Adding upstream version 110.0.1.upstream/110.0.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

2 files changed, 3117 insertions, 0 deletions

diff --git a/third_party/rust/unix_path/src/lib.rs b/third_party/rust/unix_path/src/lib.rs
new file mode 100644
index 0000000000..258a9fea2c
--- /dev/null
+++ b/third_party/rust/unix_path/src/lib.rs
@@ -0,0 +1,2929 @@
+//! Unix path manipulation.
+//!
+//! This crate provides two types, [`PathBuf`] and [`Path`] (akin to `String`
+//! and `str`), for working with paths abstractly. These types are thin wrappers
+//! around `UnixString` and `UnixStr` respectively, meaning that they work
+//! directly on strings independently from the local platform's path syntax.
+//!
+//! Paths can be parsed into [`Component`]s by iterating over the structure
+//! returned by the [`components`] method on [`Path`]. [`Component`]s roughly
+//! correspond to the substrings between path separators (`/`). You can
+//! reconstruct an equivalent path from components with the [`push`] method on
+//! [`PathBuf`]; note that the paths may differ syntactically by the
+//! normalization described in the documentation for the [`components`] method.
+//!
+//! ## Simple usage
+//!
+//! Path manipulation includes both parsing components from slices and building
+//! new owned paths.
+//!
+//! To parse a path, you can create a [`Path`] slice from a `str`
+//! slice and start asking questions:
+//!
+//! ```
+//! use unix_path::Path;
+//! use unix_str::UnixStr;
+//!
+//! let path = Path::new("/tmp/foo/bar.txt");
+//!
+//! let parent = path.parent();
+//! assert_eq!(parent, Some(Path::new("/tmp/foo")));
+//!
+//! let file_stem = path.file_stem();
+//! assert_eq!(file_stem, Some(UnixStr::new("bar")));
+//!
+//! let extension = path.extension();
+//! assert_eq!(extension, Some(UnixStr::new("txt")));
+//! ```
+//!
+//! To build or modify paths, use [`PathBuf`]:
+//!
+//! ```
+//! use unix_path::PathBuf;
+//!
+//! // This way works...
+//! let mut path = PathBuf::from("/");
+//!
+//! path.push("feel");
+//! path.push("the");
+//!
+//! path.set_extension("force");
+//!
+//! // ... but push is best used if you don't know everything up
+//! // front. If you do, this way is better:
+//! let path: PathBuf = ["/", "feel", "the.force"].iter().collect();
+//! ```
+//!
+//! [`Component`]: enum.Component.html
+//! [`components`]:struct.Path.html#method.components
+//! [`PathBuf`]: struct.PathBuf.html
+//! [`Path`]: struct.Path.html
+//! [`push`]: struct.PathBuf.html#method.push
+
+#![cfg_attr(not(feature = "std"), no_std)]
+#![cfg_attr(feature = "shrink_to", feature(shrink_to))]
+
+#[cfg(feature = "alloc")]
+extern crate alloc;
+
+use unix_str::UnixStr;
+#[cfg(feature = "alloc")]
+use unix_str::UnixString;
+
+#[cfg(feature = "alloc")]
+use core::borrow::Borrow;
+use core::cmp;
+use core::fmt;
+use core::hash::{Hash, Hasher};
+#[cfg(feature = "alloc")]
+use core::iter;
+use core::iter::FusedIterator;
+#[cfg(feature = "alloc")]
+use core::ops::{self, Deref};
+
+#[cfg(feature = "alloc")]
+use alloc::{
+    borrow::{Cow, ToOwned},
+    boxed::Box,
+    rc::Rc,
+    str::FromStr,
+    string::String,
+    sync::Arc,
+    vec::Vec,
+};
+
+#[cfg(feature = "std")]
+use std::error::Error;
+
+mod lossy;
+
+////////////////////////////////////////////////////////////////////////////////
+// Exposed parsing helpers
+////////////////////////////////////////////////////////////////////////////////
+
+/// Determines whether the character is the permitted path separator for Unix,
+/// `/`.
+///
+/// # Examples
+///
+/// ```
+/// assert!(unix_path::is_separator('/'));
+/// assert!(!unix_path::is_separator('❤'));
+/// ```
+pub fn is_separator(c: char) -> bool {
+    c == '/'
+}
+
+/// The separator of path components for Unix, `/`.
+pub const MAIN_SEPARATOR: char = '/';
+
+////////////////////////////////////////////////////////////////////////////////
+// Misc helpers
+////////////////////////////////////////////////////////////////////////////////
+
+// Iterate through `iter` while it matches `prefix`; return `None` if `prefix`
+// is not a prefix of `iter`, otherwise return `Some(iter_after_prefix)` giving
+// `iter` after having exhausted `prefix`.
+fn iter_after<'a, 'b, I, J>(mut iter: I, mut prefix: J) -> Option<I>
+where
+    I: Iterator<Item = Component<'a>> + Clone,
+    J: Iterator<Item = Component<'b>>,
+{
+    loop {
+        let mut iter_next = iter.clone();
+        match (iter_next.next(), prefix.next()) {
+            (Some(ref x), Some(ref y)) if x == y => (),
+            (Some(_), Some(_)) => return None,
+            (Some(_), None) => return Some(iter),
+            (None, None) => return Some(iter),
+            (None, Some(_)) => return None,
+        }
+        iter = iter_next;
+    }
+}
+
+fn unix_str_as_u8_slice(s: &UnixStr) -> &[u8] {
+    unsafe { &*(s as *const UnixStr as *const [u8]) }
+}
+unsafe fn u8_slice_as_unix_str(s: &[u8]) -> &UnixStr {
+    &*(s as *const [u8] as *const UnixStr)
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// Cross-platform, iterator-independent parsing
+////////////////////////////////////////////////////////////////////////////////
+
+/// Says whether the first byte after the prefix is a separator.
+fn has_physical_root(path: &[u8]) -> bool {
+    !path.is_empty() && path[0] == b'/'
+}
+
+// basic workhorse for splitting stem and extension
+fn split_file_at_dot(file: &UnixStr) -> (Option<&UnixStr>, Option<&UnixStr>) {
+    unsafe {
+        if unix_str_as_u8_slice(file) == b".." {
+            return (Some(file), None);
+        }
+
+        // The unsafety here stems from converting between &OsStr and &[u8]
+        // and back. This is safe to do because (1) we only look at ASCII
+        // contents of the encoding and (2) new &OsStr values are produced
+        // only from ASCII-bounded slices of existing &OsStr values.
+
+        let mut iter = unix_str_as_u8_slice(file).rsplitn(2, |b| *b == b'.');
+        let after = iter.next();
+        let before = iter.next();
+        if before == Some(b"") {
+            (Some(file), None)
+        } else {
+            (
+                before.map(|s| u8_slice_as_unix_str(s)),
+                after.map(|s| u8_slice_as_unix_str(s)),
+            )
+        }
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// The core iterators
+////////////////////////////////////////////////////////////////////////////////
+
+/// Component parsing works by a double-ended state machine; the cursors at the
+/// front and back of the path each keep track of what parts of the path have
+/// been consumed so far.
+///
+/// Going front to back, a path is made up of a prefix, a starting
+/// directory component, and a body (of normal components)
+#[derive(Copy, Clone, PartialEq, PartialOrd, Debug)]
+enum State {
+    Prefix = 0,
+    StartDir = 1, // / or . or nothing
+    Body = 2,     // foo/bar/baz
+    Done = 3,
+}
+
+/// A single component of a path.
+///
+/// A `Component` roughly corresponds to a substring between path separators
+/// (`/`).
+///
+/// This `enum` is created by iterating over [`Components`], which in turn is
+/// created by the [`components`][`Path::components`] method on [`Path`].
+///
+/// # Examples
+///
+/// ```rust
+/// use unix_path::{Component, Path};
+///
+/// let path = Path::new("/tmp/foo/bar.txt");
+/// let components = path.components().collect::<Vec<_>>();
+/// assert_eq!(&components, &[
+///     Component::RootDir,
+///     Component::Normal("tmp".as_ref()),
+///     Component::Normal("foo".as_ref()),
+///     Component::Normal("bar.txt".as_ref()),
+/// ]);
+/// ```
+///
+/// [`Components`]: struct.Components.html
+/// [`Path`]: struct.Path.html
+/// [`Path::components`]: struct.Path.html#method.components
+#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub enum Component<'a> {
+    /// The root directory component, appears after any prefix and before anything else.
+    ///
+    /// It represents a separator that designates that a path starts from root.
+    RootDir,
+
+    /// A reference to the current directory, i.e., `.`.
+    CurDir,
+
+    /// A reference to the parent directory, i.e., `..`.
+    ParentDir,
+
+    /// A normal component, e.g., `a` and `b` in `a/b`.
+    ///
+    /// This variant is the most common one, it represents references to files
+    /// or directories.
+    Normal(&'a UnixStr),
+}
+
+impl<'a> Component<'a> {
+    /// Extracts the underlying `UnixStr` slice.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use unix_path::Path;
+    ///
+    /// let path = Path::new("./tmp/foo/bar.txt");
+    /// let components: Vec<_> = path.components().map(|comp| comp.as_unix_str()).collect();
+    /// assert_eq!(&components, &[".", "tmp", "foo", "bar.txt"]);
+    /// ```
+    pub fn as_unix_str(self) -> &'a UnixStr {
+        match self {
+            Component::RootDir => UnixStr::new("/"),
+            Component::CurDir => UnixStr::new("."),
+            Component::ParentDir => UnixStr::new(".."),
+            Component::Normal(path) => path,
+        }
+    }
+}
+
+impl AsRef<UnixStr> for Component<'_> {
+    fn as_ref(&self) -> &UnixStr {
+        self.as_unix_str()
+    }
+}
+
+impl AsRef<Path> for Component<'_> {
+    fn as_ref(&self) -> &Path {
+        self.as_unix_str().as_ref()
+    }
+}
+
+/// An iterator over the [`Component`]s of a [`Path`].
+///
+/// This `struct` is created by the [`components`] method on [`Path`].
+/// See its documentation for more.
+///
+/// # Examples
+///
+/// ```
+/// use unix_path::Path;
+///
+/// let path = Path::new("/tmp/foo/bar.txt");
+///
+/// for component in path.components() {
+///     println!("{:?}", component);
+/// }
+/// ```
+///
+/// [`Component`]: enum.Component.html
+/// [`components`]: struct.Path.html#method.components
+/// [`Path`]: struct.Path.html
+#[derive(Clone)]
+pub struct Components<'a> {
+    // The path left to parse components from
+    path: &'a [u8],
+
+    // true if path *physically* has a root separator;.
+    has_physical_root: bool,
+
+    // The iterator is double-ended, and these two states keep track of what has
+    // been produced from either end
+    front: State,
+    back: State,
+}
+
+/// An iterator over the [`Component`]s of a [`Path`], as `UnixStr` slices.
+///
+/// This `struct` is created by the [`iter`] method on [`Path`].
+/// See its documentation for more.
+///
+/// [`Component`]: enum.Component.html
+/// [`iter`]: struct.Path.html#method.iter
+/// [`Path`]: struct.Path.html
+#[derive(Clone)]
+pub struct Iter<'a> {
+    inner: Components<'a>,
+}
+
+impl fmt::Debug for Components<'_> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        struct DebugHelper<'a>(&'a Path);
+
+        impl fmt::Debug for DebugHelper<'_> {
+            fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+                f.debug_list().entries(self.0.components()).finish()
+            }
+        }
+
+        f.debug_tuple("Components")
+            .field(&DebugHelper(self.as_path()))
+            .finish()
+    }
+}
+
+impl<'a> Components<'a> {
+    // Given the iteration so far, how much of the pre-State::Body path is left?
