library/std/src/ffi/os_str.rs

   1 #[cfg(test)]
   2 mod tests;
   3
   4 use crate::borrow::{Borrow, Cow};
   5 use crate::cmp;
   6 use crate::collections::TryReserveError;
   7 use crate::fmt;
   8 use crate::hash::{Hash, Hasher};
   9 use crate::iter::Extend;
  10 use crate::ops;
  11 use crate::rc::Rc;
  12 use crate::str::FromStr;
  13 use crate::sync::Arc;
  14
  15 use crate::sys::os_str::{Buf, Slice};
  16 use crate::sys_common::{AsInner, FromInner, IntoInner};
  17
  18 /// A type that can represent owned, mutable platform-native strings, but is
  19 /// cheaply inter-convertible with Rust strings.
  20 ///
  21 /// The need for this type arises from the fact that:
  22 ///
  23 /// * On Unix systems, strings are often arbitrary sequences of non-zero
  24 ///   bytes, in many cases interpreted as UTF-8.
  25 ///
  26 /// * On Windows, strings are often arbitrary sequences of non-zero 16-bit
  27 ///   values, interpreted as UTF-16 when it is valid to do so.
  28 ///
  29 /// * In Rust, strings are always valid UTF-8, which may contain zeros.
  30 ///
  31 /// `OsString` and [`OsStr`] bridge this gap by simultaneously representing Rust
  32 /// and platform-native string values, and in particular allowing a Rust string
  33 /// to be converted into an "OS" string with no cost if possible. A consequence
  34 /// of this is that `OsString` instances are *not* `NUL` terminated; in order
  35 /// to pass to e.g., Unix system call, you should create a [`CStr`].
  36 ///
  37 /// `OsString` is to <code>&[OsStr]</code> as [`String`] is to <code>&[str]</code>: the former
  38 /// in each pair are owned strings; the latter are borrowed
  39 /// references.
  40 ///
  41 /// Note, `OsString` and [`OsStr`] internally do not necessarily hold strings in
  42 /// the form native to the platform; While on Unix, strings are stored as a
  43 /// sequence of 8-bit values, on Windows, where strings are 16-bit value based
  44 /// as just discussed, strings are also actually stored as a sequence of 8-bit
  45 /// values, encoded in a less-strict variant of UTF-8. This is useful to
  46 /// understand when handling capacity and length values.
  47 ///
  48 /// # Capacity of `OsString`
  49 ///
  50 /// Capacity uses units of UTF-8 bytes for OS strings which were created from valid unicode, and
  51 /// uses units of bytes in an unspecified encoding for other contents. On a given target, all
  52 /// `OsString` and `OsStr` values use the same units for capacity, so the following will work:
  53 /// ```
  54 /// use std::ffi::{OsStr, OsString};
  55 ///
  56 /// fn concat_os_strings(a: &OsStr, b: &OsStr) -> OsString {
  57 ///     let mut ret = OsString::with_capacity(a.len() + b.len()); // This will allocate
  58 ///     ret.push(a); // This will not allocate further
  59 ///     ret.push(b); // This will not allocate further
  60 ///     ret
  61 /// }
  62 /// ```
  63 ///
  64 /// # Creating an `OsString`
  65 ///
  66 /// **From a Rust string**: `OsString` implements
  67 /// <code>[From]<[String]></code>, so you can use <code>my_string.[into]\()</code> to
  68 /// create an `OsString` from a normal Rust string.
  69 ///
  70 /// **From slices:** Just like you can start with an empty Rust
  71 /// [`String`] and then [`String::push_str`] some <code>&[str]</code>
  72 /// sub-string slices into it, you can create an empty `OsString` with
  73 /// the [`OsString::new`] method and then push string slices into it with the
  74 /// [`OsString::push`] method.
  75 ///
  76 /// # Extracting a borrowed reference to the whole OS string
  77 ///
  78 /// You can use the [`OsString::as_os_str`] method to get an <code>&[OsStr]</code> from
  79 /// an `OsString`; this is effectively a borrowed reference to the
  80 /// whole string.
  81 ///
  82 /// # Conversions
  83 ///
  84 /// See the [module's toplevel documentation about conversions][conversions] for a discussion on
  85 /// the traits which `OsString` implements for [conversions] from/to native representations.
  86 ///
  87 /// [`CStr`]: crate::ffi::CStr
  88 /// [conversions]: super#conversions
  89 /// [into]: Into::into
  90 #[cfg_attr(not(test), rustc_diagnostic_item = "OsString")]
  91 #[stable(feature = "rust1", since = "1.0.0")]
  92 pub struct OsString {
  93     inner: Buf,
  94 }
  95
  96 /// Allows extension traits within `std`.
  97 #[unstable(feature = "sealed", issue = "none")]
  98 impl crate::sealed::Sealed for OsString {}
  99
 100 /// Borrowed reference to an OS string (see [`OsString`]).
 101 ///
 102 /// This type represents a borrowed reference to a string in the operating system's preferred
 103 /// representation.
 104 ///
 105 /// `&OsStr` is to [`OsString`] as <code>&[str]</code> is to [`String`]: the
 106 /// former in each pair are borrowed references; the latter are owned strings.
 107 ///
 108 /// See the [module's toplevel documentation about conversions][conversions] for a discussion on
 109 /// the traits which `OsStr` implements for [conversions] from/to native representations.
 110 ///
 111 /// [conversions]: super#conversions
 112 #[cfg_attr(not(test), rustc_diagnostic_item = "OsStr")]
 113 #[stable(feature = "rust1", since = "1.0.0")]
 114 // FIXME:
 115 // `OsStr::from_inner` current implementation relies
 116 // on `OsStr` being layout-compatible with `Slice`.
 117 // When attribute privacy is implemented, `OsStr` should be annotated as `#[repr(transparent)]`.
 118 // Anyway, `OsStr` representation and layout are considered implementation details, are
 119 // not documented and must not be relied upon.
 120 pub struct OsStr {
 121     inner: Slice,
 122 }
 123
 124 /// Allows extension traits within `std`.
 125 #[unstable(feature = "sealed", issue = "none")]
 126 impl crate::sealed::Sealed for OsStr {}
 127
 128 impl OsString {
 129     /// Constructs a new empty `OsString`.
 130     ///
 131     /// # Examples
 132     ///
 133     /// ```
 134     /// use std::ffi::OsString;
 135     ///
 136     /// let os_string = OsString::new();
 137     /// ```
 138     #[stable(feature = "rust1", since = "1.0.0")]
 139     #[must_use]
 140     #[inline]
 141     pub fn new() -> OsString {
 142         OsString { inner: Buf::from_string(String::new()) }
 143     }
 144
 145     /// Converts to an [`OsStr`] slice.
 146     ///
 147     /// # Examples
 148     ///
 149     /// ```
 150     /// use std::ffi::{OsString, OsStr};
 151     ///
 152     /// let os_string = OsString::from("foo");
 153     /// let os_str = OsStr::new("foo");
 154     /// assert_eq!(os_string.as_os_str(), os_str);
 155     /// ```
 156     #[stable(feature = "rust1", since = "1.0.0")]
 157     #[must_use]
 158     #[inline]
 159     pub fn as_os_str(&self) -> &OsStr {
 160         self
 161     }
 162
 163     /// Converts the `OsString` into a [`String`] if it contains valid Unicode data.
