src/libstd/ffi/c_str.rs

   1 // Copyright 2012 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use ascii;
  12 use borrow::{Cow, ToOwned, Borrow};
  13 use boxed::Box;
  14 use convert::{Into, From};
  15 use cmp::{PartialEq, Eq, PartialOrd, Ord, Ordering};
  16 use error::Error;
  17 use fmt::{self, Write};
  18 use io;
  19 use iter::Iterator;
  20 use libc;
  21 use mem;
  22 use memchr;
  23 use ops;
  24 use option::Option::{self, Some, None};
  25 use os::raw::c_char;
  26 use result::Result::{self, Ok, Err};
  27 use slice;
  28 use str::{self, Utf8Error};
  29 use string::String;
  30 use vec::Vec;
  31
  32 /// A type representing an owned C-compatible string
  33 ///
  34 /// This type serves the primary purpose of being able to safely generate a
  35 /// C-compatible string from a Rust byte slice or vector. An instance of this
  36 /// type is a static guarantee that the underlying bytes contain no interior 0
  37 /// bytes and the final byte is 0.
  38 ///
  39 /// A `CString` is created from either a byte slice or a byte vector. After
  40 /// being created, a `CString` predominately inherits all of its methods from
  41 /// the `Deref` implementation to `[c_char]`. Note that the underlying array
  42 /// is represented as an array of `c_char` as opposed to `u8`. A `u8` slice
  43 /// can be obtained with the `as_bytes` method.  Slices produced from a `CString`
  44 /// do *not* contain the trailing nul terminator unless otherwise specified.
  45 ///
  46 /// # Examples
  47 ///
  48 /// ```no_run
  49 /// # fn main() {
  50 /// use std::ffi::CString;
  51 /// use std::os::raw::c_char;
  52 ///
  53 /// extern {
  54 ///     fn my_printer(s: *const c_char);
  55 /// }
  56 ///
  57 /// let c_to_print = CString::new("Hello, world!").unwrap();
  58 /// unsafe {
  59 ///     my_printer(c_to_print.as_ptr());
  60 /// }
  61 /// # }
  62 /// ```
  63 ///
  64 /// # Safety
  65 ///
  66 /// `CString` is intended for working with traditional C-style strings
  67 /// (a sequence of non-null bytes terminated by a single null byte); the
  68 /// primary use case for these kinds of strings is interoperating with C-like
  69 /// code. Often you will need to transfer ownership to/from that external
  70 /// code. It is strongly recommended that you thoroughly read through the
  71 /// documentation of `CString` before use, as improper ownership management
  72 /// of `CString` instances can lead to invalid memory accesses, memory leaks,
  73 /// and other memory errors.
  74
  75 #[derive(PartialEq, PartialOrd, Eq, Ord, Hash, Clone)]
  76 #[stable(feature = "rust1", since = "1.0.0")]
  77 pub struct CString {
  78     inner: Box<[u8]>,
  79 }
  80
  81 /// Representation of a borrowed C string.
  82 ///
  83 /// This dynamically sized type is only safely constructed via a borrowed
  84 /// version of an instance of `CString`. This type can be constructed from a raw
  85 /// C string as well and represents a C string borrowed from another location.
  86 ///
  87 /// Note that this structure is **not** `repr(C)` and is not recommended to be
  88 /// placed in the signatures of FFI functions. Instead safe wrappers of FFI
  89 /// functions may leverage the unsafe `from_ptr` constructor to provide a safe
  90 /// interface to other consumers.
