diff options
Diffstat (limited to 'ctr-std/src/ffi/c_str.rs')
| -rw-r--r-- | ctr-std/src/ffi/c_str.rs | 738 |
1 files changed, 643 insertions, 95 deletions
diff --git a/ctr-std/src/ffi/c_str.rs b/ctr-std/src/ffi/c_str.rs index ad40660..a19fe82 100644 --- a/ctr-std/src/ffi/c_str.rs +++ b/ctr-std/src/ffi/c_str.rs @@ -14,27 +14,80 @@ use cmp::Ordering; use error::Error; use fmt::{self, Write}; use io; -use libc::{self, c_char}; use mem; use memchr; use ops; +use os::raw::c_char; use ptr; +use rc::Rc; use slice; use str::{self, Utf8Error}; +use sync::Arc; +use sys; -/// A type representing an owned C-compatible string +/// A type representing an owned, C-compatible, nul-terminated string with no nul bytes in the +/// middle. /// -/// This type serves the primary purpose of being able to safely generate a +/// 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 and the final byte is 0. +/// bytes ("nul characters") and that the final byte is 0 ("nul terminator"). /// -/// A `CString` is created from either a byte slice or a byte vector. After -/// being created, a `CString` predominately inherits all of its methods from -/// the `Deref` implementation to `[c_char]`. Note that the underlying array -/// is represented as an array of `c_char` as opposed to `u8`. A `u8` slice -/// can be obtained with the `as_bytes` method. Slices produced from a `CString` -/// do *not* contain the trailing nul terminator unless otherwise specified. +/// `CString` is to [`CStr`] as [`String`] is to [`&str`]: 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 [`Into`]`<`[`Vec`]`<`[`u8`]`>>` (for +/// example, you can build a `CString` straight out of a [`String`] or +/// a [`&str`], since both implement that trait). +/// +/// The [`new`] method will actually check that the provided `&[u8]` +/// 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 a [`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()`. +/// +/// # Extracting a slice of the whole C string +/// +/// Alternatively, you can obtain a `&[`[`u8`]`]` slice from a +/// `CString` with the [`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 `&[`[`u8`]`]` slice *with* the nul terminator, you +/// can use [`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 raw pointer to pass to +/// extern functions. See the documentation for that function for a +/// discussion on ensuring the lifetime of the raw pointer. +/// +/// [`Into`]: ../convert/trait.Into.html +/// [`Vec`]: ../vec/struct.Vec.html +/// [`String`]: ../string/struct.String.html +/// [`&str`]: ../primitive.str.html +/// [`u8`]: ../primitive.u8.html +/// [`new`]: #method.new +/// [`as_bytes`]: #method.as_bytes +/// [`as_bytes_with_nul`]: #method.as_bytes_with_nul +/// [`as_ptr`]: #method.as_ptr +/// [slice.as_ptr]: ../primitive.slice.html#method.as_ptr +/// [slice.len]: ../primitive.slice.html#method.len +/// [`Deref`]: ../ops/trait.Deref.html +/// [`CStr`]: struct.CStr.html /// /// # Examples /// @@ -47,6 +100,8 @@ use str::{self, Utf8Error}; /// fn my_printer(s: *const c_char); /// } /// +/// // We are certain that our string doesn't have 0 bytes in the middle, +/// // so we can .unwrap() /// let c_to_print = CString::new("Hello, world!").unwrap(); /// unsafe { /// my_printer(c_to_print.as_ptr()); @@ -57,7 +112,7 @@ use str::{self, Utf8Error}; /// # Safety /// /// `CString` is intended for working with traditional C-style strings -/// (a sequence of non-null bytes terminated by a single null byte); the +/// (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 @@ -76,18 +131,24 @@ pub struct CString { /// Representation of a borrowed C string. /// -/// This dynamically sized type is only safely constructed via a borrowed -/// version of an instance of `CString`. This type can be constructed from a raw -/// C string as well and represents a C string borrowed from another location. +/// 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 `from_ptr` constructor to provide a safe +/// placed in the signatures of FFI functions. Instead, safe wrappers of FFI +/// functions may leverage the unsafe [`from_ptr`] constructor to provide a safe /// interface to other consumers. /// /// # Examples /// -/// Inspecting a foreign C string +/// Inspecting a foreign C string: /// /// ```no_run /// use std::ffi::CStr; @@ -97,11 +158,11 @@ pub struct CString { /// /// unsafe { /// let slice = CStr::from_ptr(my_string()); -/// println!