ruby-core@ruby-lang.org archive (unofficial mirror)
 help / color / mirror / code / Atom feed
42e99435cbf2bc0693ff5ba34d464c6e6b783db5 blob 89858 bytes (raw)

   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
 
# encoding: US-ASCII
# frozen_string_literal: true
# = csv.rb -- CSV Reading and Writing
#
# Created by James Edward Gray II on 2005-10-31.
#
# See CSV for documentation.
#
# == Description
#
# Welcome to the new and improved CSV.
#
# This version of the CSV library began its life as FasterCSV. FasterCSV was
# intended as a replacement to Ruby's then standard CSV library. It was
# designed to address concerns users of that library had and it had three
# primary goals:
#
# 1.  Be significantly faster than CSV while remaining a pure Ruby library.
# 2.  Use a smaller and easier to maintain code base. (FasterCSV eventually
#     grew larger, was also but considerably richer in features. The parsing
#     core remains quite small.)
# 3.  Improve on the CSV interface.
#
# Obviously, the last one is subjective. I did try to defer to the original
# interface whenever I didn't have a compelling reason to change it though, so
# hopefully this won't be too radically different.
#
# We must have met our goals because FasterCSV was renamed to CSV and replaced
# the original library as of Ruby 1.9. If you are migrating code from 1.8 or
# earlier, you may have to change your code to comply with the new interface.
#
# == What's the Different From the Old CSV?
#
# I'm sure I'll miss something, but I'll try to mention most of the major
# differences I am aware of, to help others quickly get up to speed:
#
# === \CSV Parsing
#
# * This parser is m17n aware. See CSV for full details.
# * This library has a stricter parser and will throw MalformedCSVErrors on
#   problematic data.
# * This library has a less liberal idea of a line ending than CSV. What you
#   set as the <tt>:row_sep</tt> is law. It can auto-detect your line endings
#   though.
# * The old library returned empty lines as <tt>[nil]</tt>. This library calls
#   them <tt>[]</tt>.
# * This library has a much faster parser.
#
# === Interface
#
# * CSV now uses Hash-style parameters to set options.
# * CSV no longer has generate_row() or parse_row().
# * The old CSV's Reader and Writer classes have been dropped.
# * CSV::open() is now more like Ruby's open().
# * CSV objects now support most standard IO methods.
# * CSV now has a new() method used to wrap objects like String and IO for
#   reading and writing.
# * CSV::generate() is different from the old method.
# * CSV no longer supports partial reads. It works line-by-line.
# * CSV no longer allows the instance methods to override the separators for
#   performance reasons. They must be set in the constructor.
#
# If you use this library and find yourself missing any functionality I have
# trimmed, please {let me know}[mailto:james@grayproductions.net].
#
# == Documentation
#
# See CSV for documentation.
#
# == What is CSV, really?
#
# CSV maintains a pretty strict definition of CSV taken directly from
# {the RFC}[http://www.ietf.org/rfc/rfc4180.txt]. I relax the rules in only one
# place and that is to make using this library easier. CSV will parse all valid
# CSV.
#
# What you don't want to do is to feed CSV invalid data. Because of the way the
# CSV format works, it's common for a parser to need to read until the end of
# the file to be sure a field is invalid. This consumes a lot of time and memory.
#
# Luckily, when working with invalid CSV, Ruby's built-in methods will almost
# always be superior in every way. For example, parsing non-quoted fields is as
# easy as:
#
#   data.split(",")
#
# == Questions and/or Comments
#
# Feel free to email {James Edward Gray II}[mailto:james@grayproductions.net]
# with any questions.

require "forwardable"
require "date"
require "stringio"

require_relative "csv/fields_converter"
require_relative "csv/input_record_separator"
require_relative "csv/match_p"
require_relative "csv/parser"
require_relative "csv/row"
require_relative "csv/table"
require_relative "csv/writer"

using CSV::MatchP if CSV.const_defined?(:MatchP)

