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//! # multi-map //! //! `MultiMap` is like a `std::collection::HashMap`, but allows you to use either of //! two different keys to retrieve items. //! //! The keys have two distinct types - `K1` and `K2` - which may be the same. //! Accessing on the primary `K1` key is via the usual `get`, `get_mut` and //! `remove_alt` methods, while accessing via the secondary `K2` key is via new //! `get_alt`, `get_mut_alt` and `remove_alt` methods. The value is of type `V`. //! //! Internally, two `HashMap`s are created - a main one on `<K1, (K2, //! V)>` and a second one on `<K2, K1>`. The `(K2, V)` tuple is so //! that when an item is removed using the `K1` key, the appropriate `K2` //! value is available so the `K2->K1` map can be removed from the second //! `MultiMap`, to keep them in sync. //! //! Using two `HashMap`s instead of one naturally brings a slight performance //! and memory penalty. Notably, indexing by `K2` requires two `HashMap` lookups. //! //! ``` //! extern crate multi_map; //! use multi_map::MultiMap; //! //! # fn main() { //! #[derive(Hash,Clone,PartialEq,Eq)] //! enum ThingIndex { //! IndexOne, //! IndexTwo, //! IndexThree, //! }; //! //! let mut map = MultiMap::new(); //! map.insert(1, ThingIndex::IndexOne, "Chicken Fried Steak"); //! map.insert(2, ThingIndex::IndexTwo, "Blueberry Pancakes"); //! //! assert!(*map.get_alt(&ThingIndex::IndexOne).unwrap() == "Chicken Fried Steak"); //! assert!(*map.get(&2).unwrap() == "Blueberry Pancakes"); //! assert!(map.remove_alt(&ThingIndex::IndexTwo).unwrap() == "Blueberry Pancakes"); //! # } //! ``` use std::borrow::Borrow; use std::collections::hash_map; use std::collections::HashMap; use std::fmt::{self, Debug}; use std::hash::Hash; #[derive(Eq)] pub struct MultiMap<K1: Eq + Hash, K2: Eq + Hash, V> { value_map: HashMap<K1, (K2, V)>, key_map: HashMap<K2, K1>, } impl<K1: Eq + Hash + Clone, K2: Eq + Hash + Clone, V> MultiMap<K1, K2, V> { /// Creates a new MultiMap. The primary key is of type `K1` and the /// secondary key is of type `K2`. The value is of type `V`. This is as /// compared to a `std::collections::HashMap` which is typed on just `K` and /// `V`. /// /// Internally, two HashMaps are created - a main one on `<K1, (K2, /// V)>` and a second one on `<K2, K1>`. The `(K2, V)` tuple is so /// that when an item is removed using the `K1` key, the appropriate `K2` /// value is available so the `K2->K1` map can be removed from the second /// HashMap, to keep them in sync. pub fn new() -> MultiMap<K1, K2, V> { MultiMap { value_map: HashMap::new(), key_map: HashMap::new(), } } /// Creates an empty MultiMap with the specified capacity. /// /// The multi map will be able to hold at least `capacity` elements without reallocating. If `capacity` is 0, the multi map will not allocate. pub fn with_capacity(capacity: usize) -> MultiMap<K1, K2, V> { MultiMap { value_map: HashMap::with_capacity(capacity), key_map: HashMap::with_capacity(capacity), } } /// Insert an item into the MultiMap. You must supply both keys to insert /// an item. The keys cannot be modified at a later date, so if you only /// have one key at this time, use a placeholder value for the second key /// (perhaps `K2` is `Option<...