c_str.rs - source
Description: Source of the Rust file `library/std/src/ffi/c_str.rs`.
Keywords: rust, rustlang, rust-lang

       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

    #![deny(unsafe_op_in_unsafe_fn)]

    #[cfg(test)]
    mod tests;

    use crate::ascii;
    use crate::borrow::{Borrow, Cow};
    use crate::cmp::Ordering;
    use crate::error::Error;
    use crate::fmt::{self, Write};
    use crate::io;
    use crate::mem;
    use crate::memchr;
    use crate::num::NonZeroU8;
    use crate::ops;
    use crate::os::raw::c_char;
    use crate::ptr;
    use crate::rc::Rc;
    use crate::slice;
    use crate::str::{self, Utf8Error};
    use crate::sync::Arc;
    use crate::sys;

    /// A type representing an owned, C-compatible, nul-terminated string with no nul bytes in the
    /// middle.
    ///
    /// This type serves the purpose of being able to safely generate a
    /// C-compatible string from a Rust byte slice or vector. An instance of this
    /// type is a static guarantee that the underlying bytes contain no interior 0
    /// bytes ("nul characters") and that the final byte is 0 ("nul terminator").
    ///
    /// `CString` is to [`&CStr`] as [`String`] is to [`&str`]: the former
    /// in each pair are owned strings; the latter are borrowed
    /// references.
    ///
    /// # Creating a `CString`
    ///
    /// A `CString` is created from either a byte slice or a byte vector,
    /// or anything that implements [`Into`]`<`[`Vec`]`<`[`u8`]`>>` (for
    /// example, you can build a `CString` straight out of a [`String`] or
    /// a [`&str`], since both implement that trait).
    ///
    /// The [`CString::new`] method will actually check that the provided `&[u8]`
    /// does not have 0 bytes in the middle, and return an error if it
    /// finds one.
    ///
    /// # Extracting a raw pointer to the whole C string
    ///
    /// `CString` implements a [`as_ptr`][`CStr::as_ptr`] method through the [`Deref`]
    /// trait. This method will give you a `*const c_char` which you can
    /// feed directly to extern functions that expect a nul-terminated
    /// string, like C's `strdup()`. Notice that [`as_ptr`][`CStr::as_ptr`] returns a
    /// read-only pointer; if the C code writes to it, that causes
    /// undefined behavior.
    ///
    /// # Extracting a slice of the whole C string
    ///
    /// Alternatively, you can obtain a `&[`[`u8`]`]` slice from a
    /// `CString` with the [`CString::as_bytes`] method. Slices produced in this
    /// way do *not* contain the trailing nul terminator. This is useful
    /// when you will be calling an extern function that takes a `*const
    /// u8` argument which is not necessarily nul-terminated, plus another
    /// argument with the length of the string — like C's `strndup()`.
    /// You can of course get the slice's length with its
    /// [`len`][slice.len] method.
    ///
    /// If you need a `&[`[`u8`]`]` slice *with* the nul terminator, you
    /// can use [`CString::as_bytes_with_nul`] instead.
    ///
    /// Once you have the kind of slice you need (with or without a nul
    /// terminator), you can call the slice's own
    /// [`as_ptr`][slice.as_ptr] method to get a read-only raw pointer to pass to
    /// extern functions. See the documentation for that function for a
    /// discussion on ensuring the lifetime of the raw pointer.
    ///
    /// [`&str`]: prim@str
    /// [slice.as_ptr]: ../primitive.slice.html#method.as_ptr
    /// [slice.len]: ../primitive.slice.html#method.len
    /// [`Deref`]: ops::Deref
    /// [`&CStr`]: CStr
    ///
    /// # Examples
    ///
    /// ```ignore (extern-declaration)
    /// # fn main() {
    /// use std::ffi::CString;
    /// use std::os::raw::c_char;
    ///
    /// extern {
    ///     fn my_printer(s: *const c_char);
    /// }
    ///
    /// // We are certain that our string doesn't have 0 bytes in the middle,
    /// // so we can .expect()
    /// let c_to_print = CString::new("Hello, world!").expect("CString::new failed");
    /// unsafe {
    ///     my_printer(c_to_print.as_ptr());
    /// }
    /// # }
    /// ```
    ///
    /// # Safety
    ///
    /// `CString` is intended for working with traditional C-style strings
    /// (a sequence of non-nul bytes terminated by a single nul byte); the
    /// primary use case for these kinds of strings is interoperating with C-like
    /// code. Often you will need to transfer ownership to/from that external
    /// code. It is strongly recommended that you thoroughly read through the
    /// documentation of `CString` before use, as improper ownership management
    /// of `CString` instances can lead to invalid memory accesses, memory leaks,
    /// and other memory errors.
    #[derive(PartialEq, PartialOrd, Eq, Ord, Hash, Clone)]
    #[cfg_attr(not(test), rustc_diagnostic_item = "cstring_type")]
    #[stable(feature = "rust1", since = "1.0.0")]
    pub struct CString {
        // Invariant 1: the slice ends with a zero byte and has a length of at least one.
        // Invariant 2: the slice contains only one zero byte.
        // Improper usage of unsafe function can break Invariant 2, but not Invariant 1.
        inner: Box<[u8]>,
    }

    /// Representation of a borrowed C string.
    ///
    /// This type represents a borrowed reference to a nul-terminated
    /// array of bytes. It can be constructed safely from a `&[`[`u8`]`]`
    /// slice, or unsafely from a raw `*const c_char`. It can then be
    /// converted to a Rust [`&str`] by performing UTF-8 validation, or
    /// into an owned [`CString`].
    ///
    /// `&CStr` is to [`CString`] as [`&str`] is to [`String`]: the former
    /// in each pair are borrowed references; the latter are owned
    /// strings.
    ///
    /// Note that this structure is **not** `repr(C)` and is not recommended to be
    /// placed in the signatures of FFI functions. Instead, safe wrappers of FFI
    /// functions may leverage the unsafe [`CStr::from_ptr`] constructor to provide
    /// a safe interface to other consumers.
    ///
    /// # Examples
    ///
    /// Inspecting a foreign C string:
    ///
    /// ```ignore (extern-declaration)
    /// use std::ffi::CStr;
    /// use std::os::raw::c_char;
    ///
    /// extern { fn my_string() -> *const c_char; }
    ///
    /// unsafe {
    ///     let slice = CStr::from_ptr(my_string());
    ///     println!("string buffer size without nul terminator: {}", slice.to_bytes().len());
    /// }
    /// ```
    ///
    /// Passing a Rust-originating C string:
    ///
    /// ```ignore (extern-declaration)
    /// use std::ffi::{CString, CStr};
    /// use std::os::raw::c_char;
    ///
    /// fn work(data: &CStr) {
    ///     extern { fn work_with(data: *const c_char); }
    ///
    ///     unsafe { work_with(data.as_ptr()) }
    /// }
    ///
    /// let s = CString::new("data data data data").expect("CString::new failed");
    /// work(&s);
    /// ```
    ///
    /// Converting a foreign C string into a Rust [`String`]:
    ///
    /// ```ignore (extern-declaration)
    /// use std::ffi::CStr;
    /// use std::os::raw::c_char;
    ///
    /// extern { fn my_string() -> *const c_char; }
    ///
    /// fn my_string_safe() -> String {
    ///     unsafe {
    ///         CStr::from_ptr(my_string()).to_string_lossy().into_owned()
    ///     }
    /// }
    ///
    /// println!("string: {}", my_string_safe());
    /// ```
    ///
    /// [`&str`]: prim@str
    #[derive(Hash)]
    #[stable(feature = "rust1", since = "1.0.0")]
    // FIXME:
    // `fn from` in `impl From<&CStr> for Box<CStr>` current implementation relies
    // on `CStr` being layout-compatible with `[u8]`.
    // When attribute privacy is implemented, `CStr` should be annotated as `#[repr(transparent)]`.
    // Anyway, `CStr` representation and layout are considered implementation detail, are
    // not documented and must not be relied upon.
    pub struct CStr {
        // FIXME: this should not be represented with a DST slice but rather with
        //        just a raw `c_char` along with some form of marker to make
        //        this an unsized type. Essentially `sizeof(&CStr)` should be the
        //        same as `sizeof(&c_char)` but `CStr` should be an unsized type.
        inner: [c_char],
    }

