1 #![deny(unsafe_op_in_unsafe_fn)]
3 use crate::borrow::{Borrow, Cow};
4 use crate::cmp::Ordering;
5 use crate::error::Error;
6 use crate::fmt::{self, Write};
10 use crate::num::NonZeroU8;
12 use crate::os::raw::c_char;
16 use crate::str::{self, Utf8Error};
20 /// A type representing an owned, C-compatible, nul-terminated string with no nul bytes in the
23 /// This type serves the purpose of being able to safely generate a
24 /// C-compatible string from a Rust byte slice or vector. An instance of this
25 /// type is a static guarantee that the underlying bytes contain no interior 0
26 /// bytes ("nul characters") and that the final byte is 0 ("nul terminator").
28 /// `CString` is to [`&CStr`] as [`String`] is to [`&str`]: the former
29 /// in each pair are owned strings; the latter are borrowed
32 /// # Creating a `CString`
34 /// A `CString` is created from either a byte slice or a byte vector,
35 /// or anything that implements [`Into`]`<`[`Vec`]`<`[`u8`]`>>` (for
36 /// example, you can build a `CString` straight out of a [`String`] or
37 /// a [`&str`], since both implement that trait).
39 /// The [`CString::new`] method will actually check that the provided `&[u8]`
40 /// does not have 0 bytes in the middle, and return an error if it
43 /// # Extracting a raw pointer to the whole C string
45 /// `CString` implements a [`as_ptr`][`CStr::as_ptr`] method through the [`Deref`]
46 /// trait. This method will give you a `*const c_char` which you can
47 /// feed directly to extern functions that expect a nul-terminated
48 /// string, like C's `strdup()`. Notice that [`as_ptr`][`CStr::as_ptr`] returns a
49 /// read-only pointer; if the C code writes to it, that causes
50 /// undefined behavior.
52 /// # Extracting a slice of the whole C string
54 /// Alternatively, you can obtain a `&[`[`u8`]`]` slice from a
55 /// `CString` with the [`CString::as_bytes`] method. Slices produced in this
56 /// way do *not* contain the trailing nul terminator. This is useful
57 /// when you will be calling an extern function that takes a `*const
58 /// u8` argument which is not necessarily nul-terminated, plus another
59 /// argument with the length of the string — like C's `strndup()`.
60 /// You can of course get the slice's length with its
61 /// [`len`][slice.len] method.
63 /// If you need a `&[`[`u8`]`]` slice *with* the nul terminator, you
64 /// can use [`CString::as_bytes_with_nul`] instead.
66 /// Once you have the kind of slice you need (with or without a nul
67 /// terminator), you can call the slice's own
68 /// [`as_ptr`][slice.as_ptr] method to get a read-only raw pointer to pass to
69 /// extern functions. See the documentation for that function for a
70 /// discussion on ensuring the lifetime of the raw pointer.
73 /// [slice.as_ptr]: ../primitive.slice.html#method.as_ptr
74 /// [slice.len]: ../primitive.slice.html#method.len
75 /// [`Deref`]: ops::Deref
80 /// ```ignore (extern-declaration)
82 /// use std::ffi::CString;
83 /// use std::os::raw::c_char;
86 /// fn my_printer(s: *const c_char);
89 /// // We are certain that our string doesn't have 0 bytes in the middle,
90 /// // so we can .expect()
91 /// let c_to_print = CString::new("Hello, world!").expect("CString::new failed");
93 /// my_printer(c_to_print.as_ptr());
100 /// `CString` is intended for working with traditional C-style strings
101 /// (a sequence of non-nul bytes terminated by a single nul byte); the
102 /// primary use case for these kinds of strings is interoperating with C-like
103 /// code. Often you will need to transfer ownership to/from that external
104 /// code. It is strongly recommended that you thoroughly read through the
105 /// documentation of `CString` before use, as improper ownership management
106 /// of `CString` instances can lead to invalid memory accesses, memory leaks,
107 /// and other memory errors.
108 #[derive(PartialEq, PartialOrd, Eq, Ord, Hash, Clone)]
109 #[stable(feature = "rust1", since = "1.0.0")]
111 // Invariant 1: the slice ends with a zero byte and has a length of at least one.
112 // Invariant 2: the slice contains only one zero byte.
113 // Improper usage of unsafe function can break Invariant 2, but not Invariant 1.
117 /// Representation of a borrowed C string.
119 /// This type represents a borrowed reference to a nul-terminated
120 /// array of bytes. It can be constructed safely from a `&[`[`u8`]`]`
121 /// slice, or unsafely from a raw `*const c_char`. It can then be
122 /// converted to a Rust [`&str`] by performing UTF-8 validation, or
123 /// into an owned [`CString`].
125 /// `&CStr` is to [`CString`] as [`&str`] is to [`String`]: the former
126 /// in each pair are borrowed references; the latter are owned
129 /// Note that this structure is **not** `repr(C)` and is not recommended to be
130 /// placed in the signatures of FFI functions. Instead, safe wrappers of FFI
131 /// functions may leverage the unsafe [`CStr::from_ptr`] constructor to provide
132 /// a safe interface to other consumers.
136 /// Inspecting a foreign C string:
138 /// ```ignore (extern-declaration)
139 /// use std::ffi::CStr;
140 /// use std::os::raw::c_char;
142 /// extern { fn my_string() -> *const c_char; }
145 /// let slice = CStr::from_ptr(my_string());
146 /// println!("string buffer size without nul terminator: {}", slice.to_bytes().len());
150 /// Passing a Rust-originating C string:
152 /// ```ignore (extern-declaration)
153 /// use std::ffi::{CString, CStr};
154 /// use std::os::raw::c_char;
156 /// fn work(data: &CStr) {
157 /// extern { fn work_with(data: *const c_char); }
159 /// unsafe { work_with(data.as_ptr()) }
162 /// let s = CString::new("data data data data").expect("CString::new failed");
166 /// Converting a foreign C string into a Rust [`String`]:
168 /// ```ignore (extern-declaration)
169 /// use std::ffi::CStr;
170 /// use std::os::raw::c_char;
172 /// extern { fn my_string() -> *const c_char; }
174 /// fn my_string_safe() -> String {
176 /// CStr::from_ptr(my_string()).to_string_lossy().into_owned()
180 /// println!("string: {}", my_string_safe());
185 #[stable(feature = "rust1", since = "1.0.0")]
187 // `fn from` in `impl From<&CStr> for Box<CStr>` current implementation relies
188 // on `CStr` being layout-compatible with `[u8]`.
189 // When attribute privacy is implemented, `CStr` should be annotated as `#[repr(transparent)]`.
190 // Anyway, `CStr` representation and layout are considered implementation detail, are
191 // not documented and must not be relied upon.
193 // FIXME: this should not be represented with a DST slice but rather with
194 // just a raw `c_char` along with some form of marker to make
195 // this an unsized type. Essentially `sizeof(&CStr)` should be the
196 // same as `sizeof(&c_char)` but `CStr` should be an unsized type.
200 /// An error indicating that an interior nul byte was found.
202 /// While Rust strings may contain nul bytes in the middle, C strings
203 /// can't, as that byte would effectively truncate the string.
