Linux debugging

Check our new training course

Linux debugging, tracing, profiling & perf. analysis

Check our new training course
with Creative Commons CC-BY-SA
lecture and lab materials

Bootlin logo

Elixir Cross Referencer

   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
/* vi: set sw=4 ts=4: */
/*
 * Mini less implementation for busybox
 *
 * Copyright (C) 2005 by Rob Sullivan <cogito.ergo.cogito@gmail.com>
 *
 * Licensed under the GPL v2 or later, see the file LICENSE in this tarball.
 */

/*
 * TODO:
 * - Add more regular expression support - search modifiers, certain matches, etc.
 * - Add more complex bracket searching - currently, nested brackets are
 *   not considered.
 * - Add support for "F" as an input. This causes less to act in
 *   a similar way to tail -f.
 * - Allow horizontal scrolling.
 *
 * Notes:
 * - the inp file pointer is used so that keyboard input works after
 *   redirected input has been read from stdin
 */

#include <sched.h>	/* sched_yield() */

#include "libbb.h"
#if ENABLE_FEATURE_LESS_REGEXP
#include "xregex.h"
#endif

/* The escape codes for highlighted and normal text */
#define HIGHLIGHT "\033[7m"
#define NORMAL "\033[0m"
/* The escape code to clear the screen */
#define CLEAR "\033[H\033[J"
/* The escape code to clear to end of line */
#define CLEAR_2_EOL "\033[K"

enum {
/* Absolute max of lines eaten */
	MAXLINES = CONFIG_FEATURE_LESS_MAXLINES,
/* This many "after the end" lines we will show (at max) */
	TILDES = 1,
};

/* Command line options */
enum {
	FLAG_E = 1 << 0,
	FLAG_M = 1 << 1,
	FLAG_m = 1 << 2,
	FLAG_N = 1 << 3,
	FLAG_TILDE = 1 << 4,
	FLAG_I = 1 << 5,
	FLAG_S = (1 << 6) * ENABLE_FEATURE_LESS_DASHCMD,
/* hijack command line options variable for internal state vars */
	LESS_STATE_MATCH_BACKWARDS = 1 << 15,
};

#if !ENABLE_FEATURE_LESS_REGEXP
enum { pattern_valid = 0 };
#endif

struct globals {
	int cur_fline; /* signed */
	int kbd_fd;  /* fd to get input from */
	int less_gets_pos;
/* last position in last line, taking into account tabs */
	size_t last_line_pos;
	unsigned max_fline;
	unsigned max_lineno; /* this one tracks linewrap */
	unsigned max_displayed_line;
	unsigned width;
#if ENABLE_FEATURE_LESS_WINCH
	unsigned winch_counter;
#endif
	ssize_t eof_error; /* eof if 0, error if < 0 */
	ssize_t readpos;
	ssize_t readeof; /* must be signed */
	const char **buffer;
	const char **flines;
	const char *empty_line_marker;
	unsigned num_files;
	unsigned current_file;
	char *filename;
	char **files;
#if ENABLE_FEATURE_LESS_MARKS
	unsigned num_marks;
	unsigned mark_lines[15][2];
#endif
#if ENABLE_FEATURE_LESS_REGEXP
	unsigned *match_lines;
	int match_pos; /* signed! */
	int wanted_match; /* signed! */
	int num_matches;
	regex_t pattern;
	smallint pattern_valid;
#endif
	smallint terminated;
	smalluint kbd_input_size;
	struct termios term_orig, term_less;
	char kbd_input[KEYCODE_BUFFER_SIZE];
};
#define G (*ptr_to_globals)
#define cur_fline           (G.cur_fline         )
#define kbd_fd              (G.kbd_fd            )
#define less_gets_pos       (G.less_gets_pos     )
#define last_line_pos       (G.last_line_pos     )
#define max_fline           (G.max_fline         )
#define max_lineno          (G.max_lineno        )
#define max_displayed_line  (G.max_displayed_line)
#define width               (G.width             )
#define winch_counter       (G.winch_counter     )
/* This one is 100% not cached by compiler on read access */
#define WINCH_COUNTER (*(volatile unsigned *)&winch_counter)
#define eof_error           (G.eof_error         )
#define readpos             (G.readpos           )
#define readeof             (G.readeof           )
#define buffer              (G.buffer            )
#define flines              (G.flines            )
#define empty_line_marker   (G.empty_line_marker )
#define num_files           (G.num_files         )
#define current_file        (G.current_file      )
#define filename            (G.filename          )
#define files               (G.files             )
#define num_marks           (G.num_marks         )
#define mark_lines          (G.mark_lines        )
#if ENABLE_FEATURE_LESS_REGEXP
#define match_lines         (G.match_lines       )
#define match_pos           (G.match_pos         )
#define num_matches         (G.num_matches       )
#define wanted_match        (G.wanted_match      )
#define pattern             (G.pattern           )
#define pattern_valid       (G.pattern_valid     )
#endif
#define terminated          (G.terminated        )
#define term_orig           (G.term_orig         )
#define term_less           (G.term_less         )
#define kbd_input_size      (G.kbd_input_size    )
#define kbd_input           (G.kbd_input         )
#define INIT_G() do { \
	SET_PTR_TO_GLOBALS(xzalloc(sizeof(G))); \
	less_gets_pos = -1; \
	empty_line_marker = "~"; \
	num_files = 1; \
	current_file = 1; \
	eof_error = 1; \
	terminated = 1; \
	USE_FEATURE_LESS_REGEXP(wanted_match = -1;) \
} while (0)

/* flines[] are lines read from stdin, each in malloc'ed buffer.
 * Line numbers are stored as uint32_t prepended to each line.
 * Pointer is adjusted so that flines[i] points directly past
 * line number. Accesor: */
#define MEMPTR(p) ((char*)(p) - 4)
#define LINENO(p) (*(uint32_t*)((p) - 4))


/* Reset terminal input to normal */
static void set_tty_cooked(void)
{
	fflush(stdout);
	tcsetattr(kbd_fd, TCSANOW, &term_orig);
}

/* Move the cursor to a position (x,y), where (0,0) is the
   top-left corner of the console */
static void move_cursor(int line, int row)
{
	printf("\033[%u;%uH", line, row);
}

static void clear_line(void)
{
	printf("\033[%u;0H" CLEAR_2_EOL, max_displayed_line + 2);
}

static void print_hilite(const char *str)
{
	printf(HIGHLIGHT"%s"NORMAL, str);
}

static void print_statusline(const char *str)
{
	clear_line();
	printf(HIGHLIGHT"%.*s"NORMAL, width - 1, str);
}

/* Exit the program gracefully */
static void less_exit(int code)
{
	set_tty_cooked();
	clear_line();
	if (code < 0)
		kill_myself_with_sig(- code); /* does not return */
	exit(code);
}

