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, Clone, Eq, PartialEq, Ord, PartialOrd, Hash)]
58#[unstable(feature = "ascii_char", issue = "110998")]
59#[repr(u8)]
60pub enum AsciiChar {
61    /// U+0000 (The default variant)
62    #[unstable(feature = "ascii_char_variants", issue = "110998")]
63    Null = 0,
64    /// U+0001
65    #[unstable(feature = "ascii_char_variants", issue = "110998")]
66    StartOfHeading = 1,
67    /// U+0002
68    #[unstable(feature = "ascii_char_variants", issue = "110998")]
69    StartOfText = 2,
70    /// U+0003
71    #[unstable(feature = "ascii_char_variants", issue = "110998")]
72    EndOfText = 3,
73    /// U+0004
74    #[unstable(feature = "ascii_char_variants", issue = "110998")]
75    EndOfTransmission = 4,
76    /// U+0005
77    #[unstable(feature = "ascii_char_variants", issue = "110998")]
78    Enquiry = 5,
79    /// U+0006
80    #[unstable(feature = "ascii_char_variants", issue = "110998")]
81    Acknowledge = 6,
82    /// U+0007
83    #[unstable(feature = "ascii_char_variants", issue = "110998")]
84    Bell = 7,
85    /// U+0008
86    #[unstable(feature = "ascii_char_variants", issue = "110998")]
87    Backspace = 8,
88    /// U+0009
89    #[unstable(feature = "ascii_char_variants", issue = "110998")]
90    CharacterTabulation = 9,
91    /// U+000A
92    #[unstable(feature = "ascii_char_variants", issue = "110998")]
93    LineFeed = 10,
94    /// U+000B
95    #[unstable(feature = "ascii_char_variants", issue = "110998")]
96    LineTabulation = 11,
97    /// U+000C
98    #[unstable(feature = "ascii_char_variants", issue = "110998")]
99    FormFeed = 12,
100    /// U+000D
101    #[unstable(feature = "ascii_char_variants", issue = "110998")]
102    CarriageReturn = 13,
103    /// U+000E
104    #[unstable(feature = "ascii_char_variants", issue = "110998")]
105    ShiftOut = 14,
106    /// U+000F
107    #[unstable(feature = "ascii_char_variants", issue = "110998")]
108    ShiftIn = 15,
109    /// U+0010
110    #[unstable(feature = "ascii_char_variants", issue = "110998")]
111    DataLinkEscape = 16,
112    /// U+0011
113    #[unstable(feature = "ascii_char_variants", issue = "110998")]
114    DeviceControlOne = 17,
115    /// U+0012
116    #[unstable(feature = "ascii_char_variants", issue = "110998")]
117    DeviceControlTwo = 18,
118    /// U+0013
119    #[unstable(feature = "ascii_char_variants", issue = "110998")]
120    DeviceControlThree = 19,
121    /// U+0014
122    #[unstable(feature = "ascii_char_variants", issue = "110998")]
123    DeviceControlFour = 20,
124    /// U+0015
125    #[unstable(feature = "ascii_char_variants", issue = "110998")]
126    NegativeAcknowledge = 21,
127    /// U+0016
128    #[unstable(feature = "ascii_char_variants", issue = "110998")]
129    SynchronousIdle = 22,
130    /// U+0017
131    #[unstable(feature = "ascii_char_variants", issue = "110998")]
132    EndOfTransmissionBlock = 23,
133    /// U+0018
134    #[unstable(feature = "ascii_char_variants", issue = "110998")]
135    Cancel = 24,
136    /// U+0019
137    #[unstable(feature = "ascii_char_variants", issue = "110998")]
138    EndOfMedium = 25,
139    /// U+001A
140    #[unstable(feature = "ascii_char_variants", issue = "110998")]
141    Substitute = 26,
142    /// U+001B
143    #[unstable(feature = "ascii_char_variants", issue = "110998")]
144    Escape = 27,
145    /// U+001C
146    #[unstable(feature = "ascii_char_variants", issue = "110998")]
147    InformationSeparatorFour = 28,
148    /// U+001D
149    #[unstable(feature = "ascii_char_variants", issue = "110998")]
150    InformationSeparatorThree = 29,
151    /// U+001E
