Enum collections::borrow::Cow [] [src]

pub enum Cow<'a, B: ?Sized + 'a> where B: ToOwned {
    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

fn main() { use std::borrow::Cow; #[allow(dead_code)] 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; } } } }
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: ?Sized> Cow<'a, B> where B: ToOwned

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

fn main() { 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]); }
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

fn main() { 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); }
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: ?Sized> Borrow<B> for Cow<'a, B> where B: ToOwned, B::Owned: 'a

fn borrow(&self) -> &B

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

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

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

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

type Target = B

fn deref(&self) -> &B

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

impl<'a, 'b, A: Clone, B> PartialEq<Vec<B>> for Cow<'a, [A]> where A: 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: IntoIterator<Item=T>>(it: I) -> Cow<'a, [T]>