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 [`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`] 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`] 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 [`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 [`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.
72 /// [`Into`]: ../convert/trait.Into.html
73 /// [`Vec`]: ../vec/struct.Vec.html
74 /// [`String`]: ../string/struct.String.html
75 /// [`&str`]: ../primitive.str.html
76 /// [`u8`]: ../primitive.u8.html
77 /// [`new`]: #method.new
78 /// [`as_bytes`]: #method.as_bytes
79 /// [`as_bytes_with_nul`]: #method.as_bytes_with_nul
80 /// [`as_ptr`]: #method.as_ptr
81 /// [slice.as_ptr]: ../primitive.slice.html#method.as_ptr
82 /// [slice.len]: ../primitive.slice.html#method.len
83 /// [`Deref`]: ../ops/trait.Deref.html
84 /// [`CStr`]: struct.CStr.html
85 /// [`&CStr`]: struct.CStr.html
89 /// ```ignore (extern-declaration)
91 /// use std::ffi::CString;
92 /// use std::os::raw::c_char;
95 /// fn my_printer(s: *const c_char);
98 /// // We are certain that our string doesn't have 0 bytes in the middle,
99 /// // so we can .expect()
100 /// let c_to_print = CString::new("Hello, world!").expect("CString::new failed");
102 /// my_printer(c_to_print.as_ptr());
109 /// `CString` is intended for working with traditional C-style strings
110 /// (a sequence of non-nul bytes terminated by a single nul byte); the
111 /// primary use case for these kinds of strings is interoperating with C-like
112 /// code. Often you will need to transfer ownership to/from that external
113 /// code. It is strongly recommended that you thoroughly read through the
114 /// documentation of `CString` before use, as improper ownership management
115 /// of `CString` instances can lead to invalid memory accesses, memory leaks,
116 /// and other memory errors.
118 #[derive(PartialEq, PartialOrd, Eq, Ord, Hash, Clone)]
119 #[stable(feature = "rust1", since = "1.0.0")]
121 // Invariant 1: the slice ends with a zero byte and has a length of at least one.
122 // Invariant 2: the slice contains only one zero byte.
123 // Improper usage of unsafe function can break Invariant 2, but not Invariant 1.
127 /// Representation of a borrowed C string.
129 /// This type represents a borrowed reference to a nul-terminated
130 /// array of bytes. It can be constructed safely from a `&[`[`u8`]`]`
131 /// slice, or unsafely from a raw `*const c_char`. It can then be
132 /// converted to a Rust [`&str`] by performing UTF-8 validation, or
133 /// into an owned [`CString`].
135 /// `&CStr` is to [`CString`] as [`&str`] is to [`String`]: the former
136 /// in each pair are borrowed references; the latter are owned
139 /// Note that this structure is **not** `repr(C)` and is not recommended to be
140 /// placed in the signatures of FFI functions. Instead, safe wrappers of FFI
141 /// functions may leverage the unsafe [`from_ptr`] constructor to provide a safe
142 /// interface to other consumers.
146 /// Inspecting a foreign C string:
148 /// ```ignore (extern-declaration)
149 /// use std::ffi::CStr;
150 /// use std::os::raw::c_char;
152 /// extern { fn my_string() -> *const c_char; }
155 /// let slice = CStr::from_ptr(my_string());
156 /// println!("string buffer size without nul terminator: {}", slice.to_bytes().len());
160 /// Passing a Rust-originating C string:
162 /// ```ignore (extern-declaration)
163 /// use std::ffi::{CString, CStr};
164 /// use std::os::raw::c_char;
166 /// fn work(data: &CStr) {
167 /// extern { fn work_with(data: *const c_char); }
169 /// unsafe { work_with(data.as_ptr()) }
172 /// let s = CString::new("data data data data").expect("CString::new failed");
176 /// Converting a foreign C string into a Rust [`String`]:
178 /// ```ignore (extern-declaration)
179 /// use std::ffi::CStr;
180 /// use std::os::raw::c_char;
182 /// extern { fn my_string() -> *const c_char; }
184 /// fn my_string_safe() -> String {
186 /// CStr::from_ptr(my_string()).to_string_lossy().into_owned()
190 /// println!("string: {}", my_string_safe());
193 /// [`u8`]: ../primitive.u8.html
194 /// [`&str`]: ../primitive.str.html
195 /// [`String`]: ../string/struct.String.html
196 /// [`CString`]: struct.CString.html
197 /// [`from_ptr`]: #method.from_ptr
199 #[stable(feature = "rust1", since = "1.0.0")]
201 // `fn from` in `impl From<&CStr> for Box<CStr>` current implementation relies
202 // on `CStr` being layout-compatible with `[u8]`.
203 // When attribute privacy is implemented, `CStr` should be annotated as `#[repr(transparent)]`.
204 // Anyway, `CStr` representation and layout are considered implementation detail, are
205 // not documented and must not be relied upon.
207 // FIXME: this should not be represented with a DST slice but rather with
208 // just a raw `c_char` along with some form of marker to make
209 // this an unsized type. Essentially `sizeof(&CStr)` should be the
210 // same as `sizeof(&c_char)` but `CStr` should be an unsized type.
214 /// An error indicating that an interior nul byte was found.
216 /// While Rust strings may contain nul bytes in the middle, C strings
217 /// can't, as that byte would effectively truncate the string.
219 /// This error is created by the [`new`][`CString::new`] method on
220 /// [`CString`]. See its documentation for more.
222 /// [`CString`]: struct.CString.html
223 /// [`CString::new`]: struct.CString.html#method.new
228 /// use std::ffi::{CString, NulError};
230 /// let _: NulError = CString::new(b"f\0oo".to_vec()).unwrap_err();
232 #[derive(Clone, PartialEq, Eq, Debug)]
233 #[stable(feature = "rust1", since = "1.0.0")]
234 pub struct NulError(usize, Vec<u8>);
236 /// An error indicating that a nul byte was not in the expected position.
238 /// The slice used to create a [`CStr`] must have one and only one nul byte,
239 /// positioned at the end.
241 /// This error is created by the [`from_bytes_with_nul`] method on [`CStr`].
242 /// See its documentation for more.
244 /// [`CStr`]: struct.CStr.html
245 /// [`from_bytes_with_nul`]: struct.CStr.html#method.from_bytes_with_nul
250 /// use std::ffi::{CStr, FromBytesWithNulError};
252 /// let _: FromBytesWithNulError = CStr::from_bytes_with_nul(b"f\0oo").unwrap_err();
254 #[derive(Clone, PartialEq, Eq, Debug)]
255 #[stable(feature = "cstr_from_bytes", since = "1.10.0")]
256 pub struct FromBytesWithNulError {
257 kind: FromBytesWithNulErrorKind,
260 /// An error indicating that a nul byte was not in the expected position.
262 /// The vector used to create a [`CString`] must have one and only one nul byte,
263 /// positioned at the end.
265 /// This error is created by the [`from_vec_with_nul`] method on [`CString`].
266 /// See its documentation for more.
