1 // SPDX-License-Identifier: GPL-2.0
2
3 //! String representations.
4
5 use crate::alloc::{flags::*, vec_ext::VecExt,
6 use alloc::vec::Vec;
7 use core::fmt::{self, Write};
8 use core::ops::{self, Deref, DerefMut, Index};
9
10 use crate::error::{code::*, Error};
11
12 /// Byte string without UTF-8 validity guarant
13 #[repr(transparent)]
14 pub struct BStr([u8]);
15
16 impl BStr {
17 /// Returns the length of this string.
18 #[inline]
19 pub const fn len(&self) -> usize {
20 self.0.len()
21 }
22
23 /// Returns `true` if the string is empty.
24 #[inline]
25 pub const fn is_empty(&self) -> bool {
26 self.len() == 0
27 }
28
29 /// Creates a [`BStr`] from a `[u8]`.
30 #[inline]
31 pub const fn from_bytes(bytes: &[u8]) -> &
32 // SAFETY: `BStr` is transparent to `[
33 unsafe { &*(bytes as *const [u8] as *c
34 }
35 }
36
37 impl fmt::Display for BStr {
38 /// Formats printable ASCII characters, es
39 ///
40 /// ```
41 /// # use kernel::{fmt, b_str, str::{BStr,
42 /// let ascii = b_str!("Hello, BStr!");
43 /// let s = CString::try_from_fmt(fmt!("{}
44 /// assert_eq!(s.as_bytes(), "Hello, BStr!
45 ///
46 /// let non_ascii = b_str!("🦀");
47 /// let s = CString::try_from_fmt(fmt!("{}
48 /// assert_eq!(s.as_bytes(), "\\xf0\\x9f\\
49 /// ```
50 fn fmt(&self, f: &mut fmt::Formatter<'_>)
51 for &b in &self.0 {
52 match b {
53 // Common escape codes.
54 b'\t' => f.write_str("\\t")?,
55 b'\n' => f.write_str("\\n")?,
56 b'\r' => f.write_str("\\r")?,
57 // Printable characters.
58 0x20..=0x7e => f.write_char(b
59 _ => write!(f, "\\x{:02x}", b)
60 }
61 }
62 Ok(())
63 }
64 }
65
66 impl fmt::Debug for BStr {
67 /// Formats printable ASCII characters wit
68 /// escaping the rest.
69 ///
70 /// ```
71 /// # use kernel::{fmt, b_str, str::{BStr,
72 /// // Embedded double quotes are escaped.
73 /// let ascii = b_str!("Hello, \"BStr\"!")
74 /// let s = CString::try_from_fmt(fmt!("{:
75 /// assert_eq!(s.as_bytes(), "\"Hello, \\\
76 ///
77 /// let non_ascii = b_str!("😺");
78 /// let s = CString::try_from_fmt(fmt!("{:
79 /// assert_eq!(s.as_bytes(), "\"\\xf0\\x9f
80 /// ```
81 fn fmt(&self, f: &mut fmt::Formatter<'_>)
82 f.write_char('"')?;
83 for &b in &self.0 {
84 match b {
85 // Common escape codes.
86 b'\t' => f.write_str("\\t")?,
87 b'\n' => f.write_str("\\n")?,
88 b'\r' => f.write_str("\\r")?,
89 // String escape characters.
90 b'\"' => f.write_str("\\\"")?,
91 b'\\' => f.write_str("\\\\")?,
92 // Printable characters.
93 0x20..=0x7e => f.write_char(b
94 _ => write!(f, "\\x{:02x}", b)
95 }
96 }
97 f.write_char('"')
98 }
99 }
100
101 impl Deref for BStr {
102 type Target = [u8];
103
104 #[inline]
105 fn deref(&self) -> &Self::Target {
106 &self.0
107 }
108 }
109
110 /// Creates a new [`BStr`] from a string liter
111 ///
112 /// `b_str!` converts the supplied string lite
113 /// characters can be included.
