Struct slotmap::SlotMap

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pub struct SlotMap<K: Key, V> { /* private fields */ }

Expand description

Slot map, storage with stable unique keys.

See crate documentation for more details.

Implementations§

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impl<V> SlotMap<DefaultKey, V>

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pub fn new() -> Self

Constructs a new, empty SlotMap.

§Examples

let mut sm: SlotMap<_, i32> = SlotMap::new();

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pub fn with_capacity(capacity: usize) -> Self

Creates an empty SlotMap with the given capacity.

The slot map will not reallocate until it holds at least capacity elements.

§Examples

let mut sm: SlotMap<_, i32> = SlotMap::with_capacity(10);

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impl<K: Key, V> SlotMap<K, V>

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pub fn with_key() -> Self

Constructs a new, empty SlotMap with a custom key type.

§Examples

new_key_type! {
    struct PositionKey;
}
let mut positions: SlotMap<PositionKey, i32> = SlotMap::with_key();

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pub fn with_capacity_and_key(capacity: usize) -> Self

Creates an empty SlotMap with the given capacity and a custom key type.

The slot map will not reallocate until it holds at least capacity elements.

§Examples

new_key_type! {
    struct MessageKey;
}
let mut messages = SlotMap::with_capacity_and_key(3);
let welcome: MessageKey = messages.insert("Welcome");
let good_day = messages.insert("Good day");
let hello = messages.insert("Hello");

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pub fn len(&self) -> usize

Returns the number of elements in the slot map.

§Examples

let mut sm = SlotMap::with_capacity(10);
sm.insert("len() counts actual elements, not capacity");
let key = sm.insert("removed elements don't count either");
sm.remove(key);
assert_eq!(sm.len(), 1);

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pub fn is_empty(&self) -> bool

Returns if the slot map is empty.

§Examples

let mut sm = SlotMap::new();
let key = sm.insert("dummy");
assert_eq!(sm.is_empty(), false);
sm.remove(key);
assert_eq!(sm.is_empty(), true);

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pub fn capacity(&self) -> usize

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

§Examples

let sm: SlotMap<_, f64> = SlotMap::with_capacity(10);
assert_eq!(sm.capacity(), 10);

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pub fn reserve(&mut self, additional: usize)

Reserves capacity for at least additional more elements to be inserted in the SlotMap. The collection may reserve more space to avoid frequent reallocations.

§Panics

Panics if the new allocation size overflows usize.

§Examples

let mut sm = SlotMap::new();
sm.insert("foo");
sm.reserve(32);
assert!(sm.capacity() >= 33);

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

Returns true if the slot map contains key.

§Examples

let mut sm = SlotMap::new();
let key = sm.insert(42);
assert_eq!(sm.contains_key(key), true);
sm.remove(key);
assert_eq!(sm.contains_key(key), false);

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pub fn insert(&mut self, value: V) -> K

Inserts a value into the slot map. Returns a unique key that can be used to access this value.

§Panics

Panics if the number of elements in the slot map equals 2³² - 2.

§Examples

let mut sm = SlotMap::new();
let key = sm.insert(42);
assert_eq!(sm[key], 42);

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pub fn insert_with_key<F>(&mut self, f: F) -> K
where F: FnOnce(K) -> V,

Inserts a value given by f into the slot map. The key where the value will be stored is passed into f. This is useful to store values that contain their own key.

§Panics

Panics if the number of elements in the slot map equals 2³² - 2.

§Examples

let mut sm = SlotMap::new();
let key = sm.insert_with_key(|k| (k, 20));
assert_eq!(sm[key], (key, 20));

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pub fn try_insert_with_key<F, E>(&mut self, f: F) -> Result<K, E>
where F: FnOnce(K) -> Result<V, E>,

Inserts a value given by f into the slot map. The key where the value will be stored is passed into f. This is useful to store values that contain their own key.

If f returns Err, this method returns the error. The slotmap is untouched.

§Panics

Panics if the number of elements in the slot map equals 2³² - 2.

