core/ascii/
ascii_char.rs

1//! This uses the name `AsciiChar`, even though it's not exposed that way right now,
2//! because it avoids a whole bunch of "are you sure you didn't mean `char`?"
3//! suggestions from rustc if you get anything slightly wrong in here, and overall
4//! helps with clarity as we're also referring to `char` intentionally in here.
5
6use crate::mem::transmute;
7use crate::{assert_unsafe_precondition, fmt};
8
9/// One of the 128 Unicode characters from U+0000 through U+007F,
10/// often known as the [ASCII] subset.
11///
12/// Officially, this is the first [block] in Unicode, _Basic Latin_.
13/// For details, see the [*C0 Controls and Basic Latin*][chart] code chart.
14///
15/// This block was based on older 7-bit character code standards such as
16/// ANSI X3.4-1977, ISO 646-1973, and [NIST FIPS 1-2].
17///
18/// # When to use this
19///
20/// The main advantage of this subset is that it's always valid UTF-8.  As such,
21/// the `&[ascii::Char]` -> `&str` conversion function (as well as other related
22/// ones) are O(1): *no* runtime checks are needed.
23///
24/// If you're consuming strings, you should usually handle Unicode and thus
25/// accept `str`s, not limit yourself to `ascii::Char`s.
26///
27/// However, certain formats are intentionally designed to produce ASCII-only
28/// output in order to be 8-bit-clean.  In those cases, it can be simpler and
29/// faster to generate `ascii::Char`s instead of dealing with the variable width
30/// properties of general UTF-8 encoded strings, while still allowing the result
31/// to be used freely with other Rust things that deal in general `str`s.
32///
33/// For example, a UUID library might offer a way to produce the string
34/// representation of a UUID as an `[ascii::Char; 36]` to avoid memory
35/// allocation yet still allow it to be used as UTF-8 via `as_str` without
36/// paying for validation (or needing `unsafe` code) the way it would if it
37/// were provided as a `[u8; 36]`.
38///
39/// # Layout
40///
41/// This type is guaranteed to have a size and alignment of 1 byte.
42///
43/// # Names
44///
45/// The variants on this type are [Unicode names][NamesList] of the characters
46/// in upper camel case, with a few tweaks:
47/// - For `<control>` characters, the primary alias name is used.
48/// - `LATIN` is dropped, as this block has no non-latin letters.
49/// - `LETTER` is dropped, as `CAPITAL`/`SMALL` suffices in this block.
50/// - `DIGIT`s use a single digit rather than writing out `ZERO`, `ONE`, etc.
51///
52/// [ASCII]: https://www.unicode.org/glossary/index.html#ASCII
53/// [block]: https://www.unicode.org/glossary/index.html#block
54/// [chart]: https://www.unicode.org/charts/PDF/U0000.pdf
55/// [NIST FIPS 1-2]: https://nvlpubs.nist.gov/nistpubs/Legacy/FIPS/fipspub1-2-1977.pdf
56/// [NamesList]: https://www.unicode.org/Public/15.0.0/ucd/NamesList.txt
57#[derive(Copy, Hash)]
58#[derive_const(Clone, Eq, PartialEq, Ord, PartialOrd)]
59#[unstable(feature = "ascii_char", issue = "110998")]
60#[repr(u8)]
61#[ferrocene::prevalidated]
62pub enum AsciiChar {
63    /// U+0000 (The default variant)
64    #[unstable(feature = "ascii_char_variants", issue = "110998")]
65    Null = 0,
66    /// U+0001
67    #[unstable(feature = "ascii_char_variants", issue = "110998")]
68    StartOfHeading = 1,
69    /// U+0002
70    #[unstable(feature = "ascii_char_variants", issue = "110998")]
71    StartOfText = 2,
72    /// U+0003
73    #[unstable(feature = "ascii_char_variants", issue = "110998")]
74    EndOfText = 3,
75    /// U+0004
76    #[unstable(feature = "ascii_char_variants", issue = "110998")]
77    EndOfTransmission = 4,
78    /// U+0005
79    #[unstable(feature = "ascii_char_variants", issue = "110998")]
80    Enquiry = 5,
81    /// U+0006
82    #[unstable(feature = "ascii_char_variants", issue = "110998")]
83    Acknowledge = 6,
84    /// U+0007
85    #[unstable(feature = "ascii_char_variants", issue = "110998")]
86    Bell = 7,
87    /// U+0008
88    #[unstable(feature = "ascii_char_variants", issue = "110998")]
89    Backspace = 8,
90    /// U+0009
91    #[unstable(feature = "ascii_char_variants", issue = "110998")]
92    CharacterTabulation = 9,
93    /// U+000A
94    #[unstable(feature = "ascii_char_variants", issue = "110998")]
95    LineFeed = 10,
96    /// U+000B
97    #[unstable(feature = "ascii_char_variants", issue = "110998")]
98    LineTabulation = 11,
99    /// U+000C
100    #[unstable(feature = "ascii_char_variants", issue = "110998")]
101    FormFeed = 12,
102    /// U+000D
103    #[unstable(feature = "ascii_char_variants", issue = "110998")]
104    CarriageReturn = 13,
105    /// U+000E
106    #[unstable(feature = "ascii_char_variants", issue = "110998")]
107    ShiftOut = 14,
108    /// U+000F
109    #[unstable(feature = "ascii_char_variants", issue = "110998")]
110    ShiftIn = 15,
111    /// U+0010
112    #[unstable(feature = "ascii_char_variants", issue = "110998")]
113    DataLinkEscape = 16,
114    /// U+0011
115    #[unstable(feature = "ascii_char_variants", issue = "110998")]
116    DeviceControlOne = 17,
117    /// U+0012
118    #[unstable(feature = "ascii_char_variants", issue = "110998")]
119    DeviceControlTwo = 18,
120    /// U+0013
121    #[unstable(feature = "ascii_char_variants", issue = "110998")]
122    DeviceControlThree = 19,
123    /// U+0014
124    #[unstable(feature = "ascii_char_variants", issue = "110998")]
125    DeviceControlFour = 20,
126    /// U+0015
127    #[unstable(feature = "ascii_char_variants", issue = "110998")]
128    NegativeAcknowledge = 21,
129    /// U+0016
130    #[unstable(feature = "ascii_char_variants", issue = "110998")]
131    SynchronousIdle = 22,
132    /// U+0017
133    #[unstable(feature = "ascii_char_variants", issue = "110998")]
134    EndOfTransmissionBlock = 23,