152    #[unstable(feature = "ascii_char_variants", issue = "110998")]
153    InformationSeparatorTwo = 30,
154    /// U+001F
155    #[unstable(feature = "ascii_char_variants", issue = "110998")]
156    InformationSeparatorOne = 31,
157    /// U+0020
158    #[unstable(feature = "ascii_char_variants", issue = "110998")]
159    Space = 32,
160    /// U+0021
161    #[unstable(feature = "ascii_char_variants", issue = "110998")]
162    ExclamationMark = 33,
163    /// U+0022
164    #[unstable(feature = "ascii_char_variants", issue = "110998")]
165    QuotationMark = 34,
166    /// U+0023
167    #[unstable(feature = "ascii_char_variants", issue = "110998")]
168    NumberSign = 35,
169    /// U+0024
170    #[unstable(feature = "ascii_char_variants", issue = "110998")]
171    DollarSign = 36,
172    /// U+0025
173    #[unstable(feature = "ascii_char_variants", issue = "110998")]
174    PercentSign = 37,
175    /// U+0026
176    #[unstable(feature = "ascii_char_variants", issue = "110998")]
177    Ampersand = 38,
178    /// U+0027
179    #[unstable(feature = "ascii_char_variants", issue = "110998")]
180    Apostrophe = 39,
181    /// U+0028
182    #[unstable(feature = "ascii_char_variants", issue = "110998")]
183    LeftParenthesis = 40,
184    /// U+0029
185    #[unstable(feature = "ascii_char_variants", issue = "110998")]
186    RightParenthesis = 41,
187    /// U+002A
188    #[unstable(feature = "ascii_char_variants", issue = "110998")]
189    Asterisk = 42,
190    /// U+002B
191    #[unstable(feature = "ascii_char_variants", issue = "110998")]
192    PlusSign = 43,
193    /// U+002C
194    #[unstable(feature = "ascii_char_variants", issue = "110998")]
195    Comma = 44,
196    /// U+002D
197    #[unstable(feature = "ascii_char_variants", issue = "110998")]
198    HyphenMinus = 45,
199    /// U+002E
200    #[unstable(feature = "ascii_char_variants", issue = "110998")]
201    FullStop = 46,
202    /// U+002F
203    #[unstable(feature = "ascii_char_variants", issue = "110998")]
204    Solidus = 47,
205    /// U+0030
206    #[unstable(feature = "ascii_char_variants", issue = "110998")]
207    Digit0 = 48,
208    /// U+0031
209    #[unstable(feature = "ascii_char_variants", issue = "110998")]
210    Digit1 = 49,
211    /// U+0032
212    #[unstable(feature = "ascii_char_variants", issue = "110998")]
213    Digit2 = 50,
214    /// U+0033
215    #[unstable(feature = "ascii_char_variants", issue = "110998")]
216    Digit3 = 51,
217    /// U+0034
218    #[unstable(feature = "ascii_char_variants", issue = "110998")]
219    Digit4 = 52,
220    /// U+0035
221    #[unstable(feature = "ascii_char_variants", issue = "110998")]
222    Digit5 = 53,
223    /// U+0036
224    #[unstable(feature = "ascii_char_variants", issue = "110998")]
225    Digit6 = 54,
226    /// U+0037
227    #[unstable(feature = "ascii_char_variants", issue = "110998")]
228    Digit7 = 55,
229    /// U+0038
230    #[unstable(feature = "ascii_char_variants", issue = "110998")]
231    Digit8 = 56,
232    /// U+0039
233    #[unstable(feature = "ascii_char_variants", issue = "110998")]
234    Digit9 = 57,
235    /// U+003A
236    #[unstable(feature = "ascii_char_variants", issue = "110998")]
237    Colon = 58,
238    /// U+003B
239    #[unstable(feature = "ascii_char_variants", issue = "110998")]
240    Semicolon = 59,
241    /// U+003C
242    #[unstable(feature = "ascii_char_variants", issue = "110998")]
243    LessThanSign = 60,
244    /// U+003D
245    #[unstable(feature = "ascii_char_variants", issue = "110998")]
246    EqualsSign = 61,
247    /// U+003E
248    #[unstable(feature = "ascii_char_variants", issue = "110998")]
249    GreaterThanSign = 62,
250    /// U+003F