("string length: {}", slice.to_bytes().len()); +/// println!("string buffer size without nul terminator: {}", slice.to_bytes().len()); /// } /// ``` /// -/// Passing a Rust-originating C string +/// Passing a Rust-originating C string: /// /// ```no_run /// use std::ffi::{CString, CStr}; @@ -117,7 +178,7 @@ pub struct CString { /// work(&s); /// ``` /// -/// Converting a foreign C string into a Rust `String` +/// Converting a foreign C string into a Rust [`String`]: /// /// ```no_run /// use std::ffi::CStr; @@ -133,6 +194,12 @@ pub struct CString { /// /// println!("string: {}", my_string_safe()); /// ``` +/// +/// [`u8`]: ../primitive.u8.html +/// [`&str`]: ../primitive.str.html +/// [`String`]: ../string/struct.String.html +/// [`CString`]: struct.CString.html +/// [`from_ptr`]: #method.from_ptr #[derive(Hash)] #[stable(feature = "rust1", since = "1.0.0")] pub struct CStr { @@ -143,20 +210,85 @@ pub struct CStr { inner: [c_char] } -/// An error returned from `CString::new` to indicate that a nul byte was found -/// in the vector provided. +/// 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. +/// +/// [`CString`]: struct.CString.html +/// [`CString::new`]: struct.CString.html#method.new +/// +/// # Examples +/// +/// ``` +/// use std::ffi::{CString, NulError}; +/// +/// let _: NulError = CString::new(b"f\0oo".to_vec()).unwrap_err(); +/// ``` #[derive(Clone, PartialEq, Eq, Debug)] #[stable(feature = "rust1", since = "1.0.0")] pub struct NulError(usize, Vec<u8>); -/// An error returned from `CStr::from_bytes_with_nul` to indicate that a nul -/// byte was found too early in the slice provided or one wasn't found at all. +/// 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. +/// +/// [`CStr`]: struct.CStr.html +/// [`CStr::from_bytes_with_nul`]: struct.CStr.html#method.from_bytes_with_nul +/// +/// # Examples +/// +/// ``` +/// use std::ffi::{CStr, FromBytesWithNulError}; +/// +/// let _: FromBytesWithNulError = CStr::from_bytes_with_nul(b"f\0oo").unwrap_err(); +/// ``` #[derive(Clone, PartialEq, Eq, Debug)] #[stable(feature = "cstr_from_bytes", since = "1.10.0")] -pub struct FromBytesWithNulError { _a: () } +pub struct FromBytesWithNulError { + kind: FromBytesWithNulErrorKind, +} + +#[derive(Clone, PartialEq, Eq, Debug)] +enum FromBytesWithNulErrorKind { + InteriorNul(usize), + NotNulTerminated, +} -/// An error returned from `CString::into_string` to indicate that a UTF-8 error -/// was encountered during the conversion. +impl FromBytesWithNulError { + fn interior_nul(pos: usize) -> FromBytesWithNulError { + FromBytesWithNulError { + kind: FromBytesWithNulErrorKind::InteriorNul(pos), + } + } + fn not_nul_terminated() -> FromBytesWithNulError { + FromBytesWithNulError { + kind: FromBytesWithNulErrorKind::NotNulTerminated, + } + } +} + +/// 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; [`into_string`][`CString::into_string`] performs UTF-8 +/// validation on those bytes and may return this error. +/// +/// This `struct` is created by the +/// [`into_string`][`CString::into_string`] method on [`CString`]. See +/// its documentation for more. +/// +/// [`String`]: ../string/struct.String.html +/// [`CString`]: struct.CString.html +/// [`CString::into_string`]: struct.CString.html#method.into_string #[derive(Clone, PartialEq, Eq, Debug)] #[stable(feature = "cstring_into", since = "1.7.0")] pub struct IntoStringError { @@ -167,8 +299,11 @@ pub struct IntoStringError { impl CString { /// Creates a new C-compatible string from a container of bytes. /// - /// This method will consume the provided data and use the underlying bytes - /// to construct a new string, ensuring that there is a trailing 0 byte. + /// 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 /// @@ -186,9 +321,11 @@ impl CString { /// /// # Errors /// - /// This function will