268 /// [`CString`]: struct.CString.html
269 /// [`from_vec_with_nul`]: struct.CString.html#method.from_vec_with_nul
274 /// #![feature(cstring_from_vec_with_nul)]
275 /// use std::ffi::{CString, FromVecWithNulError};
277 /// let _: FromVecWithNulError = CString::from_vec_with_nul(b"f\0oo".to_vec()).unwrap_err();
279 #[derive(Clone, PartialEq, Eq, Debug)]
280 #[unstable(feature = "cstring_from_vec_with_nul", issue = "73179")]
281 pub struct FromVecWithNulError {
282 error_kind: FromBytesWithNulErrorKind,
286 #[derive(Clone, PartialEq, Eq, Debug)]
287 enum FromBytesWithNulErrorKind {
292 impl FromBytesWithNulError {
293 fn interior_nul(pos: usize) -> FromBytesWithNulError {
294 FromBytesWithNulError { kind: FromBytesWithNulErrorKind::InteriorNul(pos) }
296 fn not_nul_terminated() -> FromBytesWithNulError {
297 FromBytesWithNulError { kind: FromBytesWithNulErrorKind::NotNulTerminated }
301 #[unstable(feature = "cstring_from_vec_with_nul", issue = "73179")]
302 impl FromVecWithNulError {
303 /// Returns a slice of [`u8`]s bytes that were attempted to convert to a [`CString`].
310 /// #![feature(cstring_from_vec_with_nul)]
311 /// use std::ffi::CString;
313 /// // Some invalid bytes in a vector
314 /// let bytes = b"f\0oo".to_vec();
316 /// let value = CString::from_vec_with_nul(bytes.clone());
318 /// assert_eq!(&bytes[..], value.unwrap_err().as_bytes());
321 /// [`CString`]: struct.CString.html
322 pub fn as_bytes(&self) -> &[u8] {
326 /// Returns the bytes that were attempted to convert to a [`CString`].
328 /// This method is carefully constructed to avoid allocation. It will
329 /// consume the error, moving out the bytes, so that a copy of the bytes
330 /// does not need to be made.
337 /// #![feature(cstring_from_vec_with_nul)]
338 /// use std::ffi::CString;
340 /// // Some invalid bytes in a vector
341 /// let bytes = b"f\0oo".to_vec();
343 /// let value = CString::from_vec_with_nul(bytes.clone());
345 /// assert_eq!(bytes, value.unwrap_err().into_bytes());
348 /// [`CString`]: struct.CString.html
349 pub fn into_bytes(self) -> Vec<u8> {
354 /// An error indicating invalid UTF-8 when converting a [`CString`] into a [`String`].
356 /// `CString` is just a wrapper over a buffer of bytes with a nul
357 /// terminator; [`into_string`][`CString::into_string`] performs UTF-8
358 /// validation on those bytes and may return this error.
360 /// This `struct` is created by the
361 /// [`into_string`][`CString::into_string`] method on [`CString`]. See
362 /// its documentation for more.
364 /// [`String`]: ../string/struct.String.html
365 /// [`CString`]: struct.CString.html
366 /// [`CString::into_string`]: struct.CString.html#method.into_string
367 #[derive(Clone, PartialEq, Eq, Debug)]
368 #[stable(feature = "cstring_into", since = "1.7.0")]
369 pub struct IntoStringError {
375 /// Creates a new C-compatible string from a container of bytes.
377 /// This function will consume the provided data and use the
378 /// underlying bytes to construct a new string, ensuring that
379 /// there is a trailing 0 byte. This trailing 0 byte will be
380 /// appended by this function; the provided data should *not*
381 /// contain any 0 bytes in it.
385 /// ```ignore (extern-declaration)
386 /// use std::ffi::CString;
387 /// use std::os::raw::c_char;
389 /// extern { fn puts(s: *const c_char); }
391 /// let to_print = CString::new("Hello!").expect("CString::new failed");
393 /// puts(to_print.as_ptr());
399 /// This function will return an error if the supplied bytes contain an
400 /// internal 0 byte. The [`NulError`] returned will contain the bytes as well as
401 /// the position of the nul byte.
403 /// [`NulError`]: struct.NulError.html
404 #[stable(feature = "rust1", since = "1.0.0")]
405 pub fn new<T: Into<Vec<u8>>>(t: T) -> Result<CString, NulError> {
407 fn into_vec(self) -> Vec<u8>;
409 impl<T: Into<Vec<u8>>> SpecIntoVec for T {
410 default fn into_vec(self) -> Vec<u8> {
414 // Specialization for avoiding reallocation.
415 impl SpecIntoVec for &'_ [u8] {
416 fn into_vec(self) -> Vec<u8> {
417 let mut v = Vec::with_capacity(self.len() + 1);
422 impl SpecIntoVec for &'_ str {
423 fn into_vec(self) -> Vec<u8> {
424 let mut v = Vec::with_capacity(self.len() + 1);
425 v.extend(self.as_bytes());
430 Self::_new(SpecIntoVec::into_vec(t))
433 fn _new(bytes: Vec<u8>) -> Result<CString, NulError> {
434 match memchr::memchr(0, &bytes) {
435 Some(i) => Err(NulError(i, bytes)),
436 None => Ok(unsafe { CString::from_vec_unchecked(bytes) }),
440 /// Creates a C-compatible string by consuming a byte vector,
441 /// without checking for interior 0 bytes.
443 /// This method is equivalent to [`new`] except that no runtime assertion
444 /// is made that `v` contains no 0 bytes, and it requires an actual
445 /// byte vector, not anything that can be converted to one with Into.
447 /// [`new`]: #method.new
452 /// use std::ffi::CString;
454 /// let raw = b"foo".to_vec();
456 /// let c_string = CString::from_vec_unchecked(raw);
459 #[stable(feature = "rust1", since = "1.0.0")]
460 pub unsafe fn from_vec_unchecked(mut v: Vec<u8>) -> CString {
463 CString { inner: v.into_boxed_slice() }
466 /// Retakes ownership of a `CString` that was transferred to C via [`into_raw`].
468 /// Additionally, the length of the string will be recalculated from the pointer.
472 /// This should only ever be called with a pointer that was earlier
473 /// obtained by calling [`into_raw`] on a `CString`. Other usage (e.g., trying to take
474 /// ownership of a string that was allocated by foreign code) is likely to lead
475 /// to undefined behavior or allocator corruption.
477 /// It should be noted that the length isn't just "recomputed," but that
478 /// the recomputed length must match the original length from the
479 /// [`into_raw`] call. This means the [`into_raw`]/`from_raw` methods
480 /// should not be used when passing the string to C functions that can
481 /// modify the string's length.
483 /// > **Note:** If you need to borrow a string that was allocated by
484 /// > foreign code, use [`CStr`]. If you need to take ownership of
485 /// > a string that was allocated by foreign code, you will need to
486 /// > make your own provisions for freeing it appropriately, likely
487 /// > with the foreign code's API to do that.
489 /// [`into_raw`]: #method.into_raw
490 /// [`CStr`]: struct.CStr.html
494 /// Creates a `CString`, pass ownership to an `extern` function (via raw pointer), then retake
495 /// ownership with `from_raw`:
497 /// ```ignore (extern-declaration)
498 /// use std::ffi::CString;
499 /// use std::os::raw::c_char;
502 /// fn some_extern_function(s: *mut c_char);
505 /// let c_string = CString::new("Hello!").expect("CString::new failed");
506 /// let raw = c_string.into_raw();
508 /// some_extern_function(raw);
509 /// let c_string = CString::from_raw(raw);
512 #[stable(feature = "cstr_memory", since = "1.4.0")]
513 pub unsafe fn from_raw(ptr: *mut c_char) -> CString {
514 // SAFETY: This is called with a pointer that was obtained from a call
515 // to `CString::into_raw` and the length has not been modified. As such,
516 // we know there is a NUL byte (and only one) at the end and that the
517 // information about the size of the allocation is correct on Rust's
520 let len = sys::strlen(ptr) + 1; // Including the NUL byte
521 let slice = slice::from_raw_parts_mut(ptr, len as usize);
522 CString { inner: Box::from_raw(slice as *mut [c_char] as *mut [u8]) }
526 /// Consumes the `CString` and transfers ownership of the string to a C caller.
