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#![allow(clippy::missing_safety_doc)] use crate::ffi::{c_char, libc::strlen, CString}; use alloc::{borrow::Cow, rc::Rc, sync::Arc}; use core::{ ascii, cmp::Ordering, fmt::{self, Write}, slice::{self, memchr}, str, }; /// Representation of a borrowed C string. /// /// This type represents a borrowed reference to a nul-terminated array of /// bytes. It can be constructed safely from a `&`[`u8`] slice, or unsafely from /// a raw `*const c_char`. It can then be converted to a Rust `&`[`str`] by /// performing UTF-8 validation, or into an owned [`CString`]. /// /// `&CStr` is to [`CString`] as `&`[`str`] is to [`String`]: the former in each /// pair are borrowed references; the latter are owned strings. /// /// Note that this structure is **not** `repr(C)` and is not recommended to be /// placed in the signatures of FFI functions. Instead, safe wrappers of FFI /// functions may leverage the unsafe [`CStr::from_ptr`] constructor to provide /// a safe interface to other consumers. /// /// # Examples /// /// Inspecting a foreign C string: /// /// ``` /// use drone_core::ffi::{c_char, CStr}; /// /// extern "C" fn my_string() -> *const c_char { /// "example".as_ptr() /// } /// /// unsafe { /// let slice = CStr::from_ptr(my_string()); /// println!("string buffer size without nul terminator: {}", slice.to_bytes().len(),); /// } /// ``` /// /// Passing a Rust-originating C string: /// /// ``` /// use drone_core::ffi::{c_char, CStr, CString}; /// /// fn work(data: &CStr) { /// extern "C" fn work_with(_data: *const c_char) {} /// /// unsafe { work_with(data.as_ptr()) } /// } /// /// let s = CString::new("data data data data").expect("CString::new failed"); /// work(&s); /// ``` /// /// Converting a foreign C string into a Rust [`String`]: /// /// ``` /// use drone_core::ffi::{c_char, CStr}; /// /// extern "C" fn my_string() -> *const c_char { /// "example".as_ptr() /// } /// /// fn my_string_safe() -> String { /// unsafe { CStr::from_ptr(my_string()).to_string_lossy().into_owned() } /// } /// /// println!("string: {}", my_string_safe()); /// ``` #[allow(clippy::derive_hash_xor_eq)] #[derive(Hash)] pub struct CStr { inner: [c_char], } /// An error indicating that a nul byte was not in the expected position. /// /// The slice used to create a [`CStr`] must have one and only one nul byte at /// the end of the slice. /// /// This error is created by the /// [`from_bytes_with_nul`](CStr::from_bytes_with_nul) method on [`CStr`]. See /// its documentation for more. /// /// # Examples /// /// ``` /// use drone_core::ffi::{CStr, FromBytesWithNulError}; /// /// let _: FromBytesWithNulError = CStr::from_bytes_with_nul(b"f\0oo").unwrap_err(); /// ``` #[derive(Clone, PartialEq, Eq, Debug)] pub struct FromBytesWithNulError { kind: FromBytesWithNulErrorKind, } #[derive(Clone, PartialEq, Eq, Debug)] enum FromBytesWithNulErrorKind { InteriorNul(usize), NotNulTerminated, } impl CStr { /// Wraps a raw C string with a safe C string wrapper. /// /// This function will wrap the provided `ptr` with a `CStr` wrapper, which /// allows inspection and interoperation of non-owned C strings. This method /// is unsafe for a number of reasons: /// /// * There is no guarantee to the validity of `ptr`. /// * The returned lifetime is not guaranteed to be the actual lifetime of /// `ptr`. /// * There is no guarantee that the memory pointed to by `ptr` contains a /// valid nul terminator byte at the end of the string. /// * It is not guaranteed that the memory pointed by `ptr` won't change /// before the `CStr` has been destroyed. /// /// > **Note**: This operation is intended to be a 0-cost cast but it is /// > currently implemented with an up-front calculation of the length of /// > the string. This is not guaranteed to always be the case. /// /// # Examples /// /// ``` /// use drone_core::ffi::{c_char, CStr}; /// /// extern "C" fn my_string() -> *const c_char { /// "example\0".as_ptr() /// } /// /// unsafe { /// let slice = CStr::from_ptr(my_string()); /// println!