2 use crate::borrow::{Cow, Borrow};
3 use crate::cmp::Ordering;
4 use crate::error::Error;
5 use crate::fmt::{self, Write};
10 use crate::os::raw::c_char;
14 use crate::str::{self, Utf8Error};
18 /// A type representing an owned, C-compatible, nul-terminated string with no nul bytes in the
21 /// This type serves the purpose of being able to safely generate a
22 /// C-compatible string from a Rust byte slice or vector. An instance of this
23 /// type is a static guarantee that the underlying bytes contain no interior 0
24 /// bytes ("nul characters") and that the final byte is 0 ("nul terminator").
26 /// `CString` is to [`&CStr`] as [`String`] is to [`&str`]: the former
27 /// in each pair are owned strings; the latter are borrowed
30 /// # Creating a `CString`
32 /// A `CString` is created from either a byte slice or a byte vector,
33 /// or anything that implements [`Into`]`<`[`Vec`]`<`[`u8`]`>>` (for
34 /// example, you can build a `CString` straight out of a [`String`] or
35 /// a [`&str`], since both implement that trait).
37 /// The [`new`] method will actually check that the provided `&[u8]`
38 /// does not have 0 bytes in the middle, and return an error if it
41 /// # Extracting a raw pointer to the whole C string
43 /// `CString` implements a [`as_ptr`] method through the [`Deref`]
44 /// trait. This method will give you a `*const c_char` which you can
45 /// feed directly to extern functions that expect a nul-terminated
46 /// string, like C's `strdup()`. Notice that [`as_ptr`] returns a
47 /// read-only pointer; if the C code writes to it, that causes
48 /// undefined behavior.
50 /// # Extracting a slice of the whole C string
52 /// Alternatively, you can obtain a `&[`[`u8`]`]` slice from a
53 /// `CString` with the [`as_bytes`] method. Slices produced in this
54 /// way do *not* contain the trailing nul terminator. This is useful
55 /// when you will be calling an extern function that takes a `*const
56 /// u8` argument which is not necessarily nul-terminated, plus another
57 /// argument with the length of the string — like C's `strndup()`.
58 /// You can of course get the slice's length with its
59 /// [`len`][slice.len] method.
61 /// If you need a `&[`[`u8`]`]` slice *with* the nul terminator, you
62 /// can use [`as_bytes_with_nul`] instead.
64 /// Once you have the kind of slice you need (with or without a nul
65 /// terminator), you can call the slice's own
66 /// [`as_ptr`][slice.as_ptr] method to get a read-only raw pointer to pass to
67 /// extern functions. See the documentation for that function for a
68 /// discussion on ensuring the lifetime of the raw pointer.
70 /// [`Into`]: ../convert/trait.Into.html
71 /// [`Vec`]: ../vec/struct.Vec.html
72 /// [`String`]: ../string/struct.String.html
73 /// [`&str`]: ../primitive.str.html
74 /// [`u8`]: ../primitive.u8.html
75 /// [`new`]: #method.new
76 /// [`as_bytes`]: #method.as_bytes
77 /// [`as_bytes_with_nul`]: #method.as_bytes_with_nul
78 /// [`as_ptr`]: #method.as_ptr
79 /// [slice.as_ptr]: ../primitive.slice.html#method.as_ptr
80 /// [slice.len]: ../primitive.slice.html#method.len
81 /// [`Deref`]: ../ops/trait.Deref.html
82 /// [`CStr`]: struct.CStr.html
83 /// [`&CStr`]: struct.CStr.html
87 /// ```ignore (extern-declaration)
89 /// use std::ffi::CString;
90 /// use std::os::raw::c_char;
93 /// fn my_printer(s: *const c_char);
96 /// // We are certain that our string doesn't have 0 bytes in the middle,
97 /// // so we can .expect()
98 /// let c_to_print = CString::new("Hello, world!").expect("CString::new failed");
100 /// my_printer(c_to_print.as_ptr());
107 /// `CString` is intended for working with traditional C-style strings
108 /// (a sequence of non-nul bytes terminated by a single nul byte); the
109 /// primary use case for these kinds of strings is interoperating with C-like
110 /// code. Often you will need to transfer ownership to/from that external
111 /// code. It is strongly recommended that you thoroughly read through the
112 /// documentation of `CString` before use, as improper ownership management
113 /// of `CString` instances can lead to invalid memory accesses, memory leaks,
114 /// and other memory errors.
116 #[derive(PartialEq, PartialOrd, Eq, Ord, Hash, Clone)]
117 #[stable(feature = "rust1", since = "1.0.0")]
119 // Invariant 1: the slice ends with a zero byte and has a length of at least one.
120 // Invariant 2: the slice contains only one zero byte.
121 // Improper usage of unsafe function can break Invariant 2, but not Invariant 1.
125 /// Representation of a borrowed C string.
127 /// This type represents a borrowed reference to a nul-terminated
128 /// array of bytes. It can be constructed safely from a `&[`[`u8`]`]`
129 /// slice, or unsafely from a raw `*const c_char`. It can then be
130 /// converted to a Rust [`&str`] by performing UTF-8 validation, or
131 /// into an owned [`CString`].
133 /// `&CStr` is to [`CString`] as [`&str`] is to [`String`]: the former
134 /// in each pair are borrowed references; the latter are owned
137 /// Note that this structure is **not** `repr(C)` and is not recommended to be
138 /// placed in the signatures of FFI functions. Instead, safe wrappers of FFI
139 /// functions may leverage the unsafe [`from_ptr`] constructor to provide a safe
140 /// interface to other consumers.
