use a linked list for filter runs. (#5206)

* Changed the filterrunprefixes to use LinkedList

* Testing for Linked List

* Finishing touches to LinkedList

* Minor corrections to link-list coding style

* Corrected for sneaky bug in linkedList

core/modules/filterrunprefixes/all.js

@@ -18,7 +18,7 @@ Export our filter prefix function
 */
 exports.all = function(operationSubFunction) {
 	return function(results,source,widget) {
-		Array.prototype.push.apply(results,operationSubFunction(source,widget));
+		results.push.apply(results, operationSubFunction(source,widget));
 	};
 };
 

core/modules/filterrunprefixes/and.js

@@ -19,9 +19,9 @@ Export our filter prefix function
 exports.and = function(operationSubFunction,options) {
 	return function(results,source,widget) {
 		// This replaces all the elements of the array, but keeps the actual array so that references to it are preserved
-		source = options.wiki.makeTiddlerIterator(results);
-		results.splice(0,results.length);
-		$tw.utils.pushTop(results,operationSubFunction(source,widget));
+		source = options.wiki.makeTiddlerIterator(results.toArray());
+		results.clear();
+		results.pushTop(operationSubFunction(source,widget));
 	};
 };
 

core/modules/filterrunprefixes/else.js

@@ -19,7 +19,7 @@ exports.else = function(operationSubFunction) {
 	return function(results,source,widget) {
 		if(results.length === 0) {
 			// Main result so far is empty
-			$tw.utils.pushTop(results,operationSubFunction(source,widget));
+			results.pushTop(operationSubFunction(source,widget));
 		}
 	};
 };

core/modules/filterrunprefixes/except.js

@@ -18,7 +18,7 @@ Export our filter prefix function
 */
 exports.except = function(operationSubFunction) {
 	return function(results,source,widget) {
-		$tw.utils.removeArrayEntries(results,operationSubFunction(source,widget));
+		results.remove(operationSubFunction(source,widget));
 	};
 };
 

core/modules/filterrunprefixes/filter.js

@@ -17,13 +17,13 @@ exports.filter = function(operationSubFunction,options) {
 	return function(results,source,widget) {
 		if(results.length > 0) {
 			var resultsToRemove = [];
-			$tw.utils.each(results,function(result) {
+			results.each(function(result) {
 				var filtered = operationSubFunction(options.wiki.makeTiddlerIterator([result]),widget);
 				if(filtered.length === 0) {
 					resultsToRemove.push(result);
 				}
 			});
-			$tw.utils.removeArrayEntries(results,resultsToRemove);
+			results.remove(resultsToRemove);
 		}
 	}
 };

core/modules/filterrunprefixes/intersection.js

@@ -17,7 +17,8 @@ exports.intersection = function(operationSubFunction) {
 	return function(results,source,widget) {
 		if(results.length !== 0) {
 			var secondRunResults = operationSubFunction(source,widget);
-			var firstRunResults = results.splice(0);
+			var firstRunResults = results.toArray();
+			results.clear();
 			$tw.utils.each(firstRunResults,function(title) {
 				if(secondRunResults.indexOf(title) !== -1) {
 					results.push(title);

core/modules/filterrunprefixes/or.js

@@ -17,7 +17,7 @@ Export our filter prefix function
 */
 exports.or = function(operationSubFunction) {
 	return function(results,source,widget) {
-		$tw.utils.pushTop(results,operationSubFunction(source,widget));
+		results.pushTop(operationSubFunction(source,widget));
 	};
 };
 

core/modules/filterrunprefixes/reduce.js

@@ -16,9 +16,9 @@ exports.reduce = function(operationSubFunction,options) {
 	return function(results,source,widget) {
 		if(results.length > 0) {
 			var accumulator = "";
-			for(var index=0; index<results.length; index++) {
-				var title = results[index],
-					list = operationSubFunction(options.wiki.makeTiddlerIterator([title]),{
+			var index = 0;
+			results.each(function(title) {
+				var list = operationSubFunction(options.wiki.makeTiddlerIterator([title]),{
 						getVariable: function(name) {
 							switch(name) {
 								case "currentTiddler":
@@ -39,8 +39,9 @@ exports.reduce = function(operationSubFunction,options) {
 				if(list.length > 0) {
 					accumulator = "" + list[0];
 				}
-			}
-			results.splice(0,results.length);
+				++index;
+			});
+			results.clear();
 			results.push(accumulator);	
 		}
 	}