 164     ///
 165     /// On failure, ownership of the original `OsString` is returned.
 166     ///
 167     /// # Examples
 168     ///
 169     /// ```
 170     /// use std::ffi::OsString;
 171     ///
 172     /// let os_string = OsString::from("foo");
 173     /// let string = os_string.into_string();
 174     /// assert_eq!(string, Ok(String::from("foo")));
 175     /// ```
 176     #[stable(feature = "rust1", since = "1.0.0")]
 177     #[inline]
 178     pub fn into_string(self) -> Result<String, OsString> {
 179         self.inner.into_string().map_err(|buf| OsString { inner: buf })
 180     }
 181
 182     /// Extends the string with the given <code>&[OsStr]</code> slice.
 183     ///
 184     /// # Examples
 185     ///
 186     /// ```
 187     /// use std::ffi::OsString;
 188     ///
 189     /// let mut os_string = OsString::from("foo");
 190     /// os_string.push("bar");
 191     /// assert_eq!(&os_string, "foobar");
 192     /// ```
 193     #[stable(feature = "rust1", since = "1.0.0")]
 194     #[inline]
 195     pub fn push<T: AsRef<OsStr>>(&mut self, s: T) {
 196         self.inner.push_slice(&s.as_ref().inner)
 197     }
 198
 199     /// Creates a new `OsString` with at least the given capacity.
 200     ///
 201     /// The string will be able to hold at least `capacity` length units of other
 202     /// OS strings without reallocating. This method is allowed to allocate for
 203     /// more units than `capacity`. If `capacity` is 0, the string will not
 204     /// allocate.
 205     ///
 206     /// See the main `OsString` documentation information about encoding and capacity units.
 207     ///
 208     /// # Examples
 209     ///
 210     /// ```
 211     /// use std::ffi::OsString;
 212     ///
 213     /// let mut os_string = OsString::with_capacity(10);
 214     /// let capacity = os_string.capacity();
 215     ///
 216     /// // This push is done without reallocating
 217     /// os_string.push("foo");
 218     ///
 219     /// assert_eq!(capacity, os_string.capacity());
 220     /// ```
 221     #[stable(feature = "osstring_simple_functions", since = "1.9.0")]
 222     #[must_use]
 223     #[inline]
 224     pub fn with_capacity(capacity: usize) -> OsString {
 225         OsString { inner: Buf::with_capacity(capacity) }
 226     }
 227
 228     /// Truncates the `OsString` to zero length.
 229     ///
 230     /// # Examples
 231     ///
 232     /// ```
 233     /// use std::ffi::OsString;
 234     ///
 235     /// let mut os_string = OsString::from("foo");
 236     /// assert_eq!(&os_string, "foo");
 237     ///
 238     /// os_string.clear();
 239     /// assert_eq!(&os_string, "");
 240     /// ```
 241     #[stable(feature = "osstring_simple_functions", since = "1.9.0")]
 242     #[inline]
 243     pub fn clear(&mut self) {
 244         self.inner.clear()
 245     }
 246
 247     /// Returns the capacity this `OsString` can hold without reallocating.
 248     ///
 249     /// See the main `OsString` documentation information about encoding and capacity units.
 250     ///
 251     /// # Examples
 252     ///
 253     /// ```
 254     /// use std::ffi::OsString;
 255     ///
 256     /// let os_string = OsString::with_capacity(10);
 257     /// assert!(os_string.capacity() >= 10);
 258     /// ```
 259     #[stable(feature = "osstring_simple_functions", since = "1.9.0")]
 260     #[must_use]
 261     #[inline]
 262     pub fn capacity(&self) -> usize {
 263         self.inner.capacity()
 264     }
 265
 266     /// Reserves capacity for at least `additional` more capacity to be inserted
 267     /// in the given `OsString`. Does nothing if the capacity is
 268     /// already sufficient.
 269     ///
 270     /// The collection may reserve more space to speculatively avoid frequent reallocations.
 271     ///
 272     /// See the main `OsString` documentation information about encoding and capacity units.
 273     ///
 274     /// # Examples
 275     ///
 276     /// ```
 277     /// use std::ffi::OsString;
 278     ///
 279     /// let mut s = OsString::new();
 280     /// s.reserve(10);
 281     /// assert!(s.capacity() >= 10);
 282     /// ```
 283     #[stable(feature = "osstring_simple_functions", since = "1.9.0")]
 284     #[inline]
 285     pub fn reserve(&mut self, additional: usize) {
 286         self.inner.reserve(additional)
 287     }
 288
 289     /// Tries to reserve capacity for at least `additional` more length units
 290     /// in the given `OsString`. The string may reserve more space to speculatively avoid
 291     /// frequent reallocations. After calling `try_reserve`, capacity will be
 292     /// greater than or equal to `self.len() + additional` if it returns `Ok(())`.
 293     /// Does nothing if capacity is already sufficient.
 294     ///
 295     /// See the main `OsString` documentation information about encoding and capacity units.
 296     ///
 297     /// # Errors
 298     ///
 299     /// If the capacity overflows, or the allocator reports a failure, then an error
 300     /// is returned.
 301     ///
 302     /// # Examples
 303     ///
 304     /// ```
 305     /// use std::ffi::{OsStr, OsString};
 306     /// use std::collections::TryReserveError;
 307     ///
 308     /// fn process_data(data: &str) -> Result<OsString, TryReserveError> {
 309     ///     let mut s = OsString::new();
 310     ///
 311     ///     // Pre-reserve the memory, exiting if we can't
 312     ///     s.try_reserve(OsStr::new(data).len())?;
 313     ///
 314     ///     // Now we know this can't OOM in the middle of our complex work
 315     ///     s.push(data);
 316     ///
 317     ///     Ok(s)
 318     /// }
 319     /// # process_data("123").expect("why is the test harness OOMing on 3 bytes?");
 320     /// ```
 321     #[stable(feature = "try_reserve_2", since = "1.63.0")]
 322     #[inline]
 323     pub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError> {
 324         self.inner.try_reserve(additional)
 325     }
 326
 327     /// Reserves the minimum capacity for at least `additional` more capacity to
 328     /// be inserted in the given `OsString`. Does nothing if the capacity is
 329     /// already sufficient.
 330     ///
 331     /// Note that the allocator may give the collection more space than it
 332     /// requests. Therefore, capacity can not be relied upon to be precisely
 333     /// minimal. Prefer [`reserve`] if future insertions are expected.
 334     ///
 335     /// [`reserve`]: OsString::reserve
 336     ///
 337     /// See the main `OsString` documentation information about encoding and capacity units.