return an error if the bytes yielded contain an - /// internal 0 byte. The error returned will contain the bytes as well as + /// 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. + /// + /// [`NulError`]: struct.NulError.html #[stable(feature = "rust1", since = "1.0.0")] pub fn new<T: Into<Vec<u8>>>(t: T) -> Result<CString, NulError> { Self::_new(t.into()) @@ -201,13 +338,15 @@ impl CString { } } - /// Creates a C-compatible string from a byte vector without checking for - /// interior 0 bytes. + /// Creates a C-compatible string by consuming a byte vector, + /// without checking for interior 0 bytes. /// - /// This method is equivalent to `new` except that no runtime assertion + /// This method is equivalent to [`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. /// + /// [`new`]: #method.new + /// /// # Examples /// /// ``` @@ -225,39 +364,110 @@ impl CString { CString { inner: v.into_boxed_slice() } } - /// Retakes ownership of a `CString` that was transferred to C. + /// Retakes ownership of a `CString` that was transferred to C via [`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 `into_raw` on a `CString`. Other usage (e.g. trying to take + /// obtained by calling [`into_raw`] on a `CString`. 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. + /// + /// > **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. + /// + /// [`into_raw`]: #method.into_raw + /// [`CStr`]: struct.CStr.html + /// + /// # Examples + /// + /// Create a `CString`, pass ownership to an `extern` function (via raw pointer), then retake + /// ownership with `from_raw`: + /// + /// ```no_run + /// use std::ffi::CString; + /// use std::os::raw::c_char; + /// + /// extern { + /// fn some_extern_function(s: *mut c_char); + /// } + /// + /// let c_string = CString::new("Hello!").unwrap(); + /// let raw = c_string.into_raw(); + /// unsafe { + /// some_extern_function(raw); + /// let c_string = CString::from_raw(raw); + /// } + /// ``` #[stable(feature = "cstr_memory", since = "1.4.0")] pub unsafe fn from_raw(ptr: *mut c_char) -> CString { - let len = libc::strlen(ptr) + 1; // Including the NUL byte - let slice = slice::from_raw_parts(ptr, len as usize); - CString { inner: mem::transmute(slice) } + let len = sys::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]) } } - /// Transfers ownership of the string to a C caller. + /// Consumes the `CString` and transfers ownership of the string to a C caller. /// - /// The pointer must be returned to Rust and reconstituted using - /// `from_raw` to be properly deallocated. Specifically, one - /// should *not* use the standard C `free` function to deallocate + /// The pointer which this function returns must be returned to Rust and reconstituted using + /// [`from_raw`] to be properly deallocated. Specifically, one + /// should *not* use the standard C `free()` function to deallocate /// this string. /// - /// Failure to call `from_raw` will lead to a memory leak. + /// Failure to call [`from_raw`] will lead to a memory leak. + /// + /// [`from_raw`]: #method.from_raw + /// + /// # Examples + /// + /// ``` + /// use std::ffi::CString; + /// + /// let c_string = CString::new("foo").unwrap(); + /// + /// 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] #[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 Unicode data. + /// Converts the `CString` into a [`String`] if it contains valid UTF-8 data. /// /// On failure, ownership of the original `CString` is returned. + /// + /// [`String`]: ../string/struct.String.html + /// + /// # Examples + /// + /// ``` + /// use std::ffi::CString; + /// + /// let valid_utf8 = vec![b'f', b'o', b'o']; + /// let cstring = CString::new(valid_utf8).unwrap(); + /// assert_eq!(cstring.into_string().unwrap(), "foo"); + /// + /// let invalid_utf8 = vec![b'f', 0xff, b'o', b'o']; + /// let cstring = CString::new(invalid_utf8).unwrap(); + /// let err = cstring.into_string().err().unwrap(); + /// 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()) @@ -267,10 +477,21 @@ impl CString { }) } - /// Returns the underlying byte buffer. + /// 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; /// - /// The returned buffer does **not** contain the trailing nul separator and - /// it is guaranteed to not have any interior nul bytes. + /// let c_string = CString::new("foo").unwrap(); + /// let bytes = c_string.into_bytes(); + /// assert_eq!