# == \CSV
# \CSV (comma-separated variables) data is a text representation of a table:
# - A _row_ _separator_ delimits table rows.
#   A common row separator is the newline character <tt>"\n"</tt>.
# - A _column_ _separator_ delimits fields in a row.
#   A common column separator is the comma character <tt>","</tt>.
#
# This \CSV \String, with row separator <tt>"\n"</tt>
# and column separator <tt>","</tt>,
# has three rows and two columns:
#   "foo,0\nbar,1\nbaz,2\n"
#
# Despite the name \CSV, a \CSV representation can use different separators.
#
# For more about tables, see the Wikipedia article
# "{Table (information)}[https://en.wikipedia.org/wiki/Table_(information)]",
# especially its section
# "{Simple table}[https://en.wikipedia.org/wiki/Table_(information)#Simple_table]"
#
# == \Class \CSV
#
# Class \CSV provides methods for:
# - Parsing \CSV data from a \String object, a \File (via its file path), or an \IO object.
# - Generating \CSV data to a \String object.
#
# To make \CSV available:
#   require 'csv'
#
# All examples here assume that this has been done.
#
# == Keeping It Simple
#
# A \CSV object has dozens of instance methods that offer fine-grained control
# of parsing and generating \CSV data.
# For many needs, though, simpler approaches will do.
#
# This section summarizes the singleton methods in \CSV
# that allow you to parse and generate without explicitly
# creating \CSV objects.
# For details, follow the links.
#
# === Simple Parsing
#
# Parsing methods commonly return either of:
# - An \Array of Arrays of Strings:
#   - The outer \Array is the entire "table".
#   - Each inner \Array is a row.
#   - Each \String is a field.
# - A CSV::Table object.  For details, see
#   {\CSV with Headers}[#class-CSV-label-CSV+with+Headers].
#
# ==== Parsing a \String
#
# The input to be parsed can be a string:
#   string = "foo,0\nbar,1\nbaz,2\n"
#
# \Method CSV.parse returns the entire \CSV data:
#   CSV.parse(string) # => [["foo", "0"], ["bar", "1"], ["baz", "2"]]
#
# \Method CSV.parse_line returns only the first row:
#   CSV.parse_line(string) # => ["foo", "0"]
#
# \CSV extends class \String with instance method String#parse_csv,
# which also returns only the first row:
#   string.parse_csv # => ["foo", "0"]
#
# ==== Parsing Via a \File Path
#
# The input to be parsed can be in a file:
#   string = "foo,0\nbar,1\nbaz,2\n"
#   path = 't.csv'
#   File.write(path, string)
#
# \Method CSV.read returns the entire \CSV data:
#  CSV.read(path) # => [["foo", "0"], ["bar", "1"], ["baz", "2"]]
#
# \Method CSV.foreach iterates, passing each row to the given block:
#  CSV.foreach(path) do |row|
#    p row
#  end
# Output:
#   ["foo", "0"]
#   ["bar", "1"]
#   ["baz", "2"]
#
# \Method CSV.table returns the entire \CSV data as a CSV::Table object:
#   CSV.table(path) # => #<CSV::Table mode:col_or_row row_count:3>
#
# ==== Parsing from an Open \IO Stream
#
# The input to be parsed can be in an open \IO stream:
#
# \Method CSV.read returns the entire \CSV data:
#   File.open(path) do |file|
#     CSV.read(file)
#   end # => [["foo", "0"], ["bar", "1"], ["baz", "2"]]
#
# As does method CSV.parse:
#   File.open(path) do |file|
#     CSV.parse(file)
#   end # => [["foo", "0"], ["bar", "1"], ["baz", "2"]]
#
# \Method CSV.parse_line returns only the first row:
#   File.open(path) do |file|
#    CSV.parse_line(file)
#   end # => ["foo", "0"]
#
# \Method CSV.foreach iterates, passing each row to the given block:
#   File.open(path) do |file|
#     CSV.foreach(file) do |row|
#       p row
#     end
#   end
# Output:
#   ["foo", "0"]
#   ["bar", "1"]
#   ["baz", "2"]
#
# \Method CSV.table returns the entire \CSV data as a CSV::Table object:
#   File.open(path) do |file|
#     CSV.table(file)
#   end # => #<CSV::Table mode:col_or_row row_count:3>
#
# === Simple Generating
#
# \Method CSV.generate returns a \String;
# this example uses method CSV#<< to append the rows
# that are to be generated:
#   output_string = CSV.generate do |csv|
#     csv << ['foo', 0]
#     csv << ['bar', 1]
#     csv << ['baz', 2]
#   end
#   output_string # => "foo,0\nbar,1\nbaz,2\n"
#
# \Method CSV.generate_line returns a \String containing the single row
# constructed from an \Array:
#   CSV.generate_line(['foo', '0']) # => "foo,0\n"
#
# \CSV extends class \Array with instance method <tt>Array#to_csv</tt>,
# which forms an \Array into a \String:
#   ['foo', '0'].to_csv # => "foo,0\n"
#
# === "Filtering" \CSV
#
# \Method CSV.filter provides a Unix-style filter for \CSV data.
# The input data is processed to form the output data:
#   in_string = "foo,0\nbar,1\nbaz,2\n"
#   out_string = ''
#   CSV.filter(in_string, out_string) do |row|
#     row[0] = row[0].upcase
#     row[1] *= 4
#   end
#   out_string # => "FOO,0000\nBAR,1111\nBAZ,2222\n"
#
# == \CSV Objects
#
# There are three ways to create a \CSV object:
# - \Method CSV.new returns a new \CSV object.
# - \Method CSV.instance returns a new or cached \CSV object.
# - \Method \CSV() also returns a new or cached \CSV object.
#
# === Instance Methods
#
# \CSV has three groups of instance methods:
# - Its own internally defined instance methods.
# - Methods included by module Enumerable.
# - Methods delegated to class IO. See below.
#
# ==== Delegated Methods
#
# For convenience, a CSV object will delegate to many methods in class IO.
# (A few have wrapper "guard code" in \CSV.) You may call:
# * IO#binmode
# * #binmode?
# * IO#close
# * IO#close_read
# * IO#close_write
# * IO#closed?
# * #eof
# * #eof?
# * IO#external_encoding
# * IO#fcntl
# * IO#fileno
# * #flock
# * IO#flush
# * IO#fsync
# * IO#internal_encoding
# * #ioctl
# * IO#isatty
# * #path
# * IO#pid
# * IO#pos
# * IO#pos=
# * IO#reopen
# * #rewind
# * IO#seek
# * #stat
# * IO#string
# * IO#sync
# * IO#sync=
# * IO#tell
# * #to_i
# * #to_io
# * IO#truncate
# * IO#tty?
#
# === Options
#
# The default values for options are:
#   DEFAULT_OPTIONS = {
#     # For both parsing and generating.
#     col_sep:            ",",
#     row_sep:            :auto,
#     quote_char:         '"',
#     # For parsing.
#     field_size_limit:   nil,
#     converters:         nil,
#     unconverted_fields: nil,
#     headers:            false,
#     return_headers:     false,
#     header_converters:  nil,
#     skip_blanks:        false,
#     skip_lines:         nil,
#     liberal_parsing:    false,
#     nil_value:          nil,
#     empty_value:        "",
#     # For generating.
#     write_headers:      nil,
#     quote_empty:        true,
#     force_quotes:       false,
#     write_converters:   nil,
#     write_nil_value:    nil,
#     write_empty_value:  "",
#     strip:              false,
#   }
#
# ==== Options for Parsing
#
# Options for parsing, described in detail below, include:
# - +row_sep+: Specifies the row separator; used to delimit rows.
# - +col_sep+: Specifies the column separator; used to delimit fields.
# - +quote_char+: Specifies the quote character; used to quote fields.
# - +field_size_limit+: Specifies the maximum field size allowed.
# - +converters+: Specifies the field converters to be used.
# - +unconverted_fields+: Specifies whether unconverted fields are to be available.
# - +headers+: Specifies whether data contains headers,
#   or specifies the headers themselves.
# - +return_headers+: Specifies whether headers are to be returned.
# - +header_converters+: Specifies the header converters to be used.
# - +skip_blanks+: Specifies whether blanks lines are to be ignored.
# - +skip_lines+: Specifies how comments lines are to be recognized.
# - +strip+: Specifies whether leading and trailing whitespace are
#   to be stripped from fields..
# - +liberal_parsing+: Specifies whether \CSV should attempt to parse
#   non-compliant data.
# - +nil_value+: Specifies the object that is to be substituted for each null (no-text) field.
# - +empty_value+: Specifies the object that is to be substituted for each empty field.
#
# :include: ../doc/csv/options/common/row_sep.rdoc
#
# :include: ../doc/csv/options/common/col_sep.rdoc
#
# :include: ../doc/csv/options/common/quote_char.rdoc
#
# :include: ../doc/csv/options/parsing/field_size_limit.rdoc
#
# :include: ../doc/csv/options/parsing/converters.rdoc
#
# :include: ../doc/csv/options/parsing/unconverted_fields.rdoc
#
# :include: ../doc/csv/options/parsing/headers.rdoc
#
# :include: ../doc/csv/options/parsing/return_headers.rdoc
#
# :include: ../doc/csv/options/parsing/header_converters.rdoc
#
# :include: ../doc/csv/options/parsing/skip_blanks.rdoc
#
# :include: ../doc/csv/options/parsing/skip_lines.rdoc
#
# :include: ../doc/csv/options/parsing/strip.rdoc
#
# :include: ../doc/csv/options/parsing/liberal_parsing.rdoc
#
# :include: ../doc/csv/options/parsing/nil_value.rdoc
#
# :include: ../doc/csv/options/parsing/empty_value.rdoc
#
# ==== Options for Generating
#
# Options for generating, described in detail below, include:
# - +row_sep+: Specifies the row separator; used to delimit rows.
# - +col_sep+: Specifies the column separator; used to delimit fields.
# - +quote_char+: Specifies the quote character; used to quote fields.
# - +write_headers+: Specifies whether headers are to be written.
# - +force_quotes+: Specifies whether each output field is to be quoted.
# - +quote_empty+: Specifies whether each empty output field is to be quoted.
# - +write_converters+: Specifies the field converters to be used in writing.
# - +write_nil_value+: Specifies the object that is to be substituted for each +nil+-valued field.
# - +write_empty_value+: Specifies the object that is to be substituted for each empty field.
#
# :include: ../doc/csv/options/common/row_sep.rdoc
#
# :include: ../doc/csv/options/common/col_sep.rdoc
#
# :include: ../doc/csv/options/common/quote_char.rdoc
#
# :include: ../doc/csv/options/generating/write_headers.rdoc
#
# :include: ../doc/csv/options/generating/force_quotes.rdoc
#
# :include: ../doc/csv/options/generating/quote_empty.rdoc
#
# :include: ../doc/csv/options/generating/write_converters.rdoc
#
# :include: ../doc/csv/options/generating/write_nil_value.rdoc
#
# :include: ../doc/csv/options/generating/write_empty_value.rdoc
#
# === \CSV with Headers
#
# CSV allows to specify column names of CSV file, whether they are in data, or
# provided separately. If headers are specified, reading methods return an instance
# of CSV::Table, consisting of CSV::Row.
#
#   # Headers are part of data
#   data = CSV.parse(<<~ROWS, headers: true)
#     Name,Department,Salary
#     Bob,Engineering,1000
#     Jane,Sales,2000
#     John,Management,5000
#   ROWS
#
#   data.class      #=> CSV::Table
#   data.first      #=> #<CSV::Row "Name":"Bob" "Department":"Engineering" "Salary":"1000">
#   data.first.to_h #=> {"Name"=>"Bob", "Department"=>"Engineering", "Salary"=>"1000"}
#
#   # Headers provided by developer
#   data = CSV.parse('Bob,Engineering,1000', headers: %i[name department salary])
#   data.first      #=> #<CSV::Row name:"Bob" department:"Engineering" salary:"1000">
#
# === \Converters
#
# By default, each value (field or header) parsed by \CSV is formed into a \String.
# You can use a _field_ _converter_ or  _header_ _converter_
# to intercept and modify the parsed values:
# - See {Field Converters}[#class-CSV-label-Field+Converters].
# - See {Header Converters}[#class-CSV-label-Header+Converters].
#
# Also by default, each value to be written during generation is written 'as-is'.
# You can use a _write_ _converter_ to modify values before writing.
# - See {Write Converters}[#class-CSV-label-Write+Converters].
#
# ==== Specifying \Converters
#
# You can specify converters for parsing or generating in the +options+
# argument to various \CSV methods:
# - Option +converters+ for converting parsed field values.
# - Option +header_converters+ for converting parsed header values.
# - Option +write_converters+ for converting values to be written (generated).
#
# There are three forms for specifying converters:
# - A converter proc: executable code to be used for conversion.
# - A converter name: the name of a stored converter.
# - A converter list: an array of converter procs, converter names, and converter lists.
#
# ===== Converter Procs
#
# This converter proc, +strip_converter+, accepts a value +field+
# and returns <tt>field.strip</tt>:
#   strip_converter = proc {|field| field.strip }
# In this call to <tt>CSV.parse</tt>,
# the keyword argument <tt>converters: string_converter</tt>
# specifies that:
# - \Proc +string_converter+ is to be called for each parsed field.
# - The converter's return value is to replace the +field+ value.
# Example:
#   string = " foo , 0 \n bar , 1 \n baz , 2 \n"
#   array = CSV.parse(string, converters: strip_converter)
#   array # => [["foo", "0"], ["bar", "1"], ["baz", "2"]]
#
# A converter proc can receive a second argument, +field_info+,
# that contains details about the field.
# This modified +strip_converter+ displays its arguments:
#   strip_converter = proc do |field, field_info|
#     p [field, field_info]
#     field.strip
#   end
#   string = " foo , 0 \n bar , 1 \n baz , 2 \n"
#   array = CSV.parse(string, converters: strip_converter)
#   array # => [["foo", "0"], ["bar", "1"], ["baz", "2"]]
# Output:
#  [" foo ", #<struct CSV::FieldInfo index=0, line=1, header=nil>]
#  [" 0 ", #<struct CSV::FieldInfo index=1, line=1, header=nil>]
#  [" bar ", #<struct CSV::FieldInfo index=0, line=2, header=nil>]
#  [" 1 ", #<struct CSV::FieldInfo index=1, line=2, header=nil>]
#  [" baz ", #<struct CSV::FieldInfo index=0, line=3, header=nil>]
#  [" 2 ", #<struct CSV::FieldInfo index=1, line=3, header=nil>]
# Each CSV::FieldInfo object shows:
# - The 0-based field index.
# - The 1-based line index.
# - The field header, if any.
#
# ===== Stored \Converters
#
# A converter may be given a name and stored in a structure where
# the parsing methods can find it by name.
#
# The storage structure for field converters is the \Hash CSV::Converters.
# It has several built-in converter procs:
# - <tt>:integer</tt>: converts each \String-embedded integer into a true \Integer.
# - <tt>:float</tt>: converts each \String-embedded float into a true \Float.
# - <tt>:date</tt>: converts each \String-embedded date into a true \Date.
# - <tt>:date_time</tt>: converts each \String-embedded date-time into a true \DateTime
# .
# This example creates a converter proc, then stores it:
#   strip_converter = proc {|field| field.strip }
#   CSV::Converters[:strip] = strip_converter
# Then the parsing method call can refer to the converter
# by its name, <tt>:strip</tt>:
#   string = " foo , 0 \n bar , 1 \n baz , 2 \n"
#   array = CSV.parse(string, converters: :strip)
#   array # => [["foo", "0"], ["bar", "1"], ["baz", "2"]]
#
# The storage structure for header converters is the \Hash CSV::HeaderConverters,
# which works in the same way.
# It also has built-in converter procs:
# - <tt>:downcase</tt>: Downcases each header.
# - <tt>:symbol</tt>: Converts each header to a \Symbol.
#
# There is no such storage structure for write headers.
#
# In order for the parsing methods to access stored converters in non-main-Ractors, the
# storage structure must be made shareable first.
# Therefore, <tt>Ractor.make_shareable(CSV::Converters)</tt> and
# <tt>Ractor.make_shareable(CSV::HeaderConverters)</tt> must be called before the creation
# of Ractors that use the converters stored in these structures. (Since making the storage
# structures shareable involves freezing them, any custom converters that are to be used
# must be added first.)
#
# ===== Converter Lists
#
# A _converter_ _list_ is an \Array that may include any assortment of:
# - Converter procs.
# - Names of stored converters.
# - Nested converter lists.
#
# Examples:
#   numeric_converters = [:integer, :float]
#   date_converters = [:date, :date_time]
#   [numeric_converters, strip_converter]
#   [strip_converter, date_converters, :float]
#
# Like a converter proc, a converter list may be named and stored in either
# \CSV::Converters or CSV::HeaderConverters:
#   CSV::Converters[:custom] = [strip_converter, date_converters, :float]
#   CSV::HeaderConverters[:custom] = [:downcase, :symbol]
#
# There are two built-in converter lists:
#   CSV::Converters[:numeric] # => [:integer, :float]
#   CSV::Converters[:all] # => [:date_time, :numeric]
#
# ==== Field \Converters
#
# With no conversion, all parsed fields in all rows become Strings:
#   string = "foo,0\nbar,1\nbaz,2\n"
#   ary = CSV.parse(string)
#   ary # => # => [["foo", "0"], ["bar", "1"], ["baz", "2"]]
#
# When you specify a field converter, each parsed field is passed to the converter;
# its return value becomes the stored value for the field.
# A converter might, for example, convert an integer embedded in a \String
# into a true \Integer.
# (In fact, that's what built-in field converter +:integer+ does.)
#
# There are three ways to use field \converters.
#
# - Using option {converters}[#class-CSV-label-Option+converters] with a parsing method:
#     ary = CSV.parse(string, converters: :integer)
#     ary # => [0, 1, 2] # => [["foo", 0], ["bar", 1], ["baz", 2]]
# - Using option {converters}[#class-CSV-label-Option+converters] with a new \CSV instance:
#     csv = CSV.new(string, converters: :integer)
#     # Field converters in effect:
#     csv.converters # => [:integer]
#     csv.read # => [["foo", 0], ["bar", 1], ["baz", 2]]
# - Using method #convert to add a field converter to a \CSV instance:
#     csv = CSV.new(string)
#     # Add a converter.
#     csv.convert(:integer)
#     csv.converters # => [:integer]
#     csv.read # => [["foo", 0], ["bar", 1], ["baz", 2]]
#
# Installing a field converter does not affect already-read rows:
#   csv = CSV.new(string)
#   csv.shift # => ["foo", "0"]
#   # Add a converter.
#   csv.convert(:integer)
#   csv.converters # => [:integer]
#   csv.read # => [["bar", 1], ["baz", 2]]
#
# There are additional built-in \converters, and custom \converters are also supported.
#
# ===== Built-In Field \Converters
#
# The built-in field converters are in \Hash CSV::Converters:
# - Each key is a field converter name.
# - Each value is one of:
#   - A \Proc field converter.
#   - An \Array of field converter names.
#
# Display:
#   CSV::Converters.each_pair do |name, value|
#     if value.kind_of?(Proc)
#       p [name, value.class]
#     else
#       p [name, value]
#     end
#   end
# Output:
#   [:integer, Proc]
#   [:float, Proc]
#   [:numeric, [:integer, :float]]
#   [:date, Proc]
#   [:date_time, Proc]
#   [:all, [:date_time, :numeric]]
#
# Each of these converters transcodes values to UTF-8 before attempting conversion.
# If a value cannot be transcoded to UTF-8 the conversion will
# fail and the value will remain unconverted.
#
# Converter +:integer+ converts each field that Integer() accepts:
#   data = '0,1,2,x'
#   # Without the converter
#   csv = CSV.parse_line(data)
#   csv # => ["0", "1", "2", "x"]
#   # With the converter
#   csv = CSV.parse_line(data, converters: :integer)
#   csv # => [0, 1, 2, "x"]
#
# Converter +:float+ converts each field that Float() accepts:
#   data = '1.0,3.14159,x'
#   # Without the converter
#   csv = CSV.parse_line(data)
#   csv # => ["1.0", "3.14159", "x"]
#   # With the converter
#   csv = CSV.parse_line(data, converters: :float)
#   csv # => [1.0, 3.14159, "x"]
#
# Converter +:numeric+ converts with both +:integer+ and +:float+..
#
# Converter +:date+ converts each field that Date::parse accepts:
#   data = '2001-02-03,x'
#   # Without the converter
#   csv = CSV.parse_line(data)
#   csv # => ["2001-02-03", "x"]
#   # With the converter
#   csv = CSV.parse_line(data, converters: :date)
#   csv # => [#<Date: 2001-02-03 ((2451944j,0s,0n),+0s,2299161j)>, "x"]
#
# Converter +:date_time+ converts each field that DateTime::parse accepts:
#   data = '2020-05-07T14:59:00-05:00,x'
#   # Without the converter
#   csv = CSV.parse_line(data)
#   csv # => ["2020-05-07T14:59:00-05:00", "x"]
#   # With the converter
#   csv = CSV.parse_line(data, converters: :date_time)
#   csv # => [#<DateTime: 2020-05-07T14:59:00-05:00 ((2458977j,71940s,0n),-18000s,2299161j)>, "x"]
#
# Converter +:numeric+ converts with both +:date_time+ and +:numeric+..
#
# As seen above, method #convert adds \converters to a \CSV instance,
# and method #converters returns an \Array of the \converters in effect:
#   csv = CSV.new('0,1,2')
#   csv.converters # => []
#   csv.convert(:integer)
#   csv.converters # => [:integer]
#   csv.convert(:date)
#   csv.converters # => [:integer, :date]
#
# ===== Custom Field \Converters
#
# You can define a custom field converter:
#   strip_converter = proc {|field| field.strip }
#   string = " foo , 0 \n bar , 1 \n baz , 2 \n"
#   array = CSV.parse(string, converters: strip_converter)
#   array # => [["foo", "0"], ["bar", "1"], ["baz", "2"]]
# You can register the converter in \Converters \Hash,
# which allows you to refer to it by name:
#   CSV::Converters[:strip] = strip_converter
#   string = " foo , 0 \n bar , 1 \n baz , 2 \n"
#   array = CSV.parse(string, converters: :strip)
#   array # => [["foo", "0"], ["bar", "1"], ["baz", "2"]]
#
# ==== Header \Converters
#
# Header converters operate only on headers (and not on other rows).
#
# There are three ways to use header \converters;
# these examples use built-in header converter +:dowhcase+,
# which downcases each parsed header.
#
# - Option +header_converters+ with a singleton parsing method:
#     string = "Name,Count\nFoo,0\n,Bar,1\nBaz,2"
#     tbl = CSV.parse(string, headers: true, header_converters: :downcase)
#     tbl.class # => CSV::Table
#     tbl.headers # => ["name", "count"]
#
# - Option +header_converters+ with a new \CSV instance:
#     csv = CSV.new(string, header_converters: :downcase)
#     # Header converters in effect:
#     csv.header_converters # => [:downcase]
#     tbl = CSV.parse(string, headers: true)
#     tbl.headers # => ["Name", "Count"]
#
# - Method #header_convert adds a header converter to a \CSV instance:
#     csv = CSV.new(string)
#     # Add a header converter.
#     csv.header_convert(:downcase)
#     csv.header_converters # => [:downcase]
#     tbl = CSV.parse(string, headers: true)
#     tbl.headers # => ["Name", "Count"]
#
# ===== Built-In Header \Converters
#
# The built-in header \converters are in \Hash CSV::HeaderConverters.
# The keys there are the names of the \converters:
#   CSV::HeaderConverters.keys # => [:downcase, :symbol]
#
# Converter +:downcase+ converts each header by downcasing it:
#   string = "Name,Count\nFoo,0\n,Bar,1\nBaz,2"
#   tbl = CSV.parse(string, headers: true, header_converters: :downcase)
#   tbl.class # => CSV::Table
#   tbl.headers # => ["name", "count"]
#
# Converter +:symbol+ converts each header by making it into a \Symbol:
#   string = "Name,Count\nFoo,0\n,Bar,1\nBaz,2"
#   tbl = CSV.parse(string, headers: true, header_converters: :symbol)
#   tbl.headers # => [:name, :count]
# Details:
# - Strips leading and trailing whitespace.
# - Downcases the header.
# - Replaces embedded spaces with underscores.
# - Removes non-word characters.
# - Makes the string into a \Symbol.
#
# ===== Custom Header \Converters
#
# You can define a custom header converter:
#   upcase_converter = proc {|header| header.upcase }
#   string = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
#   table = CSV.parse(string, headers: true, header_converters: upcase_converter)
#   table # => #<CSV::Table mode:col_or_row row_count:4>
#   table.headers # => ["NAME", "VALUE"]
# You can register the converter in \HeaderConverters \Hash,
# which allows you to refer to it by name:
#   CSV::HeaderConverters[:upcase] = upcase_converter
#   table = CSV.parse(string, headers: true, header_converters: :upcase)
#   table # => #<CSV::Table mode:col_or_row row_count:4>
#   table.headers # => ["NAME", "VALUE"]
#
# ===== Write \Converters
#
# When you specify a write converter for generating \CSV,
# each field to be written is passed to the converter;
# its return value becomes the new value for the field.
# A converter might, for example, strip whitespace from a field.
#
# Using no write converter (all fields unmodified):
#   output_string = CSV.generate do |csv|
#     csv << [' foo ', 0]
#     csv << [' bar ', 1]
#     csv << [' baz ', 2]
#   end
#   output_string # => " foo ,0\n bar ,1\n baz ,2\n"
# Using option +write_converters+ with two custom write converters:
#   strip_converter = proc {|field| field.respond_to?(:strip) ? field.strip : field }
#   upcase_converter = proc {|field| field.respond_to?(:upcase) ? field.upcase : field }
#   write_converters = [strip_converter, upcase_converter]
#   output_string = CSV.generate(write_converters: write_converters) do |csv|
#     csv << [' foo ', 0]
#     csv << [' bar ', 1]
#     csv << [' baz ', 2]
#   end
#   output_string # => "FOO,0\nBAR,1\nBAZ,2\n"
#
# === Character Encodings (M17n or Multilingualization)
#
# This new CSV parser is m17n savvy.  The parser works in the Encoding of the IO
# or String object being read from or written to. Your data is never transcoded
# (unless you ask Ruby to transcode it for you) and will literally be parsed in
# the Encoding it is in. Thus CSV will return Arrays or Rows of Strings in the
# Encoding of your data. This is accomplished by transcoding the parser itself
# into your Encoding.
#
# Some transcoding must take place, of course, to accomplish this multiencoding
# support. For example, <tt>:col_sep</tt>, <tt>:row_sep</tt>, and
# <tt>:quote_char</tt> must be transcoded to match your data.  Hopefully this
# makes the entire process feel transparent, since CSV's defaults should just
# magically work for your data. However, you can set these values manually in
# the target Encoding to avoid the translation.
#
# It's also important to note that while all of CSV's core parser is now
# Encoding agnostic, some features are not. For example, the built-in
# converters will try to transcode data to UTF-8 before making conversions.
# Again, you can provide custom converters that are aware of your Encodings to
# avoid this translation. It's just too hard for me to support native
# conversions in all of Ruby's Encodings.
#
# Anyway, the practical side of this is simple: make sure IO and String objects
# passed into CSV have the proper Encoding set and everything should just work.
# CSV methods that allow you to open IO objects (CSV::foreach(), CSV::open(),
# CSV::read(), and CSV::readlines()) do allow you to specify the Encoding.
#
# One minor exception comes when generating CSV into a String with an Encoding
# that is not ASCII compatible. There's no existing data for CSV to use to
# prepare itself and thus you will probably need to manually specify the desired
# Encoding for most of those cases. It will try to guess using the fields in a
# row of output though, when using CSV::generate_line() or Array#to_csv().
#
# I try to point out any other Encoding issues in the documentation of methods
# as they come up.
#
# This has been tested to the best of my ability with all non-"dummy" Encodings
# Ruby ships with. However, it is brave new code and may have some bugs.
# Please feel free to {report}[mailto:james@grayproductions.net] any issues you
# find with it.
#
class CSV

