pub enum Cow<'a, B> where
B: 'a + ToOwned + ?Sized, {
Borrowed(&'a B),
Owned(<B as ToOwned>::Owned),
}
Expand description
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.
If you need reference-counting pointers, note that
Rc::make_mut
and
Arc::make_mut
can provide clone-on-write
functionality as well.
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's 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.
Implementations
sourceimpl<'_, B> Cow<'_, B> where
B: ToOwned + ?Sized,
impl<'_, B> Cow<'_, B> where
B: ToOwned + ?Sized,
const: unstable · sourcepub fn is_borrowed(&self) -> bool
🔬 This is a nightly-only experimental API. (cow_is_borrowed
)
pub fn is_borrowed(&self) -> bool
cow_is_borrowed
)Returns true if the data is borrowed, i.e. if to_mut
would require additional work.
Examples
#![feature(cow_is_borrowed)]
use std::borrow::Cow;
let cow = Cow::Borrowed("moo");
assert!(cow.is_borrowed());
let bull: Cow<'_, str> = Cow::Owned("...moo?".to_string());
assert!(!bull.is_borrowed());
const: unstable · sourcepub fn is_owned(&self) -> bool
🔬 This is a nightly-only experimental API. (cow_is_borrowed
)
pub fn is_owned(&self) -> bool
cow_is_borrowed
)Returns true if the data is owned, i.e. if to_mut
would be a no-op.
Examples
#![feature(cow_is_borrowed)]
use std::borrow::Cow;
let cow: Cow<'_, str> = Cow::Owned("moo".to_string());
assert!(cow.is_owned());
let bull = Cow::Borrowed("...moo?");
assert!(!bull.is_owned());
sourcepub fn to_mut(&mut self) -> &mut <B as ToOwned>::Owned
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>
);
sourcepub fn into_owned(self) -> <B as ToOwned>::Owned
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
1.14.0 · sourceimpl<'a> AddAssign<&'a str> for Cow<'a, str>
impl<'a> AddAssign<&'a str> for Cow<'a, str>
sourcefn add_assign(&mut self, rhs: &'a str)
fn add_assign(&mut self, rhs: &'a str)
Performs the +=
operation. Read more
1.14.0 · sourceimpl<'a> AddAssign<Cow<'a, str>> for Cow<'a, str>
impl<'a> AddAssign<Cow<'a, str>> for Cow<'a, str>
sourcefn add_assign(&mut self, rhs: Cow<'a, str>)
fn add_assign(&mut self, rhs: Cow<'a, str>)
Performs the +=
operation. Read more
sourceimpl<'_, T> BorshDeserialize for Cow<'_, T> where
T: ToOwned + ?Sized,
<T as ToOwned>::Owned: BorshDeserialize,
impl<'_, T> BorshDeserialize for Cow<'_, T> where
T: ToOwned + ?Sized,
<T as ToOwned>::Owned: BorshDeserialize,
sourceimpl<'_, T> BorshSerialize for Cow<'_, T> where
T: BorshSerialize + ToOwned + ?Sized,
impl<'_, T> BorshSerialize for Cow<'_, T> where
T: BorshSerialize + ToOwned + ?Sized,
sourceimpl<'_, B> Debug for Cow<'_, B> where
B: Debug + ToOwned + ?Sized,
<B as ToOwned>::Owned: Debug,
impl<'_, B> Debug for Cow<'_, B> where
B: Debug + ToOwned + ?Sized,
<B as ToOwned>::Owned: Debug,
sourceimpl<'a, T> Decode for Cow<'a, T> where
T: ToOwned + ?Sized,
<T as ToOwned>::Owned: Decode,
impl<'a, T> Decode for Cow<'a, T> where
T: ToOwned + ?Sized,
<T as ToOwned>::Owned: Decode,
sourcefn decode<I>(input: &mut I) -> Result<Cow<'a, T>, Error> where
I: Input,
fn decode<I>(input: &mut I) -> Result<Cow<'a, T>, Error> where
I: Input,
Attempt to deserialise the value from input.
sourcefn skip<I>(input: &mut I) -> Result<(), Error> where
I: Input,
fn skip<I>(input: &mut I) -> Result<(), Error> where
I: Input,
Attempt to skip the encoded value from input. Read more
sourcefn encoded_fixed_size() -> Option<usize>
fn encoded_fixed_size() -> Option<usize>
Returns the fixed encoded size of the type. Read more
1.11.0 · sourceimpl<'_, B> Default for Cow<'_, B> where
B: ToOwned + ?Sized,
<B as ToOwned>::Owned: Default,
impl<'_, B> Default for Cow<'_, B> where
B: ToOwned + ?Sized,
<B as ToOwned>::Owned: Default,
const: unstable · sourceimpl<'_, B> Deref for Cow<'_, B> where
B: ToOwned + ?Sized,
<B as ToOwned>::Owned: Borrow<B>,
impl<'_, B> Deref for Cow<'_, B> where
B: ToOwned + ?Sized,
<B as ToOwned>::Owned: Borrow<B>,
sourceimpl<'de, 'a, T> Deserialize<'de> for Cow<'a, T> where
T: ToOwned + ?Sized,
<T as ToOwned>::Owned: Deserialize<'de>,
impl<'de, 'a, T> Deserialize<'de> for Cow<'a, T> where
T: ToOwned + ?Sized,
<T as ToOwned>::Owned: Deserialize<'de>,
sourcefn deserialize<D>(
deserializer: D
) -> Result<Cow<'a, T>, <D as Deserializer<'de>>::Error> where
D: Deserializer<'de>,
fn deserialize<D>(
deserializer: D
) -> Result<Cow<'a, T>, <D as Deserializer<'de>>::Error> where
D: Deserializer<'de>,
Deserialize this value from the given Serde deserializer. Read more
sourceimpl<'_, B> Display for Cow<'_, B> where
B: Display + ToOwned + ?Sized,
<B as ToOwned>::Owned: Display,
impl<'_, B> Display for Cow<'_, B> where
B: Display + ToOwned + ?Sized,
<B as ToOwned>::Owned: Display,
1.19.0 · sourceimpl<'a> Extend<Cow<'a, str>> for String
impl<'a> Extend<Cow<'a, str>> for String
sourcefn extend<I>(&mut self, iter: I) where
I: IntoIterator<Item = Cow<'a, str>>,
fn extend<I>(&mut self, iter: I) where
I: IntoIterator<Item = Cow<'a, str>>,
Extends a collection with the contents of an iterator. Read more
sourcefn extend_one(&mut self, s: Cow<'a, str>)
fn extend_one(&mut self, s: Cow<'a, str>)
extend_one
)Extends a collection with exactly one element.