    /// An error indicating that an interior nul byte was found.
    ///
    /// While Rust strings may contain nul bytes in the middle, C strings
    /// can't, as that byte would effectively truncate the string.
    ///
    /// This error is created by the [`new`][`CString::new`] method on
    /// [`CString`]. See its documentation for more.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::ffi::{CString, NulError};
    ///
    /// let _: NulError = CString::new(b"f\0oo".to_vec()).unwrap_err();
    /// ```
    #[derive(Clone, PartialEq, Eq, Debug)]
    #[stable(feature = "rust1", since = "1.0.0")]
    pub struct NulError(usize, Vec<u8>);

    /// An error indicating that a nul byte was not in the expected position.
    ///
    /// The slice used to create a [`CStr`] must have one and only one nul byte,
    /// positioned at the end.
    ///
    /// This error is created by the [`CStr::from_bytes_with_nul`] method.
    /// See its documentation for more.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::ffi::{CStr, FromBytesWithNulError};
    ///
    /// let _: FromBytesWithNulError = CStr::from_bytes_with_nul(b"f\0oo").unwrap_err();
    /// ```
    #[derive(Clone, PartialEq, Eq, Debug)]
    #[stable(feature = "cstr_from_bytes", since = "1.10.0")]
    pub struct FromBytesWithNulError {
        kind: FromBytesWithNulErrorKind,
    }

    /// An error indicating that a nul byte was not in the expected position.
    ///
    /// The vector used to create a [`CString`] must have one and only one nul byte,
    /// positioned at the end.
    ///
    /// This error is created by the [`CString::from_vec_with_nul`] method.
    /// See its documentation for more.
    ///
    /// # Examples
    ///
    /// ```
    /// #![feature(cstring_from_vec_with_nul)]
    /// use std::ffi::{CString, FromVecWithNulError};
    ///
    /// let _: FromVecWithNulError = CString::from_vec_with_nul(b"f\0oo".to_vec()).unwrap_err();
    /// ```
    #[derive(Clone, PartialEq, Eq, Debug)]
    #[unstable(feature = "cstring_from_vec_with_nul", issue = "73179")]
    pub struct FromVecWithNulError {
        error_kind: FromBytesWithNulErrorKind,
        bytes: Vec<u8>,
    }

    #[derive(Clone, PartialEq, Eq, Debug)]
    enum FromBytesWithNulErrorKind {
        InteriorNul(usize),
        NotNulTerminated,
    }

    impl FromBytesWithNulError {
        fn interior_nul(pos: usize) -> FromBytesWithNulError {
            FromBytesWithNulError { kind: FromBytesWithNulErrorKind::InteriorNul(pos) }
        }
        fn not_nul_terminated() -> FromBytesWithNulError {
            FromBytesWithNulError { kind: FromBytesWithNulErrorKind::NotNulTerminated }
        }
    }

    #[unstable(feature = "cstring_from_vec_with_nul", issue = "73179")]
    impl FromVecWithNulError {
        /// Returns a slice of [`u8`]s bytes that were attempted to convert to a [`CString`].
        ///
        /// # Examples
        ///
        /// Basic usage:
        ///
        /// ```
        /// #![feature(cstring_from_vec_with_nul)]
        /// use std::ffi::CString;
        ///
        /// // Some invalid bytes in a vector
        /// let bytes = b"f\0oo".to_vec();
        ///
        /// let value = CString::from_vec_with_nul(bytes.clone());
        ///
        /// assert_eq!(&bytes[..], value.unwrap_err().as_bytes());
        /// ```
        pub fn as_bytes(&self) -> &[u8] {
            &self.bytes[..]
        }

        /// Returns the bytes that were attempted to convert to a [`CString`].
        ///
        /// This method is carefully constructed to avoid allocation. It will
        /// consume the error, moving out the bytes, so that a copy of the bytes
        /// does not need to be made.
        ///
        /// # Examples
        ///
        /// Basic usage:
        ///
        /// ```
        /// #![feature(cstring_from_vec_with_nul)]
        /// use std::ffi::CString;
        ///
        /// // Some invalid bytes in a vector
        /// let bytes = b"f\0oo".to_vec();
        ///
        /// let value = CString::from_vec_with_nul(bytes.clone());
        ///
        /// assert_eq!(bytes, value.unwrap_err().into_bytes());
        /// ```
        pub fn into_bytes(self) -> Vec<u8> {
            self.bytes
        }
    }

    /// An error indicating invalid UTF-8 when converting a [`CString`] into a [`String`].
    ///
    /// `CString` is just a wrapper over a buffer of bytes with a nul terminator;
    /// [`CString::into_string`] performs UTF-8 validation on those bytes and may
    /// return this error.
    ///
    /// This `struct` is created by [`CString::into_string()`]. See
    /// its documentation for more.
    #[derive(Clone, PartialEq, Eq, Debug)]
    #[stable(feature = "cstring_into", since = "1.7.0")]
    pub struct IntoStringError {
        inner: CString,
        error: Utf8Error,
    }

    impl CString {
        /// Creates a new C-compatible string from a container of bytes.
        ///
        /// This function will consume the provided data and use the
        /// underlying bytes to construct a new string, ensuring that
        /// there is a trailing 0 byte. This trailing 0 byte will be
        /// appended by this function; the provided data should *not*
        /// contain any 0 bytes in it.
        ///
        /// # Examples
        ///
        /// ```ignore (extern-declaration)
        /// use std::ffi::CString;
        /// use std::os::raw::c_char;
        ///
        /// extern { fn puts(s: *const c_char); }
        ///
        /// let to_print = CString::new("Hello!").expect("CString::new failed");
        /// unsafe {
        ///     puts(to_print.as_ptr());
        /// }
        /// ```
        ///
        /// # Errors
        ///
        /// This function will return an error if the supplied bytes contain an
        /// internal 0 byte. The [`NulError`] returned will contain the bytes as well as
        /// the position of the nul byte.
        #[stable(feature = "rust1", since = "1.0.0")]
        pub fn new<T: Into<Vec<u8>>>(t: T) -> Result<CString, NulError> {
            trait SpecIntoVec {
                fn into_vec(self) -> Vec<u8>;
            }
            impl<T: Into<Vec<u8>>> SpecIntoVec for T {
                default fn into_vec(self) -> Vec<u8> {
                    self.into()
                }
            }
            // Specialization for avoiding reallocation.
            impl SpecIntoVec for &'_ [u8] {
                fn into_vec(self) -> Vec<u8> {
                    let mut v = Vec::with_capacity(self.len() + 1);
                    v.extend(self);
                    v
                }
            }
            impl SpecIntoVec for &'_ str {
                fn into_vec(self) -> Vec<u8> {
                    let mut v = Vec::with_capacity(self.len() + 1);
                    v.extend(self.as_bytes());
                    v
                }
            }