(bytes, vec![b'f', b'o', b'o']); + /// ``` #[stable(feature = "cstring_into", since = "1.7.0")] pub fn into_bytes(self) -> Vec<u8> { let mut vec = self.into_inner().into_vec(); @@ -279,8 +500,20 @@ impl CString { vec } - /// Equivalent to the `into_bytes` function except that the returned vector - /// includes the trailing nul byte. + /// Equivalent to the [`into_bytes`] function except that the returned vector + /// includes the trailing nul terminator. + /// + /// [`into_bytes`]: #method.into_bytes + /// + /// # Examples + /// + /// ``` + /// use std::ffi::CString; + /// + /// let c_string = CString::new("foo").unwrap(); + /// let bytes = c_string.into_bytes_with_nul(); + /// assert_eq!(bytes, vec![b'f', b'o', b'o', b'\0']); + /// ``` #[stable(feature = "cstring_into", since = "1.7.0")] pub fn into_bytes_with_nul(self) -> Vec<u8> { self.into_inner().into_vec() @@ -288,21 +521,88 @@ impl CString { /// Returns the contents of this `CString` as a slice of bytes. /// - /// The returned slice does **not** contain the trailing nul separator and - /// it is guaranteed to not have any interior nul 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 + /// [`as_bytes_with_nul`] instead. + /// + /// [`as_bytes_with_nul`]: #method.as_bytes_with_nul + /// + /// # Examples + /// + /// ``` + /// use std::ffi::CString; + /// + /// let c_string = CString::new("foo").unwrap(); + /// let bytes = c_string.as_bytes(); + /// assert_eq!(bytes, &[b'f', b'o', b'o']); + /// ``` + #[inline] #[stable(feature = "rust1", since = "1.0.0")] pub fn as_bytes(&self) -> &[u8] { &self.inner[..self.inner.len() - 1] } - /// Equivalent to the `as_bytes` function except that the returned slice - /// includes the trailing nul byte. + /// Equivalent to the [`as_bytes`] function except that the returned slice + /// includes the trailing nul terminator. + /// + /// [`as_bytes`]: #method.as_bytes + /// + /// # Examples + /// + /// ``` + /// use std::ffi::CString; + /// + /// let c_string = CString::new("foo").unwrap(); + /// let bytes = c_string.as_bytes_with_nul(); + /// assert_eq!(bytes, &[b'f', b'o', b'o', b'\0']); + /// ``` + #[inline] #[stable(feature = "rust1", since = "1.0.0")] pub fn as_bytes_with_nul(&self) -> &[u8] { &self.inner } - // Bypass "move out of struct which implements `Drop` trait" restriction. + /// Extracts a [`CStr`] slice containing the entire string. + /// + /// [`CStr`]: struct.CStr.html + /// + /// # Examples + /// + /// ``` + /// use std::ffi::{CString, CStr}; + /// + /// let c_string = CString::new(b"foo".to_vec()).unwrap(); + /// let c_str = c_string.as_c_str(); + /// assert_eq!(c_str, CStr::from_bytes_with_nul(b"foo\0").unwrap()); + /// ``` + #[inline] + #[stable(feature = "as_c_str", since = "1.20.0")] + pub fn as_c_str(&self) -> &CStr { + &*self + } + + /// Converts this `CString` into a boxed [`CStr`]. + /// + /// [`CStr`]: struct.CStr.html + /// + /// # Examples + /// + /// ``` + /// use std::ffi::{CString, CStr}; + /// + /// let c_string = CString::new(b"foo".to_vec()).unwrap(); + /// let boxed = c_string.into_boxed_c_str(); + /// assert_eq!(&*boxed, CStr::from_bytes_with_nul(b"foo\0").unwrap()); + /// ``` + #[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. + /// + /// [`Drop`]: ../ops/trait.Drop.html fn into_inner(self) -> Box<[u8]> { unsafe { let result = ptr::read(&self.inner); @@ -327,8 +627,9 @@ impl Drop for CString { impl ops::Deref for CString { type Target = CStr; + #[inline] fn deref(&self) -> &CStr { - unsafe { mem::transmute(self.as_bytes_with_nul()) } + unsafe { CStr::from_bytes_with_nul_unchecked(self.as_bytes_with_nul()) } } } @@ -341,6 +642,7 @@ impl fmt::Debug for CString { #[stable(feature = "cstring_into", since = "1.7.0")] impl From<CString> for Vec<u8> { + #[inline] fn from(s: CString) -> Vec<u8> { s.into_bytes() } @@ -360,7 +662,7 @@ impl fmt::Debug for