 338     ///
 339     /// # Examples
 340     ///
 341     /// ```
 342     /// use std::ffi::OsString;
 343     ///
 344     /// let mut s = OsString::new();
 345     /// s.reserve_exact(10);
 346     /// assert!(s.capacity() >= 10);
 347     /// ```
 348     #[stable(feature = "osstring_simple_functions", since = "1.9.0")]
 349     #[inline]
 350     pub fn reserve_exact(&mut self, additional: usize) {
 351         self.inner.reserve_exact(additional)
 352     }
 353
 354     /// Tries to reserve the minimum capacity for at least `additional`
 355     /// more length units in the given `OsString`. After calling
 356     /// `try_reserve_exact`, capacity will be greater than or equal to
 357     /// `self.len() + additional` if it returns `Ok(())`.
 358     /// Does nothing if the capacity is already sufficient.
 359     ///
 360     /// Note that the allocator may give the `OsString` more space than it
 361     /// requests. Therefore, capacity can not be relied upon to be precisely
 362     /// minimal. Prefer [`try_reserve`] if future insertions are expected.
 363     ///
 364     /// [`try_reserve`]: OsString::try_reserve
 365     ///
 366     /// See the main `OsString` documentation information about encoding and capacity units.
 367     ///
 368     /// # Errors
 369     ///
 370     /// If the capacity overflows, or the allocator reports a failure, then an error
 371     /// is returned.
 372     ///
 373     /// # Examples
 374     ///
 375     /// ```
 376     /// use std::ffi::{OsStr, OsString};
 377     /// use std::collections::TryReserveError;
 378     ///
 379     /// fn process_data(data: &str) -> Result<OsString, TryReserveError> {
 380     ///     let mut s = OsString::new();
 381     ///
 382     ///     // Pre-reserve the memory, exiting if we can't
 383     ///     s.try_reserve_exact(OsStr::new(data).len())?;
 384     ///
 385     ///     // Now we know this can't OOM in the middle of our complex work
 386     ///     s.push(data);
 387     ///
 388     ///     Ok(s)
 389     /// }
 390     /// # process_data("123").expect("why is the test harness OOMing on 3 bytes?");
 391     /// ```
 392     #[stable(feature = "try_reserve_2", since = "1.63.0")]
 393     #[inline]
 394     pub fn try_reserve_exact(&mut self, additional: usize) -> Result<(), TryReserveError> {
 395         self.inner.try_reserve_exact(additional)
 396     }
 397
 398     /// Shrinks the capacity of the `OsString` to match its length.
 399     ///
 400     /// See the main `OsString` documentation information about encoding and capacity units.
 401     ///
 402     /// # Examples
 403     ///
 404     /// ```
 405     /// use std::ffi::OsString;
 406     ///
 407     /// let mut s = OsString::from("foo");
 408     ///
 409     /// s.reserve(100);
 410     /// assert!(s.capacity() >= 100);
 411     ///
 412     /// s.shrink_to_fit();
 413     /// assert_eq!(3, s.capacity());
 414     /// ```
 415     #[stable(feature = "osstring_shrink_to_fit", since = "1.19.0")]
 416     #[inline]
 417     pub fn shrink_to_fit(&mut self) {
 418         self.inner.shrink_to_fit()
 419     }
 420
 421     /// Shrinks the capacity of the `OsString` with a lower bound.
 422     ///
 423     /// The capacity will remain at least as large as both the length
 424     /// and the supplied value.
 425     ///
 426     /// If the current capacity is less than the lower limit, this is a no-op.
 427     ///
 428     /// See the main `OsString` documentation information about encoding and capacity units.
 429     ///
 430     /// # Examples
 431     ///
 432     /// ```
 433     /// use std::ffi::OsString;
 434     ///
 435     /// let mut s = OsString::from("foo");
 436     ///
 437     /// s.reserve(100);
 438     /// assert!(s.capacity() >= 100);
 439     ///
 440     /// s.shrink_to(10);
 441     /// assert!(s.capacity() >= 10);
 442     /// s.shrink_to(0);
 443     /// assert!(s.capacity() >= 3);
 444     /// ```
 445     #[inline]
 446     #[stable(feature = "shrink_to", since = "1.56.0")]
 447     pub fn shrink_to(&mut self, min_capacity: usize) {
 448         self.inner.shrink_to(min_capacity)
 449     }
 450
 451     /// Converts this `OsString` into a boxed [`OsStr`].
 452     ///
 453     /// # Examples
 454     ///
 455     /// ```
 456     /// use std::ffi::{OsString, OsStr};
 457     ///
 458     /// let s = OsString::from("hello");
 459     ///
 460     /// let b: Box<OsStr> = s.into_boxed_os_str();
 461     /// ```
 462     #[must_use = "`self` will be dropped if the result is not used"]
 463     #[stable(feature = "into_boxed_os_str", since = "1.20.0")]
 464     pub fn into_boxed_os_str(self) -> Box<OsStr> {
 465         let rw = Box::into_raw(self.inner.into_box()) as *mut OsStr;
 466         unsafe { Box::from_raw(rw) }
 467     }
 468 }
 469
 470 #[stable(feature = "rust1", since = "1.0.0")]
 471 impl From<String> for OsString {
 472     /// Converts a [`String`] into an [`OsString`].
 473     ///
 474     /// This conversion does not allocate or copy memory.
 475     #[inline]
 476     fn from(s: String) -> OsString {
 477         OsString { inner: Buf::from_string(s) }
 478     }
 479 }
 480
 481 #[stable(feature = "rust1", since = "1.0.0")]
 482 impl<T: ?Sized + AsRef<OsStr>> From<&T> for OsString {
 483     /// Copies any value implementing <code>[AsRef]&lt;[OsStr]&gt;</code>
 484     /// into a newly allocated [`OsString`].
 485     fn from(s: &T) -> OsString {
 486         s.as_ref().to_os_string()
 487     }
 488 }
 489
 490 #[stable(feature = "rust1", since = "1.0.0")]
 491 impl ops::Index<ops::RangeFull> for OsString {
 492     type Output = OsStr;
 493
 494     #[inline]
 495     fn index(&self, _index: ops::RangeFull) -> &OsStr {
 496         OsStr::from_inner(self.inner.as_slice())
 497     }
 498 }
 499
 500 #[stable(feature = "mut_osstr", since = "1.44.0")]
 501 impl ops::IndexMut<ops::RangeFull> for OsString {
 502     #[inline]
 503     fn index_mut(&mut self, _index: ops::RangeFull) -> &mut OsStr {
 504         OsStr::from_inner_mut(self.inner.as_mut_slice())
 505     }
 506 }
 507
 508 #[stable(feature = "rust1", since = "1.0.0")]
 509 impl ops::Deref for OsString {
 510     type Target = OsStr;
 511
 512     #[inline]
 513     fn deref(&self) -> &OsStr {
 514         &self[..]
 515     }
 516 }
 517
 518 #[stable(feature = "mut_osstr", since = "1.44.0")]
 519 impl ops::DerefMut for OsString {
 520     #[inline]
 521     fn deref_mut(&mut self) -> &mut OsStr {
 522         &mut self[..]
 523     }
 524 }
 525
 526 #[stable(feature = "osstring_default", since = "1.9.0")]
 527 impl Default for OsString {
 528     /// Constructs an empty `OsString`.