144 /// Inspecting a foreign C string:
146 /// ```ignore (extern-declaration)
147 /// use std::ffi::CStr;
148 /// use std::os::raw::c_char;
150 /// extern { fn my_string() -> *const c_char; }
153 /// let slice = CStr::from_ptr(my_string());
154 /// println!("string buffer size without nul terminator: {}", slice.to_bytes().len());
158 /// Passing a Rust-originating C string:
160 /// ```ignore (extern-declaration)
161 /// use std::ffi::{CString, CStr};
162 /// use std::os::raw::c_char;
164 /// fn work(data: &CStr) {
165 /// extern { fn work_with(data: *const c_char); }
167 /// unsafe { work_with(data.as_ptr()) }
170 /// let s = CString::new("data data data data").expect("CString::new failed");
174 /// Converting a foreign C string into a Rust [`String`]:
176 /// ```ignore (extern-declaration)
177 /// use std::ffi::CStr;
178 /// use std::os::raw::c_char;
180 /// extern { fn my_string() -> *const c_char; }
182 /// fn my_string_safe() -> String {
184 /// CStr::from_ptr(my_string()).to_string_lossy().into_owned()
188 /// println!("string: {}", my_string_safe());
191 /// [`u8`]: ../primitive.u8.html
192 /// [`&str`]: ../primitive.str.html
193 /// [`String`]: ../string/struct.String.html
194 /// [`CString`]: struct.CString.html
195 /// [`from_ptr`]: #method.from_ptr
197 #[stable(feature = "rust1", since = "1.0.0")]
199 // `fn from` in `impl From<&CStr> for Box<CStr>` current implementation relies
200 // on `CStr` being layout-compatible with `[u8]`.
201 // When attribute privacy is implemented, `CStr` should be annotated as `#[repr(transparent)]`.
202 // Anyway, `CStr` representation and layout are considered implementation detail, are
203 // not documented and must not be relied upon.
205 // FIXME: this should not be represented with a DST slice but rather with
206 // just a raw `c_char` along with some form of marker to make
207 // this an unsized type. Essentially `sizeof(&CStr)` should be the
208 // same as `sizeof(&c_char)` but `CStr` should be an unsized type.
212 /// An error indicating that an interior nul byte was found.
214 /// While Rust strings may contain nul bytes in the middle, C strings
215 /// can't, as that byte would effectively truncate the string.
217 /// This error is created by the [`new`][`CString::new`] method on
218 /// [`CString`]. See its documentation for more.
220 /// [`CString`]: struct.CString.html
221 /// [`CString::new`]: struct.CString.html#method.new
226 /// use std::ffi::{CString, NulError};
228 /// let _: NulError = CString::new(b"f\0oo".to_vec()).unwrap_err();
230 #[derive(Clone, PartialEq, Eq, Debug)]
231 #[stable(feature = "rust1", since = "1.0.0")]
232 pub struct NulError(usize, Vec<u8>);
234 /// An error indicating that a nul byte was not in the expected position.
236 /// The slice used to create a [`CStr`] must have one and only one nul
237 /// byte at the end of the slice.
239 /// This error is created by the
240 /// [`from_bytes_with_nul`][`CStr::from_bytes_with_nul`] method on
241 /// [`CStr`]. See its documentation for more.
243 /// [`CStr`]: struct.CStr.html
244 /// [`CStr::from_bytes_with_nul`]: struct.CStr.html#method.from_bytes_with_nul
249 /// use std::ffi::{CStr, FromBytesWithNulError};
251 /// let _: FromBytesWithNulError = CStr::from_bytes_with_nul(b"f\0oo").unwrap_err();
253 #[derive(Clone, PartialEq, Eq, Debug)]
254 #[stable(feature = "cstr_from_bytes", since = "1.10.0")]
255 pub struct FromBytesWithNulError {
256 kind: FromBytesWithNulErrorKind,
259 #[derive(Clone, PartialEq, Eq, Debug)]
260 enum FromBytesWithNulErrorKind {
265 impl FromBytesWithNulError {
266 fn interior_nul(pos: usize) -> FromBytesWithNulError {
267 FromBytesWithNulError {
268 kind: FromBytesWithNulErrorKind::InteriorNul(pos),
271 fn not_nul_terminated() -> FromBytesWithNulError {
272 FromBytesWithNulError {
273 kind: FromBytesWithNulErrorKind::NotNulTerminated,
278 /// An error indicating invalid UTF-8 when converting a [`CString`] into a [`String`].
280 /// `CString` is just a wrapper over a buffer of bytes with a nul
281 /// terminator; [`into_string`][`CString::into_string`] performs UTF-8
282 /// validation on those bytes and may return this error.
284 /// This `struct` is created by the
285 /// [`into_string`][`CString::into_string`] method on [`CString`]. See
286 /// its documentation for more.
288 /// [`String`]: ../string/struct.String.html
289 /// [`CString`]: struct.CString.html
290 /// [`CString::into_string`]: struct.CString.html#method.into_string
291 #[derive(Clone, PartialEq, Eq, Debug)]
292 #[stable(feature = "cstring_into", since = "1.7.0")]
293 pub struct IntoStringError {
299 /// Creates a new C-compatible string from a container of bytes.
301 /// This function will consume the provided data and use the
302 /// underlying bytes to construct a new string, ensuring that
303 /// there is a trailing 0 byte. This trailing 0 byte will be
304 /// appended by this function; the provided data should *not*
305 /// contain any 0 bytes in it.
309 /// ```ignore (extern-declaration)
310 /// use std::ffi::CString;
311 /// use std::os::raw::c_char;
313 /// extern { fn puts(s: *const c_char); }
315 /// let to_print = CString::new("Hello!").expect("CString::new failed");
317 /// puts(to_print.as_ptr());
323 /// This function will return an error if the supplied bytes contain an
324 /// internal 0 byte. The [`NulError`] returned will contain the bytes as well as
325 /// the position of the nul byte.
327 /// [`NulError`]: struct.NulError.html
328 #[stable(feature = "rust1", since = "1.0.0")]
329 pub fn new<T: Into<Vec<u8>>>(t: T) -> Result<CString, NulError> {
331 fn into_vec(self) -> Vec<u8>;
333 impl<T: Into<Vec<u8>>> SpecIntoVec for T {
334 default fn into_vec(self) -> Vec<u8> {
338 // Specialization for avoiding reallocation.
339 impl SpecIntoVec for &'_ [u8] {
340 fn into_vec(self) -> Vec<u8> {
341 let mut v = Vec::with_capacity(self.len() + 1);
346 impl SpecIntoVec for &'_ str {
347 fn into_vec(self) -> Vec<u8> {
348 let mut v = Vec::with_capacity(self.len() + 1);
349 v.extend(self.as_bytes());
354 Self::_new(SpecIntoVec::into_vec(t))
357 fn _new(bytes: Vec<u8>) -> Result<CString, NulError> {
358 match memchr::memchr(0, &bytes) {
359 Some(i) => Err(NulError(i, bytes)),
360 None => Ok(unsafe { CString::from_vec_unchecked(bytes) }),
364 /// Creates a C-compatible string by consuming a byte vector,
365 /// without checking for interior 0 bytes.
