performance improvements; shaved off about 10% on my work app (which is db bound) and over 50% on dom benchmarks standing alone

dom.d

@@ -83,37 +83,54 @@ bool isInArray(T)(T item, T[] arr) {
 }
 
 ///.
-class Stack(T) {
+final class Stack(T) {
+	this() {
+		internalLength = 0;
+		arr = initialBuffer;
+	}
 
 	///.
 	void push(T t) {
-		arr ~= t;
+		if(internalLength >= arr.length) {
+			if(arr.length < 4096)
+				arr = new T[arr.length * 2];
+			else
+				arr = new T[arr.length + 4096];
+		}
+
+		arr[internalLength] = t;
+		internalLength++;
 	}
 
 	///.
 	T pop() {
-		assert(arr.length);
+		assert(internalLength);
-		T tmp = arr[$-1];
+		internalLength--;
-		arr.length = arr.length - 1;
+		return arr[internalLength];
-		return tmp;
 	}
 
 	///.
 	T peek() {
-		return arr[$-1];
+		assert(internalLength);
+		return arr[internalLength - 1];
 	}
 
 	///.
 	bool empty() {
-		return arr.length ? false : true;
+		return internalLength ? false : true;
 	}
 
 	///.
-	T[] arr;
+	private T[] arr;
+	private size_t internalLength;
+	private T[64] initialBuffer;
+	// the static array is allocated with this object, so if we have a small stack (which we prolly do; dom trees usually aren't insanely deep),
+	// using this saves us a bunch of trips to the GC. In my last profiling, I got about a 50x improvement in the push()
+	// function thanks to this, and push() was actually one of the slowest individual functions in the code!
 }
 
 ///.
-class ElementStream {
+final class ElementStream {
 
 	///.
 	Element front() {
@@ -139,6 +156,8 @@ class ElementStream {
 	    more:
 	    	if(isEmpty) return;
 
+		// FIXME: the profiler says this function is somewhat slow (noticeable because it can be called a lot of times)
+
 		current.childPosition++;
 		if(current.childPosition >= current.element.children.length) {
 			if(stack.empty())
@@ -213,21 +232,8 @@ class Element {
 	private bool selfClosed;
 
 	/// Get the parent Document object that contains this element.
-	/// It may return null and/or run in O(n) time with the height of the tree.
+	/// It may be null, so remember to check for that.
-	pure Document parentDocument() {
+	Document parentDocument;
-		auto e = this;
-		while(e !is null && e._parentDocument is null)
-			e = e.parentNode;
-		if(e is null)
-			return null;
-		return e._parentDocument;
-	}
-
-	pure void parentDocument(Document pd) {
-		_parentDocument = pd;
-	}
-
-	private Document _parentDocument;
 
 	///.
 	this(Document _parentDocument, string _tagName, string[string] _attributes = null, bool _selfClosed = false) {
@@ -239,7 +245,11 @@ class Element {
 	}
 
 	/// Removes all inner content from the tag; all child text and elements are gone.
-	void removeAllChildren() {
+	void removeAllChildren()
+		out {
+			assert(this.children.length == 0);
+		}
+	body {
 		children = null;
 	}
 
@@ -345,7 +355,12 @@ class Element {
 	// Back to the regular dom functions
 
 	///.
-	@property Element cloned() {
+	@property Element cloned()
+		out(ret) {
+			assert(ret.children.length == this.children.length);
+			assert(ret.tagName == this.tagName);
+		}
+	body {
 		auto e = new Element(parentDocument, tagName, attributes.dup, selfClosed);
 		foreach(child; children) {
 			e.appendChild(child.cloned);
@@ -370,6 +385,10 @@ class Element {
 		if(_attributes !is null)
 			attributes = _attributes;
 		selfClosed = tagName.isInArray(selfClosedElements);
+
+		// this is meant to reserve some memory. It makes a small, but consistent improvement.
+		//children.length = 8;
+		//children.length = 0;
 	}
 
 	/*
@@ -413,6 +432,7 @@ class Element {
 		}
 		out (ret) {
 			assert(e.parentNode is this);
+			assert(e.parentDocument is this.parentDocument);
 			assert(e is ret);
 		}
 	body {
@@ -430,7 +450,7 @@ class Element {
 	}
 
