Struct thincollections::thin_map::ThinMap

pub struct ThinMap<K: ThinSentinel + Eq + Hash, V, H: BuildHasher = OneFieldHasherBuilder> { /* private fields */ }

A fast, low memory replacement for HashMap.

Keys must implement ThinSentinel, which is already implemented for all primitives. Ideally, mem::size_of::<(K,V)>() should be 18 bytes or less. The key size is the critical factor for performance, and generally should be 64 bits or less. The map will work fine for larger V sizes, but it will start to lose its advantage over HashMap. Keys that have a Drop impl have not been tested and should be avoided (it’s theoretically possible to have such keys with a proper implementation of ThinSentinel, but it’s hard).

Implementations

impl<K: ThinSentinel + Eq + Hash, V, H: BuildHasher> ThinMap<K, V, H>

pub fn with_hasher(hash_builder: H) -> ThinMap<K, V, H>

Creates an empty ThinMap which will use the given hash builder to hash keys.

The hash map is initially created with a capacity of 0, so it will not heap-allocate until it is first inserted into. On first insert, enough room is reserved for 8 pairs.

Examples

use thincollections::thin_map::ThinMap;
use thincollections::thin_hasher::OneFieldHasherBuilder;

let s = OneFieldHasherBuilder::new();
let mut map = ThinMap::with_hasher(s);
map.insert(1, 2);

pub fn with_capacity_and_hasher( capacity: usize, hash_builder: H ) -> ThinMap<K, V, H>

Creates an empty ThinMap with the specified capacity, using hash_builder to hash the keys.

The map will be able to hold at least capacity elements without reallocating. If capacity is 0, the map will not heap-allocate.

Examples

use thincollections::thin_map::ThinMap;
use thincollections::thin_hasher::OneFieldHasherBuilder;

let s = OneFieldHasherBuilder::new();
let mut map: ThinMap<u64, i32, OneFieldHasherBuilder> = ThinMap::with_capacity_and_hasher(10, s);
map.insert(1, 2);

impl<K: ThinSentinel + Eq + Hash, V> ThinMap<K, V, OneFieldHasherBuilder>

pub fn new() -> Self

Creates an empty ThinMap.

The hash map is initially created with a capacity of 0, so it will not heap-allocate until it is first inserted into. On first insert, enough room is reserved for 8 pairs.

Examples

use thincollections::thin_map::ThinMap;
let mut map: ThinMap<u64, i32> = ThinMap::new();

pub fn with_capacity(capacity: usize) -> Self

Creates an empty ThinMap with the specified capacity, using OneFieldHasherBuilder

The hash map will be able to hold at least capacity elements without reallocating. If capacity is 0, the map will not heap-allocate.

Examples

use thincollections::thin_map::ThinMap;
let mut map: ThinMap<u64, i32> = ThinMap::with_capacity(10);

impl<K: ThinSentinel + Eq + Hash, V, H: BuildHasher> ThinMap<K, V, H>

pub fn hasher(&self) -> &H

Returns a reference to the map’s BuildHasher.

Examples

use thincollections::thin_map::ThinMap;
use thincollections::thin_hasher::OneFieldHasherBuilder;

let s = OneFieldHasherBuilder::new();
let map: ThinMap<i32, u64> = ThinMap::with_hasher(s);
let hasher: &OneFieldHasherBuilder = map.hasher();

pub fn capacity(&self) -> usize

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

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

Examples

use thincollections::thin_map::ThinMap;
let map: ThinMap<i32, i32> = ThinMap::with_capacity(100);
assert!(map.capacity() >= 100);

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

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

Panics

Panics if the new allocation size overflows usize.

Examples

use thincollections::thin_map::ThinMap;
let mut map: ThinMap<u64, i32> = ThinMap::new();
map.reserve(10);

pub fn shrink_to_fit(&mut self)

Shrinks the capacity of the map as much as possible. It will drop down as much as possible while maintaining the internal rules and possibly leaving some space in accordance with the resize policy.

Examples

use thincollections::thin_map::ThinMap;

let mut map: ThinMap<i32, i32> = ThinMap::with_capacity(100);
map.insert(7, 2);
map.insert(3, 4);
assert!(map.capacity() >= 100);
map.shrink_to_fit();
assert!(map.capacity() < 100);

pub fn entry(&mut self, key: K) -> Entry<'_, K, V>

Gets the given key’s corresponding entry in the map for in-place manipulation.