367 /// This method is equivalent to [`new`] except that no runtime assertion
368 /// is made that `v` contains no 0 bytes, and it requires an actual
369 /// byte vector, not anything that can be converted to one with Into.
371 /// [`new`]: #method.new
376 /// use std::ffi::CString;
378 /// let raw = b"foo".to_vec();
380 /// let c_string = CString::from_vec_unchecked(raw);
383 #[stable(feature = "rust1", since = "1.0.0")]
384 pub unsafe fn from_vec_unchecked(mut v: Vec<u8>) -> CString {
387 CString { inner: v.into_boxed_slice() }
390 /// Retakes ownership of a `CString` that was transferred to C via [`into_raw`].
392 /// Additionally, the length of the string will be recalculated from the pointer.
396 /// This should only ever be called with a pointer that was earlier
397 /// obtained by calling [`into_raw`] on a `CString`. Other usage (e.g., trying to take
398 /// ownership of a string that was allocated by foreign code) is likely to lead
399 /// to undefined behavior or allocator corruption.
401 /// > **Note:** If you need to borrow a string that was allocated by
402 /// > foreign code, use [`CStr`]. If you need to take ownership of
403 /// > a string that was allocated by foreign code, you will need to
404 /// > make your own provisions for freeing it appropriately, likely
405 /// > with the foreign code's API to do that.
407 /// [`into_raw`]: #method.into_raw
408 /// [`CStr`]: struct.CStr.html
412 /// Creates a `CString`, pass ownership to an `extern` function (via raw pointer), then retake
413 /// ownership with `from_raw`:
415 /// ```ignore (extern-declaration)
416 /// use std::ffi::CString;
417 /// use std::os::raw::c_char;
420 /// fn some_extern_function(s: *mut c_char);
423 /// let c_string = CString::new("Hello!").expect("CString::new failed");
424 /// let raw = c_string.into_raw();
426 /// some_extern_function(raw);
427 /// let c_string = CString::from_raw(raw);
430 #[stable(feature = "cstr_memory", since = "1.4.0")]
431 pub unsafe fn from_raw(ptr: *mut c_char) -> CString {
432 let len = sys::strlen(ptr) + 1; // Including the NUL byte
433 let slice = slice::from_raw_parts_mut(ptr, len as usize);
434 CString { inner: Box::from_raw(slice as *mut [c_char] as *mut [u8]) }
437 /// Consumes the `CString` and transfers ownership of the string to a C caller.
439 /// The pointer which this function returns must be returned to Rust and reconstituted using
440 /// [`from_raw`] to be properly deallocated. Specifically, one
441 /// should *not* use the standard C `free()` function to deallocate
444 /// Failure to call [`from_raw`] will lead to a memory leak.
446 /// [`from_raw`]: #method.from_raw
451 /// use std::ffi::CString;
453 /// let c_string = CString::new("foo").expect("CString::new failed");
455 /// let ptr = c_string.into_raw();
458 /// assert_eq!(b'f', *ptr as u8);
459 /// assert_eq!(b'o', *ptr.offset(1) as u8);
460 /// assert_eq!(b'o', *ptr.offset(2) as u8);
461 /// assert_eq!(b'\0', *ptr.offset(3) as u8);
463 /// // retake pointer to free memory
464 /// let _ = CString::from_raw(ptr);
468 #[stable(feature = "cstr_memory", since = "1.4.0")]
469 pub fn into_raw(self) -> *mut c_char {
470 Box::into_raw(self.into_inner()) as *mut c_char
473 /// Converts the `CString` into a [`String`] if it contains valid UTF-8 data.
475 /// On failure, ownership of the original `CString` is returned.
477 /// [`String`]: ../string/struct.String.html
482 /// use std::ffi::CString;
484 /// let valid_utf8 = vec![b'f', b'o', b'o'];
485 /// let cstring = CString::new(valid_utf8).expect("CString::new failed");
486 /// assert_eq!(cstring.into_string().expect("into_string() call failed"), "foo");
488 /// let invalid_utf8 = vec![b'f', 0xff, b'o', b'o'];
489 /// let cstring = CString::new(invalid_utf8).expect("CString::new failed");
490 /// let err = cstring.into_string().err().expect("into_string().err() failed");
491 /// assert_eq!(err.utf8_error().valid_up_to(), 1);
494 #[stable(feature = "cstring_into", since = "1.7.0")]
495 pub fn into_string(self) -> Result<String, IntoStringError> {
496 String::from_utf8(self.into_bytes())
497 .map_err(|e| IntoStringError {
498 error: e.utf8_error(),
499 inner: unsafe { CString::from_vec_unchecked(e.into_bytes()) },
503 /// Consumes the `CString` and returns the underlying byte buffer.
505 /// The returned buffer does **not** contain the trailing nul
506 /// terminator, and it is guaranteed to not have any interior nul
512 /// use std::ffi::CString;
514 /// let c_string = CString::new("foo").expect("CString::new failed");
515 /// let bytes = c_string.into_bytes();
516 /// assert_eq!(bytes, vec![b'f', b'o', b'o']);
518 #[stable(feature = "cstring_into", since = "1.7.0")]
519 pub fn into_bytes(self) -> Vec<u8> {
520 let mut vec = self.into_inner().into_vec();
521 let _nul = vec.pop();
522 debug_assert_eq!(_nul, Some(0u8));
526 /// Equivalent to the [`into_bytes`] function except that the returned vector
527 /// includes the trailing nul terminator.
529 /// [`into_bytes`]: #method.into_bytes
534 /// use std::ffi::CString;
536 /// let c_string = CString::new("foo").expect("CString::new failed");
537 /// let bytes = c_string.into_bytes_with_nul();
538 /// assert_eq!(bytes, vec![b'f', b'o', b'o', b'\0']);
540 #[stable(feature = "cstring_into", since = "1.7.0")]
541 pub fn into_bytes_with_nul(self) -> Vec<u8> {
542 self.into_inner().into_vec()
545 /// Returns the contents of this `CString` as a slice of bytes.
547 /// The returned slice does **not** contain the trailing nul
548 /// terminator, and it is guaranteed to not have any interior nul
549 /// bytes. If you need the nul terminator, use
550 /// [`as_bytes_with_nul`] instead.
