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//! An unordered multiset/bag implementation backed by `HashMap`. //! //! A bag, unlike a set, allows duplicate values, and keeps track of how many //! duplicates each value holds. This type of collection is often referred to //! as an unordered multiset (see also C++'s [`std::unordered_multiset`]). //! //! This multiset/bag is implemented using a `HashMap<T, usize>` and so requires //! that the stored type implements `Hash + Eq`. //! //! For usage examples, see the primary type [`HashBag`]. //! //! If you want to use a hash table with [amortized resizes](https://github.com/jonhoo/griddle/), //! set the `amortize` feature. //! //! [`std::unordered_multiset`]: http://www.cplusplus.com/reference/unordered_set/unordered_multiset/ #![deny( missing_docs, missing_debug_implementations, unreachable_pub, intra_doc_link_resolution_failure )] #![warn(rust_2018_idioms)] #[cfg(feature = "amortize")] use griddle::HashMap; use std::borrow::Borrow; use std::collections::hash_map::RandomState; #[cfg(not(feature = "amortize"))] use std::collections::HashMap; use std::hash::{BuildHasher, Hash}; /// A hash bag implemented as a `HashMap` where the value is `usize`. /// /// A bag, unlike a set, allows duplicate values, and keeps track of how many /// duplicates each value holds. This type of collection is often referred to /// as an unordered multiset. /// /// As with the [`HashMap`] type, a `HashBag` requires that the elements /// implement the [`Eq`] and [`Hash`] traits. This can frequently be achieved by /// using `#[derive(PartialEq, Eq, Hash)]`. If you implement these yourself, /// it is important that the following property holds: /// /// ```text /// k1 == k2 -> hash(k1) == hash(k2) /// ``` /// /// In other words, if two keys are equal, their hashes must be equal. /// /// It is a logic error for an item to be modified in such a way that the /// item's hash, as determined by the [`Hash`] trait, or its equality, as /// determined by the [`Eq`] trait, changes while it is in the bag. /// /// # Examples /// /// ``` /// use hashbag::HashBag; /// // Type inference lets us omit an explicit type signature (which /// // would be `HashBag<String>` in this example). /// let mut books = HashBag::new(); /// /// // Add some books. /// // Since we are a library, we have many copies. /// books.insert("A Dance With Dragons".to_string()); /// books.insert("To Kill a Mockingbird".to_string()); /// books.insert("To Kill a Mockingbird".to_string()); /// books.insert("The Odyssey".to_string()); /// books.insert("The Odyssey".to_string()); /// books.insert("The Odyssey".to_string()); /// books.insert("The Great Gatsby".to_string()); /// books.insert("The Great Gatsby".to_string()); /// books.insert("The Great Gatsby".to_string()); /// books.insert("The Great Gatsby".to_string()); /// /// // When we count the number of books, duplicates are included. /// assert_eq!(books.len(), 10); /// /// // Check for a specific one. /// if books.contains("The Winds of Winter") == 0 { /// println!("We have {} books, but The Winds of Winter ain't one.", /// books.len()); /// } /// /// // Remove a book. /// let had_copies = books.remove("The Odyssey"); /// // Remove returns how many copies of that book we had. /// assert_eq!(had_copies, 3); /// /// // Iterate over everything. /// // Duplicates will be listed multiple times. /// for book in &books { /// println!("{}", book); /// } /// /// // Iterate over each distinct book. /// for (book, copies) in books.set_iter() { /// println!