135    /// U+0018
136    #[unstable(feature = "ascii_char_variants", issue = "110998")]
137    Cancel = 24,
138    /// U+0019
139    #[unstable(feature = "ascii_char_variants", issue = "110998")]
140    EndOfMedium = 25,
141    /// U+001A
142    #[unstable(feature = "ascii_char_variants", issue = "110998")]
143    Substitute = 26,
144    /// U+001B
145    #[unstable(feature = "ascii_char_variants", issue = "110998")]
146    Escape = 27,
147    /// U+001C
148    #[unstable(feature = "ascii_char_variants", issue = "110998")]
149    InformationSeparatorFour = 28,
150    /// U+001D
151    #[unstable(feature = "ascii_char_variants", issue = "110998")]
152    InformationSeparatorThree = 29,
153    /// U+001E
154    #[unstable(feature = "ascii_char_variants", issue = "110998")]
155    InformationSeparatorTwo = 30,
156    /// U+001F
157    #[unstable(feature = "ascii_char_variants", issue = "110998")]
158    InformationSeparatorOne = 31,
159    /// U+0020
160    #[unstable(feature = "ascii_char_variants", issue = "110998")]
161    Space = 32,
162    /// U+0021
163    #[unstable(feature = "ascii_char_variants", issue = "110998")]
164    ExclamationMark = 33,
165    /// U+0022
166    #[unstable(feature = "ascii_char_variants", issue = "110998")]
167    QuotationMark = 34,
168    /// U+0023
169    #[unstable(feature = "ascii_char_variants", issue = "110998")]
170    NumberSign = 35,
171    /// U+0024
172    #[unstable(feature = "ascii_char_variants", issue = "110998")]
173    DollarSign = 36,
174    /// U+0025
175    #[unstable(feature = "ascii_char_variants", issue = "110998")]
176    PercentSign = 37,
177    /// U+0026
178    #[unstable(feature = "ascii_char_variants", issue = "110998")]
179    Ampersand = 38,
180    /// U+0027
181    #[unstable(feature = "ascii_char_variants", issue = "110998")]
182    Apostrophe = 39,
183    /// U+0028
184    #[unstable(feature = "ascii_char_variants", issue = "110998")]
185    LeftParenthesis = 40,
186    /// U+0029
187    #[unstable(feature = "ascii_char_variants", issue = "110998")]
188    RightParenthesis = 41,
189    /// U+002A
190    #[unstable(feature = "ascii_char_variants", issue = "110998")]
191    Asterisk = 42,
192    /// U+002B
193    #[unstable(feature = "ascii_char_variants", issue = "110998")]
194    PlusSign = 43,
195    /// U+002C
196    #[unstable(feature = "ascii_char_variants", issue = "110998")]
197    Comma = 44,
198    /// U+002D
199    #[unstable(feature = "ascii_char_variants", issue = "110998")]
200    HyphenMinus = 45,
201    /// U+002E
202    #[unstable(feature = "ascii_char_variants", issue = "110998")]
203    FullStop = 46,
204    /// U+002F
205    #[unstable(feature = "ascii_char_variants", issue = "110998")]
206    Solidus = 47,
207    /// U+0030
208    #[unstable(feature = "ascii_char_variants", issue = "110998")]
209    Digit0 = 48,
210    /// U+0031
211    #[unstable(feature = "ascii_char_variants", issue = "110998")]
212    Digit1 = 49,
213    /// U+0032
214    #[unstable(feature = "ascii_char_variants", issue = "110998")]
215    Digit2 = 50,
216    /// U+0033
217    #[unstable(feature = "ascii_char_variants", issue = "110998")]
218    Digit3 = 51,
219    /// U+0034
220    #[unstable(feature = "ascii_char_variants", issue = "110998")]
221    Digit4 = 52,
222    /// U+0035
223    #[unstable(feature = "ascii_char_variants", issue = "110998")]
224    Digit5 = 53,
225    /// U+0036
226    #[unstable(feature = "ascii_char_variants", issue = "110998")]
227    Digit6 = 54,
228    /// U+0037
229    #[unstable(feature = "ascii_char_variants", issue = "110998")]
230    Digit7 = 55,
231    /// U+0038
232    #[unstable(feature = "ascii_char_variants", issue = "110998")]
233    Digit8 = 56,
234    /// U+0039
235    #[unstable(feature = "ascii_char_variants", issue = "110998")]
236    Digit9 = 57,
237    /// U+003A
238    #[unstable(feature = "ascii_char_variants", issue = "110998")]
239    Colon = 58,
240    /// U+003B
241    #[unstable(feature = "ascii_char_variants", issue = "110998")]
242    Semicolon = 59,
243    /// U+003C
244    #[unstable(feature = "ascii_char_variants", issue = "110998")]
245    LessThanSign = 60,
246    /// U+003D
247    #[unstable(feature = "ascii_char_variants", issue = "110998")]
248    EqualsSign = 61,
249    /// U+003E
250    #[unstable(feature = "ascii_char_variants", issue = "110998")]
251    GreaterThanSign = 62,
252    /// U+003F
253    #[unstable(feature = "ascii_char_variants", issue = "110998")]
254    QuestionMark = 63,
255    /// U+0040
256    #[unstable(feature = "ascii_char_variants", issue = "110998")]
257    CommercialAt = 64,
258    /// U+0041
259    #[unstable(feature = "ascii_char_variants", issue = "110998")]
260    CapitalA = 65,
261    /// U+0042
262    #[unstable(feature = "ascii_char_variants", issue = "110998")]
263    CapitalB = 66,
264    /// U+0043
265    #[unstable(feature = "ascii_char_variants", issue = "110998")]
266    CapitalC = 67,
267    /// U+0044
268    #[unstable(feature = "ascii_char_variants", issue = "110998")]
269    CapitalD = 68,
270    /// U+0045
271    #[unstable(feature = "ascii_char_variants", issue = "110998")]
272    CapitalE = 69,
273    /// U+0046
274    #[unstable(feature = "ascii_char_variants", issue = "110998")]
275    CapitalF = 70,
276    /// U+0047
277    #[unstable(feature = "ascii_char_variants", issue = "110998")]
278    CapitalG = 71,
279    /// U+0048
280    #[unstable(feature = "ascii_char_variants", issue = "110998")]
281    CapitalH = 72,
282    /// U+0049
283    #[unstable(feature = "ascii_char_variants", issue = "110998")]
284    CapitalI = 73,
285    /// U+004A
286    #[unstable(feature = "ascii_char_variants", issue = "110998")]
287    CapitalJ = 74,
288    /// U+004B
289    #[unstable(feature = "ascii_char_variants", issue = "110998")]
290    CapitalK = 75,
