Enum std::borrow::Cow

pub enum Cow<'a, B> where
    B: 'a + ToOwned + 'a + ?Sized,  {
    Borrowed(&'a B),
    Owned(<B as ToOwned>::Owned),
}

A clone-on-write smart pointer.

The type Cow is a smart pointer providing clone-on-write functionality: it can enclose and provide immutable access to borrowed data, and clone the data lazily when mutation or ownership is required. The type is designed to work with general borrowed data via the Borrow trait.

Cow implements Deref, which means that you can call non-mutating methods directly on the data it encloses. If mutation is desired, to_mut will obtain a mutable reference to an owned value, cloning if necessary.

Examples

use std::borrow::Cow;

fn abs_all(input: &mut Cow<[i32]>) {
    for i in 0..input.len() {
        let v = input[i];
        if v < 0 {
            // Clones into a vector if not already owned.
            input.to_mut()[i] = -v;
        }
    }
}

// No clone occurs because `input` doesn't need to be mutated.
let slice = [0, 1, 2];
let mut input = Cow::from(&slice[..]);
abs_all(&mut input);

// Clone occurs because `input` needs to be mutated.
let slice = [-1, 0, 1];
let mut input = Cow::from(&slice[..]);
abs_all(&mut input);

// No clone occurs because `input` is already owned.
let mut input = Cow::from(vec![-1, 0, 1]);
abs_all(&mut input);

Another example showing how to keep Cow in a struct:

use std::borrow::Cow;

struct Items<'a, X: 'a> where [X]: ToOwned<Owned = Vec<X>> {
    values: Cow<'a, [X]>,
}

impl<'a, X: Clone + 'a> Items<'a, X> where [X]: ToOwned<Owned = Vec<X>> {
    fn new(v: Cow<'a, [X]>) -> Self {
        Items { values: v }
    }
}

// Creates a container from borrowed values of a slice
let readonly = [1, 2];
let borrowed = Items::new((&readonly[..]).into());
match borrowed {
    Items { values: Cow::Borrowed(b) } => println!("borrowed {:?}", b),
    _ => panic!("expect borrowed value"),
}

let mut clone_on_write = borrowed;
// Mutates the data from slice into owned vec and pushes a new value on top
clone_on_write.values.to_mut().push(3);
println!("clone_on_write = {:?}", clone_on_write.values);

// The data was mutated. Let check it out.
match clone_on_write {
    Items { values: Cow::Owned(_) } => println!("clone_on_write contains owned data"),
    _ => panic!("expect owned data"),
}

Variants

Borrowed(&'a B)

Borrowed data.

Owned(<B as ToOwned>::Owned)

Owned data.

Methods

impl<'_, B> Cow<'_, B> where
    B: ToOwned + ?Sized, 

pub fn to_mut(&mut self) -> &mut <B as ToOwned>::Owned

Acquires a mutable reference to the owned form of the data.

Clones the data if it is not already owned.

Examples

use std::borrow::Cow;

let mut cow = Cow::Borrowed("foo");
cow.to_mut().make_ascii_uppercase();

assert_eq!(
  cow,
  Cow::Owned(String::from("FOO")) as Cow<str>
);

pub fn into_owned(self) -> <B as ToOwned>::Owned

Extracts the owned data.

Clones the data if it is not already owned.

Examples

Calling into_owned on a Cow::Borrowed clones the underlying data and becomes a Cow::Owned:

use std::borrow::Cow;

let s = "Hello world!";
let cow = Cow::Borrowed(s);

assert_eq!(
  cow.into_owned(),
  String::from(s)
);

Calling into_owned on a Cow::Owned is a no-op:

use std::borrow::Cow;

let s = "Hello world!";
let cow: Cow<str> = Cow::Owned(String::from(s));

assert_eq!(
  cow.into_owned(),
  String::from(s)
);