+    #[inline]
+    fn len_before_body(&self) -> usize {
+        let root = if self.front <= State::StartDir && self.has_physical_root {
+            1
+        } else {
+            0
+        };
+        let cur_dir = if self.front <= State::StartDir && self.include_cur_dir() {
+            1
+        } else {
+            0
+        };
+        root + cur_dir
+    }
+
+    // is the iteration complete?
+    #[inline]
+    fn finished(&self) -> bool {
+        self.front == State::Done || self.back == State::Done || self.front > self.back
+    }
+
+    #[inline]
+    fn is_sep_byte(&self, b: u8) -> bool {
+        b == b'/'
+    }
+
+    /// Extracts a slice corresponding to the portion of the path remaining for iteration.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use unix_path::Path;
+    ///
+    /// let mut components = Path::new("/tmp/foo/bar.txt").components();
+    /// components.next();
+    /// components.next();
+    ///
+    /// assert_eq!(Path::new("foo/bar.txt"), components.as_path());
+    /// ```
+    pub fn as_path(&self) -> &'a Path {
+        let mut comps = self.clone();
+        if comps.front == State::Body {
+            comps.trim_left();
+        }
+        if comps.back == State::Body {
+            comps.trim_right();
+        }
+        unsafe { Path::from_u8_slice(comps.path) }
+    }
+
+    /// Is the *original* path rooted?
+    fn has_root(&self) -> bool {
+        self.has_physical_root
+    }
+
+    /// Should the normalized path include a leading . ?
+    fn include_cur_dir(&self) -> bool {
+        if self.has_root() {
+            return false;
+        }
+        let mut iter = self.path[..].iter();
+        match (iter.next(), iter.next()) {
+            (Some(&b'.'), None) => true,
+            (Some(&b'.'), Some(&b)) => self.is_sep_byte(b),
+            _ => false,
+        }
+    }
+
+    // parse a given byte sequence into the corresponding path component
+    fn parse_single_component<'b>(&self, comp: &'b [u8]) -> Option<Component<'b>> {
+        match comp {
+            b"." => None, // . components are normalized away, except at
+            // the beginning of a path, which is treated
+            // separately via `include_cur_dir`
+            b".." => Some(Component::ParentDir),
+            b"" => None,
+            _ => Some(Component::Normal(unsafe { u8_slice_as_unix_str(comp) })),
+        }
+    }
+
+    // parse a component from the left, saying how many bytes to consume to
+    // remove the component
+    fn parse_next_component(&self) -> (usize, Option<Component<'a>>) {
+        debug_assert!(self.front == State::Body);
+        let (extra, comp) = match self.path.iter().position(|b| self.is_sep_byte(*b)) {
+            None => (0, self.path),
+            Some(i) => (1, &self.path[..i]),
+        };
+        (comp.len() + extra, self.parse_single_component(comp))
+    }
+
+    // parse a component from the right, saying how many bytes to consume to
+    // remove the component
+    fn parse_next_component_back(&self) -> (usize, Option<Component<'a>>) {
+        debug_assert!(self.back == State::Body);
+        let start = self.len_before_body();
+        let (extra, comp) = match self.path[start..]
+            .iter()
+            .rposition(|b| self.is_sep_byte(*b))
+        {
+            None => (0, &self.path[start..]),
+            Some(i) => (1, &self.path[start + i + 1..]),
+        };
+        (comp.len() + extra, self.parse_single_component(comp))
+    }
+
+    // trim away repeated separators (i.e., empty components) on the left
+    fn trim_left(&mut self) {
+        while !self.path.is_empty() {
+            let (size, comp) = self.parse_next_component();
+            if comp.is_some() {
+                return;
+            } else {
+                self.path = &self.path[size..];
+            }
+        }
+    }
+
+    // trim away repeated separators (i.e., empty components) on the right
+    fn trim_right(&mut self) {
+        while self.path.len() > self.len_before_body() {
+            let (size, comp) = self.parse_next_component_back();
+            if comp.is_some() {
+                return;
+            } else {
+                self.path = &self.path[..self.path.len() - size];
+            }
+        }
+    }
+}
+
+impl AsRef<Path> for Components<'_> {
+    fn as_ref(&self) -> &Path {
+        self.as_path()
+    }
+}
+
+impl AsRef<UnixStr> for Components<'_> {
+    fn as_ref(&self) -> &UnixStr {
+        self.as_path().as_unix_str()
+    }
+}
+
+impl fmt::Debug for Iter<'_> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        struct DebugHelper<'a>(&'a Path);
+
+        impl fmt::Debug for DebugHelper<'_> {
+            fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+                f.debug_list().entries(self.0.iter()).finish()
+            }
+        }
+
+        f.debug_tuple("Iter")
+            .field(&DebugHelper(self.as_path()))
+            .finish()
+    }
+}
+
+impl<'a> Iter<'a> {
+    /// Extracts a slice corresponding to the portion of the path remaining for iteration.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use unix_path::Path;
+    ///
+    /// let mut iter = Path::new("/tmp/foo/bar.txt").iter();
+    /// iter.next();
+    /// iter.next();
+    ///
+    /// assert_eq!(Path::new("foo/bar.txt"), iter.as_path());
+    /// ```
+    pub fn as_path(&self) -> &'a Path {
+        self.inner.as_path()
+    }
+}
+
+impl AsRef<Path> for Iter<'_> {
+    fn as_ref(&self) -> &Path {
+        self.as_path()
+    }
+}
+
+impl AsRef<UnixStr> for Iter<'_> {
+    fn as_ref(&self) -> &UnixStr {
+        self.as_path().as_unix_str()
+    }
+}
+
+impl<'a> Iterator for Iter<'a> {
+    type Item = &'a UnixStr;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        self.inner.next().map(Component::as_unix_str)
+    }
+}
+
+impl<'a> DoubleEndedIterator for Iter<'a> {
+    fn next_back(&mut self) -> Option<Self::Item> {
+        self.inner.next_back().map(Component::as_unix_str)
+    }
+}
+
+impl FusedIterator for Iter<'_> {}
+
+impl<'a> Iterator for Components<'a> {
+    type Item = Component<'a>;
+
+    fn next(&mut self) -> Option<Component<'a>> {
+        while !self.finished() {
+            match self.front {
+                State::Prefix => {
+                    self.front = State::StartDir;
+                }
+                State::StartDir => {
+                    self.front = State::Body;
+                    if self.has_physical_root {
+                        debug_assert!(!self.path.is_empty());
+                        self.path = &self.path[1..];
+                        return Some(Component::RootDir);
+                    } else if self.include_cur_dir() {
+                        debug_assert!(!self.path.is_empty());
+                        self.path = &self.path[1..];
+                        return Some(Component::CurDir);
+                    }
+                }
+                State::Body if !self.path.is_empty() => {
+                    let (size, comp) = self.parse_next_component();
+                    self.path = &self.path[size..];
+                    if comp.is_some() {
+                        return comp;
+                    }
+                }
+                State::Body => {
+                    self.front = State::Done;
+                }
+                State::Done => unreachable!(),
+            }
+        }
+        None
+    }
+}
+
+impl<'a> DoubleEndedIterator for Components<'a> {
+    fn next_back(&mut self) -> Option<Component<'a>> {
+        while !self.finished() {
+            match self.back {
+                State::Body if self.path.len() > self.len_before_body() => {
+                    let (size, comp) = self.parse_next_component_back();
+                    self.path = &self.path[..self.path.len() - size];
+                    if comp.is_some() {
+                        return comp;
+                    }
+                }
+                State::Body => {
+                    self.back = State::StartDir;
+                }
+                State::StartDir => {
+                    self.back = State::Prefix;
+                    if self.has_physical_root {
+                        self.path = &self.path[..self.path.len() - 1];
+                        return Some(Component::RootDir);
+                    } else if self.include_cur_dir() {
+                        self.path = &self.path[..self.path.len() - 1];
+                        return Some(Component::CurDir);
+                    }
+                }
+                State::Prefix => {
+                    self.back = State::Done;
+                    return None;
+                }
+                State::Done => unreachable!(),
+            }
+        }
+        None
+    }
+}
+
+impl FusedIterator for Components<'_> {}
+
+impl<'a> cmp::PartialEq for Components<'a> {
+    fn eq(&self, other: &Components<'a>) -> bool {
+        Iterator::eq(self.clone(), other.clone())
+    }
+}
+
+impl cmp::Eq for Components<'_> {}
+
+impl<'a> cmp::PartialOrd for Components<'a> {
+    fn partial_cmp(&self, other: &Components<'a>) -> Option<cmp::Ordering> {
+        Iterator::partial_cmp(self.clone(), other.clone())
+    }
+}
+
+impl cmp::Ord for Components<'_> {
+    fn cmp(&self, other: &Self) -> cmp::Ordering {
+        Iterator::cmp(self.clone(), other.clone())
+    }
+}
+
+/// An iterator over [`Path`] and its ancestors.
+///
+/// This `struct` is created by the [`ancestors`] method on [`Path`].
+/// See its documentation for more.
+///
+/// # Examples
+///
+/// ```
+/// use unix_path::Path;
+///
+/// let path = Path::new("/foo/bar");
+///
+/// for ancestor in path.ancestors() {
+///     println!("{:?}", ancestor);
+/// }
+/// ```
+///
+/// [`ancestors`]: struct.Path.html#method.ancestors
+/// [`Path`]: struct.Path.html
+#[derive(Copy, Clone, Debug)]
+pub struct Ancestors<'a> {
+    next: Option<&'a Path>,
+}
+
+impl<'a> Iterator for Ancestors<'a> {
+    type Item = &'a Path;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let next = self.next;
+        self.next = next.and_then(Path::parent);
+        next
+    }
+}
+
+impl FusedIterator for Ancestors<'_> {}
+
+////////////////////////////////////////////////////////////////////////////////
+// Basic types and traits
+////////////////////////////////////////////////////////////////////////////////
+
+/// An owned, mutable path (akin to `String`).
+///
+/// This type provides methods like [`push`] and [`set_extension`] that mutate
+/// the path in place. It also implements `Deref` to [`Path`], meaning that
+/// all methods on [`Path`] slices are available on `PathBuf` values as well.
+///
+/// [`Path`]: struct.Path.html
+/// [`push`]: struct.PathBuf.html#method.push
+/// [`set_extension`]: struct.PathBuf.html#method.set_extension
+///
+/// More details about the overall approach can be found in
+/// the [crate documentation](index.html).
+///
+/// # Examples
+///
+/// You can use [`push`] to build up a `PathBuf` from
+/// components:
+///
+/// ```
+/// use unix_path::PathBuf;
+///
+/// let mut path = PathBuf::new();
+///
+/// path.push("/");
+/// path.push("feel");
+/// path.push("the");
+///
+/// path.set_extension("force");
+/// ```
+///
+/// However, [`push`] is best used for dynamic situations. This is a better way
+/// to do this when you know all of the components ahead of time:
+///
+/// ```
+/// use unix_path::PathBuf;
+///
+/// let path: PathBuf = ["/", "feel", "the.force"].iter().collect();
+/// ```
+///
+/// We can still do better than this! Since these are all strings, we can use
+/// `From::from`:
+///
+/// ```
+/// use unix_path::PathBuf;
+///
+/// let path = PathBuf::from(r"/feel/the.force");
+/// ```
+///
+/// Which method works best depends on what kind of situation you're in.