Examples

use thincollections::thin_map::ThinMap;

let mut letters = ThinMap::new();

for ch in "a short treatise on fungi".chars() {
    let counter = letters.entry(ch).or_insert(0);
    *counter += 1;
}

assert_eq!(letters[&'s'], 2);
assert_eq!(letters[&'t'], 3);
assert_eq!(letters[&'u'], 1);
assert_eq!(letters.get(&'y'), None);

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

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

Examples

use thincollections::thin_map::ThinMap;

let mut a = ThinMap::new();
a.insert(1, 100);
a.insert(2, 101);

for (k, v) in a.drain().take(1) {
    assert!(k == 1 || k == 2);
    assert!(v == 100 || v == 200);
}

assert!(a.is_empty());

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 thincollections::thin_map::ThinMap;

let mut map = ThinMap::new();
map.insert(101, 1);
map.insert(202, 2);
map.insert(303, 3);

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

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

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

Examples

use thincollections::thin_map::ThinMap;

let mut map = ThinMap::new();
map.insert(100, 1);
map.insert(-100, 2);
map.insert(17, 3);

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

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.

Examples

use thincollections::thin_map::ThinMap;

let mut map = ThinMap::new();

map.insert(100, 1);
map.insert(101, 2);
map.insert(102, 3);

for val in map.values_mut() {
    *val = *val + 10;
}

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

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

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

Examples

use thincollections::thin_map::ThinMap;

let mut map = ThinMap::new();
map.insert(700, 1);
map.insert(800, 2);
map.insert(900, 3);

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

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 (&'a K, &'a mut V).

Examples

use thincollections::thin_map::ThinMap;

let mut map = ThinMap::new();
map.insert(0, 1);
map.insert(1, 2);
map.insert(4, 3);

// Update all values
for (_, val) in map.iter_mut() {
    *val *= 2;
}

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

pub fn is_empty(&self) -> bool

Returns true if the map contains no elements.

Examples

use thincollections::thin_map::ThinMap;

let mut a = ThinMap::new();
assert!(a.is_empty());
a.insert(1, 2);
assert!(!a.is_empty());

pub fn len(&self) -> usize

Returns the number of elements in the map.

Examples

use thincollections::thin_map::ThinMap;

let mut a = ThinMap::new();
assert_eq!(a.len(), 0);
a.insert(1, 17);
assert_eq!(a.len(), 1);

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

Inserts a key-value pair 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. The key is not updated, though; this matters for types that can be == without being identical. See the module-level documentation for more.

Examples

use thincollections::thin_map::ThinMap;

let mut map = ThinMap::new();
assert_eq!(map.insert(37, 123), None);
assert_eq!(map.is_empty(), false);

map.insert(37, 289);
assert_eq!(map.insert(37, 333), Some(289));
assert_eq!(map[&37], 333);

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

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

Examples

use thincollections::thin_map::ThinMap;

let mut map = ThinMap::new();
map.insert(1, 17);
map.insert(7, 42);
assert_eq!(map.get_key_value(&1), Some((&1, &17)));
assert_eq!(map.get_key_value(&7), Some((&7, &42)));
assert_eq!(map.get_key_value(&2), None);

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

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 thincollections::thin_map::ThinMap;

let mut map = ThinMap::new();
map.insert(1, 200);
map.insert(7, 300);
assert_eq!(map.get(&1), Some(&200));
assert_eq!(map.get(&7), Some(&300));
assert_eq!(map.get(&2), None);

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

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

Examples

use thincollections::thin_map::ThinMap;

let mut map = ThinMap::new();
map.insert(1, 200);
map.insert(7, 300);
if let Some(x) = map.get_mut(&1) {
    *x = 42;
}
assert_eq!(map[&1], 42);

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

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

Examples

use thincollections::thin_map::ThinMap;

let mut map = ThinMap::new();
map.insert(1, 200);
map.insert(7, 42);
assert_eq!(map.contains_key(&1), true);
assert_eq!(map.contains_key(&7), true);
assert_eq!(map.contains_key(&2), false);

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

Removes a key from the map, returning the value at the key if the key was previously in the map.

Examples

use thincollections::thin_map::ThinMap;

let mut map = ThinMap::new();
map.insert(7, 123);
assert_eq!(1, map.len());
assert_eq!(map.remove(&7), Some(123));
assert_eq!(map.remove(&7), None);
assert!(map.is_empty());

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

Removes a key from the map, returning the stored key and value if the key was previously in the map.

Examples

use thincollections::thin_map::ThinMap;

let mut map = ThinMap::new();

map.insert(7, 123);
assert_eq!(map.remove_entry(&7), Some((7, 123)));
assert_eq!(map.remove(&7), None);

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

Retains only the elements specified by the predicate.

In other words, remove all pairs (k, v) such that f(&k,&mut v) returns false.

Examples

use thincollections::thin_map::ThinMap;

let mut map: ThinMap<i32, i32> = (0..8).map(|x|(x, x*10)).collect();
map.retain(|&k, _| k % 2 == 0);
assert_eq!(map.len(), 4);

pub fn clear(&mut self)

Clears the map, removing all key-value pairs. Keeps the allocated memory for reuse.