sourcefn extend_reserve(&mut self, additional: usize)
fn extend_reserve(&mut self, additional: usize)
extend_one
)Reserves capacity in a collection for the given number of additional elements. Read more
1.45.0 · sourceimpl<'_, T> From<Cow<'_, [T]>> for Box<[T], Global> where
T: Copy,
impl<'_, T> From<Cow<'_, [T]>> for Box<[T], Global> where
T: Copy,
sourcefn from(cow: Cow<'_, [T]>) -> Box<[T], Global>ⓘNotable traits for Box<R, Global>impl<R> Read for Box<R, Global> where
R: Read + ?Sized, impl<W> Write for Box<W, Global> where
W: Write + ?Sized, impl<I, A> Iterator for Box<I, A> where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;impl<F, A> Future for Box<F, A> where
F: Future + Unpin + ?Sized,
A: Allocator + 'static, type Output = <F as Future>::Output;
fn from(cow: Cow<'_, [T]>) -> Box<[T], Global>ⓘNotable traits for Box<R, Global>impl<R> Read for Box<R, Global> where
R: Read + ?Sized, impl<W> Write for Box<W, Global> where
W: Write + ?Sized, impl<I, A> Iterator for Box<I, A> where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;impl<F, A> Future for Box<F, A> where
F: Future + Unpin + ?Sized,
A: Allocator + 'static, type Output = <F as Future>::Output;
R: Read + ?Sized, impl<W> Write for Box<W, Global> where
W: Write + ?Sized, impl<I, A> Iterator for Box<I, A> where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;impl<F, A> Future for Box<F, A> where
F: Future + Unpin + ?Sized,
A: Allocator + 'static, type Output = <F as Future>::Output;
Converts a Cow<'_, [T]>
into a Box<[T]>
When cow
is the Cow::Borrowed
variant, this
conversion allocates on the heap and copies the
underlying slice. Otherwise, it will try to reuse the owned
Vec
’s allocation.
1.45.0 · sourceimpl<'_> From<Cow<'_, CStr>> for Box<CStr, Global>
impl<'_> From<Cow<'_, CStr>> for Box<CStr, Global>
sourcefn from(cow: Cow<'_, CStr>) -> Box<CStr, Global>ⓘNotable traits for Box<R, Global>impl<R> Read for Box<R, Global> where
R: Read + ?Sized, impl<W> Write for Box<W, Global> where
W: Write + ?Sized, impl<I, A> Iterator for Box<I, A> where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;impl<F, A> Future for Box<F, A> where
F: Future + Unpin + ?Sized,
A: Allocator + 'static, type Output = <F as Future>::Output;
fn from(cow: Cow<'_, CStr>) -> Box<CStr, Global>ⓘNotable traits for Box<R, Global>impl<R> Read for Box<R, Global> where
R: Read + ?Sized, impl<W> Write for Box<W, Global> where
W: Write + ?Sized, impl<I, A> Iterator for Box<I, A> where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;impl<F, A> Future for Box<F, A> where
F: Future + Unpin + ?Sized,
A: Allocator + 'static, type Output = <F as Future>::Output;
R: Read + ?Sized, impl<W> Write for Box<W, Global> where
W: Write + ?Sized, impl<I, A> Iterator for Box<I, A> where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;impl<F, A> Future for Box<F, A> where
F: Future + Unpin + ?Sized,
A: Allocator + 'static, type Output = <F as Future>::Output;
Converts a Cow<'a, CStr>
into a Box<CStr>
,
by copying the contents if they are borrowed.