("{} ({} copies)", book, copies); /// } /// /// // Extract the books and their counts. /// for (book, copies) in books { /// println!("{} ({} copies)", book, copies); /// } /// ``` /// /// The easiest way to use `HashBag` with a custom type is to derive /// [`Eq`] and [`Hash`]. We must also derive [`PartialEq`], this will in the /// future be implied by [`Eq`]. /// /// ``` /// use hashbag::HashBag; /// #[derive(Hash, Eq, PartialEq, Debug, Clone)] /// struct Viking { /// name: String, /// power: usize, /// } /// /// let mut vikings = HashBag::new(); /// /// vikings.insert(Viking { name: "Einar".to_string(), power: 9 }); /// vikings.insert(Viking { name: "Einar".to_string(), power: 9 }); /// vikings.insert(Viking { name: "Olaf".to_string(), power: 4 }); /// vikings.insert(Viking { name: "Olaf".to_string(), power: 5 }); /// vikings.insert(Viking { name: "Harald".to_string(), power: 8 }); /// /// // Use derived implementation to print the vikings. /// // Notice that all duplicates are printed. /// for v in &vikings { /// println!("{:?}", v); /// } /// /// // Since the derived implementation compares all the fields, /// // vikings that share a name but not a power are not duplicates. /// for (v, n) in vikings.set_iter() { /// println!("{:?} ({} of them!)", v, n); /// } /// /// // HashBags themselves can also be compared for equality, /// // and will do so by considering both the values and their counts. /// let mut vikings2 = vikings.clone(); /// assert_eq!(vikings, vikings2); /// let fallen = vikings.iter().next().unwrap(); /// vikings2.remove(fallen); /// assert_ne!(vikings, vikings2); /// vikings2.insert(Viking { name: "Snorre".to_string(), power: 1 }); /// assert_ne!(vikings, vikings2); /// ``` /// /// A `HashBag` with fixed list of elements can be initialized from an array: /// /// ``` /// use hashbag::HashBag; /// /// let mut viking_names: HashBag<&'static str> = /// [ "Einar", "Olaf", "Harald" ].iter().cloned().collect(); /// // use the values stored in the bag /// ``` /// /// You can also extend the bag easily: /// /// ``` /// use hashbag::HashBag; /// /// let mut vikings: HashBag<String> = HashBag::new(); /// vikings.extend(std::iter::once("Snorre".to_string())); /// assert_eq!(vikings.contains("Snorre"), 1); /// /// // You can extend with many instances at once: /// vikings.extend(std::iter::once(("Snorre".to_string(), 4))); /// assert_eq!(vikings.contains("Snorre"), 5); /// /// // Extension also works with reference iterators if the type is Clone: /// let einar = String::from("Einar"); /// vikings.extend(std::iter::once(&einar)); /// assert_eq!(vikings.contains(&einar), 1); /// /// // And extend with many instances at once: /// vikings.extend(std::iter::once((&einar, 4))); /// assert_eq!(vikings.contains(&einar), 5); /// ``` pub struct HashBag<T, S = RandomState> { items: HashMap<T, usize, S>, count: usize, } impl<T: Clone + Hash, S: Clone + BuildHasher> Clone for HashBag<T, S> { fn clone(&self) -> Self { Self { items: self.items.clone(), count: self.count, } } fn clone_from(&mut self, source: &Self) { self.items.clone_from(&source.items); self.count = source.count; } } impl<T: Hash + Eq> HashBag<T, RandomState> { /// Creates an empty `HashBag`. /// /// The hash bag is initially created with a capacity of 0, so it will not allocate until it /// is first inserted into. /// /// # Examples /// /// ``` /// use hashbag::HashBag; /// let bag: HashBag<i32> = HashBag::new(); /// ``` #[inline] pub fn new() -> HashBag<T, RandomState> { Self::with_hasher(RandomState::new()) } /// Creates an empty `HashBag` with the specified capacity. /// /// The hash bag will be able to hold at least `capacity` distinct values without /// reallocating. If `capacity` is 0, the hash bag will not allocate. /// /// # Examples /// /// ``` /// use hashbag::HashBag; /// let bag: HashBag<i32> = HashBag::with_capacity(10); /// assert!