251    #[unstable(feature = "ascii_char_variants", issue = "110998")]
252    QuestionMark = 63,
253    /// U+0040
254    #[unstable(feature = "ascii_char_variants", issue = "110998")]
255    CommercialAt = 64,
256    /// U+0041
257    #[unstable(feature = "ascii_char_variants", issue = "110998")]
258    CapitalA = 65,
259    /// U+0042
260    #[unstable(feature = "ascii_char_variants", issue = "110998")]
261    CapitalB = 66,
262    /// U+0043
263    #[unstable(feature = "ascii_char_variants", issue = "110998")]
264    CapitalC = 67,
265    /// U+0044
266    #[unstable(feature = "ascii_char_variants", issue = "110998")]
267    CapitalD = 68,
268    /// U+0045
269    #[unstable(feature = "ascii_char_variants", issue = "110998")]
270    CapitalE = 69,
271    /// U+0046
272    #[unstable(feature = "ascii_char_variants", issue = "110998")]
273    CapitalF = 70,
274    /// U+0047
275    #[unstable(feature = "ascii_char_variants", issue = "110998")]
276    CapitalG = 71,
277    /// U+0048
278    #[unstable(feature = "ascii_char_variants", issue = "110998")]
279    CapitalH = 72,
280    /// U+0049
281    #[unstable(feature = "ascii_char_variants", issue = "110998")]
282    CapitalI = 73,
283    /// U+004A
284    #[unstable(feature = "ascii_char_variants", issue = "110998")]
285    CapitalJ = 74,
286    /// U+004B
287    #[unstable(feature = "ascii_char_variants", issue = "110998")]
288    CapitalK = 75,
289    /// U+004C
290    #[unstable(feature = "ascii_char_variants", issue = "110998")]
291    CapitalL = 76,
292    /// U+004D
293    #[unstable(feature = "ascii_char_variants", issue = "110998")]
294    CapitalM = 77,
295    /// U+004E
296    #[unstable(feature = "ascii_char_variants", issue = "110998")]
297    CapitalN = 78,
298    /// U+004F
299    #[unstable(feature = "ascii_char_variants", issue = "110998")]
300    CapitalO = 79,
301    /// U+0050
302    #[unstable(feature = "ascii_char_variants", issue = "110998")]
303    CapitalP = 80,
304    /// U+0051
305    #[unstable(feature = "ascii_char_variants", issue = "110998")]
306    CapitalQ = 81,
307    /// U+0052
308    #[unstable(feature = "ascii_char_variants", issue = "110998")]
309    CapitalR = 82,
310    /// U+0053
311    #[unstable(feature = "ascii_char_variants", issue = "110998")]
312    CapitalS = 83,
313    /// U+0054
314    #[unstable(feature = "ascii_char_variants", issue = "110998")]
315    CapitalT = 84,
316    /// U+0055
317    #[unstable(feature = "ascii_char_variants", issue = "110998")]
318    CapitalU = 85,
319    /// U+0056
320    #[unstable(feature = "ascii_char_variants", issue = "110998")]
321    CapitalV = 86,
322    /// U+0057
323    #[unstable(feature = "ascii_char_variants", issue = "110998")]
324    CapitalW = 87,
325    /// U+0058
326    #[unstable(feature = "ascii_char_variants", issue = "110998")]
327    CapitalX = 88,
328    /// U+0059
329    #[unstable(feature = "ascii_char_variants", issue = "110998")]
330    CapitalY = 89,
331    /// U+005A
332    #[unstable(feature = "ascii_char_variants", issue = "110998")]
333    CapitalZ = 90,
334    /// U+005B
335    #[unstable(feature = "ascii_char_variants", issue = "110998")]
336    LeftSquareBracket = 91,
337    /// U+005C
338    #[unstable(feature = "ascii_char_variants", issue = "110998")]
339    ReverseSolidus = 92,
340    /// U+005D
341    #[unstable(feature = "ascii_char_variants", issue = "110998")]
342    RightSquareBracket = 93,
343    /// U+005E
344    #[unstable(feature = "ascii_char_variants", issue = "110998")]
345    CircumflexAccent = 94,
346    /// U+005F
347    #[unstable(feature = "ascii_char_variants", issue = "110998")]
348    LowLine = 95,
