Weblabor

function du(path, callback) {
	async.waterfall([
		function info(summarize){
			fs.stat(path, summarize);
		},
		function summarize(stat, result){
			if (stat.isFile())
				fs.readFile(path, function(err, data) {
					if (err)
						return result(err)
					result(null, data.length);
				});
			else if (stat.isDirectory())
				fs.readdir(path, function(err, files) {
					if (err)
						return result(err);
					var total = 0;
					async.forEach(files, function (file, done){
						du(path + "/" + file, function(err, length) {
							if (err)
								return done(err);
							total += length;
							done();
						});
					}, function (err){
						result(err, total);
					});
				});
			else
				result("odd file");
		}
	], callback);
}

var du = function (){
	var drive = {
		usage: function (path, next) {
			async.waterfall([
				function (next){
					fs.stat(path, next);
				},
				function (stat, next){
					if (stat.isFile())
						drive.fileSize(path, next)
					else if (stat.isDirectory())
						drive.dirSize(path, next)
					else
						next("odd file");
				}
			], next);
		},
		fileSize: function (path, next){
			async.waterfall([
				function (next){
					fs.readFile(path, next);
				},
				function (data, next){
					next(null, data.length);
				}
			], next);
		},
		dirSize: function (path, next){
			async.waterfall([
				function(next){
					fs.readdir(path, next); 
				},
				function(files, next){
					var total = 0;
					async.forEach(files, function (file, done){
						async.waterfall([
							function (next){
								drive.usage(path + "/" + file, next);
							},
							function (length, next){
								total += length;
								next();
							}
						], done);
					}, function (err){
						next(err, total);
					});
				}
			], next);
		}
	};
	return drive.usage;
}();

Function.prototype.err = function (next){
	var f = this;
	return function (err){
		if (err)
			next(err);
		else {
			var args = Array.prototype.slice.call(arguments, 1);
			args.push(next);
			f.apply(this, args);
		}	
	};
};

Function.prototype.waitSeries = function (){
	var f = this;
	for (var i=arguments.length-1; i>=0; --i)
		f = arguments[i].err(f);
	return f;
};

function du (path, next) {
	next.waitSeries(fs.stat, function (stat, next){
		if (stat.isFile())
			next.waitSeries(fs.readFile, function (data, next){
				next(null, data.length);
			})(null, path);
		else if (stat.isDirectory())
			next.waitSeries(fs.readdir, function(files, next){
				var total = 0;
				async.forEach(files, function (file, done){
					done.waitSeries(du, function (length, next){
						total += length;
						next();
					})(null, path + "/" + file);
				}, function (err){
					next(err, total);
				});
			})(null, path);
		else
			next("odd file");
	})(null, path);
}

function du (path) {
	var stat = fs.stat(path);
	if (stat.isFile())
		return fs.readFile(path).length;
	else if (stat.isDirectory()) {
		var total = 0;
		_.each(fs.readdir(path), function (file){
			total += du(path + "/" + file);
		});
		return total;
	}
	else
		throw "odd file";
}