  91 ///
  92 /// # Examples
  93 ///
  94 /// Inspecting a foreign C string
  95 ///
  96 /// ```no_run
  97 /// use std::ffi::CStr;
  98 /// use std::os::raw::c_char;
  99 ///
 100 /// extern { fn my_string() -> *const c_char; }
 101 ///
 102 /// fn main() {
 103 ///     unsafe {
 104 ///         let slice = CStr::from_ptr(my_string());
 105 ///         println!("string length: {}", slice.to_bytes().len());
 106 ///     }
 107 /// }
 108 /// ```
 109 ///
 110 /// Passing a Rust-originating C string
 111 ///
 112 /// ```no_run
 113 /// use std::ffi::{CString, CStr};
 114 /// use std::os::raw::c_char;
 115 ///
 116 /// fn work(data: &CStr) {
 117 ///     extern { fn work_with(data: *const c_char); }
 118 ///
 119 ///     unsafe { work_with(data.as_ptr()) }
 120 /// }
 121 ///
 122 /// fn main() {
 123 ///     let s = CString::new("data data data data").unwrap();
 124 ///     work(&s);
 125 /// }
 126 /// ```
 127 ///
 128 /// Converting a foreign C string into a Rust `String`
 129 ///
 130 /// ```no_run
 131 /// use std::ffi::CStr;
 132 /// use std::os::raw::c_char;
 133 ///
 134 /// extern { fn my_string() -> *const c_char; }
 135 ///
 136 /// fn my_string_safe() -> String {
 137 ///     unsafe {
 138 ///         CStr::from_ptr(my_string()).to_string_lossy().into_owned()
 139 ///     }
 140 /// }
 141 ///
 142 /// fn main() {
 143 ///     println!("string: {}", my_string_safe());
 144 /// }
 145 /// ```
 146 #[derive(Hash)]
 147 #[stable(feature = "rust1", since = "1.0.0")]
 148 pub struct CStr {
 149     // FIXME: this should not be represented with a DST slice but rather with
 150     //        just a raw `c_char` along with some form of marker to make
 151     //        this an unsized type. Essentially `sizeof(&CStr)` should be the
 152     //        same as `sizeof(&c_char)` but `CStr` should be an unsized type.
 153     inner: [c_char]
 154 }
 155
 156 /// An error returned from `CString::new` to indicate that a nul byte was found
 157 /// in the vector provided.
 158 #[derive(Clone, PartialEq, Debug)]
 159 #[stable(feature = "rust1", since = "1.0.0")]
 160 pub struct NulError(usize, Vec<u8>);
 161
 162 /// An error returned from `CString::into_string` to indicate that a UTF-8 error
 163 /// was encountered during the conversion.
 164 #[derive(Clone, PartialEq, Debug)]
 165 #[stable(feature = "cstring_into", since = "1.7.0")]
 166 pub struct IntoStringError {
 167     inner: CString,
 168     error: Utf8Error,
 169 }
 170
 171 impl CString {
 172     /// Creates a new C-compatible string from a container of bytes.
 173     ///
 174     /// This method will consume the provided data and use the underlying bytes
 175     /// to construct a new string, ensuring that there is a trailing 0 byte.
 176     ///
 177     /// # Examples
 178     ///
 179     /// ```no_run
 180     /// use std::ffi::CString;
 181     /// use std::os::raw::c_char;
 182     ///
 183     /// extern { fn puts(s: *const c_char); }
 184     ///
 185     /// fn main() {
 186     ///     let to_print = CString::new("Hello!").unwrap();
 187     ///     unsafe {
 188     ///         puts(to_print.as_ptr());
 189     ///     }
 190     /// }
 191     /// ```
 192     ///
 193     /// # Errors
 194     ///
 195     /// This function will return an error if the bytes yielded contain an
 196     /// internal 0 byte. The error returned will contain the bytes as well as
 197     /// the position of the nul byte.
 198     #[stable(feature = "rust1", since = "1.0.0")]
 199     pub fn new<T: Into<Vec<u8>>>(t: T) -> Result<CString, NulError> {
 200         Self::_new(t.into())
 201     }
 202
 203     fn _new(bytes: Vec<u8>) -> Result<CString, NulError> {
 204         match memchr::memchr(0, &bytes) {
 205             Some(i) => Err(NulError(i, bytes)),
 206             None => Ok(unsafe { CString::from_vec_unchecked(bytes) }),
 207         }
 208     }
 209
 210     /// Creates a C-compatible string from a byte vector without checking for
 211     /// interior 0 bytes.
 212     ///
 213     /// This method is equivalent to `new` except that no runtime assertion
 214     /// is made that `v` contains no 0 bytes, and it requires an actual
 215     /// byte vector, not anything that can be converted to one with Into.
 216     #[stable(feature = "rust1", since = "1.0.0")]
 217     pub unsafe fn from_vec_unchecked(mut v: Vec<u8>) -> CString {
 218         v.push(0);
 219         CString { inner: v.into_boxed_slice() }
 220     }
 221
 222     /// Retakes ownership of a `CString` that was transferred to C.
 223     ///
 224     /// This should only ever be called with a pointer that was earlier
 225     /// obtained by calling `into_raw` on a `CString`. Additionally, the length
 226     /// of the string will be recalculated from the pointer.