349    /// U+0060
350    #[unstable(feature = "ascii_char_variants", issue = "110998")]
351    GraveAccent = 96,
352    /// U+0061
353    #[unstable(feature = "ascii_char_variants", issue = "110998")]
354    SmallA = 97,
355    /// U+0062
356    #[unstable(feature = "ascii_char_variants", issue = "110998")]
357    SmallB = 98,
358    /// U+0063
359    #[unstable(feature = "ascii_char_variants", issue = "110998")]
360    SmallC = 99,
361    /// U+0064
362    #[unstable(feature = "ascii_char_variants", issue = "110998")]
363    SmallD = 100,
364    /// U+0065
365    #[unstable(feature = "ascii_char_variants", issue = "110998")]
366    SmallE = 101,
367    /// U+0066
368    #[unstable(feature = "ascii_char_variants", issue = "110998")]
369    SmallF = 102,
370    /// U+0067
371    #[unstable(feature = "ascii_char_variants", issue = "110998")]
372    SmallG = 103,
373    /// U+0068
374    #[unstable(feature = "ascii_char_variants", issue = "110998")]
375    SmallH = 104,
376    /// U+0069
377    #[unstable(feature = "ascii_char_variants", issue = "110998")]
378    SmallI = 105,
379    /// U+006A
380    #[unstable(feature = "ascii_char_variants", issue = "110998")]
381    SmallJ = 106,
382    /// U+006B
383    #[unstable(feature = "ascii_char_variants", issue = "110998")]
384    SmallK = 107,
385    /// U+006C
386    #[unstable(feature = "ascii_char_variants", issue = "110998")]
387    SmallL = 108,
388    /// U+006D
389    #[unstable(feature = "ascii_char_variants", issue = "110998")]
390    SmallM = 109,
391    /// U+006E
392    #[unstable(feature = "ascii_char_variants", issue = "110998")]
393    SmallN = 110,
394    /// U+006F
395    #[unstable(feature = "ascii_char_variants", issue = "110998")]
396    SmallO = 111,
397    /// U+0070
398    #[unstable(feature = "ascii_char_variants", issue = "110998")]
399    SmallP = 112,
400    /// U+0071
401    #[unstable(feature = "ascii_char_variants", issue = "110998")]
402    SmallQ = 113,
403    /// U+0072
404    #[unstable(feature = "ascii_char_variants", issue = "110998")]
405    SmallR = 114,
406    /// U+0073
407    #[unstable(feature = "ascii_char_variants", issue = "110998")]
408    SmallS = 115,
409    /// U+0074
410    #[unstable(feature = "ascii_char_variants", issue = "110998")]
411    SmallT = 116,
412    /// U+0075
413    #[unstable(feature = "ascii_char_variants", issue = "110998")]
414    SmallU = 117,
415    /// U+0076
416    #[unstable(feature = "ascii_char_variants", issue = "110998")]
417    SmallV = 118,
418    /// U+0077
419    #[unstable(feature = "ascii_char_variants", issue = "110998")]
420    SmallW = 119,
421    /// U+0078
422    #[unstable(feature = "ascii_char_variants", issue = "110998")]
423    SmallX = 120,
424    /// U+0079
425    #[unstable(feature = "ascii_char_variants", issue = "110998")]
426    SmallY = 121,
427    /// U+007A
428    #[unstable(feature = "ascii_char_variants", issue = "110998")]
429    SmallZ = 122,
430    /// U+007B
431    #[unstable(feature = "ascii_char_variants", issue = "110998")]
432    LeftCurlyBracket = 123,
433    /// U+007C
434    #[unstable(feature = "ascii_char_variants", issue = "110998")]
435    VerticalLine = 124,
436    /// U+007D
437    #[unstable(feature = "ascii_char_variants", issue = "110998")]
438    RightCurlyBracket = 125,
439    /// U+007E
440    #[unstable(feature = "ascii_char_variants", issue = "110998")]
441    Tilde = 126,
442    /// U+007F
443    #[unstable(feature = "ascii_char_variants", issue = "110998")]
444    Delete = 127,
445}
446
447impl AsciiChar {
448    /// Creates an ascii character from the byte `b`,
449    /// or returns `None` if it's too large.