("string returned: {}", slice.to_str().unwrap()); /// } /// ``` pub unsafe fn from_ptr<'a>(ptr: *const c_char) -> &'a Self { unsafe { let len = strlen(ptr); let ptr = ptr.cast::<u8>(); Self::from_bytes_with_nul_unchecked(slice::from_raw_parts(ptr, len as usize + 1)) } } /// Creates a C string wrapper from a byte slice. /// /// This function will cast the provided `bytes` to a `CStr` wrapper after /// ensuring that the byte slice is nul-terminated and does not contain any /// interior nul bytes. /// /// # Examples /// /// ``` /// use drone_core::ffi::CStr; /// /// let cstr = CStr::from_bytes_with_nul(b"hello\0"); /// assert!(cstr.is_ok()); /// ``` /// /// Creating a `CStr` without a trailing nul terminator is an error: /// /// ``` /// use drone_core::ffi::CStr; /// /// let c_str = CStr::from_bytes_with_nul(b"hello"); /// assert!(c_str.is_err()); /// ``` /// /// Creating a `CStr` with an interior nul byte is an error: /// /// ``` /// use drone_core::ffi::CStr; /// /// let c_str = CStr::from_bytes_with_nul(b"he\0llo\0"); /// assert!(c_str.is_err()); /// ``` pub fn from_bytes_with_nul(bytes: &[u8]) -> Result<&Self, FromBytesWithNulError> { let nul_pos = memchr::memchr(0, bytes); if let Some(nul_pos) = nul_pos { if nul_pos + 1 != bytes.len() { return Err(FromBytesWithNulError::interior_nul(nul_pos)); } Ok(unsafe { Self::from_bytes_with_nul_unchecked(bytes) }) } else { Err(FromBytesWithNulError::not_nul_terminated()) } } /// Unsafely creates a C string wrapper from a byte slice. /// /// This function will cast the provided `bytes` to a `CStr` wrapper without /// performing any sanity checks. The provided slice **must** be /// nul-terminated and not contain any interior nul bytes. /// /// # Examples /// /// ``` /// use drone_core::ffi::{CStr, CString}; /// /// unsafe { /// let cstring = CString::new("hello").expect("CString::new failed"); /// let cstr = CStr::from_bytes_with_nul_unchecked(cstring.to_bytes_with_nul()); /// assert_eq!(cstr, &*cstring); /// } /// ``` #[allow(unsafe_op_in_unsafe_fn)] // FIXME https://github.com/rust-lang/rust/issues/74156 #[inline] pub const unsafe fn from_bytes_with_nul_unchecked(bytes: &[u8]) -> &Self { &*(bytes as *const [u8] as *const Self) } /// Returns the inner pointer to this C string. /// /// The returned pointer will be valid for as long as `self` is, and points /// to a contiguous region of memory terminated with a 0 byte to represent /// the end of the string. /// /// **WARNING** /// /// The returned pointer is read-only; writing to it (including passing it /// to C code that writes to it) causes undefined behavior. /// /// It is your responsibility to make sure that the underlying memory is not /// freed too early. For example, the following code will cause undefined /// behavior when `ptr` is used inside the `unsafe` block: /// /// ```no_run /// # #![allow(unused_must_use)] /// use drone_core::ffi::CString; /// /// let ptr = CString::new("Hello").expect("CString::new failed").as_ptr(); /// unsafe { /// // `ptr` is dangling /// *ptr; /// } /// ``` /// /// This happens because the pointer returned by `as_ptr` does not carry any /// lifetime information and the [`CString`] is deallocated immediately /// after the `CString::new("Hello").expect("CString::new failed").as_ptr()` /// expression is evaluated. To fix the problem, bind the `CString` to a /// local variable: /// /// ```no_run /// # #![allow(unused_must_use)] /// use drone_core::ffi::CString; /// /// let hello = CString::new("Hello").expect("CString::new failed"); /// let ptr = hello.as_ptr(); /// unsafe { /// // `ptr` is valid because `hello` is in scope /// *ptr; /// } /// ``` /// /// This way, the lifetime of the `CString` in `hello` encompasses the /// lifetime of `ptr` and the `unsafe` block. #[inline] pub const fn as_ptr(&self) -> *const c_char { self.inner.as_ptr() } /// Converts this C string to a byte slice. /// /// The returned slice will **not** contain the trailing nul terminator that /// this C string has. /// /// > **Note**: This method is currently implemented as a constant-time /// > cast, but it is planned to alter its definition in the future to /// > perform the length calculation whenever this method is called. /// /// # Examples /// /// ``` /// use drone_core::ffi::CStr; /// /// let c_str = CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed"); /// assert_eq!