Struct cretonne_entity::SparseMap [−][src]
pub struct SparseMap<K, V> where
K: EntityRef,
V: SparseMapValue<K>, { /* fields omitted */ }
A sparse mapping of entity references.
A SparseMap<K, V>
map provides:
- Memory usage equivalent to
EntityMap<K, u32>
+Vec<V>
, so much smaller thanEntityMap<K, V>
for sparse mappings of largerV
types. - Constant time lookup, slightly slower than
EntityMap
. - A very fast, constant time
clear()
operation. - Fast insert and erase operations.
- Stable iteration that is as fast as a
Vec<V>
.
Compared to EntityMap
When should we use a SparseMap
instead of a secondary EntityMap
? First of all, SparseMap
does not provide the functionality of a PrimaryMap
which can allocate and assign entity
references to objects as they are pushed onto the map. It is only the secondary entity maps
that can be replaced with a SparseMap
.
- A secondary entity map assigns a default mapping to all keys. It doesn't distinguish between
an unmapped key and one that maps to the default value.
SparseMap
does not requireDefault
values, and it tracks accurately if a key has been mapped or not. - Iterating over the contents of an
EntityMap
is linear in the size of the key space, while iterating over aSparseMap
is linear in the number of elements in the mapping. This is an advantage precisely when the mapping is sparse. SparseMap::clear()
is constant time and super-fast.EntityMap::clear()
is linear in the size of the key space. (Or, rather the requiredresize()
call following theclear()
is).SparseMap
requires the values to implementSparseMapValue<K>
which means that they must contain their own key.
Methods
impl<K, V> SparseMap<K, V> where
K: EntityRef,
V: SparseMapValue<K>,
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impl<K, V> SparseMap<K, V> where
K: EntityRef,
V: SparseMapValue<K>,
pub fn new() -> Self
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pub fn new() -> Self
Create a new empty mapping.
pub fn len(&self) -> usize
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pub fn len(&self) -> usize
Returns the number of elements in the map.
pub fn is_empty(&self) -> bool
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pub fn is_empty(&self) -> bool
Returns true is the map contains no elements.
pub fn clear(&mut self)
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pub fn clear(&mut self)
Remove all elements from the mapping.
pub fn get(&self, key: K) -> Option<&V>
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pub fn get(&self, key: K) -> Option<&V>
Returns a reference to the value corresponding to the key.
pub fn get_mut(&mut self, key: K) -> Option<&mut V>
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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.
Note that the returned value must not be mutated in a way that would change its key. This would invalidate the sparse set data structure.
pub fn contains_key(&self, key: K) -> bool
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pub fn contains_key(&self, key: K) -> bool
Return true
if the map contains a value corresponding to key
.
pub fn insert(&mut self, value: V) -> Option<V>
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pub fn insert(&mut self, value: V) -> Option<V>
Insert a value into the map.
If the map did not have this key present, None
is returned.
If the map did have this key present, the value is updated, and the old value is returned.
It is not necessary to provide a key since the value knows its own key already.
pub fn remove(&mut self, key: K) -> Option<V>
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pub fn remove(&mut self, key: K) -> Option<V>
Remove a value from the map and return it.
pub fn pop(&mut self) -> Option<V>
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pub fn pop(&mut self) -> Option<V>
Remove the last value from the map.
pub fn values(&self) -> Iter<V>
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pub fn values(&self) -> Iter<V>
Get an iterator over the values in the map.
The iteration order is entirely determined by the preceding sequence of insert
and
remove
operations. In particular, if no elements were removed, this is the insertion
order.
pub fn as_slice(&self) -> &[V]
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pub fn as_slice(&self) -> &[V]
Get the values as a slice.
Trait Implementations
impl<'a, K, V> IntoIterator for &'a SparseMap<K, V> where
K: EntityRef,
V: SparseMapValue<K>,
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impl<'a, K, V> IntoIterator for &'a SparseMap<K, V> where
K: EntityRef,
V: SparseMapValue<K>,
Iterating over the elements of a set.