core/modules/filters.js

@@ -311,11 +311,11 @@ exports.compileFilter = function(filterString) {
 		} else if(typeof source === "object") { // Array or hashmap
 			source = self.makeTiddlerIterator(source);
 		}
-		var results = [];
+		var results = new $tw.utils.LinkedList();
 		$tw.utils.each(operationFunctions,function(operationFunction) {
 			operationFunction(results,source,widget);
 		});
-		return results;
+		return results.toArray();
 	});
 };
 

core/modules/utils/linked-list.js

@@ -0,0 +1,118 @@
+/*\
+module-type: utils
+title: $:/core/modules/utils/linkedlist.js
+type: application/javascript
+
+This is a doubly-linked indexed list intended for manipulation, particularly
+pushTop, which it does with significantly better performance than an array.
+
+\*/
+(function(){
+
+function LinkedList() {
+	this.clear();
+};
+
+LinkedList.prototype.clear = function() {
+	this.index = Object.create(null);
+	// LinkedList performs the duty of both the head and tail node
+	this.next = this;
+	this.prev = this;
+	this.length = 0;
+};
+
+LinkedList.prototype.remove = function(value) {
+	if($tw.utils.isArray(value)) {
+		for(var t=0; t<value.length; t++) {
+			this._removeOne(value[t]);
+		}
+	} else {
+		this._removeOne(value);
+	}
+};
+
+LinkedList.prototype._removeOne = function(value) {
+	var node = this.index[value];
+	if(node) {
+		node.prev.next = node.next;
+		node.next.prev = node.prev;
+		this.length -= 1;
+		// Point index to the next instance of the same value, maybe nothing.
+		this.index[value] = node.copy;
+	}
+	return node;
+};
+
+LinkedList.prototype._linkToEnd = function(node) {
+	// Sticks the given node onto the end of the list.
+	this.prev.next = node;
+	node.prev = this.prev;
+	this.prev = node;
+	node.next = this;
+	this.length += 1;
+};
+
+LinkedList.prototype.push = function(/* values */) {
+	for(var i = 0; i < arguments.length; i++) {
+		var value = arguments[i];
+		var node = {value: value};
+		var preexistingNode = this.index[value];
+		this._linkToEnd(node);
+		if(preexistingNode) {
+			// We want to keep pointing to the first instance, but we want
+			// to have that instance (or chain of instances) point to the
+			// new one.
+			while (preexistingNode.copy) {
+				preexistingNode = preexistingNode.copy;
+			}
+			preexistingNode.copy = node;
+		} else {
+			this.index[value] = node;
+		}
+	}
+};
+
+LinkedList.prototype.pushTop = function(value) {
+	if($tw.utils.isArray(value)) {
+		for(var t=0; t<value.length; t++) {
+			this._removeOne(value[t]);
+		}
+		this.push.apply(this, value);
+	} else {
+		var node = this._removeOne(value);
+		if(!node) {
+			node = {value: value};
+			this.index[value] = node;
+		} else {
+			// Put this node at the end of the copy chain.
+			var preexistingNode = node;
+			while(preexistingNode.copy) {
+				preexistingNode = preexistingNode.copy;
+			}
+			// The order of these three statements is important,
+			// because sometimes preexistingNode == node.
+			preexistingNode.copy = node;
+			this.index[value] = node.copy;
+			node.copy = undefined;
+		}
+		this._linkToEnd(node);
+	}
+};
+
+LinkedList.prototype.each = function(callback) {
+	for(var ptr = this.next; ptr !== this; ptr = ptr.next) {
+		callback(ptr.value);
+	}
+};
+
+LinkedList.prototype.toArray = function() {
+	var output = [];
+	for(var ptr = this.next; ptr !== this; ptr = ptr.next) {
+		output.push(ptr.value);
+	}
+	return output;
+};
+
+exports.LinkedList = LinkedList;
+
+})();