205 /// This error is created by the [`new`][`CString::new`] method on
206 /// [`CString`]. See its documentation for more.
211 /// use std::ffi::{CString, NulError};
213 /// let _: NulError = CString::new(b"f\0oo".to_vec()).unwrap_err();
215 #[derive(Clone, PartialEq, Eq, Debug)]
216 #[stable(feature = "rust1", since = "1.0.0")]
217 pub struct NulError(usize, Vec<u8>);
219 /// An error indicating that a nul byte was not in the expected position.
221 /// The slice used to create a [`CStr`] must have one and only one nul byte,
222 /// positioned at the end.
224 /// This error is created by the [`CStr::from_bytes_with_nul`] method.
225 /// See its documentation for more.
230 /// use std::ffi::{CStr, FromBytesWithNulError};
232 /// let _: FromBytesWithNulError = CStr::from_bytes_with_nul(b"f\0oo").unwrap_err();
234 #[derive(Clone, PartialEq, Eq, Debug)]
235 #[stable(feature = "cstr_from_bytes", since = "1.10.0")]
236 pub struct FromBytesWithNulError {
237 kind: FromBytesWithNulErrorKind,
240 /// An error indicating that a nul byte was not in the expected position.
242 /// The vector used to create a [`CString`] must have one and only one nul byte,
243 /// positioned at the end.
245 /// This error is created by the [`CString::from_vec_with_nul`] method.
246 /// See its documentation for more.
251 /// #![feature(cstring_from_vec_with_nul)]
252 /// use std::ffi::{CString, FromVecWithNulError};
254 /// let _: FromVecWithNulError = CString::from_vec_with_nul(b"f\0oo".to_vec()).unwrap_err();
256 #[derive(Clone, PartialEq, Eq, Debug)]
257 #[unstable(feature = "cstring_from_vec_with_nul", issue = "73179")]
258 pub struct FromVecWithNulError {
259 error_kind: FromBytesWithNulErrorKind,
263 #[derive(Clone, PartialEq, Eq, Debug)]
264 enum FromBytesWithNulErrorKind {
269 impl FromBytesWithNulError {
270 fn interior_nul(pos: usize) -> FromBytesWithNulError {
271 FromBytesWithNulError { kind: FromBytesWithNulErrorKind::InteriorNul(pos) }
273 fn not_nul_terminated() -> FromBytesWithNulError {
274 FromBytesWithNulError { kind: FromBytesWithNulErrorKind::NotNulTerminated }
278 #[unstable(feature = "cstring_from_vec_with_nul", issue = "73179")]
279 impl FromVecWithNulError {
280 /// Returns a slice of [`u8`]s bytes that were attempted to convert to a [`CString`].
287 /// #![feature(cstring_from_vec_with_nul)]
288 /// use std::ffi::CString;
290 /// // Some invalid bytes in a vector
291 /// let bytes = b"f\0oo".to_vec();
293 /// let value = CString::from_vec_with_nul(bytes.clone());
295 /// assert_eq!(&bytes[..], value.unwrap_err().as_bytes());
297 pub fn as_bytes(&self) -> &[u8] {
301 /// Returns the bytes that were attempted to convert to a [`CString`].
303 /// This method is carefully constructed to avoid allocation. It will
304 /// consume the error, moving out the bytes, so that a copy of the bytes
305 /// does not need to be made.
312 /// #![feature(cstring_from_vec_with_nul)]
313 /// use std::ffi::CString;
315 /// // Some invalid bytes in a vector
316 /// let bytes = b"f\0oo".to_vec();
318 /// let value = CString::from_vec_with_nul(bytes.clone());
320 /// assert_eq!(bytes, value.unwrap_err().into_bytes());
322 pub fn into_bytes(self) -> Vec<u8> {
327 /// An error indicating invalid UTF-8 when converting a [`CString`] into a [`String`].
329 /// `CString` is just a wrapper over a buffer of bytes with a nul terminator;
330 /// [`CString::into_string`] performs UTF-8 validation on those bytes and may
331 /// return this error.
333 /// This `struct` is created by [`CString::into_string()`]. See
334 /// its documentation for more.
335 #[derive(Clone, PartialEq, Eq, Debug)]
336 #[stable(feature = "cstring_into", since = "1.7.0")]
337 pub struct IntoStringError {
343 /// Creates a new C-compatible string from a container of bytes.
345 /// This function will consume the provided data and use the
346 /// underlying bytes to construct a new string, ensuring that
347 /// there is a trailing 0 byte. This trailing 0 byte will be
348 /// appended by this function; the provided data should *not*
349 /// contain any 0 bytes in it.
353 /// ```ignore (extern-declaration)
354 /// use std::ffi::CString;
355 /// use std::os::raw::c_char;
357 /// extern { fn puts(s: *const c_char); }
359 /// let to_print = CString::new("Hello!").expect("CString::new failed");
361 /// puts(to_print.as_ptr());
367 /// This function will return an error if the supplied bytes contain an
368 /// internal 0 byte. The [`NulError`] returned will contain the bytes as well as
369 /// the position of the nul byte.
370 #[stable(feature = "rust1", since = "1.0.0")]
371 pub fn new<T: Into<Vec<u8>>>(t: T) -> Result<CString, NulError> {
373 fn into_vec(self) -> Vec<u8>;
375 impl<T: Into<Vec<u8>>> SpecIntoVec for T {
376 default fn into_vec(self) -> Vec<u8> {
380 // Specialization for avoiding reallocation.
381 impl SpecIntoVec for &'_ [u8] {
382 fn into_vec(self) -> Vec<u8> {
383 let mut v = Vec::with_capacity(self.len() + 1);
388 impl SpecIntoVec for &'_ str {
389 fn into_vec(self) -> Vec<u8> {
390 let mut v = Vec::with_capacity(self.len() + 1);
391 v.extend(self.as_bytes());
396 Self::_new(SpecIntoVec::into_vec(t))
399 fn _new(bytes: Vec<u8>) -> Result<CString, NulError> {
400 match memchr::memchr(0, &bytes) {
401 Some(i) => Err(NulError(i, bytes)),
402 None => Ok(unsafe { CString::from_vec_unchecked(bytes) }),
406 /// Creates a C-compatible string by consuming a byte vector,
407 /// without checking for interior 0 bytes.
409 /// This method is equivalent to [`CString::new`] except that no runtime
410 /// assertion is made that `v` contains no 0 bytes, and it requires an
411 /// actual byte vector, not anything that can be converted to one with Into.
416 /// use std::ffi::CString;
418 /// let raw = b"foo".to_vec();
420 /// let c_string = CString::from_vec_unchecked(raw);
423 #[stable(feature = "rust1", since = "1.0.0")]
424 pub unsafe fn from_vec_unchecked(mut v: Vec<u8>) -> CString {
427 CString { inner: v.into_boxed_slice() }
430 /// Retakes ownership of a `CString` that was transferred to C via
431 /// [`CString::into_raw`].
433 /// Additionally, the length of the string will be recalculated from the pointer.
437 /// This should only ever be called with a pointer that was earlier
438 /// obtained by calling [`CString::into_raw`]. Other usage (e.g., trying to take
439 /// ownership of a string that was allocated by foreign code) is likely to lead
440 /// to undefined behavior or allocator corruption.