291    /// U+004C
292    #[unstable(feature = "ascii_char_variants", issue = "110998")]
293    CapitalL = 76,
294    /// U+004D
295    #[unstable(feature = "ascii_char_variants", issue = "110998")]
296    CapitalM = 77,
297    /// U+004E
298    #[unstable(feature = "ascii_char_variants", issue = "110998")]
299    CapitalN = 78,
300    /// U+004F
301    #[unstable(feature = "ascii_char_variants", issue = "110998")]
302    CapitalO = 79,
303    /// U+0050
304    #[unstable(feature = "ascii_char_variants", issue = "110998")]
305    CapitalP = 80,
306    /// U+0051
307    #[unstable(feature = "ascii_char_variants", issue = "110998")]
308    CapitalQ = 81,
309    /// U+0052
310    #[unstable(feature = "ascii_char_variants", issue = "110998")]
311    CapitalR = 82,
312    /// U+0053
313    #[unstable(feature = "ascii_char_variants", issue = "110998")]
314    CapitalS = 83,
315    /// U+0054
316    #[unstable(feature = "ascii_char_variants", issue = "110998")]
317    CapitalT = 84,
318    /// U+0055
319    #[unstable(feature = "ascii_char_variants", issue = "110998")]
320    CapitalU = 85,
321    /// U+0056
322    #[unstable(feature = "ascii_char_variants", issue = "110998")]
323    CapitalV = 86,
324    /// U+0057
325    #[unstable(feature = "ascii_char_variants", issue = "110998")]
326    CapitalW = 87,
327    /// U+0058
328    #[unstable(feature = "ascii_char_variants", issue = "110998")]
329    CapitalX = 88,
330    /// U+0059
331    #[unstable(feature = "ascii_char_variants", issue = "110998")]
332    CapitalY = 89,
333    /// U+005A
334    #[unstable(feature = "ascii_char_variants", issue = "110998")]
335    CapitalZ = 90,
336    /// U+005B
337    #[unstable(feature = "ascii_char_variants", issue = "110998")]
338    LeftSquareBracket = 91,
339    /// U+005C
340    #[unstable(feature = "ascii_char_variants", issue = "110998")]
341    ReverseSolidus = 92,
342    /// U+005D
343    #[unstable(feature = "ascii_char_variants", issue = "110998")]
344    RightSquareBracket = 93,
345    /// U+005E
346    #[unstable(feature = "ascii_char_variants", issue = "110998")]
347    CircumflexAccent = 94,
348    /// U+005F
349    #[unstable(feature = "ascii_char_variants", issue = "110998")]
350    LowLine = 95,
351    /// U+0060
352    #[unstable(feature = "ascii_char_variants", issue = "110998")]
353    GraveAccent = 96,
354    /// U+0061
355    #[unstable(feature = "ascii_char_variants", issue = "110998")]
356    SmallA = 97,
357    /// U+0062
358    #[unstable(feature = "ascii_char_variants", issue = "110998")]
359    SmallB = 98,
360    /// U+0063
361    #[unstable(feature = "ascii_char_variants", issue = "110998")]
362    SmallC = 99,
363    /// U+0064
364    #[unstable(feature = "ascii_char_variants", issue = "110998")]
365    SmallD = 100,
366    /// U+0065
367    #[unstable(feature = "ascii_char_variants", issue = "110998")]
368    SmallE = 101,
369    /// U+0066
370    #[unstable(feature = "ascii_char_variants", issue = "110998")]
371    SmallF = 102,
372    /// U+0067
373    #[unstable(feature = "ascii_char_variants", issue = "110998")]
374    SmallG = 103,
375    /// U+0068
376    #[unstable(feature = "ascii_char_variants", issue = "110998")]
377    SmallH = 104,
378    /// U+0069
379    #[unstable(feature = "ascii_char_variants", issue = "110998")]
380    SmallI = 105,
381    /// U+006A
382    #[unstable(feature = "ascii_char_variants", issue = "110998")]
383    SmallJ = 106,
384    /// U+006B
385    #[unstable(feature = "ascii_char_variants", issue = "110998")]
386    SmallK = 107,
387    /// U+006C
388    #[unstable(feature = "ascii_char_variants", issue = "110998")]
389    SmallL = 108,
390    /// U+006D
391    #[unstable(feature = "ascii_char_variants", issue = "110998")]
392    SmallM = 109,
393    /// U+006E
394    #[unstable(feature = "ascii_char_variants", issue = "110998")]
395    SmallN = 110,
396    /// U+006F
397    #[unstable(feature = "ascii_char_variants", issue = "110998")]
398    SmallO = 111,
399    /// U+0070
400    #[unstable(feature = "ascii_char_variants", issue = "110998")]
401    SmallP = 112,
402    /// U+0071
403    #[unstable(feature = "ascii_char_variants", issue = "110998")]
404    SmallQ = 113,
405    /// U+0072
406    #[unstable(feature = "ascii_char_variants", issue = "110998")]
407    SmallR = 114,
408    /// U+0073
409    #[unstable(feature = "ascii_char_variants", issue = "110998")]
410    SmallS = 115,
411    /// U+0074
412    #[unstable(feature = "ascii_char_variants", issue = "110998")]
413    SmallT = 116,
414    /// U+0075
415    #[unstable(feature = "ascii_char_variants", issue = "110998")]
416    SmallU = 117,
417    /// U+0076
418    #[unstable(feature = "ascii_char_variants", issue = "110998")]
419    SmallV = 118,
420    /// U+0077
421    #[unstable(feature = "ascii_char_variants", issue = "110998")]
422    SmallW = 119,
423    /// U+0078
424    #[unstable(feature = "ascii_char_variants", issue = "110998")]
425    SmallX = 120,
426    /// U+0079
427    #[unstable(feature = "ascii_char_variants", issue = "110998")]
428    SmallY = 121,
429    /// U+007A
430    #[unstable(feature = "ascii_char_variants", issue = "110998")]
431    SmallZ = 122,
432    /// U+007B
433    #[unstable(feature = "ascii_char_variants", issue = "110998")]
434    LeftCurlyBracket = 123,
435    /// U+007C
436    #[unstable(feature = "ascii_char_variants", issue = "110998")]
437    VerticalLine = 124,
438    /// U+007D
439    #[unstable(feature = "ascii_char_variants", issue = "110998")]
440    RightCurlyBracket = 125,
441    /// U+007E
442    #[unstable(feature = "ascii_char_variants", issue = "110998")]
443    Tilde = 126,
444    /// U+007F
445    #[unstable(feature = "ascii_char_variants", issue = "110998")]
446    Delete = 127,
447}
448
449impl AsciiChar {
450    /// The character with the lowest ASCII code.