CStr { #[stable(feature = "cstr_default", since = "1.10.0")] impl<'a> Default for &'a CStr { fn default() -> &'a CStr { - static SLICE: &'static [c_char] = &[0]; + const SLICE: &'static [c_char] = &[0]; unsafe { CStr::from_ptr(SLICE.as_ptr()) } } } @@ -376,12 +678,83 @@ impl Default for CString { #[stable(feature = "cstr_borrow", since = "1.3.0")] impl Borrow<CStr> for CString { + #[inline] fn borrow(&self) -> &CStr { self } } +#[stable(feature = "box_from_c_str", since = "1.17.0")] +impl<'a> From<&'a CStr> for Box<CStr> { + fn from(s: &'a 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 = "c_string_from_box", since = "1.18.0")] +impl From<Box<CStr>> for CString { + #[inline] + fn from(s: Box<CStr>) -> CString { + s.into_c_string() + } +} + +#[stable(feature = "box_from_c_string", since = "1.20.0")] +impl From<CString> for Box<CStr> { + #[inline] + fn from(s: CString) -> Box<CStr> { + s.into_boxed_c_str() + } +} + +#[stable(feature = "shared_from_slice2", since = "1.24.0")] +impl From<CString> for Arc<CStr> { + #[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) } + } +} + +#[stable(feature = "shared_from_slice2", since = "1.24.0")] +impl<'a> From<&'a CStr> for Arc<CStr> { + #[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> { + #[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<'a> From<&'a CStr> for Rc<CStr> { + #[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) } + } +} + +#[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 was provided to - /// `CString::new`. + /// Returns the position of the nul byte in the slice that caused + /// [`CString::new`] to fail. + /// + /// [`CString::new`]: struct.CString.html#method.new /// /// # Examples /// @@ -432,9 +805,34 @@ impl From<NulError> for io::Error { } } +#[stable(feature = "frombyteswithnulerror_impls", since = "1.17.0")] +impl Error for FromBytesWithNulError { + fn description(&self) -> &str { + match self.kind { + FromBytesWithNulErrorKind::InteriorNul(..) => + "data provided contains an interior nul byte", + FromBytesWithNulErrorKind::NotNulTerminated => + "data provided is not nul terminated", + } + } +} + +#[stable(feature = "frombyteswithnulerror_impls", since = "1.17.0")] +impl fmt::Display for FromBytesWithNulError { + fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { + f.write_str(self.description())?; + if let FromBytesWithNulErrorKind::InteriorNul(pos) = self.kind { + write!(f, " at byte pos {}", pos)?; + } + Ok(()) + } +} + impl IntoStringError { - /// Consumes this error, returning original `CString` which generated the + /// Consumes this error, returning original [`CString`] which generated the /// error. + /// + /// [`CString`]: struct.CString.html #[stable(feature = "cstring_into", since = "1.7.0")] pub fn into_cstring(self) -> CString { self.inner @@ -466,15 +864,15 @@ impl fmt::Display for IntoStringError { } impl CStr { - /// Casts a raw C string to a safe C string wrapper. + /// Wraps a raw C string with a safe C string wrapper. /// - /// This function will cast the provided `ptr` to the `CStr` wrapper which + /// 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` + /// * There is no guarantee to the validity of `ptr`. /// * The returned lifetime is not guaranteed to be the actual lifetime of - /// `ptr` + /// `ptr`. /// * There is no guarantee that the memory pointed to by `ptr` contains a /// valid nul terminator byte at the end of the string. /// @@ -501,15 +899,16 @@ impl CStr { /// ``` #[stable(feature = "rust1", since = "1.0.0")] pub unsafe fn from_ptr<'a>(ptr: *const c_char) -> &'a CStr { - let len = libc::strlen(ptr); - mem::transmute(slice::from_raw_parts(ptr, len as usize + 1)) + let len = sys::strlen(ptr); + let ptr = ptr as *const u8; + CStr::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 it is null terminated and does not contain any interior - /// nul bytes. + /// 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 /// @@ -519,20 +918,42 @@ impl 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 std::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 std::ffi::CStr; + /// + /// let c_str = CStr::from_bytes_with_nul(b"he\0llo\0"); + /// assert!