 	/// Inserts the second element to this node, right before the first param
-	Element insertBefore(Element where, Element what)
+	Element insertBefore(in Element where, Element what)
 		in {
 			assert(where !is null);
 			assert(where.parentNode is this);
@@ -440,12 +460,15 @@ class Element {
 		out (ret) {
 			assert(where.parentNode is this);
 			assert(what.parentNode is this);
+
+			assert(what.parentDocument is this.parentDocument);
 			assert(ret is what);
 		}
 	body {
 		foreach(i, e; children) {
 			if(e is where) {
 				children = children[0..i] ~ what ~ children[i..$];
+				what.parentDocument = this.parentDocument;
 				what.parentNode = this;
 				return what;
 			}
@@ -457,7 +480,7 @@ class Element {
 	}
 
 	///.
-	Element insertAfter(Element where, Element what)
+	Element insertAfter(in Element where, Element what)
 		in {
 			assert(where !is null);
 			assert(where.parentNode is this);
@@ -467,6 +490,7 @@ class Element {
 		out (ret) {
 			assert(where.parentNode is this);
 			assert(what.parentNode is this);
+			assert(what.parentDocument is this.parentDocument);
 			assert(ret is what);
 		}
 	body {
@@ -474,6 +498,7 @@ class Element {
 			if(e is where) {
 				children = children[0 .. i + 1] ~ what ~ children[i + 1 .. $];
 				what.parentNode = this;
+				what.parentDocument = this.parentDocument;
 				return what;
 			}
 		}
@@ -571,9 +596,16 @@ class Element {
 	/// convenience function to quickly add a tag with some text or
 	/// other relevant info (for example, it's a src for an <img> element
 	/// instead of inner text)
-	Element addChild(string tagName, string childInfo = null, string childInfo2 = null) {
+	Element addChild(string tagName, string childInfo = null, string childInfo2 = null)
+		in {
+			assert(tagName !is null);
+		}
+		out(e) {
+			assert(e.parentNode is this);
+			assert(e.parentDocument is this.parentDocument);
+		}
+	body {
 		auto e = Element.make(tagName, childInfo, childInfo2);
-		e.parentDocument = this.parentDocument;
 		return appendChild(e);
 	}
 
@@ -602,6 +634,9 @@ class Element {
 		assert(ret !is null);
 		assert(ret.parentNode is this);
 		assert(firstChild.parentNode is ret);
+
+		assert(ret.parentDocument is this.parentDocument);
+		assert(firstChild.parentDocument is this.parentDocument);
 	}
 	body {
 		auto e = parentDocument.createElement(tagName);
@@ -616,6 +651,7 @@ class Element {
 	out(ret) {
 		assert(ret !is null);
 		assert(ret.parentNode is this);
+		assert(ret.parentDocument is this.parentDocument);
 	}
 	body {
 		auto e = Element.make(tagName);
@@ -650,12 +686,25 @@ class Element {
 	}
 
 	/// swaps one child for a new thing. Returns the old child which is now parentless.
-	Element swapNode(Element child, Element replacement) {
+	Element swapNode(Element child, Element replacement)
+		in {
+			assert(child !is null);
+			assert(replacement !is null);
+			assert(child.parentNode is this);
+		}
+		out(ret) {
+			assert(ret is child);
+			assert(ret.parentNode is null);
+			assert(replacement.parentNode is this);
+			assert(replacement.parentDocument is this.parentDocument);
+		}
+	body {
 		foreach(ref c; this.children)
 			if(c is child) {
 				c.parentNode = null;
 				c = replacement;
 				c.parentNode = this;
+				c.parentDocument = this.parentDocument;
 				return child;
 			}
 		assert(0);
@@ -664,6 +713,8 @@ class Element {
 
 	///.
 	Element getElementById(string id) {
+		// FIXME: I use this function a lot, and it's kinda slow
+		// not terribly slow, but not great.
 		foreach(e; tree)
 			if(e.id == id)
 				return e;
@@ -703,7 +754,7 @@ class Element {
 	/// Note: you can give multiple selectors, separated by commas.
 	/// It will return the first match it finds.
 	Element querySelector(string selector) {
-		// FIXME: inefficient
+		// FIXME: inefficient; it gets all results just to discard most of them
 		auto list = getElementsBySelector(selector);
 		if(list.length == 0)
 			return null;
@@ -717,6 +768,10 @@ class Element {
 