528 /// The pointer which this function returns must be returned to Rust and reconstituted using
529 /// [`from_raw`] to be properly deallocated. Specifically, one
530 /// should *not* use the standard C `free()` function to deallocate
533 /// Failure to call [`from_raw`] will lead to a memory leak.
535 /// The C side must **not** modify the length of the string (by writing a
536 /// `NULL` somewhere inside the string or removing the final one) before
537 /// it makes it back into Rust using [`from_raw`]. See the safety section
540 /// [`from_raw`]: #method.from_raw
545 /// use std::ffi::CString;
547 /// let c_string = CString::new("foo").expect("CString::new failed");
549 /// let ptr = c_string.into_raw();
552 /// assert_eq!(b'f', *ptr as u8);
553 /// assert_eq!(b'o', *ptr.offset(1) as u8);
554 /// assert_eq!(b'o', *ptr.offset(2) as u8);
555 /// assert_eq!(b'\0', *ptr.offset(3) as u8);
557 /// // retake pointer to free memory
558 /// let _ = CString::from_raw(ptr);
562 #[stable(feature = "cstr_memory", since = "1.4.0")]
563 pub fn into_raw(self) -> *mut c_char {
564 Box::into_raw(self.into_inner()) as *mut c_char
567 /// Converts the `CString` into a [`String`] if it contains valid UTF-8 data.
569 /// On failure, ownership of the original `CString` is returned.
571 /// [`String`]: ../string/struct.String.html
576 /// use std::ffi::CString;
578 /// let valid_utf8 = vec![b'f', b'o', b'o'];
579 /// let cstring = CString::new(valid_utf8).expect("CString::new failed");
580 /// assert_eq!(cstring.into_string().expect("into_string() call failed"), "foo");
582 /// let invalid_utf8 = vec![b'f', 0xff, b'o', b'o'];
583 /// let cstring = CString::new(invalid_utf8).expect("CString::new failed");
584 /// let err = cstring.into_string().err().expect("into_string().err() failed");
585 /// assert_eq!(err.utf8_error().valid_up_to(), 1);
588 #[stable(feature = "cstring_into", since = "1.7.0")]
589 pub fn into_string(self) -> Result<String, IntoStringError> {
590 String::from_utf8(self.into_bytes()).map_err(|e| IntoStringError {
591 error: e.utf8_error(),
592 inner: unsafe { CString::from_vec_unchecked(e.into_bytes()) },
596 /// Consumes the `CString` and returns the underlying byte buffer.
598 /// The returned buffer does **not** contain the trailing nul
599 /// terminator, and it is guaranteed to not have any interior nul
605 /// use std::ffi::CString;
607 /// let c_string = CString::new("foo").expect("CString::new failed");
608 /// let bytes = c_string.into_bytes();
609 /// assert_eq!(bytes, vec![b'f', b'o', b'o']);
611 #[stable(feature = "cstring_into", since = "1.7.0")]
612 pub fn into_bytes(self) -> Vec<u8> {
613 let mut vec = self.into_inner().into_vec();
614 let _nul = vec.pop();
615 debug_assert_eq!(_nul, Some(0u8));
619 /// Equivalent to the [`into_bytes`] function except that the returned vector
620 /// includes the trailing nul terminator.
622 /// [`into_bytes`]: #method.into_bytes
627 /// use std::ffi::CString;
629 /// let c_string = CString::new("foo").expect("CString::new failed");
630 /// let bytes = c_string.into_bytes_with_nul();
631 /// assert_eq!(bytes, vec![b'f', b'o', b'o', b'\0']);
633 #[stable(feature = "cstring_into", since = "1.7.0")]
634 pub fn into_bytes_with_nul(self) -> Vec<u8> {
635 self.into_inner().into_vec()
638 /// Returns the contents of this `CString` as a slice of bytes.
640 /// The returned slice does **not** contain the trailing nul
641 /// terminator, and it is guaranteed to not have any interior nul
642 /// bytes. If you need the nul terminator, use
643 /// [`as_bytes_with_nul`] instead.
645 /// [`as_bytes_with_nul`]: #method.as_bytes_with_nul
650 /// use std::ffi::CString;
652 /// let c_string = CString::new("foo").expect("CString::new failed");
653 /// let bytes = c_string.as_bytes();
654 /// assert_eq!(bytes, &[b'f', b'o', b'o']);
657 #[stable(feature = "rust1", since = "1.0.0")]
658 pub fn as_bytes(&self) -> &[u8] {
659 &self.inner[..self.inner.len() - 1]
662 /// Equivalent to the [`as_bytes`] function except that the returned slice
663 /// includes the trailing nul terminator.
665 /// [`as_bytes`]: #method.as_bytes
670 /// use std::ffi::CString;
672 /// let c_string = CString::new("foo").expect("CString::new failed");
673 /// let bytes = c_string.as_bytes_with_nul();
674 /// assert_eq!(bytes, &[b'f', b'o', b'o', b'\0']);
677 #[stable(feature = "rust1", since = "1.0.0")]
678 pub fn as_bytes_with_nul(&self) -> &[u8] {
682 /// Extracts a [`CStr`] slice containing the entire string.
684 /// [`CStr`]: struct.CStr.html
689 /// use std::ffi::{CString, CStr};
691 /// let c_string = CString::new(b"foo".to_vec()).expect("CString::new failed");
692 /// let cstr = c_string.as_c_str();
694 /// CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed"));
697 #[stable(feature = "as_c_str", since = "1.20.0")]
698 pub fn as_c_str(&self) -> &CStr {
702 /// Converts this `CString` into a boxed [`CStr`].
704 /// [`CStr`]: struct.CStr.html
709 /// use std::ffi::{CString, CStr};
711 /// let c_string = CString::new(b"foo".to_vec()).expect("CString::new failed");
712 /// let boxed = c_string.into_boxed_c_str();
713 /// assert_eq!(&*boxed,
714 /// CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed"));
716 #[stable(feature = "into_boxed_c_str", since = "1.20.0")]
717 pub fn into_boxed_c_str(self) -> Box<CStr> {
718 unsafe { Box::from_raw(Box::into_raw(self.into_inner()) as *mut CStr) }
721 /// Bypass "move out of struct which implements [`Drop`] trait" restriction.
723 /// [`Drop`]: ../ops/trait.Drop.html
724 fn into_inner(self) -> Box<[u8]> {
725 // Rationale: `mem::forget(self)` invalidates the previous call to `ptr::read(&self.inner)`
726 // so we use `ManuallyDrop` to ensure `self` is not dropped.
727 // Then we can return the box directly without invalidating it.
728 // See https://github.com/rust-lang/rust/issues/62553.