442 /// It should be noted that the length isn't just "recomputed," but that
443 /// the recomputed length must match the original length from the
444 /// [`CString::into_raw`] call. This means the [`CString::into_raw`]/`from_raw`
445 /// methods should not be used when passing the string to C functions that can
446 /// modify the string's length.
448 /// > **Note:** If you need to borrow a string that was allocated by
449 /// > foreign code, use [`CStr`]. If you need to take ownership of
450 /// > a string that was allocated by foreign code, you will need to
451 /// > make your own provisions for freeing it appropriately, likely
452 /// > with the foreign code's API to do that.
456 /// Creates a `CString`, pass ownership to an `extern` function (via raw pointer), then retake
457 /// ownership with `from_raw`:
459 /// ```ignore (extern-declaration)
460 /// use std::ffi::CString;
461 /// use std::os::raw::c_char;
464 /// fn some_extern_function(s: *mut c_char);
467 /// let c_string = CString::new("Hello!").expect("CString::new failed");
468 /// let raw = c_string.into_raw();
470 /// some_extern_function(raw);
471 /// let c_string = CString::from_raw(raw);
474 #[stable(feature = "cstr_memory", since = "1.4.0")]
475 pub unsafe fn from_raw(ptr: *mut c_char) -> CString {
476 // SAFETY: This is called with a pointer that was obtained from a call
477 // to `CString::into_raw` and the length has not been modified. As such,
478 // we know there is a NUL byte (and only one) at the end and that the
479 // information about the size of the allocation is correct on Rust's
482 let len = sys::strlen(ptr) + 1; // Including the NUL byte
483 let slice = slice::from_raw_parts_mut(ptr, len as usize);
484 CString { inner: Box::from_raw(slice as *mut [c_char] as *mut [u8]) }
488 /// Consumes the `CString` and transfers ownership of the string to a C caller.
490 /// The pointer which this function returns must be returned to Rust and reconstituted using
491 /// [`CString::from_raw`] to be properly deallocated. Specifically, one
492 /// should *not* use the standard C `free()` function to deallocate
495 /// Failure to call [`CString::from_raw`] will lead to a memory leak.
497 /// The C side must **not** modify the length of the string (by writing a
498 /// `NULL` somewhere inside the string or removing the final one) before
499 /// it makes it back into Rust using [`CString::from_raw`]. See the safety section
500 /// in [`CString::from_raw`].
505 /// use std::ffi::CString;
507 /// let c_string = CString::new("foo").expect("CString::new failed");
509 /// let ptr = c_string.into_raw();
512 /// assert_eq!(b'f', *ptr as u8);
513 /// assert_eq!(b'o', *ptr.offset(1) as u8);
514 /// assert_eq!(b'o', *ptr.offset(2) as u8);
515 /// assert_eq!(b'\0', *ptr.offset(3) as u8);
517 /// // retake pointer to free memory
518 /// let _ = CString::from_raw(ptr);
522 #[stable(feature = "cstr_memory", since = "1.4.0")]
523 pub fn into_raw(self) -> *mut c_char {
524 Box::into_raw(self.into_inner()) as *mut c_char
527 /// Converts the `CString` into a [`String`] if it contains valid UTF-8 data.
529 /// On failure, ownership of the original `CString` is returned.
534 /// use std::ffi::CString;
536 /// let valid_utf8 = vec![b'f', b'o', b'o'];
537 /// let cstring = CString::new(valid_utf8).expect("CString::new failed");
538 /// assert_eq!(cstring.into_string().expect("into_string() call failed"), "foo");
540 /// let invalid_utf8 = vec![b'f', 0xff, b'o', b'o'];
541 /// let cstring = CString::new(invalid_utf8).expect("CString::new failed");
542 /// let err = cstring.into_string().err().expect("into_string().err() failed");
543 /// assert_eq!(err.utf8_error().valid_up_to(), 1);
546 #[stable(feature = "cstring_into", since = "1.7.0")]
547 pub fn into_string(self) -> Result<String, IntoStringError> {
548 String::from_utf8(self.into_bytes()).map_err(|e| IntoStringError {
549 error: e.utf8_error(),
550 inner: unsafe { CString::from_vec_unchecked(e.into_bytes()) },
554 /// Consumes the `CString` and returns the underlying byte buffer.
556 /// The returned buffer does **not** contain the trailing nul
557 /// terminator, and it is guaranteed to not have any interior nul
563 /// use std::ffi::CString;
565 /// let c_string = CString::new("foo").expect("CString::new failed");
566 /// let bytes = c_string.into_bytes();
567 /// assert_eq!(bytes, vec![b'f', b'o', b'o']);
569 #[stable(feature = "cstring_into", since = "1.7.0")]
570 pub fn into_bytes(self) -> Vec<u8> {
571 let mut vec = self.into_inner().into_vec();
572 let _nul = vec.pop();
573 debug_assert_eq!(_nul, Some(0u8));
577 /// Equivalent to [`CString::into_bytes()`] except that the
578 /// returned vector includes the trailing nul terminator.
583 /// use std::ffi::CString;
585 /// let c_string = CString::new("foo").expect("CString::new failed");
586 /// let bytes = c_string.into_bytes_with_nul();
587 /// assert_eq!(bytes, vec![b'f', b'o', b'o', b'\0']);
589 #[stable(feature = "cstring_into", since = "1.7.0")]
590 pub fn into_bytes_with_nul(self) -> Vec<u8> {
591 self.into_inner().into_vec()
594 /// Returns the contents of this `CString` as a slice of bytes.
596 /// The returned slice does **not** contain the trailing nul
597 /// terminator, and it is guaranteed to not have any interior nul
598 /// bytes. If you need the nul terminator, use
599 /// [`CString::as_bytes_with_nul`] instead.
604 /// use std::ffi::CString;
606 /// let c_string = CString::new("foo").expect("CString::new failed");
607 /// let bytes = c_string.as_bytes();
608 /// assert_eq!(bytes, &[b'f', b'o', b'o']);
611 #[stable(feature = "rust1", since = "1.0.0")]
612 pub fn as_bytes(&self) -> &[u8] {
613 &self.inner[..self.inner.len() - 1]
616 /// Equivalent to [`CString::as_bytes()`] except that the
617 /// returned slice includes the trailing nul terminator.
622 /// use std::ffi::CString;
624 /// let c_string = CString::new("foo").expect("CString::new failed");
625 /// let bytes = c_string.as_bytes_with_nul();
626 /// assert_eq!(bytes, &[b'f', b'o', b'o', b'\0']);
629 #[stable(feature = "rust1", since = "1.0.0")]
630 pub fn as_bytes_with_nul(&self) -> &[u8] {
634 /// Extracts a [`CStr`] slice containing the entire string.
639 /// use std::ffi::{CString, CStr};
641 /// let c_string = CString::new(b"foo".to_vec()).expect("CString::new failed");
642 /// let cstr = c_string.as_c_str();
644 /// CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed"));
647 #[stable(feature = "as_c_str", since = "1.20.0")]
648 pub fn as_c_str(&self) -> &CStr {
652 /// Converts this `CString` into a boxed [`CStr`].
