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-rw-r--r--library/alloc/src/ffi/c_str.rs1123
-rw-r--r--library/alloc/src/ffi/c_str/tests.rs228
-rw-r--r--library/alloc/src/ffi/mod.rs88
3 files changed, 1439 insertions, 0 deletions
diff --git a/library/alloc/src/ffi/c_str.rs b/library/alloc/src/ffi/c_str.rs
new file mode 100644
index 000000000..ae61b1f1e
--- /dev/null
+++ b/library/alloc/src/ffi/c_str.rs
@@ -0,0 +1,1123 @@
+#[cfg(test)]
+mod tests;
+
+use crate::borrow::{Cow, ToOwned};
+use crate::boxed::Box;
+use crate::rc::Rc;
+use crate::slice::hack::into_vec;
+use crate::string::String;
+use crate::vec::Vec;
+use core::borrow::Borrow;
+use core::ffi::{c_char, CStr};
+use core::fmt;
+use core::mem;
+use core::num::NonZeroU8;
+use core::ops;
+use core::ptr;
+use core::slice;
+use core::slice::memchr;
+use core::str::{self, Utf8Error};
+
+#[cfg(target_has_atomic = "ptr")]
+use crate::sync::Arc;
+
+/// A type representing an owned, C-compatible, nul-terminated string with no nul bytes in the
+/// middle.
+///
+/// This type serves the purpose of being able to safely generate a
+/// C-compatible string from a Rust byte slice or vector. An instance of this
+/// type is a static guarantee that the underlying bytes contain no interior 0
+/// bytes ("nul characters") and that the final byte is 0 ("nul terminator").
+///
+/// `CString` is to <code>&[CStr]</code> as [`String`] is to <code>&[str]</code>: the former
+/// in each pair are owned strings; the latter are borrowed
+/// references.
+///
+/// # Creating a `CString`
+///
+/// A `CString` is created from either a byte slice or a byte vector,
+/// or anything that implements <code>[Into]<[Vec]<[u8]>></code> (for
+/// example, you can build a `CString` straight out of a [`String`] or
+/// a <code>&[str]</code>, since both implement that trait).
+///
+/// The [`CString::new`] method will actually check that the provided <code>&[[u8]]</code>
+/// does not have 0 bytes in the middle, and return an error if it
+/// finds one.
+///
+/// # Extracting a raw pointer to the whole C string
+///
+/// `CString` implements an [`as_ptr`][`CStr::as_ptr`] method through the [`Deref`]
+/// trait. This method will give you a `*const c_char` which you can
+/// feed directly to extern functions that expect a nul-terminated
+/// string, like C's `strdup()`. Notice that [`as_ptr`][`CStr::as_ptr`] returns a
+/// read-only pointer; if the C code writes to it, that causes
+/// undefined behavior.
+///
+/// # Extracting a slice of the whole C string
+///
+/// Alternatively, you can obtain a <code>&[[u8]]</code> slice from a
+/// `CString` with the [`CString::as_bytes`] method. Slices produced in this
+/// way do *not* contain the trailing nul terminator. This is useful
+/// when you will be calling an extern function that takes a `*const
+/// u8` argument which is not necessarily nul-terminated, plus another
+/// argument with the length of the string — like C's `strndup()`.
+/// You can of course get the slice's length with its
+/// [`len`][slice::len] method.
+///
+/// If you need a <code>&[[u8]]</code> slice *with* the nul terminator, you
+/// can use [`CString::as_bytes_with_nul`] instead.
+///
+/// Once you have the kind of slice you need (with or without a nul
+/// terminator), you can call the slice's own
+/// [`as_ptr`][slice::as_ptr] method to get a read-only raw pointer to pass to
+/// extern functions. See the documentation for that function for a
+/// discussion on ensuring the lifetime of the raw pointer.
+///
+/// [str]: prim@str "str"
+/// [`Deref`]: ops::Deref
+///
+/// # Examples
+///
+/// ```ignore (extern-declaration)
+/// # fn main() {
+/// use std::ffi::CString;
+/// use std::os::raw::c_char;
+///
+/// extern "C" {
+/// fn my_printer(s: *const c_char);
+/// }
+///
+/// // We are certain that our string doesn't have 0 bytes in the middle,
+/// // so we can .expect()
+/// let c_to_print = CString::new("Hello, world!").expect("CString::new failed");
+/// unsafe {
+/// my_printer(c_to_print.as_ptr());
+/// }
+/// # }
+/// ```
+///
+/// # Safety
+///
+/// `CString` is intended for working with traditional C-style strings
+/// (a sequence of non-nul bytes terminated by a single nul byte); the
+/// primary use case for these kinds of strings is interoperating with C-like
+/// code. Often you will need to transfer ownership to/from that external
+/// code. It is strongly recommended that you thoroughly read through the
+/// documentation of `CString` before use, as improper ownership management
+/// of `CString` instances can lead to invalid memory accesses, memory leaks,
+/// and other memory errors.
+#[derive(PartialEq, PartialOrd, Eq, Ord, Hash, Clone)]
+#[cfg_attr(not(test), rustc_diagnostic_item = "cstring_type")]
+#[stable(feature = "alloc_c_string", since = "1.64.0")]
+pub struct CString {
+ // Invariant 1: the slice ends with a zero byte and has a length of at least one.
+ // Invariant 2: the slice contains only one zero byte.
+ // Improper usage of unsafe function can break Invariant 2, but not Invariant 1.
+ inner: Box<[u8]>,
+}
+
+/// An error indicating that an interior nul byte was found.
+///
+/// While Rust strings may contain nul bytes in the middle, C strings
+/// can't, as that byte would effectively truncate the string.
+///
+/// This error is created by the [`new`][`CString::new`] method on
+/// [`CString`]. See its documentation for more.
+///
+/// # Examples
+///
+/// ```
+/// use std::ffi::{CString, NulError};
+///
+/// let _: NulError = CString::new(b"f\0oo".to_vec()).unwrap_err();
+/// ```
+#[derive(Clone, PartialEq, Eq, Debug)]
+#[stable(feature = "alloc_c_string", since = "1.64.0")]
+pub struct NulError(usize, Vec<u8>);
+
+#[derive(Clone, PartialEq, Eq, Debug)]
+enum FromBytesWithNulErrorKind {
+ InteriorNul(usize),
+ NotNulTerminated,
+}
+
+/// An error indicating that a nul byte was not in the expected position.
+///
+/// The vector used to create a [`CString`] must have one and only one nul byte,
+/// positioned at the end.
+///
+/// This error is created by the [`CString::from_vec_with_nul`] method.
+/// See its documentation for more.
+///
+/// # Examples
+///
+/// ```
+/// use std::ffi::{CString, FromVecWithNulError};
+///
+/// let _: FromVecWithNulError = CString::from_vec_with_nul(b"f\0oo".to_vec()).unwrap_err();
+/// ```
+#[derive(Clone, PartialEq, Eq, Debug)]
+#[stable(feature = "alloc_c_string", since = "1.64.0")]
+pub struct FromVecWithNulError {
+ error_kind: FromBytesWithNulErrorKind,
+ bytes: Vec<u8>,
+}
+
+#[stable(feature = "cstring_from_vec_with_nul", since = "1.58.0")]
+impl FromVecWithNulError {
+ /// Returns a slice of [`u8`]s bytes that were attempted to convert to a [`CString`].