729 let this = mem::ManuallyDrop::new(self);
730 unsafe { ptr::read(&this.inner) }
733 /// Converts a `Vec` of `u8` to a `CString` without checking the invariants
734 /// on the given `Vec`.
738 /// The given `Vec` **must** have one nul byte as its last element.
739 /// This means it cannot be empty nor have any other nul byte anywhere else.
744 /// #![feature(cstring_from_vec_with_nul)]
745 /// use std::ffi::CString;
747 /// unsafe { CString::from_vec_with_nul_unchecked(b"abc\0".to_vec()) },
748 /// unsafe { CString::from_vec_unchecked(b"abc".to_vec()) }
751 #[unstable(feature = "cstring_from_vec_with_nul", issue = "73179")]
752 pub unsafe fn from_vec_with_nul_unchecked(v: Vec<u8>) -> Self {
753 Self { inner: v.into_boxed_slice() }
756 /// Attempts to converts a `Vec` of `u8` to a `CString`.
758 /// Runtime checks are present to ensure there is only one nul byte in the
759 /// `Vec`, its last element.
763 /// If a nul byte is present and not the last element or no nul bytes
764 /// is present, an error will be returned.
768 /// A successful conversion will produce the same result as [`new`] when
769 /// called without the ending nul byte.
772 /// #![feature(cstring_from_vec_with_nul)]
773 /// use std::ffi::CString;
775 /// CString::from_vec_with_nul(b"abc\0".to_vec())
776 /// .expect("CString::from_vec_with_nul failed"),
777 /// CString::new(b"abc".to_vec()).expect("CString::new failed")
781 /// A incorrectly formatted vector will produce an error.
784 /// #![feature(cstring_from_vec_with_nul)]
785 /// use std::ffi::{CString, FromVecWithNulError};
786 /// // Interior nul byte
787 /// let _: FromVecWithNulError = CString::from_vec_with_nul(b"a\0bc".to_vec()).unwrap_err();
789 /// let _: FromVecWithNulError = CString::from_vec_with_nul(b"abc".to_vec()).unwrap_err();
792 /// [`new`]: #method.new
793 #[unstable(feature = "cstring_from_vec_with_nul", issue = "73179")]
794 pub fn from_vec_with_nul(v: Vec<u8>) -> Result<Self, FromVecWithNulError> {
795 let nul_pos = memchr::memchr(0, &v);
797 Some(nul_pos) if nul_pos + 1 == v.len() => {
798 // SAFETY: We know there is only one nul byte, at the end
800 Ok(unsafe { Self::from_vec_with_nul_unchecked(v) })
802 Some(nul_pos) => Err(FromVecWithNulError {
803 error_kind: FromBytesWithNulErrorKind::InteriorNul(nul_pos),
806 None => Err(FromVecWithNulError {
807 error_kind: FromBytesWithNulErrorKind::NotNulTerminated,
814 // Turns this `CString` into an empty string to prevent
815 // memory-unsafe code from working by accident. Inline
816 // to prevent LLVM from optimizing it away in debug builds.
817 #[stable(feature = "cstring_drop", since = "1.13.0")]
818 impl Drop for CString {
822 *self.inner.get_unchecked_mut(0) = 0;
827 #[stable(feature = "rust1", since = "1.0.0")]
828 impl ops::Deref for CString {
832 fn deref(&self) -> &CStr {
833 unsafe { CStr::from_bytes_with_nul_unchecked(self.as_bytes_with_nul()) }
837 #[stable(feature = "rust1", since = "1.0.0")]
838 impl fmt::Debug for CString {
839 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
840 fmt::Debug::fmt(&**self, f)
844 #[stable(feature = "cstring_into", since = "1.7.0")]
845 impl From<CString> for Vec<u8> {
846 /// Converts a [`CString`] into a [`Vec`]`<u8>`.
848 /// The conversion consumes the [`CString`], and removes the terminating NUL byte.
850 /// [`Vec`]: ../vec/struct.Vec.html
851 /// [`CString`]: ../ffi/struct.CString.html
853 fn from(s: CString) -> Vec<u8> {
858 #[stable(feature = "cstr_debug", since = "1.3.0")]
859 impl fmt::Debug for CStr {
860 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
862 for byte in self.to_bytes().iter().flat_map(|&b| ascii::escape_default(b)) {
863 f.write_char(byte as char)?;
869 #[stable(feature = "cstr_default", since = "1.10.0")]
870 impl Default for &CStr {
871 fn default() -> Self {
872 const SLICE: &[c_char] = &[0];
873 unsafe { CStr::from_ptr(SLICE.as_ptr()) }
877 #[stable(feature = "cstr_default", since = "1.10.0")]
878 impl Default for CString {
879 /// Creates an empty `CString`.
880 fn default() -> CString {
881 let a: &CStr = Default::default();
886 #[stable(feature = "cstr_borrow", since = "1.3.0")]
887 impl Borrow<CStr> for CString {
889 fn borrow(&self) -> &CStr {
894 #[stable(feature = "cstring_from_cow_cstr", since = "1.28.0")]
895 impl<'a> From<Cow<'a, CStr>> for CString {
897 fn from(s: Cow<'a, CStr>) -> Self {
902 #[stable(feature = "box_from_c_str", since = "1.17.0")]
903 impl From<&CStr> for Box<CStr> {
904 fn from(s: &CStr) -> Box<CStr> {
905 let boxed: Box<[u8]> = Box::from(s.to_bytes_with_nul());
906 unsafe { Box::from_raw(Box::into_raw(boxed) as *mut CStr) }
910 #[stable(feature = "box_from_cow", since = "1.45.0")]
911 impl From<Cow<'_, CStr>> for Box<CStr> {
913 fn from(cow: Cow<'_, CStr>) -> Box<CStr> {
915 Cow::Borrowed(s) => Box::from(s),
916 Cow::Owned(s) => Box::from(s),
921 #[stable(feature = "c_string_from_box", since = "1.18.0")]
922 impl From<Box<CStr>> for CString {
923 /// Converts a [`Box`]`<CStr>` into a [`CString`] without copying or allocating.
925 /// [`Box`]: ../boxed/struct.Box.html
926 /// [`CString`]: ../ffi/struct.CString.html
928 fn from(s: Box<CStr>) -> CString {
933 #[stable(feature = "cstring_from_vec_of_nonzerou8", since = "1.43.0")]
934 impl From<Vec<NonZeroU8>> for CString {
935 /// Converts a [`Vec`]`<`[`NonZeroU8`]`>` into a [`CString`] without
936 /// copying nor checking for inner null bytes.
938 /// [`CString`]: ../ffi/struct.CString.html
939 /// [`NonZeroU8`]: ../num/struct.NonZeroU8.html
940 /// [`Vec`]: ../vec/struct.Vec.html
942 fn from(v: Vec<NonZeroU8>) -> CString {
944 // Transmute `Vec<NonZeroU8>` to `Vec<u8>`.
947 // - transmuting between `NonZeroU8` and `u8` is sound;
948 // - `alloc::Layout<NonZeroU8> == alloc::Layout<u8>`.
949 let (ptr, len, cap): (*mut NonZeroU8, _, _) = Vec::into_raw_parts(v);
950 Vec::from_raw_parts(ptr.cast::<u8>(), len, cap)
952 // Safety: `v` cannot contain null bytes, given the type-level
953 // invariant of `NonZeroU8`.
