1 // Copyright 2012 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
12 use borrow::{Cow, Borrow};
15 use fmt::{self, Write};
24 use str::{self, Utf8Error};
26 /// A type representing an owned C-compatible string.
28 /// This type serves the primary purpose of being able to safely generate a
29 /// C-compatible string from a Rust byte slice or vector. An instance of this
30 /// type is a static guarantee that the underlying bytes contain no interior 0
31 /// bytes and the final byte is 0.
33 /// A `CString` is created from either a byte slice or a byte vector. A [`u8`]
34 /// slice can be obtained with the `as_bytes` method. Slices produced from a
35 /// `CString` do *not* contain the trailing nul terminator unless otherwise
38 /// [`u8`]: ../primitive.u8.html
44 /// use std::ffi::CString;
45 /// use std::os::raw::c_char;
48 /// fn my_printer(s: *const c_char);
51 /// let c_to_print = CString::new("Hello, world!").unwrap();
53 /// my_printer(c_to_print.as_ptr());
60 /// `CString` is intended for working with traditional C-style strings
61 /// (a sequence of non-null bytes terminated by a single null byte); the
62 /// primary use case for these kinds of strings is interoperating with C-like
63 /// code. Often you will need to transfer ownership to/from that external
64 /// code. It is strongly recommended that you thoroughly read through the
65 /// documentation of `CString` before use, as improper ownership management
66 /// of `CString` instances can lead to invalid memory accesses, memory leaks,
67 /// and other memory errors.
69 #[derive(PartialEq, PartialOrd, Eq, Ord, Hash, Clone)]
70 #[stable(feature = "rust1", since = "1.0.0")]
72 // Invariant 1: the slice ends with a zero byte and has a length of at least one.
73 // Invariant 2: the slice contains only one zero byte.
74 // Improper usage of unsafe function can break Invariant 2, but not Invariant 1.
78 /// Representation of a borrowed C string.
80 /// This dynamically sized type is only safely constructed via a borrowed
81 /// version of an instance of `CString`. This type can be constructed from a raw
82 /// C string as well and represents a C string borrowed from another location.
84 /// Note that this structure is **not** `repr(C)` and is not recommended to be
85 /// placed in the signatures of FFI functions. Instead safe wrappers of FFI
86 /// functions may leverage the unsafe [`from_ptr`] constructor to provide a safe
87 /// interface to other consumers.
89 /// [`from_ptr`]: #method.from_ptr
93 /// Inspecting a foreign C string:
96 /// use std::ffi::CStr;
97 /// use std::os::raw::c_char;
99 /// extern { fn my_string() -> *const c_char; }
102 /// let slice = CStr::from_ptr(my_string());
103 /// println!("string length: {}", slice.to_bytes().len());
107 /// Passing a Rust-originating C string:
110 /// use std::ffi::{CString, CStr};
111 /// use std::os::raw::c_char;
113 /// fn work(data: &CStr) {
114 /// extern { fn work_with(data: *const c_char); }
116 /// unsafe { work_with(data.as_ptr()) }
119 /// let s = CString::new("data data data data").unwrap();
123 /// Converting a foreign C string into a Rust [`String`]:
125 /// [`String`]: ../string/struct.String.html
128 /// use std::ffi::CStr;
129 /// use std::os::raw::c_char;
131 /// extern { fn my_string() -> *const c_char; }
133 /// fn my_string_safe() -> String {
135 /// CStr::from_ptr(my_string()).to_string_lossy().into_owned()
139 /// println!("string: {}", my_string_safe());
142 #[stable(feature = "rust1", since = "1.0.0")]
144 // FIXME: this should not be represented with a DST slice but rather with
145 // just a raw `c_char` along with some form of marker to make
146 // this an unsized type. Essentially `sizeof(&CStr)` should be the
147 // same as `sizeof(&c_char)` but `CStr` should be an unsized type.
151 /// An error returned from [`CString::new`] to indicate that a nul byte was found
152 /// in the vector provided.
