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//! # Queues //! //! `queues` provides a number of efficient FIFO Queue data structures for //! usage in your libraries. These are all implemented on top of rust's `Vector` //! type. //! //! A queue is a linear data structure that commonly defines three methods: //! //! 1. `add`: Also called `queue` or `push`, this adds elements to the queue. //! 2. `remove`: Also called `deque` or `pop`, this removes the _oldest_ //! element from the queue. //! 3. `peek`: Show the next element in the queue scheduled for removal. //! //! There are a number of variants of queues. In this crate, the available //! variants are: //! //! - `Queue<T>`: A simple FIFO queue with a growable size and no limit on its //! capacity. //! - `Buffer<T>`: A FIFO queue with with a limited capacity. The buffer can //! have a growable size (up to the defined capacity), or it can be //! initialized at capacity, with empty slots being occupied by default //! values. //! - `CircularBuffer<T>`: Similar to the buffer above, but allowing for //! overflow. Any additions to the circular buffer that would exceed its //! capacity causes its oldest element to be pushed out. //! //! # Quick start //! //! Quick guide to getting started with the project: //! //! ## Installation //! //! ### Library usage //! //! To use the library in your project, simply ensure that the `queues` crate //! has been added to your dependencies in your `Cargo.toml` file. //! //! ```yaml //! [dependencies] //! queues = "1.0.0" //! ``` //! //! In your files, import the crate and use it's members: //! //! ```rust //! # #[macro_use] //! extern crate queues; //! use queues::*; //! # fn main() { } //! ``` //! //! ### Source code //! //! To get the project up and running: //! //! ```bash //! > cd ${WORKING_DIR} //! > git clone <this_repo> //! > cargo build //! ``` //! //! ## Testing //! //! Run the test suite using `cargo`: //! //! ```bash //! > cd ${PROJECT_FOLDER} //! > cargo test //! ``` //! //! ## Examples //! //! The project has a number of examples you can run to see how the library members work. //! //! The example names are: //! //! - `queue` Queue example //! - `buf` Buffer example //! - `cbuf` Circular buffer example //! - `cbuf_def` Circular buffer with default values example //! //! ```bash //! > cd ${PROJECT_FOLDER} //! > cargo run --example ${EXAMPLE_NAME} //! ``` //! //! # Usage //! //! Simple usage is described below: //! //! ```rust //! #[macro_use] //! extern crate queues; //! //! use queues::*; //! //! fn main() { //! // Create a simple Queue //! let mut q: Queue<isize> = queue![]; //! //! // Add some elements to it //! q.add(1); //! q.add(-2); //! q.add(3); //! //! // Check the Queue's size //! q.size(); // 3 //! //! // Remove an element //! q.remove(); // Ok(1) //! //! // Check the Queue's size //! q.size(); // 2 //! //! // Peek at the next element scheduled for removal //! q.peek(); // Ok(-2) //! //! // Confirm that the Queue size hasn't changed //! q.size(); // 2 //! //! // Remove the remaining elements //! q.remove(); // Ok(-2) //! q.remove(); // Ok(3) //! //! // Peek into an empty Queue //! q.peek(); // Raises an error //! //! // Attempt to remove an element from an empty Queue //! q.remove(); // Raises an error //! } //! ``` //! //! The examples contain more information on `Buffer` and `CircularBuffer` //! usage #![warn(missing_docs)] /// Defines methods that would be expected on a queue data structure pub trait IsQueue<T: Clone> { /// Adds a new value to a queue /// /// # Parameters /// - `val`: Value to add to the queue /// /// # Returns /// - `Ok(_)`: If the element add was successful. /// - `Some(T)`: If adding an element resulted in the removal of an /// existing one (in the case of a circular buffer, for instance) /// - `None`: Adding an element did not return any value /// - `Error`: If the element add was unsuccessful /// /// # Errors /// Attempting to add an element to a full queue that does not allow for /// overflow will return an error. fn add(&mut self, val: T) -> Result<Option<T>, &str>; /// Removes an element from the queue and returns it /// /// For queues with default values, removing an element will add a new /// default value into the queue. /// /// # Returns /// - `Ok(T)`: The oldest element in the queue /// - `Error` /// /// # Errors /// Returns an error if an attempt is made to remove an element from /// an empty queue fn remove(&mut self) -> Result<T, &str>; /// Peek at the head of the queue /// /// # Returns /// - `Ok(T)`: The next element scheduled for removal from the queue /// - `Error` /// /// # Errors /// Returns an error if an attempt is made to peek into an empty queue fn peek(&self) -> Result<T, &str>; /// Gets the size of the queue /// /// # Returns /// The number of elements in the queue. Note, this _includes_ default /// values when specified, which means that the `size` of a queue with /// default values should always be equal to its `capacity` fn size(&self) -> usize; } /// A simple FIFO queue with a growable size and no limit on its capacity. /// /// # Type parameters /// - `T`: Any type that implements the `Clone` trait. /// /// # Examples /// /// This example uses the `queue!` macro to add elements to the queue. Note /// that the first element in the list of elements passed to the macro is /// considered the 'oldest'. /// /// ``` /// # #[macro_use] extern crate queues; /// # use queues::*; /// # fn main() { /// let mut q = queue![3isize, 4, 5]; /// /// // Add an element /// assert_eq!(q.add(6), Ok(None)); /// /// // Remove some elements /// assert_eq!(q.remove(), Ok(3)); /// assert_eq!(q.remove(), Ok(4)); /// /// // Peek at the next element scheduled for removal /// assert_eq!(q.peek(), Ok(5)); /// /// // Check the queue size /// assert_eq!(q.size(), 2); /// # } /// ``` #[derive(Debug)] pub struct Queue<T: Clone> { queue: Vec<T>, } impl<T: Clone> Queue<T> { /// Create a new queue /// /// # Returns /// A new, empty `Queue<T>` /// /// # Examples /// /// ``` /// # use queues::*; /// let q: Queue<isize> = Queue::new(); /// assert_eq!(q.size(), 0); /// ``` pub fn new() -> Queue<T> { Queue { queue: vec![] } } } impl<T: Clone> Default for Queue<T> { /// Default queue initializer /// /// # Returns /// A new, empty `Queue<T>` /// /// # Examples /// /// ``` /// # use queues::*; /// let q: Queue<isize> = Queue::default(); /// assert_eq!(q.size(), 0); /// ``` fn default() -> Queue<T> { Queue { queue: vec![] } } } impl<T: Clone> IsQueue<T> for Queue<T> { /// Adds an element to a queue /// /// # Parameters /// - `val`: Value to add to the queue /// /// # Returns /// `Ok(None)` as the element addition should always be successful /// /// # Examples /// /// ``` /// # use queues::*; /// let mut q: Queue<isize> = Queue::new(); /// assert_eq!(q.add(42), Ok(None)); /// assert_eq!(q.size(), 1); /// ``` fn add(&mut self, val: T) -> Result<Option<T>, &str> { self.queue.push(val); Ok(None) } /// Removes an element from the queue and returns it /// /// # Returns /// - `Ok(T)`: The oldest element in the queue /// - `Error` /// /// # Errors /// Returns an error if an attempt is made to remove an element from /// an empty queue /// /// # Examples /// /// ``` /// # use queues::*; /// let mut q: Queue<isize> = Queue::new(); /// q.add(42); /// assert_eq!