 529     #[inline]
 530     fn default() -> OsString {
 531         OsString::new()
 532     }
 533 }
 534
 535 #[stable(feature = "rust1", since = "1.0.0")]
 536 impl Clone for OsString {
 537     #[inline]
 538     fn clone(&self) -> Self {
 539         OsString { inner: self.inner.clone() }
 540     }
 541
 542     #[inline]
 543     fn clone_from(&mut self, source: &Self) {
 544         self.inner.clone_from(&source.inner)
 545     }
 546 }
 547
 548 #[stable(feature = "rust1", since = "1.0.0")]
 549 impl fmt::Debug for OsString {
 550     fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
 551         fmt::Debug::fmt(&**self, formatter)
 552     }
 553 }
 554
 555 #[stable(feature = "rust1", since = "1.0.0")]
 556 impl PartialEq for OsString {
 557     #[inline]
 558     fn eq(&self, other: &OsString) -> bool {
 559         &**self == &**other
 560     }
 561 }
 562
 563 #[stable(feature = "rust1", since = "1.0.0")]
 564 impl PartialEq<str> for OsString {
 565     #[inline]
 566     fn eq(&self, other: &str) -> bool {
 567         &**self == other
 568     }
 569 }
 570
 571 #[stable(feature = "rust1", since = "1.0.0")]
 572 impl PartialEq<OsString> for str {
 573     #[inline]
 574     fn eq(&self, other: &OsString) -> bool {
 575         &**other == self
 576     }
 577 }
 578
 579 #[stable(feature = "os_str_str_ref_eq", since = "1.29.0")]
 580 impl PartialEq<&str> for OsString {
 581     #[inline]
 582     fn eq(&self, other: &&str) -> bool {
 583         **self == **other
 584     }
 585 }
 586
 587 #[stable(feature = "os_str_str_ref_eq", since = "1.29.0")]
 588 impl<'a> PartialEq<OsString> for &'a str {
 589     #[inline]
 590     fn eq(&self, other: &OsString) -> bool {
 591         **other == **self
 592     }
 593 }
 594
 595 #[stable(feature = "rust1", since = "1.0.0")]
 596 impl Eq for OsString {}
 597
 598 #[stable(feature = "rust1", since = "1.0.0")]
 599 impl PartialOrd for OsString {
 600     #[inline]
 601     fn partial_cmp(&self, other: &OsString) -> Option<cmp::Ordering> {
 602         (&**self).partial_cmp(&**other)
 603     }
 604     #[inline]
 605     fn lt(&self, other: &OsString) -> bool {
 606         &**self < &**other
 607     }
 608     #[inline]
 609     fn le(&self, other: &OsString) -> bool {
 610         &**self <= &**other
 611     }
 612     #[inline]
 613     fn gt(&self, other: &OsString) -> bool {
 614         &**self > &**other
 615     }
 616     #[inline]
 617     fn ge(&self, other: &OsString) -> bool {
 618         &**self >= &**other
 619     }
 620 }
 621
 622 #[stable(feature = "rust1", since = "1.0.0")]
 623 impl PartialOrd<str> for OsString {
 624     #[inline]
 625     fn partial_cmp(&self, other: &str) -> Option<cmp::Ordering> {
 626         (&**self).partial_cmp(other)
 627     }
 628 }
 629
 630 #[stable(feature = "rust1", since = "1.0.0")]
 631 impl Ord for OsString {
 632     #[inline]
 633     fn cmp(&self, other: &OsString) -> cmp::Ordering {
 634         (&**self).cmp(&**other)
 635     }
 636 }
 637
 638 #[stable(feature = "rust1", since = "1.0.0")]
 639 impl Hash for OsString {
 640     #[inline]
 641     fn hash<H: Hasher>(&self, state: &mut H) {
 642         (&**self).hash(state)
 643     }
 644 }
 645
 646 impl OsStr {
 647     /// Coerces into an `OsStr` slice.
 648     ///
 649     /// # Examples
 650     ///
 651     /// ```
 652     /// use std::ffi::OsStr;
 653     ///
 654     /// let os_str = OsStr::new("foo");
 655     /// ```
 656     #[inline]
 657     #[stable(feature = "rust1", since = "1.0.0")]
 658     pub fn new<S: AsRef<OsStr> + ?Sized>(s: &S) -> &OsStr {
 659         s.as_ref()
 660     }
 661
 662     #[inline]
 663     fn from_inner(inner: &Slice) -> &OsStr {
 664         // SAFETY: OsStr is just a wrapper of Slice,
 665         // therefore converting &Slice to &OsStr is safe.
 666         unsafe { &*(inner as *const Slice as *const OsStr) }
 667     }
 668
 669     #[inline]
 670     fn from_inner_mut(inner: &mut Slice) -> &mut OsStr {
 671         // SAFETY: OsStr is just a wrapper of Slice,
 672         // therefore converting &mut Slice to &mut OsStr is safe.
 673         // Any method that mutates OsStr must be careful not to
 674         // break platform-specific encoding, in particular Wtf8 on Windows.
 675         unsafe { &mut *(inner as *mut Slice as *mut OsStr) }
 676     }
 677
 678     /// Yields a <code>&[str]</code> slice if the `OsStr` is valid Unicode.
 679     ///
 680     /// This conversion may entail doing a check for UTF-8 validity.
 681     ///
 682     /// # Examples
 683     ///
 684     /// ```
 685     /// use std::ffi::OsStr;
 686     ///
 687     /// let os_str = OsStr::new("foo");
 688     /// assert_eq!(os_str.to_str(), Some("foo"));
 689     /// ```
 690     #[stable(feature = "rust1", since = "1.0.0")]
 691     #[must_use = "this returns the result of the operation, \
 692                   without modifying the original"]
 693     #[inline]
 694     pub fn to_str(&self) -> Option<&str> {
 695         self.inner.to_str()
 696     }
 697
 698     /// Converts an `OsStr` to a <code>[Cow]<[str]></code>.
 699     ///
 700     /// Any non-Unicode sequences are replaced with
 701     /// [`U+FFFD REPLACEMENT CHARACTER`][U+FFFD].
 702     ///
 703     /// [U+FFFD]: crate::char::REPLACEMENT_CHARACTER
 704     ///
 705     /// # Examples
 706     ///
 707     /// Calling `to_string_lossy` on an `OsStr` with invalid unicode:
 708     ///
 709     /// ```
 710     /// // Note, due to differences in how Unix and Windows represent strings,
 711     /// // we are forced to complicate this example, setting up example `OsStr`s
 712     /// // with different source data and via different platform extensions.
 713     /// // Understand that in reality you could end up with such example invalid
 714     /// // sequences simply through collecting user command line arguments, for
 715     /// // example.
 716     ///
 717     /// #[cfg(unix)] {
 718     ///     use std::ffi::OsStr;
 719     ///     use std::os::unix::ffi::OsStrExt;
 720     ///
 721     ///     // Here, the values 0x66 and 0x6f correspond to 'f' and 'o'
 722     ///     // respectively. The value 0x80 is a lone continuation byte, invalid
 723     ///     // in a UTF-8 sequence.