§Examples

let mut sm = SlotMap::new();
let key = sm.try_insert_with_key::<_, ()>(|k| Ok((k, 20))).unwrap();
assert_eq!(sm[key], (key, 20));

sm.try_insert_with_key::<_, ()>(|k| Err(())).unwrap_err();

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pub fn remove(&mut self, key: K) -> Option<V>

Removes a key from the slot map, returning the value at the key if the key was not previously removed.

§Examples

let mut sm = SlotMap::new();
let key = sm.insert(42);
assert_eq!(sm.remove(key), Some(42));
assert_eq!(sm.remove(key), None);

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pub fn retain<F>(&mut self, f: F)
where F: FnMut(K, &mut V) -> bool,

Retains only the elements specified by the predicate.

In other words, remove all key-value pairs (k, v) such that f(k, &mut v) returns false. This method invalidates any removed keys.

This function must iterate over all slots, empty or not. In the face of many deleted elements it can be inefficient.

§Examples

let mut sm = SlotMap::new();

let k1 = sm.insert(0);
let k2 = sm.insert(1);
let k3 = sm.insert(2);

sm.retain(|key, val| key == k1 || *val == 1);

assert!(sm.contains_key(k1));
assert!(sm.contains_key(k2));
assert!(!sm.contains_key(k3));

assert_eq!(2, sm.len());

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pub fn clear(&mut self)

Clears the slot map. Keeps the allocated memory for reuse.

This function must iterate over all slots, empty or not. In the face of many deleted elements it can be inefficient.

§Examples

let mut sm = SlotMap::new();
for i in 0..10 {
    sm.insert(i);
}
assert_eq!(sm.len(), 10);
sm.clear();
assert_eq!(sm.len(), 0);

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pub fn drain(&mut self) -> Drain<'_, K, V> ⓘ

Clears the slot map, returning all key-value pairs in arbitrary order as an iterator. Keeps the allocated memory for reuse.

When the iterator is dropped all elements in the slot map are removed, even if the iterator was not fully consumed. If the iterator is not dropped (using e.g. std::mem::forget), only the elements that were iterated over are removed.

This function must iterate over all slots, empty or not. In the face of many deleted elements it can be inefficient.

§Examples

let mut sm = SlotMap::new();
let k = sm.insert(0);
let v: Vec<_> = sm.drain().collect();
assert_eq!(sm.len(), 0);
assert_eq!(v, vec![(k, 0)]);

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pub fn get(&self, key: K) -> Option<&V>

Returns a reference to the value corresponding to the key.

§Examples

let mut sm = SlotMap::new();
let key = sm.insert("bar");
assert_eq!(sm.get(key), Some(&"bar"));
sm.remove(key);
assert_eq!(sm.get(key), None);

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pub unsafe fn get_unchecked(&self, key: K) -> &V

Returns a reference to the value corresponding to the key without version or bounds checking.

§Safety

This should only be used if contains_key(key) is true. Otherwise it is potentially unsafe.

§Examples

let mut sm = SlotMap::new();
let key = sm.insert("bar");
assert_eq!(unsafe { sm.get_unchecked(key) }, &"bar");
sm.remove(key);
// sm.get_unchecked(key) is now dangerous!

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pub fn get_mut(&mut self, key: K) -> Option<&mut V>

Returns a mutable reference to the value corresponding to the key.

§Examples

let mut sm = SlotMap::new();
let key = sm.insert(3.5);
if let Some(x) = sm.get_mut(key) {
    *x += 3.0;
}
assert_eq!(sm[key], 6.5);

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pub unsafe fn get_unchecked_mut(&mut self, key: K) -> &mut V

Returns a mutable reference to the value corresponding to the key without version or bounds checking.

§Safety

This should only be used if contains_key(key) is true. Otherwise it is potentially unsafe.

§Examples

let mut sm = SlotMap::new();
let key = sm.insert("foo");
unsafe { *sm.get_unchecked_mut(key) = "bar" };
assert_eq!(sm[key], "bar");
sm.remove(key);
// sm.get_unchecked_mut(key) is now dangerous!