552 /// [`as_bytes_with_nul`]: #method.as_bytes_with_nul
557 /// use std::ffi::CString;
559 /// let c_string = CString::new("foo").expect("CString::new failed");
560 /// let bytes = c_string.as_bytes();
561 /// assert_eq!(bytes, &[b'f', b'o', b'o']);
564 #[stable(feature = "rust1", since = "1.0.0")]
565 pub fn as_bytes(&self) -> &[u8] {
566 &self.inner[..self.inner.len() - 1]
569 /// Equivalent to the [`as_bytes`] function except that the returned slice
570 /// includes the trailing nul terminator.
572 /// [`as_bytes`]: #method.as_bytes
577 /// use std::ffi::CString;
579 /// let c_string = CString::new("foo").expect("CString::new failed");
580 /// let bytes = c_string.as_bytes_with_nul();
581 /// assert_eq!(bytes, &[b'f', b'o', b'o', b'\0']);
584 #[stable(feature = "rust1", since = "1.0.0")]
585 pub fn as_bytes_with_nul(&self) -> &[u8] {
589 /// Extracts a [`CStr`] slice containing the entire string.
591 /// [`CStr`]: struct.CStr.html
596 /// use std::ffi::{CString, CStr};
598 /// let c_string = CString::new(b"foo".to_vec()).expect("CString::new failed");
599 /// let cstr = c_string.as_c_str();
601 /// CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed"));
604 #[stable(feature = "as_c_str", since = "1.20.0")]
605 pub fn as_c_str(&self) -> &CStr {
609 /// Converts this `CString` into a boxed [`CStr`].
611 /// [`CStr`]: struct.CStr.html
616 /// use std::ffi::{CString, CStr};
618 /// let c_string = CString::new(b"foo".to_vec()).expect("CString::new failed");
619 /// let boxed = c_string.into_boxed_c_str();
620 /// assert_eq!(&*boxed,
621 /// CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed"));
623 #[stable(feature = "into_boxed_c_str", since = "1.20.0")]
624 pub fn into_boxed_c_str(self) -> Box<CStr> {
625 unsafe { Box::from_raw(Box::into_raw(self.into_inner()) as *mut CStr) }
628 /// Bypass "move out of struct which implements [`Drop`] trait" restriction.
630 /// [`Drop`]: ../ops/trait.Drop.html
631 fn into_inner(self) -> Box<[u8]> {
632 // Rationale: `mem::forget(self)` invalidates the previous call to `ptr::read(&self.inner)`
633 // so we use `ManuallyDrop` to ensure `self` is not dropped.
634 // Then we can return the box directly without invalidating it.
635 // See https://github.com/rust-lang/rust/issues/62553.
636 let this = mem::ManuallyDrop::new(self);
637 unsafe { ptr::read(&this.inner) }
641 // Turns this `CString` into an empty string to prevent
642 // memory-unsafe code from working by accident. Inline
643 // to prevent LLVM from optimizing it away in debug builds.
644 #[stable(feature = "cstring_drop", since = "1.13.0")]
645 impl Drop for CString {
648 unsafe { *self.inner.get_unchecked_mut(0) = 0; }
652 #[stable(feature = "rust1", since = "1.0.0")]
653 impl ops::Deref for CString {
657 fn deref(&self) -> &CStr {
658 unsafe { CStr::from_bytes_with_nul_unchecked(self.as_bytes_with_nul()) }
662 #[stable(feature = "rust1", since = "1.0.0")]
663 impl fmt::Debug for CString {
664 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
665 fmt::Debug::fmt(&**self, f)
669 #[stable(feature = "cstring_into", since = "1.7.0")]
670 impl From<CString> for Vec<u8> {
671 /// Converts a [`CString`] into a [`Vec`]`<u8>`.
673 /// The conversion consumes the [`CString`], and removes the terminating NUL byte.
675 /// [`Vec`]: ../vec/struct.Vec.html
676 /// [`CString`]: ../ffi/struct.CString.html
678 fn from(s: CString) -> Vec<u8> {
683 #[stable(feature = "cstr_debug", since = "1.3.0")]
684 impl fmt::Debug for CStr {
685 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
687 for byte in self.to_bytes().iter().flat_map(|&b| ascii::escape_default(b)) {
688 f.write_char(byte as char)?;
694 #[stable(feature = "cstr_default", since = "1.10.0")]
695 impl Default for &CStr {
696 fn default() -> Self {
697 const SLICE: &[c_char] = &[0];
698 unsafe { CStr::from_ptr(SLICE.as_ptr()) }
702 #[stable(feature = "cstr_default", since = "1.10.0")]
703 impl Default for CString {
704 /// Creates an empty `CString`.
705 fn default() -> CString {
706 let a: &CStr = Default::default();
711 #[stable(feature = "cstr_borrow", since = "1.3.0")]
712 impl Borrow<CStr> for CString {
714 fn borrow(&self) -> &CStr { self }
717 #[stable(feature = "cstring_from_cow_cstr", since = "1.28.0")]
718 impl<'a> From<Cow<'a, CStr>> for CString {
720 fn from(s: Cow<'a, CStr>) -> Self {
725 #[stable(feature = "box_from_c_str", since = "1.17.0")]
726 impl From<&CStr> for Box<CStr> {
727 fn from(s: &CStr) -> Box<CStr> {
728 let boxed: Box<[u8]> = Box::from(s.to_bytes_with_nul());
729 unsafe { Box::from_raw(Box::into_raw(boxed) as *mut CStr) }
733 #[stable(feature = "c_string_from_box", since = "1.18.0")]
734 impl From<Box<CStr>> for CString {
735 /// Converts a [`Box`]`<CStr>` into a [`CString`] without copying or allocating.
737 /// [`Box`]: ../boxed/struct.Box.html
738 /// [`CString`]: ../ffi/struct.CString.html
740 fn from(s: Box<CStr>) -> CString {
745 #[stable(feature = "more_box_slice_clone", since = "1.29.0")]
746 impl Clone for Box<CStr> {
748 fn clone(&self) -> Self {
753 #[stable(feature = "box_from_c_string", since = "1.20.0")]
754 impl From<CString> for Box<CStr> {
755 /// Converts a [`CString`] into a [`Box`]`<CStr>` without copying or allocating.