 227     #[stable(feature = "cstr_memory", since = "1.4.0")]
 228     pub unsafe fn from_raw(ptr: *mut c_char) -> CString {
 229         let len = libc::strlen(ptr) + 1; // Including the NUL byte
 230         let slice = slice::from_raw_parts(ptr, len as usize);
 231         CString { inner: mem::transmute(slice) }
 232     }
 233
 234     /// Transfers ownership of the string to a C caller.
 235     ///
 236     /// The pointer must be returned to Rust and reconstituted using
 237     /// `from_raw` to be properly deallocated. Specifically, one
 238     /// should *not* use the standard C `free` function to deallocate
 239     /// this string.
 240     ///
 241     /// Failure to call `from_raw` will lead to a memory leak.
 242     #[stable(feature = "cstr_memory", since = "1.4.0")]
 243     pub fn into_raw(self) -> *mut c_char {
 244         Box::into_raw(self.inner) as *mut c_char
 245     }
 246
 247     /// Converts the `CString` into a `String` if it contains valid Unicode data.
 248     ///
 249     /// On failure, ownership of the original `CString` is returned.
 250     #[stable(feature = "cstring_into", since = "1.7.0")]
 251     pub fn into_string(self) -> Result<String, IntoStringError> {
 252         String::from_utf8(self.into_bytes())
 253             .map_err(|e| IntoStringError {
 254                 error: e.utf8_error(),
 255                 inner: unsafe { CString::from_vec_unchecked(e.into_bytes()) },
 256             })
 257     }
 258
 259     /// Returns the underlying byte buffer.
 260     ///
 261     /// The returned buffer does **not** contain the trailing nul separator and
 262     /// it is guaranteed to not have any interior nul bytes.
 263     #[stable(feature = "cstring_into", since = "1.7.0")]
 264     pub fn into_bytes(self) -> Vec<u8> {
 265         let mut vec = self.inner.into_vec();
 266         let _nul = vec.pop();
 267         debug_assert_eq!(_nul, Some(0u8));
 268         vec
 269     }
 270
 271     /// Equivalent to the `into_bytes` function except that the returned vector
 272     /// includes the trailing nul byte.
 273     #[stable(feature = "cstring_into", since = "1.7.0")]
 274     pub fn into_bytes_with_nul(self) -> Vec<u8> {
 275         self.inner.into_vec()
 276     }
 277
 278     /// Returns the contents of this `CString` as a slice of bytes.
 279     ///
 280     /// The returned slice does **not** contain the trailing nul separator and
 281     /// it is guaranteed to not have any interior nul bytes.
 282     #[stable(feature = "rust1", since = "1.0.0")]
 283     pub fn as_bytes(&self) -> &[u8] {
 284         &self.inner[..self.inner.len() - 1]
 285     }
 286
 287     /// Equivalent to the `as_bytes` function except that the returned slice
 288     /// includes the trailing nul byte.
 289     #[stable(feature = "rust1", since = "1.0.0")]
 290     pub fn as_bytes_with_nul(&self) -> &[u8] {
 291         &self.inner
 292     }
 293 }
 294
 295 #[stable(feature = "rust1", since = "1.0.0")]
 296 impl ops::Deref for CString {
 297     type Target = CStr;
 298
 299     fn deref(&self) -> &CStr {
 300         unsafe { mem::transmute(self.as_bytes_with_nul()) }
 301     }
 302 }
 303
 304 #[stable(feature = "rust1", since = "1.0.0")]
 305 impl fmt::Debug for CString {
 306     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 307         fmt::Debug::fmt(&**self, f)
 308     }
 309 }
 310
 311 #[stable(feature = "cstring_into", since = "1.7.0")]
 312 impl From<CString> for Vec<u8> {
 313     fn from(s: CString) -> Vec<u8> {
 314         s.into_bytes()
 315     }
 316 }
 317
 318 #[stable(feature = "cstr_debug", since = "1.3.0")]
 319 impl fmt::Debug for CStr {
 320     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 321         write!(f, "\"")?;
 322         for byte in self.to_bytes().iter().flat_map(|&b| ascii::escape_default(b)) {
 323             f.write_char(byte as char)?;
 324         }
 325         write!(f, "\"")
 326     }
 327 }
 328
 329 #[stable(feature = "cstr_borrow", since = "1.3.0")]
 330 impl Borrow<CStr> for CString {
 331     fn borrow(&self) -> &CStr { self }
 332 }
 333
 334 impl NulError {
 335     /// Returns the position of the nul byte in the slice that was provided to
 336     /// `CString::new`.