(c_str.to_bytes(), b"foo"); /// ``` #[inline] pub fn to_bytes(&self) -> &[u8] { let bytes = self.to_bytes_with_nul(); &bytes[..bytes.len() - 1] } /// Converts this C string to a byte slice containing the trailing 0 byte. /// /// This function is the equivalent of [`CStr::to_bytes`] except that it /// will retain the trailing nul terminator instead of chopping it off. /// /// > **Note**: This method is currently implemented as a 0-cost cast, but /// > it is planned to alter its definition in the future to perform the /// > length calculation whenever this method is called. /// /// # Examples /// /// ``` /// use drone_core::ffi::CStr; /// /// let c_str = CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed"); /// assert_eq!(c_str.to_bytes_with_nul(), b"foo\0"); /// ``` #[inline] pub fn to_bytes_with_nul(&self) -> &[u8] { unsafe { &*(&self.inner as *const [c_char] as *const [u8]) } } /// Yields a `&`[`str`] slice if the `CStr` contains valid UTF-8. /// /// If the contents of the `CStr` are valid UTF-8 data, this function will /// return the corresponding `&`[`str`] slice. Otherwise, it will return an /// error with details of where UTF-8 validation failed. /// /// > **Note**: This method is currently implemented to check for validity /// > after a constant-time cast, but it is planned to alter its definition /// > in the future to perform the length calculation in addition to the /// > UTF-8 check whenever this method is called. /// /// # Examples /// /// ``` /// use drone_core::ffi::CStr; /// /// let c_str = CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed"); /// assert_eq!(c_str.to_str(), Ok("foo")); /// ``` pub fn to_str(&self) -> Result<&str, str::Utf8Error> { // N.B., when `CStr` is changed to perform the length check in `.to_bytes()` // instead of in `from_ptr()`, it may be worth considering if this should // be rewritten to do the UTF-8 check inline with the length calculation // instead of doing it afterwards. str::from_utf8(self.to_bytes()) } /// Converts a `CStr` into a [`Cow`]`<`[`str`]`>`. /// /// If the contents of the `CStr` are valid UTF-8 data, this function will /// return a [`Cow::Borrowed`]`(&`[`str`]`)` with the corresponding /// `&`[`str`] slice. Otherwise, it will replace any invalid UTF-8 sequences /// with [`U+FFFD REPLACEMENT CHARACTER`](core::char::REPLACEMENT_CHARACTER) /// and return a [`Cow::Owned`]`(`[`String`]`)` with the result. /// /// > **Note**: This method is currently implemented to check for validity /// > after a constant-time cast, but it is planned to alter its definition /// > in the future to perform the length calculation in addition to the /// > UTF-8 check whenever this method is called. /// /// # Examples /// /// Calling `to_string_lossy` on a `CStr` containing valid UTF-8: /// /// ``` /// # #![feature(alloc)] /// # extern crate alloc; /// use alloc::borrow::Cow; /// use drone_core::ffi::CStr; /// /// let c_str = /// CStr::from_bytes_with_nul(b"Hello World\0").expect("CStr::from_bytes_with_nul failed"); /// assert_eq!(c_str.to_string_lossy(), Cow::Borrowed("Hello World")); /// ``` /// /// Calling `to_string_lossy` on a `CStr` containing invalid UTF-8: /// /// ``` /// # #![feature(alloc)] /// # extern crate alloc; /// use alloc::borrow::Cow; /// use drone_core::ffi::CStr; /// /// let c_str = CStr::from_bytes_with_nul(b"Hello \xF0\x90\x80World\0") /// .expect("CStr::from_bytes_with_nul failed"); /// assert_eq!