#if (ENABLE_FEATURE_LESS_DASHCMD && ENABLE_FEATURE_LESS_LINENUMS) \
 || ENABLE_FEATURE_LESS_WINCH
static void re_wrap(void)
{
	int w = width;
	int new_line_pos;
	int src_idx;
	int dst_idx;
	int new_cur_fline = 0;
	uint32_t lineno;
	char linebuf[w + 1];
	const char **old_flines = flines;
	const char *s;
	char **new_flines = NULL;
	char *d;

	if (option_mask32 & FLAG_N)
		w -= 8;

	src_idx = 0;
	dst_idx = 0;
	s = old_flines[0];
	lineno = LINENO(s);
	d = linebuf;
	new_line_pos = 0;
	while (1) {
		*d = *s;
		if (*d != '\0') {
			new_line_pos++;
			if (*d == '\t') /* tab */
				new_line_pos += 7;
			s++;
			d++;
			if (new_line_pos >= w) {
				int sz;
				/* new line is full, create next one */
				*d = '\0';
 next_new:
				sz = (d - linebuf) + 1; /* + 1: NUL */
				d = ((char*)xmalloc(sz + 4)) + 4;
				LINENO(d) = lineno;
				memcpy(d, linebuf, sz);
				new_flines = xrealloc_vector(new_flines, 8, dst_idx);
				new_flines[dst_idx] = d;
				dst_idx++;
				if (new_line_pos < w) {
					/* if we came here thru "goto next_new" */
					if (src_idx > max_fline)
						break;
					lineno = LINENO(s);
				}
				d = linebuf;
				new_line_pos = 0;
			}
			continue;
		}
		/* *d == NUL: old line ended, go to next old one */
		free(MEMPTR(old_flines[src_idx]));
		/* btw, convert cur_fline... */
		if (cur_fline == src_idx)
			new_cur_fline = dst_idx;
		src_idx++;
		/* no more lines? finish last new line (and exit the loop) */
		if (src_idx > max_fline)
			goto next_new;
		s = old_flines[src_idx];
		if (lineno != LINENO(s)) {
			/* this is not a continuation line!
			 * create next _new_ line too */
			goto next_new;
		}
	}

	free(old_flines);
	flines = (const char **)new_flines;

	max_fline = dst_idx - 1;
	last_line_pos = new_line_pos;
	cur_fline = new_cur_fline;
	/* max_lineno is screen-size independent */
#if ENABLE_FEATURE_LESS_REGEXP
	pattern_valid = 0;
#endif
}
#endif

#if ENABLE_FEATURE_LESS_REGEXP
static void fill_match_lines(unsigned pos);
#else
#define fill_match_lines(pos) ((void)0)
#endif

/* Devilishly complex routine.
 *
 * Has to deal with EOF and EPIPE on input,
 * with line wrapping, with last line not ending in '\n'
 * (possibly not ending YET!), with backspace and tabs.
 * It reads input again if last time we got an EOF (thus supporting
 * growing files) or EPIPE (watching output of slow process like make).
 *
 * Variables used:
 * flines[] - array of lines already read. Linewrap may cause
 *      one source file line to occupy several flines[n].
 * flines[max_fline] - last line, possibly incomplete.
 * terminated - 1 if flines[max_fline] is 'terminated'
 *      (if there was '\n' [which isn't stored itself, we just remember
 *      that it was seen])
 * max_lineno - last line's number, this one doesn't increment
 *      on line wrap, only on "real" new lines.
 * readbuf[0..readeof-1] - small preliminary buffer.
 * readbuf[readpos] - next character to add to current line.
 * last_line_pos - screen line position of next char to be read
 *      (takes into account tabs and backspaces)
 * eof_error - < 0 error, == 0 EOF, > 0 not EOF/error
 */
static void read_lines(void)
{
#define readbuf bb_common_bufsiz1
	char *current_line, *p;
	int w = width;
	char last_terminated = terminated;
#if ENABLE_FEATURE_LESS_REGEXP
	unsigned old_max_fline = max_fline;
	time_t last_time = 0;
	unsigned seconds_p1 = 3; /* seconds_to_loop + 1 */
#endif

	if (option_mask32 & FLAG_N)
		w -= 8;

 USE_FEATURE_LESS_REGEXP(again0:)

	p = current_line = ((char*)xmalloc(w + 4)) + 4;
	max_fline += last_terminated;
	if (!last_terminated) {
		const char *cp = flines[max_fline];
		strcpy(p, cp);
		p += strlen(current_line);
		free(MEMPTR(flines[max_fline]));
		/* last_line_pos is still valid from previous read_lines() */
	} else {
		last_line_pos = 0;
	}

	while (1) { /* read lines until we reach cur_fline or wanted_match */
		*p = '\0';
		terminated = 0;
		while (1) { /* read chars until we have a line */
			char c;
			/* if no unprocessed chars left, eat more */
			if (readpos >= readeof) {
				ndelay_on(0);
				eof_error = safe_read(STDIN_FILENO, readbuf, sizeof(readbuf));
				ndelay_off(0);
				readpos = 0;
				readeof = eof_error;
				if (eof_error <= 0)
					goto reached_eof;
			}
			c = readbuf[readpos];
			/* backspace? [needed for manpages] */
			/* <tab><bs> is (a) insane and */
			/* (b) harder to do correctly, so we refuse to do it */
			if (c == '\x8' && last_line_pos && p[-1] != '\t') {
				readpos++; /* eat it */
				last_line_pos--;
			/* was buggy (p could end up <= current_line)... */
				*--p = '\0';
				continue;
			}
			{
				size_t new_last_line_pos = last_line_pos + 1;
				if (c == '\t') {
					new_last_line_pos += 7;
					new_last_line_pos &= (~7);
				}
				if ((int)new_last_line_pos >= w)
					break;
				last_line_pos = new_last_line_pos;
			}
			/* ok, we will eat this char */
			readpos++;
			if (c == '\n') {
				terminated = 1;
				last_line_pos = 0;
				break;
			}
			/* NUL is substituted by '\n'! */
			if (c == '\0') c = '\n';
			*p++ = c;
			*p = '\0';
		} /* end of "read chars until we have a line" loop */
		/* Corner case: linewrap with only "" wrapping to next line */
		/* Looks ugly on screen, so we do not store this empty line */
		if (!last_terminated && !current_line[0]) {
			last_terminated = 1;
			max_lineno++;
			continue;
		}
 reached_eof:
		last_terminated = terminated;
		flines = xrealloc_vector(flines, 8, max_fline);

		flines[max_fline] = (char*)xrealloc(MEMPTR(current_line), strlen(current_line) + 1 + 4) + 4;
		LINENO(flines[max_fline]) = max_lineno;
		if (terminated)
			max_lineno++;