 	///.
 	Element[] getElementsBySelector(string selector) {
+		// FIXME: this function could probably use some performance attention
+		// ... but only mildly so according to the profiler in the big scheme of things; probably negligible in a big app.
+
+
 		// POSSIBLE FIXME: this also sends attribute things to lower in the selector,
 		// but the actual get selector check is still case sensitive...
 		if(parentDocument && parentDocument.loose)
@@ -895,6 +950,7 @@ class Element {
 				i++;
 				children = children[0..i] ~ child ~ children[i..$];
 				child.parentNode = this;
+				child.parentDocument = this.parentDocument;
 				break;
 			}
 		}
@@ -908,12 +964,18 @@ class Element {
 			if(position !is null)
 				assert(isInArray(position, children));
 		}
-		out {
+		out (ret) {
 			assert(e.children.length == 0);
+			debug foreach(child; ret) {
+				assert(child.parentNode is this);
+				assert(child.parentDocument is this.parentDocument);
+			}
 		}
 	body {
-		foreach(c; e.children)
+		foreach(c; e.children) {
 			c.parentNode = this;
+			c.parentDocument = this.parentDocument;
+		}
 		if(position is null)
 			children ~= e.children;
 		else {
@@ -941,10 +1003,12 @@ class Element {
 		}
 		out {
 			assert(e.parentNode is this);
+			assert(e.parentDocument is this.parentDocument);
 			assert(children[0] is e);
 		}
 	body {
 		e.parentNode = this;
+		e.parentDocument = this.parentDocument;
 		children = e ~ children;
 		return e;
 	}
@@ -983,22 +1047,19 @@ class Element {
 		Returns a string containing all child elements, formatted such that it could be pasted into
 		an XML file.
 	*/
-	@property string innerHTML() const {
+	@property string innerHTML(Appender!string where = appender!string()) const {
-		string s = "";
+		if(children is null)
-		if(children is null) {
+			return "";
-			assert(s !is null);
+
-			return s;
+		auto start = where.data.length;
-		}
+
 		foreach(child; children) {
 			assert(child !is null);
-			auto ts = child.toString();
+
-			assert(ts !is null);
+			child.writeToAppender(where);
-			s ~= ts;
 		}
 
-		assert(s !is null);
+		return where.data[start .. $];
-
-		return s;
 	}
 
 	/**
@@ -1021,12 +1082,10 @@ class Element {
 		children = doc.root.children;
 		foreach(c; children) {
 			c.parentNode = this;
+			c.parentDocument = this.parentDocument;
 		}
 
-		auto newpd = this.parentDocument;
+		reparentTreeDocuments();
-		foreach(c; this.tree) {
-			c.parentDocument = newpd;
-		}
 
 		doc.root.children = null;
 	}
@@ -1036,6 +1095,11 @@ class Element {
 		this.innerHTML = html.source;
 	}
 
+	private void reparentTreeDocuments() {
+		foreach(c; this.tree)
+			c.parentDocument = this.parentDocument;
+	}
+
 	/**
 		Replaces this node with the given html string, which is parsed
 
@@ -1051,9 +1115,13 @@ class Element {
 		children = doc.root.children;
 		foreach(c; children) {
 			c.parentNode = this;
+			c.parentDocument = this.parentDocument;
 		}
 
 
+		reparentTreeDocuments();
+
+
 		stripOut();
 
 		return doc.root.children;
@@ -1080,7 +1148,7 @@ class Element {
 		Note that the returned string is decoded, so it no longer contains any xml entities.
 	*/
 	string getAttribute(string name) const {
-		if(_parentDocument && _parentDocument.loose)
+		if(parentDocument && parentDocument.loose)
 			name = name.toLower();
 		auto e = name in attributes;
 		if(e)
@@ -1093,14 +1161,16 @@ class Element {
 		Sets an attribute. Returns this for easy chaining
 	*/
 	Element setAttribute(string name, string value) {
-		if(_parentDocument && _parentDocument.loose)
+		if(parentDocument && parentDocument.loose)
 			name = name.toLower();
 
 		// I never use this shit legitimately and neither should you
-		if(name.toLower == "href" || name.toLower == "src") {
+		auto it = name.toLower;
-			if(value.strip.toLower.startsWith("vbscript:"))
+		if(it == "href" || it == "src") {
+			auto v = value.strip.toLower();
+			if(v.startsWith("vbscript:"))
 				value = value[9..$];
-			if(value.strip.toLower.startsWith("javascript:"))
+			if(v.startsWith("javascript:"))
 				value = value[11..$];
 		}
 