1.45.0 · sourceimpl<'_> From<Cow<'_, OsStr>> for Box<OsStr, Global>
impl<'_> From<Cow<'_, OsStr>> for Box<OsStr, Global>
sourcefn from(cow: Cow<'_, OsStr>) -> Box<OsStr, Global>ⓘNotable traits for Box<R, Global>impl<R> Read for Box<R, Global> where
R: Read + ?Sized, impl<W> Write for Box<W, Global> where
W: Write + ?Sized, impl<I, A> Iterator for Box<I, A> where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;impl<F, A> Future for Box<F, A> where
F: Future + Unpin + ?Sized,
A: Allocator + 'static, type Output = <F as Future>::Output;
fn from(cow: Cow<'_, OsStr>) -> Box<OsStr, Global>ⓘNotable traits for Box<R, Global>impl<R> Read for Box<R, Global> where
R: Read + ?Sized, impl<W> Write for Box<W, Global> where
W: Write + ?Sized, impl<I, A> Iterator for Box<I, A> where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;impl<F, A> Future for Box<F, A> where
F: Future + Unpin + ?Sized,
A: Allocator + 'static, type Output = <F as Future>::Output;
R: Read + ?Sized, impl<W> Write for Box<W, Global> where
W: Write + ?Sized, impl<I, A> Iterator for Box<I, A> where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;impl<F, A> Future for Box<F, A> where
F: Future + Unpin + ?Sized,
A: Allocator + 'static, type Output = <F as Future>::Output;
1.45.0 · sourceimpl<'_> From<Cow<'_, Path>> for Box<Path, Global>
impl<'_> From<Cow<'_, Path>> for Box<Path, Global>
sourcefn from(cow: Cow<'_, Path>) -> Box<Path, Global>ⓘNotable traits for Box<R, Global>impl<R> Read for Box<R, Global> where
R: Read + ?Sized, impl<W> Write for Box<W, Global> where
W: Write + ?Sized, impl<I, A> Iterator for Box<I, A> where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;impl<F, A> Future for Box<F, A> where
F: Future + Unpin + ?Sized,
A: Allocator + 'static, type Output = <F as Future>::Output;
fn from(cow: Cow<'_, Path>) -> Box<Path, Global>ⓘNotable traits for Box<R, Global>impl<R> Read for Box<R, Global> where
R: Read + ?Sized, impl<W> Write for Box<W, Global> where
W: Write + ?Sized, impl<I, A> Iterator for Box<I, A> where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;impl<F, A> Future for Box<F, A> where
F: Future + Unpin + ?Sized,
A: Allocator + 'static, type Output = <F as Future>::Output;
R: Read + ?Sized, impl<W> Write for Box<W, Global> where
W: Write + ?Sized, impl<I, A> Iterator for Box<I, A> where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;impl<F, A> Future for Box<F, A> where
F: Future + Unpin + ?Sized,
A: Allocator + 'static, type Output = <F as Future>::Output;
Creates a boxed Path
from a clone-on-write pointer.
Converting from a Cow::Owned
does not clone or allocate.
1.45.0 · sourceimpl<'_> From<Cow<'_, str>> for Box<str, Global>
impl<'_> From<Cow<'_, str>> for Box<str, Global>
sourcefn from(cow: Cow<'_, str>) -> Box<str, Global>ⓘNotable traits for Box<R, Global>impl<R> Read for Box<R, Global> where
R: Read + ?Sized, impl<W> Write for Box<W, Global> where
W: Write + ?Sized, impl<I, A> Iterator for Box<I, A> where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;impl<F, A> Future for Box<F, A> where
F: Future + Unpin + ?Sized,
A: Allocator + 'static, type Output = <F as Future>::Output;
fn from(cow: Cow<'_, str>) -> Box<str, Global>ⓘNotable traits for Box<R, Global>impl<R> Read for Box<R, Global> where
R: Read + ?Sized, impl<W> Write for Box<W, Global> where
W: Write + ?Sized, impl<I, A> Iterator for Box<I, A> where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;impl<F, A> Future for Box<F, A> where
F: Future + Unpin + ?Sized,
A: Allocator + 'static, type Output = <F as Future>::Output;
R: Read + ?Sized, impl<W> Write for Box<W, Global> where
W: Write + ?Sized, impl<I, A> Iterator for Box<I, A> where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;impl<F, A> Future for Box<F, A> where
F: Future + Unpin + ?Sized,
A: Allocator + 'static, type Output = <F as Future>::Output;
Converts a Cow<'_, str>
into a Box<str>
When cow
is the Cow::Borrowed
variant, this
conversion allocates on the heap and copies the
underlying str
. Otherwise, it will try to reuse the owned
String
’s allocation.
Examples
use std::borrow::Cow;
let unboxed = Cow::Borrowed("hello");
let boxed: Box<str> = Box::from(unboxed);
println!("{}", boxed);
let unboxed = Cow::Owned("hello".to_string());
let boxed: Box<str> = Box::from(unboxed);
println!("{}", boxed);
1.14.0 · sourceimpl<'a, T> From<Cow<'a, [T]>> for Vec<T, Global> where
[T]: ToOwned,
<[T] as ToOwned>::Owned == Vec<T, Global>,
impl<'a, T> From<Cow<'a, [T]>> for Vec<T, Global> where
[T]: ToOwned,
<[T] as ToOwned>::Owned == Vec<T, Global>,
sourcefn from(s: Cow<'a, [T]>) -> Vec<T, Global>ⓘNotable traits for Vec<u8, A>impl<A> Write for Vec<u8, A> where
A: Allocator,
fn from(s: Cow<'a, [T]>) -> Vec<T, Global>ⓘNotable traits for Vec<u8, A>impl<A> Write for Vec<u8, A> where
A: Allocator,
A: Allocator,
Convert a clone-on-write slice into a vector.
If s
already owns a Vec<T>
, it will be returned directly.
If s
is borrowing a slice, a new Vec<T>
will be allocated and
filled by cloning s
’s items into it.