757 /// [`CString`]: ../ffi/struct.CString.html
758 /// [`Box`]: ../boxed/struct.Box.html
760 fn from(s: CString) -> Box<CStr> {
765 #[stable(feature = "cow_from_cstr", since = "1.28.0")]
766 impl<'a> From<CString> for Cow<'a, CStr> {
768 fn from(s: CString) -> Cow<'a, CStr> {
773 #[stable(feature = "cow_from_cstr", since = "1.28.0")]
774 impl<'a> From<&'a CStr> for Cow<'a, CStr> {
776 fn from(s: &'a CStr) -> Cow<'a, CStr> {
781 #[stable(feature = "cow_from_cstr", since = "1.28.0")]
782 impl<'a> From<&'a CString> for Cow<'a, CStr> {
784 fn from(s: &'a CString) -> Cow<'a, CStr> {
785 Cow::Borrowed(s.as_c_str())
789 #[stable(feature = "shared_from_slice2", since = "1.24.0")]
790 impl From<CString> for Arc<CStr> {
791 /// Converts a [`CString`] into a [`Arc`]`<CStr>` without copying or allocating.
793 /// [`CString`]: ../ffi/struct.CString.html
794 /// [`Arc`]: ../sync/struct.Arc.html
796 fn from(s: CString) -> Arc<CStr> {
797 let arc: Arc<[u8]> = Arc::from(s.into_inner());
798 unsafe { Arc::from_raw(Arc::into_raw(arc) as *const CStr) }
802 #[stable(feature = "shared_from_slice2", since = "1.24.0")]
803 impl From<&CStr> for Arc<CStr> {
805 fn from(s: &CStr) -> Arc<CStr> {
806 let arc: Arc<[u8]> = Arc::from(s.to_bytes_with_nul());
807 unsafe { Arc::from_raw(Arc::into_raw(arc) as *const CStr) }
811 #[stable(feature = "shared_from_slice2", since = "1.24.0")]
812 impl From<CString> for Rc<CStr> {
813 /// Converts a [`CString`] into a [`Rc`]`<CStr>` without copying or allocating.
815 /// [`CString`]: ../ffi/struct.CString.html
816 /// [`Rc`]: ../rc/struct.Rc.html
818 fn from(s: CString) -> Rc<CStr> {
819 let rc: Rc<[u8]> = Rc::from(s.into_inner());
820 unsafe { Rc::from_raw(Rc::into_raw(rc) as *const CStr) }
824 #[stable(feature = "shared_from_slice2", since = "1.24.0")]
825 impl From<&CStr> for Rc<CStr> {
827 fn from(s: &CStr) -> Rc<CStr> {
828 let rc: Rc<[u8]> = Rc::from(s.to_bytes_with_nul());
829 unsafe { Rc::from_raw(Rc::into_raw(rc) as *const CStr) }
833 #[stable(feature = "default_box_extra", since = "1.17.0")]
834 impl Default for Box<CStr> {
835 fn default() -> Box<CStr> {
836 let boxed: Box<[u8]> = Box::from([0]);
837 unsafe { Box::from_raw(Box::into_raw(boxed) as *mut CStr) }
842 /// Returns the position of the nul byte in the slice that caused
843 /// [`CString::new`] to fail.
845 /// [`CString::new`]: struct.CString.html#method.new
850 /// use std::ffi::CString;
852 /// let nul_error = CString::new("foo\0bar").unwrap_err();
853 /// assert_eq!(nul_error.nul_position(), 3);
855 /// let nul_error = CString::new("foo bar\0").unwrap_err();
856 /// assert_eq!(nul_error.nul_position(), 7);
858 #[stable(feature = "rust1", since = "1.0.0")]
859 pub fn nul_position(&self) -> usize { self.0 }
861 /// Consumes this error, returning the underlying vector of bytes which
862 /// generated the error in the first place.
867 /// use std::ffi::CString;
869 /// let nul_error = CString::new("foo\0bar").unwrap_err();
870 /// assert_eq!(nul_error.into_vec(), b"foo\0bar");
872 #[stable(feature = "rust1", since = "1.0.0")]
873 pub fn into_vec(self) -> Vec<u8> { self.1 }
876 #[stable(feature = "rust1", since = "1.0.0")]
877 impl Error for NulError {
878 fn description(&self) -> &str { "nul byte found in data" }
881 #[stable(feature = "rust1", since = "1.0.0")]
882 impl fmt::Display for NulError {
883 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
884 write!(f, "nul byte found in provided data at position: {}", self.0)
888 #[stable(feature = "rust1", since = "1.0.0")]
889 impl From<NulError> for io::Error {
890 /// Converts a [`NulError`] into a [`io::Error`].
892 /// [`NulError`]: ../ffi/struct.NulError.html
893 /// [`io::Error`]: ../io/struct.Error.html
894 fn from(_: NulError) -> io::Error {
895 io::Error::new(io::ErrorKind::InvalidInput,
896 "data provided contains a nul byte")
900 #[stable(feature = "frombyteswithnulerror_impls", since = "1.17.0")]
901 impl Error for FromBytesWithNulError {
902 fn description(&self) -> &str {
904 FromBytesWithNulErrorKind::InteriorNul(..) =>
905 "data provided contains an interior nul byte",
906 FromBytesWithNulErrorKind::NotNulTerminated =>
907 "data provided is not nul terminated",
912 #[stable(feature = "frombyteswithnulerror_impls", since = "1.17.0")]
913 impl fmt::Display for FromBytesWithNulError {
914 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
915 f.write_str(self.description())?;
916 if let FromBytesWithNulErrorKind::InteriorNul(pos) = self.kind {
917 write!(f, " at byte pos {}", pos)?;
923 impl IntoStringError {
924 /// Consumes this error, returning original [`CString`] which generated the
927 /// [`CString`]: struct.CString.html
928 #[stable(feature = "cstring_into", since = "1.7.0")]
929 pub fn into_cstring(self) -> CString {
933 /// Access the underlying UTF-8 error that was the cause of this error.
934 #[stable(feature = "cstring_into", since = "1.7.0")]
935 pub fn utf8_error(&self) -> Utf8Error {
940 #[stable(feature = "cstring_into", since = "1.7.0")]
941 impl Error for IntoStringError {
942 fn description(&self) -> &str {
943 "C string contained non-utf8 bytes"
946 fn source(&self) -> Option<&(dyn Error + 'static)> {
951 #[stable(feature = "cstring_into", since = "1.7.0")]
952 impl fmt::Display for IntoStringError {
953 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
954 self.description().fmt(f)
959 /// Wraps a raw C string with a safe C string wrapper.