		if (max_fline >= MAXLINES) {
			eof_error = 0; /* Pretend we saw EOF */
			break;
		}
		if (!(option_mask32 & FLAG_S)
		  ? (max_fline > cur_fline + max_displayed_line)
		  : (max_fline >= cur_fline
		     && max_lineno > LINENO(flines[cur_fline]) + max_displayed_line)
		) {
#if !ENABLE_FEATURE_LESS_REGEXP
			break;
#else
			if (wanted_match >= num_matches) { /* goto_match called us */
				fill_match_lines(old_max_fline);
				old_max_fline = max_fline;
			}
			if (wanted_match < num_matches)
				break;
#endif
		}
		if (eof_error <= 0) {
			if (eof_error < 0) {
				if (errno == EAGAIN) {
					/* not yet eof or error, reset flag (or else
					 * we will hog CPU - select() will return
					 * immediately */
					eof_error = 1;
				} else {
					print_statusline("read error");
				}
			}
#if !ENABLE_FEATURE_LESS_REGEXP
			break;
#else
			if (wanted_match < num_matches) {
				break;
			} else { /* goto_match called us */
				time_t t = time(NULL);
				if (t != last_time) {
					last_time = t;
					if (--seconds_p1 == 0)
						break;
				}
				sched_yield();
				goto again0; /* go loop again (max 2 seconds) */
			}
#endif
		}
		max_fline++;
		current_line = ((char*)xmalloc(w + 4)) + 4;
		p = current_line;
		last_line_pos = 0;
	} /* end of "read lines until we reach cur_fline" loop */
	fill_match_lines(old_max_fline);
#if ENABLE_FEATURE_LESS_REGEXP
	/* prevent us from being stuck in search for a match */
	wanted_match = -1;
#endif
#undef readbuf
}

#if ENABLE_FEATURE_LESS_FLAGS
/* Interestingly, writing calc_percent as a function saves around 32 bytes
 * on my build. */
static int calc_percent(void)
{
	unsigned p = (100 * (cur_fline+max_displayed_line+1) + max_fline/2) / (max_fline+1);
	return p <= 100 ? p : 100;
}

/* Print a status line if -M was specified */
static void m_status_print(void)
{
	int percentage;

	if (less_gets_pos >= 0)	/* don't touch statusline while input is done! */
		return;

	clear_line();
	printf(HIGHLIGHT"%s", filename);
	if (num_files > 1)
		printf(" (file %i of %i)", current_file, num_files);
	printf(" lines %i-%i/%i ",
			cur_fline + 1, cur_fline + max_displayed_line + 1,
			max_fline + 1);
	if (cur_fline >= (int)(max_fline - max_displayed_line)) {
		printf("(END)"NORMAL);
		if (num_files > 1 && current_file != num_files)
			printf(HIGHLIGHT" - next: %s"NORMAL, files[current_file]);
		return;
	}
	percentage = calc_percent();
	printf("%i%%"NORMAL, percentage);
}
#endif

/* Print the status line */
static void status_print(void)
{
	const char *p;

	if (less_gets_pos >= 0)	/* don't touch statusline while input is done! */
		return;

	/* Change the status if flags have been set */
#if ENABLE_FEATURE_LESS_FLAGS
	if (option_mask32 & (FLAG_M|FLAG_m)) {
		m_status_print();
		return;
	}
	/* No flags set */
#endif

	clear_line();
	if (cur_fline && cur_fline < (int)(max_fline - max_displayed_line)) {
		bb_putchar(':');
		return;
	}
	p = "(END)";
	if (!cur_fline)
		p = filename;
	if (num_files > 1) {
		printf(HIGHLIGHT"%s (file %i of %i)"NORMAL,
				p, current_file, num_files);
		return;
	}
	print_hilite(p);
}

static void cap_cur_fline(int nlines)
{
	int diff;
	if (cur_fline < 0)
		cur_fline = 0;
	if (cur_fline + max_displayed_line > max_fline + TILDES) {
		cur_fline -= nlines;
		if (cur_fline < 0)
			cur_fline = 0;
		diff = max_fline - (cur_fline + max_displayed_line) + TILDES;
		/* As the number of lines requested was too large, we just move
		to the end of the file */
		if (diff > 0)
			cur_fline += diff;
	}
}

static const char controls[] ALIGN1 =
	/* NUL: never encountered; TAB: not converted */
	/**/"\x01\x02\x03\x04\x05\x06\x07\x08"  "\x0a\x0b\x0c\x0d\x0e\x0f"
	"\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f"
	"\x7f\x9b"; /* DEL and infamous Meta-ESC :( */
static const char ctrlconv[] ALIGN1 =
	/* '\n': it's a former NUL - subst with '@', not 'J' */
	"\x40\x41\x42\x43\x44\x45\x46\x47\x48\x49\x40\x4b\x4c\x4d\x4e\x4f"
	"\x50\x51\x52\x53\x54\x55\x56\x57\x58\x59\x5a\x5b\x5c\x5d\x5e\x5f";

static void lineno_str(char *nbuf9, const char *line)
{
	nbuf9[0] = '\0';
	if (option_mask32 & FLAG_N) {
		const char *fmt;
		unsigned n;

		if (line == empty_line_marker) {
			memset(nbuf9, ' ', 8);
			nbuf9[8] = '\0';
			return;
		}
		/* Width of 7 preserves tab spacing in the text */
		fmt = "%7u ";
		n = LINENO(line) + 1;
		if (n > 9999999) {
			n %= 10000000;
			fmt = "%07u ";
		}
		sprintf(nbuf9, fmt, n);
	}
}


#if ENABLE_FEATURE_LESS_REGEXP
static void print_found(const char *line)
{
	int match_status;
	int eflags;
	char *growline;
	regmatch_t match_structs;

	char buf[width];
	char nbuf9[9];
	const char *str = line;
	char *p = buf;
	size_t n;

	while (*str) {
		n = strcspn(str, controls);
		if (n) {
			if (!str[n]) break;
			memcpy(p, str, n);
			p += n;
			str += n;
		}
		n = strspn(str, controls);
		memset(p, '.', n);
		p += n;
		str += n;
	}
	strcpy(p, str);