 337     #[stable(feature = "rust1", since = "1.0.0")]
 338     pub fn nul_position(&self) -> usize { self.0 }
 339
 340     /// Consumes this error, returning the underlying vector of bytes which
 341     /// generated the error in the first place.
 342     #[stable(feature = "rust1", since = "1.0.0")]
 343     pub fn into_vec(self) -> Vec<u8> { self.1 }
 344 }
 345
 346 #[stable(feature = "rust1", since = "1.0.0")]
 347 impl Error for NulError {
 348     fn description(&self) -> &str { "nul byte found in data" }
 349 }
 350
 351 #[stable(feature = "rust1", since = "1.0.0")]
 352 impl fmt::Display for NulError {
 353     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 354         write!(f, "nul byte found in provided data at position: {}", self.0)
 355     }
 356 }
 357
 358 #[stable(feature = "rust1", since = "1.0.0")]
 359 impl From<NulError> for io::Error {
 360     fn from(_: NulError) -> io::Error {
 361         io::Error::new(io::ErrorKind::InvalidInput,
 362                        "data provided contains a nul byte")
 363     }
 364 }
 365
 366 impl IntoStringError {
 367     /// Consumes this error, returning original `CString` which generated the
 368     /// error.
 369     #[stable(feature = "cstring_into", since = "1.7.0")]
 370     pub fn into_cstring(self) -> CString {
 371         self.inner
 372     }
 373
 374     /// Access the underlying UTF-8 error that was the cause of this error.
 375     #[stable(feature = "cstring_into", since = "1.7.0")]
 376     pub fn utf8_error(&self) -> Utf8Error {
 377         self.error
 378     }
 379 }
 380
 381 #[stable(feature = "cstring_into", since = "1.7.0")]
 382 impl Error for IntoStringError {
 383     fn description(&self) -> &str {
 384         "C string contained non-utf8 bytes"
 385     }
 386
 387     fn cause(&self) -> Option<&Error> {
 388         Some(&self.error)
 389     }
 390 }
 391
 392 #[stable(feature = "cstring_into", since = "1.7.0")]
 393 impl fmt::Display for IntoStringError {
 394     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 395         self.description().fmt(f)
 396     }
 397 }
 398
 399 impl CStr {
 400     /// Casts a raw C string to a safe C string wrapper.
 401     ///
 402     /// This function will cast the provided `ptr` to the `CStr` wrapper which
 403     /// allows inspection and interoperation of non-owned C strings. This method
 404     /// is unsafe for a number of reasons:
 405     ///
 406     /// * There is no guarantee to the validity of `ptr`
 407     /// * The returned lifetime is not guaranteed to be the actual lifetime of
 408     ///   `ptr`
 409     /// * There is no guarantee that the memory pointed to by `ptr` contains a
 410     ///   valid nul terminator byte at the end of the string.
 411     ///
 412     /// > **Note**: This operation is intended to be a 0-cost cast but it is
 413     /// > currently implemented with an up-front calculation of the length of
 414     /// > the string. This is not guaranteed to always be the case.
 415     ///
 416     /// # Examples
 417     ///
 418     /// ```no_run
 419     /// # fn main() {
 420     /// use std::ffi::CStr;
 421     /// use std::os::raw::c_char;
 422     ///
 423     /// extern {
 424     ///     fn my_string() -> *const c_char;
 425     /// }
 426     ///
 427     /// unsafe {
 428     ///     let slice = CStr::from_ptr(my_string());
 429     ///     println!("string returned: {}", slice.to_str().unwrap());
 430     /// }
 431     /// # }
 432     /// ```
 433     #[stable(feature = "rust1", since = "1.0.0")]
 434     pub unsafe fn from_ptr<'a>(ptr: *const c_char) -> &'a CStr {
 435         let len = libc::strlen(ptr);
 436         mem::transmute(slice::from_raw_parts(ptr, len as usize + 1))
 437     }
 438
 439     /// Creates a C string wrapper from a byte slice.