            Self::_new(SpecIntoVec::into_vec(t))
        }

        fn _new(bytes: Vec<u8>) -> Result<CString, NulError> {
            match memchr::memchr(0, &bytes) {
                Some(i) => Err(NulError(i, bytes)),
                None => Ok(unsafe { CString::from_vec_unchecked(bytes) }),
            }
        }

        /// Creates a C-compatible string by consuming a byte vector,
        /// without checking for interior 0 bytes.
        ///
        /// This method is equivalent to [`CString::new`] except that no runtime
        /// assertion is made that `v` contains no 0 bytes, and it requires an
        /// actual byte vector, not anything that can be converted to one with Into.
        ///
        /// # Examples
        ///
        /// ```
        /// use std::ffi::CString;
        ///
        /// let raw = b"foo".to_vec();
        /// unsafe {
        ///     let c_string = CString::from_vec_unchecked(raw);
        /// }
        /// ```
        #[stable(feature = "rust1", since = "1.0.0")]
        pub unsafe fn from_vec_unchecked(mut v: Vec<u8>) -> CString {
            v.reserve_exact(1);
            v.push(0);
            CString { inner: v.into_boxed_slice() }
        }

        /// Retakes ownership of a `CString` that was transferred to C via
        /// [`CString::into_raw`].
        ///
        /// Additionally, the length of the string will be recalculated from the pointer.
        ///
        /// # Safety
        ///
        /// This should only ever be called with a pointer that was earlier
        /// obtained by calling [`CString::into_raw`]. Other usage (e.g., trying to take
        /// ownership of a string that was allocated by foreign code) is likely to lead
        /// to undefined behavior or allocator corruption.
        ///
        /// It should be noted that the length isn't just "recomputed," but that
        /// the recomputed length must match the original length from the
        /// [`CString::into_raw`] call. This means the [`CString::into_raw`]/`from_raw`
        /// methods should not be used when passing the string to C functions that can
        /// modify the string's length.
        ///
        /// > **Note:** If you need to borrow a string that was allocated by
        /// > foreign code, use [`CStr`]. If you need to take ownership of
        /// > a string that was allocated by foreign code, you will need to
        /// > make your own provisions for freeing it appropriately, likely
        /// > with the foreign code's API to do that.
        ///
        /// # Examples
        ///
        /// Creates a `CString`, pass ownership to an `extern` function (via raw pointer), then retake
        /// ownership with `from_raw`:
        ///
        /// ```ignore (extern-declaration)
        /// use std::ffi::CString;
        /// use std::os::raw::c_char;
        ///
        /// extern {
        ///     fn some_extern_function(s: *mut c_char);
        /// }
        ///
        /// let c_string = CString::new("Hello!").expect("CString::new failed");
        /// let raw = c_string.into_raw();
        /// unsafe {
        ///     some_extern_function(raw);
        ///     let c_string = CString::from_raw(raw);
        /// }
        /// ```
        #[stable(feature = "cstr_memory", since = "1.4.0")]
        pub unsafe fn from_raw(ptr: *mut c_char) -> CString {
            // SAFETY: This is called with a pointer that was obtained from a call
            // to `CString::into_raw` and the length has not been modified. As such,
            // we know there is a NUL byte (and only one) at the end and that the
            // information about the size of the allocation is correct on Rust's
            // side.
            unsafe {
                let len = sys::strlen(ptr) + 1; // Including the NUL byte
                let slice = slice::from_raw_parts_mut(ptr, len as usize);
                CString { inner: Box::from_raw(slice as *mut [c_char] as *mut [u8]) }
            }
        }

        /// Consumes the `CString` and transfers ownership of the string to a C caller.
        ///
        /// The pointer which this function returns must be returned to Rust and reconstituted using
        /// [`CString::from_raw`] to be properly deallocated. Specifically, one
        /// should *not* use the standard C `free()` function to deallocate
        /// this string.
        ///
        /// Failure to call [`CString::from_raw`] will lead to a memory leak.
        ///
        /// The C side must **not** modify the length of the string (by writing a
        /// `NULL` somewhere inside the string or removing the final one) before
        /// it makes it back into Rust using [`CString::from_raw`]. See the safety section
        /// in [`CString::from_raw`].
        ///
        /// # Examples
        ///
        /// ```
        /// use std::ffi::CString;
        ///
        /// let c_string = CString::new("foo").expect("CString::new failed");
        ///
        /// let ptr = c_string.into_raw();
        ///
        /// unsafe {
        ///     assert_eq!(b'f', *ptr as u8);
        ///     assert_eq!(b'o', *ptr.offset(1) as u8);
        ///     assert_eq!(b'o', *ptr.offset(2) as u8);
        ///     assert_eq!(b'\0', *ptr.offset(3) as u8);
        ///
        ///     // retake pointer to free memory
        ///     let _ = CString::from_raw(ptr);
        /// }
        /// ```
        #[inline]
        #[stable(feature = "cstr_memory", since = "1.4.0")]
        pub fn into_raw(self) -> *mut c_char {
            Box::into_raw(self.into_inner()) as *mut c_char
        }

        /// Converts the `CString` into a [`String`] if it contains valid UTF-8 data.
        ///
        /// On failure, ownership of the original `CString` is returned.
        ///
        /// # Examples
        ///
        /// ```
        /// use std::ffi::CString;
        ///
        /// let valid_utf8 = vec![b'f', b'o', b'o'];
        /// let cstring = CString::new(valid_utf8).expect("CString::new failed");
        /// assert_eq!(cstring.into_string().expect("into_string() call failed"), "foo");
        ///
        /// let invalid_utf8 = vec![b'f', 0xff, b'o', b'o'];
        /// let cstring = CString::new(invalid_utf8).expect("CString::new failed");
        /// let err = cstring.into_string().err().expect("into_string().err() failed");
        /// assert_eq!(err.utf8_error().valid_up_to(), 1);
        /// ```

        #[stable(feature = "cstring_into", since = "1.7.0")]
        pub fn into_string(self) -> Result<String, IntoStringError> {
            String::from_utf8(self.into_bytes()).map_err(|e| IntoStringError {
                error: e.utf8_error(),
                inner: unsafe { CString::from_vec_unchecked(e.into_bytes()) },
            })
        }