editions/test/tiddlers/tests/test-linked-list.js

@@ -0,0 +1,130 @@
+/*\
+title: test-linked-list.js
+type: application/javascript
+tags: [[$:/tags/test-spec]]
+
+Tests the utils.LinkedList class.
+
+LinkedList was built to behave exactly as $tw.utils.pushTop and
+Array.prototype.push would behave with an array.
+
+\*/
+(function(){
+
+/*jslint node: true, browser: true */
+/*global $tw: false */
+"use strict";
+
+describe("LinkedList class tests", function() {
+
+	it("can pushTop", function() {
+		var list = new $tw.utils.LinkedList();
+		list.push('A', 'B', 'C');
+		// singles
+		list.pushTop('X');
+		list.pushTop('B');
+		expect(list.toArray()).toEqual(['A', 'C', 'X', 'B']);
+		expect(list.length).toBe(4);
+		//arrays
+		list.pushTop(['X', 'A', 'G', 'A']);
+		// If the pushedTopped list has duplicates, they go in unempeded.
+		expect(list.toArray()).toEqual(['C', 'B', 'X', 'A', 'G', 'A']);
+		expect(list.length).toBe(6);
+	});
+
+	it("can pushTop with tricky duplicates", function() {
+		var list = new $tw.utils.LinkedList();
+		list.push('A', 'B', 'A', 'C', 'A', 'end');
+		// If the original list contains duplicates, only one instance is cut
+		list.pushTop('A');
+		expect(list.toArray()).toEqual(['B', 'A', 'C', 'A', 'end', 'A']);
+		expect(list.length).toBe(6);
+
+		// And the Llist properly knows the next 'A' to cut if pushed again
+		list.pushTop(['X', 'A']);
+		expect(list.toArray()).toEqual(['B', 'C', 'A', 'end', 'A', 'X', 'A']);
+		expect(list.length).toBe(7);
+
+		// One last time, to make sure we maintain the linked chain of copies
+		list.pushTop('A');
+		expect(list.toArray()).toEqual(['B', 'C', 'end', 'A', 'X', 'A', 'A']);
+		expect(list.length).toBe(7);
+	});
+
+	it("can handle particularly nasty pushTop pitfall", function() {
+		var list = new $tw.utils.LinkedList();
+		list.push('A', 'B', 'A', 'C');
+		list.pushTop('A'); // BACA
+		list.pushTop('X'); // BACAX
+		list.remove('A');  // BCAX
+		list.pushTop('A'); // BCXA
+		list.remove('A');  // BCX
+		// But! The way I initially coded the copy chains, a mystery A could
+		// hang around.
+		expect(list.toArray()).toEqual(['B', 'C', 'X']);
+		expect(list.length).toBe(3);
+	});
+
+	it("can push", function() {
+		var list = new $tw.utils.LinkedList();
+		list.push('A', 'B', 'C');
+		// singles
+		list.push('B');
+		expect(list.toArray()).toEqual(['A', 'B', 'C', 'B']);
+		expect(list.length).toBe(4);
+
+		// multiple args
+		list.push('A', 'B', 'C');
+		expect(list.toArray()).toEqual(['A', 'B', 'C', 'B', 'A', 'B', 'C']);
+		expect(list.length).toBe(7);
+	});
+
+	it("can clear", function() {
+		var list = new $tw.utils.LinkedList();
+		list.push('A', 'B', 'C');
+		list.clear();
+		expect(list.toArray()).toEqual([]);
+		expect(list.length).toBe(0);
+	});
+
+	it("can remove", function() {
+		var list = new $tw.utils.LinkedList();
+		list.push('A', 'x', 'C', 'x', 'D', 'x', 'E', 'x');
+		// single
+		list.remove('x');
+		expect(list.toArray()).toEqual(['A', 'C', 'x', 'D', 'x', 'E', 'x']);
+		expect(list.length).toBe(7);
+
+		// arrays
+		list.remove(['x', 'A', 'x']);
+		expect(list.toArray()).toEqual(['C', 'D', 'E', 'x']);
+		expect(list.length).toBe(4);
+	});
+
+	it('can ignore removal of nonexistent items', function() {
+		var list = new $tw.utils.LinkedList();
+		list.push('A', 'B', 'C', 'D');
+		// single
+		list.remove('Z');
+		expect(list.toArray()).toEqual(['A', 'B', 'C', 'D']);
+		expect(list.length).toBe(4);
+
+		// array
+		list.remove(['Z', 'B', 'X']);
+		expect(list.toArray()).toEqual(['A', 'C', 'D']);
+		expect(list.length).toBe(3);
+	});
+
+	it('can iterate with each', function() {
+		var list = new $tw.utils.LinkedList();
+		list.push('0', '1', '2', '3');
+		var counter = 0;
+		list.each(function(value) {
+			expect(value).toBe(counter.toString());
+			counter = counter + 1;
+		});
+		expect(counter).toBe(4);
+	});
+});
+
+})();