 724     ///     let source = [0x66, 0x6f, 0x80, 0x6f];
 725     ///     let os_str = OsStr::from_bytes(&source[..]);
 726     ///
 727     ///     assert_eq!(os_str.to_string_lossy(), "fo�o");
 728     /// }
 729     /// #[cfg(windows)] {
 730     ///     use std::ffi::OsString;
 731     ///     use std::os::windows::prelude::*;
 732     ///
 733     ///     // Here the values 0x0066 and 0x006f correspond to 'f' and 'o'
 734     ///     // respectively. The value 0xD800 is a lone surrogate half, invalid
 735     ///     // in a UTF-16 sequence.
 736     ///     let source = [0x0066, 0x006f, 0xD800, 0x006f];
 737     ///     let os_string = OsString::from_wide(&source[..]);
 738     ///     let os_str = os_string.as_os_str();
 739     ///
 740     ///     assert_eq!(os_str.to_string_lossy(), "fo�o");
 741     /// }
 742     /// ```
 743     #[stable(feature = "rust1", since = "1.0.0")]
 744     #[must_use = "this returns the result of the operation, \
 745                   without modifying the original"]
 746     #[inline]
 747     pub fn to_string_lossy(&self) -> Cow<'_, str> {
 748         self.inner.to_string_lossy()
 749     }
 750
 751     /// Copies the slice into an owned [`OsString`].
 752     ///
 753     /// # Examples
 754     ///
 755     /// ```
 756     /// use std::ffi::{OsStr, OsString};
 757     ///
 758     /// let os_str = OsStr::new("foo");
 759     /// let os_string = os_str.to_os_string();
 760     /// assert_eq!(os_string, OsString::from("foo"));
 761     /// ```
 762     #[stable(feature = "rust1", since = "1.0.0")]
 763     #[must_use = "this returns the result of the operation, \
 764                   without modifying the original"]
 765     #[inline]
 766     pub fn to_os_string(&self) -> OsString {
 767         OsString { inner: self.inner.to_owned() }
 768     }
 769
 770     /// Checks whether the `OsStr` is empty.
 771     ///
 772     /// # Examples
 773     ///
 774     /// ```
 775     /// use std::ffi::OsStr;
 776     ///
 777     /// let os_str = OsStr::new("");
 778     /// assert!(os_str.is_empty());
 779     ///
 780     /// let os_str = OsStr::new("foo");
 781     /// assert!(!os_str.is_empty());
 782     /// ```
 783     #[stable(feature = "osstring_simple_functions", since = "1.9.0")]
 784     #[must_use]
 785     #[inline]
 786     pub fn is_empty(&self) -> bool {
 787         self.inner.inner.is_empty()
 788     }
 789
 790     /// Returns the length of this `OsStr`.
 791     ///
 792     /// Note that this does **not** return the number of bytes in the string in
 793     /// OS string form.
 794     ///
 795     /// The length returned is that of the underlying storage used by `OsStr`.
 796     /// As discussed in the [`OsString`] introduction, [`OsString`] and `OsStr`
 797     /// store strings in a form best suited for cheap inter-conversion between
 798     /// native-platform and Rust string forms, which may differ significantly
 799     /// from both of them, including in storage size and encoding.
 800     ///
 801     /// This number is simply useful for passing to other methods, like
 802     /// [`OsString::with_capacity`] to avoid reallocations.
 803     ///
 804     /// See the main `OsString` documentation information about encoding and capacity units.
 805     ///
 806     /// # Examples
 807     ///
 808     /// ```
 809     /// use std::ffi::OsStr;
 810     ///
 811     /// let os_str = OsStr::new("");
 812     /// assert_eq!(os_str.len(), 0);
 813     ///
 814     /// let os_str = OsStr::new("foo");
 815     /// assert_eq!(os_str.len(), 3);
 816     /// ```
 817     #[stable(feature = "osstring_simple_functions", since = "1.9.0")]
 818     #[must_use]
 819     #[inline]
 820     pub fn len(&self) -> usize {
 821         self.inner.inner.len()
 822     }
 823
 824     /// Converts a <code>[Box]<[OsStr]></code> into an [`OsString`] without copying or allocating.
 825     #[stable(feature = "into_boxed_os_str", since = "1.20.0")]
 826     #[must_use = "`self` will be dropped if the result is not used"]
 827     pub fn into_os_string(self: Box<OsStr>) -> OsString {
 828         let boxed = unsafe { Box::from_raw(Box::into_raw(self) as *mut Slice) };
 829         OsString { inner: Buf::from_box(boxed) }
 830     }
 831
 832     /// Gets the underlying byte representation.
 833     ///
 834     /// Note: it is *crucial* that this API is not externally public, to avoid
 835     /// revealing the internal, platform-specific encodings.
 836     #[inline]
 837     pub(crate) fn bytes(&self) -> &[u8] {
 838         unsafe { &*(&self.inner as *const _ as *const [u8]) }
 839     }
 840
 841     /// Converts this string to its ASCII lower case equivalent in-place.
 842     ///
 843     /// ASCII letters 'A' to 'Z' are mapped to 'a' to 'z',
 844     /// but non-ASCII letters are unchanged.
 845     ///
 846     /// To return a new lowercased value without modifying the existing one, use
 847     /// [`OsStr::to_ascii_lowercase`].
 848     ///
 849     /// # Examples
 850     ///
 851     /// ```
 852     /// use std::ffi::OsString;
 853     ///
 854     /// let mut s = OsString::from("GRÜßE, JÜRGEN ❤");
 855     ///
 856     /// s.make_ascii_lowercase();
 857     ///
 858     /// assert_eq!("grÜße, jÜrgen ❤", s);
 859     /// ```
 860     #[stable(feature = "osstring_ascii", since = "1.53.0")]
 861     #[inline]
 862     pub fn make_ascii_lowercase(&mut self) {
 863         self.inner.make_ascii_lowercase()
 864     }
 865
 866     /// Converts this string to its ASCII upper case equivalent in-place.
 867     ///
 868     /// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z',
 869     /// but non-ASCII letters are unchanged.
 870     ///
 871     /// To return a new uppercased value without modifying the existing one, use
 872     /// [`OsStr::to_ascii_uppercase`].
 873     ///
 874     /// # Examples
 875     ///
 876     /// ```
 877     /// use std::ffi::OsString;
 878     ///
 879     /// let mut s = OsString::from("Grüße, Jürgen ❤");
 880     ///
 881     /// s.make_ascii_uppercase();
 882     ///
 883     /// assert_eq!("GRüßE, JüRGEN ❤", s);
 884     /// ```
 885     #[stable(feature = "osstring_ascii", since = "1.53.0")]
 886     #[inline]
 887     pub fn make_ascii_uppercase(&mut self) {
 888         self.inner.make_ascii_uppercase()
 889     }
 890
 891     /// Returns a copy of this string where each character is mapped to its
 892     /// ASCII lower case equivalent.
 893     ///
 894     /// ASCII letters 'A' to 'Z' are mapped to 'a' to 'z',
 895     /// but non-ASCII letters are unchanged.
 896     ///
 897     /// To lowercase the value in-place, use [`OsStr::make_ascii_lowercase`].