657 /// use std::ffi::{CString, CStr};
659 /// let c_string = CString::new(b"foo".to_vec()).expect("CString::new failed");
660 /// let boxed = c_string.into_boxed_c_str();
661 /// assert_eq!(&*boxed,
662 /// CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed"));
664 #[stable(feature = "into_boxed_c_str", since = "1.20.0")]
665 pub fn into_boxed_c_str(self) -> Box<CStr> {
666 unsafe { Box::from_raw(Box::into_raw(self.into_inner()) as *mut CStr) }
669 /// Bypass "move out of struct which implements [`Drop`] trait" restriction.
670 fn into_inner(self) -> Box<[u8]> {
671 // Rationale: `mem::forget(self)` invalidates the previous call to `ptr::read(&self.inner)`
672 // so we use `ManuallyDrop` to ensure `self` is not dropped.
673 // Then we can return the box directly without invalidating it.
674 // See https://github.com/rust-lang/rust/issues/62553.
675 let this = mem::ManuallyDrop::new(self);
676 unsafe { ptr::read(&this.inner) }
679 /// Converts a [`Vec`]`<u8>` to a [`CString`] without checking the
680 /// invariants on the given [`Vec`].
684 /// The given [`Vec`] **must** have one nul byte as its last element.
685 /// This means it cannot be empty nor have any other nul byte anywhere else.
690 /// #![feature(cstring_from_vec_with_nul)]
691 /// use std::ffi::CString;
693 /// unsafe { CString::from_vec_with_nul_unchecked(b"abc\0".to_vec()) },
694 /// unsafe { CString::from_vec_unchecked(b"abc".to_vec()) }
697 #[unstable(feature = "cstring_from_vec_with_nul", issue = "73179")]
698 pub unsafe fn from_vec_with_nul_unchecked(v: Vec<u8>) -> Self {
699 Self { inner: v.into_boxed_slice() }
702 /// Attempts to converts a [`Vec`]`<u8>` to a [`CString`].
704 /// Runtime checks are present to ensure there is only one nul byte in the
705 /// [`Vec`], its last element.
709 /// If a nul byte is present and not the last element or no nul bytes
710 /// is present, an error will be returned.
714 /// A successful conversion will produce the same result as [`CString::new`]
715 /// when called without the ending nul byte.
718 /// #![feature(cstring_from_vec_with_nul)]
719 /// use std::ffi::CString;
721 /// CString::from_vec_with_nul(b"abc\0".to_vec())
722 /// .expect("CString::from_vec_with_nul failed"),
723 /// CString::new(b"abc".to_vec()).expect("CString::new failed")
727 /// A incorrectly formatted [`Vec`] will produce an error.
730 /// #![feature(cstring_from_vec_with_nul)]
731 /// use std::ffi::{CString, FromVecWithNulError};
732 /// // Interior nul byte
733 /// let _: FromVecWithNulError = CString::from_vec_with_nul(b"a\0bc".to_vec()).unwrap_err();
735 /// let _: FromVecWithNulError = CString::from_vec_with_nul(b"abc".to_vec()).unwrap_err();
737 #[unstable(feature = "cstring_from_vec_with_nul", issue = "73179")]
738 pub fn from_vec_with_nul(v: Vec<u8>) -> Result<Self, FromVecWithNulError> {
739 let nul_pos = memchr::memchr(0, &v);
741 Some(nul_pos) if nul_pos + 1 == v.len() => {
742 // SAFETY: We know there is only one nul byte, at the end
744 Ok(unsafe { Self::from_vec_with_nul_unchecked(v) })
746 Some(nul_pos) => Err(FromVecWithNulError {
747 error_kind: FromBytesWithNulErrorKind::InteriorNul(nul_pos),
750 None => Err(FromVecWithNulError {
751 error_kind: FromBytesWithNulErrorKind::NotNulTerminated,
758 // Turns this `CString` into an empty string to prevent
759 // memory-unsafe code from working by accident. Inline
760 // to prevent LLVM from optimizing it away in debug builds.
761 #[stable(feature = "cstring_drop", since = "1.13.0")]
762 impl Drop for CString {
766 *self.inner.get_unchecked_mut(0) = 0;
771 #[stable(feature = "rust1", since = "1.0.0")]
772 impl ops::Deref for CString {
776 fn deref(&self) -> &CStr {
777 unsafe { CStr::from_bytes_with_nul_unchecked(self.as_bytes_with_nul()) }
781 #[stable(feature = "rust1", since = "1.0.0")]
782 impl fmt::Debug for CString {
783 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
784 fmt::Debug::fmt(&**self, f)
788 #[stable(feature = "cstring_into", since = "1.7.0")]
789 impl From<CString> for Vec<u8> {
790 /// Converts a [`CString`] into a [`Vec`]`<u8>`.
792 /// The conversion consumes the [`CString`], and removes the terminating NUL byte.
794 fn from(s: CString) -> Vec<u8> {
799 #[stable(feature = "cstr_debug", since = "1.3.0")]
800 impl fmt::Debug for CStr {
801 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
803 for byte in self.to_bytes().iter().flat_map(|&b| ascii::escape_default(b)) {
804 f.write_char(byte as char)?;
810 #[stable(feature = "cstr_default", since = "1.10.0")]
811 impl Default for &CStr {
812 fn default() -> Self {
813 const SLICE: &[c_char] = &[0];
814 unsafe { CStr::from_ptr(SLICE.as_ptr()) }
818 #[stable(feature = "cstr_default", since = "1.10.0")]
819 impl Default for CString {
820 /// Creates an empty `CString`.
821 fn default() -> CString {
822 let a: &CStr = Default::default();
827 #[stable(feature = "cstr_borrow", since = "1.3.0")]
828 impl Borrow<CStr> for CString {
830 fn borrow(&self) -> &CStr {
835 #[stable(feature = "cstring_from_cow_cstr", since = "1.28.0")]
836 impl<'a> From<Cow<'a, CStr>> for CString {
838 fn from(s: Cow<'a, CStr>) -> Self {
843 #[stable(feature = "box_from_c_str", since = "1.17.0")]
844 impl From<&CStr> for Box<CStr> {
845 fn from(s: &CStr) -> Box<CStr> {
846 let boxed: Box<[u8]> = Box::from(s.to_bytes_with_nul());
847 unsafe { Box::from_raw(Box::into_raw(boxed) as *mut CStr) }
851 #[stable(feature = "box_from_cow", since = "1.45.0")]
852 impl From<Cow<'_, CStr>> for Box<CStr> {
854 fn from(cow: Cow<'_, CStr>) -> Box<CStr> {
856 Cow::Borrowed(s) => Box::from(s),
857 Cow::Owned(s) => Box::from(s),
862 #[stable(feature = "c_string_from_box", since = "1.18.0")]
863 impl From<Box<CStr>> for CString {
864 /// Converts a [`Box`]`<CStr>` into a [`CString`] without copying or allocating.
866 fn from(s: Box<CStr>) -> CString {
871 #[stable(feature = "cstring_from_vec_of_nonzerou8", since = "1.43.0")]
872 impl From<Vec<NonZeroU8>> for CString {
873 /// Converts a [`Vec`]`<`[`NonZeroU8`]`>` into a [`CString`] without
874 /// copying nor checking for inner null bytes.
