_SetObjResult(interp, err);
	Tcl_DecrRefCount(resObj);
	goto error;
    }

    methods = 0;
    while (listc > 0) {
	if (Tcl_GetIndexFromObj(interp, listv[listc-1], methodNames,
		"method", TCL_EXACT, &methIndex) != TCL_OK) {
	    TclNewLiteralStringObj(err, "chan handler \"");
	    Tcl_AppendObjToObj(err, cmdObj);
	    Tcl_AppendToObj(err, " initialize\" returned ", -1);
	    Tcl_AppendObjToObj(err, Tcl_GetObjResult(interp));
	    Tcl_SetObjResult(interp, err);
	    Tcl_DecrRefCount(resObj);
	    goto error;
	}

	methods |= FLAG(methIndex);
	listc--;
    }
    Tcl_DecrRefCount(resObj);

    if ((REQUIRED_METHODS & methods) != REQUIRED_METHODS) {
	TclNewLiteralStringObj(err, "chan handler \"");
	Tcl_AppendObjToObj(err, cmdObj);
	Tcl_AppendToObj(err, "\" does not support all required methods", -1);
	Tcl_SetObjResult(interp, err);
	goto error;
    }

    if ((mode & TCL_READABLE) && !HAS(methods, METH_READ)) {
	TclNewLiteralStringObj(err, "chan handler \"");
	Tcl_AppendObjToObj(err, cmdObj);
	Tcl_AppendToObj(err, "\" lacks a \"read\" method", -1);
	Tcl_SetObjResult(interp, err);
	goto error;
    }

    if ((mode & TCL_WRITABLE) && !HAS(methods, METH_WRITE)) {
	TclNewLiteralStringObj(err, "chan handler \"");
	Tcl_AppendObjToObj(err, cmdObj);
	Tcl_AppendToObj(err, "\" lacks a \"write\" method", -1);
	Tcl_SetObjResult(interp, err);
	goto error;
    }

    if (!IMPLIES(HAS(methods, METH_CGET), HAS(methods, METH_CGETALL))) {
	TclNewLiteralStringObj(err, "chan handler \"");
	Tcl_AppendObjToObj(err, cmdObj);
	Tcl_AppendToObj(err, "\" supports \"cget\" but not \"cgetall\"", -1);
	Tcl_SetObjResult(interp, err);
	goto error;
    }

    if (!IMPLIES(HAS(methods, METH_CGETALL), HAS(methods, METH_CGET))) {
	TclNewLiteralStringObj(err, "chan handler \"");
	Tcl_AppendObjToObj(err, cmdObj);
	Tcl_AppendToObj(err, "\" supports \"cgetall\" but not \"cget\"", -1);
	Tcl_SetObjResult(interp, err);
	goto error;
    }

    Tcl_ResetResult(interp);

    /*
     * Everything is fine now.
     */

    rcPtr->methods = methods;

    if ((methods & NULLABLE_METHODS) != NULLABLE_METHODS) {
	/*
	 * Some of the nullable methods are not supported. We clone the
	 * channel type, null the associated C functions, and use the result
	 * as the actual channel type.
	 */

	Tcl_ChannelType *clonePtr = (Tcl_ChannelType *)
		ckalloc(sizeof(Tcl_ChannelType));

	memcpy(clonePtr, &tclRChannelType, sizeof(Tcl_ChannelType));

	if (!(methods & FLAG(METH_CONFIGURE))) {
	    clonePtr->setOptionProc = NULL;
	}

	if (!(methods & FLAG(METH_CGET)) && !(methods & FLAG(METH_CGETALL))) {
	    clonePtr->getOptionProc = NULL;
	}
	if (!(methods & FLAG(METH_BLOCKING))) {
	    clonePtr->blockModeProc = NULL;
	}
	if (!(methods & FLAG(METH_SEEK))) {
	    clonePtr->seekProc = NULL;
	    clonePtr->wideSeekProc = NULL;
	}

	chanPtr->typePtr = clonePtr;
    }

    /*
     * Register the channel in the I/O system, and in our our map for 'chan
     * postevent'.
     */

    Tcl_RegisterChannel(interp, chan);

    rcmPtr = GetReflectedChannelMap (interp);
    hPtr   = Tcl_CreateHashEntry(&rcmPtr->map,
				 chanPtr->state->channelName, &isNew);
    if (!isNew) {
	if (chanPtr != Tcl_GetHashValue(hPtr)) {
	    Tcl_Panic("TclChanCreateObjCmd: duplicate channel names");
	}
    }
    Tcl_SetHashValue(hPtr, chan);
#ifdef TCL_THREADS
    rcmPtr = GetThreadReflectedChannelMap();
    hPtr   = Tcl_CreateHashEntry(&rcmPtr->map,
				 chanPtr->state->channelName, &isNew);
    Tcl_SetHashValue(hPtr, chan);
#endif

    /*
     * Return handle as result of command.
     */

    Tcl_SetObjResult(interp, rcId);
    return TCL_OK;

 error:
    /*
     * Signal to ReflectClose to not call 'finalize'.
     */

    rcPtr->methods = 0;
    Tcl_Close(interp, chan);
    return TCL_ERROR;

#undef MODE
#undef CMD
}

/*
 *----------------------------------------------------------------------
 *
 * TclChanPostEventObjCmd --
 *
 *	This function is invoked to process the "chan postevent" Tcl command.
 *	See the user documentation for details on what it does.
 *
 * Results:
 *	A standard Tcl result.
 *
 * Side effects:
 *	Posts events to a reflected channel, invokes event handlers. The
 *	latter implies that arbitrary side effects are possible.
 *
 *----------------------------------------------------------------------
 */

int
TclChanPostEventObjCmd(
    ClientData clientData,
    Tcl_Interp *interp,
    int objc,
    Tcl_Obj *const *objv)
{
    /*
     * Syntax:   chan postevent CHANNEL EVENTSPEC
     *           [0]  [1]       [2]     [3]
     *
     * Actually: rPostevent CHANNEL EVENTSPEC
     *           [0]        [1]     [2]
     *
     * where EVENTSPEC = {read write ...} (Abbreviations allowed as well).
     */

#define CHAN	(1)
#define EVENT	(2)

    const char *chanId;		/* Tcl level channel handle */
    Tcl_Channel chan;		/* Channel associated to the handle */
    const Tcl_ChannelType *chanTypePtr;
				/* Its associated driver structure */
    ReflectedChannel *rcPtr;	/* Associated instance data */
    int events;			/* Mask of events to post */
    ReflectedChannelMap* rcmPtr; /* Map of reflected channels with handlers in this interp */
    Tcl_HashEntry* hPtr;         /* Entry in the above map */

    /*
     * Number of arguments...
     */

    if (objc != 3) {
	Tcl_WrongNumArgs(interp, 1, objv, "channel eventspec");
	return TCL_ERROR;
    }

    /*
     * First argument is a channel, a reflected channel, and the call of this
     * command is done from the interp defining the channel handler cmd.
     */

    chanId = TclGetString(objv[CHAN]);

    rcmPtr = GetReflectedChannelMap (interp);
    hPtr = Tcl_FindHashEntry (&rcmPtr->map, chanId);

    if (hPtr == NULL) {
	Tcl_AppendResult(interp, "can not find reflected channel named \"", chanId,
		"\"", NULL);
	Tcl_SetErrorCode(interp, "TCL", "LOOKUP", "CHANNEL", chanId, NULL);
	return TCL_ERROR;
    }

    /*
     * Note that the search above subsumes several of the older checks, namely:
     *
     * (1) Does the channel handle refer to a reflected channel ?
     * (2) Is the post event issued from the interpreter holding the handler
     *     of the reflected channel ?
     *
     * A successful search answers yes to both. Because the map holds only
     * handles of reflected channels, and only of such whose handler is
     * defined in this interpreter.
     *
     * We keep the old checks for both, for paranioa, but abort now instead of
     * throwing errors, as failure now means that our internal datastructures
     * have gone seriously haywire.
     */

    chan        = Tcl_GetHashValue(hPtr);
    chanTypePtr = Tcl_GetChannelType(chan);

    /*
     * We use a function referenced by the channel type as our cookie to
     * detect calls to non-reflecting channels. The channel type itself is not
     * suitable, as it might not be the static definition in this file, but a
     * clone thereof. And while we have reserved the name of the type nothing
     * in the core checks against violation, so someone else might have
     * created a channel type using our name, clashing with ourselves.
     */

    if (chanTypePtr->watchProc != &ReflectWatch) {
	Tcl_Panic ("TclChanPostEventObjCmd: channel is not a reflected channel");
    }

    rcPtr = (ReflectedChannel *) Tcl_GetChannelInstanceData(chan);

    if (rcPtr->interp != interp) {
	Tcl_Panic ("TclChanPostEventObjCmd: postevent accepted for call from outside interpreter");
    }

    /*
     * Second argument is a list of events. Allowed entries are "read",
     * "write". Expect at least one list element. Abbreviations are ok.
     */

    if (EncodeEventMask(interp, "event", objv[EVENT], &events) != TCL_OK) {
	return TCL_ERROR;
    }