 898     ///
 899     /// # Examples
 900     ///
 901     /// ```
 902     /// use std::ffi::OsString;
 903     /// let s = OsString::from("Grüße, Jürgen ❤");
 904     ///
 905     /// assert_eq!("grüße, jürgen ❤", s.to_ascii_lowercase());
 906     /// ```
 907     #[must_use = "to lowercase the value in-place, use `make_ascii_lowercase`"]
 908     #[stable(feature = "osstring_ascii", since = "1.53.0")]
 909     pub fn to_ascii_lowercase(&self) -> OsString {
 910         OsString::from_inner(self.inner.to_ascii_lowercase())
 911     }
 912
 913     /// Returns a copy of this string where each character is mapped to its
 914     /// ASCII upper case equivalent.
 915     ///
 916     /// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z',
 917     /// but non-ASCII letters are unchanged.
 918     ///
 919     /// To uppercase the value in-place, use [`OsStr::make_ascii_uppercase`].
 920     ///
 921     /// # Examples
 922     ///
 923     /// ```
 924     /// use std::ffi::OsString;
 925     /// let s = OsString::from("Grüße, Jürgen ❤");
 926     ///
 927     /// assert_eq!("GRüßE, JüRGEN ❤", s.to_ascii_uppercase());
 928     /// ```
 929     #[must_use = "to uppercase the value in-place, use `make_ascii_uppercase`"]
 930     #[stable(feature = "osstring_ascii", since = "1.53.0")]
 931     pub fn to_ascii_uppercase(&self) -> OsString {
 932         OsString::from_inner(self.inner.to_ascii_uppercase())
 933     }
 934
 935     /// Checks if all characters in this string are within the ASCII range.
 936     ///
 937     /// # Examples
 938     ///
 939     /// ```
 940     /// use std::ffi::OsString;
 941     ///
 942     /// let ascii = OsString::from("hello!\n");
 943     /// let non_ascii = OsString::from("Grüße, Jürgen ❤");
 944     ///
 945     /// assert!(ascii.is_ascii());
 946     /// assert!(!non_ascii.is_ascii());
 947     /// ```
 948     #[stable(feature = "osstring_ascii", since = "1.53.0")]
 949     #[must_use]
 950     #[inline]
 951     pub fn is_ascii(&self) -> bool {
 952         self.inner.is_ascii()
 953     }
 954
 955     /// Checks that two strings are an ASCII case-insensitive match.
 956     ///
 957     /// Same as `to_ascii_lowercase(a) == to_ascii_lowercase(b)`,
 958     /// but without allocating and copying temporaries.
 959     ///
 960     /// # Examples
 961     ///
 962     /// ```
 963     /// use std::ffi::OsString;
 964     ///
 965     /// assert!(OsString::from("Ferris").eq_ignore_ascii_case("FERRIS"));
 966     /// assert!(OsString::from("Ferrös").eq_ignore_ascii_case("FERRöS"));
 967     /// assert!(!OsString::from("Ferrös").eq_ignore_ascii_case("FERRÖS"));
 968     /// ```
 969     #[stable(feature = "osstring_ascii", since = "1.53.0")]
 970     pub fn eq_ignore_ascii_case<S: AsRef<OsStr>>(&self, other: S) -> bool {
 971         self.inner.eq_ignore_ascii_case(&other.as_ref().inner)
 972     }
 973 }
 974
 975 #[stable(feature = "box_from_os_str", since = "1.17.0")]
 976 impl From<&OsStr> for Box<OsStr> {
 977     /// Copies the string into a newly allocated <code>[Box]&lt;[OsStr]&gt;</code>.
 978     #[inline]
 979     fn from(s: &OsStr) -> Box<OsStr> {
 980         let rw = Box::into_raw(s.inner.into_box()) as *mut OsStr;
 981         unsafe { Box::from_raw(rw) }
 982     }
 983 }
 984
 985 #[stable(feature = "box_from_cow", since = "1.45.0")]
 986 impl From<Cow<'_, OsStr>> for Box<OsStr> {
 987     /// Converts a `Cow<'a, OsStr>` into a <code>[Box]&lt;[OsStr]&gt;</code>,
 988     /// by copying the contents if they are borrowed.
 989     #[inline]
 990     fn from(cow: Cow<'_, OsStr>) -> Box<OsStr> {
 991         match cow {
 992             Cow::Borrowed(s) => Box::from(s),
 993             Cow::Owned(s) => Box::from(s),
 994         }
 995     }
 996 }
 997
 998 #[stable(feature = "os_string_from_box", since = "1.18.0")]
 999 impl From<Box<OsStr>> for OsString {
1000     /// Converts a <code>[Box]<[OsStr]></code> into an [`OsString`] without copying or
1001     /// allocating.
1002     #[inline]
1003     fn from(boxed: Box<OsStr>) -> OsString {
1004         boxed.into_os_string()
1005     }
1006 }
1007
1008 #[stable(feature = "box_from_os_string", since = "1.20.0")]
1009 impl From<OsString> for Box<OsStr> {
1010     /// Converts an [`OsString`] into a <code>[Box]<[OsStr]></code> without copying or allocating.
1011     #[inline]
1012     fn from(s: OsString) -> Box<OsStr> {
1013         s.into_boxed_os_str()
1014     }
1015 }
1016
1017 #[stable(feature = "more_box_slice_clone", since = "1.29.0")]
1018 impl Clone for Box<OsStr> {
1019     #[inline]
1020     fn clone(&self) -> Self {
1021         self.to_os_string().into_boxed_os_str()
1022     }
1023 }
1024
1025 #[stable(feature = "shared_from_slice2", since = "1.24.0")]
1026 impl From<OsString> for Arc<OsStr> {
1027     /// Converts an [`OsString`] into an <code>[Arc]<[OsStr]></code> by moving the [`OsString`]
1028     /// data into a new [`Arc`] buffer.
1029     #[inline]
1030     fn from(s: OsString) -> Arc<OsStr> {
1031         let arc = s.inner.into_arc();
1032         unsafe { Arc::from_raw(Arc::into_raw(arc) as *const OsStr) }
1033     }
1034 }
1035
1036 #[stable(feature = "shared_from_slice2", since = "1.24.0")]
1037 impl From<&OsStr> for Arc<OsStr> {
1038     /// Copies the string into a newly allocated <code>[Arc]&lt;[OsStr]&gt;</code>.
1039     #[inline]
1040     fn from(s: &OsStr) -> Arc<OsStr> {
1041         let arc = s.inner.into_arc();
1042         unsafe { Arc::from_raw(Arc::into_raw(arc) as *const OsStr) }
1043     }
1044 }
1045
1046 #[stable(feature = "shared_from_slice2", since = "1.24.0")]
1047 impl From<OsString> for Rc<OsStr> {
1048     /// Converts an [`OsString`] into an <code>[Rc]<[OsStr]></code> by moving the [`OsString`]
1049     /// data into a new [`Rc`] buffer.
1050     #[inline]
1051     fn from(s: OsString) -> Rc<OsStr> {
1052         let rc = s.inner.into_rc();
1053         unsafe { Rc::from_raw(Rc::into_raw(rc) as *const OsStr) }
1054     }
1055 }
1056
1057 #[stable(feature = "shared_from_slice2", since = "1.24.0")]
1058 impl From<&OsStr> for Rc<OsStr> {
1059     /// Copies the string into a newly allocated <code>[Rc]&lt;[OsStr]&gt;</code>.