  # The error thrown when the parser encounters illegal CSV formatting.
  class MalformedCSVError < RuntimeError
    attr_reader :line_number
    alias_method :lineno, :line_number
    def initialize(message, line_number)
      @line_number = line_number
      super("#{message} in line #{line_number}.")
    end
  end

  #
  # A FieldInfo Struct contains details about a field's position in the data
  # source it was read from.  CSV will pass this Struct to some blocks that make
  # decisions based on field structure.  See CSV.convert_fields() for an
  # example.
  #
  # <b><tt>index</tt></b>::  The zero-based index of the field in its row.
  # <b><tt>line</tt></b>::   The line of the data source this row is from.
  # <b><tt>header</tt></b>:: The header for the column, when available.
  #
  FieldInfo = Struct.new(:index, :line, :header)

  # A Regexp used to find and convert some common Date formats.
  DateMatcher     = / \A(?: (\w+,?\s+)?\w+\s+\d{1,2},?\s+\d{2,4} |
                            \d{4}-\d{2}-\d{2} )\z /x
  # A Regexp used to find and convert some common DateTime formats.
  DateTimeMatcher =
    / \A(?: (\w+,?\s+)?\w+\s+\d{1,2}\s+\d{1,2}:\d{1,2}:\d{1,2},?\s+\d{2,4} |
            \d{4}-\d{2}-\d{2}\s\d{2}:\d{2}:\d{2} |
            # ISO-8601
            \d{4}-\d{2}-\d{2}
              (?:T\d{2}:\d{2}(?::\d{2}(?:\.\d+)?(?:[+-]\d{2}(?::\d{2})|Z)?)?)?
        )\z /x

  # The encoding used by all converters.
  ConverterEncoding = Encoding.find("UTF-8")

  # A \Hash containing the names and \Procs for the built-in field converters.
  # See {Built-In Field Converters}[#class-CSV-label-Built-In+Field+Converters].
  #
  # This \Hash is intentionally left unfrozen, and may be extended with
  # custom field converters.
  # See {Custom Field Converters}[#class-CSV-label-Custom+Field+Converters].
  Converters  = {
    integer:   lambda { |f|
      Integer(f.encode(ConverterEncoding)) rescue f
    },
    float:     lambda { |f|
      Float(f.encode(ConverterEncoding)) rescue f
    },
    numeric:   [:integer, :float],
    date:      lambda { |f|
      begin
        e = f.encode(ConverterEncoding)
        e.match?(DateMatcher) ? Date.parse(e) : f
      rescue  # encoding conversion or date parse errors
        f
      end
    },
    date_time: lambda { |f|
      begin
        e = f.encode(ConverterEncoding)
        e.match?(DateTimeMatcher) ? DateTime.parse(e) : f
      rescue  # encoding conversion or date parse errors
        f
      end
    },
    all:       [:date_time, :numeric],
  }

