Struct slotmapd::SparseSecondaryMap
source · pub struct SparseSecondaryMap<K: Key, V> { /* private fields */ }
Expand description
Sparse secondary map, associate data with previously stored elements in a slot map.
A SparseSecondaryMap
allows you to efficiently store additional
information for each element in a slot map. You can have multiple secondary
maps per slot map, but not multiple slot maps per secondary map. It is safe
but unspecified behavior if you use keys from multiple different slot maps
in the same SparseSecondaryMap
.
A SparseSecondaryMap
does not leak memory even if you never remove
elements. In return, when you remove a key from the primary slot map, after
any insert the space associated with the removed element may be reclaimed.
Don’t expect the values associated with a removed key to stick around after
an insertion has happened!
Unlike SecondaryMap
, the SparseSecondaryMap
is backed by a
BTreeMap
. This means its access times are higher, but it uses less memory
and iterates faster if there are only a few elements of the slot map in the
secondary map. If most or all of the elements in a slot map are also found
in the secondary map, use a SecondaryMap
instead.
The current implementation of SparseSecondaryMap
requires std
and is
thus not available in no_std
environments.
Example usage:
let mut players = SlotMap::new();
let mut health = SparseSecondaryMap::new();
let mut ammo = SparseSecondaryMap::new();
let alice = players.insert("alice");
let bob = players.insert("bob");
for p in players.keys() {
health.insert(p, 100);
ammo.insert(p, 30);
}
// Alice attacks Bob with all her ammo!
health[bob] -= ammo[alice] * 3;
ammo[alice] = 0;
Implementations§
source§impl<K: Key, V> SparseSecondaryMap<K, V>
impl<K: Key, V> SparseSecondaryMap<K, V>
sourcepub fn new() -> Self
pub fn new() -> Self
Constructs a new, empty SparseSecondaryMap
.
Examples
let mut sec: SparseSecondaryMap<DefaultKey, i32> = SparseSecondaryMap::new();
source§impl<K: Key, V> SparseSecondaryMap<K, V>
impl<K: Key, V> SparseSecondaryMap<K, V>
sourcepub fn len(&self) -> usize
pub fn len(&self) -> usize
Returns the number of elements in the secondary map.
Examples
let mut sm = SlotMap::new();
let k = sm.insert(4);
let mut squared = SparseSecondaryMap::new();
assert_eq!(squared.len(), 0);
squared.insert(k, 16);
assert_eq!(squared.len(), 1);
sourcepub fn is_empty(&self) -> bool
pub fn is_empty(&self) -> bool
Returns if the secondary map is empty.
Examples
let mut sec: SparseSecondaryMap<DefaultKey, i32> = SparseSecondaryMap::new();
assert!(sec.is_empty());
sourcepub fn contains_key(&self, key: K) -> bool
pub fn contains_key(&self, key: K) -> bool
sourcepub fn insert(&mut self, key: K, value: V) -> Option<V>
pub fn insert(&mut self, key: K, value: V) -> Option<V>
Inserts a value into the secondary map at the given key
. Can silently
fail if key
was removed from the originating slot map.
Returns None
if this key was not present in the map, the old value
otherwise.
Examples
let mut sm = SlotMap::new();
let k = sm.insert(4);
let mut squared = SparseSecondaryMap::new();
assert_eq!(squared.insert(k, 0), None);
assert_eq!(squared.insert(k, 4), Some(0));
// You don't have to use insert if the key is already in the secondary map.
squared[k] *= squared[k];
assert_eq!(squared[k], 16);
sourcepub fn remove(&mut self, key: K) -> Option<V>
pub fn remove(&mut self, key: K) -> Option<V>
Removes a key from the secondary map, returning the value at the key if
the key was not previously removed. If key
was removed from the
originating slot map, its corresponding entry in the secondary map may
or may not already be removed.