954 CString::from_vec_unchecked(v)
959 #[stable(feature = "more_box_slice_clone", since = "1.29.0")]
960 impl Clone for Box<CStr> {
962 fn clone(&self) -> Self {
967 #[stable(feature = "box_from_c_string", since = "1.20.0")]
968 impl From<CString> for Box<CStr> {
969 /// Converts a [`CString`] into a [`Box`]`<CStr>` without copying or allocating.
971 /// [`CString`]: ../ffi/struct.CString.html
972 /// [`Box`]: ../boxed/struct.Box.html
974 fn from(s: CString) -> Box<CStr> {
979 #[stable(feature = "cow_from_cstr", since = "1.28.0")]
980 impl<'a> From<CString> for Cow<'a, CStr> {
982 fn from(s: CString) -> Cow<'a, CStr> {
987 #[stable(feature = "cow_from_cstr", since = "1.28.0")]
988 impl<'a> From<&'a CStr> for Cow<'a, CStr> {
990 fn from(s: &'a CStr) -> Cow<'a, CStr> {
995 #[stable(feature = "cow_from_cstr", since = "1.28.0")]
996 impl<'a> From<&'a CString> for Cow<'a, CStr> {
998 fn from(s: &'a CString) -> Cow<'a, CStr> {
999 Cow::Borrowed(s.as_c_str())
1003 #[stable(feature = "shared_from_slice2", since = "1.24.0")]
1004 impl From<CString> for Arc<CStr> {
1005 /// Converts a [`CString`] into a [`Arc`]`<CStr>` without copying or allocating.
1007 /// [`CString`]: ../ffi/struct.CString.html
1008 /// [`Arc`]: ../sync/struct.Arc.html
1010 fn from(s: CString) -> Arc<CStr> {
1011 let arc: Arc<[u8]> = Arc::from(s.into_inner());
1012 unsafe { Arc::from_raw(Arc::into_raw(arc) as *const CStr) }
1016 #[stable(feature = "shared_from_slice2", since = "1.24.0")]
1017 impl From<&CStr> for Arc<CStr> {
1019 fn from(s: &CStr) -> Arc<CStr> {
1020 let arc: Arc<[u8]> = Arc::from(s.to_bytes_with_nul());
1021 unsafe { Arc::from_raw(Arc::into_raw(arc) as *const CStr) }
1025 #[stable(feature = "shared_from_slice2", since = "1.24.0")]
1026 impl From<CString> for Rc<CStr> {
1027 /// Converts a [`CString`] into a [`Rc`]`<CStr>` without copying or allocating.
1029 /// [`CString`]: ../ffi/struct.CString.html
1030 /// [`Rc`]: ../rc/struct.Rc.html
1032 fn from(s: CString) -> Rc<CStr> {
1033 let rc: Rc<[u8]> = Rc::from(s.into_inner());
1034 unsafe { Rc::from_raw(Rc::into_raw(rc) as *const CStr) }
1038 #[stable(feature = "shared_from_slice2", since = "1.24.0")]
1039 impl From<&CStr> for Rc<CStr> {
1041 fn from(s: &CStr) -> Rc<CStr> {
1042 let rc: Rc<[u8]> = Rc::from(s.to_bytes_with_nul());
1043 unsafe { Rc::from_raw(Rc::into_raw(rc) as *const CStr) }
1047 #[stable(feature = "default_box_extra", since = "1.17.0")]
1048 impl Default for Box<CStr> {
1049 fn default() -> Box<CStr> {
1050 let boxed: Box<[u8]> = Box::from([0]);
1051 unsafe { Box::from_raw(Box::into_raw(boxed) as *mut CStr) }
1056 /// Returns the position of the nul byte in the slice that caused
1057 /// [`CString::new`] to fail.
1059 /// [`CString::new`]: struct.CString.html#method.new
1064 /// use std::ffi::CString;
1066 /// let nul_error = CString::new("foo\0bar").unwrap_err();
1067 /// assert_eq!(nul_error.nul_position(), 3);
1069 /// let nul_error = CString::new("foo bar\0").unwrap_err();
1070 /// assert_eq!(nul_error.nul_position(), 7);
1072 #[stable(feature = "rust1", since = "1.0.0")]
1073 pub fn nul_position(&self) -> usize {
1077 /// Consumes this error, returning the underlying vector of bytes which
1078 /// generated the error in the first place.
1083 /// use std::ffi::CString;
1085 /// let nul_error = CString::new("foo\0bar").unwrap_err();
1086 /// assert_eq!(nul_error.into_vec(), b"foo\0bar");
1088 #[stable(feature = "rust1", since = "1.0.0")]
1089 pub fn into_vec(self) -> Vec<u8> {
1094 #[stable(feature = "rust1", since = "1.0.0")]
1095 impl Error for NulError {
1096 #[allow(deprecated)]
1097 fn description(&self) -> &str {
1098 "nul byte found in data"
1102 #[stable(feature = "rust1", since = "1.0.0")]
1103 impl fmt::Display for NulError {
1104 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1105 write!(f, "nul byte found in provided data at position: {}", self.0)
1109 #[stable(feature = "rust1", since = "1.0.0")]
1110 impl From<NulError> for io::Error {
1111 /// Converts a [`NulError`] into a [`io::Error`].
1113 /// [`NulError`]: ../ffi/struct.NulError.html
1114 /// [`io::Error`]: ../io/struct.Error.html
1115 fn from(_: NulError) -> io::Error {
1116 io::Error::new(io::ErrorKind::InvalidInput, "data provided contains a nul byte")
1120 #[stable(feature = "frombyteswithnulerror_impls", since = "1.17.0")]
1121 impl Error for FromBytesWithNulError {
1122 #[allow(deprecated)]
1123 fn description(&self) -> &str {
1125 FromBytesWithNulErrorKind::InteriorNul(..) => {
1126 "data provided contains an interior nul byte"
1128 FromBytesWithNulErrorKind::NotNulTerminated => "data provided is not nul terminated",
1133 #[stable(feature = "frombyteswithnulerror_impls", since = "1.17.0")]
1134 impl fmt::Display for FromBytesWithNulError {
1135 #[allow(deprecated, deprecated_in_future)]
1136 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1137 f.write_str(self.description())?;
1138 if let FromBytesWithNulErrorKind::InteriorNul(pos) = self.kind {
1139 write!(f, " at byte pos {}", pos)?;
1145 #[unstable(feature = "cstring_from_vec_with_nul", issue = "73179")]
1146 impl Error for FromVecWithNulError {}
1148 #[unstable(feature = "cstring_from_vec_with_nul", issue = "73179")]
1149 impl fmt::Display for FromVecWithNulError {
1150 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1151 match self.error_kind {
1152 FromBytesWithNulErrorKind::InteriorNul(pos) => {
1153 write!(f, "data provided contains an interior nul byte at pos {}", pos)
1155 FromBytesWithNulErrorKind::NotNulTerminated => {
1156 write!(f, "data provided is not nul terminated")
1162 impl IntoStringError {
1163 /// Consumes this error, returning original [`CString`] which generated the
1166 /// [`CString`]: struct.CString.html
1167 #[stable(feature = "cstring_into", since = "1.7.0")]
1168 pub fn into_cstring(self) -> CString {
1172 /// Access the underlying UTF-8 error that was the cause of this error.