  # A \Hash containing the names and \Procs for the built-in header converters.
  # See {Built-In Header Converters}[#class-CSV-label-Built-In+Header+Converters].
  #
  # This \Hash is intentionally left unfrozen, and may be extended with
  # custom field converters.
  # See {Custom Header Converters}[#class-CSV-label-Custom+Header+Converters].
  HeaderConverters = {
    downcase: lambda { |h| h.encode(ConverterEncoding).downcase },
    symbol:   lambda { |h|
      h.encode(ConverterEncoding).downcase.gsub(/[^\s\w]+/, "").strip.
                                           gsub(/\s+/, "_").to_sym
    }
  }

  # Default values for method options.
  DEFAULT_OPTIONS = {
    # For both parsing and generating.
    col_sep:            ",",
    row_sep:            :auto,
    quote_char:         '"',
    # For parsing.
    field_size_limit:   nil,
    converters:         nil,
    unconverted_fields: nil,
    headers:            false,
    return_headers:     false,
    header_converters:  nil,
    skip_blanks:        false,
    skip_lines:         nil,
    liberal_parsing:    false,
    nil_value:          nil,
    empty_value:        "",
    # For generating.
    write_headers:      nil,
    quote_empty:        true,
    force_quotes:       false,
    write_converters:   nil,
    write_nil_value:    nil,
    write_empty_value:  "",
    strip:              false,
  }.freeze

  class << self
    # :call-seq:
    #   instance(string, **options)
    #   instance(io = $stdout, **options)
    #   instance(string, **options) {|csv| ... }
    #   instance(io = $stdout, **options) {|csv| ... }
    #
    # Creates or retrieves cached \CSV objects.
    # For arguments and options, see CSV.new.
    #
    # This API is not Ractor-safe.
    #
    # ---
    #
    # With no block given, returns a \CSV object.
    #
    # The first call to +instance+ creates and caches a \CSV object:
    #   s0 = 's0'
    #   csv0 = CSV.instance(s0)
    #   csv0.class # => CSV
    #
    # Subsequent calls to +instance+ with that _same_ +string+ or +io+
    # retrieve that same cached object:
    #   csv1 = CSV.instance(s0)
    #   csv1.class # => CSV
    #   csv1.equal?(csv0) # => true # Same CSV object
    #
    # A subsequent call to +instance+ with a _different_ +string+ or +io+
    # creates and caches a _different_ \CSV object.
    #   s1 = 's1'
    #   csv2 = CSV.instance(s1)
    #   csv2.equal?(csv0) # => false # Different CSV object
    #
    # All the cached objects remains available:
    #   csv3 = CSV.instance(s0)
    #   csv3.equal?(csv0) # true # Same CSV object
    #   csv4 = CSV.instance(s1)
    #   csv4.equal?(csv2) # true # Same CSV object
    #
    # ---
    #
    # When a block is given, calls the block with the created or retrieved
    # \CSV object; returns the block's return value:
    #   CSV.instance(s0) {|csv| :foo } # => :foo
    def instance(data = $stdout, **options)
      # create a _signature_ for this method call, data object and options
      sig = [data.object_id] +
            options.values_at(*DEFAULT_OPTIONS.keys.sort_by { |sym| sym.to_s })

      # fetch or create the instance for this signature
      @@instances ||= Hash.new
      instance = (@@instances[sig] ||= new(data, **options))

      if block_given?
        yield instance  # run block, if given, returning result
      else
        instance        # or return the instance
      end
    end

    # :call-seq:
    #   filter(**options) {|row| ... }
    #   filter(in_string, **options) {|row| ... }
    #   filter(in_io, **options) {|row| ... }
    #   filter(in_string, out_string, **options) {|row| ... }
    #   filter(in_string, out_io, **options) {|row| ... }
    #   filter(in_io, out_string, **options) {|row| ... }
    #   filter(in_io, out_io, **options) {|row| ... }
    #
    # Reads \CSV input and writes \CSV output.
    #
    # For each input row:
    # - Forms the data into:
    #   - A CSV::Row object, if headers are in use.
    #   - An \Array of Arrays, otherwise.
    # - Calls the block with that object.
    # - Appends the block's return value to the output.
    #
    # Arguments:
    # * \CSV source:
    #   * Argument +in_string+, if given, should be a \String object;
    #     it will be put into a new StringIO object positioned at the beginning.
    #   * Argument +in_io+, if given, should be an IO object that is
    #     open for reading; on return, the IO object will be closed.
    #   * If neither  +in_string+ nor +in_io+ is given,
    #     the input stream defaults to {ARGF}[https://ruby-doc.org/core/ARGF.html].
    # * \CSV output:
    #   * Argument +out_string+, if given, should be a \String object;
    #     it will be put into a new StringIO object positioned at the beginning.
    #   * Argument +out_io+, if given, should be an IO object that is
    #     ppen for writing; on return, the IO object will be closed.
    #   * If neither +out_string+ nor +out_io+ is given,
    #     the output stream defaults to <tt>$stdout</tt>.
    # * Argument +options+ should be keyword arguments.
    #   - Each argument name that is prefixed with +in_+ or +input_+
    #     is stripped of its prefix and is treated as an option
    #     for parsing the input.
    #     Option +input_row_sep+ defaults to <tt>$INPUT_RECORD_SEPARATOR</tt>.
    #   - Each argument name that is prefixed with +out_+ or +output_+
    #     is stripped of its prefix and is treated as an option
    #     for generating the output.
    #     Option +output_row_sep+ defaults to <tt>$INPUT_RECORD_SEPARATOR</tt>.
    #   - Each argument not prefixed as above is treated as an option
    #     both for parsing the input and for generating the output.
    #   - See {Options for Parsing}[#class-CSV-label-Options+for+Parsing]
    #     and {Options for Generating}[#class-CSV-label-Options+for+Generating].
    #
    # Example:
    #   in_string = "foo,0\nbar,1\nbaz,2\n"
    #   out_string = ''
    #   CSV.filter(in_string, out_string) do |row|
    #     row[0] = row[0].upcase
    #     row[1] *= 4
    #   end
    #   out_string # => "FOO,0000\nBAR,1111\nBAZ,2222\n"
    def filter(input=nil, output=nil, **options)
      # parse options for input, output, or both
      in_options, out_options = Hash.new, {row_sep: InputRecordSeparator.value}
      options.each do |key, value|
        case key.to_s
        when /\Ain(?:put)?_(.+)\Z/
          in_options[$1.to_sym] = value
        when /\Aout(?:put)?_(.+)\Z/
          out_options[$1.to_sym] = value
        else
          in_options[key]  = value
          out_options[key] = value
        end
      end

      # build input and output wrappers
      input  = new(input  || ARGF, **in_options)
      output = new(output || $stdout, **out_options)

      # process headers
      need_manual_header_output =
        (in_options[:headers] and
         out_options[:headers] == true and
         out_options[:write_headers])
      if need_manual_header_output
        first_row = input.shift
        if first_row
          if first_row.is_a?(Row)
            headers = first_row.headers
            yield headers
            output << headers
          end
          yield first_row
          output << first_row
        end
      end

      # read, yield, write
      input.each do |row|
        yield row
        output << row
      end
    end

    #
    # :call-seq:
    #   foreach(path, mode='r', **options) {|row| ... )
    #   foreach(io, mode='r', **options {|row| ... )
    #   foreach(path, mode='r', headers: ..., **options) {|row| ... )
    #   foreach(io, mode='r', headers: ..., **options {|row| ... )
    #   foreach(path, mode='r', **options) -> new_enumerator
    #   foreach(io, mode='r', **options -> new_enumerator
    #
    # Calls the block with each row read from source +path+ or +io+.
    #
    # * Argument +path+, if given, must be the path to a file.
    # :include: ../doc/csv/arguments/io.rdoc
    # * Argument +mode+, if given, must be a \File mode
    #   See {Open Mode}[IO.html#method-c-new-label-Open+Mode].
    # * Arguments <tt>**options</tt> must be keyword options.
    #   See {Options for Parsing}[#class-CSV-label-Options+for+Parsing].
    # * This method optionally accepts an additional <tt>:encoding</tt> option
    #   that you can use to specify the Encoding of the data read from +path+ or +io+.
    #   You must provide this unless your data is in the encoding
    #   given by <tt>Encoding::default_external</tt>.
    #   Parsing will use this to determine how to parse the data.
    #   You may provide a second Encoding to
    #   have the data transcoded as it is read. For example,
    #     encoding: 'UTF-32BE:UTF-8'
    #   would read +UTF-32BE+ data from the file
    #   but transcode it to +UTF-8+ before parsing.
    #
    # ====== Without Option +headers+
    #
    # Without option +headers+, returns each row as an \Array object.
    #
    # These examples assume prior execution of:
    #   string = "foo,0\nbar,1\nbaz,2\n"
    #   path = 't.csv'
    #   File.write(path, string)
    #
    # Read rows from a file at +path+:
    #   CSV.foreach(path) {|row| p row }
    # Output:
    #   ["foo", "0"]
    #   ["bar", "1"]
    #   ["baz", "2"]
    #
    # Read rows from an \IO object:
    #   File.open(path) do |file|
    #     CSV.foreach(file) {|row| p row }
    #   end
    #
    # Output:
    #   ["foo", "0"]
    #   ["bar", "1"]
    #   ["baz", "2"]
    #
    # Returns a new \Enumerator if no block given:
    #   CSV.foreach(path) # => #<Enumerator: CSV:foreach("t.csv", "r")>
    #   CSV.foreach(File.open(path)) # => #<Enumerator: CSV:foreach(#<File:t.csv>, "r")>
    #
    # Issues a warning if an encoding is unsupported:
    #   CSV.foreach(File.open(path), encoding: 'foo:bar') {|row| }
    # Output:
    #   warning: Unsupported encoding foo ignored
    #   warning: Unsupported encoding bar ignored
    #
    # ====== With Option +headers+
    #
    # With {option +headers+}[#class-CSV-label-Option+headers],
    # returns each row as a CSV::Row object.
    #
    # These examples assume prior execution of:
    #   string = "Name,Count\nfoo,0\nbar,1\nbaz,2\n"
    #   path = 't.csv'
    #   File.write(path, string)
    #
    # Read rows from a file at +path+:
    #   CSV.foreach(path, headers: true) {|row| p row }
    #
    # Output:
    #   #<CSV::Row "Name":"foo" "Count":"0">
    #   #<CSV::Row "Name":"bar" "Count":"1">
    #   #<CSV::Row "Name":"baz" "Count":"2">
    #
    # Read rows from an \IO object:
    #   File.open(path) do |file|
    #     CSV.foreach(file, headers: true) {|row| p row }
    #   end
    #
    # Output:
    #   #<CSV::Row "Name":"foo" "Count":"0">
    #   #<CSV::Row "Name":"bar" "Count":"1">
    #   #<CSV::Row "Name":"baz" "Count":"2">
    #
    # ---
    #
    # Raises an exception if +path+ is a \String, but not the path to a readable file:
    #   # Raises Errno::ENOENT (No such file or directory @ rb_sysopen - nosuch.csv):
    #   CSV.foreach('nosuch.csv') {|row| }
    #
    # Raises an exception if +io+ is an \IO object, but not open for reading:
    #   io = File.open(path, 'w') {|row| }
    #   # Raises TypeError (no implicit conversion of nil into String):
    #   CSV.foreach(io) {|row| }
    #
    # Raises an exception if +mode+ is invalid:
    #   # Raises ArgumentError (invalid access mode nosuch):
    #   CSV.foreach(path, 'nosuch') {|row| }
    #
    def foreach(path, mode="r", **options, &block)
      return to_enum(__method__, path, mode, **options) unless block_given?
      open(path, mode, **options) do |csv|
        csv.each(&block)
      end
    end