Examples
let mut sm = SlotMap::new();
let mut squared = SparseSecondaryMap::new();
let k = sm.insert(4);
squared.insert(k, 16);
squared.remove(k);
assert!(!squared.contains_key(k));
// It's not necessary to remove keys deleted from the primary slot map, they
// get deleted automatically when their slots are reused on a subsequent insert.
squared.insert(k, 16);
sm.remove(k); // Remove k from the slot map, making an empty slot.
let new_k = sm.insert(2); // Since sm only has one empty slot, this reuses it.
assert!(!squared.contains_key(new_k)); // Space reuse does not mean equal keys.
assert!(squared.contains_key(k)); // Slot has not been reused in squared yet.
squared.insert(new_k, 4);
assert!(!squared.contains_key(k)); // Old key is no longer available.
sourcepub fn retain<F>(&mut self, f: F)where
F: FnMut(K, &mut V) -> bool,
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.
Examples
let mut sm = SlotMap::new();
let mut sec = SparseSecondaryMap::new();
let k1 = sm.insert(0); sec.insert(k1, 10);
let k2 = sm.insert(1); sec.insert(k2, 11);
let k3 = sm.insert(2); sec.insert(k3, 12);
sec.retain(|key, val| key == k1 || *val == 11);
assert!(sec.contains_key(k1));
assert!(sec.contains_key(k2));
assert!(!sec.contains_key(k3));
assert_eq!(2, sec.len());
sourcepub fn clear(&mut self)
pub fn clear(&mut self)
Clears the secondary map. Keeps the allocated memory for reuse.
Examples
let mut sm = SlotMap::new();
let mut sec = SparseSecondaryMap::new();
for i in 0..10 {
sec.insert(sm.insert(i), i);
}
assert_eq!(sec.len(), 10);
sec.clear();
assert_eq!(sec.len(), 0);
sourcepub fn get(&self, key: K) -> Option<&V>
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("foo");
let mut sec = SparseSecondaryMap::new();
sec.insert(key, "bar");
assert_eq!(sec.get(key), Some(&"bar"));
sec.remove(key);
assert_eq!(sec.get(key), None);
sourcepub unsafe fn get_unchecked(&self, key: K) -> &V
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("foo");
let mut sec = SparseSecondaryMap::new();
sec.insert(key, "bar");
assert_eq!(unsafe { sec.get_unchecked(key) }, &"bar");
sec.remove(key);
// sec.get_unchecked(key) is now dangerous!
sourcepub fn get_mut(&mut self, key: K) -> Option<&mut V>
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("test");
let mut sec = SparseSecondaryMap::new();
sec.insert(key, 3.5);
if let Some(x) = sec.get_mut(key) {
*x += 3.0;
}
assert_eq!(sec[key], 6.5);
sourcepub unsafe fn get_unchecked_mut(&mut self, key: K) -> &mut V
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");
let mut sec = SparseSecondaryMap::new();
sec.insert(key, "bar");
unsafe { *sec.get_unchecked_mut(key) = "baz" };
assert_eq!(sec[key], "baz");
sec.remove(key);
// sec.get_unchecked_mut(key) is now dangerous!