154 /// [`CString::new`]: struct.CString.html#method.new
155 #[derive(Clone, PartialEq, Eq, Debug)]
156 #[stable(feature = "rust1", since = "1.0.0")]
157 pub struct NulError(usize, Vec<u8>);
159 /// An error returned from [`CStr::from_bytes_with_nul`] to indicate that a nul
160 /// byte was found too early in the slice provided or one wasn't found at all.
162 /// [`CStr::from_bytes_with_nul`]: struct.CStr.html#method.from_bytes_with_nul
163 #[derive(Clone, PartialEq, Eq, Debug)]
164 #[stable(feature = "cstr_from_bytes", since = "1.10.0")]
165 pub struct FromBytesWithNulError {
166 kind: FromBytesWithNulErrorKind,
169 #[derive(Clone, PartialEq, Eq, Debug)]
170 enum FromBytesWithNulErrorKind {
175 impl FromBytesWithNulError {
176 fn interior_nul(pos: usize) -> FromBytesWithNulError {
177 FromBytesWithNulError {
178 kind: FromBytesWithNulErrorKind::InteriorNul(pos),
181 fn not_nul_terminated() -> FromBytesWithNulError {
182 FromBytesWithNulError {
183 kind: FromBytesWithNulErrorKind::NotNulTerminated,
188 /// An error returned from [`CString::into_string`] to indicate that a UTF-8 error
189 /// was encountered during the conversion.
191 /// [`CString::into_string`]: struct.CString.html#method.into_string
192 #[derive(Clone, PartialEq, Eq, Debug)]
193 #[stable(feature = "cstring_into", since = "1.7.0")]
194 pub struct IntoStringError {
200 /// Creates a new C-compatible string from a container of bytes.
202 /// This method will consume the provided data and use the underlying bytes
203 /// to construct a new string, ensuring that there is a trailing 0 byte.
208 /// use std::ffi::CString;
209 /// use std::os::raw::c_char;
211 /// extern { fn puts(s: *const c_char); }
213 /// let to_print = CString::new("Hello!").unwrap();
215 /// puts(to_print.as_ptr());
221 /// This function will return an error if the bytes yielded contain an
222 /// internal 0 byte. The error returned will contain the bytes as well as
223 /// the position of the nul byte.
224 #[stable(feature = "rust1", since = "1.0.0")]
225 pub fn new<T: Into<Vec<u8>>>(t: T) -> Result<CString, NulError> {
229 fn _new(bytes: Vec<u8>) -> Result<CString, NulError> {
230 match memchr::memchr(0, &bytes) {
231 Some(i) => Err(NulError(i, bytes)),
232 None => Ok(unsafe { CString::from_vec_unchecked(bytes) }),
236 /// Creates a C-compatible string from a byte vector without checking for
237 /// interior 0 bytes.
239 /// This method is equivalent to [`new`] except that no runtime assertion
240 /// is made that `v` contains no 0 bytes, and it requires an actual
241 /// byte vector, not anything that can be converted to one with Into.
243 /// [`new`]: #method.new
248 /// use std::ffi::CString;
250 /// let raw = b"foo".to_vec();
252 /// let c_string = CString::from_vec_unchecked(raw);
255 #[stable(feature = "rust1", since = "1.0.0")]
256 pub unsafe fn from_vec_unchecked(mut v: Vec<u8>) -> CString {
259 CString { inner: v.into_boxed_slice() }
262 /// Retakes ownership of a `CString` that was transferred to C.
264 /// Additionally, the length of the string will be recalculated from the pointer.
268 /// This should only ever be called with a pointer that was earlier
269 /// obtained by calling [`into_raw`] on a `CString`. Other usage (e.g. trying to take
270 /// ownership of a string that was allocated by foreign code) is likely to lead
271 /// to undefined behavior or allocator corruption.
273 /// [`into_raw`]: #method.into_raw
274 #[stable(feature = "cstr_memory", since = "1.4.0")]
275 pub unsafe fn from_raw(ptr: *mut c_char) -> CString {
276 let len = libc::strlen(ptr) + 1; // Including the NUL byte
277 let slice = slice::from_raw_parts(ptr, len as usize);
278 CString { inner: mem::transmute(slice) }
281 /// Transfers ownership of the string to a C caller.