    #
    # :call-seq:
    #   generate(csv_string, **options) {|csv| ... }
    #   generate(**options) {|csv| ... }
    #
    # * Argument +csv_string+, if given, must be a \String object;
    #   defaults to a new empty \String.
    # * Arguments +options+, if given, should be generating options.
    #   See {Options for Generating}[#class-CSV-label-Options+for+Generating].
    #
    # ---
    #
    # Creates a new \CSV object via <tt>CSV.new(csv_string, **options)</tt>;
    # calls the block with the \CSV object, which the block may modify;
    # returns the \String generated from the \CSV object.
    #
    # Note that a passed \String *is* modified by this method.
    # Pass <tt>csv_string</tt>.dup if the \String must be preserved.
    #
    # This method has one additional option: <tt>:encoding</tt>,
    # which sets the base Encoding for the output if no no +str+ is specified.
    # CSV needs this hint if you plan to output non-ASCII compatible data.
    #
    # ---
    #
    # Add lines:
    #   input_string = "foo,0\nbar,1\nbaz,2\n"
    #   output_string = CSV.generate(input_string) do |csv|
    #     csv << ['bat', 3]
    #     csv << ['bam', 4]
    #   end
    #   output_string # => "foo,0\nbar,1\nbaz,2\nbat,3\nbam,4\n"
    #   input_string # => "foo,0\nbar,1\nbaz,2\nbat,3\nbam,4\n"
    #   output_string.equal?(input_string) # => true # Same string, modified
    #
    # Add lines into new string, preserving old string:
    #   input_string = "foo,0\nbar,1\nbaz,2\n"
    #   output_string = CSV.generate(input_string.dup) do |csv|
    #     csv << ['bat', 3]
    #     csv << ['bam', 4]
    #   end
    #   output_string # => "foo,0\nbar,1\nbaz,2\nbat,3\nbam,4\n"
    #   input_string # => "foo,0\nbar,1\nbaz,2\n"
    #   output_string.equal?(input_string) # => false # Different strings
    #
    # Create lines from nothing:
    #   output_string = CSV.generate do |csv|
    #     csv << ['foo', 0]
    #     csv << ['bar', 1]
    #     csv << ['baz', 2]
    #   end
    #   output_string # => "foo,0\nbar,1\nbaz,2\n"
    #
    # ---
    #
    # Raises an exception if +csv_string+ is not a \String object:
    #   # Raises TypeError (no implicit conversion of Integer into String)
    #   CSV.generate(0)
    #
    def generate(str=nil, **options)
      encoding = options[:encoding]
      # add a default empty String, if none was given
      if str
        str = StringIO.new(str)
        str.seek(0, IO::SEEK_END)
        str.set_encoding(encoding) if encoding
      else
        str = +""
        str.force_encoding(encoding) if encoding
      end
      csv = new(str, **options) # wrap
      yield csv         # yield for appending
      csv.string        # return final String
    end

    # :call-seq:
    #   CSV.generate_line(ary)
    #   CSV.generate_line(ary, **options)
    #
    # Returns the \String created by generating \CSV from +ary+
    # using the specified +options+.
    #
    # Argument +ary+ must be an \Array.
    #
    # Special options:
    # * Option <tt>:row_sep</tt> defaults to <tt>"\n"> on Ruby 3.0 or later
    #   and <tt>$INPUT_RECORD_SEPARATOR</tt> (<tt>$/</tt>) otherwise.:
    #     $INPUT_RECORD_SEPARATOR # => "\n"
    # * This method accepts an additional option, <tt>:encoding</tt>, which sets the base
    #   Encoding for the output. This method will try to guess your Encoding from
    #   the first non-+nil+ field in +row+, if possible, but you may need to use
    #   this parameter as a backup plan.
    #
    # For other +options+,
    # see {Options for Generating}[#class-CSV-label-Options+for+Generating].
    #
    # ---
    #
    # Returns the \String generated from an \Array:
    #   CSV.generate_line(['foo', '0']) # => "foo,0\n"
    #
    # ---
    #
    # Raises an exception if +ary+ is not an \Array:
    #   # Raises NoMethodError (undefined method `find' for :foo:Symbol)
    #   CSV.generate_line(:foo)
    #
    def generate_line(row, **options)
      options = {row_sep: InputRecordSeparator.value}.merge(options)
      str = +""
      if options[:encoding]
        str.force_encoding(options[:encoding])
      else
        fallback_encoding = nil
        output_encoding = nil
        row.each do |field|
          next unless field.is_a?(String)
          fallback_encoding ||= field.encoding
          next if field.ascii_only?
          output_encoding = field.encoding
          break
        end
        output_encoding ||= fallback_encoding
        if output_encoding
          str.force_encoding(output_encoding)
        end
      end
      (new(str, **options) << row).string
    end

    #
    # :call-seq:
    #   open(file_path, mode = "rb", **options ) -> new_csv
    #   open(io, mode = "rb", **options ) -> new_csv
    #   open(file_path, mode = "rb", **options ) { |csv| ... } -> object
    #   open(io, mode = "rb", **options ) { |csv| ... } -> object
    #
    # possible options elements:
    #   hash form:
    #     :invalid => nil      # raise error on invalid byte sequence (default)
    #     :invalid => :replace # replace invalid byte sequence
    #     :undef => :replace   # replace undefined conversion
    #     :replace => string   # replacement string ("?" or "\uFFFD" if not specified)
    #
    # * Argument +path+, if given, must be the path to a file.
    # :include: ../doc/csv/arguments/io.rdoc
    # * Argument +mode+, if given, must be a \File mode
    #   See {Open Mode}[IO.html#method-c-new-label-Open+Mode].
    # * Arguments <tt>**options</tt> must be keyword options.
    #   See {Options for Generating}[#class-CSV-label-Options+for+Generating].
    # * This method optionally accepts an additional <tt>:encoding</tt> option
    #   that you can use to specify the Encoding of the data read from +path+ or +io+.
    #   You must provide this unless your data is in the encoding
    #   given by <tt>Encoding::default_external</tt>.
    #   Parsing will use this to determine how to parse the data.
    #   You may provide a second Encoding to
    #   have the data transcoded as it is read. For example,
    #     encoding: 'UTF-32BE:UTF-8'
    #   would read +UTF-32BE+ data from the file
    #   but transcode it to +UTF-8+ before parsing.
    #
    # ---
    #
    # These examples assume prior execution of:
    #   string = "foo,0\nbar,1\nbaz,2\n"
    #   path = 't.csv'
    #   File.write(path, string)
    #
    # ---
    #
    # With no block given, returns a new \CSV object.
    #
    # Create a \CSV object using a file path:
    #   csv = CSV.open(path)
    #   csv # => #<CSV io_type:File io_path:"t.csv" encoding:UTF-8 lineno:0 col_sep:"," row_sep:"\n" quote_char:"\"">
    #
    # Create a \CSV object using an open \File:
    #   csv = CSV.open(File.open(path))
    #   csv # => #<CSV io_type:File io_path:"t.csv" encoding:UTF-8 lineno:0 col_sep:"," row_sep:"\n" quote_char:"\"">
    #
    # ---
    #
    # With a block given, calls the block with the created \CSV object;
    # returns the block's return value:
    #
    # Using a file path:
    #   csv = CSV.open(path) {|csv| p csv}
    #   csv # => #<CSV io_type:File io_path:"t.csv" encoding:UTF-8 lineno:0 col_sep:"," row_sep:"\n" quote_char:"\"">
    # Output:
    #   #<CSV io_type:File io_path:"t.csv" encoding:UTF-8 lineno:0 col_sep:"," row_sep:"\n" quote_char:"\"">
    #
    # Using an open \File:
    #   csv = CSV.open(File.open(path)) {|csv| p csv}
    #   csv # => #<CSV io_type:File io_path:"t.csv" encoding:UTF-8 lineno:0 col_sep:"," row_sep:"\n" quote_char:"\"">
    # Output:
    #   #<CSV io_type:File io_path:"t.csv" encoding:UTF-8 lineno:0 col_sep:"," row_sep:"\n" quote_char:"\"">
    #
    # ---
    #
    # Raises an exception if the argument is not a \String object or \IO object:
    #   # Raises TypeError (no implicit conversion of Symbol into String)
    #   CSV.open(:foo)
    def open(filename, mode="r", **options)
      # wrap a File opened with the remaining +args+ with no newline
      # decorator
      file_opts = {universal_newline: false}.merge(options)
      options.delete(:invalid)
      options.delete(:undef)
      options.delete(:replace)

      begin
        f = File.open(filename, mode, **file_opts)
      rescue ArgumentError => e
        raise unless /needs binmode/.match?(e.message) and mode == "r"
        mode = "rb"
        file_opts = {encoding: Encoding.default_external}.merge(file_opts)
        retry
      end
      begin
        csv = new(f, **options)
      rescue Exception
        f.close
        raise
      end

      # handle blocks like Ruby's open(), not like the CSV library
      if block_given?
        begin
          yield csv
        ensure
          csv.close
        end
      else
        csv
      end
    end

    #
    # :call-seq:
    #   parse(string) -> array_of_arrays
    #   parse(io) -> array_of_arrays
    #   parse(string, headers: ..., **options) -> csv_table
    #   parse(io, headers: ..., **options) -> csv_table
    #   parse(string, **options) {|row| ... }
    #   parse(io, **options) {|row| ... }
    #
    # Parses +string+ or +io+ using the specified +options+.
    #
    # - Argument +string+ should be a \String object;
    #   it will be put into a new StringIO object positioned at the beginning.
    # :include: ../doc/csv/arguments/io.rdoc
    # - Argument +options+: see {Options for Parsing}[#class-CSV-label-Options+for+Parsing]
    #
    # ====== Without Option +headers+
    #
    # Without {option +headers+}[#class-CSV-label-Option+headers] case.
    #
    # These examples assume prior execution of:
    #   string = "foo,0\nbar,1\nbaz,2\n"
    #   path = 't.csv'
    #   File.write(path, string)
    #
    # ---
    #
    # With no block given, returns an \Array of Arrays formed from the source.
    #
    # Parse a \String:
    #   a_of_a = CSV.parse(string)
    #   a_of_a # => [["foo", "0"], ["bar", "1"], ["baz", "2"]]
    #
    # Parse an open \File:
    #   a_of_a = File.open(path) do |file|
    #     CSV.parse(file)
    #   end
    #   a_of_a # => [["foo", "0"], ["bar", "1"], ["baz", "2"]]
    #
    # ---
    #
    # With a block given, calls the block with each parsed row:
    #
    # Parse a \String:
    #   CSV.parse(string) {|row| p row }
    #
    # Output:
    #   ["foo", "0"]
    #   ["bar", "1"]
    #   ["baz", "2"]
    #
    # Parse an open \File:
    #   File.open(path) do |file|
    #     CSV.parse(file) {|row| p row }
    #   end
    #
    # Output:
    #   ["foo", "0"]
    #   ["bar", "1"]
    #   ["baz", "2"]
    #
    # ====== With Option +headers+
    #
    # With {option +headers+}[#class-CSV-label-Option+headers] case.
    #
    # These examples assume prior execution of:
    #   string = "Name,Count\nfoo,0\nbar,1\nbaz,2\n"
    #   path = 't.csv'
    #   File.write(path, string)
    #
    # ---
    #
    # With no block given, returns a CSV::Table object formed from the source.
    #
    # Parse a \String:
    #   csv_table = CSV.parse(string, headers: ['Name', 'Count'])
    #   csv_table # => #<CSV::Table mode:col_or_row row_count:5>
    #
    # Parse an open \File:
    #   csv_table = File.open(path) do |file|
    #     CSV.parse(file, headers: ['Name', 'Count'])
    #   end
    #   csv_table # => #<CSV::Table mode:col_or_row row_count:4>
    #
    # ---
    #
    # With a block given, calls the block with each parsed row,
    # which has been formed into a CSV::Row object:
    #
    # Parse a \String:
    #   CSV.parse(string, headers: ['Name', 'Count']) {|row| p row }
    #
    # Output:
    #   # <CSV::Row "Name":"foo" "Count":"0">
    #   # <CSV::Row "Name":"bar" "Count":"1">
    #   # <CSV::Row "Name":"baz" "Count":"2">
    #
    # Parse an open \File:
    #   File.open(path) do |file|
    #     CSV.parse(file, headers: ['Name', 'Count']) {|row| p row }
    #   end
    #
    # Output:
    #   # <CSV::Row "Name":"foo" "Count":"0">
    #   # <CSV::Row "Name":"bar" "Count":"1">
    #   # <CSV::Row "Name":"baz" "Count":"2">
    #
    # ---
    #
    # Raises an exception if the argument is not a \String object or \IO object:
    #   # Raises NoMethodError (undefined method `close' for :foo:Symbol)
    #   CSV.parse(:foo)
    def parse(str, **options, &block)
      csv = new(str, **options)

      return csv.each(&block) if block_given?