450    #[unstable(feature = "ascii_char", issue = "110998")]
451    #[inline]
452    pub const fn from_u8(b: u8) -> Option<Self> {
453        if b <= 127 {
454            // SAFETY: Just checked that `b` is in-range
455            Some(unsafe { Self::from_u8_unchecked(b) })
456        } else {
457            None
458        }
459    }
460
461    /// Creates an ASCII character from the byte `b`,
462    /// without checking whether it's valid.
463    ///
464    /// # Safety
465    ///
466    /// `b` must be in `0..=127`, or else this is UB.
467    #[unstable(feature = "ascii_char", issue = "110998")]
468    #[inline]
469    pub const unsafe fn from_u8_unchecked(b: u8) -> Self {
470        // SAFETY: Our safety precondition is that `b` is in-range.
471        unsafe { transmute(b) }
472    }
473
474    /// When passed the *number* `0`, `1`, …, `9`, returns the *character*
475    /// `'0'`, `'1'`, …, `'9'` respectively.
476    ///
477    /// If `d >= 10`, returns `None`.
478    #[unstable(feature = "ascii_char", issue = "110998")]
479    #[inline]
480    pub const fn digit(d: u8) -> Option<Self> {
481        if d < 10 {
482            // SAFETY: Just checked it's in-range.
483            Some(unsafe { Self::digit_unchecked(d) })
484        } else {
485            None
486        }
487    }
488
489    /// When passed the *number* `0`, `1`, …, `9`, returns the *character*
490    /// `'0'`, `'1'`, …, `'9'` respectively, without checking that it's in-range.
491    ///
492    /// # Safety
493    ///
494    /// This is immediate UB if called with `d > 64`.
495    ///
496    /// If `d >= 10` and `d <= 64`, this is allowed to return any value or panic.
497    /// Notably, it should not be expected to return hex digits, or any other
498    /// reasonable extension of the decimal digits.
499    ///
500    /// (This loose safety condition is intended to simplify soundness proofs
501    /// when writing code using this method, since the implementation doesn't
502    /// need something really specific, not to make those other arguments do
503    /// something useful. It might be tightened before stabilization.)
504    #[unstable(feature = "ascii_char", issue = "110998")]
505    #[inline]
506    pub const unsafe fn digit_unchecked(d: u8) -> Self {
507        assert_unsafe_precondition!(
508            check_language_ub,
509            "`ascii::Char::digit_unchecked` input cannot exceed 9.",
510            (d: u8 = d) => d < 10
511        );
512
513        // SAFETY: `'0'` through `'9'` are U+00030 through U+0039,
514        // so because `d` must be 64 or less the addition can return at most
515        // 112 (0x70), which doesn't overflow and is within the ASCII range.
516        unsafe {
517            let byte = b'0'.unchecked_add(d);
518            Self::from_u8_unchecked(byte)
519        }
520    }
521
522    /// Gets this ASCII character as a byte.