283 /// The pointer must be returned to Rust and reconstituted using
284 /// [`from_raw`] to be properly deallocated. Specifically, one
285 /// should *not* use the standard C `free` function to deallocate
288 /// Failure to call [`from_raw`] will lead to a memory leak.
290 /// [`from_raw`]: #method.from_raw
295 /// use std::ffi::CString;
297 /// let c_string = CString::new("foo").unwrap();
299 /// let ptr = c_string.into_raw();
302 /// assert_eq!(b'f', *ptr as u8);
303 /// assert_eq!(b'o', *ptr.offset(1) as u8);
304 /// assert_eq!(b'o', *ptr.offset(2) as u8);
305 /// assert_eq!(b'\0', *ptr.offset(3) as u8);
307 /// // retake pointer to free memory
308 /// let _ = CString::from_raw(ptr);
311 #[stable(feature = "cstr_memory", since = "1.4.0")]
312 pub fn into_raw(self) -> *mut c_char {
313 Box::into_raw(self.into_inner()) as *mut c_char
316 /// Converts the `CString` into a [`String`] if it contains valid Unicode data.
318 /// On failure, ownership of the original `CString` is returned.
320 /// [`String`]: ../string/struct.String.html
321 #[stable(feature = "cstring_into", since = "1.7.0")]
322 pub fn into_string(self) -> Result<String, IntoStringError> {
323 String::from_utf8(self.into_bytes())
324 .map_err(|e| IntoStringError {
325 error: e.utf8_error(),
326 inner: unsafe { CString::from_vec_unchecked(e.into_bytes()) },
330 /// Returns the underlying byte buffer.
332 /// The returned buffer does **not** contain the trailing nul separator and
333 /// it is guaranteed to not have any interior nul bytes.
338 /// use std::ffi::CString;
340 /// let c_string = CString::new("foo").unwrap();
341 /// let bytes = c_string.into_bytes();
342 /// assert_eq!(bytes, vec![b'f', b'o', b'o']);
344 #[stable(feature = "cstring_into", since = "1.7.0")]
345 pub fn into_bytes(self) -> Vec<u8> {
346 let mut vec = self.into_inner().into_vec();
347 let _nul = vec.pop();
348 debug_assert_eq!(_nul, Some(0u8));
352 /// Equivalent to the [`into_bytes`] function except that the returned vector
353 /// includes the trailing nul byte.
355 /// [`into_bytes`]: #method.into_bytes
360 /// use std::ffi::CString;
362 /// let c_string = CString::new("foo").unwrap();
363 /// let bytes = c_string.into_bytes_with_nul();
364 /// assert_eq!(bytes, vec![b'f', b'o', b'o', b'\0']);
366 #[stable(feature = "cstring_into", since = "1.7.0")]
367 pub fn into_bytes_with_nul(self) -> Vec<u8> {
368 self.into_inner().into_vec()
371 /// Returns the contents of this `CString` as a slice of bytes.
373 /// The returned slice does **not** contain the trailing nul separator and
374 /// it is guaranteed to not have any interior nul bytes.
379 /// use std::ffi::CString;
381 /// let c_string = CString::new("foo").unwrap();
382 /// let bytes = c_string.as_bytes();
383 /// assert_eq!(bytes, &[b'f', b'o', b'o']);
385 #[stable(feature = "rust1", since = "1.0.0")]
386 pub fn as_bytes(&self) -> &[u8] {
387 &self.inner[..self.inner.len() - 1]
390 /// Equivalent to the [`as_bytes`] function except that the returned slice
391 /// includes the trailing nul byte.
393 /// [`as_bytes`]: #method.as_bytes
398 /// use std::ffi::CString;
400 /// let c_string = CString::new("foo").unwrap();
401 /// let bytes = c_string.as_bytes_with_nul();
402 /// assert_eq!(bytes, &[b'f', b'o', b'o', b'\0']);
404 #[stable(feature = "rust1", since = "1.0.0")]
405 pub fn as_bytes_with_nul(&self) -> &[u8] {
409 /// Extracts a [`CStr`] slice containing the entire string.