@@ -1113,7 +1183,7 @@ class Element {
 		Extension
 	*/
 	bool hasAttribute(string name) {
-		if(_parentDocument && _parentDocument.loose)
+		if(parentDocument && parentDocument.loose)
 			name = name.toLower();
 
 		if(name in attributes)
@@ -1126,7 +1196,7 @@ class Element {
 		Extension
 	*/
 	void removeAttribute(string name) {
-		if(_parentDocument && _parentDocument.loose)
+		if(parentDocument && parentDocument.loose)
 			name = name.toLower();
 		if(name in attributes)
 			attributes.remove(name);
@@ -1161,8 +1231,10 @@ class Element {
 			assert(replace !is null);
 			assert(replace.parentNode is null);
 		}
-		out {
+		out(ret) {
+			assert(ret is replace);
 			assert(replace.parentNode is this);
+			assert(replace.parentDocument is this.parentDocument);
 			assert(find.parentNode is null);
 		}
 	body {
@@ -1171,6 +1243,7 @@ class Element {
 				replace.parentNode = this;
 				children[i].parentNode = null;
 				children[i] = replace;
+				replace.parentDocument = this.parentDocument;
 				return replace;
 			}
 		}
@@ -1189,7 +1262,7 @@ class Element {
 			assert(c.parentNode is this);
 		}
 		out {
-			foreach(child; children)
+			debug foreach(child; children)
 				assert(child !is c);
 			assert(c.parentNode is null);
 		}
@@ -1209,7 +1282,7 @@ class Element {
 	Element[] removeChildren()
 		out (ret) {
 			assert(children.length == 0);
-			foreach(r; ret)
+			debug foreach(r; ret)
 				assert(r.parentNode is null);
 		}
 	body {
@@ -1232,15 +1305,15 @@ class Element {
 			assert(find !is null);
 			assert(replace !is null);
 			assert(find.parentNode is this);
-			foreach(r; replace)
+			debug foreach(r; replace)
 				assert(r.parentNode is null);
 		}
 		out {
 			assert(find.parentNode is null);
 			assert(children.length >= replace.length);
-			foreach(child; children)
+			debug foreach(child; children)
 				assert(child !is find);
-			foreach(r; replace)
+			debug foreach(r; replace)
 				assert(r.parentNode is this);
 		}
 	body {
@@ -1253,9 +1326,13 @@ class Element {
 			if(children[i] is find) {
 				children[i].parentNode = null; // this element should now be dead
 				children[i] = replace[0];
-				children = .insertAfter(children, i, replace[1..$]);
+				foreach(e; replace) {
-				foreach(e; replace)
 					e.parentNode = this;
+					e.parentDocument = this.parentDocument;
+				}
+
+				children = .insertAfter(children, i, replace[1..$]);
+
 				return;
 			}
 		}
@@ -1394,7 +1471,7 @@ class Element {
 
 	invariant () {
 		if(children !is null)
-		foreach(child; children) {
+		debug foreach(child; children) {
 		//	assert(parentNode !is null);
 			assert(child !is null);
 			assert(child.parentNode is this, format("%s is not a parent of %s (it thought it was %s)", tagName, child.tagName, child.parentNode is null ? "null" : child.parentNode.tagName));
@@ -1402,6 +1479,13 @@ class Element {
 			assert(child !is parentNode);
 		}
 
+		/+ // only depend on parentNode's accuracy if you shuffle things around and use the top elements - where the contracts guarantee it on out
+		if(parentNode !is null) {
+			// if you have a parent, you should share the same parentDocument; this is appendChild()'s job
+			auto lol = cast(TextNode) this;
+			assert(parentDocument is parentNode.parentDocument, lol is null ? this.tagName : lol.contents);
+		}
+		+/
 		//assert(parentDocument !is null); // no more; if it is present, we use it, but it is not required
 		// reason is so you can create these without needing a reference to the document
 	}
@@ -1411,29 +1495,45 @@ class Element {
 		an XML file.
 	*/
 	override string toString() const {
+		return writeToAppender();
+	}
+
+	/// This is the actual implementation used by toString. You can pass it a preallocated buffer to save some time.
+	/// Returns the string it creates.
+	string writeToAppender(Appender!string where = appender!string()) const {
 		assert(tagName !is null);
-		string s = "<" ~ tagName;
+
+		where.reserve((this.children.length + 1) * 512);
+
+		auto start = where.data.length;
+
+		where.put("<");
+		where.put(tagName);
 