961 /// This function will wrap the provided `ptr` with a `CStr` wrapper, which
962 /// allows inspection and interoperation of non-owned C strings. The total
963 /// size of the raw C string must be smaller than `isize::MAX` **bytes**
964 /// in memory due to calling the `slice::from_raw_parts` function.
965 /// This method is unsafe for a number of reasons:
967 /// * There is no guarantee to the validity of `ptr`.
968 /// * The returned lifetime is not guaranteed to be the actual lifetime of
970 /// * There is no guarantee that the memory pointed to by `ptr` contains a
971 /// valid nul terminator byte at the end of the string.
972 /// * It is not guaranteed that the memory pointed by `ptr` won't change
973 /// before the `CStr` has been destroyed.
975 /// > **Note**: This operation is intended to be a 0-cost cast but it is
976 /// > currently implemented with an up-front calculation of the length of
977 /// > the string. This is not guaranteed to always be the case.
981 /// ```ignore (extern-declaration)
983 /// use std::ffi::CStr;
984 /// use std::os::raw::c_char;
987 /// fn my_string() -> *const c_char;
991 /// let slice = CStr::from_ptr(my_string());
992 /// println!("string returned: {}", slice.to_str().unwrap());
996 #[stable(feature = "rust1", since = "1.0.0")]
997 pub unsafe fn from_ptr<'a>(ptr: *const c_char) -> &'a CStr {
998 let len = sys::strlen(ptr);
999 let ptr = ptr as *const u8;
1000 CStr::from_bytes_with_nul_unchecked(slice::from_raw_parts(ptr, len as usize + 1))
1003 /// Creates a C string wrapper from a byte slice.
1005 /// This function will cast the provided `bytes` to a `CStr`
1006 /// wrapper after ensuring that the byte slice is nul-terminated
1007 /// and does not contain any interior nul bytes.
1012 /// use std::ffi::CStr;
1014 /// let cstr = CStr::from_bytes_with_nul(b"hello\0");
1015 /// assert!(cstr.is_ok());
1018 /// Creating a `CStr` without a trailing nul terminator is an error:
1021 /// use std::ffi::CStr;
1023 /// let cstr = CStr::from_bytes_with_nul(b"hello");
1024 /// assert!(cstr.is_err());
1027 /// Creating a `CStr` with an interior nul byte is an error:
1030 /// use std::ffi::CStr;
1032 /// let cstr = CStr::from_bytes_with_nul(b"he\0llo\0");
1033 /// assert!(cstr.is_err());
1035 #[stable(feature = "cstr_from_bytes", since = "1.10.0")]
1036 pub fn from_bytes_with_nul(bytes: &[u8])
1037 -> Result<&CStr, FromBytesWithNulError> {
1038 let nul_pos = memchr::memchr(0, bytes);
1039 if let Some(nul_pos) = nul_pos {
1040 if nul_pos + 1 != bytes.len() {
1041 return Err(FromBytesWithNulError::interior_nul(nul_pos));
1043 Ok(unsafe { CStr::from_bytes_with_nul_unchecked(bytes) })
1045 Err(FromBytesWithNulError::not_nul_terminated())
1049 /// Unsafely creates a C string wrapper from a byte slice.
1051 /// This function will cast the provided `bytes` to a `CStr` wrapper without
1052 /// performing any sanity checks. The provided slice **must** be nul-terminated
1053 /// and not contain any interior nul bytes.
1058 /// use std::ffi::{CStr, CString};
1061 /// let cstring = CString::new("hello").expect("CString::new failed");
1062 /// let cstr = CStr::from_bytes_with_nul_unchecked(cstring.to_bytes_with_nul());
1063 /// assert_eq!(cstr, &*cstring);
1067 #[stable(feature = "cstr_from_bytes", since = "1.10.0")]
1068 #[rustc_const_unstable(feature = "const_cstr_unchecked")]
1069 pub const unsafe fn from_bytes_with_nul_unchecked(bytes: &[u8]) -> &CStr {
1070 &*(bytes as *const [u8] as *const CStr)
1073 /// Returns the inner pointer to this C string.
1075 /// The returned pointer will be valid for as long as `self` is, and points
1076 /// to a contiguous region of memory terminated with a 0 byte to represent
1077 /// the end of the string.
1081 /// The returned pointer is read-only; writing to it (including passing it
1082 /// to C code that writes to it) causes undefined behavior.
1084 /// It is your responsibility to make sure that the underlying memory is not
1085 /// freed too early. For example, the following code will cause undefined
1086 /// behavior when `ptr` is used inside the `unsafe` block:
1089 /// # #![allow(unused_must_use)]
1090 /// use std::ffi::CString;
1092 /// let ptr = CString::new("Hello").expect("CString::new failed").as_ptr();
1094 /// // `ptr` is dangling
1099 /// This happens because the pointer returned by `as_ptr` does not carry any
1100 /// lifetime information and the [`CString`] is deallocated immediately after
1101 /// the `CString::new("Hello").expect("CString::new failed").as_ptr()` expression is evaluated.
1102 /// To fix the problem, bind the `CString` to a local variable:
1105 /// # #![allow(unused_must_use)]
1106 /// use std::ffi::CString;
1108 /// let hello = CString::new("Hello").expect("CString::new failed");
1109 /// let ptr = hello.as_ptr();
1111 /// // `ptr` is valid because `hello` is in scope
1116 /// This way, the lifetime of the `CString` in `hello` encompasses
1117 /// the lifetime of `ptr` and the `unsafe` block.
1119 /// [`CString`]: struct.CString.html
1121 #[stable(feature = "rust1", since = "1.0.0")]
1122 pub const fn as_ptr(&self) -> *const c_char {
1126 /// Converts this C string to a byte slice.
1128 /// The returned slice will **not** contain the trailing nul terminator that this C
1131 /// > **Note**: This method is currently implemented as a constant-time
1132 /// > cast, but it is planned to alter its definition in the future to
1133 /// > perform the length calculation whenever this method is called.
1138 /// use std::ffi::CStr;
1140 /// let cstr = CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed");
1141 /// assert_eq!(cstr.to_bytes(), b"foo");
1144 #[stable(feature = "rust1", since = "1.0.0")]
1145 pub fn to_bytes(&self) -> &[u8] {
1146 let bytes = self.to_bytes_with_nul();
1147 &bytes[..bytes.len() - 1]
1150 /// Converts this C string to a byte slice containing the trailing 0 byte.