1173 #[stable(feature = "cstring_into", since = "1.7.0")]
1174 pub fn utf8_error(&self) -> Utf8Error {
1179 #[stable(feature = "cstring_into", since = "1.7.0")]
1180 impl Error for IntoStringError {
1181 #[allow(deprecated)]
1182 fn description(&self) -> &str {
1183 "C string contained non-utf8 bytes"
1186 fn source(&self) -> Option<&(dyn Error + 'static)> {
1191 #[stable(feature = "cstring_into", since = "1.7.0")]
1192 impl fmt::Display for IntoStringError {
1193 #[allow(deprecated, deprecated_in_future)]
1194 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1195 self.description().fmt(f)
1200 /// Wraps a raw C string with a safe C string wrapper.
1202 /// This function will wrap the provided `ptr` with a `CStr` wrapper, which
1203 /// allows inspection and interoperation of non-owned C strings. The total
1204 /// size of the raw C string must be smaller than `isize::MAX` **bytes**
1205 /// in memory due to calling the `slice::from_raw_parts` function.
1206 /// This method is unsafe for a number of reasons:
1208 /// * There is no guarantee to the validity of `ptr`.
1209 /// * The returned lifetime is not guaranteed to be the actual lifetime of
1211 /// * There is no guarantee that the memory pointed to by `ptr` contains a
1212 /// valid nul terminator byte at the end of the string.
1213 /// * It is not guaranteed that the memory pointed by `ptr` won't change
1214 /// before the `CStr` has been destroyed.
1216 /// > **Note**: This operation is intended to be a 0-cost cast but it is
1217 /// > currently implemented with an up-front calculation of the length of
1218 /// > the string. This is not guaranteed to always be the case.
1222 /// ```ignore (extern-declaration)
1224 /// use std::ffi::CStr;
1225 /// use std::os::raw::c_char;
1228 /// fn my_string() -> *const c_char;
1232 /// let slice = CStr::from_ptr(my_string());
1233 /// println!("string returned: {}", slice.to_str().unwrap());
1237 #[stable(feature = "rust1", since = "1.0.0")]
1238 pub unsafe fn from_ptr<'a>(ptr: *const c_char) -> &'a CStr {
1239 // SAFETY: The caller has provided a pointer that points to a valid C
1240 // string with a NUL terminator of size less than `isize::MAX`, whose
1241 // content remain valid and doesn't change for the lifetime of the
1244 // Thus computing the length is fine (a NUL byte exists), the call to
1245 // from_raw_parts is safe because we know the length is at most `isize::MAX`, meaning
1246 // the call to `from_bytes_with_nul_unchecked` is correct.
1248 // The cast from c_char to u8 is ok because a c_char is always one byte.
1250 let len = sys::strlen(ptr);
1251 let ptr = ptr as *const u8;
1252 CStr::from_bytes_with_nul_unchecked(slice::from_raw_parts(ptr, len as usize + 1))
1256 /// Creates a C string wrapper from a byte slice.
1258 /// This function will cast the provided `bytes` to a `CStr`
1259 /// wrapper after ensuring that the byte slice is nul-terminated
1260 /// and does not contain any interior nul bytes.
1265 /// use std::ffi::CStr;
1267 /// let cstr = CStr::from_bytes_with_nul(b"hello\0");
1268 /// assert!(cstr.is_ok());
1271 /// Creating a `CStr` without a trailing nul terminator is an error:
1274 /// use std::ffi::CStr;
1276 /// let cstr = CStr::from_bytes_with_nul(b"hello");
1277 /// assert!(cstr.is_err());
1280 /// Creating a `CStr` with an interior nul byte is an error:
1283 /// use std::ffi::CStr;
1285 /// let cstr = CStr::from_bytes_with_nul(b"he\0llo\0");
1286 /// assert!(cstr.is_err());
1288 #[stable(feature = "cstr_from_bytes", since = "1.10.0")]
1289 pub fn from_bytes_with_nul(bytes: &[u8]) -> Result<&CStr, FromBytesWithNulError> {
1290 let nul_pos = memchr::memchr(0, bytes);
1291 if let Some(nul_pos) = nul_pos {
1292 if nul_pos + 1 != bytes.len() {
1293 return Err(FromBytesWithNulError::interior_nul(nul_pos));
1295 Ok(unsafe { CStr::from_bytes_with_nul_unchecked(bytes) })
1297 Err(FromBytesWithNulError::not_nul_terminated())
1301 /// Unsafely creates a C string wrapper from a byte slice.
1303 /// This function will cast the provided `bytes` to a `CStr` wrapper without
1304 /// performing any sanity checks. The provided slice **must** be nul-terminated
1305 /// and not contain any interior nul bytes.
1310 /// use std::ffi::{CStr, CString};
1313 /// let cstring = CString::new("hello").expect("CString::new failed");
1314 /// let cstr = CStr::from_bytes_with_nul_unchecked(cstring.to_bytes_with_nul());
1315 /// assert_eq!(cstr, &*cstring);
1319 #[stable(feature = "cstr_from_bytes", since = "1.10.0")]
1320 #[rustc_const_unstable(feature = "const_cstr_unchecked", issue = "none")]
1321 pub const unsafe fn from_bytes_with_nul_unchecked(bytes: &[u8]) -> &CStr {
1322 // SAFETY: Casting to CStr is safe because its internal representation
1323 // is a [u8] too (safe only inside std).
1324 // Dereferencing the obtained pointer is safe because it comes from a
1325 // reference. Making a reference is then safe because its lifetime
1326 // is bound by the lifetime of the given `bytes`.
1327 unsafe { &*(bytes as *const [u8] as *const CStr) }
1330 /// Returns the inner pointer to this C string.
1332 /// The returned pointer will be valid for as long as `self` is, and points
1333 /// to a contiguous region of memory terminated with a 0 byte to represent
1334 /// the end of the string.
1338 /// The returned pointer is read-only; writing to it (including passing it
1339 /// to C code that writes to it) causes undefined behavior.
1341 /// It is your responsibility to make sure that the underlying memory is not
1342 /// freed too early. For example, the following code will cause undefined
1343 /// behavior when `ptr` is used inside the `unsafe` block:
1346 /// # #![allow(unused_must_use)]
1347 /// use std::ffi::CString;
1349 /// let ptr = CString::new("Hello").expect("CString::new failed").as_ptr();
1351 /// // `ptr` is dangling
1356 /// This happens because the pointer returned by `as_ptr` does not carry any
1357 /// lifetime information and the [`CString`] is deallocated immediately after
1358 /// the `CString::new("Hello").expect("CString::new failed").as_ptr()` expression is evaluated.
1359 /// To fix the problem, bind the `CString` to a local variable:
1362 /// # #![allow(unused_must_use)]
1363 /// use std::ffi::CString;
1365 /// let hello = CString::new("Hello").expect("CString::new failed");
1366 /// let ptr = hello.as_ptr();
1368 /// // `ptr` is valid because `hello` is in scope
1373 /// This way, the lifetime of the `CString` in `hello` encompasses
1374 /// the lifetime of `ptr` and the `unsafe` block.
1376 /// [`CString`]: struct.CString.html
1378 #[stable(feature = "rust1", since = "1.0.0")]
1379 #[rustc_const_stable(feature = "const_str_as_ptr", since = "1.32.0")]
1380 pub const fn as_ptr(&self) -> *const c_char {
1384 /// Converts this C string to a byte slice.