Trait Implementations

impl<'_, B> Eq for Cow<'_, B> where
    B: Eq + ToOwned + ?Sized, 

impl<'a> Extend<Cow<'a, str>> for String

fn extend<I>(&mut self, iter: I) where
    I: IntoIterator<Item = Cow<'a, str>>, 

Extends a collection with the contents of an iterator.

impl<'a, B> PartialOrd<Cow<'a, B>> for Cow<'a, B> where
    B: PartialOrd<B> + ToOwned + ?Sized, 

fn partial_cmp(&self, other: &Cow<'a, B>) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

#[must_use] fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

#[must_use] fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

#[must_use] fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

#[must_use] fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl<'_, B> Hash for Cow<'_, B> where
    B: Hash + ToOwned + ?Sized, 

fn hash<H>(&self, state: &mut H) where
    H: Hasher, 

Feeds this value into the given [Hasher].

fn hash_slice<H>(data: &[Self], state: &mut H) where
    H: Hasher, 

Feeds a slice of this type into the given [Hasher].

impl<'a, T> From<Vec<T>> for Cow<'a, [T]> where
    T: Clone, 

fn from(v: Vec<T>) -> Cow<'a, [T]>

Performs the conversion.

impl<'a, T> From<Cow<'a, [T]>> for Vec<T> where
    [T]: ToOwned,
    <[T] as ToOwned>::Owned == Vec<T>, 

Important traits for Vec<u8>

impl Write for Vec<u8>

fn from(s: Cow<'a, [T]>) -> Vec<T>

Performs the conversion.

impl<'a> From<String> for Cow<'a, str>

fn from(s: String) -> Cow<'a, str>

Performs the conversion.

impl<'a, T> From<&'a Vec<T>> for Cow<'a, [T]> where
    T: Clone, 

fn from(v: &'a Vec<T>) -> Cow<'a, [T]>

Performs the conversion.

impl<'a> From<Cow<'a, str>> for String

fn from(s: Cow<'a, str>) -> String

Performs the conversion.

impl<'a, T> From<&'a [T]> for Cow<'a, [T]> where
    T: Clone, 

fn from(s: &'a [T]) -> Cow<'a, [T]>

Performs the conversion.

impl<'a> From<&'a str> for Cow<'a, str>

fn from(s: &'a str) -> Cow<'a, str>

Performs the conversion.

impl<'a> From<&'a String> for Cow<'a, str>

fn from(s: &'a String) -> Cow<'a, str>

Performs the conversion.

impl<'_, B> Ord for Cow<'_, B> where
    B: Ord + ToOwned + ?Sized, 

fn cmp(&self, other: &Cow<'_, B>) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

🔬 This is a nightly-only experimental API. (clamp #44095)

Restrict a value to a certain interval.

impl<'a, 'b> PartialEq<str> for Cow<'a, str>

fn eq(&self, other: &str) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &str) -> bool

This method tests for !=.

impl<'a, 'b, A, B> PartialEq<Vec<B>> for Cow<'a, [A]> where
    A: Clone + PartialEq<B>, 

fn eq(&self, other: &Vec<B>) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Vec<B>) -> bool

This method tests for !=.

impl<'a, 'b, A, B> PartialEq<&'b [B]> for Cow<'a, [A]> where
    A: Clone + PartialEq<B>, 

fn eq(&self, other: &&'b [B]) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &&'b [B]) -> bool

This method tests for !=.

impl<'a, 'b, A, B> PartialEq<&'b mut [B]> for Cow<'a, [A]> where
    A: Clone + PartialEq<B>, 

fn eq(&self, other: &&'b mut [B]) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &&'b mut [B]) -> bool

This method tests for !=.

impl<'a, 'b> PartialEq<Cow<'a, str>> for String

fn eq(&self, other: &Cow<'a, str>) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Cow<'a, str>) -> bool

This method tests for !=.

impl<'a, 'b> PartialEq<String> for Cow<'a, str>

fn eq(&self, other: &String) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &String) -> bool

This method tests for !=.

impl<'a, 'b, B, C> PartialEq<Cow<'b, C>> for Cow<'a, B> where
    B: PartialEq<C> + ToOwned + ?Sized,
    C: ToOwned + ?Sized, 

fn eq(&self, other: &Cow<'b, C>) -> bool

This method tests for self and other values to be equal, and is used by ==.