114 ///
115 /// # Examples
116 ///
117 /// ```
118 /// # use kernel::b_str;
119 /// # use kernel::str::BStr;
120 /// const MY_BSTR: &BStr = b_str!("My awesome
121 /// ```
122 #[macro_export]
123 macro_rules! b_str {
124 ($str:literal) => {{
125 const S: &'static str = $str;
126 const C: &'static $crate::str::BStr =
127 C
128 }};
129 }
130
131 /// Possible errors when using conversion func
132 #[derive(Debug, Clone, Copy)]
133 pub enum CStrConvertError {
134 /// Supplied bytes contain an interior `NU
135 InteriorNul,
136
137 /// Supplied bytes are not terminated by `
138 NotNulTerminated,
139 }
140
141 impl From<CStrConvertError> for Error {
142 #[inline]
143 fn from(_: CStrConvertError) -> Error {
144 EINVAL
145 }
146 }
147
148 /// A string that is guaranteed to have exactl
149 /// end.
150 ///
151 /// Used for interoperability with kernel APIs
152 #[repr(transparent)]
153 pub struct CStr([u8]);
154
155 impl CStr {
156 /// Returns the length of this string excl
157 #[inline]
158 pub const fn len(&self) -> usize {
159 self.len_with_nul() - 1
160 }
161
162 /// Returns the length of this string with
163 #[inline]
164 pub const fn len_with_nul(&self) -> usize
165 // SAFETY: This is one of the invarian
166 // We add a `unreachable_unchecked` he
167 // the value returned from this functi
168 if self.0.is_empty() {
169 unsafe { core::hint::unreachable_u
170 }
171 self.0.len()
172 }
173
174 /// Returns `true` if the string only incl
175 #[inline]
176 pub const fn is_empty(&self) -> bool {
177 self.len() == 0
178 }
179
180 /// Wraps a raw C string pointer.
181 ///
182 /// # Safety
183 ///
184 /// `ptr` must be a valid pointer to a `NU
185 /// last at least `'a`. When `CStr` is ali
186 /// must not be mutated.
187 #[inline]
188 pub unsafe fn from_char_ptr<'a>(ptr: *cons
189 // SAFETY: The safety precondition gua
190 // to a `NUL`-terminated C string.
191 let len = unsafe { bindings::strlen(pt
192 // SAFETY: Lifetime guaranteed by the
193 let bytes = unsafe { core::slice::from
194 // SAFETY: As `len` is returned by `st
195 // As we have added 1 to `len`, the la
196 unsafe { Self::from_bytes_with_nul_unc
197 }
198
199 /// Creates a [`CStr`] from a `[u8]`.
200 ///
201 /// The provided slice must be `NUL`-termi
202 /// interior `NUL` bytes.
203 pub const fn from_bytes_with_nul(bytes: &[
204 if bytes.is_empty() {
205 return Err(CStrConvertError::NotNu
206 }
207 if bytes[bytes.len() - 1] != 0 {
208 return Err(CStrConvertError::NotNu
209 }
210 let mut i = 0;
211 // `i + 1 < bytes.len()` allows LLVM t
212 // while it couldn't optimize away bou
213 while i + 1 < bytes.len() {
214 if bytes[i] == 0 {
215 return Err(CStrConvertError::I
216 }
217 i += 1;
218 }
219 // SAFETY: We just checked that all pr
220 Ok(unsafe { Self::from_bytes_with_nul_
221 }
222
223 /// Creates a [`CStr`] from a `[u8]` witho
224 /// checks.
225 ///
226 /// # Safety
227 ///
228 /// `bytes` *must* end with a `NUL` byte,
229 /// `NUL` byte (or the string will be trun
230 #[inline]
231 pub const unsafe fn from_bytes_with_nul_un
232 // SAFETY: Properties of `bytes` guara
233 unsafe { core::mem::transmute(bytes) }
234 }
235
236 /// Creates a mutable [`CStr`] from a `[u8
237 /// additional checks.
238 ///
239 /// # Safety
240 ///
241 /// `bytes` *must* end with a `NUL` byte,
242 /// `NUL` byte (or the string will be trun
243 #[inline]
244 pub unsafe fn from_bytes_with_nul_unchecke
245 // SAFETY: Properties of `bytes` guara
246 unsafe { &mut *(bytes as *mut [u8] as
247 }
248
249 /// Returns a C pointer to the string.
