src/fixed-priority-queue.ts

   1 /**
   2  * Default buffer size.
   3  */
   4 export const defaultQueueSize = 2048
   5
   6 /**
   7  * Fixed priority queue node.
   8  * @typeParam T - Type of priority queue node data.
   9  * @internal
  10  */
  11 export interface FixedPriorityQueueNode<T> {
  12   data: T
  13   priority: number
  14 }
  15
  16 /**
  17  * Fixed priority queue.
  18  * @typeParam T - Type of fixed priority queue data.
  19  * @internal
  20  */
  21 export class FixedPriorityQueue<T> {
  22   private start!: number
  23   private readonly nodeArray: FixedPriorityQueueNode<T>[]
  24   /** The fixed priority queue capacity. */
  25   public readonly capacity: number
  26   /** The fixed priority queue size. */
  27   public size!: number
  28   /** Whether to enable priority. */
  29   public enablePriority: boolean
  30
  31   /**
  32    * Constructs a fixed priority queue.
  33    * @param size - Fixed priority queue size. @defaultValue defaultQueueSize
  34    * @param enablePriority - Whether to enable priority. @defaultValue false
  35    * @returns FixedPriorityQueue.
  36    */
  37   constructor (size: number = defaultQueueSize, enablePriority = false) {
  38     this.checkSize(size)
  39     this.capacity = size
  40     this.enablePriority = enablePriority
  41     this.nodeArray = new Array<FixedPriorityQueueNode<T>>(this.capacity)
  42     this.clear()
  43   }
  44
  45   /**
  46    * Checks if the fixed priority queue is empty.
  47    * @returns `true` if the fixed priority queue is empty, `false` otherwise.
  48    */
  49   public empty (): boolean {
  50     return this.size === 0
  51   }
  52
  53   /**
  54    * Checks if the fixed priority queue is full.
  55    * @returns `true` if the fixed priority queue is full, `false` otherwise.
  56    */
  57   public full (): boolean {
  58     return this.size === this.capacity
  59   }
  60
  61   /**
  62    * Enqueue data into the fixed priority queue.
  63    * @param data - Data to enqueue.
  64    * @param priority - Priority of the data. Lower values have higher priority.
  65    * @returns The new size of the priority queue.
  66    * @throws If the fixed priority queue is full.
  67    */
  68   public enqueue (data: T, priority?: number): number {
  69     if (this.full()) {
  70       throw new Error('Priority queue is full')
  71     }
  72     priority = priority ?? 0
  73     let inserted = false
  74     if (this.enablePriority) {
  75       let index = this.start
  76       for (let i = 0; i < this.size; i++) {
  77         if (this.nodeArray[index].priority > priority) {
  78           this.nodeArray.splice(index, 0, { data, priority })
  79           this.nodeArray.length = this.capacity
  80           inserted = true
  81           break
  82         }
  83         ++index
  84         if (index === this.capacity) {
  85           index = 0
  86         }
  87       }
  88     }
  89     if (!inserted) {
  90       let index = this.start + this.size
  91       if (index >= this.capacity) {
  92         index -= this.capacity
  93       }
  94       this.nodeArray[index] = { data, priority }
  95     }
  96     return ++this.size
  97   }
  98
  99   /**
 100    * Gets data from the fixed priority queue.
 101    * @param index - The index of the data to get.
 102    * @returns The data at the index or `undefined` if the fixed priority queue is empty or the index is out of bounds.
 103    */
 104   public get (index: number): T | undefined {
 105     if (this.empty() || index >= this.size) {
 106       return undefined
 107     }
 108     index += this.start
 109     if (index >= this.capacity) {
 110       index -= this.capacity
 111     }
 112     return this.nodeArray[index].data
 113   }
 114
 115   /**
 116    * Dequeue data from the fixed priority queue.
 117    * @returns The dequeued data or `undefined` if the priority queue is empty.
 118    */
 119   public dequeue (): T | undefined {
 120     if (this.empty()) {
 121       return undefined
 122     }
 123     const index = this.start
 124     --this.size
 125     ++this.start
 126     if (this.start === this.capacity) {
 127       this.start = 0
 128     }
 129     return this.nodeArray[index].data
 130   }
 131
 132   /**
 133    * Clears the fixed priority queue.
 134    */
 135   public clear (): void {
 136     this.start = 0
 137     this.size = 0
 138   }
 139
 140   /**
 141    * Returns an iterator for the fixed priority queue.
 142    * @returns An iterator for the fixed priority queue.
 143    * @see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols
 144    */
 145   public [Symbol.iterator] (): Iterator<T> {
 146     let index = this.start
 147     let i = 0
 148     return {
 149       next: () => {
 150         if (i >= this.size) {
 151           return {
 152             value: undefined,
 153             done: true,
 154           }
 155         }
 156         const value = this.nodeArray[index].data
 157         ++index
 158         ++i
 159         if (index === this.capacity) {
 160           index = 0
 161         }
 162         return {
 163           value,
 164           done: false,
 165         }
 166       },
 167     }
 168   }
 169
 170   /**
 171    * Checks the queue size.
 172    * @param size - Queue size.
 173    */
 174   private checkSize (size: number): void {
 175     if (!Number.isSafeInteger(size)) {
 176       throw new TypeError(
 177         `Invalid fixed priority queue size: '${size.toString()}' is not an integer`
 178       )
 179     }
 180     if (size < 0) {
 181       throw new RangeError(
 182         `Invalid fixed priority queue size: ${size.toString()} < 0`
 183       )
 184     }
 185   }
 186 }