(c_str.is_err()); + /// ``` #[stable(feature = "cstr_from_bytes", since = "1.10.0")] pub fn from_bytes_with_nul(bytes: &[u8]) -> Result<&CStr, FromBytesWithNulError> { - if bytes.is_empty() || memchr::memchr(0, &bytes) != Some(bytes.len() - 1) { - Err(FromBytesWithNulError { _a: () }) + 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 { CStr::from_bytes_with_nul_unchecked(bytes) }) } else { - Ok(unsafe { Self::from_bytes_with_nul_unchecked(bytes) }) + 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 null terminated + /// performing any sanity checks. The provided slice **must** be nul-terminated /// and not contain any interior nul bytes. /// /// # Examples @@ -546,14 +967,15 @@ impl CStr { /// assert_eq!(cstr, &*cstring); /// } /// ``` + #[inline] #[stable(feature = "cstr_from_bytes", since = "1.10.0")] pub unsafe fn from_bytes_with_nul_unchecked(bytes: &[u8]) -> &CStr { - mem::transmute(bytes) + &*(bytes as *const [u8] as *const CStr) } /// Returns the inner pointer to this C string. /// - /// The returned pointer will be valid for as long as `self` is and points + /// 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. /// @@ -561,7 +983,7 @@ impl CStr { /// /// It is your responsibility to make sure that the underlying memory is not /// freed too early. For example, the following code will cause undefined - /// behaviour when `ptr` is used inside the `unsafe` block: + /// behavior when `ptr` is used inside the `unsafe` block: /// /// ```no_run /// use std::ffi::{CString}; @@ -574,9 +996,9 @@ impl CStr { /// ``` /// /// This happens because the pointer returned by `as_ptr` does not carry any - /// lifetime information and the string is deallocated immediately after + /// lifetime information and the [`CString`] is deallocated immediately after /// the `CString::new("Hello").unwrap().as_ptr()` expression is evaluated. - /// To fix the problem, bind the string to a local variable: + /// To fix the problem, bind the `CString` to a local variable: /// /// ```no_run /// use std::ffi::{CString}; @@ -588,6 +1010,12 @@ impl CStr { /// *ptr; /// } /// ``` + /// + /// This way, the lifetime of the `CString` in `hello` encompasses + /// the lifetime of `ptr` and the `unsafe` block. + /// + /// [`CString`]: struct.CString.html + #[inline] #[stable(feature = "rust1", since = "1.0.0")] pub fn as_ptr(&self) -> *const c_char { self.inner.as_ptr() @@ -595,16 +1023,22 @@ impl CStr { /// Converts this C string to a byte slice. /// - /// This function will calculate the length of this string (which normally - /// requires a linear amount of work to be done) and then return the - /// resulting slice of `u8` elements. - /// - /// The returned slice will **not** contain the trailing nul that this C + /// The returned slice will **not** contain the trailing nul terminator that this C /// string has. /// /// > **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 std::ffi::CStr; + /// + /// let c_str = CStr::from_bytes_with_nul(b"foo\0").unwrap(); + /// assert_eq!(c_str.to_bytes(), b"foo"); + /// ``` + #[inline] #[stable(feature = "rust1", since = "1.0.0")] pub fn to_bytes(&self) -> &[u8] { let bytes = self.to_bytes_with_nul(); @@ -613,26 +1047,50 @@ impl CStr { /// Converts this C string to a byte slice containing the trailing 0 byte. /// - /// This function is the equivalent of `to_bytes` except that it will retain - /// the trailing nul instead of chopping it off. + /// This function is the equivalent of [`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. + /// + /// [`to_bytes`]: #method.to_bytes + /// + /// # Examples + /// + /// ``` + /// use std::ffi::CStr; + /// + /// let c_str = CStr::from_bytes_with_nul(b"foo\0").unwrap(); + /// assert_eq!