Enum boo::Boo

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

A clone-on-write smart pointer.

The type Boo 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.

Boo 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::Boo;

fn abs_all(input: &mut Boo<[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 = Boo::from(&slice[..]);
abs_all(&mut input);

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

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

Variants

Borrowed(&'a B)

Borrowed data.

Owned(<B as ToOwned>::Owned)

Owned data.

Methods

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

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::Boo;

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

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

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 Boo::Borrowed clones the underlying data and becomes a Boo::Owned:

use std::borrow::Boo;

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

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

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

use std::borrow::Boo;

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

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

Trait Implementations

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

fn borrow(&self) -> &B

Immutably borrows from an owned value.

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

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

Returns a copy of the value.

fn clone_from(&mut self, source: &Boo<'a, B>)

Performs copy-assignment from source.

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

type Target = B

The resulting type after dereferencing.

fn deref(&self) -> &B

Dereferences the value.

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

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

fn cmp(&self, other: &Boo<'a, 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.

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

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

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

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

This method tests for !=.

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

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

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

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

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

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

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

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

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

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

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

Formats the value using the given formatter.

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

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

Formats the value using the given formatter.

impl<'a, B: ?Sized> Default for Boo<'a, B> where
    B: ToOwned,
    <B as ToOwned>::Owned: Default, 

fn default() -> Boo<'a, B>

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

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

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

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

fn as_ref(&self) -> &T

Performs the conversion.