451    #[unstable(feature = "ascii_char", issue = "110998")]
452    pub const MIN: Self = Self::Null;
453
454    /// The character with the highest ASCII code.
455    #[unstable(feature = "ascii_char", issue = "110998")]
456    pub const MAX: Self = Self::Delete;
457
458    /// Creates an ASCII character from the byte `b`,
459    /// or returns `None` if it's too large.
460    #[unstable(feature = "ascii_char", issue = "110998")]
461    #[inline]
462    pub const fn from_u8(b: u8) -> Option<Self> {
463        if b <= 127 {
464            // SAFETY: Just checked that `b` is in-range
465            Some(unsafe { Self::from_u8_unchecked(b) })
466        } else {
467            None
468        }
469    }
470
471    /// Creates an ASCII character from the byte `b`,
472    /// without checking whether it's valid.
473    ///
474    /// # Safety
475    ///
476    /// `b` must be in `0..=127`, or else this is UB.
477    #[unstable(feature = "ascii_char", issue = "110998")]
478    #[inline]
479    #[ferrocene::prevalidated]
480    pub const unsafe fn from_u8_unchecked(b: u8) -> Self {
481        // SAFETY: Our safety precondition is that `b` is in-range.
482        unsafe { transmute(b) }
483    }
484
485    /// When passed the *number* `0`, `1`, …, `9`, returns the *character*
486    /// `'0'`, `'1'`, …, `'9'` respectively.
487    ///
488    /// If `d >= 10`, returns `None`.
489    #[unstable(feature = "ascii_char", issue = "110998")]
490    #[inline]
491    pub const fn digit(d: u8) -> Option<Self> {
492        if d < 10 {
493            // SAFETY: Just checked it's in-range.
494            Some(unsafe { Self::digit_unchecked(d) })
495        } else {
496            None
497        }
498    }
499
500    /// When passed the *number* `0`, `1`, …, `9`, returns the *character*
501    /// `'0'`, `'1'`, …, `'9'` respectively, without checking that it's in-range.
502    ///
503    /// # Safety
504    ///
505    /// This is immediate UB if called with `d > 64`.
506    ///
507    /// If `d >= 10` and `d <= 64`, this is allowed to return any value or panic.
508    /// Notably, it should not be expected to return hex digits, or any other
509    /// reasonable extension of the decimal digits.
510    ///
511    /// (This loose safety condition is intended to simplify soundness proofs
512    /// when writing code using this method, since the implementation doesn't
513    /// need something really specific, not to make those other arguments do
514    /// something useful. It might be tightened before stabilization.)
515    #[unstable(feature = "ascii_char", issue = "110998")]
516    #[inline]
517    #[track_caller]
518    pub const unsafe fn digit_unchecked(d: u8) -> Self {
519        assert_unsafe_precondition!(
520            check_library_ub,
521            "`ascii::Char::digit_unchecked` input cannot exceed 9.",
522            (d: u8 = d) => d < 10
523        );
524
525        // SAFETY: `'0'` through `'9'` are U+00030 through U+0039,
526        // so because `d` must be 64 or less the addition can return at most
527        // 112 (0x70), which doesn't overflow and is within the ASCII range.
528        unsafe {
529            let byte = b'0'.unchecked_add(d);
530            Self::from_u8_unchecked(byte)
531        }
532    }
533
534    /// Gets this ASCII character as a byte.
535    #[unstable(feature = "ascii_char", issue = "110998")]
536    #[inline]
537    #[ferrocene::prevalidated]
538    pub const fn to_u8(self) -> u8 {
539        self as u8
540    }
541
542    /// Gets this ASCII character as a `char` Unicode Scalar Value.
543    #[unstable(feature = "ascii_char", issue = "110998")]
544    #[inline]
545    pub const fn to_char(self) -> char {
546        self as u8 as char
547    }
548
549    /// Views this ASCII character as a one-code-unit UTF-8 `str`.
550    #[unstable(feature = "ascii_char", issue = "110998")]
551    #[inline]
552    #[ferrocene::prevalidated]
553    pub const fn as_str(&self) -> &str {
554        crate::slice::from_ref(self).as_str()
555    }
556
557    /// Makes a copy of the value in its upper case equivalent.
558    ///
559    /// Letters 'a' to 'z' are mapped to 'A' to 'Z'.
560    ///
561    /// To uppercase the value in-place, use [`make_uppercase`].
562    ///
563    /// # Examples
564    ///
565    /// ```
566    /// #![feature(ascii_char, ascii_char_variants)]
567    /// use std::ascii;
568    ///
569    /// let lowercase_a = ascii::Char::SmallA;
570    ///
571    /// assert_eq!(
572    ///     ascii::Char::CapitalA,
573    ///     lowercase_a.to_uppercase(),
574    /// );
575    /// ```
576    ///
577    /// [`make_uppercase`]: Self::make_uppercase
578    #[must_use = "to uppercase the value in-place, use `make_uppercase()`"]
579    #[unstable(feature = "ascii_char", issue = "110998")]
580    #[inline]
581    pub const fn to_uppercase(self) -> Self {
582        let uppercase_byte = self.to_u8().to_ascii_uppercase();
583        // SAFETY: Toggling the 6th bit won't convert ASCII to non-ASCII.
584        unsafe { Self::from_u8_unchecked(uppercase_byte) }
585    }
586
587    /// Makes a copy of the value in its lower case equivalent.
588    ///
589    /// Letters 'A' to 'Z' are mapped to 'a' to 'z'.
590    ///
591    /// To lowercase the value in-place, use [`make_lowercase`].
592    ///
593    /// # Examples
594    ///
595    /// ```
596    /// #![feature(ascii_char, ascii_char_variants)]
597    /// use std::ascii;
598    ///
599    /// let uppercase_a = ascii::Char::CapitalA;
600    ///
601    /// assert_eq!(
602    ///     ascii::Char::SmallA,
603    ///     uppercase_a.to_lowercase(),
604    /// );
605    /// ```
606    ///
607    /// [`make_lowercase`]: Self::make_lowercase
608    #[must_use = "to lowercase the value in-place, use `make_lowercase()`"]
609    #[unstable(feature = "ascii_char", issue = "110998")]
610    #[inline]
611    pub const fn to_lowercase(self) -> Self {
612        let lowercase_byte = self.to_u8().to_ascii_lowercase();
613        // SAFETY: Setting the 6th bit won't convert ASCII to non-ASCII.
614        unsafe { Self::from_u8_unchecked(lowercase_byte) }
615    }
616
617    /// Checks that two values are a case-insensitive match.
618    ///
619    /// This is equivalent to `to_lowercase(a) == to_lowercase(b)`.