1386 /// The returned slice will **not** contain the trailing nul terminator that this C
1389 /// > **Note**: This method is currently implemented as a constant-time
1390 /// > cast, but it is planned to alter its definition in the future to
1391 /// > perform the length calculation whenever this method is called.
1396 /// use std::ffi::CStr;
1398 /// let cstr = CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed");
1399 /// assert_eq!(cstr.to_bytes(), b"foo");
1402 #[stable(feature = "rust1", since = "1.0.0")]
1403 pub fn to_bytes(&self) -> &[u8] {
1404 let bytes = self.to_bytes_with_nul();
1405 &bytes[..bytes.len() - 1]
1408 /// Converts this C string to a byte slice containing the trailing 0 byte.
1410 /// This function is the equivalent of [`to_bytes`] except that it will retain
1411 /// the trailing nul terminator instead of chopping it off.
1413 /// > **Note**: This method is currently implemented as a 0-cost cast, but
1414 /// > it is planned to alter its definition in the future to perform the
1415 /// > length calculation whenever this method is called.
1417 /// [`to_bytes`]: #method.to_bytes
1422 /// use std::ffi::CStr;
1424 /// let cstr = CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed");
1425 /// assert_eq!(cstr.to_bytes_with_nul(), b"foo\0");
1428 #[stable(feature = "rust1", since = "1.0.0")]
1429 pub fn to_bytes_with_nul(&self) -> &[u8] {
1430 unsafe { &*(&self.inner as *const [c_char] as *const [u8]) }
1433 /// Yields a [`&str`] slice if the `CStr` contains valid UTF-8.
1435 /// If the contents of the `CStr` are valid UTF-8 data, this
1436 /// function will return the corresponding [`&str`] slice. Otherwise,
1437 /// it will return an error with details of where UTF-8 validation failed.
1439 /// [`&str`]: ../primitive.str.html
1444 /// use std::ffi::CStr;
1446 /// let cstr = CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed");
1447 /// assert_eq!(cstr.to_str(), Ok("foo"));
1449 #[stable(feature = "cstr_to_str", since = "1.4.0")]
1450 pub fn to_str(&self) -> Result<&str, str::Utf8Error> {
1451 // N.B., when `CStr` is changed to perform the length check in `.to_bytes()`
1452 // instead of in `from_ptr()`, it may be worth considering if this should
1453 // be rewritten to do the UTF-8 check inline with the length calculation
1454 // instead of doing it afterwards.
1455 str::from_utf8(self.to_bytes())
1458 /// Converts a `CStr` into a [`Cow`]`<`[`str`]`>`.
1460 /// If the contents of the `CStr` are valid UTF-8 data, this
1461 /// function will return a [`Cow`]`::`[`Borrowed`]`(`[`&str`]`)`
1462 /// with the corresponding [`&str`] slice. Otherwise, it will
1463 /// replace any invalid UTF-8 sequences with
1464 /// [`U+FFFD REPLACEMENT CHARACTER`][U+FFFD] and return a
1465 /// [`Cow`]`::`[`Owned`]`(`[`String`]`)` with the result.
1467 /// [`Cow`]: ../borrow/enum.Cow.html
1468 /// [`Borrowed`]: ../borrow/enum.Cow.html#variant.Borrowed
1469 /// [`Owned`]: ../borrow/enum.Cow.html#variant.Owned
1470 /// [`str`]: ../primitive.str.html
1471 /// [`String`]: ../string/struct.String.html
1472 /// [U+FFFD]: ../char/constant.REPLACEMENT_CHARACTER.html
1476 /// Calling `to_string_lossy` on a `CStr` containing valid UTF-8:
1479 /// use std::borrow::Cow;
1480 /// use std::ffi::CStr;
1482 /// let cstr = CStr::from_bytes_with_nul(b"Hello World\0")
1483 /// .expect("CStr::from_bytes_with_nul failed");
1484 /// assert_eq!(cstr.to_string_lossy(), Cow::Borrowed("Hello World"));
1487 /// Calling `to_string_lossy` on a `CStr` containing invalid UTF-8:
1490 /// use std::borrow::Cow;
1491 /// use std::ffi::CStr;
1493 /// let cstr = CStr::from_bytes_with_nul(b"Hello \xF0\x90\x80World\0")
1494 /// .expect("CStr::from_bytes_with_nul failed");
1496 /// cstr.to_string_lossy(),
1497 /// Cow::Owned(String::from("Hello �World")) as Cow<'_, str>
1500 #[stable(feature = "cstr_to_str", since = "1.4.0")]
1501 pub fn to_string_lossy(&self) -> Cow<'_, str> {
1502 String::from_utf8_lossy(self.to_bytes())
1505 /// Converts a [`Box`]`<CStr>` into a [`CString`] without copying or allocating.
1507 /// [`Box`]: ../boxed/struct.Box.html
1508 /// [`CString`]: struct.CString.html
1513 /// use std::ffi::CString;
1515 /// let c_string = CString::new(b"foo".to_vec()).expect("CString::new failed");
1516 /// let boxed = c_string.into_boxed_c_str();
1517 /// assert_eq!(boxed.into_c_string(), CString::new("foo").expect("CString::new failed"));
1519 #[stable(feature = "into_boxed_c_str", since = "1.20.0")]
1520 pub fn into_c_string(self: Box<CStr>) -> CString {
1521 let raw = Box::into_raw(self) as *mut [u8];
1522 CString { inner: unsafe { Box::from_raw(raw) } }
1526 #[stable(feature = "rust1", since = "1.0.0")]
1527 impl PartialEq for CStr {
1528 fn eq(&self, other: &CStr) -> bool {
1529 self.to_bytes().eq(other.to_bytes())
1532 #[stable(feature = "rust1", since = "1.0.0")]
1534 #[stable(feature = "rust1", since = "1.0.0")]
1535 impl PartialOrd for CStr {
1536 fn partial_cmp(&self, other: &CStr) -> Option<Ordering> {
1537 self.to_bytes().partial_cmp(&other.to_bytes())
1540 #[stable(feature = "rust1", since = "1.0.0")]
1542 fn cmp(&self, other: &CStr) -> Ordering {
1543 self.to_bytes().cmp(&other.to_bytes())
1547 #[stable(feature = "cstr_borrow", since = "1.3.0")]
1548 impl ToOwned for CStr {
1549 type Owned = CString;
1551 fn to_owned(&self) -> CString {
1552 CString { inner: self.to_bytes_with_nul().into() }
1555 fn clone_into(&self, target: &mut CString) {
1556 let mut b = Vec::from(mem::take(&mut target.inner));
1557 self.to_bytes_with_nul().clone_into(&mut b);
1558 target.inner = b.into_boxed_slice();
1562 #[stable(feature = "cstring_asref", since = "1.7.0")]
1563 impl From<&CStr> for CString {