411 /// [`CStr`]: struct.CStr.html
412 #[unstable(feature = "as_c_str", issue = "40380")]
413 pub fn as_c_str(&self) -> &CStr {
417 /// Converts this `CString` into a boxed [`CStr`].
419 /// [`CStr`]: struct.CStr.html
420 #[unstable(feature = "into_boxed_c_str", issue = "40380")]
421 pub fn into_boxed_c_str(self) -> Box<CStr> {
422 unsafe { mem::transmute(self.into_inner()) }
425 // Bypass "move out of struct which implements [`Drop`] trait" restriction.
427 /// [`Drop`]: ../ops/trait.Drop.html
428 fn into_inner(self) -> Box<[u8]> {
430 let result = ptr::read(&self.inner);
437 // Turns this `CString` into an empty string to prevent
438 // memory unsafe code from working by accident. Inline
439 // to prevent LLVM from optimizing it away in debug builds.
440 #[stable(feature = "cstring_drop", since = "1.13.0")]
441 impl Drop for CString {
444 unsafe { *self.inner.get_unchecked_mut(0) = 0; }
448 #[stable(feature = "rust1", since = "1.0.0")]
449 impl ops::Deref for CString {
452 fn deref(&self) -> &CStr {
453 unsafe { CStr::from_bytes_with_nul_unchecked(self.as_bytes_with_nul()) }
457 #[stable(feature = "rust1", since = "1.0.0")]
458 impl fmt::Debug for CString {
459 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
460 fmt::Debug::fmt(&**self, f)
464 #[stable(feature = "cstring_into", since = "1.7.0")]
465 impl From<CString> for Vec<u8> {
466 fn from(s: CString) -> Vec<u8> {
471 #[stable(feature = "cstr_debug", since = "1.3.0")]
472 impl fmt::Debug for CStr {
473 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
475 for byte in self.to_bytes().iter().flat_map(|&b| ascii::escape_default(b)) {
476 f.write_char(byte as char)?;
482 #[stable(feature = "cstr_default", since = "1.10.0")]
483 impl<'a> Default for &'a CStr {
484 fn default() -> &'a CStr {
485 static SLICE: &'static [c_char] = &[0];
486 unsafe { CStr::from_ptr(SLICE.as_ptr()) }
490 #[stable(feature = "cstr_default", since = "1.10.0")]
491 impl Default for CString {
492 /// Creates an empty `CString`.
493 fn default() -> CString {
494 let a: &CStr = Default::default();
499 #[stable(feature = "cstr_borrow", since = "1.3.0")]
500 impl Borrow<CStr> for CString {
501 fn borrow(&self) -> &CStr { self }
504 #[stable(feature = "box_from_c_str", since = "1.17.0")]
505 impl<'a> From<&'a CStr> for Box<CStr> {
506 fn from(s: &'a CStr) -> Box<CStr> {
507 let boxed: Box<[u8]> = Box::from(s.to_bytes_with_nul());
508 unsafe { mem::transmute(boxed) }
512 #[stable(feature = "c_string_from_box", since = "1.18.0")]
513 impl From<Box<CStr>> for CString {
514 fn from(s: Box<CStr>) -> CString {
519 #[stable(feature = "box_from_c_string", since = "1.18.0")]
520 impl Into<Box<CStr>> for CString {
521 fn into(self) -> Box<CStr> {
522 self.into_boxed_c_str()
526 #[stable(feature = "default_box_extra", since = "1.17.0")]
527 impl Default for Box<CStr> {
528 fn default() -> Box<CStr> {
529 let boxed: Box<[u8]> = Box::from([0]);
530 unsafe { mem::transmute(boxed) }
535 /// Returns the position of the nul byte in the slice that was provided to
536 /// [`CString::new`].
538 /// [`CString::new`]: struct.CString.html#method.new
543 /// use std::ffi::CString;
545 /// let nul_error = CString::new("foo\0bar").unwrap_err();
546 /// assert_eq!(nul_error.nul_position(), 3);
548 /// let nul_error = CString::new("foo bar\0").unwrap_err();
549 /// assert_eq!(nul_error.nul_position(), 7);
551 #[stable(feature = "rust1", since = "1.0.0")]
552 pub fn nul_position(&self) -> usize { self.0 }
554 /// Consumes this error, returning the underlying vector of bytes which
555 /// generated the error in the first place.