523    #[unstable(feature = "ascii_char", issue = "110998")]
524    #[inline]
525    pub const fn to_u8(self) -> u8 {
526        self as u8
527    }
528
529    /// Gets this ASCII character as a `char` Unicode Scalar Value.
530    #[unstable(feature = "ascii_char", issue = "110998")]
531    #[inline]
532    pub const fn to_char(self) -> char {
533        self as u8 as char
534    }
535
536    /// Views this ASCII character as a one-code-unit UTF-8 `str`.
537    #[unstable(feature = "ascii_char", issue = "110998")]
538    #[inline]
539    pub const fn as_str(&self) -> &str {
540        crate::slice::from_ref(self).as_str()
541    }
542}
543
544macro_rules! into_int_impl {
545    ($($ty:ty)*) => {
546        $(
547            #[unstable(feature = "ascii_char", issue = "110998")]
548            impl From<AsciiChar> for $ty {
549                #[inline]
550                fn from(chr: AsciiChar) -> $ty {
551                    chr as u8 as $ty
552                }
553            }
554        )*
555    }
556}
557
558into_int_impl!(u8 u16 u32 u64 u128 char);
559
560impl [AsciiChar] {
561    /// Views this slice of ASCII characters as a UTF-8 `str`.
562    #[unstable(feature = "ascii_char", issue = "110998")]
563    #[inline]
564    pub const fn as_str(&self) -> &str {
565        let ascii_ptr: *const Self = self;
566        let str_ptr = ascii_ptr as *const str;
567        // SAFETY: Each ASCII codepoint in UTF-8 is encoded as one single-byte
568        // code unit having the same value as the ASCII byte.
569        unsafe { &*str_ptr }
570    }
571
572    /// Views this slice of ASCII characters as a slice of `u8` bytes.
573    #[unstable(feature = "ascii_char", issue = "110998")]
574    #[inline]
575    pub const fn as_bytes(&self) -> &[u8] {
576        self.as_str().as_bytes()
577    }
578}
579
580#[unstable(feature = "ascii_char", issue = "110998")]
581impl fmt::Display for AsciiChar {
582    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
583        <str as fmt::Display>::fmt(self.as_str(), f)
584    }
585}
586
587#[unstable(feature = "ascii_char", issue = "110998")]
588impl fmt::Debug for AsciiChar {
589    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
590        use AsciiChar::{Apostrophe, Null, ReverseSolidus as Backslash};
591
592        fn backslash(a: AsciiChar) -> ([AsciiChar; 6], usize) {
593            ([Apostrophe, Backslash, a, Apostrophe, Null, Null], 4)
594        }
595
596        let (buf, len) = match self {
597            AsciiChar::Null => backslash(AsciiChar::Digit0),
598            AsciiChar::CharacterTabulation => backslash(AsciiChar::SmallT),
599            AsciiChar::CarriageReturn => backslash(AsciiChar::SmallR),
600            AsciiChar::LineFeed => backslash(AsciiChar::SmallN),
601            AsciiChar::ReverseSolidus => backslash(AsciiChar::ReverseSolidus),
602            AsciiChar::Apostrophe => backslash(AsciiChar::Apostrophe),
603            _ if self.to_u8().is_ascii_control() => {
604                const HEX_DIGITS: [AsciiChar; 16] = *b"0123456789abcdef".as_ascii().unwrap();
605
606                let byte = self.to_u8();
607                let hi = HEX_DIGITS[usize::from(byte >> 4)];
608                let lo = HEX_DIGITS[usize::from(byte & 0xf)];
609                ([Apostrophe, Backslash, AsciiChar::SmallX, hi, lo, Apostrophe], 6)
610            }
611            _ => ([Apostrophe, *self, Apostrophe, Null, Null, Null], 3),
612        };
613
614        f.write_str(buf[..len].as_str())
615    }
616}
core/ascii/ascii_char.rs

Pfad - The Proxy pFad of © 2024 Garber Painting. All rights reserved.

core/ascii/
ascii_char.rs