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pub fn get_disjoint_mut<const N: usize>( &mut self, keys: [K; N], ) -> Option<[&mut V; N]>

Returns mutable references to the values corresponding to the given keys. All keys must be valid and disjoint, otherwise None is returned.

Requires at least stable Rust version 1.51.

§Examples

let mut sm = SlotMap::new();
let ka = sm.insert("butter");
let kb = sm.insert("apples");
let kc = sm.insert("charlie");
sm.remove(kc); // Make key c invalid.
assert_eq!(sm.get_disjoint_mut([ka, kb, kc]), None); // Has invalid key.
assert_eq!(sm.get_disjoint_mut([ka, ka]), None); // Not disjoint.
let [a, b] = sm.get_disjoint_mut([ka, kb]).unwrap();
std::mem::swap(a, b);
assert_eq!(sm[ka], "apples");
assert_eq!(sm[kb], "butter");

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pub unsafe fn get_disjoint_unchecked_mut<const N: usize>( &mut self, keys: [K; N], ) -> [&mut V; N]

Returns mutable references to the values corresponding to the given keys. All keys must be valid and disjoint.

Requires at least stable Rust version 1.51.

§Safety

This should only be used if contains_key(key) is true for every given key and no two keys are equal. Otherwise it is potentially unsafe.

§Examples

let mut sm = SlotMap::new();
let ka = sm.insert("butter");
let kb = sm.insert("apples");
let [a, b] = unsafe { sm.get_disjoint_unchecked_mut([ka, kb]) };
std::mem::swap(a, b);
assert_eq!(sm[ka], "apples");
assert_eq!(sm[kb], "butter");

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

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

This function must iterate over all slots, empty or not. In the face of many deleted elements it can be inefficient.

§Examples

let mut sm = SlotMap::new();
let k0 = sm.insert(0);
let k1 = sm.insert(1);
let k2 = sm.insert(2);

for (k, v) in sm.iter() {
    println!("key: {:?}, val: {}", k, v);
}

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pub fn iter_mut(&mut self) -> IterMut<'_, K, V> ⓘ

An iterator visiting all key-value pairs in arbitrary order, with mutable references to the values. The iterator element type is (K, &'a mut V).

This function must iterate over all slots, empty or not. In the face of many deleted elements it can be inefficient.

§Examples

let mut sm = SlotMap::new();
let k0 = sm.insert(10);
let k1 = sm.insert(20);
let k2 = sm.insert(30);

for (k, v) in sm.iter_mut() {
    if k != k1 {
        *v *= -1;
    }
}

assert_eq!(sm[k0], -10);
assert_eq!(sm[k1], 20);
assert_eq!(sm[k2], -30);

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

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

This function must iterate over all slots, empty or not. In the face of many deleted elements it can be inefficient.

§Examples

let mut sm = SlotMap::new();
let k0 = sm.insert(10);
let k1 = sm.insert(20);
let k2 = sm.insert(30);
let keys: HashSet<_> = sm.keys().collect();
let check: HashSet<_> = vec![k0, k1, k2].into_iter().collect();
assert_eq!(keys, check);

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

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

This function must iterate over all slots, empty or not. In the face of many deleted elements it can be inefficient.

§Examples

let mut sm = SlotMap::new();
let k0 = sm.insert(10);
let k1 = sm.insert(20);
let k2 = sm.insert(30);
let values: HashSet<_> = sm.values().collect();
let check: HashSet<_> = vec![&10, &20, &30].into_iter().collect();
assert_eq!(values, check);

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pub fn values_mut(&mut self) -> ValuesMut<'_, K, V> ⓘ

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

This function must iterate over all slots, empty or not. In the face of many deleted elements it can be inefficient.

§Examples

let mut sm = SlotMap::new();
sm.insert(1);
sm.insert(2);
sm.insert(3);
sm.values_mut().for_each(|n| { *n *= 3 });
let values: HashSet<_> = sm.into_iter().map(|(_k, v)| v).collect();
let check: HashSet<_> = vec![3, 6, 9].into_iter().collect();
assert_eq!(values, check);