(bag.capacity() >= 10); /// ``` #[inline] pub fn with_capacity(capacity: usize) -> HashBag<T, RandomState> { Self::with_capacity_and_hasher(capacity, RandomState::new()) } } impl<T, S> HashBag<T, S> { /// Returns the number of distinct values the bag can hold without reallocating. /// /// # Examples /// /// ``` /// use hashbag::HashBag; /// let bag: HashBag<i32> = HashBag::with_capacity(100); /// assert!(bag.capacity() >= 100); /// ``` #[inline] pub fn capacity(&self) -> usize { self.items.capacity() } /// An iterator visiting all elements in arbitrary order. /// /// The iterator element type is `&'a T`. /// Duplicates are yielded as many times as they appear in the bag. /// /// # Examples /// /// ``` /// use hashbag::HashBag; /// let mut bag = HashBag::new(); /// bag.insert("a"); /// bag.insert("b"); /// bag.insert("b"); /// /// // Will print in an arbitrary order. /// // b will be printed twice. /// for x in bag.iter() { /// println!("{}", x); /// } /// ``` #[inline] pub fn iter(&self) -> Iter<'_, T> { Iter::new(self.items.iter(), self.count) } /// An iterator visiting all distinct elements in arbitrary order. /// /// The iterator element type is `(&'a T, usize)`. /// Duplicated values are yielded once along with a count of the number of occurrences. /// /// # Examples /// /// ``` /// use hashbag::HashBag; /// let mut bag = HashBag::new(); /// bag.insert("a"); /// bag.insert("b"); /// bag.insert("b"); /// /// // Will print in an arbitrary order. /// for (x, n) in bag.set_iter() { /// println!("{} {}", x, n); /// } /// ``` #[inline] pub fn set_iter(&self) -> SetIter<'_, T> { SetIter(self.items.iter()) } /// Returns the number of elements in the bag. /// /// Duplicates are counted. /// /// # Examples /// /// ``` /// use hashbag::HashBag; /// /// let mut bag = HashBag::new(); /// assert_eq!(bag.len(), 0); /// bag.insert(1); /// assert_eq!(bag.len(), 1); /// bag.insert(1); /// assert_eq!(bag.len(), 2); /// ``` #[inline] pub fn len(&self) -> usize { self.count } /// Returns the number of elements in the bag. /// /// Duplicates are not counted. /// /// # Examples /// /// ``` /// use hashbag::HashBag; /// /// let mut bag = HashBag::new(); /// assert_eq!(bag.set_len(), 0); /// bag.insert(1); /// assert_eq!(bag.set_len(), 1); /// bag.insert(1); /// assert_eq!(bag.set_len(), 1); /// ``` #[inline] pub fn set_len(&self) -> usize { self.items.len() } /// Returns `true` if the bag contains no elements. /// /// # Examples /// /// ``` /// use hashbag::HashBag; /// /// let mut bag = HashBag::new(); /// assert!(bag.is_empty()); /// bag.insert(1); /// assert!(!bag.is_empty()); /// ``` #[inline] pub fn is_empty(&self) -> bool { self.count == 0 } /// Clears the bag, returning all elements in an iterator. /// /// Duplicates appear only in the count yielded for each element. /// /// # Examples /// /// ``` /// use hashbag::HashBag; /// /// let mut bag: HashBag<_> = [1, 2, 3, 3].iter().cloned().collect(); /// assert!(!bag.is_empty()); /// /// // prints /// // 1 1 /// // 2 1 /// // 3 2 /// // in an arbitrary order /// for (i, n) in bag.drain() { /// println!