      # slurp contents, if no block is given
      begin
        csv.read
      ensure
        csv.close
      end
    end

    # :call-seq:
    #   CSV.parse_line(string) -> new_array or nil
    #   CSV.parse_line(io) -> new_array or nil
    #   CSV.parse_line(string, **options) -> new_array or nil
    #   CSV.parse_line(io, **options) -> new_array or nil
    #   CSV.parse_line(string, headers: true, **options) -> csv_row or nil
    #   CSV.parse_line(io, headers: true, **options) -> csv_row or nil
    #
    # Returns the data created by parsing the first line of +string+ or +io+
    # using the specified +options+.
    #
    # - Argument +string+ should be a \String object;
    #   it will be put into a new StringIO object positioned at the beginning.
    # :include: ../doc/csv/arguments/io.rdoc
    # - Argument +options+: see {Options for Parsing}[#class-CSV-label-Options+for+Parsing]
    #
    # ====== Without Option +headers+
    #
    # Without option +headers+, returns the first row as a new \Array.
    #
    # These examples assume prior execution of:
    #   string = "foo,0\nbar,1\nbaz,2\n"
    #   path = 't.csv'
    #   File.write(path, string)
    #
    # Parse the first line from a \String object:
    #   CSV.parse_line(string) # => ["foo", "0"]
    #
    # Parse the first line from a File object:
    #   File.open(path) do |file|
    #     CSV.parse_line(file) # => ["foo", "0"]
    #   end # => ["foo", "0"]
    #
    # Returns +nil+ if the argument is an empty \String:
    #   CSV.parse_line('') # => nil
    #
    # ====== With Option +headers+
    #
    # With {option +headers+}[#class-CSV-label-Option+headers],
    # returns the first row as a CSV::Row object.
    #
    # These examples assume prior execution of:
    #   string = "Name,Count\nfoo,0\nbar,1\nbaz,2\n"
    #   path = 't.csv'
    #   File.write(path, string)
    #
    # Parse the first line from a \String object:
    #   CSV.parse_line(string, headers: true) # => #<CSV::Row "Name":"foo" "Count":"0">
    #
    # Parse the first line from a File object:
    #   File.open(path) do |file|
    #     CSV.parse_line(file, headers: true)
    #   end # => #<CSV::Row "Name":"foo" "Count":"0">
    #
    # ---
    #
    # Raises an exception if the argument is +nil+:
    #   # Raises ArgumentError (Cannot parse nil as CSV):
    #   CSV.parse_line(nil)
    #
    def parse_line(line, **options)
      new(line, **options).each.first
    end

    #
    # :call-seq:
    #   read(source, **options) -> array_of_arrays
    #   read(source, headers: true, **options) -> csv_table
    #
    # Opens the given +source+ with the given +options+ (see CSV.open),
    # reads the source (see CSV#read), and returns the result,
    # which will be either an \Array of Arrays or a CSV::Table.
    #
    # Without headers:
    #   string = "foo,0\nbar,1\nbaz,2\n"
    #   path = 't.csv'
    #   File.write(path, string)
    #   CSV.read(path) # => [["foo", "0"], ["bar", "1"], ["baz", "2"]]
    #
    # With headers:
    #   string = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
    #   path = 't.csv'
    #   File.write(path, string)
    #   CSV.read(path, headers: true) # => #<CSV::Table mode:col_or_row row_count:4>
    def read(path, **options)
      open(path, **options) { |csv| csv.read }
    end

    # :call-seq:
    #   CSV.readlines(source, **options)
    #
    # Alias for CSV.read.
    def readlines(path, **options)
      read(path, **options)
    end

    # :call-seq:
    #   CSV.table(source, **options)
    #
    # Calls CSV.read with +source+, +options+, and certain default options:
    # - +headers+: +true+
    # - +converters+: +:numeric+
    # - +header_converters+: +:symbol+
    #
    # Returns a CSV::Table object.
    #
    # Example:
    #   string = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
    #   path = 't.csv'
    #   File.write(path, string)
    #   CSV.table(path) # => #<CSV::Table mode:col_or_row row_count:4>
    def table(path, **options)
      default_options = {
        headers:           true,
        converters:        :numeric,
        header_converters: :symbol,
      }
      options = default_options.merge(options)
      read(path, **options)
    end
  end

  # :call-seq:
  #   CSV.new(string)
  #   CSV.new(io)
  #   CSV.new(string, **options)
  #   CSV.new(io, **options)
  #
  # Returns the new \CSV object created using +string+ or +io+
  # and the specified +options+.
  #
  # - Argument +string+ should be a \String object;
  #   it will be put into a new StringIO object positioned at the beginning.
  # :include: ../doc/csv/arguments/io.rdoc
  # - Argument +options+: See:
  #   * {Options for Parsing}[#class-CSV-label-Options+for+Parsing]
  #   * {Options for Generating}[#class-CSV-label-Options+for+Generating]
  #   For performance reasons, the options cannot be overridden
  #   in a \CSV object, so those specified here will endure.
  #
  # In addition to the \CSV instance methods, several \IO methods are delegated.
  # See {Delegated Methods}[#class-CSV-label-Delegated+Methods].
  #
  # ---
  #
  # Create a \CSV object from a \String object:
  #   csv = CSV.new('foo,0')
  #   csv # => #<CSV io_type:StringIO encoding:UTF-8 lineno:0 col_sep:"," row_sep:"\n" quote_char:"\"">
  #
  # Create a \CSV object from a \File object:
  #   File.write('t.csv', 'foo,0')
  #   csv = CSV.new(File.open('t.csv'))
  #   csv # => #<CSV io_type:File io_path:"t.csv" encoding:UTF-8 lineno:0 col_sep:"," row_sep:"\n" quote_char:"\"">
  #
  # ---
  #
  # Raises an exception if the argument is +nil+:
  #   # Raises ArgumentError (Cannot parse nil as CSV):
  #   CSV.new(nil)
  #
  def initialize(data,
                 col_sep: ",",
                 row_sep: :auto,
                 quote_char: '"',
                 field_size_limit: nil,
                 converters: nil,
                 unconverted_fields: nil,
                 headers: false,
                 return_headers: false,
                 write_headers: nil,
                 header_converters: nil,
                 skip_blanks: false,
                 force_quotes: false,
                 skip_lines: nil,
                 liberal_parsing: false,
                 internal_encoding: nil,
                 external_encoding: nil,
                 encoding: nil,
                 nil_value: nil,
                 empty_value: "",
                 quote_empty: true,
                 write_converters: nil,
                 write_nil_value: nil,
                 write_empty_value: "",
                 strip: false)
    raise ArgumentError.new("Cannot parse nil as CSV") if data.nil?

    if data.is_a?(String)
      @io = StringIO.new(data)
      @io.set_encoding(encoding || data.encoding)
    else
      @io = data
    end
    @encoding = determine_encoding(encoding, internal_encoding)

    @base_fields_converter_options = {
      nil_value: nil_value,
      empty_value: empty_value,
    }
    @write_fields_converter_options = {
      nil_value: write_nil_value,
      empty_value: write_empty_value,
    }
    @initial_converters = converters
    @initial_header_converters = header_converters
    @initial_write_converters = write_converters

    @parser_options = {
      column_separator: col_sep,
      row_separator: row_sep,
      quote_character: quote_char,
      field_size_limit: field_size_limit,
      unconverted_fields: unconverted_fields,
      headers: headers,
      return_headers: return_headers,
      skip_blanks: skip_blanks,
      skip_lines: skip_lines,
      liberal_parsing: liberal_parsing,
      encoding: @encoding,
      nil_value: nil_value,
      empty_value: empty_value,
      strip: strip,
    }
    @parser = nil
    @parser_enumerator = nil
    @eof_error = nil

    @writer_options = {
      encoding: @encoding,
      force_encoding: (not encoding.nil?),
      force_quotes: force_quotes,
      headers: headers,
      write_headers: write_headers,
      column_separator: col_sep,
      row_separator: row_sep,
      quote_character: quote_char,
      quote_empty: quote_empty,
    }

    @writer = nil
    writer if @writer_options[:write_headers]
  end

  # :call-seq:
  #   csv.col_sep -> string
  #
  # Returns the encoded column separator; used for parsing and writing;
  # see {Option +col_sep+}[#class-CSV-label-Option+col_sep]:
  #   CSV.new('').col_sep # => ","
  def col_sep
    parser.column_separator
  end

  # :call-seq:
  #   csv.row_sep -> string
  #
  # Returns the encoded row separator; used for parsing and writing;
  # see {Option +row_sep+}[#class-CSV-label-Option+row_sep]:
  #   CSV.new('').row_sep # => "\n"
  def row_sep
    parser.row_separator
  end

  # :call-seq:
  #   csv.quote_char -> character
  #
  # Returns the encoded quote character; used for parsing and writing;
  # see {Option +quote_char+}[#class-CSV-label-Option+quote_char]:
  #   CSV.new('').quote_char # => "\""
  def quote_char
    parser.quote_character
  end

  # :call-seq:
  #   csv.field_size_limit -> integer or nil
  #
  # Returns the limit for field size; used for parsing;
  # see {Option +field_size_limit+}[#class-CSV-label-Option+field_size_limit]:
  #   CSV.new('').field_size_limit # => nil
  def field_size_limit
    parser.field_size_limit
  end

  # :call-seq:
  #   csv.skip_lines -> regexp or nil
  #
  # Returns the \Regexp used to identify comment lines; used for parsing;
  # see {Option +skip_lines+}[#class-CSV-label-Option+skip_lines]:
  #   CSV.new('').skip_lines # => nil
  def skip_lines
    parser.skip_lines
  end

  # :call-seq:
  #   csv.converters -> array
  #
  # Returns an \Array containing field converters;
  # see {Field Converters}[#class-CSV-label-Field+Converters]:
  #   csv = CSV.new('')
  #   csv.converters # => []
  #   csv.convert(:integer)
  #   csv.converters # => [:integer]
  #   csv.convert(proc {|x| x.to_s })
  #   csv.converters
  #
  # Notes that you need to call
  # +Ractor.make_shareable(CSV::Converters)+ on the main Ractor to use
  # this method.
  def converters
    parser_fields_converter.map do |converter|
      name = Converters.rassoc(converter)
      name ? name.first : converter
    end
  end

  # :call-seq:
  #   csv.unconverted_fields? -> object
  #
  # Returns the value that determines whether unconverted fields are to be
  # available; used for parsing;
  # see {Option +unconverted_fields+}[#class-CSV-label-Option+unconverted_fields]:
  #   CSV.new('').unconverted_fields? # => nil
  def unconverted_fields?
    parser.unconverted_fields?
  end