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a, 'b> PartialEq<Cow<'a, str>> for &'b str

fn eq(&self, other: &Cow<'a, str>) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Cow<'a, str>) -> bool

This method tests for !=.

impl<'a, 'b> PartialEq<&'b str> for Cow<'a, str>

fn eq(&self, other: &&'b str) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &&'b str) -> bool

This method tests for !=.

impl<'a, 'b> PartialEq<Cow<'a, str>> for str

fn eq(&self, other: &Cow<'a, str>) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Cow<'a, str>) -> bool

This method tests for !=.

impl<'_, B> Clone for Cow<'_, B> where
    B: ToOwned + ?Sized, 

fn clone(&self) -> Cow<'_, B>

Returns a copy of the value.

fn clone_from(&mut self, source: &Cow<'_, B>)

Performs copy-assignment from source.

impl<'a> AddAssign<Cow<'a, str>> for Cow<'a, str>

fn add_assign(&mut self, rhs: Cow<'a, str>)

Performs the += operation.

impl<'a> AddAssign<&'a str> for Cow<'a, str>

fn add_assign(&mut self, rhs: &'a str)

Performs the += operation.

impl<'_, B> Default for Cow<'_, B> where
    B: ToOwned + ?Sized,
    <B as ToOwned>::Owned: Default, 

fn default() -> Cow<'_, B>

Creates an owned Cow<'a, B> with the default value for the contained owned value.

impl<'a> Add<Cow<'a, str>> for Cow<'a, str>

type Output = Cow<'a, str>

The resulting type after applying the + operator.

fn add(self, rhs: Cow<'a, str>) -> <Cow<'a, str> as Add<Cow<'a, str>>>::Output

Performs the + operation.

impl<'a> Add<&'a str> for Cow<'a, str>

type Output = Cow<'a, str>

The resulting type after applying the + operator.

fn add(self, rhs: &'a str) -> <Cow<'a, str> as Add<&'a str>>::Output

Performs the + operation.

impl<'_, B> Display for Cow<'_, B> where
    B: Display + ToOwned + ?Sized,
    <B as ToOwned>::Owned: Display, 

fn fmt(&self, f: &mut Formatter) -> Result<(), Error>

Formats the value using the given formatter.

impl<'_, B> Debug for Cow<'_, B> where
    B: Debug + ToOwned + ?Sized,
    <B as ToOwned>::Owned: Debug, 

fn fmt(&self, f: &mut Formatter) -> Result<(), Error>

Formats the value using the given formatter.

impl<'a, B> Borrow<B> for Cow<'a, B> where
    B: ToOwned + ?Sized,
    <B as ToOwned>::Owned: 'a, 

Important traits for &'_ mut F

impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,  type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<'_, R: Read + ?Sized> Read for &'_ mut Rimpl<'_, W: Write + ?Sized> Write for &'_ mut W

fn borrow(&self) -> &B

Immutably borrows from an owned value.

impl<'_, T> AsRef<T> for Cow<'_, T> where
    T: ToOwned + ?Sized, 

Important traits for &'_ mut F

impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,  type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<'_, R: Read + ?Sized> Read for &'_ mut Rimpl<'_, W: Write + ?Sized> Write for &'_ mut W

fn as_ref(&self) -> &T

Performs the conversion.

impl<'_> ToString for Cow<'_, str>

fn to_string(&self) -> String

Converts the given value to a String.

