Struct hash_ord::hash_map::HashMap

pub struct HashMap<K, V, S = RandomState> { /* fields omitted */ }

A hash map which uses AVL to resolve collision.

Usually, hashing algorithm seems to play an important role in HashMap. However, any generated hash-value needs to be mapped into a limited collection, and that will brings in collision. Since collision is unavoidable, in this lib, we focus on solving problem in the worst case, such as Collision-Attack.

As a kind of Self-Balancing BST, AVL is not worse than RBTree, and has a few advantages like simpler structure and smaller height. So we put an AVL under every Hash-Index to resolve collision. When facing Collision Attack, the runtime complexity of STL HashMap is O(n*n), but ours is just O(n log n).

To improve performance, raw pointer is used frequently. Because Rust uses a similar memory model to C/C++, two classic macros offset_of and container_of are used to dereference member variables into main struct. Fastbin is implemented to reduce the cost of memory allocation.

Examples

use hash_ord::hash_map::HashMap;

// type inference lets us omit an explicit type signature (which
// would be `HashMap<&str, &str>` in this example).
let mut book_reviews = HashMap::new();

// review some books.
book_reviews.insert("Adventures of Huckleberry Finn",    "My favorite book.");
book_reviews.insert("Grimms' Fairy Tales",               "Masterpiece.");
book_reviews.insert("Pride and Prejudice",               "Very enjoyable.");
book_reviews.insert("The Adventures of Sherlock Holmes", "Eye lyked it alot.");

// check for a specific one.
if !book_reviews.contains_key("Les Misérables") {
    println!("We've got {} reviews, but Les Misérables ain't one.",
             book_reviews.len());
}

// oops, this review has a lot of spelling mistakes, let's delete it.
book_reviews.remove("The Adventures of Sherlock Holmes");

// look up the values associated with some keys.
let to_find = ["Pride and Prejudice", "Alice's Adventure in Wonderland"];
for book in &to_find {
    match book_reviews.get(book) {
        Some(review) => println!("{}: {}", book, review),
        None => println!("{} is unreviewed.", book)
    }
}

// iterate over everything.
for (book, review) in &book_reviews {
    println!("{}: \"{}\"", book, review);
}

HashMap also implements an Entry API, which allows for more complex methods of getting, setting, updating and removing keys and their values:

use hash_ord::hash_map::HashMap;

// type inference lets us omit an explicit type signature (which
// would be `HashMap<&str, u8>` in this example).
let mut player_stats = HashMap::new();

fn random_stat_buff() -> u8 {
    // could actually return some random value here - let's just return
    // some fixed value for now
    42
}

// insert a key only if it doesn't already exist
player_stats.entry("health").or_insert(100);

// insert a key using a function that provides a new value only if it
// doesn't already exist
player_stats.entry("defence").or_insert_with(random_stat_buff);

// update a key, guarding against the key possibly not being set
let stat = player_stats.entry("attack").or_insert(100);
*stat += random_stat_buff();

The easiest way to use HashMap with a custom type as key is to derive Ord and Hash.

use hash_ord::hash_map::HashMap;
use std::cmp::Ordering;

#[derive(Hash, Eq, Debug)]
struct Viking {
   name: String,
   country: String,
}

impl Ord for Viking {
    fn cmp(&self, other: &Self) -> Ordering {
        let tmp = self.name.cmp(&other.name);
        return if tmp != Ordering::Equal { tmp } else {
            self.country.cmp(&other.country)
        };
    }
}

impl PartialOrd for Viking {
    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
        Some(self.cmp(other))
    }
}

impl PartialEq for Viking {
    fn eq(&self, other: &Self) -> bool {
        self.name == other.name && self.country == other.country
    }
}

impl Viking {
    /// / Create a new Viking.
    fn new(name: &str, country: &str) -> Viking {
        Viking { name: name.to_string(), country: country.to_string() }
    }
}

//  Use a HashMap to store the vikings' health points.
let mut vikings = HashMap::new();

vikings.insert(Viking::new("Einar", "Norway"), 25);
vikings.insert(Viking::new("Olaf", "Denmark"), 24);
vikings.insert(Viking::new("Harald", "Iceland"), 12);

// Use derived implementation to print the status of the vikings.
for (viking, health) in &vikings {
    println!("{:?} has {} hp", viking, health);
}

A HashMap with fixed list of elements can be initialized from an array:

use hash_ord::hash_map::HashMap;

let timber_resources: HashMap<&str, i32> =
    [("Norway", 100),
     ("Denmark", 50),
     ("Iceland", 10)]
     .iter().cloned().collect();

Methods

impl<K, V, S> HashMap<K, V, S>

pub fn clear(&mut self)

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

Examples

use hash_ord::hash_map::HashMap;

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

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<isize, isize> = HashMap::with_capacity(100);
assert!(map.capacity() >= 100);

pub fn get_max_node_of_single_index(&self) -> i32

Returns the maximum node count under a simgle HashIndex

pub fn len(&self) -> usize

Returns the number of elements in the map.