  # :call-seq:
  #   csv.headers -> object
  #
  # Returns the value that determines whether headers are used; used for parsing;
  # see {Option +headers+}[#class-CSV-label-Option+headers]:
  #   CSV.new('').headers # => nil
  def headers
    if @writer
      @writer.headers
    else
      parsed_headers = parser.headers
      return parsed_headers if parsed_headers
      raw_headers = @parser_options[:headers]
      raw_headers = nil if raw_headers == false
      raw_headers
    end
  end

  # :call-seq:
  #   csv.return_headers? -> true or false
  #
  # Returns the value that determines whether headers are to be returned; used for parsing;
  # see {Option +return_headers+}[#class-CSV-label-Option+return_headers]:
  #   CSV.new('').return_headers? # => false
  def return_headers?
    parser.return_headers?
  end

  # :call-seq:
  #   csv.write_headers? -> true or false
  #
  # Returns the value that determines whether headers are to be written; used for generating;
  # see {Option +write_headers+}[#class-CSV-label-Option+write_headers]:
  #   CSV.new('').write_headers? # => nil
  def write_headers?
    @writer_options[:write_headers]
  end

  # :call-seq:
  #   csv.header_converters -> array
  #
  # Returns an \Array containing header converters; used for parsing;
  # see {Header Converters}[#class-CSV-label-Header+Converters]:
  #   CSV.new('').header_converters # => []
  #
  # Notes that you need to call
  # +Ractor.make_shareable(CSV::HeaderConverters)+ on the main Ractor
  # to use this method.
  def header_converters
    header_fields_converter.map do |converter|
      name = HeaderConverters.rassoc(converter)
      name ? name.first : converter
    end
  end

  # :call-seq:
  #   csv.skip_blanks? -> true or false
  #
  # Returns the value that determines whether blank lines are to be ignored; used for parsing;
  # see {Option +skip_blanks+}[#class-CSV-label-Option+skip_blanks]:
  #   CSV.new('').skip_blanks? # => false
  def skip_blanks?
    parser.skip_blanks?
  end

  # :call-seq:
  #   csv.force_quotes? -> true or false
  #
  # Returns the value that determines whether all output fields are to be quoted;
  # used for generating;
  # see {Option +force_quotes+}[#class-CSV-label-Option+force_quotes]:
  #   CSV.new('').force_quotes? # => false
  def force_quotes?
    @writer_options[:force_quotes]
  end

  # :call-seq:
  #   csv.liberal_parsing? -> true or false
  #
  # Returns the value that determines whether illegal input is to be handled; used for parsing;
  # see {Option +liberal_parsing+}[#class-CSV-label-Option+liberal_parsing]:
  #   CSV.new('').liberal_parsing? # => false
  def liberal_parsing?
    parser.liberal_parsing?
  end

  # :call-seq:
  #   csv.encoding -> endcoding
  #
  # Returns the encoding used for parsing and generating;
  # see {Character Encodings (M17n or Multilingualization)}[#class-CSV-label-Character+Encodings+-28M17n+or+Multilingualization-29]:
  #   CSV.new('').encoding # => #<Encoding:UTF-8>
  attr_reader :encoding

  # :call-seq:
  #   csv.line_no -> integer
  #
  # Returns the count of the rows parsed or generated.
  #
  # Parsing:
  #   string = "foo,0\nbar,1\nbaz,2\n"
  #   path = 't.csv'
  #   File.write(path, string)
  #   CSV.open(path) do |csv|
  #     csv.each do |row|
  #       p [csv.lineno, row]
  #     end
  #   end
  # Output:
  #   [1, ["foo", "0"]]
  #   [2, ["bar", "1"]]
  #   [3, ["baz", "2"]]
  #
  # Generating:
  #   CSV.generate do |csv|
  #     p csv.lineno; csv << ['foo', 0]
  #     p csv.lineno; csv << ['bar', 1]
  #     p csv.lineno; csv << ['baz', 2]
  #   end
  # Output:
  #   0
  #   1
  #   2
  def lineno
    if @writer
      @writer.lineno
    else
      parser.lineno
    end
  end

  # :call-seq:
  #   csv.line -> array
  #
  # Returns the line most recently read:
  #   string = "foo,0\nbar,1\nbaz,2\n"
  #   path = 't.csv'
  #   File.write(path, string)
  #   CSV.open(path) do |csv|
  #     csv.each do |row|
  #       p [csv.lineno, csv.line]
  #     end
  #   end
  # Output:
  #   [1, "foo,0\n"]
  #   [2, "bar,1\n"]
  #   [3, "baz,2\n"]
  def line
    parser.line
  end

  ### IO and StringIO Delegation ###

  extend Forwardable
  def_delegators :@io, :binmode, :close, :close_read, :close_write,
                       :closed?, :external_encoding, :fcntl,
                       :fileno, :flush, :fsync, :internal_encoding,
                       :isatty, :pid, :pos, :pos=, :reopen,
                       :seek, :string, :sync, :sync=, :tell,
                       :truncate, :tty?

  def binmode?
    if @io.respond_to?(:binmode?)
      @io.binmode?
    else
      false
    end
  end

  def flock(*args)
    raise NotImplementedError unless @io.respond_to?(:flock)
    @io.flock(*args)
  end

  def ioctl(*args)
    raise NotImplementedError unless @io.respond_to?(:ioctl)
    @io.ioctl(*args)
  end

  def path
    @io.path if @io.respond_to?(:path)
  end

  def stat(*args)
    raise NotImplementedError unless @io.respond_to?(:stat)
    @io.stat(*args)
  end

  def to_i
    raise NotImplementedError unless @io.respond_to?(:to_i)
    @io.to_i
  end

  def to_io
    @io.respond_to?(:to_io) ? @io.to_io : @io
  end

  def eof?
    return false if @eof_error
    begin
      parser_enumerator.peek
      false
    rescue MalformedCSVError => error
      @eof_error = error
      false
    rescue StopIteration
      true
    end
  end
  alias_method :eof, :eof?

  # Rewinds the underlying IO object and resets CSV's lineno() counter.
  def rewind
    @parser = nil
    @parser_enumerator = nil
    @eof_error = nil
    @writer.rewind if @writer
    @io.rewind
  end

  ### End Delegation ###

  # :call-seq:
  #   csv << row -> self
  #
  # Appends a row to +self+.
  #
  # - Argument +row+ must be an \Array object or a CSV::Row object.
  # - The output stream must be open for writing.
  #
  # ---
  #
  # Append Arrays:
  #   CSV.generate do |csv|
  #     csv << ['foo', 0]
  #     csv << ['bar', 1]
  #     csv << ['baz', 2]
  #   end # => "foo,0\nbar,1\nbaz,2\n"
  #
  # Append CSV::Rows:
  #   headers = []
  #   CSV.generate do |csv|
  #     csv << CSV::Row.new(headers, ['foo', 0])
  #     csv << CSV::Row.new(headers, ['bar', 1])
  #     csv << CSV::Row.new(headers, ['baz', 2])
  #   end # => "foo,0\nbar,1\nbaz,2\n"
  #
  # Headers in CSV::Row objects are not appended:
  #   headers = ['Name', 'Count']
  #   CSV.generate do |csv|
  #     csv << CSV::Row.new(headers, ['foo', 0])
  #     csv << CSV::Row.new(headers, ['bar', 1])
  #     csv << CSV::Row.new(headers, ['baz', 2])
  #   end # => "foo,0\nbar,1\nbaz,2\n"
  #
  # ---
  #
  # Raises an exception if +row+ is not an \Array or \CSV::Row:
  #   CSV.generate do |csv|
  #     # Raises NoMethodError (undefined method `collect' for :foo:Symbol)
  #     csv << :foo
  #   end
  #
  # Raises an exception if the output stream is not opened for writing:
  #   path = 't.csv'
  #   File.write(path, '')
  #   File.open(path) do |file|
  #     CSV.open(file) do |csv|
  #       # Raises IOError (not opened for writing)
  #       csv << ['foo', 0]
  #     end
  #   end
  def <<(row)
    writer << row
    self
  end
  alias_method :add_row, :<<
  alias_method :puts,    :<<

  # :call-seq:
  #   convert(converter_name) -> array_of_procs
  #   convert {|field, field_info| ... } -> array_of_procs
  #
  # - With no block, installs a field converter (a \Proc).
  # - With a block, defines and installs a custom field converter.
  # - Returns the \Array of installed field converters.
  #
  # - Argument +converter_name+, if given, should be the name
  #   of an existing field converter.
  #
  # See {Field Converters}[#class-CSV-label-Field+Converters].
  # ---
  #
  # With no block, installs a field converter:
  #   csv = CSV.new('')
  #   csv.convert(:integer)
  #   csv.convert(:float)
  #   csv.convert(:date)
  #   csv.converters # => [:integer, :float, :date]
  #
  # ---
  #
  # The block, if given, is called for each field:
  # - Argument +field+ is the field value.
  # - Argument +field_info+ is a CSV::FieldInfo object
  #   containing details about the field.
  #
  # The examples here assume the prior execution of:
  #   string = "foo,0\nbar,1\nbaz,2\n"
  #   path = 't.csv'
  #   File.write(path, string)
  #
  # Example giving a block:
  #   csv = CSV.open(path)
  #   csv.convert {|field, field_info| p [field, field_info]; field.upcase }
  #   csv.read # => [["FOO", "0"], ["BAR", "1"], ["BAZ", "2"]]
  #
  # Output:
  #   ["foo", #<struct CSV::FieldInfo index=0, line=1, header=nil>]
  #   ["0", #<struct CSV::FieldInfo index=1, line=1, header=nil>]
  #   ["bar", #<struct CSV::FieldInfo index=0, line=2, header=nil>]
  #   ["1", #<struct CSV::FieldInfo index=1, line=2, header=nil>]
  #   ["baz", #<struct CSV::FieldInfo index=0, line=3, header=nil>]
  #   ["2", #<struct CSV::FieldInfo index=1, line=3, header=nil>]
  #
  # The block need not return a \String object:
  #   csv = CSV.open(path)
  #   csv.convert {|field, field_info| field.to_sym }
  #   csv.read # => [[:foo, :"0"], [:bar, :"1"], [:baz, :"2"]]
  #
  # If +converter_name+ is given, the block is not called:
  #   csv = CSV.open(path)
  #   csv.convert(:integer) {|field, field_info| fail 'Cannot happen' }
  #   csv.read # => [["foo", 0], ["bar", 1], ["baz", 2]]
  #
  # ---
  #
  # Raises a parse-time exception if +converter_name+ is not the name of a built-in
  # field converter:
  #   csv = CSV.open(path)
  #   csv.convert(:nosuch) => [nil]
  #   # Raises NoMethodError (undefined method `arity' for nil:NilClass)
  #   csv.read
  def convert(name = nil, &converter)
    parser_fields_converter.add_converter(name, &converter)
  end

  # :call-seq:
  #   header_convert(converter_name) -> array_of_procs
  #   header_convert {|header, field_info| ... } -> array_of_procs
  #
  # - With no block, installs a header converter (a \Proc).
  # - With a block, defines and installs a custom header converter.
  # - Returns the \Array of installed header converters.
  #
  # - Argument +converter_name+, if given, should be the name
  #   of an existing header converter.
  #
  # See {Header Converters}[#class-CSV-label-Header+Converters].
  # ---
  #
  # With no block, installs a header converter:
  #   csv = CSV.new('')
  #   csv.header_convert(:symbol)
  #   csv.header_convert(:downcase)
  #   csv.header_converters # => [:symbol, :downcase]
  #
  # ---
  #
  # The block, if given, is called for each header:
  # - Argument +header+ is the header value.
  # - Argument +field_info+ is a CSV::FieldInfo object
  #   containing details about the header.
  #
  # The examples here assume the prior execution of:
  #   string = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
  #   path = 't.csv'
  #   File.write(path, string)
  #
  # Example giving a block:
  #   csv = CSV.open(path, headers: true)
  #   csv.header_convert {|header, field_info| p [header, field_info]; header.upcase }
  #   table = csv.read
  #   table # => #<CSV::Table mode:col_or_row row_count:4>
  #   table.headers # => ["NAME", "VALUE"]
  #
  # Output:
  #   ["Name", #<struct CSV::FieldInfo index=0, line=1, header=nil>]
  #   ["Value", #<struct CSV::FieldInfo index=1, line=1, header=nil>]