sourcepub fn iter(&self) -> Iter<'_, K, V> ⓘ
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 mut sec = SparseSecondaryMap::new();
let k0 = sm.insert(0); sec.insert(k0, 10);
let k1 = sm.insert(1); sec.insert(k1, 11);
let k2 = sm.insert(2); sec.insert(k2, 12);
for (k, v) in sec.iter() {
println!("key: {:?}, val: {}", k, v);
}
sourcepub fn iter_mut(&mut self) -> IterMut<'_, K, V> ⓘ
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 mut sec = SparseSecondaryMap::new();
let k0 = sm.insert(1); sec.insert(k0, 10);
let k1 = sm.insert(2); sec.insert(k1, 20);
let k2 = sm.insert(3); sec.insert(k2, 30);
for (k, v) in sec.iter_mut() {
if k != k1 {
*v *= -1;
}
}
assert_eq!(sec[k0], -10);
assert_eq!(sec[k1], 20);
assert_eq!(sec[k2], -30);
sourcepub fn keys(&self) -> Keys<'_, K, V> ⓘ
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 mut sec = SparseSecondaryMap::new();
let k0 = sm.insert(1); sec.insert(k0, 10);
let k1 = sm.insert(2); sec.insert(k1, 20);
let k2 = sm.insert(3); sec.insert(k2, 30);
let keys: HashSet<_> = sec.keys().collect();
let check: HashSet<_> = vec![k0, k1, k2].into_iter().collect();
assert_eq!(keys, check);
sourcepub fn values(&self) -> Values<'_, K, V> ⓘ
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 mut sec = SparseSecondaryMap::new();
let k0 = sm.insert(1); sec.insert(k0, 10);
let k1 = sm.insert(2); sec.insert(k1, 20);
let k2 = sm.insert(3); sec.insert(k2, 30);
let values: HashSet<_> = sec.values().collect();
let check: HashSet<_> = vec![&10, &20, &30].into_iter().collect();
assert_eq!(values, check);
sourcepub fn values_mut(&mut self) -> ValuesMut<'_, K, V> ⓘ
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();
let mut sec = SparseSecondaryMap::new();
sec.insert(sm.insert(1), 10);
sec.insert(sm.insert(2), 20);
sec.insert(sm.insert(3), 30);
sec.values_mut().for_each(|n| { *n *= 3 });
let values: HashSet<_> = sec.into_iter().map(|(_k, v)| v).collect();
let check: HashSet<_> = vec![30, 60, 90].into_iter().collect();
assert_eq!(values, check);
sourcepub fn entry(&mut self, key: K) -> Option<Entry<'_, K, V>>
pub fn entry(&mut self, key: K) -> Option<Entry<'_, K, V>>
Gets the given key’s corresponding Entry
in the map for in-place
manipulation. May return None
if the key was removed from the
originating slot map.
Examples
let mut sm = SlotMap::new();
let mut sec = SparseSecondaryMap::new();
let k = sm.insert(1);
let v = sec.entry(k).unwrap().or_insert(10);
assert_eq!(*v, 10);
Trait Implementations§
source§impl<K: Clone + Key, V: Clone> Clone for SparseSecondaryMap<K, V>
impl<K: Clone + Key, V: Clone> Clone for SparseSecondaryMap<K, V>
source§fn clone(&self) -> SparseSecondaryMap<K, V>
fn clone(&self) -> SparseSecondaryMap<K, V>
1.0.0 · source§fn clone_from(&mut self, source: &Self)
fn clone_from(&mut self, source: &Self)
source
. Read moresource§impl<K, V> Default for SparseSecondaryMap<K, V>where
K: Key,
impl<K, V> Default for SparseSecondaryMap<K, V>where K: Key,
source§impl<'a, K, V> Extend<(K, &'a V)> for SparseSecondaryMap<K, V>where
K: Key,
V: 'a + Copy,
impl<'a, K, V> Extend<(K, &'a V)> for SparseSecondaryMap<K, V>where K: Key, V: 'a + Copy,
source§fn extend<I: IntoIterator<Item = (K, &'a V)>>(&mut self, iter: I)
fn extend<I: IntoIterator<Item = (K, &'a V)>>(&mut self, iter: I)
source§fn extend_one(&mut self, item: A)
fn extend_one(&mut self, item: A)
extend_one
)source§fn extend_reserve(&mut self, additional: usize)
fn extend_reserve(&mut self, additional: usize)
extend_one
)source§impl<K, V> Extend<(K, V)> for SparseSecondaryMap<K, V>where
K: Key,
impl<K, V> Extend<(K, V)> for SparseSecondaryMap<K, V>where K: Key,
source§fn extend<I: IntoIterator<Item = (K, V)>>(&mut self, iter: I)
fn extend<I: IntoIterator<Item = (K, V)>>(&mut self, iter: I)
source§fn extend_one(&mut self, item: A)
fn extend_one(&mut self, item: A)
extend_one
)source§fn extend_reserve(&mut self, additional: usize)
fn extend_reserve(&mut self, additional: usize)
extend_one
)