	/* buf[] holds quarantined version of str */

	/* Each part of the line that matches has the HIGHLIGHT
	   and NORMAL escape sequences placed around it.
	   NB: we regex against line, but insert text
	   from quarantined copy (buf[]) */
	str = buf;
	growline = NULL;
	eflags = 0;
	goto start;

	while (match_status == 0) {
		char *new = xasprintf("%s%.*s"HIGHLIGHT"%.*s"NORMAL,
				growline ? : "",
				match_structs.rm_so, str,
				match_structs.rm_eo - match_structs.rm_so,
						str + match_structs.rm_so);
		free(growline);
		growline = new;
		str += match_structs.rm_eo;
		line += match_structs.rm_eo;
		eflags = REG_NOTBOL;
 start:
		/* Most of the time doesn't find the regex, optimize for that */
		match_status = regexec(&pattern, line, 1, &match_structs, eflags);
		/* if even "" matches, treat it as "not a match" */
		if (match_structs.rm_so >= match_structs.rm_eo)
			match_status = 1;
	}

	lineno_str(nbuf9, line);
	if (!growline) {
		printf(CLEAR_2_EOL"%s%s\n", nbuf9, str);
		return;
	}
	printf(CLEAR_2_EOL"%s%s%s\n", nbuf9, growline, str);
	free(growline);
}
#else
void print_found(const char *line);
#endif

static void print_ascii(const char *str)
{
	char buf[width];
	char nbuf9[9];
	char *p;
	size_t n;

	lineno_str(nbuf9, str);
	printf(CLEAR_2_EOL"%s", nbuf9);

	while (*str) {
		n = strcspn(str, controls);
		if (n) {
			if (!str[n]) break;
			printf("%.*s", (int) n, str);
			str += n;
		}
		n = strspn(str, controls);
		p = buf;
		do {
			if (*str == 0x7f)
				*p++ = '?';
			else if (*str == (char)0x9b)
			/* VT100's CSI, aka Meta-ESC. Who's inventor? */
			/* I want to know who committed this sin */
				*p++ = '{';
			else
				*p++ = ctrlconv[(unsigned char)*str];
			str++;
		} while (--n);
		*p = '\0';
		print_hilite(buf);
	}
	puts(str);
}

/* Print the buffer */
static void buffer_print(void)
{
	unsigned i;

	move_cursor(0, 0);
	for (i = 0; i <= max_displayed_line; i++)
		if (pattern_valid)
			print_found(buffer[i]);
		else
			print_ascii(buffer[i]);
	status_print();
}

static void buffer_fill_and_print(void)
{
	unsigned i;
#if ENABLE_FEATURE_LESS_DASHCMD
	int fpos = cur_fline;

	if (option_mask32 & FLAG_S) {
		/* Go back to the beginning of this line */
		while (fpos && LINENO(flines[fpos]) == LINENO(flines[fpos-1]))
			fpos--;
	}

	i = 0;
	while (i <= max_displayed_line && fpos <= max_fline) {
		int lineno = LINENO(flines[fpos]);
		buffer[i] = flines[fpos];
		i++;
		do {
			fpos++;
		} while ((fpos <= max_fline)
		      && (option_mask32 & FLAG_S)
		      && lineno == LINENO(flines[fpos])
		);
	}
#else
	for (i = 0; i <= max_displayed_line && cur_fline + i <= max_fline; i++) {
		buffer[i] = flines[cur_fline + i];
	}
#endif
	for (; i <= max_displayed_line; i++) {
		buffer[i] = empty_line_marker;
	}
	buffer_print();
}

/* Move the buffer up and down in the file in order to scroll */
static void buffer_down(int nlines)
{
	cur_fline += nlines;
	read_lines();
	cap_cur_fline(nlines);
	buffer_fill_and_print();
}

static void buffer_up(int nlines)
{
	cur_fline -= nlines;
	if (cur_fline < 0) cur_fline = 0;
	read_lines();
	buffer_fill_and_print();
}

static void buffer_line(int linenum)
{
	if (linenum < 0)
		linenum = 0;
	cur_fline = linenum;
	read_lines();
	if (linenum + max_displayed_line > max_fline)
		linenum = max_fline - max_displayed_line + TILDES;
	if (linenum < 0)
		linenum = 0;
	cur_fline = linenum;
	buffer_fill_and_print();
}

static void open_file_and_read_lines(void)
{
	if (filename) {
		xmove_fd(xopen(filename, O_RDONLY), STDIN_FILENO);
	} else {
		/* "less" with no arguments in argv[] */
		/* For status line only */
		filename = xstrdup(bb_msg_standard_input);
	}
	readpos = 0;
	readeof = 0;
	last_line_pos = 0;
	terminated = 1;
	read_lines();
}

/* Reinitialize everything for a new file - free the memory and start over */
static void reinitialize(void)
{
	unsigned i;

	if (flines) {
		for (i = 0; i <= max_fline; i++)
			free(MEMPTR(flines[i]));
		free(flines);
		flines = NULL;
	}

	max_fline = -1;
	cur_fline = 0;
	max_lineno = 0;
	open_file_and_read_lines();
	buffer_fill_and_print();
}

static ssize_t getch_nowait(void)
{
	int rd;
	struct pollfd pfd[2];

	pfd[0].fd = STDIN_FILENO;
	pfd[0].events = POLLIN;
	pfd[1].fd = kbd_fd;
	pfd[1].events = POLLIN;
 again:
	tcsetattr(kbd_fd, TCSANOW, &term_less);
	/* NB: select/poll returns whenever read will not block. Therefore:
	 * if eof is reached, select/poll will return immediately
	 * because read will immediately return 0 bytes.
	 * Even if select/poll says that input is available, read CAN block
	 * (switch fd into O_NONBLOCK'ed mode to avoid it)
	 */
	rd = 1;
	/* Are we interested in stdin? */
//TODO: reuse code for determining this
	if (!(option_mask32 & FLAG_S)
	   ? !(max_fline > cur_fline + max_displayed_line)
	   : !(max_fline >= cur_fline
	       && max_lineno > LINENO(flines[cur_fline]) + max_displayed_line)
	) {
		if (eof_error > 0) /* did NOT reach eof yet */
			rd = 0; /* yes, we are interested in stdin */
	}
	/* Position cursor if line input is done */
	if (less_gets_pos >= 0)
		move_cursor(max_displayed_line + 2, less_gets_pos + 1);
	fflush(stdout);

	if (kbd_input_size == 0) {
#if ENABLE_FEATURE_LESS_WINCH
		while (1) {
			int r;
			/* NB: SIGWINCH interrupts poll() */
			r = poll(pfd + rd, 2 - rd, -1);
			if (/*r < 0 && errno == EINTR &&*/ winch_counter)
				return '\\'; /* anything which has no defined function */
			if (r) break;
		}
#else
		safe_poll(pfd + rd, 2 - rd, -1);
#endif
	}

	/* We have kbd_fd in O_NONBLOCK mode, read inside read_key()
	 * would not block even if there is no input available */
	rd = read_key(kbd_fd, &kbd_input_size, kbd_input);
	if (rd == -1) {
		if (errno == EAGAIN) {
			/* No keyboard input available. Since poll() did return,
			 * we should have input on stdin */
			read_lines();
			buffer_fill_and_print();
			goto again;
		}
		/* EOF/error (ssh session got killed etc) */
		less_exit(0);
	}
	set_tty_cooked();
	return rd;
}

/* Grab a character from input without requiring the return key. If the
 * character is ASCII \033, get more characters and assign certain sequences
 * special return codes. Note that this function works best with raw input. */
static int less_getch(int pos)
{
	int i;

 again:
	less_gets_pos = pos;
	i = getch_nowait();
	less_gets_pos = -1;