620    ///
621    /// # Examples
622    ///
623    /// ```
624    /// #![feature(ascii_char, ascii_char_variants)]
625    /// use std::ascii;
626    ///
627    /// let lowercase_a = ascii::Char::SmallA;
628    /// let uppercase_a = ascii::Char::CapitalA;
629    ///
630    /// assert!(lowercase_a.eq_ignore_case(uppercase_a));
631    /// ```
632    #[unstable(feature = "ascii_char", issue = "110998")]
633    #[inline]
634    pub const fn eq_ignore_case(self, other: Self) -> bool {
635        // FIXME(const-hack) `arg.to_u8().to_ascii_lowercase()` -> `arg.to_lowercase()`
636        // once `PartialEq` is const for `Self`.
637        self.to_u8().to_ascii_lowercase() == other.to_u8().to_ascii_lowercase()
638    }
639
640    /// Converts this value to its upper case equivalent in-place.
641    ///
642    /// Letters 'a' to 'z' are mapped to 'A' to 'Z'.
643    ///
644    /// To return a new uppercased value without modifying the existing one, use
645    /// [`to_uppercase`].
646    ///
647    /// # Examples
648    ///
649    /// ```
650    /// #![feature(ascii_char, ascii_char_variants)]
651    /// use std::ascii;
652    ///
653    /// let mut letter_a = ascii::Char::SmallA;
654    ///
655    /// letter_a.make_uppercase();
656    ///
657    /// assert_eq!(ascii::Char::CapitalA, letter_a);
658    /// ```
659    ///
660    /// [`to_uppercase`]: Self::to_uppercase
661    #[unstable(feature = "ascii_char", issue = "110998")]
662    #[inline]
663    pub const fn make_uppercase(&mut self) {
664        *self = self.to_uppercase();
665    }
666
667    /// Converts this value to its lower case equivalent in-place.
668    ///
669    /// Letters 'A' to 'Z' are mapped to 'a' to 'z'.
670    ///
671    /// To return a new lowercased value without modifying the existing one, use
672    /// [`to_lowercase`].
673    ///
674    /// # Examples
675    ///
676    /// ```
677    /// #![feature(ascii_char, ascii_char_variants)]
678    /// use std::ascii;
679    ///
680    /// let mut letter_a = ascii::Char::CapitalA;
681    ///
682    /// letter_a.make_lowercase();
683    ///
684    /// assert_eq!(ascii::Char::SmallA, letter_a);
685    /// ```
686    ///
687    /// [`to_lowercase`]: Self::to_lowercase
688    #[unstable(feature = "ascii_char", issue = "110998")]
689    #[inline]
690    pub const fn make_lowercase(&mut self) {
691        *self = self.to_lowercase();
692    }
693
694    /// Checks if the value is an alphabetic character:
695    ///
696    /// - 0x41 'A' ..= 0x5A 'Z', or
697    /// - 0x61 'a' ..= 0x7A 'z'.
698    ///
699    /// # Examples
700    ///
701    /// ```
702    /// #![feature(ascii_char, ascii_char_variants)]
703    /// use std::ascii;
704    ///
705    /// let uppercase_a = ascii::Char::CapitalA;
706    /// let uppercase_g = ascii::Char::CapitalG;
707    /// let a = ascii::Char::SmallA;
708    /// let g = ascii::Char::SmallG;
709    /// let zero = ascii::Char::Digit0;
710    /// let percent = ascii::Char::PercentSign;
711    /// let space = ascii::Char::Space;
712    /// let lf = ascii::Char::LineFeed;
713    /// let esc = ascii::Char::Escape;
714    ///
715    /// assert!(uppercase_a.is_alphabetic());
716    /// assert!(uppercase_g.is_alphabetic());
717    /// assert!(a.is_alphabetic());
718    /// assert!(g.is_alphabetic());
719    /// assert!(!zero.is_alphabetic());
720    /// assert!(!percent.is_alphabetic());
721    /// assert!(!space.is_alphabetic());
722    /// assert!(!lf.is_alphabetic());
723    /// assert!(!esc.is_alphabetic());
724    /// ```
725    #[must_use]
726    #[unstable(feature = "ascii_char", issue = "110998")]
727    #[inline]
728    pub const fn is_alphabetic(self) -> bool {
729        self.to_u8().is_ascii_alphabetic()
730    }
731
732    /// Checks if the value is an uppercase character:
733    /// 0x41 'A' ..= 0x5A 'Z'.
734    ///
735    /// # Examples
736    ///
737    /// ```
738    /// #![feature(ascii_char, ascii_char_variants)]
739    /// use std::ascii;
740    ///
741    /// let uppercase_a = ascii::Char::CapitalA;
742    /// let uppercase_g = ascii::Char::CapitalG;
743    /// let a = ascii::Char::SmallA;
744    /// let g = ascii::Char::SmallG;
745    /// let zero = ascii::Char::Digit0;
746    /// let percent = ascii::Char::PercentSign;
747    /// let space = ascii::Char::Space;
748    /// let lf = ascii::Char::LineFeed;
749    /// let esc = ascii::Char::Escape;
750    ///
751    /// assert!(uppercase_a.is_uppercase());
752    /// assert!(uppercase_g.is_uppercase());
753    /// assert!(!a.is_uppercase());
754    /// assert!(!g.is_uppercase());
755    /// assert!(!zero.is_uppercase());
756    /// assert!(!percent.is_uppercase());
757    /// assert!(!space.is_uppercase());
758    /// assert!(!lf.is_uppercase());
759    /// assert!(!esc.is_uppercase());
760    /// ```
761    #[must_use]
762    #[unstable(feature = "ascii_char", issue = "110998")]
763    #[inline]
764    pub const fn is_uppercase(self) -> bool {
765        self.to_u8().is_ascii_uppercase()
766    }
767
768    /// Checks if the value is a lowercase character:
769    /// 0x61 'a' ..= 0x7A 'z'.