    /*
     * Check that the channel is actually interested in the provided events.
     */

    if (events & ~rcPtr->interest) {
	Tcl_AppendResult(interp, "tried to post events channel \"", chanId,
		"\" is not interested in", NULL);
	return TCL_ERROR;
    }

    /*
     * We have the channel and the events to post.
     */

    Tcl_NotifyChannel(chan, events);

    /*
     * Squash interp results left by the event script.
     */

    Tcl_ResetResult(interp);
    return TCL_OK;

#undef CHAN
#undef EVENT
}

/*
 * Channel error message marshalling utilities.
 */

static Tcl_Obj*
MarshallError(
    Tcl_Interp *interp)
{
    /*
     * Capture the result status of the interpreter into a string. => List of
     * options and values, followed by the error message. The result has
     * refCount 0.
     */

    Tcl_Obj *returnOpt = Tcl_GetReturnOptions(interp, TCL_ERROR);

    /*
     * => returnOpt.refCount == 0. We can append directly.
     */

    Tcl_ListObjAppendElement(NULL, returnOpt, Tcl_GetObjResult(interp));
    return returnOpt;
}

static void
UnmarshallErrorResult(
    Tcl_Interp *interp,
    Tcl_Obj *msgObj)
{
    int lc;
    Tcl_Obj **lv;
    int explicitResult;
    int numOptions;

    /*
     * Process the caught message.
     *
     * Syntax = (option value)... ?message?
     *
     * Bad syntax causes a panic. This is OK because the other side uses
     * Tcl_GetReturnOptions and list construction functions to marshall the
     * information; if we panic here, something has gone badly wrong already.
     */

    if (Tcl_ListObjGetElements(interp, msgObj, &lc, &lv) != TCL_OK) {
	Tcl_Panic("TclChanCaughtErrorBypass: Bad syntax of caught result");
    }
    if (interp == NULL) {
	return;
    }

    explicitResult = lc & 1;		/* Odd number of values? */
    numOptions = lc - explicitResult;

    if (explicitResult) {
	Tcl_SetObjResult(interp, lv[lc-1]);
    }

    (void) Tcl_SetReturnOptions(interp, Tcl_NewListObj(numOptions, lv));
    ((Interp *)interp)->flags &= ~ERR_ALREADY_LOGGED;
}

int
TclChanCaughtErrorBypass(
    Tcl_Interp *interp,
    Tcl_Channel chan)
{
    Tcl_Obj *chanMsgObj = NULL;
    Tcl_Obj *interpMsgObj = NULL;
    Tcl_Obj *msgObj = NULL;

    /*
     * Get a bypassed error message from channel and/or interpreter, save the
     * reference, then kill the returned objects, if there were any. If there
     * are messages in both the channel has preference.
     */

    if ((chan == NULL) && (interp == NULL)) {
	return 0;
    }

    if (chan != NULL) {
	Tcl_GetChannelError(chan, &chanMsgObj);
    }
    if (interp != NULL) {
	Tcl_GetChannelErrorInterp(interp, &interpMsgObj);
    }

    if (chanMsgObj != NULL) {
	msgObj = chanMsgObj;
    } else if (interpMsgObj != NULL) {
	msgObj = interpMsgObj;
    }
    if (msgObj != NULL) {
	Tcl_IncrRefCount(msgObj);
    }

    if (chanMsgObj != NULL) {
	Tcl_DecrRefCount(chanMsgObj);
    }
    if (interpMsgObj != NULL) {
	Tcl_DecrRefCount(interpMsgObj);
    }

    /*
     * No message returned, nothing caught.
     */

    if (msgObj == NULL) {
	return 0;
    }

    UnmarshallErrorResult(interp, msgObj);

    Tcl_DecrRefCount(msgObj);
    return 1;
}

/*
 * Driver functions. ================================================
 */

/*
 *----------------------------------------------------------------------
 *
 * ReflectClose --
 *
 *	This function is invoked when the channel is closed, to delete the
 *	driver specific instance data.
 *
 * Results:
 *	A posix error.
 *
 * Side effects:
 *	Releases memory. Arbitrary, as it calls upon a script.
 *
 *----------------------------------------------------------------------
 */

static int
ReflectClose(
    ClientData clientData,
    Tcl_Interp *interp)
{
    ReflectedChannel *rcPtr = (ReflectedChannel *) clientData;
    int result;			/* Result code for 'close' */
    Tcl_Obj *resObj;		/* Result data for 'close' */
    ReflectedChannelMap* rcmPtr; /* Map of reflected channels with handlers in this interp */
    Tcl_HashEntry* hPtr;         /* Entry in the above map */

    if (interp == NULL) {
	/*
	 * This call comes from TclFinalizeIOSystem. There are no
	 * interpreters, and therefore we cannot call upon the handler command
	 * anymore. Threading is irrelevant as well. We simply clean up all
	 * our C level data structures and leave the Tcl level to the other
	 * finalization functions.
	 */

	/*
	 * THREADED => Forward this to the origin thread
	 *
	 * Note: DeleteThreadReflectedChannelMap() is the thread exit handler for the origin
	 * thread. Use this to clean up the structure? Except if lost?
	 */

#ifdef TCL_THREADS
	if (rcPtr->thread != Tcl_GetCurrentThread()) {
	    ForwardParam p;

	    ForwardOpToOwnerThread(rcPtr, ForwardedClose, &p);
	    result = p.base.code;

	    /*
	     * FreeReflectedChannel is done in the forwarded operation!, in
	     * the other thread. rcPtr here is gone!
	     */

	    if (result != TCL_OK) {
		FreeReceivedError(&p);
	    }
	    return EOK;
	}
#endif

	FreeReflectedChannel(rcPtr);
	return EOK;
    }

    /*
     * -- No -- ASSERT rcPtr->methods & FLAG(METH_FINAL)
     *
     * A cleaned method mask here implies that the channel creation was
     * aborted, and "finalize" must not be called.
     */

    if (rcPtr->methods == 0) {
	FreeReflectedChannel(rcPtr);
	return EOK;
    }

    /*
     * Are we in the correct thread?
     */

#ifdef TCL_THREADS
    if (rcPtr->thread != Tcl_GetCurrentThread()) {
	ForwardParam p;

	ForwardOpToOwnerThread(rcPtr, ForwardedClose, &p);
	result = p.base.code;

	/*
	 * FreeReflectedChannel is done in the forwarded operation!, in the
	 * other thread. rcPtr here is gone!
	 */

	if (result != TCL_OK) {
	    PassReceivedErrorInterp(interp, &p);
	}
    } else {
#endif
	result = InvokeTclMethod(rcPtr, "finalize", NULL, NULL, &resObj);
	if ((result != TCL_OK) && (interp != NULL)) {
	    Tcl_SetChannelErrorInterp(interp, resObj);
	}

	Tcl_DecrRefCount(resObj);	/* Remove reference we held from the
					 * invoke */

	/*
	 * Remove the channel from the map before releasing the memory, to
	 * prevent future accesses (like by 'postevent') from finding and
	 * dereferencing a dangling pointer.
	 *
	 * NOTE: The channel may not be in the map. This is ok, that happens
	 * when the channel was created in a different interpreter and/or
	 * thread and then was moved here.
	 */
	
	rcmPtr = GetReflectedChannelMap (interp);
	hPtr = Tcl_FindHashEntry (&rcmPtr->map, 
				  Tcl_GetChannelName (rcPtr->chan));
	if (hPtr) {
	    Tcl_DeleteHashEntry (hPtr);
	}
#ifdef TCL_THREADS
        rcmPtr = GetThreadReflectedChannelMap();
	hPtr = Tcl_FindHashEntry (&rcmPtr->map, 
				  Tcl_GetChannelName (rcPtr->chan));
	if (hPtr) {
	    Tcl_DeleteHashEntry (hPtr);
	}
#endif

	FreeReflectedChannel(rcPtr);
#ifdef TCL_THREADS
    }
#endif
    return (result == TCL_OK) ? EOK : EINVAL;
}

/*
 *----------------------------------------------------------------------
 *
 * ReflectInput --
 *
 *	This function is invoked when more data is requested from the channel.
 *
 * Results:
 *	The number of bytes read.
 *
 * Side effects:
 *	Allocates memory. Arbitrary, as it calls upon a script.
 *
 *----------------------------------------------------------------------
 */

static int
ReflectInput(
    ClientData clientData,
    char *buf,
    int toRead,
    int *errorCodePtr)
{
    ReflectedChannel *rcPtr = (ReflectedChannel *) clientData;
    Tcl_Obj *toReadObj;
    int bytec;			/* Number of returned bytes */
    unsigned char *bytev;	/* Array of returned bytes */
    Tcl_Obj *resObj;		/* Result data for 'read' */