250 #[inline]
251 pub const fn as_char_ptr(&self) -> *const
252 self.0.as_ptr() as _
253 }
254
255 /// Convert the string to a byte slice wit
256 #[inline]
257 pub fn as_bytes(&self) -> &[u8] {
258 &self.0[..self.len()]
259 }
260
261 /// Convert the string to a byte slice con
262 #[inline]
263 pub const fn as_bytes_with_nul(&self) -> &
264 &self.0
265 }
266
267 /// Yields a [`&str`] slice if the [`CStr`
268 ///
269 /// If the contents of the [`CStr`] are va
270 /// function will return the corresponding
271 /// it will return an error with details o
272 ///
273 /// # Examples
274 ///
275 /// ```
276 /// # use kernel::str::CStr;
277 /// let cstr = CStr::from_bytes_with_nul(b
278 /// assert_eq!(cstr.to_str(), Ok("foo"));
279 /// ```
280 #[inline]
281 pub fn to_str(&self) -> Result<&str, core:
282 core::str::from_utf8(self.as_bytes())
283 }
284
285 /// Unsafely convert this [`CStr`] into a
286 /// valid UTF-8.
287 ///
288 /// # Safety
289 ///
290 /// The contents must be valid UTF-8.
291 ///
292 /// # Examples
293 ///
294 /// ```
295 /// # use kernel::c_str;
296 /// # use kernel::str::CStr;
297 /// let bar = c_str!("ツ");
298 /// // SAFETY: String literals are guarant
299 /// // by the Rust compiler.
300 /// assert_eq!(unsafe { bar.as_str_uncheck
301 /// ```
302 #[inline]
303 pub unsafe fn as_str_unchecked(&self) -> &
304 unsafe { core::str::from_utf8_unchecke
305 }
306
307 /// Convert this [`CStr`] into a [`CString
308 /// copying over the string data.
309 pub fn to_cstring(&self) -> Result<CString
310 CString::try_from(self)
311 }
312
313 /// Converts this [`CStr`] to its ASCII lo
314 ///
315 /// ASCII letters 'A' to 'Z' are mapped to
316 /// but non-ASCII letters are unchanged.
317 ///
318 /// To return a new lowercased value witho
319 /// [`to_ascii_lowercase()`].
320 ///
321 /// [`to_ascii_lowercase()`]: #method.to_a
322 pub fn make_ascii_lowercase(&mut self) {
323 // INVARIANT: This doesn't introduce o
324 // string.
325 self.0.make_ascii_lowercase();
326 }
327
328 /// Converts this [`CStr`] to its ASCII up
329 ///
330 /// ASCII letters 'a' to 'z' are mapped to
331 /// but non-ASCII letters are unchanged.
332 ///
333 /// To return a new uppercased value witho
334 /// [`to_ascii_uppercase()`].
335 ///
336 /// [`to_ascii_uppercase()`]: #method.to_a
337 pub fn make_ascii_uppercase(&mut self) {
338 // INVARIANT: This doesn't introduce o
339 // string.
340 self.0.make_ascii_uppercase();
341 }
342
343 /// Returns a copy of this [`CString`] whe
344 /// ASCII lower case equivalent.
345 ///
346 /// ASCII letters 'A' to 'Z' are mapped to
347 /// but non-ASCII letters are unchanged.
348 ///
349 /// To lowercase the value in-place, use [
350 ///
351 /// [`make_ascii_lowercase`]: str::make_as
352 pub fn to_ascii_lowercase(&self) -> Result
353 let mut s = self.to_cstring()?;
354
355 s.make_ascii_lowercase();
356
357 Ok(s)
358 }
359
360 /// Returns a copy of this [`CString`] whe
361 /// ASCII upper case equivalent.
362 ///
363 /// ASCII letters 'a' to 'z' are mapped to
364 /// but non-ASCII letters are unchanged.