770    ///
771    /// # Examples
772    ///
773    /// ```
774    /// #![feature(ascii_char, ascii_char_variants)]
775    /// use std::ascii;
776    ///
777    /// let uppercase_a = ascii::Char::CapitalA;
778    /// let uppercase_g = ascii::Char::CapitalG;
779    /// let a = ascii::Char::SmallA;
780    /// let g = ascii::Char::SmallG;
781    /// let zero = ascii::Char::Digit0;
782    /// let percent = ascii::Char::PercentSign;
783    /// let space = ascii::Char::Space;
784    /// let lf = ascii::Char::LineFeed;
785    /// let esc = ascii::Char::Escape;
786    ///
787    /// assert!(!uppercase_a.is_lowercase());
788    /// assert!(!uppercase_g.is_lowercase());
789    /// assert!(a.is_lowercase());
790    /// assert!(g.is_lowercase());
791    /// assert!(!zero.is_lowercase());
792    /// assert!(!percent.is_lowercase());
793    /// assert!(!space.is_lowercase());
794    /// assert!(!lf.is_lowercase());
795    /// assert!(!esc.is_lowercase());
796    /// ```
797    #[must_use]
798    #[unstable(feature = "ascii_char", issue = "110998")]
799    #[inline]
800    pub const fn is_lowercase(self) -> bool {
801        self.to_u8().is_ascii_lowercase()
802    }
803
804    /// Checks if the value is an alphanumeric character:
805    ///
806    /// - 0x41 'A' ..= 0x5A 'Z', or
807    /// - 0x61 'a' ..= 0x7A 'z', or
808    /// - 0x30 '0' ..= 0x39 '9'.
809    ///
810    /// # Examples
811    ///
812    /// ```
813    /// #![feature(ascii_char, ascii_char_variants)]
814    /// use std::ascii;
815    ///
816    /// let uppercase_a = ascii::Char::CapitalA;
817    /// let uppercase_g = ascii::Char::CapitalG;
818    /// let a = ascii::Char::SmallA;
819    /// let g = ascii::Char::SmallG;
820    /// let zero = ascii::Char::Digit0;
821    /// let percent = ascii::Char::PercentSign;
822    /// let space = ascii::Char::Space;
823    /// let lf = ascii::Char::LineFeed;
824    /// let esc = ascii::Char::Escape;
825    ///
826    /// assert!(uppercase_a.is_alphanumeric());
827    /// assert!(uppercase_g.is_alphanumeric());
828    /// assert!(a.is_alphanumeric());
829    /// assert!(g.is_alphanumeric());
830    /// assert!(zero.is_alphanumeric());
831    /// assert!(!percent.is_alphanumeric());
832    /// assert!(!space.is_alphanumeric());
833    /// assert!(!lf.is_alphanumeric());
834    /// assert!(!esc.is_alphanumeric());
835    /// ```
836    #[must_use]
837    #[unstable(feature = "ascii_char", issue = "110998")]
838    #[inline]
839    pub const fn is_alphanumeric(self) -> bool {
840        self.to_u8().is_ascii_alphanumeric()
841    }
842
843    /// Checks if the value is a decimal digit:
844    /// 0x30 '0' ..= 0x39 '9'.
845    ///
846    /// # Examples
847    ///
848    /// ```
849    /// #![feature(ascii_char, ascii_char_variants)]
850    /// use std::ascii;
851    ///
852    /// let uppercase_a = ascii::Char::CapitalA;
853    /// let uppercase_g = ascii::Char::CapitalG;
854    /// let a = ascii::Char::SmallA;
855    /// let g = ascii::Char::SmallG;
856    /// let zero = ascii::Char::Digit0;
857    /// let percent = ascii::Char::PercentSign;
858    /// let space = ascii::Char::Space;
859    /// let lf = ascii::Char::LineFeed;
860    /// let esc = ascii::Char::Escape;
861    ///
862    /// assert!(!uppercase_a.is_digit());
863    /// assert!(!uppercase_g.is_digit());
864    /// assert!(!a.is_digit());
865    /// assert!(!g.is_digit());
866    /// assert!(zero.is_digit());
867    /// assert!(!percent.is_digit());
868    /// assert!(!space.is_digit());
869    /// assert!(!lf.is_digit());
870    /// assert!(!esc.is_digit());
871    /// ```
872    #[must_use]
873    #[unstable(feature = "ascii_char", issue = "110998")]
874    #[inline]
875    pub const fn is_digit(self) -> bool {
876        self.to_u8().is_ascii_digit()
877    }
878
879    /// Checks if the value is an octal digit:
880    /// 0x30 '0' ..= 0x37 '7'.
881    ///
882    /// # Examples
883    ///
884    /// ```
885    /// #![feature(ascii_char, ascii_char_variants)]
886    ///
887    /// use std::ascii;
888    ///
889    /// let uppercase_a = ascii::Char::CapitalA;
890    /// let a = ascii::Char::SmallA;
891    /// let zero = ascii::Char::Digit0;
892    /// let seven = ascii::Char::Digit7;
893    /// let eight = ascii::Char::Digit8;
894    /// let percent = ascii::Char::PercentSign;
895    /// let lf = ascii::Char::LineFeed;
896    /// let esc = ascii::Char::Escape;
897    ///
898    /// assert!(!uppercase_a.is_octdigit());
899    /// assert!(!a.is_octdigit());
900    /// assert!(zero.is_octdigit());
901    /// assert!(seven.is_octdigit());
902    /// assert!(!eight.is_octdigit());
903    /// assert!(!percent.is_octdigit());
904    /// assert!(!lf.is_octdigit());
905    /// assert!(!esc.is_octdigit());
906    /// ```
907    #[must_use]
908    // This is blocked on two unstable features. Please ensure both are
909    // stabilized before marking this method as stable.
910    #[unstable(feature = "ascii_char", issue = "110998")]
911    // #[unstable(feature = "is_ascii_octdigit", issue = "101288")]
912    #[inline]
913    pub const fn is_octdigit(self) -> bool {
914        self.to_u8().is_ascii_octdigit()
915    }
916
917    /// Checks if the value is a hexadecimal digit:
918    ///
919    /// - 0x30 '0' ..= 0x39 '9', or
920    /// - 0x41 'A' ..= 0x46 'F', or
921    /// - 0x61 'a' ..= 0x66 'f'.