(q.remove(), Ok(42)); /// assert_eq!(q.size(), 0); /// ``` fn remove(&mut self) -> Result<T, &str> { if self.queue.len() > 0 { Ok(self.queue.remove(0usize)) } else { Err("The queue is empty") } } /// Peek at the head of the queue /// /// # Returns /// - `Ok(T)`: The next element scheduled for removal from the queue /// - `Error` /// /// # Errors /// Returns an error if an attempt is made to peek into an empty queue /// /// # Examples /// /// ``` /// # use queues::*; /// let mut q: Queue<isize> = Queue::new(); /// q.add(42); /// assert_eq!(q.peek(), Ok(42)); /// ``` fn peek(&self) -> Result<T, &str> { match self.queue.first() { Some(val) => Ok(val.clone()), None => Err("The Queue is empty"), } } /// Gets the size of the queue /// /// # Returns /// The number of elements in the queue /// /// # Examples /// /// ``` /// # use queues::*; /// let mut q: Queue<isize> = Queue::new(); /// assert_eq!(q.size(), 0); /// let _ = q.add(42); /// assert_eq!(q.size(), 1); /// ``` fn size(&self) -> usize { self.queue.len() } } /// Creates a new `Queue<T>` /// /// Delegates to the default queue initializer. Note that the elements are /// added to the queue from left to right, therefore the first element in the /// list of parameters passed to the macro is considered the 'oldest' element /// in the queue. /// /// # Example /// ``` /// # #[macro_use] /// # extern crate queues; /// # use queues::*; /// /// # fn main() { /// let q = queue![3isize, 4, 5]; /// assert_eq!(q.peek(), Ok(3)); /// /// let q_empty: Queue<isize> = queue![]; /// assert_eq!(q_empty.size(), 0); /// # } /// ``` #[macro_export] macro_rules! queue { () => { Queue::new() }; ($($x:expr),+) => { { let mut temp_q = Queue::default(); $( let _ = temp_q.add($x); )* temp_q } }; } /// A FIFO buffer with a growable size and a capacity limit /// /// # Type parameters /// - `T`: Any type that implements the `Clone` trait. /// /// # Examples /// /// ``` /// # use queues::*; /// let mut buf = Buffer::new(3); /// /// // Add some elements /// assert_eq!(buf.add(6), Ok(None)); /// assert_eq!(buf.add(7), Ok(None)); /// /// // Remove an element /// assert_eq!(buf.remove(), Ok(6)); /// /// // Peek at the next element scheduled for removal /// assert_eq!(buf.peek(), Ok(7)); /// /// // Check the queue size /// assert_eq!(buf.size(), 1); /// ``` #[derive(Debug)] pub struct Buffer<T: Clone> { queue: Vec<T>, capacity: usize, } impl<T: Clone> Buffer<T> { /// Create a new buffer /// /// # Returns /// A new, empty `Buffer<T>` /// /// # Examples /// /// ``` /// # use queues::*; /// let buf: Buffer<isize> = Buffer::new(3); /// assert_eq!(buf.size(), 0); /// ``` pub fn new(capacity: usize) -> Buffer<T> { Buffer { queue: vec![], capacity, } } /// Gets the capacity of the buffer /// /// # Returns /// The number of allowed elements in the buffer /// /// # Examples /// /// ``` /// # use queues::*; /// let mut buf: Buffer<isize> = Buffer::new(5); /// assert_eq!(buf.capacity(), 5); /// ``` pub fn capacity(&self) -> usize { self.capacity } } impl<T: Clone> IsQueue<T> for Buffer<T> { /// Adds an element to a buffer /// /// # Parameters /// - `val`: Value to add to the buffer /// /// # Returns /// - `Ok(None)`: Element addition was successful /// - `Error` /// /// # Errors /// Returns an error if an attempt is made to add an element to a full /// buffer /// /// # Examples /// /// ``` /// use queues::*; /// /// let mut buf: Buffer<isize> = Buffer::new(3); /// assert_eq!