function substr(f_string, f_start, f_length) {
	f_string = f_string + "";

	if (f_start < 0) {
		f_start += f_string.length;
	}

	if (f_length == undefined) {
		f_length = f_string.length;
	} else if(f_length < 0){
		f_length += f_string.length;
	} else {
		f_length += f_start;
	}

	if (f_length < f_start) {
		f_length = f_start;
	}

	return f_string.substring(f_start, f_length);
}

function strpos(haystack, needle, offset) {
	var i = haystack.indexOf(needle, offset); // returns -1
	return i >= 0 ? i : false;
}

function track_download(link) {
	if (typeof(pageTracker) != "undefined") {
		if (substr(link, 0, 7) == "http://") {
			link = substr(link, 7);
			if ((pos = strpos(link, "/")) == false) {
				return;
			}
			link = substr(link, pos);
		}
		pageTracker._trackPageview(link);
	}
}