1152 /// This function is the equivalent of [`to_bytes`] except that it will retain
1153 /// the trailing nul terminator instead of chopping it off.
1155 /// > **Note**: This method is currently implemented as a 0-cost cast, but
1156 /// > it is planned to alter its definition in the future to perform the
1157 /// > length calculation whenever this method is called.
1159 /// [`to_bytes`]: #method.to_bytes
1164 /// use std::ffi::CStr;
1166 /// let cstr = CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed");
1167 /// assert_eq!(cstr.to_bytes_with_nul(), b"foo\0");
1170 #[stable(feature = "rust1", since = "1.0.0")]
1171 pub fn to_bytes_with_nul(&self) -> &[u8] {
1172 unsafe { &*(&self.inner as *const [c_char] as *const [u8]) }
1175 /// Yields a [`&str`] slice if the `CStr` contains valid UTF-8.
1177 /// If the contents of the `CStr` are valid UTF-8 data, this
1178 /// function will return the corresponding [`&str`] slice. Otherwise,
1179 /// it will return an error with details of where UTF-8 validation failed.
1181 /// > **Note**: This method is currently implemented to check for validity
1182 /// > after a constant-time cast, but it is planned to alter its definition
1183 /// > in the future to perform the length calculation in addition to the
1184 /// > UTF-8 check whenever this method is called.
1186 /// [`&str`]: ../primitive.str.html
1191 /// use std::ffi::CStr;
1193 /// let cstr = CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed");
1194 /// assert_eq!(cstr.to_str(), Ok("foo"));
1196 #[stable(feature = "cstr_to_str", since = "1.4.0")]
1197 pub fn to_str(&self) -> Result<&str, str::Utf8Error> {
1198 // N.B., when `CStr` is changed to perform the length check in `.to_bytes()`
1199 // instead of in `from_ptr()`, it may be worth considering if this should
1200 // be rewritten to do the UTF-8 check inline with the length calculation
1201 // instead of doing it afterwards.
1202 str::from_utf8(self.to_bytes())
1205 /// Converts a `CStr` into a [`Cow`]`<`[`str`]`>`.
1207 /// If the contents of the `CStr` are valid UTF-8 data, this
1208 /// function will return a [`Cow`]`::`[`Borrowed`]`(`[`&str`]`)`
1209 /// with the corresponding [`&str`] slice. Otherwise, it will
1210 /// replace any invalid UTF-8 sequences with
1211 /// [`U+FFFD REPLACEMENT CHARACTER`][U+FFFD] and return a
1212 /// [`Cow`]`::`[`Owned`]`(`[`String`]`)` with the result.
1214 /// > **Note**: This method is currently implemented to check for validity
1215 /// > after a constant-time cast, but it is planned to alter its definition
1216 /// > in the future to perform the length calculation in addition to the
1217 /// > UTF-8 check whenever this method is called.
1219 /// [`Cow`]: ../borrow/enum.Cow.html
1220 /// [`Borrowed`]: ../borrow/enum.Cow.html#variant.Borrowed
1221 /// [`Owned`]: ../borrow/enum.Cow.html#variant.Owned
1222 /// [`str`]: ../primitive.str.html
1223 /// [`String`]: ../string/struct.String.html
1224 /// [U+FFFD]: ../char/constant.REPLACEMENT_CHARACTER.html
1228 /// Calling `to_string_lossy` on a `CStr` containing valid UTF-8:
1231 /// use std::borrow::Cow;
1232 /// use std::ffi::CStr;
1234 /// let cstr = CStr::from_bytes_with_nul(b"Hello World\0")
1235 /// .expect("CStr::from_bytes_with_nul failed");
1236 /// assert_eq!(cstr.to_string_lossy(), Cow::Borrowed("Hello World"));
1239 /// Calling `to_string_lossy` on a `CStr` containing invalid UTF-8:
1242 /// use std::borrow::Cow;
1243 /// use std::ffi::CStr;
1245 /// let cstr = CStr::from_bytes_with_nul(b"Hello \xF0\x90\x80World\0")
1246 /// .expect("CStr::from_bytes_with_nul failed");
1248 /// cstr.to_string_lossy(),
1249 /// Cow::Owned(String::from("Hello �World")) as Cow<'_, str>
1252 #[stable(feature = "cstr_to_str", since = "1.4.0")]
1253 pub fn to_string_lossy(&self) -> Cow<'_, str> {
1254 String::from_utf8_lossy(self.to_bytes())
1257 /// Converts a [`Box`]`<CStr>` into a [`CString`] without copying or allocating.
