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ullist.js

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+/*
+    ullist.js
+
+    Description: Defines ULList, which represents a doubly linked list
+    in which each item has a unique identifier stored in the `uid` field.
+
+*/
+
+function ULList() {
+    this.first = null;
+    this.last = null;
+    this.length = 0;
+}
+
+/* Add an item to the beginning of the list */
+ULList.prototype.prepend = function(item) {
+    if(this.first !== null) {
+        item.next = this.first;
+        this.first.prev = item;
+    }
+    else {
+        this.last = item;
+    }
+    this.first = item;
+    this.first.prev = null;
+    this.length++;
+    return true;
+}
+
+/* Add an item to the end of the list */
+ULList.prototype.append = function(item) {
+    if(this.last !== null) {
+        item.prev = this.last;
+        this.last.next = item;
+    }
+    else {
+        this.first = item;
+    }
+    this.last = item;
+    this.last.next = null;
+    this.length++;
+    return true;
+}
+
+/* Insert an item after one which has a specified UID */
+ULList.prototype.insertAfter = function(item, uid) {
+    var after = this.find(uid);
+
+    if(!after)
+        return false;
+
+    // Update links
+    item.next = after.next;
+    if(item.next)
+        item.next.prev = item;
+    item.prev = after;
+    after.next = item;
+
+    // New end of list
+    if(after == this.last)
+        this.last = item;
+
+    this.length++;
+
+    return true;
+}
+
+/* Insert an item before one that has a specified UID */
+ULList.prototype.insertBefore = function(item, uid) {
+    var before = this.find(uid);
+
+    if(!before)
+        return false;
+
+    // Update links
+    item.next = before;
+    item.prev = before.prev;
+    if(item.prev)
+        item.prev.next = item;
+    before.prev = item;
+
+    // New beginning of list
+    if(before == this.first)
+        this.first = item;
+
+    this.length++;
+
+    return true;
+}
+
+/* Remove an item from the list */
+ULList.prototype.remove = function(uid) {
+    var item = this.find(uid);
+    if(!item)
+        return false;
+
+    // Boundary conditions
+    if(item == this.first)
+        this.first = item.next;
+    if(item == this.last)
+        this.last = item.prev;
+
+    // General case
+    if(item.prev)
+        item.prev.next = item.next;
+    if(item.next)
+        item.next.prev = item.prev;
+
+    this.length--;
+    return true;
+}
+
+/* Find an element in the list, return false if specified UID not found */
+ULList.prototype.find = function(uid) {
+    // Can't possibly find it in an empty list
+    if(this.first === null)
+        return false;
+
+    var item = this.first;
+    var iter = this.first;
+    while(iter !== null && item.uid != uid) {
+        item = iter;
+        iter = iter.next;
+    }
+
+    if(item && item.uid == uid)
+        return item;
+    return false;
+}
+
+/* Clear all elements from the list */
+ULList.prototype.clear = function() {
+    this.first = null;
+    this.last = null;
+    this.length = 0;
+}
+
+/* Dump the contents of the list into an array */
+ULList.prototype.toArray = function() {
+    var arr = new Array(this.length);
+    var item = this.first;
+    var i = 0;
+    while(item !== null) {
+        if(typeof item.pack == "function")
+            arr[i++] = item.pack();
+        else
+            arr[i++] = item;
+        item = item.next;
+    }
+    return arr;
+}
+
+exports.ULList = ULList;