(c_str.to_bytes_with_nul(), b"foo\0"); + /// ``` + #[inline] #[stable(feature = "rust1", since = "1.0.0")] pub fn to_bytes_with_nul(&self) -> &[u8] { - unsafe { mem::transmute(&self.inner) } + unsafe { &*(&self.inner as *const [c_char] as *const [u8]) } } - /// Yields a `&str` slice if the `CStr` contains valid UTF-8. + /// Yields a [`&str`] slice if the `CStr` contains valid UTF-8. /// - /// This function will calculate the length of this string and check for - /// UTF-8 validity, and then return the `&str` if it's valid. + /// 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 0-cost 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. + /// + /// [`&str`]: ../primitive.str.html + /// + /// # Examples + /// + /// ``` + /// use std::ffi::CStr; + /// + /// let c_str = CStr::from_bytes_with_nul(b"foo\0").unwrap(); + /// assert_eq!(c_str.to_str(), Ok("foo")); + /// ``` #[stable(feature = "cstr_to_str", since = "1.4.0")] pub fn to_str(&self) -> Result<&str, str::Utf8Error> { // NB: When CStr is changed to perform the length check in .to_bytes() @@ -642,21 +1100,73 @@ impl CStr { str::from_utf8(self.to_bytes()) } - /// Converts a `CStr` into a `Cow<str>`. + /// Converts a `CStr` into a [`Cow`]`<`[`str`]`>`. /// - /// This function will calculate the length of this string (which normally - /// requires a linear amount of work to be done) and then return the - /// resulting slice as a `Cow<str>`, replacing any invalid UTF-8 sequences - /// with `U+FFFD REPLACEMENT CHARACTER`. + /// If the contents of the `CStr` are valid UTF-8 data, this + /// function will return a [`Cow`]`::`[`Borrowed`]`(`[`&str`]`)` + /// with the the corresponding [`&str`] slice. Otherwise, it will + /// replace any invalid UTF-8 sequences with `U+FFFD REPLACEMENT + /// CHARACTER` and return a [`Cow`]`::`[`Owned`]`(`[`String`]`)` + /// with the result. /// /// > **Note**: This method is currently implemented to check for validity /// > after a 0-cost 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. + /// + /// [`Cow`]: ../borrow/enum.Cow.html + /// [`Borrowed`]: ../borrow/enum.Cow.html#variant.Borrowed + /// [`str`]: ../primitive.str.html + /// [`String`]: ../string/struct.String.html + /// + /// # Examples + /// + /// Calling `to_string_lossy` on a `CStr` containing valid UTF-8: + /// + /// ``` + /// use std::borrow::Cow; + /// use std::ffi::CStr; + /// + /// let c_str = CStr::from_bytes_with_nul(b"Hello World\0").unwrap(); + /// assert_eq!(c_str.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 c_str = CStr::from_bytes_with_nul(b"Hello \xF0\x90\x80World\0").unwrap(); + /// assert_eq!( + /// c_str.to_string_lossy(), + /// Cow::Owned(String::from("Hello �World")) as Cow<str> + /// ); + /// ``` #[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 [`Box`]`<CStr>` into a [`CString`] without copying or allocating. + /// + /// [`Box`]: ../boxed/struct.Box.html + /// [`CString`]: struct.CString.html + /// + /// # Examples + /// + /// ``` + /// use std::ffi::CString; + /// + /// let c_string = CString::new(b"foo".to_vec()).unwrap(); + /// let boxed = c_string.into_boxed_c_str(); + /// assert_eq!(boxed.into_c_string(), CString::new("foo").unwrap()); + /// ``` + #[stable(feature = "into_boxed_c_str", since = "1.20.0")] + pub fn into_c_string(self: Box<CStr>) -> CString { + let raw = Box::into_raw(self) as *mut [u8]; + CString { inner: unsafe { Box::from_raw(raw) } } + } } #[stable(feature = "rust1", since = "1.0.0")] @@ -685,7 +1195,7 @@ impl ToOwned for CStr { type Owned = CString; fn to_owned(&self) -> CString { - unsafe { CString::from_vec_unchecked(self.to_bytes().to_vec()) } + CString { inner: self.to_bytes_with_nul().into() } } } @@ -708,6 +1218,7 @@ impl ops::Index<ops::RangeFull> for CString { #[stable(feature = "cstring_asref", since = "1.7.0")] impl AsRef<CStr> for CStr { + #[inline] fn as_ref(&self) -> &CStr { self } @@ -715,6 +1226,7 @@ impl AsRef<CStr> for CStr { #[stable(feature = "cstring_asref", since = "1.7.0")] impl AsRef<CStr> for CString { + #[inline] fn as_ref(&self) -> &CStr { self } @@ -727,6 +1239,8 @@ mod tests { use borrow::Cow::{Borrowed, Owned}; use hash::{Hash, Hasher}; use collections::hash_map::DefaultHasher; + use rc::Rc; + use sync::Arc; #[test] fn c_to_rust() { @@ -846,4 +1360,38 @@ mod tests { let cstr = CStr::from_bytes_with_nul(data); assert!(cstr.is_err()); } + + #[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 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); + } } |