560 /// use std::ffi::CString;
562 /// let nul_error = CString::new("foo\0bar").unwrap_err();
563 /// assert_eq!(nul_error.into_vec(), b"foo\0bar");
565 #[stable(feature = "rust1", since = "1.0.0")]
566 pub fn into_vec(self) -> Vec<u8> { self.1 }
569 #[stable(feature = "rust1", since = "1.0.0")]
570 impl Error for NulError {
571 fn description(&self) -> &str { "nul byte found in data" }
574 #[stable(feature = "rust1", since = "1.0.0")]
575 impl fmt::Display for NulError {
576 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
577 write!(f, "nul byte found in provided data at position: {}", self.0)
581 #[stable(feature = "rust1", since = "1.0.0")]
582 impl From<NulError> for io::Error {
583 fn from(_: NulError) -> io::Error {
584 io::Error::new(io::ErrorKind::InvalidInput,
585 "data provided contains a nul byte")
589 #[stable(feature = "frombyteswithnulerror_impls", since = "1.17.0")]
590 impl Error for FromBytesWithNulError {
591 fn description(&self) -> &str {
593 FromBytesWithNulErrorKind::InteriorNul(..) =>
594 "data provided contains an interior nul byte",
595 FromBytesWithNulErrorKind::NotNulTerminated =>
596 "data provided is not nul terminated",
601 #[stable(feature = "frombyteswithnulerror_impls", since = "1.17.0")]
602 impl fmt::Display for FromBytesWithNulError {
603 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
604 f.write_str(self.description())?;
605 if let FromBytesWithNulErrorKind::InteriorNul(pos) = self.kind {
606 write!(f, " at byte pos {}", pos)?;
612 impl IntoStringError {
613 /// Consumes this error, returning original [`CString`] which generated the
616 /// [`CString`]: struct.CString.html
617 #[stable(feature = "cstring_into", since = "1.7.0")]
618 pub fn into_cstring(self) -> CString {
622 /// Access the underlying UTF-8 error that was the cause of this error.
623 #[stable(feature = "cstring_into", since = "1.7.0")]
624 pub fn utf8_error(&self) -> Utf8Error {
629 #[stable(feature = "cstring_into", since = "1.7.0")]
630 impl Error for IntoStringError {
631 fn description(&self) -> &str {
632 "C string contained non-utf8 bytes"
635 fn cause(&self) -> Option<&Error> {
640 #[stable(feature = "cstring_into", since = "1.7.0")]
641 impl fmt::Display for IntoStringError {
642 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
643 self.description().fmt(f)
648 /// Casts a raw C string to a safe C string wrapper.
650 /// This function will cast the provided `ptr` to the `CStr` wrapper which
651 /// allows inspection and interoperation of non-owned C strings. This method
652 /// is unsafe for a number of reasons:
654 /// * There is no guarantee to the validity of `ptr`.
655 /// * The returned lifetime is not guaranteed to be the actual lifetime of
657 /// * There is no guarantee that the memory pointed to by `ptr` contains a
658 /// valid nul terminator byte at the end of the string.
660 /// > **Note**: This operation is intended to be a 0-cost cast but it is
661 /// > currently implemented with an up-front calculation of the length of
662 /// > the string. This is not guaranteed to always be the case.
668 /// use std::ffi::CStr;
669 /// use std::os::raw::c_char;
672 /// fn my_string() -> *const c_char;
676 /// let slice = CStr::from_ptr(my_string());
677 /// println!("string returned: {}", slice.to_str().unwrap());
681 #[stable(feature = "rust1", since = "1.0.0")]
682 pub unsafe fn from_ptr<'a>(ptr: *const c_char) -> &'a CStr {
683 let len = libc::strlen(ptr);
684 let ptr = ptr as *const u8;
685 CStr::from_bytes_with_nul_unchecked(slice::from_raw_parts(ptr, len as usize + 1))
688 /// Creates a C string wrapper from a byte slice.