        /// Consumes the `CString` and returns the underlying byte buffer.
        ///
        /// The returned buffer does **not** contain the trailing nul
        /// terminator, and it is guaranteed to not have any interior nul
        /// bytes.
        ///
        /// # Examples
        ///
        /// ```
        /// use std::ffi::CString;
        ///
        /// let c_string = CString::new("foo").expect("CString::new failed");
        /// let bytes = c_string.into_bytes();
        /// assert_eq!(bytes, vec![b'f', b'o', b'o']);
        /// ```
        #[stable(feature = "cstring_into", since = "1.7.0")]
        pub fn into_bytes(self) -> Vec<u8> {
            let mut vec = self.into_inner().into_vec();
            let _nul = vec.pop();
            debug_assert_eq!(_nul, Some(0u8));
            vec
        }

        /// Equivalent to [`CString::into_bytes()`] except that the
        /// returned vector includes the trailing nul terminator.
        ///
        /// # Examples
        ///
        /// ```
        /// use std::ffi::CString;
        ///
        /// let c_string = CString::new("foo").expect("CString::new failed");
        /// let bytes = c_string.into_bytes_with_nul();
        /// assert_eq!(bytes, vec![b'f', b'o', b'o', b'\0']);
        /// ```
        #[stable(feature = "cstring_into", since = "1.7.0")]
        pub fn into_bytes_with_nul(self) -> Vec<u8> {
            self.into_inner().into_vec()
        }

        /// Returns the contents of this `CString` as a slice of bytes.
        ///
        /// The returned slice does **not** contain the trailing nul
        /// terminator, and it is guaranteed to not have any interior nul
        /// bytes. If you need the nul terminator, use
        /// [`CString::as_bytes_with_nul`] instead.
        ///
        /// # Examples
        ///
        /// ```
        /// use std::ffi::CString;
        ///
        /// let c_string = CString::new("foo").expect("CString::new failed");
        /// let bytes = c_string.as_bytes();
        /// assert_eq!(bytes, &[b'f', b'o', b'o']);
        /// ```
        #[inline]
        #[stable(feature = "rust1", since = "1.0.0")]
        pub fn as_bytes(&self) -> &[u8] {
            &self.inner[..self.inner.len() - 1]
        }

        /// Equivalent to [`CString::as_bytes()`] except that the
        /// returned slice includes the trailing nul terminator.
        ///
        /// # Examples
        ///
        /// ```
        /// use std::ffi::CString;
        ///
        /// let c_string = CString::new("foo").expect("CString::new failed");
        /// let bytes = c_string.as_bytes_with_nul();
        /// assert_eq!(bytes, &[b'f', b'o', b'o', b'\0']);
        /// ```
        #[inline]
        #[stable(feature = "rust1", since = "1.0.0")]
        pub fn as_bytes_with_nul(&self) -> &[u8] {
            &self.inner
        }

        /// Extracts a [`CStr`] slice containing the entire string.
        ///
        /// # Examples
        ///
        /// ```
        /// use std::ffi::{CString, CStr};
        ///
        /// let c_string = CString::new(b"foo".to_vec()).expect("CString::new failed");
        /// let cstr = c_string.as_c_str();
        /// assert_eq!(cstr,
        ///            CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed"));
        /// ```
        #[inline]
        #[stable(feature = "as_c_str", since = "1.20.0")]
        pub fn as_c_str(&self) -> &CStr {
            &*self
        }

        /// Converts this `CString` into a boxed [`CStr`].
        ///
        /// # Examples
        ///
        /// ```
        /// use std::ffi::{CString, CStr};
        ///
        /// let c_string = CString::new(b"foo".to_vec()).expect("CString::new failed");
        /// let boxed = c_string.into_boxed_c_str();
        /// assert_eq!(&*boxed,
        ///            CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed"));
        /// ```
        #[stable(feature = "into_boxed_c_str", since = "1.20.0")]
        pub fn into_boxed_c_str(self) -> Box<CStr> {
            unsafe { Box::from_raw(Box::into_raw(self.into_inner()) as *mut CStr) }
        }

        /// Bypass "move out of struct which implements [`Drop`] trait" restriction.
        fn into_inner(self) -> Box<[u8]> {
            // Rationale: `mem::forget(self)` invalidates the previous call to `ptr::read(&self.inner)`
            // so we use `ManuallyDrop` to ensure `self` is not dropped.
            // Then we can return the box directly without invalidating it.
            // See https://github.com/rust-lang/rust/issues/62553.
            let this = mem::ManuallyDrop::new(self);
            unsafe { ptr::read(&this.inner) }
        }

        /// Converts a [`Vec`]`<u8>` to a [`CString`] without checking the
        /// invariants on the given [`Vec`].
        ///
        /// # Safety
        ///
        /// The given [`Vec`] **must** have one nul byte as its last element.
        /// This means it cannot be empty nor have any other nul byte anywhere else.
        ///
        /// # Example
        ///
        /// ```
        /// #![feature(cstring_from_vec_with_nul)]
        /// use std::ffi::CString;
        /// assert_eq!(
        ///     unsafe { CString::from_vec_with_nul_unchecked(b"abc\0".to_vec()) },
        ///     unsafe { CString::from_vec_unchecked(b"abc".to_vec()) }
        /// );
        /// ```
        #[unstable(feature = "cstring_from_vec_with_nul", issue = "73179")]
        pub unsafe fn from_vec_with_nul_unchecked(v: Vec<u8>) -> Self {
            Self { inner: v.into_boxed_slice() }
        }

        /// Attempts to converts a [`Vec`]`<u8>` to a [`CString`].
        ///
        /// Runtime checks are present to ensure there is only one nul byte in the
        /// [`Vec`], its last element.
        ///
        /// # Errors
        ///
        /// If a nul byte is present and not the last element or no nul bytes
        /// is present, an error will be returned.
        ///
        /// # Examples
        ///
        /// A successful conversion will produce the same result as [`CString::new`]
        /// when called without the ending nul byte.
        ///
        /// ```
        /// #![feature(cstring_from_vec_with_nul)]
        /// use std::ffi::CString;
        /// assert_eq!(
        ///     CString::from_vec_with_nul(b"abc\0".to_vec())
        ///         .expect("CString::from_vec_with_nul failed"),
        ///     CString::new(b"abc".to_vec()).expect("CString::new failed")
        /// );
        /// ```
        ///
        /// A incorrectly formatted [`Vec`] will produce an error.
        ///
        /// ```
        /// #![feature(cstring_from_vec_with_nul)]
        /// use std::ffi::{CString, FromVecWithNulError};
        /// // Interior nul byte
        /// let _: FromVecWithNulError = CString::from_vec_with_nul(b"a\0bc".to_vec()).unwrap_err();
        /// // No nul byte
        /// let _: FromVecWithNulError = CString::from_vec_with_nul(b"abc".to_vec()).unwrap_err();
        /// ```
        #[unstable(feature = "cstring_from_vec_with_nul", issue = "73179")]
        pub fn from_vec_with_nul(v: Vec<u8>) -> Result<Self, FromVecWithNulError> {
            let nul_pos = memchr::memchr(0, &v);
            match nul_pos {
                Some(nul_pos) if nul_pos + 1 == v.len() => {
                    // SAFETY: We know there is only one nul byte, at the end
                    // of the vec.
                    Ok(unsafe { Self::from_vec_with_nul_unchecked(v) })
                }
                Some(nul_pos) => Err(FromVecWithNulError {
                    error_kind: FromBytesWithNulErrorKind::InteriorNul(nul_pos),
                    bytes: v,
                }),
                None => Err(FromVecWithNulError {
                    error_kind: FromBytesWithNulErrorKind::NotNulTerminated,
                    bytes: v,
                }),
            }
        }
    }

