mod.rs.html -- source
Description: Source to the Rust file `src/libcore/char/mod.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

    //! A character type.
    //!
    //! The `char` type represents a single character. More specifically, since
    //! 'character' isn't a well-defined concept in Unicode, `char` is a '[Unicode
    //! scalar value]', which is similar to, but not the same as, a '[Unicode code
    //! point]'.
    //!
    //! [Unicode scalar value]: http://www.unicode.org/glossary/#unicode_scalar_value
    //! [Unicode code point]: http://www.unicode.org/glossary/#code_point
    //!
    //! This module exists for technical reasons, the primary documentation for
    //! `char` is directly on [the `char` primitive type](../../std/primitive.char.html)
    //! itself.
    //!
    //! This module is the home of the iterator implementations for the iterators
    //! implemented on `char`, as well as some useful constants and conversion
    //! functions that convert various types to `char`.

    #![allow(non_snake_case)]
    #![stable(feature = "core_char", since = "1.2.0")]

    mod convert;
    mod decode;
    mod methods;

    // stable re-exports
    #[stable(feature = "char_from_unchecked", since = "1.5.0")]
    pub use self::convert::from_u32_unchecked;
    #[stable(feature = "try_from", since = "1.34.0")]
    pub use self::convert::CharTryFromError;
    #[stable(feature = "char_from_str", since = "1.20.0")]
    pub use self::convert::ParseCharError;
    #[stable(feature = "rust1", since = "1.0.0")]
    pub use self::convert::{from_digit, from_u32};
    #[stable(feature = "decode_utf16", since = "1.9.0")]
    pub use self::decode::{decode_utf16, DecodeUtf16, DecodeUtf16Error};
    #[stable(feature = "unicode_version", since = "1.45.0")]
    pub use crate::unicode::UNICODE_VERSION;

    // perma-unstable re-exports
    #[unstable(feature = "char_internals", reason = "exposed only for libstd", issue = "none")]
    pub use self::methods::encode_utf16_raw;
    #[unstable(feature = "char_internals", reason = "exposed only for libstd", issue = "none")]
    pub use self::methods::encode_utf8_raw;

    use crate::fmt::{self, Write};
    use crate::iter::FusedIterator;

    // UTF-8 ranges and tags for encoding characters
    const TAG_CONT: u8 = 0b1000_0000;
    const TAG_TWO_B: u8 = 0b1100_0000;
    const TAG_THREE_B: u8 = 0b1110_0000;
    const TAG_FOUR_B: u8 = 0b1111_0000;
    const MAX_ONE_B: u32 = 0x80;
    const MAX_TWO_B: u32 = 0x800;
    const MAX_THREE_B: u32 = 0x10000;

    /*
        Lu  Uppercase_Letter        an uppercase letter
        Ll  Lowercase_Letter        a lowercase letter
        Lt  Titlecase_Letter        a digraphic character, with first part uppercase
        Lm  Modifier_Letter         a modifier letter
        Lo  Other_Letter            other letters, including syllables and ideographs
        Mn  Nonspacing_Mark         a nonspacing combining mark (zero advance width)
        Mc  Spacing_Mark            a spacing combining mark (positive advance width)
        Me  Enclosing_Mark          an enclosing combining mark
        Nd  Decimal_Number          a decimal digit
        Nl  Letter_Number           a letterlike numeric character
        No  Other_Number            a numeric character of other type
        Pc  Connector_Punctuation   a connecting punctuation mark, like a tie
        Pd  Dash_Punctuation        a dash or hyphen punctuation mark
        Ps  Open_Punctuation        an opening punctuation mark (of a pair)
        Pe  Close_Punctuation       a closing punctuation mark (of a pair)
        Pi  Initial_Punctuation     an initial quotation mark
        Pf  Final_Punctuation       a final quotation mark
        Po  Other_Punctuation       a punctuation mark of other type
        Sm  Math_Symbol             a symbol of primarily mathematical use
        Sc  Currency_Symbol         a currency sign
        Sk  Modifier_Symbol         a non-letterlike modifier symbol
        So  Other_Symbol            a symbol of other type
        Zs  Space_Separator         a space character (of various non-zero widths)
        Zl  Line_Separator          U+2028 LINE SEPARATOR only
        Zp  Paragraph_Separator     U+2029 PARAGRAPH SEPARATOR only
        Cc  Control                 a C0 or C1 control code
        Cf  Format                  a format control character
        Cs  Surrogate               a surrogate code point
        Co  Private_Use             a private-use character
        Cn  Unassigned              a reserved unassigned code point or a noncharacter
    */