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// use std::ffi::CString;
+ ///
+ /// // Some invalid bytes in a vector
+ /// let bytes = b"f\0oo".to_vec();
+ ///
+ /// let value = CString::from_vec_with_nul(bytes.clone());
+ ///
+ /// assert_eq!(&bytes[..], value.unwrap_err().as_bytes());
+ /// ```
+ #[must_use]
+ #[stable(feature = "cstring_from_vec_with_nul", since = "1.58.0")]
+ pub fn as_bytes(&self) -> &[u8] {
+ &self.bytes[..]
+ }
+
+ /// Returns the bytes that were attempted to convert to a [`CString`].
+ ///
+ /// This method is carefully constructed to avoid allocation. It will
+ /// consume the error, moving out the bytes, so that a copy of the bytes
+ /// does not need to be made.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// use std::ffi::CString;
+ ///
+ /// // Some invalid bytes in a vector
+ /// let bytes = b"f\0oo".to_vec();
+ ///
+ /// let value = CString::from_vec_with_nul(bytes.clone());
+ ///
+ /// assert_eq!(bytes, value.unwrap_err().into_bytes());
+ /// ```
+ #[must_use = "`self` will be dropped if the result is not used"]
+ #[stable(feature = "cstring_from_vec_with_nul", since = "1.58.0")]
+ pub fn into_bytes(self) -> Vec<u8> {
+ self.bytes
+ }
+}
+
+/// An error indicating invalid UTF-8 when converting a [`CString`] into a [`String`].
+///
+/// `CString` is just a wrapper over a buffer of bytes with a nul terminator;
+/// [`CString::into_string`] performs UTF-8 validation on those bytes and may
+/// return this error.
+///
+/// This `struct` is created by [`CString::into_string()`]. See
+/// its documentation for more.
+#[derive(Clone, PartialEq, Eq, Debug)]
+#[stable(feature = "alloc_c_string", since = "1.64.0")]
+pub struct IntoStringError {
+ inner: CString,
+ error: Utf8Error,
+}
+
+impl CString {
+ /// Creates a new C-compatible string from a container of bytes.
+ ///
+ /// This function will consume the provided data and use the
+ /// underlying bytes to construct a new string, ensuring that
+ /// there is a trailing 0 byte. This trailing 0 byte will be
+ /// appended by this function; the provided data should *not*
+ /// contain any 0 bytes in it.
+ ///
+ /// # Examples
+ ///
+ /// ```ignore (extern-declaration)
+ /// use std::ffi::CString;
+ /// use std::os::raw::c_char;
+ ///
+ /// extern "C" { fn puts(s: *const c_char); }
+ ///
+ /// let to_print = CString::new("Hello!").expect("CString::new failed");
+ /// unsafe {
+ /// puts(to_print.as_ptr());
+ /// }
+ /// ```
+ ///
+ /// # Errors
+ ///
+ /// This function will return an error if the supplied bytes contain an
+ /// internal 0 byte. The [`NulError`] returned will contain the bytes as well as
+ /// the position of the nul byte.
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn new<T: Into<Vec<u8>>>(t: T) -> Result<CString, NulError> {
+ trait SpecNewImpl {
+ fn spec_new_impl(self) -> Result<CString, NulError>;
+ }
+
+ impl<T: Into<Vec<u8>>> SpecNewImpl for T {
+ default fn spec_new_impl(self) -> Result<CString, NulError> {
+ let bytes: Vec<u8> = self.into();
+ match memchr::memchr(0, &bytes) {
+ Some(i) => Err(NulError(i, bytes)),
+ None => Ok(unsafe { CString::_from_vec_unchecked(bytes) }),
+ }
+ }
+ }
+
+ // Specialization for avoiding reallocation
+ #[inline(always)] // Without that it is not inlined into specializations
+ fn spec_new_impl_bytes(bytes: &[u8]) -> Result<CString, NulError> {
+ // We cannot have such large slice that we would overflow here
+ // but using `checked_add` allows LLVM to assume that capacity never overflows
+ // and generate twice shorter code.
+ // `saturating_add` doesn't help for some reason.
+ let capacity = bytes.len().checked_add(1).unwrap();
+
+ // Allocate before validation to avoid duplication of allocation code.
+ // We still need to allocate and copy memory even if we get an error.
+ let mut buffer = Vec::with_capacity(capacity);
+ buffer.extend(bytes);
+
+ // Check memory of self instead of new buffer.
+ // This allows better optimizations if lto enabled.
+ match memchr::memchr(0, bytes) {
+ Some(i) => Err(NulError(i, buffer)),
+ None => Ok(unsafe { CString::_from_vec_unchecked(buffer) }),
+ }
+ }
+
+ impl SpecNewImpl for &'_ [u8] {
+ fn spec_new_impl(self) -> Result<CString, NulError> {
+ spec_new_impl_bytes(self)
+ }
+ }
+
+ impl SpecNewImpl for &'_ str {
+ fn spec_new_impl(self) -> Result<CString, NulError> {
+ spec_new_impl_bytes(self.as_bytes())
+ }
+ }
+
+ impl SpecNewImpl for &'_ mut [u8] {
+ fn spec_new_impl(self) -> Result<CString, NulError> {
+ spec_new_impl_bytes(self)
+ }
+ }
+
+ t.spec_new_impl()
+ }
+
+ /// Creates a C-compatible string by consuming a byte vector,
+ /// without checking for interior 0 bytes.
+ ///
+ /// Trailing 0 byte will be appended by this function.
+ ///
+ /// This method is equivalent to [`CString::new`] except that no runtime
+ /// assertion is made that `v` contains no 0 bytes, and it requires an
+ /// actual byte vector, not anything that can be converted to one with Into.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::ffi::CString;
+ ///
+ /// let raw = b"foo".to_vec();
+ /// unsafe {
+ /// let c_string = CString::from_vec_unchecked(raw);
+ /// }
+ /// ```
+ #[must_use]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub unsafe fn from_vec_unchecked(v: Vec<u8>) -> Self {
+ debug_assert!(memchr::memchr(0, &v).is_none());
+ unsafe { Self::_from_vec_unchecked(v) }
+ }
+
+ unsafe fn _from_vec_unchecked(mut v: Vec<u8>) -> Self {
+ v.reserve_exact(1);
+ v.push(0);
+ Self { inner: v.into_boxed_slice() }
+ }
+
+ /// Retakes ownership of a `CString` that was transferred to C via
+ /// [`CString::into_raw`].
+ ///
+ /// Additionally, the length of the string will be recalculated from the pointer.
+ ///
+ /// # Safety
+ ///
+ /// This should only ever be called with a pointer that was earlier
+ /// obtained by calling [`CString::into_raw`]. Other usage (e.g., trying to take
+ /// ownership of a string that was allocated by foreign code) is likely to lead
+ /// to undefined behavior or allocator corruption.