 440     ///
 441     /// This function will cast the provided `bytes` to a `CStr` wrapper after
 442     /// ensuring that it is null terminated and does not contain any interior
 443     /// nul bytes.
 444     ///
 445     /// # Examples
 446     ///
 447     /// ```
 448     /// # #![feature(cstr_from_bytes)]
 449     /// use std::ffi::CStr;
 450     ///
 451     /// # fn main() {
 452     /// let cstr = CStr::from_bytes_with_nul(b"hello\0");
 453     /// assert!(cstr.is_some());
 454     /// # }
 455     /// ```
 456     #[unstable(feature = "cstr_from_bytes", reason = "recently added", issue = "31190")]
 457     pub fn from_bytes_with_nul(bytes: &[u8]) -> Option<&CStr> {
 458         if bytes.is_empty() || memchr::memchr(0, &bytes) != Some(bytes.len() - 1) {
 459             None
 460         } else {
 461             Some(unsafe { Self::from_bytes_with_nul_unchecked(bytes) })
 462         }
 463     }
 464
 465     /// Unsafely creates a C string wrapper from a byte slice.
 466     ///
 467     /// This function will cast the provided `bytes` to a `CStr` wrapper without
 468     /// performing any sanity checks. The provided slice must be null terminated
 469     /// and not contain any interior nul bytes.
 470     ///
 471     /// # Examples
 472     ///
 473     /// ```
 474     /// # #![feature(cstr_from_bytes)]
 475     /// use std::ffi::{CStr, CString};
 476     ///
 477     /// # fn main() {
 478     /// unsafe {
 479     ///     let cstring = CString::new("hello").unwrap();
 480     ///     let cstr = CStr::from_bytes_with_nul_unchecked(cstring.to_bytes_with_nul());
 481     ///     assert_eq!(cstr, &*cstring);
 482     /// }
 483     /// # }
 484     /// ```
 485     #[unstable(feature = "cstr_from_bytes", reason = "recently added", issue = "31190")]
 486     pub unsafe fn from_bytes_with_nul_unchecked(bytes: &[u8]) -> &CStr {
 487         mem::transmute(bytes)
 488     }
 489
 490     /// Returns the inner pointer to this C string.
 491     ///
 492     /// The returned pointer will be valid for as long as `self` is and points
 493     /// to a contiguous region of memory terminated with a 0 byte to represent
 494     /// the end of the string.
 495     #[stable(feature = "rust1", since = "1.0.0")]
 496     pub fn as_ptr(&self) -> *const c_char {
 497         self.inner.as_ptr()
 498     }
 499
 500     /// Converts this C string to a byte slice.
 501     ///
 502     /// This function will calculate the length of this string (which normally
 503     /// requires a linear amount of work to be done) and then return the
 504     /// resulting slice of `u8` elements.
 505     ///
 506     /// The returned slice will **not** contain the trailing nul that this C
 507     /// string has.
 508     ///
 509     /// > **Note**: This method is currently implemented as a 0-cost cast, but
 510     /// > it is planned to alter its definition in the future to perform the
 511     /// > length calculation whenever this method is called.
 512     #[stable(feature = "rust1", since = "1.0.0")]
 513     pub fn to_bytes(&self) -> &[u8] {
 514         let bytes = self.to_bytes_with_nul();
 515         &bytes[..bytes.len() - 1]
 516     }
 517
 518     /// Converts this C string to a byte slice containing the trailing 0 byte.
 519     ///
 520     /// This function is the equivalent of `to_bytes` except that it will retain
 521     /// the trailing nul instead of chopping it off.
 522     ///
 523     /// > **Note**: This method is currently implemented as a 0-cost cast, but
 524     /// > it is planned to alter its definition in the future to perform the
 525     /// > length calculation whenever this method is called.
 526     #[stable(feature = "rust1", since = "1.0.0")]
 527     pub fn to_bytes_with_nul(&self) -> &[u8] {
 528         unsafe { mem::transmute(&self.inner) }
 529     }
 530
 531     /// Yields a `&str` slice if the `CStr` contains valid UTF-8.
 532     ///
 533     /// This function will calculate the length of this string and check for
 534     /// UTF-8 validity, and then return the `&str` if it's valid.
 535     ///
 536     /// > **Note**: This method is currently implemented to check for validity
 537     /// > after a 0-cost cast, but it is planned to alter its definition in the
 538     /// > future to perform the length calculation in addition to the UTF-8
 539     /// > check whenever this method is called.