1564 fn from(s: &CStr) -> CString {
1569 #[stable(feature = "cstring_asref", since = "1.7.0")]
1570 impl ops::Index<ops::RangeFull> for CString {
1574 fn index(&self, _index: ops::RangeFull) -> &CStr {
1579 #[stable(feature = "cstr_range_from", since = "1.47.0")]
1580 impl ops::Index<ops::RangeFrom<usize>> for CStr {
1583 fn index(&self, index: ops::RangeFrom<usize>) -> &CStr {
1584 let bytes = self.to_bytes_with_nul();
1585 // we need to manually check the starting index to account for the null
1586 // byte, since otherwise we could get an empty string that doesn't end
1588 if index.start < bytes.len() {
1589 unsafe { CStr::from_bytes_with_nul_unchecked(&bytes[index.start..]) }
1592 "index out of bounds: the len is {} but the index is {}",
1600 #[stable(feature = "cstring_asref", since = "1.7.0")]
1601 impl AsRef<CStr> for CStr {
1603 fn as_ref(&self) -> &CStr {
1608 #[stable(feature = "cstring_asref", since = "1.7.0")]
1609 impl AsRef<CStr> for CString {
1611 fn as_ref(&self) -> &CStr {
1619 use crate::borrow::Cow::{Borrowed, Owned};
1620 use crate::collections::hash_map::DefaultHasher;
1621 use crate::hash::{Hash, Hasher};
1622 use crate::os::raw::c_char;
1624 use crate::sync::Arc;
1628 let data = b"123\0";
1629 let ptr = data.as_ptr() as *const c_char;
1631 assert_eq!(CStr::from_ptr(ptr).to_bytes(), b"123");
1632 assert_eq!(CStr::from_ptr(ptr).to_bytes_with_nul(), b"123\0");
1638 let s = CString::new("1234").unwrap();
1639 assert_eq!(s.as_bytes(), b"1234");
1640 assert_eq!(s.as_bytes_with_nul(), b"1234\0");
1644 fn build_with_zero1() {
1645 assert!(CString::new(&b"\0"[..]).is_err());
1648 fn build_with_zero2() {
1649 assert!(CString::new(vec![0]).is_err());
1653 fn build_with_zero3() {
1655 let s = CString::from_vec_unchecked(vec![0]);
1656 assert_eq!(s.as_bytes(), b"\0");
1662 let s = CString::new(&b"abc\x01\x02\n\xE2\x80\xA6\xFF"[..]).unwrap();
1663 assert_eq!(format!("{:?}", s), r#""abc\x01\x02\n\xe2\x80\xa6\xff""#);
1669 let s = CStr::from_ptr(b"12\0".as_ptr() as *const _);
1670 assert_eq!(s.to_bytes(), b"12");
1671 assert_eq!(s.to_bytes_with_nul(), b"12\0");
1677 let data = b"123\xE2\x80\xA6\0";
1678 let ptr = data.as_ptr() as *const c_char;
1680 assert_eq!(CStr::from_ptr(ptr).to_str(), Ok("123…"));
1681 assert_eq!(CStr::from_ptr(ptr).to_string_lossy(), Borrowed("123…"));
1683 let data = b"123\xE2\0";
1684 let ptr = data.as_ptr() as *const c_char;
1686 assert!(CStr::from_ptr(ptr).to_str().is_err());
1687 assert_eq!(CStr::from_ptr(ptr).to_string_lossy(), Owned::<str>(format!("123\u{FFFD}")));
1693 let data = b"123\0";
1694 let ptr = data.as_ptr() as *const c_char;
1696 let owned = unsafe { CStr::from_ptr(ptr).to_owned() };
1697 assert_eq!(owned.as_bytes_with_nul(), data);
1702 let data = b"123\xE2\xFA\xA6\0";
1703 let ptr = data.as_ptr() as *const c_char;
1704 let cstr: &'static CStr = unsafe { CStr::from_ptr(ptr) };
1706 let mut s = DefaultHasher::new();
1708 let cstr_hash = s.finish();
1709 let mut s = DefaultHasher::new();
1710 CString::new(&data[..data.len() - 1]).unwrap().hash(&mut s);
1711 let cstring_hash = s.finish();
1713 assert_eq!(cstr_hash, cstring_hash);
1717 fn from_bytes_with_nul() {
1718 let data = b"123\0";
1719 let cstr = CStr::from_bytes_with_nul(data);
1720 assert_eq!(cstr.map(CStr::to_bytes), Ok(&b"123"[..]));
1721 let cstr = CStr::from_bytes_with_nul(data);
1722 assert_eq!(cstr.map(CStr::to_bytes_with_nul), Ok(&b"123\0"[..]));
1725 let cstr = CStr::from_bytes_with_nul(data);
1726 let cstr_unchecked = CStr::from_bytes_with_nul_unchecked(data);
1727 assert_eq!(cstr, Ok(cstr_unchecked));
1732 fn from_bytes_with_nul_unterminated() {
1734 let cstr = CStr::from_bytes_with_nul(data);
1735 assert!(cstr.is_err());
1739 fn from_bytes_with_nul_interior() {
1740 let data = b"1\023\0";
1741 let cstr = CStr::from_bytes_with_nul(data);
1742 assert!(cstr.is_err());
1747 let orig: &[u8] = b"Hello, world!\0";
1748 let cstr = CStr::from_bytes_with_nul(orig).unwrap();
1749 let boxed: Box<CStr> = Box::from(cstr);
1750 let cstring = cstr.to_owned().into_boxed_c_str().into_c_string();
1751 assert_eq!(cstr, &*boxed);
1752 assert_eq!(&*boxed, &*cstring);
1753 assert_eq!(&*cstring, cstr);
1757 fn boxed_default() {
1758 let boxed = <Box<CStr>>::default();
1759 assert_eq!(boxed.to_bytes_with_nul(), &[0]);
1763 fn test_c_str_clone_into() {
1764 let mut c_string = CString::new("lorem").unwrap();
1765 let c_ptr = c_string.as_ptr();
1766 let c_str = CStr::from_bytes_with_nul(b"ipsum\0").unwrap();
1767 c_str.clone_into(&mut c_string);
1768 assert_eq!(c_str, c_string.as_c_str());
1769 // The exact same size shouldn't have needed to move its allocation
1770 assert_eq!(c_ptr, c_string.as_ptr());
1775 let orig: &[u8] = b"Hello, world!\0";
1776 let cstr = CStr::from_bytes_with_nul(orig).unwrap();
1777 let rc: Rc<CStr> = Rc::from(cstr);
1778 let arc: Arc<CStr> = Arc::from(cstr);
1780 assert_eq!(&*rc, cstr);
1781 assert_eq!(&*arc, cstr);
1783 let rc2: Rc<CStr> = Rc::from(cstr.to_owned());
1784 let arc2: Arc<CStr> = Arc::from(cstr.to_owned());
1786 assert_eq!(&*rc2, cstr);
1787 assert_eq!(&*arc2, cstr);
1791 fn cstr_const_constructor() {
1792 const CSTR: &CStr = unsafe { CStr::from_bytes_with_nul_unchecked(b"Hello, world!\0") };
1794 assert_eq!(CSTR.to_str().unwrap(), "Hello, world!");
1798 fn cstr_index_from() {
1799 let original = b"Hello, world!\0";
1800 let cstr = CStr::from_bytes_with_nul(original).unwrap();
1801 let result = CStr::from_bytes_with_nul(&original[7..]).unwrap();
1803 assert_eq!(&cstr[7..], result);
1808 fn cstr_index_from_empty() {
1809 let original = b"Hello, world!\0";
1810 let cstr = CStr::from_bytes_with_nul(original).unwrap();
1811 let _ = &cstr[original.len()..];