("{} {}", i, n); /// } /// /// assert!(bag.is_empty()); /// ``` #[inline] pub fn drain(&mut self) -> Drain<'_, T> { self.count = 0; Drain(self.items.drain()) } /// Clears the bag, removing all values. /// /// # Examples /// /// ``` /// use hashbag::HashBag; /// /// let mut bag = HashBag::new(); /// bag.insert(1); /// bag.clear(); /// assert!(bag.is_empty()); /// ``` #[inline] pub fn clear(&mut self) { self.count = 0; self.items.clear(); } } impl<T, S> HashBag<T, S> where T: Eq + Hash, S: BuildHasher, { /// Creates a new empty hash bag which will use the given hasher to hash /// keys. /// /// The hash bag is also created with the default initial capacity. /// /// Warning: `hasher` is normally randomly generated, and /// is designed to allow `HashBag`s 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 hashbag::HashBag; /// use std::collections::hash_map::RandomState; /// /// let s = RandomState::new(); /// let mut bag = HashBag::with_hasher(s); /// bag.insert(2); /// ``` #[inline] pub fn with_hasher(hash_builder: S) -> HashBag<T, S> { HashBag { items: HashMap::with_hasher(hash_builder), count: 0, } } /// Creates an empty `HashBag` with the specified capacity, using /// `hasher` to hash the keys. /// /// The hash bag will be able to hold at least `capacity` distinct values /// without reallocating. If `capacity` is 0, the hash bag will not allocate. /// /// Warning: `hasher` is normally randomly generated, and /// is designed to allow `HashBag`s 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 hashbag::HashBag; /// use std::collections::hash_map::RandomState; /// /// let s = RandomState::new(); /// let mut bag = HashBag::with_capacity_and_hasher(10, s); /// bag.insert(1); /// ``` #[inline] pub fn with_capacity_and_hasher(capacity: usize, hash_builder: S) -> HashBag<T, S> { HashBag { items: HashMap::with_capacity_and_hasher(capacity, hash_builder), count: 0, } } /// Returns a reference to the bag's [`BuildHasher`]. /// /// # Examples /// /// ``` /// use hashbag::HashBag; /// use std::collections::hash_map::RandomState; /// /// let hasher = RandomState::new(); /// let bag: HashBag<i32> = HashBag::with_hasher(hasher); /// let hasher: &RandomState = bag.hasher(); /// ``` #[inline] pub fn hasher(&self) -> &S { self.items.hasher() } /// Reserves capacity for at least `additional` more distinct values /// to be inserted in the `HashBag`. The collection may reserve more /// space to avoid frequent reallocations. /// /// # Panics /// /// Panics if the new allocation size overflows `usize`. /// /// # Examples /// /// ``` /// use hashbag::HashBag; /// let mut bag: HashBag<i32> = HashBag::new(); /// bag.reserve(10); /// assert!(bag.capacity() >= 10); /// ``` #[inline] pub fn reserve(&mut self, additional: usize) { self.items.reserve(additional) } /// Shrinks the capacity of the ba 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 hashbag::HashBag; /// /// let mut bag = HashBag::with_capacity(100); /// bag.insert(1); /// bag.insert(2); /// assert!(bag.capacity() >= 100); /// bag.shrink_to_fit(); /// assert!(bag.capacity() >= 2); /// ``` #[inline] pub fn shrink_to_fit(&mut self) { self.items.shrink_to_fit() } /// Returns the number of instances of `value` in the bag. /// /// The value may be any borrowed form of the bag's value type, but /// [`Hash`] and [`Eq`] on the borrowed form *must* match those for /// the value type. /// /// # Examples /// /// ``` /// use hashbag::HashBag; /// /// let bag: HashBag<_> = [1, 2, 3, 3].iter().cloned().collect(); /// assert_eq!