876 fn from(v: Vec<NonZeroU8>) -> CString {
878 // Transmute `Vec<NonZeroU8>` to `Vec<u8>`.
881 // - transmuting between `NonZeroU8` and `u8` is sound;
882 // - `alloc::Layout<NonZeroU8> == alloc::Layout<u8>`.
883 let (ptr, len, cap): (*mut NonZeroU8, _, _) = Vec::into_raw_parts(v);
884 Vec::from_raw_parts(ptr.cast::<u8>(), len, cap)
886 // Safety: `v` cannot contain null bytes, given the type-level
887 // invariant of `NonZeroU8`.
888 CString::from_vec_unchecked(v)
893 #[stable(feature = "more_box_slice_clone", since = "1.29.0")]
894 impl Clone for Box<CStr> {
896 fn clone(&self) -> Self {
901 #[stable(feature = "box_from_c_string", since = "1.20.0")]
902 impl From<CString> for Box<CStr> {
903 /// Converts a [`CString`] into a [`Box`]`<CStr>` without copying or allocating.
905 fn from(s: CString) -> Box<CStr> {
910 #[stable(feature = "cow_from_cstr", since = "1.28.0")]
911 impl<'a> From<CString> for Cow<'a, CStr> {
913 fn from(s: CString) -> Cow<'a, CStr> {
918 #[stable(feature = "cow_from_cstr", since = "1.28.0")]
919 impl<'a> From<&'a CStr> for Cow<'a, CStr> {
921 fn from(s: &'a CStr) -> Cow<'a, CStr> {
926 #[stable(feature = "cow_from_cstr", since = "1.28.0")]
927 impl<'a> From<&'a CString> for Cow<'a, CStr> {
929 fn from(s: &'a CString) -> Cow<'a, CStr> {
930 Cow::Borrowed(s.as_c_str())
934 #[stable(feature = "shared_from_slice2", since = "1.24.0")]
935 impl From<CString> for Arc<CStr> {
936 /// Converts a [`CString`] into a [`Arc`]`<CStr>` without copying or allocating.
938 fn from(s: CString) -> Arc<CStr> {
939 let arc: Arc<[u8]> = Arc::from(s.into_inner());
940 unsafe { Arc::from_raw(Arc::into_raw(arc) as *const CStr) }
944 #[stable(feature = "shared_from_slice2", since = "1.24.0")]
945 impl From<&CStr> for Arc<CStr> {
947 fn from(s: &CStr) -> Arc<CStr> {
948 let arc: Arc<[u8]> = Arc::from(s.to_bytes_with_nul());
949 unsafe { Arc::from_raw(Arc::into_raw(arc) as *const CStr) }
953 #[stable(feature = "shared_from_slice2", since = "1.24.0")]
954 impl From<CString> for Rc<CStr> {
955 /// Converts a [`CString`] into a [`Rc`]`<CStr>` without copying or allocating.
957 fn from(s: CString) -> Rc<CStr> {
958 let rc: Rc<[u8]> = Rc::from(s.into_inner());
959 unsafe { Rc::from_raw(Rc::into_raw(rc) as *const CStr) }
963 #[stable(feature = "shared_from_slice2", since = "1.24.0")]
964 impl From<&CStr> for Rc<CStr> {
966 fn from(s: &CStr) -> Rc<CStr> {
967 let rc: Rc<[u8]> = Rc::from(s.to_bytes_with_nul());
968 unsafe { Rc::from_raw(Rc::into_raw(rc) as *const CStr) }
972 #[stable(feature = "default_box_extra", since = "1.17.0")]
973 impl Default for Box<CStr> {
974 fn default() -> Box<CStr> {
975 let boxed: Box<[u8]> = Box::from([0]);
976 unsafe { Box::from_raw(Box::into_raw(boxed) as *mut CStr) }
981 /// Returns the position of the nul byte in the slice that caused
982 /// [`CString::new`] to fail.
987 /// use std::ffi::CString;
989 /// let nul_error = CString::new("foo\0bar").unwrap_err();
990 /// assert_eq!(nul_error.nul_position(), 3);
992 /// let nul_error = CString::new("foo bar\0").unwrap_err();
993 /// assert_eq!(nul_error.nul_position(), 7);
995 #[stable(feature = "rust1", since = "1.0.0")]
996 pub fn nul_position(&self) -> usize {
1000 /// Consumes this error, returning the underlying vector of bytes which
1001 /// generated the error in the first place.
1006 /// use std::ffi::CString;
1008 /// let nul_error = CString::new("foo\0bar").unwrap_err();
1009 /// assert_eq!(nul_error.into_vec(), b"foo\0bar");
1011 #[stable(feature = "rust1", since = "1.0.0")]
1012 pub fn into_vec(self) -> Vec<u8> {
1017 #[stable(feature = "rust1", since = "1.0.0")]
1018 impl Error for NulError {
1019 #[allow(deprecated)]
1020 fn description(&self) -> &str {
1021 "nul byte found in data"
1025 #[stable(feature = "rust1", since = "1.0.0")]
1026 impl fmt::Display for NulError {
1027 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1028 write!(f, "nul byte found in provided data at position: {}", self.0)
1032 #[stable(feature = "rust1", since = "1.0.0")]
1033 impl From<NulError> for io::Error {
1034 /// Converts a [`NulError`] into a [`io::Error`].
1035 fn from(_: NulError) -> io::Error {
1036 io::Error::new(io::ErrorKind::InvalidInput, "data provided contains a nul byte")
1040 #[stable(feature = "frombyteswithnulerror_impls", since = "1.17.0")]
1041 impl Error for FromBytesWithNulError {
1042 #[allow(deprecated)]
1043 fn description(&self) -> &str {
1045 FromBytesWithNulErrorKind::InteriorNul(..) => {
1046 "data provided contains an interior nul byte"
1048 FromBytesWithNulErrorKind::NotNulTerminated => "data provided is not nul terminated",
1053 #[stable(feature = "frombyteswithnulerror_impls", since = "1.17.0")]
1054 impl fmt::Display for FromBytesWithNulError {
1055 #[allow(deprecated, deprecated_in_future)]
1056 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1057 f.write_str(self.description())?;
1058 if let FromBytesWithNulErrorKind::InteriorNul(pos) = self.kind {
1059 write!(f, " at byte pos {}", pos)?;
1065 #[unstable(feature = "cstring_from_vec_with_nul", issue = "73179")]
1066 impl Error for FromVecWithNulError {}
1068 #[unstable(feature = "cstring_from_vec_with_nul", issue = "73179")]
1069 impl fmt::Display for FromVecWithNulError {
1070 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1071 match self.error_kind {
1072 FromBytesWithNulErrorKind::InteriorNul(pos) => {
1073 write!(f, "data provided contains an interior nul byte at pos {}", pos)
1075 FromBytesWithNulErrorKind::NotNulTerminated => {
1076 write!(f, "data provided is not nul terminated")
1082 impl IntoStringError {
1083 /// Consumes this error, returning original [`CString`] which generated the
1085 #[stable(feature = "cstring_into", since = "1.7.0")]
1086 pub fn into_cstring(self) -> CString {
1090 /// Access the underlying UTF-8 error that was the cause of this error.