 		foreach(n, v ; attributes) {
 			assert(n !is null);
 			//assert(v !is null);
-			s ~= " " ~ n ~ "=\"" ~ htmlEntitiesEncode(v) ~ "\"";
+			where.put(" ");
+			where.put(n);
+			where.put("=\"");
+			htmlEntitiesEncode(v, where);
+			where.put("\"");
 		}
 
 		if(selfClosed){
-			s ~= " />";
+			where.put(" />");
-			return s;
+			return where.data[start .. $];
 		}
 
-		s ~= ">";
+		where.put('>');
 
-		s ~= innerHTML();
+		innerHTML(where);
 
-		s ~= "</" ~ tagName ~ ">";
+		where.put("</");
+		where.put(tagName);
+		where.put('>');
 
-		assert(s !is null);
+		return where.data[start .. $];
-
-		return s;
 	}
 
 	/**
@@ -1459,25 +1559,48 @@ class DocumentFragment : Element {
 }
 
 ///.
-string htmlEntitiesEncode(string data) {
+string htmlEntitiesEncode(string data, Appender!string output = appender!string()) {
-	char[] output = "".dup;
+	// if there's no entities, we can save a lot of time by not bothering with the
+	// decoding loop. This check cuts the net toString time by better than half in my test.
+	// let me know if it made your tests worse though, since if you use an entity in just about
+	// every location, the check will add time... but I suspect the average experience is like mine
+	// since the check gives up as soon as it can anyway.
+
+	bool shortcut = true;
+	foreach(char c; data) {
+		// non ascii chars are always higher than 127 in utf8; we'd better go to the full decoder if we see it.
+		if(c == '<' || c == '>' || c == '"' || c == '&' || cast(uint) c > 127) {
+			shortcut = false; // there's actual work to be done
+			break;
+		}
+	}
+
+	if(shortcut) {
+		output.put(data);
+		return data;
+	}
+
+	auto start = output.data.length;
+
+	output.reserve(data.length + 64); // grab some extra space for the encoded entities
+
 	foreach(dchar d; data) {
 		if(d == '&')
-			output ~= "&amp;";
+			output.put("&amp;");
 		else if (d == '<')
-			output ~= "&lt;";
+			output.put("&lt;");
 		else if (d == '>')
-			output ~= "&gt;";
+			output.put("&gt;");
 		else if (d == '\"')
-			output ~= "&quot;";
+			output.put("&quot;");
 		else if (d < 128 && d > 0)
-			output ~= d;
+			output.put(d);
 		else
-			output ~= "&#" ~ std.conv.to!string(cast(int) d) ~ ";";
+			output.put("&#" ~ std.conv.to!string(cast(int) d) ~ ";");
 	}
 
 	//assert(output !is null); // this fails on empty attributes.....
-	return assumeUnique(output);
+	return output.data[start .. $];
 
 //	data = data.replace("\u00a0", "&nbsp;");
 }
@@ -1559,7 +1682,13 @@ import std.utf;
 
 ///.
 string htmlEntitiesDecode(string data, bool strict = false) {
-	dchar[] a;
+	// this check makes a *big* difference; about a 50% improvement of parse speed on my test.
+	if(data.indexOf("&") == -1) // all html entities begin with &
+		return data; // if there are no entities in here, we can return the original slice and save some time
+
+	char[] a; // this seems to do a *better* job than appender!
+
+	char[4] buffer;
 
 	bool tryingEntity = false;
 	dchar[] entityBeingTried;
@@ -1572,14 +1701,14 @@ string htmlEntitiesDecode(string data, bool strict = false) {
 
 			if(ch == ';') {
 				tryingEntity = false;
-				a ~= parseEntity(entityBeingTried);
+				a ~= buffer[0.. std.utf.encode(buffer, parseEntity(entityBeingTried))];
 			} else {
 				if(entityAttemptIndex >= 7) {
 					if(strict)
 						throw new Exception("unterminated entity at " ~ to!string(entityBeingTried));
 					else {
 						tryingEntity = false;
-						a ~= entityBeingTried;
+						a ~= to!(char[])(entityBeingTried);
 					}
 				}
 			}
@@ -1590,12 +1719,12 @@ string htmlEntitiesDecode(string data, bool strict = false) {
 				entityBeingTried ~= ch;
 				entityAttemptIndex = 0;
 			} else {
-				a ~= ch;
+				a ~= buffer[0 .. std.utf.encode(buffer, ch)];
 			}
 		}
 	}
 