690 /// This function will cast the provided `bytes` to a `CStr` wrapper after
691 /// ensuring that it is null terminated and does not contain any interior
697 /// use std::ffi::CStr;
699 /// let cstr = CStr::from_bytes_with_nul(b"hello\0");
700 /// assert!(cstr.is_ok());
702 #[stable(feature = "cstr_from_bytes", since = "1.10.0")]
703 pub fn from_bytes_with_nul(bytes: &[u8])
704 -> Result<&CStr, FromBytesWithNulError> {
705 let nul_pos = memchr::memchr(0, bytes);
706 if let Some(nul_pos) = nul_pos {
707 if nul_pos + 1 != bytes.len() {
708 return Err(FromBytesWithNulError::interior_nul(nul_pos));
710 Ok(unsafe { CStr::from_bytes_with_nul_unchecked(bytes) })
712 Err(FromBytesWithNulError::not_nul_terminated())
716 /// Unsafely creates a C string wrapper from a byte slice.
718 /// This function will cast the provided `bytes` to a `CStr` wrapper without
719 /// performing any sanity checks. The provided slice must be null terminated
720 /// and not contain any interior nul bytes.
725 /// use std::ffi::{CStr, CString};
728 /// let cstring = CString::new("hello").unwrap();
729 /// let cstr = CStr::from_bytes_with_nul_unchecked(cstring.to_bytes_with_nul());
730 /// assert_eq!(cstr, &*cstring);
733 #[stable(feature = "cstr_from_bytes", since = "1.10.0")]
734 pub unsafe fn from_bytes_with_nul_unchecked(bytes: &[u8]) -> &CStr {
735 mem::transmute(bytes)
738 /// Returns the inner pointer to this C string.
740 /// The returned pointer will be valid for as long as `self` is and points
741 /// to a contiguous region of memory terminated with a 0 byte to represent
742 /// the end of the string.
746 /// It is your responsibility to make sure that the underlying memory is not
747 /// freed too early. For example, the following code will cause undefined
748 /// behaviour when `ptr` is used inside the `unsafe` block:
751 /// use std::ffi::{CString};
753 /// let ptr = CString::new("Hello").unwrap().as_ptr();
755 /// // `ptr` is dangling
760 /// This happens because the pointer returned by `as_ptr` does not carry any
761 /// lifetime information and the string is deallocated immediately after
762 /// the `CString::new("Hello").unwrap().as_ptr()` expression is evaluated.
763 /// To fix the problem, bind the string to a local variable:
766 /// use std::ffi::{CString};
768 /// let hello = CString::new("Hello").unwrap();
769 /// let ptr = hello.as_ptr();
771 /// // `ptr` is valid because `hello` is in scope
775 #[stable(feature = "rust1", since = "1.0.0")]
776 pub fn as_ptr(&self) -> *const c_char {
780 /// Converts this C string to a byte slice.
782 /// This function will calculate the length of this string (which normally
783 /// requires a linear amount of work to be done) and then return the
784 /// resulting slice of `u8` elements.
786 /// The returned slice will **not** contain the trailing nul that this C
789 /// > **Note**: This method is currently implemented as a 0-cost cast, but
790 /// > it is planned to alter its definition in the future to perform the
791 /// > length calculation whenever this method is called.
792 #[stable(feature = "rust1", since = "1.0.0")]
793 pub fn to_bytes(&self) -> &[u8] {
794 let bytes = self.to_bytes_with_nul();
795 &bytes[..bytes.len() - 1]
798 /// Converts this C string to a byte slice containing the trailing 0 byte.
800 /// This function is the equivalent of [`to_bytes`] except that it will retain
801 /// the trailing nul instead of chopping it off.
803 /// > **Note**: This method is currently implemented as a 0-cost cast, but
804 /// > it is planned to alter its definition in the future to perform the
805 /// > length calculation whenever this method is called.
807 /// [`to_bytes`]: #method.to_bytes
808 #[stable(feature = "rust1", since = "1.0.0")]
809 pub fn to_bytes_with_nul(&self) -> &[u8] {
810 unsafe { mem::transmute(&self.inner) }
813 /// Yields a [`&str`] slice if the `CStr` contains valid UTF-8.