impl<'a> FromIterator<String> for Cow<'a, str>

fn from_iter<I>(it: I) -> Cow<'a, str> where
    I: IntoIterator<Item = String>, 

Creates a value from an iterator.

impl<'a> FromIterator<Cow<'a, str>> for String

fn from_iter<I>(iter: I) -> String where
    I: IntoIterator<Item = Cow<'a, str>>, 

Creates a value from an iterator.

impl<'a, 'b> FromIterator<&'b str> for Cow<'a, str>

fn from_iter<I>(it: I) -> Cow<'a, str> where
    I: IntoIterator<Item = &'b str>, 

Creates a value from an iterator.

impl<'a, T> FromIterator<T> for Cow<'a, [T]> where
    T: Clone, 

fn from_iter<I>(it: I) -> Cow<'a, [T]> where
    I: IntoIterator<Item = T>, 

Creates a value from an iterator.

impl<'a> FromIterator<char> for Cow<'a, str>

fn from_iter<I>(it: I) -> Cow<'a, str> where
    I: IntoIterator<Item = char>, 

Creates a value from an iterator.

impl<'_, B> Deref for Cow<'_, B> where
    B: ToOwned + ?Sized, 

type Target = B

The resulting type after dereferencing.

Important traits for &'_ mut F

impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,  type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<'_, R: Read + ?Sized> Read for &'_ mut Rimpl<'_, W: Write + ?Sized> Write for &'_ mut W

fn deref(&self) -> &B

Dereferences the value.

impl<'a, 'b> PartialEq<OsStr> for Cow<'a, OsStr>

fn eq(&self, other: &OsStr) -> bool

This method tests for self and other values to be equal, and is used by ==.

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a, 'b> PartialEq<Cow<'a, OsStr>> for OsStr

fn eq(&self, other: &Cow<'a, OsStr>) -> bool

This method tests for self and other values to be equal, and is used by ==.

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a, 'b> PartialEq<&'b OsStr> for Cow<'a, OsStr>

fn eq(&self, other: &&'b OsStr) -> bool

This method tests for self and other values to be equal, and is used by ==.

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a, 'b> PartialEq<Cow<'a, OsStr>> for &'b OsStr

fn eq(&self, other: &Cow<'a, OsStr>) -> bool

This method tests for self and other values to be equal, and is used by ==.

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a, 'b> PartialEq<OsString> for Cow<'a, OsStr>

fn eq(&self, other: &OsString) -> bool

This method tests for self and other values to be equal, and is used by ==.

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a, 'b> PartialEq<Cow<'a, OsStr>> for OsString

fn eq(&self, other: &Cow<'a, OsStr>) -> bool

This method tests for self and other values to be equal, and is used by ==.

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a, 'b> PartialEq<Path> for Cow<'a, Path>

fn eq(&self, other: &Path) -> bool

This method tests for self and other values to be equal, and is used by ==.

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a, 'b> PartialEq<Cow<'a, Path>> for Path

fn eq(&self, other: &Cow<'a, Path>) -> bool

This method tests for self and other values to be equal, and is used by ==.

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a, 'b> PartialEq<&'b Path> for Cow<'a, Path>

fn eq(&self, other: &&'b Path) -> bool

This method tests for self and other values to be equal, and is used by ==.

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a, 'b> PartialEq<Cow<'a, Path>> for &'b Path

fn eq(&self, other: &Cow<'a, Path>) -> bool

This method tests for self and other values to be equal, and is used by ==.

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a, 'b> PartialEq<PathBuf> for Cow<'a, Path>

fn eq(&self, other: &PathBuf) -> bool

This method tests for self and other values to be equal, and is used by ==.

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a, 'b> PartialEq<Cow<'a, Path>> for PathBuf

fn eq(&self, other: &Cow<'a, Path>) -> bool

This method tests for self and other values to be equal, and is used by ==.