1259 /// [`Box`]: ../boxed/struct.Box.html
1260 /// [`CString`]: struct.CString.html
1265 /// use std::ffi::CString;
1267 /// let c_string = CString::new(b"foo".to_vec()).expect("CString::new failed");
1268 /// let boxed = c_string.into_boxed_c_str();
1269 /// assert_eq!(boxed.into_c_string(), CString::new("foo").expect("CString::new failed"));
1271 #[stable(feature = "into_boxed_c_str", since = "1.20.0")]
1272 pub fn into_c_string(self: Box<CStr>) -> CString {
1273 let raw = Box::into_raw(self) as *mut [u8];
1274 CString { inner: unsafe { Box::from_raw(raw) } }
1278 #[stable(feature = "rust1", since = "1.0.0")]
1279 impl PartialEq for CStr {
1280 fn eq(&self, other: &CStr) -> bool {
1281 self.to_bytes().eq(other.to_bytes())
1284 #[stable(feature = "rust1", since = "1.0.0")]
1286 #[stable(feature = "rust1", since = "1.0.0")]
1287 impl PartialOrd for CStr {
1288 fn partial_cmp(&self, other: &CStr) -> Option<Ordering> {
1289 self.to_bytes().partial_cmp(&other.to_bytes())
1292 #[stable(feature = "rust1", since = "1.0.0")]
1294 fn cmp(&self, other: &CStr) -> Ordering {
1295 self.to_bytes().cmp(&other.to_bytes())
1299 #[stable(feature = "cstr_borrow", since = "1.3.0")]
1300 impl ToOwned for CStr {
1301 type Owned = CString;
1303 fn to_owned(&self) -> CString {
1304 CString { inner: self.to_bytes_with_nul().into() }
1308 #[stable(feature = "cstring_asref", since = "1.7.0")]
1309 impl From<&CStr> for CString {
1310 fn from(s: &CStr) -> CString {
1315 #[stable(feature = "cstring_asref", since = "1.7.0")]
1316 impl ops::Index<ops::RangeFull> for CString {
1320 fn index(&self, _index: ops::RangeFull) -> &CStr {
1325 #[stable(feature = "cstring_asref", since = "1.7.0")]
1326 impl AsRef<CStr> for CStr {
1328 fn as_ref(&self) -> &CStr {
1333 #[stable(feature = "cstring_asref", since = "1.7.0")]
1334 impl AsRef<CStr> for CString {
1336 fn as_ref(&self) -> &CStr {
1344 use crate::os::raw::c_char;
1345 use crate::borrow::Cow::{Borrowed, Owned};
1346 use crate::hash::{Hash, Hasher};
1347 use crate::collections::hash_map::DefaultHasher;
1349 use crate::sync::Arc;
1353 let data = b"123\0";
1354 let ptr = data.as_ptr() as *const c_char;
1356 assert_eq!(CStr::from_ptr(ptr).to_bytes(), b"123");
1357 assert_eq!(CStr::from_ptr(ptr).to_bytes_with_nul(), b"123\0");
1363 let s = CString::new("1234").unwrap();
1364 assert_eq!(s.as_bytes(), b"1234");
1365 assert_eq!(s.as_bytes_with_nul(), b"1234\0");
1369 fn build_with_zero1() {
1370 assert!(CString::new(&b"\0"[..]).is_err());
1373 fn build_with_zero2() {
1374 assert!(CString::new(vec![0]).is_err());
1378 fn build_with_zero3() {
1380 let s = CString::from_vec_unchecked(vec![0]);
1381 assert_eq!(s.as_bytes(), b"\0");
1387 let s = CString::new(&b"abc\x01\x02\n\xE2\x80\xA6\xFF"[..]).unwrap();
1388 assert_eq!(format!("{:?}", s), r#""abc\x01\x02\n\xe2\x80\xa6\xff""#);
1394 let s = CStr::from_ptr(b"12\0".as_ptr() as *const _);
1395 assert_eq!(s.to_bytes(), b"12");
1396 assert_eq!(s.to_bytes_with_nul(), b"12\0");
1402 let data = b"123\xE2\x80\xA6\0";
1403 let ptr = data.as_ptr() as *const c_char;
1405 assert_eq!(CStr::from_ptr(ptr).to_str(), Ok("123…"));
1406 assert_eq!(CStr::from_ptr(ptr).to_string_lossy(), Borrowed("123…"));
1408 let data = b"123\xE2\0";
1409 let ptr = data.as_ptr() as *const c_char;
1411 assert!(CStr::from_ptr(ptr).to_str().is_err());
1412 assert_eq!(CStr::from_ptr(ptr).to_string_lossy(), Owned::<str>(format!("123\u{FFFD}")));
1418 let data = b"123\0";
1419 let ptr = data.as_ptr() as *const c_char;
1421 let owned = unsafe { CStr::from_ptr(ptr).to_owned() };
1422 assert_eq!(owned.as_bytes_with_nul(), data);
1427 let data = b"123\xE2\xFA\xA6\0";
1428 let ptr = data.as_ptr() as *const c_char;
1429 let cstr: &'static CStr = unsafe { CStr::from_ptr(ptr) };
1431 let mut s = DefaultHasher::new();
1433 let cstr_hash = s.finish();
1434 let mut s = DefaultHasher::new();
1435 CString::new(&data[..data.len() - 1]).unwrap().hash(&mut s);
1436 let cstring_hash = s.finish();
1438 assert_eq!(cstr_hash, cstring_hash);
1442 fn from_bytes_with_nul() {
1443 let data = b"123\0";
1444 let cstr = CStr::from_bytes_with_nul(data);
1445 assert_eq!(cstr.map(CStr::to_bytes), Ok(&b"123"[..]));
1446 let cstr = CStr::from_bytes_with_nul(data);
1447 assert_eq!(cstr.map(CStr::to_bytes_with_nul), Ok(&b"123\0"[..]));
1450 let cstr = CStr::from_bytes_with_nul(data);
1451 let cstr_unchecked = CStr::from_bytes_with_nul_unchecked(data);
1452 assert_eq!(cstr, Ok(cstr_unchecked));
1457 fn from_bytes_with_nul_unterminated() {
1459 let cstr = CStr::from_bytes_with_nul(data);
1460 assert!(cstr.is_err());
1464 fn from_bytes_with_nul_interior() {
1465 let data = b"1\023\0";
1466 let cstr = CStr::from_bytes_with_nul(data);
1467 assert!(cstr.is_err());
1472 let orig: &[u8] = b"Hello, world!\0";
1473 let cstr = CStr::from_bytes_with_nul(orig).unwrap();
1474 let boxed: Box<CStr> = Box::from(cstr);
1475 let cstring = cstr.to_owned().into_boxed_c_str().into_c_string();
1476 assert_eq!(cstr, &*boxed);
1477 assert_eq!(&*boxed, &*cstring);
1478 assert_eq!(&*cstring, cstr);
1482 fn boxed_default() {
1483 let boxed = <Box<CStr>>::default();
1484 assert_eq!(boxed.to_bytes_with_nul(), &[0]);
1489 let orig: &[u8] = b"Hello, world!\0";
1490 let cstr = CStr::from_bytes_with_nul(orig).unwrap();
1491 let rc: Rc<CStr> = Rc::from(cstr);
1492 let arc: Arc<CStr> = Arc::from(cstr);
1494 assert_eq!(&*rc, cstr);
1495 assert_eq!(&*arc, cstr);
1497 let rc2: Rc<CStr> = Rc::from(cstr.to_owned());
1498 let arc2: Arc<CStr> = Arc::from(cstr.to_owned());
1500 assert_eq!(&*rc2, cstr);
1501 assert_eq!(&*arc2, cstr);
1505 fn cstr_const_constructor() {
1506 const CSTR: &CStr = unsafe {
1507 CStr::from_bytes_with_nul_unchecked(b"Hello, world!\0")
1510 assert_eq!(CSTR.to_str().unwrap(), "Hello, world!");