+#[derive(Clone)]
+#[cfg(feature = "alloc")]
+pub struct PathBuf {
+    inner: UnixString,
+}
+
+#[cfg(feature = "alloc")]
+impl PathBuf {
+    fn as_mut_vec(&mut self) -> &mut Vec<u8> {
+        unsafe { &mut *(self as *mut PathBuf as *mut Vec<u8>) }
+    }
+
+    /// Allocates an empty `PathBuf`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use unix_path::PathBuf;
+    ///
+    /// let path = PathBuf::new();
+    /// ```
+    pub fn new() -> PathBuf {
+        PathBuf {
+            inner: UnixString::new(),
+        }
+    }
+
+    /// Creates a new `PathBuf` with a given capacity used to create the
+    /// internal `UnixString`. See `with_capacity` defined on `UnixString`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use unix_path::PathBuf;
+    ///
+    /// let mut path = PathBuf::with_capacity(10);
+    /// let capacity = path.capacity();
+    ///
+    /// // This push is done without reallocating
+    /// path.push("/");
+    ///
+    /// assert_eq!(capacity, path.capacity());
+    /// ```
+    pub fn with_capacity(capacity: usize) -> PathBuf {
+        PathBuf {
+            inner: UnixString::with_capacity(capacity),
+        }
+    }
+
+    /// Coerces to a [`Path`] slice.
+    ///
+    /// [`Path`]: struct.Path.html
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use unix_path::{Path, PathBuf};
+    ///
+    /// let p = PathBuf::from("/test");
+    /// assert_eq!(Path::new("/test"), p.as_path());
+    /// ```
+    pub fn as_path(&self) -> &Path {
+        self
+    }
+
+    /// Extends `self` with `path`.
+    ///
+    /// If `path` is absolute, it replaces the current path.
+    ///
+    /// # Examples
+    ///
+    /// Pushing a relative path extends the existing path:
+    ///
+    /// ```
+    /// use unix_path::PathBuf;
+    ///
+    /// let mut path = PathBuf::from("/tmp");
+    /// path.push("file.bk");
+    /// assert_eq!(path, PathBuf::from("/tmp/file.bk"));
+    /// ```
+    ///
+    /// Pushing an absolute path replaces the existing path:
+    ///
+    /// ```
+    /// use unix_path::PathBuf;
+    ///
+    /// let mut path = PathBuf::from("/tmp");
+    /// path.push("/etc");
+    /// assert_eq!(path, PathBuf::from("/etc"));
+    /// ```
+    pub fn push<P: AsRef<Path>>(&mut self, path: P) {
+        self._push(path.as_ref())
+    }
+
+    fn _push(&mut self, path: &Path) {
+        // in general, a separator is needed if the rightmost byte is not a separator
+        let need_sep = self
+            .as_mut_vec()
+            .last()
+            .map(|c| *c != b'/')
+            .unwrap_or(false);
+
+        // absolute `path` replaces `self`
+        if path.is_absolute() || path.has_root() {
+            self.as_mut_vec().truncate(0);
+        } else if need_sep {
+            self.inner.push("/");
+        }
+
+        self.inner.push(path.as_unix_str());
+    }
+
+    /// Truncates `self` to [`self.parent`].
+    ///
+    /// Returns `false` and does nothing if [`self.parent`] is `None`.
+    /// Otherwise, returns `true`.
+    ///
+    /// [`self.parent`]: struct.PathBuf.html#method.parent
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use unix_path::{Path, PathBuf};
+    ///
+    /// let mut p = PathBuf::from("/test/test.rs");
+    ///
+    /// p.pop();
+    /// assert_eq!(Path::new("/test"), p);
+    /// p.pop();
+    /// assert_eq!(Path::new("/"), p);
+    /// ```
+    pub fn pop(&mut self) -> bool {
+        match self.parent().map(|p| p.as_unix_str().len()) {
+            Some(len) => {
+                self.as_mut_vec().truncate(len);
+                true
+            }
+            None => false,
+        }
+    }
+
+    /// Updates [`self.file_name`] to `file_name`.
+    ///
+    /// If [`self.file_name`] was `None`, this is equivalent to pushing
+    /// `file_name`.
+    ///
+    /// Otherwise it is equivalent to calling [`pop`] and then pushing
+    /// `file_name`. The new path will be a sibling of the original path.
+    /// (That is, it will have the same parent.)
+    ///
+    /// [`self.file_name`]: struct.PathBuf.html#method.file_name
+    /// [`pop`]: struct.PathBuf.html#method.pop
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use unix_path::PathBuf;
+    ///
+    /// let mut buf = PathBuf::from("/");
+    /// assert!(buf.file_name() == None);
+    /// buf.set_file_name("bar");
+    /// assert!(buf == PathBuf::from("/bar"));
+    /// assert!(buf.file_name().is_some());
+    /// buf.set_file_name("baz.txt");
+    /// assert!(buf == PathBuf::from("/baz.txt"));
+    /// ```
+    pub fn set_file_name<S: AsRef<UnixStr>>(&mut self, file_name: S) {
+        self._set_file_name(file_name.as_ref())
+    }
+
+    fn _set_file_name(&mut self, file_name: &UnixStr) {
+        if self.file_name().is_some() {
+            let popped = self.pop();
+            debug_assert!(popped);
+        }
+        self.push(file_name);
+    }
+
+    /// Updates [`self.extension`] to `extension`.
+    ///
+    /// Returns `false` and does nothing if [`self.file_name`] is `None`,
+    /// returns `true` and updates the extension otherwise.
+    ///
+    /// If [`self.extension`] is `None`, the extension is added; otherwise
+    /// it is replaced.
+    ///
+    /// [`self.file_name`]: struct.PathBuf.html#method.file_name
+    /// [`self.extension`]: struct.PathBuf.html#method.extension
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use unix_path::{Path, PathBuf};
+    ///
+    /// let mut p = PathBuf::from("/feel/the");
+    ///
+    /// p.set_extension("force");
+    /// assert_eq!(Path::new("/feel/the.force"), p.as_path());
+    ///
+    /// p.set_extension("dark_side");
+    /// assert_eq!(Path::new("/feel/the.dark_side"), p.as_path());
+    /// ```
+
+    pub fn set_extension<S: AsRef<UnixStr>>(&mut self, extension: S) -> bool {
+        self._set_extension(extension.as_ref())
+    }
+
+    fn _set_extension(&mut self, extension: &UnixStr) -> bool {
+        let file_stem = match self.file_stem() {
+            None => return false,
+            Some(f) => unix_str_as_u8_slice(f),
+        };
+
+        // truncate until right after the file stem
+        let end_file_stem = file_stem[file_stem.len()..].as_ptr() as usize;
+        let start = unix_str_as_u8_slice(&self.inner).as_ptr() as usize;
+        let v = self.as_mut_vec();
+        v.truncate(end_file_stem.wrapping_sub(start));
+
+        // add the new extension, if any
+        let new = unix_str_as_u8_slice(extension);
+        if !new.is_empty() {
+            v.reserve_exact(new.len() + 1);
+            v.push(b'.');
+            v.extend_from_slice(new);
+        }
+
+        true
+    }
+
+    /// Consumes the `PathBuf`, yielding its internal `UnixString` storage.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use unix_path::PathBuf;
+    ///
+    /// let p = PathBuf::from("/the/head");
+    /// let bytes = p.into_unix_string();
+    /// ```
+    pub fn into_unix_string(self) -> UnixString {
+        self.inner
+    }
+
+    /// Converts this `PathBuf` into a boxed [`Path`].
+    ///
+    /// [`Path`]: struct.Path.html
+    pub fn into_boxed_path(self) -> Box<Path> {
+        let rw = Box::into_raw(self.inner.into_boxed_unix_str()) as *mut Path;
+        unsafe { Box::from_raw(rw) }
+    }
+
+    /// Invokes `capacity` on the underlying instance of `UnixString`.
+    pub fn capacity(&self) -> usize {
+        self.inner.capacity()
+    }
+
+    /// Invokes `clear` on the underlying instance of `UnixString`.
+    pub fn clear(&mut self) {
+        self.inner.clear()
+    }
+
+    /// Invokes `reserve` on the underlying instance of `UnixString`.
+    pub fn reserve(&mut self, additional: usize) {
+        self.inner.reserve(additional)
+    }
+
+    /// Invokes `reserve_exact` on the underlying instance of `UnixString`.
+    pub fn reserve_exact(&mut self, additional: usize) {
+        self.inner.reserve_exact(additional)
+    }
+
+    /// Invokes `shrink_to_fit` on the underlying instance of `UnixString`.
+    pub fn shrink_to_fit(&mut self) {
+        self.inner.shrink_to_fit()
+    }
+
+    /// Invokes `shrink_to` on the underlying instance of `UnixString`.
+    #[cfg(feature = "shrink_to")]
+    pub fn shrink_to(&mut self, min_capacity: usize) {
+        self.inner.shrink_to(min_capacity)
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl From<&Path> for Box<Path> {
+    fn from(path: &Path) -> Box<Path> {
+        let boxed: Box<UnixStr> = path.inner.into();
+        let rw = Box::into_raw(boxed) as *mut Path;
+        unsafe { Box::from_raw(rw) }
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl From<Cow<'_, Path>> for Box<Path> {
+    #[inline]
+    fn from(cow: Cow<'_, Path>) -> Box<Path> {
+        match cow {
+            Cow::Borrowed(path) => Box::from(path),
+            Cow::Owned(path) => Box::from(path),
+        }
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl From<Box<Path>> for PathBuf {
+    /// Converts a `Box<Path>` into a `PathBuf`
+    ///
+    /// This conversion does not allocate or copy memory.
+    fn from(boxed: Box<Path>) -> PathBuf {
+        boxed.into_path_buf()
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl From<PathBuf> for Box<Path> {
+    /// Converts a `PathBuf` into a `Box<Path>`
+    ///
+    /// This conversion currently should not allocate memory,
+    /// but this behavior is not guaranteed in all future versions.
+    fn from(p: PathBuf) -> Self {
+        p.into_boxed_path()
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl Clone for Box<Path> {
+    #[inline]
+    fn clone(&self) -> Self {
+        self.to_path_buf().into_boxed_path()
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl<T: ?Sized + AsRef<UnixStr>> From<&T> for PathBuf {
+    fn from(s: &T) -> Self {
+        PathBuf::from(s.as_ref().to_unix_string())
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl From<UnixString> for PathBuf {
+    /// Converts a `UnixString` into a `PathBuf`
+    ///
+    /// This conversion does not allocate or copy memory.
+    #[inline]
+    fn from(s: UnixString) -> Self {
+        PathBuf { inner: s }
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl From<PathBuf> for UnixString {
+    /// Converts a `PathBuf` into a `UnixString`
+    ///
+    /// This conversion does not allocate or copy memory.
+    fn from(path_buf: PathBuf) -> Self {
+        path_buf.inner
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl From<String> for PathBuf {
+    /// Converts a `String` into a `PathBuf`
+    ///
+    /// This conversion does not allocate or copy memory.
+    fn from(s: String) -> PathBuf {
+        PathBuf::from(UnixString::from(s))
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl FromStr for PathBuf {
+    type Err = core::convert::Infallible;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        Ok(PathBuf::from(s))
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl<P: AsRef<Path>> iter::FromIterator<P> for PathBuf {
+    fn from_iter<I: IntoIterator<Item = P>>(iter: I) -> PathBuf {
+        let mut buf = PathBuf::new();
+        buf.extend(iter);
+        buf
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl<P: AsRef<Path>> iter::Extend<P> for PathBuf {
+    fn extend<I: IntoIterator<Item = P>>(&mut self, iter: I) {
+        iter.into_iter().for_each(move |p| self.push(p.as_ref()));
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl fmt::Debug for PathBuf {
+    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Debug::fmt(&**self, formatter)
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl ops::Deref for PathBuf {
+    type Target = Path;
+    #[inline]
+    fn deref(&self) -> &Path {
+        Path::new(&self.inner)
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl Borrow<Path> for PathBuf {
+    fn borrow(&self) -> &Path {
+        self.deref()
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl Default for PathBuf {
+    fn default() -> Self {
+        PathBuf::new()
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl<'a> From<&'a Path> for Cow<'a, Path> {
+    #[inline]
+    fn from(s: &'a Path) -> Cow<'a, Path> {
+        Cow::Borrowed(s)
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl<'a> From<PathBuf> for Cow<'a, Path> {
+    #[inline]
+    fn from(s: PathBuf) -> Cow<'a, Path> {
+        Cow::Owned(s)
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl<'a> From<&'a PathBuf> for Cow<'a, Path> {
+    #[inline]
+    fn from(p: &'a PathBuf) -> Cow<'a, Path> {
+        Cow::Borrowed(p.as_path())
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl<'a> From<Cow<'a, Path>> for PathBuf {
+    #[inline]
+    fn from(p: Cow<'a, Path>) -> Self {
+        p.into_owned()
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl From<PathBuf> for Arc<Path> {
+    /// Converts a `PathBuf` into an `Arc` by moving the `PathBuf` data into a new `Arc` buffer.
