Enum Entry

pub enum Entry<'a, T: 'a> {
    Occupied(OccupiedEntry<'a, T>),
    Vacant(VacantEntry<'a, T>),
}

A view into a single location in a HeaderMap, which may be vacant or occupied.

Variants

Occupied(OccupiedEntry<'a, T>)

An occupied entry

Vacant(VacantEntry<'a, T>)

A vacant entry

Implementations

impl<'a, T> Entry<'a, T>

pub fn or_insert(self, default: T) -> &'a mut T

Ensures a value is in the entry by inserting the default if empty.

Returns a mutable reference to the first value in the entry.

Panics

This method panics if capacity exceeds max HeaderMap capacity

Examples

let mut map: HeaderMap<u32> = HeaderMap::default();

let headers = &[
    "content-length",
    "x-hello",
    "Content-Length",
    "x-world",
];

for &header in headers {
    let counter = map.entry(header)
        .or_insert(0);
    *counter += 1;
}

assert_eq!(map["content-length"], 2);
assert_eq!(map["x-hello"], 1);

pub fn or_try_insert(self, default: T) -> Result<&'a mut T, MaxSizeReached>

Ensures a value is in the entry by inserting the default if empty.

Returns a mutable reference to the first value in the entry.

Errors

This function may return an error if HeaderMap exceeds max capacity

Examples

let mut map: HeaderMap<u32> = HeaderMap::default();

let headers = &[
    "content-length",
    "x-hello",
    "Content-Length",
    "x-world",
];

for &header in headers {
    let counter = map.entry(header)
        .or_try_insert(0)
        .unwrap();
    *counter += 1;
}

assert_eq!(map["content-length"], 2);
assert_eq!(map["x-hello"], 1);

pub fn or_insert_with<F: FnOnce() -> T>(self, default: F) -> &'a mut T

Ensures a value is in the entry by inserting the result of the default function if empty.

The default function is not called if the entry exists in the map. Returns a mutable reference to the first value in the entry.

Examples

Basic usage.

let mut map = HeaderMap::new();

let res = map.entry("x-hello")
    .or_insert_with(|| "world".parse().unwrap());

assert_eq!(res, "world");

The default function is not called if the entry exists in the map.

let mut map = HeaderMap::new();
map.try_insert(HOST, "world".parse().unwrap()).unwrap();

let res = map.try_entry("host")
    .unwrap()
    .or_try_insert_with(|| unreachable!())
    .unwrap();


assert_eq!(res, "world");

pub fn or_try_insert_with<F: FnOnce() -> T>( self, default: F, ) -> Result<&'a mut T, MaxSizeReached>

Ensures a value is in the entry by inserting the result of the default function if empty.

The default function is not called if the entry exists in the map. Returns a mutable reference to the first value in the entry.

Examples

Basic usage.

let mut map = HeaderMap::new();

let res = map.entry("x-hello")
    .or_insert_with(|| "world".parse().unwrap());

assert_eq!(res, "world");

The default function is not called if the entry exists in the map.

let mut map = HeaderMap::new();
map.try_insert(HOST, "world".parse().unwrap()).unwrap();

let res = map.try_entry("host")
    .unwrap()
    .or_try_insert_with(|| unreachable!())
    .unwrap();


assert_eq!(res, "world");

pub fn key(&self) -> &HeaderName

Returns a reference to the entry’s key

Examples

let mut map = HeaderMap::new();

assert_eq!(map.entry("x-hello").key(), "x-hello");

Trait Implementations

impl<'a, T: Debug + 'a> Debug for Entry<'a, T>

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

Formats the value using the given formatter.

Layout

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain repr(...) attributes. Please see the Rust Reference's “Type Layout” chapter for details on type layout guarantees.

Size: 56 bytes

Size for each variant:

• Occupied: 24 bytes
• Vacant: 56 bytes