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a, 'b> PartialEq<Cow<'a, OsStr>> for PathBuf

fn eq(&self, other: &Cow<'a, OsStr>) -> bool

This method tests for self and other values to be equal, and is used by ==.

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a, 'b> PartialEq<PathBuf> for Cow<'a, OsStr>

fn eq(&self, other: &PathBuf) -> bool

This method tests for self and other values to be equal, and is used by ==.

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a, 'b> PartialEq<Cow<'a, OsStr>> for Path

fn eq(&self, other: &Cow<'a, OsStr>) -> bool

This method tests for self and other values to be equal, and is used by ==.

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a, 'b> PartialEq<Path> for Cow<'a, OsStr>

fn eq(&self, other: &Path) -> bool

This method tests for self and other values to be equal, and is used by ==.

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a, 'b> PartialEq<Cow<'b, OsStr>> for &'a Path

fn eq(&self, other: &Cow<'b, OsStr>) -> bool

This method tests for self and other values to be equal, and is used by ==.

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a, 'b> PartialEq<&'a Path> for Cow<'b, OsStr>

fn eq(&self, other: &&'a Path) -> bool

This method tests for self and other values to be equal, and is used by ==.

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a, 'b> PartialEq<OsStr> for Cow<'a, Path>

fn eq(&self, other: &OsStr) -> bool

This method tests for self and other values to be equal, and is used by ==.

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a, 'b> PartialEq<Cow<'a, Path>> for OsStr

fn eq(&self, other: &Cow<'a, Path>) -> bool

This method tests for self and other values to be equal, and is used by ==.

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a, 'b> PartialEq<&'b OsStr> for Cow<'a, Path>

fn eq(&self, other: &&'b OsStr) -> bool

This method tests for self and other values to be equal, and is used by ==.

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a, 'b> PartialEq<Cow<'a, Path>> for &'b OsStr

fn eq(&self, other: &Cow<'a, Path>) -> bool

This method tests for self and other values to be equal, and is used by ==.

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a, 'b> PartialEq<OsString> for Cow<'a, Path>

fn eq(&self, other: &OsString) -> bool

This method tests for self and other values to be equal, and is used by ==.

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a, 'b> PartialEq<Cow<'a, Path>> for OsString

fn eq(&self, other: &Cow<'a, Path>) -> bool

This method tests for self and other values to be equal, and is used by ==.

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a, 'b> PartialOrd<OsStr> for Cow<'a, OsStr>

fn partial_cmp(&self, other: &OsStr) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

#[must_use] fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

#[must_use] fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

#[must_use] fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

#[must_use] fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl<'a, 'b> PartialOrd<Cow<'a, OsStr>> for OsStr

fn partial_cmp(&self, other: &Cow<'a, OsStr>) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

#[must_use] fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

#[must_use] fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

#[must_use] fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

#[must_use] fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl<'a, 'b> PartialOrd<&'b OsStr> for Cow<'a, OsStr>

fn partial_cmp(&self, other: &&'b OsStr) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

#[must_use] fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

#[must_use] fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

#[must_use] fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

#[must_use] fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl<'a, 'b> PartialOrd<Cow<'a, OsStr>> for &'b OsStr

fn partial_cmp(&self, other: &Cow<'a, OsStr>) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

#[must_use] fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

#[must_use] fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

#[must_use] fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

#[must_use] fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl<'a, 'b> PartialOrd<OsString> for Cow<'a, OsStr>

fn partial_cmp(&self, other: &OsString) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

#[must_use] fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

#[must_use] fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

#[must_use] fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

#[must_use] fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl<'a, 'b> PartialOrd<Cow<'a, OsStr>> for OsString

fn partial_cmp(&self, other: &Cow<'a, OsStr>) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

#[must_use] fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

#[must_use] fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

#[must_use] fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

#[must_use] fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl<'a, 'b> PartialOrd<Path> for Cow<'a, Path>

fn partial_cmp(&self, other: &Path) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