+    #[inline]
+    fn from(s: PathBuf) -> Arc<Path> {
+        let arc: Arc<UnixStr> = Arc::from(s.into_unix_string());
+        unsafe { Arc::from_raw(Arc::into_raw(arc) as *const Path) }
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl From<&Path> for Arc<Path> {
+    /// Converts a `Path` into an `Arc` by copying the `Path` data into a new `Arc` buffer.
+    #[inline]
+    fn from(s: &Path) -> Arc<Path> {
+        let arc: Arc<UnixStr> = Arc::from(s.as_unix_str());
+        unsafe { Arc::from_raw(Arc::into_raw(arc) as *const Path) }
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl From<PathBuf> for Rc<Path> {
+    /// Converts a `PathBuf` into an `Rc` by moving the `PathBuf` data into a new `Rc` buffer.
+    #[inline]
+    fn from(s: PathBuf) -> Rc<Path> {
+        let rc: Rc<UnixStr> = Rc::from(s.into_unix_string());
+        unsafe { Rc::from_raw(Rc::into_raw(rc) as *const Path) }
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl From<&Path> for Rc<Path> {
+    /// Converts a `Path` into an `Rc` by copying the `Path` data into a new `Rc` buffer.
+    #[inline]
+    fn from(s: &Path) -> Rc<Path> {
+        let rc: Rc<UnixStr> = Rc::from(s.as_unix_str());
+        unsafe { Rc::from_raw(Rc::into_raw(rc) as *const Path) }
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl ToOwned for Path {
+    type Owned = PathBuf;
+    fn to_owned(&self) -> PathBuf {
+        self.to_path_buf()
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl cmp::PartialEq for PathBuf {
+    fn eq(&self, other: &PathBuf) -> bool {
+        self.components() == other.components()
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl Hash for PathBuf {
+    fn hash<H: Hasher>(&self, h: &mut H) {
+        self.as_path().hash(h)
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl cmp::Eq for PathBuf {}
+
+#[cfg(feature = "alloc")]
+impl cmp::PartialOrd for PathBuf {
+    fn partial_cmp(&self, other: &PathBuf) -> Option<cmp::Ordering> {
+        self.components().partial_cmp(other.components())
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl cmp::Ord for PathBuf {
+    fn cmp(&self, other: &PathBuf) -> cmp::Ordering {
+        self.components().cmp(other.components())
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl AsRef<UnixStr> for PathBuf {
+    fn as_ref(&self) -> &UnixStr {
+        &self.inner[..]
+    }
+}
+
+/// A slice of a path (akin to `str`).
+///
+/// This type supports a number of operations for inspecting a path, including
+/// breaking the path into its components (separated by `/` ), extracting the
+/// file name, determining whether the path is absolute, and so on.
+///
+/// This is an *unsized* type, meaning that it must always be used behind a
+/// pointer like `&` or `Box`. For an owned version of this type,
+/// see [`PathBuf`].
+///
+/// [`PathBuf`]: struct.PathBuf.html
+///
+/// More details about the overall approach can be found in
+/// the [crate documentation](index.html).
+///
+/// # Examples
+///
+/// ```
+/// use unix_path::Path;
+/// use unix_str::UnixStr;
+///
+/// let path = Path::new("./foo/bar.txt");
+///
+/// let parent = path.parent();
+/// assert_eq!(parent, Some(Path::new("./foo")));
+///
+/// let file_stem = path.file_stem();
+/// assert_eq!(file_stem, Some(UnixStr::new("bar")));
+///
+/// let extension = path.extension();
+/// assert_eq!(extension, Some(UnixStr::new("txt")));
+/// ```
+pub struct Path {
+    inner: UnixStr,
+}
+
+/// An error returned from [`Path::strip_prefix`][`strip_prefix`] if the prefix
+/// was not found.
+///
+/// This `struct` is created by the [`strip_prefix`] method on [`Path`].
+/// See its documentation for more.
+///
+/// [`strip_prefix`]: struct.Path.html#method.strip_prefix
+/// [`Path`]: struct.Path.html
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct StripPrefixError(());
+
+impl Path {
+    // The following (private!) function allows construction of a path from a u8
+    // slice, which is only safe when it is known to follow the OsStr encoding.
+    unsafe fn from_u8_slice(s: &[u8]) -> &Path {
+        Path::new(u8_slice_as_unix_str(s))
+    }
+    // The following (private!) function reveals the byte encoding used for OsStr.
+    fn as_u8_slice(&self) -> &[u8] {
+        unix_str_as_u8_slice(&self.inner)
+    }
+
+    /// Directly wraps a string slice as a `Path` slice.
+    ///
+    /// This is a cost-free conversion.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use unix_path::Path;
+    ///
+    /// Path::new("foo.txt");
+    /// ```
+    ///
+    /// You can create `Path`s from `String`s, or even other `Path`s:
+    ///
+    /// ```
+    /// use unix_path::Path;
+    ///
+    /// let string = String::from("foo.txt");
+    /// let from_string = Path::new(&string);
+    /// let from_path = Path::new(&from_string);
+    /// assert_eq!(from_string, from_path);
+    /// ```
+    pub fn new<S: AsRef<UnixStr> + ?Sized>(s: &S) -> &Path {
+        unsafe { &*(s.as_ref() as *const UnixStr as *const Path) }
+    }
+
+    /// Yields the underlying bytes.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use unix_path::Path;
+    /// use unix_str::UnixStr;
+    ///
+    /// let os_str = Path::new("foo.txt").as_unix_str();
+    /// assert_eq!(os_str, UnixStr::new("foo.txt"));
+    /// ```
+    pub fn as_unix_str(&self) -> &UnixStr {
+        &self.inner
+    }
+
+    /// Yields a `&str` slice if the `Path` is valid unicode.
+    ///
+    /// This conversion may entail doing a check for UTF-8 validity.
+    /// Note that validation is performed because non-UTF-8 strings are
+    /// perfectly valid for some OS.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use unix_path::Path;
+    ///
+    /// let path = Path::new("foo.txt");
+    /// assert_eq!(path.to_str(), Some("foo.txt"));
+    /// ```
+    pub fn to_str(&self) -> Option<&str> {
+        self.inner.to_str()
+    }
+
+    /// Converts a `Path` to a `Cow<str>`.
+    ///
+    /// Any non-Unicode sequences are replaced with
+    /// `U+FFFD REPLACEMENT CHARACTER`.
+    ///
+    ///
+    /// # Examples
+    ///
+    /// Calling `to_string_lossy` on a `Path` with valid unicode:
+    ///
+    /// ```
+    /// use unix_path::Path;
+    ///
+    /// let path = Path::new("foo.txt");
+    /// assert_eq!(path.to_string_lossy(), "foo.txt");
+    /// ```
+    ///
+    /// Had `path` contained invalid unicode, the `to_string_lossy` call might
+    /// have returned `"fo�.txt"`.
+    #[cfg(feature = "alloc")]
+    pub fn to_string_lossy(&self) -> Cow<'_, str> {
+        self.inner.to_string_lossy()
+    }
+
+    /// Converts a `Path` to an owned [`PathBuf`].
+    ///
+    /// [`PathBuf`]: struct.PathBuf.html
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use unix_path::Path;
+    ///
+    /// let path_buf = Path::new("foo.txt").to_path_buf();
+    /// assert_eq!(path_buf, unix_path::PathBuf::from("foo.txt"));
+    /// ```
+    #[cfg(feature = "alloc")]
+    pub fn to_path_buf(&self) -> PathBuf {
+        PathBuf::from(&self.inner)
+    }
+
+    /// Returns `true` if the `Path` is absolute, i.e., if it is independent of
+    /// the current directory.
+    ///
+    /// A path is absolute if it starts with the root, so `is_absolute` and
+    /// [`has_root`] are equivalent.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use unix_path::Path;
+    ///
+    /// assert!(!Path::new("foo.txt").is_absolute());
+    /// ```
+    ///
+    /// [`has_root`]: #method.has_root
+    pub fn is_absolute(&self) -> bool {
+        self.has_root()
+    }
+
+    /// Returns `true` if the `Path` is relative, i.e., not absolute.
+    ///
+    /// See [`is_absolute`]'s documentation for more details.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use unix_path::Path;
+    ///
+    /// assert!(Path::new("foo.txt").is_relative());
+    /// ```
+    ///
+    /// [`is_absolute`]: #method.is_absolute
+    pub fn is_relative(&self) -> bool {
+        !self.is_absolute()
+    }
+
+    /// Returns `true` if the `Path` has a root.
+    ///
+    /// A path has a root if it begins with `/`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use unix_path::Path;
+    ///
+    /// assert!(Path::new("/etc/passwd").has_root());
+    /// ```
+    pub fn has_root(&self) -> bool {
+        self.components().has_root()
+    }
+
+    /// Returns the `Path` without its final component, if there is one.
+    ///
+    /// Returns `None` if the path terminates in a root or prefix.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use unix_path::Path;
+    ///
+    /// let path = Path::new("/foo/bar");
+    /// let parent = path.parent().unwrap();
+    /// assert_eq!(parent, Path::new("/foo"));
+    ///
+    /// let grand_parent = parent.parent().unwrap();
+    /// assert_eq!(grand_parent, Path::new("/"));
+    /// assert_eq!(grand_parent.parent(), None);
+    /// ```
+    pub fn parent(&self) -> Option<&Path> {
+        let mut comps = self.components();
+        let comp = comps.next_back();
+        comp.and_then(|p| match p {
+            Component::Normal(_) | Component::CurDir | Component::ParentDir => {
+                Some(comps.as_path())
+            }
+            _ => None,
+        })
+    }
+
+    /// Produces an iterator over `Path` and its ancestors.
+    ///
+    /// The iterator will yield the `Path` that is returned if the [`parent`] method is used zero
+    /// or more times. That means, the iterator will yield `&self`, `&self.parent().unwrap()`,
+    /// `&self.parent().unwrap().parent().unwrap()` and so on. If the [`parent`] method returns
+    /// `None`, the iterator will do likewise. The iterator will always yield at least one value,
+    /// namely `&self`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use unix_path::Path;
+    ///
+    /// let mut ancestors = Path::new("/foo/bar").ancestors();
+    /// assert_eq!(ancestors.next(), Some(Path::new("/foo/bar")));
+    /// assert_eq!(ancestors.next(), Some(Path::new("/foo")));
+    /// assert_eq!(ancestors.next(), Some(Path::new("/")));
+    /// assert_eq!(ancestors.next(), None);
+    /// ```
+    ///
+    /// [`parent`]: struct.Path.html#method.parent
+    pub fn ancestors(&self) -> Ancestors<'_> {
+        Ancestors { next: Some(&self) }
+    }
+
+    /// Returns the final component of the `Path`, if there is one.
+    ///
+    /// If the path is a normal file, this is the file name. If it's the path of a directory, this
+    /// is the directory name.