Examples

use thincollections::thin_map::ThinMap;

let mut a = ThinMap::new();
a.insert(1, 20);
a.clear();
assert!(a.is_empty());

impl<K, V, S> ThinMap<K, V, S>where K: Eq + Hash + ThinSentinel + Debug, V: Debug, S: BuildHasher,

pub fn debug(&self)

Trait Implementations

impl<K, V, S> Clone for ThinMap<K, V, S>where K: Eq + Hash + ThinSentinel + Clone, V: PartialEq + Clone, S: BuildHasher + Clone,

fn clone(&self) -> Self

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<K, V, S> Debug for ThinMap<K, V, S>where K: Eq + Hash + ThinSentinel + Debug, V: Debug, S: BuildHasher,

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

Formats the value using the given formatter.

impl<K, V, S> Default for ThinMap<K, V, S>where K: Eq + Hash + ThinSentinel, S: BuildHasher + Default,

fn default() -> ThinMap<K, V, S>

Creates an empty ThinMap<K, V, S>, with the Default value for the hasher.

impl<K: ThinSentinel + Eq + Hash, V, H: BuildHasher> Drop for ThinMap<K, V, H>

fn drop(&mut self)

Executes the destructor for this type.

impl<'a, K, V, S> Extend<(&'a K, &'a V)> for ThinMap<K, V, S>where K: Eq + Hash + Copy + ThinSentinel, V: Copy, S: BuildHasher,

fn extend<T: IntoIterator<Item = (&'a K, &'a V)>>(&mut self, iter: T)

Extends a collection with the contents of an iterator.

fn extend_one(&mut self, item: A)

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

Extends a collection with exactly one element.

fn extend_reserve(&mut self, additional: usize)

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

Reserves capacity in a collection for the given number of additional elements.

impl<K, V, S> Extend<(K, V)> for ThinMap<K, V, S>where K: Eq + Hash + ThinSentinel, S: BuildHasher,

fn extend<T: IntoIterator<Item = (K, V)>>(&mut self, iter: T)

Extends a collection with the contents of an iterator.

fn extend_one(&mut self, item: A)

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

Extends a collection with exactly one element.

fn extend_reserve(&mut self, additional: usize)

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

Reserves capacity in a collection for the given number of additional elements.

impl<K, V, S> FromIterator<(K, V)> for ThinMap<K, V, S>where K: Eq + Hash + ThinSentinel, S: BuildHasher + Default,

fn from_iter<T: IntoIterator<Item = (K, V)>>(iter: T) -> ThinMap<K, V, S>

Creates a value from an iterator.

impl<'a, K, V, S> Index<&'a K> for ThinMap<K, V, S>where K: Eq + Hash + ThinSentinel + 'a, S: BuildHasher,

fn index(&self, key: &K) -> &V

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

Panics

Panics if the key is not present in the ThinMap.

type Output = V

The returned type after indexing.

impl<'a, K, V, S> IntoIterator for &'a ThinMap<K, V, S>where K: Eq + Hash + ThinSentinel, S: BuildHasher,

type Item = (&'a K, &'a V)

The type of the elements being iterated over.

type IntoIter = Iter<'a, K, V>

Which kind of iterator are we turning this into?

fn into_iter(self) -> Iter<'a, K, V>

Creates an iterator from a value.

impl<'a, K, V, S> IntoIterator for &'a mut ThinMap<K, V, S>where K: Eq + Hash + ThinSentinel, S: BuildHasher,

type Item = (&'a K, &'a mut V)

The type of the elements being iterated over.

type IntoIter = IterMut<'a, K, V>

Which kind of iterator are we turning this into?

fn into_iter(self) -> IterMut<'a, K, V>

Creates an iterator from a value.

impl<K, V, S> IntoIterator for ThinMap<K, V, S>where K: Eq + Hash + ThinSentinel, S: BuildHasher,

fn into_iter(self) -> IntoIter<K, V>

Creates a consuming iterator, that is, one that moves each key-value pair out of the map in arbitrary order. The map cannot be used after calling this.

Examples

use thincollections::thin_map::ThinMap;

let mut map = ThinMap::new();
map.insert(100, 1);
map.insert(101, 2);
map.insert(102, 3);

// Not possible with .iter()
let vec: Vec<(u8, i32)> = map.into_iter().collect();

type Item = (K, V)

The type of the elements being iterated over.

type IntoIter = IntoIter<K, V>

Which kind of iterator are we turning this into?

impl<K, V, S> PartialEq<ThinMap<K, V, S>> for ThinMap<K, V, S>where K: Eq + Hash + ThinSentinel, V: PartialEq, S: BuildHasher,

fn eq(&self, other: &ThinMap<K, V, S>) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<K, V, S> Eq for ThinMap<K, V, S>where K: Eq + Hash + ThinSentinel, V: Eq, S: BuildHasher,