+ ///
+ /// It should be noted that the length isn't just "recomputed," but that
+ /// the recomputed length must match the original length from the
+ /// [`CString::into_raw`] call. This means the [`CString::into_raw`]/`from_raw`
+ /// methods should not be used when passing the string to C functions that can
+ /// modify the string's length.
+ ///
+ /// > **Note:** If you need to borrow a string that was allocated by
+ /// > foreign code, use [`CStr`]. If you need to take ownership of
+ /// > a string that was allocated by foreign code, you will need to
+ /// > make your own provisions for freeing it appropriately, likely
+ /// > with the foreign code's API to do that.
+ ///
+ /// # Examples
+ ///
+ /// Creates a `CString`, pass ownership to an `extern` function (via raw pointer), then retake
+ /// ownership with `from_raw`:
+ ///
+ /// ```ignore (extern-declaration)
+ /// use std::ffi::CString;
+ /// use std::os::raw::c_char;
+ ///
+ /// extern "C" {
+ /// fn some_extern_function(s: *mut c_char);
+ /// }
+ ///
+ /// let c_string = CString::new("Hello!").expect("CString::new failed");
+ /// let raw = c_string.into_raw();
+ /// unsafe {
+ /// some_extern_function(raw);
+ /// let c_string = CString::from_raw(raw);
+ /// }
+ /// ```
+ #[must_use = "call `drop(from_raw(ptr))` if you intend to drop the `CString`"]
+ #[stable(feature = "cstr_memory", since = "1.4.0")]
+ pub unsafe fn from_raw(ptr: *mut c_char) -> CString {
+ // SAFETY: This is called with a pointer that was obtained from a call
+ // to `CString::into_raw` and the length has not been modified. As such,
+ // we know there is a NUL byte (and only one) at the end and that the
+ // information about the size of the allocation is correct on Rust's
+ // side.
+ unsafe {
+ extern "C" {
+ /// Provided by libc or compiler_builtins.
+ fn strlen(s: *const c_char) -> usize;
+ }
+ let len = strlen(ptr) + 1; // Including the NUL byte
+ let slice = slice::from_raw_parts_mut(ptr, len as usize);
+ CString { inner: Box::from_raw(slice as *mut [c_char] as *mut [u8]) }
+ }
+ }
+
+ /// Consumes the `CString` and transfers ownership of the string to a C caller.
+ ///
+ /// The pointer which this function returns must be returned to Rust and reconstituted using
+ /// [`CString::from_raw`] to be properly deallocated. Specifically, one
+ /// should *not* use the standard C `free()` function to deallocate
+ /// this string.
+ ///
+ /// Failure to call [`CString::from_raw`] will lead to a memory leak.
+ ///
+ /// The C side must **not** modify the length of the string (by writing a
+ /// `null` somewhere inside the string or removing the final one) before
+ /// it makes it back into Rust using [`CString::from_raw`]. See the safety section
+ /// in [`CString::from_raw`].
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::ffi::CString;
+ ///
+ /// let c_string = CString::new("foo").expect("CString::new failed");
+ ///
+ /// let ptr = c_string.into_raw();
+ ///
+ /// unsafe {
+ /// assert_eq!(b'f', *ptr as u8);
+ /// assert_eq!(b'o', *ptr.offset(1) as u8);
+ /// assert_eq!(b'o', *ptr.offset(2) as u8);
+ /// assert_eq!(b'\0', *ptr.offset(3) as u8);
+ ///
+ /// // retake pointer to free memory
+ /// let _ = CString::from_raw(ptr);
+ /// }
+ /// ```
+ #[inline]
+ #[must_use = "`self` will be dropped if the result is not used"]
+ #[stable(feature = "cstr_memory", since = "1.4.0")]
+ pub fn into_raw(self) -> *mut c_char {
+ Box::into_raw(self.into_inner()) as *mut c_char
+ }
+
+ /// Converts the `CString` into a [`String`] if it contains valid UTF-8 data.
+ ///
+ /// On failure, ownership of the original `CString` is returned.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::ffi::CString;
+ ///
+ /// let valid_utf8 = vec![b'f', b'o', b'o'];
+ /// let cstring = CString::new(valid_utf8).expect("CString::new failed");
+ /// assert_eq!(cstring.into_string().expect("into_string() call failed"), "foo");
+ ///
+ /// let invalid_utf8 = vec![b'f', 0xff, b'o', b'o'];
+ /// let cstring = CString::new(invalid_utf8).expect("CString::new failed");
+ /// let err = cstring.into_string().err().expect("into_string().err() failed");
+ /// assert_eq!(err.utf8_error().valid_up_to(), 1);
+ /// ```
+ #[stable(feature = "cstring_into", since = "1.7.0")]
+ pub fn into_string(self) -> Result<String, IntoStringError> {
+ String::from_utf8(self.into_bytes()).map_err(|e| IntoStringError {
+ error: e.utf8_error(),
+ inner: unsafe { Self::_from_vec_unchecked(e.into_bytes()) },
+ })
+ }
+
+ /// Consumes the `CString` and returns the underlying byte buffer.
+ ///
+ /// The returned buffer does **not** contain the trailing nul
+ /// terminator, and it is guaranteed to not have any interior nul
+ /// bytes.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::ffi::CString;
+ ///
+ /// let c_string = CString::new("foo").expect("CString::new failed");
+ /// let bytes = c_string.into_bytes();
+ /// assert_eq!(bytes, vec![b'f', b'o', b'o']);
+ /// ```
+ #[must_use = "`self` will be dropped if the result is not used"]
+ #[stable(feature = "cstring_into", since = "1.7.0")]
+ pub fn into_bytes(self) -> Vec<u8> {
+ let mut vec = into_vec(self.into_inner());
+ let _nul = vec.pop();
+ debug_assert_eq!(_nul, Some(0u8));
+ vec
+ }
+
+ /// Equivalent to [`CString::into_bytes()`] except that the
+ /// returned vector includes the trailing nul terminator.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::ffi::CString;
+ ///
+ /// let c_string = CString::new("foo").expect("CString::new failed");
+ /// let bytes = c_string.into_bytes_with_nul();
+ /// assert_eq!(bytes, vec![b'f', b'o', b'o', b'\0']);
+ /// ```
+ #[must_use = "`self` will be dropped if the result is not used"]
+ #[stable(feature = "cstring_into", since = "1.7.0")]
+ pub fn into_bytes_with_nul(self) -> Vec<u8> {
+ into_vec(self.into_inner())
+ }
+
+ /// Returns the contents of this `CString` as a slice of bytes.