(c_str.to_string_lossy(), Cow::Owned(String::from("Hello �World")) as Cow<'_, str>); /// ``` pub fn to_string_lossy(&self) -> Cow<'_, str> { String::from_utf8_lossy(self.to_bytes()) } /// Converts a [`Box`]`<CStr>` into a [`CString`] without copying or /// allocating. /// /// # Examples /// /// ``` /// use drone_core::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")); /// ``` #[allow(clippy::wrong_self_convention)] pub fn into_c_string(self: Box<Self>) -> CString { let raw = Box::into_raw(self) as *mut [u8]; CString { inner: unsafe { Box::from_raw(raw) } } } } impl FromBytesWithNulError { fn interior_nul(pos: usize) -> Self { Self { kind: FromBytesWithNulErrorKind::InteriorNul(pos) } } fn not_nul_terminated() -> Self { Self { kind: FromBytesWithNulErrorKind::NotNulTerminated } } } impl fmt::Debug for CStr { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { write!(f, "\"")?; for byte in self.to_bytes().iter().flat_map(|&b| ascii::escape_default(b)) { f.write_char(byte as char)?; } write!(f, "\"") } } impl Default for &CStr { fn default() -> Self { const SLICE: &[c_char] = &[0]; unsafe { CStr::from_ptr(SLICE.as_ptr()) } } } impl PartialEq for CStr { fn eq(&self, other: &Self) -> bool { self.to_bytes().eq(other.to_bytes()) } } impl Eq for CStr {} impl PartialOrd for CStr { fn partial_cmp(&self, other: &Self) -> Option<Ordering> { self.to_bytes().partial_cmp(&other.to_bytes()) } } impl Ord for CStr { fn cmp(&self, other: &Self) -> Ordering { self.to_bytes().cmp(&other.to_bytes()) } } impl ToOwned for CStr { type Owned = CString; fn to_owned(&self) -> CString { CString { inner: self.to_bytes_with_nul().into() } } } impl AsRef<CStr> for CStr { #[inline] fn as_ref(&self) -> &Self { self } } impl Default for Box<CStr> { fn default() -> Self { let boxed: Box<[u8]> = Box::from([0]); unsafe { Box::from_raw(Box::into_raw(boxed) as *mut CStr) } } } impl Clone for Box<CStr> { #[inline] fn clone(&self) -> Self { (**self).into() } } impl From<&CStr> for Box<CStr> { fn from(s: &CStr) -> Self { let boxed: Box<[u8]> = Box::from(s.to_bytes_with_nul()); unsafe { Box::from_raw(Box::into_raw(boxed) as *mut CStr) } } } impl From<CString> for Box<CStr> { /// Converts a [`CString`] into a [`Box`]`<`[`CStr`]`>` without copying or /// allocating. #[inline] fn from(s: CString) -> Self { s.into_boxed_c_str() } } impl From<CString> for Arc<CStr> { /// Converts a [`CString`] into a [`Arc`]`<`[`CStr`]`>` without copying or /// allocating. #[inline] fn from(s: CString) -> Self { let arc: Arc<[u8]> = Arc::from(s.into_inner()); unsafe { Arc::from_raw(Arc::into_raw(arc) as *const CStr) } } } impl From<&CStr> for Arc<CStr> { #[inline] fn from(s: &CStr) -> Self { let arc: Arc<[u8]> = Arc::from(s.to_bytes_with_nul()); unsafe { Arc::from_raw(Arc::into_raw(arc) as *const CStr) } } } impl From<CString> for Rc<CStr> { /// Converts a [`CString`] into a [`Rc`]`<`[`CStr`]`>` without copying or /// allocating. #[inline] fn from(s: CString) -> Self { let rc: Rc<[u8]> = Rc::from(s.into_inner()); unsafe { Rc::from_raw(Rc::into_raw(rc) as *const CStr) } } } impl From<&CStr> for Rc<CStr> { #[inline] fn from(s: &CStr) -> Self { let rc: Rc<[u8]> = Rc::from(s.to_bytes_with_nul()); unsafe { Rc::from_raw(Rc::into_raw(rc) as *const CStr) } } } impl<'a> From<CString> for Cow<'a, CStr> { #[inline] fn from(s: CString) -> Self { Cow::Owned(s) } } impl<'a> From<&'a CStr> for Cow<'a, CStr> { #[inline] fn from(s: &'a CStr) -> Self { Cow::Borrowed(s) } } impl<'a> From<&'a CString> for Cow<'a, CStr> { #[inline] fn from(s: &'a CString) -> Self { Cow::Borrowed(s.as_c_str()) } } impl fmt::Display for FromBytesWithNulError { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { write!(f, "{}", self.kind) } } impl fmt::Display for FromBytesWithNulErrorKind { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { match self { FromBytesWithNulErrorKind::InteriorNul(pos) => { write!(f, "data provided contains an interior nul byte at byte pos {}", pos) } FromBytesWithNulErrorKind::NotNulTerminated => { write!(f, "data provided is not nul terminated") } } } }