Examples
let o: Cow<[i32]> = Cow::Owned(vec![1, 2, 3]);
let b: Cow<[i32]> = Cow::Borrowed(&[1, 2, 3]);
assert_eq!(Vec::from(o), Vec::from(b));
1.45.0 · sourceimpl<'a, B> From<Cow<'a, B>> for Arc<B> where
B: ToOwned + ?Sized,
Arc<B>: From<&'a B>,
Arc<B>: From<<B as ToOwned>::Owned>,
impl<'a, B> From<Cow<'a, B>> for Arc<B> where
B: ToOwned + ?Sized,
Arc<B>: From<&'a B>,
Arc<B>: From<<B as ToOwned>::Owned>,
1.45.0 · sourceimpl<'a, B> From<Cow<'a, B>> for Rc<B> where
B: ToOwned + ?Sized,
Rc<B>: From<&'a B>,
Rc<B>: From<<B as ToOwned>::Owned>,
impl<'a, B> From<Cow<'a, B>> for Rc<B> where
B: ToOwned + ?Sized,
Rc<B>: From<&'a B>,
Rc<B>: From<<B as ToOwned>::Owned>,
1.22.0 · sourceimpl<'a> From<Cow<'a, str>> for Box<dyn Error + 'static, Global>
impl<'a> From<Cow<'a, str>> for Box<dyn Error + 'static, Global>
sourcefn from(err: Cow<'a, str>) -> Box<dyn Error + 'static, Global>ⓘNotable traits for Box<R, Global>impl<R> Read for Box<R, Global> where
R: Read + ?Sized, impl<W> Write for Box<W, Global> where
W: Write + ?Sized, impl<I, A> Iterator for Box<I, A> where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;impl<F, A> Future for Box<F, A> where
F: Future + Unpin + ?Sized,
A: Allocator + 'static, type Output = <F as Future>::Output;
fn from(err: Cow<'a, str>) -> Box<dyn Error + 'static, Global>ⓘNotable traits for Box<R, Global>impl<R> Read for Box<R, Global> where
R: Read + ?Sized, impl<W> Write for Box<W, Global> where
W: Write + ?Sized, impl<I, A> Iterator for Box<I, A> where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;impl<F, A> Future for Box<F, A> where
F: Future + Unpin + ?Sized,
A: Allocator + 'static, type Output = <F as Future>::Output;
R: Read + ?Sized, impl<W> Write for Box<W, Global> where
W: Write + ?Sized, impl<I, A> Iterator for Box<I, A> where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;impl<F, A> Future for Box<F, A> where
F: Future + Unpin + ?Sized,
A: Allocator + 'static, type Output = <F as Future>::Output;
1.14.0 · sourceimpl<'a> From<Cow<'a, str>> for String
impl<'a> From<Cow<'a, str>> for String
sourcefn from(s: Cow<'a, str>) -> String
fn from(s: Cow<'a, str>) -> String
Converts a clone-on-write string to an owned
instance of String
.
This extracts the owned string, clones the string if it is not already owned.
Example
// If the string is not owned...
let cow: Cow<str> = Cow::Borrowed("eggplant");
// It will allocate on the heap and copy the string.
let owned: String = String::from(cow);
assert_eq!(&owned[..], "eggplant");
1.22.0 · sourceimpl<'a, 'b> From<Cow<'b, str>> for Box<dyn Error + Sync + Send + 'a, Global>
impl<'a, 'b> From<Cow<'b, str>> for Box<dyn Error + Sync + Send + 'a, Global>
sourcefn from(err: Cow<'b, str>) -> Box<dyn Error + Sync + Send + 'a, Global>ⓘNotable traits for Box<R, Global>impl<R> Read for Box<R, Global> where
R: Read + ?Sized, impl<W> Write for Box<W, Global> where
W: Write + ?Sized, impl<I, A> Iterator for Box<I, A> where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;impl<F, A> Future for Box<F, A> where
F: Future + Unpin + ?Sized,
A: Allocator + 'static, type Output = <F as Future>::Output;
fn from(err: Cow<'b, str>) -> Box<dyn Error + Sync + Send + 'a, Global>ⓘNotable traits for Box<R, Global>impl<R> Read for Box<R, Global> where
R: Read + ?Sized, impl<W> Write for Box<W, Global> where
W: Write + ?Sized, impl<I, A> Iterator for Box<I, A> where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;impl<F, A> Future for Box<F, A> where
F: Future + Unpin + ?Sized,
A: Allocator + 'static, type Output = <F as Future>::Output;
R: Read + ?Sized, impl<W> Write for Box<W, Global> where
W: Write + ?Sized, impl<I, A> Iterator for Box<I, A> where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;impl<F, A> Future for Box<F, A> where
F: Future + Unpin + ?Sized,
A: Allocator + 'static, type Output = <F as Future>::Output;
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))
1.12.0 · sourceimpl<'a, 'b> FromIterator<&'b str> for Cow<'a, str>
impl<'a, 'b> FromIterator<&'b str> for Cow<'a, str>
1.19.0 · sourceimpl<'a> FromIterator<Cow<'a, str>> for String
impl<'a> FromIterator<Cow<'a, str>> for String
1.12.0 · sourceimpl<'a> FromIterator<String> for Cow<'a, str>
impl<'a> FromIterator<String> for Cow<'a, str>
1.12.0 · sourceimpl<'a> FromIterator<char> for Cow<'a, str>
impl<'a> FromIterator<char> for Cow<'a, str>
sourceimpl<'de, 'a, E> IntoDeserializer<'de, E> for Cow<'a, str> where
E: Error,
impl<'de, 'a, E> IntoDeserializer<'de, E> for Cow<'a, str> where
E: Error,
type Deserializer = CowStrDeserializer<'a, E>
type Deserializer = CowStrDeserializer<'a, E>
The type of the deserializer being converted into.