>`) and remove then re-insert when the /// second key becomes available. pub fn insert(&mut self, key_one: K1, key_two: K2, value: V) { self.key_map.insert(key_two.clone(), key_one.clone()); self.value_map.insert(key_one, (key_two, value)); } /// Obtain a reference to an item in the MultiMap using the primary key, /// just like a HashMap. pub fn get(&self, key: &K1) -> Option<&V> { let mut result = None; if let Some(pair) = self.value_map.get(key) { result = Some(&pair.1) } result } /// Obtain a mutable reference to an item in the MultiMap using the /// primary key, just like a HashMap. pub fn get_mut(&mut self, key: &K1) -> Option<&mut V> { let mut result = None; if let Some(pair) = self.value_map.get_mut(key) { result = Some(&mut pair.1) } result } /// Obtain a reference to an item in the MultiMap using the secondary key. /// Ordinary HashMaps can't do this. pub fn get_alt(&self, key: &K2) -> Option<&V> { let mut result = None; if let Some(key_a) = self.key_map.get(key) { if let Some(pair) = self.value_map.get(key_a) { result = Some(&pair.1) } } result } /// Obtain a mutable reference to an item in the MultiMap using the /// secondary key. Ordinary HashMaps can't do this. pub fn get_mut_alt(&mut self, key: &K2) -> Option<&mut V> { let mut result = None; if let Some(key_a) = self.key_map.get(key) { if let Some(pair) = self.value_map.get_mut(key_a) { result = Some(&mut pair.1) } } result } /// Remove an item from the HashMap using the primary key. The value for the /// given key is returned (if it exists), just like a HashMap. This removes /// an item from the main HashMap, and the second `<K2, K1>` HashMap. pub fn remove<Q: ?Sized>(&mut self, key: &Q) -> Option<V> where K1: Borrow<Q>, Q: Hash + Eq, { let mut result = None; if let Some(pair) = self.value_map.remove(key) { self.key_map.remove(&pair.0); result = Some(pair.1) } result } /// 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 Eq on the borrowed form must match those for the /// key type /// /// ## Example /// ``` /// #[macro_use] /// extern crate multi_map; /// use multi_map::MultiMap; /// # fn main() { /// let map = multimap! { /// 1, "One" => String::from("Eins"), /// 2, "Two" => String::from("Zwei"), /// 3, "Three" => String::from("Drei"), /// }; /// assert!(map.contains_key(&1)); /// assert!(!map.contains_key(&4)); /// # } /// ``` pub fn contains_key<Q: ?Sized>(&self, key: &Q) -> bool where K1: Borrow<Q>, Q: Hash + Eq, { self.value_map.contains_key(key) } /// Returns true if the map contains a value for the specified alternative 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 /// /// ## Example /// ``` /// #[macro_use] /// extern crate multi_map; /// use multi_map::MultiMap; /// # fn main() { /// let map = multimap! { /// 1, "One" => String::from("Eins"), /// 2, "Two" => String::from("Zwei"), /// 3, "Three" => String::from("Drei"), /// }; /// assert!(map.contains_key_alt(&"One")); /// assert!(!map.contains_key_alt(&"Four")); /// # } /// ``` pub fn contains_key_alt<Q: ?Sized>(&self, key: &Q) -> bool where K2: Borrow<Q>, Q: Hash + Eq, { self.key_map.contains_key(key) } /// Remove an item from the HashMap using the secondary key. The value for /// the given key is returned (if it exists). Ordinary HashMaps can't do /// this. This removes an item from both the main HashMap and the second /// `<K2, K1>` HashMap. pub fn remove_alt<Q: ?Sized>(&mut self, key: &Q) -> Option<V> where K2: Borrow<Q>, Q: Hash + Eq, { let mut result = None; if let Some(key_a) = self.key_map.remove(key) { if let Some(pair) = self.value_map.remove(&key_a) { result = Some(pair.1) } } result } /// Iterate through all the values in the MultiMap in random order. /// Note that