Linked list structure for polygon renderer

src/ol/structs/linkedlist.js

@@ -0,0 +1,247 @@
+goog.provide('ol.structs.LinkedList');
+
+/**
+ * Creates an empty linked list structure.
+ *
+ * @constructor
+ * @param {boolean=} opt_circular The last item is connected to the first one,
+ * and the first item to the last one. Default is true.
+ */
+ol.structs.LinkedList = function(opt_circular) {
+
+  /**
+   * @private
+   * @type {ol.LinkedListItem|undefined}
+   */
+  this.first_ = undefined;
+
+  /**
+   * @private
+   * @type {ol.LinkedListItem|undefined}
+   */
+  this.last_ = undefined;
+
+  /**
+   * @private
+   * @type {ol.LinkedListItem|undefined}
+   */
+  this.head_ = undefined;
+
+  /**
+   * @private
+   * @type {boolean}
+   */
+  this.circular_ = opt_circular === undefined ? true : opt_circular;
+
+  /**
+   * @private
+   * @type {number}
+   */
+  this.length_ = 0;
+};
+
+/**
+ * Inserts an item into the linked list right after the current one.
+ *
+ * @param {?} data Item data.
+ */
+ol.structs.LinkedList.prototype.insertItem = function(data) {
+
+  /** @type {ol.LinkedListItem} */
+  var item = {
+    prev: undefined,
+    next: undefined,
+    data: data
+  };
+
+  var head = this.head_;
+
+  //Initialize the list.
+  if (!head) {
+    this.first_ = item;
+    this.last_ = item;
+    if (this.circular_) {
+      item.next = item;
+      item.prev = item;
+    }
+  } else {
+    //Link the new item to the adjacent ones.
+    var next = head.next;
+    item.prev = head;
+    item.next = next;
+    head.next = item;
+    if (next) {
+      next.prev = item;
+    }
+
+    if (head === this.last_) {
+      this.last_ = item;
+    }
+  }
+  this.head_ = item;
+  this.length_++;
+};
+
+/**
+ * Removes the current item from the list. Sets the cursor to the next item,
+ * if possible.
+ */
+ol.structs.LinkedList.prototype.removeItem = function() {
+  var head = this.head_;
+  if (head) {
+    var next = head.next;
+    var prev = head.prev;
+    if (next) {
+      next.prev = prev;
+    }
+    if (prev) {
+      prev.next = next;
+    }
+    this.head_ = next || prev;
+
+    if (this.first_ === this.last_) {
+      this.head_ = undefined;
+      this.first_ = undefined;
+      this.last_ = undefined;
+    } else if (this.first_ === head) {
+      this.first_ = this.head_;
+    } else if (this.last_ === head) {
+      this.last_ = prev ? this.head_.prev : this.head_;
+    }
+    this.length_--;
+  }
+};
+
+/**
+ * Sets the cursor to the first item, and returns the associated data.
+ *
+ * @return {?} Item data.
+ */
+ol.structs.LinkedList.prototype.firstItem = function() {
+  this.head_ = this.first_;
+  if (this.head_) {
+    return this.head_.data;
+  }
+  return undefined;
+};
+
+/**
+* Sets the cursor to the last item, and returns the associated data.
+*
+* @return {?} Item data.
+*/
+ol.structs.LinkedList.prototype.lastItem = function() {
+  this.head_ = this.last_;
+  if (this.head_) {
+    return this.head_.data;
+  }
+  return undefined;
+};
+
+/**
+ * Sets the cursor to the next item, and returns the associated data.
+ *
+ * @return {?} Item data.
+ */
+ol.structs.LinkedList.prototype.nextItem = function() {
+  if (this.head_ && this.head_.next) {
+    this.head_ = this.head_.next;
+    return this.head_.data;
+  }
+  return undefined;
+};
+
+/**
+ * Returns the next item's data without moving the cursor.
+ *
+ * @return {?} Item data.
+ */
+ol.structs.LinkedList.prototype.getNextItem = function() {
+  if (this.head_ && this.head_.next) {
+    return this.head_.next.data;
+  }
+  return undefined;
+};
+
+/**
+ * Sets the cursor to the previous item, and returns the associated data.
+ *
+ * @return {?} Item data.
+ */
+ol.structs.LinkedList.prototype.prevItem = function() {
+  if (this.head_ && this.head_.prev) {
+    this.head_ = this.head_.prev;
+    return this.head_.data;
+  }
+  return undefined;
+};
+
+/**
+ * Returns the previous item's data without moving the cursor.
+ *
+ * @return {?} Item data.
+ */
+ol.structs.LinkedList.prototype.getPrevItem = function() {
+  if (this.head_ && this.head_.prev) {
+    return this.head_.prev.data;
+  }
+  return undefined;
+};
+
+/**
+ * Returns the current item's data.
+ *
+ * @return {?} Item data.
+ */
+ol.structs.LinkedList.prototype.getCurrItem = function() {
+  if (this.head_) {
+    return this.head_.data;
+  }
+  return undefined;
+};
+
+/**
+ * Sets the first item of the list. This only works for circular lists, and sets
+ * the last item accordingly.
+ */
+ol.structs.LinkedList.prototype.setFirstItem = function() {
+  if (this.circular_ && this.head_) {
+    this.first_ = this.head_;
+    this.last_ = this.head_.prev;
+  }
+};
+
+/**
+ * Concatenates two lists.
+ * @param {ol.structs.LinkedList} list List to merge into the current list.
+ */
+ol.structs.LinkedList.prototype.concat = function(list) {
+  if (list.head_) {
+    if (this.head_) {
+      var end = this.head_.next;
+      this.head_.next = list.first_;
+      list.first_.prev = this.head_;
+      end.prev = list.last_;
+      list.last_.next = end;
+      this.length_ += list.length_;
+    } else {
+      this.head_ = list.head_;
+      this.first_ = list.first_;
+      this.last_ = list.last_;
+      this.length_ = list.length_;
+    }
+    list.head_ = undefined;
+    list.first_ = undefined;
+    list.last_ = undefined;
+    list.length_ = 0;
+  }
+};
+
+/**
+ * Returns the current length of the list.
+ *
+ * @return {number} Length.
+ */
+ol.structs.LinkedList.prototype.getLength = function() {
+  return this.length_;
+};