    /*
     * The following check can be done before thread redirection, because we
     * are reading from an item which is readonly, i.e. will never change
     * during the lifetime of the channel.
     */

    if (!(rcPtr->methods & FLAG(METH_READ))) {
	SetChannelErrorStr(rcPtr->chan, msg_read_unsup);
	*errorCodePtr = EINVAL;
	return -1;
    }

    /*
     * Are we in the correct thread?
     */

#ifdef TCL_THREADS
    if (rcPtr->thread != Tcl_GetCurrentThread()) {
	ForwardParam p;

	p.input.buf = buf;
	p.input.toRead = toRead;

	ForwardOpToOwnerThread(rcPtr, ForwardedInput, &p);

	if (p.base.code != TCL_OK) {
	    PassReceivedError(rcPtr->chan, &p);
	    *errorCodePtr = EINVAL;
	    p.input.toRead = -1;
	} else {
	    *errorCodePtr = EOK;
	}

	return p.input.toRead;
    }
#endif

    /* ASSERT: rcPtr->method & FLAG(METH_READ) */
    /* ASSERT: rcPtr->mode & TCL_READABLE */

    toReadObj = Tcl_NewIntObj(toRead);
    if (InvokeTclMethod(rcPtr, "read", toReadObj, NULL, &resObj)!=TCL_OK) {
	Tcl_SetChannelError(rcPtr->chan, resObj);
	Tcl_DecrRefCount(resObj);	/* Remove reference held from invoke */
	*errorCodePtr = EINVAL;
	return -1;
    }

    bytev = Tcl_GetByteArrayFromObj(resObj, &bytec);

    if (toRead < bytec) {
	Tcl_DecrRefCount(resObj);	/* Remove reference held from invoke */
	SetChannelErrorStr(rcPtr->chan, msg_read_toomuch);
	*errorCodePtr = EINVAL;
	return -1;
    }

    *errorCodePtr = EOK;

    if (bytec > 0) {
	memcpy(buf, bytev, (size_t)bytec);
    }

    Tcl_DecrRefCount(resObj);		/* Remove reference held from invoke */
    return bytec;
}

/*
 *----------------------------------------------------------------------
 *
 * ReflectOutput --
 *
 *	This function is invoked when data is writen to the channel.
 *
 * Results:
 *	The number of bytes actually written.
 *
 * Side effects:
 *	Allocates memory. Arbitrary, as it calls upon a script.
 *
 *----------------------------------------------------------------------
 */

static int
ReflectOutput(
    ClientData clientData,
    const char *buf,
    int toWrite,
    int *errorCodePtr)
{
    ReflectedChannel *rcPtr = (ReflectedChannel *) clientData;
    Tcl_Obj *bufObj;
    Tcl_Obj *resObj;		/* Result data for 'write' */
    int written;

    /*
     * The following check can be done before thread redirection, because we
     * are reading from an item which is readonly, i.e. will never change
     * during the lifetime of the channel.
     */

    if (!(rcPtr->methods & FLAG(METH_WRITE))) {
	SetChannelErrorStr(rcPtr->chan, msg_write_unsup);
	*errorCodePtr = EINVAL;
	return -1;
    }

    /*
     * Are we in the correct thread?
     */

#ifdef TCL_THREADS
    if (rcPtr->thread != Tcl_GetCurrentThread()) {
	ForwardParam p;

	p.output.buf = buf;
	p.output.toWrite = toWrite;

	ForwardOpToOwnerThread(rcPtr, ForwardedOutput, &p);

	if (p.base.code != TCL_OK) {
	    PassReceivedError(rcPtr->chan, &p);
	    *errorCodePtr = EINVAL;
	    p.output.toWrite = -1;
	} else {
	    *errorCodePtr = EOK;
	}

	return p.output.toWrite;
    }
#endif

    /* ASSERT: rcPtr->method & FLAG(METH_WRITE) */
    /* ASSERT: rcPtr->mode & TCL_WRITABLE */

    bufObj = Tcl_NewByteArrayObj((unsigned char *) buf, toWrite);
    if (InvokeTclMethod(rcPtr, "write", bufObj, NULL, &resObj) != TCL_OK) {
	Tcl_SetChannelError(rcPtr->chan, resObj);
	Tcl_DecrRefCount(resObj);	/* Remove reference held from invoke */
	*errorCodePtr = EINVAL;
	return -1;
    }

    if (Tcl_GetIntFromObj(rcPtr->interp, resObj, &written) != TCL_OK) {
	Tcl_DecrRefCount(resObj);	/* Remove reference held from invoke */
	Tcl_SetChannelError(rcPtr->chan, MarshallError(rcPtr->interp));
	*errorCodePtr = EINVAL;
	return -1;
    }

    Tcl_DecrRefCount(resObj);		/* Remove reference held from invoke */

    if ((written == 0) && (toWrite > 0)) {
	/*
	 * The handler claims to have written nothing of what it was
	 * given. That is bad.
	 */

	SetChannelErrorStr(rcPtr->chan, msg_write_nothing);
	*errorCodePtr = EINVAL;
	return -1;
    }
    if (toWrite < written) {
	/*
	 * The handler claims to have written more than it was given. That is
	 * bad. Note that the I/O core would crash if we were to return this
	 * information, trying to write -nnn bytes in the next iteration.
	 */

	SetChannelErrorStr(rcPtr->chan, msg_write_toomuch);
	*errorCodePtr = EINVAL;
	return -1;
    }

    *errorCodePtr = EOK;
    return written;
}

/*
 *----------------------------------------------------------------------
 *
 * ReflectSeekWide / ReflectSeek --
 *
 *	This function is invoked when the user wishes to seek on the channel.
 *
 * Results:
 *	The new location of the access point.
 *
 * Side effects:
 *	Allocates memory. Arbitrary, as it calls upon a script.
 *
 *----------------------------------------------------------------------
 */

static Tcl_WideInt
ReflectSeekWide(
    ClientData clientData,
    Tcl_WideInt offset,
    int seekMode,
    int *errorCodePtr)
{
    ReflectedChannel *rcPtr = (ReflectedChannel *) clientData;
    Tcl_Obj *offObj, *baseObj;
    Tcl_Obj *resObj;		/* Result for 'seek' */
    Tcl_WideInt newLoc;

    /*
     * Are we in the correct thread?
     */

#ifdef TCL_THREADS
    if (rcPtr->thread != Tcl_GetCurrentThread()) {
	ForwardParam p;

	p.seek.seekMode = seekMode;
	p.seek.offset = offset;

	ForwardOpToOwnerThread(rcPtr, ForwardedSeek, &p);

	if (p.base.code != TCL_OK) {
	    PassReceivedError(rcPtr->chan, &p);
	    *errorCodePtr = EINVAL;
	    p.seek.offset = -1;
	} else {
	    *errorCodePtr = EOK;
	}

	return p.seek.offset;
    }
#endif

    /* ASSERT: rcPtr->method & FLAG(METH_SEEK) */

    offObj = Tcl_NewWideIntObj(offset);
    baseObj = Tcl_NewStringObj((seekMode == SEEK_SET) ? "start" :
	    ((seekMode == SEEK_CUR) ? "current" : "end"), -1);
    if (InvokeTclMethod(rcPtr, "seek", offObj, baseObj, &resObj)!=TCL_OK) {
	Tcl_SetChannelError(rcPtr->chan, resObj);
	Tcl_DecrRefCount(resObj);	/* Remove reference held from invoke */
	*errorCodePtr = EINVAL;
	return -1;
    }

    if (Tcl_GetWideIntFromObj(rcPtr->interp, resObj, &newLoc) != TCL_OK) {
	Tcl_DecrRefCount(resObj);	/* Remove reference held from invoke */
	Tcl_SetChannelError(rcPtr->chan, MarshallError(rcPtr->interp));
	*errorCodePtr = EINVAL;
	return -1;
    }

    Tcl_DecrRefCount(resObj);		/* Remove reference held from invoke */

    if (newLoc < Tcl_LongAsWide(0)) {
	SetChannelErrorStr(rcPtr->chan, msg_seek_beforestart);
	*errorCodePtr = EINVAL;
	return -1;
    }

    *errorCodePtr = EOK;
    return newLoc;
}

static int
ReflectSeek(
    ClientData clientData,
    long offset,
    int seekMode,
    int *errorCodePtr)
{
    /*
     * This function can be invoked from a transformation which is based on
     * standard seeking, i.e. non-wide. Because of this we have to implement
     * it, a dummy is not enough. We simply delegate the call to the wide
     * routine.
     */

    return (int) ReflectSeekWide(clientData, Tcl_LongAsWide(offset), seekMode,
	    errorCodePtr);
}

/*
 *----------------------------------------------------------------------
 *
 * ReflectWatch --
 *
 *	This function is invoked to tell the channel what events the I/O
 *	system is interested in.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Allocates memory. Arbitrary, as it calls upon a script.
 *
 *----------------------------------------------------------------------
 */

static void
ReflectWatch(
    ClientData clientData,
    int mask)
{
    ReflectedChannel *rcPtr = (ReflectedChannel *) clientData;
    Tcl_Obj *maskObj;

    /* ASSERT rcPtr->methods & FLAG(METH_WATCH) */

    /*
     * We restrict the interest to what the channel can support. IOW there
     * will never be write events for a channel which is not writable.
     * Analoguously for read events and non-readable channels.
     */

    mask &= rcPtr->mode;

    if (mask == rcPtr->interest) {
	/*
	 * Same old, same old, why should we do something?
	 */

	return;
    }

    rcPtr->interest = mask;

    /*
     * Are we in the correct thread?
     */

#ifdef TCL_THREADS
    if (rcPtr->thread != Tcl_GetCurrentThread()) {
	ForwardParam p;

	p.watch.mask = mask;
	ForwardOpToOwnerThread(rcPtr, ForwardedWatch, &p);

	/*
	 * Any failure from the forward is ignored. We have no place to put
	 * this.
	 */

	return;
    }
#endif

    maskObj = DecodeEventMask(mask);
    (void) InvokeTclMethod(rcPtr, "watch", maskObj, NULL, NULL);
    Tcl_DecrRefCount(maskObj);
}

/*
 *----------------------------------------------------------------------
 *
 * ReflectBlock --
 *
 *	This function is invoked to tell the channel which blocking behaviour
 *	is required of it.
 *
 * Results:
 *	A posix error number.
 *
 * Side effects:
 *	Allocates memory. Arbitrary, as it calls upon a script.
 *
 *----------------------------------------------------------------------
 */

static int
ReflectBlock(
    ClientData clientData,
    int nonblocking)
{
    ReflectedChannel *rcPtr = (ReflectedChannel *) clientData;
    Tcl_Obj *blockObj;
    int errorNum;		/* EINVAL or EOK (success). */
    Tcl_Obj *resObj;		/* Result data for 'blocking' */

    /*
     * Are we in the correct thread?
     */

#ifdef TCL_THREADS
    if (rcPtr->thread != Tcl_GetCurrentThread()) {
	ForwardParam p;

	p.block.nonblocking = nonblocking;

	ForwardOpToOwnerThread(rcPtr, ForwardedBlock, &p);

	if (p.base.code != TCL_OK) {
	    PassReceivedError(rcPtr->chan, &p);
	    return EINVAL;
	}

	return EOK;
    }
#endif

    blockObj = Tcl_NewBooleanObj(!nonblocking);

    if (InvokeTclMethod(rcPtr, "blocking", blockObj, NULL, &resObj) != TCL_OK) {
	Tcl_SetChannelError(rcPtr->chan, resObj);
	errorNum = EINVAL;
    } else {
	errorNum = EOK;
    }

    Tcl_DecrRefCount(resObj);		/* Remove reference held from invoke */
    return errorNum;
}

/*
 *----------------------------------------------------------------------
 *
 * ReflectSetOption --
 *
 *	This function is invoked to configure a channel option.
 *
 * Results:
 *	A standard Tcl result code.
 *
 * Side effects:
 *	Arbitrary, as it calls upon a Tcl script.
 *
 *----------------------------------------------------------------------
 */

static int
ReflectSetOption(
    ClientData clientData,	/* Channel to query */
    Tcl_Interp *interp,		/* Interpreter to leave error messages in */
    const char *optionName,	/* Name of requested option */
    const char *newValue)	/* The new value */
{
    ReflectedChannel *rcPtr = (ReflectedChannel *) clientData;
    Tcl_Obj *optionObj, *valueObj;
    int result;			/* Result code for 'configure' */
    Tcl_Obj *resObj;		/* Result data for 'configure' */

    /*
     * Are we in the correct thread?
     */

#ifdef TCL_THREADS
    if (rcPtr->thread != Tcl_GetCurrentThread()) {
	ForwardParam p;

	p.setOpt.name = optionName;
	p.setOpt.value = newValue;

	ForwardOpToOwnerThread(rcPtr, ForwardedSetOpt, &p);

	if (p.base.code != TCL_OK) {
	    Tcl_Obj *err = Tcl_NewStringObj(p.base.msgStr, -1);

	    UnmarshallErrorResult(interp, err);
	    Tcl_DecrRefCount(err);
	    FreeReceivedError(&p);
	}

	return p.base.code;
    }
#endif

    optionObj = Tcl_NewStringObj(optionName, -1);
    valueObj = Tcl_NewStringObj(newValue, -1);
    result = InvokeTclMethod(rcPtr, "configure",optionObj,valueObj, &resObj);
    if (result != TCL_OK) {
	UnmarshallErrorResult(interp, resObj);
    }

    Tcl_DecrRefCount(resObj);		/* Remove reference held from invoke */
    return result;
}

/*
 *----------------------------------------------------------------------
 *
 * ReflectGetOption --
 *
 *	This function is invoked to retrieve all or a channel option.
 *
 * Results:
 *	A standard Tcl result code.
 *
 * Side effects:
 *	Arbitrary, as it calls upon a Tcl script.
 *
 *----------------------------------------------------------------------
 */

static int
ReflectGetOption(
    ClientData clientData,	/* Channel to query */
    Tcl_Interp *interp,		/* Interpreter to leave error messages in */
    const char *optionName,	/* Name of reuqested option */
    Tcl_DString *dsPtr)		/* String to place the result into */
{
    /*
     * This code is special. It has regular passing of Tcl result, and errors.
     * The bypass functions are not required.
     */

    ReflectedChannel *rcPtr = (ReflectedChannel*) clientData;
    Tcl_Obj *optionObj;
    Tcl_Obj *resObj;		/* Result data for 'configure' */
    int listc;
    Tcl_Obj **listv;
    const char *method;

    /*
     * Are we in the correct thread?
     */

#ifdef TCL_THREADS
    if (rcPtr->thread != Tcl_GetCurrentThread()) {
	int opcode;
	ForwardParam p;

	p.getOpt.name = optionName;
	p.getOpt.value = dsPtr;

	if (optionName == NULL) {
	    opcode = ForwardedGetOptAll;
	} else {
	    opcode = ForwardedGetOpt;
	}

	ForwardOpToOwnerThread(rcPtr, opcode, &p);

	if (p.base.code != TCL_OK) {
	    Tcl_Obj *err = Tcl_NewStringObj(p.base.msgStr, -1);

	    UnmarshallErrorResult(interp, err);
	    Tcl_DecrRefCount(err);
	    FreeReceivedError(&p);
	}

	return p.base.code;
    }
#endif

    if (optionName == NULL) {
	/*
	 * Retrieve all options.
	 */

	method = "cgetall";
	optionObj = NULL;
    } else {
	/*
	 * Retrieve the value of one option.
	 */

	method = "cget";
	optionObj = Tcl_NewStringObj(optionName, -1);
    }

    if (InvokeTclMethod(rcPtr, method, optionObj, NULL, &resObj)!=TCL_OK) {
	UnmarshallErrorResult(interp, resObj);
	Tcl_DecrRefCount(resObj);	/* Remove reference held from invoke */
	return TCL_ERROR;
    }

    /*
     * The result has to go into the 'dsPtr' for propagation to the caller of
     * the driver.
     */

    if (optionObj != NULL) {
	Tcl_DStringAppend(dsPtr, TclGetString(resObj), -1);
	Tcl_DecrRefCount(resObj);	/* Remove reference held from invoke */
	return TCL_OK;
    }

    /*
     * Extract the list and append each item as element.
     */

    /*
     * NOTE (4): If we extract the string rep we can assume a properly quoted
     * string. Together with a separating space this way of simply appending
     * the whole string rep might be faster. It also doesn't check if the
     * result is a valid list. Nor that the list has an even number elements.
     */

    if (Tcl_ListObjGetElements(interp, resObj, &listc, &listv) != TCL_OK) {
	Tcl_DecrRefCount(resObj);	/* Remove reference held from invoke */
	return TCL_ERROR;
    }

    if ((listc % 2) == 1) {
	/*
	 * Odd number of elements is wrong.
	 */

	Tcl_ResetResult(interp);
	Tcl_SetObjResult(interp, Tcl_ObjPrintf(
		"Expected list with even number of "
		"elements, got %d element%s instead", listc,
		(listc == 1 ? "" : "s")));
	Tcl_DecrRefCount(resObj);	/* Remove reference held from invoke */
	return TCL_ERROR;
    } else {
	int len;
	char *str = Tcl_GetStringFromObj(resObj, &len);

	if (len) {
	    Tcl_DStringAppend(dsPtr, " ", 1);
	    Tcl_DStringAppend(dsPtr, str, len);
	}
	Tcl_DecrRefCount(resObj);	/* Remove reference held from invoke */
	return TCL_OK;
    }
}

/*
 * Helpers. =========================================================
 */

/*
 *----------------------------------------------------------------------
 *
 * EncodeEventMask --
 *
 *	This function takes a list of event items and constructs the
 *	equivalent internal bitmask. The list must contain at least one
 *	element. Elements are "read", "write", or any unique abbreviation of
 *	them. Note that the bitmask is not changed if problems are
 *	encountered.
 *
 * Results:
 *	A standard Tcl error code. A bitmask where TCL_READABLE and/or
 *	TCL_WRITABLE can be set.
 *
 * Side effects:
 *	May shimmer 'obj' to a list representation. May place an error message
 *	into the interp result.
 *
 *----------------------------------------------------------------------
 */

static int
EncodeEventMask(
    Tcl_Interp *interp,
    const char *objName,
    Tcl_Obj *obj,
    int *mask)
{
    int events;			/* Mask of events to post */
    int listc;			/* #elements in eventspec list */
    Tcl_Obj **listv;		/* Elements of eventspec list */
    int evIndex;		/* Id of event for an element of the eventspec
				 * list. */

    if (Tcl_ListObjGetElements(interp, obj, &listc, &listv) != TCL_OK) {
	return TCL_ERROR;
    }

    if (listc < 1) {
	Tcl_AppendResult(interp, "bad ", objName, " list: is empty", NULL);
	return TCL_ERROR;
    }

    events = 0;
    while (listc > 0) {
	if (Tcl_GetIndexFromObj(interp, listv[listc-1], eventOptions,
		objName, 0, &evIndex) != TCL_OK) {
	    return TCL_ERROR;
	}
	switch (evIndex) {
	case EVENT_READ:
	    events |= TCL_READABLE;
	    break;
	case EVENT_WRITE:
	    events |= TCL_WRITABLE;
	    break;
	}
	listc --;
    }

    *mask = events;
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * DecodeEventMask --
 *
 *	This function takes an internal bitmask of events and constructs the
 *	equivalent list of event items.
 *
 * Results:
 *	A Tcl_Obj reference. The object will have a refCount of one. The user
 *	has to decrement it to release the object.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

static Tcl_Obj *
DecodeEventMask(
    int mask)
{
    register const char *eventStr;
    Tcl_Obj *evObj;

    switch (mask & RANDW) {
    case RANDW:
	eventStr = "read write";
	break;
    case TCL_READABLE:
	eventStr = "read";
	break;
    case TCL_WRITABLE:
	eventStr = "write";
	break;
    default:
	eventStr = "";
	break;
    }

    evObj = Tcl_NewStringObj(eventStr, -1);
    Tcl_IncrRefCount(evObj);
    return evObj;
}

/*
 *----------------------------------------------------------------------
 *
 * NewReflectedChannel --
 *
 *	This function is invoked to allocate and initialize the instance data
 *	of a new reflected channel.
 *
 * Results:
 *	A heap-allocated channel instance.
 *
 * Side effects:
 *	Allocates memory.
 *
 *----------------------------------------------------------------------
 */

static ReflectedChannel *
NewReflectedChannel(
    Tcl_Interp *interp,
    Tcl_Obj *cmdpfxObj,
    int mode,
    Tcl_Obj *handleObj)
{
    ReflectedChannel *rcPtr;
    int i, listc;
    Tcl_Obj **listv;

    rcPtr = (ReflectedChannel *) ckalloc(sizeof(ReflectedChannel));

    /* rcPtr->chan: Assigned by caller. Dummy data here. */
    /* rcPtr->methods: Assigned by caller. Dummy data here. */

    rcPtr->chan = NULL;
    rcPtr->methods = 0;
    rcPtr->interp = interp;
#ifdef TCL_THREADS
    rcPtr->thread = Tcl_GetCurrentThread();
#endif
    rcPtr->mode = mode;
    rcPtr->interest = 0;		/* Initially no interest registered */

    /*
     * Method placeholder.
     */

    /* ASSERT: cmdpfxObj is a Tcl List */

    Tcl_ListObjGetElements(interp, cmdpfxObj, &listc, &listv);

    /*
     * See [==] as well.
     * Storage for the command prefix and the additional words required for
     * the invocation of methods in the command handler.
     *
     * listv [0] [listc-1] | [listc]  [listc+1] |
     * argv  [0]   ... [.] | [argc-2] [argc-1]  | [argc]  [argc+2]
     *       cmd   ... pfx | method   chan      | detail1 detail2
     */

    rcPtr->argc = listc + 2;
    rcPtr->argv = (Tcl_Obj **) ckalloc(sizeof(Tcl_Obj *) * (listc+4));

    /*
     * Duplicate object references.
     */

    for (i=0; i<listc ; i++) {
	Tcl_Obj *word = rcPtr->argv[i] = listv[i];

	Tcl_IncrRefCount(word);
    }

    i++;				/* Skip placeholder for method */

    /*
     * [Bug 1667990]: See [x] in FreeReflectedChannel for release
     */

    rcPtr->argv[i] = handleObj;
    Tcl_IncrRefCount(handleObj);

    /*
     * The next two objects are kept empty, varying arguments.
     */

    /*
     * Initialization complete.
     */

    return rcPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * NextHandle --
 *
 *	This function is invoked to generate a channel handle for a new
 *	reflected channel.
 *
 * Results:
 *	A Tcl_Obj containing the string of the new channel handle. The
 *	refcount of the returned object is -- zero --.
 *
 * Side effects:
 *	May allocate memory. Mutex protected critical section locks out other
 *	threads for a short time.
 *
 *----------------------------------------------------------------------
 */

static Tcl_Obj *
NextHandle(void)
{
    /*
     * Count number of generated reflected channels. Used for id generation.
     * Ids are never reclaimed and there is no dealing with wrap around. On
     * the other hand, "unsigned long" should be big enough except for
     * absolute longrunners (generate a 100 ids per second => overflow will
     * occur in 1 1/3 years).
     */

    TCL_DECLARE_MUTEX(rcCounterMutex)
    static unsigned long rcCounter = 0;
    Tcl_Obj *resObj;

    Tcl_MutexLock(&rcCounterMutex);
    resObj = Tcl_ObjPrintf("rc%lu", rcCounter);
    rcCounter++;
    Tcl_MutexUnlock(&rcCounterMutex);

    return resObj;
}

static void
FreeReflectedChannel(
    ReflectedChannel *rcPtr)
{
    Channel *chanPtr = (Channel *) rcPtr->chan;
    int i, n;

    if (chanPtr->typePtr != &tclRChannelType) {
	/*
	 * Delete a cloned ChannelType structure.
	 */

	ckfree((char*) chanPtr->typePtr);
    }

    n = rcPtr->argc - 2;
    for (i=0; i<n; i++) {
	Tcl_DecrRefCount(rcPtr->argv[i]);
    }

    /*
     * [Bug 1667990]: See [x] in NewReflectedChannel for lock. n+1 = argc-1.
     */

    Tcl_DecrRefCount(rcPtr->argv[n+1]);

    ckfree((char*) rcPtr->argv);
    ckfree((char*) rcPtr);
}

/*
 *----------------------------------------------------------------------
 *
 * InvokeTclMethod --
 *
 *	This function is used to invoke the Tcl level of a reflected channel.
 *	It handles all the command assembly, invokation, and generic state and
 *	result mgmt. It does *not* handle thread redirection; that is the
 *	responsibility of clients of this function.
 *
 * Results:
 *	Result code and data as returned by the method.
 *
 * Side effects:
 *	Arbitrary, as it calls upon a Tcl script.
 *
 *----------------------------------------------------------------------
 */

static int
InvokeTclMethod(
    ReflectedChannel *rcPtr,
    const char *method,
    Tcl_Obj *argOneObj,		/* NULL'able */
    Tcl_Obj *argTwoObj,		/* NULL'able */
    Tcl_Obj **resultObjPtr)	/* NULL'able */
{
    int cmdc;			/* #words in constructed command */
    Tcl_Obj *methObj = NULL;	/* Method name in object form */
    Tcl_InterpState sr;		/* State of handler interp */
    int result;			/* Result code of method invokation */
    Tcl_Obj *resObj = NULL;	/* Result of method invokation. */

    if (!rcPtr->interp) {
	/*
	 * The channel is marked as dead. Bail out immediately, with an
	 * appropriate error.
	 */

	if (resultObjPtr != NULL) {
	    resObj = Tcl_NewStringObj(msg_dstlost,-1);
	    *resultObjPtr = resObj;
	    Tcl_IncrRefCount(resObj);
	}
	return TCL_ERROR;
    }

    /*
     * NOTE (5): Decide impl. issue: Cache objects with method names? Needs
     * TSD data as reflections can be created in many different threads.
     * NO: Caching of command resolutions means storage per channel.
     */

    /*
     * Insert method into the pre-allocated area, after the command prefix,
     * before the channel id.
     */

    methObj = Tcl_NewStringObj(method, -1);
    Tcl_IncrRefCount(methObj);
    rcPtr->argv[rcPtr->argc - 2] = methObj;

    /*
     * Append the additional argument containing method specific details
     * behind the channel id. If specified.
     */

    cmdc = rcPtr->argc;
    if (argOneObj) {
	Tcl_IncrRefCount(argOneObj);
	rcPtr->argv[cmdc] = argOneObj;
	cmdc++;
	if (argTwoObj) {
	    Tcl_IncrRefCount(argTwoObj);
	    rcPtr->argv[cmdc] = argTwoObj;
	    cmdc++;
	}
    }

    /*
     * And run the handler... This is done in auch a manner which leaves any
     * existing state intact.
     */

    sr = Tcl_SaveInterpState(rcPtr->interp, 0 /* Dummy */);
    Tcl_Preserve(rcPtr->interp);
    result = Tcl_EvalObjv(rcPtr->interp, cmdc, rcPtr->argv, TCL_EVAL_GLOBAL);

    /*
     * We do not try to extract the result information if the caller has no
     * interest in it. I.e. there is no need to put effort into creating
     * something which is discarded immediately after.
     */

    if (resultObjPtr) {
	if (result == TCL_OK) {
	    /*
	     * Ok result taken as is, also if the caller requests that there
	     * is no capture.
	     */

	    resObj = Tcl_GetObjResult(rcPtr->interp);
	} else {
	    /*
	     * Non-ok result is always treated as an error. We have to capture
	     * the full state of the result, including additional options.
	     *
	     * This is complex and ugly, and would be completely unnecessary
	     * if we only added support for a TCL_FORBID_EXCEPTIONS flag.
	     */

	    if (result != TCL_ERROR) {
		Tcl_Obj *cmd = Tcl_NewListObj(cmdc, rcPtr->argv);
		int cmdLen;
		const char *cmdString = Tcl_GetStringFromObj(cmd, &cmdLen);

		Tcl_IncrRefCount(cmd);
		Tcl_ResetResult(rcPtr->interp);
		Tcl_SetObjResult(rcPtr->interp, Tcl_ObjPrintf(
			"chan handler returned bad code: %d", result));
		Tcl_LogCommandInfo(rcPtr->interp, cmdString, cmdString,
			cmdLen);
		Tcl_DecrRefCount(cmd);
		result = TCL_ERROR;
	    }
	    Tcl_AppendObjToErrorInfo(rcPtr->interp, Tcl_ObjPrintf(
		    "\n    (chan handler subcommand \"%s\")", method));
	    resObj = MarshallError(rcPtr->interp);
	}
	Tcl_IncrRefCount(resObj);
    }
    Tcl_RestoreInterpState(rcPtr->interp, sr);
    Tcl_Release(rcPtr->interp);

    /*
     * Cleanup of the dynamic parts of the command.
     */

    Tcl_DecrRefCount(methObj);
    if (argOneObj) {
	Tcl_DecrRefCount(argOneObj);
	if (argTwoObj) {
	    Tcl_DecrRefCount(argTwoObj);
	}
    }

    /*
     * The resObj has a ref count of 1 at this location. This means that the
     * caller of InvokeTclMethod has to dispose of it (but only if it was
     * returned to it).
     */

    if (resultObjPtr != NULL) {
	*resultObjPtr = resObj;
    }

    /*
     * There no need to handle the case where nothing is returned, because for
     * that case resObj was not set anyway.
     */

    return result;
}

/*
 *----------------------------------------------------------------------
 *
 * GetReflectedChannelMap --
 *
 *	Gets and potentially initializes the reflected channel map for an
 *	interpreter.
 *
 * Results:
 *	A pointer to the map created, for use by the caller.
 *
 * Side effects:
 *	Initializes the reflected channel map for an interpreter.
 *
 *----------------------------------------------------------------------
 */

static ReflectedChannelMap *
GetReflectedChannelMap(
    Tcl_Interp *interp)
{
    ReflectedChannelMap* rcmPtr = Tcl_GetAssocData(interp, RCMKEY, NULL);

    if (rcmPtr == NULL) {
	rcmPtr = (ReflectedChannelMap *) ckalloc(sizeof(ReflectedChannelMap));
	Tcl_InitHashTable(&rcmPtr->map, TCL_STRING_KEYS);
	Tcl_SetAssocData(interp, RCMKEY,
		(Tcl_InterpDeleteProc *) DeleteReflectedChannelMap, rcmPtr);
    }
    return rcmPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * DeleteReflectedChannelMap --
 *
 *	Deletes the channel table for an interpreter, closing any open
 *	channels whose refcount reaches zero. This procedure is invoked when
 *	an interpreter is deleted, via the AssocData cleanup mechanism.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Deletes the hash table of channels. May close channels. May flush
 *	output on closed channels. Removes any channeEvent handlers that were
 *	registered in this interpreter.
 *
 *----------------------------------------------------------------------
 */

static void
DeleteReflectedChannelMap(
    ClientData clientData,	/* The per-interpreter data structure. */
    Tcl_Interp *interp)		/* The interpreter being deleted. */
{
    ReflectedChannelMap* rcmPtr; /* The map */
    Tcl_HashSearch hSearch;	 /* Search variable. */
    Tcl_HashEntry *hPtr;	 /* Search variable. */
    ReflectedChannel* rcPtr;
    Tcl_Channel chan;

#ifdef TCL_THREADS
    ForwardingResult *resultPtr;
    ForwardingEvent *evPtr;
    ForwardParam *paramPtr;
#endif

    /*
     * Delete all entries. The channels may have been closed already, or will
     * be closed later, by the standard IO finalization of an interpreter
     * under destruction.  Except for the channels which were moved to a
     * different interpreter and/or thread. They do not exist from the IO
     * systems point of view and will not get closed. Therefore mark all as
     * dead so that any future access will cause a proper error. For channels
     * in a different thread we actually do the same as
     * DeleteThreadReflectedChannelMap(), just restricted to the channels of
     * this interp.
     */

    rcmPtr = clientData;
    for (hPtr = Tcl_FirstHashEntry(&rcmPtr->map, &hSearch);
	 hPtr != NULL;
	 hPtr = Tcl_FirstHashEntry(&rcmPtr->map, &hSearch)) {

	chan  = (Tcl_Channel) Tcl_GetHashValue (hPtr);
	rcPtr = (ReflectedChannel *) Tcl_GetChannelInstanceData(chan);

	rcPtr->interp = NULL;

	Tcl_DeleteHashEntry(hPtr);
    }
    Tcl_DeleteHashTable(&rcmPtr->map);
    ckfree((char *) &rcmPtr->map);

#ifdef TCL_THREADS
    /*
     * The origin interpreter for one or more reflected channels is gone.
     */

    /*
     * Go through the list of pending results and cancel all whose events were
     * destined for this interpreter. While this is in progress we block any
     * other access to the list of pending results.
     */

    Tcl_MutexLock(&rcForwardMutex);

    for (resultPtr = forwardList;
	 resultPtr != NULL;
	 resultPtr = resultPtr->nextPtr) {
	if (resultPtr->dsti != interp) {
	    /* Ignore results/events for other interpreters. */
	    continue;
	}

	/*
	 * The receiver for the event exited, before processing the event. We
	 * detach the result now, wake the originator up and signal failure.
	 */

	evPtr = resultPtr->evPtr;
	paramPtr = evPtr->param;

	evPtr->resultPtr = NULL;
	resultPtr->evPtr = NULL;
	resultPtr->result = TCL_ERROR;

	ForwardSetStaticError(paramPtr, msg_send_dstlost);

	Tcl_ConditionNotify(&resultPtr->done);
    }

    /*
     * Get the map of all channels handled by the current thread. This is a
     * ReflectedChannelMap, but on a per-thread basis, not per-interp. Go
     * through the channels and remove all which were handled by this
     * interpreter. They have already been marked as dead.
     */

    rcmPtr = GetThreadReflectedChannelMap();
    for (hPtr = Tcl_FirstHashEntry(&rcmPtr->map, &hSearch);
	 hPtr != NULL;
	 hPtr = Tcl_NextHashEntry(&hSearch)) {

	chan  = (Tcl_Channel) Tcl_GetHashValue (hPtr);
	rcPtr = (ReflectedChannel *) Tcl_GetChannelInstanceData(chan);

	if (rcPtr->interp != interp) {
	    /* Ignore entries for other interpreters */
	    continue;
	}

	Tcl_DeleteHashEntry(hPtr);
    }

    Tcl_MutexUnlock(&rcForwardMutex);
#endif
}

#ifdef TCL_THREADS
/*
 *----------------------------------------------------------------------
 *
 * GetThreadReflectedChannelMap --
 *
 *	Gets and potentially initializes the reflected channel map for a
 *	thread.
 *
 * Results:
 *	A pointer to the map created, for use by the caller.
 *
 * Side effects:
 *	Initializes the reflected channel map for a thread.
 *
 *----------------------------------------------------------------------
 */

static ReflectedChannelMap *
GetThreadReflectedChannelMap()
{
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    if (!tsdPtr->rcmPtr) {
	tsdPtr->rcmPtr = (ReflectedChannelMap *) ckalloc(sizeof(ReflectedChannelMap));
	Tcl_InitHashTable(&tsdPtr->rcmPtr->map, TCL_STRING_KEYS);
	Tcl_CreateThreadExitHandler(DeleteThreadReflectedChannelMap, NULL);
    }

    return tsdPtr->rcmPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * DeleteThreadReflectedChannelMap --
 *
 *	Deletes the channel table for a thread. This procedure is invoked when
 *	a thread is deleted. The channels have already been marked as dead, in
 *      DeleteReflectedChannelMap().
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Deletes the hash table of channels.
 *
 *----------------------------------------------------------------------
 */

static void
DeleteThreadReflectedChannelMap(
    ClientData clientData)	/* The per-thread data structure. */
{
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);
    Tcl_HashSearch hSearch;	 /* Search variable. */
    Tcl_HashEntry *hPtr;	 /* Search variable. */
    Tcl_ThreadId self = Tcl_GetCurrentThread();

    ReflectedChannelMap* rcmPtr; /* The map */
    Tcl_Channel chan;
    ReflectedChannel* rcPtr;
    ForwardingResult *resultPtr;
    ForwardingEvent *evPtr;
    ForwardParam *paramPtr;

    /*
     * The origin thread for one or more reflected channels is gone.
     * NOTE: If this function is called due to a thread getting killed the
     *       per-interp DeleteReflectedChannelMap is apparently not called.
     */

    /*
     * Go through the list of pending results and cancel all whose events were
     * destined for this thread. While this is in progress we block any
     * other access to the list of pending results.
     */

    Tcl_MutexLock(&rcForwardMutex);

    for (resultPtr = forwardList;
	 resultPtr != NULL;
	 resultPtr = resultPtr->nextPtr) {
	if (resultPtr->dst != self) {
	    /* Ignore results/events for other threads. */
	    continue;
	}

	/*
	 * The receiver for the event exited, before processing the event. We
	 * detach the result now, wake the originator up and signal failure.
	 */

	evPtr = resultPtr->evPtr;
	paramPtr = evPtr->param;

	evPtr->resultPtr = NULL;
	resultPtr->evPtr = NULL;
	resultPtr->result = TCL_ERROR;

	ForwardSetStaticError(paramPtr, msg_send_dstlost);

	Tcl_ConditionNotify(&resultPtr->done);
    }

    /*
     * Get the map of all channels handled by the current thread. This is a
     * ReflectedChannelMap, but on a per-thread basis, not per-interp. Go
     * through the channels, remove all, mark them as dead.
     */

    rcmPtr = GetThreadReflectedChannelMap();
    for (hPtr = Tcl_FirstHashEntry(&rcmPtr->map, &hSearch);
	 hPtr != NULL;
	 hPtr = Tcl_FirstHashEntry(&rcmPtr->map, &hSearch)) {

	chan  = (Tcl_Channel) Tcl_GetHashValue (hPtr);
	rcPtr = (ReflectedChannel *) Tcl_GetChannelInstanceData(chan);

	rcPtr->interp = NULL;

	Tcl_DeleteHashEntry(hPtr);
    }

    Tcl_MutexUnlock(&rcForwardMutex);
}

static void
ForwardOpToOwnerThread(
    ReflectedChannel *rcPtr,	/* Channel instance */
    ForwardedOperation op,	/* Forwarded driver operation */
    const VOID *param)		/* Arguments */
{
    Tcl_ThreadId dst = rcPtr->thread;
    ForwardingEvent *evPtr;
    ForwardingResult *resultPtr;
    int result;

    /*
     * We gather the lock early. This allows us to check the liveness of the
     * channel without interference from DeleteThreadReflectedChannelMap().
     */

    Tcl_MutexLock(&rcForwardMutex);

    if (rcPtr->interp == NULL) {
	/*
	 * The channel is marked as dead. Bail out immediately, with an
	 * appropriate error. Do not forget to unlock the mutex on this path.
	 */

	ForwardSetStaticError((ForwardParam *)param, msg_send_dstlost);
	Tcl_MutexUnlock(&rcForwardMutex);
	return;
    }

    /*
     * Create and initialize the event and data structures.
     */

    evPtr = (ForwardingEvent *) ckalloc(sizeof(ForwardingEvent));
    resultPtr = (ForwardingResult *) ckalloc(sizeof(ForwardingResult));

    evPtr->event.proc = ForwardProc;
    evPtr->resultPtr = resultPtr;
    evPtr->op = op;
    evPtr->rcPtr = rcPtr;
    evPtr->param = (ForwardParam *) param;

    resultPtr->src  = Tcl_GetCurrentThread();
    resultPtr->dst  = dst;
    resultPtr->dsti = rcPtr->interp;
    resultPtr->done = NULL;
    resultPtr->result = -1;
    resultPtr->evPtr = evPtr;

    /*
     * Now execute the forward.
     */

    TclSpliceIn(resultPtr, forwardList);
    /* Do not unlock here. That is done by the ConditionWait */

    /*
     * Ensure cleanup of the event if the origin thread exits while this event
     * is pending or in progress. Exitus of the destination thread is handled
     * by DeleteThreadReflectionChannelMap(), this is set up by
     * GetThreadReflectedChannelMap().  This is what we use the 'forwardList'
     * (see above) for.
     */

    Tcl_CreateThreadExitHandler(SrcExitProc, (ClientData) evPtr);

    /*
     * Queue the event and poke the other thread's notifier.
     */

    Tcl_ThreadQueueEvent(dst, (Tcl_Event *)evPtr, TCL_QUEUE_TAIL);
    Tcl_ThreadAlert(dst);

    /*
     * (*) Block until the other thread has either processed the transfer or
     * rejected it.
     */

    while (resultPtr->result < 0) {
	/*
	 * NOTE (1): Is it possible that the current thread goes away while
	 * waiting here? IOW Is it possible that "SrcExitProc" is called while
	 * we are here? See complementary note (2) in "SrcExitProc"
	 *
	 * The ConditionWait unlocks the mutex during the wait and relocks it
	 * immediately after.
	 */

	Tcl_ConditionWait(&resultPtr->done, &rcForwardMutex, NULL);
    }

    /*
     * Unlink result from the forwarder list.
     * No need to lock. Either still locked, or locked by the ConditionWait
     */

    TclSpliceOut(resultPtr, forwardList);

    resultPtr->nextPtr = NULL;
    resultPtr->prevPtr = NULL;

    Tcl_MutexUnlock(&rcForwardMutex);
    Tcl_ConditionFinalize(&resultPtr->done);

    /*
     * Kill the cleanup handler now, and the result structure as well, before
     * returning the success code.
     *
     * Note: The event structure has already been deleted.
     */

    Tcl_DeleteThreadExitHandler(SrcExitProc, (ClientData) evPtr);

    result = resultPtr->result;
    ckfree((char*) resultPtr);
}

static int
ForwardProc(
    Tcl_Event *evGPtr,
    int mask)
{
    /*
     * Notes regarding access to the referenced data.
     *
     * In principle the data belongs to the originating thread (see
     * evPtr->src), however this thread is currently blocked at (*), i.e.
     * quiescent. Because of this we can treat the data as belonging to us,
     * without fear of race conditions. I.e. we can read and write as we like.
     *
     * The only thing we cannot be sure of is the resultPtr. This can be be
     * NULLed if the originating thread went away while the event is handled
     * here now.
     */

    ForwardingEvent *evPtr = (ForwardingEvent *) evGPtr;
    ForwardingResult *resultPtr = evPtr->resultPtr;
    ReflectedChannel *rcPtr = evPtr->rcPtr;
    Tcl_Interp *interp = rcPtr->interp;
    ForwardParam *paramPtr = evPtr->param;
    Tcl_Obj *resObj = NULL;	/* Interp result of InvokeTclMethod */
    ReflectedChannelMap* rcmPtr; /* Map of reflected channels with handlers in this interp */
    Tcl_HashEntry* hPtr;         /* Entry in the above map */

    /*
     * Ignore the event if no one is waiting for its result anymore.
     */

    if (!resultPtr) {
	return 1;
    }

    paramPtr->base.code = TCL_OK;
    paramPtr->base.msgStr = NULL;
    paramPtr->base.mustFree = 0;

    switch (evPtr->op) {
	/*
	 * The destination thread for the following operations is
	 * rcPtr->thread, which contains rcPtr->interp, the interp we have to
	 * call upon for the driver.
	 */

    case ForwardedClose:
	/*
	 * No parameters/results.
	 */

	if (InvokeTclMethod(rcPtr, "finalize", NULL, NULL, &resObj)!=TCL_OK) {
	    ForwardSetObjError(paramPtr, resObj);
	}

	/*
	 * Freeing is done here, in the origin thread, because the argv[]
	 * objects belong to this thread. Deallocating them in a different
	 * thread is not allowed
	 *
	 * We remove the channel from both interpreter and thread maps before
	 * releasing the memory, to prevent future accesses (like by
	 * 'postevent') from finding and dereferencing a dangling pointer.
	 */

	rcmPtr = GetReflectedChannelMap (interp);
	hPtr = Tcl_FindHashEntry (&rcmPtr->map, 
				  Tcl_GetChannelName (rcPtr->chan));
	Tcl_DeleteHashEntry (hPtr);

        rcmPtr = GetThreadReflectedChannelMap();
	hPtr = Tcl_FindHashEntry (&rcmPtr->map, 
				  Tcl_GetChannelName (rcPtr->chan));
	Tcl_DeleteHashEntry (hPtr);

	FreeReflectedChannel(rcPtr);
	break;

    case ForwardedInput: {
	Tcl_Obj *toReadObj = Tcl_NewIntObj(paramPtr->input.toRead);

	if (InvokeTclMethod(rcPtr, "read", toReadObj, NULL, &resObj)!=TCL_OK){
	    ForwardSetObjError(paramPtr, resObj);
	    paramPtr->input.toRead = -1;
	} else {
	    /*
	     * Process a regular result.
	     */

	    int bytec;			/* Number of returned bytes */
	    unsigned char *bytev;	/* Array of returned bytes */

	    bytev = Tcl_GetByteArrayFromObj(resObj, &bytec);

	    if (paramPtr->input.toRead < bytec) {
		ForwardSetStaticError(paramPtr, msg_read_toomuch);
		paramPtr->input.toRead = -1;
	    } else {
		if (bytec > 0) {
		    memcpy(paramPtr->input.buf, bytev, (size_t)bytec);
		}
		paramPtr->input.toRead = bytec;
	    }
	}
	break;
    }

    case ForwardedOutput: {
	Tcl_Obj *bufObj = Tcl_NewByteArrayObj((unsigned char *)
		paramPtr->output.buf, paramPtr->output.toWrite);

	if (InvokeTclMethod(rcPtr, "write", bufObj, NULL, &resObj) != TCL_OK) {
	    ForwardSetObjError(paramPtr, resObj);
	    paramPtr->output.toWrite = -1;
	} else {
	    /*
	     * Process a regular result.
	     */

	    int written;

	    if (Tcl_GetIntFromObj(interp, resObj, &written) != TCL_OK) {
		ForwardSetObjError(paramPtr, MarshallError(interp));
		paramPtr->output.toWrite = -1;
	    } else if (written==0 || paramPtr->output.toWrite<written) {
		ForwardSetStaticError(paramPtr, msg_write_toomuch);
		paramPtr->output.toWrite = -1;
	    } else {
		paramPtr->output.toWrite = written;
	    }
	}
	break;
    }

    case ForwardedSeek: {
	Tcl_Obj *offObj = Tcl_NewWideIntObj(paramPtr->seek.offset);
	Tcl_Obj *baseObj = Tcl_NewStringObj(
		(paramPtr->seek.seekMode==SEEK_SET) ? "start" :
		(paramPtr->seek.seekMode==SEEK_CUR) ? "current" : "end", -1);

	if (InvokeTclMethod(rcPtr, "seek", offObj, baseObj, &resObj)!=TCL_OK){
	    ForwardSetObjError(paramPtr, resObj);
	    paramPtr->seek.offset = -1;
	} else {
	    /*
	     * Process a regular result. If the type is wrong this may change
	     * into an error.
	     */

	    Tcl_WideInt newLoc;

	    if (Tcl_GetWideIntFromObj(interp, resObj, &newLoc) == TCL_OK) {
		if (newLoc < Tcl_LongAsWide(0)) {
		    ForwardSetStaticError(paramPtr, msg_seek_beforestart);
		    paramPtr->seek.offset = -1;
		} else {
		    paramPtr->seek.offset = newLoc;
		}
	    } else {
		ForwardSetObjError(paramPtr, MarshallError(interp));
		paramPtr->seek.offset = -1;
	    }
	}
	break;
    }

    case ForwardedWatch: {
	Tcl_Obj *maskObj = DecodeEventMask(paramPtr->watch.mask);

	(void) InvokeTclMethod(rcPtr, "watch", maskObj, NULL, NULL);
	Tcl_DecrRefCount(maskObj);
	break;
    }

    case ForwardedBlock: {
	Tcl_Obj *blockObj = Tcl_NewBooleanObj(!paramPtr->block.nonblocking);

	if (InvokeTclMethod(rcPtr, "blocking", blockObj, NULL,
		&resObj) != TCL_OK) {
	    ForwardSetObjError(paramPtr, resObj);
	}
	break;
    }

    case ForwardedSetOpt: {
	Tcl_Obj *optionObj = Tcl_NewStringObj(paramPtr->setOpt.name, -1);
	Tcl_Obj *valueObj = Tcl_NewStringObj(paramPtr->setOpt.value, -1);

	if (InvokeTclMethod(rcPtr, "configure", optionObj, valueObj,
		&resObj) != TCL_OK) {
	    ForwardSetObjError(paramPtr, resObj);
	}
	break;
    }

    case ForwardedGetOpt: {
	/*
	 * Retrieve the value of one option.
	 */

	Tcl_Obj *optionObj = Tcl_NewStringObj(paramPtr->getOpt.name, -1);

	if (InvokeTclMethod(rcPtr, "cget", optionObj, NULL, &resObj)!=TCL_OK){
	    ForwardSetObjError(paramPtr, resObj);
	} else {
	    Tcl_DStringAppend(paramPtr->getOpt.value,
		    TclGetString(resObj), -1);
	}
	break;
    }

    case ForwardedGetOptAll:
	/*
	 * Retrieve all options.
	 */

	if (InvokeTclMethod(rcPtr, "cgetall", NULL, NULL, &resObj) != TCL_OK){
	    ForwardSetObjError(paramPtr, resObj);
	} else {
	    /*
	     * Extract list, validate that it is a list, and #elements. See
	     * NOTE (4) as well.
	     */

	    int listc;
	    Tcl_Obj **listv;

	    if (Tcl_ListObjGetElements(interp, resObj, &listc,
		    &listv) != TCL_OK) {
		ForwardSetObjError(paramPtr, MarshallError(interp));
	    } else if ((listc % 2) == 1) {
		/*
		 * Odd number of elements is wrong. [x].
		 */

		char *buf = ckalloc(200);
		sprintf(buf,
			"{Expected list with even number of elements, got %d %s instead}",
			listc, (listc == 1 ? "element" : "elements"));

		ForwardSetDynamicError(paramPtr, buf);
	    } else {
		int len;
		const char *str = Tcl_GetStringFromObj(resObj, &len);

		if (len) {
		    Tcl_DStringAppend(paramPtr->getOpt.value, " ", 1);
		    Tcl_DStringAppend(paramPtr->getOpt.value, str, len);
		}
	    }
	}
	break;

    default:
	/*
	 * Bad operation code.
	 */

	Tcl_Panic("Bad operation code in ForwardProc");
	break;
    }

    /*
     * Remove the reference we held on the result of the invoke, if we had
     * such.
     */

    if (resObj != NULL) {
	Tcl_DecrRefCount(resObj);
    }

    if (resultPtr) {
	/*
	 * Report the forwarding result synchronously to the waiting caller.
	 * This unblocks (*) as well. This is wrapped into a conditional
	 * because the caller may have exited in the mean time.
	 */

	Tcl_MutexLock(&rcForwardMutex);
	resultPtr->result = TCL_OK;
	Tcl_ConditionNotify(&resultPtr->done);
	Tcl_MutexUnlock(&rcForwardMutex);
    }

    return 1;
}

static void
SrcExitProc(
    ClientData clientData)
{
    ForwardingEvent *evPtr = (ForwardingEvent *) clientData;
    ForwardingResult *resultPtr;
    ForwardParam *paramPtr;

    /*
     * NOTE (2): Can this handler be called with the originator blocked?
     */

    /*
     * The originator for the event exited. It is not sure if this can happen,
     * as the originator should be blocked at (*) while the event is in
     * transit/pending.
     *
     * We make sure that the event cannot refer to the result anymore, remove
     * it from the list of pending results and free the structure. Locking the
     * access ensures that we cannot get in conflict with "ForwardProc",
     * should it already execute the event.
     */

    Tcl_MutexLock(&rcForwardMutex);

    resultPtr = evPtr->resultPtr;
    paramPtr = evPtr->param;

    evPtr->resultPtr = NULL;
    resultPtr->evPtr = NULL;
    resultPtr->result = TCL_ERROR;

    ForwardSetStaticError(paramPtr, msg_send_originlost);

    /*
     * See below: TclSpliceOut(resultPtr, forwardList);
     */

    Tcl_MutexUnlock(&rcForwardMutex);

    /*
     * This unlocks (*). The structure will be spliced out and freed by
     * "ForwardProc". Maybe.
     */

    Tcl_ConditionNotify(&resultPtr->done);
}

static void
ForwardSetObjError(
    ForwardParam *paramPtr,
    Tcl_Obj *obj)
{
    int len;
    const char *msgStr = Tcl_GetStringFromObj(obj, &len);

    len++;
    ForwardSetDynamicError(paramPtr, ckalloc((unsigned) len));
    memcpy(paramPtr->base.msgStr, msgStr, (unsigned) len);
}
#endif

/*
 * Local Variables:
 * mode: c
 * c-basic-offset: 4
 * fill-column: 78
 * End:
 */