123

node_modules/generic-pool/lib/Deque.js

@@ -0,0 +1,106 @@
+"use strict";
+
+const DoublyLinkedList = require("./DoublyLinkedList");
+const DequeIterator = require("./DequeIterator");
+/**
+ * DoublyLinkedList backed double ended queue
+ * implements just enough to keep the Pool
+ */
+class Deque {
+  constructor() {
+    this._list = new DoublyLinkedList();
+  }
+
+  /**
+   * removes and returns the first element from the queue
+   * @return {any} [description]
+   */
+  shift() {
+    if (this.length === 0) {
+      return undefined;
+    }
+
+    const node = this._list.head;
+    this._list.remove(node);
+
+    return node.data;
+  }
+
+  /**
+   * adds one elemts to the beginning of the queue
+   * @param  {any} element [description]
+   * @return {any}         [description]
+   */
+  unshift(element) {
+    const node = DoublyLinkedList.createNode(element);
+
+    this._list.insertBeginning(node);
+  }
+
+  /**
+   * adds one to the end of the queue
+   * @param  {any} element [description]
+   * @return {any}         [description]
+   */
+  push(element) {
+    const node = DoublyLinkedList.createNode(element);
+
+    this._list.insertEnd(node);
+  }
+
+  /**
+   * removes and returns the last element from the queue
+   */
+  pop() {
+    if (this.length === 0) {
+      return undefined;
+    }
+
+    const node = this._list.tail;
+    this._list.remove(node);
+
+    return node.data;
+  }
+
+  [Symbol.iterator]() {
+    return new DequeIterator(this._list);
+  }
+
+  iterator() {
+    return new DequeIterator(this._list);
+  }
+
+  reverseIterator() {
+    return new DequeIterator(this._list, true);
+  }
+
+  /**
+   * get a reference to the item at the head of the queue
+   * @return {any} [description]
+   */
+  get head() {
+    if (this.length === 0) {
+      return undefined;
+    }
+    const node = this._list.head;
+    return node.data;
+  }
+
+  /**
+   * get a reference to the item at the tail of the queue
+   * @return {any} [description]
+   */
+  get tail() {
+    if (this.length === 0) {
+      return undefined;
+    }
+    const node = this._list.tail;
+    return node.data;
+  }
+
+  get length() {
+    return this._list.length;
+  }
+}
+
+module.exports = Deque;