1091 #[stable(feature = "cstring_into", since = "1.7.0")]
1092 pub fn utf8_error(&self) -> Utf8Error {
1097 #[stable(feature = "cstring_into", since = "1.7.0")]
1098 impl Error for IntoStringError {
1099 #[allow(deprecated)]
1100 fn description(&self) -> &str {
1101 "C string contained non-utf8 bytes"
1104 fn source(&self) -> Option<&(dyn Error + 'static)> {
1109 #[stable(feature = "cstring_into", since = "1.7.0")]
1110 impl fmt::Display for IntoStringError {
1111 #[allow(deprecated, deprecated_in_future)]
1112 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1113 self.description().fmt(f)
1118 /// Wraps a raw C string with a safe C string wrapper.
1120 /// This function will wrap the provided `ptr` with a `CStr` wrapper, which
1121 /// allows inspection and interoperation of non-owned C strings. The total
1122 /// size of the raw C string must be smaller than `isize::MAX` **bytes**
1123 /// in memory due to calling the `slice::from_raw_parts` function.
1124 /// This method is unsafe for a number of reasons:
1126 /// * There is no guarantee to the validity of `ptr`.
1127 /// * The returned lifetime is not guaranteed to be the actual lifetime of
1129 /// * There is no guarantee that the memory pointed to by `ptr` contains a
1130 /// valid nul terminator byte at the end of the string.
1131 /// * It is not guaranteed that the memory pointed by `ptr` won't change
1132 /// before the `CStr` has been destroyed.
1134 /// > **Note**: This operation is intended to be a 0-cost cast but it is
1135 /// > currently implemented with an up-front calculation of the length of
1136 /// > the string. This is not guaranteed to always be the case.
1140 /// ```ignore (extern-declaration)
1142 /// use std::ffi::CStr;
1143 /// use std::os::raw::c_char;
1146 /// fn my_string() -> *const c_char;
1150 /// let slice = CStr::from_ptr(my_string());
1151 /// println!("string returned: {}", slice.to_str().unwrap());
1155 #[stable(feature = "rust1", since = "1.0.0")]
1156 pub unsafe fn from_ptr<'a>(ptr: *const c_char) -> &'a CStr {
1157 // SAFETY: The caller has provided a pointer that points to a valid C
1158 // string with a NUL terminator of size less than `isize::MAX`, whose
1159 // content remain valid and doesn't change for the lifetime of the
1162 // Thus computing the length is fine (a NUL byte exists), the call to
1163 // from_raw_parts is safe because we know the length is at most `isize::MAX`, meaning
1164 // the call to `from_bytes_with_nul_unchecked` is correct.
1166 // The cast from c_char to u8 is ok because a c_char is always one byte.
1168 let len = sys::strlen(ptr);
1169 let ptr = ptr as *const u8;
1170 CStr::from_bytes_with_nul_unchecked(slice::from_raw_parts(ptr, len as usize + 1))
1174 /// Creates a C string wrapper from a byte slice.
1176 /// This function will cast the provided `bytes` to a `CStr`
1177 /// wrapper after ensuring that the byte slice is nul-terminated
1178 /// and does not contain any interior nul bytes.
1183 /// use std::ffi::CStr;
1185 /// let cstr = CStr::from_bytes_with_nul(b"hello\0");
1186 /// assert!(cstr.is_ok());
1189 /// Creating a `CStr` without a trailing nul terminator is an error:
1192 /// use std::ffi::CStr;
1194 /// let cstr = CStr::from_bytes_with_nul(b"hello");
1195 /// assert!(cstr.is_err());
1198 /// Creating a `CStr` with an interior nul byte is an error:
1201 /// use std::ffi::CStr;
1203 /// let cstr = CStr::from_bytes_with_nul(b"he\0llo\0");
1204 /// assert!(cstr.is_err());
1206 #[stable(feature = "cstr_from_bytes", since = "1.10.0")]
1207 pub fn from_bytes_with_nul(bytes: &[u8]) -> Result<&CStr, FromBytesWithNulError> {
1208 let nul_pos = memchr::memchr(0, bytes);
1209 if let Some(nul_pos) = nul_pos {
1210 if nul_pos + 1 != bytes.len() {
1211 return Err(FromBytesWithNulError::interior_nul(nul_pos));
1213 Ok(unsafe { CStr::from_bytes_with_nul_unchecked(bytes) })
1215 Err(FromBytesWithNulError::not_nul_terminated())
1219 /// Unsafely creates a C string wrapper from a byte slice.
1221 /// This function will cast the provided `bytes` to a `CStr` wrapper without
1222 /// performing any sanity checks. The provided slice **must** be nul-terminated
1223 /// and not contain any interior nul bytes.
1228 /// use std::ffi::{CStr, CString};
1231 /// let cstring = CString::new("hello").expect("CString::new failed");
1232 /// let cstr = CStr::from_bytes_with_nul_unchecked(cstring.to_bytes_with_nul());
1233 /// assert_eq!(cstr, &*cstring);
1237 #[stable(feature = "cstr_from_bytes", since = "1.10.0")]
1238 #[rustc_const_unstable(feature = "const_cstr_unchecked", issue = "none")]
1239 pub const unsafe fn from_bytes_with_nul_unchecked(bytes: &[u8]) -> &CStr {
1240 // SAFETY: Casting to CStr is safe because its internal representation
1241 // is a [u8] too (safe only inside std).
1242 // Dereferencing the obtained pointer is safe because it comes from a
1243 // reference. Making a reference is then safe because its lifetime
1244 // is bound by the lifetime of the given `bytes`.
1245 unsafe { &*(bytes as *const [u8] as *const CStr) }
1248 /// Returns the inner pointer to this C string.
1250 /// The returned pointer will be valid for as long as `self` is, and points
1251 /// to a contiguous region of memory terminated with a 0 byte to represent
1252 /// the end of the string.
1256 /// The returned pointer is read-only; writing to it (including passing it
1257 /// to C code that writes to it) causes undefined behavior.
1259 /// It is your responsibility to make sure that the underlying memory is not
1260 /// freed too early. For example, the following code will cause undefined
1261 /// behavior when `ptr` is used inside the `unsafe` block:
1264 /// # #![allow(unused_must_use)]
1265 /// use std::ffi::CString;
1267 /// let ptr = CString::new("Hello").expect("CString::new failed").as_ptr();
1269 /// // `ptr` is dangling
1274 /// This happens because the pointer returned by `as_ptr` does not carry any
1275 /// lifetime information and the [`CString`] is deallocated immediately after
1276 /// the `CString::new("Hello").expect("CString::new failed").as_ptr()`
1277 /// expression is evaluated.
1278 /// To fix the problem, bind the `CString` to a local variable:
1281 /// # #![allow(unused_must_use)]
1282 /// use std::ffi::CString;
1284 /// let hello = CString::new("Hello").expect("CString::new failed");
1285 /// let ptr = hello.as_ptr();
1287 /// // `ptr` is valid because `hello` is in scope
1292 /// This way, the lifetime of the [`CString`] in `hello` encompasses
1293 /// the lifetime of `ptr` and the `unsafe` block.