365 ///
366 /// To uppercase the value in-place, use [
367 ///
368 /// [`make_ascii_uppercase`]: str::make_as
369 pub fn to_ascii_uppercase(&self) -> Result
370 let mut s = self.to_cstring()?;
371
372 s.make_ascii_uppercase();
373
374 Ok(s)
375 }
376 }
377
378 impl fmt::Display for CStr {
379 /// Formats printable ASCII characters, es
380 ///
381 /// ```
382 /// # use kernel::c_str;
383 /// # use kernel::fmt;
384 /// # use kernel::str::CStr;
385 /// # use kernel::str::CString;
386 /// let penguin = c_str!("🐧");
387 /// let s = CString::try_from_fmt(fmt!("{}
388 /// assert_eq!(s.as_bytes_with_nul(), "\\x
389 ///
390 /// let ascii = c_str!("so \"cool\"");
391 /// let s = CString::try_from_fmt(fmt!("{}
392 /// assert_eq!(s.as_bytes_with_nul(), "so
393 /// ```
394 fn fmt(&self, f: &mut fmt::Formatter<'_>)
395 for &c in self.as_bytes() {
396 if (0x20..0x7f).contains(&c) {
397 // Printable character.
398 f.write_char(c as char)?;
399 } else {
400 write!(f, "\\x{:02x}", c)?;
401 }
402 }
403 Ok(())
404 }
405 }
406
407 impl fmt::Debug for CStr {
408 /// Formats printable ASCII characters wit
409 ///
410 /// ```
411 /// # use kernel::c_str;
412 /// # use kernel::fmt;
413 /// # use kernel::str::CStr;
414 /// # use kernel::str::CString;
415 /// let penguin = c_str!("🐧");
416 /// let s = CString::try_from_fmt(fmt!("{:
417 /// assert_eq!(s.as_bytes_with_nul(), "\"\
418 ///
419 /// // Embedded double quotes are escaped.
420 /// let ascii = c_str!("so \"cool\"");
421 /// let s = CString::try_from_fmt(fmt!("{:
422 /// assert_eq!(s.as_bytes_with_nul(), "\"s
423 /// ```
424 fn fmt(&self, f: &mut fmt::Formatter<'_>)
425 f.write_str("\"")?;
426 for &c in self.as_bytes() {
427 match c {
428 // Printable characters.
429 b'\"' => f.write_str("\\\"")?,
430 0x20..=0x7e => f.write_char(c
431 _ => write!(f, "\\x{:02x}", c)
432 }
433 }
434 f.write_str("\"")
435 }
436 }
437
438 impl AsRef<BStr> for CStr {
439 #[inline]
440 fn as_ref(&self) -> &BStr {
441 BStr::from_bytes(self.as_bytes())
442 }
443 }
444
445 impl Deref for CStr {
446 type Target = BStr;
447
448 #[inline]
449 fn deref(&self) -> &Self::Target {
450 self.as_ref()
451 }
452 }
453
454 impl Index<ops::RangeFrom<usize>> for CStr {
455 type Output = CStr;
456
457 #[inline]
458 fn index(&self, index: ops::RangeFrom<usiz
459 // Delegate bounds checking to slice.
460 // Assign to _ to mute clippy's unnece
461 let _ = &self.as_bytes()[index.start..
462 // SAFETY: We just checked the bounds.
463 unsafe { Self::from_bytes_with_nul_unc
464 }
465 }
466
467 impl Index<ops::RangeFull> for CStr {
468 type Output = CStr;
469
470 #[inline]
471 fn index(&self, _index: ops::RangeFull) ->
472 self
473 }
474 }
475
476 mod private {
477 use core::ops;
478
479 // Marker trait for index types that can b
480 pub trait CStrIndex {}
481
482 impl CStrIndex for usize {}
483 impl CStrIndex for ops::Range<usize> {}
484 impl CStrIndex for ops::RangeInclusive<usi
485 impl CStrIndex for ops::RangeToInclusive<u
486 }
487
488 impl<Idx> Index<Idx> for CStr
489 where
490 Idx: private::CStrIndex,
491 BStr: Index<Idx>,
492 {
493 type Output = <BStr as Index<Idx>>::Output
494
495 #[inline]
496 fn index(&self, index: Idx) -> &Self::Outp
497 &self.as_ref()[index]
498 }
499 }
500
501 /// Creates a new [`CStr`] from a string liter
502 ///
503 /// The string literal should not contain any
504 ///
505 /// # Examples
506 ///
507 /// ```
508 /// # use kernel::c_str;
509 /// # use kernel::str::CStr;
510 /// const MY_CSTR: &CStr = c_str!("My awesome
511 /// ```
512 #[macro_export]
513 macro_rules! c_str {
514 ($str:expr) => {{
515 const S: &str = concat!($str, "\0");