(bag.contains(&1), 1); /// assert_eq!(bag.contains(&3), 2); /// assert_eq!(bag.contains(&4), 0); /// ``` #[inline] pub fn contains<Q: ?Sized>(&self, value: &Q) -> usize where T: Borrow<Q>, Q: Hash + Eq, { self.items.get(value).cloned().unwrap_or(0) } /// Returns a reference to the value in the bag, if any, that is equal to the given value, /// along with its number of occurrences. /// /// The value may be any borrowed form of the bag's value type, but /// [`Hash`] and [`Eq`] on the borrowed form *must* match those for /// the value type. /// /// # Examples /// /// ``` /// use hashbag::HashBag; /// /// let bag: HashBag<_> = [1, 2, 3, 3].iter().cloned().collect(); /// assert_eq!(bag.get(&2), Some((&2, 1))); /// assert_eq!(bag.get(&3), Some((&3, 2))); /// assert_eq!(bag.get(&4), None); /// ``` #[inline] pub fn get<Q: ?Sized>(&self, value: &Q) -> Option<(&T, usize)> where T: Borrow<Q>, Q: Hash + Eq, { self.items .get_key_value(value) .map(|(t, count)| (t, *count)) } /// Adds a value to the bag. /// /// The number of occurrences of the value previously in the bag is returned. /// /// # Examples /// /// ``` /// use hashbag::HashBag; /// /// let mut bag = HashBag::new(); /// /// assert_eq!(bag.insert(2), 0); /// assert_eq!(bag.insert(2), 1); /// assert_eq!(bag.insert(2), 2); /// assert_eq!(bag.set_len(), 1); /// assert_eq!(bag.len(), 3); /// ``` #[inline] pub fn insert(&mut self, value: T) -> usize { self.insert_many(value, 1) } /// Adds multiple occurrences of a value to the bag. /// /// The number of occurrences of the value previously in the bag is returned. /// /// # Examples /// /// ``` /// use hashbag::HashBag; /// /// let mut bag = HashBag::new(); /// /// assert_eq!(bag.insert_many(2, 1), 0); /// assert_eq!(bag.insert_many(2, 2), 1); /// assert_eq!(bag.insert_many(2, 4), 3); /// assert_eq!(bag.set_len(), 1); /// assert_eq!(bag.len(), 7); /// ``` #[inline] pub fn insert_many(&mut self, value: T, count: usize) -> usize { self.count += count; let n = self.items.entry(value).or_insert(0); let was_there = *n; *n += count; was_there } /// Adds a value to the bag, replacing all existing occurrences, if any, that equal the given /// one. /// /// The number of occurrences of the value previously in the bag is returned. /// /// # Examples /// /// ``` /// use hashbag::HashBag; /// /// let mut bag = HashBag::new(); /// bag.insert(Vec::<i32>::new()); /// bag.insert(Vec::<i32>::new()); /// assert_eq!(bag.contains(&[][..]), 2); /// assert_eq!(bag.get(&[][..]).unwrap().0.capacity(), 0); /// /// bag.replace(Vec::with_capacity(10)); /// assert_eq!(bag.contains(&[][..]), 1); /// assert_eq!(bag.get(&[][..]).unwrap().0.capacity(), 10); /// ``` #[inline] pub fn replace(&mut self, value: T) -> usize { let n = self.items.remove(&value).unwrap_or(0); self.count -= n; self.items.insert(value, 1); self.count += 1; n } /// Removes a value from the bag. /// /// The number of occurrences of the value previously in the bag is returned. /// /// The value may be any borrowed form of the bag's value type, but /// [`Hash`] and [`Eq`] on the borrowed form *must* match those for /// the value type. /// /// # Examples /// /// ``` /// use hashbag::HashBag; /// /// let mut bag = HashBag::new(); /// /// bag.insert_many('x', 2); /// assert_eq!(bag.contains(&'x'), 2); /// assert_eq!(bag.remove(&'x'), 2); /// assert_eq!(bag.contains(&'x'), 1); /// assert_eq!(bag.remove(&'x'), 1); /// assert_eq!(bag.contains(&'x'), 0); /// assert_eq!