	/* Discard Ctrl-something chars */
	if (i >= 0 && i < ' ' && i != 0x0d && i != 8)
		goto again;
	return i;
}

static char* less_gets(int sz)
{
	int c;
	unsigned i = 0;
	char *result = xzalloc(1);

	while (1) {
		c = '\0';
		less_gets_pos = sz + i;
		c = getch_nowait();
		if (c == 0x0d) {
			result[i] = '\0';
			less_gets_pos = -1;
			return result;
		}
		if (c == 0x7f)
			c = 8;
		if (c == 8 && i) {
			printf("\x8 \x8");
			i--;
		}
		if (c < ' ') /* filters out KEYCODE_xxx too (<0) */
			continue;
		if (i >= width - sz - 1)
			continue; /* len limit */
		bb_putchar(c);
		result[i++] = c;
		result = xrealloc(result, i+1);
	}
}

static void examine_file(void)
{
	char *new_fname;

	print_statusline("Examine: ");
	new_fname = less_gets(sizeof("Examine: ") - 1);
	if (!new_fname[0]) {
		status_print();
 err:
		free(new_fname);
		return;
	}
	if (access(new_fname, R_OK) != 0) {
		print_statusline("Cannot read this file");
		goto err;
	}
	free(filename);
	filename = new_fname;
	/* files start by = argv. why we assume that argv is infinitely long??
	files[num_files] = filename;
	current_file = num_files + 1;
	num_files++; */
	files[0] = filename;
	num_files = current_file = 1;
	reinitialize();
}

/* This function changes the file currently being paged. direction can be one of the following:
 * -1: go back one file
 *  0: go to the first file
 *  1: go forward one file */
static void change_file(int direction)
{
	if (current_file != ((direction > 0) ? num_files : 1)) {
		current_file = direction ? current_file + direction : 1;
		free(filename);
		filename = xstrdup(files[current_file - 1]);
		reinitialize();
	} else {
		print_statusline(direction > 0 ? "No next file" : "No previous file");
	}
}

static void remove_current_file(void)
{
	unsigned i;

	if (num_files < 2)
		return;

	if (current_file != 1) {
		change_file(-1);
		for (i = 3; i <= num_files; i++)
			files[i - 2] = files[i - 1];
		num_files--;
	} else {
		change_file(1);
		for (i = 2; i <= num_files; i++)
			files[i - 2] = files[i - 1];
		num_files--;
		current_file--;
	}
}

static void colon_process(void)
{
	int keypress;

	/* Clear the current line and print a prompt */
	print_statusline(" :");

	keypress = less_getch(2);
	switch (keypress) {
	case 'd':
		remove_current_file();
		break;
	case 'e':
		examine_file();
		break;
#if ENABLE_FEATURE_LESS_FLAGS
	case 'f':
		m_status_print();
		break;
#endif
	case 'n':
		change_file(1);
		break;
	case 'p':
		change_file(-1);
		break;
	case 'q':
		less_exit(EXIT_SUCCESS);
		break;
	case 'x':
		change_file(0);
		break;
	}
}

#if ENABLE_FEATURE_LESS_REGEXP
static void normalize_match_pos(int match)
{
	if (match >= num_matches)
		match = num_matches - 1;
	if (match < 0)
		match = 0;
	match_pos = match;
}

static void goto_match(int match)
{
	if (!pattern_valid)
		return;
	if (match < 0)
		match = 0;
	/* Try to find next match if eof isn't reached yet */
	if (match >= num_matches && eof_error > 0) {
		wanted_match = match; /* "I want to read until I see N'th match" */
		read_lines();
	}
	if (num_matches) {
		normalize_match_pos(match);
		buffer_line(match_lines[match_pos]);
	} else {
		print_statusline("No matches found");
	}
}

static void fill_match_lines(unsigned pos)
{
	if (!pattern_valid)
		return;
	/* Run the regex on each line of the current file */
	while (pos <= max_fline) {
		/* If this line matches */
		if (regexec(&pattern, flines[pos], 0, NULL, 0) == 0
		/* and we didn't match it last time */
		 && !(num_matches && match_lines[num_matches-1] == pos)
		) {
			match_lines = xrealloc_vector(match_lines, 4, num_matches);
			match_lines[num_matches++] = pos;
		}
		pos++;
	}
}

static void regex_process(void)
{
	char *uncomp_regex, *err;

	/* Reset variables */
	free(match_lines);
	match_lines = NULL;
	match_pos = 0;
	num_matches = 0;
	if (pattern_valid) {
		regfree(&pattern);
		pattern_valid = 0;
	}

	/* Get the uncompiled regular expression from the user */
	clear_line();
	bb_putchar((option_mask32 & LESS_STATE_MATCH_BACKWARDS) ? '?' : '/');
	uncomp_regex = less_gets(1);
	if (!uncomp_regex[0]) {
		free(uncomp_regex);
		buffer_print();
		return;
	}

	/* Compile the regex and check for errors */
	err = regcomp_or_errmsg(&pattern, uncomp_regex,
				(option_mask32 & FLAG_I) ? REG_ICASE : 0);
	free(uncomp_regex);
	if (err) {
		print_statusline(err);
		free(err);
		return;
	}

	pattern_valid = 1;
	match_pos = 0;
	fill_match_lines(0);
	while (match_pos < num_matches) {
		if ((int)match_lines[match_pos] > cur_fline)
			break;
		match_pos++;
	}
	if (option_mask32 & LESS_STATE_MATCH_BACKWARDS)
		match_pos--;

	/* It's possible that no matches are found yet.
	 * goto_match() will read input looking for match,
	 * if needed */
	goto_match(match_pos);
}
#endif

static void number_process(int first_digit)
{
	unsigned i;
	int num;
	int keypress;
	char num_input[sizeof(int)*4]; /* more than enough */

	num_input[0] = first_digit;

	/* Clear the current line, print a prompt, and then print the digit */
	clear_line();
	printf(":%c", first_digit);

	/* Receive input until a letter is given */
	i = 1;
	while (i < sizeof(num_input)-1) {
		keypress = less_getch(i + 1);
		if ((unsigned)keypress > 255 || !isdigit(num_input[i]))
			break;
		num_input[i] = keypress;
		bb_putchar(keypress);
		i++;
	}

	num_input[i] = '\0';
	num = bb_strtou(num_input, NULL, 10);
	/* on format error, num == -1 */
	if (num < 1 || num > MAXLINES) {
		buffer_print();
		return;
	}

	/* We now know the number and the letter entered, so we process them */
	switch (keypress) {
	case KEYCODE_DOWN: case 'z': case 'd': case 'e': case ' ': case '\015':
		buffer_down(num);
		break;
	case KEYCODE_UP: case 'b': case 'w': case 'y': case 'u':
		buffer_up(num);
		break;
	case 'g': case '<': case 'G': case '>':
		cur_fline = num + max_displayed_line;
		read_lines();
		buffer_line(num - 1);
		break;
	case 'p': case '%':
		num = num * (max_fline / 100); /* + max_fline / 2; */
		cur_fline = num + max_displayed_line;
		read_lines();
		buffer_line(num);
		break;
#if ENABLE_FEATURE_LESS_REGEXP
	case 'n':
		goto_match(match_pos + num);
		break;
	case '/':
		option_mask32 &= ~LESS_STATE_MATCH_BACKWARDS;
		regex_process();
		break;
	case '?':
		option_mask32 |= LESS_STATE_MATCH_BACKWARDS;
		regex_process();
		break;
#endif
	}
}