922    ///
923    /// # Examples
924    ///
925    /// ```
926    /// #![feature(ascii_char, ascii_char_variants)]
927    /// use std::ascii;
928    ///
929    /// let uppercase_a = ascii::Char::CapitalA;
930    /// let uppercase_g = ascii::Char::CapitalG;
931    /// let a = ascii::Char::SmallA;
932    /// let g = ascii::Char::SmallG;
933    /// let zero = ascii::Char::Digit0;
934    /// let percent = ascii::Char::PercentSign;
935    /// let space = ascii::Char::Space;
936    /// let lf = ascii::Char::LineFeed;
937    /// let esc = ascii::Char::Escape;
938    ///
939    /// assert!(uppercase_a.is_hexdigit());
940    /// assert!(!uppercase_g.is_hexdigit());
941    /// assert!(a.is_hexdigit());
942    /// assert!(!g.is_hexdigit());
943    /// assert!(zero.is_hexdigit());
944    /// assert!(!percent.is_hexdigit());
945    /// assert!(!space.is_hexdigit());
946    /// assert!(!lf.is_hexdigit());
947    /// assert!(!esc.is_hexdigit());
948    /// ```
949    #[must_use]
950    #[unstable(feature = "ascii_char", issue = "110998")]
951    #[inline]
952    pub const fn is_hexdigit(self) -> bool {
953        self.to_u8().is_ascii_hexdigit()
954    }
955
956    /// Checks if the value is a punctuation character:
957    ///
958    /// - 0x21 ..= 0x2F `! " # $ % & ' ( ) * + , - . /`, or
959    /// - 0x3A ..= 0x40 `: ; < = > ? @`, or
960    /// - 0x5B ..= 0x60 `` [ \ ] ^ _ ` ``, or
961    /// - 0x7B ..= 0x7E `{ | } ~`
962    ///
963    /// # Examples
964    ///
965    /// ```
966    /// #![feature(ascii_char, ascii_char_variants)]
967    /// use std::ascii;
968    ///
969    /// let uppercase_a = ascii::Char::CapitalA;
970    /// let uppercase_g = ascii::Char::CapitalG;
971    /// let a = ascii::Char::SmallA;
972    /// let g = ascii::Char::SmallG;
973    /// let zero = ascii::Char::Digit0;
974    /// let percent = ascii::Char::PercentSign;
975    /// let space = ascii::Char::Space;
976    /// let lf = ascii::Char::LineFeed;
977    /// let esc = ascii::Char::Escape;
978    ///
979    /// assert!(!uppercase_a.is_punctuation());
980    /// assert!(!uppercase_g.is_punctuation());
981    /// assert!(!a.is_punctuation());
982    /// assert!(!g.is_punctuation());
983    /// assert!(!zero.is_punctuation());
984    /// assert!(percent.is_punctuation());
985    /// assert!(!space.is_punctuation());
986    /// assert!(!lf.is_punctuation());
987    /// assert!(!esc.is_punctuation());
988    /// ```
989    #[must_use]
990    #[unstable(feature = "ascii_char", issue = "110998")]
991    #[inline]
992    pub const fn is_punctuation(self) -> bool {
993        self.to_u8().is_ascii_punctuation()
994    }
995
996    /// Checks if the value is a graphic character:
997    /// 0x21 '!' ..= 0x7E '~'.
998    ///
999    /// # Examples
1000    ///
1001    /// ```
1002    /// #![feature(ascii_char, ascii_char_variants)]
1003    /// use std::ascii;
1004    ///
1005    /// let uppercase_a = ascii::Char::CapitalA;
1006    /// let uppercase_g = ascii::Char::CapitalG;
1007    /// let a = ascii::Char::SmallA;
1008    /// let g = ascii::Char::SmallG;
1009    /// let zero = ascii::Char::Digit0;
1010    /// let percent = ascii::Char::PercentSign;
1011    /// let space = ascii::Char::Space;
1012    /// let lf = ascii::Char::LineFeed;
1013    /// let esc = ascii::Char::Escape;
1014    ///
1015    /// assert!(uppercase_a.is_graphic());
1016    /// assert!(uppercase_g.is_graphic());
1017    /// assert!(a.is_graphic());
1018    /// assert!(g.is_graphic());
1019    /// assert!(zero.is_graphic());
1020    /// assert!(percent.is_graphic());
1021    /// assert!(!space.is_graphic());
1022    /// assert!(!lf.is_graphic());
1023    /// assert!(!esc.is_graphic());
1024    /// ```
1025    #[must_use]
1026    #[unstable(feature = "ascii_char", issue = "110998")]
1027    #[inline]
1028    pub const fn is_graphic(self) -> bool {
1029        self.to_u8().is_ascii_graphic()
1030    }
1031
1032    /// Checks if the value is a whitespace character:
1033    /// 0x20 SPACE, 0x09 HORIZONTAL TAB, 0x0A LINE FEED,
1034    /// 0x0C FORM FEED, or 0x0D CARRIAGE RETURN.
1035    ///
1036    /// Rust uses the WhatWG Infra Standard's [definition of ASCII
1037    /// whitespace][infra-aw]. There are several other definitions in
1038    /// wide use. For instance, [the POSIX locale][pct] includes
1039    /// 0x0B VERTICAL TAB as well as all the above characters,
1040    /// but—from the very same specification—[the default rule for
1041    /// "field splitting" in the Bourne shell][bfs] considers *only*
1042    /// SPACE, HORIZONTAL TAB, and LINE FEED as whitespace.
1043    ///
1044    /// If you are writing a program that will process an existing
1045    /// file format, check what that format's definition of whitespace is
1046    /// before using this function.
1047    ///
1048    /// [infra-aw]: https://infra.spec.whatwg.org/#ascii-whitespace
1049    /// [pct]: https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap07.html#tag_07_03_01
1050    /// [bfs]: https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_06_05
1051    ///
1052    /// # Examples
1053    ///
1054    /// ```
1055    /// #![feature(ascii_char, ascii_char_variants)]
1056    /// use std::ascii;
1057    ///
1058    /// let uppercase_a = ascii::Char::CapitalA;
1059    /// let uppercase_g = ascii::Char::CapitalG;
1060    /// let a = ascii::Char::SmallA;
1061    /// let g = ascii::Char::SmallG;
1062    /// let zero = ascii::Char::Digit0;
1063    /// let percent = ascii::Char::PercentSign;
1064    /// let space = ascii::Char::Space;
1065    /// let lf = ascii::Char::LineFeed;
1066    /// let esc = ascii::Char::Escape;
1067    ///
1068    /// assert!(!uppercase_a.is_whitespace());
1069    /// assert!(!uppercase_g.is_whitespace());
1070    /// assert!(!a.is_whitespace());
1071    /// assert!(!g.is_whitespace());
1072    /// assert!(!zero.is_whitespace());
1073    /// assert!(!percent.is_whitespace());
1074    /// assert!(space.is_whitespace());
1075    /// assert!(lf.is_whitespace());
1076    /// assert!(!esc.is_whitespace());
1077    /// ```
1078    #[must_use]
1079    #[unstable(feature = "ascii_char", issue = "110998")]
1080    #[inline]
1081    pub const fn is_whitespace(self) -> bool {
1082        self.to_u8().is_ascii_whitespace()
1083    }
1084
1085    /// Checks if the value is a control character:
1086    /// 0x00 NUL ..= 0x1F UNIT SEPARATOR, or 0x7F DELETE.
1087    /// Note that most whitespace characters are control
1088    /// characters, but SPACE is not.