(bag.remove(&'x'), 0); /// ``` #[inline] pub fn remove<Q: ?Sized>(&mut self, value: &Q) -> usize where T: Borrow<Q>, Q: Hash + Eq, { match self.items.get_mut(value) { None => 0, #[cfg(debug_assertions)] Some(n) if *n == 0 => unreachable!(), Some(n) if *n == 1 => { self.count -= 1; self.items.remove(value); 1 } Some(n) => { self.count -= 1; *n -= 1; *n + 1 } } } /// Removes a value that is equal to the given one, and returns it if it was the last. /// /// If the matching value is not the last, a reference to the remainder is given, along with /// the number of occurrences prior to the removal. /// /// The value may be any borrowed form of the bag's value type, but /// [`Hash`] and [`Eq`] on the borrowed form *must* match those for /// the value type. /// /// # Examples /// /// ``` /// use hashbag::HashBag; /// /// let mut bag: HashBag<_> = [1, 2, 3, 3].iter().cloned().collect(); /// assert_eq!(bag.try_take(&2), Ok(2)); /// assert_eq!(bag.try_take(&3), Err(Some((&3, 2)))); /// assert_eq!(bag.try_take(&3), Ok(3)); /// assert_eq!(bag.try_take(&4), Err(None)); /// ``` #[inline] pub fn try_take<Q: ?Sized>(&mut self, value: &Q) -> Result<T, Option<(&T, usize)>> where T: Borrow<Q>, Q: Hash + Eq, { // TODO: it should be possible to make this more efficient match self.items.remove_entry(value) { Some((t, 1)) => { self.count -= 1; Ok(t) } Some((t, n)) => { self.count -= 1; self.items.insert(t, n - 1); Err(Some( self.items .get_key_value(value) .map(|(t, n)| (t, *n + 1)) .unwrap(), )) } None => Err(None), } } /// Removes and returns all occurrences of the value, if any, that is equal to the given one. /// /// The value may be any borrowed form of the bag's value type, but /// [`Hash`] and [`Eq`] on the borrowed form *must* match those for /// the value type. /// /// # Examples /// /// ``` /// use hashbag::HashBag; /// /// let mut bag: HashBag<_> = [1, 2, 3, 3].iter().cloned().collect(); /// assert_eq!(bag.take_all(&2), Some((2, 1))); /// assert_eq!(bag.take_all(&3), Some((3, 2))); /// assert_eq!(bag.take_all(&2), None); /// assert_eq!(bag.take_all(&3), None); /// ``` #[inline] pub fn take_all<Q: ?Sized>(&mut self, value: &Q) -> Option<(T, usize)> where T: Borrow<Q>, Q: Hash + Eq, { let (t, n) = self.items.remove_entry(value)?; self.count -= n; Some((t, n)) } /// Retains only the values specified by the predicate. /// /// In other words, for each value `v` retain only `f(&v)` occurrences. /// /// # Examples /// /// ``` /// use hashbag::HashBag; /// /// let xs = [0,0,0,0,0,1,1,1,1,2,2,2,3,3,4]; /// let mut bag: HashBag<i32> = xs.iter().cloned().collect(); /// bag.retain(|&k, _| k as usize); /// assert_eq!(bag.set_len(), 4); // >= 1 of all but value 0 /// assert_eq!(bag.len(), 6); /// assert_eq!(bag.contains(&0), 0); /// assert_eq!(bag.contains(&1), 1); /// assert_eq!(bag.contains(&2), 2); /// assert_eq!(bag.contains(&3), 2); /// assert_eq!(bag.contains(&4), 1); /// ``` pub fn retain<F>(&mut self, mut f: F) where F: FnMut(&T, usize) -> usize, { let count = &mut self.count; self.items.retain(|t, n| { let keep = std::cmp::min(*n, f(t, *n)); *count -= *n - keep; if keep == 0 { false } else { *n = keep; true } }); } } // ======== standard traits use std::fmt; impl<T> fmt::Debug for HashBag<T> where T: fmt::Debug, { fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { fmt.debug_set().entries(self.iter()).finish() } } impl<T, S> Default for HashBag<T, S> where T: Eq + Hash, S: BuildHasher + Default, { fn default() -> Self { Self::with_hasher(S::default()) } } impl<T, S> PartialEq<HashBag<T, S>> for