815 /// This function will calculate the length of this string and check for
816 /// UTF-8 validity, and then return the [`&str`] if it's valid.
818 /// > **Note**: This method is currently implemented to check for validity
819 /// > after a 0-cost cast, but it is planned to alter its definition in the
820 /// > future to perform the length calculation in addition to the UTF-8
821 /// > check whenever this method is called.
823 /// [`&str`]: ../primitive.str.html
824 #[stable(feature = "cstr_to_str", since = "1.4.0")]
825 pub fn to_str(&self) -> Result<&str, str::Utf8Error> {
826 // NB: When CStr is changed to perform the length check in .to_bytes()
827 // instead of in from_ptr(), it may be worth considering if this should
828 // be rewritten to do the UTF-8 check inline with the length calculation
829 // instead of doing it afterwards.
830 str::from_utf8(self.to_bytes())
833 /// Converts a `CStr` into a [`Cow`]`<`[`str`]`>`.
835 /// This function will calculate the length of this string (which normally
836 /// requires a linear amount of work to be done) and then return the
837 /// resulting slice as a [`Cow`]`<`[`str`]`>`, replacing any invalid UTF-8 sequences
838 /// with `U+FFFD REPLACEMENT CHARACTER`.
840 /// > **Note**: This method is currently implemented to check for validity
841 /// > after a 0-cost cast, but it is planned to alter its definition in the
842 /// > future to perform the length calculation in addition to the UTF-8
843 /// > check whenever this method is called.
845 /// [`Cow`]: ../borrow/enum.Cow.html
846 /// [`str`]: ../primitive.str.html
847 #[stable(feature = "cstr_to_str", since = "1.4.0")]
848 pub fn to_string_lossy(&self) -> Cow<str> {
849 String::from_utf8_lossy(self.to_bytes())
852 /// Converts a [`Box`]`<CStr>` into a [`CString`] without copying or allocating.
854 /// [`Box`]: ../boxed/struct.Box.html
855 /// [`CString`]: struct.CString.html
856 #[unstable(feature = "into_boxed_c_str", issue = "40380")]
857 pub fn into_c_string(self: Box<CStr>) -> CString {
858 unsafe { mem::transmute(self) }
862 #[stable(feature = "rust1", since = "1.0.0")]
863 impl PartialEq for CStr {
864 fn eq(&self, other: &CStr) -> bool {
865 self.to_bytes().eq(other.to_bytes())
868 #[stable(feature = "rust1", since = "1.0.0")]
870 #[stable(feature = "rust1", since = "1.0.0")]
871 impl PartialOrd for CStr {
872 fn partial_cmp(&self, other: &CStr) -> Option<Ordering> {
873 self.to_bytes().partial_cmp(&other.to_bytes())
876 #[stable(feature = "rust1", since = "1.0.0")]
878 fn cmp(&self, other: &CStr) -> Ordering {
879 self.to_bytes().cmp(&other.to_bytes())
883 #[stable(feature = "cstr_borrow", since = "1.3.0")]
884 impl ToOwned for CStr {
885 type Owned = CString;
887 fn to_owned(&self) -> CString {
888 CString { inner: self.to_bytes_with_nul().into() }
892 #[stable(feature = "cstring_asref", since = "1.7.0")]
893 impl<'a> From<&'a CStr> for CString {
894 fn from(s: &'a CStr) -> CString {
899 #[stable(feature = "cstring_asref", since = "1.7.0")]
900 impl ops::Index<ops::RangeFull> for CString {
904 fn index(&self, _index: ops::RangeFull) -> &CStr {
909 #[stable(feature = "cstring_asref", since = "1.7.0")]
910 impl AsRef<CStr> for CStr {
911 fn as_ref(&self) -> &CStr {