    /// The highest valid code point a `char` can have.
    ///
    /// A [`char`] is a [Unicode Scalar Value], which means that it is a [Code
    /// Point], but only ones within a certain range. `MAX` is the highest valid
    /// code point that's a valid [Unicode Scalar Value].
    ///
    /// [`char`]: ../../std/primitive.char.html
    /// [Unicode Scalar Value]: http://www.unicode.org/glossary/#unicode_scalar_value
    /// [Code Point]: http://www.unicode.org/glossary/#code_point
    #[stable(feature = "rust1", since = "1.0.0")]
    pub const MAX: char = char::MAX;

    /// `U+FFFD REPLACEMENT CHARACTER` (�) is used in Unicode to represent a
    /// decoding error.
    ///
    /// It can occur, for example, when giving ill-formed UTF-8 bytes to
    /// [`String::from_utf8_lossy`](../../std/string/struct.String.html#method.from_utf8_lossy).
    #[stable(feature = "decode_utf16", since = "1.9.0")]
    pub const REPLACEMENT_CHARACTER: char = char::REPLACEMENT_CHARACTER;

    /// Returns an iterator that yields the hexadecimal Unicode escape of a
    /// character, as `char`s.
    ///
    /// This `struct` is created by the [`escape_unicode`] method on [`char`]. See
    /// its documentation for more.
    ///
    /// [`escape_unicode`]: ../../std/primitive.char.html#method.escape_unicode
    /// [`char`]: ../../std/primitive.char.html
    #[derive(Clone, Debug)]
    #[stable(feature = "rust1", since = "1.0.0")]
    pub struct EscapeUnicode {
        c: char,
        state: EscapeUnicodeState,

        // The index of the next hex digit to be printed (0 if none),
        // i.e., the number of remaining hex digits to be printed;
        // increasing from the least significant digit: 0x543210
        hex_digit_idx: usize,
    }

    // The enum values are ordered so that their representation is the
    // same as the remaining length (besides the hexadecimal digits). This
    // likely makes `len()` a single load from memory) and inline-worth.
    #[derive(Clone, Debug)]
    enum EscapeUnicodeState {
        Done,
        RightBrace,
        Value,
        LeftBrace,
        Type,
        Backslash,
    }

    #[stable(feature = "rust1", since = "1.0.0")]
    impl Iterator for EscapeUnicode {
        type Item = char;

        fn next(&mut self) -> Option<char> {
            match self.state {
                EscapeUnicodeState::Backslash => {
                    self.state = EscapeUnicodeState::Type;
                    Some('\\')
                }
                EscapeUnicodeState::Type => {
                    self.state = EscapeUnicodeState::LeftBrace;
                    Some('u')
                }
                EscapeUnicodeState::LeftBrace => {
                    self.state = EscapeUnicodeState::Value;
                    Some('{')
                }
                EscapeUnicodeState::Value => {
                    let hex_digit = ((self.c as u32) >> (self.hex_digit_idx * 4)) & 0xf;
                    let c = from_digit(hex_digit, 16).unwrap();
                    if self.hex_digit_idx == 0 {
                        self.state = EscapeUnicodeState::RightBrace;
                    } else {
                        self.hex_digit_idx -= 1;
                    }
                    Some(c)
                }
                EscapeUnicodeState::RightBrace => {
                    self.state = EscapeUnicodeState::Done;
                    Some('}')
                }
                EscapeUnicodeState::Done => None,
            }
        }

        #[inline]
        fn size_hint(&self) -> (usize, Option<usize>) {
            let n = self.len();
            (n, Some(n))
        }

        #[inline]
        fn count(self) -> usize {
            self.len()
        }

        fn last(self) -> Option<char> {
            match self.state {
                EscapeUnicodeState::Done => None,

                EscapeUnicodeState::RightBrace
                | EscapeUnicodeState::Value
                | EscapeUnicodeState::LeftBrace
                | EscapeUnicodeState::Type
                | EscapeUnicodeState::Backslash => Some('}'),
            }
        }
    }

    #[stable(feature = "exact_size_escape", since = "1.11.0")]
    impl ExactSizeIterator for EscapeUnicode {
        #[inline]
        fn len(&self) -> usize {
            // The match is a single memory access with no branching
            self.hex_digit_idx
                + match self.state {
                    EscapeUnicodeState::Done => 0,
                    EscapeUnicodeState::RightBrace => 1,
                    EscapeUnicodeState::Value => 2,
                    EscapeUnicodeState::LeftBrace => 3,
                    EscapeUnicodeState::Type => 4,
                    EscapeUnicodeState::Backslash => 5,
                }
        }
    }

    #[stable(feature = "fused", since = "1.26.0")]
    impl FusedIterator for EscapeUnicode {}