HashBag<T, S> where T: Eq + Hash, S: BuildHasher, { fn eq(&self, other: &Self) -> bool { self.count == other.count && self.items == other.items } } impl<T, S> Eq for HashBag<T, S> where T: Eq + Hash, S: BuildHasher, { } impl<'a, T, S> Extend<&'a T> for HashBag<T, S> where T: 'a + Eq + Hash + Clone, S: BuildHasher, { fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I) { for e in iter { self.insert(e.clone()); } } } impl<'a, T, S> Extend<(&'a T, usize)> for HashBag<T, S> where T: 'a + Eq + Hash + Clone, S: BuildHasher, { fn extend<I: IntoIterator<Item = (&'a T, usize)>>(&mut self, iter: I) { for (e, n) in iter { self.count += n; *self.items.entry(e.clone()).or_insert(0) += n; } } } impl<T, S> Extend<T> for HashBag<T, S> where T: Eq + Hash, S: BuildHasher, { fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) { for e in iter { self.insert(e); } } } impl<T, S> Extend<(T, usize)> for HashBag<T, S> where T: Eq + Hash, S: BuildHasher, { fn extend<I: IntoIterator<Item = (T, usize)>>(&mut self, iter: I) { for (e, n) in iter { self.count += n; *self.items.entry(e).or_insert(0) += n; } } } impl<T, S> std::iter::FromIterator<T> for HashBag<T, S> where T: Eq + Hash, S: BuildHasher + Default, { fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Self { let mut bag = Self::default(); bag.extend(iter); bag } } impl<'a, T, S> IntoIterator for &'a HashBag<T, S> { type Item = &'a T; type IntoIter = Iter<'a, T>; fn into_iter(self) -> Iter<'a, T> { self.iter() } } impl<T, S> IntoIterator for HashBag<T, S> { type Item = (T, usize); type IntoIter = IntoIter<T>; fn into_iter(self) -> IntoIter<T> { IntoIter(self.items.into_iter()) } } // ======== iterators #[cfg(feature = "amortize")] type IterInner<'a, T> = griddle::hash_map::Iter<'a, T, usize>; #[cfg(not(feature = "amortize"))] type IterInner<'a, T> = std::collections::hash_map::Iter<'a, T, usize>; /// An iterator over the items of a `HashBag`. /// /// Each value is repeated as many times as it occurs in the bag. /// /// This `struct` is created by [`HashBag::iter`]. /// See its documentation for more. pub struct Iter<'a, T> { iter: IterInner<'a, T>, repeat: Option<(&'a T, usize)>, left: usize, } impl<'a, T> std::iter::FusedIterator for Iter<'a, T> where IterInner<'a, T>: std::iter::FusedIterator {} impl<'a, T> ExactSizeIterator for Iter<'a, T> where IterInner<'a, T>: ExactSizeIterator {} impl<'a, T> Clone for Iter<'a, T> { fn clone(&self) -> Self { Iter { iter: self.iter.clone(), repeat: self.repeat.clone(), left: self.left, } } } impl<T: fmt::Debug> fmt::Debug for Iter<'_, T> { fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { fmt.debug_set().entries(self.clone()).finish() } } impl<'a, T> Iter<'a, T> { fn new(it: IterInner<'a, T>, n: usize) -> Self { Self { iter: it, repeat: None, left: n, } } } impl<'a, T> Iterator for Iter<'a, T> { type Item = &'a T; fn next(&mut self) -> Option<Self::Item> { if let Some((t, ref mut n)) = self.repeat { if *n == 0 { self.repeat = None; } else { *n -= 1; self.left -= 1; return Some(t); } } let (next, n) = self.iter.next()?; if *n > 1 { self.repeat = Some((next, *n - 1)); } self.left -= 1; Some(next) } fn size_hint(&self) -> (usize, Option<usize>) { (self.left, Some(self.left)) } } /// An iterator over the distinct items of a `HashBag` and their occurrence counts. /// /// This `struct` is created by [`HashBag::set_iter`]. /// See its documentation for more. pub struct SetIter<'a, T>(IterInner<'a, T>); impl<'a, T> std::iter::FusedIterator for