916 #[stable(feature = "cstring_asref", since = "1.7.0")]
917 impl AsRef<CStr> for CString {
918 fn as_ref(&self) -> &CStr {
927 use borrow::Cow::{Borrowed, Owned};
928 use hash::{Hash, Hasher};
929 use collections::hash_map::DefaultHasher;
934 let ptr = data.as_ptr() as *const c_char;
936 assert_eq!(CStr::from_ptr(ptr).to_bytes(), b"123");
937 assert_eq!(CStr::from_ptr(ptr).to_bytes_with_nul(), b"123\0");
943 let s = CString::new("1234").unwrap();
944 assert_eq!(s.as_bytes(), b"1234");
945 assert_eq!(s.as_bytes_with_nul(), b"1234\0");
949 fn build_with_zero1() {
950 assert!(CString::new(&b"\0"[..]).is_err());
953 fn build_with_zero2() {
954 assert!(CString::new(vec![0]).is_err());
958 fn build_with_zero3() {
960 let s = CString::from_vec_unchecked(vec![0]);
961 assert_eq!(s.as_bytes(), b"\0");
967 let s = CString::new(&b"abc\x01\x02\n\xE2\x80\xA6\xFF"[..]).unwrap();
968 assert_eq!(format!("{:?}", s), r#""abc\x01\x02\n\xe2\x80\xa6\xff""#);
974 let s = CStr::from_ptr(b"12\0".as_ptr() as *const _);
975 assert_eq!(s.to_bytes(), b"12");
976 assert_eq!(s.to_bytes_with_nul(), b"12\0");
982 let data = b"123\xE2\x80\xA6\0";
983 let ptr = data.as_ptr() as *const c_char;
985 assert_eq!(CStr::from_ptr(ptr).to_str(), Ok("123…"));
986 assert_eq!(CStr::from_ptr(ptr).to_string_lossy(), Borrowed("123…"));
988 let data = b"123\xE2\0";
989 let ptr = data.as_ptr() as *const c_char;
991 assert!(CStr::from_ptr(ptr).to_str().is_err());
992 assert_eq!(CStr::from_ptr(ptr).to_string_lossy(), Owned::<str>(format!("123\u{FFFD}")));
999 let ptr = data.as_ptr() as *const c_char;
1001 let owned = unsafe { CStr::from_ptr(ptr).to_owned() };
1002 assert_eq!(owned.as_bytes_with_nul(), data);
1007 let data = b"123\xE2\xFA\xA6\0";
1008 let ptr = data.as_ptr() as *const c_char;
1009 let cstr: &'static CStr = unsafe { CStr::from_ptr(ptr) };
1011 let mut s = DefaultHasher::new();
1013 let cstr_hash = s.finish();
1014 let mut s = DefaultHasher::new();
1015 CString::new(&data[..data.len() - 1]).unwrap().hash(&mut s);
1016 let cstring_hash = s.finish();
1018 assert_eq!(cstr_hash, cstring_hash);
1022 fn from_bytes_with_nul() {
1023 let data = b"123\0";
1024 let cstr = CStr::from_bytes_with_nul(data);
1025 assert_eq!(cstr.map(CStr::to_bytes), Ok(&b"123"[..]));
1026 let cstr = CStr::from_bytes_with_nul(data);
1027 assert_eq!(cstr.map(CStr::to_bytes_with_nul), Ok(&b"123\0"[..]));
1030 let cstr = CStr::from_bytes_with_nul(data);
1031 let cstr_unchecked = CStr::from_bytes_with_nul_unchecked(data);
1032 assert_eq!(cstr, Ok(cstr_unchecked));
1037 fn from_bytes_with_nul_unterminated() {
1039 let cstr = CStr::from_bytes_with_nul(data);
1040 assert!(cstr.is_err());
1044 fn from_bytes_with_nul_interior() {
1045 let data = b"1\023\0";
1046 let cstr = CStr::from_bytes_with_nul(data);
1047 assert!(cstr.is_err());
1052 let orig: &[u8] = b"Hello, world!\0";
1053 let cstr = CStr::from_bytes_with_nul(orig).unwrap();
1054 let boxed: Box<CStr> = Box::from(cstr);
1055 let cstring = cstr.to_owned().into_boxed_c_str().into_c_string();
1056 assert_eq!(cstr, &*boxed);
1057 assert_eq!(&*boxed, &*cstring);
1058 assert_eq!(&*cstring, cstr);
1062 fn boxed_default() {
1063 let boxed = <Box<CStr>>::default();
1064 assert_eq!(boxed.to_bytes_with_nul(), &[0]);