 540     #[stable(feature = "cstr_to_str", since = "1.4.0")]
 541     pub fn to_str(&self) -> Result<&str, str::Utf8Error> {
 542         // NB: When CStr is changed to perform the length check in .to_bytes()
 543         // instead of in from_ptr(), it may be worth considering if this should
 544         // be rewritten to do the UTF-8 check inline with the length calculation
 545         // instead of doing it afterwards.
 546         str::from_utf8(self.to_bytes())
 547     }
 548
 549     /// Converts a `CStr` into a `Cow<str>`.
 550     ///
 551     /// This function will calculate the length of this string (which normally
 552     /// requires a linear amount of work to be done) and then return the
 553     /// resulting slice as a `Cow<str>`, replacing any invalid UTF-8 sequences
 554     /// with `U+FFFD REPLACEMENT CHARACTER`.
 555     ///
 556     /// > **Note**: This method is currently implemented to check for validity
 557     /// > after a 0-cost cast, but it is planned to alter its definition in the
 558     /// > future to perform the length calculation in addition to the UTF-8
 559     /// > check whenever this method is called.
 560     #[stable(feature = "cstr_to_str", since = "1.4.0")]
 561     pub fn to_string_lossy(&self) -> Cow<str> {
 562         String::from_utf8_lossy(self.to_bytes())
 563     }
 564 }
 565
 566 #[stable(feature = "rust1", since = "1.0.0")]
 567 impl PartialEq for CStr {
 568     fn eq(&self, other: &CStr) -> bool {
 569         self.to_bytes().eq(other.to_bytes())
 570     }
 571 }
 572 #[stable(feature = "rust1", since = "1.0.0")]
 573 impl Eq for CStr {}
 574 #[stable(feature = "rust1", since = "1.0.0")]
 575 impl PartialOrd for CStr {
 576     fn partial_cmp(&self, other: &CStr) -> Option<Ordering> {
 577         self.to_bytes().partial_cmp(&other.to_bytes())
 578     }
 579 }
 580 #[stable(feature = "rust1", since = "1.0.0")]
 581 impl Ord for CStr {
 582     fn cmp(&self, other: &CStr) -> Ordering {
 583         self.to_bytes().cmp(&other.to_bytes())
 584     }
 585 }
 586
 587 #[stable(feature = "cstr_borrow", since = "1.3.0")]
 588 impl ToOwned for CStr {
 589     type Owned = CString;
 590
 591     fn to_owned(&self) -> CString {
 592         unsafe { CString::from_vec_unchecked(self.to_bytes().to_vec()) }
 593     }
 594 }
 595
 596 #[stable(feature = "cstring_asref", since = "1.7.0")]
 597 impl<'a> From<&'a CStr> for CString {
 598     fn from(s: &'a CStr) -> CString {
 599         s.to_owned()
 600     }
 601 }
 602
 603 #[stable(feature = "cstring_asref", since = "1.7.0")]
 604 impl ops::Index<ops::RangeFull> for CString {
 605     type Output = CStr;
 606
 607     #[inline]
 608     fn index(&self, _index: ops::RangeFull) -> &CStr {
 609         self
 610     }
 611 }
 612
 613 #[stable(feature = "cstring_asref", since = "1.7.0")]
 614 impl AsRef<CStr> for CStr {
 615     fn as_ref(&self) -> &CStr {
 616         self
 617     }
 618 }
 619
 620 #[stable(feature = "cstring_asref", since = "1.7.0")]
 621 impl AsRef<CStr> for CString {
 622     fn as_ref(&self) -> &CStr {
 623         self
 624     }
 625 }
 626
 627 #[cfg(test)]
 628 mod tests {
 629     use prelude::v1::*;
 630     use super::*;
 631     use os::raw::c_char;
 632     use borrow::Cow::{Borrowed, Owned};
 633     use hash::{SipHasher, Hash, Hasher};
 634
 635     #[test]
 636     fn c_to_rust() {
 637         let data = b"123\0";
 638         let ptr = data.as_ptr() as *const c_char;
 639         unsafe {
 640             assert_eq!(CStr::from_ptr(ptr).to_bytes(), b"123");
 641             assert_eq!(CStr::from_ptr(ptr).to_bytes_with_nul(), b"123\0");