516 const C: &$crate::str::CStr = match $c
517 Ok(v) => v,
518 Err(_) => panic!("string contains
519 };
520 C
521 }};
522 }
523
524 #[cfg(test)]
525 mod tests {
526 use super::*;
527 use alloc::format;
528
529 const ALL_ASCII_CHARS: &'static str =
530 "\\x01\\x02\\x03\\x04\\x05\\x06\\x07\\
531 \\x10\\x11\\x12\\x13\\x14\\x15\\x16\\x
532 !\"#$%&'()*+,-./0123456789:;<=>?@\
533 ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcde
534 \\x80\\x81\\x82\\x83\\x84\\x85\\x86\\x
535 \\x90\\x91\\x92\\x93\\x94\\x95\\x96\\x
536 \\xa0\\xa1\\xa2\\xa3\\xa4\\xa5\\xa6\\x
537 \\xb0\\xb1\\xb2\\xb3\\xb4\\xb5\\xb6\\x
538 \\xc0\\xc1\\xc2\\xc3\\xc4\\xc5\\xc6\\x
539 \\xd0\\xd1\\xd2\\xd3\\xd4\\xd5\\xd6\\x
540 \\xe0\\xe1\\xe2\\xe3\\xe4\\xe5\\xe6\\x
541 \\xf0\\xf1\\xf2\\xf3\\xf4\\xf5\\xf6\\x
542
543 #[test]
544 fn test_cstr_to_str() {
545 let good_bytes = b"\xf0\x9f\xa6\x80\0"
546 let checked_cstr = CStr::from_bytes_wi
547 let checked_str = checked_cstr.to_str(
548 assert_eq!(checked_str, "🦀");
549 }
550
551 #[test]
552 #[should_panic]
553 fn test_cstr_to_str_panic() {
554 let bad_bytes = b"\xc3\x28\0";
555 let checked_cstr = CStr::from_bytes_wi
556 checked_cstr.to_str().unwrap();
557 }
558
559 #[test]
560 fn test_cstr_as_str_unchecked() {
561 let good_bytes = b"\xf0\x9f\x90\xA7\0"
562 let checked_cstr = CStr::from_bytes_wi
563 let unchecked_str = unsafe { checked_c
564 assert_eq!(unchecked_str, "🐧");
565 }
566
567 #[test]
568 fn test_cstr_display() {
569 let hello_world = CStr::from_bytes_wit
570 assert_eq!(format!("{}", hello_world),
571 let non_printables = CStr::from_bytes_
572 assert_eq!(format!("{}", non_printable
573 let non_ascii = CStr::from_bytes_with_
574 assert_eq!(format!("{}", non_ascii), "
575 let good_bytes = CStr::from_bytes_with
576 assert_eq!(format!("{}", good_bytes),
577 }
578
579 #[test]
580 fn test_cstr_display_all_bytes() {
581 let mut bytes: [u8; 256] = [0; 256];
582 // fill `bytes` with [1..=255] + [0]
583 for i in u8::MIN..=u8::MAX {
584 bytes[i as usize] = i.wrapping_add
585 }
586 let cstr = CStr::from_bytes_with_nul(&
587 assert_eq!(format!("{}", cstr), ALL_AS
588 }
589
590 #[test]
591 fn test_cstr_debug() {
592 let hello_world = CStr::from_bytes_wit
593 assert_eq!(format!("{:?}", hello_world
594 let non_printables = CStr::from_bytes_
595 assert_eq!(format!("{:?}", non_printab
596 let non_ascii = CStr::from_bytes_with_
597 assert_eq!(format!("{:?}", non_ascii),
598 let good_bytes = CStr::from_bytes_with
599 assert_eq!(format!("{:?}", good_bytes)
600 }
601
602 #[test]
603 fn test_bstr_display() {
604 let hello_world = BStr::from_bytes(b"h
605 assert_eq!(format!("{}", hello_world),
606 let escapes = BStr::from_bytes(b"_\t_\
607 assert_eq!(format!("{}", escapes), "_\
608 let others = BStr::from_bytes(b"\x01")
609 assert_eq!(format!("{}", others), "\\x
610 let non_ascii = BStr::from_bytes(b"d\x
611 assert_eq!(format!("{}", non_ascii), "
612 let good_bytes = BStr::from_bytes(b"\x
613 assert_eq!(format!("{}", good_bytes),
614 }
615
616 #[test]
617 fn test_bstr_debug() {
618 let hello_world = BStr::from_bytes(b"h
619 assert_eq!(format!("{:?}", hello_world
620 let escapes = BStr::from_bytes(b"_\t_\
621 assert_eq!(format!("{:?}", escapes), "
622 let others = BStr::from_bytes(b"\x01")
623 assert_eq!(format!("{:?}", others), "\
624 let non_ascii = BStr::from_bytes(b"d\x
625 assert_eq!(format!("{:?}", non_ascii),
626 let good_bytes = BStr::from_bytes(b"\x
627 assert_eq!(format!("{:?}", good_bytes)
628 }
629 }
630
631 /// Allows formatting of [`fmt::Arguments`] in
632 ///
633 /// It does not fail if callers write past the
634 /// size required to fit everything.