sourcefn into_deserializer(self) -> CowStrDeserializer<'a, E>
fn into_deserializer(self) -> CowStrDeserializer<'a, E>
Convert this value into a deserializer.
sourceimpl<'_, B> Ord for Cow<'_, B> where
B: Ord + ToOwned + ?Sized,
impl<'_, B> Ord for Cow<'_, B> where
B: Ord + ToOwned + ?Sized,
sourceimpl<'a, 'b, B, C> PartialEq<Cow<'b, C>> for Cow<'a, B> where
B: PartialEq<C> + ToOwned + ?Sized,
C: ToOwned + ?Sized,
impl<'a, 'b, B, C> PartialEq<Cow<'b, C>> for Cow<'a, B> where
B: PartialEq<C> + ToOwned + ?Sized,
C: ToOwned + ?Sized,
sourceimpl<'_, T, U, A> PartialEq<Vec<U, A>> for Cow<'_, [T]> where
A: Allocator,
T: PartialEq<U> + Clone,
impl<'_, T, U, A> PartialEq<Vec<U, A>> for Cow<'_, [T]> where
A: Allocator,
T: PartialEq<U> + Clone,
1.8.0 · sourceimpl<'a, 'b> PartialOrd<&'a Path> for Cow<'b, OsStr>
impl<'a, 'b> PartialOrd<&'a Path> for Cow<'b, OsStr>
sourcefn partial_cmp(&self, other: &&'a Path) -> Option<Ordering>
fn partial_cmp(&self, other: &&'a Path) -> Option<Ordering>
This method returns an ordering between self
and other
values if one exists. Read more
sourcefn lt(&self, other: &Rhs) -> bool
fn lt(&self, other: &Rhs) -> bool
This method tests less than (for self
and other
) and is used by the <
operator. Read more
sourcefn le(&self, other: &Rhs) -> bool
fn le(&self, other: &Rhs) -> bool
This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
1.8.0 · sourceimpl<'a, 'b> PartialOrd<&'b OsStr> for Cow<'a, OsStr>
impl<'a, 'b> PartialOrd<&'b OsStr> for Cow<'a, OsStr>
sourcefn partial_cmp(&self, other: &&'b OsStr) -> Option<Ordering>
fn partial_cmp(&self, other: &&'b OsStr) -> Option<Ordering>
This method returns an ordering between self
and other
values if one exists. Read more
sourcefn lt(&self, other: &Rhs) -> bool
fn lt(&self, other: &Rhs) -> bool
This method tests less than (for self
and other
) and is used by the <
operator. Read more
sourcefn le(&self, other: &Rhs) -> bool
fn le(&self, other: &Rhs) -> bool
This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
1.8.0 · sourceimpl<'a, 'b> PartialOrd<&'b OsStr> for Cow<'a, Path>
impl<'a, 'b> PartialOrd<&'b OsStr> for Cow<'a, Path>
sourcefn partial_cmp(&self, other: &&'b OsStr) -> Option<Ordering>
fn partial_cmp(&self, other: &&'b OsStr) -> Option<Ordering>
This method returns an ordering between self
and other
values if one exists. Read more
sourcefn lt(&self, other: &Rhs) -> bool
fn lt(&self, other: &Rhs) -> bool
This method tests less than (for self
and other
) and is used by the <
operator. Read more
sourcefn le(&self, other: &Rhs) -> bool
fn le(&self, other: &Rhs) -> bool
This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
1.8.0 · sourceimpl<'a, 'b> PartialOrd<&'b Path> for Cow<'a, Path>
impl<'a, 'b> PartialOrd<&'b Path> for Cow<'a, Path>
sourcefn partial_cmp(&self, other: &&'b Path) -> Option<Ordering>
fn partial_cmp(&self, other: &&'b Path) -> Option<Ordering>
This method returns an ordering between self
and other
values if one exists. Read more
sourcefn lt(&self, other: &Rhs) -> bool
fn lt(&self, other: &Rhs) -> bool
This method tests less than (for self
and other
) and is used by the <
operator. Read more
sourcefn le(&self, other: &Rhs) -> bool
fn le(&self, other: &Rhs) -> bool
This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
sourceimpl<'a, B> PartialOrd<Cow<'a, B>> for Cow<'a, B> where
B: PartialOrd<B> + ToOwned + ?Sized,
impl<'a, B> PartialOrd<Cow<'a, B>> for Cow<'a, B> where
B: PartialOrd<B> + ToOwned + ?Sized,
sourcefn partial_cmp(&self, other: &Cow<'a, B>) -> Option<Ordering>
fn partial_cmp(&self, other: &Cow<'a, B>) -> Option<Ordering>
This method returns an ordering between self
and other
values if one exists. Read more
sourcefn lt(&self, other: &Rhs) -> bool
fn lt(&self, other: &Rhs) -> bool
This method tests less than (for self
and other
) and is used by the <
operator. Read more
sourcefn le(&self, other: &Rhs) -> bool
fn le(&self, other: &Rhs) -> bool
This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
1.8.0 · sourceimpl<'a, 'b> PartialOrd<Cow<'a, OsStr>> for &'b OsStr
impl<'a, 'b> PartialOrd<Cow<'a, OsStr>> for &'b OsStr
sourcefn partial_cmp(&self, other: &Cow<'a, OsStr>) -> Option<Ordering>
fn partial_cmp(&self, other: &Cow<'a, OsStr>) -> Option<Ordering>
This method returns an ordering between self
and other
values if one exists. Read more
sourcefn lt(&self, other: &Rhs) -> bool
fn lt(&self, other: &Rhs) -> bool
