Struct nats::header::HeaderMap

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pub struct HeaderMap { /* private fields */ }

Expand description

A multi-map from header name to a set of values for that header

Implementations§

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impl HeaderMap

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pub fn new() -> HeaderMap

Creates a new header map

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pub fn clear(&mut self)

Clears the map, removing all key-value pairs.

§Examples

let mut map = HeaderMap::new();
map.insert(STATUS, "200".to_string());

map.clear();
assert!(map.is_empty());

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pub fn is_empty(&self) -> bool

Returns true if the map contains no elements.

§Examples

let mut map = HeaderMap::new();

assert!(map.is_empty());

map.insert(STATUS, "200".to_string());

assert!(!map.is_empty());

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pub fn contains_key(&self, key: &str) -> bool

Returns true if the map contains a value for the specified key.

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impl HeaderMap

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pub fn insert<K, V>(&mut self, key: K, value: V) -> Option<HashSet<String>>
where K: Into<String>, V: Into<String>,

Inserts a key-value pair into the map.

If the map did not previously have this key present, then None is returned.

If the map did have this key present, the new value is associated with the key and all previous values are removed.

§Examples

let mut map = HeaderMap::new();
map.insert(STATUS, "200");
assert!(!map.is_empty());

let mut previous_set = map.insert(STATUS, "302").unwrap();
assert_eq!(HashSet::from_iter(["200".to_string()]), previous_set);

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pub fn append<K, V>(&mut self, key: K, value: V) -> bool
where K: Into<String>, V: Into<String>,

Inserts a key-value pair into the map.

If the map did not previously have this key present, then false is returned.

If the map did have this key present, the new value is inserted to the end of the set of values currently associated with the key.

§Examples

let mut map = HeaderMap::new();
map.append(STATUS, "200");
assert!(!map.is_empty());

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pub fn get<K: ToString + ?Sized>(&self, key: &K) -> Option<&String>

Returns a reference to the value associated with the key.

If there are multiple values associated with the key, then the first one is returned. Use get_all to get all values associated with a given key. Returns None if there are no values associated with the key.

§Examples

let mut map = HeaderMap::new();
assert!(map.get(STATUS).is_none());

map.insert(STATUS, "200".to_string());
assert_eq!(map.get(STATUS).unwrap(), &"200");

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pub fn get_all<K: ToString + ?Sized>(&self, key: &K) -> GetAll<'_>

Returns a view of all values associated with a key.

The returned view does not incur any allocations and allows iterating the values associated with the key. See GetAll for more details. Returns None if there are no values associated with the key.

§Examples

let mut map = HeaderMap::new();

map.insert(STATUS, "hello");
map.append(STATUS, "goodbye");

let values = map.get_all(STATUS);

// Will print in an arbitrary order.
for x in values {
    println!("{}", x);
}

Methods from Deref<Target = HashMap<String, HashSet<String>>>§

1.0.0 · source

pub fn capacity(&self) -> usize

Returns the number of elements the map can hold without reallocating.

This number is a lower bound; the HashMap<K, V> might be able to hold more, but is guaranteed to be able to hold at least this many.

§Examples

use std::collections::HashMap;
let map: HashMap<i32, i32> = HashMap::with_capacity(100);
assert!(map.capacity() >= 100);

1.0.0 · source

pub fn keys(&self) -> Keys<'_, K, V>

An iterator visiting all keys in arbitrary order. The iterator element type is &'a K.

§Examples

use std::collections::HashMap;

let map = HashMap::from([
    ("a", 1),
    ("b", 2),
    ("c", 3),
]);

for key in map.keys() {
    println!("{key}");
}

§Performance

In the current implementation, iterating over keys takes O(capacity) time instead of O(len) because it internally visits empty buckets too.

1.0.0 · source

pub fn values(&self) -> Values<'_, K, V>

An iterator visiting all values in arbitrary order. The iterator element type is &'a V.

§Examples

use std::collections::HashMap;

let map = HashMap::from([
    ("a", 1),
    ("b", 2),
    ("c", 3),
]);

for val in map.values() {
    println!("{val}");
}

§Performance

In the current implementation, iterating over values takes O(capacity) time instead of O(len) because it internally visits empty buckets too.

1.0.0 · source

pub fn iter(&self) -> Iter<'_, K, V>

An iterator visiting all key-value pairs in arbitrary order. The iterator element type is (&'a K, &'a V).

§Examples

use std::collections::HashMap;

let map = HashMap::from([
    ("a", 1),
    ("b", 2),
    ("c", 3),
]);

for (key, val) in map.iter() {
    println!("key: {key} val: {val}");
}

§Performance

In the current implementation, iterating over map takes O(capacity) time instead of O(len) because it internally visits empty buckets too.

1.0.0 · source

pub fn len(&self) -> usize

Returns the number of elements in the map.

§Examples

use std::collections::HashMap;

let mut a = HashMap::new();
assert_eq!(a.len(), 0);
a.insert(1, "a");
assert_eq!(a.len(), 1);

1.0.0 · source

pub fn is_empty(&self) -> bool

Returns true if the map contains no elements.

§Examples

use std::collections::HashMap;

let mut a = HashMap::new();
assert!(a.is_empty());
a.insert(1, "a");
assert!(!a.is_empty());

1.9.0 · source

pub fn hasher(&self) -> &S

Returns a reference to the map’s BuildHasher.

§Examples

use std::collections::HashMap;
use std::hash::RandomState;

let hasher = RandomState::new();
let map: HashMap<i32, i32> = HashMap::with_hasher(hasher);
let hasher: &RandomState = map.hasher();

1.0.0 · source

pub fn get<Q>(&self, k: &Q) -> Option<&V>
where K: Borrow<Q>, Q: Hash + Eq + ?Sized,

Returns a reference to the value corresponding to the key.

The key may be any borrowed form of the map’s key type, but Hash and Eq on the borrowed form must match those for the key type.

§Examples

use std::collections::HashMap;

let mut map = HashMap::new();
map.insert(1, "a");
assert_eq!(map.get(&1), Some(&"a"));
assert_eq!(map.get(&2), None);

1.40.0 · source

pub fn get_key_value<Q>(&self, k: &Q) -> Option<(&K, &V)>
where K: Borrow<Q>, Q: Hash + Eq + ?Sized,

Returns the key-value pair corresponding to the supplied key.

The supplied key may be any borrowed form of the map’s key type, but Hash and Eq on the borrowed form must match those for the key type.

§Examples

use std::collections::HashMap;

let mut map = HashMap::new();
map.insert(1, "a");
assert_eq!(map.get_key_value(&1), Some((&1, &"a")));
assert_eq!(map.get_key_value(&2), None);

1.0.0 · source

pub fn contains_key<Q>(&self, k: &Q) -> bool
where K: Borrow<Q>, Q: Hash + Eq + ?Sized,

Returns true if the map contains a value for the specified key.

The key may be any borrowed form of the map’s key type, but Hash and Eq on the borrowed form must match those for the key type.

§Examples

use std::collections::HashMap;

let mut map = HashMap::new();
map.insert(1, "a");
assert_eq!(map.contains_key(&1), true);
assert_eq!(map.contains_key(&2), false);

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pub fn raw_entry(&self) -> RawEntryBuilder<'_, K, V, S>

🔬This is a nightly-only experimental API. (hash_raw_entry)

Creates a raw immutable entry builder for the HashMap.

Raw entries provide the lowest level of control for searching and manipulating a map. They must be manually initialized with a hash and then manually searched.

This is useful for