635 ///
636 /// # Invariants
637 ///
638 /// The memory region between `pos` (inclusive
639 /// is less than `end`.
640 pub(crate) struct RawFormatter {
641 // Use `usize` to use `saturating_*` funct
642 beg: usize,
643 pos: usize,
644 end: usize,
645 }
646
647 impl RawFormatter {
648 /// Creates a new instance of [`RawFormatt
649 fn new() -> Self {
650 // INVARIANT: The buffer is empty, so
651 Self {
652 beg: 0,
653 pos: 0,
654 end: 0,
655 }
656 }
657
658 /// Creates a new instance of [`RawFormatt
659 ///
660 /// # Safety
661 ///
662 /// If `pos` is less than `end`, then the
663 /// (exclusive) must be valid for writes f
664 pub(crate) unsafe fn from_ptrs(pos: *mut u
665 // INVARIANT: The safety requirements
666 Self {
667 beg: pos as _,
668 pos: pos as _,
669 end: end as _,
670 }
671 }
672
673 /// Creates a new instance of [`RawFormatt
674 ///
675 /// # Safety
676 ///
677 /// The memory region starting at `buf` an
678 /// for the lifetime of the returned [`Raw
679 pub(crate) unsafe fn from_buffer(buf: *mut
680 let pos = buf as usize;
681 // INVARIANT: We ensure that `end` is
682 // guarantees that the memory region i
683 Self {
684 pos,
685 beg: pos,
686 end: pos.saturating_add(len),
687 }
688 }
689
690 /// Returns the current insert position.
691 ///
692 /// N.B. It may point to invalid memory.
693 pub(crate) fn pos(&self) -> *mut u8 {
694 self.pos as _
695 }
696
697 /// Returns the number of bytes written to
698 pub(crate) fn bytes_written(&self) -> usiz
699 self.pos - self.beg
700 }
701 }
702
703 impl fmt::Write for RawFormatter {
704 fn write_str(&mut self, s: &str) -> fmt::R
705 // `pos` value after writing `len` byt
706 // don't want it to wrap around to 0.