1295 #[stable(feature = "rust1", since = "1.0.0")]
1296 #[rustc_const_stable(feature = "const_str_as_ptr", since = "1.32.0")]
1297 pub const fn as_ptr(&self) -> *const c_char {
1301 /// Converts this C string to a byte slice.
1303 /// The returned slice will **not** contain the trailing nul terminator that this C
1306 /// > **Note**: This method is currently implemented as a constant-time
1307 /// > cast, but it is planned to alter its definition in the future to
1308 /// > perform the length calculation whenever this method is called.
1313 /// use std::ffi::CStr;
1315 /// let cstr = CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed");
1316 /// assert_eq!(cstr.to_bytes(), b"foo");
1319 #[stable(feature = "rust1", since = "1.0.0")]
1320 pub fn to_bytes(&self) -> &[u8] {
1321 let bytes = self.to_bytes_with_nul();
1322 &bytes[..bytes.len() - 1]
1325 /// Converts this C string to a byte slice containing the trailing 0 byte.
1327 /// This function is the equivalent of [`CStr::to_bytes`] except that it
1328 /// will retain the trailing nul terminator instead of chopping it off.
1330 /// > **Note**: This method is currently implemented as a 0-cost cast, but
1331 /// > it is planned to alter its definition in the future to perform the
1332 /// > length calculation whenever this method is called.
1337 /// use std::ffi::CStr;
1339 /// let cstr = CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed");
1340 /// assert_eq!(cstr.to_bytes_with_nul(), b"foo\0");
1343 #[stable(feature = "rust1", since = "1.0.0")]
1344 pub fn to_bytes_with_nul(&self) -> &[u8] {
1345 unsafe { &*(&self.inner as *const [c_char] as *const [u8]) }
1348 /// Yields a [`&str`] slice if the `CStr` contains valid UTF-8.
1350 /// If the contents of the `CStr` are valid UTF-8 data, this
1351 /// function will return the corresponding [`&str`] slice. Otherwise,
1352 /// it will return an error with details of where UTF-8 validation failed.
1359 /// use std::ffi::CStr;
1361 /// let cstr = CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed");
1362 /// assert_eq!(cstr.to_str(), Ok("foo"));
1364 #[stable(feature = "cstr_to_str", since = "1.4.0")]
1365 pub fn to_str(&self) -> Result<&str, str::Utf8Error> {
1366 // N.B., when `CStr` is changed to perform the length check in `.to_bytes()`
1367 // instead of in `from_ptr()`, it may be worth considering if this should
1368 // be rewritten to do the UTF-8 check inline with the length calculation
1369 // instead of doing it afterwards.
1370 str::from_utf8(self.to_bytes())
1373 /// Converts a `CStr` into a [`Cow`]`<`[`str`]`>`.
1375 /// If the contents of the `CStr` are valid UTF-8 data, this
1376 /// function will return a [`Cow`]`::`[`Borrowed`]`(`[`&str`]`)`
1377 /// with the corresponding [`&str`] slice. Otherwise, it will
1378 /// replace any invalid UTF-8 sequences with
1379 /// [`U+FFFD REPLACEMENT CHARACTER`][U+FFFD] and return a
1380 /// [`Cow`]`::`[`Owned`]`(`[`String`]`)` with the result.
1382 /// [`Borrowed`]: Cow::Borrowed
1383 /// [`Owned`]: Cow::Owned
1384 /// [U+FFFD]: crate::char::REPLACEMENT_CHARACTER
1388 /// Calling `to_string_lossy` on a `CStr` containing valid UTF-8:
1391 /// use std::borrow::Cow;
1392 /// use std::ffi::CStr;
1394 /// let cstr = CStr::from_bytes_with_nul(b"Hello World\0")
1395 /// .expect("CStr::from_bytes_with_nul failed");
1396 /// assert_eq!(cstr.to_string_lossy(), Cow::Borrowed("Hello World"));
1399 /// Calling `to_string_lossy` on a `CStr` containing invalid UTF-8:
1402 /// use std::borrow::Cow;
1403 /// use std::ffi::CStr;
1405 /// let cstr = CStr::from_bytes_with_nul(b"Hello \xF0\x90\x80World\0")
1406 /// .expect("CStr::from_bytes_with_nul failed");
1408 /// cstr.to_string_lossy(),
1409 /// Cow::Owned(String::from("Hello �World")) as Cow<'_, str>
1412 #[stable(feature = "cstr_to_str", since = "1.4.0")]
1413 pub fn to_string_lossy(&self) -> Cow<'_, str> {
1414 String::from_utf8_lossy(self.to_bytes())
1417 /// Converts a [`Box`]`<CStr>` into a [`CString`] without copying or allocating.
1422 /// use std::ffi::CString;
1424 /// let c_string = CString::new(b"foo".to_vec()).expect("CString::new failed");
1425 /// let boxed = c_string.into_boxed_c_str();
1426 /// assert_eq!(boxed.into_c_string(), CString::new("foo").expect("CString::new failed"));
1428 #[stable(feature = "into_boxed_c_str", since = "1.20.0")]
1429 pub fn into_c_string(self: Box<CStr>) -> CString {
1430 let raw = Box::into_raw(self) as *mut [u8];
1431 CString { inner: unsafe { Box::from_raw(raw) } }
1435 #[stable(feature = "rust1", since = "1.0.0")]
1436 impl PartialEq for CStr {
1437 fn eq(&self, other: &CStr) -> bool {
1438 self.to_bytes().eq(other.to_bytes())
1441 #[stable(feature = "rust1", since = "1.0.0")]
1443 #[stable(feature = "rust1", since = "1.0.0")]
1444 impl PartialOrd for CStr {
1445 fn partial_cmp(&self, other: &CStr) -> Option<Ordering> {
1446 self.to_bytes().partial_cmp(&other.to_bytes())
1449 #[stable(feature = "rust1", since = "1.0.0")]
1451 fn cmp(&self, other: &CStr) -> Ordering {
1452 self.to_bytes().cmp(&other.to_bytes())
1456 #[stable(feature = "cstr_borrow", since = "1.3.0")]
1457 impl ToOwned for CStr {
1458 type Owned = CString;
1460 fn to_owned(&self) -> CString {
1461 CString { inner: self.to_bytes_with_nul().into() }
1464 fn clone_into(&self, target: &mut CString) {
1465 let mut b = Vec::from(mem::take(&mut target.inner));
1466 self.to_bytes_with_nul().clone_into(&mut b);
1467 target.inner = b.into_boxed_slice();
1471 #[stable(feature = "cstring_asref", since = "1.7.0")]
1472 impl From<&CStr> for CString {
1473 fn from(s: &CStr) -> CString {