    // Turns this `CString` into an empty string to prevent
    // memory-unsafe code from working by accident. Inline
    // to prevent LLVM from optimizing it away in debug builds.
    #[stable(feature = "cstring_drop", since = "1.13.0")]
    impl Drop for CString {
        #[inline]
        fn drop(&mut self) {
            unsafe {
                *self.inner.get_unchecked_mut(0) = 0;
            }
        }
    }

    #[stable(feature = "rust1", since = "1.0.0")]
    impl ops::Deref for CString {
        type Target = CStr;

        #[inline]
        fn deref(&self) -> &CStr {
            unsafe { CStr::from_bytes_with_nul_unchecked(self.as_bytes_with_nul()) }
        }
    }

    #[stable(feature = "rust1", since = "1.0.0")]
    impl fmt::Debug for CString {
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            fmt::Debug::fmt(&**self, f)
        }
    }

    #[stable(feature = "cstring_into", since = "1.7.0")]
    impl From<CString> for Vec<u8> {
        /// Converts a [`CString`] into a [`Vec`]`<u8>`.
        ///
        /// The conversion consumes the [`CString`], and removes the terminating NUL byte.
        #[inline]
        fn from(s: CString) -> Vec<u8> {
            s.into_bytes()
        }
    }

    #[stable(feature = "cstr_debug", since = "1.3.0")]
    impl fmt::Debug for CStr {
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            write!(f, "\"")?;
            for byte in self.to_bytes().iter().flat_map(|&b| ascii::escape_default(b)) {
                f.write_char(byte as char)?;
            }
            write!(f, "\"")
        }
    }

    #[stable(feature = "cstr_default", since = "1.10.0")]
    impl Default for &CStr {
        fn default() -> Self {
            const SLICE: &[c_char] = &[0];
            unsafe { CStr::from_ptr(SLICE.as_ptr()) }
        }
    }

    #[stable(feature = "cstr_default", since = "1.10.0")]
    impl Default for CString {
        /// Creates an empty `CString`.
        fn default() -> CString {
            let a: &CStr = Default::default();
            a.to_owned()
        }
    }

    #[stable(feature = "cstr_borrow", since = "1.3.0")]
    impl Borrow<CStr> for CString {
        #[inline]
        fn borrow(&self) -> &CStr {
            self
        }
    }

    #[stable(feature = "cstring_from_cow_cstr", since = "1.28.0")]
    impl<'a> From<Cow<'a, CStr>> for CString {
        #[inline]
        fn from(s: Cow<'a, CStr>) -> Self {
            s.into_owned()
        }
    }

    #[stable(feature = "box_from_c_str", since = "1.17.0")]
    impl From<&CStr> for Box<CStr> {
        fn from(s: &CStr) -> Box<CStr> {
            let boxed: Box<[u8]> = Box::from(s.to_bytes_with_nul());
            unsafe { Box::from_raw(Box::into_raw(boxed) as *mut CStr) }
        }
    }

    #[stable(feature = "box_from_cow", since = "1.45.0")]
    impl From<Cow<'_, CStr>> for Box<CStr> {
        #[inline]
        fn from(cow: Cow<'_, CStr>) -> Box<CStr> {
            match cow {
                Cow::Borrowed(s) => Box::from(s),
                Cow::Owned(s) => Box::from(s),
            }
        }
    }

    #[stable(feature = "c_string_from_box", since = "1.18.0")]
    impl From<Box<CStr>> for CString {
        /// Converts a [`Box`]`<CStr>` into a [`CString`] without copying or allocating.
        #[inline]
        fn from(s: Box<CStr>) -> CString {
            s.into_c_string()
        }
    }

    #[stable(feature = "cstring_from_vec_of_nonzerou8", since = "1.43.0")]
    impl From<Vec<NonZeroU8>> for CString {
        /// Converts a [`Vec`]`<`[`NonZeroU8`]`>` into a [`CString`] without
        /// copying nor checking for inner null bytes.
        #[inline]
        fn from(v: Vec<NonZeroU8>) -> CString {
            unsafe {
                // Transmute `Vec<NonZeroU8>` to `Vec<u8>`.
                let v: Vec<u8> = {
                    // SAFETY:
                    //   - transmuting between `NonZeroU8` and `u8` is sound;
                    //   - `alloc::Layout<NonZeroU8> == alloc::Layout<u8>`.
                    let (ptr, len, cap): (*mut NonZeroU8, _, _) = Vec::into_raw_parts(v);
                    Vec::from_raw_parts(ptr.cast::<u8>(), len, cap)
                };
                // SAFETY: `v` cannot contain null bytes, given the type-level
                // invariant of `NonZeroU8`.
                CString::from_vec_unchecked(v)
            }
        }
    }

    #[stable(feature = "more_box_slice_clone", since = "1.29.0")]
    impl Clone for Box<CStr> {
        #[inline]
        fn clone(&self) -> Self {
            (**self).into()
        }
    }

    #[stable(feature = "box_from_c_string", since = "1.20.0")]
    impl From<CString> for Box<CStr> {
        /// Converts a [`CString`] into a [`Box`]`<CStr>` without copying or allocating.
        #[inline]
        fn from(s: CString) -> Box<CStr> {
            s.into_boxed_c_str()
        }
    }

    #[stable(feature = "cow_from_cstr", since = "1.28.0")]
    impl<'a> From<CString> for Cow<'a, CStr> {
        #[inline]
        fn from(s: CString) -> Cow<'a, CStr> {
            Cow::Owned(s)
        }
    }

    #[stable(feature = "cow_from_cstr", since = "1.28.0")]
    impl<'a> From<&'a CStr> for Cow<'a, CStr> {
        #[inline]
        fn from(s: &'a CStr) -> Cow<'a, CStr> {
            Cow::Borrowed(s)
        }
    }

    #[stable(feature = "cow_from_cstr", since = "1.28.0")]
    impl<'a> From<&'a CString> for Cow<'a, CStr> {
        #[inline]
        fn from(s: &'a CString) -> Cow<'a, CStr> {
            Cow::Borrowed(s.as_c_str())
        }
    }

    #[stable(feature = "shared_from_slice2", since = "1.24.0")]
    impl From<CString> for Arc<CStr> {
        /// Converts a [`CString`] into a [`Arc`]`<CStr>` without copying or allocating.
        #[inline]
        fn from(s: CString) -> Arc<CStr> {
            let arc: Arc<[u8]> = Arc::from(s.into_inner());
            unsafe { Arc::from_raw(Arc::into_raw(arc) as *const CStr) }
        }
    }

