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//! Implementation of an "adressable queue", that is a FIFO queue where it is //! possible to directly remove values directly by a key. // Copyright 2018 Leonardo Schwarz <mail@leoschwarz.com> // // Licensed under the Apache License, Version 2.0 (the "License"); // you may not use this file except in compliance with the License. // You may obtain a copy of the License at // // http://www.apache.org/licenses/LICENSE-2.0 // // Unless required by applicable law or agreed to in writing, software // distributed under the License is distributed on an "AS IS" BASIS, // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. // See the License for the specific language governing permissions and // limitations under the License. use std::collections::{HashMap, VecDeque}; use std::hash::Hash; use std::sync::{Arc, Mutex}; struct Item<K, V> { pub key: K, pub val: Mutex<Option<V>>, } /// An addressable FIFO queue. /// /// This data structure combines operations from a FIFO queue with the option to remove elements by /// directly specifying their key, in an efficient manner. pub struct Queue<K, V> { items: VecDeque<Arc<Item<K, V>>>, pointers: HashMap<K, Arc<Item<K, V>>>, } impl<K, V> Queue<K, V> where K: Clone + Eq + Hash, { /// Create a new instance of a queue. pub fn new() -> Self { Queue { items: VecDeque::new(), pointers: HashMap::new(), } } /// Create a new instance of a queue, populated with the provided pairs. /// /// ``` /// use addressable_queue::fifo::Queue; /// /// let mut queue = Queue::new_with(vec![(2u8, 4u8), (3, 6), (4, 8)]); /// /// assert_eq!(Some((2, 4)), queue.remove_head()); /// assert_eq!(Some((3, 6)), queue.remove_head()); /// assert_eq!(Some((4, 8)), queue.remove_head()); /// assert_eq!(None, queue.remove_head()); /// ``` pub fn new_with(pairs: Vec<(K, V)>) -> Self { let mut queue = Queue::new(); for (k, v) in pairs { queue.insert(k, v); } queue } /// Returns the lenght of the queue. /// /// ``` /// use addressable_queue::fifo::Queue; /// /// let mut queue = Queue::new(); /// queue.insert(2u8, 4u8); /// queue.insert(3u8, 6u8); /// queue.insert(4u8, 8u8); /// /// assert_eq!(3, queue.len()); /// queue.remove_head(); /// assert_eq!(2, queue.len()); /// queue.remove_head(); /// queue.remove_head(); /// assert_eq!(0, queue.len()); /// ``` pub fn len(&self) -> usize { self.pointers.len() } /// Returns true if the queue contains an element for the specified key. /// /// ``` /// use addressable_queue::fifo::Queue; /// /// let mut queue = Queue::new(); /// queue.insert(2u8, 4u8); /// queue.insert(3u8, 6u8); /// queue.insert(4u8, 8u8); /// queue.remove_key(&3); /// /// assert_eq!(queue.contains_key(&2), true); /// assert_eq!(queue.contains_key(&3), false); /// assert_eq!(queue.contains_key(&4), true); /// ``` pub fn contains_key(&self, key: &K) -> bool { self.pointers.contains_key(key) } /// Insert an entry at the end of the queue. /// /// ``` /// use addressable_queue::fifo::Queue; /// /// let mut queue = Queue::new(); /// queue.insert(2u8, 4u8); /// queue.insert(3u8, 6u8); /// queue.insert(4u8, 8u8); /// /// assert_eq!(Some((2, 4)), queue.remove_head()); /// assert_eq!(Some((3, 6)), queue.remove_head()); /// assert_eq!(Some((4, 8)), queue.remove_head()); /// assert_eq!(None, queue.remove_head()); /// ``` pub fn insert(&mut self, key: K, value: V) { let arc = Arc::new(Item { key: key.clone(), val: Mutex::new(Some(value)), }); self.items.push_back(Arc::clone(&arc)); self.pointers.insert(key, arc); } /// Insert an entry at the front of the queue. /// /// This is mostly useful when removing the head and /// then deciding to put it back into the queue. /// /// ``` /// use addressable_queue::fifo::Queue; /// /// let mut queue = Queue::new(); /// queue.insert_head(2u8, 4u8); /// queue.insert_head(3u8, 6u8); /// queue.insert_head(4u8, 8u8); /// /// assert_eq!(Some((4, 8)), queue.remove_head()); /// assert_eq!(Some((3, 6)), queue.remove_head()); /// assert_eq!(Some((2, 4)), queue.remove_head()); /// assert_eq!