This method tests less than (for self
and other
) and is used by the <
operator. Read more
sourcefn le(&self, other: &Rhs) -> bool
fn le(&self, other: &Rhs) -> bool
This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
1.8.0 · sourceimpl<'a, 'b> PartialOrd<Cow<'a, OsStr>> for Path
impl<'a, 'b> PartialOrd<Cow<'a, OsStr>> for Path
sourcefn partial_cmp(&self, other: &Cow<'a, OsStr>) -> Option<Ordering>
fn partial_cmp(&self, other: &Cow<'a, OsStr>) -> Option<Ordering>
This method returns an ordering between self
and other
values if one exists. Read more
sourcefn lt(&self, other: &Rhs) -> bool
fn lt(&self, other: &Rhs) -> bool
This method tests less than (for self
and other
) and is used by the <
operator. Read more
sourcefn le(&self, other: &Rhs) -> bool
fn le(&self, other: &Rhs) -> bool
This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
1.8.0 · sourceimpl<'a, 'b> PartialOrd<Cow<'a, OsStr>> for OsStr
impl<'a, 'b> PartialOrd<Cow<'a, OsStr>> for OsStr
sourcefn partial_cmp(&self, other: &Cow<'a, OsStr>) -> Option<Ordering>
fn partial_cmp(&self, other: &Cow<'a, OsStr>) -> Option<Ordering>
This method returns an ordering between self
and other
values if one exists. Read more
sourcefn lt(&self, other: &Rhs) -> bool
fn lt(&self, other: &Rhs) -> bool
This method tests less than (for self
and other
) and is used by the <
operator. Read more
sourcefn le(&self, other: &Rhs) -> bool
fn le(&self, other: &Rhs) -> bool
This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
1.8.0 · sourceimpl<'a, 'b> PartialOrd<Cow<'a, Path>> for Path
impl<'a, 'b> PartialOrd<Cow<'a, Path>> for Path
sourcefn partial_cmp(&self, other: &Cow<'a, Path>) -> Option<Ordering>
fn partial_cmp(&self, other: &Cow<'a, Path>) -> Option<Ordering>
This method returns an ordering between self
and other
values if one exists. Read more
sourcefn lt(&self, other: &Rhs) -> bool
fn lt(&self, other: &Rhs) -> bool
This method tests less than (for self
and other
) and is used by the <
operator. Read more
sourcefn le(&self, other: &Rhs) -> bool
fn le(&self, other: &Rhs) -> bool
This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
1.8.0 · sourceimpl<'a, 'b> PartialOrd<Cow<'a, Path>> for OsStr
impl<'a, 'b> PartialOrd<Cow<'a, Path>> for OsStr
sourcefn partial_cmp(&self, other: &Cow<'a, Path>) -> Option<Ordering>
fn partial_cmp(&self, other: &Cow<'a, Path>) -> Option<Ordering>
This method returns an ordering between self
and other
values if one exists. Read more
sourcefn lt(&self, other: &Rhs) -> bool
fn lt(&self, other: &Rhs) -> bool
This method tests less than (for self
and other
) and is used by the <
operator. Read more
sourcefn le(&self, other: &Rhs) -> bool
fn le(&self, other: &Rhs) -> bool
This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
1.8.0 · sourceimpl<'a, 'b> PartialOrd<Cow<'a, Path>> for &'b Path
impl<'a, 'b> PartialOrd<Cow<'a, Path>> for &'b Path
sourcefn partial_cmp(&self, other: &Cow<'a, Path>) -> Option<Ordering>
fn partial_cmp(&self, other: &Cow<'a, Path>) -> Option<Ordering>
This method returns an ordering between self
and other
values if one exists. Read more
sourcefn lt(&self, other: &Rhs) -> bool
fn lt(&self, other: &Rhs) -> bool
This method tests less than (for self
and other
) and is used by the <
operator. Read more
sourcefn le(&self, other: &Rhs) -> bool
fn le(&self, other: &Rhs) -> bool
This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
1.8.0 · sourceimpl<'a, 'b> PartialOrd<Cow<'a, Path>> for &'b OsStr
impl<'a, 'b> PartialOrd<Cow<'a, Path>> for &'b OsStr
sourcefn partial_cmp(&self, other: &Cow<'a, Path>) -> Option<Ordering>
fn partial_cmp(&self, other: &Cow<'a, Path>) -> Option<Ordering>
This method returns an ordering between self
and other
values if one exists. Read more
sourcefn lt(&self, other: &Rhs) -> bool
fn lt(&self, other: &Rhs) -> bool
This method tests less than (for self
and other
) and is used by the <
operator. Read more
sourcefn le(&self, other: &Rhs) -> bool
fn le(&self, other: &Rhs) -> bool
This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
1.8.0 · sourceimpl<'a, 'b> PartialOrd<Cow<'b, OsStr>> for &'a Path
impl<'a, 'b> PartialOrd<Cow<'b, OsStr>> for &'a Path
sourcefn partial_cmp(&self, other: &Cow<'b, OsStr>) -> Option<Ordering>
fn partial_cmp(&self, other: &Cow<'b, OsStr>) -> Option<Ordering>
This method returns an ordering between self
and other
values if one exists. Read more
sourcefn lt(&self, other: &Rhs) -> bool