+    ///
+    /// Returns `None` if the path terminates in `..`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use unix_path::Path;
+    /// use unix_str::UnixStr;
+    ///
+    /// assert_eq!(Some(UnixStr::new("bin")), Path::new("/usr/bin/").file_name());
+    /// assert_eq!(Some(UnixStr::new("foo.txt")), Path::new("tmp/foo.txt").file_name());
+    /// assert_eq!(Some(UnixStr::new("foo.txt")), Path::new("foo.txt/.").file_name());
+    /// assert_eq!(Some(UnixStr::new("foo.txt")), Path::new("foo.txt/.//").file_name());
+    /// assert_eq!(None, Path::new("foo.txt/..").file_name());
+    /// assert_eq!(None, Path::new("/").file_name());
+    /// ```
+    pub fn file_name(&self) -> Option<&UnixStr> {
+        self.components().next_back().and_then(|p| match p {
+            Component::Normal(p) => Some(p),
+            _ => None,
+        })
+    }
+
+    /// Returns a path that, when joined onto `base`, yields `self`.
+    ///
+    /// # Errors
+    ///
+    /// If `base` is not a prefix of `self` (i.e., [`starts_with`]
+    /// returns `false`), returns `Err`.
+    ///
+    /// [`starts_with`]: #method.starts_with
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use unix_path::{Path, PathBuf};
+    ///
+    /// let path = Path::new("/test/haha/foo.txt");
+    ///
+    /// assert_eq!(path.strip_prefix("/"), Ok(Path::new("test/haha/foo.txt")));
+    /// assert_eq!(path.strip_prefix("/test"), Ok(Path::new("haha/foo.txt")));
+    /// assert_eq!(path.strip_prefix("/test/"), Ok(Path::new("haha/foo.txt")));
+    /// assert_eq!(path.strip_prefix("/test/haha/foo.txt"), Ok(Path::new("")));
+    /// assert_eq!(path.strip_prefix("/test/haha/foo.txt/"), Ok(Path::new("")));
+    /// assert_eq!(path.strip_prefix("test").is_ok(), false);
+    /// assert_eq!(path.strip_prefix("/haha").is_ok(), false);
+    ///
+    /// let prefix = PathBuf::from("/test/");
+    /// assert_eq!(path.strip_prefix(prefix), Ok(Path::new("haha/foo.txt")));
+    /// ```
+    pub fn strip_prefix<P>(&self, base: P) -> Result<&Path, StripPrefixError>
+    where
+        P: AsRef<Path>,
+    {
+        self._strip_prefix(base.as_ref())
+    }
+
+    fn _strip_prefix(&self, base: &Path) -> Result<&Path, StripPrefixError> {
+        iter_after(self.components(), base.components())
+            .map(|c| c.as_path())
+            .ok_or(StripPrefixError(()))
+    }
+
+    /// Determines whether `base` is a prefix of `self`.
+    ///
+    /// Only considers whole path components to match.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use unix_path::Path;
+    ///
+    /// let path = Path::new("/etc/passwd");
+    ///
+    /// assert!(path.starts_with("/etc"));
+    /// assert!(path.starts_with("/etc/"));
+    /// assert!(path.starts_with("/etc/passwd"));
+    /// assert!(path.starts_with("/etc/passwd/"));
+    ///
+    /// assert!(!path.starts_with("/e"));
+    /// ```
+    pub fn starts_with<P: AsRef<Path>>(&self, base: P) -> bool {
+        self._starts_with(base.as_ref())
+    }
+
+    fn _starts_with(&self, base: &Path) -> bool {
+        iter_after(self.components(), base.components()).is_some()
+    }
+
+    /// Determines whether `child` is a suffix of `self`.
+    ///
+    /// Only considers whole path components to match.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use unix_path::Path;
+    ///
+    /// let path = Path::new("/etc/passwd");
+    ///
+    /// assert!(path.ends_with("passwd"));
+    /// ```
+    pub fn ends_with<P: AsRef<Path>>(&self, child: P) -> bool {
+        self._ends_with(child.as_ref())
+    }
+
+    fn _ends_with(&self, child: &Path) -> bool {
+        iter_after(self.components().rev(), child.components().rev()).is_some()
+    }
+
+    /// Extracts the stem (non-extension) portion of [`self.file_name`].
+    ///
+    /// [`self.file_name`]: struct.Path.html#method.file_name
+    ///
+    /// The stem is:
+    ///
+    /// * `None`, if there is no file name;
+    /// * The entire file name if there is no embedded `.`;
+    /// * The entire file name if the file name begins with `.` and has no other `.`s within;
+    /// * Otherwise, the portion of the file name before the final `.`
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use unix_path::Path;
+    ///
+    /// let path = Path::new("foo.rs");
+    ///
+    /// assert_eq!("foo", path.file_stem().unwrap());
+    /// ```
+    pub fn file_stem(&self) -> Option<&UnixStr> {
+        self.file_name()
+            .map(split_file_at_dot)
+            .and_then(|(before, after)| before.or(after))
+    }
+
+    /// Extracts the extension of [`self.file_name`], if possible.
+    ///
+    /// The extension is:
+    ///
+    /// * `None`, if there is no file name;
+    /// * `None`, if there is no embedded `.`;
+    /// * `None`, if the file name begins with `.` and has no other `.`s within;
+    /// * Otherwise, the portion of the file name after the final `.`
+    ///
+    /// [`self.file_name`]: struct.Path.html#method.file_name
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use unix_path::Path;
+    /// use unix_str::UnixStr;
+    ///
+    /// let path = Path::new("foo.rs");
+    ///
+    /// assert_eq!(UnixStr::new("rs"), path.extension().unwrap());
+    /// ```
+    pub fn extension(&self) -> Option<&UnixStr> {
+        self.file_name()
+            .map(split_file_at_dot)
+            .and_then(|(before, after)| before.and(after))
+    }
+
+    /// Creates an owned [`PathBuf`] with `path` adjoined to `self`.
+    ///
+    /// See [`PathBuf::push`] for more details on what it means to adjoin a path.
+    ///
+    /// [`PathBuf`]: struct.PathBuf.html
+    /// [`PathBuf::push`]: struct.PathBuf.html#method.push
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use unix_path::{Path, PathBuf};
+    ///
+    /// assert_eq!(Path::new("/etc").join("passwd"), PathBuf::from("/etc/passwd"));
+    /// ```
+    #[must_use]
+    #[cfg(feature = "alloc")]
+    pub fn join<P: AsRef<Path>>(&self, path: P) -> PathBuf {
+        self._join(path.as_ref())
+    }
+
+    #[cfg(feature = "alloc")]
+    fn _join(&self, path: &Path) -> PathBuf {
+        let mut buf = self.to_path_buf();
+        buf.push(path);
+        buf
+    }
+
+    /// Creates an owned [`PathBuf`] like `self` but with the given file name.
+    ///
+    /// See [`PathBuf::set_file_name`] for more details.
+    ///
+    /// [`PathBuf`]: struct.PathBuf.html
+    /// [`PathBuf::set_file_name`]: struct.PathBuf.html#method.set_file_name
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use unix_path::{Path, PathBuf};
+    ///
+    /// let path = Path::new("/tmp/foo.txt");
+    /// assert_eq!(path.with_file_name("bar.txt"), PathBuf::from("/tmp/bar.txt"));
+    ///
+    /// let path = Path::new("/tmp");
+    /// assert_eq!(path.with_file_name("var"), PathBuf::from("/var"));
+    /// ```
+    #[cfg(feature = "alloc")]
+    pub fn with_file_name<S: AsRef<UnixStr>>(&self, file_name: S) -> PathBuf {
+        self._with_file_name(file_name.as_ref())
+    }
+
+    #[cfg(feature = "alloc")]
+    fn _with_file_name(&self, file_name: &UnixStr) -> PathBuf {
+        let mut buf = self.to_path_buf();
+        buf.set_file_name(file_name);
+        buf
+    }
+
+    /// Creates an owned [`PathBuf`] like `self` but with the given extension.
+    ///
+    /// See [`PathBuf::set_extension`] for more details.
+    ///
+    /// [`PathBuf`]: struct.PathBuf.html
+    /// [`PathBuf::set_extension`]: struct.PathBuf.html#method.set_extension
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use unix_path::{Path, PathBuf};
+    ///
+    /// let path = Path::new("foo.rs");
+    /// assert_eq!(path.with_extension("txt"), PathBuf::from("foo.txt"));
+    /// ```
+    #[cfg(feature = "alloc")]
+    pub fn with_extension<S: AsRef<UnixStr>>(&self, extension: S) -> PathBuf {
+        self._with_extension(extension.as_ref())
+    }
+
+    #[cfg(feature = "alloc")]
+    fn _with_extension(&self, extension: &UnixStr) -> PathBuf {
+        let mut buf = self.to_path_buf();
+        buf.set_extension(extension);
+        buf
+    }
+
+    /// Produces an iterator over the [`Component`]s of the path.
+    ///
+    /// When parsing the path, there is a small amount of normalization:
+    ///
+    /// * Repeated separators are ignored, so `a/b` and `a//b` both have
+    ///   `a` and `b` as components.
+    ///
+    /// * Occurrences of `.` are normalized away, except if they are at the
+    ///   beginning of the path. For example, `a/./b`, `a/b/`, `a/b/.` and
+    ///   `a/b` all have `a` and `b` as components, but `./a/b` starts with
+    ///   an additional [`CurDir`] component.
+    ///
+    /// * A trailing slash is normalized away, `/a/b` and `/a/b/` are equivalent.
+    ///
+    /// Note that no other normalization takes place; in particular, `a/c`
+    /// and `a/b/../c` are distinct, to account for the possibility that `b`
+    /// is a symbolic link (so its parent isn't `a`).
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use unix_path::{Path, Component};
+    /// use unix_str::UnixStr;
+    ///
+    /// let mut components = Path::new("/tmp/foo.txt").components();
+    ///
+    /// assert_eq!(components.next(), Some(Component::RootDir));
+    /// assert_eq!(components.next(), Some(Component::Normal(UnixStr::new("tmp"))));
+    /// assert_eq!(components.next(), Some(Component::Normal(UnixStr::new("foo.txt"))));
+    /// assert_eq!(components.next(), None)
+    /// ```
+    ///
+    /// [`Component`]: enum.Component.html
+    /// [`CurDir`]: enum.Component.html#variant.CurDir
+    pub fn components(&self) -> Components<'_> {
+        Components {
+            path: self.as_u8_slice(),
+            has_physical_root: has_physical_root(self.as_u8_slice()),
+            front: State::Prefix,
+            back: State::Body,
+        }
+    }
+
+    /// Produces an iterator over the path's components viewed as `UnixStr`
+    /// slices.
+    ///
+    /// For more information about the particulars of how the path is separated
+    /// into components, see [`components`].
+    ///
+    /// [`components`]: #method.components
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use unix_path::{self, Path};
+    /// use unix_str::UnixStr;
+    ///
+    /// let mut it = Path::new("/tmp/foo.txt").iter();
+    /// assert_eq!(it.next(), Some(UnixStr::new("/")));
+    /// assert_eq!(it.next(), Some(UnixStr::new("tmp")));
+    /// assert_eq!(it.next(), Some(UnixStr::new("foo.txt")));
+    /// assert_eq!(it.next(), None)
+    /// ```
+    pub fn iter(&self) -> Iter<'_> {
+        Iter {
+            inner: self.components(),
+        }
+    }
+
+    /// Converts a `Box<Path>` into a [`PathBuf`] without copying or
+    /// allocating.
+    ///
+    /// [`PathBuf`]: struct.PathBuf.html
+    #[cfg(feature = "alloc")]
+    pub fn into_path_buf(self: Box<Path>) -> PathBuf {
+        let rw = Box::into_raw(self) as *mut UnixStr;
+        let inner = unsafe { Box::from_raw(rw) };
+        PathBuf {
+            inner: UnixString::from(inner),
+        }
+    }
+
+    /// Returns a newtype that implements Display for safely printing paths
+    /// that may contain non-Unicode data.