1089    ///
1090    /// # Examples
1091    ///
1092    /// ```
1093    /// #![feature(ascii_char, ascii_char_variants)]
1094    /// use std::ascii;
1095    ///
1096    /// let uppercase_a = ascii::Char::CapitalA;
1097    /// let uppercase_g = ascii::Char::CapitalG;
1098    /// let a = ascii::Char::SmallA;
1099    /// let g = ascii::Char::SmallG;
1100    /// let zero = ascii::Char::Digit0;
1101    /// let percent = ascii::Char::PercentSign;
1102    /// let space = ascii::Char::Space;
1103    /// let lf = ascii::Char::LineFeed;
1104    /// let esc = ascii::Char::Escape;
1105    ///
1106    /// assert!(!uppercase_a.is_control());
1107    /// assert!(!uppercase_g.is_control());
1108    /// assert!(!a.is_control());
1109    /// assert!(!g.is_control());
1110    /// assert!(!zero.is_control());
1111    /// assert!(!percent.is_control());
1112    /// assert!(!space.is_control());
1113    /// assert!(lf.is_control());
1114    /// assert!(esc.is_control());
1115    /// ```
1116    #[must_use]
1117    #[unstable(feature = "ascii_char", issue = "110998")]
1118    #[inline]
1119    pub const fn is_control(self) -> bool {
1120        self.to_u8().is_ascii_control()
1121    }
1122
1123    /// Returns an iterator that produces an escaped version of a
1124    /// character.
1125    ///
1126    /// The behavior is identical to
1127    /// [`ascii::escape_default`](crate::ascii::escape_default).
1128    ///
1129    /// # Examples
1130    ///
1131    /// ```
1132    /// #![feature(ascii_char, ascii_char_variants)]
1133    /// use std::ascii;
1134    ///
1135    /// let zero = ascii::Char::Digit0;
1136    /// let tab = ascii::Char::CharacterTabulation;
1137    /// let cr = ascii::Char::CarriageReturn;
1138    /// let lf = ascii::Char::LineFeed;
1139    /// let apostrophe = ascii::Char::Apostrophe;
1140    /// let double_quote = ascii::Char::QuotationMark;
1141    /// let backslash = ascii::Char::ReverseSolidus;
1142    ///
1143    /// assert_eq!("0", zero.escape_ascii().to_string());
1144    /// assert_eq!("\\t", tab.escape_ascii().to_string());
1145    /// assert_eq!("\\r", cr.escape_ascii().to_string());
1146    /// assert_eq!("\\n", lf.escape_ascii().to_string());
1147    /// assert_eq!("\\'", apostrophe.escape_ascii().to_string());
1148    /// assert_eq!("\\\"", double_quote.escape_ascii().to_string());
1149    /// assert_eq!("\\\\", backslash.escape_ascii().to_string());
1150    /// ```
1151    #[must_use = "this returns the escaped character as an iterator, \
1152                  without modifying the original"]
1153    #[unstable(feature = "ascii_char", issue = "110998")]
1154    #[inline]
1155    pub fn escape_ascii(self) -> super::EscapeDefault {
1156        super::escape_default(self.to_u8())
1157    }
1158}
1159
1160macro_rules! into_int_impl {
1161    ($($ty:ty)*) => {
1162        $(
1163            #[unstable(feature = "ascii_char", issue = "110998")]
1164            #[rustc_const_unstable(feature = "const_convert", issue = "143773")]
1165            impl const From<AsciiChar> for $ty {
1166                #[inline]
1167                fn from(chr: AsciiChar) -> $ty {
1168                    chr as u8 as $ty
1169                }
1170            }
1171        )*
1172    }
1173}
1174
1175into_int_impl!(u8 u16 u32 u64 u128 char);
1176
1177impl [AsciiChar] {
1178    /// Views this slice of ASCII characters as a UTF-8 `str`.
1179    #[unstable(feature = "ascii_char", issue = "110998")]
1180    #[inline]
1181    #[ferrocene::prevalidated]
1182    pub const fn as_str(&self) -> &str {
1183        let ascii_ptr: *const Self = self;
1184        let str_ptr = ascii_ptr as *const str;
1185        // SAFETY: Each ASCII codepoint in UTF-8 is encoded as one single-byte
1186        // code unit having the same value as the ASCII byte.
1187        unsafe { &*str_ptr }
1188    }
1189
1190    /// Views this slice of ASCII characters as a slice of `u8` bytes.
1191    #[unstable(feature = "ascii_char", issue = "110998")]
1192    #[inline]
1193    #[ferrocene::prevalidated]
1194    pub const fn as_bytes(&self) -> &[u8] {
1195        self.as_str().as_bytes()
1196    }
1197}
1198
1199#[unstable(feature = "ascii_char", issue = "110998")]
1200impl fmt::Display for AsciiChar {
1201    #[ferrocene::prevalidated]
1202    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1203        <str as fmt::Display>::fmt(self.as_str(), f)
1204    }
1205}
1206
1207#[unstable(feature = "ascii_char", issue = "110998")]
1208impl fmt::Debug for AsciiChar {
1209    #[ferrocene::prevalidated]
1210    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1211        use AsciiChar::{Apostrophe, Null, ReverseSolidus as Backslash};
1212
1213        #[ferrocene::prevalidated]
1214        fn backslash(a: AsciiChar) -> ([AsciiChar; 6], usize) {
1215            ([Apostrophe, Backslash, a, Apostrophe, Null, Null], 4)
1216        }
1217
1218        let (buf, len) = match self {
1219            AsciiChar::Null => backslash(AsciiChar::Digit0),
1220            AsciiChar::CharacterTabulation => backslash(AsciiChar::SmallT),
1221            AsciiChar::CarriageReturn => backslash(AsciiChar::SmallR),
1222            AsciiChar::LineFeed => backslash(AsciiChar::SmallN),
1223            AsciiChar::ReverseSolidus => backslash(AsciiChar::ReverseSolidus),
1224            AsciiChar::Apostrophe => backslash(AsciiChar::Apostrophe),
1225            _ if self.to_u8().is_ascii_control() => {
1226                const HEX_DIGITS: [AsciiChar; 16] = *b"0123456789abcdef".as_ascii().unwrap();
1227
1228                let byte = self.to_u8();
1229                let hi = HEX_DIGITS[usize::from(byte >> 4)];
1230                let lo = HEX_DIGITS[usize::from(byte & 0xf)];
1231                ([Apostrophe, Backslash, AsciiChar::SmallX, hi, lo, Apostrophe], 6)
1232            }
1233            _ => ([Apostrophe, *self, Apostrophe, Null, Null, Null], 3),
1234        };
1235
1236        f.write_str(buf[..len].as_str())
1237    }
1238}
core/ascii/ascii_char.rs

core/ascii/
ascii_char.rs