the values /// are `(K2, V)` tuples, not `V`, as you would get with a HashMap. pub fn iter(&self) -> Iter<'_, K1, K2, V> { Iter { base: self.value_map.iter(), } } } impl<K1: Eq + Hash, K2: Eq + Hash, V: Eq> PartialEq for MultiMap<K1, K2, V> { fn eq(&self, other: &MultiMap<K1, K2, V>) -> bool { self.value_map.eq(&other.value_map) } } impl<K1: Eq + Hash + Debug, K2: Eq + Hash + Debug, V: Debug> fmt::Debug for MultiMap<K1, K2, V> { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { f.debug_map() .entries( self.value_map .iter() .map(|(key_one, &(ref key_two, ref value))| ((key_one, key_two), value)), ) .finish() } } impl<K1, K2, V> Default for MultiMap<K1, K2, V> where K1: Eq + Hash + Clone, K2: Eq + Hash + Clone, { /// Creates an empty `MultiMap<K1, K2, V>` #[inline] fn default() -> MultiMap<K1, K2, V> { MultiMap::new() } } /// An iterator over the entries of a `MultiMap` like in a `HashMap` but with /// values of the form (K2, V) instead of V. /// /// /// This `struct` is created by the [`iter`] method on [`MultiMap`]. See its /// documentation for more. /// #[derive(Clone, Debug)] pub struct Iter<'a, K1: 'a, K2: 'a, V: 'a> { base: hash_map::Iter<'a, K1, (K2, V)>, } /// An owning iterator over the entries of a `MultiMap`. /// /// This `struct` is created by the [`into_iter`] method on [`MultiMap`] /// (provided by the `IntoIterator` trait). See its documentation for more. /// pub struct IntoIter<K1, K2, V> { base: hash_map::IntoIter<K1, (K2, V)>, } // TODO: `HashMap` also implements this, do we need this as well? // impl<K, V> IntoIter<K, V> { // /// Returns a iterator of references over the remaining items. // #[inline] // pub(super) fn iter(&self) -> Iter<'_, K, V> { // Iter { base: self.base.rustc_iter() } // } // } impl<K1, K2, V> IntoIterator for MultiMap<K1, K2, V> where K1: Eq + Hash + Debug, K2: Eq + Hash + Debug, V: Debug, { type Item = (K1, (K2, V)); type IntoIter = IntoIter<K1, K2, 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. /// fn into_iter(self) -> IntoIter<K1, K2, V> { IntoIter { base: self.value_map.into_iter(), } } } impl<'a, K1, K2, V> IntoIterator for &'a MultiMap<K1, K2, V> where K1: Eq + Hash + Debug + Clone, K2: Eq + Hash + Debug + Clone, V: Debug, { type Item = (&'a K1, &'a (K2, V)); type IntoIter = Iter<'a, K1, K2, V>; fn into_iter(self) -> Iter<'a, K1, K2, V> { self.iter() } } impl<'a, K1, K2, V> Iterator for Iter<'a, K1, K2, V> { type Item = (&'a K1, &'a (K2, V)); fn next(&mut self) -> Option<(&'a K1, &'a (K2, V))> { self.base.next() } #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.base.size_hint() } } impl<K1, K2, V> Iterator for IntoIter<K1, K2, V> { type Item = (K1, (K2, V)); #[inline] fn next(&mut self) -> Option<(K1, (K2, V))> { self.base.next() } #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.base.size_hint() } } #[macro_export] /// Create a `MultiMap` from a list of key-value tuples /// /// ## Example /// /// ``` /// #[macro_use] /// extern crate multi_map; /// use multi_map::MultiMap; /// /// # fn main() { /// #[derive(Hash,Clone,PartialEq,Eq)] /// enum ThingIndex { /// IndexOne, /// IndexTwo, /// IndexThree, /// }; /// /// let map = multimap!{ /// 1, ThingIndex::IndexOne => "Chicken Fried Steak", /// 2, ThingIndex::IndexTwo => "Blueberry Pancakes", /// }; /// /// assert!(*map.get_alt(&ThingIndex::IndexOne).unwrap() == "Chicken Fried Steak"); /// assert!(*map.get(&2).unwrap() == "Blueberry Pancakes"); /// # } /// ``` macro_rules! multimap { (@single $($x:tt)*) => (()); (@count $($rest:expr),*) => (<[()]>::len(&[$(multimap!