-	return std.conv.to!string(a);
+	return cast(string) a; // assumeUnique is actually kinda slow, lol
 }
 
 ///.
@@ -1671,10 +1800,10 @@ class TextNode : Element {
 	}
 
 	///.
-	override string toString() const {
+	override string writeToAppender(Appender!string where = appender!string()) const {
 		string s;
 		if(contents.length)
-			s = htmlEntitiesEncode(contents);
+			s = htmlEntitiesEncode(contents, where);
 		else
 			s = "";
 
@@ -2417,6 +2546,9 @@ class Document : FileResource {
 
 	*/
 	void parse(in string rawdata, bool caseSensitive = false, bool strict = false, string dataEncoding = "UTF-8") {
+		// FIXME: this parser could be faster; it's in the top ten biggest tree times according to the profiler
+		// of my big app.
+
 		// gotta determine the data encoding. If you know it, pass it in above to skip all this.
 		if(dataEncoding is null) {
 			dataEncoding = tryToDetermineEncoding(cast(const(ubyte[])) rawdata);
@@ -2493,19 +2625,9 @@ class Document : FileResource {
 
 		// &amp; and friends are converted when I know them, left the same otherwise
 
-		try {
+
-			validate(data); // it *must* be UTF-8 for this to work correctly
+		// this it should already be done correctly.. so I'm leaving it off to net a ~10% speed boost on my typical test file (really)
-		} catch (Throwable t) {
+		//validate(data); // it *must* be UTF-8 for this to work correctly
-			if(strict)
-			throw new MarkupError("This document is not UTF-8.");
-			else {
-				string newData;
-				foreach(char c; data)
-					if(c < 128)
-						newData ~= cast(char) c;
-				data = newData;
-			}
-		}
 
 		sizediff_t pos = 0;
 
@@ -2605,18 +2727,6 @@ class Document : FileResource {
 			return new RawSource(this, data[start..pos]);
 		}
 
-		char readEntity() {
-			return ' ';
-		}
-
-		string readComment() {
-			return "";
-		}
-
-		string readScript() {
-			return "";
-		}
-
 
 		struct Ele {
 			int type; // element or closing tag or nothing
@@ -2625,6 +2735,8 @@ class Document : FileResource {
 		}
 		// recursively read a tag
 		Ele readElement(string[] parentChain = null) {
+			// FIXME: this is the closest function in this module, by far, even in strict mode.
+			// Loose mode should perform decently, but strict mode is the important one.
 			if(!strict && parentChain is null)
 				parentChain = [];
 
@@ -3269,6 +3381,8 @@ int intFromHex(string hex) {
 		// USEFUL
 		///.
 		bool matchElement(Element e) {
+			// FIXME: this can be called a lot of times, and really add up in times according to the profiler.
+			// Each individual call is reasonably fast already, but it adds up.
 			if(e is null) return false;
 			if(e.nodeType != 1) return false;
 

mysql.d

@@ -656,13 +656,15 @@ string fromCstring(cstring c, int len = -1) {
 	if(c is null)
 		return null;
 	if(len == -1) {
-		while(*c) {
+		auto iterator = c;
-			ret ~= cast(char) *c;
+		while(*iterator)
-			c++;
+			iterator++;
+
+		len = cast(int) iterator - cast(int) c;
+		assert(len >= 0);
 	}
-	} else
+
-		for(int a = 0; a < len; a++)
+	ret = cast(string) (c[0 .. len].idup);
-			ret ~= cast(char) *(a+c);
 
 	return ret;
 }

web.d

@@ -2530,55 +2530,99 @@ class Session {
 	*/
 }
 
-/// sets a site-wide cookie, meant to simplify login code
+/// sets a site-wide cookie, meant to simplify login code. Note: you often might not want a side wide cookie, but I usually do since my projects need single sessions across multiple thingies, hence, this.
 void setLoginCookie(Cgi cgi, string name, string value) {
 	cgi.setCookie(name, value, 0, "/", null, true);
 }
 