(buf.add(42), Ok(None)); /// ``` fn add(&mut self, val: T) -> Result<Option<T>, &str> { if self.queue.len() < self.capacity { self.queue.push(val); Ok(None) } else { Err("The buffer is full") } } /// Removes an element from the buffer and returns it. /// /// # Returns /// - `Ok(T)`: The oldest element in the buffer /// - `Error` /// /// # Errors /// Returns an error if an attempt is made to remove an element from /// an empty buffer /// /// # Examples /// /// ``` /// # use queues::*; /// let mut buf: Buffer<isize> = Buffer::new(3); /// buf.add(42); /// assert_eq!(buf.remove(), Ok(42)); /// assert_eq!(buf.size(), 0); /// ``` fn remove(&mut self) -> Result<T, &str> { if self.queue.len() > 0 { Ok(self.queue.remove(0usize)) } else { Err("The buffer is empty") } } /// Peek at the head of the buffer /// /// # Returns /// - `Ok(T)`: The next element scheduled for removal from the buffer /// - `Error` /// /// # Errors /// Returns an error if an attempt is made to peek into an empty buffer /// /// # Examples /// /// ``` /// # use queues::*; /// let mut buf: Buffer<isize> = Buffer::new(3); /// buf.add(42); /// assert_eq!(buf.peek(), Ok(42)); /// ``` fn peek(&self) -> Result<T, &str> { match self.queue.first() { Some(val) => Ok(val.clone()), None => Err("The buffer is empty"), } } /// Gets the size of the buffer /// /// # Returns /// The number of elements in the buffer. /// /// # Examples /// /// ``` /// # use queues::*; /// let mut buf: Buffer<isize> = Buffer::new(3); /// assert_eq!(buf.size(), 0); /// buf.add(42); /// assert_eq!(buf.size(), 1); /// ``` fn size(&self) -> usize { self.queue.len() } } /// Represents a FIFO `CircularBuffer<T>` data structure. /// /// This structure is a limited capacity queue, with optional provisions /// for default values. Under normal circumstances, the `size` of the /// queue grows until it reaches its `capacity`, at which point any /// further additions push out its oldest member. /// /// If default values are specified, then the `size` of the queue /// is always equal to its `capacity`, with empty slots occupied by the /// specified default value. /// /// # Type parameters /// - `T`: Any type that implements the `Clone` trait. /// /// # Examples /// /// ``` /// # use queues::*; /// # fn main() { /// let mut cbuf = CircularBuffer::<isize>::new(3); /// let mut cbuf_def = CircularBuffer::with_default(3, 0isize); /// /// // Check sizes /// assert_eq!(cbuf.size(), 0); /// assert_eq!(cbuf_def.size(), 3); /// /// // Add elements /// cbuf.add(6); /// cbuf_def.add(7); /// /// // Peek at the next element scheduled for removal /// assert_eq!(cbuf.peek().unwrap(), 6); /// assert_eq!(cbuf_def.peek().unwrap(), 0); /// # } /// ``` #[derive(Debug)] pub struct CircularBuffer<T: Clone> { queue: Vec<T>, capacity: usize, default_value: Option<T>, } impl<T: Clone> CircularBuffer<T> { /// Default `CircularBuffer<T>` initializer /// /// # Returns /// A new, empty `CircularBuffer<T>` /// /// # Examples /// /// ``` /// # use queues::*; /// let cbuf: CircularBuffer<isize> = CircularBuffer::new(3); /// assert_eq!(cbuf.size(), 0); /// assert_eq!(cbuf.capacity(), 3); /// ``` pub fn new(capacity: usize) -> CircularBuffer<T> { CircularBuffer { queue: vec![], capacity, default_value: None, } } /// Create a `CircularBuffer<T>` with default values /// /// # Returns /// A new `CircularBuffer<T>` filled with default values /// /// # Examples /// /// ``` /// # use queues::*; /// let cbuf_def = CircularBuffer::with_default(3, -1isize); /// assert_eq!