    #[stable(feature = "shared_from_slice2", since = "1.24.0")]
    impl From<&CStr> for Arc<CStr> {
        #[inline]
        fn from(s: &CStr) -> Arc<CStr> {
            let arc: Arc<[u8]> = Arc::from(s.to_bytes_with_nul());
            unsafe { Arc::from_raw(Arc::into_raw(arc) as *const CStr) }
        }
    }

    #[stable(feature = "shared_from_slice2", since = "1.24.0")]
    impl From<CString> for Rc<CStr> {
        /// Converts a [`CString`] into a [`Rc`]`<CStr>` without copying or allocating.
        #[inline]
        fn from(s: CString) -> Rc<CStr> {
            let rc: Rc<[u8]> = Rc::from(s.into_inner());
            unsafe { Rc::from_raw(Rc::into_raw(rc) as *const CStr) }
        }
    }

    #[stable(feature = "shared_from_slice2", since = "1.24.0")]
    impl From<&CStr> for Rc<CStr> {
        #[inline]
        fn from(s: &CStr) -> Rc<CStr> {
            let rc: Rc<[u8]> = Rc::from(s.to_bytes_with_nul());
            unsafe { Rc::from_raw(Rc::into_raw(rc) as *const CStr) }
        }
    }

    #[stable(feature = "default_box_extra", since = "1.17.0")]
    impl Default for Box<CStr> {
        fn default() -> Box<CStr> {
            let boxed: Box<[u8]> = Box::from([0]);
            unsafe { Box::from_raw(Box::into_raw(boxed) as *mut CStr) }
        }
    }

    impl NulError {
        /// Returns the position of the nul byte in the slice that caused
        /// [`CString::new`] to fail.
        ///
        /// # Examples
        ///
        /// ```
        /// use std::ffi::CString;
        ///
        /// let nul_error = CString::new("foo\0bar").unwrap_err();
        /// assert_eq!(nul_error.nul_position(), 3);
        ///
        /// let nul_error = CString::new("foo bar\0").unwrap_err();
        /// assert_eq!(nul_error.nul_position(), 7);
        /// ```
        #[stable(feature = "rust1", since = "1.0.0")]
        pub fn nul_position(&self) -> usize {
            self.0
        }

        /// Consumes this error, returning the underlying vector of bytes which
        /// generated the error in the first place.
        ///
        /// # Examples
        ///
        /// ```
        /// use std::ffi::CString;
        ///
        /// let nul_error = CString::new("foo\0bar").unwrap_err();
        /// assert_eq!(nul_error.into_vec(), b"foo\0bar");
        /// ```
        #[stable(feature = "rust1", since = "1.0.0")]
        pub fn into_vec(self) -> Vec<u8> {
            self.1
        }
    }

    #[stable(feature = "rust1", since = "1.0.0")]
    impl Error for NulError {
        #[allow(deprecated)]
        fn description(&self) -> &str {
            "nul byte found in data"
        }
    }

    #[stable(feature = "rust1", since = "1.0.0")]
    impl fmt::Display for NulError {
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            write!(f, "nul byte found in provided data at position: {}", self.0)
        }
    }

    #[stable(feature = "rust1", since = "1.0.0")]
    impl From<NulError> for io::Error {
        /// Converts a [`NulError`] into a [`io::Error`].
        fn from(_: NulError) -> io::Error {
            io::Error::new(io::ErrorKind::InvalidInput, "data provided contains a nul byte")
        }
    }

    #[stable(feature = "frombyteswithnulerror_impls", since = "1.17.0")]
    impl Error for FromBytesWithNulError {
        #[allow(deprecated)]
        fn description(&self) -> &str {
            match self.kind {
                FromBytesWithNulErrorKind::InteriorNul(..) => {
                    "data provided contains an interior nul byte"
                }
                FromBytesWithNulErrorKind::NotNulTerminated => "data provided is not nul terminated",
            }
        }
    }

    #[stable(feature = "frombyteswithnulerror_impls", since = "1.17.0")]
    impl fmt::Display for FromBytesWithNulError {
        #[allow(deprecated, deprecated_in_future)]
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            f.write_str(self.description())?;
            if let FromBytesWithNulErrorKind::InteriorNul(pos) = self.kind {
                write!(f, " at byte pos {}", pos)?;
            }
            Ok(())
        }
    }

    #[unstable(feature = "cstring_from_vec_with_nul", issue = "73179")]
    impl Error for FromVecWithNulError {}

    #[unstable(feature = "cstring_from_vec_with_nul", issue = "73179")]
    impl fmt::Display for FromVecWithNulError {
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            match self.error_kind {
                FromBytesWithNulErrorKind::InteriorNul(pos) => {
                    write!(f, "data provided contains an interior nul byte at pos {}", pos)
                }
                FromBytesWithNulErrorKind::NotNulTerminated => {
                    write!(f, "data provided is not nul terminated")
                }
            }
        }
    }

    impl IntoStringError {
        /// Consumes this error, returning original [`CString`] which generated the
        /// error.
        #[stable(feature = "cstring_into", since = "1.7.0")]
        pub fn into_cstring(self) -> CString {
            self.inner
        }

        /// Access the underlying UTF-8 error that was the cause of this error.
        #[stable(feature = "cstring_into", since = "1.7.0")]
        pub fn utf8_error(&self) -> Utf8Error {
            self.error
        }
    }

    #[stable(feature = "cstring_into", since = "1.7.0")]
    impl Error for IntoStringError {
        #[allow(deprecated)]
        fn description(&self) -> &str {
            "C string contained non-utf8 bytes"
        }

        fn source(&self) -> Option<&(dyn Error + 'static)> {
            Some(&self.error)
        }
    }

    #[stable(feature = "cstring_into", since = "1.7.0")]
    impl fmt::Display for IntoStringError {
        #[allow(deprecated, deprecated_in_future)]
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            self.description().fmt(f)
        }
    }

    impl CStr {
        /// Wraps a raw C string with a safe C string wrapper.
        ///
        /// This function will wrap the provided `ptr` with a `CStr` wrapper, which
        /// allows inspection and interoperation of non-owned C strings. The total
        /// size of the raw C string must be smaller than `isize::MAX` **bytes**
        /// in memory due to calling the `slice::from_raw_parts` function.
        /// This method is unsafe for a number of reasons:
        ///
        /// * There is no guarantee to the validity of `ptr`.
        /// * The returned lifetime is not guaranteed to be the actual lifetime of
        ///   `ptr`.
        /// * There is no guarantee that the memory pointed to by `ptr` contains a
        ///   valid nul terminator byte at the end of the string.
        /// * It is not guaranteed that the memory pointed by `ptr` won't change
        ///   before the `CStr` has been destroyed.
        ///
        /// > **Note**: This operation is intended to be a 0-cost cast but it is
        /// > currently implemented with an up-front calculation of the length of
        /// > the string. This is not guaranteed to always be the case.
        ///
        /// # Examples
        ///
        /// ```ignore (extern-declaration)
        /// # fn main() {
        /// use std::ffi::CStr;
        /// use std::os::raw::c_char;
        ///
        /// extern {
        ///     fn my_string() -> *const c_char;
        /// }
        ///
        /// unsafe {
        ///     let slice = CStr::from_ptr(my_string());
        ///     println!("string returned: {}", slice.to_str().unwrap());
        /// }
        /// # }
        /// ```
        #[stable(feature = "rust1", since = "1.0.0")]
        pub unsafe fn from_ptr<'a>(ptr: *const c_char) -> &'a CStr {
            // SAFETY: The caller has provided a pointer that points to a valid C
            // string with a NUL terminator of size less than `isize::MAX`, whose
            // content remain valid and doesn't change for the lifetime of the
            // returned `CStr`.
            //
            // Thus computing the length is fine (a NUL byte exists), the call to
            // from_raw_parts is safe because we know the length is at most `isize::MAX`, meaning
            // the call to `from_bytes_with_nul_unchecked` is correct.
            //
            // The cast from c_char to u8 is ok because a c_char is always one byte.
            unsafe {
                let len = sys::strlen(ptr);
                let ptr = ptr as *const u8;
                CStr::from_bytes_with_nul_unchecked(slice::from_raw_parts(ptr, len as usize + 1))
            }
        }