(@single $rest)),*])); ($($key1:expr, $key2:expr => $value:expr,)+) => { multimap!($($key1, $key2 => $value),+) }; ($($key1:expr, $key2:expr => $value:expr),*) => { { let _cap = multimap!(@count $($key1),*); let mut _map = MultiMap::with_capacity(_cap); $( _map.insert($key1, $key2, $value); )* _map } }; } mod test { #[test] fn big_test() { use MultiMap; let mut map = MultiMap::new(); map.insert(1, "One", String::from("Ein")); map.insert(2, "Two", String::from("Zwei")); map.insert(3, "Three", String::from("Drei")); assert!(*map.get(&1).unwrap() == String::from("Ein")); assert!(*map.get(&2).unwrap() == String::from("Zwei")); assert!(*map.get(&3).unwrap() == String::from("Drei")); assert!(map.contains_key(&1)); assert!(!map.contains_key(&4)); assert!(map.contains_key_alt(&"One")); assert!(!map.contains_key_alt(&"Four")); map.get_mut_alt(&"One").unwrap().push_str("s"); assert!(*map.get_alt(&"One").unwrap() == String::from("Eins")); assert!(*map.get_alt(&"Two").unwrap() == String::from("Zwei")); assert!(*map.get_alt(&"Three").unwrap() == String::from("Drei")); map.remove(&3); assert!(*map.get_alt(&"One").unwrap() == String::from("Eins")); assert!(*map.get_alt(&"Two").unwrap() == String::from("Zwei")); assert!(map.get_alt(&"Three") == None); assert!(map.get(&3) == None); assert!(map.remove_alt(&"Three") == None); assert!(*map.remove_alt(&"One").unwrap() == String::from("Eins")); map.get_mut(&2).unwrap().push_str("!"); assert!(map.get(&1) == None); assert!(*map.get(&2).unwrap() == String::from("Zwei!")); assert!(map.get_alt(&"Three") == None); assert!(map.get(&3) == None); } #[derive(Debug, Eq, Ord, PartialEq, PartialOrd)] struct MultiCount<'a>(i32, &'a str, &'a str); #[derive(Debug, Eq, Ord, PartialEq, PartialOrd)] struct MultiCountOwned(i32, String, String); #[test] fn into_iter_test() { use MultiMap; let mut map = MultiMap::new(); map.insert(1, "One", String::from("Eins")); map.insert(2, "Two", String::from("Zwei")); map.insert(3, "Three", String::from("Drei")); let mut vec_borrow = Vec::new(); for (k1, (k2, v)) in &map { vec_borrow.push(MultiCount(*k1, *k2, v)); } vec_borrow.sort(); assert_eq!( vec_borrow, vec!( MultiCount(1, "One", "Eins"), MultiCount(2, "Two", "Zwei"), MultiCount(3, "Three", "Drei") ) ); let mut vec_owned = Vec::new(); for (k1, (k2, v)) in map { vec_owned.push(MultiCountOwned(k1, String::from(k2), v)); } vec_owned.sort(); assert_eq!( vec_owned, vec!( MultiCountOwned(1, String::from("One"), String::from("Eins")), MultiCountOwned(2, String::from("Two"), String::from("Zwei")), MultiCountOwned(3, String::from("Three"), String::from("Drei")) ) ) } #[test] fn macro_test() { use MultiMap; let map: MultiMap<i32, &str, String> = MultiMap::new(); assert_eq!(map, multimap! {}); let mut map = MultiMap::new(); map.insert(1, "One", String::from("Eins")); assert_eq!( map, multimap! { 1, "One" => String::from("Eins"), } ); assert_eq!( map, multimap! { 1, "One" => String::from("Eins") } ); let mut map = MultiMap::new(); map.insert(1, "One", String::from("Eins")); map.insert(2, "Two", String::from("Zwei")); map.insert(3, "Three", String::from("Drei")); assert_eq!( map, multimap! { 1, "One" => String::from("Eins"), 2, "Two" => String::from("Zwei"), 3, "Three" => String::from("Drei"), } ); assert_eq!( map, multimap! { 1, "One" => String::from("Eins"), 2, "Two" => String::from("Zwei"), 3, "Three" => String::from("Drei") } ); } }