1060     #[inline]
1061     fn from(s: &OsStr) -> Rc<OsStr> {
1062         let rc = s.inner.into_rc();
1063         unsafe { Rc::from_raw(Rc::into_raw(rc) as *const OsStr) }
1064     }
1065 }
1066
1067 #[stable(feature = "cow_from_osstr", since = "1.28.0")]
1068 impl<'a> From<OsString> for Cow<'a, OsStr> {
1069     /// Moves the string into a [`Cow::Owned`].
1070     #[inline]
1071     fn from(s: OsString) -> Cow<'a, OsStr> {
1072         Cow::Owned(s)
1073     }
1074 }
1075
1076 #[stable(feature = "cow_from_osstr", since = "1.28.0")]
1077 impl<'a> From<&'a OsStr> for Cow<'a, OsStr> {
1078     /// Converts the string reference into a [`Cow::Borrowed`].
1079     #[inline]
1080     fn from(s: &'a OsStr) -> Cow<'a, OsStr> {
1081         Cow::Borrowed(s)
1082     }
1083 }
1084
1085 #[stable(feature = "cow_from_osstr", since = "1.28.0")]
1086 impl<'a> From<&'a OsString> for Cow<'a, OsStr> {
1087     /// Converts the string reference into a [`Cow::Borrowed`].
1088     #[inline]
1089     fn from(s: &'a OsString) -> Cow<'a, OsStr> {
1090         Cow::Borrowed(s.as_os_str())
1091     }
1092 }
1093
1094 #[stable(feature = "osstring_from_cow_osstr", since = "1.28.0")]
1095 impl<'a> From<Cow<'a, OsStr>> for OsString {
1096     /// Converts a `Cow<'a, OsStr>` into an [`OsString`],
1097     /// by copying the contents if they are borrowed.
1098     #[inline]
1099     fn from(s: Cow<'a, OsStr>) -> Self {
1100         s.into_owned()
1101     }
1102 }
1103
1104 #[stable(feature = "box_default_extra", since = "1.17.0")]
1105 impl Default for Box<OsStr> {
1106     #[inline]
1107     fn default() -> Box<OsStr> {
1108         let rw = Box::into_raw(Slice::empty_box()) as *mut OsStr;
1109         unsafe { Box::from_raw(rw) }
1110     }
1111 }
1112
1113 #[stable(feature = "osstring_default", since = "1.9.0")]
1114 impl Default for &OsStr {
1115     /// Creates an empty `OsStr`.
1116     #[inline]
1117     fn default() -> Self {
1118         OsStr::new("")
1119     }
1120 }
1121
1122 #[stable(feature = "rust1", since = "1.0.0")]
1123 impl PartialEq for OsStr {
1124     #[inline]
1125     fn eq(&self, other: &OsStr) -> bool {
1126         self.bytes().eq(other.bytes())
1127     }
1128 }
1129
1130 #[stable(feature = "rust1", since = "1.0.0")]
1131 impl PartialEq<str> for OsStr {
1132     #[inline]
1133     fn eq(&self, other: &str) -> bool {
1134         *self == *OsStr::new(other)
1135     }
1136 }
1137
1138 #[stable(feature = "rust1", since = "1.0.0")]
1139 impl PartialEq<OsStr> for str {
1140     #[inline]
1141     fn eq(&self, other: &OsStr) -> bool {
1142         *other == *OsStr::new(self)
1143     }
1144 }
1145
1146 #[stable(feature = "rust1", since = "1.0.0")]
1147 impl Eq for OsStr {}
1148
1149 #[stable(feature = "rust1", since = "1.0.0")]
1150 impl PartialOrd for OsStr {
1151     #[inline]
1152     fn partial_cmp(&self, other: &OsStr) -> Option<cmp::Ordering> {
1153         self.bytes().partial_cmp(other.bytes())
1154     }
1155     #[inline]
1156     fn lt(&self, other: &OsStr) -> bool {
1157         self.bytes().lt(other.bytes())
1158     }
1159     #[inline]
1160     fn le(&self, other: &OsStr) -> bool {
1161         self.bytes().le(other.bytes())
1162     }
1163     #[inline]
1164     fn gt(&self, other: &OsStr) -> bool {
1165         self.bytes().gt(other.bytes())
1166     }
1167     #[inline]
1168     fn ge(&self, other: &OsStr) -> bool {
1169         self.bytes().ge(other.bytes())
1170     }
1171 }
1172
1173 #[stable(feature = "rust1", since = "1.0.0")]
1174 impl PartialOrd<str> for OsStr {
1175     #[inline]
1176     fn partial_cmp(&self, other: &str) -> Option<cmp::Ordering> {
1177         self.partial_cmp(OsStr::new(other))
1178     }
1179 }
1180
1181 // FIXME (#19470): cannot provide PartialOrd<OsStr> for str until we
1182 // have more flexible coherence rules.
1183
1184 #[stable(feature = "rust1", since = "1.0.0")]
1185 impl Ord for OsStr {
1186     #[inline]
1187     fn cmp(&self, other: &OsStr) -> cmp::Ordering {
1188         self.bytes().cmp(other.bytes())
1189     }
1190 }
1191
1192 macro_rules! impl_cmp {
1193     ($lhs:ty, $rhs: ty) => {
1194         #[stable(feature = "cmp_os_str", since = "1.8.0")]
1195         impl<'a, 'b> PartialEq<$rhs> for $lhs {
1196             #[inline]
1197             fn eq(&self, other: &$rhs) -> bool {
1198                 <OsStr as PartialEq>::eq(self, other)
1199             }
1200         }
1201
1202         #[stable(feature = "cmp_os_str", since = "1.8.0")]
1203         impl<'a, 'b> PartialEq<$lhs> for $rhs {
1204             #[inline]
1205             fn eq(&self, other: &$lhs) -> bool {
1206                 <OsStr as PartialEq>::eq(self, other)
1207             }
1208         }
1209
1210         #[stable(feature = "cmp_os_str", since = "1.8.0")]
1211         impl<'a, 'b> PartialOrd<$rhs> for $lhs {
1212             #[inline]
1213             fn partial_cmp(&self, other: &$rhs) -> Option<cmp::Ordering> {
1214                 <OsStr as PartialOrd>::partial_cmp(self, other)
1215             }
1216         }
1217
1218         #[stable(feature = "cmp_os_str", since = "1.8.0")]
1219         impl<'a, 'b> PartialOrd<$lhs> for $rhs {
1220             #[inline]
1221             fn partial_cmp(&self, other: &$lhs) -> Option<cmp::Ordering> {
1222                 <OsStr as PartialOrd>::partial_cmp(self, other)
1223             }
1224         }
1225     };
1226 }
1227
1228 impl_cmp!(OsString, OsStr);
1229 impl_cmp!(OsString, &'a OsStr);
1230 impl_cmp!(Cow<'a, OsStr>, OsStr);
1231 impl_cmp!(Cow<'a, OsStr>, &'b OsStr);
1232 impl_cmp!(Cow<'a, OsStr>, OsString);
1233
1234 #[stable(feature = "rust1", since = "1.0.0")]
1235 impl Hash for OsStr {
1236     #[inline]
1237     fn hash<H: Hasher>(&self, state: &mut H) {
1238         self.bytes().hash(state)
1239     }
1240 }
1241
1242 #[stable(feature = "rust1", since = "1.0.0")]
1243 impl fmt::Debug for OsStr {
1244     fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
1245         fmt::Debug::fmt(&self.inner, formatter)
1246     }
1247 }
1248
1249 impl OsStr {
1250     pub(crate) fn display(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
1251         fmt::Display::fmt(&self.inner, formatter)
1252     }
1253 }
1254
1255 #[unstable(feature = "slice_concat_ext", issue = "27747")]
1256 impl<S: Borrow<OsStr>> alloc::slice::Join<&OsStr> for [S] {
1257     type Output = OsString;
1258
1259     fn join(slice: &Self, sep: &OsStr) -> OsString {
1260         let Some((first, suffix)) = slice.split_first() else {
1261             return OsString::new();
1262         };
1263         let first_owned = first.borrow().to_owned();
1264         suffix.iter().fold(first_owned, |mut a, b| {
1265             a.push(sep);
1266             a.push(b.borrow());
1267             a
1268         })
1269     }
1270 }
1271
1272 #[stable(feature = "rust1", since = "1.0.0")]
1273 impl Borrow<OsStr> for OsString {
1274     #[inline]
1275     fn borrow(&self) -> &OsStr {
1276         &self[..]