    #[stable(feature = "char_struct_display", since = "1.16.0")]
    impl fmt::Display for EscapeUnicode {
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            for c in self.clone() {
                f.write_char(c)?;
            }
            Ok(())
        }
    }

    /// An iterator that yields the literal escape code of a `char`.
    ///
    /// This `struct` is created by the [`escape_default`] method on [`char`]. See
    /// its documentation for more.
    ///
    /// [`escape_default`]: ../../std/primitive.char.html#method.escape_default
    /// [`char`]: ../../std/primitive.char.html
    #[derive(Clone, Debug)]
    #[stable(feature = "rust1", since = "1.0.0")]
    pub struct EscapeDefault {
        state: EscapeDefaultState,
    }

    #[derive(Clone, Debug)]
    enum EscapeDefaultState {
        Done,
        Char(char),
        Backslash(char),
        Unicode(EscapeUnicode),
    }

    #[stable(feature = "rust1", since = "1.0.0")]
    impl Iterator for EscapeDefault {
        type Item = char;

        fn next(&mut self) -> Option<char> {
            match self.state {
                EscapeDefaultState::Backslash(c) => {
                    self.state = EscapeDefaultState::Char(c);
                    Some('\\')
                }
                EscapeDefaultState::Char(c) => {
                    self.state = EscapeDefaultState::Done;
                    Some(c)
                }
                EscapeDefaultState::Done => None,
                EscapeDefaultState::Unicode(ref mut iter) => iter.next(),
            }
        }

        #[inline]
        fn size_hint(&self) -> (usize, Option<usize>) {
            let n = self.len();
            (n, Some(n))
        }

        #[inline]
        fn count(self) -> usize {
            self.len()
        }

        fn nth(&mut self, n: usize) -> Option<char> {
            match self.state {
                EscapeDefaultState::Backslash(c) if n == 0 => {
                    self.state = EscapeDefaultState::Char(c);
                    Some('\\')
                }
                EscapeDefaultState::Backslash(c) if n == 1 => {
                    self.state = EscapeDefaultState::Done;
                    Some(c)
                }
                EscapeDefaultState::Backslash(_) => {
                    self.state = EscapeDefaultState::Done;
                    None
                }
                EscapeDefaultState::Char(c) => {
                    self.state = EscapeDefaultState::Done;

                    if n == 0 { Some(c) } else { None }
                }
                EscapeDefaultState::Done => None,
                EscapeDefaultState::Unicode(ref mut i) => i.nth(n),
            }
        }

        fn last(self) -> Option<char> {
            match self.state {
                EscapeDefaultState::Unicode(iter) => iter.last(),
                EscapeDefaultState::Done => None,
                EscapeDefaultState::Backslash(c) | EscapeDefaultState::Char(c) => Some(c),
            }
        }
    }

    #[stable(feature = "exact_size_escape", since = "1.11.0")]
    impl ExactSizeIterator for EscapeDefault {
        fn len(&self) -> usize {
            match self.state {
                EscapeDefaultState::Done => 0,
                EscapeDefaultState::Char(_) => 1,
                EscapeDefaultState::Backslash(_) => 2,
                EscapeDefaultState::Unicode(ref iter) => iter.len(),
            }
        }
    }

    #[stable(feature = "fused", since = "1.26.0")]
    impl FusedIterator for EscapeDefault {}

    #[stable(feature = "char_struct_display", since = "1.16.0")]
    impl fmt::Display for EscapeDefault {
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            for c in self.clone() {
                f.write_char(c)?;
            }
            Ok(())
        }
    }

    /// An iterator that yields the literal escape code of a `char`.
    ///
    /// This `struct` is created by the [`escape_debug`] method on [`char`]. See its
    /// documentation for more.
    ///
    /// [`escape_debug`]: ../../std/primitive.char.html#method.escape_debug
    /// [`char`]: ../../std/primitive.char.html
    #[stable(feature = "char_escape_debug", since = "1.20.0")]
    #[derive(Clone, Debug)]
    pub struct EscapeDebug(EscapeDefault);

    #[stable(feature = "char_escape_debug", since = "1.20.0")]
    impl Iterator for EscapeDebug {
        type Item = char;
        fn next(&mut self) -> Option<char> {
            self.0.next()
        }
        fn size_hint(&self) -> (usize, Option<usize>) {
            self.0.size_hint()
        }
    }

    #[stable(feature = "char_escape_debug", since = "1.20.0")]
    impl ExactSizeIterator for EscapeDebug {}

    #[stable(feature = "fused", since = "1.26.0")]
    impl FusedIterator for EscapeDebug {}