#if ENABLE_FEATURE_LESS_DASHCMD
static void flag_change(void)
{
	int keypress;

	clear_line();
	bb_putchar('-');
	keypress = less_getch(1);

	switch (keypress) {
	case 'M':
		option_mask32 ^= FLAG_M;
		break;
	case 'm':
		option_mask32 ^= FLAG_m;
		break;
	case 'E':
		option_mask32 ^= FLAG_E;
		break;
	case '~':
		option_mask32 ^= FLAG_TILDE;
		break;
	case 'S':
		option_mask32 ^= FLAG_S;
		buffer_fill_and_print();
		break;
#if ENABLE_FEATURE_LESS_LINENUMS
	case 'N':
		option_mask32 ^= FLAG_N;
		re_wrap();
		buffer_fill_and_print();
		break;
#endif
	}
}

#ifdef BLOAT
static void show_flag_status(void)
{
	int keypress;
	int flag_val;

	clear_line();
	bb_putchar('_');
	keypress = less_getch(1);

	switch (keypress) {
	case 'M':
		flag_val = option_mask32 & FLAG_M;
		break;
	case 'm':
		flag_val = option_mask32 & FLAG_m;
		break;
	case '~':
		flag_val = option_mask32 & FLAG_TILDE;
		break;
	case 'N':
		flag_val = option_mask32 & FLAG_N;
		break;
	case 'E':
		flag_val = option_mask32 & FLAG_E;
		break;
	default:
		flag_val = 0;
		break;
	}

	clear_line();
	printf(HIGHLIGHT"The status of the flag is: %u"NORMAL, flag_val != 0);
}
#endif

#endif /* ENABLE_FEATURE_LESS_DASHCMD */

static void save_input_to_file(void)
{
	const char *msg = "";
	char *current_line;
	unsigned i;
	FILE *fp;

	print_statusline("Log file: ");
	current_line = less_gets(sizeof("Log file: ")-1);
	if (current_line[0]) {
		fp = fopen_for_write(current_line);
		if (!fp) {
			msg = "Error opening log file";
			goto ret;
		}
		for (i = 0; i <= max_fline; i++)
			fprintf(fp, "%s\n", flines[i]);
		fclose(fp);
		msg = "Done";
	}
 ret:
	print_statusline(msg);
	free(current_line);
}

#if ENABLE_FEATURE_LESS_MARKS
static void add_mark(void)
{
	int letter;

	print_statusline("Mark: ");
	letter = less_getch(sizeof("Mark: ") - 1);

	if (isalpha(letter)) {
		/* If we exceed 15 marks, start overwriting previous ones */
		if (num_marks == 14)
			num_marks = 0;

		mark_lines[num_marks][0] = letter;
		mark_lines[num_marks][1] = cur_fline;
		num_marks++;
	} else {
		print_statusline("Invalid mark letter");
	}
}

static void goto_mark(void)
{
	int letter;
	int i;

	print_statusline("Go to mark: ");
	letter = less_getch(sizeof("Go to mark: ") - 1);
	clear_line();

	if (isalpha(letter)) {
		for (i = 0; i <= num_marks; i++)
			if (letter == mark_lines[i][0]) {
				buffer_line(mark_lines[i][1]);
				break;
			}
		if (num_marks == 14 && letter != mark_lines[14][0])
			print_statusline("Mark not set");
	} else
		print_statusline("Invalid mark letter");
}
#endif

#if ENABLE_FEATURE_LESS_BRACKETS
static char opp_bracket(char bracket)
{
	switch (bracket) {
		case '{': case '[': /* '}' == '{' + 2. Same for '[' */
			bracket++;
		case '(':           /* ')' == '(' + 1 */
			bracket++;
			break;
		case '}': case ']':
			bracket--;
		case ')':
			bracket--;
			break;
	};
	return bracket;
}

static void match_right_bracket(char bracket)
{
	unsigned i;

	if (strchr(flines[cur_fline], bracket) == NULL) {
		print_statusline("No bracket in top line");
		return;
	}
	bracket = opp_bracket(bracket);
	for (i = cur_fline + 1; i < max_fline; i++) {
		if (strchr(flines[i], bracket) != NULL) {
			buffer_line(i);
			return;
		}
	}
	print_statusline("No matching bracket found");
}

static void match_left_bracket(char bracket)
{
	int i;

	if (strchr(flines[cur_fline + max_displayed_line], bracket) == NULL) {
		print_statusline("No bracket in bottom line");
		return;
	}

	bracket = opp_bracket(bracket);
	for (i = cur_fline + max_displayed_line; i >= 0; i--) {
		if (strchr(flines[i], bracket) != NULL) {
			buffer_line(i);
			return;
		}
	}
	print_statusline("No matching bracket found");
}
#endif  /* FEATURE_LESS_BRACKETS */

static void keypress_process(int keypress)
{
	switch (keypress) {
	case KEYCODE_DOWN: case 'e': case 'j': case 0x0d:
		buffer_down(1);
		break;
	case KEYCODE_UP: case 'y': case 'k':
		buffer_up(1);
		break;
	case KEYCODE_PAGEDOWN: case ' ': case 'z': case 'f':
		buffer_down(max_displayed_line + 1);
		break;
	case KEYCODE_PAGEUP: case 'w': case 'b':
		buffer_up(max_displayed_line + 1);
		break;
	case 'd':
		buffer_down((max_displayed_line + 1) / 2);
		break;
	case 'u':
		buffer_up((max_displayed_line + 1) / 2);
		break;
	case KEYCODE_HOME: case 'g': case 'p': case '<': case '%':
		buffer_line(0);
		break;
	case KEYCODE_END: case 'G': case '>':
		cur_fline = MAXLINES;
		read_lines();
		buffer_line(cur_fline);
		break;
	case 'q': case 'Q':
		less_exit(EXIT_SUCCESS);
		break;
#if ENABLE_FEATURE_LESS_MARKS
	case 'm':
		add_mark();
		buffer_print();
		break;
	case '\'':
		goto_mark();
		buffer_print();
		break;
#endif
	case 'r': case 'R':
		buffer_print();
		break;
	/*case 'R':
		full_repaint();
		break;*/
	case 's':
		save_input_to_file();
		break;
	case 'E':
		examine_file();
		break;
#if ENABLE_FEATURE_LESS_FLAGS
	case '=':
		m_status_print();
		break;
#endif
#if ENABLE_FEATURE_LESS_REGEXP
	case '/':
		option_mask32 &= ~LESS_STATE_MATCH_BACKWARDS;
		regex_process();
		break;
	case 'n':
		goto_match(match_pos + 1);
		break;
	case 'N':
		goto_match(match_pos - 1);
		break;
	case '?':
		option_mask32 |= LESS_STATE_MATCH_BACKWARDS;
		regex_process();
		break;
#endif
#if ENABLE_FEATURE_LESS_DASHCMD
	case '-':
		flag_change();
		buffer_print();
		break;
#ifdef BLOAT
	case '_':
		show_flag_status();
		break;
#endif
#endif
#if ENABLE_FEATURE_LESS_BRACKETS
	case '{': case '(': case '[':
		match_right_bracket(keypress);
		break;
	case '}': case ')': case ']':
		match_left_bracket(keypress);
		break;
#endif
	case ':':
		colon_process();
		break;
	}