+    pub fn display(&self) -> Display<'_> {
+        Display { path: self }
+    }
+}
+
+impl AsRef<UnixStr> for Path {
+    fn as_ref(&self) -> &UnixStr {
+        &self.inner
+    }
+}
+
+impl fmt::Debug for Path {
+    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Debug::fmt(&self.inner, formatter)
+    }
+}
+
+impl cmp::PartialEq for Path {
+    fn eq(&self, other: &Path) -> bool {
+        self.components().eq(other.components())
+    }
+}
+
+impl Hash for Path {
+    fn hash<H: Hasher>(&self, h: &mut H) {
+        for component in self.components() {
+            component.hash(h);
+        }
+    }
+}
+
+impl cmp::Eq for Path {}
+
+impl cmp::PartialOrd for Path {
+    fn partial_cmp(&self, other: &Path) -> Option<cmp::Ordering> {
+        self.components().partial_cmp(other.components())
+    }
+}
+
+impl cmp::Ord for Path {
+    fn cmp(&self, other: &Path) -> cmp::Ordering {
+        self.components().cmp(other.components())
+    }
+}
+
+impl AsRef<Path> for Path {
+    fn as_ref(&self) -> &Path {
+        self
+    }
+}
+
+impl AsRef<Path> for UnixStr {
+    fn as_ref(&self) -> &Path {
+        Path::new(self)
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl AsRef<Path> for Cow<'_, UnixStr> {
+    fn as_ref(&self) -> &Path {
+        Path::new(self)
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl AsRef<Path> for UnixString {
+    fn as_ref(&self) -> &Path {
+        Path::new(self)
+    }
+}
+
+impl AsRef<Path> for str {
+    #[inline]
+    fn as_ref(&self) -> &Path {
+        Path::new(self)
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl AsRef<Path> for String {
+    fn as_ref(&self) -> &Path {
+        Path::new(self)
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl AsRef<Path> for PathBuf {
+    #[inline]
+    fn as_ref(&self) -> &Path {
+        self
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl<'a> IntoIterator for &'a PathBuf {
+    type Item = &'a UnixStr;
+    type IntoIter = Iter<'a>;
+    fn into_iter(self) -> Iter<'a> {
+        self.iter()
+    }
+}
+
+impl<'a> IntoIterator for &'a Path {
+    type Item = &'a UnixStr;
+    type IntoIter = Iter<'a>;
+    fn into_iter(self) -> Iter<'a> {
+        self.iter()
+    }
+}
+
+#[cfg(feature = "serde")]
+use serde::{
+    de::{self, Deserialize, Deserializer, Unexpected, Visitor},
+    ser::{self, Serialize, Serializer},
+};
+
+#[cfg(feature = "serde")]
+impl Serialize for Path {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        match self.to_str() {
+            Some(s) => s.serialize(serializer),
+            None => Err(ser::Error::custom("path contains invalid UTF-8 characters")),
+        }
+    }
+}
+
+#[cfg(feature = "serde")]
+impl Serialize for PathBuf {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        self.as_path().serialize(serializer)
+    }
+}
+
+#[cfg(feature = "serde")]
+struct PathVisitor;
+
+#[cfg(feature = "serde")]
+impl<'a> Visitor<'a> for PathVisitor {
+    type Value = &'a Path;
+
+    fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("a borrowed path")
+    }
+
+    fn visit_borrowed_str<E>(self, v: &'a str) -> Result<Self::Value, E>
+    where
+        E: de::Error,
+    {
+        Ok(v.as_ref())
+    }
+
+    fn visit_borrowed_bytes<E>(self, v: &'a [u8]) -> Result<Self::Value, E>
+    where
+        E: de::Error,
+    {
+        core::str::from_utf8(v)
+            .map(AsRef::as_ref)
+            .map_err(|_| de::Error::invalid_value(Unexpected::Bytes(v), &self))
+    }
+}
+
+#[cfg(feature = "serde")]
+impl<'de: 'a, 'a> Deserialize<'de> for &'a Path {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        deserializer.deserialize_str(PathVisitor)
+    }
+}
+
+#[cfg(feature = "serde")]
+struct PathBufVisitor;
+
+#[cfg(feature = "serde")]
+impl<'de> Visitor<'de> for PathBufVisitor {
+    type Value = PathBuf;
+
+    fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("path string")
+    }
+
+    fn visit_str<E>(self, v: &str) -> Result<Self::Value, E>
+    where
+        E: de::Error,
+    {
+        Ok(From::from(v))
+    }
+
+    fn visit_string<E>(self, v: String) -> Result<Self::Value, E>
+    where
+        E: de::Error,
+    {
+        Ok(From::from(v))
+    }
+
+    fn visit_bytes<E>(self, v: &[u8]) -> Result<Self::Value, E>
+    where
+        E: de::Error,
+    {
+        core::str::from_utf8(v)
+            .map(From::from)
+            .map_err(|_| de::Error::invalid_value(Unexpected::Bytes(v), &self))
+    }
+
+    fn visit_byte_buf<E>(self, v: Vec<u8>) -> Result<Self::Value, E>
+    where
+        E: de::Error,
+    {
+        String::from_utf8(v)
+            .map(From::from)
+            .map_err(|e| de::Error::invalid_value(Unexpected::Bytes(&e.into_bytes()), &self))
+    }
+}
+
+#[cfg(feature = "serde")]
+impl<'de> Deserialize<'de> for PathBuf {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        deserializer.deserialize_string(PathBufVisitor)
+    }
+}
+
+#[cfg(feature = "serde")]
+impl<'de> Deserialize<'de> for Box<Path> {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        Deserialize::deserialize(deserializer).map(PathBuf::into_boxed_path)
+    }
+}
+
+#[cfg(feature = "alloc")]
+macro_rules! impl_cmp {
+    ($lhs:ty, $rhs: ty) => {
+        impl<'a, 'b> PartialEq<$rhs> for $lhs {
+            #[inline]
+            fn eq(&self, other: &$rhs) -> bool {
+                <Path as PartialEq>::eq(self, other)
+            }
+        }
+
+        impl<'a, 'b> PartialEq<$lhs> for $rhs {
+            #[inline]
+            fn eq(&self, other: &$lhs) -> bool {
+                <Path as PartialEq>::eq(self, other)
+            }
+        }
+
+        impl<'a, 'b> PartialOrd<$rhs> for $lhs {
+            #[inline]
+            fn partial_cmp(&self, other: &$rhs) -> Option<cmp::Ordering> {
+                <Path as PartialOrd>::partial_cmp(self, other)
+            }
+        }
+
+        impl<'a, 'b> PartialOrd<$lhs> for $rhs {
+            #[inline]
+            fn partial_cmp(&self, other: &$lhs) -> Option<cmp::Ordering> {
+                <Path as PartialOrd>::partial_cmp(self, other)
+            }
+        }
+    };
+}
+
+#[cfg(feature = "alloc")]
+impl_cmp!(PathBuf, Path);
+#[cfg(feature = "alloc")]
+impl_cmp!(PathBuf, &'a Path);
+#[cfg(feature = "alloc")]
+impl_cmp!(Cow<'a, Path>, Path);
+#[cfg(feature = "alloc")]
+impl_cmp!(Cow<'a, Path>, &'b Path);
+#[cfg(feature = "alloc")]
+impl_cmp!(Cow<'a, Path>, PathBuf);
+
+impl fmt::Display for StripPrefixError {
+    #[allow(deprecated, deprecated_in_future)]
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        "prefix not found".fmt(f)
+    }
+}
+
+#[cfg(feature = "std")]
+impl Error for StripPrefixError {
+    #[allow(deprecated)]
+    fn description(&self) -> &str {
+        "prefix not found"
+    }
+}
+
+pub struct Display<'a> {
+    path: &'a Path,
+}
+
+impl fmt::Debug for Display<'_> {
+    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Debug::fmt(&self.path, formatter)
+    }
+}
+
+impl fmt::Display for Display<'_> {
+    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Display::fmt(
+            &lossy::Utf8Lossy::from_bytes(&self.path.as_unix_str().as_bytes()),
+            formatter,
+        )
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    use alloc::rc::Rc;
+    use alloc::sync::Arc;
+
+    macro_rules! t(
+        ($path:expr, iter: $iter:expr) => (
+            {
+                let path = Path::new($path);
+
+                // Forward iteration
+                let comps = path.iter()
+                    .map(|p| p.to_string_lossy().into_owned())
+                    .collect::<Vec<String>>();
+                let exp: &[&str] = &$iter;
+                let exps = exp.iter().map(|s| s.to_string()).collect::<Vec<String>>();
+                assert!(comps == exps, "iter: Expected {:?}, found {:?}",
+                        exps, comps);
+
+                // Reverse iteration
+                let comps = Path::new($path).iter().rev()
+                    .map(|p| p.to_string_lossy().into_owned())
+                    .collect::<Vec<String>>();
+                let exps = exps.into_iter().rev().collect::<Vec<String>>();
+                assert!(comps == exps, "iter().rev(): Expected {:?}, found {:?}",
+                        exps, comps);
+            }
+        );
+
+        ($path:expr, has_root: $has_root:expr, is_absolute: $is_absolute:expr) => (
+            {
+                let path = Path::new($path);
+
+                let act_root = path.has_root();
+                assert!(act_root == $has_root, "has_root: Expected {:?}, found {:?}",
+                        $has_root, act_root);
+
+                let act_abs = path.is_absolute();
+                assert!(act_abs == $is_absolute, "is_absolute: Expected {:?}, found {:?}",
+                        $is_absolute, act_abs);
+            }
+        );
+
+        ($path:expr, parent: $parent:expr, file_name: $file:expr) => (
+            {
+                let path = Path::new($path);
+
+                let parent = path.parent().map(|p| p.to_str().unwrap());
+                let exp_parent: Option<&str> = $parent;
+                assert!(parent == exp_parent, "parent: Expected {:?}, found {:?}",
+                        exp_parent, parent);
+
+                let file = path.file_name().map(|p| p.to_str().unwrap());
+                let exp_file: Option<&str> = $file;
+                assert!(file == exp_file, "file_name: Expected {:?}, found {:?}",
+                        exp_file, file);
+            }
+        );
+
+        ($path:expr, file_stem: $file_stem:expr, extension: $extension:expr) => (
+            {
+                let path = Path::new($path);
+
+                let stem = path.file_stem().map(|p| p.to_str().unwrap());
+                let exp_stem: Option<&str> = $file_stem;
+                assert!(stem == exp_stem, "file_stem: Expected {:?}, found {:?}",
+                        exp_stem, stem);
+
+                let ext = path.extension().map(|p| p.to_str().unwrap());
+                let exp_ext: Option<&str> = $extension;
+                assert!(ext == exp_ext, "extension: Expected {:?}, found {:?}",
+                        exp_ext, ext);
+            }
+        );
+
+        ($path:expr, iter: $iter:expr,
+                     has_root: $has_root:expr, is_absolute: $is_absolute:expr,
+                     parent: $parent:expr, file_name: $file:expr,
+                     file_stem: $file_stem:expr, extension: $extension:expr) => (
+            {
+                t!($path, iter: $iter);
+                t!($path, has_root: $has_root, is_absolute: $is_absolute);
+                t!($path, parent: $parent, file_name: $file);
+                t!($path, file_stem: $file_stem, extension: $extension);
+            }
+        );
+    );
+
+    #[test]
+    fn into() {
+        use alloc::borrow::Cow;
+
+        let static_path = Path::new("/home/foo");
+        let static_cow_path: Cow<'static, Path> = static_path.into();
+        let pathbuf = PathBuf::from("/home/foo");
+
+        {
+            let path: &Path = &pathbuf;
+            let borrowed_cow_path: Cow<'_, Path> = path.into();
+
+            assert_eq!(static_cow_path, borrowed_cow_path);
+        }
+
+        let owned_cow_path: Cow<'static, Path> = pathbuf.into();
+
+        assert_eq!(static_cow_path, owned_cow_path);
+    }
+
+    #[test]
+    pub fn test_decompositions_unix() {
+        t!("",
+        iter: [],
+        has_root: false,
+        is_absolute: false,
+        parent: None,
+        file_name: None,
+        file_stem: None,
+        extension: None
+        );
+
+        t!("foo",
+        iter: ["foo"],
+        has_root: false,