#[must_use] fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

#[must_use] fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

#[must_use] fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

#[must_use] fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl<'a, 'b> PartialOrd<Cow<'a, Path>> for Path

fn partial_cmp(&self, other: &Cow<'a, Path>) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

#[must_use] fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

#[must_use] fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

#[must_use] fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

#[must_use] fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl<'a, 'b> PartialOrd<&'b Path> for Cow<'a, Path>

fn partial_cmp(&self, other: &&'b Path) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

#[must_use] fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

#[must_use] fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

#[must_use] fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

#[must_use] fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl<'a, 'b> PartialOrd<Cow<'a, Path>> for &'b Path

fn partial_cmp(&self, other: &Cow<'a, Path>) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

#[must_use] fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

#[must_use] fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

#[must_use] fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

#[must_use] fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl<'a, 'b> PartialOrd<PathBuf> for Cow<'a, Path>

fn partial_cmp(&self, other: &PathBuf) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

#[must_use] fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

#[must_use] fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

#[must_use] fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

#[must_use] fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl<'a, 'b> PartialOrd<Cow<'a, Path>> for PathBuf

fn partial_cmp(&self, other: &Cow<'a, Path>) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

#[must_use] fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

#[must_use] fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

#[must_use] fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

#[must_use] fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl<'a, 'b> PartialOrd<Cow<'a, OsStr>> for PathBuf

fn partial_cmp(&self, other: &Cow<'a, OsStr>) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

#[must_use] fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

#[must_use] fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

#[must_use] fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

#[must_use] fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl<'a, 'b> PartialOrd<PathBuf> for Cow<'a, OsStr>

fn partial_cmp(&self, other: &PathBuf) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

#[must_use] fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

#[must_use] fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

#[must_use] fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

#[must_use] fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl<'a, 'b> PartialOrd<Cow<'a, OsStr>> for Path

fn partial_cmp(&self, other: &Cow<'a, OsStr>) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

#[must_use] fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

#[must_use] fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

#[must_use] fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

#[must_use] fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl<'a, 'b> PartialOrd<Path> for Cow<'a, OsStr>

fn partial_cmp(&self, other: &Path) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

#[must_use] fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

#[must_use] fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

#[must_use] fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

#[must_use] fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl<'a, 'b> PartialOrd<Cow<'b, OsStr>> for &'a Path

fn partial_cmp(&self, other: &Cow<'b, OsStr>) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

#[must_use] fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

#[must_use] fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

#[must_use] fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

#[must_use] fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl<'a, 'b> PartialOrd<&'a Path> for Cow<'b, OsStr>

fn partial_cmp(&self, other: &&'a Path) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

#[must_use] fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

#[must_use] fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

#[must_use] fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

#[must_use] fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl<'a, 'b> PartialOrd<OsStr> for Cow<'a, Path>

fn partial_cmp(&self, other: &OsStr) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

#[must_use] fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

#[must_use] fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

#[must_use] fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

#[must_use] fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl<'a, 'b> PartialOrd<Cow<'a, Path>> for OsStr

fn partial_cmp(&self, other: &Cow<'a, Path>) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

#[must_use] fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

#[must_use] fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

#[must_use] fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

#[must_use] fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl<'a, 'b> PartialOrd<&'b OsStr> for Cow<'a, Path>

fn partial_cmp(&self, other: &&'b OsStr) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

#[must_use] fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

#[must_use] fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

#[must_use] fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

#[must_use] fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl<'a, 'b> PartialOrd<Cow<'a, Path>> for &'b OsStr

fn partial_cmp(&self, other: &Cow<'a, Path>) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

#[must_use] fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

#[must_use] fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

#[must_use] fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

#[must_use] fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl<'a, 'b> PartialOrd<OsString> for Cow<'a, Path>

fn partial_cmp(&self, other: &OsString) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

