Enum std::borrow::Cow

pub enum Cow<'a, B> where B: 'a + ToOwned + ?Sized {
    Borrowed(&'a B),
    Owned(B::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 the first time (if not already owned)
            input.to_mut()[i] = -v;
        }
    }
}

Variants

Borrowed	Borrowed data.
Owned	Owned data.

Methods

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

fn to_mut(&mut self) -> &mut B::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<[_]> = Cow::Owned(vec![1, 2, 3]);

let hello = cow.to_mut();

assert_eq!(hello, &[1, 2, 3]);

fn into_owned(self) -> B::Owned

Extracts the owned data.

Clones the data if it is not already owned.

Examples

use std::borrow::Cow;

let cow: Cow<[_]> = Cow::Owned(vec![1, 2, 3]);

let hello = cow.into_owned();

assert_eq!(vec![1, 2, 3], hello);

Trait Implementations

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

fn borrow(&self) -> &B

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

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

fn clone_from(&mut self, source: &Self)

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

type Target = B

fn deref(&self) -> &B

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

fn assert_receiver_is_total_eq(&self)

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

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

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

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

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>

fn lt(&self, other: &Rhs) -> bool

fn le(&self, other: &Rhs) -> bool

fn gt(&self, other: &Rhs) -> bool

fn ge(&self, other: &Rhs) -> bool

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

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

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

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

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

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

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

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

fn into_cow(self) -> Cow<'a, B>

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

fn as_ref(&self) -> &T

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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>