(cbuf_def.size(), 3); /// assert_eq!(cbuf_def.capacity(), 3); /// assert_eq!(cbuf_def.peek(), Ok(-1)); /// ``` pub fn with_default(capacity: usize, default_value: T) -> CircularBuffer<T> { let queue = vec![default_value.clone(); capacity]; CircularBuffer { queue, capacity, default_value: Some(default_value), } } /// Gets the capacity of the `CircularBuffer<T>` /// /// # Returns /// The number of allowed elements in the buffer /// /// # Examples /// /// ``` /// # use queues::CircularBuffer; /// let mut cbuf: CircularBuffer<isize> = CircularBuffer::new(3); /// assert_eq!(cbuf.capacity(), 3); /// ``` pub fn capacity(&self) -> usize { self.capacity } } impl<T: Clone> IsQueue<T> for CircularBuffer<T> { /// Adds an element to a circular buffer /// /// # Parameters /// - `val`: Value to add to the buffer /// /// # Returns /// - `Ok(Some(T))`: The oldest value in the buffer, in case the addition /// causes an overflow. /// - `Ok(None)`: Nothing, if the buffer has room for the added element /// /// # Examples /// /// ``` /// # use queues::*; /// let mut cbuf: CircularBuffer<isize> = CircularBuffer::new(3); /// let mut cbuf_def = CircularBuffer::with_default(3, 5isize); /// assert_eq!(cbuf.add(42), Ok(None)); /// assert_eq!(cbuf_def.add(42), Ok(Some(5))); /// ``` fn add(&mut self, val: T) -> Result<Option<T>, &str> { if self.queue.len() < self.capacity { self.queue.push(val); Ok(None) } else { self.queue.push(val); Ok(Some(self.queue.remove(0usize))) } } /// Removes an element from the circular buffer and returns it. /// /// For circular buffers with default values, removing an element will add /// a new default value into the buffer. /// /// # Returns /// - `Ok(T)`: The oldest element in the buffer /// - `Error` /// /// # Errors /// Returns an error if an attempt is made to remove an element from /// an empty buffer /// /// # Examples /// /// ``` /// # use queues::*; /// let mut cbuf: CircularBuffer<isize> = CircularBuffer::new(3); /// cbuf.add(42); /// assert_eq!(cbuf.remove(), Ok(42)); /// assert_eq!(cbuf.size(), 0); /// /// let mut cbuf_def = CircularBuffer::with_default(3, 4isize); /// cbuf_def.add(42); /// assert_eq!(cbuf_def.remove(), Ok(4)); /// ``` fn remove(&mut self) -> Result<T, &str> { if self.queue.len() > 0 { if let Some(val) = self.default_value.clone() { self.queue.push(val); }; Ok(self.queue.remove(0usize)) } else { Err("The Buffer is empty") } } /// Peek at the head of the circular buffer /// /// # Returns /// - `Ok(T)`: The next element scheduled for removal from the buffer /// - `Error` /// /// # Errors /// Returns an error if an attempt is made to peek into an empty buffer /// /// # Examples /// /// ``` /// # use queues::*; /// let mut cbuf: CircularBuffer<isize> = CircularBuffer::new(3); /// cbuf.add(42); /// assert_eq!(cbuf.peek(), Ok(42)); /// ``` fn peek(&self) -> Result<T, &str> { match self.queue.first() { Some(val) => Ok(val.clone()), None => Err("The Queue is empty"), } } /// Gets the size of the circular buffer /// /// # Returns /// The number of elements in the buffer. Note, this _includes_ default /// values, which means that the `size` of a buffer with default values /// should always be equal to its `capacity` /// /// # Examples /// /// ``` /// # use queues::*; /// let mut cbuf: CircularBuffer<isize> = CircularBuffer::new(3); /// assert_eq!(cbuf.size(), 0); /// cbuf.add(42); /// assert_eq!(cbuf.size(), 1); /// ``` fn size(&self) -> usize { self.queue.len() } }