+ ///
+ /// The returned slice does **not** contain the trailing nul
+ /// terminator, and it is guaranteed to not have any interior nul
+ /// bytes. If you need the nul terminator, use
+ /// [`CString::as_bytes_with_nul`] instead.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::ffi::CString;
+ ///
+ /// let c_string = CString::new("foo").expect("CString::new failed");
+ /// let bytes = c_string.as_bytes();
+ /// assert_eq!(bytes, &[b'f', b'o', b'o']);
+ /// ```
+ #[inline]
+ #[must_use]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn as_bytes(&self) -> &[u8] {
+ // SAFETY: CString has a length at least 1
+ unsafe { self.inner.get_unchecked(..self.inner.len() - 1) }
+ }
+
+ /// Equivalent to [`CString::as_bytes()`] except that the
+ /// returned slice includes the trailing nul terminator.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::ffi::CString;
+ ///
+ /// let c_string = CString::new("foo").expect("CString::new failed");
+ /// let bytes = c_string.as_bytes_with_nul();
+ /// assert_eq!(bytes, &[b'f', b'o', b'o', b'\0']);
+ /// ```
+ #[inline]
+ #[must_use]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn as_bytes_with_nul(&self) -> &[u8] {
+ &self.inner
+ }
+
+ /// Extracts a [`CStr`] slice containing the entire string.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::ffi::{CString, CStr};
+ ///
+ /// let c_string = CString::new(b"foo".to_vec()).expect("CString::new failed");
+ /// let cstr = c_string.as_c_str();
+ /// assert_eq!(cstr,
+ /// CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed"));
+ /// ```
+ #[inline]
+ #[must_use]
+ #[stable(feature = "as_c_str", since = "1.20.0")]
+ pub fn as_c_str(&self) -> &CStr {
+ &*self
+ }
+
+ /// Converts this `CString` into a boxed [`CStr`].
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::ffi::{CString, CStr};
+ ///
+ /// let c_string = CString::new(b"foo".to_vec()).expect("CString::new failed");
+ /// let boxed = c_string.into_boxed_c_str();
+ /// assert_eq!(&*boxed,
+ /// CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed"));
+ /// ```
+ #[must_use = "`self` will be dropped if the result is not used"]
+ #[stable(feature = "into_boxed_c_str", since = "1.20.0")]
+ pub fn into_boxed_c_str(self) -> Box<CStr> {
+ unsafe { Box::from_raw(Box::into_raw(self.into_inner()) as *mut CStr) }
+ }
+
+ /// Bypass "move out of struct which implements [`Drop`] trait" restriction.
+ #[inline]
+ fn into_inner(self) -> Box<[u8]> {
+ // Rationale: `mem::forget(self)` invalidates the previous call to `ptr::read(&self.inner)`
+ // so we use `ManuallyDrop` to ensure `self` is not dropped.
+ // Then we can return the box directly without invalidating it.
+ // See https://github.com/rust-lang/rust/issues/62553.
+ let this = mem::ManuallyDrop::new(self);
+ unsafe { ptr::read(&this.inner) }
+ }
+
+ /// Converts a <code>[Vec]<[u8]></code> to a [`CString`] without checking the
+ /// invariants on the given [`Vec`].
+ ///
+ /// # Safety
+ ///
+ /// The given [`Vec`] **must** have one nul byte as its last element.
+ /// This means it cannot be empty nor have any other nul byte anywhere else.
+ ///
+ /// # Example
+ ///
+ /// ```
+ /// use std::ffi::CString;
+ /// assert_eq!(
+ /// unsafe { CString::from_vec_with_nul_unchecked(b"abc\0".to_vec()) },
+ /// unsafe { CString::from_vec_unchecked(b"abc".to_vec()) }
+ /// );
+ /// ```
+ #[must_use]
+ #[stable(feature = "cstring_from_vec_with_nul", since = "1.58.0")]
+ pub unsafe fn from_vec_with_nul_unchecked(v: Vec<u8>) -> Self {
+ debug_assert!(memchr::memchr(0, &v).unwrap() + 1 == v.len());
+ unsafe { Self::_from_vec_with_nul_unchecked(v) }
+ }
+
+ unsafe fn _from_vec_with_nul_unchecked(v: Vec<u8>) -> Self {
+ Self { inner: v.into_boxed_slice() }
+ }
+
+ /// Attempts to converts a <code>[Vec]<[u8]></code> to a [`CString`].
+ ///
+ /// Runtime checks are present to ensure there is only one nul byte in the
+ /// [`Vec`], its last element.
+ ///
+ /// # Errors
+ ///
+ /// If a nul byte is present and not the last element or no nul bytes
+ /// is present, an error will be returned.
+ ///
+ /// # Examples
+ ///
+ /// A successful conversion will produce the same result as [`CString::new`]
+ /// when called without the ending nul byte.
+ ///
+ /// ```
+ /// use std::ffi::CString;
+ /// assert_eq!(
+ /// CString::from_vec_with_nul(b"abc\0".to_vec())
+ /// .expect("CString::from_vec_with_nul failed"),
+ /// CString::new(b"abc".to_vec()).expect("CString::new failed")
+ /// );
+ /// ```
+ ///
+ /// An incorrectly formatted [`Vec`] will produce an error.
+ ///
+ /// ```
+ /// use std::ffi::{CString, FromVecWithNulError};
+ /// // Interior nul byte
+ /// let _: FromVecWithNulError = CString::from_vec_with_nul(b"a\0bc".to_vec()).unwrap_err();
+ /// // No nul byte
+ /// let _: FromVecWithNulError = CString::from_vec_with_nul(b"abc".to_vec()).unwrap_err();
+ /// ```
+ #[stable(feature = "cstring_from_vec_with_nul", since = "1.58.0")]
+ pub fn from_vec_with_nul(v: Vec<u8>) -> Result<Self, FromVecWithNulError> {
+ let nul_pos = memchr::memchr(0, &v);
+ match nul_pos {
+ Some(nul_pos) if nul_pos + 1 == v.len() => {
+ // SAFETY: We know there is only one nul byte, at the end
+ // of the vec.
+ Ok(unsafe { Self::_from_vec_with_nul_unchecked(v) })
+ }
+ Some(nul_pos) => Err(FromVecWithNulError {
+ error_kind: FromBytesWithNulErrorKind::InteriorNul(nul_pos),
+ bytes: v,
+ }),
+ None => Err(FromVecWithNulError {
+ error_kind: FromBytesWithNulErrorKind::NotNulTerminated,
+ bytes: v,
+ }),
+ }
+ }
+}
+
+// Turns this `CString` into an empty string to prevent
+// memory-unsafe code from working by accident. Inline
+// to prevent LLVM from optimizing it away in debug builds.
+#[stable(feature = "cstring_drop", since = "1.13.0")]
+impl Drop for CString {
+ #[inline]
+ fn drop(&mut self) {
+ unsafe {
+ *self.inner.get_unchecked_mut(0) = 0;
+ }
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl ops::Deref for CString {
+ type Target = CStr;
+
+ #[inline]
+ fn deref(&self) -> &CStr {
+ unsafe { CStr::from_bytes_with_nul_unchecked(self.as_bytes_with_nul()) }
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl fmt::Debug for CString {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ fmt::Debug::fmt(&**self, f)
+ }
+}
+
+#[stable(feature = "cstring_into", since = "1.7.0")]
+impl From<CString> for Vec<u8> {
+ /// Converts a [`CString`] into a <code>[Vec]<[u8]></code>.
+ ///
+ /// The conversion consumes the [`CString`], and removes the terminating NUL byte.
+ #[inline]
+ fn from(s: CString) -> Vec<u8> {
+ s.into_bytes()
+ }
+}
+
+#[stable(feature = "cstr_default", since = "1.10.0")]
+impl Default for CString {
+ /// Creates an empty `CString`.