1277     }
1278 }
1279
1280 #[stable(feature = "rust1", since = "1.0.0")]
1281 impl ToOwned for OsStr {
1282     type Owned = OsString;
1283     #[inline]
1284     fn to_owned(&self) -> OsString {
1285         self.to_os_string()
1286     }
1287     #[inline]
1288     fn clone_into(&self, target: &mut OsString) {
1289         self.inner.clone_into(&mut target.inner)
1290     }
1291 }
1292
1293 #[stable(feature = "rust1", since = "1.0.0")]
1294 impl AsRef<OsStr> for OsStr {
1295     #[inline]
1296     fn as_ref(&self) -> &OsStr {
1297         self
1298     }
1299 }
1300
1301 #[stable(feature = "rust1", since = "1.0.0")]
1302 impl AsRef<OsStr> for OsString {
1303     #[inline]
1304     fn as_ref(&self) -> &OsStr {
1305         self
1306     }
1307 }
1308
1309 #[stable(feature = "rust1", since = "1.0.0")]
1310 impl AsRef<OsStr> for str {
1311     #[inline]
1312     fn as_ref(&self) -> &OsStr {
1313         OsStr::from_inner(Slice::from_str(self))
1314     }
1315 }
1316
1317 #[stable(feature = "rust1", since = "1.0.0")]
1318 impl AsRef<OsStr> for String {
1319     #[inline]
1320     fn as_ref(&self) -> &OsStr {
1321         (&**self).as_ref()
1322     }
1323 }
1324
1325 impl FromInner<Buf> for OsString {
1326     #[inline]
1327     fn from_inner(buf: Buf) -> OsString {
1328         OsString { inner: buf }
1329     }
1330 }
1331
1332 impl IntoInner<Buf> for OsString {
1333     #[inline]
1334     fn into_inner(self) -> Buf {
1335         self.inner
1336     }
1337 }
1338
1339 impl AsInner<Slice> for OsStr {
1340     #[inline]
1341     fn as_inner(&self) -> &Slice {
1342         &self.inner
1343     }
1344 }
1345
1346 #[stable(feature = "osstring_from_str", since = "1.45.0")]
1347 impl FromStr for OsString {
1348     type Err = core::convert::Infallible;
1349
1350     #[inline]
1351     fn from_str(s: &str) -> Result<Self, Self::Err> {
1352         Ok(OsString::from(s))
1353     }
1354 }
1355
1356 #[stable(feature = "osstring_extend", since = "1.52.0")]
1357 impl Extend<OsString> for OsString {
1358     #[inline]
1359     fn extend<T: IntoIterator<Item = OsString>>(&mut self, iter: T) {
1360         for s in iter {
1361             self.push(&s);
1362         }
1363     }
1364 }
1365
1366 #[stable(feature = "osstring_extend", since = "1.52.0")]
1367 impl<'a> Extend<&'a OsStr> for OsString {
1368     #[inline]
1369     fn extend<T: IntoIterator<Item = &'a OsStr>>(&mut self, iter: T) {
1370         for s in iter {
1371             self.push(s);
1372         }
1373     }
1374 }
1375
1376 #[stable(feature = "osstring_extend", since = "1.52.0")]
1377 impl<'a> Extend<Cow<'a, OsStr>> for OsString {
1378     #[inline]
1379     fn extend<T: IntoIterator<Item = Cow<'a, OsStr>>>(&mut self, iter: T) {
1380         for s in iter {
1381             self.push(&s);
1382         }
1383     }
1384 }
1385
1386 #[stable(feature = "osstring_extend", since = "1.52.0")]
1387 impl FromIterator<OsString> for OsString {
1388     #[inline]
1389     fn from_iter<I: IntoIterator<Item = OsString>>(iter: I) -> Self {
1390         let mut iterator = iter.into_iter();
1391
1392         // Because we're iterating over `OsString`s, we can avoid at least
1393         // one allocation by getting the first string from the iterator
1394         // and appending to it all the subsequent strings.
1395         match iterator.next() {
1396             None => OsString::new(),
1397             Some(mut buf) => {
1398                 buf.extend(iterator);
1399                 buf
1400             }
1401         }
1402     }
1403 }
1404
1405 #[stable(feature = "osstring_extend", since = "1.52.0")]
1406 impl<'a> FromIterator<&'a OsStr> for OsString {
1407     #[inline]
1408     fn from_iter<I: IntoIterator<Item = &'a OsStr>>(iter: I) -> Self {
1409         let mut buf = Self::new();
1410         for s in iter {
1411             buf.push(s);
1412         }
1413         buf
1414     }
1415 }
1416
1417 #[stable(feature = "osstring_extend", since = "1.52.0")]
1418 impl<'a> FromIterator<Cow<'a, OsStr>> for OsString {
1419     #[inline]
1420     fn from_iter<I: IntoIterator<Item = Cow<'a, OsStr>>>(iter: I) -> Self {
1421         let mut iterator = iter.into_iter();
1422
1423         // Because we're iterating over `OsString`s, we can avoid at least
1424         // one allocation by getting the first owned string from the iterator
1425         // and appending to it all the subsequent strings.
1426         match iterator.next() {
1427             None => OsString::new(),
1428             Some(Cow::Owned(mut buf)) => {
1429                 buf.extend(iterator);
1430                 buf
1431             }
1432             Some(Cow::Borrowed(buf)) => {
1433                 let mut buf = OsString::from(buf);
1434                 buf.extend(iterator);
1435                 buf
1436             }
1437         }
1438     }
1439 }