	if (isdigit(keypress))
		number_process(keypress);
}

static void sig_catcher(int sig)
{
	less_exit(- sig);
}

#if ENABLE_FEATURE_LESS_WINCH
static void sigwinch_handler(int sig UNUSED_PARAM)
{
	winch_counter++;
}
#endif

int less_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int less_main(int argc, char **argv)
{
	int keypress;

	INIT_G();

	/* TODO: -x: do not interpret backspace, -xx: tab also */
	/* -xxx: newline also */
	/* -w N: assume width N (-xxx -w 32: hex viewer of sorts) */
	getopt32(argv, "EMmN~I" USE_FEATURE_LESS_DASHCMD("S"));
	argc -= optind;
	argv += optind;
	num_files = argc;
	files = argv;

	/* Another popular pager, most, detects when stdout
	 * is not a tty and turns into cat. This makes sense. */
	if (!isatty(STDOUT_FILENO))
		return bb_cat(argv);

	if (!num_files) {
		if (isatty(STDIN_FILENO)) {
			/* Just "less"? No args and no redirection? */
			bb_error_msg("missing filename");
			bb_show_usage();
		}
	} else {
		filename = xstrdup(files[0]);
	}

	if (option_mask32 & FLAG_TILDE)
		empty_line_marker = "";

	kbd_fd = open(CURRENT_TTY, O_RDONLY);
	if (kbd_fd < 0)
		return bb_cat(argv);
	ndelay_on(kbd_fd);

	tcgetattr(kbd_fd, &term_orig);
	term_less = term_orig;
	term_less.c_lflag &= ~(ICANON | ECHO);
	term_less.c_iflag &= ~(IXON | ICRNL);
	/*term_less.c_oflag &= ~ONLCR;*/
	term_less.c_cc[VMIN] = 1;
	term_less.c_cc[VTIME] = 0;

	get_terminal_width_height(kbd_fd, &width, &max_displayed_line);
	/* 20: two tabstops + 4 */
	if (width < 20 || max_displayed_line < 3)
		return bb_cat(argv);
	max_displayed_line -= 2;

	/* We want to restore term_orig on exit */
	bb_signals(BB_FATAL_SIGS, sig_catcher);
#if ENABLE_FEATURE_LESS_WINCH
	signal(SIGWINCH, sigwinch_handler);
#endif

	buffer = xmalloc((max_displayed_line+1) * sizeof(char *));
	reinitialize();
	while (1) {
#if ENABLE_FEATURE_LESS_WINCH
		while (WINCH_COUNTER) {
 again:
			winch_counter--;
			get_terminal_width_height(kbd_fd, &width, &max_displayed_line);
			/* 20: two tabstops + 4 */
			if (width < 20)
				width = 20;
			if (max_displayed_line < 3)
				max_displayed_line = 3;
			max_displayed_line -= 2;
			free(buffer);
			buffer = xmalloc((max_displayed_line+1) * sizeof(char *));
			/* Avoid re-wrap and/or redraw if we already know
			 * we need to do it again. These ops are expensive */
			if (WINCH_COUNTER)
				goto again;
			re_wrap();
			if (WINCH_COUNTER)
				goto again;
			buffer_fill_and_print();
			/* This took some time. Loop back and check,
			 * were there another SIGWINCH? */
		}
#endif
		keypress = less_getch(-1); /* -1: do not position cursor */
		keypress_process(keypress);
	}
}

/*
Help text of less version 418 is below.
If you are implementing something, keeping
key and/or command line switch compatibility is a good idea:


                   SUMMARY OF LESS COMMANDS

      Commands marked with * may be preceded by a number, N.
      Notes in parentheses indicate the behavior if N is given.
  h  H                 Display this help.
  q  :q  Q  :Q  ZZ     Exit.
 ---------------------------------------------------------------------------
                           MOVING
  e  ^E  j  ^N  CR  *  Forward  one line   (or N lines).
  y  ^Y  k  ^K  ^P  *  Backward one line   (or N lines).
  f  ^F  ^V  SPACE  *  Forward  one window (or N lines).
  b  ^B  ESC-v      *  Backward one window (or N lines).
  z                 *  Forward  one window (and set window to N).
  w                 *  Backward one window (and set window to N).
  ESC-SPACE         *  Forward  one window, but don't stop at end-of-file.
  d  ^D             *  Forward  one half-window (and set half-window to N).
  u  ^U             *  Backward one half-window (and set half-window to N).
  ESC-)  RightArrow *  Left  one half screen width (or N positions).
  ESC-(  LeftArrow  *  Right one half screen width (or N positions).
  F                    Forward forever; like "tail -f".
  r  ^R  ^L            Repaint screen.
  R                    Repaint screen, discarding buffered input.
        ---------------------------------------------------
        Default "window" is the screen height.
        Default "half-window" is half of the screen height.
 ---------------------------------------------------------------------------
                          SEARCHING
  /pattern          *  Search forward for (N-th) matching line.
  ?pattern          *  Search backward for (N-th) matching line.
  n                 *  Repeat previous search (for N-th occurrence).
  N                 *  Repeat previous search in reverse direction.
  ESC-n             *  Repeat previous search, spanning files.
  ESC-N             *  Repeat previous search, reverse dir. & spanning files.
  ESC-u                Undo (toggle) search highlighting.
        ---------------------------------------------------
        Search patterns may be modified by one or more of:
        ^N or !  Search for NON-matching lines.
        ^E or *  Search multiple files (pass thru END OF FILE).
        ^F or @  Start search at FIRST file (for /) or last file (for ?).
        ^K       Highlight matches, but don't move (KEEP position).
        ^R       Don't use REGULAR EXPRESSIONS.
 ---------------------------------------------------------------------------
                           JUMPING
  g  <  ESC-<       *  Go to first line in file (or line N).
  G  >  ESC->       *  Go to last line in file (or line N).
  p  %              *  Go to beginning of file (or N percent into file).
  t                 *  Go to the (N-th) next tag.
  T                 *  Go to the (N-th) previous tag.
  {  (  [           *  Find close bracket } ) ].
  }  )  ]           *  Find open bracket { ( [.
  ESC-^F <c1> <c2>  *  Find close bracket <c2>.
  ESC-^B <c1> <c2>  *  Find open bracket <c1>
        ---------------------------------------------------
        Each "find close bracket" command goes forward to the close bracket
          matching the (N-th) open bracket in the top line.
        Each "find open bracket" command goes backward to the open bracket
          matching the (N-th) close bracket in the bottom line.
  m<letter>            Mark the current position with <letter>.
  '<letter>            Go to a previously marked position.
  ''                   Go to the previous position.
  ^X^X                 Same as '.
        ---------------------------------------------------
        A mark is any upper-case or lower-case letter.
        Certain marks are predefined:
             ^  means  beginning of the file
             $  means  end of the file
 ---------------------------------------------------------------------------
                        CHANGING FILES
  :e [file]            Examine a new file.
  ^X^V                 Same as :e.
  :n                *  Examine the (N-th) next file from the command line.
  :p                *  Examine the (N-th) previous file from the command line.
  :x                *  Examine the first (or N-th) file from the command line.
  :d                   Delete the current file from the command line list.
  =  ^G  :f            Print current file name.
 ---------------------------------------------------------------------------
                    MISCELLANEOUS COMMANDS
  -<flag>              Toggle a command line option [see OPTIONS below].
  --<name>             Toggle a command line option, by name.
  _<flag>              Display the setting of a command line option.
  __<name>             Display the setting of an option, by name.
  +cmd                 Execute the less cmd each time a new file is examined.
  !command             Execute the shell command with $SHELL.
  |Xcommand            Pipe file between current pos & mark X to shell command.
  v                    Edit the current file with $VISUAL or $EDITOR.
  V                    Print version number of "less".
 ---------------------------------------------------------------------------
                           OPTIONS
        Most options may be changed either on the command line,
        or from within less by using the - or -- command.
        Options may be given in one of two forms: either a single
        character preceded by a -, or a name preceeded by --.
  -?  ........  --help
                  Display help (from command line).
  -a  ........  --search-skip-screen
                  Forward search skips current screen.
  -b [N]  ....  --buffers=[N]
                  Number of buffers.
  -B  ........  --auto-buffers
                  Don't automatically allocate buffers for pipes.
  -c  ........  --clear-screen
                  Repaint by clearing rather than scrolling.
  -d  ........  --dumb
                  Dumb terminal.
  -D [xn.n]  .  --color=xn.n
                  Set screen colors. (MS-DOS only)
  -e  -E  ....  --quit-at-eof  --QUIT-AT-EOF
                  Quit at end of file.
  -f  ........  --force
                  Force open non-regular files.
  -F  ........  --quit-if-one-screen
                  Quit if entire file fits on first screen.
  -g  ........  --hilite-search
                  Highlight only last match for searches.
  -G  ........  --HILITE-SEARCH
                  Don't highlight any matches for searches.
  -h [N]  ....  --max-back-scroll=[N]
                  Backward scroll limit.
  -i  ........  --ignore-case
                  Ignore case in searches that do not contain uppercase.
  -I  ........  --IGNORE-CASE
                  Ignore case in all searches.
  -j [N]  ....  --jump-target=[N]
                  Screen position of target lines.
  -J  ........  --status-column
                  Display a status column at left edge of screen.
  -k [file]  .  --lesskey-file=[file]
                  Use a lesskey file.
  -L  ........  --no-lessopen
                  Ignore the LESSOPEN environment variable.
  -m  -M  ....  --long-prompt  --LONG-PROMPT
                  Set prompt style.
  -n  -N  ....  --line-numbers  --LINE-NUMBERS
                  Don't use line numbers.
  -o [file]  .  --log-file=[file]
                  Copy to log file (standard input only).
  -O [file]  .  --LOG-FILE=[file]
                  Copy to log file (unconditionally overwrite).
  -p [pattern]  --pattern=[pattern]
                  Start at pattern (from command line).
  -P [prompt]   --prompt=[prompt]
                  Define new prompt.
  -q  -Q  ....  --quiet  --QUIET  --silent --SILENT
                  Quiet the terminal bell.
  -r  -R  ....  --raw-control-chars  --RAW-CONTROL-CHARS
                  Output "raw" control characters.
  -s  ........  --squeeze-blank-lines
                  Squeeze multiple blank lines.
  -S  ........  --chop-long-lines
                  Chop long lines.
  -t [tag]  ..  --tag=[tag]
                  Find a tag.
  -T [tagsfile] --tag-file=[tagsfile]
                  Use an alternate tags file.
  -u  -U  ....  --underline-special  --UNDERLINE-SPECIAL
                  Change handling of backspaces.
  -V  ........  --version
                  Display the version number of "less".
  -w  ........  --hilite-unread
                  Highlight first new line after forward-screen.
  -W  ........  --HILITE-UNREAD
                  Highlight first new line after any forward movement.
  -x [N[,...]]  --tabs=[N[,...]]
                  Set tab stops.
  -X  ........  --no-init
                  Don't use termcap init/deinit strings.
                --no-keypad
                  Don't use termcap keypad init/deinit strings.
  -y [N]  ....  --max-forw-scroll=[N]
                  Forward scroll limit.
  -z [N]  ....  --window=[N]
                  Set size of window.
  -" [c[c]]  .  --quotes=[c[c]]
                  Set shell quote characters.
  -~  ........  --tilde
                  Don't display tildes after end of file.
  -# [N]  ....  --shift=[N]
                  Horizontal scroll amount (0 = one half screen width)

 ---------------------------------------------------------------------------
                          LINE EDITING
        These keys can be used to edit text being entered
        on the "command line" at the bottom of the screen.
 RightArrow                       ESC-l     Move cursor right one character.
 LeftArrow                        ESC-h     Move cursor left one character.
 CNTL-RightArrow  ESC-RightArrow  ESC-w     Move cursor right one word.
 CNTL-LeftArrow   ESC-LeftArrow   ESC-b     Move cursor left one word.
 HOME                             ESC-0     Move cursor to start of line.
 END                              ESC-$     Move cursor to end of line.
 BACKSPACE                                  Delete char to left of cursor.
 DELETE                           ESC-x     Delete char under cursor.
 CNTL-BACKSPACE   ESC-BACKSPACE             Delete word to left of cursor.
 CNTL-DELETE      ESC-DELETE      ESC-X     Delete word under cursor.
 CNTL-U           ESC (MS-DOS only)         Delete entire line.
 UpArrow                          ESC-k     Retrieve previous command line.
 DownArrow                        ESC-j     Retrieve next command line.
 TAB                                        Complete filename & cycle.
 SHIFT-TAB                        ESC-TAB   Complete filename & reverse cycle.
 CNTL-L                                     Complete filename, list all.
*/