+ fn default() -> CString {
+ let a: &CStr = Default::default();
+ a.to_owned()
+ }
+}
+
+#[stable(feature = "cstr_borrow", since = "1.3.0")]
+impl Borrow<CStr> for CString {
+ #[inline]
+ fn borrow(&self) -> &CStr {
+ self
+ }
+}
+
+#[stable(feature = "cstring_from_cow_cstr", since = "1.28.0")]
+impl<'a> From<Cow<'a, CStr>> for CString {
+ /// Converts a `Cow<'a, CStr>` into a `CString`, by copying the contents if they are
+ /// borrowed.
+ #[inline]
+ fn from(s: Cow<'a, CStr>) -> Self {
+ s.into_owned()
+ }
+}
+
+#[cfg(not(test))]
+#[stable(feature = "box_from_c_str", since = "1.17.0")]
+impl From<&CStr> for Box<CStr> {
+ /// Converts a `&CStr` into a `Box<CStr>`,
+ /// by copying the contents into a newly allocated [`Box`].
+ fn from(s: &CStr) -> Box<CStr> {
+ let boxed: Box<[u8]> = Box::from(s.to_bytes_with_nul());
+ unsafe { Box::from_raw(Box::into_raw(boxed) as *mut CStr) }
+ }
+}
+
+#[stable(feature = "box_from_cow", since = "1.45.0")]
+impl From<Cow<'_, CStr>> for Box<CStr> {
+ /// Converts a `Cow<'a, CStr>` into a `Box<CStr>`,
+ /// by copying the contents if they are borrowed.
+ #[inline]
+ fn from(cow: Cow<'_, CStr>) -> Box<CStr> {
+ match cow {
+ Cow::Borrowed(s) => Box::from(s),
+ Cow::Owned(s) => Box::from(s),
+ }
+ }
+}
+
+#[stable(feature = "c_string_from_box", since = "1.18.0")]
+impl From<Box<CStr>> for CString {
+ /// Converts a <code>[Box]<[CStr]></code> into a [`CString`] without copying or allocating.
+ #[inline]
+ fn from(s: Box<CStr>) -> CString {
+ let raw = Box::into_raw(s) as *mut [u8];
+ CString { inner: unsafe { Box::from_raw(raw) } }
+ }
+}
+
+#[stable(feature = "cstring_from_vec_of_nonzerou8", since = "1.43.0")]
+impl From<Vec<NonZeroU8>> for CString {
+ /// Converts a <code>[Vec]<[NonZeroU8]></code> into a [`CString`] without
+ /// copying nor checking for inner null bytes.
+ #[inline]
+ fn from(v: Vec<NonZeroU8>) -> CString {
+ unsafe {
+ // Transmute `Vec<NonZeroU8>` to `Vec<u8>`.
+ let v: Vec<u8> = {
+ // SAFETY:
+ // - transmuting between `NonZeroU8` and `u8` is sound;
+ // - `alloc::Layout<NonZeroU8> == alloc::Layout<u8>`.
+ let (ptr, len, cap): (*mut NonZeroU8, _, _) = Vec::into_raw_parts(v);
+ Vec::from_raw_parts(ptr.cast::<u8>(), len, cap)
+ };
+ // SAFETY: `v` cannot contain null bytes, given the type-level
+ // invariant of `NonZeroU8`.
+ Self::_from_vec_unchecked(v)
+ }
+ }
+}
+
+#[cfg(not(test))]
+#[stable(feature = "more_box_slice_clone", since = "1.29.0")]
+impl Clone for Box<CStr> {
+ #[inline]
+ fn clone(&self) -> Self {
+ (**self).into()
+ }
+}
+
+#[stable(feature = "box_from_c_string", since = "1.20.0")]
+impl From<CString> for Box<CStr> {
+ /// Converts a [`CString`] into a <code>[Box]<[CStr]></code> without copying or allocating.
+ #[inline]
+ fn from(s: CString) -> Box<CStr> {
+ s.into_boxed_c_str()
+ }
+}
+
+#[stable(feature = "cow_from_cstr", since = "1.28.0")]
+impl<'a> From<CString> for Cow<'a, CStr> {
+ /// Converts a [`CString`] into an owned [`Cow`] without copying or allocating.
+ #[inline]
+ fn from(s: CString) -> Cow<'a, CStr> {
+ Cow::Owned(s)
+ }
+}
+
+#[stable(feature = "cow_from_cstr", since = "1.28.0")]
+impl<'a> From<&'a CStr> for Cow<'a, CStr> {
+ /// Converts a [`CStr`] into a borrowed [`Cow`] without copying or allocating.
+ #[inline]
+ fn from(s: &'a CStr) -> Cow<'a, CStr> {
+ Cow::Borrowed(s)
+ }
+}
+
+#[stable(feature = "cow_from_cstr", since = "1.28.0")]
+impl<'a> From<&'a CString> for Cow<'a, CStr> {
+ /// Converts a `&`[`CString`] into a borrowed [`Cow`] without copying or allocating.
+ #[inline]
+ fn from(s: &'a CString) -> Cow<'a, CStr> {
+ Cow::Borrowed(s.as_c_str())
+ }
+}
+
+#[cfg(target_has_atomic = "ptr")]
+#[stable(feature = "shared_from_slice2", since = "1.24.0")]
+impl From<CString> for Arc<CStr> {
+ /// Converts a [`CString`] into an <code>[Arc]<[CStr]></code> by moving the [`CString`]
+ /// data into a new [`Arc`] buffer.
+ #[inline]
+ fn from(s: CString) -> Arc<CStr> {
+ let arc: Arc<[u8]> = Arc::from(s.into_inner());
+ unsafe { Arc::from_raw(Arc::into_raw(arc) as *const CStr) }
+ }
+}
+
+#[cfg(target_has_atomic = "ptr")]
+#[stable(feature = "shared_from_slice2", since = "1.24.0")]
+impl From<&CStr> for Arc<CStr> {
+ /// Converts a `&CStr` into a `Arc<CStr>`,
+ /// by copying the contents into a newly allocated [`Arc`].
+ #[inline]
+ fn from(s: &CStr) -> Arc<CStr> {
+ let arc: Arc<[u8]> = Arc::from(s.to_bytes_with_nul());
+ unsafe { Arc::from_raw(Arc::into_raw(arc) as *const CStr) }
+ }
+}
+
+#[stable(feature = "shared_from_slice2", since = "1.24.0")]
+impl From<CString> for Rc<CStr> {
+ /// Converts a [`CString`] into an <code>[Rc]<[CStr]></code> by moving the [`CString`]
+ /// data into a new [`Arc`] buffer.
+ #[inline]
+ fn from(s: CString) -> Rc<CStr> {
+ let rc: Rc<[u8]> = Rc::from(s.into_inner());
+ unsafe { Rc::from_raw(Rc::into_raw(rc) as *const CStr) }
+ }
+}
+
+#[stable(feature = "shared_from_slice2", since = "1.24.0")]
+impl From<&CStr> for Rc<CStr> {
+ /// Converts a `&CStr` into a `Rc<CStr>`,
+ /// by copying the contents into a newly allocated [`Rc`].