SetIter<'a, T> where IterInner<'a, T>: std::iter::FusedIterator { } impl<'a, T> ExactSizeIterator for SetIter<'a, T> where IterInner<'a, T>: ExactSizeIterator {} impl<'a, T> Clone for SetIter<'a, T> { fn clone(&self) -> Self { SetIter(self.0.clone()) } } impl<T: fmt::Debug> fmt::Debug for SetIter<'_, T> { fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { fmt.debug_set().entries(self.clone()).finish() } } impl<'a, T> Iterator for SetIter<'a, T> { type Item = (&'a T, usize); fn next(&mut self) -> Option<Self::Item> { self.0.next().map(|(t, n)| (t, *n)) } fn size_hint(&self) -> (usize, Option<usize>) { self.0.size_hint() } } #[cfg(feature = "amortize")] type IntoIterInner<T> = griddle::hash_map::IntoIter<T, usize>; #[cfg(not(feature = "amortize"))] type IntoIterInner<T> = std::collections::hash_map::IntoIter<T, usize>; /// An owning iterator over the distinct items of a `HashBag` and their occurrence counts. /// /// This `struct` is created by using the implementation of [`IntoIterator`] for [`HashBag`]. pub struct IntoIter<T>(IntoIterInner<T>); impl<T> std::iter::FusedIterator for IntoIter<T> where IntoIterInner<T>: std::iter::FusedIterator {} impl<T> ExactSizeIterator for IntoIter<T> where IntoIterInner<T>: ExactSizeIterator {} impl<T: fmt::Debug> fmt::Debug for IntoIter<T> { fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { self.0.fmt(fmt) } } impl<T> Iterator for IntoIter<T> { type Item = (T, usize); fn next(&mut self) -> Option<Self::Item> { self.0.next() } fn size_hint(&self) -> (usize, Option<usize>) { self.0.size_hint() } } #[cfg(feature = "amortize")] type DrainInner<'a, T> = griddle::hash_map::Drain<'a, T, usize>; #[cfg(not(feature = "amortize"))] type DrainInner<'a, T> = std::collections::hash_map::Drain<'a, T, usize>; /// An draining iterator over the distinct items of a `HashBag` and their occurrence counts. /// /// This `struct` is created by [`HashBag::drain`]. /// See its documentation for more. pub struct Drain<'a, T>(DrainInner<'a, T>); impl<'a, T> std::iter::FusedIterator for Drain<'a, T> where DrainInner<'a, T>: std::iter::FusedIterator { } impl<'a, T> ExactSizeIterator for Drain<'a, T> where DrainInner<'a, T>: ExactSizeIterator {} impl<'a, T: fmt::Debug> fmt::Debug for Drain<'a, T> { fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { self.0.fmt(fmt) } } impl<'a, T> Iterator for Drain<'a, T> { type Item = (T, usize); fn next(&mut self) -> Option<Self::Item> { self.0.next() } fn size_hint(&self) -> (usize, Option<usize>) { self.0.size_hint() } } #[cfg(test)] mod tests { use super::*; #[test] fn format_all_the_things() { let mut vikings: HashBag<&'static str> = ["Einar", "Olaf", "Harald"].iter().cloned().collect(); println!("{:?}", vikings); println!("{:?}", vikings.iter()); println!("{:?}", vikings.set_iter()); println!("{:?}", vikings.clone().into_iter()); println!("{:?}", vikings.drain()); } #[test] fn sane_iterators() { let mut vikings: HashBag<&'static str> = ["Einar", "Einar", "Harald"].iter().cloned().collect(); assert_eq!(vikings.iter().count(), 3); assert_eq!(vikings.iter().size_hint(), (3, Some(3))); assert_eq!(vikings.iter().clone().count(), 3); assert_eq!(vikings.set_iter().count(), 2); assert_eq!(vikings.set_iter().clone().count(), 2); assert_eq!(vikings.set_iter().size_hint(), (2, Some(2))); let ii = vikings.clone().into_iter(); assert_eq!(ii.size_hint(), (2, Some(2))); assert_eq!(ii.count(), 2); let di = vikings.drain(); assert_eq!(di.size_hint(), (2, Some(2))); assert_eq!(di.count(), 2); } }