Examples

use hash_ord::hash_map::HashMap;

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

pub fn is_empty(&self) -> bool

Returns true if the map contains no element.

Examples

use hash_ord::hash_map::HashMap;

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

Important traits for Keys<'a, K, V, S>

impl<'a, K, V, S> Iterator for Keys<'a, K, V, S> where
    K: 'a,
    V: 'a,
    S: 'a,  type Item = &'a K;

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

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

Examples

use hash_ord::hash_map::HashMap;

let mut map = HashMap::new();
map.insert("a", 1);
map.insert("b", 2);
map.insert("c", 3);

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

Important traits for Values<'a, K, V, S>

impl<'a, K, V, S> Iterator for Values<'a, K, V, S> where
    K: 'a,
    V: 'a,
    S: 'a,  type Item = &'a V;

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

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

Examples

use hash_ord::hash_map::HashMap;

let mut map = HashMap::new();
map.insert("a", 1);
map.insert("b", 2);
map.insert("c", 3);

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

Important traits for ValuesMut<'a, K, V, S>

impl<'a, K, V, S> Iterator for ValuesMut<'a, K, V, S> where
    K: 'a,
    V: 'a,
    S: 'a,  type Item = &'a mut V;

pub fn values_mut(&mut self) -> ValuesMut<K, V, S>

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

Examples

use hash_ord::hash_map::HashMap;

let mut map = HashMap::new();

map.insert("a", 1);
map.insert("b", 2);
map.insert("c", 3);

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

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

Important traits for Iter<'a, K, V, S>

impl<'a, K, V, S> Iterator for Iter<'a, K, V, S> where
    K: 'a,
    V: 'a,
    S: 'a,  type Item = (&'a K, &'a V);

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

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

Examples

use hash_ord::hash_map::HashMap;

let mut map = HashMap::new();
map.insert("a", 1);
map.insert("b", 2);
map.insert("c", 3);

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

Important traits for IterMut<'a, K, V, S>

impl<'a, K, V, S> Iterator for IterMut<'a, K, V, S> where
    K: 'a,
    V: 'a,
    S: 'a,  type Item = (&'a K, &'a mut V);

pub fn iter_mut(&mut self) -> IterMut<K, V, S>

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 hash_ord::hash_map::HashMap;

let mut map = HashMap::new();
map.insert("a", 1);
map.insert("b", 2);
map.insert("c", 3);

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

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

Important traits for Drain<'a, K, V, S>

impl<'a, K, V, S> Iterator for Drain<'a, K, V, S> type Item = (K, V);

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

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

Examples

use hash_ord::hash_map::HashMap;

let mut a = HashMap::new();
a.insert(1, "a");
a.insert(2, "b");

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

assert!(a.is_empty());

impl<K, V, S> HashMap<K, V, S> where     K: Ord + Hash,     S: BuildHasher,

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

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

Examples

use hash_ord::hash_map::HashMap;

let mut letters = HashMap::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 with_hasher(hash_builder: S) -> Self

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

The created map has the default initial capacity.

Warning: hash_builder is normally randomly generated, and is designed to allow HashMaps to be resistant to attacks that cause many collisions and very poor performance. Setting it manually using this function can expose a DoS attack vector.

Examples

use hash_ord::hash_map::HashMap;
use std::collections::hash_map::RandomState;

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

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

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 Ord on the borrowed form must match those for the key type.

Examples

use hash_ord::hash_map::HashMap;

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

pub fn get_mut<Q: ?Sized>(&mut self, q: &Q) -> Option<&mut V> where     K: Borrow<Q>,     Q: Hash + Ord,

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

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

Examples

use hash_ord::hash_map::HashMap;

let mut map = HashMap::new();
map.insert(1, "a");
if let Some(x) = map.get_mut(&1) {
    *x = "b";
}
assert_eq!(map[&1], "b");

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

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

Examples

use hash_ord::hash_map::HashMap;

let mut map: HashMap<&str, isize> = HashMap::new();
map.reserve(10);

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

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

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 Ord on the borrowed form must match those for the key type.

Examples

use hash_ord::hash_map::HashMap;

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

pub fn insert(&mut self, key: K, value: V) -> Option<(K, 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, update map with new (key, value) and return the old one.