+ #[inline]
+ fn from(s: &CStr) -> Rc<CStr> {
+ let rc: Rc<[u8]> = Rc::from(s.to_bytes_with_nul());
+ unsafe { Rc::from_raw(Rc::into_raw(rc) as *const CStr) }
+ }
+}
+
+#[cfg(not(test))]
+#[stable(feature = "default_box_extra", since = "1.17.0")]
+impl Default for Box<CStr> {
+ fn default() -> Box<CStr> {
+ let boxed: Box<[u8]> = Box::from([0]);
+ unsafe { Box::from_raw(Box::into_raw(boxed) as *mut CStr) }
+ }
+}
+
+impl NulError {
+ /// Returns the position of the nul byte in the slice that caused
+ /// [`CString::new`] to fail.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::ffi::CString;
+ ///
+ /// let nul_error = CString::new("foo\0bar").unwrap_err();
+ /// assert_eq!(nul_error.nul_position(), 3);
+ ///
+ /// let nul_error = CString::new("foo bar\0").unwrap_err();
+ /// assert_eq!(nul_error.nul_position(), 7);
+ /// ```
+ #[must_use]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn nul_position(&self) -> usize {
+ self.0
+ }
+
+ /// Consumes this error, returning the underlying vector of bytes which
+ /// generated the error in the first place.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::ffi::CString;
+ ///
+ /// let nul_error = CString::new("foo\0bar").unwrap_err();
+ /// assert_eq!(nul_error.into_vec(), b"foo\0bar");
+ /// ```
+ #[must_use = "`self` will be dropped if the result is not used"]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn into_vec(self) -> Vec<u8> {
+ self.1
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl fmt::Display for NulError {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ write!(f, "nul byte found in provided data at position: {}", self.0)
+ }
+}
+
+#[stable(feature = "cstring_from_vec_with_nul", since = "1.58.0")]
+impl fmt::Display for FromVecWithNulError {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ match self.error_kind {
+ FromBytesWithNulErrorKind::InteriorNul(pos) => {
+ write!(f, "data provided contains an interior nul byte at pos {pos}")
+ }
+ FromBytesWithNulErrorKind::NotNulTerminated => {
+ write!(f, "data provided is not nul terminated")
+ }
+ }
+ }
+}
+
+impl IntoStringError {
+ /// Consumes this error, returning original [`CString`] which generated the
+ /// error.
+ #[must_use = "`self` will be dropped if the result is not used"]
+ #[stable(feature = "cstring_into", since = "1.7.0")]
+ pub fn into_cstring(self) -> CString {
+ self.inner
+ }
+
+ /// Access the underlying UTF-8 error that was the cause of this error.
+ #[must_use]
+ #[stable(feature = "cstring_into", since = "1.7.0")]
+ pub fn utf8_error(&self) -> Utf8Error {
+ self.error
+ }
+
+ #[doc(hidden)]
+ #[unstable(feature = "cstr_internals", issue = "none")]
+ pub fn __source(&self) -> &Utf8Error {
+ &self.error
+ }
+}
+
+impl IntoStringError {
+ fn description(&self) -> &str {
+ "C string contained non-utf8 bytes"
+ }
+}
+
+#[stable(feature = "cstring_into", since = "1.7.0")]
+impl fmt::Display for IntoStringError {
+ #[allow(deprecated, deprecated_in_future)]
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ self.description().fmt(f)
+ }
+}
+
+#[stable(feature = "cstr_borrow", since = "1.3.0")]
+impl ToOwned for CStr {
+ type Owned = CString;
+
+ fn to_owned(&self) -> CString {
+ CString { inner: self.to_bytes_with_nul().into() }
+ }
+
+ fn clone_into(&self, target: &mut CString) {
+ let mut b = into_vec(mem::take(&mut target.inner));
+ self.to_bytes_with_nul().clone_into(&mut b);
+ target.inner = b.into_boxed_slice();
+ }
+}
+
+#[stable(feature = "cstring_asref", since = "1.7.0")]
+impl From<&CStr> for CString {
+ fn from(s: &CStr) -> CString {
+ s.to_owned()
+ }
+}
+
+#[stable(feature = "cstring_asref", since = "1.7.0")]
+impl ops::Index<ops::RangeFull> for CString {
+ type Output = CStr;
+
+ #[inline]
+ fn index(&self, _index: ops::RangeFull) -> &CStr {
+ self
+ }
+}
+
+#[stable(feature = "cstring_asref", since = "1.7.0")]
+impl AsRef<CStr> for CString {
+ #[inline]
+ fn as_ref(&self) -> &CStr {
+ self
+ }
+}
+
+#[cfg(not(test))]
+impl CStr {
+ /// Converts a `CStr` into a <code>[Cow]<[str]></code>.
+ ///
+ /// If the contents of the `CStr` are valid UTF-8 data, this
+ /// function will return a <code>[Cow]::[Borrowed]\(&[str])</code>
+ /// with the corresponding <code>&[str]</code> slice. Otherwise, it will
+ /// replace any invalid UTF-8 sequences with
+ /// [`U+FFFD REPLACEMENT CHARACTER`][U+FFFD] and return a
+ /// <code>[Cow]::[Owned]\(&[str])</code> with the result.