 642         }
 643     }
 644
 645     #[test]
 646     fn simple() {
 647         let s = CString::new("1234").unwrap();
 648         assert_eq!(s.as_bytes(), b"1234");
 649         assert_eq!(s.as_bytes_with_nul(), b"1234\0");
 650     }
 651
 652     #[test]
 653     fn build_with_zero1() {
 654         assert!(CString::new(&b"\0"[..]).is_err());
 655     }
 656     #[test]
 657     fn build_with_zero2() {
 658         assert!(CString::new(vec![0]).is_err());
 659     }
 660
 661     #[test]
 662     fn build_with_zero3() {
 663         unsafe {
 664             let s = CString::from_vec_unchecked(vec![0]);
 665             assert_eq!(s.as_bytes(), b"\0");
 666         }
 667     }
 668
 669     #[test]
 670     fn formatted() {
 671         let s = CString::new(&b"abc\x01\x02\n\xE2\x80\xA6\xFF"[..]).unwrap();
 672         assert_eq!(format!("{:?}", s), r#""abc\x01\x02\n\xe2\x80\xa6\xff""#);
 673     }
 674
 675     #[test]
 676     fn borrowed() {
 677         unsafe {
 678             let s = CStr::from_ptr(b"12\0".as_ptr() as *const _);
 679             assert_eq!(s.to_bytes(), b"12");
 680             assert_eq!(s.to_bytes_with_nul(), b"12\0");
 681         }
 682     }
 683
 684     #[test]
 685     fn to_str() {
 686         let data = b"123\xE2\x80\xA6\0";
 687         let ptr = data.as_ptr() as *const c_char;
 688         unsafe {
 689             assert_eq!(CStr::from_ptr(ptr).to_str(), Ok("123…"));
 690             assert_eq!(CStr::from_ptr(ptr).to_string_lossy(), Borrowed("123…"));
 691         }
 692         let data = b"123\xE2\0";
 693         let ptr = data.as_ptr() as *const c_char;
 694         unsafe {
 695             assert!(CStr::from_ptr(ptr).to_str().is_err());
 696             assert_eq!(CStr::from_ptr(ptr).to_string_lossy(), Owned::<str>(format!("123\u{FFFD}")));
 697         }
 698     }
 699
 700     #[test]
 701     fn to_owned() {
 702         let data = b"123\0";
 703         let ptr = data.as_ptr() as *const c_char;
 704
 705         let owned = unsafe { CStr::from_ptr(ptr).to_owned() };
 706         assert_eq!(owned.as_bytes_with_nul(), data);
 707     }
 708
 709     #[test]
 710     fn equal_hash() {
 711         let data = b"123\xE2\xFA\xA6\0";
 712         let ptr = data.as_ptr() as *const c_char;
 713         let cstr: &'static CStr = unsafe { CStr::from_ptr(ptr) };
 714
 715         let mut s = SipHasher::new_with_keys(0, 0);
 716         cstr.hash(&mut s);
 717         let cstr_hash = s.finish();
 718         let mut s = SipHasher::new_with_keys(0, 0);
 719         CString::new(&data[..data.len() - 1]).unwrap().hash(&mut s);
 720         let cstring_hash = s.finish();
 721
 722         assert_eq!(cstr_hash, cstring_hash);
 723     }
 724
 725     #[test]
 726     fn from_bytes_with_nul() {
 727         let data = b"123\0";
 728         let cstr = CStr::from_bytes_with_nul(data);
 729         assert_eq!(cstr.map(CStr::to_bytes), Some(&b"123"[..]));
 730         assert_eq!(cstr.map(CStr::to_bytes_with_nul), Some(&b"123\0"[..]));
 731
 732         unsafe {
 733             let cstr_unchecked = CStr::from_bytes_with_nul_unchecked(data);
 734             assert_eq!(cstr, Some(cstr_unchecked));
 735         }
 736     }
 737
 738     #[test]
 739     fn from_bytes_with_nul_unterminated() {
 740         let data = b"123";
 741         let cstr = CStr::from_bytes_with_nul(data);
 742         assert!(cstr.is_none());
 743     }
 744
 745     #[test]
 746     fn from_bytes_with_nul_interior() {
 747         let data = b"1\023\0";
 748         let cstr = CStr::from_bytes_with_nul(data);
 749         assert!(cstr.is_none());
 750     }
 751 }