707 let pos_new = self.pos.saturating_add(
708
709 // Amount that we can copy. `saturatin
710 let len_to_copy = core::cmp::min(pos_n
711
712 if len_to_copy > 0 {
713 // SAFETY: If `len_to_copy` is non
714 // yet, so it is valid for write p
715 unsafe {
716 core::ptr::copy_nonoverlapping
717 s.as_bytes().as_ptr(),
718 self.pos as *mut u8,
719 len_to_copy,
720 )
721 };
722 }
723
724 self.pos = pos_new;
725 Ok(())
726 }
727 }
728
729 /// Allows formatting of [`fmt::Arguments`] in
730 ///
731 /// Fails if callers attempt to write more tha
732 pub(crate) struct Formatter(RawFormatter);
733
734 impl Formatter {
735 /// Creates a new instance of [`Formatter`
736 ///
737 /// # Safety
738 ///
739 /// The memory region starting at `buf` an
740 /// for the lifetime of the returned [`For
741 pub(crate) unsafe fn from_buffer(buf: *mut
742 // SAFETY: The safety requirements of
743 Self(unsafe { RawFormatter::from_buffe
744 }
745 }
746
747 impl Deref for Formatter {
748 type Target = RawFormatter;
749
750 fn deref(&self) -> &Self::Target {
751 &self.0
752 }
753 }
754
755 impl fmt::Write for Formatter {
756 fn write_str(&mut self, s: &str) -> fmt::R
757 self.0.write_str(s)?;
758
759 // Fail the request if we go past the
760 if self.0.pos > self.0.end {
761 Err(fmt::Error)
762 } else {
763 Ok(())
764 }
765 }
766 }
767
768 /// An owned string that is guaranteed to have
769 ///
770 /// Used for interoperability with kernel APIs
771 ///
772 /// # Invariants
773 ///
774 /// The string is always `NUL`-terminated and
775 ///
776 /// # Examples
777 ///
778 /// ```
779 /// use kernel::{str::CString, fmt};
780 ///
781 /// let s = CString::try_from_fmt(fmt!("{}{}{}
782 /// assert_eq!(s.as_bytes_with_nul(), "abc1020
783 ///
784 /// let tmp = "testing";
785 /// let s = CString::try_from_fmt(fmt!("{tmp}{
786 /// assert_eq!(s.as_bytes_with_nul(), "testing
787 ///
788 /// // This fails because it has an embedded `
789 /// let s = CString::try_from_fmt(fmt!("a\0b{}
790 /// assert_eq!(s.is_ok(), false);
791 /// ```
792 pub struct CString {
793 buf: Vec<u8>,
794 }
795
796 impl CString {
797 /// Creates an instance of [`CString`] fro
798 pub fn try_from_fmt(args: fmt::Arguments<'
799 // Calculate the size needed (formatte
800 let mut f = RawFormatter::new();
801 f.write_fmt(args)?;
802 f.write_str("\0")?;
803 let size = f.bytes_written();
804
805 // Allocate a vector with the required
806 let mut buf = <Vec<_> as VecExt<_>>::w
807 // SAFETY: The buffer stored in `buf`
808 let mut f = unsafe { Formatter::from_b
809 f.write_fmt(args)?;
810 f.write_str("\0")?;
811
812 // SAFETY: The number of bytes that ca
813 // `buf`'s capacity. The contents of t
814 unsafe { buf.set_len(f.bytes_written()
815
816 // Check that there are no `NUL` bytes
817 // SAFETY: The buffer is valid for rea
818 // (which the minimum buffer size) and
819 // so `f.bytes_written() - 1` doesn't
820 let ptr = unsafe { bindings::memchr(bu
821 if !ptr.is_null() {
822 return Err(EINVAL);
823 }
824
825 // INVARIANT: We wrote the `NUL` termi
826 // exist in the buffer.
827 Ok(Self { buf })
828 }
829 }
830
831 impl Deref for CString {
832 type Target = CStr;
833
834 fn deref(&self) -> &Self::Target {
835 // SAFETY: The type invariants guarant
836 // other `NUL` bytes exist.
837 unsafe { CStr::from_bytes_with_nul_unc
838 }
839 }
840
841 impl DerefMut for CString {
842 fn deref_mut(&mut self) -> &mut Self::Targ
843 // SAFETY: A `CString` is always NUL-t
844 // NUL bytes.
845 unsafe { CStr::from_bytes_with_nul_unc
846 }
847 }
848
849 impl<'a> TryFrom<&'a CStr> for CString {
850 type Error = AllocError;
851
852 fn try_from(cstr: &'a CStr) -> Result<CStr
853 let mut buf = Vec::new();
854
855 <Vec<_> as VecExt<_>>::extend_from_sli
856 .map_err(|_| AllocError)?;
857
858 // INVARIANT: The `CStr` and `CString`
859 // the string data, and we copied it o
860 Ok(CString { buf })
861 }
862 }
863
864 impl fmt::Debug for CString {
865 fn fmt(&self, f: &mut fmt::Formatter<'_>)
866 fmt::Debug::fmt(&**self, f)
867 }
868 }
869
870 /// A convenience alias for [`core::format_arg
871 #[macro_export]
872 macro_rules! fmt {
873 ($($f:tt)*) => ( core::format_args!($($f)*
874 }
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