-// this thing sucks in so many ways. it's kinda useful tho
+
+void applyTemplateToElement(Element e, in string[string] vars) {
+	foreach(ele; e.tree) {
+		auto tc = cast(TextNode) ele;
+		if(tc !is null) {
+			// text nodes have no attributes, but they do have text we might replace.
+			tc.contents = htmlTemplateWithData(tc.contents, vars, false);
+		} else {
+			// if it is not a text node, it has no text where templating is valid, except the attributes
+			// note: text nodes have no attributes, which is why this is in the separate branch.
+			foreach(k, v; ele.attributes)
+				ele.attributes[k] = htmlTemplateWithData(v, vars, false);
+		}
+	}
+}
+
+// this thing sucks a little less now.
+// set useHtml to false if you're working on internal data (such as TextNode.contents, or attribute);
+// it should only be set to true if you're doing input that has already been ran through toString or something.
 string htmlTemplateWithData(in string text, in string[string] vars, bool useHtml = true) {
 	if(text is null)
 		return null;
 
-	string newText = text;
+	int state = 0;
 
-	if(vars !is null)
+	string newText = null;
-	foreach(k, v; vars) {
+
-		//assert(k !is null);
+	size_t nameStart;
-		//assert(v !is null);
+	size_t replacementStart;
-		string replacement = useHtml ? htmlEntitiesEncode(v).replace("\n", "<br />") : v;
+	size_t lastAppend = 0;
-		newText = newText.replace("{$" ~ k ~ "}", replacement);
+	foreach(i, c; text) {
+		switch(state) {
+			default: assert(0);
+			case 0:
+				if(c == '{') {
+					replacementStart = i;
+					state++;
 				}
+			break;
+			case 1:
+				if(c == '$')
+					state++;
+				else
+					state--; // not a variable
+			break;
+			case 2: // just started seeing a name
+				if(c == '}') {
+					state = 0; // empty names aren't allowed; ignore it
+				} else {
+					nameStart = i;
+					state++;
+				}
+			break;
+			case 3: // reading a name
+				if(c == '}') {
+					// just finished reading it, let's do our replacement.
+					string name = text[nameStart .. i];
+					auto it = name in vars;
+					if(it !is null) {
+						newText ~= text[lastAppend .. replacementStart];
+						string replacement = *it;
+						if(useHtml)
+							replacement = htmlEntitiesEncode(replacement).replace("\n", "<br />");
+						newText ~= *it;
+						lastAppend = i + 1;
+					}
+
+					state = 0;
+				}
+			break;
+		}
+	}
+
+	if(newText is null)
+		newText = text; // nothing was found, so no need to risk allocating anything...
+	else
+		newText ~= text[lastAppend .. $]; // make sure we have everything here
 
 	return newText;
 }
 
-void applyTemplateToElement(Element e, in string[string] vars) {
+/// a specialization of Document that: a) is always in strict mode and b) provides some template variable text replacement, in addition to DOM manips. The variable text is valid in text nodes and attribute values. It takes the format of {$variable}, where variable is a key into the vars member.
-	foreach(ele; e.tree) {
-		foreach(k, v; ele.attributes)
-			ele.attributes[k] = htmlTemplateWithData(v, vars, false);
-		auto tc = cast(TextNode) ele;
-		if(tc !is null) {
-			// FIXME: this should arguably be null
-			tc.contents = htmlTemplateWithData(tc.contents, vars, false);
-		}
-	}
-}
-
-string htmlTemplate(string filename, string[string] vars) {
-	return htmlTemplateWithData(readText(filename), vars);
-}
-
-/// a specilization of Document that: a) is always in strict mode and b) provides some template variable text replacement, in addition to DOM manips.
 class TemplatedDocument : Document {
-	const override string toString() {
+	override string toString() const {
-		string s;
+		if(this.root !is null)
-		if(vars !is null)
+			applyTemplateToElement(cast() this.root, vars); /* FIXME: I shouldn't cast away const, since it's rude to modify an object in any toString.... but that's what I'm doing for now */
-			s = htmlTemplateWithData(super.toString(), vars);
-		else
-			s = super.toString();
 
-		return s;
+		return super.toString();
 	}
 
 	public: