aboutsummaryrefslogtreecommitdiff
path: root/vendor/gopkg.in/yaml.v2/scannerc.go
blob: 25808000f28f7971a7bef97530fa5eec5181abed (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
package yaml

import (
	"bytes"
	"fmt"
)

// Introduction
// ************
//
// The following notes assume that you are familiar with the YAML specification
// (http://yaml.org/spec/cvs/current.html).  We mostly follow it, although in
// some cases we are less restrictive that it requires.
//
// The process of transforming a YAML stream into a sequence of events is
// divided on two steps: Scanning and Parsing.
//
// The Scanner transforms the input stream into a sequence of tokens, while the
// parser transform the sequence of tokens produced by the Scanner into a
// sequence of parsing events.
//
// The Scanner is rather clever and complicated. The Parser, on the contrary,
// is a straightforward implementation of a recursive-descendant parser (or,
// LL(1) parser, as it is usually called).
//
// Actually there are two issues of Scanning that might be called "clever", the
// rest is quite straightforward.  The issues are "block collection start" and
// "simple keys".  Both issues are explained below in details.
//
// Here the Scanning step is explained and implemented.  We start with the list
// of all the tokens produced by the Scanner together with short descriptions.
//
// Now, tokens:
//
//      STREAM-START(encoding)          # The stream start.
//      STREAM-END                      # The stream end.
//      VERSION-DIRECTIVE(major,minor)  # The '%YAML' directive.
//      TAG-DIRECTIVE(handle,prefix)    # The '%TAG' directive.
//      DOCUMENT-START                  # '---'
//      DOCUMENT-END                    # '...'
//      BLOCK-SEQUENCE-START            # Indentation increase denoting a block
//      BLOCK-MAPPING-START             # sequence or a block mapping.
//      BLOCK-END                       # Indentation decrease.
//      FLOW-SEQUENCE-START             # '['
//      FLOW-SEQUENCE-END               # ']'
//      BLOCK-SEQUENCE-START            # '{'
//      BLOCK-SEQUENCE-END              # '}'
//      BLOCK-ENTRY                     # '-'
//      FLOW-ENTRY                      # ','
//      KEY                             # '?' or nothing (simple keys).
//      VALUE                           # ':'
//      ALIAS(anchor)                   # '*anchor'
//      ANCHOR(anchor)                  # '&anchor'
//      TAG(handle,suffix)              # '!handle!suffix'
//      SCALAR(value,style)             # A scalar.
//
// The following two tokens are "virtual" tokens denoting the beginning and the
// end of the stream:
//
//      STREAM-START(encoding)
//      STREAM-END
//
// We pass the information about the input stream encoding with the
// STREAM-START token.
//
// The next two tokens are responsible for tags:
//
//      VERSION-DIRECTIVE(major,minor)
//      TAG-DIRECTIVE(handle,prefix)
//
// Example:
//
//      %YAML   1.1
//      %TAG    !   !foo
//      %TAG    !yaml!  tag:yaml.org,2002:
//      ---
//
// The correspoding sequence of tokens:
//
//      STREAM-START(utf-8)
//      VERSION-DIRECTIVE(1,1)
//      TAG-DIRECTIVE("!","!foo")
//      TAG-DIRECTIVE("!yaml","tag:yaml.org,2002:")
//      DOCUMENT-START
//      STREAM-END
//
// Note that the VERSION-DIRECTIVE and TAG-DIRECTIVE tokens occupy a whole
// line.
//
// The document start and end indicators are represented by:
//
//      DOCUMENT-START
//      DOCUMENT-END
//
// Note that if a YAML stream contains an implicit document (without '---'
// and '...' indicators), no DOCUMENT-START and DOCUMENT-END tokens will be
// produced.
//
// In the following examples, we present whole documents together with the
// produced tokens.
//
//      1. An implicit document:
//
//          'a scalar'
//
//      Tokens:
//
//          STREAM-START(utf-8)
//          SCALAR("a scalar",single-quoted)
//          STREAM-END
//
//      2. An explicit document:
//
//          ---
//          'a scalar'
//          ...
//
//      Tokens:
//
//          STREAM-START(utf-8)
//          DOCUMENT-START
//          SCALAR("a scalar",single-quoted)
//          DOCUMENT-END
//          STREAM-END
//
//      3. Several documents in a stream:
//
//          'a scalar'
//          ---
//          'another scalar'
//          ---
//          'yet another scalar'
//
//      Tokens:
//
//          STREAM-START(utf-8)
//          SCALAR("a scalar",single-quoted)
//          DOCUMENT-START
//          SCALAR("another scalar",single-quoted)
//          DOCUMENT-START
//          SCALAR("yet another scalar",single-quoted)
//          STREAM-END
//
// We have already introduced the SCALAR token above.  The following tokens are
// used to describe aliases, anchors, tag, and scalars:
//
//      ALIAS(anchor)
//      ANCHOR(anchor)
//      TAG(handle,suffix)
//      SCALAR(value,style)
//
// The following series of examples illustrate the usage of these tokens:
//
//      1. A recursive sequence:
//
//          &A [ *A ]
//
//      Tokens:
//
//          STREAM-START(utf-8)
//          ANCHOR("A")
//          FLOW-SEQUENCE-START
//          ALIAS("A")
//          FLOW-SEQUENCE-END
//          STREAM-END
//
//      2. A tagged scalar:
//
//          !!float "3.14"  # A good approximation.
//
//      Tokens:
//
//          STREAM-START(utf-8)
//          TAG("!!","float")
//          SCALAR("3.14",double-quoted)
//          STREAM-END
//
//      3. Various scalar styles:
//
//          --- # Implicit empty plain scalars do not produce tokens.
//          --- a plain scalar
//          --- 'a single-quoted scalar'
//          --- "a double-quoted scalar"
//          --- |-
//            a literal scalar
//          --- >-
//            a folded
//            scalar
//
//      Tokens:
//
//          STREAM-START(utf-8)
//          DOCUMENT-START
//          DOCUMENT-START
//          SCALAR("a plain scalar",plain)
//          DOCUMENT-START
//          SCALAR("a single-quoted scalar",single-quoted)
//          DOCUMENT-START
//          SCALAR("a double-quoted scalar",double-quoted)
//          DOCUMENT-START
//          SCALAR("a literal scalar",literal)
//          DOCUMENT-START
//          SCALAR("a folded scalar",folded)
//          STREAM-END
//
// Now it's time to review collection-related tokens. We will start with
// flow collections:
//
//      FLOW-SEQUENCE-START
//      FLOW-SEQUENCE-END
//      FLOW-MAPPING-START
//      FLOW-MAPPING-END
//      FLOW-ENTRY
//      KEY
//      VALUE
//
// The tokens FLOW-SEQUENCE-START, FLOW-SEQUENCE-END, FLOW-MAPPING-START, and
// FLOW-MAPPING-END represent the indicators '[', ']', '{', and '}'
// correspondingly.  FLOW-ENTRY represent the ',' indicator.  Finally the
// indicators '?' and ':', which are used for denoting mapping keys and values,
// are represented by the KEY and VALUE tokens.
//
// The following examples show flow collections:
//
//      1. A flow sequence:
//
//          [item 1, item 2, item 3]
//
//      Tokens:
//
//          STREAM-START(utf-8)
//          FLOW-SEQUENCE-START
//          SCALAR("item 1",plain)
//          FLOW-ENTRY
//          SCALAR("item 2",plain)
//          FLOW-ENTRY
//          SCALAR("item 3",plain)
//          FLOW-SEQUENCE-END
//          STREAM-END
//
//      2. A flow mapping:
//
//          {
//              a simple key: a value,  # Note that the KEY token is produced.
//              ? a complex key: another value,
//          }
//
//      Tokens:
//
//          STREAM-START(utf-8)
//          FLOW-MAPPING-START
//          KEY
//          SCALAR("a simple key",plain)
//          VALUE
//          SCALAR("a value",plain)
//          FLOW-ENTRY
//          KEY
//          SCALAR("a complex key",plain)
//          VALUE
//          SCALAR("another value",plain)
//          FLOW-ENTRY
//          FLOW-MAPPING-END
//          STREAM-END
//
// A simple key is a key which is not denoted by the '?' indicator.  Note that
// the Scanner still produce the KEY token whenever it encounters a simple key.
//
// For scanning block collections, the following tokens are used (note that we
// repeat KEY and VALUE here):
//
//      BLOCK-SEQUENCE-START
//      BLOCK-MAPPING-START
//      BLOCK-END
//      BLOCK-ENTRY
//      KEY
//      VALUE
//
// The tokens BLOCK-SEQUENCE-START and BLOCK-MAPPING-START denote indentation
// increase that precedes a block collection (cf. the INDENT token in Python).
// The token BLOCK-END denote indentation decrease that ends a block collection
// (cf. the DEDENT token in Python).  However YAML has some syntax pecularities
// that makes detections of these tokens more complex.
//
// The tokens BLOCK-ENTRY, KEY, and VALUE are used to represent the indicators
// '-', '?', and ':' correspondingly.
//
// The following examples show how the tokens BLOCK-SEQUENCE-START,
// BLOCK-MAPPING-START, and BLOCK-END are emitted by the Scanner:
//
//      1. Block sequences:
//
//          - item 1
//          - item 2
//          -
//            - item 3.1
//            - item 3.2
//          -
//            key 1: value 1
//            key 2: value 2
//
//      Tokens:
//
//          STREAM-START(utf-8)
//          BLOCK-SEQUENCE-START
//          BLOCK-ENTRY
//          SCALAR("item 1",plain)
//          BLOCK-ENTRY
//          SCALAR("item 2",plain)
//          BLOCK-ENTRY
//          BLOCK-SEQUENCE-START
//          BLOCK-ENTRY
//          SCALAR("item 3.1",plain)
//          BLOCK-ENTRY
//          SCALAR("item 3.2",plain)
//          BLOCK-END
//          BLOCK-ENTRY
//          BLOCK-MAPPING-START
//          KEY
//          SCALAR("key 1",plain)
//          VALUE
//          SCALAR("value 1",plain)
//          KEY
//          SCALAR("key 2",plain)
//          VALUE
//          SCALAR("value 2",plain)
//          BLOCK-END
//          BLOCK-END
//          STREAM-END
//
//      2. Block mappings:
//
//          a simple key: a value   # The KEY token is produced here.
//          ? a complex key
//          : another value
//          a mapping:
//            key 1: value 1
//            key 2: value 2
//          a sequence:
//            - item 1
//            - item 2
//
//      Tokens:
//
//          STREAM-START(utf-8)
//          BLOCK-MAPPING-START
//          KEY
//          SCALAR("a simple key",plain)
//          VALUE
//          SCALAR("a value",plain)
//          KEY
//          SCALAR("a complex key",plain)
//          VALUE
//          SCALAR("another value",plain)
//          KEY
//          SCALAR("a mapping",plain)
//          BLOCK-MAPPING-START
//          KEY
//          SCALAR("key 1",plain)
//          VALUE
//          SCALAR("value 1",plain)
//          KEY
//          SCALAR("key 2",plain)
//          VALUE
//          SCALAR("value 2",plain)
//          BLOCK-END
//          KEY
//          SCALAR("a sequence",plain)
//          VALUE
//          BLOCK-SEQUENCE-START
//          BLOCK-ENTRY
//          SCALAR("item 1",plain)
//          BLOCK-ENTRY
//          SCALAR("item 2",plain)
//          BLOCK-END
//          BLOCK-END
//          STREAM-END
//
// YAML does not always require to start a new block collection from a new
// line.  If the current line contains only '-', '?', and ':' indicators, a new
// block collection may start at the current line.  The following examples
// illustrate this case:
//
//      1. Collections in a sequence:
//
//          - - item 1
//            - item 2
//          - key 1: value 1
//            key 2: value 2
//          - ? complex key
//            : complex value
//
//      Tokens:
//
//          STREAM-START(utf-8)
//          BLOCK-SEQUENCE-START
//          BLOCK-ENTRY
//          BLOCK-SEQUENCE-START
//          BLOCK-ENTRY
//          SCALAR("item 1",plain)
//          BLOCK-ENTRY
//          SCALAR("item 2",plain)
//          BLOCK-END
//          BLOCK-ENTRY
//          BLOCK-MAPPING-START
//          KEY
//          SCALAR("key 1",plain)
//          VALUE
//          SCALAR("value 1",plain)
//          KEY
//          SCALAR("key 2",plain)
//          VALUE
//          SCALAR("value 2",plain)
//          BLOCK-END
//          BLOCK-ENTRY
//          BLOCK-MAPPING-START
//          KEY
//          SCALAR("complex key")
//          VALUE
//          SCALAR("complex value")
//          BLOCK-END
//          BLOCK-END
//          STREAM-END
//
//      2. Collections in a mapping:
//
//          ? a sequence
//          : - item 1
//            - item 2
//          ? a mapping
//          : key 1: value 1
//            key 2: value 2
//
//      Tokens:
//
//          STREAM-START(utf-8)
//          BLOCK-MAPPING-START
//          KEY
//          SCALAR("a sequence",plain)
//          VALUE
//          BLOCK-SEQUENCE-START
//          BLOCK-ENTRY
//          SCALAR("item 1",plain)
//          BLOCK-ENTRY
//          SCALAR("item 2",plain)
//          BLOCK-END
//          KEY
//          SCALAR("a mapping",plain)
//          VALUE
//          BLOCK-MAPPING-START
//          KEY
//          SCALAR("key 1",plain)
//          VALUE
//          SCALAR("value 1",plain)
//          KEY
//          SCALAR("key 2",plain)
//          VALUE
//          SCALAR("value 2",plain)
//          BLOCK-END
//          BLOCK-END
//          STREAM-END
//
// YAML also permits non-indented sequences if they are included into a block
// mapping.  In this case, the token BLOCK-SEQUENCE-START is not produced:
//
//      key:
//      - item 1    # BLOCK-SEQUENCE-START is NOT produced here.
//      - item 2
//
// Tokens:
//
//      STREAM-START(utf-8)
//      BLOCK-MAPPING-START
//      KEY
//      SCALAR("key",plain)
//      VALUE
//      BLOCK-ENTRY
//      SCALAR("item 1",plain)
//      BLOCK-ENTRY
//      SCALAR("item 2",plain)
//      BLOCK-END
//

// Ensure that the buffer contains the required number of characters.
// Return true on success, false on failure (reader error or memory error).
func cache(parser *yaml_parser_t, length int) bool {
	// [Go] This was inlined: !cache(A, B) -> unread < B && !update(A, B)
	return parser.unread >= length || yaml_parser_update_buffer(parser, length)
}

// Advance the buffer pointer.
func skip(parser *yaml_parser_t) {
	parser.mark.index++
	parser.mark.column++
	parser.unread--
	parser.buffer_pos += width(parser.buffer[parser.buffer_pos])
}

func skip_line(parser *yaml_parser_t) {
	if is_crlf(parser.buffer, parser.buffer_pos) {
		parser.mark.index += 2
		parser.mark.column = 0
		parser.mark.line++
		parser.unread -= 2
		parser.buffer_pos += 2
	} else if is_break(parser.buffer, parser.buffer_pos) {
		parser.mark.index++
		parser.mark.column = 0
		parser.mark.line++
		parser.unread--
		parser.buffer_pos += width(parser.buffer[parser.buffer_pos])
	}
}

// Copy a character to a string buffer and advance pointers.
func read(parser *yaml_parser_t, s []byte) []byte {
	w := width(parser.buffer[parser.buffer_pos])
	if w == 0 {
		panic("invalid character sequence")
	}
	if len(s) == 0 {
		s = make([]byte, 0, 32)
	}
	if w == 1 && len(s)+w <= cap(s) {
		s = s[:len(s)+1]
		s[len(s)-1] = parser.buffer[parser.buffer_pos]
		parser.buffer_pos++
	} else {
		s = append(s, parser.buffer[parser.buffer_pos:parser.buffer_pos+w]...)
		parser.buffer_pos += w
	}
	parser.mark.index++
	parser.mark.column++
	parser.unread--
	return s
}

// Copy a line break character to a string buffer and advance pointers.
func read_line(parser *yaml_parser_t, s []byte) []byte {
	buf := parser.buffer
	pos := parser.buffer_pos
	switch {
	case buf[pos] == '\r' && buf[pos+1] == '\n':
		// CR LF . LF
		s = append(s, '\n')
		parser.buffer_pos += 2
		parser.mark.index++
		parser.unread--
	case buf[pos] == '\r' || buf[pos] == '\n':
		// CR|LF . LF
		s = append(s, '\n')
		parser.buffer_pos += 1
	case buf[pos] == '\xC2' && buf[pos+1] == '\x85':
		// NEL . LF
		s = append(s, '\n')
		parser.buffer_pos += 2
	case buf[pos] == '\xE2' && buf[pos+1] == '\x80' && (buf[pos+2] == '\xA8' || buf[pos+2] == '\xA9'):
		// LS|PS . LS|PS
		s = append(s, buf[parser.buffer_pos:pos+3]...)
		parser.buffer_pos += 3
	default:
		return s
	}
	parser.mark.index++
	parser.mark.column = 0
	parser.mark.line++
	parser.unread--
	return s
}

// Get the next token.
func yaml_parser_scan(parser *yaml_parser_t, token *yaml_token_t) bool {
	// Erase the token object.
	*token = yaml_token_t{} // [Go] Is this necessary?

	// No tokens after STREAM-END or error.
	if parser.stream_end_produced || parser.error != yaml_NO_ERROR {
		return true
	}

	// Ensure that the tokens queue contains enough tokens.
	if !parser.token_available {
		if !yaml_parser_fetch_more_tokens(parser) {
			return false
		}
	}

	// Fetch the next token from the queue.
	*token = parser.tokens[parser.tokens_head]
	parser.tokens_head++
	parser.tokens_parsed++
	parser.token_available = false

	if token.typ == yaml_STREAM_END_TOKEN {
		parser.stream_end_produced = true
	}
	return true
}

// Set the scanner error and return false.
func yaml_parser_set_scanner_error(parser *yaml_parser_t, context string, context_mark yaml_mark_t, problem string) bool {
	parser.error = yaml_SCANNER_ERROR
	parser.context = context
	parser.context_mark = context_mark
	parser.problem = problem
	parser.problem_mark = parser.mark
	return false
}

func yaml_parser_set_scanner_tag_error(parser *yaml_parser_t, directive bool, context_mark yaml_mark_t, problem string) bool {
	context := "while parsing a tag"
	if directive {
		context = "while parsing a %TAG directive"
	}
	return yaml_parser_set_scanner_error(parser, context, context_mark, "did not find URI escaped octet")
}

func trace(args ...interface{}) func() {
	pargs := append([]interface{}{"+++"}, args...)
	fmt.Println(pargs...)
	pargs = append([]interface{}{"---"}, args...)
	return func() { fmt.Println(pargs...) }
}

// Ensure that the tokens queue contains at least one token which can be
// returned to the Parser.
func yaml_parser_fetch_more_tokens(parser *yaml_parser_t) bool {
	// While we need more tokens to fetch, do it.
	for {
		// Check if we really need to fetch more tokens.
		need_more_tokens := false

		if parser.tokens_head == len(parser.tokens) {
			// Queue is empty.
			need_more_tokens = true
		} else {
			// Check if any potential simple key may occupy the head position.
			if !yaml_parser_stale_simple_keys(parser) {
				return false
			}

			for i := range parser.simple_keys {
				simple_key := &parser.simple_keys[i]
				if simple_key.possible && simple_key.token_number == parser.tokens_parsed {
					need_more_tokens = true
					break
				}
			}
		}

		// We are finished.
		if !need_more_tokens {
			break
		}
		// Fetch the next token.
		if !yaml_parser_fetch_next_token(parser) {
			return false
		}
	}

	parser.token_available = true
	return true
}

// The dispatcher for token fetchers.
func yaml_parser_fetch_next_token(parser *yaml_parser_t) bool {
	// Ensure that the buffer is initialized.
	if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
		return false
	}

	// Check if we just started scanning.  Fetch STREAM-START then.
	if !parser.stream_start_produced {
		return yaml_parser_fetch_stream_start(parser)
	}

	// Eat whitespaces and comments until we reach the next token.
	if !yaml_parser_scan_to_next_token(parser) {
		return false
	}

	// Remove obsolete potential simple keys.
	if !yaml_parser_stale_simple_keys(parser) {
		return false
	}

	// Check the indentation level against the current column.
	if !yaml_parser_unroll_indent(parser, parser.mark.column) {
		return false
	}

	// Ensure that the buffer contains at least 4 characters.  4 is the length
	// of the longest indicators ('--- ' and '... ').
	if parser.unread < 4 && !yaml_parser_update_buffer(parser, 4) {
		return false
	}

	// Is it the end of the stream?
	if is_z(parser.buffer, parser.buffer_pos) {
		return yaml_parser_fetch_stream_end(parser)
	}

	// Is it a directive?
	if parser.mark.column == 0 && parser.buffer[parser.buffer_pos] == '%' {
		return yaml_parser_fetch_directive(parser)
	}

	buf := parser.buffer
	pos := parser.buffer_pos

	// Is it the document start indicator?
	if parser.mark.column == 0 && buf[pos] == '-' && buf[pos+1] == '-' && buf[pos+2] == '-' && is_blankz(buf, pos+3) {
		return yaml_parser_fetch_document_indicator(parser, yaml_DOCUMENT_START_TOKEN)
	}

	// Is it the document end indicator?
	if parser.mark.column == 0 && buf[pos] == '.' && buf[pos+1] == '.' && buf[pos+2] == '.' && is_blankz(buf, pos+3) {
		return yaml_parser_fetch_document_indicator(parser, yaml_DOCUMENT_END_TOKEN)
	}

	// Is it the flow sequence start indicator?
	if buf[pos] == '[' {
		return yaml_parser_fetch_flow_collection_start(parser, yaml_FLOW_SEQUENCE_START_TOKEN)
	}

	// Is it the flow mapping start indicator?
	if parser.buffer[parser.buffer_pos] == '{' {
		return yaml_parser_fetch_flow_collection_start(parser, yaml_FLOW_MAPPING_START_TOKEN)
	}

	// Is it the flow sequence end indicator?
	if parser.buffer[parser.buffer_pos] == ']' {
		return yaml_parser_fetch_flow_collection_end(parser,
			yaml_FLOW_SEQUENCE_END_TOKEN)
	}

	// Is it the flow mapping end indicator?
	if parser.buffer[parser.buffer_pos] == '}' {
		return yaml_parser_fetch_flow_collection_end(parser,
			yaml_FLOW_MAPPING_END_TOKEN)
	}

	// Is it the flow entry indicator?
	if parser.buffer[parser.buffer_pos] == ',' {
		return yaml_parser_fetch_flow_entry(parser)
	}

	// Is it the block entry indicator?
	if parser.buffer[parser.buffer_pos] == '-' && is_blankz(parser.buffer, parser.buffer_pos+1) {
		return yaml_parser_fetch_block_entry(parser)
	}

	// Is it the key indicator?
	if parser.buffer[parser.buffer_pos] == '?' && (parser.flow_level > 0 || is_blankz(parser.buffer, parser.buffer_pos+1)) {
		return yaml_parser_fetch_key(parser)
	}

	// Is it the value indicator?
	if parser.buffer[parser.buffer_pos] == ':' && (parser.flow_level > 0 || is_blankz(parser.buffer, parser.buffer_pos+1)) {
		return yaml_parser_fetch_value(parser)
	}

	// Is it an alias?
	if parser.buffer[parser.buffer_pos] == '*' {
		return yaml_parser_fetch_anchor(parser, yaml_ALIAS_TOKEN)
	}

	// Is it an anchor?
	if parser.buffer[parser.buffer_pos] == '&' {
		return yaml_parser_fetch_anchor(parser, yaml_ANCHOR_TOKEN)
	}

	// Is it a tag?
	if parser.buffer[parser.buffer_pos] == '!' {
		return yaml_parser_fetch_tag(parser)
	}

	// Is it a literal scalar?
	if parser.buffer[parser.buffer_pos] == '|' && parser.flow_level == 0 {
		return yaml_parser_fetch_block_scalar(parser, true)
	}

	// Is it a folded scalar?
	if parser.buffer[parser.buffer_pos] == '>' && parser.flow_level == 0 {
		return yaml_parser_fetch_block_scalar(parser, false)
	}

	// Is it a single-quoted scalar?
	if parser.buffer[parser.buffer_pos] == '\'' {
		return yaml_parser_fetch_flow_scalar(parser, true)
	}

	// Is it a double-quoted scalar?
	if parser.buffer[parser.buffer_pos] == '"' {
		return yaml_parser_fetch_flow_scalar(parser, false)
	}

	// Is it a plain scalar?
	//
	// A plain scalar may start with any non-blank characters except
	//
	//      '-', '?', ':', ',', '[', ']', '{', '}',
	//      '#', '&', '*', '!', '|', '>', '\'', '\"',
	//      '%', '@', '`'.
	//
	// In the block context (and, for the '-' indicator, in the flow context
	// too), it may also start with the characters
	//
	//      '-', '?', ':'
	//
	// if it is followed by a non-space character.
	//
	// The last rule is more restrictive than the specification requires.
	// [Go] Make this logic more reasonable.
	//switch parser.buffer[parser.buffer_pos] {
	//case '-', '?', ':', ',', '?', '-', ',', ':', ']', '[', '}', '{', '&', '#', '!', '*', '>', '|', '"', '\'', '@', '%', '-', '`':
	//}
	if !(is_blankz(parser.buffer, parser.buffer_pos) || parser.buffer[parser.buffer_pos] == '-' ||
		parser.buffer[parser.buffer_pos] == '?' || parser.buffer[parser.buffer_pos] == ':' ||
		parser.buffer[parser.buffer_pos] == ',' || parser.buffer[parser.buffer_pos] == '[' ||
		parser.buffer[parser.buffer_pos] == ']' || parser.buffer[parser.buffer_pos] == '{' ||
		parser.buffer[parser.buffer_pos] == '}' || parser.buffer[parser.buffer_pos] == '#' ||
		parser.buffer[parser.buffer_pos] == '&' || parser.buffer[parser.buffer_pos] == '*' ||
		parser.buffer[parser.buffer_pos] == '!' || parser.buffer[parser.buffer_pos] == '|' ||
		parser.buffer[parser.buffer_pos] == '>' || parser.buffer[parser.buffer_pos] == '\'' ||
		parser.buffer[parser.buffer_pos] == '"' || parser.buffer[parser.buffer_pos] == '%' ||
		parser.buffer[parser.buffer_pos] == '@' || parser.buffer[parser.buffer_pos] == '`') ||
		(parser.buffer[parser.buffer_pos] == '-' && !is_blank(parser.buffer, parser.buffer_pos+1)) ||
		(parser.flow_level == 0 &&
			(parser.buffer[parser.buffer_pos] == '?' || parser.buffer[parser.buffer_pos] == ':') &&
			!is_blankz(parser.buffer, parser.buffer_pos+1)) {
		return yaml_parser_fetch_plain_scalar(parser)
	}

	// If we don't determine the token type so far, it is an error.
	return yaml_parser_set_scanner_error(parser,
		"while scanning for the next token", parser.mark,
		"found character that cannot start any token")
}

// Check the list of potential simple keys and remove the positions that
// cannot contain simple keys anymore.
func yaml_parser_stale_simple_keys(parser *yaml_parser_t) bool {
	// Check for a potential simple key for each flow level.
	for i := range parser.simple_keys {
		simple_key := &parser.simple_keys[i]

		// The specification requires that a simple key
		//
		//  - is limited to a single line,
		//  - is shorter than 1024 characters.
		if simple_key.possible && (simple_key.mark.line < parser.mark.line || simple_key.mark.index+1024 < parser.mark.index) {

			// Check if the potential simple key to be removed is required.
			if simple_key.required {
				return yaml_parser_set_scanner_error(parser,
					"while scanning a simple key", simple_key.mark,
					"could not find expected ':'")
			}
			simple_key.possible = false
		}
	}
	return true
}

// Check if a simple key may start at the current position and add it if
// needed.
func yaml_parser_save_simple_key(parser *yaml_parser_t) bool {
	// A simple key is required at the current position if the scanner is in
	// the block context and the current column coincides with the indentation
	// level.

	required := parser.flow_level == 0 && parser.indent == parser.mark.column

	// A simple key is required only when it is the first token in the current
	// line.  Therefore it is always allowed.  But we add a check anyway.
	if required && !parser.simple_key_allowed {
		panic("should not happen")
	}

	//
	// If the current position may start a simple key, save it.
	//
	if parser.simple_key_allowed {
		simple_key := yaml_simple_key_t{
			possible:     true,
			required:     required,
			token_number: parser.tokens_parsed + (len(parser.tokens) - parser.tokens_head),
		}
		simple_key.mark = parser.mark

		if !yaml_parser_remove_simple_key(parser) {
			return false
		}
		parser.simple_keys[len(parser.simple_keys)-1] = simple_key
	}
	return true
}

// Remove a potential simple key at the current flow level.
func yaml_parser_remove_simple_key(parser *yaml_parser_t) bool {
	i := len(parser.simple_keys) - 1
	if parser.simple_keys[i].possible {
		// If the key is required, it is an error.
		if parser.simple_keys[i].required {
			return yaml_parser_set_scanner_error(parser,
				"while scanning a simple key", parser.simple_keys[i].mark,
				"could not find expected ':'")
		}
	}
	// Remove the key from the stack.
	parser.simple_keys[i].possible = false
	return true
}

// Increase the flow level and resize the simple key list if needed.
func yaml_parser_increase_flow_level(parser *yaml_parser_t) bool {
	// Reset the simple key on the next level.
	parser.simple_keys = append(parser.simple_keys, yaml_simple_key_t{})

	// Increase the flow level.
	parser.flow_level++
	return true
}

// Decrease the flow level.
func yaml_parser_decrease_flow_level(parser *yaml_parser_t) bool {
	if parser.flow_level > 0 {
		parser.flow_level--
		parser.simple_keys = parser.simple_keys[:len(parser.simple_keys)-1]
	}
	return true
}

// Push the current indentation level to the stack and set the new level
// the current column is greater than the indentation level.  In this case,
// append or insert the specified token into the token queue.
func yaml_parser_roll_indent(parser *yaml_parser_t, column, number int, typ yaml_token_type_t, mark yaml_mark_t) bool {
	// In the flow context, do nothing.
	if parser.flow_level > 0 {
		return true
	}

	if parser.indent < column {
		// Push the current indentation level to the stack and set the new
		// indentation level.
		parser.indents = append(parser.indents, parser.indent)
		parser.indent = column

		// Create a token and insert it into the queue.
		token := yaml_token_t{
			typ:        typ,
			start_mark: mark,
			end_mark:   mark,
		}
		if number > -1 {
			number -= parser.tokens_parsed
		}
		yaml_insert_token(parser, number, &token)
	}
	return true
}

// Pop indentation levels from the indents stack until the current level
// becomes less or equal to the column.  For each indentation level, append
// the BLOCK-END token.
func yaml_parser_unroll_indent(parser *yaml_parser_t, column int) bool {
	// In the flow context, do nothing.
	if parser.flow_level > 0 {
		return true
	}

	// Loop through the indentation levels in the stack.
	for parser.indent > column {
		// Create a token and append it to the queue.
		token := yaml_token_t{
			typ:        yaml_BLOCK_END_TOKEN,
			start_mark: parser.mark,
			end_mark:   parser.mark,
		}
		yaml_insert_token(parser, -1, &token)

		// Pop the indentation level.
		parser.indent = parser.indents[len(parser.indents)-1]
		parser.indents = parser.indents[:len(parser.indents)-1]
	}
	return true
}

// Initialize the scanner and produce the STREAM-START token.
func yaml_parser_fetch_stream_start(parser *yaml_parser_t) bool {

	// Set the initial indentation.
	parser.indent = -1

	// Initialize the simple key stack.
	parser.simple_keys = append(parser.simple_keys, yaml_simple_key_t{})

	// A simple key is allowed at the beginning of the stream.
	parser.simple_key_allowed = true

	// We have started.
	parser.stream_start_produced = true

	// Create the STREAM-START token and append it to the queue.
	token := yaml_token_t{
		typ:        yaml_STREAM_START_TOKEN,
		start_mark: parser.mark,
		end_mark:   parser.mark,
		encoding:   parser.encoding,
	}
	yaml_insert_token(parser, -1, &token)
	return true
}

// Produce the STREAM-END token and shut down the scanner.
func yaml_parser_fetch_stream_end(parser *yaml_parser_t) bool {

	// Force new line.
	if parser.mark.column != 0 {
		parser.mark.column = 0
		parser.mark.line++
	}

	// Reset the indentation level.
	if !yaml_parser_unroll_indent(parser, -1) {
		return false
	}

	// Reset simple keys.
	if !yaml_parser_remove_simple_key(parser) {
		return false
	}

	parser.simple_key_allowed = false

	// Create the STREAM-END token and append it to the queue.
	token := yaml_token_t{
		typ:        yaml_STREAM_END_TOKEN,
		start_mark: parser.mark,
		end_mark:   parser.mark,
	}
	yaml_insert_token(parser, -1, &token)
	return true
}

// Produce a VERSION-DIRECTIVE or TAG-DIRECTIVE token.
func yaml_parser_fetch_directive(parser *yaml_parser_t) bool {
	// Reset the indentation level.
	if !yaml_parser_unroll_indent(parser, -1) {
		return false
	}

	// Reset simple keys.
	if !yaml_parser_remove_simple_key(parser) {
		return false
	}

	parser.simple_key_allowed = false

	// Create the YAML-DIRECTIVE or TAG-DIRECTIVE token.
	token := yaml_token_t{}
	if !yaml_parser_scan_directive(parser, &token) {
		return false
	}
	// Append the token to the queue.
	yaml_insert_token(parser, -1, &token)
	return true
}

// Produce the DOCUMENT-START or DOCUMENT-END token.
func yaml_parser_fetch_document_indicator(parser *yaml_parser_t, typ yaml_token_type_t) bool {
	// Reset the indentation level.
	if !yaml_parser_unroll_indent(parser, -1) {
		return false
	}

	// Reset simple keys.
	if !yaml_parser_remove_simple_key(parser) {
		return false
	}

	parser.simple_key_allowed = false

	// Consume the token.
	start_mark := parser.mark

	skip(parser)
	skip(parser)
	skip(parser)

	end_mark := parser.mark

	// Create the DOCUMENT-START or DOCUMENT-END token.
	token := yaml_token_t{
		typ:        typ,
		start_mark: start_mark,
		end_mark:   end_mark,
	}
	// Append the token to the queue.
	yaml_insert_token(parser, -1, &token)
	return true
}

// Produce the FLOW-SEQUENCE-START or FLOW-MAPPING-START token.
func yaml_parser_fetch_flow_collection_start(parser *yaml_parser_t, typ yaml_token_type_t) bool {
	// The indicators '[' and '{' may start a simple key.
	if !yaml_parser_save_simple_key(parser) {
		return false
	}

	// Increase the flow level.
	if !yaml_parser_increase_flow_level(parser) {
		return false
	}

	// A simple key may follow the indicators '[' and '{'.
	parser.simple_key_allowed = true

	// Consume the token.
	start_mark := parser.mark
	skip(parser)
	end_mark := parser.mark

	// Create the FLOW-SEQUENCE-START of FLOW-MAPPING-START token.
	token := yaml_token_t{
		typ:        typ,
		start_mark: start_mark,
		end_mark:   end_mark,
	}
	// Append the token to the queue.
	yaml_insert_token(parser, -1, &token)
	return true
}

// Produce the FLOW-SEQUENCE-END or FLOW-MAPPING-END token.
func yaml_parser_fetch_flow_collection_end(parser *yaml_parser_t, typ yaml_token_type_t) bool {
	// Reset any potential simple key on the current flow level.
	if !yaml_parser_remove_simple_key(parser) {
		return false
	}

	// Decrease the flow level.
	if !yaml_parser_decrease_flow_level(parser) {
		return false
	}

	// No simple keys after the indicators ']' and '}'.
	parser.simple_key_allowed = false

	// Consume the token.

	start_mark := parser.mark
	skip(parser)
	end_mark := parser.mark

	// Create the FLOW-SEQUENCE-END of FLOW-MAPPING-END token.
	token := yaml_token_t{
		typ:        typ,
		start_mark: start_mark,
		end_mark:   end_mark,
	}
	// Append the token to the queue.
	yaml_insert_token(parser, -1, &token)
	return true
}

// Produce the FLOW-ENTRY token.
func yaml_parser_fetch_flow_entry(parser *yaml_parser_t) bool {
	// Reset any potential simple keys on the current flow level.
	if !yaml_parser_remove_simple_key(parser) {
		return false
	}

	// Simple keys are allowed after ','.
	parser.simple_key_allowed = true

	// Consume the token.
	start_mark := parser.mark
	skip(parser)
	end_mark := parser.mark

	// Create the FLOW-ENTRY token and append it to the queue.
	token := yaml_token_t{
		typ:        yaml_FLOW_ENTRY_TOKEN,
		start_mark: start_mark,
		end_mark:   end_mark,
	}
	yaml_insert_token(parser, -1, &token)
	return true
}

// Produce the BLOCK-ENTRY token.
func yaml_parser_fetch_block_entry(parser *yaml_parser_t) bool {
	// Check if the scanner is in the block context.
	if parser.flow_level == 0 {
		// Check if we are allowed to start a new entry.
		if !parser.simple_key_allowed {
			return yaml_parser_set_scanner_error(parser, "", parser.mark,
				"block sequence entries are not allowed in this context")
		}
		// Add the BLOCK-SEQUENCE-START token if needed.
		if !yaml_parser_roll_indent(parser, parser.mark.column, -1, yaml_BLOCK_SEQUENCE_START_TOKEN, parser.mark) {
			return false
		}
	} else {
		// It is an error for the '-' indicator to occur in the flow context,
		// but we let the Parser detect and report about it because the Parser
		// is able to point to the context.
	}

	// Reset any potential simple keys on the current flow level.
	if !yaml_parser_remove_simple_key(parser) {
		return false
	}

	// Simple keys are allowed after '-'.
	parser.simple_key_allowed = true

	// Consume the token.
	start_mark := parser.mark
	skip(parser)
	end_mark := parser.mark

	// Create the BLOCK-ENTRY token and append it to the queue.
	token := yaml_token_t{
		typ:        yaml_BLOCK_ENTRY_TOKEN,
		start_mark: start_mark,
		end_mark:   end_mark,
	}
	yaml_insert_token(parser, -1, &token)
	return true
}

// Produce the KEY token.
func yaml_parser_fetch_key(parser *yaml_parser_t) bool {

	// In the block context, additional checks are required.
	if parser.flow_level == 0 {
		// Check if we are allowed to start a new key (not nessesary simple).
		if !parser.simple_key_allowed {
			return yaml_parser_set_scanner_error(parser, "", parser.mark,
				"mapping keys are not allowed in this context")
		}
		// Add the BLOCK-MAPPING-START token if needed.
		if !yaml_parser_roll_indent(parser, parser.mark.column, -1, yaml_BLOCK_MAPPING_START_TOKEN, parser.mark) {
			return false
		}
	}

	// Reset any potential simple keys on the current flow level.
	if !yaml_parser_remove_simple_key(parser) {
		return false
	}

	// Simple keys are allowed after '?' in the block context.
	parser.simple_key_allowed = parser.flow_level == 0

	// Consume the token.
	start_mark := parser.mark
	skip(parser)
	end_mark := parser.mark

	// Create the KEY token and append it to the queue.
	token := yaml_token_t{
		typ:        yaml_KEY_TOKEN,
		start_mark: start_mark,
		end_mark:   end_mark,
	}
	yaml_insert_token(parser, -1, &token)
	return true
}

// Produce the VALUE token.
func yaml_parser_fetch_value(parser *yaml_parser_t) bool {

	simple_key := &parser.simple_keys[len(parser.simple_keys)-1]

	// Have we found a simple key?
	if simple_key.possible {
		// Create the KEY token and insert it into the queue.
		token := yaml_token_t{
			typ:        yaml_KEY_TOKEN,
			start_mark: simple_key.mark,
			end_mark:   simple_key.mark,
		}
		yaml_insert_token(parser, simple_key.token_number-parser.tokens_parsed, &token)

		// In the block context, we may need to add the BLOCK-MAPPING-START token.
		if !yaml_parser_roll_indent(parser, simple_key.mark.column,
			simple_key.token_number,
			yaml_BLOCK_MAPPING_START_TOKEN, simple_key.mark) {
			return false
		}

		// Remove the simple key.
		simple_key.possible = false

		// A simple key cannot follow another simple key.
		parser.simple_key_allowed = false

	} else {
		// The ':' indicator follows a complex key.

		// In the block context, extra checks are required.
		if parser.flow_level == 0 {

			// Check if we are allowed to start a complex value.
			if !parser.simple_key_allowed {
				return yaml_parser_set_scanner_error(parser, "", parser.mark,
					"mapping values are not allowed in this context")
			}

			// Add the BLOCK-MAPPING-START token if needed.
			if !yaml_parser_roll_indent(parser, parser.mark.column, -1, yaml_BLOCK_MAPPING_START_TOKEN, parser.mark) {
				return false
			}
		}

		// Simple keys after ':' are allowed in the block context.
		parser.simple_key_allowed = parser.flow_level == 0
	}

	// Consume the token.
	start_mark := parser.mark
	skip(parser)
	end_mark := parser.mark

	// Create the VALUE token and append it to the queue.
	token := yaml_token_t{
		typ:        yaml_VALUE_TOKEN,
		start_mark: start_mark,
		end_mark:   end_mark,
	}
	yaml_insert_token(parser, -1, &token)
	return true
}

// Produce the ALIAS or ANCHOR token.
func yaml_parser_fetch_anchor(parser *yaml_parser_t, typ yaml_token_type_t) bool {
	// An anchor or an alias could be a simple key.
	if !yaml_parser_save_simple_key(parser) {
		return false
	}

	// A simple key cannot follow an anchor or an alias.
	parser.simple_key_allowed = false

	// Create the ALIAS or ANCHOR token and append it to the queue.
	var token yaml_token_t
	if !yaml_parser_scan_anchor(parser, &token, typ) {
		return false
	}
	yaml_insert_token(parser, -1, &token)
	return true
}

// Produce the TAG token.
func yaml_parser_fetch_tag(parser *yaml_parser_t) bool {
	// A tag could be a simple key.
	if !yaml_parser_save_simple_key(parser) {
		return false
	}

	// A simple key cannot follow a tag.
	parser.simple_key_allowed = false

	// Create the TAG token and append it to the queue.
	var token yaml_token_t
	if !yaml_parser_scan_tag(parser, &token) {
		return false
	}
	yaml_insert_token(parser, -1, &token)
	return true
}

// Produce the SCALAR(...,literal) or SCALAR(...,folded) tokens.
func yaml_parser_fetch_block_scalar(parser *yaml_parser_t, literal bool) bool {
	// Remove any potential simple keys.
	if !yaml_parser_remove_simple_key(parser) {
		return false
	}

	// A simple key may follow a block scalar.
	parser.simple_key_allowed = true

	// Create the SCALAR token and append it to the queue.
	var token yaml_token_t
	if !yaml_parser_scan_block_scalar(parser, &token, literal) {
		return false
	}
	yaml_insert_token(parser, -1, &token)
	return true
}

// Produce the SCALAR(...,single-quoted) or SCALAR(...,double-quoted) tokens.
func yaml_parser_fetch_flow_scalar(parser *yaml_parser_t, single bool) bool {
	// A plain scalar could be a simple key.
	if !yaml_parser_save_simple_key(parser) {
		return false
	}

	// A simple key cannot follow a flow scalar.
	parser.simple_key_allowed = false

	// Create the SCALAR token and append it to the queue.
	var token yaml_token_t
	if !yaml_parser_scan_flow_scalar(parser, &token, single) {
		return false
	}
	yaml_insert_token(parser, -1, &token)
	return true
}

// Produce the SCALAR(...,plain) token.
func yaml_parser_fetch_plain_scalar(parser *yaml_parser_t) bool {
	// A plain scalar could be a simple key.
	if !yaml_parser_save_simple_key(parser) {
		return false
	}

	// A simple key cannot follow a flow scalar.
	parser.simple_key_allowed = false

	// Create the SCALAR token and append it to the queue.
	var token yaml_token_t
	if !yaml_parser_scan_plain_scalar(parser, &token) {
		return false
	}
	yaml_insert_token(parser, -1, &token)
	return true
}

// Eat whitespaces and comments until the next token is found.
func yaml_parser_scan_to_next_token(parser *yaml_parser_t) bool {

	// Until the next token is not found.
	for {
		// Allow the BOM mark to start a line.
		if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
			return false
		}
		if parser.mark.column == 0 && is_bom(parser.buffer, parser.buffer_pos) {
			skip(parser)
		}

		// Eat whitespaces.
		// Tabs are allowed:
		//  - in the flow context
		//  - in the block context, but not at the beginning of the line or
		//  after '-', '?', or ':' (complex value).
		if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
			return false
		}

		for parser.buffer[parser.buffer_pos] == ' ' || ((parser.flow_level > 0 || !parser.simple_key_allowed) && parser.buffer[parser.buffer_pos] == '\t') {
			skip(parser)
			if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
				return false
			}
		}

		// Eat a comment until a line break.
		if parser.buffer[parser.buffer_pos] == '#' {
			for !is_breakz(parser.buffer, parser.buffer_pos) {
				skip(parser)
				if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
					return false
				}
			}
		}

		// If it is a line break, eat it.
		if is_break(parser.buffer, parser.buffer_pos) {
			if parser.unread < 2 && !yaml_parser_update_buffer(parser, 2) {
				return false
			}
			skip_line(parser)

			// In the block context, a new line may start a simple key.
			if parser.flow_level == 0 {
				parser.simple_key_allowed = true
			}
		} else {
			break // We have found a token.
		}
	}

	return true
}

// Scan a YAML-DIRECTIVE or TAG-DIRECTIVE token.
//
// Scope:
//      %YAML    1.1    # a comment \n
//      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
//      %TAG    !yaml!  tag:yaml.org,2002:  \n
//      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
//
func yaml_parser_scan_directive(parser *yaml_parser_t, token *yaml_token_t) bool {
	// Eat '%'.
	start_mark := parser.mark
	skip(parser)

	// Scan the directive name.
	var name []byte
	if !yaml_parser_scan_directive_name(parser, start_mark, &name) {
		return false
	}

	// Is it a YAML directive?
	if bytes.Equal(name, []byte("YAML")) {
		// Scan the VERSION directive value.
		var major, minor int8
		if !yaml_parser_scan_version_directive_value(parser, start_mark, &major, &minor) {
			return false
		}
		end_mark := parser.mark

		// Create a VERSION-DIRECTIVE token.
		*token = yaml_token_t{
			typ:        yaml_VERSION_DIRECTIVE_TOKEN,
			start_mark: start_mark,
			end_mark:   end_mark,
			major:      major,
			minor:      minor,
		}

		// Is it a TAG directive?
	} else if bytes.Equal(name, []byte("TAG")) {
		// Scan the TAG directive value.
		var handle, prefix []byte
		if !yaml_parser_scan_tag_directive_value(parser, start_mark, &handle, &prefix) {
			return false
		}
		end_mark := parser.mark

		// Create a TAG-DIRECTIVE token.
		*token = yaml_token_t{
			typ:        yaml_TAG_DIRECTIVE_TOKEN,
			start_mark: start_mark,
			end_mark:   end_mark,
			value:      handle,
			prefix:     prefix,
		}

		// Unknown directive.
	} else {
		yaml_parser_set_scanner_error(parser, "while scanning a directive",
			start_mark, "found unknown directive name")
		return false
	}

	// Eat the rest of the line including any comments.
	if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
		return false
	}

	for is_blank(parser.buffer, parser.buffer_pos) {
		skip(parser)
		if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
			return false
		}
	}

	if parser.buffer[parser.buffer_pos] == '#' {
		for !is_breakz(parser.buffer, parser.buffer_pos) {
			skip(parser)
			if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
				return false
			}
		}
	}

	// Check if we are at the end of the line.
	if !is_breakz(parser.buffer, parser.buffer_pos) {
		yaml_parser_set_scanner_error(parser, "while scanning a directive",
			start_mark, "did not find expected comment or line break")
		return false
	}

	// Eat a line break.
	if is_break(parser.buffer, parser.buffer_pos) {
		if parser.unread < 2 && !yaml_parser_update_buffer(parser, 2) {
			return false
		}
		skip_line(parser)
	}

	return true
}

// Scan the directive name.
//
// Scope:
//      %YAML   1.1     # a comment \n
//       ^^^^
//      %TAG    !yaml!  tag:yaml.org,2002:  \n
//       ^^^
//
func yaml_parser_scan_directive_name(parser *yaml_parser_t, start_mark yaml_mark_t, name *[]byte) bool {
	// Consume the directive name.
	if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
		return false
	}

	var s []byte
	for is_alpha(parser.buffer, parser.buffer_pos) {
		s = read(parser, s)
		if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
			return false
		}
	}

	// Check if the name is empty.
	if len(s) == 0 {
		yaml_parser_set_scanner_error(parser, "while scanning a directive",
			start_mark, "could not find expected directive name")
		return false
	}

	// Check for an blank character after the name.
	if !is_blankz(parser.buffer, parser.buffer_pos) {
		yaml_parser_set_scanner_error(parser, "while scanning a directive",
			start_mark, "found unexpected non-alphabetical character")
		return false
	}
	*name = s
	return true
}

// Scan the value of VERSION-DIRECTIVE.
//
// Scope:
//      %YAML   1.1     # a comment \n
//           ^^^^^^
func yaml_parser_scan_version_directive_value(parser *yaml_parser_t, start_mark yaml_mark_t, major, minor *int8) bool {
	// Eat whitespaces.
	if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
		return false
	}
	for is_blank(parser.buffer, parser.buffer_pos) {
		skip(parser)
		if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
			return false
		}
	}

	// Consume the major version number.
	if !yaml_parser_scan_version_directive_number(parser, start_mark, major) {
		return false
	}

	// Eat '.'.
	if parser.buffer[parser.buffer_pos] != '.' {
		return yaml_parser_set_scanner_error(parser, "while scanning a %YAML directive",
			start_mark, "did not find expected digit or '.' character")
	}

	skip(parser)

	// Consume the minor version number.
	if !yaml_parser_scan_version_directive_number(parser, start_mark, minor) {
		return false
	}
	return true
}

const max_number_length = 2

// Scan the version number of VERSION-DIRECTIVE.
//
// Scope:
//      %YAML   1.1     # a comment \n
//              ^
//      %YAML   1.1     # a comment \n
//                ^
func yaml_parser_scan_version_directive_number(parser *yaml_parser_t, start_mark yaml_mark_t, number *int8) bool {

	// Repeat while the next character is digit.
	if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
		return false
	}
	var value, length int8
	for is_digit(parser.buffer, parser.buffer_pos) {
		// Check if the number is too long.
		length++
		if length > max_number_length {
			return yaml_parser_set_scanner_error(parser, "while scanning a %YAML directive",
				start_mark, "found extremely long version number")
		}
		value = value*10 + int8(as_digit(parser.buffer, parser.buffer_pos))
		skip(parser)
		if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
			return false
		}
	}

	// Check if the number was present.
	if length == 0 {
		return yaml_parser_set_scanner_error(parser, "while scanning a %YAML directive",
			start_mark, "did not find expected version number")
	}
	*number = value
	return true
}

// Scan the value of a TAG-DIRECTIVE token.
//
// Scope:
//      %TAG    !yaml!  tag:yaml.org,2002:  \n
//          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
//
func yaml_parser_scan_tag_directive_value(parser *yaml_parser_t, start_mark yaml_mark_t, handle, prefix *[]byte) bool {
	var handle_value, prefix_value []byte

	// Eat whitespaces.
	if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
		return false
	}

	for is_blank(parser.buffer, parser.buffer_pos) {
		skip(parser)
		if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
			return false
		}
	}

	// Scan a handle.
	if !yaml_parser_scan_tag_handle(parser, true, start_mark, &handle_value) {
		return false
	}

	// Expect a whitespace.
	if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
		return false
	}
	if !is_blank(parser.buffer, parser.buffer_pos) {
		yaml_parser_set_scanner_error(parser, "while scanning a %TAG directive",
			start_mark, "did not find expected whitespace")
		return false
	}

	// Eat whitespaces.
	for is_blank(parser.buffer, parser.buffer_pos) {
		skip(parser)
		if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
			return false
		}
	}

	// Scan a prefix.
	if !yaml_parser_scan_tag_uri(parser, true, nil, start_mark, &prefix_value) {
		return false
	}

	// Expect a whitespace or line break.
	if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
		return false
	}
	if !is_blankz(parser.buffer, parser.buffer_pos) {
		yaml_parser_set_scanner_error(parser, "while scanning a %TAG directive",
			start_mark, "did not find expected whitespace or line break")
		return false
	}

	*handle = handle_value
	*prefix = prefix_value
	return true
}

func yaml_parser_scan_anchor(parser *yaml_parser_t, token *yaml_token_t, typ yaml_token_type_t) bool {
	var s []byte

	// Eat the indicator character.
	start_mark := parser.mark
	skip(parser)

	// Consume the value.
	if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
		return false
	}

	for is_alpha(parser.buffer, parser.buffer_pos) {
		s = read(parser, s)
		if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
			return false
		}
	}

	end_mark := parser.mark

	/*
	 * Check if length of the anchor is greater than 0 and it is followed by
	 * a whitespace character or one of the indicators:
	 *
	 *      '?', ':', ',', ']', '}', '%', '@', '`'.
	 */

	if len(s) == 0 ||
		!(is_blankz(parser.buffer, parser.buffer_pos) || parser.buffer[parser.buffer_pos] == '?' ||
			parser.buffer[parser.buffer_pos] == ':' || parser.buffer[parser.buffer_pos] == ',' ||
			parser.buffer[parser.buffer_pos] == ']' || parser.buffer[parser.buffer_pos] == '}' ||
			parser.buffer[parser.buffer_pos] == '%' || parser.buffer[parser.buffer_pos] == '@' ||
			parser.buffer[parser.buffer_pos] == '`') {
		context := "while scanning an alias"
		if typ == yaml_ANCHOR_TOKEN {
			context = "while scanning an anchor"
		}
		yaml_parser_set_scanner_error(parser, context, start_mark,
			"did not find expected alphabetic or numeric character")
		return false
	}

	// Create a token.
	*token = yaml_token_t{
		typ:        typ,
		start_mark: start_mark,
		end_mark:   end_mark,
		value:      s,
	}

	return true
}

/*
 * Scan a TAG token.
 */

func yaml_parser_scan_tag(parser *yaml_parser_t, token *yaml_token_t) bool {
	var handle, suffix []byte

	start_mark := parser.mark

	// Check if the tag is in the canonical form.
	if parser.unread < 2 && !yaml_parser_update_buffer(parser, 2) {
		return false
	}

	if parser.buffer[parser.buffer_pos+1] == '<' {
		// Keep the handle as ''

		// Eat '!<'
		skip(parser)
		skip(parser)

		// Consume the tag value.
		if !yaml_parser_scan_tag_uri(parser, false, nil, start_mark, &suffix) {
			return false
		}

		// Check for '>' and eat it.
		if parser.buffer[parser.buffer_pos] != '>' {
			yaml_parser_set_scanner_error(parser, "while scanning a tag",
				start_mark, "did not find the expected '>'")
			return false
		}

		skip(parser)
	} else {
		// The tag has either the '!suffix' or the '!handle!suffix' form.

		// First, try to scan a handle.
		if !yaml_parser_scan_tag_handle(parser, false, start_mark, &handle) {
			return false
		}

		// Check if it is, indeed, handle.
		if handle[0] == '!' && len(handle) > 1 && handle[len(handle)-1] == '!' {
			// Scan the suffix now.
			if !yaml_parser_scan_tag_uri(parser, false, nil, start_mark, &suffix) {
				return false
			}
		} else {
			// It wasn't a handle after all.  Scan the rest of the tag.
			if !yaml_parser_scan_tag_uri(parser, false, handle, start_mark, &suffix) {
				return false
			}

			// Set the handle to '!'.
			handle = []byte{'!'}

			// A special case: the '!' tag.  Set the handle to '' and the
			// suffix to '!'.
			if len(suffix) == 0 {
				handle, suffix = suffix, handle
			}
		}
	}

	// Check the character which ends the tag.
	if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
		return false
	}
	if !is_blankz(parser.buffer, parser.buffer_pos) {
		yaml_parser_set_scanner_error(parser, "while scanning a tag",
			start_mark, "did not find expected whitespace or line break")
		return false
	}

	end_mark := parser.mark

	// Create a token.
	*token = yaml_token_t{
		typ:        yaml_TAG_TOKEN,
		start_mark: start_mark,
		end_mark:   end_mark,
		value:      handle,
		suffix:     suffix,
	}
	return true
}

// Scan a tag handle.
func yaml_parser_scan_tag_handle(parser *yaml_parser_t, directive bool, start_mark yaml_mark_t, handle *[]byte) bool {
	// Check the initial '!' character.
	if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
		return false
	}
	if parser.buffer[parser.buffer_pos] != '!' {
		yaml_parser_set_scanner_tag_error(parser, directive,
			start_mark, "did not find expected '!'")
		return false
	}

	var s []byte

	// Copy the '!' character.
	s = read(parser, s)

	// Copy all subsequent alphabetical and numerical characters.
	if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
		return false
	}
	for is_alpha(parser.buffer, parser.buffer_pos) {
		s = read(parser, s)
		if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
			return false
		}
	}

	// Check if the trailing character is '!' and copy it.
	if parser.buffer[parser.buffer_pos] == '!' {
		s = read(parser, s)
	} else {
		// It's either the '!' tag or not really a tag handle.  If it's a %TAG
		// directive, it's an error.  If it's a tag token, it must be a part of URI.
		if directive && !(s[0] == '!' && s[1] == 0) {
			yaml_parser_set_scanner_tag_error(parser, directive,
				start_mark, "did not find expected '!'")
			return false
		}
	}

	*handle = s
	return true
}

// Scan a tag.
func yaml_parser_scan_tag_uri(parser *yaml_parser_t, directive bool, head []byte, start_mark yaml_mark_t, uri *[]byte) bool {
	//size_t length = head ? strlen((char *)head) : 0
	var s []byte

	// Copy the head if needed.
	//
	// Note that we don't copy the leading '!' character.
	if len(head) > 1 {
		s = append(s, head[1:]...)
	}

	// Scan the tag.
	if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
		return false
	}

	// The set of characters that may appear in URI is as follows:
	//
	//      '0'-'9', 'A'-'Z', 'a'-'z', '_', '-', ';', '/', '?', ':', '@', '&',
	//      '=', '+', '$', ',', '.', '!', '~', '*', '\'', '(', ')', '[', ']',
	//      '%'.
	// [Go] Convert this into more reasonable logic.
	for is_alpha(parser.buffer, parser.buffer_pos) || parser.buffer[parser.buffer_pos] == ';' ||
		parser.buffer[parser.buffer_pos] == '/' || parser.buffer[parser.buffer_pos] == '?' ||
		parser.buffer[parser.buffer_pos] == ':' || parser.buffer[parser.buffer_pos] == '@' ||
		parser.buffer[parser.buffer_pos] == '&' || parser.buffer[parser.buffer_pos] == '=' ||
		parser.buffer[parser.buffer_pos] == '+' || parser.buffer[parser.buffer_pos] == '$' ||
		parser.buffer[parser.buffer_pos] == ',' || parser.buffer[parser.buffer_pos] == '.' ||
		parser.buffer[parser.buffer_pos] == '!' || parser.buffer[parser.buffer_pos] == '~' ||
		parser.buffer[parser.buffer_pos] == '*' || parser.buffer[parser.buffer_pos] == '\'' ||
		parser.buffer[parser.buffer_pos] == '(' || parser.buffer[parser.buffer_pos] == ')' ||
		parser.buffer[parser.buffer_pos] == '[' || parser.buffer[parser.buffer_pos] == ']' ||
		parser.buffer[parser.buffer_pos] == '%' {
		// Check if it is a URI-escape sequence.
		if parser.buffer[parser.buffer_pos] == '%' {
			if !yaml_parser_scan_uri_escapes(parser, directive, start_mark, &s) {
				return false
			}
		} else {
			s = read(parser, s)
		}
		if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
			return false
		}
	}

	// Check if the tag is non-empty.
	if len(s) == 0 {
		yaml_parser_set_scanner_tag_error(parser, directive,
			start_mark, "did not find expected tag URI")
		return false
	}
	*uri = s
	return true
}

// Decode an URI-escape sequence corresponding to a single UTF-8 character.
func yaml_parser_scan_uri_escapes(parser *yaml_parser_t, directive bool, start_mark yaml_mark_t, s *[]byte) bool {

	// Decode the required number of characters.
	w := 1024
	for w > 0 {
		// Check for a URI-escaped octet.
		if parser.unread < 3 && !yaml_parser_update_buffer(parser, 3) {
			return false
		}

		if !(parser.buffer[parser.buffer_pos] == '%' &&
			is_hex(parser.buffer, parser.buffer_pos+1) &&
			is_hex(parser.buffer, parser.buffer_pos+2)) {
			return yaml_parser_set_scanner_tag_error(parser, directive,
				start_mark, "did not find URI escaped octet")
		}

		// Get the octet.
		octet := byte((as_hex(parser.buffer, parser.buffer_pos+1) << 4) + as_hex(parser.buffer, parser.buffer_pos+2))

		// If it is the leading octet, determine the length of the UTF-8 sequence.
		if w == 1024 {
			w = width(octet)
			if w == 0 {
				return yaml_parser_set_scanner_tag_error(parser, directive,
					start_mark, "found an incorrect leading UTF-8 octet")
			}
		} else {
			// Check if the trailing octet is correct.
			if octet&0xC0 != 0x80 {
				return yaml_parser_set_scanner_tag_error(parser, directive,
					start_mark, "found an incorrect trailing UTF-8 octet")
			}
		}

		// Copy the octet and move the pointers.
		*s = append(*s, octet)
		skip(parser)
		skip(parser)
		skip(parser)
		w--
	}
	return true
}

// Scan a block scalar.
func yaml_parser_scan_block_scalar(parser *yaml_parser_t, token *yaml_token_t, literal bool) bool {
	// Eat the indicator '|' or '>'.
	start_mark := parser.mark
	skip(parser)

	// Scan the additional block scalar indicators.
	if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
		return false
	}

	// Check for a chomping indicator.
	var chomping, increment int
	if parser.buffer[parser.buffer_pos] == '+' || parser.buffer[parser.buffer_pos] == '-' {
		// Set the chomping method and eat the indicator.
		if parser.buffer[parser.buffer_pos] == '+' {
			chomping = +1
		} else {
			chomping = -1
		}
		skip(parser)

		// Check for an indentation indicator.
		if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
			return false
		}
		if is_digit(parser.buffer, parser.buffer_pos) {
			// Check that the indentation is greater than 0.
			if parser.buffer[parser.buffer_pos] == '0' {
				yaml_parser_set_scanner_error(parser, "while scanning a block scalar",
					start_mark, "found an indentation indicator equal to 0")
				return false
			}

			// Get the indentation level and eat the indicator.
			increment = as_digit(parser.buffer, parser.buffer_pos)
			skip(parser)
		}

	} else if is_digit(parser.buffer, parser.buffer_pos) {
		// Do the same as above, but in the opposite order.

		if parser.buffer[parser.buffer_pos] == '0' {
			yaml_parser_set_scanner_error(parser, "while scanning a block scalar",
				start_mark, "found an indentation indicator equal to 0")
			return false
		}
		increment = as_digit(parser.buffer, parser.buffer_pos)
		skip(parser)

		if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
			return false
		}
		if parser.buffer[parser.buffer_pos] == '+' || parser.buffer[parser.buffer_pos] == '-' {
			if parser.buffer[parser.buffer_pos] == '+' {
				chomping = +1
			} else {
				chomping = -1
			}
			skip(parser)
		}
	}

	// Eat whitespaces and comments to the end of the line.
	if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
		return false
	}
	for is_blank(parser.buffer, parser.buffer_pos) {
		skip(parser)
		if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
			return false
		}
	}
	if parser.buffer[parser.buffer_pos] == '#' {
		for !is_breakz(parser.buffer, parser.buffer_pos) {
			skip(parser)
			if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
				return false
			}
		}
	}

	// Check if we are at the end of the line.
	if !is_breakz(parser.buffer, parser.buffer_pos) {
		yaml_parser_set_scanner_error(parser, "while scanning a block scalar",
			start_mark, "did not find expected comment or line break")
		return false
	}

	// Eat a line break.
	if is_break(parser.buffer, parser.buffer_pos) {
		if parser.unread < 2 && !yaml_parser_update_buffer(parser, 2) {
			return false
		}
		skip_line(parser)
	}

	end_mark := parser.mark

	// Set the indentation level if it was specified.
	var indent int
	if increment > 0 {
		if parser.indent >= 0 {
			indent = parser.indent + increment
		} else {
			indent = increment
		}
	}

	// Scan the leading line breaks and determine the indentation level if needed.
	var s, leading_break, trailing_breaks []byte
	if !yaml_parser_scan_block_scalar_breaks(parser, &indent, &trailing_breaks, start_mark, &end_mark) {
		return false
	}

	// Scan the block scalar content.
	if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
		return false
	}
	var leading_blank, trailing_blank bool
	for parser.mark.column == indent && !is_z(parser.buffer, parser.buffer_pos) {
		// We are at the beginning of a non-empty line.

		// Is it a trailing whitespace?
		trailing_blank = is_blank(parser.buffer, parser.buffer_pos)

		// Check if we need to fold the leading line break.
		if !literal && !leading_blank && !trailing_blank && len(leading_break) > 0 && leading_break[0] == '\n' {
			// Do we need to join the lines by space?
			if len(trailing_breaks) == 0 {
				s = append(s, ' ')
			}
		} else {
			s = append(s, leading_break...)
		}
		leading_break = leading_break[:0]

		// Append the remaining line breaks.
		s = append(s, trailing_breaks...)
		trailing_breaks = trailing_breaks[:0]

		// Is it a leading whitespace?
		leading_blank = is_blank(parser.buffer, parser.buffer_pos)

		// Consume the current line.
		for !is_breakz(parser.buffer, parser.buffer_pos) {
			s = read(parser, s)
			if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
				return false
			}
		}

		// Consume the line break.
		if parser.unread < 2 && !yaml_parser_update_buffer(parser, 2) {
			return false
		}

		leading_break = read_line(parser, leading_break)

		// Eat the following indentation spaces and line breaks.
		if !yaml_parser_scan_block_scalar_breaks(parser, &indent, &trailing_breaks, start_mark, &end_mark) {
			return false
		}
	}

	// Chomp the tail.
	if chomping != -1 {
		s = append(s, leading_break...)
	}
	if chomping == 1 {
		s = append(s, trailing_breaks...)
	}

	// Create a token.
	*token = yaml_token_t{
		typ:        yaml_SCALAR_TOKEN,
		start_mark: start_mark,
		end_mark:   end_mark,
		value:      s,
		style:      yaml_LITERAL_SCALAR_STYLE,
	}
	if !literal {
		token.style = yaml_FOLDED_SCALAR_STYLE
	}
	return true
}

// Scan indentation spaces and line breaks for a block scalar.  Determine the
// indentation level if needed.
func yaml_parser_scan_block_scalar_breaks(parser *yaml_parser_t, indent *int, breaks *[]byte, start_mark yaml_mark_t, end_mark *yaml_mark_t) bool {
	*end_mark = parser.mark

	// Eat the indentation spaces and line breaks.
	max_indent := 0
	for {
		// Eat the indentation spaces.
		if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
			return false
		}
		for (*indent == 0 || parser.mark.column < *indent) && is_space(parser.buffer, parser.buffer_pos) {
			skip(parser)
			if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
				return false
			}
		}
		if parser.mark.column > max_indent {
			max_indent = parser.mark.column
		}

		// Check for a tab character messing the indentation.
		if (*indent == 0 || parser.mark.column < *indent) && is_tab(parser.buffer, parser.buffer_pos) {
			return yaml_parser_set_scanner_error(parser, "while scanning a block scalar",
				start_mark, "found a tab character where an indentation space is expected")
		}

		// Have we found a non-empty line?
		if !is_break(parser.buffer, parser.buffer_pos) {
			break
		}

		// Consume the line break.
		if parser.unread < 2 && !yaml_parser_update_buffer(parser, 2) {
			return false
		}
		// [Go] Should really be returning breaks instead.
		*breaks = read_line(parser, *breaks)
		*end_mark = parser.mark
	}

	// Determine the indentation level if needed.
	if *indent == 0 {
		*indent = max_indent
		if *indent < parser.indent+1 {
			*indent = parser.indent + 1
		}
		if *indent < 1 {
			*indent = 1
		}
	}
	return true
}

// Scan a quoted scalar.
func yaml_parser_scan_flow_scalar(parser *yaml_parser_t, token *yaml_token_t, single bool) bool {
	// Eat the left quote.
	start_mark := parser.mark
	skip(parser)

	// Consume the content of the quoted scalar.
	var s, leading_break, trailing_breaks, whitespaces []byte
	for {
		// Check that there are no document indicators at the beginning of the line.
		if parser.unread < 4 && !yaml_parser_update_buffer(parser, 4) {
			return false
		}

		if parser.mark.column == 0 &&
			((parser.buffer[parser.buffer_pos+0] == '-' &&
				parser.buffer[parser.buffer_pos+1] == '-' &&
				parser.buffer[parser.buffer_pos+2] == '-') ||
				(parser.buffer[parser.buffer_pos+0] == '.' &&
					parser.buffer[parser.buffer_pos+1] == '.' &&
					parser.buffer[parser.buffer_pos+2] == '.')) &&
			is_blankz(parser.buffer, parser.buffer_pos+3) {
			yaml_parser_set_scanner_error(parser, "while scanning a quoted scalar",
				start_mark, "found unexpected document indicator")
			return false
		}

		// Check for EOF.
		if is_z(parser.buffer, parser.buffer_pos) {
			yaml_parser_set_scanner_error(parser, "while scanning a quoted scalar",
				start_mark, "found unexpected end of stream")
			return false
		}

		// Consume non-blank characters.
		leading_blanks := false
		for !is_blankz(parser.buffer, parser.buffer_pos) {
			if single && parser.buffer[parser.buffer_pos] == '\'' && parser.buffer[parser.buffer_pos+1] == '\'' {
				// Is is an escaped single quote.
				s = append(s, '\'')
				skip(parser)
				skip(parser)

			} else if single && parser.buffer[parser.buffer_pos] == '\'' {
				// It is a right single quote.
				break
			} else if !single && parser.buffer[parser.buffer_pos] == '"' {
				// It is a right double quote.
				break

			} else if !single && parser.buffer[parser.buffer_pos] == '\\' && is_break(parser.buffer, parser.buffer_pos+1) {
				// It is an escaped line break.
				if parser.unread < 3 && !yaml_parser_update_buffer(parser, 3) {
					return false
				}
				skip(parser)
				skip_line(parser)
				leading_blanks = true
				break

			} else if !single && parser.buffer[parser.buffer_pos] == '\\' {
				// It is an escape sequence.
				code_length := 0