+        is_absolute: false,
+        parent: Some(""),
+        file_name: Some("foo"),
+        file_stem: Some("foo"),
+        extension: None
+        );
+
+        t!("/",
+        iter: ["/"],
+        has_root: true,
+        is_absolute: true,
+        parent: None,
+        file_name: None,
+        file_stem: None,
+        extension: None
+        );
+
+        t!("/foo",
+        iter: ["/", "foo"],
+        has_root: true,
+        is_absolute: true,
+        parent: Some("/"),
+        file_name: Some("foo"),
+        file_stem: Some("foo"),
+        extension: None
+        );
+
+        t!("foo/",
+        iter: ["foo"],
+        has_root: false,
+        is_absolute: false,
+        parent: Some(""),
+        file_name: Some("foo"),
+        file_stem: Some("foo"),
+        extension: None
+        );
+
+        t!("/foo/",
+        iter: ["/", "foo"],
+        has_root: true,
+        is_absolute: true,
+        parent: Some("/"),
+        file_name: Some("foo"),
+        file_stem: Some("foo"),
+        extension: None
+        );
+
+        t!("foo/bar",
+        iter: ["foo", "bar"],
+        has_root: false,
+        is_absolute: false,
+        parent: Some("foo"),
+        file_name: Some("bar"),
+        file_stem: Some("bar"),
+        extension: None
+        );
+
+        t!("/foo/bar",
+        iter: ["/", "foo", "bar"],
+        has_root: true,
+        is_absolute: true,
+        parent: Some("/foo"),
+        file_name: Some("bar"),
+        file_stem: Some("bar"),
+        extension: None
+        );
+
+        t!("///foo///",
+        iter: ["/", "foo"],
+        has_root: true,
+        is_absolute: true,
+        parent: Some("/"),
+        file_name: Some("foo"),
+        file_stem: Some("foo"),
+        extension: None
+        );
+
+        t!("///foo///bar",
+        iter: ["/", "foo", "bar"],
+        has_root: true,
+        is_absolute: true,
+        parent: Some("///foo"),
+        file_name: Some("bar"),
+        file_stem: Some("bar"),
+        extension: None
+        );
+
+        t!("./.",
+        iter: ["."],
+        has_root: false,
+        is_absolute: false,
+        parent: Some(""),
+        file_name: None,
+        file_stem: None,
+        extension: None
+        );
+
+        t!("/..",
+        iter: ["/", ".."],
+        has_root: true,
+        is_absolute: true,
+        parent: Some("/"),
+        file_name: None,
+        file_stem: None,
+        extension: None
+        );
+
+        t!("../",
+        iter: [".."],
+        has_root: false,
+        is_absolute: false,
+        parent: Some(""),
+        file_name: None,
+        file_stem: None,
+        extension: None
+        );
+
+        t!("foo/.",
+        iter: ["foo"],
+        has_root: false,
+        is_absolute: false,
+        parent: Some(""),
+        file_name: Some("foo"),
+        file_stem: Some("foo"),
+        extension: None
+        );
+
+        t!("foo/..",
+        iter: ["foo", ".."],
+        has_root: false,
+        is_absolute: false,
+        parent: Some("foo"),
+        file_name: None,
+        file_stem: None,
+        extension: None
+        );
+
+        t!("foo/./",
+        iter: ["foo"],
+        has_root: false,
+        is_absolute: false,
+        parent: Some(""),
+        file_name: Some("foo"),
+        file_stem: Some("foo"),
+        extension: None
+        );
+
+        t!("foo/./bar",
+        iter: ["foo", "bar"],
+        has_root: false,
+        is_absolute: false,
+        parent: Some("foo"),
+        file_name: Some("bar"),
+        file_stem: Some("bar"),
+        extension: None
+        );
+
+        t!("foo/../",
+        iter: ["foo", ".."],
+        has_root: false,
+        is_absolute: false,
+        parent: Some("foo"),
+        file_name: None,
+        file_stem: None,
+        extension: None
+        );
+
+        t!("foo/../bar",
+        iter: ["foo", "..", "bar"],
+        has_root: false,
+        is_absolute: false,
+        parent: Some("foo/.."),
+        file_name: Some("bar"),
+        file_stem: Some("bar"),
+        extension: None
+        );
+
+        t!("./a",
+        iter: [".", "a"],
+        has_root: false,
+        is_absolute: false,
+        parent: Some("."),
+        file_name: Some("a"),
+        file_stem: Some("a"),
+        extension: None
+        );
+
+        t!(".",
+        iter: ["."],
+        has_root: false,
+        is_absolute: false,
+        parent: Some(""),
+        file_name: None,
+        file_stem: None,
+        extension: None
+        );
+
+        t!("./",
+        iter: ["."],
+        has_root: false,
+        is_absolute: false,
+        parent: Some(""),
+        file_name: None,
+        file_stem: None,
+        extension: None
+        );
+
+        t!("a/b",
+        iter: ["a", "b"],
+        has_root: false,
+        is_absolute: false,
+        parent: Some("a"),
+        file_name: Some("b"),
+        file_stem: Some("b"),
+        extension: None
+        );
+
+        t!("a//b",
+        iter: ["a", "b"],
+        has_root: false,
+        is_absolute: false,
+        parent: Some("a"),
+        file_name: Some("b"),
+        file_stem: Some("b"),
+        extension: None
+        );
+
+        t!("a/./b",
+        iter: ["a", "b"],
+        has_root: false,
+        is_absolute: false,
+        parent: Some("a"),
+        file_name: Some("b"),
+        file_stem: Some("b"),
+        extension: None
+        );
+
+        t!("a/b/c",
+        iter: ["a", "b", "c"],
+        has_root: false,
+        is_absolute: false,
+        parent: Some("a/b"),
+        file_name: Some("c"),
+        file_stem: Some("c"),
+        extension: None
+        );
+
+        t!(".foo",
+        iter: [".foo"],
+        has_root: false,
+        is_absolute: false,
+        parent: Some(""),
+        file_name: Some(".foo"),
+        file_stem: Some(".foo"),
+        extension: None
+        );
+    }
+
+    #[test]
+    pub fn test_stem_ext() {
+        t!("foo",
+        file_stem: Some("foo"),
+        extension: None
+        );
+
+        t!("foo.",
+        file_stem: Some("foo"),
+        extension: Some("")
+        );
+
+        t!(".foo",
+        file_stem: Some(".foo"),
+        extension: None
+        );
+
+        t!("foo.txt",
+        file_stem: Some("foo"),
+        extension: Some("txt")
+        );
+
+        t!("foo.bar.txt",
+        file_stem: Some("foo.bar"),
+        extension: Some("txt")
+        );
+
+        t!("foo.bar.",
+        file_stem: Some("foo.bar"),
+        extension: Some("")
+        );
+
+        t!(".", file_stem: None, extension: None);
+
+        t!("..", file_stem: None, extension: None);
+
+        t!("", file_stem: None, extension: None);
+    }
+
+    #[test]
+    pub fn test_push() {
+        macro_rules! tp(
+            ($path:expr, $push:expr, $expected:expr) => ( {
+                let mut actual = PathBuf::from($path);
+                actual.push($push);
+                assert!(actual.to_str() == Some($expected),
+                        "pushing {:?} onto {:?}: Expected {:?}, got {:?}",
+                        $push, $path, $expected, actual.to_str().unwrap());
+            });
+        );
+
+        tp!("", "foo", "foo");
+        tp!("foo", "bar", "foo/bar");
+        tp!("foo/", "bar", "foo/bar");
+        tp!("foo//", "bar", "foo//bar");
+        tp!("foo/.", "bar", "foo/./bar");
+        tp!("foo./.", "bar", "foo././bar");
+        tp!("foo", "", "foo/");
+        tp!("foo", ".", "foo/.");
+        tp!("foo", "..", "foo/..");
+        tp!("foo", "/", "/");
+        tp!("/foo/bar", "/", "/");
+        tp!("/foo/bar", "/baz", "/baz");
+        tp!("/foo/bar", "./baz", "/foo/bar/./baz");
+    }
+
+    #[test]
+    pub fn test_pop() {
+        macro_rules! tp(
+            ($path:expr, $expected:expr, $output:expr) => ( {
+                let mut actual = PathBuf::from($path);
+                let output = actual.pop();
+                assert!(actual.to_str() == Some($expected) && output == $output,
+                        "popping from {:?}: Expected {:?}/{:?}, got {:?}/{:?}",
+                        $path, $expected, $output,
+                        actual.to_str().unwrap(), output);
+            });
+        );
+
+        tp!("", "", false);
+        tp!("/", "/", false);
+        tp!("foo", "", true);
+        tp!(".", "", true);
+        tp!("/foo", "/", true);
+        tp!("/foo/bar", "/foo", true);
+        tp!("foo/bar", "foo", true);
+        tp!("foo/.", "", true);
+        tp!("foo//bar", "foo", true);
+    }
+
+    #[test]
+    pub fn test_set_file_name() {
+        macro_rules! tfn(
+                ($path:expr, $file:expr, $expected:expr) => ( {
+                let mut p = PathBuf::from($path);
+                p.set_file_name($file);
+                assert!(p.to_str() == Some($expected),
+                        "setting file name of {:?} to {:?}: Expected {:?}, got {:?}",
+                        $path, $file, $expected,
+                        p.to_str().unwrap());
+            });
+        );
+
+        tfn!("foo", "foo", "foo");
+        tfn!("foo", "bar", "bar");
+        tfn!("foo", "", "");
+        tfn!("", "foo", "foo");
+        tfn!(".", "foo", "./foo");
+        tfn!("foo/", "bar", "bar");
+        tfn!("foo/.", "bar", "bar");
+        tfn!("..", "foo", "../foo");
+        tfn!("foo/..", "bar", "foo/../bar");
+        tfn!("/", "foo", "/foo");
+    }
+
+    #[test]
+    pub fn test_set_extension() {
+        macro_rules! tfe(
+                ($path:expr, $ext:expr, $expected:expr, $output:expr) => ( {
+                let mut p = PathBuf::from($path);
+                let output = p.set_extension($ext);
+                assert!(p.to_str() == Some($expected) && output == $output,
+                        "setting extension of {:?} to {:?}: Expected {:?}/{:?}, got {:?}/{:?}",
+                        $path, $ext, $expected, $output,
+                        p.to_str().unwrap(), output);
+            });
+        );
+
+        tfe!("foo", "txt", "foo.txt", true);
+        tfe!("foo.bar", "txt", "foo.txt", true);
+        tfe!("foo.bar.baz", "txt", "foo.bar.txt", true);
+        tfe!(".test", "txt", ".test.txt", true);
+        tfe!("foo.txt", "", "foo", true);
+        tfe!("foo", "", "foo", true);
+        tfe!("", "foo", "", false);
+        tfe!(".", "foo", ".", false);
+        tfe!("foo/", "bar", "foo.bar", true);
+        tfe!("foo/.", "bar", "foo.bar", true);
+        tfe!("..", "foo", "..", false);
+        tfe!("foo/..", "bar", "foo/..", false);
+        tfe!("/", "foo", "/", false);
+    }
+
+    #[test]
+    fn test_eq_receivers() {
+        use alloc::borrow::Cow;
+
+        let borrowed: &Path = Path::new("foo/bar");
+        let mut owned: PathBuf = PathBuf::new();
+        owned.push("foo");
+        owned.push("bar");
+        let borrowed_cow: Cow<'_, Path> = borrowed.into();
+        let owned_cow: Cow<'_, Path> = owned.clone().into();
+
+        macro_rules! t {
+            ($($current:expr),+) => {
+                $(
+                    assert_eq!($current, borrowed);
+                    assert_eq!($current, owned);
+                    assert_eq!($current, borrowed_cow);
+                    assert_eq!($current, owned_cow);
+                )+
+            }
+        }
+
+        t!(borrowed, owned, borrowed_cow, owned_cow);
+    }
+
+    #[test]
+    pub fn test_compare() {
+        use std::collections::hash_map::DefaultHasher;
+        use std::hash::{Hash, Hasher};
+
+        fn hash<T: Hash>(t: T) -> u64 {
+            let mut s = DefaultHasher::new();
+            t.hash(&mut s);
+            s.finish()