fn lt(&self, other: &Rhs) -> bool
This method tests less than (for self
and other
) and is used by the <
operator. Read more
sourcefn le(&self, other: &Rhs) -> bool
fn le(&self, other: &Rhs) -> bool
This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
1.8.0 · sourceimpl<'a, 'b> PartialOrd<OsStr> for Cow<'a, OsStr>
impl<'a, 'b> PartialOrd<OsStr> for Cow<'a, OsStr>
sourcefn partial_cmp(&self, other: &OsStr) -> Option<Ordering>
fn partial_cmp(&self, other: &OsStr) -> Option<Ordering>
This method returns an ordering between self
and other
values if one exists. Read more
sourcefn lt(&self, other: &Rhs) -> bool
fn lt(&self, other: &Rhs) -> bool
This method tests less than (for self
and other
) and is used by the <
operator. Read more
sourcefn le(&self, other: &Rhs) -> bool
fn le(&self, other: &Rhs) -> bool
This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
1.8.0 · sourceimpl<'a, 'b> PartialOrd<OsStr> for Cow<'a, Path>
impl<'a, 'b> PartialOrd<OsStr> for Cow<'a, Path>
sourcefn partial_cmp(&self, other: &OsStr) -> Option<Ordering>
fn partial_cmp(&self, other: &OsStr) -> Option<Ordering>
This method returns an ordering between self
and other
values if one exists. Read more
sourcefn lt(&self, other: &Rhs) -> bool
fn lt(&self, other: &Rhs) -> bool
This method tests less than (for self
and other
) and is used by the <
operator. Read more
sourcefn le(&self, other: &Rhs) -> bool
fn le(&self, other: &Rhs) -> bool
This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
1.8.0 · sourceimpl<'a, 'b> PartialOrd<OsString> for Cow<'a, Path>
impl<'a, 'b> PartialOrd<OsString> for Cow<'a, Path>
sourcefn partial_cmp(&self, other: &OsString) -> Option<Ordering>
fn partial_cmp(&self, other: &OsString) -> Option<Ordering>
This method returns an ordering between self
and other
values if one exists. Read more
sourcefn lt(&self, other: &Rhs) -> bool
fn lt(&self, other: &Rhs) -> bool
This method tests less than (for self
and other
) and is used by the <
operator. Read more
sourcefn le(&self, other: &Rhs) -> bool
fn le(&self, other: &Rhs) -> bool
This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
1.8.0 · sourceimpl<'a, 'b> PartialOrd<OsString> for Cow<'a, OsStr>
impl<'a, 'b> PartialOrd<OsString> for Cow<'a, OsStr>
sourcefn partial_cmp(&self, other: &OsString) -> Option<Ordering>
fn partial_cmp(&self, other: &OsString) -> Option<Ordering>
This method returns an ordering between self
and other
values if one exists. Read more
sourcefn lt(&self, other: &Rhs) -> bool
fn lt(&self, other: &Rhs) -> bool
This method tests less than (for self
and other
) and is used by the <
operator. Read more
sourcefn le(&self, other: &Rhs) -> bool
fn le(&self, other: &Rhs) -> bool
This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
1.8.0 · sourceimpl<'a, 'b> PartialOrd<Path> for Cow<'a, OsStr>
impl<'a, 'b> PartialOrd<Path> for Cow<'a, OsStr>
sourcefn partial_cmp(&self, other: &Path) -> Option<Ordering>
fn partial_cmp(&self, other: &Path) -> Option<Ordering>
This method returns an ordering between self
and other
values if one exists. Read more
sourcefn lt(&self, other: &Rhs) -> bool
fn lt(&self, other: &Rhs) -> bool
This method tests less than (for self
and other
) and is used by the <
operator. Read more
sourcefn le(&self, other: &Rhs) -> bool
fn le(&self, other: &Rhs) -> bool
This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
1.8.0 · sourceimpl<'a, 'b> PartialOrd<Path> for Cow<'a, Path>
impl<'a, 'b> PartialOrd<Path> for Cow<'a, Path>
sourcefn partial_cmp(&self, other: &Path) -> Option<Ordering>
fn partial_cmp(&self, other: &Path) -> Option<Ordering>
This method returns an ordering between self
and other
values if one exists. Read more
sourcefn lt(&self, other: &Rhs) -> bool
fn lt(&self, other: &Rhs) -> bool
This method tests less than (for self
and other
) and is used by the <
operator. Read more
sourcefn le(&self, other: &Rhs) -> bool
fn le(&self, other: &Rhs) -> bool
This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
1.8.0 · sourceimpl<'a, 'b> PartialOrd<PathBuf> for Cow<'a, OsStr>
impl<'a, 'b> PartialOrd<PathBuf> for Cow<'a, OsStr>
sourcefn partial_cmp(&self, other: &PathBuf) -> Option<Ordering>
fn partial_cmp(&self, other: &PathBuf) -> Option<Ordering>
This method returns an ordering between self
and other
values if one exists. Read more
sourcefn lt(&self, other: &Rhs) -> bool
fn lt(&self, other: &Rhs) -> bool
This method tests less than (for self