#[must_use] fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

#[must_use] fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

#[must_use] fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

#[must_use] fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl<'a, 'b> PartialOrd<Cow<'a, Path>> for OsString

fn partial_cmp(&self, other: &Cow<'a, Path>) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

#[must_use] fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

#[must_use] fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

#[must_use] fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

#[must_use] fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl<'_> AsRef<Path> for Cow<'_, OsStr>

fn as_ref(&self) -> &Path

Performs the conversion.

impl<'a, 'b> From<Cow<'b, str>> for Box<dyn Error + Send + Sync + 'a>

Important traits for Box<I>

impl<I> Iterator for Box<I> where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<F> Future for Box<F> where
    F: Unpin + Future + ?Sized,  type Output = <F as Future>::Output;impl<R: Read + ?Sized> Read for Box<R>impl<W: Write + ?Sized> Write for Box<W>

fn from(err: Cow<'b, str>) -> Box<dyn Error + Send + Sync + 'a>

Converts a Cow into a box of dyn Error + Send + Sync.

Examples

use std::error::Error;
use std::mem;
use std::borrow::Cow;

let a_cow_str_error = Cow::from("a str error");
let a_boxed_error = Box::<dyn Error + Send + Sync>::from(a_cow_str_error);
assert!(
    mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error))

impl<'a> From<Cow<'a, str>> for Box<dyn Error>

Important traits for Box<I>

impl<I> Iterator for Box<I> where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<F> Future for Box<F> where
    F: Unpin + Future + ?Sized,  type Output = <F as Future>::Output;impl<R: Read + ?Sized> Read for Box<R>impl<W: Write + ?Sized> Write for Box<W>

fn from(err: Cow<'a, str>) -> Box<dyn Error>

Converts a Cow into a box of dyn Error.

Examples

use std::error::Error;
use std::mem;
use std::borrow::Cow;

let a_cow_str_error = Cow::from("a str error");
let a_boxed_error = Box::<dyn Error>::from(a_cow_str_error);
assert!(mem::size_of::<Box<dyn Error>>() == mem::size_of_val(&a_boxed_error))

impl<'a> From<Cow<'a, CStr>> for CString

fn from(s: Cow<'a, CStr>) -> Self

Performs the conversion.

impl<'a> From<CString> for Cow<'a, CStr>

fn from(s: CString) -> Cow<'a, CStr>

Performs the conversion.

impl<'a> From<&'a CStr> for Cow<'a, CStr>

fn from(s: &'a CStr) -> Cow<'a, CStr>

Performs the conversion.

impl<'a> From<&'a CString> for Cow<'a, CStr>

fn from(s: &'a CString) -> Cow<'a, CStr>

Performs the conversion.

impl<'a> From<OsString> for Cow<'a, OsStr>

fn from(s: OsString) -> Cow<'a, OsStr>

Performs the conversion.

impl<'a> From<&'a OsStr> for Cow<'a, OsStr>

fn from(s: &'a OsStr) -> Cow<'a, OsStr>

Performs the conversion.

impl<'a> From<&'a OsString> for Cow<'a, OsStr>

fn from(s: &'a OsString) -> Cow<'a, OsStr>

Performs the conversion.

impl<'a> From<Cow<'a, OsStr>> for OsString

fn from(s: Cow<'a, OsStr>) -> Self

Performs the conversion.

impl<'a> From<&'a Path> for Cow<'a, Path>

fn from(s: &'a Path) -> Cow<'a, Path>

Performs the conversion.

impl<'a> From<PathBuf> for Cow<'a, Path>

fn from(s: PathBuf) -> Cow<'a, Path>

Performs the conversion.

impl<'a> From<&'a PathBuf> for Cow<'a, Path>

fn from(p: &'a PathBuf) -> Cow<'a, Path>

Performs the conversion.

impl<'a> From<Cow<'a, Path>> for PathBuf

fn from(p: Cow<'a, Path>) -> Self

Performs the conversion.