        /// Creates a C string wrapper from a byte slice.
        ///
        /// This function will cast the provided `bytes` to a `CStr`
        /// wrapper after ensuring that the byte slice is nul-terminated
        /// and does not contain any interior nul bytes.
        ///
        /// # Examples
        ///
        /// ```
        /// use std::ffi::CStr;
        ///
        /// let cstr = CStr::from_bytes_with_nul(b"hello\0");
        /// assert!(cstr.is_ok());
        /// ```
        ///
        /// Creating a `CStr` without a trailing nul terminator is an error:
        ///
        /// ```
        /// use std::ffi::CStr;
        ///
        /// let cstr = CStr::from_bytes_with_nul(b"hello");
        /// assert!(cstr.is_err());
        /// ```
        ///
        /// Creating a `CStr` with an interior nul byte is an error:
        ///
        /// ```
        /// use std::ffi::CStr;
        ///
        /// let cstr = CStr::from_bytes_with_nul(b"he\0llo\0");
        /// assert!(cstr.is_err());
        /// ```
        #[stable(feature = "cstr_from_bytes", since = "1.10.0")]
        pub fn from_bytes_with_nul(bytes: &[u8]) -> Result<&CStr, FromBytesWithNulError> {
            let nul_pos = memchr::memchr(0, bytes);
            if let Some(nul_pos) = nul_pos {
                if nul_pos + 1 != bytes.len() {
                    return Err(FromBytesWithNulError::interior_nul(nul_pos));
                }
                Ok(unsafe { CStr::from_bytes_with_nul_unchecked(bytes) })
            } else {
                Err(FromBytesWithNulError::not_nul_terminated())
            }
        }

        /// Unsafely creates a C string wrapper from a byte slice.
        ///
        /// This function will cast the provided `bytes` to a `CStr` wrapper without
        /// performing any sanity checks. The provided slice **must** be nul-terminated
        /// and not contain any interior nul bytes.
        ///
        /// # Examples
        ///
        /// ```
        /// use std::ffi::{CStr, CString};
        ///
        /// unsafe {
        ///     let cstring = CString::new("hello").expect("CString::new failed");
        ///     let cstr = CStr::from_bytes_with_nul_unchecked(cstring.to_bytes_with_nul());
        ///     assert_eq!(cstr, &*cstring);
        /// }
        /// ```
        #[inline]
        #[stable(feature = "cstr_from_bytes", since = "1.10.0")]
        #[rustc_const_unstable(feature = "const_cstr_unchecked", issue = "none")]
        pub const unsafe fn from_bytes_with_nul_unchecked(bytes: &[u8]) -> &CStr {
            // SAFETY: Casting to CStr is safe because its internal representation
            // is a [u8] too (safe only inside std).
            // Dereferencing the obtained pointer is safe because it comes from a
            // reference. Making a reference is then safe because its lifetime
            // is bound by the lifetime of the given `bytes`.
            unsafe { &*(bytes as *const [u8] as *const CStr) }
        }

        /// Returns the inner pointer to this C string.
        ///
        /// The returned pointer will be valid for as long as `self` is, and points
        /// to a contiguous region of memory terminated with a 0 byte to represent
        /// the end of the string.
        ///
        /// **WARNING**
        ///
        /// The returned pointer is read-only; writing to it (including passing it
        /// to C code that writes to it) causes undefined behavior.
        ///
        /// It is your responsibility to make sure that the underlying memory is not
        /// freed too early. For example, the following code will cause undefined
        /// behavior when `ptr` is used inside the `unsafe` block:
        ///
        /// ```no_run
        /// # #![allow(unused_must_use)] #![allow(temporary_cstring_as_ptr)]
        /// use std::ffi::CString;
        ///
        /// let ptr = CString::new("Hello").expect("CString::new failed").as_ptr();
        /// unsafe {
        ///     // `ptr` is dangling
        ///     *ptr;
        /// }
        /// ```
        ///
        /// This happens because the pointer returned by `as_ptr` does not carry any
        /// lifetime information and the [`CString`] is deallocated immediately after
        /// the `CString::new("Hello").expect("CString::new failed").as_ptr()`
        /// expression is evaluated.
        /// To fix the problem, bind the `CString` to a local variable:
        ///
        /// ```no_run
        /// # #![allow(unused_must_use)]
        /// use std::ffi::CString;
        ///
        /// let hello = CString::new("Hello").expect("CString::new failed");
        /// let ptr = hello.as_ptr();
        /// unsafe {
        ///     // `ptr` is valid because `hello` is in scope
        ///     *ptr;
        /// }
        /// ```
        ///
        /// This way, the lifetime of the [`CString`] in `hello` encompasses
        /// the lifetime of `ptr` and the `unsafe` block.
        #[inline]
        #[stable(feature = "rust1", since = "1.0.0")]
        #[rustc_const_stable(feature = "const_str_as_ptr", since = "1.32.0")]
        pub const fn as_ptr(&self) -> *const c_char {
            self.inner.as_ptr()
        }

        /// Converts this C string to a byte slice.
        ///
        /// The returned slice will **not** contain the trailing nul terminator that this C
        /// string has.
        ///
        /// > **Note**: This method is currently implemented as a constant-time
        /// > cast, but it is planned to alter its definition in the future to
        /// > perform the length calculation whenever this method is called.
        ///
        /// # Examples
        ///
        /// ```
        /// use std::ffi::CStr;
        ///
        /// let cstr = CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed");
        /// assert_eq!(cstr.to_bytes(), b"foo");
        /// ```
        #[inline]
        #[stable(feature = "rust1", since = "1.0.0")]
        pub fn to_bytes(&self) -> &[u8] {
            let bytes = self.to_bytes_with_nul();
            &bytes[..bytes.len() - 1]
        }