(None, queue.remove_head()); /// ``` pub fn insert_head(&mut self, key: K, value: V) { let arc = Arc::new(Item { key: key.clone(), val: Mutex::new(Some(value)), }); self.items.push_front(Arc::clone(&arc)); self.pointers.insert(key, arc); } /// Remove the current head of the queue, and return the value if there was one. /// /// ``` /// use addressable_queue::fifo::Queue; /// /// let mut queue = Queue::new(); /// queue.insert(2u8, 4u8); /// queue.insert(3u8, 6u8); /// queue.insert(4u8, 8u8); /// /// assert_eq!(Some((2, 4)), queue.remove_head()); /// assert_eq!(Some((3, 6)), queue.remove_head()); /// assert_eq!(Some((4, 8)), queue.remove_head()); /// assert_eq!(None, queue.remove_head()); /// ``` pub fn remove_head(&mut self) -> Option<(K, V)> { while let Some(item) = self.items.pop_front() { let is_some = item.val.lock().unwrap().is_some(); if is_some { self.pointers.remove(&item.key); let key = item.key.clone(); let value = Arc::try_unwrap(item) .ok() .unwrap() .val .into_inner() .unwrap() .unwrap(); return Some((key, value)); } } None } /// Remove the current tail of the queue, and return the value if there was one. /// /// ``` /// use addressable_queue::fifo::Queue; /// /// let mut queue = Queue::new(); /// queue.insert(2u8, 4u8); /// queue.insert(3u8, 6u8); /// queue.insert(4u8, 8u8); /// /// assert_eq!(Some((4, 8)), queue.remove_tail()); /// assert_eq!(Some((3, 6)), queue.remove_tail()); /// assert_eq!(Some((2, 4)), queue.remove_tail()); /// assert_eq!(None, queue.remove_tail()); /// ``` pub fn remove_tail(&mut self) -> Option<(K, V)> { while let Some(item) = self.items.pop_back() { let is_some = item.val.lock().unwrap().is_some(); if is_some { self.pointers.remove(&item.key); let key = item.key.clone(); let value = Arc::try_unwrap(item) .ok() .unwrap() .val .into_inner() .unwrap() .unwrap(); return Some((key, value)); } } None } /// Remove a value by specifying its key. /// /// ``` /// use addressable_queue::fifo::Queue; /// /// let mut queue = Queue::new(); /// queue.insert(2u8, 4u8); /// queue.insert(3u8, 6u8); /// queue.insert(4u8, 8u8); /// /// assert_eq!(Some(4), queue.remove_key(&2)); /// assert_eq!(Some(6), queue.remove_key(&3)); /// assert_eq!(None, queue.remove_key(&3)); /// assert_eq!(Some(8), queue.remove_key(&4)); /// assert_eq!(None, queue.remove_head()); /// ``` pub fn remove_key(&mut self, key: &K) -> Option<V> { if let Some(item) = self.pointers.remove(key) { let mut val = None; ::std::mem::swap(&mut val, &mut *item.val.lock().unwrap()); return val; } None } /// Convert the queue into a vec, where the first element is the head (oldest element). /// /// ``` /// use addressable_queue::fifo::Queue; /// /// let mut queue = Queue::new(); /// queue.insert(2u8, 4u8); /// queue.insert(3u8, 6u8); /// queue.insert(4u8, 8u8); /// /// let vec = queue.into_vec(); /// assert_eq!(vec, vec![(2,4), (3,6), (4,8)]); /// ``` pub fn into_vec(mut self) -> Vec<(K, V)> { let mut vec = Vec::new(); while let Some(pair) = self.remove_head() { vec.push(pair); } vec } } #[cfg(feature = "serde")] mod serde_compat { use serde::{Deserialize, Deserializer, Serialize, Serializer}; use serde::ser::SerializeSeq; use super::Queue; use std::hash::Hash; impl<K, V> Serialize for Queue<K, V> where K: Serialize + Clone + Eq + Hash, V: Serialize, { fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error> where S: Serializer, { let mut seq = serializer.serialize_seq(Some(self.len()))?; for item in &self.items { let val = item.val.lock().unwrap(); if val.is_some() { let v = val.as_ref().unwrap(); seq.serialize_element(&(&item.key, v))?; } } seq.end() } } impl<'de, K, V> Deserialize<'de> for Queue<K, V> where K: Deserialize<'de> + Clone + Eq + Hash, V: Deserialize<'de>, { fn deserialize<D>(deserializer: D) -> Result<Self, D::Error> where D: Deserializer<'de>, { let data: Vec<(K, V)> = Vec::deserialize(deserializer)?; Ok(Queue::new_with(data)) } } #[cfg(test)] #[test] fn serde_test() { use serde_json; let queue = Queue::new_with(vec![(2u8, 4u8), (3, 6), (4, 8)]); let json = serde_json::to_string(&queue).unwrap(); let mut queue2: Queue<u8, u8> = serde_json::from_str(&json).unwrap(); assert_eq!(queue2.len(), 3); assert_eq!(queue2.remove_head(), Some((2, 4))); assert_eq!(queue2.remove_head(), Some((3, 6))); assert_eq!(queue2.remove_head(), Some((4, 8))); } }