1478 #[stable(feature = "cstring_asref", since = "1.7.0")]
1479 impl ops::Index<ops::RangeFull> for CString {
1483 fn index(&self, _index: ops::RangeFull) -> &CStr {
1488 #[stable(feature = "cstr_range_from", since = "1.47.0")]
1489 impl ops::Index<ops::RangeFrom<usize>> for CStr {
1492 fn index(&self, index: ops::RangeFrom<usize>) -> &CStr {
1493 let bytes = self.to_bytes_with_nul();
1494 // we need to manually check the starting index to account for the null
1495 // byte, since otherwise we could get an empty string that doesn't end
1497 if index.start < bytes.len() {
1498 unsafe { CStr::from_bytes_with_nul_unchecked(&bytes[index.start..]) }
1501 "index out of bounds: the len is {} but the index is {}",
1509 #[stable(feature = "cstring_asref", since = "1.7.0")]
1510 impl AsRef<CStr> for CStr {
1512 fn as_ref(&self) -> &CStr {
1517 #[stable(feature = "cstring_asref", since = "1.7.0")]
1518 impl AsRef<CStr> for CString {
1520 fn as_ref(&self) -> &CStr {
1528 use crate::borrow::Cow::{Borrowed, Owned};
1529 use crate::collections::hash_map::DefaultHasher;
1530 use crate::hash::{Hash, Hasher};
1531 use crate::os::raw::c_char;
1533 use crate::sync::Arc;
1537 let data = b"123\0";
1538 let ptr = data.as_ptr() as *const c_char;
1540 assert_eq!(CStr::from_ptr(ptr).to_bytes(), b"123");
1541 assert_eq!(CStr::from_ptr(ptr).to_bytes_with_nul(), b"123\0");
1547 let s = CString::new("1234").unwrap();
1548 assert_eq!(s.as_bytes(), b"1234");
1549 assert_eq!(s.as_bytes_with_nul(), b"1234\0");
1553 fn build_with_zero1() {
1554 assert!(CString::new(&b"\0"[..]).is_err());
1557 fn build_with_zero2() {
1558 assert!(CString::new(vec![0]).is_err());
1562 fn build_with_zero3() {
1564 let s = CString::from_vec_unchecked(vec![0]);
1565 assert_eq!(s.as_bytes(), b"\0");
1571 let s = CString::new(&b"abc\x01\x02\n\xE2\x80\xA6\xFF"[..]).unwrap();
1572 assert_eq!(format!("{:?}", s), r#""abc\x01\x02\n\xe2\x80\xa6\xff""#);
1578 let s = CStr::from_ptr(b"12\0".as_ptr() as *const _);
1579 assert_eq!(s.to_bytes(), b"12");
1580 assert_eq!(s.to_bytes_with_nul(), b"12\0");
1586 let data = b"123\xE2\x80\xA6\0";
1587 let ptr = data.as_ptr() as *const c_char;
1589 assert_eq!(CStr::from_ptr(ptr).to_str(), Ok("123…"));
1590 assert_eq!(CStr::from_ptr(ptr).to_string_lossy(), Borrowed("123…"));
1592 let data = b"123\xE2\0";
1593 let ptr = data.as_ptr() as *const c_char;
1595 assert!(CStr::from_ptr(ptr).to_str().is_err());
1596 assert_eq!(CStr::from_ptr(ptr).to_string_lossy(), Owned::<str>(format!("123\u{FFFD}")));
1602 let data = b"123\0";
1603 let ptr = data.as_ptr() as *const c_char;
1605 let owned = unsafe { CStr::from_ptr(ptr).to_owned() };
1606 assert_eq!(owned.as_bytes_with_nul(), data);
1611 let data = b"123\xE2\xFA\xA6\0";
1612 let ptr = data.as_ptr() as *const c_char;
1613 let cstr: &'static CStr = unsafe { CStr::from_ptr(ptr) };
1615 let mut s = DefaultHasher::new();
1617 let cstr_hash = s.finish();
1618 let mut s = DefaultHasher::new();
1619 CString::new(&data[..data.len() - 1]).unwrap().hash(&mut s);
1620 let cstring_hash = s.finish();
1622 assert_eq!(cstr_hash, cstring_hash);
1626 fn from_bytes_with_nul() {
1627 let data = b"123\0";
1628 let cstr = CStr::from_bytes_with_nul(data);
1629 assert_eq!(cstr.map(CStr::to_bytes), Ok(&b"123"[..]));
1630 let cstr = CStr::from_bytes_with_nul(data);
1631 assert_eq!(cstr.map(CStr::to_bytes_with_nul), Ok(&b"123\0"[..]));
1634 let cstr = CStr::from_bytes_with_nul(data);
1635 let cstr_unchecked = CStr::from_bytes_with_nul_unchecked(data);
1636 assert_eq!(cstr, Ok(cstr_unchecked));
1641 fn from_bytes_with_nul_unterminated() {
1643 let cstr = CStr::from_bytes_with_nul(data);
1644 assert!(cstr.is_err());
1648 fn from_bytes_with_nul_interior() {
1649 let data = b"1\023\0";
1650 let cstr = CStr::from_bytes_with_nul(data);
1651 assert!(cstr.is_err());
1656 let orig: &[u8] = b"Hello, world!\0";
1657 let cstr = CStr::from_bytes_with_nul(orig).unwrap();
1658 let boxed: Box<CStr> = Box::from(cstr);
1659 let cstring = cstr.to_owned().into_boxed_c_str().into_c_string();
1660 assert_eq!(cstr, &*boxed);
1661 assert_eq!(&*boxed, &*cstring);
1662 assert_eq!(&*cstring, cstr);
1666 fn boxed_default() {
1667 let boxed = <Box<CStr>>::default();
1668 assert_eq!(boxed.to_bytes_with_nul(), &[0]);
1672 fn test_c_str_clone_into() {
1673 let mut c_string = CString::new("lorem").unwrap();
1674 let c_ptr = c_string.as_ptr();
1675 let c_str = CStr::from_bytes_with_nul(b"ipsum\0").unwrap();
1676 c_str.clone_into(&mut c_string);
1677 assert_eq!(c_str, c_string.as_c_str());
1678 // The exact same size shouldn't have needed to move its allocation
1679 assert_eq!(c_ptr, c_string.as_ptr());
1684 let orig: &[u8] = b"Hello, world!\0";
1685 let cstr = CStr::from_bytes_with_nul(orig).unwrap();
1686 let rc: Rc<CStr> = Rc::from(cstr);
1687 let arc: Arc<CStr> = Arc::from(cstr);
1689 assert_eq!(&*rc, cstr);
1690 assert_eq!(&*arc, cstr);
1692 let rc2: Rc<CStr> = Rc::from(cstr.to_owned());
1693 let arc2: Arc<CStr> = Arc::from(cstr.to_owned());
1695 assert_eq!(&*rc2, cstr);
1696 assert_eq!(&*arc2, cstr);
1700 fn cstr_const_constructor() {
1701 const CSTR: &CStr = unsafe { CStr::from_bytes_with_nul_unchecked(b"Hello, world!\0") };
1703 assert_eq!(CSTR.to_str().unwrap(), "Hello, world!");
1707 fn cstr_index_from() {
1708 let original = b"Hello, world!\0";
1709 let cstr = CStr::from_bytes_with_nul(original).unwrap();
1710 let result = CStr::from_bytes_with_nul(&original[7..]).unwrap();
1712 assert_eq!(&cstr[7..], result);
1717 fn cstr_index_from_empty() {
1718 let original = b"Hello, world!\0";
1719 let cstr = CStr::from_bytes_with_nul(original).unwrap();
1720 let _ = &cstr[original.len()..];