				// Check the escape character.
				switch parser.buffer[parser.buffer_pos+1] {
				case '0':
					s = append(s, 0)
				case 'a':
					s = append(s, '\x07')
				case 'b':
					s = append(s, '\x08')
				case 't', '\t':
					s = append(s, '\x09')
				case 'n':
					s = append(s, '\x0A')
				case 'v':
					s = append(s, '\x0B')
				case 'f':
					s = append(s, '\x0C')
				case 'r':
					s = append(s, '\x0D')
				case 'e':
					s = append(s, '\x1B')
				case ' ':
					s = append(s, '\x20')
				case '"':
					s = append(s, '"')
				case '\'':
					s = append(s, '\'')
				case '\\':
					s = append(s, '\\')
				case 'N': // NEL (#x85)
					s = append(s, '\xC2')
					s = append(s, '\x85')
				case '_': // #xA0
					s = append(s, '\xC2')
					s = append(s, '\xA0')
				case 'L': // LS (#x2028)
					s = append(s, '\xE2')
					s = append(s, '\x80')
					s = append(s, '\xA8')
				case 'P': // PS (#x2029)
					s = append(s, '\xE2')
					s = append(s, '\x80')
					s = append(s, '\xA9')
				case 'x':
					code_length = 2
				case 'u':
					code_length = 4
				case 'U':
					code_length = 8
				default:
					yaml_parser_set_scanner_error(parser, "while parsing a quoted scalar",
						start_mark, "found unknown escape character")
					return false
				}

				skip(parser)
				skip(parser)

				// Consume an arbitrary escape code.
				if code_length > 0 {
					var value int

					// Scan the character value.
					if parser.unread < code_length && !yaml_parser_update_buffer(parser, code_length) {
						return false
					}
					for k := 0; k < code_length; k++ {
						if !is_hex(parser.buffer, parser.buffer_pos+k) {
							yaml_parser_set_scanner_error(parser, "while parsing a quoted scalar",
								start_mark, "did not find expected hexdecimal number")
							return false
						}
						value = (value << 4) + as_hex(parser.buffer, parser.buffer_pos+k)
					}

					// Check the value and write the character.
					if (value >= 0xD800 && value <= 0xDFFF) || value > 0x10FFFF {
						yaml_parser_set_scanner_error(parser, "while parsing a quoted scalar",
							start_mark, "found invalid Unicode character escape code")
						return false
					}
					if value <= 0x7F {
						s = append(s, byte(value))
					} else if value <= 0x7FF {
						s = append(s, byte(0xC0+(value>>6)))
						s = append(s, byte(0x80+(value&0x3F)))
					} else if value <= 0xFFFF {
						s = append(s, byte(0xE0+(value>>12)))
						s = append(s, byte(0x80+((value>>6)&0x3F)))
						s = append(s, byte(0x80+(value&0x3F)))
					} else {
						s = append(s, byte(0xF0+(value>>18)))
						s = append(s, byte(0x80+((value>>12)&0x3F)))
						s = append(s, byte(0x80+((value>>6)&0x3F)))
						s = append(s, byte(0x80+(value&0x3F)))
					}

					// Advance the pointer.
					for k := 0; k < code_length; k++ {
						skip(parser)
					}
				}
			} else {
				// It is a non-escaped non-blank character.
				s = read(parser, s)
			}
			if parser.unread < 2 && !yaml_parser_update_buffer(parser, 2) {
				return false
			}
		}

		// Check if we are at the end of the scalar.
		if single {
			if parser.buffer[parser.buffer_pos] == '\'' {
				break
			}
		} else {
			if parser.buffer[parser.buffer_pos] == '"' {
				break
			}
		}

		// Consume blank characters.
		if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
			return false
		}

		for is_blank(parser.buffer, parser.buffer_pos) || is_break(parser.buffer, parser.buffer_pos) {
			if is_blank(parser.buffer, parser.buffer_pos) {
				// Consume a space or a tab character.
				if !leading_blanks {
					whitespaces = read(parser, whitespaces)
				} else {
					skip(parser)
				}
			} else {
				if parser.unread < 2 && !yaml_parser_update_buffer(parser, 2) {
					return false
				}

				// Check if it is a first line break.
				if !leading_blanks {
					whitespaces = whitespaces[:0]
					leading_break = read_line(parser, leading_break)
					leading_blanks = true
				} else {
					trailing_breaks = read_line(parser, trailing_breaks)
				}
			}
			if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
				return false
			}
		}

		// Join the whitespaces or fold line breaks.
		if leading_blanks {
			// Do we need to fold line breaks?
			if len(leading_break) > 0 && leading_break[0] == '\n' {
				if len(trailing_breaks) == 0 {
					s = append(s, ' ')
				} else {
					s = append(s, trailing_breaks...)
				}
			} else {
				s = append(s, leading_break...)
				s = append(s, trailing_breaks...)
			}
			trailing_breaks = trailing_breaks[:0]
			leading_break = leading_break[:0]
		} else {
			s = append(s, whitespaces...)
			whitespaces = whitespaces[:0]
		}
	}

	// Eat the right quote.
	skip(parser)
	end_mark := parser.mark

	// Create a token.
	*token = yaml_token_t{
		typ:        yaml_SCALAR_TOKEN,
		start_mark: start_mark,
		end_mark:   end_mark,
		value:      s,
		style:      yaml_SINGLE_QUOTED_SCALAR_STYLE,
	}
	if !single {
		token.style = yaml_DOUBLE_QUOTED_SCALAR_STYLE
	}
	return true
}

// Scan a plain scalar.
func yaml_parser_scan_plain_scalar(parser *yaml_parser_t, token *yaml_token_t) bool {

	var s, leading_break, trailing_breaks, whitespaces []byte
	var leading_blanks bool
	var indent = parser.indent + 1

	start_mark := parser.mark
	end_mark := parser.mark

	// Consume the content of the plain scalar.
	for {
		// Check for a document indicator.
		if parser.unread < 4 && !yaml_parser_update_buffer(parser, 4) {
			return false
		}
		if parser.mark.column == 0 &&
			((parser.buffer[parser.buffer_pos+0] == '-' &&
				parser.buffer[parser.buffer_pos+1] == '-' &&
				parser.buffer[parser.buffer_pos+2] == '-') ||
				(parser.buffer[parser.buffer_pos+0] == '.' &&
					parser.buffer[parser.buffer_pos+1] == '.' &&
					parser.buffer[parser.buffer_pos+2] == '.')) &&
			is_blankz(parser.buffer, parser.buffer_pos+3) {
			break
		}

		// Check for a comment.
		if parser.buffer[parser.buffer_pos] == '#' {
			break
		}

		// Consume non-blank characters.
		for !is_blankz(parser.buffer, parser.buffer_pos) {

			// Check for 'x:x' in the flow context. TODO: Fix the test "spec-08-13".
			if parser.flow_level > 0 &&
				parser.buffer[parser.buffer_pos] == ':' &&
				!is_blankz(parser.buffer, parser.buffer_pos+1) {
				yaml_parser_set_scanner_error(parser, "while scanning a plain scalar",
					start_mark, "found unexpected ':'")
				return false
			}

			// Check for indicators that may end a plain scalar.
			if (parser.buffer[parser.buffer_pos] == ':' && is_blankz(parser.buffer, parser.buffer_pos+1)) ||
				(parser.flow_level > 0 &&
					(parser.buffer[parser.buffer_pos] == ',' || parser.buffer[parser.buffer_pos] == ':' ||
						parser.buffer[parser.buffer_pos] == '?' || parser.buffer[parser.buffer_pos] == '[' ||
						parser.buffer[parser.buffer_pos] == ']' || parser.buffer[parser.buffer_pos] == '{' ||
						parser.buffer[parser.buffer_pos] == '}')) {
				break
			}

			// Check if we need to join whitespaces and breaks.
			if leading_blanks || len(whitespaces) > 0 {
				if leading_blanks {
					// Do we need to fold line breaks?
					if leading_break[0] == '\n' {
						if len(trailing_breaks) == 0 {
							s = append(s, ' ')
						} else {
							s = append(s, trailing_breaks...)
						}
					} else {
						s = append(s, leading_break...)
						s = append(s, trailing_breaks...)
					}
					trailing_breaks = trailing_breaks[:0]
					leading_break = leading_break[:0]
					leading_blanks = false
				} else {
					s = append(s, whitespaces...)
					whitespaces = whitespaces[:0]
				}
			}

			// Copy the character.
			s = read(parser, s)

			end_mark = parser.mark
			if parser.unread < 2 && !yaml_parser_update_buffer(parser, 2) {
				return false
			}
		}

		// Is it the end?
		if !(is_blank(parser.buffer, parser.buffer_pos) || is_break(parser.buffer, parser.buffer_pos)) {
			break
		}

		// Consume blank characters.
		if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
			return false
		}

		for is_blank(parser.buffer, parser.buffer_pos) || is_break(parser.buffer, parser.buffer_pos) {
			if is_blank(parser.buffer, parser.buffer_pos) {

				// Check for tab character that abuse indentation.
				if leading_blanks && parser.mark.column < indent && is_tab(parser.buffer, parser.buffer_pos) {
					yaml_parser_set_scanner_error(parser, "while scanning a plain scalar",
						start_mark, "found a tab character that violate indentation")
					return false
				}

				// Consume a space or a tab character.
				if !leading_blanks {
					whitespaces = read(parser, whitespaces)
				} else {
					skip(parser)
				}
			} else {
				if parser.unread < 2 && !yaml_parser_update_buffer(parser, 2) {
					return false
				}

				// Check if it is a first line break.
				if !leading_blanks {
					whitespaces = whitespaces[:0]
					leading_break = read_line(parser, leading_break)
					leading_blanks = true
				} else {
					trailing_breaks = read_line(parser, trailing_breaks)
				}
			}
			if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
				return false
			}
		}

		// Check indentation level.
		if parser.flow_level == 0 && parser.mark.column < indent {
			break
		}
	}

	// Create a token.
	*token = yaml_token_t{
		typ:        yaml_SCALAR_TOKEN,
		start_mark: start_mark,
		end_mark:   end_mark,
		value:      s,
		style:      yaml_PLAIN_SCALAR_STYLE,
	}

	// Note that we change the 'simple_key_allowed' flag.
	if leading_blanks {
		parser.simple_key_allowed = true
	}
	return true
}