Examples

use hash_ord::hash_map::HashMap;

let mut map = HashMap::new();
assert_eq!(map.insert(37, "a"), None);
assert_eq!(map.is_empty(), false);

map.insert(37, "b");
assert_eq!(map.insert(37, "c"), Some((37, "b")));
assert_eq!(map[&37], "c");

pub fn remove<Q: ?Sized>(&mut self, q: &Q) -> Option<(K, V)> where     K: Borrow<Q>,     Q: Hash + Ord,

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

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

Examples

use hash_ord::hash_map::HashMap;

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

pub fn with_capacity_and_hasher(     capacity: usize,     hash_builder: S ) -> HashMap<K, V, S>

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

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

Warning: hash_builder is normally randomly generated, and is designed to allow HashMaps to be resistant to attacks that cause many collisions and very poor performance. Setting it manually using this function can expose a DoS attack vector.

Examples

use hash_ord::hash_map::HashMap;
use std::collections::hash_map::RandomState;

let s = RandomState::new();
let mut map = HashMap::with_capacity_and_hasher(10, s);
map.insert(1, 2);

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 hash_ord::hash_map::HashMap;

let mut map: HashMap<isize, isize> = HashMap::with_capacity(100);
map.insert(1, 2);
map.insert(3, 4);
assert!(map.capacity() >= 100);
map.shrink_to_fit();
assert!(map.capacity() >= 2);

impl<K, V> HashMap<K, V, RandomState> where     K: Hash + Ord,

pub fn new() -> HashMap<K, V, RandomState>

Creates an empty HashMap.

The hash map is initially created with a capacity of 0, so it will not allocate until it is first inserted into.

Examples

use hash_ord::hash_map::HashMap;
let mut map: HashMap<&str, isize> = HashMap::new();

pub fn with_capacity(capacity: usize) -> HashMap<K, V, RandomState>

Trait Implementations

impl<K, V, S> Default for HashMap<K, V, S> where     K: Ord + Hash,     S: BuildHasher + Default,

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

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

impl<K, V, S> Drop for HashMap<K, V, S>

fn drop(&mut self)

Executes the destructor for this type.

impl<'a, K, Q: ?Sized, V, S> Index<&'a Q> for HashMap<K, V, S> where     Q: Hash + Ord,     K: Hash + Ord + Borrow<Q>,     S: BuildHasher,

type Output = V

The returned type after indexing.

fn index(&self, q: &Q) -> &Self::Output

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

Panics

Panics if the key is not present in the HashMap.

impl<K, V, S> Extend<(K, V)> for HashMap<K, V, S> where     K: Ord + Hash,     S: BuildHasher,

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

Extends a collection with the contents of an iterator.

impl<'a, K, V, S> Extend<(&'a K, &'a V)> for HashMap<K, V, S> where     K: Ord + Hash + Copy,     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.

impl<'a, K, V, S> IntoIterator for &'a HashMap<K, V, S> where     K: Ord + Hash,     S: BuildHasher,

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

The type of the elements being iterated over.

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

Which kind of iterator are we turning this into?

Important traits for Iter<'a, K, V, S>

impl<'a, K, V, S> Iterator for Iter<'a, K, V, S> where
    K: 'a,
    V: 'a,
    S: 'a,  type Item = (&'a K, &'a V);

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

Creates an iterator from a value.

impl<'a, K, V, S> IntoIterator for &'a mut HashMap<K, V, S> where     K: Ord + Hash,     S: BuildHasher,

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

The type of the elements being iterated over.

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

Which kind of iterator are we turning this into?

Important traits for IterMut<'a, K, V, S>

impl<'a, K, V, S> Iterator for IterMut<'a, K, V, S> where
    K: 'a,
    V: 'a,
    S: 'a,  type Item = (&'a K, &'a mut V);

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

Creates an iterator from a value.

impl<K, V, S> IntoIterator for HashMap<K, V, S> where     K: Ord + Hash,     S: BuildHasher,

type Item = (K, V)

The type of the elements being iterated over.

type IntoIter = IntoIter<K, V, S>

Which kind of iterator are we turning this into?

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.

impl<K, V, S> FromIterator<(K, V)> for HashMap<K, V, S> where     K: Ord + Hash,     S: BuildHasher + Default,

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

Creates a value from an iterator.

impl<K, V, S> Clone for HashMap<K, V, S> where     K: Ord + Hash + Clone,     V: 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> PartialEq for HashMap<K, V, S> where     K: Ord + Hash,     V: PartialEq,     S: BuildHasher,

fn eq(&self, other: &HashMap<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 !=.

impl<K, V, S> Eq for HashMap<K, V, S> where     K: Ord + Hash,     V: Eq,     S: BuildHasher,