        /// Converts this C string to a byte slice containing the trailing 0 byte.
        ///
        /// This function is the equivalent of [`CStr::to_bytes`] except that it
        /// will retain the trailing nul terminator instead of chopping it off.
        ///
        /// > **Note**: This method is currently implemented as a 0-cost cast, but
        /// > it is planned to alter its definition in the future to perform the
        /// > length calculation whenever this method is called.
        ///
        /// # Examples
        ///
        /// ```
        /// use std::ffi::CStr;
        ///
        /// let cstr = CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed");
        /// assert_eq!(cstr.to_bytes_with_nul(), b"foo\0");
        /// ```
        #[inline]
        #[stable(feature = "rust1", since = "1.0.0")]
        pub fn to_bytes_with_nul(&self) -> &[u8] {
            unsafe { &*(&self.inner as *const [c_char] as *const [u8]) }
        }

        /// Yields a [`&str`] slice if the `CStr` contains valid UTF-8.
        ///
        /// If the contents of the `CStr` are valid UTF-8 data, this
        /// function will return the corresponding [`&str`] slice. Otherwise,
        /// it will return an error with details of where UTF-8 validation failed.
        ///
        /// [`&str`]: prim@str
        ///
        /// # Examples
        ///
        /// ```
        /// use std::ffi::CStr;
        ///
        /// let cstr = CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed");
        /// assert_eq!(cstr.to_str(), Ok("foo"));
        /// ```
        #[stable(feature = "cstr_to_str", since = "1.4.0")]
        pub fn to_str(&self) -> Result<&str, str::Utf8Error> {
            // N.B., when `CStr` is changed to perform the length check in `.to_bytes()`
            // instead of in `from_ptr()`, it may be worth considering if this should
            // be rewritten to do the UTF-8 check inline with the length calculation
            // instead of doing it afterwards.
            str::from_utf8(self.to_bytes())
        }

        /// Converts a `CStr` into a [`Cow`]`<`[`str`]`>`.
        ///
        /// If the contents of the `CStr` are valid UTF-8 data, this
        /// function will return a [`Cow`]`::`[`Borrowed`]`(`[`&str`]`)`
        /// with the corresponding [`&str`] slice. Otherwise, it will
        /// replace any invalid UTF-8 sequences with
        /// [`U+FFFD REPLACEMENT CHARACTER`][U+FFFD] and return a
        /// [`Cow`]`::`[`Owned`]`(`[`String`]`)` with the result.
        ///
        /// [`str`]: primitive@str
        /// [`&str`]: primitive@str
        /// [`Borrowed`]: Cow::Borrowed
        /// [`Owned`]: Cow::Owned
        /// [U+FFFD]: crate::char::REPLACEMENT_CHARACTER
        ///
        /// # Examples
        ///
        /// Calling `to_string_lossy` on a `CStr` containing valid UTF-8:
        ///
        /// ```
        /// use std::borrow::Cow;
        /// use std::ffi::CStr;
        ///
        /// let cstr = CStr::from_bytes_with_nul(b"Hello World\0")
        ///                  .expect("CStr::from_bytes_with_nul failed");
        /// assert_eq!(cstr.to_string_lossy(), Cow::Borrowed("Hello World"));
        /// ```
        ///
        /// Calling `to_string_lossy` on a `CStr` containing invalid UTF-8:
        ///
        /// ```
        /// use std::borrow::Cow;
        /// use std::ffi::CStr;
        ///
        /// let cstr = CStr::from_bytes_with_nul(b"Hello \xF0\x90\x80World\0")
        ///                  .expect("CStr::from_bytes_with_nul failed");
        /// assert_eq!(
        ///     cstr.to_string_lossy(),
        ///     Cow::Owned(String::from("Hello �World")) as Cow<'_, str>
        /// );
        /// ```
        #[stable(feature = "cstr_to_str", since = "1.4.0")]
        pub fn to_string_lossy(&self) -> Cow<'_, str> {
            String::from_utf8_lossy(self.to_bytes())
        }

        /// Converts a [`Box`]`<CStr>` into a [`CString`] without copying or allocating.
        ///
        /// # Examples
        ///
        /// ```
        /// use std::ffi::CString;
        ///
        /// let c_string = CString::new(b"foo".to_vec()).expect("CString::new failed");
        /// let boxed = c_string.into_boxed_c_str();
        /// assert_eq!(boxed.into_c_string(), CString::new("foo").expect("CString::new failed"));
        /// ```
        #[stable(feature = "into_boxed_c_str", since = "1.20.0")]
        pub fn into_c_string(self: Box<CStr>) -> CString {
            let raw = Box::into_raw(self) as *mut [u8];
            CString { inner: unsafe { Box::from_raw(raw) } }
        }
    }

    #[stable(feature = "rust1", since = "1.0.0")]
    impl PartialEq for CStr {
        fn eq(&self, other: &CStr) -> bool {
            self.to_bytes().eq(other.to_bytes())
        }
    }
    #[stable(feature = "rust1", since = "1.0.0")]
    impl Eq for CStr {}
    #[stable(feature = "rust1", since = "1.0.0")]
    impl PartialOrd for CStr {
        fn partial_cmp(&self, other: &CStr) -> Option<Ordering> {
            self.to_bytes().partial_cmp(&other.to_bytes())
        }
    }
    #[stable(feature = "rust1", since = "1.0.0")]
    impl Ord for CStr {
        fn cmp(&self, other: &CStr) -> Ordering {
            self.to_bytes().cmp(&other.to_bytes())
        }
    }

    #[stable(feature = "cstr_borrow", since = "1.3.0")]
    impl ToOwned for CStr {
        type Owned = CString;

        fn to_owned(&self) -> CString {
            CString { inner: self.to_bytes_with_nul().into() }
        }

        fn clone_into(&self, target: &mut CString) {
            let mut b = Vec::from(mem::take(&mut target.inner));
            self.to_bytes_with_nul().clone_into(&mut b);
            target.inner = b.into_boxed_slice();
        }
    }

    #[stable(feature = "cstring_asref", since = "1.7.0")]
    impl From<&CStr> for CString {
        fn from(s: &CStr) -> CString {
            s.to_owned()
        }
    }

    #[stable(feature = "cstring_asref", since = "1.7.0")]
    impl ops::Index<ops::RangeFull> for CString {
        type Output = CStr;

        #[inline]
        fn index(&self, _index: ops::RangeFull) -> &CStr {
            self
        }
    }

    #[stable(feature = "cstr_range_from", since = "1.47.0")]
    impl ops::Index<ops::RangeFrom<usize>> for CStr {
        type Output = CStr;

        fn index(&self, index: ops::RangeFrom<usize>) -> &CStr {
            let bytes = self.to_bytes_with_nul();
            // we need to manually check the starting index to account for the null
            // byte, since otherwise we could get an empty string that doesn't end
            // in a null.
            if index.start < bytes.len() {
                unsafe { CStr::from_bytes_with_nul_unchecked(&bytes[index.start..]) }
            } else {
                panic!(
                    "index out of bounds: the len is {} but the index is {}",
                    bytes.len(),
                    index.start
                );
            }
        }
    }

    #[stable(feature = "cstring_asref", since = "1.7.0")]
    impl AsRef<CStr> for CStr {
        #[inline]
        fn as_ref(&self) -> &CStr {
            self
        }
    }

    #[stable(feature = "cstring_asref", since = "1.7.0")]
    impl AsRef<CStr> for CString {
        #[inline]
        fn as_ref(&self) -> &CStr {
            self
        }
    }