  # The block need not return a \String object:
  #   csv = CSV.open(path, headers: true)
  #   csv.header_convert {|header, field_info| header.to_sym }
  #   table = csv.read
  #   table.headers # => [:Name, :Value]
  #
  # If +converter_name+ is given, the block is not called:
  #   csv = CSV.open(path, headers: true)
  #   csv.header_convert(:downcase) {|header, field_info| fail 'Cannot happen' }
  #   table = csv.read
  #   table.headers # => ["name", "value"]
  # ---
  #
  # Raises a parse-time exception if +converter_name+ is not the name of a built-in
  # field converter:
  #   csv = CSV.open(path, headers: true)
  #   csv.header_convert(:nosuch)
  #   # Raises NoMethodError (undefined method `arity' for nil:NilClass)
  #   csv.read
  def header_convert(name = nil, &converter)
    header_fields_converter.add_converter(name, &converter)
  end

  include Enumerable

  # :call-seq:
  #   csv.each -> enumerator
  #   csv.each {|row| ...}
  #
  # Calls the block with each successive row.
  # The data source must be opened for reading.
  #
  # Without headers:
  #   string = "foo,0\nbar,1\nbaz,2\n"
  #   csv = CSV.new(string)
  #   csv.each do |row|
  #     p row
  #   end
  # Output:
  #   ["foo", "0"]
  #   ["bar", "1"]
  #   ["baz", "2"]
  #
  # With headers:
  #   string = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
  #   csv = CSV.new(string, headers: true)
  #   csv.each do |row|
  #     p row
  #   end
  # Output:
  #   <CSV::Row "Name":"foo" "Value":"0">
  #   <CSV::Row "Name":"bar" "Value":"1">
  #   <CSV::Row "Name":"baz" "Value":"2">
  #
  # ---
  #
  # Raises an exception if the source is not opened for reading:
  #   string = "foo,0\nbar,1\nbaz,2\n"
  #   csv = CSV.new(string)
  #   csv.close
  #   # Raises IOError (not opened for reading)
  #   csv.each do |row|
  #     p row
  #   end
  def each(&block)
    parser_enumerator.each(&block)
  end

  # :call-seq:
  #   csv.read -> array or csv_table
  #
  # Forms the remaining rows from +self+ into:
  # - A CSV::Table object, if headers are in use.
  # - An \Array of Arrays, otherwise.
  #
  # The data source must be opened for reading.
  #
  # Without headers:
  #   string = "foo,0\nbar,1\nbaz,2\n"
  #   path = 't.csv'
  #   File.write(path, string)
  #   csv = CSV.open(path)
  #   csv.read # => [["foo", "0"], ["bar", "1"], ["baz", "2"]]
  #
  # With headers:
  #   string = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
  #   path = 't.csv'
  #   File.write(path, string)
  #   csv = CSV.open(path, headers: true)
  #   csv.read # => #<CSV::Table mode:col_or_row row_count:4>
  #
  # ---
  #
  # Raises an exception if the source is not opened for reading:
  #   string = "foo,0\nbar,1\nbaz,2\n"
  #   csv = CSV.new(string)
  #   csv.close
  #   # Raises IOError (not opened for reading)
  #   csv.read
  def read
    rows = to_a
    if parser.use_headers?
      Table.new(rows, headers: parser.headers)
    else
      rows
    end
  end
  alias_method :readlines, :read

  # :call-seq:
  #   csv.header_row? -> true or false
  #
  # Returns +true+ if the next row to be read is a header row\;
  # +false+ otherwise.
  #
  # Without headers:
  #   string = "foo,0\nbar,1\nbaz,2\n"
  #   csv = CSV.new(string)
  #   csv.header_row? # => false
  #
  # With headers:
  #   string = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
  #   csv = CSV.new(string, headers: true)
  #   csv.header_row? # => true
  #   csv.shift # => #<CSV::Row "Name":"foo" "Value":"0">
  #   csv.header_row? # => false
  #
  # ---
  #
  # Raises an exception if the source is not opened for reading:
  #   string = "foo,0\nbar,1\nbaz,2\n"
  #   csv = CSV.new(string)
  #   csv.close
  #   # Raises IOError (not opened for reading)
  #   csv.header_row?
  def header_row?
    parser.header_row?
  end

  # :call-seq:
  #   csv.shift -> array, csv_row, or nil
  #
  # Returns the next row of data as:
  # - An \Array if no headers are used.
  # - A CSV::Row object if headers are used.
  #
  # The data source must be opened for reading.
  #
  # Without headers:
  #   string = "foo,0\nbar,1\nbaz,2\n"
  #   csv = CSV.new(string)
  #   csv.shift # => ["foo", "0"]
  #   csv.shift # => ["bar", "1"]
  #   csv.shift # => ["baz", "2"]
  #   csv.shift # => nil
  #
  # With headers:
  #   string = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
  #   csv = CSV.new(string, headers: true)
  #   csv.shift # => #<CSV::Row "Name":"foo" "Value":"0">
  #   csv.shift # => #<CSV::Row "Name":"bar" "Value":"1">
  #   csv.shift # => #<CSV::Row "Name":"baz" "Value":"2">
  #   csv.shift # => nil
  #
  # ---
  #
  # Raises an exception if the source is not opened for reading:
  #   string = "foo,0\nbar,1\nbaz,2\n"
  #   csv = CSV.new(string)
  #   csv.close
  #   # Raises IOError (not opened for reading)
  #   csv.shift
  def shift
    if @eof_error
      eof_error, @eof_error = @eof_error, nil
      raise eof_error
    end
    begin
      parser_enumerator.next
    rescue StopIteration
      nil
    end
  end
  alias_method :gets,     :shift
  alias_method :readline, :shift

  # :call-seq:
  #   csv.inspect -> string
  #
  # Returns a \String showing certain properties of +self+:
  #   string = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
  #   csv = CSV.new(string, headers: true)
  #   s = csv.inspect
  #   s # => "#<CSV io_type:StringIO encoding:UTF-8 lineno:0 col_sep:\",\" row_sep:\"\\n\" quote_char:\"\\\"\" headers:true>"
  def inspect
    str = ["#<", self.class.to_s, " io_type:"]
    # show type of wrapped IO
    if    @io == $stdout then str << "$stdout"
    elsif @io == $stdin  then str << "$stdin"
    elsif @io == $stderr then str << "$stderr"
    else                      str << @io.class.to_s
    end
    # show IO.path(), if available
    if @io.respond_to?(:path) and (p = @io.path)
      str << " io_path:" << p.inspect
    end
    # show encoding
    str << " encoding:" << @encoding.name
    # show other attributes
    ["lineno", "col_sep", "row_sep", "quote_char"].each do |attr_name|
      if a = __send__(attr_name)
        str << " " << attr_name << ":" << a.inspect
      end
    end
    ["skip_blanks", "liberal_parsing"].each do |attr_name|
      if a = __send__("#{attr_name}?")
        str << " " << attr_name << ":" << a.inspect
      end
    end
    _headers = headers
    str << " headers:" << _headers.inspect if _headers
    str << ">"
    begin
      str.join('')
    rescue  # any encoding error
      str.map do |s|
        e = Encoding::Converter.asciicompat_encoding(s.encoding)
        e ? s.encode(e) : s.force_encoding("ASCII-8BIT")
      end.join('')
    end
  end

  private

  def determine_encoding(encoding, internal_encoding)
    # honor the IO encoding if we can, otherwise default to ASCII-8BIT
    io_encoding = raw_encoding
    return io_encoding if io_encoding

    return Encoding.find(internal_encoding) if internal_encoding

    if encoding
      encoding, = encoding.split(":", 2) if encoding.is_a?(String)
      return Encoding.find(encoding)
    end

    Encoding.default_internal || Encoding.default_external
  end

  def normalize_converters(converters)
    converters ||= []
    unless converters.is_a?(Array)
      converters = [converters]
    end
    converters.collect do |converter|
      case converter
      when Proc # custom code block
        [nil, converter]
      else # by name
        [converter, nil]
      end
    end
  end

  #
  # Processes +fields+ with <tt>@converters</tt>, or <tt>@header_converters</tt>
  # if +headers+ is passed as +true+, returning the converted field set. Any
  # converter that changes the field into something other than a String halts
  # the pipeline of conversion for that field. This is primarily an efficiency
  # shortcut.
  #
  def convert_fields(fields, headers = false)
    if headers
      header_fields_converter.convert(fields, nil, 0)
    else
      parser_fields_converter.convert(fields, @headers, lineno)
    end
  end

  #
  # Returns the encoding of the internal IO object.
  #
  def raw_encoding
    if @io.respond_to? :internal_encoding
      @io.internal_encoding || @io.external_encoding
    elsif @io.respond_to? :encoding
      @io.encoding
    else
      nil
    end
  end

  def parser_fields_converter
    @parser_fields_converter ||= build_parser_fields_converter
  end

  def build_parser_fields_converter
    specific_options = {
      builtin_converters_name: :Converters,
    }
    options = @base_fields_converter_options.merge(specific_options)
    build_fields_converter(@initial_converters, options)
  end

  def header_fields_converter
    @header_fields_converter ||= build_header_fields_converter
  end

  def build_header_fields_converter
    specific_options = {
      builtin_converters_name: :HeaderConverters,
      accept_nil: true,
    }
    options = @base_fields_converter_options.merge(specific_options)
    build_fields_converter(@initial_header_converters, options)
  end

  def writer_fields_converter
    @writer_fields_converter ||= build_writer_fields_converter
  end

  def build_writer_fields_converter
    build_fields_converter(@initial_write_converters,
                           @write_fields_converter_options)
  end

  def build_fields_converter(initial_converters, options)
    fields_converter = FieldsConverter.new(options)
    normalize_converters(initial_converters).each do |name, converter|
      fields_converter.add_converter(name, &converter)
    end
    fields_converter
  end

  def parser
    @parser ||= Parser.new(@io, parser_options)
  end

  def parser_options
    @parser_options.merge(header_fields_converter: header_fields_converter,
                          fields_converter: parser_fields_converter)
  end

  def parser_enumerator
    @parser_enumerator ||= parser.parse
  end

  def writer
    @writer ||= Writer.new(@io, writer_options)
  end

  def writer_options
    @writer_options.merge(header_fields_converter: header_fields_converter,
                          fields_converter: writer_fields_converter)
  end
end

# Passes +args+ to CSV::instance.
#
#   CSV("CSV,data").read
#     #=> [["CSV", "data"]]
#
# If a block is given, the instance is passed the block and the return value
# becomes the return value of the block.
#
#   CSV("CSV,data") { |c|
#     c.read.any? { |a| a.include?("data") }
#   } #=> true
#
#   CSV("CSV,data") { |c|
#     c.read.any? { |a| a.include?("zombies") }
#   } #=> false
#
# CSV options may also be given.
#
#   io = StringIO.new
#   CSV(io, col_sep: ";") { |csv| csv << ["a", "b", "c"] }
#
# This API is not Ractor-safe.
#
def CSV(*args, **options, &block)
  CSV.instance(*args, **options, &block)
end

require_relative "csv/version"
require_relative "csv/core_ext/array"
require_relative "csv/core_ext/string"
debug log:

solving 42e99435cbf2 ...
found 42e99435cbf2 in https://80x24.org/mirrors/ruby.git

Code repositories for project(s) associated with this inbox:

	https://80x24.org/mirrors/ruby.git

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).