+ ///
+ /// [str]: prim@str "str"
+ /// [Borrowed]: Cow::Borrowed
+ /// [Owned]: Cow::Owned
+ /// [U+FFFD]: core::char::REPLACEMENT_CHARACTER "std::char::REPLACEMENT_CHARACTER"
+ ///
+ /// # Examples
+ ///
+ /// Calling `to_string_lossy` on a `CStr` containing valid UTF-8:
+ ///
+ /// ```
+ /// use std::borrow::Cow;
+ /// use std::ffi::CStr;
+ ///
+ /// let cstr = CStr::from_bytes_with_nul(b"Hello World\0")
+ /// .expect("CStr::from_bytes_with_nul failed");
+ /// assert_eq!(cstr.to_string_lossy(), Cow::Borrowed("Hello World"));
+ /// ```
+ ///
+ /// Calling `to_string_lossy` on a `CStr` containing invalid UTF-8:
+ ///
+ /// ```
+ /// use std::borrow::Cow;
+ /// use std::ffi::CStr;
+ ///
+ /// let cstr = CStr::from_bytes_with_nul(b"Hello \xF0\x90\x80World\0")
+ /// .expect("CStr::from_bytes_with_nul failed");
+ /// assert_eq!(
+ /// cstr.to_string_lossy(),
+ /// Cow::Owned(String::from("Hello �World")) as Cow<'_, str>
+ /// );
+ /// ```
+ #[rustc_allow_incoherent_impl]
+ #[must_use = "this returns the result of the operation, \
+ without modifying the original"]
+ #[stable(feature = "cstr_to_str", since = "1.4.0")]
+ pub fn to_string_lossy(&self) -> Cow<'_, str> {
+ String::from_utf8_lossy(self.to_bytes())
+ }
+
+ /// Converts a <code>[Box]<[CStr]></code> into a [`CString`] without copying or allocating.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::ffi::CString;
+ ///
+ /// let c_string = CString::new(b"foo".to_vec()).expect("CString::new failed");
+ /// let boxed = c_string.into_boxed_c_str();
+ /// assert_eq!(boxed.into_c_string(), CString::new("foo").expect("CString::new failed"));
+ /// ```
+ #[rustc_allow_incoherent_impl]
+ #[must_use = "`self` will be dropped if the result is not used"]
+ #[stable(feature = "into_boxed_c_str", since = "1.20.0")]
+ pub fn into_c_string(self: Box<Self>) -> CString {
+ CString::from(self)
+ }
+}
diff --git a/library/alloc/src/ffi/c_str/tests.rs b/library/alloc/src/ffi/c_str/tests.rs
new file mode 100644
index 000000000..0b7476d5c
--- /dev/null
+++ b/library/alloc/src/ffi/c_str/tests.rs
@@ -0,0 +1,228 @@
+use super::*;
+use crate::rc::Rc;
+use crate::sync::Arc;
+use core::assert_matches::assert_matches;
+use core::ffi::FromBytesUntilNulError;
+use core::hash::{Hash, Hasher};
+
+#[allow(deprecated)]
+use core::hash::SipHasher13 as DefaultHasher;
+
+#[test]
+fn c_to_rust() {
+ let data = b"123\0";
+ let ptr = data.as_ptr() as *const c_char;
+ unsafe {
+ assert_eq!(CStr::from_ptr(ptr).to_bytes(), b"123");
+ assert_eq!(CStr::from_ptr(ptr).to_bytes_with_nul(), b"123\0");
+ }
+}
+
+#[test]
+fn simple() {
+ let s = CString::new("1234").unwrap();
+ assert_eq!(s.as_bytes(), b"1234");
+ assert_eq!(s.as_bytes_with_nul(), b"1234\0");
+}
+
+#[test]
+fn build_with_zero1() {
+ assert!(CString::new(&b"\0"[..]).is_err());
+}
+#[test]
+fn build_with_zero2() {
+ assert!(CString::new(vec![0]).is_err());
+}
+
+#[test]
+fn formatted() {
+ let s = CString::new(&b"abc\x01\x02\n\xE2\x80\xA6\xFF"[..]).unwrap();
+ assert_eq!(format!("{s:?}"), r#""abc\x01\x02\n\xe2\x80\xa6\xff""#);
+}
+
+#[test]
+fn borrowed() {
+ unsafe {
+ let s = CStr::from_ptr(b"12\0".as_ptr() as *const _);
+ assert_eq!(s.to_bytes(), b"12");
+ assert_eq!(s.to_bytes_with_nul(), b"12\0");
+ }
+}
+
+#[test]
+fn to_owned() {
+ let data = b"123\0";
+ let ptr = data.as_ptr() as *const c_char;
+
+ let owned = unsafe { CStr::from_ptr(ptr).to_owned() };
+ assert_eq!(owned.as_bytes_with_nul(), data);
+}
+
+#[test]
+fn equal_hash() {
+ let data = b"123\xE2\xFA\xA6\0";
+ let ptr = data.as_ptr() as *const c_char;
+ let cstr: &'static CStr = unsafe { CStr::from_ptr(ptr) };
+
+ #[allow(deprecated)]
+ let mut s = DefaultHasher::new();
+ cstr.hash(&mut s);
+ let cstr_hash = s.finish();
+ #[allow(deprecated)]
+ let mut s = DefaultHasher::new();
+ CString::new(&data[..data.len() - 1]).unwrap().hash(&mut s);
+ let cstring_hash = s.finish();
+
+ assert_eq!(cstr_hash, cstring_hash);
+}
+
+#[test]
+fn from_bytes_with_nul() {
+ let data = b"123\0";
+ let cstr = CStr::from_bytes_with_nul(data);
+ assert_eq!(cstr.map(CStr::to_bytes), Ok(&b"123"[..]));
+ let cstr = CStr::from_bytes_with_nul(data);
+ assert_eq!(cstr.map(CStr::to_bytes_with_nul), Ok(&b"123\0"[..]));
+
+ unsafe {
+ let cstr = CStr::from_bytes_with_nul(data);
+ let cstr_unchecked = CStr::from_bytes_with_nul_unchecked(data);
+ assert_eq!(cstr, Ok(cstr_unchecked));
+ }
+}
+
+#[test]
+fn from_bytes_with_nul_unterminated() {
+ let data = b"123";
+ let cstr = CStr::from_bytes_with_nul(data);
+ assert!(cstr.is_err());
+}
+
+#[test]
+fn from_bytes_with_nul_interior() {
+ let data = b"1\023\0";
+ let cstr = CStr::from_bytes_with_nul(data);
+ assert!(cstr.is_err());
+}
+
+#[test]
+fn cstr_from_bytes_until_nul() {
+ // Test an empty slice. This should fail because it
+ // does not contain a nul byte.
+ let b = b"";
+ assert_matches!(CStr::from_bytes_until_nul(&b[..]), Err(FromBytesUntilNulError { .. }));
+
+ // Test a non-empty slice, that does not contain a nul byte.