and other
) and is used by the <
operator. Read more
sourcefn le(&self, other: &Rhs) -> bool
fn le(&self, other: &Rhs) -> bool
This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
1.8.0 · sourceimpl<'a, 'b> PartialOrd<PathBuf> for Cow<'a, Path>
impl<'a, 'b> PartialOrd<PathBuf> for Cow<'a, Path>
sourcefn partial_cmp(&self, other: &PathBuf) -> Option<Ordering>
fn partial_cmp(&self, other: &PathBuf) -> Option<Ordering>
This method returns an ordering between self
and other
values if one exists. Read more
sourcefn lt(&self, other: &Rhs) -> bool
fn lt(&self, other: &Rhs) -> bool
This method tests less than (for self
and other
) and is used by the <
operator. Read more
sourcefn le(&self, other: &Rhs) -> bool
fn le(&self, other: &Rhs) -> bool
This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
sourceimpl<'a, T> Serialize for Cow<'a, T> where
T: Serialize + ToOwned + ?Sized,
impl<'a, T> Serialize for Cow<'a, T> where
T: Serialize + ToOwned + ?Sized,
sourcefn serialize<S>(
&self,
serializer: S
) -> Result<<S as Serializer>::Ok, <S as Serializer>::Error> where
S: Serializer,
fn serialize<S>(
&self,
serializer: S
) -> Result<<S as Serializer>::Ok, <S as Serializer>::Error> where
S: Serializer,
Serialize this value into the given Serde serializer. Read more
impl<'a, T> EncodeLike<Cow<'a, T>> for T where
T: ToOwned + Encode,
impl<'a, T> EncodeLike<Cow<'a, T>> for Cow<'a, T> where
T: ToOwned + Encode + ?Sized,
impl<'a, T> EncodeLike<T> for Cow<'a, T> where
T: ToOwned + Encode,
impl<'_, B> Eq for Cow<'_, B> where
B: Eq + ToOwned + ?Sized,
impl<'a, T> WrapperTypeEncode for Cow<'a, T> where
T: ToOwned + ?Sized,
Auto Trait Implementations
impl<'a, B: ?Sized> RefUnwindSafe for Cow<'a, B> where
B: RefUnwindSafe,
<B as ToOwned>::Owned: RefUnwindSafe,
impl<'a, B: ?Sized> Send for Cow<'a, B> where
B: Sync,
<B as ToOwned>::Owned: Send,
impl<'a, B: ?Sized> Sync for Cow<'a, B> where
B: Sync,
<B as ToOwned>::Owned: Sync,
impl<'a, B: ?Sized> Unpin for Cow<'a, B> where
<B as ToOwned>::Owned: Unpin,
impl<'a, B: ?Sized> UnwindSafe for Cow<'a, B> where
B: RefUnwindSafe,
<B as ToOwned>::Owned: UnwindSafe,
Blanket Implementations
impl<U> AsSliceOf for U where
U: AsRef<[u8]> + ?Sized,
impl<U> AsSliceOf for U where
U: AsRef<[u8]> + ?Sized,
fn as_slice_of<T>(&self) -> Result<&[T], Error> where
T: FromByteSlice,
sourceimpl<T> BorrowMut<T> for T where
T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
const: unstable · sourcefn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
Mutably borrows from an owned value. Read more
sourceimpl<T> DecodeLimit for T where
T: Decode,
impl<T> DecodeLimit for T where
T: Decode,
sourcefn decode_all_with_depth_limit(limit: u32, input: &[u8]) -> Result<T, Error>
fn decode_all_with_depth_limit(limit: u32, input: &[u8]) -> Result<T, Error>
Decode Self
and consume all of the given input data. Read more
sourceimpl<T, X> Encode for X where
T: Encode + ?Sized,
X: WrapperTypeEncode<Target = T>,
impl<T, X> Encode for X where
T: Encode + ?Sized,
X: WrapperTypeEncode<Target = T>,
sourcefn size_hint(&self) -> usize
fn size_hint(&self) -> usize
If possible give a hint of expected size of the encoding. Read more
sourcefn using_encoded<R, F>(&self, f: F) -> R where
F: FnOnce(&[u8]) -> R,
fn using_encoded<R, F>(&self, f: F) -> R where
F: FnOnce(&[u8]) -> R,
Convert self to a slice and then invoke the given closure with it.
sourcefn encode(&self) -> Vec<u8, Global>ⓘNotable traits for Vec<u8, A>impl<A> Write for Vec<u8, A> where
A: Allocator,
fn encode(&self) -> Vec<u8, Global>ⓘNotable traits for Vec<u8, A>impl<A> Write for Vec<u8, A> where
A: Allocator,
A: Allocator,
Convert self to an owned vector.
sourcefn encode_to<W>(&self, dest: &mut W) where
W: Output + ?Sized,
fn encode_to<W>(&self, dest: &mut W) where
W: Output + ?Sized,
Convert self to a slice and append it to the destination.
sourcefn encoded_size(&self) -> usize
fn encoded_size(&self) -> usize
Calculates the encoded size. Read more
sourceimpl<Out, S> FromSeed<S> for Out where
S: SeedBoxGen<Out>,
impl<Out, S> FromSeed<S> for Out where
S: SeedBoxGen<Out>,
sourceimpl<T> ToOwned for T where
T: Clone,
impl<T> ToOwned for T where
T: Clone,
type Owned = T
type Owned = T
The resulting type after obtaining ownership.
sourcefn clone_into(&self, target: &mut T)
fn clone_into(&self, target: &mut T)
toowned_clone_into
)Uses borrowed data to replace owned data, usually by cloning. Read more