+        }
+
+        macro_rules! tc(
+            ($path1:expr, $path2:expr, eq: $eq:expr,
+             starts_with: $starts_with:expr, ends_with: $ends_with:expr,
+             relative_from: $relative_from:expr) => ({
+                 let path1 = Path::new($path1);
+                 let path2 = Path::new($path2);
+
+                 let eq = path1 == path2;
+                 assert!(eq == $eq, "{:?} == {:?}, expected {:?}, got {:?}",
+                         $path1, $path2, $eq, eq);
+                 assert!($eq == (hash(path1) == hash(path2)),
+                         "{:?} == {:?}, expected {:?}, got {} and {}",
+                         $path1, $path2, $eq, hash(path1), hash(path2));
+
+                 let starts_with = path1.starts_with(path2);
+                 assert!(starts_with == $starts_with,
+                         "{:?}.starts_with({:?}), expected {:?}, got {:?}", $path1, $path2,
+                         $starts_with, starts_with);
+
+                 let ends_with = path1.ends_with(path2);
+                 assert!(ends_with == $ends_with,
+                         "{:?}.ends_with({:?}), expected {:?}, got {:?}", $path1, $path2,
+                         $ends_with, ends_with);
+
+                 let relative_from = path1.strip_prefix(path2)
+                                          .map(|p| p.to_str().unwrap())
+                                          .ok();
+                 let exp: Option<&str> = $relative_from;
+                 assert!(relative_from == exp,
+                         "{:?}.strip_prefix({:?}), expected {:?}, got {:?}",
+                         $path1, $path2, exp, relative_from);
+            });
+        );
+
+        tc!("", "",
+        eq: true,
+        starts_with: true,
+        ends_with: true,
+        relative_from: Some("")
+        );
+
+        tc!("foo", "",
+        eq: false,
+        starts_with: true,
+        ends_with: true,
+        relative_from: Some("foo")
+        );
+
+        tc!("", "foo",
+        eq: false,
+        starts_with: false,
+        ends_with: false,
+        relative_from: None
+        );
+
+        tc!("foo", "foo",
+        eq: true,
+        starts_with: true,
+        ends_with: true,
+        relative_from: Some("")
+        );
+
+        tc!("foo/", "foo",
+        eq: true,
+        starts_with: true,
+        ends_with: true,
+        relative_from: Some("")
+        );
+
+        tc!("foo/bar", "foo",
+        eq: false,
+        starts_with: true,
+        ends_with: false,
+        relative_from: Some("bar")
+        );
+
+        tc!("foo/bar/baz", "foo/bar",
+        eq: false,
+        starts_with: true,
+        ends_with: false,
+        relative_from: Some("baz")
+        );
+
+        tc!("foo/bar", "foo/bar/baz",
+        eq: false,
+        starts_with: false,
+        ends_with: false,
+        relative_from: None
+        );
+
+        tc!("./foo/bar/", ".",
+        eq: false,
+        starts_with: true,
+        ends_with: false,
+        relative_from: Some("foo/bar")
+        );
+    }
+
+    #[test]
+    fn test_components_debug() {
+        let path = Path::new("/tmp");
+
+        let mut components = path.components();
+
+        let expected = "Components([RootDir, Normal(\"tmp\")])";
+        let actual = format!("{:?}", components);
+        assert_eq!(expected, actual);
+
+        let _ = components.next().unwrap();
+        let expected = "Components([Normal(\"tmp\")])";
+        let actual = format!("{:?}", components);
+        assert_eq!(expected, actual);
+
+        let _ = components.next().unwrap();
+        let expected = "Components([])";
+        let actual = format!("{:?}", components);
+        assert_eq!(expected, actual);
+    }
+
+    #[test]
+    fn test_iter_debug() {
+        let path = Path::new("/tmp");
+
+        let mut iter = path.iter();
+
+        let expected = "Iter([\"/\", \"tmp\"])";
+        let actual = format!("{:?}", iter);
+        assert_eq!(expected, actual);
+
+        let _ = iter.next().unwrap();
+        let expected = "Iter([\"tmp\"])";
+        let actual = format!("{:?}", iter);
+        assert_eq!(expected, actual);
+
+        let _ = iter.next().unwrap();
+        let expected = "Iter([])";
+        let actual = format!("{:?}", iter);
+        assert_eq!(expected, actual);
+    }
+
+    #[test]
+    fn into_boxed() {
+        let orig: &str = "some/sort/of/path";
+        let path = Path::new(orig);
+        let boxed: Box<Path> = Box::from(path);
+        let path_buf = path.to_owned().into_boxed_path().into_path_buf();
+        assert_eq!(path, &*boxed);
+        assert_eq!(&*boxed, &*path_buf);
+        assert_eq!(&*path_buf, path);
+    }
+
+    #[test]
+    fn into_rc() {
+        let orig = "hello/world";
+        let path = Path::new(orig);
+        let rc: Rc<Path> = Rc::from(path);
+        let arc: Arc<Path> = Arc::from(path);
+
+        assert_eq!(&*rc, path);
+        assert_eq!(&*arc, path);
+
+        let rc2: Rc<Path> = Rc::from(path.to_owned());
+        let arc2: Arc<Path> = Arc::from(path.to_owned());
+
+        assert_eq!(&*rc2, path);
+        assert_eq!(&*arc2, path);
+    }
+}
diff --git a/third_party/rust/unix_path/src/lossy.rs b/third_party/rust/unix_path/src/lossy.rs
new file mode 100644
index 0000000000..2e5f137a0b
--- /dev/null
+++ b/third_party/rust/unix_path/src/lossy.rs
@@ -0,0 +1,188 @@
+use core::char;
+use core::fmt::{self, Write};
+use core::mem;
+use core::str as core_str;
+
+// https://tools.ietf.org/html/rfc3629
+static UTF8_CHAR_WIDTH: [u8; 256] = [
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+    1, // 0x1F
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+    1, // 0x3F
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+    1, // 0x5F
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+    1, // 0x7F
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, // 0x9F
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, // 0xBF
+    0, 0, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
+    2, // 0xDF
+    3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, // 0xEF
+    4, 4, 4, 4, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 0xFF
+];
+
+/// Given a first byte, determines how many bytes are in this UTF-8 character.
+#[inline]
+pub fn utf8_char_width(b: u8) -> usize {
+    UTF8_CHAR_WIDTH[b as usize] as usize
+}
+
+/// Lossy UTF-8 string.
+pub struct Utf8Lossy {
+    bytes: [u8],
+}
+
+impl Utf8Lossy {
+    pub fn from_bytes(bytes: &[u8]) -> &Utf8Lossy {
+        // SAFETY: Both use the same memory layout, and UTF-8 correctness isn't required.
+        unsafe { mem::transmute(bytes) }
+    }
+
+    pub fn chunks(&self) -> Utf8LossyChunksIter<'_> {
+        Utf8LossyChunksIter {
+            source: &self.bytes,
+        }
+    }
+}
+
+/// Iterator over lossy UTF-8 string
+pub struct Utf8LossyChunksIter<'a> {
+    source: &'a [u8],
+}
+
+#[derive(PartialEq, Eq, Debug)]
+pub struct Utf8LossyChunk<'a> {
+    /// Sequence of valid chars.
+    /// Can be empty between broken UTF-8 chars.
+    pub valid: &'a str,
+    /// Single broken char, empty if none.
+    /// Empty iff iterator item is last.
+    pub broken: &'a [u8],
+}
+
+impl<'a> Iterator for Utf8LossyChunksIter<'a> {
+    type Item = Utf8LossyChunk<'a>;
+
+    fn next(&mut self) -> Option<Utf8LossyChunk<'a>> {
+        if self.source.is_empty() {
+            return None;
+        }
+
+        const TAG_CONT_U8: u8 = 128;
+        fn safe_get(xs: &[u8], i: usize) -> u8 {
+            *xs.get(i).unwrap_or(&0)
+        }
+
+        let mut i = 0;
+        while i < self.source.len() {
+            let i_ = i;
+
+            // SAFETY: `i` starts at `0`, is less than `self.source.len()`, and
+            // only increases, so `0 <= i < self.source.len()`.
+            let byte = unsafe { *self.source.get_unchecked(i) };
+            i += 1;
+
+            if byte < 128 {
+            } else {
+                let w = utf8_char_width(byte);
+
+                macro_rules! error {
+                    () => {{
+                        // SAFETY: We have checked up to `i` that source is valid UTF-8.
+                        unsafe {
+                            let r = Utf8LossyChunk {
+                                valid: core_str::from_utf8_unchecked(&self.source[0..i_]),
+                                broken: &self.source[i_..i],
+                            };
+                            self.source = &self.source[i..];
+                            return Some(r);
+                        }
+                    }};
+                }
+
+                match w {
+                    2 => {
+                        if safe_get(self.source, i) & 192 != TAG_CONT_U8 {
+                            error!();
+                        }
+                        i += 1;
+                    }
+                    3 => {
+                        match (byte, safe_get(self.source, i)) {
+                            (0xE0, 0xA0..=0xBF) => (),
+                            (0xE1..=0xEC, 0x80..=0xBF) => (),
+                            (0xED, 0x80..=0x9F) => (),
+                            (0xEE..=0xEF, 0x80..=0xBF) => (),
+                            _ => {
+                                error!();
+                            }
+                        }
+                        i += 1;
+                        if safe_get(self.source, i) & 192 != TAG_CONT_U8 {
+                            error!();
+                        }
+                        i += 1;
+                    }
+                    4 => {
+                        match (byte, safe_get(self.source, i)) {
+                            (0xF0, 0x90..=0xBF) => (),
+                            (0xF1..=0xF3, 0x80..=0xBF) => (),
+                            (0xF4, 0x80..=0x8F) => (),
+                            _ => {
+                                error!();
+                            }
+                        }
+                        i += 1;
+                        if safe_get(self.source, i) & 192 != TAG_CONT_U8 {
+                            error!();
+                        }
+                        i += 1;
+                        if safe_get(self.source, i) & 192 != TAG_CONT_U8 {
+                            error!();
+                        }
+                        i += 1;
+                    }
+                    _ => {
+                        error!();
+                    }
+                }
+            }
+        }
+
+        let r = Utf8LossyChunk {
+            // SAFETY: We have checked that the entire source is valid UTF-8.
+            valid: unsafe { core_str::from_utf8_unchecked(self.source) },
+            broken: &[],
+        };
+        self.source = &[];
+        Some(r)
+    }
+}
+
+impl fmt::Display for Utf8Lossy {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        // If we're the empty string then our iterator won't actually yield
+        // anything, so perform the formatting manually
+        if self.bytes.is_empty() {
+            return "".fmt(f);
+        }
+
+        for Utf8LossyChunk { valid, broken } in self.chunks() {
+            // If we successfully decoded the whole chunk as a valid string then
+            // we can return a direct formatting of the string which will also
+            // respect various formatting flags if possible.
+            if valid.len() == self.bytes.len() {
+                assert!(broken.is_empty());
+                return valid.fmt(f);
+            }
+
+            f.write_str(valid)?;
+            if !broken.is_empty() {
+                f.write_char(char::REPLACEMENT_CHARACTER)?;
+            }
+        }
+        Ok(())
+    }
+}