+ let b = b"hello";
+ assert_matches!(CStr::from_bytes_until_nul(&b[..]), Err(FromBytesUntilNulError { .. }));
+
+ // Test an empty nul-terminated string
+ let b = b"\0";
+ let r = CStr::from_bytes_until_nul(&b[..]).unwrap();
+ assert_eq!(r.to_bytes(), b"");
+
+ // Test a slice with the nul byte in the middle
+ let b = b"hello\0world!";
+ let r = CStr::from_bytes_until_nul(&b[..]).unwrap();
+ assert_eq!(r.to_bytes(), b"hello");
+
+ // Test a slice with the nul byte at the end
+ let b = b"hello\0";
+ let r = CStr::from_bytes_until_nul(&b[..]).unwrap();
+ assert_eq!(r.to_bytes(), b"hello");
+
+ // Test a slice with two nul bytes at the end
+ let b = b"hello\0\0";
+ let r = CStr::from_bytes_until_nul(&b[..]).unwrap();
+ assert_eq!(r.to_bytes(), b"hello");
+
+ // Test a slice containing lots of nul bytes
+ let b = b"\0\0\0\0";
+ let r = CStr::from_bytes_until_nul(&b[..]).unwrap();
+ assert_eq!(r.to_bytes(), b"");
+}
+
+#[test]
+fn into_boxed() {
+ let orig: &[u8] = b"Hello, world!\0";
+ let cstr = CStr::from_bytes_with_nul(orig).unwrap();
+ let boxed: Box<CStr> = Box::from(cstr);
+ let cstring = cstr.to_owned().into_boxed_c_str().into_c_string();
+ assert_eq!(cstr, &*boxed);
+ assert_eq!(&*boxed, &*cstring);
+ assert_eq!(&*cstring, cstr);
+}
+
+#[test]
+fn boxed_default() {
+ let boxed = <Box<CStr>>::default();
+ assert_eq!(boxed.to_bytes_with_nul(), &[0]);
+}
+
+#[test]
+fn test_c_str_clone_into() {
+ let mut c_string = CString::new("lorem").unwrap();
+ let c_ptr = c_string.as_ptr();
+ let c_str = CStr::from_bytes_with_nul(b"ipsum\0").unwrap();
+ c_str.clone_into(&mut c_string);
+ assert_eq!(c_str, c_string.as_c_str());
+ // The exact same size shouldn't have needed to move its allocation
+ assert_eq!(c_ptr, c_string.as_ptr());
+}
+
+#[test]
+fn into_rc() {
+ let orig: &[u8] = b"Hello, world!\0";
+ let cstr = CStr::from_bytes_with_nul(orig).unwrap();
+ let rc: Rc<CStr> = Rc::from(cstr);
+ let arc: Arc<CStr> = Arc::from(cstr);
+
+ assert_eq!(&*rc, cstr);
+ assert_eq!(&*arc, cstr);
+
+ let rc2: Rc<CStr> = Rc::from(cstr.to_owned());
+ let arc2: Arc<CStr> = Arc::from(cstr.to_owned());
+
+ assert_eq!(&*rc2, cstr);
+ assert_eq!(&*arc2, cstr);
+}
+
+#[test]
+fn cstr_const_constructor() {
+ const CSTR: &CStr = unsafe { CStr::from_bytes_with_nul_unchecked(b"Hello, world!\0") };
+
+ assert_eq!(CSTR.to_str().unwrap(), "Hello, world!");
+}
+
+#[test]
+fn cstr_index_from() {
+ let original = b"Hello, world!\0";
+ let cstr = CStr::from_bytes_with_nul(original).unwrap();
+ let result = CStr::from_bytes_with_nul(&original[7..]).unwrap();
+
+ assert_eq!(&cstr[7..], result);
+}
+
+#[test]
+#[should_panic]
+fn cstr_index_from_empty() {
+ let original = b"Hello, world!\0";
+ let cstr = CStr::from_bytes_with_nul(original).unwrap();
+ let _ = &cstr[original.len()..];
+}
+
+#[test]
+fn c_string_from_empty_string() {
+ let original = "";
+ let cstring = CString::new(original).unwrap();
+ assert_eq!(original.as_bytes(), cstring.as_bytes());
+ assert_eq!([b'\0'], cstring.as_bytes_with_nul());
+}
+
+#[test]
+fn c_str_from_empty_string() {
+ let original = b"\0";
+ let cstr = CStr::from_bytes_with_nul(original).unwrap();
+ assert_eq!([] as [u8; 0], cstr.to_bytes());
+ assert_eq!([b'\0'], cstr.to_bytes_with_nul());
+}
diff --git a/library/alloc/src/ffi/mod.rs b/library/alloc/src/ffi/mod.rs
new file mode 100644
index 000000000..e8530fbc1
--- /dev/null
+++ b/library/alloc/src/ffi/mod.rs
@@ -0,0 +1,88 @@
+//! Utilities related to FFI bindings.
+//!
+//! This module provides utilities to handle data across non-Rust
+//! interfaces, like other programming languages and the underlying
+//! operating system. It is mainly of use for FFI (Foreign Function
+//! Interface) bindings and code that needs to exchange C-like strings
+//! with other languages.
+//!
+//! # Overview
+//!
+//! Rust represents owned strings with the [`String`] type, and
+//! borrowed slices of strings with the [`str`] primitive. Both are
+//! always in UTF-8 encoding, and may contain nul bytes in the middle,
+//! i.e., if you look at the bytes that make up the string, there may
+//! be a `\0` among them. Both `String` and `str` store their length
+//! explicitly; there are no nul terminators at the end of strings
+//! like in C.
+//!
+//! C strings are different from Rust strings:
+//!
+//! * **Encodings** - Rust strings are UTF-8, but C strings may use
+//! other encodings. If you are using a string from C, you should
+//! check its encoding explicitly, rather than just assuming that it
+//! is UTF-8 like you can do in Rust.
+//!
+//! * **Character size** - C strings may use `char` or `wchar_t`-sized
+//! characters; please **note** that C's `char` is different from Rust's.
+//! The C standard leaves the actual sizes of those types open to
+//! interpretation, but defines different APIs for strings made up of
+//! each character type. Rust strings are always UTF-8, so different
+//! Unicode characters will be encoded in a variable number of bytes
+//! each. The Rust type [`char`] represents a '[Unicode scalar
+//! value]', which is similar to, but not the same as, a '[Unicode
+//! code point]'.
+//!
+//! * **Nul terminators and implicit string lengths** - Often, C
+//! strings are nul-terminated, i.e., they have a `\0` character at the
+//! end. The length of a string buffer is not stored, but has to be
+//! calculated; to compute the length of a string, C code must
+//! manually call a function like `strlen()` for `char`-based strings,
+//! or `wcslen()` for `wchar_t`-based ones. Those functions return
+//! the number of characters in the string excluding the nul
+//! terminator, so the buffer length is really `len+1` characters.
+//! Rust strings don't have a nul terminator; their length is always
+//! stored and does not need to be calculated. While in Rust
+//! accessing a string's length is an *O*(1) operation (because the
+//! length is stored); in C it is an *O*(*n*) operation because the
+//! length needs to be computed by scanning the string for the nul
+//! terminator.
+//!
+//! * **Internal nul characters** - When C strings have a nul
+//! terminator character, this usually means that they cannot have nul
+//! characters in the middle — a nul character would essentially
+//! truncate the string. Rust strings *can* have nul characters in
+//! the middle, because nul does not have to mark the end of the
+//! string in Rust.
+//!
+//! # Representations of non-Rust strings
+//!
+//! [`CString`] and [`CStr`] are useful when you need to transfer
+//! UTF-8 strings to and from languages with a C ABI, like Python.
+//!
+//! * **From Rust to C:** [`CString`] represents an owned, C-friendly
+//! string: it is nul-terminated, and has no internal nul characters.
+//! Rust code can create a [`CString`] out of a normal string (provided
+//! that the string doesn't have nul characters in the middle), and
+//! then use a variety of methods to obtain a raw <code>\*mut [u8]</code> that can
+//! then be passed as an argument to functions which use the C
+//! conventions for strings.
+//!
+//! * **From C to Rust:** [`CStr`] represents a borrowed C string; it
+//! is what you would use to wrap a raw <code>\*const [u8]</code> that you got from
+//! a C function. A [`CStr`] is guaranteed to be a nul-terminated array
+//! of bytes. Once you have a [`CStr`], you can convert it to a Rust
+//! <code>&[str]</code> if it's valid UTF-8, or lossily convert it by adding
+//! replacement characters.
+//!
+//! [`String`]: crate::string::String
+//! [`CStr`]: core::ffi::CStr
+
+#![stable(feature = "alloc_ffi", since = "1.64.0")]
+
+#[stable(feature = "alloc_c_string", since = "1.64.0")]
+pub use self::c_str::FromVecWithNulError;
+#[stable(feature = "alloc_c_string", since = "1.64.0")]
+pub use self::c_str::{CString, IntoStringError, NulError};
+
+mod c_str;
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-03 07:10:44 +0000