    #[stable(feature = "char_escape_debug", since = "1.20.0")]
    impl fmt::Display for EscapeDebug {
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            fmt::Display::fmt(&self.0, f)
        }
    }

    /// Returns an iterator that yields the lowercase equivalent of a `char`.
    ///
    /// This `struct` is created by the [`to_lowercase`] method on [`char`]. See
    /// its documentation for more.
    ///
    /// [`to_lowercase`]: ../../std/primitive.char.html#method.to_lowercase
    /// [`char`]: ../../std/primitive.char.html
    #[stable(feature = "rust1", since = "1.0.0")]
    #[derive(Debug, Clone)]
    pub struct ToLowercase(CaseMappingIter);

    #[stable(feature = "rust1", since = "1.0.0")]
    impl Iterator for ToLowercase {
        type Item = char;
        fn next(&mut self) -> Option<char> {
            self.0.next()
        }
        fn size_hint(&self) -> (usize, Option<usize>) {
            self.0.size_hint()
        }
    }

    #[stable(feature = "fused", since = "1.26.0")]
    impl FusedIterator for ToLowercase {}

    #[stable(feature = "exact_size_case_mapping_iter", since = "1.35.0")]
    impl ExactSizeIterator for ToLowercase {}

    /// Returns an iterator that yields the uppercase equivalent of a `char`.
    ///
    /// This `struct` is created by the [`to_uppercase`] method on [`char`]. See
    /// its documentation for more.
    ///
    /// [`to_uppercase`]: ../../std/primitive.char.html#method.to_uppercase
    /// [`char`]: ../../std/primitive.char.html
    #[stable(feature = "rust1", since = "1.0.0")]
    #[derive(Debug, Clone)]
    pub struct ToUppercase(CaseMappingIter);

    #[stable(feature = "rust1", since = "1.0.0")]
    impl Iterator for ToUppercase {
        type Item = char;
        fn next(&mut self) -> Option<char> {
            self.0.next()
        }
        fn size_hint(&self) -> (usize, Option<usize>) {
            self.0.size_hint()
        }
    }

    #[stable(feature = "fused", since = "1.26.0")]
    impl FusedIterator for ToUppercase {}

    #[stable(feature = "exact_size_case_mapping_iter", since = "1.35.0")]
    impl ExactSizeIterator for ToUppercase {}

    #[derive(Debug, Clone)]
    enum CaseMappingIter {
        Three(char, char, char),
        Two(char, char),
        One(char),
        Zero,
    }

    impl CaseMappingIter {
        fn new(chars: [char; 3]) -> CaseMappingIter {
            if chars[2] == '\0' {
                if chars[1] == '\0' {
                    CaseMappingIter::One(chars[0]) // Including if chars[0] == '\0'
                } else {
                    CaseMappingIter::Two(chars[0], chars[1])
                }
            } else {
                CaseMappingIter::Three(chars[0], chars[1], chars[2])
            }
        }
    }

    impl Iterator for CaseMappingIter {
        type Item = char;
        fn next(&mut self) -> Option<char> {
            match *self {
                CaseMappingIter::Three(a, b, c) => {
                    *self = CaseMappingIter::Two(b, c);
                    Some(a)
                }
                CaseMappingIter::Two(b, c) => {
                    *self = CaseMappingIter::One(c);
                    Some(b)
                }
                CaseMappingIter::One(c) => {
                    *self = CaseMappingIter::Zero;
                    Some(c)
                }
                CaseMappingIter::Zero => None,
            }
        }

        fn size_hint(&self) -> (usize, Option<usize>) {
            let size = match self {
                CaseMappingIter::Three(..) => 3,
                CaseMappingIter::Two(..) => 2,
                CaseMappingIter::One(_) => 1,
                CaseMappingIter::Zero => 0,
            };
            (size, Some(size))
        }
    }

    impl fmt::Display for CaseMappingIter {
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            match *self {
                CaseMappingIter::Three(a, b, c) => {
                    f.write_char(a)?;
                    f.write_char(b)?;
                    f.write_char(c)
                }
                CaseMappingIter::Two(b, c) => {
                    f.write_char(b)?;
                    f.write_char(c)
                }
                CaseMappingIter::One(c) => f.write_char(c),
                CaseMappingIter::Zero => Ok(()),
            }
        }
    }

    #[stable(feature = "char_struct_display", since = "1.16.0")]
    impl fmt::Display for ToLowercase {
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            fmt::Display::fmt(&self.0, f)
        }
    }

    #[stable(feature = "char_struct_display", since = "1.16.0")]
    impl fmt::Display for ToUppercase {
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            fmt::Display::fmt(&self.0, f)
        }
    }